Effect of Co substitution for Fe on microstructure and magnetic properties of FeNiSiBCuNb alloy ribbons

This work investigated the microstructure, magnetic properties, and crystallization kinetics of the as-spun and annealed alloy ribbons of (Fe_40−xCo_xNi₄₀Si_6.33B_12.66Cu₁) _0.97Nb_0.03, where x = 0, 6, 7, 8, 9, prepared using the melt-spinning method. The results show that adding a moderate amount of Co can improve the glass forming ability (GFA), the first peak crystallization temperature, and thermal stability of the as-spun alloy ribbons. With x = 7, the two-stage crystallization temperature interval ΔT_x = 90 exhibits optimal thermal stability, and the alloy annealed at 673 K for 10 minutes shows the favorable combined magnetic properties, with H_c = 0.12 A/m, M_s = 88.7 A⋅m²/kg, and μ_e = 13800. The magnetic domain results show that annealing removes numerous pinning points in the magnetic domains of the alloy ribbons, making the domain walls smoother and effectively reducing the pinning effect.