A composite treatment method for inhibiting natural aging of an aluminum alloy plate and improving artificial aging response and strength

Abstract

The present application belongs to the technical field of aluminum alloy plate, and discloses a composite treatment method for inhibiting natural aging of aluminum alloy plate and improving artificial aging response and strength. The method comprises the following steps: S1) Zn and La composite alloying treatment is performed on aluminum alloy melt; then, a cast ingot is prepared, homogenization treatment, hot rolling, cold rolling and solid solution treatment are performed, and a supersaturated solid solution plate is obtained; S2) the supersaturated solid solution plate is cold-rolled to complete pre-deformation; and S3) the alloy plate after pre-deformation is subjected to natural aging and artificial aging treatment to complete final aging. The method fully utilizes the interactive effect of La and Zn element composite and pre-deformation, fully inhibits the formation of room temperature atom clusters in the natural aging process, promotes the precipitation of strengthening phase in the artificial aging process, so that the alloy has a significant artificial aging response, the strength and hardness of the alloy after response are significantly improved, and excellent plasticity is exhibited. The present application is easy to mass produce.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy sheet preparation technology for automobile bodies, and specifically relates to a composite treatment method for inhibiting the natural aging of aluminum alloy sheets and improving the artificial aging response and strength. Background Technology

[0002] Energy conservation and emission reduction are critical issues that the automotive industry urgently needs to address. Studies show that a 10% reduction in vehicle weight can save 5% to 8% on fuel consumption. Regarding the greenhouse effect, every 100kg reduction in vehicle weight can reduce CO2 emissions by 12.5g / km. 2 It is evident that reducing vehicle weight is one of the most effective measures to make cars more fuel-efficient and environmentally friendly. Currently, the use of lightweight materials in manufacturing is the main direction of automotive lightweighting development, and aluminum alloys, with their advantages of low density, corrosion resistance, and recyclability, are one of the ideal lightweight materials for automotive lightweighting.

[0003] 6xxx series aluminum alloys possess characteristics such as rapid aging response, good corrosion resistance, and excellent weldability, making them widely used as materials for automotive structural components and body parts. Before service, car body panels typically undergo a baking paint treatment, a process that involves heat-treating the panels at 180°C for 30 minutes to improve material strength. To enhance the aging response speed and strength of 6xxx series alloys, some Cu can be added to the alloy, resulting in Al-Mg-Si-Cu alloys. While the aging response and strength of these alloys are improved, they still do not meet the demands of industrial production. Currently, the main method for developing automotive body panel materials is to control the alloy composition to ensure good stamping formability before painting, rapid aging response during painting, and higher strength after painting. Therefore, accelerating the development and design of 6xxx series aluminum alloys is of positive significance for reducing vehicle body weight.

[0004] Natural aging refers to the slow aging at room temperature that occurs during the alloy production process after solution quenching and subsequent resting at room temperature. For 6xxx series aluminum alloys, natural aging reduces the alloy's subsequent artificial aging hardening potential, resulting in significantly lower achievable mechanical properties compared to direct artificial aging—a negative effect of natural aging. Researchers have conducted various studies to mitigate the adverse effects of natural aging on 6xxx series aluminum alloys and improve their artificial aging response for paint hardening.

[0005] Patent CN112941378B discloses a method for slow-aging 6xxx series aluminum alloys. By adjusting the composition of the 6xxx series aluminum alloy, Sn element is used to suppress the formation of MgSi atomic clusters during natural aging, thereby avoiding the increase in strength of the aluminum alloy during natural aging and achieving the effect of slowing down the natural aging process. Patent application CN115141990A discloses a pretreatment method for improving the paint hardening performance of automotive 6xxx series aluminum alloys. The alloy after solution treatment is subjected to high-temperature pre-stretching deformation treatment. After solution quenching, the alloy sheet is held at 165℃~180℃ for 4~6 minutes, and pre-stretching deformation treatment is performed simultaneously, with a deformation amount of 1~10%. Then, natural aging is performed followed by artificial aging treatment. The treated alloy has lower T4 hardness and higher paint hardness.

[0006] In the aforementioned aluminum alloy processing methods, while the addition of Sn can significantly suppress natural aging, it is difficult to improve the alloy's response to subsequent artificial aging with paint baking. The resulting sheet material exhibits limited strength increase after baking, failing to meet the requirements of automotive aluminum alloys for high formability and high paint baking strength. Furthermore, the simultaneous high-temperature pre-stretching deformation method is difficult to control in production, with short high-temperature holding times, making it difficult for the alloy to reach the appropriate temperature, particularly hindering rapid isothermalization between the surface and core. The high-temperature short-time pre-aging and low-temperature long-time pre-aging methods have long pretreatment cycles, resulting in high energy consumption and low production efficiency in actual production.

[0007] This invention employs a La and Zn composite alloying synergistic pretreatment process to treat aluminum alloys. With natural aging, the tensile strength increases significantly during the artificial aging process before painting, resulting in high strength and hardness after painting, while maintaining good plasticity and an elongation at break exceeding 30%. This invention effectively inhibits natural aging while significantly improving the hardening performance of the paint. Furthermore, this invention is easy to operate and control, which helps improve production efficiency. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, the present invention aims to provide a composite treatment method for suppressing the natural aging of aluminum alloy sheets and improving the response and strength of artificial aging. The present invention optimizes the determination of alloy composition and obtains an optimal range of process parameters. This process requires no additional equipment; it is simply a flow of alloy preparation and pretreatment. The method of the present invention not only suppresses the natural aging of aluminum alloy sheets and improves the response and strength of artificial aging, but also increases production efficiency.

[0009] This invention is achieved through the following technical solution:

[0010] A composite treatment method for inhibiting the natural aging of aluminum alloy sheets and improving the response and strength of artificial aging includes the following steps:

[0011] S1) The aluminum alloy melt is subjected to Zn and La composite alloying treatment; then ingots are prepared, homogenized, hot rolled, cold rolled and solution treated to obtain supersaturated solution plate.

[0012] S2) The supersaturated solid solution plate is cold rolled to complete the pre-deformation;

[0013] S3) The pre-deformed alloy sheet is subjected to natural aging and artificial aging treatments to complete the final aging; the natural aging refers to placing it at room temperature, and the artificial aging refers to heat preservation treatment.

