AA5754 Sheets Research Articles

The Effects of Cold Rolling and Stabilization Treatment on the Improvement of Microstructure, Mechanical Properties, and Corrosion Behavior of AA5083 Sheet

The Effects of Cold Rolling and Stabilization Treatment on the Improvement of Microstructure, Mechanical Properties, and Corrosion Behavior of AA5083 Sheet

Mechanical properties and fatigue failure mechanisms of purely self-piercing riveted (SPR) and hybrid (SPR-bonded) joints under salt spray environment

Automotive light-weighting has become an important direction for the development of the automotive industry, and the light-weighting materials are inevitable to be joined. Self-piercing riveting (SPR) is a kind of new process to joint various materials. The SPR and SPR-bonded (SPR-A) joints of AA6061 and DP590 sheets were prepared. The mechanical properties of SPR and SPR-A joints after exposure to neutral salt spray environments for different aging times were tested. The results showed that the shear and fatigue properties of the joints gradually reduced with the increase of salt spray time. In addition, the SPR-A joints not only have higher maximum failure loads but also have larger energy absorption values in shear tests when compared with that of the SPR joints under the same salt spray time. The fatigue test results showed that fretting wear between the rivet-foot and the lower sheet is the main failure mechanism of joints. Moreover, the salt spray time has no obvious effect on the fatigue failure modes of the two kinds of joints.

A Novel Method for the Determination of High Temperature FLCs of ECAP-Processed Aluminum AA5083 Sheet Metal

In this study, investigations into the deformation behavior of aluminum AA5083 at elevated temperatures were carried out on a newly developed test rig. The test rig was developed jointly with ZwickRoell GmbH & Co. KG (Germany) and is based on a Nakajima test carried out with heated dies. In this way, statements can be made about the lightweight potential of the alloy. Additionally, equal-channel angular pressing (ECAP) was performed to process the aluminum sheet metal. The conventional ECAP process is mainly used for bulk material in laboratory use and therefore is often not suitable for many industrial applications, especially for large series. The use of sheet metal allows a significant increase in the areas of application. It is documented in conventional ECAP that grain refinement is achieved by the severe plastic deformation. At room temperature this primarily increases the mechanical strength. Formability is improved in fine-grained materials, especially at elevated temperatures, which is related to diffusion-controlled deformation mechanisms and grain boundary sliding. The advantages of ECAP for sheet materials are thus also in lightweight construction and can even optimize the use of the AA5083 alloy. ECAP-route C was used for the process to provide the most homogeneous microstructure possible (180° rotation around the ECAP-axis after the first pass). Nakajima specimens were taken from the processed sheet materials to determine the Forming Limit Curve (FLC) compared to the reference material (four different specimen geometries). FLCs under elevated temperatures (250 °C, 375 °C) were performed on the novel Nakajima test bench. A special feature of the test rig is the rapid heating to avoid microstructural changes. Microscopic examinations were performed after the deformation to study the deformation mechanisms. Differences of the forming and fracture mechanisms between the reference alloy and the ECAP material were found.

Theoretical and experimental study of FLDs of AA5083 sheet and investigation of advanced anisotropic yield criteria coefficients

Theoretical and experimental study of FLDs of AA5083 sheet and investigation of advanced anisotropic yield criteria coefficients

Numerical and Experimental Validation for Prediction of Failure in Electromagnetic Forming of AA6061 Sheet

Numerical and Experimental Validation for Prediction of Failure in Electromagnetic Forming of AA6061 Sheet

The effect of different preaging conditions on mechanical properties and clustering behavior of AA6016 sheets for automotive outer panels

Preaging (PA) is an important process to enhance the performance of automotive aluminum outer panels through regulating solute clustering. In this work, we investigated the effect of PA temperatures in the range of 60°C-225 °C on the hardness before and after paint baking (PB) with different holding times. Tensile properties of partial alloys were checked to help explore the optimum PA condition. Before PB, the PA hardness of alloys preaged in the low-temperature regime (60°C-100 °C) was relatively stable with increasing PA time, but it increased significantly in the high-temperature regime (120°C-200 °C). After PB, the hardness of alloys preaged at temperatures up to 80 °C was low. Alloys preaged at 100 °C for 4 h could reach the same PB hardness as the solution-treated (ST) alloy. However, after reaching saturation of the hardness of preaged alloys in the low-temperature regime, extending the PA time did not induce a higher PB hardness. By contrast, the hardness decreased after long-term PA. The saturation PB hardness of the alloy further increased when preaged at a higher PA temperature and reached a maximum at 170 °C. The optimum PA condition for this alloy is 150 °C for 10 min as it produced better elongation before PB and the highest BHR after PB. The related mechanisms, including clustering and precipitation behaviors, have been discussed in detail.

