Фазовая диаграмма системы Cr-Ir

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Cr-Ir (Chromium-Iridium) M. Venkatraman and J.P. Neumann The assessed Cr-Ir phase diagram is based on the experimental data of [73Wat], which are in essential agreement with the earlier solid-state studies of [ 55Rau] and [58Kna]. The diagram is characterized by broad homogeneity ranges of the (Cr) and (Ir) terminal solid solutions and by the presence of three intermediate phases-Cr3Ir, e, and CrIr3. The Cr-Ir phase diagram closely resembles the Cr-Rh diagram. The solidus curves were determined by heating alloy samples to increasingly higher temperatures until evidence for incipient melting could be observed in the microstructure. The estimated accuracy of the solidus data is с50 C. No determination of the liquidus curves was carried out. Cr3Ir forms the cubic A15-type structure, the e phase has a disordered cph structure, and CrIr3 forms the ordered fcc L12-type structure. CrIr3 occurs at the Cr-rich solubility limit of the (Ir) phase in the composition range 71 to 84 at.% Ir [55Rau, 73Wat] at lower temperatures. The formation of the ordered L12 structure cannot be suppressed by quenching from high temperatures [55Rau, 73Wat]. Because the stability range of the phase is not clearly established, it is not shown in the assessed phase diagram. The existence of an unidentified phase at 25 at.% Ir was reported by [58Kna]. This phase has not been observed by other investigators; its existence is highly questionable. The Cr3Ir (A15) phase exhibits a high degree of order [66Wat, 68Reu]; the e ( A3) phase is disordered [55Rau, 73Wat]. Small additions of Ir (1.4 at.%) increase the N‚el temperature of Cr (311.5 K) rapidly to 532 K [80But]. The influence of Ir on the N‚el temperature of Cr is very similar to that of Ru, Rh, and Os. The phase equilibria between the two antiferromagnetic structures, AF1, and AF0, and the paramagnetic structure of the (Cr) solid solution were studied by [80But] from 0 to 0.4 at.% Ir. The ordered CrIr3 phase is ferromagnetic [55Rau, 59Rau, 68Kus]. The Curie temperature of this phase has a value of about 425 K at 71 at.% Ir [68Kus]. Superconductivity has been observed in the Cr3Ir [74Flu] and in the e phase [ 62Mat]. The maximum critical transition temperature is ~0.8 K in both phases. 55Rau: E. Raub and W. Mahler, Z. Metallkd., 46, 210-215 (1955) in German. 58Kna: A.G. Knapton, J. Inst. Met., 87, 28-32 (1958/1959). 59Rau: E. Raub, J. Less-Common Met., 1, 3-18 (1959). 62Mat: B.T. Matthias, T.H. Geballe, V.B. Compton, E. Corenzwit, and G.W. Hull, Jr., Phys. Rev., 128(2), 588-590 (1962). 66Wat: R.M. Waterstrat and E.C. van Reuth, Trans. Metall. Soc. AIME, 236, 1232- 1233 (1966). 68Kus: A. Kussmann, K. MЃller, and E. Raub, Z. Metallkd., 59, 859-863 (1968) in German. 68Reu: E.C. van Reuth and R.M. Waterstrat, Acta Crystallogr. B, 24, 186-196 ( 1968). 73Wat: R.M. Waterstrat and R.C. Manuszewski, J. Less-Common Met., 32, 79-89 ( 1973). 74Flu: R. Flukiger, A. Paoli, and J. Muller, Solid State Commun., 14, 443-447 ( 1974). 80But: A.K. Butylenko and V.V. Nevdacha, Dop. Akad. Nauk Ukr. RSR, Ser. A, (5), 66-69 (1980) in Ukrainian. Published in Bull. Alloy Phase Diagrams, 11(1), Feb 1990. Complete evaluation contains 1 figure, 3 tables, and 17 references. Special Points of the Cr-Ir System