Structure and magnetic properties of Sm15Co70-xFe10B5Alx ribbons

This paper focuses on the phase transition, microstructure and magnetic properties of amorphous-nanocrystal-line Sm15Co70-xFe10B5Alx (x = 0, 5, 10, 15, 20) ribbons melt-spun at a speed of 40 m/s. The results show that the five ribbons are all composed of a high content of amorphous and several nanocrystalline phases, and these crystalline ones are Sm(Co,M)(7) main phase and minor phases including Sm-2(Co,M)(7), Sm2Co7B3, Co72Fe28, etc. Al addition alters the crystallization processes of different ribbons, particularly, a uniform cellular microstructure is formed in x = 15 ribbons which win the maximum coercivity of 15,409.0 +/- 2075.2 Oe. The coercivity of five ribbons is first dominated by the nucleation mechanism, and then the pinning mechanism. The strong pinning effect, stemmed from a combination of uniform cellular microstructure, high volume ratio of cell-walls, high solubility of Al in the Sm(Co,M)(7) and the multiphase interfaces in the wide cell walls, is the main reason for the high coercivity. Finally, the relational models among composition, microstructure and magnetic mechanism were established.