Lightweight ultrahigh-strength high-modulus weldable aluminum-lithium alloy material and preparation method thereof

Abstract

The invention discloses a lightweight ultrahigh-strength high-modulus weldable aluminum-lithium alloy material and a preparation method thereof. The aluminum-lithium alloy comprises 3.20 wt%-3.49 wt% of Cu, 1.45 wt%-1.75 wt% of Li, 0.35 wt%-0.50 wt% of Mg, 0.20 wt%-0.40 wt% of Ag, 0.11 wt%-0.17 wt% of Sc, at least one of Zr, Mn, Ti, Hf and V with the total content not larger than 0.60 wt%, the balance Al and inevitable impurities, each impurity element is smaller than or equal to 0.15 wt%, and the sum of the impurity elements is smaller than or equal to 0.40 wt%. The preparation method of the alloy deformation processing material comprises the following steps: (1) manufacturing an aluminum-lithium alloy ingot blank; (2) homogenizing heat treatment; (3) thermally processing the ingot blank into a required processing material or a pre-processing material; (4) optionally reheating the pre-processing material, and processing the pre-processing material into a required processing material through cold deformation; (5) carrying out solid solution heat treatment on the processing material; (6) the machined material subjected to solution heat treatment is rapidly cooled to the room temperature; and (7) aging treatment is conducted on the machined material. The aluminum-lithium alloy material shows excellent comprehensive performance of low density, high strength, high modulus, weldability and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloys and their preparation and processing, and particularly relates to Al-Cu-Li series aluminum alloys. More specifically, the present invention relates to a lightweight, ultra-high strength, high modulus, weldable Al-Cu-Li-Sc aluminum alloy material and a preparation method thereof. Background Art

[0002] Due to the characteristics of low specific gravity (the density of pure Al is 2.70 g / cm 3 ), high specific strength, easy processing, and low cost, aluminum alloys have been widely used in the fields of aviation, aerospace, high-speed rail, automobiles, ships, etc. As a new generation of lightweight structural materials, aluminum-lithium alloys have shown great application prospects and development potential in the fields of high-end equipment manufacturing such as aerospace, national defense, and transportation. With the continuous increase in the weight reduction requirements of modern aircraft, launch vehicles and other equipment, traditional aluminum alloys are difficult to meet the growing requirements of high specific strength and high specific modulus. Aluminum-lithium alloys are gradually becoming the first choice for key structural materials due to their unique performance advantages. As the lightest metallic element, the addition of lithium can significantly reduce the density of aluminum alloys. Each addition of 1% of lithium can reduce the alloy density by about 3%, and at the same time increase the elastic modulus by about 6%. This excellent lightweight effect makes it irreplaceable in the aviation field. In the application of commercial aircraft, the fuel economy benefits brought by structural weight reduction are very significant, which drives the development of aluminum-lithium alloys towards higher performance and wider applications.

[0003] The most widely used ultra-high strength Al-Cu-Li alloys at present, such as 2195 aluminum-lithium alloy, and newly developed aluminum-lithium alloys such as 2060 and 2065 in recent years, through alloy design with a high Cu / Li ratio (the Cu content is usually greater than 3.5 wt%, and the Li content is less than 1.5 wt%), utilize nano-strengthening phases such as T1 (Al2CuLi) and θ' (Al2Cu), and the tensile strength of the material reaches about 600 MPa, and its specific strength is increased by about 15-20% compared with traditional 2xxx and 7xxx series aluminum alloys. Such alloys have been successfully applied to the key load-bearing structures of new generation aircraft and launch vehicles. For example, the storage tanks of space shuttles and launch vehicles use ultra-high strength 2195 alloy, achieving significant weight reduction effects. However, this high copper content design also brings prominent weldability problems, seriously restricting its application in large welded structures. During the welding process, the high copper content leads to the formation of low melting point eutectic phases (such as Al-Cu binary eutectic, melting point about 548 °C), significantly increasing the sensitivity of liquation cracks in the heat affected zone. At the same time, the welding heat cycle will cause the dissolution and coarsening of the strengthening phases, making the strength of the welded joint usually only reach 60% of the base metal. This technical bottleneck makes it difficult for existing ultra-high strength aluminum-lithium alloys to meet the manufacturing requirements of large welded structural parts. At the same time, the density of such alloys is relatively high, reaching 2.70 g / cm 3And above, with the elastic modulus not high enough, only about 77 GPa, it is difficult to meet the development needs of lightweight and high-performance aerospace vehicles. There is an urgent need to develop new lightweight high-performance aluminum-lithium alloys with excellent weldability.

[0004] To improve the welding performance of aluminum-lithium alloys, research teams at home and abroad have tried various technical approaches, among which microalloying modification is considered one of the most promising solutions. Among many microalloying elements, scandium (Sc) has attracted much attention due to its unique physical metallurgical properties. Sc can form nano-scale Al3Sc phases in aluminum alloys. When added in combination with Zr, it can also form Al3(Sc,Zr) dispersion phases with better strengthening effects. These phases act as heterogeneous nucleation sites during solidification, significantly refining the as-cast grains. At the same time, during subsequent heat treatment or hot deformation processes, they inhibit dislocation movement and grain boundary migration through pinning effects, effectively hindering the recrystallization process. In addition, the addition of Sc can refine the weld grains, reduce the tendency of hot cracking during welding, and the formed Al3Sc dispersion phases can reduce the softening of the heat-affected zone of the welded joint. Meanwhile, Sc can also form Al3(Li,Sc) strengthening phases with Li, further enhancing the strength of the alloy. Research shows that adding a small amount of Sc can effectively improve the welding performance, strength, plasticity, corrosion resistance and welding performance of aluminum-lithium alloys. However, in the Al-Cu-Li-Sc alloy system with a high Cu content, Sc will react preferentially with Cu to form the W phase (Al8Cu4Sc). This thermodynamically more stable intermetallic compound not only consumes the effective Sc element, reducing its strengthening effect, but also easily coarsens at high temperatures, becoming a crack source and damaging the plasticity, fracture toughness, fatigue crack growth rate and corrosion resistance of the alloy. More seriously, the W phase will coarsen significantly during the welding thermal cycle, further deteriorating the performance of the welded joint. This phenomenon seriously restricts the application effect of Sc elements in ultra-high-strength aluminum-lithium alloys.

