Lightweight high-strength damage-resistant aluminum alloy sheet and applications

Abstract

The present application belongs to the technical field of non-ferrous metal material processing, and particularly relates to a light-weight high-strength damage-resistant aluminum alloy sheet and application. The present application takes light-weight aluminum alloy ingot as a processing object, and after two-stage homogenization, large reduction hot rolling with a total deformation of greater than or equal to 85%, intermediate annealing and cold rolling are performed; then multi-stage solid solution treatment and water quenching are performed; then 2-6% pre-deformation and combined aging are performed; finally, electromagnetic pulse strengthening treatment is performed. Through the whole-process collaborative process of "component optimization-large reduction hot rolling-multi-stage solid solution-combined aging-electromagnetic pulse strengthening", the light-weight aluminum alloy sheet with good strength and plasticity and excellent fatigue crack propagation resistance is obtained. The present application has reasonable component design, simple and controllable preparation process, and the obtained product has superior performance and is convenient for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal material processing technology, specifically relating to a lightweight, high-strength, damage-resistant aluminum alloy sheet and its applications. Background Technology

[0002] Lightweight, high-strength aluminum alloys, due to their low density, high specific strength, and specific stiffness, have become key materials for achieving structural weight reduction in the aerospace field. These materials not only require high strength but also excellent damage resistance, namely high fracture toughness and low fatigue crack propagation rate, to ensure safety and reliability.

[0003] In existing technologies, patent applications CN113215423A and CN113215460A have achieved lightweight aluminum alloys with good overall strength and damage resistance by controlling the Cu and Li content and using multi-stage annealing and hot rolling processes. Patent application CN118086805A improves fatigue performance while maintaining strength through a non-isothermal aging process. However, these methods still have room for improvement in synergistically enhancing strength, fracture toughness, and fatigue crack propagation rate. For example, the pursuit of high strength is often accompanied by a decrease in toughness and plasticity. Furthermore, how to achieve the optimal balance among these three properties by controlling the microstructure through more refined heat treatment and other processes, and how to further improve corrosion resistance and fatigue crack propagation resistance, are current research challenges. Summary of the Invention

[0004] In view of the above-mentioned technical problems existing in the prior art, the present invention provides a lightweight, high-strength, damage-resistant aluminum alloy sheet and its application.

[0005] This invention achieves high strength, high plasticity, and excellent resistance to fatigue crack propagation in the target aluminum alloy sheet through the synergistic effect of the entire process, including composition optimization, large-reduction hot rolling, multi-stage solution treatment, combined aging, and electromagnetic pulse strengthening, thus meeting the stringent service requirements of aerospace structural materials.

[0006] One of the objectives of this invention is to provide a lightweight, high-strength, and damage-resistant aluminum alloy sheet.

[0007] The second objective of this invention is to provide applications of the aforementioned lightweight aluminum alloy sheet in fields such as aerospace and transportation.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] This invention discloses a lightweight, high-strength, and damage-resistant aluminum alloy sheet, which is prepared through the following steps:

[0010] Step 1:

[0011] After undergoing a two-stage homogenization process, the lightweight aluminum alloy ingot is hot-rolled. The total deformation during hot rolling is controlled to be above 85%, and the number of rolling passes is 5 to 10 to obtain a hot-rolled slab. The average reduction per hot rolling pass reaches more than 15%, and the last 1 to 2 passes use a reduction of not less than 18% for finishing rolling. The initial rolling temperature is 440 to 480℃.

[0012] Step Two:

[0013] The hot-rolled slab is subjected to intermediate annealing at a temperature of 390~440℃ and held for at least 1 hour; then it is cold-rolled with a total cold rolling deformation of 50~80% to obtain cold-rolled sheet.

