Al-si series die-casting aluminum alloy based on recycled aluminum and preparation method and structural member thereof

Abstract

This invention provides an Al-Si die-cast aluminum alloy based on recycled aluminum, its preparation method, and structural components. The method includes adding industrial silicon, steel scrap, and Ni to a recycled aluminum melt to obtain a mixed melt; subjecting the mixed melt to boronizing and a first refining treatment; adjusting the temperature to 710-780°C, adding magnesium alloy scrap, Sr, and an Al-Ti-B alloy, and then performing a second refining treatment; and die-casting the mixed melt to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum, containing 6-12% Si, 0.1-1% Fe, 0.4-3% Mg, 0-0.1% Sr, 0-0.3% Ti, 0-0.05% B, and 0-2.5% Ni by mass.

Description

[0001] This invention is a divisional application. The original application number is 2025101739540, the application date is February 15, 2025, and the title is Al-Si die-cast aluminum alloy based on recycled aluminum, its preparation method and structural parts. Technical Field

[0002] This invention relates to the field of aluminum alloy technology, and in particular to an Al-Si die-cast aluminum alloy based on recycled aluminum, its preparation method, and structural components. Background Technology

[0003] The energy consumption and carbon emissions of recycled aluminum production are only 4.9% of those of primary aluminum, making recycled aluminum a clear leader in energy conservation and emission reduction. However, recycled aluminum accounts for approximately 20% of my country's total aluminum production, while in Japan, it accounted for nearly 100% in 2019. Therefore, there is significant room for improvement in the proportion of recycled aluminum production in my country.

[0004] The difficulty in utilizing recycled aluminum lies in the excessive levels of elements such as Fe and Mn, as well as the high content of impurities such as oxide slag and organic matter, making it difficult to compare its performance with that of virgin aluminum. Specifically, Fe impurities form coarse needle-like or plate-like β-iron-rich phases, which severely fragment the aluminum matrix; Mn drastically reduces the electrical conductivity of aluminum alloys, leading to a sharp decline in the conductivity of aluminum castings, and also reduces the plasticity of aluminum alloys; oxide slag and organic matter also reduce the mechanical and electrical properties of aluminum alloys. The presence of these impurities greatly restricts the recycling of aluminum and the sustainable development of aluminum resources.

[0005] Therefore, there is an urgent need for a method to prepare aluminum alloys using recycled aluminum. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, the present invention provides a method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum, aiming to provide an Al-Si die-cast aluminum alloy based on recycled aluminum with excellent comprehensive performance.

[0007] This invention provides a method for preparing Al-Si die-cast aluminum alloys based on recycled aluminum, comprising the following steps: Recycled aluminum is heated to obtain recycled aluminum melt; The temperature is adjusted to 740-860°C, and industrial silicon, steel scrap, and Ni are added to the recycled aluminum melt to obtain a mixed melt; The mixed melt is subjected to borying and a first refining process; The temperature was adjusted to 710-780°C, and magnesium alloy scrap, Sr, and Al-Ti-B alloy were added to the mixed melt after the first refining treatment. The mixed melt was then subjected to a second refining treatment. The components and their contents in the mixed melt after the second refining process are measured. When the components and their contents in the mixed melt after the second refining process meet the standards, the mixed melt is subjected to die casting to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum contains 6-12% Si, 0.1-1% Fe, 0.4-3% Mg, 0-0.1% Sr, 0-0.3% Ti, 0-0.05% B, and 0-2.5% Ni by mass percentage.

[0008] Furthermore, the method for preparing the Al-Si die-cast aluminum alloy based on recycled aluminum also includes the step of adding RE, Mo, Co and Be to the recycled aluminum melt. In the Al-Si die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Mn is 0.0001-0.1%, the mass percentage content of Cr is 0.0001-0.2%, the mass percentage content of RE is 0.001-0.2%, the mass percentage content of Mo is 0-0.3%, the mass percentage content of Co is 0-0.5%, and the mass percentage content of Be is 0-0.2%.

[0009] Furthermore, the method for preparing the Al-Si die-cast aluminum alloy based on recycled aluminum also includes the step of adding Mn, Cr, RE, Mo, Co and Be to the recycled aluminum melt. In the Al-Si die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Mn is 0.0001-0.2%, the mass percentage content of Cr is 0.001-0.3%, the mass percentage content of RE is 0.01-0.2%, the mass percentage content of Mo is 0-0.3%, the mass percentage content of Co is 0-0.5%, and the mass percentage content of Be is 0-0.2%.

[0010] Furthermore, the method for preparing the Al-Si die-cast aluminum alloy based on recycled aluminum further includes the step of adding at least one of Cu, Zr, Ca, Te, Ag, Sb, Bi, and Nb to the recycled aluminum melt. In the Al-Si die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Cu is 0.0001-1%, the mass percentage content of Zr is 0.0001-0.5%, the mass percentage content of Ca is 0.0001-0.3%, the mass percentage content of Te is 0-0.2%, the mass percentage content of Ag is 0-0.2%, the mass percentage content of Sb is 0-0.5%, the mass percentage content of Bi is 0-0.2%, and the mass percentage content of Nb is 0-0.5%.

[0011] Furthermore, the method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum also includes a step of surface treatment of the mold, wherein the surface treatment is to form a boron carbide layer on the parting surface of the mold.

[0012] Furthermore, at least one of the following conditions must be met: The borizing agent used in the borization treatment is potassium fluoroborate and / or aluminum-boron alloy; The mass ratio of the borizing agent to the mixed melt in the borination treatment is 0.001-0.005:1; The first refining process is carried out at a temperature of 740-800°C for 20-60 minutes. The refining agent for the first refining process is at least one of chloride salts, fluoride salts, and rare earth elements. The mass ratio of the refining agent to the mixed melt in the first refining treatment is 0.0001-0.0005:1; The second refining process is carried out at a temperature of 690-750°C for 10-40 minutes. The refining agent for the second refining process includes at least one of chloride salts, fluoride salts, and rare earth elements. The mass ratio of the refining agent to the mixed melt in the second refining process is 0.001-0.2:1.

[0013] Furthermore, after die-casting the mixed melt to obtain aluminum alloy parts, the method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum further includes an aging treatment step for the aluminum alloy parts, wherein... The aging treatment is performed at a temperature of 150-250℃ for a time of 0.05-30 hours; or The aging treatment includes a first-stage low-temperature electric field aging treatment and a second-stage high-temperature aging treatment. The first-stage low-temperature electric field aging treatment is performed at a temperature of 50-120℃ for a time of 0.1-100h, with an electric field strength of 2-50kV / cm. The second-stage high-temperature aging treatment is performed at a temperature of 140-250℃ for a time of 0.1-50h.

[0014] The present invention also provides an Al-Si die-cast aluminum alloy based on recycled aluminum, containing Al, and further containing 6-12% Si, 0.1-1% Fe, 0.4-3% Mg, 0-0.1% Sr, 0-0.3% Ti, 0-0.05% B, and 0-2.5% Ni by mass.

[0015] Furthermore, the Al-Si die-cast aluminum alloy based on recycled aluminum also contains at least one of Cu, Mn, Cr, V, Ca, RE, Mo, Co, Be, Zr, Te, Ag, Sb, Bi, and Nb, wherein the mass percentage content of Cu is 0.0001-1%, the mass percentage content of V is 0.005-0.2%, the mass percentage content of Ca is 0.0001-0.3%, the mass percentage content of Zr is 0.0001-0.5%, the mass percentage content of Te is 0-0.2%, the mass percentage content of Ag is 0-0.2%, the mass percentage content of Sb is 0-0.5%, the mass percentage content of Bi is 0-0.2%, the mass percentage content of Nb is 0-0.5%, the mass percentage content of SiC is 0-1%, the mass percentage content of TiC is 0-1%, and the mass percentage content of BN is 0-0.5%.

[0016] The present invention also provides a structural component, wherein the material of the structural component is the Al-Si die-cast aluminum alloy based on recycled aluminum obtained by the above-mentioned preparation method of Al-Si die-cast aluminum alloy based on recycled aluminum, or the above-mentioned Al-Si die-cast aluminum alloy based on recycled aluminum.

