A lightweight super-high-strength high-modulus weldable aluminum-lithium alloy material and a preparation method thereof

Abstract

The application discloses a kind of lightweight superhigh-strength high-modulus weldable aluminum lithium alloy material and preparation method thereof.The aluminum lithium alloy contains: Cu 3.20~3.49wt%, Li 1.45~1.75wt%, Mg 0.35~0.50wt%, Ag 0.20~0.40wt%, Sc 0.11~0.17wt%, and total content of at least one of Zr, Mn, Ti, Hf, V elements is not more than 0.60wt%, the rest is Al and inevitable impurities, wherein impurity element is ≤0.15wt%, total is ≤0.40wt%.The preparation method of the alloy deformation processing material includes the following steps: (1) manufacturing aluminum lithium alloy ingot blank; (2) homogenization heat treatment; (3) ingot blank is hot worked into the processing material required, or pre-processing material; (4) optionally, pre-processing material is reheated, and cold deformation is processed into the processing material required; (5) the processing material is solid solution heat treated; (6) the processing material is rapidly cooled to room temperature after solid solution heat treatment; (7) the processing material is aged. The aluminum lithium alloy material shows low density-high strength-high modulus-weldable and other excellent comprehensive performance.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloys and their preparation and processing technology, and particularly relates to Al-Cu-Li series aluminum alloys. More specifically, this invention relates to a lightweight, ultra-high strength, high modulus, weldable Al-Cu-Li-Sc aluminum alloy material and its preparation method. Background Technology

[0002] Aluminum alloys are lightweight (pure Al has a density of 2.70 g / cm³). 3 With its high specific strength, ease of processing, and low cost, aluminum-lithium alloy has a wide range of applications in aviation, aerospace, high-speed rail, automobiles, and shipbuilding. As a new generation of lightweight structural materials, aluminum-lithium alloys have shown enormous application prospects and development potential in high-end equipment manufacturing fields such as aerospace, defense, and transportation. With the increasing demand for weight reduction in modern aircraft and launch vehicles, traditional aluminum alloys can no longer meet the growing requirements for high specific strength and high specific modulus. Aluminum-lithium alloys, due to their unique performance advantages, are gradually becoming the preferred choice for key structural materials. Lithium, as the lightest metallic element, can significantly reduce the density of aluminum alloys; adding 1% lithium can reduce the alloy density by about 3% while increasing the elastic modulus by about 6%. This excellent lightweighting effect makes it irreplaceable in the aerospace field. In commercial aircraft applications, the fuel economy benefits brought by structural weight reduction are significant, driving the development of aluminum-lithium alloys towards higher performance and wider applications.

[0003] Currently, the most widely used ultra-high strength Al-Cu-Li alloys, such as 2195 aluminum-lithium alloy and the newly developed 2060 and 2065 aluminum-lithium alloys, utilize high Cu / Li ratios (Cu content typically greater than 3.5 wt%, Li content less than 1.5 wt%) and nano-reinforcing phases such as T1 (Al2CuLi) and θ' (Al2Cu) to achieve tensile strengths of around 600 MPa. Their specific strength is approximately 15-20% higher than that of traditional 2xxx and 7xxx series aluminum alloys. These alloys have been successfully applied to key load-bearing structures of next-generation aircraft and launch vehicles; for example, the propellant tanks of the Space Shuttle and launch vehicles use ultra-high strength 2195 alloy, achieving significant weight reduction. However, this high copper content design also brings significant weldability problems, severely restricting its application in large welded structures. During welding, the high copper content leads to the formation of low-melting-point eutectic phases (such as Al-Cu binary eutectic, with a melting point of approximately 548℃), significantly increasing the susceptibility to liquefaction cracking in the heat-affected zone. Simultaneously, the welding thermal cycle causes the re-dissolution and coarsening of the strengthening phases, resulting in welded joint strength typically only reaching 60% of the base metal's strength. This technical bottleneck makes it difficult for existing ultra-high-strength aluminum-lithium alloys to meet the manufacturing requirements of large welded structural components. Furthermore, these alloys have a relatively high density, reaching 2.70 g / cm³. 3and the elastic modulus is not high enough, only about 77 GPa, which is difficult to meet the development needs of lightweight and high performance of aerospace vehicles. It is urgent to develop new lightweight high-performance aluminum lithium alloys with good weldability.

