Coarsening kinetics of solid and liquid silver particles in nickel

Abstract

The coarsening kinetics of solid and liquid silver particles in a nickel matrix have been investigated at temperatures in the ranges 850–935°C and 1000–1100°C. The silver particles and nickel matrix grow in a coupled manner that corresponds to a scaling enlargement. In both temperature ranges the observed growth data correspond to a fourth power rate law, but the rate constants are several orders of magnitude greater than those predicted by classical theories of Ostwald ripening. The accelerated coarsening kinetics are attributed to a coalescence mechanism resulting from the coupled migration of particles and grain boundaries. In the range where the particles are solid a kinetic model gives close agreement with the experimental data, the controlling mechanism being boundary diffusion. In the range where the particles are liquid, however, interpretation of the data is more problematic; an activation energy comparable to that for volume diffusion suggests either that diffusive flow between the leading and trailing edges of the particles controls the kinetics, or that transport through the liquid is controlled by transfer across the liquid/solid interface.

MST/1496