Low-cost high-strength aluminum-lithium alloy for space cabin and preparation method thereof

Abstract

The application discloses a low-cost high-strength aluminum-lithium alloy for a space cabin body and a preparation method thereof, and belongs to the technical field of aluminum-lithium alloys.The aluminum-lithium alloy comprises the following components in mass fraction: 91.5-94.5 parts of aluminum, 3.9-4.2 parts of copper, 1.0-1.5 parts of lithium, 0.2-1.0 parts of magnesium, 0.2-0.4 parts of silver, 0.3-0.8 parts of zinc, 0.10-0.12 parts of zirconium and 0.15-0.25 parts of mixed rare earth; the mixed rare earth is a mixed rare earth of cerium and lanthanum, and the mass ratio of cerium to lanthanum is (1.5-2.5):1; the total mass of metal impurities in the aluminum-lithium alloy is not more than 0.15 parts, and the single metal impurity is not more than 0.05 parts; through multi-component micro-alloying design and a precise controllable thermal mechanical treatment process, the application solves the technical problems that the existing aluminum-lithium alloy is high in cost due to the dependence on high-content noble metals and is anisotropic in mechanical properties due to strong deformation texture, and provides an ideal material which is excellent in comprehensive performance and economically feasible for a space cabin structure.

Description

Technical Field

[0001] This invention relates to the field of aluminum-lithium alloy technology, and in particular to a low-cost, high-strength aluminum-lithium alloy for aerospace cabins and its preparation method. Background Technology

[0002] With the advancement of the aerospace industry, especially the development of large passenger aircraft, heavy-lift launch vehicles, and deep space probes, more stringent requirements have been placed on the core structural materials of spacecraft: extreme lightweighting, high strength, and high rigidity must be achieved while ensuring high reliability. Aluminum-lithium alloys, due to their outstanding advantages of low density and high specific strength, have become an ideal material for meeting this requirement and manufacturing key structural components for spacecraft cabins.

[0003] Existing technologies, exemplified by third-generation aluminum-lithium alloys, generally rely on adding large amounts of precious metals such as silver, coupled with complex thermomechanical treatments, to enhance strength in pursuit of high power. However, this approach has two inherent drawbacks: First, the high cost of precious metals leads to a sharp increase in the cost of alloy raw materials, severely restricting its large-scale application in large-size, low-cost aerospace cabin structures. Second, during traditional rolling or forging processes, strong deformation textures easily form within the alloy, resulting in significant anisotropy in the mechanical properties of the final product. This anisotropy makes it difficult to predict the load-bearing capacity and deformation behavior of cabin components under different stress directions, posing a significant hidden danger to the overall structural design and long-term service safety.

[0004] Therefore, developing a new type of aluminum-lithium alloy and its preparation technology that can significantly reduce the amount of precious metals used to control costs while fundamentally solving the anisotropy problem has become a key bottleneck that urgently needs to be overcome in the field of aerospace materials. Summary of the Invention

[0005] The purpose of this invention is to provide a low-cost, high-strength aluminum-lithium alloy for aerospace cabins and its preparation method, in order to solve the technical problems of high cost caused by the reliance on high content of precious metal elements in existing aluminum-lithium alloys, and significant anisotropy of mechanical properties caused by strong deformation texture. This invention breaks through the technical bottleneck of traditional high-strength aluminum-lithium alloys, which must use high silver content in pursuit of high strength, and it is difficult to achieve both low cost and low anisotropy. Through innovative microalloying design and precise and controllable thermomechanical processing, the invention achieves a synergistic improvement in strength, plasticity and isotropy while significantly reducing the amount of precious metals used.

[0006] To achieve the above objectives, the present invention provides the following solution: The key to using low-cost, high-strength aluminum-lithium alloy for aerospace cabins lies in the fact that the aforementioned aluminum-lithium alloy contains the following components in parts by mass: 91.5 to 94.5 parts of aluminum, 3.9 to 4.2 parts of copper, 1.0 to 1.5 parts of lithium, 0.2 to 1.0 parts of magnesium, 0.2 to 0.4 parts of silver, 0.3 to 0.8 parts of zinc, 0.10 to 0.12 parts of zirconium, and 0.15 to 0.25 parts of mixed rare earth elements; the aforementioned mixed rare earth elements are a mixture of cerium and lanthanum, with a mass ratio of cerium to lanthanum of (1.5 to 2.5):1; the total mass of metallic impurities in the aforementioned aluminum-lithium alloy does not exceed 0.15 parts, and the mass of a single metallic impurity does not exceed 0.05 parts.

