Effect of pre-deformation on hot workability of super austenitic stainless steel

Abstract

The hot compression behavior of 7Mo-0.37N-RE super austenitic stainless steel (SASS), subjected to solution treatment and pre-deformation, is systematically investigated in the temperature range of 900–1200 °C and strain rates of 0.01–10 s−1. The results reveal that, compared with the solution-treated super austenitic stainless steel (ST-SASS), the pre-deformation super austenitic stainless steel (PD-SASS) exhibits high density of dislocations. Consequently, the flow behavior, dynamic softening mechanism, hot workability, and microstructural evolution of the PD-SASS are influenced. In the strain range of 0.1–0.7, the deformation activation energy (Q), Zener-Hollomon parameter (Z) and critical stress for dynamic recrystallization (σc) of the PD-SASS are lower than those of the ST-SASS, implying that dynamic recrystallization (DRX) and dynamic recovery (DRV) are more likely to happen in the PD-SASS. Meanwhile, the distribution and range of power dissipation and instability regions of the ST-SASS and PD-SASS are quite different. Therefore, hot workability and microstructural evolution are significantly altered when the thermal processing range of the ST-SASS and PD-SASS is 1025–1150 °C/0.09–5 s−1 and 980–1150 °C/0.05–10 s−1, respectively. Overall, the processing maps and microstructure reveal that the pre-deformation treatment broadens the hot working range of SASS under same conditions.