An etch-resistant aluminum alloy having an exfoliation corrosion rating of N

Abstract

The application belongs to the field of aluminum alloy materials, and provides an aluminum alloy with a tensile strength exceeding 780 MPa and N-grade exfoliation corrosion and a preparation method thereof.The aluminum alloy comprises the following chemical components by weight percentage: Zn 10.0-12.0%, Mg 2.5-3.5%, Zr 0.08-0.25%, Ti 0.03-0.10%, Fe ≤0.10%, Si ≤0.10%, other impurities ≤0.05% individually, a total amount ≤0.15%, and the balance being Al.The preparation method comprises the following steps: alloy component distribution, water-cooled mold casting to obtain an alloy round ingot with a required specification; two-stage homogenization process treatment and extrusion process forming; two-stage solid solution and T6 peak aging, so that the tensile strength exceeds 780 MPa and the exfoliation corrosion resistance grade is N grade; and the prepared plate can be widely applied to lightweight components in the fields of aerospace, transportation and weapons.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal materials, and relates to an aluminum alloy and a preparation method thereof, in particular to a preparation method of an ultrahigh-strength aluminum alloy extruded plate with a tensile strength exceeding 780 MPa and an exfoliation corrosion resistance grade N. BACKGROUND

[0002] Al-Zn-Mg series aluminum alloys have advantages of low density, high strength and toughness, and low cost, and are structural materials with great application prospects in the fields of aerospace, navigation, military industry, and rail transportation. With the expansion of applications to offshore, industry, and atmosphere, the corrosion resistance and mechanical properties of traditional Al-Zn-Mg alloys have gradually failed to meet the requirements of component design. How to have high tensile strength while maintaining good corrosion resistance has become a key problem in the development of Al-Zn-Mg series alloys. Adding Cu elements to Al-Zn-Mg series alloys for micro-alloying can promote the formation of clusters at the early stage of aging and increase the volume fraction of strengthening phases, significantly affect the types, shapes and distribution of precipitates, and thus improve the mechanical properties of the alloy. Numerous studies have shown that adding Cu elements to Al-Zn-Mg series aluminum alloys can increase the hardness and tensile strength of the alloy, but will also increase the exfoliation corrosion sensitivity (exfoliation corrosion grade is generally below EB grade) of the alloy, limiting the wide application of Al-Zn-Mg alloys.

