Фазовая диаграмма системы Cu-Ge

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Cu-Ge (Copper-Germanium) R.W. Olesinski and G.J. Abbaschian The equilibrium phases of the Ge-Cu system are (1) the liquid, L; (2) the terminal solid solution, (Ge), with negligible solubility of Cu; (3) the terminal solid solution, (Cu), with a maximum solubility of 12 at.% Ge at the peritectic temperature of 824 C; (4) the cubic intermediate phase, e2, which is stable at 614 to 698 C; (5) the orthorhombic intermediate phase, e, which is stable above 549.5 C and melts congruently at 747 C; (6) the intermediate phase, e1, which is stable below 636 C, with a trigonally distorted cubic structure; and (7) the hexagonal intermediate phase, z, which decomposes peritectically at 824 C. The assessed phase diagram has been obtained by thermodynamic modeling and is based on the available experimental data [34Hum, 34Sch, 40Hum, 40Owe, 56Rey]. The (Ge) and (Cu) liquidus boundaries have been assessed using the common- tangent method to the Gibbs energy functions of the liquid and solid phases. (Cu) dissolves both interstitially and subtitutionally in Ge. The solubility of Cu in Ge is retrograde, with a maximum of 8.5 x 10-5 at.% Cu at 900 C. The transformation of supersaturated (Cu) solution was studied by [68Kot] and [ 76Mor] on alloys containing 88.9 and 89.5 at.% Cu, respectively. Electron microscopy and X-ray diffraction examinations showed that the stress-induced transformation of supersaturated (Cu) to z is martensitic; the z phase precipitates nucleate heterogeneously on stacking faults and grow normal to the octahedral fcc planes [68Kot]. The formation of the z phase is nucleation, rather than growth, controlled [ 76Mor]. The z precipitates were also found to be completely coherent with the matrix. The precipitation of z was found to start most rapidly between 425 and 450 C; for samples quenched from 600 C, the precipitation began after 6 min, whereas in the samples quenched from 800 C, z began to precipitate after 14 min. Amorphous Ge-Cu films were produced from 23 to 60 at.% Cu [75Hau]. Electron diffraction patterns of as-deposited and annealed films showed that stability of the amorphous films decreases with Cu concentration. The formation of crystalline metastable phases was investigated from 60 to 90 at.% Cu using rapid solidification techniques [73Pol]. A new phase, "gm", of cubic structure, was identified with a narrow homogeneity range around 78 at.% Cu; the phase was reported to decompose to the equilibrium phases z and e1 upon annealing between 500 and 700 C. 34Hum: W. Hume-Rothery, G.W. Mabbott, and K.M. Channel-Evans, Philos. Trans. R. Soc., (London) A, 233, 1-97 (1934). 34Sch: R. Schwarz and G. Elstner, Z. Anorg. Chem., 217, 289-297 (1934) in German. 40Hum: W. Hume-Rothery, G.V. Raynor, P.W. Reynolds, and H.K. Packer, J. Inst. Met., 66, 209-239 (1940). 40Owe: E.A. Owen and V.W. Rowlands, J. Inst. Met., 66, 361-378 (1940). 56Rey: J. Reynolds and W. Hume-Rothery, J. Inst. Met., 85, 119-127 (1956-57). 68Kot: P.S. Kotval and R.W.K. Honeycomb, Acta Metall., 16, 597-607 (1968). 73Pol: A.F. Polesya and V.N. Gudzenko, Izv. Akad. Nauk SSSR, Met., (5), 221- 224 (1973) in Russian. 75Hau: E. Haug, N. Hedgecock, and W. Buckel, Z. Phys. B, 22, 237-243 (1975). 76Mor: P.J. Moroz, Jr., Ph.D. thesis, University of Washington (1976). Published in Bull. Alloy Phase Diagrams 7(1), Feb 1986. Complete evaluation contains 5 figures, 7 tables, and 51 references. Special Points of the Ge-Cu System