Al-Mg-Li-based aluminum alloy for additive manufacturing and additive manufacturing method

Abstract

The invention provides an Al-Mg-Li-based aluminum alloy for additive manufacturing and an additive manufacturing method. The Al-Mg-Li-based aluminum alloy is prepared from the following chemical components in percentage by mass: 5 to 7 percent of Mg, 1.7 to 2.3 percent of Li, 1.3 to 1.9 percent of Zn, 1.7 to 2.3 percent of Cu, 1.7 to 2.3 percent of Mn, 0.8 to 1.2 percent of Sc, 0.4 to 0.8 percent of Zr, 0.6 to 1.0 percent of Ti, 0.1 to 0.3 percent of Si and the balance of Al and inevitable impurities. According to the Al-Mg-Li-based aluminum alloy and the preparation method thereof, the alloy density is effectively reduced by introducing high-content light elements Mg and Li, on the basis of the Al-Mg-Li-based alloy, by compositely adding Cu, Zn, Mn, Sc, Zr and Ti and controlling the content of Si, collaborative optimization of multiple properties is achieved, the alloy density is remarkably lower than that of a traditional high-strength aluminum alloy, the density of the Al-Mg-Li-based aluminum alloy is smaller than 2.6 g / cm < 3 >, and the Al-Mg-Li-based aluminum alloy is suitable for being used as a high-strength aluminum alloy. And after heat treatment, the yield strength of the steel plate is higher than 520 MPa, the tensile strength of the steel plate is higher than 600 MPa, and the Young modulus of the steel plate is higher than 90 GPa.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of additive manufacturing, and particularly relates to an Al-Mg-Li-based aluminum alloy for additive manufacturing and an additive manufacturing method. BACKGROUND

[0002] With the increasing demand for structural lightweight in the fields of aerospace and transportation, developing metal materials with low density and high mechanical properties has become a research hotspot. Traditional high-strength aluminum alloys, such as 7075 aluminum alloy (density about 2.81 g / cm³), have good tensile and yield strength, but the density is relatively large, which is difficult to meet the requirements of extreme lightweight.

[0003] In order to reduce the density, researchers have developed various lightweight series alloys. For example, magnesium alloys (such as AZ series, density about 1.8 g / cm³) have the lowest density, but generally have low strength (yield strength < 300 MPa), poor machinability, and corrosion problems; titanium alloys (such as TC4, density about 4.5 g / cm³) have high specific strength, but the density is much higher than that of aluminum alloys, and the cost is relatively high; carbon fiber composites (such as T700, density about 1.8 g / cm³) have significant weight reduction effect, but the processing is complex, the cost is high, and there are connection and anisotropy problems in some applications; beryllium aluminum alloys (such as Be-Al 562, density about 2.13 g / cm³) have excellent performance, but beryllium element is toxic, and the toughness of the alloy is poor, which limits its application.

[0004] Aluminum-lithium (Al-Li) alloys have low density and high modulus due to the addition of Li element (about 3% reduction in density and about 6% increase in modulus for each addition of 1 wt% Li), and have become important aerospace structural materials. The first and second generation Al-Li alloys (such as 8090, 2091) have achieved weight reduction (density about 2.54-2.58 g / cm³), but may have problems such as insufficient plasticity and toughness, and anisotropy; the third generation Al-Li alloy (such as 2195 Al-Cu-Li, density about 2.68 g / cm³) improves the strength by adding Cu and other elements, but the weight reduction effect is relatively limited; the Al-Mg series alloy (such as Al-7.5Mg, density about 2.61 g / cm³) has acceptable weight reduction effect, but the strength and Young's modulus are slightly low.

[0005] Additive manufacturing (AM) (also known as 3D printing) technology provides the possibility for manufacturing complex structures, but traditional aluminum alloys are prone to thermal cracks during AM process. Therefore, developing new high-performance aluminum alloys suitable for AM process, especially alloys with low density, high strength, high modulus and good AM processability, has important application value and challenge. SUMMARY

[0006] The Al-Mg-Li-based aluminum alloy for additive manufacturing provided by the present application can at least solve some defects in the prior art.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] The Al-Mg-Li-based aluminum alloy for additive manufacturing comprises the following chemical components in percentage by mass: Mg 5-7%, Li 1.7-2.3%, Zn 1.3-1.9%, Cu 1.7-2.3%, Mn 1.7-2.3%, Sc 0.8-1.2%, Zr 0.4-0.8%, Ti 0.6-1.0%, Si 0.1-0.3%, and the balance of Al and inevitable impurities.