[0004] To improve the welding performance of aluminum lithium alloy, domestic and foreign research teams have tried various technical approaches, among which micro-alloying modification is considered one of the most promising solutions. Among the many micro-alloying elements, scandium (Sc) is of great concern due to its unique physical and metallurgical properties. Sc can form Al3Sc phase at the nanoscale in aluminum alloy, and when combined with Zr, it can also form Al3(Sc, Zr) dispersion phase with better strengthening effect. It significantly refines the as-cast grains during solidification as a heterogeneous nucleation site; at the same time, it inhibits dislocation movement and grain boundary migration through pinning effect during subsequent heat treatment or hot deformation, effectively hindering the recrystallization process; in addition, the addition of Sc can refine the weld grain and reduce the tendency of welding hot cracking, and the Al3Sc dispersion phase can reduce the softening of the heat-affected zone of the welded joint. At the same time, Sc can also form Al3(Li, Sc) strengthening phase with Li, further enhancing the strength of the alloy. Studies have shown that adding a small amount of Sc can effectively improve the welding performance, strength, plasticity, corrosion resistance and welding performance of aluminum lithium alloy. However, in the Al-Cu-Li-Sc alloy system with high Cu content, Sc will preferentially react with Cu to form W phase (Al8Cu4Sc), which not only consumes effective Sc elements and reduces its strengthening effect, but also easily coarsens at high temperature, becoming a crack source, damaging the plasticity, fracture toughness, fatigue crack propagation rate and corrosion resistance of the alloy. More seriously, W phase will significantly coarsen during welding thermal cycle, further deteriorating the performance of the welded joint, which seriously restricts the application effect of Sc element in ultra-high strength aluminum lithium alloy.

[0005] In recent years, some studies have found that special preparation processes can improve the performance of Sc-containing aluminum-lithium alloys. For example, patent document CN117165880A discloses a process for improving the strength of a Sc-containing aluminum-lithium alloy. The 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. The invention directly deforms 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 improvement of the strength of the Sc-containing Al-Cu-Li alloy. Another study reduces the Cu content and strictly controls the addition amount of Sc (actual addition amount controlled within 0.1 wt%), and forms Al3(Sc, Zr) particles by combining with Zr to refine the grain and inhibit recrystallization, and obtains performance improvement. For example, patent document CN110546288A discloses a low-density aluminum-copper-lithium alloy product, the 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.%, so 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, 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 total ≤0.15, the rest is aluminum, the 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 grain.Patent document CN117684060A discloses an aluminum-lithium alloy with good damage resistance and a preparation method, the basic component range is 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.%, the balance is Al, the mass ratio of Cu / Li is 2.23-4.28, the alloy adds appropriate Sc and Zr elements, the Al3(Sc, Zr) particles formed can effectively hinder grain boundary migration and inhibit recrystallization growth during solid solution treatment, so as to ensure that the alloy has high strength, high heat resistance and good cold plastic processability, and at the same time, controlling the mass ratio of Cu / Li can significantly improve the fatigue crack propagation rate.

[0006] For the performance improvement and lightweight of aluminum lithium alloy, in recent years, some studies have found that by controlling the total amount of Li+Cu, adding Zr+Mn jointly, supplemented by adding trace elements such as Mg, Zn and Ag, the strength and toughness of the alloy can be improved. Special preparation process can be used to improve the performance of Sc-containing aluminum lithium alloy. For example: patent document CN102021457A discloses a high strength and toughness aluminum lithium alloy and its preparation method, the basic component 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≤0.05 wt.%, total amount≤0.15 wt.%, the balance is Al, the total amount of Li+Cu of the alloy is close to 5 wt.%, Zr+Mn is added jointly, thereby greatly reducing the anisotropy of the alloy, and the addition of trace elements such as Mg, Zn and Ag improves the strength and toughness of the alloy. It has been found that by controlling the Cu / Li ratio and the Ag+Mg+Zn content, low density, high strength and high elastic modulus can be obtained. For example: patent document CN114086044A discloses a lightweight high-strength Al-Cu-Li alloy extrusion material and its processing method, the basic component 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.%, the balance is Al and unavoidable impurity elements, the weight percentage ratio of Cu and Li is not less than 1.45, 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, low density, high strength, high elastic modulus and good plasticity performance characteristics are obtained.

