Development of Texture and Microstructure During Cold Rolling and Annealing of a Fe-Based Shape Memory Alloy

Texture evolution and microstructural changes during cold rolling and annealing of Fe-14Mn-6Si-9Cr-5Ni shape memory alloy have been investigated. The starting solution-annealed material has a nearly random texture with microstructure composed of equiaxed austenite grains with ε martensite plates inside. Cold rolling induces a strong alloy type texture with Brass {011}〈211〉 and Goss {011}〈100〉 as major components. Annealing of the cold-deformed material produces a nearly random texture. The microstructural investigation reveals that with increase in cold deformation, the amount of stress-induced ε and α′ martensite volumes increase. The electron back-scattered diffraction (EBSD) phase mapping shows that reversion of the ε martensite begins only after recrystallization sets in at a temperature of 1073 K.     

电工钢中黄铜织构行为及其对Goss织构的影响

本文通过EBSD取向成像技术检测追踪了取向硅钢热轧、脱碳退火及二次再结晶过程中黄铜取向晶粒的形成规律.结果表明,黄铜取向的形成是热轧时Goss取向在剪切力作用下向铜型取向转动受阻而绕法向转动的结果.与Goss晶粒和{111}〈112〉取向晶粒类似,黄铜取向和{111}〈110〉取向晶粒之间存在形变与再结晶相互转化的密切关系;二次再结晶时若抑制剂钉扎控制不当,在次表层的Goss晶粒快速长入中心层之前,黄铜取向晶粒已长成大尺寸并接触样品表面,随后的Goss大晶粒就很难吞并黄铜取向晶粒.     

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.     

Effect of large strain cross rolling on microstructure and properties of Al−Li alloy plates with high magnesium content

Transmission electron microscopy (TEM), electron backscattered diffraction imaging (EBSD) and X-ray diffractometry were used to analyze the microstructure and texture characteristics of Al?9.8Mg?1.5Li?0.4Mn alloy cross-rolled and extruded plates, and the tensile properties and deep drawing performance were measured. The results show that the occurrence of dynamic recrystallization was promoted, the grains were refined and the preferred orientation of the recrystallized grains was improved by large strain cross rolling. Compared with CBA and CCB rolling methods, CBB rolling method significantly reduced the orientation density of the typical Brass texture {110}〈112〉 in the extruded plates. The orientation densities of Copper texture {112}〈111〉 and Brass texture {110}〈112〉 on the β orientation line in the CBB rolled plates were the lowest, and there were no typical texture features in the plates. Meanwhile, better deep drawing could be gained in the CBB rolled plates, and the mechanical properties of the 0°, 45° and 90° directions were basically the same. The tensile strength, yield strength and elongation at room temperature for the CBB rolled plates were 617 MPa, 523 MPa and over 20.1%, respectively. The deviation of the mechanical properties at different directions was less than 3%.     

Evolution of Annealing Twins and Recrystallization Texture in Thin-Walled Copper Tube During Heat Treatment

Thin-walled copper tubes are usually produced by multi-pass float-plug drawing deformation. In general, the annealing treatment subsequently is necessary to release the stored energy and adjusts the microstructure. In this study, an investigation on the evolution of annealing twins as well as textures in the thin-walled (Ф6 mm×0.3 mm) copper tube underwent holding time-free heat treatment was reported. Electron backscattered diffraction analysis reveals that a large number of Σ3 boundaries (60° 〈111〉 twin relationship) are produced at the early stage of heat treatment, which is due to the lower boundary energy. With the recrystallization proceeding, the migration rate of grain boundaries decreases on account of the grain growth; meanwhile, the unique Σ9 boundaries (38.9° 〈110〉 relationship) are formed due to the interaction of the Σ3 boundaries. As a result, the number fractions of Σ3 boundaries and high-angle grain boundaries decrease rapidly. During the grain growth stage, a strong recrystallization texture was formed due to the fact that the grains of Goss orientation have a growth advantage over the others. As a result, the initial copper texture was transferred into the Goss texture in domination.     

搅拌摩擦焊焊接5083铝合金板材焊核区的晶体取向

采用搅拌摩擦焊焊接了5083铝合金板材,借助电子背散射衍射技术和取向成像分析软件,对比性地分析了母材和焊核区的晶粒形貌、取向差分布、织构组分及取向分布函数,分析了焊核区晶体取向的变化.结果表明,在热-力作用下,焊核区发生动态再结晶,显示等轴晶粒形貌,平均晶粒尺寸约为15.8μm,同时大角度晶界比例明显增加.母材的黄铜织构B{011} <211> 和S织构{123} <634> 的比例分别达到30.6%和13.6%以上;搅拌摩擦焊后,焊核区的B织构和S织构的比例分别降至4%和1.8%,原位再结晶形成的R{124} <211> 织构组分约为7.7%,焊核区其它常见面心立方金属织构组分的比例均低于8%,意味着焊核区由强取向组织转变为弱取向组织.     