[0009] Further, in the Al-Mg-Li-based aluminum alloy for additive manufacturing, the mass percentage ratio of Zn to Mg is 0.19-0.38.

[0010] Further, in the Al-Mg-Li-based aluminum alloy for additive manufacturing, the total content of Sc+Zr is controlled in the range of 1.2-2.0%.

[0011] Further, the Al-Mg-Li-based aluminum alloy for additive manufacturing comprises the following chemical components in percentage by mass: Mg 6.0%, Li 2.0%, Zn 1.6%, Cu 2.0%, Mn 2.0%, Sc 1.0%, Zr 0.6%, Ti 0.8%, Si 0.2%, and the balance of Al and inevitable impurities.

[0012] In addition, the present application also provides an additive manufacturing method, comprising the following processes:

[0013] The Al-Mg-Li-based aluminum alloy is made into aluminum alloy metal powder, and the laser additive manufacturing technology is used to print a 3D printed part; the process parameters of the laser additive manufacturing technology printing are as follows: laser power is 100-600 W, scanning speed is 200-1000 mm / s, scanning interval is 0.06-0.14 mm, powder layer thickness is 0.02-0.06 mm, and laser volume energy density is controlled in the range of 40-120 J / mm³.

[0014] Further, the particle size of the aluminum alloy metal powder is 15-53 μm.

[0015] Further, the additive manufacturing method further comprises heat treatment on the 3D printed part after printing, and the heat treatment process comprises solid solution, quenching and artificial aging treatment on the 3D printed part in sequence; the quenching adopts room temperature water quenching or 60-100 DEG C hot water quenching or polymer quenching liquid; the artificial aging adopts two-stage aging, first aging at 120-160 DEG C for 4-12h, and then aging at 160-190 DEG C for 8-48h.

[0016] Further, after the two-stage aging artificial aging treatment, a dispersion body including 、 a plurality of nano precipitates, and 、 a core-shell structure is formed.

[0017] Further, the solid solution treatment process is: the 3D printed part is kept at 300-350 DEG C for 1-2h to reduce residual stress, and then kept at 500-530 DEG C in an inert atmosphere or a salt bath furnace for 2-12h to make alloy elements fully dissolve into the matrix.

[0018] Further, the density of the Al-Mg-Li-based aluminum alloy is not higher than 2.6g / cm3, the yield strength of the Al-Mg-Li-based aluminum alloy after heat treatment is not less than 520MPa, the tensile strength is not less than 600MPa, and the Young's modulus is not less than 90GPa.

[0019] Compared with the prior art, the beneficial effects of the present application are:

[0020] The present application effectively reduces the density of the alloy by introducing a higher content of light elements Mg and Li, and on the basis of the Al-Mg-Li-based alloy, the performance is synergistically optimized by composite addition of Cu, Zn, Mn, Sc, Zr, Ti and control of Si content. Among them, the phase formed by Cu and Li is one of the main strength contributors, which has a significant strengthening effect; the phase formed by Cu and Mg is also one of the key aging strengthening phases, which plays an important role in improving strength, and the phase (formed by Li) dispersedly precipitated in the Al matrix also provides basic strengthening; in addition, by controlling the ratio of Zn and Mg, an appropriate amount of T(AlZnMgCu) phase (formed by Al, Zn, Mg and Cu) will be formed in the alloy, which has a beneficial complementary strengthening effect on the overall strength, and the formation of the T phase is adjusted to ensure the synergistic precipitation of the main strengthening phases such as and the optimization of comprehensive performance; at the same time, Sc, Zr and Ti together form the The nanoparticles, on one hand, strongly refine the solidified structure as high-efficiency heterogeneous nucleation particles, improve the toughness of the material, and greatly improve the thermal crack resistance in the additive manufacturing process; on the other hand, the nanoparticles themselves are excellent strengthening phases, improve the strength through dispersion strengthening, and effectively pin the grain boundaries and dislocations, inhibit recrystallization, and endow the alloy with excellent microstructure stability and thermal stability; the addition of Mn mainly provides the auxiliary dispersion strengthening effect and helps to stabilize the microstructure, while the Si content is strictly controlled at a low level (≤0.3%) to inhibit the formation of low-melting-point brittle phases, which is particularly crucial for ensuring the plasticity and toughness of the alloy and reducing the thermal crack sensitivity in the additive manufacturing process . Through the optimization design of the alloy components in the application, the density of the Al-Mg-Li-based aluminum alloy of the application is significantly lower than that of traditional high-strength aluminum alloys, and the density of the Al-Mg-Li-based aluminum alloy of the application is less than 2.6 g / cm 3 , and has excellent mechanical properties, and after heat treatment, the yield strength can reach more than 520 MPa, the tensile strength can reach more than 600 MPa, and the Young's modulus is higher than 90 GPa.

