Kinetics of isothermal and non-isothermal precipitation in an Al-6at% Si alloy

Abstract

A novel theory which describes the progress of a thermally activated reaction under isothermal and linear heating conditions is presented. It incorporates nucleation, growth and impingement and takes account of temperature dependent solubility. The model generally fits very well to isothermal calorimetry and differential scanning calorimetry data on precipitation in an Al-6 at.% Si alloy. Analysis of the data shows that two processes occur in this precipitation reaction: growth of large Si particles and growth of pre-existing small nuclei. Determination of the sizes of Si precipitates by transmission electron microscopy indicates that interfacial energy contributions are small and have a negligible influence on solubility