Search Results (883)

Hybrid joining methods combining adhesive bonding (AB) and friction stir spot welding (FSSW) have attracted increasing attention for lightweight multi-material structures due to their potential to combine the advantages of both techniques. In this study, a numerical investigation of hybrid AB + FSSW joints for dissimilar AA6082 aluminum and AZ31 magnesium alloys was conducted using finite-element analysis. Three joint types were considered: adhesively bonded (AB), friction-stir-spot-welded (FSSW), and hybrid AB + FSSW joints. The influence of weld location and adhesive type on joint performance, failure behavior, and stress distribution was evaluated. Cohesive zone modeling was employed to simulate adhesive failure, while the modified Mohr–Coulomb ductile fracture criterion was used to predict fracture in the metallic substrates and weld regions. Two structural adhesives with distinct mechanical characteristics, Araldite AV138 and Nagase XNR6852 E-3, were considered. The results showed that the hybrid configuration with the weld located at the center of the overlap and the Nagase adhesive provided the most favorable performance, reaching a maximum load of approximately 9.4 kN, comparable to that of the adhesively bonded joint. In contrast, FSSW-only joints exhibited lower load-bearing capacity and predominantly failed through the weld interface. Stress analysis suggested that the adhesive layer significantly reduced stress concentrations around the weld spot, particularly when adhesive was present on both sides of the weld. The findings demonstrate that appropriate weld positioning and adhesive selection are critical parameters for maximizing the efficiency of hybrid AB + FSSW joints and indicate the feasibility of this joining strategy, based on the numerical models developed, pending experimental confirmation for dissimilar aluminum–magnesium structures. Full article

Tungsten inert gas (TIG) welding of AA5083 aluminum alloy is sensitive to heat input and shielding conditions, which can lead to defects such as porosity and burn-through that compromise weld quality. Conventional non-destructive testing methods are generally performed after welding and therefore provide limited capability for real-time process monitoring. This study presents an acoustic emission (AE)-based frequency-domain framework for real-time classification of weld conditions during TIG welding of AA5083. Acoustic signals were acquired at a sampling rate of 10 kHz and transformed into frequency-domain representations using the Fast Fourier Transform (FFT). Decision Tree (DT), Support Vector Machine (SVM), Artificial Neural Network (ANN), and ensemble-learning classifiers were evaluated using the resulting spectral features. To address the high dimensionality of the FFT representation, Principal Component Analysis (PCA) was incorporated into the modeling workflow, with the retained components determined from the model-development data. Five-fold cross-validation and grid-search-based hyperparameter tuning were used during model development, while an independent test set was reserved for final evaluation. The best-performing classifiers achieved a classification accuracy of approximately 0.99 for distinguishing good-weld, porosity, and burn-through conditions. Weld-condition labels were independently validated using visual inspection and radiographic testing. FFT and Short-Time Fourier Transform (STFT) analyses were used to characterize global and time-dependent spectral behavior, respectively, while SHapley Additive exPlanations (SHAP) were employed to identify frequency regions contributing to model predictions. A comparative analysis with time-domain statistical features further demonstrated the stronger discriminative capability of the FFT-derived representation under the investigated conditions. The proposed framework combines high classification performance with interpretable frequency-domain information and provides a basis for in-process weld-condition monitoring and quality control of TIG-welded AA5083. Full article

Fracture is one of the most common defects that occur during the roll forming process. However, several process-based strategies can be employed to minimize its occurrence. This paper investigates the fracture mechanisms of AA3105 aluminum alloy sheets during the flexible roll forming (FRF) process, focusing on methods to reduce damage and prevent failure throughout forming. Experimental tests were carried out to determine the mechanical properties of the sheet and to calibrate the modified Mohr–Coulomb fracture criterion. The digital image correlation technique was used to measure the experimental strain field at the onset of fracture. Finite element simulations of the calibration tests were then performed to validate the failure criterion, showing good agreement with experimental results. After calibration, the FRF process was simulated in ABAQUS, and a user subroutine was implemented to predict fracture evolution during forming. The simulation results were validated against experimental data obtained from the FRF machine, confirming the model’s accuracy. The results revealed that increasing the sheet thickness from 0.5 mm to 1.5 mm increased the damage at the critical element by approximately 52%, whereas increasing the transition radius from 250 mm to 550 mm and the bending radius from 1 mm to 3 mm reduced the damage by approximately 28% and 13%, respectively. In addition, increasing the number of forming stands reduced the damage by approximately 10%. These findings demonstrate that both thinner sheets and multi-stage forming significantly enhance formability and reduce fracture risk in FRF of aluminum sheets. Full article

