Friction Stir Welding Of Aluminum Research Articles

Advancements in Friction Stir Welding Techniques for Enhanced Performance in Aluminum Alloy Structures

Abstract: Friction Stir Welding (FSW) is a solid- state welding method that can be utilized on both comparable and dissimilar materials. The technology is frequently utilized because it generates quality welds and avoids common issues like solidification and liquefaction cracks that are connected with fusion welding processes. The FSW of Aluminum 5086 andits alloys has been commercialized, and there is renewed interest in connecting dissimilar materials. However, before the process can be commercialized, research studies must be conducted to describe and set process windows. In particular, FSW has prompted researchers to try combining incompatible materials with different characteristics, such as Aluminum 5086, and sound welds with no or few intermetallic compounds have been formed.

Modeling and Simulation of Friction Stir Welding of Aluminum and Magnesium Alloys Using Finite Element Analysis

Modeling and Simulation of Friction Stir Welding of Aluminum and Magnesium Alloys Using Finite Element Analysis

Experimental study on mechanical behaviour of friction stir welded aluminium alloy butt joints

The purpose of this paper is to understand the softening extent and stress-strain behavior of the normal-strength 6061-T6, 6013-T6, and high-strength 7075-T6 aluminium alloy butt joints using the novel friction stir welding (FSW) technique. A total of 107 monotonic tensile coupons and 33 Vickers hardness coupons were prepared from 8- or 12-mm thick welded plates using various tool rotation speed, welding transverse speed and tool configurations. The surface morphology, stress-strain curves and hardness distribution laws after welding were evaluated. The W-shaped hardness profiles were clearly observed, with the fracture location positively correlated at the lowest point of Vickers hardness near the edge of the weld toe. The strength reduction and softening extent of extruded aluminium alloys in T6 temper induced by FSW were superior to those of aluminium alloys using fusing welding process outlined in the Chinese and European standards, indicating the effectiveness and applicability of the FSW technique in the formation of components and connections for aluminium alloy structures. Additionally, the current widely used constitutive models generally yielded under-estimations on the strength under large strains. The developed three-stage Ramberg-Osgood model, using seven key input parameters, significantly improved the accuracy and consistent predictions in the full-range stress-strain curve of FSW aluminium alloys. Furthermore, the suggested model could still achieve a great balance between accuracy and practicality when using just three common available parameters with the employment of predictive expressions on other four parameters.

Optimizing the Mechanical Properties of the Weld in the Friction Stir Welding of Aluminum and Magnesium (A365–AZ91C)

The friction stir welding of A365 and AZ91C alloys was conducted in this study to assess the effect of tilt angle, linear velocity and rotating speed on the elongation, hardness and tensile strength using the response surface method. Then, the weld microstructure was investigated by SEM, TEM and EDS analysis to deeply investigate the structure of A365–AZ91C weld. It was realized that the grain size of weld joint has grown and the crack and tunnel were formed when the rotating speed improved from 1000 to 2000[Formula: see text]rpm, which produced a decline in the hardness and strength and a rise in the elongation. Moreover, an increment of linear velocity up to 60[Formula: see text]mm/min led to the refinement of the weld microstructure, which was followed by an enhancement in the strength and hardness of the weld, whereas the elongation deteriorated. In the case of tilt angle, the highest elongation and strength were detected at a tilt angle of 2∘, but the highest hardness was observed at a tilt angle of 4∘ because of the nucleation of Al3Mg2 and Al[Formula: see text]Mg[Formula: see text] intermetallics. Results of optimization exhibited that the concurrent improvement of the strength, hardness and elongation can be acquired with the tilt angle of 3∘, rotating speed of 1600[Formula: see text]rpm and linear velocity of 53[Formula: see text]mm/min.

Investigation of Tool Degradation during Friction Stir Welding of Hybrid Aluminum-Steel Sheets in a Combined Butt and Overlap Joint.