[0014] The composite treatment method for inhibiting the natural aging of aluminum alloy sheets and improving the response and strength of artificial aging specifically includes the following steps:

[0015] 1) Alloying treatment: The aluminum alloy melt is subjected to Zn and La composite alloying treatment; then ingots are prepared;

[0016] 2) Homogenization treatment: The ingot is kept at a constant temperature to obtain a homogenized alloy;

[0017] 3) The homogenized alloy is hot-rolled and cold-rolled to obtain cold-rolled sheet;

[0018] 4) The cold-rolled sheet is placed in an insulation device for insulation, and then rapidly cooled to obtain a supersaturated solid solution sheet;

[0019] 5) The supersaturated solid solution plate is cold-rolled to complete the pre-deformation;

[0020] 6) Place the pre-deformed alloy sheet at room temperature and then heat it to complete the final aging.

[0021] The aluminum alloy mentioned in step 1) is a 6xxx series aluminum alloy.

[0022] The composition of the 6xxx series aluminum alloy ingot, by mass percentage, is: Si: 0.70%–1.00%, Mg: 0.60%–0.90%, Cu: 0.60%–0.80%, Mn: 0.10%–0.30%, Fe: 0.10%–0.20%, Zn: 0.50%–1.00%, La: 0.05%–0.20%, impurity elements ≤0.15%, and the balance is Al.

[0023] The homogenization process described in step 2) involves placing the 6xxx series wrought aluminum alloy casting billet in a heat preservation device for heat preservation at a temperature of 550–580°C for 7–9 hours, and then cooling it to room temperature with the furnace.

[0024] The hot rolling temperature in step 3) is 450–480°C, and the total reduction is 45%–55%; the cold rolling is carried out after the plate has been cooled to room temperature after hot rolling, and the total reduction is 45%–55%.

[0025] The rolling process is a multi-pass rolling process, with a reduction of 5-15% per pass in hot or cold rolling; the number of rolling passes is 10-25. When the reduction per pass is controlled at 10%, the number of rolling passes is 13-17.

[0026] The temperature for heat preservation in step 4) is 510–530℃, and the heat preservation time is 20–40 min.

[0027] The rapid cooling refers to cooling with room temperature water. Specifically, it means immersing the insulated board in water for cooling or spraying water mist to cool the board.

[0028] The total reduction of cold rolling in step 5) is 2-5% (preferably 2-4%), and it is a single rolling process.

[0029] This invention involves the synergistic control of Zn / La alloying and pretreatment. If the deformation amount in the pretreatment is too small, the effect of such a small deformation amount on the inhibition of natural aging of the alloy and the improvement of the response capability of artificial aging in paint baking is not significant, and the improvement effect of synergistic control with element alloying becomes small. If the deformation amount in the pretreatment is too large, it will significantly increase the hardness of the T4 state and reduce the hardness increment of natural aging, but the effect on the hardness increment of artificial aging in paint baking is not very significant.

[0030] The time to place the product at room temperature as described in step 6) is 14 days to 1 month, the heat preservation temperature is 170℃~190℃, and the heat preservation time is 20~60min.

[0031] The alloy prepared by this invention is an aluminum alloy for the casing of power batteries for new energy vehicles.

[0032] This invention combines La / Zn composite material with pre-deformation. La can bind with quenching vacancies to suppress natural aging, while Zn enhances the aging response. Furthermore, the deformation pretreatment process generates dislocations, increasing internal defects in the alloy and providing nucleation sites for the formation of the GP zone. This accelerates the transformation of the GP zone to the β” phase during the artificial aging process with paint baking, leading to the accelerated precipitation of the dominant strengthening phase, β”. The combined and synergistic effects of these factors help suppress natural aging while simultaneously improving the artificial aging response rate and the strength of the alloy after paint baking. The alloy can maintain high aging response and strength properties even after a short period of artificial aging following a period of storage at room temperature.

[0033] Compared with the existing manufacturing process of 6xxx series aluminum alloys for automotive body panels, it has the following outstanding advantages:

[0034] (1) The mechanical properties of the alloy prepared by the present invention are significantly delayed during the natural aging process at room temperature, while still having high plasticity and retaining excellent stamping performance; after being left at room temperature for a period of time, it undergoes short-term artificial aging and has a significant rapid response capability for artificial aging.

[0035] (2) The present invention achieves that the changes in alloy strength and hardness remain almost constant during natural aging, and the increase in artificial aging of paint does not decrease with daily natural aging.

[0036] (3) For 6111 aluminum alloy, which is widely used in automotive sheet materials, the alloy treated by this invention has a T4 hardness increase of ΔH≤5HV within 2 to 4 weeks of natural aging. Even after long-term natural aging, the hardness is significantly affected by short-term artificial aging and baking paint hardening, with an increase of ΔH≥25HV.

[0037] (4) The tensile mechanical property increment ΔRm after natural aging for 2 weeks and short-term artificial aging is above 60MPa, and the elongation at break is still above 25%. It has high artificial aging increment while maintaining good plasticity.

[0038] (5) Compared with traditional pre-aging or pre-deformation processes, the present invention can reduce the number of pretreatment processes and has significant cost-saving advantages in production.

[0039] (6) The process of the present invention does not require the addition of new equipment. It only requires the adjustment of the production steps of the existing production line to produce 6xxx series aluminum alloys for automotive sheet metal that reduce the adverse effects of natural aging and improve the response capability of artificial aging, and is easy to achieve mass production. Attached Figure Description

[0040] Figure 1 This is a flow chart of the traditional production process for 6xxx series aluminum alloys.

[0041] Figure 2 To compare the changes in T4 hardness of the alloy under natural aging at different times and the corresponding changes in hardness under short-time artificial aging with paint in Example 1;

[0042] Figure 3 The mechanical property curves of the alloy in Comparative Example 1 after 14 days of natural aging in the T4 state and the corresponding changes in strength after short-time baking paint artificial aging are shown.

[0043] Figure 4 This is a process flow diagram of the present invention;

[0044] Figure 5 The changes in T4 hardness and corresponding short-time artificial aging hardness of the alloy under natural aging at different times are shown in Example 1.

[0045] Figure 6 The mechanical property curves of the alloy in Example 1 after 14 days of natural aging in the T4 state and the changes in mechanical properties after short-time baking paint artificial aging are shown. Detailed Implementation

[0046] The present invention will be described in further detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0047] To better illustrate the implementation effect of the present invention, the solution aging and pre-aging process of 6111 aluminum alloy used in the production of power battery shells for new energy vehicles is used as Comparative Example 1.

