Conventional Friction Stir Welding Research Articles

Control of the Weld Heterogeneity by Using a Novel Counter Variable Pin Shoulder Rotation Friction Stir Welding: A Simulation and Experimental Study

Abstract Friction stir welding (FSW) produces inhomogeneous mechanical and metallurgical properties in the weld, which further require post-weld processing to control the heterogeneity. In the present study, the heterogeneity in the weld is reduced through counter-variable rotation friction stir welding (CVRFSW). The material flow and temperature distribution significantly affect the inhomogeneity of the FSWed properties which has been studied by developing a three-dimensional Lagrangian method-based viscoplastic model. The material flow, strain rate, and temperature distribution in conventional FSW (CFSW) and CVRFSW are studied quantitatively. The study revealed that CVRFSW improved joint strength and reduced the inhomogeneity of temperature, strain, and hardness. At a 10% lower shoulder speed than a pin, the weld strength improved by 16%. The simulation predicted that the temperature difference between the advancing side (AS) and the retreating side (RS) was 36 °C in CFSW, which was reduced to 8 °C in CVRFSW. Material deformation in CVRFSW occurred at a strain rate more than twice that of CFSW, and the asymmetry of strain rate between AS and RS reduced to one-fifth. Microstructures and their orientations of the welds were studied in detail. These findings contribute to the understanding of CVRFSW processes for enhanced weld quality and mechanical performance for industrial applications.

Friction stir welding and processing of pipes: a status report on joining, materials, and industry applications

Purpose The purpose of this paper is to compile a comprehensive status report on pipes/piping networks across different industrial sectors, along with specifications of materials and sizes, and showcase welding avenues. It further extends to highlight the promising friction stir welding as a single solid-state pipe welding procedure. This paper will enable all piping, welding and friction stir welding stakeholders to identify scope for their engagement in a single window. Design/methodology/approach The paper is a review paper, and it is mainly structured around sections on materials, sizes and standards for pipes in different sectors and the current welding practice for joining pipe and pipe connections; on the process and principle of friction stir welding (FSW) for pipes; identification of main welding process parameters for the FSW of pipes; effects of process parameters; and a well-carved-out concluding summary. Findings A well-carved-out concluding summary of extracts from thoroughly studied research is presented in a structured way in which the avenues for the engagement of FSW are identified. Research limitations/implications The implications of the research are far-reaching. The FSW is currently expanding very fast in the welding of flat surfaces and has evolved into a vast number of variants because of its advantages and versatility. The application of FSW is coming up late but catching up fast, and as a late starter, the outcomes of such a review paper may support stake holders to expand the application of this process from pipe welding to pipe manufacturing, cladding and other high-end applications. Because the process is inherently inclined towards automation, its throughput rate is high and it does not need any consumables, the ultimate benefit can be passed on to the industry in terms of financial gains. Originality/value To the best of the authors’ knowledge, this is the only review exclusively for the friction stir welding of pipes with a well-organized piping specification detailed about industrial sectors. The current pipe welding practice in each sector has been presented, and the avenues for engaging FSW have been highlighted. The FSW pipe process parameters are characteristically distinguished from the conventional FSW, and the effects of the process parameters have been presented. The summary is concise yet comprehensive and organized in a structured manner.

Improving bonding strength of medium-thick Al-Cu dissimilar joint by a novel splat cooling assisted double side friction stir welding

To obtain a high-strength medium-thick Al-Cu dissimilar joint, a novel splat cooling assisted double side friction stir welding (SDS-FSW) is proposed. The microstructure and tensile properties of conventional double-side friction stir welding (DS-FSW) and the novel SDS-FSW joints under optimal welding parameters are systematically compared, it shows that the utilization of in-process splat cooling significantly reduces the welding peak temperature and the high-temperature dwell time. The in-process splat cooling causes significant grain refinement in the welding nugget zone (WNZ) of the Al-Cu dissimilar SDS-FSWed joint, it exists the lower recrystallization fraction and the higher KAM value. Although both DS-FSW and SDS-FSW joints fracture at the Al-Cu interface, the DS-FSW joint represents a brittle fracture characteristic, while the SDS-FSW joint represents a mixed ductile-brittle fracture mode. Under the drive of the mechanical stirring of the tool and the welding thermal cycle, the aluminium atoms and copper atoms diffuse to the copper base material and aluminium base material, respectively. Since copper diffuses in aluminium at a higher diffusion rate than aluminium diffuses in copper, and the solubility of copper in aluminium is much smaller than that of aluminium in copper, thus the Al2Cu becomes the first phase with the nucleation and growth. As the welding temperature and time continue to increase, Al2Cu reaches the supersaturation state, and the Al4Cu9 phase is produced between the Cu (Al) and the Al2Cu phase. In the end, the interface forms the stable double-layer IMCs structure (Al2Cu/Al4Cu9). The optimal tensile strength of the SDS-FSWed joint is 159 MPa, which is increased by 42% compared to the DS-FSWed joint at the same welding parameter. This was mainly because in-process splat cooling contributed to forming a thinner IMCs layer at the A-Al-Cu interface. It reveals that the application of in-process splat cooling is a versatile method to thin the IMCs layer at the Al-Cu medium-thick DS-FSW process.

Double side friction stir Z shape butt lap welding of dissimilar titanium aluminum alloys

Achieving excellent mechanical performance of medium-thick Ti/Al dissimilar joints is important in many industrial applications. However, due to the inherent heat generation mode associated with conventional friction stir welding (FSW), it is impossible to achieve sound medium-thick Ti/Al dissimilar joints. Although double side friction stir welding (DS-FSW) has been reported to solve the problems of conventional FSW. The inherent problems of forming hook structure and interface cracking in the center of the DS-FSW joints significantly weaken the joint performance. Therefore, an innovative double-side friction stir Z shape butt-lap welding (DS-FSZW) process was proposed to eliminate the inherent problems of conventional DS-FSW. The research objective of this work was to reveal the physical mechanisms of the novel DS-FSZW by the combination of numerical simulation and experimental characterization for optimizing the welding parameters. The influence of tool shoulder diameter on the heat generation, heat transfer, plastic material flow, microstructure evolution and mechanical properties of medium-thick dissimilar Ti/Al DS-FSZW joint has been systematically studied. The results indicate that the innovative DS-FSZW process lowers the axial force compared to the conventional DS-FSW, and the centerlines of the first and the second sides welds are staggered. Those are beneficial to inhibiting the cracking of the first-side weld at the interface. In addition, the DS-FSZW method eliminates the hook structures and cracks at the center of the conventional DS-FSW joint and also adds a lap joining interface, which significantly enhances the tensile strength of the joint from 150.7 MPa to 262.5 MPa, which is increased by 74%. Optimization of the shoulder diameter of DS-FSZW from 18 mm to 12 mm reduces the welding heat input and significantly thins the thickness of the IMCs layers at the Ti/Al interface. This helps to suppress the cracking at the Ti/Al lap interface and refine the grains. As a result, thus the tensile strength of the DS-FSZW joint increases from 262.5 MPa to 312.5 MPa, which is increased by 19%. The medium-thick Ti/Al dissimilar DS-FSZW joint at the tool shoulder diameter of 12 mm fracture at the SZ. It proves that the novel DS-FSZW is a suitable welding method for joining medium-thick dissimilar Ti to Al alloys.

Effect of rotational speed and penetration depth on Al-Mg-Si welded T-joints through underwater and conventional friction stir welding

The present work deals with the effect of penetration depth on welding T-joints through conventional friction stir welding (FSW) as well as underwater friction stir welding (UFSW). Various set of parameters have been used such as tool rotational speeds of 1000, 1400, and 1800 rpm, and depths of penetration, such as 6, 7, and 8 mm. In UFSW, lower heat generation prevents the development of complex intermetallic compounds and defects in welding. Additionally, in the weld region, a rapid cooling rate in UFSW generates fine microstructural particles. Mechanical and microstructural characteristics has been compared in both UFSW and FSW. There was a substantial grain size effect on mechanical properties. The stir zone shows comparatively finer grains with average grain size of 49.76 µm at 1800 rpm and 7 mm depth of penetration. It was seen that the tensile strength of UFSW was 189.9 MPa and the nugget zone hardness was 70 VHN, compared to the FSW that has 175.2 MPa and 62 VHN, respectively, obtained at a rotation speed of 1800 rpm and a travel speed of 60 mm/min. The joints tested at various penetration depths show a significant number of uniform and equiaxed dimples. The presence of ductile rupture and the formation of dimples suggest that the joints were effectively bonded and tested at different strain rates.

In-situ rolling friction stir welding of aluminum alloys towards corrosion resistance

In-situ rolling friction stir welding (IRFSW) was proposed to improve corrosion resistance of 7075-T6 aluminum alloy joint via microstructural design and residual stress regulation. The residual stress at the weld edge was changed from +58.3 MPa to –25.7 MPa. The dissolution of precipitates and narrowing of precipitate-free zones reduced corrosion potential difference between the precipitates and the matrices. The active corrosion path was cut off by discontinuous distribution of fine precipitates in grain boundary. The ultimate tensile strength and elongation of IRFSW joints were increased by 24.1 % and 100.0 % compared to conventional FSW joints after constant load stress corrosion.

Enhancing corrosion resistance of the nugget in a 2519-T87 aluminum alloy friction stir welded joint via tungsten inert gas arc

The corrosion resistance of the nugget zone (NZ) in two 2519-T87 aluminum alloy joints obtained by conventional friction stir welding (FSW) and tungsten inert gas arc-assisted FSW (TIG-FSW) was evaluated by immersion corrosion tests and electrochemical measurements. The results show that TIG arc significantly enhances the corrosion resistance of the nugget, the maximum corrosion depth is reduced by about 59.6%, and the polarization resistance is increased by about 14.5%. The mechanism was discussed based on microstructural examination. TIG-FSW decreases the area fraction of coarse intermetallic compounds (IMCs) with an equivalent diameter larger than 2.0 μm and increases the number of submicron IMCs, avoids the accumulation of IMCs, leads to low local electrochemical activity, and consequently enhances the corrosion resistance of the NZ.

The Feasibility of Static Shoulder Friction Stir Welding in Joining Dissimilar Metals of Al6061 and Ti6Al4V

In this study, static shoulder friction stir welding (SSFSW) is innovatively employed to join Al6061 and Ti6Al4V, aiming to minimize material mixing and intermetallic formation, significantly influencing the interfacial microstructure and joint strength. The results revealed that SSFSW reduced the intermetallic layer thickness at the interface, improving joint quality. The mutual interdiffusion of Al and Ti at the interface was influenced by an exothermic chemical reaction, forming an Al5Ti2–Al3Ti sequence due to the diffusion of Al into the Ti matrix. The microstructural analysis demonstrated better interfacial microstructural homogeneity in SSFSW joints than conventional FSW (CFSW), with finer titanium particle distribution. The larger particles resulted in coarser grains in CFSW, affecting the mobility of dislocations, which potentially led to the inhomogeneous concentration of dislocations at the interface. Recrystallization mechanisms varied between CFSW and SSFSW, with the Ti interface showing equiaxed and recrystallized grains due to the dynamic recovery driven by adiabatic shear bands. The tensile testing results of SSFSW exhibited a joint efficiency of 88%, demonstrating a 20.2% increase compared to CFSW, which can be attributed to differences in fracture modes. This study contributes to an understanding of dissimilar Al-Ti joining and provides insights for industries seeking to leverage the benefits of such combinations in lightweight and high-performance structures.

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

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

Effect of Water Cooling on the Microhardness of Friction Stir Welded High-Density Polyethylene Sheets: Experimental Study

The objective of the current work is to analyze the influence of water cooling of high density polyethylene (HDPE) sheet welding by friction stir process (FSW) on mechanical strength, based on microhardness tests. In the present work, the process using the conventional tool (C-FSW) is presented with the new procedure developed for FSW for HDPE, called water conventional friction stir welding (W-FSW). Test results for water-cooled and non-cooled welded samples were compared. HDPE sheets were initially welded by FSW process, and intensive water cooling was performed to weld after the tool exceeded the initial welding position by 30mm. The tool rotation speed of 1100 rpm and welding speed of 26 mm/min was used. The results were compared and evaluated with the hardness tests. A decrease in the hardness was observed when the sheets were treated by quenching, especially in the weld cores. It was found that the average hardness was much lower than that of untreated welded plates. Additionally, there is a region outside the core that has more or less the same stiffness value. The use of intensive quenching and conventional tooling has proven to be of great importance in improving surface finish, reducing defects, and increasing the mechanical strength of welds. The resulting recrystallization modified the hardness and thus increased the efficiency of the joint. These findings indicate the welding quality of the studied polyethylene.

