EFFECTS OF NON-EQUILIBRIUM SEGREGATION ON NEAR-SURFACE DIFFUSION

A non-equilibrium segregation process is presented which involves the coupled flow of vacancies and solute atoms in solids. This process can give rise to either enrichment or depletion adjacent to a free surface or other primary defect sinks depending upon the solute-solvent diffusivity ratio,DB/DA, and upon the size of the solute-vacancy binding energy. This phenomenon can give rise to near-surface diffusion anomalies reported in recent years and to other important near surface effects. A new explanation of quench-induced near-interfacial hardening is proposed based upon the effects of changes of solute concentration on the structure and density of secondary nucleated defects. A remarkable correlation between the DB/DA ratio and the solute distribution coefficient in noble metal solvents is shown and discussed. © 1969.