Preparation of isotropic and anisotropic Nd-Fe-B/Fe composite magnets with high magnetic properties

Bulk isotropic and anisotropic composite magnets were synthesized by blending a Nd-Fe-B powder with an Fe powder using vacuum induction sintering technique.Effects of Fe content,variable sintering temperature and press on the magnetic properties and microstructure of hot-pressed magnets were studied.The result showed that the magnetic properties of hot-pressed magnets could be enhanced by proper addition of Fe powder(3wt.%).The density could be enhanced by increasing sintering temperature or press.However,grains grew seriously and magnetic properties were deteriorated when temperature was higher than 700℃;the densification of magnets was more difficult when temperature was lower than 650℃.The best magnetic properties were obtained with 3wt.%Fe addition and the density reached 7.72g/cm3 at hot-pressing temperature 650℃ and 400MPa: Br=0.852T,Hcj=798kA/m,(BH)m=131.5kJ/m3.After hot-deformation,the magnetic energy product increased to 331kJ/m3.