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• For the first time, fully dense Nd-Fe-B precursors were prepared by hot rolling. • The large-size hot-rolled Nd-Fe-B magnet has excellent homogeneity. The hot-rolled magnets undergo densification and deformation simultaneously. • The microstructural evolution of hot rolling and hot deformation was systematically investigated. • Dissolution-precipitation, anisotropic grain growth, and regular grain arrangement were the deformation mechanisms. • The hot rolling technology enables the industrial production of anisotropic nanocrystalline Nd-Fe-B magnets. The application of bulk nanocrystalline Nd-Fe-B permanent magnets manufactured by hot deformation methods was severely limited by production efficiency. Therefore, this work proposed an efficient preparation method combining hot rolling and deformation. Using the melt-spun Nd-Fe-B magnetic powders as original materials, dense, large-sized, and well-uniform precursors for deformation can be obtained through cold pressing and hot rolling. The large-sized hot-rolled magnet can be cut into small pieces and subjected to hot deformation. The deformed magnet exhibits obvious crystallographic anisotropy, and the optimal maximum energy product can reach 35.7 MGOe. Furthermore, the mechanism of deformation and texture formation has been systematically studied, according to the microstructure and texture characterization of different height reduction magnets. The results indicated that there was a typical heterogeneous structure in the hot-rolled and hot-deformed Nd-Fe-B magnets. Dissolution precipitation, grain growth, and regular grain arrangement were the main reasons for deformation and texture formation during the deformation process. Our strategy of replacing traditional hot-pressing with large-sized hot-rolling can produce massively deformed precursors at once, greatly improving production efficiency, which is crucial for promoting the application of bulk nanocrystalline anisotropic Nd-Fe-B permanent magnets. [Display omitted] [ABSTRACT FROM AUTHOR]

• Effects of hard/soft Al 2 RE phases on damage behaviors of Mg alloys have been uncovered by using a CPFEM model. • Microscale damage mechanisms have been found by DIC tests and Al 2 RE quantifications using TEM and 3D XCT. • Crystal plasticity model based on dislocation density proves crack initiation at Al 2 RE phases. • CPFEM predicts stiffer Al 2 RE having better damage resistance than soft ones matching SEM fracture analysis. The influence of hard Al 2 RE phases (Sc , Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) on the overall and local deformation as well as damage mechanism of Mg alloys has been studied by using a crystal plasticity model based on dislocation density with a brittle damage criterion. Microcracks that lead to swift damage initiation and propagation throughout the matrix have been predicted. It has been found that the hard Al 2 RE with higher elastic modulus enhances the damage resistance of the Mg matrix, which was confirmed by fracture SEM/EDS characterizations and phase-field damage simulation. This discovery provides valuable insights for designing Mg alloys with both high stiffness and enhanced damage resistance. [Display omitted] [ABSTRACT FROM AUTHOR]

• An ultra-high strength friction stir welded (FSW) joint of twin-induced plasticity steel was obtained, and the mechanical strength was higher than that of basal material. • The deformation behavior of entire FSW joint and the microstructure evolution of micro-zones in FSW joint were investigated by in-situ EBSD at the first time. • The weakest zone of mechanical properties in FSW joint was stir zone, but not heat affect zone, due to the content of annealing twins. The weldability of twin-induced plasticity (TWIP) steel with ultra-high strength via friction stir welding (FSW) technique was investigated, and microstructural evolution and deformation behavior of whole and micro-zones of FSW TWIP joint were studied for the first time. The results showed that the content of recrystallized grains in the stir zone (SZ) increased from 10.5% of basal material (BM) to 14.2%, and that of heat affected zone (HAZ) increased to 78.6%. The percentage of annealing twins decreased from 26.8% in BM to 11% in SZ, while increased to 35% in HAZ. Compared with the BM, the ultimate tensile strength and yield strength of the FSW joint increased to 1036 and 550 MPa, respectively, reaching 106.7% and 110.9% of BM, respectively. The elongation of the entire joint was 50.5%, which was lower than that of BM due to the nonuniform deformation during the tensile test. The engineering strain was mainly concentrated in BM and SZ and transferred to each other during the tensile test, while the engineering strain in HAZ was always the lowest. Finally, the tensile fracture occurred in the SZ. The order of ultimate tensile strength of micro-zones in the FSW joint was as follows: HAZ > BM ≈ SZ. The order of yield strength was as follows: HAZ > BM > SZ. [Display omitted] [ABSTRACT FROM AUTHOR]

