Фазовая диаграмма системы Be-Ca

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Be-Ca (Beryllium-Calcium) V.P. Itkin, C.B. Alcock, H. Okamoto, and L.E. Tanner The assessed (calculated) diagram for the Be-Ca system is based on the experimental data of [67Kle] and [68Pot] and was obtained by thermodynamic modeling. The nature of the reaction between (aCa) and Be13Ca is unknown. Therefore, a dashed line was drawn at the temperature of the a = b transformation in Ca in the assessed diagram. Only small portions of the phase diagram have been investigated<294>the terminal solutions, (Be) and (Ca), and the compound Be13Ca. The thermodynamic properties of the Be-Ca phases have not been measured. The calculated temperatures and compositions must be regarded as qualitative because the information on which the assumed thermodynamic model is based is very limited. Nevertheless, the calculated phase diagram gives more information about the system than the experimental data. According to [50Kau] the solid solubility of Ca in (Be) is less than 0.23 at.%. The solubility of Be in both forms of (Ca) is not known. The presence of Be13Ca was confirmed in several investigations. [67Kle] showed that Be13Ca is solid at 1450 C and reacts with a tantalum crucible at 1500 C. Therefore, they suggested the existence of liquid immiscibility above this temperature. Because the boiling point of Ca is relatively low (1440 с 10 C), it is reasonable to assume that Be13Ca decomposes into Be(L) + Ca(g) at high temperatures. 50Kau: A.R. Kaufmann, P. Gordon, and D.W. Lillie, Trans. ASM, 42, 785-844 ( 1950). 55Bak: T.W. Baker and R.W. Williams, Acta Crystallogr., 8(8), 519 (1955). 62Bak: T.W. Baker, Acta Crystallogr., 15, 175-179 (1962). 67Kle: W. Klemm and D. Kunze, The Alkali Metals, Proc. Int. Symp. Nottingham 1966, Chem. Soc., London, Spec. Publ. 22, 3-22 (1967). 68Pot: C. Potard, G. Bienvenu, and B. Schaub, Thermodynamics of Nuclear Materials, 1967, Int. At. Energy Agency, Vienna, 795-807 (1968) in French. Published in Phase Diagrams of Binary Beryllium Alloys, 1987. Complete evaluation contains 4 figures, 4 tables, and 10 references. Special Points of the Be-Ca System