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With the development of high-speed and heavy-haul railway transportation, the surface failure of rail turnouts has become increasingly severe due to insufficient high hardness-toughness combination. In this work, in situ bainite steel matrix composites with WC primary reinforcement were fabricated via direct laser deposition (DLD). With the increased primary reinforcement content, the adaptive adjustments of the matrix microstructure and in situ reinforcement were obtained at the same time. Furthermore, the dependence of the adaptive adjustment of the composite microstructure on the composites’ balance of hardness and impact toughness was evaluated. During DLD, the laser induces an interaction among the primary composite powders, which leads to obvious changes in the phase composition and morphology of the composites. With the increased WC primary reinforcement content, the dominant sheaves of the lath-like bainite and the few island-like retained austenite are changed into needle-like lower bainite and plenty of block-like retained austenite in the matrix, and the final reinforcement of Fe3W3C and WC is obtained. In addition, with the increased primary reinforcement content, the microhardness of the bainite steel matrix composites increases remarkably, but the impact toughness decreases. However, compared with conventional metal matrix composites, the in situ bainite steel matrix composites manufactured via DLD possess a much better hardness-toughness balance, which can be attributed to the adaptive adjustment of the matrix microstructure. This work provides a new insight into obtaining new materials with a good combination of hardness and toughness.

Compared with conventional casting process, laser direct metal deposition (LDMD) can effectively reduce component segregation in non-equiatomic high entropy alloys (HEAs). However, the non-equilibrium thermal history imparted by this method has a significant effect on the microstructure and mechanical properties of the HEA. The present work prepared non-equiatomic (FeNiCo)-(AlCrSiTi) HEAs using the LDMD process, after which some samples were subjected to a subsequent vacuum remelting (VRM) treatment. The variations in phase composition, microstructure and hardness between the HEAs processed using the LDMD or VRM methods were investigated. Differences in phase composition increased with increases in the proportion of the Al, Cr, Si and Ti components. Compared with the HEA samples processed using the VRM method, the LDMD specimens possessed much finer and simpler microstructures mainly comprising solid solution phases. At relatively high concentrations of the Al, Cr, Si and Ti components (32 at% and 40 at% in total), the HEAs processed under LDMD conditions had similar grain morphologies, intermetallic phases and microhardness values, while the VRM specimens presented completely different microstructures and properties.

Stallion sperm is typically cryopreserved using low cooling rates and low concentrations of cryoprotective agents (CPAs). The inevitable water-to-ice phase transition during cryopreservation is damaging and can be prevented using vitrification. Vitrification requires high cooling rates and high CPA concentrations. In this study, the feasibility of stallion sperm vitrification was investigated. A dual-syringe pump system was used to mix sperm equilibrated in a solution with a low concentration of CPAs, with a solution containing a high CPA concentration, and to generate droplets of a defined size (i.e., ~20 μL) that were subsequently cooled by depositing on an aluminum alloy block placed in liquid nitrogen. Mathematical modeling was performed to compute the heat transfer and rate of cooling. The minimum CPA concentration needed for vitrification was determined for various CPAs (glycerol, ethylene glycol, propylene glycol, dimethyl sulfoxide) and combinations thereof, while effects of droplet size and carrier solution were also identified. Sperm vitrification was eventually done using a glycerol/propylene glycol (1/1) mixture at a final concentration of 45% in buffered saline supplemented with 3% albumin and polyvinylpyrrolidon, while warming was done in standard diluent supplemented with 100 mM sucrose. The sperm concentration was found to greatly affect sperm membrane integrity after vitrification-and-warming, i.e., was found to be 21 ± 12% for 10 × 106 sperm mL-1 and 54 ± 8% for 1 × 106 sperm mL-1. However, an almost complete loss of sperm motility was observed. In conclusion, successful sperm vitrification requires establishing the narrow balance between droplet size, sperm concentration, CPA type and concentration, and exposure time.

