A high-strength corrosion-resistant aluminum alloy ultra-thick forging and a preparation method and application thereof

Abstract

The application discloses a high-strength corrosion-resistant aluminum alloy super-thick forge piece and a preparation method and application thereof, and has the advantages that by reasonably adjusting the content and proportion of main alloy elements, the alloy has high strength, the content of Cu element in grain boundary precipitated phase is increased, the potential difference between the grain boundary phase and the matrix is reduced, the galvanic corrosion at the grain boundary is inhibited, and the stress corrosion resistance of the alloy is improved; by controlling the content and proportion of Fe and Mn elements, the content of difficult-to-dissolve coarse phases in the alloy is reduced, the corrosion cracking caused by the difficult-to-dissolve coarse phases is reduced, and the stress corrosion resistance is improved; the ingot is upset and thickened by the forging process, the parameters such as the distribution of the drawing reduction, the drawing feed, and the reduction speed are innovatively distributed, the strain is transmitted from the center of the ingot to the surface of the ingot, and is uniformly distributed in the thickness direction of the ingot, so that the surface of the super-thick forge piece has the same grain structure and uniform mechanical properties as the center of the plate.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy technology, specifically relating to a high-strength, corrosion-resistant, ultra-thick aluminum alloy forging, its preparation method, and its application. Background Technology

[0002] Al-Zn-Mg-Cu alloys are highly suitable for aerospace equipment due to their high specific strength, low density, and good formability. A common problem with Al-Zn-Mg-Cu high-strength aluminum alloys is the trade-off between strength and stress corrosion resistance. Stress corrosion cracking occurs without obvious warning signs and is extremely dangerous, severely restricting the widespread application of high-strength aluminum alloys.

[0003] Large aluminum alloy sheets are raw materials used in the aerospace industry to manufacture large parts. With the development of integrated part design, the demand for large sheets is increasing, and the performance requirements are also becoming more stringent. Large sheets are typically manufactured using ingot rolling. However, for thicker sheets, limitations imposed by ingot thickness and equipment capabilities mean that existing ingot rolling methods cannot introduce sufficient strain at the center of the sheet thickness, resulting in poor uniformity of the grain structure. Poor grain uniformity directly affects the uniformity of mechanical properties and stress corrosion resistance, severely impacting the service life of the sheet metal.

[0004] Currently, there are relevant patent reports on methods for improving the stress corrosion resistance of Al-Zn-Mg-Cu alloys and methods for preparing forgings. For example, patent CN115710661A discloses an Al-Zn-Mg-Cu aluminum alloy and a method for improving its stress corrosion resistance. The aluminum alloy composition by weight percentage is Zn 7.0~10.0%, Mg 1.0~1.8%, Cu 1.0~2.3%, Zr 0.08~0.12%, Ti 0.02~0.06%, Fe ≤0.08%, Si ≤0.06%, Mn ≤0.05%, Cr ≤0.05%, and also includes Sc and Er, and the content of Sc and Er satisfies 0.5≤Sc / Er≤1.0, with the balance being Al. This patent primarily improves stress corrosion resistance by adding Sc and Er to promote the precipitation of the MgZn2 phase within the grains and reduce the amount of MgZn2 phase at grain boundaries. However, the addition of expensive Sc and Er elements to the alloy is detrimental to the low-cost manufacturing and application of aluminum alloys. Patent CN111974919A discloses a forging method to improve the anisotropy of 7XXX aluminum alloy forgings. It adopts a forging process with temperature gradients of high-temperature forging → medium-temperature forging → low-temperature forging to increase the recrystallization volume fraction of the forgings and reduce the strength and toughness differences between the three dimensions. However, this invention does not consider the microstructure uniformity of aluminum alloy forgings with large thicknesses. Patent CN111644548A discloses a reforging technology for high-strength homogeneous aluminum alloy forgings for aerospace applications. Through multiple small-deformation upsetting and drawing processes, it reduces the generation of cracks during forging. However, this invention does not address the improvement of stress corrosion resistance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-strength, corrosion-resistant, ultra-thick aluminum alloy forging, its preparation method, and applications through component design, precise control of the forging process, and novel aging treatment technology. The aluminum alloy forgings of this invention exhibit high strength, low stress corrosion sensitivity, and good microstructure and property uniformity. Furthermore, they are free of rare and precious metal elements such as Sc, effectively reducing production costs. The forgings prepared are suitable for load-bearing structural components in aerospace equipment. Specifically, this invention includes the following: A method for preparing a high-strength, corrosion-resistant, ultra-thick aluminum alloy forging includes the following steps: (1) The aluminum alloy ingot is homogenized to obtain aluminum alloy billet; (2) Forging the homogenized aluminum alloy billet: First, the aluminum alloy billet is subjected to 1-2 passes of wide-direction upsetting deformation and 2-3 passes of wide-direction drawing, and then subjected to 1-2 passes of wide-direction upsetting deformation and 7-9 passes of wide-direction drawing to obtain an ultra-thick forging with a thickness of not less than 200 mm; the reduction of the wide-direction upsetting deformation is 20%-40%, and the thickness of the aluminum alloy billet is reduced by 10%-15% for each pass of wide-direction drawing, and the reduction speed of the wide-direction upsetting and wide-direction drawing is ≤4 mm / s; (3) The ultra-thick forging obtained in step (2) is subjected to solution treatment to obtain forging billet; (4) The forging billet after solution treatment in step (3) is subjected to cold deformation to reduce residual stress; (5) The cold-deformed forging billet is subjected to three-stage artificial aging treatment within 30 days. The temperature of the first stage of aging treatment is 115~125℃ and the holding time is 4~8h; the temperature of the second stage of aging treatment is 152~157℃ and the holding time is 12~24h; the temperature of the third stage of aging treatment is 110~130℃ and the holding time is 6~24h.

