基于粘塑性自洽模型AZ31镁合金塑性变形行为研究

Study on plastic deformation behavior of AZ31 magnesium alloy based onviscoplastic self-consistent model

以挤压态AZ31镁合金为研究对象,通过修正的VPSC模型,构建耦合滑移和孪生的晶体塑性力学模型,从微观变形机制的角度研究镁合金在不同加载方式下的塑性变形行为。通过EBSD等实验结果与模拟结果对比发现,轴向压缩过程中,协调变形的主要机制为拉伸孪生和基面滑移,拉伸孪晶的大量开启导致晶粒c-轴发生约90°的旋转,使得{0002}基面织构的极密度向挤压(ED)的正反方向偏移,{11-20}和{10-10}棱柱面织构的极密度逐渐向垂直于挤压方向的TD方向偏移;轴向拉伸过程中,变形初期的变形机制以基面滑移为主,棱柱面滑移为辅,随着变形的增加,主导变形机制变为棱柱面滑移;且无论变形百分比多少,{0002}和{11-20}极图基本没有发生变化,只是织构强度有所增加,而棱柱面滑移的大量开启,使得{10-10}棱柱面织构的极密度向ED方向偏移。

The visco-plastic self-consistent(VPSC)model has a good applicability to the texture evolution and plasticity simulation of metal alloy materials under different loading modes.In this study,the extrusion AZ31 magnesium alloy tube was investigated,through the modified VPSC model,a crystal plastic mechanical model coupled with slip and twin was constructed to study the plastic deformation behavior of magnesium alloy under different loading modes from the perspective of micro deformation mechanism.The results of XRD,EBSD and other experiments were compared with the simulation results.It was found that the basal slip and tensile twinning were the main deformation mode in the early stage of deformation during axial compression.A high activity of the twins caused the crystal c-axis to rotate by about 90°,which caused the basal texture to transfer to the extrusion direction in the{0002}pole figure and the texture to transfer to the TD direction perpendicular to extrusion direction in the{11-20}and{10-10}prismatic pole figure.The basal slip was the main deformation mode in the early stage of deformation during axial tension.With the increase of deformation,the pyramidal slip became the dominant deformation mechanism.The{0002}and{11-20}pole figure was almost unchanged and just the texture strength was increased as the strain increases.However the texture transferred to the extrusion direction in the{10-10}prismatic pole figure during axial tension was related to the large opening of the prismatic slip during axial tension in the ED direction.