Effect of Deformation on the Magnetic Domain Orientation of Rapidly Solidified Nd–Fe–B Powders Using Pulsed Current Assisted Sintering

A new approach to synthesize Nd-Fe-B permanent magnets has been investigated using a combination of rapid solidification and deformation processes, unlike the conventional processes such as strip casting and melt spinning. In order to endow anisotropic property to the intrinsically isotropic as-atomized powder, we attempted the die-upset process by spark plasma sintering. The atomized powder was pre-compacted into billets at elevated temperatures by spark plasma sintering. The pre-compacted billet was then hot deformed by the die-upset process by varying the temperature and pressure. The domain orientation of the billets was confirmed by X-ray diffraction analysis, and the orientation factor value was calculated according to the ease of magnetization. The magnetic domain shifted from the (214) plane to the (105) plane with increasing deformation temperature, pressure and strain ratio. We concluded that the best domain alignment of the billet was obtained at the temperature of 750 degrees C, pressure of 40 MPa, and strain ratio of 75%.