A high-strength high-toughness Al-Mg-Si alloy

Abstract

This invention discloses a high-strength, high-toughness Al-Mg-Si alloy, belonging to the field of high-strength, high-toughness aluminum alloy preparation technology. This invention optimizes the alloy composition by adding Cu, Mn, Sc, and Zr elements, and combines this with vacuum melting, homogenization treatment, asymmetric hot extrusion, solution treatment, pre-strain treatment, and three-stage aging treatment processes to synergistically achieve a significant improvement in the strength and toughness of the aluminum alloy. Compared with conventional high-strength, high-toughness aluminum alloy production, the addition of Cu, Sc, Zr, and Mn elements, and the use of asymmetric hot extrusion + solution treatment + pre-strain treatment + three-stage aging treatment processes, results in a significant increase in both strength and toughness through the synergistic effects of grain refinement strengthening, dislocation strengthening, deformation strengthening, and second-phase strengthening. This ensures that the aluminum alloy achieves improved strength and toughness simultaneously, guaranteeing the overall performance of the finished product.

Description

Technical Field

[0001] This invention belongs to the field of high-strength and high-toughness aluminum alloy technology, specifically relating to a high-strength and high-toughness Al-Mg-Si alloy. Background Technology

[0002] With the development of the national economy, increasing emphasis is being placed on the environmental performance and recyclability of materials. Al-Mg-Si aluminum alloys possess excellent properties in these areas, including low density, high specific strength, good formability, low stress corrosion sensitivity, and high recyclability; and have been widely used in construction, rail transportation, aerospace, and other fields. However, with continuous technological advancements, existing Al-Mg-Si aluminum alloys are increasingly unable to meet the mechanical property requirements of manufacturers.

[0003] Currently, methods to improve the strength of Al-Mg-Si aluminum alloys by adding alloying elements, adjusting heat treatment processes, and modifying processing techniques have reached a bottleneck. Therefore, new approaches are needed that combine the four strengthening methods, addressing the strengthening mechanism of aluminum alloys to improve their strength and toughness.

[0004] Invention patent CN113621903B describes a heat treatment method to improve the strength and toughness of aluminum alloys. This method mainly involves treating the aluminum alloy through processes such as homogenization, solution treatment, tensile treatment, and aging treatment. This can significantly improve the mechanical properties of aluminum alloy sheets, increasing tensile strength by 5-10%, yield strength by 10-15%, and elongation by over 50%. However, the final strength and toughness still do not meet the requirements for aluminum alloys in production.

[0005] Invention patent CN111118418B discloses an aging treatment method to improve the strength and toughness of Al-Zn-Mg-Cu aluminum alloys. This method involves a three-stage aging heat treatment of the Al-Zn-Mg-Cu alloy, which enables the aluminum alloy to achieve good strength and fracture toughness. However, the three-stage aging time is too long, resulting in high time costs, and it neglects the plasticity of the aluminum alloy, failing to demonstrate an enhancement effect on plasticity.

[0006] Invention patent CN115011846B discloses a high-strength, high-stability Al-Mg-Si-Cu-Sc aluminum alloy and its preparation method. The process involves melting, casting, homogenization, extrusion, solution treatment, pre-strain treatment, and aging treatment to obtain an aluminum alloy material with a yield strength ≥320MPa and an elongation ≥10%. However, the aluminum alloy obtained by this invention has relatively low strength, insufficient to meet production requirements. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, this invention provides a high-strength and high-toughness Al-Mg-Si alloy. This invention improves the strength and toughness of the aluminum-lithium alloy by adding Cu, Mn, Sc, and Zr elements, and employing vacuum melting, homogenization treatment, asymmetric hot extrusion, solution treatment, pre-strain treatment, and three-stage aging treatment.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A high-strength and high-toughness Al-Mg-Si alloy is developed by optimizing the alloy composition through the addition of Cu, Mn, Sc and Zr elements, and by combining vacuum melting, homogenization treatment, asymmetric hot extrusion, solution treatment, pre-strain treatment and three-stage aging treatment processes to achieve the best performance of strength and toughness in the Al-Mg-Si alloy.

