Grain-oriented electrical steel (GOES) is characterized by a strong crystallographic texture, which is crucial for its magnetic properties. However, this texture also induces significant anisotropy in its elastic characteristics, which is less studied but important for manufacturing and application. This work investigates the anisotropy of the elastic modulus in GOES at different stages of its production - specifically after the first cold rolling (CR1), after subsequent decarburization-recrystallization annealing (DRA), and after the second cold rolling (CR2). The study employs a combined approach using Electron Backscatter Diffraction (EBSD) for texture analysis and Dynamic Mechanical Analysis (DMA) for direct measurement of storage modulus. Using the EBSD analysis the evolution of the crystallographic texture across the manufacturing stages was studied. The key texture components were qualified and quantified by 20 degrees deviation of standard crystallographic directions <100>, <110> and <111> from CR axes: RD, TD and ND. These data were compared to the spatial maps of Young's modulus, showing a uniform distribution in the rolling direction (RD) and the greatest dispersion of values in the normal direction (ND) for all processing stages. The maximum modulus values were consistently observed in the transverse direction (TD). A comparative analysis demonstrated a correlation between the elastic moduli values obtained via EBSD calculations and direct DMA measurements. A more significant divergence was noted for the thinner CR2 sheet (0.27 mm), which is attributed to the specific stress state during three-point bending in DMA, which amplifies the contribution of the near-surface layers.
Fluorinated nanometer-scaled diamond particles (NDs) C26F32, C84F64 and C148F96 have been theoretically investigated using the dispersion-corrected density functional theory. We justify that fluorinated NDs are more thermodynamically stable than fluorinated fullerenes of comparable size due to the stronger C-F bonds. Consequently, NDs are also more resistant to defluorination. The differences in lengths and energies of C-F bonds formed on the NDs edges and surfaces are discussed in details. We observe that fluorine atoms contribute significantly to both frontier molecular orbitals of fluorinated NDs. The HOMO-LUMO gap has a tendency to decrease with the ND size. The electron density transfer from the carbon core to the fluorine shell is found to be about 0.1 electrons per fluorine atom. Global optimization of the polymethyl methacrylate (PMMA) + ND configuration have been carried out with the genetic algorithm. A weak interaction of fluorinated NDs with PMMA polymer has been established. The concrete value and sign of the binding energy depends on the ND size. The electronic orbitals of NDs almost do not hybridize with those of the PMMA, so the optical properties of NDs into the polymer matrix remain unchanged. The paper discusses the effect of ND coating with fluorine and other functional groups on the mechanical and optical characteristics of the resulting NDs / polymer composite.
Ti-Zr-based alloys have a valuable property: the element ratio can be selected so that the neutron scattering length is reduced to zero, eliminating Bragg reflections. This property makes Ti-Zr-based alloys highly useful in neutron diffraction experiments, where certain devices must be placed directly in the neutron beam. This work studies the potential of as-melted Ti-32.4Zr alloy and thermomechanically treated and laser powder bed fused Ti-18Zr-15Nb shape memory alloy as materials in direct contact with specimens in a neutron beam - for example, in powder containers or pressure gas cells in neutron diffraction experiments. As a result, all tested alloys have no pronounced Bragg reflections of the neutrons. Their linear neutron attenuation coefficient is on similar level and about 1.7 times lower than those of commonly used vanadium. Reference silicon powder can be easily studied by neutron diffraction experiment in a custom-made container of the Ti-32.4Zr alloy with thick (2.5 mm) walls. Functional properties of Ti-32.4Zr and Ti-18Zr-15Nb alloys are on a similar level, while Ti-18Zr-15Nb alloy has a significant advantage due to ease of manufacturing and material availability. Thus, the Ti-18Zr-15Nb shape memory alloy is a promising candidate for devices staying in the direct contact with the specimen and placed in a neutron beam and which should be transparent to neutrons not to affect the results of the experiment, as for example fixtures, the powder container, pressure gas cells, high-pressure cell elements and gaskets in a neutron diffraction experiment.
