Фазовая диаграмма системы Au-Cu
К оглавлению: Другие диаграммы (Others phase diargams)
Au-Cu (Gold-Copper)
H. Okamoto, D.J. Chakrabarti, D.E. Laughlin, and T.B. Massalski
The Au-Cu system is one of the earliest systems for which several order-
disorder type transformations were established. Although a very large volume
of work exists on the ordered AuCu and AuCu3 phases, only limited phase
diagram details for the Au-Cu system have been generated during the past two
decades. The assessed phase diagram is based on review of the experimental
phase diagram data [00Rob, 07Kur, 34Bro, 62Ben, 64Zai], and was obtained by
thermodynamic modeling. The system is characterized by a continuous solid
solution phase below the solidus.
The liquidus and solidus boundaries established by [62Ben], who used cooling
and heating curves (~2 to 3 C/min), and whose experimental work appears to be
the most reliable, are accepted in the assessed diagram. The decrease in the
melting temperature of Cu with additions of Au (up to 3.3 at.%) determined by [
1897Hey] is also consistent with the presently accepted liquidus.
The liquidus in the assessed diagram can also be derived from the present
thermodynamic assessment, which is consistent with the reported thermodynamic
quantities. The solidus temperatures of [62Ben] are lower than the
calculated values (maximum difference ~10 C) in the composition range ~80 to
90 at.% Cu, where the actual thermodynamic properties may be slightly
different from the model properties.
The experimental phase boundary data related to the ordered Au3Cu phase have
been reported as various values by different investigators, presumably
because of the difficulty in attaining a full equilibrium state at low
transformation temperatures (<240 C). Most of the presently assessed phase
boundaries are based on the isothermal change in the electrical resistivity
measured by [55Rhi], [59Hir], and [59Kor].
The occurrence of compound-like phases at the AuCu and the AuCu3
stoichiometric compositions was first observed by [15Kur], who employed
thermal analysis, hardness, and X-ray measurements. [23Bail], [23Bai2], and [
23Bai3] associated the occurrence of atomic ordering with these compounds on
the basis of observed X-ray diffraction lines. [36Joh] discovered an
additional order-order transformation in AuCu at higher temperatures, in which
an orthorhombic AuCu(II) phase forms from the tetragonal AuCu(I) phase. Prior
to this, AuCu(I) was thought to transform directly to the disordered fcc phase
(AuCu(D)) at higher temperatures.
Detailed phase boundary determinations, including the indications of congruent
transformations at AuCu3 and AuCu compositions, were made by [31Gru] and [
31Hau]. They also correctly indicated the existence of two-phase fields
between the ordered and disordered phases. A third low-temperature phase with
an extended phase field that included the stoichiometry Au3Cu was reported to
form peritectoidally by [31Gru]. [53New], [53Rhi], [54New1], and [55Rhi]
defined precise boundaries for the different phase fields and confirmed the
congruent formation of AuCu and AuCu3 and the peritectoidal formation of Au3Cu.
The assessed diagram is based primarily on [55Rhi], [57Pia], and [59Pia1] for
the high-temperature boundaries and on [57Pia] for the AuCu(II) = AuCu(I)
boundaries, for which [55Rhi] did not present any data. The AuCu(D) = AuCu(II)
transformation temperature is accepted as 410 с 2 C. The AuCu(II) = AuCu(I)
temperature is accepted as 385 с 2 C based on [73Bar] and [73Gol].
The existence of a two-phase field between AuCu3 and AuCu(I), from 34 to 37 at.
% Au, and the associated eutectoid decomposition of the fcc solid solution was
proposed by [31Gru]. [55Rhi] confirmed the eutectoid transformation of (Cu, Au)
and precisely determined the eutectoid point to lie at 36 at.% Au and at 284
C.
The accepted AuCu3(I) phase boundaries are based primarily on [55Rhi]. [54New2]
confirmed that a two-phase field occurs not only on the Au-rich side of the
AuCu3 composition, but also on the Cu-rich side. The AuCu3(I) phase is stable
over wide composition limits on both sides of the stoichiometric point. It
forms from the disordered phase by a congruent transformation at the
stoichiometric composition and at Au-rich limits by a eutectoid transformation.
The congruent and eutectoid temperatures at 390 and 284 C, respectively, and
the eutectoid composition at 36 at.% Au are accepted from [55Rhi] as being the
most precise.
By analogy with the occurrence of the AuCu(II) structure, [60Sco] proposed
that a one-dimensional long-period superlattice (LPS) structure, designated
AuCu3(II), occurs at Au-rich off-stoichiometric compositions. The narrow
single-phase field was shown to lie inside the (Cu, Au) and AuCu3(I) two-phase
field, and the likely boundaries were also proposed [60Sco, 74Per].
According to [80Wil], the AuCu3(II) phase does not exist. The existence of a
two-phase mixture of AuCu3(I) and a disordered Au-Cu solid solution is
sufficient to explain the scattering phenomenon usually associated with the
AuCu3(II) LPS [80Wil]. This is an interesting suggestion, but experimental
observation of the disordered regions must be presented before the LPS
structure is rejected.
The long-period superlattice structure [62Sat, 66Tac1, 66Tac2] is associated
with a particular energy band structure of conduction electrons that can be
altered by pressure. The AuCu(II) = AuCu(I) transition temperature was found
to increase with the measured pressure, up to 70 kbar, at the rate of 1.5 с 0.
2 C/kbar by [72Iwa] and [74Iwa]. Above 50 kbar, the AuCu(II) structure
disappeared and only the ordered structure AuCu(I) was present.
