Microstructure and texture evolution of AZ31 Mg alloy after uniaxial compression and annealing

The effect of initial texture on the microstructure and texture evolution of as extruded AZ31 alloy after hot uniaxial compression at 430°C and subsequent annealing at 450°C for 72h has been investigated using electron backscatter diffraction.Samples were machined from the extruded block in such orientations that the compression axis,CD,was parallel(CD0ED)or perpendicular(CD90ED)to the initial extrusion direction,ED,respectively.Results show that the deformation microstructure for both samples was characterized by equiaxed grains that resulted from dynamic recrystallization.Annealing at 450°C for 72 h led to the increase of grains size to 28 and 25μm for CD0ED and CD90ED samples,respectively.A random deformation texture was developed in CD0ED sample while the deformation of CD90ED developed typical(0002)basal texture.The deformation textures of both samples were retained after subsequent annealing at 450°C for 72 h.The flow behavior was affected by the initial texture.The CD0ED sample showed the highest work hardening.These evolutions were explained in term of the activation and suppression of basal,non-basal slip and mechanical twinning.©2018 Published by Elsevier B.V.on behalf of Chongqing University.This is an open access article under the CC BY-NC-ND license.

Effects of Deformation Modes on Texture Evolution during Hot Working of Al-Zn-Mg-Cu-Zr Alloy

Deformation modes have strong effects on deformation textures and subsequent annealing textures during hot working of metals. Micro-textures and macro-textures during hot axisymmetric and planar compressive deformation and subsequent annealing processes of Al-Zn-Mg-Cu-Zr alloy were investigated by EBSD and XRD respectively. The EBSD testing indicated that for the axisymmetric compressive deformation, Brass along the a-fiber and Goss present in the sample deformed at 350 ~C, Rotated-Cube was present and Brass transformed to Goss along a-fiber after annealing; Rotated-Cube appeared only in the deformation at 420 ~C, which decreased and Brass appeared after annealing. For the planar compressive deformation, Rotated-Cube and Brass aligned to a and fl fibers present in the deformation at 350 ~C, Rotated-Cube texture transformed to Brass along the ct-fiber after annealing; Rotated-Cube and Brass were present in the deformation at 420 ~C, and the Rotated-Cube was enhanced and Brass transformed to Goss after annealing. Shearing textures dominated on the surface of the specimen. XRD testing showed that Rotated-Cube and a few Goss dominated in the thickplates formed by upsetting and drawing, which transformed to Cube after annealing; However, Brass and Cube textures present in the thick-plates formed by rolling besides Rotated-Cube and Goss textures, which remained in the plates after annealing.

AZ31镁合金热成形及退火过程的组织与织构

研究了热轧板及不同挤压比的热挤压棒的组织和织构特征 ,确定了热挤压时 <110 0 >织构随应变的加大取代 <112 0 >织构的原因。分析了退火对热成形组织及织构的影响 ,确定了 <110 0 >织构的消失与残余形变晶粒再结晶的联系。估算了退火时两类样品的平均晶粒长大速度并讨论了其与织构的关系。综合分析表明 ,AZ31镁合金热成形后总产生较强的织构 ,织构提高了热成形后的力学性能。高温退火虽使织构减弱 ,但伴随晶粒的明显长大。

合金元素对双相钢形变及退火织构的影响

分析了双相钢冷变形过程中形变织构的演变规律以及合金元素对双相钢形变织构的影响规律。分析结果表明,虽然存在有少量珠光体,但双相钢冷变形织构与体心立方金属相近;非碳化物形成元素Si的加入对形变织构没有明显的影响;碳化物形成元素Cr和Nb导致形变织构在α取向线的{112}<110>取向位置上的取向密度增强。测试分析了双相退火过程中钢的织构演变规律。结果表明,退火时晶粒的取向将沿着α取向线向γ取向线位置转变,Si或Cr对晶粒取向改变的阻碍作用不明显,微合金元素Nb明显阻碍晶粒取向改变,退火织构仍保持很高的α取向线织构组分。对上述的实验结果进行了理论分析。