[0014] Step 3:

[0015] The cold-rolled sheet undergoes a multi-stage solution treatment, including: the first stage involves heating from room temperature to 380-420℃ at a heating rate of 3-15℃ / min and holding at that temperature for at least 1 hour; then heating to 500-530℃ at a heating rate of 3-15℃ / min and holding at that temperature for at least 0.5 hours; and immediately water quenching after the solution treatment is completed, with the quenching transfer time not exceeding 15 seconds.

[0016] Step Four:

[0017] The thin plate after solution quenching is immediately subjected to pre-deformation treatment, with a pre-deformation amount of 2-6%;

[0018] Step 5:

[0019] The pre-deformed thin plate is subjected to a combined aging treatment, including: heating from room temperature to 135-155℃ at a heating rate of 20-40℃ / h and holding for 20-60 min; then heating to 210-230℃ at a heating rate of 3-10℃ / h and holding for 10-30 min; and then cooling to 135-155℃ at a cooling rate of 10-30℃ / h and holding for 8-36 h.

[0020] Step Six:

[0021] Electromagnetic pulse strengthening treatment was applied to the thin plate after combined aging treatment. During the electromagnetic pulse strengthening treatment, the pulse voltage was controlled at 5~8kV, the frequency at 1~5Hz, and the treatment time at 1~5min to obtain a lightweight, high-strength, and damage-resistant aluminum alloy thin plate.

[0022] The lightweight aluminum alloy ingot comprises, by mass percentage: Cu 3.0~4.1%, Li 0.7~1.6%, Mg 0.3~0.9%, Ag 0.2~0.6%, Zn 0.2~0.6%, Mn 0.1~0.5%, Zr 0.05~0.25%, Sc 0.05~0.12%, Ce 0.02~0.1%, Fe≤0.06%, Si≤0.05%, with the balance being Al; wherein the mass ratio of Cu to Li is 1.9~5.8, and the mass ratio of Cu to Mg is 3.3~13.0.

[0023] Alloy ingots are prepared using conventional processes, such as batching, smelting, and casting according to a set alloy composition to obtain ingots.

[0024] This invention balances the precipitation of strengthening phases such as T1 (Al2CuLi) and θ' (Al2Cu) by optimizing the Cu / Li ratio (1.9~5.8) and Cu / Mg ratio (3.3~13.0). A higher Cu / Li ratio promotes the precipitation of the T1 phase, which effectively hinders dislocation movement and improves strength and resistance to fatigue crack propagation. Appropriate amounts of Mg and Ag synergistically accelerate the nucleation and growth of the T1 phase.

[0025] Preferably, this invention introduces trace amounts of Ce into the lightweight aluminum alloy. The Ce content in the ingot is 0.02~0.1wt%. The functions of Ce include: ① purifying the melt, combining with impurity elements such as O and S to reduce oxide inclusions; ② refining the grains, as Ce forms a fine, dispersed phase that hinders grain growth, thereby improving the alloy's plasticity, fracture toughness, and fatigue performance.

[0026] Preferably, the ingot undergoes a two-stage homogenization treatment, with the following process: the first stage involves holding at 380–450℃ for 8–24 hours, and the second stage involves holding at 490–520℃ for 18–36 hours. This two-stage homogenization treatment aims to: firstly, hold at low temperature for a long time to allow the low-melting-point eutectic phase to gradually dissolve, while simultaneously promoting the nucleation of Al3(Zr, Sc) and Ce-containing dispersed phases; secondly, hold at high temperature for a long time to fully dissolve the remaining non-equilibrium phases, eliminate compositional segregation, and obtain a homogeneous supersaturated solid solution, thus providing a uniformly structured ingot for subsequent hot working.

[0027] The present invention involves hot rolling the homogenized ingot with appropriate parameters; this is one of the key technologies of the present invention.

[0028] The benefits of this process are twofold:

[0029] Promotes recrystallization and refines grains: The large reduction introduces high-density dislocations and deformation energy storage inside the alloy, providing a strong driving force for subsequent recrystallization, thereby obtaining a finer and more uniform recrystallized grain structure, and simultaneously improving strength and toughness.