[0017] In the technical solution of this invention, industrial silicon, steel waste and magnesium alloy waste are used as the main raw materials, which can greatly reduce the cost; by adding Sr, Al-Ti-B alloy and Ni alloy elements, and with multiple refining and boronizing treatments, Al-Si die-cast aluminum alloy based on recycled aluminum with excellent comprehensive performance can be obtained. Detailed Implementation

[0018] 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 the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention provides a method for preparing Al-Si die-cast aluminum alloys based on recycled aluminum, comprising the following steps: Recycled aluminum is heated to obtain recycled aluminum melt; The temperature is adjusted to a high temperature, approximately 740-860°C, and industrial silicon, steel scrap, and Ni are added to the recycled aluminum melt to obtain a mixed melt. The mixed melt is subjected to borying and a first refining process; Adjust the temperature to 710-780°C, add magnesium alloy scrap, Sr, and Al-Ti-B alloy to the mixed melt after the first refining treatment, and then perform a second refining treatment, slag removal treatment, degassing treatment, and settling treatment on the mixed melt. After the settling treatment, remove the surface slag. The components and their contents in the mixed melt after the settling treatment are measured. When the components and their contents in the mixed melt after the settling treatment meet the standards, the mixed melt after the settling treatment is subjected to die casting to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum contains 6-12% Si, 0.1-1% Fe, 0.4-3% Mg, 0-0.1% Sr, 0-0.3% Ti, 0-0.05% B, and 0-2.5% Ni by mass.

[0020] Understandably, organic matter can be effectively removed at high temperatures of 740-860°C.

[0021] The mass percentage content of Si can be 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, or 12%.

[0022] The mass percentage content of Fe can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, or 1%.

[0023] The mass percentage content of Mg can be 0.4%, 0.45%, 0.45%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.78%, 0.85%, 0.9%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3%.

[0024] The mass percentage content of Sr can be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%.

[0025] The mass percentage content of Ti can be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%.

[0026] The mass percentage content of B can be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, or 0.05%.

[0027] The mass percentage content of Ni can be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.45%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.78%, 0.85%, 0.9%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, or 2.5%.

[0028] The mass ratio of recycled aluminum, industrial silicon, steel scrap, and magnesium alloy scrap can be 84-93.5:6-12:0.1-1:0.4-3. When adding industrial silicon, steel scrap, and magnesium alloy scrap to the recycled aluminum melt, the burn-off rate of these materials must be considered to ensure that the components and their contents in the refined mixed melt meet the standards. Spectroscopic analysis can be used to determine the composition and content of the mixed melt. If the components and their contents do not meet the standards, the corresponding elements can be added, or a second refining and slag removal process can be performed until the standards are met. Furthermore, the standard for each component and its content in the mixed melt is as follows: it contains 6-12% Si by mass, 0.1-1% Fe by mass, 0.4-3% Mg by mass, 0-0.1% Sr by mass, 0-0.3% Ti by mass, 0-0.05% B by mass, and 0-2.5% Ni by mass.

[0029] When the content of impurity elements in the mixed melt is too high and does not meet the standard, the content of impurities can be diluted by adding pure Al ingots to the mixed melt, so that the content is lower than the standard.

[0030] When the mixed melt is cooled to 680-700°C, it is then die-cast. The mold temperature for die-casting can be 220-300°C, and the die-casting speed can be 0.23-2.5 m / s. The mold used in the die-casting process includes a moving mold and a fixed mold, both of which have parting surfaces. The two parting surfaces together form a cavity to accommodate the mixed melt, forming an aluminum alloy product with a specific shape. Before die-casting, both parting surfaces can undergo surface treatment, which involves forming a boron carbide layer on the parting surfaces. The boron carbide layer not only improves demolding performance but also enhances the wear resistance of the mold and resists corrosion from chemicals such as acids, alkalis, and salts, as well as thermal erosion of the aluminum alloy, thereby extending the mold's service life. The thickness of the boron carbide layer can be 1-10 mm, specifically 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm.

[0031] The surface treatment can be performed by mixing a boron-containing gas (such as BCl3) and a carbon-containing gas (such as CH4) to obtain a mixed gas; introducing the mixed gas into a cavity, and using chemical vapor deposition (CVD), the boron-containing gas and the carbon-containing gas react chemically and deposit on the parting surface to form a boron carbide layer. The CVD temperature is 900-1200°C, the deposition pressure is 200-500 Pa, and the carrier gas flow rate is 100-200 sccm.

[0032] During the die-casting process, the boron carbide layer can increase the hardness of the mold steel to 3000-4000 Hv; the boron carbide layer can reduce the affinity of the mixed melt to the mold surface, improve the demolding performance of the aluminum alloy, and allow for smooth demolding even without the addition of Fe and Mn, greatly improving the elongation of the aluminum alloy; the boron carbide layer can resist the corrosion of chemicals such as acids, alkalis, and salts, improving the corrosion resistance of the aluminum alloy; the boron carbide layer can maintain good physical and chemical properties at high temperatures, improving the thermal stability of the aluminum alloy; the boron carbide layer has an extremely low coefficient of friction, improving the surface smoothness of the aluminum alloy, and significantly reducing wear and energy consumption caused by mechanical friction in aluminum alloy products; the boron carbide layer also has high heat transfer properties, allowing heat to be quickly conducted away during aluminum alloy forming, increasing the heat transfer rate of the mold by 2-4 times compared to ordinary molds, enabling the formed aluminum alloy to cool faster and have a finer microstructure, thereby improving the strength and elongation of the aluminum alloy.

[0033] In one embodiment, the aging treatment is performed at a temperature of 150-250°C for a time of 0.05-30 hours. Specifically, the aging treatment temperature can be 150°C, 200°C, or 250°C, and the time can be 0.05 hours, 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, 25 hours, or 30 hours.

[0034] In another embodiment, the aging treatment includes a primary low-temperature electric field aging treatment and a secondary high-temperature aging treatment. The primary low-temperature electric field aging treatment is performed at a temperature of 50-120℃ for a duration of 0.1-100 hours, with an electric field strength of 2-50 kV / cm. Specifically, the temperature of the primary low-temperature electric field aging treatment can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, or 120℃, and the duration can be 0.1h, 0.5h, 1h, 5h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, or 5... The time for the secondary high-temperature aging treatment is 0h, 55h, 60h, 65h, 70h, 75h, 80h, 85h, 90h, 95h, or 100h, with specific electric field strengths of 2kV / cm, 5kV / cm, 10kV / cm, 15kV / cm, 20kV / cm, 25kV / cm, 30kV / cm, 35kV / cm, 40kV / cm, 45kV / cm, or 50kV / cm. The secondary high-temperature aging treatment is performed without an electric field, with a temperature of 140-250℃ and a time of 0.1-50h. The specific temperature for the secondary high-temperature aging treatment can be 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, or 250℃, and the specific time can be 0.1h, 0.5h, 1h, 5h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, or 50h.

[0035] During the first-stage low-temperature electric field aging treatment, the low temperature of 50-120℃ inhibits the segregation of atoms such as Mg, Cu, Ni, Zn, and Si, while simultaneously increasing the supercooling of the alloy, significantly expanding the GP region and facilitating increased nucleation rate in subsequent high-temperature processes, allowing for more complete precipitation of alloying elements. Secondly, the application of an electric field at low temperature reduces the precipitation activation energy of phases in the alloy, accelerating the nucleation rate of precipitated phases during aging and increasing the volume fraction of nucleation sites. The alloy exhibits a significant increase in hardness during the initial stage of electric field aging, shortening the time required to reach peak hardness during the subsequent second-stage high-temperature aging treatment, increasing the volume fraction of precipitated phases, and refining the size of precipitated phases. With increasing electric field strength during the first-stage low-temperature electric field aging treatment, the number of nucleation sites for the strengthening phases precipitated in the alloy increases dramatically, indicating that increasing the electric field strength can improve the nucleation rate of precipitated phases, and has no significant impact on the growth of phases during the second-stage high-temperature aging treatment without an electric field, thus preventing phase coarsening.

[0036] The degassing process involves introducing an inert gas, such as helium, neon, argon, krypton, or nitrogen, into the molten mixture. The degassing time is 10-15 minutes, and the gas pressure is 0.2-0.4 MPa. The settling time is 20-30 minutes. By introducing an inert gas into the molten mixture and performing degassing and settling treatments, the gas can be removed from the molten mixture, thereby reducing the bubble content and ensuring the casting of high-quality aluminum alloys.

[0037] The borizing agent used in the borination treatment is potassium fluoroborate and / or an aluminum-boron alloy. The aluminum-boron alloy has a ratio of 0.001-0.005:1, specifically 0.001:1, 0.002:1, 0.003:1, 0.004:1, or 0.005:1.

[0038] In one embodiment, the boriding agent comprises 20-80 wt% potassium fluoroborate and 20-80 wt% aluminum-boron alloy.

