High Strength Aluminum Alloy Research Articles

Investigation on evolution of microstructure and mechanical properties of heat-treatable 6010-S aluminium alloy during gas-based hot sheet metal forming process

Modern hot sheet metal forming processes offer the opportunity, especially in the automotive sector, to meet current demands for ultra-lightweight design. Due to the increased formability at the high process temperatures, high-strength aluminium alloys are increasingly coming into the focus of the industry. However, the complex thermo-mechanical interactions within these processes can lead to undesirable microstructural changes that could have a negative impact on the final mechanical properties. The purpose of this work is therefore to investigate the microstructural evolution of age-hardenable EN AW 6010-S alloy in the course of a modern gas-based sheet metal forming process and to quantify its influence on the resulting mechanical T6 properties. For this purpose, two different components were first formed at laboratory scale and the areas of microstructural interest were identified. Metallographic examinations and EBSD measurements were performed to visualize the influence of process temperature and deformation on the microstructure. EDX analysis helped to identify non-metallic phases. In the next step, artificial aging of the components was performed to increase the mechanical properties. Tensile tests and hardness measurements showed that the deformation and temperature have no negative influence on the final mechanical properties of the alloy.

Influence of process and material parameters on the twist springback prediction of a panel

Both advanced high strength steels and aluminum alloys gained increasing popularity because of the constant effort to meet the social pressure of reducing the vehicle weight while keeping their safety. The ratio between material strength and weight is much higher when compared to other materials but, the high springback after forming is one of the disadvantages of these materials, particularly when exhibiting twisting and side wall curl, which are the two most difficult types of springback to control and compensate in die engineering. This study analysis the influence of several material and numerical parameters on the prediction of the twist springback, using the Twist Die. Two processing conditions were considered: (i) blank-holder force that constrains the metal flow and (ii) a stake bead, which changes the forming conditions from draw to stretch forming, at the end of the process. The modelling of the elastoplastic behavior of the sheet materials uses a wide range of experimental data, for a DP980 steel and a 6xxx aluminum alloy. In addition to the effect of the sheet material on springback, the effect of the following parameters is also analyzed numerically: (i) friction coefficient; (ii) beads; (iii) modulus of elasticity; (iv) work hardening law and (v) yield criterion. All numerical simulations were performed with the finite element in-house code DD3IMP. The process parameter that most affects the twist springback is the presence of the stake bead, reducing significantly the springback. In addition, the reduction of the friction coefficient and of the elastic modulus also leads to an increase in springback. On the other hand, the yield criterion has little influence on springback of this component. The twist springback shows a different trend for the steel and the aluminum alloy that seems to be related with the different yield strength but also with the distinct gap between the punch and the die.

A new anisotropic-asymmetric yield criterion covering wider stress states in sheet metal forming

The stress state-dependent plastic anisotropy of sheet metals has drawn significant attention. Nevertheless, existing phenomenological plasticity models limitedly capture the distinctive yield strengths and plastic flow (r-values) under a wide range of stress states covering uniaxial tension (UT), equi-biaxial tension (EBT), uniaxial compression (UC), plane strain tension (PS), and pure shear (SH). This study aims to propose a new anisotropic-asymmetric plasticity model with enhanced flexibility based on the non-associated flow rule. The yield function is formulated based on the additive coupling of two stress potentials: coupling between a new anisotropic pressure-sensitive fourth-order polynomial function, and an isotropic stress invariant-based function. Then, all the anisotropic/asymmetric parameters of the yield function can be analytically identified from 7 yield stresses measured from UT tests along 0°, 45°, and 90° to the rolling direction (RD), UC tests along 0° and 90° to the RD, EBT test, and SH test along 45° to the RD. Within the scheme of no-associated flow rule, a new asymmetric fourth-order plastic potential function is proposed to analytically describe the plastic flow of sheet metals under UT, UC, EBT and SH. The additively coupled stress invariant-based term is introduced to adjust the yield stresses and plastic flow under biaxial tension including PS, which leads to an independent description of the yield stresses and plastic strain directions under SH and PS states. Various automotive sheet metals such as advanced high-strength steels, aluminum alloy, and magnesium alloy with strong asymmetry and anisotropy are investigated to verify the proposed yield criterion. The results demonstrate remarkable flexibility and accuracy of the proposed yield criterion against other existing models. Evolving yield surface and plastic potential of a quenching and partitioning steel are accurately captured by the proposed anisotropic-asymmetric yield criterion. Besides, the advantages of new model are further discussed in terms of the proof of yield surface convexity, identified parameters, and the regulation between anisotropy and isotropy in comparison with existing multiplicative coupling method.

