冷轧方式和退火温度对Al-4Cu-0.73Mg合金织构和微观组织的影响

采用硬度测试、X射线衍射(XRD)、电子背散射衍射(EBSD)等方法研究了单向轧制、交叉轧制和退火温度对Al-4Cu-0.73Mg(wt%)合金织构演变和微观组织的影响。结果表明:单向轧制试样在100~300 ℃退火保温1 h后显示出明显的Copper织构{112} <111>、S织构{123} <634>和Brass织构{011}<211>,而交叉轧制试样表现出强烈的Brass织构和H织构{011}<755>。当退火温度高于300 ℃,单向轧制和交叉轧制试样中的变形织构逐渐沿α取向线转变为由P织构{011}<001>、L织构{011}<011>、E织构{111}<110>和R织构{124}<211>等组成的再结晶织构。单向轧制和交叉轧制试样的晶粒尺寸随退火温度的升高先增加后减小,均在350 ℃退火1 h后有最大晶粒尺寸,分别约为8.2 μm和11.5 μm。单向轧制和交叉轧制试样均在冷轧后硬度值最高,约为108 HV,之后硬度值随退火温度的升高而逐渐下降,两种轧制试样的硬度值最终均稳定在50 HV左右。总体来看,轧制方式对试样织构的影响比对力学性能的影响大。     

Revealing substructure in clock-rolled Ta aided with triple focused ion beam

Clock rolling was developed to make deformation microstructure homogenize in high-purity Ta. The substructure of deformed Ta was revealed by electron back-scatter diffraction(EBSD) technique aided with triple focused ion beam(FIB). The results indicate that the triple FIB method can produce a mirror surface required by EBSD analysis. The clock rolling works well for the homogenization of deformed microstructure. Particularly,the local stored energy in {111} orientated grains is largely reduced by clock rolling, whereas it is enhanced in {100}orientated grains because of the occurrence of grain subdivision.     

高纯铝箔在异步轧制和再结晶过程中取向的演变

采用不同速比的异步轧制技术对99.99%的高纯铝板进行不同形变量的冷轧,并对冷轧样品进行不同温度和时间的再结晶退火.利用X射线衍射技术和TEM观测探讨了异步轧制条件下高纯铝箔中变形织构和再结晶织构的演变.结果表明:高速比的异步轧制(i=1.28)在样品中产生相对较强的旋转立方织构{001}(110).异步轧制后退火的高纯铝箔样品中,立方{001}(100)织构组分的再结晶晶核的形成和长大存在一个临界转变温度,此温度与异步轧制的速比成反比.异步轧制有利于降低高纯铝箔的再结晶温度,这与异步轧制提高高纯铝箔的形变储能有关.异步轧制有利于在低温时形成强的立方{001}(100)织构组分,但此时漫散较大;随着退火温度的升高,漫散范围明显缩至8°-10°.     

{411}<148> Texture in Thin-Gauge Grain-Oriented Silicon Steel

The significant occupancy of {411}148texture exists in the thin-gauge grain-oriented silicon steel(TGCRGO is defined that thickness of the sheet is0.25 mm and the reduction in cold rolling is more than 90%) which has been considered to have obviously effects on the abnormal growth of Goss-oriented grains during the secondary recrystallization process. The microstructures of the TG-CRGO were investigated by X-ray diffraction and electron back-scattered diffraction in this study. It was found that {411}148texture mainly exists in the center layer of hot-rolled as well as normalized plates.With the increase in cold rolling reduction, {411}148 orientation gradually rotates to a-fiber texture(110//RD).Finally, few {411}148would retain at the boundaries of deformed a-fiber grains(110//RD) as the reduction in cold rolling reaches 90%. After annealing treatment, a small amount of c-fiber textures(111//ND) preferably nucleates and recrystallizes between the DBs(deformation bands) at first; then, the {411}148 recrystallization texture occurs and mainly nucleates at the grains boundaries of the deformed a-fiber grains, and also quite a few {411}148orientation grains nucleate in the inner of {112}110grains. But this phenomenon was not observed in the {100}011deformation grains.With respect to the occurrence of {411}148recrystallization texture, it is mainly induced by strong a-fiber as well as weak c-fiber textures formed during cold rolling other than originating from {411}148 regions in hot bands.     

