Effect of Zn and Y Additions on Grain Boundary Movement of Mg Binary Alloys During Static Recrystallization

Texture evolution in rolled Mg–1 wt% Zn and Mg–1 wt% Y binary alloys was analyzed by quasi-in situ electron backscatter diffraction (EBSD) during static recrystallization. Mg–1 wt% Zn and Mg–1 wt% Y alloys exhibited strong basal texture at the initial recrystallization state. After grain growth annealing, the basal texture component {0001} < $11\overline{2}0$ > was increased in Mg–1 wt% Zn alloy and that of Mg–1 wt% Y alloy was decreased to be a random texture. Zn and Y atoms segregated strongly to the recrystallized grain boundaries in Mg–1 wt% Zn alloy and Mg–1 wt% Y alloy, respectively. Thus, Zn and Y elements facilitated the grain boundary movements along contrary directions during grain growth. In Mg–1 wt% Zn alloy, due to the Zn element segregation on grain boundaries, the grains consisted of a strong texture grew more easily because the grain boundary migration tended to move from the orientation close to normal direction to the orientation near to transverse direction or rolling direction. Therefore, after grain growth, the volume fraction of texture component {0001} < $11\overline{2}0$ > was increased by consuming the neighboring grains, leading to a stronger basal texture. On the contrary, in the Mg–1 wt% Y alloy, the Y element segregation caused the opposite direction of grain boundary migration, resulting in a random texture.     

Microstructure and Mechanical Property of Hot-Rolled Mg-2Ag Alloy Prepared with Multi-pass Rolling

A conventional multi-pass rolling is designed to form different microstructures in a Mg-2Ag alloy. The relationship between microstructure and mechanical property is investigated. The result shows that twin-induced nucleation plays a prominent role for the dynamic recrystallization (DRX) behavior of the rolled Mg-2Ag alloys. The DRXed grains distributed around elongated grains have random orientations but gradually turn to the concentrated orientation with strong basal texture when the rolling pass increases. The yield strength and ultimate tensile strength of rolled Mg-2Ag alloy gradually increase with increasing rolling pass. The elongation of rolled sample is gradually improved when the rolling pass increases from one to three, while a significant drop of elongation shows in the four-pass rolling sample. The strong basal texture, refined grains, high-density dislocations, and Ag segregation along grain boundaries are suggested to play a prominent role for enhancing the strength of Mg-Ag alloys, while the low-density dislocations, homogeneously fine-grained microstructure, and weak texture are critical for improving the ductility.     

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.     

Ti6Al4V钛合金的变形组织及织构

在温度850~930°C、应变速率0.01~1 s-1的条件下,对初始组织为等轴组织的Ti6Al4V钛合金进行变形程度为70%的热压缩变形实验,研究合金的变形组织及织构。结果表明,当温度低于900°C、应变速率高于0.1 s-1时,合金的组织主要是拉长的α晶粒;而在高于900°C以及低应变速率下,则会发生动态再结晶。电子背散射衍射（EBSD）结果显示,合金在再结晶过程中亚晶界吸收位错,最终形成大角晶界。在930°C时动态再结晶已基本完成,水冷至室温时形成针状α相。与原始组织相比,合金在930°C变形时织构得到增强,低于930°C变形时织构变弱。     

Microstructure and texture evolution of AZ31 magnesium alloy during rolling

The production of magnesium alloy sheets normally involves several processing stages including hot rolling,cold rolling and intermediate annealing.The microstructure and texture evolution of AZ31 magnesium alloy sheets in different processing states were investigated by optical microscopy and X-ray diffraction technique.It is found that the microstructure of hot-rolled sheets is dominated by recrystallized equiaxed grains,while that of cold-rolled sheets is dominated by deformation twins.With final annea...     

