Search Results (3,066)

Electrical discharge machining (EDM) demonstrates significant advantages in machining difficult-to-cut materials, particularly those with high hardness and brittleness, owing to its thermally driven material removal mechanism in which the arc plasma serves as the heat source. However, machining performance varies markedly across different workpiece materials. Such differences are likely attributable to the coupled effects of arc plasma characteristics, which may vary with tool–workpiece material combinations, and the thermophysical properties of the workpiece. Nevertheless, the mechanisms underlying this coupling remain poorly understood. In this study, arc plasma characteristics and material removal behavior under different material combinations were investigated using arc plasma and thermo-hydrodynamic simulation models. Under positive polarity, a copper tool electrode was paired with 304 stainless steel, Ti-6Al-4V, and Inconel 718 workpieces, while copper and tungsten electrodes were compared using a 304 stainless steel workpiece. Simulation results show that material combinations significantly affect anode heat flux and energy distribution, with 304 stainless steel exhibiting the highest heat flux and Inconel 718 receiving the largest energy distribution ratio. Crater depth correlates strongly with heat flux magnitude, while crater diameter is jointly determined by heat flux radius and melt flow dynamics, with the selected cathode material exerting only minor influence. High-speed imaging and crater morphology measurements validate the simulation results, confirming model reliability. These findings provide theoretical guidance for process optimization in EDM. Full article

Ultra-cold neutrons (UCNs) play an important role in the modern frontier of low-energy physics related to fundamental symmetries. They have enabled an improvement of two orders of magnitude in the measurement of the upper limit of the neutron electric dipole moment (nEDM) compared to beam experiments. Further improvements in both the design of UCN sources and nEDM measurements critically depend on the availability and development of materials which satisfy specific requirements. We present innovative materials used for the fabrication of the cryogenic UCN source at the PULSTAR reactor (NC State University, USA) and for the cryogenic non-magnetic environment required for a new high-precision nEDM experiment seeking a further two-orders-of-magnitude improvement in nEDM sensitivity. Full article

Laser directed energy deposition (LDED) can fabricate Ti-6Al-4V thin-walled structures efficiently, but the deposited sidewalls usually contain adhered particles, layer steps, and waviness that limit surface quality. This study combined square-spot laser surface reshaping with machine learning-assisted parameter design to control sidewall roughness. Sixteen single-factor experiments were first conducted to clarify the effects of laser power, scanning speed, spot overlap ratio, and scan number. An 80-sample dataset was then established to train and compare random forest (RF), support vector regression (SVR), and eXtreme Gradient Boosting (XGBoost) models, and SHapley Additive exPlanations (SHAP) were used to interpret feature contributions. RF showed the best predictive performance, with R² = 0.940 and RMSE = 1.760 μm, and was coupled with Bayesian optimization (BO) for inverse parameter design. For a target arithmetic mean roughness (Ra) of 5 μm, the optimized condition was 500 W, 2.57 mm/s, 48.09% overlap, and five scans. The predicted Ra was 5.02 μm, while the validation experiment yielded 5.76 μm, reducing the initial roughness from 28.98 μm by 80.1%. These results demonstrate that interpretable machine learning can support target-driven square-spot laser reshaping for LDED Ti-6Al-4V thin-walled structures. Full article

The Ti6Al7Nb alloy is increasingly applied as a vanadium-free alternative to Ti6Al4V for biomedical implants; however, implant performance is governed predominantly by the physicochemical properties of the surface layer. In this study, anodic oxidation was employed as a controlled surface engineering process to generate a functional oxide layer on Ti6Al7Nb alloy and to modify its structural, chemical, and electrochemical characteristics. The anodically formed surface layer was comprehensively characterized in terms of surface morphology, wettability, microhardness, crystallographic phase composition, electrochemical behavior, and surface chemistry combined with depth profiling analysis. In addition, the biological response of the modified surface was assessed using in vitro cytotoxicity tests. The results confirm the formation of a stable and chemically defined oxide layer with enhanced electrochemical stability and tailored surface properties. The modified surface exhibits improved corrosion resistance, controlled physicochemical parameters, and favorable cytocompatibility. These findings demonstrate that anodic oxidation enables precise engineering of the surface layer and highlight its key role as a functional interface controlling implant–environment interactions, confirming this approach as an effective strategy for the development of advanced Ti-based biomedical implant surfaces. Full article

