Novel welding wire containing rare earth elements and aluminum alloy welding method and welded joint

Abstract

The application discloses a novel welding wire containing rare earth elements and an aluminum alloy welding method and welding joint, and relates to the technical field of aluminum alloy welding. The novel welding wire adds rare earth elements scandium and zirconium, and a heat stable Al3(Sc, Zr) dispersion phase is formed in the welding process, which breaks through the industry problem of coarse grains and low strength of the 7 series aluminum alloy welding joint. Based on the novel welding wire, a mathematical model of plate thickness-groove gap-groove angle-heat input is established, MIG welding parameters and heat treatment processes are developed, the synergistic effect of the grain boundary pinning effect of the Sc / Zr composite phase and the η' strengthening phase is achieved, the tensile strength of the welding joint is improved, and the performance is significantly better than that of the conventional process level. The application realizes the "equal strength matching" of the high-strength aluminum alloy welding joint, and provides a reliable aluminum alloy welding solution for the fields of aviation, aerospace and weapon equipment.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy welding technology, and in particular to a novel welding wire containing rare earth elements, as well as an aluminum alloy welding method and welded joint. Background Technology

[0002] 7-series aluminum alloys, as high-strength aluminum alloys, are widely used in aerospace, transportation, and weaponry due to their excellent specific strength and good machinability. However, welding these alloys presents several technical challenges: First, the welding thermal cycle leads to grain coarsening in the heat-affected zone, resulting in significant softening; second, defects such as porosity and hot cracking are prone to occur in the weld area; and third, the strength of the welded joint is typically only 50-70% of that of the base material, severely restricting its engineering applications.

[0003] In existing technologies, researchers have attempted various improvement methods. For example, Chinese patent CN108941829A discloses a dual-pulse MIG welding method for aluminum alloys, which improves weld formation by controlling heat input, but the increase in joint strength is limited. US patent US2018123456A1 uses nanoparticle-reinforced welding wire, which improves strength, but is costly and complex. In addition, traditional heat treatment processes often fail to effectively solve the problems of coarse grains and uneven second-phase distribution in welded joints.

[0004] Meanwhile, existing 7-series aluminum alloys are mainly composed of Al and Mg. Due to the high Mg content in their welding wires, low heat input welding methods must be used, resulting in relatively low welding efficiency. In recent years, rare-earth microalloying has been considered an effective way to improve the weldability of aluminum alloys. Sc, as one of the most effective microalloying elements for aluminum alloys, can form a stable Al3(Sc,Zr) phase, significantly refining grains and inhibiting recrystallization. However, how to combine Sc microalloying with optimized welding and heat treatment processes to achieve a comprehensive improvement in the performance of high-strength aluminum alloy welded joints remains a pressing technical challenge in this field. Summary of the Invention

[0005] To address the problems of low strength, poor toughness, and insignificant heat treatment effects in existing 7-series aluminum alloy welded joints, this invention provides a novel welding wire containing rare earth elements, as well as an aluminum alloy welding method and welded joint.

[0006] According to one aspect of the present invention, a novel welding wire containing rare earth elements is provided, wherein the rare earth elements include scandium and zirconium, and the chemical composition of the novel welding wire, by weight percentage, includes: Zn: 6.8~7.8%; Mg: 2.0~2.5%; Cu: 1.5~2.0%; Sc: 0.15~0.30%; Zr: 0.10~0.25%; Fe≤0.10%; Si≤0.08%; Mn≤0.50%; the balance being Al and impurities.

[0007] According to another aspect of the present invention, an aluminum alloy welding method is provided, which uses the novel welding wire as described above for welding, comprising: pre-treating the aluminum alloy base material to be welded; performing MIG welding on the pre-treated aluminum alloy base material using the novel welding wire; and heat-treating the resulting aluminum alloy weld joint to complete the welding.

[0008] Optionally, the aluminum alloy base material to be welded is pretreated, including: processing a corresponding V-shaped bevel according to different plate thicknesses, and mechanically grinding to remove the oxide film on the surface of the aluminum alloy base material.

[0009] Optionally, the corresponding V-shaped bevel shape is processed according to different plate thicknesses, including: determining the V-shaped bevel gap according to the formula G=0.171t-0.026, where G represents the V-shaped bevel root gap and t represents the aluminum alloy plate thickness; and determining the V-shaped bevel angle according to the formula θ=1.25t+42.5, where θ represents the V-shaped bevel angle.

