Mechanical property isotropic high-strength aluminum alloy by additive manufacturing and preparation method

Abstract

The application belongs to the technical field of non-ferrous metal alloys and preparation, in particular to a high-strength aluminum alloy with isotropic mechanical properties prepared by additive manufacturing and a preparation method. First, raw materials are smelted and cast into ingots according to the component ratio, then the ingots are first hot-extruded and then cold-drawn to prepare wire materials. Finally, the high-strength aluminum alloy is prepared by using the electric arc wire melting additive manufacturing technology and by precisely controlling the wire feeding speed and the welding speed. The high-strength aluminum alloy has uniform and fine equiaxed crystal structure, the average grain size in the scanning direction and the deposition direction, the tensile strength, the elongation, and the anisotropy index of the average grain size between layers and within layers are all significantly reduced. Compared with the traditional forged 7000 series aluminum alloy, the high-strength aluminum alloy has more excellent high-temperature resistance, and is universal for the production of high-strength aluminum alloys in the fields of aerospace and automobiles.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal alloys and their preparation technology, specifically a high-strength aluminum alloy with isotropic mechanical properties produced by additive manufacturing and its preparation method, which is applicable to the manufacture of high-performance aluminum alloy materials such as aerospace structural components and lightweight automotive parts. Background Technology

[0002] Additive manufacturing (AM), also known as 3D printing, is an advanced manufacturing technology that forms three-dimensional entities by layering materials based on digital models. Compared with traditional subtractive or equal-material manufacturing, additive manufacturing has triggered a paradigm shift in manufacturing in fields such as aerospace, automotive, and biomedicine due to its significant advantages in integrated molding of complex structures, efficient material utilization, high design freedom, and short production cycles. In the field of metallic materials, aluminum alloys, with their low density, good specific strength, and corrosion resistance, have become one of the most widely used lightweight alloy systems for additive manufacturing technology.

[0003] Al-Zn-Mg-Cu alloys (typical grades such as AA7075 and AA7050) are a class of heat-treatable, ultra-high-strength aluminum alloys, and their traditional forgings or castings occupy a core position in aerospace structural components. However, when these alloys are applied to typical metal additive manufacturing processes, such as wire and arc additive manufacturing (WAAM), they face severe challenges: 1) Severe susceptibility to hot cracking: Al-Zn-Mg-Cu alloys have a wide solidification range. Under the rapid cooling of additive manufacturing, significant solute segregation and low-melting-point eutectic films form between dendrites. At the end of solidification, strong thermal stress easily tears this liquid film, leading to macroscopic solidification cracks, which seriously impair the density of the formed components and is the main bottleneck restricting its forming. 2) Anisotropy of microstructure and mechanical properties: The inherent directional heat flow in layer-by-layer additive manufacturing promotes the epitaxial growth of crystals along the heat flow direction, forming coarse columnar crystals and strong textures that penetrate multiple layers. Meanwhile, heterogeneous structures are easily formed at the molten pool boundary. This structural characteristic makes the mechanical properties exhibit a significant direction dependence, with properties parallel to the deposition direction often being inferior to those along the deposition plane. 3) Insufficient high-temperature mechanical properties: At high temperatures, the precipitated strengthening phases in Al-Zn-Mg-Cu alloys are prone to coarsening and transformation, α-Al grains undergo dynamic recovery and recrystallization, and original structural defects deteriorate, resulting in a significant reduction in high-temperature mechanical properties.

[0004] To address these challenges, researchers have conducted extensive studies: 1) optimizing process parameters to suppress cracks and refine grains, but with limited effectiveness in eliminating anisotropy; 2) introducing heterogeneous nucleating agents, which is currently the mainstream research direction. This aims to introduce high-melting-point ceramic particles (such as TiB2, TiC) or intermetallic compound particles (Al3Sc, Al3Ti, Al3Zr, Al3(Sc,Zr)) with good lattice mismatch with the aluminum matrix into high-strength aluminum alloys, serving as heterogeneous nucleation nuclei during solidification to promote equiaxed crystal formation and interrupt the epitaxial growth of columnar crystals. However, these technical solutions still have significant limitations. On the one hand, the uniformity of nucleating agent particle distribution in the wire and its flow and distribution behavior in the molten pool are significantly affected by molten pool dynamics, making them prone to enrichment or depletion at the edges or specific areas of the molten pool during printing. This results in significant differences in grain refinement effects at both the macroscopic and microscopic scales, and the anisotropy problem in mechanical properties remains prominent. On the other hand, excessive or agglomerated heterogeneous particles may become microcrack initiation points or stress concentration sources, impairing the toughness or fatigue performance of the material. Furthermore, 7xxx series high-strength aluminum alloys typically contain Si or Zr elements, which have a significant "poisoning effect" on TiB2 ceramic particles. Rare metals such as Sc are also expensive, limiting their large-scale application.

