Search Results (1,295)

Chromium–aluminum nitride (CrAlN) coatings were deposited on polished H13 tool steel substrates using direct current (DC) magnetron sputtering. The Cr/Al composition in the target was varied by inserting either four or eight chromium (Cr) plugs into cavities machined into an aluminum (Al) plate target. Nitrogen was introduced as a reactive gas to facilitate the formation of the nitride phase. Coatings were deposited at substrate bias voltages of −30 V, −50 V, and −60 V to study the combined effects of composition and ion energy on coating properties. Compositional analysis of coatings deposited at a −50 V bias revealed Cr/Al ratios of approximately 0.8 and 1.7 for the 4- and 8-plug configurations, respectively. This increase in the Cr/Al ratio led to a 2.6-fold improvement in coating hardness. Coatings produced using the eight-Cr-plug target exhibited a nearly linear increase in hardness with increasing substrate bias voltage. Cross-sectional scanning electron microscopy revealed a uniform bilayer structure consisting of an approximately 0.5 µm metal interlayer beneath a 2–3 µm CrAlN coating. Surface morphology analysis indicated the presence of coarse microdroplets in coatings with the lower Cr/Al ratio. These microdroplets were significantly suppressed in coatings with higher Cr/Al content, especially at increased bias voltages. This suppression is likely due to enhanced ion bombardment associated with the increased Cr content, attributed to Cr’s relatively higher atomic mass compared to Al. Coatings with lower hardness exhibited greater scratch resistance, likely due to the influence of residual compressive stresses. The findings highlight the critical role of both Cr/Al content and substrate bias in tailoring the tribo-mechanical performance of PVD CrAlN coatings for wear-resistant applications. Full article

Al-Mg-Si (6XXX) series aluminum alloys are widely applied in aerospace and transportation industries. However, exploring how varying compositions affect alloy properties and deformation mechanisms is often time-consuming and labor-intensive due to the complexity of the multicomponent composition space and the diversity of processing and heat treatments. This study, inspired by the Materials Genome Initiative, employs high-throughput experimentation—specifically the kinetic diffusion multiple (KDM) method—to systematically investigate how the pop-in effect, indentation size effect (ISE), and creep behavior vary with the composition of Al-Mg-Si alloys at room temperature. To this end, a 6016/Al-3Si/Al-1.2Mg/Al KDM material was designed and fabricated. After diffusion annealing at 530 °C for 72 h, two junction areas were formed with compositional and microstructural gradients extending over more than one thousand micrometers. Subsequent solution treatment (530 °C for 30 min) and artificial aging (185 °C for 20 min) were applied to simulate industrial processing conditions. Comprehensive characterization using electron probe microanalysis (EPMA), nanoindentation with continuous stiffness measurement (CSM), and nanoindentation creep tests across these gradient regions revealed key insights. The results show that increasing Mg and Si content progressively suppresses the pop-in effect. When the alloy composition exceeds 1.0 wt.%, the pop-in events are nearly eliminated due to strong interactions between solute atoms and mobile dislocations. In addition, adjustments in the ISE enabled rapid evaluation of the strengthening contributions from Mg and Si in the microscale compositional array, demonstrating that the optimum strengthening occurs when the Mg-to-Si atomic ratio is approximately 1 under a fixed total alloy content. Furthermore, analysis of the creep stress exponent and activation volume indicated that dislocation motion is the dominant creep mechanism. Overall, this enhanced KDM method proves to be an effective conceptual tool for accelerating the study of composition–deformation relationships in Al-Mg-Si alloys. Full article

