Unified treatment of Kirkendall shift and migration of phase interfaces

A recent treatment of diffusion in a lattice-fixed frame of reference, which can predict the Kirkendall shift, is modified to be applicable also to the migration of phase interfaces. The net flux across a reference point in the lattice, yielding the Kirkendall shift, as well as the net flux across a phase interface, yielding its migration, are obtained from the same flux equation. Numerical calculations are presented and demonstrate that the method gives expected results. The strength of the method is that it is not based on the assumption of local equilibrium and it is capable of automatically yielding close to local equilibrium conditions except at high supersaturations. There it describes an increasing deviation from local equilibrium as the initial alloy composition is moved inside the one-phase field for the new phase. The interaction of a migrating phase interface and Kirkendall markers is also illustrated.