• Interaction of local residual stress and internal void altered overall weld-joint ductility. • Residual stress was characterized at micron scale by focused ion beam (FIB) and digital image correlation (DIC). • Multi-scale DIC revealed strain concentration location was sensitive to the local residual stress state. • Fracture mode switched from ductile to brittle upon stress removal. Laser-welded Ti-6Al-4 V is prone to severe residual stresses, microstructural variation, and structural defects which are known detrimental to the mechanical properties of weld joints. Residual stress removal is typically applied to weld joints for engineering purposes via heat treatment, in order to avoid premature failure and performance degradation. In the present work, we found that proper welding residual stresses in laser-welded Ti-6Al-4 V sheets can maintain better ductility during uniaxial tension, as opposed to the stress-relieved counterparts. A detailed experimental investigation has been performed on the deformation behaviours of Ti-6Al-4 V butt welds, including residual stress distribution characterizations by focused ion beam ring-coring coupled with digital image correlation (FIB-DIC), X-ray computerized tomography (CT) for internal voids, and in-situ DIC analysis of the subregional strain evolutions. It was found that the pores preferentially distributed near the fusion zone (FZ) boundary, where the compressive residual stress was up to -330 MPa. The removal of residual stress resulted in a changed failure initiation site from the base material to the FZ boundary, the former with ductile and the latter with brittle fracture characteristics under tensile deformation. The combined effects of residual stresses, microstructures, and internal pores on the mechanical responses are discussed in detail. This work highlights the importance of inevitable residual stress and pores in laser weld pieces, leading to key insights for post-welding treatment and service performance evaluations. [Display omitted] [ABSTRACT FROM AUTHOR]

• Synergistic enhancement in yield strength of over 95 % and ductility by more than 140 % in Ti-32Nb base alloys were achieved by interstitial oxygen doping. • Transformation induced plasticity and twinning induced plasticity were regulated by oxygen doping. • Complex sequence of strain induced twinning/phase transformation behaviors from β twinning to αʺ was revealed by ex-situ TEM, EBSD and in-situ HE-XRD. • Outlines a new approach for design of advanced TRIP/TWIP titanium alloys. Metastable β-Ti alloys exhibiting twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) generally have excellent ductility, but typically at the expense of relatively low yield strengths which has restricted their widespread use. Our work shows that interstitial oxygen can be employed to regulate β phase stability to significantly enhance both strength and ductility of TWIP/TRIP alloys. For a Ti-32Nb wt.% base alloy, inclusion of 0.3 wt.% O enhanced ductility by more than 140 %, reaching up to 54 % strain, and improved the tensile yield strength by over 95 % to 632 MPa. Compared to other common engineering alloys such as Ti-45Nb, elongation was increased by 29 %, and the yield strength increased by 182 MPa, respectively. Here, we elucidate on impacts of oxygen doping on TWIP/TRIP behaviors in the Ti-32Nb alloy. We reveal that oxygen regulates the critical stress for martensitic transformation, twinning, and dislocation slip. At lower oxygen doping concentrations (≤0.3 wt.% O), multi-stage martensitic transformation and martensitic twinning resulted in high ductility. In higher oxygen content alloys (≥0.5 wt.% O), deformation occurred initially via twinning, while strain induced martensite was subsequently induced in retained β phase regions. Oxygen concentrations control the deformation mechanisms, providing a flexible means to synergistically balance an alloy's strength and ductility. The use of oxygen to enhance stability of the β phase and regulate deformation behaviors is a promising new approach for creating high-performance TWIP/TRIP metastable β-Ti alloys with outstanding mechanical properties. [Display omitted] [ABSTRACT FROM AUTHOR]

• 1.8 GPa CoCrNiMo 0.2 MEA with strength-ductility trade off was developed. • Non-coherent δ phase and semi-coherent µ phase were precipitated progressively. • Ultra strength attribute to precipitation strengthening and fine grain strengthening. • Twins' deformation and deformation nanotwins are benefit for ductility improvement. Normal strengthening methods through precipitations and deformation obviously enhance the strength of metallic materials while resulting in the sacrifice of ductility, and synergistic improvement of strength and ductility is currently an urgent requirement. Herein we developed a cryogenic deformation combined with an annealing method to fabricate CoCrNiMo 0.2 medium entropy alloy, which achieved an ultrahigh strength of 1.8 GPa with synergistic improvement in strength and ductility. Microstructure, mechanical performance, and strengthening mechanisms of the developed alloys were investigated compared with that prepared by the regular room temperature deformation method. It was found that high-density nanotwins were produced in CoCrNiMo 0.2 MEA via cryogenic deformation. Fine grains, hard precipitations, and high volume fraction of nanotwins greatly strengthened the alloy, obtaining a yield and ultimate tensile strength of 1400 MPa and 1800 MPa. Ductility improvement of the developed alloy was mainly attributed to the production of deformation nanotwins due to the lower stacking fault energy, which greatly increases the dislocation storage ability, and thus, the ductility of the alloy was enhanced. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel B2-ordered Ti 3 Zr 1.5 NbVAl x refractory complex concentrated alloys were designed and prepared. • The desirable combination of strength-ductility was realized in these alloys. • Relatively low densities of less than 6 g/cm3 and ultra-high specific yield strength (134.4–199.4 MPa cm3 g−1) were exhibited in these alloys. • The influence of B2-ordered structure on deformation behavior was clarified. Combining high strength and good ductility is an urgent requirement for traditional structural materials, but yet a challenge. Newly emerging ductile Ti 3 Zr 1.5 VNbAl x (x = 0, 0.25, 0.5, 0.75) refractory complex concentrated alloys (RCCAs) with high specific strength were designed and synthesized via vacuum arc-melting. Alloying effects of Al on microstructure and mechanical properties were systematically investigated. It was found that the phase composition in this alloy system changes from the single disordered body-centered cubic (BCC) phase to a nano-scale mixture of co-continuous disordered BCC and ordered B2 phases with the increase of Al concentration. This structure transition results in a remarkable increase in the yield strength of the RCCAs, i.e., from 790 to 1118 MPa, leading to a superior specific yield strength of 199.4 MPa cm3 g−1 for the Al0.75 alloy, meanwhile, the tension plasticity maintained at ∼10%. TEM observation demonstrates that cell-forming structure and HDDWs induced by wave slip play a crucial role of considerable plasticity in Al0.25 alloy, whereas in Al0.5 alloy, microbands induced by planar slip dominant deformation behavior. The current work is important not only for providing novel high strength and tough structural materials with low density, but also sheds light on designing high-performance lightweight alloys with tunable microstructure. [Display omitted] [ABSTRACT FROM AUTHOR]

Based on the general [Mo] equivalent criterion and d-electron orbital theory, a new ultrahigh-strength β titanium alloy with eight major elements (Ti-4.5Al-6.5Mo-2Cr-2.6Nb-2Zr-2Sn-1V, TB17) for industrial applications was developed. An ingot of five tons was successfully melted by thrice vacuum consumable arc melting. The microstructure and elements partitioning of different conditions were investigated systematically. The results suggest that the hierarchical structures of micro-scale first α phase (α f), nano-scale secondary α phase (α s), and ultrafine FCC substructures can be tailored by solution plus aging (STA) heat treatment. The lateral and epitaxial growth of α f phase promotes the HCP-α to FCC substructure transformation with the help of elements partitioning during the aging process. Moreover, the element V, generally regarded as β stabilizer, is found to mainly concentrate in the Al-rich α f phase in this study probably due to its relatively lower content and the strong bonding energy of Al-V. The hierarchical structure has a strong interaction with dislocations, which contributes to achieve a superhigh strength of 1376 MPa. In addition, the plastic strain is partitioned in the multi-scale precipitates (such as the α and FCC substructures) and β matrix, resulting in a considerable plasticity. TEM observation demonstrates that high density entangled dislocations at interfaces and mechanical twins exist in the STA sample after tensile test. It can be deduced that both dislocation slipping and twinning mechanisms are present in this alloy. Therefore, TB17 alloy can serve as an excellent candidate for structural materials on aircrafts that require high strength and lightweight. • A novel β titanium alloy with ultrahigh strength of 1376 MPa was developed. • The multi-scale hierarchical structures were tailored by heat treatment. • The transformation from HCP-α to FCC-substructure was observed. • The V element mainly concentrated in the micro-scale α lath. [ABSTRACT FROM AUTHOR]

