A method of synergistically strengthening and toughening the weld zone and heat-affected zone of an age-hardened aluminum alloy

Abstract

The application provides a synergistic toughening method for age-hardened aluminum alloy weld seam area and heat-affected area, the thickness of aluminum alloy base material to be welded is less than or equal to 2 mm, a low-composition filler wire which is matched with the composition of the aluminum alloy base material to be welded is selected, and a weld reinforcement with a deformation amount of 40%-150% relative to the thickness of the base material is obtained in the rolling process; the aluminum alloy welded joint is subjected to solid solution heat treatment to dissolve coarse overage strengthening phases; by adjusting the sequence of weld reinforcement rolling and aging heat treatment, setting the rolling depression amount and the aging time, the synergistic toughening of the joint strength and plasticity is realized. The application can completely solve the problem that the age-hardened aluminum alloy fusion welding seam cannot be effectively strengthened through post-weld heat treatment due to the evaporation of strengthening elements, and through the combination of rolling and heat treatment processes, the strength and hardness of the weld seam area and the heat-affected area are equivalent to those of the base material, so that the comprehensive mechanical properties such as the strength and plasticity of the age-hardened aluminum alloy welded joint are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of materials engineering technology and relates to a method for improving the mechanical properties of aluminum alloy welded joints. More specifically, it relates to a method for synergistic strengthening and toughening of the weld zone and heat-affected zone of age-hardening aluminum alloys. Background Technology

[0002] Using lighter and stronger materials in the automotive and aerospace manufacturing industries is one of the effective strategies to meet the energy-saving demands of global transportation applications. Age-hardening aluminum alloys, due to their excellent properties such as light weight, high specific strength, and good corrosion resistance, have become the most popular material in the transportation manufacturing industry. Welding is a crucial part of the manufacturing process for structural components. Unfortunately, age-hardening aluminum alloys have poor weldability; the tensile strength of the joint can only reach 50%-70% of the base material, while the elongation after fracture is only 40%-50% of the base material. This greatly limits the application potential of welded age-hardening aluminum alloy components.

[0003] Magnesium, zinc, and lithium, which play a major role in the age hardening of aluminum alloys, evaporate in large quantities during the welding process. Although filler wire can compensate for the evaporation of these elements, the high cracking tendency of age-hardening aluminum alloys during welding means that filler wire is generally not strengthened by heat treatment. Post-weld heat treatment can significantly strengthen the heat-affected zone by re-precipitating strengthening phases, but its strengthening effect on the weld is limited.

[0004] Furthermore, the invention patent with patent number 201911320768.6 proposes a process using excess roll forming to significantly work harden the weld and the heat-affected zone near the weld. However, aluminum alloys have high thermal conductivity, and the strengthening phases are easily affected by the welding thermal cycle. Therefore, the weld heat-affected zone is not only severely softened but also large in size. The excess roll forming process has limited strengthening effect on the heat-affected zone far from the weld. For age-hardening aluminum alloys with a base metal thickness greater than 2 mm, the joint strength and toughness using the excess roll forming process are still significantly lower than those of the base metal.

[0005] In summary, no process currently exists that can simultaneously strengthen both the weld zone and the heat-affected zone, leading to deformation concentration in the softening zone and significantly reducing the strength and plasticity of the welded joint. Therefore, there is an urgent need to develop new methods for the synergistic strengthening of age-hardening aluminum alloy joints, enabling a more uniform distribution of properties across all regions of the joint, reducing stress-strain concentration during service, improving the mechanical properties of the joint, and further exploring the application potential of age-hardening aluminum alloys. Summary of the Invention

[0006] To address the aforementioned issue of poor weldability in age-hardening aluminum alloys, and considering the limitations of current joint softening processes—specifically, the inability to simultaneously strengthen the weld zone and heat-affected zone—this invention provides a method for synergistic strengthening and toughening of the weld zone and heat-affected zone in age-hardening aluminum alloys. First, a filler wire welding process is used to achieve a weld reinforcement of a certain size. Then, solution heat treatment is applied to dissolve the coarse over-aged strengthening phases. Next, the sequence of reinforcement rolling and aging heat treatment, the aging time, and the rolling reduction are controlled to resolve the softening of the heat-affected zone through aging precipitation strengthening, while simultaneously resolving the softening of the weld through rolling work hardening. By controlling the matching of the strengthening effects of both, a consistent distribution of overall joint performance is achieved, thereby realizing synergistic strengthening and toughening of the joint's strength and plasticity. This invention can improve joint softening, enhance the uniformity of microhardness distribution in the joint, and enable the joint strength to reach 100% of the base metal strength, with elongation after fracture reaching over 90% of the base metal, achieving a significant improvement in the strength and plasticity of age-hardening aluminum alloy welded joints.

