Magnetic and microstructural properties of sintered FeNdB-based magnets with W, Mo and Nb additions

The alloying elements W, Mo and Nb were added into the intergranular regions of sintered FeNdB-based magnets and their effects on microstructure and magnetic properties were investigated. Results showed that small amounts of W, Mo and Nb additives could enhance the coercivity and had little effect on the remanence of the magnets. However, higher amounts of additives led to a loss of both the coercivity and the remanence. The effect of W, Mo was superior to that of Nb. The variation of the coercivity was attributed to the occurrence of a new intergranular TFeB(T=W, Mo and Nb) phase which not only inhibited the growth of the main phase grain during sintering, resulting in a finer microstructure, but also changed the distribution of the Nd-rich phase. A further analysis revealed that compared with the conventional alloying method, where the alloying elements were added before melting, microalloying of the intergranular region is a promising way to improve the properties of FeNdB-based magnets. (C) 1997 Elsevier Science S.A.