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Dissimilar aluminum joints have widespread applications across various industries, including the electronics and automotive sectors, owing to their unique combination of advantages, including reduced density and enhanced mechanical properties. These characteristics make them an innovative solution for multi-material processing challenges presented in the engineering industry. This article focuses on Friction Stir-Welded butt joints made using a weld–flip–weld approach between aluminum AA6061-T6 and pure copper C11000, exploring the effects of varying rotational speeds (1000, 1200, and 1400 RPM), offsets (0 and 1 mm) in the joint soundness, mechanical strength, and electrical conductivity. The welds were evaluated using non-destructive testing with phased-array ultrasound and tensile testing. Additionally, the electrical conductivity was measured to assess their response to electrical currents. The findings reveal a significant correlation between joint efficiency and electrical conductivity, with the highest values corresponding to a weld executed with a rotational speed of 1400 rpm, traverse speed of 40 mm/min, and 1 mm offset towards the aluminum, achieving the highest joint efficiency, reaching a joint efficiency of approximately 75% and 82.42% of the IACS for electrical conductivity. [ABSTRACT FROM AUTHOR]

Aluminium (Al) and magnesium (Mg) alloys are extensively used in the automobile sector because of their high strength‐to‐weight ratio, excellent castability low density and simplicity of recycling. Al‐Mg structures used in the automotive sector can potentially reduce their weight. Although there is a significant opportunity for substantial cost reduction, the use of magnesium in aluminium structures remains restricted. This study aims to weld 3 mm‐thick rolled sheets of AA6061 Al and AZ31B Mg alloy using the cold metal transfer (CMT) arc welding process. Three different filler wires (ER1100, ER4043, and ER5356) were used in the experiment. In this article, the mechanical and microstructure characteristics of Al/Mg dissimilar joints manufactured by CMT are evaluated and discussed in detail. Optical microscope (OM), scanning electron microscopy (SEM), energy dispersive x‐ray spectroscopy (EDX), and x‐ray diffraction (XRD) were used to analyze the CMT‐welded Al/Mg dissimilar joints. Of the three filler wires used, ER4043 (Al‐5%Si) filler wire yielded defect‐free sound joints due to the presence of Si, which improves the flow ability of molten filler during welding. The presence of Mg‐rich intermetallics‐Al12Mg17) and Al‐rich intermetallics‐Al3Mg2 were observed. The fractured area of the CMT‐welded Al/Mg dissimilar joints revealed the presence of the Mg‐rich intermetallics (Al12Mg17), which is responsible for the decrease in tensile strength. The reduction of intermetallics, particularly of Mg‐rich intermetallics (Al12Mg17) is important for improving joint strength. Research Highlights: Cold metal transfer (CMT) arc welding was used to control the Al‐Mg‐rich intermetallics in the Al/Mg dissimilar joints.The microstructure, morphology and phase composition of the welded joints were studied by OM, SEM, TEM, EDS and XRD.The weld metal and AL substrate bonded with a strong interface, while weld metal and Mg substrate were joined at the epitaxial solidification area where the intermetallic compounds of Mg2Al3, Mg17Al12 and Mg2Si are generated.The weld metal on the Mg side experienced brittle fracture, with a continuous distribution of Mg2Al3, Mg17Al12 and Mg2Si. [ABSTRACT FROM AUTHOR]

Adhesive bonding of dissimilar materials introduces stress concentrations due to stiffness mismatch between the substrates, thereby exacerbating the peel and shear stresses leading to premature failures in single lap configurations. This work demonstrates that the stress distribution can be improved by decreasing the thickness of the stiffer substrate, and presents a structured approach to find the optimum thickness to improve overall joint performance. First, the critical stress components and critical locations in the single lap joint were identified for each mode of failure. Then, a minimax-type optimization framework was developed using severity-weighted parameters for each critical stress component. Optimal thickness obtained from the proposed framework agreed with FEA-based parametric studies within 10% variation. Overall, this approach can generate design charts and aid in efficient designs for multi-material joining. [ABSTRACT FROM AUTHOR]

AbstractSeveral potential benefits in joining thin, dissimilar and highly conductive metals in a solid-state environment make ultrasonic welding (USW) a popular method for building Li-ion battery packs. The USW method is highly complex and relies on multiple factors. In this study, aluminum (AA1100) and nickel (UNS N02200) dissimilar sheets were ultrasonically welded using various process parameters. Plastic deformation, microstructural development, and the corresponding mechanical characteristics of the joints were evaluated qualitatively and quantitatively. The joint strength and critical intensity factor values seemed to rise until the welding duration of 0.3 s, following which there was a subsequent drop in their values. Based on the mechanical analysis, it is observed that the optimal condition records an amplitude of 68 µm, a weld time of 0.3 s, and a clamping pressure of 0.24 MPa. It showed that the joint performance was significantly impacted by the plastic deformation and microstructural changes at the weld region. On the Al side, substantial plastic deformation was observed, and it was primarily attributed to the sonotrode knurls’ penetration. The Al sheet’s thickness was reduced by more than 40%. The microhardness readings at the welding region experienced diminution due to the acoustic softening effect. The cross-section and fracture surfaces of the Al/Ni weld exhibited several distinct microstructural characteristics, such as atomic diffusion, crimped interface, dimple pattern, and swirl pattern flow. Additionally, the diffusion zone is also investigated using X-ray diffraction analysis. These observations offer valuable insights for enhancing weld quality and controlling the overall welding process. [ABSTRACT FROM AUTHOR]

The objective of this work is to improve the mechanical properties of friction stir welded square butt joints of AA6061 and pure copper employing activated flux of B4C micro powder. Rotational speed, transverse feed and tool penetration depth were optimized using Taguchi method to produce joints devoid of defects. Rotational speed was found to be the most influential process parameter in achieving the higher ultimate tensile strength and has 49% contribution followed by feed and penetration depth. Model predictions for the optimal strength were validated and found to have 5 % variation. Highest ultimate tensile strength and micro Vickers hardness of 259.57 MPa and 98.58 HV respectively were obtained for joints made with speed, feed and penetration depth of 1250 rpm, 20 mm/min and 0.1 mm respectively. The microstructural analysis revealed that B4C particles were distributed uniformly in the stir zone which could be the reason for improved mechanical properties. [ABSTRACT FROM AUTHOR]

