Ultrahigh-strength high-toughness 7-series aluminum alloy for automobile anti-collision beam and preparation method of ultrahigh-strength high-toughness 7-series aluminum alloy

Abstract

The invention discloses an ultrahigh-strength and high-toughness 7-series aluminum alloy for an automobile anti-collision beam and a preparation method of the ultrahigh-strength and high-toughness 7-series aluminum alloy, and belongs to the field of aluminum alloy materials. The components of the 7-series aluminum alloy are optimized, the contents of main elements Zn, Mg and Cu are controlled within the optimal range, Zn / Mg is accurately limited to be larger than or equal to 3 and smaller than or equal to 4.5, Zn-3Mg-Cu is accurately limited to be larger than or equal to 0.5 and smaller than or equal to 2.1, it can be effectively guaranteed that a strengthening phase is separated out in a better strengthening and toughening form, size and density, the grain refining effect of a refiner is matched, the obtained 7-series aluminum alloy has high strength and high toughness, the tensile strength can reach 540 MPa or above, and the tensile strength can reach 540 MPa or above. The yield strength can reach 520 MPa or above, meanwhile, the ductility is kept at 14% or above, and the practical requirements for high strength and high toughness of the automobile anti-collision beam in collision are met. In addition, through three-stage homogenization treatment, a product with excellent strength, toughness and corrosion resistance is promoted to be obtained, so that the use requirements of the automobile anti-collision beam are met.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy preparation technology, and more specifically, to a 7-series aluminum alloy for automotive anti-collision beams with ultra-high strength and high toughness and its preparation method. Background Technology

[0002] The automotive industry faces stringent carbon emission restrictions, making lightweighting a core approach to reducing the energy consumption of traditional gasoline vehicles and increasing the driving range of electric vehicles. Research by the International Energy Agency (IEA) shows that a 10% reduction in vehicle weight can reduce fuel consumption by 6%-8% and increase the driving range of electric vehicles by 5%-10%. 7-series aluminum alloys, due to their high specific strength, good formability, and low density (approximately 2.78 g / cm³), have significant advantages in structural components such as automotive crash beams and door sill beams, making them one of the ideal materials for achieving lightweighting. However, the high degree of alloying in 7-series aluminum alloys results in high deformation resistance during hot extrusion, leading to difficulties in extruding closed sections and poor formability. Simultaneously, the high alloying also reduces corrosion resistance and stress corrosion cracking (SCC) performance, limiting their widespread application in automotive safety structural components.

[0003] Existing technologies also include solutions to improve the performance of 7-series aluminum alloys through composition optimization or process improvement. For example, Chinese Patent Publication No. CN 120272788 A discloses a high-strength aluminum alloy profile for crash beams and its preparation method. By optimizing the aluminum alloy composition to form a coherent composite phase, the strength is improved, but its overall mechanical properties still cannot meet the high requirements of crash beams. Another example is Chinese Patent Publication No. CN 117107131 A, which discloses a manufacturing process for aluminum alloy crash beams for new energy vehicles. Rare earth elements lanthanum and cerium are added to the 7-series alloy to reduce the melt gas content and increase the tensile strength to 464 MPa, but the cost is high and the improvement in corrosion resistance is limited. For example, Chinese patent publication number CN113388764 A discloses a high-strength 7-series aluminum alloy for automobile anti-collision beams and automobile anti-collision beams. By adjusting the composition and heat treatment process to suppress the formation of atomic clusters during natural aging, it achieves a yield strength >430 MPa and an elongation >8%, but its overall toughness and stress corrosion resistance still need to be improved.

