AZ80和AZ80-Ca-Ce镁合金热变形组织演变及其加工图建立

Microstructure evolution and processing maps establishment of AZ80 and AZ80-Ca-Ce magnesium alloy during hot deformation

采用Gleeble 3800数控式热-力物理模拟试验机对AZ80和AZ80-Ca-Ce两种镁合金开展了热压缩研究,在压缩变形温度300℃~500℃、应变速率0.0005 s^(-1)~0.5 s^(-1)范围内研究热变形过程中两种镁合金流变行为及微观组织演变规律,建立了热加工图。结果表明:Ca和Ce联合微合金化使AZ80镁合金的热变形激活能从142 kJ/mol提高到172 kJ/mol。通过建立两种镁合金热加工图及组织观察可知,Ca、Ce联合微合金化使AZ80镁合金的高温高应变速率变形区由失稳区转变为安全区,确定AZ80-Ca-Ce镁合金最佳的热塑性加工区间为应变速率0.01 s^(-1)~0.0003 s^(-1)、温度340℃~425℃。通过对不同热加工条件下的微观组织变形和演变机制分析表明,在变形失稳区,两种镁合金的软化机制均以动态回复为主;在变形安全区,Ca和Ce联合微合金化使AZ80镁合金的组织演变和软化机制向动态再结晶转变。

The hot compression of AZ80 and AZ80-Ca-Ce magnesium alloys was investigated by Gleeble 3800 thermal simulator.The deformation behavior and microstructure evolution of the two alloys during hot deformation were studied with compression deformation tern・perature of 300℃-500℃ and strain rate of 0.0005 s^(-1)-0.5 s^(-1),and the hot compression processing diagram was established.The results indicate that the thermal deformation activation energy of AZ80 magnesium alloy is increased from 142 kJ/mol to 172 kJ/mol by Ca and Ce microalloying.According to the hot working diagram and microstructure observation of the two alloys,the combined microalloying of Ca and Ce makes the high temperature and high strain rate deformation zone of AZ80 magnesium alloy transform from the unstable zone to the safe zone.The optimal thermoplastic processing range of AZ80-Ca-Ce magnesium alloy is determined as 0.01 s^(-1)-0.0003 s^(-1) for strain rate and 340℃-425℃for temperature approximately.By analyzing the deformation and evolution mechanism of microstructure under different hot working conditions,it is found that the softening mechanism of the two alloys is mainly dynamic recovery in the instable deformation zone.In the safe deformation zone,the combined microalloying of Ca and Ce causes the microstructure evolution and softening mechanism of the AZ80 magnesium alloy to turn to dynamic recrystallization.