Abstract Aluminum Alloys Research Articles

Friction Stir Welding of Aluminium Alloy Sheets

Aluminium alloy 7050 in a T7451 temper was friction-stir welded (FSW) to investigate the effects of different process parameters on the microstructure and mechanical properties. Butt joints were obtained in 10mm thick-sheets, keeping a constant rotational speed of 550 rpm. Weld power and torque were recorded for each weld in order to obtain the heat input of the process, since the final properties of the welds are strongly related to this variable. The joints were characterized by optical microscopy and microhardness indentation through the stir zone (SZ), thermo-mechanically affected zone (TMAZ), and heat affected zone (HAZ) at different cross section heights. The processing of FSW, the microstructure in FSW alloys and the factors influencing weld quality are introduced.

Investigation of tension force in stretch forming of doubly curved aluminum alloy (Al5083) sheet

Aluminum alloys, which are suitable for lightweight applications, are being applied widely in diverse industries, especially to the external bodies of automobiles, ships, and aircraft. The external bodies of these vehicles have a three-dimensional geometric shape with various double curvatures. However, aluminum sheets with double curvatures are difficult to form because of their elastic recovery characteristic, known as the springback effect. As a consequence, the stretch-forming process is widely used to reduce the springback phenomenon and to obtain the desired quality product. In the stretch-forming process for aluminum sheets, the stretching conditions should be precisely designed to achieve high accuracy and minimum product defects. In particular, thickness reduction and elastic recovery of the formed plate must be considered during the determination of the stretching force. In this study, the deformation of an aluminum plate according to the magnitude of a tension force was analyzed and an optimal tension force proposed, while considering changes in the mechanical properties of the formed material. FE simulations and experiments show that the proposed tension force can be used to manufacture doubly curved aluminum surfaces with minimum thickness reduction and high accuracy

Mechanical Properties and Microstructures of 5052 Al Alloy Processed by Asymmetric Cryorolling

Aluminum alloy sheets were asymmetrically rolled at room and cryogenic temperatures by imposing different velocity ratios of 1~1.5 between the upper and bottom rolls. After rolling, the stress-strain curves, microhardness as well as the microstructures of the rolled samples were characterized and analyzed. The experimental results showed that the asymmetric cryorolling could improve the grain refinement and offered (~12%) higher room temperature tensile strength than that processed by symmetrical rolling with velocity ration of 1.0 (~280 MPa). However, at cryogenic temperature, the strength of asymmetrically cryorolling sheet (with velocity ratio of 1.5) was 5.1%, which is less than that processed by symmetrical rolling.

Localized Corrosion Inhibition of 7075-T6 by Calcium Sulfate

Aluminum alloy 7075-T6 is used in aerospace applications as a result of its high strength-to-weight ratio, but this material is susceptible to localized corrosion in condensing atmospheric exposure conditions and is usually protected with an anti-corrosion coating system. CaSO4 is sometimes found as an extender component in corrosion inhibition primer pigment systems, such as commercial Pr-rich primer, which has been qualified for military use. The role CaSO4 might play in corrosion protection afforded by the coating system has not been addressed thoroughly in the scientific literature. The goal of this study was to isolate and characterize any inhibiting effect of CaSO4 on AA7075-T6 to understand how it might play a role in non-chromate primer coatings. Samples of AA7075-T6 were exposed to chloride solutions with varying pH via static immersion exposure with and without CaSO4 as an inhibitor for times ranging up to 30 d. The solution pH was varied from 3 to 10 and the chloride concentration was fixed at ...

Effect of nanoparticle Al2O3 addition on microstructure and mechanical properties of 7075 alloy

Aluminium alloy matrix composites reinforced with 0.5, 1.0, 1.5 and 2.5 wt-% nanoparticle Al2O3 were fabricated by low frequency mechanical vibration combined with multi-frequency ultrasonic treatment. A microstructural study was carried out by optical, scanning electron and transmission electron microscopy and X-ray diffraction. The effect of reinforcements on the microstructural feature of the composites was investigated. Tensile and compression tests were carried out in order to identify the mechanical properties. The results of the microstructural study revealed a uniform distribution of nanoparticles in the matrix and dendrite refinement of the matrix alloy. It was also found that adding reinforcement content beyond 1.5 wt-% led to an increase in dendrite size values. Compared to the 7075 alloy, the yield strength, ultimate tensile strength and 0.2 compressive yield strength of 1.5 wt-% nano-Al2O3/7075 composite were increased by 74%, 57% and 100% respectively. The improved mechanical properties were due to particle pushing dendrite refinement and particle strengthening.

