Refinement Mechanism and Influence of Grain Size in Sintered Nd-Fe-B

With the development of science and technology, the demand for high-performance sintered Nd-Fe-B magnets has increased dramatically. Since the grain refinement has a significant effect on the coercivity of sintered Nd-Fe-B magnets, a low-temperature sintering process using fine powder is proposed to control the grain size to improve the coercivity. Through this method, the grain size of the magnets is controlled to about 3.1 μm, which is smaller than the grain size of the conventionally processed magnet (4.2 μm). As a result, the intrinsic coercivity is increased by 1.24 kOe and the maximum magnetic energy product is increased by 1.23 MGOe, for the same composition. The influence of grain refinement on the magnet performance is studied in detail, which provides a guiding reference for the development of high-performance Nd-Fe-B sintered magnets.