Hybrid Welding Of Aluminum Alloy Research Articles

Gap tolerance and molten pool destabilization mechanism in oscillating laser-arc hybrid welding of aluminum alloys

Oscillating laser-arc hybrid welding (O-LAHW) offers significant advantages in enhancing efficiency and mechanical properties. However, in actual production, gap fluctuations can cause instability, limiting its application in large-scale structure manufacturing. In this study, we explored the impact of gap fluctuation on the destabilization of the molten pool in aluminum alloy O-LAHW and identified the maximum gap tolerance for various conditions. High-speed photography revealed that the oscillating molten pool undergoes a transitional state of periodic collapse before complete instability, a behavior distinct from that of a non-oscillating molten pool. We also analyzed the variations in weld geometry prior to destabilization and developed a global force model of the molten pool to identify key geometrical parameters and related driving forces contributing to destabilization. The results show that maintaining a surface tension ratio of over 55% at the root of the molten pool is crucial for its stability. Additionally, the effects of oscillatory behavior and gap variations on the laser-substrate interaction were explored, revealing the physical mechanisms behind the changes in key geometrical parameters of the melt pool cross-section. The centrifugal effect generated by high-frequency oscillation is identified as a crucial mechanism for extending the duration of periodic collapse compared to non-oscillating molten pools. By discussing the interactions between energy absorption, molten pool shape, and molten pool forces, the study reveals the evolution process of weld destabilization and explains the differences in gap tolerance between oscillating and non-oscillating laser-arc hybrid welding, providing a reference for improving weld stability.

Numerical and experimental study on spatter in oscillating laser-arc hybrid welding of aluminum alloy

Spatter serves as a crucial metric for assessing welding stability, with excessive spatter posing significant risks to weld quality, performance, and equipment integrity while also impacting the environment adversely. In oscillating laser-arc hybrid welding (O-LAHW), the spatter exhibits a distinct pattern: an initial sharp decline followed by a gradual increase as oscillation speed rises. Existing research struggles to fully explain this trend due to challenges in developing a precise numerical spatter model. This paper introduces a novel heat flow labeling model and establishes an O-LAHW spatter validation model with 90 % accuracy based on it. Combined with hydrodynamics, this model explores the mechanisms behind spatter formation and suppression based on laser beam oscillation. Firstly, high-speed photography and numerical analysis reveal a third type of spattering in O-LAHW, distinct from spatter caused by keyhole collapse and droplet impact—spatter occurs when liquid metal is expelled from the melt pool due to laser beam oscillation. Secondly, hydrodynamic insights show that laser beam oscillation significantly reduces steam-induced driving force and metal vapor resistance to droplets. Consequently, as oscillation speed increases, the prevalence of the first two spatter types diminishes while the third type becomes dominant. Large-particle spatters decrease while small-particle spatters increase. Finally, by analyzing spatter statistics across various oscillating parameters, we observe a competitive mechanism among the three types of spatters. In non-oscillating welding, Type I spatter predominates; under low-frequency oscillation, Type II gains dominance; in high-frequency oscillation, Type III takes over. Optimal spatter reduction occurs at low-frequency oscillation, achieving a 27.1 % decrease compared to non-oscillating conditions.

Porosity suppression mechanism analysis in narrow-gap oscillating laser-MIG hybrid welding of aluminum alloys based on keyhole stability and molten pool flow behavior

In this study, the keyhole dynamic behavior and molten pool flow were investigated to elucidate the effects of oscillating laser on porosity in narrow-gap oscillating laser-MIG hybrid welding of aluminum alloys. A weld with a porosity of 0.08% was produced at the laser oscillating frequency of 600 Hz and diameter of 1 mm, while 2.27% without oscillating laser. Compared to non-oscillating laser, keyhole opening size increased by about 2.3 times and keyhole depth fluctuation was suppressed. The forces acted on the interface between keyhole wall and molten pool became more balanced. The increased vapor recoil pressure overcame the combined closure effect of gravity and molten pool pressure. While applying oscillating laser, the vortex in molten pool was eliminated and the liquid metal flow was more stable. The combined impact force caused by droplets transfer and liquid metal convection due to constraining effect of narrow gap was buffered, which had less effect on molten pool and keyhole stability. The liquid metal tended to flow from the molten pool inside to surface, which favored the escape of bubbles from the molten pool.

