High-corrosion-resistance aluminum alloy with micro-shear band penetrating type structure and preparation method and application of high-corrosion-resistance aluminum alloy

Abstract

The invention discloses a high-corrosion-resistance aluminum alloy with a micro-shear band penetrating type structure and a preparation method and application of the high-corrosion-resistance aluminum alloy, and belongs to the technical field of aluminum alloy material machining. Through high-strain asymmetric rolling and specific aging compound treatment, a penetrating type micro shear belt structure is successfully constructed in the 7xxx series aluminum alloy, the internal small-angle grain boundary proportion of the 7xxx series aluminum alloy is larger than or equal to 60%, the alloy intergranular corrosion depth is smaller than or equal to 38 micrometers, the tensile strength is larger than or equal to 440 MPa, and the corrosion resistance and the mechanical property can be synchronously improved. According to the scheme, the experimental design is simple and easy to implement, dependence on expensive and rare alloy components is not needed, the production cost can be remarkably lowered, alloy recycling and regeneration can be facilitated, the resource utilization efficiency is improved, native resource consumption is reduced, the core requirement for low-cost and high-environment-friendly materials in the industrial profile field with the distinct cost performance guiding is perfectly met, and the method is suitable for popularization and application. And the method has important industrial application value and is suitable for key force-bearing components such as aerospace and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a high corrosion-resistant aluminum alloy with micro-shear band penetrating structure and its preparation method and application, in particular to a preparation method of an aluminum alloy with high strength and toughness and intergranular corrosion resistance by synergistic regulation of micro-shear band penetrating structure through high strain rolling and aging, belonging to the technical field of aluminum alloy material processing. BACKGROUND

[0002] With the urgent demand for lightweight materials in the fields of aerospace, automobile manufacturing and marine engineering, aluminum alloys with high strength and corrosion resistance have become a research hotspot. The traditional 7xxx series (Al-Zn-Mg-(Cu)) aluminum alloy has a strong plasticity-erosion resistance inversion contradiction: although large plastic deformation can improve the strength, but due to strain concentration, dislocations gather at the grain boundaries, which increases the number of intergranular corrosion pits and aggravates intergranular corrosion (such as corrosion depth of 90 μm when rolling 80% under pressure). (Existing patent (2021112457041 - A high-strength and high-toughness aluminum alloy with micro-shear band induced multi-mixed crystal structure and its preparation method and application) uses micro-shear band to form mixed crystal structure to strengthen the alloy, but does not solve the problem of corrosion resistance. The present application constructs a micro-shear band structure penetrating multiple grains in the alloy by high strain rolling combined with a specific aging process, which forms small-angle grain boundary surrounded recrystallized grains inside, which can effectively block the corrosion path, and at the same time, η' phase is dispersed to improve the strength, realizing the synergistic optimization of strength, plasticity and corrosion resistance. SUMMARY

[0003] The purpose of the present application is to provide a preparation method of a high corrosion-resistant aluminum alloy with micro-shear band penetrating structure, which uses high rolling strain to induce dense micro-shear bands, and through specific aging treatment, the micro-shear bands cross ≥3 grains, and a penetrating structure of small-angle grain boundary (2°<θ<15°) surrounded recrystallized grains is formed inside. The formation of different staggered regions inside the grains can effectively block the intergranular corrosion path, break through the inherent strength-plasticity-erosion resistance inversion relationship of 7xxx series aluminum alloy materials, and realize the synergistic improvement of both. The structure can reduce the intergranular corrosion depth to 25 μm (about 70% lower than the conventional process), and at the same time, the tensile strength is ≥440 MPa.

[0004] At the same time, the present application provides a high corrosion-resistant aluminum alloy with micro-shear band penetrating structure, which realizes the synergistic improvement of strength, plasticity and corrosion resistance, aims to improve the resource recycling rate, reduce the consumption of primary mineral resources, and at the same time, reduce carbon emissions by simplifying the recycling process, realizing the synergistic optimization of economic benefits and ecological benefits.

[0005] At the same time, the present application provides an application of a high corrosion-resistant aluminum alloy with micro-shear band penetrating structure in lightweight, high service life materials.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is: A high corrosion-resistant aluminum alloy with micro-shear band through structure, comprising multiple micro-shear bands formed by high-strain asymmetric rolling, under the action of aging, the internal structure of the micro-shear band is transformed from dislocation-enclosed subgrain boundary structure to small-angle grain boundary-enclosed recrystallized grain, which increases the width of the micro-shear band, and further connects different micro-shear bands. In addition, the interaction between the micro-shear band and the grain boundary leads to grain boundary migration, and under the action of recrystallization, the micro-shear band at the grain boundary migration position is more likely to develop into other grains, ultimately forming a wide (3.0-4.2 μm) micro-shear band that spans multiple grains (≥3 grains).