A healing method for fatigue damage was investigated by laser shock treatment with a Nd:YAG nanosecond laser shock device for AA 7075-T651 aluminum alloy. It was found that a stable residual compressive stress field was generated by the improved laser parameters, and this stable residual compressive stress field could be responsible for the improvement in the total fatigue life of the damaged curved structural specimen due to the improved laser treatment. Further analysis is gained from the fracture morphology, and it is concluded that the fatigue crack initiation and early propagation at the notch root may be effectively delayed for the damaged curved specimen by the improved laser treatment. Based on a proposed equivalent stress concentration factor $K_{teq}$, a total fatigue life prediction method is established during the damage-healing process for the curved structural specimen manufactured from AA 7075-T651 aluminum alloy. The predicted lives by the proposed method agree well with the experimental results. Full article

Post-quench natural aging can alter the response of Al–Mg–Si alloys to further artificial aging, while post-artificial-aging hardness, H_post-AA, may obscure changes in the retained artificial-aging response. Five high-purity alloys containing 0.95–0.99 mol% Mg + Si, with Mg/Si ratios of 0.52, 1.1, 1.9, 3.0, and 4.0, were solution-treated at 848 K for 3.6 ks, quenched, and artificially aged at 473 K. Under direct artificial aging, after a minimum practical delay of approximately 0.1 ks, the Mg/Si = 1.1 alloy showed the highest H_peak of approximately 72–73 HV0.1, whereas Mg/Si = 4.0 reached approximately 53–55 HV0.1. The precipitate areal density was highest near Mg/Si = 1 and decreased markedly in Mg-rich alloys. Operational HRTEM classification indicated that β″-related precipitates predominated in the Si-excess alloys, whereas β′-like and parallelogram-type precipitates were more prominent in the Mg-rich alloy. For Mg/Si ratios of 0.52, 1.9, and 4.0, quench-to-aging delays of up to 6000 ks produced non-monotonic changes in H_post-AA. However, the additional hardening increment, ΔH_AA, decreased from 38.5 to 26.1 HV0.1 at Mg/Si = 0.52 and from 33.5 to 26.9 HV0.1 at Mg/Si = 1.9. These results show that both H_post-AA and ΔH_AA are required to evaluate quench-to-aging delays. 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

In this work, conventional friction stir lap welding (FSLW), self-riveting FSLW (R-FSLW) and ultrasonic-assisted R-FSLW (UR-FSLW) were employed to join dissimilar AA6061 and AZ31 alloys. The relatively thick Al-Mg intermetallic compound (IMC) layer provided limited metallurgical bonding, causing the FSLW joint to fail in a brittle manner at a low tensile shear force of 875 N. The self-riveting introduced additional mechanical interlocking: the R-FSLW joint, featuring AA6061 rivets, exhibited a 22% increase in tensile shear force compared with the FSLW joint. Nevertheless, cracks formed along the thick Al-Mg IMC layer around the AA6061 rivets, which retained the brittle fracture characteristic. In contrast, ultrasonic assistance not only improved the rivet filling rate (reducing the unfilled area from 0.83 mm² to 0.61 mm²) but also suppressed Al-Mg IMC layer growth and eliminated cracks. Moreover, ultrasonic assistance increased the stored energy and promoted material flow, refining the grains in the nugget zone (NZ) and thereby raising the average hardness of NZ. Consequently, with AA6061 rivets and refined microstructures, the UR-FSLW joint delivered a tensile shear force of 1280 N and an elongation double that of the FSLW joint, accompanied by a fracture mode transition from brittle to ductile-brittle. Full article

