Formability Of Aluminum Alloys Research Articles

Investigation on the formability and deformation mechanism of aluminum alloy thin-walled parts at cryogenic temperature

Due to the poor ductility of aluminum alloy sheet at room temperature, which results in the difficulty in forming complex thin-walled parts, a novel forming method for thin-walled parts at cryogenic temperatures is proposed in this research, at which its strength and ductility are significantly improved. In this work, the cryogenic forming tests of the typical aluminum alloy thin-walled part were carried out, the formability and forming quality of the parts were evaluated, and the mechanism of the increase of strength-ductility at cryogenic temperature was discussed. The results of these experiments indicate that compared to room temperature, the formability of 2024-O aluminum alloy sheet at cryogenic temperature is significantly improved; the maximum forming height of aluminum alloy thin-walled part increases by 21.5% to 96 mm at − 180 ℃; in addition, the quality of parts formed at cryogenic temperature is better, whose maximum thinning rate is only half of the corresponding value at room temperature, and the hardness increases by 8.6%. It can be seen from the microstructure that when aluminum alloy deforming at low temperature, the dynamic recovery is restrained, the accumulation of dislocations leads to the increase of resistance to dislocation’s motion. The deformation of aluminum alloy at low temperature is more uniform, the work hardening ability is significantly improved, and its strength and ductility are enhanced. This study proves the feasibility of forming aluminum alloy thin-walled parts at cryogenic temperature, and provides a new idea for high-quality forming of complex thin-walled parts.

Comparison of underwater friction stir welded and conventional friction stir welded AA 5052 alloys based on the mechanical, formability and microstructure behaviour

Solid state joining of 1 mm thick AA 5052 aluminium alloys is carried out in the current study using both traditional friction stir welding (FSW) and underwater friction stir welding procedures. In the underwater FSW process, the tool and the welding plates are totally submerged underwater while the welding is being done. The underwater welding procedure contributes to improving the mechanical characteristics and formability of aluminium alloys by lowering heat dissipation. The current study compares the mechanical characteristics, formability, microstructure, and fractography of the joints made of the AA5052 aluminium alloy using the two different welding procedures. When performing FSW or underwater FSW, a process parameter called welding speed is changed from 30 mm/min to 60 mm/min at intervals of 15 mm/min while keeping a constant speed of 1200 rpm. Both FSWed and underwater FSWed samples are subjected to the Erichsen cupping test, where the dome height is taken into account as a metric of formability and the strains created during the deformation is also measured. Optical microscopes and scanning electron microscopes were utilized to analyse microstructure and fracture. At various speeds, the mechanical characteristics, formability behaviour, and microstructure of the two weldings were examined. Due to underwater welding's lower heat dissipation than conventional friction stir welding, it has been discovered that underwater welding has better mechanical, formability, and microstructure behaviour, making them more appropriate for automotive applications.

Effect of high-density pulsed electric current on the formability of aluminum alloy

Effect of high-density pulsed electric current on the formability of aluminum alloy

Forming of aluminium alloys with macro-structured tools at cryogenic temperature

The novel concept of macro-structuring deep drawing tools is used here for cryogenic forming of AA6014 in order to improve formability. In addition to known advantages of macro-structuring in tooling like friction force reduction, heat flux can also be directly influenced. This enables cryogenic sheet metal forming without active cooling of the tools. The improved formability and increased strength of aluminium alloys, which is attributed to the effects in the FCC crystal structure at cryogenic temperature, are utilised for increasing the drawing depth. Successful process routes, boundary conditions and design rules are demonstrated and influencings effects are discussed.

Mechanical and Tribological Properties Correlations of Die Cast and Spray Formed Aluminum 2.5wt.% Cu-2.5wt.% Mg - 5wt.% Zn Alloy