[0007] Although the research and development of Al-Cu-Li series alloys has made some achievements in recent years, there is still a lot of 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, the strength and elastic modulus can be improved by adjusting the Cu / Li ratio, Cu and Li content, and adding Mg, Ag, and Zn elements, but the plasticity and weldability of the alloy will be affected, and there is a matching problem between low density and ultra-high strength, high elastic modulus and ultra-high strength. The low density advantage of aluminum lithium alloy is easily lost, and the elastic modulus is low. Adding enough Sc element can significantly improve the welding performance, but in order to avoid the formation of harmful W phase, the Cu content needs to be greatly reduced or the Sc element needs to be strictly controlled at a low content level, and the competitive advantage of the alloy's ultra-high strength and good weldability is difficult to play. 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

[0008] The present application is based on a large number of research and industrial practice, and the existing Al-Cu-Li-Sc series aluminum alloy mainly uses Cu and Li as the main strengthening component, and Sc as the micro-alloying strengthening component. The main strengthening phases are T1 phase and Al3Sc phase, the precipitation sequence and the main strengthening phase type are relatively simple, and harmful W (AlCuSc) phase is easily produced, which makes it difficult to obtain ideal low density-high strength-high modulus-weldable comprehensive performance matching. If the addition amount of Cu element is reduced and the addition amount of Li element is increased in the existing Al-Cu-Li-Sc series aluminum alloy, and the Cu / Li ratio and Sc addition amount of the alloy are optimized, the alloy will be further lightened, and the δ' (Al3Li) phase and δ' / GPI / δ' composite precipitation phase (GPI zone is the enrichment zone of solute atoms Cu, and δ' phase is aggregated on both sides of GPI zone to form a composite phase) will be added, which can significantly enhance the aging strengthening response ability of the alloy and improve the elastic modulus of the alloy. At the same time, the generation of W phase is inhibited and reduced by combining composition design and process optimization, a large number of fine and dispersed Al3(Sc,Zr) particles are precipitated, and the comprehensive performance of the material is obviously improved. Fine optimization design of the composition range and element ratio of the alloy is an important guarantee to obtain excellent performance matching. Through reasonable design, the alloy can synergistically precipitate T1 phase and δ' / GPI / δ' composite structure precipitation strengthening phase during aging process, and Sc element can refine the grain size of welding joint and inhibit thermal cracking, so that the Al-Cu-Li-Sc series alloy of the present application can obtain high strength and high modulus while maintaining good welding performance.

[0009] The present application aims to overcome the shortcomings of the current Al-Cu-Li series aluminum alloy material in low density-high strength-high modulus-weldable-comprehensive performance matching, and further improve the comprehensive performance matching by optimizing the composition and preparation process on the basis of the current alloy, thereby providing an ideal material of lightweight-ultra-high strength-high modulus and weldable Al-Cu-Li-Sc aluminum lithium alloy for high-end manufacturing industry.

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

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

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

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

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

[0015] As a fourth preferred scheme of the present application, in the aluminum-lithium alloy, the contents of Cu, Li, and Sc satisfy the relationship: 4.70wt%≤Cu+Li≤5.20wt%, Cu / Li≤2.25, 89Sc≤5Cu / Li; preferably, 4.85wt%≤Cu+Li≤5.15wt% is satisfied.

[0016] As a fifth preferred scheme of the present application, in the aluminum-lithium alloy, the contents of Mg and Ag satisfy the relationship: 0.65wt%≤Mg+Ag≤0.78wt%.

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

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

[0019] As an eighth preferred scheme of the present application, in the aluminum-lithium alloy, the contents of Sc and Zr satisfy the relationship: 0.22wt%≤Sc+Zr≤0.28wt%.

[0020] As a ninth preferred scheme of the present application, the unavoidable impurities contained in the above-mentioned aluminum-lithium alloy include elements unintentionally brought in as impurities during the process of manufacturing the alloy ingot, and need to satisfy: Zn≤0.12wt%, Fe≤0.12wt%, Si≤0.10wt%, and each of other impurity elements≤0.05wt%, and the total≤0.15wt%. Preferably, Zn≤0.10wt%, Fe≤0.10wt%, and Si≤0.08wt% is satisfied.

[0021] The present application also relates to a production method of the above-mentioned aluminum-lithium alloy material. The process of the aluminum-lithium alloy wrought material can be described as "alloy preparation and melting-semi-continuous casting or spray forming to prepare ingot-uniformizing heat treatment of the ingot-thermal deformation processing-(intermediate annealing)-(cold deformation processing)-solid solution treatment-(pre-deformation or straightening)-aging treatment-delivery product".

[0022] The production method of the aluminum-lithium alloy wrought material includes the following steps:

[0023] (1) manufacturing the ingot of the aluminum-lithium alloy material as described in the present application;

[0024] (2) performing stage uniformizing heat treatment on the obtained ingot;

[0025] (3) hot deforming the ingot into a desired form of a processed material or into a pre-processed material by one or more hot deformation processes selected from rolling, extrusion and forging;

[0026] (4) optionally re-heating the pre-processed material and cold deforming it into a desired form of a processed material;

[0027] (5) solution heat treating the processed material;

[0028] (6) rapidly cooling the solution heat treated processed material to room temperature; and

[0029] (7) naturally aging or artificially aging the cooled processed material to obtain an aged processed material of the alloy.

