Texture Produced by Abnormal Grain Growth in Friction Stir-Welded Aluminum Alloy 1050

The texture produced by abnormal grain growth in friction stir-welded (FSWed) aluminum alloy 1050 was shown to be dominated by the Brass {110}〈112〉, R {124}〈211〉 and S {123}〈634〉 orientations. These orientations were present in the simple shear texture developed during friction stir welding (FSW) and their preferential growth was hypothesized to be induced by relatively low stored energy.     

Microtexture in the friction-stir weld of an aluminum alloy

In order to characterize plastic flow during friction-stir welding, the microtextures in a friction-stir weld of the precipitation-hardened aluminum alloy 6063 have been analyzed by orientation imaging microscopy (OIM). The base-material plate has a Goss orientation. The weld center region, except for the upper surface, takes a typical shear texture component with two types of orientations. The orientations have a pair of common {111} and 〈110〉 parallel to the cylindrical pin surface and transverse direction of the plate, respectively. The typical texture component is also observed around the weld center on the midsection, although it rotates about the plate normal direction. A microtexture analysis after postweld heat treatment has suggested that dynamic recrystallization during friction-stir welding generates the recrystallized grains at the weld center.     

低温加热取向硅钢组织与织构演变研究

采用OM、EBSD、XRD分析研究了含Cu低温加热取向硅钢组织、织构的演变特征,研究结果表明：热轧板中存在铁素体层和珠光体层彼此交替的带状组织,且显微组织在厚度方向上分布不均匀,热轧板中{001}〈110〉、{112}〈110〉织构以及{110}〈001〉织构在板厚方向上分布不均匀;经过冷轧后,铁素体晶粒被严重拉长,形成了沿轧向伸长的纤维状组织,冷轧板织构类型主要是α织构和γ织构;脱碳时基体发生回复再结晶,显微组织为单一的铁素体等轴晶粒,织构主要为γ织构;二次冷轧板经渗氮后织构仅从强度上有所降低,其织构类型变化不明显。成品二次再结晶组织发展比较完善,晶粒尺寸约为10~20 mm。织构类型为锋锐的Goss织构。成品磁感B800达到了1.926 T,铁损P1.7/50为1.047 W/kg。     

Grain size effects on the texture evolution of α-Zr

The texture evolution during the plastic deformation at room temperature of Zr-2.5Nb round bars was studied in specimens with two different α-Zr grain sizes. It was found that during axisymmetric compression the strain producing mechanisms active during deformation depended on the grain size. In fine grained specimens there are two main phenomena characterizing the evolution of texture: (i) a rapid rotation of the grains about their 〈c〉 axis to form a <112¯0> fiber at strains below −0.20 and, (ii) a slow and progressive reorientation of the 〈c〉 axes of the grains towards the compression axis to form a [0001] fiber texture tilted approx. 20°. The latter process takes strains larger than −0.80. In coarse grained material, the texture evolution is characterized by a sudden rotation of the 〈c〉 axes to become aligned parallel to the compression axis at strains as low as −0.05. It is shown using a self-consistent viscoplastic model of texture evolution that the type of texture obtained depends on the mechanism controlling 〈c〉 axis deformation. In fine grained material prismatic slip, with basal and pyramidal 〈c + a〉 slip acting as complementary deformation modes, control the texture evolution process. In coarse grained material twinning is responsible for the final texture observed.     

半工艺无取向硅钢加临界变形的织构演变

测定了半工艺无取向电工钢热轧(终轧温度在Ar1以下)到成品各工序的织构,以取向分布函数(ODF)的形式对加临界变形的半工艺无取向硅钢的织构演变作了分析.发现其热轧板表层织构基本是典型的铁素体再结晶{111}组分,心部和1/4厚度处以铁素体剪切织构和轧制变形织构为主.冷轧变形后,心部和表层织构组分比较接近,{111}、{112}和{100}面织构都增加,但{111}组分增加最明显.软化退火后,{001}<110>与{112}<110>组分迅速降低,织构组分以γ纤维织构为主.通过增加临界变形,在最终去应力退火后,{111}不利面织构大量减少,高斯组分增加明显.Taylor因子可以表征不同取向晶粒对变形能的储存能力,从轧制变形时Taylor因子的分布可以解释该实验结果.     

