Search Results (943)

The application of aluminium-based metallic phase change materials (mPCMs) in latent heat thermal energy storage is limited by the poor compatibility of molten alloys with conventional stainless steel containers. This work evaluates thermally sprayed oxide coatings deposited directly on 304 stainless steel as protective barriers for molten Al–Si and Al–Cu–Si phase change materials. Alumina (Al₂O₃), zirconia (ZrO₂) and Al₂O₃/ZrO₂ (60/40 wt. %) coatings were produced by atmospheric plasma spraying (APS) and high-velocity suspension flame spraying (HVSFS) and assessed through coating characterisation, long-term static compatibility tests, thermal cycling experiments and thermal contact resistance measurements. APS coatings exhibited a pronounced dependence of coating thickness on spray angle, whereas the HVSFS coating provided a more uniform thickness distribution. After two weeks of static exposure, no reaction layer formation, coating dissolution or detectable elemental interdiffusion was observed for the investigated coating systems. For the Al₂O₃/Al–12.3 wt. % Si system, no coating degradation or interfacial reaction was detected after approximately 300 thermal cycles. Furthermore, average liquid thermal contact resistances of 0.31 × 10⁻³ and 0.39 × 10⁻³ m² K W⁻¹ were measured for smooth and rough Al–Si/coating interfaces, respectively. These results demonstrate that thermally sprayed oxide coatings can effectively protect stainless steel from molten aluminium-based PCMs while providing design-relevant data for the development of high-temperature latent heat thermal energy storage systems. Full article

Friction stir welding of T- and corner-joint configurations is challenging due to restricted tool accessibility, complex material flow and the limited availability of material for the formation of load-bearing fillet-weld geometries. This study introduces wire-based corner fillet friction stir welding (W-CFFSW), a solid-state joining process in which filler wire is continuously transported, plasticised and supplied into the internal corner region through a rotating extrusion screw. A stationary shoulder confines and shapes the deposited material, enabling the formation of fillet welds with a defined throat thickness. Single- and double-sided fillet-weld geometries were produced in 3.0 mm thick EN AW-6082-T6 sheets using EN AW-6082 filler wire. A throat thickness of 4.5 mm was successfully generated by adapting the supplied filler volume to the targeted fillet geometry. Metallographic investigations revealed characteristic FSW microstructural zones and pronounced material flow within the weld nugget zone, while no macroscopic pores or voids were observed in the investigated cross-sections. The hardness distribution exhibited the characteristic W-shaped profile of precipitation-hardenable aluminium alloys. Bending tests showed no separation of the bonding interfaces, with cracking occurring in the adjacent sheet material rather than within the fillet welds. Tensile strengths of 231.55 MPa and 217.49 MPa were achieved for stiffener- and stringer-loaded specimens, corresponding to joint efficiencies of 66 % and 62 %, respectively. The results demonstrate that W-CFFSW enables the controlled addition of filler material to produce mechanically load-bearing fillet welds with a defined throat thickness and represents a promising alternative to existing friction-stir-based T- and corner-joint processes. Full article

Electromagnetic stirring is an established strategy for improving the quality of continuously cast metals. In thin aluminium slabs, however, its implementation is constrained by short solidification length, limited installation space, and magnetic-field distortion caused by surrounding metallic components. This work presents a staged design assessment of three compact electromagnetic stirring configurations conceived for the Wheel and Belt continuous casting line of Continuus-Properzi S.p.A. Harmonic electromagnetic simulations were performed for all three configurations, whereas a coupled steady-state, isothermal electromagnetic–fluid-dynamic analysis, based on a fully liquid melt assumption, was carried out only for the axial-flux configuration. Qualitative experiments on a low-melting-point GaInSn alloy were used as proof-of-concept support for the predicted stirring patterns, rather than as a full quantitative validation of the industrial process. Because the three configurations were investigated at different levels and under different operating conditions, the results do not establish a quantitative performance ranking. The axial-flux configuration was selected for further development based on its compactness, integration feasibility, and the circular flow topology obtained numerically and observed qualitatively. Future work will focus on quantitative velocity measurements, transient and thermo-solidification modelling, and industrial-scale validation. Full article

