Objective Aluminum-lithium(Al-Li)alloys are regarded as the most ideal structural material in the aerospace field due to their excellent mechanical properties and resistance to stress corrosion.A large solidification temperature range and coefficient of linear expansion result in high hot cracking susceptibility for Al-Li alloys during laser welding.Expanding the butt gap to fill the weld with crack-resistant materials helps suppress crack initiation.However,limited by the low gap tolerance of traditional laser wire feeding welding technology,this limitation causes difficulty in joint formation.Oscillating laser wire feeding welding can significantly improve the adaptability to butt gaps.However,systematic research on oscillating laser wire feeding welding of Al-Li alloys with large butt gaps is lacking both domestically and internationally,and the adaptability of its welding process remains unclear.In this study,oscillating laser wire feeding welding is employed to investigate the joint formation effect and mechanical properties of 2198 Al-Li alloy with large butt gap.By optimizing butt gap size and selecting appropriate welding wire type,welding joints with good formation and a low pore rate are obtained.The research reveals the influence of molten pool fluid flow behavior on pore formation and clarifies the correlation between weld microstructure morphology and mechanical properties. Methods This study employs the oscillating laser wire feeding welding method to investigate the forming characteristics of 1.8 mm thick 2198 Al-Li alloy welding joints under different preset butt gaps.The used filler materials are ER5356 and ER2319 welding wires with a diameter of 1.2 mm.The preset butt gap dimensions for the connection joints are 0.8 mm,1.0 mm,and 1.2 mm,respectively.The parameters for the oscillating laser wire feeding welding are as follows:laser power of 3200 W,welding speed of 4.8 m/min,wire feeding speed of 9.6 m/min,oscillation mode of'8'-shape,oscillation frequency of 200 Hz,oscillation amplitudes for the 0.8 mm,1.0 mm,and 1.2 mm butt gaps are 0.8 mm,1.0 mm,and 1.2 mm,respectively,and laser scanning diameters are 1.6 mm,2.0 mm,and 2.4 mm,respectively.The metallographic samples of the welding joints are prepared after welding,and the microstructure morphology is observed using an optical microscope(Leica DMI8C).The viscosity and phase diagram of the liquid metal for the welding wires are calculated using Jmatpro 9.0 software.The strength and hardness of the welding joints are tested using a tensile testing machine(MTS 370 Load Frame)and a microhardness tester(VH1102),respectively. Results and Discussions Results show that the optimal matching butt gap is 1.0 mm under the specific laser welding parameters of this study,either too small or too large a butt gap will result in welding defects such as uneven root formation and edge biting(Fig.3).Using ER5356 and ER2319,uniform welding joints of 2198 Al-Li alloy with no macroscopic surface defects can be obtained(Fig.4).From the cross-sectional view,it can be observed that when ER2319 welding wire is used as the filler metal,the number and size of gas pores are significantly greater than ER5356(Fig.5).The viscosities of the liquid metals for the two welding wires are calculated using Jmatpro 9.0 software(Fig.6).The viscosity of the ER2319 liquid metal is always higher than that of the ER5356.The lower the viscosity of the liquid metal,the better its fluidity.Compared with ER2319,the more fluid ER5356 not only facilitates the timely escape of bubbles during the melting process but also reduces the aggregation of supersaturated bubbles in local areas,thereby lowering the pore rate of the weld.The laser oscillation causes the coarse columnar crystals at the local center of the weld to break down,forming fine equiaxed crystals.However,near the fine-grained zone at the fusion line,a columnar crystal structure remains(Fig.7).The calculation results of the phase diagrams show that Mg2Si and Al2Cu strengthening phases may form in the weld(Fig.8),which can enhance the performance of the weld.The tensile test results show that the welding joint strength when using ER5356 is higher than ER2319.The approximately parallel arranged grain boundaries in the columnar crystal zone of the weld provide a low-resistance path for crack propagation during the tensile process,resulting in both types of joints fracturing along the fusion line towards the columnar crystal zone on the weld side(Fig.9).Size and quantity of the pores in ER2319 weld are much larger than ER5356,resulting in a more significant weakening effect of the welding joint.The fracture morphologies of the welding joints for ER2319 and ER5356 exhibit characteristics of ductile and brittle fracture,respectively(Fig.10).Furthermore,the softening effect results in the microhardness of both the weld and the heat-affected zone being significantly lower than that of the base material(Fig.11). Conclusions The oscillating laser wire feeding welding method is adopted to achieve excellent weld formation for 2198 Al-Li alloy with a 1.0 mm large-sized preset butt gap.By feeding the with crack-resistant welding materials,the generation of welding hot cracks can also be effectively suppressed.Although both ER2319 and ER5356 welding wires can achieve good formation of weld,due to the poor fluidity of the ER2319,bubbles in the liquid metal cannot be promptly expelled during the molten pool solidification process,resulting in the formation of numerous pores in the weld and significantly worse joint strength.Therefore,ER5356 is more suitable for the oscillating laser wire feeding welding of 2198 Al-Li alloy with large butt gap.

