Fabrication of intermetallic NiAl by self-propagating high-temperature synthesis reaction using aluminium nanopowder under high pressure

By using aluminium nanopowder prepared by wire electrical explosion, pure monophase NiAl compound with fine crystallites (<10 mum) and good densification (98% of the theoretical green density) was successfully fabricated by means of self-propagating high-temperature synthesis (SHS) under a high pressure of 50 MPa. Investigation shows that. due to the physical and chemical characteristics of the nanoparticles, the SHS reaction mode and mechanism are distinct from those when using conventional coarse-grained reactants. The SHS reaction process depends on the thermal conditions related to pressure and can occur at a dramatically low temperature of 308 degreesC, which cannot be expected in conventional SHS reaction. With increasing pressure, the SHS explosive ignition temperature (T-ig) of forming NiAl decreases due to thermal and kinetic effects.