Dense, pore-free interpenetrating phase Al2O3/ Al composites were synthesised by a condensed phase displacement reaction between silica and aluminium, and their elastic costants were determined by an ultrasonic technique. Comparisons are made between he experimental data and analytical theoretical models of Voigt-Reuss (V-R) and Hashin-Shtrikman (H-S). Young's moduius of these composites obey both the V-R and H-S bounds but is better predicted by the Hashin-Shtrikman model. The H-S bounds for the bulk and shear moduli are very narrow and the experimental values are close to the limit calculated on the basis of aluminia as the matrix phase. The microstructural features of these composites, namely, a limited variation in the phase content and somewhat larger range of contiguity values seem not to have any significant influence on the elastic behaviour of the composites. Poissons ratio is essentially constant in these composites. Within a small range of phase composition used in this study, it can still be deduced from the results that the contiguity of the Al2O3 phase influences the elastic properties to an extent.
