Process for improving the strength of aluminum-lithium alloys containing the element scandium

Abstract

The application discloses a process method for improving the strength of an aluminum-lithium alloy containing a scandium element, and the process method comprises the following steps: performing multi-pass hot rolling on a cast ingot of the aluminum-lithium alloy containing the scandium element to obtain a hot-rolled plate, performing annealing treatment on the hot-rolled plate to obtain an annealed piece, performing multi-pass cold rolling on the annealed piece to obtain a cold-rolled plate, and finally performing solid solution treatment and aging treatment on the cold-rolled plate in sequence to obtain the aluminum-lithium alloy containing the scandium element. The initial cast ingot is directly subjected to plastic deformation, the morphology of a primary phase is significantly improved, the content of Cu atoms in an aluminum solid solution is increased, the microstructure is adjusted through the plastic deformation and heat treatment process, and then the strength of the third-generation Al-Cu-Li alloy containing Sc is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of aluminum-lithium alloy preparation technology, specifically relating to a process method for improving the strength of scandium-containing aluminum-lithium alloys. Background Technology

[0002] The increasing demand for high-strength, high-performance, lightweight, and cost-effective structural materials in the aerospace industry has greatly promoted the improvement and development of novel aluminum-lithium alloy structural materials. Research shows that adding 1 wt.% Li to Al can reduce the alloy density by 3% and increase the elastic modulus by approximately 6%. Therefore, adding Li to Al can effectively reduce the alloy's weight, improve its overall performance, and meet the critical requirements of aerospace. Furthermore, compared with traditional commercial 2xxx and 7xxx aluminum-lithium alloys, Al-Cu-Li alloys have advantages such as lower density, higher specific strength, and higher elastic modulus, making them the most attractive alloy material in the aerospace industry. They have already been applied in rocket fuel tanks and the tail, fuselage, and upper and lower wings of large passenger aircraft.

[0003] The increasing pressure from increased payload, fuel efficiency, and fierce competition from titanium alloys and composite materials has led to more stringent performance requirements for structural materials in the development of next-generation aerospace aircraft, forcing aluminum alloy manufacturers to continuously develop new high-performance aerospace aluminum alloys. The performance of existing aluminum alloys can be improved to meet aerospace needs by controlling their alloy composition, microstructure, and heat treatment regime. Numerous studies have shown that the addition of rare earth element Sc is an excellent choice for improving the microstructure and properties of aluminum alloys: (1) Adding Sc to aluminum and aluminum alloys can refine the grain size of cast billets, mainly forming equiaxed crystals rather than long dendrites; (2) Sc has a strong anti-recrystallization effect in aluminum alloys, stabilizing grain size at higher temperatures, especially when Sc and Zr are added together, the anti-recrystallization effect is more pronounced; (3) It assists in strengthening the nucleation of precipitates and improves their resistance to coarsening under high-temperature exposure. (4) It has good resistance to hot cracking during welding. (5) The addition of Sc element in aluminum alloy reduces the content of brass texture, thereby reducing the anisotropy of mechanical properties and improving formability. (6) It significantly reduces the crack propagation rate. However, after homogenization heat treatment, the Cu-rich residual W (AlCuSc) second phase induced by Sc in the third-generation Al-Cu-Li alloy containing Sc element makes it difficult to improve the solid solubility of Cu element in the aluminum matrix, which greatly limits the mechanical properties of the third-generation Al-Cu-Li alloy in the aged state. A large number of studies have shown that the formation of W phase during homogenization is closely related to Cu content and has a positive or negative impact on the properties of alloys with different Cu contents. When the Cu content is less than 3 wt.%, the W phase is not detected in casting and subsequent homogenization. However, in some alloys with Cu content of 3-6 wt.%, when the Sc content is less than 0.1 wt.%, the W phase is not found in the cast alloy. The W phase nucleates around some AlCu phases and shows a discontinuous distribution with the diffusion of Sc element during the homogenization process. This indicates that the homogenization process did not completely dissolve the coarse phase, but rather formed another high-temperature Cu-containing phase, thus reducing the copper atom concentration in the aluminum solid solution. Furthermore, adding Sc to Al-Cu-Li alloys is not always beneficial; for example, adding a small amount of Sc to Al-Cu-Li alloys with high Cu content can lead to a decrease in mechanical properties. This is mainly due to the formation of the W phase during homogenization, which consumes Cu and inhibits the precipitation of the T1 phase. Clearly, this traditional homogenization method cannot maximize the Cu atom concentration in the aluminum solid solution. Therefore, an effective measure must be taken to mitigate the adverse effects of Sc addition, fully utilize the advantages of Sc in Al-Cu-Li alloys, and provide theoretical support and an application basis for developing aerospace aluminum alloys with superior overall performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies in improving the strength of Sc-containing third-generation Al-Cu-Li alloys, the present invention aims to provide a process method for enhancing the strength of scandium-containing aluminum-lithium alloys. The process method provided by this invention, through a combination of suitable rolling and heat treatment processes, controls the primary AlCu phase in the Sc-containing third-generation Al-Cu-Li alloy ingot to dissolve as fully as possible in the aluminum matrix while suppressing the formation of a large amount of W phase. This promotes the solid solubility of Cu in the aluminum matrix and obtains a higher volume fraction of aging precipitates during the aging process, significantly increasing their contribution to strength and achieving a significant improvement in the strength of Sc-containing third-generation Al-Cu-Li alloys.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention discloses a process for improving the strength of scandium-containing aluminum-lithium alloys. The process involves hot rolling a scandium-containing aluminum-lithium alloy ingot through multiple passes to obtain a hot-rolled plate, annealing the hot-rolled plate to obtain an annealed part, cold rolling the annealed part through multiple passes to obtain a cold-rolled plate, and finally performing solution treatment and aging treatment on the cold-rolled plate to obtain the scandium-containing aluminum-lithium alloy.

[0007] The process of this invention involves directly hot rolling a scandium-containing aluminum-lithium alloy ingot through multiple passes. Due to the incompatibility between the elastic constants and deformation behavior of the coarse phase and the Al matrix in the ingot, stress concentration occurs during deformation. When the stress concentration exceeds a critical value, the coarse phase cracks and breaks into fine particles. The fine particles, with a larger radius of curvature (i.e., higher surface energy), are more easily dissolved than the coarse phase and undergo dynamic dissolution during the multi-pass hot rolling process. This dissolves the coarse phase and inhibits the formation of the W phase. After hot rolling, annealing is performed to further promote the formation of some residual low-melting-point primary phases from the hot rolling process. Dissolution promotes the uniform distribution of solute atoms and improves the plastic deformation capacity during cold rolling. Subsequent multi-pass cold rolling further effectively breaks down the Cu-rich second phase through deformation energy storage, forming high-density dislocations, etc., providing favorable channels for rapid atomic diffusion and improving the effect of Cu atoms re-dissolving into the Al matrix during solution heat treatment. Then, solution heat treatment is used to fully dissolve the second phase in the cold-rolled sheet into the aluminum matrix to obtain a supersaturated solid solution. Finally, aging treatment is carried out to obtain a uniformly distributed and high-volume-fraction fine strengthening phase, which significantly improves the strength of the alloy.

[0008] The process of this invention is applicable to all aluminum-lithium alloys containing scandium, so the composition of aluminum-lithium alloys containing scandium is not limited. However, the inventors have found that the process of this invention can be further improved for aluminum-lithium alloys with the following compositions, ultimately obtaining better performance.

[0009] In a preferred embodiment, the scandium-containing aluminum-lithium alloy ingot has the following composition by mass percentage: Cu: 3.50-4.38%, Li: 0.76-1.42%, Mg: 0.35-0.95%, Ag: 0.10-0.39%, Mn: 0.30-0.50%, Zn: 0.20-0.51%, Sc: 0.05-0.20%, Zr: 0.11-0.30%, with the balance being Al.

[0010] The scandium-containing aluminum-lithium alloy provided by this invention is based on the third-generation Al-Cu-Li alloy, and its aging process mainly follows (111). Al The semi-coherent T1 phase, forming a hexagonal structure, exhibits a significant strengthening effect. Furthermore, elements such as Sc, Zr, Zn, and Mn are added. Zn atoms can accumulate on the T1 phase, promoting its precipitation and improving the variety of grain boundary precipitates, thus enhancing corrosion resistance. Additionally, the addition of Mn can form Al... 20 The Cu2Mn3 dispersed phase possesses high thermal stability, effectively hindering dislocation slip during deformation and grain boundary migration during recrystallization. Dislocations formed around it during pre-deformation act as non-uniform nucleation sites, contributing to the strengthening of phase precipitation. Furthermore, the composite addition of Sc and Zr reduces dendritic segregation in the ingot, refining the ingot's grain structure and laying the foundation for direct hot rolling. Moreover, the Sc and Zr-containing phases formed in the aluminum matrix effectively inhibit grain boundary migration during solution heat treatment, reducing recrystallization growth and resulting in a finer grain structure.

