Highly oriented NdFeB nanocrystalline magnets from partially recombined compacts with ultrafine grain size by reactive deformation under low pressure

The partially recombined compacts with ultrafine grain size were taken advantage of preparing anisotropic nanocrystalline magnets with full density and homogenous microstructure and texture by reactive deformation under low pressure. Because of the ultrafine grain size of the precursors, the partially recombined phases could quickly achieve recombination. The results suggested that the newly recombined Nd2Fe14B grains with fine grain size could undergo deformation immediately during the desorption-recombination reaction, and then an obvious anisotropy and uniform alignment would be obtained. The magnetic properties, (BH)max=214 kJ/m3, Br= 1.26 T, Hcj=463 kA/m, were obtained after being treated for 5 min at 820 °C in high vacuum under low pressure less than 26 MPa. Microstructures of the magnets were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. Magnetic measurements were carried out using a vibrating sample magnetometer (VSM) with the maximum field of 2.88 T. Accurate phase contents were measured by a Mossbauer spectrometer.

Graphical AbstractXRD patterns of PR compacts treated by RD at 820 °C for various time: (a) 1 min; (b) 5 min; (c) 15 min; (d) 30 min (The black solid line is a fit to experimental data using the dotted curves which are separated from the measured data for Nd2Fe14B phase in 1 min (e), 5 min (f), 15 min (g) and 30 min (h))Figure optionsDownload as PowerPoint slide