Amorphous Metallic Alloys Research Articles

ОСОБЛИВОСТІ ФОРМУВАННЯ ПОВЕРХНЕВИХ ШАРІВ НА МЕТАЛАХ

The practical application of metal alloys, in particular amorphous ones, often necessitates the creation of multifunctional coatings of various nature and purpose on their surfaces. The main requirements for obtaining optimal results of applying such coatings are as follows: 1. Understanding of the morphology of the surface before coating. 2. Information on the physical and mechanical properties of the metal-coating composition. 3. Testing of the adhesion strength immediately after coating. 4. The use of different methods of control of the application and functionality of the coating, depending on the operating conditions of the product. The reliability of functional coatings also depends on the preparation of the surface of the material, as well as the choice of appropriate conditions for its formation. However, regardless of the purpose, a general requirement that all coatings must meet is a good adhesion to the surface of the substrate material. It is also important to ensure the uniform thickness in different areas (protrusions and depressions), because the thickness of the coating determines the longevity of its protective effect. Also, the coatings should have very low rate of dissolution even in the most aggressive environments in which they work. Therefore, the problem of creating optimal coatings is complex and requires a comprehensive study in each specific case. In the case of industrial use of amorphous metal alloys (AMA) based on transition metals with different alloying elements, special attention must be paid to the elemental composition of the surface of the finished products, which can differ significantly from the quantitative composition of the initial charge, which depends on the nature of the components and the applied protocol of ultra-fast cooling of the melt. The difference in the elemental composition on the surface and in the volume of the amorphous alloy is also due to the possible formation of surface chemical compound i.e. metal oxides. The protective properties are evaluated by the speed of metal oxidation, the formation of a layer and the duration of its action. Comparative assessment of the reactivity of amorphous alloys Al87.0Y5.0Ni8.0, Fe73.6Cu1.0Nb2.4Si15.8B1.2, Fe78.5Ni1.0Mo0.5Si6.0B14.0, Co75.5Fe4.6Si6,B16.7 in an aqueous solution of sodium chloride was carried out using electrochemical studies. The main requirements for obtaining optimal results of applying protective coatings on crystalline and amorphous surfaces have been analyzed.

Adsorption of organic peroxides on the surface of amourphous alloys for the drugs immobilization

It was investigated wetting of surfaces of the amorphous metallic alloys (AMA) based on iron and cobalt with aqueous-ammonium solutions of oligoperoxides based on vinyl acetate, 2-tert-butylperoxy-2-methyl-5-hexen-3-yne and maleic anhydride (OP-1) and based on vinyl acetate, 3-tert-butylperoxy-3-phenylbutylmethacrylate and maleic anhydride (OP-2). The surface tension of thin films of oligoperoxideʼs aqueous-ammonia solutions was determined and were calculated values of the macromolecules adsorption. A higher surface activity of OP-2 was observed in comparison with OP-1. The values ​​of the adhesion work between contact and external metallic surfaces and solutions of oligomers were calculated.

Investigation on Vibration Characteristics of Amorphous Metal Alloy Core Dry-type Distribution Transformer

Large power transformers have severe vibration and noise problems. Thus, as the source of noise, it is vitally important to have accurate core vibration calculations. The calculation of the vibration is incredibly difficult to consider the complex propagation pathway of the vibration in the clamp and the Amorphous Metal Alloy Core Distribution Transformer (AMACDT). To understand the vibration characteristics of AMACDT, this manuscript provides a different approach on investigation of the vibration characteristics of an SCBH15-200/10 type. Based on the vibration characteristics calculation and displacement of an Amorphous Metal Alloy Core Distribution Transformer (AMACDT), they are obtained and solved using Finite Element Analysis software (FEA). Conferring to the outcomes of the vibration analysis, the method by adding bar-reinforcements on the upper clamp of transformer is proposed to lessen the vibration amplitude. To verify the usefulness and application of the suggested approach, the analytical results are obtained. The suggested approach is analyzed with those of experimental.

Cavity nucleation in single-component homogeneous amorphous solids under negative pressure

Understanding the cavity formation and cavity growth mechanisms in solids has fundamental and applied importance for the correct determination of their exploitation capabilities and mechanical characteristics. In this work, we present the molecular dynamics simulation results for the process of homogeneous formation of nanosized cavities in a single-component amorphous metallic alloy. To identify cavities of various shapes and sizes, an original method has been developed, which is based on filling cavities by virtual particles (balls) of the same diameter. By means of the mean first-passage time analysis, it was shown that the cavity formation in an amorphous metallic melt is the activation-type process. This process can be described in terms of the classical nucleation theory, which is usually applied to the case of first order phase transitions. Activation energy, critical size and nucleation rate of cavities are calculated, the values of which are comparable with those for the case of crystal nucleation in amorphous systems.