Friction stir welding, as a solid-state welding technique, is especially suitable for effectively joining high-strength aluminum alloys, as well as for multi-material welds. This research investigates the friction stir welding of thin aluminum and steel sheets, an essential process in the production of hybrid tailor-welded blanks employed in deep drawing applications. Despite its proven advantages, the welding process exhibits variable outcomes concerning formability and joint strength when utilizing an H13 welding tool. To better understand these inconsistencies, multiple welds were performed in this study, joining 1 mm thick steel to 2 mm thick aluminum sheets, with a cumulative length of 7.65 m. The accumulation of material on the welding tool was documented through 3D scanning and weighing. The integrity of the resulting weld seam was analyzed through metallographic sections and X-ray imaging. It was found that the adhering material built up continuously around the tool pin over several welds totaling between 1.5 m and 2.5 m before ultimately detaching. This accretion of material notably affected the welding process, resulting in increased intermixing of steel particles within the aluminum matrix. This research provides detailed insights into the dynamics of friction stir welding in multi-material welds, particularly in the context of tool material interaction and its impact on weld quality.

A Novel Procedure for Friction Stir Welding Aluminium to Copper by Using an Aluminium Run-On Plate

Conventional friction stir welding of aluminium to copper often results in the formation of deleterious intermetallic compounds. In order to overcome this concern, an innovative procedure consisting of using an aluminium run-on plate is presented. Long continuous aluminium-copper welds, without any defect, were obtained by this procedure. The run-on plate inhibits the formation of intermetallic compounds around the pin by allowing the use of high tool offset, without the formation of discontinuities at the interface. The generation of an aluminium volume around the tool, which detaches very small copper particles from the copper plate, gives rise to stir zones composed of a uniform distribution of copper particles in an aluminium matrix and with a minimal formation of intermetallic compounds. Comparing to the conventional welds, a significant improvement in the mechanical strength was achieved by welding with this non-conventional procedure.

Mechanical Properties of Welded by Friction Stir Welding Aluminium Alloy AA 5754

Friction stir welding is one of the most original methods for welding devised in recent years. As this welding method possesses advantages compared to conventional fusing welding methods, scientific research on its features and improvement is increasing. The advances in the knowledge of the process of friction stir welding allow its increasing application in different areas, such as aircraft and automotive industries, railway transport, nuclear industries etc. During friction stir welding the joined parts are in a solid state. This welding method is mainly used for joining aluminium and its alloys.The stirring and mixing of the material and the temperature during friction stir welding are the main factors that determine the possibility of obtaining weldments with precise mechanical properties.The present study aims to research the influence of the pin`s configuration on different quality aspects of the weldments at chosen parameters of the welding mode. To achieve this, pins with different geometry and coatings were used. Results that demonstrate the influence of the pin`s geometry and the process parameters on the temperature, structure, and mechanical properties of joined by friction stir welding weldments of aluminium alloy AA 5754 4 mm thick are presented. The influence of the pin`s geometry on defect formation during welding was determined.

Friction stir welding of aluminum to titanium: quest for optimum tool-offset, deformation of titanium, and mechanism of joint formation

Friction stir welding of aluminum to titanium: quest for optimum tool-offset, deformation of titanium, and mechanism of joint formation

Microstructural Evolution and Material Flow during Friction Stir Welding of 6013 Aluminum Alloy Studied by the Stop-Action Technique

This work is part of a wide-ranging study aiming to enhance the technology of dissimilar friction-stir welding of aluminum and titanium. In the previous study, a new approach was proposed that provided an exceptionally narrow intermetallic layer. However, an essential disadvantage of this technique was the significant material softening in the aluminum part. Hence, the present work was undertaken in order to obtain insight into microstructural processes and material flow in the aluminum part. To this end, the stop-action technique was applied. It was found that the microstructural evolution included several stages. Specifically, the initial material underwent the discontinuous static recrystallization in the heat-affected zone. With the approach of the rotating tool, the recrystallized grains experienced continuous dynamic recrystallization, which resulted in grain refinement. The subsequent transportation of material around the rotating tool provided no significant alterations in microstructure. This “superplastic-like” character of material flow was attributed to a dynamic balance between grain refinement and grain coarsening. It was also found that the stirred material experienced a secondary deformation induced by the rotating tool shoulder far behind the welding tool. The concomitant microstructural changes were most pronounced at the upper weld surface and gave rise to a fine-grained layer.

