The influence of Ti and Zr,Nb alloying on the microstructures and performance of laser-welded molybdenum socket joints was investigated.Following Nb alloying,the average microhardness of the fusion zone(FZ)increased f...The influence of Ti and Zr,Nb alloying on the microstructures and performance of laser-welded molybdenum socket joints was investigated.Following Nb alloying,the average microhardness of the fusion zone(FZ)increased from HV 194.7 to HV 283.3.Additionally,Nb can react with O to form dispersed Nb_(2)O_(5) along grain boundaries,impeding grain boundary migration and dislocation movement while reducing the content of volatile Mo oxide along these boundaries.The incorporation of Nb in FZ partially inhibits pore defects and enhances joint load-bearing capacity.In comparison to the laser-welded joints without adding Nb(LW),the tensile strength of the laser-welded joints with Nb alloying(LW-Nb)was significantly improved by approximately 69%from 327.5 to 551.7 MPa.Furthermore,the fracture mechanism of the joints transitioned from intergranular fracture to transgranular fracture.展开更多
To address the limitations of traditional finite element methods,particularly the continuum assumption and difficulties in tracking the solid-liquid interface,this study introduces a lattice Boltzmann-based mathematic...To address the limitations of traditional finite element methods,particularly the continuum assumption and difficulties in tracking the solid-liquid interface,this study introduces a lattice Boltzmann-based mathematical and physical model to simulate flow and heat transfer in the laser welding molten pool of tin-coated copper used in solar panel busbars(a thin strip or wire of conductive metal embedded on the surface of a solar cell to collect and conduct the electricity generated by the photovoltaic cell).The model incorporates key external forces,including surface tension,solid-liquid interface tension,and recoil pressure.A moving and rotating Gaussian-body heat source is adopted,with temperature treated as an implicit function of enthalpy.Coupled iterative schemes for the temperature and velocity fields are constructed using a dual-distribution function approach with a D3Q15 lattice structure.The model is implemented in Python,utilizing libraries such as NumPy,SciPy,Mayavi,and Matplotlib for computation and visualization.Simulation results reveal that the heat transfer mechanism in the molten pool transitions from pure conduction to conduction-convection due to surface tension effects,leading to the formation of multiple counter-rotating vortex structures.The peak temperature at the pool center reaches 3200 K,with maximum melt depth and width measured at 0.5 and 1.2 mm,respectively.Over time,both penetration depth and melt width increase,though the width exhibits a more pronounced growth.Comparison with experimental thermal cycling data from laser weld joints shows strong agreement,with a maximum error of less than 1%,validating the accuracy of the proposed method.展开更多
The packaging quality of coaxial laser diodes(CLDs)plays a pivotal role in determining their optical performance and long-term reliability.As the core packaging process,high-precision laser welding requires precise co...The packaging quality of coaxial laser diodes(CLDs)plays a pivotal role in determining their optical performance and long-term reliability.As the core packaging process,high-precision laser welding requires precise control of process parameters to suppress optical power loss.However,the complex nonlinear relationship between welding parameters and optical power loss renders traditional trial-and-error methods inefficient and imprecise.To address this challenge,a physics-informed(PI)and data-driven collaboration approach for welding parameter optimization is proposed.First,thermal-fluid-solid coupling finite element method(FEM)was employed to quantify the sensitivity of welding parameters to physical characteristics,including residual stress.This analysis facilitated the identification of critical factors contributing to optical power loss.Subsequently,a Gaussian process regression(GPR)model incorporating finite element simulation prior knowledge was constructed based on the selected features.By introducing physics-informed kernel(PIK)functions,stress distribution patterns were embedded into the prediction model,achieving high-precision optical power loss prediction.Finally,a Bayesian optimization(BO)algorithm with an adaptive sampling strategy was implemented for efficient parameter space exploration.Experimental results demonstrate that the proposedmethod effectively establishes explicit physical correlations between welding parameters and optical power loss.The optimized welding parameters reduced optical power loss by 34.1%,providing theoretical guidance and technical support for reliable CLD packaging.展开更多
Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pu...Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pulsed laser welding parameters on the microstructure,crystallization degree,and mechanical properties of Zr57Nb5Cu15.4Ni12.6Al10 BMG is investigated.Non-crystallized welding forming of a zirconium-based amorphous alloy is achieved by optimizing the process parameters of pulsed laser welding.The crystallization degree of Zr-based BMG is mainly determined by the welding speed and power.The welding depth and crystallization area fraction increase with an increase in the effective peak power density.The optimized welding process can effectively reduce the heat accumulation of the weld,thus avoiding crystallization.The flexural strength of the weld can be maintained at 96.5%of the matrix.展开更多
In this study,a novel multi-physics multi-scale model with the dilute multicomponent phase-field method in three-dimensional(3D)space was developed to investigate the complex microstructure evolu-tion in the molten po...In this study,a novel multi-physics multi-scale model with the dilute multicomponent phase-field method in three-dimensional(3D)space was developed to investigate the complex microstructure evolu-tion in the molten pool during laser welding of Al-Li alloy.To accurately compute mass data within both two and three-dimensional computational domains,three efficient computing methods,including central processing unit parallel computing,adaptive mesh refinement,and moving-frame algorithm,were uti-lized.Emphasis was placed on the distinctive equiaxed-to-columnar-to-equiaxed transition phenomenon that occurs during the entire solidification process of Al-Li alloy laser welding.Simulation results indi-cated that the growth distance of columnar grains that epitaxially grew from the base metal(BM)de-creased as the nucleation rate increased.As the nucleation rate increased,the morphology of the newly formed grains near the fusion boundary(FB)changed from columnar to equiaxed,and newly formed equiaxed grains changed from having high-order dendrites to no obvious dendrite structure.When the nucleation rate was sufficiently high,non-dendritic equiaxed grains could directly form near the FB,and there was nearly no epitaxial growth from the BM.Additionally,simulation results illustrated the com-petition among multiple grains with varying orientations that grow in 3D space near the FB.Finally,how equiaxed grain bands develop was elucidated.The equiaxed band not only hindered the growth of early columnar grains but also some of its grains could grow epitaxially to form new columnar grains.These predicted results were in good agreement with experimental measurements and observations.展开更多