[0010] The high-strength and high-toughness Al-Mg-Si alloy comprises the following components by mass percentage: Si: 0.6%–1.2%, Mg: 0.7%–1.1%, Mn: 0.2%–0.8%, Cu: 0.5%–1.3%, Sc: 0.15%–0.5%, Zr: 0.15%–0.4%, with unavoidable impurities totaling less than 0.2%, and the balance being Al.

[0011] The preparation method of the high-strength and high-toughness Al-Mg-Si alloy includes the following steps:

[0012] (1) Heat and melt pure Al, pure Mg, pure Cu, Al-Si20 master alloy, Al-Mn10 master alloy, Al-Zr20 master alloy and Al-Sc2 master alloy. When the alloy is completely melted, the alloy melt is obtained. The alloy melt is poured into a preheated mold to form an aluminum alloy ingot.

[0013] (2) The aluminum alloy ingot is homogenized to obtain a homogeneous ingot;

[0014] (3) The homogeneous ingot is subjected to asymmetric hot extrusion, and then solution treatment, pre-strain treatment and three-stage aging treatment are performed in sequence to obtain a high-strength and high-toughness Al-Mg-Si alloy.

[0015] In a preferred embodiment of the present invention, the heating and melting temperature in step (1) is 750-850°C.

[0016] As a preferred embodiment of the present invention, in step (1), the alloy melt is kept at 700℃~750℃ for 20 minutes before being poured.

[0017] As a preferred embodiment of the present invention, in step (2), the homogenization treatment temperature is 450℃~520℃ and the heat preservation time is 3h~6h.

[0018] As a preferred embodiment of the present invention, in step (3), the temperature of asymmetric hot extrusion is 450℃~510℃, the extrusion deformation is 75%~97%, the asymmetry ratio is (3:1)~(5:1), and the extrusion ratio is (20:1)~(25:1).

[0019] In a preferred embodiment of the present invention, in step (3), the solution temperature is 525℃~545℃ and the time is 1h~3h.

[0020] In a preferred embodiment of the present invention, in step (3), the deformation amount of the pre-strain is 0.5-5%.

[0021] As a preferred embodiment of the present invention, in step (3), the three-stage aging treatment is as follows: the first aging temperature is 140℃~160℃ and the time is 4h~8h; the second aging temperature is 160℃~185℃ and the time is 6h~10h; the third aging temperature is 140℃~160℃ and the time is 4h~8h.

[0022] The principle of this invention: The combined process of asymmetric hot extrusion, solution treatment, pre-straining, and three-stage aging can significantly improve the strength and toughness of aluminum alloys. During asymmetric hot extrusion, the large plastic deformation causes grain breakage. Simultaneously, due to the asymmetry of the extrusion orifice, a large amount of shear stress is generated, further breaking down the grains and generating numerous dislocations, resulting in grain refinement and dislocation strengthening. During solution treatment, Cu, Mn, Sc, and Zr elements are added and dissolved into the aluminum alloy through the dislocations generated by asymmetric extrusion, providing channels for atomic diffusion and resulting in solid solution strengthening. During pre-straining, a large number of dislocations are generated in the aluminum alloy, providing numerous channels for atomic diffusion during subsequent aging, precipitating a large number of strengthening phases and significantly enhancing the properties of the aluminum alloy.

[0023] The aluminum alloy of this invention incorporates elements such as Mn, Cu, Sc, and Zr. The addition of Mn causes the alloy to produce a large amount of AlSiMnCu precipitates during aging, enhancing the precipitation strengthening effect and enabling the alloy to form Al... 12Dispersed phases such as Mn3Si can effectively increase the recrystallization temperature of the alloy and inhibit recovery, recrystallization, and grain growth during the solid solution process. This effectively improves the strength and plasticity of the alloy. The addition of Cu will form Cu-containing phases (QP1 phase, QP2 phase, Q phase) in the alloy. These new precipitates can enhance the peak strength and toughness of the aluminum alloy. The addition of Sc and Zr can generate primary Al3Sc and Al3Zr particles in the alloy, which can act as nuclei for heterogeneous formation during solidification, significantly refining the grains. Furthermore, the residual Sc and Zr elements are enriched at the grain boundaries, inhibiting the diffusion of other elements, slowing down the growth rate of the α-Al matrix, and refining the alloy grains.