TiAl alloy exhibits excellent strength, oxidation resistance and creep resistance, making it a preferred candidate material to replace high-temperature alloys. Currently, TiAl alloy has been widely applied in aerospace, the marine industry and other fields involving high-stress contact or highly corrosive environments. Selective laser melting (SLM) technology provides a brand-new approach for the fabrication of TiAl alloys, which enables direct forming of workpieces with complex structures and significantly reduces manufacturing cycles. However, the quality and performance of SLM fabricated TiAl alloys are highly dependent on laser energy input. Therefore, this study fabricated TiAl4822 alloy under different SLM process parameters, and systematically conducted investigations on its tribological properties and electrochemical corrosion behavior. The experimental results show that the SLM process did not alter the basic phase composition of TiAl4822 alloy, with Ti_0.6Al_0.4 as the dominant phase. TiAl4822 alloys fabricated under the parameter combinations of 1000 mm/s + 140 W exhibited outstanding wear resistance, and the wear mechanism transformed from severe adhesion and abrasive wear to mild oxidative wear. When the laser power was 100 W and the scanning speed was 1200 mm/s, the alloy achieved the highest corrosion resistance, with the corrosion potential reaching the maximum value of −390.065 mV and the corrosion current density decreasing to the minimum value of 8.73 × 10⁻⁶ A/cm². Thus, different parameter combinations can realize the optimization of tribological properties and electrochemical corrosion performance respectively. This study lays a theoretical foundation for promoting the high-performance engineering application of this alloy in harsh wear-resistant and corrosion-resistant environments. Full article

To address the challenges of procedural complexity, the lack of an integrated heating–forming capability, and poor formability in the hot forming of titanium alloy skin components, an electrically assisted forming (EAF) process is proposed. A Johnson–Cook constitutive model was established to characterize the flow behavior of Ti–6Al–4V alloy under electric-assisted conditions, achieving a correlation coefficient of 0.968 and an average relative error of 7.67%. Forming parameters were investigated through a combined approach of numerical simulation and experimentation. At a current density of 7.59 A/mm², a forming speed of 1 mm/min, and a friction coefficient of 0.1, the maximum springback of the component was 1.04 mm. Compared with isothermal forming, the EAF process reduced the springback by 7.14% and enhanced the ultimate tensile strength by 5.34%. Microstructural characterization revealed that, under pulsed current, the α-phase grains of the material were refined, whereas the β-phase fraction and the average grain size increased, accompanied by a 15.3% reduction in the geometrically necessary dislocation (GND) density. This study validates the process feasibility of electrically assisted forming for thin-walled titanium alloy skin components. Full article

This research work investigates the machinability of WP7V die steel of very high toughness and wear resistance in turning with a TiAlN-coated carbide tool, with the chip reduction coefficient (CRC) serving as a guide for machining performance and energy requirements. The machining parameters, like cutting speed, feed rate, depth of cut, and machining environment, were assessed to find parameter combinations that encourage established cutting and enhanced chip control. The results illustrate that the CRC is strongly influenced by cutting speed, and at a higher cutting speed (210 m/min), the lowest CRC values are obtained. In dry machining, a medium feed rate (0.1 mm/rev) favors chip breaking, and wet machining results in medium-spiral chips. Long, continuous chips with laminar and sheared surfaces are produced at a low cutting speed (70 m/min). The findings suggest that low CRC values are correlated with stable machining behavior and decreased energy utilization. High cutting speed and the suitable selection of feed rates are needed for the efficient machining of WP7V steel. Full article

A large-size ingot (Φ200 mm × 800 mm) with the nominal composition Ti-46Al-8Nb-2.5V (in at.%) was fabricated via triple vacuum consumable electrode arc remelting in this study. XRD, SEM-EDS, TEM, tensile testing, and chemical analysis were employed to examine phase composition, microstructure, mechanical properties, and impurity contents across the height direction of the large-size ingot. Phase composition differences across different positions arose from the solidification path and elemental distributions. The redistribution of major elements during solid–liquid, allotropic and eutectoid transformations contributed to three types of segregation—namely S-segregation, β-segregation, and α-segregation. The maximum deviations in Al, Nb and V content along the height direction of the ingot were 2.05 at.%, 2.24 at.%, and 0.36 at.%, respectively. The bottom position of the ingot exhibited superior tensile properties at both room and elevated temperatures. The average oxygen and nitrogen contents in the ingot were 717 wt. ppm and 183 wt. ppm, respectively. Full article

