Improved energy product in grained aligned and sintered MRE_2Fe_(14)B magnets (MRE=Y+Dy+Nd)

摘要

Sintered [Nd_(0.45)(Y_3Dy_1)_(0.25~*0.55)]_(2.8)Fe_(14)B magnets were prepared for the first time. Magnetic properties and microstructures of the magnets were investigated by magnetic measurements and electron microprobe analysis. The microstructure consists of a MRE_2Fe_(14)B (2-14-1) phase matrix having a grain size of ～ 10 μm and a RE-rich grain boundary phase. However, sintering resulted in segregation of Y to the inner and Nd to the outside of the 2-14-1 grains. The magnet has a room temperature (BH)_(max) of 25.4 MGOe, which is two times higher than that of the isotropic melt spun ribbons with similar compositions. The temperature coefficients of Br (α) and Hcj (β) for the magnet are -0.150 and -0.632%/℃ from 27 to 127℃, respectively. These temperature coefficients, especially for β, are also much higher than those of melt spun ribbons. The composition segregation in the 2-14-1 grains is believed to be responsible for the higher temperature coefficients.