ALBERT

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 176〈/p〉 〈p〉Author(s): Hoheok Kim, Tatsuki Yamamoto, Yushi Sato, Junya Inoue〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We investigate the viability of establishing low-cost surrogate structure-property (S–P) linkages by introducing a Bayesian model selection method to extend the Materials Knowledge Systems (MKS) homogenization framework, which employs the n-point spatial correlation function, principal component analysis, and regression techniques. In particular, we place emphasis not only on choosing the important structural features but also on interpreting their implications for the property under consideration. First, the yield strengths of synthetic microstructures with various morphological characteristics are estimated by physics-based crystal plasticity simulation. Then, the dimension-reduced microstructural features are revealed by a combination of 2-point spatial correlations and principal component analysis. The Bayesian model selection method is further applied to establish a microstructure-to-yield-strength surrogate model. Finally, the model is validated with an independent dataset and its constituent features are interpreted with a morphology reconstruction based on a Monte Carlo algorithm. The method is found to be capable of interpreting the key microstructural features as well as modeling the mechanical response of a dual-phase metallic composite in consideration of the diverse microstructural factors.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419304367-fx1.jpg" width="274" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 176〈/p〉 〈p〉Author(s): Denise C. Ford, David Hicks, Corey Oses, Cormac Toher, Stefano Curtarolo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Metallic glasses are excellent candidates for biomedical implant applications due to their inherent strength and corrosion resistance. However, use of metallic glasses in structural applications is limited because bulk dimensions are challenging to achieve. Glass-forming ability (GFA) varies strongly with alloy composition and becomes more difficult to predict as the number of chemical species in a system increases. Here, we present a theoretical model — implemented in the AFLOW framework — for predicting GFA based on the competition between crystalline phases. The model is applied to biologically relevant binary and ternary systems. Elastic properties of Ca- and Mg-based systems are estimated for use in biodegradable orthopedic support applications. Alloys based on Ag〈sub〉0.33〈/sub〉Mg〈sub〉0.67〈/sub〉, Cu〈sub〉0.5〈/sub〉Mg〈sub〉0.5〈/sub〉, Cu〈sub〉0.37〈/sub〉Mg〈sub〉0.63〈/sub〉, and Cu〈sub〉0.25〈/sub〉Mg〈sub〉0.5〈/sub〉Zn〈sub〉0.25〈/sub〉, and in the Ag-Ca-Mg and Ag-Mg-Zn systems, are recommended for further study.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419304380-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Maryam Mohammadi, Esmaeil Poursaeidi, Kaveh Torkashvand〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study provides a numerical simulation of the interface crack development in thermal barrier coatings, deposited using plasma spray method. The proposed model benefited from the SEM image obtained from our previous experimental studies so that the geometry was placed in a model with the dimensions of the tested specimens. In this study, the longitudinal and lateral growth effects of TGO, the creep effect of all coating layers, and the effect of thermal mismatch between layers were investigated on the stress distribution of the coating. The results obtained from previous experimental observations revealed that the separation occurs in the TC/TGO interface. Therefore, in the numerical study, it was defined as the cohesive layer. The separation of cohesive layer in various thermal ageing periods was further explored alongside the cooling-heating thermal cycles. The results obtained by the finite element analysis indicated that as the thermal ageing period increased, the interface separation was enlarged and cracks started to nucleate from other points of the interface. Separation behavior of TC/TGO interface was evaluated once increasing ageing period and thermal cycles.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 176〈/p〉 〈p〉Author(s): Manuel J. Pfeifenberger, Vladica Nikolić, Stanislav Žák, Anton Hohenwarter, Reinhard Pippan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The brittleness of tungsten at room temperature represents a severe challenge particularly for structural applications. Tungsten composites, consisting of foils or wires, overcome this low ductility by utilizing the remarkable mechanical properties of ultrafine grained tungsten materials. A comprehensive understanding of the fracture behaviour of these ultrafine grained tungsten materials is therefore essential for a further development of high performance structural composites. However, the dimensions of specimens used for classical fracture toughness experiments are not applicable to test all important crack growth directions in the case of thin foils and wires, especially, in the direction of the presumably lowest fracture toughness, which is along their characteristically elongated microstructure. Femtosecond laser processing allows to fabricate micro single leg bending specimens, which enable to properly evaluate the fracture toughness in this orientation. The fracture toughness value at crack initiation found for the foil is 2.4  〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mtext〉MPa〈/mtext〉〈msqrt〉〈mtext〉m〈/mtext〉〈/msqrt〉〈/math〉, whereas for the wire a value of 5.3  〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mtext〉MPa〈/mtext〉〈msqrt〉〈mtext〉m〈/mtext〉〈/msqrt〉〈/math〉 was determined. In both cases the results are significantly below the values reported for other orientations. This strongly anisotropic fracture behaviour is responsible for the reduced brittle to ductile transition temperature and the delamination induced toughening for crack orientations perpendicular to the elongated ultrafine grained structure. The distinct difference of the fracture toughness at crack initiation and the R-curve between wire and foil specimens could be primarily explained by the morphologies of the fracture surfaces, exhibiting significantly different roughnesses of the evolving crack paths.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419304252-fx1.jpg" width="497" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 176〈/p〉 〈p〉Author(s): Peter Müllner〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recent reports on highly mobile type II twin boundaries challenge the established understanding of deformation twinning and motivate this study. We consider the motion of twin boundaries through the nucleation and growth of disconnection loops and develop a mechanism-based model for twin boundary motion in the framework of isotropic linear elasticity. While such mechanisms are well established for type I and compound twins, we demonstrate based on the elastic properties of crystals that type II twin boundaries propagate in a similar way. Nucleation of a type I twinning disconnection loop occurs in a discrete manner. In contrast, nucleation of a type II twinning disconnection loop occurs gradually with increasing Burgers vector. The gradual nucleation of a type II disconnection loop accounts for the higher mobility of type II twin boundaries compared with type I twin boundaries. We consider the homogeneous nucleation of a disconnection loop, which is adequate for twinning in shape memory alloys with a low-symmetry crystal lattice. For the magnetic shape memory alloy Ni–Mn-Ga, the model predicts twinning stresses of 0.33 MPa for type II twinning and 4.7 MPa for type I twinning. Over a wide temperature range, the twinning stress depends on temperature only through the temperature dependence of the elastic constants, in agreement with experimental results.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419304343-fx1.jpg" width="374" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 3 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia〈/p〉 〈p〉Author(s): Cuncai Fan, Qiang Li, Jie Ding, Yanxiang Liang, Zhongxia Shang, Jin Li, Ruizhe Su, Jaehun Cho, Di Chen, Yongqiang Wang, Jian Wang, Haiyan Wang, Xinghang Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉There are increasing studies that show nanotwinned (NT) metals have enhanced radiation tolerance. However, the mechanical deformability of irradiated nanotwinned metals is a largely under explored subject. Here we investigate the mechanical properties of He ion irradiated nanotwinned Cu with preexisting nanovoids. In comparison with coarse-grained Cu, nanovoid nanotwinned (NV-NT) Cu exhibits prominently improved radiation tolerance. Furthermore, 〈em〉in situ〈/em〉 micropillar compression tests show that the irradiated NV-NT Cu has an ultrahigh yield strength of ∼ 1.6 GPa with significant plasticity. Post radiation analyses show that twin boundaries are decorated with He bubbles and thick stacking faults. These stacking fault modified twin boundaries introduce significant strengthening in NT Cu. This study provides further insight into the design of high-strength, advanced radiation tolerant nanostructured materials for nuclear reactor applications.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419304331-fx1.jpg" width="307" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 176〈/p〉 〈p〉Author(s): Y. Kobayashi, J. Takahashi, K. Kawakami〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The influence of a pre-deformation with a true strain of 0.5 on the precipitation behavior during isothermal aging at 580 °C in ferritic steel containing 0.03C-0.1Ti-0.20Mn–3Al (mass %) was investigated. Atom probe tomography (APT) analysis revealed that titanium carbide (TiC) precipitates much earlier and more finely in pre-deformed steel than in steel without a pre-deformation. It was found that the precipitation sites of TiC are not only located on the dislocations but are also distributed homogeneously in a matrix in pre-deformed steel. In steel without a pre-deformation, coarse cementite first precipitates during the early stage of aging, and the cementite then dissolves owing to the subsequent precipitation of TiC. Meanwhile, in pre-deformed steel, cementite has difficulty precipitating, and carbon atoms are considered to segregate to high-density dislocations during the early stage of aging prior to the precipitation of TiC. A kinetic model that explains the difference between the precipitation behaviors of steel with and without a pre-deformation is proposed. Moreover, the difference observed between TiC particle strengthening in steel with and without a pre-deformation is discussed.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S135964541930429X-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 25 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 374〈/p〉 〈p〉Author(s): H. Tian, K. Zhou, Y.C. Zou, H. Cai, Y.M. Wang, J.H. Ouyang, X.W. Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The aluminide coating was prepared on Ti-6Al-2Zr-1Mo-1 V titanium alloy by pack cementation to enhance the high temperature oxidation resistance for aircraft and aerospace applications. High temperature oxidation behaviors of packing cementation coated and uncoated titanium alloy samples were comparatively investigated by isothermal oxidation at 800 °C and 900 °C in air. The results show that the compact coating with about 60 μm thick was composed of TiAl〈sub〉3〈/sub〉. With isothermal oxidation for 100 h at 800 and 900 °C, the weight gains of the coated samples are 1.29 mg·cm〈sup〉−2〈/sup〉 and 4.06 mg·cm〈sup〉−2〈/sup〉 respectively, which are about 2/5 and 1/5 of that of titanium alloy substrates (3.20 mg·cm〈sup〉−2〈/sup〉 and 20.33 mg·cm〈sup〉−2〈/sup〉). The excellent oxidation resistance performance is attributed to the formation of a continuous and dense Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 layer on the TiAl〈sub〉3〈/sub〉 coating surface, which was effective to prevent the O element diffusing into the coating and then reduce the oxidation rate.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 374〈/p〉 〈p〉Author(s): Marzieh Mardali, Hamidreza Salimijazi, Fathallah Karimzadeh, Berengere Luthringer-Feyerabend〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Lightweight magnesium alloys are currently being investigated as implants due to their biodegradability and mechanical properties. However, their clinical applications are limited by their high corrosion rate in the physiological environment. Coating Mg-based alloys is an approach that is used to delay primary corrosion and increase their lifetime. Therefore, hydroxyapatite was coated on anodized and non-anodized magnesium substrates using high-velocity oxy-fuel spraying. This study aimed to evaluate the effect of the MgO intermediate layer between the hydroxyapatite coating and Mg alloy substrate. The microstructure and corrosion behaviour of the coated samples are the main focuses of this study. X-ray diffraction spectroscopy was used to analyse the phases. Electrochemical impedance spectroscopy was performed in simulated body fluid. The results revealed that the presence of an anodized layer increased corrosion resistance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): L.A. Ardila-Rodríguez, B.R.C. Menezes, L.A. Pereira, R.J. Takahashi, A.C. Oliveira, D.N. Travessa〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Carbon nanotubes (CNTs) could be an excellent reinforcement for metal matrix composites, specifically for composites with aluminum or aluminum alloy matrix. Surface modification to improve hardness and other material properties has been performed by laser surface melting (LSM) process, where the laser beam melts the substrate together with alloying elements or reinforcing phase additives. In this work, Multiwalled CNTs (MWCNTs) were mixed by the electrostatic adsorption process with aluminum powder and the resulting mixed powder was laser melted on the surface of a 6061-aluminum alloy substrate. As a result, a modified substrate surface has been obtained from the Al/MWCNT – substrate co-melting, dilution and re-solidification processes. This modified layer was obtained by different LSM parameters and were characterized by Optical (OM) and Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Field Emission Gun Scanning Electron Microscopy (FEG-SEM), X-Ray Diffraction (XRD) and Raman Spectroscopy (RS). The resulting mechanical behavior was evaluated by Vickers microhardness tests. The results showed that the presence of MWCNT in the aluminum powder improves the laser energy absorption, leading to the formation of a deeper modified layer, with segregation of Si particles homogeneously dispersed and improving the hardness. The formation of Al〈sub〉4〈/sub〉C〈sub〉3〈/sub〉 was not observed, evidencing that the MWCNTs did not react with the molten Al matrix during the LSM process.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): Chunguang Shen, Chenchong Wang, Xiaolu Wei, Yong Li, Sybrand van der Zwaag, Wei Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉With the development of the materials genome philosophy and data mining methodologies, machine learning (ML) has been widely applied for discovering new materials in various systems including high-end steels with improved performance. Although recently, some attempts have been made to incorporate physical features in the ML process, its effects have not been demonstrated and systematically analysed nor experimentally validated with prototype alloys. To address this issue, a physical metallurgy (PM) -guided ML model was developed, wherein intermediate parameters were generated based on original inputs and PM principles, e.g., equilibrium volume fraction (〈em〉V〈/em〉〈sub〉〈em〉f〈/em〉〈/sub〉) and driving force (〈em〉D〈/em〉〈sub〉〈em〉f〈/em〉〈/sub〉) for precipitation, and these were added to the original dataset vectors as extra dimensions to participate in and guide the ML process. As a result, the ML process becomes more robust when dealing with small datasets by improving the data quality and enriching data information. Therefore, a new material design method is proposed combining PM-guided ML regression, ML classifier and a genetic algorithm (GA). The model was successfully applied to the design of advanced ultrahigh-strength stainless steels using only a small database extracted from the literature. The proposed prototype alloy with a leaner chemistry but better mechanical properties has been produced experimentally and an excellent agreement was obtained for the predicted optimal parameter settings and the final properties. In addition, the present work also clearly demonstrated that implementation of PM parameters can improve the design accuracy and efficiency by eliminating intermediate solutions not obeying PM principles in the ML process. Furthermore, various important factors influencing the generalizability of the ML model are discussed in detail.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305452-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia〈/p〉 〈p〉Author(s): Hao Chen, Valery Levitas, Liming Xiong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Molecular dynamics (MD) simulations of the amorphous band nucleation and growth ahead of the tip of a shuffle 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msup〉〈mrow〉〈mn〉60〈/mn〉〈/mrow〉〈mrow〉〈mi〉o〈/mi〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 dislocation pileup at different grain boundaries (GBs) in diamond-cubic (dc) silicon (Si) bicrystal under shear are performed. Amorphization initiates when the local resolved shear stress reaches approximately the same value required for amorphization in a perfect single crystal (8.6-9.3GPa) for the same amorphization plane. Since the local stresses at the tip of a dislocation pileup increase when the number of dislocations in the pileup is increased, the critical applied shear stress 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉τ〈/mi〉〈/mrow〉〈mrow〉〈mi〉a〈/mi〉〈mi〉p〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 for the formation of an amorphous shear band significantly decreases with the dislocation accumulation at the GBs. In particular, when the number of the dislocations in a pileup increases from 3 to 8, the critical shear stress drops from 4.7GPa to 1.6GPa for both the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈mtext〉Σ〈/mtext〉〈mn〉9〈/mn〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈mrow〉〈mtext〉Σ〈/mtext〉〈mn〉19〈/mn〉〈/mrow〉〈/math〉 GBs and from 4.6GPa to 2.1GPa for the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.svg"〉〈mrow〉〈mtext〉Σ〈/mtext〉〈mn〉3〈/mn〉〈/mrow〉〈/math〉 GB, respectively. After the formation of steps and disordered embryos at the GBs, the atomistic mechanisms responsible for the subsequent amorphous shear band formations near different GBs are found to distinct from each other. For a high-angle GB, such as 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.svg"〉〈mrow〉〈mtext〉Σ〈/mtext〉〈mn〉3〈/mn〉〈/mrow〉〈/math〉, an amorphous band propagates through the crystalline phase along the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si6.svg"〉〈mrow〉〈mrow〉〈mo〉(〈/mo〉〈mrow〉〈mn〉112〈/mn〉〈/mrow〉〈mo〉)〈/mo〉〈/mrow〉〈/mrow〉〈/math〉 plane. For the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈mtext〉Σ〈/mtext〉〈mn〉9〈/mn〉〈/mrow〉〈/math〉 GB, partial dislocations forming a stacking fault precede the formation of an amorphous band along the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si7.svg"〉〈mrow〉〈mrow〉〈mo〉(〈/mo〉〈mrow〉〈mn〉110〈/mn〉〈/mrow〉〈mo〉)〈/mo〉〈/mrow〉〈/mrow〉〈/math〉 plane. For the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈mrow〉〈mtext〉Σ〈/mtext〉〈mn〉19〈/mn〉〈/mrow〉〈/math〉 GB, the one-layer stacking fault along the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si8.svg"〉〈mrow〉〈mrow〉〈mo〉(〈/mo〉〈mrow〉〈mn〉111〈/mn〉〈/mrow〉〈mo〉)〈/mo〉〈/mrow〉〈/mrow〉〈/math〉 plane transforms into an interesting intermediate phase: a two-layer band with the atomic bonds being aligned along the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si8.svg"〉〈mrow〉〈mrow〉〈mo〉(〈/mo〉〈mrow〉〈mn〉111〈/mn〉〈/mrow〉〈mo〉)〈/mo〉〈/mrow〉〈/mrow〉〈/math〉 plane (i.e., rotated by 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si9.svg"〉〈mrow〉〈msup〉〈mrow〉〈mn〉30〈/mn〉〈/mrow〉〈mrow〉〈mi〉o〈/mi〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 with respect to the atomic bonds outside the band). This intermediate phase transforms to the amorphous band along the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si8.svg"〉〈mrow〉〈mrow〉〈mo〉(〈/mo〉〈mrow〉〈mn〉111〈/mn〉〈/mrow〉〈mo〉)〈/mo〉〈/mrow〉〈/mrow〉〈/math〉 plane under a further shearing. The obtained results represent an atomic-level confirmation of the effectiveness of dislocation pileup at the nucleation site for various strain-induced phase transformations (PTs), and exhibit some limitations.