Hot rolling deformation behavior of nanocrystalline Nd-Fe-B magnets: One-step powder forming at large size

Anisotropic nanocrystalline Nd-Fe-B magnets were successfully prepared by hot rolling technique. A systematic study of the microstructure, texture, and magnetic properties of hot-rolled (HR) Nd-Fe-B magnets was conducted to gain an insight into the deformation process. The results indicate that: the hot-rolled magnets have good uniformity after one-step rolling of the cold pressed precursors. As the deformation increases, the Br and (BH)max increase from 7.1 kG to 11.9 kG and from 10.9 MGOe to 30.1 MGOe, respectively. Platelet grains were gradually formed and arranged in the fine grain region, resulting in a c-axis texture. During the deformation process, fine grain region of the rare-earth-rich phase was rapidly squeezed into the coarse grain region, which deteriorated the magnetic properties. The microstructural evolution and deformation processes of hot-rolled Nd-Fe-B magnets were analyzed. The conclusion was that the process of deformation involved melt-spun ribbon densification, dissolution-precipitation, anisotropic grain growth, and grain alignment. Additionally, the preparation process and development prospects of hot-rolled magnets were also discussed.