A 7-series aluminum alloy profile resistant to medium and high temperatures, its preparation method and application

Abstract

This invention relates to the field of aluminum alloy preparation technology, specifically to a 7-series aluminum alloy profile resistant to medium and high temperatures, its preparation method, and its applications. This invention optimizes the alloy composition: by optimizing the aluminum alloy composition, homogenization process, extrusion process, and aging process, the resulting 7-series aluminum alloy maintains its high strength while exhibiting minimal strength loss within 20-40 minutes at 170-200℃. This significantly expands the application range of high-strength aluminum alloys in automotive parts, allowing for applications in components such as vehicle frames, cabin crossbeams, and door sill beams. After aging, the profile produced by this invention achieves a tensile strength exceeding 450 MPa, a yield strength exceeding 420 MPa, and an elongation exceeding 12%. After holding at 200℃ for 40 minutes, the yield strength remains above 400 MPa, making the material more suitable for producing complex structural components such as automotive door sill beams. Furthermore, it does not exhibit cracking after three-point bending or column compression tests.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy preparation technology, specifically to a 7-series aluminum alloy profile resistant to medium and high temperatures, its preparation method, and its application. Background Technology

[0002] In the automotive industry, aluminum alloys are widely used in the production of automotive parts due to their lightweight and high strength. Among them, 7-series aluminum alloys are widely used in various high-strength structural components due to their excellent strength and hardness. However, after electrophoresis and curing treatment, the precipitates in traditional 7-series aluminum alloys tend to coarsen and grow, leading to a significant decrease in material strength. This limits the use of traditional 7-series aluminum alloys in automotive parts. To improve the high-temperature performance of aluminum alloys, rare earth trace elements are often added to form more precipitates or adjust the precipitate structure to improve the material's strength.

[0003] However, existing technologies still face some challenges in improving the high-temperature performance of aluminum alloys. First, rare earth elements, which enhance high-temperature strength, are generally expensive, increasing raw material costs. Second, while rare earth elements improve the structure of precipitated phases, they cannot solve the performance degradation caused by coarsening of the precipitated phase size; a certain degree of performance decline still occurs. Therefore, existing technologies still have limitations in improving the high-temperature performance of aluminum alloys. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of this invention is to provide a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, and a method for preparing the same, so as to provide at least one beneficial option or create conditions for solving one or more technical problems existing in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] A method for preparing a 7-series aluminum alloy profile resistant to medium and high temperatures, which mainly includes the following optimized processes: 1) Alloy composition optimization: By optimizing the composition of the aluminum alloy, the alloy contains elements such as Zn, Mg, Si, and Cu, and the performance of the aluminum alloy is improved by the precipitation of two strengthening phases at different temperatures.

[0007] 2) Homogenization process optimization: By optimizing the homogenization heat treatment process and using two-stage homogenization treatment, elements such as Zn, Mg, and Si in the alloy are completely dissolved, avoiding overheating defects during high-temperature homogenization. At the same time, it promotes the transformation of the Fe phase from the β phase to the α phase, thereby improving the performance of the aluminum alloy.

[0008] 3) Extrusion process optimization: By optimizing the extrusion process, including increasing the extrusion bar temperature, extrusion profile speed, and extrusion discharge temperature, the solution treatment effect is ensured, while the cooling rate is increased, thereby improving the performance of aluminum alloys.

[0009] 4) Aging Process Optimization: The aging process is optimized, including two-stage aging treatment. Because the formation enthalpy ΔHMg-Si is much lower than that of Mg-Zn solute atom clusters ΔHMg-Zn, precipitation will primarily consist of the Mg-Si phase, while also forming Mg-Si-Cu-Zn composite solute atom clusters or Mg-Zn solute atom clusters. Therefore, only low-temperature aging first can form sufficient MgZn phase within the grains to further enhance material strength. Simultaneously, the secondary high-temperature aging promotes the precipitation of MgZn and MgSi phases, coarsens the MgZn phase at grain boundaries, improves resistance to intergranular corrosion, and thus enhances the performance of the aluminum alloy.

