An Al-Mg-Sc alloy with an ultrafine equiaxed grain structure and its manufacturing method

Abstract

This invention belongs to the field of metal laser additive manufacturing technology and discloses an Al-Mg-Sc alloy with an ultrafine fully equiaxed grain structure and its manufacturing method. This invention induces the transformation of columnar crystals to equiaxed crystals in the alloy structure by adding heterogeneous nucleating agents, thereby obtaining an ultrafine fully equiaxed grain structure, wherein the equiaxed grain size D < 3 μm, and the proportion of ultrafine grains (D < 1 μm) is 85-100%, and the proportion of fine grains (1 ≤ D < 3 μm) is 0-15%. While improving strength, it can also eliminate the anisotropy of mechanical properties, so as to meet the requirements of the service environment.

Description

Technical Field

[0001] This invention belongs to the field of metal laser additive manufacturing technology, and particularly relates to an Al-Mg-Sc alloy with an ultrafine equiaxed crystal structure and its manufacturing method. Background Technology

[0002] Aluminum alloys, as the most widely used structural material after steel, possess characteristics such as low density, good plasticity, high specific strength and specific stiffness, excellent electrical and thermal conductivity, and corrosion resistance. They are the preferred structural material for achieving product lightweighting and have broad application prospects in aerospace, transportation, and other fields. Aluminum alloys are generally classified according to their nominal yield strength into ordinary strength (<300MPa), medium strength (300–400MPa), high strength (400–600MPa), and ultra-high strength (>600MPa) aluminum alloys. Currently, most printable aluminum alloys are still limited to eutectic Al-Si based alloys. The strength of these alloys is still difficult to match that of traditional cast high-strength aluminum alloys. This necessitates the development of high-strength, high-toughness, and corrosion-resistant aluminum alloys and their composites for SLM (Screen Printing Machine) to meet the stringent requirements of aerospace applications.

[0003] Airbus has developed Scalmalloy, a high-strength aluminum alloy specifically for additive manufacturing. This alloy is an Al-Mg alloy with added Sc and Zr elements, giving it excellent machinability, high strength, high ductility, and corrosion resistance. Due to the extremely high cooling rate during additive manufacturing, the solidification time is very short, resulting in a fine microstructure; even the coarser grains are 5 to 10 times smaller than those in conventionally processed alloys. However, during laser additive manufacturing of Al-Mg-Sc alloys, heat is conducted downwards from the solidified layer, creating a large negative temperature gradient along the manufacturing direction. Grains grow epitaxially along this temperature gradient, forming columnar crystals. This microstructure characteristic results in significant anisotropy in the mechanical properties of the formed parts, severely limiting their application range. Therefore, for certain functional applications, it is desirable to obtain Al-Mg-Sc alloy structural parts with a fine, equiaxed grain structure and no obvious orientation to meet the stringent requirements of high strength, high toughness, and isotropic performance.

[0004] Chinese invention patent CN108620584A discloses a laser additive manufacturing method and apparatus for fully equiaxed crystal metal components. It utilizes an electromagnetic field-assisted device to control the rapid laser solidification process, inducing a transformation from columnar crystals to equiaxed crystals, resulting in high-performance fully equiaxed crystal metal components. However, this method requires the addition of an electromagnetic auxiliary device during the additive manufacturing process, leading to high equipment costs. Furthermore, the strength and distribution of the magnetic field need to be adjusted during manufacturing, making the overall preparation process quite complex.

[0005] Chinese invention patent CN115971514A discloses a method for laser shock stabilization of aerospace additive components to achieve full equiaxed structure. Experiments verified the matching rules between laser deposition manufacturing and laser shock stabilization processes, successfully preventing columnar crystals from continuing to grow along the additive direction and achieving the fabrication of equiaxed crystal microstructures across the entire depth direction. However, this method also requires auxiliary shock stabilization equipment and adjustments to the additive manufacturing and shock stabilization processes to achieve a matching state. Furthermore, laser shock stabilization is performed on each layer only after deposition. Therefore, this method is costly, time-consuming, and has low forming efficiency.

