Search Results (1,238)

This study investigated the corrosion resistance of laser-cladded AlCoCrFeNi high-entropy alloy coatings with varying TiO₂ content (0 wt.%, 0.5 wt.%, 1.0 wt.%, and 1.5 wt.%) in 3.5 wt.% NaCl solution. Optimal cladding parameters (1500 W, 40 mm/s, 11.9 g/min) were determined via orthogonal experiments. TiO₂ promoted Ti-rich BCC2-phase precipitation, increased corrosion potential (from −1.4185 V to −0.6841 V), decreased corrosion current density (from 2.33 × 10⁻⁴ to 2.28 × 10⁻⁶ A/cm²), and enhanced charge-transfer resistance. XPS analysis demonstrated that TiO₂ promoted the enrichment of FeO, Cr₂O₃, and TiO₂ components in the passive film while reducing the Al₂O₃ fraction, leading to the formation of a dense and stable composite passive film that effectively inhibited chloride ion attack. In summary, an appropriate amount of TiO₂ doping significantly enhances the corrosion resistance of laser-cladded AlCoCrFeNi HEA coatings, with the 1.5 wt.% addition being the best-performing among the investigated compositions. Full article

Water-jet guided laser (WJGL) technology has gained significant attention in precision manufacturing due to its extremely small heat-affected zone. However, laser-induced water breakdown severely constrains the achievable laser power and processing efficiency. This paper presents and validates an optical solution employing a custom-designed rotationally symmetric aspheric lens. The lens is designed to generate a sequence of discrete focal points distributed along the optical axis. This configuration maintains a high average laser power while suppressing the peak power density at each individual focus below the water breakdown threshold. Theoretical modeling and ray tracing simulations confirm the superior performance of the lens in creating a controllable multi-focal beam. Experimental results demonstrate that a WJGL system incorporating the six-focus aspheric lens operates stably at 350 W. This represents a 300 W increase compared to the conventional spherical lens, which had a stable operating power limit of approximately 50 W within this experimental system. In microgroove machining experiments on NiTi alloy, the new system achieved an approximately 3.5-fold increase in groove depth and a 2.7-fold reduction in taper angle. This study provides a practical and effective beam shaping strategy to overcome the fundamental power limitation in WJGL technology. Full article

The superelastic behavior of shape memory alloys (SMAs) arises from stress-induced martensitic transformation and plays an important role in the design of smart engineering systems, including aerospace components. Reliable constitutive modeling is therefore essential for accurately predicting their mechanical response in numerical simulations of SMA-based engineering systems. In this study, a localized plateau-based comparative evaluation framework is employed to compare the classical Brinson and Liang–Rogers phenomenological models using published experimental stress–strain data of superelastic NiTi alloys under isothermal tensile loading–unloading conditions at two different temperatures. Model performance is assessed using global RMSE, localized plateau RMSE, and hysteretic energy dissipation. The results show that both constitutive models provide close agreement with the overall superelastic hysteresis response and predict comparable hysteretic energy dissipation. However, the Liang–Rogers model consistently provides lower localized RMSE values within the forward and reverse transformation plateau regions. The principal contribution of this work is the introduction of a localized comparative evaluation framework that complements conventional global error measures for comparing phenomenological SMA constitutive models. Full article

The transition towards sustainable cities requires material selection strategies capable of balancing environmental, economic and social performance while accounting for the emerging functionalities offered by smart materials. This work proposes a sustainability-driven methodology based on normalized multi-dimensional indicators for the objective comparison of functionally equivalent conventional and smart materials in the built environment and demonstrates its application through the parametric design of an urban bench. The quantitative assessment showed substantial differences among the investigated materials: Shape Memory Polymers (SMPs) resulted in a panel mass of 5 kg, CO₂ emissions of 2.4 kg CO₂/kg, and embodied energy of 37 MJ/kg, compared with 32 kg, 13 kg CO₂/kg, and 260 MJ/kg for NiTi, and 40 kg, 15 kg CO₂/kg, and 320 MJ/kg for magnetic Shape Memory Alloys, respectively. Finite element analysis further demonstrated the influence of structural design, with the maximum principal stress decreasing from approximately 0.073 MPa at a panel thickness of 10 mm to 0.015 MPa at 50 mm, corresponding to a reduction of approximately 79%. The results demonstrate that smart materials do not inherently represent more sustainable alternatives than conventional materials; rather, their adoption should be justified when their adaptive functionalities provide measurable benefits capable of compensating for their environmental and economic burdens. The proposed framework provides a practical decision-support tool that shifts material selection from property-driven choices toward function-oriented, sustainability-based design, supporting more informed decisions for next-generation urban infrastructure. Full article

