This study investigates the influence of post-weld friction stir processing (FSP) on 6-mm-thick AA6061 butt joints fabricated by low-heat-input cold metal transfer (CMT) welding using ER2219 filler. Weld integrity was evaluated using X-ray radiography, while microstructural features were examined by optical microscopy. Hardness was measured using Vickers micro-hardness testing, tensile properties were determined in accordance with ASTM E8, impact toughness was assessed by the Izod test, and corrosion behavior was characterized through potentiodynamic polarization in 3.5 wt.% NaCl solution. Friction stir processing produced a fine, equiaxed stir zone characterized by onion-ring flow patterns and clean, defect-free interfaces. The as-CMT joints exhibited an ultimate tensile strength of 216MPa, a yield strength of 198MPa, and an elongation of 12.6%. After applying friction stir processing (FSP), these values increased to 252MPa, 215MPa, and 23.8%, respectively, indicating substantial improvements in both strength and ductility. The Izod impact energy also increased markedly from 9.5J in the as-CMT condition to 15.4J after FSP, representing a 62% enhancement. The as-CMT sample displayed a lower corrosion current density than the CMT + FSP sample in 3.5 wt.% NaCl solution. Nevertheless, FSP resulted in notable improvements in strength, ductility, and hardness uniformity, whereas the as-CMT condition retained comparatively improved corrosion resistance, primarily due to its surface condition.

Welding is a critical process in various industries; however, it generates temperature gradients that induce residual stresses and deformations near the joint, potentially compromising structural performance. This study employs the Finite Element Method (FEM) using coupled temperature–displacement analysis to evaluate the influence of key Metal Inert Gas (MIG) welding parameters on stress and displacement distributions in an aluminium butt joint. The study examines parameter variations such as weld groove shape, heat input, and welding speed to assess their impact on structural behaviour. Simulations are performed on a two-pass Al 6061-T6 plate model measuring 300 mm × 182 mm × 10.5 mm , with a centrally positioned weld zone. The model is developed in ABAQUS, with a Python subroutine used to automate scenario variations. The analysis assumes a homogeneous material with temperature-dependent properties, neglects phase transformation effects, and considers the filler metal to be identical to the base metal due to chemical similarity. Among the variations, the bevelled U-groove offers improved deformation control with similar stress levels, while the highest voltage (26.5 V) and slowest welding speed (4 mm/s) provide the most effective overall control of residual stress and deformation.

Failure analysis on copper-steel butt joints produced by friction stir welding

Research on experiment and engineering application of 9 %Ni LNG steel storage tank butt joint using digital radiography testing technique

Shielded Metal Arc Welding (SMAW) is widely used in the fabrication industry; however, its relatively lower productivity has led to the increasing adoption of Gas Metal Arc Welding (GMAW) in many industrial applications. This study compares the performance of SMAW and GMAW for welding AISI 201 stainless steel, focusing on joint design and mechanical properties. Test specimens with thicknesses of 3 mm and 5 mm were welded using stainless steel filler metal grade 308L with butt joint configurations and groove preparation. For 5 mm thick plates, GMAW achieved complete penetration in a single pass, whereas SMAW typically required two passes. Radiographic examination revealed that GMAW welds were free from significant defects, while SMAW welds showed minor porosity and slag inclusions. Tensile test results indicated that V-groove butt joints provided higher tensile strength and elongation compared to square butt joints due to improved fusion and penetration. Furthermore, GMAW welds exhibited better mechanical properties and overall weld soundness than SMAW welds. Bend tests confirmed excellent ductility, as no cracks were observed. Hardness results showed the base metal had the highest hardness, followed by the HAZ, and the weld metal had the lowest hardness.

