Kinetics of austenite decomposition in manganese-based steel

In this work, pearlite formation in undeformed and deformed austenitic manganese-based steel is investigated by means of in situ magnetization measurements and optical and scanning electron microscopy. The metastable austenitic microstructure partially transforms to pearlite upon isothermal aging in the temperature range 500-600 °C on a time scale of tens of hours. The observed transformation kinetics and microstructure development are interpreted in terms of the nucleation and growth of pearlite colonies. Preferential nucleation sites for pearlite formation are grain boundaries, and prior plastic deformation increases the density of nucleation sites. Manganese partitioning between the ferrite and cementite lamellae in pearlite appears to control the growth rate, and is the underlying reason for the slow transformation kinetics.