Wrought Aluminum Research Articles

EFFECT OF PRE-HEATING ON THE MECHANICAL PROPERTIES OF FRICTION STIR WELDING FOR 6061 ALUMINUM ALLOY

Friction stir welding (FSW) process is a solid-state joining invented via the Welding Institute in 1991 at a great rate emerging as an application by fusion welding for joining different alloys. The wrought aluminum alloy 6061 is heat treatable and possesses a high corrosion resistance. This alloy has been used in a wide range of applications, like arenas gymnasiums and trains bodies. Aluminum alloy 6061 cannot be easily welded by the conventional fusion welding process because of the cracks that make the mechanical of welding joint very weak. In FSW, many parameters effect on its welding process. In the present research, the pre-heating effect on the aluminum 6061 sheet at 100°C and 150°C was studied. This heat has to be given for obtaining a defect-free as well as quality joint. Result manifested that the welding without pre-heating the parent metal at a (1120 r.p.m) rotational speed and a (30 mm/min) welding speed gave the best result of the ultimate tensile strength (236 N/mm2).

Topological Optimization of Artificial Neural Networks to Estimate Mechanical Properties in Metal Forming Using Machine Learning

The ability of a metal to be subjected to forming processes depends mainly on its plastic behavior and, thus, the mechanical properties belonging to this region of the stress–strain curve. Forming techniques are among the most widespread metalworking procedures in manufacturing, and aluminum alloys are of great interest in fields as diverse as the aerospace sector or the food industry. A precise characterization of the mechanical properties is crucial to estimate the forming capability of equipment, but also for a robust numerical modeling of metal forming processes. Characterizing a material is a very relevant task in which large amounts of resources are invested, and this paper studies how to optimize a multilayer neural network to be able to make, through machine learning, precise and accurate predictions about the mechanical properties of wrought aluminum alloys. This study focuses on the determination of the ultimate tensile strength, closely related to the strain hardening of a material; more precisely, a methodology is developed that, by randomly partitioning the input dataset, performs training and prediction cycles that allow estimating the average performance of each fully-connected topology. In this way, trends are found in the behavior of the networks, and it is established that, for networks with at least 150 perceptrons in their hidden layers, the average predictive error stabilizes below 4%. Beyond this point, no really significant improvements are found, although there is an increase in computational requirements.

Friction Stir Welding of Wrought Aluminium Alloy EN AW- 6082

The article presents results of the friction stir welding of 6 mm thick plates made of wrought aluminium alloy EN AW-6082. Tests discussed in the article involved the identification of the effect of primary welding process parameters on the quality of welds. Test welds were subjected to visual tests, measurements of temperature (inside the weld), tensile strength tests as well as macro and microscopic metallographic tests and structural tests (performed using a scanning electron microscope). The application of the appropriate values of the primary welding process parameters (i.e. the tool rotation rate and the welding rate) enabled the obtainment of the high and repeatable quality of FSW joints made of aluminium alloy EN AW-6082. The test results presented in the article can offer technological solutions for potential

Effect of environmental relative humidity on hydrogen-induced mechanical degradation in an Al–Zn–Mg–Cu alloy

The influence of relative humidity (RH) on mechanical properties of a 7075 alloy, cold finished aluminum wrought product, was studied by slow strain rate technique in atmospheres with various RHs. Hydrogen was introduced into specimens from the testing environment during deformation and then thermal desorption spectrometry was utilized to determine the content of absorbed hydrogen. By increasing the RH in slow strain rate tensile tests, the ultimate tensile strength remained unchanged, the content of hydrogen increased, and the total tensile elongation reduced, revealing an increase in the hydrogen embrittlement sensitivity (HES). In RHs below 40%, the HES was insignificant. However, by increasing the RH, a sharp increase in HES was observed due to the formation of secondary cracks. The results firstly showed that even a normal humidity (40–60%) of the testing environment at room temperature can lead to a significant HES in a wrought aluminum alloy.

