Ultrahigh-strength aluminum alloy cold pressure welding connection and heat treatment method

Abstract

The invention discloses a cold pressure welding connection and heat treatment method for ultrahigh-strength aluminum alloy. The cold pressure welding connection and heat treatment method comprises the steps of material preparation, cold pressure welding connection, subsequent heat treatment and the like. According to the method, room-temperature cold pressure welding and subsequent overall heat treatment are combined, end face butt joint of the ultrahigh-strength aluminum alloy is completed on the premise that an additional high-temperature melting process is not introduced, and a base metal area and a joint area are cooperatively adjusted through a unified heat treatment process, so that the structure state and mechanical performance of a joint are closer to those of original base metal; and the welding coefficient of the connector can reach 82%-90%, so that the consistency and the stability of the whole component can be considered while the high connection reliability is kept. Meanwhile, the process route has good combination and expansion capacity, different routes such as direct aging, solid solution quenching aging or cold pressure welding and aging after solid solution softening can be selected after cold pressure welding according to production requirements, and the method is suitable for connection of ultrahigh-strength aluminum alloy components in various forms such as wires, bars and pipes.

Description

Technical Field

[0001] This invention relates to the field of metal material joining and processing, and specifically to a cold pressure welding connection and heat treatment method for ultra-high strength aluminum alloy. Background Technology

[0002] Ultra-high strength aluminum alloys based on the Al-Zn-Mg-Cu system, such as 7075, 7A04, and 7050, have been widely used in key load-bearing structural components in aerospace, defense industries, and high-end transportation equipment due to their extremely high specific strength and excellent comprehensive mechanical properties. The ultra-high strength of these alloys mainly comes from the solution quenching-aging heat treatment process, which forms a fine microstructure composed of dispersed nanoscale reinforcing phases in the aluminum matrix. This microstructure is extremely sensitive to temperature.

[0003] In existing joint manufacturing processes, traditional fusion welding methods generally suffer from high-temperature heat input problems. For Al-Zn-Mg-Cu aluminum alloys, due to the high copper content, the melting and solidification processes easily form weld metal with a wide crystallization temperature range and containing low-melting-point eutectics, significantly increasing the susceptibility to welding hot cracking. Simultaneously, the weld heat-affected zone is prone to microstructural evolution such as recovery, recrystallization, dissolution of strengthening phases, and over-aging, leading to severe joint softening and strength loss. The joint strength is typically only 35%–62% of the base metal strength, making it difficult to meet the requirements of ultra-high-strength joints for critical load-bearing components.

[0004] To mitigate the adverse effects of melting, solid-state joining technologies such as friction stir welding (FSW) have been proposed and applied to some aluminum alloy structures. This process achieves solid-state bonding through friction and plastic flow between the stirring head and the workpiece, avoiding the melting process and helping to reduce the risk of metallurgical defects such as hot cracking. The weld coefficient can typically reach 80%–90%. However, when joining Al-Zn-Mg-Cu ultra-high-strength aluminum alloys, the temperature in the stirring zone can still reach approximately 300–560°C, sufficient to cause partial dissolution or coarsening of the strengthening phase, making it difficult to restore the joint strength to the level of the base material. Furthermore, FSW equipment is complex, requires precise clamping conditions, and is not suitable for butt joints of complex spatial curves or long, strip-shaped components such as wires and bars, significantly limiting its application scenarios.

[0005] In summary, the core contradiction of existing joining technologies lies in the fundamental incompatibility between the unavoidable heat input during the joining process and the strengthening mechanism of Al-Zn-Mg-Cu ultra-high-strength aluminum alloys through fine precipitates. Both high-temperature welding and solid-state stirring processes involving significant heat accumulation will, to varying degrees, damage the fine microstructure formed by the original heat treatment, causing softening in the joint area and making it difficult to achieve joint strength close to that of the base material. This limits the further application of such ultra-high-strength aluminum alloys in high-reliability load-bearing structures.

