Coercivity Enhancement of TbH _x Grain Boundary‐Diffused High Ce‐Content Magnets With CeFe ₂ Phase

To reduce the cost of rare‐earth permanent magnets and achieve balanced resource utilization, there is an urgent need to develop higher performance high Ce‐content magnets. This study investigates the grain boundary diffusion process for high Ce‐content magnets to enhance their magnetic properties. TbH _x was used to perform grain boundary diffusion on high Ce‐content magnets (with Ce accounting for 66 at.% of the total rare‐earth content) under different processing conditions. The impact of diffusion temperature on magnetic properties and microstructure was analyzed. Below 925 °C, Tb primarily diffuses along the solid CeFe ₂ grain boundary phase. Due to the poor fluidity of CeFe ₂ , the diffusion of Tb from the surface to the interior is hindered, thereby obstructing the formation of Tb‐rich shells. Above 925 °C, Tb primarily diffuses along the liquid CeFe ₂ grain boundary phase, entering the main phase grains to form Tb‐rich shells. However, excessively high temperatures lead to the predominance of harmful liquid grain boundary phase behavior, beginning to damage the microstructure of the magnets. These two diffusion behaviors, varying with the diffusion temperature, influence the microstructure and elemental distribution of the grain boundary diffusion magnets, thereby affecting their magnetic properties.