Nanocrystalline (Fe,Co,Ni)₈₆B₁₄ soft magnetic alloys prepared by ultra-rapid annealing

In this study, the glass-forming range, microstructural and soft magnetic properties of (Fe_1−x-yCo_xNi_y)₈₆B₁₄ alloys were investigated in the as-cast state and after ultra-rapid annealing. The glass-forming range is seen to be the greatest for Fe-rich compositions and is limited to x ≤ 0.8 and y ≤ 0.3. Within the glass-forming range, this alloy system is observed to contain nano-scale grains with bcc and fcc structures after ultra-rapid annealing and a clear bcc-fcc transition is seen for Ni-rich compositions. Both the coercivity (H_c) and saturation magnetic polarization (J_s) for the nanocrystalline (Fe_1−x-yCo_xNi_y)₈₆B₁₄ alloys are generally increased by Co addition and reduced by Ni addition. J_s is confirmed to be the largest for (Fe_0.8Co_0.2)₈₆B₁₄ at 1.88 T in the as-cast state and 1.98 T for (Fe_0.7Co_0.3)₈₆B₁₄ in the nanocrystalline state. The minimum H_c of 2.0 A/m is obtained for nanocrystalline (Fe_0.80Co_0.05Ni_0.15)₈₆B₁₄ with a J_s of 1.71 T. This composition also exhibits a lower core loss compared to the nanocrystalline Fe₈₆B₁₄ and Fe-based amorphous alloys at frequencies up to 1 kHz.