Aluminum Alloy Surface Research Articles

Investigation of the Influence of Machining Parameters and Surface Roughness on the Wettability of the Al6082 Surfaces Produced with WEDM.

Electrical Discharge Machining (EDM) is a non-conventional machining technique, capable of processing any kind of conductive material. Recently, it has been successfully utilized for producing hydrophobic characteristics in inherently hydrophilic metallic materials. In this work, Wire Electrical Discharge Machining (WEDM) was utilized for producing hydrophobic characteristics on the surface of the aluminum alloy 6082, and various parameters that can affect wettability were investigated. Adopting an orthogonal Taguchi approach, the effects of the process parameter values of peak current, pulse-on time, and gap voltage on the contact angles of the machined surfaces were investigated. After machining, all samples were observed to have obtained hydrophobic properties, reaching contact angles up to 132°. The peak current was identified as the most influential parameter regarding the contact angle, while the gap voltage was the less influential parameter. A contact angle variation of 30° was observed throughout different combinations of machining parameters. Each combination of the machining parameters resulted in a distinct surface morphology. The samples with moderate roughness values (3.4 μm > Sa > 5.7 μm) were found to be more hydrophobic than the samples with high or low values, where the contact angle was measured under 115°. In addition, the finite element modeling of the experimental setup, with parametric surfaces of uniform random and Perlin noise types of roughness, was implemented. Time dependent simulations coupling phase field and laminar flow for the modelingof the wetting of surfaces with different surface roughness characteristics showed that an increase in the Sa roughness and total wetted area can lead to an increase in the contact angle. The combination of experimental and computational results suggests that the complexity of the wettability outcomes of aluminum alloy surfaces processed with WEDM lies in the interplay between variations of the surface chemical composition, roughness, micro/nano morphology, and the surface capability of forming a composite air/water interface.

Dense Amorphous Passivation Layer Formed on Aluminum Alloy Surfaces by Femtosecond Laser-Assisted Oxygen-Rich Doping.

Aluminum (Al) alloy surfaces are prone to serious corrosion in humid and salt-laden environments, which promotes the development of numerous protective approaches. Although the amorphous state is more conducive to improve corrosion resistance compared with the crystalline state, it still faces coating design problems like insufficient adhesive strength and flaking-off tendency. Here, we propose a strategy of femtosecond laser-assisted oxygen-rich doping to in situ create a dense high-quality passivation layer on Al alloy surfaces. With respect to the femtosecond laser processing in traditional air ambience, the material surface modifications within the oxygen-rich environment demonstrate some distinctiveness. For the ridge area of the laser ablation grooves, the oxidation surface is separated into two layers: the outer region presents a loose and porous appearance similar to the observations in the air ambience, while the inner region exhibits complete and homogeneous oxidation, especially associated with the continuous distribution of the amorphous substance, in sharp contrast to the nanoscale discrete amorphous formation in the air case. Simultaneously, the high degree of material oxidization with the amorphous phase is also developed on the wallside area of the groove valleys, which is much different from the incomplete oxidation in the air ambience. As a result, the measured corrosion current decreases by 49 times to a value of Icorr = 1.19 × 10-10 A/cm2 relative to the laser treatment in the air environment. Such a method offers the prospect for elevating the anticorrosion performance of metal surfaces.

Hydrophilic properties of the aluminum alloy induced by femtosecond laser structuring

This study explored the changes in wetting property and surface morphology in aluminum alloy plates due to femtosecond laser structuring. The laser scanning produced a hierarchical micro- and nano-scale structure consisting of microchannels decorated by irregular shape particles. The surface morphology was controlled by laser power and scanning line density. The surface wettability gradually changed from hydrophilic to hydrophobic one due to various chemical reactions for low laser power and scanning line density. However, femtosecond laser structuring with appropriate laser power and scanning line density was demonstrated to maintain strong and stable hydrophilic properties of aluminum alloy surfaces.

Experimental and theoretical investigations of the anti-corrosion film derivated from bio-based melatonin on AA5052 aluminum alloy surface

In this work, the effect of the bio-based melatonin (MEL) on the corrosion inhibition of AA5052 aluminum alloy in 3 wt% NaCl solution has been studied by weight-loss experiments, electrochemical measurements and surface analysis. MEL inhibits the corrosion of AA5052 aluminum alloy in 3 wt% NaCl solution very well, resulting in a positive shift of the corrosion potential and the pitting potential. The corrosion inhibition efficiency reaches 71.76% at 2 mM MEL. The FT-IR, SEM, XPS and theoretical calculation are used to investigate its corrosion inhibition mechanism. It indicates that MEL coordinates with Al3+ ions via its N (9) atom and O (10) atom to form a surface complex film. This protective film retards the corrosion of AA5052 aluminum alloy significantly. This biomolecule is a promising anti-corrosion additive to protect aluminum alloys heat-exchange in seawater desalination plant.