Development of forming methods for surface-coated metals is a current concern due to their economic and environmental advantages. For a successful forming operation, it is necessary that both components, the substrate and the coating, are able to withstand stress without damage until the final shape and dimensions are reached. This goal can be achieved through good knowledge of the elastic and plastic properties of the substrate and the coating, the compatibility between them, the appropriate surface treatment, and the rigorous control of technological forming parameters. Our study was carried out with flat specimens of pre-painted Al 99.0 sheet that were electromagnetically formed by bulging. Forming behavior was investigated as depending on the initial thickness of the substrate, on the aluminum sheet pretreatment, as well as on the plastic deformation path of the metal–paint structure. To verify the damage to the paint layer, tests with increasing strains were performed, and the interface between the metal and the coating layer was investigated by scanning electron microscopy. The obtained results indicate that electromagnetic forming of pre-painted sheets can be a feasible method for specific applications if the forming degree of the substrate is tightly correlated with the type of desired coating and with the pretreatment method used for the metal surface. Full article

Difficult, extreme operating conditions of parabolic antennas under precipitation and sub-zero temperatures require the creation of effective heating systems. The purpose of the research is to develop a multilayer coating containing two metal-ceramic layers, epoxy composite layers, carbon fabric, and an outer layer of basalt fabric, which allows for effective heating of the antenna, and to study the properties of this coating. The multilayer coating was formed on an aluminum base that was subjected to abrasive jet processing. The first and second metal-ceramic layers, Al₂O₃ + 5% Al, which were applied by high-speed multi-chamber cumulative detonation spraying (CDS), respectively, provide maximum adhesion strength to the aluminum base and high adhesion strength to the third layer of the epoxy composite containing Al₂O₃. On this not-yet-polymerized layer of epoxy composite containing Al₂O₃, a layer of carbon fabric (impregnated with epoxy resin) was formed, which serves as a resistive heating element. On top of this carbon fabric, a layer of epoxy composite containing Cr₂O₃ and SiO₂ was applied. Next, basalt fabric was applied to this still-not-yet-polymerized layer. Then, the resulting layered coating was compacted and dried. To study this multilayer coating, X-ray analysis, light and raster scanning microscopy, and transmission electron microscopy were used. The thickness of the coating layers and microhardness were measured on transverse microsections. The adhesion strength of the metal-ceramic coating layers to the aluminum base was determined by both bending testing and peeling using the adhesive method. It was established that CDS provides the formation of metal-ceramic layers with a maximum fraction of lamellae and a microhardness of 7900–10,520 MPa. In these metal-ceramic layers, a dispersed subgrain structure, a uniform distribution of nanoparticles, and a gradient-free level of dislocation density are observed. Such a structure prevents the formation of local concentrators of internal stresses, thereby increasing the level of dispersion and substructural strengthening of the metal-ceramic layers’ material. The formation of materials with a nanostructure increases their strength and crack resistance. The effectiveness of using aluminum, chromium, and silicon oxides as nanofillers in epoxy composite layers was demonstrated. The presence of structures near the surface of these nanofillers, which differ from the properties of the epoxy matrix in the coating, was established. Such zones, specifically the outer surface layers (OSL), significantly affect the properties of the epoxy composite. The results of industrial tests showed the high performance of the multilayer coating during antenna heating. Full article

Aluminum (Al) stress is an important factor that inhibits crop growth in acidic soils and poses a threat to pumpkin (Cucurbita moschata) production. In this study, we investigated the effect of endophyte (endophyte) strain J01 of blueberry (Vaccinium uliginosum) on the growth, development, and transcriptional regulatory mechanisms of pumpkin under aluminum stress. The results showed that the blueberry endophyte strain J01 significantly increased the root length of pumpkin under aluminum stress, promoted the growth of lateral roots, and increased root vigor; strain J01 reduced the content of MDA and the relative conductivity in the root system; strain J01 enhanced the activities of superoxide dismutase and catalase in the root system but inhibited ascorbate peroxidase activity. Transcriptome analysis further revealed that strain J01 significantly regulated the expression of key genes associated with aluminum tolerance, including the upregulation of transporter protein genes (aluminum-activated malate transporter and aquaporin), affecting the gene expression levels of genes encoding antioxidant enzymes (ascorbate peroxidase and glutathione S-transferase) and cell wall modification genes (xyloglucan endotransglucosylase/hydrolase and pectin methylesterase). This study provides a theoretical basis and practical guidance for using microbial resources to improve aluminum tolerance in cucurbit crops. Full article

