Фазовая диаграмма системы Be-Sr

К оглавлению: Другие диаграммы (Others phase diargams)

Be-Sr (Beryllium-Strontium) H. Okamoto, L.E. Tanner, V.P. Itkin, and C.B. Alcock The assessed phase diagram for the Be-Sr system is drawn according to a thermodynamic model based on the experimental work of [67Kle]. The phase in equilibrium with the Sr-rich liquid is Be13Sr. Because of the low boiling point of Sr, the gas phase probably interacts with Be13Sr, as shown in the assessed diagram. The thermodynamic properties of the Be-Sr system are considered similar to those of the Be-Ca and Ba-Be systems because of the similarity in the properties of elements and intermediate phases. Therefore, the same approach has been used for the thermodynamic modeling of this system. However, the liquidus data provided by [67Kle] for 900 C has been disregarded in the present evaluation, because it disturbs the systematic variation of the liquidus slopes in the Be-alkaline earth systems and also because it demands an unrealistic thermodynamic parameter for Be13Sr. In addition, the following assumptions were made: the liquid is a subregular solution; the DCp values between gas, liquid, and solid states are zero for pure elements and Be13Sr; and the volume solubility of Be13Sr in liquid Be is the same as that of Be13Ca in a low concentration range. (This last assumption is based on the fact that Be13Sr and Be13Ca have the same structure and differ only slightly in molecular size.) The assessed diagram may be considered qualitative, especially at high temperatures. [64Mat] obtained Be13Sr by heating a mixture of 98% Be and 99.5% SrO in vacuum at 1200 to 1250 C. [67Kle] pointed out that this compound has a high melting temperature. The reaction between L, Be13Sr, and (bSr) is unknown. The allotropic transformation, melting point, and boiling point temperatures of Be are 1270 с 6 C, 1289 с 5 C, and 2472 C, respectively [Melt]. The transformation, melting point, and boiling point temperatures of Sr are 547, 769, and 1382 C, respectively [Melt]. 64Mat: N.N. Matyushenko, L.F. Verkhorobin, and V.N. Karev, Kristallografiya, 9( 2), 273-275 (1964) in Russian; TR: Sov. Phys. Crystallogr., 9(2), 213-214 ( 1964). 67Kle: W. Klemm and D. Kunze, Chem. Soc., London, Spec. Publ. 22, The Alkali Metals, Proc. Int. Symp., Nottingham, 3-22 (1966). Published in Phase Diagrams of Binary Beryllium Alloys, 1987. Complete evaluation contains 1 figure, 2 tables, and 3 references. 1