2004 Fiscal Year Final Research Report Summary
A giant strain associated with magnetic field-induced martensitic transformation in ferromagnetic shape memory alloys
| Project/Area Number |
15360367
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Structural/Functional materials
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| Research Institution | Osaka University |
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Principal Investigator |
KAKESHITA Tomoyuki Osaka University, Department of materials Science and Engineering, Graduate school of Engineering, Professor, 大学院・工学研究科, 教授 (90127209)
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| Co-Investigator(Kenkyū-buntansha) |
FUKUDA Takashi Osaka University, Department of materials Science and Engineering, Graduate school of Engineering, Associate Professor, 大学院・工学研究科, 講師 (50228912)
TERAI Tomoyuki Osaka University, Department of materials Science and Engineering, Graduate school of Engineering, Assistance Professor, 大学院・工学研究科, 助手 (20346183)
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| Project Period (FY) |
2003 – 2004
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| Keywords | martensitic transformation / shape memory alloys / magnetocrystalline anisotropy / magnetostriction / twinning deformation / shear stress / magnetization curve / single crystal |
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| Research Abstract |
Recently, ferromagnetic shape memory alloys have attracted considerable attention because some of them show a giant magnetic field-induced strain of several percent in association with rearrangement of martensite variants. The shape change is due to twinning plane movement, and it does not recover by only removing the magnetic field. In order to recover the strain we need to apply a bias stress or heat up the specimen above the transformation temperature. However, if the martensite phase is induced by magnetic field, and the strain appears in this process, the strain will recover in the field removing process because the reverse transformation occurs in this process. In the present study, therefore, we investigated the effect of magnetic field on the martensitic transformations of Ni_2MnGa,Ni_<2.14>Mn_<0.84>Ga_<1.02> and Ni_<2.14>Mn_<0.92>Ga_<0.94>, which exhibit P (parent phase)-I (intermediate phase)-10M, P-14M-2M and P-2M transformations, respectively. The following results are obtained : (i)the P-I transformation temperature does not change by magnetic field. (ii)the I-10M and the P-14M transformation temperatures decrease under the magnetic field up to 0.8 MA/m and 0.4 MA/m, respectively, and then increase with increasing magnetic fields higher than those fields. (iii)the 14M-2M transformation temperature increases under the magnetic field up to 0.4 MA/m and decreases under the magnetic field up to 0.8 MA/m and then the transformation temperature increases again when magnetic field is applied higher than 0.8 MA/m. (iv)the P-2M transformation temperature increases linearly with increasing magnetic field. These results are well explained by the Clausius-Clapeyron.
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Research Products
(11 results)
