Фазовая диаграмма системы Be-U

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Be-U (Beryllium-Uranium) H. Okamoto, L.E. Tanner, and D.E. Peterson The assessed phase diagram for the Be-U system is a combined diagram based partially on the experimental work of [53Buz] and partially on a thermodynamic model. The transition temperatures of pure elements given by [53Buz] are lower than the assessed values by 0 to 11 C, but no correction has been attempted. Because most of the temperatures were measured using an optical pyrometer, the accuracy may not be very high. The scatter in liquidus data on the U-rich side of Be13U was smoothed in the original paper of [53Buz] (see [Hansen]). The phase diagram of [53Buz] indicated liquid immiscibility of about 1.5 at.% width with a monotectic point at ~2.5 at.% U (~2.2 at.% U in the assessed diagram) and 1550 C. Its presence has never been refuted or confirmed experimentally and was questioned by [Hansen]. The form of this miscibility gap is unusual, based on implications regarding thermodynamic behavior. The presence of such a miscibility gap may be possible if there is a rather strong Be13U-type clustering tendency in the liquid state. Further experimental studies on the phase boundaries and thermodynamic properties for this composition range are obviously needed. However, because of the lack of further work in this region, the diagram of [53Buz] is accepted in the assessed diagram. Part of the liquidus between Be13U and the L = Be13U + (gU) eutectic in the assessed diagram is drawn according to the present thermodynamic model. This model provides a possible alternative liquidus boundary for the composition range between U and Be13U. [49Bae] suggested that Be13U has a small homogeneity range, which could explain the lattice parameter variations observed by [46Gor]. Because no further details are available, this phase is shown as a line compound in the assessed diagram. No solid solubility of U in (Be) was observed [50Kau, 53Buz]. The solubility of Be in (bU) and (aU) was not observed [53Buz]. However, 1.09 to 2.04 at.% (0. 042 to 0.079 wt.%) Be is dissolved in (gU) at 1075 C [53Buz]. [58Rou] reported that the solid solubility of Be in U is between 2.8 and 8.4 at.%. The solubility limit of Be in (gU) is tentatively shown at 2 at.% in the assessed diagram. The Be13U liquidus curve on the U-rich side has a sigmoidal shape, indicating that metastable liquid immiscibility could exist at lower temperatures, although this has not been verified experimentally. Such a calculated miscibility gap and its spinodal curve based on available thermochemical data are shown in the assessed diagram. The magnetic susceptibility of Be13U was measured [71Tro] in the temperature range between 4.2 and 1000 K. The effective magnetic moment is 3.4 mB. 46Gor: E. Gordon, Manhattan Project Report CT-3459 (1946), as quoted in [ Hansen]. 49Bae: N.C. Baenziger and R.E. Rundle, Acta Crystallogr., 2(4), 258 (1949). 50Kau: A.R. Kaufmann, P. Gordon, and D.W. Lillie, Trans., ASM, 42, 785-844 ( 1950). 52Koe: W.C. Koehler, J. Singer, and A.S. Coffinberry, Acta Crystallogr., 5(3), 394 (1952). 53Buz: R.W. Buzzard, J. Natl. Bur. Standards, 50(2), 63-67 (1953). 58Rou: F.A. Rough and A.A. Bauer, in Constitution of Uranium and Thorium Alloys, Battelle Memorial Institute, Report No. BMI-1300, 14-15 (1958). 59Iva: M.I. Ivanov and V.A. Tumbakov, At. Energy, 7(1), 33-35 (1959) in Russian; TR: Sov. J. At. Energy, 7(1), 559-561 (1959). 63Han: G.L. Hanna and D.N. Turner, U.S. At. Energy Comm. AAEC/E-102, 16 p ( 1963). 71Tro: R. Troc, W. Trzebiatowski, and K. Piprek, Bull. Acad. Pol. Sci., Ser. Sci. Chim., 19(6-7), 427-432 (1971). 75Buc: E. Bucher, J.P. Maita, G.W. Hull, R.C. Fulton, and A.S. Cooper, Phys. Rev. B, 11(1), 440-449 (1975). 83Ott: H.R. Ott, H. Rudigier, Z. Fisk, and J.L. Smith, Phys. Rev. Lett., 50(20) , 1595-1598 (1983). 84Ste1: G.R. Stewart, Z. Fisk, J.L. Smith, J.O. Willis, and M.S. Wire, Phys. Rev. B, 30(3), 1249-1252 (1984). 84Ste2: G.R. Stewart and A.L. Giorgi, J. Low Temp. Phys., 56(3/4), 379-381 ( 1984). 85Gol: A.I. Goldman, S.M. Shapiro, D.E. Cox, J.L. Smith, and Z. Fisk, Phys. Rev. B, 32(9), 6042-6044 (1985). 85Smi: J.L. Smith, Z. Fisk, J.O. Willis, A.L. Giorgi, R.B. Roof, H.R. Ott, H. Rudigier, and E. Felder, Physica, B, 135, 3-8 (1985). Published in Phase Diagrams of Binary Beryllium Alloys, 1987. Complete evaluation contains 2 figures, 5 tables, and 28 references. Special Points of the Be-U System