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The friction stir welding (FSW) butt joint of 2mm 6061-T6 aluminum alloy was tested. The effects of welding speed and lower shoulder pressure on the microstructure and mechanical properties of the joint were analyzed, and the possible problems in the welding process of thin plate were analyzed in depth. The results show that the yield strength of the welded joint of 6061-T6 aluminum alloy increases with the increase of welding speed, and the mechanical properties of the joint are not sensitive to the change of the pressure under the shoulder. The core area of the welded joint is the weakest area due to the softening of the welded joint and the insufficient amount of plastic metal transfer.

The double-pass butt welding process was carried out on 9-mm-thick 2014-T4 aluminum alloy T-joints by stationary tool shoulder friction stir welding (STS-FSW). Microstructure changes were analyzed by grain and EBSD, combined with the evolution of the precipitation phase, to explore the influence of regulations of different process parameters on T-joints’ mechanical properties. Defect-free T-butt joints were obtained within the rotational speed range of 400–500 rpm and the welding speed range of 100–140 mm/min. Due to severe dynamic recrystallization, the weld nugget zone exhibits fine equiaxed grain characteristics, with a grain size of approximately 10 μm. The degree of recrystallization and deformation in the weld nugget overlapped zone (WNOZ) did not significantly change, and the grain size of WNOZ was approximately 4 μm. T-joints’ hardness has an uneven distribution, and the hardness is greatest in the weld nugget zone at 110–125 HV. The T-butt joints have the weakest hardness at the skin and stringer in the TMAZ, approximately 70–80 HV. The ultimate tensile strength of the skin and stringer in the T-butt joints is equivalent to 85% and 59.6% of the base material. According to the fitting of a quadratic polynomial with multiple variables, it is found that the maximum tensile strength of the skin and stringer can only be achieved when the thermal input is within a reasonable range. The fracture is a ductile fracture with numerous dimples visible on the fracture surface. The tensile fracture of the specimen is analyzed by the finite element method. T-butt joints exhibit lower stress concentrations during the tensile test than T-fillet joints.

The development of high-strength advanced additively manufactured (AM) aluminum alloys is driven by the need for weight reduction in complex-shaped structural applications. In this context, heat-treatable aluminum-scandium alloy, known commercially as Scalmalloy®, offers high strength and lightness, also at high temperatures, due to solution strengthening Al 3 (Sc, Zr) particles. A widespread diffusion of such AM alloy is also related to welding technologies that could preserve its engineered microstructure. This study investigates the microstructural and mechanical properties of butt friction stir welding (FSW) joints of LPBF Scalmalloy® plates under different welding settings. Joint performance was evaluated under quasi-static and cyclic loading conditions. Porosity in Scalmalloy® and welds was assessed using 3D X-ray computed tomography. An aging heat treatment assessed the extent of precipitation hardening in the FSW joints. Results show that metal stirring during FSW notably reduced the intrinsic porosity of Scalmalloy®, decreasing the equivalent pore diameter from about 200 μm to 60 μm in the welded joints. Under quasi-static loading, welded specimens failed at the interface between the thermo-mechanically affected and the stir zones on the advancing side. The aging heat treatment improved the mechanical strength of Scalmalloy® from approximately 400 to 480 MPa, albeit at the expense of ductility (elongation at fracture decreased from 16 to 4%). The higher heat input and stirring developed at a low welding speed reduced lazy S defects but limited the effectiveness of subsequent aging. In fatigue testing, welded joints consistently failed within the aged base material due to the intrinsic porosity of Scalmalloy®.

Friction stir welding of aluminum alloys is today an essential joining technic for various industrial sectors. However, making a quality joint is relatively expensive compared to the electric arc welding processes. The aim of this work is to maximize the ultimate tensile strength (UTS) of AA3004-H32 aluminum alloy butt joint and minimize its production cost. The welding parameters are rotational speed, welding speed, and pin shape of the tool. Then, a test campaign is carried out according to the Box-Behnken design of experiments. Mathematical models of power consumption and ultimate tensile strength were developed by multiple linear regression. The analysis of variance (ANOVA) of the experimental data revealed the preponderant effect of the tool rotational speed and the pin profile on the studied responses. The bi-objective optimization problem was solved using the genetic algorithm and optimal welding parameters were presented. In terms of joint quality and electrical energy consumption, the results showed that the tool rotational speed plays a key role, and that the threaded cylindrical profile of the pin is the most preferred compared to other studied shapes. The welding speed is the most significant parameter in reducing welding costs. The approach proposed in this study can be used as a guide and recommendation to reduce FSW costs and at the same time ensure the quality of the AA3004-H32 alloy joint.

The paper describes the influence of the friction stir welding travel speed on the mechanical properties of the butt joints of copper plates. The results of static and fatigue tests of the base material (Cu-ETP R220) and welded specimens produced at various travel speeds were compared, considering a loading applied both parallel and perpendicularly to the rolling direction of the plates. The mechanical properties of the FSW joints were evaluated with respect to parameters of plates’ material in the delivery state and after recrystallisation annealing. The strength parameters of friction stir welding joints were compared with the data on tungsten inert gas welded joints of copper plates available in the literature. The results of microhardness tests and fractographic analysis of tested joints are also presented. Based on the above test results, it was shown that although in the whole range of considered traverse speeds (from 40 to 80 mm/min), comparable properties were obtained for FSW copper joints in terms of their visual and microstructural evaluation, their static and especially fatigue parameters were different, most apparent in the nine-fold greater observed average fatigue life. The fatigue tests turned out to be more sensitive criteria for evaluation of the FSW joints’ qualities.

