Effect of melt superheating treatment on crystallization behavior and magnetic properties of melt-spun Fe-rich Nd-Fe-B ribbons

Melt-spun Nd7Fe90B3 ribbons were prepared under different melt treatment conditions, i.e., the melt temperature was varied prior to ejection onto the quenching wheel. The microstructure characteristics, crystallization behavior, and subsequent magnetic properties of α-Fe/Nd2Fe14B-based exchange-spring magnets were investigated using X-ray diffraction, differential scanning calorimeter, transmission electron microscopy, and vibrating sample magnetometer. It was shown that melt spinning at different quenching temperatures caused the as-quenched ribbons to have distinctive crystallization behavior. Under high quenching temperature, precipitation of TbCu7 type phase was inhibited during crystallization, resulting in remarkable reduction of grain size. This led to strengthening of exchange coupling effect between the magnetically hard and soft phase and improvement of magnetic properties of annealed ribbons.