Effect of wheel speed on the microstructure and exchange coupling interaction of nanocomposite Nd2Fe14B/α-Fe magnets

The exchange coupled Nd2Fe14B/α-Fe nanocomposite magnets have been synthesized by melt-spinning. The effect of wheel speed on the microstructure and exchange coupling interaction has been studied. The results show that a uniform Nd2Fe14B/α-Fe nanocomposite structure with fine α-Fe grains can be developed at an optimum wheel speed of about 12 m s−1. After a low temperature annealing, the ribbons show a stronger exchange coupling interaction and the magnetic properties reach a maximum value: jHc=432.2 kA m−1, Jr=1.08 T, (BH)max=115 kJ m−3. With further increase in wheel speed, the microstructure of the ribbons becomes non-uniform after a subsequent high temperature crystallization, and several α-Fe grains abnormally grow to about 100 nm, deteriorating the magnetic properties of the ribbons.