Porous ceramics possess numerous advanced applications such as filters for molten metals and hot fuel gases, catalyst supports, separation membranes in bioreactors, bone scaffolds and biomaterials, radome materials, etc. Porous ceramics with sufficient open porosity also find application as preforms for infiltration by liquid metal to fabricate interpenetrating phase composites. IPCs with 3D percolating metallic and ceramic phases offer manifold benefits over conventional particulate reinforced and fibre reinforced composites. As a result, IPCs are used in various fields like thermal management, aerospace, automobile industries, light-weight armor materials, etc.

In the present work, a novel low-cost Al-Si alloy/Si3N4 composite was fabricated using open porous Si3N4 preforms fabricated at a low temperature of only 1200 °C using phosphoric acid (H3PO4) as pore former. Infiltration of the Al-Si alloy in the open porous Si3N4 preform was performed using squeeze casting. An in-depth study of the dual role of H3PO4 as an inorganic binder and pore former and the effect of its content on the porosity, elastic behavior, and mechanical properties of the fabricated porous Si3N4 has been critically analysed. A thorough analysis of the properties of 3D interpenetrating Al-Si alloy/Si3N4 composite material is carried out in this work. The properties of porous Si3N4 and the IPC have been compared with the predictions from relevant micromechanical models.