• Pure copper bulk materials were manufactured by cold spray additive manufacturing (CSAM). • Gas species effect on the microstructure, mechanical property and deformation mechanisms of CSAM pure copper was investigated. • The CSAM copper fabricated with He gas shows yield strength of 415 MPa, indicating that CSAM enables ultra-high strength in metallic material. • Work softening behavior, which does not occur easily at room temperature, occurred in both materials. Cold spray (CS) which has recently become a promising additive manufacturing (AM) technology, was used to fabricate ultra-strong pure copper. In addition, the effects of carrier gas species on the microstructural characteristics, mechanical properties and deformation mechanisms were systemically explored. The CSAM copper manufactured with N 2 carrier gas reveals a heterogeneous bimodal microstructure consisting of ultra-fine grains at the particle interface and relatively coarse grains in inner particles. With He carrier gas, a homogeneous grain structure consisting of ultra-fine grains in most areas was obtained. Compressive tests showed that N 2 and He carrier gasses enabled ultra-high yield strengths of 340 and 415 MPa, respectively. These values are comparable to severely plastic deformed copper, which has extremely low ductility and shape fidelity. On the other hand, both samples showed a strain-softening phenomenon that does not commonly occur at room temperature. The deformation microstructures revealed that dynamic recovery (DRV) and dynamic recrystallization (DRX) phenomena were generated despite being deformed at room temperature. Based on the above findings, the overall deformation mechanisms according to the carrier gas species in the CSAM copper manufacturing process were discussed. Furthermore, the work hardening and softening behaviors of CSAM Cu are predicted by using a constitutive equation. [ABSTRACT FROM AUTHOR]

• L-PBF-processed Al-Mg-Sc-Zr alloy exhibited dual heterogeneous microstructure of both α-Al matrix and nano-precipitates. • Correlations between the heterogeneous microstructure and strength-ductility balance were discussed. • Low strain-hardening capability promoted necking instabilities while inducing a large Lüders elongation. Laser powder bed fusion (L-PBF) of Sc/Zr-modified Al-based alloys has recently become a promising method for developing a new generation of high-performance Al alloys. To clarify the modification roles of Sc/Zr elements, an Al–4.66Mg–0.48Mn–0.72Sc–0.33Zr (wt.%) alloy was processed using L-PBF. The effect of the local solidification condition of the molten pool on the precipitation behavior of primary Al 3 (Sc,Zr) was analyzed based on time-dependent nucleation theory. It was found that primary Al 3 (Sc,Zr) inevitably precipitated at the fusion boundary, while its precipitation could be effectively suppressed in the inner region of the molten pool. This subsequently induced the formation of a heterogeneous α-Al matrix. After direct aging, the heredity of solidification microstructure introduced heterogeneous secondary Al 3 (Sc,Zr) precipitates within α-Al matrix. Owing to the inverse relationship between grain boundary strengthening and precipitation strengthening, the direct-aged sample with dual heterogeneous structures exhibited reduced mechanical heterogeneity, resulting in lowered hetero-deformation-induced hardening. The low strain-hardening capability in the direct-aged sample promoted necking instability while inducing a large Lüders elongation, which effectively improved the tensile ductility. [Display omitted] [ABSTRACT FROM AUTHOR]

