Al-7.0Zn-2.9Mg合金高温变形行为和加工图

Hot deformation behavior and processing map of Al-7.0Zn-2.9 Mg alloy

采用Gleeble-3500热模拟试验机在温度为400℃~500℃,应变速率为0.01 s^(-1)~10 s^(-1)条件下对Al-7.0Zn-2.9Mg合金进行热压缩试验,研究该合金的热变形行为及热加工特征,建立了应力-应变本构方程和加工图。结果表明,Al-7.0Zn-2.9Mg合金在热压缩变形过程中,随着应变速率的增加和变形温度的降低,合金流变应力逐渐增大,流变应力达到峰值后曲线呈现稳态流变特征;合金在试验条件下的平均变形激活能为157.8 k J/mol。真应变为0.5的加工图表明,该合金在400℃~500℃高温变形时安全区域主要存在于低应变速率的条件下,较合适的加工温度为450℃~475℃,应变速率为0.1 s^(-1)~0.01 s^(-1)。

The hot compression tests for Al-7.0Zn-2.9Mg aluminum alloy were carried out in the temperature range of 400 -500~C and the strain rate range of 0.01 s^-1 ~ 10 s^-1 by the Gleeble-3500 hot-simulation machine, to investigate the hot deformation behavior and hot workability of the alloy, and establish the constitutive equation and processing map. The results show that the flow stress of the Al-7.0Zn-2.9Mg aluminum alloy increases with the increase of strain rate and the decrease of deformation temperature, and flow behavior stays steady when the flow stress reaches the peak value. The deformation activation energy of the Al-7.0Zn-2.9Mg alloy under experimental conditions is 157, 8 kJ/mol. The processing map established at the true strain of 0.5 shows that the safe deformation zone at the deformation temperature of 400 -500 ℃ is mainly attained at the low strain rate. The preferred processing conditions are the deformation temperature of 450 -500℃ and the strain rate of 0.1 s^-1 ~0.01 s^-1.