Metastable transition temperature in undercooled hypereutectic Al-Si alloys

Abstract

The present study proposes a novel approach to predict the transition temperature at which the metastable zone changes to the labile zone during the undercooling of hypereutectic Al-Si alloys. The results show that the silicon content and the undercooling strongly affect the transition temperature and the energy barrier to start the spontaneous nucleation. The energy barrier predicted at the transition temperature was in the order of 10−19J. Mixing of two precursor alloys, Ostwald-Miers diagram, and transition temperature were employed to design conditions at which the microstructure of Al-14 and Al-17 wt%Si alloys forming with free primary silicon or small size primary silicon compared with conventional microstructure without adding a grain refiner.