Фазовая диаграмма системы Cu-Sn

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Cu-Sn (Copper-Tin) N. Saunders and A.P. Miodownik The assessed Cu-Sn phase diagram is taken from [44Ray]. The system is characterized by a series of peritectic reactions and the formation of a number of ordered, intermetallic phases. Both the fcc a phase and the bcc b phase dissolve substantial quantities of Sn. The g phase also has a wide range of solubility and is formed by ordering of the b phase. The solid solubility of Cu in Sn at the eutectic temperature is reported to be 0.01 at.% Cu [39Hom]. The z phase is hexagonal and is a superstructure based on the z-AgZn prototype [75Bra]. The exact structure of the e phase is uncertain, but is a large superstructure based on a cph unit cell [Pearson]. The h phase undergoes an ordering change between 186 and 189 C. At low temperatures, its structure can be regarded as a long-period superlattice (LPS) based on the NiAs-type structure and on heating it transforms to the conventional NiAs structure [ 73Gan]. Three types of martensite are formed on quenching from the high-temperature b and g phases-b1‚, b1‚‚, and g1‚. b1‚ martensite has an ordered orthorhombic structure and is found between 13 and 13.8 at.% Sn. During the quench, the high-temperature b phase orders to the D03 structure before the martensite transformation, and therefore, b1‚ inherits this order. b1‚‚ martensite, found between 13.8 and 15 at.% Sn, is a lamellar composite of orthorhombic b1‚ and hexagonal g1‚, with a composition that depends on orthorhombic distortion. g1‚ martensite, formed between 15 and 15.8 at.% Sn, is a twinned cph structure with inherited order from the D03 parent phase. It is possible to extend the range of b1‚ martensite to 11.8 at.% Sn by rapid quenching from the melt [ 70Van]. Between 16 and ~25 at.% Sn, the martensite start temperature is reduced to the point where g phase does not transform and is retained. The g1‚ martensite is, however, observed again at ~25 at.% Sn. This makes the Cu-Sn system unique in that the g1‚ martensite is observed in two composition ranges. Another martensite, b› with an ordered, faulted orthorhombic structure, has also been reported [72Ken]. This martensite is observed between 13 and 16.2 at.% Sn when quenched from above some minimum temperature and does not form part of the b1‚- b1‚‚ -g1‚ sequence. The g1‚ martensite, at ~15 to 16 at.% Sn, exhibits thermoelastic behavior [75Miu]. The w and a› phases can form in quenched or aged b and g alloys. The w phase has been reported in alloys quenched from the g phase [81Zak] and is usually observed as a fine-scale precipitation within the matrix g phase. The w phase is more commonly associated with Ti- and Zr-based alloys. A metastable phase, a›, has been observed in both quenched and aged b and g phase alloys [73Van]. [67Deb] suggested that this phase might also be described as a very highly faulted fcc structure with a stacking fault density of ~0.5. [34Bug] observed an intermediate phase on tempering a quenched g phase alloy whose structure they identified as either tetragonal or hexagonal, isomorphous with the z-AgZn structure. [57Bag] confirmed that the diffraction pattern was more consistent with that of the hexagonal structure and therefore closely related to the equilibrium phase z. The z phase has been observed on annealing quenched 16.5 at.% Sn g phase alloys at 300 C [67Deb]. It co-existed with the metastable a› phase and the equilibrium d and a phases before final decomposition to the equilibrium two- phase structure of (a + e). The z or d phases appeared either separately or together, depending on specimen size and its previous thermal and mechanical history [67Deb]. A series of metastable structures has been reported on vapor quenching of alloys of 11.5 and 19.5 at.% Sn; the occurrence of the various phases is controlled by the composition and substrate temperature [87Sau]. Below 200 C, a cph phase, denoted a›, and a bcc phase, g›, were observed. The a› phase, observed at ~11.5 at.% Sn is probably equivalent to the phase found in earlier studies of quenched b and g phase alloys [73Van]. On deposition at room temperature, only cph lines were observed. However, depositing at ~130 C produced a pattern containing both fcc and cph lines. The bcc g› phase observed at 19.5 at.% Sn was considered [87Sau] to be isomorphous with the more usual g-brass structures observed in Cu-Al and Cu-Zn alloys [Pearson1]. At ~200 and ~300 C, 19.5 at.% Sn alloys contained primarily the z phase, whereas 11.5 at.% Sn alloys contained a mixture of z an d supersaturated a. Amorphous phases have been observed on vapor codeposition at <77 K in a 90 at.% Sn alloy [54Buc], at 77 K in a 60 at.% Sn alloy [68Cho], and between ~30 to 80 at.% Sn at 4.2 K [83Hau]. A metastable phase has been reported on annealing of thin layered structures produced by the sequential vapor deposition of pure Cu and Sn [79She]. 34Bug: V. Bugakov, I.V. Isaichev, and G.V. Kurdyumov, Z. Phys. (USSR), 5, 22- 30 (1934). 39Hom: C.E. Homer and H. Plummer, J. Inst. Met., 64, 169-200 (1939). 44Ray: G.V. Raynor, Annoted Equilibrium Diagram Series, No. 2, The Institute of Metals, London (1944). 54Buc: W. Buckel, Z. Physik, 138, 136-150 (1954). 57Bag: I.A. Bagariatskii, Sov. Phys. Crystallogr., 2, 277-280 (1957). 67Deb: M.De Bondt and A. Deruyttere, Acta Metall., 15, 993-1005 (1967). 68Cho: K.L. Chopra, Ledgemont Lab. report TR-179, August, 1968. 70Van: W. Vandermeulen and A. Deruyterre, Fizika, 2(2), 8 (1970). 72Ken: N.F. Kennon and T.M. Miller, Trans. Jpn. Inst. Met., 13, 322-326 (1972). 73Gan: A. Gangulee, G.C. Das, and M.B. Bever, Metall. Trans., 4, 2063-2066 ( 1973). 73Van: W. Vandermeulen and A. Deruyttere, Metall. Trans. 4, 1659-1664 (1973). 75Bra: J.K. Brandon, W.B. Pearson, and D.J.N. Tozer, Acta Crystallogr. B, 31, 774-779 (1975). 75Miu: S. Miuri, Y. Morita and N. Nakanishi, in Shape Memory Effects in Alloys, J. Perkins, Ed., Plenum Press, New York, 389-405 (1975). 79She: Y. Shevakin, L. Kharitonova, and L. Ostravskaya, Thin Solid Films, 62, 337-346 (1979). 81Zak: M.I. Zakharova and G.N. Dudchenko, Fiz. Met. Metalloved., 49, 174-177 ( 1980). 83Hau: P. Haussler and F. Baumann, Z. Phys. B, 49, 303-312 (1983). 87Sau: N. Saunders and A.P. Miodownik, J. Mater. Sci., 22, 629-637 (1987). Published in Bull. Alloy Phase Diagrams, 11(3), Jun 1990. Complete evaluation contains 2 figures, 3 tables, and 47 references. 1