[0048] Comparative Example 1

[0049] 6111 aluminum alloy is a common wrought aluminum alloy used in the manufacture of automotive body panels. In mass production, its manufacturing process includes smelting, water-cooled crystallizer ingot production, homogenization annealing, high-temperature hot rolling, and cold rolling to obtain the sheet material. In the comparative example, the composition of the 6111 alloy is 0.72% Mg, 0.86% Si, 0.72% Cu, 0.30% Mn, 0.21% Fe, with the balance being Al.

[0050] The wrought aluminum alloy used in this invention is first processed through casting ingot equipment, homogenization heat treatment, high-temperature hot rolling, and cold rolling to obtain sheet metal. The homogenization treatment involves holding at 560℃ for 8 hours, followed by furnace cooling to room temperature to dissolve the alloy phases as much as possible and ensure sufficient compositional homogeneity. After homogenization annealing, the ingot is heated to 460℃ and hot-rolled to a 10mm sheet metal, with a rolling deformation exceeding 50%. The hot-rolled sheet metal is then cooled to room temperature and cold-rolled to a 5mm sheet metal, with a rolling deformation exceeding 50%. The resulting cold-rolled sheet metal undergoes solution aging treatment to obtain the desired properties. This comparative example uses a traditional solution aging process, which is currently the most widely used production process for manufacturing 6111 alloy automotive body sheet metal.

[0051] Solution aging treatment: First, the sheet material cooled to room temperature undergoes solution treatment at 530℃ for 30 minutes, followed by quenching in room temperature water to obtain a supersaturated solution-treated sheet. Then, it is placed at room temperature for 0–14 days. Each day, the hardness of the T4 state alloy is tested, followed by short-term artificial aging with paint baking at 180℃ for 30 minutes. Finally, the hardness of the aged alloy (T61 state) is tested. It should be noted that in actual production, the artificial aging temperature for paint baking is around 180℃, and the baking time is controlled within 30–60 minutes to ensure production efficiency.

[0052] This comparative example describes the treatment of homogenized rolled sheets using traditional heat treatment processes, the process flow diagram of which is shown below. Figure 1 As shown.

[0053] The hardness of the alloy in the T4 state after daily natural aging and the corresponding hardness in the T61 state after short-time baking were measured using a Vickers hardness tester (model: HVS-10A, standard: GB / T 4340.1-2009). The mechanical properties of the alloy under different conditions and times were measured using an electronic multi-material testing machine (model: AG-X-100KN, standard: BG / T 228-2010), and the corresponding tensile strength, yield strength, and elongation at break were obtained.

[0054] Figure 2 To compare the hardness changes of the alloy in Example 1 at different aging times in the T4 state and the corresponding hardness changes in the T61 state after short-term painting, it can be seen that the hardness of the alloy is very low immediately after solution treatment, but gradually increases with natural aging, from 55.7 HV to 72.7 HV. The hardness increase ΔH in the T4 state brought about by natural aging is 17.0 HV. From the hardness change in the T61 state, it can be seen that with the progress of natural aging, the hardness change after daily painting gradually decreases, and on the 14th day, the hardness increase brought about by painting is only 4.9 HV, meaning the alloy obtained after painting shows almost no improvement compared to before painting.

[0055] The mechanical properties of the alloy were tested under different conditions of natural aging (0 days and 14 days), with a focus on comparing the changes in tensile strength before and after baking paint. Figure 3 The tensile mechanical properties curves of the alloy in Comparative Example 1 after 14 days of natural aging are shown. The tensile mechanical properties show that the tensile strength of the alloy after solution treatment is 190.2 MPa, and the elongation at break is 38.6%. After baking paint, the tensile strength of the T61 alloy increases to 220.3 MPa, an increase of 30.1 MPa, while the elongation at break is 34.5%, a decrease of 4.2%. The tensile strength of the T4 state after 14 days of natural aging is 214.0 MPa, an increase of 23.8 MPa compared to after solution quenching, with an elongation at break of 35.7%. After baking paint, the tensile strength of the alloy is 219.6 MPa, an increase of only 5.6 MPa.

[0056] To further illustrate the effects of the present invention, the present invention will be described below in conjunction with embodiments.

[0057] Example 1

[0058] The alloy used in this embodiment is 6111 alloy. The homogenization annealing, hot rolling, and cold rolling process parameters are the same as those in Comparative Example 1. The difference lies in the specific alloy composition and the subsequent heat treatment process for the rolled sheet. The process flow of this embodiment is as follows: Figure 4 As shown.

[0059] In this embodiment, the composite pretreatment process refers to the process whereby after the alloy is alloyed with La / Zn elements, the homogenized, hot-rolled and cold-rolled plates are subjected to solution treatment, followed by continuous quenching and pre-deformation treatment. After the treatment is completed, the alloy is left at room temperature for a period of time, and then subjected to short-time baking paint artificial aging to obtain the final product.

[0060] The composite pretreatment process in this embodiment specifically includes the following steps:

[0061] (1) Alloy melting

[0062] Melt 6xxx alloy and perform Zn / La composite alloying treatment on the alloy melt.

[0063] (2) Ingot preparation

[0064] 6xxx series aluminum alloy ingots treated with Zn / La composite alloying were prepared using a semi-continuous casting method. In this embodiment, the composition of the ingot is 0.72% Mg, 0.84% ​​Si, 0.72% Cu, 0.29% Mn, 0.20% Fe, 0.50% Zn, 0.10% La, with the balance being Al.

[0065] (3) Homogenization treatment

[0066] The alloy ingot was kept at a constant temperature of 560℃ for 8 hours to obtain a homogenized alloy.

[0067] (4) Hot rolling and cold rolling

[0068] The homogenized alloy was subjected to hot rolling and cold rolling respectively to obtain cold-rolled sheet. The hot rolling temperature was 460℃, the total reduction was 50%, and the reduction per pass was 10%. The total reduction of the cold rolling was 50%, and the reduction per pass was 10%.

[0069] (5) Solution quenching

[0070] The rolled sheet material cooled to room temperature was subjected to solution treatment at a temperature of 530℃ and a holding time of 30 minutes, followed by quenching in room temperature water to obtain a supersaturated solution-treated sheet material.

[0071] (6) Pre-deformation

[0072] The alloy sheet after solution quenching is subjected to cold rolling deformation with a reduction of 2%.

[0073] (7) Store at room temperature

[0074] The pre-deformed alloy is left at room temperature for 14 days to 1 month to allow it to age naturally.

[0075] (8) Final Validity Period

[0076] The alloy, after being left at room temperature for several days, underwent final aging, namely short-time baking paint artificial aging, with an aging temperature of 180℃ and an aging time of 30 minutes.

