A high-performance aluminum alloy wire for electric arc additive and a preparation method thereof

Abstract

This invention belongs to the field of additive manufacturing technology for metal materials, specifically relating to a high-performance aluminum alloy wire for electric arc additive manufacturing and its preparation method; the wire composition includes 4.0-6.0% Mg, 0.5-1.5% Si, 0.5-1.5% Cu, 2.0-4.0% Zn, 0.3-0.8% Mn, 0.05-0.20% Ti, 0.05-0.15% Zr, 0.05-0.15% Sc, with the balance being Al and unavoidable impurities, wherein the content of a single impurity is ≤0.05%, and the total impurity content is ≤0.15%. The preparation method includes: S1. Weighing the raw materials, melting them under a protective atmosphere, and subjecting the melt to electromagnetic stirring and ultrasonic combined treatment; S2. Semi-continuously casting the refined melt to obtain an ingot; S3. Performing a stepped heating homogenization heat treatment on the ingot; S4. Hot extruding the homogenized ingot and rapidly cooling the wire rod online at the extrusion outlet; S5. Performing multiple cold drawing reductions on the quenched wire rod, and performing intermediate stress-relief annealing when the cumulative deformation reaches a certain value; S6. Finally drawing and sizing the wire and surface treating it to obtain the finished product. This invention can achieve in-situ refinement of the microstructure during WAAM deposition, obtaining high-strength, low-anisotropy deposited components.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology for metal materials, specifically relating to a high-performance aluminum alloy wire for arc additive manufacturing and its preparation method. Background Technology

[0002] Arc filament additive manufacturing is an additive manufacturing technology based on electric arc as a heat source and metal wire as a material. It has the advantages of high deposition efficiency, low cost, and suitability for manufacturing large-size components, and has broad application prospects in aerospace, shipbuilding, heavy machinery and other fields.

[0003] However, the WAAM process involves high heat input, rapid solidification, and complex thermal cycling, placing special demands on the composition and microstructure of the wire used. Currently, the WAAM process mainly uses traditional welding aluminum alloy wires, such as standard grades ER4043 and ER5356. The composition of these wires was originally designed to meet the processability and joint performance requirements of conventional welding, not specifically for the extreme non-equilibrium solidification conditions unique to WAAM.

[0004] The existing technology has the following main drawbacks: 1) During the rapid solidification process of WAAM, traditional filaments are prone to forming coarse columnar crystal structures, resulting in significant anisotropy in the mechanical properties of the deposited components. The transverse properties (especially the yield strength) are much lower than the longitudinal properties, which seriously restricts the load-bearing reliability and design freedom of the components.

[0005] 2) Due to the lack of an effective in-situ refinement mechanism, the strength of the as-cast microstructure is limited. WAAM components using existing wire materials typically have a yield strength in the deposited state that is difficult to exceed 350 MPa, often requiring subsequent heat treatment processes to improve performance.

[0006] 3) To improve the microstructure and properties of WAAM components, existing technologies employ the addition of high-content scandium (Sc) and other precious rare earth elements. Although Sc can significantly refine grains and improve strength, its cost is extremely high, making it difficult to promote in large-scale industrial applications.

[0007] 4) To obtain the required performance, WAAM components typically require complex heat treatments such as solution treatment and aging. This not only increases the production cycle and cost, but may also introduce new quality problems due to heat treatment deformation, grain growth, or the generation of new anisotropies.

[0008] Therefore, there is an urgent need to develop a new type of aluminum alloy wire and its supporting preparation method specifically designed for the WAAM process. This wire should be able to achieve in-situ refinement of the microstructure during the WAAM deposition process, directly obtain high-strength, low-anisotropy deposited components, and at the same time have good cost controllability. Summary of the Invention

[0009] This invention aims to overcome the aforementioned deficiencies of the prior art and provide a high-performance aluminum alloy wire specifically designed for arc additive manufacturing (WAAM) and its preparation method. Through optimized multi-component composition design and a specific preparation process, this wire can promote equiaxed grain formation and significantly refine the deposited microstructure during WAAM, thereby achieving a balance between high strength and low anisotropy in components without relying on expensive alloying elements or complex post-heat treatment.

