Doped element modified cast aluminum alloy, preparation method and application thereof

Abstract

The application discloses a kind of doped element modified casting aluminum alloy, preparation method and its application, the aluminum alloy is Al-Si-Mg-Cu as matrix, doping any one or more in La, Ce, Zn, and the mass ratio of doping element is 0.1%~1.9%.Preparation method includes raw material smelting, melt purification pouring, solid solution-ageing treatment, and the doped element modified casting aluminum alloy is obtained by using metal type gravity pouring, and then extrusion casting is made into structural member.The application realizes α-Al dendrite refinement and eutectic Si efficient modification by the synergistic effect of doping element, greatly improves the mechanical properties such as tensile strength and hardness of alloy, while maintaining excellent plasticity, and the matching of strength and plasticity is excellent, which can be used for preparing automobile lightweight castings, and solves the technical shortcomings of traditional casting aluminum alloy, such as coarse structure and insufficient matching of strength and plasticity.

Description

Technical Field

[0001] This application relates to the technical field of cast aluminum alloys and their preparation processes, specifically to a doped element modified cast aluminum alloy, its preparation method, and its application. Background Technology

[0002] Lightweighting is a core development direction for the modern automotive industry. Against the backdrop of increasingly stringent global energy conservation and emission reduction policies and the rapid iteration of the new energy vehicle industry, the material application standards for automotive structural components, support components, connectors, shell-type parts, and load-bearing components are continuously improving. These components not only require materials with low density to achieve weight reduction goals, but also need to possess high mechanical strength, good plastic deformation capacity, and excellent casting performance. Developing high-performance cast aluminum alloy materials suitable for lightweight automotive castings has become an important research topic in the field of automotive materials.

[0003] Al-Si cast aluminum alloys, with their excellent casting fluidity, low shrinkage, high filling capacity, low hot cracking tendency, and good wear resistance, have become core candidate materials for automotive lightweighting. By further adding alloying elements such as Mg and Cu to the Al-Si alloy system and using standardized heat treatment processes, the internal phase structure of the alloy can be effectively controlled, resulting in better comprehensive mechanical properties that can initially meet the requirements for conventional automotive castings.

[0004] Currently, conventional Al-Si-Mg-Cu cast aluminum alloys still suffer from several technical shortcomings: First, coarse α-Al dendrites and eutectic Si structures easily appear in the as-cast microstructure, and the phase size and distribution are difficult to control precisely, directly leading to insufficient matching between the alloy's strength and plasticity. Second, traditional single-element alloying methods have limited effectiveness in refining the alloy microstructure, modifying eutectic Si, and improving overall performance. Third, there is still considerable room for optimization in the dedicated material systems for lightweight high-performance automotive castings, and they cannot fully meet the stringent material performance requirements of high-end automotive castings. Therefore, developing Al-Si-Mg-Cu-based cast aluminum alloys that can improve microstructure and enhance overall mechanical properties is of significant practical importance for promoting the development of automotive lightweighting technology. Summary of the Invention

[0005] The purpose of this application is to provide an Al-Si-Mg-Cu based cast aluminum alloy with excellent comprehensive performance.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: a doped element modified cast aluminum alloy is provided, comprising, by mass percentage, 6.8%–7.2% Si, 0.3%–0.5% Mg, 0.4%–0.6% Cu, 0.1%–0.3% Fe, 0.05%–0.15% Mn and 0.1%–1.9% doping elements, with the balance being Al. The doping elements are any one or a combination of La, Ce, and Zn.

[0007] As a preferred option, the doping elements are La and Zn.

[0008] As a preferred option, the composition by mass percentage includes 6.8%–7.2% Si, 0.3%–0.5% Mg, 0.4%–0.6% Cu, 0.1%–0.3% Fe, 0.05%–0.15% Mn, 0.1%–0.4% La, 0.5%–1.5% Zn, with the balance being Al.

[0009] As a preferred option, by mass percentage, it includes 7.0% Si, 0.4% Mg, 0.5% Cu, 0.2% Fe, 0.1% Mn, 0.3% La, 1.5% Zn, with the balance being Al.