[0011] However, the aforementioned Al-Cu-Li alloy ingots containing Sc will form a large number of coarse W phases during the homogenization process. If existing technology is used, these phases are difficult to dissolve during the solid solution process. These coarse phases consume a large number of Cu atoms, which is not conducive to the formation of precipitated phases during the subsequent aging process and seriously reduces the strength of the material. However, through the specific process of this invention, the coarse phases can be transformed into fine particle distribution. Combined with intermediate annealing and solid solution regime adjustment, the Cu phases in the alloy can be significantly dissolved, promoting a higher Cu content in the aluminum solid solution. This results in a homogeneous distribution and a high volume fraction of strengthening phases during the aging process, significantly improving the strength of the alloy.

[0012] In a preferred embodiment, the temperature of the multi-pass hot rolling is 460℃-500℃, preferably 490℃-500℃. Before the first pass of hot rolling, the temperature is 460℃-500℃, preferably 490℃-500℃, and the holding temperature is 1h-10h, preferably 1-3h. Between passes, the temperature is 460℃-500℃, preferably 490℃-500℃, and the holding temperature is 10-30min.

[0013] In a preferred embodiment, during the multi-pass hot rolling, the rolling reduction per pass is 10%-15%, and the total reduction is 70%-90%.

[0014] The inventors discovered that controlling the reduction in each pass to between 10% and 15%, and holding the temperature for 10-30 minutes after each pass, can prevent dislocation accumulation from causing localized microcracks in the ingot, thus ensuring the quality of the rolled sheet. Furthermore, hot rolling deformation can break up the primary phase to a certain extent and introduce a certain amount of deformation energy storage.

[0015] In a preferred embodiment, the annealing temperature is 480℃-530℃ and the annealing time is 1h-10h.

[0016] The inventors discovered that the high-temperature annealing process further promotes the dissolution of some residual low-melting-point primary phases during hot rolling, which is beneficial to the uniform distribution of solute atoms, improves the plastic deformation capacity during cold rolling, and prevents overheating during high-temperature solution treatment.

[0017] In a preferred embodiment, the total deformation of the multi-pass cold rolling is 50%-90%, and the deformation per pass is 10-15%.

[0018] In this invention, further cold rolling allows for rapid accumulation of deformation energy storage and effective breakage of the Cu-rich second phase, forming high-density dislocations, etc., providing favorable channels for rapid atomic diffusion and improving the effect of Cu atoms resolving back into the Al matrix during the solid solution heat preservation process.

[0019] In a preferred embodiment, the solution treatment temperature is 520℃-555℃, the solution treatment time is 1h-3h, and after the solution treatment is completed, it is immediately cooled to room temperature with water.

[0020] In this invention, solution heat treatment allows the second phase in the cold-rolled sheet to fully dissolve in the aluminum matrix, resulting in a supersaturated solid solution, which is beneficial for subsequent aging precipitation.

[0021] In practice, the solution-treated sheet is immediately placed in room temperature water for quenching. Rapid water cooling to room temperature is used to prevent the formation of coarse second phases due to excessively low cooling rates, which would affect aging precipitation.

[0022] In a preferred embodiment, a pre-deformation process is performed before the aging treatment, with a pre-deformation amount of 2-6%.

[0023] In a further preferred embodiment, the pre-deformation is a pre-stretch deformation.

[0024] Pre-deformation can effectively release residual stress during the quenching process. Furthermore, this invention introduces dislocations through pre-stretch deformation, effectively promoting precipitate nucleation and further improving the material's mechanical properties. However, the amount of pre-deformation needs to be effectively controlled; too small a pre-deformation amount cannot effectively introduce dislocation density, while too large a pre-deformation amount will significantly reduce the alloy's plasticity.

[0025] In a preferred embodiment, the aging treatment temperature is 145℃-175℃, and the aging treatment time is 10h-80h.

[0026] After solution treatment, peak aging treatment is performed. The aging temperature is controlled within the above range to obtain the aluminum-lithium alloy with the highest strength. If the aging temperature is too low, it will not be conducive to the precipitation of the main T1 phase. If the aging temperature is too high, it will accelerate the coarsening of the strengthening phase and reduce the peak hardness.

