Method for preparing 3D printing filaments using waste aluminum alloy

Abstract

This invention discloses a method for preparing 3D printing filaments from waste aluminum alloys, comprising the following steps: classifying the waste aluminum alloys; cleaning the waste aluminum alloys using a pulsed laser cleaning method; cutting the cleaned waste aluminum alloys into blocks; heating the waste aluminum alloy blocks; preheating the extrusion die; loading the heated waste aluminum alloy blocks into the preheated extrusion die; extrude the waste aluminum alloy blocks using the extrusion die to obtain an ultrafine-grained aluminum alloy; performing a solution treatment on the obtained ultrafine-grained aluminum alloy; drawing the solution-treated ultrafine-grained aluminum alloy, followed by polishing, cleaning, heat treatment, and straightening treatments, resulting in the 3D printing filament. The 3D printing aluminum alloy filament prepared by this invention produces filaments with uniform microstructure, fine grains, few and small pores, and excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy filament preparation technology for 3D printing. Specifically, it relates to a method for preparing filaments for 3D printing using waste aluminum alloy. Background Technology

[0002] Aluminum alloys are currently the second most widely used alloy, generating a large amount of scrap aluminum annually. Failure to effectively recycle this aluminum leads to a serious waste of resources. Scrap aluminum primarily originates from aluminum shavings from machining aluminum alloy parts and from discarded aluminum components used in construction and aerospace. Aluminum is an important recyclable resource; using scrap aluminum to regenerate aluminum alloys can significantly reduce production costs, energy consumption, and emissions of carbon dioxide, dust, and solid waste. Currently, the main method for recycling scrap aluminum is smelting. However, alloy production through high-temperature smelting still consumes significant amounts of energy and causes environmental pollution. Furthermore, iron scrap is easily mixed in during smelting, resulting in excessively high iron content in the molten solution and reducing alloy quality. Therefore, solid-state recycling, while maximizing the added value of recycled aluminum alloys, is crucial for reducing energy consumption, minimizing environmental pollution, and improving the quality of alloy products.

[0003] Aluminum alloy materials for 3D printing come in two forms: powder and filament. Powder provides high precision and is suitable for producing small, complex products, but it has low material utilization and causes some environmental pollution. In contrast, aluminum alloy filament produces stronger products, making it more suitable for larger items. It also boasts high material utilization, is pollution-free, and has better application prospects. However, 3D printing aluminum alloy filaments require high-quality aluminum alloys and have high production costs, especially requiring high mechanical properties to prevent breakage during filament feeding. Waste aluminum alloys, due to their high oxygen content, numerous impurities, and poor quality, cannot meet the requirements for 3D printing filament preparation. Therefore, finding a method to prepare 3D printing filaments from waste aluminum alloys is crucial for improving their recycling value. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a method for preparing filaments for 3D printing using waste aluminum alloys, so as to solve the problems of high energy consumption, serious environmental pollution, and low added value and poor quality of waste aluminum alloys that make them unsuitable for the preparation of filaments for 3D printing.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A method for preparing filaments for 3D printing using waste aluminum alloy includes the following steps:

[0007] Step (1): Classify the waste aluminum alloy;

[0008] Step (2): Use a pulsed laser cleaning device to clean the waste aluminum alloy to remove the oil stains on the surface of the waste aluminum alloy. As the laser power increases, the quality of the cleaned surface gradually improves, and a waste aluminum alloy block with a clean surface and no residue is obtained.

[0009] Step (3): Cut the cleaned waste aluminum alloy into waste aluminum alloy blocks with a maximum size of less than 30mm;

[0010] Step (4): Heat the waste aluminum alloy block;

[0011] Step (5): Preheat the extrusion die;

[0012] Step (6): Load the heated waste aluminum alloy block into the preheated extrusion die;

[0013] Step (7): Start the extrusion die to extrude the waste aluminum alloy block to obtain ultrafine-grained aluminum alloy; the die extrusion refines the internal grain structure of the waste aluminum alloy block material after large plastic deformation, which is a processing method to obtain ultrafine-grained material; ultrafine-grained aluminum alloy has superplasticity and its mechanical properties are significantly improved. After processing, it can be used as filament for 3D printing, with excellent elongation and tensile strength.