[0003] In order to increase the strength and corrosion resistance of Al-Zn-Mg alloy, a series of schemes have been tried, such as: patent application CN118497566A relates to a light high modulus high strength toughness corrosion resistant aluminum alloy material, characterized in that the aluminum alloy contains: Mg 5.0~7.9wt%, Zn 2.2~4.6wt%, Li 0.5~1.9wt%, and total content of at least one of Mn, Ti, Zr, Sc, Er elements is not more than 0.7wt%, the rest is Al and inevitable impurities, wherein the impurity elements are ≤0.25wt% each, total ≤0.50wt%. The preparation process is: taking ingot as raw material, uniformizing heat treatment and / or preheating, then adopting hot deformation, followed by solid solution treatment and aging to obtain high quality products, the best performance case disclosed in the examples, the tensile strength of the product is 569MPa, the stripping corrosion level is N level.The patent application CN119082564A relates to a high-strength corrosion-resistant A-Zn-Mg-Cu alloy, which comprises the following mass percentage components: Cu 2.0-2.5%, Mg 2.0-2.8%, Zn 6.0-6.8%, Zr 0.05-0.1%, Be 0.05-0.1%, Fe ≤0.05%, Si ≤0.03%, and the balance being aluminum and non-removable impurities; the high-strength corrosion-resistant Al-Zn-Mg-Cu alloy is prepared by the following process: A, smelting: using aluminum, magnesium, zinc, aluminum copper intermediate alloy, aluminum zirconium intermediate alloy, and aluminum beryllium intermediate alloy as raw materials; weighing the raw materials according to the component ratio, and loading them into a smelting furnace for heating and melting; B, refining, impurity removal, and degassing: after the metal melt is completely alloyed, the alloy melt is added with a decontaminating agent for slagging, and argon is simultaneously introduced for 10-20 minutes, an appropriate amount of hexachlorocyclohexane is added, and the alloy melt is left to stand and slagging is performed, the above operation is repeated 2-3 times, and then the aluminum alloy melt is left to stand for more than 20 minutes; C, pouring: after the aluminum alloy melt is refined, impurity-removed, and degassed, the melt temperature is maintained at 730±5℃, and the melt is poured into a mold, cooled and solidified to obtain an ingot; D, single-stage homogenization heat treatment: the ingot obtained in step C is heated to 465±5℃, and after being kept at this temperature for 12-36h, it is taken out of the furnace and air-cooled to room temperature; E, hot rolling: the homogenized ingot obtained in step D is heated to 420±5℃ and kept for 60-120min, and then subjected to multi-pass hot rolling to the set thickness of the alloy, during rolling, the pass reduction rate is controlled at 5-20% and the total reduction rate is controlled at 75-85%; the rolling passes are annealed at 420±5℃; after rolling, the ingot is air-cooled and / or water-cooled to room temperature; isothermal deformation processing is performed; F, heat treatment: first, solid solution treatment is performed, the isothermally deformed processing piece is heated to 465±5℃, kept for 90-150min, taken out of the furnace and water quenched; then, T74 two-stage aging treatment is performed; the T74 two-stage aging treatment is as follows: the solid solution treated piece is heated to 120-130℃ and kept for 6-7h, then heated to 175-185℃ and kept for 7-8h, taken out of the furnace and water quenched to room temperature. The homogenization treatment is single-stage homogenization heat treatment, the heating rate is 10-15℃ / min, the homogenization temperature is 465±5℃, the holding time is 20-28h, and the strength of the obtained product is 585MPa and the intergranular corrosion is grade 1.In order to further improve the strength of the product, patent application CN118880134A opens an Al-Zn-Mg alloy with a strength of up to 800MPa, which includes the following weight percentage of chemical components: Zn 10~12%, Mg 2.5%~3.5%, Cu 0.9~2.2%, Zr 0.2%~0.25%, Cr 0%~0.1%, Ni 0%~0.1%, Fe≤0.1%, Si≤0.1%, other impurities≤0.05%, total amount≤0.15%, the balance is Al, and the rare earth content is less than 0.005%, the content of Cr and Ni cannot be zero at the same time, but the patent does not involve the corrosion resistance of the product.

[0004] At present, there are few reports on corrosion-resistant aluminum alloys with N-grade anti-exfoliation corrosion and tensile strength greater than or equal to 740MPa. SUMMARY

[0005] Based on patent application CN118880134A, in order to further improve the corrosion resistance of the product and ensure its strength, the present application is proposed.

[0006] The corrosion-resistant aluminum alloy with N-grade anti-exfoliation corrosion includes the following chemical components in mass percentage: Zn 10.0-12.0%, Mg 2.5%-3.5%, Zr 0.08-0.25%, Ti 0.03-0.10%, Fe≤0.10%, Si≤0.10%, other impurities≤0.05%, total amount≤0.15%, the balance is Al; the corrosion-resistant aluminum alloy has N-grade anti-exfoliation corrosion and tensile strength greater than or equal to 740MPa;

[0007] The corrosion-resistant aluminum alloy is prepared by the following steps:

[0008] Step one: according to the above chemical composition and weight percentage requirements, aluminum alloy ingot is obtained by water-cooled mold casting;

[0009] Step two: the ingot obtained in step one is treated according to the two-stage homogenization process, specifically as follows: the first-stage homogenization temperature is 400-450℃, the holding time is 8-16h; the second-stage homogenization temperature is A℃, the second-stage homogenization treatment time is 30-48h; the holding time is 20-60h; after the homogenization of the ingot is completed, it is air-cooled; the value of A is 460-475℃;

[0010] Step three: the ingot obtained in step two is peeled and then hot extruded, with an extrusion ratio of 20~50.