[0027] Principles and advantages

[0028] The process of this invention involves directly hot rolling a scandium-containing aluminum-lithium alloy ingot through multiple passes. Due to the incompatibility between the elastic constants and deformation behavior of the coarse phase and the Al matrix in the ingot, stress concentration occurs during deformation. When the stress concentration exceeds a critical value, the coarse phase cracks and breaks into fine particles. The fine particles, with a larger radius of curvature (i.e., higher surface energy), are more easily dissolved than the coarse phase and undergo dynamic dissolution during the multi-pass hot rolling process. This dissolves the coarse phase and inhibits the formation of the W phase. After hot rolling, annealing is performed to further promote the formation of some residual low-melting-point primary phases from the hot rolling process. Dissolution promotes the uniform distribution of solute atoms and improves the plastic deformation capacity during cold rolling. Subsequent multi-pass cold rolling further effectively breaks down the Cu-rich second phase through deformation energy storage, forming high-density dislocations, etc., providing favorable channels for rapid atomic diffusion and improving the effect of Cu atoms re-dissolving into the Al matrix during solution heat treatment. Then, solution heat treatment is used to fully dissolve the second phase in the cold-rolled sheet into the aluminum matrix to obtain a supersaturated solid solution. Finally, aging treatment is carried out to obtain a uniformly distributed and high-volume-fraction fine strengthening phase, which significantly improves the strength of the alloy.

[0029] This invention directly plastically deforms the initial ingot, significantly improving the morphology of the primary phase and increasing the Cu atom content in the aluminum solid solution. By adjusting the plastic deformation and heat treatment processes, the microstructure is controlled, resulting in a significant increase in the strength of the Sc-containing third-generation Al-Cu-Li alloy. Furthermore, by adjusting the thermomechanical treatment process, this invention minimizes the residual crystalline phases in the aluminum-lithium alloy ingot, significantly improving the strength of scandium-added aluminum-lithium alloys and achieving a short-process technology for preparing ultra-high-strength Sc-containing aluminum-lithium alloys. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 SEM image of the second phase of the aluminum-lithium alloy plate prepared in Example 1;

[0032] Figure 2 SEM image of the second phase of the aluminum-lithium alloy plate prepared for Comparative Example 1;

[0033] Figure 3 SEM image of the second phase of the aluminum-lithium alloy plate prepared for Comparative Example 4. Detailed Implementation

[0034] This invention provides a process for improving the strength of scandium-containing aluminum-lithium alloys. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0035] Example 1

[0036] This embodiment provides a process method for improving the strength of scandium-containing aluminum-lithium alloys. The process method includes the following steps:

[0037] ① Heat preservation: After machining the outer surface of the ingot, it is heat-preserved in a heat treatment furnace at 490℃ for 2 hours.

[0038] ② Hot rolling: The ingot after heat preservation is directly and immediately subjected to multiple hot rolling passes to obtain the initial alloy rolled plate. The rolling reduction per pass is 10%-15%, the total reduction is 80%, and the heat preservation between passes is 10 minutes.

[0039] ③ Annealing: The hot-rolled alloy sheet obtained in step ② above is annealed at 520℃ for 1 hour.

[0040] ④ Cold rolling: The annealed sheet is directly subjected to multiple cold rolling passes, with a total rolling reduction of 70%.

[0041] ⑤ Solution treatment and aging: The alloy cold-rolled sheet was solution treated at 540℃ for 1 hour, then immediately quenched in water at room temperature, and then artificially aged at 165℃ for 30 hours to reach the peak value. The final mechanical properties of the resulting material are shown in Table 1.

[0042] Example 2

[0043] This embodiment provides a process method for improving the strength of scandium-containing aluminum-lithium alloys. The process method includes the following steps:

[0044] ① Heat preservation: After machining the outer surface of the ingot, it is heat-preserved in a heat treatment furnace at 490℃ for 2 hours.

[0045] ② Hot rolling: The ingot after heat preservation is directly and immediately subjected to multiple hot rolling passes to obtain the initial alloy rolled plate. The rolling reduction per pass is 10%-15%, and the total reduction is 80%.

[0046] ③ Annealing: The hot-rolled alloy sheet obtained in step ② above is annealed at 520℃ for 1 hour.

[0047] ④ Cold rolling: The annealed sheet is directly subjected to multiple cold rolling passes, with a total rolling reduction of 70%.

