Aluminum alloy plate for electronic screen back plate as well as preparation method and application of aluminum alloy plate

Abstract

The invention provides an aluminum alloy plate for an electronic screen back plate and a preparation method and application of the aluminum alloy plate. The thickness of the aluminum alloy plate for the electronic screen back plate is 0.1-0.4 mm, and the aluminum alloy plate comprises Cu, Li, Mg, Mn, Zr, Si, Fe, Ti, Al and impurities with specific contents. The preparation method comprises the steps of thermal deformation, cold rolling, short-time intermediate annealing, short-time solid solution, quenching, cold deformation and annealing treatment. The density of the aluminum alloy plate ranges from 2.55 g / cm < 3 > to 2.62 g / cm < 3 >, the room-temperature tensile strength is larger than or equal to 430 MPa, the yield strength is larger than or equal to 380 MPa, the ductility is larger than or equal to 11%, the elasticity modulus is 77-81 GPa, cracks do not appear after the aluminum alloy plate is bent by 180 degrees for 3-5 times, the comprehensive performance is excellent, and the aluminum alloy plate is suitable for the field of new-generation ultra-thin and ultra-light mobile phones, computers, liquid crystal displays and intelligent wearable products.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to an aluminum alloy plate for an electronic screen back plate, and a preparation method and application thereof. Background Art

[0002] With the rapid development of modern electronic products, especially the popularity of portable electronic devices such as smart phones, tablets, and smart wearable devices, higher requirements are placed on the selection of materials. Lightweight, thin, high stiffness, and high strength have become key indicators in the design of a new generation of electronic products, aiming to achieve a balance between the portability, durability, and performance of the equipment. In the early stages of research, the LCD screen backplane was mainly made of steel, which has high strength, but has limitations in practical applications. First, the high density of steel (about 7.85g / cm 3 ) leads to an increase in the overall weight of electronic products, which runs counter to the trend of pursuing thin and light designs. Secondly, the low thermal conductivity of steel (about 45W / (m·K)) makes it difficult to effectively dissipate the heat generated by electronic products during operation, which can easily cause equipment overheating and affect the user experience. Furthermore, the magnetic properties of steel may interfere with the signal reception and transmission of electronic products, affecting communication performance. Based on these inherent shortcomings of steel, finding a more suitable backplane material has become the focus of industry attention.

[0003] In recent years, 5XXX series aluminum alloys have been widely used due to their lower density (about 2.65g / cm 3 ) and higher strength (tensile strength exceeds 370MPa), as well as good 90° bending without cracking performance, and gradually become the preferred material for LCD screen backplanes. This not only significantly reduces the weight of electronic equipment, but also meets the strength and formability requirements to a certain extent. For example, the Chinese patent with publication number CN113981282A discloses an Al-(5.2~6.2)Mg alloy strip, whose tensile strength reaches 390MPa, showing better performance. The Chinese patent with publication number CN117601522A discloses an aluminum alloy material for manufacturing mobile phone backplanes and a manufacturing method thereof. The tensile strength of the material is about 340MPa. 1060 aluminum alloy is used as the surface layer, and Al-(5.7~5.95)Mg alloy is used as the middle layer, in order to achieve a balance between performance and cost through the optimization of the multi-layer structure.

[0004] However, with the technological innovation of electronic products and the continuous upgrading of user needs, the above-mentioned aluminum alloy backplane materials are facing new challenges. On the one hand, in order to further improve the portability and aesthetics of the product, the thickness of the backplane material needs to be further thinned to an unprecedented level; on the other hand, the thinning of the material is often accompanied by a decrease in stiffness, which poses a threat to the structural stability of electronic products. Therefore, the aluminum alloy used for the backplane is required to have a higher elastic modulus to compensate for the loss of stiffness caused by the thinning thickness and maintain the stability of the device structure; in addition, good bending and forming performance and sufficient strength are still key considerations for selecting backplane materials. In short, the ideal characteristics of aluminum alloys for LCD screen backplanes in the future should include: further thinning the sheet, improving stiffness, and ensuring excellent formability while maintaining or even improving strength. However, materials that can meet these high standards have not yet been reported in current technical literature.

[0005] Therefore, there is an urgent need to provide a material that can combine high strength, lightness, and high rigidity to provide strong technical support for material innovation in future electronic products. Summary of the invention

[0006] The main purpose of the present invention is to provide an aluminum alloy plate for electronic screen back panels and a preparation method and application thereof, so as to solve the problem that the materials for electronic screen back panels in the prior art cannot have lightness, high rigidity, high strength and good bending and forming properties.

[0007] In order to achieve the above-mentioned object, according to one aspect of the present invention, a method for preparing an aluminum alloy material for an electronic screen back plate is provided, wherein the thickness of the aluminum alloy plate is 0.1-0.4 mm, and the elements and their weight percentages contained in the aluminum alloy plate are: Cu: 2.5-2.9%, Li: 1.6-2.6%, Mg: 0.3-0.5%, Mn: 0.3-0.5%, Zr: 0.10-0.15%, Si≤0.03%, Fe≤0.04%, Ti≤0.08%, and the remainder is Al and unavoidable impurities, each unavoidable impurity is less than 0.04%, and the total impurities are less than 0.12%; the preparation method comprises the following steps: step S1, according to the aluminum The composition ratio of the alloy plate is used to manufacture an aluminum alloy ingot, and the aluminum alloy ingot is hot-deformed to obtain a hot-deformed plate with a thickness of 2 to 5 mm; step S2, cold rolling the hot-deformed plate, and intermediate annealing is performed during the cold rolling process to obtain a cold-rolled plate; wherein the temperature of the intermediate annealing is 300 to 400°C, and the insulation time is 15 to 30 minutes; step S3, sequentially performing solid solution and quenching treatments on the cold-rolled plate to obtain a quenched plate; wherein the heating time of the solid solution is 3 to 5 minutes, and the insulation time is 10 to 15 minutes; step S4, cold deforming the quenched plate to obtain a cold-deformed plate, and annealing the cold-deformed plate to obtain an aluminum alloy plate.

[0008] Furthermore, the elements contained in the aluminum alloy plate and their weight percentage are: Cu: 2.5-2.7%, Li: 2.1-2.6%, Mg: 0.3-0.5%, Mn: 0.3-0.5%, Zr: 0.10-0.12%, Si≤0.03%, Fe≤0.04%, Ti≤0.06%, and the remainder is Al and unavoidable impurities, each unavoidable impurity is <0.03%, and the total impurities are <0.1%.

[0009] Furthermore, in the aluminum alloy plate, the weight ratio of Cu to Li is 1.0 to 1.7; and / or the sum of the weight percentages of Mn and Zr is 0.45 to 0.65%.

[0010] Furthermore, in step S1, thermal deformation includes hot extrusion and / or hot rolling; preferably, when hot extrusion is performed, the heating temperature of the aluminum alloy ingot is 470-490°C; preferably, when hot rolling is performed, the heating temperature of the aluminum alloy ingot is 480-500°C.

[0011] Furthermore, in step S2, the cold rolling pass reduction rate is 15-50% and the temperature is 10-45°C.

[0012] Furthermore, in step S3, the temperature of the solid solution is 500-550°C; and / or the quenching treatment is completed within 1-5 seconds after the completion of the solid solution treatment; preferably, the cooling rate of the quenching is 150-450°C / s.

[0013] Furthermore, in step S4, the deformation amount of cold deformation is 0.5-5%; and / or, the cold deformation includes stretching deformation and / or calendering treatment, preferably, the stretching speed of the stretching deformation is 10-30 mm / min; preferably, the calendering speed of the calendering treatment is 300-600 mm / min, and the number of calendering times is 1-3 times; and / or, the temperature of the annealing treatment is 160-180°C, and the insulation time is 4-32 hours.

[0014] According to another aspect of the present invention, there is provided an aluminum alloy plate material for an electronic screen back plate, which is obtained by the above-mentioned preparation method.

[0015] Furthermore, in the aluminum alloy plate, the average diameter of the grains is ≤50 μm; and / or the aluminum alloy plate includes an optional coarse phase, the coarse phase includes one or more of AlCuFeMn, AlCuFe, AlCuMn and AlFeMn, and the maximum diameter of any compound of AlCuFeMn, AlCuFe, AlCuMn and AlFeMn is ≤1.5 μm, preferably ≤1 μm; the density of the aluminum alloy plate is 2.55-2.62 g / cm 3, room temperature tensile strength ≥430MPa, yield strength ≥380MPa, elongation ≥11%, elastic modulus 77~81GPa, no cracks appear after 180° bending 3~5 times.

[0016] According to another aspect of the present invention, there is provided application of the above-mentioned aluminum alloy sheet in the fields of mobile phones, computers, liquid crystal displays, and smart wearables.