Microstructures, mechanical properties and solidification mechanism of a hot tearing sensitive aluminum alloy asymmetric part fabricated by squeeze casting

In this work, 7075 Al alloy, a high-strength wrought aluminum alloy with high hot tearing sensibility, was used in the squeeze casting of an asymmetric part. The solidification defects, microstructures and mechanical properties of the part solidified under different forming pressures were studied. Furthermore, the uniformities of the microstructures, mechanical properties and the solidification mechanisms were investigated. Results show that increasing the forming pressure is helpful to improve the liquid/solid feeding for counteracting the particularly serious shrinkage during the wide mushy zone of 7075 Al alloy. Therefore, the solidification defect can be avoided. Moreover, increasing the forming pressure is helpful to not only obtaining fine equiaxed grains, but also diminishing the intergranular segregation of alloying elements. With the increasement of forming pressures, the strengths of the part increased, along with the decreases in the ductile due to the work hardening resulted from the serious solid feeding. The microstructures and mechanical properties are impacted by the solidification rate of the melt at different regions. When the forming pressure was 150 MPa, fine microstructures and excellent mechanical properties were obtained. The uniformity of the microstructures and mechanical properties are dominated by the solidification location sequence of the melt. Further on, it is determined by the thermal gradient of the melt at different locations. For 7xxx series alloys, more solid feeding is needed for counteracting the serious shrinkage at the first solidified regions, causing a work hardening and associated strengths increasements. A near uniform part thickness and direct feeding loads are appreciated to improve the uniformities. In this work, the optimal tensile properties tested in the part were tested to be as follows: the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) are 345.5 MPa, 483.2 MPa, and 7.6%, respectively. The UTS uniformity is tested to be 86.4%.

A Critical Conception of Hot-Tearing Susceptibility: Shape Casting with Wrought Aluminum Alloys

A Critical Conception of Hot-Tearing Susceptibility: Shape Casting with Wrought Aluminum Alloys

A high-strength heat-resistant Al−5.7Ni eutectic alloy with spherical Al3Ni nano-particles by selective laser melting

Traditional high-strength wrought aluminum alloys are sensitive to cracks in additive manufacturing (AM) while the eutectic aluminum alloys can be reliably printed. To explore a high-strength heat-resistant aluminum alloys by AM, in this paper, we proposed to retard the solidification range by using an Al−5.7Ni alloy, thus alleviate crack formation tendency. The AM parts of this alloy was featured by uniformly distributed spherical Al3Ni nano-particles with an average size of ~33 nm, showing a novel coherent crystallographic relationship with the matrix, <110>Al//<113>Al3Ni and {111}Al//{211}Al3Ni. Excellent mechanical property was achieved in this crack-free alloy with tensile strength of 410 MPa at room temperature and 140 MPa at 300°C, mainly attributed to the dispersion strengthening from the Al3Ni nano-particles with superior thermal stability.

Multistep anodization of 7075 – T6 aluminum alloy

This study successfully demonstrated the overall advantages of multistep anodization of heat-treated wrought aluminum alloy AA7075-T6 that is a widely used in aerospace, automotive and fracture-critical applications. The coating properties and morphology are studied in detail for four anodization regimes: a conventional R1 with a constant electric current and R2, R3, R4 with raising the current in two, four and eight steps, respectively. Whereas processes R1 and R2 form coatings with the atomic Al/O ratio of 0.53 that is smaller than 0.67 for oxide Al2O3, R3 and R4 create coatings with the Al/O ratio of 0.83. Due to a higher level of infused oxygen, coatings built in R1 and R2 have burns and powdery appearance, while coatings formed in processes R3 and R4 form exhibit smooth solid-like surfaces. Compared to R1 and R2, R3 and R4 increase the overall growth rate of oxides by 23.4% and 25.6%, respectively, reduce the pore size by 94% and 45% respectively and decrease by 8.4% the amount of a transferred electric charge per one micrometer of the layer thickness. Process R4 creates coatings that are 74.0% more resistant to abrasion, 14.6% harder and 25.4% thicker than coatings formed in R1. As no specialized equipment is required, presented regimes of multistep anodization are well suited for large-scale manufacturing.

