Fabrication of nickel aluminide intermetallic-alumina nanocomposite via reaction synthesis

Nickel aluminide–alumina nanocomposite was prepared by a conventional powder metallurgy technique. Nanosize alumina as dispersed phase was mixed with Ni and Al powder in a planetary ball mill for 4 h at 175 rpm. The mixture was then compacted using a hydraulic press at 400 MPa for 15 min. Sintering was done under inert condition in a tube furnace at 660 °C with 5 h soaking time. The occurrence of reaction synthesis during sintering was detected by the presence of a ‘large’ exothermic peak of the differential thermal analysis curve, which occurred below 600 °C. The hardness value for the composite containing 5% alumina was about two times higher than Ni3Al intermetallic. Its saturation magnetization (Ms) was very low indicating the presence of a small amount of elemental Ni. X-ray diffraction (XRD) measurements showed peaks corresponding to Ni–Al and Ni3Al indicating the formation of the desired intermetallics.