[0017] By applying the technical solution of the present invention, the coordinated optimization of light weight, high strength and excellent processing performance is achieved by rationally controlling the types of elements and optimizing their contents. The precise proportions of elements such as Cu, Li, Mg, Mn, and Zr, combined with the preparation processes of hot deformation, cold rolling, short intermediate annealing, short solid solution, quenching, cold deformation, and annealing treatment, effectively form a stable strengthening phase, fragment the coarse phase, and accurately control the grain size and morphology.

[0018] The aluminum alloy sheet of the present invention can balance low density, high rigidity, high strength and easy forming processability on the basis of being light and thin. Specifically, the density of the aluminum alloy sheet is 2.55-2.62 g / cm 3 The room temperature tensile strength is ≥430MPa, the yield strength is ≥380MPa, the elongation is ≥11%, the elastic modulus is 77-81GPa, and no cracks appear after 180° bending 3-5 times. The comprehensive performance is excellent and it is suitable for the structural backplane of thin or ultra-thin electronic products. In addition, the raw material of the aluminum alloy sheet of the present invention does not contain rare precious metals such as Ag, and the material cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0020] Figure 1 The microstructure of the aluminum alloy ingot of Example 1 of the present invention is shown;

[0021] Figure 2 The SEM image of the coarse phase of the aluminum alloy ingot of Example 2 of the present invention is shown;

[0022] Figure 3 The EBSD image of the grain structure of the thermally deformed plate of Example 3 of the present invention is shown;

[0023] Figure 4 The room temperature tensile curves of the aluminum alloy plates of Examples 2 and 3 of the present invention are shown;

[0024] Figure 5 The microstructure of the aluminum alloy plate of Example 4 of the present invention is shown;

[0025] Figure 6 The microstructure of the aluminum alloy plate of Example 5 of the present invention is shown;

[0026] Figure 7 The microstructure of the aluminum alloy plate of Example 6 of the present invention is shown;

[0027] Figure 8 The room temperature tensile curves of the aluminum alloy plates of Example 6 and Example 7 of the present invention are shown;

[0028] Fig. 9 The microstructure of the aluminum alloy ingot of Comparative Example 1 of the present invention is shown;

[0029] Fig.10 The SEM image of the coarse phase of the aluminum alloy ingot of Comparative Example 2 of the present invention is shown;

[0030] Fig.11 The microstructure metallographic structure of the aluminum alloy plate of Comparative Example 2 of the present invention is shown;

[0031] Fig.12 The microstructure metallographic structure of the aluminum alloy plate of Comparative Example 3 of the present invention is shown;

[0032] Fig.13 The room temperature tensile curves of the aluminum alloy plates of Comparative Examples 3 and 4 of the present invention are shown; and

[0033] Fig.14 The room temperature tensile curve of the aluminum alloy plate of Comparative Example 5 of the present invention is shown. DETAILED DESCRIPTION

[0034] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] As described in the background of the present invention, there is a problem in the prior art that the materials for the back panel of an electronic screen cannot be light, thin, high rigidity, high strength and good bending and forming performance. In order to solve the above problems, in a typical embodiment of the present invention, a method for preparing an aluminum alloy plate for an electronic screen back panel is provided, the thickness of the aluminum alloy plate is 0.1-0.4 mm, and the elements contained in the aluminum alloy plate and their weight percentage are: Cu: 2.5-2.9%, Li: 1.6-2.6%, Mg: 0.3-0.5%, Mn: 0.3-0.5%, Zr: 0.10-0.15%, Si≤0.03%, Fe≤0.04%, Ti≤0.08%, and the balance is Al and unavoidable impurities, each unavoidable impurity is <0.04%, and the total impurities are <0.12%; the preparation method comprises the following steps: Step S1, according to The composition ratio of the aluminum alloy plate is used to manufacture an aluminum alloy ingot, and the aluminum alloy ingot is hot-deformed to obtain a hot-deformed plate with a thickness of 2 to 5 mm; step S2, cold rolling the hot-deformed plate, and intermediate annealing is performed during the cold rolling process to obtain a cold-rolled plate; wherein the temperature of the intermediate annealing is 300 to 400°C, and the insulation time is 15 to 30 minutes; step S3, sequentially performing solid solution and quenching treatments on the cold-rolled plate to obtain a quenched plate; wherein the heating time of the solid solution treatment is 3 to 5 minutes, and the insulation time is 10 to 15 minutes; step S4, cold deforming the quenched plate to obtain a cold-deformed plate, and annealing the cold-deformed plate to obtain an aluminum alloy plate.

[0036] The components of the aluminum alloy sheet of the present application include Cu, Li, Mg, Mn, and Zr. Among them, Cu, as a strengthening element, can participate in the formation of AlCuLi phase with good toughness, which is beneficial to improve the strength and toughness of the alloy. However, if the Cu content is too high, too much CuAl2 coarse phase will be formed, and plastic instability will easily occur during hot and cold processing, leading to cracking, which will reduce the plasticity and processing performance of the material, and even increase the risk of material forming brittleness. More importantly, it will cause the density of the alloy to increase, which is not conducive to making the alloy take into account high strength, light weight and good processing performance; if the Cu content is too low, it will lead to poor element strengthening effect and insufficient strength of the alloy. The present application specifically controls the Cu content to be within the range of 2.5-2.9%. Under this condition, the alloy density, strength and plasticity can be balanced, and the processing performance of the sheet can be optimized.

[0037] Adding Li can significantly reduce the density of the alloy, greatly improve the stiffness, and can cooperate with the Cu element to form an AlCuLi strengthening phase to improve the strength of the alloy. However, if the Li content is too high, excessive AlLi phase will be formed, which is prone to plastic instability and cracking during hot and cold working, and the plasticity and processing performance of the material will decrease. More seriously, it will increase the risk of material forming brittleness; if the Li content is too low, the improvement of the strength and density of the alloy is limited, which is not conducive to meeting the requirements of light weight and low density. This application specifically controls the Li content range to 1.6-2.6%, which can effectively balance the matching relationship between the low density, high stiffness, and high forming performance of the alloy.

[0038] The added Mg element can play a role in binding vacancies during the annealing process of alloy preparation, promote the formation of AlCuLi strengthening phase, thereby significantly improving the strength and stiffness of the alloy, and can also keep the alloy in good plasticity. However, if the Mg content is too high, an AlMgLi phase that is not conducive to formability will be formed, which will lead to poor plasticity of the alloy; if the Mg content is too low, the strengthening effect is not obvious. The present application specifically controls the Mg content range to 0.3-0.5%. Within this range, the hardness and yield strength of the alloy can be appropriately improved, while effectively ensuring the formability of the sheet.

[0039] Adding Mn and Zr elements can form micron-scale and nano-scale dispersed phases, which inhibit grain growth by pinning grain boundary migration. If the Mn content is too high, a hard and brittle phase may be formed, which in turn leads to poor plasticity of the alloy; if the Mn content is too low, the element strengthening effect is limited. If the Zr content is too high, the solid solubility is low and it cannot be dissolved into the aluminum matrix, forming coarse compounds, resulting in an increase in impurity phases; if the Zr content is too low, the grain refinement effect is limited. The present application specifically controls the Mn content to 0.3-0.5% and the Zr content to 0.10-0.15%. When Mn and Zr are within this range, the distribution of the Mn-containing dispersed phase and the Zr-containing dispersed phase can achieve better mutual complementation, inhibit nucleation on the grain boundary and recrystallization formation within the crystal, so that the thin material has a fine, rather than growing grain structure, and the fine grain structure can enhance the material's coordinated deformation ability, which is beneficial to improving the cold deformation ability of the thin material.

[0040] The present application also defines the content of Si, Fe, Ti and impurity elements. Among them, if the content of Si and Fe is too high, it may lead to the formation of hard and brittle phases such as Al(FeSi), AlCuFe, AlFeMn, AlCuFeMn, etc., thereby significantly reducing the plasticity and formability of the alloy. The present application specifically defines Si≤0.03% and Fe≤0.04%. The purpose of adding Ti is mainly to form small and stable compounds such as Al3Ti during the preparation of the ingot and to play a role in refining the ingot grains, but its excessive content may lead to the formation of too many hard phases, affecting the plasticity of the alloy. Therefore, the present application specifically defines Ti≤0.08%.

