High-strength corrosion-resistant Al-Zn-Mg-Cu-Zr-Be alloy and application thereof

Abstract

The application provides a high-strength corrosion-resistant aluminum alloy material, in particular to a high-strength corrosion-resistant Al-Zn-Mg-Cu alloy and application thereof, and belongs to the field of aluminum alloys. The alloy is preferably composed of the following components in percentage by mass: 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 of aluminum and non-removable impurities. The application obtains a high-quality product with excellent T74-state mechanical properties and outstanding corrosion resistance through the synergistic use of components and preparation processes. The component design of the application is reasonable, the process is simple and controllable, and the obtained product is convenient to use as an airplane skin or other rolled plate parts.

Description

TECHNICAL FIELD

[0001] The application provides a high-strength corrosion-resistant aluminum alloy material, and particularly relates to a high-strength corrosion-resistant Al-Zn-Mg-Cu alloy and application thereof, and belongs to the field of aluminum alloys. BACKGROUND

[0002] 7xxx (Al-Zn-Mg-Cu) alloy is a typical representative of age hardenable aluminum alloy, has excellent comprehensive mechanical properties, and is generally considered to be a series of aluminum-based alloys with better high-strength corrosion resistance. Aircraft flight paths often pass over the ocean, and the humid and electrolyte-rich environment will exacerbate the corrosion of the fuselage material. Under this environmental condition, the traditional aluminum alloy rapidly deteriorates in microstructure, resulting in a sharp decline in mechanical properties, and cannot meet the high-strength corrosion resistance requirements of aircrafts flying at high speed in complex environments. Al-Zn-Mg-Cu alloy has a wide range of applications in the industrial field due to its very high strength and excellent corrosion resistance, especially in the aerospace field, and is an important structural material for aircrafts.

[0003] At present, the corrosion resistance comprehensive performance of the Al-Zn-Mg-Cu alloy used in China still has a certain gap compared with the foreign level, and needs to be further optimized in composition and process, mainly by controlling the microstructure evolution, improving the performance, and meeting the demand of aerospace. The main method for the research of Al-Zn-Mg-Cu alloy is to improve the comprehensive performance of the material by adjusting the main element ratio and micro-alloying addition, and the micro-mechanism is to inhibit the coarsening of the main strengthening phase η phase and increase the precipitation of the strengthening phase. Although the above optimization methods of composition and process improve the strength and corrosion resistance of the aluminum alloy to a certain extent, the use environment of the material is variable, and in actual application occasions, the problem of insufficient corrosion resistance often occurs, stress corrosion cracking or serious corrosion occurs, and the complex working conditions faced by the aircrafts cannot be coped with. Therefore, there is an urgent need in the market for an aluminum alloy material with higher strength and better corrosion resistance. SUMMARY

[0004] In view of the deficiencies of the prior art, a first object of the present application is to provide a high-strength corrosion-resistant Al-Zn-Mg-Cu alloy, which is based on the synergistic effect between the elements, and by adding appropriate amounts of Be and Zr elements and micro-alloying, the microstructure grain is refined, the second phase is formed in the aluminum alloy, the precipitation of the eta phase is increased, the dispersion distribution of the eta phase is improved, and the coarsening of the eta phase is inhibited, so that the prepared aluminum alloy has higher strength, and the service life in a corrosion environment is improved by adjusting the grain structure proportion; During the preparation of the alloy, the mechanical properties of the aluminum alloy are controlled by controlling the key process parameters of each step, and by single-stage homogenization treatment, hot rolling and other treatment methods, the substructure strengthening is realized while avoiding excessive deformation energy, and by combining solid solution and double-stage T74 aging heat treatment, the purpose of maintaining high strength and high corrosion resistance of the aluminum alloy in a long-time corrosion environment is realized.

[0005] The high-strength corrosion-resistant aluminum alloy provided by the present application has excellent mechanical properties and corrosion resistance. After being tested, the alloy material still does not fail after being tested in a 3.5% NaCl corrosion environment C ring stress corrosion of 260MPa for 30 days, the yield strength is not less than 540MPa, and the tensile strength is not less than 580MPa; After 48 hours of standard aluminum alloy exfoliation corrosion test, the corrosion grade is not less than EA, the intergranular corrosion test maximum depth of the aluminum alloy is not higher than 100um, and the intergranular corrosion grade is not more than 3 levels.

[0006] To achieve the above technical purpose, the present application provides a high-strength corrosion-resistant Al-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.

