Preparation and magnetic properties of bulk Nd2Fe14B/α-Fe nanocomposite magnets by hot compression of amorphous NdFeCoNbB alloy powders

摘要

The fully dense bulk nanocomposite magnets have been successfully prepared by hot compression of amorphous Nd9Fe81Co3NbB6 alloy powders under high pressure of 0.2-1Gpa using Gleeble3500 simulator. The nanocrystalline structure was characterized by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), and the magnetic properties of the specimens were estimated by a vibrating sample magnetometer (VSM). The results show that the grain size of both Nd2Fe14B and α-Fe phases decreased with increasing pressure, but more significant effect of pressure on grain coarsening was observed in the α-Fe phase. A nanocomposite magnet with an average grain size of 20~30 nm for both the two phases has been obtained by hot-comperssion at 750℃ for 6 minutes under the pressure of 1GPa. The magnetic properties (Br, Hci and (BH)max) were enhanced with the increase of the comperssion pressure and the optimum magnetic properties is Br = 9.2 Kg, Hci = 4.9 kOe and (BH)max = 12.3 MGOe.