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| 1 | Texture control by {10-12} twinning to improve the formability of Mg alloys: A review显示文摘Texture control of wrought Mg alloys, particularly in rolled Mg alloy sheets, has been an important research topic for the past several decades because it has significant influence on stretch formability at room temperature. For Mg alloys, {10-12} twinning can be easily activated and causes a 86.3° lattice rotation. Thus, pre-twinning deformation is considered as an effective and low-cost method for texture control in wrought Mg and its alloys. Furthermore, it has been verified that texture control via pre-twinning deformation can remarkably improve stretch formability of rolled Mg alloy sheets. In this review, recent researches on texture control via twinning deformation and its influence on stretch formability will be critically reviewed. The main contents include the micro-mechanism and impact factors of control in twin-orientation, plastic processing techniques of pre-inducing twins and the application of pre-induced twins in improvement of stretch formability. Finally, further research directions on this field were proposed. | Bo Song Qingshan Yang Tao Zhou Linjiang Chai Ning Guo Tingting Liu Shengfeng Guo Renlong Xin | 2019 | Journal of Materials Science & Technology2019，35，10： | 8 |
| 2 | Electron backscatter diffraction investigation of duplex-phase microstructure in a forged Zr-2.5Nb alloy显示文摘Microstructural features of a duplex-phase Zr-2.5Nb alloy were investigated in detail using electron channeling contrast(ECC)imaging and electron backscatter diffraction(EBSD)technique in an emission gun scanning electron microscope(FEGSEM).The excellent resolution provided by the FEGSEM promises the combined utilization of both techniques to be quite adequate for characterizing the duplex-phase microstructures.Results show that the microstructure of the Zr-2.5Nb alloy is composed of bulkαgrains(majority)in equiaxed or plate shape and thinβfilms(minority)surrounding the bulk grains,with their average grain size and thickness measured to be 1.4μm and 72 nm,respectively.Analyses onα-grain boundaries reveal a number of low angle boundaries,most of which belong to deformation-induced dislocation boundaries.Measurements on relative proportions of various Burgers boundaries suggest very weak(if any)variant selection duringβ→αcooling,which should be related to deformation-induced higher nucleation rate ofαphases.Compared to earlier attempts,more satisfactory indexing of fineβphases(down to nanoscale)is attained by the FEGSEM-based EBSD.Examples are presented to clearly reveal well-obeyed Burgers orientation relationships between adjacentαandβphases.Finally,it is deduced that continuing application of the FEGSEM-based EBSD to duplex-phase Zr alloys could help clarify controversies like the deformation priority of the two phases. | CHAI LinJiang WANG ShuYan LUAN BaiFeng LIU Qing | 2016 | Science China(Technological Sciences)2016，59，4： | 5 |
| 3 | Effect of cooling rate on β→α transformation during quenching of a Zr-0.85Sn-0.4Nb-0.4Fe-0.1Cr-0.05Cu alloy显示文摘The effect of β→α cooling rate during quenching on a new Zr-Sn-Nb-Fe-Cr-Cu alloy is reported.The microstructure evolution is well characterized by electron channeling contrast(ECC) imaging and transmission electron microscopy(TEM) techniques.The results show that specimens cooled by water,liquid nitrogen,air and furnace from β-phase present martensitic,coarse basket-weave,parallel-plate and lenticular structure,respectively.Residual β phase is detected by performing electron diffraction and composition analysis in the furnace cooled specimen.Micro hardness values of specimens decrease while the width of α laths increase with the cooling rate decreasing.The preliminarily established quantitative relationship among the cooling rate,microstructure and mechanical properties will shed light on the microstructure control and property optimization. | CHAI LinJiang LUAN BaiFeng CHEN JianWei ZHOU Jun LIU Qing | 2012 | Science China(Technological Sciences)2012，55，10： | 5 |
