Self-propagating high-temperature synthesis of nial intermetallic compounds

Abstract

In this work, the self-propagating high-temperature synthesis (SHS) method was utilized for the synthesis of the B2 NiAl compound. Elemental nickel and aluminum powders were mixed, die-pressed, and pre-heated in a furnace in which the SHS reaction was initiated and propagated. The influence of pre-heating temperature was evaluated against the final composition, phase formation, microstructure and hardness of the final compact. Conditions were found under which, the final product forms through solidification from the melt and (irrespective of the furnace temperature) consists only of the B2 NiAl. The NiAl compacts formed consisted of a core which is essentially pore free and accounts for ~80% of the total volume and a high porosity shell around it. The microstructure consists of large, equiaxial grains with linear grain boundaries indicative of high phase stability. Finally, it was found that as the pre-heating temperature increases the hardness of the NiAl compact decreases; a transient temperature analysis enabled to interpret this observation.
Practical significance of the results: NiAl is an extremely useful industrial material with many high temperature applications.