The Effect of Tool Rotation Speed on the Formation of Eutectic Structure during Friction Stir Welding of Aluminum to Magnesium

Friction stir welding (FSW) is a solid-state welding process capable of joining a wide range of light metals. However, liquation and solidification may occur during joining of dissimilar metals which leads to eutectic formation. This article aims to discover the influence of tool rotation speed on the formation of eutectic structure during friction stir welding of aluminum to magnesium. To do so, friction stir welding was performed at 600 and 950 rpm to join pure aluminum and ECO-AZ91 magnesium alloy in a lap configuration. In order to investigate the influence of the welding speed, the welding speeds of 23.5 and 37.5 mm/min were also chosen. Scanning electron microscopy (SEM) was used to study the microstructure of the joints. A shear-tensile test was used to evaluate the joints’ strengths. The fracture surfaces were also studied by SEM. The results revealed that changing the rotation speed directly affects the eutectic formation, whereas the welding speed had no influence. A lower rotation speed resulted in a thin, continuous intermetallic layer, whereas a higher speed led to the formation of a massive Mg-Al12Mg17 eutectic microstructure. The formation of eutectic, as an indicative of liquation, may affect the material flow during the process due to decreasing the friction coefficient between the tool and material. The macrostructure analyses showed that the phase evolution as well as the mechanism of material flow are highly affected by liquation.

A Novel Lap-Butt Joint Design for FSW of Aluminum to Steel in Tee-Configuration: Joining Mechanism, Intermetallic Formation, and Fracture Behavior

The development of new joint configurations suitable for dissimilar materials enables a wider range of applications and allows for an accelerated replacement of traditional structural construction materials by lightweight materials. The T-configuration is a joint configuration that has not been sufficiently studied for use with dissimilar materials, especially when created using the friction stir welding (FSW) process. In this study, a combined lap/butt design was introduced and implemented, seeking to create a T-joint between aluminum and steel. Characterization of the joints showed that FSW could be successfully used to join aluminum and steel in a T-configuration. The formation of intermetallic bonds and kissing bonds was carefully analyzed, and their contribution to the fracture behavior during loading in the skin and stringer directions was studied. Finite element simulation was used to determine the stress state at the interface during loading. The characterization results showed that the intermetallic, as an indicator of metallurgical bonding, is formed when special features are observed in the pattern of material flow. The fractography images showed that the stress state has a major impact on the fracture. The results of the present study can be effectively used to design and fabricate dissimilar joints, taking into account the loading condition.

Fatigue Damage Study of Steel–Aluminum Friction Stir Welding Joints Based on Equivalent Damage Model

Abstract An equivalent damage model was established to study the fatigue damage behavior of steel–aluminum friction stir welding (FSW) joints. Internal defects of friction stir welding joint under various cyclic loading stages were observed by X-ray microcomputed tomography (X-CT). For the characteristics of defects of the steel–aluminum FSW joints, a simplified method of defects considering key parameters is proposed, and then, the defect model is established. The FSW joint model was established based on the steel–aluminum boundary contour identified by using image processing techniques. Based on the defect model and the FSW joint model, the equivalent damage model was developed. The equivalent damage model was subjected to finite element analysis and compared with the test using strain amplitude as the damage variable. The equivalent damage model can be used to assess fatigue damage in steel–aluminum FSW joints, which provides some theoretical basis for fatigue life prediction.

Interfacial microstructural evolution and mechanical properties in dissimilar A1050 aluminium and S45C carbon steel friction stir welded joints using Zn interlayers

This study investigated the effect of Zn interlayers on the dissimilar friction stir welding of A1050 pure aluminium and S45C carbon steel. Two joints were made by adding Zn foils of two different thicknesses (100 μm and 200 μm) between the A1050 and S45C base metals in addition to a third joint without any interlayer. The joining experiments were conducted in constant process parameters at tool rotational speed and welding speed of 1500 rpm and 250 mm/min, respectively. The differences in joints microstructure were correlated with their mechanical properties and fracture mode. The results showed that Zn inhibited the growth of the interfacial Al–Fe IMCs, altered their composition and contributed to strengthening the A1050 stir zones by forming Al–Zn solid solution. Compared to the Zn-free joint, the ultimate tensile strength of the joints fabricated with the 100 μm and 200 μm thick Zn interlayers was improved by 14% and 26%, respectively. Also, the brittleness inside their interfacial IMCs was eliminated. As a result, the joints fabricated with Zn interlayers exhibited higher elongation and their fracture occurred at the A1050 instead of the joint interface as in the Zn-free joint. The Zn interlayer is expected to widen the joining process window by minimizing the detrimental effects of the Al–Fe IMCs.

X-ray quantification of second-phase precipitates in friction-stir welded 2519-T820 aluminum alloy

In this study, a new X-ray approach was applied to quantify the second-phase precipitates in the friction-stir welded 2519-T820 aluminum alloy. It was found that the stir zone material contained a significant fraction of secondary phases, including the non-equilibrium θ′ and θ″ ones. Based on this result, it was concluded that the widely accepted concept of FSW-induced precipitation phenomena is oversimplified and requires revision.