[0010] Therefore, the purpose of this invention is to provide a high-performance aluminum alloy wire for electric arc additive manufacturing, the chemical composition of which, by mass percentage, is: Mg: 4.0-6.0%, Si: 0.5-1.5%, Cu: 0.5-1.5%, Zn: 2.0-4.0%, Mn: 0.3-0.8%, Ti: 0.05-0.20%, Zr: 0.05-0.15%, Sc: 0.05-0.15%, with the balance being Al and unavoidable impurities, wherein the content of a single impurity is ≤0.05%, and the total impurity content is ≤0.15%.

[0011] A method for preparing the above-mentioned high-performance aluminum alloy wire for arc additive manufacturing, characterized by comprising the following steps: S1. Weigh the raw materials according to the target composition, melt them under a protective atmosphere, and then apply a combination of electromagnetic stirring and ultrasonic treatment to the melt. S2. The refined melt is semi-continuously cast to obtain an ingot; S3. Perform a stepped heating homogenization heat treatment on the ingot; S4. The homogenized ingot is hot-extruded, and the extruded wire rod is rapidly cooled online at the extrusion outlet; S5. The quenched wire rod is reduced in diameter by multiple cold drawing passes, and intermediate stress-relieving annealing is performed when the cumulative deformation reaches a certain value. S6. Perform final drawing, sizing, and surface treatment on the filament to obtain the finished filament.

[0012] As a preferred technical solution, in step S1, the frequency of the ultrasonic treatment is 20-40kHz.

[0013] As a preferred technical solution, in step S2, the temperature of the semi-continuous casting is 680-720℃, and the casting cooling rate is controlled at 10-50℃ / s.

[0014] As a preferred technical solution, in step S3, the multi-stage homogenization process specifically includes: first, maintaining the temperature at 300-350℃ for 4-8 hours, and then raising the temperature to 460-480℃ and maintaining it for 12-24 hours.

[0015] As a preferred technical solution, in step S4, the hot extrusion temperature is 420-450℃, the extrusion ratio is not less than 25:1; and / or, the online rapid cooling is forced water mist quenching, which rapidly reduces the wire rod temperature to below room temperature.

[0016] As a preferred technical solution, in step S5, the deformation amount of each pass of the multi-pass cold drawing is controlled between 15% and 25%.

[0017] As a preferred technical solution, in step S5, the intermediate stress-relief annealing temperature is 260-280℃; the intermediate stress-relief annealing is carried out when the cumulative deformation reaches 60-70%, the annealing temperature is 250-300℃, and the holding time is 1-2 hours.

[0018] As a preferred technical solution, in step S6, the surface treatment is electropolishing or coating with a lubricating film.

[0019] As a preferred technical solution, the wire material prepared by the method has an average grain size of less than 50 μm in the arc additive manufacturing deposited state structure, and the ratio of longitudinal to transverse yield strength is less than 1.2; tensile strength is greater than 415 MPa, elongation after fracture is greater than 6.5%; and an anisotropy ratio is not greater than 1.08.

[0020] The advantages and positive effects of this invention are: 1) This invention, by adding Ti, Zr and Sc microalloying elements in combination and controlling their precipitation behavior during the preparation process, enables the wire to provide a large number of effective heterogeneous nucleation cores in the WAAM arc molten pool. This results in the depositional structure changing from traditional coarse columnar crystals to uniform equiaxed fine crystals or fine columnar / equiaxed mixed crystals, fundamentally reducing the anisotropy of mechanical properties.

[0021] 2) Thanks to the synergistic effect of fine grain strengthening, nano-precipitated phase strengthening and multi-component aging strengthening, the WAAM component printed using the filament of this invention achieves a balance between high strength and good plasticity without any post-heat treatment.

[0022] 3) This invention adopts a Ti, Zr, and Sc composite microalloying strategy. Through the synergistic effect between the elements, it achieves a microstructure refinement and strengthening effect that is close to or even better than that of a single high Sc addition scheme with a low total addition amount. This significantly reduces raw material costs and improves the market competitiveness of the product.

