Abstract Wire Arc Additive Manufacturing (WAAM) utilises the process of arc welding for the additive manufacturing of components and is suitable for functionally graded additive manufacturing. The aim of the present study is to illustrate the possibility of systematically generating pores in additively manufactured AlSi10Mg components when customised shielding gas conditions are used. For this purpose, Gas Metal Arc Welding-WAAM was used with variation of shielding gas composition and shielding gas quantity to produce vertical multilayer walls consisting of AlSi10Mg. Micrographs revealed the well-known Al matrix with Al-Si eutectic and statistical analysis showed strong influence of shielding gas composition on porosity, number of pores and pore diameter. Using N 2 + 10 vol% H 2 as shielding gas increased the porosity and pore diameter significantly while using Ar or Ar + 10 vol% H 2 led to smaller pores which, however, are present in larger numbers. Varying the amount of the respective shielding gas between 3 Nl/min, 12 Nl/min, 18 Nl/min and 30 Nl/min had only a minor influence on porosity, number of pores and pore diameter. However, the usage of 3 Nl/min led to higher porosity when Ar shielding gas was used and to less porosity and pore diameter when N2 + 10 vol% H2 was used. Finally, when Ar + 10 vol% H2 was used, the parameter set with 3 Nl/min was not suitable for the manufacturing of a wall with WAAM. The use of the N 2 -H 2 gas mixture appears to be a promising approach for manufacturing of continuously porous structures whereby nitride precipitates appear to stabilise the pores during remelting. However, as only few samples were tested, a stable process window has not been established yet.

In this work, an attempt was made to study the effects of various shielding gases on the quality of SS304H welded using a CO2 laser. The SS 304H sheets of 5 mm thickness were welded using three different shielding gases, viz. 100% CO2100% Argon and 80% Argon + 20% CO2 shielding gases at a flow rate of 15 liters/min. Weld quality was evaluated based on the analysis of mechanical properties, including hardness, tensile strength, and impact strength. The property variations are justified through metallurgical investigations, including scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD) analyses. Overall, the usage of 100% CO2 as shielding gas resulted optimum microstructural and mechanical characteristics with a hardness value of 280 HV and tensile strength of 729 MPa, though with a low impact toughness value of 33 J.

This study reviews the application of wire arc additive manufacturing (WAAM) technology in maritime engineering and investigates an experimentally driven analytical approach for prediction of thermal distributions based on the Rosenthal solution. Two ER70S-6 low-carbon steel WAAM cylinders were fabricated using gas metal arc welding (GMAW) and plasma arc welding (PAW) processes, with interlayer temperatures of 453 °C and 250 °C, respectively. Accurately measuring the temperature field to tailor the microstructure has long been a challenge. The results indicated a significant deviation between the analytical predictions and the experimental data. To address this discrepancy, a hybrid approach combining analytical and experimental results was implemented. Time intervals between layers, extracted from the experimental data, were incorporated into the Rosenthal equation to improve the accuracy of temperature field predictions. The microstructure at the bottom, middle, and top regions of the WAAM components was examined using optical microscopy. Tensile testing and Vickers microhardness measurements were conducted to evaluate mechanical properties. Scanning electron microscopy (SEM) was used to analyze fracture surfaces and identify fracture modes. The results were consistent with those reported for other ER70S-6 cylindrical WAAM components. This work highlights limitations of the Rosenthal solution and emphasizes the need for thermal models in WAAM applications.

This study presents an integrated modeling and optimization framework for laser transmission welding (LTW) of transparent polymethyl methacrylate (PMMA) joints using single- and multi-core copper wires as energy absorbers. The highly nonlinear relationships between laser power, welding speed, and spot diameter and the resulting shear force and weld width were modeled using a hybrid neuro-regression strategy combining data-driven learning with physically interpretable analytical formulations. A wide range of candidate mathematical models were systematically evaluated based on training and testing performance, residual behavior, and physical consistency. The results demonstrate that models exhibiting near-perfect training accuracy frequently suffered from severe overfitting and poor generalization, whereas intermediate-complexity formulations provided a more reliable balance between accuracy and robustness. Comparative analysis further showed that multi-core absorbers consistently produced higher shear strength and more uniform weld seams than single-core configurations. The selected robust models were subsequently integrated into a two-level ensemble meta-optimization framework employing Differential Evolution, Nelder–Mead, Random Search, and Simulated Annealing algorithms under multiple design scenarios. The meta-optimization process successfully eliminated model- and algorithm-dependent extreme solutions and identified stable consensus parameter regions. For the multi-core system, an optimal combination of 30 W laser power, 20 mm/s welding speed, and 0.7 mm spot diameter was obtained, achieving improved mechanical performance while remaining within experimentally validated limits. The proposed framework provides a physically grounded and reliable strategy for surrogate-based optimization of nonlinear welding processes.