A composite based on the conductive polymer PEDOT:PSS and unique graphene flakes has been developed, which can be used in various health monitoring technologies. Graphene's unique properties are due to the dry synthesis method. Using plasma generated by a direct current plasma torch at 350 Torr, the flakes were produced in uniform sizes. Modes for producing nanostructures with a minimum lateral size of 100 nm have been developed. A technique has been suggested for preparing the nanostructure suspension for two-dimensional (2D) printing of active films on substrates. The printed structures were tested as wearable sensors for human sweat glucose, and exhaled air analysis, as well as humidity and touch sensors. The possibility of analysis of various solutions using such sensor substrates as non-woven fabric (spunlace) and polycarbonate fishing line has been demonstrated. As a result, simple and accessible diagnostics of the human nervous system and detection of enhanced reactions to various external influences are offered. In the systems presented, the sensor conductivity surges in response to the chemical reactions occurring between the graphene surface and the liquid components. In general, due to the use of plasma-synthesized flakes, sensors that combine the simplicity and low production cost technology with high sensitivity have been manufactured.
The theoretical research of the potential existence and synthesizability of novel nanostructured diamond-like carbon clathrates has been carried out. Within the framework of density functional theory calculations, two previously unknown orthorhombic clathrate structures, C24 and C28, have been identified. The crystal lattices of these diamond-like compounds belong to the spa & scy;e group Pmmm and are characterized by five crystallographically inequivalent atomic positions. The C24 clathrate, composed of polyhedral blocks C20, C24, and C28, should be stable up to at least 500 K, whereas the C28 clathrate is stable only at low temperatures or high pressure. The cohesive energy of the most stable clathrate (C24) is less than the corresponding energy of diamond by 0.299 eV / atom. The densities of the new clathrates and their bulk modulus are lower than those of diamond by at least 14 % and 24 %, respectively. The orthorhombic clathrates are expected to be wide-bandgap semiconductors with bandgap in the range from 3.7 to 4.0 eV. The research has revealed that ultrathin hybrid carbon layers, consisting of sp2 and sp3 hybridized atoms, are the most plausible clathrate precursors. For the first time, it has been established that the structural variant of clathrate CA6 (carbon sodalite) can be obtained via high-pressure compression of crystals composed of layered or molecular precursors. In particular, CA6 clathrate can be formed by the process of strong compression of graphite consisting of L4-6-12 graphene perpendicular to the planes of the graphene layers when the pressure reaches approximate to 29 GPa. The pressure required for complete structural transformation of precursors into this diamond-like phase can be significantly reduced to 1.1 GPa if hydrostatic compression of dense fullerite composed of C24 clusters is applied. The experimental identification of the new carbon clathrates can be accomplished using calculated powder X-ray diffraction patterns and Raman spectra.
Ultrasonic metal welding (USMW), a prominent solid-state joining technique, stands out by producing joints with high strength and minimal electrical resistance while consuming far less energy than traditional welding methods. This unique combination makes it particularly well-suited for precision welding of small components and thin metal sheets across various industries. At present, USMW attracts growing attention and adoption within the automotive industry, with a particular surge in applications for new energy vehicles. Its ability to reliably join delicate battery components, conductive materials, and lightweight structures aligns perfectly with the sector's demands for efficiency, durability, and innovation. This paper attempts to summarize the effect of various enhancement strategies employed in UMSW on the mechanical performance of joints, including the process parameter optimization, the weldability between materials and their combinations, the methods of the thermal assistance and implanting interlayer materials between interfaces of the metal sheets. Furthermore, the related application of numerical simulation and online monitoring techniques were introduced, which provided a desirable platform for explaining the joint formation process and improving the welding process robustness. In addition, the mechanism of USMWed interface bonding evolution was discussed in detail. The research results synthesized in this review will provide valuable information for engineers developing USMW systems, researchers exploring related mechanisms, and future studies aiming to advance innovations in the USMW fields.