[0011] Step four: the plate obtained in step three is subjected to two-stage solid solution and peak aging treatment, specifically as follows: the first-stage solid solution temperature is B ℃, the holding time is 1-2 h; the second-stage solid solution temperature is C ℃, the holding time is 20-45 min; after the solid solution stage, water quenching is performed, and after quenching, peak aging treatment is performed; the peak aging temperature is 110-130 ℃, and the holding time is 16-32 h; the value of B is 450-470, the value of C is 475-490, and B < C < A.

[0012] Preferably, the alloy contains high contents of Zn and Mg in the chemical composition, and the weight percentages are: Zn 10.0-12.0%, Mg 2.5-3.5%. In the present application, the content of Zn is not less than 10 wt%, the content of Mg is not less than 2.5%, and no Cu element is contained, which, in combination with subsequent extrusion and heat treatment processes, provides necessary conditions for realizing ultra-high strength in a peak aging state and also provides necessary conditions for having super strong exfoliation corrosion resistance.

[0013] As a further preferred solution, the present application provides an N-grade exfoliation corrosion resistant corrosion-resistant aluminum alloy, which contains the following chemical components in mass percentages: Zn 11-11.5%, Mg 2.8-3.3%, Zr 0.1-0.15%, Ti 0.03-0.07%, Fe ≤0.10%, Si ≤0.10%, other impurities ≤0.05% individually, total amount ≤0.15%, and the balance being Al.

[0014] As a further preferred solution, the present application provides an N-grade exfoliation corrosion resistant corrosion-resistant aluminum alloy, which contains the following chemical components in mass percentages: Zn 11-11.5%, Mg 2.8-3.3%, Zr 0.1-0.15%, Ti 0.03-0.07%, Fe ≤0.10%, Si ≤0.10%, other impurities ≤0.05% individually, total amount ≤0.15%, and the balance being Al.

[0015] The present application adopts special two-stage solid solution, in which the second-stage solid solution temperature breaks through the overburning temperature (i.e. slightly higher than the overburning temperature), so that more difficult-to-dissolve second phases are dissolved into the matrix, and the heat extrusion process is further combined to improve the strengthening effect.

[0016] In the present application, the reason why C is greater than A and B is that the second-stage solid solution temperature is higher than the homogenization and first-stage solid solution temperature, so that the difficult-to-dissolve second phases at A / B temperature are dissolved into the matrix, and the over-saturation of the alloy after quenching is improved.

[0017] As a further preferred solution, B < A < C.

[0018] Preferably, in step one, the aluminum alloy round ingot is obtained by water-cooled mold casting, and the size of the ingot is Φ110-130 mm in diameter.

[0019] Preferably, the extrusion temperature in the third step is 410-430 DEG C, further preferably 413-417 DEG C, and the extrusion ratio is 26-28.

[0020] As a preference, the first-stage solution temperature is 450-470 DEG C, and the holding time is 80-100 min; the second-stage solution temperature is 475-482 DEG C, further preferably 480 DEG C, and the holding time is 28-32 min. Because the temperature of the second-stage aging is greater than the overburning temperature, the time must be strictly controlled, and the temperature also cannot be too high.

[0021] As a further preference, the fourth step solution process adopts two-stage strengthened solution, specifically as follows:

[0022] The first-stage solution temperature is 463-468 DEG C, and the holding time is 80-100 min; the second-stage solution temperature is 478-482 DEG C, further preferably 480 DEG C, and the holding time is 28-32 min. Because the temperature of the second-stage aging is greater than the overburning temperature, the time must be strictly controlled, and the temperature also cannot be too high.

[0023] Preferably, after the fourth step solution process, water quenching is adopted, the quenching time is less than 5 s, and the quenching temperature is room temperature; the peak aging temperature is 115-125 DEG C, and the holding time is 20-28 h.

[0024] After optimization, the tensile strength of the peak aging product is greater than 788 MPa, the yield strength is greater than 786 MPa, the elongation is greater than 5.0%, and the exfoliation corrosion grade is N grade.