[0004] In summary, existing 7-series aluminum alloys generally suffer from problems such as a mismatch between strength and toughness, difficulty in forming, poor corrosion resistance, and high cost when used in automotive crash beams. Therefore, there is an urgent need to develop a 7-series aluminum alloy and its preparation method that combine ultra-high strength, high toughness, excellent formability, and corrosion resistance to meet the application requirements of automotive crash beams. Summary of the Invention

[0005] Based on this, in order to solve one of the above-mentioned technical problems, the present invention provides an ultra-high strength and high toughness 7-series aluminum alloy for automotive anti-collision beams and its preparation method, the specific technical solution of which is as follows: A high-strength, high-toughness 7-series aluminum alloy for automotive anti-collision beams, wherein the 7-series aluminum alloy comprises the following chemical composition by weight percentage: Zn: 6.4%-7.0%, Mg: 1.50%-2.0%, Cu: 0.1-0.4%, (Zr+Sc): 0.1%-0.3%, balance Al and unavoidable impurity elements; The mass ratio of Zn to Mg satisfies: 3 ≤ Zn / Mg ≤ 4.5, and the contents of Zn, Mg and Cu satisfy 0.5 ≤ Zn - 3Mg - Cu ≤ 2.1; Unavoidable impurity elements: Si: ≤0.03%, Fe: ≤0.08%; other single impurity elements <0.05%.

[0006] Preferably, (Zr+Sc) is one or both of Zr and Sc, and when both are added, the content of Zr and Sc satisfies Zr+Sc: 0.1%-0.3%.

[0007] Preferably, the 7-series aluminum alloy has a tensile strength ≥ 540 MPa, a yield strength ≥ 520 MPa, an elongation ≥ 14%, an electrical conductivity ≥ 39% IACS, and a stress corrosion susceptibility factor (ISSRT) of = ≤ 0.001.

[0008] In addition, the present invention also provides a method for preparing an ultra-high strength and high toughness 7-series aluminum alloy for automotive anti-collision beams, the preparation method comprising the following steps: S1. Melting and Casting: Raw materials are added to a melting furnace according to the chemical composition ratio of 7-series aluminum alloys for melting. After refining, high-purity argon degassing, and double-stage filtration, the mixture is cast into ingots. S2. Homogenization Treatment: The ingots undergo a three-stage stepped homogenization treatment, wherein the three-stage stepped homogenization treatment is as follows: First stage: 350-380℃, holding for 20-32 h; Second stage: T... e -(5-20℃), keep warm for 20-26 hours; Level 3: T e +(20-50℃), hold at this temperature for 8-14 hours, and after homogenization, cool; wherein, T e S3. Extrusion molding: The cast rod is heated and extruded into an extrusion cylinder for extrusion molding, and the exit temperature of the profile is controlled; S4. Quenching and cooling: The extruded profile is water-quenched; S5. Aging treatment: The profile is subjected to two-stage aging treatment.

[0009] Preferably, in step S1, the raw materials include high-purity aluminum ingots, Al-Cu alloys, refining agents, Zn ingots, and Mg ingots.

[0010] Preferably, in step S1, the refining process is performed at least twice, with each refining process lasting no less than 15-20 minutes. High-purity argon gas (purity ≥99.999%) is used for degassing, and a 40 ppi + 60 ppi dual-stage ceramic filter is used for melt filtration.

[0011] Preferably, in step S2, after homogenization is completed, the mixture is cooled to room temperature by strong spraying at a cooling rate of more than 300°C / h.

[0012] Preferably, in step S3, the casting rod is heated to 430-470°C, and the outlet temperature of the profile is controlled at 505-540°C.

[0013] Preferably, the two-stage aging treatment is as follows: first stage: 85-110℃, heat preservation for 10-16 h; second stage: 130-150℃, heat preservation for 8-14 h.

[0014] In addition, the present invention also provides an automotive anti-collision beam, which is made of the ultra-high strength and high toughness 7-series aluminum alloy, or is made of the profile obtained by the preparation method described above.

