Aluminum Alloy 2024-T3 Research Articles

Material characterisation of anodising effects on small fatigue crack nucleation in AA7XXX alloys

The precursor cleaning steps in the anodising surface finish process for aluminium alloy aircraft parts are known to lead to etching of surface-breaking intermetallic particles and grain boundaries, which in turn leads to preferential sites for fatigue crack nucleation. Type 1C anodising per MIL-A-8625F, is a favoured aircraft aluminium part corrosion protection treatment meeting modern health and environmental requirements. Type 1C anodising uses electrolysis in a non-chromic acid bath (typically based on sulphuric, boric-sulphuric or phosphoric acid formulations) to develop a thick aluminium oxide surface layer. In previous studies the equivalent initial damage sizes of these nucleation sites was calculated from near surface fatigue crack growth measurements using quantitative fractography in both Type 1C anodised aluminium alloy 7050-T7451 and 7085-T7452. A notable difference was observed in the values for these two materials with AA7085-T7452 equivalent initial damage sizes being significantly smaller. Since these values are critical crack starting size assumptions in fatigue life analysis for aircraft fleets, the observed differences must be investigated and explained for notionally similar alloys under identical conditions.In this work, the material surrounding the population of crack nucleation sites in several Type 1C anodised fatigue tested specimens manufactured from AA7050-T7451 and AA7085-T7452 materials has been characterised using precise surface preparation methods and scanning electron microscopy techniques. It has been demonstrated that there is a statistically significant difference in the number, size, aspect ratio and distribution of surface breaking Al7Cu2Fe intermetallic particles beneath the anodising layer that, when etched out during the anodising process, are responsible for fatigue crack nucleation in 7050-T7451 over 7085-T7452 material. The increased size, angular shape and coverage of these intermetallics in AA7050 serves to increase their effectiveness as preferential locations for fatigue crack nucleation through two mechanisms, as a highly localised stress concentrating feature, as well as through their ability to sample more of the material's microstructural features ensuring a discontinuity is present in the most favourable orientation and location for fatigue crack nucleation.

Evaluations of low-temperature mechanical properties and full-range constitutive models of AA 5083-H112/6061-T6

The low-temperature mechanical properties of aluminium alloys (AAs) are important for the analysis and design of infrastructures in cold regions and LNG storage tanks made of AAs. This paper investigated the stress-strain behaviours of AA 5083-H112/6061-T6 materials through conducting tensile tests on 32 AA coupons at 20 ℃ ∼ −165 ℃. All the tested AA coupons exhibited ductile failure modes. Their results showed that the stress-strain curves of AA 5083-H112 exhibited the Portevin-Le Chatelier effects that gradually weakened with the decreasing temperature. Reducing the temperature from 20 ℃ to −165 ℃ increased the elastic modulus, yield and ultimate strengths of AA 5083-H112 (or 6061-T6) by 5.1% (6.5%), 8.7% (12.0%) and 7.8% (13.1%), but reduced the fracture strain by 16.4% (12.4%). The fracture surfaces of all AA 5083-H112 and 6061-T6 coupons displayed localised cross-sectional area reductions and substantial plastic deformation. Meanwhile, precipitation-hardened AA 6061-T6 exhibits a more pronounced enhancement compared to strain-hardened AA 5083-H112. Furthermore, regression analyses were performed to establish prediction equations for the low-temperature mechanical indexes of AAs. Subsequently, a full-range constitutive model was proposed to estimate the stress-strain behaviours of AA 5083-H112 and 6061-T6. Validations against reported experimental observations demonstrated that the developed model reasonably described the stress-strain responses of AA 5083-H112 and 6061-T6 from 20 ℃ to −165 ℃.

Study of optimization for material processing parameters by means of probabilistic methodology for multi-objective optimization

Optimization for material processing parameters is a typical problem of multi-objective optimization, therefore selection and use of proper multi-objective optimization approach is indispensible. The inherent characteristic of newly proposed probabilistic methodology for multi-objective optimization is that it is with the feature of optimization of multiple objectives at the same time in viewpoint of system theory and in spirit of probability theory. In the present paper, the probabilistic methodology is employed to perform the designs of materials processing for improving quality and cost saving at the same time. The laser welding process of ANSI 304 austenitic stainless steel by using a pulsed Nd: YAG laser welding system and thin-wall machining of milling aluminum alloy 2024-T351 are taken as two examples. The quantitative optimum design of materials processing is performed equitably by conducting the assessment of preferable probability of each alternative. The studies indicate that: (1). the optimized parametric combination for the laser welding process of 2 mm thickness ANSI 304 austenitic stainless steel by using a pulsed Nd: YAG laser welding system is at laser parameters of 2.7 kW peak power, welding speed of 2 cm/min and pulse duration of 4 ms; (2). the optimized combination parameter for the thin-wall machining of milling aluminum alloy 2024-T351 is at tool diameter of 8 mm, feed per tooth of 0.06 mm/z, axial cut depth of 24 mm and radial cut depth of 0.625 mm. The optimal configurations guarantee the comprehensive quality of product and reducing energy consumption.

