Aluminum Alloy Sheets Research Articles

The Forming Limit Diagram of 2A16 Aluminum Alloy Sheet Based on Hydraulic Bulging Test of Elliptical Die

An elliptical die hydraulic bulging test was carried out to explore the forming performance of 2A16 aluminum alloy sheets during hydroforming. By using five groups of elliptical dies with ovality of 1.0, 0.9, 0.8, 0.6, and 0.4, the effects of different pressure rates of 0.02 MPa/s, 0.04 MPa/s, and 0.08 MPa/s on the test results were studied, and different sheets thicknesses of 2 mm and 2.5 mm were also explored, then the equivalent stress and strain values obtained by theoretical calculation were also analyzed. Finally, the complete forming limit diagram (FLD) of the 2A16 aluminum alloy sheet at room temperature was plotted through the elliptical hydraulic bulging test and the uniaxial tensile test under the same test conditions. The results show that as the ellipticity increases, the maximum equivalent stress-strain value of sheets gradually increases; reducing the hydroforming pressure rate or increasing the thickness of the sheet can slightly increase the maximum bulging height of the sheet, but it has no significant impact on the maximum equivalent stress and strain value of this material. There is no noticeable difference in the FLD on the right side, indicating that its FLD is universal for a material.

Effect of chemical milling and anodizing on the high cycle fatigue behaviour of 2024-T3 aluminium alloy

Aluminium 2024-T3 alloy, widely employed in transport aircraft wing and fuselage skin structures, necessitates thickness reduction for weight optimization. Chemical milling is utilized for this purpose; however, it removes Cladding (as a standard corrosion protection layer), prompting subsequent anodizing and sealing to provide corrosion protection. Literature indicates that anodizing or chemical milling can significantly reduce fatigue life, and limited data have been available on the life of chemically milled anodized materials. In this study, constant amplitude stress-life (S-N) testing was performed on two sets of fatigue samples: Cladded Aluminium Alloy (CAA) 2024-T3 sheet specimens (1.6 mm thick) and chemically milled, anodized and sealed (CMAS-AA) Aluminum Alloy sheet specimens (1 mm thick). S-N curves were generated at R=0.1 and room temperature under stress control. SEM micrographs showed micropores in CMAS-AA and a standard plain surface in CAA, consistent with prior findings. Both types exhibited 3-5 times shorter fatigue life than electropolished samples, as reported in MIL Handbook HDBK-5J, highlighting the importance of corrosion protection techniques for structural integrity. Residual stresses were observed, with cladded samples displaying compressive and CMAS-AA exhibiting tensile stresses. Fractography revealed no abnormal fatigue fracture features, and computed plane stress fracture toughness values estimated using measured crack size from the failed specimens matched standard values of aluminium alloys.

Technological features of fusion welding of Al – Mg system alloys rationally alloyed with scandium

The results of the formation of macro- and microstructure of welded joints of aluminum alloy sheets of the Al– Mg–Sc system obtained by automatic argon-arc and electron-beam welding are presented. The mechanical characteristics of welded joints and weld metal under the types of welding used are given. Satisfactory weldability of the studied alloy by fusion welding methods is established with the provision of strength properties of welded joints at the level of 0.8...0.85 of temporary resistance of the base metal. The effect of the welding direction in relation to the rolling direction of the sheets on the mechanical properties of welded joints is studied. The destruction of welded joints during the tests occurred in the metal and fusion zone. The fractures are of a macro viscous nature with a viscous pit micro mechanism of destruction. The strength factor of welded joints of aluminum V-1579 alloy is at the level of 0.89 for automatic argon arc welding and 0.79 for electron beam welding.

Fast-cooling of aluminium alloy sheet metal for hot-stamping applications

The paper reports an investigation into two rapid sheet metal cooling designs that are suitable for applications in hot-stamping production -air cooling and contact cooling, aiming at improving formability of the high-strength aluminium sheets for the forming of components with complex geometries with enhanced overall process efficiency. The investigation involved both numerical modelling and experimental trials using an in-house developed prototype cooling tools. A series of contact cooling experiments were conducted, considering process variables such as initial blank temperatures, cooling die temperatures, die materials, surface conditions, etc. The results demonstrated that the cooling rate of the aluminium blank could be accurately controlled by both methods with appropriate pre-setting of the equipment and control of the process parameters. The integration of the cooling system into a polit hot-stamping production was also tried, considering industry-scale applications related factors. The results can serve as a design guidance for an industry to introduce such cooling methods and manufacturing facilities.

