Metal Joints Research Articles

Ultrasonic Welding Parameter Optimization for Electric Component Welding

Industrial requirements to establish metallic joints between dissimilar metals in the electric area. The ultrasonic welding process is an optimal process to joint thin sheets or foils. The goal of the research was to optimize the ultrasonic welding parameters to join thin nickel-coated copper sheets and aluminium sheets. It used a 0.5 mm thick high-purity copper (Cu-OF-R200) sheet coated with a 10 μm pure nickel layer and a 0.5 mm thick aluminium (1050A H24) sheet. The ultrasonic welding is made by a Branson Ultraweld L20 ultrasonic welder equipment. The mechanical properties and exacting geometrical tolerance of the joint were required. The welding parameter optimization is made empirically, with several welding tests. The optimal welding parameters were confirmed by non-destructive and destructive tests of the joints. The non-destructive tests were the visual inspection and geometrical measurements of the joint sizes. The destructive tests were tensile tests and macroscopic and microscopic tests. The completed test results confirmed the process applicability and the quality of the joint.

Magnetic pulse welding for dissimilar metals and corrosion studies at interface

Magnetic Pulse Welding (MPW) is an eco-friendly, solid-state welding method that utilizes high-velocity impacts. It operates without the necessity for fillers or flux and generates no harmful fumes. The process harnesses electromagnetic forces to weld two dissimilar job pieces by rapidly discharging current (∼100 µs) from a capacitor bank into a tool coil. This action produces a significant magnetic field (∼35 T) in the tool coil, which induces eddy currents in the job pieces, causing the outer piece to strike the inner piece at high velocities. Dissimilar metal joints such as Al-Cu, Cu-SS304, Al-SS304 and Ti-SS304 were successfully welded under these conditions using a 200 kJ MPW system. The resulting joints passed helium leak tests and exhibited a characteristic wavy morphology at the interface. Hardness measurements are conducted to investigate the mechanical properties of these joints, which provide valuable insights into the weldability and interface bond strength. Corrosion behaviour was evaluated, revealing bimetallic corrosion at the interface area. The welds were found to be flawless, instantaneous, and stronger than the base materials, confirming the potential of MPW for joining dissimilar metals with minimal corrosion rate of 0.441 mpy attained for the Ti-SS304 joint.

Study on the bending mechanical properties of composite tube and metal joint bonding structure

Abstract The study of the mechanical properties of composite adhesively bonded joints is a very important issue, which directly affects the safety and reliability of the structure. This article studies the bending performance of carbon fiber composite tubes and metal joint bonding structures, as well as obtains the structural bearing capacity, influencing factors, and structural failure modes. Through mechanical analysis and static bending load tests, it is shown that the failure model of composite tube adhesively bonded metal joints under bending load is manifested as the first layer peeling or interlayer failure of the composite material in the bonding area between the tube and the joint, leading to local crushing at the end of the tube. There is no gap between the tube and the joint, which has little effect on the bending bearing capacity. The thickness gradient treatment at the end of the joint does not help improve the bending bearing capacity. The adhesive layer is at a 90 ° angle, which makes it easy for the first layer to peel off; it should be avoided. Other angle layers have little impact on load-bearing capacity. The longer the bonding length is, the stronger the bending capacity is. The adhesive J133 or 420 has a similar load-bearing. Wrapping a carbon fiber unidirectional layer around the ends of tubes and joints is helpful in improving their bending load-bearing capacity.

Improvement of strength in single-lap adhesive joints of AlSi10Mg alloys fabricated by laser powder bed fusion

This study deals with the mechanical strength of metallic single-lap joints bonded with adhesive and fabricated by Additive Manufacturing (AM). To this aim, AlSi10Mg alloy has been used to manufacture the specimens using Laser Powder Bed Fusion (LPBF) process. Based on a series of tensile tests on AMed joints, the mechanical strength of the joints was determined. In this paper, a procedure is recommended to improve the strength of AMed single-lap joints. Particularly, a notch is introduced in the adherends, which plays a crucial role in the mechanical strength and failure load of the joints. Therefore, a series of single-lap joints with notch have been printed and examined. Based on the conducted tests, failure load and fracture behavior of the joints with and without notches have been compared. Here, we used the digital image correlation technique to determine strain fields on the surface of the joints. In addition, a series of finite element models has been developed to investigate the stress distributions in the adhesive and simulate the load-carrying behavior of the joints. The obtained results confirm the effective role of notches in adhesive joints for strength improvement of AMed single-lap joints. The outcome of this study can be utilized for fabrication of AMed metallic joints with a higher mechanical strength.