[0006] Therefore, it is necessary to propose a connection method that can be carried out at room temperature, avoid external heat input, and at the same time restore or optimize the overall component structure and performance through subsequent processes, so as to solve the technical bottleneck in ultra-high strength connection of ultra-high strength aluminum alloy wires, bars and other components.

[0007] Chinese patent literature discloses a welding wire for welding 7XXX aluminum alloys and its preparation process [Application No.: 202211331764.X, Publication No.: CN115570294B]. By adjusting the composition of the welding wire, using a cladding layer to protect the core material, and simultaneously adjusting and controlling the Zn and Mg content of the core material, the loss of Zn and Mg elements in the welding core material is reduced. This better compensates for the loss of Zn and Mg elements in the weld and its surrounding substrate due to welding, thus achieving a higher Zn and Mg content in the weld and its surrounding substrate. While this patent can improve the strength and composition matching of 7XXX aluminum alloy welds through special welding wire and fusion welding process, especially the Al-Zn-Mg-Cu composition, which is suitable for MIG / TIG fusion welding and easy to promote in existing welding production lines, this invention uses room temperature cold pressure welding to achieve solid-to-solid connection of ultra-high strength Al-Zn-Mg-Cu wires and bars, and is matched with overall solution / aging heat treatment, so that the microstructure and strengthening state of the joint area are close to the base material, reducing joint softening caused by high heat input, making it more suitable for ultra-high strength butt joints. Summary of the Invention

[0008] In view of the problems existing in the prior art, the purpose of this invention is to provide a method for cold pressure welding connection and heat treatment of ultra-high strength aluminum alloy.

[0009] A method for cold-press welding and heat treatment of ultra-high strength aluminum alloys, characterized by comprising the following steps: (1) Material preparation: Select ultra-high strength Al-Zn-Mg-Cu series aluminum alloy wire or bar in heat treatment state as the base material, and grind the end faces of the two base materials to be connected. (2) Cold pressure welding connection: At room temperature and without applying an external heat source to the base material, the two base material end faces are clamped together in a cold pressure welding machine mold that matches its shape. Axial pressure is applied by displacement control, causing the end face metal to undergo plastic deformation and extruding the end face oxide film and surface contaminants to the periphery of the joint to form annular flash. This allows the fresh metal atoms inside to come into close contact under continuous high pressure and form a dense joint with solid metallurgical bonding. (3) Subsequent heat treatment: After the cold pressure welding is completed, the connected integral component is subjected to heat treatment, which is aging treatment or a combination of solution treatment and aging treatment.

[0010] Preferably, the Al-Zn-Mg-Cu series ultra-high strength aluminum alloy is one or more of 7075, 7A04 or 7050 aluminum alloy, the base material is in the form of wire, bar or tube, and is in a heat treatment state such as T6 or T7X or solution treatment.

[0011] The above technical solution enables the connection method to form a clear and stable applicable object for typical Al-Zn-Mg-Cu ultra-high strength aluminum alloys. Under the premise that the base material is in a heat treatment state such as T6 or T7X or solution treatment, it is compatible with the connection of various forms of components such as wire, bar and tube, thereby ensuring the matching relationship between the joint design and the performance of the base material and improving the consistency and repeatability of the process.

[0012] Specifically, this approach, which uses 7075, 7A04, or 7050 aluminum alloys as the preferred base material and employs a solution-quenching-aging process to create a stable and strengthened microstructure, ensures that the base material is in a state of ultra-high strength and stable microstructure before joining. This facilitates predictable plastic deformation behavior and interfacial metal flow during cold pressure welding. The base material is limited to wire, bar, or tube, which allows for end-to-end joining and axial upsetting in the mold, ensuring good controllability in the geometry and microstructure of the deformation zone, flash zone, and base material zone in the joint area.