We have for the first time elucidated the microstructural evolution and deformation behaviors of a gradient textured AZ31B Mg alloy plate under the ultrahigh strain rate of ~106 s−1 that is generated by a two-stage light gas gun with the hypervelocities of 1.6−4.4 km s−1. The hypervelocity impact cratering behaviors indicate that the cratering deformation of AZ31B Mg alloy is mainly affected by the inertia and strength of the target material. The crater prediction equation of AZ31B Mg alloy target under impact velocity of 5 km s−1 is given. The 2017Al projectile completely melts in the Mg alloy target plate at the impact velocities of 3.8 km s−1 and 4.4 km s−1, and the microstructural evolution around the crater is: dynamic recrystallization zone, high-density twinning zone, low-density twinning zone, and Mg alloy matrix. It is found that the dynamic recrystallization, twinning and cracking are the main deformation behaviors for the AZ31B Mg alloy to absorb the shock wave energy and release the stress generated by the hypervelocity impact. The main plastic deformation mechanisms of the Mg alloy target during hypervelocity impact are twinning and dislocation slip. Microstructure analysis shows the interactions of twins-twins, dislocations-dislocations, and twins-dislocations determine the strain hardening during the hypervelocity impact process, which eventually contributes the dynamic mechanical properties. The evolution of microhardness around the crater further demonstrates the microstructural evolutions and their interactions under the hypervelocity impacts. • The microstructural evolution and deformation behaviors of a gradient textured AZ31B Mg alloy plate under the ultrahigh strain rate of ~106 s are demonstrated and systematically investigated for the first time. • The DRX, twinning and crack formation are found to be the main deformation mechanisms for the magnesium alloy to absorb the shock wave energy and release the stress. • The interaction between texture, dislocations and twins determines the strain hardening and deformation mechanism during the HVI to eventually contribute the dynamic mechanical properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • The grain texture of retained austenite tends to evolve towards F orientation. • The gradually increasing number of austenite grains with high Schmid factor before 10% strain increases the martensite transformation rate. • The strain in the austenite grain prefers to spread among adjacent austenite grains because of their coordinated deformation. • Martensite transformation accompanied by TWIP effect and high density dislocations maintains the continuous hardening stage. The strain-induced martensite transformation is of great importance in the strain hardening process of ferrite based low-density steel. Based on the microstructure analysis, the texture evolution and martensite transformation behavior in the strain hardening process were studied. The results show that martensite transformation accompanied by TWIP effect and high density dislocations maintains the continuous hardening stage. As the strain increases, the texture of retained austenite evolves towards the F orientation {111}<112>, which is not conducive to martensite transformation. After the strain of 5%, the number of austenite grains with high Schmid factor orientations is gradually increased, and then significantly reduced when the strain is over 10 % due to the occurrence of martensitic transformation, which results in a high martensitic transformation rate. However, the unfavorable orientation and the reduced grain size of austenite slow down the martensite transformation at the final hardening stage. Moreover, because of the coordination deformation of austenite grains, strain preferentially spreads between adjacent austenite grains. Consequently, the martensite transformation rate in strain hardening process is dependent on the orientation and grain size evolution of austenite, leading to a differential contribution to each strain hardening stage. [ABSTRACT FROM AUTHOR]

A high-performance Mg-4.9Gd-3.2Y-1.1Zn-0.5 Zr alloy has been fabricated by multidirectional forging (MDF) after analyzing its compression behavior. The as-homogenized alloy exhibits a high activation energy Q of deformation (∼285 kJ/mol). The size of DRXed grains after compression tends to decrease as the Z-H parameter (Z) increases, showing a grain size exponent m of ∼4.0. Lamellar LPSO phases, kinking deformation, and bimodal microstructure are detected at the relatively low compression temperature of 350 and 400 °C, while sufficient DRX can be achieved at 500 °C, accompanied by the dissolution of lamellar LPSO. According to the processing maps, MDF was successfully conducted under an appropriate condition. After peak-aged at 200 °C for 78 h, the MDFed billet exhibits a tensile yield strength (TYS) of 331 and 305 MPa at room temperature and 200 °C, respectively. The high strength mainly results from the combination of fine grains, low Schmid factor for basal slip, sufficient β ' ageing precipitates, and directionally arranged interdendritic LPSO phases, etc. This paper provides a feasible way for the fabrication of high-performance, low-RE-content, and large-scale Mg components for industrial production. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is a promising material processing method which gains significant momentum in the aerospace and biomedical industries. However, the anisotropy in the mechanical properties of additively-manufactured materials is still poorly understood. This study was aimed at elucidating crystallographic feature-anisotropy-mechanical property relationship for a Ti-6Al-4V alloy manufactured via selective electron beam melting (SEBM). Abundant α lamellae with six variants were present inside the columnar prior-β grains with a <100> fiber texture during β→α phase transformation. The six α variants followed the Burgers orientation relationship of {110} β //{0001} α and <1-11> β //<11-20> α. Multiple sub-variants in each α variant were observed for the first time. The anisotropy in the mechanical properties was mainly related to the relative amount of six α variants. While the horizontally-oriented samples had a lower yield strength, they exhibited a higher ductility and longer fatigue life than the vertically-oriented samples. Cyclic softening occurred at higher strain amplitudes, and cyclic stabilization sustained at lower strain amplitudes. Fatigue crack mainly initiated from the specimen surface at lower strain amplitudes, while multiple crack initiation tended to occur at higher strain amplitudes. Crack propagation was characterized by fatigue striations along with some secondary cracks. [ABSTRACT FROM AUTHOR]

