Fracture toughness of commercial magnets

Nd/sub 2/Fe/sub 14/B is currently the best (highest energy product) hard magnet available. Like most permanent 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 Nd/sub 2/Fe/sub 14/B magnets ranged from 2.5 to 5.5 MPa/spl radic/m. In comparison, SmCo/sub 5/ was measured to have a fracture toughness of 1.9 MPa/spl radic/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.