[0007] The aluminum alloy is a 7xxx series aluminum alloy, the zinc content in the alloy is 7wt%-9wt%, the magnesium content is 1wt%-3wt%, the copper content is 0.1wt%-0.25wt%, and the rest is aluminum.

[0008] The micro-shear band is at an angle of 30°-35° to the rolling direction, the small-angle grain boundary angle θ is (2°<θ<15°), and the volume fraction of the small-angle grain boundary is ≥60%.

[0009] A preparation method of a high corrosion-resistant aluminum alloy with micro-shear band through structure, comprising the following steps: Step one, casting aluminum alloy: according to the composition content of the 7xxx series aluminum alloy, prepare the raw materials. Put the crucible into the vacuum melting furnace preheated to 490-510°C, add the raw materials, set the temperature to 690-710°C, and keep it for 25-35 min until the raw materials are completely melted. Then open the melting furnace to remove the slag, and slowly stir the metal liquid with a stirring spoon to make the composition uniformly distributed. Then take out the mold to prepare for casting, ensure that the metal liquid flows out uniformly during the casting process, and finally obtain the block-shaped 7xxx series aluminum alloy required for the experiment; Step two, multi-graded solid solution treatment: first, increase the temperature of the cast aluminum alloy at room temperature to 240-260°C at a rate of 4-6°C / min and keep it for 25-35 min to eliminate residual stress. Then increase the temperature to 390-410°C at a rate of 2-4°C / min and keep it for 55-65 min (pre-solid solution of low melting point phase). Finally, increase the temperature to 460-480°C at a rate of 1-3°C / min and keep it for 1-2 h, and use Ar+0.5%H2 (i.e. 99.5% Ar and 0.5% H2) as the protective gas to eliminate the macroscopic segregation of elements in the as-cast structure and achieve high solid solution of alloy elements. After the holding period is over, immediately quench the alloy to 140-160°C at a cooling rate of 190-210°C / s, and then air cool to room temperature to reduce residual stress; Step three, asymmetric rolling, the alloy obtained in step one is subjected to asymmetric rolling at room temperature, the upper roller speed is 35-45 mm / s, the lower roller speed is 45-55 mm / s, the total reduction is 75%-85%, and the single reduction is not more than 5%; Step four, the rolled alloy is subjected to artificial aging treatment at 110-130℃ for 20h-28h, and a nitrogen circulation system (flow rate is 0.5-1m³ / h) is used to ensure that the temperature uniformity in the furnace is controlled within ±2℃. After aging, a three-stage cooling system is used, first, the cooling rate is 1-3℃ / h from the aging temperature to 75-85℃, then the cooling rate is 0.5-1.5℃ / h from 75-85℃ to 45-55℃, and finally, the furnace is cooled to room temperature. The whole experiment is carried out under nitrogen protection, and the final product is obtained.

[0010] After step three, a large number of layered dislocation structures in different directions are formed in the alloy.

[0011] After step three, a large number of Zn and Mg solute atoms in high solid solution have strong interaction with the layered dislocation structure, resulting in high-density micro-shear bands that cross each other.

[0012] After step four, the width of the linear high dislocation density region near the shear band in the sample is significantly reduced. A large number of recrystallized grains and subgrains along the shear band direction are formed in the shear band, and the internal structure changes from dislocation-enclosed subgrain boundaries to small-angle grain boundary-enclosed recrystallized grains. In addition, the interaction between the micro-shear band and the grain boundary leads to grain boundary migration. Under the action of recrystallization, the micro-shear band at the grain boundary migration position is more likely to develop into other grain interiors, eventually forming a wider micro-shear band that spans multiple grains.

[0013] The high corrosion-resistant alloy has a tensile strength of 440-460MPa and an intergranular corrosion depth of 25-38μm.

[0014] The application of a high corrosion-resistant aluminum alloy with a micro-shear band through structure in lightweight and long-service-life materials.

[0015] The materials with the advantages of lightweight and ultra-long service life include aerospace materials, rail transportation materials, and automotive industry materials.

[0016] The present application utilizes the principle that 7xxx series aluminum alloy is easy to form micro-shear bands in large plastic deformation, and the micro-shear bands can evolve in structure during room temperature rolling and subsequent aging treatment. On the one hand, by room temperature asymmetric rolling with a reduction of 75%-85%, a high density of dislocations and multiple intersecting micro-shear bands are introduced in the alloy; on the other hand, aging treatment promotes the recombination of dislocations in the micro-shear bands into small-angle grain boundaries, and induces the formation of recrystallized grains, the internal structure changes from dislocation-enclosed subgrain boundary structure to small-angle grain boundary-enclosed recrystallized grain structure, the width of the micro-shear bands increases, forming a wide intersecting micro-shear band spanning multiple grains. Finally, through the synergistic effect of "dislocation regulation-grain boundary recombination-trans-grain distribution" of the micro-shear bands, the mechanical properties and corrosion resistance are simultaneously improved (on the one hand, fine-grain strengthening and dislocation strengthening: the high density of dislocations and a large number of small-angle grain boundaries in the micro-shear bands improve the mechanical properties of the alloy; on the other hand, the special structure of the shear band-small-angle grain boundary-enclosed recrystallized grain: can effectively block the corrosion propagation path, especially when the shear band traverses multiple grains, intergranular corrosion is difficult to propagate from one grain to another).

