通过热压缩实验和3种本构分析方法, 系统研究了35Mn2钢的奥氏体热变形本构关系. 首先建立了传统的利用峰值应力求得表观材料常数的双曲正弦本构方程, 求得实验钢的热变形激活能为278 kJ/mol, 与奥氏体的自扩散激活能(270 kJ/mol)十分接近, 表明其热变形速率控制机制是扩散控制的位错攀移. 其次建立了考虑应变量对表观材料常数影响的改进型双曲正弦本构方程, 利用这种改进型本构方程预测实验钢的流变应力, 预测值与实验值相关系数为0.991, 平均相对误差为4.19%, 表明预测值与实验值吻合良好,可用以准确预测实验钢的热变形流变应力. 第三种方法是基于物理的本构模型, 考虑了Young’s模量和奥氏体的自扩散系数与温度的关系,利用这种方法同样可以获得峰值应力与变形条件的关系, 但拟合精度不及双曲正弦本构方程, 本工作对其进行一定的修正后, 其拟合精度有明显提高.

The constitutive relationships of a 35Mn2 steel during hot compression testing were systematically investigated using three methods. The first method is a conventional hyperbolic sine equation with peak stress dependent constants, the activation energy Q determined by this method is about 278 kJ/mol, very close to the austenite lattice self--diffusion activation energy (270 kJ/mol), indicating the rate-controlling mechanism is dislocation climb controlled by diffusion. The second method is a developed hyperbolic sine equation with strain dependent constants, comparing with experimental results, the correlation coefficient and average relative error ofpredicted and measured values are 0.991 and 4.19%, respectively, indicating that the developed equations can give an accurate estimate of the flow stress for the experimental steel. The third method is a physically based approach accounting for the dependence of the Young’s modulus and the self-diffusion coefficient of austenite on temperature, which is also capable of representing the flow stress of the material as a function of the deformation conditions, but the fitting precision by this method is lower than by the conventional hyperbolic sine equation, and through modification, the fitting precision of the physically based approach is improved in this work.