Lattice orientation dependence of the stored energy during cold-rolling of polycrystalline steels

During cold deformation, about 10% of the energy spent is stored in the polycrystalline material in the form of the elastic energy associated to crystal defects. The latter can be measured experimentally by calorimetry, X-ray diffraction. In this work, we propose a direct calculation based on an elastic-plastic self-consistent model. The part of the stored energy related to second order (intergranular) stresses is estimated for a cold-rolled Ti–IF steel. The stored energy as well as the accumulated plastic strain are reported as a function of the final crystallographic orientation of the grains. Along the α-fiber, the stored energy increases from {001}<110> to {111}<110> while the plastic strain decreases. This dependence with the crystallographic orientation is in good agreement with experimental results. With respect to recrystallization, experiments show that {111}-grains nucleate first. This highlights the specific role of second order (intergranular) stresses for recrystallization.     

高锰TWIP钢的冷轧变形行为

研究了低层错能奥氏体TWIP钢的冷轧组织和织构的演变。随着应变的增加,孪晶变形机制被激活。TEM、XRD等观察结果显示:随着应变量的增加,孪晶增加。在不同应变水平上,G{011}<100>织构都占主要位置。变形初始时,B{011}<211>织构强度较低,随着应变增加其强度显著增加。而E{111}<011>、Y{111}<112>、RG{011}<011>、Cu{112}<111>、CuT{552}<115>等织构在不同应变水平呈不同变化趋势。与其他织构相比,Cube{001}<100>织构强度相当低。     

横轧3 104铝合金变形织构的研究

应用极图分析及织构定量计算的方法，研究了横轧对3104铝合金变形织构的影响，结果表明：在与常规轧制相同压下量的横向轧制下，3104铝合金中的｛112｝，｛213｝丝织构体积百分数均低于常规轧制时各组分的体积百分数，而横向轧制则使得｛102｝丝织构增加较多，在横向轧制过程中出现强旋转立方织构和新｛110｝＜557＞取向的织构。     

柱状晶对Fe-3%Si电工钢冷轧织构演变规律的影响

Fe-3%Si电工钢铸锭中普遍存在柱状晶,其晶体学及形状各向异性对随后的热轧、冷轧及退火织构产生很大的影响.利用xRD与EBSD技术对长轴分别平行于轧面法向(ND),轧制方向(RD)和横向(TD)的柱状晶冷轧样品的织构及组织进行了研究,并对晶界的特殊作用进行了分析.结果表明,中等压下量下,3种柱状晶样品具有不同程度的{001}织构遗传性,即3种样品均不同程度的摆脱了{111}线织构的形成;柱状晶长轴平行于ND和TD时,{001}取向在冷轧时得到大的保留;柱状晶长轴平行于RD时,得到最强的{111}〈112〉织构;柱状晶长轴平行于TD时,冷轧组织中旋转立方织构及{111}〈110〉织构较强.此外,3种样品的织构均表现出由立方→{001}〈130〉→{113}〈251〉的过渡路径,与等轴多晶样品沿α线和γ线转动的路径不同.不同方向的柱状晶晶界对冷轧变形过程中晶粒转动的作用不同,但因晶粒尺寸大而作用有限,且与初始取向相关.     

Quasi-In-Situ EBSD Observation of the Orientation Evolution in Polycrystalline Tantalum During Rolling Deformation

The evolution of crystallographic orientation of polycrystalline tantalum(Ta) during rolling was characterized by electron backscatter diffraction technique in a quasi-in-situ way, and the microstructure and microtexture before and after the deformation were characterized and analyzed, respectively.In the specimen, 164 individual grains were exacted singly from the testing region and their corresponding orientations were reconstructed and analyzed, respectively.Results show that the heterogeneous deformation in a grain can be reflected by the accidented surface microstructure.Moreover, the orientations close to {111} orientations came closer to the {111} corner, while the orientation evolution is more complicated for the orientations close {100} corner, indicating that the evolution of these orientations close to {100} corner seemed to be irregular.     

