Search Results (175)

To investigate the effect of femtosecond laser scanning path on the surface integrity of 7075 aluminum alloy after paint removal, parallel, Z-shape, and loop-shape scanning were compared in terms of surface morphology, microstructure, chemical composition, roughness, wettability, and corrosion resistance. Parallel scanning effectively removed the paint while maintaining a surface roughness of 0.27 μm, close to that of the original substrate. The resulting regular unidirectional laser-induced periodic surface structures (LIPSS) yielded a water contact angle of 85°, consistent with the Wenzel wetting model. X-ray photoelectron spectroscopy (XPS) showed the lowest C 1s and O 1s peak intensities, the lowest lattice-oxygen fraction in Al₂O₃, the strongest metallic Al⁰ signal, and limited thermal oxidation. Electrochemical measurements showed the most positive corrosion potential (−0.974 V), the highest film resistance and charge-transfer resistance, and the best corrosion resistance for parallel scanning. By contrast, energy accumulation at the ends during Z-shape scanning and thermal accumulation at the corners and center during loop-shape scanning increased pit and recast-defect densities, oxidation, and corrosion degradation. Loop-shape scanning produced a surface roughness of 3.60 μm and a contact angle of 140.7°, indicating superhydrophobicity, but also the highest corrosion current density and the poorest corrosion resistance, showing that superhydrophobicity does not necessarily correspond to high corrosion resistance. The results show that scanning path affects LIPSS evolution, oxide-film integrity, and corrosion resistance through the spatial distribution of laser energy and thermal accumulation. Among the three paths, parallel scanning provided the best combination of paint removal, low substrate damage, and corrosion resistance, supporting its use in femtosecond-laser paint removal from aircraft aluminum alloy skins. Full article

A solid solution treatment (SST) followed by single-stage aging (0–30 h, 140 °C) was performed on 7075 aluminum alloy specimens with longitudinal axes oriented at 0°, 45° and 90° to the rolling direction. The mechanical properties and microstructure were analyzed by tensile testing, optical microscope (OM), electron backscatter diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that the average tensile strengths of the as-received 7075 aluminum alloy in the three directions were 304 MPa (0°), 295 MPa (45°) and 297 MPa (90°), respectively, with an anisotropy index (AI) of 0.97, indicating that the as-received samples exhibited negligible anisotropic mechanical properties. After SST, elongated grains with coarse size were formed, which is primarily attributed to the inheritance of the deformed fiber texture introduced by hot rolling. EBSD analysis of the 30 h aged specimens revealed that, within the same analyzed area, the total grain-boundary length in the 45° direction (16.4 cm) was much larger than that in the 0° (10.4 cm) and 90° (13.5 cm) directions. As the grain morphology showed no significant change between the SST and aged conditions, this grain-boundary distribution was representative of the microstructural state established during SST and persisted throughout the artificial aging process, contributing to the anisotropic mechanical properties. During artificial aging, prolonged aging time significantly facilitated the precipitation, with the 30 h aged sample exhibiting a significantly higher density of precipitates compared to the 6 h aged sample, leading to enhanced mechanical properties. The tensile strengths of the 30 h aged samples increased to 165 MPa, 236 MPa and 196 MPa in the three directions, respectively. Meanwhile, due to the fixed crystallographic orientation relationship between the precipitates and the Al matrix, the precipitates tended to form on specific planes, which enhanced the anisotropic mechanical properties. Consequently, the AI value increased from 0.97 (as-received) to 1.43 (30 h aged) with prolonged aging time. Full article

