ALBERT

Description: The precipitates, magnetism, and corrosion resistance of Fe 78 Si 9 B 13 glassy samples fabricated in vacuum and air atmospheres (labeled as VAC and AIR samples, respectively) were studied. The findings show that the fraction of the amorphous phase in VAC samples is lower than that in the AIR counterparts. The Fe phase in VAC samples grows preferentially along the 〈200〉 orientation. The distribution of magnetization M 4000 of VAC samples oriented parallel and orthogonal to the field ( H // and H ⊥ ) at H = 4000 Oe is more scattered than AIR samples. The corrosion resistance of VAC samples is lower than AIR counterparts, which can be attributed to the minor alloying effect of oxygen and the passive effect of silicon atoms supplied from the amorphous phase.

Description: Al-Si alloy A356 was modified by TiC nanoparticles. First, the nanoparticles were mechanochemically activated together with aluminum powder. Next, the activated particles were hot extruded in a home-made extruder. Finally, nanoparticles thus prepared in the aluminum matrix were added to the liquid Al-Si alloy, which was then cast into sand molds. A comparison of the microstructure and mechanical properties of the modified alloy thus produced with those of the alloy without the nanoparticles demonstrated that the grain size of the modified alloy decreased. The mechanical properties determined after T6 heat treatment indicated unusual behavior, where the elongation of the modified alloys increased by 20 to 50 pct in different regions of the cast, while the tensile strength remained unchanged and the hardness increased by 18 pct. An electron microscopy study revealed concentration of dislocations near grain boundaries in the modified alloy samples. These grain boundaries serve as obstacles to dislocation motion. It was therefore concluded that the improvement in the mechanical properties of the aluminum alloy modified by TiC nanoparticles was caused by the grain-size-strengthening mechanism.

Description: Martensite pole figures from three different steels have been studied using electron backscatter diffraction (EBSD) and mathematical models to show that the two stage transformation theory is not necessary for correct prediction of pole figure and popular orientation relationships, like Kurdjumov–Sachs. These theories can give misleading prediction. It has been proved that the use of correct crystallographic data can lead to a better texture prediction. The typical features of a pole figure in a {2 5 2} γ habit system have been studied in detail.

Description: Friction stir welding (FSW) of Al - Li alloy 2195 plate produces strong texture gradients. The microstructural characteristics evolve from the base plate, through the thermomechanically affected zone (TMAZ), to the weld nugget interface. In the current study, electron backscattered diffraction (EBSD) analyses were employed to quantify the spatial distribution of texture gradients associated with the evolution of texture within the TMAZ. The strong texture of the base plate enabled the texture evolution to be characterized as a function of location. Systematic partitioning of EBSD data relative to the degree of lattice rotation at each point accurately captured the crystallographic transitions across the advancing side TMAZ. Over a large section of this region, the texture evolves as a result of continuous rigid body rotations. The rigid body rotations were correlated with the complex material flow patterns commonly associated with the FSW process and prior observations of shear-related textures. Finally, a correlation between texture and fracture in a subscale tensile specimen is observed, where failure occurs within a visible band of low-Taylor factor grains.

Description: Sulfidation may occur even in an overall oxidizing environment beneath a corrosion product which assumes the role of a diffusion barrier allowing sulfur species transport at a faster rate when compared with that of oxygen species. The current paper presents sulfidation characteristics of an advanced single-crystal nickel-based superalloy (ANS) and compares performance with IN 792 and CMSX-4 superalloys. The results showed that all the superalloys were highly vulnerable to sulfidation and their lives were significantly reduced. Among them, the ANS was more susceptible to sulfidation and its life was reduced considerably. This is attributed to the changed chemistry of the advanced alloy. The results for ANS are compared with its oxidation data and the difference in its behavior is discussed. A degradation mechanism, which represents the deterioration of ANS under sulfidation conditions, is proposed based on the results obtained from different techniques. Finally, the necessity of protective coatings for shielding against high temperature sulfidation for potential application in enhanced efficiency of gas turbine engines is emphasized.

Description: A model is proposed to predict the room temperature austenite volume fraction as a function of the intercritical annealing temperature for medium Mn transformation-induced plasticity steel. The model takes into account the influence of the austenite composition on the martensite transformation kinetics and the influence of the intercritical annealing temperature dependence of the austenite grain size on the martensite start temperature. A maximum room temperature austenite volume fraction was obtained at a specific intercritical annealing temperature T M . Ultrafine-grained ferrite and austenite were observed in samples intercritically annealed below the T M temperature. The microstructure contained a large volume fraction of athermal martensite in samples annealed at an intercritical temperature higher than the T M temperature.

Description: Controlled rolling followed by accelerated cooling was carried out in-house to study the microstructure and mechanical properties of a low carbon dual-phase steel. The objective of the study described here was to explore the effect of cooling schedule, such as air cooling temperature and coiling temperature, on the final microstructure and mechanical properties of dual-phase steels. Furthermore, the precipitation behavior and yield ratio are discussed. The study demonstrates that it is possible to obtain tensile strength and elongation of 780 MPa and 22 pct, respectively, at the two cooling schedules investigated. The microstructure consists of 90 pct ferrite and 10 pct martensite when subjected to moderate air cooling and low temperature coiling, such that the yield ratio is a low 0.69. The microstructure consists of 75 pct ferrite and 25 pct granular bainite with a high yield ratio of 0.84 when the steel is directly cooled to the coiling temperature. Compared to the conventional dual-phase steels, the high yield strength is attributed to precipitation hardening induced by nanoscale TiC particles and solid solution strengthening by high Si content. The interphase precipitates form at a suitable ledge mobility, and the row spacing changes with the rate of ferrite transformation. There are different orientations of the rows in the same grain because of the different growth directions of the ferrite grain boundaries, and the interface of the two colonies is devoid of precipitates because of the competitive mechanisms of the two orientations.

Description: The goal of this work was to identify the inclusions in lamellar graphite cast iron in an effort to explain the nucleation of the phases of interest. Four samples of approximately the same carbon equivalent but different levels of sulfur and titanium were studied. The Ti/S ratios were from 0.15 to 29.2 and the Mn/S ratios from 4.2 to 48.3. Light and electron microscopy were used to examine the unetched, color-etched, and deep-etched samples. It was confirmed that in irons with high sulfur content (0.12 wt pct) nucleation of type-A and type-D graphite occurs on Mn sulfides that have a core of complex Al, Ca, Mg oxide. An increased titanium level of 0.35 pct produced superfine interdendritic graphite (~10  μ m) at low (0.012 wt pct) as well as at high-S contents. Ti also caused increased segregation in the microstructure of the analyzed irons and larger eutectic grains (cells). TiC did not appear to be a nucleation site for the primary austenite as it was found mostly at the periphery of the secondary arms of the austenite, in the last region to solidify. The effect of titanium in refining the graphite and increasing the austenite fraction can be explained through the widening of the liquidus-eutectic temperature interval (more time for austenite growth) and the decrease in the growth rate of the graphite because of Ti absorption on the graphite. The fact that Ti addition produced larger eutectic cells supports the theory that Ti is not producing finer graphite because of a change in the nucleation potential, but because of lower growth rate of the graphite in between the dendrite arms of a larger fraction of austenite. In the presence of high-Ti and S, (MnTi)S star-like and rib-like inclusions precipitate and act as nuclei for the austenite.

Description: This research work studied the effect of boron additions (14, 33, 82, 126, and 214 ppm) on the hot ductility behavior of a low carbon advanced ultra-high strength steel. For this purpose, specimens were subjected to a hot tensile test at different temperatures [923 K, 973 K, 1023 K, 1073 K, 1173 K, and 1273 K (650 °C, 700 °C, 750 °C, 800 °C, 900 °C, and 1000 °C)] under a constant true strain rate of 10 −3  s −1 . The reduction of area (RA) of the tested samples until fracture was taken as a measure of the hot ductility. In general, results revealed a marked improvement in hot ductility from 82 ppm B when the stoichiometric composition for BN (0.8:1) was exceeded. By comparing the ductility curve of the steel with the highest boron content (B5, 214 ppm B) and the curve for the steel without boron (B0), the increase of hot ductility in terms of RA is over 100 pct. In contrast, the typical recovery of hot ductility at temperatures below the Ar 3 , where large amounts of normal transformation ferrite usually form in the structure, was not observed in these steels. On the other hand, the fracture surfaces indicated that the fracture mode tends to be more ductile as the boron content increases. It was shown that precipitates and/or inclusions coupled with voids play a meaningful role on the crack nucleation mechanism, which in turn causes hot ductility loss. In general, results are discussed in terms of boron segregation and precipitation on austenitic grain boundaries during cooling from the austenitic range and subsequent plastic deformation.

Description: Intergranular cracking and void nucleation occur over extended periods of time in alloy 617 when subjected to stress at high temperatures. Damage occurs inhomogeneously with some boundaries suffering failure, while others are seemingly immune to creep. Crack propagation associated with grain size, and grain boundary character was investigated to determine which types of grain boundaries are susceptible to damage and which are more resistant. Electron backscatter diffraction and a stereological approach to obtain the five-parameter grain boundary distribution were used to measure the proportions of each type of boundary in the initial and damaged structures. The samples were crept at 1273.15 K (1000 °C) at 25 MPa until fracture. It was found that in addition to low-angle and coherent twin boundaries, other low index boundary plane grain boundaries with twist character are relatively resistant to creep.

Description: Microstructural characterization was used to examine the changes that occur in an Mg-6Sn-5Zn-0.3Na alloy from casting to extrusion at either 623 K or 723 K (350 °C or 450 °C) followed by artificial aging at 473 K (200 °C). In particular, the partitioning of Na was examined at each step using STEM-EDS mapping. Na atoms were found to preferentially partition to the Mg-Zn phase when present. After extrusion, when no Mg-Zn was observed, the spherical Mg 2 Sn particles were found to be enriched in Na, particularly at the higher extrusion temperature. Artificial aging following extrusion resulted in a change in Na partitioning, and a coarse distribution of Mg-Zn precipitate rods. Na microadditions led to a high as-extruded hardness, but a significant tension–compression yield asymmetry was still observed at room temperature. The compressive yield strength was found to decrease significantly after 1000 hours of aging.

Description: A metallographic method was used to determine the solvus temperature of β phase in 5083 aluminum alloy. For a more accurate investigation, experiments were carried out from two directions. Consequently, the first reported actual solvus temperature of the Mg-rich phase in the alloy was determined to be 562.5 ± 1.5 K (289.5 ± 1.5 °C), which was 50 K (50 °C) higher than that of the commonly accepted value of the alloy 5083 deduced from the binary phase diagram. A new Cu-bearing phase in the alloy was also first identified metallographically with scanning electron microscopy and its implications in determining the β solvus temperature were discussed.

Description: The durability against electromigration of an annealing twinned Ag-8Au-3Pd wire is about double that of the conventional grained wire under electrical current stressing of 1.23 × 10 5  A/cm 2 . During electromigration, a particular morphology of surface reconstruction comprising a stepwise structure and hillocks can be observed in this annealing twinned wire. The stepwise structure, which has been correlated to longer electromigration life, is postulated to result from dislocation slips driven by electron wind collisions and thermal diffusion of metallic atoms. The simultaneous processes of primary and secondary slips in crossing directions cause hillocks to form at the intersections of both slips. The results also indicated that the electrical current could enhance the grain growth in both wires but had an insignificant effect on the formation of annealing twins.

Description: Carbon enrichment in the austenite transformed from martensite during intercritical annealing was measured by electron probe microanalyzer and three-dimensional atom probe microscopy in Fe-2Mn-0.3C and Fe-0.35C alloys. At early stages of the transformation, negligible Mn partitioning occurs, and carbon content in austenite is higher than orthoequilibrium and paraequilibrium predictions. This is presumably attributed to finite intrinsic interface mobility and/or solute drag effect. The resultant free energy dissipation at interface was estimated.

Description: Nanocrystalline neodymium-doped ceria solid solutions with Nd 3+ concentrations varying from 4 to 20 mol pct have been synthesized by gel combustion method, using urea-formaldehyde as fuel for Nd doping. The combustion reaction is explained through differential scanning calorimetry (DSC)-differential thermogravimetric analysis (TGA), whereas the synthesized materials are characterized through X-ray diffractometry (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The phase obtained from the exothermic reaction contains Nd-substituted CeO 2 . The deviation of the lattice parameter from Vegard’s law and the decrease in crystallite size with dopant concentration has been explained. The as-synthesized particles are largely nanoporous single crystallites, existing in loosely held spherical-shaped agglomerates. The size of the agglomerates increases with increasing dopant content. High-resolution TEM (HRTEM) reveals the fact that the unit cells are strained.

Description: The three-dimensional morphologies of the Fe-bearing intermetallics in a semisolid-processed Al-Mg-Si alloy were examined after extracting the intermetallics. α c -AlFeSi and β -AlFeSi are the major Fe-bearing intermetallics. Addition of Al-Ti-B grain refiner typically promotes β -AlFeSi formation. β -AlFeSi was observed with a flat, plate-like morphology with angular edges in the alloy with and without grain refiner, whereas α c -AlFeSi was observed as “flower”-like morphology in the alloy with grain refiner.

Description: The competitive grain growth in bicrystal samples during unidirectional solidification of a Ni-based superalloy was found to depend on secondary dendrites perpendicular to the grain boundary of bicrystal samples, rather than primary dendrites parallel to the thermal gradient as generally recognized. The primary dendrite orientation, however, had significance for the dendrite blocking in overgrowth processes and the resultant overgrowth rate during competitive grain growth.

Description: Additive-manufactured aluminum alloy deposits were analyzed using neutron diffraction to characterize the effect of intermediate stress relief anneal heat treatment on bulk residual stresses in the final part. Based on measured interplanar spacing, stresses were calculated at various locations along a single bead, stacked wall deposit. A comparison between an uninterrupted deposited wall and an interrupted, stress-relieved, and annealed deposited wall showed a measureable reduction in residual stress magnitude at the interface with a corresponding shift in stress character into the deposit. This shift changes the interface stresses from purely compressive to partially tensile. The residual stress profile varied along the length of the deposit, and the heat-treatment procedure reduced the overall magnitude of the stress at the interface by 10 through 25 MPa. These results are interpreted in terms of thermal gradients inherent to the process and compared with prior residual stress-characterization studies in additive-manufactured metallic structures.

