A 5-series aluminum alloy strengthening method based on laser melting combined with cross rolling

Abstract

The present invention relates to a 5-series aluminum alloy strengthening method based on laser melting combined with cross-rolling, and the steps are as follows: first, a high-frequency pulse nanosecond laser melting treatment is performed on the surface of the 5-series aluminum alloy plate, and the low-temperature pad at the bottom is used to melt the aluminum alloy surface and then rapidly cool it; then, the workpiece after the laser melting treatment is subjected to a heat preservation treatment to eliminate or reduce the internal stress generated during the laser melting process; finally, the annealed workpiece is subjected to a cross-rolling deformation treatment, and the grains inside the material are deformed in different directions, the dislocation density inside the grains is significantly increased, and the number of mobile dislocations is reduced, so that a hardened banded structure is formed inside the material, further improving the yield strength of the material. The surface layer of the aluminum alloy finally prepared is a submicron equiaxed crystal, and the interior is a banded structure. Through the coupling effect of multiple processes, the strength and plasticity of the material are simultaneously improved, solving the technical problem that it is difficult for aluminum alloys to maintain good plasticity while improving strength.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy material production, and in particular relates to a 5 series aluminum alloy strengthening method based on laser melting combined with cross rolling. Background Art

[0002] The development of aluminum alloys began in the early 20th century. With the rapid development of industry, the requirements for material performance have continued to increase. Aluminum alloys have attracted widespread attention due to their high specific strength and good corrosion resistance. In the field of aerospace, aluminum alloys have played an important role in the development of simple structural parts from the initial application to the key materials of complex load-bearing components. In addition, aluminum alloys also have many performance advantages. Its density is about 2.7g / cm 3 , which is much lower than many common metals, thus significantly reducing the weight of the structure.

[0003] Aluminum alloys are the most widely used metal material after steel. Based on their composition, microstructure, and processing characteristics, they can be divided into nine series in practical applications. 5-series aluminum alloys contain magnesium as the primary alloying element, with a content between 3% and 7%. Due to the difficulty in nucleating precipitates, 5-series aluminum alloys struggle to improve material properties through precipitation strengthening. Instead, they typically rely on methods such as solid solution strengthening and grain refinement. However, while solid solution strengthening can improve the strength of aluminum alloys to a certain extent by increasing the magnesium content, increasing the solid solubility of magnesium hinders dislocation movement within the alloy due to the pinning effect of solute atoms, resulting in reduced plasticity. Furthermore, grain refinement through annealing after plastic deformation presents challenges such as complex processes, high costs, and stringent requirements for production equipment. Therefore, improving the strength of 5-series aluminum alloys while maintaining good plasticity has become a key issue that needs to be addressed in their current development. Summary of the Invention

[0004] The present invention addresses the problem that the current 5-series aluminum alloy strengthening method is difficult to maintain good plasticity while improving the strength of the aluminum alloy. This invention innovatively proposes a 5-series aluminum alloy strengthening method based on laser melting combined with cross-rolling. Its characteristic is that a high-frequency nanosecond laser beam (pulse frequency is at the KHz level, and pulse width is at the ns level) is used to perform surface melting treatment on the aluminum alloy surface. Compared with ordinary laser treatment, the high-frequency nanosecond laser has an extremely short action time and high instantaneous action energy, which can produce a smaller molten pool. The small molten pool itself cools very quickly. During the processing, the bottom low-temperature pad is used to accelerate cooling, achieving ultra-fast cooling of the molten pool, forming ultrafine grains with a size of 300nm to 600nm on the material surface, and improving the material strength and plasticity through fine grain strengthening. Due to the ultrafine grains on the surface, dislocations are easily moved and multiplied during cross-rolling, prompting deformation to be transmitted to the inside to form an internal hardened banded structure, further improving the material strength to achieve high-strength design. The present invention first performs high-frequency nanosecond laser surface melting treatment on a 5182 aluminum alloy plate, and uses a low-temperature pad and argon protection to remelt a layer of submicron-sized ultrafine equiaxed crystals on the surface of the material; then the remelted material is subjected to a heat preservation treatment to reduce or eliminate the internal stress generated by crystallization and reduce the influence of stress concentration on the plasticity of the material; finally, the annealed material is cross-rolled to introduce a hardened deformation structure into the interior of the material, thereby constructing a 5-series aluminum alloy material with submicron equiaxed crystals of 300 to 600 nm on the surface and a banded structure inside.

