Microstructures and mechanical properties of Nb–Ti–C alloys

The microstructures and mechanical properties of a series of ternary Nb–Ti–C alloys have been investigated. The microstructures were characterized using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The alloys contain only two phases: (Nb,Ti)C carbide and Nb solid solution. The solid solution is a ductile phase while the carbides strengthen the alloy. Compression tests were performed at room temperature and 1473 K. All of the alloys showed good ductility at room temperature, and the alloy with 20 at.% Ti and 20 at.% C showed a 0.2% offset yield stress of 197 MPa at 1473 K. The room-temperature and high-temperature strengths increased with increasing Ti and C content, but the room-temperature ductility decreased with increasing C content. The carbides deformed plastically, even at room temperature. Strategies for the future development of these alloys, aimed at balancing the high-temperature strength and room-temperature ductility, are discussed.