Cryogenic deformation behavior and failure mechanism of AA7075 alloy sheets tempered at different conditions

The enhancement of cryogenic plasticity for some aluminum alloys has attracted broad attention, which provides a new approach to the formability improvement of high-strength aluminum alloys. However, the hardening behavior and the ductility of aluminum alloys at cryogenic temperatures are very sensitive to the microstructure tempered at different conditions, with complex combination of GP zones, second phase precipitates, coarse and equilibrium phases. In this paper, three groups of tempered AA7075 aluminum alloy sheets are elaborately designed by means of different approaches, i.e., solution-treated (W), peak artificial aged (T6), and fast re-dissolved (FD) from T6, to investigate their cryogenic deformation behavior and failure mechanism. The effect on cryogenic plasticity of second phases, including the coarse particles in the matrix and the precipitate free zones (PFZs) accompanied by chain distributed particles along grain boundary, can be isolated by comparison among these three kinds of AA7075 alloys. The cryogenic mechanical properties of AA7075 sheets are evaluated by uniaxial tensile test, and the microstructure evolution observed by transmission electron microscope (TEM), scanning electron microscope (SEM) and laser confocal microscope (LCM). It shows that the enhancement of both ductility and continuous work hardening for W- and FD-tempered AA7075 sheets at cryogenic temperatures results from the uniformly distributed dislocations in the matrix of supersaturated solid solution (SSSS). The relatively low cryogenic ductility of AA7075-FD in comparison with AA7075-W results from the cracked η phases in the interior of grain, which has an increasing brittleness and high stresses on the particle due to the bypassing process at cryogenic condition. Furthermore, the undesirable early fracture of AA7075-T6 alloy during cryogenic deformation process is systematically illustrated from the aspect of interaction between dislocation and second-phase particles. Beside the cracked η phases in the interior of grains, defects also appear in the non-coherent interface between PFZ and the equilibrium η phase due to stain localization at grain boundary. As a result, AA7075-T6 alloy exhibits a ductile-brittle mixed fracture mode dominated by PFZ and the equilibrium η phase at grain boundary.

Superplastic behaviour of AA5083 sheets in the presence of an oscillating load

The superplastic flow behaviour of AA5083 sheets was investigated at 450°C in the presence of a minor oscillating load. Uniaxial tensile specimens were tested to fracture at constant strain rates with a minor oscillating load superimposed onto the monotonically increasing tensile load. In each test, the oscillating load was applied as a sine wave having a constant amplitude of 0.5 N and a constant frequency. A series of tests was conducted in which the strain rate ranged from 0.001 to 0.4 s-1 and the frequency of the oscillating load ranged from 10 to 40 Hz. And other tensile specimens were subject to a constant mean load with a superimposed oscillating load until a predetermined elongation was reached. The flow behaviour of AA5083 showed a significant sensitivity to the oscillations although the tensile strengths remained practically unchanged. The addition of a minor oscillating load resulted in a 20% - 50% relative increase in fracture strain for the strain rates considered compared to the same tensile tests without oscillation. Finite element simulation of the tensile tests conducted at constant mean load with superimposed oscillations were carried out with LS-Dyna using material data obtained from the experiments. The numerical simulation results were compared with experimental results obtained under the same loading conditions to confirm their validity. The addition of a minor oscillating load led to greater uniformity in thickness in the specimen gauge. It can be concluded that superimposing a minor oscillating load during superplastic forming results in significantly greater deformation prior to fracture.