{411}<148> Texture in Thin-Gauge Grain-Oriented Silicon Steel

The significant occupancy of {411}<148> texture exists in the thin-gauge grain-oriented silicon steel (TG-CRGO is defined that thickness of the sheet is <0.25 mm and the reduction in cold rolling is more than 90%) which has been considered to have obviously effects on the abnormal growth of Goss-oriented grains during the secondary recrystallization process. The microstructures of the TG-CRGO were investigated by X-ray diffraction and electron back-scattered diffraction in this study. It was found that {411}<148> texture mainly exists in the center layer of hot-rolled as well as normalized plates. With the increase in cold rolling reduction, {411}<148> orientation gradually rotates to α-fiber texture (<110>//RD). Finally, few {411}<148> would retain at the boundaries of deformed α-fiber grains (<110>//RD) as the reduction in cold rolling reaches 90%. After annealing treatment, a small amount of γ-fiber textures (<111>//ND) preferably nucleates and recrystallizes between the DBs (deformation bands) at first; then, the {411}<148> recrystallization texture occurs and mainly nucleates at the grains boundaries of the deformed α-fiber grains, and also quite a few {411}<148> orientation grains nucleate in the inner of {112}<110> grains. But this phenomenon was not observed in the {100}<011> deformation grains. With respect to the occurrence of {411}<148> recrystallization texture, it is mainly induced by strong α-fiber as well as weak γ-fiber textures formed during cold rolling other than originating from {411}<148> regions in hot bands.     

Microstructure Evolution and Hardness of an Ultra-High Strength Cu-Ni-Si Alloy During Thermo-mechanical Processing

Microstructure evolution and hardness changes of an ultra-high strength Cu-Ni-Si alloy during thermo-mechanical processing have been investigated. For hot-compressive deformation specimens, dynamic recrystallization preferentially appeared on deformation bands. As deformation temperature increased from 750 to 900 °C, elongated grains with the Cubic texture {001} 〈100〉 were substituted by recrystallized grains with Copper texture {112} 〈111〉. For the samples having undergone cold rolling followed by annealing, static recrystallization preferentially occurred in the deformation bands, and then complete recrystallization occurred. Goss, Cubic, and Brass textures remained after annealing at 600 and 700 °C for 1 h; R texture {111} 〈211〉 and recrystallization texture {001} 〈100〉 were formed in samples annealed at 800 and 900 °C for 1 h, respectively. For samples processed under multi-directional forging at cryogenic temperature, the hardness was increased as a result of work hardening and grain refinement strengthening. These were attributed to the formation of equiaxed sub-grain structures and a high dislocation density.     

低温轧制纯锆的形变孪晶及织构演变

通过在77K温度下进行不同变形量的低温轧制实验,研究了具有强烈单轴织构的工业纯锆板材在低温轧制变形条件下的孪生行为及变形机理。采用扫描电镜（SEM）和电子背散射衍衬（EBSD）分析和表征了变形材料的微观组织和织构。结果表明,在沿C轴加载的低应变条件下{1022}〈1123〉压缩孪生是主要的变形机制,同时在{1022}〈1123〉压缩孪晶中产生了二次孪晶（{10}-2}〈10T1〉拉伸孪晶）以协调变形。施密特因子计算及孪晶分布的EBSD模拟结果表明,在低温变形条件下的孪生模式的选择是由施密特因子的数值大小决定的。探讨并解释了轧制过程中随着应变量增加由孪生所导致的织构演变。     

