Kinetics and microstructure evolution of dynamic recrystallization of medium-Mn steel during hot working

Abstract

The dynamic recrystallization (DRX) behavior and microstructure evolution of medium-Mn (0.15C–10Mn) steel were investigated through isothermal hot compression tests. The flow stress–strain curves and microstructure analysis, in wide ranges of temperatures (900–1150 °C) and strain rates (10−3 - 1 s−1), were employed to establish constitutive equations and a grain size evolution model. Since the material constants were calculated based on polynomial function of strains, strain compensation was introduced into constitutive analysis. Comparison and verification showed that the constitutive equation had a high predictive ability. The correlation coefficient and average absolute relative error were 0.99 and 4.46%, respectively, which confirm the accuracy and guidance of the model. Metallographic observation was used to implement the grain size evolution analysis of the medium-Mn steel. Microstructure evolution was characterized with a gradual increase in average recrystallized grain size and an obvious expansion in the range of grain size distribution with both deformation temperature and strain rate, which were attributed to the competition between nucleation and grain boundary migration. Besides, a grain size evolution model was established to analyze the microstructure evolution.

Keywords

• Medium-Mn steel
• Dynamic recrystallization
• Microstructure evolution
• Hot compression