The polytetrafluoroethylene/aluminum (PTFE/Al) granular composite, a common formulation in impact-initiated energetic materials, undergoes mechanochemical coupling reactions under sufficiently strong dynamic loading. This investigation discusses the dynamic properties and the constitutive relationship of the PTFE/Al granular composite to provide a preliminary guide for the research on mechanical properties of a series of composite materials based on PTFE/Al as the matrix. Firstly, the 26.5Al-73.5PTFE (wt.%) composite specimens are prepared by preprocessing, mixing, molding, high-temperature sintering, and cooling. Then, the quasi-static compression and Hopkinson bar tests are performed to explore the mechanical properties of the PTFE/Al composite. Influences of the strain rate of loading on the yield stress, the ultimate strength, and the limited strain are also analyzed. Lastly, based on the experimental results, the material parameters in the Johnson–Cook constitutive model are obtained by the method of piecewise fitting to describe the stress–strain relation of the PTFE/Al composite. Combining the experimental details and the obtained material parameters, the numerical simulation of the dynamic compression of the PTFE/Al composite specimen is carried out by using the ANSYS/LS-DYNA platform. The results show that the computed stress–strain curves present a reasonable agreement with the experimental data. It should be declared that this research does not involve the energy release behavior of the 26.5Al-73.5PTFE (wt.%) reactive material because the material is not initiated within the strain rate range of the dynamic test in this paper. Full article

Superhydrophobic coatings possess distinct wettability characteristics and hold significant potential in metal corrosion protection and underwater drag reduction. However, their practical application is often hindered by poor durability arising from the fragility of their micro/nanostructured surface roughness. In this study, a durable superhydrophobic coating featuring a hierarchical, hydrangea-like micro/nanostructure was successfully fabricated on an aluminum alloy substrate via a simple one-step cold-spraying technique. The coating consisted of hydrangea-shaped SiO₂ nanoparticles modified with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (PFDT) to produce multiscale roughness, while epoxy resin (EP) served as the binding matrix to enhance mechanical integrity. The hydrangea-like SiO₂ nanostructures were characterized by solid cores and wrinkled, petal-like outgrowths. This unique morphology not only increased the surface roughness but also provided more active sites for air entrapment, thereby enhancing the coating’s overall performance. The h-SiO₂@PFDT-EP composite coating exhibited excellent superhydrophobicity, with a WCA of 170.1° ± 0.8° and a SA of 2.7° ± 0.5°. Durability was evaluated through sandpaper abrasion, tape peeling, acid and alkali immersion, artificial weathering, and salt spray tests. The results demonstrated that the coating retained stable superhydrophobic performance under various environmental stresses. Compared with bare 6061 aluminum and EP coatings, its corrosion current density was reduced by four and three orders of magnitude, respectively. Furthermore, the coating achieved a maximum drag-reduction rate of 31.01% within a velocity range of 1.31–7.86 m/s. The coating also displayed excellent self-cleaning properties. Owing to its outstanding durability, corrosion resistance, and drag-reducing capability, this one-step fabricated superhydrophobic coating showed great promise for applications in marine engineering and defense. Full article

Residual stresses generated during the casting process significantly affect the reliability of the final product, making accurate prediction and analysis of these stresses crucial. In particular, to minimize the difference between simulation results and actual measurements, it is essential to develop predictive simulations that incorporate microstructural characteristics. Therefore, in this study, residual stress prediction simulations were conducted for aluminum components manufactured by high-pressure die casting (HPDC), and measurement locations were selected based on the simulation results. Subsequently, the microstructural characteristics at each location (Si and intermetallic compounds) were quantitatively analyzed, and significant factors affecting residual stress were identified through design of experiments (DOE). As a result, Si sphericity (p-value ≤ 0.05) was observed to be the most significant factor among Si area fraction, IMC area fraction, and Si sphericity, and the residual stress and Si sphericity showed a positive interaction due to the rapid cooling rate and inhomogeneous microstructure distribution. Furthermore, the study demonstrated the effectiveness of DOE in clearly distinguishing the significance of variables with strong interdependencies. Full article

