High-strength and high-ductility al-mg alloy and method for manufacturing the same

Abstract

This invention provides a high-strength, high-ductility, and high-hardness Al-Mg alloy and its preparation method. The alloy composition, by mass percentage, is: Mg: 5-15%, Mn: 0.4-2.3%, Sc: 0.4-1.5%, Zr: 0.2-1.5%, Si: 0.2-1%, Fe: 0.04-0.2%, with the balance being Al and unavoidable impurities, wherein the impurities are ≤0.02%. The alloy preparation method includes: laser additive manufacturing under high-purity argon protection, followed by heat treatment to obtain the high-strength, high-ductility, and high-hardness Al-Mg alloy. The Al-Mg alloy possesses high-density nanoscale Al6(Mn,Fe) (diameter ≤147nm), Mg2Si (diameter ≤131nm), and Al3(Sc,Zr) (diameter ≤4nm) reinforcing phases, achieving excellent comprehensive properties (tensile strength σ). b ≥598MPa, yield strength σ 0.2 ≥584MPa, elongation ≥11.2%, Vickers hardness ≥180HV), wherein the ultrafine nano-Al3(Sc,Zr) reinforcing phase is of type L12 with a number density ≥7.2×10 23 m ‑3 .

Description

Technical Field

[0001] This invention relates to the field of high-performance alloy materials, and in particular to a high-strength, high-ductility, and high-hardness Al-Mg alloy and its preparation method. Background Technology

[0002] Due to their low density, high specific strength, excellent electrical and thermal conductivity, and good corrosion resistance, 5xxx series Al-Mg alloys are increasingly used in transportation, building structures, medical equipment, and other fields. However, for high-performance applications such as aerospace, their absolute strength is relatively insufficient and they cannot be strengthened by heat treatment (heat treatment is not suitable for improving the strength of this series of alloys), thus limiting their widespread application in aerospace and other fields.

[0003] Existing research approaches to addressing these issues primarily include employing complex plastic deformation processes such as forging and extrusion, or adding large amounts of precious metals like Ti and V. However, these methods significantly increase production costs. Furthermore, while adding high-cost alloying elements allows for heat treatment strengthening or complex processing to enhance alloy strength, it often reduces alloy ductility, making it difficult to simultaneously improve strength and ductility. In addition, complex deformation processes can lead to decreased alloy hardness and induce cracking. For example, Yaneva et al. achieved a yield strength of 404.1 MPa in an Al-8.8Fe-2V-7.3Si alloy prepared through rapid solidification and hot extrusion, but the elongation was only 2%. Therefore, how to reduce the content of precious metals, lower costs, and simplify processes to obtain Al-Mg alloys with simultaneously improved strength and ductility is a pressing technical challenge. Summary of the Invention

[0004] To address the aforementioned technical challenges, this invention provides a high-strength, high-ductility, and high-hardness Al-Mg alloy. By mass percentage, the Al-Mg alloy composition is: Mg: 5-15%, Mn: 0.4-2.3%, Sc: 0.4-1.5%, Zr: 0.2-1.5%, Si: 0.2-1%, Fe: 0.04-0.2%, with the balance being Al and unavoidable impurities, wherein the impurities are ≤0.02%. Its preparation method includes the following steps:

[0005] (1) By mass percentage, commercial pure aluminum, Al-20Mn, Al-2Sc, Al-5Zr, Al-20Si and Al-20Fe are melted at 680-800℃, then cooled to 600-750℃, and commercial pure magnesium is added until completely melted. After stirring for 10-60 minutes, an alloy melt is obtained.

[0006] (2) The alloy melt obtained in step (1) is crushed and solidified by a high-pressure nitrogen atomizer to form metal powder. After screening, Al-Mg alloy powder is obtained, and the particle size of the Al-Mg alloy powder is 5-80μm.