| 4 | α→β Transformation characteristics revealed by pulsed laser-induced non-equilibrium microstructures in duplex-phase Zr alloy显示文摘Microstructures of a duplex-phase Zr-2.5Nb alloy treated by pulsed laser were characterized by electron backscatter diffraction(EBSD) and electron channeling contrast(ECC) imaging techniques.Major attention has been paid to non-equilibrium hybrid microstructure consisting of both prior a and β phases,and a plates transformed from new β phases to probe α→β transformation characteristics in the alloy.The origin of the hybrid microstructure is attributed to the specific thermodynamic conditions induced by the pulsed laser treatment.ECC observation shows that newly formed β phases during laser heating prefer to nucleate and grow at the expense of edges of prior a grains rather than their interiors.EBSD analyses further reveal that orientations of the new βphases are not determined by the prior a grains according to the Burgers relationship but maintain those of the prior β phases in an epitaxial growth way. | CHAI LinJiang WANG Shu Yan WU Hao GUO Ning PAN HuCheng CHEN Liang Yu MURTY K.L. SONG Bo | 2017 | Science China(Technological Sciences)2017，60，8： | 5 |
| 5 | Evolution of surface microstructure of Cu-50Cr alloy treated by high current pulsed electron beam显示文摘A Cu-50Cr alloy was treated by the high current pulsed electron beam(HCPEB)at 20 and 30 ke V with pulse numbers ranging from 1 to 100.Surface morphologies and microstructures of specimens before and after the treatments were investigated by employing scanning electron microscopy and X-ray diffraction.Results show that the HCPEB technique is able to induce remarkable surface modifications for the Cu-50Cr alloy.Cracks in Cr phases appear even after one-pulse treatment and their density always increases with the pulse number.Formation reason for these cracks is attributed to quasi-static thermal stresses accumulated along the specimen surface.Craters with typical morphologies are formed due to the dynamic thermal field induced by the HCPEB and they are found to prefer the sites near cracks or boundaries between neighboring Cr phases.Another microstructural characteristic produced by the HCPEB is the fine Cr spheroids,which are determined to be due to occurrence of liquid phase separation in the Cu-50Cr alloy.Finally,a general microstructural evolution profile that incorporates various HCPEB-induced surface features is tentatively outlined. | CHAI LinJiang ZHOU ZhiMing XIAO ZhiPei TU Jian WANG YaPing HUANG WeiJiu | 2015 | Science China(Technological Sciences)2015，58，3： | 5 |
| 6 | Deformation mode-determined misorientation and microstructural characteristics in rolled pure Zr sheet显示文摘In this work, commercially pure Zr sheets were subjected to β air cooling and then rolled to different reductions(10% and 50%)at room temperature. Microstructures of both the β-air-cooled and the rolled specimens were well characterized by electron channelling contrast imaging and electron backscatter diffraction techniques, with special attentions paid to their misorientation characteristics. Results show that the β-air-cooled specimen owns a Widmanst?tten structure featured by lamellar grains with typical phase transformation misorientations. The 10% rolling allows prismatic slip and tensile twinning({11-21}<11-2-6> and{10-12}<10-11>) to be activated profusely, which produce new low-angle(~3°–5°) and high-angle(~35° and ~85°) misorientation peaks, respectively. After increasing the rolling reduction to 50%, twinning is suppressed and dislocation slip becomes the dominant deformation mode, with the lamellar grains highly elongated and aligned towards the rolling direction.Meanwhile, only one strong low-angle misorientation peak related to the prismatic slip is presented in the 50%-rolled specimen,with all other peaks disappeared. Analyses on local misorientations reveal that hardly any residual strains exist in the β-air-cooled specimen, which should be related to their sufficient relaxation during slow cooling. Residual strains introduced by 10% rolling are heterogeneously distributed near grain/twin boundaries while heavier deformation(50% rolling) produces much larger residual strains pervasively existing throughout the specimen microstructure. | CHAI LinJiang XIA JiYing ZHI Yan GOU YinNing CHEN LiangYu YANG ZhiNan GUO Ning | 2018 | Science China(Technological Sciences)2018，61，9： | 3 |
