Recrystallization Grain Research Articles

A physically based constitutive model considering dynamic recrystallization of ERNiCrMo-3 alloy

ERNiCrMo-3 alloy is widely used in the welding of nickel-based alloys. This study investigated the hot deformation and discontinuous dynamic recrystallization (DRX) behavior of ERNiCrMo-3 alloy through hot compression tests at deformation temperatures ranging from 990 °C to 1170 °C and strain rates ranging from 0.01 to 10 s−1. Experimental results showed that under conditions of elevated temperatures and lower strain rates, discontinuous dynamic recrystallization was prone to occur upon reaching critical strain, and the distribution of carbide and nitride particles within the alloy matrix affects recrystallization nucleation and grain boundary migration. A two-stage constitutive model was established based on classical dislocation density theory and DRX kinetics. Comparison between predicted and experimental data demonstrated a strong agreement, highlighting the accuracy and utility of the proposed constitutive model.

Tailoring the microstructure of Al/Ti laminated composite through hot press sintering process to achieve superior mechanical properties

A novel method based on hot press sintering was proposed to fabricate the Al/Ti laminated composite, and the effects of sintering parameters on microstructure, interfacial structure, and mechanical properties were thoughtful examined. The results showed that insufficient sintering caused obvious voids and cracks at Al/Ti interface. With the increase of temperature or holding time, a good metallurgical bonding without defects was achieved, and both the recrystallization fraction and grain size of α phase in Ti layer increased, accompanied by the transformation of α to β phase and growth of intermetallic phase. The microstructure variation of Al layer is not evident with changing the sintering parameters. Due to the relatively low formation energy, the nanoscale TiAl3 phase with massive stacking faults formed at Al/Ti interface, and lots of dislocations existed at Al layer near the interface. The voids and cracks formed at Al/Ti interface led to the premature failure of laminate. On the basis of the metallurgical bonding and small TiAl3 phase, the high fraction and texture intensity of α phase were the dominated strengthening factors. Moreover, the back stress generated at Al/Ti interface contributes to an extra strengthening. The superior mechanical properties of Al/Ti laminate with a tensile strength of 670.9 MPa and a fracture strain of 0.33 were obtained with the sintering temperature of 600 °C and holding time of 2 h.

Research on the Hot Deformation Process of A100 Steel Based on High-Temperature Rheological Behavior and Microstructure.

To obtain the optimal hot deformation process, the rheological and dynamic recrystallization behaviors of A100 steel were researched through isothermal compression tests. Firstly, a Hensel-Spittel constitutive model was established based on the stress-strain curves. Secondly, dynamic recrystallization percentage and grain size models were established to identify the necessary conditions for complete dynamic recrystallization. Finally, microstructural analysis was employed to validate the accuracy of the recrystallization model. The results indicate that the flow stress is highly sensitive to both the strain rate and the temperature, and the HS model demonstrates a high predictive accuracy, with a correlation coefficient of 0.9914. There exists a contradictory relationship between decreasing the average grain size and increasing the recrystallization percentage. The higher the percentage of dynamic recrystallization, the larger the average grain size tends to be. This situation should be avoided when devising the actual processing procedures. The optimal hot working processes for achieving complete dynamic recrystallization and a smaller average grain size are as follows: a strain equal to or greater than 0.6, a temperature between 1193 and 1353 K, and a strain rate between 0.1 and 1 s-1.

