Search Results (1,893)

Bacterial biofilms represent a major clinical challenge, being responsible for the majority of chronic infections and significantly reducing the effectiveness of antibiotic therapy. Their formation on implant surfaces, particularly those made of titanium and its alloys, is strongly associated not only with antimicrobial tolerance but also with persistent, hard-to-eradicate infections, implant loosening or failure, repeated surgical interventions, prolonged hospitalization, and increased morbidity. These complications contribute substantially to the growing problem of antimicrobial resistance and impose significant economic burdens on healthcare systems. This review discusses the mechanisms of biofilm formation, factors influencing bacterial adhesion, and the clinical implications associated with implant-related infections. Special attention is given to titanium-based biomaterials, including conventional Ti–6Al–4V and next-generation alloys such as Ti–13Nb–13Zr, highlighting their advantages and limitations in the context of biocompatibility and susceptibility to biofilm formation. Various strategies for combating biofilms are presented, including physical, chemical, and biological approaches, with emphasis on surface modification techniques. Advanced methods, particularly atomic layer deposition (ALD), are identified as promising solutions for creating uniform, antibacterial coatings, including those based on tin dioxide (SnO₂). Such modifications offer potential for reducing bacterial adhesion, improving osseointegration, and enhancing long-term implant performance. Full article

Despite the advantages of powder bed fusion–laser beam (PBF-LB), Ti6Al4V components often exhibit high yield strength but limited ductility, which restricts their use in critical structural applications. This study aims to identify the most effective heat treatment to optimize the strength–ductility balance in Ti6Al4V parts produced by PBF-LB and to establish direct correlations between microstructural states, mechanical properties and corrosion behavior. Two distinct post-processing heat treatments were applied, specifically, the first at 500 °C for 5 h and the second at 800 °C for 2 h, both followed by air cooling. The microstructure was characterized using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Mechanical behavior was assessed through Vickers microhardness testing and tensile testing, while corrosion resistance was evaluated via electrochemical measurements. Residual stress profiles were determined using the hole-drilling strain gauge method, in both as-built and heat-treated conditions. The as-built samples displayed a fully martensitic α′ structure with columnar grains aligned parallel to the laser scanning direction, resulting from rapid solidification. Heat treatment at 500 °C caused only partial decomposition of acicular martensite into substructures without altering its acicular morphology, leading to a strengthening effect alongside a reduction in ductility. Conversely, heat treatment at 800 °C offered the most balanced combination of strength and ductility among the conditions studied, albeit with a moderate reduction in corrosion resistance. Full article

CoCrNiTiAl_x high-entropy alloy films with varied Al contents were fabricated on 42CrMo steel substrates via magnetron sputtering. By adjusting the sputtering power of the Al target, an investigation was systematically carried out to explore the effect of different Al contents on the microstructural evolution, mechanical properties, and corrosion resistance of the film, with the underlying synergistic mechanism governing these properties being elucidated. With increasing Al content, the film microstructure gradually transforms from an amorphous phase at low Al contents to a nanocrystalline–amorphous composite structure, until it is converted into the BCC phase, and the film’s crystallinity exhibits a trend of first increasing and then decreasing. In terms of mechanical properties, the film hardness is significantly enhanced from 7.6 ± 1.3 GPa to 18.9 ± 1.1 GPa with increasing Al content, while the toughness gradually declines. Wear tests show that the film wear rate first decreases and then increases with rising Al content, reaching a minimum of 2.06 × 10⁻⁵ mm³/N·m. The superior protective state, characterized by a corrosion potential reaching −361.2 mV and corrosion current density dropping to 1.12 μA/cm², arises from the generation of an integrated, consistently structured composite passivation barrier in 3.5 wt.% solution. This study confirms that appropriate Al doping can synergistically optimize the microstructure, mechanical properties, and corrosion resistance of CoCrNiTiAl_x films, providing experimental and theoretical support for the compositional design and engineering applications of high-performance high-entropy alloy protective films. Full article

