Effect of sigma () phase precipitation on the recrystallization kinetics of AISI 904L superaustenitic stainless steel

Microstructural evolutions, a-phase precipitation, and recrystallization kinetics of cold-rolled AISI 904L stainless steel during annealing were studied in the present work. The microstructure and hardness evolution were different in the temperature ranges of T < 950 degree celsius (with a-phase precipitation) and T >= 950 degree celsius. The former range was associated with the fall of hardness due to recrystallization softening, followed by hardening due to the concurrent a-phase precipitation; while the latter range was associated with the continuous fall of hardness. Using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) analysis, the recrystallization activation energy in these ranges were respectively determined as 325 and 257 kJ/mol, where the higher activation energy in the former range was correlated to the retardation effect of the a-phase. Via applying the Kissinger's equation to the dif-ferential scanning calorimetry (DSC) results, the activation energy of similar to 332 kJ/mol was obtained, which was consistent with the precipitation of the a-phase.