AA6061-T6 Aluminum Alloy Research Articles

Effectiveness of Sodium Silicate on the Corrosion Protection of AA7075-T6 Aluminium Alloy in Sodium Chloride Solution

Effectiveness of Sodium Silicate on the Corrosion Protection of AA7075-T6 Aluminium Alloy in Sodium Chloride Solution

The Role of APTES as a Primer for Polystyrene Coated AA2024-T3.

(3-Aminopropyl)triethoxysilane (APTES) silane possesses one terminal amine group and three ethoxy groups extending from each silicon atom, acting as a crucial interface between organic and inorganic materials. In this study, after APTES was deposited on the aluminum alloy AA2024-T3 as a primer for an optional top coating with polystyrene (PS), its role with regard to stability as a protection layer and interaction with the topcoat were studied via combinatorial experimentation. The aluminum alloy samples primed with APTES under various durations of concentrated vapor deposition (20, 40, or 60 min) with an optional post heat treatment and/or PS topcoat were comparatively characterized via electrochemical impedance spectroscopy (EIS) and surface energy. The samples top-coated with PS on an APTES layer primed for 40 min with a post heat treatment revealed excellent performance regarding corrosion impedance. A primed APTES surface with higher surface energy accounted for this higher corrosion impedance. Based on the SEM images and the surface energy calculated from the measured contact angles on the APTES-primed surfaces, four mechanisms are suggested to explain that the good protection performance of the APTES/PS coating system can be attributed to the enhanced wettability of PS on the cured APTES primer with higher surface energy. The results also suggest that, in the early stages of exposure to the corrosion solution, a thinner APTES primer (deposited for 20 min) enhances protection against corrosion, which can be attributed to the hydrolytic stability and hydrolyzation/condensation of the soaked APTES and the dissolution of the naturally formed aluminum oxide pre-existing in the bare samples. An APTES primer subjected to additional heat treatment will increase the impedance of the coating system significantly. APTES, and silanes, in general, used as adherent agents or surface modifiers, have a wide range of potential applications in micro devices, as projected in the Discussion section.

The effect of heat treatment on the microstructure and electrochemical corrosion behavior of multilayer AA6061 alloy fabricated by additive friction stir deposition

Multilayer AA6061 aluminum alloy components were successfully fabricated by additive friction stir deposition (AFSD). The effect of heat treatment on the microstructure and electrochemical corrosion behavior of the AA6061-T6 aluminum alloy components was studied. The average grain size in AFSD samples was 2.67 μm, where 89.7 % of grains were smaller than 5 μm. Abnormal grain growth was observed in the heat-treated AFSD (AFSD-HT) sample, and the average grain size of AFSD-HT sample was 592 μm. In the base material (BM) sample, apart from the β″ strengthening phases, hard-brittle Al5FeSi intermetallic compounds (IMCs) aggregated along the boundaries of the coarser grains. Due to the high temperature generated during the process of AFSD, β″ phases dissolved into the matrix. After heat treatment, a larger amount of fine needle-like β″ phases were re-precipitated in the AFSD-HT sample. Al5FeSi IMCs accelerated the corrosion of the Al matrix. Fine β″ phases significantly inhibited the corrosion expansion to Al matrix and improved the corrosion resistance of AA6061 alloys.

The effect of chemical etching and nanostructure additive epoxy coating technique on adhesion strength in aluminum joints bonded with nanostructure additive adhesive

