A high-strength connection method for 6000 series medium-strength aluminum alloys

Abstract

This invention belongs to the field of metal material joining technology, specifically relating to a high-strength joining method for 6000 series medium-strength aluminum alloys. The method includes: surface treatment and clamping of the end faces of the 6000 series medium-strength aluminum alloy workpieces to be joined; performing cold pressure welding or electro-pulse assisted pressure welding on the workpieces to be joined, causing plastic deformation of the end faces and forming a joint; subsequently performing electro-pulse aging treatment on the joint, or performing electro-pulse solution treatment followed by electro-pulse aging treatment. This invention utilizes the grain refinement, dislocation multiplication, and work hardening generated by the plastic deformation of pressure welding, combined with the Joule heating effect, electroplastic effect, and electron wind effect generated by electro-pulse treatment, to promote the diffusion of Mg and Si atoms and the precipitation of the Mg2Si strengthening phase. Through the above method, welding defects and joint softening problems can be reduced, and the strength of 6000 series medium-strength aluminum alloy joints can be improved. It is suitable for solid-state joining of 6000 series aluminum alloy wires, bars, or plates such as 6061, 6063, and 6082.

Description

Technical Field

[0001] This invention relates to the field of metal material joining technology, specifically a high-strength joining method for 6000 series medium-strength aluminum alloys. Background Technology

[0002] 6000 series aluminum alloys mainly include 6061, 6063, and 6082, etc. They have good machinability, moderate strength, and corrosion resistance, and are widely used in transportation, building structures, electronic product casings, and other lightweight structural components. These aluminum alloys are typical heat-treatable aluminum alloys, and their mechanical properties mainly come from the strengthening phases such as Mg2Si precipitated after aging treatment.

[0003] In the joining of 6000 series aluminum alloys, traditional fusion welding methods such as tungsten inert gas welding (TIG) and metal inert gas welding (MIG) subject the joint area to melting and solidification processes. Due to the large heat input during welding, the weld zone and heat-affected zone are prone to microstructural changes such as grain growth, dissolution or coarsening of strengthening phases, recovery, and recrystallization, resulting in welded joints with significantly lower mechanical properties than the base metal. Furthermore, the melting and rapid solidification processes of aluminum alloys can easily generate metallurgical defects such as porosity and hot cracks, affecting the joint's density and reliability.

[0004] To avoid defects in fusion welding, solid-state joining techniques such as friction stir welding have been used for joining aluminum alloys. While these methods can prevent complete melting of the weld area, they still generate high temperatures during the welding process, which can easily cause softening in the joint area of ​​6000 series aluminum alloys. Furthermore, friction stir welding has high requirements for equipment, workpiece shape, and clamping conditions, limiting its application scenarios.

[0005] Therefore, there is an urgent need for a connection method that can effectively connect 6000 series medium-strength aluminum alloys and reduce joint softening, welding defects and equipment application limitations, so that the connection joint can obtain mechanical properties equivalent to or even exceeding those of the base material, in order to meet the demand for high-quality connections of 6000 series aluminum alloys in transportation, lightweight structural components and engineering equipment.

[0006] A search revealed Chinese patent documents, such as the patents for a cold-press welding connection and heat treatment method for ultra-high-strength aluminum alloys [Application No.: 202511764663.5, Publication No.: CN121491741A] and a patent for a cold-press welding connection and heat treatment method for high-strength weldable aluminum alloys [Application No.: 202511762828.5, Publication No.: CN121315646A]. While these technologies can improve the joint strength of 7000 series aluminum alloys, their alloy systems, strengthening mechanisms, welding temperatures, and heat treatment methods differ from those of 6000 series aluminum alloys. 6000 series aluminum alloys primarily rely on Mg and Si atomic diffusion and Mg2Si strengthening phase precipitation for strengthening; therefore, the post-joining microstructure recovery and performance improvement mechanisms differ from those of 7000 series aluminum alloys. Thus, it remains necessary to develop suitable high-strength joining methods for medium-strength 6000 series aluminum alloys. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of this invention is to provide a high-strength connection method for 6000 series medium-strength aluminum alloys.

[0008] A high-strength connection method for 6000 series medium-strength aluminum alloys, characterized by comprising the following steps: S1. Perform surface treatment on the end faces of the 6000 series medium-strength aluminum alloy workpieces to be joined, and clamp the workpieces to be joined in the pressure welding equipment to align the end faces to be joined. S2. Perform pressure welding on the workpieces to be connected to cause plastic deformation of the end faces to be connected and form a connecting joint; S3. Apply an electrical pulse treatment to the connection joint, the electrical pulse treatment including electrical pulse aging treatment, or including electrical pulse solution treatment and electrical pulse aging treatment; The pressure welding process is either cold pressure welding or electric pulse assisted pressure welding. The electric pulse process is used to promote the diffusion of Mg and Si atoms and the precipitation of Mg2Si strengthening phase in the joint, so as to improve the strength of the 6000 series medium-strength aluminum alloy joint.

