A novel composite hot-extruded Nd-Fe-B permanent magnetic ring.

• A novel composite hot-extruded Nd-Fe-B permanent magnetic ring has been fabricated using a set of composite hot-extrusion molds. • The B r and (BH) max of the backward-extruded (BE) part of the ring decrease monotonically from the ring top to the spacer layer along the axial direction. The (BH) max , B r , H cj of the BE part close to the ring top show the highest values of 38.52 MGOe, 13.35 kGs, and 11.65 kOe, respectively, which are higher than that of the foreward-extruded part corresponding position. The B r of the FE part increases monotonically along the axis of the magnetic ring from the ring bottom to the spacer layer, and their H cj increases first and then decreases. A novel composite hot-extrusion mold has been designed and the composite hot-extruded Nd-Fe-B permanent magnetic ring has been fabricated and analyzed. The results show that the magnetic properties of the composite hot-extruded Nd-Fe-B ring are not uniform in the axial direction. The B r and (BH) max of the backward-extruded (BE) part of the ring decrease monotonically from the ring top to the spacer layer along the axial direction. The (BH) max , B r , H cj of the BE part close to the ring top show the highest values of 38.52 MGOe, 13.35 kGs, and 11.65 kOe, respectively, which are higher than that of the foreward-extruded (FE) part corresponding position. The B r of the FE part increases monotonically along the axis of the magnetic ring from the ring bottom to the spacer layer, and their H cj increases first and then decreases. The microstructures of the magnetic ring appear an alternatively-arranged coarse-grained region and fine-grained region and show deviation from the axial direction of the ring, leading to the difference of their magnetic properties. [ABSTRACT FROM AUTHOR]