W含量对Ni-W合金基带取向及织构形成的影响

采用压延辅助双轴织构基板制备路线,结合X射线衍射和电子背散射衍射技术,系统研究了W量(原子分数)分别为5%、7%和9.3%的Ni-W合金基带在冷轧形变和再结晶热处理过程中的取向及织构形成的变化规律。研究发现,在冷轧形变过程中,随着W含量的增加,Ni-W合金基带中S和Copper取向含量的增量逐渐降低,而Brass取向含量的增量则呈现上升趋势,最终低W合金获得Copper型轧制织构,而高W合金获得Brass型轧制织构。在再结晶热处理过程中,低W合金立方晶粒形核较早并迅速长大,吞并其它取向,容易获得立方织构;高W合金的立方取向晶粒则和其它取向晶粒一同形核和长大,且长大速度不及其它取向晶粒,最后形成杂乱取向。     

涂层导体用Ni9W合金基带再结晶及强立方织构的形成研究

采用X射线四环衍射技术对比分析了通过冷轧和轧制中间热处理制备的2种Ni-9.3at%W(Ni9W)合金基带的轧制织构和再结晶织构,研究了不同Ni9W合金基带在热处理过程中轧制织构向再结晶织构的演变。其次,采用背散射电子衍射(EBSD)技术对以上2种Ni9W合金基带的微观组织和立方织构进行了表征。结果表明,与传统冷轧Ni9W合金基带的轧制织构相比,经轧制中间热处理后其轧制织构中S取向和Copper取向的含量增加、Brass取向的含量减少,使其轧制织构的类型介于Brass型轧制织构与Copper型轧制织构之间。2种Ni9W合金基带经低温回复后,其轧制织构含量均有一定的增加;另外,再结晶过程中轧制织构的含量均迅速降低,但立方取向的含量并没有明显增加,而是出现大量的随机取向,Ni9W的再结晶具有了连续再结晶的特征,这也是导致Ni9W合金基带较难形成立方织构的一个主要原因。虽然经过轧制中间热处理后Ni9W合金基带在初始再结晶完成后并没有形成一定强度的立方织构,但其立方取向的含量仍然能在进一步热处理过程中通过立方取向晶粒的长大而得到加强。最后,采用轧制中间热处理制备的Ni9W合金基带经两步高温热处理后其立方织构的含量达到84.5%(15°)。     

热变形温度对7055铝合金热处理组织和力学性能的影响(英文)

采用Gleeble-1500D热模拟试验机对7055铝合金进行多道次热压缩试验,并对热压缩试样进行T6热处理。采用TEM、OM观察热压缩试样与热处理试样的组织形貌,并对热处理7055-T6试样进行拉伸试验,研究变形温度对7055铝合金多道次热压缩后组织、热处理后的显微组织与力学性能的影响。结果表明:热变形温度不仅影响多道次热压缩后试样的组织,而且显著影响该合金热处理后的组织和力学性能。在本试验条件范围内,随着温度的升高,经多道次热压缩后试样的晶粒长宽比先减小然后增加,位错密度降低,亚晶尺寸增加,热压缩过程中发生再结晶;热处理后合金中再结晶晶粒体积分数先降低后增加。再结晶体积分数越小,合金的强度越高。当温度为400°C时,再结晶体积分数最小,约为45%,并且合金的抗拉强度和伸长率达到最大值。     

Zr-sn-Nb新型锆合金板材加工过程中不均匀组织与织构演变

利用XRD,SEM-ECC,TEM和EBSD技术,研究了Zr-Sn-Nb系新型锆合金板材加工过程的微观组织及织构演变.结果表明,β相淬火得到的随机织构经热轧后形成沿横向倾斜的基面织构,随后的加工过程均保留该织构;热轧及两次冷轧后的基面织构都为(1010)方向平行于轧向((1010)∥RD),而退火后转变为(1210)方向平行于轧向((1210)∥RD).淬火形成的网状魏氏组织经热轧转变为不均匀形变组织,两次冷轧使组织的不均匀性更显著,最终退火得到完全再结晶组织;轧制形成的难变形晶粒多为晶粒C轴平行于轧板法向(C∥ND)的取向;最终退火板材的大晶粒多为(1210)∥RD的基面织构,小晶粒则以(1010)∥RD为主.结合锆合金的变形及再结晶机制对轧制时产生的不均匀组织及再结晶过程的织构转变进行了分析.     