Synergy of multiple precipitate/matrix interface structures for a heat resistant high-strength Al alloy

High strength aluminum alloys are widely used but their strength is reduced as nano-precipitates coarsen rapidly in medium and high temperatures, which greatly limits their application. Single solute segregation layers at precipitate/matrix interfaces are not satisfactory in stabilizing precipitates. Here we obtain multiple interface structures in an Al-Cu-Mg-Ag-Si-Sc alloy including Sc segregation layers, C and L phases as well as a newly discovered χ-AgMg phase, which partially cover the θ′ precipitates. By atomic resolution characterizations and ab initio calculations, such interface structures have been confirmed to synergistically retard coarsening of precipitates. Therefore, the designed alloy shows the good combination of heat resistance and strength among all series of Al alloys, with 97% yield strength retained after thermal exposure, which is as high as 400 MPa. This concept of covering precipitates with multiple interface phases and segregation layers provides an effective strategy for designing other heat resistant materials.

Microstructural characterization and mechanical properties of 6061 aluminum alloy processed with short-time solid solution and aging treatment

In order to reduce the cost of hot stamping of aluminum alloys and develop high-strength aluminum alloy parts for light-weight car body, short-time solid solution (SS) followed by shot-time artificial aging process was implemented for 6061 aluminum alloy with salt bath furnace and silicone oil bath. X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM-EDS) and high-resolution transmission electron microscope (HR-TEM) were used to characterize the microstructural evolution in details. The holding time for SS can be reduced by 80 % with short-time SS treatment because of the decreased vacancy generation energy and effective boundary areas. Peak aging can be obtained at 200 °C for only 60 min, and the microstructure was characterized by a lot amount of acicular nano-size β’’ phase in the coherent with matrix, while precipitate-free-zone (PFZ) also appeared along the grain boundaries. All tensile properties such as 327 MPa yield strength, 362 MPa tensile strength and 13.1 % elongation meet the 6061 T6-standard. The micro stress introduced by superheated degree along with short-time treatment should be attributed to the accelerated diffusion of magnesium and silicon atoms, which greatly affects the diffusion hermodynamics and kinetics, especially nearby the grain boundaries.

Strain rate effect and dynamic constitutive model of 7A04-T6 high-strength aluminium alloy

In recent decades, various aluminium alloys have been developed and employed in construction engineering. They are light, corrosion-resisting and recyclable, making them attractive to engineers and researchers. Among these aluminium alloys, 7A04 high-strength aluminium alloy, which is an Al-Zn-Mg-Cu alloy, has now gained focus for its excellent strength-to-weight ratio, hardness, formability, etc. To date, the investigations into its dynamic mechanical properties are still limited. In this context, the mechanical behaviour of 7A04-T6 aluminium alloy at high strain rates was studied in this work. A split Hopkinson pressure bar test system was employed to conduct the dynamic experiments. 6061-T6 aluminium alloy was also included in the tests for reference. Then, comparisons were made between the tested 7A04-T6 and 6061-T6 aluminium alloys and among the studied 7A04-T6 aluminium alloy and steels with approximate yield strengths (Q420 and Q550 structural steels) and similar strength-density ratios (4340 M and Aermet 100 steels), to assess the strain rate sensitivity of 7A04-T6 aluminium alloy. Based on the Johnson-Cook model and the Cowper-Symonds model, which are widely used models that describe the dynamic constitutive behaviour of metallic materials, a modified dynamic constitutive model was developed for 7A04-T6 aluminium alloy, in which the influence of deformation-induced temperature rise on the dynamic mechanical properties is well considered.

Influence of Novel Beam Shapes on Laser-Based Processing of High-Strength Aluminium Alloys on the Basis of EN AW-5083 Single Weld Tracks