[0041] In the preparation method of the aluminum alloy plate of the present application, step S1, hot deforming the aluminum alloy ingot can refine the coarse phase and grain structure, achieve a lower dislocation density, and make the hot deformed plate present a soft state, providing a prerequisite for subsequent cold rolling processing; step S2, further fragmenting the coarse phase through cold rolling, and at the same time entering high deformation energy storage, laying the foundation for the fine grain structure of the subsequent solid solution process, and intermediate annealing treatment can eliminate stress, improve material plasticity, and facilitate thin plate forming; step S3, through solid solution and quenching treatment, the alloy elements can be dissolved and evenly distributed, effectively controlling the growth of grain size and its morphology, and ensuring that the aluminum alloy plate has good bending forming performance; in step S4, the combination of cold deformation and annealing can optimize the microstructure, so that the alloy has good ductility and excellent dimensional stability.

[0042] It should be noted that in the present application, hot deformation and cold rolling work together to not only achieve precise control of the thickness of the plate, but also significantly enhance the stiffness and comprehensive mechanical properties of the aluminum alloy plate without sacrificing the plasticity of the material.

[0043] Moreover, for the aluminum alloy with specific composition of the present application, the inventor has optimized the conditions of intermediate annealing and solution treatment after a large number of experiments. Specifically, in the control step S2, the temperature of the intermediate annealing is 300-400°C, and the holding time is 15-30min. Through short-time intermediate annealing, the stress accumulated in the alloy with specific composition of the present application during cold rolling can be effectively relieved, work hardening can be eliminated, the plasticity of the material can be restored, and the subsequent processing such as solution and annealing can be smoothly carried out. At the same time, the stability of the alloy strengthening phase can be maintained, excessive softening can be avoided, and the grain size growth and morphology can be effectively controlled to achieve the balance between high rigidity and bending forming performance and processing forming performance of the aluminum alloy sheet. In addition, in step S3, the heating time of the solution treatment is 3-5min, and the holding time is 10-15min. Under the above conditions, a stable solid solution can be formed, thereby significantly improving the strength and rigidity of the aluminum alloy sheet. At the same time, short-time insulation is also conducive to avoiding excessive growth of grains, maintaining good formability of the material, and ensuring the effect of subsequent annealing.

[0044] The above steps are combined to finally produce a high-performance aluminum alloy sheet that can meet the requirements of thin and light electronic products. In addition, the preparation method of the present application has simple steps and few processes, which is convenient for preparing thin, high-rigidity, high-strength, and easy-to-form aluminum alloy sheets.

[0045] In summary, this application achieves the coordinated optimization of light weight, high strength, high rigidity and excellent processing performance by designing specific alloy components and optimizing process flow. Among them, Cu and Li elements work together to form AlCuLi phase, which effectively improves the strength and toughness of the alloy. At the same time, this application reasonably controls the content of Cu and Li elements within a specific range, effectively reduces density and enhances rigidity on the basis of ensuring the strength and toughness of the alloy, and takes into account high strength, lightness and plasticity. Mg can promote the formation of strengthening phase, optimize the hardness and plasticity of the alloy, and Mn and Zr can synergistically refine the grains to keep the sheet metal in good cold deformation ability. In addition, the content of Si, Fe and Ti is also limited to avoid the formation of hard and brittle phases and ensure the plasticity and formability of the alloy. During the preparation process, hot deformation, cold rolling, short intermediate annealing, short solid solution, quenching, cold deformation, annealing and other steps are matched with each other, so that in the process of converting aluminum alloy ingots into ultra-thin sheets, a stable strengthening phase can be formed, the coarse phase can be broken, and the grain structure size and morphology can be accurately controlled.

[0046] The above methods make the aluminum alloy sheet thin (thickness is 0.1-0.4mm, which is thinner than the commonly used 5XXX aluminum alloy sheet 0.4-0.6mm), and can balance high stiffness (such as elastic modulus ≥77GPa, which is 13.0-15.5% higher than the commonly used 5XXX aluminum alloy, and the sheet can still maintain a good plate shape when the thickness is thin), high strength (such as room temperature tensile strength ≥430MPa, yield strength ≥380MPa, which is higher than the currently commonly used 5XXX aluminum alloy), low density (such as density ≤2.62g / cm 3 , which is lighter than the commonly used 5XXX aluminum alloy), good bending and forming performance (no cracks appear after the plate is bent 180° 3 to 5 times) and easy forming processability (elongation ≥ 11%), suitable for the structural backplane of thin or ultra-thin electronic products. In addition, the aluminum alloy plate of the present application does not contain rare precious metals such as Ag, and the material cost is low.

[0047] In order to further optimize the microstructure of the alloy and improve the strength and rigidity, in a preferred embodiment, the elements and their weight percentages contained in the aluminum alloy plate are: Cu: 2.5-2.7%, Li: 2.1-2.6%, Mg: 0.3-0.5%, Mn: 0.3-0.5%, Zr: 0.10-0.12%, Si≤0.03%, Fe≤0.04%, Ti≤0.06%, and the remainder is Al and unavoidable impurities, each unavoidable impurity is <0.03%, and the total impurities are <0.1%. Under the above conditions, Cu and Li can be more effectively coordinated and matched, which is more conducive to the formation of strengthening phases such as AlCuLi and avoids the formation of impurity phases, thereby more effectively improving the tensile strength and elastic modulus of the alloy, reducing the alloy density, maintaining the high ductility and low density characteristics of the alloy, and further meeting the fine forming requirements of the electronic screen structure plate.

[0048] In a preferred embodiment, the weight ratio of Cu to Li is 1.0 to 1.7, preferably 1.0 to 1.55, more preferably 1.0 to 1.19; and / or the sum of the weight percentages of Mn and Zr is 0.45 to 0.65%, more preferably 0.5 to 0.65%. Under the above conditions, grain refinement can be further promoted, and grain growth at high temperature can be suppressed, thereby further enhancing the processing performance and plasticity of the alloy.

[0049] In order to promote the uniform distribution of strengthening phase particles and enhance the comprehensive mechanical properties of the plate, in a preferred embodiment, in step S1, the hot deformation includes hot extrusion and / or hot rolling; preferably, when hot extrusion is performed, the heating temperature of the aluminum alloy ingot is 470-490°C; preferably, when hot rolling is performed, the heating temperature of the aluminum alloy ingot is 480-500°C. Hot extrusion or hot pressing at high temperature can ensure the coordinated deformation ability of coarse phases and grains under pressure conditions, more effectively prevent the formation of micro defects during deformation, and form a low energy storage microstructure, which is conducive to subsequent cold rolling processing.

[0050] In a preferred embodiment, in step S2, the cold rolling pass reduction rate is 15-50%, and the temperature is 10-45° C. The large reduction deformation method can more effectively break up the coarse phase and form uniformly distributed particles, while introducing higher deformation energy storage to provide conditions for grain evolution.

[0051] In order to more effectively maintain the highly saturated microstructure in the solid solution state and avoid the precipitation of harmful phases, thereby further improving the strengthening potential of the aluminum alloy plate and maintaining the high plasticity of the material, in a preferred embodiment, in step S3, the temperature of the solid solution is 500-550°C; and / or, the quenching treatment is completed within 1-5s after the solid solution is completed; preferably, the cooling rate of the quenching is 150-450°C / s. The above rapid quenching is more suitable for light and thin plates to inhibit the formation of harmful precipitation phases during the transfer process between solid solution and quenching, while ensuring the shape and dimensional stability of the plate.

[0052] In a preferred embodiment, in step S4, the amount of cold deformation is 0.5-5%. Under the above conditions, the surface quality, flatness, and thickness uniformity of the plate can be further optimized, while the mechanical properties of the aluminum alloy plate can be improved, ensuring that the plate still has high tensile strength and good elongation at a thickness of 0.1-0.4 mm.

[0053] In order to further improve the surface quality and dimensional accuracy of aluminum alloy plates, maintain the formability of aluminum alloy plates, and improve the mechanical properties of materials, in a preferred embodiment, cold deformation includes stretching deformation and / or calendering treatment. Preferably, the stretching speed of stretching deformation is 10-30 mm / min; preferably, the calendering speed of calendering treatment is 300-600 mm / min, and the number of calendering is 1-3 times. The above cold deformation rate more effectively avoids cracks on the surface of the plate, ensures the flatness and dimensional accuracy of the plate, and balances production efficiency and material performance.

[0054] The temperature and holding time of annealing directly affect the microstructure and properties of the alloy, and the inventors have optimized its parameters. In a preferred embodiment, the temperature of the annealing is 160-180°C, and the holding time is 4-32h. If the temperature is too high or the time is too long, the stress may be eliminated more thoroughly, but it may also lead to the formation of excessive strengthening phases, which is not conducive to comprehensive performance; if the temperature is too low or the holding time is too short, the stress may not be completely eliminated and the strength and plasticity may not match. Under the above conditions, the internal stress and work hardening of the alloy can be eliminated more effectively, and the strength and hardness of the alloy can be taken into account while maintaining good plasticity and formability.

