AbstractResults are reported on the compositional and structural features of metal/ceramic interfacial reactions in a series of magnesium based composites containing Al2O3fibres (3μm diameter) produced via liquid metal infiltration of preforms. The composites employed a range of matrix compositions and fibres of different porosities and in some cases binders were used. The practical objective was to optimise the combination of matrix and fibre to reduce the extent to which alumina reacts with liquid magnesium. Detailed electron microscopy has shown that the dominant factor in minimising this reaction is reduction in the extent of interconnecting porosity in the fibres. The presence of alloying elements, such as aluminium in the matrix plays a more limited role in reducing the extent of interface reaction.MST/3021