In the present study, in order to increase the strength of adhesively bonded joints, the surface of the adherend was chemically etched with an anodizing treatment process at different temperatures and the surface was coated with nanostructure doped epoxy. Additionally, carbon nanostructures were added to the adhesive at different ratios to increase the strength of both the adhesive and the joint. In the study, in order to clean the surfaces of AA2024-T3 aluminum alloy plates and eliminate the oxide layer, the plates were chemically treated with a sodium hydroxide solution. Afterwards, the surfaces of these aluminum alloy plates were chemically etched with an anodizing treatment process at temperatures of 25, 40 and 60 °C. The aim here is to create different surface roughness and surface energy on the aluminum alloy surface. Epoxy pre-coating (EPC) was applied to the chemically etched aluminum alloy surfaces. Furthermore, a single-lap joint was produced by adding 0.5 %, 1 % and 2 % carboxylated carbon nanotube (CNT-COOH) by weight to the EPC and adhesive applied to the surfaces and the failure loads of the joints were examined. As a result, when the failure load obtained from the experiments was examined, it was found that chemical etching alone increased the joint strength by 22 % while the chemical etching and EPC application increased it by 46 %, the chemical etching and nanostructure doped EPC application increased it by 61 % and nanostructure addition to the adhesive increased it by 93 %. However, these increases in joint strength vary depending on the duration of the anodizing treatment process and the nanostructure additive ratio. In the chemical analyses performed to interpret these results, surface roughness test, surface contact angle test, X-ray photoelectron spectroscopy (XPS), fourier-transform-infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and images obtained from the failure surfaces were used, respectively.

Superhydrophobic and self-healing silane-ceria composite coating implanted with 1,5-naphthalenediol inhibitor for corrosion protection of AA2024-T3 aluminum alloy

A superhydrophobic silane coating was modified by incorporating hollow CeO2 nanocontainers loaded with 1,5-naphthalenediol (ND) and used for the corrosion protection of an AA2024-T3 aluminum alloy. The CeO2 nanocontainers exhibited a high loading capacity of 22.1 % for the ND inhibitor. After 8 h immersion, 93 % of the ND inhibitor was desorbed from CeO2@ND nanoparticles in a 3.5 wt% NaCl solution. Electrochemical impedance spectroscopy results indicated that the incorporation of CeO2@ND particles significantly enhanced the polarization resistance and the protection efficiency of the fabricated silane-CeO2@ND hybrid coating was 98.3 %. Additionally, the protection efficiency of the coating slightly decreased to 98.2 % after 25 days of corrosion. Moreover, the scratch test indicated an excellent self-healing capability of silane-CeO2@ND nanocomposite. The outstanding self-repairing property of the coating was depended on the synergistic effects of inhibitive CeO2 nanocontainers and the loaded ND inhibitor.

Effect of process parameters on friction stir welding of aluminium alloy AA6082–T6 with an interlayer using response surface methodology

In the present study, the effects of variation of process parameters on the mechanical properties of friction stir welded A6082–T6 aluminium alloy joints with Zinc (Zn) interlayer are experimentally investigated. Four process parameters, viz. rotational speed, welding speed, interlayer thickness and tool pin diameter are selected to fabricate the Friction Stir Welding (FSW) joints. After filling the Zn particles into the gap maintained between the plates, FSW is performed using different process parameters. Thereafter, tensile and impact strength tests are performed to evaluate the performance of the joints. It is analyzed that the tensile and impact strength of the joints vary from 121 to 197 MPa and 6 to 17 J, respectively. Subsequently, mathematical models are developed using Response Surface Methodology (RSM) to predict the effect of FSW process parameters on the tensile and impact strength of joints. Analysis of Variance (ANOVA) is used to check the level and degree of direct effect of process variables on the tensile and impact strength of the joints. It is observed from the results that tool rotational speed is the most influential process parameter, which enhances the mechanical properties of FSW joints, whereas an increase in welding speed reduces the mechanical properties of the joints.

Achieving an improved performance in double-sided friction stir weld joints by adjusting the welding conditions during the passes of AA6061-T6 aluminium alloy