In this study, we explored the impact of intercritical tempering on the microstructural evolution and mechanical properties of dissimilar welds formed through laser welding between 5%Ni steel (SA645) and austenitic stainless steel (AISI304L). Upon tempering at 500 °C, reversed austenite manifested within the weld metal. The volume proportion of reversed austenite in weld metal at room temperature increased first, exhibiting a maximum (∼10%) at ∼600 °C, and then decreased with increasing tempering temperature, which was associated with the diminished stability of austenite. Due to the change in tempering temperatures, two distinct types of reversed austenite were present, with one being located at the high-angle grain boundaries and the other within the martensite blocks. As the tempering temperature increased, the weld metal hardness decreased, reaching a minimum of ∼306 HV at 600 °C, and then increased. The dislocation density within the martensite matrix and the quantity of reversed austenite are the crucial factors to determine the hardness of weld metal. The cryogenic impact toughness of weld metal increased at first and then decreased as the tempering temperature increased. The maximum of ∼40 J for the cryogenic impact toughness was obtained when tempering at 600 °C. The low-temperature impact toughness of the weld metal was determined by the synergy of the TRIP effect of reversed austenite, the compatible deformation capability of dual-phase structure, and the crack propagation behavior.

The article examines the influence of energy characteristics on the process of formation of dissimilar metals of aluminum and copper alloys during friction stir welding. The relationship between machine engine power consumption and stir welding friction regimes for a dissimilar joint of technically pure aluminum AD1 and copper M1 is studied. The influence of production regimes on weld appearance and the possibility of stabilizing power consumption during friction stir welding due to formation of a welded metal superplastic state are revealed. A relationship between capabilities of the equipment used and the permissible geometrical parameters of the welding tool is estimated. [ABSTRACT FROM AUTHOR]

In the present study, an anodizing process was applied to aluminum alloy (AA2024-T3) to enhance interlocking in dissimilar joints with glass fiber-reinforced polyetherimide (GF/PEI) composite, using ytterbium-doped laser fiber welding as a heat source. A factorial Central Composite Design (CCD) was conducted to determine the most appropriate processing and optimization parameters, with lap shear strength (LSS) as the response variable. The obtained and fractured joints were characterized. Anodizing effectively improved the interlocking between dissimilar joints, resulting in LSS values of around 16 MPa. Surface impressions were observed in joints with lower shear values, likely due to the ineffective heat distribution in the processed joint. In the AA2024-T3 alloy, the annealing process occurred, beginning with the segregation of the alloy elements at the grain boundaries and subsequently reducing its hardness. The SEM analysis of the laminate in the best welding condition revealed a well-established fracture surface, with cusps, fibers covered by the polymer matrix, and river marks, indicating good consolidation of the process applied to the metal/polymer junction, which is consistent with the highest shear values obtained. These findings have important implications for future research and industrial applications and can help advance the understanding of these materials and processes. [ABSTRACT FROM AUTHOR]

The laser lap welding method using a disk laser with a dual beam laser welding (DBLW) configuration was used to join DP780 dual phase steel and 5083 Al alloy. The macrostructure and microstructure were observed and it was found that there were five different intermetallic compounds (IMCs) formed in the steel/Al interface. The mechanical properties of the laser welded joints were tested and the relationships between the mechanical properties, microstructure, welding parameters and the failure modes for the joints at different laser energy densities were established. At low and high welding speeds the steel/Al joint has two different fracture modes. The failures occurred in the heat affected zone (HAZ) of weld seam and the interface of steel/Al joint, respectively. These two failure modes were ductile fracture and brittle fracture, with cleavages occurring in fracture surfaces. [ABSTRACT FROM AUTHOR]

Autogenous joints of Inconel-718 to AISI-316L sheets produced using the electron beam welding process were subjected to defect analysis by the X-ray computed tomography technique. Such investigations revealed variations in undercut and porosity formation tendencies for change in weld processing conditions. The undercut rate has been found to be effectively reduced for the double-side pass and oscillating beam (infinity pattern) conditions. An increase in welding speed from 750 to 1500 mm/min has resulted in the formation of finer pores and reduced its count by 35%. For the same heat input rate, the double-side pass joint has reported formation of uniformly distributed pores with an 80% reduction in number. Compared to static beam joints, the oscillating beam welds have reported an extensive decrease in porosity content (62–87%) and pore-size distribution. The triangular and infinity patterns have reported a more efficient reduction in porosities and size distribution than other patterns. [ABSTRACT FROM AUTHOR]

Lightweight materials that offer a good strength-to-weight ratio have a significant demand in automotive, transportation, marine, defence, rail, and other industrial applications. In this work, friction stir welding (FSW) an eco-friendly process was used to make solid state joints with newly developed hybrid pin profiles. Weld trails were designed considering an orthogonal array of L27 runs with 5 parameters and 3 levels. FSW was carried out on a 10-mm-thick AA6061/AA7075 Al-alloys dissimilar combination. The present work mainly focused on finding the optimum weld parameters with good joint strength of FSW welded samples processed by using different hybrid pin profiles. Zener–Hollomon parameter studied the material flow pattern at the stir zone. XRD patterns revealed the presence of Al as a major phase and the presence of precipitation compounds as minor phase. Microstructural analysis revealed the formation of onion ring structured fine-grains at stir zone with well-mixed two different base materials. The joint efficiency factor achieved was 97%, which confirmed the AWS standards for aerospace applications. [ABSTRACT FROM AUTHOR]

Dissimilar joining through solid-state welding is an important engineering tool to address the transportation industry's sustainable goals. The dissimilar friction stir lap welding (FSLW) of two different aluminium alloys (AA5182 and AA5052 with two different thicknesses) to steels AISI1010 and DP1000 was performed in this work, in order to analyse the effect of the mismatch in base material properties and plate thickness on the joint strength and fracture location. The mechanical behaviour and the strength of the welds were assessed using transverse tensile–shear testing and hardness measurements. Strain data acquisition through Digital Image Correlation (DIC) was used. The differences in fracture location registered for the different joints are explained based on the alloy's plastic properties and on the mismatch in thickness between the plates. Local stress–strain curves were plotted, using the strain data acquired through DIC, to highlight the mechanisms resulting in the differences in tensile behaviour among the joints. It is concluded that despite the differences in failure location and tensile behaviour, the strength of the joints was very similar, irrespective of the base material combinations. [ABSTRACT FROM AUTHOR]