Ultralight broadband microwave-absorbing materials based on the short fibers of glass-coated amorphous magnetic microwires

Glass-coated amorphous magnetic microwires (GAWs) typically have a glass skin and amorphous metal alloy inner core, giving them special electromagnetic (EM) properties. GAWs not only exhibit multiple EM losses and suitable impedance matching but also have a conductive core with magnetic properties. In this study, GAW filament fibers (LFs) and short fibers (SFs) were prepared, and they exhibited completely different EM performance. LFs with filaments closely arrayed reflected EM waves and could thus act as an EM shielding material, whereas SFs with randomly distributed fibers demonstrated excellent microwave-absorbing (MA) properties. Single-layer SFs of just 3 g/m2 and a length of 5 mm had a minimum reflectivity (RL) of −20.4 dB at 12.3 GHz, and the effective absorption bandwidth (EAB) of RL< −10 dB was 5.36 GHz with a thickness of just 1 mm. Moreover, the MA properties of the SFs were obtained and controlled by adjusting the length, content, and lamination of the SFs in accordance with their multiple MA mechanisms. Double-layer SFs with a thickness of 2 mm could also achieve an EAB (RL< −10 dB) above 10 GHz. The novel and effective strategy proposed in this study can thus produce SFs GAWs from ultralight MA fabric that exhibit excellent MA properties and broadband.

Analysis of surface roughness and oxidation of FeNi-based metal amorphous nanocomposite alloys

We report on a systematic investigation of newly developed (Fe 70 Ni 30 ) 80 Nb 4 B 14 Si 2 metal amorphous nanocomposites (MANCs) and the factors affecting their surface roughness, including oxide formation and phase evolution during the nanocrystallization process. Analysis of surface roughness using atomic force microscopy (AFM) revealed an average roughness of 9.33 nm after heat treatment compared with as-cast amorphous ribbons, which exhibited a roughness of 4.21 nm. A surface oxide layer thickness has been determined using X-ray photoelectron spectroscopy (XPS). For samples annealed at 400 °C for 1 h, 450 °C for 1 h, and 550 °C for 3 h in air, the average surface oxide layer thickness was determined to be 10.9, 11.7, and 54.4 nm, respectively. It was observed that oxygen is enriched at the outermost surface and decreases rapidly as the XPS sputtering depth increases. Fe-oxide appeared as a predominant metal oxide at the top surface, followed by the presence of Nb oxide. A boron content increase was observed at the interface between the top surface oxide layer and the bulk of the sample. A protective surface oxide layer on FeNi-MANCs, such as observed in this work, can provide sufficient electrical insulation to reduce interlaminate eddy current losses and lower overall losses in magnetic components. • Surface roughness and oxidation of FeNi-based metal amorphous nanocomposites. • Surface roughness in amorphous ribbon using atomic force microscopy (AFM). • Crystallization and activation energies in metal amorphous nanocomposite ribbons. • Phase fractions in metal amorphous nanocomposite ribbons. • Surface oxides partitioning in amorphous and nanocrystalline alloys.

Influence of mechanical stress on magnetization processes in amorphous FINEMET alloy

The influence of mechanical stress on magnetization processes in an amorphous metal alloy have been investigated. The rapidly quenched amorphous metallic ribbons with nominal composition Fe73.5Cu1Nb3Si13.5B9 (precursor of FINEMET) were chosen for this study. The significant differences in the magnetic properties of the studied material were observed at different degrees of mechanical stress applied to the sample. The origin of these effects arises from changes in the dynamics of domain walls. They are primarily caused by variation of their fundamental properties (thickness, energy per unit area of the domain wall) as well as changes in the properties of internal stress areas, which are obstacles to their movement. Impact of stress areas was demonstrated by analysis of influence of mechanical load on the internal demagnetization factor.