Investigation of Gas Turbine Blade Materials for Efficient Energy System

The present study aims to determine the best and most economical material for a gas turbine blade, which operates under high-temperature conditions and experiences high static structural and thermal loads. To achieve this objective, three different types of material alloys, namely Titanium alloy Ti6AL4V, Magnesium alloy AZ80, and Aluminum alloy 7075-T6, were selected for comparison. A turbine blade model was designed using Solid Works software, and structural and thermal analyses were performed using ANYAS 15.0 under steady-state conditions. The structural analysis aimed to determine the stress, strain, and deformation results on turbine blades by applying high pressure, while the thermal analysis aimed to determine the temperature distribution influences and heat flux generation by applying high temperatures. Based on the results obtained from both analyses of the three different materials, Titanium alloy Ti6AL4V is the best and most economical material. This material showed low stress, strain, and little deformation and the best material properties at high temperatures when compared to Magnesium alloy AZ80 and Aluminum alloy 7075-T6.

Effect of joint configurations on joint strength of different thickness AA6061-T6 friction stir welded blank

This paper presents a comparative study of the mechanical properties and microstructures of three friction stir welded joint configurations, namely square butt (SB), scarf (SC), and double butt lap (DBL) of the aluminium alloy 6061-T6. The experiment was conducted on two aluminium plates of different thicknesses, 2.0 mm on the advancing side and 1.5 mm on the retreating side, at constant welding parameters, such as welding speed, spindle rotation, tool tilt angle, and tool profile. The study compared the joints at different rolling angles, i.e. 0/0, 90/90, 0/90, and 90/0°. Tensile tests were conducted on the joints, and the ultimate tensile strength (UTS) was found to be 6–11% higher in the DBL joint configuration compared to the SC and SB joint configurations. The Vickers hardness values of the SC and DBL joints were also found to be higher than those of the SB joint configuration. The formation of the ‘S’ line was observed to influence the tensile test, hardness, and grain size, which in turn are determined by the shape of the faying surface.

Effect of pre-corrosion on crack initiation behavior of friction stir welded aluminum alloy 2024-T3 in high and low cycle fatigue regimes

The effect of microstructural inhomogeneity and pre-corrosion in 3.5% NaCl solution is investigated on the fatigue crack nucleation behavior of welded AA2024-T3. The localized corrosion affects the heat-affected zone more than the weld nugget zone. The formation of corrosion pits often occurs in the region between the adjacent Al-matrix and intermetallic particles due to the reverse polarity behavior of S-phase precipitates (Al2CuMg) in the saltwater environment. Further, the long-term stability of the welded joint is examined by immersing the specimens in 3.5% NaCl solution for different time intervals ranging from 10 hrs to 200 hrs. After 100 hrs of immersion in the salt water, high and low cycle fatigue behavior of the corroded samples has been examined. Long-term exposure to the saltwater environment results in intergranular corrosion due to localized pitting. The micro-mechanism of the pitting process under salt water and its effect on fatigue lives is studied.

Augmented Laser Impact Welding: A New Process Demonstration in Welding Aluminum Alloy 2024-T3

Augmented Laser Impact Welding: A New Process Demonstration in Welding Aluminum Alloy 2024-T3

Conceptual Design and Numerical Validation of a Carbon-Based Ink Injector.

This paper shows the design of an injector, using carbon nanotubes as inkjet material, implemented in a 3D printer. According to the available literature, few injectors are capable of depositing material. Due to the lack of information, the central part of this research is to develop a suitable device for ink injection that is capable of applying the Fused Deposition Modeling (FDM) method to print nanomaterial ink. The injector was designed using a CAD program based on an open-source desktop 3D printer, which allows it to be modified according to the needs of the injector. This prototype was manufactured in aluminum alloy 7075T6. Computational fluid dynamics (CFD) were carried out to analyze the behavior of the fluid when it passes through the injector, obtaining parameters such as pressure, velocity, and vorticity. An experimental matrix of the injector operation was carried out to achieve an adequate printing speed. The results show that the optimum speed was 250 ms, considering that a temperature of 100 °C is needed in the heated bed to dry the ink so that it does not undergo expansion.