[0017] The beneficial effects of the above technical solutions are: the present application provides a high-strength and high-corrosion-resistant 7xxx series aluminum alloy and a preparation method thereof, which can be prepared on a large scale, has a simple process and controllable cost, and can realize optimization of the comprehensive performance of the material without relying on complex alloy elements or extreme processing conditions, and mainly has the following advantages: (1) The aluminum alloy of the present application does not contain expensive other alloy elements, the zinc content in the alloy is 7wt%-9wt%, the magnesium content is 1wt%-3wt%, the copper content is 0.1wt%-0.25wt%, and the rest is aluminum. Therefore, the material cost is lower, the recycling is simpler, and it perfectly meets the core needs of the industrial profile field with clear cost-effective orientation for low-cost and high-environmental-friendly materials.

[0018] (2) The present application adopts room temperature asymmetric rolling to introduce plastic deformation energy storage and aging treatment to promote microstructure optimization, realizes the structural evolution of micro-shear bands from "dislocation entanglement" to "small-angle grain boundary-enclosed recrystallized grain", and does not need complex hot working equipment, the process is easy to operate and the energy consumption is low.

[0019] (3) The present application significantly improves the comprehensive performance of 7xxx series aluminum alloy by regulating the structure of micro-shear bands: On the one hand, by introducing high strain rolling, the alloy is fine-grain strengthened and dislocation strengthened: the high density of dislocations and a large number of small-angle grain boundaries in the micro-shear band make the mechanical properties of the alloy improved, and the tensile strength is greater than or equal to 440 MPa. On the other hand, the special structure in the shear band - small-angle grain boundaries surrounding the recrystallized grains: can effectively block the corrosion propagation path, when the shear band traverses multiple grains, intergranular corrosion is difficult to spread from one grain to another, and the intergranular corrosion depth can be as low as 25 μm.

[0020] In summary, the present application proposes a high-strength and high-corrosion-resistant 7xxx series aluminum alloy and a preparation method thereof by room temperature asymmetric rolling combined with aging treatment to regulate the structure of micro-shear bands, the alloy has excellent corrosion resistance and mechanical property matching degree, and the experimental scheme is simple and easy to implement, the production cost is significantly reduced, perfectly meets the core demand of the low-cost and high environmental protection material in the industrial profile field with clear cost-effective orientation, has important industrial application value, and is suitable for key load-bearing components in aerospace and the like.

[0021] The present application relates to aluminum alloy material processing technology, in particular to a kind of by high strain asymmetric rolling and aging synergistically regulate micro-shear band through structure, realize the preparation of high strength and toughness intergranular corrosion resistant aluminum alloy and its application in light weight, high service life material.The present application is successfully built through high strain asymmetric rolling and the composite processing of specific aging in 7xxx series aluminum alloy, its inside small-angle grain boundary ratio is greater than or equal to 60%, alloy intergranular corrosion depth is 25-38 μm, tensile strength is 440-460 MPa, can improve corrosion resistance and mechanical property simultaneously.This scheme experimental design is simple and easy to implement, does not need to rely on expensive rare alloy composition, can significantly reduce production cost, also can facilitate alloy recycling, improve resource utilization efficiency, reduce primary resource consumption, perfectly meet the core demand of low-cost and high environmental protection material in the industrial profile field with clear cost-effective orientation, have important industrial application value, and be suitable for aircraft fuselage, wing, landing gear, rocket engine frame, missile shell and other aerospace key load-bearing components. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a micro-shear band through grain structure schematic diagram of high corrosion-resistant 7xxx series aluminum alloy in the present application; Figure 2 It is intergranular corrosion morphology comparison chart of high corrosion-resistant 7xxx series aluminum alloy in the present application; Figure 3 It is preparation process flow chart of high corrosion-resistant 7xxx series aluminum alloy in the present application; Figure 4 It is microstructure diagram of micro-shear band of high corrosion-resistant 7xxx series aluminum alloy in the present application. DETAILED DESCRIPTION

[0023] The application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are only used to illustrate the application and not to limit the scope of the application. Example 1

[0024] A high corrosion-resistant 7xxx-series aluminum alloy sheet sample with a size of 45 mm x 20 mm x 6 mm was prepared.

