Preparation of interpenetrating ceramic–metal composites

Ceramic reinforced metals are attractive because of their enhanced elastic modulus, high strength, tribological properties and low thermal expansion. Most work in this sector has focused on particle- or fiber-reinforced composites where the ceramic phase is not continuous. This work presents aluminium–alumina composites where both phases are interpenetrating throughout the microstructure. Ceramic preforms were produced with sacrificial pore forming agents leading to porosities between 50% and 67%. Pore wall microstructure was varied by changing the sintering temperature. Permeability and strength was measured for the porous preforms and infiltration results were compared with theoretical predictions based on capillary law and Darcian flow. A direct squeeze-casting process was used to infiltrate the preforms with aluminium resulting in an interpenetrating microstructure on both macropore and micropore scale.