Elucidation of role of carbon fibers on joining of metal to composite

Weight reduction in the various application fields has propelled to the forefront in investigations of combining metal with polymer. Different from other studies, this work focused on exploring the effect of carbon fibers on the thermal joining of metal to composite. Three plastics with different fiber contents including pure polyether-ether-ketone (PEEK), short carbon fibers reinforced PEEK (SCF/PEEK), and continuous reinforced PEEK (CF/PEEK) were chosen to join to the 6061aluminum alloy using a fiber laser. Results showed the thermal transfer was fostered along the carbon fiber orientation due to a higher thermal conductivity, decreasing the heat accumulation at the interface. However, the existence of carbon fibers also hindered the spreading of plastics on the aluminum alloy surface. This led to a smaller adhesion width and lower tensile-shear force of joints. In addition, the tensile-shear strength of joints prepared with carbon fibers was enhanced owing to lower thermal expansion coefficient, which improved the thermal shrinkage and reduced the stress concentration at the interface. Ultimately, the role of carbon fibers during laser joining of aluminum alloy to plastics was explained, clarifying the bonding mechanism of two materials.

Laser-induced selective wettability transition of 6061 aluminum alloy surfaces

Laser-induced selective wettability transition of 6061 aluminum alloy surfaces

Studies of the mechanism of adhesion of polymer coatings on the oxidized surface of aluminum and magnesium alloys

Studies of the mechanism of adhesion of polymer coatings on the oxidized surface of aluminum and magnesium alloys

Friction and wear performances of 7075 aluminum alloy surface with V-shaped microtexture via numerical simulation and experimental characterizations

Purpose The purpose of this study is to design and process the optimal V-shaped microstructure for 7075 aluminum alloy and reveal its wear resistance mechanism and performance. Design/methodology/approach The hydrodynamic pressure lubrication models of the nontextured, V-shaped, circular and square microtextures are established. The corresponding oil film pressure distributions are explored. The friction and wear experiments are conducted on a rotating device. The effects of the microstructure shapes and sizes on the wear mechanisms are investigated via the friction coefficients and surface morphologies. Findings In comparison, the V-shaped microtexture has the largest oil film carrying capacity and the lowest friction coefficient. The wear mechanism of the V-shaped microtexture is dominated by abrasive and adhesive wear. The V-shaped microtexture has excellent wear resistance under a side length of 300 µm, an interval of 300 µm and a depth of 20 µm. Originality/value This study is conductive to the design of wear-resistant surfaces for friction components.

Study on oxidation mechanism of aluminum surface under applied electric field

The oxidation behavior of aluminum alloy has a significant impact on its industrial application of aluminum alloy, and studying how aluminum alloy oxidizes in electrolyte solutions is crucial. However, current research predominantly focuses on aluminum anodization at higher voltages and the second-phase corrosion behaviors in halide ion-containing solutions. The research on the formation mechanism of the oxide film on the aluminum surface lacks in-depth analysis, and there is no unified opinion on the method of oxygen invasion into the oxide film. This study establishes an experiment on the corrosion of aluminum alloy in an oxygen-free water environment. By scrutinizing the oxidation behaviors of aluminum surface under conditions of no voltage and low voltage, we investigate the effect of applied electric field on the mode of oxygen invasion in alumina. The findings reveal that under the condition of no external voltage and an alkaline environment, self-passivation products of aluminum undergo a transformation from AlO(OH) to Al(OH)3 as the pH value increases. At a pH of 10, complete transformation into Al(OH)3 occurs. When external voltage is applied, Al(OH)3 is initially formed on the aluminum surface with an increase of potential. As the potential reaches a certain value, the potential energy barrier for the reaction of H and O in OH− is disrupted, leading to the reaction of Al3+ replacing H+ and generating an Al2O3 film, with the current on the membrane surface changes unevenly during this process, resulting in the emergence of a double-layer film structure on the aluminum surface. Therefore, under the electrochemical environment of applying a small current, the film formation process on the surface of aluminum alloy is carried out under the action of OH− heterocracking in water, and the O in the water molecule forms two distinct oxide films with the Al matrix in the form of O2− and OH−.

