Re-investigation of phase equilibria in the system Al-Cu and structural analysis of the high-temperature phase η1-Al1-δCu.
The phase equilibria and reaction temperatures in the system Al-Cu were re-investigated by a combination of optical microscopy, powder X-ray diffraction (XRD) at ambient and elevated temperature, differential thermal analysis (DTA) and scanning electron microscopy (SEM). A full description of the phase diagram is given. The phase equilibria and invariant reactions in the Cu-poor part of the phase diagram could be confirmed. The Cu-rich part shows some differences in phase equilibria and invariant reactions compared to the known phase diagram. A two phase field was found between the high temperature phase η1and the low temperature phase η2thus indicating a first order transition. In the ζ1/ζ2region of the phase diagram recent findings on the thermal stability could be widely confirmed. Contrary to previous results, the two phase field between δ and γ1is very narrow. The results of the current work indicate the absence of the high temperature β0phase as well as the absence of a two phase field between γ1and γ0suggesting a higher order transition between γ1and γ0. The structure of γ0(I-43m, Cu5Zn8-type) was confirmed by means of high-temperature XRD. Powder XRD was also used to determine the structure of the high temperature phase η1-Al1-δCu. The phase is orthorhombic (space groupCmmm) and the lattice parameters area= 4.1450(1) Å,b= 12.3004(4) Å andc= 8.720(1) Å; atomic coordinates are given.
University of Vienna, Department of Inorganic Chemistry/Materials Chemistry, Waehringer, Straße 42, 1090 Wien, Austria.
Norbert
N
Ponweiser
University of Vienna, Department of Mineralogy and Crystallography, Althanstraße 14, 1090 Wien, Austria.
Christian L
CL
Lengauer
University of Vienna, Department of Inorganic Chemistry/Materials Chemistry, Waehringer, Straße 42, 1090 Wien, Austria.
Klaus W
KW
Richter
A: Aluminides, Miscellaneous; B: Crystal chemistry of intermetallics; B: Crystallography; B: Phase diagrams