High corrosion resistant aluminum alloy with micro-shear band through structure, preparation method and application thereof

Abstract

This invention discloses a high corrosion-resistant aluminum alloy with a through-grain micro-shear band structure, its preparation method, and its applications, belonging to the field of aluminum alloy material processing technology. Through a composite treatment of high-strain asymmetric rolling and specific aging, this invention successfully constructs a through-grain micro-shear band structure in 7xxx series aluminum alloys. The structure exhibits a small-angle grain boundary ratio ≥60%, an intergranular corrosion depth ≤38μm, and a tensile strength ≥440MPa, simultaneously improving corrosion resistance and mechanical properties. The experimental design of this method is simple and easy to implement, requiring no reliance on expensive or rare alloy components. It significantly reduces production costs, facilitates alloy recycling and regeneration, improves resource utilization efficiency, and reduces primary resource consumption. This perfectly aligns with the core demand for low-cost, environmentally friendly materials in the cost-effective industrial profile sector, possessing significant industrial application value and suitable for critical load-bearing components in aerospace and other applications.

Description

Technical Field

[0001] This invention relates to a high corrosion-resistant aluminum alloy with a micro-shear band through-hole structure, its preparation method, and its application. Specifically, it relates to a method for preparing an aluminum alloy with high strength, toughness, and resistance to intergranular corrosion by synergistically controlling the micro-shear band through-hole structure through high-strain rolling and aging. This method belongs to the field of aluminum alloy material processing technology. Background Technology

[0002] With the urgent need for lightweight materials in aerospace, automotive manufacturing, and marine engineering, aluminum alloys that combine high strength and corrosion resistance have become a research hotspot. Traditional 7xxx series (Al-Zn-Mg-(Cu)) aluminum alloys exhibit a contradiction between high plasticity and corrosion resistance: while large plastic deformation can improve strength, strain concentration leads to dislocation accumulation at grain boundaries, increasing the number of intergranular corrosion pits and exacerbating intergranular corrosion (e.g., corrosion depth reaches 90 μm when rolled at 80% reduction). Existing patent (2021112457041 - A high-strength and tough aluminum alloy with a diverse mixed-grain structure induced by micro-shear bands, its preparation method, and application) utilizes micro-shear bands to form a mixed-grain structure to strengthen the alloy, but it does not solve the corrosion resistance problem. This invention constructs a micro-shear band structure penetrating multiple grains within the alloy through high-strain rolling combined with a specific aging process. The recrystallized grains surrounded by small-angle grain boundaries within this structure effectively block corrosion paths. Simultaneously, the dispersed precipitation of the η′ phase enhances strength, achieving a synergistic optimization of high plasticity and corrosion resistance. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a highly corrosion-resistant aluminum alloy with a micro-shear band through-grain structure. This method utilizes high rolling strain to induce dense micro-shear bands, which, after specific aging treatment, span ≥3 grains, forming a through-grain structure with small-angle grain boundaries (2° < θ < 15°) surrounding the recrystallized grains. The formation of different interlaced regions within the grains effectively blocks intergranular corrosion paths, overcoming the inherent inverse relationship between strong plasticity and corrosion resistance in 7xxx series aluminum alloys, achieving a synergistic improvement in both. This structure allows for intergranular corrosion depth as low as 25 μm (approximately 70% lower than conventional processes), while maintaining a tensile strength ≥ 440 MPa.

[0004] Meanwhile, this invention provides a high corrosion-resistant aluminum alloy with a micro-shear band through-hole structure, which achieves a synergistic improvement in strength and corrosion resistance. It aims to improve the resource recycling rate, reduce the consumption of primary minerals, and reduce carbon emissions by simplifying the recycling process, thereby achieving synergistic optimization of economic and ecological benefits.

[0005] Meanwhile, this invention provides an application of a highly corrosion-resistant aluminum alloy with a micro-shear band through-structure in lightweight, long-service-life materials.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A highly corrosion-resistant aluminum alloy with a through-grain microshear band structure comprises multiple microshear bands formed by high-strain asymmetric rolling. Under aging, the internal structure of the microshear bands transforms from a dislocation-surrounded subgrain boundary structure to a small-angle grain boundary-surrounded recrystallized grain structure, increasing the width of the microshear bands and allowing different microshear bands to connect with each other. Furthermore, the interaction between the microshear bands and grain boundaries leads to grain boundary shift. Under recrystallization, the microshear bands at the shifted grain boundary locations more easily propagate into other grains, ultimately forming relatively wide (3.0~4.2 μm) microshear bands spanning multiple grains (≥3 grains).

