M50NiL钢热变形过程中的物理型本构方程及微观组织演变

A physically-based constitutive model and microstructure evolution of M50NiL steel during hot deformation

利用Gleeble-3500型热模拟试验机对M50NiL钢进行了温度为900~1200℃、应变速率为0.01~50 s^(-1)的热压缩试验,研究了M50NiL钢的热变形行为。结果表明:在本实验条件下M50NiL钢出现了3种组织,即具有变形晶粒和孪晶的微观组织、新形核再结晶晶粒和锯齿状晶粒的微观组织和完全动态再结晶的微观组织。Z参数值越低,动态再结晶组织就越充分,Z参数值越高,越容易形成变形晶粒和孪晶的微观组织。基于位错密度理论和Avrami形核长大动力学建立了M50NiL钢的物理型本构方程,其能够揭示动态回复和再结晶两种物理机制对流动应力的影响规律。预测的流动应力与实验数据具有很好的相关性,表明该本构方程能够准确地描述M50NiL钢在较宽温度和应变速率范围下的动态回复和动态再结晶行为。

Hot compression test of M50NiL steel under the conditions of deformation temperature of 900-1200℃ and strain rate of 0.01-50 s^(-1) was carried out by using a thermal simulation machine,and the hot deformation behavior of the M50NiL steel was investigated.The results show that under the experiment conditions,three kinds of microstructure are observed in the M50NiL steel,and they are deformed grains and twins,new nuclear recrystallization and serrated grains,and completely dynamic recrystallization grains,respectively.The lower the Z parameter value,the more sufficient the dynamic recrystallization,and the higher the Z parameter value,the easier it is to form a microstructure with deformed grains and twins.Based on the dislocation density theory and Avrami nucleation and growth kinetics,the physically-based constitutive equation of the M50NiL steel is established,and can reveal the influence of dynamic recovery and recrystallization on flow stress.The predicted flow stress has a good correlation with the experimental data,which indicates that the constitutive equation can accurately describe the dynamic recovery and dynamic recrystallization behavior of the M50NiL steel in a wide range of temperature and strain rate.