Butt welding of SiCp/2009 Al MMCs with a 1.3 mm preset gap was achieved by the oscillating laser filler wire welding process. The influence of wire feeding speed on weld formation was investigated, and the microstructure characteristics, mechanical properties, and fracture characteristics of welded joints under the optimal wire filling amount were systematically analyzed. Results indicate that when other welding process parameters are constant, an appropriate wire feeding speed can effectively fill the preset gap. Wire feeding speeds that are too low or too high lead to poor weld formation. The microstructure of the welded joints exhibits heterogeneity. Compared with the base metal, the size of Al2Cu in the heat-affected zone decreases, but its quantity increases due to the influence of the welding thermal cycle, while only a small amount of SiC and Al2Cu particles exist in the weld seam. Because the dilution rate of the base metal decreases, and more laser energy is used to melt the ER5356 filler wire, the dissolution degree of SiC is reduced, which effectively inhibits the formation of Al4C3. Tensile test results show that the tensile strength of the welded joints reaches 68.9% of that of the base metal, and brittle fracture occurs near the fusion line of the specimen. The main reason for the fracture is that the formation of void-like defects reduces the effective load-bearing area at this location.

Aiming at the problem that silicon carbide particle reinforced aluminum matrix composites (SiCp/Al MMCs) are prone to interfacial reaction between the matrix Al alloy and reinforced SiC particles at high temperature, which forms Al4C3 brittle compounds that affects the joint performance, an oscillating laser wire-filling welding process with preseted gap was developed. The high-quality welding connection of SiCp/2009Al MMCs with a thickness of 1.6 mm and 30

Conventional laser directed energy deposition (LDED) of aluminum alloy is challenged by anisotropy of microstructure and mechanical properties, as well as low deposition efficiency. This study attempted to mitigate these deficiencies by designing and realizing the deposition of gradient samples via a self-designed test platform that combined multi-wire deposition and oscillating laser technologies. The microstructure and mechanical properties of the Al-Cu-Si gradient wall (GW) and Al-Cu homogeneous block (HB) were explored in two deposition directions, studying the heat treatment effects on the HB microstructure and mechanical properties. The experimental results proved that the deposition direction did not significantly affect the microstructure and properties of aluminum alloy samples deposited by multi-wire laser. The GW cross-section had a lower-arched layered structure, and the microstructure comprised equiaxed and columnar crystals. With the increased Si content, the porosity, grain size, and hardness decreased. The deposited HB mainly comprised equiaxed crystals, accompanied by many reticular precipitates, with an average hardness of 80 HV and tensile strengths of 218, 217, and 215 MPa in X, Y, and Z directions, respectively. The deposition efficiency was improved, while the mechanical properties showed no anisotropy. After T6 solid solution treatment + aging, the precipitated phase was dissolved, the Cu element was uniformly distributed, the hardness grew to 150 HV, and the tensile strength exceeded 420 MPa. High isotropy of mechanical properties in the deposited and heat-treated states proved an effective mitigation of the anisotropy problem faced by conventional LDED.

The Sc microalloying effects on Al-Cu alloy thin-wall components fabricated by wire arc additive manufacturing (WAAM) with friction stir processing (FSP) assistance were investigated. The microstructure of as-deposited Al-Cu-Sc alloy was composed of overall fine equiaxed grains, the grain refinement effect was produced resulting from increasing heterogeneous nucleation rate induced by the formation of primary Al3Sc nanophases. In addition, primary theta-Al2Cu phases were refined and densified by Sc microalloying. The finer precipitates involving theta phase, Al3Sc particles, and secondary theta ' phases facilitate the precipitation strengthening effects in as- deposited Al-Cu-Sc alloy. Besides, FSP introduced the dynamic recrystallization (DRX) and precipitate fragmentation effects in deposited alloy, the grain refinement in plastic deformation zone was elicited by the combination of DRX and Al3Sc. The deposited Al-Cu-Sc wall structures with FSP assistance exhibited a higher tensile strength above 300 MPa, and a better plasticity and less anisotropy due to the elimination of columnar grains. The synergic mechanical performance enhancement was mainly attributed to the precipitation strengthening effects and grain refinement caused by the combination of Al3Sc nanoparticles and FSP extrusion.

