Фазовая диаграмма системы Be-Nb

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Be-Nb (Beryllium-Niobium) H. Okamoto and L.E. Tanner The assessed phase diagram for the Be-Nb system is based primarily on the liquidus boundaries proposed by [60Kri] (for the range 0 to 50 at.% Nb) and the invariant temperatures reported by [68Ray], with review of the experimental data of [60Gel], [63Arz], and [76Ana]. However, the phase relations proposed in this evaluation differ significantly from both [60Kri] and [68Ray]. The initial slope of the L/[L + (Nb)] liquidus in the assessed diagram is estimated from the [L + (Nb)]/(Nb) solidus slope. Six stable intermediate phases have been reliably established: (1) Be12Nb ( Mn12Th type); (2) Be17Nb2 (proto-type); (3) Be5Nb (CaCu5 type); (4) Be3Nb ( prototype); (5) Be2Nb (Cu2Mg type); and (6) Be2Nb3 (Si2U3 type). The value given by [60Kri] for the melting point of Be12Nb is shown as the L + Be17Nb2 = Be12Nb peritectic temperature in the assessed diagram. The assessed congruent melting point of Be17Nb2 is 1800 с 50 C [60Kri]. The melting point of Be2Nb3 [60Zal] is controversial. [60Kri] reported that the liquidus within this composition range (between ~50 to 80 at.% Nb) was uncertain. More reliable results were obtained by [68Ray], and their pro-posed diagram for the range ~50 to 100 at.% Nb is adopted in the assessed diagram. The melting point of bBe and the bBe = aBe allotropic transformation temperature are 1289 с 5 and 1270 с 6 C, respectively [Melt]. The melting point of Nb is 2469 C [Melt]. [50Kau] reported that a 1.1 at.% Nb alloy as cooled from the melt was two phase. From the study of a series of Be-transition metal systems, [80Tan] pre-dicted the possible existence of a stable or metastable phase, BeNb, with either the CsCl-type or CrB-type crystal structure. The existence of Be19Nb2 was suggested by [64Sto] and [65Bea], between Be12Nb and Be17Nb2, and with a melting point of ~1700 C. [61CEN] reported that Be19Nb2 would be commercially available as a high-temperature- and oxidation- resistant compound. No subsequent reports re-garding this phase are available. Another phase, with a fcc structure, was found by [60Kri] and [60Zal], always in the presence of Be2Nb3. It may be a stable binary phase, but more likely is stabilized by an oxygen and/or nitrogen impurity (e.g., an h phase as found recently in Be-Ti alloys [79Gie]. 50Kau: A.R. Kaufmann, P. Gordon, and D.W. Lillie, Trans. ASM, 42, 785-844 ( 1950). 55Kri: P.I. Kripyakevich and E.I. Gladyshevskii, Dokl. Akad. Nauk SSSR, 103, 82-84 (1955) in Russian. 57Bat: F.W. von Batchelder and R.F. Raeuchle, Acta Crystallogr., 10(10), 648- 649 (1957). 59San: D.E. Sands, A. Zalkin, and O.H. Krikorian, Acta Crystallogr., 12(6), 461-464 (1959). 59Zal: A. Zalkin, D.E. Sands, and O.H. Krikorian, Acta Crystallogr., 12(10), 713-715 (1959). 60Gel: S.H. Gelles and J.J. Pickett, U.S. Energy Comm., NMI-1218, 44 p (1960). 60Kri: O.H. Krikorian, U.S. At. Energy Comm. UCRL-5989-T, 9 p (1960). 60Zal: A. Zalkin, D.E. Sands, and O.H. Krikorian, Acta Crystallogr., 13, 160 ( 1960). 61Arz: P.M. Arzhanyi, R.M. Volkova, and D.A. Prokoshkin, Izv. Acad. Nauk SSSR, Otd. Techn. Nauk, Met. Toplivo, (2), 119-121 (1961) in Russian. 61CEN: Chem. Eng. News, 39(46), 65-66 (1961). 63Arz: P.M. Arzhanyi, R.M. Volkova, and D.A. Prokoshkin, Dokl. Acad. Nauk SSSR, 150, 96-98 (1963) in Russian; TR: Dokl. Chem., Proc. Acad. Sci. USSR, 150, 388-389 (1963). 64Sto: A.J. Stonehouse, R.M. Paine, and W.W. Beaver, Metall. Soc. AIME, Inst. Met. Div., Spec. Rep. Ser., No. 13, 445-455 (1964). 65Bea: W.W. Beaver, A.J. Stonehouse, and R.M. Paine, Metals for the Space Age, Plansee Proceedings 1964, Metallwerk Plansee AG, Reutte/Tirol, 682-700 (1965). 68Ray: I.I. Rayevskiy and A.T. Grigor'yev, Izv. Akad. Nauk SSSR, Met., (5), 198-202 (1968) in Russian; TR: Russ. Metall., (5), 134-136 (1968). 75Stu: M. Stumke and G. Petzow, Z. Metallkd., 66(5), 292-297 (1975) in German. 76Ana: V.M. Anan'in, V.P. Gladkov, A.V. Svetlov, D.M. Skorov, and V.I. Tenishev, At. Energ. USSR, 40(3), 256-257 (1976) in Russian; TR: Sov. J. At. Energy, 40(3), 304-305 (1976). 77Ray: G.V. Raynor, J. Less-Common Met., 53(2), 167-176 (1977). 79Gie: B.C. Giessen, J.C. Barrick, and L.E. Tanner, Mater. Sci. Eng., 38, 211- 216 (1979). 80Tan: L.E. Tanner, Acta Metall., 28(12), 1805-1816 (1980). Published in Phase Diagrams of Binary Beryllium Alloys, 1987. Complete evaluation contains 1 figure, 5 tables, and 29 references. 1