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

摘要

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℃ possess a single 1:7 H 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℃,2:17 H or 1:5 H secondary phase will also form besides 1:7 H 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 1:7 H 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℃ up to 60.73 kJ·m^(-3) and 553.88 kA·m^(-1) were prepared by powder metallurgy method.