[0006] Preferably, the composition and weight percentage of the aluminum alloy ingot in step (1) are: Zn 7.3~7.7%, Mg 1.4~1.6%, Cu 1.9~2.2%, Zr 0.08~0.12%, Fe ≤0.08%, Si ≤0.04%, Mn ≤0.04%, Cr ≤0.03%, Ti≤0.03%, of which Fe+Mn≤0.08%, and the remainder is Al.

[0007] Preferably, the thickness of the aluminum alloy ingot in step (1) is 450 ~ 550 mm.

[0008] Preferably, the feed amount for width drawing in step (2) is set as follows: when the width length of the aluminum alloy billet is less than 1000mm, the feed amount for width drawing is controlled to be 250~300mm; when the width length of the aluminum alloy billet is greater than 1000mm and less than 1500mm, the feed amount for width drawing is controlled to be 200~250mm; when the width length of the aluminum alloy billet is greater than 1500mm, the feed amount for width drawing is controlled to be no greater than 200mm.

[0009] Preferably, step (2) further includes: heating the aluminum alloy ingot to 400℃~430℃ and holding it at that temperature for ≥350min before the first wide-axis roughing deformation.

[0010] Preferably, the heat preservation temperature of the solution treatment in step (3) is 470~480℃.

[0011] Preferably, after the solution treatment and heat preservation in step (3) are completed, the forging billet is quenched and the quenching water temperature is controlled at 40~50℃.

[0012] Preferably, in step (5): the heating rate of the first stage aging treatment is 10~30℃ / h; the heating rate of the second stage aging treatment is 6~12℃ / h; the third stage aging treatment adopts a method of rapid cooling to the aging temperature or cooling first and then heating to the aging temperature. The rapid cooling to the aging temperature method controls the cooling time to be 10~30min. The cooling method of cooling first and then heating to the aging temperature method is air cooling and the heating rate is 10~30℃ / h.

[0013] A high-strength, corrosion-resistant aluminum alloy ultra-thick forging prepared by the aforementioned method.

[0014] The high-strength corrosion-resistant aluminum alloy ultra-thick forgings of the present invention have a longitudinal tensile strength ≥530MPa, a yield strength ≥530MPa, and an elongation ≥10%. They do not crack when cyclically immersed in 241MPa stress conditions for 20 days according to GB / T 22640-2008.

[0015] Application of the aforementioned high-strength, corrosion-resistant aluminum alloy ultra-thick forging in aerospace equipment.

[0016] The beneficial effects of this invention are: (1) The aluminum alloy forging of the present invention, by reasonably adjusting the content and ratio of the main alloying elements Zn, Mg and Cu, not only ensures that the alloy has high strength, but also increases the Cu content in the grain boundary precipitate, reduces the potential difference between the grain boundary phase and the matrix, inhibits the galvanic corrosion at the grain boundary, and improves the stress corrosion resistance of Al-Zn-Mg-Cu alloy.

[0017] (2) The aluminum alloy ultra-thick forging of the present invention effectively reduces the content of refractory coarse phase in the alloy by controlling the content and ratio of Fe and Mn elements, thereby reducing corrosion cracking caused by refractory coarse phase and improving stress corrosion resistance.

[0018] (3) The present invention adopts a novel forging process of casting upsetting and thickness elongation. By innovatively allocating parameters such as elongation pressing amount, elongation feed amount, and pressing speed, the strain is transferred from the core of the casting to the surface of the casting and uniformly distributed in the thickness direction of the casting. Ultimately, this ensures that the surface of the ultra-thick forging has the same grain structure and uniform mechanical properties as the core of the plate.