薄板坯连铸连轧流程Fe-3%Si钢热轧板和常化板织构

在实验室按照薄板坯连铸连轧工艺流程试制了Fe-3%Si硅钢热轧板,采用EBSD和X射线衍射方法观察了A钢和B钢热轧板和常化板的织构组织,分析了α、ε和γ取向线上织构取向密度变化规律。A和B钢热轧板具有相似的{110}〈112〉和、{001}〈110〉和{001}〈010〉和高斯织构组织,A试样表层的晶粒均匀性较差,B试样具有较强的γ织构取向。采用EBSD观察比较了A钢和B钢热轧板和常化板的垂直TD面的EBSD微观织构组织,A钢和B钢常化退火后基本保留了热轧时形成的中心部位的组织,而次表层和表层晶粒发生了再结晶长大,晶粒组织和织构梯度减小,织构主要集中在{001}〈^-1^-10〉和{001}〈0^10〉和之间以及高斯织构上。常化后织构的总体强度下降,高斯强度减弱。试验研究结果为开发薄板坯连铸连轧短流程生产电工钢技术提供理论依据和参考数据。     

Fe-6.5%Si合金温轧后退火过程中再结晶行为

用电子背散射技术观察了700℃温轧板在退火过程中的组织及织构演变以了解其再结晶行为.结果表明,温轧织构由强的（111）〈112〉、较弱的〈110〉∥RD及Goss组成,再结晶织构与之相似.〈110〉∥RD及（111）〈112〉新晶粒首先形成于与之构成小角度晶界的形变晶粒的晶界附近,而在角隅及组织不均匀区等位置孕育出与周围晶粒构成大角度晶界的晶核,择优取向不明显.退火过程中（111）〈112〉在形变组织中累积,最终转化为（111）〈112〉再结晶晶粒.分析认为,温轧后退火是不均匀组织在低储存能驱动下的再结晶过程.（112）〈110〉及（111）〈112〉形变拉长晶粒多发生连续再结晶从而退火织构与形变态相似.在角隅区形成核心进而发生不连续再结晶,核心取向的统计性及不连续晶核的长大弱化再结晶织构,其中Goss晶粒多以此方式形成于（111）〈112〉晶粒内部.     

稀土Y对6.5%Si高硅钢热轧和温轧组织织构演变的影响

摘要：以无稀土与含质量分数为0.03%的Y的6.5%（质量分数）Si高硅钢为研究对象,经过热轧、常化、温轧及退火工艺制备出0.5mm高硅钢薄板,采用EBSD、SEM和EDS测试技术,研究了稀土Y对高硅钢热、温轧组织织构演变的影响。结果表明,热轧板中以{001}〈110〉和{110}〈001〉织构为主,常化板织构类型遗传了热轧板,添加稀土Y削弱了热轧、常化板中整体织构强度。含Y高硅钢较无稀土高硅钢温轧剪切带增多,位错密度增加,α织构减弱且γ织构增强。随着退火温度升高,温轧板以{001}〈140〉为主的λ织构和{114}〈481〉为主的α*织构强度不断增强。添加稀土Y削弱了相同退火温度下温轧板的λ织构与α*织构的强度,然而η织构却有所增强,这与稀土Y促进剪切带形核有关。添加质量分数为0.03%的Y具有细化晶粒的作用,细小弥散的稀土Y氧化物阻碍晶界迁移是导致高硅钢温轧板再结晶晶粒细化的重要原因。     

Precipitation and grain refinement in a 2195 Al friction stir weld

The microstructure across a friction stir weld in aluminum alloy 2195 was analyzed to reveal the precipitation processes, grain evolution mechanisms, and crystallographic texture within that weld. The complex microhardness variations across the weld are explained by the observed precipitation sequence, in which the original precipitates coarsen and dissolve during welding, and are then replaced by different precipitates, which form during cooling. The grain development from the thermomechanically affected zone (TMAZ) into the weld nugget reveals that subgrains form within the TMAZ grains and develop increasing boundary misorientations through continuous dynamic recrystallization by subgrain rotation to eventually form the refined grains observed within the weld nugget. Within the weld nugget, a {112}〈110〉 texture is observed, corresponding to a high strain/high temperature shear strain component.     

