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采用等温压缩实验获得了变形温度为200~400℃,应变速率为0.001~1 s-1的AZ80镁合金的流变应力曲线,考虑动态硬化及软化特性描述了AZ80镁合金热变形过程动态再结晶主导的软化行为.提出基于动态材料模型的应变速率敏感性指数表征动态再结晶引起的能量耗散,该指数通过引入动态再结晶体积分数描述微观组织演化的耗散功.考虑变形温度和应变速率构建了不同应变的应变速率敏感性指数图,实现应变速率敏感性指数对动态再结晶软化行为的量化表征.在此基础上,研究了变形温度、应变速率对动态再结晶临界条件及演化过程的影响,重点分析了不同应变的应变速率敏感性指数图特征.结果表明:随着变形温度的升高和应变速率的降低,动态再结晶软化临界应变减小,动态再结晶体积分数增加;应变速率敏感性指数与动态再结晶体积分数正相关,指数大于0.21的区域对应着高动态再结晶体积分数,且均位于低应变速率下,并通过动态再结晶软化的微观组织进行了验证.
The flow stress curves of AZ80 magnesium alloy with deformation temperature of 200 ~ 400 ℃ and strain rate of 0.001 ~ 1 s-1 were obtained by isothermal compression experiments. The dynamic recrystallization of AZ80 magnesium alloy during thermal deformation was described considering dynamic hardening and softening properties Leading softening behavior.According to the strain rate sensitivity index of dynamic material model, the energy dissipation caused by dynamic recrystallization is proposed.This index describes the dissipative work of microstructure evolution by introducing dynamic recrystallization volume fraction.Considering deformation temperature and strain rate The strain rate sensitivity index maps of different strains were constructed to realize the quantitative characterization of the dynamic recrystallization softening behavior of the strain rate sensitivity index.On the basis of this, the effects of deformation temperature and strain rate on the critical conditions and the evolution of dynamic recrystallization The results show that with the increase of deformation temperature and strain rate, the critical strain of dynamic recrystallization softening decreases and the volume fraction of dynamic recrystallization increases. The strain rate Sensitivity index and dynamic recrystallization volume fraction positive correlation, the index is greater than 0.21 area corresponds to Dynamic recrystallized volume fraction, and are located at a low strain rate, and is verified by dynamic recrystallization microstructure softened.