The commonly used Gaussian intensity distribution during the laser-based processing of metals can negatively affect melt pool stability, which might lead to defects such as porosity, hot cracking, or poor surface quality. Hot cracking is a major factor in limiting production rates of high-strength aluminium alloys in laser-based processes such as welding or the powder bed fusion of metals (PBF-LB/M). Going away from a Gaussian intensity distribution to ring-shaped profiles allows for a more even heat distribution during processing, resulting in more stable melt pools and reduced defect formations. Therefore, the aim of this study is to investigate the influence of different laser beam profiles on the processing of high-strength aluminium alloys by using a multicore fiber laser, allowing for in-house beam shaping. Single weld tracks on the aluminium alloy EN AW-5083 are produced with varying laser powers and weld speeds, as well as different beam profiles, ranging from Gaussian intensity distribution to point/ring profiles. The molten cross sections are analyzed regarding their geometry and defects, and the surface roughness of the weld tracks is measured. By using point/ring beam profiles, the processing window can be significantly increased. Hot cracking is considerably reduced for weld speeds of up to 1000 mm/s compared to the Gaussian beam profile. Furthermore, the melt pool width and depth are more stable, with varying parameters for the point/ring profiles, while the Gaussian beam tends to keyhole formation at higher beam powers. Finally, a strong decrease in surface roughness for the point/ring profiles, accompanied by a significantly reduced humping effect, starting even at lower beam powers of 200 W, can be observed. Therefore, these results show the potential of beam shaping for further applications in laser-based processing of high-strength aluminium alloys.

New High-strength Aluminum Alloy Used for Distribution Circuit Fittings

Traditional Q235A distribution circuit fittings have high operation energy consumption and galvanized pollution problems, which is not in line with our carbon peaking and carbon neutrality goals. A new type of high-strength aluminum alloy with tensile strength up to 407.3 MPa and elongation at break up to 11% is created. It can be used to replace the traditional Q235A in the preparation of distribution circuit fittings.

Control of microstructure and solidification cracks in laser powder bed fusion additive manufacturing of high-strength aluminum alloys

Control of microstructure and solidification cracks in laser powder bed fusion additive manufacturing of high-strength aluminum alloys

Optimization of porosity and surface roughness of CMT-P wire arc additive manufacturing of AA2024 using response surface methodology and NSGA-Ⅱ

A novel cold metal transfer and pulse (CMT-P) hybrid arc technology was introduced for additive manufacturing of high-strength aluminum alloy 2024 (AA2024). The effects of process parameters, namely the wire-feed speed, travel speed, and CMT/P ratio (ratio of number of CMT stages to pulse stages in a cycle), on the porosity and surface roughness of AA2024 CMT-P additive manufacturing were systematically investigated using the response surface methodology and an improved non-dominated sorting genetic algorithm (NSGA). The results showed that the wire-feed speed had the greatest effect on the porosity and surface roughness. The porosity initially decreased and then increased with an increase in the wire-feed speed. However, the surface roughness decreased with an increase in the wire-feed speed. Moreover, the porosity was reduced with a decrease in the travel speed. With an increasing travel speed, the surface roughness initially decreased and then increased. Furthermore, for both porosity and surface roughness, the best results were obtained at a CMT/P ratio of 1/4. Thus, high porosity and surface roughness in the additive-manufactured parts were caused by high values of wire-feed speed, travel speed, and CMT/P ratio. In addition, using the optimized process parameters, additive parts with low porosity and low surface roughness could be produced.

Optimization strategy for the indirect isothermal extrusion of high-strength aluminum alloy based on temporal fusion transformer

Optimization strategy for the indirect isothermal extrusion of high-strength aluminum alloy based on temporal fusion transformer

Evaluation of Riveting Force Influence on the Quality of Riveted Joint of Aluminium Alloy EN AW - 6016

Joining technologies are very important aspects of production process in the automotive. Especially regarding the use of newly developed types of materials (e.g. ultra high-strength steels or aluminium alloys), in addition to welding technology, e.g. riveting or adhesive bonding technologies are used. Submitted article evaluates the effect of the riveting force on the final quality of riveted joint when joining aluminium alloy EN AW-6016 (thickness 2 mm). The actual evaluation of the riveted joint was carried out using a shear test, measuring the hardness HV01 and deformation analysis of specimen using non-contact optical scanning (ATOS III Triple Scan system).

Interfacial reaction kinetics of (Al63Cu25Fe12) 99Ce1 quasicrystal reinforced 6061 aluminum matrix composites

Due to its superior overall characteristics and effective interface wetting, quasicrystal reinforced aluminum matrix composite is regarded as a type of material with significant development potential. The procedure of hot pressing and sintering was used to create a quasicrystal particle reinforced 6061 aluminum matrix composite made of (Al63Cu25Fe12)99Ce1. Investigated in the composite were the element diffusion and the microstructure of the contact between the reinforcement and matrix. The findings demonstrate that mutual diffusion between reinforcement and matrix leads to the formation of the I-phase, Cu9Al4 phase, Al23CuFe4 phase, and ω-phase. Always present in the reinforcement, which has a strong link to the matrix, is the Al13Ce2Cu13 phase. At the same time, the diffusion kinetics of the transition layer between the quasi-crystalline phase and the matrix during the hot pressing process was revealed, and the most suitable thickness of the transition layer was determined to be 4.85 µm, which plays a great role in the improvement of the composite properties. The study of the microstructure and interfacial dynamics of (Al63Cu25Fe12)99Ce1 quasicrystal-reinforced 6061 aluminum matrix composites has laid the foundation for the creation of long-life, high-strength aluminum alloy materials with excellent properties.