[0005] Regarding the beneficial effects of Sc element, in recent years, it has been found that the properties of Sc-containing Al-Li alloys can be improved by using special preparation processes. For example: Patent document CN117165880A discloses a process method for enhancing the strength of Sc-containing Al-Li alloys, and its basic composition range is Cu: 3.50 - 4.38 wt.%, Li: 0.76 - 1.42 wt.%, Mg: 0.35 - 0.95 wt.%, Ag: 0.10 - 0.39 wt.%, Mn: 0.30 - 0.50 wt.%, Zn: 0.20 - 0.51 wt.%, Sc: 0.05 - 0.20 wt.%, Zr: 0.11 - 0.30 wt.%, and the balance is Al. This invention directly conducts plastic deformation on the initial ingot, significantly improves the morphology of the primary phase, increases the content of Cu atoms in the aluminum solid solution, and realizes the enhancement of the strength of Sc-containing Al-Cu-Li alloys. There is also research that by reducing the Cu content and strictly controlling the addition amount of Sc (the actual addition amount is controlled within 0.1 wt.%) and jointly acting with Zr to form Al3(Sc,Zr) particles to refine grains and inhibit recrystallization, performance improvement has been obtained. For example: Patent document CN110546288A discloses a low-density aluminum-copper-lithium alloy product, and its basic composition range is Cu: 2.4 - 3.2 wt.%, Li: 1.6 - 2.3 wt.%, Mg: 0.3 - 0.9 wt.%, Mn: 0.2 - 0.6 wt.%, Zr: 0.12 - 0.18 wt.%, such that Zr ≥ -0.06 * Li + 0.242; Zn: < 1.0; Ag: < 0.15; Fe + Si ≤ 0.20; optionally at least one element selected from Ti, Sc, Cr, Hf, and V, and the content of the element (if selected) is: Ti: 0.01 - 0.1; Sc: 0.01 - 0.15; Cr: 0.01 - 0.3; Hf: 0.01 - 0.5; V: 0.01 - 0.3; other elements are each ≤ 0.05 and in total ≤ 0.15, and the rest is aluminum. This alloy reduces the density of the alloy by reducing the Cu / Li ratio, adds Zr element to reduce the risk of thermal cracking during casting, and refines the alloy grains.Patent Document CN117684060A discloses an aluminum-lithium alloy with good damage resistance and a preparation method thereof. The basic composition ranges are as follows: Cu: 3.19 - 3.73 wt.%, Li: 0.87 - 1.43 wt.%, Mg: 0.31 - 0.71 wt.%, Mn: 0.24 - 0.36 wt.%, Zn: 0.06 - 0.47 wt.%, Ag: 0 - 0.41 wt.%, Sc: 0 - 0.15 wt.%, Zr: 0 - 0.20 wt.%, and the balance is Al. The mass ratio of Cu / Li is 2.23 - 4.28. Appropriate Sc and Zr elements are added to the alloy. During the solution treatment process, the formed Al3(Sc,Zr) particles can effectively hinder grain boundary migration and inhibit recrystallization growth to ensure that the alloy has high strength, high heat resistance, and good cold plastic workability. At the same time, by controlling the Cu / Li mass ratio, the fatigue crack growth rate can be significantly increased.

[0006] In recent years, in order to improve the properties and lightweight of aluminum-lithium alloys, some studies have found that by controlling the total amount of Li+Cu, jointly adding Zr+Mn, and adding trace elements such as Mg, Zn, and Ag, the strength and toughness of the alloy can be improved. Special preparation processes can be used to improve the properties of scandium-containing aluminum-lithium alloys. For example, patent document CN102021457A discloses a high-strength and tough aluminum-lithium alloy and its preparation method. The basic composition range is: Cu: 3.2-4.2 wt.%, Li: 0.7-1.8 wt.%, Mn: 0.20-0.60 wt.%, Zn: 0.20-0.60 wt.%, Zr: 0.06-0.20 wt.%, Mg: 0.20-0.80 wt.%, Ag: 0.2-0.7 wt.%, Si≤0.10 wt.%, Fe≤0.10 wt.%, Ti≤0.12 wt.%, other impurities are individually ≤0.05 wt.%, and the total amount is ≤0.15 wt.%, with the balance being Al. The alloy controls the total amount of Li+Cu to be close to 5 wt.% and adopts the method of jointly adding Zr+Mn, thereby greatly reducing the anisotropy of the alloy. The addition of trace elements such as Mg, Zn, and Ag improves the strength and toughness of the alloy. Some studies have also found that by controlling the Cu / Li ratio and the content of Ag+Mg+Zn, low density, high strength, and high elastic modulus can be obtained. For example, patent document CN114086044A discloses a lightweight and high-strength Al-Cu-Li alloy extrusion material and its processing method. The basic composition range is: Cu: 3.1-3.5 wt.%, Li: 1.7-2.3 wt.%, Mg: 0.3-0.6 wt.%, Ag: 0-0.35 wt.%, Zn: 0.2-0.6 wt.%, Zr: 0.08-0.15 wt.%, with the balance being Al and inevitable impurity elements. The weight percentage ratio of Cu to Li is not less than 1.45, and the sum of the weight percentages of Ag, Mg, and Zn is not less than 0.9%. The alloy extrusion material has good hot extrusion forming performance and at the same time has the characteristics of low density, high strength, high elastic modulus, and good plastic properties.

