Effect of Al and Al/Mo addition on microstructure and
magnetic properties of sintered Nd22Fe71B7magnets①
magnetic properties of sintered Nd22Fe71B7magnets①
(School of Materials Science and Engineering, Xi′an Jiaotong University, Xi′an 710049, P.R.China)
Abstract: The alloying elements Al and Al/Mo were added into the intergranular regions of sintered NdFeB magnets and their effects on microstructure and magnetic properties were investigated. Results show that a small amount of Al and Al/Mo additives can largely enhance the coercivity with a little loss of the remanence of NdFeB magnets. Apart from the improvement of Nd-rich phase wetting ability arising from the individual pure Al addition, the improvement of coercivity can be attributed to the occurrence of a net-shaped Nd(FeAl)2phase in the intergranular region of the Al-doped and Al/ Mo-doped magnets and the segregation of Mo on the surface of the main phase grains,which reduces the magnetic coupling of the Nd2Fe14B grains and impedes effectively the propagation of the domain walls. Compared with the single element alloying method, the combined alloying of different elements to the intergranular region is more efficient to modify the properties of NdFeB magnets.
Key words: NdFeB magnets; alloying; coercivity