[0039] The temperature of the first refining treatment is 740-800°C, specifically 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, or 800°C, and the time is 20-60 minutes, specifically 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes. The refining agent in the first refining treatment can be at least one of chloride salts, fluoride salts, and rare earth elements. The chloride salt is at least one of sodium chloride, potassium chloride, and lithium chloride. The fluoride salt can be at least one of potassium fluoride, calcium fluoride, potassium fluoroborate, and sodium aluminum fluoride. The rare earth element can be at least one of La, Ce, Pr, Nd, Er, Sm, Y, Sc, and Gd. The mass ratio of the refining agent to the mixed melt in the first refining treatment is 0.0001-0.0005:1, specifically 0.0001:1, 0.0002:1, 0.0003:1, 0.0004:1, or 0.0005:1. This first refining treatment simultaneously refines and purifies the aluminum alloy, thereby improving its strength and elongation. Specifically, chloride and fluoride salts can increase the strength of the aluminum alloy, while rare earth elements can increase its elongation.

[0040] In one embodiment, the refining agent for the first refining process includes 10-80 wt% of chloride salt, 10-80 wt% of fluoride salt, and 1-20 wt% of rare earth elements.

[0041] The second refining treatment is carried out at a temperature of 690-750°C, specifically 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, or 750°C, for a time of 10-40 minutes, specifically 10 minutes, 20 minutes, 30 minutes, or 40 minutes. The mass ratio of the refining agent to the mixed melt in the second refining treatment is 0.001-0.2:1, specifically 0.001:1, 0.005:1, 0.01:1, 0.05:1, 0.1:1, 0.15:1, or 0.2:1. This second refining treatment simultaneously refines and purifies the aluminum alloy, thereby improving its strength and elongation. Specifically, chloride and fluoride salts can improve the strength of the aluminum alloy, while rare earth elements can improve its elongation.

[0042] The refining agent for the second refining process may be at least one selected from chloride salts, fluoride salts, and rare earth elements. The chloride salt may be at least one selected from sodium chloride, potassium chloride, and lithium chloride. The fluoride salt may be at least one selected from potassium fluoride, calcium fluoride, potassium fluoroborate, and sodium aluminum fluoride. The rare earth element may be at least one selected from La, Ce, Pr, Nd, Er, Sm, Y, Sc, and Gd. In one embodiment, the refining agent for the first refining process comprises 10-80 wt% chloride salt, 10-80 wt% fluoride salt, and 1-20 wt% rare earth element.

[0043] Recycled aluminum is an aluminum alloy obtained by remelting scrap aluminum and aluminum alloy materials, or by remelting aluminum-containing waste. Recycled aluminum can include recycled cast aluminum alloys and recycled wrought aluminum alloys. Recycled cast aluminum alloys have a higher impurity content than recycled wrought aluminum alloys, but are cheaper. This application can use recycled cast aluminum alloys to reduce costs and achieve better performance, or it can use recycled wrought aluminum alloys.

[0044] Fe, Si, Cu, Mn, Ti, Cr, V, Mg, Zn, and Pb are impurities in recycled aluminum. In recycled cast aluminum alloy raw materials, Al ≥ 80 wt%, Fe 1.2-4 wt%, Si 1-20 wt%, Cu ≤ 6 wt%, Mn ≤ 1 wt%, Ti ≤ 0.2 wt%, Cr ≤ 0.3 wt%, V ≤ 0.3 wt%, Mg ≤ 8 wt%, Zn ≤ 8 wt%, Pb ≤ 0.2 wt%, and organic matter ≤ 0.2 wt%. In recycled wrought aluminum alloys, Al ≥ 95 wt%, Fe 0.2-1 wt%, Si ≤ 5 wt%, Cu ≤ 1 wt%, Mg ≤ 3 wt%, Mn ≤ 0.3 wt%, Ti ≤ 0.3 wt%, Cr ≤ 0.3 wt%, V ≤ 0.3 wt%, Zn ≤ 6 wt%, Pb ≤ 0.2 wt%, and organic matter ≤ 0.2 wt%.

[0045] Pre-treatment of recycled aluminum can be performed, such as sorting, crushing, magnetic separation for iron removal, and washing. The composition and content of recycled aluminum can also be tested using methods such as photoelectric direct-reading spectrometry or chemical analysis. This allows recycled aluminum with similar compositions and contents to be mixed together based on the test results, avoiding situations where the mixed recycled aluminum has an overly complex composition, excessive levels of certain elements, or insufficient levels of certain elements.

[0046] Industrial silicon can include Si1101, Si2202, Si3303, Si4110, Si4210, Si4410, Si5210, Si5530, etc. Fe, Ca, Al, Mn, Ti, Cr, and V are impurities in industrial silicon.

[0047] In Si1101, Si ≥ 99.79 wt%, Fe ≤ 0.10 wt%, Al ≤ 0.1 wt%, Ca ≤ 0.01 wt%, Mn ≤ 0.3 wt%, Ti ≤ 0.1 wt%, Cr ≤ 0.1 wt%, and V ≤ 0.1 wt%. In Si22O2, Si ≥ 99.58 wt%, Fe ≤ 0.2 wt%, Al ≤ 0.2 wt%, Ca ≤ 0.02 wt%, Mn ≤ 0.3 wt%, Ti ≤ 0.1 wt%, Cr ≤ 0.1 wt%, and V ≤ 0.1 wt%. In Si3303, Si≥99.37wt%, Fe≤0.3wt%, Al≤0.3wt%, Ca≤0.03wt%, Mn≤0.3wt%, Ti≤0.1wt%, Cr≤0.1wt%, V≤0.1wt%; In Si4110, Si ≥ 99.40 wt%, Fe ≤ 0.4 wt%, Al ≤ 0.1 wt%, Ca ≤ 0.1 wt%, Mn ≤ 0.3 wt%, Ti ≤ 0.1 wt%, Cr ≤ 0.1 wt%, and V ≤ 0.1 wt%. In Si4210, Si ≥ 99.30 wt%, Fe ≤ 0.4 wt%, Al ≤ 0.2 wt%, Ca ≤ 0.1 wt%, Mn ≤ 0.3 wt%, Ti ≤ 0.1 wt%, Cr ≤ 0.1 wt%, and V ≤ 0.1 wt%. In Si4410, Si ≥ 99.10 wt%, Fe ≤ 0.4 wt%, Al ≤ 0.4 wt%, Ca ≤ 0.1 wt%, Mn ≤ 0.3 wt%, Ti ≤ 0.1 wt%, Cr ≤ 0.1 wt%, and V ≤ 0.1 wt%. In Si5210, Si ≥ 99.20 wt%, Fe ≤ 0.5 wt%, Al ≤ 0.2 wt%, Ca ≤ 0.1 wt%, Mn ≤ 0.3 wt%, Ti ≤ 0.1 wt%, Cr ≤ 0.1 wt%, and V ≤ 0.1 wt%. In Si5530, Si ≥ 98.70 wt%, Fe ≤ 0.5 wt%, Al ≤ 0.5 wt%, Ca ≤ 0.3 wt%, Mn ≤ 0.3 wt%, Ti ≤ 0.1 wt%, Cr ≤ 0.1 wt%, and V ≤ 0.1 wt%.

[0048] In steel scrap, Fe is 95-97 wt%, C is 0.04-2.3 wt%, Si is 0.04-2.3 wt%, Mn is 0.04-2.3 wt%, P is 0.04-2.3 wt%, S is 0.04-2.3 wt%, Sn≤0.6 wt%, Ti≤0.1 wt%, Cr≤0.1 wt%, and V≤0.1 wt%. C, Si, Mn, Ti, Cr, V, P, Sn, and S are impurities in steel scrap.

[0049] In magnesium alloy scrap, Mg is 96.8-99.9 wt%, Al is 1-3 wt%, Zn is 0.1-1 wt%, Mn≤0.1 wt%, Ti≤0.1 wt%, and Zr≤0.1 wt%. Al, Zn, Mn, Ti, and Zr are impurities in magnesium alloy scrap.

[0050] Waste recycling and reuse not only saves costs but also enables the sustainable development of aluminum, magnesium, silicon, and iron resources. Since the raw materials are mostly waste or recycled materials, this invention introduces a wide variety of impurities in high total content, resulting in a high number of impurities and a high overall impurity content. Of course, it is possible that one or more impurities may be present in high concentrations and difficult to remove. When using recycled aluminum, industrial silicon, steel scrap, and magnesium alloy scrap as raw materials, this invention introduces at least the following elements: Al, Fe, Si, Cu, Mn, Ti, Cr, V, Mg, Zn, Zr, Pb, Ca, C, P, Sn, and S. When using recycled aluminum, industrial silicon, steel scrap, and magnesium alloy scrap as raw materials, and without adding Zn, Zr, Cu, Mn, Cr, V, and Ca to the recycled aluminum melt, the Al-Si die-cast aluminum alloy based on recycled aluminum may contain 0.0001-0.2% Zn, 0.0001-0.1% Zr, 0.0001-0.2% Cu, 0.0001-0.1% Mn, 0.0001-0.2% Cr, 0.0001-0.1% V, and 0.0001-0.1% Ca by mass percentage. Alternatively, at least one of Zn, Zr, Cu, Mn, Cr, V, and Ca may be added to the recycled aluminum melt to increase the content of the added elements.

