Effect of Dy additions on microstructure and magnetic properties of Fe-Nd-B magnets

This paper addresses the effect of Dy addition upon the magnetic properties, microstructure and microcomposition of Fe-Nd-B magnets. It is shown that increasing additions of By causes the remanence, B/sub r/ to decrease linearly. The intrinsic coercivity, iHc, increases sharply for small additions of Dy, but the increase is not proportional for higher Dy contents. The iHc increases almost linearly with the effective anisotropy field of the RE/sub 2/Fe/sub 14/B phase until the Dy content is about 10% of the total rare earth content. Above this concentration, there is a strong deviation from linearity. Various types of possible concentration profiles of the substituted rare earth are suggested. It is also argued that preferential segregation of Dy to the interfaces could be beneficial in increasing the nucleation field. Morphologically there is no apparent effect of Dy on the microstructure. However, in the 5 atomic % Dy sample, Dy rich oxides were observed. It is shown through Energy Dispersive Xray Spectroscopy (EDXS) line profiling that Dy partitions preferentially into the RE/sub 2/Fe/sub 14/B phase in all the cases. No segregation of Dy to the interphase interfaces has been detected