Abstract
The interfacial phases were studied in pressure-cast Saffil/Al-4.5Cu-3Mg composite material using a variety of characterization techniques. The magnesium- and copper-rich phases were found to segregate near the fibre-matrix interfaces. The major phases were identified as MgAl2O4, Al2CuMg and CuAl2. Significant diffusion of silicon from the fibres into the matrix took place during the pressure-casting. A conclusion was drawn that solidification started with the less alloyed aluminium in the bulk of the matrix and proceeded towards the fibres. Auger and XPS analyses of composite materials fracturedin situ showed the fracture surface to lie within magnesium-rich (and not copper-rich) phases, most likely within the MgAl2O4 spinel phase. The fibre surface treatments which are being developed to improve interfacial wetting may also reverse the direction of crystallization and prevent formation of brittle phases in the vicinity of fibres, thereby improving the toughness of the composite materials.
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