Frictional characteristics of EN AW-6082 aluminium alloy sheets used in metal forming

This article is devoted to testing EN AW-6082 aluminium alloy sheets in friction pair with NC6 (1.2063) tool steel. A special tribometer designed to simulate the friction conditions in sheet metal forming processes was used for friction testing. The research aimed to determine the influence of contact pressure, surface roughness of the tool, and lubrication conditions on the value of the coefficient of friction in the strip drawing test. Three grades of typical petroleum-based lubricants with kinematic viscosities between 21.9 and 97 mm2/s were used in the tests. The surface morphologies of the sheet metal after the friction process were observed using a scanning electron microscope. A tendency for the coefficient of friction to decrease with increasing contact pressure was observed. LHL32 and 75W-85 oils lost their lubricating properties at a certain pressure value and with further increase in pressure, the coefficient of friction value tended to increase. The 10W-40 oil with the highest viscosity reduced the coefficient of friction more intensively than the LHL32 oil.

Study on microstructure, mechanical properties, and texture of the CC AA 3105 aluminum alloy processed by high-pressure heat treatment

The hot band of CC AA 3105 aluminum alloy sheets underwent 6 h of preheating treatment at 599 °C. Then, it was cold-rolled to various reductions, followed by 1 h of annealing at 482 °C under various pressures. The study investigated the alternation of microstructure, mechanical properties, and texture of these sheets. High-pressure heat treatment (HPHT) remarkably weakens the pinning effect and refines recrystallized grains. In the case of the annealed sheets of which the rolling reduction reached 91.3%, in the atmospheric pressure-to-6 GPa pressure increasing range, the fine precipitates (1–3 nm) disappeared. In contrast, there is an increase in large precipitates and a reduction in the average grain size. Furthermore, the aspect ratio elevated from 0.19 to 0.87, and the average grain size along the rolling direction (RD) reduced from 182.4 µm to 57.9 µm. Pressure elevation was accompanied by enhanced strengths of the P and r-cubeND textures but remarkably decreased strengths of the M texture. The elongation of the sheets decreased with increasing pressure. The ultimate tensile strength (UTS), yield strength (YS), and hardness decreased when the pressure rose from atmospheric pressure to 2 GPa and increased in the 2 GPa-to-6 GPa pressure increasing range.

Identification of thermo-viscoplastic behavior for AA6061 under in-plane biaxial loadings

This work aims to investigate the thermo-visco-plastic behavior of an aluminum alloy (AA6061) sheet metal submitted to in-plane biaxial loadings under warm conditions. Biaxial tensile tests are performed in a temperature range from room temperature to 160 °C, and in a strain rate range from quasi-static to the so-called “intermediate” strain rate (up to few s−1). The specimen shape used in this study has been previously defined and validated by the authors to identify the viscoplastic hardening models of metallic alloys at large strains. A specific device leading to a uniform temperature in the sample is associated with a dynamic biaxial traction bench to carry out the temperature and strain rate dependent characterizations. From these experiments, both the experimental forces measured on each axis of the in-plane biaxial specimen and the principal strains at the center of the specimen are obtained. These experimental data are then used in an inverse analysis loop, based on a finite element model of the biaxial test, to calibrate the parameters of a thermo-viscoplastic strain hardening model by minimizing the difference between the experimental and numerical principal strains at the center point of the specimen. Finally, it is shown that the identified hardening model well predicts the flow stress of AA6061 under different temperatures and strain rates for a strain level of up to 40%.

Fracture Prediction of Aluminum Alloy Sheet AA2024-T3 Using Analytical Stress and Experimental Strain Based Failure Criteria

In this work, the fracture prediction of aluminium alloy sheet, grade AA2024-T3 was investigated using the Fracture Forming Limit Curve (FFLC) and Analytical Fracture Forming Limit Stress Curve (FFLSC) as failure criteria. Initially, the FFLC was experimentally achieved by means of the Nakajima Stretch forming test coupled with GOM strain measurement system, providing the Digital Image Correlation (DIC) technique. Subsequently, the analytical FFLSC was plastically computed using experimental FFLC data combination with Swift hardening model and anisotropic Hill’48 yield model for representing anisotropic plastic deformation behaviour on examined sheet. Finally, Fukui stretch drawing and Three point bending tests were conducted both experiment and numerical simulation to evaluate the fracture state and verifying an applicability of obtained FFLC and FFLSC. In the simulation, the ABAQUS 2017 element deletion function was employed for directly implementing the fracture criteria regarding the FFLC and FFLSC. It was concluded that the analytical FFLSC could more realistically predict fracture behaviour better than the FFLC based on strain. In term of percentage error, the analytical FFLSC generated an error less than the FFLC.