The present study aims at investigating the effect of interaction between the process parameters of each weld pass (1st pass and 2nd pass) to improve the joint performance during the double-sided friction stir welded joints of AA6061-T6 aluminium alloy. Experimental designs were conducted following a design matrix developed using response surface methodology to investigate the impact on the microstructural changes and tensile properties. Pronounced interaction between the process parameters of each weld pass of the joint was observed and indicated a strong interdependency between them. The detailed microstructural study conducted through EBSD insights into the extent of homogenization, and abnormal grain refinement and reflects a vast transformation of low-angle grain boundaries into high-angle grain boundaries within the stir zone. The profound examination through scanning electron microscopy and transmission electron microscopy analysis validated the uniform homogeneous distribution of Al-Fe and Al-Si-rich precipitates. The significant improvement in the grain refinement and distribution of the strengthening precipitates within the stir zone led to a substantial enhancement in the microhardness, along with achieving a maximum ultimate tensile strength of 223 MPa and a percentage elongation of 14%. A study of the fracture morphology ensures the ductile fracture behavior of the tensile fracture specimen by observing the presence of numerous dimples within a well-bonded joint.

Design and Development of Novel AA7075-T6 based Armor Plate through Numerical and Experimental Approach

The materials used for ballistic applications have always taken a special spot in the manufacturing and study of protective amours. Although metals like steel provide adequate ballistic protection, they compromise the mobility of the soldier and since high mobility is a primary requirement for soldiers during combat. Therefore, at present most of the researchers are currently focusing on materials with properties like high impact resistance and high strength to weight ratio. In recent times, Aluminum alloys are recognized as the alternative materials which can provide good impact resistance and have a high strength to weight ratio and having better corrosion resistant properties which ultimately make it a suitable material for several military applications. In this research, one of the toughest aluminum alloys AA7075-T6 is considered for designing an armor plate and studied for its ballistic resistance. Initially, the monolithic AA7075-T6 alloy of 18 mm was tested for its ballistic resistance limit and further it is designed with the ceramic plate of 3 mm and base alloy AA7075-T6 of 15 mm was tested to evaluate. Later the monolithic alloy of 18 mm was surface reinforced up to a thickness of 3 mm with different types of reinforcements and evaluated the bullet residual velocity after penetration of the armor piercing projectile. Numerical simulation was conducted using the prominent non-linear dynamic analysis software i.e., Ansys AUTODYNE version 19.2 and the respective values for the surface reinforced metal matrix composites revealed excellent results for the depth of penetration and residual velocity of the projectile.

An experimental method for choosing the tool pin profile and shoulder size to join dissimilar aluminum alloys AA7075-T651 and AA6061-T6 joints

Many military and light weight aircraft designs call for joints between two different grades of aluminium alloy. This present study looked at the effect of tool shoulder diameter and tool pin profile on the tensile strength properties of dissimilar aluminium alloy AA6061-T6 and AA7075-T651 joints created by friction stir welding. The joints were fabricated utilizing three distinct tool shoulder diameters 15 mm, 20 mm and 25 mm along with two distinct tool pin profiles namely taper and square. The microstructure and microhardness of weld stir zone (WSZ) were examined and linked with the strength parameters of the joints. Adequate frictional heat generation from 20 mm shoulder diameter and pulsating stirring action of square pin revealed the formation of very fine grains in the weld nugget zone (WNZ). Due to enhanced material flow and the production of a defect-free stir zone, the joint created using a tool with a 20 mm shoulder diameter and square pin profile had the maximum hardness of 117 HV and the highest tensile strength of 284 MPa. The ductile mechanism of fracture is revealed by the presence of fine dimples accumulating in the tensile fractured surface of the joint fabricated by 20 mm tool shoulder diameter and square pin.

Welding characteristics of ultrasonic-assisted laser-MIG hybrid welding for AA6082-T6 aluminum alloy plate with different vibration modes

Welding characteristics of ultrasonic-assisted laser-MIG hybrid welding for AA6082-T6 aluminum alloy plate with different vibration modes

Ductilization and grain refinement of AA7075-T651 alloy via stationary shoulder friction stir processing