The formation of hot tearing during direct chill casting of aluminum alloys, specifically AA6111, is a significant challenge in the production of ingots for industrial applications. This study investigates the role of hydrostatic pressure and tensile stress in the formation of hot tearing during direct chill casting of rectangular ingots. Combining experimental results and finite element modeling with ABAQUS/CAE 2022, the mechanical behavior of the semi-solid AA6111 alloy was analyzed under different cooling conditions. “Hot” (low water flow) and “Cold” (high water flow) conditions were the two types of cooling conditions that produced cracked and sound ingots, respectively. The outcomes indicate that high tensile stress and localized negative hydrostatic pressure in the hot condition are the main factors promoting the initiation and propagation of cracks in the mushy zone, whereas the improvement of the cooling conditions reduces these defects. Full article

Aluminum (Al) alloys exhibit exceptional mechanical properties, seeing widespread use in various industrial fields. Here, we use a multiscale simulation method combining phase field method, dislocation dynamics, and crystal plasticity finite element method to reveal the evolution law of precipitates, the interaction mechanism between dislocations and precipitates, and the grain-level creep deformation mechanism in 7A09 Al alloy under creep loading. The phase field method indicates that Al alloys tend to form fewer but larger precipitates during the creep process, under the dominant effect of stress-assisted Ostwald ripening. The dynamic equilibrium process of precipitate is not only controlled by classical diffusion mechanisms, but also closely related to the local strain field induced by dislocations and the elastic interaction between precipitates. Dislocation dynamics simulations indicate that the appearance of multiple dislocation loops around the precipitate during the creep process is the main dislocation creep deformation mechanism. A crystal plasticity finite element model is established based on experimental characterization to investigate the macroscopic creep mechanism. The dislocation climb is hindered by grain boundaries during creep, and high-density dislocation bands are formed around specific grains, promoting non-uniform plastic strain and leading to strong strain gradients. This work provides fundamental insights into understanding creep behavior and deformation mechanism of Al alloy for deep-sea environments. Full article

This study investigates the fabrication and residual stress behavior of a 0.5 wt.% graphene-reinforced AA2195 aluminum matrix composite, developed for advanced aerospace structural applications. The composite was synthesized via squeeze casting, followed by a multi-pass hot rolling process and subsequent T8 heat treatment. The evolution of residual stress was systematically examined after each rolling pass and during thermal treatments. The successful incorporation of graphene into the matrix was confirmed through Energy-Dispersive Spectroscopy (EDS) analysis. Residual stress measurements after each pass revealed a progressive increase in compressive stress, reaching a maximum of −68 MPa after the fourth hot rolling pass. Prior to the fifth pass, a solution treatment at 530 °C was performed to dissolve coarse precipitates and relieve internal stresses. Cold rolling during the fifth pass reduced the compressive residual stress to −40 MPa, and subsequent artificial aging at 180 °C for 48 h further decreased it to −23 MPa due to recovery and stress relaxation mechanisms. Compared to the unreinforced AA2195 alloy in the T8 condition, which exhibited a tensile residual stress of +29 MPa, the graphene-reinforced composite in the same condition retained a compressive residual stress of −23 MPa. This represents a net improvement of 52 MPa, highlighting the composite’s superior capability to retain compressive residual stress. The presence of graphene significantly influenced the stress distribution by introducing thermal expansion mismatch and acting as a barrier to dislocation motion. Overall, the composite demonstrated enhanced residual stress characteristics, making it a promising candidate for lightweight, fatigue-resistant aerospace components. Full article