A hybrid additive manufacturing (HAM) technology combined by friction stirring processing (FSP) and laser deposition melting (LMD) has been investigated. It can provide an attractive and cost-effective approach for aluminum engineering components. However, the mechanisms of the effects of different stirring strategies on microstructure and mechanical properties are still unclear. The effect of multiple repetitions in the process of FSP on the microstructure and mechanical properties of Al -Cu -Mg alloys prepared by LMD has been studied, and the unavoidable defects, such as pores and cracks are eliminated by repetitive FSPs, so as to refined microstructure as well as enhance the properties. Especially after 2 cycles of overlap -track full area lap friction stir processing (2CFSP), the grain refinement reaches its optimal state, with a grain size of 2.57 mu m and the average microhardness also reaches its optimal level (153.3 HV). At the same time, the ultimate tensile strength (UTS) was improved by 49.3 %, yield strength (YS) by 44.8 %, and elongation (EL) by 8.39 % compared with the deposition layer. Simultaneously, the dominant mechanisms of microstructural evolution and tensile property enhancement generated by hybrid additive manufacturing are revealed.

The influence of trace elements variation and constraint conditions on welding hot cracking was investigated to reveal the cracking characteristics of nickel-based alloy NS1402. The fishbone tests and full restraint welding tests have been conducted to determine the cracking ratio. The mechanical and metallurgical fracture mechanisms were elaborated simultaneously. And the low-melting point liquid membrane, which was a key metallurgical factor, was found in cracking fracture surface. Numerical simulations were conducted to illustrate the effects of transverse tensile stress/strain during welding processing. Results show that the liquid membranes were composed of FeNi, FeP, Co3Fe7, etc., indicating that liquid membranes were developed to higher melting point by Co3Fe7 eutectics due to the addition of Co, and it contributes to reducing cracking susceptibility of NS1402. The cracking was ductility-dip cracking (DDC), which propagated in the forms of intergranular or transgranular fracture. Thus, adjusting element content and degrees of constraint could control the cracking tendency.

Weld scam tracking is the key technology for achieving automated welding. In this paper, a scam tracking method based on a line array camera and a feature recognition algorithm is constructed to provide gapless seam recognition under laser welding. The workpiece surface image is captured by a line array camera and denoised by mean filtering. By analyzing the gray value of the image, the change in the gray value of the image, the gray gradient of the image, and the width of the weld area, the weld track is identified, and the identification and tracking of the gapless weld are realized. Welding experiments are conducted, and the results show that the error of the weld identification method based on a line array camera is less than 0. 05 mm. Weld seam tracking experiments on welds with different a gap are conducted, and the results show that the proposed method has a good recognition effect for welds with a gap less than 0. 3 mm.

To mitigate the adverse effects of residual stress and deformation during high-power laser welding, this study established a finite element model based on thermodynamic conditions for high-power laser welding of CLF-1 steel for nuclear fusion applications. The temperature field and residual stress of the weld were simulated by using the composite heat source model together with Gaussian model and conical model. The results showed that the temperature field simulation was in good agreement with the real temperature field. The simulation results of the weld metal (WM) and the heat affected zone (HAZ) in the cross sections were basically consistent with those of the real cross sections. Moreover, the margin of error between the simulation results and the real data was & LE; 1.3% (the largest error & LE;0.04 mm). The Von Mises equivalent stress in WM was distributed irregularly, and its largest value was & LE; 220 MPa; the equivalent stress declined with an increase in distance from the center of WM. The transverse stress distribution in the center of WM was in accordance with the vertical stress distribution, which was essentially the same as the experimental data of the vertical stress. The simulation results of deformation in the Z direction of the weld showed that the maximum deformation was about -0.2 mm at the center of the weld corresponding to the length of 300 mm. In summary, the thermal source model, combined with laser welding process parameters, can provide high-precision prediction of stress variations and deformation control during the actual welding manufacturing process of the test blanket module (TBM) structure.

