Toughening alumina with nickel aluminide inclusions

Both ceramics and intermetallics are potential materials for high temperature applications. Recent studies indicated that the toughness of ceramics can be improved by adding intermetallics. Among the intermetallics studied, NiAl is an attracting material for its low density and high melting point. In the present study, the toughening behaviour of Al2O3-NiAl composites is investigated. In order to determine the contribution from the matrix and reinforcement, the composites containing 0-100 vol% NiAl are prepared by hot-pressing. The toughness of the Al2O3-NiAl composites is higher than the values predicted by the rule of mixtures, i.e. the contribution from only the matrix and reinforcement. The toughness enhancement is contributed by the combination of crack deflection and the plastic deformation of NiAl grains. The toughening mechanism for the Al2O3-rich composites is mainly crack deflection. The contribution of the plastic deformation of NiAl to toughening effect increases with increasing NiAl content. It is due to the fact that more NiAl grains are interconnected with each other as NiAl content is increased. © 2000 Elsevier Science Ltd.