PROJECT TITLE :

Corrosion Losses in Sintered (Nd, Dy)–Fe–B Magnets for Different Geometries

ABSTRACT:

Sintered neodymium-iron-boron (Nd-Fe-B) magnets with cube and flat geometries were exposed to pressurized heat-humidity corrosion tests for 96 and 240 h. Measurements of weight and flux losses were performed when the corrosion tests. The corroded specimens were additional characterized using scanning electron microscopy and optical profilometry. The microcrystalline anisotropy of sintered magnets gave rise to heterogeneous corrosion, where the pole faces degraded preferentially to the facet faces. The magnetic field from the magnet itself so contributed to the amount and location of detached ferromagnetic grains. The magnets with cube geometry suffered greater losses than the flat magnets, while the flat magnets had a higher relative pole-face area. The higher total flux (thanks to the larger volume) of the cube-formed magnets led to the higher overall losses. Within the flat magnets, the corrosion targeted heavily on areas close to the corners.