Systemic capillary leak syndrome (SCLS) is a rare and complex adverse effect of immune checkpoint inhibitors (ICIs). The diagnosis of drug-induced SCLS is based on diffuse infusions of exudative fluid into the interstitial areas and the exclusion of other causes. The best management of ICIs-induced SCLS is not settled, though proper supportive care and corticosteroids were commonly applied as the first-line treatment. In our patient with advanced gastroesophageal junction squamous cell carcinoma, although ICIs-induced SCLS was successfully controlled with corticosteroids, the patient soon experienced cancer progress and died of pulmonary infections. Based on our experience and the reported cases by other hospitals, different stages of SCLS might respond differently to the same treatment. Therefore, a grading of ICIs-induced SCLS might help to stratify the patient for different treatment strategies. Besides, corticosteroids-sensitive patients, though waived from deadly SCLS, might be at higher risk of cancer progress and subsequent infections due to the application of corticosteroids. Considering that the inflammatory factors should be closely involved in the development of ICIs-induced SCLS, targeted therapy against the driver inflammatory cytokine might offer treatment regimens that are more effective and safer.

In this paper, the fatigue crack growth rates of A7N01 aluminum alloy welded joint in weld zone (WZ) and heat affected zone (HAZ) are compared under the stress ratio of 0.1. At the same time, the fatigue crack growth rate of WZ under different stress ratios is studied. The results show that the difference of microstructure leads to different fatigue crack growth rates in different areas of welded joints. The HAZ shows better fatigue crack growth resistance and slower fatigue crack growth rate. However, due to the burning loss of Zn element in the WZ, the precipitation of strengthening phase after solidification in the molten pool is less, and the fatigue crack propagation resistance is weak. After 60 days of natural aging, the number of precipitated phases in the WZ and HAZ increased, and the fatigue crack propagation resistance is improved compared with that in the welded condition. Compared with grain boundary strengthening, precipitation strengthening is more important. With the increase of stress ratio, the fatigue crack closure effect in WZ gradually weakens, and the fatigue crack propagation rate increases.

To improve the metallurgical defects and microstructure during laser melting deposition (LMD), the effects of the number of repetitions during friction stirring processing (FSP) on the microstructure and mechanical properties of Al-Cu-Mg aluminum alloys prepared by laser melting deposition were investigated. Finally, defects such as porosity and cracks in the LMD process were effectively eliminated by multiple FSPs, while grain refinement was achieved. The experimental results showed that grain refinement was significantly improved by FSP. Especially after two cycles of overlap-track full area lap friction stir processing (2C-FSP), the grain refinement was optimized (87.5%) and the average microhardness also reaches its optimal level (153.3 HV). Moreover, the defects obtained by LMD were eliminated in three cycles of overlap-track full area lap friction stir processing (3C-FSP) due to the repetitive FSP. At the same time, the ultimate tensile strength (UTS) was improved by 49.3%, yield strength (YS) by 44.8%, and elongation (EL) by 8.39% compared with the deposition layer. This study provides a new method and corresponding data for improving the microstructure and mechanical properties of Al-Cu-Mg alloy produced by laser additive manufacturing (LAM).

In this study, AA1060 aluminum alloy and T2 copper with a thickness of 3 mm were joined by Yb:YAG Disc laser welding. Three joint types, namely laser fusion welding (LF joints), laser deep penetration braze-fusion welding (LPBF joints) and laser deep penetration braze welding (LPB joints) were obtained depending on the amount of melted copper in the Al/Cu interface. Furthermore, the micro-hardness and mechanical properties of these joints were investigated in detail. The experimental results show that the tensile strengths of LF joint, LPB-F joint and LPB joint are 79 MPa, 94.5 MPa and 52 MPa, respectively. A maximum tensile strength is obtained in LPB-F joint, which is close to that of the 1060 aluminium alloy. The primary reason is that Al2Cu3 and Al2Cu intermetallic compounds with a comparatively greater hardness exist in the transition layer.