[0025] A high corrosion-resistant aluminum alloy with a micro-shear band through structure, comprising multiple micro-shear bands formed by high-strain asymmetric rolling, after aging, the internal structure of the micro-shear band is transformed from a dislocation-enclosed subgrain boundary structure to a small-angle grain boundary (the angle θ of the small-angle grain boundary is 2°-15°, and the volume fraction of the small-angle grain boundary is 69%), which increases the width of the micro-shear band, and further connects different micro-shear bands. In addition, the interaction between the micro-shear band and the grain boundary causes the grain boundary to shift, and under the action of recrystallization, the micro-shear band at the grain boundary shift position is more likely to develop into other grains, ultimately forming a wider micro-shear band across multiple grains.

[0026] The aluminum alloy is a 7xxx-series aluminum alloy, the zinc content in the alloy is 7.14wt%, the magnesium content is 1.73wt%, the copper content is 0.22wt%, and the rest is aluminum.

[0027] A preparation method of a high corrosion-resistant aluminum alloy with a micro-shear band through structure is as follows: (1) Casting aluminum alloy: according to the composition content of the 7xxx-series aluminum alloy, the raw materials are prepared. Put the crucible into the vacuum melting furnace preheated to 500℃, add the raw materials, set the temperature to 700℃, and keep it for 30 min until the raw materials are completely melted. Then open the melting furnace to remove the slag, and slowly stir the metal liquid with a stirring spoon to make the composition uniformly distributed. Then take out the mold to prepare for casting, ensure that the metal liquid flows out uniformly during the casting process, and finally obtain the block-shaped 7xxx-series aluminum alloy required for the experiment, i.e. the casting aluminum alloy; (2) Multi-graded solid solution treatment: first, the casting aluminum alloy is heated to 250℃ at a rate of 5℃ / min and kept for 30 min at room temperature to eliminate residual stress. Then, it is heated to 400℃ at a rate of 3℃ / min and kept for 1h (pre-solid solution of low melting point phase). Finally, it is heated to 470℃ at a rate of 2℃ / min and kept for 1.5h, and Ar+0.5%H2 (i.e. 99.5% Ar and 0.5% H2) is used as the protective gas to eliminate the macroscopic segregation of elements in the as-cast structure and achieve high solid solution of alloy elements. After the end of the holding period, the alloy is immediately water quenched to 150℃ at a cooling rate of 200℃ / s, and then air cooled to room temperature to reduce residual stress; (3) Asymmetric rolling: The alloy obtained in step (2) is subjected to asymmetric rolling at room temperature. The upper roll speed is 40 mm / s, the lower roll speed is 47 mm / s, the total reduction is 80%, and the single reduction does not exceed 5%. (4) Time-sensitive processing: such as Figure 3 As shown, the rolled alloy was artificially aged at 120℃ for 24 hours, with a nitrogen circulation system (flow rate of 0.8 m³ / h) used to ensure that the temperature uniformity inside the furnace was controlled within ±2℃. After aging, a three-stage cooling regime was adopted: first, the temperature was reduced from the aging temperature to 80℃ at a cooling rate of 2℃ / h, then to 50℃ at a cooling rate of 1℃ / h, and finally cooled to room temperature in the furnace. The entire experiment was conducted under nitrogen protection, and the final product was obtained.

[0028] This embodiment describes the application of a highly corrosion-resistant aluminum alloy with a micro-shear band through-structure in materials that combine lightweight and ultra-long service life.

[0029] Materials that combine lightweight design with ultra-long service life include materials for aerospace, rail transportation, and the automotive industry.

[0030] Materials used in aerospace include key load-bearing components such as aircraft fuselages, wings, landing gear, rocket engine frames, and missile casings.

[0031] like Figure 4 As shown, the microshear bands in the sample microstructure penetrate three grains and have a width of 3.5 μm. The intergranular corrosion depth is 25 μm, and the polarization resistance is 2.36 × 10⁻⁶. 4 Ω·cm 2 The tensile strength is 456 MPa. Example 2

[0032] High corrosion-resistant 7xxx series aluminum alloy sheet samples with dimensions of 45 mm × 20 mm × 6 mm were prepared.

[0033] A highly corrosion-resistant aluminum alloy with a through-grain micro-shear band structure comprises multiple micro-shear bands formed by high-strain asymmetric rolling. After aging, the internal structure of the micro-shear bands transforms from a dislocation-surrounded subgrain boundary structure to a small-angle grain boundary (the angle θ of the small-angle grain boundary is 2°~15°, and the volume ratio of the small-angle grain boundary is 60%) surrounding recrystallized grains, increasing the width of the micro-shear bands and allowing different micro-shear bands to connect with each other. Furthermore, the interaction between the micro-shear bands and grain boundaries leads to grain boundary shift. Under recrystallization, the micro-shear bands at the shifted grain boundary locations are more likely to propagate into other grains, ultimately forming wider micro-shear bands spanning multiple grains.