[0048] ⑤ Solution treatment and aging: The alloy cold-rolled sheet was solution treated at 540℃ for 1 hour, then immediately quenched in water at room temperature and subjected to 3% pre-stretch deformation. Finally, it was artificially aged at 165℃ for 24 hours to reach the peak value. The final mechanical properties of the resulting material are shown in Table 1.

[0049] Example 3

[0050] This embodiment provides a process method for improving the strength of scandium-containing aluminum-lithium alloys. The process method includes the following steps:

[0051] ① Heat preservation: After machining the outer surface of the ingot, it is heat-preserved in a heat treatment furnace at 490℃ for 2 hours.

[0052] ② Hot rolling: The ingot after heat preservation is directly and immediately subjected to multiple hot rolling passes to obtain the initial alloy rolled plate. The rolling reduction per pass is 10%-15%, and the total reduction is 80%.

[0053] ③ Annealing: The hot-rolled alloy sheet obtained in step ② above is annealed at 520℃ for 1 hour.

[0054] ④ Cold rolling: The annealed sheet is directly subjected to multiple cold rolling passes, with a total rolling reduction of 70%.

[0055] ⑤ Solution treatment and aging: The alloy cold-rolled sheet was solution treated at 540℃ for 1 hour, then immediately quenched in water at room temperature and subjected to 5% pre-stretch deformation. Finally, it was artificially aged at 165℃ for 20 hours to reach the peak value. The final mechanical properties of the resulting material are shown in Table 1.

[0056] Comparative Example 1

[0057] The process method provided in this comparative example includes the following steps:

[0058] ① Homogenization annealing: After machining the outer surface of the ingot, it is homogenized in a heat treatment furnace. The process is 350℃ / 5h + 460℃ / 8h + 520℃ / 24h.

[0059] ② Hot rolling: The homogenized ingot is hot rolled in multiple passes to obtain the initial aluminum-lithium alloy plate. The rolling reduction per pass is 10%-15%, and the total reduction is 80%.

[0060] ③ Annealing: The aluminum-lithium alloy hot-rolled sheet obtained in step ② above is subjected to multi-stage annealing treatment, with an annealing regime of 520℃ / 1h;

[0061] ④ Cold rolling: The annealed sheet is cold rolled with a total reduction of 70%.

[0062] ⑤ Solution treatment and aging: The aluminum-lithium alloy cold-rolled sheet was solution treated at 520℃ for 1 hour, immediately quenched in water at room temperature, and then artificially aged at 165℃ for 50 hours to reach the peak value. The final mechanical properties of the resulting material are shown in Table 1.

[0063] Comparative Example 2

[0064] The process method provided in this comparative example includes the following steps:

[0065] ① Homogenization annealing: After machining the outer surface of the ingot, it is homogenized in a heat treatment furnace. The process is 350℃ / 5h + 460℃ / 8h + 520℃ / 24h.

[0066] ② Hot rolling: The homogenized ingot is hot rolled in multiple passes to obtain the initial aluminum-lithium alloy plate. The rolling reduction per pass is 10%-15%, and the total reduction is 80%.

[0067] ③ Annealing: The aluminum-lithium alloy hot-rolled sheet obtained in step ② above is subjected to multi-stage annealing treatment, with an annealing regime of 520℃ / 1h;

[0068] ④ Cold rolling: The annealed sheet is cold rolled with a total reduction of 70%.

[0069] ⑤ Solution treatment and aging: The aluminum-lithium alloy cold-rolled sheet was solution treated at 520℃ for 1 hour, immediately quenched in water at room temperature, and subjected to 3% pre-stretch deformation. Then it was aged at 165℃ for 40 minutes to reach the peak value. The final mechanical properties of the resulting material are shown in Table 1.

[0070] Comparative Example 3

[0071] The process method provided in this comparative example includes the following steps:

[0072] ① Homogenization annealing: After machining the outer surface of the ingot, it is homogenized in a heat treatment furnace. The process is 350℃ / 5h + 460℃ / 8h + 520℃ / 24h.

[0073] ② Hot rolling: The homogenized ingot is hot rolled in multiple passes to obtain the initial aluminum-lithium alloy plate. The rolling reduction per pass is 10%-15%, and the total reduction is 80%.