Optimizing tool offset in static shoulder friction stir welding of Al6061 to Ti6Al4V for enhanced joint integrity

The precise control of tool offset in static shoulder friction stir welding (SSFSW) is vital for enhancing the mechanical properties and overall effectiveness of dissimilar metal joints. The present study investigates the impact of tool offset on the development of microstructural features, intermetallic compound formation, texture analysis, and mechanical characteristics of SSFSWed Al6061 to Ti6Al4V joints. The results demonstrate that a 2.5 mm tool offset results in an average grain size of 2.65 μm, compared to larger grains of about 4.76 μm and 7.31 μm observed at 2.0 mm and 1.5 mm offsets, respectively. The percentage of low-angle grain boundaries also varies, reaching up to 42.2% at a 2.5 mm offset compared to 48.6% at 2.0 mm and 64.1% at 1.5 mm, indicating enhanced homogeneity in the microstructural properties. Moreover, the ultimate tensile strength at the 2.5 mm tool offset reaches 279 MPa, which is 5.7% higher than at the 2.0 mm offset and 13.4% higher than at the 1.5 mm offset. This improvement is attributed to more uniform distribution of Ti particles over the stir zone. Texture analysis further supports these findings, with the development of alpha fibre at 2.5 mm offset enhancing ductility, thereby underscoring the critical role of tool offset in achieving sound dissimilar metal weldments.

Exploring the cutting edge: Recent trends in cold metal transfer welding

Cold metal transfer welding is known for its automated welding process, which is equipped with shortcircuit-based deposition of filler wire, which allows it to control its heat input parameter properly along with a wire feed rate. Cold metal transfer’s main characteristic, which greatly affected the manufacturing industries, is joining thin, similar, or dissimilar metal sheets as the processing heat input is minimal. This review paper (covering 104 studies) examines how joining different metals with varying welding parameters affects their weld appearance, microstructure, tensile strength, and the formation of joint failure. The main focus was on what additional methods, like hardfacing or post-heat treatment of material, must be adopted to enhance the joint's weld quality and appearance. The paper starts with the investigation of numerous dissimilar weld joints formed by the cold metal transfer technique, along with the effect of varying welding parameters and ultrasonic-assisted cold metal transfer hybrid welding on the weld quality and post–pre-weld heat treatment of materials. A comparison of different cold metal transfer arc modes employed in wire-arc additive manufacturing has also been discussed briefly. At the end of the analysis, it was noted that some metal joints had a positive impact, and some gained a negative effect while increasing the heat input. The research articles studied in this paper indicate that not every material would exhibit the same welding property when subjected to a specific set of varying welding parameters.

Copper-supported MOF-derived carbon materials for highly efficient antibiotics removal

Facing the escalating issue of antibiotic pollution and the emergence of bacterial resistance in water ecosystems, photocatalytic technology has been widely studied as one of the efficient methods to remove antibiotics in aquatic ecosystem. Herein, the bimetallic organic framework materials Cu/Zn-BTC were synthesized with varying proportions of copper and zinc as metal joints and 1,3,5-phthalic acid as organic ligands. Subsequently, the zinc elements within the MOF were eliminated through high pyrolysis to obtain carbon materials derived from Cu/Zn-BTC (referred to as 1.3CZC, 1.4CZC, and 1.5CZC based on the copper-to-zinc ratio). Notably, the presence of different valence copper species facilitated to form type II heterojunction within MOF-derived carbon materials, where internal Cu0/Cu+ species combined with oxygen vacancies to create localized bands that prolonged the lifetime of photogenerated carriers and enhanced photocatalytic activity. X-ray photoelectron spectroscopy, Brunauer-Emmett-Taylor and other characterization methods were used to analyze the difference in structure and performance of different catalysts. 1.4CZC showed excellent performance, upon exposure to visible light for 30 min, the removal rate of tetracycline significantly increased to an impressive 92.4 %, while extending the exposure time to 60 min further improved the removal rate of ciprofloxacin to approximately 82.6 %. It provides a highly efficient antibiotics removal pathway by MOF-derived carbon materials.