[0007] The technical means employed in this invention are as follows:

[0008] A method for synergistic strengthening and toughening of the weld zone and heat-affected zone of age-hardening aluminum alloy is disclosed. The thickness of the aluminum alloy base material to be welded is less than or equal to 2 mm. A low-composition filler wire compatible with the composition of the base material is selected to weld the joint, resulting in a weld with a certain height of excess material. This certain height refers to a deformation of 40%-150% relative to the thickness of the base material during rolling. After solution heat treatment of the welded aluminum alloy joint, the order of excess material rolling and aging heat treatment, the aging time, and the rolling reduction are controlled to address the softening of the heat-affected zone through aging precipitation strengthening, while simultaneously addressing the softening of the weld through rolling work hardening. By controlling the matching of the strengthening effects of both methods, a consistent distribution of the overall joint performance is achieved. This results in a more uniform hardness distribution among the locally rolled weld zone, the heat-affected softened zone strengthened by heat treatment, and the base material region, significantly improving both the strength and plasticity of the aluminum alloy joint, thereby achieving synergistic strengthening and toughening of the joint's strength and plasticity.

[0009] Furthermore, the welded joint adopts the filler wire welding method, and the welding parameters are adjusted as follows: welding speed, welding current, wire feed speed, wire feed angle and weld formation method.

[0010] Furthermore, the filler wire welding method refers to using a traditional heat source: either gas metal arc welding or tungsten inert gas welding; or using a high-energy beam heat source: either a laser-gas metal arc welding composite welding heat source, a laser-tungsten inert gas welding composite welding heat source, a laser beam welding heat source, an electron beam welding heat source, or a plasma arc welding heat source.

[0011] Furthermore, the welding process parameter range should meet the following requirements:

[0012] The wire feed speed ranges from 800 to 5000 mm / min, the wire feed angle ranges from 20 to 70°, the welding speed ranges from 120 mm to 1500 mm / min, the arc current range for gas metal arc welding or tungsten inert gas welding is 40 to 200 A, the welding torch angle is 45 to 90°, and the electrode height ranges from 1 mm to 3 mm. When using high-energy beam laser-arc hybrid welding, the laser power ranges from 350 to 2000 W, the laser defocusing adjustment range is -5 to 5 mm, the arc current range is 40 to 180 A, the laser beam-arc electrode spacing (Dla) adjustment range is 1.0 to 3.0 mm, and the wire spacing range is 2.0 to 5.0 mm.

[0013] Furthermore, the weld formation methods include free forming and forced forming. The free forming process involves the molten metal of the weld being formed under the action of gravity and surface tension during fusion welding. The forced forming process controls the size of the weld reinforcement by the shape of the groove in the backing plate.

[0014] Furthermore, during rolling, the final spacing of the rolls is set to be greater than or equal to the thickness of the base material being welded, meaning that only the weld reinforcement area is rolled. The rolling process parameters, namely the number of rolling passes and the amount of pressure applied per pass, are adjusted according to the weld performance requirements.

[0015] Furthermore, the temperature and time of the solution heat treatment process and the temperature and time of the aging heat treatment process after welding should be the same as those of the initial base material, so as to ensure that the heat-affected zone of the joint and the mechanical properties of the base material can be restored to the initial base material state after the post-weld heat treatment.

[0016] Furthermore, the sequence of rolling and aging heat treatment processes is adjusted according to the cracking tendency of the weld during the rolling process; the aging time allocation is determined based on the initial heat treatment process and properties of the base material, and the sequence of post-weld rolling and aging heat treatment, i.e., whether to adopt a step-by-step aging process.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The age-hardening aluminum alloy provided by this invention uses fusion welding, resulting in the evaporation of weld strengthening elements. A single post-weld heat treatment process cannot effectively improve the softening of the weld zone. Furthermore, due to severe softening in the heat-affected zone, a single post-weld excess roll process cannot effectively improve its softening. The method proposed in this invention combines the strengthening of the heat-affected zone by post-weld heat treatment with the strengthening of the weld zone by excess roll process, thus solving the softening problem of welded joints in age-hardening aluminum alloys.

[0019] 2. This invention can strengthen 2XXX and 7XXX high-strength aluminum alloy joints that are prone to cracking during the rolling process by changing the sequence of rolling and aging heat treatment.