A ELASTO-PLASTIC CONSTITUTIVE MODEL BASED ON CHABOCHE KINEMATIC HARDENING OF ALUMINUM ALLOY 7050-T7451

The elasto-plastic behavior of the aluminum alloy 7050-T7451 subjected to cyclic loading was investigated and modeled. The objective of this work is to improve the constitutive model of Chaboche with a special emphasis in the compression. In the proposed model, the part under tension of the stress-strain curve in the stable hysteresis cycle is modeled separately from the compressed one, where it is considered that they have different Modulus of Elasticity. The work includes both simulation and experimental data, and they are compared to each other. The values were collected experimentally by the application of symmetric cyclic strain-driven loading in the strain range between 0.75% and 2.25%. The experimental results were used to calculate the parameters of the constitutive model in a MATLAB® software. The responses obtained with the proposed model have greater adherence to the experimental results than those obtained with the Chaboche model.

Joining of PP/EPDM TPV to aluminium alloy 6061-T6 directly via generating sorbate in situ and adjusting the heat input of welding

At present, it is difficult to join the non-polar thermoplastic vulcanization based on Polypropylene (PP)/Ethylene-Propylene-Diene (EPDM) to aluminium alloy 6061-T6 (A6061) directly because of the great difference in physical and chemical properties between them. In this paper, zinc sorbate (ZDS) was introduced into the dynamic vulcanization process of PP/EPDM TPV to achieve high performance TPV interface modification. The results show that the polymerization of ZDS can enhance the interface compatibility, melt strength and surface energy of PP/EPDM/ZDS TPV while reducing the linear expansion coefficient of TPV. On this basis, the plate curing machine is used to simulate friction stir welding, and the heat input (temperature:180 °C, pressure:20 MPa, welding time:60 s) was optimized. PP/EPDM/ZDS TPV was directly connected to A6061, and the influencing factors of the joint strength were analyzed. The results show that the tensile shear strength of composite joints decreases with the static time and then keeps stable, reaching 3.53 MPa. The chemical bond (Al-C) is formed at the interface between A6061 and PP/EPDM/ZDS TPV, which plays a key role in improving the strength of the joint. The results of this work can expand the application range of PP/EPDM TPV, and provide basic data and theoretical support for the connection between TPV and metal.

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.

Corrosion resistance assessment of copper, mild steel, and aluminum alloy 2024-T3 in acidic solution by a novel imidazothiazole derivative

In this study, the corrosion resistance of three different metals such as copper (Cu), mild steel (MS), & aluminium alloy 2024 - T3 (Al) in contact with a molar hydrochloric acid solution containing a novel imidazothiazole-based heterocyclic compound, namely, (E)-1-(4-methoxyphenyl)-3-(6-phenylimidazo[2,1-b]thiazol-5-yl)prop-2-en-1-one (IMT) were evaluated. The interaction of the titled compound and the surface of the selected metals was analyzed using electrochemical techniques, Scanning electron microscope (SEM), DFT and molecular dynamic (MD) simulations. EIS results reveal that the inhibition efficiency at 10−4 M is ranked as follows: 96.9% (Cu) > 95.4%, MS) > 91.0% (Al). The recorded results reveal that the IMT compound could successfully inhibit the corrosion of all studied metals. The results of EIS and PDP reveal the corrosion inhibition process is charge transfer controlled, and the studied compound acts as a mixed-type inhibitor. The inhibition mechanism involved the adsorption of the IMT compound on the metal surface via Langmuir isotherm. In addition, the IMT showed a high inhibition performance at a long immersion time of 12 h. The surface examination showed substantially lower surface degradation in all metal samples exposed to the acid in the presence of IMT. DFT gives insights into charge-sharing (donor-acceptor) interactions between inhibitor molecules and metallic surfaces. MD simulation indicates that the investigated molecule adsorbed nearly parallel to Fe (110), Cu (111), and Al (111) surfaces. The adsorption mechanism is revealed by theoretical calculations.

Inter-void shearing effect on damage evolution under plane strain deformation in high-strength aluminum alloy sheet

In this study, the ductile damage responses of high-strength 7000 series aluminum alloy (AA), AA 7075-T6 sheet samples, subjected to the plane strain deformation mode were investigated using finite element (FE) simulations. In the experiments, uniaxial tension (UT) and plane strain tension (PST) tests were conducted to characterize the plasticity and ductile damage behavior of the AA 7075-T6 sheet samples. The limiting dome height (LDH) and V-die air bending tests were conducted to evaluate the ductility of the material subjected to plastic deformation and friction between the tools, and the corresponding fractured samples were qualitatively analyzed in terms of dimples using fractography. FE simulations were performed to predict the ductility of the AA 7075-T6 sheet samples under plane strain deformation using an enhanced Gurson−Tvergaard−Needleman (GTN) model, namely the GTN-shear model. The model was improved by adding the shear dimple effect to the original GTN model. The predicted results in terms of the load–displacement curves and displacements at the onset of failure were in good agreement with experimental data from the aforementioned tests. Furthermore, virtual roll forming simulations were conducted using the GTN-shear model to determine the effect of the prediction on ductile behavior for industrial applications.