This study investigates the microstructural evolution, mechanical properties, and fracture behavior of AA7075-T651 aluminium alloy subjected to stationary shoulder friction stir processing (SSFSP). SSFSP samples were produced at three different rotational speeds in a range of 600–1000 rpm. The results reveal that SSFSP leads to a uniform grain refinement within the Stir Zone (SZ), reducing the grain size to approximately 2–3 μm from the initial 15 μm in the base material (BM) irrespective of the probe rotational speeds. After SSFSP, the elongation increased by over 50 % at the cost of 10 % reduction in the ultimate tensile strength for all samples. It was worth to note that variations in tool rotational speed exhibited minimal influence on the microstructure and mechanical properties, offering wide range of probe rotational speeds. This could be attributed to the use of non-rotating shoulder with prob dominated microstructure in the SZ. Fractographic analysis confirmed the ductile nature of fractures, revealing development of fine dimples due to grain refinement. This work underscores the effectiveness of SSFSP in achieving significant grain refinement followed by drastic increase in ductility, which offers valuable insights for using stationary shoulder at wider range of rotational speed.

Machining aerospace aluminium alloy with cryo-treated and untreated HSS cutting tools

ABSTRACT In this study, effects of drilling parameters and cryogenic treatment, which were applied to the cutting tool (M35 HSS drill bit), on the burr width, surface roughness (Ra), chip formation and tool wear were investigated in drilling of AA2024-T3 aluminium alloy under dry drilling conditions. In this context, the drilling parameters determined based on the Taguchi experimental design were employed, and also, the analysis of variance (ANOVA) and regression analysis were performed. The spindle speed (1500, 3000 and 4500 rev/min), feed rate (100, 150 and 200 mm/min) and cutting tool (cryo-treated and untreated M35 HSS tools) were selected as machining parameters. In terms of average burr width, the performance of the cryo-treated (DC&T) HSS drill bit was 28.91% (for the highest value) and 46.96% (for the lowest value) better than that of the untreated (UT) HSS drill bit. According to Ra values, the performance of DC&T HSS drill bit was 13.29% (for highest value) and 12.01% (for lowest value) better than that of UT HSS drill bit. The flank wear (VB) of UT HSS drill bit was found to be approximately four times greater than the flank wear of DC&T HSS drill bit.

Probing corrosion using a simple and versatile in situ multimodal corrosion measurement system

In this work, we have developed a unique in situ multimodal corrosion system that is capable of acquiring electrochemical data, sample imaging/visualization and hydrogen collection, simultaneously. Each of these modalities yield valuable information pertaining to the ongoing corrosion process. Combining them can yield holistic information on the role of microstructure, processing history, presence of coatings, etc., on the sequence of steps occurring during the corrosion process, and how they correlate with the acquired electrochemical data. Four materials systems, namely AA6061-T6 aluminum alloy, AZ91 magnesium alloy, galvanized DP590 steel, and pure Zn, were investigated under open circuit potential and under potentiodynamic polarization. The multimodal corrosion system was utilized to observe processes such as surface passivation and dissolution, pit and filiform corrosion initiation and propagation, and was correlated with location and magnitude of hydrogen evolution. This approach is shown to yield a truly multimodal understanding of the ongoing corrosion processes.

Fatigue life simulation of AA7075-T651 FSW joints using experimental data

The friction stir welding (FSW) process is a solid phase type applied in this study to connect AA7075-T651 aluminum alloy plates. This study investigates the impact of welding input quantities such as tool rotational speed, welding speed, shoulder radius, and tool geometry on welding joint quality, including strength, toughness, hardness, fractography, and fatigue behavior. Also, in this study, the fatigue life in the base material (BM) and joints obtained from the simple, threaded, and truncated triangular pyramid pins as an FSW effective input parameter was obtained by the finite element analysis (FEA). The experimental outcomes represented that the mechanical attributes of the threaded pin are higher than that of the simple and truncated triangular pyramid pins with the same input parameters. Also, the outcomes of the numerical simulation with the experimental outcomes of fatigue life for the BM were in acceptable agreement, and the error value of the validation result for σmax=0.5σy for the stress ratio R=-1 was equal to 0.4%. In addition, the FEA results indicated that the fatigue strength of FSW joints in the stir zone for the threaded, simple, and truncated triangular pyramid pins in the fatigue life of 107 cycles was 64%, 63%, and 43% of the BM, respectively.

