Improvement of Microstructure and Magnetic Properties of Hot-Deformed Nd-Fe-B Magnets by Doping Dy-Fe Powder

摘要

The effects of Dy80Fe20 (wt%) powder doping on the magnetic properties and thermal stability of the hot-deformed (HD) Nd-Fe-B magnets are studied. The coercivity (H-cj) greatly increases from 12.55 kOe for the original magnet to 18.23 kOe by doping 2 wt% Dy80Fe20 powder, which shows an increase of 45.3%. Interdiffusion occurs between the Dy80Fe20 additive and matrix phase. Dy diffuses from the Dy80Fe20 additive to the matrix phase and replaces Nd around the Nd2Fe14B grains. Nd migrates into the grain boundary (GB) phase. The formation of (Nd, Dy)(2)Fe14B regions improves the magnetic anisotropy field (H-A) and effectively suppresses the nucleation of reverse magnetic domains. The magnetic isolation is strengthened by the improved GB phase. This explains the H-cj enhancement of the Dy80Fe20 doped magnet. The thermal stability of the Dy80Fe20 doped magnet is improved due to the high Curie temperature (T-C) of (Nd, Dy)(2)Fe14B hard magnetic phase. The relationship between recoil loops and demagnetization of the HD magnets is also discussed.