Owing to the high strength and plasticity, high-entropy alloys (HEAs) can be used as filler metals to achieve high-quality joints. However, the melting base metal in fusion welding can significantly change the chemical composition of the weld zone (WZ), which may cause the failure of high-entropy effects in the WZ. In the present study, a high-entropy filler metal of CoCrNiMnAl0.6Ti0.3Si0.1 was used to join the dissimilar metals of SMA490BW steel and 304 stainless steel. Two types of joints were obtained by whether the welding plates had a V-groove or not. The effects of workpiece groove on the microstructure, element distribution, phase structure, microhardness, and tensile strength of dissimilar joints, as well as the controllability of the high-entropy effects in WZ were explored. It was found that a 60° V-groove in the workpiece could significantly reduce the amount of Fe element in the WZ. Microstructures in the WZs were changed from columnar/equiaxed grains of the No V-groove sample to lamellar structures of the V-groove sample. The microhardness in the WZ of the latter was 33% higher than that of the former. The reason was mainly related to the phase structures in two WZs. Two types of samples had a similar notched tensile strength, which was higher than SMA490BW steel, and lower than 304 stainless steel.

Fe-Al intermetallic compounds (IMCs) have huge adverse effects on the dissimilar metal joining of aluminum to steel. High-entropy alloys can use high mixing entropy to promote the formation of single-phase solid solution structures, which would have significant advantages in inhibiting the formation of Fe-Al IMCs in the welding of Al/steel joints. In this study, three types of filler metals, including CoZnCuMn0.8Si0.2 powders with a high-entropy design, the FeCoCrNiMn high-entropy alloy powders, and the comparative Al-12Si powders, were used to join the dissimilar metals between Al 6061 alloy and 304 stainless steel by laser deposition welding. It was found that high-entropy filler metals, including CoZnCuMn0.8Si0.2 and FeCoCrNiMn powders, could successfully be used to join dissimilar metals of aluminum to steel. The high-entropy effect could be achieved in the weld zones (WZs) by using CoZnCuMn0.8Si0.2 and FeCoCrNiMn powders, which could significantly inhibit the formation of Fe-Al IMCs in the WZs, and promote the formation of fine and equiaxed grains, without element segregation, in the WZs. An unmixed zone with a width of 10−20 μm was formed between the WZ and HAZ in the Al 6061 alloy side for those two dissimilar joints. And some Fe-Al IMCs with submicron or nanoscale size were presented in the unmixed zones.

Increasing magnetically favorable //ND texture components is a key challenge in the preparation of high-efficiency non-oriented electrical steels. In this study, an Fe-1.3 wt% Si steel with strong Cube ({100} ) and Goss ({110} ) texture was successfully produced by novel twin-roll strip casting, cold rolling and annealing process. The microstructure and texture of the material was characterized by optical microscopy, electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). The origin and formation mechanism of texture are described from the perspective of deformation and recrystallization behavior of specifically oriented grains. It was observed that initial Cube rotated toward {013} -{110} besides rotation toward {001} -{001} during cold rolling. In addition, new Cube deformation bands were developed in the deformed {115} -{115} grains. Cube components were partly retained as large block, small band structure and crystallite after heavy cold rolling. The Cube deformation structures served as nucleation sites of new Cube grains. The shear band within {114} , {112} and {111} matrix also provided some Cube nuclei. Morphology change from near bar-shaped to equiaxed occurred during the growth of Cube and Goss grains. The formation of recrystallization texture is attributed to the oriented nucleation mechanism, and the orientation pinning and size effects that impacted the intensity of texture component. The low thickness of strip and coarse solidification microstructure with strong {100} texture are the decisive factors to obtain strong Cube and Goss texture in strip-cast non-oriented electrical steel.