[0007] Although certain achievements have been made in the research and development of Al-Cu-Li series alloys in recent years, there is still significant room for improvement in the excellent matching of key properties such as low density, ultra-high strength, high modulus, high plasticity, corrosion resistance, and weldability. For example, in Al-Cu-Li series aluminum alloys, by adjusting the Cu / Li ratio, the contents of Cu and Li, and adding elements such as Mg, Ag, and Zn, the strength and elastic modulus can be increased, but the plasticity and welding performance of the alloy will be affected. Moreover, there are difficulties in matching low density with ultra-high strength, and high elastic modulus with ultra-high strength, which easily leads to the loss of the low-density advantage of aluminum-lithium alloys and results in a relatively low elastic modulus. Adding sufficient Sc element can significantly improve the welding performance, but in order to avoid the formation of harmful W phase, it is often necessary to greatly reduce the Cu content or strictly control the Sc element at a relatively low content level, making it difficult to exert the competitive advantages of ultra-high strength and good weldability of the alloy. Therefore, it is necessary to further research and develop new Al-Cu-Li-Sc series aluminum alloy materials with excellent matching of key properties such as low density, high modulus, ultra-high strength, high plasticity, corrosion resistance, and weldability. Summary of the Invention

[0008] Through a large amount of research and industrial practice, the present invention finds that the existing Al-Cu-Li-Sc series aluminum alloys mainly use Cu and Li as the main strengthening components and Sc as the microalloying strengthening component, with T1 phase and Al3Sc phase as the main strengthening phases. Their precipitation sequences and the types of main strengthening phases are relatively single, and it is easy to generate harmful W (AlCuSc) phase, making it difficult to obtain an ideal comprehensive performance matching of low density, high strength, high modulus, and weldability. If in the existing Al-Cu-Li-Sc series aluminum alloys, the addition amount of Cu element is reduced and the addition amount of Li element is increased, by optimizing the Cu / Li ratio and Sc addition amount of the alloy, while the alloy is further lightened, new δ' (Al3Li) phase and δ' / GPI / δ' composite precipitation phases will be added (the GPI region is the enrichment region of solute atoms Cu, and the δ' phase segregates on both sides of the GPI region to form a composite phase), which can significantly enhance the age-hardening response ability of the alloy and improve the elastic modulus of the alloy. At the same time, through composition design and process optimization, the generation of W phase is suppressed and eliminated, and a large number of fine and dispersed Al3(Sc,Zr) particles are precipitated, realizing an obvious improvement in the comprehensive performance of the material. Fine optimization design of the composition range and element ratios of the alloy is an important guarantee to ensure its excellent performance matching. Through reasonable design, the alloy can co-precipitate T1 phase and δ' / GPI / δ' composite structure precipitation strengthening phases during the aging process while ensuring light weight, and at the same time play the role of Sc element in refining the grains of the welded joint and suppressing hot cracks, so that the Al-Cu-Li-Sc series alloy of the present invention can obtain high strength and high modulus while maintaining good welding performance.

[0009] The object of the present invention is to overcome the deficiencies of the existing Al-Cu-Li series aluminum alloy materials in terms of the matching of low density-high strength-high modulus-weldability-comprehensive properties. On the basis of the existing alloys, through the optimized design of the composition and preparation and processing technology, further improve the matching of its comprehensive properties, and provide an ideal material selection of lightweight, ultra-high strength, high modulus and weldable Al-Cu-Li-Sc aluminum-lithium alloy for high-end manufacturing.

[0010] The first technical problem to be solved by the present invention is to propose a lightweight-ultra-high strength-high modulus-weldable aluminum-lithium alloy material. The second technical problem to be solved by the present invention is to propose a preparation method of the aluminum-lithium alloy material; the third technical problem to be solved by the present invention is to propose that the aluminum-lithium alloy material is processed into a final component through various surface treatments, stamping forming, and machining methods.

[0011] The present invention relates to a lightweight ultra-high strength high modulus weldable aluminum-lithium alloy material. The aluminum-lithium alloy contains: 3.20-3.49 wt% of Cu, 1.45-1.75 wt% of Li, 0.35-0.50 wt% of Mg, 0.20-0.40 wt% of Ag, 0.10-0.17 wt% of Sc, and at least one of Zr, Mn, Ti, Hf, and V elements with a total content not exceeding 0.60 wt%, and the balance is Al and inevitable impurities, where each impurity element ≤ 0.15 wt% and the total sum ≤ 0.40 wt%.

[0012] As the first preferred embodiment of the present invention, the aluminum-lithium alloy contains: 3.22-3.49 wt% of Cu, 1.46-1.70 wt% of Li, 0.36-0.48 wt% of Mg, 0.20-0.35 wt% of Ag, 0.11-0.16 wt% of Sc, and at least one of Zr, Mn, Ti, Hf, and V elements with a total content not exceeding 0.50 wt%, and the balance is Al and inevitable impurities.

[0013] As the second preferred embodiment of the present invention, the aluminum-lithium alloy contains: 3.25-3.48 wt% of Cu, 1.50-1.68 wt% of Li, 0.36-0.46 wt% of Mg, 0.23-0.34 wt% of Ag, 0.12-0.16 wt% of Sc, and at least one of Zr, Mn, Ti, Hf, and V elements with a total content not exceeding 0.40 wt%, and the balance is Al and inevitable impurities.

[0014] As the third preferred embodiment of the present invention, the aluminum-lithium alloy contains: 3.26-3.46 wt% of Cu, 1.52-1.67 wt% of Li.

