Effects of Cu Addition on Magnetic Properties and Microstructures of Annealed Zr–Co–Cu–B Ribbons

The magnetic properties and microstructures of Zr
₁₈
Co
_82-x
Cu
_x
B
₂
(x = 0, 1, 2, 3, and 4) ribbons fabricated by melt-spinning technique were investigated to analyze the effects of Cu addition on the stabilization of a hard magnetic rhombohedral Zr
₂
Co
₁₁
phase. In as-spun ribbons, the proportion of the rhombohedral Zr2Co11 phase increased up to x = 3. In addition, it was found that the Cu addition inhibited the decomposition of the rhombohedral Zr
₂
Co
₁₁
phase into Co and ZrCo5 phases during the post-annealing process. In particular, annealed Zr
₁₈
Co
₇₉
Cu
₃
B
₂
ribbons showed that the recrystallized grains having rhombohedral Zr
₂
Co
₁₁
phase were grown as aligned rod-shaped grains with lengths of 200 nm. Thus, the Cu addition increased the coercivity of both as-spun and annealed ribbons. A maximum coercivity of 4.7 kOe was obtained in Zr
₁₈
Co
₈₀
Cu
₂
B
₂
ribbons annealed at 550 °C.