In this study, a new Al 0.9 CoFeNi 2 eutectic high entropy alloy (EHEA) was designed, and the microstructures as well as the deformation behavior were investigated. The bulk cast Al 0.9 CoFeNi 2 EHEA exhibited an order face-centered cubic FCC (L1 2) and an order body-centered cubic (B2) dual-phase lamellar eutectic microstructure. The volume fractions of FCC (L1 2) and B2 phases are measured to be 60 % and 40 %, respectively. The combination of the soft and ductile FCC (L1 2) phase together with the hard B2 phase resulted in superior strength of 1005 MPa and ductility as high as 6.2 % in tension at room temperature. The Al 0.9 CoFeNi 2 EHEA exhibited obvious three-stage work hardening characteristics and high work-hardening ability. The evolving dislocation substructures during uniaxial tensile deformation found that planar slip dominates in both FCC (L1 2) and B2 phases, and the FCC (L1 2) phase is easier to deform than the B2 phase. The post-deformation transmission electron microscopy revealed that the sub-structural evolution of the FCC (L1 2) phase is from planar dislocations to bending dislocations, high-density dislocations, dislocation network, and then to dislocation walls, and Taylor lattices, while the sub-structural evolution of the B2 phase is from a very small number of short dislocations to a number of planar dislocations. Moreover, obvious ductile fracture in the FCC (L1 2) phase and a brittle-like fracture in the B2 phase were observed on the fracture surface of the Al 0.9 CoFeNi 2 EHEA. The research results provide some insight into the microstructure-property relationship. [ABSTRACT FROM AUTHOR]

High-entropy amorphous alloys present high hardness, but low tensile ductility. Here, deformation behavior of the amorphous/crystalline FeCoCrNi high-entropy alloy (HEA) composite prepared by the previous experiment is investigated using atomic simulations. The result shows the partial dislocations in the crystal HEA layer, and the formation of shear bands in the amorphous HEA layer occurs after yielding. The strength of the amorphous/crystalline HEA composite reduces with increasing the thickness of the amorphous layer, agreeing with the previous experiments. The coupled interaction between the crystal plasticity and amorphous plasticity in amorphous/crystalline HEA composites results in a more homogeneous redistribution of plastic deformation to cause interface hardening, due to the complex stress field in the amorphous layer. The current findings provide the insight into the deformation behavior of the amorphous/crystalline HEA composite at the nanoscale, which are useful for optimizing the structure of the HEA composite with high strength and good plasticity. [ABSTRACT FROM AUTHOR]

The variation of stacking fault energy (SFE) in a number of binary Cu alloys is predicted through considering the Suzuki segregation by the full potential linearly augmented plane wave (FPLAPW) method. The calculated results show that some solute atoms (Mg, Al, Si, Zn, Ga, Ge, Cd, Sn, and Pb), which prefer to form the Suzuki segregation, may decrease the value of SFE; while the others (Ti, Mn, Fe, Ni, Zr, Ag, and Au), which do not cause the Suzuki segregation may not decrease the SFE. Furthermore, it is interesting to find that the former alloying elements are located on the right of Cu group while the latter on the left of Cu group in the periodic table of elements. The intrinsic reasons for the new findings can be traced down to the valences electronic structure of solute and Cu atoms, i.e., the similarity of valence electronic structure between solute and Cu atoms increases the value of SFE, while the difference decreases the value of SFE. [ABSTRACT FROM AUTHOR]

