Oscillatory regime of ordering during interdiffusion

The coupling of composition changes and ordering at the initial stage of interdiffusion is considered. Both phenomenological and microscopic approaches are used. In the phenomenological model diffusivity is assumed to depend exponentially on the local order parameter. Relaxation of local order is described by linearized reaction with equilibrium order depending on local composition. This scheme leads to nonmonotonous ordering for a certain range of parameters. Monte Carlo simulations of ordering in the process of interdiffusion for square and triangular lattices give similar results. Moreover, local blinking of ordered domains is observed in the contact zone. It was specially checked that nonmonotonous ordering is typical for nonhomogeneous systems. The magnitude of deviations from the monotonous ordering depends on the initial concentration step at the interface of diffusion couple.