Effect of Cu doping and annealing treatment on the microstructure and magnetic properties of nanocrystalline single-phase Nd-Fe-B alloys

The effects of Cu addition and annealing treatment on the magnetic properties and microstructure of Nd12.3Fe81.7-xCuxB6 (x=0-1.2 ribbons melt-spun and annealed were systematically investigated by the methods of vibrating sample magnetometer (VSM),X-ray diffraction (XRD),and transmission electron microscopy (TEM).Optimum magnetic properties were achieved by annealing melt-spun Nd12.3Fe81.5Cu0.2B6 ribbons at 550℃ for 15 min,which only contained Nd2Fe14B phase.The remanence,coercive force,and maximum energy product increase by 18.4%,36.2%,and 49% respectively compared with those of Cu-free samples.The significant improvement in magnetic properties originates from the finer grains of the samples by introducing Cu,which leads to the stronger exchange-coupling between neighboring grains.