Crystal structure of η'-Fe3Al8; low-temperature phase of η-Fe2Al5 accompanied by an ordered arrangement of Al atoms of full occupancy in the c-axis chain sites

Norihiko L. Okamoto, Jumpei Okumura, Masaya Higashi, Haruyuki Inui

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

The low-temperature phase of η-Fe2Al5 has been identified experimentally for the first time and the crystal structure of the low-temperature phase (designated as η') has been refined by scanning transmission electron microscopy, combined with first-principles calculations. The low-temperature η' phase has a tripled superlattice structure based on the orthorhombic η-Fe2Al5 (space group Cmcm), in which Al atoms occupy two ninths of the partially occupied Al sites (Al2 and Al3) in a chain along the c-axis of the orthorhombic parent lattice in an ordered manner, giving rise to the monoclinic space group C2/c, the stoichiometric composition Fe3Al8 (Al-27.3 at.%Fe), and the Pearson symbol mC44. The partially occupied Al sites along the c-axis of the orthorhombic parent lattice are converted to the Al site (Al3″ site) of full occupancy in the monoclinic superlattice of the η'-Fe3Al8. The η-η' phase transformation temperature decreases from between 350 and 400 °C at the composition of Al-26.7 at.%Fe to between 300 and 350 °C at compositions in the range of Al-27.3 to 28.6 at.%Fe, indicating that the η' phase exists primarily at the Fe-lean side of the solid-solubility region of the η-Fe2Al5 phase.

Original languageEnglish
Pages (from-to)290-299
Number of pages10
JournalActa Materialia
Volume129
DOIs
Publication statusPublished - 2017 May 1
Externally publishedYes

Keywords

  • Intermetallic compound
  • Orientation variant
  • Phase diagram
  • Scanning transmission electron microscopy
  • ab-initio total energy calculations

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

Fingerprint Dive into the research topics of 'Crystal structure of η'-Fe<sub>3</sub>Al<sub>8</sub>; low-temperature phase of η-Fe<sub>2</sub>Al<sub>5</sub> accompanied by an ordered arrangement of Al atoms of full occupancy in the c-axis chain sites'. Together they form a unique fingerprint.

Cite this