Aluminum with –2.5wt.% Cu–2.5wt.% Mg – 5wt.% Zn alloy was synthesized by die cast and spray formed technique. The average density of die cast and spray formed Al alloy was measured by water displacement method. The compression strength, hardness and tribological properties of the Al alloy produced by die cast and spray formed technique was studied as per the ASTM test standards and recorded the average values. The surface morphology of die cast Al alloy depicts the dendritic structures and spray formed Al alloy contains the equiaxed grains, coarse grains and fine grains across the surface. The elemental analysis of both die cast and spray formed Al alloy was measured by using scanning electron microscope. Average percentage of porosity of die cast and spray formed aluminum alloy is 1.79 ± 0.23 and 1.10 ± 0.3 respectively. The hardness of spray formed Al alloy is 10.54 % lesser than that of die cast Al alloy. Average ultimate compression strength of spray formed and die cast Al alloys are 360.07 ± 9.58 MPa and 353.33 ± 5.56 MPa respectively. The study also recorded the wear rate and coefficient of friction of die cast and spray formed Al alloy at different load and speed conditions. The precipitation strengthening mechanism is found to be involved in spray formed alloy.

Tailoring of the microstructure and mechanical properties of the flow formed aluminum alloy sheet

Tube flow forming followed by flattening is an effective way to make ultra-wide sheet for plastic forming of large thin-walled components. However, the work hardening and poor plasticity of flow formed sheet seriously restrict the subsequent plastic formability. To tailor the plastic formability, two types of heat treatments (recrystallization annealing and solution quenching) were conducted on the flow formed 2219 aluminum alloy sheet, and their microstructure evolution and mechanical properties were comparatively studied to obtain a suitable heat treatment scheme. It is found that the deformation in flow forming produces quantities of deformed substructures and the rotating cubic texture. In the recrystallization annealing, recrystallization occurs with the co-existence of two nucleation mechanisms, i.e., subgrain nucleation and particle stimulated nucleation, which produce a weak {100}//RD-CD texture and higher plasticity than that of the flow formed sheet. In addition, it is found that the annealing temperature and holding time have complex interactive effects on the average grain size, the uniformity of grain size and the resultant plasticity. In contrast, the solution quenching obtains weak {100}∥RD-CD texture at lower solution temperature and cube texture at higher solution temperature, respectively; meanwhile, it produces larger average grain size and better grain size uniformity than the recrystallization annealing. Because the uniform grain size can suppress the heterogeneous deformation and the dissolution of second phase particles can delay the generation of crack, the solution quenched sheet presents better plasticity than the recrystallization annealed sheet. Moreover, increasing the solution temperature can improve the plasticity. Therefore, it is suggested to take a solution quenching scheme with higher temperature (535 °C for 30 min) to tailor the flow formed sheet, which can get a similar elongation as that of the initial tube blank.

Study on cryogenic deep drawing of 2219 aluminum alloy spherical shell

In order to meet the urgent needs of aluminum alloy integral shell, a new forming process is required to solve the problem of splitting at room temperature. The plasticity of aluminum alloy is significantly improved at cryogenic temperature, and a novel cryogenic forming method was developed recently. In this paper, a cryogenic forming unit was established to study the cryogenic drawing behavior. The effects of sheet diameter on the wrinkling and deformation behaviors were analyzed by experiments and numerical simulations. The study showed that a spherical shell with a diameter of 200mm and a thickness-diameter-ratio of 1.0% could be formed at -160°C, which split at room temperature. The drawing depth was increased 74.3% at cryogenic temperature. The tendencies of wrinkling and splitting were controlled by the appropriate sheet diameter. It is concluded that cryogenic deep drawing has great potential for forming aluminum alloy integral shells.

Formability of Aluminum Alloys During Single Point Incremental Forming

Single point incremental sheet metal forming has passed through a period of ample improvement with developing responsiveness from research societies and industries globally. The process has expressively spared the practice of using costly dies, which makes it an appropriate process for manufacturing prototypes and small batch production. It also discovers easiness in fabricating components of timeworn equipment. Additionally, in recent years, aluminum alloys become the most commonly used materials in the automotive, aeronautics, and transportation industries for their structural and other applications. The effect of various process parameters on the formability of Single Point Incremental Forming of aluminum alloys has been critically surveyed. Ultimately, this article also debated the dares associated with the Single Point Incremental Forming process and recommended some correlated research regions which probably charm significant research considerations in the future.

