Search Results (1,572)

To improve the seismic performance and post-earthquake recoverability of low- and mid-rise steel frames, this study investigates the seismic performance and layout strategy of a self-centering friction damper (SCFD) through experimental and numerical studies. The SCFD combines the superelastic restoring capability of shape memory alloy (SMA) bars with the energy dissipation provided by non-asbestos organic (NAO) friction materials. Monotonic and cyclic tests were conducted to characterize the mechanical behavior of Ni–50.8 at. % Ti SMA bars and the hysteretic performance of the SCFD, based on which a numerical model of the damper was established and validated. An uncontrolled frame and four controlled frames employing diagonal, chevron, improved lower toggle-brace, and improved upper toggle-brace layouts were comparatively investigated to evaluate the effects of brace configuration, installation position, and damper quantity on seismic performance. The proposed damper exhibited an equivalent damping ratio ranging from 24% to 32%. When the SMA strain exceeded 6%, the residual deformation of the damper increased significantly, indicating that excessive SMA deformation should be avoided in practical design. Among the investigated configurations, the improved upper toggle-brace layout, combined with additional dampers installed at the first story, showed the best overall performance. Compared with the uncontrolled multi-story structure, the residual inter-story drift ratio was reduced by 76.7–93.5%, while the maximum acceleration reduction reached 28.9%. However, local acceleration amplification was observed in some cases because of the increased structural stiffness. These findings provide practical guidance for the layout design and engineering application of self-centering friction dampers in low- and mid-rise steel frames. Full article

A combined CALPHAD-guided thermodynamic and experimental approach was employed to investigate the influence of boron on phase evolution and microstructural development in the Fe–Ni–Cr–Cu–Si–B–C alloy system. Thermodynamic calculations were performed using Thermo-Calc (FE13-2025b) and the TTFe thermodynamic database. Vertical phase-diagram sections and response surface analysis were used to evaluate phase stability over the temperature range of 400–1500 °C and to identify temperature–composition domains favorable for the formation of strengthening phases. The calculations predicted complex multiphase equilibrium behavior involving boride-, carbide-, and silicide-containing phases. Within the investigated composition range, approximately 4 wt.% B provided a favorable balance between the metallic matrix and strengthening phases, while 638 °C corresponded to a thermodynamically favorable equilibrium phase constitution. Response surface analysis further demonstrated that temperature governs phase evolution, whereas boron primarily controls phase redistribution. The optimized alloy composition was characterized experimentally using scanning electron microscopy (SEM), wavelength dispersion spectroscopy (WDS), elemental mapping, and X-ray diffraction (XRD). The experimentally observed heterogeneous multiphase microstructure showed good agreement with the CALPHAD-predicted phase evolution at a qualitative level, demonstrating the usefulness of thermodynamic modeling for guiding alloy design. The proposed CALPHAD-guided workflow integrates thermodynamic modeling with targeted experimental characterization and provides a transferable framework for the accelerated design and optimization of complex Fe-based multicomponent alloys. Full article

A multicomponent Ni₅₄Cr₂₈Mo₈Nb₅Ta₅ nickel-based superalloy was produced by vacuum induction melting followed by homogenization, hot forging, solution treatment, and aging to investigate its microstructural and mechanical behavior. The X Ray Fluorescence (XRF) analysis confirmed excellent agreement between the nominal and experimental chemical compositions. The X Ray Diffraction(XRD) combined with Rietveld refinement revealed a microstructure dominated by three closely related to face-centered cubic (FCC) (A1) solid-solution regions with slightly different lattice parameters, indicating local compositional variations. The Scanning Electron Microscopy(SEM)/Energy Dispersive Spectroscopy (EDS) observations showed a generally homogeneous elemental distribution, while optical and electron microscopy identified a dendritic microstructure with elongated interdendritic constituents enriched in refractory elements. Mechanical characterization yielded an average hardness of 497 HV_0.5, a compressive strength of approximately 1950 MPa, and room-temperature yield and ultimate tensile strengths of 1050 MPa and 1320 MPa, respectively. Tensile strength gradually decreased with increasing temperature up to 900 °C, while ductility increased from 16% to 25% total elongation. The results indicate that the alloy develops a stable FCC matrix primarily strengthened by solid-solution hardening, with the measured mechanical performance suggesting an additional contribution from precipitation hardening. This study provides an experimental baseline for the development and optimization of conventionally processed Ni–Cr–Mo–Nb–Ta superalloys for high-temperature applications. Full article