IF钢退火过程中再结晶行为的EBSD表征

借助EBSD等技术研究了从冷轧到退火过程中IF钢中铁素体再结晶晶粒的取向演变。研究结果表明,从冷轧到退火过程中,铁素体晶粒取向向着平行于法向的[111]晶粒演变,而平行于法向的[100]晶粒逐渐消失;在冷轧变形过程中,铁素体晶粒的晶体取向决定着发生滑移变形的难易程度,与[100]晶粒相比,[111]晶粒更易于发生滑移变形,并在晶粒内部积累大量的位错,储存了大量的应变能,在随后的退火过程中,应变能较高的[111]晶粒优先形核并长大,优先发生再结晶,而应变能较低的[100]晶粒的再结晶受到阻碍。随着退火温度的升高,γ织构([111]//ND)明显增强,其织构组分(111)[112]尤为明显。     

中低应变量冷轧AA1050铝合金中晶粒取向与形变位错界面的演变

采用ECC和EBSD技术研究了AA1050铝合金冷轧至中低应变量下位错界面结构的演变. 结果表明, 冷轧至中低应变量下形成典 型的位错胞块结构,其微观组织结构强烈依赖于晶粒的取向. 变形后主要形成三种典型的组织结构: Type A------两组交叉的几何必须位错界面 (GNBs) 结构,Type B------一组GNBs结构, Type C------近似等轴的普通胞状结构. 绝大多数Copper, Brass和Goss取向的晶粒具有Type A结构, S取向的晶粒具有Type B结构, 而Cube取向的晶粒主要具有Type C结构. 变形过程中的GNBs不仅具有与RD成±(30°---40°) 的宏观取向, 而且大多数GNBs位错界面近似平行于由最大Schmid因子所确定的{111}滑移面的迹线.     

Orientation-Dependent Characteristics for Residual Grains during Hot Deformation of Nickel-Based Alloy 925

In the present work, the orientation characteristics of residual grains during hot deformation of an age-hardening Ni-Fe-Cr alloy(Alloy 925) at different conditions were systematically analyzed through high-resolution electron back-scatter diffraction. Based on the measurement of the kernel average misorientation, the density of geometrical necessary dislocations(GNDs) was further calculated. The orientation-dependent deformation mechanism of the residual grains was also discussed using Schmid factor difference ratio(SFDR) analysis. The results show that the deformed microstructure features typical "necklace" structures. Many distorted twin boundaries can be observed within the residual grains at 950 ℃. When the deformation temperature increases to 1150 ℃, the volume fraction of dynamic recrystallization(DRX) increases, leading to the extensive formation of primary Σ3 twin boundaries. Additionally, the GNDs are widely distributed in the residual grains, while they are rare for the recrystallized grains. The maximum GND density value can be obtained at the interface of "soft–hard" grains. The GND density also increases at higher strain rates, and the number of DRX grains significantly affects the distribution of the GND density. Moreover, based on the calculations and SFDR analysis, it can be summarized that the {100} and {111} grains are prone to deform in the uniserial slip mode and the multiple slip mode, respectively.     

Textures, models and experiments relating to drawable low carbon steels

This paper reports three distinct but related projects. In the first, an attempt is made to simulate BCC rolling textures by including a conditional deformation banding criterion modeled in a Taylor/Chin framework. The model is then run backwards to find the origins of the α and γ fibers. The practical importance of this work is to produce an ideal deformation texture from which it might be possible to maximise the development of {111} hkl and to minimise {100}hkl during rolling, since it is well known that {111} recrystallized components are associated with the γ fibre. The second investigation is concerned with the origins of the {111}hkl texture in a batch annealing steel. It is demonstrated that the γ fibre grains are heavily shear banded, and the nucleation of {111} grains occurs in these bands. The shear band material is a ND-rotated {111} component. Clearly, the condition leading to extreme strain localisation is determined by both the slip geometry and the solute/precipitate state. Finally an investigation into the origins of {111}hkl in IF steels using EBSP (Electron Back-Scattering Pattern) on longitudinal sections has failed to identify any sites of strain localisation for nucleation of these grains but it is shown that grain growth strengthens {111} components. This article based on a presentation made in the symposium “ ’99 International Symposium on Textures of Materials”, held at Sunchon National University, Sunchon, Korea, April 21–22, 1999 under the auspices of The Korean Institute of Metals and Materials and Research and Development Center for Automobile Parts and Materials.     