[0008] The aluminum alloy is a 7xxx series aluminum alloy, with a zinc content of 7wt%~9wt%, a magnesium content of 1wt%~3wt%, a copper content of 0.1wt%~0.25wt%, and the remainder being aluminum.

[0009] The micro-shearing band is at an angle of 30° to 35° to the rolling direction, the small-angle grain boundary angle θ is (2° < θ < 15°), and the volume ratio of the small-angle grain boundary is ≥ 60%.

[0010] A method for preparing a highly corrosion-resistant aluminum alloy with a micro-shear band through-hole structure includes the following steps:

[0011] Step 1, Casting the Aluminum Alloy: Prepare the raw materials according to the composition of the 7xxx series aluminum alloy. Place the crucible in a vacuum melting furnace preheated to 490~510℃, add the raw materials, set the temperature to 690~710℃, and hold for 25~35 minutes until the raw materials are completely melted. Then open the melting furnace to skim off the slag, and slowly stir the molten metal with a stirring spoon to ensure a uniform distribution of its composition. Next, remove the mold to prepare for casting. During the casting process, ensure that the flow rate of the molten metal is uniform, and finally obtain the block-shaped 7xxx series aluminum alloy required for the experiment.

[0012] Step 2, multi-gradient solution treatment: First, the cast aluminum alloy is heated to 240-260℃ at room temperature at 4-6℃ / min and held for 25-35min to eliminate residual stress. Then, it is heated to 390-410℃ at 2-4℃ / min and held for 55-65min (pre-solution of low-melting-point phases). Finally, it is heated to 460-480℃ at 1-3℃ / min and held for 1-2h, using Ar + 0.5% H2 (i.e., 99.5% Ar and 0.5% H2) as a protective gas to eliminate macroscopic element segregation in the as-cast microstructure and achieve high solid solution of alloying elements. After the holding period, the alloy is immediately water-quenched to 140-160℃ at a cooling rate of 190-210℃ / s, and then air-cooled to room temperature to reduce residual stress.

[0013] Step 3, asymmetric rolling: The alloy obtained in Step 1 is subjected to asymmetric rolling on the sample at room temperature. The upper roll speed is 35~45 mm / s, the lower roll speed is 45~55 mm / s, the total reduction is 75%-85%, and the single reduction does not exceed 5%.

[0014] Step four involves artificially aging the rolled alloy at 110-130℃ for 20-28 hours, using a nitrogen circulation system (flow rate 0.5-1 m³ / h) to ensure temperature uniformity within ±2℃. After aging, a three-stage cooling process is employed: first, the temperature is reduced from the aging temperature to 75-85℃ at a cooling rate of 1-3℃ / h; then, it is reduced to 45-55℃ at a cooling rate of 0.5-1.5℃ / h; finally, it is cooled to room temperature in the furnace. The entire experiment is conducted under nitrogen protection, ultimately yielding the final product.

[0015] After step three, a large number of layered dislocation structures with different orientations are formed in the alloy.

[0016] After step three, the abundant Zn and Mg solute atoms with high solid solubility interact strongly with the layered dislocation structure, generating highly dense, intersecting micro-shear bands. The internal structure of the shear bands consists of a small number of subgrain boundaries surrounded by dislocations.

[0017] After step four, the width of the linear high dislocation density region near the shear band in the sample significantly decreased. Numerous recrystallized grains and subgrains distributed along the shear band direction appeared within the shear band, and the internal structure transformed from a dislocation-surrounded subgrain boundary structure to a small-angle grain boundary-surrounded recrystallized grain structure, increasing the width of the shear band. Furthermore, the interaction between the micro-shear band and grain boundaries led to grain boundary shift. Under recrystallization, the micro-shear band at the shifted grain boundary position more easily propagated into other grains, ultimately forming a relatively wide micro-shear band spanning multiple grains.

[0018] The high corrosion-resistant alloy has a tensile strength of 440~460MPa and an intergranular corrosion depth of 25~38μm.

