Effect of wheel speed on the microstructures and magnetic properties of rapidly solidified Sm-Co alloys

Melt-spinning of Sm11Co89 alloys modified with Nb and C resulted in the formation of the metastable (1:7) structure irrespective of the variations in wheel speed (20-60 m/s), with the formation of fcc-Co phase observed at v=60m/s. At higher wheel speed the higher chances of formation of Co precipitate and the reduced size of Co precipitates helped to improve the remanence. Moreover, wheel speeds up to 50 m/s resulted in refined (1:7) grain sizes and thus resulted in higher coercivity. At extremely high wheel speed (v=60m/s), short contact time with the wheel for the molten pool caused in-flight annealing and thus resulted in coarser grain and lower coercivity value. Most of the alloys exhibited a high reduced remanence ratio (∼0.7) indicating significant exchange-spring interactions between the grains. At higher wheel speed the magnetization process was dominated by pinning mechanism.