拉伸取向控制对AZ31镁合金孪生和织构演化的影响

以室温单轴拉伸实验与晶体塑性有限元相结合的方法，通过拉伸取向控制，研究了AZ31镁合金拉伸变形过程中孪生行为、织构演化规律、塑性各向异性之间的关系。基于率相关晶体塑性本构理论，建立了滑移和孪生机制耦合的具有不同取向的晶体塑性本构模型，引入孪晶体积分数研究孪生对AZ31镁合金塑性变形过程中织构演变和力学性能的影响。结果表明，2种不同取向的样品在塑性变形过程中呈现出明显不同的织构演变规律，表现出明显的各向异性。轴向拉伸时孪生被抑制，孪晶激活体积分数低，径向拉伸时孪晶极易产生，孪晶激活体积分数高。轴向试样在整个塑性变形过程中{0001}极图偏移较小，径向试样因大量拉伸孪晶的开启，使得{0001}棱柱面织构的极密度逐渐向RD的正反方向发生明显偏移。

Effect of Tensile Orientation on Twinning and Texture Evolution of AZ31 Magnesium Alloy

The relationship between the twin behavior, the evolution law of texture and the plastic anisotropy of AZ31 magnesium alloy during tensile deformation was studied by combining room temperature uniaxial tensile experiment with crystal plastic finite element through tensile orientation control. Based on the rate-dependent crystal plastic constitutive theory, a plastic constitutive model of crystals with different orientations coupled by slip and twin mechanisms was established, and the effect of twins on the structural evolution and mechanical properties of AZ31 magnesium alloy during plastic deformation was studied by introducing twin crystal integrals. Results show that the specimens with two different orientations show significantly different texture evolution laws during the plastic deformation process, and exhibit obvious anisotropy. When the specimen is axially stretched, the twin is suppressed, and the twin activation volume fraction is low. The twin crystal is easily generated when the specimen is radially stretched, and the twin activation volume fraction is high. The axial specimen has a small shift in the {0001} polar map throughout the plastic deformation process, and the radial specimen has a significant shift in the polar density of the {0001} prismatic surface texture gradually towards the positive and negative directions of RD due to the activation of a large number of tensile twins.