[0024] After asymmetric hot extrusion, the grains are elongated and fragmented under high plasticity and shear deformation, and then the grains break into smaller grains. At the same time, high-density dislocations are generated inside the grains. As the dislocations slip, the grains are continuously refined, forming even smaller grains. After solid solution treatment, pre-strain treatment, and three-stage aging, the alloying elements Mn, Cu, Sc, and Zr in the aluminum alloy continuously accumulate at the dislocation sites, precipitating second phases to form clusters. After three-stage aging, the grain boundary precipitates coarsen, the spacing increases, and fine precipitates of quasi-stable phases appear, which strengthen the grain boundary strength and further increase the toughness of the aluminum alloy.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention achieves a significant improvement in the strength and toughness of aluminum alloys through the synergistic effect between alloy composition and preparation process. Compared with conventional high-strength and high-toughness aluminum alloy production, Cu, Sc, Zr, and Mn elements are added to the composition, and an asymmetric hot extrusion + solution treatment + pre-strain + three-stage aging treatment process is adopted. Under the synergistic effect of grain refinement strengthening, dislocation strengthening, deformation strengthening, and second-phase strengthening, the strength and toughness of the aluminum alloy are greatly improved. This results in improved strength and toughness of the aluminum alloy, ensuring the comprehensive performance of the finished product. Attached Figure Description

[0026] Figure 1 This is a process flow diagram for the preparation of high-strength and high-toughness Al-Mg-Si alloys. Detailed Implementation

[0027] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0028] Example 1

[0029] A method for preparing a high-strength, high-toughness Al-Mg-Si alloy includes the following steps:

[0030] (1) Pure Al, pure Mg, pure Cu, Al-Si20 master alloy, Al-Mn10 master alloy, Al-Zr20 master alloy and Al-Sc2 master alloy are vacuum smelted and cast. The smelting temperature is 800℃ and the casting temperature is 750℃ to form an aluminum alloy ingot with a diameter of 90mm.

[0031] (2) The aluminum alloy ingot is homogenized at 520℃ for 5 hours to make all elements evenly distributed in order to obtain a homogeneous ingot.

[0032] (3) The homogeneous ingot was air-cooled to 510℃ and subjected to asymmetric hot extrusion. The total deformation was 96.43%, the asymmetric ratio was 4:1, and the extrusion ratio was 23:1. Then it was water-cooled to room temperature and solution-treated at 525℃ for 2 hours. After water-cooling again, 1% pre-strain was performed. Finally, three-stage aging treatment was performed: the first stage aging was 140℃ for 6 hours; the second stage aging was 185℃ for 6 hours; and the third stage aging was 140℃ for 4 hours. Finally, a high-strength and high-toughness Al-Mg-Si alloy was obtained. Its composition is shown in Table 1, and the strength and toughness results are shown in Table 2.

[0033] Table 1. Chemical composition (wt%) of high-strength, high-toughness Al-Mg-Si alloys according to specific embodiments of the present invention.

[0034]

[0035] Table 2

[0036] Yield strength / MPa Tensile strength / MPa elongation 403 458 15.1％

[0037] Example 2

[0038] A method for preparing a high-strength, high-toughness Al-Mg-Si alloy includes the following steps:

[0039] (1) Pure Al, pure Mg, pure Cu, Al-Si20 master alloy, Al-Mn10 master alloy, Al-Zr20 master alloy and Al-Sc2 master alloy are vacuum smelted and cast. The smelting temperature is 800℃ and the casting temperature is 750℃ to form an aluminum alloy ingot with a diameter of 90mm.

[0040] (2) The aluminum alloy ingot is homogenized at 500℃ for 5 hours to make all elements evenly distributed in order to obtain a homogeneous ingot.

[0041] (3) The homogeneous ingot was air-cooled to 480℃ and subjected to asymmetric hot extrusion with a total deformation of 97%, an asymmetric ratio of 3:1, and an extrusion ratio of 20:1. Then it was water-cooled to room temperature and solution-treated at 525℃ for 2 hours. After water-cooling again, a 3% pre-strain was performed. Finally, a three-stage aging treatment was performed: the first stage aging was 150℃ for 6 hours; the second stage aging was 180℃ for 6 hours; and the third stage aging was 150℃ for 4 hours. Finally, a high-strength and high-toughness Al-Mg-Si alloy was obtained. Its composition is shown in Table 3, and the strength and toughness results are shown in Table 4.