[0005] In summary, while current additive manufacturing technology for high-strength aluminum alloys (especially Al-Zn-Mg-Cu alloys) has made some progress in suppressing macroscopic hot cracks through process and compositional modifications, it still faces fundamental challenges in achieving uniform microstructure across all scales and levels, and consequently, isotropic mechanical properties. Existing technologies primarily focus on "crack suppression" and "grain refinement," but fail to systematically address the anisotropy of mechanical properties in high-strength aluminum alloys while simultaneously improving high-temperature mechanical properties, considering aspects such as molten pool solidification kinetics control, crystal orientation randomization, and precise control of component heat input. Therefore, developing a novel alloy system and a matching additive manufacturing method that can fundamentally weaken or even eliminate microstructure and mechanical property anisotropy while maintaining the excellent mechanical properties of high-strength aluminum alloys has become an urgent technological requirement for propelling high-strength aluminum alloy additive manufacturing from "formable" to "high-performance, high-reliability, and directly serviceable." Summary of the Invention

[0006] This invention addresses the common problems of anisotropic mechanical properties and insufficient high-temperature mechanical properties of high-strength aluminum alloys (Al-Zn-Mg-Cu series) in the arc-wire additive manufacturing process in the prior art. It provides an additive manufacturing method for high-strength aluminum alloys with isotropic mechanical properties. At the same time, this alloy has superior high-temperature resistance compared with traditional forged Al-Zn-Mg-Cu alloys (7000 series aluminum alloys) and has the advantages of simple operation and universality.

[0007] The complete technical solution of this invention includes:

[0008] A high-strength aluminum alloy with isotropic mechanical properties produced by additive manufacturing.

[0009] The high-strength aluminum alloy is manufactured using aluminum alloy wire through electric arc wire additive manufacturing.

[0010] The high-strength aluminum alloy includes TiC nano-ceramic particles, with a TiC nano-ceramic particle content of 0.5%~1.8%. The TiC nano-ceramic particles are added by preparing an Al-5TiC master alloy using a flux KAlF4 combined with ultrasonic stirring, and then adding the Al-5TiC master alloy during the aluminum alloy melt smelting process. The aluminum alloy melt is then cast to obtain an ingot, which is then processed into aluminum alloy wire.

[0011] The high-strength aluminum alloy exhibits a tensile strength anisotropy index of less than 5.0% and a fracture elongation anisotropy index of less than 10.0% in both the arc wire additive manufacturing scanning and deposition directions.

[0012] Furthermore, the high-strength aluminum alloy undergoes solution treatment and aging heat treatment after arc wire additive manufacturing.

[0013] Furthermore, the high-strength aluminum alloy composition by mass percentage is as follows: Zn: 5.0%~9.0%, Mg: 1.5%~3.0%, Cu: 1.0%~3.0%, Cr or Zr: 0.1%~0.3%, TiC: 0.5%~1.8%, Fe: ≤0.10%, Si: ≤0.10%, with the remainder being Al and unavoidable impurities.

[0014] Furthermore, the wire feeding speed in the arc wire additive manufacturing process is 6~9 m / min, the welding speed is 15~20 mm / s, and the high-strength aluminum alloy has a uniform equiaxed grain structure, wherein the α-Al grain size is 1~15 μm, and the anisotropy index of the average grain size in the scanning direction and deposition direction of the arc wire additive manufacturing, as well as the anisotropy index of the average grain size between layers and within layers, are all less than 20%.

[0015] Furthermore, the wire feeding speed in the arc wire additive manufacturing process is 6~9 m / min, and the welding speed is 15~20 mm / s.

[0016] Furthermore, the high-strength aluminum alloy has a uniform equiaxed crystal structure, wherein the α-Al grain size is 1~15 μm, and the anisotropy index of the average grain size in the scanning direction and deposition direction of the arc-wire additive manufacturing, as well as the anisotropy index of the average grain size between layers and within layers, are all less than 20%.

[0017] Furthermore, the anisotropy index of average grain size in the scanning direction and deposition direction, as well as the anisotropy index of average grain size between layers and within layers, are less than 10%.

[0018] Furthermore, the anisotropy index of average grain size in the scanning direction and deposition direction, as well as the anisotropy index of average grain size between layers and within layers, are less than 1%.

[0019] Furthermore, the high-strength aluminum alloy has a tensile strength of not less than 180 MPa at 200~250 ℃.

[0020] Furthermore, the high-strength aluminum alloy has a tensile strength of not less than 250 MPa at 200~250 ℃.

[0021] Furthermore, the high-strength aluminum alloy has a tensile strength of not less than 350 MPa at 200~250 ℃.

[0022] Furthermore, the method for preparing an additively manufactured high-strength aluminum alloy with isotropic mechanical properties includes the following steps:

[0023] (1) The raw materials are proportioned according to the composition and smelted. During the smelting process, Zn is added in the form of pure Zn, Mg and Cu are added in the intermediate form of Al-50Mg and Al-50Cu respectively, Cr or Zr is added in the intermediate form of Al-10Cr or Al-10Zr respectively, TiC is added in the intermediate form of Al-5TiC, and the remaining Al is added in the form of pure Al. After the smelting is completed, the ingot is cast into a water-cooled metal mold.

[0024] (2) The ingot is hot-extruded into a bar, and then the bar is cold-drawn to obtain aluminum alloy wire;

[0025] (3) The printing process is carried out using an electric arc wire additive manufacturing system, and no interlayer stops are set in the printing path.

[0026] Furthermore, the diameter of the TiC ceramic particles is 40~60 nm.