[0013] In practical applications, this design, which uses typical ultra-high-strength aluminum alloys such as 7075, 7A04, or 7050 as the base material and uniformly adopts T6 or T7X heat treatment, allows the connection process of this invention to directly interface with existing standard profile systems in aerospace, high-end equipment, and other fields, reducing the need for material replacement and recertification. Furthermore, the coverage of multiple base material forms makes this method applicable to the connection scenarios of rods, pipes, and long wires of different specifications, facilitating the formation of serialized and modular connection process solutions in engineering mass production.

[0014] Preferably, in step (1), the end face to be connected is basically flat after mechanical grinding.

[0015] The above technical solution enables a relatively regular initial state for the end faces to be joined without adding complex processing steps. Mechanical grinding makes the end faces basically flat, which helps reduce macroscopic unevenness and local gaps caused by large scratches and burrs, and can appropriately reduce the number of cold welding operations.

[0016] Specifically, the basically flat end face formed by grinding allows the two base materials to achieve a closer end face contact during clamping and docking, making the distribution of plastic deformation area of ​​end face metal more concentrated during axial upsetting, and the formation of flash more continuous. This avoids excessive or insufficient local strain due to uneven end face height, and makes the morphology of the joint transition zone more regular, which is conducive to obtaining a dense and continuous joint structure.

[0017] In practical applications, this end-face pretreatment method is simple to implement, highly operable, and can be stably carried out under normal production conditions. By controlling the pretreatment of the end-face geometry and surface condition, the upsetting deformation, flash formation, and geometric contour of the joint area in the subsequent cold-press welding process are made more consistent. This is beneficial for maintaining high consistency and repeatability when connecting different batches and specifications of wires or bars using the method of this invention, thereby improving the overall engineering applicability of the connection process.

[0018] Preferably, in step (2), a hydraulic cold welding machine is used to clamp the two sections of base material into a closed mold that matches their outer diameter. The mold is driven by a hydraulic cylinder to perform multi-pass displacement control upsetting. After each upsetting is completed, the mold is reset and upsetting is repeated, so that the end face metal is gradually extruded and a continuous annular flash is formed around the joint.

[0019] The above technical solution enables multiple axial plastic deformations to be applied to the end face of the base material under controlled constraints, allowing the end face metal to flow gradually within the closed mold and form a geometrically regular contour with continuous annular flash on the periphery. This results in a cold-pressed welded joint with a stable forming process and uniform deformation, providing a foundation for subsequent joint processing and performance consistency.

[0020] Specifically, two sections of base material are clamped in a closed mold that matches their outer diameter, limiting the outer circle of the base material by the mold cavity. This constrains the radial metal flow during upsetting, while the end-face metal mainly flows axially and peripherally and is extruded around the joint. Multi-pass upsetting is achieved by driving the mold with a hydraulic cylinder, keeping the upsetting amount controllable in each pass. This allows the end-face metal to form a continuous, symmetrical annular flash under gradually accumulating plastic deformation, reducing the potential for localized cracking and joint geometric instability caused by large deformation in a single pass.

[0021] In practical applications, this forming method helps maintain a stable upsetting path and flash morphology when cold-pressing and welding wires or bars of different batches and specifications are connected. It makes the width of the deformation zone, the height of the flash, and the shape of the transition zone around the joint more consistent, which facilitates flash removal and subsequent dimensional processing according to a unified standard, thereby improving the appearance quality of the joint and the process repeatability during mass production.

[0022] Preferably, step (3) adopts the process route of direct aging after cold pressing: after removing the circumferential flash at the cold pressing weld joint, the whole component is placed in an aging furnace, kept at about 120°C for about 24 hours, and then air-cooled to room temperature to perform artificial aging treatment on the base material area and the joint area.

[0023] The above technical solution enables a uniform heat treatment of the entire component after room temperature cold pressing welding, through an aging process. This ensures that the base material area and the joint area operate under the same aging regime, resulting in an overall component with essentially consistent microstructure and strengthening degree. By removing the circumferential flash before aging, the joint shape is ensured to be regular, which is beneficial for subsequent assembly and dimensional control, while not affecting the temperature field distribution of the overall component during the aging process.

