Al-si-mg aluminum alloy, method for preparing same, and use thereof

Abstract

The application provides an Al-Si-Mg aluminum alloy, a preparation method and application thereof. The Al-Si-Mg aluminum alloy comprises, in terms of weight percentage of the Al-Si-Mg aluminum alloy: 7.6-8.6wt% Si, 0.3-0.6wt% Mg, 0.08-0.15wt% Cu, 0.05-0.15wt% Mn, 0.08-0.13wt% Fe, 0.07-0.2wt% Ti, 0.01-0.025wt% Sr, 0.01-0.03wt% V, 0.005-0.01wt% Nb, and the balance of Al and inevitable impurity elements; wherein the total content of the inevitable impurity elements is less than or equal to 0.3%, the weight ratio of Cu to Mg is 1:(2-6), the weight ratio of Mn to Fe is (0.5-1):1, and Fe+2Mn is less than or equal to 0.4%.

Description

Technical Field

[0001] This invention relates to the field of metallic materials technology, and more specifically, to an Al-Si-Mg aluminum alloy, its preparation method, and its applications. Background Technology

[0002] The primary challenge in using aluminum alloy materials for lightweight subframes in new energy vehicles lies in their high material cost. In the new energy vehicle sector, the frame, as a core component, typically requires extensive use of aluminum alloys for lightweight design, significantly increasing overall vehicle manufacturing costs. Optimizing lightweight aluminum alloy subframes also involves material selection and processing. Choosing high-strength aluminum alloys improves the frame's strength-to-weight ratio, allowing it to withstand greater loads for the same weight. Furthermore, processes such as heat treatment and alloying can further enhance the performance of aluminum alloys. Heat treatment significantly improves the strength and ductility of aluminum alloys, while alloying improves their corrosion resistance and processing properties. The application of these material processing technologies allows aluminum alloy frames to maintain lightweight design while achieving better overall performance.

[0003] Lightweighting is driving the continuous thinning of aluminum castings and their development into high-load hollow structural components, leading to increasingly demanding performance requirements for aluminum alloys in product development. While A356 aluminum alloy has been used in low-pressure, gravity, and differential pressure casting, it can no longer meet the lightweighting needs of high-load components. For large automotive low-pressure cast aluminum alloy structural components, which require high strength, toughness, excellent corrosion resistance, and casting performance, OEMs and die-casting companies typically require a yield strength exceeding 260 MPa and an elongation exceeding 8%. Therefore, there is an urgent need to develop a new type of high-strength, high-toughness low-pressure cast aluminum alloy.

[0004] Existing literature (publication number CN117737523A) discloses a method for preparing a low-pressure cast aluminum alloy and its thin-walled parts. The chemical composition and mass percentage of the aluminum alloy are as follows: Si: 6.5–9 wt.%, Mg: 0.2–0.7 wt.%, Fe: 0.1–0.25 wt.%, Ti: 0.01–0.18 wt.%, Mn: 0.05–0.3 wt.%, Cr: 0.05–0.2 wt.%, Cu: 0.01–0.5 wt.%, with the balance being Al and unavoidable impurity elements. This literature optimizes the microalloying composition of the aluminum alloy, strengthens it through composite solid solution treatment of Cr, Mn, and Cu, and combines appropriate preparation and aging processes to achieve a yield strength greater than 135 MPa and an elongation of 8.3–9.8%. However, the Cr element added in this paper will significantly increase the viscosity of the aluminum alloy, reduce its flow properties, and reduce the yield of castings, which is not conducive to industrial application. In addition, the actual mechanical properties of the aluminum alloy are low, which does not meet the service requirements of automobiles for hollow low-pressure structural components.

[0005] Existing literature (publication number CN116254442B) discloses a high-yield-strength cast Al-Si alloy and its preparation method. The cast Al-Si alloy comprises the following components and mass percentages: Si: 9.0–12.5%, but not equal to 9.0%; Mg: 0.3–0.8%; Cu: 0.2–1.6%; Zn: 0.2–1.6%; Mn: 0–1.0%; Fe ≤0.5%; Zr: 0–0.25%; Ti: 0.05–0.25%; Cr: 0–0.25%; Re: 0–0.3%; Sr: 0.02–0.2%, with the balance being Al and unavoidable impurities. The total impurity content in the alloy is ≤1.0%, and the content of a single impurity is ≤0.15%. This literature optimizes the proportions of each alloying element, increasing the Si and Mg content, and introducing other alloying elements to further enhance the solid solution strengthening effect in the alloy, resulting in high strength while maintaining high plasticity. However, excessive Cu content in the alloy can easily lead to hot cracking, reducing the casting performance and yield of castings, and also significantly reducing the corrosion resistance of the alloy. Moreover, the addition of Zn will significantly reduce the corrosion resistance of the alloy, which does not meet the corrosion resistance requirements of automotive hollow low-pressure structural components. Excessive Si content will significantly reduce the elongation and toughness of the alloy.

[0006] Existing literature (CN115852212B) discloses an aluminum alloy material for integral low-pressure casting hollow subframes, comprising the following components by weight percentage: Si: 6.5–7.5%, Cu: 0.6–1.0%, Zn: 0.6–1.5%, Mg: 0.25–0.45%, Ti: 0.08–0.2%, Zr: ≤0.2%, Fe: ≤0.2%, Mn: ≤0.1%, Sn: ≤0.01%, with the remainder being Al. The aluminum alloy material provided in this literature exhibits good casting properties, with good fluidity, low linear shrinkage, and high airtightness. However, the excessively high Cu content in this aluminum alloy easily leads to hot cracking, reducing the casting performance and yield of the castings, and also significantly reducing the alloy's corrosion resistance. Furthermore, the addition of Zn significantly reduces the alloy's corrosion resistance, failing to meet the corrosion resistance requirements of automotive hollow low-pressure structural components. The low Si content has no significant effect on improving the alloy's fluidity.

[0007] Based on this, it is urgent to research and develop an Al-Si-Mg aluminum alloy with high yield strength, high tensile strength and good flow properties and its low-pressure casting process. Summary of the Invention

[0008] The main objective of this invention is to provide an Al-Si-Mg aluminum alloy, its preparation method, and its application, in order to solve the problem that Al-Si-Mg aluminum alloys in the prior art are difficult to simultaneously possess high yield strength, high tensile strength, and good flow properties.

[0009] To achieve the above objectives, the present invention provides an Al-Si-Mg aluminum alloy, comprising, by weight percentage, 7.6–8.6 wt% Si, 0.3–0.6 wt% Mg, 0.08–0.15 wt% Cu, 0.05–0.15 wt% Mn, 0.08–0.13 wt% Fe, 0.07–0.2 wt% Ti, 0.01–0.025 wt% Sr, 0.01–0.03 wt% V, 0.005–0.01 wt% Nb, and the balance Al and unavoidable impurity elements; wherein the total content of unavoidable impurity elements is ≤0.3%, the weight ratio of Cu to Mg is 1:(2–6), the weight ratio of Mn to Fe is (0.5–1):1, and Fe+2Mn≤0.4%.

