Effect of low temperature annealing on the coercive force of permanent magnets of (Nd, Pr, Sm)Co5 alloys

The investigations concerned the effect of low temperature annealings at 150-600 deg C upon the coercive force of Ndsub(0.5)Prsub(0.25)Smsub(0.25)Cosub(5) and Ndsub(0.5)Smsub(0.5)Cosub(5) type powder magnets. Experiments led to a conclusion that prolonged thermal treatments of powder magnets result in structure-and-phase transformations in the base matrix, which strongly affect the magnitude of the coercive force of the magnets. A proper combination of the temperature and of the duration of the low-temperature annealings can increase the coercive force by 30-40%