[75Asa] observed the transition temperature to increase with pressure at the
rate of 2.0 C/kbar, which compares well with the theoretically predicted rate
of 1.95 C/kbar, as derived from the Clausius-Clapeyron equation [74Iwa].
Measurements extended to 100 kbar using electrical resistivity showed a linear
relation between pressure and the transition temperature.
1897Hey: C.T. Heycock and F.H. Neville, Philos. Trans. R. Soc. (London) A, 189,
25-69 (1897).
00Rob: W.C. Roberts-Austen and T.K. Rose, Proc. R. Soc. (London) A, 67, 105-
112 (1900).
07Kur: N.S. Kurnakov and S.F..Zemczuzny, Zh. Russ. Fiz-Khim. Obshchestva, 39,
211-219 (1907) in Russian; TR: Z. Anorg. Chem, 54, 149-169 (1907) in German.
15Kur: N.S. Kurnakov, S.F. Zemczuzny, and M. Zasedatelev, Zh. Russ. Fiz-Khim.
Obshchestva, 47, 871-897 (1915) Russian; TR: J. Inst. Met., 15, 305-331 (1916).
23Bai1: E.C. Bain, Chem. Met. Eng., 28, 21-24 (1923).
23Bai2: E.C. Bain, Chem. Met. Eng., 28, 67-68 (1923).
23Bai3: E.C. Bain, Trans. AIME, 68, 637-638 (1923).
31Gru: G. Grube, G. Schoenmann, F. Vaupel, and W. Weber, Z. Anorg. Chem., 201,
41-74 (1931) in German.
31Hau: J.L. Haughton and R.J.M. Payne, J. Inst. Met., 46, 457-480 (1931).
34Bro: W. Bronievski and K. Wesolowski, Compt. Rend., 198, 370-372 (1934) in
French.
36Joh: C.H. Johansson and J.O. Linde, Ann. Phys., 25, 1-48 (1936) in German.
53New: J.B. Newkirk, Trans. AIME, 197, 823-826 (1953).
53Rhi: F.N. Rhines and J.B. Newkirk, Trans. ASM, 45, 1029-1055 (1953).
54New1: J.B. Newkirk, Trans. AIME, 200(5), 673-675 (1954).
54New2: J.B. Newkirk, Acta Metall., 2(7), 644-645 (1954).
55Rhi: F.N. Rhines, W.E. Bond, and R.A. Rummel, Trans. Am. Soc. Met., 47, 578-
597 (1955).
57Pia: A. Pianelli and R. Faivre, Compt. Rend., 245, 1537-1539 (1957).
59Hir: M. Hirabayashi, J. Phys. Soc. Jpn., 14, 262-273 (1959).
59Kor: B.M. Korevaar, Physica, 25, 1021-1032 (1959).
59Pia1: A. Pianelli and R.A. Faivre, Compt. Rend., 248, 1661-1663 (1959).
59Wri: P. Wright and K.F. Goddard, Acta Metall., 7(12), 757-761 (1959).
60Fli: P.A. Flinn, G.M. McManus, and J.A. Rayne, J. Phys. Chem. Sol., 15, 189-
195 (1960).
60Sco: R.E. Scott, J. Appl. Phys., 31, 2112-2117 (1960).
62Ben: H.E. Bennett, J. Inst. Met., 91, 158 (1962-1963).
62Sat: K. Sato, D. Watanabe, and S. Ogawa, J. Phys. Soc. Jpn., 17(10), 1647-
1651 (1962).
64Zai: S.A. Zaitseva and Yu.A. Priselkov, Vestn. Mosk. Univ., Ser. II, Khim.,
19(6), 22-23 (1964) in Russian.
66Lul: S.S. Lu and C.K. Liang, K'o Hsueh T'ung Pao, 17(9), 395-396 (1966) in
Chinese.
66Lu2: S.S. Lu and C.K. Liang, K'o Hsueh T'ung Pao, 17(11), 495-496 (1966) in
Chinese.
66Tac1: M. Tachiki and K. Teramoto, J. Phys. Chem. Sol., 27(2), 335-348 (1966).
66Tac2: M. Tachiki, Phys. Rev., 150(2), 440-447 (1966).
67Bje: E. Bjerkelund, W.B. Pearson, K. Selte, and A. Kjekshus, Acta Chem.
Scand., 21(10), 2900-2902 (1967).
68Oka: K. Okamura, H. Iwasaki, and S. Ogawa, J. Phys. Soc. Jpn., 24(3), 569-
579 (1968).
72Iwa: H. Iwasaki, J. Phys. Soc. Jpn., 33(6), 1721 (1972).
73Bar: R.D. Barnard and A.J.M. Chivers, Metal. Sci. J., 7, 147-152 (1973).
73Gol: N.S. Golosov, L.E. Popov, and L.Ya. Pudan, J. Phys. Chem. Sol., 34(7),
1149-1163 (1973).
74Iwa: H. Iwasaki, H. Yoshida, and S. Ogawa, J. Phys. Soc. Jpn., 36(4), 1037-
1042 (1974).
74Per: G. van der Perre, H. Goeminne, R. Geerts, and J. van der Planken, Acta
Metall., 22(2), 227-237 (1974).
75Asa: K. Asaumi, Jpn. J. Appl. Phys., 14(3), 336-340 (1975).
80Wil: R.O. Williams, Metall. Trans. A, 11(2), 247-253 (1980).
Published in Phase Diagrams of Binary Gold Alloys, 1987, and Bull. Alloy Phase
Diagrams, 8(5), Oct 1987. Complete evaluation contains 13 figures, 9 tables,
and 258 references.
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