Site-specific preparation of plan-view samples with large field of view for atomic resolution STEM and TEM studies of rapidly solidified multi-phase Al Cu thin films

The present work describes application of a method for site-specific plan-view sample preparation for atomic column resolution scanning transmission and transmission electron microscopy (STEM and TEM) from free-standing thin films of multi-phase Al-alloys after laser irradiation induced rapid solidification (RS). The electron-transparent multilayer thin film samples (amorphous Si3N4 substrate plus metal alloy layer) had a total initial thickness of ≈ 130–200 nm. At such large total sample thickness frequently multiple grains of the same or different phases overlap along the electron beam path in the RS microstructures of the alloys. Consequently, accurate atomic resolution images in TEM and STEM mode, and composition sensitive analytical data of the metastable microstructural features presenting in the RS microstructures cannot be obtained with confidence. Using low-energy concentrated Ar ion beam milling, locally thinned regions with thickness of 20–30 nm with large fields of view ≥ (30 μm)2 suitable for high-resolution TEM/STEM studies have been created with micron-scale site-specificity. As example application, atomic scale resolution TEM/STEM imaging has been performed of the banded grain regions of the RS microstructure established in multi-phase AlCu alloy thin films. The sample preparation strategy described here appears to be readily applicable to freestanding thin film specimens in general.

Anomalous magnetoresistance and Hall effect in amorphous Pt/TbFeCo thin films

Among the magnetic materials in technological usage, amorphous rare-earth transition metal (RE–TM) alloys are of great interest due to their adjustable magnetic properties and favorable perpendicular magnetic anisotropic (PMA) advantages. In this study, the properties of Tb25Fe61Co14 system with 2, 5, and 10 nm Pt underlayers have been systematically explored by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature and magnetic field dependence of Hall resistivity, magnetoresistivity, and magneto-optic Kerr Effect (MOKE) measurements. According to the results, whole thin films are amorphous in nature and display an out-of-plane magnetic anisotropy without annealing. Increasing the Pt underlayer thickness helps the TbFeCo layer to reach significantly enhanced perpendicular magnetic anisotropic values and visualize the appearance of anomalous magnetoresistance in the Hall effect measurements. The thin films with 5 and 10 nm Pt underlayer has a ratio of remanence magnetization/saturation magnetization (MR/MS) of around 1, which is the out of plane direction of MOKE signal. Besides, the present study also includes some pieces of evidence that might be related to the Berry phase trend.

Finding order in disorder: Magnetic coupling distributions and competing anisotropies in an amorphous metal alloy

Amorphous metals have unusual magnetic properties that arise due to the disordered atomic arrangement. We show that Cox(Al70Zr30)100−x (65 &amp;lt; x &amp;lt; 92 at. %) amorphous alloys have a distribution in the local magnetic coupling and ordering temperature, which can be explained by nanoscale composition variations. We use competing anisotropies induced by the substrate and an applied field during growth to probe the Co concentration distribution. Only regions with high enough Co concentration develop a magnetic anisotropy along the magnetic field during growth, whereas regions of low Co concentration have an anisotropy dictated by the substrate. A Gaussian distribution in the Co concentration of width 5.1 at. % is obtained from the variation in anisotropy. The results demonstrate the importance of composition variations for emergent magnetic properties and have far reaching implications for the properties of disordered materials in general.

Atomic transport in amorphous metals

Abstract A novel mechanism of atomic transport in amorphous metallic alloys, or metallic glasses, is proposed based upon the fluctuations in the local structure. The proposed mechanism is very different from those in crystalline solids and from the free volume model, and is characterized by the bond-exchange action triggered by the local topological instability of the atomic environment. The implications of this mechanism on the liquid fragility and bulk metallic glass formation are discussed.

Influence of Environment at Laser Processing on Microhardness of Amorphous-Nanocrystalline Metal Alloy

Amorphous metal alloys have unique properties and are widely used. The unique properties of such materials are accompanied by problems of mechanical strength. The existing methods of their processing are not unambiguous and require a certain approach. In practice, laser technologies allow us to optimize the complex properties of such materials. The selection of optimal processing modes, including the influence of the gas phase, allows you to locally affect the material, increase the microhardness in certain areas. The absence of the influence of the processing medium on the mechanical properties is confirmed. Local impact on the surface sample also leads to an increase in crack resistance. In general, nanosecond laser exposure can be an effective tool for controlling the mechanical characteristics of an amorphous nanocrystalline material.

