Microstructural evolution in ductile β(B2) + γ ′(L12) Ni-Al-Fe alloys

R. Kainuma, S. Imano, H. Ohtani, K. Ishida

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Results of investigations on the microstructural features of β(B2) + γ′ (L12) two-phase Ni-Al-Fe alloys fabricated through various thermomechanical processes are reported. It is found that three types of β + γ′structures: blocky, lamellar and widmanstätten structures, are formed when alloys quenched from high temperatures are reannealed at 800°C. The formation of the blocky structure is brought about by the following successive reactions, the β → β′(L10) martensitic transformation, the β′ → Ni5Al3 (Pt5Ga3 type) ordering reaction and the Ni5Al3 → β + γ′ transition similar to a discontinuous transition occurring during heating up to 800°C. On the other hand, the lamellar structure results from the Ni5Al3 → γ′ transition and a heterogeneous precipitation of the β phase on the boundaries between the γ′ variants after the formation of the Ni5Al3 from the β′ phase. It is also observed that the mechanical properties are affected by the type of microstructures present. These results suggest that the Ni-Al-Fe dual-phase alloys are amenable to microstructural control through thermomechanical treatments to realise optimum mechanical properties as in the case of Fe base alloys.

Original languageEnglish
Pages (from-to)37-45
Number of pages9
Issue number1
Publication statusPublished - 1996


  • Lamellar structure
  • Martensitic transformation
  • Microstructural control
  • Nickel aluminides
  • Order-disorder transition


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