Dy-distribution in the grains of high-energy (Nd,Dy)-Fe-B magnets

Sintered (Nd,Dy)-Fe-B-magnets were manufactured by adding low melting RE/sub 3/Co or RE/sub 3/Co/sub 2/ alloys (RE=Nd or/and Dy) to basic alloys with compositions close to the Nd/sub 2/Fe/sub 14/B stoichiometry. The remanent polarizations and the coercivities of sintered and annealed magnets with about 2 wt.% Dy range from 1.39 to 1.42 T and from 6.6 to 13.5 kOe, respectively. For example the magnet manufactured with an addition of 5 wt.% Dy/sub 1.5/Nd/sub 1.5/Co/sub 2/ achieves a remanence of 1.42 T and a coercivity of 9.0 kOe. The energy density of this magnet amounts to 46.8 MGOe (375 kJ/m/sup 3/). The microstructure of the magnets consists of large RE/sub 2/Fe/sub 14/B-grains with dimensions up to 50 /spl mu/m. WDX analysis revealed that the Dy-distribution in these grains is inhomogeneous: there is no Dy in the central region, while a Dy-concentration of 5 wt.% was detected in the border region of the /spl phi/-grains. Adjustment of the composition and of the processing route results in magnets with a remanent polarization of 1.4 T and a coercivity of 15 kOe.