[0027] Furthermore, the high-strength aluminum alloy after printing is subjected to solution treatment and aging heat treatment, wherein the solution treatment process is held at 465~475 ℃ for 1.5~2 h, and the aging process is held at 120~125 ℃ for 20~24 h.

[0028] Furthermore, in the Al-5TiC master alloy, TiC and Al3Ti phases achieve a synergistic effect. TiC promotes the nucleation of Al3Ti, while Al3Ti serves as the nucleation substrate for α-Al and the heat-resistant Al phase. 18 The nucleation core of Mg3Ti2. Furthermore, based on the relationship between heat input and welding speed:

[0029]

[0030] To control wire feeding speed and welding speed;

[0031] Where Q is the heat input per unit length in J / mm, U is the welding voltage in V, I is the welding current in A, V is the welding speed in mm / s, and η is the thermal efficiency coefficient, ranging from 0.6 to 0.8.

[0032] The beneficial effects of this invention are as follows:

[0033] 1. Refined and homogenized microstructure: The synergistic effect of introducing TiC ceramic particles and optimizing deposition parameters promotes the complete transformation of α-Al columnar crystals into fine equiaxed crystals with an average grain size of 1~15 μm. The anisotropy index of average grain size in both the scanning and deposition directions, as well as the anisotropy index of average grain size between and within layers, are all less than 20%. The grain size anisotropy index is reduced by at least 60% compared to other additive manufacturing Al-Zn-Mg-Cu alloys.

[0034] 2. Improved mechanical properties and anisotropy: The tensile strength of the deposited sample in the scanning direction is 330~420 MPa, and the elongation is 5%~15%; after T6 heat treatment, the tensile strength can reach 520~620 MPa, and the elongation is 3%~10%; the anisotropy index of tensile strength of this high-strength aluminum alloy in the deposited and T6 samples in the scanning and deposition directions is less than 5.0%, and the anisotropy index of fracture elongation is less than 10.0%. The anisotropy index of tensile strength and elongation is at least 2 times lower than that of other additively manufactured Al-Zn-Mg-Cu alloys; the tensile strength of this high-strength aluminum alloy at 200~250 ℃ is at least 1.5 times higher than that of traditional forged 7000 series aluminum alloys.

[0035] 3. Reduced Process Costs: Compared to expensive Sc-containing intermetallic compound particles, the method described in this invention uses ordinary TiC ceramic particles and achieves isotropic mechanical properties through synergistic effects of optimized deposition parameters, effectively reducing production costs. Furthermore, the core of the optimized deposition parameters is controlling the welding speed to 15~20 mm / s, compared to the 4~10 mm / s welding speed used in conventional arc wire additive manufacturing. This will significantly improve production efficiency while enhancing performance, making it suitable for mass production. Attached Figure Description

[0036] Figure 1 The image shows the microstructure of the deposited TiC / Al-Zn-Mg-Cu alloy along the scanning and deposition directions.

[0037] Figure 2The image shows the microstructure of the deposited Al-Zn-Mg-Cu alloy without the addition of TiC ceramic particles along the deposition direction.

[0038] Figure 3 The anisotropy of grain size along the deposition direction of deposited TiC / Al-Zn-Mg-Cu alloys at different welding speeds is shown. Detailed Implementation

[0039] The present invention will now be described in detail with reference to embodiments and accompanying drawings. However, it should be understood that the embodiments and drawings are for illustrative purposes only and do not constitute any limitation on the scope of protection of the present invention. All reasonable modifications and combinations included within the inventive spirit of the present invention fall within the scope of protection of the present invention.

[0040] A high-strength aluminum alloy with isotropic mechanical properties and its preparation method are disclosed. First, the alloy composition is precisely designed. The high-strength aluminum alloy is composed of the following mass percentages: Zn: 5.0%~9.0%, Mg: 1.5%~3.0%, Cu: 1.0%~3.0%, Cr or Zr: 0.1%~0.3%, TiC: 0.5%~1.8%, Fe: ≤0.10%, Si: ≤0.10%, with the remainder being Al and unavoidable impurities.

[0041] Furthermore, a method for preparing an additively manufactured high-strength aluminum alloy with isotropic mechanical properties is provided, with specific process parameters and step control as follows:

[0042] First, an Al-5TiC master alloy was prepared by adding TiC ceramic particles with a diameter of 40–60 nm and using a flux (KAlF4) combined with ultrasonic stirring. Then, Al-50Mg, Al-50Cu, Al-10Zr, or Al-Cr master alloys were prepared sequentially. Pure Al was melted at 790–820 °C, and Al-5TiC, pure Zn, Al-50Cu, and Al-10Zr or Al-10Cr master alloys were added sequentially, holding at this temperature for 20–40 min. The melt was degassed and purified using argon gas, with the rotor speed maintained at 200–250 rpm. After degassing and slag removal, the temperature was lowered to 750–770 °C, and the Al-50Mg master alloy was added. After thorough stirring, the mixture was held at this temperature for 15–30 min. Finally, after degassing and slag removal, the casting is completed at 750~770 ℃ using a water-cooled metal mold to obtain a cylindrical ingot with a diameter of 90~110 mm and a height of 500~600 mm.

