Electric arc additive manufacturing process for improving strength and plasticity of aluminum alloy, special wire material and preparation method of special wire material

Abstract

The invention belongs to the technical field of metal additive manufacturing. The invention particularly relates to an electric arc additive manufacturing process for improving the strength and plasticity of aluminum alloy, a special wire and a preparation method thereof. The wire comprises the following components in percentage by mass: 7.0 to 8.0 percent of Zn, 1.8 to 2.5 percent of Mg, 1.2 to 2.0 percent of Cu, 0.15 to 0.3 percent of Sc, 0.1 to 0.2 percent of Zr, 0.2 to 0.3 percent of TiN, less than or equal to 0.1 percent of impurity element Si, less than or equal to 0.15 percent of Fe and the balance of Al. TiN particles and aluminum powder are used as raw materials, and an Al-TiN intermediate alloy is prepared through multi-pass stirring friction processing; raw materials are added according to the components of the wire for smelting, and an aluminum alloy ingot is obtained after casting; extruding, rolling and post-processing the aluminum alloy cast ingot to obtain a finished wire; and a special wire and a CMT + P mode are adopted for electric arc additive manufacturing. According to the method, the Sc and Zr elements and the TiN particles are jointly added, the use amount of the TiN particles can be greatly reduced while the structure refining effect is guaranteed, and through the CMT + P mode in electric arc additive manufacturing, the gas content of an additive layer is obviously reduced, and the strength and plasticity of an additive component are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of metal additive manufacturing technology. Specifically, it relates to an arc additive manufacturing process for improving the strength and plasticity of aluminum alloys, as well as a special wire and its preparation method. Background Technology

[0002] Arc additive manufacturing boasts advantages such as low cost and the ability to fabricate large-size components, making it widely applicable in aerospace, weaponry, and other fields. With the continuous improvement of equipment lightweighting and technical specifications, the demand for arc additive manufacturing of 7xxx series ultra-high-strength aluminum alloys is urgent, requiring strengths exceeding 600 MPa and elongation exceeding 5% in both the transverse and longitudinal directions of the additive thin-walled structure. However, due to its extremely high alloy element content, especially volatile elements like Zn and Mg, the arc additive manufacturing process is highly prone to cracking and suffers from severe porosity issues. The interlayer problems are particularly prominent, resulting in a significant decrease in longitudinal strength and plasticity, with strength below 500 MPa and plasticity less than 5%, severely hindering the development of arc additive manufacturing of 7xxx series ultra-high-strength aluminum alloys.

[0003] While tungsten inert gas (TIG) welding offers flexible power supply modes and is effective at eliminating porosity in arc additive manufacturing, its performance remains unsatisfactory in 7xxx series aluminum alloys. Currently, the mainstream arc additive manufacturing method is cold metal transfer (CMT), whose coaxial wire feeding mechanism provides greater flexibility, making it ideal for manufacturing complex shapes. However, when using conventional CMT for 7xxx series aluminum alloy additive manufacturing, the plasticity is significantly reduced compared to TIG.

[0004] High-quality new wire materials are key to overcoming the bottlenecks in arc additive manufacturing of 7xxx series ultra-high strength aluminum alloys. Currently, researchers have effectively solved the cracking problem in additive components by adding Sc and Zr microalloying elements and nano-ceramic particles; however, the aforementioned strength and plasticity issues remain unresolved. While adding Sc and Zr can significantly increase strength to 600 MPa, it cannot effectively solve the porosity problem, which remains severe, resulting in poor longitudinal plasticity (less than 5%). Adding nano-ceramic particles can significantly reduce porosity and greatly increase transverse elongation to 10%, but due to the currently high addition levels (above 0.5 wt%), severe nanoparticle agglomeration occurs, leading to interlayer aggregation and even worse longitudinal plasticity. Furthermore, the method and content of ceramic particle addition also significantly affect wire preparation and arc additive manufacturing. Summary of the Invention

[0005] To address the bottleneck of insufficient strength and ductility in the arc additive manufacturing of 7xxx series ultra-high strength aluminum alloys, this invention provides an arc additive manufacturing process and a dedicated wire and its preparation method to improve the strength and ductility of aluminum alloys. The wire preparation process employs a combination of Sc and Zr microalloying and a small amount (0.2-0.3 wt%) of submicron ceramic reinforcing phase to significantly refine the microstructure while greatly eliminating porosity. Then, the arc additive manufacturing process is performed using CMT+P (cold metal transfer + pulse) to further eliminate interlayer porosity and particle aggregation.