[0025] The product obtained by the present application fully meets the requirements of existing aerospace and transportation equipment for super-high-strength aluminum alloy, and also meets the requirements of future new-generation aerospace technology.

[0026] The present application is a corrosion-resistant aluminum alloy with an exfoliation corrosion resistance grade of N grade and a tensile strength greater than or equal to 740 MPa under the synergistic effect of composition and preparation process; after optimization, the exfoliation corrosion resistance grade of the product obtained by the present application is N grade and the tensile strength is greater than or equal to 780 MPa.

[0027] The use of copper must be eliminated in the present application, otherwise the exfoliation corrosion resistance of the product will be significantly reduced. Under the action of a large amount of zinc in combination with appropriate Zr and Ti without copper, a product with excellent exfoliation corrosion resistance performance can be obtained while ensuring high product strength. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 48h exfoliation corrosion results of the alloy obtained in Comparative Example 1 in T6 peak aging state;

[0029] Figure 2 Exfoliation corrosion results of the alloy obtained in Comparative Example 2 in T6 peak aging state for 48h;

[0030] Figure 3 Exfoliation corrosion results of the alloy obtained in Comparative Example 3 in T6 peak aging state for 48h;

[0031] Figure 4 Exfoliation corrosion results of the alloy obtained in Example 1 in T6 peak aging state for 48h;

[0032] Figure 5 Exfoliation corrosion results of the alloy obtained in Comparative Example 4 in T6 peak aging state for 48h;

[0033] Figure 6 Exfoliation corrosion results of the alloy obtained in Example 2 in T6 peak aging state for 48h. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions, features and advantages of the embodiments of the present application more clear, the following will make a clear and complete description of the technical solutions of the embodiments.

[0035] Comparative Example 1:

[0036] The preparation process steps of the alloy are as follows:

[0037] (1) The alloy ratio is Zn 11.0%, Mg 3.0%, Cu 0.5%, Zr 0.12%, Ti 0.05%; according to the above weight percentage, 99.99% high-purity Al ingot, pure Zn ingot, pure Mg ingot, Al-Cu intermediate alloy, Al-Zr intermediate alloy and Al-Ti-B wire are used; the measured composition is: Zn 11.3%, Mg 3.2%, Cu 0.57%, Zr 0.12%, Ti 0.04;

[0038] (2) Melting is carried out in a high-temperature resistance furnace, and the melting temperature is 730-780℃; after the metal is completely melted, stirring is continuously carried out and a refining agent is added, and the refining is carried out in three batches, and the refining temperature is 760℃; after the refining, the temperature is kept at 740℃ for 30min; after sufficient standing, casting is carried out, and the ingot is cast by using a water-cooled mold, and the cooling water is kept flowing during the casting process, and a Φ120mm diameter aluminum alloy ingot is obtained after casting;

[0039] (3) The ingot is subjected to two-stage homogenization treatment, and the homogenization process is as follows: the first-stage homogenization temperature is 440℃, and the holding time is 12h; the second-stage homogenization temperature is 470℃, and the holding time is 36h;

[0040] (4) After the homogenization is completed, the ingot is taken out and air-cooled;

[0041] (5) The homogenized ingot is skinned, and the diameter of the ingot after skinning is Φ98mm;

[0042] (6) Select a mold to extrude the ingot, the extrusion temperature is 415℃, and the extrusion ratio is 27;

[0043] (7) The extruded sheet is subjected to two-stage solution treatment and peak aging treatment, wherein the first-stage solution treatment temperature is 465℃ and the holding time is 90min; the second-stage solution treatment temperature is 480℃ and the holding time is 30min.

[0044] (8) After solution treatment, water quenching and peak aging treatment are performed. The aging temperature is 120℃ and the aging time is 24h.

[0045] The alloy obtained in Comparative Example 1 exhibits the following peak-aging state exfoliation corrosion resistance and tensile properties: Figure 1 As shown in Figure 1 and Table 1, where σ b For tensile strength, σ 0.2 δ represents the yield strength, and δ represents the elongation.

[0046]

[0047] The resulting product has an EC grade of resistance to peeling corrosion.