[0007] (3) After vacuum drying the Al-Mg alloy powder obtained in step (2) at 80-120℃ for 3-8 hours, an aluminum alloy plate is used as the substrate, and 50-600 layers of laser additive manufacturing are performed under high-purity argon protection to obtain an Al-Mg alloy molded part. The laser additive manufacturing process is as follows: the laser scanning is in strip mode, and each layer of laser additive manufacturing requires two laser scanning melting processes. Each laser scanning melting process is as follows: the laser power is 150-420W, the scanning speed is 600-2000mm / s, the powder layer thickness is 20-50μm, and the laser scanning spacing is 100-130μm. Compared with the upper layer of laser additive manufacturing, the scanning path of the lower layer of laser additive manufacturing is deflected counterclockwise by 50-90°, and the additive manufacturing process is performed according to the upper layer process. The density of the Al-Mg alloy molded part is ≥99.7%, and the tensile strength σ b ≥475MPa, yield strength σ 0.2 ≥411MPa, elongation ≥16%;

[0008] (4) The Al-Mg alloy molded part obtained in step (3) is kept at 300-400℃ for 2-12 hours to obtain a high-strength, high-ductility, and high-hardness Al-Mg alloy; the high-strength, high-ductility, and high-hardness Al-Mg alloy has high-density nanoscale Al6(Mn,Fe) with a diameter ≤147nm; Mg2Si with a diameter ≤131nm; and ultrafine nanoscale Al3(Sc,Zr) reinforcing phase with a diameter ≤4nm. At the same time, a bimodal structure with alternating coarse and fine grains is obtained, with fine grains accounting for the majority, the area of ​​fine grains ≥55.7%, the average diameter of fine grains ≤558nm, and the average diameter of coarse grains ≤2.6μm. The Al3(Sc,Zr) reinforcing phase is of type L12 with a number density ≥7.2×10 23 m -3 The high-strength, high-hardness Al-Mg alloy has a tensile strength σ b ≥598MPa, yield strength σ 0.2 ≥584MPa, elongation ≥11.2%, Vickers hardness ≥180HV.

[0009] Furthermore, the Al-Mg alloy powder in step (2) has a particle size of 15-53 μm.

[0010] Furthermore, the aluminum alloy plate mentioned in step (3) is either 5A06 or AA5083.

[0011] Furthermore, in step (3), an Al-Mg alloy molded part is obtained after undergoing 150-400 layers of laser additive manufacturing under the protection of high-purity argon gas.

[0012] Furthermore, in step (3), compared to the upper laser additive manufacturing process, the scanning path of the lower laser additive manufacturing process is deflected counterclockwise by 60-80°.

[0013] Compared to existing technologies, this invention, through the synergistic control of component interactions, component ratios, processes, and process parameters, significantly reduces alloy addition costs, simplifies processes, achieves shorter production cycles, and enables industrial-scale production without the addition of large amounts of precious metals or complex processes such as large deformation. The beneficial effects are as follows:

[0014] 1. Compared with existing processes, the Al-Mg alloy molded parts obtained by this invention have a density ≥99.7% and a tensile strength σ b ≥475MPa, yield strength σ 0.2 ≥411MPa, elongation EL≥16%;

[0015] 2. While existing forging and extrusion processes can achieve grain refinement, the degree of refinement is only at the micrometer level, making it difficult to reach the nanometer scale. Alternatively, high-density dislocations can be introduced to improve strength, but high-density dislocations will reduce plasticity. For example, the average grain size of Al-6Zn-3Mg-Cu alloys treated with plasma sintering, hot forging, hot extrusion, and T6 in existing technologies is 2.66 μm, the size of the MgZn2 strengthening phase is ~1 μm, and the elongation is ~8%. This invention simultaneously achieves nanoscale grain refinement, nanoscale second-phase refinement, and improved solid solution strengthening, thereby enhancing the alloy's strength, plasticity, and hardness while preventing cracking. It also yields a bimodal microstructure with alternating coarse and fine grains (with fine grains dominating, average fine grain diameter ≤558 nm, average coarse grain diameter ≤2.6 μm, and fine grain area ≥55.7%) and significantly improves the solid solution strengthening effect of Mg in the Al matrix (by mass percentage, conventional processes typically yield ≤1.4 wt.% Mg in the Al matrix, while this invention yields ≥5.8 wt.%). Simultaneously, it forms high-density refined Al6(Mn,Fe) (diameter ≤147 nm), Mg2Si (diameter ≤131 nm), and Al3(Sc,Zr) (diameter ≤4 nm) nanoscale strengthening phases, among which the ultrafine nano-Al3(Sc,Zr) strengthening phase is of type L12 with a number density ≥7.2 × 10⁻⁶. 23 m -3 The final tensile strength σ of the Al-Mg alloy was obtained b ≥598MPa, yield strength σ 0.2≥584MPa, elongation EL≥11.2%, Vickers hardness≥180HV. Detailed Implementation

