On the mobility of the austenite-ferrite interface in Fe-Co and Fe-Cu

The kinetics of diffusional transformations in steels depend on a large num ber of parameters, such as grain geometry, nucleation behavior, and growth kinetics. An essential step in the process is the lattice transformation, t he kinetics of which can be expressed by the mobility of the interface betw een the matrix and the newly forming phase. To study the intrinsic mobility of the austenite-ferrite interface, i.e., the mobility of the interface in the absence of long-range diffusion, differential thermal analysis (DTA) e xperiments were performed on high-purity dilute Fe-Co and Fe-Cu alloys. The data obtained were analyzed using a three-dimensional geometry, based on a tetrakaidecahedron model for the austenite grain and a recent interface mo bility model. The observed transformation behavior is described accurately, with the interface mobility being composition dependent.