[0051] The method for preparing Al-Si die-cast aluminum alloys based on recycled aluminum of the present invention uses recycled aluminum, industrial silicon, steel scrap, and magnesium alloy scrap as raw materials, which can reduce costs. The addition of certain amounts of Sr, B, Ti, and Ni raw materials, combined with multiple refining processes, boriding processes, and aging processes, can achieve better overall performance. Specifically: (1) Industrial silicon can provide Si. When the mass percentage content of Si is 6-12%, it can improve the fluidity and density of aluminum alloys, thereby improving the forming performance and mechanical properties of aluminum alloys. When the mass percentage content of Si is 6-9%, the elongation is high, but the strength is low. When the mass percentage content of Si is 9-12%, the strength is high, but the elongation is low. When the mass percentage content of Si exceeds 12%, coarse elemental Si will appear, which will drastically reduce the elongation of aluminum alloys. (2) Iron scrap can provide Fe. When the mass percentage of Fe is 0.1-1%, Fe can reduce the sticking tendency of aluminum alloy castings and improve the forming performance of aluminum alloys. Fe can react with other elements to form a second phase, so as to avoid the adverse effects of Fe and other elements dissolved in the aluminum matrix on the thermal conductivity of aluminum alloys. Specifically, Fe can react with Al, Si, Mg, Cu, Mn, Ni, B and other elements to form second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiNi, AlFeMgSiNi, AlFeMnSi, FeNiAl9, and AlFeSiB. However, the presence of β-iron-rich phase in the aluminum matrix will reduce the elongation and thermal conductivity of aluminum alloys. (3) Magnesium alloy scrap can provide Mg. When the mass percentage of Mg is 0.4-3%, Mg can significantly improve the mechanical properties of aluminum alloys. Mg can react with other elements to form a second phase, so as to avoid the adverse effects of Mg elements dissolved in the aluminum matrix on the thermal conductivity of aluminum alloys. Specifically, Mg can react with Al, Fe, Si, Cu, Zn, B, Ni and other elements to form second phases such as MgB, Mg2Si, Mg2Zn, Mg2SiZn, (CuMg)Al2, AlFeMgSi, AlFeMgSiNi. Mg can also promote the precipitation of second phases such as CuAl2, AlFeSiCu, Al2CuZn, (CuMg)Al2, and increase their volume fraction and dispersion, so as to reduce the solid solubility of the above elements in the aluminum matrix and improve the thermal conductivity of aluminum alloys. (4) The mass percentage content of Sr is not greater than 0.1%. Sr can be modified by heterogeneous nucleation theory or twin valley mechanism to refine grains, eutectic silicon and other second phases and precipitated phases, thereby improving the elongation and thermal conductivity of aluminum alloys. Sr can also transform β-AlFeSi phase into Chinese character-shaped α-AlFeSi phase to improve the mechanical properties of aluminum alloys. Sr can also promote the precipitation of CuAl2, Mg2Si and other phases to reduce the solid solubility of these alloying elements in the aluminum matrix, thereby improving the thermal conductivity of aluminum alloys. (5) The mass percentage content of Ti is not greater than 0.3%. Ti can improve the strength and elongation of aluminum alloys. Specifically, the TiAl2 phase generated by the reaction of Ti and Al can serve as a non-spontaneous nucleus during crystallization, which can refine the grains, the second phase and the precipitated phase, thereby improving the strength and elongation of aluminum alloys. (6) The mass percentage content of B is not greater than 0.05%. B can transform the β-AlFeSi phase into the Chinese character-shaped α-AlFeSi phase to improve the mechanical properties of aluminum alloys. B can remove / improve the Fe phase and remove Mn+Ti+V+Cr through borylation reaction to purify the mixed solution, thereby improving the elongation and thermal conductivity of aluminum alloys. B can also refine the grains and modify and refine elemental Si to further improve the strength and elongation of aluminum alloys. B can also react with other elements to generate a second phase to avoid the adverse effects of B dissolved in the aluminum matrix on the thermal conductivity of aluminum alloys. Specifically, B can react with Al, Fe, Si, Mg, Cu, etc. to generate second phases such as AlFeSiB, MgB, and CuB. B can also inhibit the segregation of Ti3Al. The effect is better when Ti and B are used together, significantly improving the strength and elongation of aluminum alloys. (7) The mass percentage content of Ni is not greater than 2.5%. Ni can refine grains, form second phases and precipitates to improve the elongation of aluminum alloys. Ni can react with other elements to form second phases to avoid the adverse effects of Ni dissolved in the aluminum matrix on the thermal conductivity of aluminum alloys. Specifically, Ni can react with Al, Fe, Mg, Si and other elements to form second phases such as Al3Ni, AlFeSiNi, AlFeMgSiNi, and FeNiAl9. Ni can also promote the precipitation of phases such as CuAl2 and (CuMg)Al2, increase the volume fraction and dispersion of precipitates, reduce the solid solubility of alloying elements in the aluminum matrix, and improve the thermal conductivity of aluminum alloys. Ni can promote the precipitation of Cu and Mg to improve the thermal conductivity and mechanical properties of aluminum alloys. The content of Mg and Ni can be proportional. When the content of Mg is high, the content of Ni can also be set higher to generate more AlFeMgSiNi dispersed second phases to significantly improve the strength of aluminum alloys. (8) The two refining and boronizing processes can remove impurities such as oxide slag and organic matter, as well as low-melting-point impurities such as Pb, Sn, Fe, Mn, C, P, and S, reducing the content of Pb, Sn, C, P and S to below 0.001% or even 0%, thus avoiding the influence of Pb, Sn, coarse β-Fe, Mn, C, P, and S on the strength, elongation and thermal conductivity of the aluminum alloy. (9) The aging treatment can further improve the strength, elongation and thermal conductivity of aluminum alloys.

[0052] In summary, this invention adds a certain amount of industrial silicon, steel scrap, magnesium alloy scrap, Sr, B, Ti, and Ni to recycled aluminum melt. Si, Fe, Mg, Sr, B, Ti, and Ni interact and influence each other as a whole. After multiple refining, boronizing, and aging treatments, a high-performance Al-Si die-cast aluminum alloy based on recycled aluminum can be obtained. The Al-Si die-cast aluminum alloy based on recycled aluminum has a tensile strength of not less than 420 MPa, a yield strength of not less than 330 MPa, an elongation of not less than 9%, and a thermal conductivity of not less than 160 W / mK. The Al-Si die-cast aluminum alloy based on recycled aluminum has higher tensile strength, yield strength, elongation, and thermal conductivity than recycled aluminum alloys, which typically have higher tensile strength (250-280 MPa), yield strength (130-150 MPa), elongation (4-5%), and thermal conductivity (110-120 W / mK), and thus exhibits better overall performance.

[0053] Transition metal elements, such as Mn, Ti, Cr, and V, have a significant impact on the thermal conductivity of aluminum alloys. They are typically restricted from being added as impurities to aluminum alloys requiring high thermal performance. Excessive impurity content or inadequate treatment can also reduce the elongation of the aluminum alloy. The Al-Si die-cast aluminum alloy of this invention, based on recycled aluminum, uses recycled aluminum, industrial silicon, steel scrap, and magnesium alloy scrap as raw materials. These low-cost raw materials inevitably contain the aforementioned Mn, Ti, Cr, and V impurities, and it is possible that at least one of Mn, Ti, Cr, and V may be present in high concentrations. Completely removing or reducing these impurities to a low level (below 0.001 wt% or even 0.0001 wt%) would be costly. To avoid increasing costs, some impurities are often not completely removed or reduced to a low level, which is why many aluminum alloys made from recycled aluminum have low elongation and thermal conductivity. However, this application utilizes industrial silicon, steel scrap, and magnesium alloy scrap as raw materials, combined with two refining processes and boronizing treatment, and the combined effects of Sr, B, Ti, and Ni, to produce Al-Si die-cast aluminum alloys with excellent comprehensive performance. It eliminates the need for Mn, Ti, Cr, and V as impurities, and also avoids the need for extensive removal of Mn, Ti, Cr, and V, thus obtaining Al-Si die-cast aluminum alloys with superior comprehensive performance while controlling costs. Specifically, Ti, Cr, and V can act as strengthening elements to improve the strength of the aluminum alloy, while Mn can improve the elongation of the coarse β-Fe.