In this research, the temperature field characteristics and melt flow behaviors of 5A06/6061 aluminum alloy lock-butt joint during the electron beam welding (EBW) process are investigated by numerical simulation involving heat transfer and flow of fluid. The calculated mesh model of the lock-butt joint is established with the computational domain divided into three phases. The rotating Gauss heat source is applied to simulate the electron beam energy loaded on the base metal during the welding process. Immediately, not only the temperature filed distributions on the surface and different sections of the molten pool are analyzed carefully, but the flow behaviors of the liquid metal in the molten pool are studied in detail. The results demonstrate that the asymmetric distribution of the temperature field, keyhole, and molten pool morphology exist constantly during the welding process. Besides, there are asymmetric metal flows on both sides of the molten pool and obvious vortex metal flows near the rear and the surface of the molten pool. The melt flow on the keyhole wall represents diversity including the surrounding, downstream, and upstream flow. Moreover, the corresponding experiment is conducted to verify the accuracy of the established model and the simulation results are in good agreement with the experimental results in this work.

Developed countries are distinguished by their large-scale infrastructure, including bridges, towers, and power plants, most of which are constructed using various types of steel, such as mild and stainless steel. Strength and durability of steel in low budget make it an ultimate choice. In the construction of these structures, welding plays a crucial role, utilizing various joint configurations such as butt, T, and lap joints. This study examines the effect of multiple weld repairs on mild steel, using a welding speed of 150 mm/min and a current of 100 amperes for 3 mm thick sheets. Initially, the weld’s microstructure exhibited several cracks within the Weld Zone due to inadequate weld material filling. After the first repair, significant changes were observed, with elongated and distorted grains and an increase in hardness due to pearlite formation and Sulfur segregation. A second repair further highlighted the effects of repeated thermal cycles, causing increased brittleness and Sulfur segregation. The hardness of the weld joints increased by 16% and 24% after the first and second repairs, respectively, when compared to the base mild steel material. However, the Ultimate Tensile Strength (UTS) decreased to 48%, and the Yield Strength (YS) fell to approximately 54% after the second repair. Interestingly, the weld joint showed improved tensile properties after the first repair, attributed to the effective filling of cracks that appeared after the initial welding pass. This resulted in a slight increase in UTS and YS. However, the percent elongation of the material decreased due to the repeated thermal cycles involved in the welding repairs, with reductions of 44.3% and 63.6% after the first and second repairs, respectively. This increase in hardness and decrease in ductility after repairs suggest that the weld joints became more brittle.

Sisal and jute woven mat epoxy composites offer uniform fiber distribution and ease of fabrication, with the mat structure significantly enhancing wear resistance. This study compares the adhesive bond strength of these composites using sisal, jute, and hybrid mats joined with single lap, butt, and scarf configurations (ASTM D5868‐01R14) and two epoxy adhesives: LY‐556/HY951 and XIN‐100 IN/XIN‐900. Results demonstrate that enhanced fiber/matrix interfacial bonding increases joint strength, with both fibers exhibiting superior adhesion to XIN‐100 IN/XIN‐900. The hybrid mat achieved the highest tensile strength in both matrices compared to sisal or jute alone. Tensile tests and Field Emission Scanning Electron Microscopy (FE‐SEM) conducted at room temperature revealed the failure mechanisms of the bonded laminates. This study experimentally investigates the development and properties of sisal and jute woven mat epoxy composites that offer uniform fiber distribution and ease of fabrication, with the mat structure significantly enhancing wear resistance. This study compares the adhesive bond strength of these composites using sisal, jute, and hybrid mats joined with single lap, butt, and scarf configurations (ASTM D5868‐01R14) and two epoxy adhesives: LY‐556/HY951 and XIN‐100 IN/XIN‐900. Results demonstrate that enhanced fiber/matrix interfacial bonding increases joint strength, with both fibers exhibiting superior adhesion to XIN‐100 IN/XIN‐900. The hybrid mat achieved the highest tensile strength in both matrices compared to sisal or jute alone. Tensile tests and Field Emission Scanning Electron Microscopy (FE‐SEM) conducted at room temperature revealed the failure mechanisms of the bonded laminates.

In the present study, friction stir welding (FSW) of butt and scarf joints of Al 6063-T6 were investigated. Five different tool pin profiles (cylindrical, tapered cylindrical, square, triangular, and hexagonal) were applied for performing welding. Scarf joint, being a new joint configuration, was used and effect of pin profiles was investigated on this type of joint configuration. The effect of pin profiles on microstructure, micro-hardness, impact and tensile properties of friction stir welded Al 6063-T6 was investigated. Scanning electron and optical microscopy were employed to characterize the different zones of welded joints. A thorough discussion on correlation between mechanical properties and microstructure has been made. In addition, the formation of various defects during the FSW was discussed with the help of fractography of the fractured surfaces.

To improve the automation level of the welding robots, the automatic extraction and identification of the weld seam is the pre-requisite of the intelligent welding robots. During the real industrial environment, the welding environment often has the characteristics of weak texture, poor contrast, reflections from metallic surfaces, and imperfections on the work piece. These characteristics will seriously affect the accurate extraction of weld seam. To realize the automatic path planning of welding robots, a new method of automatic extraction and identification of narrow butt joint under weak contrast is realized to serve the 3D path teaching of welding robots. To achieve accurate extraction of narrow butt joint under weak contrast, this paper designs a new seam extraction operator to achieve accurate and fast extraction of weld seam with various shapes and sizes. And the shape feature of weld seam is used to construct feature vector. Finally, to get optimal classification performance, the adaptive network-based fuzzy inference system (ANFIS) is adopted in this paper to finish identification of narrow butt joints. The experimental results show that the proposed algorithm could quickly and accurately realize the extraction and identification of the narrow butt joints under weak contrast.