[0019] (4) This invention employs a different three-stage aging process than conventional methods, applied to ultra-thick forgings, which significantly improves the stress corrosion resistance of the alloy while ensuring sufficient strength. The longitudinal, transverse, and vertical tensile strengths of the Al-Zn-Mg-Cu alloy forgings of this invention are 30-40 MPa higher than the minimum strength of the American AMS standard. According to GB / T 22640-2008 Stress Corrosion Test Method for C-ring Specimens of Aluminum Alloy Processed Products, the forgings do not crack after 20 days of cyclic immersion under a stress of 241 MPa, thus meeting the performance requirements of aluminum alloys for aerospace structural components. Attached Figure Description

[0020] Figure 1 This refers to the homogenized microstructure of the aluminum alloy ingot in Embodiment 1 of the present invention; Figure 2 The grain structure of the ultra-thick aluminum alloy forging in Example 2 of this invention; Figure 3 The TEM microstructure of the grain boundary precipitates in the ultra-thick aluminum alloy forging in Example 3 of this invention; Figure 4 The C-ring fracture of the ultra-thick aluminum alloy forging in Embodiment 1 of the present invention; Figure 5 The C-ring fracture of the ultra-thick aluminum alloy forging in Embodiment 3 of the present invention; Figure 6 The grain structure of the ultra-thick aluminum alloy forging in Comparative Example 2 of this invention; Figure 7 The C-ring fracture surface of the ultra-thick aluminum alloy forging in Comparative Example 1 of this invention; Figure 8 The fracture surface of the C-ring of the ultra-thick aluminum alloy forging in Comparative Example 3 of this invention. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments shown below do not limit the scope of the invention as described in the claims. Furthermore, the complete contents of the configurations illustrated in the following embodiments are not limited to those necessary for the solution of the invention as described in the claims.

[0022] The high-strength corrosion-resistant aluminum alloy ultra-thick forgings of the present invention have the following composition and weight percentage: Zn 7.3~7.7%, Mg 1.4~1.6%, Cu 1.9~2.2%, Zr 0.08~0.12%, Fe ≤0.08%, Si ≤0.04%, Mn ≤0.04%, Cr ≤0.03%, Ti ≤0.03%, with the remainder being Al, wherein the total amount of Fe and Mn is not greater than 0.08%.

[0023] The method for preparing the high-strength, corrosion-resistant, ultra-thick aluminum alloy forgings of the present invention includes the following steps: (1) The aluminum alloy ingot has a thickness of 450 mm to 550 mm and is homogenized. (2) The homogenized billet is forged, including the following steps: the aluminum alloy ingot is heated to 400℃~430℃ before wide-direction upsetting deformation, and the holding time is ≥350 minutes; then the ingot is subjected to one wide-direction upsetting deformation and 2~3 passes of wide-direction drawing; then it is subjected to one more wide-direction upsetting deformation and 6~10 passes of wide-direction drawing; the reduction of the ingot during wide-direction upsetting deformation is 20%~40%; the thickness of the ingot is reduced by 10%~15% after each pass of wide-direction drawing, and the reduction speed of wide-direction upsetting and wide-direction drawing is ≤4 mm / s; when the length of the ingot in the width direction is less than 1000mm, the elongation feed in the width direction is 250~300mm; when the length of the ingot in the width direction is greater than 1000mm and less than 1500mm, the elongation feed in the width direction is 200~250mm; when the length of the ingot in the width direction is greater than 1500mm, the elongation feed in the width direction is not greater than 200mm; the thickness of the obtained ultra-thick forging is not less than 200mm; (3) The obtained ultra-thick forgings are subjected to solution treatment at a temperature of 470~480℃. After the solution treatment and heat preservation are completed, the quenching water temperature is controlled at 40~50℃. (4) Reduce residual stress by cold deformation of the cooled forging billet; (5) The cold-deformed forging billet is subjected to three-stage artificial aging treatment within 30 days. The heating rate of the first stage of aging is 10~30℃ / h, the aging temperature is 120℃, and the holding time is 4~8h. The heating rate of the second stage of aging is 6~12℃ / h, the aging temperature is 152~157℃, and the holding time is 12~24h. The third stage of aging adopts the method of rapid cooling to the aging temperature or cooling and then heating. The cooling method is air cooling, the heating rate is 10~30℃ / h, the aging temperature is 110~130℃, and the holding time is 6~24h.

[0024] The principle followed by the preparation method of the high-strength corrosion-resistant aluminum alloy ultra-thick forgings of the present invention is: (1) The aluminum alloy forging of the present invention ensures sufficient precipitation of MgZn2 phase by reasonably adjusting the content of the main alloying elements Zn, Mg and Cu, so that the alloy has high strength. In addition, the Cu content in the grain boundary precipitate is increased, the potential difference between the grain boundary phase and the matrix is ​​reduced, and the stress corrosion resistance of Al-Zn-Mg-Cu alloy is improved.

[0025] (2) The aluminum alloy ultra-thick forging of the present invention effectively reduces the content of refractory coarse phase in the alloy by controlling the content of Fe and Mn elements, thereby reducing corrosion cracking caused by refractory coarse phase and improving stress corrosion resistance.

[0026] (3) The present invention adopts a novel forging process of casting upsetting and thickness elongation. By innovatively allocating parameters such as elongation pressing amount, elongation feed amount, and pressing speed, the strain is transferred from the core of the casting to the surface of the casting and uniformly distributed in the thickness direction of the casting. Ultimately, this ensures that the surface of the ultra-thick forging has the same grain structure and uniform mechanical properties as the core of the plate.