[0030] Completely break down harmful hard and brittle phases: Coarse, Mn-rich hard and brittle compound phases (such as Al) that are unavoidable in lightweight aluminum alloys. 20 Cu2Fe3 and similar compounds have weak interfacial bonding with the aluminum matrix, making them highly susceptible to becoming microcrack initiation sites under stress. The intense shear deformation generated by high-reduction rolling effectively breaks down these coarse compounds, making them smaller and more dispersed. This significantly reduces potential crack initiation sites and forces fatigue cracks to continuously bypass these small particles during propagation, thus consuming more energy and greatly improving the material's damage tolerance.

[0031] Preferably, in step two, the hot-rolled slab undergoes intermediate annealing at a temperature of 410~430℃ for 1~5 hours; subsequently, it is cold-rolled with a total deformation of 50~80%, yielding a cold-rolled sheet with a thickness of 1.5~2.5 mm. In this invention, appropriate cold rolling can further refine the grains and store deformation energy.

[0032] Preferably, in step three, the cold-rolled sheet undergoes a multi-stage solution treatment, including: in the first stage, the temperature is raised from room temperature to 380-400℃ at a heating rate of 3-15℃ / min and held for 1-3 hours; then the temperature is raised to 505-520℃ at a heating rate of 3-15℃ / min and held for 1-2 hours.

[0033] Performing multi-stage solution treatment with appropriate parameters on cold-rolled thin sheets is one of the key technologies of this invention.

[0034] The beneficial effects of this multi-stage solution treatment are as follows: the first stage of medium-temperature holding allows for partial release of the energy stored during cold rolling, promoting the preservation of the subcrystalline structure while gradually dissolving the low-melting-point eutectic phase; the second stage of high-temperature holding allows the alloying elements to fully dissolve into the matrix, resulting in a supersaturated solid solution. The staged heating effectively avoids localized overheating caused by direct high-temperature heating, while preserving the substructure in the alloy.

[0035] In step four of this invention, the thin plate after solution quenching is immediately subjected to pre-deformation treatment with appropriate parameters. Immediate pre-deformation treatment can effectively utilize the high concentration of vacancies retained after solution quenching, and the introduced dislocations provide non-uniform nucleation sites for T1 phase, promoting their dispersed precipitation.

[0036] Preferably, in step four, the pre-deformation treatment adopts cold rolling pre-deformation or tensile pre-deformation.

[0037] The aging process using a combination of specific parameter ranges in step five of this invention works as follows:

[0038] First stage (135~155℃ heat preservation): short-term heat preservation at conventional aging temperature, and the nuclei of each second phase in the solid solution precipitate.

[0039] The second stage (heating to 210~230℃ and holding for a short time): The temperature is increased to a higher level for re-aging treatment. The purpose of this stage is: ① Intragranular: Some metastable phases, such as the δ' phase, undergo re-dissolution, forming a "blank" matrix, providing a uniform solute atom distribution for subsequent re-aging; ② Grain boundaries: High temperature causes the precipitated phases at the grain boundaries to coarsen, forming discontinuous, coarse particles, effectively blocking intergranular corrosion channels, thereby significantly improving resistance to stress corrosion.

[0040] The third stage (cooling to 135~155℃ and holding): Cooling to the conventional aging temperature for re-aging. This promotes the re-precipitation of a large number of fine, uniform T1 phases and inhibits their excessive coarsening. The final low-temperature long-term holding further promotes the precipitation of residual solute atoms, optimizes the size distribution and volume fraction of the precipitated phases, and obtains a mixed strengthening structure dominated by fine, dispersed T1 phases and supplemented by a small amount of θ' phase.

[0041] Preferably, in step six, a residual compressive stress layer with a depth of 0.1~0.2 mm is introduced on the surface of the thin plate by means of electromagnetic pulse.

[0042] Preferably, in step six, the thickness of the resulting lightweight, high-strength, and damage-resistant aluminum alloy sheet is 1.5~2.5 mm.