[0043] Furthermore, the cylindrical ingot is homogenized and annealed at 450–465 °C for 24 h, followed by turning to obtain a smooth-surfaced ingot. The ingot is then hot-extruded into bars at 420–450 °C with an extrusion ratio of 10:1; subsequently, the bars are cold-drawn to a diameter of 0.8–1.6 mm. During the drawing process, the reduction in surface area per pass is controlled within 15%, and when the total reduction in surface area reaches approximately 50%, an intermediate annealing at 450–465 °C / 1 h is interspersed. Finally, after descaling and length-cutting, aluminum alloy wire for arc-fused additive manufacturing is obtained.

[0044] Furthermore, the substrate is cleaned to remove oxides and oil stains from its surface. The substrate composition is similar to that of the high-strength aluminum alloy being prepared, with a thickness of not less than 10 mm and a smooth surface. An arc-wire additive manufacturing system is used for printing. High-purity argon gas (99.999%) is used as the shielding gas, with a flow rate of 25-30 L / min. The welding speed is controlled at 15-20 mm / s, the wire feed speed at 6-9 m / min, the welding current at 100-150 A, the welding voltage at 15-22 V, and the working distance at 12 mm. No interlayer pauses are set in the printing path; a simple reciprocating scanning strategy is employed, with a 30% overlap between adjacent weld passes. After printing, the high-strength aluminum alloy component undergoes T6 heat treatment (solution + aging). The solution treatment process involves holding at 465-475 ℃ for 1.5-2 h, and the aging process involves holding at 120-125 ℃ for 20-24 h.

[0045] The main control mechanisms and requirements of this invention are as follows:

[0046] The reason this invention controls the TiC ceramic particle content to be between 0.5% and 1.8% is that when the TiC ceramic particle content is below 0.5%, the TiC ceramic particles do not significantly agglomerate at the grain boundaries. Their main function is to act as heterogeneous nucleation nuclei, which can achieve grain refinement. However, due to the lack of sufficient TiC ceramic particles at the grain boundaries, they cannot achieve the pinning effect on the grain boundaries, thus hindering grain boundary migration and inhibiting grain growth. When the TiC ceramic particle content is controlled to be no less than 0.5%, TiC can both act as heterogeneous nucleation nuclei to achieve grain refinement and can also be pushed to the grain boundary position during solidification to achieve the pinning effect on the grain boundaries, thereby achieving a dual refinement effect of TiC ceramic particles. In addition, the agglomeration of TiC ceramic particles at the grain boundaries also helps to hinder the growth of α-Al grains at high temperatures, improving the high-temperature resistance of the alloy. Meanwhile, the reason why the content of TiC ceramic particles is precisely controlled to be no more than 1.8% in this invention is that TiC is prone to agglomeration in aluminum melt, and excessive content will aggravate agglomeration, form stress concentration points, and reduce the number of effective nucleation sites; secondly, TiC may react with aluminum to form brittle Al4C3 phase, and the higher the content, the greater the risk of this harmful phase formation, which will damage the mechanical properties of the alloy; thirdly, excessive TiC content will increase the viscosity of the melt and deteriorate the casting and printing forming performance.

[0047] This invention prepares an Al-5TiC master alloy by adding TiC ceramic particles with a diameter of 40-60 nm and using a flux (KAlF4) combined with ultrasonic stirring. One reason is that in-situ generation of TiC ceramic particles (such as through the Al-Ti-C reaction) occurs in a melt environment, resulting in rapid atomic diffusion and the formation of micron-sized particles. This makes precise control of the TiC particle size impossible, hindering the improvement of grain refinement and uniformity. Therefore, this invention uses an external addition method and precisely limits the TiC ceramic particle size to 40-60 nm. Furthermore, this invention selects a flux (KAlF4) and combines it with ultrasonic stirring. The former improves the wettability of the TiC ceramic particles, while the latter prevents sedimentation due to the high density of the TiC particles. Finally, this invention requires the preparation of an Al-5TiC master alloy before the formulation and melting of the target composition. Firstly, in addition to TiC, the master alloy usually contains the Al3Ti phase, and the two can work synergistically. TiC promotes the nucleation of Al3Ti, and Al3Ti then serves as an effective nucleation substrate for α-Al, achieving efficient and stable refinement. At the same time, the Al3Ti phase can serve as the heat-resistant Al phase in this alloy. 18 The formation of Mg3Ti2 provides the nucleation core, Al 18Adding Mg3Ti2 will further enhance the high-temperature resistance of this alloy. However, directly introducing TiC ceramic particles into the melt relies solely on their own nucleation and lacks a synergistic mechanism, leading to particle failure, unstable refining effect, and easy degradation. Secondly, because nano-sized TiC ceramic particles have high surface energy, they are prone to agglomeration; direct introduction makes uniform dispersion in viscous aluminum melt difficult, resulting in uneven distribution or even defects. Thirdly, since TiC ceramic particles are already uniformly distributed in the aluminum matrix, adding the target composition to the melt allows for the direct and uniform release of effective nucleation points, further improving the uniform dispersion effect.