| 7 | Microstructural characteristics of cold-rolled Zr-2.5Nb alloy annealed near the monotectoid temperature显示文摘A dual-phase Zr-2.5 Nb alloy was rolled at room temperature to 50% reduction and then annealed at two temperatures(560 and580°C) near the monotectoid temperature. X-ray diffraction, electron channeling contrast imaging and electron backscatter diffraction techniques were jointly used to characterize microstructural characteristics developed in the as-rolled and annealed specimens. Results show that plastic deformation occurs in both bulk α-Zr grains and thin β-Zr films during rolling, allowing large lattice strains to be accumulated in β-Zr and active dislocation slip(especially the prismatic áa?slip) to be initiated in α-Zr. During subsequent annealing at 580°C, the prior β-Zr films are transformed into submicron β-Zr particles, which lose coherency(the Burgers orientation relationship) with surrounding α grains. In the specimen annealed at 560°C, however, the prior β-Zr films are found to be decomposed into nanoscale β-Nb particles. In both the annealed specimens, the β-Zr and the β-Nb particles appeared to be linearly distributed along the rolling direction. Two types of α structures, i.e., small equiaxed crystallites formed by recovery of dislocation structures and coarse bamboo-like recrystallized grains, are revealed in the annealed specimens. Effective boundary pinning due to the dense β-phase particles is demonstrated to play a key role in forming such unusual bamboo-like grains. | CHAI LinJiang WU Hao WANG ShuYan LUAN BaiFeng WU Yue HUANG XiaoYu | 2018 | Science China(Technological Sciences)2018，61，4： | 3 |
| 8 | Bimodal plate structures induced by pulsed laser in duplex-phase Zr alloy显示文摘A duplex-phase Zr-2.5Nb alloy was treated by pulsed laser, followed by careful microstructural characterization using field emission gun scanning electron microscope and attached electron backscatter diffraction. Beneath the modification zones with common uniform α-plate structures(UPS), a layer of unreported bimodal α-plate structures(BPS) featured by coarse(submicron)plates forming multiple cores surrounded by dense fine(nanoscale) plates was found. Presence of such BPS is attributed to non-equilibrium thermodynamic conditions induced by the pulsed laser treatments. Limited diffusion of Nb due to the short pulse during laser heating allows β phases with distinctly different Nb contents to be presented: Nb-enriched prior β films and Nb-depleted β phases, transforming into the fine and the coarse plates during cooling, respectively. Orientation analyses show that both types of plates in the BPS are aroused essentially from a single β orientation, suggesting epitaxial growth of the Nb-depletedβ phases from the preexisting β films. | CHAI LinJiang WANG ShuYan WU Hao YANG ZhiNan PAN HuCheng SONG Bo GUO Ning | 2017 | Science China(Technological Sciences)2017，60，4： | 2 |
| 9 | Concurrent inheritance of microstructure and texture after slow β→α cooling of commercially pure Zr显示文摘A rolled and recrystallized commercially pure Zr sheet was β-solution treated and then cooled at two rates, i.e. air cooling(AC)and furnace cooling(FC). Microstructures and textures of original and β-cooled specimens were characterized by use of electron channeling contrast imaging, electron backscatter diffraction and X-ray diffraction techniques. Results reveal a novel phenomenon, i.e. the concurrent inheritance of microstructure and texture in the FC specimen cooled at a very slow rate. In contrast, for the AC specimen with faster cooling, typical lamellar α phases are obtained with relatively scattered texture.Based on comparatively crystallographic and thermodynamic analyses, reasons accounting for microstructure and texture differences in both cases are discussed, highlighting the significant role played by the variant selection behavior. It is postulated that increasing cooling rates should be more feasible to change the transformed texture in Zr materials. | CHAI LinJiang LUAN BaiFeng CHEN BaoFeng YANG HuiLong LIU Qing HUANG WeiJiu | 2016 | Science China(Technological Sciences)2016，59，11： | 1 |