For single-motor Formula Student Electric China (FSEC) race cars, current powertrain design methodologies commonly suffer from the disconnection among parameter matching, dynamic simulation, and structural optimization: gear ratio selection is mostly based on static theoretical calculations, lightweight design does not incorporate full-vehicle dynamic load spectra constraints, and the simulation toolchain (CarSim 2024, OptimumLap version 5, ANSYS 2022) lacks a standardized data closed-loop, leading to prolonged iteration cycles and unquantifiable reliability. To address these issues, this paper takes the Nanning University electric formula race car E66 as the research object and proposes a three-phase integrated design framework of “requirement-driven, multi-simulation co-validation, and lightweight iteration.” The study includes three core contributions: (1) establishing a powertrain parameter matching method based on power boundary calculations and multi-dimensional selection criteria, achieving the integrated selection of the Emrax 228 motor (power density 9.2 kW/kg, Emrax d.o.o., Kamnik, Slovenia) and the Unitek-D3 controller through comparative analysis with the JJE motor (5.7 kW/kg, Jing-Jin Electric Technologies Co., Ltd., Beijing, China); (2) constructing a co-simulation mechanism combining OptimumLap version 5 and CarSim 2024, completing the closed-loop optimization of the gear ratio from the range of 1.6–4.3 to the optimal value of 3.9 under the Hefei NIO track operating conditions, with a 75 m acceleration simulation result of 4.4 s and an endurance lap time of 86 s; (3) introducing ANSYS 2022 topology optimization technology to perform two-iteration lightweight design on the 7075 aluminum alloy main sprocket, achieving 35% mass reduction and 40% volume reduction while maintaining the maximum principal stress at 73.16 MPa (below yield strength). The expected outcome is a replicable development paradigm for single-motor powertrain systems, transforming drivetrain matching from experience-driven to simulation-driven, providing reliable data boundaries for physical vehicle commissioning, and effectively reducing trial-and-error costs. Full article

Spindle-current-based force estimation provides a nonintrusive alternative to dynamometer-based milling-force measurement, but its accuracy is limited by the nonlinear and time-dependent relationship between spindle current and cutting force. This study proposes a CNN–ResNet–RF model for instantaneous milling-force prediction using only spindle current signals as input. In the proposed architecture, CNN layers extract local temporal features from windowed current sequences, residual blocks refine multiscale force-related representations, and a random-forest regressor performs nonlinear force regression. Milling experiments were conducted on 7075 aluminum alloy and steel 45 using a five-axis machining center. To prevent temporal data leakage, the synchronized and preprocessed current–force data were divided at the continuous cutting trial level into training, validation, and independent test subsets. On the independent test subset, the proposed model achieved an R² value of 0.952, an MAE of 2.793 N, and an RMSE of 4.301 N, outperforming the CNN, CNN–ResNet, and RF baseline models in terms of prediction accuracy and error reduction. These results demonstrate that the CNN–ResNet–RF framework improves test-set milling-force prediction within the tested machining range. Full article

To improve the laser-induced damage resistance of 7075 aluminum alloy, a typical aerospace material, a laser-resistant coating material for the surface of 7075 aluminum alloy was prepared in this paper. The performance of 7075 aluminum alloy coated with this coating was analyzed and tested by combining numerical simulation and experimental verification. The test results show that under the same laser irradiation conditions and geometric dimensions, the breakdown time of 7075 aluminum alloy coated with the laser-resistant coating is prolonged by 541.6%, and its laser-induced damage resistance is significantly improved. Full article

In order to improve the poor wear resistance and adhesive wear of 7075 aluminum alloy under dry friction conditions, a nanosecond pulse laser was used to prepare surface micro-textures with different shapes, surface densities, and feature sizes. Subsequently, their friction and wear behavior, as well as the corresponding failure mechanisms, were systematically investigated. Circular, square, and hexagonal micro-pit textures were selected as the research objects. Combined with surface morphology characterization, ball-on-disk dry wear tests, reciprocating friction tests, and contact stress and wear model analyses, the effects of texture parameters on tribological performance were systematically revealed. The results indicate that laser microtexturing can reduce the coefficient of friction on the surface of 7075 aluminum alloy to a certain extent and improve its wear resistance, with the friction-reducing effect closely related to the texture shape, areal density, and feature size. Among these, hexagonal texturing exhibited the best friction-reducing effect, while circular texturing demonstrated superior formation quality and friction stability. Compared to other specimens, the T8 group with a 7.5% areal density and a feature size of 100 µm exhibited the lowest average coefficient of friction. During the friction process, the microstructures gradually fail due to plastic flow filling, wear debris accumulation, and edge collapse. The research findings provide a reference for the optimized design and engineering applications of surface microstructures on aluminum alloys. Full article