[0020] 3. By controlling the sequence of high-pressure rolling and aging treatment, the rolling pressure, and the aging time allocation, the strengthening effect of the weld and heat-affected zone can be controlled. This can make the properties of the weld, heat-affected zone, and base material more consistent. While improving the joint strength, it can also significantly improve the joint plasticity, thus meeting the welding and manufacturing requirements of key components under high dynamic loads.

[0021] In summary, this invention addresses two key aspects: First, by using low-composition welding wire for filler welding, it achieves weld reinforcement in age-hardening aluminum alloys, and employs a forced forming process to control the dimensions of the reinforcement during welding. Second, it utilizes a solution treatment process on the welded joint to dissolve the over-aged strengthening phases back into the matrix. Then, by controlling the sequence of reinforcement rolling and aging treatment, the rolling reduction, and the aging time distribution, the strengthening effect of the weld zone and heat-affected zone is controlled. This results in more uniform properties across the joint area, significantly improving joint strength while simultaneously enhancing its plasticity and reducing the tendency for hot cracking.

[0022] This invention can completely solve the problem that age-hardening aluminum alloy fusion welds cannot be effectively strengthened by post-weld heat treatment due to the evaporation of strengthening elements, making the properties of the weld and heat-affected zone approach those of the base material, and achieving a significant improvement in the strength and plasticity of the welded joint. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the free forming (a) and forced forming (b) of the welding process in the synergistic strengthening and toughening method of the weld zone and heat-affected zone of age-hardening aluminum alloy of the present invention.

[0025] Figure 2 This is a schematic diagram of the residual height rolling process and joint microstructure evolution in the synergistic strengthening and toughening method of age-hardening aluminum alloy weld zone and heat-affected zone of the present invention.

[0026] Figure 3 This is a cloud map showing the joint hardness distribution of the weld zone and heat-affected zone of the age-hardening aluminum alloy according to the present invention. (a)-(d) show the microhardness distribution of the welded joint, the heat-treated joint, the high-residue rolled joint, and the synergistically strengthened joint, respectively.

[0027] Figure 4 This is the strain distribution during the tensile process of the synergistic strengthening and toughening method for the weld zone and heat-affected zone of age-hardening aluminum alloy according to the present invention.

[0028] Figure 5 This is a schematic diagram illustrating the strengthening mechanism of the synergistic strengthening and toughening method for the weld zone and heat-affected zone of age-hardening aluminum alloys according to the present invention.

[0029] Figure 6 These are the experimental results of the mechanical properties of the synergistic strengthening and toughening method for the weld zone and heat-affected zone of age-hardening aluminum alloys according to the present invention.

[0030] Figure 7 The diagram shows the microhardness distribution and tensile mechanical properties of the joints after aging treatment with different rolling reduction amounts and distributions for the synergistic strengthening and toughening method of the weld zone and heat-affected zone of the age-hardening aluminum alloy of the present invention. (a), (c) and (e) show the hardness distribution of the joints after synergistic strengthening treatment with rolling reduction amounts of 1.7 mm, 1.2 mm and 0.7 mm, respectively; (b), (d) and (f) show the tensile mechanical properties of the joints after synergistic strengthening treatment with rolling reduction amounts of 1.7 mm, 1.2 mm and 0.7 mm, respectively.

[0031] Figure 8 This is a flowchart of the method for synergistic strengthening and toughening of the weld zone and heat-affected zone of age-hardening aluminum alloy according to the present invention. Detailed Implementation

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0035] like Figure 8 As shown, the present invention provides a method for synergistic strengthening and toughening of the weld zone and heat-affected zone of age-hardening aluminum alloys, specifically including the following steps:

[0036] First, based on the composition of the aluminum alloy base material (i.e., the grade of the aluminum alloy base material), determine the composition of the filler wire, select a low-composition filler wire, and determine the filler wire welding method and optimized welding process parameters according to the thickness of the base material to achieve a specific size of excess height in the welded joint; in order to ensure that the weld can achieve effective work hardening through the excess height rolling process, the excess height should have a deformation of 40%-150% relative to the thickness of the base material during the rolling process.

[0037] Filler wire welding refers to the use of traditional heat sources: gas metal arc welding, tungsten inert gas welding; or high-energy beam heat sources: laser-gas metal arc welding composite welding heat source, laser-tungsten inert gas welding composite welding heat source, laser beam welding heat source, electron beam welding heat source or plasma arc welding heat source.

