AZ91D镁合金热塑性行为及热辊轧制过程再结晶组织模拟

Plastic deformation of AZ91D magnesium alloy and recrystallization structure simulation in heated roll rolling

采用单道次压缩试验在温度200~450℃、应变率0.001~1 s^(−1)范围内对AZ91D镁合金的热变形行为进行研究。依据应力−应变曲线通过线性拟合和非线性回归建立了AZ91D镁合金热变形下动态再结晶体积分数模型,并通过二次程序开发实现了热辊轧制过程的组织模拟。结果表明:随着辊面温度的升高和压下率的增加,动态再结晶体积分数显著增加,单道次轧制过程动态再结晶发生不充分。多道次轧制过程有利于轧制过程动态再结晶充分发生,辊面温度为300℃时,三道次轧制后动态再结晶体积分数接近85%,在五道次轧制后动态再结晶基本完成;当辊面温度继续升高至350℃时,三道次轧制后继续进行轧制会导致再结晶晶粒长大。实测金相组织分布与预测结果较为吻合,建立的动态再结晶模型可用于动态再结晶演变规律的定量模拟和定性分析。

The hot deformation behavior of AZ91D magnesium alloy was studied using single-pass compression experiments at temperature of 200−450℃and strain rate of 0.001−1 s^(−1).An exponential function model was proposed to describe the dynamic recrystallization volume fraction equations of AZ91D magnesium alloy based on stress−strain curves.The numerical simulation of microstructure in heated roll rolling of magnesium alloy was realized through embedding the developed program into the finite element software platform.The results show that,with the increase of roll surface temperature and reduction,the dynamic recrystallization volume fraction increases obviously,and the dynamic recrystallization is incomplete during single pass rolling.The multi-pass rolling process is conducive to the full occurrence of dynamic recrystallization.When the roll surface temperature is 300℃,the dynamic recrystallization fraction is close to 85%after three passes of heated roll rolling,and the dynamic recrystallization is completed after five passes.Furthermore,the dynamic recrystallization grain sizes will grow up with more rolling passes than three passes or higher roll surface temperature than 350℃.The measured results are in agreement with the values predicted by the model,and the dynamic recrystallization model is significant to microstructure simulation and parameter optimization of AZ91D alloy in hot plastic deformation.