Aluminum alloy laser welding method with microalloying and light beam scanning coordinated regulation and control

Abstract

The invention belongs to the technical field of welding, and relates to a microalloying and light beam scanning coordinated regulation aluminum alloy laser welding method which comprises the following steps: clamping a microalloying metal foil between a pair of cleaned aluminum alloy plates to be welded; a continuous optical fiber laser with the output power of 10 kW to 20 kW is used as a heat source, laser beams are emitted to a to-be-welded aluminum alloy plate through a galvanometer system for welding, during welding, a molten pool is generated through laser beam scanning and heating, laser energy is distributed in the molten pool in a periodic offset mode, and the laser energy is converted into laser energy; and then the microalloyed metal foil is gradually melted under the action of periodic stirring and enters a weld joint to react with a base metal melt to separate out an L12-Al3X precipitated phase, and X is a trace alloying element in the microalloyed metal foil. The microalloy elements and the high-melting-point compound formed by the microalloy elements serve as heterogeneous nucleation cores to participate in the molten pool solidification process, molten pool convection is enhanced, and the stability of a solidification interface is changed, so that refined regulation and control of a weld joint structure are achieved.

Description

Technical Field

[0001] This application belongs to the field of welding technology, and more specifically, relates to a laser welding method for aluminum alloys that combines microalloying and beam scanning. Background Technology

[0002] With the technological advancements in aerospace, rail transportation, and new energy vehicles, the demand for high-speed operation, lightweight structures, and optimized energy efficiency continues to grow. Against this backdrop, structural strengthening and lightweighting have become core research topics. Aluminum alloys, with their excellent specific strength, good thermal and electrical conductivity, outstanding corrosion resistance, and good formability, are considered key materials for achieving lightweight structures and energy conservation and emission reduction goals. Gas metal arc welding (MIG) is a widely used traditional welding method for aluminum alloy structural connections; however, this method, due to its high heat input and low welding speed, easily leads to significant welding deformation and severe joint softening. Laser welding has attracted considerable attention due to its advantages such as high power density, low welding heat input, high welding speed, narrow heat-affected zone, and minimal welding deformation. However, under the high energy density of high-power lasers, low-boiling-point elements in aluminum alloys are easily evaporated, causing the disappearance of age-strengthening phases after weld solidification, severely reducing the strength and toughness of the joint.

[0003] Therefore, there is an urgent need for a welding method that can improve the strength and toughness of aluminum alloy welded joints. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this application is to provide a laser welding method for aluminum alloys that combines micro-alloying and beam scanning, aiming to solve the problems of obvious deformation, severe softening, and poor weld strength and toughness of aluminum alloy welded joints obtained by existing welding methods.

[0005] To achieve the above objectives, this application provides a laser welding method for aluminum alloys with coordinated control of micro-alloying and beam scanning, comprising: S1 sandwiches micro-alloyed metal foil between two cleaned aluminum alloy plates to be welded; S2 uses a continuous fiber laser with an output power of 10kW~20kW as a heat source, and directs the laser beam toward the aluminum alloy plate to be welded via a galvanometer system. During welding, the laser beam scans and heats to generate a molten pool, and the laser energy is periodically shifted within the molten pool. This causes the microalloyed metal foil to gradually melt under periodic stirring and enter the weld to react with the base metal melt to precipitate the L12-Al3X precipitate phase, where X is a trace alloying element in the microalloyed metal foil.

[0006] Furthermore, the microalloyed metal foil is a single sheet of pure metal foil or a double layer of different metal foils.

[0007] Furthermore, the trace alloying element in the monolithic pure metal foil is any one of Zr, Ti, or Ni.

[0008] Furthermore, the trace alloying elements in the double-layered different metal foils are Ti and Cu, Zr and Nb, or Zr and Cu, respectively.

[0009] Furthermore, the scanning amplitude of the laser beam is 0.2mm~1mm, and the scanning frequency is 100Hz~500Hz.

[0010] Furthermore, the laser beam has a closed scanning trajectory, and the welding speed during scanning is 30mm / s to 100mm / s.

[0011] Furthermore, the spacing between adjacent laser points within the closed scanning trajectory is 0.06mm to 1mm, and the spacing between adjacent closed scanning trajectories is 0.06mm to 1mm.

[0012] Furthermore, the closed scanning trajectory is circular, and the radius of the circular scanning trajectory is 0.2mm~0.8mm.

[0013] Furthermore, in step S2, the defocusing amount of the laser beam is 0 mm.