[0014] Step (8): The obtained ultrafine-grained aluminum alloy is subjected to solution treatment; solution treatment can significantly affect the grain size and solute atom solubility of the ultrafine-grained aluminum alloy, laying the foundation for the precipitation of the second phase, and can effectively alleviate some of the grain coarsening phenomenon caused by extrusion of alloys at high temperature, thus improving the overall performance of the alloy.

[0015] Step (9): The solution-treated ultrafine-grained aluminum alloy is drawn and then polished, cleaned, heat-treated and straightened in sequence. After the straightening process is completed, the filament for 3D printing is obtained.

[0016] In the above method for preparing 3D printing filaments using waste aluminum alloys, in step (1), the waste aluminum is first classified according to its source; then, the composition of waste aluminum alloys from different sources is determined by direct reading spectrometer, and the waste aluminum is classified a second time according to its composition.

[0017] In the above method for preparing 3D printing filament using waste aluminum alloy, the source of waste aluminum alloy in step (1) is: decoration, packaging, construction, transportation, electronics, aviation, aerospace or weaponry.

[0018] Waste aluminum alloys are classified into four categories according to their composition: 2xxx series: Al-Cu-Mg-(Fe-Ni) alloys, 4xxx series: Al-Si alloys, 6xxx series: Al-Mg-Si alloys, and 7xxx series: Al-Zn-Mg-(Cu) alloys.

[0019] In the above method for preparing 3D printing filaments using waste aluminum alloy, in step (2), during laser cleaning: the average working power of the pulsed laser cleaning device is 50-70W, the scanning speed is 5500-6500mm / s, and the line spacing is 0.04-0.08mm; in step (3), the cutting machine used during cutting is a band saw, and the maximum size of the waste aluminum alloy block is less than or equal to 30mm.

[0020] In the above method for preparing 3D printing filament using waste aluminum alloy, in step (4), the temperature of the waste aluminum alloy block after heating is 100-150℃; the drying temperature of the waste aluminum alloy block is within the range of 100-150℃. Treating the unanodized waste aluminum alloy will not cause surface modification of the aluminum alloy.

[0021] In step (5), the preheating temperature of the extrusion die is 500-520℃; the extrusion die is a variable diameter corner extrusion die; the waste aluminum alloy block passes through the feeding section, upsetting torsion section, sealing section, upsetting shearing section and drawing section of the variable diameter corner extrusion die in sequence to complete the extrusion; the feeding section is cylindrical, with a cylinder height L1 of 600mm and a diameter D1 of 80-120mm; the upsetting torsion section is spherical, with a spherical radius R1 of (1.3-1.5)D1; the sealing section is cylindrical, with a cylinder length L2 of 15-20mm and a diameter D2 of 0.5D1; the upsetting shearing section is spherical, with a spherical radius R2 of (1.3-1.5)D2; the drawing section is cylindrical, with a cylinder length L3 of 8-10mm and a diameter D3 of 6-20mm. This die integrates upsetting, shearing, and torsional deformation, resulting in a significant grain refinement effect. Compared to other extrusion dies, metal wires extruded using a variable diameter, angled extrusion die can produce greater cumulative plastic deformation, significantly improving the overall mechanical properties of the wires and achieving superplasticity.

[0022] In the above method for preparing 3D printing filament using waste aluminum alloy, in step (6), a cylindrical aluminum alloy of the same grade with a diameter 1-2 mm smaller than the inner diameter of the extrusion cylinder and a thickness of 10-15 mm is first placed into the extrusion cylinder of the extrusion mold to act as a seal. Then, the waste aluminum alloy block heated in step (4) is loaded into the extrusion cylinder. In this invention, the cylindrical aluminum alloy of the same grade is also recycled aluminum alloy material of various series (2xxx series, 4xxx series, 6xxx series, 7xxx series). In step (7), the extrusion speed of the extrusion mold is 0.001-1 m / s.

[0023] In the above method for preparing 3D printing filaments using waste aluminum alloy, in step (8), the heating rate of the solution treatment is 1-5℃ / min, the treatment temperature is 460-540℃, and the treatment time is 180-720℃ / min.

