Tailoring magnetic properties and corrosion resistance of hot-deformed NdFeB magnets via nano-NbC doping

Abstract

Doping nano-NbC is discovered to effectively improve magnetic parameters closely depending on its size. The best magnetic energy product and comprehensive magnetic properties are obtained in the 20 nm-NbC-doped magnet due to the larger amount of Nd-rich phases and their more even distribution than the others. The remanence and magnetic energy product are increased by 7.0% and 13.8%, respectively, after intergranular addition of 20 nm-NbC. With the NbC size further increases to 60 nm, the magnetic properties are deteriorated. The corrosion resistance of magnets also gradually decreases with dopant size increasing, and the 20 nm-NbC-doped one shows best corrosion resistance. Although the corrosion current density is apparently reduced in NbC-doped magnets, their corrosion resistance will be impaired when doped by larger NbC, i.e., 40 nm and 60 nm. This may be attributed to the formation of micropores acting as additional active reaction channels during corrosion.