Phase Equilibria and Phase Transformations in New B2-type Ferromagnetic Shape Memory Alloys of Co-Ni-Ga and Co-Ni-Al Systems
Open Access
- 1 January 2001
- journal article
- Published by Japan Institute of Metals in MATERIALS TRANSACTIONS
- Vol. 42 (11), 2472-2475
- https://doi.org/10.2320/matertrans.42.2472
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.Keywords
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