Ti70合金板的组织与力学性能的各向异性

通过拉伸及低温冲击试验、光学显微镜、扫描电镜及X射线衍射仪,对Ti70合金板的组织与力学性能的各向异性进行了研究。结果表明,Ti70合金板热轧及退火后组织未出现明显差异,退火过程中主要以回复为主,但在高密度位错的剪切带上出现了一定数量的再结晶晶粒。退火态Ti70合金板横向屈服强度及低温冲击吸收能量都高于纵向,但抗拉强度低于纵向,表现出了明显的各向异性。退火后Ti70合金板形成了较强的{0002}基面织构,其晶面法向向RD方向(纵向)偏转±30°,向TD(横向)方向偏转±41°。由于基面织构更向RD方向集中,因此造成了Ti70合金板力学性能的各向异性。     

Static recrystallization behavior of hot-deformed magnesium alloy AZ31 during isothermal annealing

The static recrystallization of hot-deformed magnesium alloy AZ31 during isothermal annealing was studied at temperature of 503 K by optical and SEM/EBSD metallographic observation. The grain size change during isothermal annealing is categorized into three regions, i.e. an incubation period for grain growth, rapid grain coarsening, and normal grain growth. The number of fine grains per unit area, however, decreases remarkably even in incubation period. This leads to grain coarsening taking place continuously in the whole period of annealing. In contrast, the deformation texture scarcely changes even after full annealing at high temperatures. It is concluded that the annealing processes operating in hot-deformed magnesium alloy with continuous dynamic recrystallized grain structures can be mainly controlled by grain coarsening without texture change, that is, continuous static recrystallization.     

再结晶退火对Mg-1.5Y板材组织、织构及性能的影响

利用十字交叉轧制工艺制备了Mg-1.5Y合金板材,研究了再结晶退火(475℃/15min)对其微观组织、宏观织构、力学性能及成形性能的影响。结果表明,退火促使轧制板材发生强烈的静态再结晶,形成均匀的等轴晶组织。轧制态板材呈现出近圆形-双峰织构分布特征,(0002)面极点由法向(ND)向轧制方向2(RD2)倾转大约±20o;再结晶退火后,基面极点沿轧制交角方向发生劈裂,形成蝴蝶状-多峰弱织构分布特征,且晶粒取向更加随机化,最大极密度由轧制态的5.0降低至2.8。退火态板材的断后伸长率、杯突值分别达到30.5%、4.4mm,相对于轧制态分别提高了63%、42%。     

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.     

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.     

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.     

Tailoring the Texture and Mechanical Anisotropy of Multi-cross Rolled Mg-Zn-Gd Alloy by Annealing

The unidirectional rolled Mg-Zn-Gd sheet usually exhibited non-basal texture with two peaks whose tilting angle were about 42° from normal direction to transverse direction (TD), which would cause the mechanical anisotropy. In this study, multi-cross rolling followed by annealing was used to tailor the texture and mechanical anisotropy for Mg-Zn-Gd alloy. With increasing annealing temperature, the rolled basal texture with two peaks gradually transformed into the circle texture with multi-peaks. In order to figure out different texture components evolution during annealing, the basal texture, R-texture and T-texture component were defined and studied. The results showed that the change of R-texture and T-texture component was asynchronous with increasing annealing temperature from 250 to 400 °C. The tilting angle of R-texture component increased slightly, while the tilting angle of T-texture component increased obviously, and this phenomenon was attributed to the preferential nucleation at grain nucleation stage rather than preferential grain growth. The yield strength along TD was more sensitive to annealing temperature compared with that along rolling direction (RD), resulting in different descending slopes and yield strength anisotropy with increasing annealing temperature. Annealing at 300 °C was the best annealing temperature due to low yield strength anisotropy, moderate strength and good elongation among these annealing temperatures. The Schmid factor for basal slip indicated that the activity of basal slip along RD increased slightly, while that along TD increased obviously with increasing annealing temperature from 250 to 400 °C, which should be caused by the asynchronous change of R-texture component and T-texture component, consequently resulting in the transformation from isotropic yield strength to anisotropic yield strength.     