Impact of different welding processes on the pneumatic bulge test at a high temperature: Gas Tungsten Arc Welding and Laser Beam Welding

Enhancing the resistance of pipe joint to riboflavin mediated microbial corrosion via increasing heat input.

Influence of laser power on weld formation, microstructure, and mechanical properties of Q235B steel joined by Laser-CMT hybrid welding process

Abstract Aluminum alloy serves as a key material for lightweighting in vehicles and is extensively utilized in manufacturing processes. Laser welding is regarded as an effective technique for welding aluminum alloys, owing to its high speed and efficiency. However, challenges such as ensuring welding quality and insufficient detection methods persist in the laser welding of aluminum alloys. Therefore, this study employs infrared temperature measurement technology and line-structured laser beam scanning technology to collect real-time data on temperature changes and morphological characteristics of the weld seam during the welding process. By integrating BP neural network and random forest algorithms, the quality of 6061 aluminum alloy dual-beam coaxial composite laser lap welds is predicted in real time.Through the analysis of the cross-sectional morphological characteristics of lap welds, this paper proposes the A and L characteristic parameters to represent weld width, H and D characteristic parameters to represent penetration depth, and the cross-sectional area characteristic closely related to the mechanical properties of the weld. The results indicate that the real-time surface temperature and surface morphological characteristics of the weld exhibit strong linear correlations with weld width, penetration depth, cross-sectional area, and mechanical properties of the lap weld. This provides a reliable information source for the real-time prediction of weld quality.Compared to the conventional BP neural network, the BP neural network optimized by the random forest algorithm significantly improves prediction accuracy and stability, reduces high-error predictions, enhances the model's generalization ability, and holds significant practical application value.

Abstract Duplex stainless steel, consisting of ferrite and austenite, has attracted wide attention in the past 20 years by exhibiting superior performance with excellent strength and corrosion performance. In this study, 2205 type steel joints were manufactured by plasma arc welding technique. The structure and strength properties of the joints were detected through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), elemental mapping, tensile test, X-ray diffraction (XRD), and microhardness evaluations. Fractographic analysis was carried out utilizing SEM. The plasma arc welding (PAW) process resulted in a limited heat-affected zone and achieved a high depth-to-width penetration ratio. Moreover, this technique helped maintain the ferrite and austenite phases within the desired ranges. The maximum tensile strength was detected as 455 MPa in S3 Sample. A ductile fracture pattern appeared in the weld metal.

In response to the challenge of achieving highly reliable interface fabrication in the fields of microelectronics and micro-electromechanical system (MEMS) packaging, this study harnesses the superior characteristics of solid-state bonding inherent in explosive welding (EXW) technology. This study investigates the precise EXW of milligram-scale metallic foils by employing focused laser energy to control the explosion behavior of liquid energetic materials, thereby generating shockwaves that induce high-velocity oblique collisions between metallic foils and base plates. Laser-focused energy was utilized to regulate energetic materials for conducting precision EXW experiments on Al/Cu couples. The technical feasibility and interfacial quality of this method for fabricating Al/Cu bonding interfaces were systematically evaluated through in situ observation of the dynamic welding process, comprehensive analysis of interfacial microstructures, and numerical simulations. The results reveal distinct Al/Cu elemental diffusion at the bonding interface, confirming the technical viability of the approach. However, an unloading rebound phenomenon is observed at the interface, which is inherently associated with the dynamic impact process, indicating the need for further optimization in the precise control of impact loading.

Abstract The work analyzes the effect of weld configuration on the load-bearing performance of TIG-welded joints in AA2219 aluminum alloy. The direct current electrode negative gas tungsten arc welding process was used to fabricate two types of joints, butt and lap, in optimum parameters. To assess the mechanical integrity of the joint, mechanical test was conducted to indicate that the lap joint had a better peak load capacity of 29.8 kN than 22.8 kN of butt joint due to the presence of higher effective load-bearing area. The butt joint showed higher load carrying capacity due to higher hardness in the weld metal and heat-affected zone. Microstructural analysis of both joints under low- and high-resolution imaging revealed differences in grain morphology and precipitate size. Fine and densely distributed precipitates were observed in the butt joint, whereas coarse and larger second-phase particles were observed in the lap joint. This difference may be attributed to variations in the thermal cycle during TIG welding. Fractographic examination also confirmed ductile fracture in the butt joint and quasi-cleavage fracture in the lap joint.

