Friction Stir Welding Technique Research Articles

Improving the Quality of Friction Stir Welds in Aluminium Alloys

The Stationary Shoulder Friction Stir Welding (SS-FSW) technique benefits from reduced heat input, improved mechanical properties and surface finish of the weld, avoiding the need for post weld processing. Coatings on the tool probe and the shoulder for welding of aggressive Aluminium alloys have rarely been successful. Such coatings must be well adherent and inert. In this study, coated tools were used for SS-FSW of AA6082-T6 alloy. Performance of a nanoscale multilayer TiAlN/VN coating deposited by High Power Impulse Magnetron Sputtering (HIPIMS) technology was compared with amorphous Diamond Like Carbon (a-C:H) by Plasma Assisted Chemical Vapour Deposition (PACVD), AlTiN deposited by arc evaporation and TiBCN along with TiB2 produced by Chemical Vapour Deposition (CVD) methods. The TiAlN/VN coating was found to have low affinity to aluminium, acceptable coefficient of friction and provided excellent weld quality by inhibiting intermixing between the tool and workpiece materials resulting in a significant reduction in tool wear.

Al-Based Surface Composites and Strengthening Of Welded Joints Through Multi-Pass FSP Technique: A Review

Friction stir processing (FSP) is a microstructural modifying technique that uses the same principles as the friction stir welding technique. FSP technique can be employed on the same surface repeatedly as desiredand this repetition is called multi-pass friction stir processing (MFSP). The recent developments have shown that MFSP technique is very useful towards uniform dispersion of reinforcement particles during fabrication of surface composites. Some studies have also demonstrated that MFSP technique can be employed on welded joints as a way of improving the mechanical properties of the welded joints. This paper reports on the progress made in using the multi-pass friction stir processing (MFSP) technique in producing aluminium-based surface composites. It further looks at the progress made in using the MFSP on aluminium-based welded joints. An effort is made to identify the gap that requires some exploration for the better utilization and understanding of this technique

Sustainable Processing of Dissimilar Aluminium Alloy Joints by Friction Stir Welding

Friction stir welding is one of the unique solid state welding technique that is fast gaining importance because of its excellent properties pertaining to the strength, wear, hardness and better joining capabilities. The friction stir welding technique is effectively used in this research to join 5 mm thick dissimilar aluminium alloys of AA 7075 and AA 5052 grade. The friction stir welding joints are obtained by using three different tool profiles viz., straight cylinder, taper cylinder, and straight triangular at a speed of 800, 1000, 1200 rpm and a feed rate of 100, 120, 140 mm/min. The experiments are designed based on L9 orthogonal array considering Taguchi techniques. From the experimental results, the process methodology is validated and the outcomes of the experiment are considered for fabrication of strong joints. The design and optimization of the process has led to better process control and thereby extended its scope for the use of the optimized process parameters for joining dissimilar aluminium alloys in real time engineering applications with sustained methodologies involving reduced dwell time and optimized friction forces and torque during the friction stir welding of dissimilar aluminium alloys.

Experimental analysis on friction stir welded AA 7075/AA 6061 using Taguchi grey relational analysis

In recent years, the applications of aluminium and its alloys are inevitable in aerospace, automobile, railway and shipbuilding industries due to its strength to weight ratio, resistance to corrosion and machine ability. In this experimental study, an effective approach, Grey Relational Analysis (GRA) is a novel methodology substantiated for optimizing the dissimilar aluminium alloys. The process parameters for AA 7075 and AA 6061 considered with the specimen thickness of 6 mm were experimentally examined by friction stir welding (FSW) technique. In FSW technique, tensile properties have been investigated, which exhibits superior metallurgical and mechanical properties after the post weld treatment. Moreover, the multi response optimization with L9 orthogonal array being carried out to process the optimized parameters on FSW nuggets and ANOVA (Analysis of Variance) resulted ascertains the mathematical responses to minimize the cracks, defects and flaws during the solidification and recrystallization processes. In spite of numerous commercial applications, the aluminium and its alloys are exploited to yield the intense tensile strength. The GRA is codified by the optimum parameters and the experimental number 8 graded the utmost tensile strength. This investigation facilitates to accomplish the enhanced mechanical properties and techniques in FSW over conventional welding process.

