Aluminum alloy and preparation method thereof

Abstract

The invention relates to an aluminum alloy and a preparation method thereof.The preparation method comprises the following steps that an aluminum alloy ingot is sequentially subjected to first-time forward extrusion treatment, annealing treatment and second-time forward extrusion treatment, and the aluminum alloy is obtained; wherein the preheating temperature of the second-time forward extrusion treatment is higher than that of the first-time forward extrusion treatment, and the extrusion speed of the second-time forward extrusion treatment is higher than that of the first-time forward extrusion treatment. According to the preparation method, the average grain size of the aluminum alloy can be refined to be 100 microns or below, the strength of the aluminum alloy is effectively improved, and the preparation method has universality and is particularly suitable for preparing the 6-series aluminum alloy which is high in strength and low in Mn and Cr element content.

Description

Technical Field

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

[0002] Aluminum alloy has a series of advantages such as light weight, high strength, corrosion resistance, high thermal conductivity, etc., and has been widely used in 3C electronics, transportation, electrical equipment, sports equipment and other fields. With the continuous iteration and upgrading of products, higher requirements are also put forward for the mechanical properties of aluminum alloy materials.

[0003] Refining the structure of aluminum alloy is an effective way to improve the strength of the material. Especially for 6 series aluminum alloy materials, adding fine grain elements such as Mn and Cr is usually adopted. Among them, adding Mn element can increase the recrystallization temperature, and Mn element will form dispersed Al 6 Mn particles prevent the coarsening of recrystallized grains; adding Cr elements can form (CrFe)Al 7 or (CrMn)Al 12 Intermetallic compounds such as ferrites, by pinning at grain boundaries, hinder the nucleation and growth of recrystallization.

[0004] However, for 6-series aluminum alloys with low Mn and Cr content, since the relevant standards stipulate that the content of Mn and Cr elements should not exceed 0.1%, it is impossible to refine the structure by adding Mn and Cr elements. In addition, the traditional preparation method of increasing the extrusion ratio or low-temperature and high-speed extrusion process may make the grains coarser, which is not conducive to improving the strength of the material.

[0005] Therefore, in order to overcome the technical defect that it is difficult to improve the strength of 6-series aluminum alloys with low Mn and Cr content, it is necessary to propose a universal method to improve the strength of aluminum alloys. Summary of the invention

[0006] Based on this, it is necessary to provide an aluminum alloy and a preparation method thereof to address the above-mentioned problems; the preparation method provided by the present invention can refine the average grain size of the aluminum alloy to below 100 μm, effectively improving the strength of the aluminum alloy, and the preparation method has universal applicability, and is particularly suitable for preparing high-strength 6 series aluminum alloys with low Mn and Cr content.

[0007] A method for preparing an aluminum alloy comprises the following steps: The aluminum alloy ingot is sequentially subjected to a first forward extrusion treatment, an annealing treatment, and a second forward extrusion treatment to obtain an aluminum alloy; Wherein, the preheating temperature of the second forward extrusion process is greater than the preheating temperature of the first forward extrusion process, and the extrusion speed of the second forward extrusion process is greater than the extrusion speed of the first forward extrusion process.

[0008] In one embodiment, the difference between the preheating temperature of the first forward extrusion process and the preheating temperature of the second forward extrusion process is 130°C-150°C.

[0009] In one embodiment, the preheating temperature of the first forward extrusion process is 330°C-350°C.

[0010] In one embodiment, the preheating temperature of the second forward extrusion process is 470°C-490°C.

[0011] In one embodiment, the difference between the extrusion speed of the first forward extrusion process and the extrusion speed of the second forward extrusion process is 2m / min-3m / min.

[0012] In one embodiment, the extrusion speed of the first forward extrusion process is 1 m / min-2 m / min.

[0013] In one embodiment, the extrusion speed of the second forward extrusion process is 3m / min-5m / min.

[0014] In one embodiment, the extrusion ratio of the first forward extrusion process is 7-11, and the extrusion ratio of the second forward extrusion process is 10-20.