Local scanning electrochemical microscopy analysis of a lithium-based conversion layer on AA2024-T3 at progressive stages of formation

Scanning electrochemical microscopy (SECM) is employed to characterize the evolution of local electrochemical surface activity during lithium-based conversion layer formation on legacy aerospace aluminium alloy AA2024-T3. Initially, three types of studied intermetallic particles - S-, θ- and constituent phases - act as active cathodic areas. Subsequently, θ- and constituent phases show passivation preceding that of S-phase particles during the later conversion layer formation stages. The entire surface, including the matrix region, shows a higher reactivity at the beginning and then gradually shows decreasing reactivity. Hydrogen evolution-generated bubbles attach to the alloy surface and locally hinder the conversion layer formation, weakening the corrosion protection the conversion layer provides at those locations.

Significance of FSW process parameters and tialite particle reinforcement at the weld zone of AA6082 alloy

In the current work, tialite (Al2TiO5) ceramic particles are added at the weldment during the friction stir welding of AA6082-T6 aluminium alloy. Three different values of tool rotational speed (TRS) (1000, 1200 and 1400 rpm) and welding speed (WS) (35, 40 and 45 mm/min) are taken into consideration in fabricating joints. Totally nine joints are fabricated by adding tialite particles and examinations like microstructural analysis and mechanical properties are carried out to find the quality of the joints. Defect-free welds are obtained for optimal process parameters which is a result of good mixing of base materials with uniform particle distribution. The highest ultimate tensile strength (UTS) (273 MPa) is noticed for specimen fabricated using TRS 1200 rpm and WS 40 mm/min. The peaks from the X-Ray diffraction (XRD) analysis have confirmed the presence of tialite particles in the welded samples. According to the micro hardness profile, the stir zone (SZ) (136.4 HV) and heat affected zone (HAZ) (79.8 HV) have the highest and lowest micro hardness values, respectively.

Polyorganosilazane/GPTMS functionalized silica coatings as an integrated corrosion–resistance system for AA2024-T3 aluminum alloy

A hybrid coating based on polyorganosilazane (Durazane® 1800) combined with 3-glycidyloxypropyltrimethoxysilane (GPTMS) was successfully synthesized to improve the corrosion resistance of the AA2024-T3 aluminum alloy. The polymers were cross–linked with the addition of tetra-n-butylammonium fluoride (TBAF), and the hybrid coatings were deposited on aluminum substrates by dip coating and dried at 120 °C. Crack-free films with a thickness of 13 μm were obtained. Field emission electron microscopy (FESEM) analysis indicated that the synthesized hybrid films were smooth, homogenous, and devoid of cracks. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) studies demonstrated that the intensity of the Si–N–Si peak was maintained, showing that the backbone of the polysilazane was preserved after the addition of GPTMS. Nuclear magnetic resonance (NMR) spectroscopy indicated that glycidoxypropyl groups were still present in the Si–O–N network of the modified polysilazane. Contact angle measurements indicated that the hybrid coatings were hydrophobic, with a measured contact angle of 93 ± 6°. The electrochemical results confirmed that the synthesized hybrid coatings improved the corrosion resistance of the aluminum substrate in 3.5 wt% NaCl solution. This suggest that the modified polyorganosilazane coating is an effective solution for developing anti-corrosive coatings on metal substrates, offering excellent adhesion strength and good scratch resistance.

Additive Friction Stir Deposition of AA7075-T6 Alloy: Impact of Process Parameters on the Microstructures and Properties of the Continuously Deposited Multilayered Parts

