Reactive casting of B2-ordered Ni-Al-Co ternary intermetallic alloys

Abstract

Extremely superheated liquid of high-melting-point NiAl-base intermetallic alloys have been produced and cast into a cylindrical bar using the reactive casting method, which is based on the exothermic self-propagating high-temperature synthesis (SHS) reaction between elemental liquids. When liquid aluminum of 1023 K and a molten nickel-cobalt alloy of 1773 K are mixed, they exothermically react and produce a cobalt-containing NiAl liquid with a temperature over 2300 K. The liquid solidifies into a B2-ordered β-phase intermetallic alloy. When the cobalt concentration of the alloy increases, the density, hardness, wear resistance, coefficient of thermal expansion and corrosion resistance to hydrochloric acid increase, while the thermal conductivity decreases. The effect of cobalt concentration on the oxidation resistance of the alloy to hot air is negligible.