[0009] Preferably, the 6000 series medium-strength aluminum alloy is one of 6061 aluminum alloy, 6063 aluminum alloy, or 6082 aluminum alloy; the workpiece to be connected is a wire, bar, or plate.

[0010] The above technical solution enables this connection method to be applied to common 6000 series medium-strength aluminum alloys, and allows for connection based on the actual workpiece shape. 6000 series aluminum alloys are all heat-treatable and their performance improvement is closely related to Mg and Si atomic diffusion and Mg2Si strengthening phase precipitation. Therefore, a combination of pressure welding and electrical pulse treatment is suitable for improving the strength of the joint.

[0011] Specifically, 6061, 6063, and 6082 aluminum alloys all possess a certain degree of plastic deformation capability and age-hardening potential. They can undergo end-face plastic flow during pressure welding and subsequently exhibit microstructure recovery and precipitation strengthening during electro-pulse solution treatment or aging. Wire, bar, and small plate materials offer good operability in clamping, upsetting, and electro-pulse energizing path setup, which is beneficial for forming stable joints.

[0012] In practical applications, the limitation of materials and workpiece types enables the present invention to be applied to the connection of 6000 series aluminum alloy parts commonly used in transportation, lightweight structural components, electronic product housings and engineering equipment, and allows for the selection of appropriate pressure welding and electrical pulse processing solutions according to different sizes and shapes.

[0013] Preferably, in the cold pressure welding process, the single-pass upsetting displacement is 4-8mm, the pressure welding is repeated 4-6 times, the burrs formed by the pressure welding are removed after the pressure welding is completed, and the joint is ground.

[0014] The above technical solution enables sufficient plastic deformation of the end faces to be joined through multiple cold pressure welding passes, forming an initial joint. This method, which controls the upsetting displacement of each pass and repeats the welding passes, helps to break the oxide film on the surface of the end faces to be joined and allows the fresh metal substrate to come into contact and form a solid bond.

[0015] Specifically, during cold pressure welding, the end faces to be joined undergo plastic flow under significant upsetting pressure. The surface oxide film is broken up and expelled with the flash, allowing the internal metals of the end faces to gradually come into direct contact. Repeated pressure welding increases the degree of plastic deformation, resulting in grain refinement, dislocation multiplication, and work hardening in the joint area. Removing flash and grinding improve the joint shape, providing stable clamping and energizing conditions for subsequent electroporation solution treatment or aging.

[0016] In practical applications, this cold pressure welding step can avoid melting and solidification defects in the fusion welding process, reduce problems such as porosity and hot cracking, and provide a solid-phase connection base for subsequent electrical pulse processing, thereby improving the reliability of 6000 series aluminum alloy connection joints.

[0017] Preferably, the electrical pulse aging process includes: clamping the connector between the electrodes of the electrical pulse processing device, positioning the connector between the two electrodes, starting the pulse power supply and monitoring the temperature of the connector; when the temperature reaches 170-180°C, maintaining the temperature stability by adjusting the duty cycle or current density; keeping the temperature for 2-10 minutes, then turning off the pulse power supply and allowing the connector to cool naturally to room temperature.

[0018] The above technical solution enables aging strengthening of the joint in a short time, resulting in precipitation strengthening in the joint area that enhances strength. This method of heating by electric pulse and maintaining the aging temperature facilitates the combined promotion of Mg and Si atom diffusion and accelerates the formation of the Mg2Si strengthening phase by utilizing the Joule heating effect and the non-thermal effect of the electric pulse.

[0019] Specifically, placing the connector between the two electrodes allows the pulsed current to pass through the connector area and generate a localized heating effect. Real-time monitoring of the connector temperature and adjustment of the temperature by duty cycle or current density can keep the connector stable within the aging temperature range. Compared with conventional furnace aging, electric pulse aging can enable the connector area to quickly reach the target temperature and complete the precipitation process of the strengthening phase in a shorter time.

[0020] In practical applications, this electrical pulse aging method can reduce the time required for traditional aging treatment, improve the efficiency of post-processing of joints, and make the high-density dislocations introduced by cold pressure welding become non-uniform nucleation sites for strengthening phases, thereby improving the strength and service stability of joints.

[0021] Preferably, the parameters for the electrical pulse aging process are: pulse frequency 20-40kHz, peak current density 40-60A / mm², duty cycle 20%-40%, and pulse width 10-20μs.

[0022] The above technical solution provides a stable range of electrical parameters for electrical pulse aging treatment, enabling the joint to complete the strengthening treatment under appropriate heating and insulation conditions. This method of limiting the pulse frequency, peak current density, duty cycle, and pulse width helps to avoid insufficient aging due to excessively low electrical pulse input, and also avoids overheating of the joint due to excessively high electrical pulse input.

[0023] Specifically, the pulse frequency and pulse width affect the current application time and frequency, the peak current density affects the joint heating rate and electro-induced intensity, and the duty cycle affects the average heat input. By coordinating these parameters, the joint area can be kept stable within the range of 170-180℃, and the diffusion of Mg and Si atoms and the precipitation of the Mg2Si strengthening phase can be promoted.

[0024] In practical applications, this parameter range is easy to adjust according to different sizes of wires, rods or plates, which helps to control heat input while ensuring aging effect, so that the joint can obtain better mechanical properties and structural stability.

[0025] Preferably, the electro-pulse solution treatment includes: clamping the cold-pressed welded connector between the electrodes of the electro-pulse treatment equipment, applying a pulse current to heat the connector to 520-540℃, holding it at that temperature for 3-10 seconds, stopping the pulse current, and then rapidly quenching the connector; the parameters of the electro-pulse solution treatment are: pulse frequency 40-80kHz, peak current density 100-120A / mm², duty cycle 15%-30%, and pulse width 3-6μs.

[0026] The above technical solution enables solution treatment of the joint to be completed in a short time, providing a supersaturated solution basis for subsequent aging strengthening. This method of rapid heating with high-density pulsed current, short-time holding and rapid quenching is beneficial for promoting the rapid solution of Mg and Si atoms and preserving the solution state of the joint to room temperature.

[0027] Specifically, during the electro-pulse solution treatment process, the high-density pulsed current generates Joule heating when passing through the connector, rapidly raising the connector to the solution temperature range. Simultaneously, the electron wind effect generated by the electro-pulse promotes the diffusion of Mg and Si atoms, allowing them to dissolve into the aluminum matrix within a short holding time. Rapid quenching inhibits premature precipitation of solute atoms during cooling, providing conditions for the formation of fine strengthening phases during subsequent electro-pulse aging.

[0028] In practical applications, this electro-pulse solution treatment can significantly shorten the conventional solution treatment time and reduce grain coarsening and joint softening problems caused by prolonged high-temperature treatment. Combining it with subsequent electro-pulse aging treatment enables 6000 series aluminum alloy joints to achieve higher strength.

[0029] Preferably, the electro-pulse assisted pressure welding process includes: clamping the workpiece to be joined in the pressure welding equipment, and connecting the pulse power supply electrode to the workpiece to be joined so that the current path passes through the end face to be joined; performing upsetting pressure welding while starting the pulse power supply, with an upsetting displacement of 4-8 mm and the workpiece temperature controlled at 150-180℃; wherein, the parameters of the electro-pulse assisted pressure welding process are: pulse frequency 20-40 kHz, peak current density 50-80 A / mm², duty cycle 40%-60%, and pulse width 10-30 μs.

[0030] The above technical solution enables the simultaneous introduction of electrical pulses during the pressure welding process, causing the end faces to be joined to undergo plastic deformation under the assistance of the electrical pulses and form a joint. This method of allowing the current path to pass through the end faces to be joined is beneficial for generating Joule heating and electroplastic effects in the interface region, thereby reducing the resistance to pressure welding deformation and improving the interface bonding quality.

[0031] Specifically, when the electrical pulse current passes through the end face to be joined, it can maintain the temperature of the joint area within a certain range and promote dislocation movement and atomic diffusion. Under the action of the electrical pulse, the high-density dislocations introduced by cold pressure welding may rearrange and annihilate, thereby reducing the local deformation resistance of the material. At the same time, the upsetting pressure causes the oxide film on the end face to break and be discharged, making it easier for the fresh metal surface to form a stable bond under the assistance of the electrical pulse.

[0032] In practical applications, pulse-assisted pressure welding can reduce the deformation resistance required for simple cold pressure welding, improve the controllability of the pressure welding process, and help improve the joint interface quality. It is especially suitable for 6000 series aluminum alloy connection scenarios where joint strength, processing efficiency and equipment load are required.

