Friction Stir Research Articles

Failure Analysis of AA 7075 Joints Processed by FSW and SFSW

This paper presents a failure analysis of AA 7075 Aluminium 7075 joints processed by Friction Stir Welding (FSW) and Submerged Friction Stir Welding (SFSW) techniques. AA 7075 is a high-strength aluminium alloy commonly used in aerospace, automotive, and other industries due to its excellent mechanical properties. Understanding the failure mechanisms in these joining processes is essential for ensuring the structural integrity and reliability of AA 7075 joints. The study investigates the failures encountered in FSW and SFSW joints of AA 7075. Macroscopic and microscopic examinations are conducted to analyse the root causes of these failures. Macroscopic observations include visual inspection, dimensional measurements, and identification of fracture locations. Microscopic investigations utilize techniques scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) to examine the microstructure, fracture surfaces, and elemental composition of the failed joints. Based on the failure analysis findings, recommendations are provided to enhance the quality and reliability of AA 7075 joints processed by FSW and SFSW. The results of this failure analysis contribute to the understanding of AA 7075 joining processes using FSW and SFSW methods. By identifying the failure mechanisms and proposing preventive measures, this research aids in improving the quality and performance of AA 7075 joints, thereby ensuring the integrity and reliability of joined structures in industries that rely on aluminium alloys for critical applications.

Failure Analysis of Al 6082 Joints Processed by FSW and SFSW

This paper presents a failure analysis of Al 6082 joints processed by Friction Stir Welding (FSW) and Self-Reacting Friction Stir Welding (SFSW) techniques. Aluminium alloy Al 6082 is commonly used in structural and automotive applications due to its excellent strength, corrosion resistance, and weldability. The study focuses on investigating the failures encountered in FSW and SFSW joints of Al 6082. Macroscopic and microscopic examinations are conducted to analyse the root causes of these failures. Macroscopic observations include visual inspection, dimensional measurements, and identification of fracture locations. Microscopic investigations utilize techniques such as optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) to examine the microstructure, fracture surfaces, and elemental composition of the failed joints. The results of this failure analysis contribute to the understanding of Al 6082 joining processes using FSW and SFSW methods. By identifying the failure mechanisms and proposing preventive measures, this research aids in improving the quality and performance of Al 6082 joints, thereby ensuring the integrity and reliability of joined structures in industries that rely on aluminium alloys for critical applications.

Progress in Additive Manufacturing of High-Entropy Alloys

High-entropy alloys (HEAs) have drawn substantial attention on account of their outstanding properties. Additive manufacturing (AM), which has emerged as a successful approach for fabricating metallic materials, allows for the production of complex components based on three-dimensional (3D) computer-aided design (CAD) models. This paper reviews the advancements in the AM of HEAs, encompassing a variety of AM techniques, including selective laser melting (SLM), selective laser sintering (SLS), selective electron beam melting (SEBM), directed energy deposition (DED), binder jetting (BJT), direct ink writing (DIW), and additive friction stir deposition (AFSD). Additionally, the study discusses the powders and wires utilized in AM, the post-processing of AM-processed HEAs, as well as the mechanical and corrosion properties of these alloys. The unique ultra-fine and non-equilibrium microstructures achieved through AM result in superior mechanical properties of HEAs, like improved strength and ductility. However, research regarding certain aspects of HEA AM, such as fatigue properties and creep deformation behavior, is still relatively scarce. Future research should focus on overcoming the existing limitations and exploring the potential of HEAs in various applications.

Experimental investigation and parametric optimization of FSW of mineral-reinforced AA6061 matrix composite

Abstract In this work, rutile reinforced AA 6061 matrix composites were joined using friction stir welding and the process variables were optimized using Taguchi L27 orthogonal design of experiments. The rotational speed, axia force and tool tilt angle were the parameters taken into consideration. The optimum process variables were determined with reference to tensile strength, impact strength and hardness of the joint. The predicted optimal value of output responses were confirmed by conducting the confirmation run using optimum parameters. The optimal process variables combination values that resulted in improved mechanical properties were observed at a tool rotational speed of 1400 rpm, a tool tilt angle of 2 degree, and an axial force of 3KN. Scanning electron microscopy (SEM) analysis were used to probe the microstructures.