Thick dissimilar joints of steel and aluminum are still of high interest for shipbuilding in order to reduce the weight and the center of gravity of the ship. Thereby, a reduction of the CO2 emissions as a result of lower fuel consumption and a higher ship stability are achievable. The steel and aluminum ship parts are joined with the aid of an explosive-welded adapter, whose manufacturing is complex, time-consuming, and expensive. Furthermore, the adapter must be oversized to meet strength requirements. Therefore, the shipbuilding industry demands a better alternative. In this study, laser beam welding processes are developed for joining steel S355 J2 (t = 5 mm) with aluminum alloy AA6082-T651 (t = 10 mm) in a lap configuration using a laser beam source with a maximum output power of PL = 6 kW. Laser beam welding of this dissimilar material combination brings certain challenges, such as the formation of brittle microstructures in the weld metal depending on the aluminum content. To improve the microstructure and the associated mechanical properties of the weld seam, a filler material in the form of iron welding powder is used. The welding powder is provided in a groove in the aluminum bottom sheet. In this way, an iron-rich microstructure results, which leads to an increase in the weld seam quality, as shown in metallographic analysis and tensile tests. For example, the cross tension force can be increased by 100%. [ABSTRACT FROM AUTHOR]

In order to fabricate high-performance dissimilar joints of Al and Cu, it is critical to inhibit the growth of brittle intermetallic compounds (IMCs) at the interface. Therefore, submerged friction stir welding (SFSW) technology was used to join the Al/Cu dissimilar materials. The results revealed that the SFSW with water cooling significantly reduced the thickness of interfacial IMCs layer, and finer grains were formed at the Al side in nugget zone of SFSW joint compared to conventional friction stir welding (FSW). The mechanical properties of the joints produced by SFSW were improved. The tensile strength of the SFSW joint reached 221.5 MPa, which was 24.02% higher than that of the FSW joint. In addition, the SFSW could change the fracture position of joints, resulting in the fracture in the Al matrix. [ABSTRACT FROM AUTHOR]

Dissimilar aluminum joints have widespread applications across various industries, including the electronics and automotive sectors, owing to their unique combination of advantages, including reduced density and enhanced mechanical properties. These characteristics make them an innovative solution for multi-material processing challenges presented in the engineering industry. This article focuses on Friction Stir-Welded butt joints made using a weld–flip–weld approach between aluminum AA6061-T6 and pure copper C11000, exploring the effects of varying rotational speeds (1000, 1200, and 1400 RPM), offsets (0 and 1 mm) in the joint soundness, mechanical strength, and electrical conductivity. The welds were evaluated using non-destructive testing with phased-array ultrasound and tensile testing. Additionally, the electrical conductivity was measured to assess their response to electrical currents. The findings reveal a significant correlation between joint efficiency and electrical conductivity, with the highest values corresponding to a weld executed with a rotational speed of 1400 rpm, traverse speed of 40 mm/min, and 1 mm offset towards the aluminum, achieving the highest joint efficiency, reaching a joint efficiency of approximately 75% and 82.42% of the IACS for electrical conductivity.

Dissimilar metal welded joints are increasingly and widely applied in any field of manufacturing. Meanwhile, a novel keyhole gas tungsten arc (K-TIG) welding technology presents the advantages of high productivity, high precision as well as low cost. This paper investigated microstructural characterization of K-TIG welded SAF2205/Q235 dissimilar joints with different welding torch deviations. Moreover, evolution of local microstructure and stress–strain behavior from transition zone was discussed by means of crystal plasticity finite element modeling. The results show that solid–solid phase transformation mode in the weld metal changes due to the change of constituent alloy elements. Noted that transition zone on the Q235 side includes compact martensite with high hardness, and the elements and mechanical properties present a severe gradient distribution. Transition zone with high strength has a greater resistance to plastic deformation. In addition, a large strain gradient takes place near the transition zone and on the side of an austenite grain with a high Schmid factor. Besides, the twin boundary is prone to deform at a lower stress level, which leads to a new strain partition. Therefore, stress–strain incompatibility caused by a difference in both mechanical properties and crystal structure is the root cause of K-TIG DMWJs failure.

The transportation industry has played a crucial role in advancing human society, but it has also raised concerns about carbon emissions and environmental pollution. As a result, significant research is being conducted in various areas, such as electric vehicles, powertrain energy efficiency, shared mobility, and autonomous driving. However, vehicles remain essential, and reducing their energy consumption is vital. One effective way to achieve this is by light–weighting vehicle materials. In the past, steel was the primary material used, but the transition to materials like aluminum has shown better weight-to-strength ratios. To drive change, we must explore the use of diverse materials since no single material is perfect. By combining specific materials, we can complement their weaknesses and enhance their strengths, opening up new possibilities for the future of mobility. One critical factor in advancing future mobility is the joining of dissimilar materials. This paper delves into various methods of joining dissimilar materials, their characteristics, and techniques to improve their joining performance. The joint strength for each joining method is also summarized in this study. The joining methods are primarily divided into mechanical joining, chemical joining using adhesives, and thermal fusion welding. Methods to enhance the joint include combining each joining method and improving surface interactions through surface treatments. The joint exhibiting the highest strength was the laser-welded joint of strength 312 MPa between Ti3Al-Nb alloy and Ni-based superalloy, while the lightest and strong joint was the friction stir-welded joint of strength 63.4 MPa in Polyamide 6 GFRP. Welded joints of polymer materials appear promising for the future mobility industry, particularly in terms of being lightweight. Additionally, there is a need to develop new methods to measure strength as the units used to represent the physical characteristics of the joints are not standardized. Some joints suffer from issues due to unclear joint area, highlighting the necessity to develop new strength measurement methods for future advancements.

Stress wave propagation in a metal–plastic bonded laminate immersed in a fluid is investigated based on linear viscoelastic theory. The reflection spectrum is theoretically derived for normal wave incidence. For the incidence from the plastic layer, the amplitude of the reflection spectrum is shown to have local minima at the resonance frequencies of every single layer. Resonance in the metal layer leads to the destructive interference of the reflected wave components, while resonance in the plastic layer appears due to its viscoelastic damping. Experimental results obtained for bonded specimens are discussed from the viewpoint of the characterization for dissimilar joints. [ABSTRACT FROM AUTHOR]

In the present work, the corrosion behavior of ultra-high strength steel (UHSS)-high strength steel (HSS) welded joint is investigated. In situ scanning Kelvin probe (SKP) and scanning vibrating electrode technique (SVET) are used to study the galvanic corrosion of the dissimilar welded joint in natural seawater medium. The UHSS zone is revealed to be the most cathodic region. Meanwhile, the HSS has a high anodic activity. The corroded surface shows that the calcareous deposit is observed in UHSS zone, and the rust layer is formed in HSS and weld metal (WM) zones. When the corrosion product layer is removed, the UHSS zone is revealed to suffer from the pitting corrosion, and the HSS and WM zones exhibit the uniform corrosion. [ABSTRACT FROM AUTHOR]

The aim of this paper is to analyse the mechanical properties of butt joints between S355 steel and 6061-T6 aluminium alloy, as well as their relationship to changes in the structure of the material caused by welding. The effect of the tool offset was analysed in particular. For the analysis, tensile tests were carried out using macro- and mini-specimens taken from S355/AA6061-T6 joints and base materials. In addition, the macro- and microstructure of the joints was determined, the hardness profiles in the joints were analysed, and fractographic analysis of the fractures of the specimens was carried out. Based on the results of the macro- and microstructure examinations, typical friction stir welding (FSW) joint zones were characterised. The microstructure was observed in the interface line of the materials on the root side, the negative effect of which on the quality of the joint was confirmed by digital image correlation (DIC) strain analysis during the monotonic tensile test. The highest average value of su = 141 MPa for the entire joint was obtained for a 0.4 mm tool offset. The highest average value of su = 185 MPa for the selected joint layer was obtained for a 0.3 mm tool offset. Fracturing of the joint in the selected layer for the tool offset values of 0.3 mm and 0.4 mm occurred in the weld nugget zone (WNZ) where the lowest hardness was recorded. [ABSTRACT FROM AUTHOR]

Due to their distinctive qualities, ultra-lightweight alloys like AA6061 and AZ31B find use in a variety of significant applications. However, they are challenging to fusion weld due to incompatible metallurgical properties that result in significant cooling stresses and solidification defects like hot cracking and porosity. To address the problems brought on by the fusion welding process, solid state technology is employed to combine various materials. The goal of this study is to pinpoint the impacts of friction stir spot welding process variables on shear fracture stress, including rotation speed, plunge rate, dwell period, and shoulder to pin diameter ratio. At a rotational speed of 1000 rpm, a plunge rate of 16 mm/min, a dwell time of 5 min, and a tool shoulder to pin diameter ratio of 2.5, the FSSW joint encounters a greater shear fracture strain. According to the hook height, width, and initiation point, an appropriate fracture load was discovered, which improved the mechanical and metallurgical qualities of the joints.

An engineering grade polymer—glass fiber-reinforced polyphenylene ether blended with polystyrene—and an aluminum alloy—AA6082-T6—were joined by friction stir welding in an overlap configuration. A comprehensive analysis was conducted of the effects of the tool penetration by adjusting the pin length and the process control on the joints' mechanical performance. To this end, a series of welds with a fixed 3° tilt angle, a travel speed of 120 mm/min, and 600 RPM of rotational speed was carried out. The analysis encompassed the mechanical strength of the fabricated joints and the mechanical energy input throughout the joining processes, the resulting cross-sectional interfaces, both on macro and micro scales, and the observed defects. The quasi-static shear tensile tests resulted in average tensile strengths varying between 5.5 and 26.1 MPa, representing joint efficiencies ranging from 10.1% to 47.4%, respectively. The joints that exhibited the lowest mechanical performance were fabricated with the highest level of tool penetration (higher pin length) with the process being position-controlled, while the best performance was recorded in joints welded with the lowest tool penetration and a force-controlled process. Nonetheless, the joint welded with a 2 mm long pin and position-controlled process exhibited a mechanical strength comparable with the highest one with a significantly lower standard deviation, a promising attribute for technological industrialization. In this way, it was found that the tool penetration, controlled by adjusting the pin length, played a significant role in the development of the joints' morphology and, consequently, mechanical performance, whereas the process control exhibited a minor influence on the mechanical performance of the joints, but a considerable effect on process repeatability. [ABSTRACT FROM AUTHOR]

This article addresses the phase evolutions and mechanical properties of dissimilar spot welds formed between AISI 430 stainless steel (FSS) and AISI 321 austenitic stainless steel (ASS). It was revealed that the fusion zone (FZ) microstructure consisted of three phases of ferrite, austenite, and martensite as well as precipitates. The heat-affected zone (HAZ) of 430 FSS had a dual-phase microstructure including coarse ferrite grains and martensite at the ferrite grain boundaries. Also, there are relatively large austenite grains, precipitates, and abundant twins in the HAZ microstructure of 321 ASS. The results of the tensile-shear test showed that peak load and failure energy were increased by enhancing the welding current from 1 to 4 kA. On the other hand, peak load and failure energy were firstly enhanced by an increase in the welding time from 1 to 2 s. Then, the peak load decreased by an enhancement in the welding time from 2 to 3 s. Finally, they improved by increasing the welding time from 3 to 4 s. In addition, it was found that the resistance spot welds failed by the pull-out failure (PF) mode in all welding currents of 1, 2, 3, and 4 kA and all welding times of 1, 2, 3, and 4 s. [ABSTRACT FROM AUTHOR]

Dissimilar joints between duplex stainless steels and nickel-based superalloys are of high significance in some industries. In this research, 2304 duplex stainless steel and Inconel 718 superalloy were welded by the resistance spot welding technique. The studies showed that the fusion zone microstructure was composed of a dendritic structure related to the grains of nickel-based solid solution (γ -phase) and γ ′ islands. The heat-affected zone microstructure of 2304 duplex stainless steel includes the austenite phase with a slight volume fraction and the ferrite phase with a high volume fraction. The austenite phase was formed with two morphologies of Widmanstätten and grain boundary allotriomorphs. The heat-affected zone microstructure of Inconel 718 superalloy also contained γ phase (nickel-based solid solution), annealing twins, and some precipitates. The results of the tensile-shear test revealed that tensile-shear strength (i.e. peak load) and fracture energy were increased by increasing the welding current from 1 to 2 kA and the welding time from 1 to 2 s. However, they were reduced by increasing the welding current from 2 to 4 kA and the welding time from 2 to 4 s. This was caused by the surface splash between the electrodes and the sheets. In the above-mentioned range, an increase in the welding current and time may also intensify the surface splash. It was also found that when the welding time was constant (i.e. 2 s), the spot weld obtained at the welding current of 1 kA failed by interfacial fracture mode. All spot welds obtained at the welding currents of 2, 3, and 4 kA failed by pull-out fracture mode. On the other hand, all spot welds associated with the welding times of 1, 2, 3, and 4 s failed by PF mode when the welding current was constant (i.e. 3 kA). [ABSTRACT FROM AUTHOR]

Ultrasonic metal welding (USMW) is widely used in assembling lithium-ion (Li-ion) battery packs due to its advantages in joining dissimilar and conductive materials in the solid state. However, the welding process and mechanisms are not yet clearly understood. In this study, dissimilar joints of aluminum alloy EN AW 1050 to copper alloy EN CW 008A were welded by USMW to simulate the tab-to-bus bar interconnects for Li-ion battery assembly. Qualitative and quantitative investigations were carried out on plastic deformation, microstructural evolution, and the correlated mechanical properties. During USMW, the plastic deformation concentrated on the Al side. The thickness of Al was reduced by more than 30%; complex dynamic recrystallization and grain growth occurred near the weld interface. The mechanical performance of the Al/Cu joint was evaluated with the tensile shear test. The failure load gradually increased until a welding duration of 400 ms, and then remained almost constant. The obtained results showed that the mechanical properties were greatly influenced by plastic deformation and microstructure evolution, which provides guidance for improving the weld quality and the process in general. [ABSTRACT FROM AUTHOR]

Dissimilarities in metal laser welding lead to brittleness in welded joints due to differences in the thermophysical and chemical properties between dissimilar base materials. To overcome such brittleness, the addition of a preset coating onto the base materials as an interlayer is a method for attaining reliable welded joints. Nd:YAG laser butt welding of DP590 dual-phase steel and 304 stainless, both with a thickness of 1 mm, was performed with a preset nickel coating as an interlayer using an electroplating process. The relationship between the microstructure and the mechanical properties of the welded joints was researched, the microstructure and composition of the weldment were analyzed, and the microhardness, tensile strength and corrosion resistance were tested. The results showed that the preset nickel coating increased the content of Ni element in the welded joints, which is beneficial to the formation of lath martensite. The average hardness of the welded joints increased by 12%, and the tensile strength was higher than 370 MPa. The corrosion rate of the welded joints can be slowed down, and the corrosion resistance can be improved by increasing the nickel coating. [ABSTRACT FROM AUTHOR]

Due to their distinctive qualities, ultra-lightweight alloys like AA6061 and AZ31B find use in a variety of significant applications. However, they are challenging to fusion weld due to incompatible metallurgical properties that result in significant cooling stresses and solidification defects like hot cracking and porosity. To address the problems brought on by the fusion welding process, solid state technology is employed to combine various materials. The goal of this study is to pinpoint the impacts of friction stir spot welding process variables on shear fracture stress, including rotation speed, plunge rate, dwell period, and shoulder to pin diameter ratio. At a rotational speed of 1000 rpm, a plunge rate of 16 mm/min, a dwell time of 5 min, and a tool shoulder to pin diameter ratio of 2.5, the FSSW joint encounters a greater shear fracture strain. According to the hook height, width, and initiation point, an appropriate fracture load was discovered, which improved the mechanical and metallurgical qualities of the joints. [ABSTRACT FROM AUTHOR]

Electrical-current-assisted friction stir welding (EA-FSW) is a procedure developed for the joining of similar and dissimilar materials. EA-FSW is a newly invented solid-state process to increase welded components' efficacy in various applications, such as marine structures. EA-FSW joints have investigated the dissimilar joints on aluminum–magnesium, aluminum–steel, and polymer-to-steel. Similar joints have been performed on aluminum, magnesium, and steel. The main parameters that affect the temperature of the nugget in EA-FSW are electrical current and tool rotational velocity. This review paper presents the fundamental principle of EA-FSW, its processes mechanism, and various types of tools, and discusses the different joints that EA-FSW welded. The effect of electrical current on the quality of similar and dissimilar joints is discussed. The simulation process and detailed modeling of the EA-FSW process are discussed in the last section. [ABSTRACT FROM AUTHOR]

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Dissimilar joining through solid-state welding is an important engineering tool to address the transportation industry’s sustainable goals. The dissimilar friction stir lap welding (FSLW) of two different aluminium alloys (AA5182 and AA5052 with two different thicknesses) to steels AISI1010 and DP1000 was performed in this work, in order to analyse the effect of the mismatch in base material properties and plate thickness on the joint strength and fracture location. The mechanical behaviour and the strength of the welds were assessed using transverse tensile–shear testing and hardness measurements. Strain data acquisition through Digital Image Correlation (DIC) was used. The differences in fracture location registered for the different joints are explained based on the alloy’s plastic properties and on the mismatch in thickness between the plates. Local stress–strain curves were plotted, using the strain data acquired through DIC, to highlight the mechanisms resulting in the differences in tensile behaviour among the joints. It is concluded that despite the differences in failure location and tensile behaviour, the strength of the joints was very similar, irrespective of the base material combinations.

