Training, constraints, and high-cycle magneto-mechanical properties of Ni-Mn-Ga magnetic shape-memory alloys

Markus Chmielus 1Volodymyr A. Chernenko 2William B. Knowlton 1,3Gernot Kostorz 4Peter Mullner 1

1. Department of Materials Science and Engineering, Boise State University, 1910 University Dr., Boise ID-83725, United States
2. Institute of Magnetism, NAS of Ukraine, 36-B Vernadsky str., Kiev 03142, Ukraine
3. Department of Electrical and Computer Engineering, Boise State University, 1910 University Dr., Boise ID-83725, United States
4. ETH Zürich (ETHZ), Wolfgang-Pauli-Strasse 10, Zürich 8093, Switzerland

Abstract

Magneto-mechanical experiments with a rotating magnetic field of 0.97 T were performed with a Ni-Mn-Ga single crystal. Periodic strains exceeding 1% were recorded over a hundred million magneto-mechanical cycles. The twin-microstructure of the cycled crystal was characterized using atomic force microscopy and magnetic force microscopy. In the center of the sample, no twin boundaries were found. At the sample edges, the microstructure consists of a dense twin pattern. The results are compared with previous experiments of differently trained crystals. It is distinguished between "less efficient training" which results in a nearly self-accomodated martensite and "efficient training" which results in a nearly single variant state. The evolution of twin-microstructure is discussed in terms of training, magneto-mechanical cycling, and extrinsic constraints imposed by the experimental setting. It is concluded that the response of a magnetic shape-memory alloy to an alternating excitation depends strongly on the initial twin-microstructure established through training. In particular, a less efficent training results in a twin-microstructure which can adapt to extrinsic constraints resulting in continued large periodic magnetic-field-induced deformation. In contrast, the twin-microstructure of an efficiently trained crystal cannot adapt to extrinsic constraints resulting in early failure by fracture.

 

Related papers
  1. Reversible and irreversible martensitic transformations in Fe-Pd and Fe-Pd-Co alloys
  2. Residual stress in Ni-Mn-Ga thin films deposited on different substrates
  3. Transformation behavior of Ni-Mn-Ga/Si(100) thin film composites with different film thicknesses
  4. Effect of magnetic field on the TA2 phonon branch softening in Ni2MnGa
  5. Texture and Stress in Ni-Mn-Ga Thin Films Deposited on Alumina
  6. Properties of martensitic Ni-Mn-Ga thin films deposited on Mo foils
  7. Pre-martensitic phenomena in a near stoichiometric Ni2MnGa polycrystalline alloy
  8. MAGNETORESISTANCE OF Ni-Mn-Ga THIN FILMS IN THE VICINITY OF MAGNETOSTRUCTURAL TRANSFORMATION
  9. Magnetomechanical Properties of Polycrystalline Ni-Mn-Ga Thin Film Actuators
  10. The broadband magneto-electric energy conversion by the NiMnGa single crystal/piezoceramic system
  11. Neutron study of the martensitic transformation in Ni-Fe-Ga alloys
  12. Stress-temperature relationship in a Ni-Mn-Ga single crystal
  13. PROPERTIES OF SPUTTER-DEPOSITED Ni-Mn-Ga THIN FILMS
  14. DEPENDENCE OF THE MAGNETIC ANISOTROPY ON THE THICKNESS AND ANNEALING OF SPUTTER-DEPOSITED Ni-Mn-Ga THIN FILMS

Presentation: Oral at E-MRS Fall Meeting 2007, Symposium E, by Markus Chmielus
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 16:03
Revised:   2009-06-07 00:44