[0016] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be described in detail below with reference to specific embodiments. These embodiments are merely preferred implementations of the invention and are not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0017] Example 1

[0018] A high-strength, high-ductility, high-hardness Al-6.8Mg-0.53Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy (by mass percentage, Mg: 6.8%, Mn: 0.53%, Sc: 0.72%, Zr: 0.57%, Si: 0.36%, Fe: 0.055%, with the balance being Al and unavoidable impurities ≤ 0.02%), its preparation method includes the following steps:

[0019] (1) By mass percentage, commercial pure aluminum, Al-20Mn, Al-2Sc, Al-5Zr, Al-20Si and Al-20Fe are melted at 800℃, then cooled to 730℃, commercial pure magnesium is added until completely melted, and stirred for 60 min to obtain alloy melt.

[0020] (2) The alloy melt obtained in step (1) is crushed and solidified by a high-pressure nitrogen atomizer to form metal powder. After screening, Al-6.8Mg-0.53Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy powder with a particle size of 15-53μm is obtained.

[0021] (3) After vacuum drying the Al-6.8Mg-0.53Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy powder obtained in step (2) at 80-120℃ for 3 hours, a 5A06 aluminum alloy plate is used as the substrate. Under high-purity argon protection, a 333-layer laser additive manufacturing process is performed to obtain an Al-6.8Mg-0.53Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy molded part. The laser additive manufacturing process is as follows: laser scanning is in strip mode, and each layer of powder laser additive manufacturing requires... Two laser scanning melting processes were performed. Each process had the following parameters: laser power of 180W, scanning speed of 1300mm / s, powder layer thickness of 30μm, and laser scanning interval of 100μm. Compared to the upper laser additive manufacturing process, the lower process involved a 67° counterclockwise rotation of the scanning path, but followed the same additive manufacturing process. The resulting Al-6.8Mg-0.53Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy part had a density of 99.7% and a tensile strength σ... b The yield strength is 475 MPa, and the yield strength σ is 475 MPa. 0.2 It has a strength of 415 MPa and an elongation of 16%.

[0022] (4) The Al-6.8Mg-0.53Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy molded part obtained in step (3) was kept at 325℃ for 2.5h to obtain a high-strength, high-ductility, and high-hardness Al-6.8Mg-0.53Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy. This alloy has a bimodal structure with alternating coarse and fine grains, with fine grains accounting for the majority, accounting for 59.7% of the area. The average diameter of the fine grains is 486nm, and the average diameter of the coarse grains is 2.6μm. This forms a high-density, refined Al6(Mn,Fe) (diameter 147nm), Mg2Si (diameter 131nm), and Al3(Sc,Zr) (diameter 4nm) nanoscale reinforcing phases. Among them, the ultrafine nano Al3(Sc,Zr) reinforcing phase is of type L12 with a number density of 7.2×10 23 m -3 Alloy tensile strength σ b The yield strength is 600 MPa, and the yield strength σ is 600 MPa. 0.2 It has a strength of 584 MPa, an elongation of 12.2%, and a Vickers hardness of 180 HV.

[0023] Example 2

[0024] A high-strength, high-ductility, high-hardness Al-8Mg-0.57Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy (by mass percentage, Mg: 8%, Mn: 0.57%, Sc: 0.72%, Zr: 0.57%, Si: 0.36%, Fe: 0.055%, with the balance being Al and unavoidable impurities ≤ 0.02%), its preparation method includes the following steps:

[0025] (1) By mass percentage, commercial pure aluminum, Al-20Mn, Al-2Sc, Al-5Zr, Al-20Si and Al-20Fe are melted at 780℃, then cooled to 720℃, commercial pure magnesium is added until completely melted, and the alloy melt is obtained after stirring for 55 minutes.

[0026] (2) The alloy melt obtained in step (1) is crushed and solidified by a high-pressure nitrogen atomizer to form metal powder. After screening, Al-8Mg-0.57Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy powder with a particle size of 15-53μm is obtained.

