Casting aluminum-silicon alloy raw material, preparation method and application thereof

Abstract

The present disclosure relates to a cast aluminum-silicon alloy raw material, a preparation method and application thereof. The cast aluminum-silicon alloy raw material comprises, based on the total weight of the cast aluminum-silicon alloy raw material, 7.0-9.0 wt% Si, 0.1-0.36 wt% Fe, 0.2-0.65 wt% Mn, 0.06-0.32 wt% Mg, 0.001-0.3 wt% Cu, 0.01-0.15 wt% Ti, 0.015-0.03 wt% Sr, 0.01-0.06 wt% M, M being one or more selected from Zr, Cr and V, less than or equal to 0.06 wt% other impurity elements and the balance Al, and the content of Mn, Fe and Si satisfies the formula: 0.08Si+0.2≥Mn+Fe, and the average size of Fe-rich phase in the micro solidification structure of the cast aluminum-silicon alloy raw material is not greater than 40 μm. The cast aluminum-silicon alloy raw material has significantly improved elongation and mechanical property stability, and excellent demolding processability, and can meet the application requirements of alloy materials in high toughness and high reliability for automobile structural parts.

Description

Technical Field

[0001] This disclosure relates to a cast aluminum-silicon alloy raw material, its preparation method, and its application. Background Technology

[0002] Al-Si alloys have become the mainstream material in the field of integrated die casting for automobiles due to their excellent casting properties. However, the use of primary aluminum has the problems of high energy consumption and high carbon emissions, while the energy consumption of recycled aluminum is only 3-5% of that of electrolytic aluminum, and the carbon emissions are only 2.1% of those of primary aluminum. Therefore, the use of recycled aluminum, that is, the recycling and reuse of aluminum alloys, can significantly reduce the overall energy consumption and greenhouse gas emissions of the metal smelting process and promote the development of a green economy.

[0003] However, compared with primary aluminum, recycled aluminum has the characteristics of lower quality, more structural defects, poor plasticity, and poor mechanical property stability. According to existing literature 1 (HY Zhan, G. Zeng, QG Wang, et al., Unifiedcasting (UniCast) aluminum alloy-a sustainable and low-carbon materials solution for vehicle lightweighting, J. Mater. Sci. Technol., 154(2023), p.251.), the reason is that recycled aluminum has a high impurity content, especially Fe impurities, which can reach 0.2~1.3 wt.%. However, according to existing literature 2 (F. Liao, S. Zhao, Y. Liao, et al, Enhanced Fe tolerance in recycled Al-7Si-0.3Mg alloys via refining microstructure, Int. J. Miner. Metall. Mater., (2025). https: / / doi.org / 10.1007 / s12613-025-3365-z), the elongation of Al-Si alloys decreases by 17% when the Fe content increases from 0.1 wt.% to 0.2 wt.%, and by 54% when the Fe content increases to 0.5 wt.%.

[0004] However, during the actual smelting process of recycled aluminum, it is impossible to effectively remove Fe, and Fe impurities are inevitably introduced during the production process. Furthermore, as the number of casting cycles of recycled aluminum increases, the Fe content gradually accumulates. For these reasons, different grades of aluminum alloys have strict regulations regarding the content of impurity iron, especially in the field of high-performance automotive chassis parts, where the Fe content must be controlled below 0.1 wt.%. Therefore, currently, directly replacing primary aluminum with recycled aluminum in the preparation of Al-Si alloys based on primary aluminum cannot meet the application requirements of automotive parts.

[0005] Existing research indicates that when preparing Al-Si alloys from recycled aluminum, the microstructure of the solidified recycled aluminum typically contains Al due to variations in the proportions of impurity elements within the recycled aluminum. 13 Fe-rich intermetallic compounds include Fe4, α-AlFeSi, β-AlFeSi, and π-AlSiMgFe phases. Among them, the β-AlFeSi phase is usually a coarse needle-like compound that easily adsorbs gas to form large shrinkage pores. The tips of the needle-like Fe-rich phases can cause stress concentration and become crack initiation points, leading to a sharp decrease in the plasticity of the alloy.