[0054] Understandably, the presence of Fe, Mn, Ti, V, and Cr in aluminum alloys causes a sharp decrease in thermal conductivity. During boriding, boron reacts with Fe, Mn, Ti, V, and Cr to form relatively heavy, insoluble borides, which are then precipitated and removed. Simultaneously, the Fe, Mn, Ti, V, and Cr compounds dissolved in the aluminum aggregate at the grain boundaries, significantly improving both mechanical and electrical properties. However, compared to alloys without the addition of Fe, Mn, Ti, V, and Cr, while mechanical properties are improved, thermal conductivity is still somewhat reduced.

[0055] In one embodiment, RE, Mo, Co, and Be elements can be added to the mixed melt. RE can be at least one of La, Ce, Pr, Nd, Er, Sm, Y, Sc, and Gd. Of course, one or more of RE, Mo, Co, and Be elements can also be added. The interaction of Mn, Cr, RE, Mo, Co, Be, and Sr elements can not only reduce their maximum solid solubility in the aluminum matrix to improve thermal conductivity, but also promote the reaction between Mn and Fe. Mn can occupy the position of Fe element in the second phase, making the Fe-containing phase more dispersed and fine, and promoting the effect of modified Fe. Mn, Cr, RE, Mo, Co, Be, and Sr elements can also form a finely dispersed α-Al(MnFeX)Si phase (where X is at least one of Cr, RE, Mo, Co, Be, and Sr) to improve the elongation and thermal conductivity of the aluminum alloy. In this case, the mass percentage content of Mn in the Al-Si die-cast aluminum alloy based on recycled aluminum can be 0.0001-0.1%, specifically 0.0001%, 0.0002%, 0.0003%, 0.0004%, 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.0 0.07%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1% by mass; the Cr content can be 0.0001-0.2%, specifically 0.0001%, 0.0005%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, or 0.007%. 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%; the percentage content of RE by mass can be 0.001-0.2%, specifically 0.001%, 0. 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%; the mass percentage content of Mo can be 0-0.3%, specifically 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%. The percentages of Co (co) can be 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3% by mass; specifically, the percentage of Co can be 0-0.5%, specifically 0.0001%, 0.0005%, 0.0006%, 0.0007%, 0.0008%, or 0.00%. 0.9%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5% by mass; the Be content can be 0-0.2%, specifically 0.0001%, 0.0005%, 0. 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%.

[0056] When Mn, Cr, RE, Mo, Co, Be, and Sr elements are combined, Mn and Cr can be excluded as impurities in high thermal conductivity aluminum alloys. In fact, when Mn and Cr are combined with RE, Mo, Co, Be, and Sr, they can improve the elongation and thermal conductivity of aluminum alloys. Of course, Mn and Cr can also be added to the mixed melt as raw materials, or Mn can be omitted. In this case, the mass percentage content of Mn in the Al-Si die-cast aluminum alloy based on recycled aluminum is 0.0001-0.2%, specifically 0.0001%, 0.0002%, 0.0003%, 0.0004%, 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.0 2%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2% by mass; the Cr content is 0.001-0.3%, specifically 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%. %, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%; the mass percentage content of RE is 0.01-0.2%, specifically 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%; the mass percentage content of Mo can be 0-0.3%, specifically 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%; the mass percentage content of Co can be 0-0.5%, specifically 0.0001%, 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%. The content of Be (Be) can be 0.35%, 0.4%, 0.45%, or 0.5% by mass; specifically, it can be 0.0001%, 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%.

[0057] In the Al-Si die-cast aluminum alloy based on recycled aluminum, when the Ni mass percentage reaches 2% or more, primary Al-Ni-Cu ternary compounds and eutectic Al-Ni-Cu ternary compounds will form in the aluminum alloy microstructure, which can significantly improve the thermal conductivity and strength of the aluminum alloy. If the Al-Si die-cast aluminum alloy based on recycled aluminum also contains Mn (Mn can come from waste materials), eutectic Al-Si-Cu-Ni-Mn pentagonal compounds will also crystallize, reducing the solid solubility of Mn in the matrix and further improving the thermal conductivity and strength of the aluminum alloy.

[0058] The method for preparing the high-strength Al-Si die-cast aluminum alloy further includes the step of adding at least one of SiC, AlTiC, and BN to the recycled aluminum melt. In the high-strength Al-Si die-cast aluminum alloy, the mass percentage content of SiC is 0.1-8%, the mass percentage content of AlTiC is 0.1-8%, and the mass percentage content of BN is 0.1-0.5%. Specifically, the mass percentage content of SiC and AlTiC can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8%. The specific percentage content of BN by mass can be 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.5%.

[0059] SiC, AlTiC, and BN all exhibit excellent grain refinement effects. When used in combination, reducing the content of each individual component can achieve optimal grain refinement. When SiC is combined with Ti and B, a C-TiB2 particle complex is formed at the SiC-Al interface. The C atoms in SiC tend to enhance the adhesion energy of the C-TiB2 / Al interface, causing the originally elongated TiAl3 to break down and shorten, thus preventing the enrichment and growth of TiAl3 and greatly enhancing the composite grain refinement effect. BN disperses AlB2 and AlN nanonuclei at the aluminum matrix interface and grain boundaries, which can refine the grains and promote uniform grain nucleation, thereby improving the elongation of the aluminum alloy. Under the influence of SiC, Ti, B, and BN, AlTiC is less prone to aggregation and has a better grain refinement strengthening effect.

[0060] The preparation method of the high-strength Al-Si die-cast aluminum alloy further includes the step of adding V to the recycled aluminum melt, wherein the mass percentage content of V is 0.005-0.2%. Specifically, the mass percentage content of V can be 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. Although V reduces thermal conductivity, it can improve the elongation and strength of the aluminum alloy. Specifically, V forms Al3V, Al... 10 V, VAl11, VB2, AlB 2、 Al(VB)₂, a refractory compound, can refine grains and promote dispersion strengthening, thereby improving the strength and elongation of aluminum alloys. Especially in Al-Si alloys with a Si content greater than 4%, the addition of Si lowers the melting point of Al melt, resulting in a liquidus temperature lower than the Al-B eutectic temperature, thus promoting the formation of Al(VB)₂ in the Al-Si alloy. Under the influence of Si, the structure of Al(VB)₂ changes, its stability increases, thereby enhancing its heterogeneous nucleation ability and significantly promoting grain refinement.

[0061] Since most elements (except V in this invention) are already dissolved in the aluminum matrix to avoid adverse effects on thermal conductivity, and certain elements (such as B, Ni, Mn, Cr, RE, Mo, Co, Be, SiC, AlTiC, Ti, B, BN, and Sr) significantly improve thermal conductivity, V can also be added as a raw material to the recycled aluminum melt to improve the elongation and strength of the aluminum alloy. When Ti, V, Cr, and Ni are added simultaneously, the original blocky or coarse strip-shaped Al-Ti, Al-V, Al-Cr, and Al-Ni compounds will be transformed into round, fine, blocky, and complex Al-Ti-V-Cr-Ni compounds distributed within the grains and at the grain boundaries. In this way, Ti, V, and Cr can be added as raw materials to the recycled aluminum melt.

[0062] When Cu, Zn, Zr, and Ca are not added to the mixed melt, the Al-Si die-cast aluminum alloy based on recycled aluminum may also contain 0.0001-0.2% Cu, 0.0001-0.2% Zn, 0.0001-0.1% Zr, and 0.0001-0.1% Ca by mass percentage. Cu, Zn, Zr, and Ca can all improve the strength of the aluminum alloy. Ca can also remove H from the recycled aluminum melt, refine grains and second phases, and improve the morphology of β-Fe phase and eutectic silicon, thereby increasing the elongation of the aluminum alloy. Zr can also refine grains, second phases, and precipitated phases, thereby increasing the elongation of the aluminum alloy. Zn can eliminate elemental Si to reduce the adverse effects of elemental Si on the properties of the aluminum alloy. Zn can also promote the precipitation of second phases such as Mg2Si, Al2Cu, and Mg3Sb2, thereby improving strength and thermal conductivity. Elements such as Cu, Zn, Zr, and Ca introduced from waste materials can react with other elements to form Al2CuZn, AlFeSiCu, (CuMg)Al2, AlCaCu, AlCa, Mg2SiZn, Al2CuZn, MgZn2, Al3Zr, etc., thus avoiding the adverse effects of Cu, Zn, Zr, and Ca dissolving in the aluminum matrix on the strength, elongation, and thermal conductivity of the aluminum alloy. The mass percentage content of Cu can be 0.0001%, 0.0005%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. The mass percentage content of Zn and Zr can be 0.0001%, 0.0005%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%.The mass percentage content of Ca can be 0.0001%, 0.0005%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0063] At least one of Cu, Zn, Zr, and Ca may also be added to the recycled aluminum melt. In this case, the Al-Si die-cast aluminum alloy based on recycled aluminum contains 0.0001-1% Cu, 0.0001-1% Zn, 0.0001-0.5% Zr, and 0.0001-0.3% Ca by mass. The mass percentage content of Cu and Zn can be 0.0001%, 0.0005%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, or 1%. The Zr content by mass percentage can be 0.0001%, 0.0005%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%. %, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.5%.The mass percentage content of Ca can be 0.0001%, 0.0005%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%.