Abstract This study investigates the laser beam welding of steel to aluminium plates using a lap joint configuration, emphasising the potential of dissimilar material designs for achieving lightweight components. It focuses on both the welding process and the static and fatigue strength characteristics of the welded joints. Specimens were tested under static loads and cyclical fatigue conditions to determine the endurable stresses. A comparative analysis was conducted against the endurable nominal stresses of T-stake welded joints, providing insights into the mechanical behaviour and durability of steel-aluminium connections. On the one hand, the findings underscore the significant influence of welding parameters on joint performance, revealing how an adequate welding process can enhance the strength and longevity of dissimilar metal joints in structural applications. On the other hand, robustness of laser beam welding is shown as the expected variations in the welding process lead to minor deviations on the tensile and fatigue strength.

The Failure Assessment Diagram (FAD), as a significant method for evaluating the suitability of defective metallic structures, has been subject to considerable debate regarding its applicability in assessing ring welded joints for high-grade steel and large-diameter pipelines. To address this issue, this study first designed and conducted two sets of full-scale pressure-tension tests on large-diameter X80 pipeline ring welded joints, considering factors such as different welding processes, joint configurations, defect dimensions, and locations. Subsequently, three widely adopted failure assessment diagram methodologies—BS 7910, API 579, and API 1104—were selected. Corresponding assessment curves were established based on material performance parameters obtained from the ring weld tests. Finally, predictive outcomes from each assessment method were compared against experimental data to investigate the applicability of failure assessment diagrams for evaluating high-strength, large-diameter, thick-walled ring welds. The research findings indicate that, under the specific material and defect assessment conditions employed in this study, the API 1104 assessment results exhibited significant conservatism (two sets matched). Conversely, the BS 7910 and API 579 assessment results showed a high degree of agreement with the experimental data (eight sets matched), with the BS 7910 assessment providing a relatively higher safety margin compared to API 579. The data from this study provides valuable experimental reference for selecting assessment methods under specific conditions, such as similar materials, defects, and loading patterns.

The present study investigates the static and dynamic strength of HS800 steel weldments of 5 mm thickness fabricated using the Gas Metal Arc Welding (GMAW) process and subsequently treated with High-Frequency Mechanical Impact (HFMI) process. Initially, joint strength was enhanced by optimizing weld bead profiles—achieved by increasing the weld toe angle and bead width while reducing reinforcement height. Further improvement in dynamic strength was obtained through HFMI treatment. HFMI significantly improves the fatigue life of welded joints by reducing stress concentration at the weld toe through geometry refinement, introducing compressive residual stresses at the weld toe (replacing tensile residual stresses from welding), enhancing material properties near the weld toe via work hardening through localized impact indentation. Fatigue performance was compared between as-welded (AW) and HFMI-treated specimens. Results indicate that optimizing weld bead shape improves both static and dynamic strength; however, HFMI treatment does not affect static strength. In contrast, fatigue strength shows substantial improvement with HFMI, yielding a fatigue life enhancement factor of 1.5–2 times at high stress ranges and 3–4 times at low stress ranges compared to AW conditions.

In this work, a laser lap-welded joint of galvanized steel/Mg and a laser lap-welded joint of galvanized steel/Mg assisted by ultrasonic vibration were compared. By adjusting the laser beam power and ultrasonic amplitude, the appropriate welding process parameters were obtained. The weld formation, microstructure and mechanical properties were studied and analyzed. The results indicated that the addition of ultrasonic vibration generated an excitation force with a certain frequency and amplitude on the weldment, making the molten metal in the molten pool produce ultrasonic forced vibration, and producing the effects of cavitation, acoustic streaming, mechanical stirring and heat, thus reducing welding residual stress and welding-deformation, porosity and incomplete-fusion defects. In addition, it can make the fusion zone transition evenly, improve the wettability, refine the weld grain, and reduce the average grain area from 583 μm2 to 324 μm2. Moreover, the distribution of Mg-Zn reinforcing phase at the interface was more uniform and denser, and the maximum tensile shear strength increased from 179.9 N/mm to 290 N/mm, indicating that the addition of ultrasonic vibration was conducive to improving the comprehensive mechanical properties of the joint.