[0006] Chinese invention patent CN113414405A discloses a method for adjusting the grain morphology in laser additive manufacturing. This method, through a combination of multiple parameters, alternates different additive manufacturing parameters during the manufacturing process, allowing equiaxed grains within the molten pool to be partially retained and prevented from remelting. This method achieves control over the grain morphology of metal components manufactured by laser additive manufacturing, from columnar grains to equiaxed grains. While this method is simple to operate and requires no auxiliary equipment, it cannot achieve fully equiaxed crystallization of the microstructure; it can only effectively reduce the size and number of columnar grains. Furthermore, the alternating use of different process parameters during the forming process may affect the printing quality of the formed parts, leading to manufacturing defects such as incomplete fusion, voids, and cracks, especially for alloys with narrow process parameter windows.

[0007] In summary, existing preparation methods are not well-suited for additive manufacturing of Al-Mg-Sc alloys with equiaxed crystal structures, and it is difficult to obtain fine, fully equiaxed crystal microstructures. Therefore, a simple, efficient, easy-to-operate, and controllable preparation method is needed to adjust the microstructure of Al-Mg-Sc alloys, thereby improving strength and eliminating anisotropy. Summary of the Invention

[0008] To address the shortcomings of current methods for obtaining Al-Mg-Sc alloys with ultrafine fully equiaxed grain structures through additive manufacturing, this invention provides an Al-Mg-Sc alloy with an ultrafine fully equiaxed grain structure and its manufacturing method. This invention promotes the transformation of columnar crystals to equiaxed crystals in the alloy structure by adding heterogeneous nucleating agents, thereby obtaining a fine fully equiaxed grain structure, eliminating anisotropy in mechanical properties, and improving the mechanical properties of the Al-Mg-Sc alloy to meet the requirements of the service environment.

[0009] To achieve the above objectives, the following technical solutions are adopted:

[0010] A method for manufacturing an Al-Mg-Sc alloy with an ultrafine equiaxed grain structure includes the following steps:

[0011] Al-Mg-Sc based composite powder material is melted and solidified layer by layer using laser additive manufacturing to ultimately form a three-dimensional solid part.

[0012] The Al-Mg-Sc based composite powder material is a mixture of Al-Mg-Sc alloy powder material and nucleating agent powder.

[0013] Preferably, the nucleating agent powder is one or a mixture of several of SiC powder, TiC powder, B4C powder, TiB2 powder, Al2O3 powder, AlN powder and ZrO2 powder.

[0014] Preferably, the particle size of the nucleating agent powder is 30–500 nm;

[0015] Among them, the nucleating agent powder with a particle size of 30-100 nm is added at a ratio of 0.3 wt.% to 1 wt.% of the mass of the Al-Mg-Sc alloy powder material.

[0016] For nucleating agent powder with a particle size of 100–300 nm, the addition ratio is 1 wt.%–2.5 wt.% of the Al-Mg-Sc alloy powder material mass.

[0017] For nucleating agent powder with a particle size of 300–500 nm, the addition ratio is 2.5 wt.%–5.5 wt.% of the mass of Al-Mg-Sc alloy powder.

[0018] Preferably, the particle size of the Al-Mg-Sc alloy powder is 15-65 μm.

[0019] Preferably, the flowability of the Al-Mg-Sc based composite powder material is 60-120 s / 50g.

[0020] Preferably, the chemical composition of the Al-Mg-Sc alloy powder, by mass percentage, includes:

[0021] Mg is 4.5%–5.1%, Sc is 0.68%–0.88%, Zr is 0.2%–0.5%, Mn is 0.3%–0.8%, Si ≤0.4%, Fe ≤0.4%, Ti ≤0.15%, O ≤0.05%, and the balance is Al.

[0022] Preferably, when Al-Mg-Sc based composite powder material is melted and solidified layer by layer using laser additive manufacturing, the forming process parameters include:

[0023] The laser power is 200-300W, the laser scanning speed is 1000-1500mm / s, the scanning interval is 0.06-0.10mm, and the powder layer thickness is 30-40μm.