[0010] Furthermore, based on the weight percentage of the Al-Si-Mg aluminum alloy, the Al-Si-Mg aluminum alloy comprises: 7.6–8.6 wt% Si, 0.3–0.5 wt% Mg, 0.08–0.14 wt% Cu, 0.05–0.12 wt% Mn, 0.08–0.13 wt% Fe, 0.07–0.2 wt% Ti, 0.01–0.025 wt% Sr, 0.01–0.03 wt% V, 0.005–0.01 wt% Nb, and the balance Al and unavoidable impurity elements; wherein the total content of unavoidable impurity elements is ≤0.2%.

[0011] Furthermore, the weight ratio of Cu to Mg is 1:(2.5-5); and / or the weight ratio of Mn to Fe is (0.5-0.8):1, with Fe+2Mn≤0.35%.

[0012] Furthermore, the ultimate tensile strength of Al-Si-Mg aluminum alloys is 340–390 MPa, the yield strength is 260–310 MPa, and the elongation after fracture is 8–13%.

[0013] Furthermore, unavoidable impurity elements include one or more of Sn, Pb, Ni, P, Ca, and Zn.

[0014] This application also provides a method for preparing the Al-Si-Mg aluminum alloy provided in this application. The method includes: step S1, mixing aluminum-containing raw materials, manganese-containing raw materials, copper-containing raw materials, titanium-containing raw materials and silicon-containing raw materials and performing a first smelting to obtain a first alloy melt; the temperature of the first smelting is 750-790℃, and the time is 4-6 hours; wherein, one or more of the aluminum-containing raw materials, manganese-containing raw materials, copper-containing raw materials, titanium-containing raw materials and silicon-containing raw materials contain Fe element; step S2, cooling the first alloy melt to 740-760℃ to obtain a second alloy melt; step S3, mixing the second alloy melt with magnesium-containing raw materials and performing a second smelting to obtain a third alloy melt; step S4, mixing the third alloy melt with a first slag remover and performing a first slag removal treatment to obtain a fourth alloy melt. Step S5: Mix the fourth alloy melt with a refining agent and perform a third smelting to obtain the fifth alloy melt; the refining agent includes one or more elements selected from Al, Ti, V, and Nb; Step S6: Mix the fifth alloy melt with strontium-containing raw materials and perform a fourth smelting, then perform degassing and slag removal treatment in an inert atmosphere to obtain the sixth alloy melt; a covering agent is added during the degassing and slag removal treatment; Step S7: Perform compositional analysis on the sixth alloy melt, and screen out qualified products whose weight percentage content of Al, Mn, Cu, Ti, Si, Mg, and Sr elements meets the requirements of claim 1; Step S8: Perform low-pressure casting at 1000-2000 mbar on the qualified products to obtain castings; Step S9: Perform heat treatment on the castings to obtain Al-Si-Mg aluminum alloy.

[0015] Furthermore, the aluminum-containing raw material is selected from elemental aluminum and / or electrolytic aluminum; and / or, the manganese-containing raw material is selected from aluminum-manganese master alloy; and / or, the copper-containing raw material is selected from elemental copper and / or Al-Cu master alloy; and / or, the titanium-containing raw material is selected from Al-Ti master alloy; and / or, the silicon-containing raw material is selected from one or more of aluminum-silicon master alloy, industrial silicon, and readily soluble silicon; and / or, the magnesium-containing raw material is selected from elemental magnesium; and / or, the strontium-containing raw material is selected from aluminum-strontium master alloy.

[0016] Further, step S2 includes: cooling the first alloy melt to 740-760°C, then mixing it with the second slag remover, letting it stand for 10-20 minutes, and then performing a second slag removal process to obtain the second alloy melt.

[0017] Furthermore, in step S3, the temperature of the second melting is 730–750°C, and the time is 10–30 min.

[0018] Furthermore, in step S4, the first slag remover accounts for 0.05 to 0.15 wt% of the weight of the third alloy melt.

[0019] Furthermore, the first and second slag removers are each independently selected from sodium-free refining agents.

[0020] Furthermore, in step S4, the mixing temperature is 730–740°C, and the time is 10–15 min.

[0021] Furthermore, in step S5, the temperature of the third melting is 725–735°C, and the time is 5–10 min.

[0022] Furthermore, the refining agent accounts for 0.2 to 0.7 wt% of the weight of the fourth alloy melt.

[0023] Furthermore, the refining agent is a mixture of AlTiB master alloy, AlVB master alloy and AlNbB master alloy, and the weight ratio of the three is 100: (5-7): (2-3).

[0024] Furthermore, the mixing step in step S6 is carried out within 10 to 20 minutes after the fifth alloy melt is obtained; the fourth melting temperature is 710 to 730°C and the time is 10 to 25 minutes.

[0025] Furthermore, the covering agent is selected from sodium-free covering agents.

[0026] Furthermore, the weight percentage of the covering agent is 0.05 to 0.1 wt% based on the total weight of the fifth alloy melt and the strontium-containing raw materials.

[0027] Further, in step S6, the inert atmosphere is selected from argon or nitrogen, and the flow rate of argon or nitrogen is 3 to 8 L / min; during the degassing and slag removal process, stirring is carried out at a speed of 300 to 600 rpm.

[0028] Furthermore, the degassing and slag removal treatment is carried out at a temperature of 720–730℃ for a time of 10–25 minutes.

[0029] Furthermore, between steps S6 and S7, the following steps are also included: performing density and slag content tests on the sixth alloy melt, and screening for a reduced pressure solidification density value ≥ 2.625 g / cm³. 3 Qualified products with a K modulus value ≤ 1 / 20.

[0030] Further, the heat treatment in step S9 includes a first solution treatment and a first aging treatment performed sequentially; the temperature of the first solution treatment is 520-545℃ and the time is 250-480 min; the temperature of the first aging treatment is 155-210℃ and the time is 180-480 min.

[0031] To achieve the above objectives, another aspect of the present invention provides a method for preparing a hollow structural component, the method comprising: sequentially casting, straightening or shaping, performing a second solution treatment, quenching and cooling treatment, and a second aging treatment on the Al-Si-Mg aluminum alloy prepared by the method provided in this application, to obtain a hollow structural component.

[0032] Furthermore, the casting temperature is 710–730℃; the temperature of the built-in sand core of the mold used in the casting process is 25–65℃, and the gas emission is ≤12mL / g; the casting pressure is 1000–2000mbar, and the time is 150–450s.

[0033] Furthermore, during the straightening or shaping process, the mold temperature is 200–350°C.

[0034] Furthermore, the quenching and cooling process takes 100–200 seconds.

[0035] Furthermore, the temperature of the second solution treatment is 520–545°C, and the time is 300–480 min.