[0010] This application also provides a method for preparing the above-mentioned doped element modified cast aluminum alloy, comprising the following preparation steps: S1: Melting various metal raw materials to obtain an alloy melt, and adjusting the content of each element in the alloy melt so that the measured value of the content of each metal element in the alloy melt matches the target value; the metal raw materials include elemental metals and / or aluminum alloys, wherein the elemental metals are any one or more combinations of Al, Si, Mg, Cu, Fe, Mn or doping elements, the aluminum alloys are any one or more combinations of Al-Si alloys, Al-Fe alloys, Al-Mn alloys, Al-Cu alloys and alloys formed by the doping elements and aluminum, and the doping elements are any one or more combinations of La, Ce, Zn; S2: The alloy melt is purified and optimized before casting to obtain a cast alloy; S3: The cast alloy is subjected to solution-aging treatment to obtain the doped element modified cast aluminum alloy.

[0011] As a preferred option, the casting method in step S2 is gravity casting with a metal mold.

[0012] As a preferred embodiment, the solution treatment temperature in step S3 is 500~560℃, the holding time is 1~3 hours, followed by water quenching, and the aging treatment temperature is 160~200℃, the aging treatment time is 0.5~18 hours.

[0013] As another preferred option, step S1 specifically involves: first, melting high-purity aluminum in a container, then adding Al-Si alloy, Al-Cu alloy, Al-Fe alloy, Al-Mn alloy, and the alloy of the doping element with aluminum and fully melting them, then adding pure Mg until completely dissolved, taking a sample for composition analysis, and adding the elemental metal or the aluminum alloy to ensure that the measured values ​​of the content of each metal element in the alloy melt match the target values.

[0014] Further preferably, step S2 specifically involves: refining the alloy melt with argon and a refining agent, removing surface slag, then introducing a mixture of argon and chlorine for hydrogen removal treatment, adding a grain refiner, and casting at 700~730℃ to obtain the as-cast alloy.

[0015] This application also provides a structural component made of cast aluminum alloy by extrusion casting process. The cast aluminum alloy is the above-mentioned doped element modified cast aluminum alloy, or is made by the above-mentioned preparation method. The extrusion pressure of the extrusion casting is 900~1100 bar, the extrusion speed is 0.1~0.2 m / s, and the holding time is 14~18 s.

[0016] Compared with the prior art, the beneficial effects of this application are as follows: (1) By combining doping elements, dendrite refinement of α-Al matrix and efficient modification of eutectic Si structure are achieved, and coarse needle-like or blocky eutectic Si is transformed into fine, round and uniformly distributed particles, eliminating stress concentration in the structure and solving the problem of coarse structure in the basic alloy. (2) The refining effect of La and the solid solution strengthening effect of Zn work together to break through the bottleneck of the limited effect of single microalloying. The tensile strength, yield strength and hardness of the alloy are greatly improved, while maintaining excellent elongation after fracture. The strength and plasticity are optimally matched. (3) The alloy is compatible with metal mold gravity casting and extrusion casting processes, and can produce lightweight automotive castings with good formability, dense internal structure and few defects, which can meet the stringent performance requirements of high-end automotive structural parts, shells and load-bearing parts, and help the development of automotive lightweighting. Attached Figure Description

[0017] Figure 1 This is a diagram of the as-cast microstructure, in which... Figure 1 (a)~ Figure 1 (d) are as-cast microstructure diagrams of Comparative Example 1, Example 1, Example 4 and Example 5, respectively.

[0018] Figure 2 For scanning tissue images, where Figure 2 (a)~ Figure 2 (d) are scanned tissue images of Comparative Example 1, Example 1, Example 4 and Example 5, respectively.

[0019] Figure 3 This is a grain structure diagram, in which... Figure 3 (a)~ Figure 3 (d) are grain structure diagrams of Comparative Example 1, Example 1, Example 4 and Example 5, respectively.

[0020] Figure 4 This is a grain structure diagram of the peak-aging alloy, where... Figure 4 (a)~ Figure 4 (d) are the grain structure diagrams of the peak-aging alloys of Comparative Example 1, Example 1, Example 4 and Example 5, respectively.

[0021] Figure 5 The image shows the microstructure of the peak-aged alloy, in which... Figure 5 (a)~ Figure 5 (d) are scanning microstructures of the peak-aged alloys of Comparative Example 1, Example 1, Example 4 and Example 5, respectively.

[0022] Figure 6 A blank for the front end cover of a battery prepared by extrusion casting process.

[0023] Figure 7 The results are from X-ray flaw detection, among which Figure 7 (a)~ Figure 7 (k) are the X-ray flaw detection results of Examples 5-1 to 5-11, respectively.