[0006] First, an Al-TiN master alloy ingot is prepared by filling pre-drilled holes in an aluminum plate with a mixture of aluminum powder and TiN particles (≤1 μm) using a four-pass friction stir machining method. Second, the aforementioned Al-TiN master alloy containing TiN particles, Al-Sc and Al-Zr master alloys, and other master alloys are smelted and cast according to typical 7xxx series aluminum alloy compositions to obtain a raw ingot (diameter ~110 mm). The ingot is then machined and peeled to a diameter of approximately 105 mm, followed by extrusion and rolling to produce a 3.0 mm diameter wire. Finally, after multi-pass annealing, drawing, mechanical scraping, ultrasonic cleaning, and passivation, it is processed into the most commonly used 1.2 mm diameter finished wire. Other diameter coiled wires can also be processed as needed. After wire preparation, arc additive manufacturing is performed using the CMT+P mode, with a current of 80-90A and a voltage of 15-20V. The arc-added components undergo T6 heat treatment to improve their comprehensive mechanical properties.

[0007] This invention provides a special wire for electric arc additive manufacturing process. The composition of the wire by mass percentage is: Zn: 7.0~8.0%, Mg: 1.8~2.5%, Cu: 1.2~2.0%, Sc: 0.15~0.3%, Zr: 0.1~0.2%, TiN: 0.2~0.3%, impurity elements Si: ≤0.1%, Fe: ≤0.15%, and the remainder is Al.

[0008] This invention provides a method for preparing a special wire for electric arc additive manufacturing process, comprising the following steps: (1) An Al-TiN master alloy was prepared by friction stirring using TiN particles and aluminum powder as raw materials; (2) The Al-TiN master alloy and other alloy raw materials are added to the special wire material according to claim 1 and smelted and cast to obtain an aluminum alloy ingot; (3) Extruding and rolling aluminum alloy ingots to obtain wire semi-finished products; (4) After post-processing the semi-finished silk material, the finished silk material is obtained.

[0009] Further, the Al-TiN master alloy preparation method in step (1) is as follows: mix TiN particles with aluminum powder, fill the mixture into an aluminum plate with pre-drilled blind holes, and prepare an Al-TiN master alloy with a TiN particle mass fraction of 20-30% by stirring and friction processing.

[0010] Furthermore, the TiN particles have a particle size of 0.5~1 μm; the aluminum powder has a particle size of 15-60 μm; the volume ratio of TiN particles to aluminum powder is 7:3~7.5:2.5; the prefabricated blind hole processing parameters are: diameter 5~6 mm, depth 5.0~5.5 mm, center-to-center distance between adjacent holes is 10.0~10.5 mm, hole center distance from plate edge is not less than 5 mm, and all blind holes are processed perpendicular to the plate surface.

[0011] Furthermore, the friction stir processing is a multi-pass friction stir processing, with specific process parameters of an overlap rate of 30%-40%, a rotation speed of 1500-2000 rpm, a travel speed of 50-100 mm / min, and the materials used for the stirring head are: cubic boron nitride for the stirring needle and TiN particle-reinforced cermet for the shoulder.

[0012] Further, the other alloy raw materials mentioned in step (2) are pure aluminum, Al-Zn master alloy or pure Zn, Al-Mg master alloy or pure Mg, Al-Cu master alloy or pure Cu, Al-Sc master alloy, Al-Zr master alloy; the melting temperature is 740℃-780℃, and the casting temperature is 755℃-765℃.

[0013] Further, the extrusion temperature in step (3) is 370℃-385℃, the extrusion speed is 0.8-1.2mm / s, the diameter of the extrusion die is 9.0-10.0mm, and the rolling speed is 5-6m / min.

[0014] Furthermore, the post-processing described in step (4) includes annealing, drawing, mechanical scraping, ultrasonic cleaning, and passivation treatment performed sequentially.

[0015] This invention provides an arc additive manufacturing process for improving the strength and plasticity of aluminum alloys. It uses the aforementioned arc additive manufacturing special wire and adopts the CMT+P (cold metal transition + pulse) mode for arc additive manufacturing.

