(1. 中南大学 材料科学与工程学院，长沙410083；
2. 中南大学 有色金属材料科学与工程教育部重点实验室，长沙410083)
摘 要: 对AZ31镁合金热轧板材在423 K进行6道次双向反复弯曲变形，随后在523 K退火1 000 s，利用光学显微镜和电子背散射衍射(EBSD)技术研究该工艺过程中组织及织构的演变规律。结果表明：孪生是主要变形机制；在523 K退火1 000 s后，边部组织已经完全静态再结晶，晶粒明显细化，而中部组织仅发生晶粒长大，最终形成两边晶粒细小、中间晶粒粗大的双向梯度组织。退火态样品内部织构得到弱化，从板材几何中心处至两表面，织构强度逐渐降低，沿板厚方向呈不严格的对称梯度分布；靠近板材上表面区域织构发生弱化和随机化，靠近板材下表面区域晶粒取向集中在取向因子为0.5的方向，而板材几何中心处仅部分晶粒取向发生偏转，取向因子呈双峰分布。
关键字: 镁合金；双向反复弯曲；孪晶；晶粒细化；织构弱化
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education,
Central South University, Changsha 410083, China）
Abstract:The microstructure and texture evolution in the sheets of AZ31 Mg alloy was studied by bidirectional cyclic bending for 6 passes at 423 K followed by annealing at 523 K for 1 000 s. The deformed and subsequent annealed microstructures were investigated by optical microscopy and EBSD techniques. The results show that twinning is the main deformation mechanism. After annealing at 523 K for 1 000 s, the grains near the surfaces have full recrystallization. Thus, they are obviously refined. But the grains in the middle of the sheet just grow up. Finally, a gradient structure with fine grains in the regions near the surfaces and, in contrast, the coarse grains in the center of the sheet are induced. The texture in the annealed sample is weakened. The texture intensity decreases gradually from the center of the sheet to the surfaces, and has a relaxed gradient distribution along the thickness direction. The texture of the regions near the upper surface is weakened and randomized. Near the lower surface, the crystal orientation focuses on the direction that Schmid factor is 0.5. However, only a few grains tilt in the center of the sheet, in which the Schmid factor has a bimodal distribution.
Key words: magnesium alloy; bidirectional cyclic bending; twin; grain refinement; texture weakening