[0010] The specific preparation steps are as follows.

[0011] 1) Configure the alloy composition. By weight percentage, the alloy contains 2.0%-3.5% Zn, 0.9%-1.2% Mg, 0.5%-0.8% Si, 0.1%-0.3% Cu, 0.1%-0.3% Mn, ≤0.3% Fe, and 0.05%-0.20% Zr, with the balance being aluminum and unavoidable impurities.

[0012] 2) Casting and homogenization: First, the alloy raw materials are melted in a smelting furnace to obtain aluminum alloy melt, which is then cast into aluminum rods. Then, the aluminum rods are subjected to a two-stage homogenization process: the first-stage homogenization temperature is 420℃-460℃, and the holding time is 4h-12h; the second-stage homogenization temperature is 530℃-570℃, and the holding time is 2h-10h. The homogenized aluminum rods are then air-cooled.

[0013] 3) Extrusion; heating the aluminum rod and placing it in an extruder for extrusion, with the extrusion rod temperature at 470℃-520℃, the extrusion speed at 2m / min-12m / min, and the extrusion discharge temperature at 500℃-550℃.

[0014] 4) Aging treatment: The extruded profiles undergo a two-stage aging process. The first-stage aging temperature is 110℃-140℃, and the holding time is 6h-20h. The second-stage aging temperature is 160℃-190℃, and the holding time is 2h-6h.

[0015] More preferably, in the alloy composition preparation step, the alloy contains 2.24% Zn, 0.96% Mg, 0.54% Si, 0.13% Cu, 0.14% Mn, 0.15% Fe, and 0.08% Zr by weight percentage; in the two-stage homogenization process, the first-stage homogenization temperature is 430℃ and the holding time is 5h, and the second-stage homogenization temperature is 535℃ and the holding time is 5h; in the two-stage aging process, the first-stage aging temperature is 115℃ and the holding time is 18h; and the second-stage aging temperature is 170℃ and the holding time is 6h.

[0016] More preferably, in the alloy composition preparation step, the alloy contains 3.38% Zn, 1.17% Mg, 0.76% Si, 0.28% Cu, 0.27% Mn, 0.25% Fe, and 0.18% Zr by weight percentage; in the two-stage homogenization process, the first-stage homogenization temperature is 460℃ and the holding time is 10h, and the second-stage homogenization temperature is 565℃ and the holding time is 9h; in the two-stage aging process, the first-stage aging temperature is 130℃ and the holding time is 10h; and the second-stage aging temperature is 180℃ and the holding time is 4h.

[0017] More preferably, in the alloy composition preparation step, the content of Zn element is 2.39%, Mg element is 1.1%, Si element is 0.69%, Cu element is 0.25%, Mn element is 0.25%, Fe element is 0.21%, and Zr element is 0.15% by weight percentage; in the two-stage homogenization treatment step, the first-stage homogenization temperature is 440℃ and the holding time is 8h, and the second-stage homogenization temperature is 560℃ and the holding time is 8h; in the two-stage aging process, the first-stage aging temperature is 120℃ and the holding time is 12h; the second-stage aging temperature is 175℃ and the holding time is 5h.

[0018] More preferably, in the alloy composition preparation step, the content of Zn is 3.41%, Mg is 0.95%, Si is 0.59%, Cu is 0.12%, Mn is 0.19%, Fe is 0.14%, and Zr is 0.12% by weight percentage; in the two-stage homogenization treatment step, the first-stage homogenization temperature is 420℃ and the holding time is 12h, and the second-stage homogenization temperature is 550℃ and the holding time is 6h; in the two-stage aging process, the first-stage aging temperature is 110℃ and the holding time is 20h; and the second-stage aging temperature is 165℃ and the holding time is 3h.