In powder-based additive manufacturing (AM), thermal exposure during processing can modify powder surface chemistry and promote oxide growth, even under inert atmospheres from residual oxygen contamination. This study investigates the effect of thermal oxidation on the surface chemistry and triboelectric charging behavior of three AM metal alloy powders: AlSi10Mg, 316L stainless steel (SS 316L), and Ti6Al4V. The work examines the evolution of the oxide layer during baking at 100 and 300 °C using triboelectric charging corroborated by X-ray photoelectron spectroscopy (XPS), diffuse-reflectance spectroscopy, and work-function measurements. The results show that heating modifies the surface oxide state of all powders, with changes dependent on the alloy composition and baking temperature. For AlSi10Mg, heating modified the Al₂O₃-rich surface oxide, with changes consistent with increased oxide ordering and γ-Al₂O₃-like characteristics, with the work function increasing from 4.34 ± 0.01 eV in the as-received (AR) condition to 4.92 ± 0.03 eV after baking at 300 °C. The corresponding triboelectric $n$-exponent increased from 0.91 to 1.38. For SS 316L, transformation of Cr(OH)₃ to Cr₂O₃ reduced triboelectric charge accumulation, while the oxygen concentration increased from 49.92 to 54.87 at.% and the work function decreased from 5.74 ± 0.02 to 5.28 ± 0.04 eV after baking at 300 °C. This reflected a drop in the $n$-exponent from 0.82 for AR to 0.73 at 300 °C. For Ti6Al4V, charging variations were associated with titanium oxide evolution and surface modifications consistent with rutile-related titanium oxide characteristics, with the work function increasing from 5.33 ± 0.01 to 5.44 ± 0.03 eV after baking at 300 °C. The corresponding triboelectric $n$-exponent increased from 0.49 to 0.52. Overall, triboelectric charging is a sensitive approach for detecting thermally driven surface oxide modifications in additive manufacturing powders. Full article

Technological development in surface treatment for biomedical implants has advanced rapidly, yet the integration of additive manufacturing with controlled nano topography remains underexplored. This study investigates a novel bioactive kinetic screw (BKS) produced by 3D printing and CNC machining, followed by different anodization treatments: plasma electrolytic oxidation (PEO), hard anodization (HA), and soft anodization for TiO₂ nanotube (TNT) formation. Scanning electron microscopy revealed that PEO created a uniform macro–micro porous surface with pore sizes ranging from 5–15 µm and porosity values of 22.4 ± 3.2%, while HA produced smaller, less homogeneous pores (0.5–2 µm, porosity 10.7 ± 2.6%). TNTs were successfully formed with an average diameter of 80 ± 12 nm, although distribution was non-uniform in screw grooves. Preliminary finite element analysis demonstrated that Ti6Al4V nanotubes (diameter 50 nm, length 500 nm) withstood applied torque with maximum von Mises stress of 1.5 × 10⁻⁸ N/nm² and maximum strain of 3.56, indicating mechanical resilience compatible with early implant loading. The findings demonstrate that the proposed anodization protocols generate distinct hierarchical surface morphologies on BKS implants while preserving implant geometry. These results provide a structural basis for future investigations of biological performance. Full article

The influence of hydrogenation, mechanical milling, and dehydrogenation parameters on the structure and properties of titanium powders produced from titanium sponge via the hydride–dehydride (HDH) process was investigated. The aim of the study was to compare representative HDH processing routes and identify the processing route that provided the most favorable structural characteristics for subsequent mechanical alloying and powder metallurgy applications. Commercially pure Grade 0 titanium sponge was used as the starting material and was subjected to hydrogenation at temperatures ranging from 350 to 650 °C, short-duration mechanical milling in an argon atmosphere, and vacuum dehydrogenation at temperatures between 750 and 950 °C. The resulting powders were characterized using laser particle size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The results showed that increasing the hydrogenation temperature promoted the formation of the TiH₂ hydride phase and enhanced powder fragmentation during subsequent mechanical milling. XRD analysis demonstrated effective dehydrogenation, as evidenced by the disappearance of detectable TiH₂ reflections and the restoration of the α-titanium phase within the detection limits of the technique. Qualitative SEM observations indicated that the investigated HDH processing routes influenced particle morphology and agglomeration behavior, whereas EDS analysis demonstrated a relatively uniform distribution of the detected elements without revealing detectable contamination within the analyzed regions. Mechanical alloying of the selected powders with aluminum and vanadium showed that, among the investigated processing routes, the H2–M2–D2 condition provided the most favorable combination of particle size distribution, phase composition, morphology, and elemental distribution for the production of a mechanically alloyed Ti–Al–V powder mixture. Full article