Ultrathin titanium alloy foils are attractive for engineering components requiring flexural compliance and mechanical support, yet their recoverable deformation behavior at the foil scale remains insufficiently characterized. This study evaluates 30 μm Ti–24Nb–4Zr–8Sn (wt.%, Ti2448) foils in the as-rolled and solution-treated states and compares their tensile loading–unloading response with same-thickness CP Ti and Ti–6Al–4V reference foils. The Ti2448 foils exhibit a larger recoverable-deformation window and a lower apparent loading modulus than the reference foils under the same testing protocol. The highest recoverable strain is obtained in the solution-treated longitudinal condition, indicating that the recoverable deformation is sensitive to both processing state and loading direction. These results suggest Ti2448 foils as potential candidates for flexure-related applications requiring large recoverable deformation. Full article

Accurate prediction of hydrogen storage properties is needed for accelerating the design of body-centered cubic (BCC)-type V-based alloys, where the composition–property space is too large for trial-and-error experimentation alone. Here we report a stacking ensemble framework that combines XGBoost, Random Forest, Extra Trees, and Gradient Boosting as base learners with linear or ridge meta-learners, with hyperparameters tuned by a genetic algorithm (GA). Three descriptor strategies are compared across seven target properties: composition-only (C), property-only (P), and composition–property fusion (CP). On target-specific subsets containing 95–901 experimental records and 17 alloying elements (the smallest subset, 95 records, corresponds to maximum hydrogen capacity $C_{\max }$, which may limit model stability for that property), the best model for each target gives $R^2$ values from 0.865 to 0.981 (all metrics are from five-fold cross-validation; no independent external test set was employed); the P-type model for desorption plateau pressure reaches $R^2=0.981$. SHapley Additive exPlanations (SHAP) analysis shows that physically derived descriptors, including valence electron concentration, atomic size mismatch, and electronegativity difference, dominate in P and CP models, whereas Ti and Cr contents are the leading compositional features. A Non-dominated Sorting Genetic Algorithm II (NSGA-II) optimizer then ranks 3000 final candidate alloy compositions in six alloy families using four objectives: high predicted retention, high predicted cycle count, high predicted BCC phase ratio, and a low cost proxy; these candidates represent model-based predictions and await experimental synthesis and cycling validation. The V–Ti–Cr–Fe–Mn system contains the largest number of candidates with predicted retention above 99%, while Ti-free V–Cr–Fe–Mn–Al alloys provide low-cost alternatives in the model search space. First-principles calculations on four representative alloys only show that BCC structures are lower in energy than FCC structures by about 0.08–0.13 eV/atom and that hydrogenated structures exhibit clear charge accumulation around H sites, supporting the physical plausibility of the data-driven screening results, though density functional theory (DFT) validation does not replace experimental measurement of PCI curves and cyclic stability. Full article

This paper establishes a multi-scale nested sub-modeling finite element simulation framework for the deformation and damage analysis of large-scale structures under complex loading conditions. By sequentially transferring displacement solutions from the global model to local sub-models, the framework enables progressive high-resolution analysis from the macroscopic scale (>10 m) down to the microscopic scale (~1 μm), thereby significantly improving solution accuracy in critical regions while maintaining computational efficiency. The proposed approach is validated on a shell structure subjected to hydrostatic pressure and on a plate with a central crack. The results show that the relative errors of stress and strain along specified paths in the shell structure are within 5%, while the relative errors of the stress intensity factor along the crack front in the cracked plate are also below 5%. Furthermore, the framework is integrated with the crystal plasticity finite element method, and a fatigue indicator parameter model based on the accumulated equivalent plastic strain is established to predict the shear fatigue life of Ti-6Al-4V ELI titanium alloy. The predicted fatigue lives are in good agreement with experimental data, with all errors below 10%. This study demonstrates that the proposed sub-modeling method can accurately transfer multi-scale mechanical responses and achieve localized refinement analysis of large-scale structures and can be effectively used for crystal plasticity simulations and fatigue life assessment. Full article

