Aa. Albutov et al., DESIGN OF THE ND-FE-B-BASED ALLOYS WITH IMPROVED THERMAL-STABILITY OFSTRUCTURAL AND MECHANICAL-PROPERTIES, Russian metallurgy. Metally, (2), 1996, pp. 67-73
The permanent magnets produced from the Nd-Fe-B alloys with additions
of Dy, Tb. Co. Nb, and Ga are studied. Investigations of the effects o
f Nb and Ga on magnetic properties and microstructure of sintered magn
ets showed that these additions increase the magnetization coercive fo
rce H-lc, up to 2000 kA/m and improves the thermal stability of perman
ent magnets. The long-term and short-term service temperatures increas
e up to 150 degrees C and 180 - 200 degrees C, respectively. Microstru
ctural examinations ai sintered magnets showed the presence of the pre
cipitates of Nb-bearing Nd-(Co, Fe)-B-type precipitates (H phase) betw
een the grains of the dominant Nd2Fe14B phase (Phi phase). The benefic
ial effect of Nb on H-lc is caused by the elimination of chemical inho
mogeneity of grain-boundary areas of Phi phase and by the smoothing of
the surfaces of the Phi-phase grains. Gallium is dissolved primarily
in the Phi phase and in the NdCo-based phase (K-2 phase). The presence
of gallium in the K-2 phase weaken its magnetic properties, and this
improves the magnetic insulation of the grains of major phase.