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

A Kirkendall-eŒect-mediated behaviour (migration) of fiducial markers originally situated at the contact surface of a diŒusion 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 diŒusion-controlled growth of the b 0-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.