[0024] Specifically, the cold-pressed welded integral component is placed in an aging furnace at approximately 120°C and held for about 24 hours. After the holding period, it is air-cooled to room temperature. The base material region and the joint region undergo artificial aging under the same temperature and time conditions. The interior of the joint top forging plastic deformation zone and the interior of the base material matrix respectively form diffusely distributed aging strengthening phases. The strengthening state of the joint region tends to be consistent with that of the base material region, thereby reducing the performance difference between the two.

[0025] In practical applications, this direct aging process after cold-press welding is simple in its heat treatment regime and has a clear cycle, making it easy to integrate with existing aging processes for Al-Zn-Mg-Cu ultra-high-strength aluminum alloy components. It can be used for the batch processing of wires, bars, or tubes after room-temperature cold-press welding. By implementing uniform aging treatment on the entire component, it is beneficial to improve the consistency of joint performance between different batches of products and the engineering applicability of the connection process.

[0026] Preferably, step (3) adopts a process route of cold-pressed welding followed by solution quenching and aging: after removing the circumferential flash at the cold-pressed weld joint, the whole component is heated to 470-480°C and held for 1-2 hours, then water-quenched to room temperature, then held at about 120°C for about 24 hours for artificial aging treatment, and finally air-cooled to room temperature.

[0027] The above technical solution introduces a solution quenching-aging process after cold pressure welding, enabling the overall component to re-establish a unified strengthened microstructure through a complete solution treatment and secondary aging process after room temperature cold pressure welding and large plastic deformation. This process route allows for simultaneous heat treatment control of the base material and joint areas within the overall component scale, significantly mitigating the microstructure differences between the deformed joint area and the undeformed base material area, and improving the mechanical property coordination and dimensional stability of the overall component.

[0028] Specifically, heating the cold-pressed welded integral component to 470–480°C and holding it for 1–2 hours allows the original aging precipitates in the base material and the upsetting deformation zone of the joint to be basically dissolved back into the aluminum matrix. The work-hardened structure generated by the cold-pressed welding in the joint area is restored and recrystallized, thus forming a supersaturated solid solution with a relatively uniform composition and defect distribution. Subsequently, it is rapidly cooled to room temperature by water quenching, retaining the supersaturated solid solution state, and then artificially aged at about 120°C for about 24 hours, so that the fine and dispersed strengthening phases precipitate synergistically in the base material and joint areas, and the strengthening level of the joint area approaches that of the base material area.

[0029] In practical applications, this process is suitable for situations requiring high strength, plasticity, and long-term service stability of ultra-high-strength aluminum alloy joints. It can be used for wire, bar, or tubular components that still need to withstand large loads or complex stress conditions after connection. By performing integrated solution treatment and aging heat treatment on the entire component after connection, the softening zone of the joint is reduced, and the consistency of joint performance between different batches and specifications of components is improved, providing a more robust connection and strengthening process solution for high-requirement load-bearing structures.

[0030] Preferably, in step (1), the base material is first heated to about 475°C and kept at that temperature for about 1 hour, then water-quenched to make it soft, and then cold-pressed welded together at room temperature according to step (2). In step (3), the overall component after cold-pressing is kept at about 120°C for about 24 hours for artificial aging treatment and then air-cooled to room temperature.

[0031] The above technical solution allows the base material to be adjusted to a soft state before cold pressure welding, so that the base material has high plasticity and low deformation resistance during the connection stage, which facilitates the formation of sufficient plastic deformation zone and regular flash profile by axial upsetting at room temperature. After the cold pressure welding connection is completed, the mechanical properties of the overall component are restored and improved by a unified artificial aging process, so that the joint area and the base material area remain consistent in the strengthening state.

[0032] Specifically, after the base material is water-quenched at approximately 475°C for about 1 hour, it is in a soft state. During cold pressure welding, the end face metal is more likely to undergo uniform plastic flow, which helps to reduce the upsetting load and equipment burden, reduce the risk of forming defects such as cracking and delamination in the joint area, and make the flash morphology and the geometric profile of the joint transition area more stable. After the cold pressure welding is completed and an integrated component is formed, artificial aging treatment at approximately 120°C for about 24 hours causes fine and dispersed strengthening phases to precipitate simultaneously in both the base material area and the joint area. The joint area gradually recovers from a soft state to a strength level similar to that of the base material.