[0034] The aluminum alloy is a 7xxx series aluminum alloy, the zinc content in the alloy is 7wt%, the magnesium content is 1wt%, the copper content is 0.1wt%, and the rest is aluminum.

[0035] A preparation method of the micro-shear band through structure high corrosion-resistant aluminum alloy is as follows: (1) Casting aluminum alloy: according to the component content of the 7xxx series aluminum alloy, the raw materials are prepared. Put the crucible into the vacuum melting furnace preheated to 490℃, add the raw materials, set the temperature to 690℃, and keep for 25min until the raw materials are completely melted. Then open the melting furnace to remove the slag, and slowly stir the metal liquid with a stirring spoon to make the components uniformly distributed. Then take out the mold to prepare for casting, ensure the uniformity of the metal liquid flow during casting, and finally obtain the block-shaped 7xxx series aluminum alloy required by the experiment, that is, the casting aluminum alloy; (2) Multi- gradient solid solution treatment: first, the casting aluminum alloy is heated to 240℃ at a rate of 4℃ / min and kept for 25min at room temperature to eliminate residual stress. Then, it is heated to 390℃ at a rate of 2℃ / min and kept for 55min (pre- solid solution low melting point phase). Finally, it is heated to 460℃ at a rate of 1℃ / min and kept for 1h, and Ar+0.5%H2 (that is, 99.5% Ar and 0.5% H2) is used as the protective gas to eliminate the macroscopic segregation of elements in the as-cast structure and achieve high solid solution of alloy elements. After the heat preservation is over, the alloy is immediately water quenched to 140℃ at a cooling rate of 190℃ / s, and then air cooled to room temperature to reduce residual stress; (3) Asymmetric rolling, the alloy obtained in step (2) is subjected to asymmetric rolling treatment at room temperature, the upper roller speed is 35mm / s, the lower roller speed is 45mm / s, the total reduction is 75%, and the single reduction is not more than 5%; (4) Aging treatment: the above-mentioned rolled alloy is subjected to artificial aging treatment at 110℃ for 28h, and a nitrogen circulation system (flow rate is 0.5m³ / h) is used to ensure that the temperature uniformity in the furnace is controlled within ±2℃. After aging, a three-stage cooling system is adopted, first, the cooling rate is 1℃ / h from the aging temperature to 75℃, then the cooling rate is 0.5℃ / h from 75℃ to 45℃, and finally, the furnace is cooled to room temperature. The whole experiment is carried out under nitrogen protection, and finally the finished product is obtained.

[0036] The micro-shear band through structure high corrosion-resistant aluminum alloy of the embodiment is applied to materials with light weight and super long service life.

[0037] The materials with light weight and super long service life include aerospace materials, rail transit materials, and automotive industry materials.

[0038] The aerospace materials include aircraft fuselage, wings, landing gear, rocket engine frame, missile shell and other key load-bearing components in aerospace.

[0039] A micro-shear band in the sample tissue penetrates 3 grains, with a width of 3.0 μm. The intergranular corrosion depth is 38 μm, and the polarization resistance value is 1.98 x 10 4 Ω·cm 2 The tensile strength is 440 MPa. Example 3

[0040] A high-corrosion-resistant 7xxx-series aluminum alloy sheet sample with a size of 45 mm x 20 mm x 6 mm is prepared.

[0041] A high-corrosion-resistant aluminum alloy with a micro-shear band penetrating structure, including multiple micro-shear bands formed by high-strain asymmetric rolling, after aging, the internal structure of the micro-shear band is transformed from a dislocation-enclosed subgrain boundary structure to a small-angle grain boundary (the angle θ of the small-angle grain boundary is 2°-15°, and the volume fraction of the small-angle grain boundary is 64%) surrounding recrystallized grains, which increases the width of the micro-shear band, and further connects different micro-shear bands. In addition, the interaction between the micro-shear band and the grain boundary leads to grain boundary migration, and under the action of recrystallization, the micro-shear band at the grain boundary migration position is more likely to develop into other grains, ultimately forming a wider micro-shear band that spans multiple grains.

[0042] The aluminum alloy is a 7xxx-series aluminum alloy, the zinc content in the alloy is 9wt%, the magnesium content is 3wt%, the copper content is 0.25wt%, and the rest is aluminum.

