Solute redistribution during internal oxidation of Ag-Cd alloys containing tin as an additive

Abstract

1) During internal oxidation of Ag-Cd-Sn alloys, the oxide particles grow as an intimate mixture of the oxides of cadmium and tin. 2) The large difference in the driving force for the formation of oxides between cadmium and tin (free energies of formation per oxygen atom, at 800°C are −27.8 kcal and −44.2 kcal for CdO and SnO2, respectively2) makes reasonable the expectation that early formation of the oxide with lower free energy of formation1 (i.e. SnO2), acts as a nucleating agent for the growth of CdO particles. The formation of spikes which is dependent on the relationship between grain crystal orientation and the direction of motion of the oxidation front results from the influence of tin and/or tin oxide on the various particle growth parameters,i.e. surface energies, oxygen and cadmium distributions, diffusion rates of different elements, and supersaturation levels.