Crystallization Kinetics of Fe76.5−x C6.0Si3.3B5.5P8.7Cu x (x = 0, 0.5, and 1 at. pct) Bulk Amorphous Alloy

Abstract

The influence of Cu on crystallization kinetics of Fe 76.5Àx C 6.0 Si 3.3 B 5.5 P 8.7 Cu x (x = 0, 0.5, and 1 at. pct) bulk amorphous alloys was investigated by isothermal and isochronal differential scanning calorimetry combined with X-ray diffraction. The thermal analysis revealed that the crystallization of the amorphous matrix proceeds through at least two exothermic events. The Cufree glassy alloy forms by primary crystallization the metastable Fe 23 C 6 phase, while upon 0.5 at. pct Cu addition the primary crystallized phase is a-Fe. The activation energy for crystallization, calculated using both Kissinger and Ozawa methods, decreases from about 500 kJ/mol to about 330 kJ/mol. Further increase of Cu addition to 1 at. pct promotes the concomitant crystallization of several phases, as a-Fe, FeB, Fe 3 C, and Fe 2 P. In order to understand the crystallization behavior of the alloys as a function of Cu content, the Avrami exponent n, evaluated from the Johnson-Mehl-Avrami equation, was in details analyzed. The current study reveals that the minor Cu addition plays a crucial role at the initial stage of the crystallization. Among the studied alloys, the glassy samples with 0.5 at. pct Cu addition have the optimum compositional condition for the single a-Fe formation with a high nucleation rate.

Development of New Amorphous and Nanocrystalline Magnetic Materials for Use in Energy-Efficient Devices

“…The brittleness limits the utility of the alloys for many tape wound applications. The brittle ribbon can be crushed into a powder form and many people are studying applications where amorphous or nanocrystalline powders are being processed into complex shapes [7,16].…”

A Study of Structure and Magnetic Properties of Low Purity Fe-Co-Based Metallic Glasses

“…Cu influences the type of α Fe(Si) phase, formed during the first stage of crystallization in the MGs containing Nb and thus effectively affects the magnetic properties [27]. Results presented by Yoshizawa [28] and Müller [14] show that he optimum concentration of the Cu element for obtaining the best soft magnetic properties is 1 at % in Fe-Nb-Si-B-Cu alloys, 0.5 at % in Fe-C-Si-B-P-Cu alloys [29], and 0.6 at % in Fe-Co-B-Si-Nb-Cu alloys [2,3]. Thus, insignificant modification of the chemical composition by Cu addition allows us to achieve good soft magnetic properties.…”