Friction Stir Welding of Aluminum in the Aerospace Industry: The Current Progress and State-of-the-Art Review.

The use of the friction stir welding (FSW) process as a relatively new solid-state welding technology in the aerospace industry has pushed forward several developments in different related aspects of this strategic industry. In terms of the FSW process itself, due to the geometric limitations involved in the conventional FSW process, many variants have been required over time to suit the different types of geometries and structures, which has resulted in the development of numerous variants such as refill friction stir spot welding (RFSSW), stationary shoulder friction stir welding (SSFSW), and bobbin tool friction stir welding (BTFSW). In terms of FSW machines, significant development has occurred in the new design and adaptation of the existing machining equipment through the use of their structures or the new and specially designed FSW heads. In terms of the most used materials in the aerospace industry, there has been development of new high strength-to-weight ratios such as the 3rd generation aluminum-lithium alloys that have become successfully weldable by FSW with fewer welding defects and a significant improvement in the weld quality and geometric accuracy. The purpose of this article is to summarize the state of knowledge regarding the application of the FSW process to join materials used in the aerospace industry and to identify gaps in the state of the art. This work describes the fundamental techniques and tools necessary to make soundly welded joints. Typical applications of FSW processes are surveyed, including friction stir spot welding, RFSSW, SSFSW, BTFSW, and underwater FSW. Conclusions and suggestions for future development are proposed.

Morphology Study of the Corrosion Rate on Weld Joint of Double Side Friction Stir Welding Aluminum Alloy AA6061

DSFSW welding uses the rotating of a tool in the workpiece to create heat owing to friction between workpiece and tool to be connected. Corrosion is influenced by the presence of high heat owing to friction and a non-uniform cooling rate. The heat transforms the metal in the Heat Affected Zone (HAZ) and Weld Metal (WM) region, which can result in flaws such porosity, kissing bond, fractures, voids (from welding penetration), and flash as well as changes to the microstructure. Changes in the microstructure of welded joints can affect the resistance of welded joints to corrosion. The purpose of this study is to experimentally analyze the main causes of failure of AA6061 DSFSW joints based on welding temperature, weld defects, microstructure, corrosion rate and morphology of the corroded surface. Temperature testing using thermocouple to analyze the temperature, welding joint defects using DSLR camera and radiography test, microstructure using optical microscope, corrosion rate using AUTOLAB PGSTAT and morphology of corroded surface using SEM. The temperature analysis results show that the advancing side has a higher temperature than the retreating side, due to friction between the tool and base metal accompanied by the opposite welding direction. Visual inspection shows that all specimens and welding positions produce flash that is quite rough on the top (1G) and bottom (4G) surfaces and radiographic test results show incomplete fusion in 4 specimens. Microstructure shows a change in shape and size resulting in recrystallization in the form of fine grains. The highest corrosion rate is found in specimen B 1G welding position of 0.63856mm/year and the lowest corrosion rate in specimen A of 0.058567mm/year. SEM test results show the type of corrosion that occurs in DSFSW welding joints is pitting corrosion.

Double side friction stir welding effect on mechanical properties and corrosion rate of aluminum alloy AA6061

Friction Stir Welding (FSW) is a solid-state welding method that has diffusion and different metal structures can blend well. Friction stir welding (FSW) has a weakness, one of which is the lack of flexibility the welding process is only carried out on one side of the plate being welded, so it is not applied on thick materials. Double side friction stir welding is a double working process in which the plate to be welded is subjected to friction from two tools on opposite sides. In the DS-FSW welding process, the dimensions and geometry of the tool and pin greatly affect the quality of the joint. This study to determine the mechanical properties and corrosion rate of Double side friction stir welding aluminum 6061 with variation rotation speed and axis of top and bottom tools. The results of this radiographic test can be seen that specimen 4 welded with variations in speed and tool position has defects in the form of incomplete fusion (IF). The results of microstructural observations showed that the heat caused by the welding process resulted in recrystallization in the form of fine grains in the stirring area and there was no phase change. The highest hardness value in the welding area is specimen B. The largest bending value at the 1G welding positions is specimen D, which is 41.86 MPa with a strain value of 13.23%, while the smallest value at the 4G welding position is specimen A, which is 38.18 MPa with a strain value of 5.03%. The fracture and crack surfaces showed that crack initiation, propagation and material stirring failure occurred in all test specimens, even though the impact test specimen was cut in a small area of Incomplete Fusion, but the test results showed that there was still a surface of the parent metal that had not been stirred. The corrosion test method uses three electrode cells with corrosion media as a substitute for seawater with a salinity of 3.5% NaCl, result of corrosion test is specimen B at the 1G welding position has the highest corrosion rate value of 0.63856 mm/year and specimen An at the 1G welding position has the lowest corrosion rate of 0.058567 mm/year.