[0027] (3) After vacuum drying the Al-8Mg-0.57Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy powder obtained in step (2) at 80-120℃ for 5 hours, a 5A06 aluminum alloy plate is used as the substrate. The mixture undergoes 333-layer laser additive manufacturing under high-purity argon protection to obtain an Al-8Mg-0.57Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy molded part. The laser additive manufacturing process involves: laser scanning in strip mode, and each layer of powder laser additive manufacturing requires... Two laser scanning melting processes were performed. Each process had the following parameters: laser power of 240W, scanning speed of 1700mm / s, powder layer thickness of 40μm, and laser scanning interval of 100μm. Compared to the upper laser additive manufacturing process, the lower process involved a 67° counterclockwise rotation of the scanning path, but followed the same additive manufacturing process. The resulting Al-8Mg-0.57Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy part had a density of 99.8% and a tensile strength σ... b The yield strength is 477 MPa, and the yield strength σ is 477 MPa. 0.2 It has a strength of 411 MPa and an elongation of 16.5%.

[0028] (4) The Al-8Mg-0.57Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy molded part obtained in step (3) was kept at 325℃ for 2 hours to obtain a high-strength, high-ductility, and high-hardness Al-8Mg-0.57Mn-0.72Sc-0.57Zr-0.36Si-0.055Fe alloy. This alloy has a bimodal structure with alternating coarse and fine grains, with fine grains accounting for the majority, accounting for 55.7% of the area. The average diameter of the fine grains is 558 nm, and the average diameter of the coarse grains is 2.5 μm. This forms a high-density refined Al6(Mn,Fe) (diameter 145 nm), Mg2Si (diameter 128 nm), and Al3(Sc,Zr) (diameter 3.9 nm) nanoscale reinforcing phases. Among them, the ultrafine nano Al3(Sc,Zr) reinforcing phase is of type L12 with a number density of 7.22 × 10⁻⁶. 23 m -3 Alloy tensile strength σ b The yield strength is 604 MPa, and the yield strength σ is 604 MPa. 0.2 It has a strength of 590 MPa, an elongation of 11.5%, and a Vickers hardness of 180.9 HV.

[0029] Example 3

[0030] A high-strength, high-ductility, high-hardness Al-6Mg-0.53Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy (by mass percentage, Mg: 6%, Mn: 0.53%, Sc: 0.75%, Zr: 0.57%, Si: 0.36%, Fe: 0.055%, with the balance being Al and unavoidable impurities ≤ 0.02%), its preparation method includes the following steps:

[0031] (1) By mass percentage, commercial pure aluminum, Al-20Mn, Al-2Sc, Al-5Zr, Al-20Si and Al-20Fe are melted at 785℃, then cooled to 710℃, commercial pure magnesium is added until completely melted, and the alloy melt is obtained after stirring for 58 min.

[0032] (2) The alloy melt obtained in step (1) is crushed and solidified by a high-pressure nitrogen atomizer to form metal powder. After screening, Al-6Mg-0.53Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy powder with a particle size of 15-53μm is obtained.

[0033] (3) After vacuum drying the Al-6Mg-0.53Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy powder obtained in step (2) at 80-120℃ for 4 hours, a 5A06 aluminum alloy plate is used as the substrate. Under high-purity argon protection, a 333-layer laser additive manufacturing process is performed to obtain an Al-6Mg-0.53Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy molded part. The laser additive manufacturing process is as follows: laser scanning is in strip mode, and each layer of powder laser additive manufacturing requires... Two laser scanning melting processes were performed. Each process had the following parameters: laser power of 280W, scanning speed of 600mm / s, powder layer thickness of 30μm, and laser scanning interval of 130μm. Compared to the upper laser additive manufacturing process, the lower process involved a 67° counterclockwise rotation of the scanning path, but followed the same additive manufacturing process. The resulting Al-6Mg-0.53Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy part had a density of 99.7% and a tensile strength σ... b The yield strength is 483 MPa, and the yield strength σ is 483 MPa. 0.2 It has a strength of 439 MPa and an elongation of 18%.