[0043] In step six of this invention, an electromagnetic field pulse is used to generate a skin effect on the surface of the thin plate, inducing macroscopic residual compressive stress. Simultaneously, this alters the surface microstructure (e.g., increased dislocation density, grain refinement). These multiple effects synergistically modify the alloy structure, effectively ensuring an improvement in the alloy's strength. More importantly, the residual compressive stress layer effectively inhibits the surface initiation of fatigue cracks and hinders early crack propagation, thereby reducing the fatigue crack propagation rate of the alloy.

[0044] This invention utilizes a comprehensive process involving "composition optimization, high-reduction hot rolling, multi-stage solution treatment, combined aging, and electromagnetic pulse strengthening" to ultimately produce lightweight, high-strength, and damage-resistant aluminum alloy sheets with a thickness of 1.5~2.5mm.

[0045] Preferably, in step six, the obtained lightweight, high-strength, damage-resistant aluminum alloy sheet has a tensile strength ≥ 608 MPa, a yield strength ≥ 540 MPa, and an elongation ≥ 10.8%; at R = 0.1 and ΔK = 30 MPa·m 1 / 2 Under these conditions, the fatigue crack propagation rate is 6.8 × 10⁻⁶. -4mm / cycle≤da / dN≤7.5×10 -4 mm / cycle; planar fracture toughness KIC ≥ 38.8 MPa·m 1 / 2 .

[0046] This invention relates to the application of a lightweight, high-strength, and damage-resistant aluminum alloy sheet, including its use in sheet structural components, which can be used in aerospace, transportation, and other fields. Attached Figure Description

[0047] Figure 1 This is a process flow diagram of the present invention;

[0048] Figure 2 The stress-strain curves for Example 1 and Comparative Example 1 are shown.

[0049] Figure 3 The fatigue crack propagation curves of the specimens in Example 1, Comparative Example 1, and Comparative Example 4 are shown.

[0050] Figure 4 The images show the EBSD-IPF and EBSD-GND diagrams of the thin plate section near the surface in Example 1; where (a) is the EBSD-IPF diagram of the thin plate section near the surface in Example 1, and (b) is the EBSD-GND diagram of the thin plate section near the surface in Example 1.

[0051] Figure 5 The images show the EBSD-IPF and EBSD-GND diagrams of the thin plate section near the center in Example 1; where (a) is the EBSD-IPF diagram of the thin plate section near the center in Example 1, and (b) is the EBSD-GND diagram of the thin plate section near the center in Example 1.

[0052] Figure 6 The images are OM photographs of the cross sections of the samples obtained in Example 1 and Comparative Example 3 after intergranular corrosion tests; where (a) is an OM photograph of the cross section of the sample obtained in Example 1 after intergranular corrosion tests, and (b) is an OM photograph of the cross section of the sample obtained in Comparative Example 3 after intergranular corrosion tests. Detailed Implementation

[0053] The present invention will be further described below through specific embodiments, but the present invention is not limited to the following embodiments.

[0054] Example 1

[0055] This embodiment provides a method for preparing lightweight, high-strength, and damage-resistant aluminum alloy thin plates, including the following steps:

[0056] S1. Composition and Casting: The alloy is prepared according to the following mass percentages: Cu 3.6%, Li 1.1%, Mg 0.65%, Ag 0.32%, Zn 0.3%, Mn 0.2%, Zr 0.12%, Sc 0.08%, with the balance being Al. The Cu / Li ratio is 3.27, and the Cu / Mg ratio is 5.54. The raw materials are melted under argon protection, refined, and then semi-continuously cast to obtain the ingot.

[0057] S2. Two-stage homogenization: The ingot undergoes two-stage homogenization: the first stage is 420℃ / 12h, and the second stage is 505℃ / 24h.

