Microstructure and property characterisation of 3-3 Al(Mg)/Al2O3 interpenetrating composites produced by a pressureless infiltration technique

3-3 Interpenetrating composites, consisting of 3-dimensionally interpenetrating matrices of two different phases, are interesting materials with potentially superior properties when compared with traditional metal matrix composites. In the present research, gel-cast Al2O3 foams with open porosity in the form of spherical cells connected by circular windows were pressurelessly infiltrated using an Al-8 wt% Mg alloy. Electron backscatter diffraction (EBSD) analysis revealed that the alloy had a large grain size with single grains generally inhabiting multiple cells. The flexural strength of the composites, tested using 3-point bending, was similar to 350 MPa, rather high when compared to other Al-alloy-based Al2O3 composites. The strength increased with both decreasing foam density and cell size. The reasons for the high strength are good metal-ceramic interfacial bonding, crack bridging by plastic deformation of the metal phase and crack deflection.