[0016] The process parameters for the CMT+P mode are: current 80-90A, voltage 15-20V, and wire feeding speed 5-7 mm / min.

[0017] The principle of this invention is as follows: Traditional fluoride salt methods, which involve adding TiC and TiB2 particles, suffer from severe porosity issues. However, the TiN master alloy method in this invention eliminates the influence of fluoride salts. TiN improves the melting and nucleation of nucleation particles in the arc additive manufacturing process, significantly reducing porosity. Furthermore, compared to powder metallurgy methods that directly mix aluminum powder and TiN and hot-press to prepare Al-TiN master alloys, this method, which involves adding TiN particles and a small amount of pure aluminum powder to blind holes and then preparing the master alloy using friction stirring, effectively avoids the problems of incomplete melting and excessive oxygen content caused by the introduction of Al2O3 from the aluminum powder surface. It also allows for further refinement and effective dispersion of TiN particles through intense plastic deformation. Moreover, the TiN content in this invention is extremely low, effectively solving the agglomeration problem during smelting. Typically, added TiN particles are incompatible with the aluminum matrix, resulting in poor compatibility and insufficient mechanical properties. In this invention, the combined addition of Sc, Zr elements and TiN particles leads to the enrichment of Sc and Zr elements around the TiN particles, forming a coherent relationship with the aluminum matrix through the mediating effect of Al3(Sc, Zr). Figure 2 This can significantly improve the mechanical properties of additive components.

[0018] In the process of aluminum alloy arc additive manufacturing, the CMT mode, with its relatively stable voltage and current, is commonly used. However, for 7xxx series aluminum alloys, the porosity problem is extremely serious, especially the abundance of large-sized pores, which is very detrimental to mechanical properties and significantly reduces plasticity. This invention employs the CMT+P mode, where the pulse action can break up large-sized pores in the interlayer composition, thereby significantly reducing the size and content of interlayer pores. Figure 3 Simultaneously, the pulsed action also makes the interlayer particle distribution more uniform, avoiding the reduction in plasticity caused by agglomeration. Therefore, using the filament material and electric arc additive manufacturing process of this invention, after T6 heat treatment, the strength of the accumulated body in both the transverse and longitudinal directions exceeds 600 MPa, the elongation exceeds 8%, and the transverse elongation is as high as 16%.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: (1) This invention prepares Al-TiN master alloys by friction stirring and then melts ultra-high strength aluminum alloy ingots according to the alloy composition. Compared with ultra-high strength aluminum alloys prepared by the fluoride salt method, there are no fluoride salt residues, which significantly reduces the porosity during the arc additive manufacturing process. At the same time, compared with the addition method of Al-TiN master alloys prepared by powder metallurgy, it avoids the problems of excessive Al2O3 causing the master alloy to be difficult to melt and excessive O element.

[0020] (2) The intermediate alloy is prepared by using a cubic boron nitride stirring needle during the friction stir processing, which can avoid the severe wear of steel tools. Even if a small amount of boron nitride wears, it exists in the form of submicron or nano ceramic particles, which can achieve a similar effect to TiN.

[0021] (3) By adding Sc, Zr and TiN particles together, the amount of TiN particles can be greatly reduced while ensuring the effect of refining the microstructure. The size is in the submicron range (0.5~1μm), which can reduce porosity and effectively prevent agglomeration. Moreover, through the mediating effect of Al3(Sc, Zr), a good coherent relationship is formed with the aluminum matrix, which improves the mechanical properties.

[0022] (4) Compared with the conventional CMT mode, the CMT+P mode with added pulses enhances the "cleaning" effect between layers. It not only breaks up large bubbles through pulse action to promote bubble floating and significantly reduces the gas content between layers, but also makes the TiN particles between layers more uniformly distributed, greatly improving the strength and plasticity of additive components. Attached Figure Description

[0023] Figure 1 Schematic diagram of Al-TiN master alloy preparation by friction stir processing; Figure 2 Transmission electron microscopy morphology of TiN and Al3(Sc, Zr) in the additive structure prepared in Example 1; Figure 3 X-ray flaw detection morphology under two modes: CMT (Comparative Example 1-1) and CMT+P (Example 1); Figure 4 Tensile properties of the accumulator under both CMT (Comparative Example 1-1) and CMT+P (Example 1) modes; Figure 5 CMT+P (Example 1) mode for accumulated tissue scanning electron microscopy. Detailed Implementation