A hybrid molecular dynamics and spin modeling approach using the SPIN package within the LAMMPS software suite was employed to investigate the influence of thickness on the magnetic properties of crystalline cobalt nanofilms with a face-centered cubic structure. Film thickness acts as a critical parameter determining magnetic behavior through the dynamic interplay of surface and bulk effects. In the region of ultrathin films (thickness less than 4.5 nm), a pronouncedly inhomogeneous magnetic response is observed, stemming from the dominance of surface effects. Key contributing factors include the influence of atomic-scale roughness, which creates local demagnetizing fields. This leads to complex domain wall dynamics, manifested as abrupt changes in magnetization and fine-scale non-uniformity in its spatial distribution. When the film thickness exceeds 4.5 nm, a transition to bulk-like behavior occurs. The reduction in the relative proportion of surface atoms allows the bulk properties of cobalt to come to the fore. Consequently, the dependence of magnetization on the external field becomes more pronounced and stable, while its spatial distribution exhibits increased uniformity. The normalized magnetic energy stabilizes at a level characteristic of the bulk material. The obtained results hold practical significance for the design of spintronics and magnetic recording devices. Furthermore, by understanding the magnetic interactions and dynamic responses of nanofilms, researchers and engineers can develop more efficient and reliable magnetic memory technologies, as well as novel spintronic components that leverage their unique magnetic characteristics for applications in sensing, data processing, and quantum information systems.
This study (Part II) quantitatively demonstrates the decisive role of thermally stable nanoscale dispersoids in accelerating grain refinement during equal-channel angular pressing of the commercial AA2219 Al-Cu alloy at 300 degrees C, directly comparing it with the model Al-3 %Cu alloy (see Part I). Through scanning electron microscopy with electron backscatter diffraction and transmission electron microscopy, it is shown that the AA2219 alloy achieves a substantially more refined and homogeneous ultrafine-grained structure after a cumulative strain of e =12, with an average grain size of approximate to 2.5-3.0 mu m, a high-angle boundary fraction exceeding 55 %, and an average misorientation of approximate to 24 degrees and a volume fraction of new fine grains of approximate to 82 %. These values significantly surpass those of the model alloy processed under identical conditions. The accelerated kinetics are attributed to a synergistic effect where fine, thermally stable dispersoids (e.g., aluminides of Zr, Mn, Cr) enhance strain localization via microshear band formation, suppress dynamic recovery by pinning dislocations and subboundaries, and stabilize the deformation-induced structure against static softening during inter-pass holdings. Thus, the introduction of dispersoids is proven to be a critical strategy for overcoming the limitations of dynamic recovery and achieving extensive grain refinement during high-temperature severe plastic deformation. The work establishes that dispersoids are crucial for tailoring a well-developed ultrafine-grained microstructure in commercial aluminum alloys under high-temperature severe plastic deformation conditions.
The paper studies the kinetics of self-healing of a main crack in tungsten carbide-cobalt (WC-8 mass % Co). The self-healing in WC-Co hard alloy occurs through the liquid-phase recovery with cobalt and partially dissolved tungsten carbide acting as healing agents. Over an eight-hour holding near the sintering temperature, the total crack length was reduced by 30 %. The maximum crack width capable to self-healing through the liquid-phase recovery was approximately 50 mu m. One-hour healing led to filling of the crack zone with cobalt. Further self-healing resulted in the growth of individual grains into binder in the healed zone. Six-hour isothermal holding near the sintering temperature resulted in elimination of the differences in the microstructure between the healed area and the base material, however, a significant cobalt depletion and the formation of brittle eta-phase (Co3W3C or Co6W6C) indicating a decrease in the carbon content made further selfhealing processes impossible. As self-healing mechanism is limited by healing agent content in WC-Co alloys, large damages elimination requires the use of external healing agents. For the practical solution of the extensive defects recovery, it was proposed to use hetero-healing methods, for example, isothermal holding in a carburized atmosphere and the use of infiltrates based on WC-Co mixtures with cobalt excess.
Experimental studies of chalcogenides show that the higher mobility of Cl-and FA-liganded PbS quantum dots may be useful for efficient solar cell applications. However, a theoretical understanding of this mechanism is still lacking. This paper presents the results of modeling the electronic and optical structure as well as the carrier mobility of an array of Cl-and FA-liganded PbS quantum dots at different temperatures using the density functional theory in combination with the nonequilibrium Green's function method and the Landauer molecular dynamics approach. No signs of the formation of intermediate bands were found for the band structure of the quantum dot array with FA ligands. Instead, a continuum of bands with a lower band boundary was formed at an energy of about 0.6 eV. To better understand this phenomenon, the density of states and the optical absorption profile of PbS quantum dots with Cl and FA ligands were studied. It is found that FA-liganded quantum dots have higher mobility and improved optical absorption compared to Cl-liganded quantum dots. The differences can be explained by the features in the intermediate electronic structure.