[0005] In order to achieve the above object, the present invention is achieved by the following means:

[0006] A first aspect of the present invention provides a 5 series aluminum alloy strengthening method based on laser melting combined with cross rolling, comprising the following steps:

[0007] (1) Laser surface remelting treatment was performed on a 5 series aluminum alloy plate with a thickness of d, wherein the laser pulse frequency used was 120-300 kHz, the pulse width was 20-55 ns, the spot diameter was 20-100 μm, and the laser power density was 10-60 kW / cm 2 , the overlap rate is 10-15%, the scanning speed is 400-800 mm / s, the light-on delay is 40 μs, the light-off delay is 180 μs, the corner delay is 80 μs, the number of scans is 1-3 times, and the scanning path is a serpentine path;

[0008] (2) During the laser treatment process, a low-temperature pad is used to adjust the cooling rate of the aluminum alloy plate, and the temperature of the low-temperature pad is -65°C to -10°C;

[0009] (3) During the laser treatment process, argon is used as a protective gas and is filled into the environment to make the oxygen content in the environment 130-400 ppm;

[0010] (4) After the remelting is completed, the workpiece is subjected to heat preservation treatment, the heat preservation temperature is 105-240 ° C, the heating rate is 5-10 ° C / min, the heat preservation time is (60-100) * d minutes, and the workpiece is taken out after the heat preservation is completed;

[0011] (5) The workpiece after heat treatment is subjected to cross-rolling deformation treatment, with a cross angle of 90°, a deformation temperature of 0 to 120°C, and a total deformation of 10 to 30%.

[0012] Preferably, the grade of the 5 series aluminum alloy plate in step (1) is 5182.

[0013] Preferably, the pulse frequency in step (1) is 220-260 KHz, the pulse width is 30-50 ns, the spot diameter is 40-60 μm, and the laser power density is 12-55 kW / cm 2 , the overlap rate is 10-13%, the scanning speed is 600-700 mm / s, and the number of scans is 1-2 times.

[0014] Preferably, the thickness d of the 5 series aluminum alloy plate in step (1) is 3 to 10 mm.

[0015] Preferably, the thickness d of the 5 series aluminum alloy plate in step (1) is 3 to 8 mm.

[0016] Preferably, the temperature of the low-temperature pad in step (2) is -30 to -60°C.

[0017] Preferably, the oxygen content in step (3) is 160 to 300 ppm.

[0018] Preferably, the holding temperature in step (4) is 120-180° C., the heating rate is 6-10° C. / min, and the holding time is (60-80)*d minutes.

[0019] Preferably, the deformation temperature in step (5) is 20-50° C., and the total deformation amount is 10-20%.

[0020] The second aspect of the present invention provides a 5 series aluminum alloy material prepared according to the above 5 series aluminum alloy strengthening method, having submicron equiaxed grains of 300 to 600 nm on the surface and internal banded structure.

[0021] Grain refinement can effectively improve the strength of aluminum alloys. However, in practical applications, grain refinement methods such as large plastic deformation techniques for aluminum alloys suffer from high equipment requirements and high losses. Furthermore, it is difficult to maintain good plasticity while improving strength, limiting their widespread application. Therefore, how to improve the yield strength of 5-series aluminum alloys while maintaining good plasticity is an important research direction. First, the applicant used high-frequency laser processing technology to surface treat 5-series aluminum alloy materials. Utilizing the high energy density of high-frequency lasers, the aluminum alloy surface is rapidly melted, forming a uniform submicron equiaxed grain structure with a diameter of 300nm-600nm. The formation of this fine-grained structure can effectively improve the material's plasticity and yield strength. However, during the high-frequency laser surface melting process, the rapid melting and solidification of the material surface can generate significant internal stress due to recrystallization. This internal stress can reduce the material's plasticity. To reduce the damage to the material's plasticity caused by internal stress, the applicant subjected the material to a heat preservation treatment after the high-frequency laser treatment. By precisely controlling the temperature and time of heat preservation, the stress inside the material is fully released, effectively reducing or eliminating the internal stress generated during the crystallization process, thereby ensuring the plasticity and yield strength of the surface ultrafine grains. Although the yield strength of the material has been improved to a certain extent after high-frequency laser treatment and heat preservation treatment, it still has not reached the expected high-strength design standard. In order to further improve the yield strength of the 5-series aluminum alloy, the applicant proposed a cross-rolling treatment method. During the cross-rolling process, because the strength of the ultrafine grains formed by the surface treatment is greater than the strength of the internal coarse grains, under the action of external force, the deformation is mainly concentrated in the internal coarse grain area. This uneven deformation causes a large number of dislocations to appear in the internal coarse grain area, thereby introducing a hardened deformation structure, which effectively improves the overall strength of the material. Through this series of treatments, a 5-series aluminum alloy material with a special structure was successfully constructed. The surface of the material is a submicron equiaxed crystal structure of 300-600nm, and the interior is a banded structure. This unique structure gives the material excellent comprehensive properties, enabling it to have high yield strength while maintaining good plasticity through the fine grain strengthening mechanism, providing strong technical support for the widespread application of 5 series aluminum alloys in practical engineering.