[0023] 4) The integrated preparation process of "melt ultrasonic dispersion-multi-stage homogenization-hot extrusion online quenching-controlled cold drawing" provided by this invention effectively solves the technical problems of easy agglomeration of microalloying elements in melting and easy segregation in solidification, ensuring the uniformity and consistency of the internal composition and structure of the wire, as well as the diffuse distribution of the nano-reinforcing phase. The process has good stability and is suitable for large-scale production. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below; obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0025] The present invention provides a high-performance aluminum alloy wire for electric arc additive manufacturing, the chemical composition of which, by mass percentage, is: Mg: 4.0-6.0%, Si: 0.5-1.5%, Cu: 0.5-1.5%, Zn: 2.0-4.0%, Mn: 0.3-0.8%, Ti: 0.05-0.20%, Zr: 0.05-0.15%, Sc: 0.05-0.15%, with the balance being Al and unavoidable impurities, wherein the content of a single impurity is ≤0.05%, and the total impurity content is ≤0.15%.

[0026] Among the above components, Mg, Si, Cu, and Zn constitute the main age-hardening system, forming strengthening phases such as Mg2Si, S (Al2CuMg), and η' / η (MgZn2), providing a high-strength foundation for the alloy. The precipitation behavior of the strengthening phases is optimized by strictly controlling the Mg / Si ratio.

[0027] The addition of Mn is mainly used to improve the corrosion resistance of the alloy, and the Mn-containing dispersed phase formed at the same time helps to pin dislocations and grain boundaries.

[0028] Ti, Zr, and Sc serve as core composite microalloying elements. Ti can form high-melting-point particles such as TiB2 or TiC, acting as heterogeneous nucleation sites; Zr and Sc can form Al3Zr and Al3Sc nanoparticles coherent with the Al matrix during solidification or subsequent thermal processes. During the rapid solidification of WAAM, these particles act as nucleation substrates for primary α-Al grains, effectively promoting equiaxed crystal formation and inhibiting the growth of coarse columnar crystals. In the post-deposition thermal cycling, these stable nanoparticles can strongly pin grain boundaries and dislocations, inhibiting grain growth and recrystallization, which is key to achieving a fine-grained, isotropic microstructure.

[0029] This invention provides a method for preparing the above-mentioned aluminum alloy wire, the method comprising the following steps: S1. Weigh out pure aluminum, pure magnesium, pure zinc, and Al-Si, Al-Cu, Al-Mn, Al-Ti, Al-Zr, and Al-Sc master alloys according to the target composition; melt them under a protective atmosphere (such as argon); after melting, perform composite treatment on the melt by electromagnetic stirring combined with ultrasonic treatment, with the ultrasonic frequency controlled at 20-40kHz; this step aims to ensure that refractory microalloying elements (especially Ti and Zr) are fully dispersed and activated, prevent their agglomeration, and ensure compositional uniformity.

[0030] S2. The refined melt is semi-continuously cast at a temperature of 680-720℃ to obtain round or flat ingots; by controlling the cooling system, the cooling rate of the ingots is maintained at 10-50℃ / s to obtain a cast structure with uniform composition and minimal macroscopic segregation.

[0031] S3. Perform a step-by-step heating homogenization heat treatment on the ingot; first, hold at 300-350℃ for 4-8 hours to fully dissolve the non-equilibrium eutectic phase formed during casting; then raise the temperature to 460-480℃ and hold for 12-24 hours; this high-temperature stage aims to fully dissolve microalloying elements such as Zr and Sc in the aluminum matrix and promote the pre-precipitation of nascent, nanoscale Al3(Zr,Sc) phase particles, providing a uniform microstructure containing a large number of nucleation particles for subsequent hot working.

[0032] S4. The homogenized ingot is heated to 420-450℃ and then hot extruded to form wire rod (usually with a diameter of Φ9.5mm or similar size), with an extrusion ratio of not less than 25:1. An online forced water mist quenching device is set at the extrusion die exit to rapidly cool the high-temperature wire rod to room temperature or below immediately after demolding. This rapid cooling process can supersaturately dissolve microalloying elements (especially Zr and Sc) in the aluminum matrix and retain the high-density dislocation structure generated by hot deformation.

[0033] S5. After quenching, the wire rod is gradually reduced to the target wire diameter (e.g., Φ1.0mm, Φ1.2mm) through multiple cold drawing processes. The deformation amount in each pass is controlled between 15-25%. When the cumulative deformation reaches 60-70%, an intermediate stress-relief annealing is performed at a temperature of 250-300℃ for 1-2 hours. This annealing process can eliminate work hardening, restore the material's plasticity for subsequent drawing, and promote the dispersion and precipitation of supersaturated microalloying elements into nano-sized Al3(Zr,Sc) phases at defects such as dislocation lines, achieving further precipitation strengthening.

