Impact of Nd-Cu diffusion on microstructure and coercivity in hot-pressed and die-upset nanocomposite magnets

The microstructure evolution in hot-pressed and die-upset magnets was studied to clarify the impact of Nd-Cu diffusion on microstructure and coercivity. It was found that Nd-Cu diffusion mainly occurs at the interface of the raw powders during the hot-pressing process. In the die-upsetting process, grain boundary diffusion is main reason for the homogeneous distribution of Nd-Cu. Moreover, Nd-Cu grain boundary diffusion decoupling the hard phases, grain morphology and the presence of Nd2O3 contribute to the higher coercivity in die-upset magnets with low height reduction. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.