(1. 沈阳航空航天大学 材料科学与工程学院，沈阳 110036；
2. 中国科学院 金属研究所，沈阳 110016)
摘 要: 室温下对镁合金挤压棒材进行了最大扭转角分别为90°、180°和320°的扭转变形，依据扭转变形过程数值模拟结果，基于切应力作用下的等效施密特因子计算模型，结合扭转变形后晶粒取向的EBSD测试结果，对扭转过程中的拉伸孪晶启动机制进行了分析。结果表明：在大扭转角条件下，多数拉伸孪晶的启动遵循Schmid定律，一些Schmid因子值低的拉伸孪晶也启动。原始棒材中的晶粒c轴垂直于棒材轴向，而拉伸孪晶的启动使多数晶粒的c轴向转向平行于棒材轴向。晶粒中虽然启动较多孪晶带，但孪晶启动并没有改变扭转变形过程中应力应变曲线的硬化特征，扭转变形后棒材中仍保持为晶粒的基面平行于棒材轴向的织构特征。
关键字: 镁合金棒材；扭转；拉伸孪晶；施密特因子
（1. School of Materials Science and Engineering, Shenyang Aerospace University, Shenyang 110036, China;
2. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China）
Abstract:Magnesium alloy rods were separately twisted to 90°, 180° and 320° angles at room temperature, according to numeric simulation results of torsions, based on mathematic model of effective Schmid factor under condition of shear stress loading, combined with EBSD measured results of grains orientation after torsion, the twinning mechanism during magnesium alloy torsion was analyzed. The analysis results show that activations of the most extension twins obey the Schmid criterion, and some extension twins with lower Schmid factors also activate. The c-axes of grains in origin rods are vertical to the axis of rods, and they are tilted to parallel to the axis of rods after extension twin activations. The hardening characteristic of stress-strain curves of torsions is not changed although many twin bands formed in grains. The texture of grains basal parallel to the axis of rods are maintained after torsion.
Key words: magnesium alloy rods; torsion; extension twin; Schmid factor