[0034] (4) The Al-6Mg-0.53Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy molded part obtained in step (3) was kept at 325℃ for 3 hours to obtain a high-strength, high-ductility, and high-hardness Al-6Mg-0.53Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy. This alloy has a bimodal structure with alternating coarse and fine grains, with fine grains accounting for the majority, accounting for 58.2% of the area. The average diameter of the fine grains is 532 nm, and the average diameter of the coarse grains is 2.55 μm. This forms a high-density refined Al6(Mn,Fe) (diameter 140 nm), Mg2Si (diameter 125 nm), and Al3(Sc,Zr) (diameter 4 nm) nanoscale reinforcing phases. Among them, the ultrafine nano Al3(Sc,Zr) reinforcing phase is of type L12 with a number density of 7.23 × 10⁻⁶. 23 m -3 Alloy tensile strength σ b The yield strength is 598 MPa, and the yield strength σ is 598 MPa. 0.2 It has a strength of 584 MPa, an elongation of 11.4%, and a Vickers hardness of 180 HV.

[0035] Example 4

[0036] A high-strength, high-ductility, high-hardness Al-10Mg-0.6Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy (by mass percentage, Mg: 10%, Mn: 0.6%, Sc: 0.75%, Zr: 0.57%, Si: 0.36%, Fe: 0.055%, with the balance being Al and unavoidable impurities ≤ 0.02%), its preparation method includes the following steps:

[0037] (1) By mass percentage, commercial pure aluminum, Al-20Mn, Al-2Sc, Al-5Zr, Al-20Si and Al-20Fe are melted at 790℃, then cooled to 725℃, commercial pure magnesium is added until completely melted, and stirred for 60 min to obtain alloy melt.

[0038] (2) The alloy melt obtained in step (1) is crushed and solidified by a high-pressure nitrogen atomizer to form metal powder. After screening, Al-10Mg-0.6Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy powder with a particle size of 15-53μm is obtained.

[0039] (3) After vacuum drying the Al-10Mg-0.6Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy powder obtained in step (2) at 80-120℃ for 5 hours, a 5A06 aluminum alloy plate is used as the substrate. The mixture undergoes 333-layer laser additive manufacturing under high-purity argon protection to obtain an Al-10Mg-0.6Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy molded part. The laser additive manufacturing process involves: laser scanning in strip mode, and each layer of powder laser additive manufacturing requires... Two laser scanning melting processes were performed. Each process had the following parameters: laser power of 420W, scanning speed of 2000mm / s, powder layer thickness of 40μm, and laser scanning interval of 130μm. Compared to the upper laser additive manufacturing process, the lower process involved a 67° counterclockwise rotation of the scanning path, but followed the same additive manufacturing process. The resulting Al-10Mg-0.6Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy part had a density of 99.8% and a tensile strength σ... b The yield strength is 496 MPa, and the yield strength σ is 496 MPa. 0.2 It has a strength of 440 MPa and an elongation of 18%.

[0040] (4) The Al-10Mg-0.6Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy molded part obtained in step (3) was kept at 325℃ for 2 hours to obtain a high-strength, high-ductility, and high-hardness Al-10Mg-0.6Mn-0.75Sc-0.57Zr-0.36Si-0.055Fe alloy. This alloy has a bimodal structure with alternating coarse and fine grains, with fine grains accounting for the majority, accounting for 59.5% of the area. The average diameter of the fine grains is 496 nm, and the average diameter of the coarse grains is 2.4 μm. This forms a high-density, refined Al6(Mn,Fe) (diameter 133 nm), Mg2Si (diameter 121 nm), and Al3(Sc,Zr) (diameter 3.8 nm) nanoscale reinforcing phases. Among them, the ultrafine nano Al3(Sc,Zr) reinforcing phase is of type L12 with a number density of 7.28 × 10⁻⁶. 23 m -3 Alloy tensile strength σ b The yield strength is 609 MPa, and the yield strength σ is 609 MPa. 0.2 It has a strength of 594 MPa, an elongation of 11.2%, and a Vickers hardness of 181.5 HV.

