Structural-phase State Research Articles

Comparative Study of Microstructure and Phase Composition of Amorphous-Nanocrystalline Fe-Based Composite Material Produced by Laser Powder Bed Fusion in Argon and Helium Atmosphere.

Laser powder bed fusion (LPBF) is a prospective and promising technique of additive manufacturing of which there is a growing interest for the development and production of Fe-based bulk metallic glasses and amorphous-nanocrystalline composites. Many factors affect the quality and properties of the resulting material, and these factors are being actively investigated by many researchers, however, the factor of the inert gas atmosphere used in the process remains virtually unexplored for Fe-based metallic glasses and composites at this time. Here, we present the results of producing amorphous-nanocrystalline composites from amorphous Fe-based powder via LPBF using argon and helium atmospheres. The analysis of the microstructures and phase compositions demonstrated that using helium as an inert gas in the LPBF resulted in a nearly three-fold increase in the amorphization degree of the material. Additionally, it had a beneficial impact on phase composition and structure in a heat-affected zone. The received results may help to develop approaches to control and improve the structural-phase state of amorphous-nanocrystalline compositional materials obtained via LPBF.

Formation of the gradient of structural-phase states of high-speed steel during surfacing. Part 2. The role of the Mullins–Sekerka instability in formation of crystallization structures

Formation of the gradient of structural-phase states of high-speed steel during surfacing. Part 2. The role of the Mullins–Sekerka instability in formation of crystallization structures

Catalytic reduction of nitrogen monoxide using iron–nickel oxygen carriers derived from electroplating sludge: Novel method for the collaborative emission decrease of polluting gases

The valorization of electroplating sludge (ES) for high added value presents greater economic and environmental benefits than conventional treatment methods such as thermal processing, solidification, and landfill. Inspired by the mechanism of chemical looping combustion (CLC), this study developed a novel cost-effective method for denitrification by preparing FeNi-OCs from ES to achieve the synergistic reduction of CO and NO emissions. The phase structure, micromorphology, and valence state changes of the FeNi-OC catalyst during the CO-catalyzed reduction of NO and the pathway for catalytic denitrification using FeNi-OCs were analyzed. Results showed that CO could reduce FeNi-OCs to FeNi, and the reduced FeNi was subsequently oxidized back to FeNi-OCs by NO, a process analogous to CLC. During experiments, the simultaneous consumption of CO and NO gases was observed at 350 °C. This phenomenon was highly pronounced at 600 °C, where the CO and NO concentrations decreased from initial values of 8550 and 470 ppm, respectively, to 6719 and 0 ppm, respectively, with conversion rates of 21.41 % and 100 %, respectively. Hence, synergistic emission reduction was achieved. Further experiments also indicated that the addition of 1.5 % ES during iron ore sintering could substantially reduce the CO and NO concentrations in the sintering flue gas from 1268.32 and 244.81 ppm, respectively, to 974.51 and 161.11 ppm, respectively.

Changes in the Structural-Phase State and Dislocation Density of Ti49.8Ni50.2 Alloy Depending on the Isochronal Annealing Temperature after Severe Plastic Deformation by abc Pressing at 573 K

Changes in the Structural-Phase State and Dislocation Density of Ti49.8Ni50.2 Alloy Depending on the Isochronal Annealing Temperature after Severe Plastic Deformation by abc Pressing at 573 K

Raman spectroscopic evaluation of structural-phase state of titanium and zirconium pseudo-single crystals deformed in Bridgman anvils

A complex study of the microstructure of titanium and zirconium pseudo-single crystals subjected to severe plastic deformation in Bridgman anvils under a pressure of 8 GPa at a temperature of 80 K has been carried out. Raman spectra of the samples deformed to different degrees show a two-phase α + ω state, which indicates the realization of the pressure-induced transition during deformation process with the retention of the ω-phase in the structure of both metals after the load removal. The quantitative ratio of α- and ω- phases in the structure of deformed metals and its change with increasing degree of deformation has been analyzed.Correlation of Raman spectroscopy results with experimental data of X-ray diffraction analysis, electron microscopic analysis, as well as literature data of calorimetry and calculated thermodynamic data by DFT method on kinetics of the reverse ω → α transformation demonstrates the efficiency of Raman spectroscopy method for estimation of the phase composition of pure metals, which experienced phase transition under loading.

