基于动态再结晶动力学方程的镍基高温合金热变形流变应力预测

Prediction of flow stresses for a typical nickel-based superalloy during hot deformation based on dynamic recrystallization kinetic equationZhou Haiping1, Zhang Hongbin1,, Liu Jie1, Qin Shengxue1,2, Lv Yuting1

摘要:

采用等温热压缩实验，研究了一种典型镍基高温合金在1010-1160oC及0.001-1s-1条件下的高温流变行为。结果表明在合金的高温变形过程中发生了动态回复(DRV)以及动态再结晶(DRX)现象。通过深入分析不同变形条件下合金的高温流变行为，分别建立了合金在加工硬化-动态回复阶段以及动态再结晶阶段的流变应力本构方程。其中，在动态再结晶阶段，流变应力本构方程的建立是基于一种新型的动态再结晶动力学方程，该方程中引入了最大软化速率应变。此外，采用线性拟合的方法，建立了本构方程中材料常数与Zener-Hollomon参数间的函数关系。同时，通过对比分析流变应力的实测值和预测值，并计算两者之间的相关系数(R)和平均相对误差绝对值(AARE)，验证了所建立本构方程的准确性，它可以精确预测所研究合金的高温流变应力。

Abstract:

The hot deformation behavior of a typical nickel-based superalloy was investigated by means of isothermal compression tests in the temperature range of 1010-1160oC and strain rate range of 0.001-1s_-1. The results indicated that the work hardening, dynamic recovery (DRV) and dynamic recrystallization (DRX) occurred in the alloy during hot deformation. Considering the coupled effects of deformation parameters on the flow behaviors of the alloy, the constitutive models were established to describe the flow stresses during the work hardening-DRV period and DRX period. In the DRX period, the modified DRX kinetic equation was used to develop the constitutive models, and the strain for maximum softening rate was used in this equation. Additionally, the material constants in the constitutive models were expressed as the functions of Zener-Hollomon parameter by using linear fitting method. Meanwhile, comparisons between the measured and the predicted flow stresses were carried out, while the correlation coefficient (R) and average absolute relative error (AARE) between the measured and predicted values were also calculated. The results confirmed that the developed models could give an accurate estimation of the flow stresses.