6061-T6 Aluminum Research Articles

Investigation of Impact Properties under Instrumented Charpy Test

The Instrumented Charpy impact test is a promising method for determining a material’s impact response. Stainless steel has higher impact energy absorption capacity, high tensile, and yield strength compared to aluminum. Performance varies among grades; for instance, Aluminum 7075-T6 exceeds Aluminum 6061-T6 in tensile and yield strength. However, information regarding their energy capacity and impact signal pattern is lacking. This study investigated the impact properties using a Charpy machine, a data acquisition system, and a sensing element. Strain gauges were used to record the impact strain signal, enabling the analysis of impact duration, maximum strain, and the area under the curve. Specimens experimented include Stainless Steel 304, Aluminum Alloy 6061-T6, and Aluminum Alloy 7075-T6. The Charpy machine measures absorbed energy, while the theoretical impact energy is computed from software data. The area under the strain-time curve reflects the material energy absorption capacity. Stainless Steel 304 demonstrates superior energy absorbed, impact duration, and area under the curve, followed by Aluminum 6061-T6 and Aluminum 7075-T6. Despite higher tensile and yield strength, the inferior impact response of Aluminum 7075-T6 highlights the importance of factors like ductility, elongation, and alloy composition. Consequently, Aluminum 6061 is commonly used in the automotive industry, while Aluminum 7075 is preferred in aerospace applications.

Effect of synergistic action of anodising and graphene on the mechanical properties of fibre-reinforced metal laminates

Fibre reinforced metal laminates (FMLs) are widely used in various fields due to their excellent properties. However, the weak interlayer properties of FMLs limit their applications. In this paper, the interlayer properties of FMLs are enhanced by anodising the 2024-T3 aluminium alloy layer in FMLs or by epoxy matrix modification of graphene nanoplatelets (GNPs). The effect of both synergistic impacts on the interlayer properties of most FMLs is investigated. The FMLs were manufactured using the wet lay-up technique using 2024-T3 aluminium alloy, E51 epoxy and EW100 glass fibre. The results showed that the type I fracture toughness, tensile strength, flexural strength, interlayer shear strength and single layer shear strength of FMLs after anodic oxidation treatment were increased by 406.4%, 10.3%, 18.3%, 42.6% and 28.3%, respectively, compared with those of pure FMLs. The type I fracture toughness, tensile strength, flexural strength, interlayer shear strength and single layer shear strength of the GNPs-modified FMLs matrix were increased by 280.4%, 3.7%, 6.8%, 34.5% and 19.1%, respectively, compared with those of pure FMLs. Moreover, the synergistic effect of FMLs indicates that the simultaneous anodic oxidation and GNPs modification of FMLs can lead to the best mechanical properties of FMLs. Microscopic images and schematics illustrate the toughening mechanism of anodising and GNPs, including the enhancement of aluminium/resin interface and fibre/resin interface and the enhancement of resin matrix properties.

A novel multi-step superposition model for the dispersion analysis of multiaxial prestressed plate-like structures

Understanding the dispersion characteristics of multi-axial prestressed plate-like structures is crucial for the engineering application of guided wave non-destructive testing. However, existing analytical and semi-analytical models neglect both constitutive and geometric nonlinearities induced by the prestress and require tedious theoretical derivation and coding, which may not achieve accurate predictions. To address these issues, a convenient model based on the multi-step superposition analysis was proposed to investigate the effects of an arbitrary multiaxial prestress on the dispersion characteristics of plate-like structures. The core idea of this model involves introducing an initial configuration to describe the static pre-deformation between undeformed and final states; then, the dynamic wave motion was superimposed on the initial pre-deformation for the eigenfrequency analysis. Additionally, the strain energy density of the hyperelastic material was implanted and set as the relevant variable between the two steps by the inheritance of the solution. This model significantly improved the accuracy compared to the conventional method, as validated through biaxial acoustoelastic experiments. Subsequently, the acoustoelastic responses of the multiaxial prestressed 6061-T6 aluminum plate were investigated. The results reveal that the non-uniform in-plane prestress leads to the coupling of guided wave modes propagating along non-principal directions. Furthermore, the effects induced by multiaxial prestress in the frequency bands with low dispersion could be decomposed into the sum of the effects induced by three uniaxial prestresses with a very small deviation. This work provides new insights into the acoustoelastic behavior and a theoretical basis to optimize the guided wave mode and frequency.