[0024] Preferably, the manufacturing method of the present invention further includes a heat treatment process for the three-dimensional solid part, wherein the heat treatment is performed by holding at 325-375°C for 2-4 hours and then cooling in the furnace to complete the heat treatment.

[0025] The present invention also provides an Al-Mg-Sc alloy with an ultrafine fully equiaxed crystal structure, which is obtained by the manufacturing method of the present invention as described above.

[0026] Preferably, the microstructure of the Al-Mg-Sc alloy with ultrafine equiaxed grain structure is an equiaxed grain structure with an equiaxed grain size D < 3 μm, wherein the proportion of ultrafine grains with D < 1 μm is 85% to 100%, and the proportion of fine grains with 1 ≤ D < 3 μm is 0% to 15%.

[0027] The Al-Mg-Sc alloy with the ultrafine equiaxed grain structure has a transverse and longitudinal tensile strength of 550–580 MPa, a yield strength of 530–570 MPa, and an elongation of 8%–14%.

[0028] The difference between the transverse tensile strength and longitudinal tensile strength of the Al-Mg-Sc alloy with ultrafine equiaxed grain structure does not exceed 10 MPa, and the difference in elongation does not exceed 2%.

[0029] The present invention has the following beneficial effects:

[0030] 1. In the laser additive manufacturing process of Al-Mg-Sc alloys, this invention promotes heterogeneous nucleation within the molten pool by adding a heterogeneous nucleating agent, inducing the transformation of columnar crystals to equiaxed crystals and effectively refining the grains, resulting in ultrafine, fully equiaxed metal components. 2. This method effectively eliminates the anisotropy of the mechanical properties of metal components, obtaining high-strength metal components. 3. The entire process of this invention is simple and effective, requiring no modification to manufacturing equipment or assistance from other equipment. It has good versatility, can be applied to any powder additive manufacturing process, and boasts high production efficiency and low investment costs, making it highly conducive to the promotion of the technology. Attached Figure Description

[0031] Figure 1(a) is a grain morphology diagram of the Al-Mg-Sc alloy used in Example 1 of the present invention; Figure 1(b) is a grain morphology diagram of the Al-Mg-Sc alloy with TiC heteronucleating agent added in Example 1 of the present invention.

[0032] Figure 2(a) is a statistical diagram of the grain size of the Al-Mg-Sc alloy used in Example 1 of the present invention; Figure 2(b) is a statistical diagram of the grain size of the Al-Mg-Sc alloy with TiC heteronucleating agent added in Example 1 of the present invention.

[0033] Figure 3These are the stress-strain curves of the transverse and longitudinal tensile specimens of the Al-Mg-Sc alloy with TiC heteronucleating agent added in Example 1 of this invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the embodiment of the manufacturing method of the ultrafine equiaxed Al-Mg-Sc alloy of the present invention, a suitable nucleating agent is selected and uniformly mixed with Al-Mg-Sc alloy powder raw material to form a composite powder raw material. During the laser additive manufacturing process, the matrix alloy (i.e., Al-Mg-Sc alloy powder) melts and solidifies when heated. Due to its good thermodynamic stability, the nucleating agent will not dissolve or precipitate into the matrix at high temperatures. The dispersed nucleating agent particles can maintain a high coherence relationship with the matrix, providing enough heterogeneous nucleation sites to promote matrix nucleation, breaking the epitaxial growth characteristics of the matrix structure along the temperature gradient, promoting the formation of equiaxed grains, changing the grain orientation, eliminating anisotropy, refining the grains, and improving the mechanical properties of the Al-Mg-Sc alloy.

