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

Sintered permanent magnets based on domain-wall-pinning-type Sm
₂
Co
₁₇
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
_k
, and the microstructures of these Sm
₂
Co
₁₇
-based bulk magnets has not been widely studied. Therefore, herein, sintered permanent magnets with nominal compositions of Sm(CobalFe
_0.227
Cu
_0.070
Zr
_0.023
)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
_k
first increased and then decreased. The maximum optimal Hk of 1717 kA·m
^-1
(21.58 kOe) corresponded to the magnet with dimensions of ~52.8 mm x 49.2 mm x 36.6 mm, a maximum magnetic energy product (BH)
_max
of 232 kJ·m
^-3
(29.1 MG·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
_k
.