Computational fluid dynamics based multi-species transport simulation of auxiliary energy systems for friction stir welding of dissimilar materials

This research compares auxiliary energy-assisted friction stir welding (FSW) techniques with conventional FSW when joining dissimilar materials. Specifically, it conducts numerical modeling and experimental validation for the effectiveness of plasma-assisted FSW and induction-assisted FSW for DH36 steel and 6061-T6 aluminum alloy. Fully coupled 3D computational fluid dynamics (CFD) models, incorporating the multi-species transport method, were developed, where the species mass fractions of the workpieces are transported through diffusion, convection, and reaction sources for individual species. Based on the temperature validation, the dedicated heat flux based on the rectangular heat flux and Gaussian heat flux distribution were considered for induction coil and plasma arc heating on the DH36 steel side, respectively. The established conventional and auxiliary energy-assisted FSW models were validated against experimentally observed temperature fields and the joints’ material features. Results indicate that the assistance of plasma and induction auxiliary energy sources increased the temperature field, strain rate, and flow velocity without forming stagnant zones on the steel side caused by reduced dynamic viscosity. In plasma arc-assisted FSW, the steel could not extrude effectively from the base steel sheet due to deficient heat and flow velocity input; therefore, defect-prone coarse steel fragments were blended with the Al matrix. In induction-assisted FSW, the uninterrupted steel layer was extruded from the steel side and placed on the Al side, which was caused by enhanced heat build-up and flow velocity. Moreover, induction-assisted FSW achieved symmetric material flow on both advancing and retreating sides, resulting in defect-free welds.

Effect of shoulder diameter, tool rotation speed, and arrangement of plates on mechanical and metallurgical properties of dissimilar aluminum 2024-T3 and 7075-T6 friction stir spot welding (FSSW)

In most studies conducted on friction stir spot welding, the focus has been on process parameters and the tool pin geometry. One of the influential parameters in this process, which has received less attention, is the tool shoulder diameter. The spread or concentration of the weld can significantly affect the weld strength and mechanical properties of the joint. In this research, two tools made of H13 hot-work steel with different shoulder diameters of 20 and 25 mm were prepared. Three rotation speeds of 1000, 1600, and 2400 rpm were considered for the welding process. The arrangement of aluminum plates on top of each other was varied in two configurations, parallel and overlapped. Mechanical properties, including tensile shear strength and Vickers micro-hardness, were investigated. The microstructure of different weld zones was also examined using an optical microscope. The results showed that increasing the tool shoulder diameter could enhance the breaking force and tensile shear strength of the joints. Meanwhile, the rotation speed had an optimal value, and with its increase, the breaking force initially increased and then decreased. Placing the 2024-T3 aluminum plate on top of the stack also increased the tensile shear strength of the samples. The fracture mode of the broken specimens was entirely nugget pull-out, which became more pronounced during the use of optimal parameters. Micro-hardness in the region influenced by heat decreased, reaching a minimum in the thermo-mechanically affected zone. In the stir zone, micro-hardness increased significantly due to intense plastic deformation and material compression. The microstructure in the nugget region appeared fine-grained and compact, while the region affected by coarse grain experienced significant heat effects. Increasing the tool shoulder diameter led to an increase in the nugget zone and the length of the bonded region. However, it did not have a significant effect on grain size in the nugget region.

Web crippling behaviour of high-strength aluminium alloy channel-shaped members with strengthened web holes: Numerical study and new design rules

This study presents a detailed numerical investigation of 7075-T6 and AA-6086 high-resistance aluminium alloy channel-shaped members with strengthened web holes in web crippling. A nonlinear finite element (FE) model was developed and validated against the test results reported by the authors and other researchers. The material properties of 7075-T6 and AA-6086 high-resistance aluminium alloy were also obtained from the literature. Utilising this validated model, an extensive parametric study including 1296 models was carried out. This study examined both cases with clamped and unclamped flanges, and the variables were web thickness, bearing lengths, diameter of web holes, stiffener lengths, internal corner radii, and grades of aluminium alloys. Given the absence of existing standards for calculating the web load-bearing resistance of such members with strengthened web holes, the numerical results obtained from the parametric study were used to develop new design formulas with new coefficients through regression analysis. The design strengths calculated by the proposed design formulas were then compared against the FE results. Finally, a reliability analysis was also performed, demonstrating that the proposed design formulas can accurately predict the web load-bearing resistance for these members.

