Tuning grain boundary fine structure in Nd65Ni35-added Nd-Fe-B based magnets

Highlights: • Grain boundary fine structures in Nd-Fe-B based magnets are successfully tuned. • The dependence of their corrosion resistance on the boundary fine structures is found. • A sandwich-typed grain boundary structure contributes to better corrosion resistance. On the basis of the grain boundary additive of Nd₆₅Ni₃₅ alloy with the melting temperature of 535 °C and different annealing treatment at 500 °C, 590 °C and 680 °C, respectively, a series of Nd-Fe-B based magnets with different grain boundary fine structures were produced. Their corrosion resistance is found strongly dependent on the grain boundary fine structure. A Ni-rich layer/Nd-rich layer/Ni-rich layer sandwich-structured grain boundary, in particular, contributes to the optimal anti-corrosion performance and magnetic properties for the magnet annealed at 590 °C. The results suggest that more anti-corrosive Nd-Fe-B based magnets could be fabricated by tuning their grain boundary fine structure.