In order to overcome the problems of many pores,large deformation and unstable weld quality of traditional laser welded aluminumcopper alloy joints,a red-blue dual-beam laser source and a swinging laser were introduce...In order to overcome the problems of many pores,large deformation and unstable weld quality of traditional laser welded aluminumcopper alloy joints,a red-blue dual-beam laser source and a swinging laser were introduced for welding.T2 copper and 6063 aluminum thin plates were lap welded by coaxial dual-beam laser welding.The morphology of weld cross section was compared to explore the influence of process parameters on the formation of lap joints.The microstructure characteristics of the weld zone were observed and compared by optical microscope.The results show that the addition of laser beam swing can eliminate the internal pores of the weld.With the increase of the swing width,the weld depth decreases,and the weld width increases first and then decreases.The influence of welding speed on the weld cross section morphology is similar to that of swing width.With the increase of welding speed,the weld width increases first and then decreases,while the weld depth decreases all the time.This is because that the red laser is used as the main heat source to melt the base metals,with the increase of red laser power,the weld depth increases.As an auxiliary laser source,blue laser reduces the total energy consumption,consequently,the effective heat input increases and the spatter is restrained effectively.As a result,the increase of red laser power has an enhancement effect on the weld width and weld depth.When the swing width is 1.2 mm,the red laser power is 550 W,the blue laser power is 500 W,and the welding speed is 35 mm/s,the weld forming is the best.The lap joint of T2 copper and 6063 aluminum alloy thin plate can be connected stably with the hybrid of blue laser.The effect rules of laser beam swing on the weld formation were obtained,which improved the quality of the joints.展开更多
Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded aust...Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded austenitic stainless steel parts is limited owing to the micro bulging distortion that occurs on the back surface of the partial penetration side.In this paper,non-penetration lap laser welding experiments,were conducted on galvanized and SUS304 austenitic stainless steel plates using a fiber laser,to investigate the mechanism of bulging distortion.A comparative experiment of DC01 galvanized steel-Q235 carbon steel lap laser welding was carried out,and the deflection and distortion profile of partially penetrated side of the sheets were measured using a noncontact laser interferometer.In addition,the cold-rolled SUS304 was subjected to heat holding at different temperatures and water quenching after bending to characterize its microstructure under tensile and compressive stress.The results show that,during the heating stage of the thermal cycle of laser lap welding,the partial penetration side of the SUS304 steel sheet generates compressive stress,which extrudes the material in the heat-affected zone to the outside of the back of the SUS304 steel sheet,thereby forming a bulge.The findings of these experiments can be of great value for controlling the distortion of the partial penetrated side of austenitic stainless steel sheet during laser non-penetration lap welding.展开更多
In the welding process of SiCp/Al composites,Al reacts with SiC particles in the molten pool to form Al_(4)C_(3),a brittle phase,damaging the reinforcement and causing a sharp decline in the mechanical properties of w...In the welding process of SiCp/Al composites,Al reacts with SiC particles in the molten pool to form Al_(4)C_(3),a brittle phase,damaging the reinforcement and causing a sharp decline in the mechanical properties of weld joints.To mitigate this,a method of welding SiCp/Al composites by pulsed laser welding with powder-filling is proposed,inhibiting the interface reaction between Al and SiC particles in the molten pool.This study investigates the effect of pulse frequency on the temperature field of the molten pool,and combines thermal-fluid numerical simulation to analyze the peak temperature at different pulse frequencies,optimizing the Si content to ultimately inhibit the interface reaction in the molten pool.Results indicate that an appropriate pulse frequency achieves good welding formation and effectively regulates the peak temperature of the molten pool.Only a small amount of brittle phase is present in the weld joint,creating favorable conditions for the addition of alloying elements.The interface reaction is slowed down by adjusting the pulse frequency,though it is not completely inhibited.When the addition of Si content reaches 8%,the occurrence of the interface reaction is effectively inhibited.In weld joints with the addition of 8wt%Si powder,no Al_(4)C_(3)brittle phase is present,and the tensile strength of the weld joint is 266 MPa,up to 70%of the base material.展开更多
In order to obtain good welding quality, it is necessary to apply quality control because there are many influencing factors in laser welding process. The key to realize welding quality control is to obtain the qualit...In order to obtain good welding quality, it is necessary to apply quality control because there are many influencing factors in laser welding process. The key to realize welding quality control is to obtain the quality information. Abundant weld quality information is contained in weld pool and keyhole. Aiming at Nd：YAG laser welding of stainless steel, a coaxial visual sensing system was constructed. The images of weld pool and keyhole were obtained. Based on the gray character of weld pool and keyhole in images, an image processing algorithm was designed. The search start point and search criteria of weld pool and keyhole edge were determined respectively.展开更多
Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Ch...Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Characteristic parameters such as the area and number of spatters, the average grayscale of a spatter image, the entropy of a spatter grayscale image, the coordinate ratio of the plume centroid and the welding point, the polar coordinates of the plume centroid were defined and extracted. Karhunen-Loeve transform method was used to change the seven characteristics into three primary characteristics to reduce the dimensions. Also, K-nearest neighbor method was used to classify the plume and spatter images into two categories such as good and poor welding quality. The results show that plume and spatter have a close relationship with the welding stability, and two categories could be recognized effectively using K-nearest neighbor method based on Karhunen-Loeve transform.展开更多