Refill Friction Stir Spot Welding of an Al-Li Alloy: The Effects of Rotating Speed and Welding Time on Joint Microstructure and Mechanical Properties

In this work, 2060 Al-Li alloy was joined by refill friction stir spot welding (RFSSW). The effects of the tool’s rotating speed and welding time on the microstructure and mechanical properties of the welded joints were studied. The results showed that joints without defects can be obtained within a wide range of welding parameters. Tiny voids were formed when using a low rotating speed of 1600 rpm, and incomplete refilling was obtained when using a short welding time of 1 s. Increasing the rotating speed from 1600 to 2000 rpm increased the grain size of the stir zone (SZ). When using a short welding time of 1 s, the grains of the SZ were not completely broken with high orientation differences in the grains. Higher hardness was obtained in the SZ when using a lower rotating speed and shorter welding time. Increasing the rotating speed increased the joint strength, while short and long welding times decreased the joint strength.

Comparative study on microstructure characteristics and mechanical properties of dissimilar friction stir welded aluminum alloy using single and double rotating shoulder tools

Comparative study on microstructure characteristics and mechanical properties of dissimilar friction stir welded aluminum alloy using single and double rotating shoulder tools

Multi-Objective Optimization of Friction Stir Processing Tool with Composite Material Parameters

Compared to base aluminum alloys, the surface composites of aluminum alloys are more widely used in the automotive, aerospace, and other industries. The ability to yield enhanced physical properties and a smoother microstructure has made friction stir processing (FSP) the method of choice for developing aluminum-based surface composites in recent times. In this work, the Goal Programming (GP) approach is adopted for the Multi-Objective Optimization of FSP processes with three Artificial Intelligence (AI)-based metaheuristics, viz., Artificial Bee Colony (ABC), Particle Swarm Optimization (PSO), and Teaching–Learning-Based Optimization (TLBO). Three parameters, copper percentage (Cu%), graphite percentage (Gr%), and number of passes, are considered, and multi-factor non-linear regression prediction models are developed for the three responses, Tool Vibrations, Power Consumption, and Cutting Force. The TLBO algorithm outperformed the ABC and PSO algorithms in terms of solution quality and robustness, yielding significant improvements in tool life. The results with TLBO were improved by 20% and 14% compared to the PSO and ABC algorithms, respectively. This proves that the TLBO algorithm performed better compared with the ABC and PSO algorithms. However, the computation time required for the TLBO algorithm is higher compared to the ABC and PSO algorithms. This work has opened new avenues towards applying the GP approach for the Multi-Objective Optimization of FSP tools with composite parameters. This is a significant step towards toll life improvement for the FSP of composite alloys, contributing to sustainable manufacturing.

Investigation on Fractographic and Microstructure Evolution in AA7075/ZrO2/G Multilayer Laminated Composite Fabricated Using Friction Stir Additive Manufacturing Process

Investigation on Fractographic and Microstructure Evolution in AA7075/ZrO2/G Multilayer Laminated Composite Fabricated Using Friction Stir Additive Manufacturing Process

Comparative Study Between Friction Stir Welding and Tungsten Inert Gas Welding Processes

This study compares the properties of the aluminium alloy welded joints prepared by friction stir welding (FSW) to that of tungsten inert gas (TIG). It concentrated on the microstructure, hardness, corrosion resistance, and wear resistance. It has been found that the joints prepared by FSW have fine microstructure while coarse grains microstructure was obtained for joints produced by TIG welding. Also, the lowest Rockwell hardness measured at the centre of the welding line is 52 for joints prepared by FSW and 46 for ones produced by TIG welding. For corrosion resistance the reslt of tests indicated that the welded joints of the TIG process had higher corrosion resistance, the mass loss after 72 hours is 0.2519 grams from TIG joints and it is about double in the case of FSW joints (0.5263 grams). However, TIG joints have lower wear resistance compared to joints produced by the FSW process. It seems that the grain size of the welded joints, in these two considered welding processes, has a great effect on the investigated properties.