Innovation of thermoplastic polymers and metals hybrid structure using friction stir welding technique: challenges and future perspectives

Friction stir welding (FSW) is an innovative technique to produce a hybrid joint of thermoplastic polymers and metals in the recent past. A review of the friction stir welding processes and fabrication of polymer-based nanocomposites was developed to meet the challenges of the industry’s needs in the twenty-first century. These hybrid structures predominantly will play a vital role in future innovations. In the recent past, it is widely used in the automobile and aerospace sectors. It is due to its lightweight and high strength-to-weight ratio. This article focuses on the recent development that has been made in the joining of thermoplastic polymers and metals through the friction stir welding technique and friction stir processes. This article provides a comprehensive study of the influences of various process parameters on weld performance. The effect of surface pretreatment on the adhesive mechanisms is presented. Finally, mechanical behavior like hardness and tensile strength of joints, and the microstructural features of joints are presented. Based on the detailed survey, this paper consolidated the way to improve the thermoplastic polymers and metals joints through FSW.

Influence of tool profiles on similar Al-5083 alloys using friction stir welding

In the present investigation, the various geometry of tools on butt joints of Al 5083 alloy are fabricated by using technique of friction stir welding. The tool present in investigation is formed by High speed steel material (H.S.S) and considered profile of tool is tapered and pin having threaded and also without threaded. Review of tool profiles, tapered with thread and without thread and their effects on properties of mechanical and metallurgical of similar welded aluminum 5083–5083 alloys. It is highlighted that fabricated joint at a tool having rotational speed of 700, 825, 1120 rpm, welding speed of 20, 32, 44 mm/min and angle of 30 for combining process. Find that there are no surface level cracks in the welded region of liquid penetrant testing (NDT) method. The mechanical tested results of tapered threaded tool profile gives 34.87% rise in tensile strength and 15.65% in hardness and 57.14% rise in impact test by using threaded tool. Among all similar weldments with tapper threaded tool, rotation speed of 825 rpm weld speed of 32 mm/min gives grain size of 7 and high volume percentage of ferrite (59.14%), pearlite (36.73%) composition in weld zones due to proper stirring action.

Effect of tool geometry on microstructure and mechanical properties of submerged friction stir processed AA6082/AA8011 joints

This paper reports on the influence of the pin profile towards the microstructure and the mechanical properties of the underwater friction stir processed dissimilar (SFSP) AA6082/AA8011 joint. The friction stir processed (processed) dissimilar joints were initially produced through the friction stir welding technique. The SFSP joint produced using two different pin profiles were studied comparatively. The cylindrical threaded pin profile (TP1) and triangular pin profile with flutes (TP2) were used in performing SFSP on AA6082/AA8011 dissimilar joint. The joint produced using with TP2 pin profile had finer grains compared to the joint produced using the TP1 pin profile. The tensile properties of the joint produced with TP2 were higher compared to those produced using TP1.

Formulation of the butt joints of aluminum composite using friction stir welding and study of their mechanical properties

In this study, experiments were performed on the vertical milling machine to formulate butt joints of aluminum matrix composites (AMCs) having 5 vol% SiC as particulate using friction stir welding technique. Joints prepared were tested to find their mechanical properties using different testing methods. The butt joints were formed from the plates of Al-SiC composite plates. Alloy steel tool hardened at a temperature of 850°C was used to obtain welded joints. Three different pin shapes were used to do welding at three different tool rotations ranging from 600-1200 rpm based upon pilot experimentation. Tensile tests were done on the universal testing machine to find yield strength and ultimate strength. Hardness of the welded joint is also calculated using the vickers hardness test. The joints prepared using non tapered pin shape had better tensile properties as compared to other pin shapes. Good mechanical properties were obtained at 1200 rpm tool rotation. The hardness of the welded joint also got improved when welded at 1200 rpm using non tapered pin shape. The microstructure results also verified that refinement of grains takes place at higher tool rotations which improved mechanical properties.