[0024] In the above method for preparing 3D printing filaments using waste aluminum alloy, step (9) involves using a continuous cold drawing process to produce 3D printing filaments from ultrafine-grained aluminum alloy. The continuous cold drawing process involves 8 to 12 drawing passes (too few drawing passes make it difficult to obtain finer filaments, which is not conducive to improving the toughness and tensile strength of the aluminum alloy filament; too many drawing passes will cause internal cracks, stress cracks, or drawing fractures in the filament). During the drawing process, 1 to 3 intermediate annealing treatments are performed. The cumulative deformation of the 8 to 12 drawing passes is 55.3% to 90% (if the cumulative deformation is less than 55.3%, the aluminum alloy filament will have low plasticity and toughness, low strength and hardness, and substandard mechanical properties; if the cumulative deformation is greater than 90 ... If the annealing temperature is too high (90%), the aluminum alloy wire will generate a large amount of dislocation entanglement, which will cause stress concentration and lead to fracture. The intermediate annealing temperature is 400-530℃, and the annealing time is 1-3h. (If the intermediate annealing temperature is too high, it will not only cause high energy consumption in the annealing process, but also easily cause coarse grains in the aluminum alloy structure, which will easily cause cracking in the subsequent drawing process. If the intermediate annealing temperature is too low, it will easily cause insufficient solid-state diffusion of elements, which will be difficult to effectively eliminate segregation. If the intermediate annealing time is too short or too long, it will cause coarse grains in the aluminum alloy structure.) The diameter of the filament for 3D printing is 1.2mm-4mm. This invention can produce filaments from aluminum alloys for metal 3D printing through cold deformation drawing process according to different applications. Based on aluminum alloy filament 3D metal wire printing, filaments within this diameter range are beneficial to the strength and durability of 3D printing technology. The internal structure is dense and contains fine grain structure. The filament feeding rate is stable, and the strength and flowability are good during the filament feeding 3D printing process.

[0025] In the above method for preparing 3D printing filaments using waste aluminum alloy, step (9) involves chemical polishing and cleaning. The polishing liquid used is nano-SiO2 polishing liquid, and the cleaning agent is a 2wt% octylphenyl polyoxyethylene ether (TX-100) solution. HNO3 and NaOH are used to adjust the pH of the cleaning agent to 5.5. The aluminum alloy surface is a hydrophilic surface. During the cleaning process, a cleaning agent with high hydrophilicity should be used as much as possible to ensure good wettability of the aluminum alloy surface and reduce surface tension, thereby facilitating... For surface particle removal, octylphenyl polyoxyethylene ether TX-100 exhibits strong hydrophilicity and low surface tension, resulting in excellent wettability and ideal cleaning effect on aluminum alloys. By adjusting the pH of the cleaning solution to alter the potential between the particles and the surface, and utilizing electrostatic force, particle removal is promoted and particle aggregation on the aluminum alloy surface is prevented. A pH of 5.5 is the optimal value for dispersing and suspending surface contaminants to prevent their redeposition. If the pH is less than or greater than 5.5, the surface contaminants on the waste aluminum alloy are more likely to aggregate and deposit on the surface after dispersion and suspension.

[0026] The average particle size of SiO2 in the nano-SiO2 polishing slurry is 100nm, and the mass fraction of SiO2 in the slurry is 30wt%. The dispersibility of the SiO2 polishing slurry affects the surface cleaning effect of aluminum alloys, and silica gel agglomeration will lead to gelation and increase adhesion. A specific mass fraction of surfactant TX-100 combined with the SiO2 polishing slurry can effectively enhance the dispersibility of SiO2 particles, preventing particle agglomeration and reducing adhesion during the cleaning process after polishing, while effectively removing adhered particles. Ultrasonic polishing cleaning can comprehensively improve the smoothness of the wire. The straightening method is rotational straightening, which is used for wires with a circular cross-section.

[0027] In the above method for preparing 3D printing filaments using waste aluminum alloy, the heat treatment conditions in step (9) are: the treatment temperature is 240-390℃ and the holding time is 1-3h, so as to obtain a softened structure in the fully recrystallized state of the aluminum alloy wire, which gives it better plasticity and lower strength. If the heat treatment temperature is too high or the holding time is too long, it will easily cause coarse grains. If the heat treatment temperature is too low or the holding time is too short, it will not be able to soften the finished product and eliminate the internal stress of the filament.

