AA5083合金525℃拉伸变形的硬化特征及力学描述

Mechanical Description and Hardening Characteristic of Tensile Deformation of AA5083 at 525 ℃

在温度为525℃、应变速率为0.0008～0.032s-1条件下,采用等应变速率拉伸法研究了AA5083合金的流变行为,探讨了n、m值的测量方法,并建立了修正的粘塑性本构模型。结果表明:AA5083合金在该条件下流变应力随应变速率的升高而增加,表现应变速率硬化特征;各变形曲线呈现应变硬化、稳态变形及应变软化三阶段。应变硬化指数n随应变速率减小而增加,应变速率敏感性指数m随应变增加而减小,均为动态晶粒长大所致;合金应变软化表现为动态再结晶特征。模型预测值与实验值吻合良好。

The flow behavior of AA5083 at the strain rate ranging from 0.0008 to 0.032 sl and 525 ℃ was studied by constant-strain-rate tensile tests. The measuring methods on strain hardening exponent and strain rate sensitivity index were discussed and a constitutive equation using up-dated viscoplasticity equation was established. The results show that the tensile flow stress of AA5083 increases with enhancing strain rate under this tensile condition, showing strain rate hardening. All of the tensile curves illustrate three stages of strain hardening, steady-state and strain softening. Strain hardening exponent increases with reducing the strain rate and the strain rate sensitivity index decreases with increasing the strain, caused by dynamic grain growth. Strain softening is induced by continuous dynamic recrystallization. Good agreement is obtained between predicted and experimental flow stress.