Abstract：Several Nd-Fe-B sintered magnet samples with different Dy contents which ranges from 0-4.00%（mass percent） were prepared and were used as a base magnet for Dy GBDP （Grain boundary diffusion process）. The magnetic properties， chemical composition and microstructure of the samples were analyzed and compared. It is found that the coercivity of the samples all increase 263.4-316.7 kA/m and Dy contents increase 0.30%-0.35% （mass percent）， but the increments are not controlled by Dy content in base magnet directly. A further investigation show that， the[Hcj]increments are not proportional to the Dy increments， and the[Hcj]increase rate per Dy amount decreases gradually along with the increase of Dy content in base magnets. Considering another factor-EPMA Dy mapping images， Dy diffusion in Dy-free magnet results in a critical transformation of grain boundary structure， which is transformed from Dy-free structure to Dy-containing structure， and it makes the highest[Hcj]increase rate.
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2018, Vol. 28 