[0015] As the fourth preferred embodiment of the present invention, in the aluminum-lithium alloy, the contents of Cu, Li, and Sc satisfy the relational expressions: 4.70 wt% ≤ Cu + Li ≤ 5.20 wt%, Cu / Li ≤ 2.25, 89Sc ≤ 5Cu / Li; preferably satisfy: 4.85 wt% ≤ Cu + Li ≤ 5.15 wt%.

[0016] As the fifth preferred embodiment of the present invention, in the aluminum-lithium alloy, the contents of Mg and Ag satisfy the relational expression: 0.65 wt% ≤ Mg + Ag ≤ 0.78 wt%.

[0017] As the sixth preferred embodiment of the present invention, the aluminum-lithium alloy contains at least one of the elements Zr, Mn, Ti, Hf, and V, wherein Mn is 0.15 - 0.35 wt%, Zr is 0.10 - 0.17 wt%, Ti is 0.01 - 0.10 wt%, Hf is 0.05 - 0.10 wt%, and V is 0.05 - 0.10 wt%.

[0018] As the seventh preferred embodiment of the present invention, the aluminum-lithium alloy contains: Mn 0.15 - 0.25 wt%, Zr 0.10 - 0.12 wt%.

[0019] As the eighth preferred embodiment of the present invention, in the aluminum-lithium alloy, the contents of Sc and Zr satisfy the relational expression: 0.22 wt% ≤ Sc + Zr ≤ 0.28 wt%.

[0020] As the ninth preferred embodiment of the present invention, the inevitable impurities contained in the above aluminum-lithium alloy include the elements inadvertently introduced as impurities during the manufacturing of the alloy ingot billet, and need to satisfy: Zn ≤ 0.12 wt%, Fe ≤ 0.12 wt%, Si ≤ 0.10 wt%, each of the other impurity elements ≤ 0.05 wt%, and the total ≤ 0.15 wt%. Preferably satisfy: Zn ≤ 0.10 wt%, Fe ≤ 0.10 wt%, Si ≤ 0.08 wt%.

[0021] The present invention also relates to a preparation method for producing the above aluminum-lithium alloy material. The process of the aluminum-lithium alloy deformed processed material can be described as "alloy preparation and melting - semi-continuous casting or spray forming to prepare ingot billet - homogenization heat treatment of the ingot billet - hot deformation processing - (intermediate annealing) - (cold deformation processing) - solution treatment - (pre-deformation or straightening) - aging treatment - supply product".

[0022] Among them, the preparation method for producing the aluminum-lithium alloy deformed processed material includes the following steps: (1) Manufacturing an ingot billet of the aluminum-lithium alloy material as described in the present invention; (2) Performing stage homogenization heat treatment on the obtained ingot billet; (3) Hot-deform the ingot blank into the required form of the processed material or into a pre-processed material by one or more hot deformation processing methods selected from rolling, extrusion, and forging; (4) Optionally, reheat the pre-processed material and cold-deform it into the required form of the processed material; (5) Perform solution heat treatment on the processed material; (6) Rapidly cool the processed material that has undergone solution heat treatment to room temperature; and (7) Perform natural aging or artificial aging treatment on the cooled processed material to obtain an alloy-aged state processed material.

[0023] Among them, in step (1), the ingot blank is manufactured by melting, degassing, removing inclusions, and semi-continuous casting or spray forming; during the melting process, an inert gas is used to protect the melt, with Li as the core to precisely control the element content. Through on-line composition detection and analysis, the ratio between alloy elements is quickly supplemented and adjusted, and the entire ingot blank manufacturing process is completed. In a preferred aspect, in step (1), an electromagnetic field, an ultrasonic field, or mechanical stirring is also applied at or near the mold.

[0024] In step (2), the stage homogenization heat treatment is required to gradually reduce the coarse second phase in the ingot blank and precipitate a large number of fine and dispersed phases, mainly including the following process steps: ① Stage I: Perform single-stage, multi-stage, or gradient heating homogenization heat treatment with a total time of 12 - 48 h in the range of 490 - 525 °C; ② Stage II: Perform single-stage or gradient heating homogenization heat treatment with a total time of 12 - 36 h in the range of 545 - 558 °C, and quickly cool to room temperature after completion; ③ Stage III: Perform single-stage, multi-stage, or gradient heating homogenization heat treatment with a total time of 16 - 36 h in the range of 300 - 335 °C.

[0025] In steps (3) and (4), the preheating temperature and re-heating temperature before each hot deformation processing are 440 - 470 °C, and the treatment time is 2 - 12 h; in a preferred aspect, in step (4), an intermediate annealing treatment of 400 - 420 °C / 0.5 - 4.5 h is also included between cold deformation passes.

[0026] In step (5), the solution heat treatment is required to further regulate the subgrain size and the proportion of recrystallized structure in the material according to performance requirements, and is carried out by the following methods selected from the group: ① Perform single-stage, two-stage, or multi-stage solution heat treatment with a total time of 0.5 - 5.0 h in the range of 505 - 545 °C; and ② Perform continuous heating solution heat treatment with a total time of 0.5 - 4.0 h in the range of 505 - 545 °C, and the heating rate ≤ 60 °C / min.

[0027] In step (6), the processed material is rapidly cooled to room temperature by a method selected from spray quenching with a cooling medium, immersion quenching, forced air cooling, and combinations thereof.

[0028] In step (7), the artificial aging heat treatment is carried out by a method selected from the following group: ① natural aging at room temperature for ≥ 72 h after completion of quenching and cooling; ② artificial aging treatment at a temperature in the range of 100 - 180°C within 2 h after completion of quenching and cooling, with a total time of 6 - 72 h; and ③ a combination of natural aging and artificial aging is adopted after completion of quenching and cooling, with the artificial aging temperature being 100 - 180°C and the time being 6 - 72 h.