[0019] More preferably, in the alloy composition preparation step, the content of Zn is 2.78%, Mg is 1.15%, Si is 0.68%, Cu is 0.21%, Mn is 0.23%, Fe is 0.25%, and Zr is 0.14% by weight percentage; in the two-stage homogenization treatment step, the first-stage homogenization temperature is 450℃ and the holding time is 9h, and the second-stage homogenization temperature is 550℃ and the holding time is 7h; in the two-stage aging process, the first-stage aging temperature is 125℃ and the holding time is 14h; and the second-stage aging temperature is 175℃ and the holding time is 4h.

[0020] More preferably, the melting temperature in the casting step is 700-750℃.

[0021] More preferably, in the extrusion step, rapid cooling is performed after extrusion, with the cooling rate controlled at 150°C / min or higher.

[0022] On the other hand, the present invention also provides a 7-series aluminum alloy profile resistant to medium and high temperatures, which is prepared by the preparation method of a 7-series aluminum alloy profile resistant to medium and high temperatures as described above.

[0023] On the other hand, the present invention also provides the application of a 7-series aluminum alloy profile resistant to medium and high temperatures as described above in automotive structural components.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects.

[0025] I. The 7-series aluminum alloy of this invention maintains its high strength while exhibiting minimal strength loss within 20-40 minutes at 170-200℃, thus significantly expanding the application range of high-strength aluminum alloys in automotive parts. It can be used in components such as vehicle frames, cabin crossbeams, and sill beams, achieving the goal of reducing product weight by increasing material strength. This is significantly superior to existing technologies, solving the problem of coarsening and growth of precipitates in traditional 7-series aluminum alloys at high temperatures, which leads to a decrease in material strength.

[0026] Second, the profiles produced by this invention, after aging, achieve a tensile strength of over 450 MPa, a yield strength of over 420 MPa, and an elongation of over 12%. After holding at 200℃ for 40 minutes, the yield strength remains above 400 MPa. This not only improves the material's high-temperature performance but also enhances its plasticity and formability, making it more suitable for producing complex structural components such as automotive door sill beams. Furthermore, it does not exhibit cracking after three-point bending or column compression tests. This is significantly superior to existing technologies, solving the problem of coarsening and growth of precipitates in traditional 7-series aluminum alloys at high temperatures, which leads to a decrease in material strength.

[0027] Third, the material of this invention simultaneously contains Zn, Mg, Si, and Cu elements, and does not have excessively high requirements for Fe content. This makes it highly suitable for using recycled aluminum alloys with complex compositions, achieving a high proportion of waste material utilization and significantly reducing carbon emissions. This is significantly superior to existing technologies, solving the problem of coarsening and growth of precipitates in traditional 7-series aluminum alloys at high temperatures, which leads to a decrease in material strength. Furthermore, the material preparation process of this invention is simple, low-cost, and suitable for large-scale production. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] A method for preparing a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, the specific steps of which are as follows.

[0030] Step 1: Alloy composition preparation. The alloy contains elements such as Zn, Mg, Si, Cu, Mn, Fe, and Zr. By weight percentage, the Zn content is 2.0%-3.5%, the Mg content is 0.9%-1.2%, the Si content is 0.5%-0.8%, the Cu content is 0.1%-0.3%, the Mn content is 0.1%-0.3%, the Fe content is ≤0.3%, the Zr content is 0.05%-0.20%, and the remainder is Al and its unavoidable impurities.

[0031] Step Two: Casting and Homogenization. First, the alloy raw materials are melted in a melting furnace at 700-750℃ to obtain an aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo a two-stage homogenization process: the first stage homogenization temperature is 420℃-460℃, held for 4-12 hours; the second stage homogenization temperature is 530℃-570℃, held for 2-10 hours. The homogenized aluminum rods are then air-cooled.

[0032] Step 3: Extrusion. The extrusion bar temperature is 470℃-520℃, the extrusion speed is 2m / min-12m / min, the extrusion outlet temperature is 500℃-550℃, and rapid cooling is performed after extrusion, with the cooling rate controlled at above 150℃ / min.

[0033] Step 4: Aging Treatment. The extruded profiles undergo a two-stage aging process: the first stage aging temperature is 110℃-140℃, and the holding time is 6h-20h; the second stage aging temperature is 160℃-190℃, and the holding time is 2h-6h.

