A New Kinetic Mode During the Austenite-to-Ferrite Transformation in Fe-Mn and Fe-Mn-Mo Alloys

The kinetics of isothermal austenite (gamma)-to-ferrite (alpha) transformation at various temperatures in Fe-2Mn and Fe-2Mn-0.5Mo (wt%) alloys is investigated via dilatometry experiments and phase-field modeling. It was interestingly found that Mo addition has a marginal effect on the transformation kinetics. Besides the well-known partitioning and partitionless transformation modes, a new kinetic mode, in which interface migration is controlled by interfacial diffusion, was identified. The phase-field model with considering interfacial segregation could well predict the transformation kinetics and the kinetic mode transition.