Effect of interfacial kinetic barriers on interface motion in binary diffusion couples

A finite difference scheme is used to examine the effect of misfit strains and interfacial kinetic barriers to the establishment of local thermodynamic equilibrium on the evolution of a coherent interface in a binary diffusion couple. Impediments to the transformation of one phase into the other and to attaining chemical equilibrium at the interface were considered using a matrix of interfacial kinetic coefficients which coupled thermodynamic driving forces with interfacial velocity and fluxes. Interfacial kinetic barriers result in a decrease in the interfacial velocity, a change in temporal power laws, and large shifts in the time-dependent interfacial compositions, sometimes up to 20 at. pet from the time-independent equilibrium values. The interfacial compositions can shift into either the two-phase field or single-phase field depending upon a number of materials parameters, including the initial compositions of the phases comprising the diffusion couple.