20CrNi2Mo钢高温变形的本构方程与动态再结晶行为

在DIL805A/T热模拟机上对低碳合金钢20CrNi2Mo进行等温单向热压缩试验,研究了该钢在温度为900~1 050℃、应变速率为0.001~1 s~(-1)条件下的应变补偿本构方程及动态再结晶行为,为探索塑性变形行为和组织控制提供理论指导。对应变补偿本构方程进行验证发现,考虑应变补偿后得到的应力值与试验值的线性相关系数R=0.992 1,平均相对误差AARE为3.019 2%;采用对θ-σ曲线进行3次多项式拟和求解拐点的方法,建立了临界动态再结晶模型,并结合微观组织分析了不同变形条件下动态再结晶进行的难易程度。结果表明,20CrNi2Mo钢在试验条件范围内全部发生了动态再结晶,且变形温度越高,应变速率越小,动态再结晶进行得越充分,并建立了Z参数动态再结晶临界应力模型和临界应变模型。

Constitutive equations and dynamic recrystallization behaviors of 20CrNi2Mo steel at stage of high temperature deformation

The constitutive equation of the strain compensation and the dynamic recrystallization behavior of 20CrNi2Mo steel at temperatures ranging from 900 to 1050℃and stain rates from 0.001 to 1 s-1 were studied by iso-thermal single-pass compression tests carried out on DIL805A/T thermo-mechanical simulator,which can provide theo-retical guidance for the plastic deformation behavior and organizational control of 20CrNi2Mo steel. The correlation(R) and the average relative error(AARE)are 0.9921 and 3.0192%respectively between the magnitudes of the flow stress calculated by the proposed model and the experimental results. The critical dynamic recrystallization model was estab-lished after the inflection points were solved by fitting a third order polynomial to theθ-σcurves. And the complexity of dynamic recrystallization was analyzed by microstructure of different deformation processes. Results show that the test-ed steel all recrystallized in this study. And the higher the deformation temperature and the smaller the strain rate,the more the dynamic recrystallization volume fraction was. The critical stress model and critical strain model for dynamic recrystallization of parameter Z was established.