[0043] A method for preparing a high-corrosion-resistant aluminum alloy with a micro-shear band penetrating structure is as follows: (1) Casting aluminum alloy: according to the composition content of the 7xxx-series aluminum alloy, the raw materials are prepared. Put the crucible into the vacuum melting furnace preheated to 510℃, add the raw materials, set the temperature to 710℃, and keep it for 35min until the raw materials are completely melted. Then open the melting furnace to remove the slag, and slowly stir the metal liquid with a stirring spoon to make the composition uniformly distributed. Then take out the mold to prepare for casting, ensure that the metal liquid flows out uniformly during casting, and finally get the block-shaped 7xxx-series aluminum alloy required for the experiment, i.e. the casting aluminum alloy; (2) Multi-gradient solid solution treatment: first, the casting aluminum alloy is heated to 260℃ at a rate of 6℃ / min and kept for 35min to eliminate residual stress. Then, it is heated to 410℃ at a rate of 4℃ / min and kept for 65min (pre-solid solution of low melting point phase). Finally, it is heated to 480℃ at a rate of 3℃ / min and kept for 2h, and Ar+0.5%H2 (i.e. 99.5% Ar and 0.5% H2) is used as the protective gas to eliminate element macrosegregation in the as-cast structure and achieve high solid solution of alloy elements. After the holding period is over, the alloy is immediately water quenched to 160℃ at a cooling rate of 210℃ / s, and then air cooled to room temperature to reduce residual stress; (3) Asymmetric rolling: The alloy obtained in step (2) is subjected to asymmetric rolling at room temperature. The upper roll speed is 45 mm / s, the lower roll speed is 55 mm / s, the total reduction is 85%, and the single reduction does not exceed 5%. (4) Aging treatment: The rolled alloy was artificially aged at 130℃ for 20 hours, and a nitrogen circulation system (flow rate of 1.0 m³ / h) was used to ensure that the temperature uniformity in the furnace was controlled within ±2℃. After aging, a three-stage cooling regime was adopted: first, the aging temperature was reduced to 85℃ at a cooling rate of 3℃ / h, then to 55℃ at a cooling rate of 1.5℃ / h, and finally cooled to room temperature in the furnace. The entire experiment was carried out under nitrogen protection, and the final product was obtained.

[0044] This embodiment describes the application of a highly corrosion-resistant aluminum alloy with a micro-shear band through-structure in materials that combine lightweight and ultra-long service life.

[0045] Materials that combine lightweight design with ultra-long service life include materials for aerospace, rail transportation, and the automotive industry.

[0046] Materials used in aerospace include key load-bearing components such as aircraft fuselages, wings, landing gear, rocket engine frames, and missile casings.

[0047] like Figure 1 As shown, the microshear bands in the sample microstructure penetrate four grains, with a width of 4.2 μm. The intergranular corrosion depth is 30 μm, and the polarization resistance is 2.15 × 10⁻⁶. 4 Ω·cm 2 The tensile strength is 460 MPa.

[0048] Comparative Example 1

[0049] The only difference between this comparative example and Example 1 is that step (4) was not aged, i.e., only steps (1), (2), and (3) were performed; the shear bands in the sample obtained in this comparative example did not penetrate the grains and had a width of 1.2 μm. The angle θ of the small-angle grain boundaries was 2°~15°, and the volume ratio of the small-angle grain boundaries was 46%. The intergranular corrosion depth was 90 μm, and the polarization resistance was 6.51 × 10⁻⁶. 3 Ω·cm 2 The tensile strength is 448 MPa.

[0050] like Figure 2 The image shows a comparison of the intergranular corrosion morphology of this comparative example and Example 1. This comparative example did not undergo aging treatment, and the shear bands in the sample contain a large number of dislocations, affecting the alloy's resistance to pitting corrosion. Furthermore, the internal structure of the shear bands remains a dislocation-surrounded subgrain boundary structure, causing the shear bands to not penetrate the grains, resulting in a small width and poor resistance to intergranular corrosion.

[0051] Comparative Example 2

[0052] The difference between the present comparative example and Example 1 is only that step (3) is asymmetric rolling treatment of the sample at room temperature, and the total amount of pressing is 50%. In the sample obtained by the present comparative example, the shear band does not penetrate the grain, and the width is 2.0 μm. The angle θ of the low-angle grain boundary is 2°-15°, and the volume fraction of the low-angle grain boundary is 51%. The intergranular corrosion depth is 58 μm, and the polarization resistance value is 1.40 x 10 4 Ω·cm². The tensile strength is 424 MPa. In the present comparative example, the content of the internal micro-shear band itself is low due to the low amount of rolling. After aging treatment, although the width of the micro-shear band increases under the influence of recrystallization, the development of corrosion is limited because the distance between the shear bands is too far and the multiple micro-shear bands cannot be connected.

[0053] Comparative Example 3

[0054] The difference between the present comparative example and Example 1 is only that step (3) is symmetric rolling treatment of the sample at room temperature, and the upper roller speed is 40 mm / s and the lower roller speed is 40 mm / s.