[0074] ③ Annealing: The aluminum-lithium alloy hot-rolled sheet obtained in step ② above is subjected to multi-stage annealing treatment, with an annealing regime of 520℃ / 1h;

[0075] ④ Cold rolling: The annealed sheet is cold rolled with a total reduction of 70%.

[0076] ⑤ Solution treatment and aging: The aluminum-lithium alloy cold-rolled sheet was solution treated at 520℃ for 1 hour, immediately quenched in water at room temperature, and subjected to 5% pre-stretch deformation. Then it was aged at 165℃ for 35 hours to reach the peak value. The final mechanical properties of the resulting material are shown in Table 1.

[0077] Comparative Example 4

[0078] The process method provided in this comparative example includes the following steps:

[0079] ① Homogenization annealing: After machining the outer surface of the ingot, it is homogenized in a heat treatment furnace. The process is 350℃ / 5h + 460℃ / 8h + 520℃ / 24h.

[0080] ② Hot rolling: The homogenized ingot is hot rolled in multiple passes to obtain the initial aluminum-lithium alloy plate. The rolling reduction per pass is 10%-15%, and the total reduction is 80%.

[0081] ③ Annealing: The aluminum-lithium alloy hot-rolled sheet obtained in step ② above is subjected to multi-stage annealing treatment, with an annealing regime of 520℃ / 1h;

[0082] ④ Cold rolling: The annealed sheet is cold rolled with a total reduction of 70%.

[0083] ⑤ Solution treatment and aging: The aluminum-lithium alloy cold-rolled sheet was solution treated at 540℃ for 1 hour, immediately quenched in water at room temperature, and then artificially aged at 165℃ for 30 hours to reach the peak value. The final mechanical properties of the resulting material are shown in Table 1.

[0084] Comparative Example 5

[0085] The process method provided in this comparative example includes the following steps:

[0086] ① Homogenization annealing: After machining the outer surface of the ingot, it is homogenized in a heat treatment furnace. The process is 350℃ / 5h + 460℃ / 8h + 520℃ / 24h.

[0087] ② Hot rolling: The homogenized ingot is hot rolled in multiple passes to obtain the initial aluminum-lithium alloy plate. The rolling reduction per pass is 10%-15%, and the total reduction is 80%.

[0088] ③ Annealing: The aluminum-lithium alloy hot-rolled sheet obtained in step ② above is subjected to multi-stage annealing treatment, with an annealing regime of 520℃ / 1h;

[0089] ④ Cold rolling: The annealed sheet is cold rolled with a total reduction of 70%.

[0090] ⑤ Solution treatment and aging: The aluminum-lithium alloy cold-rolled sheet was solution treated at 540℃ for 1 hour, immediately quenched in water at room temperature, and subjected to 3% pre-stretch deformation. Then, it was artificially aged at 165℃ for 25 hours to reach the peak value. The final mechanical properties of the resulting material are shown in Table 1.

[0091] Comparative Example 6

[0092] The process method provided in this comparative example includes the following steps:

[0093] ① Homogenization annealing: After machining the outer surface of the ingot, it is homogenized in a heat treatment furnace. The process is 350℃ / 5h + 460℃ / 8h + 520℃ / 24h.

[0094] ② Hot rolling: The homogenized ingot is hot rolled in multiple passes to obtain the initial aluminum-lithium alloy plate. The rolling reduction per pass is 10%-15%, and the total reduction is 80%.

[0095] ③ Annealing: The aluminum-lithium alloy hot-rolled sheet obtained in step ② above is subjected to multi-stage annealing treatment, with an annealing regime of 520℃ / 1h;

[0096] ④ Cold rolling: The annealed sheet is cold rolled with a total reduction of 70%.

[0097] ⑤ Solution treatment and aging: The aluminum-lithium alloy cold-rolled sheet was solution treated at 540℃ for 1 hour, immediately quenched in water at room temperature, and subjected to 5% pre-stretch deformation. Then, it was artificially aged at 165℃ for 20 hours to reach the peak value. The final mechanical properties of the resulting material are shown in Table 1.

