高速冲击载荷下LZ91镁合金的动态变形行为及力学本构

The dynamic deformation behavior and mechanical constitutive of LZ91 magnesium alloy under high speed impacting

摘要:

采用金相显微镜、X射线衍射结合斯密特因子研究高速冲击载荷下LZ91镁合金的动态变形行为和力学本构。结果表明：流变应力对应变速率不敏感，发生了Portevin-LeChatelier效应；当应变速率为3600s-1时才出现绝热剪切带，这是由于β-Li相间细小均匀分布的α-Mg相增大了位错运动阻力，导致绝热剪切敏感性减弱；α-Mg相形成了偏离基面织构20~30°的特殊织构，不需要孪生来协调均匀塑性变形，这是因为α/β相界面取向接近Burgers取向关系；修正了Johnson-Cook力学本构，拟合结果与实验结果吻合。

Abstract:

The dynamic deformation behavior and mechanical constitutive of LZ91 magnesium alloy were investigated under high speed impacting using optical microscopy and X-Ray diffraction combing with Schmid factor. The results show that the flow stresses are not sensitive to strain rate and the Portevin-LeChatelier effect occurs. The fine α-Mg phase uniformly distributes in β-Li phase, causing that the dislocation motions are hindered. This finally induces that the adiabatic shear sensitivity decreases and the adiabatic shear band only occurs above 3600s-1. The special texture, which deviates the basal texture nearly 20-30°, in α-Mg phase forms, due to the Burgers orientation relationship between α/β phase interface. Twinning is not required to accommodate the uniform plastic deformation in α-Mg phase because of this orientation relationship. The Johnson-Cook (J-C) mechanical constitutive was modified and the fitting results well match with the experimental results.