Motion of diffusional transformation fronts in multi-component systems

The material properties of a steel slab produced during continuous casting are significantly influenced by the kinetics of the austenite(γ)-to-ferrite(a) phase transformation. Former theoretical models either have used a semi-empirical approach (such as the Johnson-Mehl-Avrami equation) or simplified the situation by assuming an infinite mobility of the phase interface and/or zero mobility of substitutionally dissolved components. In general the transformation kinetics in a multi-component system depends on the interface mobility and on the diffusion of the components. A finite mobility model for the phase transformation has been developed that takes into account the diffusion of substitutionally dissolved components. As an example the kinetics of the γ/α-phase transformation is simulated in the Fe-Cr-Ni system.