Dissimilar Aluminium Alloy Joints Research Articles

Process and joint quality of ultrasonic vibration enhanced friction stir lap welding

ABSTRACTIn order to improve the process effectiveness and joint quality, ultrasonic vibrations were integrated with friction stir lap welding. Effect of ultrasonic exertion on the process and joint quality of AA 6061-T6 were investigated. Upon ultrasonic exertion, joints owned larger effective lap width, shorter hooks and improved strength. Weld fracture mode changed from a ductile–brittle mixed mode to a more ductile mode while the fracture path shifted from lap interface to beyond the stir zone. Material flow and interface defects were characterised using lap welded dissimilar aluminium alloy joints. Ultrasonic vibration improved the material flow and reduced the interfacial defects. Variations in failure load of joints were found in accordance with the variations in material flow and interfacial defects.

Strain hardening behavior and mechanisms of friction stir welded dissimilar joints of aluminum alloys

Al-Cu alloy was friction stir welded (FSWed) with Al-Zn and Al-Mg alloys, respectively. Tensile properties, strain hardening behavior and fracture mechanisms of the FSWed dissimilar joints were evaluated. Results reveal that the strain-hardening rate of Al-Cu/Al-Zn dissimilar joint is higher than that of base metals due to the presence of finer recrystallized grains in the stir zone, while the strain-hardening rate of Al-Cu/Al-Mg dissimilar joint lies in-between those of base metals. The hardening level of Al-Cu/Al-Zn joint after tensile deformation, defined as HVf/HVw (a ratio of microhardness of fractured joints to that of as-welded joints), exhibits an ‘M’ shape across the welded joint.

Effect of welding parameters on mechanical properties of dissimilar Friction Stir Processed AA 8011 and AA 5083-H321 aluminium alloys

The weight reduction and fuel economy are gaining importance in marine, defence and transportation industries to get the quality of the welded joints. The problems in fusion welding of aluminium alloys such as solidification shrinkage, hot cracking and residual stresses which degrade the strength of the welded joints. The innovative green joining technology, friction stir welding (FSW) process was implemented in addition to nanoparticles such as Al2O3 and SiC in similar and dissimilar aluminium alloys. In this work, the study was done on the effects of Friction Stir Processing (FSP) parameters on microhardness and tensile properties of AA5083-H321 and AA8011-H24 dissimilar aluminium alloy joints. The tensile test was conducted to evaluate the tensile properties of the welded joints. The Vickers microhardness test was carried out to examine the quality of the welded joints. It was observed that the similar AA8011 aluminium alloy combination with nanoparticle Al2O3 has maximum tensile properties and microhardness compared to other combination of joints.

Microstructural features of friction stir welded dissimilar Aluminium alloys AA2219-AA7475

High strength, good corrosion resistance, light weight make aluminium alloys a material of choice in many industrial sectors like aerospace, marine etc. Problems associated with welding of these alloys by fusion welding processes restricted their use in various industries. Friction stir welding (FSW), a clean solid-state joining process, easily overcomes various difficulties encountered during conventional fusion welding processes. In the present work, the effect of rotational speed (710 rpm, 900 rpm and 1120 rpm) on micro-hardness distribution and microstructure of FSWed dissimilar aluminium alloy joints were analyzed. Plates of AA7475-T761 and AA2219-O having thickness of 2.5 mm were welded by fixing AA7475 on retreating side (RS) and AA2219 on advancing side (AS). Welded joints were characterized by Vickers micro-hardness testing, scanning electron microscopy (SEM) and optical microscopy (OM). Results revealed that rotational speed significantly affects the micro-hardness due to increase in grain size, coarsening and dissolution of strengthening precipitates and re-precipitation. Higher micro-hardness values were observed in stir zone due to grain refinement and re-precipitation. Minimum micro-hardness value was observed at the TMAZ/HAZ of advancing side due to thermal softening.

Digital Image Correlation Analysis Of The Effects Of The Overlap Length, Adhesive Thickness And Adherends Yield Strength Over Similar And Dissimilar Joints Of High Strength Steel And Aluminum Alloys

This work encompasses the study of the mechanical behavior of single lap joints (SLJ) with similar and dissimilar materials, joined by epoxy adhesives. The objective was to analyze the effect of the variables overlap length (OL), adhesive thickness (AT) and adherends yield strength (YS) over the SLJ failure load (FL). The stress state of the joints was analyzed through an optical technique. Tensile tests were performed with samples containing three levels of the factors OL, AT and YS. This last variable analysis was performed using aluminum (AA5083 H111) and high strength steel (DP600) adherends, combined in three different levels – similar AA, similar HSS and dissimilar. The digital image correlation (DIC) technique was used in order to analyze and quantify the incidence of deformation on the adherends and adhesive during the tensile tests, in order to verify how the tensile load was distributed through the SLJ of this work. All the variables had significance over the SLJ. The OL increased the SLJ FL, but the effect reduced as the length is increased. The adherends YS also increased the SLJ FL, but not as much as the OL. Plastic deformation of the adherends leaded to the onset of high peeling stress, which reduced considerably the joints FL. The AT had a negative effect over the SLJ FL. This relationship varied when the adherends faced remarkable plastic strain.

