Phase-field analysis of a ternary two-phase diffusion couple with multiple analytical solutions

Under certain conditions, there are multiple analytical solutions for the interface velocity in ternary two-phase diffusion couples. We have tackled this degeneracy problem by employing an isothermal phase-field model for diffusion couples that allows comparison with the analytical solutions. We find that, besides the three analytically predicted single-interface diffusion paths, a triple-interface diffusion path can also form. Furthermore, analysis of the phase-field simulation results shows that the Gibbs energies of both the bulk phases and the interfaces must be considered to determine uniquely the evolution of a diffusion couple, in case whether a single or multiple interfaces form.