The study presents a comprehensive theoretical investigation of the structural, electronic, and optical properties of lonsdaleite-type (AB stacking) diamane subjected to substitutional doping with boron, nitrogen, and iron atoms. All calculations were performed using the methods of density functional theory. We systematically examined the effects of impurity incorporation at concentrations of 7 % and 13 % on the diamane crystal lattice. The introduction of dopant atoms induces minimal lattice distortion, with changes in the lattice constant not exceeding 1 % compared to pristine diamane. Specifically, boron and iron doping at 7 % concentration results in approximately 1 % lattice expansion, while nitrogen doping causes a 0.70 % contraction. Simultaneous co-doping with nitrogen and boron atoms yields an average lattice parameter increase of 0.60 %. The electronic band structure calculations demonstrate substantial modifications in the electronic properties of doped diamanes. While pristine AB-diamane exhibits a direct bandgap of approximate to 3 eV, nitrogen doping increases this value to 3.46 eV, whereas boron doping reduces it to 2.14 eV. Notably, simultaneous incorporation of boron and nitrogen atoms at 13 % concentration, particularly when located in neighbouring diamane planes, induces a semiconductor-to-metal transition, suggesting potential applications in nanoelectronic devices. Iron doping at 7 % concentration also significantly alters the electronic structure, creating partially filled energy bands that modify charge transport properties. Vibrational spectroscopy calculations provide characteristic signatures for experimental identification of dopants. The computed Raman and infrared spectra exhibit distinct peaks associated with impurity-carbon bond vibrations, enabling reliable detection of substitutional defects. Formation energy calculations indicate that nitrogen incorporation is most energetically favourable (0.44 eV), while iron doping is least favourable (7.37 eV). These findings provide valuable insights for the controlled synthesis and characterization of functionalized diamane materials with tailored electronic and optical properties for advanced technological applications.
This study investigates the mechanical and microstructural performance of Al-5083 composites fortified with hybrid reinforcements featuring 2 to 12 wt.% SiC, Mg, and Sr particulates, synthesized by stir casting technique, in contrast to earlier research that typically utilize single reinforcement or fine compositional ranges. The outcomes of the optical microscopy and SEM-EDS, as well as the tensile, flexural, impact, and wear tests, substantiate the evaluation of matrix reinforcement, elemental incorporation, and particle dispersion. The mechanical performance improved with increasing reinforcement, and the best strength, toughness, and wear resistance are shown at 10 wt.% composition. The successful addition of hybrid particles and then resulting improvement of the aluminum matrix is confirmed by elemental mapping and microstructural analysis. The hybrid SiC-Mg-Sr reinforcement provides experimental insight into how multicomponent reinforcement affects microstructure and properties, and it enhances Al-5083 performance. Matrix regions are localized by the addition of hybrid reinforcement, produces alternative sound structures that were observed across all compositions. Effective stress transfer between the particles and matrix confirmed by the uniform rise of load bearing capacity as the reinforcement level increases. These observations highlight the appropriate stir casting for manufacturing hybrid MMCs with reasonable engineering relevance. The insights gained from this investigation may assist in designing lightweight components where simultaneous improvements in strength and wear resistance are required.
For the first time, molecular dynamics simulations have been employed to investigate energy transfer in a threedimensional fcc nickel lattice driven harmonically through a pair of neighboring atoms at frequencies lying outside the phonon spectrum. The dependence of the critical driving frequency on the driving amplitude was determined. When the driving frequency is below this threshold, energy is efficiently transmitted from the driven atoms into the lattice, leading to the spontaneous generation and emission of discrete breathers propagating in opposite directions along close-packed atomic rows. In contrast, when the driving frequency exceeds the critical value, energy transfer to the lattice ceases and the supratransmission effect is not observed. These findings provide new insights into nonlinear energy transport mechanisms in crystalline solids and the conditions necessary for the excitation of discrete breathers in three-dimensional metallic lattices.
