Characterization and modeling of the magnetic field-induced strain and work output in Ni2 MnGa magnetic shape memory alloys

B. Kiefer, H. E. Karaca, D. C. Lagoudas, I. Karaman

Research output: Contribution to journalArticlepeer-review

79 Scopus citations

Abstract

This paper is concerned with the experimental characterization and the constitutive modeling of magnetic shape memory alloys (MSMA), in terms of their applicability as actuator materials. The key properties that determine the actuation characteristics are the magnetic field-induced strain (MFIS) and the blocking stress. With the goal of increasing the corresponding actuation output, a material selection strategy was followed which was aimed at obtaining a higher magnetocrystalline anisotropy energy, while keeping the detwinning stress low. This was achieved by choosing a composition in which the separation of the Curie temperature and the martensitic transformation temperatures was large, and then selecting an operating temperature just below the phase transformation temperature. In the selected Ni51.1 Mn24.0 Ga24.9 composition a more than 50% increase of the actuation work output was observed, compared to corresponding data reported in the literature for other off-stoichiometric compositions of the Ni2 MnGa intermetallic compound. The second part of the paper describes a phenomenological constitutive model that predicts the MFIS hysteresis curves observed in the first part. The model is concerned with the field-induced reorientation of martensitic variants and changes in the magnetic microstructure. Dissipative effects are captured by introducing internal state variables into the free energy function. In its most general form the contributing energy terms are the elastic strain energy, the Zeeman energy, the magnetocrystalline anisotropy energy and appropriate mixing terms. Typical loading cases are considered and the accuracy of the model predictions is evaluated by comparison with the experimental data presented in the first part of this work.

Original languageEnglish
Pages (from-to)164-175
Number of pages12
JournalJournal of Magnetism and Magnetic Materials
Volume312
Issue number1
DOIs
StatePublished - May 2007

Bibliographical note

Funding Information:
This work was supported by the Army Research Office, Contract No. DAAD 19-02-1-0261, the National Science Foundation—Division of Materials Research, Contract No. 0244126, and the US Civilian Research & Development Foundation, Grant No. RE1-2525-TO-03. Appendix A

Keywords

  • Actuation work output
  • Blocking stress
  • Constitutive modeling
  • Magnetic field-induced strain
  • Magnetic shape memory alloys

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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