Investigation of tool offset on the microstructure and mechanical properties of AA6061-T6/PC Friction Stir Butt Welding joint

Conventional friction stir welding (FSW) is mostly applied to lap welding, which is suitable to join metal/polymer materials. In this paper, solid-state friction stir butt welding (FSBW) technology is utilized to bond the sheets with the plates of 2 mm thickness of 6061-T6 aluminum alloy (AA6061-T6) and polycarbonate (PC) in a joint design. The effects of tool offset on the temperature evolution, surface morphology, microstructural characteristics, and mechanical properties of the dissimilar joints are investigated. A sound dissimilar join with the average highest tensile strength of around 14.23 MPa is attained at the offset of 3.5 mm. Microstructural characteristics indicate an effective mechanical interlocking structure (Al anchor). The mixed fragments of polymer and metal are formed with a chaotic interface along the joint line, improving the mechanical properties of welding joints. Furthermore, a novel friction stir V shape butt welding (V-FSBW) is proposed to join dissimilar plates. The maximum tensile strength and improvement rate of the V-FSBW joint compared with conventional FSBW are 18.42 MPa and 29.4%, respectively. Results indicate that the tool offset significantly affects the welding joints, and V-FSBW can effectively increase the mechanical properties of the dissimilar AA6061-T6/PC joints.

Experimental and numerical assessment of thermomechanical and morphological characteristics of pin and pinless micro friction stir welds

In the realm of micro-Friction Stir Welding (FSW), distinct challenges arise compared to conventional FSW, encompassing faster heat dissipation through the backing surface, and higher impact of hooks on joint performance due to the reduced effective sheet thickness. Given the limited variability in tool design in micro-FSW, this study delves into the influence of pinless tool in comparison to pin tool on hook formation, temperature evolution, and bonding mechanisms. By conducting a combination of experiments and numerical investigations on 0.5 mm lap FSW joints, the study unveils that pin tool, with an 11% higher peak temperature and 46% greater effective sheet thickness, achieved 4% increase in joint strength with 26% lesser axial force during traversing. Pin tool exhibited a 10–11% higher proportion of recrystallized grains, with 11.1% and 57.6% grain refinement in the weld centre and hook regions, respectively, primarily due to pin-assisted material stirring. In contrast, pinless tool exhibited a flat nugget with directional grain growth toward the weld bottom. The pin weld demonstrated nearly three times the maximum equivalent plastic strain compared to the pinless weld, confirming the intense movement of plasticized material in the vicinity of the pin and effective intermixing across the sheet-interface.

A Comparative Study of Conventional, Dynamic Rotation and Heat-assisted Friction Stir Welding of Ti-6Al-4V Plates to Reduce Welding Defects

It is very easy to form bottom defects during friction stir welding (FSW) of medium-thick/thick Ti alloys, while there is a lack of in-depth research on its essential cause. In this study, conventional FSW (CFSW), dynamic rotation FSW (DRFSW) and back heating assisted FSW (BHAFSW) were conducted to 6mm Ti-6Al-4V plates. The combination of experimental examination and finite element modelling was utilized to deeply study the bottom defect formation mechanism. The results showed that bottom defects always existed in both CFSW and DRFSW joints, which was mainly attributed to the phase transformation difference at the joint bottom, as the result of the difference of the bottom temperature and the phase transformation point. A proper bottom temperature compensation of 150oC via BHAFSW was designed to avoid the phase transition difference and improve the material flow, which effectively eliminated the bottom defects. This is the first time to uncover the reason of the bottom defect generation during FSW, and thus defect-free Ti alloy medium-thick plate joints were achieved via BHAFSW. The BHAFSW joint achieved the 1022MPa in strength and 16% in ductility, with the equal strength to the base material (BM) but with very few losses of the ductility. The joint exhibited an impact toughness of 10.4J, 48.1% higher than the BM. This study uncovers the reason for the typical bottom defect and provides a new way to improve the quality of medium-thick/thick Ti alloy FSW joints.