A mathematical energy coupling model was developed to analyze the light transmission in the keyhole and energy distribution on the keyhole wall.The main characteristics of the model include：1） a prototype of the key...A mathematical energy coupling model was developed to analyze the light transmission in the keyhole and energy distribution on the keyhole wall.The main characteristics of the model include：1） a prototype of the keyhole and the inverse Bremsstrahlung absorption coefficient in the keyhole plasma are obtained from the experiments;2） instead of using a parallel incident beam,a focused laser beam with real Gaussian intensity distribution is implemented;3） both Fresnel absorption and inverse Bremsstrahlung absorption during multiple reflections are considered.The calculation results show that the distribution of absorbed laser intensity by the keyhole wall is not uniform.The maximum laser energy is absorbed by the bottom of the keyhole,although no rays irradiate directly onto the bottom.According to analysis of beam focusing characteristics,the location of the focal plane plays a more important role in the laser energy absorption by the front wall than by the rear wall.展开更多
In order to decrease the metallurgical porosity and keyhole-induced porosity during deep penetration laser welding of Al and its alloys, and increase the mechanical properties of work-piece, the effects of welding par...In order to decrease the metallurgical porosity and keyhole-induced porosity during deep penetration laser welding of Al and its alloys, and increase the mechanical properties of work-piece, the effects of welding parameters such as laser power, welding speed and defocusing value on both kinds of porosities were systemically analyzed respectively, and the shape and fluctuation of plume of the keyhole were observed to reflect the stability of the keyhole. The results show that increasing laser power or decreasing laser spot size can lead to the rising of both number and occupied area of pores in the weld; meanwhile, the plume fluctuates violently over the keyhole, which is always companied with the intense metallic vapor, liquid metal spatter and collapsing in the keyhole, thus more pores are generated in the weld. The porosity in the weld reaches the minimum at welding velocity of 2.0 m/min when laser power is 5 kW and defocusing value is 0.展开更多
The correlation between Si content （0.1%-0.5%, mass fraction） and pulse laser welding performance of AI-Mn-Mg aluminum alloy sheets was studied. The sheets were fabricated in the laboratory, with gauge of 0.45 mm, H...The correlation between Si content （0.1%-0.5%, mass fraction） and pulse laser welding performance of AI-Mn-Mg aluminum alloy sheets was studied. The sheets were fabricated in the laboratory, with gauge of 0.45 mm, H16 temper by pulse laser welding. It was found that no cracking existed in the welding pool as Si content was below 0.34%. However, when the Si content increased to 0.47%, cracking formed in the welding pool. Microstructure observations indicated that residual eutectic phases distributed at the grain boundaries were discontinuous and appeared to be small particles in lower Si content alloys; the residual eutectic phases distributed at the grain boundaries were partially continuous and appeared to be films in higher Si content alloys. These phenomena could explain why Si content adversely affected the laser welding performance.展开更多
In order to increase the absorption of laser energy and improve the weld appearance in laser welding of Al alloy, 1.8 mm- 6013 Al alloy plate was welded by activating flux CO2 laser welding. Activating flux includes o...In order to increase the absorption of laser energy and improve the weld appearance in laser welding of Al alloy, 1.8 mm- 6013 Al alloy plate was welded by activating flux CO2 laser welding. Activating flux includes oxide and fluoride, which was coated on the workpiece surface before welding. The experimental results show that the activating flux can effectively improve the absorption of CO2 laser energy and increase the amount of the molten base metal. The improvement on the absorption of laser energy by oxide activating flux is greater than that by fluoride activating flux or two-component activating flux, but the slag detachability made from both the single activating flux and two-activating flux is poor. The gas pore sensitivity with oxide activating flux is much higher than that with fluoride activating flux in CO2 laser welding of 6013 Al alloy.展开更多
3 mm thick 400 MPa grade ultrafine grained ferritic steel plates were bead-on-plate welded by CO2 laser with heat input of 120-480 J/mm. The microstructures of the weld metal mainly consist of bainite, which form is l...3 mm thick 400 MPa grade ultrafine grained ferritic steel plates were bead-on-plate welded by CO2 laser with heat input of 120-480 J/mm. The microstructures of the weld metal mainly consist of bainite, which form is lower bainite plates or polygonal ferrite containing quantities of dispersed cementite particles, mixed with a few of low carbon martensite laths or ferrite, depending on the heat input. The hardness and the tensile strength of the weld metal are higher than those of the base metal, and monotonously increase as the heat input decreases. No softened zone exists in heat affected zone (HAZ). Compared with the base metal, although the grains of laser weld are much larger, the toughness of the weld metal is higher within a large range of heat input. Furthermore, as the heat input increases, the toughness of the weld metal rises to a maximum value, at which point the percentage of lower bainite is the highest, and then drops.展开更多
With the rapid developments of marine resource exploitation,mounts of marine engineering equipment are settled on the ocean.When it is not possible to move the damaged equipment into a dry dock,welding operations must...With the rapid developments of marine resource exploitation,mounts of marine engineering equipment are settled on the ocean.When it is not possible to move the damaged equipment into a dry dock,welding operations must be performed in underwater environments.The underwater laser welding/cladding technique is a promising and advanced technique which could be widely applied to the maintenance of the damaged equipment.The present review paper aims to present a critical analysis and engineering overview of the underwater laser welding/cladding technique.First,we elaborated recent advances and key issues of drainage nozzles all over the world.Next,we presented the underwater laser processing and microstructural-mechanical behavior of repaired marine materials.Then,the newly developed powder-feeding based and wire-feeding based underwater laser direct metal deposition techniques were reviewed.The differences between the convection,conduction,and the metallurgical kinetics in the melt pools during underwater laser direct metal deposition and in-air laser direct metal deposition were illustrated.After that,several challenges that need to be overcame to achieve the full potential of the underwater laser welding/cladding technique are proposed.Finally,suggestions for future directions to aid the development of underwater laser welding/cladding technology and underwater metallurgical theory are provided.The present review will not only enrich the knowledge in the underwater repair technology,but also provide important guidance for the potential applications of the technology on the marine engineering.展开更多