Fiber–metal laminates (FMLs) are hybrid structures manufactured using alternating layers of aluminium alloy and epoxy-reinforced E-glass fabric, with the stacking sequence [Al/Glass/Al/Glass/Al], offering high specific strength, fatigue resistance, and damage tolerance. However, structural cutouts generate stress concentrations that can significantly affect the mechanical performance and damage behavior of these hybrid polymer-based laminates. This study develops and validates analytical cohesive zone models (CZMs) for predicting stress fields around circular and elliptical cutouts in FML plates, providing a computationally efficient analysis. Tensile specimens with two thicknesses (1.4 and 1.7 mm) were investigated using two cohesive laws: linear, and exponential softening. Model predictions were assessed against experimental results using stress concentration factors. The exponential cohesive law provided the best overall agreement, with Root Mean Square Error (RMSE) values of 24.87 and 20.99 MPa and R² values of 0.281 and 0.311 for the 1.4 and 1.7 mm laminates, respectively. Experimental stress concentration factors ranged from 1.88–3.70 and 2.04–3.51 for the two thicknesses. Elliptical cutouts aligned with the loading direction produced lower stress concentrations, whereas minor-axis alignment resulted in higher concentrations. Increasing laminate thickness improved prediction accuracy. The proposed analytical CZM provides an efficient approach for evaluating stress concentrations and damage-related behaviour in perforated polymer-based FMLs, with potential application in the design and optimization of lightweight composite structures. Full article

Hungary’s automotive industry depends largely on imported primary aluminium, while domestic end-of-life vehicle (ELV) streams may offer a lower-impact alternative. This study evaluates the environmental benefits and physical availability of domestically recycled post-consumer aluminium for automotive manufacturing. A parameterised cradle-to-gate life cycle assessment using publicly documented environmental factors and foreground parameters compares a European primary-aluminium consumption-mix route with Hungarian ELV recovery, alloy-specific sorting, quality screening, remelting, primary-aluminium dilution, and domestic transport. The functional unit is 1 kg of automotive wrought-alloy aluminium feedstock delivered to the Győr plant gate. The primary and secondary routes produce 10.124 and 0.472 kg CO₂-eq/kg, respectively, representing a 95.3% reduction under the parameterised baseline inventory. For an illustrative demand of 100,000 t/year, increasing recycled content from 25% to 75% yields approximately 483 kt CO₂-eq/year in additional modelled savings. A 100,000-iteration Monte Carlo analysis gives a 95% simulation interval of approximately 398–569 kt CO₂-eq/year. However, under central assumptions, domestic ELV streams provide only approximately 16,300 t/year of quality-assured secondary aluminium. This corresponds to a maximum domestic ELV-derived recycled-content level of approximately 16.3% of the illustrative annual demand and an associated maximum annual saving of approximately 157.5 kt CO₂-eq/year. Domestic ELV streams alone are therefore insufficient for even the 25% scenario. The secondary pathway remains substantially lower in modelled cradle-to-gate GWP across the tested parameter ranges, but the baseline inventory does not separately quantify several secondary-route activities—including shredding electricity, alloy-sorting energy, LIBS operation, chemical testing, and individual alloying-element additions. An additional-burden sensitivity parameter shows that the primary-to-secondary comparison remains directionally stable even when a substantial additional burden is added to the secondary pathway. Implementation of higher recycled-content levels would therefore require improved recovery capacity, alloy-quality control, and supplementary regional sourcing. This reproducible framework supports circular aluminium strategies under alternative regional and facility-specific assumptions. Full article