[0015] Compared with existing technologies, its beneficial effects include: 1. This invention optimizes the composition of 7-series aluminum alloys, especially by controlling the content of the main elements Zn, Mg, and Cu within the optimal range and precisely limiting 3≤Zn / Mg≤4.5 and 0.5≤Zn-3Mg-Cu≤2.1. This effectively ensures that the strengthening phase (mainly η'-MgZn2 phase) precipitates in a better form, size, and density, while also refining the grain size with a grain refiner. The resulting 7-series aluminum alloy possesses both high strength and high toughness, with a tensile strength exceeding 540MPa, a yield strength exceeding 520MPa, and an elongation exceeding 14%. This meets the practical requirements of automotive anti-collision beams, which must resist impact (high strength) and absorb energy (high toughness) during collisions.

[0016] 2. By controlling the Cu content, the remaining Zn content after the reaction of Zn and Mg is close to the Cu content, which can promote the formation of the Mg(Zn,Cu) phase, reduce the potential difference between the grain and the grain boundary, and help to improve the resistance to stress corrosion, thereby ensuring the long-term safety and service life of the automotive anti-collision beam under complex working conditions.

[0017] 3. Based on the optimized composition, this invention also employs a three-stage homogenization process to not only fully dissolve the non-equilibrium eutectic phase and eliminate casting segregation, but also raise the overheating temperature of the alloy by approximately 20-40°C. This significantly broadens the heat treatment capabilities for subsequent extrusion and quenching, enabling products with significant strength, toughness, and corrosion resistance to be obtained even under the extrusion conditions of this invention. At the same time, it reduces the risk of product scrap due to temperature fluctuations and improves production efficiency and yield.

[0018] 4. Applying the 7-series aluminum alloy of the present invention to the manufacture of automotive anti-collision beams can also endow automotive anti-collision beams with beneficial strength, toughness and corrosion resistance, so as to meet the application requirements of automotive anti-collision beams. Attached Figure Description

[0019] The invention will be further understood from the following description taken in conjunction with the accompanying drawings. The drawings focus on illustrating the principles of the embodiments.

[0020] Figure 1 This is a SEM image of a 7-series aluminum alloy after a three-stage homogenization step homogenization process prepared in Example 1 of this invention. Figure 2 SEM image of the 7-series aluminum alloy prepared for Comparative Example 6 after homogenization. Figure 3 SEM image of the 7-series aluminum alloy prepared for Comparative Example 7 after homogenization treatment; Figure 4 SEM image of the 7-series aluminum alloy after homogenization treatment, as shown in Comparative Example 8. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] An embodiment of the present invention discloses an ultra-high strength and high toughness 7-series aluminum alloy for automotive anti-collision beams, wherein the 7-series aluminum alloy comprises the following chemical composition by weight percentage: Zn: 6.4%-7.0%, Mg: 1.50%-2.0%, Cu: 0.1-0.4%, (Zr+Sc): 0.1%-0.3%, balance Al and unavoidable impurity elements; The mass ratio of Zn to Mg satisfies: 3 ≤ Zn / Mg ≤ 4.5, and the contents of Zn, Mg and Cu satisfy 0.5 ≤ Zn - 3Mg - Cu ≤ 2.1; Unavoidable impurity elements: Si: ≤0.03%, Fe: ≤0.08%; other single impurity elements <0.05%.

[0024] In one embodiment, (Zr+Sc) is one or both of Zr and Sc, and when both are added, the content of Zr and Sc satisfies Zr+Sc: 0.1%-0.3%.