[0077] To better understand the design basis of the process flow of this invention and the determination range of its process parameters, the basic principles for realizing this invention are explained as follows:

[0078] 6111 alloy is an Al-Mg-Si based wrought aluminum alloy. Its strengthening mechanisms mainly include solid solution strengthening, deformation strengthening, and second-phase strengthening. Among these, the formation of finely dispersed precipitates during aging is the primary strengthening mechanism. The aging precipitation sequence of 6111 alloy progresses with increasing temperature from solute atom clusters to the GP region, then to the β” phase, then to the β' phase, and finally to the Q' phase. The main strengthening phases, the β” and Q' phases, are coherent with the matrix. The resulting coherent distortion generates a continuous strain field around the precipitates, hindering dislocation movement and thus achieving a strengthening effect.

[0079] During the production of 6111 alloy, due to storage or transportation processes, it inevitably undergoes a period of rest at room temperature after solution quenching, during which natural aging occurs. During natural aging, Mg and Si atoms in the solute combine with quenching vacancies and gradually grow into atomic clusters through diffusion. These clusters gradually grow and stabilize with natural aging, but their size remains very small and coherent with the matrix, increasing the hardness and strength of the T4 state alloy while reducing its stamping formability. In the artificial aging stage for baking paint, these clusters hinder the formation of the β” phase, reducing the alloy's paint hardening ability. Furthermore, because artificial aging for baking paint involves a short aging period at a relatively low temperature, the alloy is usually in an under-aged stage, making it difficult to achieve considerable strength.

[0080] The addition of Zn can improve the artificial aging response of 6xxx series alloys. The Mg-Zn atom clusters formed in the early stage of aging are an important reason for the enhanced response in the early stage of aging. They can act as nucleation sites for the β” phase, and then form a higher density Mg-Si precipitate phase during the aging process. Due to the complex interaction between Zn atoms and Mg, Si, and Cu atoms, Zn increases the number of precipitates at the peak aging of 6xxx series alloys, and the peak strength of the alloy is significantly improved. The addition of La can inhibit the binding of Si and Mg atoms with vacancies by combining with the supersaturated vacancies formed after quenching, thereby inhibiting natural aging. The high binding energy between La and vacancies and the strong interaction between La and Mg and Si reduce the precipitation activation energy of the β” strengthening phase, promote the precipitation of the β” strengthening phase, and improve the aging response of the alloy.

[0081] After solution treatment and pre-deformation cold rolling, defects such as dislocations will enter the alloy, accelerating the annihilation of quenching vacancies and making it difficult for naturally aged clusters to form. At the same time, the dislocations formed in the pre-deformation stage will serve as atomic channels for subsequent artificial aging, promoting the precipitation of Mg and Si atoms and accelerating the β” transformation of the GP zone phase. Pre-deformation can not only reduce the adverse effects of natural aging, but also improve the response capability of short-time baking paint artificial aging, shorten the time required for alloy peak aging, and improve production efficiency.

[0082] Figure 5 The figures show the hardness changes of the alloy in Example 1 at different natural aging times (T4 state) and the corresponding hardness changes in the T61 state after short-term baking paint. It can be seen that after pretreatment, the initial hardness of the alloy is relatively high, reaching 83.9 HV. This is because the pretreatment applies work hardening to the alloy, increasing the material's hardness. After baking paint, the alloy's hardness increases to 117.3 HV, with a hardness increase ΔH of 33.4 HV. After 14 days of natural aging, the hardness of the alloy in the T4 state increases to 89.3 HV, an increase of 5.4 HV. After baking paint, the alloy's hardness increases to 115.0 HV, with a hardness increase ΔH of 25.7 HV. Even after 14 days of natural aging, the alloy still exhibits a high response to artificial aging with baking paint.

[0083] Similar to Comparative Example 1, the mechanical properties of the alloy were tested under different conditions of natural aging (0 days and 14 days), with a focus on comparing the changes in tensile strength before and after painting. Figure 6 The tensile mechanical property curves of the alloy in Example 1 show the changes with natural aging. After solution pretreatment, the tensile strength of the alloy in the T4 state is 237.2 MPa, and the elongation at break is 29.5%. After baking paint treatment, the tensile strength of the alloy in the T61 state is 330.2 MPa, an increase of 93.0 MPa, and the elongation at break is 33.5%. After 14 days of natural aging, the tensile strength of the alloy in the T4 state is 245.8 MPa, and the elongation at break is 30.8%. After baking paint treatment, the tensile strength of the alloy in the T61 state is 321.6 MPa, an increase of 75.8 MPa, and the elongation at break is 34.5%. After 14 days of natural aging, the alloy still maintains excellent response to artificial aging after baking paint treatment, and the elongation at break of the alloy treated by this process can still reach more than 30% after baking paint, maintaining good plasticity.

[0084] Compared to Comparative Example 1, in this embodiment, under the same natural aging time (0-14 days), the hardness increment of the alloy in the T4 state decreased significantly during natural aging, from 17.0 HV in the comparative example to 5.4 HV. On the 14th day of natural aging, artificial aging with paint baking was performed, and the hardness increment increased from 4.9 HV in the comparative example to 25.7 HV. The hardness increment during artificial aging with paint baking was also significantly increased. Furthermore, in Example 1, the hardness increment hardly decreased during natural aging, demonstrating significant stability against natural aging and rapid response to artificial aging. Simultaneously, the alloy exhibited excellent strength before and after paint baking. After 14 days of natural aging, the hardness increment of Example 1 with paint baking was 75.8 MPa, a significant improvement compared to the 5.6 MPa hardness increment of Comparative Example 1.

[0085] Example 2

[0086] The alloy used in this embodiment is 6111 alloy. The homogenization annealing, hot rolling and cold rolling process parameters are the same as those in Comparative Example 1. The difference from Comparative Example 1 is the specific composition of the alloy and the subsequent heat treatment process for the rolled plate.

[0087] In this embodiment, the composite pretreatment process refers to the process whereby after the alloy is alloyed with La / Zn elements, the homogenized, hot-rolled and cold-rolled plates are subjected to solution treatment, followed by continuous quenching and pre-deformation treatment. After the treatment is completed, the alloy is left at room temperature for a period of time, and then subjected to short-time baking paint artificial aging to obtain the final product.

[0088] The composite pretreatment process in this embodiment specifically includes the following steps:

[0089] (1) Alloy melting

[0090] Melt 6xxx alloy and perform Zn / La composite alloying treatment on the alloy melt.