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S135964541930535X-fx1.jpg" width="218" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): K. Sofinowski, M. Šmíd, I. Kuběna, S. Vivès, N. Casati, S. Godet, H. Van Swygenhoven〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A multi-phase Ti–6Al–4V prepared by electron beam melting and thermal post treatments has been shown to exhibit increased strength and ductility over standard wrought or hot isostatic pressed Ti–6Al–4V. The mechanical improvements are due to a prolonged, continuous work hardening effect not commonly observed in Ti alloys. 〈em〉In situ〈/em〉 x-ray diffraction and high resolution digital image correlation are used to examine the strain partitioning between the phases during tensile loading with post-mortem electron microscopy to characterize the deformation behavior in each phase. Specimens heat treated between 850 and 980 °C were tested and the effect of annealing temperature on the micromechanical response is discussed. It is shown that the work hardening is the result of composite load-sharing behavior between three mechanically distinct microstructures: large 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉α〈/mi〉〈/mrow〉〈/math〉 lamellae and a martensitic region of fine acicular 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈mi〉α〈/mi〉〈mo〉'〈/mo〉〈/mrow〉〈/math〉 and a third phase not previously reported in this alloy.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S135964541930549X-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): Charlette M. Grigorian, Timothy J. Rupert〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Building on the recent discovery of tough nanocrystalline Cu-Zr alloys with amorphous intergranular films, this paper investigates ternary nanocrystalline Cu-Zr-Hf alloys with a focus on understanding how alloy composition affects the formation of disordered complexions. Binary Cu-Zr and Cu–Hf alloys with similar initial grain sizes were also fabricated for comparison. The thermal stability of the nanocrystalline alloys was evaluated by annealing at 950 °C (〉95% of the solidus temperatures), followed by detailed characterization of the grain boundary structure. All of the ternary alloys exhibited exceptional thermal stability comparable to that of the binary Cu-Zr alloy, and remained nanocrystalline even after two weeks of annealing at this extremely high temperature. Despite carbide formation and growth in these alloys during milling and annealing, the thermal stability of the ternary alloys is mainly attributed to the formation of thick amorphous intergranular films at high temperatures. Our results show that ternary alloy compositions have thicker boundary films compared to the binary alloys with similar global dopant concentrations. While it is not required for amorphous complexion formation, this work shows that having at least three elements present at the interface can lead to thicker grain boundary films, which is expected to maximize the previously reported toughening effect.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305439-fx1.jpg" width="400" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Jo Sharp, Itzel Castillo Müller, Paranjayee Mandal, Ali Abbas, Magnus Nord, Alastair Doye, Arutiun Ehiasarian, Papken Hovsepian, Ian MacLaren, W. Mark Rainforth〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Thin films of C/Mo/W deposited using combined UBM/HIPIMS sputtering show 2–8 nm clusters of material richer in Mo and W than the matrix (found by EDS microanalysis), with structures that resemble graphitic onions with the metal atoms arranged regularly within them. EELS microanalysis showed the clusters to be rich in W and Mo.〈/p〉 〈p〉As the time averaged power used in the pulsed HIPIMS magnetron was increased, the clusters became more defined, larger, and arranged into layers with amorphous matrix between them. Films deposited with average HIPIMS powers of 4 kW and 6 kW also showed a periodic modulation of the cluster density within the finer layers giving secondary, wider stripes in TEM. By analysing the ratio between the finer and coarser layers, it was found that this meta-layering is related to the substrate rotation in the deposition chamber but in a non-straightforward way. Reasons for this are proposed. The detailed structure of the clusters remains unknown and is the subject of further work.〈/p〉 〈p〉Fluctuation electron microscopy results indicated the presence of crystal planes with the graphite interlayer spacing, crystal planes in hexagonal WC perpendicular to the basal plane, and some plane spacings found in Mo〈sub〉2〈/sub〉C. Other peaks in the FEM results suggested symmetry-related starting points for future determination of the structure of the clusters.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): H. Raghuram, C. Katsich, K. Pichelbauer, K. Koschatzky, C. Gachot, U. Cihak-Bayr〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Friction and wear can cause severe surface damage of machine elements and result in their complete failure. Of the several ways to limit/control friction and wear, a measure to counter the potential damage is to apply a layer of a material with more desirable surface properties, which also provides the flexibility to use cost-efficient bulk materials. In systems under dry sliding conditions, such as railway switches, replacing the components cost considerable time and money. In the current study, laser cladding, a well-known powerful process for repair engineering, was used to fabricate new innovative low friction materials for dry sliding contacts that are exposed to corrosive attacks. The successful implementation of graphite as a solid lubricant in dry sliding conditions is well-known. A homogenous coating with an austenitic FeNi-based alloy containing different percentages of graphite was applied by means of laser cladding using preplaced powder method. The effect of graphite content and its lateral distribution on the friction and wear properties is investigated using a modified ASTM 〈a href="http://www.astm.org/Standards/G65" target="_blank"〉G65〈/a〉 test rig in two-body sliding configuration. Tribological results showed that increasing graphite content in the clads significantly reduces wear, but the level of the coefficient of friction appears to be determined mainly by the composition of the matrix. The wear resistance can be further increased by maximising the inter-particle distances. On the whole, clads of all compositions had superior wear resistance compared to reference materials such as stainless steel XNi22 and cast iron GJL250. The clads were further classified in terms of corrosion resistance against synthetic sea water in a modified potentiodynamic setup. The resistance to wear and corrosion improve with graphite content.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0257897219308692-ga1.jpg" width="355" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Yu-Siang Fang, Kun-An Chiu, Hien Do, Li Chang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Highly oriented cubic (100) HfN films were grown on Si (100) substrates by direct current magnetron reactive sputtering of a metallic Hf target in an Ar/N〈sub〉2〈/sub〉 gas environment. The influence of N〈sub〉2〈/sub〉 flow ratio on the (100) preferred orientation and crystallinity of the HfN films is investigated. X-ray diffraction shows that not only HfN but also orthorhombic HfSi〈sub〉2〈/sub〉 forms in the sputtered films. Increasing the N〈sub〉2〈/sub〉 flow ratio is unfavorable for the formation of HfSi〈sub〉2〈/sub〉 while the deposition rate of HfN is decreased. X-ray diffraction and cross-sectional scanning transmission electron microscopy (STEM) reveal that epitaxial orthorhombic HfSi〈sub〉2〈/sub〉 can form on the Si substrate, and (100) HfN is in epitaxy with the epitaxial HfSi〈sub〉2〈/sub〉. As a result, a (100) oriented HfN film can grow on Si. The epitaxial relationships are shown to be HfN (100)[01〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈/math〉] // HfSi〈sub〉2〈/sub〉 (020)[001] // Si (100)[01〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈/math〉] and HfN (100)[01〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈/math〉] // HfSi〈sub〉2〈/sub〉 (020)[100] // Si (100)[01〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈/math〉]. Atomically resolved STEM images also show the bonding characteristics across the HfN/HfSi〈sub〉2〈/sub〉 and HfSi〈sub〉2〈/sub〉/Si interfaces.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): İlyas Türkmen, Emre Yalamaç, Mourad Keddam〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a substitute boriding powder including boric acid as boron source was prepared and employed for boronizing of SAE 1020 steel. The boronizing processes were performed at 850, 900 and 950 °C for 4, 8 and 12 h. The formed boride layers were identified by varied experimental methods such as optical microscope, SEM and WDS analysis. As an outcome of the analyses, the boride layer containing only Fe〈sub〉2〈/sub〉B phase with saw-tooth morphology was specified on surface of the samples. A diffusion model was proposed to estimate the coefficients of boron diffusion in the Fe〈sub〉2〈/sub〉B layers. The value of boron activation energy for SAE 1020 steel was calculated as 183.14 kJ/mol and the result was contrasted with literature data. As a result of the microhardness measurements, the average hardness value of Fe〈sub〉2〈/sub〉B layer was about between 1200 and 2000 HV〈sub〉0.1〈/sub〉. The average hardness values of the transition zone and matrix zone were determined to be approximately 160 HV〈sub〉0.1〈/sub〉 and 151 HV〈sub〉0.1〈/sub〉, respectively. This study mainly concentrates on the tribological properties of borided SAE 1020 steel with using alternative boriding powder. Coefficient of friction graph was drawn for each sample and the wear rates were calculated. It was specified that specific wear rate of borided samples was roughly 47 times lower than that of unborided samples.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): O.Yu. Goncharov, I.V. Sapegina, R.R. Faizullin, L.Kh. Baldaev〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The composition of coating layers deposited on the surface of 12Kh18N10T stainless steel (similar to 321 AISI) in the TaBr〈sub〉5〈/sub〉-Cd-He system at temperatures ranging from 623 К to 1423 К and at a pressure of 1 atm was evaluated using thermodynamic analysis. Tantalum-based coatings were deposited on 12Kh18N10T and tungsten substrates by chemical vapour deposition (CVD) using reduction of tantalum bromide vapour by cadmium vapour at а temperature of 1023 К. The formation of β-Ta, diffuse layers of Ta-Fe as well as Fe〈sub〉2〈/sub〉Ta-based Laves phase in the deposited coating layers has been analysed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): A. Kilicaslan, O. Zabeida, E. Bousser, T. Schmitt, J.E. Klemberg-Sapieha, L. Martinu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present work, we reviewed and studied the fabrication process of hard erosion resistant TiN protective coatings on the inner surfaces of narrow tubes using a Non-Line-Of-Sight (NLOS) approach. Initially, while evaluating the growth of DLC and TiN by the CW RF PECVD process, we found that the use of a hydrocarbon precursor to obtain DLC provides uniform film thickness along the tube axis, while the use of the TiCl〈sub〉4〈/sub〉 precursor for TiN leads to a significant thickness nonuniformity of 80% and large differences between the film properties in the middle of the tube compared to the edges. Following detailed plasma analysis, we demonstrate that the uniformity can be substantially enhanced by applying pulsed-DC PECVD, while uniform (better than 20%) hard TiN films were prepared by low-frequency (5 kHz) pulsed-DC PECVD. The TiN films (about 12 μm thick), systematically studied by SEM, XRD, and nanoindentation, when prepared under optimized conditions, exhibit high hardness and reduced Young's modulus (25 and 225 GPa, respectively) corresponding to the (111) preferred crystallographic orientation, and a very low Cl contamination (〈3%). The film uniformity has been correlated to that of the discharge light emission intensity along the tube axis, and the microstructural evolution is interpreted in terms of surface densification due to substrate temperature and ion bombardment of the inner surface. The pulsed DC PECVD NLOS process providing TiN coatings with a hardness markedly higher than the hardness of the erodent particles and with a solid particle erosion resistance increased by a factor of 〉15 compared to the bare substrate is well suited for the protection of aerospace, manufacturing, and other critical components with a complex shape of inner surfaces.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): J. Drieu La Rochelle, P. Godard, C. Mocuta, D. Thiaudière, J. Nicolai, M.F. Beaufort, M. Drouet, P.O. Renault〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, in situ measurements of synchrotron x-ray pole figure have been performed during incremental uniaxial deformation test on a single-crystal gold foil. The 50 nm thick Au thin film was elaborated by ion sputtering at 400 °C on NaCl single crystal as a template. The resulting film consists of a single-crystal gold foil containing a small density of thin and small {111} growth twins (few nm thick and few tens of nm long) revealed by x-ray pole figure measurement. The as-deposited gold single crystal was then transferred onto flexible polyimide substrates for deformation test. This work focuses on the relative evolution of the diffracting volume related to growth twins during a loading-unloading tensile test. Macroscopic applied deformations and x-ray pole figures were measured in situ during a uniaxial tensile test in the Au [110] direction. X-ray pole figures clearly evidenced the relative evolution of the diffracting volumes related to the (111) and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mfenced open="(" close=")"〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈mn〉1〈/mn〉〈/mrow〉〈/mfenced〉〈/math〉 twins which exhibit a huge increase of about 450% at a uniaxial applied true strain of about 4%. The concomitant variation of diffracting volumes related to the two other twin variants (namely 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mfenced open="(" close=")"〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈mn〉11〈/mn〉〈/mrow〉〈/mfenced〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.svg"〉〈mfenced open="(" close=")"〉〈mrow〉〈mn〉1〈/mn〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈mn〉1〈/mn〉〈/mrow〉〈/mfenced〉〈/math〉 twins) shows a relatively low decrease of 25%. The results open out onto a true strain-twinning volume hysteresis curve, indicative of the deformation mechanisms of gold thin films that can be interpreted as a twinning-detwinning mechanism.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Yanmeng Cheng, Pengfei Liu, Peng Xiao, Zhuan Li, Tianhui Jiang, Yanqi Huang, Yang Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Carbon fibers reinforced epoxy (CF/epoxy) composites have been used in orthopedic and dental implants. However, the inert surface of CF/epoxy composites cannot show ability of forming direct bone bonding with autologous bone during implantation. In order to improve the bioactivity of CF/epoxy composites, the different chemical modifications (concentrated sulfuric acid (97 wt%), CaCl〈sub〉2〈/sub〉 solution, concentrated sulfuric acid (97 wt%) + CaCl〈sub〉2〈/sub〉 solution) were used to modify its original surface. The bioactivity of modified CF/epoxy composites was evaluated by in vitro apatite formation ability in simulated body fluids (SBF). The result showed that -SO〈sub〉3〈/sub〉H and Ca〈sup〉2+〈/sup〉 were introduced on the of sample surface after chemical modification. Samples modified with concentrated sulfuric acid (97 wt%) and CaCl〈sub〉2〈/sub〉 solution showed the best bioactivity. In addition, a uniform and dense apatite coating was formed on the surface of functionalized CF/epoxy composites after soaking in SBF and the presence of -SO〈sub〉3〈/sub〉H would significantly improve the bond between the coating and the substrate. The transformation process of apatite morphology during its formation and the mechanism of apatite formation on the functionalized CF/epoxy composites were also analyzed systematically.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): N. López Perrusquia, M.A. Doñu Ruiz, C.R. Torres San Miguel, G.J. Pérez Mendoza, J.V. Cortes Suarez, A. Juanico Loran〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In this study present the benefit of boride coating on surface of ASTM A-36 steel and the evaluation of the properties of the hard coatings under hydrogen permeation. The ASTM A-36 steel was surface hardened by diffusion boron atoms at temperature at 950 °C for 3, 5, and 7 h using the dehydrated boron paste-pack method. The hard coatings obtained on surface A-36 steel were examined using scanning electron microscopy combined with energy dispersive spectrometry and X-ray diffraction. In addition, the hydrogen was introduce into samples with hard coating through cathodic charging applying a current density of 50 mA/cm〈sup〉2〈/sup〉 by 0.5 M sulfuric acid solution kept at a room temperature. Three-point bending and instrument nanoindentation were evaluated on sample borided before and after hydrogen charged.〈/p〉 〈p〉Microstructural characterization revealed bilayer (FeB + Fe〈sub〉2〈/sub〉B) coatings with saw-tooth morphology and the thicknes values of FeB and Fe〈sub〉2〈/sub〉B were in range of 25.30 to 45.3 μm and 77.09 to 187.10 μm, respectively. After hydrogen charged, the microstructure delayed the diffusion of hydrogen, reducing the formation of cracks by increasing the FeB and Fe〈sub〉2〈/sub〉B coatings. However. the hardness of the samples tends to increase while the elastic modulus decrease. As well as the static load by bending test decrease due to steel ASTM A-36‑hydrogen interaction.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Sayantan Ray, Suman Saha, Sk. Hasanur Rahaman, Arnab Bhattacharjee, Nina Daneu, Zoran Samardžija, Jui Chakraborty〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present communication reports the variation in surface characteristics of bilayered coating of phosphate free bioactive glass (PFBG) on SS316L substrate at simulated conditions, w.r.t both pH and temperature, to understand the suitability of the same for load bearing applications. The coated substrates were subjected to both physiological (7.4) and pathophysiological (4.5) pH conditions, considering two working temperatures of 37 °C and 45 °C, related to the real time scenario, in the post implantation period. Herewith, a faster dissolution of the PFBG network could be obtained at higher temperature (45 °C) and acidic pH (4.5) conditions, leading to a degraded surface texture, while the same at 37 °C and pH 7.4, exhibited an almost intact surface. The observation was corroborated using atomic force microscopy which exhibited an exponential increase in the nanoscale surface roughness of the coating at lower pH and at higher temperature conditions. The ionic Ca〈sup〉2+〈/sup〉 dissolution kinetics of the PFBG coating followed by their cellular interaction were assessed using MC3T3 cell line, which showed a distinct difference compared to the as prepared PFBG coated substrate. Further, we made an attempt to assess the role of the calcium binding protein, calmodulin and its major target, calcium-calmodulin kinase II alpha (CAMKIIα) in osteoblast (MC3T3) differentiation, cultured on the PFBG coated SS316L substrates, subject to the experimental parameters as abovementioned. The results indicated significance of the real time conditions at the site of application of a bioactive glass coating on load bearing SS316L based implant material.