Effect of co-addition of Nb/Zr on the microstructure and soft magnetic properties of Fe77.5Si11.5B7NbxZr3-xCu1 nanocrystalline alloys

Soft magnetic nanocrystalline alloys, exemplified by FINEMET (Fe 73.5 Si 13.5 B 9 Nb 3 Cu 1 ), are essential in electronics due to their low coercivity and high permeability. However, demand for miniaturization and enhanced efficiency in power conversion devices necessitates materials with increased saturation magnetization. Given the limited saturation magnetization (1.23 T) of FINEMET alloy, which is attributed to its lower iron content, there has been growing interest in exploring alternative alloys that potentially offer higher saturation magnetization values. The present research introduces a new alloy system that builds on FINEMET by increasing the iron content and meticulously incorporating Nb and Zr in a controlled manner, aiming for a composition that delivers enhanced soft magnetic properties . Alloy ribbons with a newly designed composition of Fe 77.5 Si 11.5 B 7 Nb x Zr 3-x Cu 1 (x = 0–3 at%) were fabricated via rapid-quenching melt spinning followed by nanocrystallization thermal annealing, and the impact of Nb/Zr content on the magnetic microstructure and magnetic properties was investigated. Strategically distributing both Zr and Nb has been found to effectively suppresses grain growth, enhancing permeability and reducing coercivity and core loss. Remarkably, the Fe 77.5 Si 11.5 B 7 Nb 1 Zr 2 Cu 1 nanocrystalline ribbon annealed at 580 °C for 10 min demonstrates outstanding soft-magnetic properties with a coercivity of 1.64 A/m and a saturation magnetization of 170.31 emu/g (1.59 T). Furthermore, a high-resolution TEM analysis revealed an impressively small average crystal size of 9.69 nm. It is anticipated that Fe 77.5 Si 11.5 B 7 Nb x Zr 3-x Cu 1 (x = 0–3 at%) soft magnetic alloys will be broadly applied in power conversion devices such as inductors and transformers, contributing significantly to efficiency and performance enhancements.