Ordering and phase separation in b.c.c. aluminides of the Ni-Fe-Al-Ti system

R. Kainuma, K. Urushiyama, K. Ishikawa, C. C. Jia, I. Ohnuma, K. Ishida

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The phase equilibria and ordering reactions in the b.c.c. aluminides of the Ni-Al-Ti-Fe system at 800-1300°C have been investigated mainly by the diffusion couple method. The compositions of the β (B2: (Ni,Fe)(Al,Ti)) and H (L21: (Ni5Fe)2AlTi) phases in equilibrium, the critical boundaries of the continuous ordering transition and the tricritical points have been determined. It is shown that the miscibility gap boundary between the β and H phases, tie line configurations and the β-H second order reaction can all be depicted inside a composition square whose corners are made up of NiAl-NiTi-FeAl-FeTi, respectively, i.e. (Ni,Fe)-50 at.% (Al,Ti). The stability region of the Heusler phase and the β + H immiscibility gap in the NiAl-NiTi pseudo-binary system are narrowed down by increasing the Fe content. The phase stability of these ordered b.c.c. aluminides is presented and discussed.

Original languageEnglish
Pages (from-to)235-244
Number of pages10
JournalMaterials Science and Engineering: A
Issue number1-2
Publication statusPublished - 1997 Dec


  • B2 phase
  • FeAlTi alloy
  • L2 phase
  • Miscibility gap
  • NiAl
  • Order-disorder transition
  • Phase stability
  • Ti alloy
  • Tricritical point
  • b.c.c. aluminides


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