[0006] To improve the mechanical properties, especially elongation, of recycled aluminum alloys, the β-AlFeSi phase can be modified by adding alloying elements such as Mn, Cr, and Ni. For example, existing literature 3 (Tian Zhanfeng, et al., ZL202510479750.X, A low-carbon, high-strength, and high-toughness aluminum alloy for a large integrated die-cast battery pack and its preparation method and die-casting process, 2025-04-17) uses Mn to replace Fe in the acicular AlFeSi phase to form a blocky AlFeMnSi phase and uses Ni to form an AlNiFe phase, thereby reducing the formation of the acicular Fe-rich phase. The elemental content is Mn: 0.25-0.65 wt.%, Fe: 0.1-0.5 wt.%, Ni: 0.006-0.18 wt.%, Si: 8.5-9.5%, Mg: 0.15-0.45%, Cu: 0.1-0.4%, and the Mn to Fe content ratio is 1.5-2.5. The existing literature concludes that Mn and Ni elements can transform the acicular AlFeSi phase into the blocky AlFeMnSi and AlNiFe phases, and combined with the faster cooling rate of the die-casting process, thereby improving the strength and toughness of aluminum alloys.

[0007] However, according to another study by the authors of existing literature 3, existing literature 4 (Tian Zhanfeng, et al., ZL202311414034.0, A Renewable High-Strength and Tough Heat-Treating-Free Aluminum Alloy and Its Preparation Method and Die-Casting Process) indicates that it is necessary to control the Mn to Fe content ratio to be 0.7-1.1, while... The content of other alloying elements is ≤1.8, with Si: 6.5-9.5%, Cu: 0.8-1.2%, Mg: 0.1-0.3%, Cr: 0.01-0.15%, and Ni: 0.01-0.06%. The existing literature concludes that the strength and toughness of aluminum alloys can be improved by controlling the Mn / Fe ratio to be less than 1.1 and the excess amounts of Fe, Mn, Cr, and Ni, combined with a faster cooling rate in the die-casting process. However, this conclusion, namely an effective Mn / Fe ratio range of 0.7-1.1, contradicts the conclusion of 1.5-2.5 obtained in existing literature 3.

[0008] Therefore, as can be seen from existing literature 3 and 4, the Mn / Fe ratio is not the only factor affecting the elongation of recycled aluminum alloys. Other elements in the alloy, such as different Cu content ranges, and different Cr and Ni contents, will also lead to completely different Mn / Fe ratio ranges. In other words, existing technology cannot be directly applied to other alloy systems.

[0009] Furthermore, based on the inventors' previous research, existing literature 5 (Luo Qun, et al., CN2025118230561, A method for improving the mechanical properties of nickel-containing Al-Si alloys by adjusting the cooling rate, 2025-12-05) shows that the addition of Ni will cause the Sr modification effect to disappear, the eutectic silicon size to grow abnormally, and the alloy elongation to decrease significantly. Therefore, the mechanical property control of recycled aluminum needs to consider the complex interactions between elements in the alloy; at the same time, since the price of elements such as Cr, Ni, and Sr is 3-20 times that of Mn, the addition of microalloying elements needs to be simplified as much as possible in terms of process simplicity and cost.

[0010] In addition to the average value of mechanical properties, the stability of mechanical properties is also an important performance evaluation parameter. For example, if the average elongation is acceptable, but the lower limit is too low, the pass rate is poor, leading to premature failure during assembly or use, or large differences in elongation between different parts of the same casting, which can easily result in catastrophic brittle fracture during service. Therefore, existing basic testing standards and product standards have strict requirements on the fluctuation and dispersion of mechanical properties. For example, existing literature 6 (ASTM B209, Standard Specification for Aluminum and Aluminum-Alloy Sheet and Plate) clearly specifies the minimum values ​​for yield strength, tensile strength, and elongation of various series of aluminum alloys; these mechanical property parameters cannot be lower than the specified minimum values. Therefore, stable and controllable casting quality and elongation are important standards for the quality of high-quality casting materials and the level of production technology.