[0010] Optionally, the welding parameters are set as follows: wire feed speed 9~11mm / s, welding current 120~155A, welding voltage 21~24V, welding speed 360mm / min, shielding gas is high-purity argon with a purity ≥99.99%, and gas flow rate 20L / min.

[0011] Optionally, the welding current waveform uses pulsed current, with pulses accounting for 50%.

[0012] Optionally, the welding process also includes selecting the corresponding heat input based on the plate thickness, where t ≤ 6mm, and the corresponding heat input is: ; 6 < t ≤ 20mm, the corresponding heat input is: For t > 20mm, the corresponding heat input is: In the formula, t is the thickness of the aluminum alloy plate; Q is the heat input; and k is the process constant.

[0013] Optionally, the heat treatment includes: solution treatment at 460℃~500℃ for 1~2 hours, followed by water quenching, aging treatment at 120℃~130℃ for 12~24 hours, and air cooling to room temperature.

[0014] Optionally, after welding is completed, the method further includes using a hybrid strengthening model of yield strength to quantitatively predict the strength of the obtained weld joint, wherein the hybrid strengthening model is the sum of solid solution strengthening, dislocation strengthening, grain boundary strengthening and precipitation strengthening.

[0015] According to another aspect of the present invention, an aluminum alloy welded joint is provided, which is welded by the aluminum alloy welding method described above.

[0016] The beneficial effects of this invention are:

[0017] (1) The novel welding wire of this invention incorporates rare earth elements Sc and Zr. Through the synergistic effect of these two rare earth elements, a thermally stable Al3(Sc, Zr) dispersed phase is formed during the welding process. The Sc / Zr elements added to the welding wire exist in the weld joint as secondary Al3(Sc, Zr) particles. During solidification, Al3(Sc, Zr) particles can act as heterogeneous nuclei, refine the microstructure, prevent grain growth during the treatment process, and inhibit recrystallization and dislocation density reduction during heat treatment. They can also play a precipitation strengthening role. In addition, Al3(Sc, Zr) particles can accelerate the nucleation and growth of the η′ phase, but this also consumes more Mg and Zn atoms in the matrix, inhibiting the formation of the η phase and the coarsening of the η′ phase during aging. These characteristics ensure that the aluminum alloy obtains good microstructure and properties during the welding process and the heat treatment of the weld joint, effectively inhibiting recrystallization and grain growth in the heat-affected zone of the weld and refining the weld microstructure.

[0018] (2) Based on this new type of welding wire, the present invention developed a suitable welding method and heat treatment process, established a mathematical model of groove gap and plate thickness, and corresponding heat input, through the grain boundary pinning effect of Sc / Zr composite phase and the synergistic effect of η' strengthening phase, and promoted the full dissolution of the second phase through solid solution treatment, and precipitated high-density nanoscale η' strengthening phase after aging treatment, so as to obtain a supersaturated solid solution with uniform composition, and obtained a high-quality welded joint (the tensile strength of the welded joint reaches up to 530 MPa, which is more than 95% of the base material).

[0019] (3) This invention achieves a synergistic improvement in high strength, high hardness and good toughness of high-strength aluminum alloy welded joints, solves the technical problems of low joint strength and unstable performance in traditional welding methods, and significantly enhances the corrosion resistance of welded joints. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 This is a schematic diagram of the welding equipment according to an embodiment of the present invention;

[0022] Figure 2 The stress-strain curve of the welded joint in Example 2;

[0023] Figure 3 Metallographic and SEM images of the weld zone of the welded joint in Example 2;

[0024] Figure 4 The stress-strain curve of the welded joint in Comparative Example 1 is shown.

[0025] Figure 5 Metallographic and SEM images of the weld zone of the welded joint in Comparative Example 1. Detailed Implementation

[0026] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this invention's description is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0028] The term "comprising" and its variations as used herein are open-ended inclusions, meaning "including but not limited to": the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the description below.