Description: Microstructure, texture, and microtexture in Ti-6Al-2Sn-4Zr-2Mo-0.1Si billet/bar of three different diameters (57, 152, and 209 mm) were quantified using backscattered electron imaging and electron backscatter diffraction. All three billets exhibited a microstructure comprising a large fraction (≥70 pct) of primary alpha particles, the average size of which decreased and aspect ratio increased with increasing reduction/decreasing billet diameter, or trends suggestive of low final hot working temperatures and/or slow cooling rates after deformation. Appreciable radial variations in the volume fraction and aspect ratio of alpha particles were noticeable only for the smallest-diameter billet. Alpha-phase textures were typical of axisymmetric deformation, but were relatively weak (~3× random) for all billet diameters. By contrast, bands of microtexture, which were multiple millimeters in length along the axial direction, were relatively strong for all of the materials. The intensity and radial thickness of the bands tended to decrease with decreasing billet diameter, thus indicating the important influence of imposed strain on the elimination of microtexture and the possible influence of surface preform microstructure following the beta quench on the evolution of microstructure and microtexture.

Description: Twin roll casting has been used to produce sheet of Mg 60 Cu 29 Gd 11 bulk metallic glass (BMG). Sheet can be produced with thicknesses between 1 and 4 mm, the width of sheet produced can be between 25 and 75 mm. The dimensional stability of the produced sheet in a cast run is ±1 mm in the width direction and ±0.05 mm in the thickness direction. As with all magnesium-based BMGs the sheet produced is strong yet brittle at room temperature. The maximum flexural stress of a twin roll cast Mg 60 Cu 29 Gd 11 BMG strip is 150 MPa with a flexural strain of 0.005. The Charpy impact energy of a Mg 60 Cu 29 Gd 11 BMG strip is 0.02 J. In order to improve the toughness values of the Mg 60 Cu 29 Gd 11 , BMG strip laminates of BMG and aluminum alloy (UNS A91100) were produced via roll bonding. The introduction of aluminum layers to the sheet structure provides a barrier to shear band movement stopping the sudden catastrophic failure of the sheet. After rolling the BMG was examined via X-ray diffraction (XRD) to confirm that the BMG layer remained amorphous. The flexural stress, flexural strain, and Charpy impact energy properties of BMG-Al laminates are improved when compared to monolithic glass properties. The flexural stress values for laminates compared to the monolithic glass improve by 60 pct from 150 to 250 MPa. The flexural strain values improve by over an order of magnitude from 0.005 to 0.14. The Charpy impact energies increase by 2 orders of magnitude from 0.02 to 2.5 J.

Description: Coarse-grained commercially pure Cu was subjected to equal channel angular pressing at room temperature for 2 passes and 12 passes resulting in grain refinement down to the ultrafine scale. Uniaxial tensile testing revealed that as-ECAP Cu samples have very high strength, but low uniform elongation and elongation to failure, whereas small punch testing showed that strain in biaxial stretching of the as-ECAP Cu specimens was comparable to that in the coarse-grained Cu. Analysis of surface relief demonstrated extensive microlocalization of plastic flow into microshear bands during biaxial stretching of the as-ECAP Cu specimens. The effect of microstructure and stress state on formability of the material and the mechanisms governing its plastic deformation are discussed. It is suggested that although the high strength as-ECAP Cu exhibits poor ductility in uniaxial tension, in other strain paths such as biaxial stretching, it can show high formability which is sufficient for metal-forming processes.

Description: Two nickel-base superalloys are joined via transient liquid phase (TLP) bonding with boron as the MPD. Boride formation is observed in the parent materials at some distance from the solid/liquid interface. The boron concentration profile over the joint is measured with glow discharge optical emission spectroscopy (GDOES). Boron concentration peaks are observed corresponding to the boride formation. Boron distribution is discussed on the basis of theoretical predictions in the literature. It is concluded that diffusion of another element is necessary to explain the results with the second element influencing the solubility of boron.

Description: Microstructure evolution of a low-carbon steel with the initial microstructure of ferrite matrix plus cementite particles during hot compression deformation was investigated at the strain rates of 0.001 s −1 , 0.01 s −1 , and 1 s −1 at 973 K (700 °C) by means of field-emission scanning electron microscope, electron backscattered diffraction, and transmission electron microscopy. The results indicated that dynamic recrystallization (DRX) of ferrite took place at all of three strain rates, which can be classified as discontinuous DRX at 0.001 s −1 , 0.01 s −1 , and as continuous DRX at 1 s −1 . The formation of the nuclei of DRX of ferrite was mainly ascribed to the occurrence of particle-stimulated nucleation (PSN), accompanied with the lattice rotation and the formation of new high-angle boundaries. The occurrence of PSN was dependent on the development of a subgrain in the regions with high density of dislocations around cementite particles, without the need for the formation of the deformation zone.

Description: The primary transformation kinetics of nanoicosahedral quasicrystalline (QC) phase formation were investigated in Zr 65 Al 7.5 Ni 10 Cu 12.5 Pd 5 bulk metallic glass (BMG) in various relaxation states. A less relaxed (unrelaxed) BMG exhibited higher activation energy for atomic diffusion in the glassy structure than that of a relaxed one, which represents a change in the nucleation and grain growth kinetics of the primary phase with the relaxation state. Actually, the grain growth rate of a QC particle near the crystallization temperature was approximately 1 × 10 −9  m/s in the less relaxed BMGs, which was less than half of that in the relaxed BMGs. In contrast, the calculated homogeneous nucleation rate significantly increased in the less relaxed samples. It increased with the volume fraction transformed in the early stage. It is concluded that the relaxation state of glassy alloys markedly affects the primary transformation kinetics. The current study also indicates a necessity of development of the relaxation state for structure controlling in industrial applications of BMGs.

Description: It has been well known that the flaking failure in rolling contact fatigue (RCF) originates from nonmetallic inclusions in steels, and their apparent size is one of the important factors affecting RCF life. However, the influence of inclusion shape on the RCF life has not been fully clarified. In this study, attention was paid to the influence of the inclusion shape on the RCF life. This was evaluated by using carburized JIS-SCM420 (SAE4320) steels that contained two different shapes of MnS—stringer type and spheroidized type—as inclusions. Sectional observations were made to investigate the relation between the occurrence of shear crack in the subsurface and the shape of MnS. It was found that the RCF life was well correlated with the length of MnS projected to the load axis, and the initiation of shear crack in subsurface was accelerated as the length of MnS increased.

Description: There is a growing demand for single-use disposable polymer devices with features at submicron scales. This requires resilient tooling which can be patterned to scales of the order of hundreds of nanometers. The requisite topology can be imparted to silicon, but it is too brittle to be of use in a die to mold thousands of plastic parts. The polycrystalline nature of tool steel means that it cannot be patterned with submicron detail. Some bulk amorphous alloys have the requisite mechanical properties to be viable as materials for such dies, and can be patterned— e.g. , via embossing as a supercooled liquid into MEMS silicon or using focused ion beam (FIB)—with submicron features which may persevere over many thousands of molding cycles. The composition of the amorphous alloy must be carefully selected to suit the particular molding application (polymer/process). The state-of-the-art methodology is presented, along with results of our recent experimental investigations.

Description: The fracture of eutectic Si particles dictates the fracture characteristics of Al-Si based cast alloys. The morphology of these particles is found to play an important role in fracture initiation. In the current study, the effects of strain rate, temperature, strain, and heat treatment on Si particle fracture under compression were investigated. Strain rates ranging from 3 × 10 −4 /s to 10 2 /s and three temperatures RT, 373 K, and 473 K (100 °C and 200 °C) are considered in this study. It is found that the Si particle fracture shows a small increase with increase in strain rate and decreases with increase in temperature at 10 pct strain. The flow stress at 10 pct strain exhibits the trend similar to particle fracture with strain rate and temperature. Particle fracture also increases with increase in strain. Large and elongated particles show a greater tendency for cracking. Most fracture occurs on particles oriented nearly perpendicular to the loading axis, and the cracks are found to occur almost parallel to the loading axis. At any strain rate, temperature, and strain, the Si particle fracture is greater for the heat-treated condition than for the non-heat-treated condition because of higher flow stress in the heat-treated condition. In addition to Si particle fracture, elongated Fe-rich intermetallic particles are also seen to fracture. These particles have specific crystallographic orientations and fracture along their major axis with the cleavage planes for their fracture being (100). Fracture of these particles might also play a role in the overall fracture behavior of this alloy since these particles cleave along their major axis leading to cracks longer than 200 μm.

Description: In the present study, surface melting of a magnesium alloy, ZE41, was performed with an Nd:YAG laser using different laser parameters. The microstructure of the laser-treated and untreated specimens was analyzed by optical and scanning electron microscopy and X-ray diffraction. Corrosion resistance of the different laser-treated specimens along with the untreated alloy was characterized using electrochemical impedance spectroscopy and weight loss measurements in 0.001 M sodium chloride solution. Although the laser processing parameters influenced the microstructure and the melt depth of the laser-treated zone, these had little effect on the corrosion resistance of the alloy.

Description: In this paper, effects of cooling rates on glass formation and magnetic behavior of the Fe 73.0 C 7.0 Si 3.3 B 5.0 P 8.7 Mo 3.0 (at. pct) alloy were investigated via different purging gases ( i.e. , helium and argon) during suction casting. X-ray diffraction patterns and transmission electron microscopy characterization confirmed that the maximum attainable diameter for glass formation is increased from 5 to 7 mm with the helium as the purging gas, relative to the argon. Meanwhile, the coercivity value ( H c ) of the sample cast in helium is almost 5 times larger than that fabricated in argon, although the magnetization saturation in these two alloys is similar. Our pair distribution function analysis, density, and positron annihilation lifetime spectroscopy measurements indicated that the sample cast in helium possesses more free volume; however, the difference between them is insubstantial. Further, experimental results revealed that the residual stress in the samples cast under helium is much larger than that in those prepared in Argon, which could be responsible for the abrupt change in the coercivity.

Description: The effect of annealing temperature on the crystallinity, thermoelectric properties, and surface morphology of the Bi 0.5 Sb 1.5 Te 3 thin films prepared on SiO 2 /Si substrate by radio-frequency (RF) magnetron sputtering was investigated using X-ray diffraction (XRD), the four-point probe method, and scanning electron microscopy (SEM). XRD results show that the crystallite structure of the Bi x Sb 2– x Te 3 thin films belong to Bi 0.5 Sb 1.5 Te 3 . When the Bi x Sb 2– x Te 3 thin films were annealed between 423 K and 523 K (150 °C and 250 °C) for 10  minutes, the crystallinity of the thin films continuously increases with the temperature increase. In addition, the (015) reflection plane as the preferred orientation and the oxidation compound of Bi 3.73 Sb 1.5 O 3 first appeared when the Bi 0.5 Sb 1.5 Te 3 thin films were annealed at 523 K (250 °C) for 10 minutes. An activation energy of 51.66 kJ/mol for crystallite growth of Bi 0.5 Sb 1.5 Te 3 thin films annealed between 423 K and 523 K (150 °C and 250 °C) for 10 minutes was obtained. The resistivity was 2.69 × 10 2 and 5.93 × 10  μ Ω·m, respectively, for the as-deposited Bi 0.5 Sb 1.5 Te 3 thin films and annealed at 523 K (250 °C) for 10 minutes. The maximum values of the Seebeck coefficient and power factor were 256.5  μ V/K and 1.12 × 10 3   μ W/m·K 2 , respectively, for the Bi 0.5 Sb 1.5 Te 3 thin films annealing treatment at 523 K (250 °C) for 10 minutes.

Description: The accurate prediction of alloys’ properties introduced by heat treatment has been considered by many researchers. The advantages of such predictions are reduction of test trails and materials’ consumption as well as time and energy saving. One of the most important methods to predict hardness in quenched steel parts is Quench Factor Analysis (QFA). Classical QFA is based on the Johnson–Mehl–Avrami-Kolmogorov (JMAK) equation. In this study, a modified form of the QFA based on the work by Rometsch et al. is compared with the classical QFA, and they are applied to prediction of hardness of steels. For this purpose, samples of CK60 steel were utilized as raw material. They were austenitized at 1103 K (830 °C). After quenching in different environments, they were cut and their hardness was determined. In addition, the hardness values of the samples were fitted using the classical and modified equations for the quench factor analysis and the results were compared. Results showed a significant improvement in fitted values of the hardness and proved the higher efficiency of the new method.

Description: In this paper, the evolution of work-hardening and dynamic recovery rates vs the flow stress increase ( σ  −  σ y ) in Al-Mg-Si alloys is presented. The experimental data have been extracted from stress–strain curves. All curves show an initial very rapid decrease in slope of the σ –ε curve, which is associated with the elastic–plastic transition. After the elastic–plastic transition, there are typically two distinctive behaviors. For underaged alloys, there is an approximately linear decrease of work-hardening rate as ( σ  −  σ y ) increases. However, for overaged alloys after elastic–plastic transition, there is a plateau in the work-hardening rate followed by an almost linear decrease. The maximum work-hardening and dynamic recovery rates are found to be dependent on the aging state. In order to investigate these phenomena, a model has been employed to simulate the work-hardening behavior of Al-Mg-Si alloys. The model is based on a modified version of Kocks–Mecking–Estrin (KME) model, in which there are three main components: (1) hardening due to forest dislocations, grain boundaries, and sub-grains; (2) hardening due to the precipitates; and (3) dynamic recovery. The modeling results are discussed and compared with the experimental data.

Description: The effect of cobalt on bainite kinetics formation in a 1C-1.5Si wt pct steel is investigated. Two laboratory casts were manufactured with no or 2.5Co wt pct. Bainite transformation kinetics at 493 K, 523 K, and 573 K (220 °C, 250 °C, and 300 °C) were measured using dilatometry. Careful control of the alloy composition, in particular with respect to carbon content, allowed unambiguous identification of the expected accelerating effect of Co. This effect was quantified and compared to that of other possible alloying additions. It is shown that Co has an acceleration effect of around 18 to 29 pct (per wt pct added) for bainite formation between 220 °C and 300 °C. Comparison with published data indicates that this influence is orders of magnitude smaller than that achieved through reduction of C, Mn, or Cr. The influence on hardness is quantified and shown to be significant, and possible origins for hardening are discussed.

