REFRACTORY-METAL INTERMETALLIC IN-SITU COMPOSITES FOR AIRCRAFT ENGINES

There has been substantial progress in the development of properties i n high-temperature in-situ composites during the last five years. For example, fracture-toughness values in excess of 20 MPa root m have bee n reported in silicide-based composites toughened by niobium-based met allic solid solutions. These composites also have oxidation resistance s and rupture lives comparable to those of single-crystal superalloys for temperatures up to 1,150 degrees C. In this article, fracture toug hness, oxidation characteristics, high-temperature mechanical behavior , and low-temperature fatigue properties of refractory metal-intermeta llic composites (RMICs) are described and compared to air-craft-engine fundamental material property goals for the next millennium. Further avenues toward the pursuit of these goals are outlined.