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Numéro
J. Phys. IV France
Volume 112, October 2003
Page(s) 93 - 100
DOI https://doi.org/10.1051/jp4:2003842


J. Phys. IV France 112 (2003) 93
DOI: 10.1051/jp4:2003842

Martensitic transformation in Fe-based shape memory alloys under magnetic field

T. Kakeshita1, T. Fukuda1, T. Terai1, T. Takeuchi2 and K. Kishio3

1  Department of Materials Science and Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
2  Low Temperature Center, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
3  Department of Applied Chemistry, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8666, Japan


Abstract
Effects of magnetic field on martensitic transformations have been examined in order to know a magnetic field-induced martensitic transformation by using Fe 3Pt and Fe-Ni-Co-Ti shape memory alloys and an Fe-Ni alloy polycrystals, and control of variants by magnetic field by using Fe-Pd, Ni 2MnGa and Fe 3Pt shape memory alloy single crystals. Following results were obtained: (i) The effects of magnetic field on the martensitic transformation start temperature is explained by the equation proposed by our group. (ii) Magnetoelastic martensitic transformation (maretensites are induced only while a magnetic field is applied and are transformed back to the parent phase when the magnetic field is removed) appears in an ausaged Fe-Ni-Co-Ti shape memory alloy. (iii) In Fe-31.2Pd(at.%), whose easy axis is the a-axis in martensite state, a large expansion of about 3% appears in [OOl] $_{\rm p}$ (P is the symbol of the parent phase) direction at 77 K by applying a magnetic field along [001] $_{\rm p}$ direction. In Ni 2MnGa, whose easy axis is the c-axis in martensite state, a large contraction of about 3.8% appears in [001] $_{\rm p}$ direction at 77 K by applying a magnetic field along [001] $_{\rm p}$ direction. These strains are nearly the same as those expected from perfect conversion to the preferred variants under magnetic field. In Fe 3Pt, whose easy axis is the c-axis in martensite state, a large contraction of about 2.3% appears in [001] $_{\rm p}$ direction at 4.2 K by applying a magnetic field along [001] $_{\rm p}$ direction, and a part of this contraction (0.6%) recovers as the field is removed. Considering results of (iii), the mechanism of conversion of variants by magnetic field is discussed.



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