[0055] In another typical embodiment of the present invention, there is also provided an aluminum alloy plate for an electronic screen back panel, which is obtained by the above-mentioned preparation method. As mentioned above, the present application optimizes the content of each element and the preparation process conditions to effectively control the microstructure of the alloy, and the prepared plate has an excellent balance of comprehensive properties, including high stiffness, high strength, good plasticity and processing properties, and can be used as an electronic screen back panel material. It should be noted that due to the particularity of the alloy field and the limitations of existing testing and characterization methods, it is difficult to conduct a comprehensive quantitative characterization of the complex microstructure of the aluminum alloy plate for the electronic screen back panel obtained above, but experiments show that the aluminum alloy plate for the electronic screen back panel obtained in this application has higher comprehensive performance.

[0056] In a preferred embodiment, in the aluminum alloy plate, the average diameter of the grains is ≤50μm, preferably 22-40μm; and / or the aluminum alloy plate includes an optional coarse phase, the coarse phase includes one or more of AlCuFeMn, AlCuFe, AlCuMn and AlFeMn, and the maximum diameter of any compound of AlCuFeMn, AlCuFe, AlCuMn and AlFeMn is ≤1.5μm, preferably ≤1μm.

[0057] In a preferred embodiment, the density of the aluminum alloy plate is 2.55-2.62 g / cm 3 , preferably 2.56 to 2.58 g / cm 3 ; Room temperature tensile strength ≥430MPa, preferably ≥440MPa, more preferably 440-550MPa; yield strength ≥380MPa, preferably ≥390MPa, more preferably 390-480MPa; elongation ≥11%, preferably ≥12%, more preferably 12-20%; elastic modulus is 77-81GPa, and no cracks appear on the aluminum alloy sheet after being bent 180° 3-5 times. The sheet of the present application is light and thin, with high rigidity, high strength, excellent bending formability, and good formability during the processing of parts, which is beneficial to high-precision components of electronic products.

[0058] In another typical embodiment of the present invention, the application of the above-mentioned aluminum alloy sheet in the fields of mobile phones, computers, liquid crystal displays and smart wearables is also provided. As mentioned above, the aluminum alloy sheet of the present application has the characteristics of thinness, high rigidity, easy formability and light weight, which can significantly improve the structural strength of the product, reduce weight, and make the product have both performance and portability. Moreover, the aluminum alloy sheet of the present application has excellent dimensional stability, which can optimize manufacturing accuracy and user experience, while the low magnetic characteristics can reduce electromagnetic interference and improve signal quality and product safety. The use of the materials of the present application in the fields of mobile phones, computers, liquid crystal displays and smart wearables can meet the urgent needs of electronic products for high performance and lightweight design.

[0059] In summary, in response to the new demand for thin, lightweight, high-rigidity, high-strength, and easy-to-form plates for current electronic screen back panels, this application has developed an aluminum alloy plate, the elements and their weight percentages of which are: Cu: 2.5-2.9%, Li: 1.6-2.6%, Mg: 0.3-0.5%, Mn: 0.3-0.5%, Zr: 0.10-0.15%, Si≤0.03%, Fe≤0.04%, Ti≤0.1%, and the remainder is Al and unavoidable impurities, each unavoidable impurity is <0.04%, and the total impurities are <0.12%. The ingot of this composition is subjected to hot deformation, cold rolling, short intermediate annealing, short solid solution, quenching, cold deformation, and annealing treatment to finely control the microstructure, and obtain an aluminum alloy plate with a thickness of 0.1-0.4 mm and a density of 2.55-2.62 g / cm 3 , room temperature tensile strength ≥430MPa, yield strength ≥380MPa, elongation ≥11%, elastic modulus 77~81GPa, no cracks appear after being bent 180° 3~5 times, and its comprehensive performance is higher than that of aluminum alloy sheets commonly used in electronic screen back panels. It is suitable for the new generation of ultra-thin and ultra-light mobile phones, computers, LCD displays and smart wearable products.

[0060] Typically but not limiting, in the aluminum alloy plate, by weight percentage, Cu accounts for 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or a range consisting of any two of them; Li accounts for 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6% or a range consisting of any two of them; Mg accounts for 0.3%, 0.4%, 0.5% or a range consisting of any two of them; Mn accounts for 0.3%, 0.4%, 0.5% or a range consisting of any two of them; Zr accounts for 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15% or a range consisting of any two of them.

[0061] Typically, but not limiting, the weight ratio of Cu to Li is 1.0, 1.04, 1.1, 1.12, 1.13, 1.19, 1.2, 1.3, 1.4, 1.5, 1.53, 1.55, 1.56, 1.6, 1.69, 1.7 or a range consisting of any two of them.

[0062] Typically but not limiting, the sum of the weight percentages of Mn and Zr is 0.4%, 0.42%, 0.45%, 0.5%, 0.52%, 0.55%, 0.6%, 0.65% or a range consisting of any two of them.

[0063] Typically but not limiting, in step S2, the temperature of the intermediate annealing treatment is 300°C, 350°C, 400°C or a range consisting of any two of them, and the holding time is 15min, 20min, 25min, 30min or a range consisting of any two of them.

[0064] Typically but not limiting, in step S3, the solution heating time is 3 min, 4 min, 5 min or a range consisting of any two of them, and the holding time is 10 min, 12 min, 15 min or a range consisting of any two of them.

[0065] Typically but not limiting, the thickness of the aluminum alloy plate is 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm or a range consisting of any two of these values.

[0066] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0067] Example 1

[0068] The composition of the aluminum alloy plate includes: Cu 2.5%, Li 1.6%, Mg 0.3%, Mn 0.3%, Zr 0.1%, Si 0.03%, Fe 0.04%, Ti 0.08%, wherein the weight ratio of Cu to Li is 1.56, and the rest is Al and inevitable impurity elements (each inevitable impurity is less than 0.04%, and the total impurity is less than 0.12%);

[0069] Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the aluminum alloy plate, and hot-extruding the aluminum alloy ingot at a heating temperature of 470° C. to obtain a hot-deformed plate with a thickness of 2 mm;

[0070] Step S2, cold rolling the hot deformed sheet, the cold rolling temperature is 25°C, the first pass reduction rate is 50%, and a cold rolled sheet with a thickness of 1 mm is obtained, and then intermediate annealing is performed at a temperature of 300°C and kept warm for 20 minutes; the second cold rolling pass reduction rate is 50%, and a cold rolled sheet with a thickness of 0.5 mm is obtained, and then intermediate annealing is performed at a temperature of 350°C and kept warm for 15 minutes; the third cold rolling pass reduction rate is 50%, and a cold rolled sheet with a thickness of 0.25 mm is obtained, and then intermediate annealing is performed at a temperature of 400°C and kept warm for 15 minutes; the fourth cold rolling pass reduction rate is 40%, and a cold rolled sheet with a thickness of 0.15 mm is obtained; the fourth cold rolling pass reduction rate is 30%, and a cold rolled sheet with a thickness of about 0.1 mm is obtained;

[0071] Step S3, subjecting the cold-rolled sheet to a solution treatment, wherein the temperature rise time for the solution treatment is 4 minutes, the treatment temperature is 530° C., the heat preservation time is 12 minutes, and after the heat preservation is completed, the sheet is water-cooled to 25° C. within 3 seconds, and the cooling rate for quenching is 168° C. / s, to obtain a quenched sheet;

[0072] Step S4, under the condition of a stretching speed of 20 mm / min, the quenched plate is subjected to a stretching deformation of 0.5% to obtain an aluminum sheet with a thickness of about 0.1 mm; the obtained aluminum sheet is annealed at a temperature of 180° C. and a holding time of 4 hours to obtain an aluminum alloy sheet.

[0073] Aluminum alloy sheets are used to make LCD screen back panels.

[0074] The microstructure of aluminum alloy ingot is shown in Figure 1 The as-cast structure is a typical dendritic structure.