[0055] The shear band of the present comparative example penetrates 2 grains, and the width is 2.5 μm. The angle θ of the low-angle grain boundary is 2°-15°, and the volume fraction of the low-angle grain boundary is 59%. The intergranular corrosion depth is 50 μm, and the polarization resistance value is 1.12 x 10 4 Ω·cm². The tensile strength is 430 MPa.

[0056] Comparative Example 4

[0057] The difference between the present comparative example and Example 1 is only that step (3) is symmetric rolling treatment of the sample at room temperature, and the upper roller speed is 47 mm / s and the lower roller speed is 47 mm / s.

[0058] The shear band of the present comparative example penetrates 2 grains, and the width is 2.6 μm. The angle θ of the low-angle grain boundary is 2°-15°, and the volume fraction of the low-angle grain boundary is 56%. The intergranular corrosion depth is 52 μm, and the polarization resistance value is 1.13 x 10 4 Ω·cm². The tensile strength is 428 MPa.

[0059] The detailed data of the high corrosion-resistant aluminum alloy obtained by Example 1-Example 3 and Comparative Example 1-Comparative Example 4 of the present application is shown in Table 1 below.

[0060] Table 1 Performance table of high corrosion-resistant aluminum alloy

[0061] Main test methods: Electron backscatter diffraction (EBSD) analysis: The sample for EBSD test should have good electrical conductivity, and the surface should be clean, flat and stress-free. During sample preparation, the sample is first mechanically polished until the surface is bright and scratch-free, and then electrolytic polishing is performed. The electrolytic polishing solution is composed of 10% HC104+90% C2H5OH, the temperature is set to -20°C, the voltage is constant at 32 V, and the electrolytic polishing time is 60 s. After electrolytic polishing, immerse the tested surface downward into a beaker containing absolute ethanol for ultrasonic cleaning, then dry with a warm air dryer, put it into a sample box, pack it for vacuum extraction, and wait for testing. The EBSD equipment used in this experiment is Hitachi S-3400N, and the results are processed and analyzed by HKL-CHANNEL5 software to obtain microstructure, grain boundary proportion, grain boundary angle and other data.

[0062] Intergranular corrosion performance test: According to GB / T 7998-2005, the intergranular corrosion experiment is carried out, the corrosion solution is composed of 1 L NaCl solution (57 g NaCl + 1 L deionized water) + 10 mL H2O2, the sample is suspended in the corrosion solution with plastic wire, the ratio of sample surface area to corrosion solution volume is less than 20 mm 2 / mL, a constant temperature water bath is used to keep the experimental temperature at 35±2°C, the sample is taken out after 6 h of corrosion, washed with alcohol and blown, the sample section is cut, and the corrosion morphology and corrosion depth are observed under a Nikon Olympus BX51M type metallographic microscope.

[0063] Electrochemical performance test: The electrochemical performance is measured by an electrochemical workstation CHI660E (Shanghai Chenhua Instrument Co., Ltd.). A three-electrode system is used, the working electrode is the sample to be tested, the working area is 100 mm 2 , the counter electrode is a platinum electrode, the reference electrode is a mercury-mercury electrode (saturated KCl solution), and the electrolyte is a 3.5 wt.% sodium chloride solution (500 mL).

[0064] Each sample is subjected to open circuit potential (OCP) alternating current impedance and dynamic polarization potential test. The OCP scan time is 3600 s, the frequency range of alternating current impedance spectrum (EIS) is 10 mHz~10 kHz, and the perturbation amplitude is 10 mV. The dynamic potential polarization (PDP) curve is measured from the position 0.25 V lower than the OCP to the positive direction at a scan rate of 0.5 mV / s. When the breakdown voltage reaches -2~-3 V, the scanning is stopped. The polarization resistance value Rp is obtained according to the equivalent circuit parameters.

[0065] Mechanical property test: room temperature tensile test was performed on a universal testing machine to obtain the tensile strength of the sample, and the tensile rate was 0.36 mm / min. The tensile test of the relevant room temperature rolling sample was all sampled from the RD-TD (Transverse direction, TD) surface.

[0066] Finally, it should be noted that the above examples are only to illustrate the technical concept and characteristics of the present application, and do not limit it. Different preparation methods can still be modified according to this technical solution, and the modified technical solution cannot deviate from the spirit and essence of the present application.

[0067] It should be understood that in order to simplify the present disclosure and to help understand one or more of the various inventive aspects, in the above description of the exemplary embodiments of the application, various features of the application are sometimes grouped together in a single embodiment, figure, or description of it. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed application requires more features than are explicitly claimed in each claim. Rather, inventive aspects lie in less than all features of the previously disclosed embodiments. Therefore, the claims at the end of the DETAILED DESCRIPTION, which each follow the specific embodiments, are hereby expressly incorporated into this DETAILED DESCRIPTION, wherein each claim is separately considered as a separate embodiment of the application.