Laser powder bed fusion (LPBF) of high-strength aluminum alloy 7075 (AA7075) is severely limited by hot cracking. However, the underlying mechanisms, particularly the coupling between thermal fields, solidification microstructure, and cracking behavior, remain insufficiently clarified. This study elucidates these mechanisms by integrating experimental characterization with thermal simulation to investigate the temperature field, microstructure, and cracking relationships in both AA7075 and a crack-resistant 7075-Er-Zr alloy. Results show that coarse hot crack morphology is highly dependent on linear energy density E_L. In AA7075, E_L < 450 J/m promotes laterally inclined cracks (short, narrow cracks extending from the melt pool boundary toward the track center), whereas E_L higher than that value leads to the continuous centerline cracks (long, wide cracks along the track center). Fine microcracks are also observed at melt pool boundaries. The 7075-Er-Zr alloy demonstrates superior crack resistance. At E_L = 600 J/m, longitudinal centerline cracks still penetrate along the track, but the alloy achieves crack-free tracks at 200 W with scanning speeds above 1000 mm/s, otherwise exhibiting only short discontinuous cracks. Microcracks at melt pool boundaries are markedly suppressed in the modified alloy. The enhanced crack resistance is attributed to Er/Zr-induced grain refinement and a transition to an equiaxed grain structure, which disrupts intergranular gaps. Critically, thermal simulations identify an annular region with a peak temperature gradient. In AA7075, this region develops aligned columnar grains that facilitate both microcracks and centerline cracks. In the 7075-Er-Zr alloy, microcracks are fully eliminated within this region. However, a residual crystallographic texture persists in the annular region, which promotes the continued occurrence of centerline cracks under high energy density (e.g., E_L = 600 J/m). The annular region remains a critical weak link, and its microstructural control determines the prevailing crack type. This work provides a fundamental understanding of the thermal-microstructural origins of cracking and offers a theoretical foundation for developing crack-resistant aluminum alloys via LPBF. Full article

Dissimilar 7075-T6 and 6061-T6 aluminum alloy joints were fabricated using pulsed metal inert gas (P-MIG) welding with ER5356 filler wire. The effects of welding current (224 A, 234 A, and 244 A) on macro-morphology, microstructure, mechanical properties, and corrosion behavior were systematically investigated. As welding current increased, the top and bottom reinforcements first increased and then decreased, reaching maximum values at 234 A, while the front weld width exhibited the opposite trend. The weld zone consisted of equiaxed and dendritic grains, with partial remelting of AlFeMnSi intermetallic compounds observed in the heat-affected zones. The microhardness and tensile strength of the joints followed a similar trend of first decreasing and then increasing with welding current, achieving a maximum tensile strength of 203.9 MPa at 244 A, corresponding to 89.5% of the 6061-T6 base metal strength. Corrosion resistance varied across regions depending on the evaluation method. In intergranular corrosion tests, the 7075-HAZ showed the highest susceptibility due to grain boundary segregation of Mg and Zn. In electrochemical tests, the WZ exhibited the poorest corrosion resistance. For the 7075-HAZ, optimal corrosion resistance was achieved at 234 A, attributed to a stable passive film and uniform precipitate distribution. These findings provide valuable guidance for optimizing P-MIG welding parameters for dissimilar 7075/6061 aluminum alloy joints. Full article