Friction stir processing (FSP) is an advanced solid-state surface modification technique for biomedical titanium alloys. This study presents a computational investigation of FSP applied to Ti-6Al-4V alloy through three-dimensional finite element modeling and Taguchi-based statistical optimization. A Taguchi L9 orthogonal array evaluated rotational speed (400–1000 rpm), traverse speed (50–100 mm/min), shoulder diameter (6–18 mm), and pin diameter (2–6 mm), reducing the required simulations from 81 (full factorial) to nine (88.9% reduction). A calibrated friction model (μ = 0.35/0.25/0.20 for 400/800/1000 rpm, F = 6000 N) yielded maximum temperatures of 870–1384 °C; all predicted temperatures remained below the melting point of Ti-6Al-4V (1660 °C). These values are consistent with experimentally reported ranges for FSW/FSP of Ti-6Al-4V. Traverse speed is the dominant parameter (ANOVA contribution: 63.1%, F = 10.44), followed by rotational speed (26.7%) and shoulder diameter (4.1%). Simulation 3 (400 rpm, 100 mm/min, Ds = 18 mm, T_max = 870 °C) appears to be the most promising thermal condition for preserving the fine-grained α + β microstructure, as it remains below the β-transus temperature (980 °C) throughout the processed zone. Full article

This review focuses on the effects of trace and residual rare-earth elements on inclusion evolution and Nb–Ti–V precipitation behavior in microalloyed steels. Existing studies indicate that trace rare-earth elements can transform conventional Al₂O₃- and MnS-type inclusions into rare-earth oxides, oxysulfides, and sulfides, while also modifying local interfacial states and solute distributions through segregation and interfacial activity. These changes further affect the nucleation sites, growth behavior, coarsening tendency, and spatial distribution of NbC, TiN, VC, and related carbonitrides. To explain the seemingly contradictory precipitation responses reported in the literature, this review examines rare-earth effects from the perspectives of inclusion inheritance, heterogeneous nucleation, interfacial energy modification, local solute redistribution, and thermomechanical processing history. The available evidence suggests that the metallurgical role of trace rare-earth elements cannot be attributed solely to inclusion modification. Instead, their effects arise from the combined influence of inclusion evolution, interfacial activity, local chemical heterogeneity, and precipitation kinetics under specific processing conditions. These insights provide practical guidance for alloy and process design by linking rare-earth addition, inclusion control, and Nb–Ti–V precipitation regulation in microalloyed steels. Full article

The study objectives were to evaluate the in vitro and in vivo performance of additive manufacturing (AM) Ti6Al4V ELI alloy compared to that of a commercially available dental implant. Two AM shapes with the solid or lattice structures on the solid substrate were used: in vitro test: disk shapes (10.0 mm/dia. 2.0 mm/thick) and in vivo test: AM shapes matching the overall geometry of a commercial implant (3.0 mm/dia. 8.0 mm/length). Six disk specimens were placed in direct contact with Balb/c 3T3 fibroblasts for 72 h. Cytotoxicity was assessed with adenosine triphosphate activity. Four implant-shaped specimens were placed in the femurs of three rabbits and retrieved after 6 weeks. Osseointegration was evaluated by push-out testing and histological analysis. Data were analyzed using one-way ANOVA (α = 0.05). Surface roughness (µm) of AM-solid, AM-lattice, and a commercial implant were 8.02, 9.00, and 1.46, respectively. Cytotoxicity was not statistically different compared to surface configuration and Teflon^® controls (p > 0.05). Push-out test results were not significant between implants: the shear stiffness of commercial > AM-lattice > AM-solid (p > 0.05). Histological analysis demonstrated osseointegration without inflammatory responses in the surrounding bone tissue for all implants. While some processes and improvements are still required, AM remains a promising method for fabricating customized porous implants in the future. Full article