Application of pulsed laser ablation thermal model in nanosecond pulsed laser removal of the epoxy resin paint film

The effect of laser surface paint removal depends on the mechanism of paint removal. The mechanism of nanosecond laser removal of epoxy resin paint film on aluminum alloy surfaces was studied theoretically and experimentally. Firstly, a laser thermal paint removal model was established based on the heat conduction equation, Hertz-Knudsen equation, and Hooke's law. The adsorption relationship between the paint film and the aluminum alloy substrate molecules and the adsorption force between the paint film and the substrate were analyzed and calculated. A laser thermal paint removal model was solved using COMSOL finite element software. By analyzing the changes in temperature and thermal stress with laser fluence, we obtained the theoretical threshold for laser paint removal. Subsequently, experimental research was conducted on laser paint removal. Through theoretical and experimental studies, it was found that the paint removal threshold of nanosecond pulse laser is 0.47 J/cm2. The primary mechanism of nanosecond laser paint removal is thermal stress stripping. When the laser fluence is low, the nanosecond pulse laser can only ablate the paint on the surface, and the thermal stress between the paint film and the substrate makes it difficult to remove the paint film. As the laser fluence increases, the nanosecond laser will ablate the surface paint film, and the thermal stress between the paint film and the substrate will cause the stripping of the underlying paint film and the substrate. The primary mechanism of laser paint removal is stripping.

Laser peening without coating fabricated superhydrophobic aluminum alloy with favorable mechanical properties

This study prepared 2024-T351 aluminum alloy surfaces with excellent hydrophobic properties by laser peening without coating(LPwC) and post-treatment process (silane solution immersion modification treatment). The surface morphology, microhardness, roughness and residual stress of the specimens before and after LPwC were characterized. Besides, the surface composition and droplet contact angle of the specimens before and after LPwC were measured to investigate the mechanism of enhancing the hydrophobic properties by LPwC. The results showed that after LPwC treatment, the surface of the specimen was uniformly distributed with a large number of micro-nano porous structures and the surface roughness was significantly increased. After the modification treatment with fluorosilane solution, the F element on the surface of the specimen significantly increased, the surface energy decreased, the droplet contact angle rose to above 150°, and the sliding angle dropped to below 10°, which imparted the superhydrophobicity on the surface. After LPwC treatment, the grain size of the specimen near-surface layer was reduced, and high magnitude residual compressive stress was generated inside the matrix, which increased the microhardness of material. The as-prepared superhydrophobic surface exhibits excellent water flow repellency and favorable mechanical properties, which promoted the application of superhydrophobic preparation process in the aerospace field.

A novel strategy for preparation of ZrB2–SiC self-transpiration cooling coating by dilution effect of high speed laser cladding

An ablation resistant coating with self-transpiration cooling effect was prepared on the surface of aluminum alloy by dilution effect of high speed laser cladding. The coatings mainly contain ablation resistant phases ZrB2 and SiC, and low-melting phases Al and Al3.21Si0.47. The ablation property of coatings was investigated at different heat fluxes (35.39, 70.77, 106.16, 141.54) MW⸱m−2. The mass ablation rate increased gradually, and the morphology of ablation region changed significantly with the increased heat flux. The self-transpiration cooling effect of coatings was studied by phase, morphology, and element distribution of ablation region. The self-transpiration cooling effect weakened the oxidation behavior of ZrB2 and SiC at heat fluxes of 35.39 and 70.77 MW⸱m−2 and protected the coating from being exhausted when the heat fluxes were 106.16 and 141.54 MW⸱m−2.

Enhancing wear resistance of aluminum alloy by fabricating a Ti-Al modified layer via surface mechanical attrition treatment

The limited wear resistance of aluminum alloys hinders their application in lightweight equipment. Herein, we present the successful fabrication of a Ti-Al modified layer on the surface of aluminum alloy 2024 via surface mechanical attrition treatment (SMAT-Ti). Tribological assessments indicate an improvement in tribological performance. Specifically, the average friction coefficient and wear rate of the SMAT-Ti treated sample decreased by 49.1% and 81.9%, respectively, compared to untreated sample. Analysis of wear surfaces and molecular dynamics simulations demonstrate that the improvements observed can be attributed to the wear-resistant tribofilm formation. Furthermore, the integration of Ti particles beneath the subsurface facilitates the formation of HCP bands and dislocation locks. These microstructural changes obstruct frictional shear deformation and crack propagation, effectively reducing wear.