| 10 | Typical Microstructural Characteristics of Ti–5Al–5Mo–5V–3Cr–1Fe Metastable β Ti Alloy Forged in α + β Region显示文摘In this study,typical microstructural characteristics of a metastableβTi alloy(Ti–5Al–5Mo–5V–3Cr–1Fe)forged in a dual-phase region(strain of 54%at 820℃)were investigated in detail by the combined use of X-ray diff raction,energy dispersive spectroscopy,electron channeling contrast imaging and electron backscatter diff raction techniques.Results show that the microstructure of the forged alloy is composed of bulkαgrains,αplates andβmatrix.The bulkαgrains correspond to retained primaryαphase(αp,average grain size^2.4μm),while theαplates are secondaryαphase(αs,width^70 nm)precipitated from theβmatrix during air cooling.During forging,theβmatrix experiences dynamic recovery with many subgrains and signifi cant orientation gradients formed.Analyses of the orientation relationship between theαandβphases show that the Burgers orientation relationship is not maintained between someα_p andβphases,which should be related to thermal deformation-induced changes of their orientations.In contrast,all of theαs plates are found to maintain well the Burgers orientation relationship with theβphase. | Zhiying Zheng Linjiang Chai Kang Xiang Weijiu Huang Yongfeng Wang Liangliang Liu Lin Tian | 2020 | Acta Metallurgica Sinica(English Letters)2020，33，12： | 1 |
| 11 | Precise determination of the α → α+β phase transformation temperature of Zr-1.0Sn-0.3Nb-0.3Fe alloy显示文摘In this investigation,differential scanning calorimetry(DSC) and metallographic experiments were performed to study α→α +β phase transformation temperature in a Zr-1.0Sn-0.3Nb-0.3Fe alloy.The deconvolution and extrapolation methods to determine the α→α+β phase transformation temperature in DSC experiment were appropriate for the Zr alloy.Moreover,precise determination of α→α+β phase transformation temperature was carried out by back-scattered electron imaging(BSEI) and electron back-scattered diffraction(EBSD) characterization techniques.The α→α+β phase transformation temperature of the Zr-1.0Sn-0.3Nb-0.3 Fe alloy was determined to be 765-770°C. | QIU RiSheng LUAN BaiFeng CHAI LinJiang ZHANG XiYan LIU Qing | 2013 | Science China(Technological Sciences)2013，56，1： | 1 |
| 12 | Misorientation characteristics and textural changes induced by dense twins in high-purity Ti sheet after small strain rolling显示文摘A high-purity Ti(HP-Ti)sheet was subjected to small strain rolling(10%reduction)with microstructural and textural characteristics examined by electron channeling contrast imaging and electron backscatter diffraction techniques.Particular attentions were paid to misorientation and textural changes aroused by twins in the rolled HP-Ti sheet.Results show that after the 10%rolling,almost all the prior equiaxed grains in the initial specimen are twinned,leading to remarkable grain refinement.The presence of two major misorientation angle peaks around 65°and 85°is ascribed to{11-22}<11-23>and{10-12}<10-11>twinning,respectively,and two minor peaks around 47°and 77°are due mainly to impingement of various variants of such twins.Distinct from earlier work,the small strain rolling is confirmed to be able to induce drastic textural changes in pure Ti sheets:largely reduced texture intensity and appearance of new textural components.This can essentially be attributed to enhanced twinning activity due to much lower impurity contents of the present material.Primary{11?22}twins are mainly responsible for the new textural component of c-axes aligned near the rolling direction with spread,while the component of caxes parallel to the normal direction is due to reorientation of secondary{10-12}twins.This study clearly demonstrates the capability of small strain rolling to effectively modify both microstructures and textures of the HP?Ti sheet and may shed some light on exploring feasible processings for such materials. | DAI JiaHong ZENG LingGuo LI ZhiJun CHAI LinJiang ZHENG ZhiYing WU Hao MURTY KL GUO Ning | 2019 | Science China(Technological Sciences)2019，62，11： | 0 |
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