[0019] Application of a highly corrosion-resistant aluminum alloy with a micro-shear band through-hole structure in lightweight, long-service-life materials.

[0020] The materials that combine lightweight advantages with ultra-long service life include materials for aerospace, rail transportation, and automotive industries.

[0021] This invention utilizes the principle that 7xxx series aluminum alloys easily form micro-shear bands during large plastic deformation, and that these micro-shear bands can undergo structural evolution during room temperature rolling and subsequent aging treatment. On one hand, room temperature asymmetric rolling with a reduction of 75%-85% introduces high-density dislocations and multiple intersecting micro-shear bands into the alloy. On the other hand, aging treatment promotes the reorganization of dislocations within the micro-shear bands into small-angle grain boundaries and induces the formation of recrystallized grains. The internal structure transforms from a structure of dislocations surrounding subgrain boundaries to a structure of small-angle grain boundaries surrounding recrystallized grains, increasing the width of the micro-shear bands and forming wider intersecting micro-shear bands spanning multiple grains. Ultimately, through the synergistic effect of "dislocation regulation-grain boundary recombination-intergranular distribution" of 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 inside the micro-shear bands improve the mechanical properties of the alloy; on the other hand, the special structure inside the shear bands - small-angle grain boundaries surrounding recrystallized grains: can effectively block the corrosion propagation path, especially when the shear bands traverse multiple grains, intergranular corrosion is difficult to propagate from one grain to another).

[0022] The beneficial effects of adopting the above technical solution are as follows: This invention provides a high-strength, high-corrosion-resistant 7xxx series aluminum alloy that can be prepared on a large scale, with a simple process and controllable cost, and its preparation method. It can optimize the comprehensive performance of the material without relying on complex alloying elements or extreme processing conditions, and mainly has the following advantages:

[0023] (1) The aluminum alloy of the present invention does not contain any other expensive alloying 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 remainder is aluminum. Therefore, the material cost is lower and recycling is simpler, perfectly meeting the core demand of the cost-effective industrial profile field for low-cost and environmentally friendly materials.

[0024] (2) The present invention adopts the technology of introducing plastic deformation energy storage by room temperature asymmetric rolling and promoting microstructure optimization by aging treatment, so as to realize the structural evolution of micro-shear band from "dislocation entanglement" to "small angle grain boundary wrapped recrystallized grains". It does not require complex thermal processing equipment, the process is easy to operate and has low energy consumption.

[0025] (3) This invention significantly improves the overall performance of 7xxx series aluminum alloys by controlling the micro-shear band structure:

[0026] On the one hand, the introduction of high-strain rolling enhances the alloy's grain refinement and dislocation strengthening: the high density of dislocations and numerous small-angle grain boundaries within the micro-shear bands improve the alloy's mechanical properties, achieving a tensile strength ≥440MPa. On the other hand, the unique structure within the shear bands—small-angle grain boundaries surrounding recrystallized grains—effectively blocks corrosion propagation paths. When the shear bands traverse multiple grains, intergranular corrosion is difficult to propagate from one grain to another, allowing for intergranular corrosion depths as low as 25μm.

[0027] In summary, this invention proposes a high-strength, high-corrosion-resistant 7xxx series aluminum alloy and its preparation method that utilizes room-temperature asymmetric rolling combined with aging treatment to control the micro-shear band structure. This alloy exhibits excellent matching between corrosion resistance and mechanical properties, and the experimental scheme is simple and easy to implement, significantly reducing production costs. It perfectly meets the core demand of the cost-effective industrial profile sector for low-cost, environmentally friendly materials, possessing significant industrial application value and suitable for key load-bearing components in aerospace and other fields.

[0028] This invention relates to aluminum alloy material processing technology, specifically to a method for preparing high-strength, tough, and corrosion-resistant aluminum alloys through the synergistic control of high-strain asymmetric rolling and aging to create a through-grained micro-shear band structure, and its application in lightweight, long-service-life materials. This invention successfully constructs a through-grained micro-shear band structure in 7xxx series aluminum alloys through a composite treatment of high-strain asymmetric rolling and specific aging. The structure exhibits a small-angle grain boundary ratio ≥60%, an intergranular corrosion depth of 25-38 μm, and a tensile strength of 440-460 MPa, simultaneously improving corrosion resistance and mechanical properties. The experimental design of this method is simple and easy to implement, requiring no reliance on expensive or rare alloy components. It significantly reduces production costs, facilitates alloy recycling and regeneration, improves resource utilization efficiency, and reduces primary resource consumption. This perfectly aligns with the core demand for low-cost, environmentally friendly materials in the cost-effective industrial profile sector, possessing significant industrial application value. It is suitable for critical load-bearing components in aerospace applications such as aircraft fuselages, wings, landing gear, rocket engine frames, and missile casings. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the micro-shear band penetrating grain structure of the high corrosion-resistant 7xxx series aluminum alloy in this invention;