[0042] Table 3. Chemical composition (wt%) of high-strength, high-toughness Al-Mg-Si alloys according to specific embodiments of the present invention.

[0043]

[0044] Table 4

[0045] Yield strength / MPa Tensile strength / MPa elongation 412 463 16.3％

[0046] Example 3

[0047] A method for preparing a high-strength, high-toughness Al-Mg-Si alloy includes the following steps:

[0048] (1) Pure Al, pure Mg, pure Cu, Al-Si20 master alloy, Al-Mn10 master alloy, Al-Zr20 master alloy and Al-Sc2 master alloy are vacuum smelted and cast. The smelting temperature is 800℃ and the casting temperature is 750℃ to form an aluminum alloy ingot with a diameter of 90mm.

[0049] (2) The aluminum alloy ingot is homogenized at 480℃ for 3 hours to make all elements evenly distributed in order to obtain a homogeneous ingot.

[0050] (3) The homogeneous ingot was air-cooled to 450℃ and subjected to asymmetric hot extrusion with a total deformation of 95%, an asymmetric ratio of 5:1, and an extrusion ratio of 25:1. Then it was water-cooled to room temperature and solution-treated at 525℃ for 2 hours. After water-cooling again, a 4% pre-strain was performed. Finally, a three-stage aging treatment was performed: the first stage aging was 145℃ for 6 hours; the second stage aging was 185℃ for 6 hours; and the third stage aging was 145℃ for 4 hours. Finally, a high-strength and high-toughness Al-Mg-Si alloy was obtained. Its composition is shown in Table 5, and the strength and toughness results are shown in Table 6.

[0051] Table 5. Chemical composition (wt%) of high-strength, high-toughness Al-Mg-Si alloys according to specific embodiments of the present invention.

[0052]

[0053] Table 6

[0054] Yield strength / MPa Tensile strength / MPa elongation 415 483 14.6％

[0055] Example 4

[0056] A method for preparing a high-strength, high-toughness Al-Mg-Si alloy includes the following steps:

[0057] (1) Pure Al, pure Mg, pure Cu, Al-Si20 master alloy, Al-Mn10 master alloy, Al-Zr20 master alloy and Al-Sc2 master alloy are vacuum smelted and cast at a melting temperature of 850℃ and a casting temperature of 750℃ to form an aluminum alloy ingot with a diameter of 90mm.

[0058] (2) The aluminum alloy ingot is homogenized at 450°C for 6 hours to make all elements evenly distributed in order to obtain a homogeneous ingot.

[0059] (3) The homogeneous ingot was air-cooled to 480℃ and subjected to asymmetric hot extrusion with a total deformation of 97%, an asymmetric ratio of 3:1, and an extrusion ratio of 20:1. Then it was water-cooled to room temperature, and solidified at 525℃ for 1 hour. After water-cooling again, a 5% pre-strain was performed. Finally, a three-stage aging treatment was performed: the first stage aging was 140℃ for 4 hours; the second stage aging was 185℃ for 6 hours; and the third stage aging was 140℃ for 5 hours. Finally, a high-strength and high-toughness Al-Mg-Si alloy was obtained. Its composition is shown in Table 7, and the strength and toughness results are shown in Table 8.

[0060] Table 7. Chemical composition (wt%) of high-strength, high-toughness Al-Mg-Si alloys according to specific embodiments of the present invention.

[0061]

[0062] Table 8

[0063] Yield strength / MPa Tensile strength / MPa elongation 423 486 16.7％

[0064] Example 5

[0065] A method for preparing a high-strength, high-toughness Al-Mg-Si alloy includes the following steps:

[0066] (1) Pure Al, pure Mg, pure Cu, Al-Si20 master alloy, Al-Mn10 master alloy, Al-Zr20 master alloy and Al-Sc2 master alloy are vacuum smelted and cast. The melting temperature is 750℃ and the casting temperature is 700℃ to form an aluminum alloy ingot with a diameter of 90mm.

