Effects of Pressure Holding Time on Magnetic Properties and Corrosion Resistance of Hot-Deformed NdFeB Magnets

Effects of pressure holding time (PHT) on magnetic properties and electrochemical corrosion behavior of hot-deformed NdFeB were investigated through x-ray diffraction, x-ray photoelectron spectrometer, scanning electron microscopy, and magnetic and anti-corrosion properties measurement technologies. 10 min PHT has been found to increase the orientation degree of matrix phase with only slight grain growth. When PHT is increased up to 40 min, however, the platelet-shaped grains obviously grow along their length direction, reducing the magnet orientation degree and worsening the distribution of Nd-rich phases. Compared to the magnet without and with longer PHT, the magnet with 10 min PHT possesses more appropriate microstructure and better magnetic/anti-corrosion properties. The increase in the intrinsic coercivity and magnetic energy product is 17.4 and 14.2%, respectively. The improved corrosion resistance is due to the difficult formation of active reaction channels in Nd-rich phases induced by their optimized distribution. Such novel findings can provide some theoretical and experimental information for improving the performance of hot-deformed NdFeB.