Magnetic properties and corrosion resistance of Nd-Fe-B magnets with Nd64Co36 intergranular addition

Although lower rare-earth content (REC) Nd-Fe-B sintered magnets possess better corrosion resistance, it is hardly to achieve full densification and high magnetic performance for near-stoichiometric Nd2Fe14B magnets. To improve magnetic performance and corrosion resistance simultaneously, Nd64Co36 eutectic alloy powders are added into (Pr, Nd)29.00Fe69.75Ga0.20B1.05 (wt.%) sintered magnets. With 0.5 wt.% addition, continuous thin grain boundary layers are formed for their better wettability with the (Pr, Nd)2Fe14B matrix phase. The coercivity Hcj is hence enhanced from 9.94 to 13.01 kOe without deteriorating remanence Br, resulting in an obvious increase of maximum magnetic energy product (BH)max from 40.02 to 47.93 MGOe accordingly. In comparison with the 48 MGOe commercial magnets, such performance is superior, but the REC is 1.24 wt.% lower, which leads to an improved corrosion resistance and reduced cost. Further investigations reveal that the stability enhancement of the intergranular phase results from the formation of more stable Co-containing phases and oxides within the intergranular regions and the blocked corrosion channels by them.