ALBERT

Description: 〈h3〉Abstract〈/h3〉 〈p〉Refractory high-entropy alloys (RHEAs) are potential candidate materials for use in next-generation nuclear reactors due to their excellent mechanical performance at high temperatures. Here, we investigate the microstructure and mechanical properties of the nanocrystalline RHEA TiZrNbHfTa before and after irradiation with He〈sup〉2+〈/sup〉 ions to determine radiation-induced property changes. Using nanoindentation and in situ microtensile testing we find only small changes in hardness after irradiation but a significant increase in yield and ultimate tensile strength without loss in ductility. This is associated with radiation hardening and a shift from shear localization failure with smooth fracture surfaces to a fracture morphology consisting of fine dimples and intergranular failure characteristics. Overall, the material shows excellent damage-tolerant properties with good combinations of strength and ductility both prior to and after ion irradiation. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The present work aims to improve strength and stretch formability of rolled AZ31 sheet by two-step twinning deformation, i.e., compression (8%) along the rolling direction (RD) and subsequent tension (5%) along RD. A recrystallization annealing was carried out between two twinning deformations to avoid detwinning. It shows that two-step twinning deformation can form strong 〈em〉c〈/em〉-axis//RD texture and generate profuse crossed twin lamellae in each grain. The former can generate a refinement hardening effect to enhance the strength and the latter can contribute to a high stretch formability at room temperature. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The results of high-temperature nanoindentation testing on both a control and a neutron-irradiated silicon carbide matrix silicon carbide fiber composite sample are presented. The mechanical properties of the chemical vapor-infiltrated matrix were observed to have slightly increased in hardness and slightly decreased in elastic modulus after irradiation. Tyranno SA3 fiber behavior results are inconclusive, possibly because residual graphite in the fibers resulting from the manufacturing process produced a large scatter in the data. This work also demonstrates the capability to measure the individual components of fabricated composites at elevated temperature, which should provide inputs for modeling the macro-scale behavior of the composites.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The effects of longitudinal slots on gas evolution and bubble-driven flow in Hall–Héroult cells by a computational fluid dynamics (CFD) model have been investigated. A similar flow pattern in the anode-to-cathode distance (ACD) or spacing was shown between unslotted and slotted cases, but more complex local flow and gas evolution behavior beneath the anodes are derived from the slots. The gas accumulates in the slots/anode gaps and is released from these paths, and over 50% of gas bubbles escape from the slot tops in the slotted case. The design of the current applied slots in smelters was optimized based on CFD simulations, and it was shown that a trisected slotted design along the width direction produced the minimum ‘gas holdup’ in the ACD regions. The effects of the slot-inclined direction on bath flow and gas holdup were further investigated to quantitatively evaluate the easily made mis-operation in the anode change process during commercial production. Based on the findings of this analysis, using the horizontal slot design instead of the current typical inclined slot design is recommended, as it avoids the issue of operator error while still providing a similar benefit to the inclined slots. At the end of this paper, an industrial application of slotted anodes is discussed as an example to indicate that the slotted anode technology should be carefully applied, especially for smelters with poor quality anodes.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An FeO-SiO〈sub〉2〈/sub〉-CaO-Na〈sub〉2〈/sub〉O quaternary slag with low melting point was developed for the bath-smelting reduction of Sb〈sub〉2〈/sub〉O〈sub〉3〈/sub〉. First, the optimum composition of the designed slag was determined through practical experiments to be 36.2% FeO, 31.9% SiO〈sub〉2〈/sub〉, 12.0% CaO, and 20.0% Na〈sub〉2〈/sub〉O, such that FeO/SiO〈sub〉2〈/sub〉 was 1.14. The effects of the main variables influencing the yield and content of antimony in the smelting slag were investigated in detail for the content-optimized slag, and the following optimum smelting conditions were determined: smelting duration of 50 min, rate of coke, i.e., coke dosage of 12.5 wt.%, and smelting temperature of 1000°C. These conditions enabled high recovery of antimony, 〉 92.0%, and low antimony content in the slag of around 0.97%; the values of both these parameters are superior to those achieved by existing processes.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Liquid-phase infiltration of nickel (Ni) nanoparticles in Ni/yttria-stabilized-zirconia (YSZ) cermet anodes for solid oxide fuel cells can improve anode performance provided that the infiltrated nanoparticles on YSZ connect to form conducting pathways and the Ni nanoparticles do not coarsen significantly. This study explores liquid phase co-infiltration of Ni with mixed conducting oxides, the latter providing microstructural stability and conductive pathways between Ni nanoparticles. Two mixed conducting oxides have been studied: Gd〈sub〉0.1〈/sub〉Ce〈sub〉0.9〈/sub〉O〈sub〉2−δ〈/sub〉 (GDC), a predominantly ionic conductor, and La〈sub〉0.6〈/sub〉Sr〈sub〉0.3〈/sub〉Ni〈sub〉0.15〈/sub〉Cr〈sub〉0.85〈/sub〉O〈sub〉3−δ〈/sub〉 (LSNC), a predominantly electronic conductor. Experimental results show that both oxides improve the nickel nanoparticle stability and charge transfer kinetics. However, the electrochemical performance of the Ni-GDC-infiltrated electrode is much better than that of the Ni-LSNC-infiltrated electrode. This is attributed to the citrate–nitrate combustion reaction required to form LSNC, which fills the pores of the anode and inhibits gas diffusion, reducing the performance of the Ni-LSNC-infiltrated electrode.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An open-source fluid flow and phase-field coupled solidification model has been developed in OpenFOAM to investigate the transient nature of the interface growth direction at different degrees of undercooling for an Fe-0.15 wt.% C binary alloy under isothermal conditions. Though there are works on melt convection effects in binary alloys, none reported the transient nature of the dendrite growth direction since thermodynamic driving force decreases with time at a particular undercooling. Developing a theoretical relation will be helpful in understanding the competition between the crystallographic growth direction and solute transport. Flow decoupled simulation results have a good quantitative agreement with the literature. The bending angle formulations on the effects of flow velocity and growth speed were separated. At the end, improved theoretical formulations for estimation of the bending angle based on the anisotropy in interface energy were put forward compared with only few available empirical correlations.〈/p〉

Description: 〈p〉Gökhan Ertugrul’s name was misspelled on the original publication of this article. It appears correctly here.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉X-ray computed tomography (XCT) was used for three-dimensional (3D) visualization of the internal microstructure and quantification of the porosity and second-phase particles in Al-4.5Cu-5TiB〈sub〉2〈/sub〉 composites prepared by an in situ liquid metallurgy casting route. The as-cast composites were subjected to hot rolling and mushy-state rolling for deagglomeration and to achieve a uniform distribution of CuAl〈sub〉2〈/sub〉-TiB〈sub〉2〈/sub〉 particle clusters. Qualitative results obtained by scanning electron microscopy (SEM) and quantitative results obtained by XCT both showed that mushy-state rolling as well as hot rolling resulted in fragmentation and a homogeneous distribution of the CuAl〈sub〉2〈/sub〉-TiB〈sub〉2〈/sub〉 particle clusters, with the mushy-state-rolled composite exhibiting the highest number of smaller-size particles. The porosity was increased in both rolling conditions through debonding of particles due to the compressive force during solid-state deformation along with the quick solidification of the solute-rich liquid during mushy-state rolling. These results show that application of secondary processes such as hot-rolling and mushy-state rolling can help to achieve a relatively more uniform particle distribution in Al-4.5Cu-5TiB〈sub〉2〈/sub〉 in situ composites.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The various elemental behaviors of copper, lead and zinc in molten copper slags under an external electrical field at 1503 K are described. The molten copper slag cleaning process can be significantly improved by a vertical electric field. Compared to the natural settling process, the copper recovery rate increased from 20% to 92%. An external electric field in the slag cleaning process can accelerate the copper enrichment in the cathode and decrease its oxygen element content. In addition, the application of external electric fields can also be propitious for the removal of some heavy metal elements including zinc and lead.