AlCoCrFeNi-based high-entropy alloys have garnered significant attention for high-end applications in aerospace, marine engineering, and the nuclear industry due to their exceptional comprehensive properties, including high strength and good corrosion resistance. However, their widespread application is critically hindered by a fatal disadvantage: poor ductility. Optimizing the ductility of this alloy system has therefore become a key research priority. Optimizing their ductility has emerged as a key research priority in recent literature. This review systematically examined the influences of diverse fabrication techniques on the mechanical properties, particularly ductility, of these alloys. Melting routes (vacuum arc melting and vacuum induction melting), powder consolidation (spark plasma sintering and hot pressing), and additive manufacturing (selective laser melting, laser melting deposition, electron beam melting, and wire arc additive manufacturing) were covered in this review. This review underscores that while each fabrication route offers distinct advantages, future breakthroughs require multi-process hybridization, data-driven optimization, and precise control of precipitation kinetics to overcome the strength–ductility trade-off and enable large-scale applications of AlCoCrFeNi-based HEAs. Full article

This article describes the use of NiP alloy-based layers for the production of conductive and resistive layers. The authors demonstrate the potential of this technology for the production of electrodes in photovoltaic structures, among other applications. To facilitate this use of NiP alloy metallization, a selective metallization process was developed. This process is our own proprietary concept and is not reported elsewhere in the literature. To simplify the process, process modeling was performed, enabling the rapid selection of chemical metallization process parameters. We used ultrasound support to ensure that the electroless metallization process with NiP alloys could be applied to all types of substrates used in electronics (including flexible substrates). The use of ultrasound-assisted electroless metallization technology shortens the production time of silicon electrodes made for photovoltaic cells. Furthermore, we proved that it is possible to produce a metallic layer on flexible substrates. The developed technology enables the production of electrodes used in, for example, flexible photovoltaic cells. This type of metallization is advantageous due to its low cost and simplicity, and its ability to produce both the top and bottom electrodes in a single process, offering a wide range of industrial applications. Our previous work demonstrated the feasibility of applying this process to ceramic and silicon substrates exclusively. This research aligns with current research trends focusing on reducing the production costs of photovoltaic cells and, consequently, minimizing the associated carbon footprint. Full article

This study investigates the atomic-scale effects of hydrogen concentration and Ni content on crack propagation in Fe-Ni alloy models using molecular dynamics methods. A Mode I crack model with a (001)[100] orientation was constructed, and hydrogen atoms were locally introduced at the crack tip with concentrations of 5.3 at.% and 14.3 at.%. Fe-Ni alloy models with 5%, 10%, 15%, and 20% Ni were compared in terms of crack growth, dislocation evolution, stacking fault energy, and hydrogen diffusion. The results show that local hydrogen introduction has a limited effect on the peak stress–strain response, while hydrogen clearly accelerates crack propagation in the middle stage, especially at high concentrations. For the 10% Ni model, the middle-stage crack growth rate increases to 0.36 Å/ps under 14.3 at.% crack-tip hydrogen. Crack growth in all models shows three stages. The 15% Ni model exhibits a clear plateau in the second stage and the shortest final crack length. Further analysis shows that Ni content regulates dislocation behavior through stacking fault energy. At 15% Ni, sustained dislocation entanglement and high-density dislocation multiplication occur near the crack tip, which helps dissipate local stress. Hydrogen diffusion analysis indicates that hydrogen mobility is lower in the 15% Ni model, which may be related to hydrogen retention near dislocation-rich regions. A normalized comparison based on hydrogen diffusion and middle-stage crack growth rate further identifies 15% Ni as the lowest crack propagation tendency composition among the studied models. These results provide atomic-scale data for Ni-content optimization in hydrogen-resistant alloys, although the direct engineering transfer of the findings is limited by the length and time scales of molecular dynamics simulations. Full article

