Computer simulation of an additive reaction process in dual-phase microstructures

Computer simulation of an additive reaction process in dual-phase microstructures was performed by a stochastic technique based on the decrease in system internal energy. The dual-phase microstructures were constructed using a two-dimensional trianglar lattice. The reaction occurred initially at the reactant interfaces, and then subsequently proceeded by transport of the reactants through the product. The driving force of the reaction is a function of the energy change due to the phase change, grain boundary energy and interface energy changes. The product formation strongly depended on the magnitude of the driving force and initial configuration of the reactant grains. The reactivity was enhanced by increasing the number of triple junctions formed by a grain boundary and interface between the reactants. Control of the initial configuration of the reactant grains localizes the formation sites of the product. Analysis of the fraction reacted as a function of time by applying the Johnson-Mehl-Avrami equation shows that the kinetics follow two-dimensional Jander-type diffusion, when the reaction proceeds only through the products.