Finite Element Formulation and Computation of Superplastic Metal Forming Processes with Optimized Rate of Deformation Control

Superplastic forming (SPF) is a material forming technique that uses superplastic exceptional elongations and deformation characteristics to form superplastic materials into certain shapes. The combination of superplastic forming with diffusion bonding (SPF/DB) gives rise to an almost unlimited extension of superplastic forming since more integral lightweight cellular structural components can be manufactured. This paper discusses numerical modelling of the mechanism of superplasticity in metallic materials. The SPF computational method based on the finite element technique augmented with the controlling rate of deformations is developed to examine a range of design or operating conditions leading to more economical forming processes. The non-Newtonian ‘viscous flow’ material is used to model the constitutive of superplastic material during the forming period. The contact mechanics between the sheet material and the mold surface and the intersheet material contact mechanics are imposed using the penalty control method, in which the sticking contact boundary conditions are employed. The space discretization is carried out using the membrane element under plane strain and axisymmetric flow stress conditions, while the implicit time integration technique is utilized to follow the shape changes of the formed sheet material. The validation of the SPF finite element formulation was performed by comparing it with the available analytical solution of Hydraulic Free Bulging of Thin strips. The SPF of a hemispherical dome made of 7475 aluminum sheet alloy was performed to demonstrate the forming process as well as to validate the results obtained between the SPF finite element numerical simulation and the experimental results. The SPF/DB of the multicell component section is considered in the final part.

Microstructure and Properties of 6 Series Aluminum Alloy Under Different Aging Treatment Systems

In the present study, an investigation is conducted into the effect of different aging treatments on the hardening properties of the 6151 aluminum alloy sheet. According to the research results, the artificial aging hardening response of the pre-aging sheet is significantly stronger compared to natural aging after the solution treatment. In the stage of artificial aging, 120 oC pre-aging treatment produces a more significant strengthening effect than 80 oC and 100 oC pre-aging treatment. The longer the artificial time, the higher the hardness value. When the artificial aging temperature reaches 200 oC, the time taken to achieve peak aging is the shortest, and the occurrence of softening is evident in the over-aged state. When the artificial aging temperature is 200 oC, the softening effect becomes more significant. Natural aging can inhibit the strengthening effect of artificial aging. With the extension of natural aging, the hardening effect of artificial aging diminishes gradually.

Strain and crack growth monitoring of aluminum alloy sheet using high-sensitivity buckypaper film sensors

Strain and crack growth monitoring of aluminum alloy sheet using high-sensitivity buckypaper film sensors

Non-destructive evaluation of FSW tool plunge depth in thin metallic sheet weld using low frequency ultrasonic Lamb waves signal

Thin aluminium alloy sheets find widespread application in industries such as automotive, marine, railway, and aerospace due to their high load capacity-to-weight ratio. Welding has emerged as an effective joining method, surpassing mechanical fasteners and semi-joining processes. However, fusion welding techniques are susceptible to hot cracking, leading to solidification and liquation cracking. When it comes to lap welded joints in thin metallic sheets, friction stir welding (FSW) has demonstrated exceptional efficiency. To assess weld morphology, non-destructive testing (NDT) methods are employed, with the ultrasonic method proving capable of measuring weld penetration depth in thick metallic plates using bulk and surface waves. Nonetheless, the role of tool plunge depth (TPD) in FSW, analogous to the weld penetration depth in fusion welding, remains unexplored through non-destructive means, despite its critical impact on the load carrying capacity of thin structures. Thisstudy aimsto predict the optimal tool plunge depth for achieving high-quality welding in thin structures by utilizing a guided Lamb wave-based non-destructive method. At a low frequency of 80 kHz, the transmission percentage of the anti-symmetric mode (A0) was calculated for FSW specimens with different tool plunge depths. The findings revealed that the transmission percentage was higher for welds with the optimum tool plunge depth compared to those with low and high tool plunge depths. This distinctive behavior of the specimens with the optimal TPD towards Lamb wave signals proved useful in predicting the FSW tool plunge depths.