[0034] Example 1.

[0035] A method for preparing a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, the specific steps of which are as follows.

[0036] 1) Alloy composition configuration: by weight percentage, the alloy contains 2.24% Zn, 0.96% Mg, 0.54% Si, 0.13% Cu, 0.14% Mn, 0.15% Fe, 0.08% Zr, and the remainder is Al and its unavoidable impurities.

[0037] 2) Casting and Homogenization. First, the alloy raw materials are melted in a melting furnace at 700℃ to obtain an aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo a two-stage homogenization process: the first stage homogenization temperature is 430℃, held for 5 hours; the second stage homogenization temperature is 535℃, held for 5 hours. The homogenized aluminum rods are then air-cooled.

[0038] 3) Extrusion. The homogenized aluminum rod is put into an extrusion press and extruded to obtain aluminum alloy profiles. The extrusion rod temperature is 480℃, the extrusion speed is 8m / min, the extrusion outlet temperature is 530℃, and the material is rapidly cooled after extrusion, with the cooling rate controlled at above 150℃ / min.

[0039] 4) Aging treatment. The extruded aluminum alloy profiles undergo a two-stage aging process: the first stage aging temperature is 115℃ and the holding time is 18h; the second stage aging temperature is 170℃ and the holding time is 6h.

[0040] Example 2.

[0041] A method for preparing a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, the specific steps of which are as follows.

[0042] 1) Alloy composition: by weight percentage, the alloy contains 3.38% Zn, 1.17% Mg, 0.76% Si, 0.28% Cu, 0.27% Mn, 0.25% Fe, 0.18% Zr, and the remainder is Al and its unavoidable impurities.

[0043] 2) Casting and Homogenization. First, the alloy raw materials are melted in a melting furnace at 750℃ to obtain an aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo a two-stage homogenization process: the first stage homogenization temperature is 460℃, held for 10 hours; the second stage homogenization temperature is 565℃, held for 9 hours. The homogenized aluminum rods are then air-cooled.

[0044] 3) Extrusion. The homogenized aluminum rod is put into an extrusion press to extrude aluminum alloy profiles. The extrusion rod temperature is 520℃, the extrusion speed is 12m / min, the extrusion outlet temperature is 550℃, and the material is rapidly cooled after extrusion, with the cooling rate controlled at above 150℃ / min.

[0045] 4) Aging treatment. The extruded aluminum alloy profiles undergo a two-stage aging process: the first stage aging temperature is 130℃ and the holding time is 10h; the second stage aging temperature is 180℃ and the holding time is 4h.

[0046] Example 3.

[0047] A method for preparing a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, the specific steps of which are as follows.

[0048] 1) Alloy composition: by weight percentage, the alloy contains 2.39% Zn, 1.1% Mg, 0.69% Si, 0.25% Cu, 0.25% Mn, 0.21% Fe, 0.15% Zr, and the remainder is Al and its unavoidable impurities.

[0049] 2) Casting and Homogenization. First, the alloy raw materials are melted in a melting furnace at 730℃ to obtain aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo a two-stage homogenization process: the first stage homogenization temperature is 440℃, held for 8 hours; the second stage homogenization temperature is 560℃, held for 8 hours. The homogenized aluminum rods are then air-cooled.

[0050] 3) Extrusion. The homogenized aluminum rod is put into an extrusion press to extrude aluminum alloy profiles. The extrusion rod temperature is 480℃, the extrusion speed is 4m / min, the extrusion outlet temperature is 520℃, and the extrusion is rapidly cooled, with the cooling rate controlled at above 150℃ / min.

[0051] 4) Aging treatment. The extruded aluminum alloy profiles undergo a two-stage aging process: the first stage aging temperature is 120℃ and the holding time is 12h; the second stage aging temperature is 175℃ and the holding time is 5h.

[0052] Example 4.

[0053] A method for preparing a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, the specific steps of which are as follows.