[0029] Between steps (6) and (7), the following steps are further included: straightening treatment and / or pre - deformation treatment are carried out on the cooled processed material. The straightening treatment is carried out by a method selected from roller straightening, stretch straightening, stretch - bend straightening, and combinations thereof to improve the flatness of the processed material. The pre - deformation is carried out by a method selected from tension, compression, and combinations thereof to reduce the residual stress formed during quenching and cooling, facilitating subsequent processing and application.

[0030] By the preparation method of the present invention, the processed material is a wire, rod, tube, thin plate, thick plate, or forging product.

[0031] Among them, the density of the aluminum - lithium alloy material of the lightweight ultra - high - strength, high - modulus weldable aluminum - lithium alloy material of the present invention ≤ 2.67 g / cm 3 , the tensile strength ≥ 580 MPa, the elastic modulus ≥ 78.0 GPa, and the welding joint strength ≥ 390 MPa. Further preferably, the ≤ 2.65 g / cm 3 of the aluminum - lithium alloy material, the tensile strength ≥ 600 MPa, the elastic modulus ≥ 80.0 GPa, and the welding joint strength ≥ 410 MPa.

[0032] The present invention also provides a final load - bearing structural member, which is processed from the lightweight ultra - high - strength, high - modulus weldable aluminum - lithium alloy material through various surface treatments, stamping forming, and machining to obtain the final load - bearing structural member.

[0033] The beneficial effects of the present invention are as follows: (1) Through the compositional optimization design of Al-Cu-Li series aluminum-lithium alloys, based on the existing ultra-high strength Al-Cu-Li alloys, by "reducing Cu, increasing Li, adding Sc", and supplemented with a matching preparation method, while maintaining the ultra-high strength, plasticity and toughness of the alloy, the density of the alloy is significantly reduced, the elastic modulus and welding performance of the alloy are improved, and at the same time, the performance advantages of high specific strength and high specific modulus are obtained. In particular, through the compositional optimization design to reduce the W phase and combined with process optimization designs such as "medium-high-low" three-stage homogenization heat treatment, the organic coordination of the new alloy composition and preparation method is realized, the harmful insoluble W phase in the Al-Cu-Li-Sc series alloys is eliminated, and the alloying effects of Cu and Sc elements are efficiently exerted, making the new alloy material exhibit excellent comprehensive properties, which is an ideal material for various load-bearing structural parts and can meet the harsh requirements of various high-end manufacturing for lightweight and high-performance aluminum alloy materials.

[0034] (2) By adding Sc element in the present invention, it not only plays the role of refining the alloy grains and inhibiting recrystallization, but also plays the role of refining the grains of the welded joint and reducing the hot crack sensitivity of the welded joint. Thus, while the alloy has high strength and plasticity, the strength and welding stability of the welded joint are significantly improved, which is beneficial to promoting the lightweight development of high-end equipment fields such as aerospace and transportation, and has important social and economic benefits.

[0035] (3) The present invention adopts "medium-high-low" three-stage temperature-controlled homogenization heat treatment. In the first stage, through appropriate medium and high temperature heat treatment, the low melting point eutectic phase is fully dissolved back, and the alloy elements are as uniform as possible; in the second stage, through higher temperature heat treatment, the remaining harmful W phase is completely eliminated, and the alloy retains the saturated solid solubility through rapid cooling; in the third stage, through lower temperature heat treatment, a large number of Sc atoms dissolved in the aluminum matrix precipitate in the form of fine and dispersed Al3(Sc,Zr) particles, so as to fully exert the role of Sc element, which is beneficial to improving the plasticity of the alloy while increasing the strength and welding performance.

[0036] (4) The materials of the present invention have excellent performance, the preparation method is simple, practical, highly operable, easy to be industrialized and popularized, and has a promising market prospect. Description of the Drawings

[0037] Figure 1 It is a TEM morphology photo of the dispersed phase in the 23# alloy in Example 2 of the present invention.

[0038] Figure 2 (a) It is a SEM morphology photo of the remaining second phase in the 23# alloy in Example 2 of the present invention; Figure 2 (b) is Figure 2 An enlarged view of the position of the square box in (a).

[0039] Figure 3 (a) is the TEM morphology photo of the strengthening phase along the <110> Al zone axis in the 23# alloy in Embodiment 2 of the present invention; Figure 3 (b) is the TEM morphology photo of the strengthening phase along the <100> Al zone axis in the 23# alloy in Embodiment 2 of the present invention. Specific Embodiments

[0040] The technical solutions of the present invention will be further described in detail below in conjunction with embodiments.

[0041] Embodiment 1 Alloy extrusion plates and strips were prepared on a laboratory scale to prove the principle of the present invention. The composition of the experimental alloy is shown in Table 1.

[0042] A φ235mm round ingot was prepared by alloy melting, degassing, inclusion removal well-known in the industry and simulating semi-continuous casting conditions. The stage homogenization heat treatment system of the ingot was selected as (518 ± 3°C / 28h) + (550 ± 3°C / 32h) + (308 ± 3°C / 32h), and air-cooled. After peeling, milling, and sawing, an extrusion blank with a φ193mm specification was obtained. The blank was preheated at 450 ± 10°C for 6h, and an extrusion deformation was carried out to obtain a 25.4 × 102mm specification plate and strip. The extrusion temperature was controlled at about 435°C. The extruded plate and strip were loaded into an air furnace at 500°C, and a continuous heating solution heat treatment with a temperature of 515 - 540°C and a total time of 150min was carried out. After water quenching, a stretching and straightening treatment with 2.8 - 3.3% was immediately carried out, and then aging treatments at 150 - 165°C / 22 - 28h were carried out respectively according to the alloy characteristics.