Effect of Layer Thickness in Cold Metal Transfer Cladding of Fe-Based ER70S-6 Alloy on AA 6061-T6 Aluminum Alloy

Effect of Layer Thickness in Cold Metal Transfer Cladding of Fe-Based ER70S-6 Alloy on AA 6061-T6 Aluminum Alloy

Ultrasonic peening-waterjet composite surface modification of 7075-T6 aluminum alloy for residual stress release and transformation mechanism

The release and transformation mechanism of residual stress contributes to the improvement of metal materials' processing and performance, enhancing their structural stability, surface integrity, and fracture resistance. This paper focuses on the Ultrasonic Impact Treatment-Solid Particle Entrainment by Waterjet (UIT-SPEWJ) composite surface modification of 7075-T6 aluminum alloy, investigating the effects of UIT-SPEWJ process parameters (jet pressure and target distance) on the alloy's surface quality, roughness, microhardness, residual stress, and the evolution mechanism of microstructure. The results indicate that the 7075-T6 aluminum alloy modified by UIT-SPEWJ mainly exhibits a "meteorite crater" effect, accompanied by significant smearing and ploughing phenomena. Surface roughness shows a trend of first decreasing and then increasing with the rise of jet pressure and target distance. The minimum surface roughness, 0.852 μm, is achieved at a jet pressure of 25 MPa and a target distance of 7.5 mm. The microhardness of the samples modified by UIT-SPEWJ gradually decreases from the surface to the substrate with increasing depth. The hardened layer depths of the samples UIT-SPEWJ-1–6 after modification are approximately 174 μm, 226 μm, 200 μm, 196 μm, 176 μm, and 172 μm, respectively. After UIT, SPEWJ, and UIT-SPEWJ surface modifications, the surface of 7075-T6 aluminum alloy mainly exhibits compressive residual stress (CRS). The surface residual stress σ_srs of samples modified by UIT and SPEWJ are approximately 195.161 and 215.752 MPa, respectively. The surface residual stresses of UIT-SPEWJ-1–6 samples are significantly improved to 277.089, 529.499, 393.615, 459.261, 368.084, and 220.635 MPa, respectively, with UIT-SPEWJ-2 sample having the highest surface residual stress, which is 2.7 and 2.4 times that of UIT and SPEWJ modified surfaces. Samples modified by UIT-SPEWJ present significant dislocation phenomena, and the precipitated phases mainly include the needle-like metastable phase η', as well as the equilibrium phase η (MgZn2) with a rod-like structure. At lower jet pressures and larger target distances, the 7075-T6 aluminum alloy exhibits a continuous PFZ with a size of approximately 12–23 nm. As jet pressure increases and target distance decreases, discontinuous grain boundary precipitate bands appear, sized around 8–17 nm. Moreover, when the jet pressure is 25 MPa and the target distance is 7.5 mm, the grain boundary precipitated phases are more dispersed.

Enhancing aircraft crack repair efficiency through novel optimization of piezoelectric actuator parameters: A design of experiments and adaptive neuro-fuzzy inference system approach

This study addressed the critical problem of repairing cracks in aging aircraft structures, a safety concern of paramount importance given the extended service life of modern fleets. Utilized a finite element (FE) method enhanced by the design of experiments (DOE) and adaptive neuro-fuzzy inference system (ANFIS) approaches to analyze the efficacy of piezoelectric actuators in mitigating stress intensity factors (SIF) at crack tips—a novel integration in structural repair strategies. Through simulations, we examined the impact of various factors on the repair process, including the plate, actuator, and adhesive bond size and characteristics. In this work, initially, the SIF estimation used the FE approach at crack tips in aluminum 2024-T3 plate under the uniform uniaxial tensile load. Next, numerous simulations have been performed by changing the parameters and their levels to collect the data information for the analysis of the DOE and ANFIS approach. The FE simulation results have shown that changing the parameters and their levels will result in changing of SIF. Several DOE and ANFIS optimization cases have been performed for the depth analysis of parameters. The current results indicated that optimal placement, size, and voltage applied to the piezoelectric actuators are crucial for maximizing crack repair efficiency, with the ability to significantly reduce the SIF by a quantified percentage under specific conditions. This research surpasses previous efforts by providing a comprehensive parameter optimization of piezoelectric actuator application, offering a methodologically advanced and practically relevant pathway to enhance aircraft structural integrity and maintenance practices. The study innovation lies in its methodological fusion, which holistically examines the parameters influencing SIF reduction in aircraft crack repair, marking a significant leap in applying intelligent materials in aerospace engineering.