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉CoCrFeNiVAl〈sub〉〈em〉x〈/em〉〈/sub〉 (〈em〉x〈/em〉 values in molar ratio, 〈em〉x〈/em〉 = 0, 0.5, 1.0, 1.5 and 2.0, respectively) high-entropy alloys have been designed and prepared. Microstructure and mechanical properties of the CoCrFeNiVAl〈sub〉〈em〉x〈/em〉〈/sub〉 alloys have been studied in as-cast conditions. The fcc (face-centered cubic structure) phase and the 〈em〉σ〈/em〉 phase (intermetallic phase) have been observed in the CoCrFeNiV alloy. With the increase of Al content, the alloy structure has a tendency to change to a single stable bcc (body-centered cubic) structure. The effect of solid solution strengthening on the compressive strength of the alloy is more obvious with the addition of Al, which is the most significant in the CoCrFeNiVAl〈sub〉1.5〈/sub〉 alloy. This alloy shows good comprehensive mechanical properties, i.e., the compressive strength, plasticity and microhardness reach as high as 2140 MPa, 9.5% and 684.9 HV, respectively. High-performance CoCrFeNiVAl〈sub〉〈em〉x〈/em〉〈/sub〉 alloys are worth further study for applications of high-entropy alloys.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A low-cost flash auto-combustion technique was used to prepare Cr-doped Ag nanoparticles at 400°C. By increasing double and half Cr ions to Ag nanoparticles, a fascinating improvement in the physical properties was displayed. X-ray analysis confirmed that the samples were of single-phase spinel structure. Fourier-transform infrared analysis showed the intrinsic cation vibrations of the spinel structure. The morphology confirmed that all the samples were in the nanoscale range. The nanoparticle AgCrO〈sub〉2〈/sub〉 had saturation magnetization (〈em〉M〈/em〉〈sub〉s〈/sub〉) nearly 1.09-fold larger than that of Ag〈sub〉0.5〈/sub〉Cr〈sub〉2.5〈/sub〉O〈sub〉4〈/sub〉. However, the coercivity (〈em〉H〈/em〉〈sub〉c〈/sub〉) of the Ag〈sub〉0.5〈/sub〉Cr〈sub〉2.5〈/sub〉O〈sub〉4〈/sub〉 nanoparticles increased nearly 1.3-fold more than that of AgCrO〈sub〉2〈/sub〉. The antimicrobial activity of both samples was studied and demonstrated that nanoparticle Ag〈sub〉0.5〈/sub〉Cr〈sub〉2.5〈/sub〉O〈sub〉4〈/sub〉 is a novel material that can be added to various drugs. Consequently, the improvement of AgCrO〈sub〉2〈/sub〉 to Ag〈sub〉0.5〈/sub〉Cr〈sub〉2.5〈/sub〉O〈sub〉4〈/sub〉 nanoparticles with a superparamagnetic nature makes them suitable to be used in biomedical applications, especially antibacterial.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The mechanical and swelling properties of an elastomeric polyurethanes have been studied. The elastomers were composed of hydroxyl-terminated polybutadiene, the chain extended with either glyceryl monoricinoleate, neopentyl glycol, trimethylolpropane and cured with toluene diisocyanate and 4,4′-methylene diphenyl diisocyanate. The mineral fillers under study were nanoclay, TiO〈sub〉2〈/sub〉, ZrO〈sub〉2〈/sub〉 and ZnO. Gel fraction, crosslinking degree and average molecular weight between crosslinks were calculated from the swelling data. The hydrogen bonding index, which is a measure of hydrogen bonding, was calculated from infrared spectrophotometric data. The most remarkable result was that crosslink density diminished for a nanoclay polyurethane nanocomposite compared to an unfilled sample. Samples with nanoclay exhibited an unusual inverse correlation between crosslink density and tensile strength. Our findings showed that nanoclay in particular is an effective inorganic filler that can modulate the microstructural and mechanical behavior of polyurethane elastomers for tuned applications.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The quench sensitivity of a 7A46 aluminum alloy is studied by an interrupted quench method. The temperature–time–property (TTP) curves for the electrical conductivity and hardness are determined by measuring the as-quenched electrical conductivity and as-aged hardness, respectively. The TTP curves for the electrical conductivity and hardness all show that the nose temperature is 295°C and that the temperature zone with quench sensitivity and a fast phase transformation ranges from 265°C to 325°C. Transmission electron microscopy (TEM) images show that Al〈sub〉3〈/sub〉Zr particles and grain boundaries are preferred nucleation sites for coarse 〈em〉η〈/em〉 phases. With the extension of the isothermal holding time at 295°C, the size and density of these coarse 〈em〉η〈/em〉 phases increase, resulting in a decreasing density of GP zones and 〈em〉η〈/em〉′ phases after aging treatment, and the precipitate-free zones (PFZ) become wide. To obtain good mechanical properties of the alloy and reduce residual stress, the cooling rate should be controlled at 1°C/s in the quench-sensitive zone and appropriately reduced outside the quench-sensitive zone.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An icosahedral quasicrystal phase (I-phase)-containing Mg-8Sn-6Zn-2(wt.%)Al (TZA862) alloy was subjected to ECAP and subsequent double aging. Thereafter, the age-hardening microstructure and tensile properties of the as-ECAPed TZA862 alloy were investigated. The results indicated that the grain size, fraction and orientation of the precipitates as well as the texture were affected by the double-aging treatment, which contributed to the enhanced hardness and tensile strength. The hardening of the aged alloy was mainly ascribed to the nucleation of the precipitates on grain boundaries and the strengthening was mainly related to the Orowan mechanism.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Recent experiments have proven that the 9R phase can dramatically improve the mechanical properties of Al alloys. This work aims to investigate the effects of solute atoms on 9R phase stabilization in Al alloys through first-principles calculations. Based on two distribution models of solute atoms, namely, the uniform distribution and the Fermi–Dirac distribution models, we discuss the influences of solute concentrations and finite temperatures on the increments of intrinsic stacking fault energy in the 9R phase structure. The results reveal that high-concentration solute atoms (Ga, Ge, Sc, Si, Sn, Sr, and Y) can promote 9R phase stabilization. Among them, the Sr atom shows the highest performance, but its stabilization can be disrupted by high temperature. These findings serve as a valuable guidance for designing and using high-performance Al alloys with the 9R phase structure.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The phase, grain, orientation and local misorientation in the bonding interface of a TC17/TC4 bond at different bonding times were carefully investigated via electron backscatter diffraction technique. Dynamic recrystallization (DRX) occurred in the primary 〈em〉α〈/em〉 (〈em〉α〈/em〉〈sub〉p〈/sub〉)-enriched region of the TC4 side, in which large 〈em〉α〈/em〉〈sub〉p〈/sub〉 grains of the TC4 side transformed into small recrystallized 〈em〉α〈/em〉 grains with random orientation. With the increasing of bonding time, DRX in the 〈em〉α〈/em〉〈sub〉p〈/sub〉-enriched region of the TC4 side was more evident and the recrystallized 〈em〉α〈/em〉 grains grew. The stored energy difference between the recrystallized 〈em〉α〈/em〉 grains of the TC4 side and the 〈em〉β〈/em〉 grains/subgrains of the TC17 side provided the driving force for the migration of the interface phase boundary (IPB). In addition, the migration of IPB was promoted as the bonding time increased, which was due to the synergistic effect of the increase in the stored energy difference and the growth of the recrystallized 〈em〉α〈/em〉 grains of the TC4 side.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Ab initio density-functional theory calculations were carried out to investigate the energetics and structure of key Fe-containing intermetallic phases that precipitate from cast Al-Si alloys. These results were compared with published experimental information and used to provide insight into developing improved models to describe the thermodynamic properties of these phases. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Novel TiN-Ni cermets with high oxidation resistance and excellent electrical conductivity were developed and evaluated as intermediate-temperature solid oxide fuel cells (IT-SOFCs) interconnects. Three TiN-Ni cermets with 30 vol.%, 50 vol.% and 70 vol.% Ni were prepared by optimizing hot-pressed sintering parameters. Their oxidation kinetics was systematically investigated in air at 600–800°C. Relative density, oxidation rate constant and electrical conductivity can be readily optimized by adjusting the Ni content in the cermets, and their corresponding maximum values reached 99.6%, 2.56 × 10〈sup〉−11〈/sup〉 g〈sup〉2〈/sup〉 cm〈sup〉−4〈/sup〉 s〈sup〉−1〈/sup〉 (at 800°C) and 1.5 × 10〈sup〉4〈/sup〉 S cm〈sup〉−1〈/sup〉 (500 h oxidation reaction at 800°C). Coefficient of thermal expansion could be adjusted as well in the 9.7 × 10〈sup〉−6〈/sup〉 k〈sup〉−1〈/sup〉 to 13.2 × 10〈sup〉−6〈/sup〉 k〈sup〉−1〈/sup〉 range to match with the IT-SOFCs components. The electrical conductivity of all samples studied in this work was above 1.0 × 10〈sup〉4〈/sup〉 S cm〈sup〉−1〈/sup〉, which is much higher than that of all other cermets reported in the literature. We demonstrated that TiN-Ni cermets are promising material as candidates for IT-SOFCs interconnects.