Study on hot compressive deformation behavior and microstructure evolution of G13Cr4Mo4Ni4V steel

To solve the problem of poor uniformity of microstructure of high alloy bearing steel G13Cr4Mo4Ni4V after rolling, the deformation behavior of the steel and its effect on the microstructure evolution was studied systematically. Gleeble-3800 thermo-mechanical simulator was used for precise control of deformation temperature ranging from 1000 to 1200 °C and deformation rate 0.01–10 s−1. Based on modified stress and strain curves by temperature and friction, the processing map of tested steel was drawn. Electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) were used to analyze the typical microstructure and carbide properties of different hot working domains respectively. The results showed the processing map could be divided into four regions: domain A 1000–1150 °C, 0.1–10 s−1; B 1000–1100 °C, 0.01–0.1 s−1; C 1100–1150 °C, 0.01–0.1 s−1 and D 1150–1200 °C, 1–10 s−1. Domain A was characterized by incomplete dynamic recrystallization (DRX) which included fine recrystallized grains and elongated deformed grains, whose softening mechanism was mainly discontinuous DRX (dDRX) and limited DRV and continuous DRX (cDRV) related to the ferrites and carbides. For domain B, the deformed grains gradually disappear with temperature rising, instead serrated grains appear with dDRX as dominating softening mechanism. A large number of carbides hinder DRX at 1000 °C with low temperature. With the increase of temperature, carbides dissolve and DRX degree increases. Grain coarsening is obvious because of high deformation temperature and low strain rate in domain C, although the nanoscale MC type carbides prevent recrystallization grain coarsening to some extent. Completely DRX resulted in uniform and fine with defect-free deformation microstructure in domain D, whose volume fraction of recrystallization reached up to 0.96 according to EBSD results. By considering the uniformity of microstructure and the distribution of carbide comprehensively, domain D is an ideal region for hot working.

Revealing the microstructure evolution mechanism and mechanical responses of a novel Al–Zn–Mg–Cu alloy by hot deformation process

The effect of hot rolling with different rolling deformations on the microstructure evolution and improvement of mechanical properties of the novel Al–Zn–Mg–Cu alloy are investigated via optical microscope (OM), scanning electron microscope (SEM), electron backscattered diffusion (EBSD) and transmission electron microscope (TEM). The findings showed that the equiaxed grains with low dislocation density gradually elongate to become fibrous with high dislocation density as hot rolling deformation growing, and the dynamic dissolution of precipitations occurs at the grain boundaries of small dynamic recrystallization (DRX) grains. Dislocation entanglement is formed when a high density of dislocation is clearly visible following various rolling deformations. Dislocation cells could evolve into sub-grains, and ultimately become recrystallized grains as a result of continuous energy absorption. The percentage of low angle grain boundaries (LAGBs) with varying rolling deformation increases swiftly then declines slightly which linked to more deformed grains and sub-grains, as well as less recrystallized grains. High angle grain boundaries (HAGBs), however, show the opposite pattern. Ultimate tensile strength (UTS) and yield strength (YS) of the alloys reach peaks at deformation of 90% (UTS: 620.0 MPa, YS: 583.7 MPa). Which is predominantly attributed to the texture enhancement, grain refinement, and pinning effect of Al3(Sc, Zr, Ti) particles of L12 structure on the grain boundaries and dislocations.

Microstructure characteristics, yield asymmetry and fracture mechanism of the fine grained thin-wall Mg-6.03Zn-0.55Zr tubes fabricated by hot spinning

In this study, thin-wall Mg-6.03Zn-0.55Zr alloy tubes consisted of fine dynamic recrystallized (DRXed) grains and ultrafine grains were successfully obtained by hot spinning process. The results showed that the microstructures of the initial extruded tubes were greatly refined with average grain sizes of 4.46–10.32 µm (300–450 ℃) due to the DRX process, especially at low spinning temperatures. Moreover, the basal texture was transformed from extruded fiber texture to spun tilted plane texture with an angle of ∼10° deviated from the axial direction (AD). More specifically, the basal texture was weakened along AD but was strengthened along the transverse direction (TD) compared with the extruded texture due to the reduced difficulty in pyramidal <c+a> slip activation and the shear deformation induced by the rollers. Consequently, the spun Mg-6.03Zn-0.55Zr alloys showed significant yield asymmetry along AD and TD at room temperature and the increase in spinning temperature had a negative influence on yield strength (YS) that the YS along AD decreased from 290 ± 5 MPa (300 ℃) to 232 ± 2 MPa (450 ℃) and the YS along TD decreased from 236 ± 6 MPa (300 ℃) to 198 ± 4 MPa (450 ℃). Both texture and grain refinement were the important factors in the mechanical properties according to the Hall-Petch relationship due to the varied activation fractions of deformation modes along AD and TD, especially the activation of prismatic <a> slip. Moreover, the fracture mechanism of the spun alloys consisting of fine DRXed grains and ultrafine grains was unusual. The aggregated ultrafine grains played a negative role in the fracture mechanism, because the ultrafine grains were transformed from the dislocation cells and the micro-crack easily occurred in the ultrafine grains.

