Cobalt-base ferromagnetic shape memory alloys

Corneliu M. Craciunescu; Yoichi Kishi; Marc De Graef; Thomas A. Lograsso; Manfred R. Wuttig

doi:10.1117/12.474980

11 July 2002 Cobalt-base ferromagnetic shape memory alloys

Corneliu M. Craciunescu, Yoichi Kishi, Marc De Graef, Thomas A. Lograsso, Manfred R. Wuttig

Proceedings Volume 4699, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics; (2002) https://doi.org/10.1117/12.474980
Event: SPIE's 9th Annual International Symposium on Smart Structures and Materials, 2002, San Diego, California, United States

Abstract

Single crystalline and polycrystalline Co_xNi_yGa_100-(x+y), 41 < x_Co< 62 and 19.3 < y_Ni < 32.7, Ferromagnetic Shape Memory Alloys have been produced in the range of the Heusler-type composition. Elasto-mechanical properties have been analyzed for the annealed and quenched states, respectively. The mechanical spectroscopy data show the occurrence of martensitic phase transformation with the transition range and characteristics depending on the state and the composition of the alloys. For X_Co approximately equals 49 +/- 1 at percent, the Ni/Ga ratio was shown to be in direct relationship with the transition temperature range, from an Ms of -100 degrees C for Ni/Ga approximately equals (21/29) to a +150 degrees C for a Ni/Ga ratio of about (26/25). For Ga approximately equals 27 +/- 0.4 at percent, the Co/Ni ratio is in indirect relationship with the transition temperature, with an Ms of -125 degrees C for a (53/19) ratio to a +175 degrees C for a ratio of about (49/26). Optical and electron microscopy shows that a typical thermoelastic martensitic transformation occurs. The L2₁ Structurbericht parent phase transforms into monoclinic or orthohombic martensitic upon cooling. The formation of a Co-rich phase has been observed for alloys with lower Ga content and is considered to be one of the reasons for the difference in the transformation range for annealed and quenched alloys.

Citation Download Citation

Corneliu M. Craciunescu, Yoichi Kishi, Marc De Graef, Thomas A. Lograsso, and Manfred R. Wuttig "Cobalt-base ferromagnetic shape memory alloys", Proc. SPIE 4699, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics, (11 July 2002); https://doi.org/10.1117/12.474980

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