Zener-Hollomon参数对Cr4Mo4Ni4V高合金钢热变形行为的影响

Effect of Zener-Hollomon parameters on hot deformation behavior of Cr4Mo4Ni4V high alloy steel

依据热模拟压缩实验结果,研究Cr4Mo4Ni4V高合金钢在变形温度为950~1100℃、应变速率为0.001~1 s^(-1)条件下的热变形行为。基于Zener-Hollomon参数(Z参数)建立Arrhenius本构方程,并表征不同应变条件下材料常数(α,n,Q和lnA)的变化规律,证实所建立的本构模型具有较高的预测精度。此外,利用Z参数建立动态再结晶的临界模型,并结合微观组织在热变形中的演化规律,获得Z参数影响微观组织变形机制和软化行为的基本规律。研究结果表明:在高温低应变速率下,材料的流变应力较低,且呈现出明显的动态再结晶特征;在高ln Z(≥45.11)条件下,绝热剪切带和混晶是主要的微观组织形态;而在38.80≤ln Z≤43.40时,微观组织是以动态再结晶的形式发生软化和细化,且随着Z参数的减小,动态再结晶体积分数相应增加;而较小的ln Z(36.49)会导致再结晶晶粒粗化,不利于热加工。据此,获得的相关结论能够为Cr4Mo4Ni4V高合金钢热加工工艺的制定提供参考。

Based on the results of the thermal simulation compression test,the hot deformation behavior of Cr4Mo4Ni4V high alloy steel was investigated in terms of deformation temperature(950−1100℃)and strain rate(0.001−1 s^(−1)).Meanwhile,the Arrhenius constitutive equation was established and the variation law of the material constants(α,n,Q and lnA)under different strain conditions was characterized based on the Zener-Hollomon parameter(Z),which confirms that the constitutive equation has high prediction accuracy.In addition,the critical model of dynamic recrystallization assisted by using Z-parameter and microstructure evolution characterization in hot deformation was performed to acquire the basic law,which reflects the effect of Z parameter on the deformation mechanism and softening behavior of microstructure.The results show that the flow stress of the material is low and shows obvious dynamic recrystallization characteristics at high temperature and low strain rate.When lnZ is high(≥45.11),the adiabatic shear band and mischcrystal structure are the main microstructure features,when 38.80≤lnZ≤43.40,the microstructure presents softening and refining characterization in the form of dynamic recrystallization,and the volume fraction of dynamic recrystallization increases with the decrease of Z parameter.However,the low lnZ(36.49)will lead to the coarsening of recrystallized grains and have detrimental effect on hot processing.So the relevant conclusions can provide a reference for the regulation of the hot processing technology of Cr4Mo4Ni4V high alloy steel.