Development of large-size dissimilar stainless steel/α-Ti alloy joints by diffusion bonding using vacuum hot press: Interface microstructure and tensile response in the temperature range of 77–773 K

In the present study, dissimilar metal joints of SS321 and Ti–5Al-2.5Sn (α-Ti alloy) are produced by diffusion bonding at temperatures of 850, 900, and 950 °C under 10 MPa pressure for 30 min duration using a vacuum hot press (VHP). The interface of the joints was characterized through scanning electron microscopy coupled with energy dispersive spectroscopy and electron backscattered diffraction analysis for examining microstructure, morphology, and microchemistry across the interface. The effect of change in the heating process during diffusion bonding on the growth kinetics of interface layers was investigated. The interface of the joints comprised of intermetallic phases of σ phase, χ phase, (Fe,Cr)2Ti, FeTi and β-Ti. The joint produced at 900 °C has exhibited a maximum tensile strength of 315 MPa, 253 MPa, and 208 MPa at the test temperatures of −196 °C (77 K), room temperature (300 K), and 500 °C (773 K), respectively. Reduction in joint strength was noticed at test temperatures of RT and −196 °C for the samples bonded at a higher temperature of 950 °C due to the increased widths of the intermetallic phases at the interface. The effect of the bonding temperature on the tensile strength of the joints at an elevated test temperature of 500 °C was found to be negligible; however, the joints displayed good retention of strength along with substantial strain hardening followed by ductility at 500 °C. Fracture surfaces of RT and −196 °C tested samples showed the mixed mode of featureless smooth and cleavage fracture, whereas the 500 °C tested sample displayed planar interface failure. The zone of failure of the joints was noted to be around the interphase layer made of (Fe,Cr)2Ti + FeTi intermetallics.

Producing of coaxial joints of dissimilar metals with the help of explosion

Producing of coaxial joints of dissimilar metals with the help of explosion

Bolt-bearing behavior of hybrid CFRP-steel laminates at low temperature

Hybrdization of CFRP with steel sheets enhances bolt-bearing performance. At room temperature, bearing strength is reported to increase while minimum edge and width distances decrease. To assess if this advantage persists under low temperature conditions, bolt-bearing tests following AITM 1-0009 are conducted at 23°C and −55°C. Various monolithic and hybrid configurations with different metal content and joint geometries are examined. Furthermore, ultrasound scanning and optical microscopy of the fracture plane is conducted. Hybridizing composites notably improves bearing capacity. However, the reinforcement effect is less pronounced at low temperatures compared to room temperature. The reduction in minimum edge and width distances with metal hybridization largely depends on the composite ply stacking, challenging general literature recommendations. Regarding damage mechanisms in the joints, fractography indicates that introduction of steel sheets relieves composite plies, isolates damage, and enhances load-bearing capacity through additional bending stiffness and significant plastic deformation of the metal.

Microhardness and Tensile Strength Analysis of SS316L/CuCrZr Interface by Laser Powder Bed Fusion.

Metallic joints within tokamak devices necessitate high interface hardness and superior bonding properties. However, conventional manufacturing techniques, specifically the hot isostatic pressing (HIP) diffusion joining process, encounter challenges, including the degradation of the SS316L/CuCrZr interface and CuCrZr hardness. To address this, we explore the potential of laser powder bed fusion (LPBF) technology. To assess its viability, we fabricated 54 SS316L/CuCrZr samples and systematically investigated the impact of varied process parameters on the microhardness and tensile strength of the dissimilar metal interfaces. Through comprehensive analysis, integrating scanning electron microscopy (SEM) imagery, we elucidated the mechanisms underlying mechanical property alterations. Notably, within a laser volumetric energy density range of 60 J/mm3 to 90 J/mm3, we achieved elevated interface hardness (around 150 HV) and commendable bonding quality. Comparative analysis against traditional methods revealed a substantial enhancement of 30% to 40% in interface hardness with additive manufacturing, effectively mitigating CuCrZr hardness degradation.