Titanium alloys have been widely used in many industrial clusters such as automotive, aerospace and biomedical industries due to their excellent comprehensive properties. In order to obtain fine microstructures and favorable properties, a well-designed multi-step thermomechanical processing (TMP) is critically needed in manufacturing of titanium components. In making of titanium components, subtransus processing is a critical step to breakdown lamellar microstructure to fine-structure in hot working process and thus plays a key role in tailoring the final microstructure and properties. To realize this goal, huge efforts have been made to investigate the mechanisms of microstructure evolution and flow behavior during the subtransus processing. This paper reviews the recent experimental and modelling progresses, which aim to provide some guidelines for the process design and microstructure tailoring for titanium alloy research community. The characteristics of the initial lamellar microstructure are presented, followed by the discussion on microstructure evolution during subtransus processing. The globularization of lamellar α is analyzed in detail from three aspects, i.e., globularization mechanism, heterogeneity and kinetics. The typical features of flow behaviors and the explanations of significant flow softening are then summarized. The recent advances in modelling of microstructure evolution and flow behaviors in the subtransus processing are also articulated. The current tantalized issues and challenges in understanding of the microstructure evolution and flow behaviors of the titanium alloys with lamellar microstructure are presented and specified in future exploration of them. [ABSTRACT FROM AUTHOR]

Double-pass hot compression tests were carried out over a wide range of holding time (0–180 s) and Zener-Hollomon parameter (1.6E15–1.3E20) to study the deformation behavior of cast Mg-8Gd-3Y alloy. The flow curves show obvious work hardening and strain softening stages, leading to the peak stress of double-pass hot compression. Holding time and Zener-Hollomon parameter can significantly affect the second pass peak stress. It is found that increasing the holding time can cause a higher peak stress in the second pass deformation. The second pass stress reaches the peak stress of 71 MPa at Zener-Hollomom parameter of 1.6E15. When the parameter rises to 1.3E20, the second pass peak goes up to 237 MPa. In addition, the second pass peak stress is significantly higher than the unloading stress, which is opposite to the flow behavior of aluminum alloys. Residual stored deformation energy caused by the first pass deformation could be consumed by metadynamic recrystallization. Therefore, more strain energy is required for subsequent dynamic recrystallization, resulting in hardening behavior. A hardening fraction is defined to describe the deformation behavior quantitatively, which shows a positive correlation with the metadynamic recrystallization fraction. The metadynamic recrystallization leads to grain growth at the inter pass holding stage, diminishing dynamic recrystallization nucleation positions in the second pass deformation. [ABSTRACT FROM AUTHOR]

The stress–strain relations for the Zr 53.5 Cu 26.5 Ni 5 Al 12 Ag 3 bulk metallic glass (BMG) over a broad range of temperatures (room temperature to its supercooled liquid region) and strain rates (10 −4 to 10 −1 s −1 ) were established in uniaxial compression using a thermal-mechanical simulation system. The superplastic flow was seen above its glass transition temperature ( T g = 694 K) and strain rates of up to 10 −1 s −1 from the variation of stress–strain curves. A deformation map of strain rate vs temperature of Zr 53.5 Cu 26.5 Ni 5 Al 12 Ag 3 was obtained, which was mainly composed of homogeneous and inhomogeneous deformation regions, the former featuring either Newtonian or non-Newtonian flow while the latter characterizing linear elastic behavior followed by shear localization, respectively. A phenomenological constitutive equation used to describe a master curve of viscosity with respect to the strain rate was obtained by fitting the experimental results, which determines the viscosity of the present alloy at the temperature near and above T g . The results show the Zr 53.5 Cu 26.5 Ni 5 Al 12 Ag 3 BMG is the subject suitable for net shape forming process at the supercooled liquid region. [ABSTRACT FROM AUTHOR]

In this study, shear tests have been performed on the as-reflowed Sn3.5Ag solder bumps and joints to investigate the deformation behavior of Sn3.5Ag lead-free solder samples. Scanning electron microscopy (SEM) was employed to characterize the microstructures of the samples and orientation imaging microscopy (OIM) with electron backscattered diffraction (EBSD) in SEM was used to obtain crystallographic orientation of grains to provide a detailed characterization of the deformation behavior in Sn3.5Ag solder samples after shear tests. The deformation behavior in solder samples under shear stress was discussed. The experimental results suggest that the dynamic recrystallization could occur under shear stress at room temperature and recrystallized grains should evolve from subgrains by rotation. Compared with that of non-recrystallized and as-reflowed microstructures, the microhardness of the recrystallized microstructure decreased after shear tests. [Copyright &y& Elsevier]