The effect of Dy addition on the microstructure and magnetic properties of the sintered NdFeB magnets was investigated. The results of the microstructure analysis showed that Dy-free and Dy-doped samples are composed of Nd 2 Fe 14 B (P42/mnm) and a trace of Nd-rich phase. Dy addition reduces significantly the pole density factor of (004), (006) and (008) crystal faces as estimated by the Horta formula. Accordingly, the coercivity of the Dy-doped sample increases from 2038 kA·m −1 up to 2288 kA·m. The H cj (T)/M s (T) versus /M s (T) (Kronmüller-plot) behavior shows that the nucleation is the dominating mechanism for the magnetization reversal in these two kinds of magnets, and two microstructural parameters of α k and N eff are obtained. The Kronmüller-Plot gives evidence for an increase of the α k responsible for an increase of the coercivity as the result of the increase of the magnetic field as the magnetic domain reversed.
The influences of Niobium doping on the glass-forming ability (GFA) and magnetization properties of Nd–Fe–B–Nb alloys were investigated. It is found that the GFA of Nd–Fe–B–Nb alloys are improved by the Nb addition. It is also revealed that the GFA of the samples increases with the Nb content. Rapidly solidified Nd4.5Fe77−
x
Nb
x
B18.5 (x = 0, 0.25, 0.5, 0.75, 1) nanocomposite strip flakes were successfully prepared by using strip casting technique with a higher production efficiency and a lower cooling rate compared to melt spinning method. The coercivity of nanocomposite Nd–Fe–B–Nb alloy strip flakes can be dramatically enhanced by 0.5 at. % Nb addition, attributing to grain refinement. The best magnetic properties with H
c
j
= 278.9 kA/m, (BH)max = 41.06 kJ/m3 have been obtained in Nd4.5Fe76.5Nb0.5B18.5 nanocomposite strip flake, which can be used for bonded magnets. The recoil loss of Nd4.5Fe76.5Nb0.5B18.5 alloy is also reduced by the Nb addition.
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