Correlation of microstructure and magnetic properties in Sm(Co _bal Fe _0.1 Cu _0.1 Zr _0.033 ) _6.93 magnets solution‐treated at different temperatures

Abstract

Abstract The correlation of microstructure and magnetic properties in Sm(Co bal Fe 0.1 Cu 0.1 Zr 0.033 ) 6.93 magnets solution‐treated at different temperatures was systematically investigated. It is found that the magnets solution‐treated at 1219 °C possess a single 1:7H phase, exhibiting the homogeneous cellular structure during further aging treatment, leading to the optimum magnetic properties. However, for the magnets solution‐treated at 1211 and 1223 °C, 2:17H or 1:5H secondary phase will also form besides 1:7H main phase, which cannot transform into cellular structure, thus deteriorating the magnetic properties greatly. The irreversible magnetization investigations with recoil loops also propose a non‐uniform pinning in the magnets induced by the secondary precipitates. At proper solution temperature, Zr is supposed to occupy the Fe–Fe dumbbell sites in the form of Zr‐vacancy pairs, leading to the minimum c / a ratio and thus stabilizing the 1:7H phase. Finally, Sm(Co bal Fe 0.1 Cu 0.1 Zr 0.033 ) 6.93 magnets with the maximum energy product and intrinsic coercivity at 550 °C up to 60.73 kJ·m −3 and 553.88 kA·m −1 were prepared by powder metallurgy method.