[0007] Preferably, the mass ratio of zinc to magnesium in the above-mentioned aluminum-lithium alloy is (0.8-1.5):1, and the mass ratio of copper to lithium is (2.6-4.2):1.

[0008] Specifically, the room temperature tensile strength of the aforementioned aluminum-lithium alloy is 540MPa to 580MPa, the elongation after fracture is 14.5% to 18.0%, and the yield strength deviation between the rolling direction and the transverse direction of the plate is 1.4% to 1.8%.

[0009] A method for preparing the above-mentioned aluminum-lithium alloy, the key feature of which is that it includes the following steps: S1. Smelting and casting: Weigh the raw materials, smelt them in an inert atmosphere, and cast them into ingots; S2. Multi-stage homogenization treatment: The above-mentioned ingot is subjected to two-stage homogenization treatment, followed by cooling; S3. Hot deformation processing: The homogenized ingot is subjected to multi-directional forging or multi-pass cross rolling. S4. Solution treatment and quenching: The deformed product is subjected to solution treatment and rapid quenching. S5. Pre-stretching: Pre-stretching plastic deformation of products after solution quenching. S6. Two-stage aging treatment: The pre-stretched product is subjected to two-stage aging treatment and then air-cooled to room temperature to obtain the above-mentioned aluminum-lithium alloy.

[0010] Furthermore, in step S2, the above two-stage homogenization process is as follows: first, the ingot is heated to 465℃~475℃ and held for 14h~18h; then, it is heated to 495℃~505℃ and held for 24h~36h; after completion, it is cooled to room temperature at a rate of 100℃ / h~130℃ / h.

[0011] Furthermore, in step S3, the initial rolling or forging temperature of the above-mentioned hot deformation processing is 450℃~470℃, the total engineering strain is 250%~350%, and the final forging or rolling temperature is 380℃~420℃.

[0012] Specifically, in step S4, the temperature of the above solution treatment is 515℃~525℃, and the holding time is 1h~2h; the solution is transferred from the solution treatment equipment to the quenching medium within 15s.

[0013] Specifically, in step S5, the engineering strain of the pre-stretching is 2.0% to 5.0%, and this step must be completed within 4 hours after solution quenching.

[0014] More specifically, in step S5, during the pre-stretching process, it is also necessary to continuously spray atomized nano-ceramic particle suspension onto the surface of the product as a process medium; the nano-ceramic particles are alumina; and the mass concentration of the suspension is 5% to 10%.

[0015] More specifically, in step S6, the above-mentioned two-stage aging treatment is as follows: first, the product is kept at 170℃~180℃ for 18h~24h; then, without cooling, the temperature is directly increased to 215℃~225℃ at a rate of 3℃ / min~5℃ / min and kept at that temperature for 2h~4h, and finally air-cooled to room temperature.

[0016] The present invention discloses the following technical effects: The present invention provides a low-cost, high-strength aluminum-lithium alloy for aerospace cabins and its preparation method. Through multi-component microalloying design and precise and controllable thermomechanical processing, it solves the technical problems of high cost caused by the reliance on high content of precious metals in existing aluminum-lithium alloys and the anisotropy of mechanical properties caused by strong deformation texture.

[0017] Specific technical effects include: First, this invention achieves a harmonious balance between low cost and high performance. Addressing the current situation where existing high-strength aluminum-lithium alloys require the addition of large amounts of the precious metal silver, this invention introduces a specific proportion of mixed rare earth elements into a Cu / Li system, creating a synergistic microalloying effect with elements such as Mg and Zn. This significantly reduces the silver content while still ensuring excellent strength-ductility matching in the alloy. This design breaks the traditional dependence of high-strength aluminum-lithium alloys on precious metals, providing a cost-effective solution for large-scale applications in aerospace cabin structures.

[0018] Secondly, this invention achieves precise control of the microstructure through the synergistic effect of multi-stage homogenization, multi-directional hot deformation, and composite aging processes. Addressing the problem of strong texture and anisotropy in aluminum-lithium alloys during traditional processing, this invention utilizes specific mixed rare earth elements that effectively pin grain boundaries and inhibit recrystallization during hot deformation. Combined with multi-directional deformation, this significantly weakens the deformation texture. Subsequent pre-stretching and two-stage aging further promote the uniform and fine precipitation of the strengthening phase. The synergistic effect of this series of processes enables the material to achieve high strength while possessing the unique advantage of extremely low anisotropy.

[0019] Third, the material of this invention exhibits excellent comprehensive mechanical properties and service reliability. Through the synergistic optimization of the above-mentioned composition and process, the resulting alloy not only possesses high strength and good plasticity, but more importantly, its mechanical properties are highly consistent in different directions. This greatly facilitates the design and safety assessment of critical structural components such as aerospace cabins, and significantly reduces the potential risks caused by material anisotropy.

