Interphase precipitation – an interfacial segregation model

The size and distribution of interphase precipitates in micro-alloyed steels is a crucial micro-structural feature to control for obtaining the necessary strength in low-cost automotive sheets. In order to optimize both alloy chemistry and thermal processing an enhanced understanding of the interphase precipitation mechanism is required. It is proposed that the evolution of inter-sheet spacing of MC carbides during the γ→α+MC transformation can be explained considering the interfacial segregation and the corresponding dissipation of Gibbs energy inside the moving interphase boundary. The inter-sheet spacing of interphase precipitates is controlled by a complex interplay between the interfacial energy and interfacial segregation, this is presented in form of an analytical model. It is shown that the general trend of refining inter-sheet spacing with growing ferrite half-thickness can be well predicted by the proposed model