The dynamic and static softening mechanisms of LX82A steel in double-pass hot compression deformation

This research aims to elucidate the regulatory mechanisms of temperature, strain, and inter-pass holding time on the static softening behavior of LX82A steel during double-pass hot deformation and to uncover the impact of dynamic-static softening coupling on the evolution of microstructure. In this study, single- and double-pass hot compression tests were performed on LX82A steel using the Gleeble-3500 thermal simulator. The dynamic and static softening behavior, as well as the evolution of microstructure, was investigated under deformation temperatures ranging from 900 to 1100 °C, a strain rate of 1 s⁻¹, and holding times varying from 1 to 120s. The results showed that the stress values in the double-pass flow curve decreased as temperature, deformation amount, and holding time increased, and the stress values were all higher than those in the single-pass flow curves. At 900 °C, the static softening mechanism was mainly static recovery. As the temperature increased, the static softening mechanism changed from static recovery to static recrystallization. The nucleation and growth mechanism of static recrystallization followed the strain-induced boundary migration (SIBM) mechanism. Compared to single-pass deformation, the double-pass deformation process was more advantageous for grain refinement. By combining static softening rate and the Avrami equation, a static recrystallization kinetics model was established, and the activation energy for static recrystallization of LX82A steel was calculated to be 218.32 kJ/mol.