| An explicit, finite difference scheme has been used to simulate the influence of coherency stresses and interface kinetic barriers on the phase evolution of a binary, thin-film diffusion couple. Thin-films, initially consisting of alternating layers of two terminal phases α and γ, were held at a temperature where the formation of an intermediate phase β at α/γ interface was thermodynamically probable. In the absence of both the coherency stresses and interface kinetic barriers, β phase nucleates to grow at the beginning of the phase evolution and all phase compositions at interfaces are constant during the evolution. When either the coherency stresses or interface kinetic barriers are present, however, the interfacial compositions become time-dependent and thus the following characteristics of phase evolution are possible: (1) thermodynamically stable phase β does not form at the early stages of the evolution but nucleates to grow in the middle of the evolution, and (2) thermodynamically unstable phase β can initially nucleate to grow and then shrink to disappear during the evolution. Even if the initial states of α/γ multilayers have the same overall composition, the presence of coherency constraint can result in different final equilibrium states depending on either the initial phase compositions of α and γ or the magnitude of interface kinetic barriers. |
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