[0014] Furthermore, the thickness of the microalloyed metal foil does not exceed 0.05 mm.

[0015] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: (1) This application significantly reduces the concentration gradient of microalloying elements in the molten pool by scanning laser-induced forced convection, avoiding their enrichment or insufficient melting in local areas; under laser scanning conditions, the weld pool exhibits a periodic unstable state before solidification, which is conducive to the participation of microalloying elements and their high-melting-point compounds as heterogeneous nucleation cores in the solidification process; unlike the ultrasonic cavitation effect, this application achieves the "heat-flow-solidification" synergistic evolution in the molten pool by laser energy modulation, which is more suitable for deep melting and high-speed 10,000-watt laser welding conditions.

[0016] (2) This application achieves butt welding by combining the "bridging" effect of microalloyed foil and the "stabilizing" effect of beam scanning on the molten pool under the continuous output of high-power laser at the 10,000-watt level, and the laser beam scanning method. This allows the microalloying elements to fully melt into the weld metal under the dynamic action of scanning the molten pool, and achieves fine control of the weld structure by enhancing the convection of the molten pool and changing the stability of the solidification interface.

[0017] (3) This application precisely introduces microalloying elements in the form of foil and uses the scanning energy of the periodically offset distribution of the beam scan to precisely control the thermal cycle and fluid movement, thereby achieving the adjustment of the solid-state phase transformation and precipitation dynamics of the weld. By adjusting the scanning amplitude, frequency and trajectory, the stirring intensity and thermal field distribution of the molten pool can be controlled, thereby regulating the precipitation size, distribution density and interaction with dislocations of the L12-Al3X phase. This in-situ generated nanoprecipitate phase is formed during the welding process. On the one hand, it acts as a reinforcing phase to hinder dislocation movement and improve weld strength. On the other hand, it enhances weld performance and hardness by refining the microstructure.

[0018] (4) The metal foil material of this application can be a single metal foil or a double metal foil. The double metal foil is made of metal foil containing different micro-alloying elements, so that the weld can be designed in terms of composition and structure according to service requirements (such as conductivity, thermal conductivity and heat resistance) to obtain ultra-fine equiaxed crystals and nano-phases with high thermal stability, thereby creating a welded structure with uniform performance or even gradient functionalization. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the welding test apparatus and circular scanning path of this application; Figure 2 This is a weld morphology image obtained in Comparative Example 1 of this application; Figure 3 This is a cross-sectional view of the weld in Comparative Example 1 of this application; Figure 4 This is a weld morphology diagram of Comparative Example 2 in this application; Figure 5 This is a cross-sectional view of the weld in Comparative Example 2 of this application; Figure 6 Comparison diagrams of weld surface formation, flaw detection results, and weld cross-sections between Comparative Examples 3 and 4 and Example 1 in this application; Figure 7 These are scanning electron microscope images comparing the weld fusion zone of Comparative Examples 3 and 4 with that of Example 1 in this application. Figure 8 The results of transmission electron microscopy of the weld fusion zone in Example 1 of this application; Figure 9 These are comparative images of the grain morphology of the weld fusion zone in Comparative Examples 3 and 4 and Example 1 in this application; Figure 10 This is a comparison diagram of the grain size of the weld fusion zone in Comparative Examples 3 and 4 and Example 1 in this application; Figure 11 This is a comparison chart of tensile strength and elongation between Comparative Examples 3 and 4 and Example 1 in this application; Figure 12Comparison diagrams of weld surface formation and flaw detection results between Comparative Examples 5 and 6 and Example 2 in this application; Figure 13 These are scanning electron microscope images comparing the weld fusion zone of Comparative Examples 5 and 6 with that of Example 2 in this application. Figure 14 The results of transmission electron microscopy of the weld fusion zone in Example 2 of this application; Figure 15 Comparison images of the grain morphology of the weld fusion zone in Comparative Examples 5 and 6 and Example 2 of this application. Figure 16 This is a comparison chart of tensile strength and elongation between Comparative Examples 5 and 6 and Example 2 in this application; Figure 17 These are comparative images of the weld surface formation in Examples 3 to 6 of this application; Figure 18 This is a comparison chart of tensile strength and elongation of Examples 3 to 6 in this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0021] The embodiments of this application are described below with reference to the accompanying drawings.

