On the Kinetics of Precipitate Dissolution

Abstract

A model is presented for the dissolution of a precipitate that is initially in equilibrium with its depleted matrix. The derived dissolution kinetics is characterized by R(t)=R ₀−K√Dt, where R(t) is the precipitate radius or half-thickness as a function of time (t) during dissolution, R₀ is the precipitate radius or half-thickness at the instant that dissolution begins, K is a material constant, and D is the volume interdiffusion coefficient of the solute in the matrix. The salient feature of the predicted dissolution kinetics is that dissolution is not simply the reverse of growth, as Thomas and Whelan assert (Phil. Mag. 1961, 6, 1103). Furthermore, the time-dependence of R(t) proposed by them is shown to be inconsistent with the results derived. It is demonstrated that dissolution experiments may provide a simple method of obtaining approximate values of volume interdiffusion coefficients that is particularly suited to thin-film specimens.