[0027] (4) The present invention adopts a different three-stage aging process than the conventional one and is applied to ultra-thick forgings. The first and second stages of aging form a high-density fine MgZn2 phase in the grain, while the MgZn2 phase is discontinuously distributed on the grain boundary. The third stage of aging causes Zn and Mg elements in the matrix to precipitate further, which greatly improves the stress corrosion resistance of the alloy while ensuring sufficient strength.

[0028] A method for preparing a high-strength, corrosion-resistant, ultra-thick aluminum alloy forging includes the following steps: (1) Aluminum alloy ingots with a thickness of 450~550 mm (e.g., 420 mm, 440 mm, 460 mm, 480 mm, 500 mm, 520 mm, 540 mm, etc.) are homogenized to obtain aluminum alloy billets. The composition and weight percentage of the aluminum alloy ingots are: Zn 7.3~7.7%, Mg 1.4~1.6%, Cu 1.9~2.2%, Zr 0.08~0.12%, Fe ≤0.08%, Si ≤0.04%, Mn ≤0.04%, Cr ≤0.03%, Ti ≤0.03%, wherein Fe+Mn≤0.08%; specifically, the Zn content in the alloy can be 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, etc.; the Mg content can be 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, etc.; the Cu content can be 1.9%, 1.95%, 2.0%, 2.1%, 2.15%, etc.; the Zr content can be 0.09%, 0.095%, 0.10%, 0.11%, etc.; F The content of electrons (e) can be 0, 0.01%, 0.02%, 0.04%, 0.06%, 0.07%, etc.; the content of silicon (Si) can be 0, 0.01%, 0.02%, 0.03%, etc.; the content of manganese (Mn) can be 0, 0.01%, 0.02%, 0.03%, etc.; the content of chromium (Cr) can be 0, 0.01%, 0.015%, 0.02%, 0.025%, etc.; and the content of titanium (Ti) can be 0, 0.01%, 0.015%, 0.02%, 0.025%, etc.

[0029] (2) Forging the homogenized aluminum alloy billet: First, heat the aluminum alloy ingot to 400~430℃ (e.g., 405℃, 410℃, 415℃, 420℃, 425℃, etc.) and hold for ≥350min (e.g., 360min, 370min, 380min, 400min, 450min, etc.). Then, perform 1~2 passes (preferably 1 pass) of wide-direction upsetting deformation and 2~3 passes of wide-direction drawing deformation on the aluminum alloy billet, and then perform 1~2 passes of wide-direction drawing deformation. The aluminum alloy billet undergoes one (preferably 1) pass of wide-direction upsetting deformation and 7-9 passes of wide-direction drawing to obtain an ultra-thick forging with a thickness of not less than 200 mm. The reduction amount of the wide-direction upsetting deformation is 20%-40% (e.g., 22%, 24%, 26%, 28%, 30%, 32%, 35%, 38%, etc.). The thickness of the aluminum alloy billet decreases by 10%-15% (e.g., 11%, 12%, 13%, 14%, etc.) for each pass of wide-direction drawing. The reduction speed of the wide-direction upsetting and wide-direction drawing is ≤4. The feed rate is set as follows: when the width length of the aluminum alloy billet is less than 1000mm, the feed rate is controlled at 250~300mm (e.g., 260mm, 270mm, 280mm, 290mm, etc.); when the width length of the aluminum alloy billet is greater than 1000mm and less than 1500mm, the feed rate is controlled at 200~250mm (e.g., 210mm, 220mm, 230mm, 240mm, etc.); when the width length of the aluminum alloy billet is greater than 1500mm, the feed rate is controlled at no more than 200mm (e.g., 100mm, 120mm, 150mm, 160mm, 180mm, 190mm, etc.). (3) The ultra-thick forging obtained in step (2) is subjected to solution treatment at a holding temperature of 470~480℃ (e.g., 470℃, 472℃, 474℃, 476℃, 478℃, etc.) to obtain a forging billet; then the forging billet is subjected to quenching treatment, and the quenching water temperature is controlled at 40~50℃ (e.g., 42℃, 44℃, 46℃, 48℃, etc.). (4) The forging billet after solution treatment in step (3) is subjected to cold deformation to reduce residual stress; (5) The cold-deformed forging billet shall be subjected to a three-stage artificial aging treatment within 30 days. The heating rate of the first stage of aging treatment shall be 10~30℃ / h (e.g., 12℃ / h, 15℃ / h, 18℃ / h, 20℃ / h, 22℃ / h, 25℃ / h, 28℃ / h, etc.), the temperature shall be 115~125℃ (e.g., 115℃, 118℃, 120℃, 122℃, 124℃, etc.), and the holding time shall be 4~8h, e.g., 4.5h. The heating rate for the second-stage aging treatment is 6~12℃ / h (e.g., 7℃ / h, 8℃ / h, 9℃ / h, 10℃ / h, 11℃ / h, etc.), the temperature is 152~157℃ (e.g., 153℃, 154℃, 155℃, 156℃, etc.), and the holding time is 12~24h (e.g., 14℃ / h, 16℃ / h, 18℃ / h, 20℃ / h, etc.). The third-stage aging treatment temperature is 110~130℃ (e.g., 112℃, 115℃, 118℃, 120℃, 122℃, 125℃, 128℃, etc.), and the holding time is 6~24h (e.g., 8h, 10h, 12h, 15h, 18h, 20h, 22h, etc.). The third-stage aging treatment adopts a method of rapid cooling to the aging temperature or cooling first and then heating to the aging temperature. The cooling time is controlled to be 10~30min, for example, 12min, 15min, 18min, 20min, 22min, 25min, 28min, etc. in the method of cooling first and then heating to the aging temperature. The cooling method is air cooling and the heating rate is 10~30℃ / h (for example, 12℃ / h, 15℃ / h, 18℃ / h, 20℃ / h, 22℃ / h, 25℃ / h, 28℃ / h, etc.).