Research on the construction of gradient nanostructure and anti-tribocorrosion behavior of aluminum alloy surface

Gradient nanostructure in aluminum alloy, constructed via a two-dimensional ultrasonic surface burnishing process, displays enhanced tribocorrosion resistance in artificial seawater. Corrosion tests are undertaken to understand the influence of gradient nanostructure on corrosion resistance, and crystal plasticity finite element models are developed to examine wear resistance. Tribocorrosion tests are performed through wear tests in the artificial seawater environment. The results indicate that the processed samples' corrosion rate decreases from 3.12 × 10−2 mm/a to 2.45 × 10−3 mm/a. The wear scar sizes of the processed samples are approximately half the unprocessed samples. The gradient nanostructure obstructs dislocation glide during wear, diminishes the accumulation shear, and promotes high-hardness corrosion product formation, effectively isolating the direct contact between the friction pairs, thus improving the tribocorrosion resistance.

One-step preparation of high performance Ni-MoS2 self-lubricating coatings via jet electrodeposition on additive manufactured aluminum alloy

Composite coatings with solid lubricants can improve the tribological performance of aluminum alloy parts prepared by Laser Powder Bed Fusion (LPBF). In this study, Ni-MoS2 self-lubricating composite coatings were one-step prepared on additive manufactured aluminum alloy surface via jet electrodeposition. The properties and lubrication performance of the coatings prepared using composite electrolyte with different MoS2 particle diameters and concentrations were investigated. The lubrication mechanism of the composite coating was discussed. The results showed that 0.8 μm MoS2 had less agglomeration than 80 nm, resulting in a uniform surface. The lubrication performance of the composite coating was affected by MoS2 particles content and coating hardness. With the increase of MoS2 concentration in the composite electrolyte, the friction coefficient and wear rate decreased, and achieved the best lubrication performance of 0.12 friction coefficient and 0.11 mg/m wear rate when MoS2 composite electrolyte is 5 g/l and MoS2 is 0.8 μm. However, the addition of soft MoS2 decreased the coating hardness, lower hardness will cause lubrication failure.

Effect of voltage on structure and properties of 2024 aluminum alloy surface anodized aluminum oxide films

In this study, anodized aluminum oxide (AAO) films were fabricated in situ on the surface of a high-strength and robust 2024 aluminum alloy using step voltage and constant voltage modes, respectively. Our study included examination of the microstructure, thickness, microhardness, and electrochemical characteristics of the AAO films. Cross-sectional morphology analysis revealed that the AAO film produced via the step-voltage approach exhibited remarkable density, uniformity, and good quality. In contrast, conspicuous cracks were observed in the AAO film generated under constant-voltage conditions when applied to the 2024 aluminum alloy substrate. Notably, the microhardness of the AAO film prepared using the step voltage method surpassed that of its constant-voltage counterpart. Specifically, the microhardness of the AAO film produced at 30 V via the step voltage reached 289 HV, whereas the equivalent AAO film produced at a constant voltage of 30 V registered only 174 HV. Furthermore, the self-corrosion potential and polarization resistance of the AAO films created using the step voltage were markedly higher than those achieved using a constant voltage. Specifically, the AAO films produced under step voltage conditions, specifically at 30 V and 60 min, exhibited the highest self-corrosion potential and polarization resistance values of namely −0.52 V and 34,888.6 Ω, respectively. In contrast, AAO films prepared under constant voltage conditions displayed values of −0.61 V and 23,292.0 Ω, respectively. Conducting AC impedance measurements and subsequent fitting calculations, the maximum thickness of the AAO film generated via step voltage and constant voltage methods amounted to 132.43 nm and 106.70 nm, respectively. Overall, the microstructure and corrosion resistance of the AAO film formed on the surface of the 2024 aluminum alloy using the step voltage approach demonstrated that it outperformed that of the AAO layer prepared under constant-voltage conditions.Chinese library classification number:TG178 Document ID:A Article ID.

Novel imidazole based ionic liquid as anti-corrosion additive for aluminum alloy: Combined experimental, DFT/MD simulation and soft computing approach

