Study on the preparation, formation mechanism, and permanent magnetic properties of anisotropic Nd–Fe–B spherical magnetic powder

Abstract

The controllable preparation of anisotropic Nd–Fe–B spherical magnetic powder is a critical breakthrough in overcoming the technical bottleneck of high-performance bonded magnets. This study reports the synthesis of Nd2Fe14B spherical single-crystal powder (particle size: 100–150 μm) and the achievement of magnetic hardening via hydrogenation–disproportionation–desorption–recombination (HDDR) technology. By establishing a spheroidization-annealing process system and integrating the Cassie–Baxter surface wetting theory with the abnormal grain growth mechanism, we elucidate the interface energy-dominated spheroidization mechanism and single-crystallization mechanism. HDDR experiments demonstrate that single-crystal powder treated under conventional process conditions exhibits outstanding permanent magnetic properties (Br = 12.33 kGs, Hcj = 13.75 kOe, and (BH)max = 30.6 MGOe). This work combines the preparation of spherical single-crystal powder with HDDR technology to produce anisotropic Nd–Fe–B permanent magnetic powder, offering an approach for developing high-performance anisotropic bonded magnets.