[0033] In practical applications, this combination of processes helps to ensure the stability of cold pressure welding while taking into account the ultra-high strength and high reliability of the final component. It is suitable for the docking of ultra-high strength aluminum alloy wires, bars or tubes where the controllability of the connection forming process is high and the load-bearing capacity needs to be maintained during service. It can form a clear and easy-to-implement process route in engineering mass production.

[0034] Compared with the prior art, the present invention has the following advantages: 1. This invention combines room temperature cold pressure welding with subsequent overall heat treatment to complete the end-to-end connection of ultra-high strength aluminum alloys without introducing an additional high-temperature melting process. By using a unified heat treatment process to coordinate the adjustment of the base material area and the joint area, the microstructure and mechanical properties of the joint are closer to the original base material. The welding coefficient of the connection joint can reach 82%-90%, which is beneficial to maintain high connection reliability while taking into account the overall consistency and stability of the components.

[0035] 2. The process path of this invention has good combination and expansion capabilities. Depending on production needs, different routes can be selected after cold pressure welding, such as direct aging, solution treatment followed by aging, or solution softening followed by cold pressure welding. It is suitable for connecting ultra-high strength aluminum alloy components in various forms, including wire, bar, and tube. Through careful attention to details such as end face treatment, die constraints, and multi-pass upsetting, it facilitates the formation of a relatively clear operating window and a replicable process scheme in engineering applications. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the process flow of the present invention; Figure 2 This is a schematic diagram comparing the mechanical properties of 7075 aluminum alloy joints produced by different processes according to the present invention. Figure 3 This is the metallographic structure of the joint in Embodiment 2 of the present invention. Detailed Implementation

[0037] 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. 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.

[0038] The present invention will be described in detail below through multiple embodiments and comparative examples. These embodiments are intended to further illustrate the technical solutions and beneficial effects of the present invention, and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, all parts mentioned in the present invention are parts by weight, and the process equipment mentioned is conventional equipment in the art.

[0039] Example 1: Cold pressure welding + direct aging process In this embodiment, two 7075-T6 aluminum alloy bars with a diameter of Φ8mm and a length greater than 150mm are selected as the base material. The initial average mechanical properties of the base material are a tensile strength of approximately 583.69MPa, a yield strength of approximately 539.27MPa, and an elongation of approximately 9.63%. The ends of the two bars to be joined are mechanically ground to be basically flat, resulting in a relatively regular butt joint surface.

[0040] After end face treatment, a hydraulic cold welding machine is used to clamp the two bar sections into a closed mold matching the outer diameter. A positioning structure ensures the axes of the two bar sections are aligned. The hydraulic cylinder is activated, and multiple upsetting passes are performed using displacement control. Each upsetting pass involves a displacement of approximately 7 mm. After each round of upsetting, the mold is reset before the next pass, for a total of 5 upsetting passes. During the upsetting process, the metal on the bar end face undergoes strong plastic flow under axial high pressure, being extruded to form a continuous annular flash around the joint, while a dense solid-phase bonding zone forms in the center of the joint.

[0041] After cold pressure welding, the exposed annular flash of the joint is removed mechanically to obtain butt bars with a basically regular shape. Then, the entire welded part is placed in an aging furnace and held at about 120°C for about 24 hours. After the holding time, it is cooled to room temperature in the air, so that the base material area and the joint area complete an artificial aging process together.

[0042] To evaluate the joint performance obtained by the process in this embodiment, the welded parts were processed into standard tensile specimens. After the surface of the specimens was sanded, room temperature tensile tests were conducted in accordance with GB / T228.1-2021. The gauge length of the specimens was 100 mm and the tensile speed was 5 mm / min. The test results are shown in Table 1. Table 1

[0043] Test results show that the average tensile strength of the joint under this process is approximately 479.52 MPa, the average yield strength is approximately 425.45 MPa, and the average elongation is approximately 2.47%. The weldability coefficient is approximately 82.15% of the tensile strength of the 7075-T6 base material. Metallographic observation shows that the joint interface is densely bonded, with no obvious cracks or porosity defects.

[0044] Example 2: Cold pressure welding + solution quenching + aging process In this embodiment, two 7075-T6 aluminum alloy bars with a diameter of Φ8mm and a length greater than 150mm are selected. The initial average tensile strength of the base material is approximately 583.69MPa, the yield strength is approximately 539.27MPa, and the elongation is approximately 9.63%. The end faces of the two bars are mechanically ground flat.

[0045] In the cold pressure welding step, two bar sections are clamped in the closed die of a hydraulic cold welding machine, ensuring that the end faces of the two bars are aligned. Axial pressure is applied by a hydraulic cylinder, causing the die to be displaced by approximately 8 mm per upsetting pass. After each upsetting pass, the die is reset, and the upsetting is repeated, for a total of four upsetting passes. This multi-pass displacement-controlled upsetting process causes the end face metal to be gradually extruded out of the joint periphery, forming a continuous annular flash, and creating a solid-state metallurgical bonding zone in the center of the joint.

[0046] After cold pressure welding, the circumferential flash at the joint is removed by mechanical grinding. Then, the welded monolithic bar is placed in a heating furnace and held at approximately 475°C for about 1 hour, allowing the precipitated phases in the base material and joint area to largely dissolve back into the matrix, forming a relatively uniform supersaturated solid solution. Immediately after holding at this temperature, it is water-quenched to room temperature. Following water quenching, the monolithic component is placed in an aging furnace and held at approximately 120°C for about 24 hours for artificial aging treatment. Finally, it is air-cooled to room temperature, resulting in the re-precipitation of fine, dispersed strengthening phases throughout the component.

[0047] The welded bars processed by the above process were processed into tensile specimens and tensile tests were conducted according to GB / T228.1-2021. The gauge length of the specimen was 100 mm and the tensile speed was 5 mm / min. The test results are shown in Table 2. Table 2

[0048] Test results show that the joint in this embodiment has an average tensile strength of approximately 529.59 MPa, an average yield strength of approximately 480.42 MPa, an average elongation of approximately 6.03%, and a weldability coefficient of approximately 90.73%. Metallographic observation shows that the joint interface is well bonded, the grains in the joint area are fine and relatively uniformly distributed, no obvious metallurgical defects were found, and the joint plasticity is significantly improved compared to Example 1.

[0049] Example 3: Solution softening + cold pressure welding + aging process This embodiment uses two 7075-T6 aluminum alloy bars with a diameter of Φ8mm, whose original tensile properties are basically the same as those in the previous embodiment. First, the bars are subjected to solution treatment by placing them in a heating furnace at about 475°C and holding them for about 1 hour. Then, they are water quenched to room temperature to change the bars from the T6 state to a soft state, which facilitates subsequent cold pressure welding under lower deformation resistance.

[0050] After solution treatment, the ends to be welded are mechanically ground smooth. Then, a hydraulic cold welding machine is used to clamp the two bar sections into a closed die that matches the outer diameter for centering. Controlled by a hydraulic cylinder, the displacement for each upsetting pass is approximately 6 mm. After each upsetting pass, the die is reset before the next upsetting pass is performed, for a total of 6 passes. During the upsetting process, the end face metal undergoes sufficient plastic flow under soft conditions, and is extruded to form a fuller annular flash around the joint.

[0051] After cold pressure welding, the flash at the joint is removed mechanically to make the joint shape regular. Then the whole welded part is placed in an aging furnace and held at about 120°C for about 24 hours. After the holding time is completed, it is air-cooled to room temperature, so that the base material area and the joint area complete the artificial aging process at the same time, restoring and improving the mechanical properties of the whole component.

