Solid-state Welding Technique Research Articles

Achieving superior mechanical and corrosion properties in medium-thickness Ti-6Al-4 V alloy joints by back heating assisted friction stir welding below β-phase transformation temperature

The equiaxed microstructure formed below the β-phase transition point of Ti alloys generally exhibits an excellent balance of mechanical properties and corrosion resistance. However, this desirable microstructure is impossible to be obtained in fusion welded joints but is prospective to be achieved by the solid-state friction stir welding (FSW) technique. Unfortunately, it generally generates bottom defects and severe tool wear in medium-thickness Ti alloy joints when conventional FSW was conducted below the β-phase transition point. In this study, 6 mm thick Ti-6Al-4 V plates were joined by both the conventional FSW and back heating assisted FSW (BHAFSW). Defects caused by significant tool wear and bottom phase transition differences occurred in the conventional FSW. It was found that the hardness difference between the base material (BM) and the tool increased to 35.6 % from 500 °C to 900 °C. The back heating (150 °C) was used to control welding temperatures remaining the 900 °C, thus largely reducing the tool wear by increasing the hardness difference. In addition, the back temperature compensation increased the bottom temperature and controlled the phase transition position from the bottom to the middle of the joint. The shoulder pressure contributed to the compression of the defects, and the defects were eliminated by increasing the pressure at the phase transition position. A significantly refined equiaxed microstructure with an average grain size of ~0.9 μm was achieved below the β-phase transition temperature in the stir zone via back heating assisted FSW, while a bimodal structure with an average grain size of 3.5 μm was formed near the β-phase transition temperature. Inconspicuous reduction of the strength was detected for the joints (98 % of the BM) which possess equiaxed microstructures, and the corrosion resistance of the joints was enhanced compared to the BM. This superior synergy of mechanical and corrosion properties exceeded the majority of Ti alloy joints previously reported. This study provided an effective method for obtaining medium-thickness Ti alloy joints with ultrafine equiaxial structures with superior mechanical properties and corrosion resistance.

Friction Stir Welding Benefits Technique over Other Welding Techniques of Dissimilar Metals

Abstract: Due to the low heat input situation, solid state welding (SSW) has demonstrated higher potential for integrating a variety of equivalent and dissimilar material combinations. The temperature stays below the melting point of the source materials throughout the solid-state welding process. Compared to fusion welding, solid state welding offers the highest quality. Aeronautics, nuclear, space, and aviation are just a few of the industrial production sectors that utilize the solid-state welding technology. Diffusion welding, explosion welding, friction welding, forge welding, cold welding, role welding, hot pressure welding, and ultrasonic welding are just a few of the SSW techniques covered in the current article. This study looks at a variety of SSW kinds and solid-state welding applications. This study examines many types of SSW and the applications of solid-state welding. Current Study includes the pros and cons of other welding techniques over friction stir welding.

Friction Stir Welding Benefits Technique over Other Welding Techniques of Dissimilar Metals

Abstract: Due to the low heat input situation, solid state welding (SSW) has demonstrated higher potential for integrating a variety of equivalent and dissimilar material combinations. The temperature stays below the melting point of the source materials throughout the solid-state welding process. Compared to fusion welding, solid state welding offers the highest quality. Aeronautics, nuclear, space, and aviation are just a few of the industrial production sectors that utilize the solid-state welding technology. Diffusion welding, explosion welding, friction welding, forge welding, cold welding, role welding, hot pressure welding, and ultrasonic welding are just a few of the SSW techniques covered in the current article. This study looks at a variety of SSW kinds and solid-state welding applications. This study examines many types of SSW and the applications of solid-state welding. Current Study includes the pros and cons of other welding techniques over friction stir welding

Joining of Al-Alloy Tubes by Carbon Steel Tubes using MPW Technique

Background/ Objectives: Joining aluminum alloys with low carbon steel (DC01) through fusion welding is a challenging task due to the occurrence of solidification defects like porosity, alloy segregation, and hot cracking. However, these issues can be addressed by employing solid-state welding techniques like explosive welding and MPW (magnetic pulse welding). MPW is a cost-effective and high-speed solid state welding method that involves creating joints in an overlap configuration. Methods: The MPW technique was employed to join dissimilar aluminum alloy AL 7075T6 hollow tube and DC01 steel rod in this study. A central composite design model was created to analyze the relationship between key MPW process parameters, including stand-off distance (SoD), overlap length, and discharge energy, and the bonding strength of the joints. Experimental setups were established and correlate with tensile-shear fracture load and interface hardness of the joints with the MPW process parameters. Findings: It is understood that the maximum TSFL of 2.404 kN was obtained under the welding condition of 23kJ discharge energy, 2.25 mm Stand-off distance, 8.5 mm overlap length, which is the optimum MP welding state for AA 7075 T6 with DC01 and confirmed by RSM. In addition, the cultivated connection can be aptly leveraged to anticipate the TSFL of MPW joints with a 95% confidence level. Novelty: The parametric mathematic samples were developed for forecasting TSFL of joints. The MPW parameters were optimized to enhance TSFL of joints. Aluminium alloys with low carbon steel joints were developed using MPW for cars and ships applications without fusion welding defects. Keywords: Magnetic Pulse Welding, Dissimilar Joint, (RSM) Response Surface Methodology, Tensile Shear-Fracture Load

Characterization of material flow behavior in friction stir welded AA2014 aluminum alloy joints

Abstract Steel rivets serve as a substitute material for connecting similar and dissimilar materials within the structural fabrication industries. However, the use of steel rivets can result in a significant increase in the structure’s weight and may trigger corrosion at the interface due to galvanic coupling. Combining dissimilar alloys through the fusion welding process poses numerous challenges for manufacturers and designers. A solid-state welding technique called friction stir welding (FSW) has been developed. FSW can effectively join materials without reaching their melting points, relying on severe plastic deformation and recrystallization to form a welded joint. The proper selection of the tool and process parameters is essential for achieving a sound weld. The findings of this study indicate that plastic deformation, material flow, and recrystallization play pivotal roles in the strength of the joint. This implies that FSW represents an ideal joining process for high-strength alloys and serves as a viable alternative to replace permanent joints like rivets.

Effect of Welding Parameters on Lap Shear Force of Similar and Dissimilar Friction Stir Spot Welded Aluminium Alloys

Friction stir spot welding (FSSW) is a solid-state single-point welding technique that uses a rotating tool consisting of a shoulder and a pin for joining nonferrous metals and alloys. FSSW produces a keyhole at the welding point, which decreases the mechanical strength of the joints. This study investigates the influences of tool rotational speed (1000, 1250, and 1500 rpm) and dwell time (5, 10, and 15 s) on the shear fracture load of the FSSW joints. Two different grades of aluminium alloy plates, i.e., AA6061 and AA7075 were used to produce similar (7075-7075 and 6061-6061) and dissimilar (6061-7075) alloy joints. The plates with a thickness of 3 mm were folded above each other before a rotating tool pin was plunged through the thickness of the top plate to obtain an FSSW lap joint. It was found that tool rotational speed and dwell time induced a considerable impact on the microstructure, and shear strength. The results indicated that the grain size of microstructure in similar and dissimilar joints was affected by the rotational speed and dwell time. The grain size of the microstructure increased as rotational speed and dwell time increased. The results also showed that a tool rotational speed of 1250 rpm and dwell time of 10 s gave the highest shear fracture load for 7075-7075 similar and 6061-7075 dissimilar joints. However, for 6061-6061 similar joints, the highest mechanical strength was obtained at 1250 rpm and 10 s.