[0038] Therefore, the welding process parameters should meet the following ranges: wire feed speed range of 800–5000 mm / min, wire feed angle range of 20–70°, welding speed range of 120 mm–1500 mm / min, arc current range of 40–200 A for gas metal arc welding or tungsten inert gas welding, welding torch angle of 45–90°, and electrode height range of 1 mm–3 mm. When using high-energy beam laser-arc hybrid welding, the laser power range is 350–2000 W, the laser defocusing adjustment range is -5–5 mm, the arc current range is 40–180 A, the laser beam-arc electrode distance (Dla) adjustment range is 1.0–3.0 mm, and the wire spacing range is 2.0–5.0 mm.

[0039] Weld formation methods include free forming and forced forming (such as...) Figure 1 (As shown). The free-form weld process involves the molten metal of the weld being shaped under the influence of gravity and surface tension during fusion welding. The forced-form process controls the weld reinforcement dimension through the shape of the groove in the backing plate.

[0040] A composite post-treatment method is applied to aluminum alloy welded joints, including solution heat treatment, and then the order of weld reinforcement rolling and aging heat treatment, rolling reduction amount, and aging time are controlled to achieve a synergistic strengthening and toughening effect on the weld zone and heat-affected zone of the aluminum alloy welded joint.

[0041] The final gap between the rolls is set to be greater than or equal to the thickness of the welded plate, and a local rolling process is used for aluminum alloy welded joints (e.g., Figure 2As shown, the softening of the weld zone is improved by utilizing the work-strengthening effect; that is, only the weld reinforcement area is rolled, and the rolling process parameters, namely the number of rolling passes and the amount of pressure per pass, are adjusted according to the weld performance requirements. The temperature and time of the solution heat treatment process and the temperature and time of the aging heat treatment process after welding should be the same as those of the initial base metal to ensure that the mechanical properties of the heat-affected zone of the joint and the base metal can be restored to the initial base metal state after post-weld heat treatment.

[0042] Adjust the rolling and aging heat treatment process sequence according to the cracking tendency of the weld during the rolling process; determine the aging time allocation, i.e. whether to adopt a step-by-step aging process, based on the initial heat treatment process and properties of the base material and the process sequence of post-weld rolling and aging heat treatment.

[0043] like Figure 8 As shown, a solution treatment and aging heat treatment process is used for aluminum alloy welded joints to improve the softening of the heat-affected zone by utilizing the aging strengthening effect. By controlling the process sequence of local rolling and aging heat treatment, the rolling pressure and aging time are adjusted to control the strengthening effect of processing and aging on the joint.

[0044] The following example illustrates how to determine the aging time allocation based on the initial heat treatment process and properties of the base material, and the process sequence of post-weld rolling and aging heat treatment.

[0045] Example 1: Tungsten inert gas welding of 1.5mm thick 6061-T6 aluminum alloy sheet

[0046] The tungsten inert gas (TIG) welding current was 130A, the TIG height was 2mm, the welding speed was 350mm / min, the wire feed speed was 5000mm / min, and the welding wire grade was ER5356. The heat source was applied to the center of the weld, the wire feed angle was 20°, and cold wire feeding was used for forced forming. After welding, the joint underwent the same solution treatment and aging heat treatment process as the original base metal. It was solution treated at 530℃ for 1 hour in a heat treatment furnace, and immediately water-quenched after removal. Then, it was artificially aged at 170℃ for 8 hours in a heat treatment furnace, and immediately water-cooled after removal. Finally, it was rolled in one pass at room temperature with a 1.5mm gap between the two rolls, resulting in a deformation of approximately 127% relative to the base metal thickness in the excess area during rolling. Using the above-mentioned synergistic strengthening and toughening method for the age-hardening aluminum alloy weld and heat-affected zone, the ultimate tensile strength of the joint can reach 100% of that of the 6061-T6 base metal, and the elongation after fracture can reach over 67% of that of the 6061-T6 base metal.

[0047] When tungsten inert gas welding is performed without using the aforementioned methods to strengthen the softened zone of the aluminum alloy weld joint, the tensile strength of the welded specimen is only 70% of that of the 6061-T6 base material, and the elongation is approximately 44% of that of the 6061-T6 base material.

