Dynamic Recrystallization Behavior and Constitutive Modeling of As-Cast 30Cr2Ni4MoV Steel Based on Flow Curves

The compression deformation of 30Cr2Ni4MoV steel at different temperatures and strain rates is carried out on Gleeble 1500 thermal mechanical simulation tester. Based on the experimental flow curves, the strain hardening rate curves (theta = d sigma/d epsilon versus sigma) are derived, from which the characteristic stresses and strains are identified. Meanwhile, the dependences of the characteristic stresses and strains on Zener-Hollomon parameter are determined and the results show that the value of the critical stress of dynamic recrystallization is close to the value of the steady stress. With the aid of the experimental flow curves, the Avrami equation is employed to describe the kinetics of dynamic recrystallization. The time exponent (n) is expressed as a power law function of Zener-Hollomon parameter and the Avrami constant (k) is determined as a function of half of the time for the complete dynamic recrystallization (t(50)). Furthermore, a constitutive model is presented based on the rule of mixtures when the dynamic recrystallization occurs. Validation of the constitutive model is implemented and the simulated results agree well with the experimental results.