Effect of Fe-Al intermetallics on fatigue properties of aluminum to steel dissimilar spot welds

Lightweight structures made of aluminum alloys and high strength steels are increasingly used for improving vehicle fuel efficiency. One barrier for joining aluminum and steel is the formation of brittle Fe-Al intermetallics that can have deleterious effects on joint ductility and strength under static loading conditions. However, it is unclear how the intermetallics affect the joint fatigue properties. In this study, the effect of intermetallics on fatigue properties of dissimilar metal joints between a 6xxx aluminum alloy and a high-strength steel is investigated on welds created by ultrasonic interlayered resistance spot welding (Ulti-RSW). Joint efficiency calculations are used to normalize the peak load so the fatigue properties of Ulti-RSW are compared with a wide range of joining processes in the literature. During fatigue testing the failure mode transitions from interfacial or button pull-out failure during low cycle fatigue loading (below 100,000 cycles) to through-thickness failure during high cycle (above 100,000 cycles). Based on the stress intensity factors calculated using a simple 2D fracture mechanics model, the transition in failure mode is attributed to the plastic deformation near the notch tip. Overall, this study shows that the intermetallics have little effect on the high-cycle fatigue properties of dissimilar spot joints.

High-resolution dynamic thermal programming platform based on micro thermoelectric device assisted by laser integrated manufacturing

Thermoelectric devices (TEDs) exhibit much application potential in thermal camouflage and encrypted display recently, requiring that TEDs possess large responsivity, high resolution and rapid response with flexible configuration design, which are hardly realized by the traditional complex fabrication process. In this work, an innovative laser integrated manufacturing technology including double-side-printing selective laser melting (D-SLM) and selective laser ablation (SLA) is developed for the construction of the dynamic thermal platform based on micro TEDs. Through experimentally determining the laser process window assisted by external temperature field regulation, a flat p-type film can be directly transformed from n-type Bi2Te3 film by D-SLM. Thus, high-precision p-n patterns without metal joints are obtained from a single locally modified film, whose thermoelectric properties are further boosted by increasing energy density and introducing a post-annealing process. Then, a dynamic thermal platform with designable shapes and small dimensions can be fabricated rapidly whose working principle is also demonstrated. The thermal platform with 4*4 arrays exhibits imaging function with a pixel size of 2 mm×2 mm, a temperature difference of ∼3 K, and a fast response time of 0.143 s. This work offers an exciting yet effective approach to fabricating TEDs for dynamic thermal programmable information displays.

Optimization of process parameters of cold metal transfer arc welding of AA 6061 aluminium Alloy-AZ31B magnesium alloy dissimilar joints using response surface methodology

The fabrication of dissimilar metal joints, particularly between AA 6061 aluminum alloy (Al) and AZ31B magnesium alloy (Mg), poses significant technical challenges due to their distinct metallurgical characteristics and the inherent difficulties associated with welding such materials. These challenges include the propensity for intermetallic compound formation, thermal cracking, and differences in thermal and mechanical properties between the two alloys. Cold Metal Transfer (CMT) welding, known for its low heat input and controlled metal transfer, offers a potential solution to these issues. However, optimizing the process parameters to ensure strong, defect-free joints requires a systematic approach. This study aims to optimize CMT welding parameters using parametric mathematical modeling (PMM) to produce high-strength Al and Mg dissimilar joints and to study the effects of CMT parameters on tensile strength (TS) and weld metal hardness (WMH), as well as the microstructural features of AA 6061 aluminum alloy/AZ31B magnesium alloy (Al/Mg) dissimilar joints. Al/Mg dissimilar butt joints were produced by the CMT process using ER4043 as filler wire. CMT, a low-heat input welding technique, was used to mitigate issues such as intermetallic compounds (IMCs), wider heat-affected zone (HAZ), and distortion. The CMT parameters, particularly wire feed speed (WFS), welding speed (WS), and arc length correction (ALC), were optimized using response surface methodology (RSM) to maximize the TS and WMH of the Al/Mg dissimilar joints. Polynomial regression was employed to create PMMs that integrated these CMT parameters to forecast the TS and WMH of the joints. An analysis of variance (ANOVA) was applied to assess the feasibility of the PMMs. The results indicated that the Al/Mg dissimilar joints, produced using a WFS of 4700 mm/min, a WS of 280 mm/min, and an ALC of 10%, exhibited higher TS and WMH values of 33 MPa and 95.8 HV, respectively. The PMMs provided precise forecasts for the TS and WMH of the Al/Mg joints with an error rate of less than 1% and a confidence level of 97%.