[0024] Example 1 TiN particles with a particle size of 0.5~1 μm and pure aluminum powder with a particle size of 15-60 μm were used as raw materials and mixed by mechanical mixing at a volume ratio of 7:3 to obtain a mixed powder; [The last part, "50 mm," appears to be an unrelated fragment and is omitted from the translation.] 50 mm Pre-drilled blind holes were made on a 6 mm thick pure aluminum plate in a lattice pattern (rectangular array). The blind holes were 5 mm in diameter and 5 mm deep, with a center-to-center distance of 10 mm between adjacent holes and a center-to-edge distance of at least 5 mm. All blind holes were machined perpendicular to the plate surface. The mixed powder was filled into the blind holes of the pure aluminum plate and compacted. Then, a combined stirring head (cubic boron nitride stirring needle with a tapered threaded needle, root diameter of 10 mm, and TiN particle-reinforced cermet shoulder with a diameter of 20 mm) was used for in-situ four-pass, large-area overlapping (30% overlap rate in the processing area) friction stirring processing. The rotation speed was 2000 rpm and the travel speed was 100 mm / min. This produced an Al-TiN master alloy with a TiN particle mass fraction of approximately 20% (see...). Figure 1 The raw materials used were pure aluminum, Al-Zn master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Sc master alloy, Al-Zr master alloy, and the developed Al-TiN master alloy, prepared according to the following composition and mass percentages, and smelted at 750℃. The composition ratio was: Zn: 7.3%, Mg: 2.1%, Cu: 1.7%, Sc: 0.15%, Zr: 0.1%, TiN: 0.3%, Fe: ≤0.1%, Si: ≤0.1%, with the remainder being Al. After smelting and casting at 760℃, an ultra-high strength aluminum alloy ingot with a mass ratio of 0.3%TiN / Al-7.3Zn-2.1Mg-1.7Cu and a diameter of 110 mm was obtained. After the ingot was peeled down to a diameter of 105 mm, it was extruded at a temperature of 380℃, an extrusion speed of 1 mm / s, an extrusion die diameter of 9.5 mm, and a rolling speed of 6 m / min to produce wire with a diameter of 3 mm. After multiple annealing processes (annealing temperature 380℃), drawing (drawing speed 10-12m / min), mechanical scraping (single-sided scraping thickness 0.05-0.07mm), ultrasonic cleaning, and passivation, a finished wire with a diameter of 1.2mm (ultra-high strength aluminum alloy wire) is obtained from a 3mm diameter wire.

[0025] Using ultra-high strength aluminum alloy wire with the above-mentioned composition, an arc additive welding machine (ABB robot system with Flüss CMT Advanced 4000R power supply) was used for arc additive manufacturing, employing CMT+P (cold metal transfer + pulse) mode. The current was 82A, the voltage was 17.6V, and the wire feed speed was 5.5 mm / min. The final additive structural part was fabricated with dimensions of 240mm × 7mm × 70mm (length × width × height).

[0026] Microstructural observation of the formed part (additive structure part) shows that the formed part is composed of fine equiaxed crystals. Figure 5 The grain size is 5.3 ± 0.4 μm. Figure 2The image shows the transmission electron microscopy (TEM) morphology of TiN and Al3(Sc, Zr) in the structural component. It can be seen from the image that the deposited alloy Al3(Sc, Zr) obtained through arc additive manufacturing contains TiN particles with a size of approximately 500 nm-1000 nm within the grains. Furthermore, Sc and Zr elements are enriched around the TiN particles, forming composite particles with a TiN core / Al3(Sc, Zr) shell structure. The Al3(Sc, Zr) phase located between the TiN particles and α-Al plays a stable bridging role, effectively reducing lattice mismatch and enhancing interfacial coherence, thereby significantly enhancing the strengthening effect of TiN particles on the Al-Zn-Mg-Cu alloy. X-ray flaw detection results show a significant reduction in porosity. Figure 3 The room temperature tensile test was conducted according to GB / T 228.1-2021 "Metallic materials, tensile testing—Part 1: Test at room temperature". The tensile test results showed that after artificial peak aging (T6) heat treatment (first holding at 480℃ for 2 hours followed by quenching, then holding at 120℃ for 24 hours, and air cooling), the alloy's transverse tensile strength was 610 MPa with an elongation of 16.3%, and its longitudinal tensile strength was 602 MPa with an elongation of 8.5%. Figure 4 ).

