Hard Magnetic Properties of Co-Zr-B Alloys Produced by Rapid Solidification Processing

Abstract

Microstructural studies revealed that a Co-Zr-B alloy ingot had coarse grains of Co₂₃Zr₆, Co₅Zr, and Co₃ZrB₂ phases. Melt-spinning of the alloy ingot resulted in the formation of fine equiaxed grains. The resultant melt-spun ribbons consisted of the Co₅Zr and Co₂₃Zr₆ phases and showed coercivities over 1 kOe. Heat treatment of Co-Zr-B melt-spun ribbons resulted in an increase in coercivity. The coercivity of annealed Co-Zr-B melt-spun ribbons was strongly dependent on the alloy composition. A high coercivity of 5 kOe was achieved in a composition of Co₇₈Zr₁₈B₄ and Co₈₀Zr₁₈B₂. The Co-Zr-B melt-spun ribbons exhibited a maximum energy product comparable to that of the hard ferrites.