[0030] The preferred embodiments of the present invention will now be described in detail. The following embodiments and comparative examples are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0031] Example 1

[0032] The composition and weight percentage of the Al-Zn-Mg-Cu alloy used in this embodiment are as follows: Zn 7.3%, Mg 1.4%, Cu 1.9%, Zr 0.1%, Fe 0.05%, Si 0.03%, Mn 0.03%, Cr 0.02%, Ti 0.01%, Fe+Mn≤0.08%, and the remainder is Al.

[0033] The aluminum alloy ingot is homogenized, and then the homogenized ingot is forged, as follows: (1) Ingot sawing: Cut an ingot with a length of 2000 mm × width of 1200 mm × thickness of 470 mm; (2) Heating of ingot and mold: Heat the ingot to 400°C and the mold to 400°C; (3) Forging: The ingot is subjected to the first wide-direction upsetting deformation with a deformation amount of 40%; then it is subjected to two wide-direction elongation passes with a reduction amount of 15% and 15% respectively; then it is subjected to the second wide-direction upsetting deformation with a deformation amount of 25%; then it is subjected to seven wide-direction elongation passes with a reduction amount of 15% each; the thickness of the ultra-thick forging is 218mm. (4) The forged billet is subjected to solution treatment at a temperature of 475℃ for 4 hours. After the solution treatment is completed, the quenching water temperature is controlled at 45℃. (5) Reduce residual stress by cold deformation of the cooled forging billet; (6) Heat treatment: The cold-deformed billet is subjected to three-stage artificial aging treatment. The first stage aging temperature is 120℃ and the holding time is 6h; the second stage aging temperature is 155℃ and the holding time is 16h; the third stage aging temperature is 120℃ and the holding time is 24h.

[0034] Example 2

[0035] The composition and weight percentage of the Al-Zn-Mg-Cu alloy used in this embodiment are as follows: Zn 7.7%, Mg 1.6%, Cu 2.2%, Zr 0.1%, Fe 0.06%, Si 0.04%, Mn 0.02%, Cr 0.01%, Ti 0.01%, Fe+Mn≤0.08%, and the remainder is Al.

[0036] The aluminum alloy ingot is homogenized, and then the homogenized ingot is forged, as follows: (1) Ingot sawing: Cut an ingot with a length of 2000 mm × width of 1200 mm × thickness of 470 mm; (2) Heating of ingot and mold: Heat the ingot to 400°C and the mold to 400°C; (3) Forging: The ingot is subjected to the first wide-direction upsetting deformation with a deformation amount of 20%; then it is subjected to two wide-direction elongation passes with a reduction amount of 15% and 15% respectively; then it is subjected to the second wide-direction upsetting deformation with a deformation amount of 30%; then it is subjected to nine wide-direction elongation passes with a reduction amount of 15%, 15%, 15%, 15%, 13%, 13%, 10%, 10%, 10% respectively; the thickness of the ultra-thick forging is 211mm. (4) The forged billet is subjected to solution treatment at a temperature of 475℃ for 4 hours. After the solution treatment is completed, the quenching water temperature is controlled at 45℃. (5) Reduce residual stress by cold deformation of the cooled forging billet; (6) Heat treatment: The cold-deformed billet is subjected to three-stage artificial aging treatment. The first stage aging temperature is 120℃ and the holding time is 6h; the second stage aging temperature is 155℃ and the holding time is 16h; the third stage aging temperature is 120℃ and the holding time is 24h.

[0037] Example 3

[0038] The composition and weight percentage of the Al-Zn-Mg-Cu alloy used in this embodiment are as follows: Zn 7.5%, Mg 1.5%, Cu 2.1%, Zr 0.1%, Fe 0.04%, Si 0.02%, Mn 0.02%, Cr 0.02%, Ti 0.01%, Fe+Mn≤0.08%, and the remainder is Al.