This study investigates the dissimilar welding of austenitic stainless steel AISI 304L and ferritic stainless steel AISI 409M using Tungsten Inert Gas (TIG) welding. Welding experiments were designed using a Taguchi L9 orthogonal array considering welding current, shielding gas flow rate, and travel speed as process parameters. Butt joints were fabricated and evaluated through visual inspection, X-ray radiography, tensile testing, and microstructural characterization. The results indicate that tensile strength of the welded joints varied significantly with process parameters and ranged from 522 to 644MPa. Among the samples, specimen S6A exhibited the highest tensile strength (644.5MPa) with 30.6% elongation due to the formation of a refined ferrite-austenite microstructure with reduced dendritic spacing. Microstructural analysis revealed the presence of lacy and vermicular ferrite within the austenitic matrix along with Widmanstätten ferrite near grain boundaries. Taguchi optimization identified the optimal welding condition as C2G3S3 corresponding to 105 A welding current, 20 L/min shielding gas flow rate, and 3mm/s travel speed. The study establishes a correlation between welding parameters, heat input, microstructural evolution, and mechanical performance in dissimilar stainless-steel TIG welding. Unlike previous studies, the present work establishes a direct correlation between heat input, solidification behavior, and resulting microstructural features in AISI 304L-409M dissimilar welds. The study provides new insight into the process-structure-property relationship specific to ferritic-austenitic stainless steel combinations.

The paper presents the results of the development and study of activating flux paste compositions based on traditional oxide elements for argon arc welding (A-TIG). The main attention is paid to the effect of the flux composition on the ionization of the arc and the ratio of the penetration depth to the weld width. Experiments were carried out with various compositions of flux pastes containing fluorspar (CAF₂) and welding flux AN-60, while the ratio of components in the composition of the pastes varied. During the experiments, the coating was carried out on steel plates with a thickness of 10 mm, steel grade – 09G2C. The greatest penetration depth was achieved by compositions No. 1 and No. 2, where the penetration depth was 6.5 mm and 7 mm respectively. It is found out that the optimal fluorspar content in the paste should not exceed 25%, which makes it possible to achieve the maximum penetration depth. The main ionizers of the welding arc are identified: Si, Ca, Mg and Mn, which content can be increased or changed to optimize the paste compositions. Based on the study results, it is found that the developed activating fluxes can be used to optimize argon arc welding of thick-walled structures, as well as to provide surface hardening of steels instead of traditional chemical and thermal treatment methods. The study objective: to develop and conduct experimental studies of complex activating fluxes based on widespread components to increase the penetration depth when welding thick-sheet structures with butt and lap weld joints. The study tasks: to study the effect of the developed activating fluxes on the ionization of the welding arc and the penetration depth of09G2C steel when performing surfacing by argon arc method. The research methods. Preparation of the initial components and activating flux pastes based on them; argon arc surfacing on the steel samples; sample preparation, measurement of the weld width and penetration depth by metallographic method; calculations of the ionization degree of the flux pastes components and assessment of their effect on the arc during surfacing. The novelty of the work. Application of the developed compositions of activating flux pastes for argon arc surfacing/welding (A-TIG) of thick-walled steels. An increase in the penetration depth and a narrowing of the weld width during active ionization of the arc. The use of compositions of activating fluxes as a basic component of flux pastes for surface hardening of steels. The study results. Activating flux pastes of No. 1 and No. 2 compositions showed the best penetration results, with their use the greatest penetration depth of 6.5-7 mm was achieved, which is 1.5-1.8 times higher than without the use of activating fluxes. When studying the composition of the fluxes, the optimal content of the components was determined, where the total amount of CaF2 should not exceed 25%. No defects were found in the macrostructure during surfacing. Conclusion: Compositions of activating flux pastes No. 1 and No. 2 for the argon arc surfacing/welding (A-TIG) method provide an increase in the penetration depth of steel samples, are recommended for further use in flux pastes for surface hardening of steels and further modification of chemical composition.

In the present study, the square butt joint was made by utilizing laser beam welding on a 10 mm thick plate of P22 steel. The post weld heat treatment (PWHT) was executed on the welded joint for 3 h at 760 °C. The microstructure evolution and mechanical characteristics of the P22 steel welded joint were characterized. The welded joint showed excellent impact toughness, high strength, and high hardness. The tensile test results of the PWHT specimen at room temperature exposed that the fracture occurred in the base metal (BM) of the P22 steel with a mean tensile strength of 525 ± 3 MPa. As this failure in the P22 BM, not from the weld metal shows the safety of the welded joint for application. The high-temperature tensile samples also failed from the P22 BM with ultimate tensile strengths of 518 MPa, 502 MPa, and 475 MPa in HT350, HT450, and HT500, respectively. The hardness is quantified along the weldments, and the maximum and minimum value of hardness was examined in the coarse-grained heat affected zone (CGHAZ) and at the inter-critical HAZ (ICHAZ), respectively. The Charpy toughness of the welded joint was 365 ± 5 J, which was significantly higher than that of the as-received BM (320 ± 8 J).