[0064] The method for preparing the Al-Si die-cast aluminum alloy based on recycled aluminum further includes the step of adding at least one of Te, Ag, Sb, Bi, and Nb to the recycled aluminum melt. In the Al-Si die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Te is 0-0.2%, the mass percentage content of Ag is 0-0.2%, the mass percentage content of Sb is 0-0.5%, the mass percentage content of Bi is 0-0.2%, and the mass percentage content of Nb is 0-0.5%. The refining effect of Te and Ag can refine the second phase, thereby improving the elongation of the aluminum alloy. Bi and Sb can improve the strength of the aluminum alloy. Nb can refine the grains and the second phase, thus improving the elongation. Bi can effectively prevent sodium embrittlement; even when the mass percentage content of Mg is high, such as 2-3%, sodium embrittlement will not occur. Bi can also reduce the surface tension of the aluminum melt, reduce the contact angle between Al and Si, making it easier for the Si growth tip to be suppressed by Al, thereby reducing the size of the eutectic silicon.

[0065] The specific mass percentage content of Te, Ag, and Bi can be 0.0001%, 0.0005%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. The specific mass percentage contents of Sb and Nb can be 0.0001%, 0.0005%, 0.001%, 0.005%, 0.01%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0. 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.5%.

[0066] This invention also provides an Al-Si die-cast aluminum alloy based on recycled aluminum, prepared by the above-described method for preparing Al-Si die-cast aluminum alloys based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum further contains 6-12% Si, 0.1-1% Fe, 0.4-3% Mg, 0-0.1% Sr, 0-0.3% Ti, 0-0.05% B, and 0-2.5% Ni by mass. The Al-Si die-cast aluminum alloy based on recycled aluminum further contains at least one of Zn, Cu, Ca, Mn, Cr, V, RE, Mo, Co, Be, Zr, Te, Ag, Sb, Bi, and Nb. In the Al-Si die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Zn is 0.0001-1%, Cu is 0.0001-1%, Ca is 0.0001-0.3%, Mn is 0.0001-0.2%, Cr is 0.001-0.3%, V is 0.005-0.2%, RE is 0.01-0.2%, Mo is 0-0.3%, Co is 0-0.5%, Be is 0-0.2%, Zr is 0.0001-0.5%, Te is 0-0.2%, Ag is 0-0.2%, Sb is 0-0.5%, Bi is 0-0.2%, and Nb is 0-0.5%.

[0067] This invention also provides a structural component, at least a portion of which is made of the aforementioned Al-Si die-cast aluminum alloy based on recycled aluminum or an Al-Si die-cast aluminum alloy based on recycled aluminum prepared by the aforementioned method. This structural component can be applied to filter housings for communication base stations, heat dissipation substrates for communication base stations, cabinet housings for communication base stations, housings for automotive electrical components, automotive housings, heat sinks for computer equipment, mid-plates for mobile phones, mobile phone housings, heat sinks for LED lights, thin components for 5G products, and applications in aerospace, high-speed rail, shipbuilding, mobile devices, home appliances, chemical industry, daily necessities, and construction.

[0068] Example 1 Recycled aluminum is heated to obtain recycled aluminum melt; The temperature was adjusted to 740°C, and industrial silicon, steel scrap, and Ni were added to the recycled aluminum melt to obtain a mixed melt. The mixed melt is subjected to boronizing treatment and a first refining treatment. The boronizing agent for the boronizing treatment is an aluminum-boron alloy, and the mass ratio of the aluminum-boron alloy to the mixed melt is 0.001:1. The temperature of the first refining treatment is 800°C, the time is 20 min, and the refining agent is sodium chloride, and the mass ratio of sodium chloride to the mixed melt is 0.0001:1. The temperature was adjusted to 710°C, and magnesium alloy scrap, Sr, and Al-Ti-B alloy were added to the mixed melt after the first refining treatment. The mixed melt underwent a second refining treatment, slag removal, degassing, and settling. After settling, surface slag was removed. The second refining treatment was performed at 690°C for 10 minutes, using potassium chloride as the refining agent, with a potassium chloride to mixed melt mass ratio of 0.2:1. The components and their contents in the mixed melt after the settling treatment are measured. When the components and their contents in the mixed melt meet the standards, the mixed melt is die-cast to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum contains 12% Si, 0.5% Fe, 3% Mg, 0.05% Sr, 0.1% Ti, 0.01% B, and 0.1% Ni by mass.

[0069] Example 2 Recycled aluminum is heated to obtain recycled aluminum melt; The temperature was adjusted to 740°C, and industrial silicon, steel scrap, and Ni were added to the recycled aluminum melt to obtain a mixed melt. The mixed melt is subjected to borying treatment and a first refining treatment. The borying agent for the borying treatment is potassium fluoroborate, and the mass ratio of potassium fluoroborate to the mixed melt is 0.001:1. The temperature of the first refining treatment is 740°C and the time is 20 min. The refining agent includes 40 wt% sodium chloride, 40 wt% calcium fluoride, and 20 wt% rare earth Y, and the mass ratio of the refining agent to the mixed melt is 0.0001:1. The temperature was adjusted to 710°C, and magnesium alloy scrap, Sr, and Al-Ti-B alloy were added to the mixed melt after the first refining treatment. The mixed melt underwent a second refining treatment, slag removal, degassing, and settling. After settling, surface slag was removed. The second refining treatment was performed at 690°C for 10 minutes. The refining agent included 50 wt% sodium chloride and 50 wt% sodium aluminum fluoride, with a refining agent to mixed melt mass ratio of 0.2:1. The components and their contents in the mixed melt after the settling treatment are measured. When the components and their contents in the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum contains 12% Si, 0.5% Fe, 1.5% Mg, 0.1% Sr, 0.1% Ti, 0.01% B, 0.1% Ni, 0.001% Zn, 0.005% Zr, 0.01% Cu, 0.0001% Mn, 0.005% Cr, 0.005% V, and 0.0001% Ca by mass. The aging treatment includes a first-stage low-temperature electric field aging treatment and a second-stage high-temperature aging treatment. The first-stage low-temperature electric field aging treatment is performed at a temperature of 40°C for 1 hour, with an electric field strength of 2V / cm. The second-stage high-temperature aging treatment is performed at a temperature of 140°C for 1 hour.

[0070] Example 3 Recycled aluminum is heated to obtain recycled aluminum melt; The temperature was adjusted to 745°C, and industrial silicon, steel scrap, and Ni were added to the recycled aluminum melt to obtain a mixed melt. The mixed melt is subjected to boronizing treatment and a first refining treatment. The boronizing agent for the boronizing treatment is an aluminum-boron alloy, and the mass ratio of the aluminum-boron alloy to the mixed melt is 0.002:1. The temperature of the first refining treatment is 800°C, the time is 25 min, and the refining agent is sodium aluminum fluoride, and the mass ratio of sodium aluminum fluoride to the mixed melt is 0.0002:1. The temperature was adjusted to 715°C, and magnesium alloy scrap, Sr, RE, Mo, Co, Cr, Be, and Al-Ti-B alloy were added to the mixed melt after the first refining treatment. The mixed melt underwent a second refining treatment, slag removal, degassing, and settling. After settling, surface slag was removed. The second refining treatment was performed at 695°C for 15 minutes. The refining agent included 60 wt% potassium chloride, 10 wt% rare earth lanthanum, and 30 wt% potassium fluoride, with a refining agent to mixed melt mass ratio of 0.001:1. The components and their contents in the mixed melt after the settling treatment are measured. When the components and their contents in the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum contains 11% Si, 0.2% Fe, 1.2% Mg, 0.02% Sr, 0.05% Ti, 0.03% B, 0.2% Ni, 0.1% RE, 0.01% Mo, 0.01% Co, 0.01% Be, 0.01% Cr, and 0.0005% Mn by mass. The aging treatment includes a first-stage low-temperature electric field aging treatment and a second-stage high-temperature aging treatment. The first-stage low-temperature electric field aging treatment is performed at a temperature of 55°C for 1.5 hours with an electric field strength of 5V / cm. The second-stage high-temperature aging treatment is performed at a temperature of 145°C for 5 hours.

