The effect of V 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 of these magnets is reduced due to the formation of Co-rich phases. In addition to the hard magnetic phase the Nd-rich intergranular phase exists, which results in bad corrosion resistance. In (Nd,Dy)-(Fe,Co)-B:Al type magnets doped with V, (V/sub 1-x/Fe/sub x/)/sub 3/B/sub 2/ intergranular phases and precipitates with Si/sub 2/U/sub 3/ structure and a Nd-rich Co-containing phase partly replacing the Nd-rich phase were found. X-ray microanalysis shows that in (Nd,Dy)-(Fe,Co)-B:(Al,V) magnets Dy is mainly dissolved in the hard magnetic phase. Comparison with W-doped Nd-Fe-B magnets shows that W also forms an intergranular WFeB phase with Co/sub 2/Si-structure and precipitates within the hard magnetic phase with presumably the same composition.<
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