[0054] 1) Alloy composition: by weight percentage, the alloy contains 3.41% Zn, 0.95% Mg, 0.59% Si, 0.12% Cu, 0.19% Mn, 0.14% Fe, 0.12% Zr, and the remainder is Al and its unavoidable impurities.

[0055] 2) Casting and Homogenization. First, the alloy raw materials are melted in a melting furnace at 730℃ to obtain an aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo a two-stage homogenization process: the first stage homogenization temperature is 420℃, held for 12 hours; the second stage homogenization temperature is 550℃, held for 6 hours. The homogenized aluminum rods are then air-cooled.

[0056] 3) Extrusion. The homogenized aluminum rod is placed in an extrusion press to extrude aluminum alloy profiles. The extrusion rod temperature is 500℃, the extrusion speed is 5m / min, the extrusion outlet temperature is 530℃, and the material is rapidly cooled after extrusion, with the cooling rate controlled at above 150℃ / min.

[0057] 4) Aging treatment. The extruded aluminum alloy profiles undergo a two-stage aging process: the first stage aging temperature is 110℃ and the holding time is 20h; the second stage aging temperature is 165℃ and the holding time is 3h.

[0058] Example 5.

[0059] A method for preparing a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, the specific steps of which are as follows.

[0060] 1) Alloy composition: by weight percentage, the alloy contains 2.78% Zn, 1.15% Mg, 0.68% Si, 0.21% Cu, 0.23% Mn, 0.25% Fe, 0.14% Zr, and the remainder is Al and its unavoidable impurities.

[0061] 2) Casting and Homogenization. First, the alloy raw materials are melted in a melting furnace at 730℃ to obtain an aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo a two-stage homogenization process: the first stage homogenization temperature is 450℃, held for 9 hours; the second stage homogenization temperature is 550℃, held for 7 hours. The homogenized aluminum rods are then air-cooled.

[0062] 3) Extrusion. The homogenized aluminum rod is placed in an extrusion press to extrude aluminum alloy profiles. The extrusion rod temperature is 510℃, the extrusion speed is 11m / min, the extrusion outlet temperature is 520℃, and the material is rapidly cooled after extrusion, with the cooling rate controlled at above 150℃ / min.

[0063] 4) Aging treatment. The extruded aluminum alloy profiles undergo a two-stage aging process: the first stage aging temperature is 125℃ and the holding time is 14h; the second stage aging temperature is 175℃ and the holding time is 4h.

[0064] Comparative Example 1

[0065] A method for preparing a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, the specific steps of which are as follows.

[0066] 1) Alloy composition configuration: by weight percentage, the alloy contains 0.01% Zn, 1.12% Mg, 0.78% Si, 0.27% Cu, 0.28% Mn, 0.27% Fe, 0% Zr, and the remainder is Al and its unavoidable impurities.

[0067] 2) Casting and Homogenization. First, the alloy raw materials are melted in a melting furnace at 730℃ to obtain an aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo homogenization treatment at 560℃ for 10 hours. The homogenized aluminum rods are then air-cooled.

[0068] 3) Extrusion. The homogenized aluminum rod is placed in an extrusion press to extrude aluminum alloy profiles. The extrusion rod temperature is 510℃, the extrusion speed is 11m / min, the extrusion outlet temperature is 520℃, and the material is rapidly cooled after extrusion, with the cooling rate controlled at above 150℃ / min.

[0069] 4) Aging treatment. The extruded aluminum alloy profiles are subjected to an aging process at a temperature of 175℃ for 10 hours.

[0070] Comparative Example 2.

[0071] A method for preparing a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, the specific steps of which are as follows.

[0072] 1) Alloy composition: by weight percentage, the alloy contains 3.45% Zn, 1.02% Mg, 0.06% Si, 0.26% Cu, 0.25% Mn, 0.22% Fe, 0.11% Zr, and the remainder is Al and its unavoidable impurities.

[0073] 2) Casting and Homogenization. First, the alloy raw materials are melted in a melting furnace at 730℃ to obtain an aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo homogenization treatment at 460℃ for 12 hours. The homogenized aluminum rods are then air-cooled.