A probability density function of stress amplitude applicable to power spectral density curves of structural random vibration response

The power spectral density curves of the random vibration response of a plate specimen with different spectral width coefficients were obtained by selecting different frequency ranges, and the probability distributions of the stress amplitudes were obtained by applying Monte Carlo method and rainflow counting method. Each probability distribution was divided into three segments by the corresponding zero-order spectral moment value, and each segment was fitted using either a Rayleigh function or an exponential function. Finally, a probability density function of stress amplitude was proposed by combining two Rayleigh functions and an exponential function. The proposed probability density function can be used to obtain the stress amplitude probability distribution for the power spectral density curves of structural random vibration response with any bandwidth, and the accuracy of the proposed function was verified based on the response data of a specimen of 7075-T651 aluminum alloy material under the action of six typical power spectral curves.

Wires using multi-hole SolidStir Extrusion

SolidStir® Extrusion, a newly-innovated manufacturing process, offers tooling design adaptability as a significant advantage over conventional extrusion processes. Aluminum 6061-T6 was extruded using a modular multi-hole three-piece die. Microstructural characterization of as-extruded 3 mm diameter wire revealed refined equiaxed grains of 9.5 ± 4.0 µm average size. Tensile testing showed that as-extruded wires exhibited a tensile yield strength (YS) of 110 MPa, ultimate tensile strength (UTS) of 171 MPa, and elongation of 15.3%. After subjected to post process heat treatment, the extruded wires had a tensile YS of 246 MPa, UTS of 298 MPa, and elongation of 9%.

Development and performance of additively manufactured Tungsten carbide tool insert: An application of additive manufacturing towards flexible and customized machining

Carbide tool manufacturing is proposed by Additive Manufacturing to introduce flexibility and customization in machining industries. Development and performance of the additively manufactured (AM) tool is reported. Crack-free deposition of 88 wt%WC was obtained at 800 °C substrate-preheat temperature. An insert was dimensioned and progressive turning of Aluminium 6061-T6 alloy was performed upto 65 min at various cutting speeds. Cutting force, chip-reduction-coefficient, shear angle, built-up-edge, flank wear, crater wear and tool life of AM tool were analysed. The flank wear of AM tool was observed as 0.219 and 0.314 µm respectively at cutting speeds of 120 and 140 m/min after 65 min of machining. The cutting performance of the AM tool was then compared with that of K20 conventional cutting tool insert.

Investigation of Two Laser Heat Treatment Strategies for Local Softening of a Sheet in Age-Hardening Aluminum Alloy by Means of Physical Simulation

AbstractCar manufacturers increasingly aid high-strength aluminum alloys for their advantageous weight-to-strength ratio, but their limited formability poses challenges in plastic deformation processes. Tailored heat-treated blanks (THTBs) are a propitious approach to improve formability. Surface laser treatment is the predominant technology for obtaining THTB. To design this process quickly and accurately, without material waste, the use of physical simulation is increasingly promising. It allows replicating the process on a lab-scale and studying posttreatment mechanical and metallurgical properties. By adopting Gleeble® physical simulator, this study investigates the softening effects of local surface laser heat treatment on a EN AW 6082 T6 aluminum alloy blank. Two laser movement strategies—single linear path and multiple rectangular paths—were investigated at two treatment speeds for each. A finite element (FE) model was developed for simulating the process under all explored conditions. FE-derived thermal cycles were reproduced by means of physical simulation. After physical tests, alloy mechanical properties were evaluated. Results show that these properties depend on both the peak temperature thermal cycle and the interaction time between the laser source and the material surface. The comparison between the two strategies revealed that the multiple rectangular paths strategy allows to achieve a wider softened area at comparable interaction times.

Temperature-gradient and isothermal creep tests on 2024 aluminum alloy: A novel approach to creep failure evaluation aided by image processing

In high-temperature working conditions, the temperature difference between parts is common, and it is necessary to perform a temperature gradient test to predict creep behavior of alloy in real working conditions. In this study, a novel temperature gradient creep (TGC) test aided by an image processing method (IPM) was designed and performed on 2024-T3 aluminum alloy. The tests were performed under the conditions of isothermal tensile creep (ITC) and TGC in the temperature range of 285–315 °C under two stresses of 90 MPa and 125 MPa. Several experimental investigations were conducted to evaluate the creep failure of the specimens. The results showed that the temperature gradient during the TGC test leads to changes in strain, strain rate, stress exponent, microstructure and damage amount in the samples. The creep strain and strain rate of the TGC are greater than those of the ITC at 300 °C and 285 °C, and the rupture life is shorter. Finally, the Larson–Miller parameter is calculated, and the mathematical relationships between the strain rates of the TGCs and ITCs in 90 MPa and 125 MPa, which can be used to predict the creep strain rate under isothermal conditions, are proposed.

