Abstract:The effect of microstructure variation by addition of alumina short fiber and optimization of tensile properties by air-cooling processing in Al₂O₃/Al-15Si composites were studied. The results show that in Al-15Si alloy matrix composites with 14% and 30%(volume fraction) fiber, the primary silicon is hardly refined, but the eutectic silicon is effectively refined and granulated. Granulation of some eutectic silicon mainly happens in fiber segregation areas. Refining and granulation of the eutectic silicon are related to the physical constraint arising from the fiber. After the 30%Al₂O₃/Al-15Si composite was remelted and air-cooled, the number of the eutectic silicon on the surface of the fiber increases, which results in the improvement of fiber/matrix interface and tensile properties for the as-cast composite. Air-cooling processing may be reliable for the optimization of the microstructure and properties of fiber reinforced hypereutectic Al-15Si alloy composites.

Key words:  metal matrix composites; aluminum-silicon alloy; solidification; microstructure; tensile properties