[0075] Example 2

[0076] The composition of the aluminum alloy plate includes: Cu 2.5%, Li 2.5%, Mg 0.3%, Mn 0.3%, Zr 0.1%, Si 0.03%, Fe 0.04%, Ti 0.08%, wherein the weight ratio of Cu to Li is 1, and the rest is Al and inevitable impurity elements (each inevitable impurity is less than 0.04%, and the total impurity is less than 0.12%);

[0077] Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the aluminum alloy plate, and hot rolling the aluminum alloy ingot at a heating temperature of 480° C. to obtain a hot-deformed plate with a thickness of 2 mm;

[0078] Step S2, cold rolling the hot deformed sheet, the cold rolling temperature is 25°C, the first pass reduction rate is 40%, and a cold rolled sheet with a thickness of 1.2 mm is obtained, and then intermediate annealing is performed at a temperature of 300°C and kept warm for 20 minutes; the second cold rolling pass reduction rate is 30%, and a cold rolled sheet with a thickness of 0.84 mm is obtained, and then intermediate annealing is performed at a temperature of 350°C and kept warm for 15 minutes; the third cold rolling pass reduction rate is 30%, and a cold rolled sheet with a thickness of 0.588 mm is obtained; the fourth cold rolling pass reduction rate is 28%, and a cold rolled sheet with a thickness of 0.423 mm is obtained;

[0079] Step S3, subjecting the cold-rolled sheet to a solution treatment, wherein the temperature rise time for the solution treatment is 4 minutes, the treatment temperature is 530° C., the heat preservation time is 12 minutes, and after the heat preservation is completed, the sheet is water-cooled to 30° C. within 3 seconds, and the cooling rate for quenching is 167° C. / s, to obtain a quenched sheet;

[0080] Step S4, under the conditions of a calendering speed of 450 mm / min and a calendering number of 2 times, the quenched plate is calendered with a deformation amount of 0.5% to obtain an aluminum sheet with a thickness of about 0.4 mm; the obtained aluminum sheet is annealed at a temperature of 170°C and a holding time of 24 hours to obtain an aluminum alloy sheet.

[0081] Aluminum alloy sheets are used to make LCD screen back panels.

[0082] The SEM image of the coarse phase of the aluminum alloy ingot is shown in Figure 2 It can be seen that coarse second phases of the solidified profiles are distributed on the cast grain boundaries, but they are all discontinuously distributed, which is conducive to fragmentation during the deformation process.

[0083] Example 3

[0084] The composition of the aluminum alloy plate includes: Cu 2.7%, Li 2.26%, Mg 0.4%, Mn 0.4%, Zr 0.12%, Si 0.03%, Fe 0.04%, Ti 0.1%, wherein the weight ratio of Cu to Li is 1.19, and the rest is Al and inevitable impurity elements (each inevitable impurity is less than 0.04%, and the total impurity is less than 0.12%);

[0085] Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the aluminum alloy plate, and hot-extruding the aluminum alloy ingot at a heating temperature of 485° C. to obtain a hot-deformed plate with a thickness of 3.5 mm;

[0086] Step S2, cold rolling the hot deformed sheet, the cold rolling temperature is 25°C, the first pass reduction rate is 50%, and a cold rolled sheet with a thickness of 1.75 mm is obtained, and then intermediate annealing is performed at a temperature of 400°C and kept warm for 30 minutes; the second cold rolling pass reduction rate is 40%, and a cold rolled sheet with a thickness of 1.05 mm is obtained, and then intermediate annealing is performed at a temperature of 350°C and kept warm for 15 minutes; the third cold rolling pass reduction rate is 50%, and a cold rolled sheet with a thickness of 0.525 mm is obtained, and then intermediate annealing is performed at a temperature of 350°C and kept warm for 15 minutes; the fourth cold rolling pass reduction rate is 42%, and a cold rolled sheet with a thickness of 0.3045 mm is obtained;

[0087] Step S3, subjecting the cold-rolled sheet to a solution treatment, wherein the temperature rise time for the solution treatment is 4 minutes, the treatment temperature is 535° C., the heat preservation time is 10 minutes, and after the heat preservation is completed, the sheet is water-cooled to 25° C. within 3 seconds, and the cooling rate for quenching is 170° C. / s, to obtain a quenched sheet;

[0088] Step S4, under the condition of a stretching speed of 20 mm / min, the quenched plate is stretched with a deformation amount of 2% to obtain an aluminum sheet with a thickness of about 0.3 mm; the obtained aluminum sheet is annealed at a temperature of 165° C. and a holding time of 16 h to obtain an aluminum alloy sheet.

[0089] Aluminum alloy sheets are used to make LCD screen back panels.

[0090] The EBSD image of the grain structure of the hot-deformed plate is shown in Figure 3 , wherein the grains are banded, the degree of recrystallization is low and has rich subgrain structure characteristics. The room temperature tensile curves of the aluminum alloy sheets of Example 2 and Example 3 are shown in Figure 4 The yield strength of the plate exceeds 400MPa, and the continuous hardening characteristics after yielding indicate good work hardening ability and good elongation.

[0091] Example 4

[0092] The composition of the aluminum alloy plate includes: Cu 2.6%, Li 2.3%, Mg 0.4%, Mn 0.4%, Zr 0.12%, Si 0.03%, Fe 0.04%, Ti 0.1%, wherein the weight ratio of Cu to Li is 1.13, and the rest is Al and inevitable impurity elements (each inevitable impurity is less than 0.04%, and the total impurity is less than 0.12%);

[0093] Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the above aluminum alloy plate, and hot extruding the aluminum alloy ingot at a heating temperature of 485° C. to obtain a hot-deformed plate with a thickness of 2 mm;

[0094] Step S2, cold rolling the hot deformed sheet, the cold rolling temperature is 45°C, the first pass reduction rate is 50%, and a cold-rolled sheet with a thickness of 1.75 mm is obtained, and then intermediate annealing is performed at a temperature of 400°C and kept warm for 30 minutes; the second cold rolling pass reduction rate is 40% to obtain a cold-rolled sheet with a thickness of 1.05 mm, and then intermediate annealing is performed at a temperature of 350°C and kept warm for 15 minutes; the third cold rolling pass reduction rate is 50% to obtain a cold-rolled sheet with a thickness of 0.525 mm, and then intermediate annealing is performed at a temperature of 300°C and kept warm for 30 minutes; the fourth cold rolling pass reduction rate is 42% to obtain a cold-rolled sheet with a thickness of 0.3 mm; the fifth cold rolling pass reduction rate is 33% to obtain a cold-rolled sheet with a thickness of 0.2 mm.

[0095] Step S3, subjecting the cold-rolled sheet to a solution treatment, wherein the temperature rise time for the solution treatment is 3 minutes, the treatment temperature is 535° C., the heat preservation time is 10 minutes, and after the heat preservation is completed, the sheet is water-cooled to 35° C. within 3 seconds, and the cooling rate for quenching is 167° C. / s, to obtain a quenched sheet;

[0096] Step S4, under the condition of a stretching speed of 10 mm / min, the quenched plate is stretched with a deformation amount of 3% to obtain an aluminum sheet with a thickness of about 0.2 mm; the obtained aluminum sheet is annealed at a temperature of 165° C. and a holding time of 20 h to obtain an aluminum alloy sheet.

[0097] Aluminum alloy sheets are used to make LCD screen back panels.

[0098] The microstructure of aluminum alloy sheet is shown in Figure 5 The plate contains fully recrystallized grains with uniform grain distribution and an average grain size of about 23 microns.

[0099] Example 5

[0100] The alloy composition is the same as that of Example 4.

[0101] Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the aluminum alloy plate, and hot rolling the aluminum alloy ingot at a heating temperature of 485° C. to obtain a hot-deformed plate with a thickness of 3.5 mm;

[0102] Step S2, cold rolling the hot deformed sheet, the cold rolling temperature is 10°C; the first pass reduction rate is 50%, and a cold-rolled sheet with a thickness of 1.75mm is obtained, and then intermediate annealing is performed at a temperature of 300°C and kept warm for 15min; the second cold rolling pass reduction rate is 40%, and a cold-rolled sheet with a thickness of 1.05mm is obtained, and then intermediate annealing is performed at a temperature of 350°C and kept warm for 15min; the third cold rolling pass reduction rate is 20%, and a cold-rolled sheet with a thickness of 0.84mm is obtained; the fourth cold rolling pass reduction rate is 20%, and a cold-rolled sheet with a thickness of 0.672mm is obtained; the fifth cold rolling pass reduction rate is 15%, and a cold-rolled sheet with a thickness of 0.5712mm is obtained, and then intermediate annealing is performed at a temperature of 400°C and kept warm for 15min; the sixth cold rolling pass reduction rate is 40%, and a cold-rolled sheet with a thickness of 0.34272mm is obtained, and the sixth cold rolling pass reduction rate is 40%, and a cold-rolled sheet with a thickness of 0.205632mm is obtained;

[0103] Step S3, subjecting the cold-rolled sheet to a solution treatment, wherein the temperature rise time for the solution treatment is 5 minutes, the treatment temperature is 535° C., the heat preservation time is 12 minutes, and after the heat preservation is completed, the sheet is water-cooled to 25° C. within 3 seconds, and the cooling rate for quenching is 170° C. / s, to obtain a quenched sheet;

[0104] Step S4, under the conditions of a calendering speed of 300 mm / min and a calendering number of 3 times, the quenched plate is calendered with a deformation amount of 2% to obtain an aluminum sheet with a thickness of about 0.2 mm; the obtained aluminum sheet is annealed at a temperature of 165°C and a holding time of 16 hours to obtain an aluminum alloy sheet.

