Microstructure and Corrosion behavior of the Dy-doped sintered Nd-Fe-B Magnets Processed by Low-temperature Heat Treatment

Abstract

The low-temperature heat treatment process can be used to replace the traditional two-stage heat treatment process during the production of the Dy-doped Nd-Fe-B magnets, which saves the energy and also shortens the production period. In this work, the microstructure and corrosion behaviors of Nd-Fe-B magnets doped with Dy were analyzed by the scanning electron microscope observation, electrochemical and mass loss test. The results indicated that the corrosion resistance of the magnet with one-stage low-temperature annealing process was better than that with two-stage annealing process. Lots of (Pr, Nd, Dy)-oxide and Dy-oxide formed on the surface of the magnets after one-stage low-temperature annealing process, which decreased the electrode potential differences between the main phase grains and these oxide particles, and this further reduced the corrosion reaction driving force of the magnets.