Фазовая диаграмма системы Nb-V

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Nb-V (Niobium-Vanadium) J.F. Smith and O.N. Carlson Nb and V form a continuous series of solid solutions, with a minimum melting point near the V-rich end of the system. The assessed phase diagram is based on the diagram proposed by [69Rud], with review of the work of [54Wil] and [ 60Bar]. It has been obtained by thermodynamic modeling of the experimental data. [85Koc] measured the liquidus and solidus temperatures across the system by means of differential thermal analysis. Their results agree as to the existence of a minimum near 25 at.% Nb, and their solidus line is in accord with both the diagram of [69Rud] and the calculated diagram. The melting point of V reported by [85Koc] is a bit low at 1885 C, but the melting point of Nb at 2468 C is very close to the accepted value. The separation of the liquidus and solidus reported by [85Koc] is in much better agreement with the calculated diagram than with the diagram of [69Rud]. Indeed, the liquidus and solidus separation on the V-rich side of the minimum [69Rud] is almost too small to measure and is thus in very close accord with the calculated diagram. Superconducting studies at very low temperatures show persistence of the continuous bcc solid solution to the vicinity of absolute zero. [54Wil] performed long-term anneals (170 h at 900 C) on several alloys in the composition range 20 to 55 at.% Nb and did not observe a second phase in the microstructure. Likewise, X-ray diffraction patterns of filings from the same alloys after annealing at 650 C for 113 h failed to show any phase other than the bcc solid solution. Work with alloys containing up to 56 at.% Nb showed microstructures indicative of continuous solid solution. 54Wil: H.A. Wilhelm, O.N. Carlson, and J.M. Dickinson, Trans. AIME, 200, 915- 918 (1954). 60Bar: V.V. Baron, K.N. Ivanova, and E.M. Savitskii, Izv. Akad. Nauk Otd. Tekhn. Nauk, Met. Topl., (4), 143-149 (1960) in Russian; TR: Russ. Met. Fuels, (4), 105-107 (1960). 69Rud: R. Rudy, Compendium of Phase Diagram Data, Air Force Materials Laboratory, Part V, 110-111 (1969). 85Koc: Yu.A. Kocherzhinsky, V.I. Vasilenki, and O.G. Kulik, Thermochim. Acta, 93, 649 (1985). Published in Phase Diagrams of Binary Vanadium Alloys, 1989, and Bull. Alloy Phase Diagrams, 4(1), Jun 1983. Complete evaluation contains 3 figures, 3 tables, and 16 references. 1