High-entropy alloy (HEA) coatings exhibit enhanced chemical stability when doped with carbon, primarily due to the strong bonding between carbon and transition metals. Typical transition metals used in these coatings include Cr, Fe, Co, Ni, Cu, Ti, V, W, Nb, Ta, and Zr. Owing to their excellent chemical stability, HEA coatings are widely employed to protect component surfaces operating in highly corrosive environments. Against this backdrop, the present study investigates the effect of carbon doping introduced via methane gas flow during the physical vapor deposition of TiAlTaZrNb HEA coatings on corrosion resistance. The morphology and structure of the coatings were analyzed by field emission scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Corrosion protection and coating resistance were assessed through potentiodynamic polarization and electrochemical impedance spectroscopy. While increasing the methane flow resulted in an approximately 34% reduction in coating thickness, the overall coating resistance increased by one order of magnitude, reaching a maximum at a methane flow rate of 9 sccm, corresponding to the carbon solubility limit. This improvement was evidenced by a decrease in the corrosion rate from 8.02 × 10⁻² mm y⁻¹ for the uncoated H13 steel to 8.00 × 10⁻⁴ mm y⁻¹ for the HEA-coated samples. However, at higher methane flow rates, carbon precipitation and the formation of parallel microcracks contributed to an increase in corrosion rate. Full article

The significant challenges of machining hard-to-cut materials pose an important problem for the manufacturing industries, as it can lead to increased tool wear, higher machining costs, and reduced productivity. Apart from experimental investigations, which are rather expensive and cannot always provide a comprehensive view of the process outcome due to limitations in measurement techniques, it is possible to use validated models to predict the temperature and stress state of the workpieces or test the effect of different process conditions. Although many Finite Element (FE) models have been developed for the turning process, usually accurate representation of the machining setup with a realistic 3D geometry for both cutting tool and workpiece is not taken into account. Thus, in this work, two different representations of the machining setup, including curved workpiece geometry, which is more rarely studied, are compared for the case of Ti-6Al-4V ELI turning under various conditions, and their effect on the accuracy of the prediction of the cutting force and chip morphology is investigated. It was found that the model with the straight workpiece overpredicts the cutting force to a higher extent compared to the model with the curved workpiece and also predicts a much higher workpiece temperature, whereas chip morphology was mainly affected by feed rate. No noticeable differences were observed between the two models. These results indicate that in most cases, the use of geometry with curved workpiece is more suitable for better prediction of the cutting forces. Full article

In this study, the Nb from the lightweight Ti₆₅(AlCrNbV)₃₅ medium-entropy alloy was replaced with Zr to create lower-density Ti_x(AlCrZrV)_100−x (x = 65, 67, 70, or 75) alloys. All alloy ingots were fabricated through vacuum arc melting and drop casting. X-ray diffraction analysis revealed all as-cast alloys exhibited only a single body-centered cubic structure. As the Ti content increased, the strength of the as-cast alloys decreased from 1247 to 981 MPa, whereas their elongation marginally improved. Moreover, the mechanical properties of these alloys were considerably enhanced through thermomechanical treatment (50% hot rolling and 80% cold rolling) and then rapid annealing at 700 °C, 800 °C, or 900 °C. An increase in the annealing temperature led to a notable decrease in the yield strength of the alloys but a considerable increase in their ductility. Ti65, Ti67, and Ti70 alloys annealed at 700 °C or 800 °C exhibited a yield strength of ≥1200 MPa and a ductility of ≥10%. Of the fabricated alloys, the Ti67 alloy annealed at 700 °C exhibited the optimal mechanical properties (yield strength of 1552 MPa and ductility of 13.6%). It exhibited low density (4.89 g/cm³) and a specific yield strength of 317 MPa·cm³/g, thus demonstrating considerable potential for transportation and energy applications. Full article

