Underwater Friction Stir Welding Research Articles

Optimization of Process Parameters in Under Water Friction Stir Welded AA2014 and AA6082 joints.

This work focuses on optimizing process parameters in underwater friction stir welding to study their impact on the mechanical characteristics of aluminum 2014 T6 and 6082 T6 joints. The aluminum plates are precisely machined to provide the necessary polish for the underwater friction stir welding process (UFSW). Experiments are designed using Taguchi L-9 orthogonal array, considering three process parameters: speed, transverse speed, and tool angles at three levels each. The aluminum plates of series 2014-T6 and 6082-T6 are securely installed in the machine. The plates will be welded using the UFSW process using a taper pin tool. The welded plates are next subjected to tests to assess their mechanical qualities. Tests for tensile strength, hardness, and impact strength are conducted on the welded area of the plate to determine its mechanical qualities. An ANOVA was conducted to determine the significant influence of each variable. The optimal values achieved are Tensile Strength of 185.592 N/mm2, Hardness of 75.1 (BHN), and Impact Strength of 21.236 Joules at a speed of 1120 rpm, transverse speed of 80 mm/min, and tilt angle of 2 degrees.

Mechanical Properties of the AlCu4Mg1 Alloy Joint Manufactured by Underwater Friction Stir Welding.

The manuscript presents the results of butt joining of 3-millimeter-thick AlCu4Mg1 alloy sheets using the FSW (friction stir welding) and UWFSW (underwater friction stir welding) methods. The aim of the research is to verify the influence of the water environment on the FSW friction welding process. The article checked three sets of joint parameters. The parameters differed in tool rotation speed and feed rate. The same sets of parameters were used for the FSW and UWFSW fusion techniques. With the supplied devices, metallographic sections are cross-sectioned, and the power supplies are subjected to a light microscope. Microhardness tests and the influence of the heat-affected zone were carried out. A monotonic test was performed. A monotonic test is available, extended with a visual correlation test. The obtained cracked fracture surfaces were examined using a scanning microscope. An analysis of the microfractographic cracking process was carried out. The obtained results did not show any improvement in the strength properties of the obtained joints made using the UWFSW technique when using a scanning microscope.

Underwater friction stir welding of ultrafine-grained laminated composites produced through accumulative roll bonding process

In this work, ultrafine-grained (UFG) plates of AA2024/AA5083 laminated composite with alternating layers of heat-treatable aluminum AA2024 and strain-hardening aluminum AA5083 were fabricated through accumulative roll bonding (ARB) technique and were subsequently joined using underwater friction stir welding (UFSW). Friction stir welding (FSW) is a solid-state welding method which is suitable for the joining of similar and dissimilar UFG alloys of AA2024 and AA5083, which are mainly used in aerospace and aviation industries. Welding variables, such as pin profile, rotational speed, welding speed, and tilt angle were optimized using the Taguchi optimization technique. Different zones of UFSWed joints including stir zone (SZ), thermo-mechanically affected zone (TMAZ), and heat affected zone (HAZ) were investigated through OM, TEM, and SEM. The results showed that the tapered cylindrical pin, 1000 rpm rotational speed, 110 mm.min−1 welding speed, and 2.5° tilt angle were the optimal welding variables in terms of tensile strength. The microstructural results showed the formation of nano-size, recrystallized equiaxed grains with a size of 500 nm (the same size as that in the UFG base metal) in the optimal sample. The hardness in the weldment of the optimal UFSW sample decreased slightly, so that the efficiency of 85% was presented and the minimum hardness location (MHL) disappeared. The ultimate tensile strength (UTS) of 425 MPa and 64% efficiency were observed in the optimal conditions. Due to the presence of very fine grains and large dislocations, and the uniform distribution of precipitates in the underwater state, high strength and elongation were obtained.

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.

Investigation of Mechanical Properties on Underwater Friction Stir Welded AA7075 With Pure Copper Dissimilar Joints

Investigation of Mechanical Properties on Underwater Friction Stir Welded AA7075 With Pure Copper Dissimilar Joints

Numerical and experimental study of underwater friction stir welding of 1Cr11Ni2W2MoV heat-resistant stainless steel

Due to the benefits of solid-state joining, friction stir welding (FSW) has seen an increase in applications in the aircraft and automotive industries. However, short tool life and heat-affected zone (HAZ) softening are the two main issues with the FSW of advanced high-strength steel. In this study, the underwater friction stir welding (UFSW) of 1Cr11Ni2W2MoV steel was investigated and compared to the Normal friction stir welding (NFSW). Besides, a 3-D thermo-mechanical finite element model was developed to understand the effect of the different cooling mediums and tool rotation rates on the thermal cycles, plastic deformation, tool wear, and microstructure evolution. The simulation results revealed that the stir zone (SZ) of the UFSW exhibits lower peak temperatures and smaller plastic strain compared to the NFSW. The experimental results showed that a high tool rotation rate can be used during UFSW without causing overheating of the workpiece and tool materials resulting in high joint quality and low tool wear. The M23C6 and Fe3C carbide fractions in the HAZ at UFSW are lower than that at NFSW. The UFSW reduces the soft HAZ's width and increases its hardness. The ultimate tensile strength was increased by 17 %, and the HAZ width was decreased by 35 % at UFSW compared to that at NFSW.

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.

Underwater friction stir welding of marine grade aluminium alloys: A review

Aluminium alloys of the 5xxx and 6xxx types are considered marine grade alloys. These alloys are highly resistant to corrosive environments and are therefore used in maritime applications. However, joining these alloys by traditional welding process is a difficult task and can also lead to defect formations in the joints. Friction stir welding being a solid-state welding process uses a special type of tool to join workpieces at a temperature below the melting point of the material. This process saves a lot of energy, is eco-friendly and also yields better mechanical properties than the conventional fusion welding processes. However there is a decrease in the mechanical properties of the joints since the heat cycles involved in FSW can lead to softening of the joints. Underwater friction stir welding is a modification of FSW where welding is performed under the influence of a liquid medium like water. UFSW reduces the peak temperature of welding and produces better mechanical properties than the normal FSW process. A review of underwater friction stir welding of marine grade aluminium alloys is provided here. A review regarding the different parameters of the process, microstructure development, and corrosion resistance is discussed in this paper. From the review, it can be inferred that UFSW is very effective for joining marine grade aluminium alloys with minimal defects and better mechanical properties.

Minimizing material flow in the dissimilar joining of Al6061 and Ti6Al4V to mitigate the adverse effects of intermetallic compounds

Static shoulder friction stir welding (SSFSW) offers a promising solution for joining Al6061 and Ti6Al4V by addressing material mixing and intermetallic formation encountered in conventional friction stir welding (CFSW). SSFSW effectively suppresses material mixing and Al-Ti interdiffusion, leading to an Al5Ti2 – Al3Ti sequence through an exothermic reaction. Comparative analysis with underwater friction stir welding (UWFSW) highlights SSFSW's effectiveness, showing a significant reduction in intermetallic layer thickness compared to UWFSW. The intermetallic layer thickness of SSFSW is measured at 2.169 µm, while UWFSW exhibits a thickness of 3.731 µm, and CFSW shows the highest at 5.485 µm. The inverse pole figure confirms reduced material flow and intermetallic formation in SSFSW compared to UWFSW and CFSW.

Enhancement of microstructure, micro-texture, and mechanical properties of Al6061 friction stir welds using the developed static shoulder welding tool

Dissolution of strengthening precipitates and grain coarsening are the key factors that dictate the mechanical properties of heat-treatable aluminium alloys. In this study, a feasible method of static shoulder friction stir welding (SSFSW) is used to reduce these adverse effects. A novel static shoulder friction welding tool is developed here in this study by incorporating rotating and non-rotating shoulders in a single tool. The effectiveness of the tool was evaluated by welding Al6061 plates under various conditions, such as conventional friction stir welding (CFSW), underwater friction stir welding (UWFSW), and SSFSW. The evolution of crystallographic texture and microstructural changes during the process is studied using electron back scattered diffraction and transmission electron microscopy. The results showed that SSFSW reduced grain size by 37% compared to UWFSW at the centre of the stir zone and increased the yield strength by 22.8% compared to CFSW. In addition, SSFSW showed a strong presence of γ-fibre, indicating improved formability and a 7.2% improvement in joint efficiency in terms of ultimate tensile strength due to a higher fraction of precipitates and higher dislocation density.

Friction Stir Welding of Aluminum in the Aerospace Industry: The Current Progress and State-of-the-Art Review.

The use of the friction stir welding (FSW) process as a relatively new solid-state welding technology in the aerospace industry has pushed forward several developments in different related aspects of this strategic industry. In terms of the FSW process itself, due to the geometric limitations involved in the conventional FSW process, many variants have been required over time to suit the different types of geometries and structures, which has resulted in the development of numerous variants such as refill friction stir spot welding (RFSSW), stationary shoulder friction stir welding (SSFSW), and bobbin tool friction stir welding (BTFSW). In terms of FSW machines, significant development has occurred in the new design and adaptation of the existing machining equipment through the use of their structures or the new and specially designed FSW heads. In terms of the most used materials in the aerospace industry, there has been development of new high strength-to-weight ratios such as the 3rd generation aluminum-lithium alloys that have become successfully weldable by FSW with fewer welding defects and a significant improvement in the weld quality and geometric accuracy. The purpose of this article is to summarize the state of knowledge regarding the application of the FSW process to join materials used in the aerospace industry and to identify gaps in the state of the art. This work describes the fundamental techniques and tools necessary to make soundly welded joints. Typical applications of FSW processes are surveyed, including friction stir spot welding, RFSSW, SSFSW, BTFSW, and underwater FSW. Conclusions and suggestions for future development are proposed.

Microstructure and mechanical properties of ultrafine-grained AA2024 sheets joined by underwater friction stir welding

Microstructure and mechanical properties of ultrafine-grained AA2024 sheets joined by underwater friction stir welding

Friction Stir Welding of Non-Heat Treatable Al Alloys: Challenges and Improvements Opportunities

Friction stir welding (FSW) is an effective solid-state joining process that has the potential to overcome common problems correlated with conventional fusion welding processes. FSW is used for the joining of metallic materials, in particular Al alloys (non-heat-treatable and heat-treatable). The heat produced by the friction between the rotating tool and the workpiece material generates a softened region near the FSW tool. Although the heat input plays a crucial role in producing a defect-free weld metal, it is a serious concern in the FSW of work-hardened non-heat-treatable Al alloys. In this group of alloys, the mechanical properties, including hardness, tensile properties, and fatigue life, are adversely affected by the softening effect because of grain growth and reduced dislocation density. Considering this challenge, work-hardened Al alloys have been limited in their industrial use, which includes aerospace, shipbuilding, automotive, and railway industries. The current comprehensive review presents the various approaches of available studies for improving the quality of FSW joints and expanding their use. First, the optimization of welding parameters, including the tool rotational and traverse speeds, tool design, plunge depth, and the tilt angle is discussed. Second, the incorporation of reinforcement particles and then underwater FSW are stated as other effective strategies to strengthen the joint. Finally, some supplementary techniques containing surface modification, bobbin tool FSW, copper backing, and double-sided FSW in relation to strain-hardened Al alloys are considered.

Underwater Friction Stir Welded Armour Grade AA5083 Aluminum Alloys: Experimental Ballistic Performance and Corrosion Investigation

Underwater Friction Stir Welded Armour Grade AA5083 Aluminum Alloys: Experimental Ballistic Performance and Corrosion Investigation

Significance of underwater friction stir welding on the weld integrity of thin sheets of aluminum (AA1050-O) and brass (CuZn34) joints

Classical friction stir welding (C-FSW), because of its solid-state joining nature, offers several benefits over traditional fusion welding for joining dissimilar materials. C-FSW conducted in open air, are affected by several weld flaws and thick Intermetallic Compounds (IMCs) that reduce the weld joint quality. In this study, FSW of thin sheets of aluminum alloy (AA1050-O) and brass (CuZn34) in lap joint configuration was performed in air and underwater. The main objective of this study was to investigate the feasibility of underwater-FSW (UW-FSW) for obtaining aluminum and brass (Al-Brass) joints at different values of shoulder plunge depth (SPD) and tool rotational speed (N). To determine the effect of welding temperature at different values of SPD and N on the formation of weld joints, K-type thermocouples were used. Underwater welding reduced the welding temperature and thermal cycle time. The optical images of C-FSW joints revealed the presence of kissing bonds, wavy patterns, cracks, tunnels, and void defects. In UW-FSW, the faster cooling rate significantly reduced these weld flaws. Electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) were used for the microstructural characterization. EBSD and TEM results show fine microstructure and precipitates in UW-FSW specimens. The X-ray diffraction results demonstrated that the weld joint interface primarily consisted of Al-Cu & Cu-Zn IMCs in the form of Al4Cu9, Al2Cu, AlCu3, AlCu4, CuZn5, and Cu5Zn8. The amount of IMCs was less in the joints produced by UW-FSW. The obtained results were used to understand the variation in the weld strength of C-FSW and UW-FSW joints at different values of SPD and N. To further evaluate the interface of the Al-Brass weld joint, energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) were employed. EDS confirmed the presence of brass fragments in the stirred zone of aluminum substrate. TEM and SEM images illustrated fine precipitates and formation of thin IMC layers in UW-FSW. The tensile test result shows that the UW-FSW remarkably improved the joint strength. The percentage increase in the joint tensile strength for UW-FSW was found 42%, 30% and 50% higher than C-FSW for lower, medium and high heat input welding conditions. The lower heat input in UW-FSW significantly suppressed the formation of weld flaws and IMCs, which collectively improved the tensile strength of the weld joint.

Evaluation of Pure Titanium Welded Joints Produced by Underwater Friction Stir Welding

Underwater friction stir welding (UWFSW) is an advancement of conventional friction stir welding, which is performed in air. The need for welding underwater calls for more information to be explored in the welding of different materials. The aim of this research is to investigate the UWFSW of 2 mm titanium sheet joints for their tensile and microstructural properties and compare them with the results of friction stir welding (FSW) performed in air. Also, nondestructive tests, such as radiography and dye penetrant tests, were carried out to identify the occurrence of any weld defects. The rotational speed of the FSW tool and its travelling speed were considered process parameters, while other parameters like the tilt angle of the tool, shape of the tool pin, etc. were kept constant. The results show that the welded joints with higher strengths were achieved at a lower travelling speed of 140 mm/min at a rotational speed of 400 and 500 rpm in FSW and UWFSW, respectively. The mechanical properties such as yield strength, tensile strength, and hardness are improved in UWFSW when compared with conventional FSW due to the proper mixing of the metal and effective cooling due to the water environment. In underwater FSW, the improved YS and TS values are observed, which are 95.9% and 75.1% of the base metal values, respectively, when the tool rotational speed is 400 rpm and the travelling speed is 140 mm/min. However, the elongation % is much lower in both FSW and UWFSW when compared with the base metal. These results are supported by microstructure and nondestructive test outcomes.

