中文摘要：

为了研究机械伺服压力机变速加载模式对AZ3l镁合金镦粗成形过程微观组织和硬度的影响，采用在机械伺服压力机上匀速加载模式和单向减速加载模式对镁合金镦粗成形过程进行了有限元分析，并进行了AZ31镁合金试样的金相分析和硬度测量。结果表明：在压缩变形初始阶段．采用单向减速模式的试样发生了动态再结晶，而采用匀速加载模式的试样未发生再结晶。在变形量达到70％时，采用两种速度模式镦粗试样的微观组织趋向一致。与匀速加载模式相比。单向减速加载模式有利于减小试样温差变化，也有助于镁合金完全动态再结晶，且试样的晶粒细小、组织分布均匀。通过单向减速加载模式的AZ31镁合金试样的硬度比匀速加载模式试样的硬度提高了49％。

英文摘要：

In order to study the influence of the mechanical servo press changing speed loading model on the microstructure and hardness of AZ31 magnesium alloy in upsetting forming, the finite element analysis of magnesium alloy upsetting forming process was performed by the constant speed loading mode and the unidirectional decelerating loading mode on the mechanical servo press. And metallographic analysis and hardness measurement of AZ31 magnesium alloy specimen were carried out. The results show that： the specimens of the unidirectional decelerating loading mode produce dynamic recrystallization in the early stages of compressive deformation, while the specimens of the constant speed loading mode don＇t produce dynamic recrystallization. The microstructure of compressive specimens of two speed modes tends to the same at the 70% deformation. Compared with the constant speed loading mode, the unidirectional decelerating loading mode is beneficial to reduce difference change in the sample temperature and also conducive to the promotion of full dynamic recrystallization of the magnesium alloy. The grain size of the specimen is fine and the grain distribution is relatively uniform. The hardness of AZ31 magnesium specimen by the unidirectional decelerating loading mode is increased by 49% than that of the uniform loading mode.