A 4 kW fiber laser was chosen to weld the new hot-rolled nano-scale precipitation-strengthened steel with a thickness of 4.5 mm. The effect of laser power, defocusing distance, and welding speed on the welded joint ap...A 4 kW fiber laser was chosen to weld the new hot-rolled nano-scale precipitation-strengthened steel with a thickness of 4.5 mm. The effect of laser power, defocusing distance, and welding speed on the welded joint appearance was examined, and the microstructure and mechanical properties on the typical butt joints were investigated. Results showed that increasing laser welding power may cause faster downward flow of molten metal to produce greater root humping. With the welding speed increasing, the average welding seam （WS） width decreased, and the average WS and heat-affected zone （HAZ） hardness increased. The microstructures of WS, fusion line, and coarse grain heat-affected zone were lath martensite, but the growth direction of the original austenite grain boundaries was significantly different. The microstructures of fine grain heat-affected zone were ferrite and martensite, and the microstructure of mixed grain heat- affected zone contained ferrite, massive M/A island, and a small amount of martensite. The micro-hardness values of WS, HAZ, and base metal （BM） were 358, 302, and 265 HV, respectively. The butt joint fracture at the BM far from the WS and the welded joint tensile strength are observed to follow proportional relationship with hardness.展开更多
Understanding the behaviors of heat transfer and fluid flow in weld pool and their effects on the solidification microstructure are significant for performance improvement of laser welds.This paper develops a three-di...Understanding the behaviors of heat transfer and fluid flow in weld pool and their effects on the solidification microstructure are significant for performance improvement of laser welds.This paper develops a three-dimensional numerical model to understand the multi-physical processes such as heat transfer,melt convection and solidification behavior in full-penetration laser welding of thin 5083 aluminum sheet.Solidification parameters including temperature gradient G and solidification rate R,and their combined forms are evaluated to interpret solidification microstructure.The predicted weld dimensions and the microstructure morphology and scale agree well with experiments.Results indicate that heat conduction is the dominant mechanism of heat transfer in weld pool,and melt convection plays a critical role in microstructure scale.The mushy zone shape/size and solidification parameters can be modulated by changing process parameters.Dendritic structures form because of the low G/R value.The scale of dendritic structures can be reduced by increasing GR via decreasing heat input.The columnar to equiaxed transition is predicted quantitatively via the process related G^3/R.These findings illustrate how heat transfer and fluid flow affect the solidification parameters and hence the microstructure,and show how to improve microstructure by optimizing the process.展开更多
Laser welding with filler wire of AZ31 magnesium alloys is investigated using a CO2 laser experimental system. The effect of three different filler wires on the joint properties is researched. The results show that th...Laser welding with filler wire of AZ31 magnesium alloys is investigated using a CO2 laser experimental system. The effect of three different filler wires on the joint properties is researched. The results show that the weld appearance can be effectively improved when using laser welding with filler wire. The microhardness and tensile strength of joints are almost the same us those of the base metal when ER AZ31 or ER AZ61 wire is adopted. However, when the filler wire of ER 5356 aluminum alloy is used, the mechanical properties of flints become worse. For ER AZ31 and ER AZ61 filler wires, the microstructure of weld zone slws small dendrite grains. In comparison, for ER 5356 filler wire, the weld shows a structure of snowy dendrites and many intermetallic compounds and eutectic phases distribute in the dendrites. These intermetallic constituents with low melting point increase the tendency of hot crack and result in fiagile joint properties. Therefore, ER AZ31 and ER AZ61 wire are more suitable filler material than ER 5356 for CO2 laser welding of AZ31 magnesium alloys.展开更多
High-speed photography was used to obtain the dynamic changes in the surface plasma during a high-power disk laser welding process. A color space clustering algorithm to extract the edge information of the surface pla...High-speed photography was used to obtain the dynamic changes in the surface plasma during a high-power disk laser welding process. A color space clustering algorithm to extract the edge information of the surface plasma region was developed in order to improve the accuracy of image processing. With a comparative analysis of the plasma features, i.e., area and height, and the characteristics of the welded seam, the relationship between the surface plasma and the stability of the laser welding process was characterized, which provides a basic understanding for the real-time monitoring of laser welding.展开更多
基金National Key Research and Development Project of China (No. 2022YFB3707602)National Natural Science Foundation of China (Nos. 52005393, 51775416)。
文摘The influence of Ti and Zr,Nb alloying on the microstructures and performance of laser-welded molybdenum socket joints was investigated.Following Nb alloying,the average microhardness of the fusion zone(FZ)increased from HV 194.7 to HV 283.3.Additionally,Nb can react with O to form dispersed Nb_(2)O_(5) along grain boundaries,impeding grain boundary migration and dislocation movement while reducing the content of volatile Mo oxide along these boundaries.The incorporation of Nb in FZ partially inhibits pore defects and enhances joint load-bearing capacity.In comparison to the laser-welded joints without adding Nb(LW),the tensile strength of the laser-welded joints with Nb alloying(LW-Nb)was significantly improved by approximately 69%from 327.5 to 551.7 MPa.Furthermore,the fracture mechanism of the joints transitioned from intergranular fracture to transgranular fracture.
