Fibre-matrix interaction in the δ-Al2O3-fibre reinforced aluminium piston alloy

The interfaces of thermal treated δ-Al2O3-fibre-reinforced AlSi12CuMgNi piston alloys were investigated applying the methods of analytical transmission electron microscopy. The interaction of the γ-Al2O3 with the piston alloy under spinel formation was investigated. Similar to the α-alumina some faces of γ-Al2O3 act as a nucleation centre for spinel formation and a similar mechanism of the fibre-matrix interaction is observed as for the α-alumina. Spinel formation is observed in the neighbourhood of the fibre both of an aluminium and of a silicon grain of the matrix; in the neighbourhood of the silicon grain, most of the spinel crystals are much smaller, however. The results indicate a diffusion-driven reaction mechanism for spinel formation under contribution of oxygen released by the SiO2 binder decomposition.