Investigation of Joinability Of 25% Recycled Al6016 Sheets By Friction Stir Butt Welding At Different Tool Rpm

In this study, 25% recycled 2 mm thick Al6016 sheets used in the production of automotive body and chassis parts were used. They were joined in the butt position using different tool speeds on the mold milling machine. The tool tip was selected as 2379 quality steel and the surface hardness was increased to 62-64 HRC. The sinking tip was designed as a conical geometry. In the joints, 400 mm/min welding progress speed, 1.8 mm tool tip immersion depth, 15 mm shoulder width and 90o tool inclination angle were kept constant. The rotation speed of the stirring tip was determined as 600 rpm, 1200 rpm, 1800 rpm, 2400 rpm, 3000 rpm, 3600 rpm as variable parameters. Heat inputs were calculated according to variable speeds. Samples taken from the welded joint with the friction stir method were examined with tensile, bending and hardness tests. Macro and micro images were examined and the fracture surfaces were compared. While the highest tensile strength at 400 mm/min feed speed was determined as 214 MPa at 1800 rpm and the lowest value was determined as 83 MPa at 600 rpm, no fracture was observed at 2400 and 3000 rpm as a result of the bending test and it was successful. The highest results of the hardness values of the joint area were measured as 97.4 Hv at 600 rpm rotation speed. It was determined that penetration occurred in the macro structure at all rpm speeds. When the micro images were examined, it was seen that the grain structure thinned from the base metal to the joint area.

A quasi-in-situ EBSD study on the effect of abnormal grain growth on mechanical properties of the friction-stir welds of 2219 aluminum alloy

Abnormal grain growth appears in the friction stir welds of 2219 aluminum alloy during solution treatment. In this study, the effect of abnormal grain growth on the mechanical properties of the friction-stir welds of 2219 aluminum alloy was investigated, combined with the quasi-in-situ EBSD experiment. The results show that the solution-treated welds with coarse grains have lower tensile strength and elongation than the base metal, but the fracture mode remains the same. According to the bulging testing results, the limiting dome height and ultimate bulging rate of the solution-treated tailor-welded blanks are 85% and 77% of the base metal, respectively. After T6 treatment, the mechanical properties of the weld with coarse grains, especially the elongation after fracture, further decrease compared to the base metal. The stress concentration caused by abnormal grains is the main reason for the decreased mechanical properties of the solution-treated weld. There are copper-poor zones along the grain boundaries because of the rapid precipitation at grain boundaries during T6 treatment. Therefore, abnormal grain growth makes intergranular cracks easier to initiate and propagate, which results in the decrease of elongation of the T6-treated weld.

An effective path planning approach for robot welding considering redundant kinematics

Robot welding with redundant kinematics demands precise coordination of the welding path and redundant axis motion for stable operation. This paper introduces an effective G3 continuous path planning approach for a 6-DOF friction stir welding robot, integrating redundant axis motion to enhance welding stability and quality. The method encompasses a two-pronged strategy: a five-axis path corner smoothing technique and a motion synchronization strategy. Initially, a robust toolpath preprocessing algorithm is presented to mitigate curvature extremities of the inserted smoothing curves within predefined error limits. Subsequently, leveraging G3 continuity criteria, a B-spline-based smoothing method is advanced for refining tool position and orientation paths, with an analytical determination of spline control points facilitated by an explicit smoothing error expression. An effective motion synchronization technique is then proposed, which formulates the tool position, tool orientation, and redundant axis path as explicit functions of the position path arc length. The effectiveness of the proposed method is demonstrated through simulations and experiments on a robot welding platform, with the integration of a jerk-continuous feedrate profile for smooth motion execution. The findings indicate a significant improvement in robotic welding quality by integrating the proposed path planning method with existing workpiece posture optimization techniques.

Experimental and numerical analysis of mixed mode bending of adhesive-bonded and hybrid honeycomb core sandwich structures

This study investigates the potential of a hybrid joining method, called friction stir spot welding with disc and adhesive bonding (FSSW_D_AB), for bonding honeycomb core sandwich structures, offering an alternative to traditional adhesive bonding (AB) sandwich structures. The research focuses on the manufacturing of these hybrid joints and evaluating their performance compared to conventional adhesive bonding (AB) methods. Mixed Mode Bending (MMB) tests were performed to assess the mechanical behaviour of the joints under different loading conditions. Additionally, numerical analysis using cohesive zone modeling (CZM) was performed using both a honeycomb core with a cohesive layer and the homogenized core with an equivalent cohesive layer. The study reveals that the hybrid joining method significantly enhances the performance of honeycomb sandwich structures. The good agreement between the numerical predictions and the experimental results for all types of joints showed the usefulness of the proposed numerical model. However, the FEM-based stress and damage analyses of the joints provided crucial results on normal and shear stress distributions and delamination.

Effect of theoretical volume fraction (TVF) of reinforcements on Al5083/SiC and Al5083/ZrB2 surface composites produced by friction stir processing

This study focuses on the effects of theoretical volume fraction (TVF) on the microstructure and mechanical properties of silicon carbide (SiC) and zirconium diboride (ZrB2) ceramic reinforced Al5083 surface composites (SC). Al5083-H111 was used as the base material (BM), SiC and ZrB2 were used as reinforcement materials, and TVFs were determined as 5, 10, 15, and 20% for SCs produced by the friction stirring process (FSP). Macrostructure, microstructure, X-ray diffraction (XRD) analysis and mechanical properties such as microhardness, tensile strength (UTS), and wear behaviour were characterised. When the TVF and AVF values of SiC and ZrB2 particles were compared, it was found that the AVFs were lower than the TVFs. Significant decreases in the changes in the SZ areas of SiC and ZrB2 particle SCs were detected depending on the reinforcement size. In the time-dependent axial load graphs of SiC and ZrB2 reinforced samples, load values ranging from 7800 to 8200 N were obtained and it was determined that these values were sufficient for friction heat, hydrostatic pressure, and plasticization in FSP. As a result of mechanical characterisation processes, the microhardness values and wear rates of ZrB2 reinforced SCs in the stir zone (SZ) were higher than SiC reinforced SCs. When the reinforcement particles were compared, it was observed that ZrB2 reinforced SCs exhibited higher microhardness and wear resistance than SiC reinforced SCs. As a result of all tests and investigations, it was determined that the ideal TVFs were 15% for SiC reinforced SCs and 5% for ZrB2 reinforced SCs. The microhardness value of ZrB2 reinforced SC with 20% TVF was 119.6 HV, while the UTS and volume loss values of ZrB2 reinforced SC with 5% TVF were found to be the highest values with 305.86 MPa and 1.83 mm3, respectively. Compared to BM, these values showed significant improvements in mechanical test results, especially in wear behavior. The results obtained showed an improvement of 55% in microhardness, 3.3% in UTS values, and 309% in wear behavior.

Effect of friction stir processing on the mechanical properties of gas metal arc welded AISI 409 L stainless steel plate

Effect of friction stir processing on the mechanical properties of gas metal arc welded AISI 409 L stainless steel plate

Effect of Hybrid Addition of Boron Nitride and Vanadium Carbide on Microstructure, Tribological, and Mechanical Properties of the AA6061 Al-Based Composites Fabricated by FSP

This work investigates the impact of friction stir processing (FSP) on the microstructure and mechanical characteristics of AA 6061 alloy and its composites, which are strengthened with boron nitride nanoparticles and vanadium carbide microparticles. Composite samples were created using different proportions of reinforcing particles, including mono and hybrid composites. The efficacy of FSP as a technological method for enhancing the grain size of AA 6061 alloy and its composites has been proven. Adding reinforcing particles led to enhanced grain refinement, especially when using VC particles, which demonstrated greater efficacy than BN particles; thus, mono composite AA6061/VC shows the highest percentage reduction (94.29%) in grain size. Hybrid composites with a higher concentration of VC particles exhibited a more symmetrical microhardness profile. The microhardness of hybrid composites with a larger concentration of VC particles (40 vol.%BN + 60 vol.%VC) shows the most significant enhancement, with an increase of 51.61%. The Young’s and shear modulus of all composite samples processed by (FSP) had greater values than the wrought AA 6061 alloy. The investigated composite samples, especially 60% BN and 40% VC, enhanced the tribological properties of AA6061 and reduced the wear rate by about 52%. The observed characteristics may be due to BN and VC particles in the hybrid compost. This is because these particles effectively prevent grain elongation and inconsistent movement. This is because reinforcing particles can be tailored to have specific properties for specific applications.