Performance Evaluation of Underwater (UW) Welding System with Friction Stir Welding (FSW) Method on 316L Stainless Steel Exposed to Sea Water

Friction Stir Welding (FSW) is a solid-state welding technique that can produce high-quality joints without defects that commonly occur in liquid welding. However, FSW has limitations in underwater applications due to the friction between the tool and the material that causes a decrease in heat efficiency and shear force. To overcome this problem, this study proposes an underwater welding (UW) system with the FSW method on 316L stainless steel exposed to seawater. This UW-FSW system uses a high-speed rotating tool surrounded by an inert gas shroud to prevent direct contact between the tool and seawater. The aim of this study is to evaluate the performance of this UW-FSW system in terms of mechanical properties, microstructure, and corrosion resistance of 316L stainless steel joints. The results of this study show that the UW-FSW system can produce joints with better tensile strength, hardness, and corrosion resistance than conventional FSW. This is due to the rapid cooling, reduction of oxidation, and formation of a thicker passive layer on the joint surface. This study provides a contribution to the development of environmentally friendly and efficient underwater welding technology.

Study on the effects of ultrasonic assistance and external heat dissipation on friction stir welded 7075 aluminum alloy joints

In this paper, conventional friction stir welding (C-FSW), ultrasonic assisted friction stir welding (Ua-FSW) and heat pipe assisted friction stir welding (Ha-FSW) were performed on 4 mm thick 7075 aluminum alloy. The effects of the two different types of assisted technologies on C-FSW were qualitatively compared and analyzed. The microstructure of the joints in the NZ, HAZ and other regions were primarily characterized via SEM-EBSD and TEM, and the strength of the joints were evaluated via the room-temperature tensile properties and microhardness tests. The test results showed that both Ua-FSW and Ha-FSW effectively improved the weld forming, while the surface quality of the joints fabricated by Ha-FSW was better. The acoustic flow effect from ultrasound reduced the temperature gradient, and the heat pipe provided excellent heat dissipation, which well controlled the peak heat and the rate of heat loss throughout FSW, resulting in finer grain sizes after both the Ua-FSW and Ha-FSW processes. EBSD analysis showed that the assistance of two technologies provided a greater effect on TMAZ and HAZ, the stress field generated by ultrasonic vibration favored the formation of subgrains, the heat dissipation of the heat pipe also inhibited the recrystallization, and more subgrains were retained. The assistance of ultrasonic vibration and the heat pipe was mainly in the elongation, especially the joints prepared by the Ha-FSW showed an improvement in elongation by 16.7 % and 33.3 % compared to the Ua-FSW and C-FSW, respectively. This work provides insight into improving welding efficiency and joint performance through modified FSW processes.

Study on the materials flow, microstructure and mechanical properties of ultrasonic vibration-assisted friction stir weld of 1500 MPa martensitic steel

In this study, friction stir welding (FSW) was conducted on 1500 MPa martensitic steel with a thickness of 2.3 mm at 500 rpm and 60 mm/min with and without the application of ultrasonic vibration. The utilization of pure nickel as a marker material could help to visualize the material flow behavior throughout the whole FSW process. In addition, the width change of the marker material was used to distinguish the welding stages. At the same time, the microstructure was also characterized to study the effect of ultrasonic vibration on the welding process. The conventional FSW (C-FSW) joint had tunnel defects due to poor material flow, while the ultrasonic vibration-assisted FSW (U-FSW) joint was defect-free. To study the microstructure and texture evolution during the process, a fully austenitized welding zone was reconstructed from martensite to prior austenite grain (PAG) based on the Kurdjumov-Sachs orientation relationship. The strain rate increased in U-FSW compared to that in C-FSW, resulting in a reduction of the PAG size and an alteration of its shear texture components from type-A to type-B. The uniaxial tensile tests showed that the ultimate tensile strength (UTS) of the stir zone (SZ) of U-FSW was significantly increased compared with that of C-FSW.

Analysis on the performance of aluminum/steel UVeFSW joints by changing ultrasonic powers

The optimization mechanism of ultrasonic power on the performance of aluminum/steel dissimilar metal ultrasonic vibration enhanced friction stir welding (UVeFSW) joints was studied. The results indicated that ultrasonic vibration can significantly improve the surface forming quality of the weld seam, increase the width of the joint interface zone, adjust the height of the hook structure, suppress the generation of intermetallic compounds, and enhance the failure load of the joints. When the ultrasonic power was 500 W, the lap joints with the best mechanical properties were obtained, and its failure load was 5.14 kN, which was 51.2% higher than that of conventional FSW (0 W).