Mechanisms of the Fatigue Failure of Band Amorphous Metal Alloys in Tensile and Bending Tests

Mechanisms of the Fatigue Failure of Band Amorphous Metal Alloys in Tensile and Bending Tests

Correlation between vibrational anomalies and emergent anharmonicity of the local potential energy landscape in metallic glasses

The boson peak (BP) is a universal feature in the Raman and inelastic scattering spectra of both disordered and crystalline materials. The current paradigm presents the boson peak as the result of a Ioffe-Regel crossover between ballistic (phonon) and diffusive-type excitations, where the loss of coherence of phonons is described as a purely harmonic process due to structural disorder. This "harmonic disorder" paradigm for the BP has never been challenged or tested at the atomistic level. Here, through a set of atomistically-resolved characterizations of amorphous metallic alloys, we uncover a robust inverse proportionality between the intensity of boson peak and the activation energy of excitations in the potential energy landscape (PEL). Larger boson peak is linked with shallower basins and lower activation barriers and, consequently, with strongly anharmonic sectors of the PEL. Numerical evidence from atomistic simulations indicates that THz atomic vibrations contributing the most to the BP in atomic glasses are strongly anharmonic, as evidenced through very large values of the atomic- and mode-resolved Gr\"{u}neisen parameter found for the atomic vibrations that constitute the BP. These results provide a direct bridge between the vibrational spectrum and the topology of the PEL in solids, and point towards a new "giant anharmonicity" paradigm for both generic disordered materials and for the phonon-glass problem in emerging materials for energy applications. In this sense, disorder and anharmonicity emerge as the two sides of the same coin.

Structural Heterogeneity of an Amorphous-Nanocrystalline Alloy Fe77Cu1Si16B6 in the Nanometer Range

In this article, an alloy of the Finemet type Fe77Cu1Si16B6 obtained by quenching from a liquid state (spinning method) in the initial state is investigated. The main research methods were scanning and transmission electron microscopy. Methods for describing multiscale structural heterogeneities in amorphous-nanocrystalline alloys have been developed, allowing the structural state to be described and its influence on the physicochemical and technical properties to be determined depending on the technological conditions for obtaining these alloys. Representation of electron microscopic images in the form of Fourier spectra made it possible to reveal the nature of the formation of short- and middle-order in amorphous-nanocrystalline alloys according to the principle of self-similar spatial structures. The analysis of electron microscopic images by integral Lebesgue measures revealed density fluctuations over the alloy volume, which corresponds to the hierarchical representation of structural inhomogeneities in amorphous metallic alloys.

Electrochemical characteristics of aluminum amorphous alloys modified by oligomeric coatings in different media

Amorphous Al-based alloys are strong, ductile and corrosion resistant. They are used widely in various fields. Oligomeric films are used to modify amorphous alloys. Еlectrochemical characteristics of amorphous metal alloys Al 87,0 Gd 5,0 Ni 8,0 and Al 87,0 Gd 5,0 Ni 4,0 Fe 4,0 in aqueous-ammonia solution of oligoperoxide (OP) based on vinyl acetate, 2-tert-butylperoxy-2-methyl-5-hexen-3-yne and maleic anhydride was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The affinity of the oligomeric coating to metal surfaces was evaluated based on the value of the wetting (cosθ) with respective solutions and the calculated values of the work of adhesion. Higher adhesion activity of contact surfaces of tapes to oligoperoxide solutions is observed. The formation of protective surface layers is indicated by the change in the electrochemical parameters of samples of amorphous alloys Al 87 Gd 5 Ni 8 and Al 87 Gd 5 Ni 4 Fe 4 in a medium of 1 % aqueous-ammonia solution of oligoperoxide, namely the expansion of the passive region on the current-voltage curve, indicates. The oligoperoxide layer formed on the surface of the alloy obtained with Fe additives shows greater resistance to polarization. The strength of oligoperoxide layers formed on the surface of aluminum amorphous alloys in 0.1 M NaCl (aq.) was estimated. For Al 87 Gd 5 Ni 8 we observed a shift of corrosion potentials to the anode side, some decrease in corrosion currents and polarization resistance. In the case of Al 87 Gd 5 Ni 4 Fe 4 , the corrosion potential is slightly shifted to the cathode side, and the value of the polarization resistance is 2-6 times higher, which confirms the higher affinity of the oligoperoxide layers. The results of studies of modified samples by electrochemical impedance spectroscopy showed that on the surface of the amorphous alloy Al 87 Gd 5 Ni 4 Fe 4 in aqueous-ammonia solution OP on the surface formed a highly conductive layer of oligoperoxide. It shows low charge transfer resistance, which changes very little during electrochemical studies in 0.1 M aqueous sodium chloride solution. Keywords : amorphous metallic alloy, aluminum, electrochemical characteristics, oligomeric coatings.