Dissimilar friction stir welding joints are widely employed in the industrial field due to the excellent microstructural and mechanical properties of the resulting joints. Nevertheless, to further enhance the weld properties, the addition of reinforcement particles on the joint-line during the process has been proven effective for increasing its mechanical performance. In the present investigation, the microstructure and the impact behaviour of FSWed joints between AA2024-T351 and AA7075-T651 aluminium plates were investigated, considering the effect of different process parameters selected through a full factorial 2k design of experiments: both the rotational and translational speed of the tool, as well as the addition of Al2O3-SiC microparticles, were considered as input parameters. Unnotched 10 x 5 x 55 mm impact specimens were tested through an instrumented 50 J Charpy pendulum: total impact energy, the two complementary initiation and propagation energies as well as the peak force were correlated to the adopted process parameters. From the performed analyses, it was found that joints with reinforcing particles are prone to form wormhole defects across the stir zone that not only affect the microstructural development, but also the impact behaviour since they require less energy at break in comparison with joints fabricated without particles addition.

Cold Metal Transfer (CMT) welding technology has improved the appearance of weld beads and revolutionized the welding of thicker materials and dissimilar metals with precise metal deposition and reduced heat input. Cold Metal Transfer welding is predominantly used in a variety of industry applications, including aerospace, shipbuilding, automotive and marine industries. In this study, aluminum bronzes and carbon steel were joined by using CMT welding, a variant of the Gas Metal Arc Welding process, with ERCuAl-A2 as the filler metal. Optical microscopy was used to examine the microstructure of the CMT weld joint between aluminum bronze and carbon steel. Results have indicated that dissimilar metals such as aluminum bronze, and carbon steel could be successfully joined by CMT under various processing parameters. The tensile and bending strengths of the dissimilar joint were 490 MPa and 822 MPa, respectively. A variety of intermetallic compounds and solid solutions were generated in the weld zone and fusion zone. The micro-hardness in the carbon steel side of the fusion zones increased sharply, which was 164 HV in the welded condition. The dissimilar joint was stronger than the carbon steel, as the ductile fracture occurred on the carbon steel during the transverse tensile test of the welded specimen. The microstructure interpretation of welded dissimilar joints was analyzed by scanning electron microscopy and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

The aim of this paper is to analyse the mechanical properties of butt joints between S355 steel and 6061-T6 aluminium alloy, as well as their relationship to changes in the structure of the material caused by welding. The effect of the tool offset was analysed in particular. For the analysis, tensile tests were carried out using macro- and mini-specimens taken from S355/AA6061-T6 joints and base materials. In addition, the macro- and microstructure of the joints was determined, the hardness profiles in the joints were analysed, and fractographic analysis of the fractures of the specimens was carried out. Based on the results of the macro- and microstructure examinations, typical friction stir welding (FSW) joint zones were characterised. The microstructure was observed in the interface line of the materials on the root side, the negative effect of which on the quality of the joint was confirmed by digital image correlation (DIC) strain analysis during the monotonic tensile test. The highest average value of su = 141 MPa for the entire joint was obtained for a 0.4 mm tool offset. The highest average value of su = 185 MPa for the selected joint layer was obtained for a 0.3 mm tool offset. Fracturing of the joint in the selected layer for the tool offset values of 0.3 mm and 0.4 mm occurred in the weld nugget zone (WNZ) where the lowest hardness was recorded.

�Machine Learning focuses on the study of algorithms that are mathematical or statistical in nature in order to extract the required information pattern from the available data. Supervised Machine Learning algorithms are further sub-divided into two types i.e. regression algorithms and classification algorithms. In the present study, four supervised machine learning-based classification models i.e. Decision Trees algorithm, K- Nearest Neighbors (KNN) algorithm, Support Vector Machines (SVM) algorithm, and Ada Boost algorithm were subjected to the given dataset for the determination of fracture location in dissimilar Friction Stir Welded AA6061-T651 and AA7075-T651 alloy. In the given dataset, rotational speed (RPM), welding speed (mm/min), pin profile, and axial force (kN) were the input parameters while Fracture location is the output parameter. The obtained results showed that the Support Vector Machine (SVM) algorithm classified the fracture location with a good accuracy score of 0.889 in comparison to the other algorithms

This paper is a study of the microstructure and other selected properties of solid-state, high-speed, rotary friction-welded tungsten and mild steel (S355) joints. Due to the high affinity of tungsten for oxygen, the welding process was carried out in a chamber with an argon protective atmosphere. Joints of suitable quality were obtained without any macroscopic defects and discontinuities. Scanning electron microscopy (SEM) was used to investigate the phase transformations taking place during the friction welding process. Chemical compositions in the interfaces of the welded joints were determined by using energy dispersive spectroscopy (EDS). The microstructure of friction welds consisted of a few zones, fine equiaxed grains (formed due to dynamic recrystallization) and ultrafine grains in the region on the steel side. A plastic deformation in the direction of the flash was visible mainly on the steel side. EDS-SEM scan line analyses across the interface did not confirm the diffusion of tungsten to iron. The nature of the friction welding dissimilar joint is non-equilibrium based on deep plastic deformation without visible diffusive processes in the interface zone. The absence of intermetallic phases was found in the weld interface during SEM observations. Mechanical properties of the friction-welded joint were defined using the Vickers hardness test and the instrumented indentation test (IIT). The results are presented in the form of a distribution in the longitudinal plane of the welded joint. The fracture during strength tests occurred mainly through the cleavage planes at the interface of the tungsten grain close to the friction surface. [ABSTRACT FROM AUTHOR]

In engineering applications, such as automobile, marine, aerospace, and railway, lightweight alloys of aluminum (Al) and magnesium (Mg) ensure design fitness for fuel economy, better efficiency, and overall cost reduction. Friction stir welding (FSW) for joining dissimilar materials has been considered better than the conventional fusion welding process because of metallurgical concerns. In this study, dissimilar joints were made between the AA6061 (A), AZ31B (B), and AZ91D (C) combinations based on the varying advancing side (AS) and retreating side (RS). The dissimilar joints prepared by the FSW process were further characterized by tensile testing, impact testing, corrosion testing, fracture, and statistical and cost analysis. The results revealed a maximum tensile strength of 192.39 MPa in AZ91 and AZ31B, maximum yield strength of 134.38 MPa in a combination of AA6061 and AZ91, maximum hardness of 114 Hv in AA6061 and AZ31B, and lowest corrosion rate of 7.03 mV/A in AA6061 and AZ31B. The results of the properties were supported by photomicrographic fracture analysis by scanning electron microscopy (SEM) observations. Further, the performance of dissimilar joints was statistically analyzed and prioritized for preference by similarity to the ideal solution (TOPSIS) method. [ABSTRACT FROM AUTHOR]