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Henning Moldenhauer, Alexandra Wittig, David Kokalj, Dominic Stangier, Andreas Brümmer, Wolfgang Tillmann, Jörg Debus〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Raman spectroscopy is used to investigate the structural and tribological properties of HiPIMS sputtered MoS〈sub〉〈em〉x〈/em〉〈/sub〉 thin films which were post-growth-annealed at different temperatures. The Raman scattering combined with X-ray diffraction determines a reduction in the residual strain within the MoS〈sub〉〈em〉x〈/em〉〈/sub〉 layers with increasing annealing temperature. In the high-temperature annealed coatings a Raman signature at 40 cm〈sup〉−1〈/sup〉 emerges, which results from a strengthening of the inter-layer van-der-Waals interaction. This observation indicates that the thermally annealed MoS〈sub〉〈em〉x〈/em〉〈/sub〉 thin films become more resistant against shear forces, which is manifested in an increase of the coefficient of friction measured with a ball-on-disc tribometer. The coefficient of friction moreover decreases with lowering the sulfur/molybdenum ratio which, in turn, depends on the substrate and annealing temperatures. Furthermore, a Raman forbidden mode may be exploited to detect stacking faults within the sputtered coatings. Its observation is realized through resonant excitation of an MoS〈sub〉2〈/sub〉 exciton at about 633 nm.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Lu Tian, Weiping Li, Hui Ye, Liqun Zhu, Haining Chen, Huicong Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Superhydrophilic and underwater superoleophobic materials for oil/water separation have recently attracted much attention due to the urgent needs of water protection. However, the environmental problems, complex preparation process and poor stabilities seriously restricted the practical applications. Herein, a waterborne organic–inorganic composite coating was prepared by mechanical mixing a silicone acrylic emulsion with nano-silica particles. The silica particles could be introduced to polymeric latexes to generate the cross-linked structure due to the polycondensation between hydroxyl groups. A simple spray technique was applied to deposit the as-prepared composite coating on a stainless steel mesh which exhibited a favourable superhydrophilicity (nearly 0°) and underwater superoleophobicity (above 155°) towards various oil droplets. The coated mesh presented a high separation efficiency of above 99% towards a series of light oil–water mixtures and it also showed a good recyclability after 30 separation cycles. Furthermore, the coated mesh kept excellent underwater superoleophobicity under a series of pH solutions and immersion tests in water and 3.5 wt% NaCl solution. Therefore, the as-prepared mesh is highlighted in its simple and environmental fabrication, high separation efficiency, good recyclability, excellent chemical stability and water resistance, exhibiting a bright prospect for scalable production.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0257897219308643-ga1.jpg" width="500" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Faiz Muhaffel, Mertcan Kaba, Grzegorz Cempura, Bora Derin, Adam Kruk, Erdem Atar, Huseyin Cimenoglu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present work, the influence of alumina (Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉) and zirconia (ZrO〈sub〉2〈/sub〉) incorporation on the structural properties and wear resistance of titania (TiO〈sub〉2〈/sub〉) based micro-arc oxidation (MAO) coatings fabricated on Ti6Al4V alloy was studied. For this purpose MAO was employed in a silicate-based electrolyte with and without additions of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and ZrO〈sub〉2〈/sub〉 particles. The structural properties were determined via X-ray diffraction (XRD) and X-ray photoelectron (XPS) spectroscopy analysis and an energy dispersive spectrometer (EDS) equipped scanning electron microscope (SEM). Furthermore, thermochemical simulations were made by using FactSage 7.3. Mechanical properties of the MAO coatings were determined by hardness measurements and dry sliding reciprocating wear tests. Structural examinations revealed that the MAO coatings fabricated in Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and ZrO〈sub〉2〈/sub〉 added electrolytes comprised of these oxides and their complex forms (Al〈sub〉2〈/sub〉TiO〈sub〉5〈/sub〉 and ZrTiO〈sub〉4〈/sub〉, respectively) along with TiO〈sub〉2〈/sub〉 and amorphous silica (SiO〈sub〉2〈/sub〉). Although incorporations of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and ZrO〈sub〉2〈/sub〉 did not remarkably improve the hardness of the MAO coatings, the highest wear resistance was obtained from the one formed in the ZrO〈sub〉2〈/sub〉 added electrolyte. On the other hand, the MAO coating fabricated in the Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 added electrolyte exhibited lower wear resistance than that of fabricated in the particle-free silicate-based electrolyte.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Balachander Gnanasekaran, Gui-Rong Liu, Yao Fu, Guangyu Wang, Weilong Niu, Tao Lin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cold spray process has been of great interest in coating and additive manufacturing because it does not need heat supply during impact. Cold spray generally uses particles of diameters 10 μm to 50 μm traveling at velocities of 300 m/s to 1200 m/s, and it takes place at very small time and length scales. Thus, it becomes difficult to observe the detailed process experimentally. The primary objective of this study is to use SPH and highlight its capability for modeling cold-spray process. A novel way of establishing boundary conditions using Monaghan type 2 particles is adopted in this study. Additionally,our SPH model includes failure modeling for copper particle impacts. Particles of different sizes and at different angles are studied to reveal the effects of impact which includes recording effective plastic strain, deformation and temperature. It was found that larger particles had greater ability to adhere to the surface of the substrate and an impact angle between 80° and 90° has higher chances of adherence to the substrate. An increase in maximum effective plastic strain is seen which causes thermal softening leading to plastic flow of material. This fluid-like flow causes adherence of the particle on the substrate. Finally, the in-house SPH procedure is extended to simulate three-dimensional cold spray problems with multiple particles.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Junrong Tang, Zhipo Zhao, Ning Li, Xiang Qiu, Yanfang Shen, Xinyu Cui, Hao Du, Jiqiang Wang, Tianying Xiong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, three types of Ta feedstock powders [i.e., hydrogenation de-hydrogenation (HDH)-1, HDH-2 and mechanical pulverization (MP)] were deposited on Ti6Al4V substrate by cold spray and the influence of feedstock powder on microstructure and mechanical properties of the deposited coating was firstly studied. All depositions showed no significant oxidation, but grain refinement. Cold sprayed coatings revealed two distinct microstructures, a large number of ultrafine grains at highly deformed splat boundaries and original grains in the middle of the particles. Powder morphology influenced deposition quality more than propellant gas temperature. Results showed that the deposition prepared by porous HDH-1-Ta powders performed the best quality with the relatively flat section, the lowest porosity (0.93–1.77%), the highest deposition efficiency, the highest microhardness (345–441 HV〈sub〉0.1〈/sub〉) and the decent adhesion bonding strength (39–41 MPa). This was mainly because HDH-1-Ta powders possess porous morphology and exhibit excellent compressibility and compaction behavior during deposition. Thus, porous HDH-1 powders may hold promise as a cost effective alternative for Ta cold spray depositions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia〈/p〉 〈p〉Author(s): Hangfeng Zhang, Bin Yang, Haixue Yan, Isaac Abrahams〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Switchable ferroelectric/antiferroelectric ceramics are of significant interest for high power energy storage applications. Grain size control of this switching is an interesting approach to controlling polarization and hence dielectric properties. However, the use of this approach in technologically relevant ceramics is hindered by difficulty in fabricating dense ceramics with small grain sizes. Here an intermediate polar ferroelectric phase (〈em〉P〈/em〉2〈sub〉1〈/sub〉〈em〉ma〈/em〉) has been isolated in dense bulk sodium niobate ceramics by grain size control through spark plasma sintering methods. Our findings, supported by XRD, DSC, P-E (I-E) loops and dielectric characterization, provide evidence that the phase transition from the antiferroelectric (AFE) R-phase, in space group 〈em〉Pnmm〈/em〉, above 300 °C, to the AFE P-phase, in space group 〈em〉Pbma〈/em〉, at room temperature, always involves the polar intermediate 〈em〉P〈/em〉2〈sub〉1〈/sub〉〈em〉ma〈/em〉 phase and that the 〈em〉P〈/em〉2〈sub〉1〈/sub〉〈em〉ma → Pbma〈/em〉 transition can be suppressed by reducing grain size.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305506-fx1.jpg" width="296" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): M.J. Konstantinović, I. Uytdenhouwen, G. Bonny, N. Castin, L. Malerba, P. Efsing〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The thermal stability and the structure of solute-vacancy clusters formed by neutron irradiation are studied by means of positron annihilation spectroscopy and hardness measurements of post-irradiation annealed reactor pressure vessel steels with high and low Ni contents. Two distinct recovery stages were observed and assigned to (a) the dissolution of vacancy clusters at about 650 K, and (b) the dissolution of solute-vacancy clusters at about 750 K. In steels with high Ni content, hardening mainly recovers during the second stage. Atomistic and coarse grain models suggest that during this stage, the removal of vacancies from vacancy-solute clusters leads to complete cluster dissolution, which indicates that solute clusters are radiation induced.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305403-fx1.jpg" width="280" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Li Zhang, Yi Chen, Mo-xian Chen, Long Huang, Hou-ping Wu, Tao Liu, Xiang-jun Xiong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To achieve a better understanding of the interaction between the film and the ductile Co-based binder phase in cemented carbide substrate and the associated interface microstructure evolution, a model alloy of 85.1Co–9.2W–4.7Cr〈sub〉3〈/sub〉C〈sub〉2〈/sub〉–1.0VC was prepared. Ti〈sub〉0.94〈/sub〉Si〈sub〉0.06〈/sub〉N/TiAlSiN/Al〈sub〉0.52〈/sub〉Ti〈sub〉0.48〈/sub〉N coating was deposited on the Co-based alloy by a DC magnetron sputtering technique. High-resolution transmission electron microscopy observation and high-resolution energy dispersion spectrum analysis reveal a complex film-substrate structure. An interface-centered bilateral transition layer, i.e., nanocrystalline AlTiN and hcp-Co, and double sub-transition layers, i.e., bcc-W and disordered arrangement of Co atoms are identified. The formation mechanisms for the sub-transition and transition layer are discussed. Based on the AlTiN transition layer phenomenon, the reason for the substantial texture coefficient 〈em〉TC〈/em〉〈sub〉(111)〈/sub〉 difference between fcc-AlTiN and fcc-TiSiN (5.9/3.6 vs. 2.9) is discussed. Considering the significance of the observed semi-coherent relationship for the bcc-W/AlTiN interface and the positive adaptability of cobalt, suggestions are proposed for the composition design of cemented carbide substrate and the film deposition rate controlling.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0257897219308771-ga1.jpg" width="301" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): Hui Chen, Qingsong Wei, Yingjie Zhang, Fan Chen, Yusheng Shi, Wentao Yan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The packing density of the powder layer plays a key role in the final quality of the parts fabricated via powder-bed-based (PBB) additive manufacturing. This paper presents a combined experimental and computational modeling study on the scraping type of powder-spreading process, in order to understand the fundamental mechanisms of the packing of the powder layer. The deposition mechanisms at the particulate scale, including particle contact stress and particle velocity, are investigated, using the discrete element method, while the macro-scale packing density is validated by experiments. It is found that there is a stress-dip at the bottom of powder pile scraped by the rake. This stress-dip makes the powder particles uniformly deposited. Three kinds of deposition mechanisms dominating the powder-spreading process are identified: cohesion effect, wall effect, and percolation effect. The cohesion effect, which leads to particle agglomerations and thus reduces the packing density, becomes stronger with the decrease of particle size. The wall effect, which leads to more vacancies in the powder layer, becomes stronger with the decrease of layer thickness or the increase of particle size. The percolation effect exists in bimodal powder particles, which leads to particle segregation within the powder layer and thus reduces the packing density. The three kinds of deposition mechanisms compete with each other during the powder-spreading process and make combined effects on the packing density of the powder layer.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305427-fx1.jpg" width="264" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): Qi-Nan Han, Shao-Shi Rui, Wenhui Qiu, Xianfeng Ma, Yue Su, Haitao Cui, Hongjian Zhang, Huiji Shi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effect of crystal orientation on fretting fatigue induced crack initiation and dislocation distribution is studied by in-situ SEM observation and electron back-scattered diffraction (EBSD) in this paper. Cracks and slip lines are observed in the fretting contact area of Ni-based single-crystal (NBSX) superalloys. The in-situ SEM observation captures different crack and slip line behaviors under different crystal orientations. The EBSD analysis results show obvious misorientation and orientation deviation in the fretting contact area. For both crystal orientations, the geometrically necessary dislocation (GND) density distributions in the contact area are obtained by using Hough-based EBSD methods. The peak position of grain reference orientation deviation (GROD) and GND density matches with the fretting fatigue crack formation position. EBSD analysis shows that the dislocation density distribution on each slip system is closely related to the crack initiation direction. The direction of slip system with the maximum dislocation density agrees with the crack initiation direction obtained by in-situ observation.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305476-fx1.jpg" width="448" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): Jinghao Xu, Hans Gruber, Dunyong Deng, Ru Lin Peng, Johan J. Moverare〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Additive manufacturing (AM) of high γ′ strengthened Nickel-base superalloys, such as IN738LC, is of high interest for applications in hot section components for gas turbines. The creep property acts as the critical indicator of component performance under load at elevated temperature. However, it has been widely suggested that the suitable service condition of AM processed IN738LC is not yet fully clear. In order to evaluate the short-term creep behavior, slow strain rate tensile (SSRT) tests were performed. IN738LC bars were built by laser powder-bed-fusion (L-PBF) and then subjected to hot isostatic pressing (HIP) followed by the standard two-step heat treatment. The samples were subjected to SSRT testing at 850 °C under strain rates of 1 × 10〈sup〉−5〈/sup〉/s, 1 × 10〈sup〉−6〈/sup〉/s, and 1 × 10〈sup〉−7〈/sup〉/s. In this research, the underlying creep deformation mechanism of AM processed IN738LC is investigated using the serial sectioning technique, electron backscatter diffraction (EBSD), transmission electron microscopy (TEM). On the creep mechanism of AM polycrystalline IN738LC, grain boundary sliding is predominant. However, due to the interlock feature of grain boundaries in AM processed IN738LC, the grain structure retains its integrity after deformation. The dislocation motion acts as the major accommodation process of grain boundary sliding. Dislocations bypass the γ′ precipitates by Orowan looping and wavy slip. The rearrangement of screw dislocations is responsible for the formation of subgrains within the grain interior. This research elucidates the short-creep behavior of AM processed IN738LC. It also shed new light on the creep deformation mechanism of additive manufactured γ′ strengthened polycrystalline Nickel-base superalloys.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305464-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): Garth C. Egan, Tae Wook Heo, Amit Samanta, Geoffrey H. Campbell〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report a novel mechanism for explosive crystallization in amorphous germanium (a-Ge), which operates through liquid-mediated nucleation occurring under extreme thermal gradient conditions. The crystallization kinetics of sputter-deposited films with thicknesses ranging from 30 to 150 nm were characterized using 〈em〉in situ〈/em〉 movie-mode dynamic transmission electron microscopy (MM-DTEM). After localized heating from a short laser pulse, explosive liquid phase nucleation (LPN) was observed to occur during the early stage (〈2 μs) of crystallization in the thicker (〉50 nm) films deposited on silicon nitride substrates. The crystallization front propagated at ∼12–15 m/s and produced nanocrystalline microstructure with ∼50 nm grains. A mechanism involving the existence of a relatively thick (〉100 nm) transient liquid layer and a high nucleation rate is proposed to explain the behavior. The key thermodynamic and kinetic features as well as the feasibility of the mechanism are further explored by employing parametric and systematic phase-field modeling and simulations.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305385-fx1.jpg" width="418" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Bo Huang, Chao Zhang, Ga Zhang, Hanlin Liao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermal sprayed Fe-based amorphous coatings exhibit excellent wear and corrosion resistance, and thus have been widely utilized for enhancing the performance of material surfaces. In this paper, important research progresses achieved in regards to deposition technologies and properties of thermal sprayed Fe-based amorphous coatings are reviewed. In particular, the dependence of wear and corrosion resistance of the coatings on processing parameters, e.g., kinetic energy, particle size, gas flow rate, and heat treatment temperature are summarized. Moreover, the utilization of reinforced phases and alloy elements for enhancing the wear and corrosion resistance of the coatings are presented. It is expected that future endeavors will be dedicated to the formation mechanism of amorphous phase and “processing parameter-microstructure-macroscopic property” relationship of Fe-based amorphous coatings.