[0015] In one embodiment, the annealing process satisfies at least one of the following conditions: (1) The annealing temperature is 500°C-530°C; (2) The heating time of the annealing treatment is 4h-6h; (3) The holding time of the annealing treatment is 3h-5h.

[0016] An aluminum alloy prepared by the above-mentioned aluminum alloy preparation method, wherein the average grain size of the aluminum alloy is less than or equal to 100 μm.

[0017] The preparation method described in the present invention adopts two forward extrusion treatments, coordinates and controls the preheating temperature and extrusion speed of the two forward extrusion treatments, and performs annealing treatment between the two forward extrusion treatments, which can effectively reduce the lattice distortion energy stored in the extrusion process, avoid the problem of tissue coarsening caused by excessive accumulation of lattice distortion energy during the extrusion process, thereby significantly reducing the grain size, and refining the average grain size of the aluminum alloy to less than 100μm, which can meet the refined tissue requirements of aluminum alloy materials with low Mn and Cr element contents, and thus effectively improve the strength of the aluminum alloy.

[0018] Therefore, this preparation method is universal, overcomes the technical defects of the traditional method, and can be used to prepare high-strength 6 series aluminum alloys, especially suitable for preparing high-strength 6 series aluminum alloys with low Mn and Cr content. DETAILED DESCRIPTION

[0019] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments or embodiments, and are not intended to limit the present invention. The optional range of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the arbitrary and all combinations include any two related listed items, any more related listed items, or all related listed items. In the present invention, it is related to a numerical range. If there is no special explanation, the above numerical range is regarded as continuous and includes the minimum and maximum values ​​of the range, and each value between such minimum and maximum values. Further, when the range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the range can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0021] After long-term and in-depth research, the applicant found that in the actual extrusion process, the grain size of aluminum alloy materials with low Mn and Cr content is mainly affected by the following three factors: (1) the grain size of the extruded ingot. If the grain size of the extruded ingot is large, even if the grains are broken during the extrusion process, the grain size of the aluminum alloy material obtained by extrusion is still large; (2) the accumulation of lattice distortion energy during the extrusion process. If the lattice distortion energy accumulates too much during the extrusion process, the recrystallization temperature will be significantly reduced, which will easily cause the grains to coarsen and form coarse crystals; (3) the size of the broken grains. If the degree of deformation during the extrusion process is not enough, the grains of the ingot may not be fully broken, resulting in the average grain size of the aluminum alloy material being too large.

[0022] Although a larger extrusion ratio can make the grain size smaller, the lattice distortion energy accumulated during the extrusion process will reduce the recrystallization temperature and cause grain coarsening. When a high extrusion speed process is used for production, the purpose is to increase the degree of deformation and make the grain size smaller. At the same time, a low rod temperature is used to avoid the temperature during the extrusion process from reaching above the recrystallization temperature, which leads to recrystallization and coarsening. However, in the actual production process, high extrusion speed and low rod temperature will accumulate a large amount of lattice distortion energy, thereby reducing the recrystallization temperature, causing the grains to recrystallize and coarsen, and ultimately cannot meet the refined structure requirements of aluminum alloy materials with low Mn and Cr content.

[0023] Based on this, the present invention provides a method for preparing an aluminum alloy, comprising the following steps: The aluminum alloy ingot is sequentially subjected to a first forward extrusion treatment, an annealing treatment, and a second forward extrusion treatment to obtain an aluminum alloy; Wherein, the preheating temperature of the second forward extrusion process is greater than the preheating temperature of the first forward extrusion process, and the extrusion speed of the second forward extrusion process is greater than the extrusion speed of the first forward extrusion process.

[0024] The preparation method described in the present invention adopts two forward extrusion treatments, coordinates and controls the preheating temperature and extrusion speed of the two forward extrusion treatments, and performs annealing treatment between the two forward extrusion treatments, which can effectively reduce the lattice distortion energy stored in the extrusion process, avoid the problem of tissue coarsening caused by excessive accumulation of lattice distortion energy during the extrusion process, thereby significantly reducing the grain size, and refining the average grain size of the aluminum alloy to less than 100μm, which can meet the refined tissue requirements of aluminum alloy materials with low Mn and Cr element contents, and thus effectively improve the strength of the aluminum alloy.

