采用改进和优化的Zerilli-Armstrong本构模型预测AZ80镁合金的高温流动应力

Prediction of high temperature flow stress of AZ80 magnesium alloy by using modified and optimized Zerilli-Armstrong constitutive models

合理的本构模型是实现精确模拟镁合金挤压过程的关键,基于均匀化态AZ80镁合金在应变速率0.001~1 s^(-1)、变形温度523~673 K下的热压缩实验数据,建立了改进的Z-A模型来描述AZ80镁合金的热变形行为,并在此基础上,通过考虑应变对材料参数的影响,提出优化的Z-A模型。对两种模型预测精度进行定量分析表明:优化的Z-A模型对流动应力的预测效果较好,相关系数R和平均绝对相对误差E_(AR)的计算值分别为0.9962和3.60%;改进的Z-A模型的预测结果相对较差,其R值和EAR值分别为0.94和8%。比较分析表明,优化的Z-A模型具有良好的适应性,可以在整个应变范围内(0~0.9)很好地预测不同变形条件下的流动应力,因而工程适用范围广;改进的Z-A模型不能描述加工硬化-动态回复阶段的流动应力,因而预测精度较低。

The reasonable constitutive model is the key to realize the accurate simulation of magnesium alloy extrusion process,based on the thermal compression test of homogenized AZ80 magnesium alloy at the strain rate of 0.001 to 1 s^(−1) and deformation temperature of 523 to 673 K,a modified Zerilli-Armstrong(Z-A)model was established to describe the thermal deformation behavior of the alloy,and on this basis,by considering the effect of strain on material parameters,an optimized model was proposed.The quantitative analysis of the prediction accuracy of the two models shows that the optimized Z-A model has a better prediction effect on the flow stress,and the calculated values of correlation coefficient R and average absolute relative error E_(AR) are 0.9962 and 3.60%,respectively.The prediction result of the modified Z-A model is relatively poor,and its R value and EAR value are 0.94 and 8%,respectively.The comparative analysis shows that the optimized Z-A model has good adaptability and can well predict the flow stress under different deformation conditions in the whole strain range(0−0.9),so its engineering application range is wide.The modified Z-A model cannot describe the flow stress in the stage of work hardening and dynamic recovery,so its prediction accuracy is low.