Investigation of grain boundary diffusion on Nd-Fe-B sintered magnet with high Dy content
LI Jian1,2, ZHOU Lei2, LIU Tao2, YU Xiao-jun2, LI Bo1
（1. China Iron & Steel Research Institute, Beijing 100081, China 2. Advanced Technology & Materials Co., Ltd., China Iron & Steel Research Institute Group, Beijing 101318, China
Abstract：Effect of grain boundary diffusion treatment on magnetic properties and structures of sintered Nd-Fe-B magnet with high Dy content was investigated. Using Dy vapor sorption process, the coercivity of high Dy content magnet increases from 1 713 kA/m to 2 161 kA/m without decrement of remanence or maximum energy product. Dy content of the whole magnet merely increased 0.30% (mass percent) after treatment. Further investigation of the flakes at different depths of magnet reveals that the coercivity of the flakes is similar although the Dy content in subsurface flakes is more than that in central flakes. Moreover, the coervity of all flakes is much higher than untreated ones. According to the EPMA mapping images, Dy is dispersed not only in the grain boundary but also among the main phases, and concentration of Dy-rich area is lower in untreated sample. However, for the treated samples, the concentration and the scale of Dy-rich area in grain boundary are both much larger than those of untreated ones. The coercivity of the flakes at different depth is all greatly increased due to remarkable Dy increase among the most of Nd-rich triple junction grain phases.
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2014, Vol. 24 