[0048] The reason for controlling the wire feeding speed in this invention is to stabilize the welding voltage and welding current by controlling the wire feeding speed, thereby establishing the correspondence between heat input and welding speed, as shown in formula (1):

[0049] (1)

[0050] in, Q Heat input per unit length (J / mm). U The welding voltage is (V). I The welding current (A) is used. V The welding speed (i.e., the speed at which the welding torch moves, mm / s) is used. η The thermal efficiency coefficient is 0.6~0.8, reflecting the proportion of arc energy converted into effective heat input. As can be seen from formula (1), increasing the welding speed can reduce the heat input. The reason for controlling the wire feed speed to be no less than 6 m / min is to ensure the stability of the molten pool volume when using high welding speed, while controlling the wire feed speed to be no more than 9 m / min is to reduce the welding voltage and welding current to control excessive heat input and avoid the grain size from continuously increasing with the increase of heat input.

[0051] The reason this invention controls the welding speed to be no less than 15 mm / s is that, in the process of arc wire additive manufacturing, increasing the welding speed has a significant impact on solidification behavior, mainly manifested in the simultaneous increase of temperature gradient (G) and solidification rate (R), which together affect compositional supercooling (ΔT). CSThe formation of compositional supercooling (G) is as follows: Specifically, the increased welding speed causes the arc heat source to sweep rapidly across the material surface, resulting in extremely short heating time per unit area. This leads to highly concentrated heat that cannot be conducted to the surrounding area or deeper within the material, causing a reduction in the molten pool volume and the formation of a steep temperature distribution around it, thus significantly increasing G. Simultaneously, the reduced heat input and smaller molten pool accelerate heat loss to the surrounding cold metal, causing a sharp increase in the cooling rate. The molten metal rapidly supercools, and this increased supercooling acts as a solidification driving force, directly propelling the solid / liquid (S / L) interface towards the liquid phase interior more quickly, i.e., a significant acceleration of R. Whether compositional supercooling occurs depends on the key criterion: whether the actual temperature gradient G in the liquid phase at the S / L interface front is less than the liquidus temperature gradient G determined by the solute distribution. L When G <G L At this time, supercooling occurs. Increasing the welding speed affects ΔT. CS The effects seem contradictory: an increase in G will inhibit ΔT. CS Because higher G makes G <G L The conditions are more difficult to satisfy; however, an increase in R strongly promotes ΔT. CS This is because the accelerated R speed leads to a faster advance of the interface front, resulting in insufficient diffusion time for solute atoms. This causes more severe solute enrichment and a thinner enrichment layer, thus increasing the liquidus temperature gradient G. L Significantly increased. Typically, G... L The increase in R far exceeds the increase in G, therefore, although G increases, the dominant role of the increase in R makes G... <G L It is easier to meet the requirements. Ultimately, the combined effect of increasing welding speed is to promote rather than inhibit component undercooling and to increase ΔT. CS The width of the region. This reveals the intrinsic mechanism by which welding speed control affects the solidification structure through the interaction of G and R. At higher welding speeds, the expanded ΔT CSThe region provides new nucleation conditions within the molten pool (not just at the S / L interface), significantly promoting the transformation of coarse columnar crystals, originally formed in the intralayer region, into fine equiaxed crystals. Simultaneously, the reduction in molten pool volume and the increase in cooling rate significantly weaken the temperature gradient and compositional differences between intralayer and interlayer regions. This change effectively reduces the size difference between equiaxed crystals in different regions, thereby significantly reducing grain size anisotropy. Furthermore, increasing the welding speed to induce significant internal stress and elemental microsegregation through rapid thermal cycling provides an effective pathway for the formation of nanotwins and the 9R phase in an Al matrix with high stacking fault energy. The presence of the 9R phase reduces the lattice mismatch at the TiC / α-Al interface to below 5%, further improving the heterogeneous nucleation efficiency of TiC and promoting more significant grain refinement. The reason why the welding speed is controlled at no more than 20 mm / s in this invention is that exceeding this speed will easily deteriorate the forming quality, produce geometric defects such as undercut and humps; aggravate micro defects such as porosity, lack of fusion and crack risk, which will seriously damage mechanical properties; and reduce process stability, making it difficult to match the electric arc with the wire feed.

[0052] When characterizing the microstructure and properties of materials, this invention uses the anisotropy index A. n Defined as:

[0053] (2)

[0054] Where n max n represents the maximum value of the parameters involved in the anisotropy index calculation process. min This represents the minimum value of the parameters involved in the anisotropy index calculation process.

[0055] For example, for the anisotropy index of average grain size in the scanning direction and the deposition direction, then n max n represents the maximum average grain size along the scanning and deposition directions. min This represents the minimum average grain size in both the scanning and deposition directions.

[0056] The anisotropy index of average grain size between and within layers, the anisotropy index of tensile strength in the scanning direction and the deposition direction, and the anisotropy index of elongation are all characterized by the above formula (2).