[0048] Comparative Example 2:

[0049] The preparation process of the alloy is as follows:

[0050] (1) The alloy composition is Zn 7.0%, Mg 2.8%, Cu 1.0%, Zr 0.12%, Ti 0.05%; according to the above weight percentages, 99.99% high-purity Al ingots, pure Zn ingots, pure Mg ingots, Al-Zr master alloy, and Al-Ti-B wire are used; the actual composition is: Zn 7.0%, Mg 2.74%, Zr 0.12%, Ti 0.05%;

[0051] (2) Melting is carried out in a high-temperature resistance furnace at a temperature of 730-780℃. After the metal is completely melted, it is stirred continuously and a refining agent is added. The refining is carried out in three batches at a temperature of 760℃. After refining, it is left to stand for 30 minutes and the temperature is kept at 740℃. After standing for a while, it is cast. The ingot is cast using a water-cooled mold. During the casting process, the cooling water is kept flowing. After casting, an aluminum alloy ingot with a diameter of Φ120mm is obtained.

[0052] (3) The ingot is subjected to a two-stage homogenization process. The homogenization process is as follows: the first stage homogenization temperature is 440℃ and the holding time is 12h; the second stage homogenization temperature is 470℃ and the holding time is 36h.

[0053] (4) After homogenization, remove the ingot and air cool it;

[0054] (5) Peel off the skin from the homogenized ingot. The diameter of the ingot after peeling is Φ98mm.

[0055] (6) Select a mold to extrude the ingot, the extrusion temperature is 415℃, and the extrusion ratio is 27;

[0056] (7) The extruded sheet is subjected to two-stage solution treatment and peak aging treatment, wherein the first-stage solution treatment temperature is 465℃ and the holding time is 90min; the second-stage solution treatment temperature is 480℃ and the holding time is 30min.

[0057] (8) After solution treatment, water quenching and peak aging treatment are performed. The aging temperature is 120℃ and the aging time is 24h.

[0058] The alloy obtained in Comparative Example 2 exhibits the following peak-aging state exfoliation corrosion resistance and tensile properties: Figure 2 As shown in Figure 1 and Table 2, where σ b For tensile strength, σ 0.2 δ represents the yield strength, and δ represents the elongation.

[0059]

[0060] The resulting product has an EB-level resistance to peeling corrosion.

[0061] Comparative Example 3:

[0062] The preparation process of the alloy is as follows:

[0063] (1) The alloy ratio is Zn 7.0%, Mg 2.0%, Cu 0.5%, Zr 0.12%, Ti 0.05%; according to the above weight percentages, 99.99% high-purity Al ingots, pure Zn ingots, pure Mg ingots, Al-Cu master alloy, Al-Zr master alloy, and Al-Ti-B wire are used; the actual composition is: Zn 6.9%, Mg 2.1%, Cu 0.4%, Zr 0.12%, Ti 0.05%;

[0064] (2) Melting is carried out in a high-temperature resistance furnace at a temperature of 730-780℃. After the metal is completely melted, it is stirred continuously and a refining agent is added. The refining is carried out in three batches at a temperature of 760℃. After refining, it is left to stand for 30 minutes and the temperature is kept at 740℃. After standing for a while, it is cast. The ingot is cast using a water-cooled mold. During the casting process, the cooling water is kept flowing. After casting, an aluminum alloy ingot with a diameter of Φ120mm is obtained.

[0065] (3) The ingot is subjected to a two-stage homogenization process. The homogenization process is as follows: the first stage homogenization temperature is 440℃ and the holding time is 12h; the second stage homogenization temperature is 470℃ and the holding time is 36h.

[0066] (4) After homogenization, the ingot is taken out and air-cooled;

[0067] (5) The homogenized ingot is scaled, and the diameter of the ingot after scaling is Φ98mm;

[0068] (6) The ingot is selected for extrusion, and the extrusion temperature is 415℃, and the extrusion ratio is 27;

[0069] (7) The extruded plate is subjected to single-stage solid solution and peak aging treatment, wherein the solid solution temperature is 465℃, and the holding time is 120min;

[0070] (8) After solid solution, water quenching is carried out, and peak aging treatment is carried out, and the aging temperature is 120℃, and the aging time is 24h.

