Fabrication and consolidation of NiaL/Al2O3 composites using simultaneously in-situ displacement reactions and hot pressing

The utilization of in-situ displacement reactions as an alternative approach to synthesize NiAl/Al2O3 composites cermets is investigated. Compacts of intensively ball milled NiO + Al2O3 + Al powder mixtures are hot pressed in an inert atmosphere. The NiO is used as a precursor to generate Al2O3 via in-situ reduction by elemental aluminum. Aluminum also reacts simultaneously with nickel to form NiAl intermetallics by reactive synthesis. The Al2O3 used in the starting materials serves for dissipating the heat generated during the reaction between NiO and aluminum. Dense and homogeneous microstructures were obtained with an Al2O3, matrix and NiAl intermetallics reinforcement. Preliminary characterization of the microstructural and compositional features subsequent to the in-situ processing cycle is presented.