Застосування ультразвукових технологій поверхневої обробки в адитивному виробництві металевих сплавів

In a modern world, additive manufacturing of metal products has reached significant volumes and variety of applied alloys. 3D-printing technologies make it possible to obtain parts with reduced mass, increased reliability, single products, experimental parts and elements designs with complex geometry and configuration. Disadvantages of metal parts additive manufacturing include anisotropy of chemical composition and properties, non-equilibrium structural-phase state, structural micro- and macrodefects and some other features, that require post-processing of as-printed products. Most often, heat treatment and its combination with microforging or intensive surface plastic deformation are used for this purpose. The manuscript provides an analytical review of the advantages of using ultrasonic technologies to support 3D-printing and post-processing of additively manufactured products. Special attention is paid to ultrasonic impact treatment (UIT). The equipment for providing UIT is compact, energy-saving and easy to use. It is noted, that this technology makes it possible to effectively reduce surface defects of printed parts, increase its hardness and fatigue strength. At the same time, nanostructuring and changes in the structural and phase state of the modified layers are also occured. It is also noted, that UIT may provide surface strengthening to a depth of ~500 μm, saturating it with alloying elements and compounds, and for conventionally produced parts, like as–cast, deformed and powder sintered – it is significantly more effective than most other similar methods. The prospects of using ultrasonic technologies to improve quality and level of operational and mechanical characteristics of additively manufactured metal parts, including the needs of aircraft construction, are outlined. Keywords: additive technologies, 3D-printing, ultrasonic impact treatment, UIT, surface strengthening, cavitation, vibration polishing, fatigue strength, Grade5, AlSi10Mg, Inconel-718.

Formation of Structural-Phase State and Elastic and Durometric Properties of Biocompatible Cold-Rolled Titanium Ti–Nb–Zr-Based Alloys during Aging

Formation of Structural-Phase State and Elastic and Durometric Properties of Biocompatible Cold-Rolled Titanium Ti–Nb–Zr-Based Alloys during Aging

The main structural-phase states of interaction between model corium of a nuclear reactor and a sacrificial material based on Al2O3 and a lead layer

This article presents the results of post-experimental studies of the interaction of model light water reactor corium with a candidate sacrificial material (SM) based on Al2O3 (corundum) and a lead layer. The purpose of the experiments was to study the features of the interaction of the sacrificial material with corium in the conditions of simulating a severe accident with core meltdown. An active interaction of corium with the sacrificial material was established as a result of the research. This is confirmed by the fact that part of the sacrificial material entered into physical and chemical interaction with the components of corium with the formation of liquid-phase reaction products and, as a result, creating different conditions for the crystallization of corium. The study of the phase composition showed that the microstructure of solidified corium in various areas after interaction with the sacrificial material is represented by a phase of the (U,Zr, …)O2±x type with different types of crystal lattice. At the same time, the phase analysis showed a close correspondence of the composition of the solid solutions to the initial ratio of uranium and zirconium in the model corium charge. This allows us to conclude that liquid zirconium interacted with aluminum oxide during the experiment. Thus, it was concluded that the proposed sacrificial material is promising based on the results obtained and the identified features of the interaction of aluminum oxide with the lead layer and the corium of a nuclear reactor.

Influence of Varying the Spraying Distance on the Structural-Phase State and Mechanotribological Properties of 86WC-10Co-4Cr-Based Coatings Obtained by the HVOF Method

This paper presents the results of a metallographic and tribological study of 86WC-10Co-4Cr coatings obtained by the HVOF method on the Termika-3 unit at varying spraying distances. The influence of spraying distance on the coating microstructure, phase composition, as well as mechanical and tribological properties, was studied. According to the results of the study, it was found that the optimum spraying distance for 86WC-10Co-4Cr coatings with improved wear resistance and hardness characteristics and low porosity is 300 mm.

Structural-Phase State and Mechanical Properties of a Laser Cladding Titanium Matrix Composite Based on Ti64 Alloy and TiB2 Ceramics

Structural-Phase State and Mechanical Properties of a Laser Cladding Titanium Matrix Composite Based on Ti64 Alloy and TiB2 Ceramics

CHANGES IN THE STRUCTURE AND PHASE STATE OF ALUMINUM ALLOY 2014, WHICH OCCURRED AS A RESULT OF IRRADIATION WITH AN ELECTRON BEAM

The use of aluminum alloys in nuclear power is limited by the properties of these alloys in the irradiation zone. The use of electron accelerators is an effective technique for simulating real operating conditions. As a result of irradiation, a whole complex of factors begins to work in the targets, which change the properties of these targets. Pulsed electric and magnetic fields appear, shock waves are generated, and gradient heating occurs. All this together changes the structure and properties of the targets. To irradiate the samples, electron beams with an energy of 8.2...8.3 MeV and a beam current of 0.8 mA were used. The work studied changes in the structural-phase state of an aluminum alloy of type 2014. For samples, before and after irradiation, an analysis of changes in mechanical characteristics (hardness, ultimate strength, proof strength) was carried out. Diffractometric studies were performed. These studies made it possible to determine changes in the phase composition. The intensity values of the diffraction lines were obtained.