Experimental investigation and numerical analysis using Taguchi and ANOVA methods for underwater friction stir welding of aluminium alloy 2017 process improvement

The effect of under water friction stir welding for 5 mm AA2017 aluminum alloy plaque on mechanical properties has been examined and optimized. Nine different tests were designed according to Taguchi orthogonal array without changing the welding tool. Three variable operating parameters (Welding velocity, rotational velocity and axial force) have been used with three levels for each parameter. The effects of each FSW parameters on the weld joint were discussed and analyzed, the analysis of variance (ANOVA) is adopted to identify the contribution of each FSW underwater parameters. Moreover, the statistical Taguchi method (TM) was employed to pridect the optimal combination of welding parameters to improve the tensile properties such astensile strength (TS) of welded joints. In addition, the experimental tests show good agreement with that obtained by the proposed mathematical model. Wherethe obtained validation results confirm the robustness of the optimization method as a useful tool to improve the quality responses of underwater friction stir welding.

Effect of tool rotation speed on microstructure and mechanical properties of underwater friction stir welding 6061 aluminium alloy

This work presents the experimental investigation of the effect of tool rotation speed (TRS) on the mechanical properties of the 6061-T6 aluminium alloy weld joint in the underwater friction stir welding (UFSW) process. The experiments are conducted with four different TRS, 710, 900, 1120, and 1400 rpm, and a constant welding speed (WS) of 20 mm/min, respectively. The welding is performed under the water in the butt joint configuration on the vertical milling machine (Model HMT FN2H). The experimental result shows that the average grain size decreases and tensile strength and hardness increases on increasing the TRS up to mid-range of the TRS and further increasing the TRS the trend of grain size and tensile strength and hardness are increases and decreases, respectively. The maximum tensile strength value is 190 MPa, and the minimum grain size is 5 µm at 1120 rpm. Additionally, the optimum condition of tensile strength and weld zone shape is compared with the conventional friction stir welding process, and it is found that tensile strength is increased by 20% and smaller weld zone shape are observed in underwater friction stir welding process. The brittle fracture dominance is observed at lower TRS and ductile dominance fracture in 900, 1120, and 1400 rpm of the weld joint.

Effect of tool rotation speed on mechanical properties of underwater friction stir welding of 6061-T6 and 5083-H12 aluminium alloys

This work presents an experimental investigation of the effect of tool rotation on the mechanical properties of 6061-T6 and 5083-H12 aluminium alloys in the UFSW weld joint. The experiments are conducted in a vertical milling machine (model no. HMT FN2H) at four different tool rotation speeds (TRS), such as 710, 900, 1120, and 1400 rpm, at constant welding speed (WS) of 63 mm/min. The welding was performed under the water in the butt joint configuration in which the 6061-T6 workpiece material is placed on the retreating side (RS) and 5083-H12 on the advancing side (AS). The results show that the performance of the weld joint quality depends on the TRS. The shape and size of the weld nugget zone (WNZ) and thermo-mechanically affected zone (TMAZ) increase with increasing the TRS. The tensile strength of the weld joint and average grain size of the stir zone (SZ) increases and decreases respectively on increasing the TRS 710 to 1120 rpm. Further increasing the TRS, the tensile strength of the weld joint and average grain size of SZ decreases and increases respectively. Additionally, the fracture surface shows the brittle dominance fracture mode at 1400 rpm, and 710 to 1120 rpm weld joints show the ductile fracture mode.

Mathematical and experimental examination of the effect of the stepped pin tool profile on the characterization of AA 6061-T6 underwater friction stir welding

This research paper presents the mathematical model to design a stepped pin profile tool and its durability index. A mathematical model is being developed by considering tools that should generate the same heat as conventional conical tools and stepped tools by varying the shoulder to pin diameter ratio (D/d). Aluminum alloy AA6061-T6 with a thickness of 6 mm fabricated using a butt-type weld configuration and newly developed conical stepped pin profile tools with water as a cooling medium. The result shows that a conical stepped tool shows better mechanical properties of the welded joints compared with a conventional conical tool. When compared to other stepped conical pin profile tools, one with a (D/d) of 3 has superior mechanical and microstructural properties and as the D/d ratio increases, the tool pin durability index falls.