[0071] The tensile properties of the alloy obtained in Comparative Example 3 in the peak aging state are shown in Table 3, wherein σ b is the tensile strength, σ 0.2 is the yield strength, and δ is the elongation.

[0072]

[0073] The anti-exfoliation corrosion grade of the product obtained is EA grade.

[0074] Example 1:

[0075] The preparation process steps of the alloy are as follows:

[0076] (1) The alloy ratio is Zn 11.0%, Mg 3.0%, Zr 0.12%, Ti 0.05%; according to the above weight percentage, 99.99% high-purity Al ingot, pure Zn ingot, pure Mg ingot, Al-Zr intermediate alloy and Al-Ti-B wire are used; the measured composition is: Zn 11.2%, Mg 3.2%, Zr 0.12%, Ti 0.05%, Fe≤0.10%, Si≤0.10%, other impurities≤0.05% individually, total amount≤0.15%, and the balance is Al.

[0077] (2) Melting is carried out in a high-temperature resistance furnace, and the melting temperature is 730-780℃; after the metal is completely melted, stirring is continuously carried out and a refining agent is added, and the refining is carried out in three batches, and the refining temperature is 760℃; after refining, the temperature is kept at 740℃ for 30min; after sufficient standing, casting is carried out, and the ingot is cast by water-cooled mold, and the cooling water is kept flowing during casting; after casting, an aluminum alloy ingot with a diameter of Φ120mm is obtained;

[0078] (3) The ingot is subjected to two-stage homogenization treatment, and the homogenization process is as follows: the first-stage homogenization temperature is 440℃, and the holding time is 12h; the second-stage homogenization temperature is 470℃, and the holding time is 36h;

[0079] (4) After homogenization, remove the ingot and air cool it;

[0080] (5) Peel off the skin from the homogenized ingot. The diameter of the ingot after peeling is Φ98mm.

[0081] (6) Select a mold to extrude the ingot, the extrusion temperature is 415℃, and the extrusion ratio is 27;

[0082] (7) The extruded sheet is subjected to two-stage solution treatment and peak aging treatment, wherein the first-stage solution treatment temperature is 465℃ and the holding time is 90min; the second-stage solution treatment temperature is 480℃ and the holding time is 30min.

[0083] (8) After solution treatment, water quenching and peak aging treatment are performed. The aging temperature is 120℃ and the aging time is 24h.

[0084] The alloy obtained in Example 1 exhibits the following peak-aging state exfoliation corrosion resistance and tensile properties: Figure 3 As shown in Figure 4 and Table 4, where σ b For tensile strength, σ 0.2 δ represents the yield strength, and δ represents the elongation.

[0085]

[0086] The results above show that the present invention can produce ultra-high strength aluminum alloys with tensile strength exceeding 780 MPa and exfoliation corrosion resistance grade N, with a tensile strength of 788 MPa and an elongation of 5.3%.

[0087] During the technical exploration process, other parameters and steps were also tried that were consistent with Example 1, except that the second-stage solution temperature in the two-stage solution process was 480℃ and the holding time was 45min; it was found that the mechanical properties of the product degraded too quickly.

[0088] Comparative Example 4

[0089] (1) The alloy ratio is Zn 12.9%, Mg 3.6%, Zr 0.12%, Cu 1.0%, Ti 0.05%; according to the above weight percentages, 99.99% high-purity Al ingots, pure Zn ingots, pure Mg ingots, Al-Zr master alloy, and Al-Ti-B wire are used.

[0090] The resulting product has a tensile strength of 765 MPa and an elongation of 4.2%; its resistance to exfoliation corrosion is rated as ED.

[0091] Example 2

[0092] In the technical exploration process, other parameters and steps were also tried, which were consistent with embodiment 1, except that in the two-stage solid solution, the first-stage solid solution was carried out at 450℃ for 90 min, and the second-stage solid solution was carried out at 480℃ for 30 min; it was found that the mechanical properties of the product also decayed too fast.