The Role of Oriented Growth in P Texture Development in Al-Mn-Mg Aluminum Alloy

The deformation and recrystallization textures in straight-rolled and cross-rolled AA 3105 aluminum alloy were investigated by x-ray diffraction to determine the role of oriented growth in the formation of the P recrystallization texture. A very strong P texture was developed in the straight-rolled sheet after recrystallization annealing. In contrast, the cross-rolled sheet did not develop the P texture on annealing even though the cross-rolling (i.e., rolling along the original transverse direction) texture contained more orientations close to the P orientation than the straight-rolling texture. The formation of the P texture in aluminum alloys requires the presence of the C component, since the P orientation has a 31.1°〈122〉 orientation relationship with respect to the C orientation. The recrystallization texture in the cross-rolled sheets was in excellent agreement with the oriented growth theory.     

1235铝合金动态再结晶动力学模型及氧化夹杂的影响

通过Gleeble热模拟试验建立动态再结晶动力学模型,研究氧化夹杂对1235铝合金的动态再结晶行为的影响。研究表明,经不同净化处理的1235铝合金在热变形条件下均发生一定程度的动态再结晶。动态再结晶体积分数的计算值与实测值接近(相关系数R大于0.92),相关性高。在相同热变形条件下,含杂量越低,热压缩时动态再结晶的速度越慢,细小的夹杂物阻碍了动态再结晶晶粒的长大,再结晶晶粒细小。     

Cu-0.35Cr-0.15Zr合金板带的织构和性能研究

采用晶体取向分布函数(ODF)研究了不同形变热处理制度下Cu-0.35Cr-0.15Zr(质量分数,下同)合金板带织构的演变规律,对各取向的体积分数进行了分析和计算,检测了不同状态材料在0°,45°和90°方向上的力学和物理性能.研究结果表明:在该合金冷轧板中主要有以{113}<332>取向为主的Copper织构、Brass取向、S取向和Goss取向,且随着冷变量的增加.Copper取向逐渐向Brass取向转变:时效态的带材中织构较弱,以Brass取向为主,S取向次之,Copper取向最弱,没有发现Copper织构的{113}<332>取向;时效态试样经过冷变形后,带材中又出现了{113}<332>取向,并且体积分数达60%以上.当带材中主要为Copper织构时.在0°→90°方向上合金的抗拉强度和延伸率逐渐升高,导电率逐渐降低;当Copper取向和Brass取向体积分数相当时,在0°→90°方向上,合金强度、延伸率和导电率的差别较小.     

Goss Texture Evolution of Grain Oriented Silicon Steel by High-Energy X-ray Diffraction

High energy synchrotron diffraction offers great potential to study the recrystallization kinetics of metallic materials. To study the formation of Goss texture （{ [10}（001）） of grain oriented （GO） silicon steel during secondary recrystallization process, an in situ experiment using hi gh energy X-ray diffraction was designed. The results showed that the secondary recrystallization began when the heating temperature was 1,494 K, and the grains grew rapidly above this temperature. With an increase in annealing temperature, the large grains with 7 orientation [〈111〉//normal direction] formed and gradually occupied the dominant position. As the annealing temperature increased even further, the grains with Goss orientation to a very large size by devouring the 7 orientation grains that formed in the early annealing stage. A single crystal with a Goss orientation was observed in the GO silicon steel when the annealing temperature was 1,540 K.     

Texture Evolution in an Al-Cu-Mg Alloy During Hot Rolling

The texture evolution in the intermediate (the 1/4 thickness) layer of hot-rolled Al-Cu-Mg alloy sheets was investigated by the x-ray diffraction technique, electron backscattered diffraction analysis and transmission electron microscopy observation. The results showed that a texture transition from the shear texture {001}<110> to the β-fiber textures occurred as the rolling temperature increased to 420 °C. The shear strain caused by friction resulted in this strong shear texture formation at the low rolling temperature. As the rolling temperature increased, the plane strain substituting the shear strain dominated in the intermediate layer, giving rise to a significant increase in the β-fiber textures. Increasing the rolling temperature was found to preferentially activate the non-octahedral {112}<110> slip system, thereby benefiting the development of strong Brass. At the low rolling reduction of 74%, the textures with low intensity tended to converge on the α-fiber, containing Goss, Brass, P and L components. As the rolling reduction increased to 90%, the textures were strengthened and gradually flew toward the β-fiber, containing Brass, Copper and S components. The S and Copper bands were found to be the preferential sites for the development of recrystallizing Cube grains during hot rolling.     

