A process model for friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. 2, HAZ microstructure and strength evolution

The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. In Part II the heat and material flow models presented in the first paper Part I) are utilized for prediction of the HAZ subgrain structure and strength evolution following welding and subsequent natural ageing. The modelling is done on the basis of well established principles from thermodynamics, kinetic theory and simple dislocation mechanics. The models are validated by comparison with experimental data, and are illustrated by means of novel mechanism maps. These show the competition between the different process variables that contribute to microstructural changes and strength losses during friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites.