Friction Stir Welding Joints Research Articles

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.

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.

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.

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.

Enhanced material flow and joint formation of FSWed AA2024 by using protruding cylinder tool

The optimization mechanism of the protruding cylinder on the modified tool for the performance of friction stir welding (FSW) joints in 2024 aluminum alloy was investigated. The results indicate that the presence of a protruding cylinder on the modified tool significantly improves the surface quality of the weld, increases the width and area of the weld nugget zone(WNZ), and refines the grain size. Additionally, the size of the precipitated phases is reduced, and their distribution becomes more uniform, which in turn enhances the tensile strength and hardness of the joint. Furthermore, the presence of a protruding cylinder facilitated material flow, stabilized the welding process, and contributed to the formation of uniform welds.

The influence of laser-induced tempering on the microstructure and mechanical properties of 1500 MPa martensitic steel friction stir welded joints

A comprehensive comparison illustrates the role of laser technology in altering the macro morphology and microstructure of martensitic steel joints produced by friction stir welding (FSW). In this study, laser-induced tempering (LIT) was introduced to the FSW of 1500 MPa martensitic steel. The mechanism by which LIT enhanced the mechanical properties of the FSW joints was elucidated by comparing joints produced with and without LIT. Experimental findings revealed that LIT effectively eradicated tunnel defects under the same FSW parameters. Even with an increase in travelling speed from 60 mm/min to 120 mm/min, flawless welds were achieved under LIT conditions. At 500 rpm and 60 mm/min, the bottom of the stir zone (SZ) in conventional FSW (C-FSW) joint exhibited a ferrite and martensite dual-phase microstructure. In contrast, the SZ of the LIT-FSW joint had a fully martensitic structure. Moreover, LIT resulted in significant variations in the martensitic hierarchical structure within the SZ. LIT reduced ferrite distribution in the dual-phase zone, caused recrystallized ferrite to appear further from the SZ. The stress concentration in the dual-phase zone attributed to joint fracture. The improvement in the mechanical properties of martensitic steel FSW joints was explained by analyzing the correlation between the stress concentration factor and phase fraction. Additionally, the increase in traveling speed narrowed the dual-phase zone, triggered a constraint effect that led to a maximum ultimate tensile strength (UTS) increase from 986 MPa at 60 mm/min joint to 1142 MPa at 120 mm/min joint.

Notch fatigue behaviour of friction stir welded AA6061-T651 aluminium alloy joints: Role of microstructure, and residual stresses

The main objective of this study was to investigate the combined effect of microstructure and residual stresses on notch fatigue behaviour of friction stir-welded (FSW) AA 6061-T651 aluminium alloy joints. Two different microstructures of FSW joints were produced at different welding speeds. A completely reverse-rotating fatigue testing machine was utilized to investigate the fatigue properties of notched specimens. The test results showed that the notch fatigue strength of a welded joint made at a speed of 25 mm/min was 33 % of the welded joint’s yield strength and 23 % of its tensile strength. To understand the overall fatigue behaviour of the welded joints, fatigue data were further analyzed using the Basquin equation variables. Microstructure investigation using optical and orientation imaging microscopy, transmission electron microscopy, and X-ray diffraction analysis of the joints was analyzed and discussed. The microstructure complexity and the weld zone tensile residual stress significantly affect the welded joints fatigue behaviour. It was found that the notch fatigue properties of the joints were extremely sensitive to their microstructural characteristics and residual stresses. An increase in tensile residual stresses decreases the notch fatigue life of the welded joints. The results of electron backscattered diffraction analysis indicated that joints with a fine grain microstructure exhibit higher microstructural stability and less initial damage. A fractography investigation showed that joints with fine grain microstructure have increased crack resistance in stage I and lower crack propagation in stage II.

Effect of strain rates on stress corrosion sensitivity of 7085-T7452 thick-plate friction stir welding joint

The stress corrosion behavior of 7085-T7452 high-strength aluminum alloy base material (BM) and its friction stir welding (FSW) joints under varying strain rates during slow strain rate tensile (SSRT) was investigated. The results show that the stress corrosion sensitivity (ISSRT) of both the BM and FSW joints decreases with the increase of strain rate from 10−7 s−1 to 10−5 s−1. Moreover, the BM demonstrates lower ISSRT than the joints. The cracks in the joints exhibit dendritic paths along grain boundaries, with evidence of crack arrest marking (CAM) at localized areas in 3.5 wt% NaCl solution, suggesting both anodic dissolution and hydrogen-induced cracking simultaneously govern the propagation of stress corrosion cracks. There is the forced more test time in the slower strain rate, and the accumulation of stress corrosion coupling damage accelerates with the time, eventually leading to the greater degradation in the stress corrosion resistance and the higher ISSRT.

Effect of high pressure-low plasticity burnishing on the mechanical and microstructural behaviour of copper foil interlayered FSW aluminium alloys

Abstract This study delves into the impact of high pressure-low plasticity burnishing (HP-LPB) on the mechanical and microstructural behaviour of friction stir welding (FSW) joints, specifically involving AA5052 and AA6082 aluminium alloys. Notably, copper foil (CF) is introduced as a novel element in the HP-LPB process to enhance the weld strength. The experiments were conducted with the tool rotational speeds (TRS) of 1000, 1100, and 1200 RPM, each paired with the welding speeds (WS) of 20, 25, and 30 mm min−1, and tool tilt angle (TTA) of 0°, 1°, and 2°. Mechanical behaviour is assessed through tensile testing along with microhardness measurements, revealing the advantages of HP-LPB with CF in enhancing joint strength and toughness. The microstructural analysis reveals the dissolution of precipitates, highlighting the influential role of copper foil in the improvement of joint efficiency. From the weld without a CF interlayer, a maximum tensile strength of 188 MPa was achieved at a TRS of 1200 RPM, WS of 25 mm min−1 and TTA of 2°. The post-processed FSW sample interlayered with copper foil, exhibited an improvement in joint efficiency by 87% at the optimum process parameter. This research demonstrates that the use of copper foil interlayers combined with HP-LPB treatment can substantially enhance the mechanical properties and structural integrity of FSW aluminum alloys, offering a valuable solution for advanced industrial applications.

Structure-property correlation for friction stir welded joints of 2219Al alloys microalloyed with Cd

Present study aimed at experimental investigation of microstructural evolution, microhardness profile, tensile and impact properties of friction stir welded (FSW) joints of 2219Al alloys microalloyed with varying (up to 0.1 wt%) Cd contents. FSW was performed on the cast and homogenized alloys. Microstructural analysis from weld line up to base metal, identified three sequential heat affected weld zones having separate grain morphologies, namely Weld Nugget Zone (WNZ), Thermo-Mechanical Affected Zone (TMAZ) and Heat Affected Zone (HAZ). Vickers microhardness value increased from weld line towards the WNZ, then decreased towards the TMAZ, and finally increased through HAZ towards the base metal, which exhibited higher hardness compared to all the heat affected weld zones. Microhardness, yield and tensile strengths of the FSW joint of 2219Al alloy increased, due to microalloying with 0.06 wt% of Cd contents, which was attributed to continuous grain refinement. While tensile ductility and toughness, and impact toughness of the welded joint reduced, resulting from trace additions of Cd. Investigated alloys retained significant mechanical strength, ductility and toughness, on the respective joints, following to the FSW operation. Cd was observed to be a potential microalloying element to control the microstructure, refine grain size and improve mechanical strength and hardness of the welded joint of 2219Al alloy. Present experimental results established a structure-property correlation, in order to validate potential application of FSW technique on investigated 2219Al alloys with trace additions of Cd, to attain desirable weld-quality avoiding welding imperfections.

Microstructure, MAO performance, interfacial characteristics and corrosion behavior of FSW joint of Al–Mg-Sc alloy

The microstructure evolution, micro-arc oxidation (MAO) performance, and corrosion behavior of Al–Mg-Sc alloy friction stir welded (FSW) joint were investigated. The microstructure observations indicated that compared with the base metal (BM), the stirring zone (SZ) and thermo-mechanical affected zone (TMAZ) showed notable grain defects and an enormous number of high angle grain boundaries (HAGBs). Additionally, a more conspicuous presence of non-uniform recrystallized grains and HAGBs was noticed in the thickness direction within the SZ. FSW process induced the precipitation of Al3Mg2 (β phase) at grain boundaries in the heat-affected zone (HAZ) of joint. The microstructural changes and precipitation induced by the FSW process influenced the electrical conductivity, resulting in the differences in micro-arc discharge in various zones of the FSW joint in MAO process, which in turn affected the thickness, porosity, and corrosion resistance of MAO ceramic film. HRTEM observation suggested that a transition layer composed of nanocrystalline and amorphous Al2O3 with average thickness of 2–4 nm was found at the film/substrate interface. Electrochemical tests suggested that a heterogeneous structure in various regions of FSW joint resulted in varying susceptibility to localized corrosion. HAZ/TMAZ had the worst anti-corrosion performance. After MAO treatment, the anti-corrosion performance of SZ and HAZ/TMAZ in FSW joint was significantly improved, especially SZ.

Influence of Bobbin Tool on Microstructure, Residual Stress, Tool and Corrosion Analysis of Al 6063 Alloy Friction Stir Welded Joint

Influence of Bobbin Tool on Microstructure, Residual Stress, Tool and Corrosion Analysis of Al 6063 Alloy Friction Stir Welded Joint

Eliminating heat-affected zone of nuclear heat-resistant steel joint via low-temperature friction stir welding

Ferritic/martensitic (F/M) heat-resistant steels are one of the most promising candidate materials applied in core fuel assemblies such as cladding and packaging in nuclear reactors, but their weldments with high performance especially the creep properties were difficult to obtain by conventional welding methods due to the formation of heat-affected zone (HAZ) and rapid dissolution of precipitates. Here we successfully averted the formation of HAZ by reducing the heat input during welding to improve the structure-property synergy of a 12Cr-F/M steel joint via a low-temperature friction stir welding (FSW) technology. Complex microstructure regions consisting of stirred zone (SZ), fine-grained HAZ and inter-critical HAZ were generated in the traditional FSW joint with a high heat input, while only SZ and thermo-mechanically affected zone were found in the low-temperature FSW joint with a peak temperature between the Ac3 and Ac1 temperature. Under dynamic recrystallization at the α+γ two-phase region, ultrafine ferrite and martensite were generated and large amounts of precipitates were retained, giving rise to the greatly improved microhardness and superior tensile strength and impact toughness on par with that of the base metal. This work recommends a feasible technique to produce high-performance heat-resistant steel joints for lengthening the service life of nuclear reactors.

Investigation on effects of nano-reinforcement on the mechanical properties, fatigue, and microstructural analysis of dissimilar AA6061- Mg AZ31B weld joints

Weld joints have been subject to substantial improvement in mechanical durability and wear resistance in recent years. This research work challenge can be answered by incorporating nano-materials into the weld zone. Mechanical and metallurgical aspects of friction stir welded (FSW) butt joints made of AA6061 aluminum and Mg AZ31B alloys have been examined in this work, both with and without the use of naturally derived biochar nanoparticles. The biochar particle was extracted from rice husk. Throughout the whole weld joint manufacturing process, a tool with a rotational speed of 1400 rpm, a welding speed of 40 mm min−1, and a tapered pin profiled tool were employed. During the joint fabrication process, the constant axial load of 7 kN, plunge depth of 0.2 mm, and constant dwell time of 0.3 s were also maintained. In order to improve the mechanical attributes of the weld joints, different wt% of biochar such as 1%, 2%, and 3%, were applied at the interface region of the weld joints. The experimental results revealed that the percentage of reinforced nano-materials plays a significant effect in improving the weld joint qualities. The testing results of reinforced friction stir-welded joint qualities were compared to those of simple friction stir welded joints made without and with adding the nanoparticles. The best results were obtained when 2 wt% of biochar particles was added to the weld interface region. The presence of biochar nano-particles, in addition to their contribution to increased grain refinement in the weld nugget region, was also seen in the region. It was discovered that the event distribution of particles at the nugget zone significantly enhanced the mechanical and wear resistance qualities of the weld joints that were manufactured. The optical microscope was used to analyze the microstructures in the weld nugget region, and a scanning electron microscope (SEM) was utilized to examine the fracture analysis of the tensile samples. The presence of 2 wt% biochar particles in the weld nugget region resulted in a considerable increase in the mechanical characteristics of the weld connections. The ultimate tensile strength, hardness, and yield strength of the weld nugget results 197 MPa, 173 HV, 163 MPa. Overall, when compared to the qualities of the base material and plain weld joints. The mechanical properties and wear resistance of the weld joints have improved significantly. When biochar particles were used as reinforcement particles during the fabrication phase of the joint, a mechanism for pinning was observed in the weld microstructure.

Research on friction stir welding technology of urban rail transit car body

Abstract In this paper, the principle and technical characteristics of friction stir welding are introduced. According to the form of the side wall of urban rail transit vehicles, a friction-stir welding joint structure with convex is proposed. In order to verify the performance of the joint, the joint tensile strength test and the static strength test of the car body are carried out. The results show that the designed friction stir welding joint has high smoothness and excellent performance, fulfilling the requirements for the standard EN12663.

Failure Analysis of Cu-DHP Joining Processes: A Comparative Study of FSW and SFSW Techniques

Abstract This article presents a failure analysis conducted on specimens extracted from 2.5 mm sheets of Cu-DHP (Cu99), which were joined using friction stir welding (FSW) and submerged friction stir welding (SFSW) processes. To evaluate the performance of the welded joints, destructive and non destructive tests, including tensile tests were performed. Additionally, morphologic analysis using scanning electron microscopy (SEM) combined with energy dispersive X-ray (EDX) and fractography investigations were carried out on the samples. The results of experimental research show refined microstructures both for FSW and SFSW welding. Improved mechanical properties have been obtained for SFSW welding, compared to FSW. SFSW specimens demonstrates superior tensile strength and a higher hardness compared to FSW specimens, by performing joining process underwater. The fracture surfaces of the tensile test specimens from the base material (BM), FSW and SFSW joints, revealed the ductile fracture mechanism of the joints. EDX analysis confirms compositional integrity of the base and welded metals. Results highlights suitability of the FSW and SFSW processes for joining of copper Cu-DHP.

Effect of Traveling Speed on Microstructure and Stress Corrosion Cracking of ATZ511 Magnesium Alloy Friction Stir Welded Joints

Effect of Traveling Speed on Microstructure and Stress Corrosion Cracking of ATZ511 Magnesium Alloy Friction Stir Welded Joints

Effect of corrosion environments on the mechanical properties of friction stir welded aluminum alloy AA3003

The article presents an experimental study on the corrosion resistance of the 3003 Aluminium alloy Friction Stir Welded (FSW) joint in different working environments. Three types of corrosive media at different temperatures were tested to see how they affected the FSW joint mechanical properties. The media were sodium chloride, hydrogen chloride, and ethylene glycol. In parallel with the study of the effect of temperature, static tensile tests were carried out on specimens taken perpendicular to the welding direction. Also, micro-hardness profiles were used to determine the influence of the parameters studied on the various weld zones. Finally, the effect of the most aggressive corrosive medium, temperature, and the inclusion of ethylene glycol on the crack propagation resistance of an FSW joint were studied. Fatigue-propagation tests at constant stress amplitude were carried out to understand what affects the fatigue crack propagation of welded joints after corrosive attack. The results showed that uniform and pitting corrosion were combined to cause FSW joint surface degradation. Corrosion damage does not appear to alter yield strength and ultimate stress values. However, FSW joints show a significant degradation in mechanical properties with increasing temperature and with the aggressiveness of the corrosive medium. The inclusion of ethylene glycol was found to delay the rate of crack propagation during testing, leading to an improvement in the service life of pre-corroded FSW joints.

Microstructure and cryogenic mechanical properties of dissimilar friction stir welding joints between nitrogen-alloyed CoCrFeMnNi high-entropy alloy and high-manganese austenite steel

The microstructures and cryogenic mechanical properties of dissimilar friction stir welding (FSW) joints between nitrogen-alloyed CoCrFeMnNi high-entropy alloys (HEAs) and Fe–32.1Mn–7.5Cr–0.6Mo–1.2 N steel were investigated. The results reveal that defect-free dissimilar joints can be achieved through FSW. Furthermore, the grains of nitrogen-alloyed CoCrFeMnNi HEAs in the stir zone of the dissimilar joint are significantly more refined than those of Fe–32.1Mn–7.5Cr–0.6Mo–1.2 N steel. Joint efficiency at room and low temperature both exceed 90% of the base metal. Moreover, the cryogenic yield and ultimate strength of the dissimilar joints are higher than those recorded at room temperature. The fracture position is at the heat-affected zone of HEAs under two temperature conditions.

Effect of Different Welding Speeds on Microstructure and Properties of Bobbin Tool Friction Stir Welded Joints of T2 Pure Copper

Effect of Different Welding Speeds on Microstructure and Properties of Bobbin Tool Friction Stir Welded Joints of T2 Pure Copper