Solid-state Welding Technique Research Articles

Role of traversing speed and axial load on the properties of friction stir welded dissimilar AA6101-T6 AND AA1350 aluminium alloys

ABSTRACT Traditionally, AA6101-T6 and AA1350 aluminum alloys find prominent place in many industrial applications like electrical bus bar utilities for the sake of better conductivity. Friction Stir Welding is a non-traditional solid-state welding technique that was invented and developed by The Welding Institute. In this analysis, AA6101-T6 and AA1350 alloys have been put on experimentation with friction stir welding by varying axial load (5 kN to 9 kN) and traversing speed (60 mm/min to 120 mm/min). In order to examine the weld quality, properties such as tensile, wear and microstructural analyses have been carried out. From the results, it was observed that the weldment made with 7 kN axial load and 90 mm/min traversing speed exhibited better joint properties. Similarly, the weldment made with 5 kN axial load and 120 mm/min traversing speed exhibited poor joint properties. This has been attained due to the variations in heat input, metals softening and grain coarsening at weld nugget. Taguchi L9 orthogonal array with ANOVA and Signal to Noise ratio have been adopted to understand the contribution of axial load and traversing speed on the properties of weldments. Results reveal that traversing speed is statistically significant on the properties of weldment, when compared to axial load.

Examination of Friction Stir-Welded AA 6262/5456 Joints through the Optimization Technique

Friction stir welding (FSW) is the solid state welding technique which is mostly utilized to join similar and dissimilar Al, Cu, Mg, and their alloys. This research investigated that the tensile strength of FSW dissimilar Al6262 and Al5456 of 4 mm thickness is carried out using an H-13 tool pin along with different process variables such as tool rotational speed (TRS), welding speed (WS), and tool tilt angle (TTA). The selected parameters are set as TRS of 900, 1100, and 1400 rpm, WS of 20, 30, and 40 mm/min with TTA of 2, 2.5, and 3° to find out significant parameters on tensile strength (TS). The Taguchi L27 method is taken to create a number of experiments to recognize the optimal level of each parameter to accomplish the highest TS value. From the experimental results witnessed, the extreme TS (202.44 MPa) is acquired at sample 22 when maintaining TRS-1400 rpm, WS-30 mm/min, and TTA-2 degree, whereas minimum TS (165.88 MPa) is attained at sample 15 of TRS-1100 rpm, WS-30 mm/min, and TTA-3 degree. The ANOVA outcome revealed that TRS is the most significant factor (23.24%) which improves the tensile property of joints, followed by a weld speed of 21.7% and a combination of tool speed and weld speed (16.17%). The increment in the tool tilt angle does not play a vital role in improving the TS value, and MINITAB -17 software helped to find a relation between the parameters in the regression equation.

Review of the advancements in aluminum and copper ultrasonic welding in electric vehicles and superconductor applications

Ultrasonic welding (UW), a most promising solid-state welding technique, is being developed for the automotive industry, more specifically, for joining components in electric vehicle batteries. It has also been used in rare-earth barium copper oxide (REBCO)-based superconductors, which have different stabilizing materials. At present, challenges remain when using UW to join aluminum (Al) and copper (Cu) in either application, and research in these areas are undeniably important for the future use of fully in-line UW applications. This paper provides a review of the current status of UW for joining Al and Cu, specifically in electric vehicle batteries and REBCO-based superconductors. Important issues about process characteristics and critical concerns about weld parameter optimization, joint structure morphology, temperature measurements, joint mechanical properties, and quality of the joints are addressed. Modeling and simulations using the finite element method in predicting the physical phenomena in the dynamic UW process are discussed. The status of electromechanical behaviors in ultrasonically welded joints in superconductors is detailed. Lastly, guidelines and valuable knowledge for the integration of Al and Cu UW in electric vehicle battery assembly and superconductors are provided as a basis for future research directions in these fields. • Process characteristics, critical issues and findings for UW of Al-Cu are explored. • Discussion on UW future integration in EV battery assembly and CC tapes’ joints. • UW in-line process suitability to join various materials’ combinations are examined. • Several aspects of UW that needed further explorations are investigated. • Joint quality control and reliability methods with uniform standards are evaluated.

