Abstract
Applying tensile stresses on straight soft magnetic ribbons before core fabrication is a routine method of inducing magnetic anisotropy, while methods of stress annealing of ribbons after core winding are seldom explored. In this study, we utilize a novel approach to induce magnetic anisotropy by applying radial stresses on tape-wound cores of Fe73.5Si13.5B9Cu3Nb1 (at. %) ribbon during crystallization heat treatment. The results show that while stress annealing does not change the structural characteristics of annealed samples, the magnetic anisotropies induced can increase to values ~3–5 times larger than the sample annealed in the absence of external stress. This increase in magnetic anisotropy energy is associated with ~25–50% decrease of magnetic inductance in the treated cores. These results suggest that the magnetic properties of nanocrystalline soft magnetic alloys can be effectively tuned by applying radial stresses.
Highlights
Soft magnetic materials are used in various types of electrical devices to store energy and convert or generate electricity [1]
We find that while stress annealing does not change the structural characteristics of annealed samples, the magnetic anisotropy induced in stress-annealed samples increases compared to the sample annealed without external stress
By applying external stress to the toroidal cores prepared from Fe73.5 Si13.5 B9 Cu3 Nb1 ribbons, the soft magnetic properties and structure of treated samples were studied
Summary
Soft magnetic materials are used in various types of electrical devices to store energy and convert or generate electricity [1]. Compared to the conventional soft magnetic materials, nanocrystalline alloys show exceptional magnetic behaviors such as higher saturation magnetic induction, lower coercivity, higher magnetic permeability, and enhanced core loss performance at high frequencies [2,3,4]. These types of alloys pave the way for reaching smaller, lighter, and more efficient electrical components. The standard method for preparing nanocrystalline soft magnetic alloys is the single roll melt spinning technique In this technique, alloys of a limited composition range are rapidly cooled down from the molten state to a noncrystalline (amorphous) state and crystallization is prevented from occurring. Annealing of the as-cast amorphous ribbons at temperatures above the glass transition temperature but below the crystallization temperature, while relieving quenched-in stresses, produce a nanocomposite structure comprised of nanometer-sized crystals of (α)Fe-Si soft magnetic phase embedded in an amorphous matrix [8]
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