[0039] The aluminum alloy ingot is homogenized, and then the homogenized ingot is forged, as follows: (1) Ingot sawing: Cut an ingot with a length of 2000 mm × width of 1200 mm × thickness of 470 mm; (2) Heating of ingot and mold: Heat the ingot to 400°C and the mold to 400°C; (3) Forging: The ingot is subjected to the first wide-direction upsetting deformation with a deformation amount of 40%; then it is subjected to three wide-direction elongation passes with a reduction amount of 15%, 10%, and 10% respectively; then it is subjected to the second wide-direction upsetting deformation with a deformation amount of 20%; then it is subjected to eight wide-direction elongation passes with a reduction amount of 15%, 15%, 15%, 13%, 13%, 10%, 10%, and 10% respectively; the thickness of the ultra-thick forging is 207mm. (4) The forged billet is subjected to solution treatment at a temperature of 475℃ for 4 hours. After the solution treatment is completed, the quenching water temperature is controlled at 45℃. (5) Reduce residual stress by cold deformation of the cooled forging billet; (6) Heat treatment: The cold-deformed billet is subjected to three-stage artificial aging treatment. The first stage aging temperature is 120℃ and the holding time is 8h; the second stage aging temperature is 152℃ and the holding time is 22h; the third stage aging temperature is 110℃ and the holding time is 6h.

[0040] Example 4

[0041] The composition and weight percentage of the Al-Zn-Mg-Cu alloy used in this embodiment are as follows: Zn 7.5%, Mg 1.5%, Cu 2.1%, Zr 0.1%, Fe 0.05%, Si 0.03%, Mn 0.01%, Cr 0.03%, Ti 0.01%, Fe+Mn≤0.08%, and the remainder is Al.

[0042] The aluminum alloy ingot is homogenized, and then the homogenized ingot is forged, as follows: (1) Ingot sawing: Cut an ingot with a length of 2000 mm × width of 1200 mm × thickness of 470 mm; (2) Heating of ingot and mold: Heat the ingot to 400°C and the mold to 400°C; (3) Forging: The ingot is subjected to the first wide-direction upsetting deformation with a deformation amount of 40%; then it is subjected to three wide-direction elongation passes with a reduction amount of 15%, 10%, and 10% respectively; then it is subjected to the second wide-direction upsetting deformation with a deformation amount of 20%; then it is subjected to eight wide-direction elongation passes with a reduction amount of 15%, 15%, 15%, 13%, 13%, 10%, 10%, and 10% respectively; the thickness of the ultra-thick forging is 207mm. (4) The forged billet is subjected to solution treatment at a temperature of 475℃ for 4 hours. After the solution treatment is completed, the quenching water temperature is controlled at 45℃. (5) Reduce residual stress by cold deformation of the cooled forging billet; (6) Heat treatment: The cold-deformed billet is subjected to three-stage artificial aging treatment. The first stage aging temperature is 120℃ and the holding time is 4h; the second stage aging temperature is 157℃ and the holding time is 12h; the third stage aging temperature is 130℃ and the holding time is 18h.

[0043] Comparative Example 1 The composition and weight percentage of the Al-Zn-Mg-Cu alloy used in this embodiment are as follows: Zn 7.5%, Mg 1.6%, Cu 1.7%, Zr 0.1%, Fe 0.04%, Si 0.02%, Mn 0.03%, Cr 0.02%, Ti 0.01%, Fe+Mn≤0.08%, and the remainder is Al.

[0044] The aluminum alloy ingot is homogenized, and then the homogenized ingot is forged, as follows: (1) Ingot sawing: Cut an ingot with a length of 2000 mm × width of 1200 mm × thickness of 470 mm; (2) Heating of ingot and mold: Heat the ingot to 400°C and the mold to 400°C; (3) Forging: The ingot is subjected to the first wide-direction upsetting deformation with a deformation amount of 40%; then it is subjected to three wide-direction elongation passes with a reduction amount of 15%, 10%, and 10% respectively; then it is subjected to the second wide-direction upsetting deformation with a deformation amount of 20%; then it is subjected to eight wide-direction elongation passes with a reduction amount of 15%, 15%, 15%, 13%, 13%, 10%, 10%, and 10% respectively; the thickness of the ultra-thick forging is 207mm. (4) The forged billet is subjected to solution treatment at a temperature of 475℃ for 4 hours. After the solution treatment is completed, the quenching water temperature is controlled at 45℃. (5) Reduce residual stress by cold deformation of the cooled forging billet; (6) Heat treatment: The cold-deformed billet is subjected to three-stage artificial aging treatment. The first stage aging temperature is 120℃ and the holding time is 6h; the second stage aging temperature is 155℃ and the holding time is 16h; the third stage aging temperature is 110℃ and the holding time is 6h.

[0045] Comparative Example 2 The composition and weight percentage of the Al-Zn-Mg-Cu alloy used in this embodiment are as follows: Zn 7.5%, Mg 1.5%, Cu 2.1%, Zr 0.1%, Fe 0.04%, Si 0.02%, Mn 0.03%, Cr 0.02%, Ti 0.01%, Fe+Mn≤0.08%, and the remainder is Al.

