AZ80镁合金动态再结晶软化行为的唯象本构描述

The Phenomenological Constitutive Description of Dynamic Recrystallization Softening Behavior of AZ80 Magnesium Alloy

采用热物理模拟机Gleeble1500对多组AZ80镁合金试样进行压缩试验,温度范围为250～400℃,应变速率范围为0.01～10s-1。真应力-应变曲线显示,应力迅速达到峰值之后发生软化,峰值应力随应变速率的增加而提高,随试验温度的升高而减小。金相分析表明,变形条件对动态再结晶软化的影响规律描述为:试样压缩60%后,晶粒大小随着应变速率的增加而减小,显微维氏硬度随细化后晶粒尺寸的减小而非线性减小,随应变速率的增加而减小。引入一种包含软化因子的唯象本构模型,并应用多元线性回归方法对相关的系数进行求解,结果发现求解获得的本构方程能够较好地描述AZ80镁合金的流变软化行为。

Compression tests are conducted on several sets of spacimen of AZ80 magnesium alloy on thermophysical simulator Gleeblel500 with a temperature range of 250℃ to 400℃ and strain rate from 0. 01s^-1 to 10s^-1. The true stress-strain curves show that softening occurs after stress swiftly reaches its peak, which rises with the increase in strain rate and falls with the increase in temperature. Mierostructure analyses indicate that after the spacimen is compressed by 60 % , the grain size reduces with the increase in strain rate, and Vickers microhardness decreases with the increase in strain rate and its nonlinearity tends to be weakened with the reduction in grain size. A phenomenological constitutive model containing a softening factor is introduced, and multiple linear regression method is applied to find out relevant coefficients and it is discovered that the constitutive equation obtained in doing so can better describe the flow softening behavior of AZ80 magnesium alloy.