Phase equilibria and stability of the B2 phase in the Ni-Mn-Al and Co-Mn-Al systems

R. Kainuma, M. Ise, K. Ishikawa, I. Ohnuma, K. Ishida

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34 Citations (Scopus)


The phase equilibria and ordering reactions in the composition region up to 50 at.% Al have been investigated in the Ni-Mn-Al and Co-Mn-Al systems at temperatures in the interval 850-1200°C mainly by the diffusion couple method. The compositions of the γ (A1: fcc-Ni, -Co, γ-Mn), γ′ (L12: Ni3Al), β (B2: NiAl, CoAl, NiMn), β-Mn (A13: β-Mn type), δ-Mn (A2: bcc-Mn) and ε (A3: hcp-(Mn, Al)) phases in equilibrium and the critical boundaries of the A2/B2 continuous ordering transition in the bcc phase region have been determined. It is shown that in the Mn-rich portion of the ternary systems both continuous and discontinuous A2 to B2 ordering transitions exist. The A2+B2 two-phase region in the isothermal sections has a lenticular shape and exists over a wide temperature range. The phase equilibria between the γ, γ′, β, β-Mn, δ-Mn and ε phases are presented and the stability of the ordered bcc aluminides is discussed.

Original languageEnglish
Pages (from-to)173-180
Number of pages8
JournalJournal of Alloys and Compounds
Issue number1-2
Publication statusPublished - 1998 May 1


  • B2 phase
  • Co-Al base alloy
  • Miscibility gap
  • Ni-Al base alloy
  • Order-disorder transition
  • Phase equilibrium
  • bcc aluminides

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry


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