X-rays structural analysis and thermal stability studies of the ternary compound α-AlFeSi

• Published in: Journal of solid state chemistry Vol. 184; no. 5; pp. 1120 - 1128
• Main Authors: Roger, J., Bosselet, F., Viala, J.C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.05.2011; Elsevier
• Subjects: Aluminide; Chemical Sciences; Condensed matter: structure, mechanical and thermal properties; Crystal structure; Exact sciences and technology; Material chemistry; Physics; Solid solution; Solid state reaction; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Ternary phase; Thermal analysis; Thermal expansion; thermomechanical effects and density; Thermal properties of condensed matter; Thermal properties of crystalline solids; Ternary phase; Aluminide; Thermal analysis; Solid solution; Solid state reaction; Crystal structure; Space groups; Structure stability; Atmospheric pressure; Ternary compounds; Differential thermal analysis; XRD; Symmetry groups; Reaction diffusion equation; Lattice parameters; Heat treatments; Thermal stability; Thermal properties; Hexagonal lattices; Monocrystals; Aluminium alloys; Solid solutions; Silicon
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2011.03.025

From literature data presently available, the decomposition temperature and the nature of the decomposition reaction of the ternary compound α-AlFeSi (also designated as α H or τ 5) are not clearly identified. Moreover, some uncertainties remain concerning its crystal structure. The crystallographic structure and thermochemical behaviour of the ternary compound α-AlFeSi were meticulously studied. The crystal structure of α-AlFeSi was examined at room temperature from X-ray single crystal intensity data. It presents hexagonal symmetry, space group P6 3 /mmc with unit cell parameters (293 K) a=12.345(2) Å and c=26.210(3) Å ( V=3459 Å 3). The average chemical formula obtained from refinement is Al 7.1Fe 2Si. From isothermal reaction-diffusion experiments and Differential Thermal Analysis, the title compound decomposes peritectically upon heating into θ-Fe 4Al 13(Si), γ-Al 3FeSi and a ternary Al-rich liquid. Under atmospheric pressure, the temperature of this reversible transformation has been determined to be 772±12 °C. Partial representation of the crystal structure of the α-Al 7.1Fe 2Si compound. [Display omitted] The main findings of our work are: ► a detailed X-rays crystal structure determination of the ternary compound α-AlFeSi. ► The precision of the silicon atoms positions in the crystal structure. ► A precised determination of the decomposition temperature of this compound.