Phase transformation, grain refinement and magnetic properties in melt-spun SmCo7−x(Cr3C2)x (x = 0–0.25) ribbons

The influence of minor addition of Cr3C2 on the microstructure and magnetic properties of as-spun SmCo7−x(Cr3C2)x (x = 0–0.25) ribbons has been investigated systematically. The coercivity increases from 0.42 kOe for x = 0 to 7.48 kOe for x = 0.2, while the remanence decreases from 71.1 emu/g to 54.4 emu/g. According to the results of microstructure analysis, it is found that the addition of Cr3C2 plays an important role in microstructure refinement and the formation of crystallographic texture. The grain size is significantly reduced from 300–600 nm to below 80 nm by the addition of Cr3C2. The smaller grain size on Cr3C2-doped ribbons results from the presence of a non-magnetic phase with a composition of Cr:Co:C 3:1:5 in the grain boundary, which inhibits the grain growth and refines the grains. It is also found that the addition of Cr3C2 promotes the formation of crystallographic texture of the 1:7H phase.