[0091] (2) Ingot preparation

[0092] 6xxx series aluminum alloy ingots treated with Zn / La composite alloying were prepared using a semi-continuous casting method. The composition of the ingot in this embodiment is 0.72% Mg, 0.84% ​​Si, 0.71% Cu, 0.29% Mn, 0.20% Fe, 1.00% Zn, 0.10% La, with the balance being Al.

[0093] (3) Homogenization treatment

[0094] The alloy ingot was kept at a constant temperature of 560℃ for 8 hours to obtain a homogenized alloy.

[0095] (4) Hot rolling and cold rolling

[0096] The homogenized alloy was subjected to hot rolling and cold rolling respectively to obtain cold-rolled sheet. The hot rolling temperature was 460℃, the total reduction was 50%, and the reduction per pass was 10%. The total reduction of the cold rolling was 50%, and the reduction per pass was 10%.

[0097] (5) Solution quenching

[0098] The rolled sheet material cooled to room temperature was subjected to solution treatment at a temperature of 530℃ and a holding time of 30 minutes, followed by quenching in room temperature water to obtain a supersaturated solution-treated sheet material.

[0099] (6) Pre-deformation

[0100] The alloy sheet after solution quenching is subjected to cold rolling deformation with a reduction of 2%.

[0101] (7) Store at room temperature

[0102] The pre-deformed alloy is left at room temperature for 14 days to 1 month to allow it to age naturally.

[0103] (8) Final Validity Period

[0104] The alloy, after being left at room temperature for several days, underwent final aging, namely short-time baking paint artificial aging, with an aging temperature of 180℃ and an aging time of 30 minutes.

[0105] The hardness of the alloy in the T4 state at different natural aging times and the corresponding hardness in the T61 state after short-time painting were tested. The influence trend of natural aging on the hardness of the alloy in the T4 state and the corresponding hardness in the T61 state after short-time painting is similar to that in Example 1, except that the specific performance data are different. After pretreatment, the initial hardness of the alloy was 86 HV. After painting, the hardness of the alloy increased to 119 HV, with a painting hardness increase ΔH of 33 HV. After 14 days of natural aging, the hardness of the alloy in the T4 state increased to 87.5 HV, an increase of 1.5 HV; after painting, the hardness of the alloy increased to 115.2 HV, with a painting hardness increase ΔH = 27.7 HV. After 14 days of natural aging, the alloy still has a high response capability to artificial aging with painting.

[0106] The variation pattern of tensile strength is similar to that in Example 1. After solution pretreatment, the tensile strength of the alloy in the T4 state is 228.7 MPa, with an elongation at break of 33.1%. After baking paint treatment, the tensile strength of the alloy in the T61 state is 319.3 MPa, an increase of 90.6 MPa, with an elongation at break of 31.5%. After 14 days of natural aging, the tensile strength of the alloy in the T4 state is 247.4 MPa, with an elongation at break of 33.0%. After baking paint treatment, the tensile strength of the alloy in the T61 state is 318.7 MPa, an increase of 71.3 MPa, with an elongation at break of 36.2%. Even after 14 days of natural aging, the alloy still maintains excellent response to artificial aging after baking paint treatment. After 14 days of natural aging, the alloy underwent short-time artificial aging with paint baking. The fracture elongation of the aged alloy was increased compared to the naturally aged T4 state. This is presumably because the overall pre-deformation applied was larger, and the alloy underwent a recovery process during the short-time artificial aging, which improved the alloy's plasticity.

[0107] Compared to Comparative Example 1, this embodiment maintains a lower hardness change in the T4 state and a higher hardening response in the T61 state under the same natural aging time. The hardness increment decreased from 17.0 HV in the Comparative Example to 1.5 HV. Artificial aging with paint baking was performed on the 14th day of natural aging, and the hardness increment increased from 4.9 HV in the Comparative Example to 33.0 HV. The increment during artificial aging with paint baking was also significantly improved. Furthermore, in Example 1, the hardness increment hardly decreased during natural aging, demonstrating significant stability against natural aging and rapid response to artificial aging. Simultaneously, the alloy exhibited excellent strength before and after paint baking. After 14 days of natural aging, the paint baking increment in Example 1 was 71.3 MPa, a significant improvement compared to the 5.6 MPa paint baking increment in Comparative Example 1.

[0108] Example 3

[0109] The alloy used in this embodiment is 6111 alloy. The homogenization annealing, hot rolling and cold rolling process parameters are the same as those in Comparative Example 1. The difference from Comparative Example 1 is the specific composition of the alloy and the subsequent heat treatment process for the rolled plate.

[0110] In this embodiment, the composite pretreatment process refers to the process whereby after the alloy is alloyed with La / Zn elements, the homogenized, hot-rolled and cold-rolled plates are subjected to solution treatment, followed by continuous quenching and pre-deformation treatment. After the treatment is completed, the alloy is left at room temperature for a period of time, and then subjected to short-time baking paint artificial aging to obtain the final product.

[0111] The composite pretreatment process in this embodiment specifically includes the following steps:

[0112] (1) Alloy melting

[0113] Melt 6xxx alloy and perform Zn / La composite alloying treatment on the alloy melt.

[0114] (2) Ingot preparation

[0115] 6xxx series aluminum alloy ingots treated with Zn / La composite alloying were prepared using a semi-continuous casting method. In this embodiment, the composition of the ingot is 0.72% Mg, 0.84% ​​Si, 0.72% Cu, 0.29% Mn, 0.20% Fe, 0.51% Zn, 0.20% La, with the balance being Al.

[0116] (3) Homogenization treatment

[0117] The alloy ingot was kept at a constant temperature of 560℃ for 8 hours to obtain a homogenized alloy.

[0118] (4) Hot rolling and cold rolling

[0119] The homogenized alloy was subjected to hot rolling and cold rolling respectively to obtain cold-rolled sheet. The hot rolling temperature was 460℃, the total reduction was 50%, and the reduction per pass was 10%. The total reduction of the cold rolling was 50%, and the reduction per pass was 10%.

[0120] (5) Solution quenching

[0121] The rolled sheet material cooled to room temperature was subjected to solution treatment at a temperature of 530℃ and a holding time of 30 minutes, followed by quenching in room temperature water to obtain a supersaturated solution-treated sheet material.

[0122] (6) Pre-deformation

[0123] The alloy sheet after solution quenching is subjected to cold rolling deformation with a reduction of 2%.

[0124] (7) Store at room temperature

[0125] The pre-deformed alloy is left at room temperature for 14 days to 1 month to allow it to age naturally.

[0126] (8) Final Validity Period

[0127] The alloy, after being left at room temperature for several days, underwent final aging, namely short-time baking paint artificial aging, with an aging temperature of 180℃ and an aging time of 30 minutes.