[0024] Figure 8 It has a metallographic structure, in which Figure 8 (a)~ Figure 8 (l) are the metallographic structures of Comparative Example 5-0, Examples 5-1 to 5-11, respectively. Detailed Implementation

[0025] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0026] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0027] This application provides a doped element modified cast aluminum alloy, comprising: Al, Si, Mg, Cu, Fe, Mn and doping elements, wherein the doping elements are any one or a combination of La, Ce and Zn, and the content of the doping elements is 0.1wt.% to 1.9wt.%.

[0028] A doped element modified cast aluminum alloy, by introducing any one or more of La, Ce and Zn into an Al-Si-Mg-Cu based cast aluminum alloy, achieves synergistic control of the α-Al matrix and eutectic Si structure through composite microalloying, which is beneficial to improve the microstructure and enhance the overall performance.

[0029] As a rare earth element, La can refine the dendritic and modified eutectic Si structure in the α-Al matrix, transforming coarse needle-like / blocky eutectic Si into fine, round, and uniformly distributed particles, eliminating stress concentration caused by coarse structure, and solving the defect of coarse structure in the basic alloy. Zn can be dissolved in the Al matrix, and with solid solution-aging treatment, it can strengthen the matrix and promote the uniform distribution of precipitates, thereby improving the overall strengthening effect of the alloy.

[0030] In some embodiments, the present application discloses a doped element modified cast aluminum alloy, which, by mass, comprises: 6.8%–7.2% Si, 0.3%–0.5% Mg, 0.4%–0.6% Cu, 0.1%–0.3% Fe, 0.05%–0.15% Mn, and 0.1%–1.9% doping elements, wherein the doping elements are any one or a combination of more than one of La, Ce, and Zn, and the balance is Al and unavoidable impurities.

[0031] Preferably, the alloy system used in this application is an Al-Si-Mg-Cu cast aluminum alloy, wherein the base alloy is Al-7Si-0.4Mg-0.5Cu, and by mass, it includes 7.0% Si, 0.4% Mg, 0.5% Cu, 0.2% Fe, and 0.1% Mn.

[0032] In a preferred embodiment, the doping elements are La and Zn, wherein the mass fraction of La is 0.1% to 0.4% and the mass fraction of Zn is 0.5% to 1.5%. This application utilizes the refining and modifying effect of La and the solid solution strengthening effect of Zn to achieve dual optimization of α-Al grains and eutectic Si structure. The alloy structure is finer, more uniform, and defect-free, which is superior to the addition of single elements La and Zn. The addition of these elements helps to overcome the problem of limited control effect of single microalloying, while improving the defects of coarsening of alloy structure and insufficient strength-plasticity matching, perfectly meeting the high performance requirements of lightweight automotive castings.

[0033] Controlling the addition amounts of La and Zn is beneficial for achieving an optimal balance between microstructure control and mechanical properties, avoiding defects caused by excessive or insufficient composition. When the La content is too low, its refining effect on the α-Al matrix and the modifying effect on eutectic Si are insufficient, failing to improve the problem of coarse microstructure. When the La content is too high, rare earth segregation is likely to occur, worsening the microstructure uniformity. Furthermore, excessive La will lead to increased alloy melt viscosity and decreased mold filling capacity, making it unsuitable for gravity casting processes in automotive castings. When the Zn content is too low, the solid solution strengthening effect is insufficient; when the content is too high, segregation at grain boundaries is likely to occur, reducing plasticity.

[0034] This application also provides a method for preparing a doped element modified cast aluminum alloy, comprising the following preparation steps: S1: Melt the various metal raw materials to obtain an alloy melt, and adjust the content of each element in the alloy melt so that the measured value of each metal content in the alloy melt matches the target value. Metal raw materials include elemental metals and / or aluminum alloys. Elemental metals are any one or more of Al, Si, Mg, Cu, Fe, Mn or doping elements. Aluminum alloys are Al-Si alloys, Al-Fe alloys, Al-Mn alloys, Al-Cu alloys or alloys formed by doping elements and aluminum. Doping elements are any one or more of La, Ce, and Zn. S2: The alloy melt is purified and optimized before being poured to obtain the as-cast alloy; S3: The as-cast alloy is subjected to solution-aging treatment to obtain the doped element modified cast aluminum alloy of this application.