[0058] S3. Hot Rolling: After homogenization, the ingot is held at 460℃ for 3 hours before rolling. Eight rolling passes are used to hot roll the 120mm thick ingot to 15mm thick (total deformation 87.5%). The average reduction in the first six passes is approximately 20%, and the reduction in the last two passes is controlled at 22% and 20% respectively. After each rolling pass, the ingot is reheated in the furnace for 5-10 minutes.

[0059] S4. Intermediate annealing and cold rolling: The hot-rolled plate is intermediate annealed at 420℃ for 2 hours, and then cold rolled to 2.0mm.

[0060] S5. Two-stage solution treatment: The cold-rolled sheet undergoes multi-stage solution treatment: In the first stage, the temperature is increased from room temperature to 400℃ at 10℃ / min and held for 2 hours, then increased to 520℃ at 10℃ / min and held for 1 hour, followed by room temperature water quenching within 10 seconds.

[0061] S6. Pre-deformation: The solution plate is subjected to 4% cold rolling pre-deformation.

[0062] S7. Combined aging: Heat from room temperature to 140℃ at 30℃ / h and hold for 40 min, then heat to 220℃ at 5℃ / h and hold for 20 min, then cool to 145℃ at 20℃ / h and hold for 24 h, and finally air cool to room temperature.

[0063] S8. Electromagnetic pulse enhancement: pulse voltage 7kV, frequency 3Hz, processing time 3min.

[0064] The final product is a lightweight aluminum alloy sheet with a thickness of 2.0 mm.

[0065] Example 2

[0066] This embodiment is basically the same as Embodiment 1, except that:

[0067] The composition of S1 is Cu 3.2%, Li 1.2%, Mg 0.5%, Ag 0.35%, Zn 0.35%, Cu / Li=2.67, Cu / Mg=6.4.

[0068] S2 two-stage homogenization: first stage 410℃ / 14h, second stage 510℃ / 22h.

[0069] S2 hot rolling uses 7 passes, with a total deformation of 86% and a reduction of 25% in the last pass.

[0070] S5 two-stage solution treatment: In the first stage, the temperature is increased to 390℃ at 8℃ / min and held for 2.5h, and then increased to 515℃ at 12℃ / min and held for 1.5h.

[0071] S7 combined aging: heat up to 135℃ at 25℃ / h, hold for 50 min, heat up to 215℃ at 8℃ / h, hold for 25 min, cool down to 140℃ at 15℃ / h, and hold for 30 h.

[0072] Example 3

[0073] This embodiment is basically the same as Embodiment 1, except that:

[0074] The composition of S1 is Cu 3.8%, Li 0.9%, Mg 0.8%, Ag 0.4%, Zn 0.4%, Cu / Li=4.22, Cu / Mg=4.75.

[0075] Two-stage homogenization: first stage 430℃ / 10h, second stage 515℃ / 20h.

[0076] S3 hot rolling uses 7 passes with a total deformation of 88%, and the reduction in the last 2 passes is 24% and 20% respectively.

[0077] Two-stage solution treatment: In the first stage, the temperature is increased to 410℃ at 12℃ / min and held for 1.5h, and then increased to 525℃ at 8℃ / min and held for 0.8h.

[0078] S7 combined aging: heat up to 145℃ at 35℃ / h, hold for 30min, heat up to 225℃ at 6℃ / h, hold for 15min, cool down to 150℃ at 25℃ / h, and hold for 18h.

[0079] S8 electromagnetic pulse enhancement: pulse voltage 8kV, frequency 4Hz, processing time 2min.

[0080] Example 4

[0081] This embodiment is basically the same as Embodiment 1, except that:

[0082] S2 two-stage homogenization: first stage 400℃ / 16h, second stage 500℃ / 30h.

[0083] S3 hot rolling uses 8 passes, with a total deformation of 85% and a reduction of 18% in the last pass.

[0084] S4 cold rolled to 1.8mm.

[0085] S5 two-stage solution treatment: In the first stage, the temperature is increased to 380℃ at 5℃ / min and held for 3 hours, and then increased to 505℃ at 5℃ / min and held for 2 hours.