Авіалі, історія створення і огляд перспективи

Scientific domestic and foreign literature touching the field of Al – Mg – Si wrought aluminum alloys are reviewed, the history of appearance of the most common brands is described. It is shown that the development of alloys was proceed gradually advancing their chemical composition along the quasi-binary Mg/Si = 1.73 сross -section in the direction of increasing concentration of just Mg and Si, and the strength of last modern brands was provided by additional alloying, primarily copper, the content of which can reach 1-1.4%. The influence of alloying elements on microstructure, mechanical and corrosion properties of alloys is described, features of their heat treatment, factors of maximum strengthening and susceptibility to intergranular corrosion are revealed. Attention is focused on the key role of the Mg/Si ratio, transition metals, Cu, Cr and Mn first of all, in the formation of balanced properties, since the positive effect of these elements on increasing the strength and the recrystallization temperature is often offset by the negative impact on intergranular corrosion and quench sensitivity. It is shown that in low-alloyed Al–Mg–Si alloys the strength premises Mg/Si≈1 and the premises for high-end corrosion resistance Mg/Si≈2 are occurred simultaneously. Alongside an increase of the absolute content of Mg and Si in alloys, alongside an increase of alloying degree with other strengthening elements, it is impossible to simultaneously fulfill both of these premises; therefore, one has to look for a reasonable compromise between strengthening, decreasing the technological plasticity and corrosion resistance of alloys. One of the effective ways to reach such a compromise is multi-stage regimes of artificial aging. The prospects of microalloying with Sc and Ca able to form with aluminum nanoscale intermetallic phases of hardening are outlined. Keywords: avials, semi - finished products, alloying system, transition metals, aging, mechanical properties, intergranular corrosion.

Deep learning computer vision for the separation of Cast- and Wrought-Aluminum scrap

In consequence of the electrification and the increased adoption of lightweight structures in the automotive industry, global demand for wrought Aluminum (Al) is expected to rise while demand for cast Al will stagnate. Since cast alloys can only be converted to wrought alloys by energy-intensive processes, the most promising strategy to avoid the emergence of excess Al cast alloys scrap is to sort cast from wrought alloys. To date, the separation of complex mixes of non-ferrous metals often implies the use of either or both sink-float techniques and/or X-ray fluorescence (XRF) based sorting. Therefore, the presented research develops an efficient method to classify cast and wrought (C&W) alloys in a real-time system with a conveyor belt using transfer learning methods, such as fine-tuning and feature extraction. Five CNNs are evaluated to classify C&W alloys using colour and depth images and transfer learning methods. In addition, the early fusion and late fusion of colour and depth images of C&W Al are investigated. For early fusion, data is added as an extra input channel to the first convolution layer of the CNN, and for later fusion, the images are fed in two separate subnetworks with the same architecture, where the parameters of the fully-connected layers are concatenated in both subnetworks. Our approach shows that late fusion CNN DenseNet allows obtaining the best performances and can achieve up to 98% accuracy.

An Evaluation of the Influence of Forward Slip on the Corrosion Behavior of Aluminum-Manganese Alloys

The tribological influence of hot rolling parameters, such as the work roll roughness, roll speed, and the number of rolling passes on the surface quality of rolled aluminum alloys, has been a subject of interest for the wrought aluminum industry. A hot rolling tribo-simulator was used to investigate the effect of forward slip on the surface damage induced by the rolling operation and the subsequent corrosion behavior of the Al-Mn alloys. A two-pass hot rolling schedule was conducted at 500–540 °C for forward slip levels of − 4, 1, 7, and 13% using an AISI 52100 steel work roll with a surface roughness (Ra) of 0.01 µm. Characterization of the rolled surfaces using scanning electron microscopy (SEM) revealed hot rolling-induced damage in the form of microcracks, nanocracks, and MgO coverage, which was more prominent for higher forward slips. Corrosion tests were subsequently conducted on the rolled Al-Mn specimens by immersion in a 0.5 wt.% NaCl solution. These tests showed greater corrosion-covered surface areas on samples rolled at lower forward slips. This relationship between the forward slip and corrosion behavior was due to the extent of surface damage induced at varying forward slip levels. The preferential corrosion mechanism was observed to be due to the dissolution of the MgO-rich near-surface microstructures induced during hot rolling.

Multi-Spot Ultrasonic Welding of Aluminum to Steel Sheets: Process and Fracture Analysis

Ultrasonic metal welding is an energy-efficient, fast and clean joining technology without the need of additional filler materials. Single spot ultrasonic metal welding of aluminum to steel sheets using automotive materials has already been investigated. Up to now, further studies to close the gap to application-relevant multi-metal structures with multiple weld spots generated are still missed. In this work, two different spot arrangements are presented, each consisting of two weld spots, joined 0.9 mm thick sheets of wrought aluminum alloy AA6005A-T4 with 1 mm sheets of galvannealed (galvanized and annealed) dual-phase steel HCT980X. An anvil equipped with variable additional clamping punches was used for the first time. The tensile shear forces reached 4076 ± 277 N for parallel connection and 3888 ± 308 N for series connection. Temperature measurements by thermocouples at the interface and through thermal imaging presented peak temperatures above 400 °C at the multi-metal interface. Microscopic investigations of fractured surfaces identified the Zn layer of the steel sheets as the strength-limiting factor. Energy-dispersive X-ray spectroscopy (EDX) indicated intermetallic phases of Fe and Zn in the border areas of the weld spots as well as the separation of the zinc layer from the steel within these areas.

