Friction Stir Welding Technology Research Articles

Microstructural evolution and mechanical performance of Al–Cu–Li alloy joined by friction stir welding

The objective of this study was to develop the technology of butt friction stir welding (FSW) for Al–Cu–Li alloy sheets of 1.4 mm thick after hot rolling and subsequent quenching. This initial state of the alloy was chosen in order to provide heat treatment of the received joints after FSW. The TEM observation was performed for the base material and different zones of the joints in order to determine the precipitates and dislocations density and distributions. The grain size in the stir zone (SZ) was increased; the width of the softened region was narrowed down with the decreasing of linear energy. The differences in mechanical properties of the FSWed joints were explained by analysis of microstructural changes and tensile fracture surfaces, supported by the results of the numerical simulation of the temperature distribution and material flow. The fracture of the high linear energy FSW joints occurred in the SZ along the remnant oxide line (ROL), while the low linear energy FSW joint raptured in the transition between HAZ and TMAZ on the AS, where lower hardness value was detected.

Evaluation of Usefulness of AlCrN Coatings for Increased Life of Tools Used in Friction Stir Welding (FSW) of Sheet Aluminum Alloy.

The study presents the results of examinations of wear in tools made of 1.2344 steel without and with an anti-wear coating in the process of welding overlap joints of sheet metal made of 7075-T6 aluminum alloy using friction stir welding (FSW) technology. A commercial anti-wear AlCrN coating (Balinit® Alcrona Pro by Oerlikon Balzers Coating Poland Sp. z o.o., Polkowice, Poland) was examined, applied using physical vapor deposition (PVD) and used to improve tool life in metalworking processes. Wear tests for the tools were conducted in industrial conditions at specific parameters of the friction stir welding process. Tool wear was evaluated through examination of the tool working surface. The results of the static tensile strength tests and metallographic examinations of the joints were used to evaluate the effect of tool wear and the coating impact on joint quality. The results obtained in the study show that the tool made of 1.2344 steel was intensively worn after the welding of a joint with the length of 200 m, increasing the risk associated with further use of the tool and suggesting the tool’s low durability. The use of the AlCrN coating led to an increase in tool life. The coating limits the process of tool wear and can be used as an anti-wear coating for tools used in the FSW of aluminum alloys.

Friction Stir Welding in the Aircraft Production

The paper presents the results of experimental development of the technology of friction stir welding to obtain a nonseparable connection of a special aerospace aluminum, titanium and magnesium alloys, high-temperature steels. Regularities and models of heat balance in the welding zone have been determined, which make it possible to predict the technological possibilities of high-speed friction welding. It is established that high-speed friction welding by mixing allows to obtain a high-quality connection at lower loads on the design of the equipment. On the basis of studies of macro-and microstructure, microhardness, level of residual stresses and strength tests, technological recommendations on the choice of welding conditions and conditions were obtained. Presented of experimental and industrial development of special equipment, high-speed friction welding, design and manufacturing of high hardness tools of complex spatial shapes for welding aircraft materials.

Development of friction stir welding technology of low-carbon steel plates

The purpose of this study is to develop recommendations for low-carbon steel (0,18% C) products assembling technology using friction stir welding. Relevant information on the status of friction stir welding of low-carbon steels is presented and an analysis of existing articles is carried out. Experiments on joining plates of 4 mm thick by using the tool of different geometry are conducted. It was found that the optimum temperature when joining using WC tool is 800–950 °C. The sound welds is manufactured when using a conical pin at a tool rotation speed 500 rpm and a traverse feed rate 50 mm/min with a plunging depth of 0,05–0,1 mm and an axial force of 15–18 kN.

Microstructure and mechanical properties of Mg-Mn alloys by friction stir welding

Mg-Mn alloy is welded by friction stir welding technology to manufacture liquid-cooled components in radar equipment. The effect of welding processes on microstructure and mechanical properties of Mg-Mn alloy was analyzed. The results show that the rotation speed has little effect on the microstructure structure when it is above 1200 rpm. The strength is increased by the increase of rotation speed from 900 rpm to 1500 rpm. The highest ultimate tensile strength is about 175 MPa. Most of the welding joints show brittle fracture during tensile test.