[0030] Figure 2 This is a comparison image of the intergranular corrosion morphology of the high corrosion-resistant 7xxx series aluminum alloy in this invention;

[0031] Figure 3 This is a flow chart of the preparation process of the high corrosion-resistant 7xxx series aluminum alloy in this invention;

[0032] Figure 4 This is a microstructure diagram of the micro-shear bands in the high corrosion-resistant 7xxx series aluminum alloy of this invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example 1

[0034] High corrosion-resistant 7xxx series aluminum alloy sheet samples with dimensions of 45 mm × 20 mm × 6 mm were prepared.

[0035] 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 percentage of the small-angle grain boundary is 69%) 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.

[0036] The aluminum alloy is a 7xxx series aluminum alloy, with a zinc content of 7.14 wt%, a magnesium content of 1.73 wt%, a copper content of 0.22 wt%, and the remainder being aluminum.

[0037] A method for preparing a highly corrosion-resistant aluminum alloy with a micro-shear band through-hole structure is as follows:

[0038] (1) Casting aluminum alloy: Based on the composition of 7xxx series aluminum alloy, prepare the raw materials. Place the crucible in a vacuum melting furnace preheated to 500℃, add the raw materials, set the temperature to 700℃, and hold for 30 minutes until the raw materials are completely melted. Then open the melting furnace to skim off the slag, and slowly stir the molten metal with a stirring spoon to make its composition evenly distributed. Then take out the mold to prepare for casting. During the casting process, ensure that the flow rate of the molten metal is uniform, and finally obtain the block 7xxx series aluminum alloy required for the experiment, that is, the cast aluminum alloy;

[0039] (2) Multi-gradient solution treatment: First, the cast aluminum alloy is heated to 250℃ at room temperature at 5℃ / min and held for 30min to eliminate residual stress. Then, it is heated to 400℃ at 3℃ / min and held for 1h (pre-solution of low-melting-point phase). Finally, it is heated to 470℃ at 2℃ / min and held for 1.5h, with Ar + 0.5% H2 (i.e., 99.5% Ar and 0.5% H2) as the protective gas to eliminate macroscopic segregation of elements in the as-cast structure and achieve high solid solution of alloying elements. After 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.

[0040] (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%.

[0041] (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.

[0042] 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.

[0043] Materials that combine lightweight design with ultra-long service life include materials for aerospace, rail transportation, and the automotive industry.

[0044] Materials used in aerospace include key load-bearing components such as aircraft fuselages, wings, landing gear, rocket engine frames, and missile casings.

[0045] 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

[0046] High corrosion-resistant 7xxx series aluminum alloy sheet samples with dimensions of 45 mm × 20 mm × 6 mm were prepared.

[0047] 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.

[0048] The aluminum alloy is a 7xxx series aluminum alloy, with a zinc content of 7wt%, a magnesium content of 1wt%, a copper content of 0.1wt%, and the remainder being aluminum.

[0049] A method for preparing a highly corrosion-resistant aluminum alloy with a micro-shear band through-hole structure is as follows:

[0050] (1) Casting aluminum alloy: Based on the composition of 7xxx series aluminum alloy, prepare the raw materials. Place the crucible in a vacuum melting furnace preheated to 490℃, add the raw materials, set the temperature to 690℃, and hold for 25 minutes until the raw materials are completely melted. Then open the melting furnace to skim off the slag, and slowly stir the molten metal with a stirring spoon to ensure that its composition is evenly distributed. Then take out the mold to prepare for casting. During the casting process, ensure that the flow rate of the molten metal is uniform, and finally obtain the block 7xxx series aluminum alloy required for the experiment, that is, the cast aluminum alloy;

[0051] (2) Multi-gradient solution treatment: First, the cast aluminum alloy is heated to 240℃ at room temperature at 4℃ / min and held for 25min to eliminate residual stress. Then, it is heated to 390℃ at 2℃ / min and held for 55min (pre-solution of low melting point phase). Finally, it is heated to 460℃ at 1℃ / min and held for 1h, with Ar+0.5%H2 (i.e., 99.5% Ar and 0.5% H2) as the protective gas to eliminate macroscopic segregation of elements in the as-cast structure and achieve high solid solution of alloying elements. After the holding period, 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.

