Orientation and deformation mechanisms of Nd-Fe-B magnets during die-upset forging process were examined. The fine Nd_2Fe_(14)B grains in the Nd-Fe-B powders annealed at 750 °C without an applied stress grew easily in the a-axis, showing aplate-like shape. Moreover, in the tensile specimens, the platelet grains perpendicular to the c-axis were aligned parallel to the tensile axis. Thus, during die-upset forging, the Nd_2Fe_(14)B platelet grains tended to be rotated by a torque force so that the platelets became perpendicular to the forging direction, resulting in the <001> fiber texture. In addition, a dislocation was never observed and grain boundary amorphous phase existed during the whole deformation process. Furthermore, the stress exponent of the Dorn equation was determined to be 3 to 4 at any strain. Thus, it is concluded that the hot deformation of the magnets is caused by a solution-precipitation creep.
展开▼
