Фазовая диаграмма системы Cu-Sc

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Cu-Sc (Copper-Scandium) P.R. Subramanian, D.E. Laughlin, and D.J. Chakrabarti The assessed Cu-Sc phase diagram is a composite of the available experimental data from [70Sav] and [78Mar]. The assessed equilibrium diagram is drawn from the data of [70Sav], primarily because of the presence of a larger number of data points in their investigation. Because of the lack of experimental data points for the liquidus in the regions L/L + Cu2Sc, L/L + Cu2Sc, and L/L + (Sc) , these phase boundaries were calculated from thermodynamic modeling. Further experimental work needs to be done in the region close to the stoichiometry of Cu2Sc to delineate the L/L + Cu2Sc and Cu2Sc + L/L liquidus boundaries. Elemental melting points have been adjusted in the assessed diagram in accordance with the accepted values listed in [Melt]. The Cu-Sc phase relationships of [70Sav] are in general agreement with those of [78Mar], with the exception of the region 30 to 40 at.% Sc. The major point of contention is the melting behavior of Cu2Sc; [70Sav] reported the peritectic formation of Cu2Sc at 890 C, whereas [78Mar] reported the congruent formation of Cu2Sc at 990 C, as well as the occurrence of a Cu2Sc- CuSc eutectic at 39 at.% Sc and 890 C. In the absence of other experimental phase diagram information, one has to rely on the systematics of alloying behavior of Cu with the rare earths [85Gsc] to resolve the conflicting data. In this context, the melting behavior of Cu2Sc, as reported by [78Mar], is in agreement with the data of Cu2Gd [83Car], Cu2Dy [82Fra], and Cu2Y [61Dom]. The alloying behavior of Sc is expected to be analogous to that of Y and Gd (a member of the heavy lanthanide group). As such, Cu2Sc is accepted as a congruently melting phase, with the melting temperature accepted from [78Mar] as 990 C. The presence of Cu2Sc as a congruently melting phase is corroborated by the results of [84Wat]. [70Sav] reported the terminal solid solubility of Sc in Cu to be ~0.5 at.% Sc and that of Cu in Sc to be <1 at.% Cu. According to [78Mar], the terminal solid solubility of Sc in (Cu) is negligible whereas the solubility of Cu in ( Sc) is estimated to be ~1.6 at.% Cu at 800 C. 61Dom: R.F. Domagala, J.J. Rausch, and G.W. Levinson, Trans. ASM, 53, 137-155 ( 1961). 62Ald: A.T. Aldred, Trans. AIME, 224, 1802-1083 (1962). 67Dwi: A.E. Dwight, J.W. Downey, and R.A. Conner, Jr., Acta Crystallogr., 22, 745-747 (1967). 70Sav: E.M. Savitskii, V.F. Terekhova, R.S. Torchinova, I.A. Markova, O.P. Naumkin, V.E. Kolesnichenko, and V.F. Stroganova, Les Elements des Terres Rares, Vol. 1, Centre National de la Recherche Scientifique, Paris, 47-60 ( 1970) in French. 77Sie: D. Siepler, B. Bremicker, V. Goebel, H. Happel, H.F. Hoenig, and B. Perrin, J. Phys. F, 7(4), 599-611 (1977). 78Mar: V.Y. Markiv, I.S. Gavrilenko, V.V. Pet'kov, and N.N. Bejyavina, Akad. Nauk Ukr. SSR, Metallofiz., 73, 39-45 (1978) in Russian. 82Fra: E. Franceschi, J. Less-Common Met., 87, 249-256 (1982). 83Car: M.M. Carnasciali, S. Cirafici, and E. Franceschi, J. Less-Common Met., 92, 143-147 (1983). 84Wat: S. Watanabe and O.J. Kleppa, Metall. Trans. B, 15, 357-368 (1984). 85Gsc: K.A. Gschneidner, Jr., private communication (1985). Published in Bull. Alloy Phase Diagrams, 9(3a), Aug 1988. Complete evaluation contains 1 figure, 7 tables, and 20 references. Special Points of the Cu-Sc System