[0007] The high-strength corrosion-resistant Al-Zn-Mg-Cu alloy is prepared by the following process:

[0008] A, smelting: taking aluminum, magnesium, zinc, aluminum copper intermediate alloy, aluminum zirconium intermediate alloy, and aluminum beryllium intermediate alloy as raw materials; the raw materials are weighed according to the component ratio, and are loaded into a smelting furnace for heating and melting;

[0009] B, refining, impurity removal and degassing: after the metal melt is completely alloyed, the decontaminating agent is added to the alloy melt for slagging, and argon is simultaneously introduced for 10-20 minutes, an appropriate amount of hexachlorocyclohexane is added, and the slag is removed after standing, and the above operation is repeated 2-3 times, and then the aluminum alloy melt is left to stand for more than 20 minutes;

[0010] C. Pouring: After the aluminum alloy melt is refined, impurities and gas are removed, the melt temperature is maintained at 730±5℃, and the melt is poured into a mold, cooled and solidified to obtain an ingot;

[0011] D. Single-stage homogenization heat treatment: the ingot obtained in step C is heated to 465±5℃, and after holding at this temperature for 12-36h, it is taken out of the furnace and air-cooled to room temperature;

[0012] E. Hot rolling: the homogenized ingot obtained in step D is heated to 420±5℃ and held for 60-120min, and then multi-pass hot rolling is carried out to the set thickness of the alloy, and during rolling, the pass reduction rate is controlled at 5-20% and the total reduction rate is controlled at 75-85%;

[0013] Inter-pass annealing at 420±5℃; after rolling, air cooling and / or water cooling to room temperature; isothermal deformation processing;

[0014] G. Heat treatment: first solid solution treatment, heat the isothermal deformation processing piece to 465±5℃, hold for 90-150min, and take out of the furnace and water quench; then T74 two-stage aging treatment; T74 two-stage aging is: heat the solid solution treated piece to 120-130℃ and hold for 6-7h, then heat to 175-185℃ and hold for 7-8h, take out of the furnace and water quench to room temperature.

[0015] The homogenization treatment is single-stage homogenization heat treatment, the heating rate is 10-15℃ / min, the homogenization temperature is 465±5℃, and the holding time is 20-28h.

[0016] The alloy material provided in the application is based on the synergistic effect between the components of each element, and through appropriate Be and Zr micro-alloying, the microstructure grain is refined, the second phase is formed in the aluminum alloy, the substructure concentrated distribution area is controlled, the intermixed distribution structure between the subgrain structure and the recrystallized structure is formed, the precipitation and dispersion distribution of η phase are increased, and the coarsening of η phase is inhibited, so that the prepared aluminum alloy has higher strength and corrosion resistance under service conditions, and the service life and upper limit of use are improved.

[0017] The preparation process of the alloy provided in the application controls the mechanical properties of the aluminum alloy by controlling the key process parameters of each step, realizes substructure strengthening while limiting deformation energy storage through single-stage homogenization treatment and hot rolling, and combines solid solution and single-stage aging heat treatment, so as to realize the purpose of improving the high strength of the aluminum alloy under the action of long-time corrosion environment.

[0018] As a preferred scheme, the high-strength and corrosion-resistant Al-Zn-Mg-Cu alloy provided by the application comprises the following components in percentage by mass: Cu 2.1-2.15%, Mg 2.4-2.5%, Zn 6.2-6.4%, Zr 0.08-0.1%, Be 0.08-0.1%, Fe ≤0.05%, Si ≤0.01%, and the balance being aluminum and non-removable impurities.

[0019] The proportions of the elements of the alloy material provided by the application should be strictly implemented according to the above requirements. If the contents of Zn and Mg exceed the limited range, the Zn / Mg ratio changes accordingly, the proportions and sizes of various strengthening phases (mainly η phase) in the structure of the alloy material change accordingly, and the alloy performance is reduced. If the proportions of alloy elements such as Be and Zr exceed the required proportions, the second phase in the alloy becomes coarse, and the alloy has poor plasticity and reduced strength due to the presence of refractory coarse second phase during smelting and casting.

[0020] As a preferred scheme, the aluminum alloy raw material comprises high-purity aluminum, industrial pure magnesium, industrial pure zinc, aluminum copper intermediate alloy, aluminum beryllium intermediate alloy, and aluminum zirconium intermediate alloy.

[0021] As a preferred scheme, the purity of the high-purity aluminum is ≥99.99%, the purity of the industrial pure magnesium is ≥99.95%, and the purity of the industrial pure zinc is ≥99.95%.

[0022] The preparation process of the application strictly controls the purity of the material, reduces the contents of Fe and Si elements, avoids the formation of coarse brittle phases, and affects the plasticity of the alloy. At the same time, the use of Be and Zr micro-alloying elements not only refines the grains and controls the substructure distribution, but also effectively suppresses the coarsening speed of η phase at high temperature, and improves the tensile and corrosion resistance of the alloy.

