7AXX铝合金在热压缩状态下的流变行为

研究7AXX铝合金在热变形过程中的流变行为对于提高专用设备锻件综合性能、避免材料热开裂有重要意义。本文利用Gleeble-3500热模拟试验机在变形温度360～460 ℃、应变速率0.001～1 s^-1的条件下，对7AXX铝合金铸锭进行高温压缩实验，研究了热压缩状态下温度和应变速率对该合金流变行为的影响程度，拟合得到了含Zener-Hollomon参数的7AXX铝合金流变应力表达式，建立了基于双曲正弦关系的合金热变形本构方程及热加工图。结果显示，变形温度及应变速率对7AXX铝合金的流变行为有显著影响。合金的流变应力随温度的升高而降低，随应变速率的增加而增加。合金在热压缩过程中的应力指数为3.21，热激活能为137.31 kJ/mol。变形温度385～450 ℃、应变速率0.01～0.1 s^-1是适用于7AXX铝合金的热加工条件范围。

Flow Stress Behavior of 7AXX Aluminum Alloy during Hot Compression

The research of hot deformation behavior of 7AXX aluminum alloy has important significance to improve forging performance and avoid hot cracking phenomenon. The flow stress behavior of 7AXX aluminum alloy during hot deformation was investigated by isothermal compression tests using Gleeble-3500 system in the temperature range from 360 ℃ to 460 ℃ and at strain rate range from 0.001 s^-1 to 1 s^-1. The relationship between the flow stress and parameters of hot deformation was studied. The flow stress of 7AXX aluminum alloy was fitted by hyperbolic sine equation containing Zener Hollomon parameter. The constitutive equation and the processing maps were evaluated by linear regression analysis. The results demonstrate that the flow stress of 7AXX aluminum alloy is significantly influenced by deformation temperature and strain rate, and the steady state flow stress decreases with the increase of temperature and increases with strain rate. The deformation activation energy of 137.31 kJ/mol and stress exponent of 3.21 were determined to be characteristic parameters of 7AXX aluminum alloy in hot deformation behavior. The area with deformation temperature of 385-450 ℃ and strain rate of 0.01-0.1 s^-1 is processing safety area for hot deformation of 7AXX aluminum alloy.