TC4钛合金轧板的织构对动态力学性能影响

利用分离式Hopkinson压杆试验装置,对具有不同织构特征的TC4合金试样进行动态压缩试验,分析织构特征对钛合金轧板各方向动态力学性能的影响。结果表明,900℃轧制板材的主织构为{1219}<12391>±30°RD,织构强度为10.557,在φ1=15°时出现峰值,有一定的织构分散,其中晶面{1219}平行板材的轧面,与基面{0001}夹角26.6°,晶向由〈1010〉向〈6 331〉方向漫散;950℃轧板的主织构为{1219}〈5321〉±20°RD,织构类型与900℃轧板相似,但织构强度为6.387,相对900℃轧板较弱,晶向由〈7341〉向〈4311〉方向漫散,在φ1=35°出现峰值;1050℃轧制板材的主织构为{12 19}〈1010〉,织构比较集中,织构强度为15.333,晶向〈101-0〉平行板材的轧向,与c轴为90°夹角。950℃轧制的TC4板材,织构强度较弱,其轧向(RD)、横向(TD)、法向(ND)的动态流变应力和动态均匀塑性应变差别不明显。900℃和1050℃轧制的TC4板材,由于织构强度较高,轧板存在明显的各向异性:TD方向的动态流变应力最高,ND次之,RD最低;RD方向的动态均匀塑性应变最大,ND次之,TD最小。     

TSCR试制低碳低硅无取向电工钢织构的演变

 研究了模拟TSCR流程生产的低碳低硅无取向电工钢在热轧-冷轧-退火过程中织构的演变。对热轧板采用EBSD技术进行织构的测定,而对冷轧板和退火板采用X射线衍射技术进行了织构的测定。结果表明：热轧板沿板厚方向织构变化比较明显,在1/10处主要织构为α纤维织构和γ纤维织构;在1/4厚度处出现了较强的γ纤维织构;在1/2厚度处主要为较强的{001}〈110〉织构,其他织构分布漫散。冷轧板表面和中心处主要织构均为α纤维织构和γ纤维织构,但是在中心处两织构强度都显著减弱。退火板表面和中心处α纤维织构基本消失,γ纤维织构织构进一步加强,出现了{110}〈001〉高斯织构和{001}〈010〉立方织构。     

Crystallographic preferred orientation induced by cyclic rolling contact loading

Fine focus X-ray diffraction methods have been applied to analyze the texture development of the ferrite phase during rolling contact fatigue of 6309 type deep groove ball bearing inner rings prepared from hardened and tempered SAE 52100 steel. Textures of the ferrite matrix as {100}〈110〉 and {111}〈211〉 (where {hkl} denotes the crystallographic plane that is preferably parallel with the contact surface and 〈uvw〉 denotes the crystallographic direction that is preferably parallel with and in the direction of over-rolling) have been identified in a small region below the rolling contact surface. These textures develop gradually with an increasing number of stress cycles and become noticeable in conjunction with changes in residual stress, microstrain, and volume fraction of retained austenite in the same region. Upon rolling contact loading, both textures can become very pronounced, while the shape of the subsurface volume, where plastic deformation takes place in particular, remains unchanged: material displacement in the subsurface volume is less than 5 μm in the three principal directions. Crack propagation in association with spalling fatigue failure has been shown to be related to the type of texture developed.     

Material Flow during Friction Stir Welding of HSLA 65 Steel

Material flow during friction stir welding of HSLA-65 steel was investigated by crystallographic texture analysis. During the welding process, the steel deforms primarily by local shear deformation in the austenite phase and then transforms upon cooling. Texture data from three weld specimens were compared to theoretical textures calculated using ideal Euler angles for shear in face centered cubic (FCC) structures transformed by the Kurdjumov–Sacks (KS) relationship. These theoretical textures show similarities to the experimental textures. Texture data from the weld specimens revealed a rotation of the shear direction corresponding to the tangent of the weld tool on both the area directly under the weld tool shoulder and weld cross sections. In addition, texture data showed that while the shear plane of the area under the weld tool shoulder remained constant, the shear plane of the weld cross sections is influenced by the weld tool pin.     

Evolution of recrystallization texture from aluminum sheet cold rolled under unlubricated condition

The texture of cold-rolled aluminum sheet has been known to vary through thickness due to inhomogeneous deformation, which can be caused by a characteristic deformation zone geometry and friction between materials and rolls during rolling. The copper texture is obtained in the center layer, which is plane strain compressed, while the shear texture is in the surface layer, which is approximated by major {001}t〈110t〉 and minor {111}t〈112t〉 and {111}t〈110t〉 components. The recrystallization texture of the surface layer is approximated by {225}t〈10 5 2t〉. The evolution of the recrystallization texture has been explained by the maximum energy release theory, in which the absolute maximum normal stress direction in the deformed state becomes parallel to the minimum elastic modulus direction of the recrystallized grains.     

