Фазовая диаграмма системы As-Cu

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As-Cu (Arsenic-Copper) P.R. Subramanian and D.E. Laughlin Extensive investigations have been reported for the Cu-As system. The assessed equilibrium Cu-As diagram follows the essential features of [Hansen] and [ Elliott], with certain revisions based on more recent experimental investigations. The main features are based primarily on the data of [05Fri], [ 08Fri], [10Ben], [40Owe], [57Hum], [72Nau], and [72Uga]. More recently, [82Ble] reported the formation of Cu3As4. The accepted phases are (1) the liquid, L; ( 2) the fcc terminal solid solution, (Cu), with a maximum solid solubility of 6. 83 at.% As at the eutectic temperature of 685 C; (3) Cu-rich cph b, forming peritectoidally from (Cu) and g› at 325 C; (4) hexagonal g, forming congruently from the liquid at 26.25 at.% As and 827 C; (5) hexagonal g›, existing over the maximum composition range of ~25.5 to 27.8 at.% As and undergoing a polymorphic transformation to hexagonal g at temperatures between 450 and 475 C; (6) cubic d, forming peritectically from L and g at 709 C and ~29 at.% As and undergoing a polymorphic transformation to orthorhombic d› at ~380 C; (7) orthorhombic d›, existing over the limited temperature range 300 to 380 C and decomposing eutectoidally into g› and (As) at 300 C and ~29 at.% As; and (8) (As), with no reported solid solubility of Cu. The exact stoichiometry of the most Cu-rich intermediate phase, b, is a subject of controversy. Although its structure has been identified to be cph Mg type, in this review, b is shown to have the range of stability ~11.1 to 14. 3 at.% As, based on the reported extrema in the stoichiometries [57Sch, 71Lie, 72Nau]. The congruent formation of g (or Cu3As) was established by [05Fri], [08Fri], [ 10Ben], and [57Hum]. The assessed phase boundaries are based on the data of [ 72Nau], and the composition and temperature at the congruent point are from [ 57Hum]. The high-temperature and low-temperature modifications reported by [ 69Ben] are accepted and are designated g and g›, respectively. High-temperature X-ray and DTA studies of [68Juz] revealed that d is dimorphic, with the high-temperature form stable between ~395 C and the peritectic melting temperature and the low-temperature form stable between 300 and 315 C. In the intermediate range, [68Juz] assumed that d is in equilibrium with (As). DTA and X-ray investigations of [71Lie] confirmed the existence of the two forms of d, together with the polymorphic transformation to the high-temperature form at 380 C. The maximum homogeneity range of d and d› is accepted provisionally as extending from the Cu5As2 composition to the Cu19As8 composition in this review. The proposed phase relationships for this phase are based tentatively on the data of [68Juz], [71Lie], and [72Uga], although further investigations are required in this region. [72Nau] reported the synthesis of Cu2As by selective wet oxidation of a Cu-As alloy with a higher starting Cu content. Selective dissolution of Cu by the action of oxidants such as ferric ions resulted in the formation of homogeneous Cu2As. It is likely that this synthetic Cu2As is metastable and, as such, does not exist in the equilibrium diagram. The occurrence of the possibly metastable compound Cu3As4 with an orthorhombic structure was reported by [82Ble]; however, no preparation details were given. 05Fri: K. Friedrich, Metallurgie, 2, 477-495 (1905) in German. 08Fri: K. Friedrich, Metallurgie, 5, 529-535 (1908) in German. 10Ben: G.D. Bengough and B.P. Hill, J. Inst. Met., 3, 34-71 (1910). 13Pus: N. Puschin and E. Dischler, Z. Anorg. Chem., 80, 65-70 (1913) in German. 37Mer: J.C. Mertz and C.H. Mathewson, Trans. AIME, 124, 59-77 (1937). 40Owe: E.A. Owen and V.W. Rowlands, J. Inst. Met., 66, 361-378 (1940). 49Owe: E.A. Owen and D.P. Morris, J. Inst. Met., 76, 145-168 (1949-1950). 57Hum: W. Hume-Rothery and J. Burns, Philos, Mag., 2, 1177-1196 (1957). 57Sch: K. Schubert, H. Breimer, W. Burkhardt, E. Gunzel, R. Haufler, H.L. Lukas, H. Vetter, J. Wegst, and M. Wilkens, Naturwissenschaften, 44, 229-230 ( 1957) in German. 68Juz: R. Juza and K.V. Benda, Z. Anorg. Allg. Chem., 357, 238-246 (1968) in German. 69Ben: K.V. Benda and R. Juza, Z. Anorg. Allg. Chem., 371, 172-192 (1969) in German. 71Lie: W. Liebisch and K. Schubert, J. Less-Common Met., 23, 231-236 (1971) in German. 72Nau: J. Naud and P. Priest, Mater. Res. Bull., 7, 783-792 (1972) in French. 72Uga: Y.A. Ugai, V.R. Pshestanchik, O.Y. Gukov, and V.Z. Anokhin, Izv. Akad. Nauk SSSR, Neorg. Mater., 8(10), 1734-1737 (1972) in Russian; TR: Inorg. Mater. (USSR), 8(10), 1526-1528 (1972). 82Ble: C. Blendl and K.J. Range, Z. Kristallogr., 159, 17-18 (1982) in German. Published in Bull. Alloy Phase Diagrams, 9(5), Oct 1988. Complete evaluation contains 4 figures, 10 tables, and 58 references. Special Points of the Cu-As System