Effect of Temperature and Rate Treatment Parameters on the Structural Phase State and Properties of Ti2AlNb Titanium Aluminide-Based Alloy

Effect of Temperature and Rate Treatment Parameters on the Structural Phase State and Properties of Ti2AlNb Titanium Aluminide-Based Alloy

EFFECT OF STRUCTURAL-PHASE STATE ON THE DEFORMATION BEHAVIOR AND MECHANICAL PROPERTIES OF NEAR β TITANIUM ALLOY VT22 IN THE TEMPERATURE RANGE 293-823 K

This paper investigates the effect of thermomechanical treatments, including deformation by radial shear rolling or severe plastic deformation by abc pressing with subsequent aging at 773 K, on the structural-phase state, deformation behavior and mechanical properties of commercial near β titanium alloy VT22 (Ti-5Al-5Mo-5V-1Cr-1Fe). The structure of the alloy after radial shear rolling and subsequent aging consists of transformed β grains with a lamellar α + β structure and primary α-phase particles. Severe plastic deformation of the alloy followed by aging causes the formation of a grain-subgrain α + β structure with an average characteristic size of 0.23 µm. It is found that after the thermomechanical treatments, the strength characteristics of the alloy at room temperature increase by ~40% compared to the as-received alloy. The alloy after radial shear rolling and aging retains a 40-20% higher strength in the temperature range of 293-823 K. The strength of the alloy after severe plastic deformation and aging becomes lower than that of the as-received alloy already at a temperature of 773 K. Analysis of creep parameters at 743 K shows that the creep deformation of the alloy in the state after radial shear rolling and aging occurs by the motion of dislocations (glide + climb). The creep deformation of the alloy in the state after severe plastic deformation and subsequent aging is largely contributed to by grain boundary sliding.

Bioengineering of one dimensional hierarchical Cu7S4 hollow nanotubes for non-enzymatic glucose sensing applications.

Herein, a novel and facile eco-friendly green chemistry approach has been devised at room temperature for synthesis of 1D hierarchical Cu7S4 hollow nanotubes on Cu substrate via volatile organosulfur compounds from Allium sativum L for non-enzymatic glucose detection. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and X-ray spectroscopy (XPS) were employed to characterize the surface morphology, structural phase, compositional, and chemical states of the obtained samples, respectively. The SEM results confirm the formation of 1D hierarchical Cu7S4 hollow nanotubes. The XRD patterns are indexed to orthogonal anilite Cu7S4 crystal planes and the EDX spectra clearly reveal the presence of Cu and S elements. XPS spectra confirms peaks of Cu 2p and S 1s core levels, which are typical characteristics of Cu(i) and S(ii), respectively. The Brunauer-Emmett-Teller (BET) specific surface area for obtained Cu7S4 hollow nanotubes is 2.07 m2 g-1 with a pore size distribution of 27.90 nm. Using Cu7S4 hollow nanotubes, the detection of non-enzymatic glucose was conducted over a dynamic range of concentrations from 0.5 to 100 μmol L-1 and reveals a high sensitivity of 1058.33 μA mM-1cm-2 and a limit of detection (LOD) of 0.127 μmol L-1. The obtained results indicated that Cu7S4 hollow nanotubes are promising candidates for non-enzymatic glucose detection.

Effect of deformation on structural-phase state of structural steel and on formation of its yield strength and degree of hardening

The work shows that the values of the yield strength of steel 20 after long-term operation and deformation, obtained experimentally and by calculation, differ significantly. This is primarily due to the fact that all coefficients require experimental verification. However, the data obtained can be used to determine the role of each contribution (in %) in relation to the total received. Relaxation of such high local internal stresses (due to the appearance and intensive growth of the elastic component) can (and does) occur only through the destruction of the sample, which is what is observed. Therefore, it is the emergence and increase of local internal stresses that leads to the destruction of the sample.