Enhancing Microstructural, Textural, and Mechanical Properties of Al-Ti Dissimilar Joints via Static Shoulder Friction Stir Welding

Abstract The present study explores the application of static shoulder friction stir welding (SSFSW) to address the challenges of poor mechanical properties in conventional Al-Ti dissimilar friction stir joints, which arise due to significant material mixing and the formation of thick intermetallic layers. The results show that SSFSW inhibited material mixing and the mutual diffusion of Al and Ti were suppressed due to lower heat input. Mutual interdiffusion of Al and Ti was directed by an exothermic chemical reaction, forming an Al5Ti2 – Al3Ti sequence due to sluggish diffusion of Al in Ti at a temperature of 512°C achieved in this study. The microstructure at stir zone (SZ) comprised equiaxed grains with Ti particles acting as dispersoids for nucleation, whereas the presence of large Ti blocks at SZ of Conventional FSW (CFSW) resisted plastic deformation, resulting in non-homogeneous concentration of dislocations near its interface. A significant decrease in grain size at all the critical zones of weldment was due to rearrangement of dislocations through slip-and-climb mechanism, as evidenced by the occurrence of dynamic recrystallization. Emergence of γ-fiber and basal fiber texture increased the tensile strength of SSFSW to 289 MPa, which is about 11.2% higher than CFSW, with joint efficiency of about 88%. The study also analysed the contribution of various strengthening mechanisms to the yield strength improvement of SSFSW weldments in detail of SSFSW weldments in detail, and the results showed that grain boundary strengthening contributed the most to strength improvement in SSFSW.

Microstructural Evolution, Intermetallic Formation, and Mechanical Performance of Dissimilar Al6061–Ti6Al4V Static Shoulder Friction Stir Welds

The present study focuses on achieving microstructural uniformity in dissimilar Al–Ti joints through static shoulder friction stir welding (SSFSW). This method restricts material mixing at the Al–Ti interface due to reduced shoulder action, resulting in peak temperatures of 317 °C (SSFSW) and 491 °C in conventional friction stir welding (CFSW). This reduction in heat input during SSFSW leads to decreased mechanical mixing, resulting in a thinner 2.169 μm intermetallic layer at interface of SSFSW compared to 5.485 μm in CFSW. The resulting weld nugget (WN) microstructure reveals the presence of Ti particles, intermetallic compounds, and fine Al‐associated grains. Rearrangement of dislocations through slip‐and‐climb mechanisms, along with distinct recrystallization processes in SSFSW, significantly reduces grain size within WN. The kernel average misorientation map highlights the presence of nonuniform dislocation concentrations at the interface of CFSW, attributed to the large Ti particles that impede the mobility of dislocations. As a result, the interface of CFSW is found to be the weakest among all the zones, eventually leading to the failure of the CFSW joint near the Ti interface after reaching an ultimate tensile strength of 259 MPa. In contrast, SSFSW welds achieve a higher tensile strength of 289 MPa.

Comparison of underwater friction stir welded and conventional friction stir welded AA 5052 alloys based on the mechanical, formability and microstructure behaviour

Solid state joining of 1 mm thick AA 5052 aluminium alloys is carried out in the current study using both traditional friction stir welding (FSW) and underwater friction stir welding procedures. In the underwater FSW process, the tool and the welding plates are totally submerged underwater while the welding is being done. The underwater welding procedure contributes to improving the mechanical characteristics and formability of aluminium alloys by lowering heat dissipation. The current study compares the mechanical characteristics, formability, microstructure, and fractography of the joints made of the AA5052 aluminium alloy using the two different welding procedures. When performing FSW or underwater FSW, a process parameter called welding speed is changed from 30 mm/min to 60 mm/min at intervals of 15 mm/min while keeping a constant speed of 1200 rpm. Both FSWed and underwater FSWed samples are subjected to the Erichsen cupping test, where the dome height is taken into account as a metric of formability and the strains created during the deformation is also measured. Optical microscopes and scanning electron microscopes were utilized to analyse microstructure and fracture. At various speeds, the mechanical characteristics, formability behaviour, and microstructure of the two weldings were examined. Due to underwater welding's lower heat dissipation than conventional friction stir welding, it has been discovered that underwater welding has better mechanical, formability, and microstructure behaviour, making them more appropriate for automotive applications.