[0071] Example 4 Recycled aluminum is heated to obtain recycled aluminum melt; The temperature was adjusted to 750°C, and industrial silicon, steel scrap, and Ni were added to the recycled aluminum melt to obtain a mixed melt. The mixed melt is subjected to boronizing treatment and a first refining treatment. The boronizing agent for the boronizing treatment is an aluminum-boron alloy, and the mass ratio of the aluminum-boron alloy to the mixed melt is 0.003:1. The temperature of the first refining treatment is 750°C, the time is 30 min, and the refining agent is potassium fluoroborate, and the mass ratio of potassium fluoroborate to the mixed melt is 0.0003:1. The temperature was adjusted to 720°C, and magnesium alloy scrap, Sr, RE, Mo, Co, Be, Cr, Mn, V, and Al-Ti-B alloy were added to the mixed melt after the first refining treatment. The mixed melt underwent a second refining treatment, slag removal, degassing, and settling. After settling, surface slag was removed. The second refining treatment was performed at 700°C for 20 minutes. The refining agent included 50 wt% potassium chloride and 50 wt% calcium fluoride, with a refining agent to mixed melt mass ratio of 0.03:1. The components and their contents in the mixed melt after the settling treatment are measured. When the components and their contents in the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum contains 10% Si, 1% Fe, 1.1% Mg, 0.05% Sr, 0.15% Ti, 0.05% B, 0.6% Ni, 0.05% RE, 0.1% Mo, 0.1% Co, 0.1% Be, 0.2% Cr, 0.2% Mn, and 0.005% V by mass. The aging treatment includes a first-stage low-temperature electric field aging treatment and a second-stage high-temperature aging treatment. The first-stage low-temperature electric field aging treatment is performed at a temperature of 60°C for 10 hours, with an electric field strength of 10V / cm. The second-stage high-temperature aging treatment is performed at a temperature of 150°C for 10 hours.

[0072] Example 5 Recycled aluminum is heated to obtain recycled aluminum melt; The temperature was adjusted to 770°C, and industrial silicon, steel scrap, and Ni were added to the recycled aluminum melt to obtain a mixed melt. The mixed melt is subjected to boronizing treatment and a first refining treatment. The boronizing agent for the boronizing treatment is an aluminum-boron alloy, and the mass ratio of the aluminum-boron alloy to the mixed melt is 0.004:1. The temperature of the first refining treatment is 780°C and the time is 40 min. The refining agent is lithium chloride, and the mass ratio of lithium chloride to the mixed melt is 0.0004:1. The temperature was adjusted to 780°C, and magnesium alloy scrap, Sr, Zn, Zr, Cu, Ca, and Al-Ti-B alloy were added to the mixed melt after the first refining treatment. The mixed melt underwent a second refining treatment, slag removal, degassing, and settling. After settling, surface slag was removed. The second refining treatment was performed at 750°C for 20 minutes. The refining agent included 80 wt% potassium chloride, 1 wt% scandium oxide, 1 wt% nano-boron nitride, and 18 wt% potassium fluoride. The mass ratio of the refining agent to the mixed melt was 0.1:1. The components and their contents in the mixed melt after the settling treatment are measured. When the components and their contents in the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum contains 9% Si, 0.1% Fe, 1% Mg, 0.02% Sr, 0.2% Ti, 0.02% B, 0.5% Ni, 0.2% Zn, 0.01% Zr, 0.1% Cu, and 0.001% Ca by mass. The aging treatment includes a first-stage low-temperature electric field aging treatment and a second-stage high-temperature aging treatment. The first-stage low-temperature electric field aging treatment is performed at a temperature of 65°C for 20 hours with an electric field strength of 20V / cm. The second-stage high-temperature aging treatment is performed at a temperature of 200°C for 50 hours.

[0073] Example 6 The mold is surface treated to form a 1mm boron carbide layer on the parting surface of the mold; Recycled aluminum is heated to obtain recycled aluminum melt; The temperature was adjusted to 800°C, and industrial silicon, steel scrap, and Ni were added to the recycled aluminum melt to obtain a mixed melt. The mixed melt is subjected to boronizing treatment and a first refining treatment. The boronizing agent for the boronizing treatment is 50 wt% aluminum-boron alloy and 50 wt% potassium fluoroborate, and the mass ratio of the boronizing agent to the mixed melt is 0.005:1. The temperature of the first refining treatment is 780°C and the time is 40 min. The refining agent is potassium fluoroborate, and the mass ratio of potassium fluoroborate to the mixed melt is 0.0005:1. The temperature was adjusted to 780°C, and magnesium alloy scrap, Sr, Te, Ag, Sb, Bi, Nb, and Al-Ti-B alloy were added to the mixed melt after the first refining treatment. The mixed melt underwent a second refining treatment, slag removal, degassing, and settling. After settling, surface slag was removed. The second refining treatment was performed at 690°C for 10 minutes. The refining agent included 80 wt% potassium chloride, 5 wt% ytterbium oxide, and 15 wt% potassium fluoride, with a refining agent to mixed melt mass ratio of 0.2:1. The components and their contents in the mixed melt after the settling treatment are measured. When the components and their contents in the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum contains 8% Si, 0.3% Fe, 2% Mg, 0.05% Sr, 0.3% Ti, 0.05% B, 1% Ni, 0.001% Te, 0.001% Ag, 0.001% Sb, 0.001% Bi, and 0.001% Nb by mass. The aging treatment includes a first-stage low-temperature electric field aging treatment and a second-stage high-temperature aging treatment. The first-stage low-temperature electric field aging treatment is performed at a temperature of 120°C for 0.1 hours with an electric field strength of 50 V / cm. The second-stage high-temperature aging treatment is performed at a temperature of 200°C for 0.1 hours.

[0074] Example 7 The mold is surface treated to form a 10mm boron carbide layer on the parting surface of the mold; Recycled aluminum is heated to obtain recycled aluminum melt; The temperature was adjusted to 860°C, and industrial silicon, steel scrap, and Ni were added to the recycled aluminum melt to obtain a mixed melt. The mixed melt is subjected to boronizing treatment and a first refining treatment. The boronizing agent for the boronizing treatment is an aluminum-boron alloy, and the mass ratio of the aluminum-boron alloy to the mixed melt is 0.001:1. The temperature of the first refining treatment is 750°C and the time is 60 min. The refining agent includes 70 wt% potassium chloride, 10 wt% ytterbium oxide, and 20 wt% potassium fluoride, and the mass ratio of the refining agent to the mixed melt is 0.0001:1. The temperature was adjusted to 760°C, and magnesium alloy scrap, Sr, V, AlTiC, SiC, BN, RE, and Al-Ti-B alloy were added to the mixed melt after the first refining treatment. The mixed melt underwent a second refining treatment, slag removal, degassing, and settling. After settling, surface slag was removed. The second refining treatment was performed at 740°C for 40 minutes. The refining agent included 70 wt% potassium chloride, 10 wt% ytterbium oxide, and 20 wt% potassium fluoride, with a refining agent to mixed melt mass ratio of 0.02:1. The components and their contents in the mixed melt after the settling treatment are measured. When the components and their contents in the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum contains 7% Si, 0.6% Fe, 2.5% Mg, 0.01% Sr, 0.25% Ti, 0.01% B, 2% Ni, 0.01% Cr, 0.01% V, 0.1% AlTiC, 0.1% SiC, 0.1% BN, 0.0001% Mn, and 0.01% RE. The aging treatment includes a first-stage low-temperature electric field aging treatment and a second-stage high-temperature aging treatment. The first-stage low-temperature electric field aging treatment is performed at a temperature of 120°C for 0.1 hours with an electric field strength of 20 V / cm. The second-stage high-temperature aging treatment is performed at a temperature of 250°C for 1 hour.

