Extension of the N-model to predict competing homogeneous and heterogeneous precipitation in Al-Sc alloys

A model has been developed to predict the precipitation and coarsening kinetics of the Al3Sc phase in Al-Sc alloys. This model is based on the N-model framework of Kampmann and Wagner (KWN), extended to account for competition between heterogeneous nucleation on dislocations and homogeneous nucleation. The predictions of the model have been tested against experimental data in the literature and also new experimental results, which are reported in this paper. Both the predicted particle size distributions and the evolution of particle size with time are in good agreement with the experimental data. The model correctly predicts the transition from homogeneous to heterogeneous domination of nucleation, as the ageing temperature is increased, and has been used to investigate the nucleation behaviour in detail. TTT diagrams for the precipitation of Al3Sc have also been predicted for Al-Sc alloys. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.