Role of the triclinic Al₂Fe structure in the formation of the Al₅Fe₂-approximant

Abstract

The structural correspondence among the bcc, ordered-bcc B2, triclinic Al₂Fe and approximant Al₅Fe₂ structures have been examined on the basis of the experimentally obtained orientation relationship of and , where N(hkl) denotes the normal direction of the (hkl) plane. The formation of the triclinic Al₂Fe structure from the bcc structure is directly associated with that of Al–Fe covalent bonds; that is, hybridization between Al and Fe atoms. The covalent bond formation results in the appearance of decagonal-like atomic arrangements in the Al₂Fe structure, which are similar to those in the approximant Al₅Fe₂ structure.

Keywords:

• aluminium alloys
• approximants
• crystal structure
• electron diffraction
• electron irradiation
• electron microscopy
• intermetallic compounds

Acknowledgements

This study was partially supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (B), 18360306, 2006.