Critical effect of heat input on joint quality in resistance element welding of Al and steel

Resistance element welding (REW) has recently attracted increasing interest, especially in the joining of high-strength steels and aluminum alloys. However, the intensity of heat input is a critical factor for the joint quality due to the possibility of excessive melting of the aluminum sheet around the element shank, which often degrades the joint's performance. This study evaluates the influence of heat input on the joint formation and mechanical performance of REW joints between ultra-high strength steel and aluminum alloy. In addition to the experimental investigations, a finite element method (FEM) was used to analyze the temperature distribution, nugget formation, and aluminum sheet melting characteristics as a function of heat input. The results show that the nugget dominates the joint's strength if the heat input is comparatively low. When heat is increased, however, the aluminum sheet plays a significant role in the joint's strength. Excessive melting of aluminum sheets reduces the load-bearing area of the joint. The competition between the weld nugget and aluminum sheet determines the joint's strength. The failure mode changes from interfacial to aluminum sheet failure as the heat input increases. The combined effect of aluminum sheet thickness and heat input on the joint strength was also evaluated. The results indicate that determining the appropriate heat input level is crucial to achieving an excellent performance of the REW joints.

Efficient depositing aluminum alloy using thick strips through severe deformation-based friction rolling additive manufacturing: processing, microstructure, and mechanical properties

Solid-state additive manufacturing is a promising technology for production of high-strength aluminum alloy components. However, most solid-state AM technologies use thin foils or powder as feeding materials, limiting the deposition thickness of each layer and thus restricting deposition efficiency. This study is the first to utilize 2-mm-thick 5052-H32 aluminum alloy strips as feed material for a severe deformation-based friction rolling additive manufacturing (FRAM) method. In this study, the effect of process parameters such as rising height, transverse speed, and rotational speed, on the forming quality, microstructure, and mechanical properties of the resulting part were investigated. The results indicated that macroscopic forming defects can be avoided by selecting appropriate process parameters. A non-planar lamellar microstructure of fine and ultra-fine equiaxed grains densely embedded in each other was obtained without porosity or unbound defects; although the deposited material was not composed of completely equiaxed grains, the anisotropy of mechanical properties was small. The ultimate tensile strength and elongation in both the longitudinal and build directions of deposited material were higher than those of the raw feeding strips owing to the non-planar lamellar microstructure and grain refinement, with maximum values of 215 MPa and 32%, respectively. Through this microstructure analysis, the mechanism behind the formation of the lamellar microstructure was elucidated. The concepts investigated here regarding defect-free, high strength, and high elongation lamellar materials by FRAM with thick strips as feeding material, provides a methodology for future preparation of laminated composites using FRAM.

Sustainable Lifecycle of Perforated Metal Materials.

In an era of rapidly growing consumer demand and the subsequent development of production, light materials and structures with a wide range of applications are becoming increasingly important in the field of construction and mechanical engineering, including aerospace engineering. At the same time, one of the trends is the use of perforated metal materials (PMMs). They are used as finishing, decorative and structural building materials. The main feature of PMMs is the presence of through holes of a given shape and size, which makes it possible to have low specific gravity; however, their tensile strength and rigidity can vary widely depending on the source material. In addition, PMMs have several properties that cannot be achieved with solid materials; for example, they can provide considerable noise reduction and partial light absorption, significantly reducing the weight of structures. They are also used for damping dynamic forces, filtering liquids and gases and shielding electromagnetic fields. For the perforation of strips and sheets, cold stamping methods are usually used, carried out on stamping presses, particularly using wide-tape production lines. Other methods of manufacturing PMMs are rapidly developing, for example, using liquid and laser cutting. An urgent but relatively new and little-studied problem is the recycling and further efficient use of PMMs, primarily such materials as stainless and high-strength steels, titanium, and aluminum alloys. The life cycle of PMMs can be prolonged because they can be repurposed for various applications such as constructing new buildings, designing elements, and producing additional products, making them more environmentally friendly. This work aimed to overview sustainable ways of PMM recycling, use or reuse, proposing different ecological methods and applications considering the types and properties of PMM technological waste. Moreover, the review is accompanied by graphical illustrations of real examples. PMM waste recycling methods that can prolong their lifecycle include construction technologies, powder metallurgy, permeable structures, etc. Several new technologies have been proposed and described for the sustainable application of products and structures based on perforated steel strips and profiles obtained from waste products during stamping. With more developers aiming for sustainability and buildings achieving higher levels of environmental performance, PMM provides significant environmental and aesthetic advantages.