[0052] (3) Asymmetric rolling: The alloy obtained in step (2) is subjected to asymmetric rolling at room temperature. The upper roll speed is 35 mm / s, the lower roll speed is 45 mm / s, the total reduction is 75%, and the single reduction does not exceed 5%.

[0053] (4) Aging treatment: The rolled alloy was artificially aged at 110℃ for 28 hours, and a nitrogen circulation system (flow rate of 0.5 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 75℃ at a cooling rate of 1℃ / h, then to 45℃ at a cooling rate of 0.5℃ / 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.

[0054] 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.

[0055] Materials that combine lightweight design with ultra-long service life include materials for aerospace, rail transportation, and the automotive industry.

[0056] Materials used in aerospace include key load-bearing components such as aircraft fuselages, wings, landing gear, rocket engine frames, and missile casings.

[0057] The microshear bands in the sample microstructure penetrated three grains, with a width of 3.0 μm. The intergranular corrosion depth was 38 μm, and the polarization resistance was 1.98 × 10⁻⁶. 4 Ω·cm 2 The tensile strength is 440 MPa. Example 3

[0058] High corrosion-resistant 7xxx series aluminum alloy sheet samples with dimensions of 45 mm × 20 mm × 6 mm were prepared.

[0059] 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 percentage of the small-angle grain boundary is 64%) 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.

[0060] The aluminum alloy is a 7xxx series aluminum alloy, with a zinc content of 9 wt%, a magnesium content of 3 wt%, a copper content of 0.25 wt%, and the remainder being aluminum.

[0061] A method for preparing a highly corrosion-resistant aluminum alloy with a micro-shear band through-hole structure is as follows:

[0062] (1) Casting aluminum alloy: Based on the composition of 7xxx series aluminum alloy, prepare the raw materials. Place the crucible in a vacuum melting furnace preheated to 510℃, add the raw materials, set the temperature to 710℃, and hold for 35 minutes until the raw materials are completely melted. Then open the melting furnace to skim off the slag, and slowly stir the molten metal with a stirring spoon to ensure that its composition is evenly distributed. Then take out the mold to prepare for casting. During the casting process, ensure that the flow rate of the molten metal is uniform, and finally obtain the block 7xxx series aluminum alloy required for the experiment, that is, the cast aluminum alloy;

[0063] (2) Multi-gradient solution treatment: First, the cast aluminum alloy is heated to 260℃ at room temperature at 6℃ / min and held for 35min to eliminate residual stress. Then, it is heated to 410℃ at 4℃ / min and held for 65min (pre-solution of low-melting-point phase). Finally, it is heated to 480℃ at 3℃ / min and held for 2h, with Ar + 0.5% H2 (i.e., 99.5% Ar and 0.5% H2) as the protective gas to eliminate macroscopic segregation of elements in the as-cast structure and achieve high solid solution of alloying elements. After the holding period, 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.

[0064] (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%.

[0065] (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.

[0066] 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.

[0067] Materials that combine lightweight design with ultra-long service life include materials for aerospace, rail transportation, and the automotive industry.

[0068] Materials used in aerospace include key load-bearing components such as aircraft fuselages, wings, landing gear, rocket engine frames, and missile casings.

[0069] 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.

[0070] Comparative Example 1

[0071] 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.

[0072] 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.

[0073] Comparative Example 2

[0074] The only difference between this comparative example and Example 1 is that: in step (3), the sample is subjected to asymmetric rolling at room temperature with a total reduction of 50%; in the microstructure of the sample obtained in this comparative example, the shear band does not penetrate the grains and has a width of 2.0 μm. The angle θ of the small-angle grain boundary is 2°~15°, and the volume ratio of the small-angle grain boundary is 51%. The intergranular corrosion depth is 58 μm, and the polarization resistance is 1.40 × 10⁻⁶. 4 Ω·cm². Tensile strength is 424 MPa. This comparative example has a lower rolling reduction, resulting in a lower content of micro-shear bands. After aging treatment, although the width of the micro-shear bands increases due to recrystallization, the large distances between the bands prevent them from connecting, thus limiting their effectiveness in inhibiting corrosion development.