This article discusses the effects of solid-state bonding (SSB) and subsequent heat treatment (HT) on the microstructure, phase composition, and mechanical properties of solid-state joints (SSJ) made of wrought (EK61) and powder (EP741NP) heat-resistant nickel superalloys. SSB was performed in a vacuum under the temperature gradually increasing from 850 degrees C to 1000 degrees C. After SSB, in the EK61 superalloy transformation of the ultrafine-grained structure into a coarse-grained one with an average grain size of 38 +/- 7 mu m is observed, while the microstructure of the EP741NP superalloy remained of fine-grained microduplex type. After subsequent HT, grain growth is observed up to the size of 300 +/- 48 mu m in the EK61 superalloy and up to 49 +/- 5 mu m in the EP741NP superalloy. The width of the diffusion zone after SSB was 18 mu m, and after HT it increased significantly, up to 150 mu m. The results of mechanical tests showed that the fracture of the obtained EK61//EP741NP joints immediately after SSB occurred in the SSJ zone, and after subsequent HT, the fracture occurred outside the SSJ zone in the less heat-resistant EK61 superalloy. The strength after SSB is 660 MPa, and after following HT it is 770 MPa. It was found that after SSB, the microhardness of the EK61 superalloy decreased from 3.9 GPa to 2.4 GPa, and in the EP741NP superalloy it remained at the level of the initial state. In the SSJ zone, the microhardness, both after SSB and after HT, possesses intermediate values between the microhardness values of the superalloys being joined.
Effect of isothermal hot compression at temperatures below the gamma' solvus temperature on the development of dynamic recrystallization was studied in a powder metallurgy (PM) gamma+gamma' nickel-based superalloy VV750P (& Vcy;& Vcy;750 & Pcy;, Ni-9.9(Al, Ti, Nb)-33.7(Co, Cr, Mo, W, Hf)-0.075(C, B) (wt.%)). This superalloy is heavily alloyed and has a high gamma' solvus temperature (Ts =1190 degrees C). In the initial HIPed condition, the average gamma grain size was d approximate to 29 mu m and volume fraction of gamma' (Ni3(Al, Ti, Nb)) phase about 70 %. Small cylindrical samples were prepared from the HIPed material and subjected to isothermal single-stage compression in the temperature range of 1125 -1175 degrees C ((Ts-65) - (Ts-15), where Ts is the gamma' solvus temperature) with an initial strain rate epsilon =10-2 s-1 to an engineering strain epsilon = 75 %. The temperature / strain rate conditions were chosen on basis of previously performed studies on other PM nickel-based superalloys such as EP741NP (& Ecy;& Pcy;741 & Ncy;& Pcy;) and VV751P (& Vcy;& Vcy;751 & Pcy;). In contrast to previously performed works, the present investigation aimed at achieving completely recrystallized and fine-grained structure without using annealing after HIP and intermediate recrystallization annealing. Hot compression at 1125 -1175 degrees C led to development of dynamic recrystallization. However, recrystallization kinetics significantly depended on deformation temperature. The fastest kinetics of recrystallization was reached during compression at 1175 degrees C (Ts-15) that is only slightly below the gamma' solvus temperature. In contrast to compression at 1125 and 1150 degrees C, hot compression at 1175 degrees C resulted in a complete disappearance of coarse prior gamma grains and formation of completely recrystallized and fine-grained structure. Thus, single-stage isothermal hot forging of HIPed PM superalloy at a slightly subsolvus temperature without additional annealing can be considered as an alternative processing route instead of two- or three-stage forging at subsolvus temperatures with intermediate annealing.
The paper presents a method for determining the elastic moduli and Poisson's ratios of a material under compression and tension. The method is based on the results of strain measurements by fiber-optic sensors in a rectangular beam subjected to four-point bending. The relationships for determining the elastic moduli follow from an analytical solution for bending a rectangular beam made of a material with different moduli in compression and tension, assuming the Euler-Bernoulli hypothesis is satisfied. The relationships for determining Poisson's ratios follow from the assumption of a uniaxial stress state in the strain measurement zone. An algorithm is presented for estimating the errors in determining the elastic constants, which are due to deviations from the conditions of the Euler-Bernoulli hypothesis and a uniaxial stress state for the corresponding beam dimensions. Relations are presented for estimating the maximum errors in determining the elastic constants, based on the obtained relationships for their determination, associated with the error in measuring strains by the fiber-optic sensors used. Options for attaching the fiber-optic sensors to the surface of the specimens are considered. For a set of rock salt samples, the results of determining the elastic moduli and Poisson's ratios are presented, along with estimates of the errors in their determination, due to strain measurement errors and sample dimensions. The qualitative results obtained for the elastic constants in compression and tension, taking into account their errors, allow to conclude that rock salt is not a bi-modulus material.