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An efficient beneficiation-hydrometallurgy combined process was proposed to treat the Jinbaoshan platinum group concentrate. The process included three steps: (1) oxygen pressure leaching of the platinum group concentrate to dissociate platinum group metals (PGMs) from base metal minerals; (2) separating PGMs from silicate minerals by physical flotation; (3) removing sulfur from the flotation concentrate by alkaline leaching. Through the beneficiation-metallurgy combined process, the grade of PGMs increased to 1193 g/t, which was 〉 27 times higher than that of the raw concentrate. The recovery of Pt and Pd was 92.29% and 90.06%, respectively. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The thermal behavior of tourmaline mineral during the whole process from solid state at room temperature to molten salt at high temperature and back to solid state at room temperature has been systematically investigated. Surface characterization based on observation of the sintering point, thermogravimetry-differential scanning calorimetry, high-temperature x-ray diffraction analysis, field-emission transmission electron microscopy, and high-temperature Raman spectrometry did not reveal any significant changes in the crystal structure of tourmaline except for a slight decrease in grain size during the heating process from room temperature to 890°C. Further increase in the temperature to 1050°C resulted in a phase transformation into cordierite along with a sharp decrease in grain size; the phase transformation was complete at 1200°C. When the temperature was decreased to 890°C, the tourmaline phase was observed to precipitate in the molten salt, and the grain size was found to grow gradually. A continuous decrease in temperature resulted in more tourmaline with slightly smaller grain size due to the pinning effect at second-phase grain boundaries.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Upgraded metallurgical grade silicon (Si) is available for high-efficiency solar cells. In the present article, Si refining with CaO-SiO〈sub〉2〈/sub〉-CaF〈sub〉2〈/sub〉 slags is carried out under open atmosphere, and orthogonal analysis is applied to evaluate the influencing factors. The results show that the influence order of the objective factors is: (1) slag/Si ratio 〉 (2) refining time 〉 (3) original slag basicity 〉 (4) CaF〈sub〉2〈/sub〉 content and that the slag/Si ratio acts as the key factor in boron removal. It is observed that boron decreases effectively within 30 min refining period. Moreover, the slags are pulverized when the basicity is 〉 1.39 because of the β-γ phase transition of Ca〈sub〉2〈/sub〉SiO〈sub〉4〈/sub〉, and the pulverization is beneficial to the separation of Si from slag.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Highly ordered ZnO-doped WO〈sub〉3〈/sub〉 thin films with good crystalline quality are prepared using radio frequency magnetron sputtering technique, and its morphological and structural properties are studied using various characterization tools such as field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction technique, micro-Raman spectroscopy, and x-ray photoelectron spectroscopy. Morphological analysis shows a smooth surface for pure film, whereas the ZnO-doped films presents a dense distribution of grains of larger sizes with well-defined grain boundary. X-ray diffraction studies reveal the enhancement of crystalline quality of the films with increase in ZnO doping concentration up to 5 wt.%, beyond which the crystalline quality gets deteriorated. A phase modification from a single monoclinic WO〈sub〉3〈/sub〉 phase to mixed monoclinic WO〈sub〉3〈/sub〉 and W〈sub〉18〈/sub〉O〈sub〉49〈/sub〉 phases is observed for films with higher ZnO doping concentrations.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The attachment of copper matte by bubbles in slags, during the copper smelting process, plays a key role in the copper loss. This paper aims to provide an in-depth insight into the copper matte entrainment by bubbles in the copper production. The bubble size distribution and matte film thickness as well as the bubble detachment height were considered based on industrial and laboratory slag samples. The results indicated that most SO〈sub〉2〈/sub〉 micro-bubbles in both slag samples were below 650 〈em〉µ〈/em〉m, which could penetrate the interface and thus transport matte into the slag phase. The matte film thickness surrounding the micro-bubbles tended to be less than 30 〈em〉µ〈/em〉m and became thinner with increasing bubble size. Furthermore, micro-bubbles larger than 350 〈em〉µ〈/em〉m could theoretically rise by 0.5 m in the slag phase even with the drag force of the matte droplets.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Extraction of scandium (Sc) from nickel processing residue using Cyanex 923 was studied. Cyanex 923 showed better selectivity for Sc compared with the other metallic components in the residue. Scandium was extracted by solvent extraction via a solvation mechanism. The aqueous-to-organic (A/O) phase ratio was set at 1:2. An increase in the scandium extraction rate was observed when increasing the concentration of H〈sup〉+〈/sup〉. Cyanex 923 was shown to be more selective for Sc than Fe. Coextracted Fe was removed from the organic phase by 3 mol L〈sup〉−1〈/sup〉 H〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉 scrubbing with Sc loss of 1.3%. Stripping of scandium from the organic phase of 84.3% was achieved using 4% oxalic acid solution. The precipitated scandium oxalate was recovered by filtration and calcination. The obtained scandium oxide presented minimum purity of 99.0%.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The work is devoted to studying the effect of a Sn trace addition on the precipitation hardening after aging of the eutectic Al-7 wt.% Si-7 wt.% Cu alloy. The addition of Sn and Si has a catalytic effect on the precipitation hardening and provides for a significantly higher hardness as compared with the binary Al-Cu alloy. The addition of 0.2 wt.% Sn leads to the formation of a substantially finer precipitation structure compared with the ternary alloy. As a result, the yield strength of the Sn containing alloy is up to 30% higher after uniaxial tensile tests. The finer precipitation structure of the quaternary alloy can be attributed to the higher stabilizing effect of Sn due to its partitioning in the 〈em〉θ〈/em〉″ and 〈em〉θ〈/em〉′ phases. The measured solubility of Sn (about 0.10 at.%) is close to the reported solubility of Si in 〈em〉θ〈/em〉′.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The need for enhanced radiation-tolerant materials for advanced nuclear energy designs has resulted in a growing number of investigations that have explored the effect of grain boundaries under irradiation. The key motivation for examining the role of grain boundaries in radiation environments is the ability to tailor grain boundary networks through either the introduction of specific grain boundaries or an increase in the grain boundary density. While traditionally thought to be efficient sinks for radiation-induced point defects, many recent experimental studies in model and pure systems have shown significant heterogeneity in grain boundary-defect interactions and associated sink efficiency as a function of grain boundary character. Furthermore, grain boundaries can migrate under irradiation, which creates an additional level of complexity. This article will provide a prospective on the experimental observations associated with defect evolution near grain boundaries including variation in sink efficiency and grain boundary mobility in radiation environments. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-TiCN-Fe composites were successfully prepared by hot pressing using natural ilmenite, aluminum, and carbon. The process of aluminothermic reduction of ilmenite and the influence of carbon on the phase evolution, synthetic products, microstructure, and properties were investigated using x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and mechanical analysis. The XRD results showed that the reduction process of the FeTiO〈sub〉3〈/sub〉-2Al system was a gradual deoxygenation process. In the FeTiO〈sub〉3〈/sub〉-2Al-〈em〉x〈/em〉C systems, carbon participates in the reduction reaction to form TiN, which gradually transforms to TiCN. The carbon content had a great influence on the presence of titanium oxides during the reaction. In addition, the grain size of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, TiCN, and Fe phases became smaller as the carbon content was increased. When the carbon content was 0.88 mol, the synthesized products achieved comprehensive mechanical properties, i.e., bending strength and Vickers hardness of 375 MPa and 15.5 GPa, respectively.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Several large ore bodies are exposed to poor environments. Thus, designing a reasonable mining scheme for the stress characteristics and stability of stope structures is essential. In this study, Fast Lagrangian Analysis of Continua 3D is used to study the stability and mechanics environment of the surrounding rock and cemented pillars in two kinds of mining scheme for continuous mining and “taking one every other one” mining. The mechanical response of stope structure to each process under different mining schemes is analyzed from the aspects of vertical stress, vertical displacement and stress distribution. The results show that, during the “taking one every other one” mining process, the maximum principal stress is between 0 MPa and 5 MPa, the vertical maximum displacement is 25 mm and the vertical stress range is 0–14 MPa. These simulation parameters are obviously better than continuous mining scheme. This mining scheme is more conducive to stope stability, increasing mine economic efficiency and ensure production safety.