Laser shock method for improving creep formability synergistic manufacturing capability of thin-walled aluminum-lithium alloy

Abstract

This invention discloses a laser shock blasting method for improving the creep resistance and synergistic manufacturing capability of thin-walled aluminum-lithium alloys. The method includes: solution-treating and water-quenching an aluminum-lithium alloy sheet, followed by aging; marking a region with a radius of 10-20 cm centered at the intersection of the sheet's maximum transverse and longitudinal dimensions as the area requiring the greatest creep; cleaning the marked area, then applying a constraint layer and an energy absorption layer, followed by laser shock blasting; cold-rolling the sheet, followed by thinning the non-laser-shocked side to obtain an aluminum-lithium alloy sheet of the target thickness; wire-cutting the aluminum-lithium alloy sheet according to the unfolded diagram of the target profile to obtain the final aluminum-lithium alloy sheet to be formed; placing the aluminum-lithium alloy sheet to be formed on a forming mold, and then performing creep aging. This invention effectively improves the local creep resistance of thin-walled aluminum-lithium alloy components through local laser shock blasting, while simultaneously increasing local strength and toughness, inhibiting the occurrence and propagation of cracks, and preventing cracking.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal component processing and manufacturing, specifically to a laser shock method for improving the collaborative manufacturing capability of thin-walled aluminum-lithium alloy creep deformation, which is particularly suitable for the forming of high-precision ultra-thin components. Background Technology

[0002] Aluminum-lithium alloys, as important "lightweight and high-strength" materials, possess advantages over traditional aluminum alloys, including lower density, higher elastic modulus, higher specific stiffness, easier processing, and corrosion resistance. They are gradually replacing traditional aluminum alloys and are widely used in the manufacture of key components for aerospace launch vehicles, such as aircraft panels and rocket propellant tanks. To achieve the goal of "weight reduction and range extension" in aerospace launch vehicles and meet the requirements of high-quality development in the aerospace field, creep aging forming technology for thin-walled components has developed rapidly and has already been applied in the aerospace industry. During creep aging forming, stress is applied while the component blank is heated, causing the component to age and strengthen at high temperatures while converting the elastic deformation caused by stress into plastic deformation, ultimately achieving the forming purpose. The creep aging forming process can simultaneously achieve forming and shaping, and the stress applied during the process is lower than the material's yield strength. The resulting component has low residual stress, stable forming quality, and high repeatability, truly achieving the goal of high-quality manufacturing with coordinated form and property. Currently, this technology has become one of the key manufacturing technologies for large aircraft panels and rocket propellant tanks.

[0003] Against the backdrop of the trends towards lightweighting, integration, thinning, and modularization of aerospace equipment components, the demand for large thin-walled aluminum-lithium alloy components in the aerospace manufacturing field is gradually increasing. Simultaneously, the application of large ultra-thin components is also becoming more prevalent. However, the trend towards thinner walls presents new difficulties and challenges to the creep aging forming technology for aluminum-lithium alloy components.

[0004] 1. Increased creep deformation means improved creep aging forming capability. The outer surface of the component, as the part with the greatest elastic deformation and stress during creep aging forming, is also the part with the greatest creep deformation required to achieve the target forming surface. Its creep capability directly determines the overall forming capability of the component. Under the same process conditions and forming mold surface, the thinner the component, the smaller the elastic deformation of the outer material after the component is pressed and film-coated during creep aging, the smaller the stress generated inside, and the lower the outer creep deformation, resulting in the component failing to form to the desired position.

[0005] 2. Due to their inherent material properties, aluminum-lithium alloys have a higher creep activation energy than traditional aluminum alloys. Taking 2195 aluminum-lithium alloy and 2219 aluminum alloy as examples: under the same temperature (160℃), time (12h), and stress (150MPa), the creep of 2195 aluminum-lithium alloy is only 0.055%, about 10% of that of 2219 aluminum alloy. Therefore, even a slight increase in creep is difficult for aluminum-lithium alloys.

[0006] 3. The outer side of the component slab experiences the greatest stress during creep aging forming, which easily leads to local micro-cracks or damage, resulting in poor local plasticity and reduced resistance to failure. In areas with local reinforcing ribs, even cracking may occur. Although aluminum-lithium alloys have significantly higher strength than other aluminum alloys, their plasticity is poor. Therefore, the above problems are more severe during the creep aging process of aluminum-lithium alloy components.

[0007] In actual production, there are generally two approaches to the creep aging forming process for thin-walled / ultra-thin aluminum-lithium alloy components:

[0008] 1. Aluminum-lithium alloy thick plates are used for creep aging forming, and then the formed components are thinned to the target thickness by chemical milling. However, after chemical milling, the internal stress of the components is released and springback occurs, resulting in a decrease in forming accuracy.

