THE EFFECT OF V-ADDITIVES OR W-ADDITIVES TO MICROSTRUCTURE AND COERCIVITY OF ND-FE-B BASED MAGNETS

Co-substituted Nd-Fe-B magnets show an increased Curie temperature. The coercivity (iHc) of these magnets is reduced due to the formation of Co rich phases. In addition to the hard magnetic phase, still the Nd-rich intergranular phase exists which results in bad corrosion resistance. In (Nd,Dy)-(Fe,Co)-B:Al type magnets doped with V we found (V1-xFex)3B2 intergranular phases and precipitates with Si2U3-structure and a Nd-rich Co-containing phase partly replacing the Nd-rich phase. X-ray microanalysis shows that in (Nd,Dy)-(Fe,Co)-B:(Al,V) magnets Dy is mainly dissolved in the hard magnetic phase. The comparison with W-doped Nd-Fe-B magnets shows that W also forms an intergranular WFeB phase with Co2Si-structure and precipitates within the hard magnetic phase with presumably the same composition. 1