[0036] Furthermore, the temperature for the second aging treatment is 155–210°C, and the time is 180–480 min.

[0037] Furthermore, the quenching cooling treatment is carried out using a quenching medium with a temperature of 50–85°C.

[0038] Another aspect of the present invention provides a hollow structural component, which is prepared by the above-described method for preparing a hollow structural component provided in this application.

[0039] Applying the technical solution of this invention, the Al-Si-Mg aluminum alloy provided in this application contains specific amounts of elements such as Si, Mg, Cu, V, and Nb. The introduction of Si can reduce hot cracking sensitivity while improving the casting performance of the aluminum alloy; the introduction of Mg can improve yield strength while enhancing corrosion resistance; the introduction of Cu can change the type of strengthening phase and improve the toughness of the aluminum alloy; the introduction of Sr can change the morphology of eutectic silicon in the Al-Si-Mg aluminum alloy from coarse needle-like to fine fibrous, but it will promote the columnar growth of the primary α-Al phase; the introduction of V, Nb, and Ti can reduce the degradation and poisoning effects of Sr, purify the melt, and increase the density of solidification nucleation points and matrix dislocations in the aluminum alloy, thereby improving the uniformity and mechanical properties of the alloy structure; the introduction of Ti can refine the microstructure and improve grain size.

[0040] Compared to other ranges, limiting the weight ratio of Cu to Mg in Al-Si-Mg aluminum alloys within the above range can improve the strength, toughness, and corrosion resistance of the aluminum alloys; limiting the weight ratio of Mn to Fe and the range of Fe+2Mn within the above range can effectively control the precipitation of iron-containing phases, achieve effective control over the morphology, size, and distribution of iron-rich phases, and reduce their adverse effects on the toughness of aluminum alloys.

[0041] In summary, Al-Si-Mg aluminum alloys containing the above-mentioned specific types and contents of components have high mechanical properties such as tensile strength, yield strength and elongation after fracture, good casting performance, and lower production costs and lighter weight compared to existing A356 alloys, and have broad application prospects (such as the preparation of hollow structural parts for automobiles). Attached Figure Description

[0042] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0043] Figure 1 The microstructure of the Al-Si-Mg aluminum alloy prepared in Example 1 is shown.

[0044] Figure 2 The microstructure of the Al-Si-Mg aluminum alloy prepared in Comparative Example 1 is shown. Detailed Implementation

[0045] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0046] As described in the background section, existing Al-Si-Mg aluminum alloys have the problem of not being able to simultaneously achieve high yield strength, high tensile strength, and good flow properties. To address the aforementioned technical problems, the first aspect of this application provides an Al-Si-Mg aluminum alloy, comprising, by weight percentage, 7.6–8.6 wt% Si, 0.3–0.6 wt% Mg, 0.08–0.15 wt% Cu, 0.05–0.15 wt% Mn, 0.08–0.13 wt% Fe, 0.07–0.2 wt% Ti, 0.01–0.025 wt% Sr, 0.01–0.03 wt% V, 0.005–0.01 wt% Nb, and the balance Al and unavoidable impurity elements; wherein the total content of unavoidable impurity elements is ≤0.3%, the weight ratio of Cu to Mg is 1:(2–6), the weight ratio of Mn to Fe is (0.5–1):1, and Fe+2Mn≤0.4%.

[0047] The Al-Si-Mg aluminum alloy provided in this application contains specific amounts of elements such as Si, Mg, Cu, V, and Nb. The introduction of Si can reduce hot cracking sensitivity while improving the casting performance of the aluminum alloy; the introduction of Mg can improve yield strength while enhancing corrosion resistance; the introduction of Cu can change the type of strengthening phase and improve the toughness of the aluminum alloy; the introduction of Sr can change the morphology of eutectic silicon in the Al-Si-Mg aluminum alloy from coarse needle-like to fine fibrous, but it will promote the columnar growth of the primary α-Al phase; the introduction of V, Nb, and Ti can reduce the modification and poisoning effects of Sr, purify the melt, and increase the density of solidification nucleation points and matrix dislocations in the aluminum alloy, thereby improving the uniformity of the alloy structure and its mechanical properties; the introduction of Ti can refine the microstructure and improve grain size.

[0048] Compared to other ranges, limiting the weight ratio of Cu to Mg in Al-Si-Mg aluminum alloys within the above range can improve the strength, toughness, and corrosion resistance of the aluminum alloys; limiting the weight ratio of Mn to Fe and the range of Fe+2Mn within the above range can effectively control the precipitation of iron-containing phases, achieve effective control over the morphology, size, and distribution of iron-rich phases, and reduce their adverse effects on the toughness of Al-Si-Mg aluminum alloys.

[0049] In summary, Al-Si-Mg aluminum alloys containing the above-mentioned specific types and contents of components have high mechanical properties such as tensile strength, yield strength and elongation after fracture, good casting performance, and lower production costs and lighter weight compared to existing A356 alloys, and have broad application prospects (such as the preparation of hollow structural parts for automobiles).

[0050] In a preferred embodiment, the Al-Si-Mg aluminum alloy comprises, by weight percentage, 7.6–8.6 wt% Si, 0.3–0.5 wt% Mg, 0.08–0.14 wt% Cu, 0.05–0.12 wt% Mn, 0.08–0.13 wt% Fe, 0.07–0.2 wt% Ti, 0.01–0.025 wt% Sr, 0.01–0.03 wt% V, 0.005–0.01 wt% Nb, and the balance Al and unavoidable impurity elements; wherein the total content of unavoidable impurity elements is ≤0.2%.

[0051] Compared to other ranges, limiting the content of elements such as Si, Mg, Cu, V, and Nb in Al-Si-Mg aluminum alloys to the above ranges is beneficial to improving the uniformity of the alloy structure of Al-Si-Mg aluminum alloys, and to improving the casting performance, mechanical properties, and corrosion resistance of Al-Si-Mg aluminum alloys.

[0052] In a preferred embodiment, the weight ratio of Cu to Mg is 1:(2.5 to 5). Compared to other ranges, limiting the weight ratio of Cu to Mg in Al-Si-Mg aluminum alloys to the above range is beneficial to improving the strength, toughness, and corrosion resistance of Al-Si-Mg aluminum alloys.

[0053] In a preferred embodiment, the weight ratio of Mn to Fe is (0.5–0.8):1; Fe+2Mn≤0.35%. Limiting the weight ratio of Mn to Fe and the range of Fe+2Mn within the above range is beneficial for controlling the precipitation of iron-containing phases and for regulating the morphology, size, and distribution of iron-rich phases, thereby reducing their adverse effects on the toughness of Al-Si-Mg aluminum alloys.

[0054] In a preferred embodiment, the Al-Si-Mg aluminum alloy has an ultimate tensile strength of 260–390 MPa, a yield strength of 230–310 MPa, and an elongation after fracture of 5–13%. Preferably, the Al-Si-Mg aluminum alloy has an ultimate tensile strength of 340–390 MPa, a yield strength of 260–310 MPa, and an elongation after fracture of 8–13%.