[0086] S7 combined aging: heat up to 135℃ at 20℃ / h, hold for 60min, heat up to 210℃ at 10℃ / h, hold for 30min, cool down to 135℃ at 10℃ / h, and hold for 36h.

[0087] S8 electromagnetic pulse enhancement: pulse voltage 6kV, frequency 1Hz, processing time 5min.

[0088] Comparative Example 1

[0089] This comparative example is basically the same as Example 1, except that: no multi-stage solution treatment is performed, and conventional solution treatment is used (directly heating to 520°C at 30°C / min and holding for 1 hour), while the other processes are exactly the same.

[0090] Comparative Example 2

[0091] This comparative example is basically the same as Example 1, except that the hot rolling adopts a 16-pass small reduction process (the average reduction per pass is about 8%, and the total deformation is the same), while the other processes are exactly the same.

[0092] Comparative Example 3

[0093] This comparative example is basically the same as Example 1, except that the aging process is only conventional single-stage aging (T6), that is, 140℃ / 30h, without combined aging treatment or electromagnetic pulse strengthening.

[0094] Comparative Example 4

[0095] This comparative example is basically the same as Example 1, except that it does not undergo electromagnetic pulse enhancement treatment, while the other processes are exactly the same.

[0096] Comparative Example 5

[0097] This comparative example is basically the same as Example 1, except that: the Cu content in S1 is adjusted to 2.5%, the Li content is adjusted to 1.8%, and the Cu / Li ratio is 1.39; at the same time, electromagnetic pulse strengthening treatment is not performed, and other processes are exactly the same.

[0098] Comparative Example 6

[0099] This comparative example is basically the same as Example 1, except that in the S3 hot rolling process, the 120mm thick ingot is only hot rolled to 40mm thick, and the total deformation is controlled at 67%. The other processes are exactly the same.

[0100] Comparative Example 7

[0101] This comparative example is basically the same as Example 1, except that in the S5 multi-stage solution treatment, the second stage is heated to 480℃ and held for 1 hour (the protection range of this invention is 500~530℃), and the other processes are exactly the same.

[0102] Comparative Example 8

[0103] This comparative example is basically the same as Example 1, except that in the S7 combined aging treatment, the third stage (low temperature long-term heat preservation after cooling to 145℃) heat preservation time is only 2 hours (the protection range of this invention is 8~36h), and the other processes are exactly the same.

[0104] Performance testing

[0105] The performance of the 2.0 mm (or equivalent thickness) sheets prepared in Examples 1-4 and Comparative Examples 1-4 was tested, and the results are shown in Table 1. Test standards: room temperature tensile strength according to GB / T 228.1-2021, fracture toughness according to ASTM E399, fatigue crack propagation rate according to ASTM E647. Intergranular corrosion test according to GB / T 7998-2023.

[0106] Table 1. Performance Comparison of Examples and Comparative Examples

[0107] As can be seen from Table 1:

[0108] The overall performance of embodiments 1-4 of this invention is superior to that of the comparative examples. Specifically:

[0109] Multi-stage solution treatment effect: Compared with Comparative Example 1, after multi-stage solution treatment (including medium-temperature heat preservation), the yield strength increased from 520 MPa to 568 MPa, the fracture toughness increased from 34.5 to 39.5 MPa·m¹ / ², and the fatigue crack propagation rate decreased by 62.2%.

[0110] Effects of high-reduction hot rolling: Compared with Comparative Example 2, high-reduction hot rolling increased the fracture toughness from 35.0 to 39.5 MPa·m¹ / ², and the fatigue crack propagation rate from 2.15 × 10⁻⁶ MPa·m¹ / ². -3 mm / cycle reduced to 6.8×10 -4 mm / cycle, a decrease of approximately 68.4%.

[0111] Combined aging effect: Compared with Example 1 and Comparative Example 3, combined aging maintains high strength while increasing elongation from 9.5% to 11.5%, fracture toughness from 30.5 to 39.5 MPa·m¹ / ², fatigue crack propagation rate is reduced by 76.1%, and corrosion resistance is significantly improved, from intergranular corrosion to pitting corrosion.

