Annealing Optimization of High Induction (> 1.7 T) Fe85−(x+y)CoxCuyB15 Alloys With Enhanced Magnetic Properties

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2024-04, Vol.55 (4), p.1174-1182
• Main Authors: Warski, Tymon, Pilśniak, Adam, Wójcik, Anna, Szlezynger, Maciej, Dadiel, Joseph Longji, Kolano-Burian, Aleksandra, Hawełek, Łukasz
• Format: Article
• Language: English
• Subjects: Alpha iron; Annealing; Characterization and Evaluation of Materials; Chemistry and Materials Science; Cobalt; Coercivity; Core loss; Crystal growth; Crystal structure; Crystallization; Magnetic induction; Magnetic permeability; Magnetic properties; Materials Science; Metallic Materials; Nanomaterials; Nanotechnology; Optimization; Original Research Article; Structural Materials; Structural stability; Surfaces and Interfaces; Thermal analysis; Thermal stability; Thin Films
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-024-07313-y

In this work, the influence of the substitution of Co and Cu for Fe on the thermal stability, crystallization process, crystal structure and magnetic properties of Fe 85−( x + y ) Co x Cu y B 15 ( x  = 2.5, 5, 7.5; y  = 0.6, 1.2) as-quenched alloys in the form of the ribbons have been studied. Thermal analysis showed that the average activation energy of the α -Fe phase crystallization decreases from 216.1 to 168.6 kJ/mol for Fe 84.4− x Co x Cu 0.6 B 15 and increases from 157 to 208.4 kJ/mol for Fe 84.8− x Co x Cu 1.2 B 15 . The relationship between the annealing temperature (260 °C to 440 °C for 20 minutes in vacuum) and magnetic properties (saturation induction, coercivity and core power losses) was determined for isothermally vacuum-annealed. The optimal annealing conditions corresponding to the minimum value of power core losses were found for temperatures between 300 °C and 330 °C. Optimally vacuum-annealed alloys are characterized by high saturation induction of 1.67 to 1.78 T, a relatively low coercivity of 14.7 to 26.4 A/m, core power losses at 1 T/50 Hz of 0.21 to 0.39 W/kg and magnetic permeability μ ′ up to 250 to 967. The X-ray diffraction was used to monitor the crystal structure evolution during annealing. It confirmed the occurrence of three stages: glass relaxation, early α -Fe(Co) crystallization stage for the minimum value of core power losses and extensive two-phase crystal growth stage with high saturation induction and deteriorated coercivity and core power losses. Transmission electron microscopy examination verified that optimally annealed alloy was the composite nanomaterial built of α -Fe(Co) nanocrystals immersed in an amorphous matrix.