Evolution of structural and magnetic properties due to nanocrystallization of mechanically milled amorphous Pr-Co-B powders

Pr2Co14B permanent magnet powders were prepared by mechanical milling of an arc-melted ingot. X-ray diffraction analysis revealed the presence of the 2:14:1 phase after 1 h of milling which transformed into an amorphous phase with additional milling time. Increasing the milling time also lowered the intrinsic coercivity while the saturation magnetization increased up to 105 emu/g. Differential scanning calorimetry measurements revealed a crystallization temperature of around 560 degrees C. Upon annealing 30 h of as-milled amorphous powders between 500 and 900 degrees C, we observed the precipitation of the 2:14:1 phase. The optimum post-milling annealing temperature was 600 degrees C with an intrinsic coercivity of 7 kOe and maximum energy product of 6 MGOe. (C) 2014 AIP Publishing LLC.