Environmental Degradation of Marine Aluminum Alloys - Past, Present and Future

Aluminum alloy usage in maritime environments has fluctuated over the past 125 years with localized corrosion or environment sensitive cracking during service repeatedly preventing their full commercial exploitation, despite a series of innovations. Following a historical overview, discussion will focus on aluminum-magnesium alloys, highlighting current corrosion-related issues (e.g., intergranular corrosion, environment sensitive cracking) and potential opportunities to eliminate these problems in future commercial alloys.

Effects of Micro and Nano-Size Al<sub>2</sub>O<sub>3</sub> Particle Reinforcement on Mechanical Behaviour of Extruded Aluminum Alloy Matrix Composite

Aluminum alloy (AA2014) matrix composites reinforced by different weight percentage of aluminum oxide (Al2O3) in micro and nano sizes were fabricated through powder metallurgy route followed by hot extrusion process. Seven different aluminium composites with varying percentages of nano and micron sized alumina particles varying from 1% to 10% were evaluated in addition to monolithic alloy. The microstructure of nano-composite and monolithic alloys were examined by optical microscope and scanning electron microscope (SEM) equipped with an energy dispersive X-ray analysis (EDAX). In addition, the effects of weight fraction of the reinforcement matrix on mechanical properties were evaluated. The results have indicated that, a significant improvement in hardness of the nano composite was found in case of nano-composite with 8% of micro Al2O3 and 2% of nano Al2O3 particles by the addition of reinforcement.

Influence of Particle Feeding Methods on Processing the AA6061/SiC Metal Matrix Nanocomposites

Aluminum alloy 6061 reinforced with 1.0 weight percentage of Silicon Carbide (SiC) nanoparticles were fabricated using the novel ultrasonic cavitation assisted stir casting approach. Three types of nanoparticle feeding mechanisms were attempted for fabricating the metal matrix nanocomposites. The fabricated nanocomposites were subjected to tension test, hardness test and scanning electron microscopic analysis. From the tested results, it was found that feeding the particles using Al foils followed by ultrasonic cavitation proved as a suitable method for obtaining the better mechanical properties of the fabricated nanocomposites. Scanning electron microscopy analysis confirmed the uniform dispersion SiC in Al matrix by capsule feeding method. Energy dispersive spectroscopy validates the incorporation of SiC in Al matrix.

The influence of grain size and grain orientation on sensitisation in AA5083

Aluminum alloy AA5083 specimens (with a nominal composition of Al-4.4Mg-0.5Mn) from the same original plate were prepared with a variation in grain size imparted by cold rolling, cryo-rolling, equal channel angular pressing and high-pressure torsion. Electron backscatter diffraction was used to determine the grain size and misorientation. The effect of grain size on the degree of sensitization for AA5083 was studied via the ASTM G67 nitric acid mass lost test, upon specimens artificially sensitized at 150°C for 7 d. It was revealed that the intergranular corrosion caused by sensitization in AA5083 was significantly influenced by the grain size and processing methods used for grain refinement.

Analysis of Mechanical Properties and Morphological Study of Coated Ceramics Using Multiwall Carbon Nanotubes with Aluminium Alloy

Aluminium alloy(A 356) has improved properties such as tension and elongation butit is decreased in hardness property compared to ceramics and therefore silicon carbideparticle (SiCp) is added with aluminium alloy to increase its hardness. Silicon Carbideparticle is abrasive and hence having poor interfacial bonding between ceramics andaluminium, so that the surface of the ceramics is coated with Multi Wall Carbon Nano Tubes(MWCNT). In this paper 10% of SiCp is taken for the experiment and coated with 1.5%, 2%,2.5% of MWCNT and this coated SiCp mixed with molten A 356 using stir casting method.The prepared castings were mechanically tested using Universal Testing Machine (UTM),Vickers hardness Testing Machine, Impact Testing Machine and Optical Microscope andtheir mechanical properties and morphological characteristics were studied