[0022] The present invention has the following beneficial effects compared to the prior art:

[0023] (1) The present invention proposes a 5-series aluminum alloy material with submicron equiaxed crystals of 300 to 600 nm on the surface and a banded structure inside. The surface fine grain strengthening is used to improve the plasticity and yield strength of the aluminum alloy material. At the same time, the banded grain structure inside the material is used to further improve the yield strength of the material. This solves the difficult problem of balancing the yield strength and plasticity of aluminum alloys and provides a new method for the design of high-performance aluminum alloys.

[0024] (2) The present invention utilizes laser surface melting combined with cross-rolling after heat preservation to achieve the strong plasticity of aluminum alloy. Compared with the existing aluminum alloy grain refinement method which has high equipment requirements, the process mentioned in the present invention does not require complex and high-demand equipment, thereby reducing the equipment investment cost.

[0025] (3) The aluminum alloy material constructed by the present invention has submicron equiaxed crystals on both the upper and lower surfaces and a banded structure inside. The interaction between the soft layer-hard layer-soft layer can effectively improve the mechanical properties of the aluminum alloy, providing a new idea for optimizing the microstructure of the aluminum alloy. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the following examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] Example 1

[0028] A method for strengthening a 5 series aluminum alloy based on laser melting combined with cross rolling comprises the following steps:

[0029] (1) The surface of a 3 mm thick 5182 aluminum alloy plate was polished with SiC sandpaper from 400 grit to 2000 grit and then ultrasonically cleaned in anhydrous ethanol;

[0030] (2) The surface of the cleaned aluminum alloy plate was laser remelted, wherein the laser pulse frequency used was 220KHz, the pulse width was 30ns, the scanning speed was 600mm / s, and the laser power density was 12kW / cm 2 , the spot diameter is 20μm, the overlap rate is 10%, the light-on delay is 40μs, the light-off delay is 180μs, the corner delay is 80μs, the scanning path is a serpentine path, and the number of scans is 1;

[0031] (3) During the laser treatment process, a low-temperature pad is used to adjust the cooling rate of the aluminum alloy plate, and the temperature of the low-temperature pad is -30°C;

[0032] (4) During the laser treatment process, argon is used as a protective gas and is filled into the environment to make the oxygen content in the environment 160 ppm;

[0033] (5) After remelting, the workpiece is kept at 150°C, the heating rate is 6°C / min, the holding time is 180 minutes, and it is taken out after the holding period is completed;

[0034] (6) The workpiece after heat treatment is subjected to cross-rolling deformation treatment, with a cross angle of 90°, a deformation temperature of 20°C, and a total deformation of 10%.

[0035] The strengthening method can produce a 5 series aluminum alloy material having submicron equiaxed crystals with a surface diameter of 300 to 600 nm and an internal strip-shaped structure.

[0036] Example 2

[0037] A method for strengthening a 5 series aluminum alloy based on laser melting combined with cross rolling comprises the following steps:

[0038] (1) The surface of a 3 mm thick 5182 aluminum alloy plate was polished with SiC sandpaper from 400 grit to 2000 grit and then ultrasonically cleaned in anhydrous ethanol;

[0039] (2) The surface of the cleaned aluminum alloy plate was laser remelted, wherein the laser pulse frequency used was 240KHz, the pulse width was 40ns, the scanning speed was 650mm / s, and the laser power density was 33kW / cm 2 , the spot diameter is 60μm, the overlap rate is 12%, the light-on delay is 40μs, the light-off delay is 180μs, the corner delay is 80μs, the scanning path is a serpentine sequence, and the number of scans is 1;

