On microstructure characterization of Fe–Cr–Ni–Mo–N super-austenitic stainless steel during hot deformation

Hot compression tests of Fe–Cr–Ni–Mo–N super-austenitic stainless steel were carried out in the temperature range of 950–1150 °C with a strain rate of 0.01–10 s−1, in which dynamic recrystallization (DRX) mechanisms and coincident site lattice (CSL) boundary evolution in consideration of adiabatic heating were investigated. The results show that discontinuous DRX was the main DRX mechanism. Due to the high stacking fault energy (162–173 mJ/m2), subgrain evolution occurring in dynamic recovery process was stimulated at high temperatures and high strain rates. DRX behavior was accelerated by higher strain rate and adiabatic heating. Also, amounts of fine annealing twin boundaries were observed in the specimens deformed at higher strain rates and higher temperatures. By analyzing the length fractions of Σ3 boundary in overall boundaries and in CSL boundaries, the results indicate that Σ3 regeneration mechanism and new twinning mechanism take effect concurrently for twin-related grain boundary when the specimens were deformed at 950 °C with a strain rate of 0.01–10 s−1. With increasing strain rate or deformation temperature, the propagation of Σ3 boundaries was mainly dominated by new twinning mechanism.