Magnetic Properties and Microstructures of Sintered Sm2Co17 Alloys With High Knee-Point Coercivity H k

Abstract

Sintered permanent magnets based on domain-wall-pinning-type Sm2Co17 have recently attracted considerable attention due to their low-temperature coefficient, excellent high-temperature magnetic properties, and remarkable oxidation and corrosion resistances. However, the relationship between the knee-point coercivity, $H_{\mathrm {k}}$ , and the microstructures of these Sm2Co17-based bulk magnets has not been widely studied. Therefore, herein, sintered permanent magnets with nominal compositions of Sm(CobalFe0.227Cu0.070Zr0.023) z ( $z =7.40$ , 7.47, 7.54, 7.61, and 7.84) (at.%) were prepared via conventional powder metallurgy, and their magnetic properties were investigated. The results showed that as $z$ increased from 7.40 to 7.84, $H_{\mathrm {k}}$ first increased and then decreased. The maximum optimal $H_{\mathrm {k}}$ of 1717 kA $\cdot \text{m}^{-1}$ (21.58 kOe) corresponded to the magnet with dimensions of ~52.8 mm $\times49.2$ mm $\times36.6$ mm, a maximum magnetic energy product ( BH )max of 232 kJ $\cdot \text{m}^{-3}$ (29.1 MG $\cdot $ Oe), and $z =7.61$ . The transmission electron microscopy revealed that the crystalline structure and chemical composition of the magnet are the two main factors determining $H_{\mathrm {k}}$ .