EFFECT OF INTERFACIAL KINETIC BARRIERS ON INTERFACE MOTION IN BINARY DIFFUSION COUPLES

A finite difference scheme is used to examine the effect of misfit str ains and interfacial kinetic barriers to the establishment of local th ermodynamic equilibrium on the evolution of a coherent interface in a binary diffusion couple. Impediments to the transformation of one phas e into the other and to attaining chemical equilibrium at the interfac e were considered using a matrix of interfacial kinetic coefficients w hich coupled thermodynamic driving forces with interfacial velocity an d fluxes. Interfacial kinetic barriers result in a decrease in the int erfacial velocity, a change in temporal power laws, and large shifts i n the time-dependent interfacial compositions, sometimes up to 20 at. pet from the time-independent equilibrium values. The interfacial comp ositions can shift into either the two-phase field or single-phase fie ld depending upon a number of materials parameters, including the init ial compositions of the phases comprising the diffusion couple.