[0055] The Al-Si-Mg aluminum alloy provided in this application has high mechanical properties such as tensile strength, yield strength and elongation after fracture, good casting performance, and lower production cost and lighter weight compared with the existing A356 alloy, and has broad application prospects (such as manufacturing hollow structural parts for automobiles).

[0056] During the preparation of Al-Si-Mg aluminum alloys, unavoidable impurity elements are introduced due to the purity of the raw materials. In a preferred embodiment, the unavoidable impurity elements include one or more of Sn, Pb, Ni, P, Ca, and Zn.

[0057] The second aspect of this application also provides a method for preparing the Al-Si-Mg aluminum alloy provided in this application. The method includes: step S1, mixing aluminum-containing raw materials, manganese-containing raw materials, copper-containing raw materials, titanium-containing raw materials, and silicon-containing raw materials and performing a first smelting to obtain a first alloy melt; the first smelting temperature is 750–790°C, and the time is 4–6 hours; wherein one or more of the aluminum-containing raw materials, manganese-containing raw materials, copper-containing raw materials, titanium-containing raw materials, and silicon-containing raw materials contain Fe element; step S2, cooling the first alloy melt to 740–760°C to obtain a second alloy melt; step S3, mixing the second alloy melt with magnesium-containing raw materials and performing a second smelting to obtain a third alloy melt; step S4, mixing the third alloy melt with a first slag remover and performing a first slag removal treatment to obtain a fourth alloy melt. Step S5: Mix the fourth alloy melt with a refining agent and perform a third smelting to obtain the fifth alloy melt; the refining agent includes one or more elements selected from Al, Ti, V, and Nb; Step S6: Mix the fifth alloy melt with strontium-containing raw materials and perform a fourth smelting, then perform degassing and slag removal treatment in an inert atmosphere to obtain the sixth alloy melt; a covering agent is added during the degassing and slag removal treatment; Step S7: Perform compositional analysis on the sixth alloy melt, and screen out qualified products whose weight percentage content of Al, Mn, Cu, Ti, Si, Mg, and Sr elements meets the requirements of claim 1; Step S8: Perform low-pressure casting at 1000-2000 mbar on the qualified products to obtain castings; Step S9: Perform heat treatment on the castings to obtain Al-Si-Mg aluminum alloy.

[0058] The Al-Si-Mg aluminum alloys with the specific compositions described above are particularly suitable for the aforementioned preparation process. In step S1, the introduction of aluminum-containing, manganese-containing, copper-containing, titanium-containing, and silicon-containing raw materials facilitates the subsequent preparation of Al-Si-Mg aluminum alloys containing Al, Mn, Cu, Ti, and Si elements. The introduction of Cu alters the type of strengthening phase, improving the toughness of the aluminum alloy; the introduction of Ti refines the microstructure; and the introduction of Si reduces hot cracking sensitivity while improving the casting performance of the aluminum alloy. After mixing the above raw materials and performing a first and second smelting, a third alloy melt is obtained. This third alloy melt is mixed with a first slag remover and subjected to a first slag removal treatment to remove oxide impurities, preventing the formation of porosity, cracks, and defects, thereby improving the surface quality and mechanical properties of the subsequently obtained Al-Si-Mg aluminum alloy. In step S5, the fourth alloy melt is mixed with a grain refiner and subjected to a third smelting, which reduces the grain size in the fourth alloy melt and improves the alloy microstructure. In step S6, the addition of strontium-containing raw materials introduces Sr into the fifth alloy melt, achieving a modification treatment that transforms the eutectic silicon morphology from coarse needle-like structures to fine fibrous structures. Simultaneously, a grain refiner containing one or more of Al, Ti, V, and Nb transforms the fibrous grains into granular grains, resulting in a more uniformly distributed alloy microstructure. The addition of a covering agent forms a liquid film on the surface of the fifth alloy melt, preventing oxidation. In step S7, the composition of the sixth alloy melt is analyzed, qualified products are selected, and then heat-treated to obtain an Al-Si-Mg aluminum alloy.

[0059] Among these, the introduction of Si can improve the casting performance of aluminum alloys while reducing hot cracking sensitivity; the introduction of Mg can improve corrosion resistance while increasing yield strength; the introduction of Cu can change the type of strengthening phase and improve the toughness of aluminum alloys; the introduction of Sr can change the morphology of eutectic silicon in Al-Si-Mg aluminum alloys from coarse needle-like to fine fibrous, but it will promote the columnar growth of primary α-Al phase; the introduction of V, Nb, and Ti can reduce the modification and poisoning effect of Sr, purify the melt, and increase the nucleation point and dislocation density of aluminum alloys, thereby improving the uniformity of the alloy structure and mechanical properties; the introduction of Ti can refine the structure and improve the grain size.

[0060] Compared to other ranges, limiting the weight ratio of Cu to Mg in Al-Si-Mg aluminum alloys within the above range can improve the strength, toughness, and corrosion resistance of the aluminum alloys; limiting the weight ratio of Mn to Fe and the range of Fe+2Mn within the above range can effectively control the precipitation of iron-containing phases, achieve effective control over the morphology, size, and distribution of iron-rich phases, and reduce their adverse effects on the toughness of aluminum alloys.

[0061] In summary, Al-Si-Mg aluminum alloys containing the above-mentioned specific types and contents of components have high mechanical properties such as tensile strength, yield strength and elongation after fracture, good casting performance, and lower production costs and lighter weight compared to existing A356 alloys, and have broad application prospects (such as the preparation of hollow structural parts for automobiles).

[0062] The aluminum-containing raw materials used in this application can be those commonly used in the art. In a preferred embodiment, the aluminum-containing raw materials include, but are not limited to, elemental aluminum and / or electrolytic aluminum.

[0063] The manganese-containing raw materials used in this application can be those commonly used in the art. In a preferred embodiment, the manganese-containing raw materials include, but are not limited to, aluminum-manganese master alloys.

[0064] The copper-containing raw materials used in this application can be those commonly used in the art. In a preferred embodiment, the copper-containing raw materials include, but are not limited to, elemental copper and / or Al-Cu master alloys.

[0065] The titanium-containing raw materials used in this application can be those commonly used in the art. In a preferred embodiment, the titanium-containing raw materials include, but are not limited to, Al-Ti master alloys.

[0066] The silicon-containing raw materials used in this application can be those commonly used in the art. In a preferred embodiment, the silicon-containing raw materials include, but are not limited to, one or more of aluminum-silicon master alloys, industrial silicon, and readily soluble silicon.

[0067] The magnesium-containing raw materials used in this application can be those commonly used in the art. In a preferred embodiment, the magnesium-containing raw materials include, but are not limited to, elemental magnesium.

[0068] The strontium-containing raw materials used in this application can be those commonly used in the art. In a preferred embodiment, the strontium-containing raw materials include, but are not limited to, aluminum-strontium master alloys.