[0029] Example 1: In related technologies, aluminum alloys possess advantages such as low density, high strength, good corrosion resistance, and excellent processing performance, making them a key material for aircraft, automobiles, ships, and national defense. Among them, 7-series aluminum alloys have high strength and are widely used in critical load-bearing components, such as fuselage beams, automobile wheel hubs, and satellite structural frames. However, 7-series aluminum alloys have poor weldability and high hot cracking sensitivity, making welded joints prone to cracking. Conventional welding methods result in coarse grains in the heat-affected zone and weld zone, with obvious dendritic structures in the joint. In terms of mechanical properties, the strengths of MIG (Melt Inert-Gas Welding) and TIG (Tungsten Inert Gas Welding) welded joints are only 207 MPa and 233 MPa, respectively, far lower than the strength of the 7075 aluminum alloy base material (560 MPa). To ensure the safety and reliability of 7075 aluminum alloy welded joints, improving the mechanical properties of the welded joints has become an urgent problem to be solved.

[0030] To address the problems existing in the aforementioned related technologies, this embodiment provides a novel welding wire containing rare earth elements, and based on this novel welding wire, provides an aluminum alloy welding method.

[0031] This new type of welding wire incorporates the rare earth elements scandium (Sc) and zirconium (Zr) into 7085 aluminum alloy welding wire. Its chemical composition, by weight percentage, includes: Zn: 6.8~7.8%; Mg: 2.0~2.5%; Cu: 1.5~2.0%; Sc: 0.15~0.30%; Zr: 0.10~0.25%; Fe≤0.10%; Si≤0.08%; Mn≤0.50%; with the balance being Al and unavoidable impurities. Through the synergistic effect of the two rare earth elements Sc and Zr, this new welding wire forms a thermally stable Al3(Sc,Zr) dispersed phase during the welding process, solving the industry problem of coarse grains and low strength in 7-series aluminum alloy welded joints.

[0032] Furthermore, based on this novel welding wire, the present invention provides an aluminum alloy welding method, comprising the following steps:

[0033] S1, perform pre-welding treatment on the aluminum alloy base material to be welded, including processing bevel shapes corresponding to different plate thicknesses on the substrate before welding and mechanically grinding to remove the surface oxide film.

[0034] S2, using a new type of welding wire to perform MIG welding on the pretreated aluminum alloy base material, the welding parameters are set as follows: wire feed speed: 9~11mm / s, welding current: 120~155A, welding voltage: 21~24V, welding speed: 360mm / min, shielding gas is high-purity argon gas with a purity ≥99.99%, gas flow rate: 20L / min;

[0035] S3. The obtained welded joint is subjected to heat treatment, which includes: solution treatment at 460℃~500℃ for 1~2 hours, followed by water quenching, aging treatment at 120℃~130℃ for 12~24 hours, and air cooling to room temperature.

[0036] Solution treatment refers to a heat treatment process in which an alloy is heated to a high-temperature single-phase region and held at a constant temperature to allow the excess phase to fully dissolve into the solid solution, followed by rapid cooling to obtain a supersaturated solid solution. Because the operation process is similar to quenching, it is also called "solution quenching".

[0037] Aging treatment refers to a heat treatment process in which metal or alloy workpieces, after solution treatment, cold plastic deformation, or casting and forging, are placed at a relatively high temperature or kept at room temperature, causing their properties, shape, and dimensions to change over time. The purposes of aging treatment include relieving internal stress, stabilizing the microstructure and dimensions, and improving mechanical properties.

[0038] Reference Figure 1 , Figure 1 This is a schematic diagram of a welding device according to an embodiment of the present invention. Figure 1 As shown, during welding, the workpiece to be welded (the substrate in the figure, i.e. the aluminum alloy base material to be welded) is clamped and fixed on the worktable by a fixture. After the welding equipment is started, the welding wire is continuously fed to the welding area through the welding gun. At the same time, protective gas is introduced into the protective cover to isolate the air and provide protection until the welding is completed.

[0039] The Sc / Zr elements added to the novel welding wire of this invention exist in the weld joint as secondary Al3(Sc,Zr) particles. These Al3(Sc,Zr) particles act as heterogeneous nuclei during solidification, refining the microstructure, preventing grain growth during processing, and inhibiting recrystallization and dislocation density reduction during heat treatment, thus also playing a precipitation strengthening role. Furthermore, Al3(Sc,Zr) particles can accelerate the nucleation and growth of the η′ phase, but this also leads to the consumption of more Mg and Zn atoms in the matrix, inhibiting the formation of the η phase and the coarsening of the η′ phase during aging. These characteristics ensure that the aluminum alloy achieves good microstructure and properties during welding and heat treatment of the weld joint. After heat treatment, the tensile strength of the weld joint can reach 530 MPa, and the elongation is 5% (e.g., ...). Figure 2 The ultimate tensile strength reaches 95% of that of the parent material.

