Фазовая диаграмма системы Cr-Os

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Cr-Os (Chromium-Osmium) M. Venkatraman and J.P. Neumann The assessed Cr-Os phase diagram is based primarily on the experimental data of [64Sve]. The diagram is characterized by extensive homogeneity ranges of the (Cr) and (Os) terminal solid solutions and the presence of two intermediate phases, which occur at ~25 and ~33 at.% Os. The assessed diagram is essentially the same as that of [Shunk]. The liquidus and solidus curves are taken from [64Sve]; they were read from a graph with an estimated uncertainty of с20 C. No liquidus and solidus measurements were carried out at compositions >50 at.% Os; the melting point of these alloys is higher than 2000 C. The phase boundaries of the (Cr) and ( Os) phases below 1400 C are a composite of [57Rau] and [64Sve]; their estimated uncertainty is с3 at.%. The existence of the two intermediate phases-Cr3Os and Cr2Os-is firmly established. These phases have the cubic A15 and the tetragonal s-type structure, respectively. The homogeneity range of these phases may be as high as 5 at.%, but the exact determination of the phase boundaries requires further studies. The s phase is more brittle and exhibits a higher hardness than the Cr3Os phase [57Rau, 64Sve]. The Cr-Os phase diagram closely resembles the Cr-Ru diagram; one noticeable difference is the fact that the A15 phase in the Cr-Os system is stable over a wider temperature range than in the Cr-Ru system. Additions of Os increase the N‚el temperature of the (Cr) solid solution from 311.5 K for pure Cr to ~575 K at 2 at.% Os [64Boo, 80But]. The effect of Os on the N‚el temperature of Cr is very similar to that of Re, Rh, and Ru [64Boo]. The A15-type phase Cr3Os is a superconductor [69Bla, 74Flu]. From 26 to 29 at.% Os, the critical superconducting transition temperature (Tc) is about 4 to 5 K. Tc increases slightly with increasing degree of long-range order [69Bla, 74Flu]. The s phase is also a superconductor, with Tc @ 1 K at 33 at.% Os [ 69Bla]. 57Rau: E. Raub, Z. Metallkd., 48, 53-56 (1957) in German. 57Wat: R.M. Waterstrat and J.S. Kasper, Trans. AIME, 209, 872-873 (1957). 58Kna: A.G. Knapton, J. Inst. Met., 87, 28-32 (1958/1959). 58Nev: M.V. Nevitt, Trans. Metall. Soc. AIME, 212, 350-355 (1958). 64Boo: J.G. Booth, Phys. Status Solidi, 7, K157-K160 (1964). 64Sve: V.N. Svechnikov, G.P. Dmitrieva, G.F. Kobzenko, and A.K. Shurin, Dokl. Akad. Nauk SSSR, 158, 668-670 (1964) in Russian; TR: Dokl. Chem., 158, 961-963 (1964). 66Wat: R.M. Waterstrat and E.C. Van Reuth, Trans Metall. Soc. AIME, 236, 1232- 1233 (1966). 68Reu: E.C. van Reuth and R.M Waterstrat, Acta Crystallogr. B, 24, 186-196 ( 1968). 69Bla: R.D. Blaugher, R.E. Hein, J.E. Cox, and R.M. Waterstrat, J. Low Temp. Phys., 1, 539-561 (1969). 74Flu: R. Flukiger, A. Paoli, and J. Muller, Solid State Commun., 14, 443-447 ( 1974). 80Alt: L.M. Alte da Veiga, M.M.R.R. Costa, M.J.M. De Almeida, L.R. Andrade, and A. Matos Beja, Acta Crystallogr. B, 36, 1750-1757 (1980). 80But: A.K. Butylenko, V.V. Nevdacha, and V.A. Chernenko, Ukr. Fiz. Zh. (Russ. Ed.), 25(9), 1424-1426 (1980) in Russian. Published in Bull. Alloy Phase Diagrams, 11(1), Feb 1990. Complete evaluation contains 1 figure, 2 tables, and 20 references. Special Points of the Cr-Os System