Fracture toughness of Nd2Fe14B magnets

Nd2Fe14B is currently the best (highest energy product) hard magnet available. Like most magnetic materials, it is rather brittle. The fracture toughness of specimens of commercially available hard magnets were measured using a chevron notch, three-point bend test. Values for Nd2Fe14B magnets ranged from 2.5 to 5.5 MPa root m. In comparison, SmCo5 was measured to have a fracture toughness of 1.9 MPa root m. It appears that this testing technique will allow differences in fracture toughness to be measured between alloys with different compositions and fabricated by different production methods and should be able to track the fracture toughness as improvements are made to a particular alloy.