[0025] In this invention, Zn and Mg are the main alloying elements in Al-Zn-Mg-Cu aluminum alloys. Fine precipitates of MgZn2 are obtained through aging heat treatment, which is the main strengthening phase of the alloy. The addition of Cu replaces Zn in the MgZn2 precipitates during aging, forming the MgZnCu phase, reducing the potential difference within the alloy and improving its corrosion resistance. The content and ratio of Zn, Mg, and Cu have a significant impact on the formation, type, and volume fraction of the strengthening phase. When the Zn content is less than 7.5% and the Zn / Mg mass fraction ratio is greater than 3, the η phase is the main strengthening phase; otherwise, the T phase is dominant. Excessive Zn addition can affect the alloy's extrudability and quenching sensitivity, while excessive Cu increases hot brittleness, so strict control is necessary. The addition of Zr and Sc refines the grains and reduces the alloy's quenching sensitivity by replacing Mn and Cr. In this invention, the ranges of Zn, Mg, Cu and Zr elements are strictly controlled according to a certain range ratio (3≤Zn / Mg≤4.5; 0.5≤Zn-3Mg-Cu≤2.1), and at the same time, combined with subsequent processing, the alloy achieves better comprehensive performance.

[0026] In one embodiment, the 7-series aluminum alloy has a tensile strength ≥540 MPa, a yield strength ≥520 MPa, an elongation ≥14%, an electrical conductivity ≥39% IACS, and a stress corrosion susceptibility factor (ISSRT) ≤0.001.

[0027] In addition, the present invention also provides a method for preparing an ultra-high strength and high toughness 7-series aluminum alloy for automotive anti-collision beams, the method comprising the following steps: S1. Melting and Casting: Raw materials are added to a melting furnace according to the chemical composition ratio of 7-series aluminum alloys for melting. After refining, degassing with high-purity argon gas, and double-stage filtration, the mixture is cast into ingots. S2. Homogenization Treatment: The ingots undergo a three-stage homogenization treatment: Stage 1: 350-380℃, holding for 20-32 hours; Stage 2: T... e -(5-20℃), keep warm for 20-26 hours; Level 3: Te +(20-50℃), hold at this temperature for 8-14 hours, and after homogenization, cool; wherein, T e S3. Extrusion molding: The cast rod is heated and extruded into an extrusion cylinder for extrusion molding, and the exit temperature of the profile is controlled; S4. Quenching and cooling: The extruded profile is water-quenched; S5. Aging treatment: The profile is subjected to two-stage aging treatment.

[0028] This invention employs a three-stage homogenization process, increasing the homogenization temperature to further promote the dissolution of non-equilibrium phases above the eutectic point temperature, thereby raising the overheating point temperature of the alloy and ensuring its subsequent extrusion processing and heat treatment properties. Additionally, a two-stage aging process is used. The first stage involves under-aging to form high-density GP zones; followed by a second stage of high-temperature over-aging, which dissolves GP zones smaller than the critical size and transforms GP zones larger than the critical size into metastable η' phases and stable η phases. Simultaneously, with prolonged aging time, the intragranular η' phase coarsens, the grain boundary η' phase stabilizes and coarsens, or transforms into the η phase, and the PFZ (precipitation-free zone) at the grain boundaries widens. This ensures that the alloy maintains good corrosion resistance and stress corrosion resistance (SCC) while possessing high mechanical properties.

[0029] In one embodiment, in step S1, the raw materials include high-purity aluminum ingots, Al-Cu alloys, refining agents, Zn ingots, and Mg ingots.

[0030] In one embodiment, the Zr is added in the form of an Al-Zr alloy.

[0031] In one embodiment, the Sc is added in the form of an Al-Sc alloy.

[0032] In one embodiment, the melting temperature is 720-760°C.

[0033] In one embodiment, in step S1, the refining process is performed at least twice, with each refining time not less than 15-20 minutes. High-purity argon gas (purity ≥99.999%) is used for degassing, and a 40 ppi + 60 ppi dual-stage ceramic filter is used for melt filtration.

[0034] In one embodiment, in step S2, after homogenization is completed, the mixture is cooled to room temperature by strong spraying at a cooling rate of more than 300°C / h.

[0035] In one embodiment, in step S3, the casting rod is heated to 430-470°C, and the outlet temperature of the profile is controlled at 505-540°C.

[0036] In one embodiment, the two-stage aging treatment is as follows: Stage 1: 85-110℃, heat preservation for 10-16 h; Stage 2: 130-150℃, heat preservation for 8-14 h.

