Fabrication of low-cost Nd–Fe–B sintered magnets reusing ultrafine powders

AbstractTo reduce the cost of Nd–Fe–B sintered magnets, the ultrafine powders recycled during the jet-milling process were added into intergranular regions by blending. The effects of ultrafine powder content on the magnetic properties, thermal stability and microstructure were investigated. It was found that the intrinsic coercivity H cj was significantly improved from 1048 to 1396 kA m−1 on increasing the ultrafine powder content to 10 wt-%. Meanwhile, the reversible temperature coefficient β H of H cj over the range 20–100°C was decreased in the absolute value, indicating that the thermal stability was improved. Moreover, the maximum energy product (BH)m increased slightly on adding 5 wt-% ultrafine powder, which can be attributed to the combined effects on the normal coercivity H cb and on the remanent induction B r.