Ti–6Al–4V is the primary titanium alloy for aerospace, biomedical, and additive manufacturing applications; however, the high cost of powders produced by atomization limits their widespread adoption. This study aims to develop a cost-effective method for producing chemically homogeneous pre-alloyed Ti–6Al–4V powders from titanium sponge. A combined process is proposed, involving the hydrogenation of titanium sponge, mechanical alloying of the hydride phase with Al and V powders, and subsequent vacuum dehydrogenation. The formation of the brittle δ-TiH₂ phase facilitated intensive material comminution and effective distribution of the alloying elements. According to laser diffraction data, the median particle size decreased from 450 to 30–35 µm. X-ray diffraction (XRD) analysis confirmed the sequential α-Ti → δ-TiH₂ transition and the formation of a stable α + β two-phase structure characteristic of Ti–6Al–4V following dehydrogenation. SEM observations demonstrated that the final powders predominantly consist of individual fractured particles with limited hard agglomeration, favorable for powder flowability and compaction behavior. EDS analysis indicated a relatively homogeneous microscale distribution of Al and V without observable large-scale segregation. The synthesized powders exhibited low impurity levels, with O < 0.07 wt.% and H < 0.02 wt.%. The developed approach represents a promising and economical alternative to expensive atomization techniques for powder metallurgy and additive manufacturing. Full article

Titanium alloys such as Ti-6Al-4V are widely used in orthopedic implants due to their strength and biocompatibility. Laser Surface Remelting (LSR) offers a promising approach to modify surface properties without altering bulk characteristics. This study investigates the effects of varying melt pool depths (MPDs) from 0 μm to 30 μm in 10 μm steps on the mechanical behavior of Ti-6Al-4V femoral components in Total Knee Replacement (TKR) using a comprehensive computational approach combining Finite Element Analysis (FEA) and computational algorithm-based automated evaluation. A three-dimensional FEA model was developed and tested under four physiological loading conditions: compression, axial distraction, medial bending, and lateral flexion at 1300 N. Results show that increasing MPD from 0 μm to 30 μm increases the maximum von Mises stress by 4.2% under compression but reduces displacement by up to 51.7% under distraction. An MPD of 20 μm reduces displacement by 48% while increasing stress by only 2.7%, representing an optimal balance. The computational algorithm framework identifies 15–25 μm as the optimal range for balancing surface enhancement with mechanical integrity. Experimental validation shows good agreement between simulated and measured results, confirming the reliability of the proposed framework for optimizing surface modification parameters in orthopedic implants. Full article

Additive–subtractive hybrid manufacturing (ASHM) allows for the rapid manufacturing of metal components with complex and precise geometries for ready-to-use or near-ready-to-use applications. Laser wire-directed energy deposition (LW-DED) can be used to quickly manufacture metal components, while CNC machining can achieve precise geometric tolerances. In this study, Ti-6Al-4V alloy specimens were fabricated using an LW-DED process combined with CNC machining and tested to evaluate the effects of ASHM on mechanical performance. Post fabrication, the Ti-6Al-4V material was evaluated through hardness mapping, monotonic tensile testing, and fully reversed axial fatigue testing. Vicker’s micro-hardness mapping showed a range of hardness results from 300 to 350 HV in the ASHM Ti-6Al-4V that remained consistent throughout the build. Tensile results showed a similar response to cast and wrought Ti-6Al-4V, with an average yield stress of 819.4 MPa, ultimate tensile strength of 935.5 MPa, and modulus of 119 GPa. When tested in fatigue, the material had a reduced life compared to wrought Ti-6Al-4V, which is attributed to defects originating from the additive process. While no run-outs were observed from the testing, the fatigue results remain aligned with trends reported for other methods of additively manufactured Ti-6Al-4V. Fully reversed high-cycle fatigue loading revealed that the ASHM-fabricated Ti-6Al-4V fell into a Basquin power-law fit with a fatigue strength coefficient of 1942 MPa with a fatigue strength exponent of −0.115. The fatigue life of the ASHM material is found to be dependent on the resulting porosity of the material that stems from the LW-DED process used in the ASHM process described. Full article