J. Phys. IV France 11 (2001) Pr8-317-Pr8-322
Study of the effect of magnetic field on the structure of Ni-Mn-Ga shape memory alloysY. Ge1, O. Söderberg1, N. Glavatska2, K. Ullakko3 and V.K. Lindroos1
1 Helsinki University of Technology, Laboratory of Physical Metallurgy and Materials Science, P.O. Box 6200, 02015 Hut, Finland
2 Institute for Metal Physics, Department of Alloyed Steels, 252680 Kiev 142, Ukraine
3 Helsinki University of Technology, Laboratory of Biomedical Engineering, P.O. Box 2200, 02015 Hut, Finland
In certain ferromagnetic shape memory Ni-Mn-Ga alloys, the shape changes of the material can be controlled by magnetic field. These changes occur in the martensitic phase and they are result of the martensitic twin boundary motion together with the change of the martensite variants. In the present study, the connection between the magnetisation of the alloys and their martensitic structure was observed by using different methods of investigation. The structure of non-stoichiometric Ni-Mn-Ga alloy was investigated by the optical metallography connected to the optical differential scanning calorimeter (DSC), scanning electron microscopy (SEM) and the X-ray diffraction θ-2θ. Also, the straining of the materials in dynamic magnetic field was studied. The results of these different investigation methods were in good agreement with each other. However, with the methods in which electron beam was applied to the specimen, it was found that the structure was affected by the research method. The images of martensitic structure obtained with the different methods were compared with each other.
© EDP Sciences 2001