Physicochemical fundamentals of designing niobium heat resisting alloys

Principal methods increasing heat resistance of niobium alloys are considered: the solid solution alloying with refractory metals possessing the higher melting temperature than niobium and the hardening with dispersed particles of high-heat and thermodynamically stable compounds of carbide, nitride and oxide type. The Nb-M4-X (where X is an interstitial element) system alloys are related to promising two-phase alloys, which phase diagrams have regions of eutectic crystallization and boundary solid dolutions. In this case niobium or one-phase alloy on its base form quasi-binary system of the eutectic type with the hardening M4X phase. Three promising groups of alloys with different composition are chosen among these alloys: 1) precipitational hardening alloys, which compositions are close to a limiting solubility of a high-heat phase in niobium; 2) dispersion hardening alloys, which compositions are close to a region of preeutectic alloys; 3)eutectic alloys