铸态镁合金AZ91D热压缩微观组织演变本构模型

Constitutive model for microstructure evolution of as-cast magnesium alloy AZ91D during hot compression

在变形温度280~400℃、应变速率0.001~1 s^(-1)、最大变形量50%的条件下,采用等温压缩实验研究了铸态镁合金AZ91D塑性变形和微观组织演变行为。结果表明:AZ91D热压缩变形中发生了不同程度的动态再结晶,提高变形温度和降低变形速率有利于促进动态再结晶晶粒的形核和长大,动态再结晶体积分数随真应变增大呈现慢-快-慢的增长规律。在对实验数据回归分析的基础上,建立了AZ91D动态再结晶临界条件、动力学方程和晶粒尺寸预测模型,并通过定量金相实验结果验证了该模型的合理性。

Isothermal compression experiment was carried out at the deformation temperatures range of 280-400 ℃,strain rate range of0. 001-1 s-（-1）and height reduction of 50% to investigate the plastic deformation and microstructure evolution of as-cast magnesium alloy AZ91 D. The results show that dynamic recrystallization occurrs during the hot compression of AZ91 D in different degree,the increase of deformation temperature and the decrease of strain rate are conductive to the nucleation and growth of dynamic recrystallized grains,the volume fraction of dynamic recrystallization exhibits slow-fast-slow growth trend with the increase of true strain. The prediction models of the critical strain,kinetics equation and grain size were developed based on the regression analysis of experiment data,and the results of quantitative metallographic experiment validate the accuracy of the prediction model.