[0040] Furthermore, the synergistic effect of Sc / Zr / Mn enhances the corrosion resistance of the material, expands the passivation zone width in the heat-treated state to 0.28 V, and reduces the self-corrosion current density to 4.378 × 10⁻⁻⁻⁶. 7 A / cm² (an order of magnitude lower than the deposited state). The Al3(Sc, Zr) phase suppresses grain boundary segregation, while Mn elements form an Al6(Mn, Fe) dispersed phase (50~100 nm) that blocks Cl⁻ penetration pathways. After heat treatment, a continuous and dense Al2O3 passivation film forms on the surface, significantly improving long-term corrosion resistance and providing a reliable material solution for harsh working environments such as marine environments.

[0041] Furthermore, before welding, aluminum alloy sheets of different thicknesses should be processed into different bevel shapes to ensure that the sheets can be fully welded, thereby obtaining a welded joint with good performance.

[0042] The relationship between 7075 aluminum alloy sheets of different thicknesses and bevel parameters and heat input was summarized in Table 1.

[0043] Table 1: Relationship between aluminum alloy sheet material, bevel parameters, and heat input

[0044] Plate thickness (mm) V-groove dimensions (angle / gap / blunt edge) Heat input (KJ / cm) 6~8 50° / 1~1.5 mm / 2~3 mm 8~10 10~12 60° / 1.5~2 mm / 1.5~2 mm 10~12 14~16 65° / 2.5 mm / 1~1.5 mm 12~14 18~20 70° / 3 mm / 1 mm 14~15

[0045] The mathematical relationship between plate thickness and V-groove gap is established as: G = 0.171t - 0.026; G = V-groove root gap; t = aluminum alloy plate thickness. Root gap is a geometric parameter reserved at the root of the joint during the welding process. It is defined as the gap reserved between the roots of the joint before welding, and its core function is to ensure complete penetration at the root during the root pass.

[0046] The mathematical relationship between plate thickness and V-groove angle is: θ = 1.25t + 42.5; θ - V-groove angle. The V-groove angle refers to the combined angle of the two sides of the groove face. 60-70 degrees is the conventional range for V-groove angles, and this range is chosen based on a comprehensive consideration of welding process and material properties. Generally, a steeper groove angle (such as 60-70 degrees) is beneficial for the welding electrode or wire to penetrate deep into the bottom of the groove, ensuring root penetration of the weld, and is suitable for welding thicker plates. A smaller angle, however, may result in incomplete root penetration, affecting weld quality.

[0047] During welding, different heat inputs should be selected for different plate thicknesses, and the corresponding relationships are as follows:

[0048] Thin plates (≤ 6 mm): ;

[0049] Medium-thick plates (6 < t ≤ 20 mm): ;

[0050] Thick plate (t > 20 mm): ;

[0051] In the formula, Q: heat input; k: process constant (arc welding: 0.05~0.06); C: plate thickness correction coefficient (thin plate: 0.4, medium-thick plate: 0.5, thick plate: 0.6, which is reflected in the formula, i.e. 0.4, 0.5, 0.6 in the formula).

[0052] In summary, this invention provides a novel welding wire by adding rare earth elements to 7085 aluminum alloy welding wire. Based on this novel welding wire, an aluminum alloy welding method is provided for MIG welding of ultra-hard aluminum alloy plates of different thicknesses. A suitable welding process and heat treatment method are developed for this novel welding wire, and a mathematical model of bevel gap and plate thickness is established to improve the performance of the welded joint.

[0053] Furthermore, this invention establishes a novel hybrid strengthening model for the yield strength of welded joints made of aluminum alloy welding wire, which can quantitatively predict the strength of the welded joints. The formula is expressed as follows: ;

[0054] Yield strength, which mainly includes: solid solution strengthening ( ), dislocation enhancement ( Grain boundary strengthening ( ) and precipitation enhancement ( By integrating four strengthening mechanisms—solid solution, dislocation, grain boundary, and precipitation—the comprehensiveness and accuracy of intensity quantitative prediction are improved.

