Development of short alumina fibre and in situ Mg2Si particle reinforced magnesium alloy hybrid composite with high temperature strength

Abstract

Short alumina fibre and in situ Mg₂Si particle reinforced hybrid composites were fabricated by infiltration with the molten magnesium alloy into the preforms consisting of the fibres having Si particles attached to their surfaces. P or CaF₂ particles were used as the refiners of the Mg₂Si particles. All of Si particles reacted with the Mg alloy and melt to form Mg₂Si particles. As the melting temperature decreased or the cooling rate after the infiltration increased, the Mg₂Si particles became finer. The introduction of P or CaF₂ further promoted the refinement of the Mg₂Si particles. When the composite was fabricated by squeeze casting in the permanent mould, fine Mg₂ Si particles with a grain size of ～5 μm were formed regardless of introducing the refiners due to the rapid solidification. The strength of the hybrid composites was higher than that of the conventional fibre reinforced composite at both room temperature and high temperature.