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Martensitic Transformation in Shape Memory Alloys under Magnetic Field and Hydrostatic Pressure
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Tomoyuki Kakeshita1), Takashi Fukuda1), Tatsuaki Sakamoto1), Tetsuya Takeuchi2), Koichi Kindo3), Syouichi Endo3) and Kohji Kishio4)
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1) Department Materials Science and Engineering, Graduate School of Engineering, Osaka University
2) Low Temperature Center, Osaka University
3) Research Center for Materials and Science at Extreme Conditions, Osaka University
4) Department of Applied Chemistry, Graduate School of Engineering, University of Tokyo
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Effects of magnetic field and hydrostatic pressure on martensitic transformation have been examined by using Fe–Pt, Cu–Al–Ni, Ni2MnGa and Fe–Pd shape memory alloys and Fe–Ni alloys. Following results are obtained; (i) in Fe–Pt, Cu–Al–Ni and Fe–Ni alloys, the experimental magnetic field and/or hydrostatic pressure dependence of martensitic transformation start temperature, Ms, is in good agreement with the dependence calculated by the equation previously proposed by our group to evaluate the relation between Ms and magnetic field and hydrostatic pressure. (ii) Giant magnetostriction has been observed in the martensite state of Ni2MnGa and Fe–31.2 at%Pd ferromagnetic shape memory alloy single crystals. The values (contraction of 3.8% for Ni2MnGa and expansion of about 3% for Fe–31.2 at%Pd) are nearly the same values as can be expected from the perfect conversion of variants, i.e., variants are converted to preferable variants whose magnetocrystalline anisotropy energy is minimum among them under the magnetic field.
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Keyword: martensitic transformation, transformation temperature, magnetic field, hydrostatic pressure, ferromagnetic shape memory alloy, magnetic anisotropy energy, giant magnetostriction
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Received: November 21, 2001
Accepted: January 07, 2002 ,
Published online: September 06, 2005 |
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Copyright (c) 2005 The Japan Institute of Metals |
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