In this paper, the effect of pre-twinning on the mechanical behavior of free-end torsion (FET) for an extruded AZ31 Mg alloy was investigated via pre-compression along extruded direction with 1.5%, 3.5%, 5.5% and 6.5% plastic strain levels. After pre-compression, torsion was performed at room temperature. The yield strength was enhanced remarkably during FET test after 3.5% pre-compression. However, the change of yield strength is small during FET with pre-compression (PRC) greater than 3.5%. Refinement hardening induced by twinning contributes to the enhancement of yield strength for PRC 3.5 specimen. With pre-strain increasing, the change of yield strength is ascribed to dislocation hardening. The stage II and stage III of strain hardening were observed during pure torsion and FET test after 1.5% pre-compression. In contrast, the stage II is suppressed and the stage III only occurs during FETs after 3.5%, 5.5% and 6.5%. The pre-twinning favor the activation of prismatic slip under torsion, which enhances multiple slip and dynamic recovery. The transition of deformation mechanisms from basal slip to multiple slip leads to the change of strain hardening during FET after different pre-strain levels.

本文通过沿挤压方向预压缩 1.5%、3.5%、5.5% 和 6.5% 塑性材料，研究了预孪晶对挤压 AZ31 镁合金自由端扭转 (FET) 力学行为的影响。应变水平。预压缩后，在室温下进行扭转。3.5%预压缩后的FET测试中屈服强度显着增强。然而，预压缩 (PRC) 大于 3.5% 的 FET 期间屈服强度的变化很小。孪生引起的细化硬化有助于提高 PRC 3.5 试样的屈服强度。随着预应变的增加，屈服强度的变化归因于位错硬化。在1.5%预压缩后的纯扭转和FET测试中观察到应变硬化的阶段II和阶段III。相反，阶段 II 受到抑制，阶段 III 仅在 3.5%、5.5% 和 6.5% 之后的 FET 期间发生。预孪晶有利于在扭转下激活棱柱滑移，从而增强多重滑移和动态恢复。变形机制从基础滑移到多重滑移的转变导致不同预应变水平后 FET 期间应变硬化的变化。