Elucidating the warm compression of CoCrCuFeNi high entropy alloy: Modeling and microstructural evolution

The warm compression tests were carried out at various temperatures of 400, 550, and 700 °C and strain rates of 0.01, 0.001, and 0.0001 s−1 to unravel the warm deformation behavior of CoCrCuFeNi high entropy alloy (HEA). The microstructural evolutions were characterized using x-ray diffraction (XRD), differential scanning calorimetry (DSC), a field emission gun scanning electron microscope (FESEM) equipped with energy dispersive spectroscopy (EDS), and electron backscattered diffraction (EBSD) detector. These microstructure studies show a dendritic structure containing a bright phase rich in Cu and a darker phase rich in Fe, Cr, and Co. The solidification and melting points of the bright phase are 1136 °C and 904 °C, respectively and the dark phase nucleates at 1365 °C based on DSC results. A Zener-Hollomon parameter was employed to model and predict the warm compression behavior by calculating the activation energy (∼451 kJ/mol), developing a precise constitutive equation (correlation coefficient: R = 0.99), and constructing a processing map for determining the stable temperature and strain rate (strain rates lower than 10−2.75 s−1 and temperatures between 400 and 700 °C) of the plastic flow behavior of the alloy. The FESEM results confirmed the stability and instability domains predicted by the processing map. Moreover, the EBSD analysis indicated that the continuous dynamic recrystallization (CDRX) grains nucleated in the strain rate of 0.0001 s−1 at temperatures higher than 400 °C. Larger grains were formed at 550 and 700 °C due to lower Z parameters in higher temperatures.

Unveiling the microstructure evolution and deformation mechanisms of micro-alloying Mg-1.5Zn-0.5Zr-0.5Sr alloy via extrusion-shearing

Obtaining high strength without sacrificing ductility in Mg alloys is of great importance. However, the hexagonal close-packed crystal structure critically limits the deformation of Mg alloys. In this work, novel Mg-1.5Zn-0.5Zr-0.5Sr (wt.%) alloys were fabricated through homogenization, direct extrusion (DE), and extrusion-shearing (ES) processes. The effects of three different processes on microstructures, texture, and mechanical properties were thoroughly investigated. The results show that the average grain size of the alloy was greatly refined after hot extrusion. The alloy after the DE process exhibited a typical bimodal microstructure with dynamic recrystallized (DRXed) grains showing a strong <101‾0 > fiber texture parallel to extrusion direction (ED), while the small-sized unDRXed grains showed relatively weak basal texture. In addition, the strength was significantly improved, with the value of yield strength (YS) reaching ∼229 MPa and ultimate tensile strength (UTS) reaching ∼262 MPa. This is mainly attributed to grain boundary strengthening and dislocation strengthening. Compared to the DE-processed alloy, the basal texture intensity was significantly decreased and non-basal slip was activated after the ES process, which indicates that the shearing deformation during ES could improve the ductility, with the fracture elongation (FE) increased from ∼13.9 % to ∼21.4 %. This work aims to unveil the deformation mechanisms in Mg-1.5Zn-0.5Zr-0.5Sr alloy and provides an efficient way for preparing micro-alloying Mg alloys with low cost and significant improvement of comprehensive properties.

