Фазовая диаграмма системы Al-Ge

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Al-Ge (Aluminum-Germanium) A.J. McAlister and J.L. Murray Al-Ge is a simple eutectic system with three phases: (1) the liquid, L; (2) the fcc (Al) solid solution; and (3) the diamond cubic (Ge) solid solution. Only the Ge-rich liquidus, the liquid integral enthalpy of mixing, and the liquid partial Al Gibbs energy of mixing are currently believed to have been determined reliably. The assessed phase diagram is the result of nonlinear least-squares optimization of model Gibbs energy functions to a selection of the available data, with emphasis placed on liquidus and liquid thermodynamic data. It is based primarily on the work of [26Kro], [39Sto], [62Gla], [66Wil], [79Esl1], and [79Esl2]. This diagram fits the select body of data within its range of reliability. The eutectic temperature has not been determined reliably. Estimates have been made based on the electrochemical cell data of [79Esl1] of 417 с 3 C. The mean of these estimates agrees quite well with the value of 420 C resulting from the present thermodynamic calculation. The present fit yields a maximum solubility of about 2 at.% Ge in (Al) at a eutectic temperature of 420 C. The retrograde solubility point occurs at 1.09 at.% Al in (Ge) at the eutectic temperature. At the maximum achievable cooling rates, rapid quenching of the liquid produces completely amorphous solid solutions in the range of 40 to 50 at.% Ge and mixtures of amorphous and crystalline (solid solution) phases in the range of 30 to 80 at.% Ge. At cooling rates normally achieved by splat quenching ( 105 to 108 C/s), rapid quenching of the liquid causes the solubility of Ge in (Al) to be extended beyond the maximum equilibrium value and causes at least two metastable compound phases to appear. The metastable solubility varies, because it depends on the cooling rate, which is affected by the quenching technique and varying cooling rates within the sample. Reported metastable solubilities of Ge in (Al) range from about 30 at.% Ge to about 3 at.% Ge. The metastable intermetallic phases are designated g1, g2, and g3. The composition of g1 is near 50 at.% Ge; g2 contains about 50 to 65 at.% Ge. The structures of g1 and g2 are rhombohedral and monoclinic, respectively, as measured by the most sensitive X-ray technique; the structure of g3 is hexagonal. X-ray diffraction, metallographic, electrical resistivity, and microhardness measurements were made on alloys in the composition range of 0 to 7 at.% Ge, which were heat treated at 400 C at 1 atm and at 20 kbar, then quenched in ice water at 1 atm pressure. Solid solubilities of 2.47 and 4.80 at.% Ge were reported for the 1-atm and 20-kbar heat treated samples, respectively. 26Kro: W. Kroll, Metall. Erz., 24, 682-684 (1926) in German. 39Sto: H. Stohr and W. Klemm, Z. Anorg. Allg. Chem., 241, 305-313 (1939) in German. 62Gla: V.M. Glazov, T. Chien, and C. Liu, Zh. Neorg. Khim., 7, 576-581 (1962) in Russian; TR: Russ. J. Inorg. Chem., 7, 293-296 (1962). 66Wil: T.C. Wilder, Trans. AIME, 236, 88-94 (1966). 79Esl1: H. Eslami, J. de Francheschi, M. Gambino, and J.P. Bros, Z. Naturforsch., 34(7), 810-817 (1979). 79Esl2: H. Eslami, J. Less-Common Met., 64(1), 31-44 (1979) in French. Published in Bull. Alloy Phase Diagrams, 5(4), Aug 1984. Complete evaluation contains 3 figures, 9 tables, and 39 references. Special Points of the Al-Ge System