[0030] In step (1), the ingot is manufactured by melting, degassing, removing inclusions and semi-continuous casting or injection molding. In the melting process, the melt is protected by inert gas, the content of elements is precisely controlled with Li as the core, the proportioning between alloy elements is quickly adjusted by online composition detection and analysis, and the whole ingot manufacturing process is completed. In a preferred aspect, in step (1), an electromagnetic field, an ultrasonic field or mechanical stirring is applied at or near the crystallizer.

[0031] In step (2), the stage homogenization heat treatment needs to reduce the coarse second phase in the ingot and precipitate a large number of fine dispersed phases, mainly including the following process steps: ① Stage I: single-stage or multi-stage or gradient temperature homogenization heat treatment at 490-525℃ for a total time of 12-48 h; ② Stage II: single-stage or gradient temperature homogenization heat treatment at 545-558℃ for a total time of 12-36 h, and then rapidly cooling to room temperature; ③ Stage III: single-stage or multi-stage or gradient temperature homogenization heat treatment at 300-335℃ for a total time of 16-36 h.

[0032] In steps (3) and (4), the preheating temperature and the re-heating temperature before each hot deformation process are 440-470℃, and the treatment time is 2-12 h. In a preferred aspect, in step (4), an intermediate annealing treatment at 400-420℃ / 0.5-4.5 h is further included between cold deformation passes.

[0033] In step (5), the solution heat treatment needs to be further regulated according to the performance requirements of the subgrain size and the proportion of recrystallized structure in the material, and is carried out by a method selected from the following group: 1) single-stage, double-stage or multi-stage solution heat treatment in the range of 505-545 DEG C for a total time of 0.5-5.0 h; and 2) continuous heating solution heat treatment in the range of 505-545 DEG C for a total time of 0.5-4.0 h, with a heating rate of ≤60 DEG C / min.

[0034] In step (6), the processed material is rapidly cooled to room temperature using a method selected from the group consisting of cooling medium spraying quenching, immersion quenching, strong air cooling and combinations thereof.

[0035] 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 after quenching cooling, for a time of ≥72 h; 2) artificial aging treatment at 100-180 DEG C within 2 h after quenching cooling, for a total time of 6-72 h; and 3) a combination of natural aging and artificial aging after quenching cooling, with an artificial aging temperature of 100-180 DEG C and a time of 6-72 h.

[0036] Between steps (6) and (7), the following step is further included: straightening treatment and / or pre-deformation treatment is carried out on the cooled processed material, the straightening treatment is carried out using a method selected from the group consisting of roll straightening, tensile straightening, tensile bending straightening and combinations thereof to improve the flatness of the processed material, and the pre-deformation is carried out using a method selected from the group consisting of stretching, compression and combinations thereof to reduce the residual stress formed by quenching cooling, facilitating subsequent processing and application.

[0037] Through the preparation method disclosed in the present application, the processed material is a wire, a rod, a pipe, a sheet, a plate or a forged product.

[0038] In the present application, the density of the aluminum-lithium alloy material of the lightweight ultrahigh-strength high-modulus weldable aluminum-lithium alloy material is ≤2.67 g / cm 3 , the tensile strength is ≥580 MPa, the elastic modulus is ≥78.0 GPa, and the strength of the welded joint is ≥390 MPa. 3 , the tensile strength is ≥600 MPa, the elastic modulus is ≥80.0 GPa, and the strength of the welded joint is ≥410 MPa.

[0039] The present application also provides a final load-bearing structural member, which is processed into a final load-bearing structural member by various surface treatments, stamping forming and machining from the lightweight ultrahigh-strength high-modulus weldable aluminum-lithium alloy material.

[0040] The present application has the following beneficial effects:

[0041] (1) Through the composition optimization design of Al-Cu-Li series aluminum lithium alloy, on the basis of existing super high strength Al-Cu-Li alloy, by means of "reducing Cu, increasing Li, adding Sc", and with the matching preparation method, while maintaining the super high strength and 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 the performance advantages of high specific strength and high specific modulus are obtained. Especially, by reducing the W phase through composition optimization design and combining with the process optimization design of "medium-high-low" three-stage homogenization heat treatment, the organic cooperation of the new alloy composition and the preparation method is realized, the harmful insoluble W phase in the Al-Cu-Li-Sc series alloy is eliminated, the alloying effect of Cu and Sc elements is efficiently exerted, so that the new alloy material exhibits excellent comprehensive performance, is an ideal material for various load-bearing structural parts, and can meet the harsh requirements of various high-end manufacturing on light-weight high-performance aluminum alloy materials.