冷轧变形量对Al-Mg-Si合金织构的影响

利用光学显微镜、扫描电镜分析了不同冷轧变形量对Al-Mg-Si合金显微组织和微观织构的影响。结果表明:随着变形量的增加,再结晶织构Cube{001}<100>会经由Goss{011}<100>逐渐演变为以Copper{112}<111>和S{123}<634>为主要取向的形变织构,而Goss{011}<100>的体积分数表现为先增大后减小的趋势;合金形变带织构主要由强度较高的Copper{112}<111>织构和强度较弱的Cube{001}<100>织构组成;当变形量小于20%时,晶粒主要取向为{001}、{012},变形量大于40%时,{011}、{112}、{123}成为主要的晶粒取向。     

Molecular dynamics simulation on mechanisms of plastic anisotropy in nanotwinned polycrystalline copper with {111} texture during tensile deformation

Based on molecular dynamics (MD) simulation, the mechanisms of plastic anisotropy in nanotwinned polycrystalline copper with {111} texture during tensile deformation were systematically studied from the aspects of Schmid factor of the dominant slip system and the dislocation mechanism. The results show that the Schmid factor of dominated slip system is altered by changing the inclining angle of the twin boundaries (TBs), while the yield stress or flow stress does not strictly follow the Schmid law. There exist hard and soft orientations involving different dislocation mechanisms during the tensile deformation. The strengthening mechanism of hard orientation lies in the fact that there exist interactions between the dislocations and the TBs during plastic deformation, which leads to the dislocation blocking and reactions. The softening mechanism of soft orientation lies in the fact that there is no interaction between the dislocations and the TBs because only the slip systems parallel to the TBs are activated and the dislocations slip on the planes parallel to the TBs. It is concluded that the plastic anisotropy in the nanotwinned polycrystalline copper with {111} texture is aroused by the combination effect of the Schmid factor of dominated slip system and the dislocation mechanism.     

Phase transformation of pure tungsten subjected to multi-directional compression

Multi-directional compression (MDC) under the reduction of 30% with 1, 2 and 3 passes was subjected to tungsten at the temperature of 900 °C. The microstructure characteristics of the initial sintered and MDC-processed tungsten (W) specimens were comparatively investigated by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The phase transformation from α-W to γ-W was observed during the MDC deformation due to the crossed-shear deformation mode and high stored strain energy. An obvious crystallographic relationship of {110} α // {111} γ was found between α-W and γ-W. And a new crystalline slip path along [101] direction was presented. Molecular dynamics simulations were performed to investigate the phase transformation mechanism of pure W during MDC. A large number of defect clusters and shear bands were formed along 〈110〉 direction. Defect clusters huddled around the slip bands with the accumulation of strain, which caused dislocation tangling with the slip bands, resulting in stress concentration leading to phase transformation. The crystalline slip direction of α-W to γ-W phase transformation was a complex of [100] and [001]. The simulation results showed that the process of microstructural evolution under multiple passes of MDC was in good agreement with the experiment. This study is significant for the phase transformation path and mechanism of pure W during plastic forming.     

3104铝合金固溶及时效处理后的冷轧织构

应用取向分布函数（ODF）研究了3104铝合金经不同温度固溶及时效处理后的冷轧织构组态。结果表明：经固溶时效处理后其冷轧织构中存在强度较高的旋转立方织构v{001}〈110〉组分,此外也含有一定强度的c{112}〈111〉、B{110}〈112〉和S{123}〈634〉织构组分,明显不同于未经固溶时效直接冷轧样品的织构组态特征。可能的原因是经固溶和时效处理后溶质原子和析出相粒子形态和数量的变化,它们在变形过程阻碍了位错滑移,使晶粒转动受阻,进而使不稳定取向旋转立方织构被不同程度的保留下来;此外,固溶温度越高,冷轧样品中不稳定取向旋转立方织构组分取向密度越小,时效温度对后继冷轧织构的影响也应归结为析出相粒子在变形过程中对位错滑移的阻碍,进而影响晶粒转动。