Hot-Deformation Behavior, Constitutive Modeling, and Recrystallization Mechanisms of 20CrMoH Steel
摘要
This study systematically characterizes the hot-deformation behavior, constitutive response, and dynamic recrystallization (DRX) mechanisms of 20CrMoH steel through isothermal compression testing. Flow stress is jointly governed by temperature and strain rate, varying from 175.4 MPa at 950 °C/10 s−1 to 42.0 MPa at 1100 °C/0.01 s−1. The stress–strain curves exhibit an initial work-hardening stage followed by softening, reflecting the interplay between dislocation accumulation and thermally activated DRX. A strain-compensated Arrhenius constitutive model was established, with an activation energy of 324.78 kJ/mol, accurately capturing strain- and temperature-dependent flow behavior. EBSD analyses reveal that 950 °C and 0.01-1 s−1 favor continuous DRX via progressive LAGB-to-HAGB transformation, whereas 950-1100 °C and 10 s−1 promote discontinuous DRX through the regulation of bulging-induced nucleation and activation energy. Processing-map results identify optimal deformation windows at 1000-1065 °C with 0.01-0.1 s−1 and 1087-1100 °C with 0.2-1.3 s−1, corresponding to regions of high-energy dissipation and low flow instability. These findings provide quantitative guidance for the forging and thermo-mechanical processing of 20CrMoH steel and offer insights into controlling microstructural evolution under complex hot-deformation conditions.