[0023] As a preferred scheme, the content of copper in the aluminum copper intermediate alloy is ≥50.0%, the content of zirconium in the aluminum zirconium intermediate alloy is ≥5.0%, and the content of beryllium in the aluminum beryllium intermediate alloy is ≥10.0%. The contents of the transition metals in the intermediate alloy should be strictly implemented according to the above requirements. By controlling the contents of the transition metals in the intermediate alloy, the valence state of the second phase during smelting and casting can be controlled. If the proportions of the transition metals in the intermediate alloy change, the alloy will contain second phases of different valence states of aluminum-transition metals.

[0024] As a preferred scheme, the smelting temperature is 750-780℃.

[0025] The single-stage homogenization heat treatment adopted in the application is determined according to the comprehensive performance improvement of the Al-Zn-Mg-Cu alloy. The holding at 465±5℃ for 12-36 hours is more conducive to the precipitation of dispersed phase particles and promotes the precipitation of η phase in the subsequent aging process, so as to realize the purpose of improving the mechanical properties of the alloy through the synergistic effect of grain boundary strengthening and precipitate phase.

[0026] As a preferred scheme, the hot rolling is multi-stage hot rolling, and the process is as follows: the cast ingot after homogenization treatment is heated to 420±5℃ and held for 70-120 min; 8-12 passes of rolling are carried out, and the thickness change of the alloy in each pass of rolling is 2-4 mm; and after rolling, air cooling is carried out to room temperature.

[0027] The alloy cast ingot is deformed by multi-pass hot rolling in the application, so that the cast ingot structure is homogenized, the content of small-angle grain boundaries is increased, and a high-strength and high-toughness high-corrosion-resistant structure feature of intermingled distribution of recrystallized structure and substructure is formed. At the same time, the coarse second phase is fully crushed and homogenized through rolling, the comprehensive performance of the alloy is improved, the deformed structure with uniform deformation, small second phase size and uniform distribution is obtained, and the mechanical properties of the material are improved.

[0028] As a preferred scheme, the heat treatment includes solution treatment and single-stage aging treatment.

[0029] As an exploration scheme, the application discloses an Al-Zn-Mg-Cu alloy with high strength and corrosion resistance, and the alloy composition is as follows in terms of weight percentage: the copper content is 2.07%, the Mg content is 2.48%, the Zr content is 0.09%, the Zn content is 6.26%, the Fe content is ≤0.05%, the Si content is ≤0.01%, and the balance is aluminum and non-removable impurities. The preparation method is as follows:

[0030] A, melting: the raw materials are weighed according to the component ratio, and are put into a resistance furnace for heating and melting;

[0031] B, refining, impurity removal and degassing: after the metal melt is completely alloyed, the impurity removal agent is added into the alloy melt for slag gathering, and argon is simultaneously introduced for 10-20 minutes; an appropriate amount of hexachlorocyclohexane is added, and the operation is repeated for 2-3 times; then the aluminum alloy melt is placed for more than 20 minutes;

[0032] C, pouring: after the aluminum alloy melt is refined, impurity removal and degassing, the melt temperature is kept at 730±5℃, and the melt is poured into a mold; after cooling and solidification, a cast ingot is obtained.

[0033] D. Single-stage homogenization heat treatment: the ingot obtained in step C is heated to 465±5℃, and after holding at this temperature for 24h, it is taken out of the furnace and air-cooled to room temperature;

[0034] E. Hot rolling: the homogenized ingot obtained in step D is heated to 420±5℃ in a resistance furnace and held for 90min, and then hot rolled in multiple passes to a final thickness of 4mm, wherein the thickness of the alloy changes in each pass as follows: 20mm→18.5mm→17mm→15.5mm→14mm→12.5mm→11mm→9.5mm→8mm→6.5mm→5mm→4mm; 420℃ annealing is performed between passes; and the rolling is completed by water cooling to room temperature; thus obtaining an isothermally deformed workpiece.

[0035] F. Heat treatment: first, solid solution treatment is performed, the isothermally deformed workpiece is heated to 465±5℃, held for 2h, and then taken out of the furnace and water quenched; then, T74 two-stage aging treatment is performed, the solid solution treated workpiece is heated to 120℃ and held for 6h, and then heated to 175℃ and held for 7h, taken out of the furnace and water quenched, thus obtaining a finished product. With the above scheme, the mechanical properties of the product are excellent, but the corrosion resistance is general.

[0036] In order to improve the corrosion resistance of the product and ensure relatively excellent mechanical properties, the following scheme can be used:

[0037] A high-strength corrosion-resistant Al-Zn-Mg-Cu alloy, the alloy composition is as follows in terms of weight percentage: copper content is 2.13%, Mg content is 2.46%, Zr content is 0.10%, Be content is 0.09%, Zn content is 6.39%, Fe: ≤0.05%, Si: ≤0.01%, and the balance is aluminum and non-removable impurities.

[0038] The specific preparation method and steps are as follows:

[0039] A. Melting: high-purity aluminum, high-purity magnesium, high-purity zinc, aluminum-copper intermediate alloy, aluminum-zirconium intermediate alloy, and aluminum-beryllium intermediate alloy are used as raw materials; wherein, the purity of high-purity aluminum is ≥99.99%, the purity of industrial pure magnesium is ≥99.95%, the purity of industrial pure zinc is ≥99.95%, the content of copper in the aluminum-copper intermediate alloy is ≥50.0%, the content of beryllium in the aluminum-beryllium intermediate alloy is ≥10.0%, and the content of zirconium in the aluminum-zirconium intermediate alloy is ≥4.0%; the raw materials are weighed according to the component ratio, and then put into a resistance furnace for heating and melting;

[0040]

[0041] B. Refining, impurity removal, and degassing: after the metal melt is completely alloyed, the alloying agent is added to the alloy melt for slagging, and argon is simultaneously introduced for 10-20 minutes; an appropriate amount of hexachlorocyclohexane is added, and the slag is removed after standing; the above operation is repeated 2-3 times, and then the aluminum alloy melt is left to stand for more than 20 minutes; ​

[0042] C, pouring: after the aluminum alloy melt is refined, impurities and gas are removed, the melt temperature is kept at 730±5 DEG C, and the melt is poured into a mold, and the ingot is obtained by cooling and solidification;

[0043] D, single-stage homogenization heat treatment: the ingot obtained in step C is heated to 465±5 DEG C, and after keeping at this temperature for 24 hours, it is taken out of the furnace and air-cooled to room temperature;

[0044] E, hot rolling: the homogenized ingot obtained in step D is heated to 420±5 DEG C in a resistance furnace and kept for 90 minutes, and then multi-pass hot rolling is carried out to an alloy final thickness of 4mm, wherein the alloy thickness changes in each pass are: 20mm→18.5mm→17mm→15.5mm→14mm→12.5mm→11mm→9.5mm→8mm→6.5mm→5mm→4mm; 420 DEG C annealing is carried out between rolling passes; and the rolling is water-cooled to room temperature; and an isothermal deformation workpiece is processed.

[0045] F, heat treatment: first, solid solution treatment is carried out, the isothermal deformation workpiece is heated to 465±5 DEG C, kept for 2 hours, taken out of the furnace and water quenched; then, T74 two-stage aging treatment is carried out, the solid solution treated piece is heated to 120 DEG C and kept for 6 hours, and then heated to 175 DEG C and kept for 7 hours, taken out of the furnace and water quenched, to obtain the finished product.

[0046] The application also provides an application of the high-strength and corrosion-resistant Al-Zn-Mg-Cu, which is used for preparing an aircraft skin. The high-strength and corrosion-resistant aluminum alloy provided by the application has excellent mechanical properties and corrosion resistance, and after testing, the yield strength of the T74 product of the alloy material at room temperature is not less than 540 MPa, and the tensile strength is not less than 580 MPa; and the mechanical property requirements of the aircraft skin for the material are met.

[0047] Compared with the prior art, the application has the following beneficial technical effects:

[0048] 1) The Al-Zn-Mg-Cu alloy provided by the application is based on the synergistic effect between the elements, and through appropriate Be and Zr micro-alloying, the grain structure is refined, the recrystallized structure is controlled, the second phase, the substructure and the recrystallized structure are distributed in the aluminum alloy, the η phase is precipitated, the dispersion distribution of the η phase is beneficial, and the coarsening of the η phase is inhibited, so that the prepared aluminum alloy has good corrosion resistance while maintaining high mechanical strength.

[0049] 2) The technical scheme provided by the present application controls the mechanical properties of the aluminum alloy by controlling the key process parameters of each step in the preparation process, realizes fine-grain and substructure strengthening by special single-stage homogenization treatment, hot rolling and other treatment methods while controlling deformation energy storage, and combines solid solution and double-stage aging heat treatment, so as to realize the improvement of the aluminum alloy in the aspects of good corrosion resistance and high mechanical strength.