Effect of Austenite Pancaking on the Microstructure,Texture, and Bendability of an Ultrahigh-Strength Strip Steel

The effect of austenite pancaking in the non-recrystallization regime on microstructure and texture evolution and thereby on bendability was investigated in an ultrahigh-strength strip steel with a martensitic-bainitic microstructure. The results indicate that an increase in rolling reduction (R _tot) below the non-recrystallization temperature, which improves the strength and toughness properties, increases the intensities of the ~{554}〈225〉 _α and ~{112}〈110〉 _α texture components along the strip centerline and of the ~{112}〈111〉 _α component at the surface region. Even with the highest R _tot of 79 pct, the bendability along the rolling direction was good, but the preferred alignment of rod-shaped MA constituents along the rolling direction led to a dramatic decrease in the bendability transverse to the rolling direction, with severe cracking occurring even at small bending angles. The early cracking is attributed to localization of the strain in narrow shear bands. It is concluded that the R_tot value has to be limited to guarantee successful bendability.     

纯铁纯度对其再结晶织构及晶粒Schmid因子的影响

 为了研究纯铁纯度对其再结晶织构及Schmid因子的影响,以商业的2N8、3N5纯铁和实验室制备的4N级公斤级高纯铁为原料,通过退火再结晶和EBSD研究了2N、3N、4N纯度纯铁再结晶织构特征和晶粒的Schmid因子。结果表明,2N8、3N5和4N3纯铁的晶粒组织均为等轴铁素体,残余应力少、位错密度低,样品再结晶完全。其中,2N8和3N5纯铁的织构呈现出相同的分散分布特征,而4N3高纯铁织构特征集中,随机织构较少。ODF图和取向线分布密度进一步表明,2N8和3N5纯铁具有相似的α织构{hkl}〈110〉和γ织构{111}〈uvw〉特征及变化趋势,即两者都在α取向线的{111}〈110〉取向具有较高的分布密度和γ取向线密度随φ₁的增大而有降低;而4N3高纯铁具有〈113〉|X和γ织构特征,且包含利于材料力学性能各向异性的{332}〈113〉织构,另外,其γ取向线密度随φ₁的增大逐渐升高,直至{111}〈112〉取向密度高于2N8和3N5纯铁。晶粒Schmid因子及其频率分布直方图结果表明,2N、3N、4N纯铁均存在低Schmid因子晶粒被高Schmid因子晶粒包围的现象,且在{110}〈111〉、{112}〈111〉和{123}〈111〉这3个滑移系下晶粒Schmid因子总和平均值为0.467(4N3)＞0.461(3N5)＞0.459(2N8),呈现出纯铁晶粒Schmid因子总和平均值随纯度增大的趋势;根据Schmid定律可知,4N3纯铁的织构特征最有利于其变形。综上所述,在本工作中,随着纯铁纯度由2N8提升至4N3,样品中杂质原子减少,促进了4N3高纯铁产生强烈的〈113〉|X和γ织构特征以及利于材料力学性能各向异性的{332}〈113〉织构,增大了其晶粒Schmid因子总和平均值。     

Texture Development in the Ni47Ti44Nb9 Shape Memory Alloy During Successive Thermomechanical Processing and Its Effect on Shape Memory and Mechanical Properties

For improving the shape memory performance and mechanical properties of shape memory alloys (SMAs), crystallographic texture and second phase are generally induced in SMAs by suitable thermomechanical processing. For this purpose, the development of texture in the Ni₄₇Ti₄₄Nb₉ SMA during successive processing (e.g., hot forging, hot rolling, cold rolling, and heat treatment) and the effects of texture, grain size, and β-Nb particle precipitation on recoverable strains and tensile properties were studied. In the hot-forged and hot-rolled Ni₄₇Ti₄₄Nb₉ alloy rods, intense 〈111〉 fibers are formed, and water quenching from 873 K and 1123 K (600 °C and 850 °C) leads to the decrease in intensity of 〈111〉 fiber in the hot-rolled rod. When the hot-forged rod is hot-rolled into sheet, intense {001} and weak {123} fibers appear, but grain growth leads to the disappearance of {001} fiber and {110}〈001〉 becomes the strongest component. Cold-rolling deformation of the hot-rolled sheet promotes the development of γ-fiber and the convergence of {332} and {123} fibers to {233}〈110〉 and {123}〈121〉 components, respectively, and the intense component is turned into {111}〈110〉; in this case, the recoverable strain (ε _SRS) and tensile yield strength (σ _YS ) exhibit an anisotropy. When the quenching temperature is 1123 K (850 °C), some weaker components appear, the anisotropy of ε _SRS disappears, and the difference level in σ _YS along the rolling direction (RD) and transverse direction (TD) becomes smaller. Therefore, an appropriate heat-treatment temperature should be selected to maintain the deformation texture and also to obtain fine grains for different thermomechanical processing.     