In the aircraft industry, the high-strength aluminum alloys AA7075 and AA2024 are extensively used for the manufacture of structural parts like stringers and skins, respectively. Additive manufacturing (AM) of the AA7075-T6 aluminum alloy via friction stir deposition to build continuously multilayered parts on a substrate of AA2024-T4 aluminum has not been attempted so far. Accordingly, the present work aimed to explore the applicability of building multilayers of AA7075-T6 alloy on a substrate sheet of AA2024-T4 alloy via the additive friction stir deposition (AFSD) technique and to optimize the deposition process parameters. The experiments were conducted over a wide range of feed rates (1–5 mm/min) and rotation speeds (200–1000 rpm). The axial deposition force and the thermal cycle were recorded. The heat input to achieve the AFSD was calculated. The AA7075 AFSD products were evaluated visually on the macroscale. The microstructures were also investigated utilizing an optical microscope and scanning electron microscope (SEM) equipped with an advanced EDS technique. As well as the presence phases, the mechanical performance of the deposited materials in terms of hardness and compressive strength was also examined. The results showed that the efficiency of the deposition process was closely related to the amount of heat generated, which was governed by the feeding rate, the rotational speed, and the downward force. AA7075 defect-free continuously multilayered parts were produced without any discontinuity defects at the interface with the substrate at deposition conditions of 1, 2, 3, and 4 mm/min and a constant 400 rpm consumable rod rotation speed (CRRS). The additively deposited AA7075-T6 layers exhibited a refined grain structure and uniformly distributed fragment precipitates compared to the base material (BM). The gain size decreased from 25 µm ± 4 for the AA7075-T6 BM to 1.75 µm ± 0.41 and 3.75 µm ± 0.78 for the AFSD materials fabricated at 1 and 4 mm/min deposition feeding rates, respectively, at 400 rpm/min. Among the feeding rates used, the 3 mm/min and 400 rpm rod rotation speed produced an AA7075 deposited part possessing the highest average hardness of 165 HV ± 5 and a compressive strength of 1320 MPa.

Prediction of Axial Force on Dissimilar Aluminum Alloys Friction Stir Welding Using Design of Experiment

Friction stir welding (FSW) has become very popular for joining similar or dissimilar aluminum alloys. The heat used for this welding process is caused by friction between the welding tool and the workpiece which the axial force, the main parameter for heat generation, plays a very important role. Insufficient heat during welding will result in defective workpieces. This research is aimed to predict the axial force from the relevant factors of the FSW of dissimilar materials (aluminum alloys AA2024-T3 and AA6061-T6). The 23 full factorial design with center point was used for this experiment that consisted of 3 main factors: 1) rotation speed (rpm), 2) welding speed (mm/min), and 3) pin geometry each factor has 2 levels and 2 replications with the total of 20 experiments. The axial force data of each experiment were collected using a stationary dynamometer which obtained the data acquisition every 0.1 seconds (frequency of 10 Hz). The results from the design of experiment were analyzed by statistical method at the significance level of α = 0.05 which found that the significance and the optimum value of the main factors were rotation speed of 1500 rpm, welding speed of 35 mm/min, pin geometry of tri flat threaded, and the 2-way interaction between rotation speed and pin geometry. Furthermore, the prediction of the average axial force value on dissimilar aluminum alloys obtained from the specified parameters equals 478.91 N.

Mechanical properties and microstructure of aluminum alloy 7075-T6 spot-welding joint

In this study, an orthogonal experiment was conducted to investigate the effects of various process parameters on the mechanical properties of resistance spot welding joints in AA7075-T6 aluminum alloy. A numerical simulation was also performed to determine the optimal parameter combination. The mechanical properties, macro-morphology, and microstructure of the joints were characterized and analyzed through a series of tests including tensile testing, super depth-of-field testing, metallographic observation, and microhardness testing. The results show that the welding parameters have a significant effect on the mechanical properties of the joints with the following order of influence: welding time > welding current > electrode pressure. The combination of 60 ms welding time, 17 kA welding current, and 0.22 MPa electrode pressure yielded the best comprehensive mechanical properties with an average tensile load of 2364N and an energy absorption value of 6.8 J. The numerical simulation results are consistent with the nugget size of this parameter combination. During spot welding, spatter defect occurs, shrinkage cavity exists at nugget interface, strengthened T-phase and finer equiaxed grain structure precipitate in nugget center. After welding process and microstructure change, the hardness of the nugget zone is lower than that of the base material while the hardness of the nugget center is higher than that of the edge. The failure mode of the joint is interface fracture.