[0021] The application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The SEM and EDS of the alloy powder of the component ratio combination of the alloy of embodiment 7 of the application for additive manufacturing are shown in (a) and (b), respectively.

[0023] Figure 2 The standard tensile sample of the alloy of the component ratio combination of embodiment 7 of the application in the directly printed state and the mechanical property curve are shown in (a) and (b), respectively.

[0024] Figure 3 The mechanical property curve of the standard tensile sample of the alloy of the component ratio combination of embodiment 7 of the application after heat treatment is shown in (a).

[0025] Figure 4 The SEM of the microstructure of the alloy of the component ratio combination of embodiment 7 of the application in the additive manufacturing state is shown in (a).

[0026] Figure 5 The XRD phase spectrum of the alloy of the component ratio combination of embodiment 7 of the application in the additive manufacturing state is shown in (a). DETAILED DESCRIPTION

[0027] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0028] The embodiment provides an Al-Mg-Li-based aluminum alloy for additive manufacturing, which comprises the following chemical components in percentage by mass: Mg 5-7%, Li 1.7-2.3%, Zn 1.3-1.9%, Cu 1.7-2.3%, Mn 1.7-2.3%, Sc 0.8-1.2%, Zr 0.4-0.8%, Ti 0.6-1.0%, Si 0.1-0.3%, and the balance of Al and inevitable impurities.

[0029] The method for additive manufacturing of the Al-Mg-Li-based aluminum alloy is specifically as follows:

[0030] The Al-Mg-Li-based aluminum alloy is made into aluminum alloy metal powder, and the laser additive manufacturing technology is used to print a 3D printed part.

[0031] Specifically, the Al-Mg-Li-based aluminum alloy is prepared into aluminum alloy metal powder by using vacuum induction melting-argon gas atomization (VIGA) according to the designed chemical component proportioning, the particle size of the aluminum alloy metal powder is controlled to be 15-53 μm through screening, the particles are nearly spherical and have good fluidity (the flow rate measured by a Hall flowmeter is <50 s / 50 g, and the repose angle is <40°), and the requirements of the LPBF (laser powder bed fusion) process are met.

[0032] Subsequently, sample preparation is performed in a selective laser melting additive manufacturing device: the prepared aluminum alloy metal powder is uniformly laid on a preheated substrate, a high-energy laser beam is used for additive manufacturing under the protection of an inert atmosphere (high-purity argon gas, The aluminum alloy metal powder layer is selectively melted according to the preset three-dimensional model path, and the powder laying and melting process is repeated layer by layer until the required 3D printed part is formed. In the process of laser melting printing, the process parameters are controlled as follows: the laser power is 100-600 W, the scanning speed is 200-1000 mm / s, the scanning interval is 0.06-0.14 mm, the powder laying layer thickness is 0.02-0.06 mm, the substrate preheating temperature is 100-200 DEG C, the strip scanning is used during laser scanning, the interlayer rotation angle is 67 DEG to reduce anisotropy, and the laser volume energy density is controlled at 40-120 J / mm3 to obtain a high density (>99.5%) and low defect printed part. Specifically, the shape and size of the 3D printed part in the embodiment are printed according to the national standard GB_Z38434-2019 "Guidelines for preparing samples for mechanical properties test of metal materials".

[0033] Further optimization of the embodiment, the 3D printed part after printing is heat treated, and the heat treatment process includes solid solution, quenching and artificial aging treatment of the 3D printed part in turn; for Al-Li alloy, in order to avoid the deformation and cracking caused by the conventional rapid cooling to room temperature quenching, the quenching in the embodiment uses room temperature water quenching or 60-100 DEG C hot water quenching or polymer quenching liquid, and the transfer time should be as short as possible (<15 seconds); the artificial aging adopts double-stage aging, first at 120-160 DEG C for 4-12 h, and then at 160-190 DEG C for 8-48 h, wherein short time aging at lower temperature stage (i.e. 120-160 DEG C) promotes the nucleation and growth of and S phase, and long time aging at higher temperature stage (i.e. 160-190 DEG C) promotes the stability of and the formation of T phase, and optimizes the distribution of phase.

