Microstructures and mechanical properties of engineered short fibre reinforced aluminium matrix composites

Aluminium matrix composites have been fabricated by squeeze casting into short fibre preforms modified on the basis of a phase contiguity model to improve mechanical performance. Fibre junctions were created in a planar random alumina fibre array by (a) sintering, (b) phosphoric acid treatment, (c) phosphoric acid/aluminium hydroxide (P/Al) treatment and (d) infiltration with alumina powder and sintering. The microstructures and mechanical properties of these composites were examined systematically. The results indicate that using phosphoric acid solution itself to create inter-fibre bonds in the preform gave rise to very low composite strength and ductility compared with that resulting from the as-received preform. This is mainly due to the severe damage to the fibres caused by chemical reaction. By employing the P/Al binder to create the cross-links, the composites reinforced with laboratory-made preforms yielded higher tensile strength relative to the uniform fibre reinforced composites without any sacrifice to the ductility and elastic modulus.