[0067] (2) The aluminum alloy ingot is homogenized at 500℃ for 5 hours to make all elements evenly distributed in order to obtain a homogeneous ingot.

[0068] (3) The homogeneous ingot was air-cooled to 480℃ and subjected to asymmetric hot extrusion with a total deformation of 75%, an asymmetric ratio of 3:1, and an extrusion ratio of 20:1. Then it was water-cooled to room temperature and solution-treated at 545℃ for 3 hours. After water-cooling again, a pre-strain of 0.5% was performed. Finally, a three-stage aging treatment was performed: the first stage aging was 160℃ for 8 hours; the second stage aging was 160℃ for 10 hours; and the third stage aging was 160℃ for 8 hours. Finally, a high-strength and high-toughness Al-Mg-Si alloy was obtained. Its composition is shown in Table 9, and the strength and toughness results are shown in Table 10.

[0069] Table 9. Chemical composition (wt%) of high-strength, high-toughness Al-Mg-Si alloys according to specific embodiments of the present invention.

[0070]

[0071] Table 10

[0072] Yield strength / MPa Tensile strength / MPa elongation 405 445 15.3％

[0073] Comparative Example 1

[0074] A method for preparing a high-strength, high-toughness Al-Mg-Si alloy includes the following steps:

[0075] (1) Pure Al, pure Mg, pure Cu, Al-Si20 master alloy, Al-Mn10 master alloy, Al-Zr20 master alloy and Al-Sc2 master alloy are vacuum smelted and cast. The smelting temperature is 800℃ and the casting temperature is 750℃ to form an aluminum alloy ingot with a diameter of 90mm.

[0076] (2) The aluminum alloy ingot is homogenized at 520℃ for 5 hours to make all elements evenly distributed in order to obtain a homogeneous ingot.

[0077] (3) The homogeneous ingot was air-cooled to 510℃ and subjected to asymmetric hot extrusion. The total deformation was 96.43%, the asymmetric ratio was 4:1, and the extrusion ratio was 23:1. Then it was water-cooled to room temperature and solidified at 525℃ for 2 hours. Finally, a single-stage aging treatment was performed at 170℃ for 12 hours. The high-strength and high-toughness Al-Mg-Si alloy was finally obtained. Its composition is shown in Table 11, and the strength and toughness results are shown in Table 12.

[0078] Table 11 Chemical composition (wt%) of the high-strength, high-toughness Al-Mg-Si alloy of Comparative Example 1

[0079]

[0080] Table 12

[0081] Yield strength / MPa Tensile strength / MPa elongation 362 406 11.5％

[0082] Comparative Example 2

[0083] A method for preparing a high-strength, high-toughness Al-Mg-Si alloy includes the following steps:

[0084] (1) Pure Al, pure Mg, pure Cu, Al-Si20 master alloy, Al-Mn10 master alloy, Al-Zr20 master alloy and Al-Sc2 master alloy are vacuum smelted and cast. The smelting temperature is 800℃ and the casting temperature is 750℃ to form an aluminum alloy ingot with a diameter of 90mm.

[0085] (2) The aluminum alloy ingot is homogenized at 520℃ for 5 hours to make all elements evenly distributed in order to obtain a homogeneous ingot.

[0086] (3) The homogeneous ingot was air-cooled to 480℃ and hot-extruded, with a total deformation of 96.43% and an extrusion ratio of 23:1; then it was water-cooled to room temperature and solidified at 525℃ for 2 hours. Finally, a single-stage aging treatment was performed at 170℃ for 12 hours. The high-strength and high-toughness Al-Mg-Si alloy was finally obtained. Its composition is shown in Table 13, and the strength and toughness results are shown in Table 14.

