AbstractAluminia composites of Al2O3–NiAl and NiAl(Fe) were prepared by hot pressing mixtures of Al2O3with NiAl and NiAl(Fe) powders respectively to a density >98·5%theoretical for evaluation of toughness as a function of intermetallic content and comparison with hot pressed Al2O3 , NiAl and NiAl(Fe). The intermetallic grain size, in both cases, was found to be smaller than the as received powder particle size in alumina rich composites because of the pinning effect of alumina particles on grain boundaries, but increased with increase in intermetallic content due to grain growth as the pinning effect decreased at lower alumina contents. The toughness of hot pressed NiAl(Fe) was ∼50% greater than for NiAl. Both intermetallic compositions showed a steady increase in the toughness of the composites with increase in intermetallic content, with NiAl(Fe) composites being somewhat tougher at higher intermetallic contents. The Fe content in NiAl(Fe) appears to increase the interfacial strength in the composites w...