Wire Arc Additive Manufacturing (WAAM) based on Cold Metal Transfer (CMT) welding produces near-net-shape metallic components, but post-process machining remains essential for dimensional accuracy and surface quality. This study investigates the dry turning machinability of EN AW-5083 aluminium alloy parts produced by CMT-based WAAM, focusing on tool-holder temperature (T_th) as a relative thermal indicator and surface roughness. T_th was monitored with a K-type thermocouple embedded in the tool holder and an Arduino-based data acquisition unit, while surface roughness (R_a) was measured with a portable contact profilometer after each pass. Three machining parameters—cutting speed, feed rate, and depth of cut—were investigated using a Taguchi L18 orthogonal array, with significance assessed through S/N ratio analysis and ANOVA. Grey Relational Analysis (GRA) was applied for multi-response optimisation, benchmarked against published machinability data for wrought and WAAM-fabricated aluminium alloys. Surface roughness was governed predominantly by feed rate, while T_th was most strongly influenced by depth of cut. The combined Taguchi–GRA optimisation identified a parameter set minimising both responses simultaneously. Benchmarking against three literature sources showed that the surface roughness achieved for the investigated CMT-WAAM material falls within the range reported for wrought EN AW-5083 under comparable machining conditions. These findings provide practical guidance for post-process machining of WAAM-produced aluminium components in hybrid manufacturing chains. Full article

The premature degradation of aluminium extrusion dies remains one of the major challenges affecting process efficiency, product quality, and tooling costs. Although numerous studies have investigated wear mechanisms and proposed solutions such as surface treatments, coatings and lubrication, the absence of a generic and reproducible laboratory methodology for evaluating tribological performance under representative extrusion die contact conditions limits the objective and systematic comparison of alternative tribological solutions. This study proposes and experimentally validates a generic tribological methodology for laboratory simulation of aluminium extrusion die contacts. Rather than reproducing the complete extrusion process, the methodology isolates the dominant physical mechanisms governing die degradation and reproduces their essential characteristics under controlled laboratory conditions, providing a representative platform for systematic tribological investigations. The methodology was developed through the selection and scaling of representative contact parameters, including contact geometry, normal load, sliding velocity and operating temperature. The experimental programme incorporated physical similarity principles, a controlled run-in procedure and repeated use of the same hardened steel counterface to reproduce cumulative die exposure under successive aluminium contacts. Two aluminium alloys (AA6063 and AA6082) were evaluated using a small ring-on-disc configuration against a hardened GCr15 steel counterface. Experimental validation was carried out using two extrusion lubricant systems, complemented by three additional commercial lubricants to assess the robustness and general applicability of the proposed methodology. The experimental results demonstrate that the proposed methodology provides repeatable and sufficiently sensitive measurements of friction and wear, allowing clear differentiation between lubricant systems and aluminium alloy–lubricant combinations while maintaining representative contact conditions. The study also demonstrates that steady-state friction should be identified from the actual friction evolution rather than by applying a fixed averaging interval. Although lubricant evaluation is employed here as the experimental validation case, the proposed methodology is intended as a generic experimental framework applicable to the assessment of surface treatments, coatings, tool materials, lubrication systems, and other tribological strategies aimed at extending extrusion die service life. Full article