Investigations on the Effect of Tool Geometries on Friction Stir Welded 5052 H32 Aluminium Alloy

Aluminium alloys are widely used in automotive, aerospace and ship industries as high strength-to-weight ratio materials. With the increasing demand for lightweight components, their application is becoming more extensive. To study the effect of Tool geometries on Metallurgical & mechanical properties of Aluminum alloy 5052 H32 using friction stir welding process. To briefly discuss about the conditions & conclude the suitable condition for Aluminium alloy 5052 H32. To plot and conclude the hardness values for various conditions. The tool material Mild Steel IS 2062 FE410 cone type and thread type has been selected for this research for various speeds to find suitable condition. The micro structure and macro structure have checking the structural formation of welded area in details to know it the strength of the joining. The present friction stir welding research is implementing the new tools for the current issues; here we try to implement new material for already available tools.

Effect of Process Parameters on Mechanical Characterization of Dissimilar Friction Stir Welded Aluminium Alloys

Aluminum alloys exhibit poor weldability by conventional fusion welding process. The heat treatable aluminum alloy AA2014 is extensively used in the aircraft industry because it has good ductility and high strength to weight ratio. In this paper the effects of welding parameters and tool profile on the mechanical properties of friction stir welded butt joints of dissimilar aluminum alloy sheets AA6082 and AA2014. The process parameters such as rotational speed, transverse speed and axial forces were considered. The effect of parameters on weld quality was analyzed. Hardness and tensile tests are carried out at room temperature to examine the mechanical properties of the welded joints. The joints produced with straight square tool pin profile have higher ultimate tensile strength, whereas the straight cylindrical tool pin profile results in lower tensile strength.

Long-Term Atmospheric Corrosion of Aluminum Alloy 2024-T4 in a Coastal Environment

Aluminum alloy 2024-T4 specimens were exposed to atmosphere for 7, 12, and 20 years, respectively, to study long-term corrosion in a coastal environment. One-directional corrosion region and cross-directional corrosion region were defined according to corrosion characters. The statistical regularities, surface appearance, corrosion products, and cross-sectional morphology of both regions were investigated. It was found that the minimum remaining thicknesses of each region can be described by a normal distribution and linearly decrease as the exposure time is increased from 7 to 20 years. The corrosion pits, chlorine ions, and interlinked inner pits are promoting exfoliation, and the alloy’s corrosion susceptibility along the long transverse direction is strongly location dependent due to the restrictions imposed by the side material.

Microstructure and properties of friction stir welded aluminium alloys

Aluminium alloy 7136 belongs to the Al–Zn–Mg–Cu group of aluminium alloys strengthened by precipitation. These alloys offer very good properties, i.e. high strength combined with good corrosion resistance, which makes them suitable for aerospace applications. The limited range of applications of these alloys is due to problems associated with their welding. The Al–Zn–Mg–Cu alloys are classified as non-weldable. The aim of this study was to determine the quality and properties of friction stir welded (FSW) joints of alloy 7136-T76. This article presents the results of a detailed study into the microstructure and mechanical properties of FSW welds. The paper demonstrates that the FSW method is suitable for joining Al–Zn–Mg–Cu alloys. The FSW joints are of good quality and high mechanical properties. Tests of joints created at various tool rotation speeds have shown that joints of suitable quality, in terms of microstructure and properties, can be obtained for a relatively wide range of process parameters. The tool rotation speeds applied during the welding process did not have a significant influence on the quality of the welds.

Overview of aluminum alloy mechanical properties during and after fires

AbstractAluminum alloys are increasingly being used in a broad spectrum of load-bearing applications such as lightweight structures, light rail, bridge decks, marine crafts, and off-shore platforms. A major concern in the design of land-based and marine aluminum structures is fire safety, at least in part due to mechanical property reduction at temperatures significantly lower than that for steel. A substantial concern also exists regarding the integrity and stability of an aluminum structure following a fire; however, little research has been reported on this topic. This paper provides a broad overview of the mechanical behavior of aluminum alloys both during and following fire. The two aluminum alloys discussed in this work, 5083-H116 and 6061-T651, were selected due to their prevalence as lightweight structural alloys and their differing strengthening mechanisms (5083 – strain hardened, 6061 – precipitation hardened). The high temperature quasi-static mechanical and creep behavior are discussed. A creep model is presented to predict the secondary and tertiary creep strains followed by creep rupture. The residual mechanical behavior following fire (with and without applied stress) is elucidated in terms of the governing kinetically-dependent microstructural mechanisms. A review is provided on modeling techniques for residual mechanical behavior following fire including empirical relations, physically-based constitutive models, and finite element implementations. The principal objective is to provide a comprehensive description of select aluminum alloys, 5083-H116 and 6061-T651, to aid design and analysis of aluminum structures during and after fire.

