Welding in the World最新文献

Ultrasonic metal welding is a solid-state joining technique widely used in electrical and electronics manufacturing, including aluminum wire connections for modern vehicles. Throughout production, transport, and storage, aluminum stranded wires are exposed to possible contamination and progressive surface oxidation, both of which can adversely affect the wire quality and, consequently, the quality of the welds. This study focuses on the influence of surface impurities and oxide-layer characteristics on the USMW performance of aluminum stranded wires. To isolate key variables, the wires were subjected to controlled storage environments with varying temperature, relative humidity, and storage duration. Despite differences in these storage parameters, all joints after USMW met the mechanical performance requirements specified in the relevant DIN standard. However, weldability and the magnitude of property degradation still varied markedly depending on the storage environment. The results of welding combined with advanced XPS surface analysis and laser vibrometry investigations show that storage humidity is the primary factor governing the surface state of the wires as well as post-weld properties, underscoring the need for strict environmental control prior to welding. A further key parameter is the condition of the native oxide film on each strand’s surface immediately after wire production. 

This study explores the feasibility of stationary shoulder friction stir welding (SSFSW) for joining dissimilar extruded aluminum alloys, AA6082-T6 and AA6005A-T6, targeted for structural applications in the transportation industry. The key objective is to achieve higher welding speeds, up to 1.5 m/min, which is significantly higher than those typically reported for SSFSW in lap joint configurations. This increased welding speed is expected to reduce heat input, narrow the heat-affected zone (HAZ), and improve the microstructural uniformity and mechanical performance of the weld. Microstructural characterization via optical microscopy, scanning electron microscopy, and electron backscattered diffraction revealed extensive dynamic recrystallization within the stir zone, resulting in a refined average grain size of approximately 2.3 µm. Hardness mapping across the weld cross-section showed a significant reduction in hardness within the stir zone and HAZ, with the minimum hardness dropping to 65 HV from the base material hardness of 110–115 HV. High-speed SSFSW at 1.5 m/min produced sound joints with good lap interface bonding, despite the presence of a small root void. Lap shear tensile testing showed an average ultimate load of 3.8 kN, with all samples failing from the advancing side hook defect due to stress concentration. Fractographic analysis confirmed ductile failure modes with dimples in the fracture surface. These results suggest that high-speed SSFSW (1.5 m/min) is a promising technique for joining dissimilar aluminum alloys in lap joint configurations, offering potential advantages in microstructural refinement and mechanical performance compared to conventional methods.

Graphical Abstract

This study addresses the residual stresses generated during multi-process chains—including stamping, welding, and aging—in the manufacturing of automotive chassis components. An integrated method for synthesizing and simulating initial stresses is proposed. By developing a coupled simulation workflow and an efficient stress mapping algorithm, the multi-process residual stress fields are systematically synthesized. Bench test validation demonstrates that this method significantly improves the accuracy of fatigue life predictions, revealing that welding-induced residual stress is the dominant factor affecting fatigue damage. The approach provides an effective solution for durability design and process optimization of chassis components.

Solid-state dissimilar joining of NiTi and Ti-6Al-4 V is a currently underexplored field with high potential to expand applications for each alloy in the aerospace industry. Friction stir welding of butted 1 mm thick sheets of NiTi and Ti-6Al-4 V was tested under a matrix of welding parameters. Six of eight tested parameter conditions joined but each showed degraded mechanical properties. Higher traverse speed conditions joined more successfully into testable samples. Upper and lower quartiles for tensile strength varied between 140 and 60 MPa with the lower rotation speed showing higher median values. Weld degradation is attributed to the formation of an up to 10 µm wide Ti₂Ni intermetallic compound layer at the weld interface. Higher rotation speeds showed a thicker intermetallic layer. The Ti₂Ni layer showed equiaxed grains on the order of 2–3 µm in diameter. It is theorized that this layer grew from pre-existing Ti-6Al-4 V via nickel diffusion from the NiTi due to in-process heating. Accelerated property mapping nanoindentation shows that the Ti₂Ni layer has a greater microhardness and reduced elastic modulus (12.42 GPa and 150.06 GPa) than the stir zone of the NiTi (5.10 GPa and 97.65 GPa) and Ti-6Al-4 V (5.93 GPa and 137.2 GPa). Crack propagation along this brittle, high stiffness intermetallic layer is proposed as the cause of failure in the welded samples.