Fatigue crack growth in AA6082-T6/AA7050-T6 bi-materials: Effect of plastic zone ahead of crack tip

The main objective here is the understanding of the effect of plastic zone ahead of crack tip on fatigue crack growth (FCG). For that, a numerical simulation of FCG was made, based on cumulative plastic strain, considering a bi-material composed by the 6082-T6 and 7050-T6 aluminium alloys. The first one has a lower yield stress but a higher critical cumulative plastic strain. The values of da/dN are higher for the 6082-T6 which means that the effect of the easier plastic deformation dominates over the effect of the higher critical cumulative plastic strain. The bi-material 6082-7050 showed a pronounced decrease of da/dN near the interface, which starts when the monotonic plastic zone ahead of crack tip reaches the material transition. This indicates that the crack tip deformation is affected by the material inside the monotonic plastic zone. On the other hand, the bi-material 7050-6082 shows an accentuated increase of da/dN, which starts when plastic deformation is observed ahead of transition. The elimination of the contact of crack flanks reduces drastically the transient effects, which indicates that these are linked with plasticity induced crack closure effects. Crack tip blunting was proposed to be the mechanism of plasticity induced crack closure explaining the trends observed.

Simulation of fatigue crack initiation life under compressive loading based on material meso-characteristics

The fatigue problem under compressive loading is common in the key components of aeroengine. Most of the fatigue life prediction methods studied in the past are macroscopic phenomenological methods based on a large amount of experimental data. Due to the difficulty in carrying out the fatigue test under compressive loading, the S-N curve or Manson-Coffin formula commonly used on the fatigue life prediction of material under compressive stress were obtained through fatigue tests under conditions where the average stress was greater than or equal to zero. Although the average stress can be corrected by some formulas, whether the life estimation formulas fitted by those fatigue test data are applicable to the fatigue life analysis with average stress less than zero has not been solved in engineering. And there were few studies on the influence of compressive stress on fatigue life at home and abroad. On the basis of Tanaka-Mura fatigue crack initiation theory, a mesoscopic model suitable for fatigue characteristic analysis under compressive loading was established in this article. The model verified the feasibility in predicting the fatigue initiation life using test data of 7075-T651 aluminum alloy under the compressive fatigue load.

Analysis of bullet impact test on aluminum alloy plates at varying thickness and velocities

Analysis of bullet impact test on aluminum alloy plates at varying thickness and velocities

Taguchi analysis on finite element results to identify the most influential parameters on stresses after impact-damage

Impact-damage can reduce the fatigue life of mechanical components as a consequence of premature crack growth due to the occurrence of high residual stresses. In this work, finite element analyses were conducted to evaluate the residual stresses in a 7075-T6 aluminium hourglass specimen for various impact cases. The Taguchi method was applied to the finite element results to identify which parameters most influence the residual stresses in the specimen. The outcomes showed that the impact speed is the most influential factor for axial stresses, followed by the material and the size of the impacting object. The factor that most affects the von Mises stresses is the object size followed by its material and the impact speed.

Impact of alternating corrosion and fatigue on the fatigue life of a 7475-T7351 aluminum alloy in an aircraft beam structure

Impact of alternating corrosion and fatigue on the fatigue life of a 7475-T7351 aluminum alloy in an aircraft beam structure

Numerical simulation of welding residual stresses in 6082-T6 thin aluminum alloy

Thin plate aluminum alloys of the 6082 series are widely used in welded car bodies because of their excellent characteristics such as light weight and high strength. For welded joints, residual stresses significantly affect fatigue strength properties, especially in thin plate welding. In this study, the residual stresses arising from inert gas welding of thin sheet aluminum alloy metals were investigated using numerical simulation techniques. The thermo-elastic–plastic method was used to calculate simulated weld temperature and stress fields. Temperature and stress variations during the welding process were discussed to investigate the causes of residual stresses. The changes in stress during the experimental welding process were tracked, and the results were in agreement with the simulations. The impact of process parameters on welding stress was analyzed through simulation and experimentation. The results showed that residual stress decreases as speed increases and increases as power increases.