Using Neural Networks to Predict the Hardness of Aluminum Alloys

Aluminum alloys have gained significant industrial importance being involved in many of the light and heavy industries and especially in aerospace engineering. The mechanical properties of aluminum alloys are defined by a number of principal microstructural features. Conventional mathematical models of these properties are sometimes very complex to be analytically calculated. In this paper, a neural network model is used to predict the correlations between the hardness of aluminum alloys in relation to certain alloying elements. A backpropagation neural network is trained using a thorough dataset. The impact of certain elements is documented and an optimum structure is proposed

Development of a predictive model for determining mechanical properties of AA 6061 using regression analysis

Aluminum alloys (AA) such as AA 6061 are difficult to weld, and their application to high-strength demands tends to be limited because of their inherently low-strength threshold levels when compared to other alloys. To effectively use this alloy to its full potential, its tensile strength, is investigated. In actual manufacturing settings, it has proven beneficial to attempt a prediction of the tensile properties of potential weld joints. To achieve this, a model was developed using the multiple linear regression analysis to predict these tensile properties such as the ultimate tensile strength, the yield strength (YS), and percentage elongation (% Elong). It was found from the scattered diagrams that the measured and predicted values were almost a perfect fit with a coefficient of determination of between 0.99 and 1.0. The analysis of variance further validated the adequacy of the model. The analysis showed that the claims observed in the study match with those of other investigators. The predictive model obtained is expected to help the welding community to pre-determine the tensile properties of AA 6061 weldment using selected values for each of the process parameters applied in this study.

The Influence of Addition of the Rare Earth Elements on the Structure and Hardness of AlZn12Mg3.5Cu2.5 Alloy

Aluminium alloys are characterized by a number of advantageous properties , which include: low density ,high relative strength , high electrical and thermal conductivity , ease of machining and good dumping features. Particular interesting are high-strength aluminum alloys of zinc, magnesium and copper. These alloys are used mainly in aircraft, building &structure, electrical, electrical power and automotive industry. A significant problem associated with the use of high-strength aluminium-zinc alloys is their insufficient resistance to corrosion. Improvement of corrosion resistance can be obtained by application of alloy micro-additives. The article shows results of examinations related to influence of rare earth additive on the structure and hardness of AlZn12Mg3.5Cu2.5 alloy. The scope of examination included: structure testing using scanning microscope, X – ray microanalysis, hardness test. Examinations have shown higher hardness of samples with rare earth additives. Was found , that rare earth addition influences on more fine –grained structure of the AlZn12Mg3.5Cu2.5 alloy.

Study on the Development of Pretreatment Processes of Electroless Nickel Plating on Al Alloy Surface

Aluminium alloy is difficult to be plated because of high chemical activity. In order to obtain electroless nickel plating with excellent adhesion to the substrate, the key lines is the pretreatment process. This study introduces several significant pretreatment processes of aluminium alloy surface at home and abroad for these years, and describes the principles of pretreatment processes. Finally, the development direction of pretreatment processes for aluminium alloy is forecasted.

Influence of Pulsed Current on the Tensile Behaviors of the 5XXX Aluminum Alloy

Aluminum (Al) alloys have great potential as ideal structural materials because of their high specific strength and stiffness. However, Al alloys exhibit poor ductility at room temperature. Enhancing the formability is a very important and challenging problem to both automotive and manufacturing engineers. In this study, the electro-plastic effects, which is first discovered in 1960s, of 5xxx Al alloy sheets are investigated to improve the formability. To begin with, a test system is built up to carry out the tensile test with heavy electric current flowing through the specimen. The evolutions of the flow stress and the electric resistivity are obtained using this test system. The significant decrease in the flow stress caused by the heavy flowing through current is observed.