Optimizing the tensile strength of friction stir welded dissimilar aluminium alloy joints using particle swarm optimization

Aluminium alloys AA2024 and AA7075 plates were friction stir welded by varying the tool rotation speed and welding speed and corresponding tensile strength of the joints were measured. A mathematical model was developed using response surface methodology to predict the tensile strength of the joints. The FSW process parameters were optimized for maximizing the tensile strength using particle swarm optimization algorithm. The optimum FSW process parameters for dissimilar welding of AA2024 and AA7075 plates were deduced as welding speed of 15 mm/min and tool rotation speed of 1087 rpm.

Investigations on remote laser beam welding of dissimilar joints of aluminum alloys and steel with varying sheet thicknesses for car body construction

For lightweight construction, different steel and aluminum materials with various thicknesses can be welded together, depending on the dimensions and the individual functions of the workpiece. Specifically for frame and body construction, remote laser beam welding has been established as a suitable and efficient joining method for similar material seams for several years. In contrast to joining similar materials, thermal joining of steel and aluminum alloys includes different technological challenges due to the formation of hard and brittle intermetallic phases, which decreases the strength and the formability of the dissimilar joints. In the context of these requirements, the presented results show, besides the influence of different steel materials, particularly the influence of different sheet thicknesses and thickness ratios on the appropriate process parameters for remote laser beam welded lap joints of steel and aluminum alloys, respectively. Different thickness ratios, process parameters, and material properties affect the geometrical formation of the weld seam regarding penetration depth tE and weld width b, which mainly influences the composition of the molten bath and accordingly the transmittable forces. Within the scope of the presented investigations, dissimilar joints of the steel materials such as HX220LAD+Z100, 22MnB5+AS150, and 1.4301 as well as the aluminum alloy such as AA6016-T4 are characterized. Among others, the influences of the energy per unit length, material grade, and sheet thickness ratio on the achievable strengths were analyzed. The characterization of the dissimilar joints includes tensile shear tests and metallographic analyses, depending on the energy per unit length.

Fracture Behavior of GMA Welded Joints of Dissimilar and Similar Aluminum Alloys of 6061-T6/5083-O

Aluminum alloys of grade 6xxx and 5xxx are used where strength and corrosion resistance both are important. This paper reports the GMA welding of dissimilar 6061 T6 and 5083 O aluminum alloys and comparison of mechanical properties and fracture behavior of dissimilar joints (6061 T6-5083 O) with similar joints of the two base materials (6061 T6-6061 T6 and 5083 O-5083 O). GMA welding is used mostly due to high deposition rate, deeper penetration and high welding speed. The fusion welding of dissimilar aluminum alloys faces many problems due to the different chemical compositions and thermal conductivities of aluminum alloys. The dissimilar joint exhibited an average tensile strength of 138 MPa and weld hardness of 74.2 VHN. The scanning electron micrograph of tensile fracture surface was obtained to investigate the mode of failure. The fractograph at top portion of the fractured surface of 6061 T6-6061 T6 joints exhibited smaller grain size and smaller spacing between grains. The fractograph at middle portion showed population of dimples, which is the indication of ductile type of fracture. The fractograph at bottom portion (root region) indicated relatively smaller cleavage facets in similar joint of 5083 O-5083 O.

Combination of nano-particle deposition system and friction stir spot welding for fabrication of carbon/aluminum metal matrix composite joints of dissimilar aluminum alloys

A nano-particle deposition system is combined with friction stir spot welding (FSSW) of dissimilar aluminum alloys to fabricate a carbon/aluminum metal matrix composite (MMC) joint. Carbon materials in the form of graphite powder are deposited on an aluminum sheet at room temperature. Lap joints of dissimilar aluminum alloys are fabricated via FSSW using the carbon-deposited aluminum sheet as the upper sheet of the joint. The Raman spectroscopy confirms that carbon/aluminum MMC is successfully fabricated in the joint. The strength and toughness of the joint are clearly enhanced by fabricating the MMC, as shown in the result of mechanical tests.