[0042] (2) The application plays the role of refining alloy grains and inhibiting recrystallization by adding Sc elements, and also plays the role of refining welding joint grains and reducing the hot crack sensitivity of the welding joint, so that the alloy has high strength and plasticity, and the strength and welding stability of the welding joint are significantly improved, which is beneficial to promote the development of lightweight in the fields of aerospace, transportation and other high-end equipment, and has important social and economic benefits.

[0043] (3) The application adopts "medium-high-low" three-stage temperature control homogenization heat treatment, the first stage is to make the low melting point eutectic phase fully dissolve and the alloying elements as uniform as possible through suitable medium-high temperature heat treatment, the second stage is to completely eliminate the harmful W phase through higher temperature heat treatment, and the alloy retains the saturated solid solubility through rapid cooling, and the third stage is to make the Sc atoms in the aluminum matrix precipitate in the form of fine dispersed Al3(Sc,Zr) particles through lower temperature heat treatment, so that the effect of Sc elements is fully exerted, and the alloy is beneficial to improve the plasticity, the strength and the welding performance.

[0044] (4) The material has excellent performance, the preparation method is simple and practical, and the operability is strong, so that the material is easy to industrialize and popularize, and has considerable market prospect. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 It is a TEM morphology photo of the dispersed phase in the 23# alloy in the embodiment 2 of the application.

[0046] Figure 2 (a) is a SEM morphology photo of the residual second phase in the 23# alloy in the embodiment 2 of the application. Figure 2 (b) is Figure 2 (a) is a magnified view of the position of the square frame.

[0047] Figure 3 (a) is a TEM morphology photograph of the strengthening phase along <110> Al crystal zone axis of the 23# alloy in Example 2 of the present application; Figure 3 (b) is a TEM morphology photograph of the strengthening phase along <100> Al crystal zone axis of the 23# alloy in Example 2 of the present application. DETAILED DESCRIPTION

[0048] The technical solutions of the present application are further described in detail below in combination with examples.

[0049] Example 1

[0050] Alloy extruded plates and strips were prepared on a laboratory scale to demonstrate the principles of the present application. The composition of the experimental alloys is shown in Table 1.

[0051] A φ235mm round ingot was prepared by alloy smelting, degassing, inclusion removal and simulation of semi-continuous casting conditions known in the art, and the stage homogenization heat treatment system of the ingot was selected as (518±3℃ / 28h)+(550±3℃ / 32h)+(308±3℃ / 32h), air cooling. After peeling, milling and sawing, a φ193mm specification extrusion billet was obtained. The billet was preheated at 450±10℃ for 6h, and a 25.4×102mm specification plate strip was obtained by extrusion deformation, with the extrusion temperature controlled at about 435℃. The extruded plate strip was loaded into a 500℃ air furnace for continuous heating solution heat treatment at a temperature of 515~540℃ for a total time of 150min, and then water quenched and immediately subjected to 2.8~3.3% tensile straightening treatment, followed by 150~165℃ / 22~28h aging treatment according to the characteristics of the alloy.

[0052] According to the relevant method, the sample was cut, and the alloy was subjected to 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 the relevant test standards to evaluate the common performance indicators of the alloy, and the results are shown in Table 2.

[0053] Table 1 Composition of experimental alloy

[0054]

[0055] *In this example, the specific value of the Zn element is added; those not marked are not added, and the content is controlled as an impurity element.

[0056] Table 2 Performance test results of experimental alloy

[0057]

