Complex intermetallic phases in the
Al-Pd-Ru and Al-Pd-Ir alloy systems
B. Grushko1 , D. Pavlyuchkov1,2 , T. Ya. Velikanova2
1
2
IFF-8: Microstructure Research
I.N. Frantsevich Institute for Problems of Materials Science, Kiev, Ukraine
Basing on the updates of the Al-Ru and Al-Ir constitutional diagrams the Al-rich parts of the Al-PdRu and Al-Pd-Ir constitutional diagrams were determined in the temperature range up to 1100◦ C.
The study was carried out using powder XRD,
DTA, SEM/EDX and TEM. Both alloy systems exhibit formation of complex intermetallic phases.
Known to date binary and ternary alloy systems of
aluminum with platinum metals (Ru, Rh, Pd, Os, Ir
and Pt) usually contain structurally complex intermetallics, including stable ternary quasicrystals (see
[1] for references). The title ternary alloy systems,
studied for the first time, are linked to either Al-Pd-Fe
(Ru and Fe belong to the same column in the periodic table) or Al-Pd-Co and Al-Pd-Rh (Co, Rh and Ir
belong to the same column in the periodic table) previously also studied in FZJ [1].
Basing on the updated Al-Ru constitutional diagram
(see in [1]), the partial isothermal sections of Al-PdRu were determined at 1000, 1050 and 1100◦ C in [2]
and completed with the partial isothermal sections at
790 and 900◦ C. The latter is presented in Fig. 1.
FIG. 1: Partial isothermal section of Al-Pd-Ru at 900◦ .
The isostructural binary AlPd and AlRu phases form
a continuous β-range of the CsCl-type solid solutions. A number of ternary phases were revealed.
Between 66 and 75 at.% Al, three structurally related cubic phases: C (primitive, a=0.7757 nm), C1
(bcc, a=1.5532 nm) and C2 (fcc, a=1.5566 nm) are
formed. The same structures are also typical of the
Al-Pd-Fe alloy system [1]. Although their compositional regions were somewhat different from those in
Al-Pd-Fe, the “chain” arrangement of these regions
and their sequence were the same in both these systems.
FIG. 2: Electron diffraction patterns of the: (a-c) P20 phase, (d-f) P40 -phase and (g-i) F40 -phase [1] along the
[1 0 0], [1 1 0], and [1 1 1] zone axes.
A stable icosahedral quasicrystalline I-phase is
formed below 1080◦ C around the Al71.5 Pd17 Ru12.5
composition. Similarly to that concluded for other AlTM alloy systems [1], the stable ternary Al-Pd-Ru Iphase is actually a ternary extension of a metastable
Al-Ru icosahedral phase stabilized by Pd. At nearby
compositions complex cubic phases were observed
(see Fig. 2): primitive P20 with the lattice parameter
a≈2.0 nm, P40 with a≈4.0 nm and fcc F40 also with
a≈4.0 nm. Despite their definite periodicity, these
phases exhibit powder X-ray diffraction patterns very
similar to that of the quasiperiodic I-phase, and the
phase boundaries between these periodic phases
and the I-phase are not clearly detectible.
The complex ε-phases, also structurally related to
quasicrystals, widely extend from “Al3 Pd” to ternary
compositions. Similarly to that in Al-Pd-Fe or Al-PdMn (see [1] for references), the orthorhombic ε6 , ε16 ,
ε22 and ε28 phases were observed. Their lattice parameters a≈2.34 and b≈1.62 nm are essentially the
same, while the c parameters are ∼1.23, 3.24, 4.49
and 5.70 nm, respectively. Apart from these regu-
sicrystalline structure were revealed. These structures are formed in a small compositional region designated E in Fig. 1.
The Al-Ir phase diagram was specified in the range
from 65 to 90 at.% Al [3]. At ∼1600◦ C the congruent Al2.7 Ir phase forms a eutectic with the congruent
AlIr phase. At higher Al concentrations four intermediate phases were found to be formed by a cascade
of peritectic reactions: Al3 Ir at 1466◦ C, Al28 Ir9 (χ) at
1446◦ , Al45 Ir13 (φ) at 993◦ C and Al9 Ir2 at 877◦ C.
Basing on the updated Al-Ir constitutional diagram,
the partial isothermal sections of Al-Pd-Ir were determined at 1100, 1000, 900 and 790◦ C [4]. As in Al-PdRu, Al-Pd-Co and Al-Pd-Rh, the isostructural binary
AlPd and AlIr phases (probably) form a continuous
β-range of the CsCl-type solid solutions (see Fig. 3).
The above-mentioned complex ε-phases extend from
“Al3 Pd” up to 22 at.% Ir, i.e. almost up to the Al-Ir
terminal. Also the Al4 Pd phase (λ-phase) dissolves
up to 15.5 at.% Ir, which significantly increases its
higher existence temperature limit. As a result, this
phase only forming in Al-Pd in the solid state, can be
in equilibrium with the liquid at its high-Ir concentrations. The C-phase, similar to that observed in Al-PdRu at ternary compositions, is already forms in the binary Al-Ir alloy system (above-mentioned Al2,7 Ir) and
it can dissolve up to 15 at.% Pd. The C2 -phase is also
formed in Al-Pd-Ir at ternary compositions, while the
C1 -phase was not observed in this alloy system. Instead, a hexagonal C3 -phase (a=1.09135, c=1.3418
nm), structurally related to the cubic C, C1 and C2
phases, was revealed. The ternary C2 phase is also
formed in Al-Pd-Co, while both C2 and C3 phases are
formed in Al-Pd-Rh.
The overall compositions of the phases in the Al-rich
parts of the Al-Pd-Co, Al-Pd-Rh and Al-Pd-Ir alloy
systems are compared in Fig. 3. In contrast to AlPd-Ru, neither of these alloy systems contain stable
quasicrystals. In Al-Pd-Rh the isostructural ε-phases
form a continuous range of solid solutions between
the binary terminals. Since in Al-Pd-Ir the Al-Pd εphases extend almost up to the Al-Ir terminal, this is
plausible to suggest that the ε-phases are also typical of this binary alloy system. In contrast to Al-Pd
and Al-Rh, in Al-Ir the ε-phases are metastable but
are stabilized by only a few at.% Pd. In Al-Pd-Co the
ε-phases “only” extend up to ∼16 at.% Co.
FIG. 3: Overall compositions of the Al-Pd-Co (a), Al-Pd-Rh
(b) and Al-Pd-Ir (c) phases.
lar structures, also structures aperiodic along the cdirection were revealed at intermediate compositions.
Thus, inside the wide ε-phase range only slight continuous variation of the orthorhombic a and b cell parameters are accompanied by complicated modulations of the c cell parameter.
The ε-range in Al-Pd-Ru broadens up to 15 at.% Ru.
In Fig. 1 only its high-temperature part is shown:
at lower temperatures it links to the Al-Pd terminal.
At compositions close to the high-Ru limit of the εrange the electron diffraction patterns of complex
orthorhombic structures and one-dimensional qua-
[1] B. Grushko and T. Velikanova, CALPHAD, 31, 217232 (2007).
[2] D. Pavlyuchkov, B. Grushko and T. Ya. Velikanova,
J. Alloys Comp. 464, 101-106 (2008).
[3] D. Pavlyuchkov, B. Grushko and T. Ya. Velikanova, Intermetallics. 16, 801-806 (2008).
[4] D. Pavlyuchkov, B. Grushko and T. Ya. Velikanova,
J. Alloys Comp. 453, 191-196 (2008).