In casting of a hypereutectic Al-Si alloy, silicon is generally known to crystallize easily as a needle or plate-like shape in the matrix, resulting in the decreased machinability as well as the decreased mechanical strength and ductility. In this work hypereutectic Al-20 mass%Si alloys were fabricated using both the conventional ingot casting and rapid solidification processes in order to investigate their fundamental aspects of machinability. In the alloy produced by the rapid solidification

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... rocess (R. S. P) the average size of silicon crystals was smaller than that in the alloy produced by the conventional casting process and both the mechanical strength and hardness increased. The tool wear and surface roughness of the R. S. P. alloy were superior to those of the conventional casting process alloy. The cutting force for the R. S. P, alloy was higher than that for the conventional process alloy. The chip treatability of the conventional casting process alloy was better than that of the R. S. P. alloy in the case that no chip breakers were used.