Spatio-temporal instabilities of the Kirkendall marker planes during interdiffusion in β'-AuZn

Abstract

A Kirkendall-effect-mediated behaviour (migration) of fiducial markers originally situated at the contact surface of a diffusion couple can be complex in both temporal and spatial domains. A phenomenological approach based on a concept of the Kirkendall velocity construction is used to rationalize the movement of the inert markers upon diffusion-controlled growth of the β'-AuZn intermetallic phase. It is demonstrated (experimentally as well as theoretically) that the Kirkendall marker planes can be multiple, stable or unstable within the single-phase reaction product. A general criterion of the microstructural instability of the Kirkendall plane is introduced.