[0105] Aluminum alloy sheets are used to make LCD screen back panels.

[0106] The microstructure of aluminum alloy sheet is shown in Figure 6 The plate contains fully recrystallized grains with uniform grain distribution and an average grain size of about 28 microns.

[0107] Example 6

[0108] The composition of the aluminum alloy plate includes: Cu 2.9%, Li 1.9%, Mg 0.5%, Mn 0.5%, Zr 0.15%, Si 0.03%, Fe 0.04%, Ti 0.1%, wherein the weight ratio of Cu to Li is 1.53, and the rest is Al and inevitable impurity elements (each inevitable impurity is less than 0.04%, and the total impurity is less than 0.12%);

[0109] Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the aluminum alloy plate, and hot-extruding the aluminum alloy ingot at a heating temperature of 490° C. to obtain a hot-deformed plate with a thickness of 5 mm;

[0110] Step S2, cold rolling the hot deformed sheet, the cold rolling temperature is 25 ° C; the first pass reduction rate is 50%, and a 2.5 mm thick cold rolled sheet is obtained; the second cold rolling reduction rate is 15%, and a 2.125 mm thick cold rolled sheet is obtained, and then intermediate annealing is performed at a temperature of 300 ° C and kept warm for 15 minutes; the third cold rolling reduction rate is 40%, and a 1.275 mm thick cold rolled sheet is obtained; the fourth cold rolling reduction rate is 20%, and a 1.02 mm thick cold rolled sheet is obtained; the fifth cold rolling reduction rate is 15%, and a 0.86 7mm thick cold-rolled sheet, then intermediate annealing at 350℃ for 15min; the sixth cold-rolling pass with a reduction rate of 50% to obtain a 0.4335mm thick cold-rolled sheet; the seventh cold-rolling pass with a reduction rate of 20% to obtain a 0.3468mm thick cold-rolled sheet, then intermediate annealing at 400℃ for 15min; the eighth cold-rolling pass with a reduction rate of 25% to obtain a 0.2601mm thick cold-rolled sheet, and the ninth cold-rolling pass with a reduction rate of 23% to obtain a cold-rolled sheet of about 0.2mm thickness;

[0111] Step S3, subjecting the cold-rolled sheet to a solution treatment, wherein the temperature rise time for the solution treatment is 3 minutes, the treatment temperature is 540°C, the heat preservation time is 10 minutes, and after the heat preservation is completed, the sheet is water-cooled to 40°C within 3 seconds, and the cooling rate for quenching is 167°C / s, to obtain a quenched sheet;

[0112] Step S4, under the condition of a stretching speed of 30 mm / min, the quenched plate is stretched with a deformation amount of 5% to obtain an aluminum sheet with a thickness of about 0.2 mm; the obtained aluminum sheet is annealed at a temperature of 160° C. and a holding time of 8 hours to obtain an aluminum alloy sheet.

[0113] Aluminum alloy sheets are used to make LCD screen back panels.

[0114] The microstructure of aluminum alloy sheet is shown in Figure 7 The plate contains fully recrystallized grains with uniform grain distribution and an average grain size of about 22 microns.

[0115] Example 7

[0116] The composition of the aluminum alloy plate includes: Cu 2.9%, Li 2.6%, Mg 0.5%, Mn 0.5%, Zr 0.15%, Si 0.03%, Fe 0.04%, Ti 0.1%, wherein the weight ratio of Cu to Li is 1.12, and the rest is Al and inevitable impurity elements (each inevitable impurity is less than 0.04%, and the total impurity is less than 0.12%);

[0117] Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the aluminum alloy plate, and hot rolling the aluminum alloy ingot at a heating temperature of 500° C. to obtain a hot-deformed plate with a thickness of 5 mm;

[0118] Step S2, cold rolling the hot deformed sheet, the cold rolling temperature is 25°C; the first pass reduction rate is 50%, and a cold rolled sheet with a thickness of 2.5mm is obtained; the second cold rolling pass reduction rate is 15%, and a cold rolled sheet with a thickness of 2.125mm is obtained, and then intermediate annealing is performed at a temperature of 300°C and kept warm for 15min; the third cold rolling pass reduction rate is 40%, and a cold rolled sheet with a thickness of 1.275mm is obtained; the fourth cold rolling pass reduction rate is 20%, and a cold rolled sheet with a thickness of 1.02mm is obtained; the fifth cold rolling pass reduction rate is 15%, and a cold rolled sheet with a thickness of 0.867mm is obtained, and then intermediate annealing is performed at a temperature of 350°C and kept warm for 15min; the sixth cold rolling pass reduction rate is 50%, and a cold rolled sheet with a thickness of 0.4335mm is obtained;

[0119] Step S3, subjecting the cold-rolled sheet to a solution treatment, wherein the temperature rise time for the solution treatment is 5 minutes, the treatment temperature is 540°C, the heat preservation time is 15 minutes, and after the heat preservation is completed, the sheet is water-cooled to 45°C within 1.1 seconds, and the cooling rate for quenching is 450°C / s, to obtain a quenched sheet;

[0120] Step S4, under the conditions of a calendering speed of 600 mm / min and a calendering number of 1 times, the quenched plate is calendered with a deformation amount of 5% to obtain an aluminum sheet with a thickness of about 0.4 mm; the obtained aluminum sheet is annealed at a temperature of 160°C and a holding time of 12 hours to obtain an aluminum alloy sheet.

[0121] Aluminum alloy sheets are used to make LCD screen back panels.

[0122] The room temperature tensile curves of the aluminum alloy plates of Example 6 and Example 7 are shown in Figure 8 As can be seen from the figure, the aluminum sheet with fine grain structure has a good balance of strength and elongation.

[0123] Example 8

[0124] The only difference from Example 1 is:

[0125] The composition of the aluminum alloy plate includes: Cu 2.6%, Li 2.5%, Mg 0.3%, Mn 0.5%, Zr 0.1%, Si 0.03%, Fe 0.04%, Ti 0.06%, wherein the weight ratio of Cu to Li is 1.04, and the rest is Al and inevitable impurity elements (each inevitable impurity is less than 0.04%, and the total impurities are less than 0.12%).

[0126] Example 9

[0127] The only difference from Example 7 is that:

[0128] The composition of the aluminum alloy plate includes: Cu 2.7%, Li 1.6%, Mg 0.5%, Mn 0.3%, Zr 0.12%, Si 0.03%, Fe 0.04%, Ti 0.06%, wherein the weight ratio of Cu to Li is 1.69, and the rest is Al and inevitable impurity elements (each inevitable impurity <0.04%, total impurities <0.12%). The aluminum sheet with a thickness of about 0.4 mm is annealed at a temperature of 160° C. and a holding time of 32 hours to obtain an aluminum alloy plate.

[0129] Comparative Example 1

[0130] The composition of the aluminum alloy plate includes: Cu 3.2%, Li 2.3%, Mg 0.4%, Mn 0.7%, Zr 0.1%, Si 0.03%, Fe 0.04%, Ti 0.1%, wherein the weight ratio of Cu to Li is 1.39, and the rest is Al and inevitable impurity elements (each inevitable impurity is less than 0.04%, and the total impurities are less than 0.12%);

[0131] Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the above aluminum alloy plate, and hot extruding the aluminum alloy ingot at a heating temperature of 485° C. to obtain a hot-deformed plate with a thickness of 2 mm;

[0132] Step S2, cold rolling the hot deformed sheet, the cold rolling temperature is 45°C, the first pass reduction rate is 50%, and a cold rolled sheet with a thickness of 1.75 mm is obtained, and then intermediate annealing is performed at a temperature of 400°C and kept warm for 30 minutes; the second cold rolling pass reduction rate is 40%, and a cold rolled sheet with a thickness of 1.05 mm is obtained, and then intermediate annealing is performed at a temperature of 350°C and kept warm for 15 minutes; the third cold rolling pass reduction rate is 50%, and a cold rolled sheet with a thickness of 0.525 mm is obtained, and then intermediate annealing is performed at a temperature of 300°C and kept warm for 30 minutes; the fourth cold rolling pass reduction rate is 23%, and a cold rolled sheet with a thickness of 0.404 mm is obtained;

[0133] Step S3, subjecting the cold-rolled sheet to a solution treatment, wherein the temperature rise time for the solution treatment is 3 minutes, the treatment temperature is 535° C., the heat preservation time is 10 minutes, and after the heat preservation is completed, the sheet is water-cooled to 25° C. within 3 seconds, and the cooling rate for quenching is 170° C. / s, to obtain a quenched sheet;

[0134] Step S4, under the condition of a stretching speed of 10 mm / min, the quenched plate is subjected to a stretching deformation of 3% to obtain an aluminum sheet with a thickness of about 0.4 mm; the obtained aluminum sheet is annealed at a temperature of 165° C. and a holding time of 20 h to obtain an aluminum alloy sheet.