[0033] Preferably, after the electro-pulse assisted pressure welding process, the process further includes a repeated pressure welding transition stage and an in-situ electro-pulse heat preservation and aging stage. In the repeated pressure welding transition stage, the electro-pulse is maintained, the upsetting pressure is stopped, the die is released and reset, the workpiece is clamped again for upsetting, and the pressure welding is repeated 3-5 times. During the repeated pressure welding process, the peak current density is adjusted to 30-50A / mm², the duty cycle is adjusted to 20%-30%, and the temperature is stabilized at 170-180℃. In the in-situ electro-pulse heat preservation and aging stage, after the pressure welding is completed and the upsetting force is removed, the electro-pulse is maintained. The pulse frequency is 10-30kHz, the peak current density is 20-40A / mm², the duty cycle is 15%-25%, the pulse width is 10-20μs, the temperature is maintained at 170-180℃, the duration is 2-8min, and then the pulse power supply is turned off and the workpiece is allowed to cool naturally to room temperature.

[0034] The above technical solution combines electrical pulse-assisted pressure welding, repeated pressure welding, and in-situ electrical pulse aging continuously, allowing the joining and strengthening processes to be completed under the same clamping condition. This process arrangement helps reduce repeated disassembly and assembly of workpieces, improves processing efficiency, and ensures that the deformed structures formed during pressure welding participate in subsequent aging strengthening in a timely manner.

[0035] Specifically, the repeated pressure welding transition stage, by reducing the peak current density and duty cycle, prevents the workpiece temperature from continuing to rise and stabilizes the temperature within the aging temperature range. Multi-pass pressure welding further promotes end-face plastic flow and interfacial bonding, forming refined grains and a high-density dislocation structure. Subsequent in-situ holding aging with continued electrical pulses utilizes the dislocations and interfacial structures formed after pressure welding as favorable sites for precipitation strengthening, promoting the formation of the Mg2Si strengthening phase.

[0036] In practical applications, this in-situ continuous processing method integrates joining, temperature control, and aging strengthening into a single process flow, shortening the process cycle and improving joint strength. For 6000 series aluminum alloy workpieces such as wires, bars, and small plates, this method offers good operational continuity and engineering applicability.

[0037] Compared with the prior art, the present invention has the following advantages: 1. This invention combines pressure welding with electro-pulse solution treatment, electro-pulse aging, or electro-pulse assisted pressure welding to further strengthen the microstructure of 6000 series medium-strength aluminum alloy joints on the basis of solid-state bonding. This method avoids defects such as porosity and hot cracking caused by melting and solidification during fusion welding. At the same time, it utilizes the grain refinement, dislocation multiplication, and work hardening brought about by the plastic deformation of pressure welding to provide a microstructure basis for subsequent electro-pulse treatment, making the joint strength closer to or exceeding the level of the base material.

[0038] 2. This invention utilizes the Joule heating effect, electroplastic effect, and electron wind effect generated by electrical pulse treatment to promote the diffusion of Mg and Si atoms and the precipitation of the Mg2Si strengthening phase. Traditional solution treatment and aging treatments, due to prolonged high-temperature heating, result in a certain degree of grain growth and microstructure recovery in the joint area, and their final strength usually cannot exceed the level of the base material, with heat treatment cycles lasting several hours. This invention, utilizing electrical pulse technology, can complete the joint heat treatment process in seconds or minutes, greatly improving efficiency and achieving a strengthening effect on the joint that surpasses traditional heat treatment processes through unique non-thermal effects.

[0039] 3. This invention provides multiple process routes, including cold pressure welding followed by electrical pulse aging, cold pressure welding followed by electrical pulse solution treatment and then electrical pulse aging, and electrical pulse-assisted pressure welding followed by in-situ electrical pulse aging. The appropriate route can be selected based on connection strength, efficiency, cost, and workpiece shape. This method is applicable to 6000 series medium-strength aluminum alloy workpieces of various shapes, such as wire, bar, and small plates, and offers good process flexibility and engineering application adaptability. Attached Figure Description

[0040] Figure 1 This is a transmission electron microscope image of the 6061 aluminum alloy cold-pressed welded head of the present invention; Figure 2 These are mechanical property diagrams of 6061 aluminum alloy joints manufactured using different processes according to this invention; Figure 3 This is a metallographic diagram of the 6061 aluminum alloy connector of the present invention. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. All equivalent substitutions, improvements, and variations made within the spirit and principles of the present invention should fall within the scope of protection of the present invention.

[0042] This invention provides a high-strength joining method for 6000 series medium-strength aluminum alloys, applicable to heat-treatable 6000 series aluminum alloys such as 6061, 6063, and 6082. The joining method combines pressure welding with electro-pulse solution treatment, electro-pulse aging, or electro-pulse assisted pressure welding. It utilizes the intense plastic deformation, grain refinement, and dislocation multiplication generated by pressure welding, combined with the Joule heating effect, electroplastic effect, and electron wind effect generated by the electro-pulse, to promote metallurgical bonding and precipitation of the Mg2Si strengthening phase in the joint, thereby improving the mechanical properties of the joint.