A6N01S-T5 physical characterization of laser-MIG hybrid welding of aluminum alloys

A 3 mm thick A6N01S-T5 aluminum alloy profile typical joint structure is used to carry out a laser-MIG hybrid welding test. The hybrid welding process parameters are optimized. The laser-MIG hybrid welding engineering adaptability is studied. The results show that the weld is well-formed and free of porosity defects under the optimum process parameters. The center of the weld is a dendritic cast organization. The region near the fusion line weld is a columnar crystal organization. The fusion zone is narrow, but there is a slight coarsening of the grain in the heat-affected zone. The hardness of the weld zone is lower than that of the parent material. The minimum hardness is located in the heat-affected zone near the fusion line. The average tensile strength of the joint under the best process parameters is 204.6 MPa, reaching 83.5% of the parent material. The fracture occurred near the fusion line, and the fracture shape showed typical plastic fracture characteristics. The bending performance of the joint was good. The optimal process parameters were universal when the pair gap was less than 1.0 mm, and the weld formation and tensile strength of the joint were good. When the pair gap increased to 1.5 mm, the optimized process parameters of the weld formation and tensile strength of the joint were still good. The results show that laser-MIG hybrid welding has good welding feasibility and engineering adaptability for typical joints in aluminum alloy bodies of high-speed trains.

Process stability in laser–MIG hybrid welding of aluminum alloys with various laser and arc distances

During laser–MIG hybrid welding process of aluminum alloys, the distance between laser and arc heat source (DLA) is one of the key factors which affect the welding process stability. Weld formation exhibited various penetration depths, since the interaction between laser and arc changed. Hybrid plasma morphology fluctuated significantly at DLA of 0 mm and hybrid plasma height decreased with the increase of DLA. Violent evaporation of droplet and spatters were generated at DLA of 0 mm. Moreover, keyhole fluctuated violently and significant downward flow of liquid metal was induced at the bottom zone of molten pool due to the impact action of droplet. Keyhole fluctuation was suppressed and molten pool stability was improved at DLA of 2 mm.

Effect of laser-arc synergy on melting energy in laser-CMT hybrid welding of aluminum alloy

The physical process of laser-arc synergy in laser-cold metal transfer (CMT) hybrid welding of aluminum alloys is extremely complex and difficult to observe, which limits our understanding of laser-arc synergy and the industrial application of laser-CMT hybrid welding. In this paper, the laser-arc synergistic effect is studied quantitatively by the change of melting energy. Therefore, the dimensionless parameter (ψ) is introduced to discuss the effect of heat source guidance, energy distribution and distance of laser and arc (DLA) on melting energy increment. The results show that the novel laser-arc simultaneous co directional hybrid welding (no-guided) process increases ψ by 4.3 times and 1.8 times compared to CMT-guided and laser-guided processes, respectively. The laser-arc synergy is strongest when the laser power is 80% of the total power and DLA is 2 mm. The quantitative analysis method in this paper can be extended to the study of other hybrid heat sources, and this research can facilitate the optimization of the welding process and a better understanding of the hybrid welding mechanism.

Numerical study on weld pool behaviors and keyhole dynamics in magnetic-field-assisted laser-arc hybrid welding of aluminum alloy

External magnetic field has been employed to improve appearance and suppress defects in the single laser or arc welding, and its physical mechanism in magnetic-field-assisted single laser or arc welding has been clearly clarified. However, few studies on the physical processes in magnetic-field-assisted laser-arc hybrid welding (MFA-LAHW) are conducted and its influencing mechanism is unclear. In this research, a comprehensive three-dimension numerical model is established to investigate the keyhole dynamics and weld pool behaviors in MFA-LAHW under the effect of different magnetic flux density. The results suggest that the interaction between a lower magnetic flux density (≤30 mT) and welding current is induced due to the existence of arc. Compared to the magnetic-field-assisted laser beam welding (MFA-LBW), this interaction induces a stronger Lorentz force up to the order of magnitude of 105 N/m3. The weld pool width is reduced while its length and height are increased because the Lorentz force facilitates the backward flow of thermal fluid, increasing the heat transfer from the keyhole and droplet to the rear weld pool edge. Moreover, the steady magnetic field improves the keyhole stability. The deform on keyhole rear wall brought by the droplet and vortex is suppressed, and keyhole size is widened under steady magnetic field, which reduced keyhole collapse. Furthermore, the comparative analysis with the case in MFA-LBW is carried out and the MFA-LAHW is verified to be more valuable for medium-thickness aluminum alloy. This work provides the underlying physics understanding of MFA-LAHW, which will broaden the application value of LAHW.

