Фазовая диаграмма системы Al-Pd
К оглавлению: Другие диаграммы (Others phase diargams)
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