Improvement of overall texture and magnetic properties in bulk hot-deformed Nd-Fe-B composite magnets by the design of macrostructure

Abstract

Four types of bulk hot-deformed Nd-Fe-B composite magnets were designed by mixing Dy-free powders (M) and Dy-containing powders (G) or stacking them: (M-G)mix, MGGM, GMMG and MGMG. The four composite magnets with same Dy content show great differences in their magnetic properties. The remanence (Br) of the MGGM magnet (13.48 kGs) is highest while the coercivity (Hc) of the GMMG magnet (22.24 kOe) is highest. The overall magnetic performance ((BH)max + Hc) of the MGGM magnet (∼65) is highest. For the (M-G)mix magnet, the ribbon texture throughout the whole magnet is inferior, indicating the poor deformability of the mixed powders. Comparing the overall texture of the MGGM and GMMG magnets, the ribbon texture of M powders located at the top and bottom sections is much better than that of G powders located at the top and bottom sections, which is the main reason for the excellent remanence and overall magnetic performance of the MGGM magnet. Finite element simulations were performed to explain the deformation behaviors of hot-deformed magnets and facilitate discussions of the overall microstructure differences of the composite magnets.