Effect of Adding Co on Crystallization Behavior and Magnetoimpedance Effect of Amorphous/Nanocrystalline FeCuNbSiB Alloy Strips

After one of the B atoms in Fe73.5Cu1Nb3Si13.5B9 alloy was replaced by both 0.7 Si and 0.3 Co, Fe73.5Co0.3Cu1Nb3Si14.2B8 alloy ribbons were prepared by single roll fast quenching method. The obtained alloy ribbons were subsequently wound into ring magnetic cores, and then these magnetic cores were annealed at different temperatures in air. The effects of adding Co on the crystallization behavior and soft magnetic properties of the as-quenched alloy ribbons with and without heat treatment were studied. The results show that the amorphous structure of the prepared Fe73.5Co0.3Cu1Nb3Si14.2B8 alloy ribbons is transformed into the coexistence of amorphous and nanocrystalline structures after heat treatment at 550°C. Comparing with Fe73.5Cu1Nb3Si13.5B9 alloy ribbons, the first initial crystallization temperature (Tx1) and crystallization peak temperature (Tp1) of Fe73.5Co0.3Cu1Nb3Si14.2B8 alloy ribbons were reduced by 1.6 and 1.7°C, respectively, While the second initial crystallization temperature (Tx1) and crystallization peak temperature (Tp2) were increased by 6.5 and 5.7°C, respectively, resulting in that the difference between the first and the second initial crystallization temperatures (∆Tx) are increased by 8.1°C; the initial permeability (μi) and saturation induction density (Bs) of the amorphous/nanocrystalline Fe73.5Co0.3Cu1Nb3Si14.2B8 magnetic cores were reduced by 0.15 H/m and 0.39 T, respectively, while the coercivity (Hc) is increased by 0.34 A/m