Recent studies indicate that the texture distribution in friction stir welded (FSW) Mg alloys can be tailored and hence improve the joint performance. In this work, a crystal plasticity finite element modeling (CPFEM) was performed to understand the effects of texture distribution in stir zone (SZ) on the non-uniform plastic deformation and fracture localization. In total, six kinds of observed or purposely tilted texture distributions were modelled. The “concave-convex” appearance, as commonly observed in the tensile sample, was successfully simulated. It reveals that the mirror-symmetrical distribution of basal planes in the region of easy to activate basal slip (EABS) determined the “concave-convex” appearance in SZ-center. The asymmetrical appearance exchanged on plane A and plane B when the directions of basal planes were switched in the two EABS regions. Furthermore, the asymmetrical feature of plastic deformation was changed with varying the texture distribution in SZ. The “embossed” feature became more obvious in SZ-center first, and then gradually weakened with the c-axis rotated away from the weld plate plane. Severe necking was successfully simulated in SZ-center of FSW-H joint and in SZ-side of FSW-L joint. That might determine the observed fracture morphology. We believe that this simulation study is helpful for further improving the performance of FSW Mg joints.

In this paper, micrometer SrMoO4:Eu[Formula: see text] phosphors with different morphologies were prepared by poly(acrylic acid)-assisted hydrothermal method, and the structure, energy band and luminescence properties of SrMoO4:Eu[Formula: see text] were studied in detail. Furthermore, the relationship between the phosphors’ structure and luminescence properties was discussed. The modified SrMoO4:Eu[Formula: see text] have great potential as functional materials in fluorescent fingerprint and LED device applications. The results indicated that the poly(acrylic acid) and the hydrothermal condition are the key factors for the achievement of better luminescent performances.

High-entropy alloys having excellent properties are particularly suitable for the application as the filler metals in welding. In the present study, multi-component mixed powders of FeCoCrNiMn and CrFeNi2.4Al0.6, based on a high-entropy design, as well as the comparative 316L stainless steel powders, were used as the filler metals, to achieve the dissimilar welding between 304 stainless steel and SMA490BW steel by laser deposition welding. By comparative analysis of the microstructure and mechanical properties of three types of joints, the feasibility and weld-ability of the filler metal powders based on a high-entropy design were studied. It was found that the melting of base metal (BM) and weld metal dilution had an impact on the set high-entropy component in the weld zone. And high-entropy structures were achieved in the weld zone by using the powders of CrFeNi2.4Al0.6. Compared to the BM of SMA490BW steel, three types of joints presented a higher notched tensile strength and had a better corrosion resistance. The joint welded using the powders of CrFeNi2.4Al0.6 had the lowest hardness value in the weld zone, in which the joint was fractured during the notched tensile tests. The other two joints fractured near the notch in the SMA490BW steel side. Transgranular fracture and a typical dimple fracture were observed in the fractured joints. In this work, multi-component mixed powders of FeCoCrNiMn and CrFeNi2.4Al0.6, based on a high-entropy design, were used as the filler metals to achieve the dissimilar welding of 304 stainless steel to SMA490BW steel by laser deposition welding. And a detailed investigation of microstructures and mechanical properties of those dissimilar joints was carried out to explore the feasibility and weld-ability of the filler metal powders based on a high-entropy design.

The effects of isothermal heat treatment on microstructures of an A356 alloy containing rare-earth gadolinium (Gd) were investigated to obtain an optimum semi-solid structure. Our results revealed that the primary α-Al phase of the semi-solid A356 alloy containing Gd was significantly refined and that its morphology was spherical or near-spherical. Increases in holding temperature and prolongation of holding time led to an initial decrease in size during the primary α-Al phase, followed by a gradual increase. Solid–liquid interfacial tension resulted in the spheroidization of the primary α-Al phase.

Multipass friction stir processing (FSP) can result in a homogeneous microstructure and significant improvement in mechanical properties of magnesium alloys. Few studies have concentrated on the surface properties of Mg–Zn–Zr alloy during multipass FSP. The aim of this study was to investigate the microstructure evolutions as well as the effects on the surface corrosion and wear resistance of ZK60 plates during multipass FSP. An interesting finding is that FSP can significantly refine the grains and improve the surface properties of ZK60 alloy. However, subsequent passes of FSP cannot further reduce the grain size in the stir zone, but they cause an increase in the grain size in the ZK60 alloy. In addition, the subsequent passes of FSP are not beneficial, but rather are, harmful to the corrosion resistance of ZK60 alloy. There is little positive effect on the improvement in the wear resistance of ZK60 plates.