Finite element simulation and industrial validation for DRX evolution of magnesium alloy thin-walled wheel formed by backward extrusion

The physical field and dynamic recrystallization (DRX) evolution of magnesium (Mg) alloy thin-walled wheels during backward extrusion (BE) were investigated by coupling the cellular automaton (CA) model with the finite element (FE) model in this study, and the simulation results were verified by industrial experiments. Findings revealed that the wheel bottom is always in a three-way compressive stress state when the lower rim is filled, while the rim is under two-way compressive stress and one-way tensile stress in the filling process. Sufficient effective strain is accumulated at the rim compared to the wheel bottom, and different from the uniform and small grain size distribution at the rim, there was insufficient DRX at the wheel bottom, as well as local grain growth due to deformation heat. The wheel bottom is dominated by the mixed grain structure, mainly consisting of necklace-like DRXed grains and initial coarse grains, and the microstructure at the rim shows equiaxed grains except for the upper rim, where are still incomplete recrystallization grains. With the increase of extrusion temperature (360–420℃), the DRX volume fraction and the average grain size of the wheel increased, but the effect on the grain size at the rim was not significant due to severe plastic deformation (SPD) above the critical strain.

Effect of induced screw twisted strain on the twin orientation regulation and the ductility of pre-twined ZM21 Mg alloys

A novel twist strain-induced twin orientation regulation (TITOR) has been developed to modify the basal texture of Mg alloys. Firstly, the {10–12} tensile twins are pre-set by pre-compression on the ZM21 Mg alloy along the extrusion direction (ED), and then the TITOR process is adjusted to regulate the twins’ orientation. The results show that the orientation of some twins deviated by 30° from the ED direction to the transverse direction (TD) direction after introducing twist strain. The introduction of multiple passes of twist strain will result in almost all grains transforming into dynamic recrystallization (DRX) grains. And the generation of DRX behavior will be updating the microstructure. The mechanism in the TITOR process is continuous dynamic recrystallization (CDRX), which does not alter the orientation of the grains. When the PT samples undergo multiple passes TITOR treatments, the orientation of the DRX grains shifts towards the twisted plane (grain c-axis deviates by ∼ 30° from ED to TD direction). The formation of twist texture results in a larger value of SF, which is beneficial for the basal slip. Compared with the extruded Mg alloys, the TITOR-8P sample fracture elongation (FE) has been increased from 14.3 % to 30.6 % due to the promotion of basal slip activities and grain refinement. The ultimate tensile strength (UTS) has been increased from 243.5 MPa to 375.5 MPa. The newly proposed TITOR scheme is of great significance for promoting the application of Mg alloys.

Microstructure evolution of high-temperature deformation behavior of nickel based alloys for advanced ultra-supercritical applications

The microstructure evolution of nickel based alloy used in advanced ultra-supercritical power plants was studied in the strain range of 0.22–0.91 at 1000–1100 °C/0.01 s−1 by using the electron backscattered diffraction technique. The interaction of the dislocation with the Σ3 twin boundary causes the Σ3 twin boundary to deviate from its specific misorientation. The Σ3 twin boundary is stripped of its signature by the interaction between the dislocation and the Σ3 within the deformed grain. In the process of recrystallization, the Σ3 twin boundaries are affected by both recrystallization fraction and the size of recrystallization grain. Three recrystallization mechanisms, including DDRX, CDRX and TDRX, play their role in the deformation of the alloy. Leading to the recrystallized grains with high misorientation, CDRX tends to grow and promote twin nucleation, and the mechanism of CDRX becomes less significant with the increase of deformation temperature. Due to deformation, the orientation of the grain shifts to <101> direction. At 1000 °C and 1050 °C, the recrystallization texture inherits the deformation texture due to the effect of CDRX and the slow diffusion of the recrystallization process, which causes the recrystallization texture to show a sharp <101> fiber texture. At 1100 °C, the enhancement of the DDRX mechanism and the high diffusivity of the recrystallization process lead to the randomization of the texture, and the oriented growth of recrystallized grains at 1100 °C/0.91 enhances the <001> texture. In addition, both recrystallization and twinning are contributory to the randomization of texture.

