Фазовая диаграмма системы Al-Pd

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Al-Pd (Aluminum-Palladium) A.J. McAlister Tentatively, the equilibrium phases of the Al-Pd system are (1) the liquid, L; (2) the fcc (Al) solid solution, with nil terminal solid solubility; (3) the fcc (Pd) solid solution-up to ~20 at.% Al dissolves in (Pd) at the eutectic; ( 4) the l phase, Al4Pd, which forms peritectoidally from (Al) and the d phase at ~560 C [80Kos, 81Sas, 82Ell] and has a complex hexagonal structure isotypic with Al4Pt; (5) the g phase, Al21Pd8, which forms peritectically from the melt at ~790 C with a probable orthorhombic structure; (6) the d phase, Al3Pt2, which has the trigonal Al3Ni2 structure and forms peritectically from the melt and the b phase at ~945 C; (7) the high-temperature b phase with the cubic CsCl structure, which forms congruently from the melt at ~1645 C and 50 at.% Pd and has a solubility range from ~44 to 56 at.% Pd; (8) the low- temperature b› phase, which apparently forms congruently from the b phase at ~850 C and ~51 at.% Pd and is soluble from ~48.5 to 52.8 at.% Pd, with an apparently complex rhombohedral symmetry; (9) the low-temperature m phase, which forms peritectoidally from b and b› at ~740 C and is soluble from ~48.0 to 49.0 at.% Pd with a cubic FeSi structure; (10) the n phase, Al3Pd5, which forms peritectically at ~1318 C and has the orthorhombic Ge3Rh5 structure; ( 11) the r phase, AlPd2, which forms congruently from the melt at ~1418 C, is soluble from ~65.0 to ~73.0 at.% Pd at 1050 C, and has the orthorhombic Co2Si structure; and (12) the t phase, with ~1% solubility range, which forms congruently from the r phase at ~980 C and has an orthorhombic structure. The Al-Pd phase diagram has not yet been determined reliably. Although the existence of nine intermediate phases is well established, the liquidus, reaction temperatures, and phase boundaries have not been established precisely. Such uncertainties are indicated by dotted lines in the assessed phase diagram. It is based on a review of the literature [64Pan, 77Mat, 77Pia, 80Kos, 81Sas, 82Ell, 82Sas, 86Kat]. In the most rapidly quenched (thinnest) portions of splat-quenched samples containing 6 to 20 at.% Pd, an amorphous phase has been observed. In more slowly cooled (thicker) sections, supersaturated (Al) solid solutions have been detected and are estimated to contain from 10 to 20 at.% Pd. A metastable phase of lattice parameter a = 0.588 nm has been observed, which might have the cubic CaF2 structure. In flash-evaporated alloys containing 6 to 20 at.% Pd, the equilibrium l phase has been found to form readily in these films. By annealing the l phase near the eutectic temperature and then quenching, a number of long-period, vacancy- ordered superstructures of the basic bcc CsCl structure were formed. In splat-quenched samples containing from 5.0 to 33.0 at.% Pd, supersaturated ( Al) solid solution has been observed, with the upper limit of solubility placed at 5 at.% Pd. A metastable phase was also observed. 64Pan: L.A. Pantaleimonov, A.Yu. Khanna, and I.G. Sokolova, Zh. Neorg. Khim., 9, 2749-2753 (1964) in Russian; TR: Russ. J. Inorg. Chem., 9, 1480-1483 (1964). 77Mat: T. Matkovic and K. Schubert, J. Less-Common Met., 55, 45-52 (1977) in German. 77Pia: G. Piatti and G. Pellegrini, J. Mater. Sci., 14, 2512-2516 (1979). 80Kos: U. Koster, P.S. Ho, and M. Ron, Thin Solid Films, 67, 35-44 (1980). 81Sas: G.V.S. Sastry and C. Suryanarayana, Mater. Sci. Eng., 47, 193-208 (1981) . 82Ell: M. Ellner, U. Kattner, and B. Predel, J. Less-Common Met., 87, 117-133 ( 1982) in German. 82Sas: G.V.S. Sastry and C. Suryanarayana, Phys. Status Solidi(a), 73, 267-278 (1982). 86Kat: U. Kattner, private communication (1986). Published in Bull. Alloy Phase Diagrams, 7(4), Aug 1986. Complete evaluation contains 5 figures, 3 tables, and 27 references. Special Points of the Al-Pd System