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Tomoya Higuchi, Masao Noma, Michiru Yamashita, Keiichiro Urabe, Shigehiko Hasegawa, Koji Eriguchi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The surface modification of a boron nitride (BN) film by plasma exposure was investigated by means of nanoindentation analyses and molecular dynamics simulations. A μm-thick BN film composed of nanoscale 〈em〉sp〈/em〉〈sup〉3〈/sup〉-bonded phases in the turbostratic (〈em〉sp〈/em〉〈sup〉2〈/sup〉-bonded) BN domain was prepared on a Si substrate using a reactive plasma-assisted coating system. Then, the BN films were exposed to an inductively coupled Ar plasma under various bias power conditions. The change of the morphology and mechanical properties in the surface region due to the plasma exposure was evaluated with respect to the dependence on the energy of incident Ar ions (〈em〉E〈/em〉〈sub〉ion〈/sub〉). A nanoindentation test under various contact depths identified the formation of a surface plasma-damaged layer (a few nm thick) where the nanoindentation hardness (〈em〉H〈/em〉〈sub〉IT〈/sub〉) was changed in response to the Ar ion irradiation. A molecular dynamics (MD) simulation predicted also the 〈em〉E〈/em〉〈sub〉ion〈/sub〉-dependence of the reconstruction of the 〈em〉sp〈/em〉〈sup〉3〈/sup〉〈em〉-〈/em〉bonded phases in a few nm-thick layer on the surface. The presence of a damaged-layer plays an important role in the mechanical properties of the BN/Si structures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Santigopal Samanta, Arup Kumar Halder, Yashwardhan Deo, Sounak Guha, Monojit Dutta〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effect of 〈em〉Mn〈/em〉 and 〈em〉Cr〈/em〉 on the surface selective oxidation, segregation and hot-dip galvanizing was studied in three 〈em〉Fe〈/em〉-〈em〉Mn〈/em〉 alloys with ∼0.2 wt% 〈em〉Al〈/em〉 and two 〈em〉Fe〈/em〉 − 〈em〉Mn〈/em〉 alloys with ∼0.5 wt% 〈em〉Cr〈/em〉 in an HDPS (Hot-dip Process Simulator) following industrial CGL (Continuous Galvanizing Line) conditions. The 〈em〉Mn〈/em〉 content was varied from 1.5 to 3.6 wt% in the alloys. The alloys were subjected to the same thermal cycle following continuous annealing (CA) at 800 °C in 〈em〉N〈/em〉〈sub〉2〈/sub〉 − 5〈em〉%H〈/em〉〈sub〉2〈/sub〉 gas atmosphere with −40 °C dew point and then hot-dipping in 〈em〉Zn〈/em〉 - 0.20 wt% 〈em〉Al〈/em〉 bath at 460 °C. The oxidation tendency of 〈em〉Mn〈/em〉, 〈em〉Al〈/em〉 and 〈em〉Cr〈/em〉 during annealing was calculated using FactSage software. GDOES (Glow Discharge Optical Emission Spectroscopy) measurements showed a higher extent and depth of segregation for 〈em〉Mn〈/em〉 with increasing bulk concentration during the CA. It was observed that 〈em〉Cr〈/em〉 segregates comparatively less near the annealed surface in the presence of more 〈em〉Mn〈/em〉. XPS (X-ray Photoelectron Spectroscopy) measurements revealed the formation of simple 〈em〉MnO〈/em〉 in 〈em〉Fe〈/em〉-〈em〉Mn〈/em〉-〈em〉Al〈/em〉 alloys and complex 〈em〉MnCr〈/em〉〈sub〉2〈/sub〉〈em〉O〈/em〉〈sub〉4〈/sub〉 in 〈em〉Fe〈/em〉-〈em〉Mn〈/em〉-〈em〉Cr〈/em〉 alloys. Contrary to the thermodynamic calculations, no 〈em〉Al〈/em〉-oxides were detected at the annealed surfaces of 〈em〉Fe〈/em〉-〈em〉Mn〈/em〉-〈em〉Al〈/em〉 alloys during the XPS study. The hot-dip 〈em〉Zn〈/em〉 coatability was determined by measuring the number density of uncoated spots using 3D CLSM (Confocal Laser Scanning Microscopy) and by visual inspection. The 〈em〉Fe〈/em〉-〈em〉Mn〈/em〉-〈em〉Cr〈/em〉 alloys displayed a better hot-dip 〈em〉Zn〈/em〉-coating compared to 〈em〉Fe〈/em〉-〈em〉Mn〈/em〉-〈em〉Al〈/em〉 alloys. The conclusions of the present study are also critically discussed considering the literature findings.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): A. Manochehrian, A. Heidarpour, Y. Mazaheri, S. Ghasemi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study described surface reinforcing of A356 aluminum alloy with 2.5, 5, and 7.5 vol% nanolayered Ti〈sub〉3〈/sub〉AlC〈sub〉2〈/sub〉 MAX phase particles. The friction stir processing (FSP) was used to fabricate these surface composites. The surface composites were characterized by different routes such as optical and electron microscopy, microhardness, tensile, and wear tests. The OM and SEM micrographs showed that the application of FSP resulted in microstructural refinement and modification because of reducing porosity, diminishing coarse dendrites of primary aluminum, fragmenting of coarse silicon needle-shaped particles, uniform distributing of fine silicon particle in the substrate. This microstructural evolution led to increasing in microhardness and tensile values. The microhardness and tensile strength values of the as-received alloy and A356-7.5 vol% Ti〈sub〉3〈/sub〉AlC〈sub〉2〈/sub〉 surface composite were about 68 HV and 112 MPa, and 87 HV and 184 MPa, respectively. Surface nanocomposites showed significantly lower friction coefficient values and lower wear rates than the substrate. Scanning electron microscopy micrographs revealed that the abrasive wear with different extent and characteristics was the dominant wear mechanism.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): A. Lanzutti, A. Raffaelli, M. Magnan, L. Fedrizzi, M. Regis, E. Marin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Ti alloys suffer from intensive wear. To improve these properties, a surface treatment is required (coatings, surface thermal treatment, etc.). One of the major concerns regarding these treatments is that the treatment temperature needs to be controlled in order to avoid microstructural modifications.〈/p〉 〈p〉In this work, an attempt to modify a thin alloy surface layer alone has been performed by means of induction nitriding. By saturating the heating chamber with N, it is possible to produce controlled thickness nitride layers. Current (650–750 A) and cycle number (2–4 with a duration of 8 s each) were varied, and the top view and cross sections of the produced samples were characterized by means of stylus profilometery, SEM (Scanning Electron Microscopy) and visible light microscopy. The produced samples were then studied by microhardness and tensile testing to determine their mechanical properties. Fretting tests were also performed in order to evaluate the wearing behaviour of the surface layers in a corrosive media.〈/p〉 〈p〉The results showed that Ti alloys can be induction nitrided. The process parameters have a strong influence on the formation of TiN and alpha case layers. These layers can affect the mechanical properties and fretting resistance of the samples.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0257897219308679-ga1.jpg" width="344" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): Le Van Lich, Minh-Tien Le, Tinh Quoc Bui, Thanh-Tung Nguyen, Takahiro Shimada, Takayuki Kitamura, Trong-Giang Nguyen, Van-Hai Dinh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A reversal of polarization vortexlike domains in ferroelectric nanostructures plays important roles for next generations of electronic nanodevices. However, a direct switching of the polarization vortexlike domains in ferroelectrics is a nontrivial task since the toroidal moment is conjugated to a curled electric field rather than a homogeneous one. This work is dedicated to developing an approach to directly switch the toroidal ordering under an irrotational (homogeneous) electric field with the use of compositionally graded ferroelectric (cgFE) nanodots. The variation in material compositions induces an additionally broken spatial inversion symmetry at a scale beyond unit-cell level, giving rise to a formation of asymmetric flux-closure domain (FCD) in a cgFE nanodot. More interestingly, such an asymmetric character facilitates to a switch of FCD by an irrotational electric field. In particular, the rotation of polarization can be directly switched from counter-clockwise to clockwise rotations and vice versa without a formation of intermediate domain structures during the switching process. This switching behavior is distinguished from that in homogeneous counterparts. We further demonstrate that the variation in material compositions tailors the distributions of electrostatic and total free energies in the cgFE nanodot that can control the annihilation/initiation process of FCD under irrotational electric field, providing fundamental reason for the direct switching of the toroidal moment. Another interesting issue is found that both the amplitude and frequency of applied electric field strongly affect the switching behavior of FCD in cgFE nanodot.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305373-fx1.jpg" width="459" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): M. Nazari, H. Eskandari, F. Khodabakhshi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, by the implementation of multi-pass friction stir processing (FSP) an advanced AA6061-Graphene-TiB〈sub〉2〈/sub〉 hybrid surface nanocomposite is produced in contrast to the AA6061-Graphene and AA6061-TiB〈sub〉2〈/sub〉 single composites. Effects of micro-sized TiB〈sub〉2〈/sub〉 (10-30 wt%) and nano-sized graphene (0.5-2 wt%) particles on the microstructure and mechanical property of aluminum alloy are investigated. Moderate chemical composition as ~20 wt% TiB〈sub〉2〈/sub〉 and 1 wt% graphene for the hybrid nanocomposite system yielded the best combinations of mechanical property overcome the wear-strength trade-off. Such optimum incorporation of hybrid inclusions mixture led a hardness increasing up to about two times higher, a yield strength improvement up to ~225 MPa (~300% increasing ratio), and an elongation loss down to ~9%. A considerable reduction in the coefficient of friction ~23% is revealed with the dominant contribution of sliding wear fractographic features on the worn-out fracture surface due to the presence of graphene in the nanocomposite structure acting as the lubricant agent.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): D. Fernández-Valdés, A. Meneses-Amador, G.A. Rodríguez-Castro, I. Arzate-Vázquez, I. Campos-Silva, J.L. Nava-Sánchez〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, an experimental-numerical evaluation of the standing contact fatigue testing of a nitrided AISI 316L steel was developed. The nitride layers were formed at the surface of an AISI 316L steel by a salt bath nitriding process at a temperature of 580 °C for 1, 3 and 5 h of exposure time, obtaining three different layer thicknesses. In order to know the mechanical response and the different mechanisms of damage associated with the standing contact fatigue test, Hertzian tests were performed on a MTS machine by cyclic loading of a sphere on a flat surface formed by the layer/substrate system. The standing contact fatigue test was developed through two main stages. First, the critical loads for each treatment condition were determined by monotonic tests, where the appearance of circular cracks was considered as the failure criterion. Subsequently, cyclic subcritical loads were applied at a frequency of 5 Hz. A numerical model based on the finite element method was developed to evaluate the stress field generated in the system by cyclic contact loads. The results indicate that the thinnest thickness of nitride layer exhibits better resistance to standing contact fatigue.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Anja Buchwalder, Rolf Zenker〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉With their specific layer features and properties, surface treatments such as thermochemical treatment (nitriding, boriding) and hard coating cover a broad field of application in the wear and corrosion protection of steels. Limitations exist, however, when applying these surface treatments to softer materials, such as cast irons and aluminum alloys in terms of both their treatability and load-bearing capacity.〈/p〉 〈p〉This contribution deals with investigations into duplex surface treatments, where a pre- and post-electron beam (EB) surface treatment (e.g., hardening, remelting, alloying etc.) was combined with one of the above-mentioned treatments. Among other characteristics, the thermal EB surface treatments were characterized by high heating and cooling rates that facilitated the generation of a variety of non-equilibrium microstructures, which exhibited increased hardness and had minimal thermal effects on the surrounding base material. Furthermore, the layer thicknesses were one or two orders of magnitude higher than those generated by thermochemical treatment or hard coating.〈/p〉 〈p〉Based on the comprehensive results and using cast irons and Al alloys as examples, the study demonstrates the extent to which duplex treatments can overcome the aforementioned limitations, and how the tribological and/or corrosive load behavior is affected. The property profiles achieved after duplex surface treatment were strongly dependent on the inherent microstructural and chemical processes. These complex processes were influenced by a range of factors, such as the thermal stability of the EB surface layer generated in the first process step, the respective temperature and time period of the secondary process, etc.〈/p〉 〈p〉Hardness measurements, scratch tests, unlubricated pin-on-disc wear tests using different normal loads and potentiodynamic corrosion tests were realized to facilitate characterization of the different load behaviors of the single- and duplex-treated layers.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): Dipak Kumar Khatua, Anupam Mishra, Naveen Kumar, Gobinda Das Adhikary, Uma Shankar, Bhaskar Majumdar, Rajeev Ranjan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Driven by environmental concerns and governmental directives, a sustained research effort in the last decade and half has led to the development of lead-free alternatives which can potentially replace the commercial lead-based piezoceramics in niche applications. Na〈sub〉0.5〈/sub〉Bi〈sub〉0.5〈/sub〉TiO〈sub〉3〈/sub〉 (NBT)-based lead-free piezoceramics have found acceptance as promising lead-free transducers in high power ultrasonic devices. An issue of concern however is the low depolarization temperature which limits the device's tolerance for temperature rise during operation. While several strategies have been reported to improve thermal depolarization in NBT-based piezoceramics, there is a lack of consensus regarding the most fundamental factor/mechanism which enhances the depolarization temperature. In this paper we unravel a coupled microstructural-structural mechanism which controls the thermal depolarization in NBT-based piezoceramics. First, we demonstrate the phenomenon of a considerable increase in the depolarization temperature, without significantly losing the piezoelectric property in unmodified NBT by increasing the grain size. We then establish a grain size controlled structural mechanism and demonstrate that the rise in depolarization temperature is primarily associated with the bigger grains allowing relatively large lattice distortion to develop in the poling stabilized long range ferroelectric phase. We reconfirmed the validity of this mechanism in the model morphotropic phase boundary (MPB) composition 0.94Na〈sub〉0.5〈/sub〉Bi〈sub〉0.5〈/sub〉TiO〈sub〉3〈/sub〉-0.06BaTiO〈sub〉3〈/sub〉. For the sake of generalization, we demonstrate that the same mechanism is operative in another lead-based relaxor-ferroelectric system 0.62PbTiO〈sub〉3〈/sub〉-0.38Bi(Ni〈sub〉0.5〈/sub〉Hf〈sub〉0.5〈/sub〉)O〈sub〉3〈/sub〉. Our study provides the fundamental structural basis for understanding thermal depolarization delay in relaxor ferroelectric based piezoceramics.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305348-fx1.jpg" width="240" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Miqi Wang, Zehua Zhou, Yu Yi, Zehua Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Residual strength method was first highlighted as a quantitative analysis method to evaluate thermal shock resistance (TSR) of coating. TSR of plasma sprayed Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-13 wt%TiO〈sub〉2〈/sub〉 coating on metal substrate was investigated by residual strength method and conventional cyclic quenching method, respectively. The results revealed that residual strength method was superior to cyclic quenching method because critical thermal-shock (TS) temperature of the coating was directly pointed out, which meant that it could be deemed as a novel method for quantitative evaluation for TSR of the coating. Critical TS temperature of the tested coating was 800 °C derived from the strength-temperature curve according to residual strength method. For cyclic quenching method, 850 °C was an un-safe temperature but 800 °C was an equivocal one in TSR evaluation of the coating. After 400 °C TS, fracture occurred at the interface between the ceramic layer and the adhesive layer, and the main mechanism was intergranular fracture. But fracture was both observed in the ceramic layer and the adhesive layer after 850 °C TS, and the mechanism transformed into quasi-cleavage of both transgranular and intergranular fracture.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Sisi Luo, Qun Wang, Renfeng Ye, Chidambaram Seshadri Ramachandran〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this investigation, the effect of electrolyte concentration parameters on the plasma electrolytic oxidation (PEO) coatings on Ti-6Al-4V alloy were investigated by an orthogonal experiment involving four factors with three levels by changing the concentration of Ca(CH〈sub〉3〈/sub〉COO)〈sub〉2〈/sub〉·H〈sub〉2〈/sub〉O, NaH〈sub〉2〈/sub〉PO〈sub〉4〈/sub〉·2H〈sub〉2〈/sub〉O, Ethylene-diamine-tetra-acetic acid (EDTA) and NaOH, respectively. The self-corrosion current density, Ca/P, bond strength, phase composition and microstructure of the coatings were studied in detail. The results indicate that the nine PEO coatings had unevenly distributed porous structures comprising different ratios of titanium, rutile, and anatase phase. The effect of electrolyte concentration parameters on the properties and performance of coatings are sequenced hierarchically as follows: EDTA 〉 NaOH 〉 Ca(CH〈sub〉3〈/sub〉COO)〈sub〉2〈/sub〉·H〈sub〉2〈/sub〉O 〉 NaH〈sub〉2〈/sub〉PO〈sub〉4〈/sub〉·2H〈sub〉2〈/sub〉O for corrosion resistance, NaOH 〉 EDTA 〉 Ca(CH〈sub〉3〈/sub〉COO)2·H〈sub〉2〈/sub〉O 〉 NaH〈sub〉2〈/sub〉PO〈sub〉4〈/sub〉·2H〈sub〉2〈/sub〉O for Ca/P, Ca(CH〈sub〉3〈/sub〉COO)〈sub〉2〈/sub〉·H〈sub〉2〈/sub〉O 〉 NaH〈sub〉2〈/sub〉PO〈sub〉4〈/sub〉·2H〈sub〉2〈/sub〉O 〉 NaOH 〉 EDTA for bond strength. The highest bond strength of the PEO coatings can reach as high as 60 MPa. The optimized electrolyte composition for the Ti-6Al-4V is: C〈sub〉Ca(g/L)〈/sub〉 = 11.44 g/L, C〈sub〉P(g/L)〈/sub〉 = 5.72 g/L, C〈sub〉EDTA(g/L)〈/sub〉 = 10 g/L, C〈sub〉NaOH(g/L)〈/sub〉 = 15 g/L and the corresponding PEO coating had adequate thickness (11.78 μm), satisfactory bond strength (33.69 MPa) and a fitting Ca/P ratio of 1.68.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Jing Liu, Yu Chen, Jian Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, Ni–Mo–Si alloy coatings with different compositions were prepared on the surface of AISI 1045 steel by laser cladding. The microstructure and phase composition of different alloy coatings were studied by SEM, EDS and XRD. The oxidation resistance of the alloy coating was investigated in the static air environment at 800 °C. The results showed that: All the γ-Ni〈sub〉ss〈/sub〉/Mo〈sub〉2〈/sub〉Ni〈sub〉3〈/sub〉Si alloy coatings exhibited similar oxidation behavior and the oxidation kinetics curves followed a comprehensive linear-parabolic law. The total mass gain of N60, N55 and N50 alloy coating were 3.28 mg/cm〈sup〉2〈/sup〉, 2.98 mg/cm〈sup〉2〈/sup〉, 2.69 mg/cm〈sup〉2〈/sup〉, respectively. The oxide layers covered on the alloys were uniform and dense, which were mainly composed of NiO, Fe〈sub〉2〈/sub〉SiO〈sub〉4〈/sub〉, SiO〈sub〉2〈/sub〉 and MoO〈sub〉3〈/sub〉. With the increasing Si content in the designed alloy, a continuous SiO〈sub〉2〈/sub〉 film formed inside the oxide layer, which could effectively hinder the diffusion of oxygen and Ni〈sup〉2+〈/sup〉 in the oxide layer. Among the designed alloy coatings, N50 coating exhibited the lowest oxidation rate and the best oxidation resistance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Yen-Yu Chen, Sheng-Bo Hung, Chaur-Jeng Wang, Wen-Chung Wei, Jyh-Wei Lee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High entropy alloys (HEA) show outstanding thermodynamic, mechanical or thermal properties as compared with pure metals or binary alloys. Among several kinds of HEAs, the refractory element containing HEAs exhibit relatively high thermal stability and better mechanical properties at elevated temperature. In this study, the V〈sub〉19.2〈/sub〉Nb〈sub〉19.4〈/sub〉Mo〈sub〉20.3〈/sub〉Ta〈sub〉19.5〈/sub〉W〈sub〉21.6〈/sub〉 high entropy alloy thin films were deposited on the AISI 304 stainless steel substrates by a magnetron sputtering process. The oxidation behavior and electrical conductivities of HEA thin films at different temperatures were evaluated. The body-centered cubic (BCC) structure of HEA thin film can be kept up to 500 °C oxidation, and it transferred to V-Nb-Mo-Ta-W based oxides and then turned to iron contained oxide phases when the oxidation temperature increased to 700 °C. The electrical resistivity of thin film increased with oxidation temperature. The electrochemical impedance spectroscope (EIS) analysis showed that the total apparent resistivity values of 304SS substrate coated with V〈sub〉19.2〈/sub〉Nb〈sub〉19.4〈/sub〉Mo〈sub〉20.3〈/sub〉Ta〈sub〉19.5〈/sub〉W〈sub〉21.6〈/sub〉 high entropy alloy thin film at 600, 700 and 800 °C were 5.80, 6.91, and 7.71 Ω·cm, respectively. The electrical resistance of the HEA coated sample was contributed by the oxide resistance and interface polarization. Through the electrical property analysis at high temperatures, the HEA thin film can provide a protection layer to the 304SS substrate and kept the sample's high temperature apparent resistivity to a relatively lower value.