Three-dimensional (3D) graphene foams are attractive as lightweight conductive scaffolds with large surface area and broadband light absorption but achieving reproducible porosity and preserving the architecture after metal-template removal remain challenging. Here we report a stepwise route to freestanding 3D multilayer graphene foams based on (i) hydrogen-bubble-assisted electrodeposition of porous Ni on Cu foils, (ii) time-controlled pre-annealing at 1000 °C to drive Cu diffusion and form porous Ni-Cu alloy templates, (iii) in situ graphene CVD at 1000 °C under fixed growth conditions, and (iv) wet etching to remove the metal scaffold without a polymer support. The influence of pre-annealing (0, 1, 3, and 7 h) on template evolution, graphene growth, and foam stability was systematically investigated via SEM, EDS, XRD and Raman studies. Before etching, Raman spectroscopy indicates low-defect graphenic coatings with locally heterogeneous few-layer-like to multilayer-like signatures. Only samples pre-annealed for at least 3 h preserved the porous 3D architecture after metal removal, indicating the formation of self-supporting graphenic networks with improved post-etch morphological stability. Raman and XRD analyses further revealed a progressive reduction in structural degradation, residual strain, and stacking disorder with increasing pre-annealing time. Among the investigated samples, the foams obtained after 3 and 7 h of template pre-annealing combined preserved 3D morphology with low sheet resistance (10–20 Ω/□), negligible optical transmittance (<5%), and strong broadband visible-light absorption (75–90%). Full article

This study investigates the synthesis, phase evolution, and high-temperature oxidation behavior of multi-component aluminide coatings on EP670 (Fe-Ni base), EP718 (Ni-Fe base), and EP648 (Ni-base) superalloys. The coatings were produced using an economical hot-dip aluminizing method, followed by diffusion heat treatment at 1100 °C. In the as-deposited state, the coatings exhibit a heterogeneous structure consisting of an aluminum matrix with various Al-rich intermetallic inclusions. Subsequent heat treatment promotes the redistribution of chemical elements, leading to the elimination of free aluminum and the stabilization of a protective β-phase matrix. Long-term oxidation tests were performed at 900 °C, 1100 °C, and 1300 °C for up to 1000 h. At 1100 °C, the coatings on EP670 and EP648 demonstrated high stability, following a near-parabolic oxidation law and significantly reducing mass gain compared to uncoated substrates. However, at 1100 °C, the EP718 alloy underwent catastrophic failure within 200 h due to pest oxidation, disintegrating into an oxide powder—a phenomenon quantitatively confirmed by the kinetic exponent dropping below 1.0. At 1300 °C, the thermal limit for all coatings was established, with protective properties failing after 50 h. Based on the aluminum depletion kinetics, the service life at 1100 °C was estimated at 1300 h for EP670 and 2200 h for EP648. Scratch testing confirmed a complete absence of interfacial adhesive cracks across all systems. Contact loading triggered only cohesive cracks localized within the near-surface zone of the coatings. The results highlight the superior thermodynamic compatibility of the EP670 and EP648 systems with aluminide coatings, making them the most suitable candidates for extreme high-temperature applications. Full article

High-velocity oxy-fuel (HVOF)-sprayed NiCrBSi coatings containing 0, 10, 30, and 50 wt.% WC-Co were evaluated on AZ91D magnesium alloy to determine how the discrete reinforcement level affects surface topography, phase constitution, Vickers microhardness, dry-sliding friction, mass loss, and wear-track microchemistry. As-sprayed surfaces were characterized by three-dimensional profilometry; coating cross-sections and worn surfaces by optical microscopy and SEM/EDS; phase constitution by XRD; and mechanical response by HV_0.1 indentation. Dry-sliding tests were performed at 10, 30, and 50 N over 100–1000 m. Increasing WC-Co content raised Sa from 8.8 ± 0.3 to 13.0 ± 0.5 µm and Vickers microhardness from 776 ± 4 to 959 ± 5 HV_0.1. XRD indicated a γ-Ni-based matrix containing boride/carbide constituents, while WC, W₂C, and Co became increasingly prominent in the reinforced coatings. Boride assignments are based on diffraction evidence, whereas B and C EDS signals were treated semi-quantitatively. The 50 wt.% WC-Co coating exhibited the lowest mass loss and mean coefficient of friction at every load. Its mean friction coefficients were 0.31, 0.35, and 0.41 at 10, 30, and 50 N, corresponding to reductions of 40.1%, 38.9%, and 36.2% relative to AZ91D. At 1000 m, its mass-normalized wear rate indices were 9.0 × 10⁻⁴, 4.0 × 10⁻⁴, and 5.3 × 10⁻⁴ mg N⁻¹ m⁻¹, respectively. Post-wear mapping showed the largest field-scale W-Co-rich fraction in the 50 wt.% coating; however, isolated spectra containing more than 94 wt.% Mg are compatible with local coating penetration/substrate exposure and/or Mg-rich debris. The 50 wt.% composition therefore provided the best combined response among the four tested levels, while intermediate compositions are required to identify a continuous-composition optimum. Full article

