Microstructure evolution and mechanical properties of Ni3Al/Al2O3 composite during self-propagation high-temperature synthesis and hot extrusion

The Ni3Al/Al2O3 composite was fabricated by self-propagation high-temperature synthesis with and without hot extrusion methods. Its microstructure and mechanical properties were investigated by using combination of optical microscope, transmission electron microscope and compression test. The results show that the Ni3Al/Al2O3 composite without hot extrusion has relative coarse microstructure, which contains γ-Ni and Ni4Al3 phases along the Ni3Al phase boundary. In addition, κ-Al2O3, θ-Al2O3, α-Al2O3 and cavities are observed in the composite without hot extrusion, which segregate greatly in original powder boundary. The hot extrusion process densifies the composite; eliminates the element segregation and redistributes Al2O3 particles homogeneously. Moreover fine Ni3Al crystalline with high density of dislocations and twinned Ni3Al crystals are observed in the extruded part. The hot extrusion improves the mechanical properties of the Ni3Al/Al2O3 composite significantly, especially its ductility.