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Wolfgang Tillmann, Nelson Filipe Lopes Dias, Dominic Stangier, Wolfgang Maus-Friedrichs, René Gustus, Carl Arne Thomann, Henning Moldenhauer, Jörg Debus〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Ensuring a high adhesion of amorphous carbon films to steel substrates remains a challenging task, sustaining continuous research efforts to improve the adhesion strength. Besides the interlayer system and the substrate material, surface pretreatments have a significant impact on the adhesion behavior. Within this context, the influence of the High Power Impulse Magnetron Sputtering (HiPIMS) pretreatment on the adhesion of magnetron sputtered hydrogenfree (a-C) and hydrogenated (a-C:H) amorphous carbon films with a chromium carbide (CrC) interlayer on 16MnCr5 steel is investigated. The plasma treatment consisted of 30 min Ar ion etching as well as a sequential 5 min of HiPIMS-pretreatment with a Cr cathode. Subsequently this pretreatment was compared to a procedure without utilizing the HiPIMS technique. The impact of the HiPIMS-pretreatment on the structure of the film was systematically analyzed by taking the CrC interlayer as well as the entire film structure into consideration.〈/p〉 〈p〉The adhesion strength of the a-C and a-C:H films is significantly improved by the formation of a Cr HiPIMS-nanolayer in the substrate/film interface. In scratch tests, the critical load 〈em〉L〈/em〉〈sub〉c3〈/sub〉 for a total film delamination increases from 43 ± 4 to 59 ± 3 N and from 48 ± 2 to 64 ± 3 N for the a-C and a-C:H film. The improved adhesion behavior of the carbon films is ascribed to the increased adhesion of the CrC interlayer, which did not delaminate when scratched with a load up to 159 ± 18 N. Complementary Rockwell indentation tests reveal that the HiPIMS-pretreatment improves the adhesion class from HF6 to HF4 and from HF5 to HF3 for a-C and a-C:H. The enhanced adhesion is essential to exploit the properties of a-C and a-C:H films in applications with high loads. In conclusion, the HiPIMS-pretreatment has proven to be a promising technique to increase the adhesion strength of carbon films.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0257897219308278-ga1.jpg" width="447" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Jian Dong, Yanhui Sun, Feiyu He〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, the aluminide coating was prepared by a combined process. The coating thickness and phase structure at different aluminizing temperatures and times were investigated. In addition, the thermodynamics and kinetics of the pack cementation aluminizing process were studied. The aluminizing temperature had influence on the coating phase structure. As the temperature and time increased, the coating thickened. In the process of pack cementation aluminizing, the Fe〈sub〉2〈/sub〉Al〈sub〉5〈/sub〉 phase was formed first, followed by the FeAl and FeAl〈sub〉3〈/sub〉 phases. As the temperature was lowered to below 422 °C, the Fe〈sub〉3〈/sub〉Al phase began to form. The kinetic study showed that the low-temperature aluminizing process had a low activation energy value of 164.78 kJ/mol. This research provided a theoretical basis for the parameter selection of low-temperature pack cementation aluminizing process.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Lu Zhu, Yousen Zhu, Xuanru Ren, Ping Zhang, Jianghao Qiao, Peizhong Feng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉MoSi〈sub〉2〈/sub〉-MoB-ZrO〈sub〉2〈/sub〉 composite powders are one-step synthesized prepared by self-propagating high-temperature synthesis (SHS), which are further utilized to prepare the oxidation protective coatings by spark plasma sintering (SPS) method on molybdenum substrate. Microstructure and properties of the coatings were investigated and determined. Oxidation behavior of the coatings at high temperature was also studied. The results showed that the composite coating is dense and crack-free due to the addition of ZrO〈sub〉2〈/sub〉, which is beneficial for the decrease of mismatch in coefficient of thermal expansion, and no void exists in the diffusion layer owing to the diffusion of Si, which is inhibited by adding MoB. Compared with the pure MoSi2 coating, the high hardness of the composite coating is enhanced by about 20% while the fracture toughness of the composite coating is improved by about 25%, which makes the occurrence of intergranular fracture, crack deflection and crack bridging. After oxidation at 1400 °C for 80 h, MoSi〈sub〉2〈/sub〉 coating failed while xMoSi〈sub〉2〈/sub〉-MoB-3ZrO〈sub〉2〈/sub〉 (x = 3, 4, 5) composite coating still kept its protective effect. Only a little substrate is consumed during oxidation and improved oxidation resistance is gained by MoSi〈sub〉2〈/sub〉-MoB-ZrO〈sub〉2〈/sub〉 composite coating. 3MoSi〈sub〉2〈/sub〉-MoB-3ZrO〈sub〉2〈/sub〉 coating shows the relatively best oxidation resistance due to the formation of crack-free oxide film on the surface of the coating.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): František Lofaj, Margita Kabátová, Lenka Kvetková, Jozef Dobrovodský, Vladimír Girman〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The plasma polymerization processes during hybrid PVD-PECVD deposition, structure, hydrogenation, hybridization, hardness and coefficients of friction in W-C:H coatings prepared by direct current magnetron sputtering (DCMS), High Power Impulse Magnetron Sputtering (HiPIMS) and High Target Utilization Sputtering (HiTUS) were reviewed as a function of acetylene (0–12 sccm C〈sub〉2〈/sub〉H〈sub〉2〈/sub〉) and hydrogen (0–20 sccm H〈sub〉2〈/sub〉) additions into Ar atmosphere. The addition of acetylene resulted in the increase of carbon and hydrogen contents in the matrix via incorporation of C〈sub〉x〈/sub〉H〈sub〉y〈/sub〉 fragments with the C〈sub〉2〈/sub〉H, 2C and CH radicals being the “primary” source for growth. The level of hydrogenation in the carbon matrix was found to be related to the level of sp〈sup〉3〈/sup〉 hybridization and cross-linking as well. Hardness and coefficient of friction of the studied W-C:H coatings were found to be affected not only by hydrogenation and hybridization, but also by the sputtering technique. HiPIMS provided the best combination of hybridization, hydrogenation and cross-linking in the carbon structure resulting in W-C:H coatings with reasonably high (~20 GPa) hardness and simultaneously sufficiently low (≤0.1) coefficients of friction. Thus, HiPIMS applied to hybrid PVD-PECVD W-C:H coatings expands the range of their mechanical and tribological properties compared to DCMS and HiTUS.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): I. Campos-Silva, A.M. Delgado-Brito, J. Oseguera-Peña, J. Martínez-Trinidad, O. Kahvecioglu-Feridun, R. Pérez Pasten-Borja, D. López-Suero〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉New results about the tribocorrosion resistance of borided ASTM F1537 alloy immersed in Hank's solution were obtained in this study. A CoB-Co〈sub〉2〈/sub〉B layer, with around 30 μm of thickness, was obtained at the surface of the cobalt-based alloy using the powder-pack boriding process at 1273 K with 6 h of exposure. The tribocorrosion tests were carried out in the borided ASTM F1537 alloy and the non-borided ASTM F1537 alloy (reference material) using a linear reciprocating tribometer coupled with a standard three-electrode electrochemical cell. A counterpart of alumina (ball of 4.8 mm-diameter) was used, with a constant applied load of 20 N, and a total sliding distance of 100 m. The total material loss rate due to tribocorrosion (T), which included the mass loss rate due to wear (W) and that due to corrosion (C), was estimated according to the ASTM 〈a href="http://www.astm.org/Standards/G119" target="_blank"〉G119〈/a〉 procedure.〈/p〉 〈p〉The results showed that the presence of CoB-Co〈sub〉2〈/sub〉B layer at the surface of the ASTM F1537 alloy increased the tribocorrosion resistance around 1.2 times compared with the reference material. In addition, for the reference material, 55% of the material loss rate was attributed to the wear-corrosion synergism in comparison with 47% estimated for the borided ASTM F1537 alloy. Finally, the influence of wear affected in greater extent than corrosion in the reference material, whilst the corrosion-wear regime was obtained for the borided ASTM F1537 alloy.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 178〈/p〉 〈p〉Author(s): Hao Sun, Shaohua Fu, Chichi Chen, Zhirui Wang, Chandra Veer Singh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nickel carbonyl vapor deposition (CVD) is a high-efficiency process used to produce nickel shell molds with high yield strength, reasonable ductility, and strong corrosion resistance. Such advantageous properties arise from the nanocrystals and nanotwins inside CVD nickel. However, the nanotwins do not persist at high temperatures, transforming into dislocation cells after 40-min annealing at 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mn〉800〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mo〉°C〈/mo〉〈/mrow〉〈/math〉. Using experimental examinations and computational simulations, we investigated the kinetics of the annealing-induced detwinning in CVD nickel. TEM examinations showed that detwinning is realized by incoherent twin boundary (ITB) migration; meanwhile, plentiful dislocations are generated from coherent twin boundaries (CTBs). Our theoretical analysis revealed that these dislocations are necessary for the formation of the ITBs. Next, using molecular dynamics simulations, we found that the dislocations nucleated from CTBs during annealing are intrinsic grain boundary dislocations (IGBDs). Driven by the internal stress intensified by grain growth in the nanocrystalline regime, the IGBDs can separate from CTBs due to creep at 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mn〉800〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mo〉°C〈/mo〉〈/mrow〉〈/math〉, resulting in a higher dislocation density inside the twin lamella than that of the outside. These dislocations can trigger the formation of ITBs. Overall, unlike grain growth, stress is necessary for detwinning, so a monolithic nanotwin structure should be more stable than the nanotwins inside a nanocrystalline matrix.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305208-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 178〈/p〉 〈p〉Author(s): Zefeng Yu, Chenyu Zhang, Paul M. Voyles, Lingfeng He, Xiang Liu, Kelly Nygren, Adrien Couet〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Proton irradiation induced Nb redistribution in Zr-xNb alloys (x = 0.4, 0.5, 1.0 wt%) has been investigated using scanning transmission electron microscopy/energy dispersive X-ray spectroscopy (STEM/EDS). Zr-xNb alloys are mainly composed of Zr matrix, native Zr–Nb–Fe phases, and β-Nb precipitates. After 2 MeV proton irradiation at 350 °C, a decrease of Nb content in native precipitates, as well as irradiation-induced precipitation of Nb-rich platelets (135 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mo〉±〈/mo〉〈/mrow〉〈/math〉 69 nm long and 27 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mo〉±〈/mo〉〈/mrow〉〈/math〉 12 nm wide) were found. Nb-rich platelets and Zr matrix form the Burgers orientation relationship, [〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈mn〉1〈/mn〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈mn〉1〈/mn〉〈/mrow〉〈/math〉]//[〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈mn〉2〈/mn〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈mn〉0〈/mn〉〈/mrow〉〈/math〉] and (011)//(0002). The platelets were found to be mostly coherent with the matrix with a few dislocations near the ends of the precipitate. The coherent strain field has been measured in the matrix and platelets by the 4D-STEM technique. The growth of Nb-rich platelets is mainly driven by coherency and dislocation-induced strain fields. Irradiation may both enhance the diffusion and induce segregation of interstitial Nb to the ends of the irradiation induced platelets, further facilitating their growth.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305221-fx1.jpg" width="250" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): K. Bobzin, T. Brögelmann, C. Kalscheuer, T. Liang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Gas turbine engines operating in environments containing solid particles such as sand, dust and ice particles are challenged by the problem of solid particle erosion (SPE), which causes contour changes especially on compressor blades. Consequently, the performance and efficiency of the engines as well as the maintenance intervals will be reduced. In order to minimize the effects of SPE and to extend the lifetime of compressor blades, the application of erosion resistant coatings represents a promising way.〈/p〉 〈p〉In the present work, (Ti,Al,Si)N coatings were deposited onto martensitic steel X3CrNiMo13-4 used for compressor blades by the high speed physical vapor deposition (HS-PVD) technology. Morphology of the coatings investigated by scanning electron microscopy (SEM) shows a dense microstructure with coating thickness s 〉 11 μm. Owing to hollow cathode discharge (HCD) and the transport function of the plasma-forming gas Ar, which are specific in HS-PVD deposition processes, high deposition rates ds/dt 〉 11 μm/h were achieved. The coated samples were then post-annealed directly in the coating chamber with varying atmosphere such as in vacuum and in nitrogen with or without bias voltage induced Ar-plasma. The post-annealing effects on the microstructure, indentation hardness as well as chemical and phase compositions were investigated by SEM, glow discharge optical emission spectroscopy (GDOES), X-ray diffraction (XRD) and nanoindentation, respectively. The erosion resistance of annealed, as-deposited and uncoated samples was investigated using a fine sand blasting facility. Basing on measured mass change and inspection of the eroded surfaces, a significantly higher erosion resistance of the (Ti,Al,Si)N coated samples compared to uncoated substrates could be revealed. Moreover, the post-annealing process led to a further improvement of the erosion resistance. Therefore, the thick (Ti,Al,Si)N coatings deposited by HS-PVD in combination with post-annealing in N〈sub〉2〈/sub〉 atmosphere provide a high potential for the protection of compressor blades against SPE.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Gaurav Malik, Satyendra Mourya, Jignesh G. Hirpara, Ramesh Chandra〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this research work, the synthesis and the electrochromic (EC) performance of the active material (γ-WO〈sub〉3〈/sub〉) is reported. Nanoporous γ-WO〈sub〉3〈/sub〉 thin film was grown directly on the indium tin oxide (ITO) coated glass substrate using DC magnetron sputtering in a reactive environment (Ar:O〈sub〉2〈/sub〉 = 2:1) at room temperature (RT). To achieve the nanoporous-nanocrystalline behaviour of the active material, a thermal treatment (250 °C) was given, which modified the compact film surface into nanospheres. This surface modification is responsible to alter the physical, optical and electrochromic properties of the active material. The physical properties of the active material were probed in detail using X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and energy-dispersive X-ray analysis (EDX). The optical and electrochromic behaviour of the active electrode material was analyzed using UV–Vis spectroscopy and cyclic voltammetry (CV). It has been found that the modified electrode exhibited large optical modulation (46%), high reversible redox behaviour (higher current density) and good cyclic stability at least upto 500 cycles, causes scaled EC behaviour. This electrochemically active architecture allow one to fabricate the device for energy harvesting applications. Our work indorse human comfort with financial benefits and may play a crucial role in “green nanotechnology”.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Yu-Heng Liu, Li-Chun Chang, Bo-Wei Liu, Yung-I Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Monolithic and multilayered W〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉N and W–Si–N coatings were fabricated through direct current magnetron cosputtering at substrate holder rotation speeds of 0 and 5 rpm. The mechanical properties, structural evolutions, and oxidation behaviors of the W〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉N and W–Si–N coatings were investigated through nanoindentation, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The mechanical properties of crystalline W〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉N coatings correlated to their textures and residual stresses. The monolithic W〈sub〉77〈/sub〉N〈sub〉23〈/sub〉 samples located closest to the W target exhibited a high deposition rate of 18.0 nm/min, a strong (200) texture coefficient, a high nanoindentation hardness of 32.7 GPa, a high Young's modulus of 392 GPa, and a high residual stress of −3.2 GPa. The addition of Si into the W〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉N matrix transformed the monolithic W–Si–N coating into an X-ray amorphous phase dominated structure that comprised Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉, W〈sub〉2〈/sub〉N, and W constituents. Ion bombardment caused the formation of multilayered W〈sub〉78〈/sub〉N〈sub〉22〈/sub〉 samples with high residual stress and mechanical properties. The mechanical properties and residual stresses of the multilayered W–Si–N coatings decreased due to the preferential formation of Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉. By contrast, oxidation resistance was improved by adding Si content higher than 24 at.% with annealing at 600 °C in a 1% O〈sub〉2〈/sub〉–99% Ar atmosphere.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): M. Mohammadtaheri, Y. Li, J. Corona-Gomez, Q. Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Coatings with superior hardness, high temperature thermal stability, and oxidation resistance are required to protect cutting tools in machining applications. Hence, the synthesis of such coatings was investigated in a ternary Cr–Zr–O system by reactive radio-frequency magnetron sputtering technique. For this purpose, the Cr–Zr–O coatings with chemical compositions up to 9 at. % Zr were deposited on Si (100) substrates. The coatings were then characterized by energy dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, and Nanoindentation and a correlation between their chemical composition, crystal structure, phase composition, and mechanical properties was established. The structural stability of the coatings was also evaluated after annealing treatments. The results indicated that adding zirconium to Cr〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 coatings shifted the onset of crystallization for the coatings to higher temperatures. The hardness measurements showed that Cr-Zr-O coatings have the potential to reach a hardness value over 40 GPa. Based on the XRD and Raman spectroscopy analysis, it was assumed that grain size refinement and solid solution hardening were the most responsible mechanisms for the enhanced hardness. Annealing treatments at elevated temperatures showed that the thermal stability of the superhard Cr-Zr-O coatings was higher than pure chromium oxide coatings. Moreover, the metastable (Cr, Zr)〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 structure in the superhard coatings decomposed to Cr〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and ZrO〈sub〉2〈/sub〉 phases at 1000 °C, indicating that Zr has 〈2 at. % solubility in Cr〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 in an equilibrium condition.