STRUCTURE AND PROPERTIES OF AL-SIC FOAM

The mechanical response of composite foam Al-SiC has been examined in compression and indentation. The foam has a closed cell structure and is made of aluminium matrix with SIC particles dispersed in it. The cell walls have a complex microstructure consisting of non-uniform distribution of particles, voids and cavities as well as micro-segregation and precipitates resulting from dendritic solidification. Consequently, the mechanical response is complex. In compression, deformation localizes in a band which extends outward with increasing strain. A similar response is observed in indentation, where localization takes place near the indenter and deformation proceeds radially outward. The mechanism of deformation in individual cell walls is identified to be a combination of processes, such as debonding at the particle/matrix interface, particle pull-out and microvoid coalescence in the ductile matrix. The growth of cracks in the cell membranes is associated with a wide damage zone, resulting in high specific energy absorption capacity.