Simultaneous and sequential transformations with nucleation at preferred sites

The advent of new materials may increase transformations that involve two or more product phases. This transformation involving two or more product phases may occur simultaneously or sequentially. It is well-known that heterogeneous nucleation has advantages over homogeneous nucleation. Several sites may become preferred because they favor heterogeneous nucleation. The interface of precipitates and the grain boundaries are one of the preferred locations for nucleation. We model simultaneous and sequential transformations nucleated at the preferred sites. This work employs both computer simulation and exact analytical solutions. Two product phases, 1 and 2, were considered. The product phase 1 nucleated at the matrix/particle interface and the product phase 2 nucleated at the grain boundaries. The analytical model showed an excellent agreement with simulation data. For each case, computer simulation obtained the microstructural evolution. We discussed the effect of nucleation at the preferred sites on the microstructure.