Microstructure and strength of powder metalurgically processed niobium aluminide base intermetallic composites

Niobium aluminide base intermetallic composites are one of the candidate materials for application at elevated temperatures in aerospace and aircraft industry because of the light-weight, superior high-temperature strength and capability of alloying to improve the inferior properties. In addition it is possible to incorporate ductile niobium rich solid solution in the intermetallic niobium aluminide matrix to improve the ductility and toughness, the most deficient property. of many' intermetallic materials. An attempt is made to prepare niobium aluminide in-situ composites with fine ceramic reinforcements to compensate the strength sacrificed due to introduction of the ductile niobium rich solid solution phase. The Nb3Al/Nb-ss and Nb3Al/Nb-ss with niobium. boride or carbide were processed from the high purity elemental powders after ball milling under inert atmosphere. Cold compacted parts are hot. pressed in high vacuum and heat treated. The microstructural characterization was performed using x-ray diffraction electron probe microanalysis and scanning electron microscope. The current process route has enabled producing niobium aluminide base composites with very less amount of impurity levels and negligible aluminium loss encountered in processing. Tensile tests conducted at 1573 K showed high strength above 190 Mpa with good ductility. The strength and ductility at elevated temperatures depends on amount of ceramic and intermetallic; phases present.