[0048] Example 2: High-energy beam laser-arc hybrid welding of 1mm 7075-T6 aluminum alloy sheet

[0049] The tungsten inert gas (TIG) welding current was 80A, tungsten electrode height was 1.5mm, laser power was 360W, laser defocusing was 0mm, the laser beam-to-arc electrode distance (Dla) was 2.0mm, the wire spacing was 2.0mm, the welding speed was 1200mm / min, the wire feed speed was 3000mm / min, the welding wire grade was ER5356, the wire feed angle was 20°, cold wire feeding was used, and the weld was freely shaped. After welding, the joint first underwent the same solution heat treatment process as the original base metal, solution treatment at 480℃ for 1 hour in a heat treatment furnace, followed by immediate water quenching. It was then rolled in one pass at room temperature, with a 1mm gap between the two rolls, resulting in a deformation of approximately 140% relative to the base metal thickness in the excess material during rolling. Finally, it underwent the same artificial aging heat treatment process as the original base metal, artificially aging at 165℃ for 6 hours in a heat treatment furnace, followed by furnace cooling to room temperature. By employing the aforementioned synergistic strengthening and toughening method for the weld zone and heat-affected zone of age-hardening aluminum alloys, the ultimate tensile strength of the joint can reach more than 90% of that of the 7075-T6 base material, and the elongation after fracture can reach more than 60% of that of the 7075-T6 base material.

[0050] Without employing the aforementioned strengthening methods for the softened zone of the aluminum alloy weld joint, the tensile strength of the welded specimen after tungsten inert gas welding (TIG) is only 70% of that of the 6061-T6 base material, and the elongation is approximately 43.2% of the 6061-T6 base material. Even with only a single heat treatment process after welding, the tensile strength of the specimen is only 80% of that of the 6061-T6 base material, and the elongation is approximately 44.7% of the 6061-T6 base material. However, with only a single excess height rolling process after welding, the tensile strength of the specimen can reach 84% of that of the 6061-T6 base material, but the elongation is only approximately 20.7% of the 6061-T6 base material. Therefore, the synergistic strengthening process proposed in this invention has significant advantages in improving joint performance.

[0051] Example 3: Optimization of Toughness of Tungsten Inert Gas Welding Joint in 1.5mm Thick 6061-T6 Aluminum Alloy Plate

[0052] according to Figure 3 It can be seen that the microhardness values ​​of the weld zone and the heat-affected zone near the weld of the synergistically strengthened joint are higher than the hardness values ​​of the original base material. Figure 4 It can be seen that the strain distribution of the joint during the tensile process is based on... Figure 3 It can be seen that the strain is concentrated in the softened region (the region with a microhardness value lower than that of the original parent material) and far away from the over-hardened region (the region with a microhardness value higher than that of the original parent material).

[0053] In Example 1, over-strengthening exists in the weld zone and the heat-affected zone near the weld, causing the joint strain to move away from this area during tensile testing. This uneven plastic deformation will reduce the toughness of the joint. Therefore, it is necessary to optimize the synergistic strengthening process to make the hardness distribution of the joint more uniform, and to significantly improve the toughness of the joint while improving its strength.

[0054] This over-hardening is due to the excessively strong work hardening effect in the weld zone and the heat-affected zone near the weld. Therefore, reducing the rolling pressure of the excess height can reduce the work hardening effect of the joint. Introducing subsequent aging processes to restore dislocations can also reduce the work hardening effect in the weld and the heat-affected zone near the weld.

[0055] The tungsten inert gas (TIG) welding current was 130A, the TIG height was 2mm, the welding speed was 350mm / min, the wire feed speed was 5000mm / min, the welding wire grade was ER5356, the heat source was applied to the center of the weld, the wire feed angle was 20°, cold wire feeding was used, and forced forming was employed. After welding, the joint underwent the same solution treatment and aging heat treatment process as the original base metal. It was solution treated at 530℃ for 1 hour in a heat treatment furnace, and immediately water-quenched after removal. Then, it underwent stepwise artificial aging at 170℃ in a heat treatment furnace, followed by a single rolling pass at room temperature. The distances between the two rolling rollers were set to 1.7mm, 1.2mm, and 0.7mm, respectively, so that the excess height portion would have approximately 113%, 80%, and 47% deformation relative to the base metal thickness during rolling, respectively. Finally, it underwent a second aging process to ensure the total aging time reached the same 8 hours as the base metal. The specific synergistic strengthening process parameters are shown in Table 1.

[0056] Figure 5 It can be seen that the strengthening mechanism of the softened zone of the 6061-T6 aluminum alloy welded joint is mainly through the superposition of precipitation strengthening and work hardening effects.

