Dynamics of multicomponent diffusion with zero flux planes

Abstract

Multicomponent diffusion induces zero flux planes (ZFPs) that are locations in a diffusion couple where fluxes of individual components vanish. We analyze the kinetics of multicomponent diffusion near ZFPs. In contrast to the usual mixing that occurs between alloys in a diffusion couple, where the average component compositions are approached through ‘global’ exchange of atoms, the presence of a ZFP requires that mixing of the blocked component occurs through the release of coupled diffusion waves consisting of a ‘depletion’ wave that reduces the blocked component concentration in the component-rich alloy, and a ‘repletion’ wave that increases the concentration in the component-poor alloy. Each wave establishes the average (equilibrium) concentration unilaterally on either side of the Matano plane. Multicomponent diffusion behaviors, such as slowed diffusive spreading and reduced atomic transport, are associated with the near collocation of multiple ZFPs, and the proximity of a zero flux plane for the major component.