Description: In the present study, the diffusion bonding of 17-4 precipitation hardening stainless steel to Ti alloy with and without nickel alloy as intermediate material was carried out in the temperature range of 1073 K to 1223 K (800 °C to 950 °C) in steps of 298 K (25 °C) for 60 minutes in vacuum. The effects of bonding temperature on interfaces microstructures of bonded joint were analyzed by light optical and scanning electron microscopy. In the case of directly bonded stainless steel and titanium alloy, the layerwise α -Fe + χ, χ, FeTi + λ, FeTi +  β -Ti phase, and phase mixture were observed at the bond interface. However, when nickel alloy was used as an interlayer, the interfaces indicate that Ni 3 Ti, NiTi, and NiTi 2 are formed at the nickel alloy-titanium alloy interface and the PHSS-nickel alloy interface is free from intermetallics up to 1148 K (875 °C) and above this temperature, intermetallics were formed. The irregular-shaped particles of Fe 5 Cr 35 Ni 40 Ti 15 have been observed within the Ni 3 Ti intermetallic layer. The joint tensile and shear strength were measured; a maximum tensile strength of ~477 MPa and shear strength of ~356.9 MPa along with ~4.2 pct elongation were obtained for the direct bonded joint when processed at 1173 K (900 °C). However, when nickel base alloy was used as an interlayer in the same materials at the bonding temperature of 1148 K (875 °C), the bond tensile and shear strengths increase to ~523.6 and ~389.6 MPa, respectively, along with 6.2 pct elongation.

Description: Bioactive monetite (anhydrous calcium hydrogen phosphate, CaHPO 4 ) has been successfully synthesized using the sonochemical method in the presence of a ternary solvent system of water/ethylene glycol (EG)/ N , N -dimethylformamide (DMF). The morphology and chemical composition of the synthesized powders were characterized using field emission scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results indicated that with increasing sonication time, the morphology changed slightly from a plate-like one to a combination of plates (flower-like). The formation of flower-like nanosheets requires an optimum time of 40 minutes, and the nanosheets have an average thickness of 210 ± 87 nm. The concentration of DMF clearly influences the morphology and crystal phase of the products. The ideal product was obtained using a water/EG DMF ratio of 1:2.

Description: The variation of morphology and mechanical properties of Al6061 automotive aluminum alloy due to friction stir welding (FSW) and gas tungsten arc welding (GTAW) was investigated by optical metallography, scanning electron microscopy, microhardness measurement, X-ray diffraction, tensile testing, and fractography. The center-line dendrite emergence and microhardness reduction in the heat-affected zone were observed in the GTAW process. Although similar microhardness reduction with respect to the base metal was observed in the FSW samples, higher HVs were obtained for the FSW rather than the GTAW process at almost all heat-affected locations. Ultimate tensile strengths of the FSW and the GTAW samples in the transverse direction were ~0.57 and ~0.35 of the base metal, respectively. Post-weld aging improved the strength, but reduced the ductility of the welding.

Description: Ni-free austenitic steels alloyed with Cr and Mn are an alternative to conventional Ni-containing steels. Nitrogen alloying of these steel grades is beneficial for several reasons such as increased strength and corrosion resistance. Low solubility in liquid and δ -ferrite restricts the maximal N-content that can be achieved via conventional metallurgy. Higher contents can be alloyed by powder-metallurgical (PM) production via gas–solid interaction. The performance of sintered parts is determined by appropriate sintering parameters. Three major PM-processing routes, hot isostatic pressing, supersolidus liquid phase sintering (SLPS), and solid-state sintering, were performed to study the influence of PM-processing route and N-content on densification, fracture, and mechanical properties. Sintering routes are designed with the assistance of thermodynamic calculations, differential thermal analysis, and residual gas analysis. Fracture surfaces were studied by X-ray photoelectron spectroscopy, secondary electron microscopy, and energy dispersive X-ray spectroscopy. Tensile tests and X-ray diffraction were performed to study mechanical properties and austenite stability. This study demonstrates that SLPS process reaches high densification of the high-Mn-containing powder material while the desired N-contents were successfully alloyed via gas–solid interaction. Produced specimens show tensile strengths 〉1000 MPa combined with strain to fracture of 60 pct and thus overcome the other tested production routes as well as conventional stainless austenitic or martensitic grades.

Description: The interface layer and discrete crystal growth in solidification are traced by analyzing the microsegregation of aluminum alloy. Based on the interface evolution and discrete crystal growth, the non-equilibrium microsegregation mechanism is qualitatively proposed. The solute content of solid is decided by the solidification temperature of interface. And the solidification temperature of interface is further decided by the evolution of interface compositions and interface temperature. The fluctuation of interface compositions and actual interface temperature persists in the whole solidification process.

Description: The weld metal of the ENiCrFe-7 nickel-based alloy-covered electrodes was investigated in terms of the microstructure, the grain boundary precipitation, and the ductility-dip cracking (DDC) susceptibility. Besides the dendritic gamma-Ni(Cr,Fe) phase, several types of precipitates dispersed on the austenitic matrix were observed, which were determined to be the Nb-rich MC-type carbides with “Chinese script” morphology and size of approximately 3 to 10 µ m, the Mn-rich MO-type oxides with size of approximately 1 to 2 µ m, and the spherical Al/Ti-rich oxides with size of less than 1 µ m. The discontinuous Cr-rich M 23 C 6 -type carbides predominantly precipitate on the grain boundaries, which tend to coarsen during reheating but begin to dissolve above approximately 1273 K (1000 °C). The threshold strain for DDC at each temperature tested shows a certain degree of correlation with the grain boundary carbides. The DDC susceptibility increases sharply as the carbides coarsen in the temperature range of 973 K to 1223 K (700 °C to 950 °C). The growth and dissolution of the carbides during the welding heat cycles deteriorate the grain boundaries and increase the DDC susceptibility. The weld metal exhibits the minimum threshold strain of approximately 2.0 pct at 1323 K (1050 °C) and the DTR less than 873 K (600 °C), suggesting that the ENiCrFe-7—covered electrode has less DDC susceptibility than the ERNiCrFe-7 bare electrode but is comparable with the ERNiCrFe-7A.

Description: Magnesium (Mg) alloys have been recently introduced as a biodegradable implant for orthopedic applications. However, their fast corrosion, low bioactivity, and mechanical integrity have limited their clinical applications. The main aim of this research was to improve such properties of the AZ91 Mg alloy through surface modifications. For this purpose, nanostructured fluoridated hydroxyapatite (FHA) was coated on AZ91 Mg alloy by micro-arc oxidation and electrophoretic deposition method. The coated alloy was characterized through scanning electron microscopy, transmission electron microscopy, X-ray diffraction, in vitro corrosion tests, mechanical tests, and cytocompatibility evaluation. The results confirmed the improvement of the corrosion resistance, in vitro bioactivity, mechanical integrity, and the cytocompatibility of the coated Mg alloy. Therefore, the nanostructured FHA coating can offer a promising way to improve the properties of the Mg alloy for orthopedic applications.

Description: Microstructural evolution of an Fe-22 pct Mn-0.4 pct C twinning-induced plasticity (TWIP) steel during high strain rate deformation has been investigated. When subjected to low strain rate deformation, the steel shows the typical TWIP phenomenon. On the other hand, when subjected to high strain rate deformation, there is a formation of nanostructured austenite, due to the occurrence of deformation twinning forming nanoscale twin/matrix lamellae followed by dynamic recovery induced by adiabatic heating during high strain rate deformation.

Description: The presence of Fe aids in establishing the mechanical and physical properties of AlSi alloys and is also one of the main impurities leading to formation of β -Al 5 FeSi intermetallics. This study aims to understand the effect of fluid flow on the dendritic microstructure with intermetallics in Al-5/7/9 wt pct Si-0.2/0.5/1.0 wt pct Fe alloys that are directionally solidified under defined thermal and fluid flow conditions. We made extensive use of 3D X-ray tomography to obtain a better insight into the morphology and formation of the intermetallics. Three-dimensional (3-D) distribution of intermetallics presented here shows that the growth of large β -Al 5 FeSi due to forced flow occurs in the eutectic specimen center and together with an increase in the number density of β precipitates. The 3D reconstructions have verified the β shaped to be curved, bent with twining, branched, and to have imprints, holes, and propeller-shaped platelets. The 3D views showed that hole-shaped β arose from the lateral growth around α -Al dendrites. These views also confirmed the phenomenon of shortening of β as an effect of flow in the dendritic region, where β could be fragmented or completely remelted, and ultimately resulting in microstructures with shorter β -Al 5 FeSi and increases in number density. The analysis revealed an interaction between melt flow, 3D distribution, and the morphology of β -Al 5 FeSi. The growth of a large and complex group of β intermetallics can reduce the melt flow between dendrites and strengthen pore nucleation and eutectic colonies nucleation, leading to lower permeability of the mushy zone and increased porosity in the castings.

Description: Due to the miniaturization of the solder joints in micro/nanoelectronic devices, the volume ratio of intermetallic (IMCs) materials has substantially increased. This increased ratio could affect the reliability of solder joints depending on the regime and the rate of the loading. Cu 6 Sn 5 is the primary IMC layer in the solder joint, and the primary crack initiation is observed in Cu 6 Sn 5 site in the literature. As the size of the joints becomes closer to the grain size, joints may only contain a few numbers of grains of Cu 6 Sn 5 . This manifests itself in statistical grain size effects, as well as anisotropy. Modeling these joints using bulk properties of Cu 6 Sn 5 does not capture the actual behavior of these joints especially when plastic deformation is involved. Plastic deformation, starting at yield point, happens to be associated with the activation of slip systems. Deformation of a slip system of single crystal largely rests on the slip parameters such as critical resolved shear stress (CRSS), initial hardening modulus, and saturation stress (Stage I stress when large plastic flow occurs). However, no efforts have been made to capture the slip parameters of Cu 6 Sn 5 experimentally or analytically because of the difficulties of using conventional mechanical tests to measure the slip parameters of HCP single crystals. Due to wide range of CRSS values, it becomes difficult to isolate a specific slip system in testing without activating the other slip systems. The crystal plasticity finite-element (CPFE) method takes into account the effect of anisotropy and slip system behavior in modeling materials. This work uses a combined strategy based upon experiments, modeling, and a comparative analysis to obtain slip system parameters that could predict the slip process of Cu 6 Sn 5 . Nanoindentation tests were performed on Cu 6 Sn 5 single crystal to extract the load–displacement curves, and a CPFE nanoindentation model analysis along with custom user material was utilized to obtain set of crystal plasticity material parameters which can represent the plastic behavior of Cu 6 Sn 5 IMC. These parameters were then used to predict shear yield strength and shear modulus of Cu 6 Sn 5 , and the findings were compared with the previously published values in the literature.

Description: Most research related to dendrite coherency point (DCP) has been done on cast aluminum alloys and at a low cooling rate condition. In this research, the DCP of a wrought aluminum alloy is calculated in the range of high cooling rates used in the direct-chill casting process. The two-thermocouple thermal analysis technique was used to determine the DCP of Al2024 alloy. The aim of this work is to investigate the effect of different cooling rates on the dendrite coherency characteristics of Al2024. The cooling rates used in the present study range from 0.4 to 17.5 °C s −1 . Also, the effect of 1.2 wt pct Al-5Ti-1B grain refiner on the DCP was studied. To calculate the solid fraction at dendrite coherency, solid fraction versus time is plotted based on Newtonian technique. The results show that by increasing the cooling rate, both time and temperature of dendrite coherency are decreased. Also, by adding the Al-5Ti-1B master alloy, dendrite coherency temperature is reduced and dendrite impingement is postponed. To reduce casting defects occurring during equiaxed solidification, e.g ., macrosegregation, porosities, and hot tearing, these two operations which lead to postpone the transition from mass to inter-dendritic feeding, or dendrite coherency, can be useful. By increasing the cooling rate, solid fraction at dendrite coherency increases initially and then decreases at higher cooling rates. Presence of grain refiner leads to increasing of solid fraction at DCP. Thus, by delaying the dendrite coherency and increasing the solid fraction at DCP, semi-solid forming can be performed on parts with higher solid fraction and less shrinkage. Microstructural evaluation was carried out to present the correlation between the cooling rate and solid fraction in 2024 aluminum alloy.