[0025] Therefore, compared with the traditional extrusion processing process, the preparation method provided by the present invention does not require homogenization treatment, can directly perform the first forward extrusion treatment, and also has the advantages of universality, etc., overcomes the technical defects of the traditional method, and can be used to prepare high-strength 6 series aluminum alloys, especially suitable for preparing high-strength 6 series aluminum alloys with low Mn and Cr element content.

[0026] It should be noted that the present invention does not limit the source of the aluminum alloy ingots, and commercial products can be used or they can be prepared by themselves; the present invention does not limit the types of aluminum alloy ingots, including but not limited to 6 series aluminum alloy ingots. Forward extrusion means that the direction of metal flow is the same as the direction of movement of the extrusion rod.

[0027] In one embodiment of the present invention, the difference between the preheating temperature of the first forward extrusion treatment and the preheating temperature of the second forward extrusion treatment is preferably 130°C-150°C, including but not limited to any point value of 130°C, 135°C, 140°C, 145°C, 150°C or any range value between the two. By regulating the preheating temperature of the first forward extrusion treatment and the preheating temperature of the second forward extrusion treatment, the preheating temperatures of the two forward extrusion treatments have a specific temperature difference, further avoiding the generation of coarse grains, thereby significantly reducing the grain size and improving the strength of the aluminum alloy.

[0028] In one embodiment of the present invention, the preheating temperature of the first forward extrusion treatment is 330°C-350°C, including but not limited to any point value of 330°C, 335°C, 340°C, 345°C, 350°C or any range value between two thereof. It should be noted that the preheating temperature of the first forward extrusion treatment in the present invention is lower than the extrusion treatment temperature of conventional 6 series aluminum alloys, which is beneficial to reduce energy consumption and save production costs.

[0029] In one embodiment of the present invention, the preheating temperature of the second forward extrusion treatment is 470°C-490°C, including but not limited to any point value of 470°C, 475°C, 480°C, 485°C, 490°C or any range value between two thereof.

[0030] In the present invention, the extrusion speed of the first forward extrusion treatment is slower, which is beneficial to reducing the lattice distortion energy stored in the first forward extrusion process. At the same time, the extrusion speed of the second forward extrusion treatment is faster than the extrusion speed of the first forward extrusion treatment, which is beneficial to further reduce the accumulation of lattice distortion energy and avoid microstructure coarsening, thereby significantly reducing the grain size and improving the strength of the aluminum alloy.

[0031] In one embodiment of the present invention, the difference between the extrusion speed of the first forward extrusion treatment and the extrusion speed of the second forward extrusion treatment is preferably 2m / min-3m / min, including but not limited to any point value of 2m / min, 2.2m / min, 2.5m / min, 2.8m / min, 3m / min or a range value between any two of them. By regulating the extrusion speed of the first forward extrusion treatment and the extrusion speed of the second forward extrusion treatment, the extrusion speeds of the two forward extrusion treatments have a specific quantitative relationship, which is beneficial to further avoid the generation of coarse grains, thereby significantly reducing the grain size and improving the strength of the aluminum alloy.

[0032] In one embodiment of the present invention, the extrusion speed of the first forward extrusion treatment is 1m / min-2m / min, including but not limited to any point value of 1m / min, 1.2m / min, 1.5m / min, 1.8m / min, 2m / min or any range value between two of them.

[0033] In one embodiment of the present invention, the extrusion speed of the second forward extrusion treatment is 3m / min-5m / min, including but not limited to any point value among 3m / min, 3.5m / min, 4m / min, 4.5m / min, 5m / min or any range value between two of them.

[0034] In one embodiment of the present invention, by adjusting the extrusion ratio of the first forward extrusion process and the extrusion ratio of the second forward extrusion process, it is beneficial to further avoid the generation of coarse grains, thereby significantly reducing the grain size and improving the strength of the aluminum alloy.