[0055] The contribution of solid solution strengthening can be evaluated using the Fleischer equation:

[0056] ;

[0057] ;

[0058] in, It is the Taylor orientation factor (3.06). It is the shear modulus (the shear modulus of 7xxx series alloys is approximately 26.9 GPa). This is the magnitude of the Burgers vector (aluminum has an FCC (face-centered cubic) structure, and its value is 0.286 nm). It is the concentration (wt.%). It is lattice strain, which can be calculated based on the size difference between solute and solvent atoms; Represents solute atoms; This represents solvent atoms.

[0059] Dislocation strengthening effects can be calculated using the Bailey-Hirsch relation:

[0060] ;

[0061] in, It is the constant of FCC metal (0.2). It is based on EBSD ( Electron Backscatter Diffraction, Dislocation density derived from electron backscatter diffraction (ESD) data.

[0062] The grain boundary strengthening contribution can be calculated using the modified Hall-Petch formula:

[0063] ;

[0064] in, This indicates high-angle grain boundary strengthening; This indicates low-angle grain boundary strengthening; The lattice friction resistance is 20 MPa. The Hall-Page constant is 0.22 MPa∙m. 1 / 2 ; It is the average grain size of high-angle grain boundaries (HAGBs); It is the grain boundary area per unit volume, which can be estimated using BA (grain boundary length per unit area), where =4BA / π; It is the average grain orientation difference of low-angle grain boundaries (LAGBs). This is the volume fraction of HAGBs.

[0065] Precipitation enhancement can be estimated using the following formula:

[0066] ;

[0067] ;

[0068] in, It is Poisson's ratio (Al is 0.33). and These are the volume fraction and radius of the precipitated phase, respectively. This represents the spacing of the precipitated phase.

[0069] The strength of the welded joint can be calculated using the above formula, which supports mechanical property testing.

[0070] Example 2: This example demonstrates the preparation of an aluminum alloy joint (i.e., the aluminum alloy welded joint of this invention) based on a novel 7085-Sc / Zr aluminum alloy welding wire (i.e., the novel welding wire containing rare earth elements in this invention) and a MIG pulsed current aluminum alloy welding method (i.e., the aluminum alloy welding method in this invention). The steps are as follows:

[0071] (1) Process 7075 super hard aluminum alloy plates of different thicknesses to form bevels with different root gap thicknesses;

[0072] (2) Continue to grind the surface of the 7075 super hard aluminum alloy sheet to remove its surface oxide layer;

[0073] (3) Use the new 7085-Sc aluminum alloy welding wire to perform MIG welding on two aluminum alloy plates of the same thickness. The welding current waveform adopts pulse current with a pulse ratio of 50%.

[0074] (4) Heat treatment of welded joints of various thicknesses: First, the sample is dissolved at 480 °C for 2 hours, then the sample is taken out and immediately placed in cold water for quenching, then aged at 120 °C for 24 hours, and finally cooled to room temperature in air to obtain a high-strength aluminum alloy welded joint.

[0075] (5) Perform tensile tests on the heat-treated welded joints, such as... Figure 2 As shown, the ultimate tensile strength of the welded joint is as high as 530 MPa, and the elongation at break is 5.5%.

[0076] (6) Conduct microstructural observation of the welded joint after heat treatment, such as... Figure 3 As shown, the weld is composed of equiaxed grains. Furthermore, the weld microstructure contains only a small amount of the second phase.

[0077] Comparative Example 1: This comparative example prepares an aluminum alloy joint based on a conventional 7085 aluminum alloy welding wire and a MIG pulsed current aluminum alloy welding method. The steps are as follows:

[0078] (1) Process 7075 super hard aluminum alloy plates of different thicknesses to form bevels with different root gap thicknesses;

[0079] (2) Continue to grind the surface of the 7075 super hard aluminum alloy sheet to remove its surface oxide layer;

[0080] (3) MIG welding was performed on two aluminum alloy plates of the same thickness using conventional 7085 aluminum alloy welding wire. The welding current waveform adopted pulse current with a pulse ratio of 50%.

[0081] (4) The welded joints of various thicknesses were subjected to T6 heat treatment: First, the sample was dissolved at 480℃ for 2 h, then the sample was taken out and immediately placed in cold water for quenching, then aged at 120℃ for 24 h, and finally cooled to room temperature in air to obtain the aluminum alloy welded joint.