[0022] This application provides a laser welding method for aluminum alloys that combines micro-alloying and beam scanning in a coordinated manner. Figure 1 As shown in Figure a, the workpiece material is 6mm thick 6082-T6 aluminum alloy (i.e., 6082 Al in the figure), and the welding method is flat butt welding. The operating platform is an IPG 20000YSL laser, and a Kuka six-axis welding robot system and an IPG oscillating laser head are used. This laser welding method specifically includes the following steps: (1) The surface of the butt weld of the aluminum alloy plate to be welded is mechanically ground to remove the oxide film and cleaned with organic solvent to reduce the influence of surface impurities in the welding area on the stability of the molten pool. (2) Fix the two aluminum alloy plates together in a butt joint manner, and clamp micro-alloyed metal foil at the butt joint along the welding direction; (3) A high-power continuous fiber laser with an output power of 10kW to 20kW is used as the heat source. The laser focus is adjusted to be located on the workpiece surface, maintaining zero defocus. The laser beam is then directed into the workpiece surface via a galvanometer scanning system, forming an angle of 5 to 10° with the workpiece surface for welding. During welding, the laser beam heats the base material to generate a molten pool. The laser beam scanning causes the laser energy to be periodically shifted within the molten pool, thereby causing the microalloyed metal foil to gradually melt under periodic stirring. The melt then enters the weld and reacts with the base material melt to precipitate L12-Al3X precipitates, where X is a trace alloying element in the microalloyed metal foil, thus achieving the effect of refining the weld structure. Pure Ar shielding gas and back shielding gas are also introduced during welding to prevent oxidation and suppress plasma shielding effects, thereby improving the stability of the molten pool.

[0023] The aforementioned L12-Al3X precipitates have a small mismatch with the parent material and a good coherent relationship with the parent material, which promotes the ultrafine grain size and achieves a significant improvement in performance.

[0024] The aforementioned laser beam scans along the welding direction to form a closed scanning trajectory; among which, such as Figure 1 As shown in (b), the closed scanning trajectory can be circular or approximately circular, with a scanning amplitude of 0.2 mm to 1 mm, a scanning frequency of 100 Hz to 500 Hz, and a welding speed of 30 mm / s to 100 mm / s.

[0025] The spacing between adjacent laser spots (hereinafter collectively referred to as laser points) within the aforementioned closed scanning trajectory is 0.06mm~1mm, and the spacing between adjacent closed scanning trajectories (i.e. adjacent circular trajectories or adjacent circular trajectories) is 0.06mm~1mm. That is, the spacing between adjacent laser points and the spacing between adjacent closed scanning trajectories are the same, ensuring that the laser points are periodically offset.

[0026] If the aforementioned closed scanning trajectory is a circular scanning trajectory, then the scanning radius A of each circular scanning trajectory is 0.2mm~0.8mm. Within this range, 6082-T6 aluminum alloy can be effectively joined. Beyond this scanning range, the weldability of the parameters decreases, the weld pool becomes unstable, and the weld pool evaporates violently. Among these, a scanning radius of 0.4mm provides better forming, reduces defects such as spatter and porosity compared to other scanning radii, and also provides better surface forming, making it the optimal value in this application.

[0027] The aforementioned microalloyed metal foil (i.e. Figure 1 The thickness of the Zr intermediate layer (as shown in a) should not exceed 0.05 mm, meaning that the thickness of a single pure metal foil should not exceed 0.05 mm, and the total thickness of two layers of different metal foils should not exceed 0.05 mm. Excessive thickness will affect the quality of the weld.

[0028] More specifically, the trace alloying element in a single pure metal foil is any one of Zr, Ti, or Ni. The trace alloying elements in the double-layered different metal foils are Ti and Cu, Zr and Nb, or Zr and Cu, that is, one metal foil is a Ti-containing microalloyed metal foil and the other is a Cu-containing metal foil, or one metal foil is a Zr-containing microalloyed metal foil and the other is a Nb-containing metal foil, or one metal foil is a Zr-containing microalloyed metal foil and the other is a Cu-containing metal foil.

[0029] The 10,000-watt laser scanning welding method provided in this application achieves full integration of microalloying elements and optimization of weld microstructure through energy modulation and molten pool dynamics control. Its core technical mechanism is as follows: during high-power (10kW~20kW) continuous laser welding, beam scanning technology is introduced, causing the laser energy to be periodically offset within the molten pool. This not only changes the transient morphology of the keyhole and the direction of the recoil pressure, but more importantly, it induces directional circulating flow (i.e., "endogenous oscillation") within the molten pool, thereby significantly enhancing the convection intensity of the molten pool and the mixing efficiency of the molten metal.