To evaluate and compare the effect of simulated aging on conventional lithium disilicate (LDS) and advanced lithium disilicate (ALD) computer-aided design-computer-aided manufacturing (CAD-CAM) glass ceramics on color stability and fracture resistance utilizing different veneer preparation designs. Two prepared typodont maxillary right central incisors were replicated into forty epoxy resin dies, which were divided into 2 groups based on preparation design (n = 20): Group butt joint (BJ), and Group incisal overlap (IO). Each group was further subdivided into two equal sub-groups based on ceramic material (n = 10): e.max (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein), and Tessera (Cerec Tessera, Dentsply Sirona, Hanau, Germany). After cementation of laminate veneers on the epoxy resin dies, color change and fracture resistance were evaluated before and after 10,000 cycles of thermal cycling. Two-way ANOVA was used to compare the materials and design on the mean color change. For fracture resistance, a three-way ANOVA was used to compare the materials, designs, and aging. Pairwise comparison was tested using independent t-test (α = 0.05). For color change, Two-way ANOVA revealed that different materials, preparation designs and their interaction showed a non-significant effect on the ΔE00 (p = 0.352, 0.158 and 0.678, respectively). For fracture resistance, different materials, preparation designs, and aging, had a significant effect on fracture resistance at p < 0.05. The interaction between all the groups showed a non-significant effect (p = 0.918). Before aging, IO showed significantly lower fracture resistance compared to BJ for both e.max and Tessera. A non-significant difference was shown between the tested materials within the same preparation design. After aging, a non-significant difference between all tested groups was shown. Within the limitations of this in vitro study, it was concluded that thermal cycling affected both color stability and fracture resistance of both tested materials. The color change for BJ for both materials was within the clinically accepted range. Both tested materials showed comparable mean fracture resistance before and after thermal cycling within the same preparation design. BJ showed significantly higher fracture resistance than IO before thermal cycling; however, the difference between the two tested preparation designs after thermal cycling was not significant. Both materials (LDS and ALD) are clinically viable; however, preparation design has a greater impact on mechanical performance than on color stability. BJ performed better than IO for veneer preparation design.

Interfacial uniformity control of Al/steel butt joint via rotating laser-GMAW hybrid welding-brazing

Effect of welding current on the mechanical performance and microstructural evolution of GTAW-welded AISI 304 stainless steel butt joints

Thermomechanical flow driven microstructure evolution in friction stir welded aluminum-steel dissimilar joints

Assessment of weld quality in blue laser light fiber welding of DP1000 dual-phase steel butt joint

Reinforcement learning-based real-time optimization of friction stir welding parameters for copper–aluminium dissimilar interfaces

Investigation on the impact of tool traverse speed on the mechanical characteristics and fracture performance of friction stir welded copper CDA101 butt joints

Abstract Identifying suitable process parameters is essential for developing effective laser welding processes. Traditionally, this involves extensive experimentation and relies heavily on expert knowledge. Bayesian optimization can be used to minimize both the experimental effort and the need for expert information. This study demonstrates the merit of Bayesian optimization for laser welding and explains the methodology for implementing the optimization technique. A strategy for selecting evaluation methods and the design of a suitable cost function to meet specific quality criteria is proposed. For the experimental demonstration, butt joint laser welding of AA1050 aluminum alloy was performed with options to adapt the laser power, welding speed, focus position, and the intensity distribution of the laser beam by changing the power distribution in a multi-core fiber. The success of the optimization was validated by finding several parameter sets producing welds that met the defined quality levels. Furthermore, the properties of the underlying surrogate model of the Bayesian optimizer generated further information that helped to improve the welding process.