Adhesive bonding is a joining technology gaining popularity in automotive and aeronautic industries because it allows weight reduction, adhesive bonds and adhesive dissimilar materials joining which could be part of assembly to be welded to other structure, resulting in thermal cycle that could affect mechanical properties. Dissimilar joints between plates of dual-ten 590/600 dual phase high strength steel and AA6061T6-590 aluminum alloy bonded by MP55420 adhesive were analyzed by means of computational stress analysis, single lap shear testing, failure analysis, thermo-gravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Results indicated that after curing at 175 ∘ C during 75 and 120 min, stiffness (measured as Young modulus) increased, ductility was reduced, two principal decomposition stages of mass loss were located from 200 to 500 ∘ C in TGA graphs, and there was no significant change in adhesive chemistry considering FTIR curves. Moreover, maximum load of single lap shear specimens was reduced, color adhesive changed from bright to dark amber, as well as joints failed by adhesive mechanism surpassing shear-strain limit as curing time increased. Computational stress analysis showed that peak normal and shear stresses were generated on both edges of adhesive joints after post-treatment time increased. [ABSTRACT FROM AUTHOR]

The aim of this work was to investigate the challenges associated with bonding Al-Mg alloys and develop a new method for bonding these alloys to steels. During an extensive R&D project, over 80 attempts, using 11 methods, were made to bond Al-6 wt.% Mg alloy (Al-5056/Al-5A06) to two types of stainless steels (heat-resistant 1Cr18Ni9Ti and conventional 316). Wide ranges of temperature (500 °C to 580 °C), pressure (0.5 MPa to 10 MPa) and time (1 min to 2 h) were used when direct diffusion bonding of these alloys. Then, effects of using various interlayers and brazing foils were investigated. The interlayers used in this work were gallium, pure titanium, copper and aluminium foils, aluminium 6061 alloy sheets, aluminium-silicon brazing foils, zinc and zinc alloy foils as well as an active brazing foil (known as Incusil-ABA containing silver, copper, indium and titanium). Several complex and multi-stage processes, using up to 3 different interlayers in the same joint, were also developed and assessed. Examination and assessment of the bonded samples, including failed attempts, paved the way of developing new methods for bonding these dissimilar materials. A number of samples with tensile strengths from 200 MPa to 226 MPa were made by using complex combinations of 2 or 3 interlayers and triple-stage bonding cycles. The highest recorded bond strength was 226 MPa in the as-bonded condition. This value is above the measured yield strength (134 MPa) and about 93% of the measured ultimate strength (243 MPa) of the parent Al-Mg alloy after it was subjected to the same bonding cycle. Since the use of complex processes was not feasible for bonding large components, a simpler and more practical bonding cycle was also developed in the project. Using the simpler process, joints with tensile strengths around 90 MPa could be made. This article also sheds light on the difficulties associated with brazing and soldering aluminium alloys with a high magnesium content. [ABSTRACT FROM AUTHOR]

Owing to the high strength and plasticity, high-entropy alloys (HEAs) can be used as filler metals to achieve high-quality joints. However, the melting base metal in fusion welding can significantly change the chemical composition of the weld zone (WZ), which may cause the failure of high-entropy effects in the WZ. In the present study, a high-entropy filler metal of CoCrNiMnAl0.6Ti0.3Si0.1 was used to join the dissimilar metals of SMA490BW steel and 304 stainless steel. Two types of joints were obtained by whether the welding plates had a V-groove or not. The effects of workpiece groove on the microstructure, element distribution, phase structure, microhardness, and tensile strength of dissimilar joints, as well as the controllability of the high-entropy effects in WZ were explored. It was found that a 60° V-groove in the workpiece could significantly reduce the amount of Fe element in the WZ. Microstructures in the WZs were changed from columnar/equiaxed grains of the No V-groove sample to lamellar structures of the V-groove sample. The microhardness in the WZ of the latter was 33% higher than that of the former. The reason was mainly related to the phase structures in two WZs. Two types of samples had a similar notched tensile strength, which was higher than SMA490BW steel, and lower than 304 stainless steel.

Exit-holes in friction stir welded dissimilar aluminum-copper (Al–Cu) joints are repaired by using probeless tools, forcing the surrounding material to fill the exit-hole cavity. The repair by refilling the same base materials is performed in two steps using probeless tools of different diameters. In this study, two different conditions are investigated, keeping the processing parameters constant and varying the tool shoulder diameters. Namely, the repair is performed using a two steps sequence of probeless tools with shoulder diameters of: (1) 12 and 19 mm, and (2) 12 and 27 mm. The refill action is achieved using only the base materials. A comprehensive experimental campaign, including tensile tests, microhardness measurements, scanning electron microscopy and energy dispersive x-ray spectroscopy investigations, have been conducted to evaluate the effectiveness of the repairing. The results showed that the usage of probeless tool is an effective strategy to repair the exit-hole of dissimilar Al–Cu friction stir welds, with exclusive contribution from the same Al and Cu base materials in the cavity of the exit-hole. The original FSW joint with exit-hole, with a diameter of about 8 mm, repaired by shoulder diameters of 12 and 19 mm exhibited ultimate tensile strength about 13% higher than the values provided by the samples taken in the steady-state region of the weld bead The maximum and minimum hardness of the repairing zone made with shoulder diameters of 12 and 19 mm are 240 and 80 HV0.1, respectively, which are within the range of the friction stir welded regions indicated in previous studies.

