摘要：采用Gleeble-3500热力模拟试验机研究了Al-8Zn-2Mg-2Cu高强铝合金在变形程度为50%-70%，应变速率为0.01s-1-10s-1，变形温度为300℃-450℃条件下的热变形行为。运用光学显微镜(OM)、扫描电镜(SEM)和透射电镜(TEM)对各状态下的合金进行显微组织观测。通过对Z参数的拟合和不同软化机制的分析，探究热加工过程中的不同变形条件（变形温度、应变速率、变形量）对后续固溶再结晶的影响规律，从而确定合金的最佳变形参数范围，为工业化塑性变形工艺的制定提供了理论指导。由此实验可得到合金高温变形的表观激活能是122.25KJ/mol，其流变应力行为满足Arrhenius本构方程：3.04108[sinh(0.012)]5.02exp(122.25/8.314T)。在实验参数范围内，当变形温度低于400℃，Al-8Zn-2Mg-2Cu合金主要发生动态回复；在变形温度为430℃-450℃，应变速率为0.01s-1-1s-1条件下出现动态再结晶现象。同时，在动态回复区域，Al-8Zn-2Mg-2Cu合金经固溶处理后的再结晶体积分数随着Z参数的增大而增大，平均再结晶晶粒尺寸随着Z参数的增大而减小。在动态再结晶区域，再结晶体积分数随着Z参数的减小而增大，平均再结晶晶粒尺寸随着Z参数的减小而减小。相同Z参数条件下，压缩量越大，固溶再结晶的体积分数增大，平均晶粒尺寸减小。

关键词：Al-8Zn-2Mg-2Cu合金；热压缩变形；Z参数；动态回复；动态再结晶；固溶；再结晶

Abstract：The hot deformation behavior of Al-8Zn-2Mg-2Cu alloy were studied by Gleeble-3500 thermal simulator at the compress deformation of 50-70% 、 strain rate of 0.01-10 s-1 and temperature of 300-450℃. The optical microscopy  (OM),  scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the microstructure characteristics of the alloy under different hot deformation parameters. The effects of deformation temperature, strain rate and strain on  the subsequent solid solution recrystallization were investigated based on the fitting of Z parameter and the analysis of different softening mechanisms. The optimum deformation parameter range of the alloy was obtained. The theoretical guidance for the development of industrial plastic deformation process was provided. We can get a conclusion that the flow stress value of Al-8Zn-2Mg-2Cu alloy decreases with the increase of deformation temperature or decrease of strain rate, showing a strong sensitivity to temperature. The flow stress behavior can be represented by the following equation with hot deformation activation energy of 122.25KJ/mol:3.04 108[sinh(0.012)]5.02 exp(122.25/ 8.314T ) .

Within the experimental parameters, Al-8Zn-2Mg-2Cu alloy mainly undergoes dynamic recovery process when the deformation temperature is lower than 400 ℃. When the deformation temperature is 430 ℃ -450 ℃, the dynamic recrystallization occurs at the strain rate of 0.01s-1-1s-1.At the same time, In the dynamic recovery region, the static recrystallization volume fraction of Al-8Zn-2Mg-2Cu alloy after solution treatment increases with the increase of Z parameter. The average recrystallized grain size increases with the decrease of Z parameter. However, in the dynamic recrystallization region, the static recrystallization volume fraction increases with the decrease of the Z parameter, and the average recrystallized grain size decreases with the decrease of the Z parameter. Under the same Z value, the larger the amount of compression, the larger the volume fraction of the static recrystallization and the smaller grain size.

Key words: Al-8Zn-2Mg-2Cu alloy; hot compression deformation; Z parameter; dynamic recovery; dynamic recrystallization; solid solution; static recrystallization.

目录

第一章 绪论 1

1.1课题背景