Effects of multi-objective optimization of friction stir welding process parameter on mechanical and ballistic properties of AA5754 aluminum alloy

Friction stir welding (FSW) is a solid-state welding process commonly used to join similar and dissimilar aluminum alloys. This study aims to investigate multi-criteria decision-making, multi-objective optimization, Taguchi’s L9 design of experiments, and the technique for order preference by similarity to the ideal solution (TOPSIS) to evaluate the effects of various FSW parameters specifically, welding speed, feed, and axial load on the mechanical properties of AA5754 aluminum alloy. Following the enhancement of the welding parameters, an analysis of variance (ANOVA) was performed to identify the most influential parameter in the FSW process. The findings indicated that tensile strength, impact strength, and microhardness were predominantly affected by welding speed (94.82%), feed (3.12%), and axial load (1.32%), respectively. With a hexagonal tool and optimal process parameters of feed (20 mm/min), axial load (7 kN), and speed (1200 rpm), the joint obtained the maximum microhardness (81 HV), impact strength (3.01 J/mm2), and tensile strength (163.89 MPa). The microstructure and X-ray diffraction analyses indicated that the crystals were tiny, with higher dislocations in the stir zone, indicating improved mechanical properties. In the FSW joint, dimples and voids were observed on the tensile and impact fracture surfaces. Finally, the ballistic properties of the optimized AA5754 FSW joint were determined. An asymmetric V-shaped deformation profile was observed around the impact point, with the highest deformation at the center. An increase in impact velocity from 134 to 187.6 m/s did not result in significant differences in the deformation of the FSW joint. The fracture surfaces of ballistic-tested friction stir welded joints exhibited shear regions and localized bands.

Residual Stresses in Welded Joints Made by Friction Stir Welding

Residual Stresses in Welded Joints Made by Friction Stir Welding

Aluminum/steel dissimilar material with high interfacial strength manufactured by additive friction stir deposition

Dissimilar metallic materials find broad applications owing to the possibility of integrating multiple functions. However, the joining interface is a vulnerable site for failure in service. The design of high-strength bonding of dissimilar materials has been urgently needed. This study showed that a combination of additive friction stir deposition coupled with post-processing annealing enables the formation of a continuous Mg/O-enriched amorphous layer dotted with nano-rivet structures at the aluminum (Al)/steel interface. As a result, a high bonding strength (138.1 MPa) of Al/steel was achieved. We clarify the formation of discontinuous nano-rivet intermetallic compounds thanks to the AFSD-induced severe plastic deformation and local chemical reaction upon annealing, and we demonstrate the highest bonding strength is achieved at the size of nano-rivet compounds of ~200 nm and the aspect ratio ~ 0.5. Our findings provide a simple but versatile strategy to reverse the adverse effects of intermetallic compounds on the interface strength of dissimilar materials.

Performance evaluation of modified refill friction stir riveting process on AA7075-T6 stacks with largely unequal thicknesses

Aluminium alloy sheets with varying thicknesses have been intensively applied to thin-walled structures in the transportation industry. However, it is still a challenging work to assemble lightweight stacks with largely unequal thicknesses (i.e., A thick top sheet but a thin bottom sheet). In this research, a modified refill friction stir riveting (RFSR) technique was developed to connect AA7075-T6 aluminium alloy stacks with 3.2 mm top sheet and 1.0 mm bottom sheet. The joint geometric quality, microstructures, thermal softening state and tensile strength were experimentally investigated. The results reveal that the modified RFSR approach is capable of joining aluminium alloy stacks with largely unequal thicknesses. A reliable mechanical interlock was generated between the rivet and bottom sheet, benefiting from the drum-shaped buckling behaviour of the rivet shank in the modified RFSR process. Thanks to the high pressure in the rivet cavity and high rotation speed of top sheet material locked on the rivet shank, solid-state bonding with a high quality was always generated between the trapped top sheet and bottom sheet at varying feed rates. The feed rate demonstrated a strong controlling effect on the joint formation quality by altering the buckling degree of the rivet shank. Benefiting from the minor insertion depth of the rivet shank into the bottom sheet, the structural integrity of the thin bottom sheet was successfully retained. The maximum lap-shear force of studied joints was 4.78 kN with the feed rate of 1.0 mm/s, whilst the maximum cross-tension force was 1.49 kN with the feed rate of 4.0 mm/s.