A sintered NdFeB magnet with super-high coercivity of 46.21 kOe was successfully obtained by two-step diffusion with Tb metal and Pr-Al-Cu-Ga alloys. Tb-containing magnets with super-high coercivity were used as base magnets; coercivity increased from 35.86 to 44.51 kOe for the Tb-diffused magnet and 46.21 kOe for the magnet with Tb and Pr-Al-Cu-Ga diffusion. Microstructure analysis indicated that two-step diffusion resulted in Tb/Pr-rich double-shell structures, optimized grain boundary structure, and the enhancement of RE-rich grain boundary phases, which is the main reason for the enhancement of coercivity. The diffusion-induced variation of remanence was also discussed. This work provides insights into further breaking the coercivity limit of sintered NdFeB magnets.

High-cerium NdFeB magnets represent an effective approach for balanced utilization of light rare-earth resources. However, morphology of the grains is highly susceptible to processing parameters, and improper settings can result in extremely low performance during hot-pressing and hot-deformation processes. In this paper, the influence of process parameters on the magnetic properties and microstructure of Nd₁₅Ce₁₅(CoFeGa)_balB_0.92 magnets was clarified by adjusting the conditions of hot-pressing and hot-deformation processes, combined with performance testing and microstructural observation. It was observed that the number of coarse-grained regions within the magnets was significantly reduced, with a substantial decrease in coarse-grain size, and uniform primary phase grains were obtained by adjusting parameters to control the morphology of the grains.