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Proceedings Paper

Cobalt-base ferromagnetic shape memory alloys
Author(s): Corneliu M. Craciunescu; Yoichi Kishi; Marc De Graef; Thomas A. Lograsso; Manfred R. Wuttig
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Paper Abstract

Single crystalline and polycrystalline CoxNiyGa100-(x+y), 41 < xCo< 62 and 19.3 < yNi < 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 XCo 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.

Paper Details

Date Published: 11 July 2002
PDF: 10 pages
Proc. SPIE 4699, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics, (11 July 2002); doi: 10.1117/12.474980
Show Author Affiliations
Corneliu M. Craciunescu, Univ. of Maryland/College Park (United States)
Yoichi Kishi, Univ. of Maryland/College Park (United States)
Marc De Graef, Carnegie Mellon Univ. (United States)
Thomas A. Lograsso, Iowa State Univ. (United States)
Manfred R. Wuttig, Univ. of Maryland/College Park (United States)

Published in SPIE Proceedings Vol. 4699:
Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics
Christopher S. Lynch, Editor(s)

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