Texture memory effect in heavily cold-rolled Ni3Al single crystals

In Ni₃Al the cold-rolled Goss texture changed to a complicated one after primary recrystallization and returned to the original Goss during the subsequent grain growth, which can be referred to as the texture memory effect. In this study, we examined the evolution of grain orientations during the grain growth using the electron backscatter diffraction (EBSD) method. It was found that just after the primary recrystallization most of the grains had a 40°〈1 1 1〉 rotation relationship to the Goss texture, the remaining grains being Goss and other textures. The formation of the 40°〈1 1 1〉 rotated grains can be explained by a multiple twinning mechanism. In the grain growth, the Goss grains, which were surrounded by the 40°〈1 1 1〉 rotated grains, grew preferentially due to the high mobility of the 40°〈1 1 1〉 grain boundaries, leading to the texture memory effect.     

Secondary recrystallization in Fe-3% Si alloy with (110)[001] single-component texture

After the primary recrystallization of a preliminarily deformed (110)[001] single crystal, the texture also has the preferred (110)[001] orientation. Furthermore, the texture contains weak orientations, a major part of which is formed at the sample surface and can be described by a spectrum of scattered orientations {120}〈210〉…{351}〈103〉. A further heating leads to two concurrent processes taking place in the samples, i.e., the normal growth of Goss grains and secondary recrystallization. Abnormally grown crystals are represented by a quartet of orientations related with the initial Goss orientation by a rotation around [011], [01 $\bar 1$ ], [101], and [10 $\bar 1$ ] axes at an angle of ～30°. The crystallographic relationship between the initial and final grain orientations can be explained by their closeness to special misorientations as follows: Σ9, Σ19a, Σ27a, and Σ33a (rotation around 〈110〉 axes to close angles).     

Effect of Laser Texturing on the Microstructure and Textures of 1050 Aluminum Alloy

To improve the surface morphology, formability, and deep drawing properties of 1050 aluminum alloy sheets, laser-textured rolls were used in cold rolling process. Effects of laser-textured rolls, comparing with conventional ones, on microstructure and texture of aluminum alloys after rolling and following recrystallization were studied. In aluminum sheets processed by laser-textured rolls and conventional rolls, microstructure and texture were similar after rolling, but significantly different after recrystallization. Laser texturing process results in finer and inhomogeneous recrystallized grains. The recrystallization texture of the specimen rolled with conventional roll has a major cube component and a minor R component. The intensity of cube component increases with increasing annealing temperature. However, recrystallization texture of the specimen rolled with laser-textured roller is much more random. The specimen shows that recrystallization texture has only a weak cube orientation but strong rotated-cube orientation as well as a much higher fraction of random orientation.     

柱状晶对Fe-3%Si电工钢再结晶织构演变规律的影响

在对长轴分别平行于板法向(ND)、轧向(RD)、横向(TD)的柱状晶样品冷轧组织及织构演变规律分析的基础上,利用XRD与EBSD技术,对不同退火温度下各样品再结晶织构的形成规律进行分析.结果表明,柱状晶样品再结晶织构的演变,一方面体现了初始取向晶粒的"遗传性",即立方织构与Goss织构的形成;另一方面又展示了柱状晶样品不同于单晶及多晶的"特殊性",即{113}织构的形成、Goss晶粒大大超过立方晶粒的生长能力及TD样品中{110}〈110〉取向晶粒的消失.退火温度的变化在不同样品中可造成立方织构的增强或减弱,这取决于再结晶时的形核及长大环境,分析认为TD样品低温时形成最强的立方织构与其在冷轧过程中最强的晶界阻力有关.综合考虑各再结晶织构的转变规律,其形成与定向形核及定向长大均相关.研究还证实,3种柱状晶样品中等压下量冷轧并退火后都可抑制γ线织构的形成.     

Recrystallization Process in Fe-Cr-Al Oxide Dispersion-Strengthened Alloy: Microstructural Evolution and Recrystallization Mechanism

Mechanically alloyed iron-base oxide dispersion-strengthened (ODS) alloys are the class of advanced materials for application in heat exchangers tubing in which creep and oxidation resistance are paramount. The yttria dispersion in such alloys improves the high-temperature creep and stress rupture life. The strength is further enhanced by the development of a coarse-grained microstructure during recrystallization. Factors controlling the evolution of this desirable microstructure are explored in this work, focusing specifically on PM 2000. The results presented in terms of orientation imaging, transmission electron microscopy, and scanning electron microscopy indicate that the recrystallization process consists of two different stages. Before the coarse grain takes place, the alloy undergoes an extended recovery process followed by abnormal grain growth. The initial microstructure consisted of subgrains (submicrometer sizes) with a strong 〈110〉∥RD fiber texture (α fiber), which are transformed into coarse grains (mm sizes) with orientations 〈112〉∥RD. The aim of this study is to describe the mechanisms involved in the intermediate stages of recrystallization process from the submicrometer grain size to the abnormal grain size.