[0035] Preferably, the extrusion ratio of the first forward extrusion treatment is 7-11, including but not limited to any point value among 7, 8, 9, 10, 11 or the range value between any two of them; the extrusion ratio of the second forward extrusion treatment is 10-20, including but not limited to any point value among 10, 12, 15, 17, 20 or the range value between any two of them.

[0036] It should be noted that the extrusion ratio refers to the ratio of the cross-sectional area of ​​the extrusion barrel cavity to the total cross-sectional area of ​​the extruded product. It is a parameter used to indicate the amount of metal deformation in extrusion production.

[0037] In one embodiment of the present invention, the temperature of the annealing treatment is greater than the preheating temperature of the second forward extrusion treatment. By adjusting the annealing temperature, the crystal transformation temperature of the aluminum alloy is first increased and then decreased during the process from the first forward extrusion treatment to the annealing treatment and then to the second forward extrusion treatment. This is not only beneficial for eliminating the lattice distortion energy accumulated during the first forward extrusion treatment and avoiding microstructure coarsening during the second forward extrusion treatment, but also can avoid grain growth during the annealing treatment, which is beneficial for reducing the average grain size of the aluminum alloy after the second forward extrusion treatment.

[0038] Preferably, the annealing temperature is 500°C-530°C, including but not limited to any value among 500°C, 505°C, 510°C, 515°C, 520°C, 525°C, 530°C or any range between two values.

[0039] In one embodiment of the present invention, the heating time of the annealing treatment is 4h-6h. By adjusting the heating time of the annealing treatment, the aluminum alloy after the first forward extrusion treatment is rapidly heated in a shorter time, which is beneficial to further refine the grains and avoid grain coarsening.

[0040] In one embodiment of the present invention, the holding time of the annealing treatment is 3h-5h. Selecting a shorter holding time can avoid the continuous growth of aluminum alloy grains during the holding process, which is beneficial to further reduce the average grain size of the aluminum alloy after the second forward extrusion treatment.

[0041] In one embodiment of the present invention, after the annealing treatment and before the second forward extrusion treatment, an air cooling treatment is performed.

[0042] It can be understood that the above temperatures all represent the working temperatures of the devices for implementing the above processing.

[0043] The present invention also provides an aluminum alloy prepared by the above-mentioned method for preparing the aluminum alloy, wherein the average grain size of the aluminum alloy is less than or equal to 100 μm.

[0044] The aluminum alloy provided by the present invention has a fine grain size and exhibits excellent mechanical properties, especially in terms of strength, and can be widely used in the fields of aerospace, automobiles, electronics, etc.

[0045] The aluminum alloy and its preparation method will be further described below by the following specific examples. However, it will be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0046] Example 1 Provide 6101B cylindrical aluminum alloy ingot (310mm in diameter).

[0047] The aluminum alloy ingot was subjected to the first forward extrusion treatment, wherein the extrusion ratio was controlled at 7.1, the preheating temperature was 350° C., and the extrusion speed was set at 1 m / min.

[0048] The aluminum alloy ingot after the first forward extrusion treatment was annealed, and the temperature was raised to 530°C for 4 hours and kept at this temperature for 5 hours. After the insulation was completed, the ingot was taken out and air-cooled.

[0049] The aluminum alloy ingot after annealing was subjected to a second forward extrusion treatment, wherein the extrusion ratio was controlled at 10.3, the preheating temperature was 490° C., and the extrusion speed was set at 3 m / min.

[0050] Example 2 The same aluminum alloy ingot as in Example 1 was used to perform the first forward extrusion treatment, wherein the extrusion ratio was controlled at 7.1, the preheating temperature was 340° C., and the extrusion speed was set at 2 m / min.

[0051] The aluminum alloy ingot after the first forward extrusion treatment was annealed, and the temperature was raised to 530°C for 4 hours and kept at this temperature for 5 hours. After the insulation was completed, the ingot was taken out and air-cooled.

[0052] The aluminum alloy ingot after annealing was subjected to a second forward extrusion treatment, wherein the extrusion ratio was controlled at 19.9, the preheating temperature was 470° C., and the extrusion speed was set at 5 m / min.