[0020] In summary, through synergistic innovation in composition system and preparation process, this invention has developed a novel aluminum-lithium alloy that combines low cost, high strength, high plasticity and low anisotropy, providing an ideal material with excellent comprehensive performance and economic feasibility for aerospace cabin structures. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0024] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0025] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0026] The aluminum ingots, pure magnesium, pure zinc, and pure silver used in this invention all have a mass purity of 99.9%; the total mass purity of aluminum copper, aluminum lithium, and aluminum zirconium in the aluminum copper master alloy, aluminum lithium master alloy, and aluminum zirconium master alloy is 99.9%; in the mixed rare earths used, the mass purity of cerium and lanthanum is 99.5%; and the α-alumina nano-ceramic particles, also known as nano-alumina, have a mass purity of 99.9%.

[0027] Example 1 This embodiment provides a low-cost, high-strength aluminum-lithium alloy for aerospace cabins. The aluminum-lithium alloy comprises the following components in parts by mass: 93.0 parts aluminum, 4.0 parts copper, 1.2 parts lithium, 0.5 parts magnesium, 0.3 parts silver, 0.5 parts zinc, 0.11 parts zirconium, and 0.20 parts mixed rare earth elements. The mixed rare earth elements are a mixture of cerium and lanthanum, with a cerium to lanthanum mass ratio of 2.0:1. The total mass of unavoidable metallic impurities in the aluminum-lithium alloy is 0.12 parts, and the maximum mass of a single metallic impurity is 0.03 parts. The mass ratio of zinc to magnesium is 1.0:1, and the mass ratio of copper to lithium is 3.3:1.

[0028] The preparation steps of the aluminum-lithium alloy in this embodiment include: S1. Smelting and Casting: Accurately weigh each raw material according to the above proportions, and melt them in a resistance crucible furnace under the protection of high-purity argon gas (purity 99.99%). First, melt the aluminum ingot. After the aluminum is completely melted, add aluminum-copper master alloy, aluminum-zirconium master alloy, pure magnesium, and pure zinc in sequence. Control the melting temperature at 735℃ and stir to allow the alloying elements to initially distribute. After all the above alloys have melted and are evenly distributed, the melt temperature is stabilized in the lower range of 725°C, and then pure silver and aluminum-lithium master alloys are added. After it has completely melted, add the mixed rare earth elements and stir thoroughly to ensure that all alloying elements are evenly distributed. Subsequently, the refined melt was poured into a preheated metal mold under the protection of high-purity argon gas to obtain an ingot with uniform chemical composition and dense structure.

[0029] S2, Multi-stage homogenization process: The ingots are placed in a temperature-controlled air-circulating furnace for two-stage homogenization. First stage treatment: Heat the ingot to 470℃ at a heating rate of 25℃ / h and hold for 16h; Second stage of treatment: Continue heating to 500℃ at a heating rate of 25℃ / h, and hold for 30h; The purpose of the entire homogenization process is to fully dissolve the non-equilibrium solidified phase, reduce dendrite segregation, and promote the precipitation of Zr-containing dispersed phases. After the heat preservation is completed, the ingot is removed from the furnace and rapidly cooled by forced air cooling at a rate of 115℃ / h until room temperature.

[0030] S3, Hot Deformation Processing: The homogenized ingot is then subjected to multi-directional forging. First, heat the ingot to 460℃ and hold it at that temperature for 1.5 hours; Subsequently, a multi-directional forging process was used for deformation; The total engineering strain is set at 300%, which is achieved by controlling the deformation amount of each pass and the total number of passes. Throughout the deformation process, by controlling the reheating time between passes, the final forging temperature of the product is maintained at 400℃ to obtain a deformed structure with sufficient recrystallization and weakened texture.

[0031] S4. Solution treatment and quenching: The heat-deformed products are placed in a precisely temperature-controlled salt bath furnace for solution treatment. The treatment temperature was 520℃, and the holding time was 1.5h to ensure that the reinforcing phase was fully dissolved; After the heat preservation is completed, the product is quickly transferred to a room temperature water quenching medium. The transfer time from the opening of the furnace door to the complete immersion of the product in the quenching medium is strictly controlled within 10 seconds in order to retain the supersaturated solid solution.

[0032] S5, Pre-stretching: Within 4 hours after solution quenching, the product was subjected to pre-stretch plastic deformation using a universal testing machine; The engineering strain is set at 3.5%, which is precisely achieved by controlling the displacement and load of the testing machine; During this pre-stretching process, a suspension of atomized nano-ceramic particles is continuously and uniformly sprayed onto the surface of the product as a process medium. The nano-ceramic particles are α-alumina with a D50 of 52.1 nm. The suspension uses deionized water as a solvent, the mass concentration of alumina particles is 7.5%, and its stability is ensured by adding sodium polyacrylate dispersant with a mass concentration of 0.5%. The atomization pressure was controlled at 0.3 MPa, the spray distance at 200 mm, and the flow rate at 50 mL / min to ensure uniform coverage and impact effect.

[0033] S6, Two-level timeliness processing: The pre-stretched and surface-treated products are placed in a temperature-controlled aging furnace for two-stage aging treatment. First-level aging: Keep warm at 175℃ for 21 hours; Second stage aging: After the first stage aging is completed, without intermediate cooling, the furnace temperature is directly raised to 220℃ at a heating rate of 4℃ / min and held at this temperature for 3 hours; After the entire aging process is completed, the product is removed from the furnace and cooled to room temperature in still air to obtain the low-cost, high-strength aluminum-lithium alloy for aerospace cabins in this embodiment, denoted as Sample 1.

[0034] Example 2 This embodiment provides a low-cost, high-strength aluminum-lithium alloy for aerospace cabins. The aluminum-lithium alloy comprises the following components in parts by mass: 91.5 parts aluminum, 4.2 parts copper, 1.0 part lithium, 0.2 parts magnesium, 0.4 parts silver, 0.3 parts zinc, 0.12 parts zirconium, and 0.15 parts mixed rare earth elements. The mixed rare earth elements are a mixture of cerium and lanthanum, with a cerium to lanthanum mass ratio of 1.5:1. The total mass of unavoidable metallic impurities in the aluminum-lithium alloy is 0.15 parts, and the maximum mass of a single metallic impurity is 0.05 parts. The mass ratio of zinc to magnesium is 1.5:1, and the mass ratio of copper to lithium is 4.2:1.

[0035] The preparation steps of the aluminum-lithium alloy in this embodiment include: S1. Smelting and Casting: Accurately weigh each raw material according to the above proportions, and melt them in a resistance crucible furnace under the protection of high-purity argon gas (purity 99.99%). First, melt the aluminum ingot. After the aluminum is completely melted, add aluminum-copper master alloy, aluminum-zirconium master alloy, pure magnesium, and pure zinc in sequence. Control the melting temperature at 730℃ and stir to allow the alloying elements to initially distribute. After all the above alloys have melted and are evenly distributed, the melt temperature is stabilized in the lower range of 720°C, and then pure silver and aluminum-lithium master alloys are added. After it has completely melted, add the mixed rare earth elements and stir thoroughly to ensure that all alloying elements are evenly distributed. Subsequently, the refined melt was poured into a preheated metal mold using a siphon method under the protection of high-purity argon gas, resulting in an ingot with uniform chemical composition and dense structure.

[0036] S2, Multi-stage homogenization process: The ingots are placed in a temperature-controlled air-circulating furnace for two-stage homogenization. First stage treatment: Heat the ingot to 465℃ at a heating rate of 30℃ / h and hold for 18h; Second stage of treatment: Continue heating to 495℃ at a heating rate of 30℃ / h, and hold for 36h; The purpose of the entire homogenization process is to fully dissolve the non-equilibrium solidified phase, reduce dendrite segregation, and promote the precipitation of Zr-containing dispersed phases. After the heat preservation is completed, the ingot is removed from the furnace and rapidly cooled by forced air cooling at a rate of 130℃ / h until room temperature.

[0037] S3, Hot Deformation Processing: The homogenized ingot is subjected to multiple cross rolling processes. First, heat the ingot to 450℃ and hold it at that temperature for 2 hours; Subsequently, a multi-pass cross-rolling process is used for deformation; The total engineering strain is set at 250%, which is achieved by controlling the deformation amount of each pass and the total number of passes. Throughout the deformation process, by controlling the reheating time between passes, the final rolling temperature of the product is maintained at 420℃ to obtain a deformed structure with sufficient recrystallization and weakened texture.

[0038] S4. Solution treatment and quenching: The heat-deformed products are placed in a precisely temperature-controlled air-circulating furnace for solution treatment. The treatment temperature was 515℃, and the holding time was 2 hours to ensure that the reinforcing phase was fully dissolved. After the heat preservation is completed, the product is quickly transferred to the polymer aqueous solution quenching medium. The transfer time from the opening of the furnace door to the complete immersion of the product in the quenching medium is strictly controlled within 15 seconds in order to retain the supersaturated solid solution.

