Nucleation, Growth and Coarsening of Spherical Precipitates in Aluminum Alloys

Abstract

A model, compatible with a thermodynamic routine previously described [1], simulates homogeneous nucleation, growth and coarsening of spherical precipitates in aluminum alloys. This kinetic subroutine considers size distribution for each type of precipitate present in the matrix. Local equilibrium is assumed at the matrix-precipitate interface; the corresponding solubility product is corrected by the curvature effect. The equilibrium concentration of each solute element at the matrix-precipitate interface is solved by an iterative method so that the flux of each element is compatible with the solubility product and with the stoichiometry of the considered precipitate. Nucleation and growth of the different precipitates are solved numerically. Coarsening of precipitates is embedded in the equations via the curvature correction of the solubility product. For simple cases, i.e. presence of only one type of precipitate in the microstructure, the coarsening rate can be solved analytically. In that case, the numerical results are the same as the analytical equation results. An example of application will be presented for a binary Al-Li alloy.