The paper presents thermodynamic data for the aluminothermic reaction used to synthesise hybrid composites (Al₃Zr, ZrB₂)/AA6063. AA6063 alloy was used with K₂ZrF₆, KBF₄ and Na₃AlF₆ as precursors. Composites containing 2.5, 5, 7.5 and 10% wt.% ZrB₂ were produced by direct melt reaction at 900 °C and characterised by optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD). The effect of the salt addition level on the resulting structures is also reported. The compressive behaviour was evaluated at room temperature to an engineering strain of 75% and complemented by tensile tests. The mechanical response is non-monotonic with reinforcement content: the flow stress decreases slightly between 2.5 and 7.5 wt.% ZrB₂ and recovers at 10 wt.%, reaching 321.5 MPa at 30% engineering strain against 278.2 MPa for the matrix. The thermodynamic data and microstructural analysis presented here describe the aluminothermic reaction and its effect on the resulting composites. Full article

Friction stir welding (FSW) is a solid-state joining process widely used for aluminum alloys due to its low heat input, reduced distortion, and ability to produce high-quality joints. However, excessive tool forces generated during the welding process can increase machine loading, accelerate tool wear, and negatively affect the process efficiency. Therefore, understanding the relationship between welding parameters, tool forces, and the joint performance is essential for achieving high-quality welds while avoiding unnecessary mechanical loads. In this study, 4 mm thick AA5754 aluminum alloy plates were joined using the FSW process, and the feasibility of using tool force measurements for process optimization was investigated. A comprehensive experimental matrix consisting of nine different rotational speeds and ten different tool travel speeds was established based on preliminary studies and previous literature. During each welding operation, forces acting on the tool in the F_x, F_y, and F_z directions were continuously recorded. The welded joints were evaluated through tensile testing (Zwick Z300 universal testing machine, ZwickRoell, Ulm, Germany), hardness measurements, and microstructural characterization using scanning electron microscopy (SEM) (ZEISS Merlin scanning electron microscope, Carl Zeiss Microscopy GmbH, Oberkochen, Jena, and Göttingen, Germany). A Pearson correlation analysis and a two-way analysis of variance (ANOVA) were performed at a 95% confidence level to quantify the relationships and statistical significance of the process parameters. The results showed that F_z was the dominant force component during welding. The rotational speed had a statistically significant effect on the tensile strength, yield strength and hardness (p < 0.05), accounting for 99.39% of the total variation in hardness. For the mean tool force, both the rotational speed and the tool travel speed were statistically significant (p < 0.0001), contributing 38.48% and 47.16% of the total variation, respectively. The rotational speed also accounted for 81.55% of the variation in the maximum axial force. The Pearson correlation analysis showed a strong negative correlation between the rotational speed and hardness (r = −0.73), whereas the tool travel speed showed positive correlations with F_x (r = 0.61), F_z (r = 0.62), and the mean tool force (r = 0.68). Despite the increased tool loading associated with higher travel speeds, no corresponding improvement in the mechanical performance was observed. The results demonstrated that appropriately selected welding conditions produced joints with a yield strength and hardness exceeding 90% of the corresponding base material properties while maintaining relatively lower tool forces. SEM observations confirmed grain refinement in the stir zone. Overall, the combined correlation and ANOVA results demonstrate that real-time tool force monitoring can provide a quantitative basis for selecting FSW parameters that achieve an adequate mechanical performance while minimizing unnecessary machine and tool loading. Full article

