Increasing magnetoplasticity in polycrystalline Ni-Mn-Ga by reducing internal constraints through porosity |
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| Authors: | Boonyongmaneerat Yuttanant Chmielus Markus Dunand David C Müllner Peter |
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| Institution: | Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA. |
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| Abstract: | 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. |
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