Search Results (96)

This study proposes a novel dynamic composite heat source combining discrete tracking and vapor heating, which can precisely capture the transient energy deposition at the keyhole wall, and further discusses the formation mechanism of weld defects by investigating keyhole evolution and melt pool flow behavior. The weld morphology and dimensions predicted by the simulation are in good agreement with the experimental data, revealing the coupled mechanism between keyhole instability and porosity formation, as well as the generation mechanism of process-type porosity mainly influenced by the keyhole dynamic characteristics and the melt pool flow field together; specifically, keyhole instability forms a vapor cavity that will generate bubbles to participate in melt pool flow if it cannot be re-fused with the keyhole, and the bubble trajectory is related to buoyancy, gravity and liquid flow in the melt pool, with larger bubbles less likely to escape due to greater liquid viscous force. In addition, this study finds that increasing weld power and weld speed helps improve keyhole stability, weaken melt pool circulation intensity and shorten bubble escape path, thereby fundamentally revealing the formation mechanism of porosity defects during electron beam welding (EBW) of aluminum alloy, providing an effective numerical tool for optimizing EBW process parameters, and proposing corresponding inhibition measures to improve weld quality. Full article

The thermodynamic effect of SiO₂ on the composition of the weld metal in submerged arc welding is analyzed by employing the basicity index model, the slag–metal model, and a multi-zone thermodynamic framework. A CaF₂-SiO₂ binary flux system is employed to isolate the intrinsic effect of SiO₂. The results show that the basicity index model captures the overall decrease in weld metal O content with increasing flux basicity index but fails to resolve variations in the high-basicity region. The slag–metal equilibrium model provides a thermodynamic description of interfacial reactions yet remains limited to the weld pool zone. In contrast, the multi-zone model incorporates reactions in the droplet and weld pool zones, revealing pronounced O enrichment in the droplet due to flux decomposition and arc–plasma interactions, followed by redistribution under gas–slag–metal equilibrium. By accounting for droplet-stage evaporation and cross-zone interactions, the multi-zone model improves the predictive accuracy of Si and Mn contents and explicitly captures their cross-zone transfer behavior compared with conventional prediction approaches. Full article

To mitigate welding defects in copper wire conductors induced by their high laser reflectivity and thermal conductivity during laser welding, this study combines numerical simulation and experimental testing to investigate the influences of laser processing parameters on the mechanical properties, molten pool dynamic evolution, and microstructural characteristics of copper self-fusion welds and pure Ni powder-filled welds. The results demonstrate that, for self-fusion welding, a moderate increase in laser power and welding time elevates the heat input, which promotes weld penetration and forming quality. The optimal parameter combination (3900 W, 1.0 s) yields a balanced internal densification and grain refinement, with the joint tensile strength reaching a peak of 245 MPa. For Ni powder-filled welding, the infinite solid solubility between Cu and Ni improves interfacial metallurgical bonding. Under the optimal parameters (3500 W, 1.2 s), the joint tensile strength increases to 282 MPa. Heat input exerts a significant effect on the temperature field evolution in both welding processes, yet the molten pool expansion behaviors differ: self-fusion welding exhibits continuous expansion with rising heat input, whereas Ni powder-filled welding displays complex nonlinear variations. Full article

Real-time management of short-term ozone peaks during arc welding remains challenging because ventilation- and enclosure-defined transport boundaries can create strong position-dependent peak behavior, even under fixed process settings. This study establishes a coordinate-referenced, event-level monitoring and analysis framework to quantify ozone–fume peak coupling under a controlled local exhaust ventilation (LEV) suction boundary during CO₂ arc welding. A controlled process–environment testbed with a defined suction condition was implemented, and synchronized ozone and fume signals were acquired at three sampling points referenced to the arc position and the LEV inlet direction. The particulate channel was anchored to a PM₄ gravimetric reference, yielding a condition-specific traceable CPM-to-mass conversion factor K₁ of 1.76 × 10⁻² mg/(m³·CPM) and enabling standardized peak-fume endpoints on a mass-concentration scale. The primary inferential analysis used the curtain-on dataset, comprising 21 sessions and 42 event-level records balanced across three sampling points. Under the same suction boundary, peak coupling was strongly monitoring-coordinate dependent: LEV-aligned locations showed statistically supported ln–ln scaling between peak ozone and peak fume, whereas the opposite-side location did not exhibit statistically supported scaling; a pooled point-parameterized ln–ln model achieved an adjusted R² of 0.777. As a descriptive control-relevant contrast, adding a curtain enclosure under continuous LEV produced strong event-level ozone peak suppression at LEV-aligned locations, with a maximum reduction of 87.8%, while attenuation at the opposite-side location remained limited. Overall, the results provide a ventilation-boundary-consistent, coordinate-specific basis for monitoring placement and control evaluation, identifying where peak translation is supported and where direct ozone monitoring remains necessary. Full article