[0035] In some embodiments, the doping elements are La and Zn, and the metal raw materials include high-purity aluminum, Al-Si master alloy, pure Mg, Al-Fe master alloy, Al-Mn master alloy, Al-Cu master alloy, Al-La master alloy, and pure Zn.

[0036] In some preferred embodiments, the casting method in step S2 is gravity casting with a metal mold.

[0037] In some preferred embodiments, step S2 involves refining, degassing, slag removal, and grain refinement of the alloy melt before casting.

[0038] In some embodiments, the solution treatment temperature in step S3 is 500~600℃, the holding time is 1~3 hours, followed by water quenching. The aging treatment temperature is 160~200℃. Step S3 is an optimization of the heat treatment process, aimed at further improving the properties of the as-cast alloy.

[0039] Preferably, the aging process time is 0.5 to 18 hours, and the peak aging state is obtained by adjusting the aging process time.

[0040] This application combines composition design with solution-aging treatment, utilizing solution treatment at 500~560℃ for 1~3 hours, water quenching, and aging treatment at 160~200℃ to tap the strengthening potential of materials, so that the precipitation strengthening effect of Mg and Cu and the microstructure regulation effect of La and Zn can work synergistically.

[0041] The doped element modified cast aluminum alloy of this application is suitable for use in the development of lightweight automotive casting materials, and is preferably used for automotive structural parts, support parts, connectors, shell-type parts or load-bearing castings.

[0042] This application provides a structural component made of aluminum alloy by extrusion casting. The aluminum alloy is the aforementioned doped element modified cast aluminum alloy, or it is made by the aforementioned preparation method. In the preferred extrusion process, the extrusion pressure is 900~1100 bar, the extrusion speed is 0.1~0.2 m / s, and the holding time is 14~18 s.

[0043] Example 1 An Al-7Si-0.4Mg-0.5Cu-0.15La alloy was prepared, comprising, by mass ratio: 7.0%Si, 0.4%Mg, 0.5%Cu, 0.15%La, with the balance being Al and unavoidable impurities.

[0044] S1: Weigh out high-purity aluminum, Al-Si master alloy, pure Mg, Al-Fe master alloy, Al-Mn master alloy, and Al-Cu master alloy according to the designed composition. First, add the high-purity aluminum to the crucible and heat to melt it, controlling the furnace temperature at 760–820℃. After the pure aluminum has completely melted, add the master alloys Al-20wt%Si, Al-50wt%Cu, Al-20wt%Fe, Al-10wt%Mn, and Al-10wt%La, and stir appropriately to promote composition homogenization. After the master alloys have fully melted, add pure Mg and continue stirring until it is completely dissolved.

[0045] When the melt temperature drops to 720-740℃, a sample is taken for composition analysis. If the measured Si, Mg, Cu or La content is lower than the design value, the corresponding raw materials are added according to the burn-off condition. If the measured value is higher than the design value, high-purity aluminum is added to dilute the melt so that the final composition meets the design range and the alloy melt is obtained.

[0046] S2: After the composition adjustment is completed, the alloy melt at 710℃ is sprayed with 99.99% pure argon and 0.2% (by weight of the alloy melt) powder refining agent for 15 minutes to remove slag floating on the surface of the alloy melt. A mixture of 99.99% pure argon and 99.99% pure chlorine is then introduced for hydrogen removal for 5 minutes, with chlorine comprising 5% of the volume in the mixture. Finally, 0.3% (by weight of the aluminum alloy melt) of Al5TiB grain refiner is added for alloy melt modification treatment.

[0047] After refining, the alloy melt is allowed to stand for 5 to 15 minutes, and then poured at 700 to 730°C. Gravity casting with a metal mold is preferred to obtain the as-cast alloy.

[0048] S3: The as-cast alloy is placed in a heat treatment furnace and held at 505℃ for 2 hours, followed by rapid water quenching to obtain a solution-treated alloy. The solution-treated alloy is then placed in an aging furnace at 180℃ for 3 hours to obtain a peak-aged alloy. The peak-aged state is obtained by adjusting the holding time. This is the doped element modified cast aluminum alloy of this application.

[0049] Example 2 An Al-7Si-0.4Mg-0.5Cu-0.3La alloy was prepared, comprising, by mass ratio: 7.0%Si, 0.4%Mg, 0.5%Cu, 0.2%Fe, 0.1%Mn, 0.3%La, with the balance being Al and unavoidable impurities.