[0093] The tensile strength of the obtained product was 740 MPa, the elongation was 2.9%, and the anti-exfoliation corrosion grade was about N grade; from the picture, it could be seen that the effect was poorer than that of the product obtained in embodiment 1.

[0094] Comparative example 5

[0095] Other conditions were consistent with embodiment 1, except that the content of Zn was 11.2%, the content of Mg was 3.0%, the content of Cu was 1.0%, and the content of Ti was 0%; the tensile strength was 765 MPa, the yield strength was 720 MPa, the elongation was 4.5%, and the anti-exfoliation corrosion grade was EC grade.

[0096] The above embodiments are merely examples for clearly illustrating the present application, and are not intended to limit the embodiments. For those skilled in the art, other different forms of changes can be made on the basis of the above description, and all the embodiments do not need to be exhausted here. The changes derived therefrom are still within the protection scope of the present application.

Claims

1. An etch-resistant aluminum alloy having an exfoliation corrosion rating of N, characterized in that: Chemical components in percentage by mass: Zn 11.2%, Mg 3.2%, Zr 0.12%, Ti 0.05%, Fe ≤0.10%, Si ≤0.10%, other impurities ≤0.05% individually, ≤0.15% in total, and the balance being Al; the exfoliation corrosion resistance of the corrosion-resistant aluminum alloy is N grade, and the tensile strength is greater than or equal to 740 MPa; The corrosion-resistant aluminum alloy is prepared by the following steps: Step one: ingredients are prepared according to the above chemical components and percentage by mass, and an aluminum alloy ingot is obtained by water-cooled mold casting; Step two: the ingot obtained in step one is treated according to a two-stage homogenization process, specifically as follows: the first-stage homogenization temperature is 400-450℃, and the holding time is 8-16h; the second-stage homogenization temperature is A℃, and the time for the second-stage homogenization treatment is 30-48h; the holding time is 20-60h; after the homogenization of the ingot is completed, the ingot is taken out and air-cooled; the value of A is 460-475; Step three: the ingot obtained in step two is peeled and then subjected to hot extrusion, and the extrusion ratio is 20-50; Step four: the plate obtained in step three is subjected to two-stage solid solution and peak aging treatment, specifically as follows: the first-stage solid solution temperature is B℃, and the holding time is 1h-2h; the second-stage solid solution temperature is C℃, and the holding time is 20-45min; after the solid solution stage is completed, water quenching is performed, and then peak aging treatment is performed after quenching; the peak aging temperature is 110-130℃, and the holding time is 16-32h; the value of B is 450-470, the value of C is 475-490, and B The tensile strength of the peak-aging product is greater than 788 MPa, the yield strength is greater than 786 MPa, the elongation is greater than 5.0%, and the exfoliation corrosion resistance is N grade.

2. The corrosion resistant aluminum alloy of claim 1 having an exfoliation corrosion rating of N. B 3. The corrosion resistant aluminum alloy of claim 1 having an exfoliation corrosion rating of N. In step one, an aluminum alloy round ingot is obtained by water-cooled mold casting, and the ingot size is Φ110-130mm in diameter.

4. The corrosion resistant aluminum alloy of claim 1 having an exfoliation corrosion rating of N. In the extrusion process in step three, the extrusion temperature is 413-417℃, and the extrusion ratio is 26-28.

5. The corrosion resistant aluminum alloy of claim 1, having an exfoliation corrosion rating of N. In the solid solution process in step four, two-stage strengthening solid solution is adopted, specifically as follows: The first-stage solid solution temperature is 450-470℃, and the holding time is 80-100min; the second-stage solid solution temperature is 475-482℃, and the holding time is 20-45min.

6. The corrosion resistant aluminum alloy of claim 1 having an exfoliation corrosion rating of N. After the solid solution process in step four is completed, water quenching is adopted, the quenching time is less than 5s, the quenching temperature is room temperature, the peak aging temperature is 115-125℃, and the holding time is 20-28h.

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