Фазовая диаграмма системы Be-W

К оглавлению: Другие диаграммы (Others phase diargams)

Be-W (Beryllium-Tungsten) H. Okamoto and L.E. Tanner The Be-W system is characterized by the presence of three intermediate phases- Be22W, Be12W, and Be2W. Although the crystal structures of these phases have been well established, the temperatures and compositions of the phases were reported only qualitatively in the form of a partial phase diagram [63Gol]. The assessed phase diagram is based on the same experimental data, supplemented by the observations of [59Pai]. The melting point of bBe and the bBe = aBe allotropic transformation temperature are 1289 с 4 and 1270 с 6 C, respectively [Melt]. Phase relationships between L, (bBe), and (aBe) are not known. Metallographic examinations by [50Kau] indicate that the solubility limit of W in (Be) is less than 0.05 at.%. Be22W forms from the melt by the eutectic reaction L + Be12W = Be22W. The superconducting transition temperature of Be22W is 4.12 K [67Buc]. The accepted stoichiometry, Be12W, was established by [57Bat] and [57Gla]. According to [59Pai], an alloy of this composition shows incipient melting at 1750 and 1790 C. This is likely to correspond to a two-phase field above a peritectic temperature. The assessed liquidus and peritectic reactions have been drawn according to this observation. The melting point of W is 3422 C [Melt]. The solubility of Be in (W) is about 3 at.% at 1000 to 1300 C and about 5 at.% at the L = Be2W + (W) eutectic temperature (estimated to be 2100 с 50 C) [63Gol, 66Gol]. The eutectic composition is reported as ~60 at.% W [63Gol, 66Gol]. 50Kau: A.R. Kaufmann, P. Gordon, and D.W. Lillie, Trans. ASM, 42, 785-844 ( 1950). 57Bat: F.W. von Batchelder and R.F. Raeuchle, Acta Crystallogr., 10(10), 648- 649 (1957). 57Gla: E.I. Gladyshevskii and P.I. Kripiakevich, Kristallografiya, 2, 742-745 ( 1957) in Russian; TR: Sov. Phys. Crystallogr., 2, 730-733 (1957). 59Pai: R.M. Paine, A.J. Stonehouse, and W.W. Beaver, WADC Tech. Rep., Part 1 ( 1959). 63Gol: H.J. Goldschmidt, E.A. Catherall, W.M. Ham, and D.A. Oliver, Tech. Rep. ASD-TDR-62-25, Part II (AD418033), 37-70 (1963). 66Gol: H.J. Goldschmidt and W.H. Ham, J. Less-Common Met., 10(1), 57-65 (1966). 67Buc: E. Bucher and C. Palmy, Phys. Lett. A, 24(7), 340-341 (1967). Published in Phase Diagrams of Binary Beryllium Alloys, 1987, and Bull. Alloy Phase Diagrams, 7(4), Aug 1986. Complete evaluation contains 1 figure, 1 table, and 20 references. 1