Description:    The evolution of γ/γ′ eutectic during the solidification of Ni-base superalloys CMSX-10 and CMSX-4 was investigated over a wide range of cooling rates. The microsegregation behavior during solidification was also quantitatively examined to clarify the influence of elemental segregation on the evolution of γ/γ′ eutectic. In the cooling rate ranges investigated (0.9 to 138.4 K/min (0.9 to 138.4 °C/min)), the γ/γ′ eutectic fraction in CMSX-10 was found to be more than 2 times higher than that in CMSX-4 at a given cooling rate. However, the dependence of the γ/γ′ eutectic fraction on the cooling rate in both alloys showed a similar tendency; i.e. , the γ/γ′ eutectic fraction increased with increasing the cooling rate and then exhibited a maximum plateau at and above the certain critical cooling rate in both alloys. This critical cooling rate was found to be dependent on the alloy composition and was estimated to be about 12 K/min (12 °C/min) and 25 K/min (25 °C/min) for CMSX-10 and CMSX-4, respectively. The calculated solid compositions based on the modified Scheil model revealed that even a small compositional difference of total γ′ forming elements in the initial composition of the alloy can play a significant role in the as-cast eutectic fraction during the solidification of Ni-base superalloys. The evolution of the γ/γ′ eutectic fraction with respect to the cooling rate could be rationalized by taking into account the effects of back-diffusion in solid and dendrite arm coarsening on decreasing the extent of microsegregation. Content Type Journal Article Pages 1-10 DOI 10.1007/s11661-011-0738-4 Authors S. M. Seo, High Temperature Materials Group, Korea Institute of Materials Science, Changwon, 641-010 South Korea J. H. Lee, Department of Metallurgy and Materials Engineering, Changwon University, Changwon, 641-773 South Korea Y. S. Yoo, High Temperature Materials Group, Korea Institute of Materials Science, Changwon, 641-010 South Korea C. Y. Jo, High Temperature Materials Group, Korea Institute of Materials Science, Changwon, 641-010 South Korea H. Miyahara, Department of Materials Science and Engineering, Kyushu University, Fukuoka, 819-0395 Japan K. Ogi, Oita National College of Technology, Oita, 870-0152 Japan Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Austenite formation during intercritical annealing was studied in a cold-rolled dual-phase (DP) steel based on a low-carbon DP780 composition processed in the mill. Two heating rates, 10 and 50 K/s, and a range of annealing temperatures from 1053 K to 1133 K (780 °C to 860 °C) were applied to study their effects on the progress of austenitization. The effect of these process parameters on the final microstructures and mechanical properties was also investigated using a fixed cooling rate of 10 K/s after corresponding annealing treatments. It was found that the heating rate affects the austenite formation not only during continuous heating, but also during isothermal holding, and the effect is more pronounced at lower annealing temperatures. Faster heating delays the recrystallization kinetics of the investigated steel. The rate of austenite formation and its distribution are strongly influenced by the extent of overlapping of the processes of recrystallization and austenitization. It appeared that the heating rate and temperature of intercritical annealing have a stronger effect on the final tensile strength (TS) of the DP steel than holding time. Both higher annealing temperatures and long holding times minimize the strength difference caused by a difference in heating rate. Content Type Journal Article Pages 1-11 DOI 10.1007/s11661-011-0753-5 Authors R. R. Mohanty, ArcelorMittal Global R&D, East Chicago, IN 46312, USA O. A. Girina, ArcelorMittal Global R&D, East Chicago, IN 46312, USA N. M. Fonstein, ArcelorMittal Global R&D, East Chicago, IN 46312, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Extremely thin plates of bainitic ferrite can now routinely be induced in steels by heat–treatment at low homologous temperatures. Given the atomic mechanism by which the transformation occurs, morphology should be dominated by the minimization of strain energy due to the displacements necessary to accomplish the change in crystal structure when austenite decomposes into bainite. Experiments were conducted using atomic force microscopy in an attempt to characterize these displacements, with a surprising outcome that the shear strain is much larger than associated with conventional, coarser bainitic structures. It appears that this might explain why the plates of bainitic ferrite tend to be slender in this new class of nanostructured alloys. Content Type Journal Article Pages 1-5 DOI 10.1007/s11661-011-0755-3 Authors M. J. PEET, Materials Science and Metallurgy Department, University of Cambridge, Cambridge, CB2 3QZ United Kingdom H. K. D. H. BHADESHIA, Materials Science and Metallurgy Department, University of Cambridge, Cambridge, CB2 3QZ United Kingdom Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The aim of this work is to partially substitute Fe and Mn for Ni in the 3HA piston alloy and to study the consequences through microstructural evaluation and the thermal analysis technique. Three types of near-eutectic alloys containing (2.6 wt pct Ni-0.2 wt pct Fe-0.1 wt pct Mn), (1.8 wt pct Ni-0.75 wt pct Fe-0.3 wt pct Mn), and (1 wt pct Ni-1.15 wt pct Fe-0.6 wt pct Mn) were produced, and their solidification was studied at the cooling rate of 0.9 K/s (°C/s) using the computer-aided thermal analysis technique. Optical microscopy and scanning electron microscopy were used to study the microstructure of the samples, and energy dispersive X-ray (EDX) analysis was used to identify the composition of the phases. Also, the quantity of the phases was measured using the image analysis technique. The results show that Ni mainly participates as Al 3 Ni, Al 9 FeNi, and Al 3 CuNi phases in the high Ni-containing alloy (2.6 wt pct Ni). In addition, substitution of Ni by Fe and Mn makes Al 9 FeNi the only Ni-rich phase, and Al 12 (Fe,Mn) 3 Si 2 appears as an important Fe-rich intermetallic compound in the alloys with the higher Fe and Mn contents. Content Type Journal Article Pages 1-12 DOI 10.1007/s11661-011-0764-2 Authors R. Gholizadeh, Center of Excellence for Advanced Materials Processing (CEAMP), School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), 16846 Narmak, Tehran, Iran S. G. Shabestari, Center of Excellence for Advanced Materials Processing (CEAMP), School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), 16846 Narmak, Tehran, Iran Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Microstructure and mechanical properties of cold-spray coatings are usually required in order to explore the potential industrial application of the latter. This article demonstrates the successful formulation of Ni-20Cr and Ni-50Cr coatings on two boiler steels, namely, SAE 213-T22 and SA 516 steel by cold-spray process. The microstructure, coating thickness, phase formation, and microhardness properties of the coatings were evaluated. The coatings were subjected to cyclic heating and cooling cycles at an elevated temperature of 1173.15 K (900 °C) to ascertain their high-temperature oxidation behavior. Moreover, these cyclic exposures can give useful information regarding the adhesion of the coatings with the substrate steels. Of all the coatings, the Ni-50Cr coating on SA 516 steel had a maximum average hardness value of 469 Hv. As observed from the surface field emission–scanning electron microscopy (FE-SEM) analysis, the coatings were found to have nearly dense microstructure with the sprayed particles in interlocked positions. It was concluded that the cold-spray process is suitable for spraying the preceding powders onto the given boiler steels to produce nearly dense and low oxide coatings. The coatings, in general, were found to follow the parabolic rate of oxidation and were successful in maintaining their surface contact with their respective substrate steels. Content Type Journal Article Pages 1-18 DOI 10.1007/s11661-011-0759-z Authors Niraj Bala, Baba Banda Singh Bahadur Engineering College, Fatehgarh Sahib, Punjab, India Harpreet Singh, School of Mechanical, Materials and Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, India Satya Prakash, Metallurgical and Materials Engineering Department, Indian Institute of Technology Roorkee, Uttrakhand, India Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Interdiffusion in the face-centered-cubic (fcc) Co-Al binary alloys was studied by the diffusion-couple approach in the temperature range of 1173 K to 1573 K (900 °C to 1300 °C). Interdiffusion coefficients of the fcc Co-Al alloys were then evaluated by using the Sauer–Freise method. The effect of magnetic ordering on the Co-Al interdiffusion was observed at 1273 K (1000 °C) by examining the Arrhenius plots. The interdiffusion data were assessed to develop the atomic mobility for the fcc Co-Al alloys, and their validity was tested by simulating the diffusion-couple experiments. Content Type Journal Article Pages 1-5 DOI 10.1007/s11661-011-0758-0 Authors Y.-W. Cui, Computational Alloy Design Group, IMDEA Materials Institute, Madrid, 28040 Spain B. Tang, State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an, 710072 People’s Republic of China R. Kato, Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai, 980-8579 Japan R. Kainuma, Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai, 980-8579 Japan K. Ishida, Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai, 980-8579 Japan Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Brazing is a widely used process to improve the performance of steels used in automotive applications. The substrate material is often exposed to harsh conditions in these applications and may affect the service life of the component. Reactive boride brazing aims to improve the mechanical properties of the substrate material by forming a ceramic-metal composite coating in a single-step process in situ . In this study, sintered Ancor 4300 low-alloy steel is used as the substrate with chromium-rich braze and chromium-lean braze materials. The mechanical properties of the brazed samples were studied in detail using microindentation hardness measurements and the transverse rupture test. The results indicate that the brazed superlayer has a 10 times higher hardness. There was a significant improvement in the transverse rupture strength of the steel brazed with the chromium-rich boride as compared to the pure substrate material. In an effort to reduce processing time, green compacts of the substrate were also directly brazed and yielded favorable results. Content Type Journal Article Pages 1-8 DOI 10.1007/s11661-011-0754-4 Authors B. Palanisamy, Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur, 208016 UP, India A. Upadhyaya, Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur, 208016 UP, India Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    In this article, grain selection in spiral selectors during investment casting of single-crystal (SX) components is simulated using a cellular automaton grain structure model (CAFE) within a finite element thermal model (PROCAST). The models were validated against experimental observations and then were applied to model the effect of geometry of the spiral selectors on grain selection through a systematic approach. It was found that the efficiency of the spiral selector is significantly dependent on its geometry; the spiral becomes more efficient in selecting single grain with a smaller wax wire diameter; larger spiral rotation diameter, and smaller take-off angle. Recommendations for optimizing the spiral geometry are provided. Content Type Journal Article Pages 1-8 DOI 10.1007/s11661-011-0757-1 Authors H. J. Dai, Department of Engineering, University of Leicester, Leicester, LE1 7RH United Kingdom H. B. Dong, Department of Engineering, University of Leicester, Leicester, LE1 7RH United Kingdom N. D’Souza, Precision Casting Facility (PCF), Rolls-Royce plc, Derby, DE24 8BJ United Kingdom J.-C. Gebelin, Metallurgy and Materials PRISM2, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom R. C. Reed, Metallurgy and Materials PRISM2, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description: During heat treatment, the work piece experiences a range of heating rates depending upon the sizes and types of furnace. When the Al-Si-Mg cast alloy is heated to the solutionizing temperature, recrystallization takes place during the ramp-up stage. The effect of heating rate on recrystallization in the A356 (Al-Si-Mg) alloy was studied using dilatometric and calorimetric methods. Recrystallization in as-cast Al-Si alloys is a localized event and is confined to the elasto-plastic zone surrounding the eutectic Si phase; there is no evidence of recrystallization in the center of the primary Al dendritic region. The size of the elasto-plastic zone is of the same order of magnitude as the Si particles, and recrystallized grains are observed in the elasto-plastic region near the Si particles. The coefficient of thermal expansion of Al is an order of magnitude greater than Si, and thermal stresses are generated due to the thermal mismatch between the Al phase and Si particles providing the driving force for recrystallization. In contrast, recrystallization in Al wrought alloy (7075) occurs uniformly throughout the matrix, stored energy due to cold work being the driving force for recrystallization in wrought alloys. The activation energy for recrystallization in as-cast A356 alloy is 127 KJ/mole. At a slow heating rate of 4.3 K/min, creep occurs during the heating stage of solution heat treatment. However, creep does not occur in samples heated at higher heating rates, namely, 520, 130, and 17.3 K/min. Content Type Journal Article Pages 1-10 DOI 10.1007/s11661-011-0716-x Authors S. K. Chaudhury, Honeywell Turbo Technologies, Torrance, CA 90505, USA V. Warke, Bodycote Thermal Processing, Andover, MA 01810, USA S. Shankar, Light Metal Casting Research Centre, McMaster University, Hamilton, ON L8S 4L7, USA D. Apelian, Worcester Polytechnic Institute, Metal Processing institute, Worcester, MA 01609, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    In-situ synchrotron radiation X-ray powder diffraction is shown to be complementary to thermal analysis for the study of the annealing of a ball-milled nanocrystalline Fe 1.5 wt pct Mo powder. The evolution of domain size distribution and defects is quantified via whole powder pattern modeling (WPPM) of the diffraction data. A possible annealing mechanism is proposed for the powder. Content Type Journal Article Pages 1-6 DOI 10.1007/s11661-011-0762-4 Authors Matteo Leoni, Department of Materials Engineering and Industrial Technologies, University of Trento-via Mesiano, 77-38123 Trento, Italy Paolo Scardi, Department of Materials Engineering and Industrial Technologies, University of Trento-via Mesiano, 77-38123 Trento, Italy Mirco D’incau, Department of Materials Engineering and Industrial Technologies, University of Trento-via Mesiano, 77-38123 Trento, Italy Giuseppina Luciani, Department of Materials and Production Engineering, University of Napoli “Federico II”-piazzale Tecchio, 80-80125 Napoli, Italy Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    We show that steel-magnesium alloy laminated metal composites (LMCs) can be produced by gas pressure infiltration of a liquid magnesium alloy between layers of stacked dimpled steel sheets. Resulting LMCs are amenable to subsequent warm rolling. The LMCs are free of pores or brittle intermetallics and feature, in the as-cast condition, metal layers of uniform thickness and spacing. The ultimate tensile strength of the as-cast LMCs, of 260 MPa, obeys the “rule-of-mixtures” (ROM). The uniform tensile elongation, of around 20 pct, makes the infiltrated LMC nearly as ductile as the bulk steel it contains, implying that the magnesium alloy in the as-cast LMCs has a substantially increased tensile ductility in comparison to its metallurgically equivalent bulk state. Rolling reduces the metal layer thicknesses, causes waviness in the interface, and makes the LMCs stronger but less ductile, by factors in the vicinity of 2 for both properties; the main cause for this is work hardening in the steel layers. Content Type Journal Article Pages 1-12 DOI 10.1007/s11661-011-0756-2 Authors Arda Çetin, Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Mechanical Metallurgy, CH-1015 Lausanne, Switzerland Jérôme Krebs, Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Mechanical Metallurgy, CH-1015 Lausanne, Switzerland Alexandre Durussel, Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Mechanical Metallurgy, CH-1015 Lausanne, Switzerland Andreas Rossoll, Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Mechanical Metallurgy, CH-1015 Lausanne, Switzerland Junya Inoue, Department of Materials Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan Toshihiko Koseki, Department of Materials Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan Shoichi Nambu, Department of Materials Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan Andreas Mortensen, Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Mechanical Metallurgy, CH-1015 Lausanne, Switzerland Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The excellent biocompatibility and corrosion properties of Pt alloys and 316 low-carbon vacuum melted (LVM) stainless steel (SS) make them attractive for biomedical applications. With the increasing complexity of medical devices and in order to lower costs, the challenge of joining dissimilar materials arises. In this study, laser microwelding (LMW) of crossed Pt-10 pct Ir to 316 LVM SS wires was performed and the weldability of these materials was determined. The joint geometry, joining mechanism, joint breaking force (JBF), and fracture modes were investigated using optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and microtensile testing. It was shown that the mechanisms of joint formation transitioned from (1) brazing, (2) a combination of brazing and fusion welding, and (3) fusion welding with increasing pulsed laser energy. The joints demonstrated various tensile failure modes including (1) interfacial failure below a peak power of 0.24 kW, (2) partial interfacial failure that propagated into the Pt-Ir wire, (3) failure in the Pt-Ir wire, and (4) failure in the SS wire due to porosity and severe undercutting caused by overwelding. During this study, the optimal laser peak power range was identified to produce joints with good joint geometry and 90 pct of the tensile strength of the Pt-10 pct Ir wire. Content Type Journal Article Pages 1-11 DOI 10.1007/s11661-011-0763-3 Authors G. S. Zou, Department of Mechanical Engineering, Tsinghua University, Beijing, 100084 People’s Republic of China Y. D. Huang, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada N2L 3G1 A. Pequegnat, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada N2L 3G1 X. G. Li, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada N2L 3G1 M. I. Khan, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada N2L 3G1 Y. Zhou, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada N2L 3G1 Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The term “gradient nanomechanics” is used here to designate a generalized continuum mechanics framework accounting for “bulk-surface” interactions in the form of extra gradient terms that enter in the balance laws or the evolution equations of the relevant constitutive variables that govern behavior at the nanoscale. In the case of nanopolycrystals, the grain boundaries may be viewed either as sources/sinks of “effective” mass and internal force or as a separate phase, interacting with the bulk phase that it surrounds, and supporting its own fields, balance laws, and constitutive equations reflecting this interaction. In either view, a further common assumption introduced is that the constitutive interaction between bulk and “interface” phases enters in the form of higher order gradient terms, independently of the details of the underlying physical mechanisms that bring these terms about. The effectiveness of the approach is shown by considering certain benchmark problems for nanoelasticity, nanoplasticity, and nanodiffusion for which standard continuum mechanics theory fails to model the observed behavior. Its implications to interpreting size-dependent stress-strain curves for nanopolycrystals with varying grain size are also discussed. Content Type Journal Article Pages 1-14 DOI 10.1007/s11661-011-0725-9 Authors E. C. Aifantis, Laboratory of Mechanics and Materials, Polytechnic School, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    A hybrid in-situ characterization system, which couples the laser scanning confocal microscopy (LSCM) with the time-resolved X-ray diffraction (TRXRD) measurement with synchrotron radiation, was used to characterize the microstructure evolution during heat-affected zone (HAZ) thermal cycling of high-strength and blast-resistant steel. The combined technique has a time resolution of 0.3 seconds that allows for high-fidelity measurements of transformation kinetics, lattice parameters, and morphological features. The measurements showed a significant reduction in the martensite start transformation temperature with a decrease in the prior austenite grain size. In addition, the LSCM images confirmed the concurrent refinement of martensite packet size with smaller austenite grain sizes. This is consistent with dilatometric observations. The austenite grain size also influenced the rate of transformation ( df m / dT ); however, the measurements from the hybrid (surface) and dilatometric (volume) measurements were inconsistent. Challenges and future directions of adopting this technique for comprehensive tracking of microstructure evolution in steels are discussed. Content Type Journal Article Pages 1-9 DOI 10.1007/s11661-011-0746-4 Authors Xinghua Yu, Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43221, USA Sudarsanam Suresh Babu, Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43221, USA John C. Lippold, Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43221, USA Hidenori Terasaki, JWRI, Osaka University, Osaka, Japan Yu-ichi Komizo, JWRI, Osaka University, Osaka, Japan Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Single-crystal diffuse scattering was collected on the Wombat high-intensity powder diffractometer at the OPAL reactor at the Bragg Institute. The difficulty in measuring diffuse scattering comes from its relatively low intensity compared to the Bragg peaks, a factor of 10 3 to 10 4 smaller. Wombat allows collection of diffuse scattering due to its high intensity and large two-dimensional detector. Diffuse scattering data from yttria-stabilized cubic zirconia (YCSZ, Y 2 O 3 stabilized ZrO 2 ) and PbZn 1/3 Nb 2/3 O 3 (PZN) were successfully collected, the latter at a range of temperatures. The data were processed, normalized, and background subtracted to reconstruct flat reciprocal space sections with a minimum of artifacts. The strategies used to tackle the collection of neutron diffuse scattering and the way in which they are implemented will be discussed. The results show that the neutron powder diffractometer with a continuous detector is capable of collecting high-quality diffuse scattering data. Content Type Journal Article Pages 1-6 DOI 10.1007/s11661-011-0740-x Authors R. E. Whitfield, Research School of Physics and Engineering, Australian National University, Canberra, 0200 Australia D. J. Goossens, Research School of Chemistry, Australian National University, Canberra, 0200 Australia A. J. Studer, Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, Sydney, 2234, Australia J. S. Forrester, School of Engineering, The University of Newcastle, Newcastle, NSW 2308, Australia Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The microstructural evolution was experimentally studied at a withdrawal velocity between 6 and 0.1 mm/s by a Bridgman technique in Zr 51.7 Cu 30 Ni 8.3 Al 10 . Our results indicate that the Zr 51.7 Cu 30 Ni 8.3 Al 10 alloy can be considered as the ZrCu-Zr 2 Cu pseudo-binary eutectic system, and the glass-forming ability (GFA) is correlated with the (L → ZrCu + Zr 2 Cu) pseudo-binary eutectic reaction. This understanding has important implications and guidance for designing and fabricating new Zr-Cu-Ni-Al bulk metallic glasses (BMGs) with superior glass formation. Moreover, compressive tests were also performed on these samples. The results show that as the precipitation of crystal, plastic strain decreases. It indicates that the precipitated crystal cannot block the fast propagation of the localized shear bands and the macroscopically brittle failure. Content Type Journal Article Pages 1-5 DOI 10.1007/s11661-011-0761-5 Authors J. L. Cheng, Engineering Research Center of Materials Behavior and Design, Ministry of Education, Nanjing University of Science and Technology, Nanjing, 210094 People’s Republic of China G. Chen, Engineering Research Center of Materials Behavior and Design, Ministry of Education, Nanjing University of Science and Technology, Nanjing, 210094 People’s Republic of China H. W. Xu, Engineering Research Center of Materials Behavior and Design, Ministry of Education, Nanjing University of Science and Technology, Nanjing, 210094 People’s Republic of China F. Xu, Engineering Research Center of Materials Behavior and Design, Ministry of Education, Nanjing University of Science and Technology, Nanjing, 210094 People’s Republic of China Y. L. Du, Engineering Research Center of Materials Behavior and Design, Ministry of Education, Nanjing University of Science and Technology, Nanjing, 210094 People’s Republic of China Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Infrared (IR) thermography was used to measure thermal profiles in the coating, consumable rod, and substrate during friction surfacing. A sudden raise followed by a steady state in thermal profile was observed and attributed to viscous heat dissipation during plastic deformation. The retreating side of the coating experienced higher temperature compared to the advancing side, indicating that the hot plasticized metal is carried from the advancing side to the retreating side. Content Type Journal Article Pages 1-5 DOI 10.1007/s11661-011-0750-8 Authors H. Khalid Rafi, Materials Joining Laboratory, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, 600 036 India Krishnan Balasubramaniam, Machine Design Section, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, 600 036 India G. Phanikumar, Materials Joining Laboratory, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, 600 036 India K. Prasad Rao, Materials Joining Laboratory, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, 600 036 India Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Microstructures and a microstructural, columnar architecture as well as mechanical behavior of as-fabricated and processed INCONEL alloy 625 components produced by additive manufacturing using electron beam melting (EBM) of prealloyed precursor powder are examined in this study. As-fabricated and hot-isostatically pressed (“hipped”) [at 1393 K (1120 °C)] cylinders examined by optical metallography (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive (X-ray) spectrometry (EDS), and X-ray diffraction (XRD) exhibited an initial EBM-developed γ ″ (bct) Ni 3 Nb precipitate platelet columnar architecture within columnar [200] textured γ (fcc) Ni-Cr grains aligned in the cylinder axis, parallel to the EBM build direction. Upon annealing at 1393 K (1120 °C) (hot-isostatic press (HIP)), these precipitate columns dissolve and the columnar, γ , grains recrystallized forming generally equiaxed grains (with coherent {111} annealing twins), containing NbCr 2 laves precipitates. Microindentation hardnesses decreased from ~2.7 to ~2.2 GPa following hot-isostatic pressing (“hipping”), and the corresponding engineering (0.2 pct) offset yield stress decreased from 0.41 to 0.33 GPa, while the UTS increased from 0.75 to 0.77 GPa. However, the corresponding elongation increased from 44 to 69 pct for the hipped components. Content Type Journal Article Pages 1-18 DOI 10.1007/s11661-011-0748-2 Authors L. E. Murr, Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA E. Martinez, Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA S. M. Gaytan, Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA D. A. Ramirez, Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA B. I. Machado, Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA P. W. Shindo, Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA J. L. Martinez, Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA F. Medina, W.M. Keck Center for 3D Innovation, The University of Texas at El Paso, El Paso, TX 79968, USA J. Wooten, CalRAM, Inc., Simi Valley, CA 93065, USA D. Ciscel, CalRAM, Inc., Simi Valley, CA 93065, USA U. Ackelid, Arcam AB, Mölndal, SE-431-37 Sweden R. B. Wicker, W.M. Keck Center for 3D Innovation, The University of Texas at El Paso, El Paso, TX 79968, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description: The spatial and temporal characteristics of propagating deformation bands in the Al-Mg alloy AA5182 in O temper were studied experimentally at room temperature. Tensile tests were carried out on flat specimens at strain rates in the range from 10 −5 to 10 −1 s −1 . Digital image correlation (DIC) and digital infrared thermography (DIT) were applied to monitor the propagating bands. It was found that the material exhibits a sharp yield point, and Lüders bands were seen at all the strain rates. Jerky flow took place all along the Lüders plateau. It thus seems that the Portevin–Le Chatelier (PLC) effect starts at incipient yielding and that there is no critical strain. At the end of the Lüders plateau, PLC bands immediately started to propagate back and forth along the gage section of the specimen. The work hardening of the material decreased consistently with increasing strain rate, while the flow stress on the Lüders plateau was rather unaffected by the strain rate. This indicates that the dynamic strain aging (DSA) mainly affects the strength of the interaction between mobile and forest dislocations. The strain to necking was found to decrease gradually with strain rate for this alloy, which is consistent with the lower work-hardening rate at the higher strain rates. Content Type Journal Article Pages 1-12 DOI 10.1007/s11661-011-0749-1 Authors R. Nogueira de Codes, LMT-Cachan, ENS de Cachan/CNRS/UPMC, F-94235 Cachan, France O. S. Hopperstad, Department of Structural Engineering, Structural Impact Laboratory-SIMLab, Centre for Research-Based Innovation (CRI), NTNU, NO-7491 Trondheim, Norway O. Engler, Hydro Aluminium Deutschland GmbH, R&D Center Bonn, D-53014 Bonn, Germany O.-G. Lademo, Department of Structural Engineering, Structural Impact Laboratory-SIMLab, Centre for Research-Based Innovation (CRI), NTNU, NO-7491 Trondheim, Norway J. D. Embury, Material Sciences and Engineering, McMaster University, Hamilton, ON, Canada L8S 4L7 A. Benallal, LMT-Cachan, ENS de Cachan/CNRS/UPMC, F-94235 Cachan, France Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Austenitic stainless steels are expected to be a major material for boiler tubes and steam turbines in future ultra-supercritical (USC) fossil power plants. It is of great interest to maximize the creep strength of the materials without increasing the cost. Precipitation strengthening was found to be the best and cheapest way for increasing the creep strength of such steels. This study is concerned with improving creep properties of a high nitrogen Nb-stabilized 15Cr-15Ni austenitic alloy through introducing a high number of nanosized particles into the austenitic matrix. The addition of around 4 wt pct Mn and 0.236 wt pct N into the 15Cr-15Ni-0.46Si-0.7Nb-1.25Mo-3Cu-Al-B-C matrix in combination with a special multicycled aging-quenching heat treatment resulted in the fine dispersion of abundant quantities of thermally stable (Nb,Cr,Fe)(C,N) precipitates with sizes of 10 to 20 nm. Apart from the carbonitrides, it was found that a high number of coherent copper precipitates with size 40 to 60 nm exist in the microstructure. Results of creep tests at 973 K and 1023 K (700 °C and 750 °C) showed that the creep properties of the investigated steel are superior compared to that of the commercial NF709 alloy. The improved creep properties are attributed to the improved morphology and thermal stability of the carbonitrides as well as to the presence of the coherent copper precipitates inside the austenitic matrix. Content Type Journal Article Pages 1-8 DOI 10.1007/s11661-011-0752-6 Authors Vu The Ha, Materials Research Division, Korea Institute of Science and Technology, Cheongryang, Seoul 130-650, Republic of Korea Woo Sang Jung, Materials Research Division, Korea Institute of Science and Technology, Cheongryang, Seoul 130-650, Republic of Korea Jin Yoo Suh, Materials Research Division, Korea Institute of Science and Technology, Cheongryang, Seoul 130-650, Republic of Korea Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The mechanical properties of rolled duplex stainless steel (DSS) products manufactured by the current industrial process exhibit a strong anisotropy. This fact is evidently due to the two-phase nature of DSSs. During industrial rolling, not only the morphology of the microstructure changes from coarse-grained isotropic in the cast slab to fine-grained anisotropic in the coil, with both phases elongated in the rolling direction (RD), but also clear and intense crystallographic rolling textures develop, especially in the ferritic phase. The objective of the present work was to modify the industrial processing route and parameters in such a way that the strong anisotropy of DSS coils and sheets is decreased and the amount of potential applications made from DSSs by deep drawing or roll forming operations is increased. To achieve this goal, after the industrial cold rolling, a heat treatment is proposed with the aim of modifying the morphology and crystallographic texture of the ferritic grains by the assistance of an enforced transformation to sigma phase. The final product obtained by this modified route showed a microstructure with grains of austenite and ferrite randomly distributed and a significant decrease of the texture intensities due to the retransformation of sigma into ferrite. As a result, DSS EN 1.4462 displayed an almost isotropic mechanical behavior and an improved aptitude to deep drawing operations. Content Type Journal Article Pages 1-12 DOI 10.1007/s11661-011-0744-6 Authors G. Fargas, Department of Materials Science and Metallurgical Engineering-CIEFMA, Universitat Politècnica de Catalunya, 08028 Barcelona, Spain N. Akdut, International Research & Education Center, Department of Materials Science and Engineering, Kyushu University, Nishi-ku, Fukuoka, 819-0395 Japan M. Anglada, Department of Materials Science and Metallurgical Engineering-CIEFMA, Universitat Politècnica de Catalunya, 08028 Barcelona, Spain A. Mateo, Department of Materials Science and Metallurgical Engineering-CIEFMA, Universitat Politècnica de Catalunya, 08028 Barcelona, Spain Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The rate-dependent deformation of Zr 38 Ti 17 Cu 10.5 Co 12 Be 22.5 bulk metallic-glass-reinforced porous tungsten matrix composites was investigated over a wide range of strain rates. The composites were examined in two forms: the as-cast composite and the as-extruded composite by extrusion. In addition to showing greater strain hardening, the as-cast composite also shows much more obvious strain rate dependence of flow stress than the as-extruded composite. Microhardness tests were performed on the tungsten and the metallic glass phase in both composites, respectively. The results from the microhardness measurements indicate that the strain rate sensitivity of the as-extruded composite is primarily a result of strain rate sensitivity of the tungsten phase. Content Type Journal Article Pages 1-6 DOI 10.1007/s11661-011-0742-8 Authors Y. F. Xue, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081 P.R. China L. Wang, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081 P.R. China H. N. Cai, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081 P.R. China F. C. Wang, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081 P.R. China H. W. Cheng, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081 P.R. China H. F. Zhang, Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016 P.R. China A. M. Wang, Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016 P.R. China Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Grain growth during sintering is a critical issue for the manufacture of nanocrystalline bulk materials from nanosized powders. The grain growth process during sintering can be viewed as consisting of two parts: initial coarsening during early and intermediate stages of sintering and latter stage grain growth during the final stage of sintering. The latter stage grain growth is the normal grain growth that has been well studied and reported in the literature. The initial coarsening, which often inevitably causes a material to lose nanoscaled grain size characteristics, however, is not well studied at all. In this investigation, the initial coarsening during sintering of nanosized powders was studied by both nonisothermal and isothermal experimental techniques using tungsten as an example material. The results show that the initial coarsening during the heat-up process of a sintering cycle is sufficient to increase the grain size beyond the nanoscale. The kinetics of initial coarsening is found to be linear rather than polynomial, as predicted by the conventional power law of grain growth. The analysis of activation energies showed that surface diffusion is the primary mechanism for interparticle mass transport during the initial coarsening. The linear kinetic behavior could be attributed to the pinning of grain boundaries by surface grooves and high concentration of defects as the result of the synthesis of nanosized powders. Content Type Journal Article Pages 1-9 DOI 10.1007/s11661-011-0751-7 Authors Hongtao Wang, Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112, USA Z. Zak Fang, Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112, USA Kyu Sup Hwang, Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Nanoinks, which contain nanometer-sized metallic particles suspended in an organic dispersant fluid, are finding numerous microelectronic applications. One characteristic of nanoinks is that they sinter at much lower temperatures than bulk metals due to their high surface area to volume ratio and small radius of curvature, which reduces their melting points significantly below their bulk values. The unusually low sintering temperatures have unique potential for materials joining, since their melting points increase dramatically afterward. In this article, the sintering kinetics of Ag nanoink is studied using in-situ synchrotron methods to determine diffraction peak characteristics during the sintering cycle, and to subsequently calculate particle size and growth during sintering. Ag nanoink is further explored as a eutectic bonding medium by tracking phase transformations between sintered Ag nanoink and a Cu substrate to high temperatures, where melting occurs at the Ag-Cu eutectic, demonstrating nanoinks as a viable eutectic bonding medium. Content Type Journal Article Pages 1-10 DOI 10.1007/s11661-011-0717-9 Authors John W. Elmer, Engineering Technologies Division, Lawrence Livermore National Laboratory, Livermore, CA 94551-0808, USA E. D. Specht, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6118, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The superelasticity and deformation behaviors of β -type TiNb 24 Zr 2 subjected to aging treatment were investigated in this study. As the aging time increased, the precipitation of isothermal ω phase was found to restrain the formations of twinning and stress-induced α″ martensite. The superelastic recovery of the sample first improves and then deteriorates with extended aging times. A maximum and stable superelastic recovery of 4.3 pct is obtained for an aging time of 7.2 ks. Content Type Journal Article Pages 1-7 DOI 10.1007/s11661-011-0713-0 Authors Qiang Li, School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 People’s Republic of China Mitsuo Niinomi, Institute for Materials Research, Tohoku University, Sendai, 980-8577 Japan Masaaki Nakai, Institute for Materials Research, Tohoku University, Sendai, 980-8577 Japan Zhenduo Cui, School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 People’s Republic of China Shengli Zhu, School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 People’s Republic of China Xianjin Yang, School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 People’s Republic of China Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    We carried out a detailed investigation of the damage behavior of SiC particle reinforced 2080 Al alloy matrix composites by in-situ X-ray synchrotron tomography. We studied the tensile damage behavior of a peak-aged aluminum matrix composite. The main damage mode was SiC particle fracture with a very small contribution from void growth. The onset of damage takes place very close to the ultimate tensile strength of the composite. Particle fracture damage is stochastic in nature and is confined to a small distance from the fracture plane. Minimal void growth is observed, primarily at pre-existing microscopic voids from processing. Microstructure-based simulations, based on two-dimensional (2-D) images from the tomography data sets, show the importance of particle distribution and morphology on the evolution of plastic strain and damage in the composite. Content Type Journal Article Pages 1-7 DOI 10.1007/s11661-011-0718-8 Authors J. J. Williams, Materials Science and Engineering Department, Arizona State University, Tempe, AZ 85287-6106, USA N. C. Chapman, Materials Science and Engineering Department, Arizona State University, Tempe, AZ 85287-6106, USA V. Jakkali, Materials Science and Engineering Department, Arizona State University, Tempe, AZ 85287-6106, USA V. A. Tanna, Materials Science and Engineering Department, Arizona State University, Tempe, AZ 85287-6106, USA N. Chawla, Materials Science and Engineering Department, Arizona State University, Tempe, AZ 85287-6106, USA X. Xiao, X-ray Imaging Group, X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA F. De Carlo, X-ray Imaging Group, X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Diffusion coefficients of Al in molten Zn in the temperature range relevant to the industrial applications of the Zn-Al alloy were experimentally measured using the long capillary technique. The diffusion coefficients were also predicted using four methods, including a predictive equation derived recently by the present authors, the Enskog expression, the “hole” theory, and the fluid theory. In addition, molecular dynamics simulation was carried out to calculate the Al diffusivity. The experimentally measured Al diffusivity agrees well with the predicted values of the new derived equation and the outcomes of the molecular dynamics computation. An evaluation of the predictions of the four diffusion models favors the density fluctuation model. Content Type Journal Article Pages 1-8 DOI 10.1007/s11661-010-0461-6 Authors Sui Yang, Faculty of Materials, Optoelectronics and Physics, Xiangtan University, Xiangtan, 411105 Hunan, People’s Republic of China Xuping Su, School of Materials Science and Engineering, Changzhou University, Changzhou, 213164 Jiangsu, People’s Republic of China Jianhua Wang, Key Laboratory of Materials Design and Preparation Technology of Hunan Province, Xiangtan University, Xiangtan, 411105 Hunan, People’s Republic of China Fucheng Yin, Faculty of Materials, Optoelectronics and Physics, Xiangtan University, Xiangtan, 411105 Hunan, People’s Republic of China Nai-Yong Tang, Zinc Metallurgy and Customer Technical Services, Teck Metals Ltd., Product Technology Centre, Mississauga, ON L5K 1B4, Canada Zhi Li, Key Laboratory of Materials Design and Preparation Technology of Hunan Province, Xiangtan University, Xiangtan, 411105 Hunan, People’s Republic of China Xinming Wang, Key Laboratory of Materials Design and Preparation Technology of Hunan Province, Xiangtan University, Xiangtan, 411105 Hunan, People’s Republic of China Zhongxi Zhu, Key Laboratory of Materials Design and Preparation Technology of Hunan Province, Xiangtan University, Xiangtan, 411105 Hunan, People’s Republic of China Hao Tu, Key Laboratory of Materials Design and Preparation Technology of Hunan Province, Xiangtan University, Xiangtan, 411105 Hunan, People’s Republic of China Xiaoqin Li, Key Laboratory of Materials Design and Preparation Technology of Hunan Province, Xiangtan University, Xiangtan, 411105 Hunan, People’s Republic of China Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Selective laser melting (SLM) is a rapid manufacturing process that enables the buildup of very complex parts in short delays directly from powder beds. Due to the high laser beam energy during very short interaction times and the high solidification rates of the melting pool, the resulting microstructure is out-of-equilibrium and particularly textured. This type of as-fabricated microstructure may not satisfy the aeronautical criterion and requires post heat treatments. Optimized heat treatments are developed, in one side, to homogenize and form the stable phases α and β while preventing exaggerated grain growth. In the other side, heat treatment is investigated to relieve the thermal stresses appearing during cooling. This study is aimed at presenting the various types of microstructure of the Ti-6Al-4V alloy after postfabrication heat treatments below or above the β transus. Tensile tests are then carried out at room temperature in order to assess the effect of the microstructures on the mechanical properties. The fine as-fabricated microstructure presents high yield and ultimate strengths, whereas the ductility is well below the standard. A strong anisotropy of fracture between the two loading directions is noted, which is attributed to the manufacturing defects. Conventional and optimized heat treatments exhibit high yield and ultimate strengths while the ductility is significantly improved. This is due to a new optimization of the process parameters allowing drastic reduction of the number of defects. These two heat treatments enable now a choice of the morphology of the grains between columnar or equiaxial as a function of the type of loading. Content Type Journal Article Pages 1-10 DOI 10.1007/s11661-011-0731-y Authors T. Vilaro, Poly-Shape, 43, rue d’Yerres, 94440 Villecresnes, France C. Colin, Materials Centre of Mines ParisTech, CNRS UMR 7633, BP87, 91003 Evry, France J. D. Bartout, Materials Centre of Mines ParisTech, CNRS UMR 7633, BP87, 91003 Evry, France Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    We have investigated the influence of melt conditioning by intensive shearing on the mechanical behavior and microstructure of Al-Mg-Mn-Fe-Cu-Si alloy sheet produced from a small book mold ingot with high added impurity content. The melt conditioned ingot has fine grains throughout its cross section, whereas a conventionally cast ingot, without melt shearing, has coarser grains and shows a wider variation of grain size. Both needle-shaped and coarse Chinese script iron bearing intermetallic particles are found in the microstructure at the center of the conventionally processed ingot, but for the melt conditioned ingot, only fine Chinese script intermetallic particles are observed. In addition to the iron bearing intermetallics, Mg 2 Si particles are also observed. The ingots were rolled to thin sheet and solution heat treated (SHT). During rolling, the iron-based intermetallics and Mg 2 Si particles are broken and aligned along the rolling direction. Yield strength (YS), ultimate tensile strength (UTS), and elongation of the intensively melt sheared and processed sheet are all improved compared to the conventionally cast and processed sheet. Fractographic analysis of the tensile fracture surfaces shows that the clustered and coarse iron bearing intermetallic particles are responsible for the observed reduction in mechanical properties of the conventionally cast sheet. We have shown that by refining the initial microstructure of the ingot by intensive shear melt conditioning, it is possible to achieve improved mechanical properties at the final sheet gage of an AlMgMn alloy with a high content of impurities. Content Type Journal Article Pages 1-9 DOI 10.1007/s11661-011-0722-z Authors S. Kumar, The EPSRC Centre—LiME, BCAST, Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom N. Hari Babu, The EPSRC Centre—LiME, BCAST, Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom G. M. Scamans, The EPSRC Centre—LiME, BCAST, Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom Z. Fan, The EPSRC Centre—LiME, BCAST, Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The present work deals with the preparation of near-full density Cu-Al-Ni shape memory alloy (SMA) strips from argon-atomized prealloyed powder via a powder metallurgy (PM) route comprising cold die compaction to prepare powder preforms, sintering, and hot densification rolling of unsheathed sintered powder preforms under protective atmosphere at 1273 K (1000 °C). It has been shown that argon-atomized spherical Cu-Al-Ni SMA powder consisted of very fine equiaxed grains and no appreciable grain growth occurred during sintering at 1273 K (1000 °C). It also has been shown that no appreciable densification occurred during sintering, and densification was primarily achieved by hot rolling. The densification behavior of the sintered powder preforms during hot rolling was discussed. The hot-rolled Cu-Al-Ni strips were heat-treated at 1223 K (950 °C) for 60 minutes and water quenched. The heat-treated strips consisted of equiaxed grains with average size approximately 90  μ m. The heat-treated Cu-Al-Ni SMA strips consisted of self-accommodated b 1 ¢ martensite primarily, and showed smooth b 1 Þ b 1 ¢ transformation behavior coupled with a very low hysteresis (≈25 K (25 °C)). The heat-treated strips exhibited an extremely good combination of mechanical properties with fracture strength of 530 MPa and 12.3 pct fracture strain. The mode of fracture in the finished strip was primarily void-coalescence-type ductile together with some brittle transgranular type. The shape memory tests showed almost 100 pct one-way shape recovery after 100 bending-unconstrained heating cycles at 4 pct applied prestrain, exhibiting good stability of Cu-Al-Ni strips under thermomechanical actuation cycling. The two-way shape memory strain was found approximately 0.45 pct after 15 training cycles at 4 pct training strain. Content Type Journal Article Pages 1-12 DOI 10.1007/s11661-011-0728-6 Authors S. K. Vajpai, Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, Uttar Pradesh 208016, India R. K. Dube, Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, Uttar Pradesh 208016, India S. Sangal, Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, Uttar Pradesh 208016, India Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The behavior of nanocrystalline (nc) copper specimens obtained by high energy ball milling (HEBM) and electromagnetic field-assisted sintering under stress and mechanical compression is explored. High yield stress values combined with plastic behavior are observed. The basic densification mechanisms involved in the production process and the peculiar action on the dislocation network are discussed. Content Type Journal Article Pages 1-5 DOI 10.1007/s11661-011-0727-7 Authors Alessandro Fais, EPoS srl, Strada delle Cacce 73, 10139 Turin, Italy Matteo Leoni, Department of Materials Engineering and Industrial Technologies, University of Trento, via Mesiano, 77, 38123 Trento, Italy Paolo Scardi, Department of Materials Engineering and Industrial Technologies, University of Trento, via Mesiano, 77, 38123 Trento, Italy Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description: Electron microscopy techniques have been used to investigate the cause of premature creep failure in the fusion zone of INCONEL ® Alloy 740H ® (INCONEL and 740H are registered trademarks of Special Metals Corporation) welds. The reduced creep rupture lives of all-weld-metal and cross-weld creep specimens (relative to base metal specimens) have been attributed to the presence of large grain boundary regions that were denuded in fine γ ′ but contained coarse, elongated particles. Investigation of creep rupture specimens has revealed four factors that influence the formation of these coarsened zones, and the large particles found within them have been identified as γ ′. Comparisons of the microstructural characteristics of these zones to the characteristics that are typical of denuded zones formed by a variety of mechanisms identified in the literature have been made. It is concluded that the mechanism of γ ′-denuded zone formation in alloy 740H is discontinuous coarsening of the γ ′ phase. The discontinuous reaction is catalyzed by the grain boundary migration and sliding which occur during creep and likely promoted by the inhomogeneous weld metal microstructure that results from solute segregation during solidification. The increased susceptibility to the formation of the observed γ ′-denuded zones in the weld metal as compared to the base metal is discussed in the context of differences in the contributions to the driving force for the discontinuous coarsening reaction.

