Search Results (25,476)

The growing demand for improved operational efficiency of cast components used in various types of equipment necessitates the development of advanced casting technologies. One of the key challenges currently faced by the foundry industry is enhancing the surface quality of castings and reducing rejection rates caused by casting defects. These requirements can be effectively met by castings produced using shell mold casting technology. Sand–resin mixtures are used for their production. Foundry molds made from such mixtures make it possible to obtain high-quality castings from various alloys. However, their widespread industrial application is limited by the relatively high cost of the binder, namely pulverbakelite. The influence of pulverbakelite content on the properties of sand–resin mixtures during shell mold formation under variational static pressure was investigated. It was established that pressure variation during the molding process increases mold strength and improves surface quality while maintaining the required level of gas permeability. The optimal binder content was determined to be 4–6%, which makes it possible to reduce binder consumption without deteriorating the mechanical and technological characteristics of the mold. With respect to novelty, it should be noted that previous studies addressed individual aspects of variable pressure application. In the present article: a wider range of pulverized bakelite content (3–9%) was investigated; the relationship between binder content, strength, and gas permeability was established; the optimal binder content range (4–6%) was determined; and microstructural analysis was extended to include composition and pressure regimes. Thus, the present work significantly extends previous findings and provides a more comprehensive investigation. Full article

To remove the oxide layer of TC1 titanium alloys in an environmentally friendly and efficient manner, this study conducted experiments using a nanosecond pulsed laser to systematically investigate the influence of different laser energy densities on the cleaning effect. The results showed that the oxide layer could be completely removed at an energy density of 6.37 J/cm², with the surface oxygen element content reduced to 4.87%. The macroscopic surface presented a silvery metallic luster. Moreover, the roughness decreased significantly with the increase in energy density. At 6.37 J/cm², the surface roughness dropped to 0.37 µm. The mechanism of removing the oxide layer of TC1 titanium alloy mainly includes laser ablation and plasma impact. At energy densities ranging from 2.55 J/cm² to 6.37 J/cm², the cleaning mechanism was mainly laser ablation. When the energy density exceeded 6.37 J/cm², the cleaning mechanism gradually shifted from laser ablation to plasma impact as the dominant factor. Meanwhile, the microhardness of the samples after laser cleaning was basically consistent with that of the samples subjected to mechanical grinding, which provides a basis for a nanosecond pulsed laser to replace traditional methods for oxide layer cleaning. Full article

Ti-6Al-4V parts fabricated via selective laser melting (SLM) often exhibit severe surface irregularities that limit their direct engineering application. This study proposes a top-hat beam laser polishing method to improve surface quality. The results show that surface roughness (Sa) is reduced to 0.48 μm, a 95.3% decrease from the as-built condition. The uniform energy distribution of the top-hat beam stabilizes melt pool behavior, enabling effective surface leveling through valley filling and lateral melt flow. In contrast, Gaussian beam polishing induces strong Marangoni convection and wake effects, resulting in higher residual roughness. Microstructural analysis indicates an increased fraction of equiaxed α grains and a β-phase content of ~6% after top-hat polishing. The heat-affected zone likely exhibits a subcritical heat-treatment-like effect, promoting fine secondary α precipitation. Additionally, localized stresses induced by steep thermal gradients during SLM are effectively relieved. Overall, top-hat laser polishing is a promising post-processing technique for enhancing the surface quality of Ti-6Al-4V components. Full article

High-grade non-oriented silicon steel is a critical material for new energy vehicles and energy-efficient appliances due to its superior magnetic properties. However, these properties are significantly degraded by non-metallic inclusions, particularly Ti(C,N). This study employs integrated thermodynamic and kinetic calculations to systematically analyze the formation and growth mechanisms of Ti(C,N) inclusions in high-grade non-oriented silicon steel, trace the sources of [Ti], and propose targeted theoretical control strategies. Results indicate that Ti(C,N) inclusions do not precipitate above the liquidus temperature (1779 K). During solidification, microsegregation enriches Ti, C, and N; however, only TiN precipitates in the final stage as its ion product exceeds the solubility limit, whereas TiC remains undersaturated—findings valid within the present composition window and modeling framework. Inclusion size is governed by cooling rate and initial Ti/N content, where higher cooling rates yield finer inclusions and lower Ti/N content suppresses precipitation. Titanium originates from primary sources (raw materials and alloys) and secondary sources (decomposition or reduction of TiO₂ in slag/refractories). Therefore, mitigating [Ti] requires strictly limiting primary input and suppressing secondary formation through optimized process control, such as reducing BOF slag carryover, lowering refining temperature, and controlling [Al] content. Full article

