通过系列等温压缩试验获得铸态7075铝合金在温度为573~723 K、应变速率0.01~10 s-1下的真应力-真应变曲线, 通过分析硬化率获得了隐含在该曲线中的动态再结晶临界应变、峰值应力对应的应变、最大软化速率对应的应变3个参数; 通过求解双曲正弦模型获得了动态再结晶激活能等重要参数, 并描述了合金热塑性变形过程中动态再结晶数量的演变过程, 设计一个无量纲的中间变量Z/A, 建立了温度、应变速率、应变量、动态再结晶体积分数之间的动态耦合关系模型。结果表明: 随着应变量的增加, 动态再结晶的体积分数将逐渐增至100%; 增大应变速率或降低变形温度都会抑制动态再结晶的发生。

The true stress-true strain curves of as-cast 7075 aluminum alloy were achieved through a series of isothermal upsetting experiments in the temperature range of 573-723 K, and the strain rate range of 0.01-10 s-1. Based on the analysis of hardened rate curves, it was uncovered that the flow stress curves of the alloy had three characteristic points including the critical strain for dynamic recrystallization, the strain for peak stress and the strain for maximum softening rate. Some main parameters such as the activation energy of dynamic recrystallization, were obtained by solving hyperbolic sine equation. The evolution of dynamic recrystallization amount during thermoplastic deformation was described. And a dimensionless intermediate variable Z/A was designed to build a dynamic coupled model between deformation temperature, strain rate, strain and dynamic recrystallization volume fraction. The results show that as the strain increased, the dynamic recrystallization volume fraction increased gradually until to 100%, in addition, with the increase of the strain rate or decreased of deformation temperature, the dynamic recrystallization would be restrained.