Characterisation of interfacial reaction in (Al2O3)(p)/6061 aluminium alloy composite

The interfacial characterisation of aluminum alloy 6061 reinforced with Al2O3 particles was carried our using scanning and transmission electron microscopy on interfacial sections and by X-ray diffraction on the reaction products extracted by electrochemical dissolution. The value of these combined techniques in elucidating the interfacial reaction mechanisms was demonstrated. Single crystals of MgAl2O4, of octahedral shape, were observed at the (Al2O3)(p)/Al interfaces together with surface erosions of (Al2O3)(p) which formed around the MgAl2O4 crystals. In the heat treated composite a reduction in precipitate density in the alloy matrix was observed in the vicinity of the (Al2O3)(p). Based on the experimental observations and thermodynamic considerations, the MgAl2O4 crystals which formed at the surface of the (Al2O3)(p) are believed to grow consuming Al2O3. (C) 1997 The Institute of Materials.