Strategy of magnetic hardening region regulation enables a record enhanced energy product and high coercivity in Nd-Fe-B magnets

By developing high comprehensive performance ((BH)_max + H_cj), Nd-Fe-B magnets can operate stably in high-temperature applications, greatly expanding the application scenarios of them. Unfortunately, there is a constraint relationship between coercivity (H_cj) and maximum magnetic energy product ((BH)_max), and an increase in H_cj always accompanies a decrease in (BH)_max. Here, the excellent comprehensive magnetic performance of up to 86.54, namely (BH)_max of 42.33 MGOe and H_cj of 44.21 kOe, is unprecedented in the sintered Nd-Fe-B magnets. This magnet is obtained by designing a unique grain structure through micrometallurgical reactions to prepare a matrix with excellent comprehensive performance, and then by stepwise diffusion, the (BH)_max and H_cj of the magnet are simultaneously enhanced. The magnet prepared in this way has a “double-shell core” structure and Tb segregation distribution inside the core. The working temperature of the magnet in this work reached 280 °C, providing a new approach for the development of high-performance Nd-Fe-B magnets.