基于VPSC仿真的ZK60镁合金拉伸变形行为

Tensile Deformation Simulation of Extruded ZK60 Alloy by VPSC Model

摘要:

通过实验和粘塑性自洽（VPSC）模型，研究了在室温下挤压态ZK60镁合金沿不同方向拉伸时的变形机制开动情况，及其与流动曲线、织构演变和显微组织的对应关系。通过调节VPSC模型的参数，建立了滑移和孪生耦合的晶体塑性力学模型。比较了不同方向拉伸过程中织构演变的差异，分析了变形机制对屈服不对称性的影响。实验和模拟结果表明：当沿垂直于挤压方向（PED）拉伸时，由于｛102｝孪晶开动，大部分晶粒发生大角度旋转（约90°）。柱面<a>滑移是导致ZK60合金沿不同方向拉伸时出现明显屈服不对称的主要变形机理。当ZK60合金沿挤压方向（ED）拉伸时，由于晶粒的择优取向分布，｛101｝孪晶难以开动，导致ZK60挤压态镁合金拉伸屈服强度较高。ZK60镁合金沿着与ED成45°的方向拉伸时，屈服应力高于沿PED拉伸，但随着拉应力逐渐增大，由于沿PED拉伸时柱面<a>滑移逐渐开动，沿PED应变后期的应力曲线逐渐高于沿与ED成45°方向应变的应力曲线。

Abstract:

The initiation condition for deformation mechanism of extrusion AZ60 Mg alloy during tensile deformation along different directions at room temperature was investigated through experiments and visco-plastic self-consistent (VPSC) modeling, and the relationship between the deformation mechanism with the flow curves, texture evolutions, and microstructure of ZK60 Mg alloys was also analyzed. By adjusting the parameters in VPSC model, the crystal plastic mechanics model with slip coupled with twin was established. The differences in texture evolution during tension along different directions were compared, and the influence of deformation mechanism on the yield asymmetry was analyzed. The experiment and simulation results show that due to the initiation of {102} twin, most grains are rotated at a large angle (about 90°) when the tensile direction is perpendicular to the extrusion direction, namely PED. The prismatic <a> slip is the main deformation mode resulting in the yield asymmetry of ZK60 alloy during tensile deformation along different directions. When the ZK60 alloys are under tensile deformation along extrusion direction (ED), due to the preferential orientation, the {101} twin is difficult to initiate and the higher yield strength can be obtained. The yield stress under tension along the direction with an angle of 45° to ED is higher than along PED. As the tensile stress gradually increases, the prismatic <a> slip is gradually initiated, resulting in the higher stress curves along PED than those along the direction with an angle of 45° to ED.