[0128] The hardness of the alloy in the T4 state at different natural aging times and the corresponding hardness in the T61 state after short-term painting were tested. The influence of natural aging on the hardness of the alloy in the T4 state and the corresponding hardness in the T61 state after short-term painting showed a similar trend to that in Example 1, except that the specific performance data differed. After solution treatment, the initial hardness of the alloy was 84.5 HV. After painting, the hardness of the alloy increased to 118.3 HV, with a painting increase of ΔH of 33.8 HV. After 14 days of natural aging, the hardness of the alloy in the T4 state was 88.1 HV. After painting, the hardness of the alloy increased to 116.5 HV, with a painting increase of ΔH of 28.4 HV. With the progress of natural aging, the hardness change of the T4 state was ΔH = 3.6 HV, while the paint increase did not change significantly with the progress of natural aging.

[0129] The mechanical properties of the alloys under different conditions after natural aging (0 days and 14 days) were tested, and the variation pattern of tensile strength was similar to that in Example 1. After solution pretreatment, the tensile strength of the alloy in the T4 state was 235.1 MPa, and the elongation at break was 34.5%. After baking paint treatment, the tensile strength of the alloy in the T61 state was 325.2 MPa, an increase of 90.1 MPa, and the elongation at break was 32.9%. After 14 days of natural aging, the tensile strength of the alloy in the T4 state was 246.8 MPa, and the elongation at break was 34.1%. After baking paint treatment, the tensile strength of the alloy in the T61 state was 312.0 MPa, an increase of 65.2 MPa, and the elongation at break was 33.9%.

[0130] Compared to Comparative Example 1, this embodiment also maintains a lower hardness change in the T4 state and a higher hardening response in the T61 state under the same natural aging time. The hardness decreased from 17.0 HV in the Comparative Example to 3.6 HV. Artificial aging with paint was performed on the 14th day of natural aging, and the hardness increment increased from 4.9 HV in the Comparative Example to 28.4 HV. The artificial aging increment with paint also significantly improved, and in Example 1, the hardness hardly decreased during natural aging, demonstrating significant stability against natural aging and rapid artificial aging response. Simultaneously, the alloy exhibited good strength before and after paint application. After 14 days of natural aging, the paint increment in Example 4 was 65.2 MPa, a significant improvement compared to the 5.6 MPa paint increment in Comparative Example 1.

[0131] Example 4

[0132] The alloy used in this embodiment is 6111 alloy. The homogenization annealing, hot rolling and cold rolling process parameters are the same as those in Comparative Example 1. The difference from Comparative Example 1 is the specific composition of the alloy and the subsequent heat treatment process for the rolled plate.

[0133] In this embodiment, the composite pretreatment process refers to the process whereby after the alloy is alloyed with La / Zn elements, the homogenized, hot-rolled and cold-rolled plates are subjected to solution treatment, followed by continuous quenching and pre-deformation treatment. After the treatment is completed, the alloy is left at room temperature for a period of time, and then subjected to short-time baking paint artificial aging to obtain the final product.

[0134] The composite pretreatment process in this embodiment specifically includes the following steps:

[0135] (1) Alloy melting

[0136] Melt 6xxx alloy and perform Zn / La composite alloying treatment on the alloy melt.

[0137] (2) Ingot preparation

[0138] 6xxx series aluminum alloy ingots treated with Zn / La composite alloying were prepared using a semi-continuous casting method. The composition of the ingot in this embodiment is 0.71% Mg, 0.84% ​​Si, 0.72% Cu, 0.29% Mn, 0.20% Fe, 0.51% Zn, 0.10% La, with the balance being Al.

[0139] (3) Homogenization treatment

[0140] The alloy ingot was kept at a constant temperature of 560℃ for 8 hours to obtain a homogenized alloy.

[0141] (4) Hot rolling and cold rolling

[0142] The homogenized alloy was subjected to hot rolling and cold rolling respectively to obtain cold-rolled sheet. The hot rolling temperature was 460℃, the total reduction was 50%, and the reduction per pass was 10%. The total reduction of the cold rolling was 50%, and the reduction per pass was 10%.

[0143] (5) Solution quenching

[0144] The rolled sheet material cooled to room temperature was subjected to solution treatment at a temperature of 530℃ and a holding time of 30 minutes, followed by quenching in room temperature water to obtain a supersaturated solution-treated sheet material.

[0145] (6) Pre-deformation

[0146] The alloy sheet after solution quenching is subjected to cold rolling deformation with a reduction of 5%.

[0147] (7) Store at room temperature

[0148] The pre-deformed alloy is left at room temperature for 14 days to 1 month to allow it to age naturally.

[0149] (8) Final Validity Period

[0150] The alloy, after being left at room temperature for several days, underwent final aging, namely short-time baking paint artificial aging, with an aging temperature of 180℃ and an aging time of 30 minutes.

[0151] The hardness of the alloy in the T4 state at different natural aging times and the corresponding hardness in the T61 state after short-term painting were tested. The influence of natural aging on the hardness of the alloy in the T4 state and the corresponding hardness in the T61 state after short-term painting showed a similar trend to that in Example 1, except that the specific performance data differed. After solution treatment, the initial hardness of the alloy was 89.5 HV. After painting, the hardness of the alloy increased to 120.3 HV, with a painting increase of ΔH of 30.8 HV. After 14 days of natural aging, the hardness of the alloy in the T4 state was 90.1 HV. After painting, the hardness of the alloy increased to 117.6 HV, with a painting increase of ΔH of 27.5 HV. With the progress of natural aging, the hardness change of the T4 state was ΔH = 0.6 HV, while the paint increase did not change significantly with the progress of natural aging.

[0152] The mechanical properties of the alloys under different conditions after natural aging (0 days and 14 days) were tested, and the variation pattern of tensile strength was similar to that in Example 1. After solution pretreatment, the tensile strength of the alloy in the T4 state was 246.6 MPa, and the elongation at break was 28.6%. After baking paint treatment, the tensile strength of the alloy in the T61 state was 326.1 MPa, an increase of 79.5 MPa, and the elongation at break was 30.7%. After 14 days of natural aging, the tensile strength of the alloy in the T4 state was 251.3 MPa, and the elongation at break was 27.5%. After baking paint treatment, the tensile strength of the alloy in the T61 state was 308.0 MPa, an increase of 56.7 MPa, and the elongation at break was 30.2%.

