The Prepartion And Study Of Bulk Anisotropic Nd₂Fe₁₄B/α-Fe Nanocomposite Magnets

Nanocomposite permanent magnets which consist of hard and soft magnetic phaseswill be the important direction of permanent magnetic materials research, which resultsfrom the fact that its theoretical energy product is two times larger than the maximumenergy product in practical sintered Nd-Fe-B. However, the energy product of practicalnanocomposite magnets is much lower than the theoretical energy product, the mostdifficult thing of which is how to get the high textured nanocomposites.Most researchers crush the precursor prepared by the method of melt spinning, andobtain the bulk anisotropic Nd2Fe14B/α-Fe nanocomposites by die-upsetting. But it is noteasy to control the micro-structure, and resulting in a poor magnetic performance. In thispaper, we combine the method of high energy ball milling and melt spinning to control themicro-structure and morphology, and we get the Nd2Fe14B/α-Fe nanocomposite magnetswith a certain orientation and excellent performance after hot deformation. And thispreparation method is rarely reported.In this paper, we mill the amorphous ribbons, and explore the milling process, gettingthe optimum milling process that the ratio of ball to materials is30:1, the milling time is3.5h. Further more, we analyze the phase transition of precursor by using differentialscanning calorimetry(DSC)、X ray diffraction(XRD) and vibrating sample magnetometer(VSM), and get the best magnetic properties, the process of which is annealed at625oCfor10min.The precursor is prepared to bulk Nd2Fe14B/α-Fe nanocomposites by hot deformation,and we analyze the influence of the magnetic properties and the orientation of Nd2Fe14Bphase for temperature、stress and strain rate. Compared with the method of high pressure,this paper analyze the effect of temperature on the magnetic properties and the orientationof Nd2Fe14B phase, showing the great advantages with the alignment of Nd2Fe14B phase;With the increase of stress, the alignment of Nd2Fe14B phase increases; And the increaseof strain rate improves the magnetic properties. Finally, we get the maximum energyproduct for19.046MGOe when the temperature is650oC, the stress is481MPa, and the strain rate is0.73. More over, the nanocomposite is anisotropic.