Friction welding of UFG copper using the W2Mi prototype machine

When welding ultra-fine-grained metals using conventional methods, the microstructure in the joint area is degraded (mainly due to recrystallization) in the heat-affected zone and a significant deterioration of mechanical properties, including joint strength. The aim of the research presented in this article was to identify the possibility of obtaining joints with strength close to initial material using friction welding of metal materials with ultra-fine grain. For this purpose, UFG (ultra-fine-grained) material was produced from technically pure M1Ez4 copper using a hybrid SPD (severe plastic deformation) process. The welding process was carried out on a machine with a prototype design that allows minimizing the welding time, while generating high force. The process parameters used on the prototype machine resulted in an increase in the hardness of the material by 4% in the joint area. The strength of the joint compared to the base material decreased slightly by 2%. The tests carried out proved that, using appropriate process parameters, it is possible to obtain a UFG metal joint without a decrease in its mechanical strength.

Strength analysis and force distribution in a tensile metal joint

One of the methods of connecting several elements of mechanical structures to form an assembly is bolting. Unlike other types of connections, such as welding or riveting, this type of connection has the advantage of being disassembled, which is why bolted connections are quite common. At the same time, like other types of connections, it is an important structural element that requires additional attention in calculations. The most common calculation of a bolted connection is using analytical formulas. Every day, the requirements for accuracy, speed and versatility of approaches to the calculation of building structures are increasing. In addition, special attention should be paid to the calculation of nodes where structures abut each other, since depending on the operating conditions of the node, different distribution of the NDP is possible, which in turn affects the geometr2ic characteristics and operation of structures. In this regard, we compared the results of the distribution of stresses and forces in the bolt using the finite element method with the use of universal quadrilateral shell FEs, universal spatial eight-node isoparametric FEs, and the semi-analytical finite element method. The obtained results of solving the test case using universal quadrilateral shell FEs and universal spatial eight-node isoparametric FEs allow us to conclude that there is a slight difference in the stress distribution in the spatial formulation of the FEM and SFEM. In addition, based on the FEM and NEM calculations and, accordingly, the calculation according to the DBN, it can be concluded that when calculating according to the DBN standards, an analytical calculation can be used to determine the safety margin of a bolt for simple tasks.

High-Temperature Oxidation of the 304/6061 Welding–Brazing Joint and Its Effects on Corrosion Characteristics

Laser–MIG hybrid welding–brazing was used to weld 304 stainless steel and 6061-T6 aluminum alloy with a thickness of 2 mm. The microstructure, morphology, chemical composition and corrosion behavior of the samples after high-temperature oxidation were investigated. The results reveal that the 304/6061 dissimilar joint had a thicker intermetallic compound layer (7–8 μm) during high-temperature oxidation (HTO) treatment than the sample without HTO treatment (2–3 μm). The oxide film thickness of the 6061 side of the weld joint treated by HTO (2401 nm) increased compared to the samples (181.1 nm) without HTO treatment. Unlike other metals treated by high-temperature oxidation, the high-temperature treatment process in this paper can reduce the corrosion resistance of the base metal and dissimilar joints, and the sequence of the corrosion current density was weld (HTO) >weld>6061 (HTO) >6061>304 (HTO) >304.

