Oxide particle densities in internally oxidised Ag–Cd alloys: Part 1 Effect of heterogeneous nucleation in alloys with high Cd content

Abstract

It is shown by quantitative evaluation of scanning electron micrographs that there is disagreement between predictions of particle density on the basis of classical theory of internal oxidation and experimental results for Ag–Cd alloys with a medium Cd content at some depth below the surface and with high Cd content over most of the specimen cross-section. It is hypothesised that a transition from homogeneous to heterogeneous nucleation takes place by which the particle density is increased. Nucleation sites are formed by agglomeration of vacancies enriched in front of the oxidation zone because of counterdiffusion of Cd which, in turn, is accelerated by the high defect concentration. Most of the experimental results can be qualitatively explained by considering these effects.

MST/900a