[0036] The specific implementation steps of the method for manufacturing the Al-Mg-Sc alloy with ultrafine equiaxed grain structure of the present invention include:

[0037] Step 1: Factors such as the type, size distribution, and addition ratio of nucleating agents can regulate the microstructure and mechanical properties of alloy materials to varying degrees. Therefore, the nucleating agent selected to match the Al-Mg-Sc alloy matrix should meet the following requirements: (1) high strength, hardness, elastic modulus, and wear resistance; (2) good thermodynamic stability; (3) low coefficient of thermal expansion; and (4) matching particle size and addition ratio. For this purpose, nucleating agents that meet the addition requirements of this invention include one or more of SiC, TiC, B4C, TiB2, Al2O3, AlN, and ZrO2. The nucleating agent has a particle size of 30–500 nm. Specifically, the addition ratio of nucleating agent with a particle size of 30–100 nm is 0.3 wt.%–1 wt.%; the addition ratio of nucleating agent with a particle size of 100–300 nm is 1 wt.%–2.5 wt.%; and the addition ratio of nucleating agent with a particle size of 300–500 nm is 2.5 wt.%–5.5 wt.%.

[0038] Step 2: The nucleating agent selected in Step 1 is mixed with Al-Mg-Sc alloy powder in a certain proportion, so that the nucleating agent particles adhere uniformly to the surface of the matrix powder without severe agglomeration, without changing the original spherical morphology of the matrix powder, and still maintaining good flowability, thus obtaining Al-Mg-Sc based composite powder material. The mixing methods between the nucleating agent particles and Al-Mg-Sc alloy powder include ball milling, homogenization, direct stirring, or vibration stirring. The chemical composition of the Al-Mg-Sc alloy powder, by mass percentage, includes: Mg 4.5%–5.1%, Sc 0.68%–0.88%, Zr 0.2%–0.5%, Mn 0.3%–0.8%, Si ≤0.4%, Fe ≤0.4%, Ti ≤0.15%, O ≤0.05%, with the balance being Al. The particle size of the Al-Mg-Sc alloy powder is 15–65 μm. The flowability of this Al-Mg-Sc based composite powder material is 60-120 s / 50g.

[0039] Step 3: Using a laser additive manufacturing device, the Al-Mg-Sc based composite powder material mixed in Step 2 is melted and solidified layer by layer according to the part model slice information and specific process parameters to finally form a three-dimensional solid part. To verify the process of this invention, the final three-dimensional solid part formed in this step can be a tensile test bar, which includes a transverse tensile test bar parallel to the substrate and a longitudinal tensile test bar perpendicular to the substrate. In this step, the forming process parameters selected by the laser additive manufacturing equipment are: laser power of 200-300W, laser scanning speed of 1000-1500mm / s, scanning spacing of 0.06-0.10mm, and powder layer thickness of 30-40μm.

[0040] Step 4: After heat treatment, the sample formed by laser additive manufacturing in Step 3 is wire-cut from the substrate, and tensile and metallographic samples are prepared. Mechanical properties are tested using a universal testing machine, and microstructure and grain size are observed using a scanning electron microscope. During the heat treatment, the sample is held at 325–375°C for 2–4 hours and then cooled in the furnace to complete the heat treatment.

[0041] In the Al-Mg-Sc alloy with ultrafine equiaxed grain structure obtained by the processing method of the present invention, the microstructure is an equiaxed grain structure with an equiaxed grain size D < 3 μm, wherein the proportion of ultrafine grains (D < 1 μm) is 85% to 100%, and the proportion of fine grains (1 ≤ D < 3 μm) is 0% to 15%.

[0042] In step 4, the tensile strength of the transverse and longitudinal tensile specimens of Al-Mg-Sc based composite materials is 550-580 MPa, the yield strength is 530-570 MPa, and the elongation is 8%-14%. The difference in strength between the transverse and longitudinal tensile specimens does not exceed 10 MPa, and the difference in elongation does not exceed 2%.

[0043] The principle of this invention is as follows:

[0044] During selective laser melting of Al-Mg-Sc alloy materials, the solidified layer is remelted multiple times along the deposition direction while the current layer is being clad. The temperature gradient of the molten pool diffuses outward from the laser incident point in a semi-circle, and the grains inside the molten pool grow into columnar crystals along the temperature gradient direction. When nucleating agent particles are added, due to their good thermal stability, they do not melt and react with the matrix during heating. The nucleating agent particles, which are dispersed inside the molten pool, can serve as heterogeneous nucleation sites, promoting the transformation of columnar crystals into equiaxed crystals. At the same time, the more nucleation sites provided by the nucleating agent particles, the more obvious the grain refinement effect.

