The effect of lattice misfit on the dissolution kinetics of γ-Ag2Al precipitates

Abstract

Abstract The dissolution kinetics of γ-Ag2Al plates at misfit values of 0.76%, 0.42% and 1.11%, corresponding to an Al-4.18% at % Ag binary alloy and with additions of Cu and Mg respectively, have been investigated. Plate thinning was found to be over forty times slower than expected under volume diffusion control for the binary and ternary Cu systems and to be nearly twenty-five times slower for ternary Mg alloy. The relative faster kinetics of the ternary Mg alloy could be correlated with its higher degree of misfit and with a lower deviation from equilibrium composition at the interface as obtained by electron probe microanalysis. A computer model developed for shortening kinetics shows plate shortening also to be inhibited in all three systems. A mechanism for dissolution involving coordinated motion of interface ledge/dislocations is discussed and the apparent difference between the processes of growth and dissolution is highlighted.