7055铝合金高温流变应力特征及本构方程

Flow Stress Characteristics and Constitutive Equation for Al-Zn-Mg-Cu-Zr at Elevated Temperature

采用Gleeble-1500热模拟机进行高温等温压缩试验,研究了7055合金在变形温度为300～450℃、应变速率为10-2～10s-1条件下的流变应力特征。结果表明,该合金为正应变速率敏感材料,流变应力随应变速率的增加而增大,随温度升高而减小。流变应力开始随应变增加而增大,达到峰值后趋于平稳,表现出动态回复的特征。通过线性回归分析计算出该材料的应变硬化指数n为5.77683以及变形激活能Q为146.4007kJ/mol,获得了该合金高温条件下的流变应力本构方程。

The flow stress characteristics of the commercial Al-Zn-Mg-Cu-Zr alloy were analyzed by isothermal compression at 300~450℃ and strain rate of 0.01~10 s-1 with the Gleeble-1500 hot simulator. The results reveal that the flow stress is controlled by strain rate and deformation temperature, where the flow stress is increased with increasing in strain rate and it is decreased with increasing in temperature. The flow stress is firstly increased to a peak value and then tends to be constant at strain rates less than 10 s-1 with increasing in strain, showing dynamic recovery, while it is decreased after a peak value with the increase of strain at astrain rate of 10 s-1 and deformation temperature higher than 350℃, exhibiting partial dynamic re-crystallization. The strain hardening exponent n and deformation activation energy Q were calculated by linear regression method. And the flow stress constitutive equation of the alloy during hot deformation is presented.