In the aircraft industry, with the growing demand for advanced, sustainable structural materials, researchers are increasingly focusing on developing Al-Zn-Mg-Cu alloys, particularly the Al 7075 alloy with micro-alloying elements. However, load and environmental conditions pose problems for the aircraft industry by significantly reducing fleet service life. Thus, researchers are keen to use micro-alloying elements such as Ni, Ce, Ag, Sn, Ti, and Cd with the Al 7xxx base alloy to achieve enhanced mechanical properties, particularly hardness and tensile strength. Besides micro-alloying, the heat treatment (HT) process and cold working also have a favorable effect on the improvement of the mechanical properties. However, the addition of micro-alloying elements improves those properties more than HT and cold working processes. In this review study, several mechanical properties of the alloy have been comprehensively covered, which helps to establish a comparative analysis between the heat-treated base alloy and heat-treated micro-alloyed Al alloy. The base alloy, after micro-alloying, becomes enriched, with a high formability and workability, high conductivity, and good erosion protection that significantly make these alloys sustainable for the aircraft industry. The impact of dynamic changes accompanying the use of this lightweight alloy, after identifying the sensible necessities for the development of techniques, can effectively change the whole concept of the structural design. Hence, the key emphasis of the present review lies in a better understanding of the correlation between the structure and properties of micro-alloyed Al 7xxx alloy, which heralds a new era for aircraft industries. Full article

Solid-state hydrogen storage is considered a promising and environmentally friendly approach for energy storage. However, several challenges, including sluggish hydrogen absorption/desorption kinetics and high dehydrogenation temperatures, continue to limit the practical implementation of many hydrogen storage materials. This review summarizes recent advances in the application of severe plastic deformation techniques to improve the hydrogen storage performance of some of the most promising material systems, including TiFe-based intermetallic compounds, titanium alloys such as Ti–V-based alloys and Ti–Mg-based alloys, LaNi₅, niobium, palladium, high-entropy alloys, and magnesium and Mg-based materials. Processing routes such as high-pressure torsion, equal-channel angular pressing, fast forging, accumulative fold-forging, and intensive cold rolling have been widely employed to introduce lattice defects, promote grain refinement, and generate a high density of grain boundaries in bulk materials to enhance their hydrogen storage kinetics, activation and air resistance. In addition to enhancing hydrogen absorption and desorption kinetic properties, these techniques offer potential pathways for synthesis of hydrogen storage materials with suitable thermodynamics for hydrogen storage at room temperature. There are also attempts to scale up material production by these techniques. This review paper discusses how plastically deformed materials generally exhibit superior hydrogen storage performance and improved cycling stability compared with their undeformed counterparts. Full article

Developing electrocatalysts with high stability under industrial current densities is crucial for practical water electrolysis toward green hydrogen production yet remains a formidable challenge. Here, Fe₄₀Ni₃₈Mo₄B₁₈ amorphous alloy ribbons are fabricated via a scalable single-roller melt-spinning method and used as self-supported oxygen evolution electrodes. The as-prepared amorphous alloy sustains continuous operation at 500 mA cm^–2 for 730 h before noticeable deactivation. Mechanistic investigations reveal that under high-current anodic conditions, surface reconstruction accompanied by Fe dissolution leads to the formation and accumulation of a Fe-depleted, Ni-rich (oxy)hydroxide passivation layer, resulting in reduced Ni–Fe synergistic sites and limited charge transfer. Based on this understanding, a rapid regeneration strategy is developed to remove the inactive surface layer and induce structural reconfiguration. The regenerated electrode exhibits reduced overpotential at 10 mA cm^–2 (from 304 to 243 mV) and sustains an additional 710 h of operation at 500 mA cm^–2 at a lower applied potential. These results indicate that catalyst deactivation and regeneration are governed by surface chemical evolution and provide insight into extending catalyst lifetime under practical operating conditions. Full article

