Modelling the austenite to ferrite phase transformation in low carbon steels in terms of the interface mobility

The kinetics of the phase transformation between the high temperature FCC-phase austenite and the low temperature BCC-phase ferrite as it occurs during controlled cooling of hot roiled low carbon steels is described using a physical model that considers austenite grain size, nucleus density, composition effects, and the austenite/ferrite interface mobility. The model is verified against experimental dilatometry data for three lean carbon-manganese steel grades. The model yields adequate reproductions of the transformation kinetics. Ferrite grain coarsening during the transformation appears to have a significant effect on the final microstructure.