7-series aluminum alloy large-size complex thin-wall part and hot stamping forming method thereof

Abstract

The invention belongs to a stamping forming method, and provides a 7-series aluminum alloy large-size complex thin-wall part and a hot stamping forming method thereof in order to solve the technical problem that the mechanical performance of high-strength aluminum alloy prepared through an existing aluminum alloy stamping forming technology can be reduced under the natural condition. The supersaturated solid solution 7-series aluminum alloy is subjected to first-stage aging treatment, and the 7-series aluminum alloy subjected to first-stage aging treatment is obtained; secondary aging treatment is conducted on the primary aging treatment result, and the 7-series aluminum alloy subjected to secondary aging treatment is obtained; the 7-series aluminum alloy subjected to secondary aging treatment is rapidly heated to the critical temperature slightly higher than the critical temperature at which a large amount of precipitated phases are dissolved, and the heated 7-series aluminum alloy is obtained; and the heated 7-series aluminum alloy is subjected to stamping forming and quenching at the same time, and a formed part is obtained. And the formed part is subjected to three-stage aging treatment, so that the mechanical property is improved. The technological process is greatly shortened, the manufacturing cost is greatly reduced, and the performance of parts exceeds a traditional T6 state peak value.

Description

Technical Field

[0001] This application belongs to a stamping forming method, and specifically relates to a large-sized complex thin-walled part of 7-series aluminum alloy and its hot stamping forming method. Background Art

[0002] In strategic emerging industries such as low-altitude aircraft and new energy vehicles, the large-scale application of high-strength lightweight materials has extremely high boosting effects, which can effectively improve the carrying performance and efficiency, enhance safety and stability, and strengthen function integration.

[0003] Due to its excellent specific strength, corrosion resistance, oxidation resistance, etc., high-strength aluminum alloy has become an ideal material. However, the plasticity of high-strength aluminum alloy at room temperature is low, making it difficult to meet the high-precision dimensional requirements of large-sized complex thin-walled components. The hot stamping forming process utilizes the key technologies of solution treatment and deformation in a cold die to achieve the integrated forming of large-sized complex thin-walled components. However, the preparation cycle using the traditional aluminum alloy stamping forming process is up to several hours, and there is a parking effect, weakening the mechanical properties, making it difficult to achieve large-scale and low-cost industrial production. Summary of the Invention

[0004] In view of the technical problem that the mechanical properties of the high-strength aluminum alloy prepared by the current aluminum alloy stamping forming process will decrease under natural conditions, this application provides a large-sized complex thin-walled part of 7-series aluminum alloy and its hot stamping forming method.

[0005] To achieve the above object, this application adopts the following technical solutions: In a first aspect, this application proposes a hot stamping forming method for a large-sized complex thin-walled part of 7-series aluminum alloy, including: Performing a first-stage aging treatment on the supersaturated solution state 7-series aluminum alloy to obtain the 7-series aluminum alloy after the first-stage aging treatment; Performing a second-stage aging treatment on the result of the first-stage aging treatment to obtain the 7-series aluminum alloy after the second-stage aging treatment; wherein, the temperature of the first-stage aging treatment is less than the temperature of the second-stage aging treatment, and the time of the first-stage aging treatment is greater than the time of the second-stage aging treatment; Heating the 7-series aluminum alloy after the second-stage aging treatment to a temperature higher than the critical temperature for precipitation phase dissolution to obtain the heated 7-series aluminum alloy; Stamping and forming the heated 7-series aluminum alloy, and simultaneously quenching to obtain the formed part.

[0006] Further, after obtaining the formed part, it further includes: Performing a third-stage aging treatment on the formed part.

[0007] Furthermore, the temperature of the three-stage aging treatment is 140-180° C., and the time is 20-40 minutes.

[0008] Furthermore, the temperature of the primary aging treatment is 70-120°C, and the temperature of the secondary aging treatment is 140-180°C.

[0009] Furthermore, the time of the primary aging treatment is 40-60 minutes, and the temperature of the secondary aging treatment is 20-40 minutes.

[0010] Furthermore, when the 7 series aluminum alloy after the secondary aging treatment is heated to a temperature greater than the critical temperature for dissolution of the precipitate phase, the 7 series aluminum alloy after the secondary aging treatment is heated to 200-400°C at a rate greater than or equal to 50°C / s.