[0087] Table 13 Chemical composition (wt%) of the high-strength, high-toughness Al-Mg-Si alloy of Comparative Example 2

[0088]

[0089] Table 14

[0090] Yield strength / MPa Tensile strength / MPa elongation 343 387 12.3％

[0091] A comparison of Examples 1-5 and Comparative Examples 1-2 shows that the yield strength, tensile strength, and elongation of the Al-Mg-Si aluminum alloys after asymmetric hot extrusion + solution treatment + pre-straining + three-stage aging treatment are all improved, with the strength improvement being the most significant. Compared with aluminum alloys of ordinary composition and traditional symmetric hot extrusion and heat treatment, the Al-Mg-Si aluminum alloys of this invention after asymmetric hot extrusion + solution treatment + pre-straining + three-stage aging treatment exhibit significantly improved yield strength, tensile strength, and elongation. The enhancement is due to the addition of elements such as Cu, Sc, and Zr in the composition. The addition of Cu will form Cu-containing phases (QP1 phase, QP2 phase, Q phase) in the alloy. These new precipitates can improve the peak strength and toughness of the aluminum alloy. The addition of Sc and Zr can generate primary Al3Sc and Al3Zr particles in the alloy, which can act as the nucleation core of heterogeneous formation during solidification and can significantly refine the grains. Furthermore, the residual Sc and Zr elements are enriched at the grain boundaries, which inhibits the diffusion of other elements, slows down the growth rate of the α-Al matrix, and refines the alloy grains.

[0092] In terms of processing and heat treatment, a combination of asymmetric hot extrusion, solution treatment, pre-straining, and three-stage aging is adopted. After asymmetric hot extrusion, the grains are elongated and fragmented under high plasticity and high shear deformation, and then the grains break into smaller grains. At the same time, high-density dislocations are generated inside the grains. As the dislocations slip, the grains are continuously refined, forming even smaller grains. After solution treatment, pre-straining, and three-stage aging, the alloying elements in the aluminum alloy continuously accumulate at the dislocation sites, precipitating a second phase to form clusters. After three-stage aging, the grain boundary precipitates coarsen, the spacing increases, and fine precipitates of quasi-stable phases appear, which strengthen the grain boundary strength and further increase the toughness of the aluminum alloy.

[0093] Comparative Example 3

[0094] A method for preparing a high-strength, high-toughness Al-Mg-Si alloy includes the following steps:

[0095] (1) Pure Al, pure Mg, pure Cu, Al-Si20 master alloy, Al-Mn10 master alloy, Al-Zr20 master alloy and Al-Sc2 master alloy are vacuum smelted and cast. The smelting temperature is 800℃ and the casting temperature is 750℃ to form an aluminum alloy ingot with a diameter of 90mm.

[0096] (2) The aluminum alloy ingot is homogenized at 520℃ for 5 hours to make all elements evenly distributed in order to obtain a homogeneous ingot.

[0097] (3) The homogeneous ingot was air-cooled to 510℃ and hot-extruded, with a total deformation of 96.43% and an extrusion ratio of 23:1. Then it was water-cooled to room temperature, and solidified at 525℃ for 2 hours. After water-cooling again, 1% pre-strain was performed. Finally, a single-stage aging treatment was performed at 170℃ for 12 hours. The high-strength and high-toughness Al-Mg-Si alloy was finally obtained. Its composition is shown in Table 1, and the strength and toughness results are shown in Table 15.

[0098] Table 15

[0099]

[0100]

[0101] Comparative Example 3 employed homogenization, hot extrusion, solution treatment, pre-straining, and aging. A comparison between Comparative Example 3 and Example 1 shows that, with the same alloy composition, the aluminum alloy obtained through asymmetric hot extrusion and three-stage aging yields better strength. This is because during asymmetric hot extrusion, the aluminum alloy undergoes large shear deformation, generating numerous dislocations and resulting in finer grains. This provides more nucleation sites and atomic diffusion channels for the precipitation of the second phase during the three-stage aging process, leading to a stronger age-hardening effect.

[0102] Comparative Example 4

[0103] The only difference between the preparation method of the high-strength, high-toughness Al-Mg-Si alloy described in this comparative example and Example 1 is the chemical composition (wt%) of the high-strength, high-toughness Al-Mg-Si alloy. The chemical composition of the alloy in this comparative example is shown in Table 16. The tensile strength and elongation of the finally obtained high-strength, high-toughness Al-Mg-Si alloy are shown in Table 17.