An engineering grade polymer—glass fiber-reinforced polyphenylene ether blended with polystyrene—and an aluminum alloy—AA6082-T6—were joined by friction stir welding in an overlap configuration. A comprehensive analysis was conducted of the effects of the tool penetration by adjusting the pin length and the process control on the joints’ mechanical performance. To this end, a series of welds with a fixed 3° tilt angle, a travel speed of 120 mm/min, and 600 RPM of rotational speed was carried out. The analysis encompassed the mechanical strength of the fabricated joints and the mechanical energy input throughout the joining processes, the resulting cross-sectional interfaces, both on macro and micro scales, and the observed defects. The quasi-static shear tensile tests resulted in average tensile strengths varying between 5.5 and 26.1 MPa, representing joint efficiencies ranging from 10.1% to 47.4%, respectively. The joints that exhibited the lowest mechanical performance were fabricated with the highest level of tool penetration (higher pin length) with the process being position-controlled, while the best performance was recorded in joints welded with the lowest tool penetration and a force-controlled process. Nonetheless, the joint welded with a 2 mm long pin and position-controlled process exhibited a mechanical strength comparable with the highest one with a significantly lower standard deviation, a promising attribute for technological industrialization. In this way, it was found that the tool penetration, controlled by adjusting the pin length, played a significant role in the development of the joints’ morphology and, consequently, mechanical performance, whereas the process control exhibited a minor influence on the mechanical performance of the joints, but a considerable effect on process repeatability.

Ultrasonic metal welding (USMW) is widely used in assembling lithium-ion (Li-ion) battery packs due to its advantages in joining dissimilar and conductive materials in the solid state. However, the welding process and mechanisms are not yet clearly understood. In this study, dissimilar joints of aluminum alloy EN AW 1050 to copper alloy EN CW 008A were welded by USMW to simulate the tab-to-bus bar interconnects for Li-ion battery assembly. Qualitative and quantitative investigations were carried out on plastic deformation, microstructural evolution, and the correlated mechanical properties. During USMW, the plastic deformation concentrated on the Al side. The thickness of Al was reduced by more than 30%; complex dynamic recrystallization and grain growth occurred near the weld interface. The mechanical performance of the Al/Cu joint was evaluated with the tensile shear test. The failure load gradually increased until a welding duration of 400 ms, and then remained almost constant. The obtained results showed that the mechanical properties were greatly influenced by plastic deformation and microstructure evolution, which provides guidance for improving the weld quality and the process in general.

This paper researches the effect of zinc coating of galvanized DP600 steel on the dynamic resistance and the delayed nugget formation of dissimilar DP600-AISI304 welded joints, obtained with resistance spot welding process (RSW). The RSW evaluations consisted of determining, from the dynamic resistance curves, the time involved in the different stages of the process, particularly the beginning of nugget formation. The experimental results showed that, from the dynamic resistance curves, it is possible to identify 8 distinct stages during the welding of galvanized DP600 steel and AISI304 stainless steel. In the case of the welding of uncoated DP600 steel with AISI304, only 6 stages are identified (except for stages 2 and 3), which are directly related to the heating, softening and melting of the galvanic coating. The energy used in stages 2 and 3, causes a delay in the beginning of nugget formation for welded joints obtained with galvanized DP600 steel compared to uncoated DP600-AISI304 welded joints, reaching values between 48 and 150 ms for all the welding conditions analyzed. Monitoring the time duration of stages 2 and 3, as defined from the analysis of the dynamic resistance curves, could be used as a tool to predict the beginning of nugget formation in the welding of galvanized steels, to avoid undesirable phenomena such as expulsion and to guarantee the quality of the welded joints. [ABSTRACT FROM AUTHOR]

In the present study, lap joints of dissimilar 5052 aluminum alloy and pure copper were fabricated by friction stir spot welding process. The work was aimed to find simultaneous effect of parameters such as tool rotary speed (1000, 1500, and 2000 rpm) and dwell time (5, 10, and 15 s) on lap shear force (LSF), hardness, and microstructure evolution. Also, statistical models of the quality characteristics were developed to understand which parameter has dominant effect on quality characteristics. Research findings showed that to obtain sound joints with high lap shear strength, tool rotary speed of 1500 rpm and dwell time of 15 s should be selected. It provides sufficient heat input for mechanical interlocking and prevents the formation of coarse and thick intermetallic compounds (IMCs) in the stir zone. On the other hand, to achieve maximum hardness, 2000 rpm tool rotary speed should be chosen to provide enough heat for formation of intermetallic compound and 10 s dwell time should be used to prevent enough time for microstructure refining. Moreover, from the statistical analyses, it was found that dwell time and tool speed are the significant factors for lap shear strength and hardness, respectively. In order to attain simultaneous maximum strength and hardness, tool speed of 1630 rpm and dwell time of 14 s should be used. In such condition, lap shear strength of 1980 N and hardness of 78 V are achieved with desirability of 86%. [ABSTRACT FROM AUTHOR]

Dissimilar friction stir welding joints are widely employed in the industrial field due to the excellent microstructural and mechanical properties of the resulting joints. Nevertheless, to further enhance the weld properties, the addition of reinforcement particles on the joint-line during the process has been proven effective for increasing its mechanical performance. In the present investigation, the microstructure and the impact behaviour of FSWed joints between AA2024-T351 and AA7075-T651 aluminium plates were investigated, considering the effect of different process parameters selected through a full factorial 2k design of experiments: both the rotational and translational speed of the tool, as well as the addition of Al2O3-SiC microparticles, were considered as input parameters. Unnotched 10 x 5 x 55 mm impact specimens were tested through an instrumented 50 J Charpy pendulum: total impact energy, the two complementary initiation and propagation energies as well as the peak force were correlated to the adopted process parameters. From the performed analyses, it was found that joints with reinforcing particles are prone to form wormhole defects across the stir zone that not only affect the microstructural development, but also the impact behaviour since they require less energy at break in comparison with joints fabricated without particles addition. [ABSTRACT FROM AUTHOR]

Dissimilar joints of SS-316L and C-276 (Hastelloy) were developed using C-276 powder with microwave exposure 600 s in microwave applicator (2.45 GHz, 900 W). A multi-physics model was validated with experimental studies and simulation were carried out to analyse the microwave-joint interaction characteristics. The simulation results showed that a concentrated electric field (5.86 × 104 V/m) and higher resistive losses (3.07 × 107 W/m3) at the joint region facilitated rapid heat generation locally. Microstructural characterization of the joint revealed the formation of cellular grains such as Fe-Ni intermetallic phases with Mo, Cr and W-carbides along the grain boundaries. Joints exhibited average microhardness of 290 HV, and tensile strength of 425 ± 10 MPa and 14% elongation with failure due to both ductile and brittle fracture modes. [ABSTRACT FROM AUTHOR]