Background: To assess the efficacy, safety, and cosmetic effects of breast-conserving surgery (BCS) combined with intraoperative radiotherapy (IORT) in Chinese people. Methods: A retrospective analysis was performed on 451 patients who received IORT at four hospitals in China. The endpoints were ipsilateral breast tumor recurrence (IBTR), locoregional recurrence (LRR), overall survival (OS), disease-free survival (DFS), IORT-related toxicities, and cosmetic outcomes. Findings: The median follow-up was 5.4 years (with a range of 1.0 to 11.9 years). The overall IBRT was 1.5%, LRR was 2.8%, and the OS rate and DFS rate were 96.2% and 99.1%, respectively. Only one (0.2%) breast cancer-related death was recorded. The cancer-related distant metastasis rate was 0.6%. There was no intraoperative or postoperative radiation-related acute hematological toxicity or other complications. Overall, 74.3% of patients graded the cosmetic effect as excellent or good. The pre-excision IORT is non-inferior to post-IORT The LRR was 2.4%, whereas the OS rate was 99.5% after adjusting for the age of patients according to the recommended criteria by the American Society of Therapeutic Radiation Oncology (ASTRO), and the DFS rate was 98.1%. Interpretation: IORT significantly reduced the treatment time while preserving a high degree of locoregional control and cosmetic effects. The outcomes of pre-excision IORT were similar to those of post--excision IORT. Patients older than 40 years old are legible for IORT. Funding: This work was supported by the Beijing Municipal Science & Technology Commission (D161100000816003), National Natural Science Foundation of China (Grant No. 82072097), National Key Research and Development Project (Grant No. 2019YFE0110000), Clinical and Translational Medicine Research Foundation of Chinese Academy of Medical Sciences(Grant No. 2020-I2M-C&T-B-069), the CAMS Initiative Fund for Medical Sciences (Grant No. 2017-I2M-3-004), the Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences (Grant No. 2018PT32013, 2017PT32001 and 2016ZX310178), the Beijing Hope Run Special Fund (Grant No. LC2017B15 and LC2020A18). Declaration of Interests: The authors declare that they have no competing interests. Ethics Approval Statement: This study was approved by the Ethics Committee of the Cancer Hospital Chinese Academy of Medical Sciences, the First Affiliated Hospital of Zhengzhou University, the Peking University Cancer Hospital, and 301 hospital.

In this study, a wire oscillating laser additive manufacturing (O-WLAM) process was used to deposit 2319 aluminum alloy samples. The optimization of the deposition process parameters made it possible to obtain samples with smooth surfaces and extremely low porosities. The effects of the deposition parameters on the formability and evolution of the microstructure and mechanical properties before and after heat treatment were studied. The oscillating laser deposition of 2319 aluminum alloy, especially the circular oscillation mode, significantly reduced the porosity and improved the process stability and formability compared with non-oscillating laser deposition. There were clear boundaries between the deposition units in the deposition state, the interior of which was dominated by columnar crystals with many rod- and point-shaped precipitates. After the heat treatment, the θ phase was significantly dissolved. The residual dot- and rod-shaped θ ' phases were dispersedly distributed, exhibiting an obvious precipitation-hardening effect. The samples in the as-deposited state had a tensile strength of 245–265 MPa, an elongation of approximately 12.6%, and an 87 HV microhardness. After heat treatment at 530°C for 20 h and aging at 175°C for 18 h, the tensile strength, elongation, and microhardness reached 425–440 MPa, approximately 10%, and 153 HV, respectively. The performance improved significantly without significant anisotropy. Compared with the samples produced by wire arc additive manufacturing (WAAM), the tensile strength increased by approximately 10%, and the strength and microhardness were significantly improved.

A high power laser welding finite element model of CLF-1 steel for nuclear fusion was established based on thermodynamics in the study. The temperature field and residual stress of the weld were simulated by using the composite heat source model grouped by Gaussian model and conical model. The results showed that the temperature field simulation was broadly in line with the real temperature field. The simulation results of the weld metal (WM) and the heat affected zone (HAZ) in the cross sections were basically consistent with that of the real cross sections. And, the margin of error between the simulation and the real data was ≤ 1.3% (the biggest error ≤0.04mm). The Von Mises equivalent stress in the weld metal distributed irregularly, and the largest value of Von Mises equivalent stress was ≤ 220Mpa, and the equivalent stress declined as the distance from the central of the weld metal became farther. The transversal stress distribution in the central of the weld metal was almost in accordance with the vertical stress distribution, which was essentially the same as the experimental data of the vertical stress. The simulation results of deformation in the Z direction of the weld showed that the maximum deformation was about -0.2 mm at the center of the weld corresponding to the length of 300mm.