[0104] Table 16 Chemical composition (wt%) of the high-strength, high-toughness Al-Mg-Si alloy of Comparative Example 4

[0105]

[0106] Table 17

[0107] Yield strength / MPa Tensile strength / MPa elongation 368 405 15.2％

[0108] A comparison between Comparative Example 4 and Example 1 shows that even with the same alloy preparation method, the alloy lacking Zr has lower strength than the alloy with Zr. This is because the addition of Zr allows for finer grains under asymmetric extrusion conditions and enables the formation of A during the third-stage aging process. l3 The Zr phase provides nucleation sites for the subsequent precipitation of precipitates, enhancing the age-hardening effect of the alloy.

[0109] Comparative Example 5

[0110] The only difference between the preparation method of the high-strength, high-toughness Al-Mg-Si alloy described in this comparative example and Example 1 is the chemical composition (wt%) of the high-strength, high-toughness Al-Mg-Si alloy. The chemical composition of the alloy in this comparative example is shown in Table 18. The tensile strength and elongation of the finally obtained high-strength, high-toughness Al-Mg-Si alloy are shown in Table 19.

[0111] Table 18 Chemical composition (wt%) of high-strength, high-toughness Al-Mg-Si alloys in Comparative Example 4

[0112]

[0113] Table 19

[0114] Yield strength / MPa Tensile strength / MPa elongation 375 408 16.3％

[0115] A comparison between Comparative Example 4 and Example 1 shows that even with the same alloy preparation method, the alloy lacking Mn has lower strength than the alloy with added Mn. This is because adding Mn allows the alloy to form Al. 12 Dispersed phases such as Mn3Si can effectively increase the recrystallization temperature of the alloy, suppress recovery, recrystallization and grain growth during the solid solution process, and effectively improve the strength of the alloy.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A high-strength, high-toughness Al-Mg-Si alloy, characterized in that, By adding Cu, Mn, Sc and Zr elements, the alloy composition is optimized, and combined with vacuum melting, homogenization treatment, asymmetric hot extrusion, solution treatment, pre-strain treatment and three-stage aging treatment processes, the best performance of strength and toughness of Al-Mg-Si alloy is achieved. The high-strength and high-toughness Al-Mg-Si alloy comprises the following components by mass percentage: Si: 0.6%~1.2%, Mg: 0.7%~1.1%, Mn: 0.2%~0.8%, Cu: 0.5%~1.3%, Sc: 0.15%~0.5%, Zr: 0.15%~0.4%, with unavoidable impurities totaling less than 0.2%, and the balance being Al; The preparation method of the high-strength and high-toughness Al-Mg-Si alloy includes the following steps: (1) Heat and melt pure Al, pure Mg, pure Cu, Al-Si20 master alloy, Al-Mn10 master alloy, Al-Zr20 master alloy and Al-Sc2 master alloy until the alloy is completely melted to obtain alloy melt. Pour the alloy melt into a preheated mold to form an aluminum alloy ingot. (2) The aluminum alloy ingot is homogenized to obtain a homogeneous ingot; (3) The homogeneous ingot is subjected to asymmetric hot extrusion, and then solution treatment, pre-strain treatment and three-stage aging treatment are performed in sequence to obtain a high-strength and high-toughness Al-Mg-Si alloy; In step (3), the temperature of asymmetric hot extrusion is 450℃~510℃, the extrusion deformation is 75%~97%, the asymmetric ratio is (3:1)~(5:1), and the extrusion ratio is (20:1)~(25:1). In step (3), the solution temperature is 525℃~545℃ and the time is 1h~3h; In step (3), the deformation amount of the pre-strain is 0.5-5%; In step (3), the three-stage aging process is as follows: the first aging temperature is 140℃~160℃ and the time is 4h~8h; the second aging temperature is 160℃~185℃ and the time is 6h~10h; the third aging temperature is 140℃~160℃ and the time is 4h~8h.

2. The high-strength, high-toughness Al-Mg-Si alloy as described in claim 1, characterized in that, In step (1), the heating and melting temperature is 750-850℃.

3. The high-strength, high-toughness Al as described in claim 1 Mg Si-based alloys, characterized in that... In step (1), the alloy melt is kept at 700℃~750℃ for 20 minutes before being poured.

4. The high-strength, high-toughness Al-Mg-Si alloy as described in claim 1, characterized in that, In step (2), the homogenization temperature is 450℃~520℃ and the holding time is 3h~6h.

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