An in situ NiAl–TiC–Al2O3 composite was successfully fabricated from elemental powders using SHS/HE technique. In the composite, TiC particles along NiAl grain boundary agglomerate and grow, but the TiC particles in NiAl grain still keep polygonal and faceted. The NiAl grain of the composite matrix has been greatly refined by the in situ formed TiC particles and subsequent hot extrusion procedure. In addition, the Ti2AlC particle with hexagonal crystal structure is formed along the NiAl grain boundary.
The phase interface between NiAl and TiC is flat and sharp, almost with no interfacial precipitate, but, in some cases, thin amorphous layer is formed along the interface. Stacking fault and microtwins can be observed frequently in TiC particles, and moreover TiC intergrowth plate is formed in some Ti2AlC particles.
The SHS/HE synthesized NiAl–TiC–Al2O3 composite has better room temperature mechanical properties, which should be ascribed to the fine microstructure and predeformation caused by hot extrusion.
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