This study evaluates the thermal and mechanical behavior of innovative copper–nickel–titanium (CuNiTi) rectangular orthodontic wires featuring rounded edges across two different sizes for clinical applications. Differential scanning calorimetry (DSC) was performed from −20 °C to +80 °C to determine phase transformation temperatures according to ASTM F2004. Three-point bending tests were conducted in accordance with ISO 15841 to evaluate unloading forces (at 3, 2, 1, and 0.5 mm deflections) and permanent residual deflection at 23 °C (room temperature) and 37 °C (oral environment). DSC analysis revealed a single-stage phase transformation within the range 10 °C to 27 °C, indicating near-superelastic behavior at room temperature. Mechanical testing demonstrated reproducible force-deflection profiles and low permanent deformation. At body temperature (37 °C), unloading forces in the 2.0–0.5 mm activation range averaged between 1.9 N and 3.2 N depending on wire cross-section. In conclusion, the evaluated CuNiTi wires provide consistent force delivery during unloading at physiological temperature, offering suitable mechanical properties for orthodontic alignment applications. Full article

Ag-Ti₃SiC₂ composites are promising electrical contact materials, yet the atomic-scale interfacial behaviour between Ti₃SiC₂ and Ag remains poorly understood. Here, first-principles calculations were performed to investigate the interfacial stability, electronic structure, and alloying effects at the Ti₃SiC₂(0001)/Ag(111) interface. Surface-energy calculations for six terminations of Ti₃SiC₂(0001) show that the TiC(TiC) termination is preferred at low carbon chemical potential, whereas the TiC(TiSi) termination becomes the most stable once ΔμC exceeds −1.50 eV. Eighteen interface models combining the six terminations with three stacking sequences (OT, MT, and HCP) were constructed, and their work of adhesion (Wad) and equilibrium spacing (d₀) were determined by the Universal Binding Energy Relation and full structural relaxation. The HCP stacking is preferred for all terminations, and the C(TiC)-terminated HCP interface exhibits the highest work of adhesion among all configurations, with Wad = 9.25 J/m² at d₀ = 1.2 Å; relaxation enhances Wad by 10%–75%. Charge density, charge density difference, and partial density of states analyses reveal that the interfacial bonding is dominated by C 2p-Ag 4d hybridization accompanied by electron transfer from Ag and Ti atoms to the interfacial C atoms, which accounts for the adhesion hierarchy. Substitutional alloying with Cu, Ni, Zn, and Cr preferentially segregates into the interfacial Ag layer, where the defect formation energies, although positive, are the lowest, and Wad increases in the order Cu < Zn < Ni < Cr, reaching 11.0 J/m² for interfacial Cr, an enhancement of 19% over the pristine interface. The strengthening correlates directly with the filling of the dopant 3d band. These results provide theoretical guidance for the interfacial design of high-performance Ag-Ti₃SiC₂ electrical contact composites. Full article

The dissimilar combination of NiTi shape memory alloy and Ti6Al4V titanium alloy offers superelasticity, biocompatibility and high specific strength, showing broad application prospects in aerospace and medical fields. However, when fabricating NiTi/Ti6Al4V composite components by multi-material laser powder bed fusion (MM-LPBF), brittle cracks or even complete delamination easily occur at the interface. In this paper, without relying on intermediate interlayer materials, we innovatively propose a root-inspired three-dimensional bio-interlocking interface structure. By means of macroscopic three-dimensional geometric interlocking, the crack propagation path and load transfer mode are forced to change. Using the branching angle (45°, 60°) and the structural size multiplier (1.2, 1.5) as variables, the influence of the bio-inspired geometric parameters on the interfacial forming quality, microstructure and mechanical properties was systematically investigated. The results show that the branching angle is the primary factor determining the performance. The 45° low-angle branched specimens exhibit overall brittle delamination along the flat metallurgical reaction interface under shear loading, with an average shear strength of only 17.47 MPa. In contrast, the 60° high-angle branched specimens, owing to their larger normal embedding depth, exhibit a failure mode transitioning to a mixed mode that includes crack deflection, branch shearing and plastic tearing of the Ti6Al4V matrix. Although TEM confirms that a continuous Ti₂Ni brittle phase still exists at the interface, the optimised 60–1.5 structure increases the average shear strength to 128.37 MPa, which is more than six times higher than that of the 45–1.2 group (17.47 MPa). This “geometrical constraint toughening” strategy provides a new paradigm for the interfacial strengthening of dissimilar metals without relying on metallurgical modification. Full article

