高速冲击载荷下LZ91镁合金的动态变形行为及力学本构

Dynamic Deformation Behavior and Mechanical Constitutive of LZ91 Magnesium Alloy under High Speed Impacting

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3600 s-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20o^30o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。

The dynamic deformation behavior and mechanical constitutive of LZ91 magnesium alloy were investigated under high speed impacting by optical microscopy and X-ray diffraction combined 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 is uniformly distributed in β-Li phase, hindering the dislocation motions. This finally induces that the adiabatic shear sensitivity decreases and the adiabatic shear band only occurs above 3600 s-1. The special texture, which deviates from the basal texture by 20°~30°, forms in α-Mg phase, 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.