[0075] Comparative Example 3

[0076] The only difference between this comparative example and Example 1 is that in step (3), the sample is subjected to symmetrical rolling at room temperature, with the upper roller speed being 40 mm / s and the lower roller speed being 40 mm / s.

[0077] In this comparative example, the shear band penetrates two grains, with a width of 2.5 μm. The small-angle grain boundary angle θ ranges from 2° to 15°, and the volume fraction of the small-angle grain boundary is 59%. The intergranular corrosion depth is 50 μm, and the polarization resistance is 1.12 × 10⁻⁶. 4 Ω·cm². Tensile strength is 430MPa.

[0078] Comparative Example 4

[0079] The only difference between this comparative example and Example 1 is that in step (3), the sample is subjected to symmetrical rolling at room temperature, with the upper roller speed being 47 mm / s and the lower roller speed being 47 mm / s.

[0080] In this comparative example, the shear band penetrates two grains, with a width of 2.6 μm. The small-angle grain boundary angle θ ranges from 2° to 15°, and the volume fraction of the small-angle grain boundary is 56%. The intergranular corrosion depth is 52 μm, and the polarization resistance is 1.13 × 10⁻⁶. 4 Ω·cm². Tensile strength is 428 MPa.

[0081] Detailed data on the high corrosion-resistant aluminum alloys obtained in Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention are shown in Table 1 below.

[0082] Table 1 Properties of High Corrosion-Resistant Aluminum Alloys

[0083]

[0084] Main testing methods:

[0085] Electron backscatter diffraction (EBSD) analysis:

[0086] Samples used for EBSD testing must possess good conductivity and have clean, smooth, and stress-free surfaces. During sample preparation, the samples are first mechanically polished until the surface is bright and scratch-free, followed by electropolishing. The electropolishing solution consists of 10% HClO4 + 90% C2H5OH, with the temperature set at -20℃, the voltage constant at 32 V, and the electropolishing time at 60 s. After electropolishing, the sample is immersed face down in a beaker containing anhydrous ethanol for ultrasonic cleaning, then dried with a warm air blower, placed in a sample box, packaged, and vacuum-sealed, awaiting testing. The EBSD equipment used in this experiment is a Hitachi S-3400N, and the results are processed and analyzed using HKL-CHANNEL5 software to obtain data such as microstructure, grain boundary ratio, and grain boundary angles.

[0087] Intergranular corrosion performance test:

[0088] Intergranular corrosion tests were conducted according to GB / T 7998-2005. The etching solution was prepared as follows: 1 L NaCl solution (57 g NaCl + 1 L deionized water) + 10 mL H2O2. The sample was suspended in the etching solution by a plastic thread, and the ratio of the sample surface area to the volume of the etching solution was less than 20 mm². 2 / mL, the experimental temperature was maintained at 35±2℃ in a constant temperature water bath. After corrosion for 6 h, the sample was taken out, cleaned with alcohol and blown dry. The sample cross section was cut and the corrosion morphology and corrosion depth were observed under a Japanese Olympus BX51M metallographic microscope.

[0089] Electrochemical performance testing:

[0090] Electrochemical performance was measured using a CHI660E electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.). A three-electrode system was employed, with the test sample as the working electrode and a working area of ​​100 mm². 2 The counter electrode was a platinum electrode, the reference electrode was a calomel electrode (saturated KCl solution), and the electrolyte was a 3.5 wt.% sodium chloride solution (500 mL).

[0091] Open-circuit potential (OCP) AC impedance and dynamic polarization potential were measured for each sample. The OCP scan time was 3600 s, the AC impedance spectrum (EIS) frequency range was 10 mHz to 10 kHz, and the perturbation amplitude was 10 mV. The potentiodynamic polarization (PDP) curve was measured at a scan rate of 0.5 mV / s from a position 0.25 V lower than the OCP towards the positive direction. The scan was stopped when the breakdown voltage reached -2 ​​to -3 V. The polarization resistance value Rp was obtained from the equivalent circuit parameters.