7xxx series aluminum alloys exhibit high strength and low density; however, their high degree of alloying results in a pronounced hot-cracking tendency, making direct casting forming challenging. In this study, a rheo-squeeze-cast AA7075 alloy was investigated. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and room-temperature tensile testing were employed to systematically examine the effects of the solution treatment window on the microstructure and mechanical properties of the castings. The distinctive contribution of this work is the quantitative correlation of solution-time-dependent second-phase evolution and porosity with the tensile behavior of ECSC-assisted rheo-squeeze-cast AA7075. The results show that, with increasing solution treatment time, the intergranular eutectic phases gradually dissolved, and their morphology evolved from lamellar structures into fine rod-like features. When the solution treatment time was extended to 12 h, a small number of pore defects appeared in the microstructure. Under the conditions of solution treatment at 470 °C for 8 h followed by aging at 120 °C for 24 h, uniformly distributed Zn–Mg-rich aging precipitates were observed in the matrix, resulting in the best comprehensive mechanical properties, with an ultimate tensile strength, yield strength, and elongation of 498.1 MPa, 413.7 MPa, and 8.2%, respectively. The optimized heat-treatment condition provides a practical route for achieving a favorable strength–ductility balance in rheo-squeeze-cast AA7075 components. Full article

To address the key problems of the dual-phase magnesium–lithium alloy LAZ931, such as easy corrosion, flammability and low strength, an AA6061 protective coating was fabricated on LAZ931 alloy via cold spraying to form an Al6061/LAZ931/Al6061 sandwich structure. The strengthening mechanism of the coating on interfacial microstructure, mechanical properties, creep behavior and corrosion resistance was systematically investigated. The results show that the cold-sprayed AA6061 coating is compact and uniform with a low porosity of 0.3% and surface roughness of 37.02 μm, which significantly improves the combustion resistance and corrosion resistance of the alloy. The coating/substrate interface exhibits jagged and tight bonding without obvious cracks or delamination. Abundant dislocations and Al–Mg–Li composite precipitates form at the interface, which effectively strengthen the interfacial bonding and enhance the tensile and yield strengths. Room-temperature creep tests reveal that the creep behavior of the composite is dominated by the LAZ931 matrix, and the coating remains intact and well-bonded throughout creep deformation without compromising the creep resistance. Electrochemical impedance spectroscopy shows that the coating increases the low-frequency impedance by more than two orders of magnitude, greatly elevating corrosion resistance. This study confirms that a cold-sprayed AA6061 protective layer can comprehensively enhance LAZ931 alloy through interfacial bonding, microstructural strengthening and protective barrier effects, providing a new strategy for protection and toughening of ultra-light Mg-Li alloys. Full article

This study systematically investigates the hot deformation behavior and microstructural evolution of AA3102 aluminum alloy through isothermal uniaxial compression tests conducted at 400–550 °C and strain rates of 0.01–10 s⁻¹. Previous studies on 3xxx-series Al–Mn alloys have mainly considered temperature and strain-rate effects while neglecting strain-dependent material parameter variations, limiting prediction accuracy under large deformation and obscuring dynamic softening mechanisms. Here, the experimental flow stress data were corrected for interfacial friction and adiabatic temperature rise. A sixth-order strain-compensated Arrhenius constitutive model was then developed to describe the coupled effects of temperature, strain rate, and strain. Full-strain-range power dissipation and flow instability maps were constructed using the dynamic material model, while optical microscopy and DEFORM-3D simulations were employed to clarify microstructural evolution and deformation inhomogeneity. The model achieved a correlation coefficient of 0.9841 and an average absolute relative error of 3.67%, demonstrating high predictive accuracy. No flow instability was detected within the investigated range, indicating excellent hot formability. The favorable compression-processing window was identified as 500–550 °C and 0.1–1 s⁻¹, while the peak power-dissipation efficiency increased from 30.55% at $\epsilon = 0.2$ to 32.90% at $\epsilon = 0.8$. Optical-microstructural observations suggest that increasing temperature and decreasing strain rate are associated with an increasing contribution of dynamic recrystallization relative to dynamic recovery. Finite-element results further reveal pronounced spatial variations in strain, temperature, strain rate, and stress during compression. These findings provide baseline constitutive and thermomechanical information for subsequent AA3102 hot-extrusion optimization. Full article