[0034] Specifically, the solid solution treatment process of the 3D printed part is as follows: after printing is completed, the 3D printed part is heat treated at 300-350 DEG C for 1-2 h to reduce residual stress, and then heat treated at 500-530 DEG C in an inert atmosphere or a salt bath furnace for 2-12 h to make the alloy elements fully dissolve into the matrix.

[0035] In the embodiment, for the chemical composition optimization design of aluminum alloy, by introducing higher content of light elements Mg and Li, the alloy density is effectively reduced; and by the synergistic superposition of multiple strengthening mechanisms, a strong obstacle to dislocation movement is formed, thereby giving the alloy extremely high strength and Young's modulus, wherein the multiple strengthening mechanisms include:

[0036] (1) strong precipitation strengthening: in the artificial aging process of double-stage aging, the , Multiple nano-precipitated phases, and , The core-shell structure dispersion, with its dispersed hard particles, greatly increases the critical stress for dislocation slip, thereby improving the yield strength of the alloy.

[0037] Specifically, Phase is one of the main age-hardening phases in aluminum-lithium alloys, and is The coherent precipitates, with Li as the lightest metal, significantly reduce the alloy density (approximately 3% decrease per wt.% Li addition) and increase the elastic modulus (approximately 6% increase). In the δ′ phase, Li atoms are strongly covalently bonded, further enhancing the alloy's elastic modulus. δ′ phase precipitation significantly improves alloy strength; higher Li content results in greater δ′ phase precipitation, leading to even higher strength. The solid solution of Li and... The synergistic effect of phase precipitation allows the alloy to achieve excellent yield strength while maintaining low density.

[0038] Cu and Zn are primarily used as potent precipitation-enhancing elements, typically forming nanoscale particles during artificial aging processes. The favorable temperature range for the precipitation of this phase is generally considered to be 150-170°C. In the two-stage aging process of this invention, The nucleation and growth of the phase are effectively promoted mainly at lower temperatures (i.e., 120-160℃), especially in the higher temperature range (150-160℃) of this stage, and may be further optimized and grown in the initial part of the higher temperature aging stage (i.e., 160-190℃); The phase has a hexagonal structure, is semi-coherent with the Al matrix, and precipitates as thin plates along the {111}Al plane. With a Young's modulus as high as approximately 350 GPa, it is one of the main strength-contributing phases in this alloy system, crucial for improving the alloy's yield strength and tensile strength. Simultaneously, Cu and Mg elements synergistically form during artificial aging. Phase precipitation typically occurs within a temperature range of 150-200°C. In the two-stage aging process of this invention, the nucleation and growth of the S-phase also begin at a lower temperature stage (i.e., 120-160°C) and can continue throughout the higher temperature aging stage (i.e., 160-190°C). The phase has an orthorhombic crystal system, appearing as needle-like or rod-like structures. The S phase, as one of the main age-hardening phases in this alloy system, can significantly improve alloy strength upon precipitation. However, excessive S phase reduces toughness and plasticity. Therefore, by optimizing the content of Cu and Mg elements in the alloy, the amount of S phase precipitation during artificial aging is controlled. Simultaneously, fluxing elements (such as Si) can promote more uniform and finer S phase precipitation, further improving yield strength. Furthermore, under specific heat treatment conditions, especially within the Zn / Mg mass percentage range of 0.19-0.38 specified in this invention, Zn, Mg, and Cu elements in the alloy will form the T(AlZnMgCu) phase (orthorhombic crystal system). This T phase, as an effective strengthening phase, can contribute to alloy strength by hindering dislocation movement. In the design of this invention, the formation and content of the T phase are precisely controlled, aiming to serve as a means to strengthen the alloy. Harmony The T phase complements the main strengthening phases and ensures that its precipitation does not adversely compete with the formation of these key phases, thereby optimizing overall performance. Therefore, the T phase contributes to synergistically enhancing strength; its small size and uniform distribution are prerequisites for its effective strengthening.

