Correlation of microstructure and magnetic properties in Sm(CobalFe0.1Cu0.1Zr0.033)6.93 magnets solution-treated at different temperatures
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The correlation of microstructure and magnetic properties in Sm(CobalFe0.1Cu0.1Zr0.033)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(CobalFe0.1Cu0.1Zr0.033)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.
KeywordsSm2Co17 Solution treatment Phase constitution Demagnetization curve squareness
This study was financially supported by the National Natural Science Foundation of China (No. 51471016), the Natural Science Foundation of Beijing (No. 2151002), and the BRICS STI Framework Program (Nos. 51761145026 and 17-52-80072). The author Raghavan Gopalan from India thanks Department of Science and Technology, Govt of India, for supporting the work under DST-BRICS proposal reg. No 258.
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