[0074] 3) Extrusion. The homogenized aluminum rod is placed in an extrusion press to extrude aluminum alloy profiles. The extrusion rod temperature is 510℃, the extrusion speed is 11m / min, the extrusion outlet temperature is 520℃, and the material is rapidly cooled after extrusion, with the cooling rate controlled at above 150℃ / min.

[0075] 4) Aging treatment. The extruded aluminum alloy profiles are subjected to an aging process at a temperature of 120℃ for 24 hours.

[0076] Comparative Example 3.

[0077] A method for preparing a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, the specific steps of which are as follows.

[0078] 1) Alloy composition: by weight percentage, the alloy contains 6.55% Zn, 1.12% Mg, 0.07% Si, 0.26% Cu, 0.22% Mn, 0.19% Fe, 0.13% Zr, and the remainder is Al and its unavoidable impurities.

[0079] 2) Casting and Homogenization. First, the alloy raw materials are melted in a melting furnace at 730℃ to obtain an aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo homogenization treatment at 460℃ for 12 hours. The homogenized aluminum rods are then air-cooled.

[0080] 3) Extrusion. The homogenized aluminum rod is placed in an extrusion press to extrude aluminum alloy profiles. The extrusion rod temperature is 510℃, the extrusion speed is 11m / min, the extrusion outlet temperature is 520℃, and the material is rapidly cooled after extrusion, with the cooling rate controlled at above 150℃ / min.

[0081] 4) Aging treatment. The extruded aluminum alloy profiles are subjected to an aging process at a temperature of 120℃ for 24 hours.

[0082] Comparative Example 4.

[0083] A method for preparing a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, the specific steps of which are as follows.

[0084] 1) Alloy composition configuration: by weight percentage, the alloy contains 2.87% Zn, 1.09% Mg, 1.35% Si, 0.01% Cu, 0.14% Mn, 0.15% Fe, 0.09% Zr, and the remainder is Al and its unavoidable impurities.

[0085] 2) Casting and Homogenization. First, the alloy raw materials are melted in a melting furnace at 730℃ to obtain aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo a two-stage homogenization process: the first homogenization temperature is 450℃ for 9 hours, and the second homogenization temperature is 550℃ for 7 hours. The homogenized aluminum rods are then air-cooled.

[0086] 3) Extrusion. The homogenized aluminum rod is put into an extrusion press to extrude aluminum alloy profiles. The extrusion rod temperature is 510℃, the extrusion speed is 10m / min, the extrusion outlet temperature is 520℃, and the material is rapidly cooled after extrusion, with the cooling rate controlled at above 150℃ / min.

[0087] 4) Aging treatment. The extruded aluminum alloy profiles undergo a two-stage aging process: the first stage aging temperature is 125℃ and the holding time is 14h; the second stage aging temperature is 175℃ and the holding time is 4h.

[0088] Comparative Example 5.

[0089] A method for preparing a 7-series automotive aluminum alloy that is resistant to medium and high temperatures and is easy to extrude, the specific steps of which are as follows.

[0090] 1) Alloy composition: by weight percentage, the alloy contains 2.78% Zn, 1.15% Mg, 0.68% Si, 0.21% Cu, 0.23% Mn, 0.25% Fe, 0.14% Zr, and the remainder is Al and its unavoidable impurities.

[0091] 2) Casting and Homogenization. First, the alloy raw materials are melted in a melting furnace at 730℃ to obtain an aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo homogenization treatment at 550℃ for 7 hours. The homogenized aluminum rods are then air-cooled.

[0092] 3) Extrusion. The homogenized aluminum rod is placed in an extrusion press to extrude aluminum alloy profiles. The extrusion rod temperature is 510℃, the extrusion speed is 11m / min, the extrusion outlet temperature is 520℃, and the material is rapidly cooled after extrusion, with the cooling rate controlled at above 150℃ / min.

[0093] 4) Aging treatment. The extruded aluminum alloy profiles are subjected to an aging process at an aging temperature of 1175℃ and a holding time of 4 hours.