[0027] Comparative Example 1-1 The preparation method of the ultra-high strength aluminum alloy wire is the same as in Example 1, using CMT (cold metal transfer) mode for arc additive manufacturing. The current is 140A, the voltage is 14.5V, and the wire feed speed is 8.5 mm / min. Finally, an additive structural part with a length, width, and height of 240mm × 7mm × 70mm is prepared.

[0028] Microstructural observation of the formed part revealed that it consisted of equiaxed crystals and equiaxed dendrites. Tensile testing showed that after T6 heat treatment, the alloy exhibited a transverse tensile strength of 610 MPa and an elongation of 8.2%, while the longitudinal tensile strength was 565 MPa and the elongation was only 1.2%. Figure 4 ).

[0029] Comparative Examples 1-2 Existing technologies commonly employ the fluoride salt method to prepare ultra-high strength aluminum alloy wires. Specifically, the process involves: First, using high-purity aluminum ingots as the base material, the feed composition is calculated strictly according to the nominal composition of Al-7.3Zn-2.1Mg-1.7Cu-0.15Sc-0.1Zr. Major alloying elements are introduced by adding intermediate alloys such as Al-Zn, Al-Mg, and Al-Cu. The base alloy is then melted at 750℃ to obtain an alloy melt. Next, a mixed salt of KBF4 and K2TiF6 is added to the melt according to the stoichiometric ratio of B to Ti to form TiB2. The mixed salt undergoes an in-situ reaction in the alloy melt, generating nano- to submicron-sized TiB2 particles (0.2-1 μm), which are then uniformly dispersed in the alloy melt through mechanical stirring. After the reaction is complete, the material is refined, slag removed, and allowed to stand before finally being cast at 760℃. Then, ultra-high strength aluminum alloy wire with a diameter of 1.2 mm was prepared by peeling, extrusion, rolling, and drawing. The wire composition was 1.5% TiB2 / Al-7.3Zn-2.1Mg-1.7Cu-0.15Sc-0.1Zr (specifically: Zn: 7.3%, Mg: 2.1%, Cu: 1.7%, Sc: 0.15%, Zr: 0.1%, TiB2: 1.5%, Fe: ≤0.1%, Si: ≤0.1%, with the remainder being Al). The peeling, extrusion, rolling, and drawing processes were the same as in Example 1. Arc additive manufacturing was performed using the CMT+P mode, with the same process parameters as in Example 1. Finally, an additive structural part with a length, width, and height of 240 mm × 7 mm × 70 mm was prepared.

[0030] Microstructural observation of the formed part revealed that it consisted of equiaxed crystals and equiaxed dendrites, but with a high porosity. Tensile testing showed that after T6 heat treatment, the alloy exhibited a transverse tensile strength of 520 MPa and an elongation of 5.9%, while the longitudinal tensile strength was 493 MPa and the elongation was only 1.9%. Analysis revealed that the porosity of the additive component was as high as 0.55%. The Al-TiB2 master alloy prepared by the fluoride salt method contained residual fluoride salts, which generated a large number of pores during the additive manufacturing process, fundamentally causing its reduced elongation. Furthermore, the preparation of TiN using the fluoride salt method is far more difficult than that of TiB2. Therefore, the addition of TiN particles in this invention directly abandons the traditional fluoride salt method.

[0031] Comparative Examples 1-3 The preparation method of the ultra-high strength aluminum alloy wire is the same as in Example 1, except that the target composition of this wire is Zn: 7.3%, Mg: 2.1%, Cu: 1.7%, Sc: 0.25%, Zr: 0.15%, Fe: ≤0.1%, Si: ≤0.1%, and the remainder is Al. Only Sc and Zr elements are added, and TiN particles are not added. Arc additive manufacturing is performed using the CMT+P mode, with a current of 82A, a voltage of 17.6V, and a wire feed speed of 5.5 mm / min. Finally, an additive structural part with a length, width, and height of 240mm × 7mm × 70mm is prepared.