[0037] In one embodiment, the present invention also provides an automotive anti-collision beam, which is prepared from the ultra-high strength and high toughness 7-series aluminum alloy, or prepared from the profile obtained by the preparation method described above.

[0038] The above solution can effectively solve the problems of difficulty in balancing strength, toughness and corrosion resistance, forming difficulties and unstable performance of existing 7-series aluminum alloys in automotive anti-collision beam applications. After optimization of composition, component ratio and process, a 7-series aluminum alloy with high strength, excellent toughness and corrosion resistance can be obtained, which can meet the application of automotive anti-collision beams.

[0039] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0040] Examples 1-2: The chemical compositions of Examples 1 and 2 are shown in Table 1; The preparation method of the ultra-high strength and high toughness 7-series aluminum alloy for automotive anti-collision beams in Examples 1 and 2 includes the following steps: S1. Melting and Casting: According to the chemical composition ratio of 7-series aluminum alloys, high-purity aluminum ingots, Al-Cu alloy, and Al-Zr alloy refining agent are added to the melting furnace. After melting, Zn ingots and Mg ingots are added, and the melting is carried out at 740℃. The mixture undergoes two refining processes, each lasting 20 minutes. High-purity argon gas (purity ≥99.999%) is used for degassing, and the melt is filtered using a 40 ppi + 60 ppi dual-stage ceramic filter before being cast into ingots. S2. Homogenization Treatment: The ingots undergo a three-stage stepped homogenization treatment: Stage 1: 350-380℃, holding for 20-32 hours; Stage 2: T... e -(5-20℃), keep warm for 20-26 hours; Level 3: T e +(20-50℃), hold at this temperature for 8-14 hours, and after homogenization, cool; wherein, T e S3. Extrusion molding: The cast rod is heated to 465℃ and then extruded. It is placed in the extrusion cylinder for extrusion molding, and the exit temperature of the profile is controlled at 520℃; S4. Quenching and cooling: The extruded profile is water-quenched; S5. Aging treatment: The profile is subjected to a two-stage aging treatment, and the two-stage aging treatment is as follows: First stage: 100℃, holding for 16 h; Second stage: 135℃, holding for 12 h.

[0041] Example 3: The difference between Example 3 and Example 1 is that (Zr+Sc) in Example 3 is a mixture of Zr and Sc, and by mass percentage, Zr: 0.1% and Sc: 0.05%, while the rest is the same as in Example 1.

[0042] Comparative Examples 1-5: The difference between Comparative Examples 1-5 and Example 1 is that the chemical composition of Comparative Examples 1-5 is different from that of Example 1, while the other components are the same as those of Example 1. The chemical composition of Comparative Examples 1-5 is shown in Table 1.

[0043] Comparative Example 6: Compared with Example 1, Comparative Example 6 differs in that the three-stage homogenization process in Comparative Example 6 is as follows: First stage: 280℃, heat preservation for 20h; Second stage: 460℃, heat preservation for 24h; Third stage: 520℃, heat preservation for 10h, and the rest is the same as in Example 1.

[0044] Comparative Example 7: Compared with Example 1, Comparative Example 7 differs in that the three-stage homogenization process in Comparative Example 7 is as follows: First stage: 320℃, heat preservation for 25 hours; Second stage: 420℃, heat preservation for 24 hours; Third stage: 520℃, heat preservation for 10 hours, and the rest is the same as in Example 1.

[0045] Comparative Example 8: Compared with Example 1, Comparative Example 8 differs in that the three-stage homogenization process in Comparative Example 8 is as follows: First stage: 320℃, heat preservation for 25 hours; Second stage: 495℃, heat preservation for 8 hours; Third stage: 520℃, heat preservation for 10 hours, and the rest is the same as in Example 1.

