Regensburg 2000 – scientific programme
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M: Metallphysik
M 14: Postersitzung
M 14.20: Poster
Thursday, March 30, 2000, 15:00–19:00, C
Orthorombic Al3TM phases in Al-Pd and Al-Rh — •M. Yurechko and B. Grushko — Forschungszentrum Jülich GmbH, Inst. f. Festkörperforschung
The orthorhombic phase usually designated Al3Pd and ternary compounds based on this structure have great interest because of their close structural relation to quasicrystals. Earlier orthorhombic structure was observed in Al-Pd-Mn [1]. The lattice parameters of a=2.3541, b=1.6566 and c=1.2339 nm were for the phase which is also called ξ-prime. In our research two related orthorhombic structures were observed in annealed binary Al-Pd alloys. The Al3Pd phase was observed at 71.5-72.5 at.% Al at 710oC and its higher Al limit the structure with c=1.23 nm was observed while at lower Al c=4.59 nm (i.e. in about 22/6 times more). The lattice parameters of about a=2.35 and b=1.65 nm were the same in both. The structures observed in Al-Pd-Mn are suggested to be ternary extensions of binary compounds. Similar was observed in Al-Pd-Fe and Al-Pd-Co. The maximal solubility of Mn in Al3Pd is about 5 at.%, of Fe about 10 at.% and of Co about 18 at.%. A phase similar to the lower-c Al3Pd was also observed in Al-Rh where it forms at 75 at.% Al. No structure corresponding to the higher-c Al3Pd was observed in Al-Rh but at 76 at.% Al another, presumably monoclinic phase was revealed.
[1] M. Boudard, et al., Phil.Mag. A 74, (1996), 939.