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Paola Luchtenberg, Paulo Tancredo de Campos, Paulo Soares, Carlos Augusto Henning Laurindo, Ossimar Maranho, Ricardo Diego Torres〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Duplex stainless steels (DSS) show good mechanical properties, wear, corrosion resistance and fatigue strength. In order to decrease operational costs in paper and pulp industry, DSS is employed through weld overlay coatings on mild or low carbon steel components. In this work, the aim was to evaluate the DSS weld overlay properties obtained through deposition of ER 2209 duplex stainless steel alloy on a mild steel plate (ASTM A 516 Gr 60). The deposition was performed through GMAW/CMT welding process. The coatings were deposited using four heat inputs: 0.53, 1.01, 1.27 and 1.74 kJ/mm. Moreover, microstructural characterization by optical microscopy showed that heat input influences ferrite/austenite phase balance. Secondary austenite that precipitates due to the welding process in DSSs are Widmanstätten austenite (WA), grain boundary austenite (GBA), partially transformed austenite (PTA) and intragranular austenite (IGA). The amount of secondary austenite increases with welding energy input. The secondary austenite improves abrasive wear resistance while corrosion resistance is the lowest when welding energy is 1.74 kJ/mm.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 178〈/p〉 〈p〉Author(s): Gi-Dong Sim, Kelvin Y. Xie, Kevin J. Hemker, Jaafar A. El-Awady〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Here, an experimental study utilizing 〈em〉in-situ〈/em〉 scanning electron microscopy (SEM) micro-compression testing and post-mortem transmission electron microscopy (TEM) imaging is presented to quantify the effect of temperature on the transition in deformation modes in twin-oriented Mg single crystals. Single crystal micropillars were fabricated using FIB milling, then tested by 〈em〉in-situ〈/em〉 SEM micro-compression from 20 °C to 225 °C. It is observed that plasticity in the deformed Mg microcrystals at temperatures at and below 100 °C is governed by 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mo stretchy="true"〉{〈/mo〉〈mn〉10〈/mn〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈mn〉2〈/mn〉〈mo stretchy="true"〉}〈/mo〉〈/mrow〉〈/math〉 extension twinning. However, an anomalous increase of the flow stresses is observed at 100 °C, which is likely due to paucity of dislocation sources that are required to promote twin boundary migration. At 150 °C and above, extension twinning is suppressed and a continuous plastic flow and strain softening induced by prismatic dislocation mediated plasticity is observed. By comparing the current results with those from bulk scale studies for other hexagonal-closed-pack single crystals (e.g. titanium (Ti) and zirconium (Zr)), a general trend for the effect of temperature on the transition in deformation modes in HCP materials is proposed.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305245-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 178〈/p〉 〈p〉Author(s): X.C. Tang, C. Li, H.Y. Li, X.H. Xiao, L. Lu, X.H. Yao, S.N. Luo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A special spallation morphology in bulk metallic glass, named as the “cup-cone” structure, is of particular interest since it manifests a unique “ductile–brittle” transition. To gain insights into the underlying mechanism for the formation of a cup-cone structure, we conduct planar impact experiments at various impact velocities, as well as finite element method analysis. Spall strength increases with increasing impact velocity. Scanning electron microscopy and X-ray computed tomography are performed on postmortem samples to characterize cup-cone structures; their average size and spacing decrease as impact velocity increases, and they dominate fracture morphology at high impact velocities. Cups and cones are generally distributed on the side away from and on the side closer to the target free surface, respectively. The initial nucleation sites of voids become the conical vertices of cup-cones, and the subsequent nucleation sites form along the conical surface and coalesce into the cracks and fracture surfaces.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305087-fx1.jpg" width="287" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Jiawei Jiang, Gui Han, Xuesong Zheng, Gang Chen, Peizhi Zhu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, we prepared a layer of hydroxyapatite (HA) coating on the surface of titanium alloy 〈em〉via〈/em〉 hydrothermal process. FTIR, SEM, Raman, XRD and electrochemical tests were used to analyze the structure of prepared HA coating. The prepared HA coating on the surface of titanium alloy demonstrated superior corrosion resistances. Antibacterial experiments proved that HA coating could adsorb drugs and act as a carrier for antibiotics to achieve inhibition of bacteria. The experimental results indicated that HUVEC cells could adhere to the surface of substrates. Animal experiments also confirmed that HA coating has good biocompatibility and promote the formation of new bone.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 178〈/p〉 〈p〉Author(s): Satoshi Okamoto, Kazunori Miyazawa, Takahiro Yomogita, Nobuaki Kikuchi, Osamu Kitakami, Kentaro Toyoki, David Billington, Yoshinori Kotani, Tetsuya Nakamura, Taisuke Sasaki, Tadakatsu Ohkubo, Kazuhiro Hono, Yukio Takada, Takashi Sato, Yuji Kaneko, Akira Kato〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A Ga-doped Nd-Fe-B sintered magnet has attracted significant attention as a heavy-rare-earth-free high-performance magnet. We have studied the temperature dependent magnetization reversal process of a Ga-doped Nd-Fe-B sintered magnet based on the first-order reversal curve (FORC) analysis. The FORC diagram pattern of the Ga-doped Nd-Fe-B sintered magnet changes from single spot in the high field region at room temperature to double spots in the low and high field regions at 200 °C, indicating that the dominant magnetization reversal process changes from single domain type to multidomain type. The single domain magnetization reversal at room temperature is well confirmed by using the soft X-ray magnetic circular dichroism microscopy observation. This change in the magnetization reversal process is well discussed by the temperature dependent local demagnetization field and the saturation field of multidomain state. Moreover, we have demonstrated the quantitative analysis of the FORC diagram pattern, which makes a deeper understanding of the magnetization reversal process of the Ga-doped Nd-Fe-B sintered magnet.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305063-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 178〈/p〉 〈p〉Author(s): Sumeet Mishra, Manasij Yadava, Kaustubh N. Kulkarni, N.P. Gurao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new methodology for analyzing strain hardening behavior of face centered cubic materials based on transition from restricted glide/single slip to multiple slip has been developed. The proposed modification considers strain dependence of orientation factor spanning between lower bound iso-stress Sachs model and upper bound iso-strain Taylor model. The modifications are suitably incorporated in the classical two internal variable model to develop a new slip activity based strain hardening model. The proposed model is shown to be performing better than the existing one parameter forest strengthening model and two internal variable model in predicting strain hardening behavior in the presence of wide range of microstructural features such as solutes, semi-coherent and incoherent precipitates, grain sizeand twins. Experimental validation of the proposed concept of transition in slip behavior is shown in terms of evolution of dislocation density and character from X-ray diffraction and surface roughness, slip lines and micro-texture from in-situ electron back scatter diffraction tests.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S135964541930504X-fx1.jpg" width="257" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): B. Christiaen, C. Domain, L. Thuinet, A. Ambard, A. Legris〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The growth of zirconium alloys under irradiation is a phenomenon experimentally identified and associated with the development beyond a threshold dose of dislocation loops with vacancy character having a Burgers vector with a component parallel to the c axis. In this work, by combining atomic simulations (DFT and empirical potential) and continuous modeling, we show that prismatic stacking fault pyramids or bipyramids whose base rests on the basal plane of the hcp structure are likely precursors to the formation of ‹c› vacancy loops. In other words, these would not be formed by progressive accretion of vacancies but rather by collapse of the pyramids or bipyramids beyond a certain size. This mechanism could explain the fact that the ‹c› vacancy loops are never observed below a size of the order of 10 nm and their appearance at high fluence.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419304707-fx1.jpg" width="389" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Adrian Chlanda, Przemysław Oberbek, Marcin Heljak, Żaneta Górecka, Katarzyna Czarnecka, Ko-Shao Chen, Michał J. Woźniak〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Biodegradable 3D-printed polycaprolactone scaffolds for bone tissue engineering applications have been extensively studied as they can provide an attractive porous architecture mimicking natural bone, with tunable physical and mechanical properties enhancing positive cellular response. The main drawbacks of polycaprolactone-based scaffolds, limiting their applications in tissue engineering are: their hydrophobic nature, low bioactivity and poor mechanical properties compared to native bone tissue. To overcome these issues, the surface of scaffolds is usually modified and covered with a ceramic layer. However, a detailed description of the adhesion forces of ceramic particles to the polymer surface of the scaffolds is still lacking. Our present work is focused on obtaining PCL-based composite scaffolds to strengthen the architecture of the final product. In this manuscript, we report qualitative and quantitative evaluation of low temperature plasma modification followed by detailed studies of the adhesion forces between chemically attached ceramic layer and the surface of polycaprolactone-nanohydroxyapatite composite 3D-printed scaffolds. The results suggest modification-dependent alteration of the internal structure and morphology, as well as mechanical and physical scaffold properties recorded with atomic force microscopy. Moreover, changes in the material surface were followed by enhanced adhesion forces binding the ceramic layer to polymer-based scaffolds.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 178〈/p〉 〈p〉Author(s): P.E. Seiler, H.C. Tankasala, N.A. Fleck〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Additive manufacture and rapid prototyping are versatile methods for the generation of lattice materials for applications in the creep regime. However, these techniques introduce defects that can degrade the macroscopic creep strength. In the present study, the uniaxial tensile response of two-dimensional PMMA lattices is measured in the visco-plastic regime: tests are performed at 100 °C which is slightly below the glass transition temperature 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mtext〉g〈/mtext〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 of PMMA. Both 〈em〉as-manufactured〈/em〉 defects (Plateau borders and strut thickness variation) and 〈em〉as-designed〈/em〉 defects (missing cell walls, solid inclusions, and randomly perturbed joints) are introduced. The dispersion in macroscopic strength is measured for relative densities in the range of 0.07–0.19. It is observed that initial failure of the lattice is diffuse in nature: struts fail at a number of uncorrelated locations, followed by the development of a single macroscopic crack transverse to the loading direction. In contrast, the same PMMA lattice fails in a correlated, brittle manner at room temperature. An FE study is performed to gain insight into the diffuse failure mode and the role played by 〈em〉as-manufactured〈/em〉 defects, including the dispersion in tensile strength of individual struts of the lattice. A high damage tolerance to 〈em〉as-designed〈/em〉 defects is observed experimentally: there is negligible knock-down in strength due to the removal of cell walls or to the presence of solid inclusions. These findings aid the design and manufacture of damage tolerant lattices in the creep regime.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉Elastic-brittle versus visco-plastic failure ofPMMA lattices.〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305026-fx1.jpg" width="229" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 177〈/p〉 〈p〉Author(s): Christopher A. Schuh〈/p〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Frederico Goncalves de Cerqueira Lima, Ulrich Mescheder, Harald Leiste, Claas Müller〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Electrodeposition of metals directly on non-metal substrates without any seed layer reduces process steps; however, adhesion of the electrodeposited layer is a challenge. In this work, the influence of current density during seedless electroplating on the adhesion of Cu layers on Si substrates was investigated. Cu was electrodeposited on phosphorus-doped Si samples having different orientations in two stages. During the first stage, higher current densities were used for a few minutes to reach instantaneous nucleation and maximize the number of Cu islands on the substrate. The second stage had the goal of growing the nuclei previously formed. Therefore, lower current densities were used to create progressive nucleation. Adhesion values of Cu layers on Si were derived from scratch tests and tensile measurements. Higher adhesion was obtained either at higher current densities or at lower cathodic potentials at the beginning of potentiostatic or galvanostatic processes. To study the influence of hydrogen evolution on the adhesion of seedless electrodeposited Cu on Si, the transition time which indicates the moment when transferred charges are used to create hydrogen at the cathode, was determined experimentally. The transition time shows a strong dependence on current density. Therefore, control and optimization of adhesion by an appropriate choice of current densities within the two-stage process is possible.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Chenglong Ma, Dongdong Gu, Donghua Dai, Han Zhang, Hongmei Zhang, Jiangkai Yang, Meng Guo, Yuexin Du, Jie Gao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, TiC ceramic particle reinforced TiAl-based composites were synthesized by selective laser melting (SLM) by using Ti, Al, and TiC multi-component powder. The results showed that a plenty of TiC dendritic crystals formed during the solidifying process. It was found that TiC dendrites exhibited three different modes of nucleation and growth, corresponding to the dissolution-precipitation of fully melted fine TiC particles, the epitaxial growth along the margin of partly melted TiC particle, and the recrystallization growth based on stress-induced nonequilibrium melting. Subsequently, the influence of laser energy density on microstructure evolution and high-temperature oxidation behaviour of SLM fabricated TiC/TiAl composites were investigated. At a high laser energy density of 189 J/mm〈sup〉3〈/sup〉, the relatively full dense SLM-fabricated part was obtained, accompanying the formation of a variety of TiC dendrites with the coarsening structure, which made a contribution to the elevated high-temperature oxidation resistance with a low oxidation kinetics constant of 1.32 × 10〈sup〉−〈/sup〉〈sup〉5〈/sup〉 mg 〈sup〉6〈/sup〉 cm〈sup〉−〈/sup〉〈sup〉12〈/sup〉 h〈sup〉−〈/sup〉〈sup〉1〈/sup〉.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0257897219307996-ga1.jpg" width="500" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): A.P. Rubshtein, K. Gao, A.B. Vladimirov, S.A. Plotnikov, B. Zhang, J. Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The structures, wear resistances, and corrosion behaviours of Cr–Al–C and multilayer [Cr–Al–C/a-C]〈sub〉〈em〉n〈/em〉〈/sub〉 coatings, fabricated by physical vapour deposition (PVD), plasma-assisted chemical vapour deposition (PACVD), or their combination, were studied. A Cr〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Al target served as a source of chromium and aluminium, while a graphite target or acetylene served as sources of carbon. Depending on the type of carbon source, Cr–Al–C or Cr–Al–C(H) coatings were obtained. Multilayer [Cr–Al–C/a-C]〈sub〉20〈/sub〉 and [Cr–Al–C(H)/a-C:H]〈sub〉20〈/sub〉 coatings were fabricated by alternating pair layers of [Cr–Al–C (PVD)/a-C (PVD)] and [Cr–Al–C(H) (PVD–PACVD)/a-C:H (PACVD)], respectively. a-C and a-C:H are hydrogen-free and hydrogenated diamond-like carbons. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy were employed to investigate the coating structures. Along with the amorphous matrix, chromium carbide, and Cr〈sub〉〈em〉x〈/em〉〈/sub〉Al〈sub〉1-〈em〉x〈/em〉〈/sub〉C nanograins, clusters of nanocrystalline graphite as spherical inclusions and plates, probably of several graphene layers, were observed in Cr–Al–C. This structure provided high hardness and corrosion resistance. Along with the amorphous matrix, Cr〈sub〉2〈/sub〉AlC and chromium carbide nanoclusters and clusters of nanoscale CVD diamond with wide boundaries of sp〈sup〉2〈/sup〉-bonded carbon were observed in Cr–Al–C(H), whose hardness did not exceed 8.9 GPa. The multilayer structures significantly increased the wear resistances. The specific coefficient of wear rate (SCWR) of [Cr–Al–C/a-C]〈sub〉20〈/sub〉 was five times lower than that of Cr–Al–C. Hybrid PVD–PACVD technology provided favourable conditions for the formation of wear-resistant coatings. The SCWR of [Cr–Al–C(H)/a-C:H]〈sub〉20〈/sub〉 was 47 times lower than that of [Cr–Al–C/a-C]〈sub〉20〈/sub〉. The high wear resistance of the multilayer coatings was associated with the structure, low friction coefficient, high crack resistance, and strengthened interface boundaries.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0257897219308849-ga1.jpg" width="232" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Sergio Pinilla, Teresa Campo, José María Sanz, Francisco Márquez, Carmen Morant〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Highly ordered metal porous membranes containing Fe and Zr in different layers have been fabricated by successive ion-beam sputtering depositions of these metals onto a porous anodic aluminum oxide (AAO) membrane. Two different membrane configurations were studied: Zr/Fe/AAO and Fe/Zr/AAO. Morphology and composition of these multi-membranes have been characterized by Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), X-ray diffraction (XRD) and Rutherford Backscattering Spectrometry (RBS). The RBS analysis allowed a precise quantification of the atomic composition of the metal membrane and the support layer. The asymmetry and long tails observed for the metallic peaks in the RBS spectra indicate the different filling of the pores during the deposition. These results provide a possible structural configuration for the metal membranes, where Fe/Zr/AAO and Zr/Fe/AAO membranes follow different behaviors.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): N. Almirall, P.B. Wells, T. Yamamoto, K. Wilford, T. Williams, N. Riddle, G.R. Odette〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Mn-Ni-Si intermetallic precipitates (MNSPs) that are observed in some Fe-based alloys following thermal aging and irradiation are of considerable scientific and technical interest. For example, large volume fractions (f) of MNSPs form in reactor pressure vessel low alloy steels irradiated to high fluence, resulting in severe hardening induced embrittlement. Nine compositionally-tailored small heats of low Cu RPV-type steels, with an unusually wide range of dissolved Mn (0.06–1.34 at.