Hot Deformation Behavior and Microstructural Evolution of a 5Mn Medium‐Mn Steel: Strain‐Compensated Arrhenius Modeling and DMM Processing Maps

Abstract

Isothermal hot‐compression tests (850–1150 °C, 0.1–10 s −1 ) were performed on a 5Mn medium‐Mn steel to elucidate its high‐temperature flow behavior and microstructural evolution. Flow stress decreases with increasing temperature and increases with strain rate. Dynamic recovery (DRV) dominates at high‐strain‐rates, whereas typical dynamic‐recrystallization (DRX) softening occurs at low strain rates because continuous DRX nucleation and growth consume stored deformation energy and progressively eliminate dislocations and substructures. A strain‐compensated Arrhenius constitutive model was developed with high predictability ( R = 0.99, AARE = 4.3%). Dynamic materials model (DMM) processing maps indicate an optimum hot‐working window of 1100–1150 °C at 0.1–0.5 s −1 . The DRX grain size coarsens with increasing temperature and decreasing strain rate, but is markedly refined under high Zener–Hollomon conditions. EBSD corroborates the map criteria: the instability regime shows dense low‐angle grain boundaries and pronounced intragranular orientation gradients, whereas the high‐power‐dissipation regime exhibits a higher fraction of high‐angle boundaries and a more homogeneous, equiaxed microstructure, providing microstructural evidence for the proposed hot‐working processing window.