Description: The activities of components of Sn-Zn system were predicted based on the molecular interaction volume model (MIVM). The separation coefficients and the vapor–liquid phase equilibrium of Sn-Zn system were also predicted using the MIVM. The predicted results indicated that the content of tin in the vapor phase was 0.000052 wt pct, while in the liquid phase, it was 99.98 wt pct at 1173 K (900 °C). Experimental investigations into the separation of Sn-Zn alloy by vacuum distillation were carried out for the proper interpretation of the predicted results. The effects of vacuum level (15 to 200 Pa), distillation temperatures [873  K to 1273  K (600 °C to 1000 °C)], and soaking time (20 to 60 minutes) were studied. The experimental results indicated that the content of tin in the vapor phase was 0.001 wt pct, while in the liquid phase, it was 99.98 wt pct at 1173 K (900 °C). The experimental results match well with the predicted data, suggesting that the MIVM is a suitable model for Sn-Zn system.

Description: In the current study, we detail a novel in situ X-ray diffraction-based bulk measurement technique, which allows for the continuous tracking of primary recrystallization kinetics. The approach is based on measuring the diffracted intensity that is correlated with the evolution of the volume fraction of particular texture components during annealing of a sample within a texture goniometer. The method is applied in an experimental study on a cold-rolled industrial Al-Fe-Si alloy. For comparison purposes, the macrotexture and the hardness evolution were monitored ex situ along isothermal and nonisothermal annealing. These measurements were then contrasted to the in situ obtained growth kinetics of recrystallizing grains in beta-fiber deformation and cube orientation. The results showed clearly that this method can be reliably utilized for the characterization of recrystallization kinetics in an industrial context.