[0030] The enhanced forced convection described above in this application has multiple functions: First, it significantly reduces the concentration gradient of microalloying elements in the molten pool, avoiding local segregation or unmelted areas and ensuring uniform element distribution; second, the enhanced flow and periodic energy input alter the stability of the solidification front, making it easier for the solidification process to utilize microalloying elements and their formed high-melting-point compounds as heterogeneous nucleation sites, thereby refining the grains. The entire process achieves the synergistic evolution and active control of "heat-fluid-solidification".

[0031] Unlike traditional methods that rely on external additional energy (such as ultrasonic cavitation), this application achieves the above-mentioned regulation entirely through the scanning modulation of the laser energy itself. Its mechanism is more direct and it is particularly suitable for deep-penetration, high-speed, 10,000-watt laser welding conditions. While ensuring high production efficiency, it improves the uniformity and performance of the weld structure.

[0032] The technical solution of this application will be described in detail below using multiple embodiments, and multiple comparative examples will be used to highlight the advantages of the technical solution of this application.

[0033] Example 1 In this embodiment, the workpiece material is 6mm thick 6082-T6 aluminum alloy, and the welding method is flat butt welding. The operating platform is an IPG 20000YSL laser, a Kuka six-axis welding robot system, and an IPG oscillating laser head. The laser welding method specifically includes the following steps: (1) The surface of the butt weld of the aluminum alloy plate to be welded is mechanically ground to remove the oxide film and cleaned with organic solvent to reduce the influence of surface impurities in the welding area on the stability of the molten pool. (2) Fix the two aluminum alloy plates together, and sandwich a 0.05mm thick pure Zr metal foil at the joint along the welding direction as a micro-alloying intermediate layer.

[0034] (3) A high-power continuous fiber laser with an output power of 11kW is used as the heat source. The laser focus is adjusted to be located on the surface of the workpiece, maintaining zero defocus. The laser beam is then injected into the surface of the workpiece through the galvanometer scanning system and welded at an angle of 5 to 10° with the surface of the workpiece. During welding, the base material is heated by the laser beam to generate a molten pool. The laser energy is periodically shifted and distributed in the molten pool by the laser beam scanning. The micro-alloyed metal foil is gradually melted under the periodic stirring action and enters the weld to react with the base material melt to precipitate L12-Al3X precipitate phase. X is a trace alloying element in the micro-alloyed metal foil, thereby achieving the effect of refining the weld structure.

[0035] In this embodiment, the specific welding parameters are as follows: welding speed is 2.4 m / min; the scanning trajectory during welding is a circular scanning trajectory with a scanning radius of 0.4 mm and a scanning frequency of 300 Hz.

[0036] In this embodiment, the spacing between adjacent laser points is 0.08 mm, and the spacing between adjacent closed scanning trajectories is also 0.08 mm.

[0037] Example 2 The difference between this embodiment and embodiment 1 is that: (1) the intermediate layer between the aluminum alloy metal base materials is a 0.01mm thick Ti metal foil as the microalloy intermediate layer source. (2) the welding parameters are different. The process parameters for beam scanning laser welding in this embodiment are: laser beam defocusing amount is 0mm, laser power is 11kW, welding speed is 1.8m / min; the welding trajectory is also a circular scanning trajectory with a scanning radius of 0.4mm and a scanning frequency of 300Hz.

[0038] Example 3 The difference between this embodiment and Embodiment 1 is that the intermediate layer between the aluminum alloy base materials is a 0.03mm Ni metal foil as the microalloy intermediate layer source. The welding parameters are set the same as in Embodiment 2.

[0039] Example 4 The difference between this embodiment and Embodiment 1 is that the intermediate layer between the aluminum alloy base materials is a 0.01mm Ti metal foil and a 0.01mm Cu metal foil as the microalloy intermediate layer source. The welding parameters are set the same as in Embodiment 2.

[0040] Example 5 The difference between this embodiment and Embodiment 1 is that the intermediate layer between the aluminum alloy base materials is a 0.01mm Zr metal foil and a 0.01mm Nb metal foil as the microalloy intermediate layer source. The welding parameters are set the same as in Embodiment 2.

[0041] Example 6 The difference between this embodiment and Embodiment 1 is that the intermediate layer between the aluminum alloy base materials is a composite microalloy intermediate layer source consisting of a 0.01mm Zr metal foil and a 0.01mm Cu metal foil. The welding parameters are set the same as in Embodiment 2.