基金Science and Technology Research Key Competitive Project of Quzhou Science and Technology Bureau(Nos.2023K266,2024K010)General Project for Cultivating Outstanding Young Teachers in Anhui Province’s Universities(2025).
文摘To address the limitations of traditional finite element methods,particularly the continuum assumption and difficulties in tracking the solid-liquid interface,this study introduces a lattice Boltzmann-based mathematical and physical model to simulate flow and heat transfer in the laser welding molten pool of tin-coated copper used in solar panel busbars(a thin strip or wire of conductive metal embedded on the surface of a solar cell to collect and conduct the electricity generated by the photovoltaic cell).The model incorporates key external forces,including surface tension,solid-liquid interface tension,and recoil pressure.A moving and rotating Gaussian-body heat source is adopted,with temperature treated as an implicit function of enthalpy.Coupled iterative schemes for the temperature and velocity fields are constructed using a dual-distribution function approach with a D3Q15 lattice structure.The model is implemented in Python,utilizing libraries such as NumPy,SciPy,Mayavi,and Matplotlib for computation and visualization.Simulation results reveal that the heat transfer mechanism in the molten pool transitions from pure conduction to conduction-convection due to surface tension effects,leading to the formation of multiple counter-rotating vortex structures.The peak temperature at the pool center reaches 3200 K,with maximum melt depth and width measured at 0.5 and 1.2 mm,respectively.Over time,both penetration depth and melt width increase,though the width exhibits a more pronounced growth.Comparison with experimental thermal cycling data from laser weld joints shows strong agreement,with a maximum error of less than 1%,validating the accuracy of the proposed method.
基金funded by the National Key R&D Program of China,Grant No.2024YFF0504904.
文摘The packaging quality of coaxial laser diodes(CLDs)plays a pivotal role in determining their optical performance and long-term reliability.As the core packaging process,high-precision laser welding requires precise control of process parameters to suppress optical power loss.However,the complex nonlinear relationship between welding parameters and optical power loss renders traditional trial-and-error methods inefficient and imprecise.To address this challenge,a physics-informed(PI)and data-driven collaboration approach for welding parameter optimization is proposed.First,thermal-fluid-solid coupling finite element method(FEM)was employed to quantify the sensitivity of welding parameters to physical characteristics,including residual stress.This analysis facilitated the identification of critical factors contributing to optical power loss.Subsequently,a Gaussian process regression(GPR)model incorporating finite element simulation prior knowledge was constructed based on the selected features.By introducing physics-informed kernel(PIK)functions,stress distribution patterns were embedded into the prediction model,achieving high-precision optical power loss prediction.Finally,a Bayesian optimization(BO)algorithm with an adaptive sampling strategy was implemented for efficient parameter space exploration.Experimental results demonstrate that the proposedmethod effectively establishes explicit physical correlations between welding parameters and optical power loss.The optimized welding parameters reduced optical power loss by 34.1%,providing theoretical guidance and technical support for reliable CLD packaging.
基金Supported by Guangdong Major Project of Basic and Applied Research,China(Grant No.2019B030302010)National Natural Science Foundation of China (Grant Nos.51735003,52205456)
文摘Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pulsed laser welding parameters on the microstructure,crystallization degree,and mechanical properties of Zr57Nb5Cu15.4Ni12.6Al10 BMG is investigated.Non-crystallized welding forming of a zirconium-based amorphous alloy is achieved by optimizing the process parameters of pulsed laser welding.The crystallization degree of Zr-based BMG is mainly determined by the welding speed and power.The welding depth and crystallization area fraction increase with an increase in the effective peak power density.The optimized welding process can effectively reduce the heat accumulation of the weld,thus avoiding crystallization.The flexural strength of the weld can be maintained at 96.5%of the matrix.
基金supported by the National Natural Science Foundation of China(Grant Nos.52075201,U22A20196,52188102)GuangDong Basic and Applied Basic Research Foundation(No.2023A1515010081).