The anti-corrosion effectiveness of novel 1‑butyl‑3-methylimidazolium tetrachloroindate ionic liquid ([C4MIM][InCl4] (IL)) for aluminum-silicon-titanium (Al-Si-Ti) based aluminum alloy in 1mole (M) potassium hydroxide (KOH) electrolyte at 303–343 K was explored in the current study. To realize this, standard methods such as weight loss, electrochemical investigation, density functional theory (DFT)/molecular dynamics simulation (MD-simulation), scanning electron microscope (SEM), and scanning force microscopy (SFM), were employed to scrutinize the anti-corrosion successfulness of [C4MIM][InCl4] for aluminum alloy in KOH solution. From our findings, the ionic liquid mitigated the corrosion of Al-Si-Ti aluminum alloy, and the inhibition efficiency (IE%) is enhanced with improved ionic liquid concentration. The inhibition efficiencies obtained at 0.8 g/L [C4MIM][InCl4] concentration were 88.46%, 82%, and 82.35%, for gravimetric, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) procedures, respectively. PDP result disclosed [C4MIM][InCl4] performed like a mixed-type inhibitor of a cathodic predominance. The SEM/SFM examination proved that the ionic liquid developed a shield coat on the metal alloy surface. The thermodynamic probe disclosed [C4MIM][InCl4] molecules fastened onto Al-Si-Ti aluminum alloy surface by physisorption mechanism and best fitted the Frumkin adsorption isotherm model. The DFT/MD-simulation procedure confirmed the adsorption configuration and orientation of [C4MIM][InCl4] molecules in gas and aqueous phase which is in harmony with the experimental discovering. Simulated neural network (SNN), and the adaptive neuro-fuzzy inference system (ANFIS) were deployed for a robust training, forecast and modeling of the interactive effects of the input parameters and the expected feedback, Herein, training via the ANN and ANFIS designs without (GA), as well as computing the statistical indices such as the mean squared error (MSE), hybrid fractional error function (HYBRID%), absolute average relative error (AARE), Marquardt's percentage standard deviation (MPSED%) and r-squared (R2) were employed to appraise the models capability. The optimal IE% forecasted was 88.4842% and 89.0643%, for the ANN and ANFIS, respectively. Based on the numerical values of the ANN and ANFIS parameters calculated much acceptance was accorded to the ANFIS model over the ANN due its high degree of precision and robustness. The aftermath of this study furnishes additional information on systematic plan of corrosion mitigation, and proffer useful instructions for the logical use of [C4MIM][InCl4] as anti-corrosion additive for Al-Si-Ti aluminum alloy threatened by alkaline solution.

Numerical Simulation and Experimental Study of Nanosecond Pulsed Laser Cleaning of Aluminum Alloy Surface Paint Layer

Numerical Simulation and Experimental Study of Nanosecond Pulsed Laser Cleaning of Aluminum Alloy Surface Paint Layer

Experimental study and mechanism analysis of a pulsed laser cleaning aluminum alloy process.

A pulse laser with a wavelength of 1064nm and a pulse width of 1µs was used to experiment on the coating of a 2024 aluminum alloy surface. The removal performance of the pulse laser cleaning coating was explored by a single factor analysis and orthogonally conditions, and the effects of the laser power, scanning speed, and pulse frequency on the quality of laser coating removal were summarized. The mechanisms of pulse laser cleaning the coating were studied. The results show that the three parameters of the laser power, scanning speed, and pulse frequency have different effects on the quality of laser coating removal. Among them, with the increase of the scanning speed and pulse frequency, the quality of laser cleaning first increases and then decreases, respectively. With the increase in laser power, the quality of laser cleaning increases. A good laser cleaning quality can be achieved at the laser power of 16.5W, a scanning speed of 600mm/s, and a pulse frequency of 30kHz. The laser cleaning coating involves a variety of mechanisms such as combustion, explosion, gasification, thermal vibration stripping, and laser plasma impact. The result can provide practical references for a better searching of the paint removal.

Review of the state of art of Li-based inhibitors and coating technology for the corrosion protection of aluminium alloys

The quest for novel alternatives to hexavalent-chromium-based corrosion inhibitors is of utmost significance and urgency. Strict international health and safety regulations, due to growing concerns regarding the impact of hexavalent chromium on human health and the environment, have pushed the commercial introduction of many alternative inhibitor types, but the implementation of alternative active protective primers for structural parts in the aerospace industry is still pending. This endeavour has proven to be remarkably challenging, as the potential replacement coating types must meet numerous functional requirements encompassing cost-effectiveness and exceptional corrosion protection for intrinsically corrosion susceptible aerospace aluminium alloys. In recent years, considerable attention has been drawn to lithium salts as environmentally friendly corrosion inhibitors forming the basis for a novel active protective coating technology. The involvement of lithium ions has been shown to play a pivotal role in the conversion process of aluminium alloy surfaces by stabilizing the reaction products, thereby facilitating the gradual development of a protective layer with a multi-layered configuration, which exhibits considerable variability in morphology, depending on local chemical and electrochemical conditions. The versatility of the lithium-based corrosion protection extends to their application as corrosion inhibiting pigments in organic coatings or as a pre-treatment, directly forming conversion layers, thereby enhancing their practical implementation. However, previous chromate replacement reviews only introduced the promising outcomes provided by the lithium technology, omitting key details of its development and formation mechanism. This paper critically reviews and summarizes the studies conducted to date on lithium-based inhibitor technologies for the corrosion protection of aluminium alloys as well as topics to be investigated in the future.