Regulating the microstructure and strength of the advancing side interface zone in AZ31 friction stir welded joint via localized selective remelting

Friction stir welding (FSW) is a solid-state welding technique widely used for various series of magnesium (Mg) alloys. However, in the process of transverse loading for FSW joints in Mg alloys, the ultimate fracture often occurs near the advancing side (AS) interface zone. To enhance the AS interface strength and overall joint strength, this research employed tungsten inert gas welding (TIG) arc to locally remelt the AS interface zone in the FSW-AZ31 joint. The microstructure characterization after remelting showed that two TIG melting zones were formed in the interface area between the AS and nugget zone (NZ). Within these zones, the grains exhibited significant coarsening and the texture intensity noticeably decreased. Conversely, the interface between the retreating side (RS) and NZ, being far from the TIG melting zone, experienced minimal changes in texture and grain size. Mechanical testing conducted at room temperature indicated that the joint ultimately fractured at the RS, resulting in an interface strength difference of ∼16 MPa between the AS and RS. The enhanced strength of the AS interface was attributed to the low Schmid factor of basal slip, reduced dislocation density, and pronounced twinning behavior.

The influence of tool shoulder size and plate position on the characteristics of friction stir welded different aluminum alloys

ABSTRACT Welding is a main manufacturing method for fabricating various engineering components. Fusion welding techniques encounter solidification associated problems while joining light weight structures. Friction stir welding is a solid state welding technique that is developed to address these shortcomings. As the superior conductive properties of AA6101-T6 and AA1350 aluminum alloys, they are frequently utilized in electrical industries. The goal of this study is to examine how the plate position and tool shoulder diameter (D) affect the qualities of these dissimilar Al-alloys joints. It is discovered that plate positioning is the most influential welding parameter in determining the tensile properties of weldment. Furthermore, the joint fabricated with AA6101-T6 as an advancing side material and a 15 mm tool shoulder diameter produces sufficient weld reaction temperature, better plastic flow and tensile properties. However, the joint fabricated with AA1350 as an advancing side material and 12 mm tool shoulder diameter generates inadequate reaction temperature, poor plasticization, and tensile properties. The formation of precipitates as well as the interface layer at the weld nugget is greatly dominated by the tool shoulder size, which affects the wear properties of weldment.

Micro-adhesive wear and microhardness behavior of friction stir welded 2524-T3 aluminium alloy

Friction Stir Welding (FSW) emerges as a compelling solid-state welding technique for aluminium alloy components used as aircfrat materials. Despite being a solid-state process and mitigating numerous solidification challenges, it retains its thermomechanical nature, affecting the material's microstructure and, consequently, its mechanical properties. This concise communication sought to assess the impact of the FSW process on the micro-adhesive wear and microhardness properties of the 2524-T3 alloy. The results showed that the FSW process was executed successfully on 2524-T3 aluminium alloy plates as well as the great influence of intermetallic particles on hardness and micro-adhesive wear.

Investigation of Tool Degradation during Friction Stir Welding of Hybrid Aluminum-Steel Sheets in a Combined Butt and Overlap Joint.

Friction stir welding, as a solid-state welding technique, is especially suitable for effectively joining high-strength aluminum alloys, as well as for multi-material welds. This research investigates the friction stir welding of thin aluminum and steel sheets, an essential process in the production of hybrid tailor-welded blanks employed in deep drawing applications. Despite its proven advantages, the welding process exhibits variable outcomes concerning formability and joint strength when utilizing an H13 welding tool. To better understand these inconsistencies, multiple welds were performed in this study, joining 1 mm thick steel to 2 mm thick aluminum sheets, with a cumulative length of 7.65 m. The accumulation of material on the welding tool was documented through 3D scanning and weighing. The integrity of the resulting weld seam was analyzed through metallographic sections and X-ray imaging. It was found that the adhering material built up continuously around the tool pin over several welds totaling between 1.5 m and 2.5 m before ultimately detaching. This accretion of material notably affected the welding process, resulting in increased intermixing of steel particles within the aluminum matrix. This research provides detailed insights into the dynamics of friction stir welding in multi-material welds, particularly in the context of tool material interaction and its impact on weld quality.