%) and Ni (0.19–3.50 at.%) contents, were irradiated at ≈ 290 °C to ≈ 1.4 × 10〈sup〉20〈/sup〉 n/cm〈sup〉2〈/sup〉 at an accelerated test reactor flux of ≈3.6 × 10〈sup〉12〈/sup〉 n/cm〈sup〉2〈/sup〉-s (E 〉 1 MeV). Atom probe tomography shows Mn-Ni interactions play the dominant role in determining the MNSP f, which correlates well with irradiation hardening. The wide range of alloy compositions results in corresponding variations in precipitates chemistries that are reasonably similar to various phases in the Mn-Ni-Si projection of the Fe based quaternary. Notably, f scales with ≈ Ni〈sup〉1.6〈/sup〉Mn〈sup〉0.8〈/sup〉. Thus f is modest even in advanced high 3.5 at.% Ni steels at very low Mn (Mn starvation); in this case Ni-silicide phase type compositions are observed.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305397-fx1.jpg" width="415" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 14 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia〈/p〉 〈p〉Author(s): Bar Danino, Gil Gur-Arieh, Doron Shilo, Dan Mordehai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ferroic materials typically exhibit a microstructure that contains twins or domains separated by twin boundaries (walls). The deformation of these materials is governed by twin boundary motion under mechanical/electrical/magnetic driving force. The Landau-Ginzburg model is a widely accepted phenomenological model used to describe twin boundary properties. However, it is incapable of describing energy barriers for motion due to the lack of atomistic description. In this work, we present a model interatomic potential for studying the relations between the lattice barrier for twin boundary motion and measurable material properties. The interatomic potential emulates the continuum Landau-Ginzburg model and reproduces known results of twin boundary thickness and energy as a function of the model parameters. An atomic model system is constructed, with a single twin boundary separating crystals of different orientations and we employ the Nudged Elastic Band method to calculate the energy barriers for the motion of twin boundaries with different thicknesses under different externally-applied shear stresses. The results are summarized in a closed-form expression relating the energy barriers with material properties and the external loading. The energy barrier function extends the Landau-Ginzburg model and allows treating the motion of twin boundary as a thermally activated process.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305282-fx1.jpg" width="446" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): Hongping Li, Mitsuhiro Saito, Chunlin Chen, Kazutoshi Inoue, Kazuto Akagi, Yuichi Ikuhara〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Metal/oxide heterointerfaces are ubiquitous in functional materials, and their microstructures frequently govern the macroscopic properties. It has been believed that the interfacial interactions are very weak at incoherent interfaces with large mismatches. Combining atomic-resolution scanning transmission electron microscopy with density functional theory calculations, we investigated the interaction and bonding reconstruction at Pd/ZnO{0001} interfaces, which have large mismatches. Molecular beam epitaxy was employed to grow Pd films on clean Zn-terminated ZnO(0001) and O-terminated ZnO(000〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈/math〉) polarized surfaces. Atomically sharp Zn-terminated interfaces formed on both substrates, and the large lattice misfits between them were not strongly accommodated, suggesting the formation of incoherent regions. The interfacial atoms were located almost at bulk lattice points in the stoichiometric Zn-terminated Pd(111)/ZnO(0001) structure, whereas the interfacial Pd and Zn atoms underwent relatively large relaxations on the interfacial plane in the nonstoichiometric Zn-terminated Pd(111)/ZnO(〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈mn〉000〈/mn〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈/mrow〉〈/math〉) interface. Effective Pd–Zn chemical bonds were formed across both interfaces, but the bonding mechanisms were quite different, depending on the local atomic geometry. The Pd–Zn bonds exhibited site-dependent characteristics and gradually transitioned from covalent to ionic at the Pd(111)/ZnO(0001) interface, whereas most of Pd–Zn bonds exhibited strong covalent behavior at the Pd/ZnO(〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈mn〉000〈/mn〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈/mrow〉〈/math〉) interface. The adhesive energies indicated that the Zn-terminated Pd/ZnO(〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈mn〉000〈/mn〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈/mrow〉〈/math〉) interface is energetically preferable to the Zn-terminated Pd/ZnO(0001) interface. Thus, the interfacial interaction can be strong and direct metal–metal interactions can play a critical role in metal/oxide heterointerfaces with large mismatches, opening up a new avenue for understanding the origins of interface-related issues.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305300-fx1.jpg" width="344" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): A.H. Abdelhameed, W. Jacob〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermally stable tungsten nitride (〈em〉W〈/em〉〈sub〉2〈/sub〉〈em〉N〈/em〉) thin films with thickness ∼ 0.9 μm were successfully deposited on 〈em〉Si〈/em〉 and graphite substrates by reactive magnetron sputtering. The produced layers show no phase change or nitrogen release up to 1300 K. These novel layers survived annealing at 1200 K for 50 h without any measurable nitrogen loss or a phase transition from 〈em〉W〈/em〉〈sub〉2〈/sub〉〈em〉N〈/em〉 to 〈em〉bcc W〈/em〉. X-ray diffraction, thermal desorption spectroscopy and Rutherford back scattering were utilized to characterize these layers and investigate the nitrogen release mechanism. The micro-structure of the layers was dominated by a grainy structure with porosity less than 16〈em〉%〈/em〉 and a strong texture in (200) orientation in contrast to the common (111) orientation. For annealing temperatures higher than 1200 K nitrogen release was observed, but this was attributed to a chemical reaction of 〈em〉W〈/em〉〈sub〉2〈/sub〉〈em〉N〈/em〉 with the substrate material(s).〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 178〈/p〉 〈p〉Author(s): Keita Nomoto, Hiroshi Sugimoto, Xiang-Yuan Cui, Anna V. Ceguerra, Minoru Fujii, Simon P. Ringer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Boron (B) and phosphorous (P) co-doped colloidal silicon nanocrystals (Si NCs) have unique size-dependent optical properties, which lead to potential applications in optoelectronic and biomedical applications. However, the microstructure of the B and P co-doped colloidal Si NCs – in particular, the exact location of the dopant atoms in real space, has not been studied. A lack of understanding of this underlying question limits our ability to better control sample fabrication, as well as our ability to further develop the optical properties. To study the microstructure, a process enabling atom probe tomography (APT) of colloidal Si NCs was developed. A dispersion of colloidal Si NCs in a SiO〈sub〉2〈/sub〉 sol-gel solution and a low temperature curing are demonstrated as the key sample preparation steps. Our APT results demonstrate that a B-rich region exists at the surface of the Si NCs, while P atoms are distributed within the Si NCs. First principles density functional theory calculations of a Si NC embedded in SiO〈sub〉2〈/sub〉 matrix reveal that P atoms, which always prefer to reside inside a Si NC, significantly influence the distribution of B atoms. Specifically, P atoms lower the B diffusion barrier at Si/SiO〈sub〉2〈/sub〉 interface and stabilize B atoms to reside within individual Si NCs. We propose that the B-modified surface changes the chemical properties of the Si NCs by (i) offering chemical resistance to attack by HF and (ii) enabling dispersibility in solution without aggregation.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305233-fx1.jpg" width="205" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Xiao-feng Zhang, Yu-xiao Cui, Xi-bei Liu, Tian-yi Sui, Chun-hui Ji, Da-wei Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The wettability of nano-crystalline diamond (NCD) films is of great importance to their bio-functional applications. In this work, the wettability of NCD films is controlled by two types of in-situ CVD process, namely oxygen doping and water vapor etching (WVE). Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), micro-Raman spectroscopy, X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS) are performed to characterize as-fabricated NCD specimens. The oxygen doping and WVE have a significant effect on the surface topography and chemical termination of NCD films respectively, which can alter their wetting properties. Angle contact measurements show that the wettability of NCD films can be modulated from weak hydrophobic to either very hydrophobic (contact angle of 140.1°) or super-hydrophilic (contact angle of 0°).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): Arthur S. Nishikawa, Goro Miyamoto, Tadashi Furuhara, André P. Tschiptschin, Hélio Goldenstein〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The modification of the matrix of ductile cast irons by heat treatments has been of interest of researchers for many years. Among these treatments, in the last years the Quenching & Partitioning (Q&P) process has emerged as a viable way to produce microstructures containing controlled amounts of martensite and retained austenite, providing a good combination of strength and ductility. In this work, the different mechanisms of phase transformations occurring during the Q&P heat treatment applied to a ductile cast iron alloy is investigated. Microsegregation, inherent to cast irons, was analyzed by means of Electron Probe Microanalysis (EPMA). Microstructural characterization was performed with Scanning Electron Microscopy (SEM) and Electron Backscattered Diffraction (EBSD), while kinetics of carbon redistribution and competitive reactions were studied using dilatometry and in situ synchrotron X-ray diffraction. It was found that either transition carbides or cementite precipitate in martensite depending on the partitioning temperature. Despite of carbides precipitation, evidence of carbon partitioning from martensite to austenite was obtained. Formation of bainitic ferrite occurs during the partitioning step, further contributing to carbon enrichment of austenite. The experimental results are compared with a local field model that computes the local kinetics of carbon redistribution by simultaneously considering carbides precipitation and growth of bainitic ferrite. Results showed that kinetics of carbon partitioning from martensite to austenite depends on the carbides free energy. More stable carbides do not dissolve and prevent the escape of carbon from martensite. Fast carbon partitioning occurs by dissolution of less stable carbides, but it is slowed down as growth of bainitic ferrite proceeds. This result is explained by the overlapping of the diffusion fields (soft impingement) of the carbon partitioned from martensite and the carbon rejected from growth of bainitic ferrite.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305038-fx1.jpg" width="346" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Xiaowei Zhou, Yuxin Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For increasing the interfacial bonding of Ni deposits onto Ti surface, the objectives of this work are to explore an effective approach for LaCl〈sub〉3〈/sub〉-modified Ni nanocrystals on porous surface of Ti substrate. Three-dimensional (3D) heterotypic nanopores were well organized with a diameter size of ~300 nm through surface anodizing in H〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉-containing acid solution at DC 180 V. In view of the above considerations, the anodized surface with a 3D-open reticular structure was processed of high adsorption capacity leading into pitting growth of Ni crystals into 3D-pores. Experimental data have referred that a leaf-like surface with the diversified orientations of Ni (111) (200) (220) (311) facets were conducted for Ni-LaCl〈sub〉3〈/sub〉 deposits instead of an exclusive growth of Ni (111) (200) facets for pure Ni. Based on Nanoindentation tests, it exhibited the ratio of micro hardness (〈em〉H〈/em〉〈sup〉3〈/sup〉) and elastic modulus (〈em〉E〈/em〉〈sup〉2〈/sup〉) of Ni samples remarkably increased with increasing LaCl〈sub〉3〈/sub〉 addition from 0 to 2.0 g/L. As excepted, the steady-state friction coefficient was ~0.28 for Ni-2.0 g/L LaCl〈sub〉3〈/sub〉 composites, which was about one order of magnitude lower than that of pure Ni sample during oxidized at 500 °C in air. The exceptional improvements of corrosion resistance for LaCl〈sub〉3〈/sub〉-modified Ni deposits were associated with the co-existence of high adsorptive La〈sup〉3+〈/sup〉 ions and the La-rich insoluble corrosive products in 1 M (mol/L) HCl solution. In light of this, Ni-based nanocomposites on 3D-heterotypic porous surface of Ti alloys would provide an effective guidance for protecting Ti alloys against wear and corrosive damages.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0257897219308035-ga1.jpg" width="274" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 178〈/p〉 〈p〉Author(s): P. Tozman, Y.K. Takahashi, H. Sepehri-Amin, D. Ogawa, S. Hirosawa, K. Hono〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Zr is one of the essential elements to stabilize the ThMn〈sub〉12〈/sub〉 structure in rare earth (R) transition metal (M) hard magnetic compounds, RM〈sub〉12〈/sub〉. In this work, the effects of Zr on the intrinsic hard magnetic properties of (Sm〈sub〉1-x〈/sub〉 Zr〈sub〉x〈/sub〉)(Fe〈sub〉0.8〈/sub〉Co〈sub〉0.2〈/sub〉)〈sub〉12〈/sub〉 compounds are investigated using epitaxially grown thin films. The increase of Zr substitution for Sm from 〈em〉x〈/em〉 = 0 to 0.26 for (Sm〈sub〉1-x〈/sub〉 Zr〈sub〉x〈/sub〉)(Fe〈sub〉0.8〈/sub〉Co〈sub〉0.2〈/sub〉)〈sub〉12〈/sub〉 increases saturation magnetization (μ〈sub〉0〈/sub〉〈em〉M〈/em〉〈sub〉s〈/sub〉) from 1.78 T to 1.90 T, the highest value reported for hard magnetic compounds. The largest μ〈sub〉0〈/sub〉〈em〉H〈/em〉〈sub〉a〈/sub〉 and 〈em〉T〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉 for Zr-doped samples were found to be 9.8 T and 671 K for 〈em〉x〈/em〉 = 0.18 which is superior to those for Nd〈sub〉2〈/sub〉Fe〈sub〉14〈/sub〉B. Sm-rich Sm〈sub〉1.30〈/sub〉Zr〈sub〉0.27〈/sub〉(Fe〈sub〉0.8〈/sub〉Co〈sub〉0.2〈/sub〉)〈sub〉12,〈/sub〉 obtained as sub-μm thick films, has remanence, μ〈sub〉0〈/sub〉〈em〉M〈/em〉〈sub〉r〈/sub〉 of 1 T, which appears to be useful for near-field applications such as micro-electro-machines and magnetic recording media if microstructure can be optimized to obtain a sufficient coercivity.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305051-fx1.jpg" width="441" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): V. Malinovschi, A. Marin, V. Andrei, E. Coaca, C.N. Mihailescu, Cristian P. Lungu, Cristiana Radulescu, Ioana Daniela Dulama〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Phosphorus-incorporated oxide layers were grown on commercially pure titanium during plasma electrolytic oxidation in sodium dihydrogen phosphate dihydrate solution. Microstructure, mechanical and electrochemical behavior of the surface oxides indicated a dominant anatase and rutile structure of TiO〈sub〉2〈/sub〉 with nanocrystallites ranging from 45 to 64 nm and 48–98 nm, respectively as well as Ti〈sup〉2+〈/sup〉, Ti〈sup〉3+〈/sup〉 and Ti〈sup〉4+〈/sup〉 chemical species. Using a combination of process time, applied current and electrolyte concentration, coating thicknesses up to about 10 μm were fabricated. Best mechanical performance was observed for potentiostatic deposited samples yielding a 453 HV〈sub〉300〈/sub〉 hardness, 19 N adhesive failure and 38 N full delamination resistance. All PEO-coated samples in this work exhibit a corrosion current density with one order of magnitude lower than CP-Ti when subjected to Ringer's physiological solution.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Zhijun Li, Qing Kuang, Xiuli Dong, Tongwei Yuan, Qinghui Ren, Xuexia Wang, Jun Wang, Xiaoyan Jing〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High-performance anti-corrosion/anti-wear coatings on superlight magnesium‑lithium (Mg〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Li) alloy with exceptional durability are of great interest for fundamental research and practical applications. In the present study, oxide coatings are produced on Mg〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Li alloy by electrochemical surface engineering––plasma electrolytic oxidation in an alkaline silicate electrolyte with addition of cerium salt. To understand the nature of coatings, we investigate their surface and cross-sectional morphologies, wettability (35 ± 3° 〈em〉vs〈/em〉 78 ± 2°), phase and chemical compositions, corrosion and tribological behaviors. Our findings show that the oxide coating prepared with cerium salt has a more compact structure with fewer defects (18 μm in thickness). Importantly, it substantially enhances the corrosion resistance of Mg〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Li alloy by three orders of magnitude and significantly retards the occurrence of localized corrosion (150 h), along with notably improved anti-wear performance (friction coefficient of 0.19).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): B. Hadzima, F. Pastorek, K. Borko, S. Fintová, D. Kajánek, S. Bagherifard, M. Gholami-Kermanshahi, L. Trško, J. Pastorková, J. Brezina〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Shot peening is a standard surface treatment primarily used for enhancement of fatigue properties of metallic materials. However, its influence on surface properties is so radical, that subsequent techniques of surface treatment used on the shot peened surface need to be reconsidered in order to minimize the possible negative side effects of shot peening. In this case, the differences between hurealite formation on the ground and shot peened surfaces of modern high strength low alloy (HSLA) steel were evaluated by morphological and electrochemical corrosion observations and measurements. The surface morphologies of the formed coatings were observed by the scanning electron microscopy (SEM) and analysed by energy-dispersive X-ray analysis (EDX). The corrosion resistance of the HSLA steel with hurealite coating was evaluated using electrochemical impedance spectroscopy (EIS) by the analysis of Nyquist plots obtained in 0.1 M NaCl solution after various phosphating times on both types of pre-treated surfaces (ground and shot peened). The results showed that used technique of shot peening negatively influenced the phosphating process by prolonging the phosphating process in order to reach the coating with maximal protection properties in tested medium. Moreover, shot peened surface caused significantly enlarged size of the hurealite crystals and greater thickness of the coating compared to the surface pre-treated by grinding on the tested HSLA steel at the expense of a lower compactness and corrosion protection.