Фазовая диаграмма системы Au-Cr

К оглавлению: Другие диаграммы (Others phase diargams)


Au-Cr (Gold-Chromium) H. Okamoto and T.B. Massalski The equilibrium phases of the Au-Cr system are (1) the liquid, L; (2) the fcc terminal solid solution, (Au), with a maximum solid solubility of about 47 at.% Cr in (Au); (3) the bcc terminal solid solution, (Cr), with a small, but not well defined, solubility of Au in (Cr); and (4) the a› phase (Au4Cr) with the MoNi4-type ordered structure, with a homogeneity range of about 10 at.% around the stoichiometric composition of 20 at.% Cr. The assessed phase diagram is based primarily on the work of [60Rau] and [61Wac] for the composition range 0 to 50 at.% Cr and on a tentative thermodynamic model for 50 to 100 at.% Cr. A thin film representing a single Au3Cr crystal was found to have the same structure as Au4Cr when annealed at 260 C, but it did not revert to Au3Cr after annealing at above the transition temperature (about 330 C) and cooling to room temperature [68Tan]. When an alloy having 27.1 at.% Cr was evaporated, the final composition of the film corresponded to Au4Cr (20 at.% Cr) because of the loss of Cr during the process [76Dut]. These observations can be explained in terms of the assessed diagram, in which the Au3Cr compound could be considered a part of the metastable extension of the Au4Cr (a›) phase. Editor's note: X-ray crystallographic investigation of a 21 с 0.5 at.% Cr alloy showed the (Au) to a› transition at 360 to 315 C [86Sta]. 60Rau: E. Raub, Z. Metallkd., 51(5), 290-291 (1960) in German 61Wac: E. Wachtel and U. Vetter, Z. Metallkd, 52(8), 525-529 (1961) in German. 68Tan: L.E. Tanner, P.C. Clapp, and R.S. Toth, Mater. Res. Bull., 3(10), 855- 861 (1968). 76Dut: J. Dutkiewicz and G. Thomas, Thin Solid Films, 32(2), 329-332 (1976). 86Sta: S.V. Starenchenko and E.V. Kozlov, Fiz. Met. Metalloved., 61(6), 1148- 1151 (1986) in Russian; TR: Phys. Met. Metallogr., 61(6), 196-110 (1986). Published in Phase Diagrams of Binary Gold Alloys, 1987, and Bull. Alloy Phase Diagrams, 6(3), Jun 1985. Complete evaluation contains 2 figures, 5 tables, and 17 references. 1