Effect of tools rotational speed on the mechanical properties of one-step double-acting friction stir welded aluminum alloy AA 6061 hollow panel

The utilization of Aluminum hollow panels enhances structural strength while simultaneously ensuring a lightweight and efficient use of materials. During their application, these panels necessitate a welding process that is susceptible to porosity due to the disparity in hydrogen gas solubility between liquid and solid aluminum. Solid-state welding techniques, such as Friction Stir Welding (FSW), have proven to be effective and appropriate solutions for overcoming this issue. However, due to the thickness of the hollow panels, FSW process is unfeasible as it requires welding on both sides, resulting in prolonged production times. Consequently, the development of a one-step double-acting FSW technique becomes necessary, involving the simultaneous utilization of two tools. The usage of two tools introduces two sources of friction-stir forces, heat, and axial forces, demanding an assessment of the novel response from the specimens. This research aims to analyze the effect of a specific parameter, namely the tool rotation speed, within the one-step double-acting FSW process on the physical and mechanical properties of the AA6061 hollow panels. The One-Step Double-Acting FSW process involved conducting variations in the tool rotation speed on both sides of the welds. Specifically, for the 4G weld position (underside of the workpiece with an overhead weld position), speeds of 1200, 1500, and 1800 rpm were employed. Meanwhile, a consistent rotation speed of 1500 rpm was maintained for the 1G weld position (overside of the material with a flat weld position). The transverse speed and tilt angle are set at 30 mm/min and 2°, respectively. Elevating the tool rotation speed results in increased hardness, load capacity, and bending strength of the weld joints. The specimen subjected to the highest rotational speed (1800 rpm) exhibits the most exceptional mechanical properties, including a hardness of 73.46 HVN, load capacity of 18.47 kN, and bending strength of 60.56 MPa.

Advancements in Friction Stir Welding: A Comprehensive Review of Process Variables and Emerging Developments

Friction stir welding (FSW) is a solid-state welding technique widely employed to join materials such as Aluminum (Al), Copper (Cu), Magnesium (Mg), and their respective alloys. These materials find extensive use in industries like transportation, where lightweight materials with superior mechanical properties are in demand due to their reduced mass. Conventional fusion welding methods can adversely affect the mechanical properties of these welds.Over the last two decades, FSW has emerged as a specific and significant advancement in welding technology. Various parameters, including shoulder diameter, shoulder profile, pin length, pin diameter, tool angle, rotating speed, feed rate, and weld speed, play crucial roles in determining weld strength, quality, heat generation, and material mixing.The current research focuses on investigating the process variables that influence the characteristics of welded products. Furthermore, it includes an in-depth exploration of FSW fundamentals, recent advancements, and comprehensive literature reviews.

Simulation Study of Critical Aspects of MIAB Welding for Analysis of Potential Factors Governing the Performance of Weld Formation

Magnetically Impelled Arc Butt (MIAB) welding, is a solid-state welding technique. The magnetic system of this technique is pivotal for the generation of the Lorentz force, which impels an arc to rotate along the periphery of the weld tubes and thus facilitates the heating of faying surfaces. The magnetic arrangement and the arc dynamics significantly impact the effectiveness of the welding process, eventually dictating the efficiency. This study case investigates the impact of the magnetic arrangement on the arc rotation and possible factors that cause irregularities in the (MIAB) welding through COMSOL simulation. The COMSOL simulation has served as a powerful tool to comprehensively analyse various arc dynamics and magnetic systems and extrapolate the observations to analyse the arc dynamics and magnetic systems involved in MIAB welding. By employing simulation studies, the research aims to unravel critical insights for an efficient design of the MIAB welding system. This work includes a study of the effect of magnetic forces on arc dynamics using various models and attempts to develop an analogy to the MIAB welding process. This is further utilized to explain the process variations in the form of arc displacement, electric potential distribution, and the possibility of self-demagnetization of AlNiCo magnets. Thus, it provides a foundation for advancing the technological aspects of MIAB welding to overcome the limitations and irregularities. This research is instrumental in enhancing the understanding of magnetic interactions involved in the MIAB process, which can further pave the way for improved welding machine designs and consequently, enable research on these lines that can help in establishing an optimized parametric window.