Effect of cryorolling on the microstructure and high-temperature mechanical properties of AA5083 sheets

To explore the effect of cryorolling on the high-temperature mechanical properties of aluminium alloys, AA5083 sheets were rolled at 83, 173, and 298 K, and the rolled sheets were then subjected to high-temperature tensile testing at 748 K. The elongation to failure of the 83 K cryorolled samples reached 150% at a strain rate of 1 × 10−3 s−1, which was higher than those of the 173 K cryorolled samples (92%) and 298 K rolled samples (80%). Under this condition, the strain rate sensitivity coefficient of the 83 K rolled samples was 0.36, which reached the standard of superplasticity. The enhancement of plasticity of the 83 K cryorolled samples was attributed to the finer grains, the smaller second phase, and the subgrains alleviating more stress concentration. The main deformation mechanisms during the high-temperature tensile deformation were grain-boundary sliding and dislocation slip. Compared to the 298 K rolled sample, the grain size of the 83 K cryorolled sample was smaller, which was suitable for the grain-boundary sliding mechanism. In addition, the uniform distribution of high-density dislocations prevented the dislocation slip mechanism but reduced the stress concentration and the nucleation and growth of cavities at high-temperature deformation.

Experimental investigation of high impact polystyrene/metal self‐piercing riveted joint

AbstractSelf‐piercing riveting was adopted to join high impact polystyrene (HIPS) and metal sheets which had huge difference in material properties. Three kinds of metal sheet (AA1060, AA5052, and HC340LA) were joined to HIPS sheet. The effect of polymer sheet thickness on mechanical properties of joints was investigated. The static loads of joints were measured in tensile and shearing tests. The failure modes of joints were analyzed. The cross sections of joints were observed by metallographic microscope. Results showed that self‐piercing riveting could effectively join HIPS and metal sheets when polymer sheet was placed as top sheet. All joints failed in the manner of polymer fracture in both tensile and shearing tests. For joints with different sheet material combinations, though the cross sections and geometrical parameters of joints had great difference, the static loads and absorbed energy values of joints were nearly the same. When AA5052 sheets were joined to HIPS sheets with different thickness values, with the increase of polymer sheet thickness, the flaring degree of rivet decreased, while static loads and absorbed energy values of joints increased. This was because the strength of interlock structure was higher than that of polymer sheet and the strength of joint was determined by the strength of polymer sheet.

Effect of concurrent accumulative roll bonding (ARB) process and various heat treatment on the microstructure, texture and mechanical properties of AA1050 sheets

This study investigated the microstructure, texture, and mechanical properties of 1050 aluminum alloy sheets that underwent the accumulative roll bonding (ARB) method. The ARB proceeded up to eight passes in three ways: conventional process, preheat between rolling passes (preheating) or anneal between rolling passes (annealing). Heat treatment was done between the ARB passes for 5 min at 150 °C. The mean grain width of the 1050 Al sheet that was 11 μm before ARB, decreased to 295.73 nm, 317.33 nm, or 339.23 nm after six ARB passes in the conventional process, annealed or preheated conditions, respectively. Concurrent heat treatments cause a decrease in the strength of the texture components of Al sheets that were elaborated by the ARB method. Even though conventional and annealed processes successfully enhanced the microhardness by ∼80% and tripled the tensile strength, these improvements were weaker in the preheated condition than the other conditions due to dynamic recovery.

Forming limit analysis of friction stir tailor welded AA5083 and AA7075 sheets in single point incremental forming

Forming limit analysis of friction stir tailor welded AA5083 and AA7075 sheets in single point incremental forming

Analysis of the incremental sheet forming process and process parameters on aluminum sheets based on the vertical step sizes

The incremental sheet forming (ISF) is an effective forming method developed especially for rapid prototyping and small-batch production of sheet metals. The selection of parameters (in particular, vertical step size and toolpath geometry) in ISF is crucial. Besides, each parameter has different effects on the desired geometry, sheet thickness, forming time, and productivity. In this study, the ISF process was analyzed by investigating the effects of ISF parameters. For this purpose, AA5754 sheets were formed by different ISF parameters. The effects of toolpath strategies (based on the vertical step size) were examined with three spindle speeds and three feed rates. To achieve that objective, constant, increasing, and decreasing vertical step sizes were used for the first time in the same study. After the forming, the forming time, geometric tolerance, and thickness values were analyzed. Besides, the efficiency of each parameter on the ISF process was investigated with the Pareto analysis. It has been revealed that each strategy has some advantages and disadvantages in ISF. The shortest forming time (1.55 min), the best geometric tolerance values (−0.05 mm, +0.2 mm), and the best thickness values (0.58 mm, 0.51 mm) were achieved following toolpath strategy 1, strategy 2, and strategy 3, respectively. The Pareto analysis showed that spindle speed and feed rate have a significant effect on toolpath strategies. The results obtained from this study will shed light on the effective advancement of small-batch production of sheets. Furthermore, the study contributes to the determination of parameters according to which of the sheet metal properties are desired.