[0043] Specifically, during cold pressure welding, the end faces of the 6000 series aluminum alloy to be joined undergo plastic flow under the upsetting pressure. As the degree of deformation increases, dislocations in the weld region continuously multiply, entangle, intersect, and slip, forming subgrain boundaries such as dislocation cells and dislocation walls, and resulting in work hardening. When the degree of deformation further increases, the original grains are broken and divided into finer subgrains, and smaller, more dispersed equiaxed grains can be formed. For example... Figure 1 As shown in (a), the severe deformation of cold pressure welding can form nanocrystals and high-density dislocations in the joint area.

[0044] Cold pressure welding can also break the surface oxide film on the ends to be joined, and remove the oxide film along with the flash generated during the pressure welding process, allowing the fresh metal substrate to directly contact and form a solid bond. Since this process does not involve metal melting and solidification, it can reduce defects such as porosity and hot cracking that are common in fusion welding.

[0045] In the process of pulse-assisted pressure welding, the pulse power supply electrode is connected to the workpiece to be joined, so that the current path passes through the interface to be joined. When the high-density pulse current passes through the metal, it can reduce the activation energy of dislocation motion and promote the rearrangement and annihilation of high-density dislocations introduced by cold pressure welding, thereby generating an electroplastic effect, reducing the deformation resistance of pressure welding and improving the bonding quality of the joint interface.

[0046] During the electro-pulse solution treatment process, a cold-pressed welding head is clamped between the electrodes of the electro-pulse treatment equipment, allowing a high-density pulsed current to pass through the connector. The Joule heat generated by the electro-pulse rapidly heats the connector to the solution temperature range. Simultaneously, the electron flow interacts with Mg and Si atoms, promoting their diffusion and allowing them to dissolve into the aluminum matrix within a short time. Subsequently, rapid quenching preserves the supersaturated solution state to room temperature, providing the microstructure basis for subsequent aging treatment.

[0047] During electro-pulse aging treatment, the cold-pressed welded joint or the joint after electro-pulse solution treatment is heated to the aging temperature range under the action of the electro-pulse. The electro-pulse can promote the diffusion of Mg and Si atoms and form a Mg2Si strengthening phase in the joint region. Figure 1 As shown in (b), after aging treatment, the precipitated phase in the joint region can interact with dislocations, thereby strengthening the joint.

[0048] like Figure 2 As shown, 6061 aluminum alloy connecting joints treated with different processes exhibit different mechanical properties. Cold pressure welding followed by electro-pulse aging treatment achieves higher joint strength; cold pressure welding followed by electro-pulse solution treatment and then electro-pulse aging treatment, as well as electro-pulse assisted pressure welding followed by in-situ electro-pulse aging treatment, can further improve the joint strength. Combined with… Figure 3 As shown in the metallographic structure, the joint obtained by the present invention has a good interface bonding, and no obvious cracks, pores or unwelded areas are observed.

[0049] In this invention, the pressure welding process can be either cold pressure welding or electrical pulse-assisted pressure welding. The electrical pulse treatment can be selected based on process requirements, such as electrical pulse aging treatment, or electrical pulse solution treatment followed by electrical pulse aging treatment. Different process combinations can be used to adapt to different workpiece sizes, connection strength requirements, and production efficiency requirements.

[0050] Example 1: Cold pressure welding followed by electrical pulse aging treatment to connect 6061-T6 aluminum alloy wire This embodiment uses a cold pressure welding and electric pulse aging treatment method to connect 6061-T6 aluminum alloy wires.

[0051] (1) Material preparation: Take two 6061-T6 aluminum alloy wires with a length of 140mm and a diameter of 3mm, and grind the end faces to be connected flat.

[0052] (2) Cold pressure welding: The two wire sections are clamped in the hydraulic butt cold pressure welding machine mold and aligned. The hydraulic cylinder is started to push the mold to clamp the wire, so that the end face to be connected undergoes a single-pass upsetting displacement of 6mm. The end face metal is extruded to form an "8" shaped flash. After completing one pass, the mold is reset and the next pass of cold pressure welding is performed. The welding is repeated for 4 passes.