[0041] Comparative Example 1

[0042] Journal Title: Powder Metallurgy Industry, Year: 2025, Authors: Zhang Kang, Shi Zimu, Wang Xingfu, Liang Juhua, Han Fusheng, Title: Influence of TiB2 on the Microstructure and Mechanical Properties of Al-6Zn-3Mg-Cu Aluminum Alloy. The process for preparing the aluminum-zinc-magnesium-copper alloy includes: preparing industrial Al powder, Zn powder, Cu powder, and Mg powder by gas atomization; high-energy ball milling of appropriate amounts of Al powder, Zn powder, Cu powder, Mg powder, and TiB2 nanoparticles to obtain TiB2 / Al-6Zn-3Mg-Cu alloy powder (by mass percentage: Zn: 6%, Mg: 3%, Cu: 1%, TiB2: 1%, balance Al). The TiB2 / Al-6Zn-3Mg-Cu alloy powder is placed in a graphite mold and pre-pressed for 5 min at 50 MPa using a cold isostatic press. After pre-compaction, the powder is hot-pressed and sintered in a spark plasma sintering furnace to obtain a disc-shaped sample. The disc-shaped sample was heated to 450℃ and held for 1 hour, followed by hot forging, hot extrusion, and T6 heat treatment (solution treatment at 470℃ for 120 min and aging treatment at 120℃ for 24 h) to obtain TiB2 / Al-6Zn-3Mg-Cu aluminum matrix composite rods. The yield strength of the T6 heat-treated TiB2 / Al-6Zn-3Mg-Cu (by mass percentage, Zn: 6%, Mg: 3%, Cu: 1%, TiB2: 1%, balance Al) aluminum matrix composite rod was 495 MPa, the elongation was 10.3%, and the average grain size of TiB2 / Al-6Zn-3Mg-Cu was 1.58 μm.

[0043] Compared to the present invention, Comparative Example 1 incorporated expensive Ti and B elements (total mass percentage ~3%) and combined them with complex deformation processes such as hot forging and hot extrusion. It also used a long-term solution treatment followed by aging heat treatment (470℃ / 120min solution treatment and 120℃ / 24h aging treatment). The resulting TiB2 / Al-6Zn-3Mg-Cu aluminum alloy exhibited a single coarse-grained structure with a grain size of 1.58 μm, a yield strength of 495 MPa, and an elongation of 10.3%. The alloy obtained in Comparative Example 1 showed significantly lower strength and plasticity than the alloy obtained in the present invention.

[0044] This invention simultaneously achieves nanoscale grain refinement, nanoscale refinement of the second phase, and improved solid solution strengthening, thereby enhancing the alloy's strength, plasticity, and hardness. It also yields a bimodal microstructure with alternating coarse and fine grains (with fine grains dominating, average fine grain diameter ≤558 nm, average coarse grain diameter ≤2.6 μm, and fine grain area ≥55.7%) and significantly improves the solid solution strengthening effect of Mg in the Al matrix (by mass percentage, conventional processes typically yield ≤1.4 wt.% Mg in the Al matrix, while this invention yields ≥5.8 wt.%). Simultaneously, it forms high-density refined Al6(Mn,Fe) (diameter ≤147 nm), Mg2Si (diameter ≤131 nm), and Al3(Sc,Zr) (diameter ≤4 nm) nanoscale strengthening phases. The ultrafine nano-Al3(Sc,Zr) strengthening phase is of the L12 type, with a number density ≥7.2 × 10⁻⁶. 23 m -3 Compared to existing technologies involving high alloy content, precious metal additions, complex deformation processes, and long-term high-temperature heat treatment, this invention does not incorporate large amounts of precious metals or employ complex processes such as deformation and high-temperature solution heat treatment. It also reduces alloy addition costs, simplifies the process, achieves a shorter production cycle, and enables industrial-scale production. Furthermore, the component ratios and process parameters differ in each embodiment of this invention, resulting in varying performance. This demonstrates that this invention achieves optimal strength and plasticity in the alloy through the synergistic regulation of component interactions, elemental ratios, processes, and process parameters, while simultaneously maintaining high hardness and preventing cracking. The laser additive manufacturing process employed in this invention effectively avoids the anisotropy of materials during additive manufacturing, effectively improving material performance uniformity and simultaneously enhancing strength and plasticity. Moreover, the simultaneous improvement of alloy strength, plasticity, and hardness can only be achieved within the scope of the processes and process parameters protected by the claims of this invention.

[0045] In summary, this invention obtains high-strength, high-ductility, and high-hardness Al-Mg alloys through the synergistic control of component interactions, element ratios, processes, and process parameters. As shown in Table 1, after aging, the tensile strength of the Al-Mg alloy parts is ≥598MPa, the yield strength is ≥584MPa, the elongation is ≥11.2%, and the Vickers hardness is ≥180HV.

