Фазовая диаграмма системы Au-Zn

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Au-Zn (Gold-Zinc) H. Okamoto and T.B. Massalski The equilibrium phases of the Au-Zn system are (1) the liquid, L; (2) the fcc terminal solid solution, (Au), with a maximum solid solubility of 33.5 at.% Zn; (3) the cph terminal solid solution, (Zn), with 7.5 at.% solid solubility of Au; (4) four intermediate phases, a3, a1, a<291>2, and a2, in the composition range between 10 and 30 at.% Zn; (5) the intermetallic compound Au5Zn3 with unknown homogeneity, which forms peritectoidally at about 300 C; (6) the CsCl- type b› phase, with a maximum solubility range from 38 to 57 at.% Zn, with a martensitic transformation to the b1 phase at very low temperatures (<~100 K); (7) the d phase at about 56 at.% Zn, forming peritectoidally at 180 C; (8) three intermediate phases, g, g2, and g3, between 63 and 83 at.% Zn, whose phase boundaries are not well established; and (8) the e phase, which is stable below 490 C between 84 and 89 at.% Zn, with an allotropic variation e› below ~275 C. The assessed phase diagram is based primarily on a review of the literature [ 06Vog, 23Sol, 25Wes, 43Kub, 58Wil, 70Yaz, 79Pea] and was obtained by thermodynamic modeling of the experimental data. Many critical points are subject to further modifications due to the scatter in experimental data and the lack of certainty concerning the phase relationships. The calculated phase boundaries represent experimental data points fairly well, but they are inconclusive. The assessed liquidus and solidus boundaries are based mainly on the data of [06Vog] and [70Yaz]. Editor's note: The liquidus and solidus boundaries of the Au-Zn system between 20 and 70 at.% Zn were clarified by [88Ips]. The congruent melting point of b› occurs at 758 C and 48.5 at.% Zn. g forms congruently at 667 C. The space group for g3 was reported by [80Kim]. An orthorhombic metastable phase was found in an alloy with 37.8 at.% Zn when rapidly cooled to room temperature after being kept at 600 C on heating. 06Vog: R. Vogel, Z. Anorg. Allg. Chem., 48, 319-332 (1906) in German. 23Sol: P. Soldau, J. Inst. Met., 30, 351-400 (1923). 25Wes: A. Westgren and G. Phragmen, Philos. Mag., 50, 311-341 (1925). 43Kub: O. Kubaschewski, Z. Phys. Chem., 192, 292-308 (1943) in German. 58Wil: M. Wilkens and K. Schubert, Z. Metallkd., 49(12), 633-646 (1958) in German. 70Yaz: A. Yazawa and A. Gubcova, Trans. Jpn. Inst. Met., 11(6), 419-423 (1970). 79Pea: W.B. Pearson, J. Less-Common Met., 68(1), P9-P15 (1979). 80Kim: H.S. Kim, thesis, Univ. Waterloo, (1980). 88Ips: H. Ipser and R. Krachler, Scr. Metall., 22(10), 1651-1654 (1988). This updates the evaluation by H. Okamoto and T.B. Massalski published in Bull. Alloy Phase Diagrams, 10(1), Feb 1989, and Phase Diagrams of Binary Gold Alloys, 1987. Complete evaluation contains 4 figures, 6 tables, and 68 references. Special Points of the Au-Zn System