Mg-Zn-Zr-Y合金高温塑性变形本构模型及流变行为预测

Constitutive Model of Hot Plastic Deformation and Flow Behavior Prediction of Mg-Zn-Zr-Y Alloy

摘要:

采用Gleeble热力模拟试验机对Mg-Zn-Zr-Y合金进行了高温压缩变形实验,分析了合金在变形温度为573~723K、应变速率为0.001~1s_-1范围内的流变行为。结果表明,热变形条件对流变特征和流变应力影响显著,流变曲线呈现“饱和非线性”和“正偏态分布”两种特征,应力水平随着变形温度的降低和应变速率的增大而提高。基于Arrhenius和Zener-Holloman方程,线性拟合确定了合金的表观变形激活能(Q=152.307 KJ.mol_-1)和应力指数(n=5.521)等参数,建立了描述塑性流变行为的本构方程。结果显示,该本构模型数值计算出的流变应力理论值与实验结果的吻合程度依赖于热变形条件的取值范围,与“饱和非线性”稳态流变特征的塑性变形行为基本吻合；而与加工硬化突出的“正偏态分布”流变行为存在一定偏差,引起理论峰值应变前移,但峰值应力水平仍基本符合。表明该本构模型在Mg-Zn-Zr-Y合金中表现出较好的实用性,尤其适用描述高变形温度(＞623K)和低应变速率(＜0.01 s _-1)下稳态塑性变形行为。

Abstract:

The flow behavior of the Mg-Zn-Zr-Y alloy was investigated by hot compressive test using Gleeble thermal simulator in the temperature range of 573~723K and strain rate range of 0.001~1s_-1. The results show that the flow stress is significantly affected by both deformation temperature and strain rate. The flow behavior were characterized by the SsaturationSnonlinearity and positiveSskewness occur simultaneously, and the flow stress increases with either decreasing deformation temperature or increasing strain rate. The average activation energy(Q=152.307 KJ.mol_-1), and stressSexponent(n=5.521)for the hot deformation have been determinded to be using the Arrhenius-type and Zener-Holloman equations. A nonlinear flow model and its constitutive equation have been established and employed for studying the deformation behavior. Meanwhile,ScalculationSresults of constitutive equations were comparedSwith experimentalSresults; the level of data match depends on temperature and strain rate. TheSsaturationSnonlinearity of flow behavior in the alloy was satisfactorily described, theStheoretical calculating valuesSmatchSwellSwithSthe experimentalSSvalues. Furthermore, the calculation values of flow stress will be bigger than its experimental values with the positiveSskewness of flow behavior , and as the peak strain of calculationSresults ahead. Research show this constitutive equations effectively depict the flow behaviors of hot compression deformation, however, it is more specifically suited to high deformation temperature(＞623K) and low strain rate(＜0.01 s _-1).