Strengthening method for 5-series aluminum alloy based on combination of laser melting and cross rolling

Abstract

The invention relates to a 5-series aluminum alloy strengthening method based on combination of laser melting and cross rolling, which comprises the following steps: firstly, carrying out high-frequency pulse nanosecond laser melting treatment on the surface of a 5-series aluminum alloy plate, melting the surface of the aluminum alloy in cooperation with a low-temperature base plate at the bottom, and then rapidly cooling; then, the workpiece subjected to laser melting treatment is subjected to heat preservation treatment, and internal stress generated in the laser melting process is eliminated or reduced; and finally, the annealed workpiece is subjected to cross rolling deformation treatment, grains in the material deform in different directions, the dislocation density in the grains is remarkably increased, the number of movable dislocations is reduced, a hardened strip-shaped structure is formed in the material, and the yield strength of the material is further improved. The surface layer of the finally prepared aluminum alloy is submicron equiaxed crystals, the interior of the finally prepared aluminum alloy is of a strip-shaped structure, the strength and plasticity of the material are improved at the same time through the coupling effect of multiple technologies, and the technical problem that good plasticity of the aluminum alloy is difficult to keep while the strength is improved is solved.

Description

Technical Field

[0001] The 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 always played an important role, from the initial application of simple structural parts to the key materials of today's complex load-bearing components. In addition, aluminum alloys also have many performance advantages. Its density is about 2.7g / cm 3 , much lower than many common metals, which can significantly reduce the weight of the structure.

[0003] Aluminum alloy is the most widely used metal material after steel. According to its composition, microstructure and process characteristics, it can be divided into 9 series in practical applications. Among them, 5 series aluminum alloy uses magnesium as the main alloying element, with a content of 3% to 7%. Due to the difficulty of nucleation of precipitation phase, it is difficult for 5 series aluminum alloy to improve material properties through precipitation strengthening, and usually relies on solid solution strengthening and fine grain strengthening to improve its performance. However, although solid solution strengthening can improve the strength of aluminum alloy to a certain extent by increasing the content of magnesium, as the solid solubility of magnesium increases, the dislocation movement in the aluminum alloy is difficult under the pinning effect of solute atoms, resulting in reduced plasticity. In addition, the fine grain strengthening method of annealing after plastic deformation has problems such as complicated process, high cost and strict requirements on the equipment required for production. Therefore, how to improve the strength of 5 series aluminum alloy while maintaining good plasticity has become a key issue that needs to be solved in its current development. Summary of the invention

[0004] The present invention aims at the problem that the current 5-series aluminum alloy strengthening method is difficult to maintain good plasticity while improving the strength of aluminum alloy, and innovatively proposes a 5-series aluminum alloy strengthening method based on laser melting combined with cross rolling. Its characteristics are that a high-frequency nanosecond laser beam (pulse frequency is KHz level, pulse width is ns level) is used to perform surface melting treatment on the surface of aluminum alloy. 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, and the molten pool is ultra-fast cooled, so that ultra-fine grains with a size of 300nm to 600nm are formed on the surface of the material, and the strength and plasticity of the material are improved through fine grain strengthening; because the surface is ultra-fine grain, dislocations are easy to move and proliferate during cross rolling, which promotes the transmission of deformation to the inside to form an internal hardened banded structure, further improving the strength of the material to achieve high-strength design. The present invention firstly performs high-frequency nanosecond laser surface melting treatment on a 5182 aluminum alloy plate, and with the help of a low-temperature pad and argon protection, a layer of ultra-fine equiaxed crystals of submicron size is remelted on the surface of the material; then the remelted material is subjected to a heat preservation treatment to reduce or eliminate the internal stress caused by crystallization and reduce the influence of stress concentration on the plasticity of the material; finally, the annealed material is subjected to a cross-rolling treatment to introduce a hardened deformation structure into the interior of the material, so as to construct 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] The 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) A 5 series aluminum alloy plate with a thickness of d is subjected to laser surface remelting treatment, wherein the laser pulse frequency used is 120 to 300 kHz, the pulse width is 20 to 55 ns, the spot diameter is 20 to 100 μm, and the laser power density is 10 to 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 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 a 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 heat-treated workpiece is subjected to cross-rolling deformation treatment, with a cross-rolling angle of 90°, a deformation temperature of 0 to 120° C., and a total deformation amount 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 160-300 ppm.

[0018] Preferably, the insulation temperature in step (4) is 120-180° C., the heating rate is 6-10° C. / min, and the insulation 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 crystals of 300 to 600 nm on the surface and internal banded structure.

[0021] Grain refinement can effectively improve the strength of aluminum alloys, but in practical applications, grain refinement methods such as large plastic deformation technology for aluminum alloys have problems such as high equipment requirements and high losses, and it is difficult to maintain good plasticity while improving its strength, which limits its widespread application. In this regard, how to ensure good plasticity while improving the yield strength of 5-series aluminum alloys is an important scientific research direction. First, the applicant uses high-frequency laser processing technology to perform surface treatment on 5-series aluminum alloy materials. Using the high energy density of high-frequency lasers, the surface of the aluminum alloy is quickly melted, so that a layer of 300nm-600nm uniform submicron equiaxed crystal structure is formed on the surface. The formation of this fine-grained structure can effectively improve the plasticity and yield strength of the material. However, during the high-frequency laser surface melting process, due to the rapid melting and solidification of the material surface, large internal stress will be generated due to recrystallization. This internal stress will reduce the plasticity of the material. In order to reduce the damage of internal stress to the plasticity of the material, the applicant performs heat preservation treatment on the material after 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 forces, the deformation is mainly concentrated in the internal coarse grain area. This uneven deformation causes a large number of dislocations 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 a high yield strength while maintaining good plasticity through a fine-grain strengthening mechanism, providing strong technical support for the widespread application of 5 series aluminum alloys in practical engineering.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[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 heat preservation followed by cross-rolling to achieve the high plasticity of the aluminum alloy. Compared with the existing aluminum alloy grain refinement methods which have high equipment requirements, the process mentioned in the present invention does not require complex and high-demand equipment, thereby reducing equipment investment costs.