Effect of deformation mode,dynamic recrystallization and twinning on rolling texture evolution of AZ31 magnesium alloys

In order to obtain quantitative relationship between (0002) texture intensity and hot rolling conditions, conventional rolling experiments on AZ31 magnesium alloys were performed with 20%–40% reductions and temperatures within the range of 300–500 °C. Shear strain and equivalent strain distributions along the thickness of the rolled sheets were calculated experimentally using embedded pin in a rolling sheet. Rolling microstructures and textures in the sheet surface and center layers of the AZ31 alloys were measured by optical microscopy (OM), X-ray diffractometry (XRD) and electron back scatter diffraction (EBSD). Effects of the rolling strain, dynamic recrystallization (DRX) and twinning on the texture evolution of the AZ31 alloys were investigated quantitatively. It is found that the highest (0002) basal texture intensities are obtained at a starting rolling temperature of 400 °C under the same strain. Strain–temperature dependency of the (0002) texture intensity of the AZ31 alloy is derived.     

Recrystallization behaviour of fine-grained magnesium alloy after hot deformation

Annealing behaviors of hot-deformed magnesium alloy AZ31 were studied at temperatures from 300 to 673 K by optical and SEM/EBSD metallographic observation. Temperature dependence of the average grain size（D） is categorized into three temperature regions, i.e. an incubation period for grain growth, rapid grain coarsening, and normal grain growth. The number of fine grains per unit area, however, is reduced remarkably even in incubation period. This leads to grain coarsening taking place continuously in the whole temperature regions. In contrast, the deformation texture scarcely changes even after full annealing at high temperatures. It is concluded that the annealing processes operating in hot-deformed magnesium alloy with continuous dynamic recrystallized grain structures can be mainly controlled by grain coarsening accompanied with no texture change, that is, continuous static recrystallization.     

Effect of rolling temperature on microstructure and texture of twin roll cast ZK60 magnesium alloy

Twin roll cast ZK60 alloy strip/sheet with final thickness of 0.5 mm was prepared,and effect of rolling temperature on microstructure and texture development was investigated using OM and XRD technique,microstructure and texture were measured on specimens subjected to rolling experiment at different rolling temperature,and macrotexture was also evaluated by X-ray diffraction method.In addition,the(1 010)and(0002) pole figures were measured,and the tensile test was performed to reveal the influence of rolling temperature on mechanical properties.The results show that the microstructure of ZK60 alloy sheet consisted of fibrous structure with elongated grains,and shear bands along the rolling direction after warm rolling.Dynamic recrystallization could be found during the warm rolling process at rolling temperature 350 °C and above.And many fine recrystallized grain could be observed in the shear bands area.It is a little difficult to see the recrystallized grain in the sheet warm rolled at 300 °C because of higher density of shear bands.The warm rolled ZK60 alloy sheet exhibited strong(0002) pole texture,the intensity of(0002) pole figure decreases with the increasing of rolling temperature and the basal pole tilted slightly to the transverse direction after warm rolling.     

Relating Initial Texture to Deformation Behavior During Cold Rolling and Static Recrystallization Upon Subsequent Annealing of an Extruded WE43 Alloy

Deformation behaviors during cold rolling and static recrystallization behaviors upon subsequent annealing of an extruded WE43 alloys with different initial textures were investigated in this study. Three types of differently textured WE43 initial alloys were labeled as samples I, II and III. The results showed that multiple twinning modes and basal slip dominated the deformation of samples during cold rolling. Cold-rolled sample I activated the larger number of double twins with high strain energy, accompanied by the more uniform strain distribution, than cold-rolled samples II and III. During subsequent annealing, recrystallized grains preferentially occurred in double twins, twin-twin intersections and grain boundaries, thereby making cold-rolled sample I have the more rapid recrystallization rate. Similar recrystallization textures formed in three types of cold-rolled samples at the recrystallization nucleation stage, and they never largely changed with the annealing time due to the uniform grain growth induced by the solute drag and the precipitation pinning at grain boundaries. After full recrystallization, the grain growth was controlled by the solute drag, instead of precipitates which were re-dissolved into the matrix. Finally, the nucleation and growth kinetics of static recrystallization were calculated, and the effects of initial texture on activation energies of recrystallization nucleation and growth were discussed.     

