Microstructure and Coercivity of Rare Earth Magnets
| Project/Area Number |
63460199
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属材料(含表面処理・腐食防食)
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| Research Institution | The University of Tokyo |
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Principal Investigator |
UMEDA Takateru the University of Tokyo, Department of Metallurgy, Professor, 工学部, 教授 (50011078)
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| Co-Investigator(Kenkyū-buntansha) |
NAGAYAMA Katsuhisa the University of Tokyo, Department of Metallurgy, Research assistant, 工学部, 助手 (80189167)
SUZUKI Toshio the University of Tokyo, Department of Metallurgy, Associate Professor, 工学部, 助教授 (70115111)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥8,700,000 (Direct Cost: ¥8,700,000)
Fiscal Year 1989: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1988: ¥6,600,000 (Direct Cost: ¥6,600,000)
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| Keywords | Nd_2Fe_<14>B / microstructure / metastable grain boundary / coercivity / Sm_2Co_<17> / TbCu_7 / TbCu_7 / 急冷薄帯 / Nd_<15>Fe_<77>B_8合金 / 液体急冷法 / 準安定相 / セル構造 / 保磁力 / 結晶配向 |
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| Research Abstract |
High coercivity of 23 kOe was obtained on melt-spun Nd_<15>Fe_<77>B_8 ribbons with 40-100 m in thichness. The samples which showed high coercivity contained a new metastable boundary phase with 20-80 nm in width Nd_2Fe_<14>B grains were surrounded with this phase and they formed smooth and coherent interface structures. These microstructures indicated a strong pinning effect on the motion of the domain wall. The new phase was identified by analysis of electron diffraction patterns as a tetragonal structure with lattice constants of a=0.512 nm, and c=0.801 nm. By heat treatment over than 760 K, it was decomposed into fcc-Nd and a small amount of NdFe_4B_4. Interface structures between Nd_2Fe_<14>B and grain boundaries became incohent and also coercivity decreased.
The vertical sections of Sm-Co-Cu-Fe quaternary and Sm-Co-Cu-Fe -Zr quinary phase diagrams were determined in composition range from 6 to 16 at%Sm. The 2/17 phase has hexagonal TbCu_7, hexagonal Th_2Ni_<17> and rhombohedral Th_2Zn_<17> type structures. Only alloys with TbCu_7 phase at high temperature have superior magnetic properties with high coercivity. The Sm content with 2/17 single phase of TbCu_7 type structure shifts to the Sm-poor side with addition of Zr.
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Report
(3 results)
Research Products
(14 results)
