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南海洋,朱立群,刘慧丛,李卫平.阴极析氢对钕铁硼磁体矫顽力和热稳定性的影响[J].稀有金属材料与工程(英文),2017,46(12):3658~3662.[Nan Haiyang,Zhu Liqun,Liu Huicong,Li Weiping.Effect of Cathodic Hydrogen Evolution on the Coercivity and Thermal Stability of Sintered NdFeB Magnets[J].Rare Metal Materials and Engineering,2017,46(12):3658~3662.]
Effect of Cathodic Hydrogen Evolution on the Coercivity and Thermal Stability of Sintered NdFeB Magnets
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Received:December 30, 2015  Revised:April 22, 2016
DOI:
Key words: NdFeB  coercivity  thermal stability  hydrogen
Foundation item:
Author NameAffiliationE-mail
Nan Haiyang 北京航空航天大学材料科学与工程学院 nanhy@buaa.edu.cn 
Zhu Liqun 北京航空航天大学材料科学与工程学院  
Liu Huicong 北京航空航天大学材料科学与工程学院 liuhc@buaa.edu.cn 
Li Weiping 北京航空航天大学材料科学与工程学院  
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Abstract:
      The effect of cathodic hydrogen evolution on coercivity and thermal stability had been investigated in sintered NdFeB magnets. The magnetic properties, phase structure and morphology were systematically studied by SQUID-VSM, DSC, XRD, TEM and SEM. After cathodic hydrogen evolution, The Hcj decreased from 13 to 12.1 kOe. The temperature coefficients α declined from -0.253 %/℃ to -0.3229 %/℃, and the β declined from -0.7518 %/℃ to -0.7738 %/℃. A mechanism was proposed to explain the results. In the process of cathodic hydrogen evolution, parts of the generated hydrogen atoms reacted with the Nd2Fe14B phase and Nd-rich phase, formed Nd2Fe14BHx and NdHx, respectively. The formation of NdHx caused a volume expansion. Which resulted in intergranular cracks and stress. X-ray diffraction and morphology characterization confirmed the presence of these defects. These defects would significantly promote the nucleation of reverse magnetic domains, and further declined the coercivity and thermal stability of magnets.