High-frequency pulsed (HFP) gas tungsten arc welding (GTAW) has shown excellent performance in welding of aluminum alloys in recent years, which makes itself a promisingly potential technique for part manufacturing in aviation industry. However, existing researches generally focuses on the effect of a single parameter while lacks multivariable researches. Considering of the fact that gap and misalignment are inevitable in real part clamping, adaptive intelligent welding is usually used during automatic manufacturing, which means under the control of filler wire amount per length of a weld, other parameters including current, welding speed and wire feed speed during one single weld are changing according to the specific clamping situation. Therefore, the influence of specific energy input led by different welding parameters within one adaptive welding program on microstructure and mechanical property of the weld needs to be clarified. This study investigates the effect of welding heat input (ranging from 1048.3J/mm to 825.6J/mm within one adaptive welding program control) on the formation quality of 3.25mm thick 6061 aluminum alloy joints fabricated by HFP-GTAW with 4043 filler wire. According to the obtained results, non-monotonic relationship between heat input and porosity, with an optimal minimum of 4.92% achieved at an intermediate heat input of 856.8J/mm. The 21.2% decrease of energy input during welding process would reduce the average grain size in the weld center and adjacent to fusion line by 18.6% and 19.4%, respectively. The ratios between fluctuation range to minimum value in average yield and the relative ranges of yield strength and ultimate tensile strength across the tested heat inputs were 14.7% and 12.7%, respectively. The findings provide a general overview on how the microstructure and mechanical properties would fluctuate in an adaptively controlled HFP-GTAW fabricated aluminum alloy weld.
To enhance the reliability of aluminum alloy welding quality, this study investigates the effects of gas pulse parameters on the arc characteristics and weld quality in pulsed plasma gas variable polarity plasma arc welding (PPG-VPPAW) of 5051 aluminum alloy. Results showed that increasing the gas duty cycle enhanced arc pressure fluctuation but reduced average arc pressure. When the duty cycle exceeded 1/2, excessive pressure fluctuations destabilized the weld pool. Arc voltage fluctuations also intensified with larger duty cycles, reducing arc heat input and stability. Severe variations in arc divergence and high-temperature area were observed at duty cycles above 1/2, leading to poor heat transfer. Weld morphology confirmed these findings: duty cycles of 1/5 and 2/5 produced uniform surfaces with dense fish-scale ripples, while 3/5 and 4/5 introduced defects such as humping and undercut. Mechanical testing showed that conventional variable polarity plasma arc welding (VPPAW) joints reached 262MPa tensile strength and 18.3% elongation, corresponding to 79.8% and 85.1% of base metal values. At a duty cycle of 2/5, the tensile strength increased to 297MPa and the elongation to 21.5%, representing the best overall performance. Variations in the gas pulse frequency did not significantly affect the average arc pressure or arc voltage. However, as the gas pulse frequency decreased, the fluctuation frequency of the arc pressure and arc voltage also decreased, while the fluctuation amplitude of the arc voltage increased. At 8Hz, the tensile strength and elongation increased by 13.4% and 17.5%, respectively, compared with lower frequencies (4 and 2.6Hz).
The development of industry stimulates the advancement of modern approaches for optimizing welded structures. This study presents three technologies for the treatment of welded structures based on the use of pulsed electromagnetic fields, plasma currents, electrodynamic forces, and their combined effects—an emerging direction in engineering practice aimed at improving the mechanical properties of metallic materials and welded joints. A pulsed electromagnetic field treatment (TwPEMF) technology is introduced, which enables the optimization of the stress-strain state in welded structures made of non-ferromagnetic materials. The study investigates the stress-strain state of ring-shaped samples of welded joints made from AMg6 aluminum alloy (δ = 1.0mm), using electronic speckle interferometry, both with and without an additional conductive shield, after TwPEMF treatment. It was found that TwPEMF reduces the displacement values by 2 and 4 times and decreases residual stresses by 50% and 80%, respectively, in samples without and with the shield. Also presented is an electrodynamic treatment (EDT) technology for butt-welded joints of AMg61 (1561) aluminum alloy with a thickness of δ = 3.0mm during TIG welding, compared to EDT applied at room temperature. Based on mathematical modeling and experimental data, EDT during TIG welding contributes to the formation of an optimal residual stress-strain state of the welded joint. Additionally, a surface treatment technology for structural optimization based on pulsed barrier discharge (PBD), which generates low-temperature plasma on the treated metal surface—is presented. It was found that PBD increased the Vickers hardness of 25KhGNMT structural steel by 20% (420 to 510kg/mm²) at depths up to 2mm and promoted microstructural refinement of the metal.
