Фазовая диаграмма системы Cr-Ni

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Cr-Ni (Chromium-Nickel) P. Nash The Ni-Cr system is characterized by a eutectic reaction and the peritectic formation of Ni2Cr. The generally accepted form of the diagram [Hansen, Metals, Hultgren,B] consists of a simple eutectic at high temperature with an ordering reaction at low temperature, around Ni2Cr. Reports of polymorphism in Cr and of s phase in the Ni-Cr system have prompted the proposal of more complex forms of the diagram. However, no conclusive evidence for any polymorphic transformations in Cr exists, and the structure of pure Cr has presently been accepted as bcc up to the melting point. The data of [37Jen] have been used to draw the (Ni) liquidus and solidus. The ( Cr) liquidus and solidus are based on the data of [62Sve]. The eutectic composition (56 at.% Cr) was determined by graphical interpolation. Problems encountered in establishing the solid-state phase equilibria at the Cr-rich end of the diagram are due to the dramatic decrease in solubility of Ni in (Cr) with temperature. Determination of the (Ni) solvus presents some problems at low temperature (<600 C) because of ordering effects and difficulties in achieving equilibrium. The (Ni) solvus is based on the work of [58Bae] and [82Kar] below 700 C and on the work of [61Bec] above 700 C. There is evidence that the ordering reaction occurring around Ni2Cr is a first- order reaction. From the data on the (Ni) solvus and the ordering reaction, it is feasible that this feature is best represented by the peritectoid decomposition of (Ni) + (Cr) to g<291> (the ordered Ni2Cr phase) at 590 C, as shown in the assessed diagram. However, this must be considered tentative. During a study of fine Cr particles produced by evaporation and condensation in argon at low pressure, [67Kim] observed a new structure, designated d. dCr has a primitive cubic structure with eight atoms per unit cell. This phase was found together with aCr only when very pure argon was used. [72Yuk] also found dCr in powders produced by evaporation of Ni-Cr alloys. The occurrence of the dCr phase in thin films seems highly dependent on substrate temperature and type and evaporation rates. [51Sul] predicted the formation of s phase in binary Ni-Cr alloys at about 71. 8 at.% Cr. There appears to be some correlation between the Curie temperature of the ferromagnetic component in binary Cr systems and the upper temperature limit of stability. Thus, in the Ni-Cr system, the s phase may not be stable above about 600 C, and at such low temperatures, there may be kinetic problems in nucleating the phase. s phase has also been observed in evaporated Ni-Cr alloys. 30Sad: C. Sadron and P. Weiss, Acad. Sci. Compt. Rend., 190, 1339-1340 (1930) in French. 37Jen: C.H.M. Jenkins, E.H. Bucknall, C.R. Austin, and G.A. Mellor, J. Iron Steel Inst., 136, 187-220 (1937). 37Mar: V. Marian, Ann. Phys., 7, 459-527 (1937) in French. 51Sul: A.H. Sully, J. Inst. Met., 80, 173-179 (1951-52). 58Bae: H.G. Baer, Z. Metallkd., 49, 614-622 (1958) in German. 61Bec: C.J. Bechtoldt and H.C. Vacher, Trans. AIME, 221, 14-18 (1961). 62Sve: V.N. Svechnikov and V.M. Pan, Sb. Nauchn. Rabot. Inst. Metallofiz., Akad. Nauk Ukr. SSR, (15), 164-178 (1962). 67Kim: K. Kimoto and I. Nishida, J. Phys. Soc. Jpn., 22(3), 744-756 (1967). 72Bes: M.J. Besnus, Y. Gottehrer, and G. Munschy, Phys. Status Solidi (b), 49, 597-607 (1972). 72Yuk: N. Yukawa, M. Hilda, T. Imura, M. Kawamura, and Y. Mzuno, Metall. Trans. , 3, 887-895 (1972). 81Tan: H. Tange, T. Yonei, and M. Goto, J. Phys. Soc. Jpn., 50(2), 454-460 ( 1981). 82Kar: L. Karamazin, Mater. Sci. Eng., 54, 247-256 (1982). 82Sim: M.A. Simpson and T.F. Smith, Aust. J. Phys., 35, 307-319 (1982). Published in Phase Diagrams of Binary Nickel Alloys, 1991. Complete evaluation contains 4 figures, 4 tables, and 128 references. 1