Influence of 1:7 H phase stability on the evolution of cellular microstructure in Fe-rich Sm-Co-Fe-Cu-Zr magnets

Fe-rich Sm2Co17-type magnets have many essential applications prospects in high-temperature operation environments. However, the formation of complete cellular microstructure becomes increasingly difficult when the Fe content of Sm2Co17-type magnets exceeds 20 wt%. Herein, the phase stability of 1:7 H phase and its effect on the precipitation of the 1:5 H precipitates in Fe-rich Sm2Co17-type magnets are in-vestigated. The results confirm that the stability of the 1:7 H phase decreases with the increasing of Fe content for the solution-treated magnets. Not only 2:17 R phase but also a lot of 2:17 R ' phase is found in solution-treated magnets when the Fe content exceeds 22 wt%. As the Fe content increases, the density of initial defects decreases for the growth of 2:17 R nanotwins in the solution-treated magnets. Furthermore, the segregation of Cu in the defects-aggregated cell boundaries weakened gradually. Consequently, the nucleation and precipitation of cell boundary precipitates is difficult, and the cellular microstructure be-comes incomplete and coarse when the Fe content is above 22 wt%. The present work may provide a further insight for understanding the evolution of cellular microstructure depending on the phase decomposition behavior in Fe-rich Sm2Co17-type magnets. (c) 2023 Elsevier B.V. All rights reserved.