[0009] 2. Directly use thin-walled aluminum-lithium alloy sheets of the target thickness for creep aging forming, and increase the creep aging temperature to obtain a larger creep amount to ensure that the forming accuracy meets the requirements. However, the increase in temperature will significantly reduce the performance of the component material.

[0010] In summary, compared to other aluminum alloys, aluminum-lithium alloys exhibit more challenging creep characteristics. This problem is exacerbated by the increasing thinning and ultra-thinning of components, severely restricting the application of creep aging forming technology in thin-walled aluminum-lithium alloy components. Increasing the temperature can significantly improve the creep tolerance of aluminum-lithium alloys, but it also leads to a substantial decrease in performance. Furthermore, chemical milling can cause springback, affecting forming accuracy. The key to creep aging forming of large thin-walled / ultra-thin aluminum-lithium alloy components lies in how to improve creep tolerance while maintaining material strength, and simultaneously improving plasticity to inhibit cracking. Therefore, there is an urgent need for a creep aging forming method for large thin-walled / ultra-thin aluminum-lithium alloy components that can simultaneously achieve good formability, high strength, and excellent plasticity. Summary of the Invention

[0011] This invention provides a laser shock method to improve the creep deformation resistance and synergistic manufacturing capability of thin-walled aluminum-lithium alloys, in order to solve the problem mentioned in the background art that large thin-walled / ultra-thin aluminum-lithium alloy components cannot guarantee the forming accuracy, material properties and crack suppression of components in the existing creep aging forming process.

[0012] The present invention is achieved through the following technical solution.

[0013] A laser shock blasting method for improving the creep deformation resistance of thin-walled aluminum-lithium alloys includes the following steps:

[0014] S1: Place the aluminum-lithium alloy sheet at 510℃-530℃ for 0.5h for solution treatment, then quench it in water, and then let it age naturally for 3-7 days;

[0015] S2: Based on the forming shape of the aluminum-lithium alloy sheet, take the intersection of the maximum transverse and longitudinal dimensions of the sheet as the center and mark the area with a radius of 10-20cm as the part where the component requires the greatest creep.

[0016] S3: Clean the marked area in step S2, then place the constraint layer and energy absorption layer, and then perform laser shock on it. The laser shock energy is 3J-5J, the shock radius is 3mm, the overlap is 50%, and the number of shocks is 4.

[0017] S4: The sheet material obtained in step S3 is cold rolled with a rolling amount of 3%-10%, and then thinned by non-laser impact side milling or milling to obtain an aluminum-lithium alloy sheet material with a target thickness of 0.5-2mm.

[0018] S5: The thinned aluminum-lithium alloy sheet is wire-cut according to the unfolded drawing of the target surface to obtain the final aluminum-lithium alloy sheet to be formed.

[0019] S6: Place the aluminum-lithium alloy sheet to be formed on the forming mold, and then perform creep aging.

[0020] Preferably, in step S3, the constraint layer is made of flowing water, and the energy absorption layer is made of black paint.

[0021] Preferably, the creep aging temperature in step S6 is 160℃-180℃, and the aging time is 2h-25h.

[0022] Preferably, the creep stress in step S6 is 30-300 MPa.

[0023] Preferably, during the creep aging process in step S6, the aluminum-lithium alloy sheet to be formed is placed with the laser impact surface facing downwards, and it is in close contact with the mold cavity.

[0024] The beneficial effects of this invention are:

[0025] 1. After local laser impact, a reverse bending pre-forming effect will appear, which is beneficial to improving the accuracy of subsequent creep forming.

[0026] 2. After laser local impact, compared with the T3 state aluminum-lithium alloy commonly used in industry, under the same creep process conditions, the creep of the impacted part is significantly increased, which improves the creep forming ability of the component.

[0027] 3. The laser local impact method proposed in this invention can effectively improve the plasticity of the outer material of the component while ensuring its strength, thus suppressing cracking. For areas with reinforcing ribs, it can effectively prevent cracking.

[0028] 4. The laser local shock method proposed in this invention can introduce a large number of dense dislocation networks on the outer side of aluminum-lithium alloy components, effectively improving local creep and providing numerous nucleation sites for precipitate formation during creep aging. Furthermore, laser shock refines the local surface grains, improving local strength and toughness, inhibiting crack initiation and propagation, and preventing cracking. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The described embodiments are for illustrative purposes only and should not be construed as limiting the present invention.

[0031] Example 1

[0032] 2195 aluminum-lithium alloy was solution treated in a solution furnace (530℃) for 0.5 h, followed by water quenching. The resulting sheet was subjected to localized laser impact testing (LAB) with an energy of 3.6 J, an impact radius of 3 mm, 50% overlap, and 4 impact cycles. The LAB-treated sheet was then rolled with a 4% reduction, followed by milling to a thickness of 1 mm. Creep aging was then performed at a temperature of 180℃, a creep stress of 220 MPa, and a creep aging time of 25 h. Finally, a room temperature tensile test was conducted on the sheet.

