Crystal structure refinement of the Γ- and Γ1-phase compounds in the Fe-Zn system and orientation relationships among α-Fe, Γ and Γ1 phases in the coating layer of galvannealed steel

JOURNAL OF ALLOYS AND COMPOUNDS

卷:732

Article

Okamoto, Norihiko L.^1,2,4  Inomoto, Masahiro¹  Takebayashi, Hiroshi³  Inui, Haruyuki^1,2 

[1] Kyoto Univ, Dept Mat Sci & Engn, Kyoto 6068501, Japan

[2] Kyoto Univ, Ctr Elements Strategy Initiat Struct Mat ESISM, Kyoto 6068501, Japan

[3] Nippon Steel & Sumitomo Met Corp Ltd, 5-3 Tokaimachi, Tokai, Aichi 4768686, Japan

[4] Tohoku Univ, Inst Mat Res, Aoba Ku, Sendai, Miyagi 9808577, Japan

关键词: Coating materials;    Intermetallics;    Solid state reactions;    Phase diagram;    Vacancy formation;    Synchrotron radiation;   

DOI  :  10.1016/j.jallcom.2017.10.146

来源: Elsevier

【 摘 要 】

The crystal structures of the Gamma- and Gamma(1)-phase compounds in the Fe-Zn system have been refined by single-crystal synchrotron X-ray diffraction. The Gamma-phase compound consists of four Fe-centred (Zn,Fe)(12) icosahedra connected with one another by face-sharing with the vertex sites of the shared triangle face being occupied by both Fe and Zn atoms. The Fe occupancy at the vertex sites increases with increasing Fe composition of the compound. The stoichiometry of the Gamma phase is described as Fe4Zn9 (Zn-30.77 at.% Fe), realized when all the vertex sites of the shared triangle face are occupied exclusively by Fe atoms. The Gamma(1)-phase compound consists of Zn-12 and (Zn,Fe)(12) icosahedra whose central site is exclusively occupied by Fe atoms, which is different from the previously reported structural model where some centres of these icosahedra are occupied by both Fe and Zn atoms. The crystal structures of all Fe-Zn intermetallic compounds can thus be best understood by considering the packing of the common structural unit; Fe-centred Zn-12 and/or Fe-centred (Zn,Fe)(12) icosahedron. Although the crystal structures of the alpha-Fe, Gamma and Gamma(1) phases with cubic symmetries are related with each other in terms of the arrangement of structural vacancies, there is no orientation relationship either between the Gamma and Gamma(1) phases or between the alpha-Fe and Gamma phases in the coating layer of galvannealed steel sheet. (C) 2017 Elsevier B.V. All rights reserved.

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