[0032] Microstructural observation of the formed part revealed that it consisted of equiaxed crystals and equiaxed dendrites. Tensile test results showed that after T6 heat treatment, the alloy had a transverse tensile strength of 595 MPa and an elongation of 6.5%, and a longitudinal tensile strength of 570 MPa and an elongation of only 2.8%.

[0033] Example 2 TiN particles with a particle size of 0.5~1 μm and pure aluminum powder with a particle size of 15-60 μm were used as raw materials and mixed by mechanical mixing in a volume ratio of 7:3 to obtain a mixed powder. The powder was then mixed at a 50 mm diameter. 50 mm Pre-drilled blind holes were made on a 6 mm thick pure aluminum plate in a dot matrix pattern (rectangular array). The blind holes were 5 mm in diameter and 5 mm deep, with a center-to-center distance of 10 mm between adjacent holes and a center-to-edge distance of no less than 5 mm. All blind holes were machined perpendicular to the plate surface. The mixed powder was filled into the blind holes of the pure aluminum plate and compacted. Then, a combined stirring head (cubic boron nitride stirring needle with a tapered threaded needle and a root diameter of 10 mm, and TiC particle-reinforced cermet with a diameter of 20 mm) was used to perform in-situ 4-pass, large-area overlapping (30% overlap rate in the processing area) friction stirring processing. The rotation speed was 2000 rpm and the travel speed was 100 mm / min. An Al-TiN master alloy with a TiN particle mass fraction of about 20% was prepared. The raw materials were prepared according to the following composition and mass percentage, and smelted at 750℃. The raw materials used were pure aluminum, Al-Zn master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Sc master alloy, Al-Zr master alloy, and a developed Al-TiN master alloy. The composition ratio was: Zn: 7.8%, Mg: 2.3%, Cu: 1.9%, Sc: 0.2%, Zr: 0.15%, TiN: 0.2%, Fe: ≤0.1%, Si: ≤0.1%, with the remainder being Al. After casting at 760℃, an ultra-high strength aluminum alloy ingot with a mass ratio of 0.2%TiN / Al-7.8Zn-2.3Mg-1.9Cu-0.2Sc-0.15Zr and a diameter of 110 mm was obtained. After peeling the ingot to a diameter of 105 mm, it was extruded and rolled using the same process as in Example 1 to prepare wire with a diameter of 3 mm. After multiple annealing processes (annealing temperature 380℃), drawing (drawing speed 10-12m / min), mechanical scraping (single-sided scraping thickness 0.05-0.07mm), ultrasonic cleaning, and passivation, a finished ultra-high strength aluminum alloy wire with a diameter of 1.2 mm is obtained from 3 mm diameter wire.

[0034] Using ultra-high strength aluminum alloy wire with the above-mentioned composition, an arc additive welding machine (ABB robot system with Flüss CMT Advanced 4000R power supply) was used for arc additive manufacturing, employing CMT+P (cold metal transfer + pulse) mode. The current was 82A, the voltage was 17.6V, and the wire feed speed was 5.5 mm / min. The final additive structural part was fabricated with dimensions of 240mm × 7mm × 70mm (length × width × height).

[0035] Microstructural observation of the formed part revealed that it consisted of fine equiaxed crystals with a grain size of 5.2 ± 0.3 μm. Tensile test results showed that after T6 heat treatment, the alloy exhibited a transverse tensile strength of 630 MPa and an elongation of 12.3%, a longitudinal tensile strength of 620 MPa, and an elongation of 6.5%.

[0036] Comparative Example 2 The preparation method of the ultra-high strength aluminum alloy wire is the same as in Example 2, except that the target composition of this wire is Zn: 7.8%, Mg: 2.3%, Cu: 1.9%, Sc: 0.2%, Zr: 0.15%, Fe: ≤0.1%, Si: ≤0.1%, and the remainder is Al. Only Sc and Zr elements are added, without adding TiN particles, and the final ultra-high strength aluminum alloy wire with the composition Al-7.8Zn-2.3Mg-1.9Cu-0.2Sc-0.15Zr is prepared. Arc additive manufacturing is performed using CMT+P (cold metal transfer + pulse) mode, with a current of 82A, a voltage of 17.6V, and a wire feed speed of 5.5 mm / min. The final additive structural part with a length, width, and height of 240mm × 7mm × 70mm is prepared. Tensile tests were conducted, and the results showed that after T6 heat treatment, the alloy had a transverse tensile strength of 620 MPa and an elongation of 6.7%, a longitudinal tensile strength of 605 MPa, and an elongation of 3.5%.