[0050] 3) The high-strength corrosion-resistant aluminum alloy provided by the present application has excellent mechanical properties and corrosion resistance. After optimization, the alloy material is still not failed after 30 days of 260MPa stress corrosion test in a 3.5% NaCl corrosion environment C ring, the yield strength is not less than 540MPa, and the tensile strength is not less than 580MPa; the corrosion grade is not less than EA after 48 hours of standard aluminum alloy exfoliation corrosion test, the maximum depth of intergranular corrosion of the aluminum alloy is not higher than 100um, and the intergranular corrosion grade is not more than 3. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to make the technical scheme and beneficial effects of the present application clearer, the following drawings are provided for further illustration:

[0052] Figure 1 The exfoliation corrosion morphology diagram of the T74 state product obtained from Example 1 after 48 hours of corrosion;

[0053] Figure 2 The exfoliation corrosion morphology diagram of the T74 state product obtained from Example 2 after 48 hours of corrosion;

[0054] Figure 3 The exfoliation corrosion morphology diagram of the T74 state product obtained from Comparative Example 1 after 48 hours of corrosion;

[0055] Figure 4 The grain boundary morphology distribution diagram of the T74 aging state product obtained from Example 1, 2 and Comparative Example 1; wherein Figure 4 a is the grain boundary morphology distribution diagram of the T74 aging state product obtained from Example 1, Figure 4 b is the grain boundary morphology distribution diagram of the T74 aging state product obtained from Example 2, Figure 4 c is the grain boundary morphology distribution diagram of the T74 aging state product obtained from Comparative Example 1.

[0056] From Figure 1 It can be seen that the metal surface is corroded black, but there is no serious delamination and peeling, the surface is relatively smooth, and it is judged as EA+ corrosion grade;

[0057] From Figure 2 It can be seen that the metal surface is corroded, and there is slight blistering and peeling, but the surface still has metal luster, and it is judged as EA grade exfoliation corrosion;

[0058] FromFigure 3 It can be seen that the metal surface is severely corroded, with serious peeling and peeling phenomenon, and is determined as EC grade peeling corrosion.

[0059] Figure 4 It can be seen that the appropriate amount of Be addition effectively promotes the grain refinement and the concentrated distribution of small-angle grain boundaries, and has a fine-grain strengthening effect on the alloy, and also improves the toughness. DETAILED DESCRIPTION

[0060] The following implementation is intended to illustrate the present application rather than further limit the present application.

[0061] Example 1

[0062] A high-strength corrosion-resistant Al-Zn-Mg-Cu alloy, the alloy composition is as follows in terms of weight percentage: copper content is 2.13%, Mg content is 2.46%, Zr content is 0.10%, Be content is 0.09%, Zn content is 6.39%, Fe:≤0.05%, Si:≤0.01%, and the balance is aluminum and non-removable impurities.

[0063] The specific preparation method and steps are as follows:

[0064] A. Melting: using high-purity aluminum, high-purity magnesium, high-purity zinc, aluminum-copper intermediate alloy, aluminum-zirconium intermediate alloy, and aluminum-beryllium intermediate alloy as raw materials; wherein the purity of high-purity aluminum is ≥99.99%, the purity of industrial pure magnesium is ≥99.95%, the purity of industrial pure zinc is ≥99.95%, the content of copper in aluminum-copper intermediate alloy is ≥50.0%, the content of beryllium in aluminum-beryllium intermediate alloy is ≥10.0%, and the content of zirconium in aluminum-zirconium intermediate alloy is ≥4.0%; the raw materials are weighed according to the component ratio and placed in an electric resistance furnace for heating and melting;

[0065] B. Refining, impurity removal, and degassing: after the metal melt is completely alloyed, the decontaminating agent is added to the alloy melt for slagging, and argon is simultaneously introduced for 10-20 minutes, an appropriate amount of hexachlorocyclohexane is added, and the slag is removed after standing and stirring; the above operation is repeated 2-3 times, and then the aluminum alloy melt is left to stand for more than 20 minutes;

[0066] C. Pouring: after the aluminum alloy melt is refined, impurity removal, and degassing are completed, the melt temperature is maintained at 730±5℃, and the melt is poured into a mold, cooled and solidified to obtain an ingot;

[0067] D. Single-stage homogenization heat treatment: the ingot obtained in step C is heated to 465±5℃, and after holding at this temperature for 24h, it is taken out of the furnace and air-cooled to room temperature;

[0068] D. Single-stage homogenization heat treatment: the ingot obtained in step C is heated to 465±5℃, and after holding at this temperature for 24h, it is taken out of the furnace and air-cooled to room temperature;

[0069] E. Hot rolling: the homogenized ingot obtained in step D is heated to 420±5℃ in an electric resistance furnace and held for 90 min, and then subjected to multi-pass hot rolling to a final thickness of 4 mm, wherein the thickness of the alloy changes in each pass as follows: 20 mm→18.5 mm→17 mm→15.5 mm→14 mm→12.5 mm→11 mm→9.5 mm→8 mm→6.5 mm→5 mm→4 mm; 420℃ annealing is performed between rolling passes; after rolling, water cooling is performed to room temperature; and isothermal deformation processing is performed.