[0039] The combined addition of Sc, Zr, and Ti elements results in a synergistic effect, causing the precipitation of Al from the supersaturated solid solution during aging treatment at higher temperatures (160-190℃). Crystal nucleus, Zr then forms outside the nucleus. Shell, thus forming Core-shell dispersions of the same phase can also be formed when Ti is present. The core-shell structure dispersion of the phase, and the addition of Ti can further improve the... By improving the phase's resistance to coarsening and adjusting its lattice mismatch, these core-shell structured dispersions can delay precipitate coarsening and improve high-temperature aging stability.

[0040] (2) Significant grain boundary strengthening: The combined addition of Sc, Zr, and Ti can also bring about a strong grain refinement effect. During the solidification of the molten pool, the high melting point (1320℃) and Al3Zr (1580℃) will precipitate first. Belongs to face-centered cubic ( The structure often forms within the grain using fine nanoparticles as heterogeneous nucleation sites; similarly, Al3Ti (1360℃) and... Having a similar structure, they also belong to the face-centered cubic (FCC) family. The structure, the addition of Ti can further improve The anti-coarsening ability of Al3Zr phase and the adjustment of its lattice mismatch degree, these fine grain structures greatly increase the grain boundary area per unit volume, effectively hinder dislocations from crossing the grain boundaries, improve the dislocation and deformation resistance, and thus significantly improve the yield strength of the alloy.

[0041] (3) Solid solution strengthening: Mg, Li, Cu, Zn, Mn, Si solute atoms will be dissolved in the Al matrix. Due to the difference in atomic radius, it will cause lattice distortion and thus improve the strength of the alloy. Specifically, the upper limit of Mg atomic solubility in the Al matrix is above 14%, the upper limit of Li atomic solubility is about 4.2%, the upper limit of Cu atomic solubility is about 5.6%, the upper limit of Zn atomic solubility is about 35%, the upper limit of Mn atomic solubility is about 1.8%, and the upper limit of Si atomic solubility is about 1.6%. Among them:

[0042] The difference between the atomic radius of Mg (150 pm) and the atomic radius of Al (143 pm) is about 12%, and the dissolution will cause lattice distortion of the matrix. This distortion will generate a stress field that resists the sliding of dislocations, thereby improving the yield strength and tensile strength of the alloy. The difference between the atomic radius of Li (152 pm) and the atomic radius of Al is about 6%, although the degree of lattice distortion is less than that of Mg, but the dissolution of Li will significantly improve the elastic modulus of the matrix (about 6% increase in elastic modulus per 1% Li, and about 3% decrease in density); At the same time, the presence of Li atoms will hinder the movement of dislocations, and can synergistically enhance the solid solution effect with other elements (such as Mg, Cu). The difference between the atomic radius of Cu (135 pm) and the atomic radius of Al is about 5.6%, the lattice distortion is smaller, but the difference in electronegativity between Cu atoms and Al atoms is larger (Al electronegativity 1.61, Cu 1.90), which will form a strong electric dipole after dissolution. The electrostatic effect of this electric dipole will produce significant resistance to dislocations, especially in the solid solution state before aging, which can lay the foundation for subsequent second phase (T(AlZnMgCu) phase) strengthening. The difference between the atomic radius of Zn (134 pm) and the atomic radius of Al is about 6.3%, the degree of lattice distortion is moderate, at the same time, Zn can synergistically form T(AlZnMgCu) phase with Mg, Cu and Al, thereby improving the strength of the alloy. The difference between the atomic radius of Mn (135 pm) and the atomic radius of Al is about 5.6%, which can still cause certain lattice distortion and improve the strength of the alloy, and the part exceeding the solid solubility limit will form Al6Mn strengthening phase. The difference between the atomic radius of Si (111 pm) and the atomic radius of Al is about 22.4%, which is the largest among all elements, and the dissolution will cause severe lattice distortion. The stress field generated by this strong distortion can effectively hinder the movement of dislocations and improve the strength of the alloy.

[0043] (4) Dispersion strengthening: Mn element in the alloy forms dispersed particles (AM rapid cooling first increases the solid solubility of Mn, and then heats to precipitate fine ), existing as a coarse eutectic phase, in appropriate amounts It can provide slight diffusion enhancement (approximately 42 MPa increase in strength per 1% Mn) and help stabilize microstructure.