Ti alloys are widely used in aerospace and biomedical fields due to their high mechanical properties under severe loading. Interest in additively manufactured Ti6Al4V has increased, but further research is needed to fully characterize their properties. This work compares the effects of surface properties, internal defects, microstructure, hardness, and Hot Isostatic Pressing (HIP) or Vacuum Heat Treatment (VHT) on the fatigue behavior of Ti6Al4V produced by Selective Laser Melting (SLM) and Electron Beam Melting (EBM). Printing parameters and post-processing were optimized to achieve high density and minimal porosity, providing a solid basis for realistic fatigue comparisons. Samples were characterized in terms of microstructure (optical microscopy and SEM), mechanical properties (hardness mapping), surface texture (confocal microscopy), and internal defects (image-based analysis). Uniaxial fatigue limits were determined by a Dixon-Mood staircase method, and failed specimens were analyzed for fracture surfaces and defect areas. Applied load on flaws was evaluated to identify root causes of fatigue failure. Results showed that fatigue of as-printed samples is governed by surface roughness, while machined specimens are controlled by internal defect size. Machining increased the fatigue limit roughly threefold, and HIP further improved it by 10–20% by reducing internal porosity. In conclusion, with properly optimized melting parameters, both EBM and SLM produce similar mechanical performance at comparable roughness, supporting their use for structural components. Full article

Seafloor hydrothermal systems at mid-ocean ridges are focal points for heat and matter exchange between the seawater and lithosphere. While seafloor seismographs (OBS) and pressure recorders (BPR) are standard for regional monitoring, achieving high-precision, vertical sub-surface data in complex hydrothermal terrains remains a significant technical objective. This study presents a novel in situ penetration probe designed for multi-parameter monitoring of marine hydrothermal vent areas. A key innovation of this work is its operational versatility and engineering efficiency: the probe is specifically designed for post-drilling deployment in boreholes, effectively utilizing existing coring sites to achieve direct coupling with the deep-seated crust, or for targeted placement via Remotely Operated Vehicles (ROVs). The device integrates a titanium-alloy conical tip and cylindrical chamber, housing tri-axial accelerometers and dual temperature-pressure sensors. Numerical simulations using the SST k-ω turbulence model and finite element analysis optimized the cone aperture and assessed fluid–structure stability under deep-sea conditions. Laboratory vibration tests and shallow-water sea trials validated the probe’s basic dynamic response, electromechanical integrity, and capability to acquire coupled environmental parameters. This compact, modular design provides a scalable and cost-effective framework for precise three-dimensional observation of sub-surface hydrothermal processes and deep-sea resource exploration. Full article

Silicon-doped diamond-like carbon (Si-DLC) coatings against aluminum alloy (A5052) were investigated for reducing friction under humid conditions. The coatings were deposited on high-speed steel (SKH51) substrates using a bipolar-type plasma-based ion implantation and deposition (PBII&D) technique, with Si content controlled by varying the tetramethylsilane (TMS)-to-toluene precursor ratio. Structural characterization by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the progressive evolution of Si–C bonding with increasing TMS ratio. The Si-DLC coating with Si 5.0 at.% exhibited the lowest coefficient of friction (COF) of 0.033 and reduced wear volume under a high normal load of 150 N in humid conditions (relative humidity > 90%). However, Si-DLC coatings with higher Si contents (Si 7.7 and 14.3 at.%) led to deteriorated tribological performance, including coating delamination and severe wear. Surface analyses of the coatings revealed that the low-friction behavior was associated with the presence of oxidized Si species at the outermost surface, which undergo hydroxylation in humid environments to form Si–OH groups. These hydroxylated surfaces promote the formation of a hydrated boundary layer that provides a low-shear sliding interface. Full article

Based on the thermodynamic design of metallurgical reduction, this paper investigates the thermodynamic principles and reaction regulation mechanism of aluminothermic self-propagating reduction for the in situ synthesis of a Ti₄₅Al₈Nb (at%) titanium–aluminum–niobium alloy. The influence of the aluminum distribution coefficient (ADC) on the self-propagating reaction process was verified via high-temperature thermal state experiments. The results show that the thermodynamically predicted trends of phase composition and alloy composition are consistent with the experimental results, with only a ~20% lateral offset in the ADC. When the ADC is set to 0.8, the mass fractions of Ti, Al, Nb, O, and N in the alloy are 51.8%, 29.5%, 17.4%, 1.2%, and 0.0016%, respectively, with a homogeneous microstructure and inclusion size no larger than 8 µm. The alloy presents a typical coarse-grained structure, where 83.1% of the total grain boundary length is low-angle grain boundaries, and the <111> orientation is dominant. A low-energy coherent interface is formed between the Ti-enriched and Nb-enriched regions by TiAl, TiAl₃ and Al₃Nb phases, which enhances the structural stability of the alloy. Full article