[0070] F. Heat treatment: first, solid solution treatment is performed, the isothermal deformation processed piece is heated to 465±5℃, held for 2 h, and then water quenched; then, T74 two-stage aging treatment is performed, the solid solution treated piece is heated to 120℃, held for 6 h, and then heated to 175℃, held for 7 h, and then water quenched, to obtain the finished piece.

[0071] After the alloy material is subjected to 260 MPa stress corrosion in a 3.5% NaCl corrosion environment C ring for 30 days, it still does not fail, the yield strength is 542 MPa, and the tensile strength is 585 MPa; after 48 h of standard aluminum alloy exfoliation corrosion test, the corrosion grade is EA+ (see Figure 1 ), the maximum depth of intergranular corrosion of the aluminum alloy is 6 um, and the intergranular corrosion grade is 1.

[0072] Example 2

[0073] A high-strength corrosion-resistant Al-Zn-Mg-Cu alloy, the alloy composition is as follows in terms of weight percentage: copper content is 2.07%, Mg content is 2.48%, Zr content is 0.09%, Zn content is 6.26%, Fe≤0.05%, Si≤0.01%, and the balance is aluminum and non-removable impurities.

[0074] A. Melting: high-purity aluminum, high-purity magnesium, high-purity zinc, aluminum-copper intermediate alloy, aluminum-zirconium intermediate alloy, and aluminum-beryllium intermediate alloy are used as raw materials; wherein the purity of high-purity aluminum is ≥99.99%, the purity of industrial pure magnesium is ≥99.95%, the purity of industrial pure zinc is ≥99.95%, the content of copper in the aluminum-copper intermediate alloy is ≥50.0%, the content of beryllium in the aluminum-beryllium intermediate alloy is ≥10.0%, and the content of zirconium in the aluminum-zirconium intermediate alloy is ≥4.0%; the raw materials are weighed according to the component ratio, and are placed in an electric resistance furnace for heating and melting;

[0075] B. Refining, impurity removal, and degassing: after the metal melt is completely alloyed, the alloy melt is added with a deoxidizing agent for slagging, and argon is simultaneously introduced for 10-20 minutes, an appropriate amount of hexachlorocyclohexane is added, and the alloy melt is statically placed for more than 20 minutes after slagging, repeating the above operation 2-3 times.

[0076] C. Pouring: After the aluminum alloy melt is refined, impurities and gas are removed, the melt temperature is maintained at 730±5℃, and the melt is poured into a mold, cooled and solidified to obtain an ingot;

[0077] D. Single-stage homogenization heat treatment: the ingot obtained in step C is heated to 465±5℃ and kept at this temperature for 24h before being taken out of the furnace and air cooled to room temperature;

[0078] E. Hot rolling: the homogenized ingot obtained in step D is heated to 420±5℃ in a resistance furnace and kept for 90min, and then hot rolled in multiple passes to an alloy final thickness of 4mm, wherein the alloy thickness changes in each pass are: 20mm→18.5mm→17mm→15.5mm→14mm→12.5mm→11mm→9.5mm→8mm→6.5mm→5mm→4mm; 420℃ annealing between passes; water cooled to room temperature after rolling; to obtain an isothermal deformation workpiece.

[0079] F. Heat treatment: first solid solution treatment, heat the isothermal deformation workpiece to 465±5℃, keep for 2h, take out of the furnace and water quench; then T74 two-stage aging treatment, heat the solid solution treated workpiece to 120℃ and keep for 6h, then 175℃ for 7h, take out of the furnace and water quench, to obtain the finished product.

[0080] The alloy material does not fail after 30 days of 3.5% NaCl corrosion environment C stress corrosion 260MPa test, the yield strength is 582MPa, and the tensile strength is 604MPa; the corrosion grade is EA after 48 hours of standard aluminum alloy exfoliation corrosion test, the maximum intergranular corrosion depth is 310um, and the intergranular corrosion grade is 5.

[0081] Comparative Example 1

[0082] A high-strength corrosion-resistant Al-Zn-Mg-Cu alloy, the alloy composition is as follows in terms of weight percentage: copper content is 2.08%, Mg content is 2.44%, Zr content is 0.10%, Be content is 0.18%, Zn content is 6.31%, Fe≤0.05%, Si:≤0.01%, and the balance is aluminum and non-removable impurities.