The crack-free welding of aluminum alloy is very significant in manufacturing lightweight components since aluminum alloys are susceptible to solidification cracking during welding. This work reviews the current understanding and advancements in the study of solidification cracking during welding aluminum alloys. Solidification cracks typically form near the end of the solidification process within the mushy zone, a region behind the molten pool where the material is partially solid and partially liquid. The complex high-temperature metallurgical behaviors in this zone play a crucial role in crack initiation. Research on the cracking resistance of filler materials has progressed significantly, offering valuable insights for mitigating cracks. The review covers the mechanisms of solidification cracking, influencing factors, and the cracking resistance of filler materials. It also highlights future research directions to deepen the understanding of metallurgical mechanisms and to support practical engineering solutions for controlling solidification cracks in welding aluminum alloys. Full article

Existing macroscopic finite element models for electron beam welding (EBW) typically assume isotropic material behavior, often failing to accurately predict residual stresses induced by strong crystallographic textures. To address this limitation, this study established a sequential dual-scale coupled numerical model bridging micro-texture to macro-mechanics by combining the crystal plasticity finite element method (CPFEM) with thermal-elastic-plastic theory. Representative volume elements (RVEs) incorporating α and β dual-phase characteristics were constructed based on electron backscatter diffraction (EBSD) data from the TA15 weld cross-section. Through simulated tensile and shear calculations on the RVEs, homogenized orthotropic stiffness matrices and Hill yield constitutive parameters were derived and mapped onto the macroscopic model. Simulation results indicate that the proposed model maintains the prediction error for molten pool morphology within 16.3%, while effectively correcting the stress overestimation inherent in isotropic models. Specifically, it adjusts the peak longitudinal residual stress at the weld center from 800 MPa to approximately 350 MPa, significantly reducing the anomalous “M-shaped” stress distribution. By successfully capturing shear stress components, this work provides a high-fidelity computational approach for predicting complex stress states in welded joints, offering critical insights for structural integrity assessment. Full article

Reliable joining of multi-layer aluminum foil current collectors is crucial for enhancing the performance and safety of high-capacity lithium-ion batteries. However, laser welding of such thin-thick aluminum combinations is often hindered by porosity, cracks and unstable weld-pool behavior. In this study, a ring-mode fiber laser combined with sinusoidal oscillation and linearly gradient power modulation was employed to achieve high-quality lap welding between 80 layers of 1060 aluminum foil (1 mm in total thickness) and a 1.5 mm thick aluminum plate. Welding experiments and thermo-mechanical simulations were conducted to investigate the effects of welding speed (15–45 mm/s) and central-power modulation parameters (−2, 0, +2, +4) on weld morphology, defect formation, and mechanical properties. The results indicate that increasing the welding speed can effectively suppress cracks and improve the shear strength from 249.8 N to 403.9 N, but it also leads to an increase in porosity from 5.78% to 12.26% and deterioration of the weld reinforcement. Higher central-power modulation (+2, +4) transformed the weld-pool geometry from an ω shape to U shape, effectively suppressing fusion-line cracks but leading to increased porosity (up to 8.41%) and deteriorated surface morphology. Overall, a low welding speed of 15 mm/s combined with an optimized power modulation strategy achieves effective crack suppression while maintaining controlled porosity, resulting in a welded joint with superior comprehensive performance. This research provides a robust process solution for high-quality laser welding of multi-layer aluminum foil current collectors in power battery manufacturing. Full article