[0040] (3) During the laser treatment process, a low-temperature pad is used to adjust the cooling rate of the aluminum alloy plate, and the temperature of the low-temperature pad is -45°C;

[0041] (4) During the laser treatment process, argon was used as a protective gas and filled into the environment to make the oxygen content in the environment 230 ppm;

[0042] (5) After the remelting is completed, the workpiece is kept at 160°C, the heating rate is 8°C / min, the holding time is 210 minutes, and the workpiece is taken out after the holding period is completed;

[0043] (6) The workpiece after heat treatment is subjected to cross-rolling deformation treatment, with a cross angle of 90°, a deformation temperature of 35°C, and a total deformation of 15%.

[0044] The strengthening method can produce a 5 series aluminum alloy material having submicron equiaxed crystals with a surface diameter of 300 to 600 nm and an internal strip-shaped structure.

[0045] Example 3

[0046] A 5 series aluminum alloy strengthening method based on laser melting combined with cross rolling, the preparation method comprising the following steps:

[0047] (1) The surface of a 3 mm thick 5182 aluminum alloy plate was polished with SiC sandpaper from 400 grit to 2000 grit and then ultrasonically cleaned in anhydrous ethanol;

[0048] (2) The surface of the cleaned aluminum alloy plate was laser remelted, wherein the laser pulse frequency used was 260KHz, the pulse width was 50ns, the scanning speed was 700mm / s, and the laser power density was 55kW / cm 2 , the spot diameter is 100μm, the overlap rate is 13%, the light-on delay is 40μs, the light-off delay is 180μs, the corner delay is 80μs, the scanning path is a serpentine sequence, and the number of scans is 1;

[0049] (3) During the laser treatment process, a low-temperature pad is used to adjust the cooling rate of the aluminum alloy plate, and the temperature of the low-temperature pad is -60°C;

[0050] (4) During the laser treatment process, argon is used as a protective gas and is filled into the environment to make the oxygen content in the environment 300 ppm;

[0051] (5) After remelting, the workpiece is kept at 170°C, the heating rate is 10°C / min, the holding time is 240 minutes, and the workpiece is taken out after the holding period is completed;

[0052] (6) The workpiece after heat treatment is subjected to cross-rolling deformation treatment, with a cross angle of 90°, a deformation temperature of 50°C, and a total deformation of 20%.

[0053] The strengthening method can produce a 5 series aluminum alloy material having submicron equiaxed crystals with a surface diameter of 300 to 600 nm and an internal strip-shaped structure.

[0054] In addition, in other embodiments of the present invention, the laser pulse frequency can be set to 120KHz, 300KHz or other values, the pulse width can be set to 20ns, 55ns or other values, the spot diameter can be set to 40μm, 60μm or other values, and the laser power density can be set to 10kW / cm 2 、60kW / cm 2or other values, the overlap rate is set to 11%, 15% or other values, the scanning speed is set to 400mm / s, 800mm / s or other values, the number of scans is 2 or 3 times, the temperature of the low-temperature pad is -10℃, -65℃ or other values, the oxygen content is controlled to 130PPm, 400PPm or other values, the holding temperature is set to 105℃, 120℃, 180℃, 240℃ or other values, the heating rate is set to 5℃ / min, 7℃ / min or other values, the holding time is set to 90*d minutes, 100*d minutes or other values, the deformation temperature is set to 0℃, 60℃, 120℃ or other values, and the total deformation is set to 25%, 30% or other values. Moreover, the 5 series aluminum alloy plate can also use an aluminum alloy plate with a thickness d of 5mm, 8mm, 10mm or other thicknesses.

[0055] Comparative Example 1

[0056] A surface strengthening method for 5 series aluminum alloy, the preparation method comprising the following steps:

[0057] (1) The 5182 aluminum alloy plate was subjected to cross-rolling deformation treatment, the deformation temperature was 25°C, and the total deformation amount was 20%.