[0057] Example 1

[0058] High-strength aluminum alloy composition: Al-5.2Zn-2.2Mg-1.7Cu-1.0TiC-0.23Cr-0.10Fe-0.10Si (wt.%)

[0059] Preparation process:

[0060] 1) An Al-5TiC master alloy was prepared by adding TiC ceramic particles with an average diameter of 50 nm and using a flux (KAlF4) combined with ultrasonic stirring. Al-50Mg, Al-50Cu, Al-10Zr, or Al-Cr master alloys were then prepared sequentially. Pure Al was melted at 800 °C, and Al-5TiC, pure Zn, Al-50Cu, and Al-10Cr master alloys were added sequentially, holding for 30 min. The melt was degassed and purified using argon gas, with the rotor speed maintained at 220 rpm. After degassing and slag removal, the temperature was lowered to 760 °C, and the Al-50Mg master alloy was added. After thorough stirring, the temperature was held for 20 min. Finally, after degassing and slag removal again, casting was completed at 760 °C using a water-cooled metal mold to obtain a cylindrical ingot with a diameter of 100 mm and a height of 550 mm.

[0061] 2) The cylindrical ingot was homogenized and annealed at 460 °C for 24 h, followed by turning to obtain a smooth surface. The ingot was then hot-extruded into bars at 430 °C with an extrusion ratio of 10:1; subsequently, the bars were cold-drawn to a diameter of 1.2 mm. During the drawing process, the reduction rate was controlled at approximately 13% per pass, and an intermediate annealing at 460 °C / 1 h was interspersed when the total reduction rate reached approximately 50%. Finally, after descaling and length-cutting, aluminum alloy wire for arc-fused additive manufacturing was obtained.

[0062] 3) The substrate is cleaned to remove oxides and oil. The substrate composition is similar to that of the high-strength aluminum alloy being prepared, the substrate thickness is not less than 10 mm, and the surface must be smooth. An arc-wire additive manufacturing system is used for printing. High-purity argon gas (99.999%) is used as the shielding gas, with a flow rate of 25 L / min. The welding speed is controlled at 15 mm / s, the wire feed speed at 6.5 m / min, the welding current at 112 A, the welding voltage at 18.5 V, and the working distance at 12 mm. No interlayer pauses are set in the printing path; a simple reciprocating scanning strategy is used, with a 30% overlap between adjacent weld passes. After printing, the component undergoes T6 heat treatment (solution + aging). The solution treatment process involves holding at 465~475 ℃ for 1.5~2 h, and the aging process involves holding at 120~125 ℃ for 20~24 h.

[0063] Results: The average grain size (d) of the sample along the scanning direction and the deposition direction were approximately 10.1 μm and 12.5 μm, respectively (e.g., ...). Figure 1 As shown, where Figure 1 In the figure, (a) represents the average grain size of the sample along the scanning direction. Figure 1(b) represents the average grain size along the deposition direction (including intralayer and interlayer dimensions). The anisotropy index of the average grain size along the scanning and deposition directions is approximately 19.2%. The average grain size within the sample layers is approximately 12.8 μm, and the average grain size between layers is approximately 10.6 μm. The anisotropy index of the average grain size along both the intralayer and interlayer dimensions is approximately 17.2%. The tensile strength of the deposited sample along the scanning and deposition directions is approximately 351 MPa and 342 MPa, respectively, with corresponding elongations at break of approximately 6.2% and 5.9%. The anisotropy index of tensile strength along the scanning and deposition directions is approximately 2.6%, and the corresponding anisotropy index of elongation at break is approximately 4.8%. The tensile strength of the T6 heat-treated sample along the scanning and deposition directions is approximately 534 MPa and 532 MPa, respectively, with corresponding elongations at break of approximately 4.9% and 5.1%. The anisotropy index of tensile strength along the scanning and deposition directions is approximately 0.4%, and the corresponding anisotropy index of elongation at break is approximately 3.9%. The T6 heat-treated specimens (along the scanning direction) exhibit tensile strengths of approximately 314 MPa and 188 MPa at 200 °C and 250 °C, respectively. The tensile strength in the deposition direction is comparable to that in the scanning direction, as shown in Table 1. Compared to conventional 7075 forged aluminum alloy (T6), the high-strength aluminum alloy described in this invention demonstrates at least a 1.5-fold increase in tensile strength at 200–250 °C.

[0064] Table 1. Comparison of high-temperature tensile strength between the high-strength aluminum alloy described in this invention and traditional 7075 forged aluminum alloy.

[0065]

[0066] Example 2

[0067] Adjustment: Based on Example 1, the welding speed is adjusted to 18 mm / s and the wire feeding speed is adjusted to 7.5 m / min.

[0068] Results: The average grain size of the deposited sample along the scanning and deposition directions was approximately 9.6 μm and 11.2 μm, respectively, with an anisotropy index of approximately 14.3% for the average grain size along both directions. The average grain size within the sample layers was approximately 11.7 μm, and the average grain size between layers was approximately 10.0 μm, with anisotropy indices of approximately 14.5% for both. The tensile strength of the deposited sample along the scanning and deposition directions was approximately 372 MPa and 365 MPa, respectively, with corresponding elongations at break of approximately 5.8% and 5.2%, respectively. The anisotropy index of tensile strength along the scanning and deposition directions was approximately 1.9%, with a corresponding anisotropy index of approximately 10.3% for elongation at break. The tensile strengths of the T6 heat-treated specimens along the scanning and deposition directions are approximately 565 MPa and 560 MPa, respectively, with corresponding elongations at break of approximately 5.0% and 4.7%. The anisotropy indices of tensile strength in the scanning and deposition directions are approximately 0.9%, and the corresponding anisotropy indices of elongation at break are approximately 6.0%. The tensile strengths of the T6 heat-treated specimens (along the scanning direction) at 200 °C and 250 °C are approximately 326 MPa and 205 MPa, respectively, with the tensile strength in the deposition direction being comparable to that in the scanning direction.

[0069] Example 3

[0070] Adjustment: Based on Example 1, the Zn and Cu contents were increased to 8.0% and 2.2% respectively, and Cr was replaced with Zr.

[0071] Results: The average grain size of the deposited sample along the scanning and deposition directions was approximately 6.2 μm and 7.5 μm, respectively, with an anisotropy index of approximately 17.3% for the average grain size along both directions. The average grain size within the sample layers was approximately 7.8 μm, and the average grain size between layers was approximately 6.6 μm, with anisotropy indices of approximately 15.4% for both. The tensile strength of the deposited sample along the scanning and deposition directions was approximately 405 MPa and 398 MPa, respectively, with corresponding elongations at break of approximately 5.8% and 5.4%, respectively. The anisotropy index of tensile strength along the scanning and deposition directions was approximately 1.7%, with a corresponding anisotropy index of approximately 6.9% for elongation at break. The tensile strengths of the T6 heat-treated specimens along the scanning and deposition directions are approximately 608 MPa and 603 MPa, respectively, with corresponding elongations at break of approximately 5.2% and 4.8%. The anisotropy indices of tensile strength in the scanning and deposition directions are approximately 0.8%, and the corresponding anisotropy indices of elongation at break are approximately 7.7%. The tensile strengths of the T6 heat-treated specimens (along the scanning direction) at 200 °C and 250 °C are approximately 341 MPa and 228 MPa, respectively, with the tensile strength in the deposition direction being comparable to that in the scanning direction.

[0072] Example 4

[0073] Adjustment: Based on Example 1, the TiC content was increased to 1.5%.

[0074] Results: The average grain size of the deposited sample along the scanning and deposition directions was approximately 5.6 μm and 6.4 μm, respectively, with an anisotropy index of approximately 12.5% ​​for the average grain size along both directions. The average grain size within the sample layers was approximately 6.6 μm, and the average grain size between layers was approximately 5.5 μm, with anisotropy indices of approximately 16.7% for both. The tensile strength of the deposited sample along the scanning and deposition directions was approximately 388 MPa and 379 MPa, respectively, with corresponding elongations at break of approximately 6.1% and 5.8%, respectively. The anisotropy index of tensile strength along the scanning and deposition directions was approximately 2.3%, with a corresponding anisotropy index of approximately 4.9% for elongation at break. The tensile strengths of the T6 heat-treated specimens along the scanning and deposition directions are approximately 587 MPa and 579 MPa, respectively, with corresponding elongations at break of approximately 5.6% and 5.1%. The anisotropy indices of tensile strength in the scanning and deposition directions are approximately 1.5%, and the corresponding anisotropy indices of elongation at break are approximately 8.9%. The tensile strengths of the T6 heat-treated specimens (along the scanning direction) at 200 °C and 250 °C are approximately 330 MPa and 215 MPa, respectively, with the tensile strength in the deposition direction being comparable to that in the scanning direction.

[0075] Comparative Example 1

[0076] Adjustment: Based on Example 1, the added TiC ceramic particles were removed.

[0077] Results: When TiC ceramic particles were not added to the Al-Zn-Mg-Cu alloy, even with optimized printing parameters, hot cracking could not be effectively suppressed (e.g., Figure 2 As shown in (a)), this alloy is difficult to print. Microstructural characterization of local samples reveals that the structure along the deposition direction is mainly composed of coarse columnar crystals (such as...). Figure 2 (as shown in (b)). In particular, the columnar crystals along the deposition direction also exhibit significant differences in grain size within and between layers, with an anisotropy index reaching 36%. This strongly confirms that the introduction of TiC ceramic particles is a necessary condition for solving the problem of anisotropy in the mechanical properties of high-strength aluminum alloy arc-fused wire additive manufacturing components.

[0078] Comparative Example 2

[0079] Adjustment: Based on Example 1, the welding speed is reduced to 5 mm / s and the wire feeding speed is reduced to 5.5 m / min.

[0080] The average grain size of the deposited sample along the scanning direction and the deposition direction is approximately 11.5 μm and 17.3 μm, respectively, with an anisotropy index of approximately 33.5% for the average grain size along both directions. The average grain size within the sample layers is approximately 16.5 μm, and the average grain size between layers is approximately 9.3 μm, with an anisotropy index of approximately 43.6% for both. Figure 3 (As shown). Furthermore, from Figure 3 It can be observed that appropriately increasing the welding speed is beneficial to reducing the anisotropy index of grain size. The tensile strength of the deposited sample along the scanning direction and the deposition direction is approximately 334 MPa and 302 MPa, respectively, with corresponding elongations at break of approximately 5.1% and 4.2%, respectively. The anisotropy index of tensile strength along the scanning direction and the deposition direction is approximately 9.6%, and the corresponding anisotropy index of elongation at break is approximately 17.6%. The tensile strength of the T6 heat-treated sample along the scanning direction and the deposition direction is approximately 517 MPa and 472 MPa, respectively, with corresponding elongations at break of approximately 4.5% and 3.8%, respectively. The anisotropy index of tensile strength along the scanning direction and the deposition direction is approximately 8.7%, and the corresponding anisotropy index of elongation at break is approximately 15.6%. This strongly confirms that, under the premise of introducing TiC ceramic particles, to solve the problem of anisotropy in the mechanical properties of high-strength aluminum alloy arc-fused wire additive manufacturing components, it is necessary to reasonably control the deposition parameters to reduce the anisotropy of grain size. In other words, the synergistic effect of introducing TiC ceramic particles and optimizing deposition parameters improves the uniformity of grain size, thereby solving the problem of anisotropic mechanical properties of high-strength aluminum alloy arc-fused wire additive manufacturing components, and providing an innovative solution for preparing large and complex aerospace components with isotropic mechanical properties through additive manufacturing technology.

