Фазовая диаграмма системы Nb-Zn

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Nb-Zn (Niobium-Zinc) Z. Moser [65Meu] established the Nb-Zn phase diagram by means of metallography, X-ray diffraction, and vapor pressure studies. There are four high-temperature intermediate phases-NbZn, NbZn1.5, NbZn2, and NbZn3-formed by peritectic reactions at 1120 с 2, 1114 с 2, 1054 с 3, and 1034 с 3 C, and two low- temperature phases-NbZn7 and NbZn15 -also formed by peritectic reactions at 478 and below 429 C. The Nb3Zn phase discovered by [68Hun] is not shown in the assessed diagram. The solubility studies of [61Mar] from 427.9 to 750.7 C and between 0.017 and 0.156 at.% Nb established the low-temperature, high-Zn portion of the Nb-Zn phase diagram. Extrapolation of the solubility data of [61Mar] to higher temperatures also indicates low solubility, which was confirmed by [65Meu]. Zn-type coatings on Nb are known to protect against oxidation and are self- healing. [65Meu] found that NbZn precipitates in NbZn1.5, then NbZn2, and finally NbZn3 on Nb after reacting with Zn vapor and diffusing for 300 h at 870 C. This was confirmed by the diffusion studies of [61See] on Nb-Zn dip- coated specimens for 48 h in air at 980 C. From microstructure examination of heat treated Zn specimens containing 0.35 to 11 at.% Nb, NbZn15 and NbZn7 were identified by [65Meu]. 61Mar: A.E. Martin, J.B. Knighton, and H.M. Feder, J. Chem. Eng. Data, 6, 596- 599 (1961). 61See: R.E. Seebold and L.S. Birks, J. Nucl. Mater., 3, 260-266 (1961). 64Wen: Z. Wendorff and W. Piotrowski, Hutnik, 31, 246-249 (1964) in Polish. 65Meu: R.A. Meussner and R.J. Goode, Trans. Metall. Soc. AIME, 233, 661-671 ( 1965). 66Gur: V.N. Gurin, A.P. Obukhov, Z.P. Terent'eva, and I.R. Bashinskaya, Izv. Akad. Nauk SSSR, Met., 6, 142-145 (1966) in Russian; TR: Russ. Metall., 6, 78- 79 (1966). 68Hun: C.R. Hunt and A. Raman, Mater. Res. Bull., 3, 489-494 (1968). Submitted to the APD Program. Complete evaluation contains 2 figures, 3 tables, and 15 references. Special Points of the Nb-Zn System