Insight on ultrasonic effect of Al[sbnd]Cu aluminum alloy joints fabricated by ultrasonic assisted non-thinning and penetrating friction stir welding

AlCu alloy joints of ultrasonic assisted non-thinning and penetrating friction stir welding (U-NTPFSW) and NTPFSW were prepared. The microstructure and mechanical properties of the joints were studied comparatively to elucidate the effect of ultrasonic. This study provided an in-depth understanding of the microstructure formation mechanism and strengthening mechanism of joints under the ultrasonic effect. Ultrasonics broadened the width of the stir zone (SZ) and stationary shoulder affected zone (SSAZ) by promoting the material plastic flow ability and changing the material flow at the weld root. The ultrasonic addition enhanced plastic heat production and promoted grain growth in SZ. Compared with NTPFSW, the SZ of both joints was dominated by continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) mechanisms, and geometric dynamic recrystallization (GDRX) grains were also present in U-NTPFSW. The mechanical properties of the joint were improved from 339 MPa to 348 MPa. Ultrasonics introduced numerous vacancies into the weld, which promoted the precipitation of the Al2Cu phase and increased the precipitated phase density of the thermal-mechanical affected zone (TMAZ). The interaction mechanism between the precipitated phase and dislocations was analyzed. The geometrically necessary dislocation (GND) density and residual stress of TMAZ were reduced due to ultrasonic vibration.

Fracture behavior of AZ31B magnesium alloy under high-temperature ultrasonic-assisted shearing with related ductile-brittle transformation mechanism

A wide width is one of the fundamental requirements for magnesium alloy sheets to fulfill the lightweight needs of the aerospace and rail transportation industries. Nevertheless, ensuring the dimensional integrity of wide-format magnesium alloy sheets is a challenge in most manufacturing facilities. Simultaneously, processing operations are susceptible to encountering production issues, including but not limited to significant loss of raw materials, elevated costs, environmental contamination, and safety risks. Therefore, to fulfill the operational demands of the hot rolling finishing line for wide sheets made of magnesium alloy, the present study employed ultrasonic-assisted shearing (UAS) to carry out a high-temperature shearing test investigation on the AZ31B magnesium alloy sheet. In this research, we employed scanning electron microscopy, optical microscopy, and a micro-hardness tester to investigate the relationship between ultrasonic amplitude and fracture behavior, deformation mechanism, and mechanical properties of magnesium alloy sheets following exposure to ultrasonic vibration. The fracture morphology of the sheet fracture demonstrates that the behavior of the magnesium alloy sheet fractures under ultrasonic vibration changes from ductile fracture under conventional shearing to brittle fracture under ultrasonic-assisted shearing. The primary cause of this transformation between ductile and brittle is the effect of ultrasonic vibration on the material's internal energy. High-energy ultrasonic amplitude action causes magnesium to absorb a significant amount of ultrasonic energy. This results in an increase in the number of dynamic re-crystallization grains in the material organization, a decrease in the number of twins, and significant refinement of the grains. The sheet's hardness also changes along the rolling and normal directions, with a uniform distribution. The magnesium alloy sheet's fracture quality is optimal when the ultrasonic amplitude is 10 μm in the UAS process. This treatment results in notable enhancements in the section's straightness and brightness. Our study aims to advance the mass manufacturing of wide-format magnesium alloy sheets by investigating a cost-effective and high-yield technique for shearing magnesium alloy sheets.