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0257897219307960-ga1.jpg" width="499" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Hang Li, Jianliang Li, Zhaoli Liu, Jiewen Huang, Jian Kong, Dangsheng Xiong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ternary transition metal nitrides have procured wide attention towards practical application due to their high hardness, wear resistance and thermal stability. In this study, Hf〈sub〉1-x〈/sub〉Mo〈sub〉x〈/sub〉N〈sub〉y〈/sub〉 thin films are deposited by reactive direct current magnetron sputtering (R-DCMS) system in an effort to improve further the properties of their analogous binary compounds. In addition, the influence of Mo content on the structure, mechanical and tribological properties of the films are also investigated. The composition and microstructure of the as-deposited Hf〈sub〉1-x〈/sub〉Mo〈sub〉x〈/sub〉N〈sub〉y〈/sub〉 films are characterized by X-ray diffraction, Raman and scanning electron microscopic techniques. Spectroscopic results show that, as-sputtered Hf〈sub〉1-x〈/sub〉Mo〈sub〉x〈/sub〉N〈sub〉y〈/sub〉 films mainly consist of single solid solution phase with rock-salt structure. Ultra-micro hardness and ball-on-disc wear tests are conducted to evaluate the mechanical and tribological properties of Hf〈sub〉1-x〈/sub〉Mo〈sub〉x〈/sub〉N〈sub〉y〈/sub〉 films. The toughness Hf〈sub〉1-x〈/sub〉Mo〈sub〉x〈/sub〉N〈sub〉y〈/sub〉 films are enhanced, and the film with x = 0.589 shows better mechanical properties, meanwhile, the lowest wear rate of 0.57 × 10〈sup〉−〈/sup〉〈sup〉6〈/sup〉 mm〈sup〉3〈/sup〉/Nm, which is two order magnitudes lower than corresponding binary compounds viz., δ-HfN and γ-Mo〈sub〉2〈/sub〉N, and lowest friction coefficient of 0.35 are also obtained. This could be attributed to the effect of solution reinforcement and valence electron concentration. The unique wear resistance of Hf〈sub〉1-x〈/sub〉Mo〈sub〉x〈/sub〉N〈sub〉y〈/sub〉 is ascribed to the outstanding oxidation resistances and higher H/E and H〈sup〉3〈/sup〉/E〈sup〉2〈/sup〉 values, which indicate the mechanical properties, wear resistance and anti-friction of δ-HfN and γ-Mo〈sub〉2〈/sub〉N can be improved by alloying with each other.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Abhay Gupta, Chandan Srivastava〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present study, microstructure-electrochemical property correlation in electrodeposited SnBi-GO composite coatings containing different amounts of graphene oxide has been investigated. The SnBi-GO coatings exhibited uniform and compact morphology for lower GO concentrations, whereas for higher GO concentrations the morphological defects appeared. X-ray diffraction analysis showed the presence of Sn rich and a Bi rich phase in the coatings. Crystallite size of Bi-rich phase decreased whereas for Sn-rich phase it remained nearly unaffected with increasing GO addition. Growth texture analysis showed that the incorporation of GO enhanced growth along the low index planes for the Sn-rich grains and along the high index planes for the Bi-rich grains. Corrosion properties of coatings examined by the potentiodynamic polarisation and impedance spectroscopy methods revealed that the corrosion rate of the coatings decreased with increase in the GO content till an “optimum” addition of GO, after which the corrosion rate significantly increased with further GO addition. Microstructural analysis conducted using the electron backscatter diffraction (EBSD) technique showed that the coating with “optimum” GO amount which yielded the minimum corrosion rate contained highest fraction of low energy low angle grain boundaries which was due to the lowering of Bi dissolution in the Sn grains. Initial decrease in the corrosion rate was attributed to coating compactness, growth of grains along low energy index planes and GO impermeability. Increase in the corrosion rate after the optimum was attributed to increase in the morphological defects and possible galvanic coupling between the GO and the metals in the coatings. The enhanced corrosion properties of SnBi-GO coatings make them a viable material for interconnections used in the electronic components.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S025789721930800X-ga1.jpg" width="344" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Ziai Liu, Xiaolong Yang, Guibing Pang, Fan Zhang, Yuqi Han, Xuyue Wang, Xin Liu, Lin Xue〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Superhydrophobic surfaces with tunable water adhesion and adjustable wettability have the capacity to manipulate water droplets under complicated conditions and, therefore, have great prospects in various domains. Hence, developing a facile method to prepare highly stable superhydrophobic surfaces with tunable water adhesion and adjustable wettability is of great importance. Herein, we prepare the superhydrophobic aluminum surface by combining laser etching and stearic acid modification. The variations of water contact angle, water sliding angle and water adhesive force with temperature of the prepared surface are characterized during the adhesion tuning process to investigate its temperature-responsive characteristics. A low/high adhesion switching of water on the prepared surface is subsequently achieved under alternating temperature. In addition, a facile approach is designed to achieve the superwettability switching process (from superhydrophobic state to superhydrophilic state) on the prepared surface. The prepared superhydrophobic surface displays excellent recoverability, stability and repeatability in the adhesion switching process and the superwettability switching process, even after being cycled for 10 times.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S025789721930773X-ga1.jpg" width="416" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): E. Ura-Bińczyk, A. Krawczyńska, R. Sitek, M. Lewandowska〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effect of nitriding on the surface structure, mechanical properties and corrosion resistance of hydrostatically extruded 316 LVM stainless steel was evaluated and compared with coarse grained counterpart. Hydrostatic extrusion was performed at either room or elevated temperature and resulted in microstructure refinement. Nitrided layers of a similar thickness were formed on the samples irrespective of their microstructure. The nitriding process was performed at 430 °C for 5 h. The processing conditions did not affect the bulk mechanical properties of the micro and HE processed samples and their mechanical strength remained unchanged after nitriding. The electrochemical measurements revealed that the nitrided hydrostatically extruded 316 LVM steels had better corrosion resistance than their microcrystalline counterpart.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Prashant Huilgol, K. Rajendra Udupa, K. Udaya Bhat〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The microstructure of the hot-dip aluminized AISI 321 stainless steel was studied after diffusion treatment at 900 °C for 3 h. The microstructural characterization was carried out by scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry. The microstructure of the as aluminized steel consisted of two regions, viz.; aluminum topcoat and aluminide layer. During the diffusion treatment, the coating transformed into a layered structure consisting of four layers. The Fe〈sub〉2〈/sub〉Al〈sub〉5〈/sub〉 phase was formed in the outermost layer and the presence of Al〈sub〉13〈/sub〉Fe〈sub〉4〈/sub〉 quasicrystalline approximant phase was observed. The innermost layer adjacent to the base metal transformed to ferrite phase with NiAl precipitates. Next, to this layer, a disordered FeAl phase was observed. The lattice parameter of the disordered FeAl phase was found to be larger than that of the ordered B2 FeAl phase. The layer between outer Fe〈sub〉2〈/sub〉Al〈sub〉5〈/sub〉 phase and disordered FeAl phase consists of a mixture of three phases, namely Fe〈sub〉2〈/sub〉Al〈sub〉5〈/sub〉, disordered FeAl and a new phase with the simple cubic structure. The phase with simple cubic structure shares cube on cube crystallographic orientation relationship with the disordered FeAl phase.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Elbert Contreras Romero, Joan Cortínez Osorio, Roberto Talamantes Soto, Abel Hurtado Macías, Maryory Gómez Botero〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Four nanostructured TiAlTaN-(TiAlN/TaN)〈sub〉n〈/sub〉 coatings were deposited, varying the volume fraction of the top quaternary coating (TiAlTaN) and the base multilayer coating (TiAlN/TaN) with percentages of: 84/16, 66/34, 48/52 and 23/77, and evaluating their effect on mechanical and tribological performance of the nanostructured coatings. The cross-sectional images obtained by FE-SEM showed the interface between each of the constituent monolayer, a well-defined columnar structure for the TiAlN/TaN multilayer coating, while in the quaternary TiAlTaN coating thicker columns were also observed. High-resolution TEM analysis revealed well-defined multilayer architecture followed by the quaternary TiAlTaN. The nanostructured TiAlTaN-(TiAlN/TaN) coatings showed preferential growth in the direction (111) corresponding to the rock-salt-like crystalline structure of the TiN. Additionally, the shift of this peak was observed as the volume fraction of TiAlTaN decreased, associated to the decrease in the residual stresses of the coatings. Regarding tribological properties, nanostructured coatings exhibited relatively high friction coefficients (~0.8) for coatings with higher TiAlTaN volume fraction, with a clear progressive decrease as the volume fraction of multilayer TiAlN/TaN coatings increases. The high friction coefficients are compensated by the low wear rates of coatings compared to the uncoated substrate. Regarding to the mechanical properties, nanostructured coatings, follow the composite rule of mixtures, with a hardness between 32 GPa (TiAlTaN) and 25 GPa (TiAlN/TaN), Young's modulus showed similar behavior. The coatings adhesion increased progressively as the percentage of TiAlN/TaN increased, reaching L〈sub〉c3〈/sub〉 values higher than 28 N. The propagation of the transverse and longitudinal crack were observed by FE-SEM, in radial direction to the direction of application of the load and oblique direction with 45° tangential to the direction of scratching, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): J.A. Lenis, G. Bejarano, P. Rico, J.L. Gómez Ribelles, F.J. Bolívar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The use of composite coatings is emerging as a great alternative to conventional coatings, allowing the combination of different superficial properties that are widely desired in surgical implants, such as osteointegration and bactericidal character, and cannot be provided by one material alone. In the present investigation the effect of the incorporation of a TiN-Ti intermediate bilayer on the chemical composition, structure, morphology, roughness, residual stresses and adhesion of a multi-layer Hydroxyapatite (HA)-Ag coating deposited on Ti-6Al-4V by magnetron sputtering was evaluated. Additionally, the cytotoxicity of the developed system was evaluated by in vitro tests. According to the results obtained, a decrease in the Ca/P ratio from 1.85 to 1.74 was obtained through the deposition of an HA-Ag system on the intermediate bilayer, and the crystallinity of the developed coating was favored. The multi-layer structure was effectively observed by field emission scanning electron microscopy, where it was possible to identify each of the HA, Ag, TiN and Ti layers. Meanwhile, an increase of 7% in crystallite size, a decrease of 36% in residual stresses and an increase of 32% in adhesion were registered for this composite coating compared to the free intermediate bilayer system. Finally, biological evaluation allowed the non-cytotoxic character of the deposited coatings to be confirmed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology〈/p〉 〈p〉Author(s): Peng Zhou, Yang Liu, Lianhe Liu, Baoxing Yu, Tao Zhang, Fuhui Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, different pretreatment condition on AA6061 was investigated by altering the alkaline cleaning time in NaOH, the concentration and composition of acidic pickling solution, respectively. The corrosion resistance of ZrCC was evaluated, and the surface property of the pretreated surface was measured by SKPFM. Results demonstrate that a longer alkaline cleaning time is detrimental to the corrosion resistance of ZrCC since it will decrease the Volta potential difference (ΔE); the acidic pickling in HNO〈sub〉3〈/sub〉 improves the corrosion resistance of ZrCC, but an increased concentration will not remarkably further improve the quality of ZrCC, due to the accompanying of increased ΔE; the addition of HF will lead to the overactivation of alloy surface since it will decrease ΔE and increase ΔH. An ideal pretreated surface shown exhibit a combination of mediate ΔH and high ΔE.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 377〈/p〉 〈p〉Author(s): Tianshi Hu, Zhijun Shi, Wei Shao, Xiaolei Xing, Yefei Zhou, Qingxiang Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The differential charge density and density of states used to analyze the bonding of atoms at the interface, the interface adhesion and spreading coefficient of the interface were calculated by first principle method. Ni-Cr-WC and Ni-Cr-WC-CeO〈sub〉2〈/sub〉 wear resistant coatings were prepared by sintering method. The density of the coatings was measured. The morphology and elemental distribution of the coatings were observed and analyzed by the scanning electron microscope. The wear scratch morphology was observed and measured by the white confocal microscope, and the wear volume was fitted. The results of differential charge density and density of states show that there are polar covalent bonds and metal bonds at the Ni/CeO〈sub〉2〈/sub〉 interface, so the wetting tendency of Ni and CeO〈sub〉2〈/sub〉 is poor. The interfacial adhesion work is −1.63 ev/Å〈sup〉2〈/sup〉, and the spreading factor is 14.63 ev/Å〈sup〉2〈/sup〉. It indicates that Ni atoms could not spontaneously wet on the surface of CeO〈sub〉2〈/sub〉, which can improve the density of the Ni-base coating. The experimental results show that CeO〈sub〉2〈/sub〉 is distributed in the matrix of the coating. The large pores in the coating disappear, and the density of the coatings is increased from 99.89% to 99.92%. The wear volume of the coating is decreased from 14.56 × 10〈sup〉6〈/sup〉 μm〈sup〉3〈/sup〉 to 7.31 × 10〈sup〉6〈/sup〉 μm〈sup〉3〈/sup〉, which indicates that the wear resistance of the coating with CeO〈sub〉2〈/sub〉 is improved.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): X. Lu, D. Wang, D. Wan, Z.B. Zhang, N. Kheradmand, A. Barnoush〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The susceptibility of age-hardened nickel-based Alloy 718 to hydrogen embrittlement was studied by the controlled electrochemical charging combined with slow strain-rate tensile tests (SSRT) and advanced characterization techniques. We proposed some novel ideas of explaining hydrogen embrittlement mechanisms of the studied material in regard to two cracking morphologies: transgranular and intergranular cracking. It is for the first time to report that electrochemical charging alone could cause slip lines, surface and subsurface cracks on nickel-based superalloys. The formation of pre-damages was discussed by calculating the hydrogen concentration gradient and the internal stress generated during cathodic charging. Pre-damages were proved to result in transgranular cracks and lead to the evident reduction of mechanical properties. In addition, the STRONG (Slip Transfer Resistance of Neighbouring Grains) model was used to analyze the dependence of hydrogen-assisted intergranular cracking on the microscopic incompatibility of the grain boundaries. The results show that in the presence of hydrogen, grain boundaries with a lower dislocation slip transmission are more prone to cracking during loading and vice versa.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305324-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): A. Michau, Y. Gazal, F. Addou, F. Maury, T. Duguet, R. Boichot, M. Pons, E. Monsifrot, H. Maskrot, F. Schuster〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Direct liquid injection – metalorganic chemical vapor deposition (DLI-MOCVD) is the most advanced process dedicated to the internal protection of nuclear fuel cladding in accident conditions such as loss of coolant. It allows the deposition of an amorphous, glassy-like chromium carbide CrC〈sub〉x〈/sub〉 coating which is resistant against high-temperature oxidation in air and steam. Since the above-mentioned material characterizations demonstrated that coatings possessed the appropriate protection properties, the DLI-MOCVD process was scaled-up.〈/p〉 〈p〉First, a joint development between experimental and numerical studies led to a deposition inside a 1 m long cladding segment with a coating of sufficiently large and uniform thickness. Optimized reactor parameters consist in a combination of low temperature (~600 K) and low pressure (~600 Pa) with a high vapor flow rate of reactive species in the reactor ensuring a short residence time. The second phase of the scale-up consisted in coating simultaneously three, then sixteen segments in a single run. 3D computational simulations of the deposition process assisted the development of specific flanges designed to distribute homogeneously the reactive vapor into the three or sixteen cladding tubes. Experimental conditions have been extrapolated from one to three and to sixteen cladding segments, resulting in the deposition of the CrC〈sub〉x〈/sub〉 coating inside all segments with a relatively uniform partition.〈/p〉 〈p〉Overall, this paper demonstrates the feasibility of the deposition of CrC〈sub〉x〈/sub〉 coating in a bundle of several, up to sixteen, nuclear fuel cladding segments of 1 m in length (ID 8 mm), in order to protect them during accident conditions. This “batch demonstration” is a first step in the course of DLI-MOCVD technological transfer. Next step will be the deposition in a full-length cladding tube (4 m) that is already supported by numerical predictions.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 179〈/p〉 〈p〉Author(s): Amin Nozariasbmarz, Mahshid Hosseini, Daryoosh Vashaee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report that microwave radiation can decompose continuous solid-solution materials into their constituent phases – a process that is thermodynamically unfavorable at equilibrium. A detailed analysis of the interaction of the electromagnetic wave with the material showed that a strong ponderomotive force preferentially separates the constituent phases via an enhanced mass transport process amplified particularly near the interfaces. The proof of concept experiments showed that the material, whether it is a solid-solution of two elements, e.g. (Si〈sub〉1-x〈/sub〉Ge〈sub〉x〈/sub〉), or two compounds, e.g. (Bi〈sub〉2〈/sub〉Te〈sub〉3〈/sub〉)〈sub〉1-x〈/sub〉(Sb〈sub〉2〈/sub〉Te〈sub〉3〈/sub〉)〈sub〉x〈/sub〉, decomposes into the constituent phases when radiated by a polarized microwave field. The dissolution happens in the bulk of the material and even below the melting point. The degree of decomposition can be controlled by radiation parameters to produce structures composed of gradient phases of the solid-solution. This offers a novel and facile method for synthesizing gradient composite and complex structures for application in thermoelectricity as well as fabrication of core-shell structures for catalysts and biomedical applications.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419305294-fx1.jpg" width="306" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Surface and Coatings Technology, Volume 375〈/p〉 〈p〉Author(s): Sheng-Bo Hung, Chaur-Jeng Wang, Yen-Yu Chen, Jyh-Wei Lee, Chia-Lin Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High entropy alloys (HEAs) have drawn lots of attentions from researchers and industries because of their outstanding properties, such as high hardness, and good corrosion resistance. Particularly, the refractory high entropy alloy is characterized by its high temperature strength and stable thermal properties. We conducted the magnetron co-sputtering process to grow one V-Nb-Mo-Ta-W and three V-Nb-Mo-Ta-W-Cr-B refractory HEA coatings. The BCC phase of V-Nb-Mo-Ta-W HEA coating was changed into the amorphous-like structures when Cr and B elements were added into the coatings. Oxidation reactions occurred and very complex refractory metal oxides were produced on all HEA coatings when the oxidation was held at 800 °C in air for 1 h. The addition of Cr and B constituents into the V-Nb-Mo-Ta-W coating can provide good oxidation resistance and anti-corrosion performance. The highest hardness of 18.4 ± 0.5 GPa, an excellent corrosion resistance at room temperature, a high hardness of 15.9 ± 1.1 GPa and good thermal stability after 500 °C oxidation test were obtained for the V〈sub〉10.4〈/sub〉Nb〈sub〉10.5〈/sub〉Mo〈sub〉10.5〈/sub〉Ta〈sub〉11.2〈/sub〉W〈sub〉10.5〈/sub〉Cr〈sub〉16.3〈/sub〉B〈sub〉28.6〈/sub〉 refractory HEA coating in this study.〈/p〉〈/div〉 〈/div〉