[0058] As can be seen from the table, the alloys 1#, 2#, 3#, 4#, 5#, 6#, 7#, 8#, 9#, 10#, 11# and 12# have good matching of density-strength-plasticity-elastic modulus-welded joint strength-corrosion resistance: the density is not more than 2.67 g / cm 3 , the tensile strength is maintained 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 alloy exfoliation corrosion grade is not lower than EA grade, the intergranular corrosion grade is point corrosion, the specific strength is higher than 235 MPa·cm 3 / g, and the specific modulus is higher than 30 GPa·cm 3 / g. The performance of the alloys 13#, 14#, 15#, 16#, 17#, 18#, 19#, 20#, 21# and 22# does not meet the good matching of density-strength-plasticity-elastic modulus-fracture toughness-fatigue performance-corrosion resistance. The alloy 13# has higher Cu, Sc and Mg contents and lower Li content, the density is higher, the plasticity is lower, the strength, elastic modulus and welded joint strength decrease, and the corrosion resistance decreases. The alloy 14# has lower Li and Sc contents and higher Mg content, the density increases, the strength and elastic modulus are lower, and the welded joint strength decreases. The alloy 15# has higher Cu and Mg contents and lower Li content, and Zn element is added, the density increases, the strength decreases, the elastic modulus is lower, the welded joint strength decreases, and the corrosion resistance decreases. The alloy 16# has lower Cu and Ag contents, does not contain Sc element, and a large amount of Zn element is added, the strength, plasticity, welded joint strength and corrosion resistance decrease seriously. The alloy 17# has lower Cu and Ag contents, and a large amount of Zn element is added, the corrosion resistance decreases, and the strength and welded joint strength decrease seriously. The alloy 18# has lower Cu and Ag contents, higher Li and Mg contents, and a large amount of Zn element is added, the corrosion resistance decreases, the strength and welded joint strength decrease seriously, and the elastic modulus increases. The alloy 19# has lower Cu content, does not contain Sc element, and Zn element is added, the strength, plasticity, welded joint strength and corrosion resistance decrease. The alloy 20# has relatively low Cu content, does not contain Sc and Ag elements, and a small amount of Zn element is added, the strength, plasticity, welded joint strength and corrosion resistance decrease obviously. The alloy 21# has lower Li content, higher Cu and Ag contents, and does not contain Sc element, the density increases, the plasticity, elastic modulus, welded joint strength and corrosion resistance decrease. The alloy 22# has lower Li content, higher Mg content, and a small amount of Zn element is added, the density increases, the strength, elastic modulus and welded joint strength decrease.

[0059] Example 2

[0060] The new alloy plates were prepared on a pilot platform, and the alloy component compositions are shown in Table 3. Under the condition of using covering agent and argon protection of the melt, 100 mm thickness specification ingots were prepared by alloy smelting, degassing, inclusion removal and simulation of semi-continuous casting conditions known in the industry, and the ingots were respectively subjected to three-stage (495±5℃ / 8h+520±5℃ / 24h)+(552±5℃ / 28h)+(310±3℃ / 36h) homogenization heat treatment, air cooling. After peeling, milling and sawing, 68 mm thickness specification rolling stock was obtained. The stock was preheated at 452±5℃ for 8h, the initial rolling temperature was 440℃, and the ingot was rolled along the width direction of the ingot for 2 passes to 45mm, and then subjected to 380±5℃ / 2h intermediate annealing treatment, and then reversed and rolled along the length direction of the ingot to about 10mm thickness specification. The plate was loaded into a 500℃ air furnace, and subjected to solid solution heat treatment at a temperature of 520℃ / 30min+530℃ / 90min, water quenched and immediately subjected to 2.9% tensile straightening treatment, and then subjected to 155℃ / 23h aging treatment according to the characteristics of the alloy.

[0061] According to the relevant method, the sample was cut, and the 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) of the alloy were tested according to the relevant test standards to evaluate the common performance indicators of the alloy, and the results are shown in Table 4.

[0062] Table 3 Experimental alloy composition

[0063]

[0064] Table 4 Performance test results of experimental alloy

[0065]

[0066] As can be seen from Table 4, the 23# alloy of the present application exhibits good strength and plasticity, high welded joint strength and corrosion resistance, and compared with the V-1464 alloy (24# alloy) prepared under the same conditions, the alloy of the present application exhibits obvious comprehensive performance advantages, higher strength and plasticity, specific strength and welded joint strength.

[0067] Figure 1 TEM morphology photographs of the dispersed phase in the 23# alloy are given, and from the figure it can be seen that a large number of fine dispersed Al3(Sc,Zr) particles are precipitated.

[0068] Figure 2The SEM morphology of the residual second phase in the 23# alloy is given. As can be seen from the figure, no coarse W phase is found in the alloy, and the residual second phase is Fe / Mn-rich phase. The element composition of the second phase is: Al 81.39 at.%, Cu 10.19 at.%, Fe 4.55 at.%, and Mn 3.97 at.%.

[0069] Figure 3 The TEM morphology of the age-hardening phase in the 23# alloy is given. As can be obviously seen, a large number of T1 phase, δ' phase and δ' / GPI / δ' composite strengthening phase are formed in the alloy, and Al3(Sc,Zr) particles are observed, and no coarse W phase is found, which is beneficial to the alloy to obtain high strength and plasticity, high welding joint strength and other properties.