Abstract Friction Stir Welding (FSW) is a solid-state welding process, which has strongly impacted welding technology, particularly for aluminum alloy applications. Reliable in-line process monitoring is not yet available for most common defects and downstream non-destructive and intermittent destructive testing are generally employed to validate weld seam quality. To reduce cost and production time significant efforts have been undertaken in the recent past to develop process-monitoring systems for FSW based on the evaluation of transient process-data. Neural Networks have been used widely to analyse FSW-process data and evaluate the process characteristics or weld seam quality. The data analysed includes welding parameters, thermal-/acoustic-measurement, image or video data and, most notably, the distinct and descriptive process feedback forces and torque. In this study, conducted within the scope of RWTH Aachen’s Cluster of Excellence (Internet of Production), a high granularity direct force measurement setup, which was adapted to the production environment, by integrating reliable, cost-efficient sensors into the machining spindle, was used. Weld data was recorded over a wide range of FSW applications with varying weld-parameters and Al-alloys. Convolutional Neural Networks (CNN) that were previously developed based on measurements of external force and torque sensors were adapted to evaluate the higher granularity data of the new sensor-system and detect volumetric defects within the welds. Good generalization was shown across the weld parameter sets, alloys and welding tool. An average classification accuracy of 98.04% was achieved over three network trainings. Due to the segmentation of data for the evaluation 100% of internal defects were successfully detected by each network iteration. The developed solution aims at offering a highly reliable, spindle integrated and cost-efficient quality monitoring solution for FSW to replace the required expensive and time-consuming testing.

Abstract This study presents a comparative analysis between conventional friction stir welding (CFSW) and flexible ultrasonic-enhanced friction stir welding (FLEX-USE-FSW) applied to a 3-mm-thick AA6082-T6 aluminum alloy. A novel ultrasonic system integrated into the tool holder was employed to introduce axial ultrasonic vibrations during the welding process. Mechanical testing, microstructural characterization, electron backscatter diffraction (EBSD), process force monitoring, and laser vibrometry were conducted to evaluate the influence of ultrasonic excitation on weld quality and process behavior. The results show that ultrasonic assistance reduces axial and traverse forces by up to 20%, broadens the operational window for tensile strength and elongation, and enhances material plasticization. EBSD analysis revealed a higher fraction of low-angle boundaries and modified grain texture in the ultrasonic-assisted stir zone (SZ), suggesting a change in recrystallization dynamics. Cross-sectional imaging revealed a larger and more homogeneous stirred zone in FLEX-USE-FSW, accompanied by reduced defect formation at elevated welding speeds. Additionally, laser vibrometry measurements showed improved energy transmission in specimens oriented parallel to the rolling direction. The findings demonstrate that ultrasonic excitation has a positive effect on weld morphology, mechanical properties, and microstructural evolution, particularly under high-speed and low-heat input conditions.

The use of resistance welding in the field of mechanical engineering is considered, its advantages are highlighted, which contribute to an increase in production efficiency. The abundence of threaded connections in modern mechanisms and the expediency of their integration into stamped elements are noted. Welding of M6 nut with four projections to a sheet part is demonstrated as an example. The equipment guaranteeing preservation of exact sizes of a product is described. The potential difficulties that may arise during welding and negatively affect the quality of the final product and the safety of workers are analyzed. The parameters affecting welding stability are studied. The welding cycle and welding parameters are selected for a specific situation, detailing the effect of each parameter on the welding process.

Dissimilar joining of AZ31B and copper-coated Ti-6Al-4V alloys using arc-based welding process: a preliminary analysis

Abstract The push for lightweighting in automotive manufacturing has necessitated the introduction of dissimilar metal joints in the automobile body, often joints between aluminum and steel. Resistance spot welding (RSW), while a well-established, cost-effective and rapid welding process, experiences problems when welding aluminum-steel joints due to the formation of brittle intermetallic compounds, which degrade joint integrity. However, a previous work has shown that stainless steel interlayers can effectively inhibit excessive growth of brittle Fe-Al intermetallic compounds during RSW. This work explores the feasibility of a novel hybrid joining concept where RSW is combined with adhesive bonding together with a 316L stainless steel interlayer deposited via cold spray. Both 1.8-mm-thick extruded 6063-T6 and 2.2-thick cast aluminum sheet materials were welded to 1.5-mm-thick Al-Si-coated Usibor 1500 AS150 press-hardened steel (PHS). Weld joints were characterized with light optical microscopy and scanning electron microscopy, which revealed the formation of a thinner Fe-Al intermetallic layer between the aluminum substrate and the 316L interlayer compared with welding aluminum directly to PHS. Quasistatic tensile testing was performed in the lap-shear configuration. Both the interlayer-only and hybrid approaches showed improved tensile strength, achieving 2.9 kN and 17 kN maximum tensile force compared with 0.92 kN achieved by the reference extruded aluminum-steel RSW specimens. This work shows that this joining technique is a promising approach for providing a fixture point for automotive components prior to curing of the adhesive.