Improvement of corrosion resistance in Nd–Fe–B magnets through grain boundaries restructuring

Abstract: Nd–Fe–B sintered magnets exhibit poor corrosion resistance due to the large electrochemical potential difference between the Nd2Fe14B matrix and the Nd-rich intergranular phase. This letter presents a new approach to improve corrosion resistance of (Pr,Nd)–Fe–B sintered magnets in both humid atmosphere and acidic environment through replacing the (Pr,Nd)-rich intergranular phase by a (Pr,Nd)6Fe13Cu one, which can reduce significantly the electrochemical potential difference. Mass loss for the restructured magnets is less than 1.0mg/cm2 after exposure to heat/humid atmosphere for 96h. Corrosion resistance in 0.005M H2SO4 solutions can also be significantly improved. In addition, the magnets still possess outstanding magnetic properties, with a maximum energy product (BH) max of ~384kJ/m3, demonstrating that the grain boundaries restructuring is a competitive method to fabricate corrosion-resistant Nd–Fe–B sintered magnets. [Copyright &y& Elsevier]