[0034] S6. Perform a final small-deformation drawing to ensure the diameter accuracy and roundness of the wire; then perform surface treatments such as electrolytic polishing or coating with a thin layer of lubricating film to obtain a finished wire with a smooth surface and stable wire feeding performance. Example

[0035] In this embodiment, the alloy is prepared according to the following mass percentages, specifically: 5.0%Mg; 1.0%Si; 1.0%Cu; 3.0%Zn; 0.5%Mn; 0.10%Ti; 0.10%Zr; 0.10%Sc, with the balance being Al and trace impurities.

[0036] Preparation process: S1: Melting is carried out in a vacuum induction furnace under the protection of high-purity argon gas. After melting, an ultrasonic probe with a frequency of 28kHz is inserted to sonicate the melt for 15 minutes, while electromagnetic stirring is applied simultaneously. S2: The treated melt is semi-continuously cast at 700℃, and the casting cooling rate is controlled at 10-50℃ / s to obtain a Φ100mm round ingot. S3: The ingot is subjected to two-stage homogenization treatment: first, it is held at 330℃ for 6 hours, then the temperature is raised to 470℃ and held for 20 hours, and then cooled with the furnace. S4: The homogenized ingot is heated to 430℃ and hot extruded to obtain a Φ9.5mm wire rod; water mist is used at the extrusion die exit for online quenching to rapidly cool the wire rod; S5: Perform multiple cold drawing operations on the quenched wire rod, with a target diameter of Φ1.2mm; control the deformation amount of each operation to about 20%; when the cumulative deformation amount reaches about 65%, perform intermediate annealing at 280℃ for 1.5 hours. S6: After annealing, continue drawing to the final diameter Φ1.0mm, and then perform electrolytic polishing to obtain a finished wire with a smooth surface.

[0037] WAAM performance test: Process: The cold metal transfer (CMT) arc additive manufacturing process was adopted, and the above-mentioned wire was used to print a single-pass multi-layer straight-walled sample.

[0038] Microstructure: Metallographic observation of the deposited sample showed that the microstructure consisted of uniform and fine equiaxed crystals with an average grain size of less than 50 μm.

[0039] Performance: Samples were taken along and perpendicular to the deposition direction for room temperature tensile tests. The test results were as follows: longitudinal yield strength was 395 MPa, tensile strength was 435 MPa, and elongation after fracture was 6.5%; transverse yield strength was 365 MPa, tensile strength was 410 MPa, and elongation after fracture was 6.0%. The anisotropy ratio was approximately 1.08. Example

[0040] In this embodiment, the alloy is prepared according to the following mass percentages, specifically: 4.5%Mg; 0.8%Si; 0.8%Cu; 2.5%Zn; 0.6%Mn; 0.15%Ti; 0.08%Zr; 0.05%Sc, with the balance being Al and trace impurities.

[0041] Preparation process: The preparation steps are basically the same as in Example 1, except that in S5, when the cumulative deformation reaches about 65%, intermediate annealing is performed at 260°C for 1.5 hours.

[0042] WAAM performance test: Process and microstructure: Printed using the same CMT process; the deposited microstructure is mainly composed of equiaxed crystals, with a small amount of refined columnar crystals.

[0043] Performance: Longitudinal yield strength is 375 MPa, tensile strength is 415 MPa, and elongation is 7.0%; transverse yield strength is 350 MPa, tensile strength is 395 MPa, and elongation is 6.5%; anisotropy ratio is approximately 1.07. Material cost is reduced by approximately 15% compared to the estimate in Example 1.

[0044] Comparative Example Printed using commercially available ER5356 welding wire (Al-5Mg) under the same WAAM process. The microstructure is a typical coarse columnar crystal with a longitudinal yield strength of 280 MPa and a transverse yield strength of only 185 MPa, and an anisotropy ratio as high as 1.51.

[0045] By comparing the data from Examples 1-2 and the comparative examples, it can be seen that the aluminum alloy wire and its preparation method provided by the present invention effectively solve all the technical problems raised in the background art: To address the problem of coarse and severely anisotropic microstructures: the deposited microstructures in Examples 1-2 are all fine equiaxed or mixed crystals, with an anisotropy ratio (1.07-1.08) much lower than that of the comparative example (1.51), thus achieving low anisotropy.