Influence of welding parameters on mechanical, microstructure, and corrosion behavior of friction stir welded Al 7017 alloy

Fusion welding of age-hardenable high strength aluminum (Al) alloys can be challenging due to the propensity of these alloys to develop solidification-related issues such as porosity and microcracking. A solid-state welding technique, such as friction stir welding (FSW), offers an excellent alternative to fusion welding by minimizing solidification-related defects in high strength Al alloys. While high quality welds of high strength Al alloys are possible with FSW, the process is highly dependent on the welding parameters. The present study attempts to correlate welding parameters to weld quality using a systematic approach spanning microscopic to macroscopic length scales. Mechanical and corrosion testing shows the influence of the traverse speed on the different weld zones. Higher traverse speed shows higher yield strength (∼287 MPa) and better re-passivation corrosion resistance (∼ −0.958V) as compared to slower traverse speed weld yield strength of ∼264 MPa and re-passivation corrosion resistance of ∼ −0.97V. The dissolution, reprecipitation, growth, and coarsening of precipitates in the weld zones have been validated via detailed differential scanning calorimetry (DSC) and microstructural evaluation using transmission electron microscopy (TEM), revealing the effect of welding parameters. In addition, the mechanical and corrosion properties of the weld improved with post-weld heat treatment, further substantiated with microscopy detailing the changes in precipitate morphology in the weld zones. Finally, some guidelines are provided to assist in selecting parameters for FSW of age hardenable high strength Al alloys to control the width of the HAZ.

Welding Techniques for High Entropy Alloys: Processes, Properties, Characterization, and Challenges.

High entropy alloys (HEAs) are the outstanding innovations in materials science and engineering in the early 21st century. HEAs consist of multiple elements with equiatomic or near equiatomic compositions, which exhibit superior mechanical properties, such as wear resistance, fatigue resistance, and corrosion resistance. HEAs are primarily used in structural and functional applications; hence, appropriate welding processes are essential to enhancing the performances and service lives of HEA components. Herein, a comprehensive overview of current state-of-art-of welding techniques for HEAs is elucidated. More specifically, the article discusses the fusion-based welding techniques, such as gas tungsten arc welding (GTAW) and laser beam welding (LBW), and solid-state welding techniques, such as friction stir welding (FSW) and explosive welding (EB), for a broad category of HEAs. In addition, the microstructural features and mechanical properties of HEAs welded using different techniques were explained for a broad spectrum of HEAs. Finally, this review discusses potential challenges in the welding of HEAs.

The Object Segmentation from the Microstructure of a FSW Dissimilar Weld

Friction stir welding (FSW) is an environmentally friendly, solid-state welding technique. In this research work, we analyze the microstructure of a new type of FSW weld applying a two- stage framework based on image processing algorithms containing a segmentation step and microstructure analysis of objects occurring in different layers. A dual-speed tool as used to prepare the tested weld. In this paper, we present the segmentation method for recognizing areas containing particles forming bands in the microstructure of a dissimilar weld of aluminum alloys made by FSW technology. A digital analysis was performed on the images obtained using an Olympus GX51 light microscope. The image analysis process consisted of basic segmentation methods in conjunction with domain knowledge and object detection located in different layers of a weld using morphological operations and point transformations. These methods proved to be effective in the analysis of the microstructure images corrupted by noise. The segmentation parts as well as single objects were separated enough to analyze the distribution on different layers of the specimen and the variability of shape and size of the underlying microstructures, which was not possible without computer vision support.

Evaluation and Origin of Residual Stress in Hybrid Metal and Extrusion Bonding and Comparison with Friction Stir Welding

Hybrid metal and extrusion bonding (HYB) is an emerging solid-state welding technique that was developed about ten years ago. HYB exploits the fundamental idea of the well-established friction stir welding (FSW) technology, but a filler material is employed to enhance control of the microstructure and the mechanical properties of the joint. HYB and FSW allow joining to be performed at lower temperatures than classical fusion welding methods. Still, thermal gradient effects seem impossible to be entirely avoided, thus leading to residual stress within the weld region and neighbouring material. Although the FSW-induced residual stress evaluation has been extensively studied and understood, the evaluation and interpretation of HYB-induced residual stress have not been tackled so far. In the present paper, a quantitative investigation on residual stress and its origin in HYB was carried out for the first time. Specifically, a 4 mm thick AA6082-T6 HYB and a 4 mm thick AA6082-T6 FSW butt welds were considered. For the particular case of HYB, an AA6082-T4 was used as the filler material. In both cases, the full-field longitudinal residual stress was experimentally assessed using the Contour Method. The results showed that the HYB joint yields a higher magnitude of tensile residual stress compared to that of the FSW counterpart. A physical explanation for this difference in magnitude was attributed to the lower yield stress point exhibited by the filler material. Furthermore, the analysis revealed peak values of residual stress as high as 205±25 MPa and 165±15 MPa, for the HYB and FSW joint, respectively. Despite this, a similar distribution of residual stress across the weld was observed in both cases. An additional qualitative analysis on the transverse distortion of the welds outlined a pronounced undesired “V-like” deformation of the HYB joint of approximately 1.4°. By contrast, the FSW joint seemed not to show any perceptible bend.

Friction based solid state welding – A review

The present paper aims to provide a review of an important class of welding process called friction based solid-state welding. Among many other advantages such as low heat input, shorter welding cycle friction based solid-state welding techniques are suitable for joining both similar and dissimilar materials and helps to eliminate the defects associated with the conventional fusion welding techniques and results in welds of high structural integrity. In this paper, two important friction based joining processes were reviewed namely rotatory friction welding (RFW) and linear friction welding (LFW). RFW is well established form of friction welding, while as, LFW is an emerging method of joining. In present article, the joining process is first described which is followed by the process parameters and their effect, finally the application of the process is introduced. In the end a conclusion section along with future outlook is introduced.

Solide State Diffusion Bonding of Al6061-SiC Nanocomposites

Aluminium matrix composites are both strong and lightweight, and are limited in their applications due to the proper choice of welding process. Conventional welding that is based on fusion at the welded joint is not suitable because it leads to the formation of certain defects at the welded joint. For this reason, solid-state welding such as diffusion bonding is one of the suitable joining methods, as there will be no melting of any of the constituents. The solid-state diffusion bonding at 520° C of Al6061-SiC nanocomposites was investigated. This composite material was made by powder metallurgy, where aluminium alloy Al6061 was selected as the base metal, and SiC nanoparticles with an average size of 50 nm were added as reinforced particles. The effects of bonding time on the microstructures and mechanical properties of the welded material were investigated. The main characterisation techniques were optical microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy, x-ray diffraction, and microhardness measurements. We have found that increasing the holding time up to 3 h at 520° C strengthens the weldability of the two basic composite materials and increases their hardness. X-ray diffraction analysis did not reveal any new phase during diffusion welding; it is considered one of the advantages of using the solid-state diffusion welding technique for the assembly of this kind of composite material. The welding success of this composite material widens its field of use, such as the automotive or space industry, because it is a light material with high mechanical properties.

Friction Stir Welding/Processing of Mg-Based Alloys: A Critical Review on Advancements and Challenges.

Friction stir welding (FSW) and friction stir processing (FSP) are two of the most widely used solid-state welding techniques for magnesium (Mg) and magnesium alloys. Mg-based alloys are widely used in the railway, aerospace, nuclear, and marine industries, among others. Their primary advantage is their high strength-to-weight ratio and usefulness as a structural material. Due to their properties, it is difficult to weld using traditional gas- or electric-based processes; however, FSW and FSP work very well for Mg and its alloys. Recently, extensive studies have been carried out on FSW and FSP of Mg-based alloys. This paper reviews the context of future areas and existing constraints for FSW/FSP. In addition, in this review article, in connection with the FSW and FSP of Mg alloys, research advancement; the influencing parameters and their influence on weld characteristics; applications; and evolution related to the microstructure, substructure, texture and phase formations as well as mechanical properties were considered. The mechanisms underlying the joining and grain refinement during FSW/FSP of Mg alloys-based alloys are discussed. Moreover, this review paper can provide valuable and vital information regarding the FSW and FSP of these alloys for different sectors of relevant industries.

Study the effect of welding pass number on the mechanical and metallurgical properties of Aluminum type Al 1050 H14 produced by friction stir welding

Friction Stir Welding (FSW) is a solid-state welding technique with non-fusible rotary welds. Heat is generated by the friction produced between the weld tool and the two opposite surfaces of the two welded parts and the tool works on mechanical mixing with the presence of heat, pressure, and heat generated, reaching approximately (80-90%) of the melting point of the metal to be welded. In this study, Al 1050 H14 aluminum with a thickness of (6mm) was used for the purpose of welding it by means of the friction stir welding process in a butt welding method to obtain similar welding joints. A set with a square stitching tool Made of alloy steel was used by using a milling machine, with fixed (rotational speed of 1008 rpm and linear velocity of 40mm / min), an inclination angle of (2o), and counterclockwise rotation. The efficiency of welded joints was evaluated through static mechanical tests. Tensile tests, microscopic hardness, and visual examination. The results for all welds showed that the mixing zone (NZ) consists of fine grains of equal axes compared to the base metal. When welding on one side and in one path, the microstructure of HAZ was similar to the base metal. TAMZ was a transition region between HAZ and NZ. As for welding on one side, with two paths and three paths, the structure turned into a fine crystalline structure. By increasing the number of paths per side, the welding efficiency of the welded sample increased as the best efficiency was from one side and three paths (76.215%). Through the results, the tensile strength increases with the increase in the number of paths, as the best tensile strength was obtained when conducting the welding process from one side and by three paths, which is (93.653 MPa). It is equivalent to 76.21% of the tensile strength of the base metal. The hardness value in the weld zone (NZ) is higher than the other two zones (HAZ, TMAZ) due to the occurrence of dynamic recrystallization, which results in very fine and equiaxial crystals, but the hardness value in the weld zone remains less than the hardness value of the base metal.

Investigation of microstructural and mechanical properties of AA1050-AZ91D dissimilar friction stir welding

Joining of aluminium and magnesium alloys frequently pose significant challenges to the extent where joining may seem impossible, due to differences in the physical, metallurgical, and chemical properties of the materials. Friction stir welding is a solid-state welding technique which uses a non-consumable tool to join metals. This study examines the dissimilar friction stir welding of 3 mm thick AA1050 and AZ91D alloy sheets. Successful defect-free joints were achieved at rotational speeds of 400 rpm and 600 rpm, and a constant traverse speed of 50 mm/min. The metallurgical investigations used to characterize the microstructure of the welds are optical microscopy (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The microstructures of the samples show distinct morphology attributed to their different rotational speeds. However, Al3Mg2 intermetallics (IMCs) phase was detected in the white bands present in both weld samples. The IMCs were formed through solid-state diffusion. The mechanical properties characterizations includes the microhardness profiles and tensile testing. The variation in the rotational speeds do not have a significant effect on the microhardness distribution of the weld samples. The tensile strength of the dissimilar weld improved substantially with the presence of an interpenetration feature (IPF).

Thermal-induced Residual Stresses and Distortions in Friction Stir Welds - A Literature Review

Friction Stir Welding (FSW) is a solid-state welding technique that uses the heat generated from friction to assemble a wide variety of materials. Irrespective of having a lower heat input as compared to conventional welding techniques, friction stir welds are still prone to significant thermal-induced stresses and distortions owing to the uneven heating and cooling cycles that a weld goes through. Surprisingly, not several reviews have addressed both the residual stresses and distortions of friction stir welds despite their crucial impact on the weld performance. Therefore, the current paper reviews their development, their correlation with process parameters, and ways to reduce them. Moreover, it explains the current status of process modeling and research gaps in the area of interest.

Exploring the application domain of friction stir welding in aluminum and other alloys

Friction stir welding (FSW) is a new solid-state welding technique used to join similar and dissimilar materials, especially aluminium alloys. Friction stir (FS) welding proposes numerous benefits compared to conventional fusion welding techniques and can be successfully applied in shipbuilding, aerospace, automobile, and railway industries. This paper gives a comprehensive review of the FSW process and its technical aspects. The effects of tool pin profiles, feed rate, tool tilt angle and welding speed, etc., and mechanical and metallurgical behavior of FS welded joints have been reviewed in this article. In addition, this paper covers the literature review of friction stir welding of similar and dissimilar aluminum alloys (AA), optimization techniques, welding defects, and fatigue behavior of FS welded joints. Furthermore, a summarized report of work done by many researchers in friction stir welding is also presented. Finally, it also identifies the future scope, applications, and research gap.

Experimental study of the defects, mechanical and microstructural characteristics of friction-stir-welded Al 6061 sheets

A promising solid-state welding technique, Friction Stir Welding- FSW- and its influence on microstructure and defects formation of the Al6061 welded plates and though consequence mechanical properties have formed the central part of the present study. The current research focuses on studying the effect of 3 crucial parameters of FSW, welding and rotating speed, and pin profile (each varying in 3 levels) on grains’ modification and the occurrence of flaws after nine designed trials with the help of the Taguchi method. Vickers micro-hardness and tensile tests were conducted to determine how the grain formation and defects affected mechanical properties. It was observed that all three central regions of the welded pieces, NZ, TMAZ, and HAZ, have experienced grain modification, plastic deformation, and defect formation with different severity. The distance of the region from the weld line, welding and rotating speeds, and ratios were affecting the severity of changes. According to the obtained results, HAZ showed less strength than others since all samples’ failure occurred in this zone. Higher values of hardness and tensile strength for each pin profile resulted from higher welding speeds and lower rotational ones.

Effects of graphene nanoplatelets and boron carbide on microstructure and mechanical behaviour of aluminium alloy (Al6061) after friction stir welding

ABSTRACT Friction stir welding (FSW) has gained enormous attention as a well-established solid-state welding technique. Loss of strength and compromise on heat-affected zone has always been an issue in welding. The addition of Graphene Nanoplatelets and Boron Carbide in Al6061 via FSW has been studied hereby. The effect of individual and hybrid combination of both reinforcements in the Al6061 matrix was explored by using a comparative approach with non-reinforced FSW reference. A detailed microstructural investigation, utilising the optical and scanning electron microscopy was conducted. The mechanical behaviour was examined by employing micro-hardness and tensile testing. Fractography was carried out to inspect the tensile tested fractured FSW samples. Maximum strength was displayed by the boron carbide added FSW joint at the cost of ductility. The tendency of graphene nanoplatelets to cluster led to the deterioration of mechanical profile at the respective FSW joint. A dominant behaviour of boron carbide was observed in the hybrid combination of the reinforcements at the FSW joint.

Application of progressive hybrid RSM-WASPAS-grey wolf method for parametric optimization of dissimilar metal welded joints in FSSW process

An eco-friendly high efficiency solid state welding technique, Friction stir spot welding (FSSW) produces the welding lap joints of two dissimilar material of aluminum alloy to a commercially used copper alloy. Generally, Copper has an excellent thermal and electrical conductivity combined with creep resistance and high ductility which are used in the current carrying electrical connection and components in the automobile and electrical Industry. A number of experiments have been carried out in this paper which focus on the maximum force required to break workpiece, maximum stress developed and heat affected zone at the welding joint by changing the different parameters such as rotational speed, pin length and tool tilt angle. In this investigation, tests were completed according to Response Surface Methodology based L15 orthogonal array. The optimum welding parameters were determined by using WASPAS (weighted aggregated sum product assessment) coupled Grey Wolf Optimization method which reported pin length as the most significant constraint. Validation of the output responses was done augmenting the mechanical performances of welded joints.

Sustainable Processing of Dissimilar Aluminium Alloy Joints by Friction Stir Welding

Friction stir welding is one of the unique solid state welding technique that is fast gaining importance because of its excellent properties pertaining to the strength, wear, hardness and better joining capabilities. The friction stir welding technique is effectively used in this research to join 5 mm thick dissimilar aluminium alloys of AA 7075 and AA 5052 grade. The friction stir welding joints are obtained by using three different tool profiles viz., straight cylinder, taper cylinder, and straight triangular at a speed of 800, 1000, 1200 rpm and a feed rate of 100, 120, 140 mm/min. The experiments are designed based on L9 orthogonal array considering Taguchi techniques. From the experimental results, the process methodology is validated and the outcomes of the experiment are considered for fabrication of strong joints. The design and optimization of the process has led to better process control and thereby extended its scope for the use of the optimized process parameters for joining dissimilar aluminium alloys in real time engineering applications with sustained methodologies involving reduced dwell time and optimized friction forces and torque during the friction stir welding of dissimilar aluminium alloys.

Effect of tool axis offset and relative position of materials on the performance of dissimilar friction stir welded aluminium alloy joints–an overview

At present most of the manufacturing sectors are looking for high strength lightweight structures with high specific stiffness and good corrosion resistance. In this context, combined use of different types of aluminium alloys are required and warrants efficient joining of the dissimilar alloys. But, efficient joining of dissimilar aluminium alloys by fusion welding techniques is very difficult due to the poor weldability of dissimilar aluminium alloys. It is reported that FSW being a solid state welding technique can avoid all problems associated with fusion welding and is a potential candidate technique for joining difficult to weld materials including dissimilar aluminium alloys. With regard to FSW dissimilar aluminium alloys, the tool axis offset and relative positioning of alloys are also reported to be important. In this article, a comprehensive discussion on the influence of tool axis offset and relative positioning of the materials on the joint performance that reported in the literature is presented. The literature showed that there is uniqueness in the value and sign of the tool axis offset that can result defect free joint with good joint properties. With regard to relative positioning of the materials also, conflicting arguments are reported in the literature.

Impulse Pressure-Assisted Diffusion Bonding (IPADB): Review and Outlook

Diffusion bonding is a solid-state welding technique used to join similar and dissimilar materials. Relatively long processing times, usually in the order of several hours as well as fine polished surfaces make it challenging to integrate diffusion bonding in other production processes and mitigate widespread use of the technology. Several studies indicate that varying pressure during diffusion bonding in contrast to the traditionally applied constant load may reduce overall processing- and bonding times. Such processes are referred to as impulse pressure-assisted diffusion bonding (IPADB) and they are, for the first time, reviewed in this work using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) methodology. Results of the review indicate that varying pressure can indeed reduce bonding times in diffusion bonding and reduce the requirements for pre-bond surface preparation. Additional research is required and should go beyond small and simple sample geometries to concentrate on making IPADB accessible to industrial applications.