Effect of overlapping region on double-sided friction stir welded joint of 120 mm ultra-thick SiCp/Al composite plates

Effective joining techniques are urgent and necessary for the rapid developments and widespread applications of aluminum matrix composite (AMC) components. Friction stir welding (FSW) is a very promising method for joining AMCs without clear defects, while double-sided FSW is especially preferred in joining thick or ultra-thick AMC plates. The overlapping region stirred twice by the two welding passes is formed during the double-sided FSW, which has an important effect on the microstructures and mechanical properties of the composite joint. In this work, 120 mm ultra-thick plates of 16 vol % SiCp/2014Al composites were successfully joined by the double-sided FSW, and an overlapping region appearing at the middle thickness of the composite joint is mainly concerned and studied. Compared with the base material and the region stirred once in the SiCp/Al composite joint, the decrease of SiC particle size, improved uniformity of particle distribution and refinement of aluminum grains and precipitates are observed in the overlapping region as a result of repetitive mechanical stirring during the double-sided FSW. The overlapping region exhibits the largest Vickers hardness and overall tensile properties: yield strength of 224 MPa, ultimate tensile strength of 369 MPa and failure elongation of 6.6%. The simultaneous enhancement in tensile strength and ductility in the overlapping region is attributed to the more effective load-transfer of reinforced particles with decreasing particle size, and the increased grain boundary strengthening due to matrix grain refinement. A comprehensive understanding the effect of overlapping region on the microstructural characterization and mechanical properties of the composite joint is positive and important to promote and accelerate the industrial applications of double-sided FSW technology in joining thick or ultra-thick metal matrix composite plates.

An Assessment of Non Consumable Welded Joint- Friction Stir Spot Welding

Friction stir spot welding (FSSW) is a pressure weldingprocess where the workpieces are operated below their melting points. FSSW is one of the processes derived from Friction Stir Welding (FSW) Technology. Friction stir welding was invented by The Welding Institute (TWI) in 1991 and proven experimentally. FSSW is found to be environment friendly and a very efficient process. This process is rapidly growing and is replacing the resistance spot welding. FSSW have various applications which include industries like automobile, aerospace, ship building, construction and electrical.FSSW has been successfullyused to join several materials used in the above mentioned industries. Inthis review, FSSW studies are briefly summarised in terms different parameters for joining processes.

Effect of ultrasonic vibration on thermal and material flow behavior, microstructure and mechanical properties of friction stir welded Al/Cu joints

Al/Cu dissimilar joint has been widely produced by using friction stir welding (FSW), but the weld quality remains limited. A recently developed ultrasonic vibration-assisted FSW (UVaFSW) technology has shown potential of enhancing the material flow and mechanical properties of Al/Cu joint. In this paper, a systematic study is presented to investigate the effect of ultrasonic energy on FSW Al/Cu joints with an optimized tool shoulder diameter of 16 mm and welding speed of 60 mm/min. It is found that the thermal effect of ultrasonic on the FSW process could be deemed negligible, which is distinguishing with other transmission method of ultrasonic energy. Correspondingly, the mechanical effect of ultrasonic is evident because of the dramatically decreased welding loads, the more intense intermixing between Al and Cu, and the more uniformly distributed micro-hardness in the stirring zone of UVaFSW Al/Cu joints. Moreover, the ultrasonic energy reveals a positive influence on the weld quality of Al/Cu joint; the maximum tensile strength by UVaFSW is achieved at the rotation speed of 500 rpm; and the value reaches 162.8 MPa, which improves by 60.7% compared with that by FSW. It is elucidated that the ultrasonic vibration effectively reduces the activation energy and flow stress of the material, stimulates stable plastic deformation in the vicinity of the tool, and is beneficial for the homogeneous of FSW Al/Cu joint.

Understanding Machine Learning for Friction Stir Welding Technology

Machine learning process drastically decreases the time it takes to develop stronger, lighter materials. This is important to the aerospace, automotive and manufacturing sectors. Machine Learning techniques like Artificial Neural Networks and Image processing are used in Friction Stir Welding Process for the optimization of mechanical properties like Ultimate Tensile Strength, Fracture Strength and elongation % and microstructure properties like grain size and understanding defects formation. In the recent paper, the application of the Machine Learning technique in Friction Stir Welding technology will be discussed.

Dry sliding wear behavior study on friction stir weld joints of dissimilar aluminum alloys

Friction stir welding (FSW) is a comparatively new emerging solid state nature welding process used for joining the various similar and dissimilar metals which were difficult to use in conventional welding. It has better mechanical properties in comparison with other welding process in the Weld zone. The aim of present work is to select the combinations of parameters for sound weld joints by friction stir welding technology of two different aluminum alloys; AA6101-T6 and AA6351-T6 of 6 mm plate thickness. Rotational speed of tool, Welding speed of tool, tilt angle of tool and axially downward force are the important combinations of process parameters. A computerized FSW machine has been employed for execution of the Welding process. The weld parameters have been used to fabricate four different joints to study their effect on wear property of joints. Optical microscopy has been carried out to study microstructural features of sound weld joints. Wear tests were performed on pin on disc machine to study the dry sliding wear behavior of weld joints. The wear test samples of the required dimensions have been cut from the nugget zone of weld joints. Scanning electron microscope (SEM) and Energy dispersive x-ray spectroscopy (EDS) analysis for compositional information for base metals and worn out surface of wear test samples of Friction stir welded dissimilar butt joints. It has been of observed that the wear rate of the base metal is lower than the friction stir welded joints. Presence of silicon content plays an important role in improving the wear resistance property of base metals. Wear properties of FSW joints were comparatively more than the base metals. Worn surfaces analysis reveal the formation of the grooves, scratches and wears debris, delamination and their combinations are the dominant mechanisms involve during material removal on sliding.

