Фазовая диаграмма системы Ni-Yb

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Ni-Yb (Nickel-Ytterbium) P. Nash The assessed Ni-Yb phase diagram is based primarily on [73Pal], with review of the data of [72Bus]. The existence of five intermediate phases-NiYb, Ni2Yb, Ni3Yb, Ni5Yb, and Ni17Yb2-has been established, as well as very restricted terminal solid solubilities. A region of liquid immiscibility has been found for Yb-rich alloys, although its extent has not been determined other than at the monotectic temperature (1025 C), where it extends from 54 to 91 at.% Yb. The measured melting point and bcc = fcc transformation temperature for elemental Yb used by [73Pal] were 825 and 740 C, which indicate the presence of impurities in their Yb starting material. This presents a problem in evaluating the [73Pal] diagram. If it is assumed that the form of the diagram of [73Pal] at the Yb-rich end is correct, then little more can be said than that the eutectic temperature lies between 819 and 795 C. For the purpose of drawing the assessed diagram, the eutectic temperature has been taken as 805 C, and the (gYb) = (bYb) + NiYb eutectoid temperature as 794 C. [73Pal] determined the monotectic temperature as 1025 C and reported the miscibility gap to extend from 54 to 91 at.% Yb. The miscibility gap phase boundary was not determined. The data between 0 and 25 at.% Yb should be viewed with some caution ( particularly liquidus data), because it is likely that Mo contaminated the alloys. However, in the absence of any other data, the results of [73Pal] have been used to construct the assessed diagram. Attempts to produce a single-phase Ni7Yb2 alloy (a phase commonly observed in RE-Ni systems) were unsuccessful. However, X-ray lines were observed that belonged to a hexagonal phase with a large c/a ratio. This result is similar to that observed in the Er-Ni system and was confirmed by [73Pal]. [72Bus] suggested that the stability of the Ni7RE2 phase depends on the size of the RE element, becoming unstable when the RE element becomes too small. To check this, [72Bus] investigated the alloy composition Lu2Ni7 and found that no phase with that composition exists, supporting the proposed theory. Thus, the stability of Ni7Yb2 remains questionable, and it has not been included in the assessed diagram. [73Pal] indicated a transformation in NiYb at 1000 C. [72Bus] and [73Pal] concluded from their work that no Ni-Yb intermediate phases are formed with compositions greater than 50 at.% Yb. This is explained on the basis that Yb is divalent at Yb-rich compositions and trivalent for Ni-rich compositions. The magnetic properties of several Ni-Yb intermediate phases were studied experimentally by [62Nes], [63Ble1], [67Now], [68Car], [73Now], and [77Kla] and theoretically by [63Ble2]. 60Has1: S.E. Haszko, Trans. AIME, 218, 763 (1960). 60Has2: S.E. Haszko, Trans. AIME, 218, 958 (1960). 62Nes: E.A. Nesbitt, H.J. Williams, J.H. Wernick, and R.C. Sherwood, J. Appl. Phys., 33(5), 1674-1678 (1962). 63Ble1: B. Bleaney, Proc. Phys. Soc., 82, 469-471 (1963). 63Ble2: B. Bleaney, Proc. Phys. Soc. A, 276, 28-38 (1963). 67Now: I. Nowik, S. Ofer, and J.H. Wernick, Phys. Lett. A, 24(2), 89-90 (1967). 68Car: P.D. Carfagna and W.E. Wallace, J. Appl. Phys., 39(11), 5259-5262 (1968) . 69Lem: R. Lemaire and D. Paccard, Bull. Soc. Fr. Min. Cristallogr., 92, 9-16 ( 1969) in French. 72Bus: K.H.J. Buschow, J. Less-Common Met., 26, 329-333 (1972). 73Now: I. Nowik and B.D. Dunlap, J. Phys. Chem. Solids, 34, 465-471 (1973). 73Pal: A. Palenzona and S. Cirafici, J. Less-Common Met., 33, 361-367 (1973). 77Kla: J.C.P. Klaasse, W.C.M. Mattens, F.R. De Boer, and P.F. De Chatel, Physica, 86-88B, 234-236 (1977). Published in Phase Diagrams of Binary Nickel Alloys, 1991, and Bull. Alloy Phase Diagrams, 10(2), Apr 1989. Complete evaluation contains 1 figure, 2 tables, and 18 references. 1