In this paper, the laser weld technology was applied to produce the welded joints of CLF-1, which is the primary material of manufacturing the TBM. After laser welding, the first welded joint kept the as-welded state, the second welded joint was treated at 710°C for 2h (abbreviation PWDT), the third welded joint was solution heat treated at 980°C for 1 h and tempered at 710°C for 2 h (abbreviation PWNT). There is some influence on the grain size at different heat treatment processes. It turned out that abundant lath martensite with width 800 nm and few δ-Fe were found in the first welded joint. Its impact energy was about 40 J, and its hardness was about 400-425 HV, which acted a brittle-hard tendency. Moreover, the tempered lath martensite in the second welded joint of PWDT state became more refined, smaller to width about 650 nm. This was because that a mass of MX-type carbides was precipitated inside the martensite. Its impact energy was also up to 237 J, equivalent to the base metal. The width of tempered lath martensite in the third welded joint of PWNT state was smallest about 350 nm. Meanwhile, the size of M23C6 carbides got larger with decreasing of MX carbides’s content. And its the elongation was up to about 27% due to the disappearing of δ-Fe.

This study was focused on welding joints of reduced-activation ferritic/martensitic (RAFM) CLF-1 steel medium-to-thick plates produced via laser beam welding (LBW) and electron beam welding (EBW). Such joints were used in the ITER project, in particular, in the back plate mockup of Helium Cooled Ceramic Breeder Test Blanket System developed in China in 2015. The microstructural evolutions and the mechanical properties of fusion zones (FZs), weld zones (WZs), and heat-affected zones (HAZs) of LBW and EBW joints were analyzed and compared using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Moreover, the microstructural differences between the two types of joints and their effect on the impact properties were discussed. Results showed that the well-formed welds without defects, such as pores, incomplete fusion, and cracks, could be obtained via LBW and EBW. Different heat inputs led to the differences in the grain size gradients, the boundary angles, the content of carbides, and the distribution of dislocations. Despite obvious differences in morphology among FZ, WZ, and HAZ, both types of joints exhibited excellent tensile properties and impact toughness. The tensile strengths of the LBW and EBW joints were 633 and 634 MPa at room temperature, respectively, versus 370 and 366 MPa at 550 degrees C. The mean impact-absorbing energy values of LBW and EBW joints were 251 and 284 J. The further analysis revealed that the low delta-ferrite content, small effective grain size, large grain size gradient, high grain boundary angle, diminutive size of M23C6 carbides, high-Ta content in MX carbides and low dislocation density led to high impact toughness of the LBW joint, while the microstructure of EBW joint failed to show the improvement of impact toughness, and the extraordinary impact toughness could be attributed to the high scattering band. (C) 2021 Elsevier B.V. All rights reserved.

Building better nuclear fusion equipment with reduced cost is important for a sustainable society. In this study, pure tungsten is deposited on different steel substrates by directed energy deposition (DED). Specifically, the deposited layers with graded tungsten content by low and high laser scanning speed are fabricated. In addition, the processing parameters were optimized by analyzing the microstructure, phases and defects. Results show that the 9-layer sample (3000 W @ 3000 mm/min) exhibits a better thermal performance, which the thermal conductivity is about 73.75 W/(m.K) at room temperature and 147.45 W/(m.K) at 900 degrees C, respectively. Finally, the surface of the manufactured thick deposited layer by high-low combined laser scanning speed can reach a high tungsten content of up to 99.78 wt%. It is believed that the additive manufacturing of pure tungsten by DED can combine the advantages of tungsten and steel substrates, and simplify the manufacturing process of thermonuclear fusion devices.

In this paper, fibre laser-cold metal transfer arc (CMT) and oscillating fibre laser-CMT hybrid welding processes were adopted for A7204P-T4 aluminium alloy sheets with thickness of 6 mm. Furthermore, the effect of Nb content on microstructure and mechanical properties, the metallurgical behaviour, and influence mechanism were investigated. Oscillating laser effectively reduced the weld porosity and increased the joint's elongation after fracture by 81%. With the addition of Nb, the heterogeneous nucleation significantly refined weld grains and removed columnar and dendritic structures which attributed to the solute segregation of Nb and primary phase NbAl3. The average tensile strength of joints with 0.43%, 0.74%, and 0.83% Nb mass fractions to 336, 334.5, and 341 MPa, respectively.