To address the prevalent defects in industrially cast 8021 aluminum alloy for battery foil, including coarse iron-rich phases that sever the matrix and hard-to-remove micrometer-scale inclusions, alloys with different chemical compositions were manufactured on a 100-ton integrated industrial melting and holding production line. The regulatory principles and underlying mechanisms of Fe–Ce composite microalloying on solidification thermal behavior, melt purification efficiency, as-cast microstructure, mechanical properties, and corrosion resistance of the alloy were systematically investigated. The results show that when the mass fractions of Fe and Ce are 1.7% and 0.3%, respectively, the mean intercept length of the α-Al grains of the alloy is reduced by 29% compared with the reference alloy. The acicular iron-rich phases are modified into dispersively distributed short rod-like and granular particles, and the filtration removal efficiency of micro-inclusions in the melt is significantly improved. The ultimate tensile strength of the alloy reaches 94.0 MPa, and the elongation is increased to 44.2%. The corrosion current density in 3.5 wt.% NaCl solution is only 20% of that of the Ce-free reference alloy. Through multi-stage effects including melt purification, grain refinement and second-phase modification induced by joint Fe and Ce additions, the combined addition of Fe and Ce simultaneously improves the metallurgical quality and service performance of the alloy. This work provides theoretical support and engineering references for the stable industrial production of high-performance aluminum foil for lithium-ion battery packaging. Full article

To improve the antifouling and self-cleaning performance of 3003 aluminum alloy, a fluorine-free water-repellent surface was fabricated by combining nanosecond laser texturing with subsequent heat treatment. The effects of scanning speed, laser power, pulse frequency, and scanning interval on surface wettability were systematically investigated. Under the optimal conditions of 2700 mm/s, 6 W, 35 kHz, and 20 μm, the surface achieved a maximum static water contact angle of 154.3 ± 0.8°. Surface characterization showed that laser processing generated hierarchical micro-/nano-scale structures, while heat treatment promoted surface chemical evolution associated with enhanced hydrophobicity. The highly water-repellent behavior resulted from the synergistic effect of hierarchical roughness and heat-treatment-induced surface chemical changes. The fabricated surface exhibited effective self-cleaning performance, achieving a SiO₂ removal efficiency of 98.8% under the specified test conditions. In addition, relatively high water repellency was retained after repeated water-impact and tape-peeling tests. These results demonstrate that nanosecond laser texturing combined with heat treatment provides a simple and environmentally friendly strategy for fabricating water-repellent AA3003 surfaces for antifouling and surface-protection applications. Full article

Cryogenic forming overcomes room-temperature limitations by leveraging the enhanced strength–ductility synergy in Al alloys. To explore the forming limits of AA5052 sheet under cryogenic forming conditions, quasi-in situ tensile tests were conducted and digital image correlation techniques were employed to examine strain distribution, surface roughness evolution, and forming limit curves of the AA5052 sheet in the tensile deformation process. Experimental results show that the maximum equivalent forming limit at −196 °C increases to 50.7% from 19.9% at room temperature, representing a 250% increase. At the same time, the surface roughness evolution rate increases by 60% from 2713 nm at room temperature to 4414 nm at −196 °C. Cryogenic conditions suppress dislocation annihilation and dynamic recovery, enhancing strain hardening, resulting in higher forming limits. Additionally, intensified grain rotation and more dislocation slip accelerate surface roughening, which influences the development of the geometric heterogeneity coefficient. By introducing a strain-dependent surface roughening coefficient, the Marciniak–Kuczyński (M-K) model was modified and was used to quantitatively characterize the heterogeneity during deformation, and subsequently analyzes its impact on the prediction of forming limits for AA5052 from room temperature (25 °C) to cryogenic temperature (−196 °C). The modified model reduces the prediction standard deviation by more than 70% and the identified mechanisms offer theoretical guidance for optimizing cryogenic forming process parameters for Al alloy components with complex geometries. Full article