Understanding Machine Learning for Friction Stir Welding Technology

Machine learning process drastically decreases the time it takes to develop stronger, lighter materials. This is important to the aerospace, automotive and manufacturing sectors. Machine Learning techniques like Artificial Neural Networks and Image processing are used in Friction Stir Welding process for the optimization of mechanical properties like Ultimate Tensile Strength, Fracture Strength and elongation % and microstructure properties like grain size and understanding defects formation. In the recent paper, application of Machine Learning technique in Friction Stir Welding technology will be discussed.

Effect of Selected Friction Stir Welding Parameters on Mechanical Properties of Joints

AbstractThe article discusses the basic issues related to the technology of friction stir welding (FSW). A short description of technology is provided. The following section provides the analysis of effect of technological parameters (tool rotation and welding speed) on the mechanical properties of the prepared joint (strength, ductility, microhardness). In both cases the analysis refers to aluminum alloys (6056 and AA2195-T0). The comparative analysis showed the phenomenon of the increase in weld strength along with the increase in the rotational speed of the tool during welding. Similarly, with the increase in welding speed, an increase in weld strength was observed. Some exceptions have been observed from the above relations, as described in the article. In addition, examples of material hardness distribution in the joint are presented, indicating their lack of symmetry, caused by the rotational movement of the tool. The analyses were performed basing on the literature data.

Review and Analysis of Mechanical Properties of Friction Stir Welds of High Strength Aluminium Alloys

There have been significant advancements of recent in the studies of friction stir welding of high strength Aluminium alloys. These studies cover developments in the welded joint properties of these alloys. This paper reviews some available literature on evolving mechanical properties of friction stir welding of high strength aluminium alloys especially those of 7075 aluminium alloy which happens to be the most versatile member of the high strength aluminium alloy group. This review is aimed at establishing a correlation between the tensile behavior, plate thickness and temper conditions of the 7075 alloy when joined by friction stir welding (FSW) in both similar and dissimilar joints with other metals. The average values of reported ultimate tensile strength, yield strength, and percentage elongation have been calculated and presented. Comparative analysis was made between the tensile properties at different temper designation and plate thickness. The analysis revealed that temper conditions significantly affect the mechanical properties of both the similar and the dissimilar joints and that similar welding at T6 and T651 temper conditions gave higher weld efficiencies than dissimilar welding with other groups in the aluminium series. However plate thickness have little or no influence on the ultimate tensile behaviour, yield strength and elongation of the welds. The review also indicates that there is a range of temperature between which post weld heat treatment (PWHT) could be performed in order to obtain maximum tensile property This paper is a significant approach to enhance high performance joining techniques and the reliability or otherwise of friction stir welding technology to join 7075 aluminium alloys under different heat treatment or temper conditions of the alloys for better industrial applications.

Modeling heat input when friction stir welding

An important element of friction stir welding technology is the determination of the temperature of the material in the mixing zone, which can be determined by calculating the amount of heat introduced into the welding zone. To determine this value, experimental studies were carried out on a stand in which the material to be welded (aluminum alloy AMg5) is modeled as an experimental tube with a diameter of 20 mm, and the tool (from tool steel P6M5) is modeled as a working plate. On the stand, studies of the dependence of the frictional moment and heat-liberation value were performed. According to the obtained experimental data, the heat-liberation dissipation and heat power on the working tool are calculated, the dependences of these values on the radius of the working tool are obtained.To increase the amount of heat input in the center of the contact area, a tool with a drive with two concentrically located (one inside the other) shafts is proposed, while the inner shaft rotates at a higher speed than the outer one. According to the obtained experimental data, the dependences of heat release for each shaft and the total heat release for a tool with two shafts at an external shaft rotation speed ω = 63 s-1 and different rotation speeds of the internal shaft are calculated. In total, for the external and internal shafts, the total heat release value is about 2 times higher than the total heat release value using a single shaft.The purpose of this work is to find the values of heat release in friction stir spot welding, as well as the development of friction spot welding tools with higher heat release.