[0112] Electromagnetic pulse strengthening effect: Compared with Comparative Example 4, electromagnetic pulse strengthening reduced the fatigue crack propagation rate from 2.9 × 10⁻⁶ to 2.9 × 10⁻⁶. -3 mm / cycle reduced to 6.8×10 -4 mm / cycle, a decrease of 76.6%.

[0113] Effects of Composition Range: Comparing Example 1 and Comparative Example 5, when using a Cu / Li ratio (1.39) outside the scope of protection of this invention, the tensile strength decreased from 622 MPa to 525 MPa, the fracture toughness decreased from 39.5 to 25.5 MPa·m¹ / ², and the fatigue crack propagation rate decreased from 6.8 × 10⁻⁶ MPa·m¹ / ². -4 mm / cycle increased to 8.2×10 -3 mm / cycle, the corrosion type deteriorates from pitting corrosion to intergranular corrosion.

[0114] Effect of total hot rolling reduction: Compared with Example 1 and Comparative Example 6, when the total hot rolling deformation is less than 85%, the tensile strength drops to 543 MPa, and the fatigue crack propagation rate increases to 4.8 × 10⁻⁶. -3 mm / cycle.

[0115] Effect of solution temperature: Compared with Example 1 and Comparative Example 7, when the second stage temperature of multi-stage solution treatment is only 480℃, the tensile strength decreases to 512MPa, the fracture toughness decreases to 26 MPa·m¹ / ², and the fatigue crack propagation rate increases to 5.5×10⁻⁶. -3 mm / cycle.

[0116] Effect of aging and heat preservation time: Compared with Example 1 and Comparative Example 8, when the heat preservation time of the third stage of combined aging is only 2 hours, the tensile strength drops to 538 MPa, the fracture toughness drops to 29.5 MPa·m¹ / ², and the fatigue crack propagation rate increases to 3.5×10⁻⁶. - 3 mm / cycle.

[0117] In summary, this invention achieves improved strength (≥600MPa), fracture toughness (≥38.8 MPa·m¹ / ²), and fatigue performance (≤7.5×10⁻⁶) through a comprehensive process of "large reduction hot rolling - multi-stage solution treatment - combined aging - electromagnetic pulse strengthening". -4 Excellent match between mm / cycle resistance and corrosion resistance (pitting corrosion).

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0119] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention.

Claims

1. A lightweight, high-strength, damage-resistant aluminum alloy sheet, characterized in that: Prepared by the following steps; Step 1: After undergoing a two-stage homogenization process, the lightweight aluminum alloy ingot is hot-rolled. The total deformation during hot rolling is controlled to be above 85%, and the number of rolling passes is 5 to 10 to obtain a hot-rolled slab. The average reduction per hot rolling pass reaches more than 15%, and the last 1 to 2 passes use a reduction of not less than 18% for finishing rolling. The initial rolling temperature is 440 to 480℃. Step Two: The hot-rolled slab is subjected to intermediate annealing at a temperature of 390~440℃ and held for at least 1 hour. Then, cold rolling is performed, with a total deformation of 50-80%, to obtain cold-rolled sheet; Step 3: The cold-rolled sheet undergoes a multi-stage solution treatment, including: the first stage involves heating from room temperature to 380-420℃ at a heating rate of 3-15℃ / min and holding at that temperature for at least 1 hour; then heating to 500-530℃ at a heating rate of 3-15℃ / min and holding at that temperature for at least 0.5 hours; and immediately water quenching after the solution treatment is completed, with the quenching transfer time not exceeding 15 seconds. Step Four: The thin plate after solution quenching is immediately subjected to pre-deformation treatment, with a pre-deformation amount of 2-6%; Step 5: The pre-deformed thin plate is subjected to a combined aging treatment, including: heating from room temperature to 135-155℃ at a heating rate of 20-40℃ / h and holding for 20-60 min; then heating to 210-230℃ at a heating rate of 3-10℃ / h and holding for 10-30 min; and then cooling to 135-155℃ at a cooling rate of 10-30℃ / h and holding for 8-36 h. Step Six: Electromagnetic pulse strengthening treatment was applied to the thin plate after combined aging treatment. During the electromagnetic pulse strengthening treatment, the pulse voltage was controlled at 5~8kV, the frequency at 1~5Hz, and the treatment time at 1~5min to obtain a lightweight, high-strength, and damage-resistant aluminum alloy thin plate.

