MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Phase Equilibria and Phase Transformations in New B2-type Ferromagnetic Shape Memory Alloys of Co-Ni-Ga and Co-Ni-Al Systems
Katsunari OikawaTakuya OtaFumihiko GejimaToshihiro OhmoriRyosuke KainumaKiyohito Ishida
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2001 Volume 42 Issue 11 Pages 2472-2475

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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.

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© 2001 The Japan Institute of Metals and Materials
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