[0058] Comparative Example 2

[0059] A method for millisecond laser strengthening of aluminum alloy surface, the preparation method comprising the following steps:

[0060] (1) The surface of a 3 mm thick 5182 aluminum alloy plate was polished using SiC sandpaper from 500 to 2000 mesh, and then ultrasonically cleaned in anhydrous ethanol;

[0061] (2) The top and bottom surfaces of the cleaned aluminum alloy plate were laser remelted with a laser frequency of 400 Hz, a pulse width of 50 ms, a scanning speed of 150 mm / s, a spot diameter of 1 mm, an overlap rate of 10%, a serpentine scanning path, and 1 scan;

[0062] (3) Place a low-temperature pad under the workpiece during the laser melting process, and set the pad temperature to -30°C;

[0063] (4) Use argon as the protective gas and fill the environment with argon to ensure that the oxygen content is 260PPm;

[0064] (5) After remelting is completed, the workpiece is kept at 150°C, the heating rate is 8°C / min, the holding time is 1h, and it is taken out after the holding period is completed;

[0065] (6) The workpiece after heat treatment is subjected to cross-rolling deformation treatment, with a cross angle of 90°, a deformation temperature of 25°C, and a total deformation of 20%.

[0066] Comparative Example 3

[0067] A method for laser strengthening the surface of an aluminum alloy, the preparation method comprising the following steps:

[0068] (1) The surface of a 3 mm thick 5182 aluminum alloy plate was polished with SiC sandpaper from 400 grit to 2000 grit and then ultrasonically cleaned in anhydrous ethanol;

[0069] (2) The surface of the cleaned aluminum alloy plate was laser remelted, wherein the laser pulse frequency was 240KHz, the pulse width was 35ns, the scanning speed was 550mm / s, and the laser power was 15kW / cm 2 , the spot diameter is 50μm, the overlap rate is 10%, the light-on delay is 40μs, the light-off delay is 180μs, the corner delay is 80μs, the scanning path is a serpentine sequence, and the number of scans is 1;

[0070] (3) During the laser treatment process, a low-temperature pad is used to adjust the cooling rate of the aluminum alloy plate, and the temperature of the low-temperature pad is -30°C;

[0071] (4) During the laser treatment process, argon was used as a protective gas and filled into the environment to make the oxygen content in the environment 260 ppm;

[0072] (5) After the remelting is completed, the workpiece is kept at 150°C, the heating rate is 8°C / min, the holding time is 1h, and it is taken out after the holding is completed.

[0073] Comparative Example 4

[0074] A method for strengthening the surface of an aluminum alloy, the preparation method of the method comprising the following steps:

[0075] (1) The surface of a 3 mm thick 5182 aluminum alloy plate was polished with SiC sandpaper from 400 grit to 2000 grit and then ultrasonically cleaned in anhydrous ethanol;

[0076] (2) The surface of the cleaned aluminum alloy plate was laser remelted, wherein the laser pulse frequency used was 240KHz, the pulse width was 35ns, the scanning speed was 550mm / s, and the laser power density was 15kW / cm 2 , the spot diameter is 50μm, the overlap rate is 10%, the light-on delay is 40μs, the light-off delay is 180μs, the corner delay is 80μs, the scanning path is a serpentine sequence, and the number of scans is 1;

[0077] (3) During the laser treatment process, a low-temperature pad is used to adjust the cooling rate of the aluminum alloy plate, and the temperature of the low-temperature pad is -30°C;

[0078] (4) During the laser treatment process, argon was used as a protective gas and filled into the environment to make the oxygen content in the environment 260 ppm;

[0079] (5) The workpiece after heat treatment is subjected to cross-rolling deformation treatment, with a cross angle of 90°, a deformation temperature of 25°C, and a total deformation of 10%.

[0080] Verification Example 1

[0081] The microstructure, yield strength and elongation of the 5182 aluminum alloy plate, the aluminum plates prepared in Examples 1-3 and Comparative Examples 1-4 were tested using conventional technical methods in the art. The specific test results are shown in Table 1 below.

[0082] Table 1 Test results of 5182 aluminum alloy plate, Examples 1-3 and Comparative Examples 1-4

[0083]

[0084]

[0085] By comparing the performance of the aluminum alloys of Examples 1-3 and the 5182 aluminum alloy plate, it was found that the construction of submicron grain size can effectively improve the strength and plasticity of the aluminum plate.

[0086] By comparing and analyzing the results of Examples 1-3 and Comparative Examples 1-4, the following conclusions can be drawn:

[0087] (1) It can be seen from the comparative examples that the structure of the surface submicron grains and the internal hardened strip structure can effectively improve the plasticity and yield strength of the 5182 aluminum alloy plate.