[0042] Comparative Example 1 The difference between this comparative example and Example 1 is that there is no intermediate layer, and the laser welding process parameters are: laser beam defocusing amount is 0mm, laser power is in the range of 10kW~12kW, welding speed is in the range of 3~6m / min; the welding method is pure laser welding, that is, the scanning radius is 0mm, the scanning frequency is 0Hz, and the welding trajectory is a linear trajectory.

[0043] Comparative Example 2 The difference between this comparative example and Comparative Example 1 is that the laser welding process parameters are: laser power of 11kW, welding speed of 4.2m / min; welding method of laser scanning welding, and welding trajectory of circular scanning trajectory, with scanning radius of 0.2~1mm for each circular scanning trajectory and scanning frequency of 100~500Hz.

[0044] Comparative Example 3 The difference between this comparative example and Comparative Example 1 is that the laser welding process parameters are: laser power of 11kW, welding speed of 2.4m / min; welding method of laser scanning welding, and welding trajectory of circular scanning trajectory with a scanning radius of 0.4mm and a scanning frequency of 100Hz.

[0045] Comparative Example 4 The difference between this comparative example and Comparative Example 1 is that a 0.05 mm thick pure Zr metal foil is sandwiched in the middle of the base material as a microalloying source. The laser welding process parameters are: laser power of 11 kW, welding speed of 2.4 m / min; welding method is laser scanning welding, and the welding trajectory is a circular scanning trajectory with a scanning radius of 0.4 mm and a scanning frequency of 100 Hz.

[0046] Comparative Example 5 The difference between this comparative example and Comparative Example 1 is that the laser power is 11kW and the welding speed is 1.8m / min.

[0047] Comparative Example 6 The difference between this comparative example and Comparative Example 1 is that the laser power is 11kW, the welding speed is 1.8m / min, the welding method is laser scanning welding, and the welding trajectory is a circular scanning trajectory with a scanning radius of 0.4mm and a scanning frequency of 300Hz.

[0048] like Figure 2 As shown, there are various weld morphology images obtained within the welding process parameter range of Comparative Example 1 (i.e., within the range of 10kW~12kW and welding speed of 50~100mm / s). It can be seen that each weld surface has a large amount of spatter, rough fish scale pattern, serious undercut, and poor weld formation.

[0049] like Figure 3 As shown, the weld cross-section obtained corresponding to the welding process parameters of Comparative Example 1 shows that the weld obtained in the range of 10kW~12kW and welding speed of 50~100mm / s contains a large number of pores, and the pores in some process welds also show a chain-like distribution.

[0050] like Figure 4 As shown, there are various weld morphology images obtained in Comparative Example 2 with amplitudes in the range of 0.2~1mm and frequencies in the range of 100~500Hz. It can be seen from the figure that the weld surface has a lot of spatter, rough fish scale pattern, serious undercut phenomenon and poor weld formation. The weld formation obtained when the frequency is in the range of 300~500Hz and the amplitude is in the range of 0.8~1mm is extremely poor.

[0051] like Figure 5 As shown, there are various weld cross-sectional images obtained in Comparative Example 2 with amplitudes in the range of 0.2~1mm and frequencies in the range of 100~500Hz. It can be seen that there are a large number of pores in the weld, and some of the pores are distributed in a chain-like manner.

[0052] like Figure 6 As shown, (a) is the surface formation result of the weld obtained in Comparative Example 3, (d) is its flaw detection result, and (g) is its weld cross-section; (b), (e), and (h) are the surface formation result, flaw detection result, and weld cross-sectional morphology of the weld obtained in Comparative Example 4, respectively; (c), (f), and (i) are the surface formation result, flaw detection result, and weld cross-section of the weld obtained in Example 1, respectively. Compared with Comparative Example 1 and Comparative Example 2, the weld obtained in Example 1 has a more uniform surface formation, clearer fish scale pattern, larger transition angle, and better welding quality.

[0053] like Figure 7As shown, (a) to (c) are the scanning electron microscope (SEM) results of the weld obtained in Comparative Example 3; (d) to (f) are the SEM results of the weld obtained in Comparative Example 4; and (g) to (i) are the SEM results of the weld obtained in Example 1. It can be seen from the figures that in Comparative Example 4 and Example 1, due to the addition of microalloyed Zr, Al3Zr was generated, and the impurity phases Mg2Si and α-AlFeMnSi distributed at the grain boundaries were significantly refined, with a reduced volume fraction.

