Synthesis and characterisation of aluminium-silicon-silicon carbide composite

Abstract

Aluminium-silicon-silicon carbide composite was prepared by mechanical mixing (300 rpm) of silicon carbide powder (-300 mesh) in solidifying solid-liquid slurry of hypoeutectic, eutectic and hypereutectic compositions of aluminium-silicon alloy. Requisite amount of hot (300°C) silicon carbide powder was charged into agitating metallic melt of aluminium-silicon matrix alloy and mixing continued while dropping the temperature of the system. The mixing period was 3-4 min during which temperature of the system dropped to 15±5°C below the liquidus. On completion of mixing, plumbago crucible containing the composite slurry was taken out from the furnace and finally solidified composite was removed from the crucible for the further study. X-ray diffraction analysis indicated the presence of silicon carbide in the composite. Silicon carbide occurred in the grain boundry regions associated with silicon and fragmented dendrites together with eutectic mixture. Strength, hardness and wear resistance of composite increased with increase of silicon carbide content. Coefficient of friction of composite having higher amount of silicon carbide was always lower than the composite with lower amount of silicon carbide, whether the tests were conducted in lubrication, semi-dry and dry sliding conditions.