A dual-gradient bainite steel matrix composite was fabricated by direct laser deposition (DLD) method. The decomposition of WC (reinforcements) during DLD is utilized to adjust the gradient microstructure of the composite. Both the matrix morphology and the reinforcement distribution present obvious gradient variation along the deposition direction. The microhardness and impact toughness exhibit the opposite tendency from the bottom to top of the composite, which shows a good agreement with the gradient microstructure. The surface microhardness and impact toughness of the dual-gradient composite are 510 HV and 75 J/cm2, respectively. The hardness and toughness combination of the composite is superior to most steels for railway frog. The dual-gradient composite has great potential in improving the performance of railway frog.

Friction stir welding (FSW) is a solid-state joining technique, which can avoid surface distortion and grain coarsening, and is very suitable for the joining of magnesium (Mg) alloys. However, a pronounced and inhomogeneous deformation texture was usually formed in the stir zone (SZ) of Mg welds. This has significant effect on the joint strength and fracture behavior of FSW Mg joints. In this review, microstructure and texture evolutions in weld zone (WZ) are analyzed based on the electron backscatter diffraction (EBSD) data. Schmid factor (SF) changes for slip and extension twinning were observed and discussed. The localized plastic deformation and fracture mechanisms of Mg welds are analyzed. In addition, some methods for improving the joint strength of FSW Mg welds are tested. Finally, the research direction of FSW Mg alloys in the future is determined.

Strain accumulation is easily formed in friction stir welded Mg alloys which significantly deteriorate the strength of the joints. However, the formation mechanisms of strain accumulation ...

Semi-solid billets of A356 alloy were fabricated using a sloping-plate device. This study investigated the effects of reheating on the microstructural evolution of the alloy. Prolonged holding times and higher reheating temperatures caused the primary α-aluminum particles to gradually grow and spheroidize, resulting in increased liquid fraction. The optimal reheating condition was 580°C for 25 min, during which the average grain size increased to 89.3 μm and the shape factor reached 1.18. The secondary phases were also refined by the reheating process.

The microstructure evolution of semi-solid SiCp/AZ91D nanocomposite during isothermal heat treatment process in the mushy-zone was investigated. The results indicate that the nano-size SiC particles in composite are distributed uniformly and the grains are refined significantly by the addition of nano-size SiC particles. The semi-solid microstructure evolution experiences four stages during isothermal heat treatment process: the initial coarsening, structural separation, spheroidization and final coarsening. The grain size of the primary α-Mg phase decreases with the increasing of holding temperature. With the prolongation of holding time, the grain size of the primary α-Mg phase decreases at first and then increases. The optimum isothermal heat treatment parameter is 575℃ for 30min, under which the average grain diameter is 58μm and shape factor is 1.25.

Although the microstructure of Mg alloys can be significantly refined after friction stir welding (FSW), the joint strength often decreases due to texture redistribution and precipitate dissolution. In this study, cast ZK60 alloy plates were successfully joined by FSW. Then, post-weld compression and aging treatment were applied on the joints, and their effects on microstructure, texture, and mechanical properties were examined. A local basal texture similar to that reported for FSW AZ31 alloy was formed in the stir zone of the ZK60 alloy after FSW, and the grain size was refined to ~3.7 µm in the stir zone. Profuse { 10 1 ¯ 2 } twinning was generated in various regions after 5% post-weld compression. Thus, the yield strength of ZK60 joint increased by 45 MPa. In contrast, the yield strength increased by 32 MPa after the aging treatment. This indicates that post-weld compression increased the number of precipitates in the ZK60 joint during subsequent aging, because the twins and dislocations generated during the compression provide more sites for precipitation.

Owing to the low corrosion and wear resistance of magnesium alloy, surface properties are the key factors affecting its application. But few studies have concentrated on the surface properties of friction stir welded Mg–Zn–Zr alloy. The aim of the present paper is to investigate the effects of friction stir welding (FSW) and subsequent ageing on the surface corrosion and wear resistance of ZK60 alloy. It is found that due to the significant grain refinement and redistribution of precipitates, the surface corrosion and wear resistance of ZK60 plates are enhanced by FSW. Morphology of inter-granular corrosion in base metal is changed into pitting corrosion after welding. Subsequent ageing can significantly reduce the corrosion resistance of the welded plates.