Study on ductile iron surface laser cladding austenitic stainless steel coating heat treatment to enhance wear resistance

In this paper, laser cladding technology coated the ductile iron surface with austenitic stainless steel. To improve the wear resistance of the coating, consider a heat treatment way to strengthen it. The effects of temperature and time on microstructure, hardness, and wear resistance of austenitic stainless steel coating were investigated. The results show that the martensitic phase was added to the samples at different times of 950 ℃, and the carbide precipitated phase was the main change in the microstructure. At 1050 ℃, the samples also changed from austenite to martensite at different deal times, and the microstructure mainly changed between dendrites. The hardness and abrasion resistance of the 1050 °C/2 h process improved with a hardness of 40.6 HRC, an increase of 26.1%, and a maximum relative abrasion resistance improvement of 84.63%. Which strengthening mechanism was mainly coating dendrites coarse and uniform diffusion occurs, martensite uniform phase transition presented on the surface, coating austenite grain size 9.08 µm smaller, martensite recrystallization and larger grain size of 28.57 µm, the coating as a whole in the uniform phase transition and dendritic crystal strengthening synergistic effect, hardness increased, resistance to wear became stronger.

Grain boundary migration behavior and microstructure evolution during multilayer additive hot-compression bonding

Multilayer additive hot-compression bonding (MAHCB) was a new technology to prepare large-size homogeneous materials, the strain hardening at the bonding interface was an urgent issue for its application. In this paper, the effect of grain boundary migration on strain hardening was studied by the MAHCB process of pure copper. The results show that prolonging the holding time can significantly promote both interfacial grain boundary migration (IGBM) and matrix grain boundary migration (MGBM). The bonding interface became tortuous due to the promotion of IGBM, accompanied by the reduction in dislocation density at the interface and the gradual elimination of interfacial defects. It occurred mainly by the evolution of the triple junction grain boundary from T-type to equal type, which was driven by the decrease in the interface energy. On the other hand, the growth of dynamic recrystallization (DRX) grains was improved with MGBM, and enlarged the low dislocation density region. With the combined effect of both, strain hardening was completely eliminated, when the strain was 0.15 and the holding time was 3 h. Then the optimal bonding properties were obtained, the average tensile-shear strength and elongation were 191.2 MPa and 212 %, and the recovery rates were 99.7 % and 98.9 %, respectively, compared to the as-cast pure Cu samples.

Insights into the evolution of texture and mechanical properties during warm rolling and annealing of Mg–2Zn-0.5Ca alloy

In this work, we systematically investigated the microstructure, texture evolution and mechanical properties of Mg–2Zn-0.5Ca alloy during warm rolling and annealing. The results showed that the net-like Mg6Zn3Ca2 secondary phases are evolved into short wire-like and fragmented into smaller pieces with the increasing rolling reduction. Besides, some recrystallization grains can be generated with a higher rolling reduction, resulting in a significant grain refinement, which is prone to suppress the activation of twinning. The formation of a double-peak texture with basal poles splitting from the normal direction (ND) towards the transverse direction (TD) can be mainly ascribed to the prismatic <a> slip during warm rolling. The formation of TD-oriented recrystallized grain leads to a transformation from a broadening of angular distribution towards the rolling direction (RD) to a broadening of angular distribution towards the TD. Moreover, the yield strength is dramatically enhanced by the synergetic strengthening effect of grain refinement, work hardening, and texture evolution. After annealing, the sample with high rolling reduction can achieve a combination of high yield strength and high formability due to the fine grains structure containing massive precipitates, which is also featured by an elliptical shape texture with basal poles inclining towards RD and TD.

Multi-scale modelling of the microstructure evolution during friction stir welding of 2195 Al–Li alloy

Al–Li alloy has a wide range of application prospects in aerospace and rail transportation fields. Friction stir welding (FSW) is suitable for joining of Al–Li alloy. The microstructure evolution in FSW of Al–Li alloy determines the final joint properties. However, it is difficult to directly observe the microstructure evolution in FSW of Al–Li alloy only by experimental methods. Therefore, a Monte Carlo model in cooperation with a thermomechanical finite element model was proposed to study the microstructure evolution in FSW of 2195 Al–Li alloy. The validated thermomechanical finite element model was first used to calculate the temperature field, strain rate and strain evolution during the FSW process. Then, the achieved thermomechanical history was used in the Monte Carlo model to predict the transient microstructure evolution and the final morphology of the grain structure. It is found that the plastic materials on the advancing side experience a higher strain compared with that on the retreating side with the same distance from the joint line. The plastic material in the middle of the weld nugget zone (WNZ) experiences a relatively high temperature with more severe plastic deformation. Therefore, fully dynamic recrystallization takes place for the material at this region as it flows across the tool during FSW, which results in a fine recrystallization grain in the middle of WNZ. However, the material on the advancing side at 2 mm away from the joint line experiences a lower strain rate, which results in partial recrystallization with some relatively large grains of the base materials. The simulated average grain size and grain morphology were in good agreement with the measured results by EBSD method.

