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 language | English |
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Pages (from-to) | 290-299 |
Number of pages | 10 |
Journal | Acta Materialia |
Volume | 129 |
DOIs | |
Publication status | Published - 2017 May 1 |
Externally published | Yes |
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