The traditional ultrasonic bonding technique for IGBT T2 copper terminals often causes physical damage to ceramic substrates, severely compromising the reliability of power modules. Meanwhile, T2 copper laser welding faces inherent challenges including low laser absorption efficiency and unstable molten pool dynamics. To address these issues, this study targets the high-quality connection of IGBT T2 copper terminals and proposes a welding solution integrating a Fiber-Diode Hybrid Laser system with galvo-scanning technology. Comparative experiments between galvo-scanning and traditional oscillation methods CNC scanning were conducted under sinusoidal and circular trajectories to explore the regulation mechanism of welding quality. The results demonstrate that CNC scanning lacks precision in thermal input control, resulting in inconsistent welding quality. Galvo-scanning enables precise modulation of laser energy distribution and molten pool behavior, effectively reducing spatter and porosity defects. It also promotes the transition from columnar grains to equiaxed grains, significantly refining the weld microstructure. Under the sinusoidal trajectory with a welding speed of 20 mm/s, the Lap-shear strength of the galvo-scanned joint reaches 277 N/mm², outperforming all CNC-scanned joints. This research proposes a non-contact welding strategy targeted at eliminating the mechanical failure mechanism associated with conventional ultrasonic bonding of ceramic substrates. It establishes the superiority of galvo-scanning for precision welding of high-reflectivity materials and lays a foundation for its potential application in new energy vehicle power modules and microelectronic packaging. Full article

The paper investigates the arc behavior and molten metal flow during Keyhole tungsten inert gas (K-TIG) welding of dissimilar materials, Invar 36 and stainless steel (types 304, 316, 309, and 310) specifically. A high-speed camera was used to capture the contour of the molten pool in real time. Results showed that in stainless steel welding, the arc shape is bell-shaped, and the distance from the tip of the molten pool to the keyhole decreases with increasing thermal conductivity (6.76–10.86 mm). When Invar 36 was butt-welded, the arc contracted. However, when Invar 36 was welded with dissimilar materials of stainless steel, the arc deflected to the Invar 36 side. The deflection angle ranged from 29.9° to 37°, resulting in an asymmetric arc shape. The distance from the tip of the molten pool to the keyhole increased to 10.88–13.33 mm, which was about 42% higher than that of the same material welding. Metallographic analysis showed that the width of the heat affected zone on the Invar 36 side increases with the decrease in thermal conductivity of the stainless steel (1.77–2.03 mm). Differences in thermophysical properties and viscosity further led to asymmetric molten pool flow and metal accumulation behavior. This study quantified the formation mechanism of arc deflection and weld pool asymmetry in K-TIG welding of dissimilar materials. Full article

This study investigates the influence of Cr₂O₃-bearing fluxes on the transfer behavior of O and Cr during the submerged arc welding process. A series of fluxes with varying Cr₂O₃ content are prepared and applied in submerged arc welding. A cross-zone model is developed to separately evaluate the transfer of O and Cr in both droplet and weld pool zones. The results reveal significant O enrichment in the droplet zone due to the decomposition of Cr₂O₃ under arc heating, followed by deoxidation in the weld pool. Cr transfer is found to be inhibited by the high oxygen potential in the droplets and further affected by evaporation loss. A comparison of predicted ΔCr values shows that the gas–slag–metal equilibrium model overestimates Cr transfer level, while the cross-zone model provides predictions more consistent with experimental results. This study highlights the critical role of Cr₂O₃ in regulating transfer behaviors O and Cr and provides valuable insights for flux design aimed at achieving precise compositional control and improved weld quality in welding applications. Full article

This study investigates the effects of anodizing and welding parameters on the microstructure and mechanical properties of laser-welded die-cast A356 aluminum alloy. The influence of different surface oxidation conditions, namely, no anodized film (NAF), single-sheet anodized film (SSAF), and double-sheet anodized films (DSAF), was assessed. The porosity, elemental distribution, and mechanical behavior was systematically analyzed. The results indicate that anodizing reduces the fusion zone (FZ) size by approximately 5%–15% and increases porosity, primarily due to the thermal-barrier effect, energy consumption during film decomposition, and hydrogen release. Welding speed and defocusing amount have a significant impact on heat input and melt-pool dynamics. Quantitative analysis revealed that lower welding speeds and positive defocusing amount increased the FZ size by 15% and porosity by 2%–5%. In contrast, optimized conditions (welding speed of 4 m/min and 0 mm defocus) enhanced gas evacuation and minimized pore formation. Elemental analysis showed that anodizing promoted Si enrichment and increased oxygen incorporation, with oxygen content rising by 10%–15%, from 0.78 wt% (NAF) to 1.31 wt% (DSAF). Microhardness testing revealed a reduction in heat-affected zone (HAZ) hardness due to thermal softening induced by anodizing, while FZ hardness peaked under optimized welding conditions, reaching a maximum value of 95.66 HV. Tensile testing indicated that anodized films enhance the yield strength (YS) of the fusion zone (FZ) but may reduce ductility. Under optimized welding conditions (4 m/min, 0 mm), the joints exhibited the best overall performance, achieving the YS of 125.28 ± 10.57 MPa, an ultimate tensile strength (UTS) of 193.18 ± 3.66 MPa, and an elongation of 3.46 ± 0.25%. These findings provide valuable insights for optimizing both anodizing and welding parameters to improve the mechanical properties of A356 joints. Full article