Metallurgical-grade silicon (MG-Si) is an important source material for many industrial applications, including the manufacture of alloys, solar photovoltaics, and electronics. The process to refine raw materials into MG-Si is energy-intensive, with the predominant method of submerged-arc furnaces requiring energy consumption of approximately 11–13 kWh/kg Si. Recent research has discussed promising methods for reducing the energy required for the silicon production process, including the use of molten-salt electrolysis (MSE), a technique that offers potential savings in energy consumption without requiring carbon inputs for the process. This paper presents a techno-economic study of a potential industrial-scale MSE plant for MG-Si production to evaluate the trade-offs between capital and operating costs of the system. Capital costs are sourced from recent MG-Si plants and an existing cost model developed for MSE processes that includes the size of the plant and the operating temperature among its inputs. The results show that MSE technology has the potential to be an economically cost-competitive option for MG-Si production if the technology successfully scales to industrial production and matures enough to allow for financing costs similar to that of a comparably sized submerged-arc furnace plant. Full article

In the 21st century, the desire for improved fuel efficiency of engines, lower fuel prices, and the need to reduce greenhouse gas emissions such as ${\mathrm{C}\mathrm{O}}_2$ and ${\mathrm{N}\mathrm{O}}_{\mathrm{x}}$ are leading the aviation industry to seek hybrid-electric jet engines for commercial aircraft. These aircraft will have greater maintenance challenges due to additional components requiring more reliable materials for the engine’s parts, such as turbine blades. Turbine blades must be composed of materials that have enhanced fatigue performance. Resistance to dynamic loads and high strength will be needed to ensure modern gas turbine blades are as reliable as possible. This review paper examines hybrid-electric engine turbine blades and subsequently introduces additive manufacturing (AM) and multi-principal element alloys (MPEAs) with a focus on laser powder bed fusion (LPBF), high-entropy alloys (HEAs), and medium-entropy alloys (MEAs). The tensile properties of LPBF HEAs range from 5 to 47% elongation and a UTS of 572–1640 MPa, while LPBF MEAs range from 8 to 73.9% and a UTS of 573–1382 MPa. This study focused on dynamic and fatigue properties while acknowledging gaps in high-temperature testing. The combination of mechanical properties with the ability to control internal geometry makes these AM alloys an attractive option for the next generation of gas turbine blades. Full article

Magnesium alloys are promising materials for orthopedic applications due to their biodegradability and mechanical properties compatible with bone. However, their rapid degradation in physiological environments limits clinical use. In this study, WE43B magnesium alloy was coated with a PEO layer followed by a P(L/G/TMC) polymer applied via ultrasonic spraying. The influence of polymer layer number (10, 20, 30) on coating properties was systematically investigated. Scanning electron microscopy (SEM) analysis revealed an approximately fourfold reduction in porosity after polymer deposition, with progressive pore filling at higher layer numbers, while Fourier transform infrared spectroscopy (FT-IR) mapping indicated uniform polymer coverage. Compared to PEO alone, polymer-modified samples exhibited an approximately 7-fold increase in water contact angle, a ~50% reduction in surface roughness, and improved adhesion. Degradation-related analyses, including ion release, post-immersion SEM, and scanning acoustic microscopy (SAM), indicated that increasing polymer thickness effectively limited degradation processes. Ion release decreased by ~40–50% for the 30-layer coating compared to PEO, with the most pronounced reduction observed between the uncoated PEO and polymer-modified samples. These results demonstrate that the number of polymer layers plays a key role in controlling the barrier properties and stability of hybrid PEO/polymer coatings under simulated physiological conditions. Full article