Enabling magnetic pulse welding for dissimilar tubular arrester cable joints

Climate change exacerbates the need for resource-efficient and cost-effective production processes across manifold industries, including the field of electrical connections. This specific field is characterized by a conflict of objectives, i.e., weight reductions while maintaining joint strength and electrical conductivity. From a material point of view, the use of aluminum as a conductor material is suitable for this application, as it is lighter than copper, a classical conductor material. Electrical conductors are often used in the form of flexible cables, so-called stranded wires. This type of conductor as well as the fact that the sole use of aluminum in electrical systems is not feasible, e.g., because the predetermined connection terminals of power electronic components are made of copper, creates a substantial demand for dissimilar aluminum-copper cable arrester joints. However, traditional fusion-based welding processes have proved incapable of reliably producing these dissimilar aluminum-copper joints because of thermophysical effects and chemical incompatibilities, the latter eventually leading to the formation of intermetallic phases. These phases adversely affect the quality of the joint in terms of both mechanical and electrical performance. Yet, magnetic pulse welding, a pressure welding process, is ideally suited for producing dissimilar metal joints on the basis of a low energy input during the welding process. Consequently, the formation of intermetallic phases is restrained. However, magnetic pulse welding has not been sufficiently investigated for the reliable contacting of stranded cables to tubular arresters. As a result, this paper focuses on the fabrication of tubular stranded cable arrester joints using magnetic pulse welding. To shed light on possible material combinations, aluminum-to-aluminum and copper-to-copper joints as well as their dissimilar counterparts are welded. Subsequently, the joints are characterized with regard to their microstructure and quasi-static material strength. Electrical characterization comprises the four-wire Kelvin measurement method to evaluate the resistance of the electrical joints. The results demonstrate that magnetic pulse welding is ideally suited to join the aforementioned material combination and joint configuration due to its process characteristics eventually leading to material continuity. As a result, the stranded wires are welded to the tubular arresters rather than crimped. Consequently, a comparative analysis of the joint properties with those of the joining partners shows that the measured electrical resistances and mechanical tensile forces may be considered very good.

Friction Welding of ETP-Cu Plate to SS304L Round Bar: An Experimental Study on Asymmetrical Dissimilar Metal Joints

This article outlines the development and examination of the properties of an asymmetrical dissimilar metal joint produced using friction welding (FW). Friction welding involving dissimilar materials, specifically a 50 mm (length) × 45 mm (width) × 20-mm (thickness) electrolytic tough pitch copper (ETP-Cu) plate and a 12.5-mm-diameter SS304L rod, was carried out. The assessment of the asymmetrically welded components encompassed ultrasonic testing, high-pressure helium gas testing, leak testing, tensile testing, scanning electron microscopy, optical microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, hardness measurements, and elemental mapping via X-ray. Significantly, there was an observed increase in tensile strength, resulting in a joint efficiency of 86.50% compared to the ETP-Cu base material, following FW between an asymmetric ETP-Cu plate and SS304L rod. The study unveiled notable variations in the microstructure near the joint interface on the ETP-Cu material side. Intermetallic compounds, such as FeCu4 and Cu9Si phases, were detected within the reaction layer at the interface between ETP-Cu and SS304L, exhibiting a variable thickness ranging from 30 to 50 μm.

An Investigation about Microstructures, Mechanical Properties and Corrosion Behaviour of the TIG - MIG Hybrid Welded Dissimilar UNS 2205 and is 2062 Steels

The connecting of contrasting metals, namely double stainless steel to steel made of carbon, has taken place. performed using a hybrid welding system. A TIG and MIG welding joining based hybrid joining method was designed. The microstructures of the dissimilar metal joints were studied and the grains are coarser as contrast to the use of a single the welding process process by itself. With the addition of TIG welding to the process of MIG welding, the water-holding capacity of the metal in molten state pool is significantly improved. The nominal corrosion behaviour of the weldments was found better than the single arc welding system alone. The passivation behaviour of the joints was in the similar line to that of double stainless steel base metal. The pitting resistance of the joints in 1 M NaCl solution was inferior to the base metals.