Physio-Mechanical Properties and Microstructural Characteristics of Friction Stir Welded Aluminium and Copper Plates Using Conical Unthreaded Tool

Friction Stir Welding (FSW) is a type of welding used to join materials for high strength applications. FSW is a well-liked solid-state welding technique for joining aluminum alloys and other non-ferrous materials in the aerospace, automotive, and marine industries. Pure copper and aluminum from the 6082 series were welded together using a specially designed milling machine. Tests for hardness, flexural rigidity, and impact are performed to assess the welding strength. Material flow and weld defects have been investigated by analyzing the microstructure of the weld junction. The modified vertical milling machine has been used to execute FSW of pure copper and aluminum plates. The aim is to explore the produced welded joints and to comprehend the difficulties encountered while utilizing milling machines as a FSW equipment. Similarly, to optimize the welding parameters in order to accomplish sound welding. FSW can be carried out on a milling machine because the flexural strength of a conical unthread thread tool is 108.58N/mm2 and 92.16N/mm2, respectively, at rotational speeds of 500 rpm and 1000 rpm with welding feed rates of 16 mm/min and 50 mm/min.

Formation mechanism for the interface between Cu and Sn formed by magnetic pulse welding

The formation of interfacial intermetallic compounds (IMCs) such as Cu6Sn5, Cu3Sn or platelet-shaped Ag3Sn which are formed in reflow soldering process will directly destroy the soldering reliability. Magnetic pulse welding (MPW), as a solid state welding technique can effectively restrain or even impede the formation of interfacial IMCs. In this paper, Cu and Sn dissimilar metals were welded by MPW under the discharge energy from 17 to 31 kJ. The typical wavy interface and metal jet flow were found in all samples. When the discharge energy reached 31 kJ, a typical gradient nanograined (GNG) interface has been observed to undergo an evolution from a sub-micron secondary solid solution of Cu6.26Sn5 IMCs to a nanoscale secondary solid solution of Cu81Sn22 IMCs, followed by the formation of nanoscale equiaxed α-Cu grains, and ultimately leading to the deformed elongated nanoscale α-Cu grains. This discontinuous distribution of the aforementioned phases occurs specifically at the interface of the 23 kJ_1.5 mm sample. In contrast, when subjected to a discharge energy of 17 kJ, there were no indications of a secondary solid solution of Cu6.26Sn5 IMCs or elongated nanoscale α-Cu grains. However, a discontinuous secondary solid solution of Cu81Sn22 IMCs was observed to form at the Cu/Sn interface under these conditions. Based on these findings, the utilization of microprojection welding (MPW) techniques involving Cu and Sn-based solder in the microscale is anticipated to serve as a highly efficient and automated technology within the field of electronic micropackaging.

Tensile behaviour of the dissimilar friction stir welding between pure copper and aluminium 1050

Copper-aluminum hybrid connectors play a crucial role in electric vehicles, but welding these metals together poses a significant challenge due to their distinct physical and mechanical properties. Friction stir welding, a solid-state welding technique, proves to be suitable for joining dissimilar metals. In this study, friction stir welding was employed to create a joint between pure copper 1100 and aluminum 1050 plates, each with a thickness of 5 mm. The fabricated results showed that a significant amount of copper was dispersed into the aluminum side to establish the bonding. The bonding strength was evaluated through tensile testing, while the macrostructure and fracture paths of the joints were monitored using an optical microscope. Despite efforts, eliminating defects in the joint proved challenging, with most defects attributed to vacancies. Increasing the tool rotation speed resulted in greater mixing intensity between the aluminum and copper. The interface between the copper and aluminum was found to be prone to crack propagation. The tensile strength of the joint improved with higher tool rotation, reaching up to 88 MPa. For further analysis, stress within the joint under tensile loading was simulated.

