Phase equilibria and phase transformations in new B2-type ferromagnetic shape memory alloys of Co-Ni-Ga and Co-Ni-Al systems

Katsunari Oikawa, Takuya Ota, Fumihiko Gejima, Toshihiro Ohmori, Ryosuke Kainuma, Kiyohito Ishida

Research output: Contribution to journalArticlepeer-review

260 Citations (Scopus)

Abstract

The phase equilibria, the martensitic and magnetic phase transformations in the β (B2) phase region of the Co-Ni-Ga and Co-Ni-Al systems have been investigated. It is shown that some compositions in the range Co-(15-30)at%Ni-30 at%Ga and Co-(30-40)at%Ni-30 at%Al exhibit both the β to β′ (L10) thermoelastic martensitic transformation and the para/ferromagnetic transition. Some of these undergo the martensitic transformation from the paramagnetic β to the ferromagnetic β′. The introduction of a small amount of the γ phase into the β phase by heat treatment, based on the results of the β/γ phase equilibria study in these systems, is shown to significantly improve the ductility in both alloy systems. The new β single phase and β + γ two-phase ferromagnetic shape memory alloys (FSMAs) of the Co-Ni-Ga and Co-Ni-Al systems hold great promise as new smart materials.

Original languageEnglish
Pages (from-to)2472-2475
Number of pages4
JournalMaterials Transactions
Volume42
Issue number11
DOIs
Publication statusPublished - 2001 Nov

Keywords

  • Cobalt-nickel-aluminium alloy
  • Cobalt-nicket-gallium alloy
  • Ferromagnetic shape memory alloy
  • Martenstic transformation
  • Phase diagram

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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