[0153] Compared to Comparative Example 1, this embodiment also maintains a lower hardness change in the T4 state and a higher hardening response in the T61 state under the same natural aging time. The hardness decreased from 17.0 HV in the Comparative Example to 0.6 HV. Artificial aging with paint baking was performed on the 14th day of natural aging, and the hardness increment increased from 4.9 HV in the Comparative Example to 27.5 HV. The increment during artificial aging with paint baking was also significantly improved. Furthermore, in Example 1, the hardness hardly decreased during natural aging, demonstrating significant stability against natural aging and rapid response to artificial aging. Simultaneously, the alloy exhibited good strength before and after paint baking. After 14 days of natural aging, the paint baking increment in Example 4 was 56.7 MPa, a significant improvement compared to the 5.6 MPa increment in Comparative Example 1. The fracture elongation of the alloy after paint baking was higher than that in the T4 state, presumably because the overall applied pre-deformation was larger, and the alloy underwent a recovery process during the short-term artificial aging, improving the alloy's plasticity.

[0154] To better compare the implementation effects of the present invention, the key performance parameters of the alloys prepared in Comparative Example 1 and Examples 1-4, and their performance improvement data compared with the traditional process, are summarized in Table 1. It should be noted that the comparative improvement ratio and comparative increase value in this table are based on the hardness data and tensile mechanical property data of Comparative Example 1 after 14 days of natural aging.

[0155] Obviously, the alloys prepared by the process of this invention show a hardness increase of less than 5 HV in the T4 state during 14 days of natural aging. Compared with the hardness increase in the T4 state during 14 days of natural aging in Comparative Example 1, the hardness increase in the T4 state caused by natural aging is much smaller than that of the alloys prepared by the traditional process, which significantly reduces the adverse effects of natural aging. After 14 days of natural aging, the hardness increase after short-term artificial aging is more than 25 HV, which is much greater than the hardness increase of the alloys prepared by the traditional process after 14 days of natural aging followed by short-term artificial aging. The alloys still maintain good paint hardening response.

[0156] Table 1. Key performance parameters and improvement data statistics of alloys prepared in Comparative Examples 1 and Examples 1-4

[0157]

[0158] Explanation: The artificial aging response ΔH of the naturally aged paint on day 14 = Hardness of the T61 state after paint baking - Hardness of the T4 state before paint baking. ΔRm = Tensile strength of the T61 state after paint baking - Tensile strength of the T4 state before paint baking.

[0159] Based on the above embodiments, the key to the composite treatment method of the present invention lies in the La / Zn composite alloying of the alloy and the application of pre-deformation before room temperature storage after solution treatment. This effectively reduces the adverse effects of natural aging and improves the artificial aging response capability for short-term paint baking after natural aging. After artificial aging, the material not only exhibits high hardness but also outstanding tensile strength and good plastic deformation capability, which can well meet the requirements of new energy vehicle power battery shells and other automotive sheet metal structural components. Furthermore, compared to traditional processes, the material retains good aging response characteristics even after pretreatment.

[0160] To better illustrate the implementation effects of the present invention, the present invention further modifies the process flow or process sequence, processes the 6111 alloy homogenized rolled plate, and provides a comparative explanation.

[0161] Comparative Example 2

[0162] The alloy used in this comparative example is 6111 alloy. The alloy composition, ingot preparation, homogenization annealing, hot rolling, cold rolling, and solution quenching process parameters are exactly the same as in Comparative Example 1. The difference lies in the subsequent heat treatment process for the rolled sheet after alloy homogenization. The main difference is the application of pre-deformation after solution quenching. The detailed process flow and parameters are as follows:

[0163] The composite pretreatment process in this embodiment specifically includes the following steps:

[0164] (1) Solution quenching

[0165] The rolled sheet material cooled to room temperature was subjected to solution treatment at a temperature of 530℃ and a holding time of 30 minutes, followed by quenching in room temperature water to obtain a supersaturated solution-treated sheet material.

[0166] (2) Pre-deformation

[0167] The alloy sheet after solution quenching is subjected to cold rolling deformation with a reduction of 2%.

[0168] (3) Store at room temperature

[0169] The pre-deformed alloy is left at room temperature for a period of time to allow it to age naturally.

[0170] (4) Final Validity Period

[0171] The alloy, after being left at room temperature for several days, underwent final aging, namely short-time baking paint artificial aging, with an aging temperature of 180℃ and an aging time of 30 minutes.

[0172] The change in hardness in the T4 state during the natural aging process of the alloy was tested. The hardness of the alloy in the T4 state after solution pretreatment was 75.7 HV, and the hardness in the T4 state on day 14 of natural aging was 78.5 HV. After short-time artificial aging with paint baking, the hardness of the alloy was 98.7 HV, and the hardening increment ΔH of the paint baking was 20.2 HV. The corresponding tensile strength in the T4 state on day 14 of natural aging was 245.1 MPa, and the tensile strength after paint baking increased to 285.5 MPa, an increase of 30.4 MPa. Compared with Comparative Example 1, the increase in hardness during natural aging was reduced, but the paint baking performance was not as good as that of this invention, mainly reflected in the fact that the hardness and tensile strength of the alloy after paint baking were lower than the corresponding parameters of this invention.

[0173] Comparative Example 3

[0174] The alloy used in this comparative example is 6111 alloy. The homogenization annealing, hot rolling, and cold rolling process parameters are the same as those in Comparative Example 1. The difference lies in the specific alloy composition and the subsequent heat treatment process for the rolled sheet. Specifically, the following steps are included:

[0175] (1) Alloy melting

[0176] Melt 6xxx alloy and perform Zn alloying treatment on the alloy melt.

[0177] (2) Ingot preparation

[0178] 6xxx series aluminum alloy ingots with Zn alloying treatment were prepared by a semi-continuous casting method. The composition of the comparative ingot was 0.72% Mg, 0.85% Si, 0.70% Cu, 0.29% Mn, 0.20% Fe, 0.51% Zn, with the balance being Al.

[0179] (3) Homogenization treatment

[0180] The alloy ingot was kept at a constant temperature of 560℃ for 8 hours to obtain a homogenized alloy.

[0181] (4) Hot rolling and cold rolling

[0182] The homogenized alloy was subjected to hot rolling and cold rolling respectively to obtain cold-rolled sheet. The hot rolling temperature was 460℃, the total reduction was 50%, and the reduction per pass was 10%. The total reduction of the cold rolling was 50%, and the reduction per pass was 10%.