Obtaining Uniform High-Strength and Ductility of 2A12 Aluminum Alloy Cabin Components via Predeformation and Annular Channel Angular Extrusion

A 2A12 aluminum alloy component with uniform high-strength and ductility was developed via predeformation (one-pass repetitive upsetting extrusion) and annular channel angular extrusion (ACAE). Moreover, the microstructure evolution and age-hardening behavior were investigated. The results show that the upsetting-extrusion predeformation improved the cumulative strain of the component and refined the grain size, and that the second Al–Cu–Mg phases were obviously broken and refined, and that, especially, the distribution of the second phases along the extrusion direction was weakened. Thus, compared with directly ACAE-formed components, after the T6 heat treatment, the axial ultimate tensile strength (UTS) of the cabin increased from 476 to 484 MPa, and the elongation (EL) increased from 12.9% to 17.5%. The circumferential UTS increased from 426 to 482 MPa, and the EL increased from 9.24% to 16.8%. A large number of dislocations were introduced into the upsetting extrusion (UE) + ACAE method, which resulted in strain hardening and higher precipitation strengthening in the late artificial aging process. The finer and denser grains and s precipitates significantly enhanced the strength and ensured the good ductility of the alloy. It is suggested that the combination of predeformation and annular channel angular extrusion is an effective method for forming aluminum alloy cabin components with higher and more uniform mechanical properties.

Biaxial formability and microstructure of an Al-Mg-Si alloy sheet post solution heat treatment

Hot forming-quenching integrated process was developed to fabricate aluminum alloy complex-shaped components by taking advantage of the enhanced formability at the temperature close to solution temperature. But, it is very difficult to evaluate the formability under biaxial tension state and continuous cooling conditions. A measuring method was proposed to evaluate the biaxial formability by combining solution heat treatment and hot gas free bulging test. The effects of temperature and pressurizing rate on the bulging ability and thickness uniformity of an Al-Mg-Si alloy sheet were clarified. The deformation mechanism was revealed by microstructure observation. It is found that excellent formability can be obtained under the high temperature with less heat loss and rapid pressurizing conditions. The limiting strain under rapid pressurizing condition decreases from 1.13 at 500 ℃ to 0.81 at 400 ℃, being at a high strain level. Thickness uniformity can be obviously improved at a higher deformation temperature accompanied by rapid loading due to the remarkable strain-rate hardening effect. Dynamic recovery is the main restoration mechanism, resulting in numerous substructures and unchanged grain size. The obtained biaxial formability closer to actual forming condition can provide fundamental guidance for forming aluminum alloy complex-shaped component by hot forming-quenching integrated process.

Dimensional accuracy in quick plastic forming of aluminum alloy using demolding mechanism

This study focuses on quick plastic forming (QPF), product dimensional tolerances, and removal methods. The traditional curled metal shell mold in QFP, has limitations such as long process time and unstable quality. Therefore, this investigation designed a demolding mechanism, in order to improve the process efficiency and dimensional accuracy of QPF, in the manufacture of metal casings. The research results show that the proposed mechanism can significantly decrease the process time, because it replaces most of the operations of specimens movement after forming completely. The shorter process time reduce the die temperature loss during operation, thus also improving the efficiency by eliminating the need to wait for the die to return to its operation temperature. In terms of dimensional tolerance, the tolerance grade of QPF process was determined using the standard deviation, and found to be between IT10 and IT14. This range covers the scope of CNC cutting and stamping processing, indicating that the process has commercial value in the production of metal casings, because the current mainstream manufacturing process of metal casings comprises casting, stamping and CNC machining.

Influence of temperature on the formability of an aluminum alloy

Warm forming is widely used as increasing the temperature is a solution to improve the formability of aluminum alloys. The stress (or strain) state is one of the most important factors affecting the formability of metals. In warm forming, the temperature and strain rate also play an important role on the deformation and fracture behavior. Figuring out the relationship between formability, temperature, strain rate and stress state is of great importance for providing more understanding of ductile fracture in warm forming conditions. Therefore, the objective of this work is to investigate the influence of temperature on the ductile fracture of a 6000 series aluminum alloy sheet metal under different stress states. Dogbone specimens, notched tensile specimens with different radius, tensile specimens with a central hole and shear specimens are used to cover a wide range of stress states. The hybrid experimental-numerical approach is used to identify the fracture strain and the corresponding stress state parameters (i.e. stress triaxiality and Lode parameter). To this end, fracture tests are carried out at 200°C using a tensile machine to determine the instant of fracture. Numerical simulations of the tensile tests are performed in 3D with the finite element code Abaqus to predict the strain field and calculate the evolution of the stress state. To accurately model the material behavior the positive strain rate sensitivity in the flow stress response at elevated temperature is considered. The results show a strong dependency of the ductile fracture on the temperature, strain rate and stress state.