[0045] The addition of nucleating agent particles results in an equiaxed crystal structure in the Al-Mg-Sc matrix alloy. Equiaxed grains exhibit relatively small size differences across all directions, while columnar grains have large dimensions along the formation direction, which can easily lead to significant differences in the transverse and longitudinal properties of the formed parts. Therefore, the addition of heterogeneous nucleating agents can effectively eliminate the anisotropy of the mechanical properties of Al-Mg-Sc alloys. Simultaneously, heterogeneous nucleating agents can act as dislocation sources to generate dislocations, and also hinder dislocation movement and store dislocations, thus playing a role in dispersion strengthening and effectively strengthening the crystalline material.

[0046] Example 1:

[0047] This embodiment provides a method for manufacturing an Al-Mg-Sc alloy with an ultrafine, fully equiaxed grain structure, including the following steps:

[0048] Step 1: TiC was selected as a nucleating agent and added during the laser additive manufacturing process of Al-Mg-Sc alloy. The physical properties of TiC are shown in Table 1. It can be seen from the data in Table 1 that TiC has high hardness, elastic modulus and good thermodynamic stability; the size of TiC is 500 nm and the particle shape is irregular.

[0049] Table 1

[0050]

[0051] Step 2: The chemical composition of the Al-Mg-Sc alloy matrix, by mass percentage, includes: 4.7% Mg, 0.79% Sc, 0.32% Zr, 0.59% Mn, 0.0536% Si, 0.0858% Fe, 0.0066% Ti, 0.0203% O, with the balance being Al. TiC nucleating agent was mixed with Al-Mg-Sc alloy powder using a ball milling method. The TiC addition ratio was 4.5 wt.%, the ball-to-powder ratio was 1:1, the milling speed was 250 r / min, and the milling time was 12 h. The flowability of the mixed powder was 78 s / 50g.

[0052] Step 3: The mixed TiC / Al-Mg-Sc alloy powder is printed into three-dimensional solid parts using a laser selective melting forming device. The three-dimensional solid parts include metallographic specimens and tensile specimens in the transverse and longitudinal architectural directions. The forming process parameters used are: laser power of 220 W, laser scanning speed of 1300 mm / s, scanning interval of 0.08 mm, and powder layer thickness of 40 μm.

[0053] Step 4: The laser additively formed sample from Step 3 was subjected to aging treatment at 350℃ for 3 hours, followed by microstructure and mechanical property testing. As shown in Figure 1(b), the Al-Mg-Sc alloy with added TiC heteronucleating agent exhibited a fully equiaxed grain structure with an equiaxed grain size D < 3 μm. Ultrafine grains (D < 1 μm) accounted for 87% of the total, and fine grains (1 ≤ D < 3 μm) accounted for 13%, as shown in Figure 2(b). Mechanical properties were as follows: Figure 3 As shown, the tensile strength of the transverse tensile test bar is 575 MPa, the yield strength is 567 MPa, and the elongation is 8.2%. The tensile strength of the longitudinal tensile test bar is 572 MPa, the yield strength is 566 MPa, and the elongation is 7.4%. The difference in strength between the transverse and longitudinal tensile test specimens does not exceed 10 MPa, and the elongation does not exceed 2%.

[0054] Example 2:

[0055] This embodiment provides a method for manufacturing an Al-Mg-Sc alloy with an ultrafine, fully equiaxed grain structure, including the following steps:

[0056] Step 1: TiB2 was selected as a nucleating agent and added during the laser additive manufacturing process of Al-Mg-Sc alloy. The physical properties of TiB2 are shown in Table 2. It can be seen from the data in Table 2 that TiB2 has high hardness, elastic modulus and good thermodynamic stability; the size of TiB2 is 100 nm.