[0046] Comparative Example 9: Compared with Example 1, Comparative Example 9 differs in that the aging process in Comparative Example 9 is as follows: First stage: 80℃, heat preservation for 16h; Second stage: 160℃, heat preservation for 10h; the rest is the same as in Example 1.

[0047] Table 1: Chemical Composition

[0048] The performance of the 7-series aluminum alloy samples prepared in Examples 1-3 and the comparative samples of 7-series aluminum alloys prepared in Comparative Examples 1-9 were tested, and the results are shown in Table 2 below.

[0049] Table 2: Performance Test Results

[0050] As can be seen from the data analysis in Table 2, the present invention, through optimization of composition and component ratio, combined with three-stage homogenization step homogenization treatment and two-stage aging treatment, can obtain 7-series aluminum alloy profiles with excellent comprehensive performance. Compared with Example 1, the composition ratios of Comparative Examples 1-5 were changed, resulting in varying degrees of performance degradation. Specifically, Comparative Example 1 altered the contents of Cu, Mg, and Zn, leading to a Zn / Mg ratio of 2.4, which is less than the range of 3 defined in this application. This resulted in a weaker formation of the strengthening phase compared to Example 1, affecting mechanical properties and corrosion resistance. In Comparative Example 2, the excessive Cu content increased the potential difference between the grains and grain boundaries, and the increased hot brittleness affected extrusion performance, thus impacting overall mechanical properties and corrosion resistance. In Comparative Example 3, the Zr content was far below the range defined in this application, resulting in insufficient grain refinement and a decline in various properties compared to Example 1. In Comparative Example 4, the excessive Zr content and the excessive Al3Zr nanoparticles led to stress concentration and adverse effects. In Comparative Example 5, no Zr (refining agent) was added. During homogenization and extrusion, the grains grew rapidly, forming coarse grains, resulting in more precipitates and elemental segregation, which in turn affected the performance of the 7-series aluminum alloy. Comparative Examples 6-8 show different homogenization process parameters. It can be seen that a low homogenization temperature, a short homogenization time, or a high homogenization temperature can lead to insufficient dissolution of non-equilibrium phases, incomplete elimination of segregation, or even overheating and poor stability, all of which will affect the performance of 7-series aluminum alloys. In Comparative Example 9, the different aging process parameters lead to insufficient formation of GP zones and excessive coarsening of the η phase, resulting in poor precipitation strengthening effect, which will also affect the overall performance of 7-series aluminum alloys.

[0051] In summary, by optimizing the composition, component ratio, and process, this invention effectively solves the technical problems faced by existing 7-series aluminum alloys in automotive anti-collision beam applications, such as difficulty in balancing strength, toughness, and corrosion resistance, forming difficulties, and unstable performance. It provides an ideal material solution with excellent comprehensive performance, reliable process, and suitability for large-scale commercial application, which is of great value in promoting the development of automotive lightweighting technology.

[0052] In addition, combined Figures 1-4 The homogenization process of the present invention will be further described, wherein, Figure 1 The image shown is a SEM image of a 7-series aluminum alloy after a three-stage homogenization step homogenization process prepared in Example 1 of this invention. Examples 2 and 3 are similar to Example 1 and will not be described in detail here. Figure 2 This is a SEM image of the 7-series aluminum alloy prepared in Comparative Example 6 after homogenization. Figure 3 This is a SEM image of the 7-series aluminum alloy prepared in Comparative Example 7 after homogenization treatment. Figure 4 SEM images of 7-series aluminum alloys after homogenization treatment prepared for Comparative Example 8, combined with... Figures 1-4Comparative analysis shows that in Comparative Example 6, the equilibrium phase was not fully dissolved, leading to stress concentration points and inducing local recrystallization. In Comparative Example 7, coarse remelted phases formed locally at grain boundaries, resulting in poor microstructure uniformity. In Comparative Example 8, local recrystallization was significant, resulting in poor microstructure uniformity, and the overall uniformity was not as good as in Example 1. This demonstrates that the present invention, through optimizing the homogenization process, significantly improves the uniformity of the microstructure, thereby promoting the acquisition of higher-performance 7-series aluminum alloys.

