- Effect of Magnetic properties and Microstructure of Hydrogenation stage in HDDR process
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S.H. Lee, J.H. Yu, Y.D. Kim
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J Korean Powder Metall Inst. 2011;18(5):443-448.
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DOI: https://doi.org/10.4150/KPMI.2011.18.5.443
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- The HDDR(hydrogenation-disproportionation-desorption-recombination) process can be used as an effective way of converting no coercivity Nd-Fe-B material, with a coarse Nd_2Fe_14B grain structure to a highly coercive one with a fine grain. Careful control of the HDDR process can lead to an anisotropic Nd_2Fe_14B without any post aligning process. In this study, the effect of hydrogen gas input at various temperature in range of 200sim500°C of hydrogenation stage (named Modified-solid HDDR, MS-HDDR) on the magnetic properties has been investigated. The powder from the modified-solid HDDR process exhibits Br of 11.7 kG and iHc of 10.7 kOe, which are superior to those of the powder prepared using the normal HDDR process.
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Citations to this article as recorded by  - The Influence of Dehydrogenation Speed on the Microstructure and Magnetic Properties of Nd-Fe-B Magnets Prepared by HDDR Process
Hee-Ryoung Cha, Ji-Hun Yu, Youn-Kyoung Baek, Hae-Woong Kwon, Yang-Do Kim, Jung-Goo Lee
Journal of Magnetics.2014; 19(1): 49. CrossRef
- Effect of Homogenization Treatment on Magnetic Properties of HDDR Treated Nd-Fe-Ga-Nb-B Alloy
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J.H. Yu, S.H. Lee, D.H. Kim, D.W. Lee, B.K. Kim, M.H. Choi, Y.D. Kim
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J Korean Powder Metall Inst. 2009;16(4):285-290.
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DOI: https://doi.org/10.4150/KPMI.2009.16.4.285
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- HDDR treated anisotropic Nd-Fe-B powders have been widely used, due to their excellent magnetic properties, especially for sheet motors and sunroof motors of hybrid and electric vehicles. Final microstructure and coercivity of such Nd-Fe-B powders depend on the state of starting mother alloys, so additional homogenization treatment is required for improving magnetic properties of them. In this study, a homogenization treatment was performed at 900sim1140°C in order to control the grain size and Nd-rich phase distribution, and at the same time to improve coercivity of the HDDR treated magnetic powders. FE-SEM was used for observing grain size of the HDDR treated powder and EPMA was employed to observe distribution of Nd-rich phase. Magnetic properties were analyzed with a vibrating sample magnetometer.
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