The tight-binding model provides a useful alternative to first-principles methods for quantum mechanical modeling of atomic structures and the physicochemical properties of materials. It is well-suited for investigating topologically complex systems with large numbers of atoms, since it substantially reduces the computational cost. However, the accuracy of the tight-binding model critically depends on the choice of parameters. In this work, we introduce a parameterized, nonorthogonal tight-binding model to calculate the electronic properties of carbon and hydrocarbon materials. We performed the parameterization using initial DFT calculations of the electronic band structures of seven carbon and hydrocarbon materials with different dimensionalities and atomic hybridizations. The calculated electronic band structures show reasonable agreement with DFT results. The proposed parameter set is transforable and suitable for different hydrocarbon crystals. As a result, the represented approach can support extensive searches for new materials of this type, as well as more efficient and accurate studies of the electronic band structures of their synthesized counterparts. Furthermore, such synthesis of methods allows the analytical advantages of tight-binding method to be retained while complementing them with the accuracy of ab initio calculations. Thus, this work should contribute to significant improvements in the key performance characteristics of computational materials science methodologies and algorithms.
This study investigates the mechanical and fatigue performance of AA7075-T4 aluminum alloy at 25, 100, and 150 degrees C. Tensile and fatigue tests were conducted to evaluate ultimate tensile strength, yield strength, Young's modulus, and ductility. Results reveal that strength and stiffness decline with increasing temperature, while ductility improves. Fatigue behavior was analyzed using a Taguchi L9 orthogonal array and ANOVA, considering stress amplitude and temperature. Stress amplitude accounted for 93 % of the variation in fatigue life, whereas temperature contributed 6 %. S-N curves confirmed greater sensitivity to stress amplitude with rising temperature. At 150 degrees C, the endurance limit improved under low-stress conditions (22 to 32 MPa) due to stress relaxation and microstructural changes, yet fatigue life at 207 MPa decreased by approximate to 47 %. Comparison with AA7001-T6 and AA2024-T4 alloys showed alloy-specific thermal responses, with AA7001-T6 displaying superior stability for thermo-mechanical fatigue applications.
The temperature dependence of friction and wear of nanostructured alloy Ti49.3Ni50.7 obtained by severe plastic deformation is investigated. The friction coefficient (Kf) and wear rate (W) are investigated under conditions of reciprocating motion and the absence of lubrication in the temperature range (25 degrees C <= & Tcy; <= 140 degrees C) corresponding to two-phase (A+M) and single-phase (A) states. It is shown that the minimum friction conditions in the range ensure the absence of a temperature flash in the contact area and allow us to state that the friction coefficient, wear intensity and volume lost by the counterbody linear increase with temperature change in the range of 25 - 90 degrees & Scy; and are drawn on a plateau at temperature Md. With an increase in the tribocontact temperature, the running-in stage is reduced. The change in friction characteristics is associated with the ratio of martensite and austenite content.
In this paper, we provide electron microscopic and in-situ X-ray study of microstructure in an Ni-Al-Cr intermetallic alloy that has been obtained by a dual-wire electron beam additive manufacturing using commercial NiCr and Al wires. As-built material possesses a dendritic microstructure that is heterogeneous in both elemental and phase compositions. Different intermetallic phases have been identified with high accuracy using transmission electron microscopy: ordered NiAl-based aluminide with particles of disordered Ni3Al-based phase in dendritic areas, and mixture of Ni and ordered Ni3Al phase in interdendrites (all alloyed with Cr). A part of the NiAl-based phase underwent the martensitic transformation B2(NiAl)-> L10 during the additive manufacturing process and post-built cooling. According to in-situ XRD analysis under heating of the alloy up to 1273 K, this transformation has a thermoelastic nature, and the L10 -> B2(NiAl) reverse transformation finish temperature is about 873 K. We have noticed the correlation between the phase composition and the tensile fracture micromechanism of the alloy at room temperature: brittle intermetallic B2-NiAl, L10-NiAl and Ni3Al-based phases are responsible for high strength but low elongation of the alloy (the tensile strength is 780 MPa and the elongation is 0.2 %). An intermetallic alloy is designed to produce intermetallic coatings or to repair bulk intermetallic details using the electron beam additive manufacturing.
