Фазовая диаграмма системы Ag-Al

К оглавлению: Другие диаграммы (Others phase diargams)


Ag-Al (Silver-Aluminum) A.J. McAlister The equilibrium phases of the Ag-Al system are the liquid, L; the Ag-rich fcc terminal solid solution, (Ag), with maximum solubility of about 20.4 at.% Al at about 450 C; the Al-rich fcc terminal solid solution, (Al), with maximum solubility of about 23.5 at.% Ag at 567 C; the cph intermediate phase, d, stable below about 726 C, extending from about 23.5 at.% Al at 610 C to 41.9 at.% Al at 567C; the high-temperature bcc intermediate phase, b, stable above about 603 C and extending from about 21.6 at.% Al at 778 C to 29.8 at.% Al at 726 C; and the low-temperature intermediate phase, m, reported to have the complex cubic bMn structure, stable below about 450 C, with the single-phase field extending from about 21.2 to 24.3 at.% Al at 300 C. Invariant temperatures in the assessed phase diagram were obtained by averaging the values of [05Pet], [31Hoa], [40Hum], [41Foo], [49Ray], [50Owe[, [ 70Mas], and [78Rob]. Invariant compositions were obtained by extrapolation of phase boundaries to the invariant temperatures. The data of [60Wil] and [75Bar] were also used to construct the assessed diagram. Aging of Al-rich Ag-Al alloys, quenched from the fcc solid solution or from the liquid, has been extensively studied. From the data, it has become clear that two types of Guinier-Preston (GP) zones occur, GP-I forming above ~170 C and GP-II below. A number of reversible property differences distinguish in two temperature regimes. Above 170 C in the GP-I region, diffuse X-ray scattering displays strong halos around the direct beam and Bragg peaks. Aging below 170 C produces asymmetric shells of scattering around super-structure positions ([42Gui], [65Aue], [71Gra]). In addition to the GP zones, a metastable cph d› phase is observed in aging of Al-rich alloys. It appears at aging times longer that those required for the initiation of zone formation and grows in the form of Widmanstatten plates. Massive am, mm, and dm products, as well as three martensitic structures structurally compatible with the b phase, were observed by [72Gup], each occurring to a greater or lesser extent at all three compositions. Evidently, b was the first solid phase to form on quenching. No mention was made of retained b, nor were assessments reported of the relative amounts of massive and martensitic products. 05Pet: G.I. Petrenko, Z. Anorg. Chem., 46, 49-59 (1905) in German. 3lHoa: T.P. Hoar and R.K. Rowntree, J. Inst. Met., 45, 119-124 (1931). 40Hum: W. Hume-Rothery, G.V. Raynor, P.W. Raynolds, and H.K. Pacher, J. Inst. Met., 66, 209-239 (1940). 41Foo: F. Foot and E.R. Jette, Trans. AIME, 143, 151-157 (1941). 42Gui: A. Guinier, J. Phys. Rad., Paris, 8, 124-139 (1942) in French. 49Ray: G.V. Raynor and D.W. Wakeman, Philos. Mag., 40, 404-417 (1949). 50Owe: E.A. Owen and D.P. Morris, J. Inst. Met., 76, 145-168 (1949-1950). 60Wil: T.C. Wilder and J.F. Elliot, J. Electrochem. Soc., 107, 628-635 (1960). 65Aue: H. Auer and V. Gerold, Z. Metallkd., 56, 2409-248 (1965) in German. 70Mas: G. Massart, P. Desre, and E. Bonnier, J. Chim. Phys., 67, 1485-1488 ( 1970). 71Gra: J.E. Gragg and J.B. Cohen, Acta Metall, 19, 507-519 (1971). 72Gup: S.P. Gupta, Mater. Sci. Eng., 10, 341-356 (1972). 75Bar: S. Barat and J.K. Mukherjee, Indian J. Tech., 13, 510-519 (1975). 78Rob: G.D. Roberts and G.A. Chadwick, Scr. Metall., 12, 381-382 (1978). Published in Bull. Alloy Phase Diagrams, 8(6), Dec 1987. Complete evaluation contains 5 figures, 3 tables, and 71 references.