[0037] Comparative Example 3 Al-TiN master alloys containing TiN were prepared using powder metallurgy. The specific process involved: firstly, TiN ceramic particles (0.5-1 μm) and pure aluminum powder (15-60 μm) of different particle sizes were mixed as needed using a mixing method; then, cold pressing and vacuum hot pressing sintering (vacuum degree 10) were performed sequentially. -2 Al-TiN master alloy ingots were obtained by treating the ingots at 640℃ for 1 hour under a pressure of 40t (Pa). In these ingots, TiN was uniformly distributed, and the mass percentage of TiN ceramic particles was 10-30% (20% in this comparative example). The Al-TiN master alloy ingots were then melted and cast with aluminum-based raw materials (including pure aluminum, Al-Zn master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Sc master alloy, and Al-Zr master alloy) at 760℃ to prepare ultra-high strength aluminum alloy ingots with a composition of 0.3% TiN / Al-7.3Zn-2.1Mg-1.7Cu (specific composition: Zn: 7.3%, Mg: 2.1%, Cu: 1.7%, Sc: 0.15%, Zr: 0.1%, TiN: 0.2%, Fe: ≤0.1%, Si: ≤0.1%, the remainder being Al). The filaments were then prepared through peeling, extrusion, rolling, and post-processing, the same as in Example 1.

[0038] Using ultra-high strength aluminum alloy wire with the above composition, an arc additive welding machine (ABB robot system with Flüss CMT Advanced 4000R power supply) was used for arc additive manufacturing in CMT+P (cold metal transfer + pulse) mode, with a current of 82A, a voltage of 17.6V, and a wire feed speed of 5.5 mm / min. The final additive structure was prepared with dimensions of 240mm × 7mm × 70mm (length × width × height). Tensile tests were conducted, and the results showed that after T6 heat treatment, the alloy's transverse tensile strength was 590 MPa with an elongation of 2.4%, and its longitudinal tensile strength was 570 MPa with an elongation of 1.7%. Regarding the addition method of Al-TiN master alloy in powder metallurgy preparation, the Al2O3 on the surface of the aluminum powder makes it difficult for the Al-TiN master alloy to melt during subsequent smelting, which prevents its inclusion in the ultra-high strength aluminum alloy. Meanwhile, due to the excessive amount of oxygen, a large number of pores are easily formed during subsequent additive manufacturing, resulting in lower strength and elongation.

[0039] Through a systematic comparison of the embodiments and comparative examples, the technical solution proposed in this invention—namely, the preparation of Al-TiN master alloy using friction stir processing, followed by the preparation of wire containing specific components of TiN, Sc, and Zr, combined with CMT+P (cold metal transfer + pulsed) arc additive manufacturing process—demonstrates a synergistic effect and is key to obtaining high-performance, low-anisotropic additively manufactured components. First, compared to Comparative Examples 1-3 without added TiN particles, the "core-shell" composite structure formed by TiN particles and Sc and Zr elements in the embodiments significantly refines the grains and strengthens the interface, resulting in a substantial increase in longitudinal elongation from an extremely low 2.8% to 8.5%, proving that the introduction of TiN is the core element for the strengthening effect of this solution. Second, compared to Comparative Examples 1-2, which use the traditional fluoride salt method to prepare TiB2 wire, the friction stir processing method used in this invention effectively avoids porosity defects, increasing the transverse tensile strength from 520 MPa to 610 MPa, highlighting the unique advantages of this specific preparation method in ensuring material purity and enhancing phase dispersion. More importantly, the process comparisons (Example 1 and Comparative Example 1-1, Example 2 and Comparative Example 2) consistently demonstrate that the CMT+P process mode is indispensable for achieving performance breakthroughs. Simply changing the manufacturing mode from CMT+P to conventional CMT leads to coarsening of the molded part's microstructure, a sharp increase in anisotropy, and a sudden drop in longitudinal elongation from better than 8.5% to 1.2% or 3.5%. This indicates a strong synergistic dependency between the lower heat input CMT+P process and the material system of this invention. Furthermore, Example 2 successfully reproduced the excellent performance, confirming that the technical solution has good compositional tolerance and reproducibility.