Internal Corrosion of Warm Formed Aluminum Alloy Automotive Heat Exchangers

The objective of this study is to evaluate the effects of sheet temper, forming conditions, and the resultant post-braze microstructure on the corrosion behavior of Al alloy heat exchangers. Accelerated corrosion tests were performed by flowing a corrosive water solution through brazed heat exchanger samples fabricated from O and H24 temper sheet formed between room temperature and 250 °C. Sheet perforations within the brazed samples were found to be concentrated at the coolant channel inlets, due to crevice corrosion, or around other formed features within the coolant channel, which was attributed to erosion corrosion. A clear relationship between corrosion initiation sites and local microstructure was not observed in the accelerated test. Potentiodynamic polarization measurements were performed using the corrosive water solution and sheet samples pre-strained to 4 and 10% and subjected to a simulated brazing heat treatment. The average corrosion current density was the same for the two conditions, but liquid film migration occurred during brazing in the sample strained to 4%, resulting in localized corrosion and greater variability in the polarization measurements. It is concluded that warm forming does not impair the corrosion resistance of H24 temper sheet, but the corrosion resistance of brazed samples fabricated from O temper sheet is altered by warm forming.

A Physical-Based Plane Stress Constitutive Model for High Strength AA7075 under Hot Forming Conditions

Physicallybased constitutive equations are increasingly used for finite element simulations of metal forming processes due to the robust capability of modelling of underlying microstructure evolutions. However, one of thelimitations of current models is the lack of practical validation using real microstructure data due to the difficulties in achieving statistically meaningful data at a sufficiently large microstructure scale. Particularly, dislocation density and grain size governing the hardening in sheet deformation are of vital importance and need to be precisely quantified. In this paper, a set of dislocation mechanics-based plane stress material model is constructed for hot forming aluminum alloy. This material model is applied to high strength 7075 aluminum alloy for the prediction of the flow behaviorsconditioned at 300–400 °C with various strain rates. Additionally, an electron backscatter diffraction (EBSD) technique was applied to examine the average grain size and geometrical necessary dislocation (GND) density evolutions, enabling both macro- and micro- characteristics to be successfully predicted. In addition, to simulate the experienced plane stress states in sheet metal forming, the calibrated model is further extended to a plane stress stateto accuratelypredict the forming limits under hot conditions.The comprehensively calibrated material model could be used for guidinga better selection of industrial processing parameters and designing process windows, taking into account both the formed shape as well as post formed microstructure and, hence, properties.

Study the Ductility of Aluminum Alloy Processed by Asymmetric Rolling Process

Asymmetric rolling refers to the conditions wherein velocities or diameters of two work rolls are different. Compared to symmetrical rolling, asymmetric rolling is more effective on microstructure modification and texture evolution. Intense shear deformation can be introduced into asymmetric rolling to enhance the ductility and formability of aluminum alloy and this is the aim of current research. The process of the asymmetrical rolling was done on specimens with different reductions (10%,15%, and 20% reductions). Then the tensile test was conducted at room temperature at the strain rate range between 0.33×10-3s-1 - 3.33×10-3s-1 to study the ductility property of the asymmetric rolling-deformed samples and also compared with as-received samples. The results show that the as-received specimen gave the highest elongation of 42.7%, while the lowest elongation of 22.4% was obtained by the (20%) thickness reduction specimen. Also, the as-received sample at an initial strain rate of 3.33×10-3s-1 gives the highest tensile strength value equal to 550MPa.

Hot Gas Forming of Aluminum Alloy Tubes Using Flame Heating

Hot metal gas forming (HMGF) is a desirable way for the automotive industry to produce complex metallic parts with poor formability, such as aluminum alloys. A simple hot gas forming method was developed to form aluminum alloy tubes using flame heating. An aluminum alloy tube was heated by a flame torch while the tube was rotated and compressed using a lathe machine and simultaneously pressurized with a constant air pressure. The effects of the internal pressure and axial feeding on expansion and wall thickness distribution were examined. The results showed that the proposed gas forming method was effective for forming aluminum alloy tubes. It was also indicated that axial feeding is a vital parameter to prevent reductions in wall thickness by supplying the material flow during the forming process.