[0043] Samples were cut according to relevant methods, and the alloy was tested for density (GB / T 1423), tensile properties (GB / T 16865), elastic modulus (GB / T 22315), exfoliation corrosion (GB / T22639), intergranular corrosion test (GB / T7998), and tensile properties of welded joints (GB / T 2651) according to relevant test standards to evaluate the common performance indicators of the alloy. The results are shown in Table 2.

[0044] Table 1 Composition of the experimental alloy

[0045] * In this embodiment, for the Zn element with specific values given, it is an added element; those not marked are not added and are controlled according to the content of impurity elements.

[0046] Table 2 Performance test results of the experimental alloy

[0047] As can be seen from the table, alloys 1#, 2#, 3#, 4#, 5#, 6#, 7#, 8#, 9#, 10#, 11#, and 12# all have a good match of density - strength - plasticity - elastic modulus - welded joint strength - corrosion resistance: the density does not exceed 2.67 g / cm 3 , the tensile strength remains above 600 MPa, the elongation after fracture is higher than 11.0%, the elastic modulus is higher than 80.0 GPa, the welded joint strength is higher than 420 MPa, the exfoliation corrosion grade of the alloy is not lower than EA grade, the intergranular corrosion grade is pitting corrosion, the specific strength is higher than 235 MPa·cm 3 / g, and the specific modulus is higher than 30 GPa·cm 3 / g. However, the properties of alloys 13#, 14#, 15#, 16#, 17#, 18#, 19#, 20#, 21#, and 22# do not meet the good match of density - strength - plasticity - elastic modulus - fracture toughness - fatigue performance - corrosion resistance. Among them, alloy 13# has relatively high contents of Cu, Sc, and Mg and a relatively low Li content, with a relatively high density, low plasticity, decreased strength, elastic modulus, and welded joint strength, and decreased corrosion resistance; alloy 14# has relatively low Li and Sc contents and a relatively high Mg content, with an increased density, low strength and elastic modulus, and decreased welded joint strength; alloy 15# has relatively high Cu and Mg contents and a relatively low Li content, and Zn element is added, with an increased density, decreased strength, low elastic modulus, and decreased welded joint strength and corrosion resistance; alloy 16# has relatively low Cu and Ag contents, no Sc element, and a relatively large amount of Zn element added, with severely decreased strength, plasticity, welded joint strength, and corrosion resistance; alloy 17# has relatively low Cu and Ag contents and a relatively large amount of Zn element added, with decreased corrosion resistance and severely decreased strength and welded joint strength; alloy 18# has relatively low Cu and Ag contents, relatively high Li and Mg contents, and a relatively large amount of Zn element added, with decreased corrosion resistance, severely decreased strength and welded joint strength, and increased elastic modulus; alloy 19# has a relatively low Cu content, no Sc element, and Zn element added, with decreased strength, plasticity, welded joint strength, and corrosion resistance; alloy 20# has a relatively low Cu content, no Sc and Ag elements, and a small amount of Zn element added, with significantly decreased strength, plasticity, welded joint strength, and corrosion resistance. Alloy 21# has a relatively low Li content, relatively high Cu and Ag contents, no Sc element added, with an increased density and decreased plasticity, elastic modulus, welded joint strength, and corrosion resistance. Alloy 22# has a relatively low Li content, relatively high Mg content, and a small amount of Zn element added, with an increased density and decreased strength, elastic modulus, and welded joint strength.

[0048] Example 2 The new alloy sheet is prepared on the pilot-plant platform, and the alloy composition is shown in Table 3. Under the conditions of using a covering agent and argon to protect the melt, a flat ingot with a thickness specification of 100 mm is prepared through alloy melting, degassing, inclusion removal, and simulating semi-continuous casting conditions well-known in the industry. The ingots are respectively subjected to three-stage (495 ± 5 °C / 8 h + 520 ± 5 °C / 24 h) + (552 ± 5 °C / 28 h) + (310 ± 3 °C / 36 h) homogenization heat treatment and air-cooled. After peeling, milling, and sawing, a rolling blank with a thickness specification of 68 mm is obtained. The blank is preheated at 452 ± 5 °C for 8 h, the initial rolling temperature is 440 °C, and it is first rolled 2 passes along the width direction of the flat ingot to 45 mm, and then subjected to an intermediate annealing treatment at 380 ± 5 °C for 2 h. Then, it is rolled in the reverse direction and rolled along the length direction of the flat ingot to a thickness of about 10 mm. The sheet is loaded into an air furnace at 500 °C and subjected to solution heat treatment at 520 °C / 30 min + 530 °C / 90 min, immediately water-quenched and then subjected to a 2.9% stretch straightening treatment. Subsequently, aging treatment at 155 °C for 23 h is carried out according to the alloy characteristics.

[0049] Samples are cut according to relevant methods, and the alloy is subjected to density (GB / T 1423), tensile properties (GB / T 16865), elastic modulus (GB / T 22315), exfoliation corrosion (GB / T22639), intergranular corrosion test (GB / T7998), and tensile properties of welded joints (GB / T 2651) in accordance with relevant test standards for evaluation as the common performance indicators of the alloy. The results are shown in Table 4.

[0050] Table 3 Experimental alloy composition

[0051] Table 4 Performance test results of the experimental alloy

[0052] It can be seen from Table 4 that the 23# alloy of the present invention exhibits good strength and plasticity, high strength of welded joints and corrosion resistance matching. Compared with the V-1464 alloy (24# alloy) prepared under the same conditions, the alloy of the present invention shows obvious comprehensive performance advantages, with higher strength and plasticity, specific strength, and strength of welded joints.

[0053] Figure 1 The TEM morphology photos of the dispersed phase in the 23# alloy are given. It can be seen from the figure that a large number of fine and dispersed Al3(Sc,Zr) particles are precipitated.