[0083] A. Melting: high-purity aluminum, high-purity magnesium, high-purity zinc, aluminum-copper intermediate alloy, aluminum-zirconium intermediate alloy, and aluminum-boron intermediate alloy are used as raw materials; wherein the purity of high-purity aluminum is ≥99.99%, the purity of industrial pure magnesium is ≥99.95%, the purity of industrial pure zinc is ≥99.95%, the content of copper in aluminum-copper intermediate alloy is ≥50.0%, the content of beryllium in aluminum-boron intermediate alloy is ≥10.0%, and the content of zirconium in aluminum-zirconium intermediate alloy is ≥4.0%; the raw materials are weighed according to the composition ratio, and are placed in a resistance furnace for heating and melting;

[0084] B, refining, removing impurities, degassing: after the metal melt is completely alloyed, the de-impurity agent is added into the alloy melt to carry out slag gathering, and argon is introduced at the same time, the time is 10-20 minutes, an appropriate amount of hexachloro hexane is added, and the alloy melt is placed and slagged, and the above operation is repeated 2-3 times, then the aluminum alloy melt is placed for more than 20 minutes;

[0085] C, pouring: after the aluminum alloy melt is refined, impurities are removed, and degassing is completed, the melt temperature is kept at 730±5℃, and the melt is poured into a mold, cooled and solidified to obtain a cast ingot;

[0086] D, single-stage homogenization heat treatment: the cast ingot obtained in step C is heated to 465±5℃, and after holding at this temperature for 24h, it is taken out of the furnace and air cooled to room temperature;

[0087] E, hot rolling: the homogenized cast ingot obtained in step D is heated to 420±5℃ in an electric resistance furnace and held for 90min, and then multi-pass hot rolling is carried out to an alloy final thickness of 4mm, wherein the alloy thickness changes in each pass are: 20mm→18.5mm→17mm→15.5mm→14mm→12.5mm→11mm→9.5mm→8mm→6.5mm→5mm→4mm; 420℃ annealing is carried out between rolling passes; and water cooling is carried out to room temperature after rolling.

[0088] F, heat treatment: first, solid solution treatment is carried out, the isothermal deformation workpiece is heated to 465±5℃, held for 2h, taken out of the furnace and water quenched; then, T74 double-stage aging treatment is carried out, the solid solution treated workpiece is heated to 120℃ and held for 6h, and then heated to 175℃ and held for 7h, taken out of the furnace and water quenched, to obtain the workpiece;

[0089] The alloy workpiece does not fail after being tested in a 3.5% NaCl corrosion environment C stress corrosion of 260MPa for 30 days. The yield strength of the alloy workpiece is 541MPa, the tensile strength is 575MPa; the corrosion grade is EC after 48h standard aluminum alloy exfoliation corrosion test, and the maximum intergranular corrosion depth is 169um, and the intergranular corrosion grade is 4.

[0090] Performance test:

[0091] The above-mentioned aluminum alloy finished products are detected, the tensile sample size is processed according to GB / T228.1-2010, and the average value is taken as the result. The detection results are shown in Table 1.

[0092] Table 1

[0093]

[0094] The above is only a preferred embodiment of the present application and is not used to limit the present application, any modification, replacement, etc. made within the principles of the present application is included in the protection scope of the present application.

Claims

1. A high-strength corrosion-resistant Al-Zn-Mg-Cu alloy, characterized by: The alloy comprises the following components in percentage by mass: 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 unavoidable impurities; The high-strength corrosion-resistant Al-Zn-Mg-Cu alloy is prepared by the following process: A. Melting: taking aluminum, magnesium, zinc, aluminum copper intermediate alloy, aluminum zirconium intermediate alloy, and aluminum beryllium intermediate alloy as raw materials; the raw materials are weighed according to the component ratio, and are loaded 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 an impurity removal agent for slag gathering, and argon is simultaneously introduced for 10-20 minutes; an appropriate amount of hexachlorocyclohexane is added, and the melt is left to stand and slag is removed; the operation is repeated for 2-3 times; 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; after cooling and solidification, a cast ingot is obtained; D. Single-stage homogenization heat treatment: the cast ingot obtained in step C is heated to 465±5℃, and is left to stand at this temperature for 12-36 hours before being taken out of the furnace and air-cooled to room temperature; E. Hot rolling: the homogenized cast ingot obtained in step D is heated to 420±5℃ and is left to stand for 60-120 minutes, and then is subjected to multi-pass hot rolling to the set thickness of the alloy; during rolling, the pass reduction rate is controlled to be 5-20%, and the total reduction rate is controlled to be 75-85%; The rolling passes are annealed at 420±5℃; after rolling, the workpiece is air-cooled and / or water-cooled to room temperature; and the workpiece is subjected to isothermal deformation processing; F. Heat treatment: first, solid solution treatment is performed; the isothermally deformed workpiece is heated to 465±5℃, and is left to stand for 90-150 minutes before being 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 workpiece is heated to 120-130℃ and is left to stand for 6-7 hours, and then is heated to 175-185℃ and is left to stand for 7-8 hours before being 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℃, and the holding time is 20-28 hours.