The initiation of ductile fractures in medium-strength AW5754 and high-strength AW6082 aluminum alloys at different quasi-static strain rates and under multiaxial stress states was investigated through a series of tensile tests using various specimen geometries. The sensitivity of the stress triaxiality locus to variations in the loading rate was examined for these two aluminum alloy families. Fractographic and elemental analyses were also conducted via SEM and EDS. Numerical simulations based on the finite element method (FEM) were performed using ABAQUS/Standard to determine the actual stress triaxialities and the equivalent plastic strains at fracture. The numerical approach was validated by comparing the simulation results with the experimental findings. These simulations facilitated the generation of a stress triaxiality locus through a curve-fitting process. Among the considered fitting functions, an exponential function was selected as it provided the most accurate relation between the equivalent plastic strain at fracture and the corresponding stress state across different strain rates. The results reveal different strain rate dependencies for the two alloys within a very low strain rate range. The resulting stress triaxiality loci provide a valuable tool for predicting fracture strains and for more accurately evaluating stress states. Overall, the findings of this study significantly advance the understanding of the fracture initiation behavior of aluminum alloys under multiaxial loading conditions and their sensitivity to various quasi-static loading rates. Full article

The increasing release of nanoparticles into aquatic environments, particularly via wastewater, raises concerns about their biological effects on microbial communities. This study investigated the molecular response of Pseudomonas putida to aluminum oxide nanoparticles (Al₂O₃NPs) under controlled conditions and in synthetic wastewater, both before and after biological treatment. Acute toxicity was evaluated using growth inhibition assays, while the expression of katE, ahpC, and ctaD—genes associated with oxidative stress and energy metabolism—was quantified via RT-qPCR. Exposure to pristine Al₂O₃NPs induced a strong, time-dependent upregulation of all tested genes (e.g., katE and ahpC up to 4.5-fold). In untreated wastewater, this effect persisted but at a lower intensity; bulk Al₂O₃ caused only moderate changes. Treated wastewater samples showed markedly reduced gene expression, indicating partial detoxification. Nanoparticles elicited stronger biological responses than their bulk counterparts, confirming the material form-specific effects. Comparative analysis with Daphnia magna revealed similar patterns of oxidative stress gene activation. These findings highlight the influence of nanoparticle form and environmental matrix on microbial responses and support the use of gene expression analysis as a sensitive biomarker for nanoparticle-induced stress in environmental risk assessment. Full article

In this paper, dedicated material models were developed and verified for three melts of EN AW-7021 alloy, differing in zinc and magnesium content, for tube extrusion conditions. Based on the plastometric tests, it was found that in the studied range of strain parameters, the analyzed melts of the same aluminum alloy showed different sensitivity to strain rate and temperature. In addition, a significant effect of magnesium and zinc content on the plasticity of the tested material was observed. Therefore, dedicated material models describing stress changes were developed for each melt analyzed. The models were then implemented into the material database of the QForm-Extrusion^® program, which was used for the theoretical analysis of the industrial extrusion process. In order to verify the results of numerical calculations, industrial tests of the extrusion process were carried out. The force parameters and the rate of the extrusion process were mainly analyzed. The use of dedicated material models for each melt contributed to the accuracy of numerical modeling. A high degree of compliance was obtained regarding the theoretical and experimental extrusion force and the velocity of metal flowing out of the die cavity, among others. Full article

Type IV composite overwrapped pressure vessels (COPVs) store hydrogen at pressures up to 70 MPa and must meet stringent safety standards through physical testing. However, full-scale burst, plug torque, axial compression, impact, and drop tests are time-consuming and costly. This study proposes a unified finite element analysis (FEA) workflow that replicates these mandatory tests and predicts failure behavior without physical prototypes. Axisymmetric and three-dimensional solid models with reduced-integration elements were constructed for the polyamide liner, aluminum boss, and carbon/epoxy composite. Burst simulations showed that increasing the hoop-to-axial stiffness ratio shifts peak stress to the cylindrical region, promoting a longitudinal rupture—considered structurally safer. Plug torque and axial load simulations revealed critical stresses at the boss–composite interface, which can be reduced through neck boss shaping and layup optimization. A localized impact with a 25 mm sphere generated significantly higher stress than a larger 180 mm impactor under equal energy. Drop tests confirmed that 45° oblique drops cause the most severe dome stresses due to thin walls and the lack of hoop support. The proposed workflow enables early-stage structural validation, supports cost-effective design optimization, and accelerates the development of safe hydrogen storage systems for automotive and aerospace applications. Full article