热处理对Mg-8Gd-0.5Zr合金热压缩行为的影响

Effect of heat treatment on hot compression deformation behavior of Mg-8Gd-0.5Zr alloy

采用铸造法制备了Mg-8Gd-0.5Zr合金,对合金分别进行固溶处理（T4）及固溶＋时效处理（T6）,在应变速率0.002～0.1 s^-1、变形温度350～500℃、最大变形量50%条件下,对不同热处理后的合金进行热压缩变形实验,分析合金在不同变形条件下的真应力-真应变曲线、激活能及组织变化,研究热处理对热压缩行为的影响。结果表明：合金时效过程中析出β＇-Mg_5Gd相,使热变形过程中峰值应力升高,激活能增加,T6态合金变形激活能（221.605 k J/mol）高于T4态合金（202.986 kJ/mol）;在同样热压缩实验条件下,T6态合金热压缩过程中再结晶开始时间延迟,再结晶晶粒更细小,500℃热压缩后再结晶平均晶粒尺寸为15μm。

Mg-8 Gd-0. 5 Zr alloy was fabricated by casting method. After solid solution and aging treatment,hot compression deformation tests of the alloy were carried out under strain rate of 0. 002-0. 1 s^（-1） and temperature of 350-500 ℃ with a maximum deformation of 50%.The curves of true stress and true strain,deformation activation energy and microstructure change of the tested alloy were analyzed,and the effect of heat treatment on hot compression behavior of the alloy was studied. The results show that the peak stress increases in the hot deformation process,and the deformation activation energy of T6 state alloy（ 221. 605 k J/mol） is higher than that of the T4 state alloy（ 202. 986 k J/mol） due to the precipitation of β＇-Mg_5Gd phase during the aging process. Under the same experimental conditions of hot compression,recrystallization is delayed in the T6 state alloy,and the recrystallization grain is finer,and the average recrystallization grain size is about 15 μm after hot compression at 500 ℃.