[0039] S5, Pre-stretching: Within 4 hours after solution quenching, the product was subjected to pre-stretch plastic deformation using a universal testing machine; The engineering strain is set at 2.0%, which is precisely achieved by controlling the displacement and load of the testing machine; During this pre-stretching process, a suspension of atomized nano-ceramic particles is continuously and uniformly sprayed onto the surface of the product as a process medium. The nano-ceramic particles are α-alumina with a D50 of 98.5 nm. The suspension uses deionized water as a solvent, the mass concentration of alumina particles is 5%, and its stability is ensured by adding sodium polyacrylate dispersant with a mass concentration of 0.3%. The atomization pressure was controlled at 0.2 MPa, the spray distance at 250 mm, and the flow rate at 30 mL / min to ensure uniform coverage and impact effect.

[0040] S6, Two-level timeliness processing: The pre-stretched and surface-treated products are placed in a temperature-controlled aging furnace for two-stage aging treatment. First-level aging: Keep warm at 170℃ for 24 hours; Second stage aging: After the first stage aging is completed, without intermediate cooling, the furnace temperature is directly raised to 225℃ at a heating rate of 3℃ / min and held at this temperature for 2 hours; After the entire aging process is completed, the product is taken out of the furnace and cooled to room temperature in still air to obtain the low-cost, high-strength aluminum-lithium alloy for aerospace cabins in this embodiment, denoted as Sample 2.

[0041] Example 3 This embodiment provides a low-cost, high-strength aluminum-lithium alloy for aerospace cabins. The aluminum-lithium alloy comprises the following components in parts by mass: 94.5 parts aluminum, 3.9 parts copper, 1.5 parts lithium, 1.0 part magnesium, 0.2 parts silver, 0.8 parts zinc, 0.10 parts zirconium, and 0.25 parts mixed rare earth elements. The mixed rare earth elements are a mixture of cerium and lanthanum, with a cerium to lanthanum mass ratio of 2.5:1. The total mass of unavoidable metallic impurities in the aluminum-lithium alloy is 0.12 parts, and the maximum mass of a single metallic impurity is 0.04 parts. The mass ratio of zinc to magnesium is 0.8:1, and the mass ratio of copper to lithium is 2.6:1.

[0042] The preparation steps of the aluminum-lithium alloy in this embodiment include: S1. Smelting and Casting: Accurately weigh each raw material according to the above proportions, and melt them in a resistance crucible furnace under the protection of high-purity argon gas (purity 99.99%). First, melt the aluminum ingot. After the aluminum is completely melted, add aluminum-copper master alloy, aluminum-zirconium master alloy, pure magnesium, and pure zinc in sequence. Control the melting temperature at 750℃ and stir to allow the alloying elements to initially distribute. After all the above alloys have melted and are evenly distributed, the melt temperature is stabilized in the lower range of 730°C, and then pure silver and aluminum-lithium master alloys are added. After it has completely melted, add the mixed rare earth elements and stir thoroughly to ensure that all alloying elements are evenly distributed. Subsequently, the refined melt was poured into a preheated metal mold under the protection of high-purity argon gas to obtain an ingot with uniform chemical composition and dense structure.

[0043] S2, Multi-stage homogenization process: The ingots are placed in a temperature-controlled air-circulating furnace for two-stage homogenization. First stage treatment: Heat the ingot to 475℃ at a heating rate of 20℃ / h and hold for 14h; Second stage of treatment: Continue heating to 505℃ at a heating rate of 20℃ / h, and hold for 24h; The purpose of the entire homogenization process is to fully dissolve the non-equilibrium solidified phase, reduce dendrite segregation, and promote the precipitation of Zr-containing dispersed phases. After the heat preservation is completed, the ingot is removed from the furnace and rapidly cooled by forced air cooling at a rate of 100℃ / h until room temperature.

[0044] S3, Hot Deformation Processing: The homogenized ingot is then subjected to multi-directional forging. First, heat the ingot to 470℃ and hold it at that temperature for 1 hour; Subsequently, a multi-directional forging process was used for deformation; The total engineering strain is set at 350%, which is achieved by controlling the deformation amount of each pass and the total number of passes. Throughout the deformation process, by controlling the reheating time between passes, the final forging temperature of the product is maintained at 380℃ to obtain a deformed structure with sufficient recrystallization and weakened texture.