Deposit return systems (DRS) can increase the capture of beverage packaging, but material circularity is not determined by return rate alone. A returned container contributes to high-value circularity only if it passes recognition, sorting, pre-processing, and material-specific quality gates. This article evaluates the material-quality performance of three returned beverage-packaging materials—polyethylene terephthalate (PET), aluminium and reusable glass—using a quality-gated high-value recovery framework. The model defines a high-quality recovery index, HQR = R × Q × Y, where R is the return rate, Q is the quality factor of the returned stream, and Y is the reprocessing or reuse yield. The HQR indicator describes the quality of the entire DRS process. The core purpose of the HQR model is to distinguish nominal packaging return from high-quality material recovery and to show whether returned PET, aluminium and reusable glass streams remain suitable for high-value circular pathways. A survey-supported early-stage return scenario (R = 0.50) is compared with the 77% and 90% separate-collection targets used in European policy. To strengthen the PET branch of the model, a pilot PET stream-quality and processing-yield dataset was incorporated, including PET purity, colour composition, non-PET impurities, residual moisture, organic residues, intrinsic viscosity, washed PET flake or pellet yield, and sorting/washing rejection. The pilot data indicate that Lithuania had higher PET quality (98.2% PET purity, 80% clear PET, 1.8% non-PET impurities, IV = 0.74 dL/g, and 84.5% washed PET yield) than the Polish regional average (94.3% PET purity, 72.7% clear PET, 5.7% non-PET impurities, IV = 0.721 dL/g, and 80.3% washed PET yield). At R = 0.50, the pilot-derived PET HQR is approximately 37.8% for Lithuania and 31.6% for the Polish regional average. The results indicate that the same nominal return rate can lead to substantially different high-quality recovery outcomes because PET is constrained by stream purity, colour, contamination, and processing yield; aluminium by alloy and remelting control; and reusable glass by inspection, breakage, and refill compatibility. The proposed framework can support structured DRS operator reporting by identifying the material-quality and yield variables that should be measured alongside mass collection; however, operator-level validation is required before the model can be used as a predictive performance tool. Full article

Corrosion of airframe alloys is managed by scheduled inspections rather than measurement. Continuous monitoring could change this. Progress in electrochemically active sensing materials has increased laboratory detectability, yet little has reached operational aircraft. We argue that the limiting factor is not sensitivity but representativeness: whether a sensor’s response reflects the true condition of the structure it monitors. We treat aerospace corrosion as a six-stage cascade and map each material and transduction principle onto the stage it observes. We review the electrochemical processing routes that set electrodes’ morphology and stability and show that the processing parameters strongly affect reported reproducibility when the process’s control is left unstated. We propose an engineering-relevant framework spanning material, environmental, and electrochemical representativeness, plus decision relevance. Across the reviewed corpus, the highest analytical sensitivity tends to coincide with the lowest material representativeness, an apparent qualitative trade-off rather than a demonstrated statistical relationship. No identified system closes the chain from the signal to a damage-based maintenance decision without independent nondestructive verification. Of the performance figures that could be traced to primary studies, none was obtained on an aerospace alloy under airframe-representative exposure, the field’s principal gap. At multi-material joints, the problem inverts: carbon-fibre composites drive alloy’s dissolution while its own matrix degrades, so surface-treatment processing, rather than sensor choice, sets the outcome. We conclude with a staged evidence architecture that couples continuous sensing to eddy current, ultrasonic, and thermographic inspection. Full article

The new Euro 7 standard will be the first legislation to limit the emissions produced by an automotive brake system. This has caused brake manufacturers to seek radical solutions to reduce the emissions generated from conventional grey cast iron (GCI) friction brakes. The regenerative braking system of electric vehicles (EVs) will require the friction brakes to be used less frequently than for an internal combustion engine vehicle. This may lead to a build-up of corrosion products on the friction surfaces that may not only affect the performance and service life of the GCI friction brake but also increase wear particle emissions when braking. Plasma electrolytic oxidation (PEO) ceramic-coated aluminium alloy rotors could be an alternative solution to reduce the effects of corrosion, produce lower brake emissions and also improve the energy efficiency of the EV by reducing its unsprung mass. To understand the interrelation between brake rotor corrosion and particulate emissions, this study concentrates on quantifying wear particles from a PEO-coated Al6082 brake rotor, both before and after exposure to salt fog corrosion. The results are compared to those for a standard uncoated GCI rotor and for an aluminium metal matrix composite (MMC) rotor subject to the same braking and corrosion test cycles. It was found that the PEO brake rotor produced a higher steady-state coefficient of friction in both the uncorroded and corroded conditions than either the GCI or MMC rotor, but emitted fewer wear particles in the uncorroded state, apart from at the highest brake line pressure. In the corroded state, the PEO rotor produced far lower emissions than either the corroded GCI or MMC rotors across all brake line pressures. Full article