Model for Prediction of the Size of Austenite Grains Upon Hot Deformation of Low-Alloyed Steels Taking into Account the Evolution of the Dislocation Structure

Abstract—A model is proposed to describe the behavior of the average size of austenite grains and the dislocation structure of low-alloyed steels during and after hot deformation. The model takes into account the processes of recovery, dynamic recrystallization of grains and normal grain growth, as well as the strain-induced precipitation of carbonitride phases and their evolution. The calculation results are compared with the experimental data available in the literature and their satisfactory agreement is shown.

Comparison of Single-Pass Differential Speed Rolling (DSR) and Conventional Rolling (CR) on the Microstructure and Mechanical Properties of Mg5Zn

Background: The primary hot rolling method implemented is differential speed rolling (DSR). The material is rolled and grains are strained, producing fine dynamic recrystallization (DRX) grains that improve material strength and ductility. Objective: The material introduced and under investigation in this paper is an Mg-based alloy, Mg5Zn (wt. %), whose microstructure is enhanced through a combination of heat treatments with proper temperature and holding time and subsequent plastic deformation through hot rolling to evaluate the effect on mechanical properties Methods: The method involves preheating the material to various temperatures in a range from 250ºC to 350ºC and rolling to various thickness reductions to analyze the effect of single-pass differential speed rolling (DSR) and conventional rolling (CR) on the DRX process and its influence on mechanical properties. Results: The effect of single-pass differential speed rolling (DSR) and conventional rolling (CR) on the DRX process shows that the process produces increasing amounts of finer DRX grains at higher rolling reductions, thereby improving the strength and ductility of the material. Conclusion: This investigation demonstrated that single-pass DSR can improve the mechanical properties and formability of Mg5Zn more effectively than CR in terms of grain refinement analyzed through OM, SEM, and EBSD resulting in enhanced tensile strength and ductility [1].

Characterization of ductile nano-TiC dispersed V4Cr4Ti/RAFMs solid diffusion joint for nuclear fusion reactor application

Reduced activation ferrite/martensite (RAFM) steel and V4Cr4Ti alloy are candidate structural materials applicable for blankets with various coolants for fusion reactor. In order to combine their advantages, a solid-state diffusion bonding bimetallic plate was designed to provide for high-temperature strength and neutron-irradiation resistance from the vanadium alloy and corrosion-resistance from the steel. However, brittle intermetallic and carbide layers can be formed during the high-temperature diffusion process, which is detrimental to the mechanical properties of the joint. To understand the mechanisms for a ductile joint, the diffusion bonding was performed at different temperatures by hot isostatic pressing (HIP). Various methods were used for the interfacial analysis, together with shear mechanical test and Vickers hardness test across the interface. The interfacial intermetallics differ significantly from each other with different bonding temperatures. Brittle σ-(Fe, V) intermetallic and continuous V2C carbide layer could be avoided by optimizing the diffusion parameters. The joint bonded at 850 °C shows the optimal ductility with highest shearing strength value of 240 MPa, resulting from the synergetic effects. The dispersed TiC nanoparticles formed at interface would play an important role to improve the mechanical performances of the V4Cr4Ti/CLF-1 joint. Besides, no continuous thick carbides or σ- (Fe, V) layer, finer grains in the decarburization layer and the ultra-fine recrystallization grains of the vanadium alloy around the interface are all helpful for joint performance improvement.