The increasing demands of application conditions urgently call for process innovations in high-performance 7xxx aluminum alloys. This study investigated the effect of differential speed rolling (DSR) on the microstructural evolution and mechanical properties of 7075 aluminum alloy subjected to DSR with a total reduction of 60%, followed by isothermal aging at 120 °C for 24 h. The results show that DSR promotes the development of grain refinement, defect accumulation, and deformation texture, while the corresponding strengthening effect exhibits a non-monotonic dependence on speed ratio. Among all conditions, the DSR2.0 sample exhibits the most favorable microstructure, characterized by the highest kernel average misorientation (KAM) value, the strongest deformation texture, and the finest as well as most densely distributed intragranular η′ precipitates. Accordingly, the DSR2.0 sample achieves the optimal strength–ductility balance, with a yield strength, ultimate tensile strength, elongation, and hardness of 582.26 MPa, 648.43 MPa, 10.75%, and 199.8 HV, respectively. Specifically, the deterioration in the properties of the DSR2.5 sample is attributed to localized recovery, shear inhomogeneity and coarsening of precipitates. The differential speed ratio enables effective optimization of the 7075 aluminum alloy by regulating the evolution of grains, dislocations, precipitate phases, and texture, among which precipitation strengthening is the dominant calculated contribution. Therefore, an appropriate differential speed ratio is key to achieving performance optimization. Full article

The corrosion of prestressed tendons in concrete structures remains a major durability concern, especially for post-tensioned members exposed to aggressive environments. High-strength aluminum alloy (AA) bars exhibit favorable characteristics such as corrosion resistance, low density, and high ductility and may therefore provide an alternative or supplementary prestressing material in durability-oriented structural design. In this study, a bonded post-tensioned T-shaped concrete beam with hybrid prestressing combining prestressed steel (PS) strands and 7075 AA bars was investigated. A refined finite element model was developed by considering the bond-slip relationship between the AA tendons and grout inside corrugated tubes. The flexural behavior of the beam was analyzed through a combination of finite element simulation and sectional theoretical analysis. In addition, a fatigue-life assessment framework was established based on vehicle fatigue loads and material fatigue constitutive models, and the fatigue performance of the proposed hybrid beams was compared with that of conventional prestressed concrete beams. The theoretical predictions agreed reasonably well with the numerical results. Results indicated that partial replacement of PS strands with corrosion-resistant AA bars could alter the governing fatigue failure mode and improve the fatigue durability of prestressed beams under corrosive conditions. These findings highlight the potential of hybrid AA–PS prestressing as a durability-oriented strategy for concrete beams in corrosive environments. Full article

The AA7075 holds significant importance in the aerospace field. Understanding its microstructure evolution and constitutive relationships during warm deformation is crucial for optimizing forming processes. To this end, isothermal compression experiments were conducted at different temperatures and strain rates to analyze their flow stress behavior. The microstructure evolution was characterized using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Microstructural analysis confirmed that dynamic recovery constitutes the predominant softening mechanism under warm forming conditions. The results indicate that flow stress is highly sensitive to deformation parameters, decreasing with increasing temperature and rising with increasing strain rate. To accurately describe the flow behavior, two distinct constitutive models were formulated: (1) a phenomenological Hensel–Spittel–Garofalo (HSG) model; (2) a novel hybrid machine-learning model that innovatively integrates the Harris Hawks Optimization (HHO) algorithm with an LSTM model. Both constitutive models demonstrate reasonable predictive accuracy. In comparison, the HHO-LSTM model demonstrated a superior ability to capture complex nonlinear relationships, achieving highly precise predictions of flow stress across the full range of deformation conditions tested in this work. The hybrid machine-learning model proposed in this study provides a highly accurate method for describing and predicting the flow behavior of the AA7075 during warm forming, offering a powerful predictive tool for engineering applications. Full article

The pass reduction in hot rolling significantly influences the properties of 7075 alloy sheets, yet its quantitative effect requires systematic investigation. Multi-pass hot rolling experiments with 11% and 16% pass reductions were conducted on forged 7075 alloy. The microstructure, texture evolution, and mechanical properties were analyzed using SEM, EBSD, and mechanical testing. As the total thickness reduction increased, a clear correlation was observed with the enhanced mechanical properties of the hot-rolled 7075 alloy, demonstrated by the concurrent rise in both ultimate tensile strength (UTS) and yield strength (YS). When the total reduction exceeded 60%, the strengthening effect was most pronounced, with UTS and YS reaching 367.09 MPa and 332.82 MPa, respectively. The average grain sizes of 31.49 μm and 27.56 μm were achieved at the 12th pass (11% reduction per pass) and the 8th pass (16% reduction per pass), respectively. Under the condition of 11% reduction per pass, the texture intensity exhibited a non-monotonic trend with increasing passes. T6, T7, and RRA heat treatments were applied to the final rolled plates, and the maximum mechanical properties obtained in the hot-rolled 7075 plate following T6 heat treatment were UTS of 607.5 MPa, YS of 580.9 MPa, and elongation of 13.6%. Full article