This study reported on the multi-objective optimization of atmospheric plasma spraying parameters for zirconia coatings by incorporating the response surface method with the desirability method, while simultaneously enhancing microhardness and reducing wear rates. The spraying variables were optimized to improve coating performance using an L18 Taguchi orthogonal experimental design combined with the response surface method. The analysis of variance revealed the primary factors to be acceleration voltage, stand-off distance, powder feed rate, and primary gas Ar/H₂; together, these factors accounted for 79.70% of the total performance variance. An R² value of 0.752 for microhardness was yielded by the fitted reduced quadratic model, whereas an R² value of 0.845 for wear volume losses was yielded by the interaction model. Within the optimised parameter range, the predicted microhardness was 1404.1 HV, with an experimental error of only 1.84%, and the wear volume loss was reduced to 4.53 mm³, with a prediction error of 3.27%. Additionally, the optimized coating was found to have fully molten droplets, less porosity, and negligible interlayer cracks, with only slight pitting observed during the wear test, as revealed by scanning electron microscopy. This multi-objective optimisation strategy, integrating the Taguchi method with the RSM, effectively enables the preparation of zirconia coatings with superior mechanical properties and provides reliable process guidelines for protective coatings on aluminium alloys. Full article

Aluminium alloy honeycomb vibration isolators, owing to their thin-walled nature and periodic structure, offer numerous advantages, including lightweight construction, high strength, structural stability and simplicity of design parameters. Traditional honeycomb structures exhibit high stiffness in the coplanar direction but offer virtually no vibration isolation. To develop the vibration isolation performance of honeycomb structures in the coplanar direction and achieve vibration isolation protection for precision electronic instrument cabinets, this paper introduces a periodic corrugated structure based on traditional straight-hole honeycombs, designs a new type of corrugated honeycomb isolator, and screens and refines its vibration isolation performance. Using finite element simulation, multiple sets of orthogonal experiments were designed to perform range analysis on the simulation results, gradually eliminating the interference of irrelevant factors on the vibration transmission rate and optimising the dimensional parameters of the corrugated honeycomb isolator. To further optimise the vibration isolation performance of the corrugated honeycomb isolator, periodic circular holes were opened in the X and Y directions of the isolator, reducing its vibration transmission rate in the Z-direction and effectively improving the vibration isolation effect. Simultaneously, sweep frequency tests were designed to verify the accuracy of the finite element model. Full article

Hydrogen storage and separation remain major technical challenges limiting the broader implementation of hydrogen-based energy systems. Metal–hydride alloys offer a promising solution because they enable reversible hydrogen storage within their crystal structure and can selectively absorb hydrogen from multicomponent gas mixtures. However, the practical application of metal–hydride systems requires storage vessels that combine sufficient mechanical strength with effective heat removal, as hydrogen absorption is accompanied by significant heat generation that can reduce the reaction rate and usable storage capacity. This study addresses hydrogen storage within the crystal structure of metal alloys and introduces the potential of metal–hydride (MH) alloys for hydrogen separation from gas mixtures. It subsequently presents the structural design and strength assessment of a low-pressure, double-walled, tubular steel MH storage vessel intended for hydrogen storage in a MnTiVFeZr-based alloy. Structural simulations were performed in ANSYS 2025 R2 Static Structural at three operating pressures: 3, 5, and 7 MPa. For all three simulated pressure conditions, the gravimetric hydrogen storage capacity of the alloy was 0.992 ± 0.016 wt.%. Following the selection of the most suitable design with an operating pressure of 3 MPa, an analytical calculation was performed to verify the results obtained from the numerical analysis. The storage vessel was subsequently manufactured and subjected to experimental strength validation using the test procedures specified in the STN EN 13322-2 standard. The design of the low-pressure tubular steel MH storage vessel also incorporates an efficient thermal management system based on a combination of active and passive cooling modules. The passive cooling module takes the form of an internal heat-transfer enhancement element, which is inserted into the primary storage vessel together with the MH alloy. The active cooling module uses a coolant flowing around the outer wall of the primary vessel. The optimal design of the aluminium passive cooling module was selected from four variants based on a steady-state temperature-field analysis conducted in ANSYS CFX. The selected module was subsequently manufactured and integrated into the proposed storage vessel. The vessel equipped with the passive cooling element was then subjected to experimental temperature measurements during hydrogen absorption by the MH alloy. The experimentally obtained data were compared with the numerical simulation results to evaluate the temperature fields within the vessel and the heat dissipation from the core of the MH storage system during hydrogen absorption. The main contribution of this work is the development of a mechanically validated and thermally managed tubular metal–hydride vessel that integrates structural design, numerical optimisation, manufacturing, and full-scale experimental testing within a single methodology. The proposed approach provides a practical basis for the further development and scaling of low-pressure metal–hydride systems for hydrogen storage, purification, and separation applications. Full article