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The effects of Ce addition on the as-cast and as-forged microstructure of Fe-TiB〈sub〉2〈/sub〉 composites were explored. Fe-TiB〈sub〉2〈/sub〉 composites with hypereutectic concentration were formed in situ from Fe-Ti-B melts at various cooling rates with the addition of the rare-earth element Ce. The size of both primary and eutectic TiB〈sub〉2〈/sub〉 particles increased with a decrease in the cooling rate. Many clustered primary particles were found in the Ce-free specimens, while the addition of Ce significantly refined the TiB〈sub〉2〈/sub〉 particles and scattered them into a dispersed distribution. Hot forging tends to further refine the size and enhance the number density of eutectic TiB〈sub〉2〈/sub〉 particles. A decrease in interparticle spacing could be achieved by an increase of cooling rate, the addition of Ce, or hot forging. Tensile strength and hardness of the Fe-TiB〈sub〉2〈/sub〉 composites both increased with decreasing interparticle spacing in accordance with the Hall–Petch relationship. Engineering strain was enhanced by Ce addition, then further improved by hot forging, and the proportion of dimpled region in the fracture surface was improved as well. Ce addition and hot forging enhanced both the tensile strength and the ductility of Fe-TiB〈sub〉2〈/sub〉 composites.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this study, a computational model of a three-dimensional (3D) hybrid nanocomposite was analyzed using the cohesive finite element method. This model contains hard mineral nanograins bonded by a relatively soft and thin organic adhesive layer to mimic the ultrastructure of biological ceramics such as bone and nacre. The simulation results showed that the adhesive phase, which comprises only a few percent of the nanocomposite volume, significantly enhanced the toughness through widespread cohesive damage, diffuse nanocrack formation, and complex trajectories of crack growth. In addition, the 3D model revealed the strain-hardening/-softening behavior of the nanocomposite, which was not captured by two-dimensional models, highlighting the importance of 3D architecture in the mechanical behavior of the natural materials. The mechanical properties of the nanocomposite were comparable to those of bone and nacre, indicating that a damage-tolerant behavior of the natural materials can be attained by using only small amount of a tough adhesive within the 3D microstructure of brittle minerals. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The thermally and deformation-induced phase transformation behaviors of high-Mn transformation-induced plasticity (TRIP) steel are complicated when there are two unstable phases (austenite and 〈em〉ε〈/em〉-martensite) in the microstructure. To study prior warm deformation dependence on microstructural evolution and tensile properties, an austenite/〈em〉ε〈/em〉-martensite dual-phase high-Mn TRIP steel was subjected to different amounts of warm deformation. The work-hardening behavior of warm deformed steel was divided into three stages and illustrated by microstructural characterization after warm deformation and tensile fracture. The results showed that both planar glide and cross slip occurred during warm deformation of austenite, and 〈em〉ε〈/em〉-martensite, and microbands formed on the close-packed planes having higher Schmid factors. During tensile deformation at room temperature, the work-hardening exponents were associated with the dislocation slip and TRIP effect. The yield and ultimate tensile strengths of steel were increased, but the ultimate elongation was decreased with increasing strain of the prior warm deformation.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Magnesium (Mg) and its alloys degrade under physiological conditions, which makes them interesting implant materials, especially for osteosynthesis and cardiovascular applications. However, how strong is the connection between the implant, the degradation layer, and the surrounding tissue, namely bone? Considering that microscopically the interface can be separated into the border between the metal and the degradation layer, the degradation layer itself, and the border between the degradation layer and the biological environment, it is not obvious that this zone with total thickness of several tens of microns is sufficient to keep an implant in place. However, biomechanical approaches such as push-out tests have shown that a degraded Mg pin is surprisingly well connected with the bone irrespective of the fragile appearance of the degradation layer. This paper provides an overview of what is known about the interface between degrading Mg implants, cells, and bone tissue.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this work, 3D plasma-metal deposition (3DPMD) is introduced as an innovative additive manufacturing process for multi-material components. The possibility of the production of multi-material parts in a layer-by-layer design with 3DPMD was investigated. Multi-material demonstrators with a continuous transition from the super duplex steel 1.4410 to the austenitic steel 1.4404 have been prepared and investigated. By analyzing the hardness, ferrite content, mechanical-technological properties and microstructure, it was shown that the production of multi-material components using 3DPMD is possible. The properties of the transition zone lie between those of the two pure metals. The evaluation of stress–strain curves showed that the strength of the transition zone is higher than that of the austenitic material. It can be concluded that the production of graded steel structures between 1.4404 and 1.4410 using 3DPMD is possible, and mixing of the materials in the transition zone does not weaken the component. The 3DPMD process is suitable to produce functionally graded multi-material components out of metal powders.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The effect of strain rate on the work-hardening behavior of high-manganese twinning-induced plasticity (TWIP) steel has been investigated. The influence of adiabatic heating and deformation rate on the mechanical properties was studied by quasi-static and dynamic tensile tests with synchronous temperature and strain measurements. TWIP steel has excellent strain-hardening behavior under both quasi-static and dynamic loading conditions. Strain rate has negligible effects on yield and tensile strength, but the uniform and total elongation decreases under dynamic tests. TWIP steel has excellent energy absorption (EA) capacity of above 55 kJ/kg at all strain rates compared to dual-phase steels, transformation-induced plasticity steel and ferritic steels. However, the EA of TWIP steel is slightly lower compared to austenitic stainless steels. A rise in temperature due to adiabatic heating has led to the increase of stacking fault energy, thereby resulting in a change of twinning behavior or the promotion of dislocation glide under dynamic loading.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Mg/Nb nanolaminates synthesized through vapor deposition techniques exhibit high flow strength without conventional twinning in Mg. In this work, we investigated the influence of laminated microstructures on deformation mechanisms of Mg nanolayers. Using molecular dynamics simulations, we explored that (0001)-oriented Mg layers transform or re-orient to {10〈span〉 〈span〉\( \bar{1} \)〈/span〉 〈/span〉0}-oriented Mg layers through nucleation and growth of {10〈span〉 〈span〉\( \bar{1} \)〈/span〉 〈/span〉2} twins by atomic shuffling, instead of conventional {10〈span〉 〈span〉\( \bar{1} \)〈/span〉 〈/span〉2} twinning shear. Such a reorientation accommodates in-plane compressive strain and out-of-plane tensile strain when Mg/Nb laminates are subjected to compression parallel to the Mg/Nb interfaces. The nucleation of {10〈span〉 〈span〉\( \bar{1} \)〈/span〉 〈/span〉2} twins is promoted at the Mg/Nb interface due to the structural change associated with the glide of interface dislocations. The growth of {10〈span〉 〈span〉\( \bar{1} \)〈/span〉 〈/span〉2} twins is accomplished through migration of basal–prismatic boundaries via nucleation and glide of one-layer and two-layer disconnections associated with atomic shuffling. The results shed light on improving mechanical properties of hexagonal close-packed metals employing laminated structures. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Magnesium (Mg) alloys are achieving good clinical success in applications as temporary biodegradable medical implants. However, the study of the corrosion in medical environments (biocorrosion) is still ongoing. Much of this study is conducted via laboratory (i.e., in vitro) immersion tests, which can be challenging. We have outlined and updated a range of recommendations on the in vitro biocorrosion assessment of Mg alloys, based on our experience in the field and the lessons learned through years of experiments. We hope these recommendations will help to improve future biocorrosion testing and provide insight for both researchers with experience in this field and those seeking to enter it.