[0050] In step S1, after the pure aluminum is completely melted, the following metal raw materials are added: Al-20wt%Si, Al-50wt%Cu, Al-20wt%Fe, Al-10wt%Mn, Al-10wt%La and pure Mg. The other preparation steps are consistent with the preparation steps in Example 1.

[0051] Example 3 An Al-7Si-0.4Mg-0.5Cu-1.5Zn alloy was prepared, comprising, by mass ratio: 7.0%Si, 0.4%Mg, 0.5%Cu, 0.2%Fe, 0.1%Mn, 1.5%Zn, with the balance being Al and unavoidable impurities.

[0052] In step S1, after the pure aluminum is completely melted, the following metal raw materials are added: Al-20wt%Si, Al-50wt%Cu, Al-20wt%Fe, Al-10wt%Mn, pure Zn, and pure Mg. The other preparation steps are consistent with the preparation steps in Example 1.

[0053] Example 4 An Al-7Si-0.4Mg-0.5Cu-0.3La-0.5Zn alloy was prepared, comprising, by mass ratio: 7.0%Si, 0.4%Mg, 0.5%Cu, 0.2%Fe, 0.1%Mn, 0.3%La, and 0.5%Zn, with the balance being Al and unavoidable impurities.

[0054] In step S1, after the pure aluminum is completely melted, the following metal raw materials are added: Al-20wt%Si, Al-50wt%Cu, Al-20wt%Fe, Al-10wt%Mn, Al-10wt%La, pure Zn, and pure Mg. The other preparation steps are consistent with the preparation steps in Example 1.

[0055] Example 5 An Al-7Si-0.4Mg-0.5Cu-0.3La-1.5Zn alloy was prepared, comprising, by mass ratio: 7.0%Si, 0.4%Mg, 0.5%Cu, 0.2%Fe, 0.1%Mn, 0.3%La, and 1.5%Zn, with the balance being Al and unavoidable impurities.

[0056] The preparation steps are consistent with those in Example 4.

[0057] Example 6 An Al-7Si-0.4Mg-0.5Cu-0.3Ce alloy was prepared, comprising, by mass ratio: 7.0%Si, 0.4%Mg, 0.5%Cu, 0.2%Fe, 0.1%Mn, 0.3%Ce, with the balance being Al and unavoidable impurities.

[0058] In step S1, after the pure aluminum is completely melted, the following metal raw materials are added: Al-20wt%Si, Al-50wt%Cu, Al-20wt%Fe, Al-10wt%Mn, Al-10wt%Ce, and pure Mg. The other preparation steps are consistent with the preparation steps in Example 1.

[0059] Example 7 An Al-7Si-0.4Mg-0.5Cu-0.15La-0.15Ce alloy was prepared, comprising, by mass ratio: 7.0%Si, 0.4%Mg, 0.5%Cu, 0.2%Fe, 0.1%Mn, 0.15%La, 0.15%Ce, with the balance being Al and unavoidable impurities.

[0060] In step S1, after the pure aluminum is completely melted, the following metal raw materials are added: Al-20wt%Si, Al-50wt%Cu, Al-20wt%Fe, Al-10wt%Mn, Al-10wt%La, Al-10wt%Ce, and pure Mg. The other preparation steps are consistent with the preparation steps in Example 1.

[0061] Comparative Example 1 An Al-7Si-0.4Mg-0.5Cu base alloy was prepared, comprising, by mass ratio: 7.0%Si, 0.4%Mg, 0.5%Cu, 0.2%Fe, 0.1%Mn, with the balance being Al and unavoidable impurities.

[0062] In step S1, after the pure aluminum is completely melted, the following metal raw materials are added: Al-20wt%Si, Al-50wt%Cu, Al-20wt%Fe, Al-10wt%Mn and pure Mg. The other preparation steps are consistent with the preparation steps in Example 1.

[0063] Performance testing Mechanical property testing: Tensile tests were conducted at room temperature according to relevant standards for tensile testing of metallic materials to obtain key mechanical properties such as tensile strength, yield strength, and elongation after fracture. An Instron 5966 electronic universal testing machine with a maximum tensile force of 10 kN was used for tensile testing. The tests were conducted in accordance with GB / T 228.1-2021 "Metallic materials, tensile testing—Part 1: Tests at room temperature".

[0064] The microhardness of aluminum alloys was tested using a Wilson VH-1102 microhardness tester. Before the experiment, a standard microhardness block with a hardness value of 540HV0.5 was used for calibration. After calibration, a load of 100g and a loading time of 30s were selected.

