Abstract
The effect of substitution of Fe by Cu on the crystal structure and magnetic properties of Fe72−xNi8Nb4CuxSi2B14 alloys (x = 0.6, 1.1, 1.6 at.%) in the form of ribbons was investigated. The chemical composition of the materials was established on the basis of the calculated minima of thermodynamic parameters: Gibbs free energy of amorphous phase formation ΔGamorph (minimum at 0.6 at.% of Cu) and Gibbs free energy of mixing ΔGmix (minimum at 1.6 at.% of Cu). The characteristic crystallization temperatures Tx1onset and Tx1 of the alpha-iron phase together with the activation energy Ea for the as-spun samples were determined by differential scanning calorimetry (DSC) with a heating rate of 10–100 °C/min. In order to determine the optimal soft magnetic properties, the wound cores were subjected to a controlled isothermal annealing process in the temperature range of 340–640 °C for 20 min. Coercivity Hc, saturation induction Bs and core power losses at B = 1 T and frequency f = 50 Hz P10/50 were determined for all samples. Moreover, for the samples with the lowest Hc and P10/50, the magnetic losses were determined in a wider frequency range 50 Hz–400 kHz. The real and imaginary parts of the magnetic permeability µ′, µ″ along with the cut-off frequency were determined for the samples annealed at 360, 460, and 560 °C. The best soft magnetic properties (i.e., the lowest value of Hc and P10/50) were observed for samples annealed at 460 °C, with Hc = 4.88–5.69 A/m, Bs = 1.18–1.24 T, P10/50 = 0.072–0.084 W/kg, µ′ = 8350–10,630 and cutoff frequency at 8–9.3 × 104 Hz. The structural study of as-spun and annealed ribbons was carried out using X-ray diffraction (XRD) and a transmission electron microscope (TEM).
Highlights
In 2019, the soft magnetic market was valued at USD 51.4 billion, with an assumed compound annual growth rate of 9.1% in the 2019–2024 period [1]
The growing demand and diversity of specialized electrical devices presents scientists and engineers with new challenges—improving or creating new materials that can improve existing technologies. This can be achieved by modifying the chemical composition and controlled heat treatment resulting from the crystallization kinetics
The present study describes the effect of Cu substitution in Fe72−x Ni8 Nb4 Cux Si2 B14 alloys on thermodynamic parameters, crystallization kinetics, crystal structure, and magnetic properties
Summary
In 2019, the soft magnetic market was valued at USD 51.4 billion, with an assumed compound annual growth rate of 9.1% in the 2019–2024 period [1]. An increasing group of these soft magnetic materials are amorphous and nanocrystalline metal alloys, mainly based on iron, which are widely used as distribution and industrial transformers [2,3], high-efficiency photovoltaic inverters [4,5], stator cores [6] or elements of wind turbines [7,8] For this kind of applications, materials should be characterized by magnetic properties such as low coercivity and core losses over a wide frequency range, high magnetization and permeability, and low weight, wide operation temperature range, simple technological process and low manufacturing cost [9]. This can be achieved by modifying the chemical composition and controlled heat treatment resulting from the crystallization kinetics
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