Preparation of high comprehensive performance hot-deformed NdFeB magnet with (BH(max)54.51MGOe, Hcj 16.62 kOe) by macro- sandwich structure design

This study addresses the issue of non-uniform plastic deformation in conventional hot-deformed Nd-Fe-B magnets, which arises due to friction between the punch and the mold. This friction-induced deformation inhomogeneity leads to the formation of dead zones, reducing the degree of texture at the end surfaces and ultimately limiting the overall magnetic performance of the magnet. To overcome this issue, an innovative sandwich-structured design strategy is proposed. By leveraging the influence of rare-earth content on texture formation, a high rare-earth content powder–low rare-earth content powder–high rare-earth content powder layered structure was introduced within the mold. This approach effectively optimized the microstructural uniformity of the magnet and significantly improved its overall homogeneity. Experimental results demonstrate that magnets fabricated with this structural design exhibit significantly enhanced magnetic properties, with remanence increasing from 14.33 kGs (pure low rare-earth content powder magnet) to 14.85kGs, the coercivity increased from 16.43 kOe to 16.62 kOe and maximum energy product improving from 50.06 MGOe to 54.51 MGOe. Microstructural analysis reveals that the high rare-earth content powder, possessing superior rheological properties, effectively enhances the rheological behavior of the near-end surfaces during plastic deformation. This improvement mitigates insufficient deformation in these regions, reduces the depth of dead zones, and enhances the overall texture degree of the magnet, ultimately leading to a substantial increase in both remanence and maximum energy product. • Prepared hot-deformed NdFeB magnet: B r =14.85 kGs, H c j =16.62 kOe, (BH) max =54.51 MGOe. • Designed macro-sandwich structure boosts HD magnets' rheological capacity. • Improved rheology enhances near-surface deformation, texture formation, and suppresses dead zones. • Enhanced <00 l > orientation in 2:14:1 grains boosts remanence and energy product.