Experimental investigation of damage detection on structures with friction stir welding (FSW) junctions

A Structural Health Monitoring system for damage detection is proposed in this paper. The Probability Ellipses method (PE) is a non-destructive method based on Guided waves. This method estimates a global index called Damage Index (DI), that represents a way to measure how much critical is the related sensing-path (actuator-sensor). The DI is high when the damage is closer to the sensing-path and it increases again when the damage severity grows. The work is being developed in the framework of the Clean Sky 2 specifically for More Affordable Small Aircraft Manufacturing (SAT-AM) project, whose main goal is the development of new technologies to be employed in the development of next generation of small aircrafts category responding to CS/FAR-23 certification specification Rules. The Friction Stir Welding (FSW) is one of key technologies to reduce cost, time and manufacturing costs. Conversely, the low historical data on structural degradation of FSW joints require a conservative approach during design stage. A possible answer to the lack of structural knowledge behavior could be overpassed by using structural health monitoring system that periodically evaluates the born of any criticalities of the FSW structures. Preliminary experimental investigations of the ET method, applied to structures with Friction Stir Welding (FSW) junctions, are illustrated. Aluminum panels were joined with FSW technique and damage was produced in the junctions. The structures were instrumented with piezoelectric actuators and sensors. The Guided waves were acquired on both undamaged and damaged configurations and the PE method was applied to identify the damage position.

Evaluation of tensile and microstructure properties of AA2014 and AA7075 FSW weldments developed by HSS-10%Co and WC tools

Difficult to weld series of high strength Al grades by fusion welding were known to join by Friction stir welding (FSW) process. Joints of high strength AA 2021 and AA7075 base materials obtained by FSW technique were discussed in the present work. Tool materials with different surface hardness, High Speed Steel and Tungsten Carbide, were developed to commence welding. FSW Process parameters were taken as 1120, 1400 and 1800 rpm with feeds rates of 30, 40 and 50 mm/min. Base material and tool material combinations were chosen to produce weldments. Weld joints were evaluated using tensile test. Microstructure analysis was presented from the results of images obtained by Metallurgical Microscope. Weldments joined by HSS tool have shown better tensile properties compared to weldments obtained by tungsten carbine tool. Tunnels effects were seen in the weldments made from WC tool.

Impact of multi-pass friction stir processing on microhardness of AA1050/AA6082 dissimilar joints

The AA1050 and AA6082 aluminum plates were used to produce a dissimilar joint using the friction stir welding (FSW) technique. The produced dissimilar joint was then processed. The processing used is the multi-pass friction stir processing (FSP). Different tests were then conducted on the processed AA1050-AA6082 joints. The results on microstructural analysis revealed that as the number of FSP passes were increased the grain sizes reduced. The ultimate tensile strength of the multi-pass increased with a decrease in elongation as compared to that of a single pass with the same material positioning AA1050-AA6082 joints. For the surface morphology, the fracture surfaces were characterized by dimples on both the first and fourth pass. As the number of passes increased it was noticed that the dimples became smaller. The microhardness was found to have a minor dependency on the number of FSP passes.

The effect of material position of multi-pass friction stir processing on friction stir welded AA1050/AA6082 dissimilar joints

The AA1050 and AA6082 plates were used in producing dissimilar joint through friction stir welding (FSW) technique. The developed dissimilar joint was then subjected to multi-pass friction stir processing (FSP) technique. Various tests for the AA1050/AA6082 (AA1050 on the advancing side) and AA6082/AA1050 (AA6082 on the advancing side) joints were conducted on joints subjected to 1pass (1P) and 4pass (4P). The microstructural analysis showed that the increase in number of FSP passes resulted in a reduced grain size regardless of the of material position. The Vickers microhardness for AA1050/AA6082 FSPed joints increased towards AA6082 side while the microhardness for AA6082/AA1050 FSPed joints decreased towards the AA 1050 side regardless the number of the passes. The ultimate tensile strength (UTS) of AA1050/AA6082 joint increased with an increase in the number of passes while AA6082/AA1050 fluctuated between the specimens sampled from different locations of the FSPed joints.