Keyhole-induced pore formation mechanism in laser-MIG hybrid welding of aluminum alloy based on experiment and multiphase numerical model

Keyhole-induced pore formation mechanism in laser-MIG hybrid welding of aluminum alloy based on experiment and multiphase numerical model

Droplet detachment and motion behaviors in laser-MIG hybrid welding of aluminum alloy

Current studies have shown that laser-arc interaction affects droplet transfer behaviors, but the mechanisms remain unclear. This study quantitatively analyzed the effects of laser power on droplet transfer frequency, detachment time, and motion behaviors in laser-metal inert gas (MIG) hybrid welding of aluminum alloy. It provided a comprehensive explanation for the variation of droplet transfer frequency by considering the full-cycle behaviors from droplet formation to fusion into the molten pool. The results revealed that the droplet growth and detachment in hybrid welding was accelerated by 22%, while the droplet flight motion was prolonged by 36% at maximum. The shortening of the growth-detachment process and the prolongation of the flight motion are the decisive factors for the increase and decrease of the droplet transfer frequency, respectively. Moreover, laser-arc interaction significantly changed the motion characteristics of droplet flight motion. Compared to arc welding, the initial velocity of droplet detaching from the wire tip increased by 8%, but the final velocity of droplet impacting the molten pool decreased by 10% at laser power of 6 kW. The mechanism was discussed based on droplet force analysis. These new findings will deepen the understanding of laser-arc interaction and improve the control capacity of the hybrid welding process.

Molten pool behavior and solidification characterization in steady magnetic field assisted laser-MIG hybrid welding of aluminum alloy

Microstructure evolution is highly correlated with the melt flow characterization in welding. In this study, a 3D heat flow model with consideration of magnetic field was constructed to describe the temperature field, the flow and keyhole behaviors in the molten pool during the laser-MIG hybrid welding. The role of magnetic flux density in the molten pool dynamics and microstructure evolution was explored. A moving hybrid heat source model including Gaussian surface heat source model and Gaussian rotary body heat source model as well as double ellipsoidal heat source model was carried out to elucidate the laser and MIG arc energy distribution. Decent agreement is realized between the measured weld geometry and predicted weld pool dimension. Numerical results indicate that an expanded molten pool is clearly observed under magnetic field. As the magnetic flux density increases, the downward flow velocity of the molten pool is enhanced. Moreover, visible difference of oscillation growth period for keyhole depth is produced and this leads to a variation in the time it takes for the molten pool to stabilize. Significant grain refinement appearing in both arc-affected zone at the weld upper part and laser-affected zone at the weld lower part is documented although the refinement degree varies at different zones. This is attributed to the formation of many initial nuclei or crystallites, originated from the enhanced flow of the molten pool with the assistance of magnetic field. This study provides a perspective in understanding the physical phenomena involved in magnetic field assisted laser-MIG hybrid welding and lays the foundation for weld microstructure optimization.

Effect of plasma welding current on heat source penetration ability of plasma-GMAW hybrid welding

The weld penetration under different plasma welding currents was compared in the plasma-gas metal arc welding (GMAW) hybrid welding of aluminum alloy. When the plasma welding current was lower than 150 A, the hybrid welding penetration was greater than the sum of the single plasma welding and the single GMAW penetration. When the plasma welding current reached 130 A, with the increase of the plasma welding current, the advantage of the weld penetration of the hybrid welding was gradually weakened, compared with that of the single welding. The above change mechanism is revealed from heat source energy distribution and molten pool stress. The results show that when the plasma welding current is lower than 110 A, the area of the high-temperature region in the arc zone of GMAW in the hybrid welding increases, compared with that in the single GMAW. The trend of arc energy transfer to the penetration direction increases under the action of arc pressure, arc shear force, electromagnetic force, and droplet impact. With the increase of plasma welding current, the high-temperature area of the GMAW arc first increases and then decreases. When the plasma current reaches 130 A, the effect of arc pressure, arc shear force, electromagnetic force, and droplet impact on increasing the penetration begins to weaken.

