Mechanism of ultra-fine microstructure formation during art-annealing of a Medium-Mn steel

The time-evolution of ultra-fine microstructure during ART annealing at 650°C was studied in a Medium-Mn steel with 0.1C - 4.6Mn (wt.%), using both experimental and modeling approaches. A particular attention was paid to the kinetics of austenite formation in connection with cementite dissolution and to the morphology of the phases. A mechanism of formation of such microstructure was proposed. Furthermore, the importance of taking into account the size distribution on the overall transformation kinetics was evidenced through the comparison between experimental and simulated austenite growth.