FIELD-INDUCED VOLUME DIFFUSION IN A 2-PHASE SYSTEM

When an applied field causes solute diffusion, second-phase redistribution is found for a two-phase system. The solute will diffuse in the primary phase with a tendency to maintain that phase saturated. However, particularly for small volume fractions, external surfaces provide flux discontinuities which can cause significant withdrawals from solute saturation. Thus, second-phase depletion, or the converse, may be totally dominated by a large withdrawal of the solute from what is expected with saturation. The general equations for such a process are derived and a detailed example is developed for electromigration.