[0068] Although the present application is described in terms of limited number of embodiments, those skilled in the art, with the benefit of the above description, will appreciate that other embodiments are possible within the scope of the application described herein. In addition, it should be noted that the language used in the specification has been chosen primarily for readability and instructional purposes and can not have been selected to convey an exclusive or exhaustive meaning. Therefore, many modifications and variations of the present application are possible in light of the above teachings without departing from the scope and spirit of the appended claims. The disclosure of the application is illustrative only and not restrictive of the scope of the application, which is defined by the appended claims.

[0069] The above is only the preferred embodiment of the present application, and it should be pointed out that for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A high corrosion resistant aluminum alloy of a micro-shear banding through structure, characterized by: The through structure has micro shear bands with a width of 3.0-4.2 microns across >3 grains, and small-angle grain boundaries formed inside to surround the recrystallized grains.

2. The high corrosion-resistant aluminum alloy with a micro-shear band through-type structure according to claim 1, characterized in that: The micro shear bands are at an angle of 30-35 degrees to the rolling direction, the angle of the small-angle grain boundaries is 2-15 degrees, and the volume fraction of the small-angle grain boundaries is >60%.

3. The high corrosion-resistant aluminum alloy with a micro-shear band through-type structure according to claim 1, characterized in that: The aluminum alloy is a 7xxx series aluminum alloy, the zinc content in the alloy is 7-9 wt%, the magnesium content is 1-3 wt%, the copper content is 0.1-0.25 wt%, and the rest is aluminum.

4. The high corrosion-resistant aluminum alloy with a micro-shear band through-type structure according to claim 1, characterized in that: The high-corrosion-resistant alloy has a tensile strength of 440-460 MPa and an intergranular corrosion depth of 25-38 microns.

5. The method for preparing the high corrosion resistant aluminum alloy of the micro-shear band through structure according to any one of claims 1-4, characterized in that: The method comprises the following steps: S01, multi-graded solid solution treatment: first, the cast aluminum alloy is raised to 240-260 DEG C at a rate of 4-6 DEG C / min at room temperature and is kept for 25-35 min; then, it is raised to 390-410 DEG C at a rate of 2-4 DEG C / min and is kept for 55-65 min; finally, it is raised to 460-480 DEG C at a rate of 1-3 DEG C / min and is kept for 1-2 h; a protective gas is applied during the solid solution process; after the keeping, the alloy is immediately water quenched to 140-160 DEG C at a cooling rate of 190-210 DEG C / s, and then is air cooled to room temperature; S02, asymmetric rolling, the alloy obtained in S01 is subjected to asymmetric rolling at room temperature, the upper roller speed is 35-45 mm / s, the lower roller speed is 45-55 mm / s, the total down pressure is 75-85%, and the single down pressure is not more than 5%; S03, the rolled alloy is subjected to artificial aging treatment at 110-130 DEG C for 20-28 h, and the in-furnace temperature uniformity is controlled within ±2 DEG C; after the aging, a three-stage cooling system is adopted, the temperature is first reduced to 75-85 DEG C at a rate of 1-3 DEG C / h, then is reduced to 45-55 DEG C at a rate of 0.5-1.5 DEG C / h, and finally is furnace cooled to room temperature to obtain the finished product.

6. The method of claim 5, wherein: In S01, the protective gas is 99.5% Ar and 0.5% H2.

7. The method of claim 5, wherein: In S03, the artificial aging treatment and the three-stage cooling process are both carried out under nitrogen protection.

8. The method of claim 5, wherein: In S01, the casting method of the aluminum alloy is as follows: according to the component content of the 7xxx series aluminum alloy, the raw materials are prepared; the crucible is put into a vacuum melting furnace preheated to 490-510 DEG C, the raw materials are added, the temperature is set to 690-710 DEG C, and is kept for 25-35 min until the raw materials are completely melted; then, the melting furnace is opened for skimming, and the metal liquid is stirred with a stirring spoon to make the components uniformly distributed; then, the mold is taken out for casting, the metal liquid flow rate is ensured to be uniform during casting, and finally the block-shaped 7xxx series aluminum alloy required by the experiment, i.e. the cast aluminum alloy, is obtained.

9. The high-corrosion-resistant aluminum alloy with a micro shear band through structure according to any one of claims 1-4 is applied to a material with light weight and super-long service life.

10. Use according to claim 9, characterized in that: The material with light weight and super-long service life includes aerospace materials, rail transit materials, and automobile industry materials; the aerospace materials include airplane fuselages, wings, landing gears, rocket engine frames, and missile casings.

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