To address the strength–ductility trade-off in titanium alloys, a comparative study was conducted on Ti-6Al-4V (TC4) alloys fabricated by laser powder bed fusion (L-PBF) and electron beam powder bed fusion (EB-PBF). The L-PBF specimen primarily consisted of acicular α′ martensite with high residual stress. In contrast, the EB-PBF specimens, owing to a substrate preheating temperature of 740 °C and a reduced cooling rate (10³~10⁵ K/s), exhibited a stable and coarse α + β lamellar structure. Combined with the high oxygen content (0.24 wt.%) that provided solid-solution strengthening, this morphology enabled simultaneous attainment of a yield strength of 1120 ± 12 MPa and an elongation at fracture of 11.1 ± 1.3%. Notably, deformation-induced HCP→FCC phase transformation occurred in EB-PBF alloys, generating a dual-phase HCP/FCC structure that effectively accommodated plastic strain. These results highlight the superior potential of EB-PBF over L-PBF for fabricating titanium alloys with an exceptional strength–ductility synergy. Full article

Contemporary patient-specific subperiosteal implants (SPIs) have re-emerged as digitally planned, additively manufactured solutions for oral and maxillofacial rehabilitation when conventional endosseous implants are limited by severe atrophy, anatomical constraints, or reconstructive defects. Unlike conventional implants, SPIs behave as fixation-based skeletal frameworks whose performance depends on passive fit, screw fixation, anchorage, framework architecture, material properties, manufacturing accuracy, and prosthetic load transfer. This scoping review evaluated the maturity of mechanical design and validation evidence for contemporary SPIs. Following a predefined internal protocol and PRISMA-ScR, MEDLINE/PubMed, Scopus, Web of Science, Embase, and the Cochrane Library were searched from inception to 13 June 2026. Reference-list screening and citation tracking supplemented the electronic search. Two reviewers independently screened records against predefined eligibility criteria. Data were charted using a predefined extraction form and synthesized descriptively by evidence type, engineering domain, validation stage, and translational status. No meta-analysis was undertaken because of methodological heterogeneity, and no formal risk-of-bias grading was applied. Across 65 included records, the evidence was dominated by descriptive technical studies and comparative computational analyses, whereas direct mechanical testing, fatigue assessment, manufacturing verification, and clinical correlation were limited. Finite element analysis was useful for comparing design alternatives and identifying stress concentrations, but models were heterogeneous and often insufficiently validated. Design modifications generally redistributed stress across the implant–prosthesis–bone system rather than reducing it globally. Titanium and Ti6Al4V were the most established framework materials, whereas polymeric, ceramic, and scaffold-assisted strategies remained preliminary. The principal contribution of this review is a cross-domain appraisal of progression from anatomical feasibility and comparative modeling to manufacturing verification, experimental testing, and clinical validation. An evidence map, minimum reporting checklist, and integrated validation pathway are provided to support reproducible device development. Full article

Two design solutions such as modular and mono-block Ti6Al4V porous implants for femoral defect repair were implemented and compared. Static stress analysis on each model was performed via finite element analysis to investigate potential critical elements that might cause system failure under physiological loads. Prior to calculations, a mesh convergence study was realized by varying the minimum element sizes. The entire bone–prosthetic system was modeled, and design optimization was performed. For mono-block implants, a less stressed configuration was found by changing the plate design. Comparison of the maximum Von Mises stress ${\sigma }_{max}$ and equivalent strain ${\epsilon }_{eq}$ between the models allowed for an understanding of the distribution of the loads and identify areas with critical stress concentration. The modular implant appeared to be highly solicited with stress shielding on epiphyses due to enhanced rigidity at the metal/bone interface. Finally, a study of the deformation on cancellous and cortical bone suggested that a more elastic junction with balanced strain delivery to the bone might improve tissue regeneration when using a mono-block implant. Full article

A Fe₅Cu₅V₃₀Ti₃₀Nb₃₀ high-entropy alloy film was designed as a Cr- and Al-free metallic sensing layer for thin-film strain gauges in high-pressure hydrogen environments. CALPHAD calculations predicted a BCC/B2-type phase field, while XRD, EBSD and GIXRD results supported a BCC-type structure without direct confirmation of long-range B2 ordering. Fe₅Cu₅V₃₀Ti₃₀Nb₃₀ films deposited on Si reference substrates at 150 and 300 W retained broad BCC-type diffraction features. The 300 W film showed a more continuous cross-sectional morphology, good metallic conductivity and a comparable nanomechanical response with slightly higher hardness. Device-level tests were then performed using Cr/AlN/Fe₅Cu₅V₃₀Ti₃₀Nb₃₀ TFSGs on 316L stainless-steel substrates. The devices exhibited average absolute apparent zero shifts of 16.08 με in 12 MPa N₂ and 17.79 με in 12 MPa H₂, with an additional H₂-associated apparent response of only 1.71 με. Static tensile tests in 12 MPa H₂ confirmed a linear strain response with a gauge factor of 1.72 ± 0.01. Full article