Interface diffusion in the Al-CuAl 2 eutectic

Abstract

The interface diffusion coefficient of Cu at the lamellar interface of an Al-CuAl 2 eutectic alloy has been determined. The experiment, the solid-solid analogue of the grain boundary grooving experiment to determine the rate of surface diffusion, measures the rate of migration of a triple junction formed between a sub-boundary in the Al and the lamellar interface. Although five possible diffusion paths could contribute to this rate of migration, the experimental results accurately fit the predictions of Mullins' theory that assumes that surface (or interface) diffusion is dominant, i.e. the shape of the interface and the time dependence of the migration rate are in excellent agreement with the theory. From the temperature dependence of the kinetic data for migration, the interface diffusion coefficient is found to be D i = 1.1 × 10 3 exp [−(23,300/ RT)] between 350 and 500°C. The influence of volume diffusion of Cu in the Al rich phase, and the effect of an array of closely-spaced sub-boundaries in the Al are considered by extending Mullins' theory.