Texture and training of magnetic shape memory foam

Cassie Witherspoon, Peiqi Zheng, Markus Chmielus, Sven C. Vogel, David C. Dunand, Peter Müllner*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Magnetic shape memory alloys display magnetic-field-induced strain (MFIS) of up to 10% as single crystals. Polycrystalline materials are much easier to create but display a near-zero MFIS because twinning of neighboring grains introduces strain incompatibility, leading to high internal stresses. Pores reduce these incompatibilities between grains and thus increase the MFIS of polycrystalline Ni-Mn-Ga, which after training (thermo-magneto-mechanical cycling) exhibits MFIS as high as 8.7%. Here, we show that this training effect results from a decoupling of struts surrounding pores in polycrystalline Ni-Mn-Ga during the martensitic transformation. To show this effect in highly textured porous samples, neutron diffraction measurements were performed as a function of temperature for phase characterization and a method for structure analysis was developed. Texture measurements were conducted with a magnetic field applied at various orientations to the porous sample, demonstrating that selection of martensite variants takes place during cooling.

Original languageEnglish (US)
Pages (from-to)2113-2120
Number of pages8
JournalActa Materialia
Volume61
Issue number6
DOIs
StatePublished - Apr 2013

Keywords

  • Heusler alloys
  • Martensitic phase transformation
  • Neutron diffraction
  • NiMnGa
  • Thermal cycling

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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