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모합금의 균질화처리가 HDDR 처리된 Nd-Fe-Ga-Nb-B 합금의 자기적 특성에 미치는 영향
유지훈,이상협,김동환,이동원,김병기,최문희,김양도,Yu, J.H.,Lee, S.H.,Kim, D.H.,Lee, D.W.,Kim, B.K.,Choi, M.H.,Kim, Y.D. 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.4
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 $900\sim1140^{\circ}C$ 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.
체심정방정 구조 Fe-Co계 합금상의 합성 및 그 자기적 특성
김경민(K. M. Kim),권해웅(H. W. Kwon),이정구(J. G. Lee),유지훈(J. H. Yu) 한국자기학회 2017 韓國磁氣學會誌 Vol.27 No.4
Bulk-type body-centered-tetragonal Fe-Co alloy was synthesised by utilising a conventional alloy preparation technologies, such as melting, solidification, and homogenising treatments, and its magnetic properties were investigated. In the (Fe<SUB>100−x</SUB>Co<SUB>x</SUB>)<SUB>1−y</SUB>C<SUB>y</SUB> alloy, the composition range, from which single phase body-centered-tetragonal alloy (martensite phase) was obtained, was severely limited: Co content x = 2.5, and C content y = 0.062. Tetragonality(c/a) of the synthesised body-centered-tetragonal (Fe<SUB>97.5</SUB>Co<SUB>2.5</SUB>)<SUB>0.938</SUB>C<SUB>0.062</SUB> alloy was 1.05. Magnetocrystalline anisotropy constant (K₁) of the body-centered-tetragonal (Fe<SUB>97.5</SUB>Co<SUB>2.5</SUB>)<SUB>0.938</SUB>C<SUB>0.062</SUB> alloy was measured to be 9.8 × 10⁵ J/㎥), which was 3.1 time as high as the pure iron (α-Fe).
희토류 자원문제 해결을 위한 모터 및 영구자석 연구개발 동향
이정구(J. G. Lee),유지훈(J. H. Yu),김휘준(H. J. Kim),장태석(T. S. Jang) 한국자기학회 2012 韓國磁氣學會誌 Vol.22 No.2
Since Nd-Fe-B magnet was first synthesized in 1983, many new applications have emerged in the past two decades. With regard to motor market, it will expand because of strong energy saving requirements from the automobile and electric application markets. Especially, permanent magnet motors for hybrid and electric vehicles are drawing great attention and the usage of Nd-Fe-B magnets will increase all the more hereafter. There is, however, a serious problem as motors in such eco-friendly cars are said to operate in high temperatures of about 200℃. Nd-Fe-B magnet has a drawback of dramatically decreasing coercive force with the rise of temperature. In order to improve this aspect. the best way is to add dysprosium (Dy) into the magnet. So, Dy has become an essential element for Nd-Fe-B high-performance magnet as it helps to maintain coercive force even at high temperatures. On the other hand, the rare earth resources in the earth crust are eccentrically-located and its majority is produced in China. There is a need to reduce its usage as, especially compared to light rare earth elements as neodymium (Nd) and samarium (Sm), heavy rare earth elements including Dy are unevenly distributed to a dramatic degree, their output low, and their prices are about 10 times that of Nd. The present article includes a summary of the trend in research and development of motors and permanent magnets to solve rare-earth resources problem.