This study established a marine atmospheric corrosion prediction model by comparing the corrosion behavior of 7075 aluminum alloy in neutral salt spray tests and outdoor exposure tests conducted in the coastal atmosphere of Hainan. The results show that severe rusting occurred after 96 h of neutral salt spray testing, with loose white cluster-like corrosion products mainly composed of Al(OH)₃ and Al₂O₃. The thickening of the corrosion product layer slowed down the corrosion process, following a nonlinear power-law kinetic relationship. In the later stage, potential dropped sharply due to product layer spallation, and recovered as new corrosion products formed, confirming that the stability of the product layer is critical for protection. Under coastal atmospheric exposure, the composition of corrosion products was similar to that observed in the salt spray test, but the actual corrosion rate was affected by environmental dynamic equilibrium. The acceleration factor of the neutral salt spray test corresponding to the same corrosion amount in the Hainan marine atmosphere exhibited a declining trend, reflecting that differences in the protective nature of the corrosion product layer were influenced by environmental factors. Electrochemical analysis indicated that both tests showed similar current–potential synergistic variation mechanisms dominated by product layer stability. In summary, while the neutral salt spray test effectively simulates the chloride-induced corrosion mechanism in marine atmospheres, its kinetic model cannot directly predict real corrosion behavior through a simple acceleration factor, as environmental complexity must be considered. Full article

The roll bonding of 7075/1060 composite laminates offers a promising approach toward the increase in toughness of aluminum layered composites. In this paper, 7075 and 1060 aluminum alloy plates were hot roll bonded to fabricate multilayered composite laminates. Solid solution at 470 °C for different holding times and subsequent aging were carried out for all the laminates. This study investigated the effect of holding times on the interfacial microstructure and interfacial bonding strength of the laminates. The interfacial shear strength was found to increase with longer holding times, which was attributed to the solid solution strengthening of the 1060 layer resulting from element diffusion. The findings also reveal that both tensile strength and toughness are positively correlated with the holding time of the solid solution, and there is a simultaneous improvement of tensile strength and toughness as the holding time increases. Microstructural characterization of the crack path profile of the Charpy impact and bending test indicates that interfacial delamination and main crack deflection become pronounced with the increase in holding time, and these lead to an increase in the fracture resistance in the crack-arrester orientation. Full article

This work quantifies the environmental sensitivity of tartaric–sulfuric acid (TSA) anodized and sealed 6061 and 7075 aluminum. Five alloy–temper states (6061-T4, 6061-T62, 7075-T0, 7075-T62, and 7075-T73) were TSA-treated, pore sealed and then exposed for eight weeks (56 days) to ambient air, 11 wt.% NaCl brine, or a microbiological medium, with weekly +20 °C/−20 °C freeze–thaw cycles. Tensile tests assessing yield strength, ultimate strength, and elongation were conducted. Strength losses were modest in ambient conditions (<5%) but increased to ≈5–10% for yield and ≈2–9% for ultimate under saline and microbial conditions, particularly in the annealed 7075-T0 and peak-aged 7075-T62 states. Ductility was more sensitive, declining up to ≈30% for 6061-T4 and 6061-T62 in harsh media. Permutation-based inference within an additive screening model indicated that environmental exposure is strongly associated with the dominant share of the observed variability (R²_env ≈ 0.91–0.93 for yield, ultimate strength, and elongation), within the limits of the present dataset. These results suggest that freeze–thaw cycling, chloride exposure, and microbiological activity are consistent with the observed degradation trends. Over-aged 7075-T73 retained properties better than T62, highlighting the roles of temper and pore sealing quality in cold, saline, and microbiologically active service. Full article