[0053] (3) Electrical pulse aging treatment: Remove the annular burrs at the cold-pressed welded joint and grind them smooth. Then, clamp the cold-pressed welded joint between the electrodes of the electrical pulse treatment equipment with a clamping length of approximately 200mm, ensuring the joint is positioned between the two electrodes. Start the pulse power supply and monitor the joint temperature in real time. When the temperature reaches 170-180℃, maintain temperature stability by adjusting the duty cycle or current density. After holding at this temperature for 6 minutes, turn off the pulse power supply and allow the joint to cool naturally to room temperature. The electrical pulse aging parameters are: pulse frequency 20-40kHz, peak current density 40-60A / mm², duty cycle 20%-40%, and pulse width 10-20μs.

[0054] (4) Performance Testing and Microstructure Observation: Tensile tests were conducted on an electronic tensile testing machine according to GB / T 228.1-2021. The connecting joint was placed in the middle of the specimen, with a specimen length of 200 mm, a gauge length of 100 mm, and a tensile speed of 9 mm / min. Three valid test samples were used for each state. The test results showed that the average tensile strength of the connecting joint was 271.4 MPa, which was 90.0% of the tensile strength of the base material; the average yield strength was 262.5 MPa, and the average elongation was 2.2%. The tensile specimens fractured near the joint, exhibiting a certain degree of plasticity. Metallographic observation showed that the joint interface was well bonded, with no defects such as cracks or pores.

[0055] The mechanical property test results of 6061-T6 aluminum alloy wires connected by cold pressure welding and electric pulse aging treatment are shown in Table 1: Table 1 process Serial Number Tensile strength / MPa Yield strength / MPa Elongation / % Average tensile strength / MPa Average yield strength / MPa Average elongation / % parent material 1 310.7 298.32 7.5 301.6 288.6 6.8 parent material 2 294.0 281.13 5.9 parent material 3 299.9 286.44 7.1 Cold pressure welding + aging 1 257.4 243.2 2.7 271.4 262.5 2.2 Cold pressure welding + aging 2 280.4 275.2 1.9 Cold pressure welding + aging 3 276.3 269.2 2.0 Example 2: Cold pressure welding with electro-pulse solution treatment and aging treatment to connect 6061-T6 aluminum alloy bars In this embodiment, 6061-T6 aluminum alloy bars are connected by cold pressure welding followed by electric pulse solution treatment and then electric pulse aging treatment.

[0056] (1) Material preparation: Take two 6061-T6 aluminum alloy rods with a length of 120mm and a diameter of 8mm, and grind the end faces to be connected flat.

[0057] (2) Cold pressure welding: The two bar sections are clamped in the hydraulic butt cold pressure welding machine mold and aligned. The mold is pushed to clamp the bar sections, causing a single-pass upsetting displacement of 7mm on the end face to be joined. The end face metal undergoes plastic deformation and is extruded to form an "8" shaped flash. After completing one pass, the mold is reset and the next pass of pressure welding is performed. The pressure welding is repeated a total of 5 passes.

[0058] (3) Electro-pulse solution treatment: The cold-pressed welding head is clamped between the electrodes of the electro-pulse treatment equipment with a clamping length of approximately 150 mm. A high-density pulsed current is applied to rapidly heat the joint to 530°C. After holding at this temperature for 3-10 seconds, the pulse is immediately stopped, and the cooling system is activated for rapid quenching. The electro-pulse solution treatment parameters are: pulse frequency 40-80 kHz, peak current density 100-120 A / mm², duty cycle 15%-30%, and pulse width 3-6 μs.

[0059] (4) Electrical pulse aging treatment: Remove the annular burrs at the cold-pressed welded joint and grind them smooth. Then, clamp the cold-pressed welded joint between the electrodes of the electrical pulse treatment equipment, start the pulse power supply, and monitor the joint temperature in real time. When the temperature reaches 170-180℃, maintain the temperature stability by adjusting the duty cycle or current density. After holding at this temperature for 10 minutes, turn off the pulse power supply and allow the joint to cool naturally to room temperature. The electrical pulse aging parameters are: pulse frequency 20-40kHz, peak current density 40-60A / mm², duty cycle 20%-40%, and pulse width 10-20μs.

[0060] (5) Performance Testing and Microstructure Observation: Tensile tests were conducted on an electronic tensile testing machine according to GB / T 228.1-2021. The connecting joint was placed in the middle of the specimen, with a specimen length of 200 mm, a gauge length of 100 mm, and a tensile speed of 9 mm / min. Three valid test samples were used for each state. The test results showed that the average tensile strength of the connecting joint was 314.6 MPa, which was 104.3% of the tensile strength of the base material; the average yield strength was 292.7 MPa, and the average elongation was 3.6%. The tensile specimens fractured at the base material. Metallographic observation showed that the joint interface was well bonded, with no cracks, pores, or other defects.

