Фазовая диаграмма системы C-Y

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C-Y (Carbon-Yttrium) K.A. Gschneidner, Jr. and F.W. Calderwood The assessed phase diagram for the Y-C system is based primarily on the work of [71Sto] and [74Car]. Above 900 C, the Y-rich g phase has a cubic structure of the Fe4N type. Below ~900 C, ordering of C atoms creates the CdCl2-type trigonal structure for Y2C. A maximum occurs in the solidus at 2000 с 15 C and 30 at.% C, and a minimum occurs at 1805 с 15 C near 54 at.% C. At 1527 C, bY15C19 decomposes to form the cubic g phase (Fe4N-type Y3C) and bY2C3, the structure of which is not known. Y15C19 undergoes a polymorphic transformation at 1304 с 20 C. The aY15C19 phase has the tetragonal Sc15C19- type structure. No information is available on the bY15C19 structure. bY2C3 forms from the g phase solid solution at 1645 C. The a = b transformation temperature for Y2C3 is 1186 C. No structural information exists on the two forms of Y2C3. [69Kru] reported that a metastable Y sesquicarbide with a bcc Pu2C3-type structure formed at high temperature under high pressure. The melting temperature of "bYC2" is 2415 C. The eutectic between "bYC2" and (C) is placed at 2290 C. The composition of the eutectic is not known. aYC2 has been observed to have the tetragonal CaC2-type structure. The high-temperature form was reported to be cubic [71Sto], but no structural data have been reported. bYC2 is assumed to have the cubic CaF2-type structure. The a = b transformation temperature is 1324 C. 69Kru: M.C. Krupka, A.L. Giorgi, N.H. Krikorian, and E.G. Szklarz, J. Less- Common Met., 17, 91 (1969). 71Sto: E.K. Storms, High Temp. Sci., 3, 99 (1971). 74Car: O.N. Carlson, R.R. Lichtenberg, and J.C. Warner, J. Less-Common Met., 35, 275 (1974). Published in Bull. Alloy Phase Diagrams, 7(6), Dec 1986. Complete evaluation contains 2 figures, 1 table, and 34 references. 1