Reaction and diffusion in multiphase systems : phenomenology and frames

The Kirkendall effect is well-known and documented for the diffusion in a single-phased substitutional solid soln. Also in multiphased systems, much exptl. evidences for the occurrence of the Kirkendall effect can also be found in the literature. However, the relevant observations are not always analyzed in terms of differing vacancy fluxes in the differing parts of such diffusion couple. The anal. recently proposed by the authors shows that the interface must be able both to create or annihilate the point defects involved in the diffusion process within the two adjoining phases. The implication of this model on the relative motion of the phase lattice with respect to the vol. center (Matano frame) and to the interface will be described and discussed. The specific case of the growth of an intermediate phase in binary systems is also considered. Some specific aspects for the case of ternary systems are discussed.