The present work focuses on developing a flexible fiber-reinforced polymer (FRP) butt joint between stiff FRP panels (adherends). The goal is to ensure the joint is flexible, moisture-resistant, and abrasion-resistant, while maintaining the original FRP strength and facilitating the casting of complex and modular shapes. To achieve this, an elastomeric resin system comprising polyurethane and polyurea in an optimized ratio of 10:6 (by weight) was formulated for the flexible joint region, whereas isophthalic polyester resin was used in the stiff FRP panels. The joint was reinforced using a hybrid layup of three layers of plain-weave Kevlar fabric, with glass fiber chopped strand mat (CSM) interleaved between the Kevlar layers, over an overlap length of 50 mm on both panel edges. Mechanical characterization revealed that the hybrid resin alone exhibited an average tensile strength of 16.3 MPa; however, no slip was observed for the 50 mm overlap of the reinforced joint, and failure occurred in the adherend. Furthermore, the joint exhibited favorable performance under abrasion, water immersion, low-temperature fatigue, and drop-weight impact testing. These results confirm that the proposed hybrid Resin-Kevlar reinforced joining approach offers a reliable pathway for fabricating flexible, durable, and high-strength FRP joints suitable for advanced structural applications.

The structural integrity of pipeline girth welds is critical, especially when the welds involve heterogeneous materials and non-uniform wall thicknesses. Current evaluation methods that compare the strength of the weld to that of the base metal (BM) are inadequate for such complex welds. This paper addresses this gap by applying micro-tensile specimen testing to characteristic zones within heterogeneous girth welds that exhibit non-uniform wall thicknesses. We conducted tensile performance tests on X80 and X60 steel pipes featuring unequal wall thickness butt joints. The analysis focused on the wall thickness direction of the girth weld as well as the transverse direction, examining differences and patterns in performance across various regions. The findings provide an improved understanding of property gradients in heterogeneous girth welds and offer practical guidance for more reliable safety evaluation of pipelines with unequal wall thickness joints.

To compare the mechanical performance differences between sleeve grouting lap and butt joints, a total of 41 lap joints, including 27 standard lap joints and 14 anti-deflection lap joints, and 20 butt joints were subjected to tensile and high-stress cyclic tensile-compression tests. The results indicate that both types of joints failed by tensile fracture of the rebars in uniaxial tension, with the load-bearing capacity, total elongation at maximum force, and ductility generally meeting the code requirements. In high-stress cyclic tests, the load-bearing capacity of both types of joints increased, while the initial stiffness and ductility decreased. The residual deformation of the anti-deflection lap joints and butt joints generally met the specification requirements. Anti-deflection measures can reduce the residual deformation of lap joints; however, their constraint stiffness is limited, resulting in slightly greater residual deformation of lap joints compared to butt joints. After the completion of the high-stress cyclic tensile–compression tests, the maximum longitudinal strain near the reinforcement side of the sleeve’s middle cross-section in lap joints and the absolute value of the maximum circumferential compressive strain were both less than those in butt joints, indicating that lap joints have lower tensile performance requirements for the sleeve. Based on experimental results, a lap length of 12.5 d is recommended, with an additional 4–6 d allowance to enhance splice reliability under high-stress cyclic loading.

Achieving high fatigue strength in as-welded butt joints requires minimizing geometrical imperfections and local defects while ensuring full penetration and a smooth transition between the base material and weld reinforcement. Different welding techniques exhibit varying capabilities to meet these requirements. The objective of the present study is to compare the fatigue strength of butt-welded joints produced using solid-state and fusion welding processes – specifically friction stir-, laser-, gas tungsten arc-, and gas metal arc welding. Fatigue tests and detailed weld geometry characterization were performed on 4 mm thick plates of aluminum alloys 5083-H111, 5754-H111, 5754-H22, and 6082-T6. Additional tests on 8 mm thick specimens were conducted to evaluate potential thickness effect. Optical profilometer data were used to create two-dimensional finite element models, enabling the determination of fatigue notch factors using the effective notch stress concept and the theory of critical distances. The experimental fatigue tests showed that FSW butt joints exhibited the highest fatigue strength, while lower fatigue strength was observed in fusion-welded joints, primarily due to higher fatigue notch factors and welding-induced angular distortions. The effective notch stress approach, applied with reference radii of 0.05 mm, 0.3 mm, and 1 mm, provided conservative estimates of fatigue strength across all joint types No significant differences were found in the fatigue strength of similar butt joints made from the different aluminum grades studied in this work. The results highlight that geometrical factors, including misalignment and notch geometry, are the primary parameters governing the fatigue strength of welded aluminum butt joints.