Strain concentration degree defining ductility and catastrophic failure of 6061 aluminum alloy

The physical control of ductile deformation and failure behaviors of aluminum alloys is still open to investigation, although this is a central problem for material design and safety evaluation. In this study, 6061 aluminum alloy sheets with different pre-cut depths were uniaxially stretched, and the evolution of strain fields was monitored to reveal the relationship between the strain concentration and failure process. The average strain/strain fluctuation ratio and the strain propagation velocity were defined to quantify the strain concentration degree. The strain concentration degree is an intrinsic factor hosting deformation ductility, maximum bearing load, and failure modes. The underlying mechanism of this changing ductility and failure process is the increased strain/stress concentration degree due to increased pre-cut depth. The experimental results indicated that higher ductility resulted in a larger catastrophic failure in the 6061 aluminum alloy. A lower deformation ductility led to a more gradual macroscopic failure. Our findings suggest that various origins inducing different strain concentration degrees can cause various effects on ductility and failure modes of 6061 aluminum alloy.

Investigation on shear and fatigue performance of CFRP/aluminum alloy single-lap adhesive joint

The size parameter is quite significant for the performance of adhesive joint. In order to investigate the effect of size parameters on the mechanical property and failure behavior of CFRP/aluminum alloy single-lap adhesive joint, T300 CFRP laminate and AA5182 aluminum alloy sheet were bonded by Sika Power 497 structural adhesive under different size parameters. The quasi-static shear test and fatigue test were implemented, and the failure behavior and failure mechanism were analyzed. Results showed that the increase of aluminum alloy sheet thickness or bonding area length could effectively improve the bonding strength of adhesive joint, when the strength of the aluminum alloy sheet or the adhesive layer was insufficient. The shear failure modes of adhesive joint mainly included adhesive failure, base material failure and mixed failure. The fatigue failure modes of adhesive joint were mainly adhesive cohesion failure and adhesive adhesion failure. At low stress levels, the aluminum alloy sheet might fracture. In addition, this work can provide a scientific guidance for the engineering application of adhesive bonding technology.

Self-piercing riveting of dissimilar carbon fiber-reinforced composites and aluminum alloy sheets: state-of-the-art achievements

Self-piercing riveting of dissimilar carbon fiber-reinforced composites and aluminum alloy sheets: state-of-the-art achievements

Mechanical Responses of Ductile Aluminum Alloy under Biaxial Non-Proportional Tensile Reverse Loading Patterns

This paper deals with the study of the mechanical responses of ductile metals under biaxial non-proportional cyclic loading tests. The biaxially loaded HC specimens manufactured from 4 mm thick aluminum alloy sheets (EN AW 6082-T6) are subjected to various loading paths, including monotonic and cyclic loading conditions. The aim is to investigate the plastic, damage, and fracture behavior of the material under these different loading scenarios. In terms of numerical aspects, a modified anisotropic two-surface cyclic plastic–damage continuum model is used to predict the material behavior in the load-displacement field and different strain fields. Numerically predicted stress states are analyzed in detail to gain a better understanding of the damage mechanisms. Moreover, the scanning electronic microscopy (SEM) pictures taken from the fracture surfaces confirm the dependency of the damage mechanisms on the loading histories. The present work indicates the importance of considering different loading conditions for the accurate prediction of material responses.

Simple Contact Sensor for Material on Die in Sheet Hydroforming

A simple material contact sensor on the forming tool was devised for sheet hydroforming. The applicability was investigated for the shallow forming of aluminum alloy sheet. A flat bottom axisymmetric die or a conical one was used. An antistatic electric tape was used as contact sensor. It is flexible and attached to the die cavity in the radial direction. Electrical resistance of the tape between the center and the contact position of the material changes as the forming progresses. The change in voltage of the resistance part corresponding to the contact length was captured continuously. The strain at the center of the circular test piece was also continuously measured using a strain gage for large deformation. A short contact length was captured for the flat bottom die, since the test piece deforms into a dome shape, and the tip of the dome contacts to the center of the die cavity. On the other hand, the captured length was longer in the forming with the conical die. The repetitive separation and contact motion of the test piece to the die in impact forming due to the impulsive water pressure was successfully captured by the contact sensor. The accuracy was relatively coarse due to that the diameter of the die cavity was small. However, it was found that the simple contact sensor can be applied to evaluate the deformation behavior of the material. The measured maximum strain of the test piece was larger in impact forming, and the strain concentration occurred. This may be due to the negative strain rate sensitivity of the material.