Selection the Material and Analysis of Knee Joint for Smart Transfemoral Prosthetic

The issue of providing healthy movement for patients with lower limb amputations requires using of a well-designed lower limb prosthesis. The purpose of this work is to boost the passive prosthesis to a microcontroller-based prosthesis to provide a rotational speed that suits the function for which it is used, the boost focuses on providing a knee mechanism design by using Maxon EC motor, a socket and foot that can be obtained from previous designs. The study required to be achieved some of the basic criteria, as the proposed knee joint must have sufficient strength to bear up the weight of the amputee’s body and also have the ability to flex the knee to 900.The single parts of the knee joint was designed by using Solid Works software. The mechanism of the knee joint will be simulated after assembling each part of the design for envisage the motion of the knee prosthesis. Three materials were selected, taking into account the properties of these materials, Aluminum alloy 6061T6, Aluminum alloy 2024 and AISI4130 Steel. To find out whether the proposed model can withstand the loads, Finite element analysis using (ANSYS computer program software) the results were discussed and the model was evaluated.

Fatigue crack growth: Validation of the Kmax-ΔK approach using the GTN damage model

Considering cyclic plastic deformation as the single damage mechanism behind the fatigue crack growth (FCG), the effect of the mean stress is null in the absence of crack closure. In this study, an additional damage mechanism was introduced, predicting the effects of the growth, nucleation and coalescence of micro-voids. Using a non-local damage model, the reverse plastic zone was identified as the fatigue process zone, allowing to establish a relation to calculate its size. Considering aluminium alloy 2024-T351, the predictions are in close agreement with the experimental da/dN-ΔK curves, for distinct stress ratios. The results highlight that the effect of Kmax on the FCG rate is small in the absence of crack closure. On the other hand, modelling the contact between the crack flanks, the effect of Kmax on the FCG rate is amplified, i.e. the ΔK-Kmax plots for a given da/dN presented a Kmax dominance zone. The developed model suggests a three-parameter approach: ΔKeff -ΔK-Kmax.

Low-temperature tensile behaviours of 6061-T6 aluminium alloy: Tests, analysis, and numerical simulation

This paper made efforts on tensile behaviours of aluminium alloy (AA) 6061-T6 at low temperatures (T). To investigate low-temperature tensile behaviours of 6061-T6 AA, this paper carried out 24 tension tests on AA coupons at varying T levels of 20, −30, −60, and −80℃. The tests revealed that reducing T from 20 to −80℃ improved mechanical properties of 6061-T6 AA including improved elastic modulus by about 15%, increased yield strength by 9%, and improved ultimate strength by 10%; however, decreasing the low temperature from 20 to −80℃ has marginal influences on the ductility of 6061-T6 AA. In addition, the ambient- and low- temperature stress–strain (σ-ε) curves of 6061-T6 AA exhibited close behaviours. Analytical constitutive models were proposed for 6061-T6 AA. These proposed analytical models predicted well low-temperature σ-ε behaviours of 6061-T6 AA. FEMs with continuum damage mechanics were also developed for the low-temperature tensile σ-ε behaviours of 6061-T6 AA. It was proved that the developed FEM provided reasonable simulations on engineering σ-ε curves of 6061-T6 AA at different low temperatures.

Ballistic Behavior of Bioinspired Nacre-like Composites.

In this paper, the ballistic performance of a multilayered composite inspired by the structural characteristics of nacre is numerically investigated using finite element (FE) simulations. Nacre is a natural composite material found in the shells of some marine mollusks, which has remarkable toughness due to its hierarchical layered structure. The bioinspired nacre-like composites investigated here were made of five wavy aluminum alloy 7075-T651 (AA7075) layers composed of ~1.1-mm thick square tablets bonded together with toughened epoxy resin. Two composite configurations with continuous layers (either wavy or flat) were also studied. The ballistic performance of the composite plates was compared to that of a bulk monolithic AA7075 plate. The ballistic impact was simulated in the 300-600 m/s range using two types of spherical projectiles, i.e., rigid and elastoplastic. The results showed that the nacre plate exhibited improved ballistic performance compared to the bulk plate and the plates with continuous layers. The structural design of the nacre plate improved the ballistic performance by producing a more ductile failure and enabling localized energy absorption via the plastic deformation of the tablets and the globalized energy dissipation due to interface debonding and friction. All the plate configurations exhibited a better ballistic performance when impacted by an elastoplastic projectile compared to a rigid one, which is explained by the projectile plastic deformation absorbing some of the impact energy and the enlarged contact area between the projectile and the plates producing more energy absorption by the plates.

