Welding in the World最新文献

This study investigates friction stir welding (FSW) of substantially different AA6061-T6 and Ti6Al4V alloys using a nickel (Ni) interlayer to enhance weld quality and mechanical performance. A full factorial (2 × 2 × 5) design of experiments was employed to vary tool rotational speed (TRS), welding speed (WS) and tool pin diameter (TPD), and the resulting joints were evaluated by microstructural analysis, microhardness measurements, tensile testing and fracture examination. Among the twenty welding conditions, the parameter combination TRS 500 rpm, WS 14 mm/min and TPD 4.7 mm with Ni interlayer (Sample S9) produced a defect-free weld with homogeneous Al–Ti–Ni mixing, suppressed Al₃Ti formation and a maximum tensile strength of 241 MPa, corresponding to 78% of the AA6061-T6 base-metal UTS. In contrast, a higher-parameter condition (Sample S20: TRS 710 rpm, WS 20 mm/min, TPD 5.5 mm) led to defective joints, with Al₃Ti intermetallic presence and a significantly lower tensile strength of 133 MPa. Microhardness results showed reduced hardness (≈120 HV) at the interface for S9 due to Ni-assisted solid-solution formation and limited Ti fragmentation, whereas S20 and the joint without interlayer (Sample S0) exhibited higher interfacial hardness associated with brittle intermetallics. Reliability analysis based on a two-parameter Weibull distribution applied to twelve replicate welds at the optimal parameters yielded a mean UTS of 240.48 MPa and a 90% survival probability at 237.9 MPa. These findings demonstrate that a Ni interlayer, combined with appropriate FSW parameter optimization, can produce reliable dissimilar Al–Ti joints suitable for demanding structural applications.

Ultrasonic metal welding (USMW) is increasingly employed for joining electrical conductors, especially in the context of lightweighting strategies that involve replacing copper with aluminum. This makes the technique highly relevant across sectors such as automotive and aerospace. However, USMW still suffers from limited process transparency. In current industrial practice, weld quality is primarily verified through selective destructive testing. As a result, it is feasible neither to inspect every joint nor to avoid false classifications, leading to both unnecessary rejects and undetected defective welds. This contribution presents a machine learning (ML)-based approach to enable real-time process monitoring using data directly obtained from the welding system. By leveraging signal characteristics captured during welding, the system not only distinguishes between “OK” and “NOK” welds but also enables a detailed categorization of defect types. In addition, a predictive model for pull-out force was integrated, allowing quantitative assessment of weld integrity without physical testing. Validation results show a classification accuracy of 99.9% and a mean absolute error for regression of 75 N, demonstrating the method’s potential to enhance process reliability while significantly reducing both scrap and test effort. The approach lays the groundwork for data-driven quality assurance in USMW and supports the implementation of robust inline monitoring.

Flange joints are widely used in pipelines, heat exchangers, and pressure-retaining aluminium structures, yet their behaviour under friction stir welding (FSW) remains insufficiently explored in the literature. This study addresses this gap by evaluating the combined effects of tool geometry and rotational speed on the microstructural and mechanical performance of FSW AA3003 flange joints, with Tungsten Inert Gas (TIG) welding used as a benchmark. The conical-pin tool produced superior weld quality, generating refined stir-zone grains (7.26 µm), higher hardness (46 HV₀.₂), and the highest tensile strength (185 MPa) owing to enhanced material flow and dynamic recrystallisation. The cylindrical pin yielded slightly lower properties (44 HV₀.₂, 165 MPa), while TIG welds exhibited coarse dendritic structures and reduced strength. Hydrostatic testing further demonstrated the sealing advantage of FSW, with conical-pin welds remaining leak-tight up to 32 bar, compared with failure at 23–25 bar in TIG joints. These results establish optimised FSW, particularly with conical-pin geometry, as a high-integrity, energy-efficient, and sustainable joining method for aluminium flange assemblies.

In response to the high standards demanded by marine engineering equipment for the strength and toughness of high-strength steel welded joints, this study systematically explores the effects and synergistic interactions of key alloy elements such as Mn, Ni, and Cu on the microstructural evolution mechanism, phase transformation behavior, and comprehensive mechanical properties of submerged arc welding deposited metal in 440 MPa grade high-strength low-alloy marine steel. Three welding wires with gradient variations in Mn, Ni, and Cu contents were designed and fabricated, followed by deposition experiments combined with OM, SEM, and TEM characterizations to analyze macroscopic morphology, microstructural constituents, and their evolution. Complementary JmatPro simulations of CCT curves and transformation temperatures further elucidated the relationships between alloying, microstructure, and properties. Mechanical testing revealed that increasing Mn, Ni, and Cu contents effectively promoted acicular ferrite (AF), significantly reduced proeutectoid ferrite (PF), ferrite side plates (FSP), and brittle M-A constituents, while refining and optimizing ferrite lath morphology, resulting in a denser and more homogeneous structure. Thermodynamic analysis indicated enhanced austenite stability and increased hardenability due to the alloying additions. The weld metal produced by wire #3 exhibited superior properties, including a yield strength of 523 MPa, tensile strength of 615 MPa, yield-to-tensile ratio of 0.85, and a high absorbed impact energy of 163 J at -40℃, with fracture mode transitioning to ductile dimples and quasi-cleavage. Overall, moderate additions of Mn, Ni, and Cu synergistically refined the microstructure and enhanced toughness, enabling wire #3 (Mn = 1.27%, Ni = 1.17%, Cu = 0.15%) to achieve optimal strength-toughness matching with the base metal, thereby fulfilling the demanding safety and reliability requirements of welded joints in harsh marine environments.