[0045] S4. Solution treatment and quenching: The heat-deformed products are placed in a precisely temperature-controlled salt bath furnace for solution treatment. The treatment temperature was 525℃, and the holding time was 1 hour to ensure that the reinforcing phase was fully dissolved. After the heat preservation is completed, the product is quickly transferred to the room temperature water quenching medium. The transfer time from the opening of the furnace door to the complete immersion of the product in the quenching medium is strictly controlled within 8 seconds in order to retain the supersaturated solid solution.

[0046] S5, Pre-stretching: Within 4 hours after solution quenching, the product was subjected to pre-stretch plastic deformation using a universal testing machine; The engineering strain is set at 5.0%, which is precisely achieved by controlling the displacement and load of the testing machine; During this pre-stretching process, a suspension of atomized nano-ceramic particles is continuously and uniformly sprayed onto the surface of the product as a process medium. The nano-ceramic particles are α-alumina with a D50 of 21.3 nm. The suspension uses deionized water as a solvent, the mass concentration of alumina particles is 10%, and its stability is ensured by adding sodium polyacrylate dispersant with a mass concentration of 0.7%. The atomization pressure was controlled at 0.4 MPa, the spray distance at 150 mm, and the flow rate at 70 mL / min to ensure uniform coverage and impact effect.

[0047] S6, Two-level timeliness processing: The pre-stretched and surface-treated products are placed in a temperature-controlled aging furnace for two-stage aging treatment. First-level aging: Keep warm at 180℃ for 18 hours; Second stage aging: After the first stage aging is completed, without intermediate cooling, the furnace temperature is directly raised to 215℃ at a heating rate of 5℃ / min and held at this temperature for 4 hours. After the entire aging process is completed, the product is taken out of the furnace and cooled to room temperature in still air to obtain the low-cost, high-strength aluminum-lithium alloy for aerospace cabins in this embodiment, denoted as sample 3.

[0048] Comparative Example 1 This comparative example provides a comparative aluminum-lithium alloy, the specific implementation of which is the same as in Example 1, except that the introduction of mixed rare earth elements is completely omitted in the alloy composition.

[0049] The preparation process of this comparative aluminum-lithium alloy specifically includes the following steps: S1. Smelting and Casting: Accurately weigh each raw material according to the proportions in Example 1, but without adding mixed rare earth elements; the mass fractions of aluminum, copper, lithium, magnesium, silver, zinc, and zirconium are the same as in Example 1; smelt in a resistance crucible furnace under high-purity argon protection, with the same order of adding materials as in Example 1; finally, without adding mixed rare earth elements, after thorough stirring, cast into an ingot using a bottom pouring method under high-purity argon protection.

[0050] S2, Multi-level homogenization treatment: Same as step S2 in Example 1.

[0051] S3. Hot deformation processing: Same as step S3 in Example 1.

[0052] S4. Solution treatment and quenching: Same as step S4 in Example 1.

[0053] S5. Pre-stretching: Same as step S5 in Example 1.

[0054] S6. Two-stage aging treatment: Same as step S6 in Example 1, finally obtaining the comparative aluminum-lithium alloy, denoted as control 1.

[0055] Comparative Example 2 This comparative example provides a comparative aluminum-lithium alloy, the specific implementation of which is the same as in Example 1, except that the mixed rare earth elements are replaced with an equal mass fraction of single high-purity cerium.

[0056] The preparation process of this comparative aluminum-lithium alloy specifically includes the following steps: S1. Smelting and Casting: Accurately weigh each raw material according to the proportions in Example 1, but replace 0.20 parts of mixed rare earth with 0.20 parts of pure cerium; the mass fractions of other components remain unchanged; the preparation process steps are the same as S1 of Comparative Example 1.

[0057] S2, Multi-level homogenization treatment: Same as step S2 in Example 1.

[0058] S3. Hot deformation processing: Same as step S3 in Example 1.

[0059] S4. Solution treatment and quenching: Same as step S4 in Example 1.

[0060] S5. Pre-stretching: Same as step S5 in Example 1.

[0061] S6. Two-stage aging treatment: Same as step S6 in Example 1, finally obtaining the comparative aluminum-lithium alloy, denoted as control 2.

[0062] Comparative Example 3 This comparative example provides a comparative aluminum-lithium alloy, the specific implementation of which is the same as in Example 1, except that the mass ratio of zinc and magnesium is adjusted.

[0063] The preparation process of this comparative aluminum-lithium alloy specifically includes the following steps: S1. Smelting and Casting: The composition was adjusted so that zinc was 0.2 parts, magnesium was 1.0 parts, and the mass ratio of zinc to magnesium was 0.2:1; the mass parts of aluminum, copper, lithium, silver, zirconium and mixed rare earth were the same as in Example 1; the preparation process steps were the same as S1 of Comparative Example 1.