[0046] Table 1 shows the mechanical properties of the aluminum alloys obtained in all embodiments and comparative examples.

[0047]

Claims

1. A high-strength, high-ductility, high-hardness Al-Mg alloy, characterized in that: The Al-Mg alloy composition, by mass percentage, is: Mg: 5-15%, Mn: 0.4-2.3%, Sc: 0.4-1.5%, Zr: 0.2-1.5%, Si: 0.2-1%, Fe: 0.04-0.2%, with the balance being Al and unavoidable impurities, wherein the impurities are ≤0.02%. Its preparation method includes the following steps: (1) By mass percentage, commercial pure aluminum, Al-20Mn, Al-2Sc, Al-5Zr, Al-20Si and Al-20Fe are melted at 680-800℃, then cooled to 600-750℃, and commercial pure magnesium is added until completely melted. After stirring for 10-60 minutes, an alloy melt is obtained. (2) The alloy melt obtained in step (1) is crushed and solidified by a high-pressure nitrogen atomizer to form metal powder. After screening, Al-Mg alloy powder is obtained, and the particle size of the Al-Mg alloy powder is 5-80μm. (3) After vacuum drying the Al-Mg alloy powder obtained in step (2) at 80-120℃ for 3-8 hours, an aluminum alloy plate is used as the substrate, and 50-600 layers of laser additive manufacturing are performed under high-purity argon protection to obtain an Al-Mg alloy molded part. The laser additive manufacturing process is as follows: the laser scanning is in strip mode, and each layer of laser additive manufacturing requires two laser scanning melting processes. Each laser scanning melting process is as follows: the laser power is 150-420W, the scanning speed is 600-2000mm / s, the powder layer thickness is 20-50μm, and the laser scanning spacing is 100-130μm. Compared with the upper layer of laser additive manufacturing, the scanning path of the lower layer of laser additive manufacturing is deflected counterclockwise by 50-90°, and the additive manufacturing process is performed according to the upper layer process. The density of the Al-Mg alloy molded part is ≥99.7%, and the tensile strength σ b ≥475MPa, yield strength σ 0.2 ≥411MPa, elongation ≥16%; (4) The Al-Mg alloy molded part obtained in step (3) is kept at 300-400℃ for 2-12 hours to obtain a high-strength, high-ductility, and high-hardness Al-Mg alloy; the high-strength, high-ductility, and high-hardness Al-Mg alloy has high-density nanoscale Al6(Mn,Fe) with a diameter ≤147nm; Mg2Si with a diameter ≤131nm; and ultrafine nanoscale Al3(Sc,Zr) reinforcing phase with a diameter ≤4nm. At the same time, a bimodal structure with alternating coarse and fine grains is obtained, with fine grains accounting for the majority, the area of ​​fine grains ≥55.7%, the average diameter of fine grains ≤558nm, and the average diameter of coarse grains ≤2.6μm. The Al3(Sc,Zr) reinforcing phase is of type L12 with a number density ≥7.2×10 23 m -3 The high-strength, high-hardness Al-Mg alloy has a tensile strength σ b ≥598MPa, yield strength σ 0.2 ≥584MPa, elongation ≥11.2%, Vickers hardness ≥180HV.

2. The high-strength, high-ductility, high-hardness Al-Mg alloy according to claim 1, characterized in that: The Al-Mg alloy powder in step (2) has a particle size of 15-53 μm.

3. The high-strength, high-ductility, high-hardness Al-Mg alloy according to claim 1, characterized in that: The aluminum alloy plate mentioned in step (3) is either 5A06 or AA5083.

4. The high-strength, high-ductility, high-hardness Al-Mg alloy according to claim 1, characterized in that: Step (3) describes obtaining Al-Mg alloy molded parts by performing 150-400 layers of laser additive manufacturing under high-purity argon protection.

5. A high-strength, high-ductility, high-hardness Al-Mg alloy according to claim 1, characterized in that: Compared to the upper-layer laser additive manufacturing process, the scanning path of the lower-layer laser additive manufacturing process is deflected counterclockwise by 60-80° in step (3).

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