Fabrication of SiC-Fiber/Al₂O₃/Al Alloy Hybrid Composites by Directed Metal Oxidation of Molten Al-Mg-Si Alloys

Abstract

Al₂O₃/Al alloy hybrid composites (SiC/Al₂O₃/Al alloy hybrid composite) reinforced with chopped and continuous SiC fiber (Nicalon^TM) have been fabricated by directed metal oxidation of Al-Mg-Si alloys. Effects of additive elements, Mg and Si on the in situ formation of SiC/Al₂O₃/Al alloy composites were studied. In situ infiltration of the Al₂O₃/Al alloy composite phase into the SiC fiber was possible only when a small quantity of Mg (5 mass%) was used. No infiltration was observed for 10 mass% Mg alloys. Composites fabricated from Al⋅5Mg⋅5Si and Al⋅5Mg⋅10Si alloys showed incorporation of Al₂O₃/Al alloy composite into the SiC fibers. The silicon content of the alloy affected the fabrication of the composite by altering the growth rate of the oxide, and the fastest fabrication of the composite was possible using Al⋅5Mg⋅5Si alloys. It was concluded that aluminum alloys of lower Mg contents (<5 mass%) are recommendable as a starting aluminum alloy for the incorporation of Al₂O₃/Al alloy composite phase into the SiC fibers with void free structure. However, degradation of the fiber during incorporation should be considered the application of this process.