[0061] The mechanical property test results of 6061-T6 aluminum alloy bars joined by cold pressure welding, electro-pulse solution treatment, and aging treatment are shown in Table 2: Table 2 process Serial Number Tensile strength / MPa Yield strength / MPa Elongation / % Average tensile strength / MPa Average yield strength / MPa Average elongation / % parent material 1 310.7 298.32 7.5 301.6 288.6 6.8 parent material 2 294.0 281.13 5.9 parent material 3 299.9 286.44 7.1 Cold pressure welding + solution treatment + aging 1 317.3 303.1 3.2 314.6 292.7 3.6 Cold pressure welding + solution treatment + aging 2 309.7 285.7 3.8 Cold pressure welding + solution treatment + aging 3 316.7 289.3 3.8 Example 3: Connection of 6061-T6 aluminum alloy wire using electrical pulse assisted pressure welding and in-situ electrical pulse aging treatment. This embodiment uses an electrical pulse-assisted pressure welding method combined with in-situ electrical pulse aging treatment to connect 6061-T6 aluminum alloy wires.

[0062] (1) Material preparation: Take two 6061-T6 aluminum alloy wires with a length of 120mm and a diameter of 3mm, and grind the end faces to be connected flat.

[0063] (2) Electrical pulse-assisted pressure welding: Clamp the wires to be connected onto the cold pressure welding machine, ensuring the two end faces to be connected are in contact. Connect pulse power supply electrodes to both ends of the wires, ensuring the current path passes through the interface to be connected. Start the pulse power supply and simultaneously start the cold pressure welding machine for upsetting. The upsetting displacement is 5mm, and the workpiece temperature fluctuation range is controlled within 150-180℃. The electrical pulse-assisted pressure welding parameters are: pulse frequency 20-40kHz, peak current density 50-80A / mm², duty cycle 40%-60%, and pulse width 10-30μs.

[0064] (3) Repeated pressure welding transition stage: Maintain the electrical pulse, stop the upsetting pressure, release the die clamp and return to the original position, clamp the wire again for the second upsetting, the upsetting displacement is 5mm, and repeat the pressure welding 4 times. During the repeated pressure welding process, adjust the peak current density to 30-50A / mm², reduce the duty cycle to 20%-30%, prevent the temperature from continuing to rise, and gradually stabilize the temperature at 170-180℃.

[0065] (4) In-situ electrical pulse heat preservation aging: After the pressure welding is completed and the upsetting force is removed, continue to maintain the electrical pulse. The pulse frequency is 10-30kHz, the peak current density is 20-40A / mm², the duty cycle is 15%-25%, and the pulse width is 10-20μs. Maintain the temperature at about 175℃ for 3 minutes. Finally, turn off the pulse power supply and allow the connecting wire to cool naturally to room temperature in the fixture.

[0066] (5) Performance Testing and Microstructure Observation: Tensile tests were conducted on an electronic tensile testing machine according to GB / T 228.1-2021. The connecting joint was placed in the middle of the specimen, with a specimen length of 200 mm, a gauge length of 100 mm, and a tensile speed of 9 mm / min. Three valid test samples were used for each state. The test results showed that the average tensile strength of the connecting joint was 313.5 MPa, which was 104.0% of the tensile strength of the base material; the average yield strength was 299.8 MPa, and the average elongation was 2.7%. The tensile specimens fractured at the base material. Metallographic observation showed that the joint interface was well bonded, with no cracks, pores, or other defects.

[0067] The mechanical property test results of 6061-T6 aluminum alloy wires connected by pulse-assisted pressure welding and in-situ pulse aging treatment are shown in Table 3. Table 3 process Serial Number Tensile strength / MPa Yield strength / MPa Elongation / % Average tensile strength / MPa Average yield strength / MPa Average elongation / % parent material 1 310.7 298.32 7.5 301.6 288.6 6.8 parent material 2 294.0 281.13 5.9 parent material 3 299.9 286.44 7.1 Pulse-assisted pressure welding + in-situ aging 1 320.0 300.0 2.9 313.5 299.8 2.7 Pulse-assisted pressure welding + in-situ aging 2 309.4 301.6 2.5 Pulse-assisted pressure welding + in-situ aging 3 311.1 297.7 2.8 The above embodiments demonstrate that the present invention, through a combination of pressure welding and electrical pulse treatment, can obtain high-strength 6000 series aluminum alloy connecting joints. Especially under conditions of cold pressure welding followed by electrical pulse solution treatment and aging, and electrical pulse-assisted pressure welding followed by in-situ electrical pulse aging, the tensile strength of the connecting joint can reach or exceed the tensile strength of the base material, indicating that the method of the present invention can improve the problems of joint softening and strength reduction during traditional connection processes.