Studies on Quasi-Static and Fatigue Crack Propagation Behaviours in Friction Stir Welded Joints Using Peridynamic Theory

The friction stir welding (FSW) technology has been widely applied in aircraft structures. The heterogeneity of mechanical properties in weld and the hole in structure will lead the crack to turn. Peridynamics (PD) has inherent advantages in calculating crack turning. The peridynamic theory is applied to study the crack turning behaviour of FSW joints in this work. The compact tension (CT) samples with and without a hole are designed. The crack propagation testing under quasistatic and fatigue loads are performed. The peridynamic microplastic model is used and a three-stage fatigue calculation model is developed to simulate the quasistatic fracture and the fatigue crack growth. The results predicted by the peridynamic models are compared with the experimental ones. The effects of welding direction on quasistatic and fatigue crack propagation behaviours are investigated and the effect of hole position on crack path geometry is also studied. It is shown that the crack turning in FSWed CT samples can be captured by the peridynamic microplastic and the three-stage fatigue calculation models. The peridynamic crack growth rates agree with the experimental results. For CT specimen without a hole, the crack turns into the weld zone where the material is softer. The effect of welding direction on crack growth rates is not obvious. For CT sample with a hole, the crack propagation direction has been mainly controlled by the hole location and the welding direction has a slight effect on crack path.

Flow Patterns, Microstructure and Mechanical Properties of AZ31/Al6061 Dissimilar Friction Stir-Welded Joints

Dissimilar joints between die-cast AZ31 and extruded Al6061-T6 were joined using friction stir welding technology at a constant transverse speed (50 mm/min) and rotation rate of 800 or 1000 rpm. The flow patterns, microstructure evolution and intermetallic compounds in dissimilar joints were studied by optical and scanning electron microscopy. The relationship between microstructure and tensile properties was analyzed. The microhardness distribution along the horizontal centerline in cross section was investigated. Local flow without obvious mixing existed between Mg and Al metals in the tool shoulder-affected zone. For the tool-pin-affected zone, two typical zones, namely, the “extrusion zone” and “flow zone” existed because of the different flow modes of the plastic metals. The phase analysis showed that intermetallic compounds, including Al12Mg17 and Al3Mg2 formed in banded structures. Phase analysis showed that a joint with welding parameters of 800 rpm and 50 mm/min (Joint-500) had good mechanical properties because of the more uniform microstructure distribution and fewer intermetallic compounds. Fracture analysis indicated some microvoids and lamellate intermetallic compounds in the fracture surface of the joint with welding parameters of 1000 rpm and 50 mm/min (Joint-1000), which deteriorated its tensile strength significantly.

Effect of Process Parameters on Structure and Mechanical Properties of Friction Stir Welding Joint of 5052 Aluminum Alloy

2.5 mm thick sheets of AA5052 were welded using friction stir welding technology. The effects of welding speed, rotational speed of pin, length of pin, single-side and double-side welding process on the morphology, microstructure and mechanical properties of welded joints were studied and analyzed. The failure mode was studied. The results show that the joints with good mechanical properties and without welding defects can be welded when the rotational speed of pin is 500-1200r/min and the welding speed is 100-480mm/min. The microstructure of weld nugget is mainly composed of α phase solid solution and β phase particles. The process parameters of friction stir welding have great influence on the static strength of welded joints. The static strength increases with the increasing of rotational speed of pin, however decreases with the increasing of welding speed. The peak load of the double-side welding increases by 30% compared with the single-side welding. The length of pin has little effect on the tensile strength. The tensile fracture of the single-side welding is located in the weld nugget zone, whereas the fracture of double-side welding is located in the base material zone.

The Influence of Tool Geometry for Refill Friction Stir Spot Welding (RFSSW) on Weld Properties During Joining Thin Sheets of Aluminum Alloys

1. Financial support of The National Centre for Research and Development, European Union, PZL Mielec / a Sikorsky Company, in the framework of European Regional Development Fund Project “Advanced techniques for the fabrication of airframe structures using innovative friction stir welding (FSW) technology”, no. INNOLOT/I/4/NCBR/2013 is gratefully acknowledged.

MACROSTRUCTURAL ANALYSIS OF FRICTION STIR WELDING (FSW) JOINTS

Friction Stir Welding (FSW) technology is increasingly used in aerospace, automotive, construction and other industries. It allows for safe, secure and long-lasting joining of materials that are difficult to weld or non-weldable with traditional methods. In engineering practice, these are primarily aluminium alloys.

Examinations of steel overlap joints obtained using the friction stir welding technology

Examinations of steel overlap joints obtained using the friction stir welding technology