種々の先端的高速固相接合法により作製したアルミニウム合金同種・異種接合材の組織形成ならびに接合メカニズムの解明—軽金属奨学会平成27年度統合的先端研究の成果—

種々の先端的高速固相接合法により作製したアルミニウム合金同種・異種接合材の組織形成ならびに接合メカニズムの解明—軽金属奨学会平成27年度統合的先端研究の成果—

Effect of shoulder diameter to pin diameter ratio on microstructure and mechanical properties of dissimilar friction stir welded AA2024-T6 and AA7075-T6 aluminum alloy joints

Friction stir welding (FSW) is a solid-state joining process that uses the frictional heat generated by the rotating tool to soften the metals to form the joint. It is an effective technique for joining dissimilar aluminum alloys and finds its application in various fields such as aerospace and automotive industries. The various FSW parameters play a vital role in determining the quality of the welded joint. The parameters included in the study are tool rotational speed, welding speed, axial load, and shoulder diameter to pin diameter ratio. This paper mainly focuses on studying the effect of shoulder diameter to pin diameter ratio (D/d ratio) on the microstructure and mechanical properties of the dissimilar AA2024-T6 and AA7075-T6 aluminum alloy joints. The weld quality characteristics like macrostructure, microstructure, microhardness, and tensile properties of the joints are analyzed and presented for five different D/d ratios. The fractography images using scanning electron microscope (SEM) were presented for the joints with high and low strength. It is observed from the result that the joint fabricated using D/d ratio of 3 exhibits the better mechanical properties when compared to other joints.

Investigations on Laser Beam Welding of Different Dissimilar Joints of Steel and Aluminum Alloys for Automotive Lightweight Construction

Due to the enormous potential of weight saving, and the consequential reduction of pollutant emissions, the use of hybrid components made of steel and aluminum alloys is increasing steadily, especially concerning automotive lightweight construction. However, thermal joining of steel and aluminum is still being researched, due to a limited solubility of the binary system of iron and aluminum causing the formation of hard and brittle intermetallic phases, which decrease the strength and the formability of the dissimilar seam.The presented results show the investigation of laser beam welding for joining different dissimilar hybrid components of the steel materials HX220LAD+Z100, 22MnB5+AS150 and 1.4301, as well as the aluminum alloy AA6016-T4 as a lap joint. Among other things, the influences of the energy per unit length, the material grade, the sheet thickness t, the weld type (lap weld, fillet weld) and the arrangement of the base materials in a lap joint (aluminum-sided irradiation, steel-sided irradiation) on the achievable strengths are analyzed. The characterization of the dissimilar joints includes tensile shear tests and metallographic analyses, depending on the energy per unit length.

Tensile strength prediction of dissimilar friction stir-welded AA6351–AA5083 using artificial neural network technique

Friction stir welding provides an alternative method of joining aluminum in a reliable way. Anticipation of the joint efficiency is then a necessary step to optimize the process of the welding operation. In the light of this, artificial neural network (ANN) technique may then be applied as a reliable method for simulating and predicting the durability of the joints for different process parameters. In the present work, an ANN model is presented that predicts the ultimate tensile strength of friction stir-welded dissimilar aluminum alloy joints. Four parameters were considered including tool pin profile (straight square, tapered square, straight hexagon, straight octagon and tapered octagon), rotational speed, welding speed and axial force. Experimental tests were conducted according to a four-parameter five level central composite design. A feed-forward back propagation ANN with a single hidden layer comprising 20 neurons was employed to simulate the ultimate tensile strength (UTS) of the joints. The neural network was trained using the data obtained from the experimental work. A comparison between the experimental and simulated data showed that the ANN model reliably predicted the UTS of dissimilar aluminum alloy friction stir-welded joints. The models developed were capable of predicting values with less than 5 % error. Furthermore, the effect of different process parameters on the tensile behavior of dissimilar joints was also investigated and reported upon.

Mathematical modeling and optimization of friction stir welding process parameters in AA5083 and AA7075 aluminum alloy joints

In this study, dissimilar joints of AA5083-H116 and AA7075-T6 aluminum alloys were successfully made by friction stir welding technique. The microstructure and mechanical behavior of the welded joints were investigated at different rotational and traverse speeds. A mathematical modeling was developed to demonstrate a relationship between the friction stir welding parameters and the ultimate tensile strength of the dissimilar joints. Then, the mathematical modeling was optimized by genetic algorithm in order to find the optimum condition in which the maximum tensile strength of welded joints can be achieved. Eventually, genetic algorithm results confirmed that the maximum tensile strength of welded joints is achievable in rotational and traverse speeds of 500 r/min and 50 mm/min, respectively. The maximum error between experimental data and predicted model was less than 1%.

Effect of Welding Parameters on Mechanical and Microstructural Properties of Dissimilar Aluminum Alloy Joints Produced by Friction Stir Welding

The effect of processing parameters on the mechanical and microstructural properties of dissimilar AA6061 t6–AA5083 0 joints produced by friction stir welding was studied. Different samples were produced by varying the advancing speeds of the tool as 20 and 40 mm/min and by varying the alloy positioned on the advancing side of the tool. In the various trials the rotating speed is varied from 600 to 900 RPM. All the welds were produced perpendicular to the rolling direction for both the alloys. Micro hardness (HV) and tensile tests performed at room temperature were used to evaluate the mechanical properties of the joints. Various tests were performed on the joints previously subjected to ageing. In order to analyze the micro structural evolution of the material, the welds’ zones were observed optically.