2. The lightweight, high-strength, damage-resistant aluminum alloy sheet according to claim 1, characterized in that: The lightweight aluminum alloy ingot comprises, by mass percentage: Cu 3.0~4.1%, Li 0.7~1.6%, Mg 0.3~0.9%, Ag 0.2~0.6%, Zn 0.2~0.6%, Mn 0.1~0.5%, Zr 0.05~0.25%, Sc 0.05~0.12%, Ce 0.02~0.1%, Fe≤0.06%, Si≤0.05%, with the balance being Al; wherein the mass ratio of Cu to Li is 1.9~5.8, and the mass ratio of Cu to Mg is 3.3~13.

0.

3. The lightweight, high-strength, damage-resistant aluminum alloy sheet according to claim 1, characterized in that: The ingots are subjected to a two-stage homogenization treatment, with the following treatment regime: the first stage is held at 380~450℃ for 8~24 hours, and the second stage is held at 490~520℃ for 18~36 hours.

4. The lightweight, high-strength, damage-resistant aluminum alloy sheet according to claim 1, characterized in that: In step two, the hot-rolled slab is subjected to intermediate annealing at a temperature of 410~430℃ for 1~5 hours; then it is cold-rolled with a total deformation of 50~80% to obtain a cold-rolled sheet with a thickness of 1.5~2.5mm.

5. The lightweight, high-strength, damage-resistant aluminum alloy sheet according to claim 1, characterized in that: In step three, the cold-rolled sheet undergoes multi-stage solution treatment, including: in the first stage, the temperature is raised from room temperature to 380-400℃ at a heating rate of 3-15℃ / min and held for 1-3 hours; then the temperature is raised to 505-520℃ at a heating rate of 3-15℃ / min and held for 1-2 hours.

6. The lightweight, high-strength, damage-resistant aluminum alloy sheet according to claim 1, characterized in that: In step four, the pre-deformation process is carried out by cold rolling pre-deformation or tensile pre-deformation.

7. The lightweight, high-strength, damage-resistant aluminum alloy sheet according to claim 1, characterized in that: In step six, a residual compressive stress layer with a depth of 0.1~0.2mm is introduced on the surface of the thin plate by electromagnetic pulse.

8. The lightweight, high-strength, damage-resistant aluminum alloy sheet according to claim 1, characterized in that: In step six, the thickness of the resulting lightweight, high-strength, and damage-resistant aluminum alloy sheet is 1.5~2.5mm.

9. A lightweight, high-strength, damage-resistant aluminum alloy sheet according to claim 1, characterized in that: In step six, the obtained lightweight, high-strength, damage-resistant aluminum alloy sheet has a tensile strength ≥ 608 MPa, a yield strength ≥ 540 MPa, and an elongation ≥ 10.8%; at R = 0.1 and ΔK = 30 MPa·m 1 / 2 Under these conditions, the fatigue crack propagation rate is 6.8 × 10⁻⁶. -4 mm / cycle≤da / dN≤7.5×10 -4 mm / cycle; planar fracture toughness KIC ≥ 38.8 MPa·m 1 / 2 .

10. An application of a lightweight, high-strength, damage-resistant aluminum alloy sheet as described in any one of claims 1-9, characterized in that: It is used to manufacture thin-plate structural components, which are used in the aerospace and transportation fields.

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