Strong local texture is usually formed in friction stir welded (FSW) Mg alloys and varies in different positions of the weld zone. Textural variation has an impact on fracture behavior and caused a poor mechanical property during the transverse tensile tests. However, due to the different stress and strain state between the inner and outer surfaces, the effect of textural variation on fracture behavior in bending tests is still unknown. The present study aims to investigate the relationship between textural variation, twinning activity and fracture behaviors in bending tests by Schmid factor analysis. It is found that sudden change of texture at the transition zone (TZ)/stir zone (SZ) interface and different twinning activity between the TZ and SZ-side have an impact on fracture behavior of bending samples, especially for crack propagation at the TZ/SZ interface for Surface bending test. The effect of textural variation on fracture behavior in bending is highly dependent on the local stress state and it can be well explained by the calculated Schmid factor in terms of the assumed stress state for bending. The present work is helpful for tailoring the local texture to change fracture behavior and improve the joint strength of FSW Mg welds.

Rational design of cryopreservation strategies for oocytes and ovarian cortex tissue requires insights in the rate at which cryoprotective agents (CPA) permeate and concomitant water transport takes place. The aim of the current study was to investigate possible differences in permeation kinetics of different CPAs (i.e., glycerol/GLY, ethylene glycol/EG, dimethyl sulfoxide/DMSO, and propylene glycol/PG), in equine oocytes as well as ovarian tissue.Membrane permeability of oocytes to water (Lp) and to CPAs (Ps) was inferred from video microscopic imaging of oocyte volume responses during perfusion with anisotonic and CPA solutions. CPA diffusion into ovarian tissue and tissue dehydration was monitored during incubation, using osmometer and weight measurements, to derive CPA diffusion coefficients (D).Membrane permeability of oocytes towards CPAs was found to increase in the order GLY EG DMSOPG. Permeability towards water in anisotonic solutions was determined to be higher than in CPA solutions, indicating CPAs alter membrane permeability properties. CPA diffusion in ovarian tissue increased in the order GLY,PG EG,DMSO. Tissue dehydration was found to increase with exposure to increasing CPA concentrations, which inversely correlated with CPA diffusivity.In conclusion, it is shown here that the rate of CPA movement across membrane bilayers is determined by different physical barrier factors than those determining CPA movement in tissues.The parameters presented in this study can be applied in models describing solute and water transport in cells and tissues, as well as in cryopreservation protocols.

Friction stir welding (FSW) has promising application potential for Mg alloys. However, softening was frequently occurred in FSW Mg joints because of the presence of a β-type fiber texture. The present study aims to understand the influence of texture distribution in stir zone (SZ) on deformation behavior and joint strength of FSW Mg welds. AZ31 Mg alloy joints were obtained by FSW with two sets of welding speed and rotation rate. Detailed microstructure and texture evolutions were examined on Mg welds by electron backscatter diffraction (EBSD) techniques. It was found that the changes of welding parameters can affect texture distribution and the characteristic of texture in the transition region between SZ and thermal-mechanical affected zone (TMAZ). As a consequence, the activation ability of basal slip and extension twinning was changed, which therefore influenced joint strength, inhomogeneous plastic deformation and fracture behaviors. The present work provided some insights into understanding the texture–property relationship in FSW Mg welds and indicated that it is effective to tailor the joint performance by texture control.

In the present study, an Mg weld with β-type fiber texture was produced by friction stir welding (FSW) and then was subjected to tension and compression along the transverse direction (TD). The deformed microstructure by 5% strain was examined in various regions of the Mg weld by electron backscatter diffraction (EBSD) technique. It was found that profuse twinning was activated in stir zone (SZ) -side after tension and in SZ-center and crown zone (CZ) -center after compression due to the presence of relatively large Schmid factor (SF). However, a few twins (2–3%) were also observed in SZ-center after tension and in SZ-side after compression. In this case, the twins have very small and even negative SF. For the twins with large SF, they were likely connected at grain boundaries forming twin pairs, while for those with small or negative SF, they were mostly confined within grains. For connected twins, most of the active variants have favorable SF and geometric compatibility factor (m′). However, the distributions of SF and m′ are different between the twins formed in compression and tension. For isolated twins, the adjacent grains connected with the twins were generally in favorable orientation for basal slip, and the selection of twin variants was likely affected by m′ between the most favorable basal slip and the twins.