[0094] Performance test comparison.

[0095] Table 1. Performance comparison of products obtained in Examples 1-5 and Comparative Examples 1-5

[0096] .

[0097] As shown in Table 1, when one or more of the alloy composition, homogenization process, and aging process change, one or more of the product's tensile strength, yield strength, elongation, and yield strength after 200℃*40min will significantly deteriorate. This is especially true in the comparative examples, where the yield strength after 200℃*40min shows a significant decrease. Therefore, this invention, by optimizing the alloy composition, homogenization process, and aging process, can effectively improve the product's resistance to medium and high temperatures, thereby better meeting the requirements for the use of 7-series aluminum alloys in automotive parts.

[0098] Due to its advanced nature, this invention has wide applications in the automotive industry. In the automotive industry, the 7-series aluminum alloy of this invention can be widely used in the manufacture of automotive structural components, such as chassis, cabin crossbeams, and sill beams. The aluminum alloy provided by this invention, after online solution treatment and aging treatment, avoids the performance degradation problem caused by coarsening of precipitated phases in traditional 7-series alloys through the superposition of multiple strengthening phases, thus maintaining high strength at high temperatures. This not only improves the structural performance of automobiles but also extends their service life. Furthermore, because the aluminum alloy of this invention is easier to cast and has lower resistance to extrusion deformation, it can reduce production costs and improve production efficiency. At the same time, due to the excellent plasticity and formability of the aluminum alloy of this invention, it can be used to manufacture automotive parts with complex structures. In summary, the 7-series aluminum alloy of this invention has broad market demand and application prospects due to its excellent performance and low production cost. The material also contains Zn, Mg, Si, and Cu elements, and does not have excessively high requirements for Fe content, making it very suitable for using recycled aluminum alloys with complex compositions, achieving a high proportion of waste utilization, and significantly reducing carbon emissions.

[0099] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Parts not described in the specific embodiments are all prior art or common knowledge.

[0101] It should also be noted that the detailed description of preferred embodiments and included examples in the description of this invention facilitate a better understanding of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In case of any discrepancy, the definitions in this specification shall prevail.

[0102] In this invention, the term "prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof, as used in this invention, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus comprising the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0103] In this invention, when a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described in this invention, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0104] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of this invention do not impose any limitation on the quantity requirement (i.e., the number of times) of the elements or components. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers to the singular form.

Claims

1. A method for preparing a 7-series aluminum alloy profile resistant to medium and high temperatures, characterized in that, The preparation steps are as follows: 1) Configure the alloy composition. By weight percentage, the alloy contains 2.0%-3.5% Zn, 0.9%-1.2% Mg, 0.5%-0.8% Si, 0.1%-0.3% Cu, 0.1%-0.3% Mn, ≤0.3% Fe, and 0.05%-0.20% Zr, with the balance being aluminum and unavoidable impurities. 2) Casting and Homogenization: First, the alloy raw materials are melted in a smelting furnace to obtain aluminum alloy melt, which is then cast into aluminum rods. Next, the aluminum rods undergo a two-stage homogenization process: the first-stage homogenization temperature is 420℃-460℃, and the holding time is 4h-12h; the second-stage homogenization temperature is 530℃-570℃, and the holding time is 2h-10h. The homogenized aluminum rods are then air-cooled. 3) Extrusion; The aluminum rod is heated and placed in an extruder for extrusion. The extrusion rod temperature is 470℃-520℃, the extrusion speed is 2m / min-12m / min, and the extrusion discharge temperature is 500℃-550℃. 4) Aging treatment: The extruded profiles undergo a two-stage aging process. The first-stage aging temperature is 110℃-140℃, and the holding time is 6h-20h. The second-stage aging temperature is 160℃-190℃, and the holding time is 2h-6h.