Experimental Evidence of Specimen-Size Effects on EN-AW6082 Aluminum Alloy in VHCF Regime

The present paper investigates the influence of the specimen size of EN-AW6082 wrought aluminium alloy subjected to very high cycle fatigue (VHCF) tests. The hourglass specimens were tested under fully reversed loading condition, up to 109 cycles, by means of the ultrasonic fatigue testing machine developed by Italsigma® (Italy). Three specimens groups were considered, with a diameter in the middle cross-section ranging from 3 mm up to 12 mm. The stress field in the specimens was determined numerically and by strain gauge measurements in correspondence of the cross-section surface. The dispersion of experimental results has been accounted for, and data are reported in P-S-N diagrams. The decrease in fatigue resistance with increasing specimen size is evident. Theoretical explanation for the observed specimen-size effect is provided, based on Fractal Geometry concepts, allowing to obtain scale independent P-S*-N curves. The fatigue life expectation in the VHCF regime of the EN-AW6082 aluminium alloy full-scale components is rather overestimated if it is assessed only from standard small specimens of 3 mm in diameter. Experimental tests carried out on larger specimens, and a proper extrapolation, are required to assure safe structural design.

Prediction of Mechanical Properties of Wrought Aluminium Alloys Using Feature Engineering Assisted Machine Learning Approach

Data-mining based machine learning (ML) method is emerging as a strategy to predict aluminium (Al) alloy properties with the promise of less intensive experimental work. However, ML models for wrought Al alloys are limited due to the difficulty in feature digitalization of the variety of manufacturing processes. Hence, most previous studies were constrained to specific alloy designations, which impeded the applicability of those ML models to broader wrought Al alloys. In the present work, we propose a novel feature engineering, called procedure-oriented decomposition (POD), assisting prediction framework to address the complexity introduced by manufacturing processes for wrought Al alloys. In this model, both chemical compositions and manufacturing processes are integrated as features. Correlation mapping of these features to the wrought Al alloys mechanical properties is established using the support vector regressor (SVR) model. The prediction framework demonstrates a high prediction accuracy and potential to design new alloys.

Aluminium Alloys as Advanced Materials: A short communication

Aluminum alloys have been one of the primary structural materials for several years due to their common mechanical behavior, design, production processes, and inspection techniques. However, it has gained much fame and occurrence in automobiles manufacturers due to its low mass and resistance to deterioration. Wrought aluminium alloys, which happen to be part of its classes from the study, have shown to be an advanced material due to its excellent extrudability, good corrosion resistance, and high strength. In the improvement of 7000 series, Al-Zn alloys have higher strength relative to other classes of aluminium alloy. Minimizing the mass to volume ratio of materials is considered one way of reducing the weight of engineering materials, especially aircraft. This paper presents a brief study on aluminum alloys and their application as advanced material for production in vehicles and ship industry. This study showed that significant improvements in aluminum aerospace alloys are due to obtain quality equilibrium of properties.

Examining the Effect of the Aging State on Strength and Plasticity of Wrought Aluminum Alloys

A general rule of strength and plasticity is proposed for three typical wrought Al alloys (2xxx, 6xxx, and 7xxx) subjected to different aging times. Investigations of the work-hardening processes and dislocation configurations in tensile and compressive testing reveal that this general rule arises because there is a common mechanism for these three kinds of wrought alloys whereby the tendency for cross-slip increases monotonously with aging time. By analyzing the work-hardening exponent and the stacking fault energy, it is demonstrated that the change in the dislocation slip mode is attributed mainly to the formation of second phases rather than to the matrix composition. Accordingly, a new work-hardening model is proposed for wrought Al alloys containing second phases and this explains the interaction between dislocations and second phases and other relevant experimental phenomena. This study is therefore beneficial for quantitatively investigating and optimizing the strength and plasticity of wrought aluminum alloys.

