Preparation of Anisotropic Nanocrystalline NdFeB Magnets from Amorphous Powders by One-Step Hot Deformation

The preparation of nanocrystalline anisotropic NdFeB permanent magnets generally includes two steps, hot pressing (HP) and hot deformation (HD). Herein, one-step HD process is proposed to fabricate NdFeB magnets using amorphous powders. The effects of deformation ratio on the microstructure, magnetic properties, and corrosion resistance are investigated. Compared to traditional HP and HD process, one-step HD can significantly reduce the volume fraction of coarse-grain zone in the magnet. The increase of deformation ratio can promote the formation of the textured platelet-shaped grains and uniform grain boundary phase. The magnetic properties, temperature stability, and corrosion resistance of the magnets increase with increasing deformation ratio until 80%. The best magnetic properties with intrinsic coercivity H-cj = 930 kA m(-1), remanence J(r) = 1.17 T, and maximum energy product (BH)(max) = 263 kJ m(-3) have been achieved for the magnet prepared by one-step HD, which are comparable to those obtained by conventional HP/HD. In addition, different Co element segregations are observed in the magnets with different deformation ratios, which have important effects on the Curie temperature and thermal stability of the magnets. The results suggest that, by replacing HP/HD process and using amorphous powder, one-step HD can simplify the process while maintaining good properties.

Automated summary

In this study, a new one-step hot deformation (HD) process was proposed for fabricating NdFeB magnets using amorphous powders. The effects of deformation ratio on the microstructure, magnetic properties, and corrosion resistance were investigated. The results showed that one-step HD process can significantly improve the properties of NdFeB magnets, and the Co element segregation has important effects on the temperature and thermal stability of the magnets.