[0044] Furthermore, based on the aforementioned high yield strength design, the internal dislocation density increases during plastic deformation of the alloy. The moving dislocations interact in complex ways with the numerous existing strengthening barriers, including with the various high-strength nanoprecipitates mentioned above. , The pinning, cutting, or bypassing of dislocations, as well as the pile-up of dislocations at numerous grain boundaries in a fine-grained structure, lead to a continuous increase in the resistance to dislocation movement with increasing strain. This allows the material to withstand higher stresses until eventual failure, thus exhibiting excellent tensile strength. Simultaneously, the finely dispersed reinforcing phase and the fine grain structure both contribute to increasing the work hardening rate, further enhancing tensile strength. This results in a high tensile strength alloy; in this embodiment, the alloy achieves a tensile strength exceeding 600 MPa after heat treatment. Furthermore, adding Li to aluminum effectively increases the elastic modulus of the aluminum alloy; approximately 1 wt% Li increases the modulus by 6%, while precipitation during artificial aging treatment... The reinforcing phase itself also has a higher elastic modulus than the aluminum matrix, and the high modulus... The δ' phase (Young's modulus approximately 350 GPa) contributes to the improvement of the overall modulus; therefore, optimizing the Li content and promoting the δ' phase and The precipitation of the phase can give the alloy a high modulus. In this embodiment, the Young's modulus of the alloy can reach more than 90 GPa.

[0045] The performance of the Al-Mg-Li based aluminum alloy for additive manufacturing according to the present invention is illustrated below through specific embodiments.

[0046] Examples 1-12 provide theoretical calculations and software simulations of alloys with different chemical composition ratios (wt.%, Al is the balance), and tensile strength, yield strength and Young's modulus obtained by simulation calculations under casting process using an initial cooling rate of 10℃ / s. Specifically, pre-alloyed powder was prepared using vacuum induction melting-argon atomization (VIGA) according to the chemical composition ratio. The particle size of the pre-alloyed powder was controlled to be 15-53 μm after sieving. The particles were nearly spherical and had good flowability, meeting the requirements of LPBF process. Subsequently, sample preparation was carried out in a selective laser additive manufacturing (SLM) device: the pre-alloyed powder was spread on a substrate preheated to about 150°C. Using parameters of laser power of about 210W, scanning speed of about 300mm / s, scanning interval of about 0.1mm, and layer thickness of about 0.03mm, the powder was melted and deposited layer by layer under the protection of high-purity argon. Standard metal mechanical tensile test specimens were prepared according to GB_Z38434-2019. To reduce experimental costs and testing cycle, the density (ρ, g / cm³) of the alloy material was calculated using JMatPro software. 3 Young's modulus (E, GPa), tensile strength (σ) b , MPa), yield strength (σ s (MPa) and specific strength (σ) b / ρ, MPa / (g / cm 3 The performance of the tests, such as those for 100% and 200% of the tests, is shown in Table 1

[0047] Table 1:

[0048]

[0049] As shown in Table 1, different chemical compositions significantly affect the alloy's properties. In Example 1, the elemental contents were at their lowest values, containing only small amounts of basic lightweight elements Mg and Li, strengthening phase elements Cu, Mn, and Zn, and trace amounts of Sc, Zr, Ti, and Si. Therefore, the density and strength were not ideal. In Examples 2 and 3, the density decreased with increasing total Mg and Li content, but due to the still low strengthening element content, the strength was relatively limited, with tensile strength less than 400 MPa and theoretical yield strength less than 280 MPa. In Examples 4 and 5, the content of Cu, Mn, and Zn strengthening phase elements was gradually increased, resulting in improved theoretical tensile and yield strengths, with the theoretical tensile strength reaching approximately 400 MPa and the yield strength exceeding 280 MPa. In Example 6, the content of Sc, Zr, and Ti was further increased, further improving the theoretical tensile and yield strengths. Example 7 further increased the content of Ti and Si elements, achieving a theoretical tensile strength of 416.7 MPa, a theoretical yield strength of 296.9 MPa, and a specific strength as high as 162.8 MPa / (g / cm²). 3In Example 8, the content of Cu, Mn, and Zn reinforcing phase elements was further increased, but the tensile strength and yield strength of the alloy began to decrease. This was because the added Mn content (2.3%) far exceeded the upper limit of solid solution in Al alloys (1.82%, which may increase at high temperatures), resulting in the precipitation of coarse-grained Mn. The addition of Sc and Zr in Example 9 further improved the alloy strength, but it was still lower than that of the alloy in Example 7. This may be because the high content of Sc and Zr makes it difficult to completely dissolve even at high temperatures, thus reducing the strength of the originally fine particles. and The primary phase becomes coarser, significantly weakening its ability to impede dislocation movement, and may even become a source of obstruction for dislocation movement, reducing the alloy's deformation resistance and resulting in a lower strength than in Example 7. Example 10 increased Ti and Si elements, resulting in a slight decrease in alloy strength, indicating that the addition of Ti and Si elements reached a balance. Reducing the content of Cu, Mn, and Zn strengthening phase elements slightly reduced the alloy strength. Example 11 significantly increased the content of Mg and Li, resulting in a significant decrease in alloy density. Simultaneously, the increased content of Ti and Si elements increased the alloy's strength and stiffness. However, due to the low content of strengthening phase elements such as Cu, Mn, and Zn, the alloy strength was lower than in Example 7. In Example 12, all element contents reached their maximum, resulting in the highest theoretical tensile strength, yield strength, and Young's modulus. However, Mn, Sc, Zr, and Ti significantly exceeded the solid solution upper limit, and the high Li content posed a risk of flammability and explosion in actual production. Considering density, strength, and additive manufacturing powder processability, the optimal embodiment, Scheme 7, was selected. Its specific strength is as high as 162.8 MPa·cm³ / g, ranking among the top of all schemes, indicating that it can bear the highest load per unit weight. The alloy composition is Al-6Mg-2Li-2Cu-1.6Zn-2Mn-1Sc-0.6Zr-0.8Ti-0.2Si.

