Фазовая диаграмма системы As-Cu
К оглавлению: Другие диаграммы (Others phase diargams)
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