Directed changing properties of amorphous and nanostructured metal alloys with help of nanosecond laser impulses

One of the most important problems of materials science is the ability to control the physical and mechanical properties of materials that differ in structure. Forming a specific structure on the surface is a time-consuming process, especially for non-standard alloys. Such materials include amorphous and nanostructured metal alloys. In practice, their use is possible after heat treatment. Additional processing often leads to the destruction of the nanostructure. The laser impulse has a number of features, including a complex effect on the surface layers of the material. The wide variable possibilities of laser processing provide the basis for the possibility of forming the mechanical properties of amorphous-nanocrystalline metal alloys. Spot irradiation with high-energy beams can preserve the unique physical properties of the samples as a whole and improve the strength characteristics. The directed change in the properties of an amorphous-nanocrystalline metal alloy by local processing with a nanosecond laser impulse is an urgent research task. This work was carried out with financial support by&nbsp;International Information Nobel Centre.

Controlling devitrification in the FeSiB system without alloying additions

Efficient electric machines require soft magnetic materials with superior properties, motivating research on the processing-structure-response correlation in Fe-based metallic glass systems. Here, significant differences in the primary devitrification process and the resulting microstructure of amorphous metallic Fe79Si11B10 alloys synthesized into two different forms by different rapid solidification methods are confirmed. Melt-spun ribbons and water-quenched microwires were investigated with calorimetric, structural, and magnetic probes. It is found that the primary devitrification process of the ribbons occurs at a higher temperature (by 80 K) with a faster exothermic heat release relative to that of the quenched microwires, despite their common chemical composition and fully devitrified structural state. Analysis of the primary devitrification reveals that the ribbons exhibit a ∼70% higher effective activation energy and a ∼110% larger value of Avrami exponent relative to those characterizing the microwires, indicating different devitrification routes taken by these two types of material. In specific, the ribbons crystallize via a continuous nucleation process that partly relies on pre-existing surface nuclei, with an interface-controlled growth mechanism. In contrast, the quenched microwires devitrify solely from pre-existing nuclei, with diffusion-controlled growth. These differences are attributed to unique quenched-in structures that are created by the specific rapid solidification conditions. These results suggest approaches to control the microstructure in FeSiB compositions without the need for non-magnetic alloying additions.

Radiation Effects in Amorphous Metallic Alloys as Revealed by Mössbauer Spectrometry: Part II. Ion Irradiation

Due to their excellent magnetic properties, amorphous metallic alloys (AMAs) are considered for the construction of magnetic cores of radio-frequency cavities in accelerators. Here, they might be exposed to ion bombardment. The influence of irradiation by both light and heavy ions featuring low and high energies, respectively, is followed by the techniques of 57Fe Mössbauer spectrometry. Modifications of surface layers in selected Fe-containing AMAs after ion irradiation are unveiled by detection of conversion electrons and photons of characteristic radiation whereas those in their bulk are derived from standard transmission spectra. Rearrangement of microstructure which favors the formation of magnetically active regions, is observed in surface regions bombarded by light ions. Heavy ions caused pronounced effects in the orientation of net magnetization of the irradiated samples. No measurable impact upon short-range order arrangement was observed. Part I of this paper is devoted to radiation effects in Fe-based AMAs induced by neutron irradiation.

Magnetostrictive loss reduction through stress relief annealing in an FeNi-based metal amorphous nanocomposite

FeNi-based metal amorphous nanocomposite alloys are emerging soft magnetic materials with promise for high-speed motor applications. Here we demonstrate a technique to optimize magnetic properties in toroidal cores wound from strain annealed (Fe70Ni30)80Nb4Si2B14 amorphous metal ribbon (AMR). In-line strain annealing (SA) of the AMR yields a strip permeability that monotonically decreases with increasing SA tensions. After winding into toroidal cores, dramatic changes in magnetic properties are observed and determined to be of magnetostrictive origin. A procedure to re-anneal wound toroidal cores to reduce hysteresis and reverse magnetostrictive effects is developed inclusive of casting curvature effects. We investigate re-annealing temperatures between 300 – 470 °C for cores produced from each SA condition. Magnetic core loss, WL, coercivity, Hc, squareness ratio, Kr, and permeability, µr are measured as a function of (stress relief) re-annealing temperature to optimally achieve W1T,400 Hz = 0.51 W/kg, Hc = 2.42 A/m, Kr = 0.22, and µr = 35,300.Graphical abstract