[0082] (5) Perform tensile tests on the heat-treated welded joints, such as... Figure 4 As shown, the ultimate tensile strength of the welded joint is only 340 MPa, and the elongation at break is 2.5%.

[0083] (6) Conduct microstructural observation of the welded joint after heat treatment, such as... Figure 5 As shown, the grains within the weld are coarser. Simultaneously, the amount of the second phase within the weld microstructure is significantly greater.

[0084] In summary, through tensile testing and microstructure observation of the welded joints in Example 2 and Comparative Example 1, the welded joint prepared in Example 2 achieved grain refinement and second phase control during the welding process through composition optimization (addition of rare earth elements), and its mechanical properties and microstructure were superior to those of Comparative Example 1. This indicates that the use of the novel welding wire in this invention improves the mechanical properties and microstructure of the joint, which is superior to the use of traditional welding wire.

[0085] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0086] Those skilled in the art will understand that the purpose of this invention is to provide a relatively universal overall preparation process or technical principle, and to cover as many different applicable scenarios and conditions as possible (such as different raw material characteristics, production scale, product demand, etc.). Therefore, some specific operations can be flexibly adjusted according to the situation in actual implementation, as long as the expected or the same or similar technical effects as those in the embodiments of this invention can be achieved.

[0087] The steps in the method of this invention can be adjusted, combined, or deleted according to actual needs. The technical features can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the embodiments are described. However, as long as the combinations of these technical features do not contradict each other, they should be considered within the scope of this invention.

[0088] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for welding aluminum alloys, characterized in that, Welding is performed using a new type of welding wire. The chemical composition of the new welding wire, by weight percentage, includes: Zn: 6.8~7.8%; Mg: 2.0~2.5%; Cu: 1.5~2.0%; Sc: 0.15~0.30%; Zr: 0.10~0.25%; Fe≤0.10%; Si≤0.08%; Mn≤0.50%; the balance being Al and impurities. Pre-treatment of the aluminum alloy base material to be welded; MIG welding was performed on pretreated aluminum alloy base material using a new type of welding wire. The obtained aluminum alloy welded joint is heat-treated to complete the welding. The V-shaped bevel is machined according to different plate thicknesses, including: The V-groove gap is determined using the formula G=0.171t-0.026, where G represents the gap at the root of the V-groove and t represents the thickness of the aluminum alloy plate. The V-bevel angle is determined using the formula θ = 1.25t + 42.5, where θ represents the V-bevel angle. The welding parameters are set as follows: wire feed speed 9~11mm / s, welding current 120~155A, welding voltage 21~24V, welding speed 360mm / min, shielding gas is high-purity argon with a purity ≥99.99%, and gas flow rate 20L / min. The welding process also includes selecting the appropriate heat input based on the plate thickness, among which, For t ≤ 6mm, the corresponding heat input is: ; For a given value of 6 < t ≤ 20 mm, the corresponding heat input is: ; When t > 20mm, the corresponding heat input is: ; In the formula, t is the thickness of the aluminum alloy plate; Q is the heat input; and k is the process constant.

2. The aluminum alloy welding method according to claim 1, characterized in that, Pretreatment of the aluminum alloy base material to be welded includes: The corresponding V-shaped bevel is processed according to different plate thicknesses, and the oxide film on the surface of the aluminum alloy base material is removed by mechanical grinding.

3. The aluminum alloy welding method according to claim 2, characterized in that, The welding current waveform uses pulsed current, with pulses accounting for 50%.

4. The aluminum alloy welding method according to claim 3, characterized in that, The heat treatment includes: Solution treatment at 460℃~500℃ for 1~2 hours, followed by water quenching, and then aging treatment at 120℃~130℃ for 12~24 hours, followed by air cooling to room temperature.

5. The aluminum alloy welding method according to claim 4, characterized in that, After welding is completed, the method further includes using a hybrid strengthening model of yield strength to quantitatively predict the strength of the obtained weld joint, wherein the hybrid strengthening model is the sum of solid solution strengthening, dislocation strengthening, grain boundary strengthening and precipitation strengthening.

6. An aluminum alloy welded joint, welded using the aluminum alloy welding method according to any one of claims 1 to 5.

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