[0068] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element 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 this invention.

[0069] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0070] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-strength connection method for 6000 series medium-strength aluminum alloys, characterized in that, Includes the following steps: S1. Perform surface treatment on the end faces of the 6000 series medium-strength aluminum alloy workpieces to be joined, and clamp the workpieces to be joined in the pressure welding equipment to align the end faces to be joined. S2. Perform pressure welding on the workpieces to be connected to cause plastic deformation of the end faces to be connected and form a connecting joint; S3. Apply an electrical pulse treatment to the connection joint, the electrical pulse treatment including electrical pulse aging treatment, or including electrical pulse solution treatment and electrical pulse aging treatment; The pressure welding process is either cold pressure welding or electric pulse assisted pressure welding. The electric pulse process is used to promote the diffusion of Mg and Si atoms and the precipitation of Mg2Si strengthening phase in the joint, so as to improve the strength of the 6000 series medium-strength aluminum alloy joint.

2. The high-strength connection method for 6000 series medium-strength aluminum alloys according to claim 1, characterized in that, The 6000 series medium-strength aluminum alloy is one of 6061 aluminum alloy, 6063 aluminum alloy or 6082 aluminum alloy; the workpiece to be connected is wire, bar or plate.

3. The high-strength connection method for 6000 series medium-strength aluminum alloys according to claim 1, characterized in that, In the cold pressure welding process, the single-pass upsetting displacement is 4-8mm, and the pressure welding is repeated 4-6 times. After the pressure welding is completed, the flash formed by the pressure welding is removed, and the joint is ground.

4. The high-strength connection method for 6000 series medium-strength aluminum alloys according to claim 1, characterized in that, The electrical pulse aging process includes: clamping the connector between the electrodes of the electrical pulse processing device, positioning the connector between the two electrodes, starting the pulse power supply and monitoring the temperature of the connector. When the temperature reaches 170-180℃, the temperature is maintained stable by adjusting the duty cycle or current density. After holding the temperature for 2-10 minutes, the pulse power supply is turned off, and the connector is allowed to cool naturally to room temperature.

5. The high-strength connection method for 6000 series medium-strength aluminum alloys according to claim 4, characterized in that, The parameters for the electrical pulse aging process are: pulse frequency 20-40kHz, peak current density 40-60A / mm², duty cycle 20%-40%, and pulse width 10-20μs.

6. The high-strength connection method for 6000 series medium-strength aluminum alloys according to claim 1, characterized in that, The electro-pulse solution treatment includes: clamping the cold-pressed welded connector between the electrodes of the electro-pulse treatment equipment, applying a pulse current to heat the connector to 520-540℃, holding it at that temperature for 3-10 seconds, stopping the pulse current, and then rapidly quenching the connector; the parameters of the electro-pulse solution treatment are: pulse frequency 40-80kHz, peak current density 100-120A / mm², duty cycle 15%-30%, and pulse width 3-6μs.

7. The high-strength connection method for 6000 series medium-strength aluminum alloys according to claim 1, characterized in that, The electro-pulse assisted pressure welding process includes: clamping the workpiece to be joined in the pressure welding equipment, and connecting the pulse power supply electrode to the workpiece to be joined so that the current path passes through the end face to be joined; performing upsetting pressure welding while starting the pulse power supply, with an upsetting displacement of 4-8mm and the workpiece temperature controlled at 150-180℃; wherein, the parameters of the electro-pulse assisted pressure welding process are: pulse frequency 20-40kHz, peak current density 50-80A / mm², duty cycle 40%-60%, and pulse width 10-30μs.

8. The high-strength connection method for 6000 series medium-strength aluminum alloys according to claim 7, characterized in that, After the electro-pulse assisted pressure welding process, the process includes a repeated pressure welding transition stage and an in-situ electro-pulse heat preservation and aging stage. In the repeated pressure welding transition stage, the electro-pulse is maintained, the upsetting pressure is stopped, the mold is released and reset, the workpiece is clamped again for upsetting, and the pressure welding is repeated 3-5 times. During the repeated pressure welding process, the peak current density is adjusted to 30-50A / mm², the duty cycle is adjusted to 20%-30%, and the temperature is stabilized at 170-180℃. In the in-situ electro-pulse heat preservation and aging stage, after the pressure welding is completed and the upsetting force is removed, the electro-pulse is maintained. The pulse frequency is 10-30kHz, the peak current density is 20-40A / mm², the duty cycle is 15%-25%, the pulse width is 10-20μs, the temperature is maintained at 170-180℃, and the duration is 2-8min. Then the pulse power supply is turned off and the workpiece is allowed to cool naturally to room temperature.

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