Skip to main content
Article
Nanomechanics and Magnetic Structure of Orthorhombic Ni–Mn–Ga Martensite
Materials Science and Engineering: A (2008)
  • Peter Müllner, Boise State University
  • Z. Clark, Boise State University
  • Linda Kenoyer, Boise State University
  • William B. Knowlton, Boise State University
  • G. Kostorz, ETH Zurich
Abstract

Atomic-force microscopy (AFM), magnetic-force microscopy (MFM), and nanoindentation experiments were performed on a Ni–Mn–Ga single crystal with orthorhombic (14 M) martensite. The surface relief was characterized and used to identify the orientation of individual twin variants. It was shown that ab- and bc-twinning modes are present. The magnetic domains are elongated along the crystallographic c direction. Twin variants with the c direction perpendicular to the surface exhibit an out-of-plane magnetization which can be identified through a strong contrast in the MFM image. The deformation caused with nanoindentation is recoverable to a large degree. No trace of deformation twinning was found after unloading. The results are discussed in the light of pseudo-elastic twinning and dislocation activity. It is concluded that although the residual deformation is due to dislocation activity, it is likely that pseudo-elastic twinning took place during loading and unloading. The results indicate a size effect on deformation twinning under localized loading.

Keywords
  • magnetic shape-memory alloys,
  • twin-microstructure,
  • atomic-force microscopy (AFM),
  • magnetic-force microscopy
Publication Date
May 25, 2008
Citation Information
Peter Müllner, Z. Clark, Linda Kenoyer, William B. Knowlton, et al.. "Nanomechanics and Magnetic Structure of Orthorhombic Ni–Mn–Ga Martensite" Materials Science and Engineering: A Vol. 481-482 (2008)
Available at: http://works.bepress.com/william_knowlton/4/