[0050] like Figure 1 The images show SEM and EDS composition diagrams of the alloy powder used in additive manufacturing for the alloy composition combination of Example 7. As can be seen from the figures, the powder particles are essentially spherical, with the alloy particle size mainly ranging from 10 to 50 μm. This spherical morphology helps improve powder flowability, which is essential for additive manufacturing (such as LPBF) to ensure uniform powder distribution, thus contributing to the manufacture of high-density parts. Furthermore, the alloy powder composition is close to the theoretical design, indicating that the compositional error of the alloy prepared by the vacuum atomization method is extremely small, laying the foundation for obtaining excellent performance.

[0051] like Figure 2The image shows a direct-printed standard metallic tensile specimen and its mechanical properties curves for the alloy of Example 7, based on its component ratio combination. The average surface hardness of this alloy sample is 141 HV0.5, and its microhardness in the untreated state is close to that of 7075T6 aluminum alloy (150 HV), indicating that the alloy composition described in this invention can achieve good hardness through additive manufacturing. The stress curve shows that Example 7 has a tensile strength of 348.3 MPa, an elongation of 1.5%, and a density of 2.55 g / cm³. 3 The Young's modulus is 84.6 GPa. The tensile strength and Young's modulus are slightly lower than the theoretical calculation results. This is because in the actual printing process, low-melting-point elements such as Mg and Li will vaporize under laser irradiation. There are also slight differences in the solid solution and second phase precipitation of other strengthening elements such as Mn, Cu, and Zn. Therefore, the alloy strength and Young's modulus are slightly lower than the theoretical values, but significantly higher than the tensile strength of 7075 aluminum alloy in the untreated state (280 MPa). The Young's modulus is also significantly higher than that of 7075 aluminum alloy (70 GPa), which has high specific strength and specific stiffness, reflecting the comprehensive advantages of lightweight and high strength of the alloy sample in Example 7.

[0052] As can be seen from the above experiments and analyses, the mechanical properties (yield strength, tensile strength, Young's modulus, etc.) of the Al-Mg-Li based aluminum alloy of the present invention in the untreated state are significantly superior to those of existing high-strength aluminum alloys (such as 7075 aluminum alloy in the 7-series aluminum alloys), and its properties can be further improved after heat treatment; for example... Figure 3 As shown, after the heat treatment (i.e., solution treatment, quenching, and double-stage aging) of the present invention, the tensile strength of the Al-Mg-Li based aluminum alloy can reach more than 600 MPa, the yield strength can reach more than 520 MPa, the Young's modulus can reach more than 90 GPa, and the elongation can increase from 1.5% (without heat treatment) to more than 5%.

[0053] Figure 4 The image shows the SEM image of the additively manufactured Al-Mg-Li based alloy of Example 7. The additively manufactured Al-Mg-Li based alloy exhibits a very fine grain structure with a grain size of 2-5 μm. The grain morphology is equiaxed and near-equiaxed, which is due to rapid laser melting and solidification, as well as the formation of Sc, Zr, and other elements. and This is due to the nano-phases acting as heterogeneous nucleation cores. This fine-grained structure is one of the important factors in achieving high strength (fine-grained strengthening). These fine-grained structures and nano-precipitates work together to hinder dislocation movement, thereby endowing the alloy with excellent mechanical properties.

