Effects of Tb Diffusion on Microstructure and Properties of NdFeB Magnets
DC magnetron sputtering technology were used to coat Tb films of different thicknesses on the unipolar surface of sintered NdFeB magnets,and the thermal diffusion and annealing treatment were carried out.The results show that,3.137 μm film thickness is the most coercivity of magnet most obviously,and under the heat treatment conditions of 850℃×7 h+500℃×2 h,the best magnetic properties are obtained,and its coercivity increases from 872.36 kA/m to 1305.67 kA/m,the temperature coefficient of remanence αat 20-160℃decreases from-0.1226%/℃to-0.1230%/℃,which are slightly lower,but the temperature coefficient of coercivity β increases from-0.5534%/℃to-0.5297%/℃.The microstructure of the near surface and deep part of the Tb diffusion magnet is observed by SEM,it can be found that the obvious(Nd,Tb)2Fe14B core-shell structure and the more uniform distribution of rich Nd phase are the main reasons for the improvement of the magnetic properties of the magnet.
heat treatmenttemperature coefficientcoercivityirreversible loss of magnetic flux
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