Soft magnetic properties of nanocrystalline Fe73B7Si16Nb3Cu1 alloy after rapid heating under tensile stress

Abstract

Amorphous Fe73B7Si16Nb3Cu1 ribbon was crystallized rapidly by electric current heating under simultaneously applied tensile stress along the ribbon axis. As a result, strong transverse magnetic anisotropy was induced in the ribbon. Dynamic magnetic properties of the ribbons rapidly heated either under the tensile stress or without tensile stress were measured using toroidal cores. Optimal electric current heating regime that provides maximum improvement of the initial magnetic permeability and core loss was determined. Tensile stress increase from 0 to 180 MPa was shown to result in the decrease of the initial magnetic permeability down to 400 and core loss at frequencies from 0.4 to 200 kHz. Comparative analysis of magnetic properties of the cut core (with non-magnetic gap) and the cores heated under tensile stress was carried out. The magnetic properties of the latter cores are advantageous for manufacturing the reactors and linear chokes of switch-mode power supplies.

Effect of Mechanical Stresses in Rapidly Heated Fe73Cu1Nb3Si16B7 Ribbon Arising During the Ring Core Formation on Their Magnetic Properties

“…One type is the tensile stress which is applied during the pre-heating of amorphous ribbons. As it was shown in [6], this procedure causes irreversible changes in the inner structure of amorphous ribbons on the nanoscale level. Another type of stress is the winding-induced bending of the ribbons.…”

“…Dynamic B-H curves and core loss at different frequencies were measured using the measuring complex MS-02 B-H ANALYZER (MSTATOR, Novgorodskaya oblast, Russia). The detailed description of this complex can be found in [6]. …”

“…Magnetic cores made of the ribbons with induced magnetic anisotropy have a number of advantages, namely, high field stability of magnetic permeability [6], low core loss in the important frequency range (1–100 kHz) [6], and DC bias immunity [7]. …”

DC bias immune nanocrystalline magnetic cores made of Fe73Nb3Cu1B7Si16 ribbon with induced transverse magnetic anisotropy

“…Amorphous ribbon crystallized under fast heating at simultaneous application of tensile stresses from 0 to 180 MPa along ribbon axis [ 18 ]. Fast heating was realized by conducting of electric current with density j h = 42 A/mm 2 and frequency 50 Hz through straight piece of the ribbon for t h = 3.7 s that ensured its heating above 600 °С.…”

“…Cores (made of Fe–Nb–Cu–B–Si alloy with tension-induced transverse magnetic anisotropy) have a number of advantages compared to cores made of other alloys, which are characterized by the same magnetic permeability. The main advantages are the following: high-frequency stability of magnetic permeability [ 12 , 15 – 18 ] and low core loss in frequency range of widest use (1–100 kHz) [ 12 , 15 – 19 ]. These cores are characterized by significantly higher remagnetization loop linearity compared to cut cores made of the same alloy and consequently by magnetic permeability independence on field strength [ 18 ].…”