[0069] In a preferred embodiment, step S2 includes: cooling the first alloy melt to 740–760°C, then mixing it with a second slag remover, allowing it to stand for 10–20 minutes, and then performing a second slag removal treatment to obtain the second alloy melt. This treatment method helps reduce oxide impurities in the second alloy melt, reducing the generation of porosity, cracks, and defects, thereby improving the surface quality and mechanical properties of the subsequently produced Al-Si-Mg aluminum alloy.

[0070] To further reduce the content of oxides and other slag in the second alloy melt, preferably, the second slag remover accounts for 0.05 to 0.15 wt% of the weight of the first alloy melt.

[0071] In a preferred embodiment, in step S3, the temperature of the second melting is 730–750°C, and the time is 10–30 min. The temperature and time of the second melting include, but are not limited to, the above-mentioned ranges. Limiting them to the above-mentioned ranges is beneficial to reducing the slag content of oxides, etc., and is beneficial to reducing the amount of hydrogen absorbed in the third alloy melt.

[0072] In a preferred embodiment, in step S4, the first slag remover accounts for 0.05 to 0.15 wt% of the weight of the third alloy melt. The amount of the first slag remover includes, but is not limited to, the above range. Limiting it to the above range is beneficial for removing oxide impurities in the third alloy melt, reducing the generation of porosity, cracks and defects, thereby improving the surface quality and mechanical properties of the Al-Si-Mg aluminum alloy subsequently produced.

[0073] To further improve the removal effect of oxide impurities and further reduce the generation of pores, cracks and defects, preferably, the first slag remover and the second slag remover each independently include, but are not limited to, sodium-free refining agents.

[0074] In a preferred embodiment, the mixing temperature in step S4 is 730–740°C, and the mixing time is 10–15 min. The mixing temperature and time in step S4 include, but are not limited to, the above range. Limiting them to the above range is beneficial for further removing oxide impurities in the third alloy melt, reducing the generation of porosity, cracks, and defects, thereby improving the surface quality and mechanical properties of the subsequently obtained Al-Si-Mg aluminum alloy.

[0075] In a preferred embodiment, in step S5, the temperature of the third melting is 725–735°C, and the time is 5–10 minutes. The temperature and time of the third melting include, but are not limited to, the above-mentioned ranges. Limiting them to the above-mentioned ranges is beneficial for reducing oxide inclusions in the fifth alloy melt and for improving the refining effect.

[0076] In a preferred embodiment, in step S5, the grain refiner accounts for 0.2 to 0.7 wt% of the weight of the fourth alloy melt. The amount of grain refiner used includes, but is not limited to, the above range. Limiting it to the above range is beneficial to reduce the grain size in the fourth alloy melt and improve the alloy microstructure.

[0077] In order to further reduce the grain size in the fourth alloy melt and improve the alloy microstructure, preferably, the grain refiner is a mixture of AlTiB master alloy, AlVB master alloy and AlNbB master alloy, and the weight ratio of the three is 100: (5-7): (2-3).

[0078] In a preferred embodiment, the mixing step in step S6 is carried out within 10 to 20 minutes after the fifth alloy melt is obtained; the fourth melting temperature is 710 to 730°C, and the time is 10 to 25 minutes. The temperature and time of the fourth melting include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to improving the modification treatment effect, transforming fibrous grains into granular grains, thereby obtaining a more uniform alloy structure.

[0079] To prevent oxidation of the surface of the fifth alloy melt, in a preferred embodiment, the covering agent includes, but is not limited to, a sodium-free covering agent.

[0080] To further prevent oxidation of the surface of the fifth alloy melt, in a preferred embodiment, the weight percentage of the covering agent is 0.05 to 0.1 wt% based on the total weight of the fifth alloy melt and the strontium-containing raw material.

[0081] In a preferred embodiment, in step S6, the inert atmosphere includes, but is not limited to, argon or nitrogen, with an argon or nitrogen flow rate of 3–8 L / min; stirring is performed during the degassing and slag removal process at a stirring rate of 300–600 rpm. Compared to other ranges, using the aforementioned inert atmosphere and limiting its flow rate within this range is beneficial for reducing the introduction of impurities and ensuring thorough mixing of the elements. Furthermore, compared to other ranges, limiting the stirring rate within this range further helps to reduce the introduction of impurities and ensure thorough mixing of the elements.

[0082] In a preferred embodiment, the degassing and slag removal treatment is carried out at a temperature of 720–730°C for 10–25 minutes. The temperature and time for the degassing and slag removal treatment include, but are not limited to, the above-mentioned ranges. Limiting them to these ranges helps to reduce the amount of hydrogen absorbed by the melt during tumbling and the content of oxides, and to ensure thorough removal of slag from the melt.

[0083] To conduct a more comprehensive test of product performance, in a preferred embodiment, the step between S6 and S7 further includes: performing density and slag content tests on the sixth alloy melt, and screening for a reduced-pressure solidification density value ≥ 2.625 g / cm³. 3 Qualified products with a K modulus value ≤ 1 / 20.

[0084] In a preferred embodiment, the heat treatment in step S9 includes a first solution treatment and a first aging treatment performed sequentially; the temperature of the first solution treatment is 520–545°C, and the time is 250–480 min; the temperature of the first aging treatment is 155–210°C, and the time is 180–480 min. The temperature and time of the first solution treatment or the first aging treatment include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to improving the tensile strength, yield strength, and elongation after fracture of the Al-Si-Mg aluminum alloy.

[0085] The third aspect of this application also provides a method for preparing a hollow structural component, the method comprising: sequentially casting, straightening or shaping, second solution treatment, quenching and cooling treatment and second aging treatment of the Al-Si-Mg aluminum alloy prepared by the above-mentioned method provided in this application, to obtain a hollow structural component.

[0086] The preparation method provided in this application obtains a hollow structure through casting, thereby achieving weight reduction; straightening or shaping can correct the deformation caused during the casting process and ensure dimensional accuracy; the second solution treatment fully dissolves and homogenizes the alloying elements, eliminating segregation; quenching and cooling treatment forms a supersaturated solid solution, inhibiting the precipitation of brittle phases; the second aging treatment can promote the dispersion precipitation of nanoscale strengthening phases, significantly improving the strength and toughness of the hollow structural parts.

[0087] The hollow structural components prepared by the above method have the advantages of dense structure and excellent mechanical properties, and can meet the needs of the automotive industry for high-performance lightweight hollow structural components.

[0088] In a preferred embodiment, the casting temperature is 710–730°C; the temperature of the built-in sand core of the mold used in the casting process is 25–65°C, and the gas emission is ≤12 mL / g; the casting pressure is 1000–2000 mbar, and the casting time is 150–450 s. The temperature, casting pressure, and time of the Al-Si-Mg aluminum alloy are not limited to the above ranges. Limiting them to the above ranges is beneficial to obtaining a hollow structure, achieving weight reduction while improving mechanical strength and density.