Friction stir welded Mg alloys usually break in transition zone (TZ), i.e., the transition region between base material (BM) and stir zone (SZ). Therefore the physical nature in TZ especially close to the tool shoulder affected region (i.e., crown zone, CZ) is the key point for understanding the weld performance. The present paper aims to investigate the microstructural and textural features in triple junction region of BM, SZ and CZ in attempt to have an in-depth understanding of the structure-property relationship in FSW Mg alloys. Banded structures and their correlation with (0001) plane traces were revealed in the triple junction region after etching by 10% acetic acid. Drastic textural changes were found, which led to inhomogeneous activation of extension twinning after 5% transverse tension. The profuse activation of twinning led to strain localization and finally developed to fracture in the tensioned specimens.

Friction stir processing (FSP) was successfully applied to modify the microstructure and texture of an Mg-8Gd-5Y-1.1Nd-0.45Zr (wt.%) alloy. Two kinds of original alloys, i.e., solid solution (SS) alloy and aging (AG) alloy were used for a comparative study. The results show that the grains in SZ were greatly refined to 3–4 μm after FSP in both SS and AG alloys. However, the form of rare earth elements (either as solute or forming precipitates) in original alloys can largely influence the homogenization of grains. Uniform equiaxed grains were found in the former, whereas fine grain bands were formed in the latter. Relatively weak texture was formed in stir zone (SZ) of the Mg–Gd–Y–Nd–Zr alloy after FSP. The texture evolution in SZ is similar to many previous reports on FSW of AZ and ZK series Mg alloys. Both types of continuous and discontinuous dynamic recrystallizations (DRX) were observed in the transition region between SZ and base material in AG-FSP alloy.

The present study aims to investigate the twinning behavior and texture evolution during bending of a friction stir welded (FSW) AZ31 Mg alloy. Two kinds of three-point bending tests (designated as Surface test and Base test) were applied at room temperature. Strong texture-dependent twinning characteristics were revealed after bending. The largest numbers of extension twins were observed in SZ-side after Surface test and in SZ-center after Base test. The texture-dependent twinning activity was well explained by the calculated Schmid factor based on a speculated local stress state. Some extension twins were likely connected with each other and formed twin chain or twin band, and most of the neighboring twins present a high geometrical compatibility factor (larger than 0.8), implying that the local strain compatibility played an important role in the formation of connected twins.

Friction stir welding was successfully applied to joint Mg–3Al–1Zn alloy sheets. Serious strain localisation was observed during transverse tensile tests of the welds. Fracture was initiated from the interface of thermal–mechanical affected zone and stir zone in retreating side. The reasons for such localised fracture behaviour were explained by analysing the texture, Schmid factor, grain size and strain localisation characteristics in retreating side and advancing side. The results suggest that the coarser grain size and higher Schmid factor resulted in the easier activation of basal slip in retreating side than advancing side, which caused more serious strain localisation and stress concentration, and hence promoted fracture initiation from the interface of thermal–mechanical affected zone and stir zone in retreating side.

Dissimilar joints of magnesium alloys were obtained by friction stir welding. Detailed microstructure and texture examinations were performed on the joints. Significant difference in microtexture distribution and microstructural features is observed between crown and stir zones in the dissimilar joints. However, an overall effect of these factors on mechanical properties of layered joints is not obvious as both the up and middle samples present quite similar yield strength and strain hardening behaviour. Moreover, both samples fracture in the Mg–3Al–1Zn alloy side. The fracture of the middle sample starts at the boundary of transition and stir zones, while the up sample starts in the crown zone side.