退火对冷轧Al0.2CoCrFe2Ni高熵合金组织和力学性能的影响

研究了不同温度退火对80%冷轧Al_0.2CoCrFe₂Ni高熵合金显微组织和力学性能的影响。使用X射线衍射仪(XRD) 、电子背散射衍射仪(EBSD)、微控电子万能试验机分别对合金进行了晶体结构、织构类型和力学性能的表征。结果表明,合金在铸态、轧制态以及退火态都表现为稳定FCC晶体结构。合金铸态下呈现典型的树枝晶组织,经80% 轧制后出现了明显的轧制变形带,在随后的退火过程中发生再结晶,其再结晶晶粒体积分数及其晶粒尺寸随着退火温度的升高而增加。合金经过80%轧制后主要表现为(111)<112>织构,其织构强度随着退火温度的升高而降低。80%轧制使Al_0.2CoCrFe₂Ni合金获得较大的抗拉强度(1005 MPa)和较低的塑性(10%), 随着退火温度的提高,合金的强度降低塑性增强,并在700 ℃退火时合金获得最佳的综合力学性能,该过程主要取决于合金中的位错密度、再结晶体积分数和晶粒尺寸及其再结晶织构的演变。     

喷射沉积2195铝锂合金轧制板材晶粒组织及性能控制研究

研究了喷射沉积制备2195铝锂合金锭坯挤压板坯经不同终轧温度热轧至6mm厚度板材,以及经不同中间退火后再冷轧至6mm厚度板材固溶后的晶粒组织。结果表明,终轧温度290℃时,热轧板固溶后表层为粗大再结晶晶粒,而中心层为细长纤维状晶粒;终轧温度降低至220℃时,虽然表层再结晶晶粒尺寸减小,但中心层转变为尺寸粗大的长条状再结晶晶粒。板材中尺寸1μm以上的富Cu第二相粒子数量随中间退火(空冷)温度的增加(从330℃提高至450℃)而增加;冷轧固溶后表层等轴状再结晶晶粒尺寸增加,而中心层晶粒逐渐由粗大长条状再结晶晶粒转变为细小等轴状再结晶晶粒。适当温度中间退火、随炉冷却并冷轧、固溶后表层和中心层全部为细小等轴状再结晶晶粒。优化中间退火后的冷轧板材T8时效态强度最高,而终轧温度220℃的热轧板材T8时效态强度最低。     

Role of shear band in texture control of Al-Mg alloys

Shear bands formed in Al-Mg alloys during cold rolling are nucleated on grain boundaries. Their mechanism of formation is different from that already proposed in the case of single crystals of the same alloy. Since recrystallized grains of non-cube orientations are nucleated on these shear bands during annealing, the development of cube recrystallization texture can be strongly suppressed by enhancing shear banding during cold rolling. Control of shear band thus provides a new fundamental technological tool to improve drawability of Al alloy sheets. In a microscopic scale, deformation in grain boundary regions also plays here a very important role, as in the case of the formation of {111}uvw recrystallization textures in low carbon steel sheets.     

EFFECTS OF MAGNETIC FIELD STRENGTH ON MICROSTRUC- TURE AND＇TEXTURE EVOLUTION IN COLD-ROLLED INTERSTI- TIAL-FREE STEEL BY MAGNETIC FIELD ANNEALING

Effects of magnetic field strength on the evolution of recrystallization microstructure and recrystallization texture in cold-rolled interstitial-flee steel were investigated after annealing at 660℃ in a magnetic field up to 12 T. Magnetic annealing was found to retard recrystallization and induce recrystallized grains elongated along the magnetic field direction. An interesting phenomenon is that the magnetic field shows the strongest effect at 1 T.