[0135] Aluminum alloy sheets are used to make LCD screen back panels.

[0136] The microstructure of aluminum alloy ingot is shown in Fig. 9 . As can be seen from the figure, and Figure 1 In comparison, the as-cast structures of the two alloys are not much different, but the Cu content and Mn content of the alloy in Comparative Example 1 are both higher, and the volume fraction of the as-cast coarse phase is greater than that in Example 1.

[0137] Comparative Example 2

[0138] The composition of the aluminum alloy plate includes: Cu 2.1%, Li 2.3%, Mg 0.7%, Mn 0.4%, Zr 0.12%, Si 0.04%, Fe 0.05%, Ti 0.1%, wherein the weight ratio of Cu to Li is 0.91; the rest is Al and inevitable impurity elements (each inevitable impurity is less than 0.04%, and the total impurity is less than 0.12%);

[0139] Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the aluminum alloy plate, and hot rolling the aluminum alloy ingot at a heating temperature of 485° C. to obtain a hot-deformed plate with a thickness of 3.5 mm;

[0140] Step S2, cold rolling the hot deformed sheet, the cold rolling temperature is 10°C; the first pass reduction rate is 50%, and a cold-rolled sheet with a thickness of 1.75mm is obtained, and then intermediate annealing is performed at a temperature of 300°C and kept warm for 15min; the second cold rolling pass reduction rate is 40%, and a cold-rolled sheet with a thickness of 1.05mm is obtained, and then intermediate annealing is performed at a temperature of 350°C and kept warm for 15min; the third cold rolling pass reduction rate is 20%, and a cold-rolled sheet with a thickness of 0.84mm is obtained; the fourth cold rolling pass reduction rate is 20%, and a cold-rolled sheet with a thickness of 0.672mm is obtained; the fifth cold rolling pass reduction rate is 15%, and a cold-rolled sheet with a thickness of 0.5712mm is obtained, and then intermediate annealing is performed at a temperature of 400°C and kept warm for 15min; the sixth cold rolling pass reduction rate is 40%, and a cold-rolled sheet with a thickness of 0.343mm is obtained, and the sixth cold rolling pass reduction rate is 40%, and a cold-rolled sheet with a thickness of 0.206mm is obtained;

[0141] Step S3, subjecting the cold-rolled sheet to a solution treatment, wherein the temperature rise time for the solution treatment is 5 minutes, the treatment temperature is 535° C., the heat preservation time is 12 minutes, and after the heat preservation is completed, the sheet is water-cooled to 25° C. within 3 seconds, and the cooling rate for quenching is 170° C. / s, to obtain a quenched sheet;

[0142] Step S4, under the conditions of a calendering speed of 300 mm / min and a calendering number of 3 times, the quenched plate is calendered with a deformation amount of 2% to obtain an aluminum sheet with a thickness of about 0.2 mm; the obtained aluminum sheet is annealed at a temperature of 165°C and a holding time of 16 hours to obtain an aluminum alloy sheet.

[0143] Aluminum alloy sheets are used to make LCD screen back panels.

[0144] The SEM image of the coarse phase of the aluminum alloy ingot is shown in Fig.10 . As can be seen from the figure, and Figure 2Compared with the alloys, the cast structures of the two alloys are not much different, but the alloy in Comparative Example 2 has a lower Cu content, a higher Li and Mg content, and a larger volume fraction of the cast coarse phase than that in Example 2. Fig.11 , the plate contains a coarse grain structure with low uniformity, and the average grain size is about 100 microns.

[0145] Comparative Example 3

[0146] The alloy composition is the same as that of Example 4 and Example 5.

[0147] Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the aluminum alloy plate, and hot-extruding the aluminum alloy ingot at a heating temperature of 490° C. to obtain a hot-deformed plate with a thickness of 10 mm;

[0148] Step S2, cold rolling the hot deformed sheet at a temperature of 25°C; the first pass reduction rate is 30% to obtain a 7mm thick cold rolled sheet, and then intermediate annealing is performed at a temperature of 450°C for 30 minutes; the second cold rolling reduction rate is 65% to obtain a 2.45mm thick cold rolled sheet, and then intermediate annealing is performed at a temperature of 450°C for 30 minutes; the third cold rolling reduction rate is 60% to obtain a 0.98mm thick cold rolled sheet, and then intermediate annealing is performed. The steel sheet was annealed at 450°C for 30 minutes; the fourth cold rolling process had a reduction rate of 45% to obtain a cold-rolled sheet with a thickness of 0.54 mm; the fifth cold rolling process had a reduction rate of 10% to obtain a cold-rolled sheet with a thickness of 0.486 mm, and then intermediate annealing was performed at 480°C for 10 minutes; the sixth cold rolling process had a reduction rate of 50% to obtain a cold-rolled sheet with a thickness of 0.243 mm; the seventh cold rolling process had a reduction rate of 10% to obtain a cold-rolled sheet with a thickness of 0.2187 mm;

[0149] Step S3, subjecting the cold-rolled sheet to a solution treatment, wherein the temperature rise time for the solution treatment is 10 minutes, the treatment temperature is 530° C., the heat preservation time is 30 minutes, and after the heat preservation is completed, the sheet is water-cooled to 25° C. within 4 seconds, and the cooling rate for quenching is 168° C. / s, to obtain a quenched sheet;

[0150] Step S4, under the condition of a stretching speed of 20 mm / min, the quenched plate is stretched with a deformation amount of 4.0% to obtain an aluminum sheet with a thickness of about 0.2 mm; the obtained aluminum sheet is annealed at a temperature of 180°C and a holding time of 4 hours to obtain an aluminum alloy sheet.

[0151] Aluminum alloy sheets are used to make LCD screen back panels.

[0152] The microstructure of aluminum alloy sheet is shown in Fig.12, the plate has coarser grains and lower size uniformity, with an average grain size of about 110 microns. Figure 5 , Figure 6 When the alloy composition is the same, the microstructure can be regulated by changing the processing parameters. When the grain size is fine, the elongation of the aluminum sheet is high, and the strength-plasticity match is more reasonable; when the grain size is large, the elongation of the aluminum sheet is low. This coarse grain comes from multiple factors such as hot working temperature, cold rolling amount, annealing temperature, and solid solution system.

[0153] Comparative Example 4

[0154] The alloy composition is the same as that of Example 4 and Example 5.

[0155] Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the aluminum alloy plate, and hot rolling the aluminum alloy ingot at a heating temperature of 500° C. to obtain a hot-deformed plate with a thickness of 3 mm;

[0156] Step S2, cold rolling the hot deformed sheet, the cold rolling temperature is 25°C; the first pass reduction rate is 50%, and a cold rolled sheet with a thickness of 1.5 mm is obtained; the second cold rolling pass reduction rate is 20%, and a cold rolled sheet with a thickness of 1.2 mm is obtained, and then intermediate annealing is performed at a temperature of 300°C and kept warm for 60 minutes; the third cold rolling pass reduction rate is 50%, and a cold rolled sheet with a thickness of 0.6 mm is obtained; the fourth cold rolling pass reduction rate is 20%, and a cold rolled sheet with a thickness of 0.48 mm is obtained; the fifth cold rolling pass reduction rate is 15%, and a cold rolled sheet with a thickness of 0.87 mm is obtained, and then intermediate annealing is performed at a temperature of 350°C and kept warm for 15 minutes; the sixth cold rolling pass reduction rate is 40%, and a cold rolled sheet with a thickness of 0.522 mm is obtained; the seventh cold rolling pass reduction rate is 22%, and a cold rolled sheet with a thickness of 0.407 mm is obtained;

[0157] Step S3, subjecting the cold-rolled sheet to a solution treatment, wherein the temperature rise time for the solution treatment is 4 minutes, the treatment temperature is 550° C., the heat preservation time is 5 minutes, and after the heat preservation is completed, the sheet is water-cooled to 40° C. within 10 seconds, and the cooling rate for quenching is 51° C. / s, to obtain a quenched sheet;

[0158] Step S4, under the condition of a stretching speed of 20 mm / min, the quenched plate is subjected to a stretching deformation of 1% to obtain an aluminum sheet with a thickness of about 0.4 mm; the obtained aluminum sheet is annealed at a temperature of 140° C. and a holding time of 36 hours to obtain an aluminum alloy sheet.

[0159] Aluminum alloy sheets are used to make LCD screen back panels.

[0160] The room temperature tensile curves of the aluminum alloy plates of Comparative Examples 3 and 4 are shown in Fig.13As can be seen from the figure, the aluminum sheet with fine grain structure has better elongation.