The interface microstructures and strain distribution of dissimilar friction stir welding (FSW) of AA7075/AZ31B joints with or without ultrasonic vibration were examined. The results reveal that the ultrasonic vibrations and tool offset greatly influence the dynamic recovery towards the Mg side by reducing the non-indexing region at the interface. Moreover, the grain recrystallization near the interface differed from the other areas due to severe deformation. Continuous dynamic recrystallization (CDRX) occurs at the AA7075 side, whereas the Mg side exhibits discontinuous dynamic recrystallization (DDRX). The higher net strain component was observed for ultrasonic-assisted FSW (UVaFSW). The strain component was changed significantly towards the AA7075 side compared with the AZ31B side. It occurred because of different recrystallization mechanisms. The strain component was well spread towards the AA7075 side, whereas the dispersed strain component was observed towards the AZ31B. Along the plate thickness direction, the intermetallic compound layer (IMC) thickness first increases, then decreases, reaching a maximum value of 1.5 to 1.8mm from the top. The ultrasonic vibration reduced the overall thickness of intermetallic in the joint interface, regardless of the tool offset conditions.
Infrared thermal imaging technology enhances the visualization and identification of surface defects in welding joints by capturing the temperature field distribution and generating thermal images with color gradients. Compared with traditional visual inspection methods—which are significantly affected by factors such as lighting conditions, background complexity, and weak defect features—infrared imaging demonstrates superior capability in representing small-scale and diverse welding defects. Given the current lack of publicly available infrared welding defect datasets, this study develops an infrared image acquisition system tailored for penetration defects in laser-Metal Active Gas Arc (MAG) hybrid welding and constructs a corresponding dataset for training and evaluating non-destructive defect detection models based on infrared sensing. On this basis, a penetration defect detection model based on the YOLOv5s architecture is established, and a feature map visualization method is introduced to improve the interpretability of the detection results. The model is trained and tested on the constructed dataset, and the experimental results demonstrate that the model achieved strong performance in the task of penetration defect detection, with a precision of 97.2%, a recall of 96.6%, and a mean average precision (mAP) of 98.6% at an Intersection over Union (IoU) threshold of 0.5.
In order to rationally select the welding current of stainless steel during metal inert-gas welding (MIG welding), its welding current under different plate thicknesses was taken as the object of study. The scatter function provided by the data fitting software was used to draw scatter plots for the welding current data from two different sources, the polynomial fit (polyfit) function and the curve fitting toolbox were used to fit polynomial curves and perform optimality analysis on the fitted equations. Scatter plots and first-, second-, and third-order curve fitting equations for welding currents at different plate thicknesses were obtained, as well as curve equations for the optimum order of welding current data from two different sources. The results show that the optimization effect of the third- order curve is superior to that of the first-order and second-order curves. Finally, through the experiment, it is verified that the curve equation has some guiding significance in determining the welding current range of stainless steel MIG welding.
Imbalanced data distribution stands as the primary cause of performance deterioration in the majority of supervised classification algorithms. The current publicly available weld defect datasets are very limited, and the samples of various defects are seriously imbalanced. The paper proposes an improved deep convolution generative adversarial network (DCGAN) to balance the weld defect dataset. To solve the problem of poor diversity in the samples generated by the traditional DCGAN, a C-Res unit is constructed, which integrates the convolutional block attention module (CBAM) into the residual block. The transposed convolution in the DCGAN’s generator is replaced with the constructed C-Res unit to enhance the attention to image details and improve the stability and learning efficiency of the model. The Pixelshuffle module is added into the generator as the up-sampling module to solve the problem that the C-Res unit can’t up-sample like the transposed convolution. CBAM is added into the DCGAN’s discriminator to further enhance the discriminator’s ability to judge the quality of the generated sample. To validate the effectiveness of the improved DCGAN, comparison experiments are carried out. The weld defect dataset is balanced by DCGAN and improved DCGAN, respectively, and then YOLOv8s-cls is used to classify the weld defect sample based on the original dataset, the dataset balanced by the DCGAN, and the dataset balanced by the improved DCGAN, respectively. Among the nine F1 scores of the nine types of samples, seven of them are higher than those of YOLOv8s-cls trained with the original dataset, and six of them are higher than those of YOLOv8s-cls trained with the dataset balanced by the traditional DCGAN. The experiments reveal that the weld defect dataset balanced with improved DCGAN can enhance the performance of the supervised classification model, and is helpful to realize automation of weld defect detection.