There is a need in the industry for a highly productive and cost-effective additive manufacturing process that is capable of processing copper-zinc alloys in such a way that acceptable material properties are achieved. To develop technologies that fulfill the requirements, wire and arc-based additive manufacturing with copper-zinc alloys is investigated. As part of the technology development, experiments on tungsten inert gas (TIG) welding with CuZn37 filler wire on CuZn37 substrates are carried out. By varying the arc length, it is shown that with shorter arcs, fewer lack of fusion occur at the seam edges. With further welding experiments, preferred parameters for the manufacturing of higher wall structures are determined. The investigations demonstrate that the reproducible build-up of 20-layer wall structures and cylindrical blanks made of CuZn37 is possible with a TIG process. The cross-sections of selected welds and wall structures are analyzed and measured using an optical microscope. Some samples are scanned using a laser scanner to create height profiles. To investigate the mechanical properties within the additive manufacturing technology, tensile tests are carried out as well.

Magnesium alloys are increasingly sought after in aerospace, automotive, biomedical, and electronic applications due to their superior strength-to-weight ratio, but their relatively poor surface integrity and erosion resistance necessitate advanced modification strategies. In this study, the QH21 magnesium alloy was engineered for enhanced surface performance using friction stir processing (FSP) reinforced with hybrid TiO₂–ZnO ceramic coatings. The processing parameters were systematically optimized through Taguchi’s design of experiments (DOE) methodology employing an L16 orthogonal array, with four critical factors: tool rotational speed (800–1400 rpm), traverse speed (15–30 mm/min), axial force (4–10 kN), and reinforcement percentage (3–12%) selected for evaluation. Performance metrics were assessed in terms of erosion factor and microhardness, which directly reflect wear resistance and structural integrity. The results revealed that a parameter set comprising 1000 rpm rotational speed, 15 mm/min traverse speed, 6 kN axial force, and 9% reinforcement minimized the erosion factor to 0.000290, indicating superior surface consolidation and particle–matrix interfacial bonding. Conversely, the maximum microhardness of 109 HV was achieved at 1400 rpm, 25 mm/min, 6 kN, and 12% reinforcement, attributed to intense dynamic recrystallization, grain refinement, and effective dispersion strengthening. Overall, the study demonstrates that optimized hybrid-particle FSP markedly enhances the surface quality and mechanical resilience of QH21 magnesium alloy, rendering it highly suitable for next-generation lightweight structural and functional components. 

Beryllium-aluminum (BeAl) alloys are widely used in the aerospace industry for their low density, high stiffness, and excellent thermal stability. However, the significant physical and metallurgical differences between Be and Al render conventional fusion welding methods ineffective for achieving high-quality joints. This study applied both conventional FSW and heat-assisted FSW to weld as-cast BeAl alloys. Comparative analysis reveals that the heat-assisted FSW process, which involves preheating both the base material and the backing plate, significantly enhances the plastic flowability of the material during welding and effectively prevents the formation of tunnel defects and surface cracks. The elevated temperature during welding promotes dynamic recrystallization, resulting in notable grain refinement in the weld nugget and an increase in microhardness to approximately 330 HV, about 2.3 times that of the base material. However, local microstructural inhomogeneity and microcracks within the Be particles still reduce the tensile strength of the joint to some extent. This study demonstrates the promising potential of heat-assisted FSW for addressing the welding challenges of BeAl alloys and provides valuable insights for future process optimization.

This study investigates the influence of martensitic start temperature on residual stress and distortion. A double-sided fully welded T-joint was fabricated by welding a high-alloy base material (1.4318) with two different filler wire combinations (G19 9, G4Si1). The temperature distribution and distortion were measured during the welding process using thermocouples and displacement transducers. The thermo-metallurgical-mechanical effect was considered when computing a numerical simulation model for a T-joint geometry. A phase transformation model was incorporated to predict martensite formation during welding, with the martensite start temperature varied as a parameter. Further, the mechanical model was developed by integrating the thermal strains, phase strains, and mechanical strains. Results from numerical simulations and experimental measurements are compared and analyzed to assess the impact of martensite start temperature on residual stresses and distortion. From the findings, it was found that, at a reduced martensitic start temperature, there was a significant reduction in residual stresses and distortion.

This study elucidates the critical role of material vorticity in governing the microstructure evolution during friction stir welding (FSW) of aluminum alloys, with particular emphasis on tool pin geometry effects. A coupled thermomechanical simulation has been exploited to critically examine the vorticity generation which is followed by experimental validation for demonstrating its influence. The square pin tool produces the most intense vorticity (2838.29 s⁻¹), driving superior dynamic recrystallization (CDRX/DDRX) through its pulsating stirring action, as evidenced by a 72% increase in high-angle grain boundaries (HAGBs) compared to cylindrical pins. This vorticity-dominated material flow generates a unique thermal-strain synergy, with peak vorticity (1588.16 s⁻¹) occurring at 445.03 °C, which optimally balances heat input and deformation energy for microstructure control. The resulting grain refinement and texture development enhance joint efficiency to 93% (UTS ~ 280 MPa) while improving ductility by 69%, achieving an exceptional strength-ductility combination. The results establish vorticity as the governing parameter linking tool design to microstructure evolution, providing a framework for process optimization through targeted flow manipulation.