Optimization of process parameters to maximize ultimate tensile strength of friction stir welded dissimilar aluminum alloys using response surface methodology

Aluminium alloys generally present low weldability by traditional fusion welding process. Development of the friction stir welding (FSW) has provided an alternative improved way of producing aluminium joints in a faster and reliable manner. The quality of a weld joint is stalwartly influenced by process parameter used during welding. An approach to develop a mathematical model was studied for predicting and optimizing the process parameters of dissimilar aluminum alloy (AA6351 T6-AA5083 H111) joints by incorporating the FSW process parameters such as tool pin profile, tool rotational speed welding speed and axial force. The effects of the FSW process parameters on the ultimate tensile strength (UTS) of friction welded dissimilar joints were discussed. Optimization was carried out to maximize the UTS using response surface methodology (RSM) and the identified optimum FSW welding parameters were reported.

On the critical technological issues of friction stir welding lap joints of dissimilar aluminum alloys

In this article, friction stir welded lap joints of innovative dissimilar aluminum alloys have been produced and tested to investigate the feasibility of using this joining technique in this configuration. The introduction of both this new welding technique alloys, such as AA 2198, could allow making lighter and stronger structures. Some experiments, carried out previously, have shown that the fixturing device, the tool geometry, and the tilt angle play a significant role in the joint soundness. A wide experimental characterization has been carried out on friction stir welded lap joints of AA 7075 T6 extrudes to AA 2198 T351 rolled plates. The results attained are allowed to put in evidence some critical issues on the investigated configuration and can be considered as a further acquired knowledge in the understanding and the design of friction stir processes. Copyright © 2013 John Wiley & Sons, Ltd.

Material properties of friction stir spot welded joints of dissimilar aluminum alloys

Mechanical properties and material mixing patterns of friction stir spot welded (FSSW) joints of dissimilar aluminum alloys were investigated. Two aluminum alloys typically used in automotive applications, 5052-H32 and 6061-T6, were selected. During the experiment, the process parameters including the z-axis force and torque histories were measured as a function of the tool displacement. The mechanical properties were investigated by microhardness measurements of the joint, and the material mixing in the stir zone was investigated by EPMA. The experimental results illustrate different process parameter histories, material mixing in the stir zone and material properties including microhardness distributions for FSSW joints of dissimilar aluminum alloys, likely due to different mechanical behaviors of the selected aluminum alloys in the FSSW process temperature range.

Heterogeneous Friction Stir Welding: Improved Properties in Dissimilar Aluminum Alloy Joints through Insertion of Copper Coupled with External Heating

Friction stir welding (FSW) experiments are conducted on AA7075 and AA6061 alloys under optimized conditions with copper as intermediate inclusion on the faying sides of the base material assisted by external heating from the root side during the process. The concept behind the experimentation is to minimize the temperature gradient that exists between the top and bottom sides of the plates. The work attempts to relocate the crack initiation point from the root of the retreating side, as in conventional friction stir weldments due to the variation in material flow along the weld cross-section. Analysis of the formed intermetallic compound (IMC) indicates that the interaction of AA7075, AA6061 alloys with copper, in coating form, enhances the bond strength by formation of Al2Cu and Al4Cu9 IMCs. High thermal conductivity of the copper in coating form along with external heating from the root side has minimized the temperature gradient and maintains homogenous material flow in the weld zone and increased bond strength.

DEVELOPMENT OF MATHEMATICAL MODEL TO PREDICT THE ULTIMATE TENSILE STRENGTH OF FRICTION STIR WELDED DISSIMILAR ALUMINUM ALLOY

Development of the Friction Stir Welding (FSW) has provided an alternative improved way of producing aluminium joints, in a faster and reliable manner. This paper presents a systematic approach to develop a mathematical model for predicting the Ultimate Tensile Strength (UTS) of dissimilar aluminum alloy (AA6351 T6 - AA5083 H111) joints by incorporating the Friction Stir Welding (FSW) process parameter such as tool pin profile, tool rotational speed, welding speed, and axial force. The experiment was conducted based on four factors five level central composite rotatable deign with full replication technique. The Response Surface Method (RSM) was employed to develop the model. The developed model was validated using the statistical tool analysis of variance (ANOVA). Conformity tests were carried out to check the accuracy of the developed model. The effects of the FSW process parameters on ultimate tensile strength of friction welded dissimilar joints were discussed in detail. DOI: http://dx.doi.org/10.5755/j01.mech.18.5.2699