Influence of Strain Rate on Metallurgical and Mechanical Properties of Friction Stir Spot Welded Aluminium Joints

Nowadays, the substitution of copper with aluminium is widely pursued in order to save weight and material costs, for battery components and wire connectors. Additionally, cost reductions can be further enhanced with effective reduction of energy consumption through efficient manufacturing. Therefore, friction stir spot welding as a solid-state welding technique is a potential choice with low energy demands and high joining performances. However, the joining of aluminium and its alloys with solid-state welding techniques is still a challenging task due to a persistent and chemically stable aluminium oxide layer formed at the sheets prior to the welding, due to the reaction between aluminium and atmospheric oxygen. In this paper, the influence of strain rate induced during friction stir spot welding process on the metallurgical, mechanical and electrical properties of friction stir spot welding of AA 5754-H111 was studied. The strain rate was calculated according to the rotational speed of the tool and the effective (average) radius and depth of the stir zone. It was observed that the specimens welded with a lower strain rate endured a 15 % higher average strain failure load compared to the specimens welded at a higher share rate. The microhardness profiles of the specimens obtained at low strain rates imply strain hardening mechanisms in the weld zone, while the microhardness of specimens welded at high strain rates expressed thermal softening. It was also found that the friction welded sheets, regardless of the strain rate, show increased electrical resistance compared to the base material, however, it decreases with an increase in strain rate. Microstructural analysis reveals a stress-induced metallurgical transformation in the narrow zone around the weld-faying interface.

Role and Effect of Friction Stir Welding Tool pin Profiles on Tensile Characteristics of Dissimilar Al6061-Al2014 Welded Joints

Friction stir welding is a non fusion solid state welding technique where sheets are welded with application of frictional heat and pressure together. In this welding process, the tool pin geometry plays a crucial role for development of good quality welded joints. In this work, Al6061 and Al2014 aluminium alloy plates were welded with use of three different tool pin geometries such as straight square, straight hexagonal and taper threaded. Tensile properties and hardness of the welded joints were evaluated. From the results, the welded joints developed with straight square geometry tool tensile properties are better than the welded joint developed with straight hexagonal and taper threaded profiled tools. The better properties are due to pulsating action and higher dynamic volume to static volume ratio of the straight square geometry tool. A microstructural evaluation revealed that formation of more homogeneous distribution throughout the weld nugget for the welded joint made with straight square geometry pin tool.

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.

Refill friction stir spot welding of thermoplastic composites: Case study on Carbon-fiber-reinforced polyphenylene sulfide

Refill Friction Stir Spot Welding (refill FSSW) is an innovative solid-state welding technique that has been successfully applied to various combinations of metallic materials. The objective of the present study is to investigate the feasibility of refill FSSW for polymer–polymer structures, with a specific emphasis on carbon-fiber-reinforced polyphenylene sulfide (CF-PPS). The influence of the key joining parameters, i.e. force, plunge depth, rotational speed, and tool diameter, has been analyzed in terms of the resulting joint microstructure, mechanical strength, and failure mechanisms. The lap shear tests revealed two primary failure modes: interfacial shear failure and nugget pull-out. Fracture surfaces exhibited broken fibers. The depth of the joint was found to play a crucial role in determining the failure mode, with interfacial shear failure resulting in higher lap shear strength. Thermal analyses conducted on the produced joints showed no evidence of thermal degradation, which aligns with the temperature measurements during the process, as they remained below the melting temperature of CF-PPS.