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉ZnO nanostructures were synthesized by solvothermal (STT), solution combustion (SCT), and template synthesis (TS) techniques, showing the formation of rod-like, dot-like, and wire-like morphology. Pure-phase wurtzite structure was observed for STT and SCT samples, and mixed-phase wurtzite structure for the TS sample. Strong excitonic peaks appeared for STT and TS samples, whereas the excitonic peak tended to shift for the SCT sample. Dye-sensitized solar cell device structures using natural anthocyanin dye were fabricated and their 〈em〉I〈/em〉–〈em〉V〈/em〉 characteristics studied. The ZnO nanowire-based device showed the maximum open-circuit voltage (〈em〉V〈/em〉〈sub〉oc〈/sub〉) and short-circuit current density (〈em〉I〈/em〉〈sub〉sc〈/sub〉) in comparison with the rod-like and flake-like ZnO nanostructures. The photoconversion efficiency (PCE) was found to be 3.2%, 4.4%, and 5.4% for the rod-, dot-, and wire-like morphology, respectively. The enhancement in the PCE can be attributed to increased charge collection at the interface of the ZnO photoanode and electrolyte layer. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The effect of the prior austenite grain size (PAGS) on the tensile properties and hole expansion ratio (HER) has been investigated. Starting from different PAGS values (4.7 〈em〉μ〈/em〉m and 15.2 〈em〉μ〈/em〉m) obtained by controlling the austenitizing temperature, microstructure consisting of martensite and austenite (〈em〉V〈/em〉〈sub〉〈em〉γ〈/em〉〈/sub〉 of 0.09–0.18) was produced by the quenching and partitioning process. Increasing 〈em〉V〈/em〉〈sub〉〈em〉γ〈/em〉〈/sub〉 had a beneficial influence on the tensile elongation regardless of the PAGS, but deteriorated the HER. However, larger PGAS alleviated the degradation of the HER. The major influence of a larger PAGS on the HER results from the decreased population of interface between neighboring martensite in the shear-affected zone, because that interface is revealed to be a major site for void formation during hole expansion testing. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A heterogeneous multiphase medium Mn steel 〈strong〉(〈/strong〉Fe-10Mn-0.47C-2Al-0.7V, wt.%) consisting of prior austenite, martensite, reverted austenite, and ferrite is, for the first time, realized by both austenite reverted transformation and ferrite transformation. The phase fraction, kinetics, mechanisms, and microstructure evolution during the transformation sequence are systematically investigated. The heterogeneous multiphase medium Mn steel has great potential for high strain hardening by a continuous transformation-induced plasticity effect, grain-size gradient, and stress–strain partitioning. The present work provides a new pathway to design a heterogeneous multiphase microstructure in medium Mn steel.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A new electrotransformation process based on bubbling CO〈sub〉2〈/sub〉 into the electrolyte in an electrolytic process to cause precipitation of aluminum salt is proposed herein to solve problems such as the high energy consumption in the process of alumina extraction by acid leaching. The effects of different additives in this electrotransformation process applied to aluminum chloride solution and the resulting roasting products were studied. When using different additives (HCl, Na〈sub〉2〈/sub〉CO〈sub〉3〈/sub〉, and NaHCO〈sub〉3〈/sub〉) at an initial concentration of 10 g/L, the solution pH value and solution temperature gradually increased with increasing electrotransformation time, and the final pH value approached 3.2. The roasting products were all sheet alumina with cubic crystal structure. Use of all the additives refined the granularity of the alumina product, improved the solution conductivity, and increased the chlorine content in the alumina product. Addition of HCl improved the recovery rate of Al, but use of the additives Na〈sub〉2〈/sub〉CO〈sub〉3〈/sub〉 and NaHCO〈sub〉3〈/sub〉 greatly reduced the recovery rate of Al. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This work reports the development and testing of a magnetic polymer (Polyamide 6, PA6) nanocomposite capable of melting when exposed to an external magnetic field. Addition of high concentrations of iron oxide nanoparticles (NPs) can induce quick melting but is detrimental to the mechanical properties of the polymer. To reduce the amount of NPs required for achieving efficient melting, they should be well dispersed in the polymer. In this study, the oleic acid loading on the surfaces of the NPs was varied to study the effect of variations in coatings on the dispersion in the polymer and on the polymer melting time. The NPs functionalized with oleic acid were added to melted monomer ε-caprolactam and polymerized using ring-opening polymerization. The resulting PA6 nanocomposite was characterized by Fourier-transform infrared spectroscopy, differential scanning calorimetry, x-ray diffraction and transmission electron microscopy. The results confirmed that the PA6 nanocomposite showed a decrease of 8–10% in its glass-transition temperature compared to commercial PA6. The crystallinity of the synthesized samples were found to vary between 42% and 57%. The 55 wt.% oleic acid-loaded NPs were found to disperse most efficiently in the PA6 matrix; however, some large agglomerates were formed due to excessive oleic acid. Therefore, the 22 wt.% oleic acid coating showed overall superior dispersion. Additionally, the magnetic induction response was tested by observing a melt-characteristic of the magnetic polymer composite using a model set-up. Oleic acid concentration is found to affect the dispersion, melting time and crystallinity of the nanocomposite.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Materials exhibiting a large magnetocaloric effect (MCE) at or near room temperature are critical for solid-state refrigeration applications. The MCE is described by a change in entropy (Δ〈em〉S〈/em〉〈sub〉M〈/sub〉) and/or temperature (Δ〈em〉T〈/em〉〈sub〉ad〈/sub〉) of a material in response to a change in applied magnetic field. Ball milled materials generally exhibit smaller Δ〈em〉S〈/em〉〈sub〉M〈/sub〉 values compared to bulk; however, milling broadens the effect, potentially increasing the relative cooling power (RCP). The as-cast Gd〈sub〉5〈/sub〉Si〈sub〉4〈/sub〉 is an attractive option due to its magnetic transition at 340 K and associated MCE. Investigation of effect of particles size and transition temperature in the binary material, Gd〈sub〉5〈/sub〉Si〈sub〉4〈/sub〉, can lead to development of functionally graded bulk material with higher MCE and RCP than the traditional bulk materials. A two-step ball-milling process, in which coarse powder of Gd〈sub〉5〈/sub〉Si〈sub〉4〈/sub〉 was first milled with poly(ethylene glycol) followed by milling in heptane was used to produce fine particles of Gd〈sub〉5〈/sub〉Si〈sub〉4〈/sub〉 that showed a broad distribution in particle size. Magnetic measurement on the milled sample obtained after washing with water show a decrease in Curie temperature and significant broadening of the magnetic transition. Compared to bulk Gd〈sub〉5〈/sub〉Si〈sub〉4〈/sub〉, the maximum MCE of the milled samples is also reduced and shifted down by close to 30 K, but the MCE remains substantial over a broader temperature range. The RCP of both milled samples increased 75% from the bulk material.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉It has been experimentally demonstrated that a carbon nanostructure (CNS)-based structure, called CNS mats, can yield superior magnetic properties. The structure is obtained by decorating CNS with γ-Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 nanoparticles (NPs) in a three-dimensional (3D) network structure. γ-Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 NPs are coated on the CNS, resulting in enhanced magnetic properties. The experimental characterization and theoretical analysis reveal that CNS mats decorated with γ-Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 NPs show superior magnetic properties compared with pristine CNS, as a result of the homogeneous dispersion of γ-Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 NPs and the highly aligned structure of the CNS. The coercive field (〈em〉H〈/em〉〈sub〉c〈/sub〉), saturation magnetization (〈em〉M〈/em〉〈sub〉s〈/sub〉), and remanent magnetization (〈em〉M〈/em〉〈sub〉r〈/sub〉) were found to be 126 Oe, 22.3 emu/g, and 7.15 emu/g, respectively. In addition, scanning electron microscopy (SEM) and atomic force microscopy (AFM) characterization showed that the carbon nanotubes (CNTs) in each CNS flake within the CNS mat remained well aligned and formed an interconnected 3D network structure. This results in a robust porous structure with high electrical conductivity. Thermogravimetric analysis (TGA) revealed that the presence of the γ-Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 NPs provides a protective layer for the CNS and results in good thermal stability. The fabricated ultrathin CNS mat offers superior magnetic and electrical performance, making it an attractive candidate for microwave absorption, along with other applications such as electromagnetic shielding, sensors, lithium-ion batteries, and polymer composites. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The overarching aim of this paper is to explore the use of machine learning (ML) to predict the microstructure-sensitive evolution of a three-dimensional (3D) crack surface in a polycrystalline alloy. A convolutional neural network (CNN)-based methodology is developed to establish spatial relationships between micromechanical/microstructural features in a cyclically loaded, uncracked microstructure and the 3D crack path, the latter quantified by the vertical deviation (i.e., 〈em〉z〈/em〉-offset) of the crack along a specified axis. The proposed methodology consists of (i) a feature selection and reduction scheme to identify a lower-dimensional representation of the experimentally measured microstructure and computed micromechanical fields, which allows for computational feasibility in predicting the 〈em〉z〈/em〉-offsets; (ii) a CNN model to compute the 〈em〉z〈/em〉-offset as a function of the local, lower-dimensional feature data; and (iii) a radial basis function smoothing spline to ensure spatial continuity between the independently predicted 〈em〉z〈/em〉-offsets. The proposed CNN-based methodology is shown to improve on the accuracies obtained using existing ML models such as XGBoost and to provide a definitive way of quantifying model uncertainty associated with CNN predictions. To further investigate the applicability of ML models, multiple prediction strategies with which to deploy ML algorithms are proposed and the relative performance of ML algorithms corresponding to each prediction strategy are analyzed. The presented work thus provides a framework to find an encoded representation of 3D microstructure and micromechanical data and develop methods to predict microstructure-sensitive crack evolution based on this encoded representation, while quantifying associated prediction uncertainties.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉With the depletion of natural mineral resources, secondary resources such as zinc leaching residue (ZLR) should be processed to recover valuable metals. In this study, flotation recovery of lead (anglesite) in ZLR from a zinc smelting plant was investigated, and the mechanism studied by using Fourier-transform infrared (FTIR) spectroscopy measurements. The flotation results indicated lead recovery and grade of the concentrates of 76.39% and 47.18%, respectively, after flotation of one-roughing, one-scavenging, three-cleaning, and middles back to the flowsheet in turn after washing ZLR with tap water. FTIR measurements suggested that salicylhydroxamic acid was chemically adsorbed onto the surface of anglesite (PbSO〈sub〉4〈/sub〉). The results of this study show that lead in ZLR can be successfully recovered by flotation, having not only economic but also environmental benefits.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Nickel acetate tetrahydrate [Ni(CH〈sub〉3〈/sub〉COO)〈sub〉2〈/sub〉·4H〈sub〉2〈/sub〉O] was used as a precursor to prepare reduced graphene oxide decorated with Ni nanoparticles (Ni-rGO) by a ball milling–thermal decomposition method. Ni-rGO was characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction analysis, Fourier-transform infrared spectroscopy, and Raman spectrometry, and the adsorption energy between Ni atom and rGO was calculated based on first-principles calculations using density functional theory. The results showed that ball milling could be used to effectively restrain the agglomeration and reduce the size of rGO, and improve the adsorption energy between Ni particles and rGO. With increase of the milling time, the nucleation sites of Ni particles increased while the size of the Ni nanoparticles decreased. The thermal decomposition products of Ni(CH〈sub〉3〈/sub〉COO)〈sub〉2〈/sub〉·4H〈sub〉2〈/sub〉O in Ar atmosphere were Ni with a very small amount of carbides. Ni-rGO was obtained by reduction of GO, ball milling, and thermal decomposition processes, and the combination between Ni atom and rGO was via chemisorption. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In terms of secondary resource recovery and environmental impact, fly ash is attracting a great deal of attention in China. This study aimed to investigate the carbochlorination process of titanium oxide to recover titanium. The extraction kinetics mechanism of titanium oxide from fly ash was investigated at temperatures ranging from 850°C to 1050°C. The effect of various experimental parameters was studied. The reactants and reaction residues were analyzed by scanning electronic microscopy and chemical analysis. The results show that the best extraction efficiency of 91.66% was obtained at a temperature of 1050°C, a coking coal content of 34.64 wt.%, a pellet diameter of 8 mm, an average gas flow of 0.35 L/min, and a time of 120 min. The carbochlorination reaction of titanium oxide is controlled by the chemical reaction. The apparent activation energy is approximately 44.45 kJ/mol between 800°C and 1050°C. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A direct numerical simulation of the cyclic response of a 250-grain polycrystalline aggregate over more than 1000 cycles is presented, being one of the few available simulations including a significant number of cycles. It provides unique results on the evolution of the accumulated plastic strain and ratcheting phenomena inside the grains. Even though the average stress–strain response stabilizes after 500 cycles, unlimited ratcheting is observed at some locations close to grain boundaries and triple junctions. A clear surface effect of the ratcheting behavior is evidenced based on an appropriate combination of Dirichlet, Neumann, and periodic boundary conditions. The magnitude of the ratcheting indicator is found to be significantly higher at the free surface than in the middle section of the aggregate. Both single- and polycrystalline samples of pure tantalum are tested at room temperature for identification of the parameters in the crystal plasticity model. Special attention is dedicated to modeling the static strain aging effects observed in this material.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The interactions of moving dislocations with various point, line and planar defects during hot working of polycrystalline face-centred cubic alloys are studied. Experimental parameters from three austenitic steels and a Ni-base superalloy are integrated with a dislocation model within a multi-scale framework. The combination of these inputs is used to explain the microstructure evolution and flow behaviour through atomic-scale phenomena and their manifestation at higher length scales.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Bronze/TiO〈sub〉2〈/sub〉 composites with 5 wt.% and 20 wt.% TiO〈sub〉2〈/sub〉 were prepared by mechanical milling and densification of the corresponding powder mixtures. The milled powders were densified by two different methods. In the first process, the powders were pressureless sintered in liquid state at three different temperatures. The observations showed that just the samples with 5 wt.% TiO〈sub〉2〈/sub〉 which were sintered at 900°C were densified by liquid phase sintering and the other samples were not consolidated via the applied sintering conditions. The sintered compacts were cold-repressed for more densification under 100 MPa. In the second method, the milled powders were consolidated via spark plasma sintering without any prepressing process. The microstructural evaluations showed a fine dispersion of TiO〈sub〉2〈/sub〉 within the bronze matrix of the spark plasma sintered samples. The highest relative density (96%), hardness (320 Vickers) and flexural strength (365 MPa) corresponded to the spark plasma sintered sample with 20 wt.% TiO〈sub〉2〈/sub〉.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The effects of the grain size and thickness of Sn films on the kinetics of spontaneous Sn whisker growth have been quantitatively analyzed separately. The results reveal that the length and diameter of the whiskers are related to the parameters of the Sn film. A thicker film has a stronger influence on the whisker morphology than does the grain size. When the biaxial stress in the film reached a steady state, the growth rate was dependent on the grain size and thickness of the film. An equation is proposed to calculate the spontaneous growth rate of Sn whiskers in correlation with the dimension and microstructure of the Sn film. Spontaneous Sn whisker growth can be suppressed by increasing the thickness and grain size of the film.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper explores a formal strategy for the extraction of single-crystal elastic constants of cubic polycrystalline metals based on the optimal design of spherical indentation experiments. Recent work has formulated the extraction of elastic constants using a two-step protocol. The first step established a surrogate model to capture the dependence of the indentation elastic modulus on the grain (i.e., crystal lattice) orientation and values of single-crystal elastic constants. The second step involved the use of Markov chain Monte Carlo to establish distributions on the elastic constants consistent with experimentally measured indentation moduli in grains of different orientations. The present study refines the second step in order to sequentially identify specific grains that should be indented to provide the most utility in improving the estimated distributions on the elastic constants. The proposed workflow is demonstrated for the extraction of elastic constants for an as-cast cubic polycrystalline Fe-3%-Si sample. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The effect of Eu〈sup〉2+〈/sup〉 and Er〈sup〉3+〈/sup〉 ions on the optical characteristics of alkaline earth metasilicate perovskite synthesized via the solid-state reaction method was studied here. The ASiO〈sub〉3〈/sub〉 (〈em〉A〈/em〉 = Ca, Ba, Sr) phosphors activated with rare earth doping Eu〈sup〉2+〈/sup〉 (0–2 mol.%) and Er〈sup〉3+〈/sup〉 (0–2 mol.%) were subjected to structural, morphologic and spectroscopic studies in this work. The synthesized phosphors show a crystalline nature with appreciable phase purity and homogeneity in powder x-ray diffractometry (PXRD) analysis. The field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses showed interesting morphology and topography of the prepared phosphors. A comparative study of molecular activities of undoped and doped phosphors was done in Fourier-transform infrared (FTIR) spectroscopy. This revealed that the spectral behaviors of phosphors were strongly influenced by the impurity ions. The photoluminescent (PL) characteristics showed distinct sharp emissions in a wide spectral region of 300–500 nm under 275-nm excitation corresponding to hypersensitive transitions of Er〈sup〉3+〈/sup〉 ions and crystal field-influenced 4f–5d transitions of Eu〈sup〉2+〈/sup〉 ions. In the afterglow decay analysis of the synthesized phosphors, the luminescence lifetime varied from 11.7226 s to 13.1266 s, which confirms the occupation of shallow trapping sites by the excited electrons.〈/p〉

Description: 〈p〉Torgom K. Akopyan’s name appeared incorrectly on the original published version of this article. It is corrected here.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The article investigates the hot deformation behavior of a homogenized Mg-13Gd-4Y-2Zn-0.6Zr (GWZK1342) alloy based on isothermal compression tests. The hot deformation characterization of the GWZK1342 alloy was investigated through the work-hardening rate θ and the inflection point of ln 〈em〉θ〈/em〉 − 〈em〉ε〈/em〉 curves; thus, the critical strain model was established. Furthermore, the hot deformation map was formulated based on the critical strain, steady strain and variation of power dissipation at different deformation parameters. The optimum parameters can be determined as the process parameters corresponding to the value of ln 〈em〉Z〈/em〉 〈 40, and the dynamic recrystallization (DRX) predominately operates to accommodate plastic deformation. The kink mechanism of the long period-stacking ordered (LPSO) phase predominately operates as ln 〈em〉Z〈/em〉 exceeds 43. The broken lamellar 14H-LPSO phase can facilitate continuous DRX because of the reduced inhibition effect on lattice rotation and promote discontinuous DRX nucleation through a particle-stimulated nucleation (PSN) mechanism as ln 〈em〉Z〈/em〉 is 〈 40. 〈/p〉

Description: 〈p〉In the last paragraph of the section “SOLIDIFICATION AND THERMODYNAMIC SIMULATIONS”, the authors would like to change the sentence “Although the solvus temperature for 〈em〉δ〈/em〉 was not predicted here, it should be near the non-equilibrium solidus temperature as it forms during the terminal stages of solidification” to “Although the solvus temperature for Laves was not predicted here, it should be near the non-equilibrium solidus temperature as it forms during the terminal stages of solidification”.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A new die attach material prepared by pressing micro-sized Sn-coated Ag powders as a preform is proposed for high-temperature power device packaging. The Sn-coated Ag powders were completely transformed into Ag〈sub〉3〈/sub〉Sn with a melting point of 480°C after bonding at 250°C for 10 min, subsequently producing a bondline which can sustain a much higher temperature than the processing temperature. The detailed microstructural analysis indicates that a fine-grained full Ag〈sub〉3〈/sub〉Sn bondline with high-density twin boundaries can be formed in a short reflow time, which contributes to the improved performance of the full Ag〈sub〉3〈/sub〉Sn bondline, with an average shear strength of 37.5 MPa at 400°C. Nano-indentation testing showed that the average hardness and elasticity modulus of the prepared full Ag〈sub〉3〈/sub〉Sn bondline were 3.1 ± 0.26 GPa and 84.56 ± 6.13 GPa, respectively. The electrical resistivity was measured to be 11.42 〈em〉μ〈/em〉Ω cm. The shear strength at 400°C was kept above 20 MPa after aging at 200°C for 200 h due to the thermostability of Ag〈sub〉3〈/sub〉Sn microstructure in the bondlines.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The creep mechanisms of Sn and Sn-1.8Ag along specific orientations are investigated by the constant-strain-rate nanoindentation method. Due to the anisotropy of Sn, the mechanical behaviors could be very different along different crystal orientations. For microelectronic applications, Ag is often added to Sn to increase its strength. Data from creep test show that Ag addition increases the stress exponent by 3, which indicates that the rupture time could be extended by Ag addition. Moreover, the creep rate of Sn (100) grain is lower than that of Sn (001) grain in a low stress regime, namely, that [100] in Sn would have better creep resistance for usual applications. After indentation, transmission electron images of Sn samples show that the slip systems are 〈span〉 〈span〉\( (1\bar{1}0) \)〈/span〉 〈/span〉〈span〉 〈span〉\( [11\bar{1}] \)〈/span〉 〈/span〉 in (100) grain and (101) 〈span〉 〈span〉\( [1\bar{1}\bar{1}] \)〈/span〉 〈/span〉 in (001) grain. Lastly, Sn-1.8Ag has better performance along [100] in creep resistance due to greater hindrance of Ag atoms on dislocation motion and its critical threshold stress.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Cu/SiC〈sub〉P〈/sub〉 composites with high strength and high conductivity were prepared by in situ carbonization reaction of silicon. The Cu-Si powder and C powder were mechanically mixed, and in situ carbonized at 850°C for 48 h, then oxidation-treated in dry air atmosphere at 650°C for 8 h, followed by reduction-treating in hydrogen atmosphere at 500°C for 90 min. The results showed that some nano-scale and micron-scale SiC〈sub〉p〈/sub〉 particles as well as a small amount of nano-scale SiO〈sub〉2〈/sub〉 formed during fabrication. The tensile strength, yield strength, elongation and conductivity of the hot-extruded composite were 279 MPa, 180 MPa, 22.80% and 91.48% IACS, respectively; and those of the composite treated by cold-rolling with a reduction of 80% and then annealing at 350°C for 30 min were 425 MPa, 403 MPa, 10.85% and 90.15% IACS, respectively.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The metallographic analysis of polycrystalline gadolinium cylinders revealed a microstructural anisotropy of some included phases in the extrusion and extrusion transversal directions. The amount of those phases in the material is not significant. However, the macroscopic anisotropy of mechanical properties needs to be verified. The strain distribution during compression loading was analyzed using finite element model (FEM) simulations. A FEM for the simulation of the elasto-plastic response of the Gd cylinders was performed. For this purpose, the experimentally obtained typical flow curve in the extrusion direction was used as the input data for the FEM model. Based on the dimensional similarity of the FEM model and the measured specimens, the potential appearance of macroscopic anisotropy is evaluated. Mechanical testing using compression cigar tests, as well as FEM, did not confirm any obvious effect of the elongated inclusions on the mechanical anisotropy of the gadolinium specimens.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Manganese ore is an important mineral having a strategic role in the development of the national economy and society. In this study, the dielectric properties, heating curve, crystal structure, and reduction ratio of a low-grade pyrolusite were investigated. The dielectric constant, dielectric loss factor, and loss tangent coefficient of low-grade pyrolusite at room temperature were evaluated using the resonant cavity perturbation method, yielding values of 5.854, 0.146, and 0.0249, respectively. Owing to the excellent microwave absorption properties of low-grade pyrolusite with 10% coal (22 g), it could be heated to a temperature of 800°C within 200 s. X-ray diffraction results confirmed that MnO〈sub〉2〈/sub〉 was partially transformed into MnO at 450°C, while, at 650°C, no diffraction peak of MnO〈sub〉2〈/sub〉 was observed. At a reduction temperature of 550°C, a reduction ratio of MnO〈sub〉2〈/sub〉 to MnO of 96.65% could be achieved within a holding time of 50 min. This study demonstrates that the microwave carbothermal reduction of a low-grade pyrolusite is efficient, and thus could promote the clean production and sustainable development of the manganese industry.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Pb-based anodes with different Ag contents (0 wt.%, 0.2 wt.%, 0.4 wt.%, 0.6 wt.%, 0.8 wt.