文摘In this study,a novel multi-physics multi-scale model with the dilute multicomponent phase-field method in three-dimensional(3D)space was developed to investigate the complex microstructure evolu-tion in the molten pool during laser welding of Al-Li alloy.To accurately compute mass data within both two and three-dimensional computational domains,three efficient computing methods,including central processing unit parallel computing,adaptive mesh refinement,and moving-frame algorithm,were uti-lized.Emphasis was placed on the distinctive equiaxed-to-columnar-to-equiaxed transition phenomenon that occurs during the entire solidification process of Al-Li alloy laser welding.Simulation results indi-cated that the growth distance of columnar grains that epitaxially grew from the base metal(BM)de-creased as the nucleation rate increased.As the nucleation rate increased,the morphology of the newly formed grains near the fusion boundary(FB)changed from columnar to equiaxed,and newly formed equiaxed grains changed from having high-order dendrites to no obvious dendrite structure.When the nucleation rate was sufficiently high,non-dendritic equiaxed grains could directly form near the FB,and there was nearly no epitaxial growth from the BM.Additionally,simulation results illustrated the com-petition among multiple grains with varying orientations that grow in 3D space near the FB.Finally,how equiaxed grain bands develop was elucidated.The equiaxed band not only hindered the growth of early columnar grains but also some of its grains could grow epitaxially to form new columnar grains.These predicted results were in good agreement with experimental measurements and observations.
基金supported by Guangdong Science and Technology Plan Project(Grant No.20170902,No.20180902)Yangjiang Science and Technology Plan Project(Grant No.SDZX2020063)+1 种基金Shenzhen Key Projects of Innovation and Entrepreneurship Plan Technology(JSGG20210420091802007)Yunfu 2023 Science and Technology Plan Project(S2023020201).
文摘In order to overcome the problems of many pores,large deformation and unstable weld quality of traditional laser welded aluminumcopper alloy joints,a red-blue dual-beam laser source and a swinging laser were introduced for welding.T2 copper and 6063 aluminum thin plates were lap welded by coaxial dual-beam laser welding.The morphology of weld cross section was compared to explore the influence of process parameters on the formation of lap joints.The microstructure characteristics of the weld zone were observed and compared by optical microscope.The results show that the addition of laser beam swing can eliminate the internal pores of the weld.With the increase of the swing width,the weld depth decreases,and the weld width increases first and then decreases.The influence of welding speed on the weld cross section morphology is similar to that of swing width.With the increase of welding speed,the weld width increases first and then decreases,while the weld depth decreases all the time.This is because that the red laser is used as the main heat source to melt the base metals,with the increase of red laser power,the weld depth increases.As an auxiliary laser source,blue laser reduces the total energy consumption,consequently,the effective heat input increases and the spatter is restrained effectively.As a result,the increase of red laser power has an enhancement effect on the weld width and weld depth.When the swing width is 1.2 mm,the red laser power is 550 W,the blue laser power is 500 W,and the welding speed is 35 mm/s,the weld forming is the best.The lap joint of T2 copper and 6063 aluminum alloy thin plate can be connected stably with the hybrid of blue laser.The effect rules of laser beam swing on the weld formation were obtained,which improved the quality of the joints.
文摘Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded austenitic stainless steel parts is limited owing to the micro bulging distortion that occurs on the back surface of the partial penetration side.In this paper,non-penetration lap laser welding experiments,were conducted on galvanized and SUS304 austenitic stainless steel plates using a fiber laser,to investigate the mechanism of bulging distortion.A comparative experiment of DC01 galvanized steel-Q235 carbon steel lap laser welding was carried out,and the deflection and distortion profile of partially penetrated side of the sheets were measured using a noncontact laser interferometer.In addition,the cold-rolled SUS304 was subjected to heat holding at different temperatures and water quenching after bending to characterize its microstructure under tensile and compressive stress.The results show that,during the heating stage of the thermal cycle of laser lap welding,the partial penetration side of the SUS304 steel sheet generates compressive stress,which extrudes the material in the heat-affected zone to the outside of the back of the SUS304 steel sheet,thereby forming a bulge.The findings of these experiments can be of great value for controlling the distortion of the partial penetrated side of austenitic stainless steel sheet during laser non-penetration lap welding.
基金Supported by Equipment Pre-Research Foundation of China(Grant No.50923030512)。
文摘In the welding process of SiCp/Al composites,Al reacts with SiC particles in the molten pool to form Al_(4)C_(3),a brittle phase,damaging the reinforcement and causing a sharp decline in the mechanical properties of weld joints.To mitigate this,a method of welding SiCp/Al composites by pulsed laser welding with powder-filling is proposed,inhibiting the interface reaction between Al and SiC particles in the molten pool.This study investigates the effect of pulse frequency on the temperature field of the molten pool,and combines thermal-fluid numerical simulation to analyze the peak temperature at different pulse frequencies,optimizing the Si content to ultimately inhibit the interface reaction in the molten pool.Results indicate that an appropriate pulse frequency achieves good welding formation and effectively regulates the peak temperature of the molten pool.Only a small amount of brittle phase is present in the weld joint,creating favorable conditions for the addition of alloying elements.The interface reaction is slowed down by adjusting the pulse frequency,though it is not completely inhibited.When the addition of Si content reaches 8%,the occurrence of the interface reaction is effectively inhibited.In weld joints with the addition of 8wt%Si powder,no Al_(4)C_(3)brittle phase is present,and the tensile strength of the weld joint is 266 MPa,up to 70%of the base material.
基金Project (10776020) supported by the Joint Foundation of the National Natural Science Foundation of China and China Academy of Engineering Physics
文摘In order to obtain good welding quality, it is necessary to apply quality control because there are many influencing factors in laser welding process. The key to realize welding quality control is to obtain the quality information. Abundant weld quality information is contained in weld pool and keyhole. Aiming at Nd：YAG laser welding of stainless steel, a coaxial visual sensing system was constructed. The images of weld pool and keyhole were obtained. Based on the gray character of weld pool and keyhole in images, an image processing algorithm was designed. The search start point and search criteria of weld pool and keyhole edge were determined respectively.
