Amorphization, Crystallization, and Magnetic Properties of Melt-Spun SmCo 7 − x ( Cr 3 C 2 ) x Alloys

Abstract

Effects of Cr 3 C 2 content and wheel surface speed on the amorphous formation ability and magnetic properties have been investigated for melt-spun SmCo 7 − x ( Cr 3 C 2 ) x ( x = 0.10 - 0.25 ) alloys. Ribbon melt-spun at lower wheel speed (30 m/s) has composite structure composed of mostly SmCo 7 , a small amount of Sm 2 Co 17 , and residual amorphous phases. The grain size of SmCo 7 phase decreases with the increase of Cr 3 C 2 content x . When melt spinning at 40 m/s, SmCo 7 − x ( Cr 3 C 2 ) x alloys can be obtained in the amorphous state for 0.15 ≤ x ≤ 0.25 with intrinsic coercive H c i of the order of 40–70 Oe. DSC analysis reveals that SmCo 7 phase first precipitates from the amorphous matrix at 650 ∘ C, followed by the crystallization of Sm 2 Co 17 phase at 770 ∘ C. Optimal coercivity H c i of 7.98 kOe and remanent magnetization M r of 55.05 emu/g have been realized in SmCo 6.8 ( Cr 3 C 2 ) 0 .20 magnet subjected to melt spinning at 40 m/s and annealing at 650 ∘ C for 5 min. The domain structure of the annealed ribbon is composed of interaction domains typically 100–400 nm in size, which indicates the presence of a strong exchange coupling between the grains.