Fatigue life improvement of similar and dissimilar aluminum friction stir welds by deep rolling

At the moment, high production costs prevent the friction stir welding (FSW) process from further industrial applications even if comparable high fatigue strength of the joints can be reached. Higher welding speed may reduce the production costs but decrease the fatigue strength of the manufactured FSW joints. A potential solution is a mechanical post weld treatment directly after welding to increase the fatigue strength of the FSW joint again. In this study, hydrostatic deep rolling was applied for fatigue strength improvement of similar and dissimilar FSW joints made of EN AW 5083 and EN AW 6082 alloys manufactured with different welding speed. Additionally, the fatigue strength was directly compared to conventional joints manufactured by metal inert gas (MIG) welding and to base material specimen made of EN AW 5083. The surface state in as-welded condition was characterized by surface roughness and residual stress measurements. Fatigue tests were performed to quantify the fatigue strength of the FSW joints. Similar compressive residual stresses were determined after deep rolling for similar and dissimilar joints. No fatigue life improvement was determined for deep-rolled similar joints made of EN AW 5083. However, in this condition, the fatigue life of the specimen was within the range of the base material. Thus, significant lower fatigue life and a high fatigue life improvement by deep rolling were reached for dissimilar joints. An increase of the welding speed from 300 to 800 mm/min strongly decreased the fatigue strength of dissimilar welded joints in the investigated case.

Distribution of the temperature in friction stir welding of aluminum and copper alloys

Friction stir welded are studied joints of pure copper M1 and aluminum alloy AD1. A technique for measuring the temperature was developed at the points of the weld. The results of measurement temperature are given in friction stir welding at various speeds of rotation of the welding tool (800-1000 rpm), welding speed (25-61 mm/min). The temperature reached in copper is about 60 K higher than in aluminum. The higher cooling rate of copper is due to the greater thermal diffusivity than that of aluminum. The maximum temperature in the copper reached 769 K, which was lower than the melting point of the eutectic in the Al-Cu system (821 K). The residence time above the temperature of formation of intermetallic compounds (623 K) is much shorter than the duration of the thermal cycle (50 s). With an increase in the welding tool rotation frequency from 800 to 1000 rpm, the maximum temperature near the pin increases from 650 to 769 K. At a tool rotation frequency of 800 rpm, the maximum temperature in copper achieved in the cycle is lower than the transition temperature to the superplastic state and is 764 K high heating and free cooling rates (50–145 K/s and 25–50 K/s) of the weld on the side of the copper alloy predetermine the short-term (from 5 to 15 s) stay of the metal in the temperature range of formation of intermetallic phases.

Effect of Pin Profile Tool on Friction Stir Welding Alumunium

This purpose of this study was to determine the effect of the pin profile tool on the results of friction stir welding aluminum. When compared to conventional welding, friction stir welding uses less energy, is non-consumable, and does not produce dangerous gas emissions, so the process becomes environmentally friendly. The variation of the tool with two profile pins, namely the straight thread pin tool (STPT) with a hardness number of 55 HRC and the tapered pin tool (TPT) with a hardness number of 54 HRC. The parameters used in both tools are 1125 rpm, a tilt angle of 20, and a 30 mm/min welding speed. The material used is Aluminum 1060, which has a size of 50x120x5 mm on one side. The friction stir welding test uses a visual, a radiography, and a macrostructure test. The results showed that the influence of the pin profile on the aluminum welding results with the tapered pin tool (TPT) has a defect in the form of a lack of fusion, so if it refers to PN-EN ISO 25239-5, then it is not permitted. In the straight thread pin tool (STPT) type, there are only imperfections in the form of a flash. The flash in the root area is due to the pin profile and welding speed, which disrupts the weld deposition flow. When viewed from the macrostructure results, there are no defects. Better results are obtained with the straight thread pin tool (STPT).