[0088] (2) Comparative Example 1 does not include laser surface treatment; Comparative Example 2 uses a millisecond laser surface remelting process; Comparative Example 3 does not include a cross-rolling process; and Comparative Example 4 does not include a heat preservation process. Comparative Example 1 improves the yield strength of the material through cross-rolling, but at the same time, the lack of surface fine grains greatly reduces the plasticity of the material; Comparative Example 2 has a slow millisecond laser processing speed, a large heat-affected zone, a large molten pool, and a slow molten pool cooling rate, so the grains are coarse after the surface remelting of the material, which greatly reduces the yield strength of the material; Comparative Example 3 uses a high-frequency pulse nanosecond laser to produce submicron equiaxed crystals on the surface, but the lack of hardened banded structure inside means that the mechanical properties of the material do not reach the optimal level; Comparative Example 4 lacks heat preservation to reduce the internal stress generated after laser surface treatment. Although the strength is improved, the plasticity is seriously damaged. The above analysis reveals that high-frequency pulse nanosecond laser surface melting, heat preservation, and cross-rolling are all essential conditions for this design. Without any of these processes, the 5182 aluminum alloy cannot achieve the optimal performance. In addition, the strengthening method described in the present invention is also applicable to other grades of 5 series aluminum alloys.

[0089] The above detailed description of the analytical methods involved in the present invention provides a detailed introduction. It should be noted that this introduction is intended solely to help those skilled in the art better understand the methods and concepts of the present invention and is not intended to limit the relevant content. Without departing from the principles of the present invention, those skilled in the art may make appropriate adjustments or modifications to the present invention, and such adjustments and modifications shall also fall within the scope of protection of the present invention.

Claims

1. A method for strengthening 5 series aluminum alloy based on laser melting combined with cross rolling, characterized in that: The steps include: (1) Laser surface remelting treatment was performed on a 5 series aluminum alloy plate with a thickness of d, wherein the laser pulse frequency used was 120~300KHz, the pulse width was 20~55ns, the spot diameter was 20~100µm, and the laser power density was 10~60kW / cm 2 The overlap rate is 10-15%, the scanning speed is 400-800 mm / s, the light-on delay is 40µs, the light-off delay is 180µs, the corner delay is 80µs, the number of scans is 1-3, and the scanning path is a serpentine path; the grade of the 5 series aluminum alloy plate is 5182, and the thickness d is 3-10 mm; (2) During the laser treatment process, a low-temperature pad is used to adjust the cooling rate of the aluminum alloy plate. The temperature of the low-temperature pad is -65℃~-10℃; (3) During the laser treatment process, argon is used as a protective gas and is filled into the environment to make the oxygen content in the environment 130~400PPm; (4) After remelting is completed, the workpiece is kept warm at a temperature of 105-240°C, a heating rate of 5-10°C / min, and a holding time of (60-100)*d minutes. After the holding is completed, the workpiece is taken out; (5) The workpiece after heat treatment is subjected to cross-rolling deformation treatment, with a cross angle of 90°, a deformation temperature of 0~120℃, and a total deformation of 10~30%.

2. The 5 series aluminum alloy strengthening method according to claim 1, characterized in that: The pulse frequency in step (1) is 220~260KHz, the pulse width is 30~50ns, the spot diameter is 40~60µm, and the laser power density is 12~55kW / cm 2 , the overlap rate is 10~13%, the scanning speed is 600~700mm / s, and the number of scans is 1~2 times.

3. The 5 series aluminum alloy strengthening method according to claim 1, characterized in that: The thickness d of the 5 series aluminum alloy plate in step (1) is 3 to 8 mm.

4. The 5 series aluminum alloy strengthening method according to claim 1, characterized in that: The temperature of the low-temperature pad in step (2) is -30~-60℃.

5. The 5 series aluminum alloy strengthening method according to claim 1, characterized in that: The oxygen content in step (3) is 160~300PPm.

6. The 5 series aluminum alloy strengthening method according to claim 1, characterized in that: The holding temperature in step (4) is 120-180°C, the heating rate is 6-10°C / min, and the holding time is (60-80)*d minutes.

7. The 5 series aluminum alloy strengthening method according to claim 1, characterized in that: The deformation temperature in step (5) is 20-50°C, and the total deformation is 10-20%.

8. A 5 series aluminum alloy material, prepared according to the 5 series aluminum alloy strengthening method according to any one of claims 1 to 7, characterized in that: The material has submicron equiaxed crystals with a diameter of 300 to 600 nm on the surface and internal striped structure.

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