Фазовая диаграмма системы Au-Ge

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Au-Ge (Gold-Germanium) H. Okamoto and T.B. Massalski The equilibrium phases of the Au-Ge system, which is a simple eutectic, are (1) the liquid, L; (2) the fcc terminal solid solution, (Au), having about 3 at.% solid solubility of Ge in (Au); and (3) the diamond-type cubic terminal solid solution, (Ge), with a very small solid solubility of Au in (Ge) (less than 13. 6 C 10 -4 at.%). The solidus and the solvus boundaries of the (Au) phase have been drawn according to a thermodynamic model, and the liquidus boundaries are based on experimental data [45Jaf, 75Pre, 77Leg]. The phase diagram calculated by [88Che] based on a thermodynamic model agrees well with the experimental phase diagram. Two types of metastable phases (b and g) occur in splat-cooled Au-Ge alloys [ 64Luo]. The crystal structure of the b phase was identified as cph, with the single-phase range between 17.5 and 22.5 at.% Ge, and the g phase was identified as bct, with the single-phase range between 40 and 50 at.% Ge [ 65Ana, 66Ana]. Subsequently, it was found that the formation and stability of the metastable b and g phases depend not only on the composition of the alloy and the cooling rate, but also on the history of the heat treatment of each alloy. The cooling rates in rapidly quenched alloys are not uniform or well controlled throughout each specimen, and they may also be quite different for different measurements. Also, a part of the metastable phase formed by rapid quenching may decompose at an equally rapid rate into another phase. Therefore, the experimentally observed effects appear to be very complicated. Amorphous alloys can be made by coevaporating Au and Ge onto a low-temperature substrate, with ion-beam mixing, and by splat cooling. The relationship between composition and stability is complex. For example, alloys containing 24, 28, and 30 at.% Ge can be made amorphous by splat cooling. Such alloys crystallize into a complex structure, which is probably a mixture of either b + g or (Au) + (Ge), above 250 K. 45Jaf: R.I. Jaffee, E.M. Smith, and B.W. Gonser, Trans. AIME, 161, 366-372 ( 1945). 64Luo: H.L. Luo and W. Klement, Jr., California Inst. Technol. Tech. Rep., (24) , 1-6 (1964). 65Ana: T.R. Anantharaman, H.L. Luo, and W. Klement, Jr., Trans. AIME, 233(11), 2014-2017 (1965). 66Ana: T.R. Anantharaman, H.L. Luo, and W. Klement, Jr., Nature, 210, 1040- 1041 (1966). 75Pre: B. Predel and H. Bankstahl, J. Less-Common Met., 43(1/2), 191-203 (1975) . 77Leg: B. Legendre and C. Souleau, J. Chem. Res., (S)12, 306-307 (1977) in French; (M)12, 3701-3742 (1977) in French. 88Che: P.Y. Chevalier, Thermochim. Acta, 141, 217-226 (1989). Published in Phase Diagrams of Binary Gold Alloys, 1987, and Bull. Alloy Phase Diagrams, 5(6), Dec 1984. Complete evaluation contains 6 figures, 9 tables, and 75 references. 1