[0070] Example 3

[0071] The alloy plate strip is prepared under industrial conditions. The composition of the alloy is shown in Table 5. Under the conditions of using covering agent and argon gas protection melt, the φ426mm round ingot is prepared by alloy smelting, degassing, inclusion removal and semi-continuous casting known in the industry. The homogenization heat treatment system of the 24# and 25# alloy ingots is selected as (520±3℃ / 24h)+(552±3℃ / 36h)+(300~330±3℃ continuous heating for 20h), and air cooling. After peeling, milling and sawing, the φ394mm extrusion billet is obtained. The billet is preheated at 445±10℃ for 8h, and the large-scale L-shaped section with a wall thickness of 25.4 is obtained by extrusion deformation. The extrusion temperature is controlled at about 435℃±5℃. The section is loaded into an air furnace at 490℃, and a suitable system is selected for solid solution heat treatment at a temperature of 520~530℃ for 120~150min, and then water quenching is performed immediately, followed by 2.8~3.0% stretching straightening treatment, and then 155℃ / 23~25h aging treatment according to the characteristics of the alloy, so that the alloy material obtains better comprehensive performance matching.

[0072] According to the related method, the sample is cut, and the 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 welding joint tensile properties (GB / T 2651) of the alloy are tested according to the related test standards as the commonly used performance indicators of the alloy, and the results are shown in Table 6.

[0073] Table 5 Composition of experimental alloy

[0074]

[0075] Table 6 Performance test results of experimental alloy

[0076]

[0077] As can be seen from Table 6, the 25# alloy of the present application has low density, high elastic modulus, high strength-plasticity, matching of welding performance and corrosion resistance; compared with the 2195 alloy (26# alloy) prepared under the same conditions, the alloy of the present application exhibits obvious comprehensive performance advantages, and has lower density, 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 by, The aluminum lithium alloy contains: Cu 3.20-3.49 wt%, Li 1.45-1.75 wt%, Mg 0.35-0.50 wt%, Ag 0.20-0.40 wt%, Sc 0.10-0.17 wt%, Zr 0.10-0.17 wt%, and at least one of Mn, Ti, Hf, V elements, the total content of Zr, Mn, Ti, Hf, V elements is not more than 0.60 wt%, the rest is Al and inevitable impurities, wherein the impurity elements are each ≤0.15 wt%, the total is ≤0.40 wt%; 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.

2. The lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material of claim 1, wherein, The aluminum-lithium alloy contains: Cu 3.22~3.49wt%, Li 1.46~1.72wt%, Mg 0.36~0.48wt%, Ag 0.20~0.35wt%, Sc 0.11~0.16wt%, Zr 0.10~0.17wt%, and at least one of Mn, Ti, Hf, V elements, the total content of Zr, Mn, Ti, Hf, V elements is not more than 0.50wt%, the rest is Al and inevitable impurities.

3. The lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material of claim 2, wherein, The aluminum-lithium alloy contains: Cu 3.25~3.48wt%, Li 1.50~1.68wt%, Mg 0.36~0.46wt%, Ag 0.23~0.34wt%, Sc 0.12~0.16wt%, Zr 0.10~0.17wt%, and at least one of Mn, Ti, Hf, V elements, the total content of Zr, Mn, Ti, Hf, V elements is not more than 0.40wt%, the rest is Al and inevitable impurities.

4. The lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material of claim 3, wherein, The aluminum-lithium alloy contains: Cu 3.26~3.46wt%, Li 1.52~1.67wt%.

5. The lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material of claim 2, wherein, In the aluminum-lithium alloy, the content of Mg and Ag satisfies the relationship: 0.65 wt%≤Mg+Ag≤0.78 wt%.

6. The lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material of claim 2, wherein, The aluminum-lithium alloy contains at least one of Mn, Ti, Hf, V elements, wherein Mn is 0.15~0.35wt%, Ti is 0.01~0.10wt%, Hf is 0.05~0.10wt%, and V is 0.05~0.10wt%.

7. The lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material of claim 6, wherein, The aluminum-lithium alloy contains: Mn 0.15~0.25wt%, Zr 0.10~0.12wt%.

8. The lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material of claim 6, wherein, In the aluminum-lithium alloy, the content of Sc and Zr satisfies the relationship: 0.22 wt%≤Sc+Zr≤0.28 wt%.

9. The lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material of claim 2, wherein, The inevitable impurities include elements unintentionally brought in as impurities in the process of manufacturing alloy ingot, wherein Zn≤0.12wt%, Fe≤0.12wt%, Si≤0.10wt%, and other impurity elements are each ≤0.05wt%, and the total is ≤0.15wt%.

10. The lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material of claim 9, wherein, The aluminum-lithium alloy contains: Zn≤0.10wt%, Fe≤0.10wt%, and Si≤0.08wt%.