[0092] Mechanical property testing: Tensile strength of the samples was obtained by room temperature tensile testing on a universal testing machine at a tensile rate of 0.36 mm / min. Tensile tests of all room temperature rolled samples were performed using samples taken from the RD-TD (Transverse direction, TD) surface.

[0093] Finally, it should be noted that the above embodiments are only for illustrating the technical concept and features of the present invention and are not intended to limit it. Different preparation methods can still be modified according to this technical solution, and the modified technical solution cannot deviate from the spirit of the technical solution of the present invention.

[0094] It should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all the features of the foregoingly disclosed embodiments. Therefore, the claims, following the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0095] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A highly corrosion-resistant aluminum alloy with a micro-shear band through-hole structure, characterized in that: It has micro-shear bands spanning ≥3 grains with a width of 3.0~4.2μm, and the micro-shear bands form a through-type structure in which small-angle grain boundaries surround recrystallized grains; The aluminum alloy is a 7xxx series aluminum alloy, with zinc content of 7wt%~9wt%, magnesium content of 1wt%~3wt%, copper content of 0.1wt%~0.25wt%, and the remainder being aluminum.

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 band is at an angle of 30° to 35° to the rolling direction, the angle θ of the small-angle grain boundary is 2° to 15°, and the volume ratio of the small-angle grain boundary 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 high corrosion-resistant alloy has a tensile strength of 440~460MPa and an intergranular corrosion depth of 25~38μm.

4. A method for preparing a high corrosion-resistant aluminum alloy with a micro-shear band through-structure according to any one of claims 1 to 3, characterized in that: Includes the following steps: S01, Multi-gradient solution treatment: First, the cast aluminum alloy is heated to 240~260℃ at room temperature at a rate of 4~6℃ / min and held for 25~35min. Then raise the temperature to 390-410℃ at a rate of 2-4℃ / min and hold for 55-65 min; Finally, raise the temperature to 460-480℃ at a rate of 1-3℃ / min and hold for 1-2 hours. Apply a protective gas during solution treatment; After the heat preservation is completed, the alloy is immediately water quenched to 140-160℃ at a cooling rate of 190-210℃ / s, and then air-cooled to room temperature. S02, asymmetric rolling, involves asymmetric rolling of the alloy obtained from S01 on the sample at room temperature, with an upper roll speed of 35~45 mm / s, a lower roll speed of 45~55 mm / s, a total reduction of 75%-85%, and a single reduction of no more than 5%; S03, the above rolled alloy is subjected to artificial aging treatment at 110~130℃ for 20h~28h to ensure that the temperature uniformity in the furnace is controlled within ±2℃; After aging, a three-stage cooling system is adopted. First, the aging temperature is reduced to 75-85℃ at a cooling rate of 1-3℃ / h, then reduced to 45-55℃ at a cooling rate of 0.5-1.5℃ / h, and finally cooled to room temperature in the furnace to obtain the finished product.

5. The preparation method according to claim 4, characterized in that: In SO1, the protective gas is 99.5% Ar and 0.5% H2.

6. The preparation method according to claim 4, characterized in that: In S03, both the artificial aging treatment and the three-stage cooling process are carried out under nitrogen protection.

7. The preparation method according to claim 4, characterized in that: In S01, the casting method for aluminum alloy is as follows: Based on the composition of 7xxx series aluminum alloy, prepare the raw materials; place the crucible into a vacuum melting furnace preheated to 490~510℃, add the raw materials, set the temperature to 690~710℃, and hold for 25~35 minutes until the raw materials are completely melted; then open the melting furnace to skim off the slag, and stir the molten metal with a stirring spoon to ensure that its composition is evenly distributed; then take out the mold to prepare for casting, and ensure that the flow rate of the molten metal is uniform during the casting process, and finally obtain the block 7xxx series aluminum alloy required for the experiment, that is, the cast aluminum alloy.

8. The application of a high corrosion-resistant aluminum alloy with a micro-shear band through-structure according to any one of claims 1 to 3 in materials that combine lightweight and ultra-long service life.

9. The application according to claim 8, characterized in that: Materials that combine lightweight design with ultra-long service life include materials for aerospace, rail transportation, and the automotive industry; aerospace materials include aircraft fuselages, wings, landing gear, rocket engine frames, and missile casings.

Images