[0040] In summary, the technical solution of this invention, through the innovative combination of material design and process control, systematically solves the common problems of high porosity, coarse grains, severe anisotropy, and insufficient plasticity in the manufacture of ultra-high strength aluminum alloys by arc additive manufacturing. It obtains components that simultaneously possess ultra-high strength, high plasticity, and low anisotropy. Its comprehensive effect is far beyond what existing technologies or simple modifications can achieve, fully demonstrating the creativity, technological advancement, and industrial application value of this invention.

Claims

1. A special wire for electric arc additive manufacturing process, characterized in that: The composition of the wire material by mass percentage is as follows: Zn: 7.0~8.0%, Mg: 1.8~2.5%, Cu: 1.2~2.0%, Sc: 0.15~0.3%, Zr: 0.1~0.2%, TiN: 0.2~0.3%, impurity elements Si: ≤0.1%, Fe: ≤0.15%, and the remainder is Al.

2. A method for preparing a special wire for electric arc additive manufacturing process, characterized in that, Includes the following steps: (1) An Al-TiN master alloy was prepared by friction stirring using TiN particles and aluminum powder as raw materials; (2) The Al-TiN master alloy and other alloy raw materials are added to the special wire material according to claim 1 and smelted and cast to obtain an aluminum alloy ingot; (3) Extruding and rolling aluminum alloy ingots to obtain wire semi-finished products; (4) After post-processing the semi-finished silk material, the finished silk material is obtained.

3. The preparation method according to claim 2, characterized in that, The Al-TiN master alloy preparation method described in step (1) is as follows: TiN particles are mixed with aluminum powder and filled into an aluminum plate with pre-drilled blind holes. An Al-TiN master alloy containing 20-30% TiN particles by mass fraction is prepared by stirring and friction processing.

4. The preparation method according to claim 3, characterized in that: The TiN particles have a particle size of 0.5~1 μm; the aluminum powder has a particle size of 15-60 μm; the volume ratio of TiN particles to aluminum powder is 7:3~7.5:2.5; the prefabricated blind hole processing parameters are: diameter 5~6 mm, depth 5.0~5.5 mm, center-to-center distance between adjacent holes is 10.0~10.5 mm, hole center distance from plate edge is not less than 5 mm, and all blind holes are processed perpendicular to the plate surface.

5. The preparation method according to claim 3, characterized in that, The aforementioned friction stir processing is a multi-pass friction stir processing, with specific process parameters including an overlap rate of 30%-40%, a rotation speed of 1500-2000 rpm, a travel speed of 50-100 mm / min, and the materials used for the stirring head being: cubic boron nitride for the stirring needle and TiN particle-reinforced cermet for the shoulder.

6. The preparation method according to claim 2, characterized in that, The other alloy raw materials mentioned in step (2) are pure aluminum, Al-Zn master alloy or pure Zn, Al-Mg master alloy or pure Mg, Al-Cu master alloy or pure Cu, Al-Sc master alloy or Al-Zr master alloy; the melting temperature is 740℃-780℃ and the casting temperature is 755℃-765℃.

7. The preparation method according to claim 2, characterized in that, The extrusion temperature in step (3) is 370℃-385℃, the extrusion speed is 0.8-1.2mm / s, the diameter of the extrusion die is 9.0-10.0mm, and the rolling speed is 5-6m / min.

8. The preparation method according to claim 2, characterized in that, The post-processing described in step (4) includes annealing, drawing, mechanical scraping, ultrasonic cleaning and passivation in sequence.

9. An electric arc additive manufacturing process for improving the strength and plasticity of aluminum alloys, characterized in that: Using the special wire for arc additive manufacturing as described in claim 1, arc additive manufacturing is performed in the CMT+P (cold metal transition + pulse) mode.

10. The electric arc additive manufacturing process according to claim 9, characterized in that: The process parameters for the CMT+P mode are: current of 80-90A, voltage of 15-20V, and wire feeding speed of 5-7 mm / min.

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