title: Phase equilibria and structural investigations in the system Al-Fe-Si.
abstract: The Al-Fe-Si system was studied for an isothermal section at 800 °C in the Al-rich part and at 900 °C in the Fe-rich part, and for half a dozen vertical sections at 27, 35, 40, 50 and 60 at.% Fe and 5 at.% Al. Optical microscopy and powder X-ray diffraction (XRD) was used for initial sample characterization, and Electron Probe Microanalysis (EPMA) and Scanning Electron Microscopy (SEM) of the annealed samples was used to determine the exact phase compositions. Thermal reactions were studied by Differential Thermal Analysis (DTA). Our experimental results are generally in good agreement with the most recent phase diagram versions of the system Al-Fe-Si. A new ternary high-temperature phaseτ12(cF96, NiTi2-type) with the composition Al48Fe36Si16was discovered and was structurally characterized by means of single-crystal and powder XRD. The variation of the lattice parameters of the triclinic phaseτ1with the composition Al2+xFe3Si3-x(-0.3 <x< 1.3) was studied in detail. For the binary phase FeSi2only small solubility of Al was found in the low-temperature modification LT-FeSi2(ζβ) but significant solubility in the high-temperature modification HT-FeSi2(ζα) (8.5 at.% Al). It was found that the high-temperature modification of FeSi2is stabilized down to much lower temperature in the ternary, confirming earlier literature suggestions on this issue. DTA results in four selected vertical sections were compared with calculated sections based on a recent CALPHAD assessment. The deviations of liquidus values are significant suggesting the need for improvement of the thermodynamic models.
authors.affiliation: University of Vienna, Department of Inorganic Chemistry/Materials Chemistry, Währingerstraße 42, 1090 Wien, Austria.
authors.forename: Martin C J
authors.initials: MC
authors.lastname: Marker
authors.affiliation: University of Vienna, Department of Inorganic Chemistry/Materials Chemistry, Währingerstraße 42, 1090 Wien, Austria.
authors.forename: Barbara
authors.initials: B
authors.lastname: Skolyszewska-Kühberger
authors.affiliation: University of Vienna, Institute of Mineralogy and Crystallography, Althanstrasse 14 (UZA II), A-1090 Wien, Austria.
authors.forename: Herta S
authors.initials: HS
authors.lastname: Effenberger
authors.affiliation: TU-Bergakademie Freiberg, ZIK, Virtuhcon - Forschungsgruppe Multiphasige Stoffsysteme, Reiche Zeche, Fuchsmuehlenweg 9, 09596 Freiberg, Germany.
authors.forename: Clemens
authors.initials: C
authors.lastname: Schmetterer
authors.affiliation: University of Vienna, Department of Inorganic Chemistry/Materials Chemistry, Währingerstraße 42, 1090 Wien, Austria.
authors.forename: Klaus W
authors.initials: KW
authors.lastname: Richter
keywords: A. Aluminides; A. Ternary alloy systems; B. Crystallography; B. Phase diagrams