Improvement of corrosion resistance and magnetic properties of Nd–Fe–B sintered magnets by Al85Cu15 intergranular addition

Abstract: To improve the corrosion resistance and magnetic properties, Al85Cu15 (at.%) compound powders were added to (Pr, Nd)14.8Fe78.7B6.5 sintered magnets as grain boundary modifiers. The corrosion resistance was found to be remarkably improved by small additions of Al85Cu15 powders. When 1.2wt% Al85Cu15 was added, the corrosion rate of magnets in humid environments was reduced by two orders of magnitude. This is partly due to the stability enhancement of the (Pr, Nd)-rich intergranular phase by Cu and Al. In addition, the occurrence of the Cu-rich phase ((Pr, Nd)22Fe56Cu10Al2O10), whose open-circuit potential is higher than the (Pr, Nd)-rich intergranular phase, may be another reason for the improvement of the corrosion resistance. Furthermore, the magnetic properties of (Pr, Nd)14.8Fe78.7B6.5 were also improved by adding 0.3–1.2wt% Al85Cu15. Optimum addition amount was 0.6wt%. The improvement of the magnetic properties may be related to the microstructural modification and the increase of magnet density. [Copyright &y& Elsevier]