Relatively low-cost titanium carbide (TiC) materials and metal matrix composites (MMC) are proposed for waste-to-hydrogen conversion. Two types of steels are used as bases prepared from EN 10088 flat products, namely X2CrTi12 (1.4512, AISI 409) and X5CrNi18-10 (1.4301, AISI 304). TiC is mixed with TRIBALOY^® T-800 alloy in powder form and applied via laser-directed energy deposition (DED-LB) over the substrates. For the powder mixture, Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) are performed. The raw materials are investigated for the processes that occur in them under heating. After the solidification of the molten mixture, grinding and polishing are performed to achieve a thin layer. The studies of the obtained MMC include interface zone assessment, hardness and Young’s modulus distribution, microstructural analysis, and visual defect evaluation. Advanced sensors for acoustic emission (AE) and Electrical Contact Resistance (ECR) provided characterization together with micro-scratch testing. The use of photoluminescence spectroscopy is proposed for the new composite materials. The electron transfer pathway can be studied with time-resolved spectroscopy. Renewable energy production by breaking down waste into hydrogen-rich syngas can be achieved through pyrolysis, followed by steam reforming and purification. The obtained novel materials show promising application solutions with increased durability, corrosion, and wear resistance. Full article

Fe-based medium-entropy alloys (MEAs) are a cost-effective class of multi-principal-element alloys with tunable mechanical behavior. Their key advantage lies in the ability of Fe-rich, non-equiatomic compositions to regulate phase stability, deformation behavior, and strain hardening without relying heavily on expensive Co, Ni, or V. Increasing evidence shows that metastable face-centered cubic (FCC) matrices can provide excellent combinations of strength and ductility when their transformation behavior is properly controlled. Through compositional tuning and microstructural regulation, the phase stability, stacking-fault energy, precipitation behavior, and deformation pathways of Fe-based MEAs can be adjusted to achieve a balance between strength, ductility, and service reliability. This review critically synthesizes the metastability, microstructure, strengthening mechanisms, and service-oriented design principles of Fe-based MEAs. The literature discussed in this review was selected from peer-reviewed studies that report clear links among alloy composition, processing history, microstructure, deformation behavior, and mechanical or service-related properties. Unlike reviews that mainly classify alloy systems or deformation modes, this work emphasizes how metastability engineering and microstructural design can be integrated to guide application-specific alloy development. Representative Fe-rich non-equiatomic alloy systems are compared to clarify how alloying and processing regulate metastability, precipitation behavior, transformation kinetics, and strain partitioning. This review highlights that superior properties arise from the coordinated control of metastability, heterogeneous microstructures, and strengthening mechanisms. A central conclusion is that controlled transformation kinetics, rather than the pursuit of a maximum martensite fraction, is the key design variable for sustaining strain hardening and achieving stable strength–ductility synergy. Remaining challenges include quantitative deconvolution of coupled mechanisms, reliable prediction of local metastability, long-term microstructural stability, manufacturability, cost–performance balance, and integration of high-throughput experiments with computational alloy design. Overall, this review provides a service-oriented design framework for high-performance, low-cost Fe-based MEAs through the integrated control of composition, metastability, microstructure, processing, strengthening mechanisms, and application-specific performance. Full article

Amorphous metal alloys (AMAs) are metastable materials that are characterized by good mechanical properties and corrosion properties. It is known that with certain thermal modifications, these properties improve or lose their value. The purpose of this research work is to investigate the optimal conditions of thermal modification that improve the mechanical properties of this alloy. The DSC method established the temperatures of phase transitions in the temperature range of 624–643 K, which correspond to the following processes: crystal nucleation (T₁ = 624 ± 1 K), growth (T₂ = 633 ± 1 K), and stable crystallization (T₃ = 643 ± 1 K). The XRD and TEM/HREM methods revealed structural changes in the amorphous matrix as a result of thermal modification. As a result of isothermal annealing for 2 min. at temperatures T₁, T₂, T₃, a solid solution based on aluminum and a thermally stable compound Al₁₉Ni₅(Y,Gd)₃ were formed. The equation for the transformation of an amorphous matrix AMA Al₈₇Y₄Gd₁Ni₈ in the temperature range (624–643) ± 1 K during isothermal 2 min annealing is given by: Am → Am′_resid+ solid solution Al(X) → Am′_{(enriched REE)} + solid solution Al(X) + nano-Al₁₉Ni₅(Y,Gd)₃ → Am′_{(enriched REE)} + solid solution Al(X) + nano-Al₁₉Ni₅(Y,Gd)₃. The Oliver–Pharr method established that AMAs annealed at temperatures T₁ and T₂ have microhardness indicators 5–9 times higher than amorphous samples; however, the material loses its elasticity under such thermal deformation conditions. Full article