7050铝合金热塑性变形流变应力和组织演变的研究

Study on Flow Stress and Microstructure Evolution of 7050 Alloy During Hot Plastic Deformation

借助Gleeble-1500热模拟试验机对7050铝合金在不同应变速率、变形温度和压下率下进行镦粗试验,获得了在250、325℃、400、475℃变形温度下变形速率分别为0.01、0.1、1、10s-1的真应力-真应变曲线,进而分析了热塑性变形条件对该合金流变应力的影响。结果表明:变形温度越低、应变速率越高,流变应力越大,变形初始阶段流变应力随变形量增加而增大,达到极限值后进入近似稳态流变。与金相实验和光学显微镜观察试验方法相结合,研究了7050铝合金的高温热塑性变形条件下微观组织的演变规律;与压力加工原理相结合,分析了热塑性变形过程中变形参数和组织演变的关系。结果表明:通过改变变形温度、压下率和压下速率能有效改变动态再结晶组织体积分数和动态再结晶晶粒尺寸,压下率对该合金动态再结晶的影响较明显,不同温度下开始动态再结晶对应的变形量不同。

7050 alloy at different strain rates, deformation temperature and reduction rate under the upsetting test was measured by thermal simulation testing machine Gleeble-1500.The true stress-true strain curve under different temperatures （250 ℃, 325 ℃, 400 ℃, 475℃）and strain rate deformation （0.01,0.1,1,10 s^-1） were obtained. The influence of thermoplastic deformation conditions on the alloy flow stress was studied. The results show that the lower the deformation temperature, and the higher the strain rate, the greater the flow stress. The flow stress at the initial stage of deformation increases with deformation increasing, which can reach the approximate steady state flow limit. The microstructure evolution of the alloy under high temperature thermoplastic deformation was studied by combining with metallurgical test methods and optical microscopy. The relationships between deformation parameters and microstructure evolution in the process of the thermoplastic deformation was analyzed by combining with pressure processing theory. The results confirm that changing the pressure temperature, reduction rate and pressure rate can effectively change the volume fraction of dynamic recrystallization and dynamic recrystaUization grain size. The effect of reduction rate on the alloy dynamic recrystallization is obvious. Different dynamic recrystallization starting temperature corresponds to different amounts of deformation.