Kinetics of Solute Partitioning During Intercritical Annealing of a Medium-Mn Steel

The evolution of austenite fraction and solute partitioning (Mn, Al, and C) during intercritical annealing was calculated for a medium-Mn steel containing 11 pct Mn. Austenite growth takes place in three stages. The first stage is growth under non-partitioning local equilibrium (NPLE) controlled by carbon diffusion in ferrite. The second stage is growth under partitioning local equilibrium (PLE) controlled by diffusion of Mn in ferrite. The third stage is shrinkage of austenite under PLE controlled by diffusion of Mn in austenite. During PLE growth, the austenite is progressively enriched in Mn. Compositional spikes evolve early during NPLE growth and broaden with annealing temperature and time. (C) The Minerals, Metals & Materials Society and ASM International 2015