On the mechanical properties of heat-treated expanded perlite-aluminium syntactic foam

In this paper, a syntactic foam is fabricated by counter-gravity infiltrating packed bed of expanded perlite particles with A356 aluminium alloy. The samples are subjected to a T6 heat treatment. The impact of heat treatment on microstructure characteristics, mechanical properties, deformation behaviour, and cell wall fracture mechanism are investigated. The compression stress-strain curves of the heat treated foams showed the three stages of elasticity, stress plateau and densification. Heat treatment resulted in a significant increase in plateau stress and absorbed energy. It is found that the effect of density on mechanical properties after heat treated conditions is more significant in comparison to untreated conditions. Under compression, the heat treated foams shows more uniform deformation. The improvement in compression characteristics by heat treatment is found to be a result of refined microstructure and higher ductility of the cell walls. Heat treatment reduces the deleterious impact of the columnar dendritic structure of the cell wall and the casting defects on mechanical properties. It limits the crack propagation by increasing the aspect ratio and interparticle distance of the Si particles in the Al matrix.