[0054] Figure 2The SEM morphology photos of the residual second phase in the 23# alloy are given. It can be seen from the figure that no coarse W phase is found in the alloy, and the residual second phase is the Fe / Mn-rich phase. After testing, the elemental composition of this second phase is: Al 81.39 at.%, Cu 10.19 at.%, Fe 4.55 at.%, Mn 3.97 at.%.

[0055] Figure 3 The TEM morphology photos of the age-hardening phase in the 23# alloy are given. It can be clearly seen that a large number of T1 phase, δ' phase and δ' / GPI / δ' composite strengthening phases are formed in the alloy, and Al3(Sc,Zr) particles are observed. No coarse W phase is found, which is beneficial for the alloy to obtain high strength and plasticity, high strength of welded joints and other properties.

[0056] Example 3 Under industrial conditions, alloy plates and strips are prepared, and the component composition of the alloy is shown in Table 5. Under the conditions of using a covering agent and argon to protect the melt, an ingot with a diameter of φ426mm is prepared by alloy melting, degassing, inclusion removal, and semi-continuous casting well-known in the industry. The homogenization heat treatment system for the 24# and 25# alloy ingots is selected as (520±3°C / 24h)+(552±3°C / 36h)+(continuous heating from 300~330±3°C for 20h), with air cooling. After peeling, milling, and sawing, an extrusion blank with a diameter of φ394mm is obtained. The blank is preheated at 445±10°C for 8h, and a large-sized L-shaped profile with a wall thickness of 25.4 is obtained by extrusion deformation. The extrusion temperature is controlled at about 435°C±5°C. The profile is loaded into an air furnace at 490°C, and a solution heat treatment is carried out at a temperature range of 520~530°C for 120~150min under a suitable system. Immediately after water quenching, a stretching and straightening treatment of 2.8~3.0% is carried out, and then age treatment at 155°C / 23~25h is carried out according to the characteristics of the alloy respectively, so that the alloy material obtains better comprehensive performance matching.

[0057] Samples are cut according to relevant methods, and the alloy is tested for density (GB / T 1423), tensile properties (GB / T 16865), elastic modulus (GB / T 22315), exfoliation corrosion (GB / T 22639), intergranular corrosion test (GB / T 7998) and tensile properties of welded joints (GB / T 2651) according to relevant test standards to evaluate the common performance indicators of the alloy. The results are shown in Table 6.

[0058] Table 5 Experimental alloy composition

[0059] Table 6 Performance test results of experimental alloys

[0060] As can be seen from Table 6, the 25# alloy of the present invention has a low density, a high elastic modulus, a high strength-plasticity combination, and a good match of welding performance and corrosion resistance; compared with the 2195 alloy (26# alloy) prepared under the same conditions, the alloy of the present invention exhibits obvious comprehensive performance advantages, having a lower density, a higher elastic modulus, plasticity, welding joint strength, corrosion resistance, specific strength and specific modulus.

Claims

1. A lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material, characterized in that, The aluminum-lithium alloy contains: 3.20 - 3.49 wt% of Cu, 1.45 - 1.75 wt% of Li, 0.35 - 0.50 wt% of Mg, 0.20 - 0.40 wt% of Ag, 0.10 - 0.17 wt% of Sc, and at least one of Zr, Mn, Ti, Hf, and V with a total content not exceeding 0.60 wt%. The balance is Al and unavoidable impurities, where each impurity element is ≤ 0.15 wt% and the total sum is ≤ 0.40 wt%.

2. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 1, characterized in that, The aluminum-lithium alloy contains: 3.22 - 3.49 wt% of Cu, 1.46 - 1.72 wt% of Li, 0.36 - 0.48 wt% of Mg, 0.20 - 0.35 wt% of Ag, 0.11 - 0.16 wt% of Sc, and at least one of Zr, Mn, Ti, Hf, and V with a total content not exceeding 0.50 wt%. The balance is Al and unavoidable impurities.

3. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 2, characterized in that, The aluminum-lithium alloy contains: 3.25 - 3.48 wt% of Cu, 1.50 - 1.68 wt% of Li, 0.36 - 0.46 wt% of Mg, 0.23 - 0.34 wt% of Ag, 0.12 - 0.16 wt% of Sc, and at least one of Zr, Mn, Ti, Hf, and V with a total content not exceeding 0.40 wt%. The balance is Al and unavoidable impurities.

4. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 3, characterized in that The aluminum-lithium alloy contains: 3.26 - 3.46 wt% of Cu, 1.52 - 1.67 wt% of Li.

5. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 1, characterized in that, In the aluminum-lithium alloy, the contents of Cu, Li, and Sc satisfy the relationships: 4.70 wt% ≤ Cu + Li ≤ 5.20 wt%, Cu / Li ≤ 2.25, 89Sc ≤ 5Cu / Li.

6. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 5, characterized in that, In the aluminum-lithium alloy, the contents of Cu and Li satisfy the relationship: 4.85 wt% ≤ Cu + Li ≤ 5.15 wt%.

7. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 2, characterized in that, In the aluminum-lithium alloy, the contents of Mg and Ag satisfy the relationship: 0.65 wt% ≤ Mg + Ag ≤ 0.78 wt%.

8. The light-weight, ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 2, characterized in that, The aluminum-lithium alloy contains at least one of Zr, Mn, Ti, Hf, and V, where 0.15 - 0.35 wt% of Mn, 0.10 - 0.17 wt% of Zr, 0.01 - 0.10 wt% of Ti, 0.05 - 0.10 wt% of Hf, and 0.05 - 0.10 wt% of V.

9. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 8, characterized in that, The aluminum-lithium alloy contains: 0.15 - 0.25 wt% of Mn, 0.10 - 0.12 wt% of Zr.

10. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 8, characterized in that, In the aluminum-lithium alloy, the contents of Sc and Zr satisfy the relationship: 0.22 wt% ≤ Sc + Zr ≤ 0.28 wt%.

11. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 2, characterized in that, The unavoidable impurities include elements inadvertently introduced as impurities during the manufacturing of alloy ingots, where Zn ≤ 0.12 wt%, Fe ≤ 0.12 wt%, Si ≤ 0.10 wt%, each of the other impurity elements is ≤ 0.05 wt%, and the total sum is ≤ 0.15 wt%.

12. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 11, characterized in that, The aluminum-lithium alloy contains: Zn ≤ 0.10 wt%, Fe ≤ 0.10 wt%, Si ≤ 0.08 wt%.

13. A method for producing a deformed aluminum-lithium alloy material, characterized in that, It includes the following steps: (1) Manufacturing an ingot blank of the aluminum-lithium alloy material described in any one of claims 1 to 12; (2) Conducting stage-controlled temperature homogenization heat treatment on the obtained ingot blank; (3) By one or more hot deformation processing methods selected from rolling, extrusion, and forging, hot-deforming the ingot blank into the required processed material form, or hot-deforming it into a pre-processed material; (4) Optionally, reheating the pre-processed material and cold-deforming it into the required processed material form; (5) Conducting solution heat treatment on the processed material; (6) Rapidly cooling the processed material subjected to solution heat treatment to room temperature; and (7) Conducting natural aging or artificial aging treatment on the cooled processed material to obtain an alloy-aged processed material.

14. The method according to claim 13, wherein In step (1), the ingot blank is manufactured by means of melting, degassing, removing inclusions, and semi-continuous casting or spray forming; during the melting process, an inert gas is used to protect the melt, the element content is precisely controlled with Li as the core, and through on-line composition detection and analysis, the ratio between alloy elements is quickly supplemented and adjusted to complete the entire ingot blank manufacturing process.

15. The method according to claim 13, wherein In step (1), applying an electromagnetic field, an ultrasonic field, or mechanical stirring at or near the mold.

16. The method according to claim 13, wherein In step (2), the stage-controlled temperature homogenization heat treatment mainly includes the following process steps: ① Stage I: Conducting single-stage, multi-stage, or gradient heating homogenization heat treatment with a total time of 12 to 48 h within the range of 490 to 525 °C; ② Stage II: Conducting single-stage or gradient heating homogenization heat treatment with a total time of 12 to 36 h within the range of 545 to 558 °C, and rapidly cooling to room temperature after completion; ③ Stage III: Conducting single-stage, multi-stage, or gradient heating homogenization heat treatment with a total time of 16 to 36 h within the range of 300 to 335 °C.

17. The method according to claim 13, wherein In steps (3) and (4), the preheating temperature and reheating temperature before each hot deformation processing are 440 to 470 °C, and the treatment time is 2 to 12 h.

18. The method according to claim 13, wherein In step (4), an intermediate annealing treatment of increasing 400 to 420 °C / 0.5 to 4.5 h is also included between cold deformation passes.

19. The method according to claim 13, characterized in that, In step (5), the solution heat treatment is carried out by a method selected from the following group: ① Conducting single-stage, two-stage, or multi-stage solution heat treatment with a total time of 0.5 to 5.0 h within the range of 505 to 545 °C; and ② Conducting continuous heating solution heat treatment with a total time of 0.5 to 4.0 h within the range of 505 to 545 °C, and the heating rate ≤ 60 °C / min.

20. The method according to claim 13, wherein In step (6), the processed material is rapidly cooled to room temperature by a method selected from spray quenching with a cooling medium, immersion quenching, strong wind cooling, and their combinations.

21. The method according to claim 13, characterized in that, In step (7), the artificial aging heat treatment is carried out by a method selected from the following group: ① Conducting natural aging at room temperature after quenching and cooling, with a time ≥ 72 h; ② Conducting artificial aging treatment within the range of 100 to 180 °C within 2 h after quenching and cooling, with a total time of 6 to 72 h; and ③ After quenching and cooling, a combination of natural aging and artificial aging is adopted, with the artificial aging temperature of 100 to 180 °C and the time of 6 to 72 h.

22. The method according to claim 13, wherein Between steps (6) and (7), the following steps are further included: straightening treatment and / or pre-deformation treatment are carried out on the cooled workpiece. The straightening treatment is carried out by means of roller straightening, stretch straightening, stretch-bending straightening and their combination to improve the flatness of the workpiece. The pre-deformation is carried out by means of stretching, compression and their combination to reduce the residual stress formed by quenching and cooling, which is convenient for subsequent processing and application.

23. The method according to claim 22, wherein The workpiece is a wire, rod, tube, thin plate, thick plate or forging product.

24. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to any one of claims 1 to 12, or the lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material manufactured by the method according to any one of claims 13 to 23, characterized in that, The density of the aluminum-lithium alloy material is ≤ 2.67 g / cm 3 , the tensile strength is ≥ 580 MPa, the elastic modulus is ≥ 78.5 GPa, and the strength of the welded joint is ≥ 390 MPa.

25. The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to claim 24, characterized in that, The density of the aluminum-lithium alloy material ≤ 2.65 g / cm 3 , the tensile strength ≥ 600 MPa, the elastic modulus ≥ 80.0 GPa, and the strength of the welded joint ≥ 410 MPa.

26. A final load-bearing structural member, characterized in that, The lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material according to any one of claims 1 to 12, 24, 25 or the lightweight ultra-high strength and high modulus weldable aluminum-lithium alloy material manufactured by the method according to any one of claims 13 to 23 is processed into a final load-bearing structural member through various surface treatments, stamping forming and machining.

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