[0028] The technical solution of the present invention achieves the following beneficial technical effects:

[0029] This invention employs a solid-state, non-heat-deformation preparation method for aluminum alloy materials, which greatly reduces the preparation cost of conventional aluminum alloy smelting. At the same time, it recycles waste aluminum alloys into finished products, following the concept of low-carbon and green manufacturing. The preparation method involves first performing variable-diameter and angle extrusion, solution treatment, and then drawing (with intermediate annealing during the drawing process). The resulting 3D printing aluminum alloy wire has a uniform microstructure, fine grains, few and small pores, and excellent mechanical properties. Attached Figure Description

[0030] Figure 1 A schematic diagram of the structure of the variable diameter corner extrusion die in an embodiment of the present invention;

[0031] Figure 2 Microstructure (100 μm) of the printing alloy printed by the 3D printing filament prepared in the embodiments of the present invention;

[0032] Figure 3 Microstructure (20 μm) of the printing alloy printed by the 3D printing filament prepared in the embodiments of the present invention;

[0033] Figure 4 The stress-strain curve of the 3D printing filament alloy prepared in the embodiments of the present invention. Detailed Implementation

[0034] In this embodiment, the method for preparing 3D printing filament using waste aluminum alloy includes the following steps:

[0035] Step (1): Classify the waste aluminum alloy; First, classify the waste aluminum according to its source. In this embodiment, high-strength waste aluminum alloys such as trusses, rods, containers, and large heat exchangers of transportation vehicles are identified from the waste aluminum alloys; Then, the composition of waste aluminum alloys from different sources is determined by direct reading spectrometer, and secondary classification is carried out according to the composition of waste aluminum, and waste 6061 aluminum alloys that meet the main component of 6xxx series (Al-Mg-Si) are selected.

[0036] Step (2): Use a pulsed laser cleaning device to clean the waste aluminum alloy block to remove the oil stains on the surface of the waste aluminum alloy. When cleaning the waste aluminum alloy with a pulsed laser cleaning device, as the laser power increases, the quality of the cleaned surface gradually improves, and a clean waste aluminum alloy with no residue is obtained. During laser cleaning: the average working power of the pulsed laser cleaning device is 60W, the scanning speed is 6000mm / s, and the line spacing is 0.06mm.

[0037] Step (3): The selected scrap aluminum alloy is cut using a band saw. A water-based emulsion with good fluidity is selected to cut the scrap 6061 aluminum alloy into scrap aluminum alloy blocks with a maximum size of less than 30mm. In this embodiment, commercially available DX-4 type (general-purpose high-efficiency water-based) cutting fluid is used. [In some other embodiments, larger scrap aluminum alloys can be mechanically cut into blocks of suitable size according to the size of the extrusion die];

[0038] Step (4): Heat the waste aluminum alloy block; the temperature of the waste aluminum alloy block after heating is 120℃;

[0039] Step (5): Preheat the extrusion die to 510℃; the extrusion die is a variable diameter corner extrusion die (its structural diagram is shown in the figure). Figure 1 As shown): Part I (material holding section) has a diameter D1 of 80-120 mm and a height L1 of 600 mm. This part is for holding the material and is used to upset the billet under the action of the extrusion rod. Part II (upsetting and torsion section) has a spherical part with a radius R1 of (1.3-1.5)D1. The purpose of this part is to subject the alloy to upsetting and torsion, refining the second phase of the grains. Part III (sealing section) has a diameter D2 of 0.5D1 and a length L2 of 15-20 mm. This part is designed to... The purpose of the structure is to act as a seal, allowing the metal in Parts I and II to be fully deformed, while simultaneously elongating the grains passing through that area; the radius R2 of the spherical part of Part IV (upsetting and shearing section) is (1.3~1.5)D2. The purpose of this structure is to further upset and shear the alloy, refine the grains and the second phase; the diameter D3 of Part V (drawing section) is 6~20mm, and the length L3 is 8~10mm, which elongates and refines the grains, while also determining the diameter of the drawn billet;

[0040] Step (6): Load the heated waste aluminum alloy block into the preheated extrusion die; first put a 6061 aluminum alloy cylinder with a diameter 1-2 mm smaller than the inner diameter of the extrusion cylinder and a thickness of 10-15 mm into the extrusion cylinder of the extrusion die, and then load the heated waste aluminum alloy block in step (4) into the extrusion cylinder.