Effect of ultrasonic vibration on porosity suppression and columnar-to-equiaxed transition in laser-MIG hybrid welding of aluminum alloy

Severe porosity and coarse columnar grain are prone to be formed in the laser-MIG welded joint of aluminum alloy, deteriorating the strength and ductility seriously. In this study, the ultrasound was designed to assist the laser-MIG hybrid welding of aluminum alloy, and the influence of ultrasonic vibration on weld formation, porosity, and microstructure was investigated. The weld depth was increased from 3.6 to 4.2 mm when external ultrasound with the pressure of amplitude transformer (PAT) of 132 N was used, indicating that the penetration ability of hybrid heat sources to the welded plate could be improved. It was attributed to the dispersion effect of ultrasound on arc plasma in the laser channel. The porosity rate was reduced from 5.66 to 1.05% under PAT of 132 N, because of the increase in escape velocity of bubbles. Moreover, the columnar to equiaxed transformation (CET) of grain in the weld was promoted and the width of columnar grain zone was gradually reduced with the increasing ultrasonic energy, owing to the breaking effect of cavitation and the stirring effect of acoustic stream. As a result, lower porosity rate and finer grain size led to improvement of the microhardness and the strength of weld by ultrasound. The study provides more guidance on employing ultrasound to improve the quality of welded joints.

Influence of Laser Power on Droplet Transfer Behavior and Spatter in Laser-MIG Hybrid Welding of Aluminum Alloy

Influence of Laser Power on Droplet Transfer Behavior and Spatter in Laser-MIG Hybrid Welding of Aluminum Alloy

Effect of kerf characteristics on microstructures and properties of laser cutting–welding of AA2219 aluminum alloy

The purification of laser keyhole is an important means to remove the oxide layer of laser-MIG hybrid welding of aluminum alloy. Four common auxiliary gases (argon, nitrogen, air and oxygen) were used to prepare kerf with different characteristics, which were defined as argon-weld, nitrogen-weld, air-weld and oxygen-weld. The results show that the remelted layer has little effect on the weld morphology. Microstructures characteristics of Argon-welds and nitrogen-welds were the same as machined welds, while the narrow columnar grain zone and coarsen grains exist in air-welds and oxygen-welds. When the thickness of kerf remelted layer increases, the width of columnar grain zone is reducing and the diameter of equiaxed grain is increasing. The argon-weld is with the best tensile property. When the thickness of remelted layer (d) is less than 70 μm, the tensile strength and elongation of argon-weld can reach 278 MPa and 3.1% respectively, which equivalent to that of machined weld. The tensile property of nitrogen-weld is slightly lower than that of argon-weld because of aluminum nitride impurities. The tensile properties of air-weld and oxygen-weld are low because of a large number of oxide impurities and grain coarsening. Regardless of the types of kerf, when the d is less than 136 μm, the tensile strength reaches more than 250 MPa, which meets the application requirements.

Welding Characteristics and Porosity Control of Weaving Laser-MIG Hybrid Welding of Aluminum Alloys

Welding Characteristics and Porosity Control of Weaving Laser-MIG Hybrid Welding of Aluminum Alloys

Effect of adhesive on laser-arc hybrid welding of aluminum alloy to high-strength steel joint

Aluminum alloy 6061 and high-strength steel Q460 were joined by laser-arc-adhesive hybrid welding technology successfully. A Cu alloy interlayer was added between Al alloy and high-strength steel. The effect of the adhesive on laser-arc-adhesive hybrid welding of Al alloy to high-strength steel was discussed. The optical microscope, scanning electron microscope and electron probe micro-analysis were applied to observe the microstructural evolution and phase transition at Al–Fe interface of laser-arc-adhesive hybrid welded joints. The results showed the maximum tensile shear strength of the joint without adhesive was 256 MPa. After adding adhesive, the maximum tensile shear strength reached 282 MPa. The combination of the mechanical bonding and the metallurgical effect could improve the mechanical performances. The shape of the joint in Al alloy changed into a canine-like morphology. There was no porosity in welds because the molten pool of Al alloy and the special keyhole phenomenon of laser welding provided a channel for the decomposed gas to escape from fusion zone.