Description: Fe-14Cr-1W oxide dispersion strengthened ferritic alloys have excellent mechanical properties at high temperatures due to a high density of thermally stable Y-Ti-O nanoclusters, which are rather stable at high temperature. The aim of this work was to study the evolutions of Y-Ti-O precipitation at high temperature as a function of nominal content of Y, Ti, and O. Different Fe-14Cr alloys were characterized by small-angle neutron scattering technique under magnetic field as well as transmission electron microscopy investigations before and after annealing at 1573 K to 1723 K (1300 °C to 1450 °C). Significant differences are observed depending on the Y/Ti/O ratios. For Ti/Y 〉1, the coarsening kinetics is low even at 1723 K (1450 °C). For Ti/Y 〈1, very large size particles are observed after annealing at 1573 K (1300 °C). We have shown that the oxygen content should be strictly controlled to avoid significant coarsening at 1573 K (1300 °C) and above.

Description: A thermodynamically consistent phase-field model is formulated for binary-alloy, particularly applicable to the systems which have a significant difference in mobilities of the solute and solvent atoms, e.g. , interstitial solutes. The model is based on the mixed-mode of growth which is considered to be the general mode of transformation. As an illustration, the model has been used to simulate austenite to ferrite transformation in one-dimension. The model is made ‘quantitative’ using a different diffusivity-interpolation function without using anti-trapping flux term. The simulation-result is compared with the experimental results, and good agreement with the mixed-mode of growth in the initial stage of the transformation (when the individual nuclei are far apart) has been observed.

Description: The unloading behavior was compared for three different steel grades: a dual-phase steel, a transformation-induced plasticity steel, and a twinning-induced plasticity steel. Steels that harden by phase transformation or deformation twinning exhibited a smaller component of microplastic strain during unloading and a smaller reduction in the chord modulus compared to the conventional hardening steel. As a result, unloading is closer to pure elastic unloading when the TRIP effect or TWIP effect is active.

