Mechanical properties of Nylon bonded Nd-Fe-B permanent magnets

Tensile and flexural strengths as well as Young's modulus of Polyamide-11 (Nylon-11) based injection molded Nd-Fe-B magnets have been determined from -40degreesC to 100degreesC. Two types of Nd-Fe-B powders were included in this study. One is the conventional melt spun powder of irregular shape, the other is the atomized powder of spherical morphology. It was found that the tensile strength varies significantly with both test temperature and morphology of Nd-Fe-B powder. For a fixed volume fraction of magnet powder, the tensile strength decreases with increasing temperature. For bonded magnets made of melt spun powder, the tensile strength increases with increasing volume fraction of magnet powder. Specimens made of spherical atomized powders exhibit much lower tensile strength and better flexibility when compared to those made of melt spun powder. Scanning electron microscopy (SEM) analysis indicated that the debonding at the Nd-Fe-B powder and Nylon interface is the main cause of failure at 23 C and 100degreesC. At -40degreesC, a different failure mechanism with the fracture of Nd-Fe-B particle was observed on magnets prepared from melt spun powders. For the specimen containing 59.7 vol% of melt spun powder, a bending strength of 41 MPa and dynamic Young's modulus of 12.7 GPa were obtained. (C) 2002 Elsevier Science B.V. All rights reserved.