[0046] To address the issue of low strength in the sedimentary state: the sedimentary yield strength (375-395 MPa) of Examples 1-2 far exceeds that of the comparative example (280 MPa), and remains stable above 370 MPa, breaking through the strength bottleneck of traditional wire materials.

[0047] To address the issue of high performance relying on expensive elements: This invention achieves high performance and significantly lower costs than high-Sc solutions by adding Ti, Zr, and Sc in combination (with a maximum total content of only 0.3%). In Examples 2 and 3, even lower Sc content is used.

[0048] To address the issue of complex post-processing steps: the superior performance of all embodiments is in the deposited state, requiring no post-heat treatment, thus simplifying the production process.

[0049] The embodiments given above are preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential additions or substitutions made by those skilled in the art based on the technical features of the present invention are within the protection scope of the present invention.

Claims

1. A high-performance aluminum alloy wire for electric arc additive manufacturing, characterized in that, Its chemical composition by mass percentage is as follows: Mg: 4.0-6.0%, Si: 0.5-1.5%, Cu: 0.5-1.5%, Zn: 2.0-4.0%, Mn: 0.3-0.8%, Ti: 0.05-0.20%, Zr: 0.05-0.15%, Sc: 0.05-0.15%, with the balance being Al and unavoidable impurities, wherein the content of a single impurity is ≤0.05% and the total content of impurities is ≤0.15%.

2. A method for preparing the high-performance aluminum alloy wire for arc additive manufacturing as described in claim 1, characterized in that, Includes the following steps: S1. Weigh the raw materials according to the target composition, melt them under a protective atmosphere, and then apply a combination of electromagnetic stirring and ultrasonic treatment to the melt. S2. The refined melt is semi-continuously cast to obtain an ingot; S3. Perform a stepped heating homogenization heat treatment on the ingot; S4. Hot extrusion is performed on the homogenized ingot, and the extruded wire rod is rapidly cooled online at the extrusion outlet; S5. The quenched wire rod is reduced in diameter by multiple cold drawing passes, and intermediate stress-relieving annealing is performed when the cumulative deformation reaches a certain value. S6. Perform final drawing, sizing, and surface treatment on the filament to obtain the finished filament.

3. The method for preparing high-performance aluminum alloy wire for arc additive manufacturing according to claim 2, characterized in that, In step S1, the frequency of the ultrasonic treatment is 20-40kHz.

4. The method for preparing high-performance aluminum alloy wire for arc additive manufacturing according to claim 2, characterized in that, In step S2, the temperature of the semi-continuous casting is 680-720℃, and the casting cooling rate is controlled at 10-50℃ / s.

5. The method for preparing high-performance aluminum alloy wire for arc additive manufacturing according to claim 1, characterized in that, In step S3, the multi-stage homogenization process specifically includes: first, maintaining the temperature at 300-350℃ for 4-8 hours, and then raising the temperature to 460-480℃ and maintaining it for 12-24 hours.

6. The method for preparing high-performance aluminum alloy wire for arc additive manufacturing according to claim 1, characterized in that, In step S4, the hot extrusion temperature is 420-450℃, and the extrusion ratio is not less than 25:1; and / or, the online rapid cooling is forced water mist quenching, which rapidly reduces the wire rod temperature to below room temperature.

7. The method for preparing high-performance aluminum alloy wire for arc additive manufacturing according to claim 1, characterized in that, In step S5, the deformation amount of each pass of the multi-pass cold drawing is controlled between 15% and 25%.

8. The method for preparing high-performance aluminum alloy wire for arc additive manufacturing according to claim 1, characterized in that, In step S5, the intermediate stress-relief annealing temperature is 260-280℃; the intermediate stress-relief annealing is carried out when the cumulative deformation reaches 60-70%, the annealing temperature is 250-300℃, and the holding time is 1-2 hours.

9. The method for preparing high-performance aluminum alloy wire for arc additive manufacturing according to claim 1, characterized in that, In step S6, the surface treatment is electropolishing or coating with a lubricating film.

10. The method for preparing high-performance aluminum alloy wire for arc additive manufacturing according to claim 1, characterized in that, The wire prepared by the method has an average grain size of less than 50 μm in the arc additive manufacturing deposited state structure, and the ratio of longitudinal to transverse yield strength is less than 1.2; tensile strength is greater than 415 MPa, elongation after fracture is greater than 6.5%; and an anisotropy ratio is not greater than 1.08.