AZ31镁合金变路径压缩的力学性能和孪晶机制

Twinning mechanism and mechanical property of AZ31 magnesium alloy during multi-paths compressions

对AZ31镁合金轧制板材进行变形方向依次为轧向(RD)、横向(TD)、轧向和横向的变路径压缩实验,研究变形过程中的力学性能,并采用电子背散射衍射(EBSD)观察上述变形过程中晶粒取向变化,分析孪晶变体的启动情况。结果表明:在变路径压缩过程中,各路径压缩过程依次对应拉伸孪晶、二次孪晶、解孪晶和拉伸孪晶的微观变形机制,首次变形所产生的预应变提高后续变形中孪晶形核启动力,使后续变形过程的屈服强度大幅增加。二次孪晶的启动遵循Schmid定律,孪晶变体启动的选择性倾向明显,由t1或t5变体来完成二次孪晶。

The multi-path compression with sequential RD→TD→RD→TD deformation direction was performed on the AZ31 magnesium alloy rolled sheet, and the mechanical property of the previous deformation was studied, the electron backscatter diffractometry（EBSD） was applied to observe the grain orientation evolution during the above deformation, and the activations of twin variants were analyzed. The results show that the deformation mechanism of {1012}extension twin, {1 012}- {1 012}secondary twin, {1 012} detwin and {1 012}extension twin are sequentially relatedto each compression during the above deformation. The activity stress for twinning nucleation during the subsequent deformation is raised by the pre-straining generated from the first compression, which increases the yielding strength significantly during the subsequent deformation. The activation of {1 012}- {1 012} secondary twin follows the Schmidcriterion, and there is an obvious selective tendency for twin variant activation, twin variant t1 or t5 are activated to start the {1 012}- {1 012} secondary twin.