[0089] In a preferred embodiment, the mold temperature is 200–350°C during the straightening or shaping process. The mold temperature includes, but is not limited to, the above range. Limiting it within this range helps reduce mold deformation and extend its service life, thereby resulting in better rigidity of the casting and preventing thermoplastic deformation.

[0090] In a preferred embodiment, the quenching and cooling treatment time is 100–200 seconds. The quenching and cooling treatment time includes, but is not limited to, the above range. Limiting it to the above range helps to reduce the thermal stress generated during the quenching and cooling treatment and reduce the risk of deformation and cracking.

[0091] To further reduce the thermal stress generated during quenching and cooling treatment and reduce the risk of deformation and cracking, it is preferable that the quenching and cooling treatment is carried out using a quenching medium with a temperature of 50-85℃.

[0092] In a preferred embodiment, the temperature of the second solution treatment is 520–545°C, and the time is 300–480 min. The temperature and time of the second solution treatment include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to improving the mechanical strength of the subsequently produced hollow structural parts, and is beneficial to the spheroidization of the eutectic structure and the full solution of each element in the aluminum matrix.

[0093] In a preferred embodiment, the temperature of the second aging treatment is 155–210°C, and the time is 180–480 min. The temperature and time of the second aging treatment include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to improving the mechanical strength of the hollow structural parts subsequently produced, and is beneficial to the full precipitation and growth of the nanophase, thereby increasing the strength of the aluminum matrix and the yield and tensile strength of the final material.

[0094] The fourth aspect of this application also provides a hollow structural component, which is prepared by the method described above. The hollow structural component prepared by the above method has the advantages of dense microstructure and excellent mechanical properties, and can meet the automotive industry's demand for high-performance, lightweight hollow structural components. It should be noted that, due to the special nature of the alloy field and the limitations of existing testing and characterization methods, it is difficult to comprehensively and quantitatively characterize the complex microstructure of the Al-Si-Mg aluminum alloy obtained above. However, experiments show that the Al-Si-Mg aluminum alloy obtained in this application has superior comprehensive mechanical properties.

[0095] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0096] Example 1

[0097] A method for preparing an Al-Si-Mg based aluminum alloy, comprising:

[0098] (1) Calculate the amount of different raw materials added according to the composition of Al-Si-Mg aluminum alloy, and then mix elemental aluminum, aluminum-manganese master alloy, elemental copper, Al-Ti master alloy and aluminum-silicon master alloy and carry out the first melting at 770℃ to obtain the first alloy melt;

[0099] (2) Reduce the temperature of the first alloy melt obtained in step (1) to 750°C to obtain the second alloy melt;

[0100] (3) Add elemental magnesium to the second alloy melt obtained in step (2) and perform a second melting at 740°C to obtain the third alloy melt;

[0101] (4) Add sodium-free refining agent to the third alloy melt obtained in step (3), and perform the first slag removal treatment at 735°C to obtain the fourth alloy melt; wherein, the sodium-free refining agent accounts for 0.1 wt% of the weight of the third alloy melt;

[0102] (5) Add a refining agent to the fourth alloy melt obtained in step (4) and perform a third smelting at 730°C to obtain a fifth alloy melt; wherein the refining agent is a mixture of AlTiB, AlVB and AlNbB master alloys, with a weight ratio of 100:6:2.5, and the refining agent accounts for 0.65 wt% of the weight of the fourth alloy melt;

[0103] (6) Add an aluminum-strontium master alloy to the fifth alloy melt and perform a fourth melting, then perform degassing and slag removal treatment under argon gas (purity ≥99.995%) and stirring conditions to obtain a sixth alloy melt; wherein, the temperature of the fourth melting and degassing and slag removal is 725℃, the argon gas flow rate is 4L / min, and the stirring rate is 350rpm;

[0104] (7) The sixth alloy melt was subjected to compositional analysis, density analysis, and slag content analysis. The content of each element was selected to meet the above-mentioned range of this application (7.6-8.6 wt% Si, 0.3-0.6 wt% Mg, 0.08-0.15 wt% Cu, 0.05-0.15 wt% Mn, 0.08-0.13 wt% Fe, 0.07-0.2 wt% Ti, 0.01-0.025 wt% Sr, 0.01-0.03 wt% V, 0.005-0.01 wt% Nb, and the balance Al and unavoidable impurity elements), and the reduced pressure solidification density value was ≥2.625 g / cm³. 3 Qualified products with K modulus value ≤ 1 / 20 are subjected to a first solution treatment at 541℃ for 380 min, followed by a first aging treatment at 165℃ for 390 min to obtain Al-Si-Mg aluminum alloy.

[0105] The elements and their weight percentages in the Al-Si-Mg aluminum alloy prepared in Example 1 are as follows: Si: 7.61 wt%, Mg: 0.5 wt%, Cu: 0.11 wt%, Mn: 0.06 wt%, Fe: 0.12 wt%, Ti: 0.17 wt%, Sr: 0.015 wt%, V: 0.01 wt%, Nb: 0.01 wt%, with the remainder being Al and unavoidable impurity elements, the total amount of which is ≤0.3 wt%.

[0106] from Figure 1 It can be seen that the Al-Si-Mg aluminum alloy prepared in Example 1 has smaller and more uniform eutectic Si particles, while the iron phase is small and the grain structure is fine.

[0107] A method for manufacturing a hollow structural component (subframe), comprising:

[0108] (1) Keep the temperature of Al-Si-Mg aluminum alloy at 710℃, transfer it to the aluminum melting furnace of low pressure casting machine for casting, the casting pressure is 1500mbar, and the time is 200s;

[0109] (2) Straighten or shape the casting in the mold to obtain the casting; wherein the temperature of the mold is 250℃;

[0110] (3) Place the casting at 541℃ for a second solution treatment for 380 min;

[0111] (4) Water is used as the quenching medium for quenching and cooling treatment. The temperature of the quenching medium is 65℃ and the quenching and cooling treatment time is 180s.

[0112] (5) The second aging treatment was carried out at 165℃ for 390 min to obtain the subframe.

[0113] Examples 2 to 6

[0114] The difference from Example 1 is that the content of each element in the Al-Si-Mg aluminum alloy is different, as shown in Table 1.

[0115] Example 7

[0116] The preparation method of Al-Si-Mg aluminum alloy is the same as that in Example 1.

[0117] The difference from Example 1 is that in the preparation method of the hollow structural component (subframe), the temperature of the Al-Si-Mg aluminum alloy is kept at 715°C in step (1), the casting pressure is 1450mbar, and the time is 150s; in step (2), the temperature of the mold is 300°C; and in step (4), the cooling time is 100s.

[0118] Example 8

[0119] The preparation method of Al-Si-Mg aluminum alloy is the same as that in Example 1.

