Abstract

In an attempt to optimize the magnetic properties of (Nd, Dy)-Fe-B sintered magnets, hydrogenation and post-sintering heat treatment processes were investigated at various hydrogenation temperatures and heat treatment temperatures. The coercivity of (Nd, Dy)-Fe-B sintered magnets hydrogenated at 400°C increased to about 1.2 kOe without any detrimental effect on the remanence. Moreover, the coercivity of the magnets was enhanced further by a consecutive 2nd and 3rd step heat treatment. These results eventually leaded to the reduction of the Dy content in a high coercive (> 30 kOe) (Nd, Dy)-Fe-B sintered magnets, as much as 10%.

• Keywords: Nd-Fe-B magnets;Hydrogen decrepitation;Jet-milling;Sintering;Heat-treatment;