Structure and magnetic properties of thermodynamically predicted rapidly quenched Fe85-xCuxB15 alloys

In this work, based on the thermodynamic prediction, the comprehensive studies of the influence of Cu for Fe substitution on the crystal structure and magnetic properties of the rapidly quenched Fe85B15 alloy in the ribbon form are performed. Using thermodynamic calculations, the parabolic shape dependence of the DGamoprh with a minimum value at 0.6% of Cu was predicted. The DGamoprh from the Cu content dependence shape is also asymmetric, and, for Cu = 0% and Cu = 1.5%, the same DGamoprh value is observed. The heat treatment optimization process of all alloys showed that the least lossy (with a minimum value of core power losses) is the nanocomposite state of nanocrystals immersed in an amorphous matrix obtained by annealing in the temperature range of 300–330 C for 20 min. The minimum value of core power losses P10/50 (core power losses at 1T@50Hz) of optimally annealed Fe85-xCuxB15 x = 0,0.6,1.2% alloys come from completely different crystallization states of nanocomposite materials, but it strongly correlates with Cu content and, thus, a number of nucleation sites. The TEM observations showed that, for the Cu-free alloy, the least lossy crystal structure is related to 2–3 nm short-ordered clusters; for the Cu = 0.6% alloy, only the limited value of several -Fe nanograins are found, while for the Cu-rich alloy with Cu = 1.2%, the average diameter of nanograins is about 26 nm, and they are randomly distributed in the amorphous matrix. The only high number of nucleation sites in the Cu = 1.2% alloy allows for a sufficient level of grains’ coarsening of the -Fe phase that strongly enhances the ferromagnetic exchange between the -Fe nanocrystals, which is clearly seen with the increasing value of saturation induction up to 1.7T. The air-annealing process tested on studied alloys for optimal annealing conditions proves the possibility of its use for this type of material

Optimization of metallic glasses for additive technologies. The role of entropy and enthalpy in formation of amorphous structure

PING 2019 is organized with the support of funds for specific university research project SVK1-2019-002.Until now, many different methods of amorphous alloys design were proposed. Generally, they are associated with the trial and error approach. In this group of methods, the influence of different chemical elements on the glass forming ability can be determined empirically based on the results of the analysis of many different alloying systems. However, this approach is time-consuming and cannot be implemented in the industry. Recently, due to the development of additive technologies, new alloying systems with high glass forming ability are sought. The usage of common alloys systems is significantly limited. Therefore, a new approach to determining the optimal chemical composition, which also can be used to describe the crystallization (especially nanocrystallization) process is required. According to that, the thermodynamic approach for alloy design was introduced and described in this work. The analysis of different parameters, such as configurational entropy, mismatch entropy, mixing enthalpy and enthalpy formation of intermetallic phases can be successfully used to determine the optimal chemical composition of alloys with high glass forming ability. Moreover, the proposed approach can be used to understand the crystallization process from the melt, amorphous phase, nanocrystallization process and influence of chemical elements on the glass forming ability in many alloying systems. In this work results of the analysis performed for different Fe-based alloys are presented. Determined influence of chemical elements, such as: copper, cobalt, silicon on the glass forming ability on the basis of the analysis of thermodynamic parameters is related to the changes in the entropy and enthalpy

Influence of Cu Content on Structure, Thermal Stability and Magnetic Properties in Fe72−xNi8Nb4CuxSi2B14 Alloys

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)

Effect of processing parameters on microstructure and properties of CuSn10P1 alloy fabricated by SLM

PING 2019 is organized with the support of funds for specific university research project SVK1-2019-002.The interest in Cu-Sn alloys is associated with excellent flexibility, wear and corrosion resistance, and high mechanical strength. CuSn10P1 alloy has the widest applications among Cu-Sn alloys and is widely used in the shaft sleeve, bearing, gears, valves, etc. The properties of this alloy are strongly depended to the manufacturing process. Usage of the traditional casting causes the intergranular segregation and crystallization of primary α-Cu phase in a coarse mesh dendritic structure. This, in turn, manifest itself in poor properties, limiting its uses in industry. According to that new manufacturing methods should be used to improve the properties of this alloy. In this work, CuSn10P1 alloy was successfully produced using selective laser melting (SLM). The powder size was between 20-63 µm and its humidity during the process was lower than 5%. The four printing strategies were selected to investigate the impact of printing parameters on the microstructure and mechanical properties of the prints. The optimal processing conditions were chosen on the basis of optimization of laser power and scanning speed. The different process parameters result in the changes of the microstructure, especially porosity and the presence of microcracks. On the basis of the analysis of wavelength-dispersive X-ray spectroscopy, it was confirmed, that all chemical elements are evenly distributed after selective laser melting. The segregation of tin and copper can be also observed, however only under remelting of the same layer

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

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

Influence of childhood asthma and allergies on occupational exposure in early adulthood: a prospective cohort study

We aimed to determine whether history of asthma/allergies in childhood was associated with avoidance of jobs with exposure to asthmagens in early adulthood. The Melbourne Atopic Cohort Study recruited 620 children at high risk of allergic diseases at birth (1990-1994). Asthma, hay fever and eczema were evaluated by questionnaires during childhood. A follow-up in early adulthood (mean age: 18 years) collected information on the current job. Occupational exposure to asthmagens/irritants was evaluated using a job-exposure matrix. The association between history of asthma/allergies in childhood and working in a job with exposure to asthmagens/irritants was evaluated by logistic regression, adjusted for age, sex and parental education. Among 363 participants followed-up until early adulthood, 17% worked in a job with exposure to asthmagens/irritants. History of asthma (35%) was not associated with working in an exposed job (adjusted OR: 1.16, 95% CI: 0.65-2.09). Subjects with history of hay fever (37%) and eczema (40%) were more likely to enter exposed jobs (significant for hay fever: 1.78, 1.00-3.17; but not eczema: 1.62, 0.91-2.87). In conclusion, young adults with history of allergies were more likely to enter exposed jobs, suggesting no avoidance of potentially hazardous exposures. Improved counselling against high risk jobs may be needed for young adults with these conditions

Electron Tomography: A Three-Dimensional Analytic Tool for Hard and Soft Materials Research

Three-dimensional (3D) structural analysis is essential to understand the relationship between the structure and function of an object. Many analytical techniques, such as X-ray diffraction, neutron spectroscopy, and electron microscopy imaging, are used to provide structural information. Transmission electron microscopy (TEM), one of the most popular analytic tools, has been widely used for structural analysis in both physical and biological sciences for many decades, in which 3D objects are projected into two-dimensional (2D) images. In many cases, 2D-projection images are insufficient to understand the relationship between the 3D structure and the function of nanoscale objects. Electron tomography (ET) is a technique that retrieves 3D structural information from a tilt series of 2D projections, and is gradually becoming a mature technology with sub-nanometer resolution. Distinct methods to overcome sample-based limitations have been separately developed in both physical and biological science, although they share some basic concepts of ET. This review discusses the common basis for 3D characterization, and specifies difficulties and solutions regarding both hard and soft materials research. It is hoped that novel solutions based on current state-of-the-art techniques for advanced applications in hybrid matter systems can be motivated