[0053] Example 3 The same aluminum alloy ingot as in Example 1 was used to perform the first forward extrusion treatment, wherein the extrusion ratio was controlled at 10.2, the preheating temperature was 330° C., and the extrusion speed was set at 2 m / min.

[0054] The aluminum alloy ingot after the first forward extrusion treatment was annealed, the temperature was raised to 500°C for 4 hours and kept at this temperature for 3 hours, and then the ingot was taken out and air-cooled after the end of the heat preservation.

[0055] The aluminum alloy ingot after annealing was subjected to a second forward extrusion treatment, wherein the extrusion ratio was controlled at 10.1, the preheating temperature was 480° C., and the extrusion speed was set at 4 m / min.

[0056] Example 4 The same aluminum alloy ingot as in Example 1 was used to perform the first forward extrusion treatment, wherein the extrusion ratio was controlled at 10.2, the preheating temperature was 330° C., and the extrusion speed was set at 2 m / min.

[0057] The aluminum alloy ingot after the first forward extrusion treatment was annealed, the temperature was raised to 500°C for 4 hours and kept at this temperature for 3 hours, and then the ingot was taken out and air-cooled after the end of the heat preservation.

[0058] The aluminum alloy ingot after annealing was subjected to a second forward extrusion treatment, wherein the extrusion ratio was controlled at 19.1, the preheating temperature was 470° C., and the extrusion speed was set at 5 m / min.

[0059] Example 5 The difference between Example 5 and Example 4 is that the preheating temperature of the second forward extrusion treatment is 490°C.

[0060] Example 6 The difference between Example 6 and Example 4 is that the preheating temperature of the first forward extrusion treatment is 350°C.

[0061] Example 7 The difference between Example 7 and Example 4 is that the extrusion speed of the first forward extrusion treatment is 1 m / min.

[0062] Example 8 The difference between Example 8 and Example 4 is that the extrusion speed of the second forward extrusion treatment is 3 m / min.

[0063] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the aluminum alloy ingot is subjected to a forward extrusion treatment at an extrusion ratio of 67.3, and a second forward extrusion and annealing treatment are not performed.

[0064] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the aluminum alloy ingot is subjected to a forward extrusion treatment at an extrusion ratio of 10.3, and a second forward extrusion and annealing treatment are not performed.

[0065] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the preheating temperature of the first forward extrusion treatment and the preheating temperature of the second forward extrusion treatment are both 490°C.

[0066] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the preheating temperature of the first forward extrusion treatment is 510°C, and the preheating temperature of the second forward extrusion treatment is 490°C.

[0067] Comparative Example 5 The same aluminum alloy ingot as in Example 1 was used to perform the first reverse extrusion treatment, wherein the extrusion ratio was controlled at 7.1, the preheating temperature was 350° C., and the extrusion speed was set at 1 m / min.

[0068] The aluminum alloy ingot after the first reverse extrusion treatment was annealed, and the temperature was raised to 530°C over 4 hours and kept at this temperature for 5 hours. After the heat preservation, the ingot was taken out and air-cooled.

[0069] The aluminum alloy ingot after annealing was subjected to a second reverse extrusion treatment, wherein the extrusion ratio was controlled at 10.3, the preheating temperature was 490° C., and the extrusion speed was set at 3 m / min.

[0070] Comparative Example 6 The same aluminum alloy ingot as in Example 1 was used to perform the first forward extrusion treatment, wherein the extrusion ratio was controlled at 7.1, the preheating temperature was 350° C., and the extrusion speed was set at 1 m / min.

[0071] The aluminum alloy ingot after the first reverse extrusion treatment was annealed, and the temperature was raised to 530°C over 4 hours and kept at this temperature for 5 hours. After the heat preservation, the ingot was taken out and air-cooled.

[0072] The aluminum alloy ingot after annealing was subjected to a second reverse extrusion treatment, wherein the extrusion ratio was controlled at 10.3, the preheating temperature was 490° C., and the extrusion speed was set at 3 m / min.