[0098] Tissue characterization and performance testing of examples and comparative examples

[0099] 1. Scanning electron microscopy analysis of aluminum-lithium alloy plates

[0100] Scanning electron microscopy (SEM) analysis was performed on the second phase of the aluminum-lithium alloy plate in this embodiment. The SEM image of the second phase of the aluminum-lithium alloy plate provided in Embodiment 1 is shown below. Figure 1 As shown. A scanning electron microscope (SEM) image of the second phase of the aluminum-lithium alloy plate prepared in Comparative Example 1 is shown below. Figure 2 As shown. A scanning electron microscope (SEM) image of the second phase of the aluminum-lithium alloy plate prepared in Comparative Example 4 is shown below. Figure 3 As shown. The aluminum-lithium alloy sheet obtained in Comparative Example 1 contains a large amount of the second phase, such as... Figure 2 As shown. The aluminum-lithium alloy sheet obtained in Comparative Example 4 contains less of the second phase compared to Comparative Example 1, such as... Figure 3 As shown, the size of the second phase in Example 1 is significantly smaller than that in Comparative Example 1, which helps to mitigate the decrease in strength properties caused by the large amount of crystalline phase formed by the addition of Sc element in the aluminum-lithium alloy.

[0101] 2. Room temperature mechanical property testing

[0102] The aluminum-lithium alloy plates prepared in Examples 1-3 and Comparative Examples 1-6 of this invention were tested for mechanical properties on a DDL100 electronic universal testing machine. The mechanical properties of the aluminum-lithium alloy plates obtained in Examples 1-3 and Comparative Examples 1-6 are listed in Table 1. Table 1 clearly shows that the strength of the aluminum-lithium alloy plates prepared in these examples is higher than that of the comparative examples, indicating that the rolling regime and heat treatment process used in this invention can significantly improve the mechanical properties of aluminum-lithium alloys, especially for aluminum-lithium alloys containing trace amounts of Sc. Comparative Examples 1-3 have the worst strength, indicating that the solution treatment temperature is relatively low, resulting in a relatively low Cu content in the aluminum solid solution, which is unfavorable for aging precipitation. Although the solution temperatures of Examples 1-3 and Comparative Examples 4-6 are the same, the strength of the plates prepared in Comparative Examples 4-6 is lower than that of Examples 1-3, indicating that adjusting the solution temperature of Comparative Examples 1-3 to that of Comparative Examples 4-6 does not achieve the strengthening effect of Examples 1-3. Therefore, the process of this invention can effectively improve the precipitation strengthening effect of alloys, especially aluminum-lithium alloys containing Sc. Furthermore, T8 aging provides an even better improvement in mechanical properties.

[0103] Table 1. Room temperature tensile properties of Examples 1-3 and Comparative Examples 1-6

[0104]

Claims

1. A process for enhancing the strength of a scandium-containing elemental aluminum lithium alloy, characterized by: The scandium-containing aluminum-lithium alloy ingot is subjected to multi-pass hot rolling to obtain a hot-rolled plate, the hot-rolled plate is subjected to annealing treatment to obtain an annealed piece, the annealed piece is subjected to multi-pass cold rolling to obtain a cold-rolled plate, and finally the cold-rolled plate is subjected to solid solution treatment and aging treatment in sequence to obtain the scandium-containing aluminum-lithium alloy; The scandium-containing aluminum-lithium alloy ingot comprises the following components in percentage by mass: Cu: 3.50-4.38%, Li: 0.76-1.42%, Mg: 0.35-0.95%, Ag: 0.10-0.39%, Mn: 0.30-0.50%, Zn: 0.20-0.51%, Sc: 0.05-0.20%, Zr: 0.11-0.30%, and the balance of Al; The temperature of the multi-pass hot rolling is 460-500 DEG C, the first-pass hot rolling is preceded by 1-10 h of holding at 460-500 DEG C, and the inter-pass holding is 10-30 min at 460-500 DEG C. The annealing treatment is performed at a temperature of 480-530 DEG C for 1-10 h.

2. The process of claim 1, wherein the process is characterized by: In the multi-pass hot rolling, the single-pass rolling reduction is 10-15%, and the total reduction is 70-90%.

3. The process of claim 1, wherein the process is characterized by: In the multi-pass cold rolling, the total deformation is 50-90%, and the single-pass deformation is 10-15%.

4. The process of claim 1, wherein the process is characterized by: The solid solution treatment is performed at a temperature of 520-555 DEG C for 1-3 h, and then water cooling is performed to room temperature.

5. The process of claim 1, wherein the process is characterized by: The pre-deformation is performed before the aging treatment, and the pre-deformation is 2-6%.

6. The process of claim 5, wherein the process is characterized by: The pre-deformation is pre-tensile deformation.

7. The process of claim 1, wherein the process is characterized by: The aging treatment is performed at a temperature of 145-175 DEG C for 10-80 h.

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