[0054] Figure 5This is the additive manufacturing XRD phase diagram of the alloy with the component ratio combination of Example 7 of the present invention. The designed alloying elements regenerated a large number of strengthening phases in situ under high-temperature laser scanning, namely the main strengthening phases T-AlCuMgZn, Al3Sc, Al3Zr, and Al3Li, and Mg2Si, etc. Al2MgLi is a secondary strengthening phase, but the content of Si, Mn, and Li elements in it cannot be excessive, otherwise it will lead to coarse microstructure and affect mechanical properties. Al3Sc and Al3Zr can refine the microstructure grains. Al3Li is a typical strengthening phase in Al-Li alloys, and Al2MgLi is a typical ternary phase in Al-Mg-Li alloys. Its fine crystal aggregation can effectively resist grain dislocations, but excessive Mg and Li content can easily coarsen the microstructure and reduce the alloy toughness. α-Al, as the matrix phase, can play a good balancing role and is beneficial to maintaining the alloy toughness.

[0055] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. An Al-Mg-Li based aluminum alloy for additive manufacturing, characterized in that, It includes the following chemical composition by mass percentage: Mg 5-7%, Li 1.7-2.3%, Zn 1.3-1.9%, Cu 1.7-2.3%, Mn 1.7-2.3%, Sc 0.8-1.2%, Zr 0.4-0.8%, Ti 0.6-1.0%, Si 0.1-0.3%, with the balance being Al and unavoidable impurities.

2. The Al-Mg-Li based aluminum alloy for additive manufacturing as described in claim 1, characterized in that, The mass percentage ratio of Zn to Mg is 0.19 to 0.

38.

3. The Al-Mg-Li based aluminum alloy for additive manufacturing as described in claim 1, characterized in that, The total Sc+Zr content, by mass percentage, is controlled within the range of 1.2% to 2.0%.

4. The Al-Mg-Li based aluminum alloy for additive manufacturing as described in any one of claims 1-3, characterized in that, The chemical composition includes the following by mass percentage: Mg 6.0%, Li 2.0%, Zn 1.6%, Cu 2.0%, Mn 2.0%, Sc 1.0%, Zr 0.6%, Ti 0.8%, Si 0.2%, with the balance being Al and unavoidable impurities.

5. An additive manufacturing method, characterized in that, The process includes the following: The Al-Mg-Li based aluminum alloy as described in any one of claims 1-4 is made into aluminum alloy metal powder, and the aluminum alloy metal powder is used to print 3D printed parts using laser additive manufacturing technology; the process parameters of the laser additive manufacturing technology are: laser power of 100-600W, scanning speed of 200-1000mm / s, scanning spacing of 0.06-0.14mm, powder layer thickness of 0.02-0.06mm, and laser volumetric energy density controlled at 40-120J / mm³.

6. The additive manufacturing method as described in claim 5, characterized in that, The particle size of the aluminum alloy metal powder is 15-53 μm.

7. The additive manufacturing method as described in claim 5, characterized in that, It also includes heat treatment of the printed 3D parts. The heat treatment process includes solution treatment, quenching and artificial aging of the 3D printed parts in sequence. The quenching is carried out by room temperature water quenching or hot water quenching at 60-100℃ or polymer quenching liquid. The artificial aging is carried out by two-stage aging, first holding at 120-160℃ for 4-12 hours, and then holding at 160-190℃ for 8-48 hours.

8. The additive manufacturing method as described in claim 7, characterized in that, After undergoing two-stage artificial aging processing, it forms the following: , , , Multiple nano-precipitated phases, and , Core-shell structured dispersion.

9. The additive manufacturing method as described in claim 7, characterized in that, The solution treatment process involves holding the 3D printed part at 300–350°C for 1–2 hours to reduce residual stress, and then holding it in an inert atmosphere or salt bath furnace at 500–530°C for 2–12 hours to allow the alloying elements to fully dissolve into the matrix.

10. The additive manufacturing method as described in claim 7, characterized in that, The density of the Al-Mg-Li based aluminum alloy is not higher than 2.6 g / cm³, and the yield strength of the Al-Mg-Li based aluminum alloy after heat treatment is not less than 520 MPa, the tensile strength is not less than 600 MPa, and the Young's modulus is not less than 90 GPa.

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