Processing and characterization of elastic and thermal expansion behaviour of interpenetrating Al12Si/alumina composites

Thorough analysis of the elastic as well as the thermal expansion behaviour of an interpenetrating Al12Si/alumina composite material is carried out in this work. The open porous preforms used for composite fabrication are also processed in this work using 1:1 mixture of one fine and one coarse polymer wax as pore formers. The ratio of ceramic powder to pore formers is varied to fabricate preforms having different ceramic contents. Study of the elastic properties shows that while the porous preforms display transverse isotropic behaviour, the composites behave as quasi-isotropic material with the composite Young's modulus being closest to the predictions of the Feng model for interpenetrating composites. Study of the thermal expansion behaviour of the composite shows that the composite behaviour is controlled by the unreinforced metallic alloy. In spite of its percolating interpenetrating phase morphology, the evolution of thermal expansion coefficient of the composite with both temperature and ceramic content shows that particle reinforced composites predict the behaviour of the composite more closely. This has been discussed in light of the microstructure of the studied composite material and an outline of the proposed future research is provided.