基金Project (51175095) supported by the National Natural Science Foundation of ChinaProjects (10251009001000001,9151009001000020) supported by the Natural Science Foundation of Guangdong Province,ChinaProject (20104420110001) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Characteristic parameters such as the area and number of spatters, the average grayscale of a spatter image, the entropy of a spatter grayscale image, the coordinate ratio of the plume centroid and the welding point, the polar coordinates of the plume centroid were defined and extracted. Karhunen-Loeve transform method was used to change the seven characteristics into three primary characteristics to reduce the dimensions. Also, K-nearest neighbor method was used to classify the plume and spatter images into two categories such as good and poor welding quality. The results show that plume and spatter have a close relationship with the welding stability, and two categories could be recognized effectively using K-nearest neighbor method based on Karhunen-Loeve transform.
基金Projects (51175162, 50805045) supported by the National Natural Science Foundation of ChinaProject supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education,China
文摘A mathematical energy coupling model was developed to analyze the light transmission in the keyhole and energy distribution on the keyhole wall.The main characteristics of the model include：1） a prototype of the keyhole and the inverse Bremsstrahlung absorption coefficient in the keyhole plasma are obtained from the experiments;2） instead of using a parallel incident beam,a focused laser beam with real Gaussian intensity distribution is implemented;3） both Fresnel absorption and inverse Bremsstrahlung absorption during multiple reflections are considered.The calculation results show that the distribution of absorbed laser intensity by the keyhole wall is not uniform.The maximum laser energy is absorbed by the bottom of the keyhole,although no rays irradiate directly onto the bottom.According to analysis of beam focusing characteristics,the location of the focal plane plays a more important role in the laser energy absorption by the front wall than by the rear wall.
基金Project(51204109)supported by the National Natural Science Foundation of China
文摘In order to decrease the metallurgical porosity and keyhole-induced porosity during deep penetration laser welding of Al and its alloys, and increase the mechanical properties of work-piece, the effects of welding parameters such as laser power, welding speed and defocusing value on both kinds of porosities were systemically analyzed respectively, and the shape and fluctuation of plume of the keyhole were observed to reflect the stability of the keyhole. The results show that increasing laser power or decreasing laser spot size can lead to the rising of both number and occupied area of pores in the weld; meanwhile, the plume fluctuates violently over the keyhole, which is always companied with the intense metallic vapor, liquid metal spatter and collapsing in the keyhole, thus more pores are generated in the weld. The porosity in the weld reaches the minimum at welding velocity of 2.0 m/min when laser power is 5 kW and defocusing value is 0.
基金Project(2011KJZD04)supported by the CHINALCO Science and Development Foundation,China
文摘The correlation between Si content （0.1%-0.5%, mass fraction） and pulse laser welding performance of AI-Mn-Mg aluminum alloy sheets was studied. The sheets were fabricated in the laboratory, with gauge of 0.45 mm, H16 temper by pulse laser welding. It was found that no cracking existed in the welding pool as Si content was below 0.34%. However, when the Si content increased to 0.47%, cracking formed in the welding pool. Microstructure observations indicated that residual eutectic phases distributed at the grain boundaries were discontinuous and appeared to be small particles in lower Si content alloys; the residual eutectic phases distributed at the grain boundaries were partially continuous and appeared to be films in higher Si content alloys. These phenomena could explain why Si content adversely affected the laser welding performance.
基金supported by State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, China
文摘In order to increase the absorption of laser energy and improve the weld appearance in laser welding of Al alloy, 1.8 mm- 6013 Al alloy plate was welded by activating flux CO2 laser welding. Activating flux includes oxide and fluoride, which was coated on the workpiece surface before welding. The experimental results show that the activating flux can effectively improve the absorption of CO2 laser energy and increase the amount of the molten base metal. The improvement on the absorption of laser energy by oxide activating flux is greater than that by fluoride activating flux or two-component activating flux, but the slag detachability made from both the single activating flux and two-activating flux is poor. The gas pore sensitivity with oxide activating flux is much higher than that with fluoride activating flux in CO2 laser welding of 6013 Al alloy.
基金This work was supported by the‘973'ScienceTechnology Development Plan of the National Basic Research Foundation(No.1998061500)the 985'Foundation of Tsinghua University.
文摘3 mm thick 400 MPa grade ultrafine grained ferritic steel plates were bead-on-plate welded by CO2 laser with heat input of 120-480 J/mm. The microstructures of the weld metal mainly consist of bainite, which form is lower bainite plates or polygonal ferrite containing quantities of dispersed cementite particles, mixed with a few of low carbon martensite laths or ferrite, depending on the heat input. The hardness and the tensile strength of the weld metal are higher than those of the base metal, and monotonously increase as the heat input decreases. No softened zone exists in heat affected zone (HAZ). Compared with the base metal, although the grains of laser weld are much larger, the toughness of the weld metal is higher within a large range of heat input. Furthermore, as the heat input increases, the toughness of the weld metal rises to a maximum value, at which point the percentage of lower bainite is the highest, and then drops.
