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

Abstract

The magnetic properties and microstructures of Zr18Co82− x Cu x B2 ( $x = 0$ , 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 Zr2Co11 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 Zr2Co11 phase into Co and ZrCo5 phases during the post-annealing process. In particular, annealed Zr18Co79Cu3B2 ribbons showed that the recrystallized grains having rhombohedral Zr2Co11 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 Zr18Co80Cu2B2 ribbons annealed at 550 °C.