[0064] S2, Multi-level homogenization treatment: Same as step S2 in Example 1.

[0065] S3. Hot deformation processing: Same as step S3 in Example 1.

[0066] S4. Solution treatment and quenching: Same as step S4 in Example 1.

[0067] S5. Pre-stretching: Same as step S5 in Example 1.

[0068] S6. Two-stage aging process: Same as step S6 in Example 1.

[0069] The final result was a control aluminum-lithium alloy, designated as control 3.

[0070] Comparative Example 4 This comparative example provides a comparative aluminum-lithium alloy, the specific implementation of which is the same as in Example 1, except that the pre-stretching and nanoparticle spraying steps are omitted in the heat treatment process.

[0071] The preparation process of this comparative aluminum-lithium alloy specifically includes the following steps: S1. Smelting and casting: Same as step S1 in Example 1.

[0072] S2, Multi-level homogenization treatment: Same as step S2 in Example 1.

[0073] S3. Hot deformation processing: Same as step S3 in Example 1.

[0074] S4. Solution treatment and quenching: Same as step S4 in Example 1.

[0075] S5. Omit the pre-stretching step: After solution quenching, proceed directly to aging treatment.

[0076] S6. Two-stage aging treatment: Same as step S6 in Example 1, finally obtaining the comparative aluminum-lithium alloy, denoted as control 4.

[0077] Comparative Example 5 This comparative example provides a comparative aluminum-lithium alloy, the specific implementation of which is the same as in Example 1, except that: during the pre-stretching process, no nano-alumina suspension is sprayed.

[0078] The preparation process of this comparative aluminum-lithium alloy specifically includes the following steps: S1. Smelting and casting: Same as step S1 in Example 1.

[0079] S2, Multi-level homogenization treatment: Same as step S2 in Example 1.

[0080] S3. Hot deformation processing: Same as step S3 in Example 1.

[0081] S4. Solution treatment and quenching: Same as step S4 in Example 1.

[0082] S5. Pre-stretching: Within 4 hours after solution quenching, the product is subjected to pre-stretching plastic deformation with an engineering strain of 3.5%; however, during this process, the nano-ceramic particle suspension is not sprayed.

[0083] S6. Two-stage aging treatment: Same as step S6 in Example 1, finally obtaining the comparative aluminum-lithium alloy, denoted as control 5.

[0084] Analysis and Testing The samples 1-3 prepared in Examples 1-3 and the material control samples 1-5 prepared in Comparative Examples 1-5 were tested for room temperature mechanical properties and anisotropy.

[0085] All performance test samples were processed into standard tensile specimens by sampling from the rolling direction (0°) and transverse direction (90°) of the corresponding sheet metal according to GB / T 228.1 standard. The tests were conducted on a universal testing machine at a strain rate of 0.005 / min, and three parallel specimens were tested in each direction and the average value was taken. The test results are shown in Table 1.

[0086] Table 1: Room Temperature Mechanical Properties and Anisotropic Test Results As can be seen from the results in Table 1, the room temperature tensile strength of samples 1 to 3 of the present invention is 540 MPa to 580 MPa, the elongation after fracture is 14.5% to 18.0%, and the yield strength deviation is 1.4% to 1.8%, which fully meets the comprehensive requirements of high strength, high toughness and low anisotropy.

[0087] Reference sample 1, by completely omitting the mixed rare earth elements, lacks their crucial role in grain boundary pinning and recrystallization inhibition, resulting in a strong deformation texture after hot deformation. This texture exhibits the most significant anisotropy, with a substantial decrease in both strength and plasticity. This demonstrates that mixed rare earth elements are indispensable for achieving isotropy.

[0088] Reference 2, which replaced the mixed rare earth elements with single cerium, exhibited superior performance compared to Reference 1, but its anisotropy and plasticity remained significantly worse than the sample of this invention. This indicates that mixed rare earth elements with a specific Ce / La ratio possess unparalleled advantages over single elements in synergistically regulating microstructure and weakening texture.

[0089] Reference standard 3, due to the imbalance of the Zn / Mg ratio, could not form an effective synergistic reinforcing cluster with Ag, resulting in the lowest strength among the samples of this invention, and also exhibiting more obvious anisotropy. This proves that controlling the Zn / Mg ratio at (0.8~1.5):1 is crucial for obtaining both high strength and low anisotropy.

