Improving the structure, magnetic properties and thermal stability of rapidly quenched TbCu7-type SmCo6.4Si0.3Zr0.3 alloy by carbon addition

The effects of carbon addition on the structure and magnetic properties of rapidly quenched TbCu 7 -type SmCo 6.4 Si 0.3 Zr 0.3 alloy have been investigated. The alloys with a small amount of C addition ( x ≤0.2) showed single Sm(Co, M ) 7 phase, while ZrC phase appeared in the alloys with x =0.3 and 0.4. With the increase of C content, the grain size decreased from approximately 850 nm for x =0.1 to approximately 300 nm for x =0.4. The coercivity H c and maximum magnetic energy product ( BH ) max increased with the C content from x =0 to 0.2 and then decreased with excessive C addition. The optimal magnetic properties of H c =1577 kA/m, J r =0.53 T and ( BH ) max =52.1 kJ/m 3 were achieved for SmCo 6.4 Si 0.3 Zr 0.3 C 0.2 alloy with a grain size of 600–700 nm, which is close to the single domain size of TbCu 7 -type Sm(Co,Zr) 7 alloy. Furthermore, C addition also improved the thermal stability by reducing the absolute values of temperature coefficients of remanence and coercivity.