11. A method of producing a wrought aluminum lithium alloy material, characterized by, The method comprises the following steps: (1) manufacturing ingot of the aluminum-lithium alloy material according to any one of claims 1~10; (2) performing stage temperature-controlled homogenization heat treatment on the obtained ingot; (3) hot deforming the ingot into a desired form of processed material or into a pre-processed material by one or more hot deformation processing methods selected from rolling, extrusion and forging; (4) optionally performing reheating treatment on the pre-processed material, and cold deforming the pre-processed material into a desired form of processed material; (5) performing solid solution heat treatment on the processed material; (6) rapidly cooling the processed material after the solid solution heat treatment to room temperature; and (7) performing natural aging or artificial aging treatment on the cooled processed material to obtain an alloy aged processed material.

12. The method of claim 11, wherein, In step (1), the ingot is manufactured by melting, degassing, removing inclusions, and semi-continuous casting or spray forming; in the melting process, the melt is protected by inert gas, the content of elements is precisely controlled with Li as the core, the proportioning between alloy elements is quickly adjusted through online composition detection and analysis, and the entire ingot manufacturing process is completed.

13. The method of claim 11, wherein, In step (1), an electromagnetic field, an ultrasonic field, or mechanical stirring is applied at the crystallizer or in the vicinity thereof.

14. The method of claim 11, wherein, In step (2), the stage-controlled temperature homogenization heat treatment mainly comprises the following process steps: ① Stage I: single-stage or multi-stage or gradient temperature rising homogenization heat treatment at 490-525 ℃ for a total time of 12-48 h; ② Stage II: single-stage or gradient temperature rising homogenization heat treatment at 545-558 ℃ for a total time of 12-36 h, followed by rapid cooling to room temperature; and ③ Stage III: single-stage or multi-stage or gradient temperature rising homogenization heat treatment at 300-335 ℃ for a total time of 16-36 h.

15. The method of claim 11, wherein, In steps (3) and (4), the preheating temperature and reheating temperature before each thermal deformation processing is 440-470 ℃, and the processing time is 2-12 h.

16. The method of claim 11, wherein, In step (4), intermediate annealing treatment at 400-420 ℃ for 0.5-4.5 h is additionally performed between cold deformation passes.

17. The method of claim 11, wherein, In step (5), the solution heat treatment is performed by a method selected from the following group: ① single-stage, double-stage or multi-stage solution heat treatment at 505-545 ℃ for a total time of 0.5-5.0 h; and ② continuous temperature rising solution heat treatment at 505-545 ℃ for a total time of 0.5-4.0 h, with a temperature rising rate of ≤60 ℃ / min. In step (6), the processed material is rapidly cooled to room temperature by using a method selected from the following group: cooling medium spraying quenching, immersion quenching, strong air cooling, and a combination thereof.

18. The method of claim 11, wherein, In step (7), the artificial aging treatment is performed by a method selected from the following group:

19. The method of claim 11, wherein, ① natural aging at room temperature after quenching cooling, for a time of ≥72 h; ② artificial aging treatment at 100-180 ℃ within 2 h after quenching cooling, for a total time of 6-72 h; and ③ a combination of natural aging and artificial aging after quenching cooling, artificial aging at 100-180 ℃ for a time of 6-72 h. Between steps (6) and (7), the following step is additionally included: straightening treatment and / or pre-deformation treatment are performed on the cooled processed material, the straightening treatment is performed by using a method selected from the following group: roll straightening, tensile straightening, tensile bending straightening, and a combination thereof, to improve the flatness of the processed material, and the pre-deformation is performed by using a method selected from the following group: stretching, compression, and a combination thereof, to reduce the residual stress formed by quenching cooling, facilitating subsequent processing and application.

20. The method of claim 11, wherein, The processed material is a wire, a rod, a pipe, a sheet, a plate, or a forged product.

21. The method of claim 20, wherein, ​ 22. The lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material of any of claims 1-10, or the lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material manufactured according to the method of any of claims 11-21, wherein, Density of the aluminum lithium alloy material is ≤ 2.65 g / cm 3 Tensile strength is ≥ 600 MPa, elastic modulus is ≥ 80.0 GPa, and weld joint strength is ≥ 410 MPa.

23. A final load bearing structural member, characterized by, The lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material according to any one of claims 1-10, 22 or the lightweight, ultra-high strength, high modulus, weldable aluminum-lithium alloy material manufactured according to any one of claims 11-21 is processed into final load-bearing structural parts by various surface treatments, stamping forming, machining.

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