[0046] The aluminum alloy ingot is homogenized, and then the homogenized ingot is forged, as follows: (1) Ingot sawing: Cut an ingot with a length of 2000 mm × width of 1200 mm × thickness of 470 mm; (2) Heating of ingot and mold: Heat the ingot to 400°C and the mold to 400°C; (3) Forging: The ingot is upsetting in the width direction with a deformation of 60%; then it is drawn in 9 passes along the width direction with a reduction of 25%, 25%, 25%, 20%, 20%, 15%, 15%, 15%, 11% respectively; the thickness of the ultra-thick forging is 207mm. (4) The forged billet is subjected to solution treatment at a temperature of 475℃ for 4 hours. After the solution treatment is completed, the quenching water temperature is controlled at 45℃. (5) Reduce residual stress by cold deformation of the cooled forging billet; (6) Heat treatment: The cold-deformed billet is subjected to three-stage artificial aging treatment. The first stage aging temperature is 120℃ and the holding time is 6h; the second stage aging temperature is 155℃ and the holding time is 22h; the third stage aging temperature is 120℃ and the holding time is 24h.

[0047] Comparative Example 3 The composition and weight percentage of the Al-Zn-Mg-Cu alloy used in this embodiment are as follows: Zn 7.5%, Mg 1.5%, Cu 2.1%, Zr 0.1%, Fe 0.05%, Si 0.03%, Mn 0.02%, Cr 0.01%, Ti 0.01%, Fe+Mn≤0.08%, and the remainder is Al.

[0048] The aluminum alloy ingot is homogenized, and then the homogenized ingot is forged, as follows: (1) Ingot sawing: Cut an ingot with a length of 2000 mm × width of 1200 mm × thickness of 470 mm; (2) Heating of ingot and mold: Heat the ingot to 400°C and the mold to 400°C; (3) Forging: The ingot is subjected to the first wide-direction upsetting deformation with a deformation amount of 40%; then it is subjected to two wide-direction elongation passes with a reduction amount of 15% and 15% respectively; then it is subjected to the second wide-direction upsetting deformation with a deformation amount of 25%; then it is subjected to seven wide-direction elongation passes with a reduction amount of 15% each; the thickness of the ultra-thick forging is 218mm. (4) The forged billet is subjected to solution treatment at a temperature of 475℃ for 4 hours. After the solution treatment is completed, the quenching water temperature is controlled at 45℃. (5) Reduce residual stress by cold deformation of the cooled forging billet; (6) Heat treatment: The cold-deformed billet is subjected to two-stage artificial aging treatment. The first stage aging temperature is 120℃ and the holding time is 6h; the second stage aging temperature is 155℃ and the holding time is 16h.

[0049] Referring to Table 1, the room temperature tensile properties, electrical conductivity, and stress corrosion resistance of the ultra-thick forgings prepared in the embodiments and comparative examples of the present invention are shown. The room temperature tensile properties, electrical conductivity, and stress corrosion resistance of the embodiments in Table 1 are significantly better than those of the comparative examples.

[0050] Figure 1 This refers to the homogenized microstructure of the aluminum alloy ingot in Example 1; Figure 2 The grain structure of the ultra-thick aluminum alloy forging in Example 2; Figure 6 The image shows the grain structure of the ultra-thick aluminum alloy forging in Comparative Example 2. It can be seen that this invention employs a novel forging process combining ingot upsetting and direct thickness elongation. By innovatively allocating parameters such as elongation reduction, elongation feed, and reduction speed, the final forging achieves uniform distribution along the ingot thickness direction, ensuring that the surface layer of the plate has the same grain structure and uniform mechanical properties as the core layer.

[0051] Figure 3 The TEM microstructure of the grain boundary precipitates in the ultra-thick aluminum alloy forging in Example 3 is shown. This invention ensures the alloy is at a high strength level by reasonably adjusting the content of the main alloying elements Zn, Mg, and Cu, while optimizing the Cu content to increase the Cu content of the grain boundary precipitates, reduce the potential difference between the matrix and the grain boundary phase, and improve the stress corrosion resistance of the alloy.

[0052] Figure 4 The stress corrosion test of the C-ring fracture surface of the ultra-thick aluminum alloy forging in Example 1; Figure 5The stress corrosion test of the C-ring fracture surface of the ultra-thick aluminum alloy forging in Example 3; Figure 7 The stress corrosion test of the C-ring fracture surface of the ultra-thick aluminum alloy forging in Comparative Example 1; Figure 8 The fracture surface of the C-ring in the stress corrosion test of the ultra-thick aluminum alloy forging in Comparative Example 3 is shown. In the example, after immersion, the surface of the C-ring for stress corrosion testing was mainly composed of corrosion pits, with no cracks. After the cross-section of the C-ring for stress corrosion testing was cut open, metallographic observation of the fracture surface showed that the depth of the corrosion pits was in the range of 0.1~0.5mm, indicating excellent stress corrosion performance. In the comparative example, after immersion, the surface of the C-ring for stress corrosion testing showed a large number of short cracks. Similarly, after the cross-section of the C-ring for stress corrosion testing was cut open, metallographic observation of the fracture surface showed that the depth of the corrosion pits was in the range of 1.5~2mm, indicating unqualified stress corrosion performance.

