Revealing the Dynamic Recrystallization Mechanism and Hot Workability of Fe-0.15C-10Mn Medium-Mn Steel through Grain Size Distribution and 3D Processing Maps

An in-depth understanding of thermal deformation of medium-Mn steels (MMnSs) is crucial for the forming fabrication of key automotive components. In this work, the Fe-0.15C-10Mn MMnSs are compressed under conditions of 900-1150 degrees C/0.001-10s(-1). Two-stage models, dynamic recovery (DRV) and dynamic recrystallization (DRX), are constructed and proved to be accurately predictive with a correlation coefficient (R) of 0.997% and average absolute relative error (AARE) of 2.67%. Based on the analysis of microstructure evolution, the discontinuous DRX occured at a specific deformation condition of 900 degrees C-10s(-1), while the continuous DRX generated at other deformed conditions. The discontinuous DRX grains only distributed along pre-existing grain boundaries, showing a necklace-like grain structure with multiple small zigzag protrusions at the boundary. While continuous DRX grains with low dislocation density distributed both along and inside the pre-existing grain boundaries. The developed 3D processing map identified high strain rate (0.1-10s(-1)) as instability domains, in which heterogeneous microstructure are observed. Consequently, optimum hot working domain is determined to be 975-1150 degrees C/0.001-0.05s(-1). Complete DRX and subsequent growth of small DRXed grains result in a homogeneous microstructure, contributing to the optimal processing zone with eta>0.29.