[0011] Furthermore, the stamping of the heated 7 series aluminum alloy is performed by transferring the heated 7 series aluminum alloy to a cold stamping die 2-5 seconds after the heated 7 series aluminum alloy is obtained.

[0012] Furthermore, when the 7 series aluminum alloy after the secondary aging treatment is heated to a temperature greater than the critical temperature of the precipitate phase dissolution, an energy field assisted method is adopted.

[0013] In the second aspect, the present application proposes a large-sized complex thin-walled part of a 7-series aluminum alloy, which is prepared by the above-mentioned hot stamping forming method of the large-sized complex thin-walled part of a 7-series aluminum alloy.

[0014] Furthermore, the yield strength is ≥490MPa, the tensile strength is ≥570MPa, and the elongation is ≥11%.

[0015] Compared with the prior art, this application has the following beneficial effects: The present application proposes a hot stamping forming method for large-sized complex thin-walled parts of 7-series aluminum alloys, and performs two-stage aging treatment on the supersaturated solid solution state 7-series aluminum alloy, wherein the temperature of the second-stage aging treatment is higher and the time is shorter. Through the two-stage pre-aging treatment, a microstructure state dominated by the GPII zone can be formed, and the precipitation of the GPI zone that is easy to naturally age can be avoided. The GPII zone is very stable under natural conditions and can ensure the long-term storage of raw materials, so that the raw materials before forming and the large-sized complex thin-walled parts after forming prepared by the present application can be stored for a long time under natural conditions. Then the 7-series aluminum alloy after the second-stage aging treatment is heated to a temperature greater than the critical temperature of the dissolution of the precipitate phase, which can not only improve the material forming performance to form complex parts in an integrated manner, but also avoid the large-scale dissolution of the GPII zone, so that the microstructure after forming still maintains the GPII zone as the main part, and can be preserved for a long time. The process flow of the forming method of the present application is greatly shortened, the manufacturing cost is greatly reduced, and the performance of the parts is improved, surpassing the T6 state peak.

[0016] The present application also provides a large-sized complex thin-walled part made of 7-series aluminum alloy. Through actual verification, its yield strength, tensile strength, and elongation rate all exceed those of the peak in the T6 state. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0018] Figure 1 It is a process schematic diagram of the hot stamping forming method for the large-sized complex thin-walled part made of 7-series aluminum alloy of the present application; Figure 2 It is a schematic diagram of the large-sized complex thin-walled part made of 7-series aluminum alloy prepared in the embodiments of the present application; Figure 3 It is a schematic diagram of the strength and fracture elongation rate of the large-sized complex thin-walled parts made of 7-series aluminum alloy prepared in Embodiments 1 to 6 of the present application. Detailed Embodiments

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Usually, the components of the embodiments of the present application described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the present application claimed, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0021] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0022] In the description of the embodiments of the present application, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed during use. This is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0023] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0024] In the description of the embodiments of the present application, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0025] Low-altitude aircraft and new energy vehicles are listed as key development directions of strategic emerging industries. Among them, the key role of the large-scale application of high-strength lightweight materials in enhancing the core competitiveness of the industry is particularly pointed out. In response to the requirements of the two types of products in terms of lightweight, functional integration, and safety performance, their structural parts show the characteristics of large size, thin walls, and complex shapes, such as key components like wings, window frames, and battery compartments.

[0026] Among them, 7-series aluminum alloy has become a preferred material for realizing low-carbon manufacturing and lightweight due to its excellent specific strength, corrosion resistance, and oxidation resistance. This 7-series alloy uses Zn and Mg as the main strengthening elements and forms nano-scale η′ (MgZn2) strengthening phases through heat treatment. However, its room-temperature plastic forming ability is limited, and it is difficult to meet the high-precision forming requirements of large-size complex thin-walled components. The hot stamping forming technology effectively solves this problem by combining solution treatment and in-die quenching processes, realizing the integrated forming of large-size complex thin-walled parts. The traditional hot stamping process includes three core stages: first, the alloy is heated to the solution temperature to obtain a single-phase supersaturated solid solution, then rapid forming and quenching are completed in a cold die, and finally, three-stage aging is used to promote the transformation of GP zones into η′ phases, so that the material reaches the strengthening effect of the T6 state. But this traditional hot stamping process has two major technical bottlenecks: (1) Natural aging sensitivity: The supersaturated solid solution after quenching is prone to natural aging during room temperature storage, resulting in non-uniform precipitation of GP zones, causing fluctuations in the mechanical properties of parts in different batches and a decline in corrosion resistance.

[0027] (2) Mismatch of aging cycle: Tertiary aging takes up to 20 hours (such as for 7075 aluminum alloy), forming a significant time difference with the minute-level solution-forming cycle, severely restricting the large-scale production efficiency and at the same time having high costs.

[0028] For the above problems, although existing improvement schemes can partially alleviate the above problems, there are new problems of competitive precipitation in the form of solute atom enrichment. During the pre-aging process, Zn atoms segregate on the {111} crystal plane to form stable GPII zones, while Mg atoms and a small amount of Zn atoms form metastable GPI zones on the {100} crystal plane. The latter continuously evolves during subsequent storage and finally transforms into η′ phase, resulting in uneven precipitation phase size distribution, producing a storage effect and weakening the material property stability. For example, in the Chinese invention patent with the publication number CN118147590A, the scheme of this patent optimizes multi-series aluminum alloys. Among them, for 7-series aluminum alloys, two forms of solute atom enrichment occur simultaneously, thus forming GPII zones and GPI zones. The GPI zones will continue to grow under natural conditions and even transform into η´ strengthening phases. Subsequently, a storage effect with uneven and irregular precipitation phase size distribution appears, reducing the mechanical properties. This competitive precipitation mechanism poses higher requirements for the control of the process window and becomes the key challenge restricting the application of this technology.

[0029] Based on the above situation, the present application proposes a large-size complex thin-walled part made of 7-series aluminum alloy and its hot stamping forming method. The present application will be described in detail below in combination with embodiments and drawings.

[0030] The present application proposes a hot stamping forming method for a large-size complex thin-walled part made of 7-series aluminum alloy, which may include: S1, performing primary aging treatment on the supersaturated solid solution state 7-series aluminum alloy to obtain the 7-series aluminum alloy after primary aging treatment.

[0031] It should be noted that the primary aging treatment can promote the ordered segregation of solute atoms (Zn, Mg) at a lower temperature to form stable GPII zones. In addition, extending the primary aging treatment time can ensure the full segregation of Zn atoms on the {111} crystal plane to form GPII zones. The GPII zones are formed by the ordered arrangement of Zn atoms on the close-packed plane of the aluminum matrix, and their thermal stability is high, which can effectively inhibit the precipitation of precipitation phases during the natural aging process and solve the problem of performance fluctuations caused by long-term storage.

[0032] S2. Perform secondary aging treatment on the result of the primary aging treatment to obtain the 7xxx series aluminum alloy after secondary aging treatment. Among them, the temperature of the primary aging treatment is lower than that of the secondary aging treatment, and the time of the primary aging treatment is longer than that of the secondary aging treatment.

[0033] It should be noted that a higher secondary aging treatment temperature can activate the diffusion of Mg atoms, accelerate the further segregation of Mg atoms and Zn atoms on the {111} crystal plane, and rapidly form GPII zones with the atomic clusters formed during primary aging as the core. At the same time, it inhibits the segregation of Mg atoms and Zn atoms on the {100} crystal plane and reduces the formation of GPI zones.

[0034] Through the above two-stage pre-aging treatment, a microstructure state mainly composed of GPII zones can be formed, enabling the prepared parts to be stored for a long time under natural conditions.

[0035] S3. Heat the 7xxx series aluminum alloy after secondary aging treatment to a temperature higher than the critical temperature at which the precipitate phase dissolves to obtain the heated 7xxx series aluminum alloy.

[0036] By such a heating method, not only can the material forming performance be improved, complex parts can be integrally formed, but also a large amount of GPII zones can be avoided from dissolving, so that the microstructure after forming still mainly remains GPII zones and can be stored for a long time.

[0037] In practical applications, an energy field-assisted method can be used for heating, quickly heating the sheet material to slightly higher than the critical temperature at which a large amount of precipitate phase dissolves, usually 200 - 400 °C, without heat preservation.

[0038] S4. Stamp and form the heated 7xxx series aluminum alloy and simultaneously quench it to obtain the formed part.

[0039] In this application, Zn atoms in the 7xxx series aluminum alloy after primary aging treatment precipitate and enrich on the {111} plane of the aluminum lattice, forming a large number of atomic clusters, providing a basis for the formation of a large number of GPII zones during secondary pre-aging. Based on the large number of atomic clusters obtained during primary aging treatment, a large number of GPII zones are rapidly formed during secondary aging treatment. The 7xxx series aluminum alloy after secondary aging treatment, as the microscopic state of the raw material, will not change in tissue properties within a one-year validity period. Energy field assistance can achieve a heating rate of not less than 50 °C / s, quickly heating the 7xxx series aluminum alloy after secondary aging treatment to 200 - 400 °C, minimizing the dissolution amount of GPII zones during the heating process, and the proportion of GPII zones in the microstructure after heating is not less than 80%. The microstructure of the formed part is GPII zones with a proportion of not less than 80%. Considering the entire heating process, the total forming stage time is less than 15 seconds.

[0040] In practical applications, after the formed parts are obtained, the formed large-size complex thin-walled 7 series aluminum alloy parts are also subjected to a three-level aging treatment, the temperature can be 140-180°C, and the time is 20-40 minutes.

[0041] Traditional aging follows the strength-toughness balance state, and the three-level aging treatment of this application can coordinate strength and toughness.

[0042] It has been verified that, using the forming method of this application, a large number of GPII areas in the formed parts are transformed into a more concentrated and evenly distributed η´ strengthening phase during the three-level aging process. The size is 10-15nm, which can be adjusted as needed, accounting for more than 98%, which can improve both strength and toughness. In addition, the process flow is greatly shortened, the manufacturing cost is greatly reduced, and the performance of the parts exceeds the peak of the T6 state.

[0043] like Figure 1 As shown, it is a process schematic diagram of the hot stamping forming method of large-size complex thin-walled parts of 7 series aluminum alloy in this application. Among them, the temperature of the first-level aging treatment is 70-120℃, the time of the first-level aging treatment is 40-60min, the temperature of the second-level aging treatment is 140-180℃, and the temperature of the second-level aging treatment is 20-40min. The 7 series aluminum alloy after the second-level aging treatment is heated to 200-400℃, and the forming cycle is less than 15s. The temperature of the third-level aging treatment is 140-180℃, and the time is 20-40min.

[0044] The temperature of the primary aging treatment is selected based on the activation energy required for Zn atoms and Mg atoms to segregate on the {111} crystal plane to form atomic clusters. If the temperature is too low (less than 70°C), this process cannot be stimulated, and if the temperature is too high (greater than 120°C), the GPI zone, which is unfavorable to the process, will be easily formed. The primary aging treatment consumes a part of the free Zn atoms and Mg atoms. The secondary aging treatment can increase the temperature appropriately to promote the diffusion of Zn atoms and Mg atoms and activate the formation of the GPII zone on the {111} crystal plane. If the temperature is lower than 140°C, the formation efficiency of the GPII zone will be affected, and if the temperature is higher than 180°C, the η´ phase will be easily formed in advance, which is not conducive to subsequent forming.

[0045] The present application is further described below through multiple embodiments: Embodiment 1 (1) The supersaturated solid solution 7 series aluminum alloy was subjected to primary aging treatment at a temperature of 100°C for 50 min.

[0046] (2) The 7 series aluminum alloy after the primary aging treatment was subjected to secondary aging treatment at a temperature of 150°C for 40 min.

[0047] (3) For the 7xxx series aluminum alloy after secondary aging treatment, use electric field heating to quickly heat the sheet material after secondary aging treatment to a temperature slightly higher than the critical temperature at which a large amount of precipitate phases dissolve. 350°C can be adopted without holding time.

[0048] (4) Quickly transfer the heated 7xxx series aluminum alloy into a cold die for stamping and forming, and quench at the same time. The transfer time is 2 s.

[0049] (5) Perform tertiary aging treatment on the formed large-size and complex thin-walled 7xxx series aluminum alloy parts at a temperature of 150°C for 20 min.

[0050] Example 2 (1) Perform primary aging treatment on the supersaturated solid solution state 7xxx series aluminum alloy at a temperature of 70°C for 60 min.

[0051] (2) Perform secondary aging treatment on the 7xxx series aluminum alloy after primary aging treatment at a temperature of 180°C for 30 min.

[0052] (3) For the 7xxx series aluminum alloy after secondary aging treatment, use electric field heating to quickly heat the sheet material after secondary aging treatment to a temperature slightly higher than the critical temperature at which a large amount of precipitate phases dissolve. 260°C can be adopted without holding time.

[0053] (4) Quickly transfer the heated 7xxx series aluminum alloy into a cold die for stamping and forming, and quench at the same time. The transfer time is 5 s.

[0054] (5) Perform tertiary aging treatment on the formed large-size and complex thin-walled 7xxx series aluminum alloy parts at a temperature of 180°C for 30 min.

[0055] Example 3 (1) Perform primary aging treatment on the supersaturated solid solution state 7xxx series aluminum alloy at a temperature of 120°C for 40 min.

[0056] (2) Perform secondary aging treatment on the 7xxx series aluminum alloy after primary aging treatment at a temperature of 150°C for 20 min.

[0057] (3) For the 7xxx series aluminum alloy after secondary aging treatment, use electric field heating to quickly heat the sheet material after secondary aging treatment to a temperature slightly higher than the critical temperature at which a large amount of precipitate phases dissolve. 200°C can be adopted without holding time.

[0058] (4) Quickly transfer the heated 7xxx series aluminum alloy into a cold die for stamping and forming, and quench at the same time. The transfer time is 5 s.

[0059] (5) Perform tertiary aging treatment on the formed large-size and complex thin-walled 7xxx series aluminum alloy parts at a temperature of 140°C for 30 min.

[0060] Example 4 (1)Perform primary aging treatment on the supersaturated solid-solution 7-series aluminum alloy at a temperature of 90 °C for 45 min.

[0061] (2)Perform secondary aging treatment on the 7-series aluminum alloy after primary aging treatment at a temperature of 140 °C for 35 min.

[0062] (3)For the 7-series aluminum alloy after secondary aging treatment, use electric field heating to rapidly heat the sheet material after secondary aging treatment to a temperature slightly higher than the critical temperature at which a large amount of precipitate phases dissolve. 400 °C can be adopted without holding.

[0063] (4)Quickly transfer the heated 7-series aluminum alloy to a cold die for stamping and forming, and quench at the same time. The transfer time is 3 s.

[0064] (5)Perform tertiary aging treatment on the formed large-size and complex thin-wall 7-series aluminum alloy parts at a temperature of 150 °C for 40 min.

[0065] Example 5 (1)Perform primary aging treatment on the supersaturated solid-solution 7-series aluminum alloy at a temperature of 80 °C for 60 min.

[0066] (2)Perform secondary aging treatment on the 7-series aluminum alloy after primary aging treatment at a temperature of 160 °C for 40 min.

[0067] (3)For the 7-series aluminum alloy after secondary aging treatment, use electric field heating to rapidly heat the sheet material after secondary aging treatment to a temperature slightly higher than the critical temperature at which a large amount of precipitate phases dissolve. 320 °C can be adopted without holding.

[0068] (4)Quickly transfer the heated 7-series aluminum alloy to a cold die for stamping and forming, and quench at the same time. The transfer time is 2 s.

[0069] (5)Perform tertiary aging treatment on the formed large-size and complex thin-wall 7-series aluminum alloy parts at a temperature of 160 °C for 35 min.

[0070] Example 6 (1)Perform primary aging treatment on the supersaturated solid-solution 7-series aluminum alloy at a temperature of 100 °C for 55 min.

[0071] (2)Perform secondary aging treatment on the 7-series aluminum alloy after primary aging treatment at a temperature of 180 °C for 35 min.

[0072] (3)For the 7-series aluminum alloy after secondary aging treatment, use electric field heating to rapidly heat the sheet material after secondary aging treatment to a temperature slightly higher than the critical temperature at which a large amount of precipitate phases dissolve. 280 °C can be adopted without holding.

[0073] (4) Rapidly transfer the heated 7-series aluminum alloy to a cold die for stamping and forming, and simultaneously quench it. The transfer time is 4 s.

