THEMICROSTRUCTURAL EFFECTS OF THE RAPID SOLIDIFICATION IN HYPEREUTECTIC Al-Si ALLOYS

摘要

The metastable crystalline alloys with extended solid state solubility and a very fine microstructure can be obtained by rapid quenching from the melt. Hypereutectic Al-Si alloys up to 25wg percent Si have been processed by the melt-extraction method of rapid solidification in various conditions for obtaining different filament thick nesses coresponding to different cooling rates. The microstructural effects induced by rapid solidification in hypereutectic Al-Si alloys were investigated by applying light-microscopical analysis. Vickers microhardness measurements on filaments showed a systematic increase of hardness as the cooling rate increased, accountable by the structural modifications induced by rapid solidification.