[0054] like Figure 8 As shown, this is a schematic diagram of the transmission electron microscope results of the weld fusion zone in Example 1. (a) and (f) are microscopic morphology images of Al3Zr at different angles, which are plate-like. (d) shows the calibration of the diffraction spot, confirming that it is L12-Al3Zr. (h) shows the Fourier transform of the high-resolution (i.e., atomic arrangement of the precipitated phase) and the calibration of the diffraction spot, confirming that it is L12-Al3Zr. (e) shows that there are dislocations at the interface between L12-Al3Zr and the matrix phase, confirming that the precipitated phase can hinder dislocation movement and improve weld performance.

[0055] like Figure 9 As shown, (a) is the overall view of the weld of Comparative Example 3, and (d) and (g) are high-magnification images of Comparative Example 3. It can be seen from the images that coarse columnar crystals grow at the fusion line of the weld obtained in Comparative Example 3, and coarse equiaxed crystals are present at the center of the weld. (b) is the overall view of the weld obtained in Comparative Example 4, (e) and (h) are high-magnification images of the weld obtained in Comparative Example 3, (c) is the overall view of the weld obtained in Example 1, and (f) and (i) are high-magnification images of the weld obtained in Example 1. Compared to Comparative Example 3, the welds obtained in Comparative Example 4 and Example 1 both contain fine equiaxed crystals.

[0056] like Figure 10 As shown, (a) to (c) are schematic diagrams of the average grain size and standard deviation of Comparative Examples 3, 4 and Example 1, respectively. The average grain size and standard error in Example 1 are smaller, that is, the weld grains are smaller and the structure is more uniform. Compared with Comparative Example 3, the reduction is up to eight times.

[0057] like Figure 11 As shown in the figure, the tensile strength and elongation of the welds obtained by Comparative Example 3, Comparative Example 4 and Example 1 are compared. It can be seen from the figure that the tensile strength and elongation of the weld obtained by Example 1 are significantly higher than those of the welds obtained by Comparative Example 3 and Comparative Example 4. The tensile strength of the weld increased from 229 MPa to 242 MPa, and the elongation also increased by 57.5%.

[0058] like Figure 12As shown, (a), (c) and (e) are weld surface morphology diagrams of Comparative Example 5, Comparative Example 6 and Example 2, respectively, and (b), (d) and (f) are weld flaw detection results of Comparative Example 5, Comparative Example 6 and Example 2, respectively. It can be seen from the figures that the weld obtained in Example 2 has a uniform shape and the porosity is reduced to 2.58%, while the weld surface morphology of Comparative Example 5 and Comparative Example 6 is poor, especially Comparative Example 5, whose porosity is much higher than that of the weld in Example 2.

[0059] like Figure 13 The figures show a comparison of scanning electron microscope (SEM) images of the weld fusion zone in Comparative Examples 5, 6, and 2. (a) and (b) are the SEM results for Comparative Example 5, (b) and (e) are the SEM results for Comparative Example 7, and (e) and (f) are the SEM results for Example 2. As can be seen from the figures, in Example 2, the addition of microalloyed Ti generated a new precipitated phase, Al3Ti, and the impurity phases Mg2Si and α-AlFeMnSi distributed at the grain boundaries were significantly refined, with a reduced volume fraction.

[0060] like Figure 14 The diagram shows the transmission electron microscope (TEM) results of the weld fusion zone obtained in Example 2. (a) shows the microstructure of the precipitated phase L12-Al3Ti, which is plate-like. (d) shows the diffraction pattern of the precipitated phase L12-Al3Ti, which was identified as L12-Al3Ti after calibration. (e) confirms that the precipitated phase is coherent with the matrix. (f) shows the high-resolution Fourier transform of the interface at the red dashed line in (e), calibrating its diffraction pattern and further confirming its good coherence with the α-Al matrix phase. (i) shows that the precipitated phase contains a large number of dislocations, confirming that the precipitated phase can hinder dislocation movement and thus improve weld performance.