Adjustable Ring Mode (ARM) laser welding has become an advanced technique to stabilize the welding process and improve joint quality. However, its application in Cu-on-Al welding remains underexplored, despite the challenges associated with conventional welding methods in achieving high-quality joints. In this study, ARM laser welding was employed to fabricate Cu-on-Al lap joints using T2 Cu and 1050 Al foils (400 μm thick). By optimizing the independent power distribution of the core and ring lasers, a hybrid bonding mechanism was achieved, consisting of fusion welding at the weld center and weld-brazing at the periphery, where molten Al infiltrated the Cu base metal. This process effectively expanded the bonding area and suppressed the formation of continuous brittle intermetallic compounds (IMCs), thereby improving joint mechanical performance. The resulting hybrid joint exhibited enhanced stability, with predominantly ductile fracture occurring in the Al base metal. At optimal process parameters, the joint demonstrated a load-bearing capacity of 30.4 ± 2.0N/mm. These findings highlight ARM laser welding as an effective strategy for Cu-on-Al welding, offering a scalable solution for critical applications, such as lithium-ion battery component welding in electric vehicles.
This work employed Fe-Cr-C alloy as the cladding material to fabricate wear-resistant coatings on dissimilar steel welded joints composed of NM450 wear-resistant steel and ZG30SiMn cast steel with ER70-G welding wire. The investigation focused on elucidating the effect of dilution ratio levels on microstructural distribution and wear behavior within this heterogeneous multi-material system. Owing to its inherently higher chromium (Cr) content, the NM450 region demonstrated more pronounced carbide formation compared to the ER70-G and ZG30SiMn regions. Microstructural analysis revealed that Cr7C3 carbides predominantly formed along grain boundaries, whereas Cr23C6 carbides mainly precipitated within grains. After cladding, the wear resistance of the NM450/ER70-G/ZG30SiMn welded joint was markedly improved, with the high-dilution coating exhibiting superior performance. This enhancement was attributed to favorable thermal conditions in the high-dilution scenario, promoting a more homogeneous precipitation of Cr23C6. Although significant elemental mixing occurred at the interfacial zones, the top region of the cladding layer remained minimally affected by dilution-induced drawbacks. Accordingly, the high-dilution sample demonstrated better wear resistance than its low-dilution counterpart due to optimized carbide precipitation characteristics. These findings provide basic insights for designing effective cladding strategies for complex multi-material components in demanding industrial applications.
The need for lightweight structures is becoming increasingly critical in our demanding world. Thus, high-quality joints in similar material combinations or hybrid metal structures are equally crucial for welding techniques. This implies that adding auxiliary assisting sources during the process can significantly mitigate the problems associated with inadequate softening, a known drawback of the friction stir welding (FSW) process. It has been discovered that laser beam preheating can soften the weld region of the workpieces when implemented in a pre-planned manner. Subsequently, it induces a temperature rise in the workpieces by enhancing their plasticization characteristics. A satisfactory laser beam induces changes in the materials’ condition, facilitating a more straightforward joining process than the traditional FSW process. Moreover, it is even easier to join aluminum alloys to other harder metals, e.g., steel or copper, let alone joining aluminum alloy, magnesium alloy, and nickel-based superalloy. This article presents the influence of incorporating a laser beam source as an auxiliary energy source during the FSW process. It discusses the most recent progress on changes in the behaviour of joints produced with and without laser beam sources, particularly in terms of temperature distribution, appearance, joint formation, microstructure, and mechanical properties. Furthermore, the benefits of laser-assisted FSW (LAFSW) joints compared to traditional FSW have been thoroughly highlighted.