[0074] (5) Perform three-stage aging treatment on the formed large-sized and complex thin-walled 7-series aluminum alloy parts at a temperature of 150 °C for 40 min.

[0075] As Figure 2 shown, it is a schematic diagram of the large-sized and complex thin-walled 7-series aluminum alloy parts prepared by this application. Detect the large-sized and complex thin-walled 7-series aluminum alloy parts prepared by this application, and the yield strength > 490 MPa, the tensile strength > 570 MPa, and the elongation > 11%. In addition, the three-stage aging of traditional 7-series aluminum alloy lasts for more than 20 hours. Combining with the overall process of this application, the three-stage aging cycle can be greatly shortened from the hour level to the minute level. As Figure 3 shown, it is a schematic diagram of the strength and fracture elongation of the large-sized and complex thin-walled 7-series aluminum alloy parts prepared in Examples 1 to 6 of this application. It can be seen from Figure 3 that the parts prepared by this application can all meet the above performance indicators.

[0076] The above are only the preferred embodiments of this application and are not used to limit this application. For those skilled in the art, this application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included in the protection scope of this application.

Claims

1. A hot stamping method for large-size complex thin-walled parts of 7 series aluminum alloy, characterized in that: include: Performing primary aging treatment on the supersaturated solid solution 7 series aluminum alloy to obtain the primary aging treated 7 series aluminum alloy; Performing a secondary aging treatment on the primary aging treatment result to obtain a 7 series aluminum alloy after the secondary aging treatment; wherein the temperature of the primary aging treatment is lower than the temperature of the secondary aging treatment, and the time of the primary aging treatment is longer than the time of the secondary aging treatment; The 7 series aluminum alloy after the secondary aging treatment is heated to a temperature greater than the critical temperature of the precipitate phase dissolution to obtain a heated 7 series aluminum alloy; The heated 7 series aluminum alloy is stamped and quenched to obtain formed parts.

2. The hot stamping forming method for large-size complex thin-walled parts of 7 series aluminum alloy according to claim 1 is characterized in that: After obtaining the formed parts, the method further comprises: The formed parts are subjected to three-level aging treatment.

3. The hot stamping forming method for large-size complex thin-walled parts of 7 series aluminum alloy according to claim 2 is characterized in that: The temperature of the three-stage aging treatment is 140-180° C., and the time is 20-40 minutes.

4. The hot stamping forming method of 7 series aluminum alloy large-size complex thin-walled parts according to claim 1 is characterized in that: The temperature of the primary aging treatment is 70-120°C, and the temperature of the secondary aging treatment is 140-180°C.

5. The hot stamping forming method of 7 series aluminum alloy large-size complex thin-walled parts according to claim 1, characterized in that: The time of the primary aging treatment is 40-60 minutes, and the temperature of the secondary aging treatment is 20-40 minutes.

6. The hot stamping forming method of 7 series aluminum alloy large-size complex thin-walled parts according to claim 1, characterized in that: When the 7 series aluminum alloy after the secondary aging treatment is heated to a temperature greater than the critical temperature for dissolution of the precipitate phase, the 7 series aluminum alloy after the secondary aging treatment is heated to 200-400° C. at a rate greater than or equal to 50° C. / s.

7. The hot stamping forming method of 7 series aluminum alloy large-size complex thin-walled parts according to claim 1, characterized in that: The stamping of the heated 7 series aluminum alloy is performed by transferring the heated 7 series aluminum alloy to a cold stamping die 2-5 seconds after the heated 7 series aluminum alloy is obtained.

8. The hot stamping forming method of 7 series aluminum alloy large-size complex thin-walled parts according to claim 1, characterized in that: When the 7 series aluminum alloy after the secondary aging treatment is heated to a temperature greater than the critical temperature of the precipitate phase dissolution, an energy field assisted method is adopted.

9. A large-sized complex thin-walled part of a 7-series aluminum alloy, prepared by the hot stamping forming method of a large-sized complex thin-walled part of a 7-series aluminum alloy as claimed in any one of claims 1 to 8.

10. The 7 series aluminum alloy large-size complex thin-walled part according to claim 9, characterized in that: Yield strength ≥490MPa, tensile strength ≥570MPa, elongation ≥11%.

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