Mechanism of dislocation promoting Al13Fe4 precipitation during friction stir-assisted incremental sheet forming in AA5052 sheet

The precipitation behavior of Al13Fe4 in AA5052 sheet during friction stir-assisted incremental sheet forming (FS-ISF) is investigated in the present work. It is found that the sizes of both incoherent and semi-coherent precipitates enlarge, and their contents increase with the increasing temperature caused by the high-speed rotation of the tool. Dense dislocations emerge and interact around these precipitates. Transmission electron microscopy (TEM) analysis reveals that dislocations can induce precipitation through prompting atomic segregations of Fe and Al elements. The strength of FS-ISFed AA5052 is further enhanced compared with conventional incremental sheet forming at room temperature (RT-ISF).

Investigations on formability of tailor laminated sheets in single point incremental forming

In this article, formability of tailor laminated sheets in single point incremental forming (SPIF) is investigated using forming limit curve (FLC) and maximum formable wall angle determined theoretically and incremental sheet forming tests. Two different sheet materials namely aluminum alloy AA5083 and polycarbonate were laminated in two different configurations, that is, AA5083/PC, and AA5083/PC/AA5083. FLCs were determined for the laminated sheets using deformation instability method and compared to that of the base sheets. It was observed that formability of the laminated sheets was higher than that of the PC and AA5083 sheets for plane strain case. The maximum formable wall angle was determined by varying the wall angle till the onset of fracture through deforming the sheet into square pyramid shapes. Deformation depths at the onset of fracture for the incrementally formed laminated sheets got decreased with the increase of forming wall angle. Optical macrographs of the cross-sections of the deformed laminated sheets with maximum forming wall angles were taken, and variations of sheet thicknesses along the center line of the deformed sheets were compared for the different cases. Higher triaxiality of AA5083/PC/AA5083 sheet results in lower formability compared to AA5083/PC sheet obtained from membrane analysis. Formation of bump structure due to delamination during SPIF of laminated sheets could be avoided using proper selection of tool path.

Tribological and mechanical characteristics of AA5083 alloy reinforced by hybridising heavy ceramic particles Ta2C & VC with light GNP and Al2O3 nanoparticles

In this study, AA5083 sheets were reinforced with four different hybrid nanoparticles by friction stir processing (FSP) for the development of surface nanocomposites used in advanced engineering applications. The present research focused on improving the properties and tribological behaviour of AA5083 alloy surfaces, including novel hybrid nanoparticles and the intermetallic phase formed during FSP. A tribometer tester with a constant normal load was used to examine the tribological performance of the hybrid composites. After the wear test, a surface profiler inspector was used to analyse the morphology and surface roughness of the examined materials. The Vickers micro-hardness of the base metal and the manufactured composites were measured. During FSP, a new intermetallic phase of AlV3 was successfully formed at 300–400 °C in the hybrid nanocomposites containing VC particles. The reinforcements resulted in additional grain refining than FSP. The AA5083/Ta2C–Al2O3 exhibited the greatest grain refinement, a sixty-fold reduction in grain size compared to that of the base alloy. The results revealed that the hybrid nanocomposites containing VC particles demonstrated the most significant microhardness values inside the stirred zone as a result of the presence of the AlV3 phase, which was increased by 25–30%. Moreover, the mechanical properties were significantly improved for all manufactured nanocomposites. The tensile strength was increased by 28% through the hybridisation of AA5083 using a hybrid of VC-GNPs. The dispersion of Ta2C-GNPs and VC-GNPs in the matrix led to excellent interfacial adhesion, resulting in an enhancement in the mechanical properties. The AA5083/VC-GNPs surface composite outperformed other manufactured composites regarding wear resistance. In addition, due to GNPs soft nature, it reduced the coefficient of friction (COF) of the manufactured composites by 20–25% compared to other reinforcements.

