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Vol.51, No.5, 371 ~ 377, 2013
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| Title |
| Synthesis of Ultra-Fine Grained Nd-Fe-B Magnetic Powder by the Control of DR Speed during HDDR Process |
| 차희령 Hee Ryoung Cha , 이정구 Jung Goo Lee , 백연경 Youn Kyoung Baek , 유지훈 Ji Hun Yu , 권해웅 Hae Woong Kwon , 김양도 Yang Do Kim |
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| Abstract |
| In the present study, the influence of desorption-recombination (DR) speed during hydrogenation- decomposition-desorption-recombination (HDDR) process on the microstructure and magnetic properties of Nd-Fe-B based magnetic powders has been studied. Nd-Fe-B based alloys were made by mold casting and homogenization heat treatment. They were then subjected to HDDR treatment. During DR reaction, pumping speed and time of hydrogenation were systematically changed to control the speed of DR reaction. It was found that the slower hydrogen desorption during DR reaction can result in a smaller grain size and significantly increases the magnetic properties of the powder. The coercivity and the remanence of the HDDR powders in the size range of 200-300 μm was 12.4 kOe and 11.4 kG, respectively. In addition, the remanence was further increased to 12.0 kG by milling the powders down to 25-90 μm, which resulted in (BH)max of 26.5 MGOe. |
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| Key Words |
| magnetic materials, HDDR, grain refinement, ribrating-sample magnetometer, anisotropy |
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