铸态P91合金钢修正本构模型及变形激活能演化

Modified constitutive model and deformation activation energy evolution of as-cast P91 alloy steel

利用Gleeble-3500多功能热模拟试验机在温度为900~1250℃,应变速率为0.01~5 s^(-1)的变形条件下对铸态P91合金钢进行热压缩实验。为更好地描述该合金钢的热变形流变行为,并鉴于变形条件对激活能和材料常量参数的影响,对传统的双曲正弦本构模型进行了修正。采用三维抛物曲面拟合的方式确定了材料参数变量和变形激活能关于变形条件的函数,得到了修正本构模型,其相关系数R^(2)=0.993,平均绝对相对误差AARE=3.64%,验证了该模型预测合金钢热流变行为的可靠性。结果表明:变形激活能在82~814 k J·mol^(-1)范围内随温度和应变速率的增大而降低;合金钢在热变形过程中由于动态回复的存在,在应变速率低于1 s^(-1)时,增加变形量降低激活能,应变速率高于1 s^(-1)时,激活能会随变形量的增加而增大。

The hot compression experiment of as-cast P91 alloy steel was carried out on Gleeble-3500 multi-functional thermo-mechanical simulator at 900-1250℃and strain rate of 0.01-5 s^(-1).To better describe the hot deformation rheological behavior of the alloy steel and in view of the influence of deformation condition on activation energy and the material constant parameter,the traditional hyperbolic sine constitutive model was modified.The function of material parameter variable and deformation activation energy on deformation condition was determined by 3 D paraboloid fitting,and the modified constitutive model was obtained.The related coefficient R=0.993 and the average absolute relative error AARE=3.64%,which verifies the reliability in predicting hot rheological behavior of alloy steel of the model.The results show that the deformation activation energy decreases with the increase of temperature and strain rate in the range of 82-814 k J·mol^(-1),and due to the exist of dynamic recovery during the hot deformation of alloy steel,when the strain rate is below 1 s^(-1),the activation energy decreases with the increase of deformation amount;when the strain rate is above 1 s^(-1),the activation energy increases with the increase of deformation amount.