[0183] (5) Solution quenching

[0184] The rolled sheet material cooled to room temperature was subjected to solution treatment at a temperature of 530℃ and a holding time of 30 minutes, followed by quenching in room temperature water to obtain a supersaturated solution-treated sheet material.

[0185] (6) Pre-deformation

[0186] The alloy sheet after solution quenching is subjected to cold rolling deformation with a reduction of 2%.

[0187] (7) Store at room temperature

[0188] The pre-deformed alloy is left at room temperature for 14 days to 1 month to allow it to age naturally.

[0189] (8) Final Validity Period

[0190] The alloy, after being left at room temperature for several days, underwent final aging, namely short-time baking paint artificial aging, with an aging temperature of 180℃ and an aging time of 30 minutes.

[0191] The change in hardness in the T4 state during the natural aging process of the alloy was tested. After solution pretreatment, the hardness of the alloy in the T4 state was 82.5 HV. On day 14 of natural aging, the hardness of the T4 state was 84.2 HV. After short-time artificial aging with paint, the hardness of the alloy was 108.3 HV, and the hardening increment ΔH after paint baking was 24.1 HV. The corresponding tensile strength in the T4 state on day 14 of natural aging was 238.1 MPa, and the tensile strength after paint baking increased to 295.1 MPa, an increase of 57.0 MPa. Compared with Comparative Example 1, the increase in hardness during natural aging was reduced, but the hardness and tensile strength after artificial aging with paint baking were not as good as those of this invention.

[0192] Comparative Example 4

[0193] The alloy used in this comparative example is 6111 alloy. The homogenization annealing, hot rolling, and cold rolling process parameters are the same as those in Comparative Example 1. The difference lies in the specific alloy composition and the subsequent heat treatment process for the rolled sheet. Specifically, the following steps are included:

[0194] (1) Alloy melting

[0195] Melt the 6xxx alloy and perform La alloying treatment on the alloy melt.

[0196] (2) Ingot preparation

[0197] 6xxx series aluminum alloy ingots with La alloying treatment were prepared by a semi-continuous casting method. The composition of the comparative ingot was 0.73% Mg, 0.85% Si, 0.70% Cu, 0.29% Mn, 0.20% Fe, 0.11% La, with the balance being Al.

[0198] (3) Homogenization treatment

[0199] The alloy ingot was kept at a constant temperature of 560℃ for 8 hours to obtain a homogenized alloy.

[0200] (4) Hot rolling and cold rolling

[0201] The homogenized alloy was subjected to hot rolling and cold rolling respectively to obtain cold-rolled sheet. The hot rolling temperature was 460℃, the total reduction was 50%, and the reduction per pass was 10%. The total reduction of the cold rolling was 50%, and the reduction per pass was 10%.

[0202] (5) Solution quenching

[0203] The rolled sheet material cooled to room temperature was subjected to solution treatment at a temperature of 530℃ and a holding time of 30 minutes, followed by quenching in room temperature water to obtain a supersaturated solution-treated sheet material.

[0204] (6) Pre-deformation

[0205] The alloy sheet after solution quenching is subjected to cold rolling deformation with a reduction of 2%.

[0206] (7) Store at room temperature

[0207] The pre-deformed alloy is left at room temperature for 14 days to 1 month to allow it to age naturally.

[0208] (8) Final Validity Period

[0209] The alloy, after being left at room temperature for several days, underwent final aging, namely short-time baking paint artificial aging, with an aging temperature of 180℃ and an aging time of 30 minutes.

[0210] The change in hardness in the T4 state during the natural aging process of the alloy was tested. After solution pretreatment, the hardness of the alloy in the T4 state was 67.5 HV. After 14 days of natural aging, the hardness of the T4 state was 70.6 HV. After short-time artificial aging with paint, the hardness of the alloy was 88.9 HV, with a paint hardening increment ΔH of 18.3 HV. The corresponding tensile strength in the T4 state after 14 days of natural aging was 228.1 MPa, which increased to 260.5 MPa after paint application, an improvement of 32.4 MPa. Compared with this invention, the overall performance of this comparative example after 14 days of natural aging with paint application is significantly lower in terms of hardness and tensile strength. This is mainly because the lack of Zn addition reduces the improvement in aging response.

[0211] The implementation of the present invention is not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A composite treatment method for inhibiting the natural aging of aluminum alloy sheets and improving the artificial aging response and strength, characterized in that: It consists of the following steps: 1) Alloying treatment: The aluminum alloy melt is subjected to Zn and La composite alloying treatment; then an ingot is prepared; the mass percentage content of Zn and La in the ingot is: 0.5%~1%Zn, 0.05%~0.2%La; 2) Homogenization treatment: The ingot is kept at a constant temperature to obtain a homogenized alloy; 3) The homogenized alloy is hot-rolled and cold-rolled to obtain cold-rolled sheet metal; 4) The cold-rolled sheet is placed in an insulation device for insulation, and then rapidly cooled to obtain a supersaturated solid solution sheet; 5) The supersaturated solid solution plate is cold rolled to complete the pre-deformation; the total reduction of the cold rolling is 2~5%, and it is a one-pass rolling process; 6) Place the pre-deformed alloy sheet at room temperature and then heat-insulate it to complete the final aging process; The aluminum alloy mentioned in step 1) is a 6xxx series aluminum alloy; the homogenization treatment mentioned in step 2) is to place the cast billet in a heat preservation device for heat preservation at a temperature of 550~580℃ for 7~9h, and then cool it to room temperature with the furnace. In step 3), the hot rolling temperature is 450~480℃, and the total reduction is 45%~55%; the cold rolling is carried out after the plate is cooled to room temperature after hot rolling, and the total reduction is 45%~55%; the rolling is a multi-pass rolling process, and the reduction per pass of hot rolling or cold rolling is 5~15%; the number of rolling passes is 10~25. The temperature for heat preservation in step 4) is 510~530℃, and the heat preservation time is 20~40min; the rapid cooling refers to cooling with room temperature water. The time to place the product at room temperature as described in step 6) is 14 days to 1 month, the heat preservation temperature is 170℃~190℃, and the heat preservation time is 20~60 minutes. In step 1), the mass percentage content of the ingot, excluding Zn and La, is as follows: Si: 0.7%~1%, Mg: 0.6%~0.9%, Cu: 0.6%~0.8%, Mn: 0.1%~0.3%, Fe: 0.1%~0.2%, impurity elements ≤0.15%, and the balance is Al.

2. An aluminum alloy obtained by the method of claim 1.

3. An application of the aluminum alloy according to claim 2, characterized in that: The aluminum alloy is used in the field of power battery casings for new energy vehicles.

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