Effect of nanocomposites rate on the crack propagation in the adhesive of single lap joint subjected to tension

The incorporation of nanofillers makes it possible to permanently modify the properties of the adhesive. Nanoparticles with structures of less than 100 nanometers can be incorporated in suitable amounts up to 30% by volume into liquid adhesives without significantly changing the rheology. Fine and nanometric particles of Si02 are now increasingly incorporated into aqueous adhesive dispersions. The objective of this study is to analyze numerically by the three-dimensional finite element method, the intensity and distribution of von Mises, shear and peeling stresses in a nanostructured adhesive joint which ensures the assembly of two plates in Aluminum alloy 2024-T3. This adhesive is epoxy DER 331 in nature, filled with spherical silica nanoparticles (SiO2) of same size, the content of which varies from 0% to 30%. These silica nanoparticles are injected into the adhesive in the liquid state in a homogeneous way in order to see their effects on the mechanical behavior of the epoxy-nanosilica composite. The stresses are also evaluated according to the length of the adhesive lap and its thickness when crossing the crack front. The results obtained numerically by the finite element method show that the addition of nanoparticles in the epoxy matrix with ductile behavior contributes to the improvement of the mechanical properties of the epoxy-nanosilica composite, by increasing its mechanical resistance to the propagation of cracks. The presence of nanoparticles makes it possible to slow down the propagation of the crack.

Tensile Behaviors and Mechanical Property Analyses of T-Welded Joint for Thin-Walled Parts in Consideration of Different TIG Welding Currents Using Multiple Damage Models and Fracture Criterions: Numerical Simulation and Experiment Validation.

In order to deeply investigate the tensile properties and fracture behaviors that are obtained by tensile tests of welded joints, constitutive and damage models are imperative for analyzing the tensile behaviors. In this work, the tensile tests are conducted on the T-welded joint specimens of aluminum alloy 6061-T6, which were cut from the T-welded joints of thin-walled parts under different welding currents of Tungsten Inert Gas Welding (TIGW). A modified Johnson-Cook (J-C) model based on the original J-C equation, Swift model, Voce model, and Hockett-Sherby (H-S) model, their linear combination model, and fracture failure model are constructed and applied to simulate tensile behaviors, combined with tensile test data. What is more, the finite element (FE) simulation of tension tests is executed with the VUMAT and VUSDFLD subroutines. Compared to those results simulated with different fracture criteria and tensile experiments, the tensile strength and yield strength of T-welded joint thin-walled parts under different welding currents were achieved, and their best mean errors were only about 1%. Furthermore, the accuracy of different fracture criteria is also evaluated by the correlation coefficient and mean squared error. The results show that the combination model can accurately predict the tensile properties and fracture behaviors of T-welded joints better than the single model, especially the results simulated with the Swift-H-S model and H-S-Voce model, which are in good agreement with tensile test results, which will provide an analysis foundation for enhancing the welding assembly quality and preventing fracture failure for complex thin-walled antenna structures.

Inhibition of the localised corrosion of AA2024 in chloride solution by 2-mercaptobenzimidazole and octylphosphonic acid

The scanning vibrating electrode technique was employed to monitor the in situ localised electrochemical activity on aluminium alloy 2024-T3 at the free corrosion potential in aggressive NaCl solutions with and without corrosion inhibitors 2-mercaptobenzimidazole (MBI) and octylphosphonic acid (OPA). MBI is a very effective inhibitor against pitting corrosion, even in a chloride environment without the reservoir of MBI. In contrast, localised corrosion was observed at several points at the early stage of immersion of AA2024 in NaCl solution containing OPA. Ex situ energy-dispersive X-ray spectroscopy analysis of the Al2CuMg particle at the cross-section revealed that MBI does not entirely prevent its dissolution but reduces the dissolution rate and the rate of oxygen reduction by forming an insoluble complex compound Cu–MBI on the partially dealloyed AlCu-based particles, i.e., on the porous copper remnants. The MBI’s action is an efficient option for mitigating the corrosion of Cu-based aluminium alloys.