Magnetic Anisotropy and Stress-Dependent Epoxy Wetting in FeNi-Based Metal Amorphous Nanocomposites

• Published in: IEEE transactions on magnetics Vol. 59; no. 11; pp. 1 - 9
• Main Authors: Egbu, J., Leary, A., Byerly, K., Simizu, S., Thiesen, E., Ohodnicki, P., McHenry, M.
• Format: Journal Article
• Language: English
• Published: New York The Institute of Electrical and Electronics Engineers, Inc. (IEEE) 01.11.2023; Institute of Electrical and Electronics Engineers. Magnetics Group
• Subjects: Anisotropy; Annealing; Annealing furnaces; Body centered cubic lattice; Contact angle; Contact stresses; Crystallization; Current loss; Droplets; Eddy currents; Engineering; Epoxy coatings; Face centered cubic lattice; Heat treatment; Image contrast; Kerr magnetooptical effect; Magnetic anisotropy; Magnetic properties; Magnetism; Mechanical properties; Nanocomposites; Physics; Strain; Tape winding; Tensile stress; Wetting
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2023.3284762

Recently developed FeNi-based metal amorphous nanocomposites (MANCs) used in high-speed motors (HSMs) exhibit reduced eddy current losses while maintaining good mechanical properties and glass-forming abilities. Magnetic anisotropy in (Fe70Ni30)80Nb4B14Si2 amorphous magnetic ribbon (AMR) in the as-cast state and upon conventional ([Formula Omitted]) and strain ([Formula Omitted]) annealing heat treatment is investigated. From ribbon samples in as-cast condition, quenched in stress from planar flow casting (PFC) induced as-cast curvature derived uniaxial magnetic anisotropy. Stress relief by conventional furnace annealing at [Formula Omitted] 350 °C achieved isotropic properties in the bulk. Annealing about the primary crystallization temperature, [Formula Omitted] 450 °C, resulted in the formation of both face-centered cubic (FCC) and body-centered cubic (BCC) nanocrystallites and evolution to isotropic bulk magnetic properties confirming the random anisotropy model. In samples strain annealed at [Formula Omitted] = 440 °C at various tensions, relatively large controlled induced uniaxial anisotropy is achieved. The largest magnetic anisotropy occurs in annealing under the stress of 250 MPa yielding an anisotropy field of [Formula Omitted] A/m. Surface anisotropy observed by the magneto-optical Kerr effect (MOKE) differs from bulk anisotropy due to image contrast from closure domains. Epoxy coatings are important for improved bonding, mechanical properties, and resistivity in tape-wound MANC cores for HSMs. Using a sessile droplet method, the equilibrium contact angle of an epoxy droplet on a tensile stress-annealed MANC exhibits stress-dependent surface energies. Anisotropic wetting in FeNi-based MANC heat treated at [Formula Omitted] = 440 °C mimics surface magnetic anisotropy observed by MOKE.