A systematic study on the dynamic recrystallization behavior of S55C during hot deformation

The hot deformation behavior of S55C steel was systematically investigated via isothermal compression tests over a temperature range of 850–1000 °C and a strain rate range of 0.01–10 s −1 . A strain-compensated Arrhenius constitutive model was established to describe the flow behavior with high predictive accuracy, validated by an average absolute relative error (AARE) of only 4.517 %. Kinetic models were also developed, accurately capturing the sigmoidal evolution of the dynamic recrystallization (DRX) volume fraction and linking the refined DRX grain size to the Zener-Hollomon (Z) parameter, and its high accuracy was validated by a low AARE of 3.628 %. Microstructural characterization using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) revealed a clear transition of the dominant softening mechanisms. At low Z values, discontinuous DRX (DDRX) led to a fully recrystallized, equiaxed microstructure. Conversely, at high Z values, dynamic recovery (DRV) and continuous DRX (CDRX) resulted in a fine, strained substructure, which corresponded to domains of flow instability. Based on these findings, processing maps were constructed to identify the optimal hot working parameters. The preferred processing window for S55C steel was determined to be a deformation temperature of 850–950 °C and a strain rate in the range of 0.01–0.1 s −1 . This work provides a robust framework for controlling the microstructure of S55C steel during hot working.