[0041] Step (7): Start the extrusion die to extrude the waste aluminum alloy to obtain ultrafine crystalline aluminum alloy; the forming speed of the extruder is 1 mm / s, and after extrusion, ultrafine crystalline (submicron and nanocrystalline structure) is formed;

[0042] Step (8): The obtained ultrafine-grained aluminum alloy is subjected to solution treatment; the heating rate of the solution treatment is 1℃ / min, the treatment temperature is 540℃, and the treatment time is 180min;

[0043] Step (9): The solution-treated ultrafine-grained aluminum alloy is drawn, and then polished, cleaned, heat-treated and straightened in sequence. After the treatment is completed, the filament for 3D printing is obtained.

[0044] The 10mm diameter ultrafine-grained aluminum alloy obtained in step (8) is selected and made into 3D printing filament using a continuous cold drawing process. The continuous cold drawing process involves 10 drawing passes with a cumulative deformation of 80%. Two intermediate annealing treatments are performed during the drawing process. After the deformation of the ultrafine-grained aluminum alloy reaches 57% and 80% respectively during the cold drawing process, an intermediate annealing heat treatment is performed. The annealing temperature of the intermediate annealing is 510℃ and the annealing time is 1.5h. The diameter of the 3D printing filament obtained by drawing is 2mm. In this embodiment, the polishing and cleaning is a chemical polishing and cleaning method. The polishing liquid used during polishing and cleaning is nano-SiO2 polishing liquid, and the cleaning agent used is 2wt% octylphenyl polyoxyethylene ether (TX-100). The pH of the cleaning agent is adjusted to 5.5 using HNO3 and NaOH.

[0045] The average particle size of SiO2 in the nano-SiO2 polishing slurry is 100nm, and the mass fraction of SiO2 in the nano-SiO2 polishing slurry is 30wt%. Ultrasonic polishing and cleaning can comprehensively improve the smoothness of the filament. The heat treatment conditions are: annealing temperature of 360℃ and holding time of 3h. The straightening method is rotary straightening. In some other embodiments, rotary straightening can be used for filaments and rods with circular cross-sections.

[0046] This implementation example yielded 6061 aluminum alloy filament for 3D printing. Experimental verification showed that it exhibited good flowability during 3D printing, produced few and small pores in the printed alloy, and had a uniform microstructure (see...). Figure 2 and Figure 3 The alloy, produced by 3D printing, exhibits excellent mechanical properties (see...). Figure 4 ).

[0047] In this embodiment, the corrosion resistance of the aluminum alloy wire was characterized by measuring its conductivity. The test results showed that the open-circuit potential-time curve of the 6061 aluminum alloy wire for 3D printing prepared in this embodiment was increased by 0.02%-0.056% in 3.5% NaCl solution, thus its corrosion resistance was significantly improved.

[0048] The fluidity of the filament refers to its properties during 3D printing based on welding technologies such as TIG, MIG, and SAW. The 6061 aluminum alloy filament prepared in this embodiment exhibits higher composition and density, more equiaxed grains, shorter solidification time, and 12%-16% increased elongation under electron microscopy compared to ordinary 6061 aluminum alloy. It also features good fluidity and a high forming rate during 3D printing. The tensile strength of the 6061 aluminum alloy filament prepared in this embodiment is 1.63-2.18 times higher than that of ordinary 6061 aluminum alloy, and the hardness is increased by 58.3%-63.4%.

