A Non-steady State Model for the Austenite-to-ferrite Transformation Kinetics under the Non-partition Condition in Fe–C–Mn Alloys

A non-steady state model describing the transition from the para-equilibrium to the local equilibrium under the non- or negligible-partition condition is proposed to investigate the austenite to ferrite transformation kinetics in Fe–C–Mn steels. The present model has been developed based on the quasi-steady state model used for calculating the solute drag force by the segregated solute within the ferrite/austenite interface, although the solute-drag force is not calculated in the present model. The calculated Mn profiles are compared with the STEM-EELS observation reported previously by some of the present authors. The temporal evolution of the Mn profiles during PE to NPLE is shown. Combining a simple C diffusion model, the transition path from PE to NPLE on the C–Mn isothermal section of an Fe–C–Mn alloy is also presented.