异步轧制AZ31镁合金板材的超塑性工艺及变形机制

Superplastic Process and Deformation Mechanism of Asymmetrically Rolled AZ31 Magnesium Alloy

经过异步轧制工艺获得AZ31镁合金薄板。在300~450℃范围内,分别通过5×10-3,1×10-3s-1和5×10-4s-1不同应变速率进行高温拉伸实验研究其超塑性变形行为,计算应变速率敏感指数m值、超塑性变形激活能Q及门槛应力σ0值。通过EBSD分析和扫描电镜观察拉伸断裂后的断口形貌,分析AZ31镁合金的超塑性变形机制。结果表明：AZ31镁合金的塑性变形能力随着变形温度的升高及应变速率的降低而增强。当拉伸温度为400℃、m=0.72、应变速率为5×10-4s-1时,AZ31具有良好的超塑性,伸长率最大为206%。温度为400℃时,异步轧制AZ31镁合金的超塑性变形是以晶格扩散控制的晶界滑移和基面滑移共同完成的。

AZ31 magnesium alloy sheet was prepared by asynchronous rolling process.From 300℃ to 450℃,tensile test was conducted with different strain rates of 5×10-3,1×10-3s-1 and 5×10-4s-1respectively to investigate the superplastic deformation behavior of AZ31 magnesium alloy.The value of the strain rate sensitive index m,the superplastic deformation activation energy Qand the threshold stress σ0 were also calculated.The superplastic deformation mechanism of AZ31 was investigated through observation of the fracture morphology of the tensile specimens by EBSD and SEM.The results show that the plastic deformation capacity of AZ31 magnesium alloy enhances with increasing deformation temperature and decreasing strain rate.AZ31 magnesium alloy exhibits good superplasticity,and maximum elongation-to-failure of 206% at 400℃ when the strain rate is 5×10-4s-1,and the m value is 0.72.Furthermore,the superplastic deformation of the asynchronous rolled AZ31 magnesium alloy at 400℃relies on the joint effects of grain boundary sliding（GBS）controlled by lattice diffusion and basal slip.