基金Supported by National Basic Scientific Research Project(Grant No.JCKY2017110B001)Jiangsu Provincial Postgraduate Research&Practice Innovation Program of China(Grant No.KYCX20_0080)。
文摘With the rapid developments of marine resource exploitation,mounts of marine engineering equipment are settled on the ocean.When it is not possible to move the damaged equipment into a dry dock,welding operations must be performed in underwater environments.The underwater laser welding/cladding technique is a promising and advanced technique which could be widely applied to the maintenance of the damaged equipment.The present review paper aims to present a critical analysis and engineering overview of the underwater laser welding/cladding technique.First,we elaborated recent advances and key issues of drainage nozzles all over the world.Next,we presented the underwater laser processing and microstructural-mechanical behavior of repaired marine materials.Then,the newly developed powder-feeding based and wire-feeding based underwater laser direct metal deposition techniques were reviewed.The differences between the convection,conduction,and the metallurgical kinetics in the melt pools during underwater laser direct metal deposition and in-air laser direct metal deposition were illustrated.After that,several challenges that need to be overcame to achieve the full potential of the underwater laser welding/cladding technique are proposed.Finally,suggestions for future directions to aid the development of underwater laser welding/cladding technology and underwater metallurgical theory are provided.The present review will not only enrich the knowledge in the underwater repair technology,but also provide important guidance for the potential applications of the technology on the marine engineering.
基金supported by the National Natural Science Foundation of China (Nos.51305285 and 51104110)the Basic Research Program of Jiangsu Province (Nos. BK20130315 and BK20130304)
文摘A 4 kW fiber laser was chosen to weld the new hot-rolled nano-scale precipitation-strengthened steel with a thickness of 4.5 mm. The effect of laser power, defocusing distance, and welding speed on the welded joint appearance was examined, and the microstructure and mechanical properties on the typical butt joints were investigated. Results showed that increasing laser welding power may cause faster downward flow of molten metal to produce greater root humping. With the welding speed increasing, the average welding seam （WS） width decreased, and the average WS and heat-affected zone （HAZ） hardness increased. The microstructures of WS, fusion line, and coarse grain heat-affected zone were lath martensite, but the growth direction of the original austenite grain boundaries was significantly different. The microstructures of fine grain heat-affected zone were ferrite and martensite, and the microstructure of mixed grain heat- affected zone contained ferrite, massive M/A island, and a small amount of martensite. The micro-hardness values of WS, HAZ, and base metal （BM） were 358, 302, and 265 HV, respectively. The butt joint fracture at the BM far from the WS and the welded joint tensile strength are observed to follow proportional relationship with hardness.
基金the National Natural Science Foundation of China under Grant No.5181101756,51861165202 and No.51721092the Major Project of Science and Technology Innovation Special for Hubei Province under Grant No.2018AAA027+3 种基金the Fundamental Research Funds for the Central Universities,HUST:No.2018JYCXJJ034 and No.2019JYCXJJ025the Postdoctoral Science Foundation of China under Grant No.2018M632837the opening project of State Key Laboratory of Digital Manufacturing Equipment and Technology(HUST)under grant No.DMETKF2018001supported by the China Scholarship Council as a visiting scholar at the University of Virginia。
文摘Understanding the behaviors of heat transfer and fluid flow in weld pool and their effects on the solidification microstructure are significant for performance improvement of laser welds.This paper develops a three-dimensional numerical model to understand the multi-physical processes such as heat transfer,melt convection and solidification behavior in full-penetration laser welding of thin 5083 aluminum sheet.Solidification parameters including temperature gradient G and solidification rate R,and their combined forms are evaluated to interpret solidification microstructure.The predicted weld dimensions and the microstructure morphology and scale agree well with experiments.Results indicate that heat conduction is the dominant mechanism of heat transfer in weld pool,and melt convection plays a critical role in microstructure scale.The mushy zone shape/size and solidification parameters can be modulated by changing process parameters.Dendritic structures form because of the low G/R value.The scale of dendritic structures can be reduced by increasing GR via decreasing heat input.The columnar to equiaxed transition is predicted quantitatively via the process related G^3/R.These findings illustrate how heat transfer and fluid flow affect the solidification parameters and hence the microstructure,and show how to improve microstructure by optimizing the process.
文摘Laser welding with filler wire of AZ31 magnesium alloys is investigated using a CO2 laser experimental system. The effect of three different filler wires on the joint properties is researched. The results show that the weld appearance can be effectively improved when using laser welding with filler wire. The microhardness and tensile strength of joints are almost the same us those of the base metal when ER AZ31 or ER AZ61 wire is adopted. However, when the filler wire of ER 5356 aluminum alloy is used, the mechanical properties of flints become worse. For ER AZ31 and ER AZ61 filler wires, the microstructure of weld zone slws small dendrite grains. In comparison, for ER 5356 filler wire, the weld shows a structure of snowy dendrites and many intermetallic compounds and eutectic phases distribute in the dendrites. These intermetallic constituents with low melting point increase the tendency of hot crack and result in fiagile joint properties. Therefore, ER AZ31 and ER AZ61 wire are more suitable filler material than ER 5356 for CO2 laser welding of AZ31 magnesium alloys.
基金supported in part by National Natural Science Foundation of China (No.51175095)the Guangdong Provincial Natural Science Foundation of China (10251009001000001, 9151009001000020, 07001764)the Specialized Research Fund for the Doctoral Program of Higher Education of China (20104420110001)
文摘High-speed photography was used to obtain the dynamic changes in the surface plasma during a high-power disk laser welding process. A color space clustering algorithm to extract the edge information of the surface plasma region was developed in order to improve the accuracy of image processing. With a comparative analysis of the plasma features, i.e., area and height, and the characteristics of the welded seam, the relationship between the surface plasma and the stability of the laser welding process was characterized, which provides a basic understanding for the real-time monitoring of laser welding.