[0065] Microstructure analysis: The metallographic microstructure was observed using a ZEISS AXIO Imager. A2m metallographic microscope. A HITACHI SU5000 field emission scanning electron microscope (SEM) was used to observe the microstructure of the alloy.

[0066] The as-cast alloys prepared in each embodiment and Comparative Example 1 were tested for yield strength, tensile strength, elongation and hardness, and the test results are recorded in Table 1 below.

[0067] Table 1 Performance test results of each embodiment and Comparative Example 1

[0068] Analysis of the performance test results in Table 1 shows that, compared with the base alloy, the La-doped aluminum alloy exhibits significant improvements in tensile strength, yield strength, and microhardness, with a simultaneous improvement in elongation at break. La effectively refines α-Al dendrites and modified eutectic Si, eliminates stress concentration in coarse microstructures, and addresses the defects of coarse microstructure and poor strength-ductility matching in the base alloy. Furthermore, the performance optimization effect is even better when the La content is in the range of 0.1% to 0.4%.

[0069] Compared to the base alloy, single Zn doping significantly improves tensile strength, yield strength, and microhardness, while slightly reducing plasticity, but still outperforming the base alloy. Zn can be dissolved in the Al matrix, and combined with heat treatment, it can achieve matrix strengthening, demonstrating Zn's solid solution strengthening effect.

[0070] Aluminum alloys co-doped with La and Zn achieve peak tensile strength, yield strength, and microhardness, while maintaining a high level of elongation after fracture. Their as-cast and peak-aged hardness are superior to both the base alloy and alloys doped with a single element. The alloy exhibits optimal strength-ductility matching. The refining and modifying effects of La and the solid solution strengthening effects of Zn work synergistically, overcoming the technical bottleneck of limited effects from single microalloying. The microstructure control and performance improvement effects are far superior to those of single-element addition. The optimal ratio of 0.3% La to 1.5% Zn yields the best overall mechanical properties.

[0071] The as-cast microstructures of the aluminum alloys prepared in Comparative Example 1, Example 1, Example 4, and Example 5 are shown in the figure. Figure 1 As shown, the microstructure of the as-cast alloy is as follows: Figure 2 As shown, the grain structure of the as-cast alloy is as follows: Figure 3 As shown, aluminum alloys with combined La and Zn doping can synergistically enhance the α-Al dendrite refinement and eutectic Si modification effects, achieving efficient modification of eutectic Si. Furthermore, it can synergistically enhance the grain refinement effect, thoroughly optimizing its size and morphology. The synergistic control effect is far superior to the addition of a single dopant element.

[0072] The grain structure of the peak-aged alloys prepared in Comparative Example 1, Example 1, Example 4 and Example 5 are as follows: Figure 4 As shown, the scanned tissue is as follows Figure 5 As shown, La and Zn can produce a synergistic regulatory effect, achieving simultaneous grain refinement and eutectic Si spheroidization, which is far superior to single-element methods. Solid solution at 505℃ and aging at 180℃ can fully utilize the precipitation strengthening effect without destroying the microstructure regulation effect of La and Zn doping, thus achieving a unity of microstructure optimization and performance enhancement.

[0073] Using the doped element modified cast aluminum alloy prepared in Preferred Example 5 as the research object, the battery front cover part was prepared by extrusion casting process. The influence of extrusion casting process parameters such as pressure and mold temperature on the microstructure and mechanical properties of the alloy was systematically studied, and the strengthening mechanism of the alloy under extrusion casting conditions was clarified, so as to provide theoretical basis and technical support for the application of high-performance Al-Si alloys in battery shell components of new energy vehicles.

[0074] The main process parameters for squeeze casting include extrusion speed, extrusion pressure, mold temperature, and pouring temperature. This experiment focuses on controlling the two key process parameters of extrusion speed and extrusion pressure, as these two factors directly determine the filling capacity, solidification and feeding effect, and final mechanical properties of squeeze-cast Al-Si alloy castings. Finally, the influence of holding time on alloy squeeze casting was considered, and two control groups were set up. Among them, Examples 5-1 to 5-9 studied the effects of different extrusion speeds and extrusion pressures, while Examples 5-10 and 5-11 studied the influence of holding time on squeeze casting. A set of parts produced by a company using A356 alloy was prepared as comparative example 5-0. The specific experimental scheme is shown in Table 2.