Effects of Hot Asymmetric Rolling on Microstructure and Formability of Aluminum Alloys

In order to analyze the effect of hot asymmetric rolling on the microstructure and texture of aluminum alloy and to investigate the effect of the texture on the formability and plastic anisotropy of aluminum alloy, aluminum 6061 alloy is asymmetrically rolled at room temperature, 200 °C, 350 °C, and 500 °C, and the results are compared with symmetrically rolled results. In the case of asymmetric rolling, the equivalent strain (εeq) is greatest in the upper roll part where the rotational speed of the roll is high and increases with increasing rolling temperature. The increase rate of the mean misorientation angle with increasing temperature is larger than that during symmetrical rolling, and dynamic recrystallization occurs the most when asymmetrical rolling is performed at 500 °C. In the case of hot symmetric rolling, the {001}<110> rotated cube orientation mainly develops, but in the case of hot asymmetric rolling, the {111}<110> orientation develops along with the {001}<100> cube orientation. The hot asymmetric rolling improves the formability (r) of the aluminum 6061 alloy to 0.9 and reduces the plastic anisotropy (Δr) to near zero due to the {111}<110> shear orientation that develops by asymmetric rolling.

Binder force effect on stretch flange forming of aluminum alloy

ABSTRACTThe present research investigates the effect of binder force in flanging of aluminum alloy sheets. FEM simulation of stretch flange forming is realized for zero, constant, and fixed binder forces. The finite element simulation is carried out to evaluate strain (circumferential and radial), flange thickness, position of commencement, and extension of cracks due to variation of binder force. The investigations reveal that the binder force has a significant effect on punch load, flange thickness (percentage thinning), circumferential and radial strain distribution, and commencement and extension of edge cracks. The results of FEM simulation are validated with results obtained by experimentation, and an excellent agreement is obtained.

Effects of intermetallic particles on cavitation during superplastic forming of aluminium alloy

ABSTRACTAn Al-4.6%Mg-1.5%Mn-0.27%Fe alloy was specially processed with friction stir processing followed by cold rolling. Half of the sheet thickness contains a large number of blocky or irregular-shaped Al6(Mn,Fe) coarse intermetallic particles, while the other half, smaller and more spherical ones. The particle-induced cavitation upon uni-axial tension at 475°C with 2 × 10−4–2 × 10−2 s−1 strain rates was investigated. The density of nuclei for cavities was estimated based on quantitative image analysis of the particles, and the strain controlled growth rate, calculated assuming the cavities are nucleated before or in the early stage of straining. The number, size and morphology of intermetallic particles are found to control the cavitation by determining the nucleation rate, but the strain controlled growth rate appears unaffected.

The Tribological Behavior of As-Sprayed Graphene Oxide–Tungsten Disulfide Hybrid Coatings

The application of solid lubricants in the metal forming of aluminum alloys is imperative due to their potential for the reduction of both friction and aluminum adhesion. This study focuses on examining the potential application of hybrid graphene oxide–tungsten disulfide (GO/WS2) coatings in the forming of aluminum alloys. A series of experiments with different GO/WS2 concentrations (between 1:1 and 12:1) was conducted to investigate the effects of increasing GO concentration on the tribological performance of the coatings. The coefficient of friction (COF) was evaluated using pin-on-disc experiments. The durability of the coatings (the sliding distance prior to the initiation of coating failure) was also recorded. Subsequent surface characterization was performed from within the sliding tracks induced on the coated Al-Mg discs and the mechanisms responsible for friction and wear are discussed. The GO/WS2 hybrid coatings provided low COF values (within the range of 0.18−0.27) and mitigated against aluminum adhesion before failure. An optimum GO/WS2 ratio (6:1) was noted as providing the optimum combination of low friction and improved durability. The concentration of GO in the hybrid coatings influenced the friction performance and durability of coatings, which was related to the formation of tribolayers on the aluminum surface and wear-induced transfer layers on the counterface surface. The formation of the tribolayers was attributed to the mixture of fragmented WS2 platelets, GO flakes, and carbon binder comprising the tribolayer.