Experimental investigation and finite element simulation of friction stir spot welding (FSSW) of high-density polyethylene joints

Friction stir spot welding (FSSW) is an essential aspect of traditional friction stir welding (FSW). When compared with standard welding methods, this method creates high-quality joints. The FSSW is a modern welding technique that is used for welding polymer materials that are hard to weld using regular welding methods. HDPE (high-density polyethylene) is a plastic material having notable material characteristics. HDPE is now the most commonly used material in a variety of manufacturing processes. However, the increased demand for joining has arisen because of the need to manufacture bigger and more diverse components from polymers like HDPE. Furthermore, thermal residual stress is an unwanted and inherent phenomenon in welding systems that induce weld distortion and decreases the material characteristics of the weld. The current work produced a new friction stir welding technique set up for improving the strength of the weld and minimizes angular distortion of welded polyethylene sheets. The distortions of the welded specimen were measured during the experimental testing. The welded model was then experimentally evaluated on the basis of temperature generation during the operation and weld strength. Based on the data produced by the experiments, finite element simulation was also used to create a thermal model for the lap (spot) welds. The finite element simulation results agree well with the experimental results.

Impact of friction stir welding tool profile on the strength of dissimilar aluminium and stainless steel welded joints

The two different grades of alloys such as Aluminum AA6063 and stainless steel SS304 of 8 mm thickness are friction stir welded by taking factors like depth of the cut, tool pin profile, feed, tilt angle, rotational speed. The friction stir (FS) welding experiment is conducted by varying the tool profile as hexagonal, circular, square, triangular, and tapered and other factors as constant. The impact of tool profile on strength of weld joint is experimentally investigated by conducting hardness and tensile tests. The FS welding is performed to weld two dissimilar metals by varying the tool profiles to identify the suitable tool profile for effective dissimilar welded joint. The hexagonal pin profile found to be best for the FS welding of Aluminum AA6063 and stainless steel SS304 metal sheets as strength (tensile) of the weld joint is produced as 54.889 MPa and hardness 280.89BHN. The research work will help to suggest the suitable pin profile for Aluminum and steel metal sheets welding by the FS welding technique.

Experimental Identification of Optimized Process Parameters for FSW of AZ91C Mg Alloy Using Quadratic Regression Models

This experimental work aims to devise and establish quadratic regression equations, including various input criteria of a friction stir welding (FSW) technique to predict and determine the responses during the fabrication of AZ91C Mg alloy joints. The input process parameters taken into consideration include the traversing speed of the tool, the speed of rotation of the tool, its pin profile (geometry) and the axial force. A five-level, 4 four-factor composite design (of central nature) was applied, and response surface methodology (RSM) was used to formulate quadratic regression models, to develop 3D response surface charts, and to anticipate the responses for various mechanical properties. The generated quadratic mathematical model was tested and validated using the technique of analysis of variance. Validation experimental trial results outlined in the form of scatter diagrams revealed precedented coincidence with that of the generated models. The AZ91C Mg alloy joints obtained using the tool having taper cylindrical pin geometry employed at 1045 rpm, 1.5 mm/s traversing speed, under the exertion of an axial load of 4.87 kN was found to exhibit improved mechanical properties.

Performance Analysis of Friction Stir Welded Lightweight Aluminum Alloy Sheet

The present research envisaged the performance analysis of a 1-mm thick 6061-T6 aluminum alloy sheet welded by the friction stir welding technique, using optical microscopy, micro-hardness measurement, a tensile test, a friction and wear test, and a salt spray corrosion test. It was found that the grain in the welded zone obtained was refined under each parameter. When the rotating speed of the tool was 15,000 rpm and the traveling speed of the tool was 300 mm·min -1 , the tensile strength of the welded zone was highest, i.e. 74.8% of the base metal. Furthermore, the hardness distribution curve of the welded zone was of the ‘W’ type under each parameter, but the hardness value was lower than that of the base metal. The friction coefficient of the welded zone was lower than that of the base metal under each parameter, and the wear form was found to be mainly adhesive wear accompanied by abrasive wear. The welded zone and the base metal were subjected to salt spray corrosion after 12 hours under each parameter, which had a negative effect on the quality. However, after 12 hours of subsequent corrosion, the quality of each sample and the base material was not obvious.

Prediction of multiple characteristics of Friction-Stir welded joints by Levenberg Marquardt algorithm based artificial neural network

The present paper investigates the influence of process parameters of friction stir welding (FSW) technique on the resulting microstructure and mechanical characteristics of the fabricated joints. The material considered for FSW is AA1100 aluminium rolled plates that are joined by using a square pin tool. In this research, parametric characterization of surface properties has been carried out by simulation using an artificial neural network (ANN) that is designed with multi layer, multi neuron and logistic sigmoid activation function. Levenberg-Marquardt algorithm including second-order error optimization has been selected to train the ANN. The ANN simulation has been done to estimate the tensile and yield strength, elongation, flexure stress and grain size with respect to tool rotational speed (RS), travel speed (TS) and plunge depth (PD), which are the process parameters of FSW process and also find an optimum condition which is essential to save energy and resources. This process finds its application in various automotive industries as there is a wide use of aluminium in the automobiles and aircrafts.

