Фазовая диаграмма системы Be-Zn

К оглавлению: Другие диаграммы (Others phase diargams)


Be-Zn (Beryllium-Zinc) H. Okamoto and L.E. Tanner The assessed phase diagram for the Be-Zn system is based on the experimental data of [62Joh]. The limited data showed strong similarities to the Be systems with Ga, In, Sn, and Bi. The existence of extensive liquid immiscibility and a monotectic reaction at elevated temperatures have been proposed for these systems, although critical temperatures and compositions are not known. A eutectic-type structure was observed at the interface of Be and Zn when sintered at 600 to 700 C [64Wen]. This suggests a eutectic reaction in proximity to the Zn-rich end of the assessed phase diagram. The liquidus trend near the eutectic has been used to model the liquid immiscibility. The critical point of the liquid miscibility gap is not satisfactorily determined due to excessive extrapolation. Therefore, the assessed diagram should be considered qualitative. The eutectic temperature has been estimated as 0.2 C lower than the melting point of Zn by assuming that the eutectic composition is 99.96 at.% Zn and that the (Zn) phase has no solubility range. There are no intermediate phases in the Be-Zn system [60Yan, 61Nic, 64Wen]. The melting point of bBe and the bBe = aBe allotropic transformation temperature are 1289 с 5 and 1270 с 6 C, respectively [Melt]. The solubility of Zn in (Be) is small; [62Joh] measured the solubility of Be in liquid Zn; these values were expressed as lnX = 2.788 - 7444/T, where X is the mole fraction of Be and T is in K. [68Dub] obtained similar results. An alloy of 0. 08 at.% Zn was prepared by adding Zn in molten Be [50Kau]. Lattice parameter measurements did not reveal Zn solubility in (Be) [60Yan]. The melting point of Zn is 419.58 C [Melt]. The boiling point of Zn (906 C) is lower than the melting point of Be, which made the investigation of the Be- Zn system difficult [62Jor]. [61Nic] reported that 23 at.% Be can be dissolved in liquid Zn, from experiments involving deposition of molten Be salt on a molten Zn cathode at 700 to 900 C. This is considerably higher than was observed by [62Joh] and [68Dub]. 50Kau: A.R. Kaufmann, P. Gordon, and D.W. Lillie, Trans. ASM, 42, 785-844 ( 1950). 60Yan: F.M. Yans, U.S. At. Energy Comm. NMI-1240, 41 p (1960). 61Nic: I.F. Nichkov and M.V. Smirnov, Izv. V.U.Z. Tsvetn. Metall., 4(3), 105- 107 (1961) in Russian. 62Joh: I. Johnson and K.E. Anderson, in Chemical Engineering Division Summary Report, U.S. At. Energy Comm. ANL-6543, 92-93 (1962). 62Jor: C. Jordan, Tech. Rept. ASD-TDR-62-181 (AD 284409), 33 p (1962). 64Wen: Z. Wendorff and W. Piotrowski, Hutnik, 31(7-8), 246-249 (1964) in Polish. 68Dub: V.A. Dubinin, V.A. Lebedev, and I.F. Nichkov, Zh. Fiz. Khim., 42(3), 678-681 (1968) in Russian; TR: Russ. J. Phys. Chem., 42(3), 356-358 (1968). Published in Phase Diagrams of Binary Beryllium Alloys, 1987. Complete evaluation contains 3 figures, 3 tables, and 8 references. 1