[0090] Reference 4 omitted the pre-stretching step and the nano-alumina spraying process. On the one hand, the lack of pre-stretching resulted in insufficient dislocation density and poor subsequent aging precipitation strengthening effect, which is why its strength was the lowest among all samples. On the other hand, although its anisotropy (yield strength deviation of 6.0%) was higher than that of the sample of this invention due to the omission of nanoparticle spraying, it was better than other references. This may be because the internal stress state of the material is simpler and more uniform after the absence of the directional dislocation structure introduced by pre-stretching, but the cost is a significant sacrifice in strength. Based on the experimental results of reference 4, it is evident that pre-stretching is the key to obtaining high strength, while nanoparticle spraying is a refined process that further optimizes performance on this basis.

[0091] Reference sample 5, which was not sprayed with nano-alumina during pre-stretching, exhibited superior strength and isotropy compared to the aforementioned comparative examples, but was still significantly inferior to sample 1 of the present invention. This demonstrates that the composite process of simultaneously spraying nano-alumina during pre-stretching can further optimize the surface microstructure and stress state, making a clear additional contribution to improving overall performance.

[0092] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A low-cost, high-strength aluminum-lithium alloy for aerospace cabins, characterized in that: The aluminum-lithium alloy comprises the following components in parts by weight: 91.5 to 94.5 parts aluminum, 3.9 to 4.2 parts copper, 1.0 to 1.5 parts lithium, 0.2 to 1.0 parts magnesium, 0.2 to 0.4 parts silver, 0.3 to 0.8 parts zinc, 0.10 to 0.12 parts zirconium, and 0.15 to 0.25 parts mixed rare earth elements; the mixed rare earth elements are a mixture of cerium and lanthanum, with a mass ratio of cerium to lanthanum of (1.5 to 2.5):1; the total mass of metallic impurities in the aluminum-lithium alloy does not exceed 0.15 parts, and the mass of a single metallic impurity does not exceed 0.05 parts.

2. The aluminum-lithium alloy according to claim 1, characterized in that, The mass ratio of zinc to magnesium in the aluminum-lithium alloy is (0.8–1.5):1, and the mass ratio of copper to lithium is (2.6–4.2):

1.

3. The aluminum-lithium alloy according to claim 1, characterized in that, The aluminum-lithium alloy has a room temperature tensile strength of 540MPa to 580MPa, an elongation after fracture of 14.5% to 18.0%, and a yield strength deviation of 1.4% to 1.8% between the rolling direction and the transverse direction of the plate.

4. A method for preparing an aluminum-lithium alloy as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Smelting and casting: Weigh the raw materials, smelt them in an inert atmosphere, and cast them into ingots; S2. Multi-stage homogenization treatment: The ingot is subjected to two-stage homogenization treatment, followed by cooling; S3. Hot deformation processing: The homogenized ingot is subjected to multi-directional forging or multi-pass cross rolling. S4. Solution treatment and quenching: The deformed product is subjected to solution treatment and rapid quenching. S5. Pre-stretching: Pre-stretching plastic deformation of products after solution quenching. S6. Two-stage aging treatment: The pre-stretched product is subjected to two-stage aging treatment and air-cooled to room temperature to obtain the aluminum-lithium alloy.

5. The preparation method according to claim 4, characterized in that, In step S2, the two-stage homogenization process is as follows: first, the ingot is heated to 465℃~475℃ and held for 14h~18h; then, it is heated to 495℃~505℃ and held for 24h~36h; after completion, it is cooled to room temperature at a rate of 100℃ / h~130℃ / h.

6. The preparation method according to claim 4, characterized in that, In step S3, the initial rolling or forging temperature of the hot deformation process is 450℃~470℃, the total engineering strain is 250%~350%, and the final forging or rolling temperature is 380℃~420℃.

7. The preparation method according to claim 4, characterized in that, In step S4, the solution treatment temperature is 515℃~525℃, and the holding time is 1h~2h; the solution is transferred from the solution treatment equipment to the quenching medium within 15s.

8. The preparation method according to claim 4, characterized in that, In step S5, the pre-stretched engineering strain is 2.0% to 5.0%, and this step must be completed within 4 hours after solution quenching.

9. The preparation method according to claim 4, characterized in that, In step S5, during the pre-stretching process, it is also necessary to continuously spray atomized nano-ceramic particle suspension onto the surface of the product as a process medium; the nano-ceramic particles are alumina; the mass concentration of the suspension is 5% to 10%.

10. The preparation method according to claim 4, characterized in that, In step S6, the two-stage aging treatment is as follows: first, the product is kept at 170℃~180℃ for 18h~24h; then, without cooling, the temperature is directly increased to 215℃~225℃ at a rate of 3℃ / min~5℃ / min and kept at that temperature for 2h~4h, and finally air-cooled to room temperature.

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