Anisotropy in Mechanical Properties and Fracture Behavior of an Oxide Dispersion Fe20Cr5Al Alloy

Anisotropy of fracture toughness and fracture behavior of Fe20Cr5Al oxide dispersion-strengthened alloy has been investigated by means of compression tests, hardness tests, and wedge splitting test. The results show a small effect of the compression direction on yield strength (YS) and strain hardening. The YS is minimum for longitudinal direction and maximum for the tangential direction. The transverse plastic strain ratio is similar for tangential and longitudinal directions but very different from that in normal direction. Hardness depends on the indentation plane; it is lower for any plane parallel to the L-T plane and of similar magnitude for the other orthogonal planes, i.e., the L-S and T-S planes. Macroscopically, two failure modes have been observed after wedge-splitting tests, those of LS and TS specimens in which fracture deviates along one or two branches normal to the notch plane, and those of LT, TL, SL, and ST specimens in which fracture propagates along the notch plane. Besides LT and TL specimens present delaminations parallel to L-T plane. Both, the fracture surface of branching cracks and that of the delaminations, show an intergranular brittle fracture appearance. It is proposed that the main cause of the delamination and crack branching is the alignment in the mesoscopic scale of the ultrafine grains structure which is enhanced by the 〈110〉-texture of the material and by the presence in the grain boundaries of both yttria dispersoids and impurity contaminations. An elastoplastic finite element analysis was performed to study what stress state is the cause of the branches and delaminations. It is concluded that the normal to the crack branches and/or the shear stress components could determine the crack bifurcation mechanism, whereas the delamination it seems that it is controlled by the magnitude of the stress component normal to the delamination plane.     

Plane strain compression of silicon-iron single crystals

Six different orientations of Fe-3 wt% Si single crystals have been deformed in plane strain compression (using a channel die) up to true strains of 0.5. The finite strain behaviours, i.e. the shape changes, lattice rotations and stress-strain curves, are compared with the predictions of the generalized Taylor analysis of partially constrained crystal deformation. The influence of the relative critical resolved shear stresses on the {110} and {112} 〈111〉 glide systems has been systematically examined. It is shown that for most crystals under multiple slip conditions the shape changes and lattice rotations are consistent with the hypothesis of glide on {112} being somewhat easier than on {110}. Comparison with previous work on b.c.c. crystals undergoing large strains leads to the suggestion that: (i) under conditions of single or colinear slip, glide on {110} is easier than on {112}; (ii) under conditions of intersecting 〈111〉 slip directions, glide on {112} is easier than on {110}. For silicon-iron, the critical resolved shear stresses on the {112} 〈111〉 systems, relative to those on the {110}〈111〉 systems are found to be 0.93 and 0.96 for the twinning and anti-twinning senses, respectively.     

Deformation textures of AA8011 aluminum alloy sheets severely deformed by accumulative roll bonding

A fully annealed AA8011 aluminum alloy sheet containing a number of large particles (∼5 μm) was severely deformed up to an equivalent strain of 12 by an accumulative roll-bonding (ARB) process. The texture evolution during the ARB process was clarified, along with the microstructure. The ARB-processed aluminum alloy sheets had a different texture distribution through the sheet thickness, due to the high friction between the roll and the material during the ARB process. The shear textures composed of {001} 〈110〉 and {111} 〈110〉 orientations developed at the sheet surface, while the rolling textures, including Cu {112} 〈111〉 and Dillamore {4,4,11} 〈11,11,8〉 orientations, developed at the sheet center. The textural change from a shear texture to a rolling texture at the sheet center during the ARB process contributed to an increase in the fraction of high-angle boundaries. Also, a large number of second-phase particles in the AA8011 alloy sheets weakened the texture. Up to the medium strain range (below ɛ=6.4), relatively weak textures developed, due to the inhomogeneous deformation around the second-phase particles; after the strain of 6.4, strong rolling-texture components, such as the Dillamore and Cu orientations, developed. This remarkable textural change can be explained by the reprecipitation of fine particles in grain interiors.