[0057] Table 2

[0058]

[0059] Step 2: The chemical composition of the Al-Mg-Sc alloy matrix, by mass percentage, includes: 4.7% Mg, 0.79% Sc, 0.32% Zr, 0.59% Mn, 0.0536% Si, 0.0858% Fe, 0.0066% Ti, 0.0203% O, with the balance being Al. The TiB2 addition ratio is 2 wt.%. The TiB2 nucleating agent is mixed with the Al-Mg-Sc alloy powder using a homogenization method. Mixing is achieved through a two-stage high-speed rotation: the first stage at 1000 rpm for 40 seconds, and the second stage at 1800 rpm for 20 seconds. The fluidity of the mixed powder is 85 s / 50g.

[0060] Step 3: The mixed TiB2 / Al-Mg-Sc alloy powder is printed into three-dimensional solid parts using a laser selective melting forming device. The three-dimensional solid parts include metallographic specimens and tensile specimens in the transverse and longitudinal architectural directions. The forming process parameters used are: laser power of 220 W, laser scanning speed of 1300 mm / s, scanning interval of 0.08 mm, and powder layer thickness of 40 μm.

[0061] Step 4: The laser additively formed sample from Step 3 was subjected to aging treatment at 350℃ for 3 hours, followed by microstructure and mechanical property testing. The Al-Mg-Sc alloy with TiB2 heterogeneous nucleating agent exhibited a fully equiaxed grain structure with an equiaxed grain size D < 3 μm. Among them, ultrafine grains (D < 1 μm) accounted for 89%, and fine grains (1 ≤ D < 3 μm) accounted for 11%. The tensile strength of the transverse tensile test bar was 576 MPa, the yield strength was 538 MPa, and the elongation was 12.1%. The tensile strength of the longitudinal tensile test bar was 572 MPa, the yield strength was 533 MPa, and the elongation was 11.3%. The difference in strength between the transverse and longitudinal tensile test bars did not exceed 10 MPa, and the elongation did not exceed 2%.

[0062] Example 3:

[0063] This embodiment provides a method for manufacturing an Al-Mg-Sc alloy with an ultrafine, fully equiaxed grain structure, including the following steps:

[0064] Step 1: TiC was selected as a nucleating agent and added during the laser additive manufacturing process of Al-Mg-Sc alloy. The physical properties of TiC are shown in Table 3. It can be seen from the data in Table 3 that TiC has high hardness, elastic modulus and good thermodynamic stability; the size of TiC is 40 nm.

[0065] Table 3

[0066]

[0067] Step 2: The chemical composition of the Al-Mg-Sc alloy matrix, by mass percentage, includes: Mg 4.7%, Sc 0.79%, Zr 0.32%, Mn 0.59%, Si 0.0536%, Fe 0.0858%, Ti 0.0066%, and O 0.0203%. The TiC addition ratio is 0.7 wt.%. The TiC nucleating agent is mixed with the Al-Mg-Sc alloy powder material by homogenization. The mixing is achieved by a three-stage high-speed rotation: the first stage is at 1000 rpm for 20 s, the second stage is at 1500 rpm for 30 s, and the third stage is at 1800 rpm for 15 s. The flowability of the mixed powder is 105 s / 50g.

[0068] Step 3: The mixed TiC / Al-Mg-Sc alloy powder is printed into three-dimensional solid parts using a laser selective melting forming device. The three-dimensional solid parts include metallographic specimens and tensile specimens in the transverse and longitudinal architectural directions. The forming process parameters used are: laser power of 205 W, laser scanning speed of 1300 mm / s, scanning interval of 0.08 mm, and powder layer thickness of 40 μm.

[0069] Step 4: The laser additively formed sample from Step 3 was subjected to aging treatment at 350℃ for 3 hours, followed by microstructure and mechanical property testing. The Al-Mg-Sc alloy with TiC heteronucleating agent exhibited a fully equiaxed grain structure with an equiaxed grain size D < 3 μm, of which ultrafine grains (D < 1 μm) accounted for 91% and fine grains (1 ≤ D < 3 μm) accounted for 9%. The tensile strength of the transverse tensile test specimen was 553 MPa, the yield strength was 539 MPa, and the elongation was 9.1%. The tensile strength of the longitudinal tensile test specimen was 550 MPa, the yield strength was 531 MPa, and the elongation was 8.2%. The difference in strength between the transverse and longitudinal tensile test specimens did not exceed 10 MPa, and the elongation did not exceed 2%.