[0081] The foregoing detailed description only illustrates preferred embodiments of the present invention and is not intended to limit the invention. Those skilled in the art, upon considering the disclosure in the specification and embodiments, will readily conceive of other embodiments of the invention. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

Claims

1. A high-strength additively manufactured aluminum alloy with isotropic mechanical properties, characterized in that, The high-strength aluminum alloy is manufactured using aluminum alloy wire by arc welding additive manufacturing; the wire feeding speed in the arc welding additive manufacturing process is 6~9 m / min, and the welding speed is 15~20 mm / s. The high-strength aluminum alloy composition by mass percentage is as follows: Zn: 5.0%~9.0%, Mg: 1.5%~3.0%, Cu: 1.0%~3.0%, Cr or Zr: 0.1%~0.3%, TiC: 0.5%~1.8%, Fe: ≤0.10%, Si: ≤0.10%, with the remainder being Al and unavoidable impurities; In the smelting process of the high-strength aluminum alloy, Zn is added in the form of pure Zn, Mg and Cu are added in the intermediate forms of Al-50Mg and Al-50Cu respectively, Cr or Zr is added in the intermediate form of Al-10Cr or Al-10Zr respectively, TiC is added in the intermediate form of Al-5TiC, and the remaining Al is added in the form of pure Al. The high-strength aluminum alloy comprises TiC nano-ceramic particles, with a TiC nano-ceramic particle content of 0.5%~1.8%. The TiC nano-ceramic particles are added externally and assisted by KAlF4 flux, combined with ultrasonic stirring technology to prepare an Al-5TiC master alloy. The diameter of the TiC ceramic particles is 40~60 nm. In the Al-5TiC master alloy, TiC and the Al3Ti phase achieve a synergistic effect; TiC promotes Al3Ti nucleation, and Al3Ti serves as the nucleation substrate for α-Al and the heat-resistant Al phase. 18 The nucleation core of Mg3Ti2 is formed, and Al-5TiC master alloy is added during the aluminum alloy melt smelting process. The aluminum alloy melt is cast to obtain ingots, which are then processed into aluminum alloy wires. The high-strength aluminum alloy exhibits a tensile strength anisotropy index of less than 5.0% and a fracture elongation anisotropy index of less than 10.0% in both the arc wire additive manufacturing scanning and deposition directions.

2. The isotropic additive manufacturing high-strength aluminum alloy according to claim 1, characterized in that, The high-strength aluminum alloy undergoes solution treatment and aging heat treatment after being manufactured by arc wire additive manufacturing.

3. The isotropic additive manufacturing high-strength aluminum alloy according to claim 2, characterized in that, The high-strength aluminum alloy has a uniform equiaxed crystal structure, wherein the α-Al grain size is 1~15 μm, and the anisotropy index of the average grain size in the scanning direction and deposition direction of the arc wire additive manufacturing, as well as the anisotropy index of the average grain size between layers and within layers, are all less than 20%.

4. The isotropic additive manufacturing high-strength aluminum alloy according to claim 3, characterized in that, The high-strength aluminum alloy has a tensile strength of not less than 180 MPa at 200~250 ℃.

5. The method for preparing an additively manufactured high-strength aluminum alloy with isotropic mechanical properties as described in claim 4, characterized in that, Includes the following steps: (1) The raw materials are proportioned according to the composition and smelted. During the smelting process, Zn is added in the form of pure Zn, Mg and Cu are added in the intermediate form of Al-50Mg and Al-50Cu respectively, Cr or Zr is added in the intermediate form of Al-10Cr or Al-10Zr respectively, TiC is added in the intermediate form of Al-5TiC, and the remaining Al is added in the form of pure Al. After the smelting is completed, the ingot is cast into a water-cooled metal mold. (2) The ingot is hot-extruded into a bar, and then the bar is cold-drawn to obtain aluminum alloy wire; (3) The printing process is carried out using an electric arc wire additive manufacturing system, and no interlayer stops are set in the printing path.

6. The method for preparing isotropic additive manufacturing high-strength aluminum alloys according to claim 5, characterized in that, The high-strength aluminum alloy after printing is subjected to solution treatment and aging heat treatment. The solution treatment process involves holding at 465~475 ℃ for 1.5~2 h, and the aging process involves holding at 120~125 ℃ for 20~24 h.

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