Magnetic-field-induced recovery strain in polycrystalline Ni-Mn-Ga foam

Markus Chmielus*, Cassie Witherspoon, Robert C. Wimpory, Andreas Paulke, Andŕ Hilger, Xuexi Zhang, David C. Dunand, Peter Müllner

*Corresponding author for this work

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Recently, we have shown that a polycrystalline Ni-Mn-Ga magnetic shape-memory alloy, when containing two populations of pore sizes, shows very high magnetic-field-induced strain of up to 8.7%. Here, this double-porosity sample is imaged by x-ray microtomography, showing a homogenous distribution of both pore populations. The orientation of six large grains-four with 10M and two with 14M structure-is identified with neutron diffraction. In situ magnetomechanical experiments with a rotating magnetic field demonstrate that strain incompatibilities between misoriented grains are effectively screened by the pores which also stop the propagation of microcracks. During uniaxial compression performed with an orthogonal magnetic bias field, a strain as high as 1% is recovered on unloading by twinning, which is much larger than the elastic value of <0.1% measured without field. At the same time, repeated loading and unloading results in a reduction in the yield stress, which is a training effect similar to that in single crystals.

Original languageEnglish (US)
Article number123526
JournalJournal of Applied Physics
Volume108
Issue number12
DOIs
StatePublished - Dec 15 2010

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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    Chmielus, M., Witherspoon, C., Wimpory, R. C., Paulke, A., Hilger, A., Zhang, X., Dunand, D. C., & Müllner, P. (2010). Magnetic-field-induced recovery strain in polycrystalline Ni-Mn-Ga foam. Journal of Applied Physics, 108(12), [123526]. https://doi.org/10.1063/1.3524503