Roll Casting of Al-Mg-Si Alloy

The aluminum alloy Al–5%Mg–2%Si, the chemical content of which is close to that of the Magsimal-59 aluminum alloy commonly for die casting, was successfully cast into strips using a vertical high-speed twin-roll caster at a speed of 30 m/min. This means that Al–5%Mg–2%Si is suitable for the high-speed twin roll-casting. The as-cast Al–5%Mg–2%Si strip was then successfully cold-rolled to a thickness of 0.7 mm. Tension and cup tests were conducted on the cold-rolled annealed strips. The tensile stress was 205 MPa and the elongation was 20% for a thickness of 1 mm. The limiting drawing ratio was 2.0 at a 0.7 mm thickness. The present results demonstrates that Al–5%Mg–2%Si can be used for die casting and sheet forming. This means that use of this alloy for both sheet forming and die casting could eliminate the need for the separation of wrought aluminum alloys from cast aluminum prior to processing at recycling plants.

A Critical Conception of Hot-Tearing Susceptibility: How Controlled Diffusion Solidification Enables Shape-Casting with Wrought Aluminum Alloys

Instrumented Constrained Rod Casting (CRC) method and the Controlled Diffusion Solidification (CDS) process were used to study the high susceptibility of the aluminum alloy AA 7068 to hot-tearing. A precise analysis of the measured hot-tearing curves is provided considering the casting design and different feeding mechanisms. Scanning Electron Microscopy was used to study the hot-tear surfaces. It was found that the solidification of the eutectic liquid at the film stage and the phenomenon of solid-feeding strongly affects the hot-tear formation. The early formation of an absorbed eutectic layer on the primary phase due to low rate of back-diffusion is proposed to explain the loss of ductility at the film stage. The layer can serve as an efficient substrate for the eutectic nucleation and growth, hence its formation can advance the eutectic solidification. The isolation of liquid eutectic by its partial solidification results in development of solid-feeding stresses breaking the solid eutectic and provide the required tearing initiators. By increasing the back-diffusion rate, the CDS process avoids formation of the adsorbed solid layer which postpones eutectic solidification and thereby mitigating the hot-tearing susceptibility.

Evaluation of mechanical properties of cold roll bonded mild steel and aluminum

Abstract The need for joints between dissimilar materials often is used in automobile industries, electrical components and so on. This need of dissimilar metal joining is fulfilled by various solid state welding processes. Cold roll bonding (CRB), as a solid phase method of bonding same or different metals by rolling at room temperature, has been widely used in manufacturing large layered composite sheets and foils. It has various advantages such as good surface quality, low cost, fast process, easy to automate and no additional equipments except rolling mills are required. In this research work, CRB of Mild Steel (MS) and wrought Aluminum (w-Al) strips was studied. Bonded sheets of w-Al and MS are used for cylinder liners and bearings. CRB of w-Al and MS sheets was carried out on two high rolling mill. These bonded sheets were then diffusion bonded with permutations of temperature and time to find out the probable phases at the interface and the intermetallic compound layer thickness. Effect of the processing parameters on bonding strength, microstructure, hardness and grain-size and the formed intermetallic phases were also studied. The tensile shear strength of the CRB strip increased to a maximum of 48.95 MPa with increase in reduction to 27%. As temperature and time of diffusion bonding increases, the thickness of intermetallic compound layer increases. During heat treatments, there was considerable Al diffusion into the MS or in other words Fe side near the interface where Al-rich intermetallics formed. XRD analysis confirmed this with the presence of high intensity peaks of aluminium rich intermetallic compounds e.g Fe2Al5, FeAl3 and FeAl2 at the interface. The activation energy for diffusion of Al to Fe was found to be 160 KJ/mol.

Effect of Aging State on Fatigue Property of Wrought Aluminum Alloys

The high-cycle fatigue (HCF) behaviors of wrought Al alloys are vitally important for their industrial application. To optimize the fatigue property of the wrought Al alloy, the effects of aging conditions on the fatigue properties of 7N01, 7075 and 2024 Al alloys were studied. The results show that the overaged samples have the lowest tensile strength among the three aging states, but their fatigue strength is the highest. Further investigations on the dislocation morphologies indicates that the dislocations are easy to accumulate and annihilate at the second phase boundaries for the overaged state, which reduces the fatigue damage degree at the grain boundaries. Besides, the discontinuous distribution of the grain boundary precipitates and the increased width of the precipitate-free zone also contributed to the improved fatigue property of the overaged state. Those results should be significantly important for the optimization of their fatigue properties and the industrial application of wrought Al alloys.