[0075] Table 2. Design of squeeze casting process parameters and test results of mechanical properties.

[0076] As shown in the table, among the extrusion-cast Al-7Si-0.4Mg-0.5Cu-0.3La-1.5Zn alloys, the alloy of Example 5-2 exhibits the highest tensile strength and elongation. Comparing the alloy properties, the alloy of Example 5-2 demonstrates the best performance, with both high tensile strength and elongation. Compared to the comparative alloy 5-0, the strength is improved, while the elongation is slightly decreased. The tensile strength of the alloy of Example 5-2 is increased by 6.1%. In summary, extrusion casting helps improve the mechanical properties of the Al-7Si-0.4Mg-0.5Cu-0.3La-1.5Zn alloy, and the optimal performance is obtained when the extrusion pressure is 1000 bar, the extrusion speed is 0.15 m / s, and the holding pressure is 16 s.

[0077] Battery front end cover blank prepared by squeeze casting process, such as Figure 6 As shown in the figure. From an appearance perspective, the blank exhibits good overall formability, complete geometry, and no obvious casting defects such as cracks, cold shuts, or incomplete pouring; the surface quality is relatively ideal. To further evaluate the internal quality of the blank, X-ray flaw detection was performed. The X-ray flaw detection results of all samples are summarized as follows: Figure 7As shown in the figure. The flaw detection results show that, except for a small number of scattered shrinkage defects in the central area, the microstructure of the remaining parts of the blank is relatively dense, and no obvious internal defects such as porosity, inclusions, or cracks are observed. Among them, the internal quality of the sample in Example 5-2 is the best, and it is difficult to observe obvious defect features in the flaw detection image, indicating that the casting obtained under this process parameter has the highest density.

[0078] The microstructure of the alloy was observed under a 200x optical microscope. For example... Figure 8 As shown, the extrusion casting process parameters have a significant impact on the alloy microstructure. All samples consisted of an α-Al matrix and a eutectic Si phase, with α-Al exhibiting an equiaxed crystal distribution and eutectic Si dispersed at grain boundaries and between dendrites. As the extrusion pressure increased from 900 bar to 1000 bar, the microstructure became significantly finer, and the eutectic Si distribution shifted from localized enrichment to a more uniform distribution. However, when the pressure was further increased to 1100 bar, some grains showed significant coarsening, and eutectic Si again showed localized aggregation. This may be because excessively high pressure exacerbates non-uniform solidification, leading to preferential precipitation of eutectic Si in certain regions. Regarding extrusion speed, a moderate speed is more conducive to the formation of fine equiaxed crystals and uniformly distributed eutectic Si, but excessively high speed may cause temperature inhomogeneity, inducing grain coarsening, while excessively slow speed may lead to non-uniform solidification and significant differences in grain size.

[0079] Furthermore, insufficient holding time can also adversely affect the microstructure. The microstructure of samples 5-10 (holding time 14s) was extremely inhomogeneous, with a significant increase in coarse grains; while the microstructure of Sample 5-11 (holding time 18s) was more uniform, similar to the superior performance of samples such as Sample 5-2. This indicates that excessively short holding time leads to the solidification of the remaining liquid phase at atmospheric pressure during depressurization, resulting in grain coarsening due to the reduced solidification rate.

[0080] The tensile strength, yield strength, and elongation of three groups of peak-aging extrusion-cast alloys (Comparative Example 5-0, Example 5-2, and Example 5-5) were compared, as shown in Table 3.

[0081] Table 3. Test results of mechanical properties of peak-aged extrusion cast alloys in three groups: Comparative Example 5-0, Example 5-2, and Example 5-5.

[0082] Of the three alloys, the alloy in Example 5-2 exhibited the best overall mechanical properties, with a tensile strength of 301 MPa and an elongation of 6.88%, both at relatively high levels. This indicates that the new extrusion casting alloy system can effectively improve the mechanical properties of Al-Si.

[0083] In summary, this application achieves synergistic control of the alloy's microstructure by introducing doping elements into Al-Si-Mg-Cu based cast aluminum alloys, combined with precise composition design and a complete preparation process including melting, purification, gravity casting in metal molds, and solution-aging treatment. Specifically, La effectively refines α-Al dendrites and modified eutectic Si structures, while Zn provides solid solution strengthening. The combined doping of these two elements creates a synergistic effect, overcoming the technical bottleneck of limited effectiveness in traditional single microalloying and fundamentally improving the defects of coarse microstructure and insufficient strength-ductility matching in conventional Al-Si cast aluminum alloys.