Metals are widely used in various types of structural applications such as the automotive, aerospace and construction industries. However, their service life is limited due to the various loads they experience during operation. Specifically, cyclic loading can lead to the early fatigue failure of these structures. Therefore, early detection of fatigue deformation is essential to prevent catastrophic failures. In this study, an automated electrical resistance data acquisition system was developed using LabVIEW to obtain measurements from a Keithley 6221 current source for fatigue damage detection. The results showed an increase in electrical resistivity after the application of cyclic loading. It was observed that electrical resistivity increased after each set of loading cycles, with an average increase of 7.38%, a stress level of 260 MPa (high-cycle fatigue), and a 6.5% increase after the application of 25,000 cycles at 165 MPa (low-cycle fatigue). Scanning Transmission Electron Microscopy (S/TEM) was used for microstructural investigation as a proof of concept for the high-cycle fatigue sample interrupted after 25,000 cycles to analyse the modification in dislocation structures as well as a qualitative increment in the dislocation density with respect to the initial microstructural state of the as-machined sample. Such a modification in dislocation structures as well as an increment in dislocation density corroborates the findings proposed by electrical resistivity measurement. The results demonstrated that electrical resistivity measurement provides a promising non-destructive approach for the early detection of fatigue damage in metallic materials. Full article

The increasing demand for lightweight and corrosion-resistant structures has accelerated the use of AA5083 aluminium alloy in automotive, aerospace, marine and transportation industries owing to its excellent corrosion resistance, weldability and favourable strength-to-weight ratio. However, the fabrication of complex AA5083 components remains challenging because of limited formability, localised thinning, fracture and springback associated with conventional forming processes. Robotic incremental sheet forming (RISF) has emerged as a promising dieless manufacturing technology capable of producing complex and customised components with reduced tooling requirements. Recent developments in assisted RISF, particularly heating-assisted and hydro-assisted approaches, have further enhanced process capability. The reviewed literature consistently demonstrates that heating-assisted RISF improves formability by reducing flow stress and fracture tendency, whereas hydro-assisted RISF provides superior thickness distribution, deformation stability and dimensional accuracy. Despite these advances, significant challenges remain, including the lack of standardised processing conditions, limited comparative studies between cold and assisted RISF, insufficient understanding of hydro-assisted RISF for AA5083, and the absence of comprehensive process–structure–performance correlations. This review critically summarises the principles of ISF, RISF and assisted RISF technologies, evaluates their technical developments, industrial potential and economic considerations, and identifies the major research gaps limiting industrial implementation. Future research should focus on standardised processing methodologies, predictive modelling, integrated process optimisation and comprehensive material characterisation to facilitate the wider adoption of assisted RISF for manufacturing advanced lightweight AA5083 components. Full article