DEVELOPMENT OF NIOBIUM ALUMINIDE-BASED COMPOSITES WITH IMPROVED TOUGHNESS USING TREATED REINFORCEMENTS

Many ordered intermetallic compounds exhibit attractive properties for high temperature structural aerospace applications. The major obstacl es limiting the use of these materials are their low ductility and tou ghness at room temperature and poor creep resistance at elevated tempe ratures. In this investigation ''treated'' silicon carbide whisker and niobium particle reinforced niobium aluminide matrix composites have been fabricated by reaction hot pressing in vacuum. Elemental matrix p owders react exothermally and form the niobium aluminide matrix in sit u. A suitable hot pressing cycle has been established for the successf ul development of the niobium aluminide matrix, while reducing adverse reactions between the matrix and the reinforcements. The composites w ith ''treated'' reinforcements are expected to have high resistance to creep at elevated temperatures and they show relatively low hardness and higher toughness in comparison with the composites reinforced with untreated whiskers.