[0053] 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.

[0054] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, 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. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A high-strength, high-toughness 7-series aluminum alloy for automotive anti-collision beams, characterized in that, The 7-series aluminum alloys comprise the following chemical composition by weight percentage: Zn: 6.4%-7.0%, Mg: 1.50%-2.0%, Cu: 0.1-0.4%, (Zr+Sc): 0.1%-0.3%, balance Al and unavoidable impurity elements; The mass ratio of Zn to Mg satisfies: 3 ≤ Zn / Mg ≤ 4.5, and the contents of Zn, Mg and Cu satisfy 0.5 ≤ Zn - 3Mg - Cu ≤ 2.1; Unavoidable impurity elements: Si: ≤0.03%, Fe: ≤0.08%; other single impurity elements <0.05%.

2. The 7-series aluminum alloy according to claim 1, characterized in that, The (Zr+Sc) is one or both of Zr and Sc, and when both are added, the content of Zr and Sc satisfies Zr+Sc: 0.1%-0.3%.

3. The 7-series aluminum alloy according to claim 1, characterized in that, The 7-series aluminum alloy has a tensile strength ≥ 540 MPa, a yield strength ≥ 520 MPa, an elongation ≥ 14%, an electrical conductivity ≥ 39% IACS, and a stress corrosion susceptibility factor (ISSRT) of = ≤ 0.

001.

4. A method for preparing an ultra-high strength and high toughness 7-series aluminum alloy for automotive anti-collision beams, characterized in that, The preparation method is used to prepare the 7-series aluminum alloy as described in any one of claims 1 to 3, and the preparation method includes the following steps: S1. Melting and Casting: Raw materials are added to a melting furnace according to the chemical composition ratio of 7-series aluminum alloys for melting. After refining, degassing with high-purity argon gas, and double-stage filtration, the mixture is cast into ingots. S2. Homogenization Treatment: The ingots undergo a three-stage homogenization treatment: Stage 1: 350-380℃, holding for 20-32 hours; Stage 2: T... e -(5-20℃), keep warm for 20-26 hours; Level 3: T e +(20-50℃), hold at this temperature for 8-14 hours, and after homogenization, cool; wherein, T e S3. Extrusion molding: The cast rod is heated and extruded into an extrusion cylinder, and the exit temperature of the profile is controlled; S4. Quenching and cooling: The extruded profile is water-quenched; S5. Aging treatment: The profile is subjected to two-stage aging treatment.

5. The preparation method according to claim 4, characterized in that, In step S1, the raw materials include high-purity aluminum ingots, Al-Cu alloys, refining agents, Zn ingots, and Mg ingots.

6. The preparation method according to claim 4, characterized in that, In step S1, the refining process is performed at least twice, with each refining process lasting no less than 15-20 minutes. High-purity argon gas (purity ≥99.999%) is used for degassing, and a 40 ppi + 60 ppi dual-stage ceramic filter is used for melt filtration.

7. The preparation method according to claim 4, characterized in that, In step S2, after homogenization is completed, the mixture is cooled to room temperature by strong spraying at a cooling rate of more than 300℃ / h.

8. The preparation method according to claim 4, characterized in that, In step S3, the casting rod is heated to 430-470℃, and the outlet temperature of the profile is controlled at 505-540℃.

9. The preparation method according to claim 4, characterized in that, The two-stage aging treatment is as follows: Stage 1: 85-110℃, heat preservation for 10-16 h; Level 2: 130-150℃, keep warm for 8-14 hours.

10. A car anti-collision beam, characterized in that, The vehicle anti-collision beam is made of the ultra-high strength and high toughness 7-series aluminum alloy as described in any one of claims 1 to 3, or is made of the profile obtained by the preparation method described in any one of claims 4 to 9.

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