In order to enhance the wear resistance of 45 steel,a WC/Stellite 6 composite layer with 30%WC which with different morphologies(spherical and irregular)was prepared on the surface of 45 steel by laser cladding technology.The effects of WC morphology on the phase composition,microstructure,microhardness,and wear resistance of the cladding layer were compared and analyzed.The res-ults show that the surface of the cladding layer was well formed.M23C6,M7C3,WC,and W2C exist in both cladding layers.With the ad-dition of spherical WC,the diffraction peaks of γ-Co appear on the left side of the main peak of Co6W6C.The area of intergranular carbides accounts for a large proportion in the surface layer which with the fine grains.During the process of laser cladding the spherical WC particles with loose structure are prone to melting,including their interior.However,the melting amount of irregular WC particles is finite,which only occurs on the periphery of the particles,and the particle interior is relatively intact.The microhard-ness of two cladding layers gradient increases from the substrate to the surface layer.The surface layer added spherical WC has high-er microhardness,which reaches 790.6 HV1.Nevertheless,the wear resistance of the cladding layer added irregular WC is better than that of the cladding layer added spherical WC.The reason is because that the incompletely melted irregular WC particles are uni-formly distributed in the cladding layer which provided the support points for the cladding layer matrix during the wear process,the wear of the cladding layer by the grinding pair is reduced consequently.
Laser twin-arc GTAW（LTA-GTAW） process has been developed by using the synergic interaction effects of laser and a coupled arc in a weld pool to achieve higher energy efficiency. In this study, bead-on-plate welding was conducted on 8-mm-thick Q235B workpieces to investigate the variation of hybrid arc profile, the influence of hybrid arc profile on weld forming, microstructure and mechanical properties of the joint during the LTA-GTAW process. The influence of Laser-GTAW and LTA-GTAW methods on weld surface appearance, heat input per unit length, and weld metal microstructure were also demonstrated systematically. The LTA-GTAW can make the distribution of arc energy more reasonable in welding depth and width. When defocus is 0, I_f is 330 A, I b is 240 A, laser power is 2.4 kW, and spacing between heat sources of tungsten electrode is 10 mm, the weld shape is better. Compared with LaserGTAW, LTA-GTAW can achieve lower heat input at the same penetration depth, and the microstructure of the weld is refined. The tensile strength of the welded joint is 121.8% of the base material, and the fracture mode of the welded joint is ductile fracture, the comprehensive mechanical properties are better.
Base on the arc phase and short-circuit phase and their relationship, the paper considers the changes of the extension of wire, the arc length, liquid bridge resistance and mass of liquid bridge, combines the improved “mass-spring” model with the loop model of welding power system, puts forward the critical judgment condition of droplet transition, and establishes a more accurate dynamic model for describing the short-circuit transition process. The dynamic changes of short-circuit transfer frequency, welding current and voltage, contact droplet and residual droplet equivalent radius and droplet equivalent radius at different wire feeding speeds were calculated and analyzed, and compared with the experimental results. It shows that the fluctuation of droplet displacement, velocity and wire extension length at the optimal arc starting point is the smallest. The smaller the initial liquid bridge curvature radius is, the better the stability of short-circuit transfer is.
The lap joint of T2 copper plate and 1 060 pure aluminum plate was made by using the plasma arc welding method with adding Fe2O3 nanoparticles in different proportions.The research analysis found that the thickness of the IMC(intermetallic compound)and eutect-ic region decreased after the addition of nanoparticles due to its inhibitory effect.When the proportion of Fe2O3 nanoparticles is 3%,the in-terface intermetallic compound layer is the thinnest.However,after this ratio is continuously increased,the inhibition effect is weakened by the agglomeration of nanoparticles,and the thickness begins to increase significantly.The mechanical and electrical properties of the joint are mainly affected by the thickness of the IMC layer.Excessive nanoparticles are agglomerated into large particles with high resistivity.Therefore,the tensile strength and relative electrical conductivity of the joint are first increasing and then decreasing with the increase of nanoparticle ratio.When the proportion of nanoparticles is 3%,the tensile strength and electrical conductivity are maximum.
Aluminum Nitride(AlN)ceramics were soldered to Cu substrate using active metallized Sn0.3Ag0.7Cu-x%Ti(wt.%,where x = 2,4,6,8)at 250℃.This process yielded a robust and closely integrated metallized layer on the AlN ceramic's surface.Employing SnAgCu solder paste within an air atmosphere,joints were formed for durations of 60s and 300 s.Through meticulous microscopic analysis,optimal metallization parameters were identified,resulting in the successful connection between metallized AlN ceramics and Cu substrate at a low temperature.The microstructure interface investigation further elucidated the impact of connection time on the low-temperature soldered joint of metallized AlN ceramics.