2. The high-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 1, characterized in that: The high-strength corrosion-resistant Al-Zn-Mg-Cu alloy comprises the following components in percentage by mass: Cu 2.1-2.15%, Mg 2.4~2.5%, Zn 6.2~6.4%, Zr 0.08~0.1%, Be 0.08-0.1%, Fe ≤0.05%, Si ≤0.01%, and the balance being aluminum and unavoidable impurities.

3. The high-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 1, characterized in that: The aluminum alloy raw materials include high-purity aluminum, industrial pure magnesium, industrial pure zinc, aluminum copper intermediate alloy, aluminum beryllium intermediate alloy, and aluminum zirconium intermediate alloy. The purity of the high-purity aluminum is ≥99.99%, the purity of the industrial pure magnesium is ≥99.95%, and the purity of the industrial pure zinc is ≥99.95%. The content of copper in the aluminum copper intermediate alloy is ≥50.0%, the content of zirconium in the aluminum zirconium intermediate alloy is ≥5.0%, and the content of beryllium in the aluminum beryllium intermediate alloy is ≥10.0%.

4. The high-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 1, characterized in that: The melting temperature is 750-780℃.

5. The high-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 1, characterized in that: The hot rolling is multi-stage hot rolling, and the process is: the homogenization treated ingot is heated to 420±5℃ and kept for 70-120min; 8-12 passes of rolling are carried out, and the thickness change of the alloy in each pass is 2-4mm.

6. The high-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 2, characterized in that: The alloy does not fail after 260MPa stress corrosion test in 3.5% NaCl corrosion environment C ring for 30 days.

7. The high-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 2, characterized in that: The yield strength of the alloy in T74 state is not less than 540MPa, and the tensile strength is not less than 580MPa.

8. The high-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 2, characterized in that: After the alloy is tested for 48 hours of standard aluminum alloy exfoliation corrosion, the corrosion grade is not less than EA, the maximum depth of intergranular corrosion test of the aluminum alloy is not higher than 100um, and the intergranular corrosion grade is not more than 3 levels.

9. The high-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 2, characterized in that: Comprising the following mass percentage components: copper content is 2.13%, Mg content is 2.46%, Zr content is 0.10%, Be content is 0.09%, Zn content is 6.39%, Fe: ≤0.05%, Si: ≤0.01%, the balance is aluminum and non-removable impurities; The specific preparation method and steps are: A. Melting: high-purity aluminum, high-purity magnesium, high-purity zinc, aluminum copper intermediate alloy, aluminum zirconium intermediate alloy, and aluminum beryllium intermediate alloy are used as raw materials; wherein, the purity of high-purity aluminum is ≥99.99%, the purity of industrial pure magnesium is ≥99.95%, the purity of industrial pure zinc is ≥99.95%, the content of copper in aluminum copper intermediate alloy is ≥50.0%, the content of beryllium in aluminum beryllium intermediate alloy is ≥10.0%, and the content of zirconium in aluminum zirconium intermediate alloy is ≥4.0%; the raw materials are weighed according to the component ratio, and are put into a resistance furnace for heating and melting; B. Refining, impurity removal and degassing: after the metal melt is completely alloyed, the alloying agent is added to the alloy melt for slagging, and argon is simultaneously introduced for 10-20 minutes, an appropriate amount of hexachlorocyclohexane is added, and the slag is removed after standing and skimming. 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 kept at 730±5℃, and then it 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 then taken out of the furnace after keeping at this temperature for 24h and air-cooled to room temperature; E. Hot rolling: the homogenized ingot obtained in step D is heated to 420±5℃ in a resistance furnace and kept for 90min, and then multi-pass hot rolling is carried out to an alloy final thickness of 4mm, wherein the alloy thickness changes in each pass are: 20mm→18.5mm→17mm→15.5mm→14mm→12.5mm→11mm→9.5mm→8mm→6.5mm→5mm→4mm; 420℃ annealing is carried out between rolling passes; water cooling is carried out to room temperature after rolling; and isothermal deformation processing is carried out.

10. Use of a high-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to any one of claims 1 to 9, characterized in that: Aircraft skin or other rolled sheet part.

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