[0049] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for preparing a wire material for 3D printing using scrap aluminum alloy, characterized by, The method comprises the following steps: Step (1): classifying waste aluminum alloy; Step (2): cleaning the waste aluminum alloy by using a pulse laser cleaning method; Step (3): cutting the cleaned waste aluminum alloy into waste aluminum alloy blocks; Step (4): heating the waste aluminum alloy blocks; Step (5): preheating an extrusion die; Step (6): loading the heated waste aluminum alloy blocks into the preheated extrusion die; Step (7): starting the extrusion die to extrude the waste aluminum alloy blocks to obtain ultra-fine-grained aluminum alloy; Step (8): subjecting the obtained ultra-fine-grained aluminum alloy to solid solution treatment; Step (9): drawing the solid solution treated ultra-fine-grained aluminum alloy, and sequentially performing polishing and cleaning, heat treatment and straightening treatment, so that a 3D printing wire is obtained after the straightening treatment; In step (5), the preheating temperature of the extrusion die is 500-520 DEG C; the extrusion die is a variable-diameter corner extrusion die; the waste aluminum alloy blocks pass through a material containing part, a upsetting and torsion part, a blocking part, a upsetting and shearing part and a drawing part of the variable-diameter corner extrusion die in sequence to complete extrusion; the material containing part is in the shape of a cylinder, the height L1 of the cylinder is 600 mm, and the diameter D1 is 80-120 mm; the upsetting and torsion part is in the shape of a sphere, the radius R1 of the sphere is (1.3-1.5) D1; the blocking part is in the shape of a cylinder, the length L2 of the cylinder is 15-20 mm, and the diameter D2 is 0.5 D1; the upsetting and shearing part is in the shape of a sphere, the radius R2 of the sphere is (1.3-1.5) D2; the drawing part is in the shape of a cylinder, the length L3 of the cylinder is 8-10 mm, and the diameter D3 is 6-20 mm; In step (6), an aluminum alloy cylinder of the same grade with a thickness of 10-15 mm and a diameter of 1-2 mm smaller than the inner diameter of the extrusion cylinder is first placed in the extrusion cylinder of the extrusion die, and then the heated waste aluminum alloy blocks in step (4) are loaded into the extrusion cylinder; In step (9), the ultra-fine-grained aluminum alloy is made into a 3D printing wire by using a continuous cold drawing process; the continuous cold drawing process is performed for 8-12 passes, and 1-3 intermediate annealing treatments are performed during the drawing process; the cumulative deformation of the 8-12 passes is 55.3-90%; the annealing temperature of the intermediate annealing is 400-530 DEG C, and the annealing time is 1-3 h; the diameter of the 3D printing wire is 1.2 mm-4 mm.

2. The method for preparing a wire material for 3D printing using scrap aluminum alloy according to claim 1, characterized by, In step (1), the waste aluminum is classified once according to the source of the waste aluminum alloy; then the composition of the waste aluminum alloy of different sources is determined by using a direct-reading spectrometer, and the waste aluminum is classified twice according to the composition of the waste aluminum.

3. The method for preparing a wire for 3D printing using scrap aluminum alloy according to claim 2, characterized by, In step (1), the source of the waste aluminum alloy is decoration, packaging, construction, transportation, electronics, aviation, aerospace or weaponry; The waste aluminum alloy is divided into four categories according to its composition: 2xxx series: Al-Cu-Mg-(Fe-Ni) alloy, 4xxx series: Al-Si alloy, 6xxx series: Al-Mg-Si alloy, and 7xxx series: Al-Zn-Mg-(Cu) alloy. 4.The method of preparing a wire for 3D printing using scrap aluminum alloy according to claim 1, characterized by, In step (2), the average working power of the pulsed laser cleaning device is 50-70 W, the scanning speed is 5500-6500 mm / s, and the line spacing is 0.04-0.08 mm. 5.The method of preparing a wire material for 3D printing using scrap aluminum alloy according to claim 1, characterized in that, In step (4), the temperature of the heated waste aluminum alloy block is 100-150℃. 6.The method of preparing a wire for 3D printing using scrap aluminum alloy according to claim 1, characterized by, In step (7), the extrusion speed of the extrusion die is 0.001-1 m / s.

7. The method for preparing 3D printing filament from waste aluminum alloy according to claim 1, characterized in that, In step (8), the heating rate of the solid solution treatment is 1-5℃ / min, the treatment temperature is 460-540℃, and the treatment time is 180-720 min. 8.The method of claim 1, wherein the method is characterized by, In step (9), the polishing cleaning is a chemical polishing cleaning method, the polishing liquid used in the polishing cleaning is a nano-SiO2 polishing liquid, the cleaning agent used is an octylphenyl polyoxyethylene ether solution with a mass concentration of 2 wt%, and HNO3 and NaOH are used to adjust the pH of the cleaning agent to 5.5; The average particle size of SiO2 in the nano-SiO2 polishing liquid is 100 nm, the mass fraction of SiO2 in the nano-SiO2 polishing liquid is 30 wt%, and the straightening method is a rotary straightening method. 9.The method of claim 8, wherein the aluminum alloy scrap is classified into a first group and a second group according to a composition of the aluminum alloy scrap, and the first group and the second group are mixed in a ratio of 1:1 to 1:

3. In step (9), the heat treatment conditions are as follows: the treatment temperature is 240-390℃, and the holding time is 1-3 h.

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