[0033] Example 2

[0034] 2195 aluminum-lithium alloy was solution treated in a solution furnace (530℃) for 0.5 h, followed by water quenching. The resulting sheet was subjected to laser local impact testing (LAIP) with an energy of 3.6 J, an impact radius of 3 mm, 50% overlap, and 4 impact cycles. The LAIP sheet was then rolled with a reduction of 4%, followed by milling to a thickness of 1 mm. Creep aging was then performed at a creep aging temperature of 180℃, a creep stress of 160 MPa, and a creep aging time of 25 h. Finally, a room temperature tensile test was conducted on the sheet.

[0035] Comparative Example 1

[0036] The 2195 aluminum-lithium alloy was solution treated in a solution furnace (530℃) for 0.5h, followed by water quenching. The resulting sheet was rolled with a rolling amount of 4% (simulating the commonly used T3 state), then milled to a thickness of 1mm, and then subjected to creep aging forming treatment at a creep aging temperature of 180℃, a creep stress of 220MPa, and a creep aging time of 25h. After the creep aging was completed, the sheet was subjected to room temperature tensile testing.

[0037] Table 1 shows the creep and mechanical properties of Comparative Example 1 and Examples 1 and 2 after being treated with the same creep aging process.

[0038] Comparative Example 1 Example 1 Example 2 Creep variables (%) 0.149 0.23 0.16 Yield strength (MPa) 567 571 565 Tensile strength (MPa) 611 599 601 Elongation (%) 7.6 12 11.6

[0039] Table 1 shows the creep values ​​and material properties after creep aging of 2195 aluminum-lithium alloy sheets obtained using the method of this invention (two embodiments) in a commonly used initial state (comparative example) and under the same creep aging forming process. The comparison results in Table 1 show that after treatment with the laser shock method proposed in this invention, the creep value is increased by approximately 50% compared to the T3 state under the same creep aging process, the elongation is increased by approximately 50%, and the strength is not reduced. In Example 2, the creep stress was reduced from 220 MPa to 160 MPa while keeping other creep aging conditions unchanged. The creep value at 160 MPa was still higher than that of the traditional creep process at 220 MPa, the strength remained the same, and the elongation was still increased by approximately 50%. These data indicate that the laser shock method proposed in this invention effectively solves the problem of the inability to achieve formability and performance coordination in the existing processes for thin-walled / ultra-thin components, especially for aluminum-lithium alloys that are difficult to creep and have poor plasticity. It can comprehensively improve the formability and performance of thin-walled / ultra-thin aluminum-lithium alloy components, while simultaneously solving the problems of difficult creep and poor plasticity in aluminum-lithium alloys.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A laser shock method for improving the creep formability synergistic manufacturing capability of thin-walled aluminum-lithium alloy, characterized in that: The method comprises the following steps: S1: placing 2195 aluminum lithium alloy plate at 510-530℃ for 0.5h, then water quenching, and then naturally aging for 3-7 days; S2: according to the forming shape of the aluminum lithium alloy plate, marking the region with a radius of 10-20cm as the largest creep position of the component at the intersection of the maximum size of the transverse and longitudinal directions of the plate as the center; S3: cleaning the marked position in S2, then arranging the constraint layer and the energy absorption layer, and then performing laser impact, the laser impact energy being 3-5J, the impact radius being 3mm, the 50% overlap, and the impact times being 4 times; S4: cold rolling the plate obtained in S3, the rolling amount being 3-10%, and then milling or milling thinning the non-laser impact side to obtain the aluminum lithium alloy plate with a target thickness, the target thickness being 0.5-2mm; S5: linear cutting the aluminum lithium alloy plate after thinning according to the development drawing of the target forming surface to obtain the final aluminum lithium alloy plate to be formed; S6: arranging the aluminum lithium alloy plate to be formed on the forming die, and then performing creep aging.

2. The laser shock method for improving the synergic manufacturing ability of creep formability of a thin-walled aluminum-lithium alloy according to claim 1, characterized in that: The constraint layer in S3 is water, and the energy absorption layer is black paint.

3. The laser shock method for improving the synergic manufacturing ability of creep formability of thin-walled aluminum-lithium alloy according to claim 1, characterized in that: The creep aging temperature in S6 is 160-180℃, and the aging time is 2-25h.

4. The laser shock method for improving the synergic manufacturing ability of creep formability of a thin-walled aluminum-lithium alloy according to claim 1, characterized in that: The creep stress in S6 is 30-300MPa.

5. The laser shock method of improving the synergistic manufacturing capability of the creep formability of a thin-walled aluminum-lithium alloy according to claim 1, characterized in that: In the creep aging process in S6, the laser impact surface of the aluminum lithium alloy plate to be formed faces downward and is attached to the die concave mold.

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