[0075] Example 8 The mold is surface treated to form a 2mm boron carbide layer on the parting surface of the mold; Recycled aluminum is heated to obtain recycled aluminum melt; The temperature was adjusted to 850°C, and industrial silicon, steel scrap, and Ni were added to the recycled aluminum melt to obtain a mixed melt. The mixed melt is subjected to boronizing treatment and a first refining treatment. The boronizing agent for the boronizing treatment is an aluminum-boron alloy, and the mass ratio of the aluminum-boron alloy to the mixed melt is 0.002:1. The temperature of the first refining treatment is 750°C and the time is 40 min. The refining agent includes 60 wt% potassium chloride, 20 wt% ytterbium oxide, and 20 wt% potassium fluoride, and the mass ratio of the refining agent to the mixed melt is 0.0001:1. The temperature was adjusted to 760°C, and magnesium alloy scrap, Sr, V, Te, RE, and Al-Ti-B alloy were added to the mixed melt after the first refining treatment. The mixed melt underwent a second refining treatment, slag removal, degassing, and settling. After settling, surface slag was removed. The second refining treatment was performed at 730°C for 10 minutes, using sodium chloride as the refining agent, with a sodium chloride to mixed melt mass ratio of 0.01:1. The components and their contents in the mixed melt after the settling treatment are measured. When the components and their contents in the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum contains 6% Si, 0.4% Fe, 2% Mg, 0.02% Sr, 0.2% Ti, 0.01% B, 2.5% Ni, 0.01% Cr, 0.01% V, 0.01% Te, 0.01% RE, and 0.0001% Mn by mass. The aging treatment includes a first-stage low-temperature electric field aging treatment and a second-stage high-temperature aging treatment. The first-stage low-temperature electric field aging treatment is performed at a temperature of 120°C for 100 hours with an electric field strength of 50 V / cm. The second-stage high-temperature aging treatment is performed at a temperature of 140°C for 50 hours.

[0076] Please refer to Table 1 for the composition and content of the aluminum alloys in Examples 1 to 8.

[0077] Table 1. Composition and content of aluminum alloys in Examples 1 to 8 For the sake of simplicity, the contents of all impurity elements are not shown in the examples.

[0078] Table 2 Performance test results of aluminum alloys in Examples 1 to 8 Table 2 shows that the aluminum alloys of Examples 1 to 8 have better tensile strength, yield strength, elongation, and thermal conductivity. The aluminum alloys of Examples 2 to 8, after aging treatment, have a tensile strength of not less than 420 MPa, a yield strength of not less than 330 MPa, an elongation of not less than 9%, and a thermal conductivity of not less than 160 W / mK.

[0079] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the content of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum, comprising the following steps: Recycled aluminum is heated to obtain recycled aluminum melt; The temperature is adjusted to 740-860°C, and industrial silicon, steel scrap, and Ni are added to the recycled aluminum melt to obtain a mixed melt; The mixed melt is subjected to borying and a first refining process; Adjust the temperature to 710-780°C, add magnesium alloy scrap, Sr source, Ag source, Nb source, V source and Al-Ti-B alloy to the mixed melt after the first refining treatment, and then perform a second refining treatment on the mixed melt. and The components and their contents in the mixed melt after the second refining process are measured. When the components and their contents in the mixed melt after the second refining process meet the standards, the mixed melt is subjected to die casting to obtain an Al-Si die-cast aluminum alloy based on recycled aluminum. The Al-Si die-cast aluminum alloy based on recycled aluminum contains 6-12% Si, 0.1-1% Fe, 0.4-3% Mg, and 0-0.1% S by mass. r, Ti with a mass percentage content of 0-0.3%, B with a mass percentage content of 0-0.05%, Ag with a mass percentage content of 0-0.2%, Nb with a mass percentage content of 0-0.5%, V with a mass percentage content of 0.005-0.2%, SiC with a mass percentage content of 0.005-0.2%, AlTiC with a mass percentage content of 0.005-0.2%, BN with a mass percentage content of 0.005-0.2%, and Ni with a mass percentage content of 0-2.5%.

2. The method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum according to claim 1, characterized in that, The method for preparing the Al-Si die-cast aluminum alloy based on recycled aluminum further includes the step of adding RE, Mo, Co and Be to the recycled aluminum melt. In the Al-Si die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Mn is 0.0001-0.1%, the mass percentage content of Cr is 0.0001-0.2%, the mass percentage content of RE is 0.001-0.2%, the mass percentage content of Mo is 0-0.3%, the mass percentage content of Co is 0-0.5%, and the mass percentage content of Be is 0-0.2%.

3. The method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum according to claim 1, characterized in that, The method for preparing the Al-Si die-cast aluminum alloy based on recycled aluminum further includes the step of adding Mn, Cr, RE, Mo, Co and Be to the recycled aluminum melt. In the Al-Si die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Mn is 0.0001-0.2%, the mass percentage content of Cr is 0.001-0.3%, the mass percentage content of RE is 0.01-0.2%, the mass percentage content of Mo is 0-0.3%, the mass percentage content of Co is 0-0.5%, and the mass percentage content of Be is 0-0.2%.

4. The method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum according to claim 1, characterized in that, The method for preparing the Al-Si die-cast aluminum alloy based on recycled aluminum further includes the step of adding at least one of Cu, Zr, Ca, Te, Sb, and Bi to the recycled aluminum melt. In the Al-Si die-cast aluminum alloy based on recycled aluminum, the mass percentage content of Cu is 0.0001-1%, the mass percentage content of Zr is 0.0001-0.5%, the mass percentage content of Ca is 0.0001-0.3%, the mass percentage content of Te is 0-0.2%, the mass percentage content of Sb is 0-0.5%, and the mass percentage content of Bi is 0-0.2%.

5. The method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum according to any one of claims 1-4, characterized in that, The method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum further includes the step of adding at least one of SiC, AlTiC, and BN to the recycled aluminum melt. In the Al-Si die-cast aluminum alloy based on recycled aluminum, the mass percentage content of SiC is 0.1-8%, the mass percentage content of AlTiC is 0.1-8%, and the mass percentage content of BN is 0.1-0.5%.

6. The method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum according to any one of claims 1-4, characterized in that, At least one of the following conditions must be met: The borizing agent used in the borization treatment is potassium fluoroborate and / or aluminum-boron alloy; The mass ratio of the borizing agent to the mixed melt in the borination treatment is 0.001-0.005:1; The first refining process is carried out at a temperature of 740-800°C for 20-60 minutes. The refining agent for the first refining process is at least one of chloride salts, fluoride salts, and rare earth elements. The mass ratio of the refining agent to the mixed melt in the first refining treatment is 0.0001-0.0005:1; The second refining process is carried out at a temperature of 690-750°C for 10-40 minutes. The refining agent for the second refining process includes at least one of chloride salts, fluoride salts, and rare earth elements. The mass ratio of the refining agent to the mixed melt in the second refining process is 0.001-0.2:

1.

7. The method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum according to any one of claims 1-4, characterized in that, After die-casting the mixed melt to obtain aluminum alloy parts, the method for preparing Al-Si die-cast aluminum alloy based on recycled aluminum further includes an aging treatment step for the aluminum alloy parts, wherein... The aging treatment is performed at a temperature of 150-250℃ for a time of 0.05-30 hours; or The aging treatment includes a first-stage low-temperature electric field aging treatment and a second-stage high-temperature aging treatment. The first-stage low-temperature electric field aging treatment is performed at a temperature of 50-120℃ for a time of 0.1-100h, with an electric field strength of 2-50kV / cm. The second-stage high-temperature aging treatment is performed at a temperature of 140-250℃ for a time of 0.1-50h.

8. An Al-Si die-cast aluminum alloy based on recycled aluminum, containing Al, characterized in that, The Al-Si die-cast aluminum alloy based on recycled aluminum also contains 6-12% Si, 0.1-1% Fe, 0.4-3% Mg, 0-0.1% Sr, 0-0.3% Ti, 0-0.05% B, 0-0.2% Ag, 0-0.5% Nb, 0.005-0.2% V, and 0-2.5% Ni by mass.

9. The Al-Si die-cast aluminum alloy based on recycled aluminum according to claim 8, characterized in that, The Al-Si die-cast aluminum alloy based on recycled aluminum further contains at least one of Cu, Ca, Zr, Te, Sb, Bi, RE, Mo, Co, Be, SiC, AlTiC, and BN, wherein the mass percentage content of Cu is 0.0001-1%, the mass percentage content of Ca is 0.0001-0.3%, the mass percentage content of Zr is 0.0001-0.5%, the mass percentage content of Te is 0-0.2%, the mass percentage content of Sb is 0-0.5%, the mass percentage content of Bi is 0-0.2%, the mass percentage content of RE is 0.001-0.2%, the mass percentage content of Mo is 0-0.3%, the mass percentage content of Co is 0-0.5%, the mass percentage content of Be is 0-0.2%, the mass percentage content of SiC is 0.1-8%, the mass percentage content of AlTiC is 0.1-8%, and the mass percentage content of BN is 0.1-0.5%.

10. A structural component, characterized in that, The material of the structural component is the Al-Si die-cast aluminum alloy based on recycled aluminum prepared by the preparation method of Al-Si die-cast aluminum alloy based on recycled aluminum as described in any one of claims 1-7, or the Al-Si die-cast aluminum alloy based on recycled aluminum as described in any one of claims 8-9.

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