Phase equilibria in the Fe-Co binary system

Ikuo Ohnuma, Hirotoshi Enoki, Osamu Ikeda, Ryosuke Kainuma, Hiroshi Ohtani, Bo Sundman, Kiyohito Ishida

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220 Citations (Scopus)


α (A2)/γ (A1) phase equilibria of the Fe-Co system between 400 and 800°C were determined by means of lattice parameter measurement using thin film specimens. Bulk specimens were also analyzed to compare the extent of attainment to the equilibrium. The thin film technique was found to be greatly advantageous for obtaining the phase equilibria at lower temperatures where solid-state reactions are too slow to reach the equilibrium state in the conventional methods using bulk specimens. It was confirmed that the α+γ two-phase region extends below the temperature at which the α (A2)/α′ (B2) transus meets the α/α+γ boundary. Thermodynamic analysis was also conducted by taking the magnetic and chemical ordering contributions of the B2 structure into account, findings of which confirmed the extension of the α+γ two-phase region below the α/α′ ordering temperature.

Original languageEnglish
Pages (from-to)379-393
Number of pages15
JournalActa Materialia
Issue number2
Publication statusPublished - 2002 Jan 22


  • Microstructure
  • Order-disorder phenomena
  • Phase equilibria
  • Thermodynamics
  • Thin films


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