Speaker
Description
Nanocrystalline soft magnetic FeCo-based alloys have gained attention in the last decades and recently also in the development of electric motors due to their excellent magnetic properties thanks to their fine microstructure, being composed of bcc-FeCo nanograins surrounded by metalloid-enriched amorphous matrix. FeCoB alloys with high saturation magnetization, low coercivity, high permeability and low core loss have potential applications also in electromagnetic shielding, microwave absorption, electric power transmission, transformers, magnetic sensors, electromagnetic noise suppression [1]. FeCo-based alloys are often used in applications where their high saturation values provide advantage in reducing weight or volume of the components. For example, a careful design of components with FeCo alloys over standard Fe–Si alloys may result in weight savings of $20$–$25\%$ [2].
In this work, we investigated the effect of addition of $1$ at $\%$ Cu to FeCoB alloys on the resulting magnetic properties and microstructure in as-cast state and after nanocrystallization. Rapidly quenched amorphous ribbons were analyzed by DSC to determine critical temperatures. Copper shifts the first crystallization temperature to the lower temperatures. Temperatures close to and above the first transformation ($450$°C – $500$°C) were chosen for heat treatment. The samples were subjected to examination and confirmation of bcc-FeCo phase formation by XRD and TEM after annealing. Magnetic properties of the FeCoB alloy with $1$ at$\%$ Cu addition showed enhancement in magnetic softness after heat treatment in the vicinity of the first crystallization ($450$°C/$30$ seconds). Tendency of $H_c$ to decrease with increasing temperature of annealing correlates with the crystalline fraction content. The achieved magnetic saturation $J_s = 1.92$T is lower compared to Cu free alloy ($J_s = 1.94$T). The achieved results help to optimize the method of annealing and, when another element such as Cu is added, to provide opportunities for the use of such materials in electrical engineering applications.
Acknowledgements
Support of the projects VEGA 2/0120/25, APVV-23-0281, JRP NOMAGRAD and 09I03-03-V01-00047 (Office of Government of Slovakia) is gratefully acknowledged. The study was performed during the implementation of the project "Research of new materials by the methods of advanced diagnostics", ITMS code 313010U400, supported by Research & Innovation Operational Program funded by the ERDF.
References
[1] Y. Yoshizawa et al., “New Fe-based soft magnetic alloys composed of ultrafine grain structure,” Journal of Applied Physics, vol. 64, no. 10. AIP Publishing, pp. 6044–6046, Nov. 15, 1988. https://doi.org/10.1063/1.342149
[2] R. S. Sundar and S. C. Deevi, “Soft magnetic FeCo alloys: alloy development, processing, and properties,” International Materials Reviews, vol. 50, no. 3. SAGE Publications, pp. 157–192, Jun. 2005. https://doi.org/10.1179/174328005x14339