Additive manufacturing (AM) offers significant potential but faces challenges in controlling rapid solidification processes due to thermal conditions. The application of magnetic fields provides a promising path to influence liquid metal behavior during solidification. Thermoelectromagnetic convection (TEMC) is one of the mechanisms by which an applied static magnetic field can induce melt flow, where thermal gradients at the solid–liquid interface generate thermoelectric currents, and in the presence of an external magnetic field induce Lorentz force that drives liquid convection, leading to enhanced heat transfer. This study investigates the impact of moderate static magnetic fields on the laser melting process of a Sn-10%wt.Pb alloy. It is found that applying a magnetic field significantly widens and deepens laser weld beads. Bead depth and width under different field strengths and orientations are measured. Numerical models are developed to calculate the TEMC current distribution and flow in the melt pool. Full article

This study investigated the influence of spatial orientation on bead morphology and molten pool dynamics during cold metal transfer wire arc additive manufacturing (CMT-WAAM). Experiments in horizontal, transverse, vertical-down, and vertical-up orientations under varying wire feed speeds revealed that increasing the feed rate improved bead uniformity and reduced defects in horizontal deposition, while gravity-induced asymmetry dominated non-horizontal orientations. Transverse cladding produced tilted, uneven beads with reduced penetration; vertical-down enhanced lateral spreading but resulted in the shallowest weld depth; vertical-up limited spreading, yielding narrow beads with higher reinforcement. Optimal cladding quality was achieved at a wire feed speed of 6.7 m/min for the first layer, with a reduced heat input applied for subsequent layers to minimize residual stress and deformation. Numerical simulations further elucidated transient temperature and flow fields. Heat accumulation and dissipation varied with orientation and layer sequence: horizontal deposition formed deep, symmetric pools; transverse deposition generated asymmetric vortices and uneven solidification; vertical-up deposition caused upward counterflow with restricted spreading; vertical-down promoted rapid spreading and faster solidification. A detailed comparison between simulated and experimental temperature distributions and cross-sectional profiles demonstrated excellent agreement, thereby validating the accuracy and predictive capability of the developed model. This integrated experimental-numerical approach provided a comprehensive understanding of orientation-dependent molten pool behavior and offered a robust framework for optimizing process parameters, enhancing dimensional accuracy, and controlling defects in CMT additive manufacturing. Full article

In this study, a novel approach was proposed for predicting the interfacial gap in copper overlap joints by using deep learning and multi-sensor fusion. In this method, an image sensor, a spectrometer, and optical sensors tomography (OCT) sensors were used to develop and validate deep learning models under various gap conditions. The results revealed that the variation in melt pool dimensions, changes in keyhole behavior, intensity variations at specific wavelengths, and keyhole depth derived from the OCT data could be used to accurately predict the interfacial gap. Among the proposed models, a binary gap classification model achieved the highest accuracy of 98.8%. The spectrometer was the most effective sensor in this study, whereas the image and OCT sensors provided complementary data. The best performance was achieved by fusing all three sensors, which emphasizes the importance of sensor fusion for precise gap prediction. This study provides valuable insights into improving weld quality assessment and optimizing manufacturing processes. Full article

While modern power sources have improved process stability, real-time monitoring and feedback control remain essential for ensuring consistent weld quality under dynamic conditions. To address this need, a vision-based closed-loop control system was developed for pulsed Metal-Active Gas (MAG) welding. The system dynamically adjusts the welding speed based on real-time visual feedback in the welding process. Otsu thresholding combined with morphological operations was applied to molten pool images for brightness-based feature extraction. These features, representing the dynamic behavior of the molten pool, were incorporated into a feedback loop for real-time control. Without relying on complex model-based prediction or sensor fusion, the proposed method reduces fluctuations in weld bead geometry and lowers the occurrence of defects. The experimental results showed that, under optimized control conditions and after a steady welding state was achieved, the weld bead’s height deviation exhibited an average standard deviation of 0.08 mm, and a process stability rate of 92%. The combination of conventional hardware and straightforward image processing makes the proposed approach practical for industrial implementation. Full article