[0052] The specimens were processed under the same conditions and tensile tests were performed according to GB / T228.1-2021. The test results are shown in Table 3. Table 3

[0053] The results show that the average tensile strength of the joint in this embodiment is approximately 497.76 MPa, the average yield strength is approximately 455.33 MPa, and the average elongation is approximately 3.17%, with a corresponding weld coefficient of approximately 85.28%. Metallographic observation shows that the joint interface is densely bonded, with no obvious cracks or pores. However, the plasticity and strength of the joint are slightly lower than those in Example 2, corresponding to the explanation of the performance differences of different process combinations in this invention.

[0054] The mechanical properties of 7075 aluminum alloy joints after different cold welding connections and heat treatments are compared with those of the 7075 aluminum alloy base material in the figure below. Figure 2 As shown; Example 2: Metallographic observation diagram of cold pressure welding + solution quenching + aging process (see figure) Figure 3 As shown.

[0055] 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 method for cold-press welding and heat treatment of ultra-high strength aluminum alloy, characterized in that, Includes the following steps: (1) Material preparation: Select ultra-high strength Al-Zn-Mg-Cu series aluminum alloy wire or bar in heat treatment state as the base material, and grind the end faces of the two base materials to be connected. (2) Cold pressure welding connection: At room temperature and without applying an external heat source to the base material, the two base material end faces are clamped together in a cold pressure welding machine mold that matches its shape. Axial pressure is applied by displacement control, causing the end face metal to undergo plastic deformation and extruding the end face oxide film and surface contaminants to the periphery of the joint to form annular flash. This allows the fresh metal atoms inside to come into close contact under continuous high pressure and form a dense joint with solid metallurgical bonding. (3) Subsequent heat treatment: After the cold pressure welding is completed, the connected integral component is subjected to heat treatment, which is aging treatment or a combination of solution treatment and aging treatment.

2. The connection method according to claim 1, characterized in that, The Al-Zn-Mg-Cu series ultra-high strength aluminum alloy is one or more of 7075, 7A04 or 7050 aluminum alloy, and the base material is in the form of wire, bar or tube, and is in a heat treatment state such as T6 or T7X or solution treatment.

3. The connection method according to claim 1, characterized in that, In step (1), the end face to be connected is basically flat after mechanical grinding.

4. The connection method according to claim 1, characterized in that, In step (2), a hydraulic cold welding machine is used to clamp the two sections of base material into a closed mold that matches their outer diameter. The mold is driven by a hydraulic cylinder to perform multiple displacement control upsetting. After each upsetting is completed, the mold is reset and upsetting is repeated, so that the end face metal is gradually extruded and a continuous annular flash is formed around the joint.

5. The connection method according to claim 1, characterized in that, In step (3), the process route of direct aging after cold pressing is adopted: after removing the circumferential flash at the cold pressing weld joint, the whole component is placed in an aging furnace and kept at about 120°C for about 24 hours. Then, it is air-cooled to room temperature, and artificial aging treatment is performed on the base material area and the joint area.

6. The connection method according to claim 1, characterized in that, In step (3), the process route of cold pressure welding followed by solution treatment and aging is adopted: after removing the circumferential flash at the cold pressure weld joint, the whole component is heated to 470-480℃ and kept at that temperature for 1-2 hours, then water-quenched to room temperature, and then kept at about 120℃ for about 24 hours for artificial aging treatment, and finally air-cooled to room temperature.

7. The connection method according to claim 1, characterized in that, In step (1), the base material is first heated to about 475°C and kept at that temperature for about 1 hour, then water-quenched to make it soft. Then, in step (2), cold-press welding is performed at room temperature. In step (3), the overall component after cold-press welding is kept at about 120°C for about 24 hours for artificial aging treatment and then air-cooled to room temperature.

8. A method for cold-press welding and heat treatment of ultra-high strength aluminum alloy, characterized in that, The weldability of the connection joint can reach 82%-90%.

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