Alloying effect on the magnetic properties of RFeB-type bulk magnets

摘要

Composition dependence on the magnetic properties of directly casted cylindrical RFeBM-type magnets with diameters from 0.7mm to 1.5 mm has been studied. In order to refine the microstructure for improving the magnetic properties of bulk magnets with various sizes, the following ways were adopted in the alloys: (1) changing the boron concentration, (2) substituting different kinds of refractory elements for Fe, (3) adding a slight carbon and finally, (4) adopting multi-component refractory elements. The experimental results showed that the Nd_(9.5)Fe_(72.5)Ti_3B_(15)bulk magnets with a diameter of 0.7 mm demonstrated the optimal magnetic properties of B_r = 6.5kG, _iH_c = 10.3 kOe and (BH) max = 8.7MGOe, while the highest _iH_c of 16.2 kOe was achieved for the Pr_(9.5)Fe_(71.5)Nb_4B _(15) magnet. Meanwhile, the diameter of the magnets could be increased to 0.9 mm preserving the attractive magnetic properties by the substitution of 0.5 at% Zr for Ti in the Nd9.5Fe72.5Ti3B 15 magnet. Finally, the directly casted Nd_(9.5)Fe _(72.5)-yTi_(2.5)Zr_(0.5)CryB _(15-x)C_x (x = 0.25-1; y = 0-3) magnets with a larger diameter of 1.3 mm exhibited attractive magnetic properties of Br = 5.3-6.1 kG, _iH_c = 7.2-12.5 kOe and (BH)_(max) = 6.5-7.2MGOe.