Origins of Radial and Axial Inhomogeneity of Magnetic Performance in Cylindrical Nd-Fe-B Magnet Prepared by Hot Deformation

Abstract

Cylindrical Nd-Fe-B magnets with different height reductions were prepared by hot deformation method. The inhomogeneity of the magnetic performance along the radial direction was revealed with a closed circuit B-H apparatus while that along the axial direction was shown with a vibrating sample magnetometer. The microstructure examined with scanning electron microscopy suggests that orientation variation and grain coarsening of Nd Fe B platelets cooperate to result in the deterioration of remanence along radial direction from center to edge. X-ray diffractometry was carried out over the end surfaces and axially across the middle cross-section of the cylindrical magnet, showing the important role of texture in determination of remanence along the axial direction. Further investigations on an intermediate hot-deformed magnets reveal the unevenness of deformation degree in the axial direction during hot deformation, which accounts for the axial variation of texture and consequent remanence.

Rare earth permanent magnets prepared by hot deformation process

“…In addition, the inhomogeneity of the microstructure also exists along the radial direction of the magnet. [23] Fig. 10.…”

“…(color online) Distribution of remanence (B r ), coercivity (H cj ) and maximum energy product ((BH) max ) along axial direction of the HD magnet with deformation of (a) 37% and (b) 52%. [23]…”