Modelling dissolution of precipitates considering overlapping of solute fields

Abstract

Upon isothermal dissolution of precipitates, the transformation is controlled by solute diffusion, where the overlapping of diffusion fields in front of the precipitate/matrix interface plays an important role. Analogous to a published model for soft impingement in isothermal precipitation, the dissolution process is classified as two stages: one without and one with overlapping of diffusion fields. In the current modelling, linear approximation for the concentration gradient and equilibrium approximation at the interface are assumed, which allow an analytical description for this kinetic process. The model was first demonstrated by numerical calculation. Then, model predictions were performed for θ′ dissolving in Al–3·0 wt-Cu alloy and Al₂Cu dissolving in Al–4·2 wt-Cu alloy; good agreement with the published experimental data was achieved.