Effect of specimen configuration and notch root angle on fatigue behavior of novel dissimilar resistance spot welds of AA5754 to HSLA steel

Facing stringent requirements for fuel economy and regulations for greenhouse gas emissions, structural lightweighting using multi-material solutions has become commonplace in the automotive industry. When joining dissimilar materials such as aluminum to steel by resistance spot welding (RSW), a thin layer of brittle intermetallic compound forms at the aluminum-steel interface and dominates mechanical behavior of the joint. In this contribution, RSW of 1.1 mm thick AA5754 sheet to 2.0 mm thick high-strength low-alloy (HSLA) steel sheet was performed using multi-ring domed (MRD) electrodes and multiple solidification weld schedules to achieve acceptable static joint strength. Load-controlled fatigue tests were conducted and the results show that the fatigue life is longer in the AA5754 to HSLA steel spot welds than that of the 1.1 mm thick AA5754 joined to itself (aluminum-aluminum). Structural stress analysis revealed that all fatigue life data points from both the lap shear and coach peel configurations fall onto a single master curve indicating that the weld nugget diameter is the controlling parameter for fatigue life. Finite element simulation considering material inhomogeneity in the weld further confirms that a large notch root angle at the weld nugget is beneficial to yield longer fatigue life as less maximum principal strain occurs in the aluminum sheet in the AA5754-HSLA steel spot welds.

Feasibility study of dissimilar metal joining by laser riveting of Ti-6Al-4V to AA6061

Aluminum of cylindrical profile (of diameter 1–4 mm) was trailed by laser metal wire deposition for potential riveting applications. The rivet was built onto a Ti6Al4V substrate through a hole in an AA6061 sheet. The built feature was postprocessed by a high-frequency laser washing technique to obtain the desired finish. Parameter optimization has allowed increased productivity by almost seven times while achieving required wetting conditions and metallurgical properties. It is found that the quality (both morphology and metallurgy) of the laser rivet joint is highly dependent on the laser wash parameters. The rivet crown and welding areas improved by the postwash process were directly reflected in the microhardness and shear tests and increased by 90% and 62%, respectively, compared with those in an unwashed rivet.

On the low-cycle fatigue behavior of thermo-mechanically processed high-strength aluminum alloys

In the present work low-cycle fatigue experiments were carried out on thermo-mechanically processed AA6082 and AA7075 sheets to evaluate mechanical properties under cyclic loading. Different cooling rates imposed by use of tempered forming tools after solutionizing and subsequent aging treatment led to the formation of precipitates with differing sizes and morphologies. Specimens thermo-mechanically processed in tools with temperatures of 24 °C and 200 °C showed superior mechanical properties under both monotonic and cyclic loading. Different behavior was observed for the specimens formed in the tool with a temperature of 350 °C. Based on thorough analysis of prevalent microstructural features, processing-property-damage relationships are established pointing at the major impact of the thermal history on the final performance of the high-strength aluminum alloys in focus.

Robust bonding and microstructure behavior of aluminum/high-strength steel lap joints using resistance element welding process for lightweight vehicles: Experimental and numerical investigation

Here we present the resistance element welding (REW) process as a novel alternative to aluminum (Al)/steel (Fe) joints for the automotive structural assembly process. Before the REW process on the SPFC980 steels and AA5052 alloys, the low-carbon steel, S20C elements were riveted to AA5052 sheets to resolve the inconsistency of properties between Al and Fe. The REW processes were conducted with the 6 input parameters from 3.5 kA to 12 kA with a welding current under 200 ms of an energization time. As a result, robust bonding was successfully achieved exceeding 9 kN of tensile-shear strengths with excellent failure energies from the welding currents in 6.5 kA–10.5 kA without any common weld defects, e.g., crack, lack of fusion, lack of penetration, undercut, etc. These results present exceptional characteristics compared with the strength of previous reported Al/Fe joining technologies. The crystallographic characteristics of the welded metals in this process were quantitatively investigated using electron backscatter diffraction (EBSD) analysis. Due to the cooling effect the phase transformation was verified by theoretical values and finite element method (FEM) computational calculation. Furthermore, the fracture behavior analysis was thoroughly performed using the in-situ digital image correlation (DIC) method. This study provides a substantial alternative to achieve robust bonding of the automotive structural Al alloy/high tensile steel through the REW process and can be extended to mass production of lightweight structural assembly applications as well.