Effect of T6I4 with different aging time on microstructure and properties of high strength aluminum alloy

Effect of T6I4 with different aging time on microstructure and properties of high strength aluminum alloy

Effect of pre-aging and precipitation behavior on mechanical properties of 7055 aluminum alloy processed by hot-forming quenching

Hot-forming Quenching (HFQ) can lead to significant changes in microstructure of high-strength aluminum alloys for car body sheet. Furthermore, through effective control, desired performance of the alloys can be achieved. Three designed processes, HFQ + Natural Aging (NA) + Simulate Baking (SB), HFQ + Pre-aging (PA) + SB and HFQ + Peak-aging (T6) were applied in this work, and the evolution of precipitated phases was systematically studied using High Resolution Transmission Electron Microscopy-Selected Area Electron Diffraction (HRTEM-SAED). The results revealed the precipitation nature of η phase in 7055 aluminum alloys is that GP zone I evolves into GP zone II, on which η’ phases directly nucleate and multiply, resulting in the transformation from η’ phases into η phases. By comparing the three processes, it is found that HFQ + PA + SB has high-density and finely distributed η’ phases, and grain boundary precipitates are small and discontinuously distributed. By adjusting the pre-aging temperature and time, it can provides a large amount of precipitation nucleation basis for the baking stage and ensure that η’ phase formation with high quantity density. The end product has a tensile strength of 660.1 MPa and a yield strength of 639.4 MPa, which is the most promising sheet material for future car body application.

Testing of high strength aluminium alloy SHS and RHS stub columns in fire

With the aim of investigating the local buckling behaviour of high strength aluminium alloy columns in fire, six room-temperature tests and eighteen steady-state tests at elevated temperatures on 7A04-T6 aluminium alloy square hollow section (SHS) and rectangular hollow section (RHS) stub columns were conducted in this study. Initial geometric imperfections of each specimen were first measured by the 3D laser scanner. Then, the test setup, procedure and instrumentation are fully reported. Test results, including failure modes, ultimate resistances and load-end shortening curves were obtained and utilised to evaluate the accuracy of current design methods for aluminium alloy stub columns in fire. The evaluation indicated that European and Chinese codes provided rather conservative predictions at 400 °C, while most of the resistances predicted by the American specification and methods proposed by Maljaars et al. were on the unsafe side. New design approaches proposed by the authors obtained more accurate and less scattered resistance predictions. Furthermore, the finite element (FE) models were also established and achieved good agreements with the test results.

Hydrogen Embrittlement and its Prevention in 7XXX Aluminum Alloys with High Zn Concentrations

7xxx aluminum alloys are representative high-strength aluminum alloys; however, mechanical property degradation due to hydrogen hinders further strengthening. We have previously reported that hydrogen embrittlement in 7xxx alloys originates from trapped hydrogen at the MgZn2 precipitate interface, providing high hydrogen trapping energy. We propose the dispersion of Mn-based second-phase particles as a novel technique for preventing 7xxx aluminum alloy hydrogen embrittlement. In this study, the deformation and fracture behaviors of high hydrogen 7xxx alloys containing 0.0% Mn and 0.6% Mn are observed in situ using synchrotron radiation x-ray tomography. Although no significant differences appear between the two alloys regarding the initiation of quasicleavage cracks, the area fractions of final quasicleavage fractures are 16.5% and 1.0% for 0.0% Mn and 0.6% Mn alloys, respectively; this finding indicates that Mn addition reduces hydrogen-induced fractures. The obtained macroscopic hydrogen embrittlement is quantitatively analyzed based on hydrogen partitioning in alloys. Adding 0.6% Mn, generating second-phase particles with high hydrogen trapping abilities, significantly suppresses hydrogen-induced quasicleavage fracture. The results of an original hydrogen partitioning analysis show that the dispersion of Mn-based particles (Al12Mn3Si) with high hydrogen trapping abilities reduces the hydrogen concentration at the semicoherent MgZn2 interface and suppresses hydrogen embrittlement.