Particle size, Particle

关键词:Rare earths, NdFeB neodymium standard state
http://www.999magnet.com/products/112-neodymium-standard-state powder, Particle size, Particle









distribution, Magnetic properties
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作者:刘湘涟,何建平,董清飞,周寿增
关键词:rare earths; NdFeB-type magnet; sintering; grain growth kinetics
摘要:The Nd  2Fe    14  B grain growth kinetics in sintered NdFeB magnets with nominal compositions of   Nd    30+x  Dy    1.5  Fe    67.08-x  Al    0.4  B    1.02     (%, x=0, 3) was studied. The grain size parameters were determined by means of the linear intercept method on SEM secondary electron images. It is observed that the grain growth process is more sensitive to sintering temperature than to sintering time although the grain size rises with both sintering temperature and time. It is also found that magnets prepared from the pre-alloy powder with a higher oxygen content exhibit a lower grain growth rate and magnets made from the pre-alloy powder with a broader particle size distribution demonstrate a higher grain growth rate. It is believed that the presence of appropriate amounts of Nd oxides effectively impedes the grain growth process and a larger difference in sizes between pre-alloy powder particles significantly accelerates the grain growth process. On the basis of experimental results, the grain growth exponent and the corresponding activation energy were obtained. A possible grain growth mechanism in NdFeB magnets during sintering was briefly discussed.