Bulk Nd₂Fe₁₄B/α-Fe Nanocomposite Magnets Perpared By Hot Deformation

Nanocomposite permanent magnets have attracted much attention due to the theoretical value of their maximum energy product (BH)max above 800 kJ/m3, since they were first reported in 1989. Research in the nanocomposite magnets are extensively carried on that focus on preparing bulk magnetic anisotropic nanocomposite magnets with optimizing the microstructure.In the dissertation, through controlling temperature and pressure, bulk anisotropic Nd₂Fe₁₄B/α-Fe nanocomposite magnets have been successfully prepared by hot pressing and following hot deforming. The microstructure and magnetic properties of the magnets have been investigated by employing X-ray diffraction(XRD) and vibrating sample magnetometer(VSM).The optimum process, the wheel speed of melt-spinning is 15 m/s and the stress of hot deforming is about 330 MPa, has been found by changing the microstructure of Nd₉Fe₈₅B₆ alloy ribbons and the compressive stress in hot deforming. The (BH)max of bulk Nd₂Fe₁₄B/α-Fe nanocomposite magnets prepared by optimum process of hot deforming is 111.51 kJ/m3, which increased by 36.1% in hot-pressing magnets with normal annealing, 83.5% of Nd₉Fe₈₅B₆ alloy ribbons prepared by melt-spinning with the optimum process.The {00l} texture formation in hot-deforming magnet is attributed to an oriented nucleation and preferential growth of Nd₂Fe₁₄B crystals during the processes of hot deforming. The magnetic anisotropy of hot-deforming magnets attributed to the {00l} texture in Nd₂Fe₁₄B phase. Reducing compressive stress or increasing deformation rate promote the formation of {00l} texture in Nd₂Fe₁₄B phase and magnetic anisotropy in hot-deforming magnet.