[0061] like Figure 15 The figures show a comparison of the grain morphology of the weld fusion zone in Comparative Examples 5, 6, and 2. (a) shows the overall weld morphology of Comparative Example 5, and (d) and (g) are high-magnification images of the weld morphology of Comparative Example 5. The figures show that in Comparative Example 5, coarse columnar crystals grow at the fusion line, and coarse equiaxed crystals are present at the weld center. (b) shows the overall weld morphology of Comparative Example 6, and (e) and (h) are high-magnification images of the weld morphology of Comparative Example 6. (c) shows the overall weld morphology of Example 2, and (f) and (i) are high-magnification images of Example 2. The figures show that, compared to Comparative Examples 5 and 6, the entire weld morphology in Example 2 consists of fine equiaxed crystals, while Comparative Examples 5 and 6 consist of columnar crystals and coarse equiaxed crystals.

[0062] like Figure 16As shown in the figure, the tensile strength and elongation of the welds obtained in Comparative Examples 5, 6 and 2 are compared. It can be seen from the figure that the tensile strength and elongation of the weld in Example 2 are much higher than those of the welds obtained in Comparative Examples 5 and 6. The tensile strength of the weld increased from 200 MPa to 250 MPa, the tensile strength increased to 25%, and the elongation increased from 5.0% to 13.8%, an increase of 276%.

[0063] like Figure 17 As shown, multiple weld surface formation diagrams obtained in Examples 3 to 6 are shown. It can be seen from the diagrams that the surface formation quality of the joint obtained by laser welding using micro-alloying and beam scanning is improved, the fish scale pattern is clear, and the weld surface collapse is improved.

[0064] like Figure 18 The figure shows schematic diagrams of the ultimate tensile strength and elongation of multiple welds obtained in Examples 3 to 6. As can be seen from the figure, the ultimate tensile strength of each joint surface obtained by laser welding using a combination of microalloying and beam scanning exceeds 233 MPa, and the elongation exceeds 10.5%. Specifically, the ultimate tensile strength and elongation of the Ni metal foil sandwiched in the weld are increased to 233 MPa and 13%, respectively; the ultimate tensile strength and elongation of the Ti+Cu composite interlayer sandwiched in the weld are increased to 238 MPa and 10.5%, respectively; the ultimate tensile strength and elongation of the Zr+Nb composite interlayer sandwiched in the weld are increased to 242 MPa and 12%, respectively; and the ultimate tensile strength and elongation of the Zr+Cu composite interlayer sandwiched in the weld are increased to 246 MPa and 13%, respectively. In summary, through multi-dimensional analysis of the weld morphology obtained in Examples 1-6 and Comparative Examples 1-6, it can be seen that the advantages of this application are as follows: (1) Compared with Comparative Examples 1-6, in Examples 1 and 2, by employing a synergistic microalloying and beam oscillation method, the weld porosity was reduced, the fish-scale pattern was clearer, the collapse was improved, and the forming was significantly improved, resulting in a significant improvement in the quality of aluminum alloy laser welding. The introduction of microalloying elements significantly improved the uniformity and stability of weld formation and increased the transition angle between the upper and lower weld passes. In addition, high-frequency beam oscillation effectively promoted the uniform distribution of microalloying elements in the weld.

[0065] (2) Compared with Comparative Examples 3, 5, and 6, in Examples 1 and 2, the introduction of microalloying suppressed the growth of columnar crystals and generated L12-Al3X precipitates (X being a microalloying element), which can serve as a good heterogeneous nucleating agent. The grain structure was made ultra-fine and homogeneous. The results showed that the average grain size was significantly reduced from 92.97 μm without the addition of Zr metal foil to 9.57 μm, and its standard error decreased from 49.21 to 5. The addition of Ti metal foil also significantly refined the grains. At the same time, the addition of Zr and Ti significantly refined the size of harmful impurity phases such as Mg2Si and α-AlFeMnSi, and their volume fraction was also reduced. The original continuous "island-like" brittle network structure was effectively suppressed, and the precipitates were more uniformly and isolated.

[0066] (3) Compared with Comparative Examples 3-6, in Examples 1-6, the grains were significantly refined and the joint performance was improved by using synergistic microalloying and beam oscillation. The test results showed that in Comparative Example 3, the tensile strength and elongation without Zr were 229 MPa and 4.0%, respectively. In Example 1, the addition of Zr increased the tensile strength and elongation to 242 MPa and 6.3%, respectively, which were about 5.7% and 57.5% higher than Comparative Example 3. The fracture mode changed from brittle fracture dominated by pores to mixed fracture dominated by dimples, achieving simultaneous enhancement of strength and toughness. At the same time, the microhardness of the welded joint of this process increased by 15.8%. In Comparative Example 5, the tensile strength and elongation without Ti were 200 MPa and 5.0%, respectively. In Example 2, the addition of Zr increased the tensile strength and elongation to 250 MPa and 13.8%, respectively, which were 25% and 176% higher than Comparative Example 5, respectively. The fracture mode changed from mixed fracture mode to ductile fracture dominated by dimples. In Example 3, the ultimate tensile strength and elongation of the Ni-inserted material were increased to 233 MPa and 13%, respectively, and the fracture mode was ductile fracture.

