Refractory metal intermetallic in-situ composites for aircraft engines

There has been substantial progress in the development of properties in high-temperature in-situ composites during the last five years. For example, fracture-toughness values in excess of 20 MPa root m have been reported in silicide-based composites toughened by niobium-based metallic solid solutions. These composites also have oxidation resistances and rupture lives comparable to those of single-crystal superalloys for temperatures up to 1,150 degrees C. In this article, fracture toughness, oxidation characteristics, high-temperature mechanical behavior, and low-temperature fatigue properties of refractory metal-intermetallic 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.