Microstructural and Mechanical Behaviour Evaluation of Mg-Al-Zn Alloy Friction Stir Welded Joint

The weight reduction concept is most effective to reduce the emissions of greenhouse gases from vehicles, which also improves fuel efficiency. Amongst lightweight materials, magnesium alloys are attractive to the automotive sector as a structural material. Welding feasibility of magnesium alloys acts as an influential role in its usage for lightweight prospects. Friction stir welding (FSW) is an appropriate technique as compared to other welding techniques to join magnesium alloys. Field of friction stir welding is emerging in the current scenario. The friction stir welding technique has been selected to weld AZ91 magnesium alloys in the current research work. The microstructure and mechanical characteristics of the produced FSW butt joints have been investigated. Further, the influence of post welding heat treatment (at 260 °C for 1 h) on these properties has also been examined. Post welding heat treatment (PWHT) resulted in the improvement of the grain structure of weld zones which affected the mechanical performance of the joints. After heat treatment, the tensile strength and elongation of the joint increased by 12.6 % and 31.9 % respectively. It is proven that after PWHT, the microhardness of the stir zone reduced and a comparatively smoothened microhardness profile of the FSW joint obtained. No considerable variation in the location of the tensile fracture was witnessed after PWHT. The results show that the impact toughness of the weld joints further decreases after post welding heat treatment.

Influence of Pin Offset and Weave Pattern on the Performance of Al-Cu Joints Reinforced with Graphene Particles

The friction stir welding technique is currently employed for different alloy combinations like magnesium, titanium, copper, nickel-based composites. Dissimilar materials may be efficiently joined by the process and this has been used in several structural applications such as automotive components, aircraft structure, shipbuilding, and space shuttle external tank and train bodies. Even though improvement in the joint strength was achieved, problems such as voids, tunnels, cracks persisted in the weldments. The objective is to achieve defect-free joints. Tool pin offset for joining of aluminum alloy enables better stirring action and an easy flow of plasticised material in the weld nugget. Hence, to overcome the above-mentioned problem, a technique of combined effect of weaving, tool pin offset, and reinforcement of self-lubricated graphene nanoplatelets was attempted. The tensile strength obtained with the effect of tool rotational speed under weave weld with pin offset condition with reinforcement was 13.82 % higher than the weld obtained under the same condition without reinforcement. IMCs such as AlCu, Al2Cu, and Al4Cu9 large size band layers were observed with the linear welding condition, whereas weave welding conditions resulted in the formation of the thin uniform layer.

Investigations on microstructural and mechanical properties of friction stir welded AA 2024-T351

Abstract In the present study, AA 2024-T351 plates with a thickness of 6 mm were joined using the friction stir welding technique with three different tool rotational speeds and two different pin profiles. Microstructural features and mechanical properties of welded joints were investigated. The grains in recrystallized regions along the stir zone were observed to be almost with invariable sizes. The grain size was revealed to increase with the increase in tool rotational speed. The average grain size was observed to dramatically increase from 2.3 μm to 5.6 μm for welded joints produced with pentagonal shaped pin. All the welded joints were observed to contain defects; the presence of defects exhibited a negative effect on the tensile properties of the welded joint. Most of the defects were observed to localize at the root region of joints. The joint, welded with the tool rotational speed of 250 rpm using pentagonal shaped pin, exhibited ultimate tensile strength with a value of 365 MPa. The ultimate tensile strength of welded joints was found to be higher with the decrease in the tool rotational speed. The welding efficiency of joints was compared with the ultimate tensile strength of base metal; notably, welding efficiency values between 46 % and 80 % were achieved. Microstructural characterizations revealed that Al2Cu (θ phase), Al2CuMg (S phase), and AlCuFeMnSi, Al7Cu2Fe intermetallic particles were dispersed in the stir zone.