Abstract
Currently, the continued high prices of the heavy rare earth (HRE) elements Dy and Tb are prompting an exploration of the development of HRE-free high-performance 2:14:1-type permanent magnets. In this paper, a high maximum energy product of 44.04 MGOe at room temperature (RT) was obtained while maintaining a coercivity greater than 20 kOe in HRE-free Pr-Fe-B sintered magnets through microstructural regulation, which reached an equivalent to the commercially 45SH level. The Pr-Fe-B sintered magnet possesses excellent magnetic properties at low temperatures, and its remanence and coercivity increased to 14.75 kG and 75.01 kOe at −170 °C, respectively. Microstructure analysis indicated that the fine and uniform columnar crystals in the strip-casting (SC) alloys provided conditions for the preparation of fine-grained jet milling (JM) powders and sintered magnets. After annealing, the continuous grain boundary (GB) layers and the fine grain size of 2.80 μm ensured high coercivity. Meanwhile, the reduction of microcracking at the GB helps densification and the improvement of c-axis alignment ensured high remanence. The above exploration of microstructural regulation throughout the metallurgical process can provide meaningful guidance for the development of HRE-free Pr-Fe-B sintered magnets with high performance.
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