Due to the layer-by-layer manufacturing characteristics,metallurgical process of selective laser melting(SLM)is inherently dif-ferent in the building direction because of varying conditions,thereby resulting inter-layer heterogeneity.To mitigate such anisotropy,it is of great significance to understand the effects of processing parameters on the property evolution and thus metallurgy of fabrication process.This research proposes one-factor-at-a-time experiment to investigate the influences of laser power and scanning speed on the surface qual-ity,microstructures and mechanical properties of selective laser melted Ti-6Al-4V parts.Surface quality is assessed by roughness around the printings while mechanical properties are evaluated through microhardness and tensile strengths.Phases in microstructure are quantified by XRD to correlate with mechanical properties.Fracture morphology is analyzed to understand the effect of defects and microstructure on mechanical performance.The optimized parameter corresponding to best surface quality and mechanical properties has been found respect-ively in laser power of 190 W and scanning speed of 800 mm/s.After optimization,surface roughness has decreased by 44.47%for upper surface.Yielding strength,tensile strength and elongation rate have improved by 13.17%,43.34%and 64.51%,respectively,with similar hardness and Young's modulus.In addition,heterogeneity of mechanical properties has great improvement by a range of 31.63%-92.68%.
The successful confinement of the arc by the flux band depends on the welding process parameters for achieving single-pass,multi-layer,and ultra-narrow gap welding.The sidewall fusion depth,the width of the heat-affected zone,and the line energy are utilized as comprehensive indications of the quality of the welded joint.In order to achieve well fusion and reduce the heat input to the base metal.Three welding process characteristics were chosen as the primary determinants,including welding voltage,welding speed,and wire feeding speed.The metamodel of the welding quality index was built by the orthogonal experiments.The metamodel and NSGA-II(Non-dominated sorting genetic algorithm II)were combined to develop a multi-objective optimization model of ultra-narrow gap welding process paramet-ers.The results showed that the optimized welding process parameters can increase the sidewall fusion depth,reduce the width of the heat-affected zone and the line energy,and to some extent improve the overall quality of the ultra-narrow gap welding process.
A new structure of 1 + 2 was designed in friction stir welding(FSW)of Al alloy sheet with unequal thickness:a specific sheet with similar composition of base metals(BMs)was placed under the thinner sheet as the supporting sheet so that the BM surfaces could be on a plane.The BMs can also be fully penetrated weld with a stirring pin longer than the thickness of the thin sheet.2 mm and 1.5 mm thick Al alloy sheets were welded by FSW,and parameters were optimized.The highest welding strength reached 96.07%of the thin base metal.Although a slight thinning phenomenon occurred at the edge of the nugget on the retreating side,the specimen still fractured in the heat-af-fected zone.
Additive manufacturing(AM)technology makes parts through layer-by-layer deposition,which can regulate the microstructure and properties of different parts of a single part well.It provides a new idea for the preparation of functionally gradient materials(FGM),and has become a research hotspot at present.By referring to and analyzing the recent research achievements in the additive manufacturing tech-nology of FGM,the latest research progress at domestic and abroad from four aspects were summaried:selective laser melting additive man-ufacturing,electron beam additive manufacturing,arc additive manufacturing,path planning,and material texture.Moreover,the existing problems in the research are pointed out,and the future research direction and focus are prospected.
For joining high Cr,Ni and Mo austenitic stainless steel(AISI 316)by direct drive friction welding(DDFW),with friction weld-ing conditions:rotation speed of 3 000 r/min,friction time of 10 s,friction pressure of 130 MPa,forge time of 5 s and forge pressure of 260 MPa.The results of microstructure showed that the temperature at the interface reached 819℃while forge applied between 357-237℃,which subdivided welded joint into four distinct regions of highly plastically deformed zone(HPDZ),thermo-mechanically affected zone(TMAZ),heat affected zone(HAZ)and the base metal,with grain size about 10µm,100µm,90µm and 30µm respectively.These re-gions were created due to dynamic recrystallization(DRX)at the interface and thermo-mechanical deformation with heat diffusion in the neighboring regions.Whereas,high level of microhardness about 300 HV0.1 and hardness roughly 240 Hv10 at the interface due to HPDZ creation while low level of 240 HV0.1 for microhardness and moderately of 205 HV10 for hardness in neighboring regions.