Wire and arc additive manufacturing (WAAM) facilitates the production of substantial near-net-shape components by layer-by-layer deposition. This work examines the effects of post-heat treatments (PHTs) on the microstructure, elemental distribution, and mechanical properties of pulsed-WAAM Hastelloy C-276 thin walls. Characterisation was performed using SEM/EDS, XRD, and EBSD on as-deposited (AD) and PHTed samples. Solution annealing (SA) yielded regenerated equiaxed grains, in contrast to the AD and double-ageing (DA) conditions. SEM/EDS of SA-1 showed a homogeneous Mo distribution devoid of coarse Mo-rich precipitates, whereas EBSD indicated a significant decrease in low-angle grain boundaries (68.3% in AD). Microhardness reached a maximum of 336 HV (SA-1) and 326 HV (SA-2), in contrast to 302 HV (AD) and 260 HV (DA). SA-1 had the most significant enhancement in strength, increasing from 790 ± 16 MPa (AD) to 892 ± 6 MPa. The fracture morphology under all conditions was primarily ductile, with infrequent transgranular and intergranular characteristics.

A novel powder-feed underwater laser metal deposition (ULMD) technology was developed for the in situ repair of the damaged components in an underwater environment. In this research, the Ti6Al4V block was fabricated by the powder-feed ULMD process in an underwater environment. A developed drainage device was used to generate a local dry cavity to realize the interaction between the laser and materials. The morphology features, microstructure, and mechanical properties of the ULMD block sample were investigated. The results show that the ULMD-produced Ti6Al4V presents a continuous and uniform surface, and no pores or incomplete fusion defects are observed in the deposited parts. The acicular α′ martensite within the columnar prior-β grains is formed due to the rapid cooling rate caused by water and gas flow. The tensile test demonstrates the ULMD sample has a higher strength and lower elongation compared with in-air LMD or wrought material.

Ultrasonic metal welding is widely used in the electronics industry, particularly in the production of lithium batteries, for joining both similar and dissimilar materials. Limited research has been conducted on optimizing welding parameters using statistical software to achieve maximum lap shear strength (LSS). In this study, the effects of welding amplitude, time, and pressure in ultrasonic metal welding were investigated for bonding similar aluminum sheets. Design Expert software and response surface methodology (RSM) were utilized to optimize these parameters and examine their interactions, aiming to maximize joint strength. Additionally, the temperature and microstructure of the joint were analyzed to evaluate and control the influence of welding parameters on the joint strength. Findings revealed that welding time, pressure, and the square of the pressure were the most influential factors affecting joint strength. Macro- and microstructural features of the joint interface were examined, and microstructural changes under various ultrasonic welding conditions were correlated with the joint strength. The formation and propagation of micro-bonding zones emerged as the primary mechanisms of joint formation, while the density of micro-bonding zones increased with welding time and the weld effective thickness decreased. In joints with a maximum temperature of 285 °C, greater plastic deformation and softening were observed.

Ultrasonic metal welding (USMW) is a widely used solid-state welding process for electrical components. Despite careful dimensioning, defective welds occur due to the large number of influencing variables, which sometimes remain undetected by existing monitoring strategies. One known major influencing factor is the surface condition of the components to be welded, which is controlled in industrial applications using mostly chemical or mechanical cleaning methods. Existing surface-based mechanisms in USMW are insufficiently described in the literature or contradict each other, so that corresponding cleaning methods are usually developed on an application-specific basis. To further complicate efforts to define an optimal process, the surfaces of the materials used are usually only standardized in general terms, but not for USMW. This work, therefore, investigates the suitability of the surfaces of commonly used copper and aluminium materials for USMW and then defines an optimal state. Based on this, a nanosecond-pulsed laser process is developed that best meets these requirements. In addition, the potential of optimizing the welding process of copper joints to the laser-treated surface condition to achieve a robust overall process chain and transfer the results to the specific requirements of aluminum-copper joints is demonstrated. The welded joints are characterized in detail mechanically, electrically and metallographically in order to quantify the surface influence on the welding result.

This research investigates the effect of process parameters on AA5083/CeO2/TiO2 nanocomposites, focusing on microstructure, hardness, tribological properties, and corrosion resistance. Additive-manufactured aluminum alloy-matrix hybrid nanocomposites were produced using a combination of six different rotational and vertical speeds through modified friction stir deposition, and an additive-manufactured non-composite sample as a reference was produced to be compared with manufactured nanocomposite samples. This study investigated microstructure evolution, characteristics, phase distribution, corrosion resistance, hardness, and tribological behavior of samples. Grain refinement improved by 28.8% to 36.6% compared to the reference (6.28 μm grain size) due to the addition of nanoparticles, shear of friction stir rotation, and heat generation. Decreasing the vertical speed from 35 to 15 mm/min and the rotation speed to 700 rpm caused higher shear and suitable nanoparticle distribution, which resulted in 4% and 10.9% grain size improvement, respectively. Decreasing the grain sizes and the addition of hard nanoparticles caused hardness to increase from 8.75% to 14% compared to the reference (89.4 Hv). Wear rates improved from 0.2 × 10^–3 to 0.1 × 10^–3 mm³/N·m, compared to the reference wear rate of 0.25 × 10^–3 mm³/N·m due to nanoparticles addition, the samples' higher hardness, and the nanoparticles' suitable distribution.