Multi-indicator optimization of riveting joint forming quality of aluminum alloy sheets based on response surface test

In this paper, the effects of the interaction between punch diameter, die depth and punch speed on the quality of riveted joints are investigated using the BBD response surface test method. The results show that the mold depth has the greatest influence on the key dimensional parameters of riveted joints, followed by the punching speed, and then the punch diameter, while the punch diameter and the mold depth are the two factors with the most obvious interaction. The optimum riveted joint process parameters determined are punch diameter of 5.24 mm, die depth of 1.44 mm, and stamping speed of 5.00 mm/s. The corresponding relative errors predicted by numerical simulation and response surface optimization objective are 5.96 % for neck thickness, 3.29 % for interlocking value, and 1.37 % for bottom thickness; and the relative errors predicted by experimental results and optimization objective are 13.42 % for neck thickness, 13.42 % for interlocking value, and 1.37 % for bottom thickness. 13.42 %, interlock value is 4.23 %, and bottom thickness is 2.23 %, the model accuracy is high, and the optimization method of response surface test can effectively improve the quality of riveted joints. Through numerical simulation, the metal flow law and stress distribution during the riveting and forming process of aluminum alloy plate were analyzed, and the strength test of riveted joint was carried out, and the maximum destructive shear load of the joint was 1.8 KN, and the strength of the joint was improved, which verified the validity of the response surface optimization method.

Evaluation of wear test on functionally graded metal-polymer tri-laminate composite interfaces of cooling-assisted friction stir additive manufacturing

In this study, a new friction stir welding (FSW) based additive manufacturing (AM) process called "cooling-assisted friction stir additive manufacturing (CA-FSAM)" was introduced to join sheets of metal-polymer hybrid structures (MPHS). Dry ice was introduced as the coolant. Thickness variations of the raw high-density polyethylene (HDPE) and 5083 aluminum alloy (Al5083) sheets were functionally graded at a rate of 0.75 mm from the former layer. The arrangement of layers in terms of thickness was arranged in the order of 3, 2.25, and 1.5 mm. Functionally graded metal-polymer tri-laminate composite fabricated with CA-FSAM technology was investigated using the pin-on-disk wear test. The results showed that mechanical locking between the layers affected the bond strength. Cross-sectional morphology examination revealed defect-free, strong joints. X-ray diffraction (XRD) results confirmed the formation of Mg2Si; however, the XRD peak was low, indicating a slight effect on the interface properties. Thermal gravimetric analysis (TGA)-Fourier transform infrared spectroscopy (FT-IR) characterization highlighted that the main evolved products during tri-laminate composite joining were CO, CC, CH3, CH2, and CH2. Oxidation occurred in the FTIR peak in the absorption band (1029.92 cm−1 to 1370.63 cm−1). Disk loading resulted in the buildup of an internal drag force that caused the dislocation/rupture of the CC or CH bonds. Defects, such as deep grooves, pits, and delamination at the interface, were observed in the composite specimen. The wear path was not visible in the worn composite material. The wear rate at 4 kg load on Al5083, HDPE, and metal-polymer tri-laminate composite specimens was 3.15 ± 0.22, 4.72 ± 0.36, and 3.42 ± 0.18 × 10−6 mm3/N. m, respectively.

Properties of 6061 aluminum alloy treated with laser alloying

In this study, a laser surface alloying method is used to alloy 1.8 mm thick 6061 aluminum alloy sheets with Ni alloy powder. The mechanical properties of the resulting alloy are investigated. The experimental results show that, following laser surface alloying, a crack-free zone can be generated but some fine porosity appears. The hardness and the wear properties of the laser alloying specimens are superior to those of the Al-matrix. A hardness of 539 HV is achieved, which is five times greater than that of the Al-matrix. As a result, the laser alloying specimens exhibit excellent wear properties and higher sliding wear distances and speeds compared to those of the Al-matrix, whereby the sliding distance is greater by up to eight times and the sliding speed is increased four-fold.