[0057] like Figure 6 The figure shows the mechanical properties of 6061-T6 aluminum alloy welded joints after different post-weld treatment processes. It can be seen that the ultimate tensile strength and elongation after fracture of the joints after the synergistic strengthening process are significantly improved, indicating that the strength and toughness of the softened zone of the welded joints are improved.

[0058] Microhardness distribution and tensile properties of the joint after optimization of synergistic strengthening process parameters are as follows: Figure 7 As shown, by employing the aforementioned synergistic strengthening and toughening method for age-hardening aluminum alloy welds and heat-affected zones, when the excess weld height undergoes deformation relative to 80% of the base metal thickness during rolling, the ultimate tensile strength of the joint can reach 100% of that of the 6061-T6 base metal, and the elongation after fracture can reach over 90% of that of the 6061-T6 base metal. This demonstrates that the optimized synergistic strengthening process can significantly improve the joint toughness.

[0059] Table 1 Optimization of Synergistic Enhancement Process Parameters

[0060]

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for synergistic strengthening and toughening of the weld zone and heat-affected zone of age-hardening aluminum alloy, characterized in that: The thickness of the aluminum alloy base material to be welded is less than or equal to 2 mm. A low-composition filler wire compatible with the composition of the base material is selected for welding the joint. A filler wire welding method is used to obtain a weld reinforcement height of a certain degree, which refers to a deformation of 40%-150% relative to the base material thickness during rolling. Solution heat treatment is applied to the aluminum alloy welded joint to dissolve the coarse over-aged strengthening phases. By controlling the sequence of weld reinforcement rolling and aging heat treatment, and setting the rolling pressure and aging time, the strengthening effects of both are matched to achieve consistency in the overall joint performance. The distribution of weld reinforcement is used to achieve synergistic strengthening and toughening of joint strength and plasticity. Specifically, the sequence of weld reinforcement rolling and aging heat treatment is adjusted according to the cracking tendency of the weld during rolling. Specifically, when the cracking tendency is high, reinforcement rolling is performed first, followed by aging heat treatment; when the cracking tendency is low, aging heat treatment is performed first, followed by reinforcement rolling. The aging time allocation, i.e., whether to adopt a step-by-step aging process, is determined based on the initial heat treatment process and properties of the base material and the sequence of post-weld rolling and aging heat treatment. During rolling, the final spacing of the rolls is set to be greater than or equal to the thickness of the base material, that is, only the weld reinforcement area is locally rolled. The rolling process parameters, namely the number of rolling passes and the amount of pressure per pass, are adjusted according to the weld performance requirements. The temperature and time of solution heat treatment after welding and the temperature and time of aging heat treatment should be the same as those of the initial base material.

2. The method for synergistic strengthening and toughening of the weld zone and heat-affected zone of age-hardening aluminum alloy according to claim 1, characterized in that, The welded joint adopts the filler wire welding method. The welding parameters to be adjusted include the following: welding speed, welding current, wire feed speed, wire feed angle and weld formation method.

3. The method for synergistic strengthening and toughening of the weld zone and heat-affected zone of age-hardening aluminum alloys according to claim 2, characterized in that, The filler wire welding method refers to using a traditional heat source: either gas metal arc welding or tungsten inert gas welding; or using a high-energy beam heat source: either a laser-gas metal arc welding composite welding heat source, a laser-tungsten inert gas welding composite welding heat source, a laser beam welding heat source, an electron beam welding heat source, or a plasma arc welding heat source.

4. The method for synergistic strengthening and toughening of the weld zone and heat-affected zone of age-hardening aluminum alloys according to claim 3, characterized in that, The welding process parameters should meet the following range: The wire feed speed range is 800~5000mm / min, the wire feed angle range is 20~70°, the welding speed range is 120mm~1500mm / min, the arc current range is 40~200A, the welding torch angle is 45~90°, and the electrode height range is 1mm~3mm when using high-energy beam laser-arc hybrid welding. The laser power range is 350~2000W, the laser defocusing adjustment range is -5~5mm, the arc current range is 40~180A, the laser beam-arc electrode spacing Dla adjustment range is 1.0~3.0mm, and the wire spacing range is 2.0~5.0mm.

5. The method for synergistic strengthening and toughening of the weld zone and heat-affected zone of age-hardening aluminum alloys according to claim 1, characterized in that, Weld formation methods include free forming and forced forming. The free forming process is the formation of the weld by the liquid metal under the action of gravity and surface tension during fusion welding. The forced forming process controls the size of the weld reinforcement by the shape of the groove in the backing plate.

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