Description:    This article discusses the effects of laser welding parameters such as power, welding speed, and focus position on the weld bead profile, microstructure, pseudo-elasticity (PE), and shape memory effect (SME) of NiTi foil with thickness of 250  μ m using 100W CW fiber laser. The parameter settings to produce the NiTi welds for analysis in this article were chosen from a fractional factorial design to ensure the welds produced were free of any apparent defect. The welds obtained were mainly of cellular dendrites with grain sizes ranging from 2.5 to 4.8  μ m at the weld centerline. A small amount of Ni 3 Ti was found in the welds. The onset of transformation temperatures ( A s and M s ) of the NiTi welds shifted to the negative side as compared to the as-received NiTi alloy. Ultimate tensile stress of the NiTi welds was comparable to the as-received NiTi alloy, but a little reduction in the pseudo-elastic property was noted. Full penetration welds with desirable weld bead profiles and mechanical properties were successfully obtained in this study. Content Type Journal Article Pages 1-7 DOI 10.1007/s11661-011-0623-1 Authors C. W. Chan, Laser Processing Group, Advanced Manufacturing Technology Research Centre, Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong P.R. China H. C. Man, Laser Processing Group, Advanced Manufacturing Technology Research Centre, Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong P.R. China T. M. Yue, Laser Processing Group, Advanced Manufacturing Technology Research Centre, Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong P.R. China Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    A novel foamable aluminum alloy has been developed. It contains sub-micron-sized MgAl 2 O 4 (spinel) particles that are generated in situ by a reaction of SiO 2 with a molten Al-Mg alloy. The study involves an optimization of parameters such as Mg concentration, SiO 2 particles size, and reaction time and shows that a composite containing MgAl 2 O 4 particles as chief reinforcement in the matrix leads to effective foaming. Composites containing large sized transition phases and particle agglomerates in the matrix yield poor foam structure. The best foamable composite obtained contained 3.4 vol. pct of ultrafine (80 nm to 1  μ m) MgAl 2 O 4 particles uniformly distributed in an Al-Si alloy matrix. The corresponding metal foam contained 75 pct porosity and exhibited a uniform distribution of cells. Content Type Journal Article Pages 1-11 DOI 10.1007/s11661-011-0709-9 Authors G. S. Vinod kumar, Structural Properties of Materials Department, Berlin Institute of Technology, Berlin, 10623 Germany M. Chakraborty, Indian Institute of Technology, Bhubaneswar, 751013 India F. Garcia-Moreno, Structural Properties of Materials Department, Berlin Institute of Technology, Berlin, 10623 Germany J. Banhart, Structural Properties of Materials Department, Berlin Institute of Technology, Berlin, 10623 Germany Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Fatigue failure due to repetitive loading of metallic devices is a pervasive engineering concern. The present work reveals extraordinary fatigue resistance in nanocrystalline (NC) alloys, which appears to be associated with the small (〈100 nm) grain size inhibiting traditional cyclic damage processes. In this study, we examine the fatigue performance of three electrodeposited NC Ni-based metals: Ni, Ni-0.5Mn, and Ni-22Fe (PERMALLOY). When subjected to fatigue stresses at and above the tensile yield strength where conventional coarse-grained (CG) counterparts undergo low-cycle fatigue failure (〈10 4 cycles to failure), these alloys exhibit exceptional fatigue lives (in some cases, 〉10 7 cycles to failure). Postmortem examinations show that failed samples contain an aggregate of coarsened grains at the crack initiation site. The experimental data and accompanying microscopy suggest that the NC matrix undergoes abnormal grain growth during cyclic loading, allowing dislocation activity to persist over length scales necessary to initiate a fatigue crack by traditional fatigue mechanisms. Thus, the present observations demonstrate anomalous fatigue behavior in two regards: (1) quantitatively anomalous when considering the extremely high stress levels needed to drive fatigue failure and (2) mechanistically anomalous in light of the grain growth process that appears to be a necessary precursor to crack initiation. Content Type Journal Article Pages 1-12 DOI 10.1007/s11661-011-0708-x Authors Brad L. Boyce, The Materials Science and Engineering Center, Sandia National Laboratories, Albuquerque, NM 87185-0889, USA Henry A. Padilla, The Materials Science and Engineering Center, Sandia National Laboratories, Albuquerque, NM 87185-0889, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Incremental diffusion couple experiments are conducted to determine the average interdiffusion coefficient and the intrinsic diffusion coefficients of the species in the Ni 6 Nb 7 ( μ phase) in the Ni-Nb system. Further, the tracer diffusion coefficients are calculated from the knowledge of thermodynamic parameters. The diffusion rate of Ni is found to be higher than that of Nb, which indicates higher defect concentration in the Ni sublattice. Content Type Journal Article Pages 1-5 DOI 10.1007/s11661-011-0715-y Authors S. S. K. Balam, Department of Materials Engineering, Indian Institute of Science, Bangalore, 560012 India H. Q. Dong, Department of Electronics, Faculty of Electronics, Communication and Automation, Aalto University School of Science and Technology, Espoo, Finland T. Laurila, Department of Electronics, Faculty of Electronics, Communication and Automation, Aalto University School of Science and Technology, Espoo, Finland V. Vuorinen, Department of Electronics, Faculty of Electronics, Communication and Automation, Aalto University School of Science and Technology, Espoo, Finland A. Paul, Department of Materials Engineering, Indian Institute of Science, Bangalore, 560012 India Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Microstructural analyses of the parent pearlitic and bainitic rail steels were performed, and the results were compared with the microstructure of the welded pearlitic and bainitic steels. An increase in the ASTM grain size number of the heat-affected zone (HAZ) for both pearlitic and bainitic slot welds was observed. The microstructural features that were identified in the weldment of both slot-welded steels were very similar. This was expected since the same welding wire was used to weld both rail steels. The weld consisted of mainly ferrite and had similar grain size. The fusion zones of the welded pearlitic and bainitic rail steels were examined after flexural tests to determine if there were any cracks present due to improper or weak fusion. Examination of the entire fusion zone under high optical magnification revealed no cracks, indicating that a perfect fusion was achieved. The three-point flexural behavior of the parent pearlitic and bainitic steels was evaluated and compared with that of the slot-welded steels. It was found that that the welded pearlitic steel has superior fracture resistance properties when compared to the parent pearlitic steel. The average fracture resistance of the parent pearlitic steel was 79 MPa√m compared to 119 MPa√m for the welded pearlitic steel. The slot-welded bainitic steel, however, showed similar fracture resistance properties to the parent bainitic steel with average values of 121 and 128 MPa√m, respectively. The failure mechanism of the welded and parent pearlitic and bainitic steels was also identified. Microvoid coalescence was observed in both welded rail steel samples. This was manifested by dimpled features, which are associated with ductile failure. Content Type Journal Article Pages 1-10 DOI 10.1007/s11661-011-0665-4 Authors Aldinton Allie, College of Engineering, Architecture and Physical Sciences, Tuskegee University, Tuskegee, AL 36088, USA Heshmat Aglan, College of Engineering, Architecture and Physical Sciences, Tuskegee University, Tuskegee, AL 36088, USA Mahmood Fateh, Federal Railroad Administration, Washington, DC 20590, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Friction maps have been developed to explain the behavior of aluminum alloys under dynamic tribological conditions generated by the simultaneous effects of temperature and strain rate. A specially designed tribometer was used to measure the coefficient of friction (COF) of AA5083 strips subjected to sliding with a simultaneous application of tensile strain in the temperature range of 693 K to 818 K (420 °C to 545 °C) and strain rates between 5 × 10 −3  s −1 and 4 × 10 −2  s −1 . The mechanisms of plastic deformation, namely, diffusional flow, grain boundary sliding (GBS), and solute drag (SD), and their operation ranges were identified. Relationships between the bulk deformation mechanism and COF were represented in a unified map by superimposing the regions of dominant deformation mechanisms on the COF map. The change in COF (from 1.0 at 693 K (420 °C) and 1 × 10 −2  s −1 to 2.1 at 818 K (545 °C) and 4 × 10 −2  s −1 ) was found to be largest in the temperature–strain rate region, where GBS was the dominant deformation mechanism, as a result of increased surface roughness. The role of bulk deformation mechanisms on the evolution of the surface oxide layer damage was also examined. Content Type Journal Article Pages 1-18 DOI 10.1007/s11661-011-0649-4 Authors S. Das, Department of Mechanical, Automotive and Materials Engineering, University of Windsor, Windsor, ON Canada N9B 3P4 A. T. Morales, Chemical Science & Materials System Lab, General Motors Global Research and Development, Warren, MI 48090, USA A. R. Riahi, Department of Mechanical, Automotive and Materials Engineering, University of Windsor, Windsor, ON Canada N9B 3P4 X. Meng-Burany, Department of Mechanical, Automotive and Materials Engineering, University of Windsor, Windsor, ON Canada N9B 3P4 A. T. Alpas, Department of Mechanical, Automotive and Materials Engineering, University of Windsor, Windsor, ON Canada N9B 3P4 Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Aluminum with an open-pore structure was fabricated through nitridation of an AA6061-2 pct Mg-1 pct Sn powder mixture, where interconnected permeable AlN shells developed on each AA6061 particle and imparted strength to the assembly. The resulting intershell spaces form an open-pore structure. When such an open-pore structure is heated above the liquidus of the core, an open-closed pore transformation occurs, where the molten core in each shell spontaneously migrates to fill the open pores outside, leaving a closed pore inside each shell. Based on this finding, porous AA6061 with different open-pore fractions was fabricated by heating open-pore structures of AA6061 into the semisolid region, where the liquid fraction changes with temperature. The mechanism for the open-closed pore transformation is identified through detailed microstructural and thermodynamic analyses. Criteria for the open-closed pore transformation are specified. Additionally, net shape fabrication of porous aluminum with controlled pore features is realized using the novel concept. Content Type Journal Article Pages 1-8 DOI 10.1007/s11661-011-0675-2 Authors Peng Yu, School of Mechanical and Mining Engineering, ARC Centre of Excellence for Design in Light Metals, The University of Queensland, Qld, 4072 Australia M. Yan, School of Mechanical and Mining Engineering, ARC Centre of Excellence for Design in Light Metals, The University of Queensland, Qld, 4072 Australia G. B. Schaffer, School of Mechanical and Mining Engineering, ARC Centre of Excellence for Design in Light Metals, The University of Queensland, Qld, 4072 Australia Ma Qian, School of Mechanical and Mining Engineering, ARC Centre of Excellence for Design in Light Metals, The University of Queensland, Qld, 4072 Australia Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    To study the influence of hydrogen on the fatigue strength of AISI type 304 metastable austenitic stainless steel, specimens were cathodically charged with hydrogen. Using tension-compression fatigue tests, the behavior of fatigue crack growth from a small drill hole in the hydrogen-charged specimen was compared with that of noncharged specimen. Hydrogen charging led to a marked increase in the crack growth rate. Typical characteristics of hydrogen effect were observed in the slip band morphology and fatigue striation. To elucidate the behavior of hydrogen diffusion microscopically in the fatigue process, the hydrogen emission from the specimens was visualized using the hydrogen microprint technique (HMT). In the hydrogen-charged specimen, hydrogen emissions were mainly observed in the vicinity of the fatigue crack. Comparison between the HMT image and the etched microstructure image revealed that the slip bands worked as a pathway for hydrogen to move preferentially. Hydrogen-charging resulted in a significant change in the phase transformation behavior in the fatigue process. In the noncharged specimen, a massive type α′ martensite was observed in the vicinity of the fatigue crack. On the other hand, in the hydrogen-charged specimen, large amounts of ε martensite and a smaller amount of α′ martensite were observed along the slip bands. The results indicated that solute hydrogen facilitated the ε martensitic transformation in the fatigue process. Comparison between the results of HMT and EBSD inferred that martensitic transformations as well as plastic deformation itself can enhance the mobility of hydrogen. Content Type Journal Article Pages 1-10 DOI 10.1007/s11661-011-0661-8 Authors Hisao Matsunaga, Department of Mechanical Engineering, Fukuoka University, Fukuoka, 814-0180 Japan Hiroshi Noda, Needle Roller Bearing Technology Department, Automotive Bearing Technology Center, NSK Ltd, Gunma, 370-3344 Japan Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The low-angle grain boundary (LAGB) stability in an ultrafine-grained (UFG) Al alloy during monotonic loading was investigated by orientation imaging microscopy (OIM). The experiments show that boundaries with misorientation below ~2.5 deg are stable, while boundaries with misorientation between 2.5 and 15 deg are unstable. Similar results were observed during cyclic loading of UFG Al alloy. This behavior was rationalized using the nonequilibrium thermodynamics concept. On the other hand, it is postulated that the grain boundary behavior in microcrystalline alloy is different because of the larger dislocation mean free path. Content Type Journal Article Category Communication Pages 1-4 DOI 10.1007/s11661-011-0912-8 Authors P. S. De, Center for Friction Stir Processing, Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA R. S. Mishra, Center for Friction Stir Processing, Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    High Mn steels demonstrate an exceptional combination of high strength and large ductility as a result of their high strain-hardening rate during deformation. The microstructure evolution and strain-hardening behavior of Fe18Mn0.6C1.5Al TWIP steel in uniaxial tension were examined. The purpose of this study was to determine the contribution of all the relevant deformation mechanisms—slip, twinning, and dynamic strain aging. Constitutive modeling was carried out based on the Kubin–Estrin model, in which the densities of mobile and forest dislocations are coupled to account for the interaction between the two dislocation populations during straining. These coupled dislocation densities were used to simulate the contribution of dynamic strain aging to the flow stress. The model was modified to include the effect of twinning. To ascertain the validity of the model, the microstructural evolution was characterized in detail by means of transmission electron microscopy and electron back-scatter diffraction. Content Type Journal Article Pages 1-12 DOI 10.1007/s11661-011-0898-2 Authors Jinkyung Kim, Materials Design Laboratory, Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, Pohang, South Korea Yuri Estrin, Center for Advanced Hybrid Materials, Department of Materials Engineering, Monash University, Clayton, VIC 3800, Australia Hossein Beladi, Center for Material and Fibre Innovation, Deakin University, Geelong, VIC 3216, Australia Ilana Timokhina, Center for Material and Fibre Innovation, Deakin University, Geelong, VIC 3216, Australia Kwang-Geun Chin, Technical Research Laboratories, POSCO Gwangyang Works, Gwangyang, Jeonnam, 545-090 South Korea Sung-Kyu Kim, Technical Research Laboratories, POSCO Gwangyang Works, Gwangyang, Jeonnam, 545-090 South Korea Bruno C. De Cooman, Materials Design Laboratory, Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, Pohang, South Korea Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Deformation-induced martensite in type 304 stainless steel during micro-tension testing was characterized. The stress-strain behavior of uncharged and hydrogen-charged specimens revealed that hydrogen hastened the onset of hardening but decreased the strain-hardening rate, leading to premature plastic instability. In both specimens, a set of twin-related α′-martensite variants with Kurdjumov–Sachs relationships was prevalent. The Nishiyama–Wasserman relationship variant was also formed, but it was suppressed by hydrogen. This may be attributed to differences in the underlying deformation microstructure. Content Type Journal Article Category Communication Pages 1-5 DOI 10.1007/s11661-011-0925-3 Authors Yoji Mine, Department of Mechanical Engineering, Kyushu University, Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan Koichi Hirashita, Department of Materials Science and Engineering, Kumamoto University, Kurokami, Kumamoto 860-8555, Japan Mitsuhiro Matsuda, Department of Materials Science and Engineering, Kumamoto University, Kurokami, Kumamoto 860-8555, Japan Kazuki Takashima, Department of Materials Science and Engineering, Kumamoto University, Kurokami, Kumamoto 860-8555, Japan Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Intercritically austempered ductile irons hold promise for applications requiring fatigue durability, excellent castability, low production energy requirements, reduced greenhouse gas emissions, and excellent machinability. In the present study, four different ductile iron alloys, containing manganese and nickel as the primary austenite-stabilizing elements, were heat treated to obtain different quantities of austenite in the final microstructure. This article reports the microstructures and phases present in these alloys. Furthermore, lattice strains and diffraction elastic constants in various crystallographic directions and the transformation characteristics of the austenite were determined as a function of applied stress using in situ loading during neutron diffraction at the second generation Neutron Residual Stress Facility at the High Flux Isotope Reactor at Oak Ridge National Laboratory. Content Type Journal Article Category Symposium: Neutron and X-Ray Studies of Advanced Materials IV Pages 1-9 DOI 10.1007/s11661-011-0921-7 Authors Alan P. Druschitz, Virginia Tech, Blacksburg, VA 24061, USA Ricardo E. Aristizabal, University of Alabama at Birmingham, Birmingham, AL 35294, USA Edward Druschitz, University of Alabama at Birmingham, Birmingham, AL 35294, USA C. R. Hubbard, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA Thomas R. Watkins, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA L. Walker, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA Mel Ostrander, Rex Heat Treat-Alabama, Inc., Anniston, AL 36207, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    A model was developed to estimate the energy transfer from milling media to the powder during milling carried out in Simoloyer CM 01 (Zoz GmbH, Wenden, Germany), a horizontal attritor high-energy ball mill. The model was then used to estimate the energy transfer in milling of iron at 1000 rpm. Furthermore, the time required to achieve a particular grain size was formulated as a function of milling speed, using the model developed for the energy transfer. The results were verified at 500 rpm and 1500 rpm for iron and aluminum. Content Type Journal Article Pages 1-5 DOI 10.1007/s11661-011-0946-y Authors B. Karthik, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, 600036 India G. Sai Gautam, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, 600036 India N. R. Karthikeyan, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, 600036 India B. S. Murty, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, 600036 India Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Mechanical milling of a Ti-2 pct Y 2 O 3 powders mixture led to the synthesizing of a composite powder with a nanocrystalline Ti matrix having a mean crystallite size of 19 nm. Both the nanocomposite powder prepared through milling and the initial mixture of powders were consolidated by hot pressing under the pressure of 7.7 GPa at the temperature of 1273 K (1000 °C). The transmission electron microscopy (TEM) investigations of the bulk sample produced from milled powder revealed that Y 2 O 3 equiaxial particles of less than 30 nm in size are distributed uniformly in the Ti matrix with a grain size in the wide range from 50 nm to 200 nm. The microhardness of the produced nanocrystalline material is 655 HV0.2, and it significantly exceeds the hardness of the microcrystalline material (the consolidated initial mixture of powders), which is equal to 273 HV0.2. This finding confirms that reducing the grain size to the nanometric level can have a beneficial influence on the hardness of titanium alloys. Dispersion hardening also contributes to the hardness increase. Content Type Journal Article Pages 1-6 DOI 10.1007/s11661-011-0952-0 Authors Marek Krasnowski, Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw, Poland Jan Ryszard Dąbrowski, Faculty of Mechanical Engineering, Bialystok University of Technology, Wiejska 45c, 15-351 Bialystok, Poland Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The carbide growth kinetics enhanced in grain interiors is mainly due to the increased diffusivity in the direction normal to the tensile stress. The accelerated kinetics at the grain boundaries normal to the tensile stress is due to the increased grain boundary energy and the widened grain boundary path producing the increased diffusivity in the direction normal to the tensile stress. A strong segregation behavior of impurities to the grain boundary carbide interfaces follows the enhanced grain boundary carbide growth kinetics. Content Type Journal Article Category Communication Pages 1-5 DOI 10.1007/s11661-011-0930-6 Authors N. H. Heo, Power Gen Lab., KEPCO Research Institute, Daejeon, 305-380 Republic of Korea J. C. Chang, Power Gen Lab., KEPCO Research Institute, Daejeon, 305-380 Republic of Korea Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    A benchmark study was undertaken for casting residual stress measurements through neutron diffraction, which was subsequently used to validate the accuracy of simulation prediction. The “stress lattice” specimen geometry was designed such that subsequent castings would generate adequate residual stresses during solidification and cooling of ductile cast iron, without any cracks. The residual stresses in the cast specimen were measured using neutron diffraction. Considering the difficulty in accessing the neutron diffraction facility, these measurements can be considered as a benchmark for casting simulation validations. Simulations were performed using the identical specimen geometry and casting conditions for predictions of residual stresses. The simulation predictions were found to agree well with the experimentally measured residual stresses. The experimentally validated model can be subsequently used to predict residual stresses in different cast components. This enables incorporation of the residual stresses at the design phase along with external loads for accurate predictions of fatigue and fracture performance of the cast components. Content Type Journal Article Category Symposium: Neutron and X-Ray Studies of Advanced Materials IV Pages 1-10 DOI 10.1007/s11661-011-0907-5 Authors E. M. Johnson, Moline Technology Innovation Center–John Deere, Moline, IL 1265, USA T. R. Watkins, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6040, USA J. E. Schmidlin, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6040, USA S. A. Dutler, MAGMA Foundry Technologies, Inc., Schaumburg, IL 60173, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    Thermal desorption analyses (TDA) were conducted in high strength martensitic steels containing carbon from 0.33 to 1.0 mass pct, which were charged with hydrogen at 1223 K (950 °C) under hydrogen of one atmospheric pressure and quenched to room temperature. In 0.33C steel, which had the highest M s temperature, only one desorption peak was observed around 373 K (100 °C), whereas two peaks, one at a similar temperature and the other around and above 573 K (300 °C), were observed in the other steels, the height of the second peak increasing with carbon content. In 0.82C steel, both peaks disappeared during exposure at room temperature in 1 week, whereas the peak heights decreased gradually over 2 weeks in specimens electrolytically charged with hydrogen and aged for varying times at room temperature. From computer simulation, by means of the McNabb–Foster theory coupled with theories of carbon segregation, these peaks are likely to be due to trapping of hydrogen in the strain fields and cores of dislocations, and presumably to a lesser extent in prior austenite grain boundaries. The results also indicate that carbon atoms prevent and even expel hydrogen from trapping sites during quenching and aging in these steels. Content Type Journal Article Pages 1-10 DOI 10.1007/s11661-011-0909-3 Authors M. Enomoto, Department of Materials Science and Engineering, Ibaraki University, Hitachi, 316-8511 Japan D. Hirakami, Steel Research Laboratories, Nippon Steel Corporation, Chiba, 293-8511 Japan T. Tarui, Steel Research Laboratories, Nippon Steel Corporation, Chiba, 293-8511 Japan Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623

Description:    The phase transformations in an as-received Zr-2.5Nb pressure tube material were characterized in detail by neutron diffraction. The texture and volume fraction of α and β phases were measured on heating at eight different temperatures 373 K to 1323 K (100 °C to 1050 °C) traversing across the α /( α  +  β ) and ( α  +  β )/ β solvus lines, and also upon cooling at 1173 K and 823 K (900 °C and 550 °C). The results indicate that the α -phase texture is quite stable, with little change in the {0002} and ì í î 11 - 2   0 ü ý þ pole figures during heating to 1123 K (850 °C). The β -phase volume fraction increased while a slight change in texture was observed until heating reached 973 K (700 °C). On further heating to 1173 K (900 °C), there appears a previously unobserved α -phase texture component due to coarsening of the prior primary α grains; meanwhile the transformed β -phase texture evolved markedly. At 1323 K (1050 °C), the α phase disappeared with only 100 pct β phase remaining but with a different texture than that observed at lower temperatures. On cooling from the full β -phase regime, a different cooldown transformed α -phase texture was observed, with no resemblance of the original texture observed at 373 K (100 °C). The transformed α -phase texture shows that the {0002} plane normals are within the radial-longitudinal plane of the pressure tube following the Burgers orientation relationship of (110) bcc //(0002) hcp and [ - 1   11] \text bcc //[11 - 2   0] \text hcp with a memory of the precursor texture of the primary α grains observed on heating at 1173 K (900 °C). Content Type Journal Article Pages 1-16 DOI 10.1007/s11661-011-0914-6 Authors R. W. L. Fong, Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, ON K0J 1J0, Canada R. Miller, Department of Mechanical & Aerospace Engineering, Carleton University, Ottawa, ON K1S 5B6, Canada H. J. Saari, Department of Mechanical & Aerospace Engineering, Carleton University, Ottawa, ON K1S 5B6, Canada S. C. Vogel, Lujan Center, LANSCE, Los Alamos National Laboratory, Los Alamos, NM 87545, USA Journal Metallurgical and Materials Transactions A Online ISSN 1543-1940 Print ISSN 1073-5623