The apparent activation energy for the dissolution of spherical Si-particles in AlSi-alloys

The apparent activation energy for the dissolution of spherical silicon particles in an aluminium matrix is analysed using a numerical dissolution model in which local equilibrium at the particle–matrix interface is assumed. The model takes into account long range diffusion, the temperature dependent solid solubility of silicon in aluminium, the shape of the particle, the finite cell size in which the particle can dissolve and the statistical distribution of the particle size. It is shown that the apparent activation energy can deviate substantially from the activation energy for diffusion, which is the rate controlling process. The model is validated using isoconfigurational annealing experiments at various temperatures for a high purity Al-1.35 mass% Si alloy. An excellent agreement between theory and experiments is obtained. With minor modifications the model can be adjusted to predict the apparent activation energy of (spherical) particle dissolution in other binary systems too.