[0084] Verification through examples and comparative examples shows that the modified aluminum alloy obtained in this application exhibits significantly improved mechanical properties such as tensile strength, yield strength, and hardness, while maintaining excellent elongation after fracture, achieving optimal strength-ductility matching. Combined with an optimized extrusion casting process, it can produce lightweight automotive castings with good formability and dense internal structure, meeting the stringent performance requirements of high-end automotive structural components, housings, and load-bearing parts. The technical solution provided in this application effectively addresses the technical shortcomings of existing cast aluminum alloys, offering a practical path for the research and application of high-performance lightweight automotive aluminum alloy materials, possessing outstanding technical practicality and broad industrial application prospects.

[0085] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A doped element modified cast aluminum alloy, characterized in that, By mass percentage, it includes 6.8%–7.2% Si, 0.3%–0.5% Mg, 0.4%–0.6% Cu, 0.1%–0.3% Fe, 0.05%–0.15% Mn and 0.1%–1.9% doping elements, with the balance being Al. The doping elements are any one or a combination of more than one of La, Ce and Zn.

2. The doped element modified cast aluminum alloy as described in claim 1, characterized in that, The doping elements are La and Zn.

3. The doped element modified cast aluminum alloy as described in claim 2, characterized in that, By mass percentage, it includes 6.8%–7.2% Si, 0.3%–0.5% Mg, 0.4%–0.6% Cu, 0.1%–0.3% Fe, 0.05%–0.15% Mn, 0.1%–0.4% La, 0.5%–1.5% Zn, with the balance being Al.

4. The doped element modified cast aluminum alloy as described in claim 3, characterized in that, By mass percentage, it includes 7.0% Si, 0.4% Mg, 0.5% Cu, 0.2% Fe, 0.1% Mn, 0.3% La, 1.5% Zn, with the balance being Al.

5. The method for preparing doped element modified cast aluminum alloy as described in claim 1, characterized in that, The preparation steps include the following: S1: Melt the various metal raw materials to obtain an alloy melt, and adjust the content of each element in the alloy melt so that the measured value of the content of each metal element in the alloy melt matches the target value. The metal raw material includes elemental metals and / or aluminum alloys. The elemental metals are any one or more of Al, Si, Mg, Cu, Fe, Mn, or doping elements. The aluminum alloys are any one or more of Al-Si alloys, Al-Fe alloys, Al-Mn alloys, Al-Cu alloys, and alloys formed by the doping elements and aluminum. The doping elements are any one or more of La, Ce, and Zn. S2: The alloy melt is purified and optimized before being poured to obtain a cast alloy; S3: The as-cast alloy is subjected to solution-aging treatment to obtain the doped element modified cast aluminum alloy.

6. The preparation method according to claim 5, characterized in that, The casting method in step S2 is gravity casting of a metal mold.

7. The preparation method according to claim 5, characterized in that, The solution treatment temperature in step S3 is 500~560℃, the holding time is 1~3 hours, followed by water quenching, and the aging treatment temperature is 160~200℃, the aging treatment time is 0.5~18 hours.

8. The preparation method according to claim 5, characterized in that, The S1 step specifically involves: first, melting high-purity aluminum in a container, then adding Al-Si alloy, Al-Cu alloy, Al-Fe alloy, Al-Mn alloy, and the alloy of the doping element with aluminum and melting them completely, then adding pure Mg until completely dissolved, taking a sample for composition analysis, and adding the elemental metal or the aluminum alloy to ensure that the measured values ​​of the content of each metal element in the alloy melt match the target values.

9. The preparation method according to claim 5, characterized in that, The S2 step specifically involves: refining the alloy melt with argon and a refining agent, removing surface slag, then introducing a mixture of argon and chlorine for hydrogen removal, adding a grain refiner, and casting at 700~730℃ to obtain the as-cast alloy.

10. A structural component, characterized in that, It is made from cast aluminum alloy by extrusion casting process, wherein the cast aluminum alloy is a doped element modified cast aluminum alloy as described in any of claims 1 to 4, or the cast aluminum alloy is made by any of the preparation methods described in claims 5 to 9, wherein the extrusion pressure of the extrusion casting is 900 to 1100 bar, the extrusion speed is 0.1 to 0.2 m / s, and the holding time is 14 to 18 s.

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