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

This systematic review aimed to evaluate whether cross-sectional geometry is associated with cyclic fatigue resistance of nickel–titanium (NiTi) endodontic instruments and to identify the geometric and materials-related features most frequently associated with improved fatigue performance. The protocol was prospectively registered on the Open Science Framework (OSF). PubMed, Scopus, Embase, Web of Science, and WorldCat were searched in April 2026 in accordance with PRISMA 2020. Eligible studies were comparative in vitro investigations that explicitly evaluated cross-sectional geometry or a related geometric parameter as a prespecified study factor and reported quantitative cyclic fatigue outcomes. Of 107 screened records, 66 full-text reports were assessed and 23 studies were included in the qualitative synthesis. Twenty-two studies had a medium risk of bias and one had a low risk of bias according to the Quality Assessment Tool for In Vitro Studies (QUIN). Cyclic fatigue resistance was most often reported as time to fracture or number of cycles to failure. Instruments with reduced metal mass, smaller core volume, lower cross-sectional area, and greater flexibility tended to demonstrate higher fatigue resistance in curved canals. S-shaped and double-S-shaped cross-sections were most consistently associated with favorable outcomes; however, this association is more plausibly related to reduced bending stiffness and canal-wall contact forces than to increased intrinsic material fatigue strength. Flat-side designs did not show a consistent advantage. The evidence was limited by heterogeneous testing protocols and residual confounding by alloy, heat treatment, taper, manufacturing, surface condition, and kinematics. No meta-analysis or quantitative dimensional correlation was feasible because testing conditions and detailed geometric parameters were inconsistently reported. Full article

This study investigates the influence of laser spot size (Ø100 µm vs. Ø50 µm) on the microstructure, transformation behavior, and hardness of Ti-51.17 at.%Ni shape memory alloy samples fabricated by laser powder bed fusion. Samples were produced using identical processing parameters covering laser powers of 50–150 W, scanning speeds of 500–750 mm/s, and matched volumetric energy densities (28–83 J/mm³), with spot size as the only variable. Although both laser spot sizes produced comparable melt pool geometries and predominantly B2 austenite matrices with minor fractions of B19′ martensite, the Ø50 µm samples exhibited finer microstructures, higher residual stresses, and lower martensitic transformation temperatures in the as-built state. Heat treatment at 800 °C reduced residual stresses and partially homogenized the microstructure; however, differences in their transformation behavior remained. These differences were attributed to the spot-size-dependent Ni evaporation. Although transformation temperatures increased with increasing energy density for both conditions, the Ø50 µm samples consistently showed lower values. In the 55–83 J/mm³ volumetric energy density range, the estimated Ni content ranged from 51.15 to 50.42 at.%, and the Ø50 µm samples showed approximately 0.1–0.2 at.% greater Ni loss than their Ø100 µm counterparts. These findings demonstrate that Ni evaporation is a laser-spot-size-dependent phenomenon that must be considered when processing near-equiatomic Ti-Ni alloys. Full article

The effect of thermomechanical processing (TMP) parameters on the structural-phase evolution and properties of Ni-enriched Ti–50.8 at.% Ni shape memory alloy was investigated. Compression deformation was performed at T = 300–500 °C, accompanied by the development of dynamic aging (DA) processes, to true strains of e = 0.5–1.3, followed by post-deformation static aging (SA) at 430 °C for 1 and 10 h. The structural-phase state and properties were characterized using optical and transmission electron microscopy, X-ray diffraction, differential scanning calorimetry, and Vickers hardness measurements. The results confirmed that DA processes were activated during compression but proved insufficient for pronounced Ti₃Ni₄ precipitate growth compared with SA. The temperature range of 430–500 °C promoted the most intensive DA processes and facilitated ultrafine-grained structure formation. The processing route combining DA at 500 °C with short-term SA (1 h) resulted in the finest precipitates of Ti₃Ni₄ phase and most homogeneous substructure. These findings demonstrate that the proposed TMP strategy enables effective tailoring of precipitate dispersion, evolution of transformation temperatures and mechanical properties (hardness), providing a viable manufacturing pathway for tailoring TiNi SMA performance in advanced biomedical and engineering applications. 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

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

Electroless coatings mark a significant improvement in surface engineering by providing superior uniformity, precision, and functional properties compared with traditional plating processes. Electroless Ni-P-Al₂O₃ composite coatings were successfully deposited on Ti-6Al-4V, forming a Ni-Ti intermediate (~14–16 µm) that ensured strong interfacial bonding. Al₂O₃ concentration (0.2–1.4 g/L) strongly influenced microstructure and performance, with 0.4 g/L yielding the most refined coating. AFM revealed a dense, uniform surface with the lowest roughness (~23.4 nm). This composition achieved the highest hardness (464.6 HV_0.1), ~157% higher than the substrate and ~53% higher than Ni-P. It also showed superior tribological behavior, reducing wear volume to ~4.46 × 10⁻⁷ mm³ and friction coefficient to ~0.32 (~85% and ~50% reductions vs. substrate). Corrosion resistance was maximized at 0.4 g/L, with the lowest corrosion current (2.45 × 10⁻⁶ A/cm²) and rate (0.0053 mpy), outperforming both Ni-P and uncoated Ti-6Al-4V due to the compact composite matrix and stable passive film. Full article