REACTIVE SINGERING OF NBAL3

NbAl3 based intermetallic alloys were obtained by reaction sintering of elemental powders. The influence of the powders particle size distribution, the compact composition and the reaction sintering thermal cycle on the sintered pellet porosity, microhardness and microstructure were investigated. Process conditions were carefully controlled for NbAl3 compact composition, which resulted in 96% dense pellets. NbAl3 was the major phase observed in these pellets and Nb2Al was seldom encountered at triple grain boundaries. When the aluminum content was decreased from 75a/o to 42a/o two phases, NbAl3 and Nb2Al, were synthesized simultaneously. The amount of each phase, the porosity and the microhardness of the resulting pellets were dependent on the initial compact composition. An explanation for the reaction sintering process of these niobium aluminides is proposed.