Assessment of Directionally Solidified Eutectic Sm–Fe(Co)–Ti Alloys as Permanent Magnet Materials

Sm–Fe–Ti and Sm–Fe0.8Co0.2–Ti alloys were prepared via arc-melting and directionally solidified on a water-cooled copper hearth. The as-solidified alloys featured cells of the Sm(Fe,Co,Ti)12–Ti(Fe,Co) $_{2 +\delta }$ –( $\alpha $ -Fe) lamellar eutectic. The lamellae of Sm(Fe,Co,Ti)12 phase with a crystal structure of the ThMn12 type were less than $0.2 \mu \text{m}$ thick and had their [001] easy-magnetization directions oriented along the temperature gradient of the solidification. The eutectic microstructure led to an increased coercivity, especially in the Co-added alloys. Below 250 °C, this coercivity was found not to vary much with temperature with a temperature coefficient of −0.18%/°C. However, the modest absolute values, reaching only 0.7 kOe, are insufficient for the utilization of the directionally solidified alloys as anisotropic permanent magnets.