[0053] The above are merely specific application examples of the present invention and do not constitute any limitation on the scope of protection of the present invention. All technical solutions formed by equivalent transformations or substitutions fall within the scope of protection of the present invention.

[0054] Table 1. Properties of aluminum alloy forgings from the examples and comparative examples

[0055] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for producing a high-strength corrosion-resistant aluminum alloy super-thick forging, characterized by comprising: Includes the following steps: ​ (1) The aluminum alloy ingot is homogenized to obtain aluminum alloy billet; (2) Forging the aluminum alloy billet after homogenization: First, the aluminum alloy billet is subjected to 1-2 passes of wide-direction upsetting deformation and 2-3 passes of wide-direction drawing, and then subjected to 1-2 passes of wide-direction upsetting deformation and 7-9 passes of wide-direction drawing to obtain an ultra-thick forging with a thickness of not less than 200 mm; the reduction of the wide-direction upsetting deformation is 20%-40%, and the thickness of the aluminum alloy billet is reduced by 10%-15% for each pass of wide-direction drawing, and the reduction speed of the wide-direction upsetting and wide-direction drawing is ≤4 mm / s; (3) The ultra-thick forging obtained in step (2) is subjected to solution treatment to obtain forging billet; (4) The forging billet after solution treatment in step (3) is subjected to cold deformation to reduce residual stress; (5) The cold-deformed forging billet shall be subjected to three-stage artificial aging treatment within 30 days. The temperature of the first stage of aging treatment is 115~125℃ and the holding time is 4~8h; the temperature of the second stage of aging treatment is 152~157℃ and the holding time is 12~24h; the temperature of the third stage of aging treatment is 110~130℃ and the holding time is 6~24h. The composition and weight percentage of the aluminum alloy ingot are as follows: Zn 7.3~7.7%, Mg 1.4~1.6%, Cu 1.9~2.2%, Zr 0.08~0.12%, Fe≤0.08%, Si≤0.04%, Mn≤0.04%, Cr≤0.03%, Ti≤0.03%, of which Fe+Mn≤0.08%, and the remainder is Al.

2. The method for preparing a high-strength, corrosion-resistant, ultra-thick aluminum alloy forging according to claim 1, characterized in that, The thickness of the aluminum alloy ingot in step (1) is 450~550mm.

3. The method for preparing a high-strength, corrosion-resistant, ultra-thick aluminum alloy forging according to claim 1, characterized in that, The feed amount for width drawing in step (2) is set as follows: when the width length of the aluminum alloy billet is less than 1000mm, the feed amount for width drawing is controlled at 250~300mm; when the width length of the aluminum alloy billet is greater than 1000mm and less than 1500mm, the feed amount for width drawing is controlled at 200~250mm; when the width length of the aluminum alloy billet is greater than 1500mm, the feed amount for width drawing is controlled at no more than 200mm.

4. The method for preparing a high-strength, corrosion-resistant, ultra-thick aluminum alloy forging according to claim 1, characterized in that, Step (2) further includes: heating the aluminum alloy ingot to 400℃~430℃ and holding it at that temperature for ≥350min before the first wide-axis upsetting deformation.

5. The method for preparing a high-strength, corrosion-resistant, ultra-thick aluminum alloy forging according to claim 1, characterized in that, The heat preservation temperature for the solution treatment in step (3) is 470~480℃.

6. The method for preparing a high-strength, corrosion-resistant, ultra-thick aluminum alloy forging according to claim 1, characterized in that, After the solution treatment and heat preservation in step (3) are completed, the forging billet is quenched, and the quenching water temperature is controlled at 40~50℃.

7. The method for preparing a high-strength, corrosion-resistant, ultra-thick aluminum alloy forging according to claim 1, characterized in that, Step (5): The heating rate of the first stage aging treatment is 10~30℃ / h; the heating rate of the second stage aging treatment is 6~12℃ / h; the third stage aging treatment adopts the method of rapid cooling to the aging temperature or cooling first and then heating to the aging temperature. The rapid cooling to the aging temperature method controls the cooling time to be 10~30min. The cooling method of cooling first and then heating to the aging temperature method is air cooling and the heating rate is 10~30℃ / h.

8. A high-strength corrosion-resistant aluminum alloy ultra-thick forging prepared by the preparation method of the high-strength corrosion-resistant aluminum alloy ultra-thick forging according to any one of claims 1-7.

9. The high-strength corrosion-resistant aluminum alloy super-thick forging according to claim 8, characterized in that, Its longitudinal tensile strength is ≥530MPa and its elongation is ≥10%. It does not crack when cyclically immersed in water for 20 days under a stress of 241MPa according to GB / T 22640-2008.

10. The application of the high-strength corrosion-resistant aluminum alloy ultra-thick forging as described in claim 8 in aerospace equipment.

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