Evaluating the Magnetic Hardening of Nd-Fe-B Magnets after Grain Boundary Diffusion: A Layer by Layer Approach

This study investigates the Grain Boundary Diffusion (GBD) of Dy-Cu in Nd-Fe-B magnets, focusing on understanding the GBD mechanism and its implications on magnetic properties. GBD operates by modifying the microstructure at the grain boundary surface to optimize magnetic performance, significantly enhancing the coercivity of these magnets. The experimental procedure involved the application of GBD of Dy-Cu elements to Nd-Fe-B magnets, and the subsequent characterization of these GBD magnets. The analysis focused on studying the shell formation via electron microscopy, and the diffusion depth via magnetometry. The diffusion depth was characterized by measuring the intrinsic coercivity (HcJ) at different depths using a destructive layer-by-layer analysis method. Preliminary results show notable improvements in the magnetic properties of magnets treated with GBD, with an increase in the magnet's HcJ by approximately 47%, without significant change in remanence. Particularly noteworthy is the identification of the almost linear dependence of HcJ on diffusion depth, providing valuable insights for future analyzes at the microstructural level of the alteration via GBD of ferromagnetic grains.