Starfish-like Zn doped In2O3 dendritic structure for superior triethylamine sensing by the facile co-precipitation method

Zn-doped In2O3 starfish-like dendritic structures (IZx, x=0, 1, 3, 5) were successfully synthesized by a facile co-precipitation method and applied for triethylamine (TEA) sensing. The influence of Zn addition on the phase structure, microstructure, chemical composition and surface state of IZx sensor was characterized by XRD, Raman, UV-vis, SEM, TEM, XPS and BET analyses. TEA-sensing performance was measured by gas-sensing test system at 40% humidity. Results show that the typical IZ3 sensor has a high response of 156.2 and short response/recovery times of 6 s/165 s after exposure to 5 ppm TEA at optimal temperature of 140 ºC. It also exhibits a low detection limit of 0.1 ppm, excellent selectivity to TEA, and long-term stability. The excellent TEA-sensing ability of IZx-based sensors may be attributed to their unique morphology with large specific surface area, suitable internal defects and band gap induced by Zn-doping. Therefore, Zn-doped In2O3 sensors have potential applications in actual TEA-detection.

Structural-phase transformations of 12% chromium ferritic-martensitic steel EP-823

The features of phase transformations of 12 % chromium ferritic-martensitic steel EP-823 under heating and cooling conditions in the temperature range from 30 to 1100 ℃ were studied by the methods of high-temperature X-ray diffraction analysis (XRD) in situ and differential scanning calorimetry (DSC). According to XRD in situ data, upon heating, the temperatures of the beginning and end of the (α → γ) transformation of ferrite (martensite – austenite) are Ac1 ≈ 880 °C, Ac3 ≈ 1000 °C, respectively. Upon cooling, a diffusion (γ → α) transformation occurs with critical points – Аr1 ≈ 860°С (beginning temperature) and Аr3 ≈ 840 °С (end temperature). According to DSC data, during heating, the critical points of the (α → γ) transformation are Ac1 ≈ 840 °C and Ac3 ≈ 900 °C. During cooling, a martensitic (γ → α) transformation is realized with critical points of the beginning of Ms = 344 ℃ and the end of Mf = 212 ℃ of this transformation. The XRD in situ analysis revealed no precipitation of carbide phases under heating and cooling conditions of steel EP-823. Position of the critical points of phase transformations depends on the research method (XRD in situ or DSC), which is determined by the difference in effective (taking into account the time for shooting in the XRD method) heating-cooling rate. The effect of elemental composition on the position of critical points of phase transformations and the formation of structural-phase states of ferritic-martensitic steels is discussed. It is shown that the increased content of ferrite-stabilizing elements (Cr, Mo, Nb) in composition of EP-823 steel, compared with other steels of the same class, expands the region of existence of the ferrite phase, which can contribute to an increase in the temperature of Ac1 .

Regularities in the Evolution of Thermoelastic Martensitic Transformations during Cooling/Heating in the Free State and under Load of Titanium Nickelide Alloyed with Niobium.

This article presents the results of studies of the features of the development of thermoelastic martensitic transformations during cooling/heating in the free state and under load of Ti50Ni49.7-XNbXMo0.3 alloys (X = 0.5, 1.0 and 1.5 at% Nb) with shape memory effects. Using X-ray diffraction analysis, it was found that all the alloys studied at room temperature contained a multiphase mixture consisting of intermetallic compounds with the TiNi (B2, B19'), Ni56Ti29Nb15, and Ti2Ni compositions. Scanning electron microscopy was used to study the microstructure of TiNi (Nb,Mo) alloys and it was found that the distribution of fine Ni56Ti29Nb15 particles in the matrix depends significantly on the concentration of the alloying element. A correlation was established between changes in the structural-phase state in TiNi (Nb,Mo) alloys and the occurrence of the B2↔B19' martensitic transition in the free state and under load. Based on physical and mechanical studies, the temperature ranges of the martensitic transformations (MT) in the free state and under load were established. Based on the thermodynamic description of the MT and the analysis of the characteristic temperatures of the MT, it was found that the MT mechanism is strongly dependent on the concentration of the alloying element.

Strengthening Mechanisms of Rail Steel under Compression

The evolution of the structure–phase states and the dislocation substructure of rail steel under uniaxial compression to the degree of 50% was studied by transmission electron microscopy. The obtained data formed the basis for a quantitative analysis of the mechanisms of rail steel strengthening at degrees of deformation by compressions of 15, 30, and 50%. Contributions to the strengthening caused by the friction of the matrix lattice, dislocation substructure, presence of carbide particles, internal stress fields, solid solution and substructural strengthening, and pearlite component of the steel structure were estimated. Using the adaptivity principle, which assumes the independent action of each of the strengthening mechanisms, the dependence of the rail steel strength on the degree of plastic deformation by compression was estimated. A comparative analysis of the stress–strain curves σ(ε) obtained experimentally and calculated theoretically was performed.

Study of the Structural-Phase State and Heat Transfer in a Metal Hydride Hydrogen Storage System

Study of the Structural-Phase State and Heat Transfer in a Metal Hydride Hydrogen Storage System