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Phys. Rev. Lett. 99, 247201 (2007) [4 pages]

Increasing Magnetoplasticity in Polycrystalline Ni-Mn-Ga by Reducing Internal Constraints through Porosity

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Yuttanant Boonyongmaneerat1,*, Markus Chmielus2,†, David C. Dunand1, and Peter Müllner2
1Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
2Department of Materials Science and Engineering, Boise State University, Boise, Idaho 83725, USA

Received 2 October 2007; published 10 December 2007

See accompanying Physics Focus

Foams with 55% and 76% open porosity were produced from a Ni-Mn-Ga magnetic shape-memory alloy by replication casting. These polycrystalline martensitic foams display a fully reversible magnetic-field-induced strain of up to 0.115% without bias stress, which is about 50 times larger than nonporous, fine-grained Ni-Mn-Ga. This very large improvement is attributed to the bamboolike structure of grains in the foam struts which, due to reduced internal constraints, deform by magnetic-field-induced twinning more easily than equiaxed grains in nonporous Ni-Mn-Ga.

© 2007 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.99.247201
DOI:
10.1103/PhysRevLett.99.247201
PACS:
75.30.Kz, 61.72.Mm, 75.80.+q

*Present address: Metallurgy and Materials Science Research Institute, Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand.

†Also at Hahn-Meitner-Institut, Smart Magnetic Materials Group, SF1, 14109, Berlin, Germany.

 
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