单轴拉伸与压缩加载下AZ31镁合金单晶的各向异性塑性行为

摘要

To investigate the deformation twinning and the plastic anisotropy of the hexagonal-close-packed (HCP) single crystal, the crystal plastic constitutive model including slip and twinning deformation was established with finite element method based on crystal plasticity theory. The model was verified by test data. Newton−Raphson iteration method was developed with the stress components directly as the basic variables of iteration. The plastic deformation behavior of single crystal AZ31 alloy was analyzed numerically under monotonic tension and compression, respectively, in four different strain paths (i.e. along 〉〈2 1 1 0 , 〉〈01 1 0 ,〈0001〉and 〉〈01 1 1 ) with this model. The stress−strain curves were obtained in the above paths. The numerical calculation results show that this crystal model is feasible to predict the activity of slip/twinning system and to describe the number of active twin variants, the types of dominant twin variants and twin intersection. Due to the polar nature of mechanical twinning in inelastic deformation of the material, the plastic behavior of the single crystal material is demonstrated to be notably anisotropic and high asymmetry.%为研究 HCP 结构单晶在塑性变形中的变形孪晶和塑性各向异性，采用基于晶体塑性本构理论的有限单元法，建立包含滑移与孪生变形机制的晶体塑性本构关系，发展了以应力作为自变量的牛顿−拉普森迭代方法，通过已有文献的试验数据验证模型的有效性，并利用此模型模拟 AZ31单晶体在4种(即沿〉〈2110，〉〈0110，〈0001〉和〉〈0111方向)拉伸与压缩变形路径下的塑性变形行为，并获得了相应加载路径下的应力−应变关系曲线。数值计算结果表明，在不同加载路径下该模型可用于预测滑移系或孪生系的活动情况，以及描述孪生变体的活动数量、主要孪生变体和孪生交叉类型。由于机械孪晶具有的极性性质及其在材料非弹性变形中的重要作用，单晶材料表现出显著的各向异性与非对称性。