Claims

1. A method for manufacturing an Al-Mg-Sc alloy with an ultrafine equiaxed grain structure, characterized in that, The process includes the following: Al-Mg-Sc based composite powder material is melted and solidified layer by layer using laser additive manufacturing to ultimately form a three-dimensional solid part. The Al-Mg-Sc based composite powder material is a mixture of Al-Mg-Sc alloy powder material and nucleating agent powder; The chemical composition of the Al-Mg-Sc alloy powder, by mass percentage, includes: Mg is 4.5%–5.1%, Sc is 0.68%–0.88%, Zr is 0.2%–0.5%, Mn is 0.3%–0.8%, Si ≤ 0.4%, Fe ≤ 0.4%, Ti ≤ 0.15%, O ≤ 0.05%, and the balance is Al; The nucleating agent powder is one or a mixture of several of the following: SiC powder, TiC powder, B4C powder, TiB2 powder, Al2O3 powder, AlN powder, and ZrO2 powder. The particle size of the nucleating agent powder is 30–500 nm; Among them, the nucleating agent powder with a particle size of 30-100 nm is added at a ratio of 0.3 wt.% to 1 wt.% of the mass of the Al-Mg-Sc alloy powder material. For nucleating agent powder with a particle size of 100–300 nm, the addition ratio is 1 wt.%–2.5 wt.% of the Al-Mg-Sc alloy powder material mass. For nucleating agent powder with a particle size of 300–500 nm, the addition ratio is 2.5 wt.%–5.5 wt.% of the mass of Al-Mg-Sc alloy powder.

2. The method for manufacturing an Al-Mg-Sc alloy with an ultrafine equiaxed grain structure according to claim 1, characterized in that, The particle size of the Al-Mg-Sc alloy powder is 15–65 μm.

3. The method for manufacturing an Al-Mg-Sc alloy with an ultrafine equiaxed grain structure according to claim 1, characterized in that, The flowability of the Al-Mg-Sc based composite powder material is 60-120 s / 50g.

4. The method for manufacturing an Al-Mg-Sc alloy with an ultrafine equiaxed grain structure according to claim 1, characterized in that, When Al-Mg-Sc based composite powder materials are melted and solidified layer by layer using laser additive manufacturing, the forming process parameters include: The laser power is 200-300W, the laser scanning speed is 1000-1500mm / s, the scanning interval is 0.06-0.10mm, and the powder layer thickness is 30-40μm.

5. The method for manufacturing an Al-Mg-Sc alloy with an ultrafine equiaxed grain structure according to claim 1, characterized in that, It also includes a heat treatment process for the three-dimensional solid part, wherein the heat treatment is carried out by holding at 325-375°C for 2-4 hours and then cooling it in the furnace to complete the heat treatment.

6. An Al-Mg-Sc alloy with an ultrafine, fully equiaxed grain structure, characterized in that, The Al-Mg-Sc alloy with an ultrafine equiaxed crystal structure is obtained by the manufacturing method according to any one of claims 1-5.

7. The Al-Mg-Sc alloy with an ultrafine equiaxed grain structure according to claim 6, characterized in that, The microstructure of the Al-Mg-Sc alloy with ultrafine equiaxed grain structure is an equiaxed grain structure with an equiaxed grain size D < 3 μm, wherein the proportion of ultrafine grains with D < 1 μm is 85% to 100%, and the proportion of fine grains with 1 ≤ D < 3 μm is 0% to 15%. The Al-Mg-Sc alloy with the ultrafine equiaxed grain structure has a transverse and longitudinal tensile strength of 550–580 MPa, a yield strength of 530–570 MPa, and an elongation of 8%–14%. The difference between the transverse tensile strength and longitudinal tensile strength of the Al-Mg-Sc alloy with ultrafine equiaxed grain structure does not exceed 10 MPa, and the difference in elongation does not exceed 2%.

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