[0120] The difference from Example 1 is that in the preparation method of the hollow structural component (subframe), the temperature of the Al-Si-Mg aluminum alloy is kept at 725°C in step (1), the casting pressure is 1350mbar, and the time is 130s; in step (2), the temperature of the mold is 300°C; and in step (4), the cooling time is 200s.

[0121] Example 9

[0122] The preparation method of Al-Si-Mg aluminum alloy is the same as that in Example 1.

[0123] The difference from Example 1 is that in the preparation method of hollow structural parts (subframes), the temperature of the second solution treatment in step (3) is 535°C and the time is 420 min; the temperature of the quenching medium in step (4) is 50°C; and the temperature of the second aging treatment in step (5) is 180°C and the time is 220 min.

[0124] Example 10

[0125] The preparation method of Al-Si-Mg aluminum alloy is the same as that in Example 1.

[0126] The difference from Example 1 is that in the preparation method of hollow structural parts (subframes), the temperature of the second solution treatment in step (3) is 535°C and the time is 480 min; the temperature of the quenching medium in step (4) is 55°C; and the temperature of the second aging treatment in step (5) is 155°C and the time is 450 min.

[0127] Example 11

[0128] The preparation method of Al-Si-Mg aluminum alloy is the same as that in Example 1.

[0129] The difference from Example 1 is that in the preparation method of the hollow structural component (subframe), the temperature of the Al-Si-Mg aluminum alloy is kept at 700℃ in step (1), the casting pressure is 1200mbar, and the time is 160s; in step (2), the temperature of the mold is 280℃; and in step (4), the cooling time is 500s.

[0130] Example 12

[0131] The preparation method of Al-Si-Mg aluminum alloy is the same as that in Example 1.

[0132] The difference from Example 1 is that in the preparation method of the hollow structural component (subframe), the temperature of the Al-Si-Mg aluminum alloy is kept at 715°C in step (1), the casting pressure is 1120mbar, and the time is 110s; in step (2), the temperature of the mold is 350°C; and in step (4), the cooling time is 260s.

[0133] Example 13

[0134] The preparation method of Al-Si-Mg aluminum alloy is the same as that in Example 1.

[0135] The difference from Example 1 is that in the preparation method of hollow structural parts (subframes), the temperature of the second solution treatment in step (3) is 525°C and the time is 350 min; the temperature of the quenching medium in step (4) is 85°C; and the temperature of the second aging treatment in step (5) is 200°C and the time is 180 min.

[0136] Example 14

[0137] The preparation method of Al-Si-Mg aluminum alloy is the same as that in Example 1.

[0138] The difference from Example 1 is that in the preparation method of hollow structural parts (subframes), the temperature of the second solution treatment in step (3) is 530°C and the time is 250 min; the temperature of the quenching medium in step (4) is 85°C; and the temperature of the second aging treatment in step (5) is 150°C and the time is 300 min.

[0139] Comparative Examples 1 to 3

[0140] The preparation method of the hollow structural component (subframe) is the same as that in Example 1.

[0141] The difference from Example 1 is that the content of each element in the Al-Si-Mg aluminum alloy is different, as shown in Table 1.

[0142] from Figure 2 It can be seen that the Al-Si-Mg aluminum alloy prepared in Comparative Example 1 has a relatively coarse grain structure and contains large-sized iron-containing phases and eutectic Si phases.

[0143] Table 1 shows the types and weight percentages of each element in the Al-Si-Mg aluminum alloys of all examples and comparative examples.

[0144] Table 1

[0145]

[0146] Mechanical properties of the Al-Si-Mg aluminum alloys prepared in all the embodiments and comparative examples of this application were tested, including tensile strength, yield strength, and elongation, all according to GB / T 228.1-2021 "Metallic materials, tensile testing—Part 1: Test method at room temperature". For each mechanical property test, 10 samples were taken, and the average value was calculated. The flow properties of the Al-Si-Mg aluminum alloys were tested using a domestically common spiral flow length metal mold at a mold temperature of 200℃ and an aluminum melt casting temperature of 720℃. Ten samples were taken, and their lengths were measured and averaged. The test results are shown in Table 2.

[0147] Table 2

[0148]

[0149] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0150] The Al-Si-Mg aluminum alloy provided in this application contains specific amounts of elements such as Si, Mg, Cu, V, and Nb. Among these, the introduction of Si can reduce the susceptibility to hot cracking while improving the casting performance of the aluminum alloy; the introduction of Mg can improve the yield strength while enhancing corrosion resistance; the introduction of Cu can change the type of strengthening phase and increase the elongation after fracture of the aluminum alloy; the introduction of Sr can change the morphology of eutectic silicon in the Al-Si-Mg aluminum alloy from coarse needle-like to fine fibrous, but it will promote the columnar growth of the primary α-Al phase; the introduction of V, Nb, and Ti can reduce the modification poisoning effect caused by the introduction of Sr, increase the solidification nucleation particles and matrix dislocation density of the aluminum alloy, thereby improving the uniformity of the alloy structure and mechanical properties; and the introduction of Ti can refine the microstructure and improve the grain size.

[0151] Compared to other ranges, limiting the weight ratio of Cu to Mg in Al-Si-Mg aluminum alloys within the above range can improve the strength, toughness, and corrosion resistance of the aluminum alloys; limiting the weight ratio of Mn to Fe and the range of Fe+2Mn within the above range can effectively control the precipitation of iron-containing phases, achieve effective control over the morphology, size, and distribution of iron-rich phases, and reduce their adverse effects on the toughness of aluminum alloys.

[0152] In summary, Al-Si-Mg aluminum alloys containing the above-mentioned specific types and contents of components have high mechanical properties such as tensile strength, yield strength and elongation after fracture, good casting performance, and lower production costs and lighter weight compared to existing A356 alloys, and have broad application prospects (such as the preparation of hollow structural parts for automobiles).

[0153] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0154] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An Al-Si-Mg based aluminum alloy, characterized in that, Based on the weight percentage of the Al-Si-Mg aluminum alloy, the Al-Si-Mg aluminum alloy comprises: 7.6–8.6 wt% Si, 0.3–0.6 wt% Mg, 0.08–0.15 wt% Cu, 0.05–0.15 wt% Mn, 0.08–0.13 wt% Fe, 0.07–0.2 wt% Ti, 0.01–0.025 wt% Sr, 0.01–0.03 wt% V, and 0.005–0.01 wt%... The aluminum alloy contains Nb and the balance Al and unavoidable impurity elements; wherein the total content of the unavoidable impurity elements is ≤0.3%, the weight ratio of Cu to Mg is 1:(2.5~5), the weight ratio of Mn to Fe is (0.5~0.8):1, and Fe+2Mn≤0.35%; the ultimate tensile strength of the Al-Si-Mg aluminum alloy is 340~390MPa, the yield strength is 260~310MPa, and the elongation after fracture is 8~13%.

