Influence of Cu Content on Structure and Magnetic Properties in Fe86-xCuxB14 Alloys.

Tymon Warski,Tymon Warski,Adrian Radon,Adrian Radon,Przemyslaw Zackiewicz,Przemyslaw Zackiewicz,Lukasz Hawelek,Aleksandra Kolano-Burian,Aleksandra Kolano-Burian,Anna Wojcik,Marcin Polak,Marcin Polak,Maciej Szlezynger,Maciej Szlezynger,Patryk Wlodarczyk

doi:10.3390/ma13061451

Abstract

Influence of Cu content on thermodynamic parameters (configurational entropy, Gibbs free energy of mixing, Gibbs free energy of amorphous phase formation), crystallization kinetics, structure and magnetic properties of Fe86-xCuxB14 (x = 0, 0.4, 0.55, 0.7, 1) alloys is investigated. The chemical composition has been optimized using a thermodynamic approach to obtain a minimum of Gibbs free energy of amorphous phase formation (minimum at 0.55 at.% of Cu). By using differential scanning calorimetry method the crystallization kinetics of amorphous melt-spun ribbons was analyzed. It was found that the average activation energy of α-Fe phase crystallization is in the range from 201.8 to 228.74 kJ/mol for studied samples. In order to obtain the lowest power core loss values, the isothermal annealing process was optimized in the temperature range from 260 °C to 400 °C. Materials annealed at optimal temperature had power core losses at 1 T/50 Hz—0.13–0.25 W/kg, magnetic saturation—1.47–1.6 T and coercivity—9.71–13.1 A/m. These samples were characterized by the amorphous structure with small amount of α-Fe nanocrystallites. The studies of complex permeability allowed to determine a minimum of both permeability values at 0.55 at.% of Cu. At the end of this work a correlation between thermodynamic parameters and kinetics, structure and magnetic properties were described.

Highlights

Fe-based alloys, such as METGLAS, FINEMET, NANOPERM or HITPERM are widely used as a replacement for silicon steel in electricity generation and in magnetic, electronic and conversion applications
Thermodynamic calculations have shown that a material with Cu = 0.55% has the lowest energy of amorphous phase formation
Tx1 crystallization temperatures equal to 380.9 ◦ C and 405.1 ◦ C, respectively. Sample with this composition has the lowest average activation energy calculated by Kissinger formula

Summary

Introduction

Fe-based alloys, such as METGLAS, FINEMET, NANOPERM or HITPERM are widely used as a replacement for silicon steel in electricity generation and in magnetic, electronic and conversion applications This is associated with wider usable frequency range, lower coercivity, weight and power losses [1]. For many years the chemical composition of soft magnetic alloys has been modified by various combinations of atomic substitutions, the development of new production techniques, especially postprocessing treatment (like ultra-rapid annealing—URA), has increased interest in binary alloys like Fe-B. This binary alloy is known for its superior glass forming ability (GFA) [2].

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