[0073] Comparative Example 7 The same aluminum alloy ingot as in Example 1 was used to perform the first reverse extrusion treatment, wherein the extrusion ratio was controlled at 7.1, the preheating temperature was 350° C., and the extrusion speed was set at 1 m / min.

[0074] The aluminum alloy ingot after the first reverse extrusion treatment was annealed, and the temperature was raised to 530°C over 4 hours and kept at this temperature for 5 hours. After the heat preservation, the ingot was taken out and air-cooled.

[0075] The aluminum alloy ingot after annealing was subjected to a second forward extrusion treatment, wherein the extrusion ratio was controlled at 10.3, the preheating temperature was 490° C., and the extrusion speed was set at 3 m / min.

[0076] Comparative Example 8 The same aluminum alloy ingot as in Example 1 was used to perform the first forward extrusion treatment, wherein the extrusion ratio was controlled at 7.1, the preheating temperature was 350° C., and the extrusion speed was set at 3 m / min.

[0077] The aluminum alloy ingot after the first reverse extrusion treatment was annealed, and the temperature was raised to 530°C over 4 hours and kept at this temperature for 5 hours. After the heat preservation, the ingot was taken out and air-cooled.

[0078] The aluminum alloy ingot after annealing was subjected to a second forward extrusion treatment, wherein the extrusion ratio was controlled at 10.3, the preheating temperature was 490° C., and the extrusion speed was set at 2 m / min.

[0079] After cutting the head and tail scraps of the aluminum alloy products obtained in all the embodiments and all the comparative examples, 50 mm samples were taken for average grain size detection, and the results are shown in Table 1. It should be noted that the specifications of the aluminum alloy products obtained in all the embodiments and all the comparative examples are the same.

[0080] Table 1 It can be seen from Table 1 that the average grain size of the aluminum alloy prepared by the preparation method provided by the present invention is refined to less than 100 μm.

[0081] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0082] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing an aluminum alloy, characterized in that: The steps include: The aluminum alloy ingot is sequentially subjected to a first forward extrusion treatment, an annealing treatment, and a second forward extrusion treatment to obtain an aluminum alloy; Wherein, the preheating temperature of the second forward extrusion process is greater than the preheating temperature of the first forward extrusion process, and the extrusion speed of the second forward extrusion process is greater than the extrusion speed of the first forward extrusion process.

2. The method for preparing an aluminum alloy according to claim 1, characterized in that: The difference between the preheating temperature of the first forward extrusion process and the preheating temperature of the second forward extrusion process is 130°C-150°C.

3. The method for preparing the aluminum alloy according to claim 1 or claim 2, characterized in that: The preheating temperature of the first forward extrusion process is 330°C-350°C.

4. The method for preparing the aluminum alloy according to claim 1 or claim 2, characterized in that: The preheating temperature of the second forward extrusion treatment is 470°C-490°C.

5. The method for preparing the aluminum alloy according to claim 1, characterized in that: The difference between the extrusion speed of the first forward extrusion process and the extrusion speed of the second forward extrusion process is 2m / min-3m / min.

6. The method for preparing the aluminum alloy according to claim 1 or claim 5, characterized in that: The extrusion speed of the first forward extrusion process is 1 m / min-2 m / min.

7. The method for preparing the aluminum alloy according to claim 1 or claim 5, characterized in that: The extrusion speed of the second forward extrusion process is 3m / min-5m / min.

8. The method for preparing an aluminum alloy according to claim 1, characterized in that: The extrusion ratio of the first forward extrusion process is 7-11, and the extrusion ratio of the second forward extrusion process is 10-20.

9. The method for preparing an aluminum alloy according to claim 1, characterized in that: The annealing treatment satisfies at least one of the following conditions: (1) The annealing temperature is 500°C-530°C; (2) The heating time of the annealing treatment is 4h-6h; (3) The holding time of the annealing treatment is 3h-5h.

10. An aluminum alloy obtained by the method for preparing an aluminum alloy according to any one of claims 1 to 9, characterized in that: The average grain size of the aluminum alloy is less than or equal to 100 μm.

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