%) were prepared by the powder-processed (PP) method. Electrochemical behaviors of Pb-Ag anodes in the sulfuric acid solution were studied by performing tests of cyclic voltammetry, galvanostatic polarization and anodic polarization. Morphologies and phases of the anode oxide layer after polarization were studied by scanning electron microscopy (SEM) and x-ray diffraction (XRD), respectively. When the Ag fraction is 〉 0.4 wt.%, stable oxygen evolution potentials of PP Pb-Ag anodes are lower than those of the cast Pb-Ag (0.6 wt.%) anode. As the Ag fraction increases, the stable potential of the alloy anode decreases while average grain sizes of oxides on anode surfaces increase. However, when the Ag content is 〉 0.4 wt.%, its effect on surface grain growth becomes insignificant. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Solid oxide electrolytes showing proton transport are extensively studied materials, which can be utilised in different types of highly efficient energy systems such as solid oxide fuel cells, solid oxide electrolysis cells, membrane converters and sensors. Here we present the results of a study of the functional properties of LaYO〈sub〉3〈/sub〉-based materials, which exhibit higher chemical stability than the more well known proton-conducting electrolytes, cerates and zirconates of alkaline earth elements. The structural, ceramic, thermal and electrical properties of La〈sub〉0.9〈/sub〉Sr〈sub〉0.1〈/sub〉YO〈sub〉3–δ〈/sub〉 have been thoroughly studied depending on the partial Y substitution with some lanthanides (10 mol.% of Yb, Dy, Ho). According to the experimental data, La〈sub〉0.9〈/sub〉Sr〈sub〉0.1〈/sub〉Y〈sub〉0.9〈/sub〉Yb〈sub〉0.1〈/sub〉O〈sub〉3−δ〈/sub〉 can be considered a promising alternative to the basic oxide because of its better transport properties and the fact that there are no detrimental changes in other functional characteristics. 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Elektron21 (E21) and its composites with additions of 0.25 wt.%, 0.5 wt.%, and 1 wt.% AlN/Al nanoparticles (NPs) were fabricated by a high shear dispersion technology. Their creep properties were investigated over a stress range between 80 MPa and 140 MPa at 240°C. The grain size exhibits an obvious increase with the addition of AlN/Al NPs compared with the monolithic E21 alloy. Increasing the content of AlN/Al NPs leads to a pronounced improvement of creep resistance. Microstructural analysis shows that, with the addition of 1% AlN/Al NPs in E21, the distribution of the intermetallics Mg〈sub〉3〈/sub〉RE becomes much more homogeneous and their size is reduced. Such Mg〈sub〉3〈/sub〉RE particles can prevent the dislocation slip more efficiently during creep. Besides these Mg〈sub〉3〈/sub〉RE particles, the additional formation of Al〈sub〉2〈/sub〉RE and Al〈sub〉2〈/sub〉Zr〈sub〉3〈/sub〉 phases, which results from the reactions of AlN/Al NPs and the alloying elements Zr and REs, could act as thermal stable particles to improve the creep resistance. Finally, the remained AlN NPs without reactions are beneficial for the improvement of the creep resistance to some extent due to Orowan strengthening.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The dissolution of Cu〈sub〉2〈/sub〉O in fayalite is one of the chief processes that cause copper loss in metallurgical processes. In this paper, the interaction between fayalite and Cu〈sub〉2〈/sub〉O is systematically studied to verify the main mechanism of copper loss as well as the variation in the fayalite microstructure. The results indicate the simultaneous occurrence of melting and dissolution of copper in fayalite. The redox reaction of 〈span〉 〈span〉\( {\text{Cu}}^{ + } + {\text{Fe}}^{2 + } = {\text{Cu}} + {\text{Fe}}^{3 + } \)〈/span〉 〈/span〉 occurs in the melt phase, resulting in the generation of metallic copper and amorphous iron. The copper dissolution impacts the fayalite microscopically. With the increase of Cu〈sub〉2〈/sub〉O, the obvious phase separation is seen in the fayalite melt, and large metal particles are dispersed in the melt. In addition, the dissolution mechanism of copper and the change in the fayalite microstructure are analyzed by x-ray photoelectron spectroscopy and Raman spectroscopy. The results show that amorphous iron trapping Cu(I) and the formation of fayalite-combined copper are the most probable mechanisms for copper dissolution and the fayalite microstructure changes. These findings provide theoretical support for the secondary extraction of copper resources from copper slag.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉W/WC composite powders formed of WC ceramic particles dispersed on the surface of tungsten powders were fabricated by vapor deposition carbonization. Furthermore, W-30 wt.%Cu composites reinforced with WC ceramic particles were prepared by mechanical mixing, compacting, sintering, and infiltration. The microstructure, phase composition, and structure of the W/WC composite powders and the W-30 wt.%Cu composites reinforced with WC were characterized. The hardness, electrical conductivity, and arc erosion resistance of the W-30 wt.%Cu composites reinforced with WC were evaluated and compared with those of a conventional W-30 wt.%Cu composite. The results confirmed successful fabrication of the W/WC composite powders and W-30 wt.%Cu composites reinforced with WC. The hardness, electrical conductivity, and arc erosion resistance of the W-30 wt.%Cu composites reinforced with WC were dramatically enhanced due to the introduction of WC ceramic particles by vapor deposition carbonization.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉To develop a more benign materials production route and encourage reuse of bauxite residue produced in the Bayer process, this study aimed to recover the alkali and alumina fractions from bauxite residue by using a novel calcification–carbonization (C–C) method. The obtained dealkalized and dealuminized residue (C–C residue) was then remediated for reclamation to consume all secondary tailings. The C–C process greatly reduced the salinity and alkalinity of the bauxite residue by extracting up to 80% of the alkali and over 40% of the alumina. The Na content in the leachate decreased significantly from 1340 mg/L in the bauxite residue to 0.26 mg/L in the C–C residue. To evaluate the environmental effects of the newly produced residue, the original bauxite residue and the C–C residue were regarded as soil samples for direct comparison with a natural soil and a nutritional soil for remediation purposes.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Dielectric properties are some of the main parameters of materials, determining their interaction with electromagnetic energy during microwave heating. The dielectric properties of spent automobile catalyst were measured by using the resonance cavity perturbation technique from room temperature to 800°C at 915 MHz and 2450 MHz. The effects of temperature and frequency on the dielectric constant, dielectric loss factor, loss tangent, and penetration depth were studied. The results indicate that spent automobile catalyst is weakly polar, making it difficult to transform electromagnetic energy into heat. The relaxation time and conductivity obtained by numerical calculations further explain from the microlevel that spent automobile catalyst cannot dissipate electromagnetic energy through dipole loss or conduction loss under microwave irradiation. This work describes an effective way to explore the dielectric heating mechanism and a basis for understanding the interactions between microwaves and spent automobile catalyst.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The recovery of rare earth elements from discarded electronic waste is gaining considerable interest due to the shortage of primary resources. NdFeB permanent magnets were collected from discarded hard disc drives and consist of ~ 28% rare earth values along with 65% Fe in the form of the Nd〈sub〉2〈/sub〉Fe〈sub〉14〈/sub〉B phase. The magnets were demagnetized, crushed and exposed to microwave irradiation for a predetermined time. It was found that, within 1.2 min of microwave exposure, significant oxidation and a temperature of ~ 600°C was attained. Recovery from the microwave-exposed product was carried out by the leaching and precipitation route. Iron values were recovered in the form of metallic iron and iron oxide in the leach residue. The process adopted is very short and yielded 56% recovery of Nd and Dy oxides with a purity of more than 98%.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A study has been carried out on the elastic modulus of cast ternary Ti-15Mo-W alloys (containing 4 up to 11 wt.% W). Tungsten was added to the Ti-15Mo alloy to improve the mechanical properties. The influence of tungsten content on the elastic modulus is discussed more thoroughly, along with other mechanical properties. Samples were obtained by successive melting using pure metals in vacuum arc re-melting equipment. The alloy microstructure proved to be homogeneous showing the β-phase predominance. The modulus of elasticity was determined by mechanical compression tests. The samples showed no cracks, having super-plasticity characteristics similar to other titanium alloys. According to the tests, the samples showed good mechanical properties. The values obtained ranged from 248–327 HV for microhardness, 782–921 MPa for compressive strength and 17.86–45.35 GPa for the elastic modulus. 〈/p〉