[0161] Comparative Example 5

[0162] The only difference from Example 4 is that:

[0163] The content of Li in the aluminum alloy sheet is relatively high, which is 3.0%. Accordingly, the weight ratio of Cu to Li is 0.9. The room temperature tensile curve of the aluminum alloy sheet of Comparative Example 5 is shown in FIG. Fig.14 As can be seen from the figure, the alloy sheet with high Li content exhibits lower elongation.

[0164] Comparative Example 6

[0165] The only difference from Example 4 is that:

[0166] In the composition of the aluminum alloy sheet, the content of Li is relatively low, which is 1.1%. Accordingly, the weight ratio of Cu to Li is 2.45.

[0167] Aluminum alloy sheets are used to make LCD screen back panels.

[0168] Comparative Example 7

[0169] Example 1 of Chinese patent publication number CN113981282A.

[0170] The test results of the microstructure parameters and characteristic parameters of the aluminum alloy plates prepared in the above embodiments and comparative examples are shown in Table 1.

[0171] Test method:

[0172] Alloy composition: The test was carried out at room temperature using the standard "Chemical Analysis Methods for Aluminum and Aluminum Alloys" (GB / T20975-2008).

[0173] Strength and elongation: The test is carried out at room temperature using the standard "Tensile Tests on Metallic Materials - Part 1: Room Temperature Test Methods" (GB / T 228.1-2021).

[0174] Density: The test was carried out at room temperature using the standard “Determination of Density of Dense Sintered Metal Materials and Cemented Carbide” (GB / T 3850-2015).

[0175] Elastic modulus: The test is carried out at room temperature using the static method of standard “Test method for elastic modulus and Poisson’s ratio of metallic materials” (GB / T 22315-2008).

[0176] Table 1

[0177]

[0178]

[0179] After analysis, it can be seen that compared with the embodiment, Example 1 contains excessive Cu and Mn elements, which produces excessive coarse phases. After conventional aging treatment, the elongation is low, and the coarse phase forms stress concentration in the thin material, which reduces the strength at the same time. In Example 2, after the Cu content is reduced, it is obvious that the strength of the plate is insufficient after conventional aging treatment. During the cold rolling process in Example 3, the intermediate annealing system used is improper, the temperature is too high and the insulation time is too long, which causes excessive grain growth and reduces the elongation and strength. In Example 4, the solid solution process used is improper, and the temperature of the thin plate drops rapidly during the quenching transfer process. The slower transfer time cannot ensure that the solid solution elements are fully retained in the matrix, making the aging effect not obvious. Example 5 uses an excessively high Li content. Although it is beneficial to improve the stiffness of the plate, it has a great impact on the formability, and the elongation is low and cannot meet the application. Example 6 excessively reduces the Li element, and both strength and stiffness cannot be balanced.

[0180] As can be seen from the above, compared with the comparative example, the embodiments of the present invention achieve the coordinated optimization of light weight, high strength, high stiffness and excellent processing performance by reasonably controlling the types of alloy elements and optimizing their contents. Among them, Cu and Li elements work together to form AlCuLi phase, which effectively improves the strength and toughness of the alloy. At the same time, the present application reasonably controls the content of Cu and Li elements within a specific range, and on the basis of ensuring the strength and toughness of the alloy, effectively reduces the density, enhances the stiffness, and takes into account high strength, light weight and plasticity. Mg can promote the formation of strengthening phases, optimize the hardness and plasticity of the alloy, and Mn and Zr can synergistically refine the grains, enhance the tensile and yield strengths, and maintain good cold deformation ability. In addition, the content of Si, Fe, and Ti is also limited to avoid the formation of hard and brittle phases and ensure the plasticity and formability of the alloy. During the preparation process, the microstructure is finely controlled by hot deformation, cold rolling, short intermediate annealing, short solid solution, quenching, cold deformation, annealing and other steps to obtain an aluminum alloy sheet with a thickness of 0.1 to 0.4 mm and a density of 2.55 to 2.62 g / cm 3 , room temperature tensile strength ≥430MPa, yield strength ≥380MPa, elongation ≥11%, elastic modulus 77~81GPa, no cracks appear after being bent 180° 3~5 times, with excellent comprehensive performance, suitable for the new generation of ultra-thin and ultra-light mobile phones, computers, LCD displays and smart wearable products.

[0181] In addition, it can be seen that when each process parameter is within the preferred range of the present invention, the comprehensive effect of the alloy is better.

[0182] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an aluminum alloy sheet for an electronic screen backplane, characterized in that: The thickness of the aluminum alloy plate is 0.1-0.4 mm, and the elements and their weight percentages contained in the aluminum alloy plate are: Cu: 2.5-2.9%, Li: 1.6-2.6%, Mg: 0.3-0.5%, Mn: 0.3-0.5%, Zr: 0.10-0.15%, Si≤0.03%, Fe≤0.04%, Ti≤0.08%, the balance is Al and unavoidable impurities, each of the unavoidable impurities is <0.04%, and the total impurities are <0.12%; The preparation method comprises the following steps: Step S1, manufacturing an aluminum alloy ingot according to the composition ratio of the aluminum alloy plate, and hot-deforming the aluminum alloy ingot to obtain a hot-deformed plate with a thickness of 2 to 5 mm; Step S2, cold rolling the thermally deformed sheet, and performing intermediate annealing during the cold rolling process to obtain a cold-rolled sheet; wherein the intermediate annealing temperature is 300-400° C., and the holding time is 15-30 min; Step S3, subjecting the cold-rolled sheet to solution treatment and quenching treatment in sequence to obtain a quenched sheet; wherein the temperature rise time for the solution treatment is 3 to 5 minutes, and the heat preservation time is 10 to 15 minutes; Step S4, cold deforming the quenched plate to obtain a cold deformed plate, and annealing the cold deformed plate to obtain the aluminum alloy plate.

2. The preparation method according to claim 1, characterized in that: The elements contained in the aluminum alloy plate and their weight percentages are: Cu: 2.5-2.7%, Li: 2.1-2.6%, Mg: 0.3-0.5%, Mn: 0.3-0.5%, Zr: 0.10-0.12%, Si≤0.03%, Fe≤0.04%, Ti≤0.06%, the balance is Al and inevitable impurities, each of the inevitable impurities is <0.03%, and the total impurities are <0.1%.

3. The preparation method according to claim 1 or 2, characterized in that: In the aluminum alloy sheet, The weight ratio of Cu to Li is 1.0 to 1.7; and / or, The sum of the weight percentages of Mn and Zr is 0.45-0.65%.

4. The preparation method according to any one of claims 1 to 3, characterized in that In the step S1, The thermal deformation includes hot extrusion and / or hot rolling; Preferably, during the hot extrusion, the heating temperature of the aluminum alloy ingot is 470-490°C; Preferably, during the hot rolling, the heating temperature of the aluminum alloy ingot is 480-500°C.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In the step S2, The cold rolling has a pass reduction rate of 15-50% and a temperature of 10-45°C.

6. The preparation method according to any one of claims 1 to 5, characterized in that In the step S3, The solid solution temperature is 500-550°C; and / or, The quenching treatment is completed within 1 to 5 seconds after the solutionizing is completed; Preferably, the cooling rate of the quenching is 150-450°C / s.

7. The preparation method according to any one of claims 1 to 6, characterized in that In the step S4, The cold deformation amount is 0.5-5%; and / or, The cold deformation includes stretching deformation and / or calendering treatment. Preferably, the stretching speed of the stretching deformation is 10 to 30 mm / min; preferably, the calendering speed of the calendering treatment is 300 to 600 mm / min, and the number of calendering is 1 to 3 times; and / or, The annealing treatment is performed at a temperature of 160 to 180° C. and a heat preservation time of 4 to 32 hours.

8. An aluminum alloy plate for an electronic screen back plate, characterized in that: The aluminum alloy sheet is obtained by the preparation method of any one of claims 1 to 7.

9. The aluminum alloy sheet according to claim 8, characterized in that: In the aluminum alloy sheet, The average diameter of the grains is ≤50 μm; and / or, The aluminum alloy plate comprises an optional coarse phase, wherein the coarse phase comprises one or more of AlCuFeMn, AlCuFe, AlCuMn and AlFeMn, and the maximum diameter of any compound of AlCuFeMn, AlCuFe, AlCuMn and AlFeMn is ≤1.5 μm, preferably ≤1 μm; The density of the aluminum alloy plate is 2.55-2.62 g / cm 3 , room temperature tensile strength ≥430MPa, yield strength ≥380MPa, elongation ≥11%, elastic modulus 77~81GPa, no cracks appear after 180° bending 3~5 times.

10. Application of the aluminum alloy sheet according to claim 8 or 9 in the fields of mobile phones, computers, liquid crystal displays and smart wearables.

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