Modeling of Keyhole-Induced Pore Formation in Laser-Arc Hybrid Welding of Aluminum Alloy with a Horizontal Fillet Joint

A three-dimensional transient model is proposed to investigate the weld pool dynamic behavior in laser + metal inert gas (MIG) hybrid fillet welding of aluminum alloy in the horizontal position, which allows for the joint configuration and coupling of the keyhole, droplet and weld pool as well as the heat and mass exchange between gas and liquid phases and is able to simulate the temperature distribution, fluid flow and formation process of a keyhole-induced pore in hybrid welding with a horizontal fillet joint. The weld porosity is also measured using x-ray nondestructive testing technology. Keyhole behavior and the formation mechanism of keyhole-induced porosity were analyzed. The calculated results are in generally good agreement with the experimental ones. A clockwise vortex always exists at the middle part of the weld pool. The formation and growth of the molten metal bulge on the keyhole wall are responsible for the occurrence of a gas bubble, which has a variation in size and shape and can be split during welding. The keyhole collapses easily at its middle or upper part in horizontal fillet welding, and the capture of the bubble by the upper molten pool boundary enhances the possibility of porosity formation to some degree. The keyhole-induced pore is mainly formed at the regions near the keyhole bottom and the upper fusion line of the weld pool.

Influences of synergy effect between laser and arc on laser-arc hybrid welding of aluminum alloys

Researchers generally believe that synergy effect between laser and arc enables laser-arc hybrid welding to acquire obvious advantages of efficiency and quality in welding aluminum alloys. However, influences of physical essence of the synergy effect on welding process were not clear. In this study, basic principle of the synergy effect and its influences on welding process were obtained by spectral analysis of hybrid plasma plume and high-speed photographic analysis of welding process. First, the principle of the synergy effect is that laser interacts with arc to render electron energy level to transition. This process emits more photons, which enhance the heat input to the weld materials. The synergy effect is quantified by spectral intensity. It increases with the laser power, and decreases with the arc current and laser-arc distance. It is proportional to the cross section of weld, especially the upper, and beneficial to improve the welding energy utilization. Secondly, the amount of spatter in laser-arc hybrid welding is significantly less than that of arc welding. The bigger weld pool, the downward melt flow, and the reduced droplet transfer force generated by the synergy effect make the transferring droplets more easily absorbed by the weld pool, which stabilizes the transfer process and reduces the generation of spatter. The research results are beneficial for understanding hybrid welding mechanism and optimizing the welding process.

Effect of kerf characteristics on weld porosity of laser cutting-welding of AA2219 aluminum alloy

The purification of laser keyhole and improving molten pool flow are important means to restrain the porosity of laser-MIG hybrid welding of aluminum alloy. In this paper, four kinds of kerf were prefabricated by four common gases (Argon, Nitrogen, Air, Oxygen), which are used for studying the effect of kerf remelted layer on weld porosity. The experimental results show that the porosity is affected by the composition and thickness of the remelted layer. The porosity of Argon-weld and Nitrogen-weld is low, and that of Air-weld and Oxygen-weld is high. It increased linearly with the thickness of remelted layer (d). Regardless of the types of kerf, when the d is less than 136 μm, the porosity is less than 2%. When the d is thin, the purification of laser keyhole avoids the adverse effect of remelted layer oxide on the molten pool and reduces the porosity. When the d is thick, the influence of oxygen on surface tension and molten pool flow driven by it starts to dominate. It makes the temperature coefficient of surface tension change from negative to positive, and the molten pool change from ‘outward flow’ to ‘inward flow’, which prevent bubbles from escaping and increasing the porosity.

Influence of Arc Power on Keyhole-Induced Porosity in Laser + GMAW Hybrid Welding of Aluminum Alloy: Numerical and Experimental Studies.

A three-dimensional numerical model is used to simulate heat transfer and fluid flow phenomena in fiber laser + gas metal arc welding (GMAW) hybrid welding of an aluminum alloy, which incorporates three-phase coupling and is able to depict the keyhole dynamic behavior and formation process of the keyhole-induced porosity. The temperature profiles and fluid flow fields for different arc powers are calculated and the percent porosities of weld beads were also examined under different conditions by X-ray non-destructive testing (NDT). The results showed that the computed results were in agreement with the experimental data. For hybrid welding, with raising arc power, the keyhole-induced porosity was reduced. Besides the solidification rate of the molten pool, the melt flow was also closely related to weld porosity. A relatively steady anti-clockwise vortex caused by arc forces tended to force the bubble to float upwards at the high temperature region close to the welding heat source, which benefits the escape of the gas bubble from the melt pool. When increasing the arc power, the anti-clockwise region was strengthened and the risk of the gas bubble for capture by the liquid/solid interface underneath the keyhole tip was diminished, which resulted in the lower weld percent porosity.