2. The Al-Si-Mg aluminum alloy according to claim 1, characterized in that, Based on the weight percentage of the Al-Si-Mg aluminum alloy, the Al-Si-Mg aluminum alloy comprises: 7.6–8.6 wt% Si, 0.3–0.5 wt% Mg, 0.08–0.14 wt% Cu, 0.05–0.12 wt% Mn, 0.08–0.13 wt% Fe, 0.07–0.2 wt% Ti, 0.01–0.025 wt% Sr, 0.01–0.03 wt% V, 0.005–0.01 wt% Nb, and the balance being Al and the unavoidable impurity elements; wherein the total content of the unavoidable impurity elements is ≤0.2%.

3. The Al-Si-Mg aluminum alloy according to claim 1, characterized in that, The unavoidable impurity elements include one or more of Sn, Pb, Ni, P, Ca, and Zn.

4. A method for preparing an Al-Si-Mg aluminum alloy according to any one of claims 1 to 3, characterized in that, The preparation method includes: Step S1: Mix aluminum-containing raw materials, manganese-containing raw materials, copper-containing raw materials, titanium-containing raw materials and silicon-containing raw materials and perform a first smelting to obtain a first alloy melt; the temperature of the first smelting is 750-790℃ and the time is 4-6h; wherein, one or more of the aluminum-containing raw materials, the manganese-containing raw materials, the copper-containing raw materials, the titanium-containing raw materials and the silicon-containing raw materials contain Fe element; Step S2: Cool the first alloy melt to 740-760°C to obtain the second alloy melt; Step S3: The second alloy melt is mixed with magnesium-containing raw materials and subjected to a second smelting to obtain a third alloy melt; Step S4: Mix the third alloy melt with the first slag remover and perform the first slag removal treatment to obtain the fourth alloy melt; Step S5: The fourth alloy melt is mixed with a refining agent and subjected to a third smelting to obtain a fifth alloy melt; the refining agent includes one or more elements selected from Al, Ti, V and Nb. Step S6: The fifth alloy melt is mixed with strontium-containing raw materials and subjected to a fourth smelting process, followed by degassing and slag removal treatment in an inert atmosphere to obtain the sixth alloy melt; a covering agent is added during the degassing and slag removal process. Step S7: Perform composition analysis on the sixth alloy melt, and screen out those whose weight percentage content of Al, Mn, Cu, Ti, Si, Mg and Sr elements meets the requirements of claim 1 as qualified products; Step S8: The qualified product is subjected to low-pressure casting at 1000-2000 mbar to obtain a casting; Step S9: Heat treat the casting to obtain the Al-Si-Mg aluminum alloy.

5. The method for preparing Al-Si-Mg aluminum alloy according to claim 4, characterized in that, The aluminum-containing raw material is selected from elemental aluminum and / or electrolytic aluminum; and / or, The manganese-containing raw material is selected from aluminum-manganese master alloy; and / or, The copper-containing raw material is selected from elemental copper and / or Al-Cu master alloys; and / or, The titanium-containing raw material is selected from Al-Ti master alloys; and / or, The silicon-containing raw material is selected from one or more of aluminum-silicon master alloys, industrial silicon, and readily soluble silicon; and / or, The magnesium-containing raw material is selected from elemental magnesium; and / or, The strontium-containing raw material is selected from aluminum-strontium master alloy.

6. The method for preparing Al-Si-Mg aluminum alloy according to claim 4, characterized in that, Step S2 includes: cooling the first alloy melt to 740-760°C, then mixing it with a second slag remover, allowing it to stand for 10-20 minutes, and then performing a second slag removal process to obtain the second alloy melt; and / or, In step S3, the temperature of the second melting is 730–750°C, and the time is 10–30 minutes; and / or, In step S4, the first slag remover accounts for 0.05–0.15 wt% of the weight of the third alloy melt; and / or, The first slag remover and the second slag remover are each independently selected from sodium-free refining agents; and / or, The mixing temperature in step S4 is 730–740°C, and the mixing time is 10–15 min.

7. The method for preparing Al-Si-Mg aluminum alloy according to claim 4, characterized in that, In step S5, the temperature of the third melting process is 725–735°C, and the time is 5–10 minutes; and / or, The refining agent comprises 0.2–0.7 wt% of the fourth alloy melt by weight; and / or, The refining agent is a mixture of AlTiB master alloy, AlVB master alloy and AlNbB master alloy, and the weight ratio of the three is 100: (5-7): (2-3).

8. The method for preparing Al-Si-Mg aluminum alloy according to claim 4, characterized in that, The mixing step in step S6 is carried out within 10 to 20 minutes after the fifth alloy melt is obtained; the fourth melting temperature is 710 to 730°C, and the time is 10 to 25 minutes; and / or, The covering agent is selected from sodium-free covering agents; and / or, The covering agent comprises 0.05–0.1 wt% of the total weight of the fifth alloy melt and the strontium-containing raw material; and / or, In step S6, the inert atmosphere is selected from argon or nitrogen, and the flow rate of argon or nitrogen is 3-8 L / min; stirring is performed during the degassing and slag removal process, and the stirring rate is 300-600 rpm; and / or; The degassing and slag removal treatment is performed at a temperature of 720–730°C for a time of 10–25 minutes. And / or, Between step S6 and step S7, the following further step is taken: density and slag content are measured in the sixth alloy melt, and a reduced-pressure solidification density value ≥ 2.625 g / cm³ is selected. 3 Qualified products with a K modulus value ≤ 1 / 20.

9. The method for preparing Al-Si-Mg aluminum alloy according to claim 4, characterized in that, The heat treatment in step S9 includes a first solution treatment and a first aging treatment performed sequentially; the temperature of the first solution treatment is 520-545℃ and the time is 250-480 min; the temperature of the first aging treatment is 155-210℃ and the time is 180-480 min.

10. A method for preparing a hollow structural component, characterized in that, The preparation method includes: The Al-Si-Mg aluminum alloy prepared by the method of any one of claims 4 to 9 is subjected to casting, straightening or shaping, second solution treatment, quenching and cooling treatment and second aging treatment in sequence to obtain the hollow structural component.

11. The method for preparing a hollow structural component according to claim 10, characterized in that, The casting temperature is 710–730℃; the temperature of the mold's internal sand core used in the casting process is 25–65℃, and the gas evolution is ≤12mL / g; the casting pressure is 1000–2000mbar, and the casting time is 150–450s; and / or, During the straightening or shaping process, the mold temperature is 200–350°C; and / or, The quenching and cooling process takes 100–200 seconds; and / or, The second solution treatment is performed at a temperature of 520–545°C for a time of 300–480 min; and / or, The second aging treatment is performed at a temperature of 155–210°C for a time of 180–480 min.

12. The method for preparing a hollow structural component according to claim 11, characterized in that, The quenching cooling treatment is carried out using a quenching medium, and the temperature of the quenching medium is 50-85℃.

13. A hollow structural component, characterized in that, The hollow structural component is prepared by the method for preparing a hollow structural component as described in any one of claims 10 to 12.

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