2. The method for preparing a 7-series aluminum alloy profile resistant to medium and high temperatures according to claim 1, characterized in that, In step 1), the alloy composition is prepared as follows (by weight percentage): Zn content 2.24%, Mg content 0.96%, Si content 0.54%, Cu content 0.13%, Mn content 0.14%, Fe content 0.15%, and Zr content 0.08%. In the two-stage homogenization process, the first-stage homogenization temperature is 430℃ and the holding time is 5h, and the second-stage homogenization temperature is 535℃ and the holding time is 5h. In the two-stage aging process, the first-stage aging temperature is 115℃ and the holding time is 18h; the second-stage aging temperature is 170℃ and the holding time is 6h.

3. The method for preparing a 7-series aluminum alloy profile resistant to medium and high temperatures according to claim 1, characterized in that, In step 1), the alloy composition is prepared as follows: by weight percentage, the alloy contains 3.38% Zn, 1.17% Mg, 0.76% Si, 0.28% Cu, 0.27% Mn, 0.25% Fe, and 0.18% Zr. In the two-stage homogenization process, the first-stage homogenization temperature is 460℃ and the holding time is 10h, and the second-stage homogenization temperature is 565℃ and the holding time is 9h. In the two-stage aging process, the first-stage aging temperature is 130℃ and the holding time is 10h; the second-stage aging temperature is 180℃ and the holding time is 4h.

4. The method for preparing a 7-series aluminum alloy profile resistant to medium and high temperatures according to claim 1, characterized in that, In step 1), the alloy composition is prepared as follows (by weight percentage): Zn content 2.39%, Mg content 1.1%, Si content 0.69%, Cu content 0.25%, Mn content 0.25%, Fe content 0.21%, and Zr content 0.15%. In the two-stage homogenization process, the first-stage homogenization temperature is 440℃ and the holding time is 8h, and the second-stage homogenization temperature is 560℃ and the holding time is 8h. In the two-stage aging process, the first-stage aging temperature is 120℃ and the holding time is 12h; the second-stage aging temperature is 175℃ and the holding time is 5h.

5. The method for preparing a 7-series aluminum alloy profile resistant to medium and high temperatures according to claim 1, characterized in that, In the alloy composition preparation step, the content of Zn element is 3.41%, Mg element is 0.95%, Si element is 0.59%, Cu element is 0.12%, Mn element is 0.19%, Fe element is 0.14%, and Zr element is 0.12% by weight. In the two-stage homogenization process, the first-stage homogenization temperature is 420℃ and the holding time is 12h, and the second-stage homogenization temperature is 550℃ and the holding time is 6h. In the two-stage aging process, the first-stage aging temperature is 110℃ and the holding time is 20h; the second-stage aging temperature is 165℃ and the holding time is 3h.

6. The method for preparing a 7-series aluminum alloy profile resistant to medium and high temperatures according to claim 1, characterized in that, In the alloy composition preparation step, the content of Zn element is 2.78%, Mg element is 1.15%, Si element is 0.68%, Cu element is 0.21%, Mn element is 0.23%, Fe element is 0.25%, and Zr element is 0.14% by weight. In the two-stage homogenization process, the first-stage homogenization temperature is 450℃ and the holding time is 9h, and the second-stage homogenization temperature is 550℃ and the holding time is 7h. In the two-stage aging process, the first-stage aging temperature is 125℃ and the holding time is 14h; the second-stage aging temperature is 175℃ and the holding time is 4h.

7. The method for preparing a 7-series aluminum alloy profile resistant to medium and high temperatures according to claim 1, characterized in that, In the casting process, the melting temperature is 700-750℃.

8. The method for preparing a 7-series aluminum alloy profile resistant to medium and high temperatures according to claim 1, characterized in that, During the extrusion process, rapid cooling is performed after extrusion, with the cooling rate controlled at 150℃ / min or higher.

9. A 7-series aluminum alloy profile resistant to medium and high temperatures, characterized in that, It is prepared using the method for preparing a medium-to-high temperature resistant 7-series aluminum alloy profile as described in any one of claims 1-8.

10. The application of the 7-series aluminum alloy profile resistant to medium and high temperatures as described in claim 9 in automotive structural components.