[0067] (4) Compared with Comparative Examples 3, 5, and 6, in Examples 4 to 6, the performance of the welded joint was significantly improved by using a synergistic composite sandwich metal interlayer and beam oscillation. The ultimate tensile strength and elongation of the Ti+Cu composite interlayer were increased to 238 MPa and 10.5%, respectively; the ultimate tensile strength and elongation of the Zr+Nb composite interlayer were increased to 242 MPa and 12%, respectively; and the ultimate tensile strength and elongation of the Zr+Cu composite interlayer were increased to 246 MPa and 13%, respectively.

[0068] In summary, this application employs an aluminum alloy welding process combining high-power laser oscillation with microalloyed metal foils such as zirconium (Zr). The resulting weld exhibits a uniformly distributed ultra-fine equiaxed grain structure, thereby improving the mechanical properties of the weld joint. Specifically, the high-power laser oscillation prevents incomplete melting of the Zr metal foil, reduces the formation of atmospheric pores, and promotes heat and mass exchange within the molten pool. Meanwhile, microalloying increases the number of heterogeneous nucleation particles and refines the grain structure, thus enhancing the mechanical properties of the weld joint.

[0069] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0070] Furthermore, in this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. The symbol " / " in this document indicates that the related objects are in an "or" relationship; for example, A / B means A or B.

[0071] The terms "first" and "second," etc., used in the specification and claims herein are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages.

[0072] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0073] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0074] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after connection. "Rotary connection" refers to a connection where the components can rotate relative to each other after connection. "Sliding connection" refers to a connection where the components can slide relative to each other after connection. The directional terms mentioned in the embodiments of this application, such as "top," "bottom," "inner," "outer," "left," and "right," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0075] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are limitations specific to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are permissible; approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. "A and B are perpendicular" means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0076] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A laser welding method for aluminum alloys with coordinated control of micro-alloying and beam scanning, characterized in that, include: S1 sandwiches micro-alloyed metal foil between two cleaned aluminum alloy plates to be welded; S2 uses a continuous fiber laser with an output power of 10kW~20kW as a heat source, and directs the laser beam toward the aluminum alloy plate to be welded via a galvanometer system. During welding, the laser beam scans and heats to generate a molten pool, and the laser energy is periodically shifted within the molten pool. This causes the microalloyed metal foil to gradually melt under periodic stirring and enter the weld to react with the base metal melt to precipitate the L12-Al3X precipitate phase, where X is a trace alloying element in the microalloyed metal foil.

2. The aluminum alloy laser welding method of claim 1, wherein, The microalloyed metal foil is a single sheet of pure metal foil or a double layer of different metal foils.

3. The aluminum alloy laser welding method of claim 2, wherein, The trace alloying element in the single piece of pure metal foil is any one of Zr, Ti, or Ni.

4. The aluminum alloy laser welding method of claim 2, wherein, The trace alloying elements in the double-layered different metal foils are Ti and Cu, Zr and Nb, or Zr and Cu.

5. The aluminum alloy laser welding method of claim 1, wherein, The scanning amplitude of the laser beam is 0.2mm~1mm, and the scanning frequency is 100Hz~500Hz.

6. The aluminum alloy laser welding method of claim 1, wherein, The laser beam has a closed scanning trajectory, and the welding speed during scanning is 30mm / s to 100mm / s.

7. The aluminum alloy laser welding method of claim 6, wherein, The distance between adjacent laser points within the closed scanning trajectory is 0.06mm to 1mm, and the distance between adjacent closed scanning trajectories is 0.06mm to 1mm.

8. The aluminum alloy laser welding method of claim 6, wherein, The closed scanning trajectory is circular, and the radius of the circular scanning trajectory is 0.2mm~0.8mm.

9. The aluminum alloy laser welding method of claim 1 wherein, In step S2, the defocusing amount of the laser beam is 0 mm.

10. The aluminum alloy laser welding method as described in claim 1, characterized in that, The thickness of the microalloyed metal foil does not exceed 0.05 mm.

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