锆铌合金冷变形与低温退火板织构的研究

测定了锆－２．５Ｗｔ％铌合金在冷变形量为２０％，５０％及４００℃退火后的板织构，计算了织构系数，讨论了织构形成、发展与工艺的关系。结果表明，冷加工变形量越大，织构越强烈；冷加工变形织构在４００℃／２４ｈ退火后不仅不会消失，反而会得到加强，这是由于择优取向的亚晶在退火回复过程中变得更加完整的原因。

多向锻造变形和退火处理对AZ31镁合金微观组织和力学性能的影响

采用空气锤在300℃下对AZ31镁合金进行多向锻造成形,并在200~400℃下进行退火处理,采用金相显微镜、电子背散射衍射和X射线衍射仪观察AZ31镁合金的微观组织,并对其力学性能进行测试。结果表明,多向锻造成形过程中,{1012}拉伸孪生和{1011}⁃{1012}二次孪生是主要的孪生机制,当累积应变􀰑Δε=0.96时,由于孪生诱发动态再结晶的作用,合金组织迅速细化至7.8μm,合金表现出优异的综合力学性能,抗拉强度、屈服强度和延伸率分别为320.3 MPa、218.5 MPa和30.3%;锻造合金经退火处理后,晶粒发生明显长大,双峰基面织构演变为典型板织构,晶粒尺寸和织构强度均随退火温度和时间增加而增大,合金强度和延伸率则随退火温度升高而下降。

形变热处理对2A12铝合金微观组织、织构及性能的影响

利用扫描电镜显微观察(含能谱分析)和电子背散射衍射技术(Electron Backscatter Diffraction,EBSD)等分析方法研究了不同形变热处理制度对2A12铝合金板材的微观组织、织构及性能的影响。结果表明:2A12铝合金经形变热处理后,晶粒沿轧制方向拉长,晶粒尺寸减小。随着形变热处理反复次数的增加,亚晶界比例降低,2°-15°的小角度晶界比例提高,大角度晶界比例先增后减,此时的退火过程由回复多边化主导转变为再结晶主导,再结晶程度提高。单步形变热处理样品因形变量较小,大小晶界和亚晶界比例较为接近。与退火制度相同的小变形样品相比,大形变热处理样品亚晶减少,大角度和小角度晶界增加,再结晶程度提高。形变量较大时,将存在Brass→R-Cu和m-Brass→Goss→R-Goss→Cube、T和P0°→Near rotated Cube和{102}<201>的织构演变路径。单步小变形退火时,路径将改变为:R-Cu和m-Brass→Goss→R-Cube。随着变形量的增加,2A12铝合金的强度和硬度增加,韧性和塑性降低。

新型高强铝合金高温平面压缩与退火微观组织和织构

采用热力模拟平面压缩实验和电子背散射衍射(EBSD)组织分析测试方法,研究了新型Al-Zn-Mg-Cu高强铝合金热压缩变形以及退火微观组织和织构。结果表明,在变形温度为350℃,应变速率为0.1 s^(-1)的条件下,合金微观组织演变机理为动态回复和大应变几何动态再结晶,出现旋转立方织构{001}<110>和黄铜织构{111}<110>,分别沿着α-取向线和β-取向线分布;退火后旋转立方织构减少,黄铜织构增多,旋转立方织构沿着α-取向线向黄铜织构转变。在变形温度为420℃,应变速率为0.1 s^(-1)的条件下,合金变形组织较均匀,再结晶晶粒分布在变形剧烈的晶界或三角晶界处,出现的织构种类主要有旋转立方织构{110}<110>、黄铜型{011}<211>织构;退火过程中发生亚动态再结晶,旋转立方织构强度增强,黄铜型{011}<211>织构有向高斯织构方向移动的趋势。