Thermal stability, crystallization and magnetic properties of Fe-Co-based metallic glasses

Abstract

The aim of the paper was to investigate thermal stability, crystallization and magnetic properties of Fe-Cobased metallic glasses (MGs 4 . Thermal properties (liquidus T l and melting T m temperatures) of the pre-alloyed ingots upon heating and cooling were analyzed by DTA at a heating/cooling rate of 0.33 K s -1 under the purified argon atmosphere. The structure of the ribbons was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM) method. Kinetics of the crystallization process was examined by applying differential scanning calorimetry (DSC) method, and experiments performed in thermal analysis involve heating at a constant rates b = 0.17, 0.33 and 0.5 K s -1 . Additionally, the conventional crystallization temperature T x was determined from the normalized isochronal resistivity curves a(T) with heating rate 0.0083 K s -1 . a is the temperature coefficient of resistance and a = q

Compelling Rejuvenated Catalytic Performance in Metallic Glasses

“…[23] During the isothermal treatment, MGs tend to reach the thermodynamic equilibrium (lower energy state) from the metastable state, interpreted as structural relaxation or aging, [5] and apparent structural variation occurs at or higher than the crystallization temperature leading to fast crystallization in a short time. MGs relaxing to lower energy states usually obtain undesirable properties, such as annealing-induced abrupt embrittlement, [24] transition from anelasticity to plasticity, [25] decreasing magnetic permeability, [26] and so on. Because of this, further crystallization behavior may be more attractive and is of significant for studying the mechanism of crystal nucleation and growth, and the unexpectedly advanced properties of crystals.…”

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

“…In turn, higher values of Δμ/μ = 11, 10, and 8% were obtained using the Fe 35.75 Co 35.75 B 18.90 Si 5 Nb 4 Cu 0.6 alloy in the form of ribbons with the thicknesss of 0.07, 0.12, and 0.27 mm, respectively (Table 1). The magnetic permeability relaxation intensity after demagnetization is proportional to the concentration of microvoids (excess volume) in the magnetic metallic glasses [10,41,42]. The share of microvoids in the alloy depends on the conditions of the casting process.…”

“…Thermal methods, such as differential thermal analysis (DTA) (NETZSCH, Selb, Germany) and differential scanning calorimetry (DSC) (NETZSCH, Selb, Germany), allowed the characteristic temperatures of the examined alloys to be determined, i.e., crystallization onset temperature ( T x1 ), eutectic temperature ( T e ), melting point ( T m ), and glass forming ability (GFA) indicators ( T g —glass transition temperature; T l —liquidus temperature; Δ T x = T x1 − T g —range of supercooled liquid; T rg = T g / T l —reduced glass transition temperature) [42,55]. The chemical composition of the examined alloys was similar to the eutectic one, which assures their good glass forming ability [42,55].…”

“…The chemical composition of the examined alloys was similar to the eutectic one, which assures their good glass forming ability [42,55]. …”

“…The applied magnetic field had a value of 0.5 A/m and a frequency of about 1 kHz. The magnetic after effects ( Δμ/μ ) were determined by measuring changes of magnetic permeability of the examined alloys as a function of time after demagnetization, where ∆µ is the difference in magnetic permeability measured at t 1 = 30 s and t 2 = 1800 s after demagnetization [41,42]. …”