[0025] (3) The aluminum alloy material constructed by the present invention has submicron equiaxed crystals on both the upper and lower surfaces and internal banded structure. 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 scheme and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Example 1

[0028] A 5 series aluminum alloy strengthening method 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 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 the workpiece is taken out after the holding period ends;

[0034] (6) The heat-treated workpiece 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 surface submicron equiaxed crystals of 300 to 600 nm and internal strip-shaped structures.

[0036] Example 2

[0037] A 5 series aluminum alloy strengthening method 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 ends;

[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 surface submicron equiaxed crystals of 300 to 600 nm and internal strip-shaped structures.

[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 260 kHz, the pulse width was 50 ns, the scanning speed was 700 mm / s, and the laser power density was 55 kW / 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 filled into the environment to make the oxygen content in the environment 300 ppm;

[0051] (5) After the remelting is completed, 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 ends;

[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 surface submicron equiaxed crystals of 300 to 600 nm and internal strip-shaped structures.

[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 insulation 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 insulation 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 5 series aluminum alloy surface strengthening method, the preparation method comprises the following steps:

[0057] (1) A 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 mesh 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 a scanning number of 1;

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

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

[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 ends;

[0065] (6) The heat-treated workpiece 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 used 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 remelting, the workpiece is kept at 150°C with a heating rate of 8°C / min for 1 hour and then taken out after the end of the heat preservation.

[0073] Comparative Example 4

[0074] A method for strengthening the surface of an aluminum alloy, the preparation method of which comprises 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 heat-treated workpiece 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 5182 aluminum alloy plate, the aluminum plates prepared in Examples 1-3 and Comparative Examples 1-4 were respectively taken, and their organizational structure, yield strength and elongation 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 organization can effectively improve the plasticity and yield strength of the 5182 aluminum alloy plate.

[0088] (2) No laser surface treatment is provided in Comparative Example 1; Comparative Example 2 is a millisecond laser surface remelting process; No cross-rolling process is provided in Comparative Example 3; No heat preservation process is provided in Comparative Example 4. Comparative Example 1 improves the yield strength of the material through cross-rolling, but at the same time, the plasticity of the material is greatly reduced due to the lack of surface fine grains; Comparative Example 2 has coarse grains after surface remelting due to the slow processing speed of the millisecond laser, large heat-affected zone, large molten pool, and slow cooling speed of the molten pool, which greatly reduces the yield strength of the material; Comparative Example 3 uses high-frequency pulse nanosecond laser to prepare submicron equiaxed crystals on the surface, but the lack of hardened band structure inside makes the mechanical properties of the material not reach the best; 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 treatment are all essential conditions for this design, and the lack of any process cannot make the 5182 aluminum alloy obtain the best 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 specific implementation method part specifically introduces the analytical method involved in the present invention. It should be noted that the above introduction is only to help those skilled in the art better understand the method and ideas of the present invention, rather than limiting the relevant content. Without departing from the principle of the present invention, those skilled in the art may also make appropriate adjustments or modifications to the present invention, and the above adjustments and modifications should also belong to the protection specifications of the present invention.

Claims

1. A 5 series aluminum alloy strengthening method based on laser melting combined with cross rolling, characterized in that: The steps include: (1) A 5 series aluminum alloy plate with a thickness of d is subjected to laser surface remelting treatment, wherein the laser pulse frequency used is 120 to 300 kHz, the pulse width is 20 to 55 ns, the spot diameter is 20 to 100 μm, and the laser power density is 10 to 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; (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; (3) During the laser treatment process, argon is used as a protective gas and filled into the environment to make the oxygen content in the environment 130-400 ppm; (4) After the remelting is completed, the workpiece is subjected to a 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; (5) The workpiece after heat treatment is subjected to cross-rolling deformation treatment, with a cross-rolling angle of 90°, a deformation temperature of 0 to 120° C., and a total deformation amount of 10 to 30%.

2. The 5-series aluminum alloy strengthening method according to claim 1, characterized in that: The grade of the 5 series aluminum alloy plate described in step (1) is 5182.

3. The 5-series aluminum alloy strengthening method according to claim 1, characterized in that: 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.

4. 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 10 mm.

5. The 5-series aluminum alloy strengthening method according to claim 4, characterized in that: The thickness d of the 5 series aluminum alloy plate in step (1) is 3 to 8 mm.

6. 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 to -60°C.

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

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

9. 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 amount is 10-20%.

10. A 5 series aluminum alloy material having surface submicron equiaxed grains of 300-600 nm and internal banded structure is prepared according to the 5 series aluminum alloy strengthening method according to any one of claims 1 to 9.

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