Graphene solution was spin coated onto an aluminum substrate to investigate its tribological behavior compared to bare 6082–T6 aluminum alloy. The coefficient of friction (COF) was measured for varying loads (1–5 N) and sliding speeds (0.05–0.25 m/s) using a pin-on-disk tribometer in a ball-on-flat configuration. Results indicated that, under all tested conditions, the graphene coating reduced the COF by more than 70–80% compared to uncoated aluminum. Specifically, at 0.25 m/s and 1 N, the COF decreased from approximately 0.63 for uncoated aluminum to about 0.13 for the coated sample. The samples were analyzed using optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS), providing insights into morphology and composition. Furthermore, the coated samples exhibited a stable friction regime, with COF values consistently in the range of 0.10–0.15, while uncoated samples showed higher and more fluctuating values between 0.40 and 0.60. The graphene coating reached steady-state conditions within the first 50 m of sliding, in contrast to the pronounced running-in behavior of uncoated aluminum. SEM and EDS analyses confirmed the formation of a graphene transfer layer on the counterface, which maintained low friction even after partial coating removal. Additionally, the average coating thickness was approximately 15 μm, and the coating significantly reduced adhesive wear and material transfer, demonstrating its effectiveness as a sacrificial, self-lubricating tribological layer. Full article

Biomedical Ti–Nb–Zr–Si alloys containing 12 and 18 wt.% Nb were fabricated by electron beam melting and subjected to thermomechanical processing, including forging, cross-helical rolling, and subsequent cooling or quenching. The effects of Nb content and processing route on phase composition, microstructure, and mechanical properties were systematically investigated using X-ray diffraction, scanning electron microscopy, and tensile testing. The results indicate that increasing Nb content promotes stabilization of the metastable α″ phase, leading to a significant reduction in elastic modulus. The Ti–18Nb–4Zr–1Si alloy exhibited a modulus of ~60 GPa after rolling, which further decreased to ~40 GPa after additional quenching. In contrast, the Ti–12Nb–4Zr–1Si alloy showed higher values of 76–94 GPa due to the predominance of the α′ phase. Both alloys demonstrated a favorable combination of strength and ductility. Microstructural analysis revealed the formation of silicides, whose type and morphology depend on Nb content and processing conditions. The Ti–12Nb–4Zr–1Si alloy predominantly contains (Ti,Zr)₅Si₃, whereas the Ti–18Nb–4Zr–1Si alloy exhibits complex silicides composed of (Ti,Zr)₅Si₃ and (Ti,Zr)₃Si phases. These results highlight the potential of controlling phase composition and silicide evolution to tailor mechanical properties, particularly the elastic modulus, for biomedical applications. Full article

Controlling the microstructure of electroless nickel coatings is crucial for optimizing the interfacial properties of carbon fibers. However, a systematic understanding of how dispersants can effectively leverage the refining effect of nanoparticles in composite plating systems remains lacking. This paper proposes the use of a composite dispersant, comprising polyethylene glycol (PEG) and sodium methylene bis-naphthalene sulfonate (NNO) at a 1:1 mass ratio, for nano-Al₂O₃ to achieve microstructure refinement of nickel coatings on carbon fiber surfaces. The results demonstrate that the composite dispersant modifies the surface state and dispersion stability of Al₂O₃ particles through synergistic adsorption, thereby regulating the nucleation and growth behavior of the Ni-P alloy. At an optimal composite dispersant concentration of 3 g/L, the coating exhibits the most compact structure, with Ni-P particle size refined to approximately 181 nm. The coating consists of two phases: crystalline Ni₃P and amorphous Ni-P. The dual adsorption effect of the dispersant—inhibiting Al₂O₃ agglomeration while improving the surface wettability of carbon fibers—is key to enhancing the refinement efficiency. Conversely, excessive dispersant addition leads to deteriorated coating quality. This study provides experimental evidence for understanding the multiphase interfacial interaction mechanism involving organic additives, nanoparticles, and metal deposition, and offers a novel strategy for controlling the surface functionalization of carbon fibers. Full article

In this paper, a novel high-shielding-effectiveness energy-selective surface (HSE–ESS) is proposed. In previous solutions regarding energy-selective surfaces (ESSs) presented in the literature, PIN diodes are usually employed as nonlinear transmission components; however, these diodes may be burnt by powerful high-power microwave (HPM) beams, causing ESSs to lose their shielding effectiveness (SE). To date, no studies have focused on maintaining the SE performance of ESSs after PIN diode failure. To address these limitations, we introduce shape memory alloys (SMAs) into ESS design. The consequences of PIN diode failure are offset by the physical deformation of SMA components caused by high-amplitude-current heating. This characteristic, featuring 30 dB SE, can be defined as high shielding effectiveness (HSE). After completing the design and performing accurate numerical simulations, we fabricated a prototype using PCB technology and characterized it in an anechoic environment, verifying the overall method. In particular, the SMA components proved to be an effective medium for guaranteeing electrical continuity under thermal stress conditions, thus paving the way for their extended adoption in ESSs by substituting or acting as a back-up for PIN diodes. Overall, this approach enhances the reliability and SE of ESSs by adding SMA components. Full article