[0011] Analysis of the above literature reveals the following technical problems associated with adding too many types of alloying elements and excessive element content: 1. Excessive alloying elements make it impossible to predict their interactions with the parent material elements using existing technology; 2. Excessive elements will form coarse Fe-rich phases. Although this effect can improve the average strength and plasticity of the alloy, the yield rate cannot meet the application requirements, increasing the risk of casting use. Summary of the Invention

[0012] The purpose of this invention is to provide a high-stability recycled aluminum-silicon alloy raw material and its preparation method, which solves the technical problems of low elongation and unstable mechanical properties of recycled aluminum in the prior art. The basic principle involved is as follows: based on the composition of the recycled aluminum matrix alloy, by adjusting the Mn / Fe ratio, β-Al5FeSi is completely transformed into α-AlFeMnSi phase, while fine eutectic α-AlFeMnSi phase is formed, thereby improving the alloy elongation and mechanical property stability; based on the Si content, the total Mn+Fe content is adjusted to suppress the formation of primary α-AlFeMnSi phase, improve the uniformity of the microstructure, enhance the stability of the alloy's mechanical properties, and coordinate the demolding performance.

[0013] Meanwhile, Cr, Zr, and V were added to this recycled cast aluminum-silicon-aluminum alloy, forming a non-equivalent, functionally complementary composite strengthening system. Their synergistic effects are manifested as follows: Cr can transform the acicular β-AlFeSi phase into granular or Chinese character-shaped α phases, which have less detrimental effects on mechanical properties, reducing the deteriorating effect of unavoidable iron elements in the recycled aluminum raw material on the alloy's plasticity, and simultaneously alleviating the tendency to stick to the mold during die casting; Zr, by forming a high-melting-point, highly dispersed Al3Zr phase, significantly refines α-Al grains in the early stage of solidification and acts as a nucleation core to improve the uniformity of the microstructure; the introduction of V, on the one hand, synergistically inhibits grain coarsening behavior during subsequent cooling with Zr, and on the other hand, further pins grain boundaries and improves the thermal stability of the microstructure by forming a vanadium-based dispersed phase. Kinetically, the three elements form a cascade effect of "Cr regulating the morphology of the iron phase, Zr dominating grain refinement, and V strengthening grain boundaries and thermal stability," enabling the recycled aluminum raw material to simultaneously obtain high strength, good plasticity, and excellent filling and demolding performance without relying on subsequent heat treatment.

[0014] The specific technical features of the design include: 1. Based on the alloy plasticity requirements and the phase diagram calculation results, control the Mn and Fe element content ratio to be ≤ 1. w Mn / Fe ≤6, so that β-Al5FeSi in the solidified structure is completely transformed into α-AlFeMnSi phase; 2. Based on the requirements for the plasticity and stability of the alloy, and based on the phase diagram calculation results and experimental results, the total content of Mn and Fe elements is controlled at 0.5~0.8 wt.%, and the Fe content is ≤0.3 wt.%. In addition, based on the measured Si content in the melt, the amount of Mn added is reduced when the Si content is low, so as to reduce the total amount of Mn+Fe elements and suppress the formation of coarse primary α-AlFeMnSi phase. 3. Based on the requirements for the ease of demolding of the alloy, control the total amount of Mn+Fe elements in the melt to ≥0.6wt.% to reduce the reaction and erosion of the mold by the melt and facilitate demolding.

[0015] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: In a first aspect, this disclosure provides a cast aluminum-silicon alloy raw material, wherein, based on the total weight of the cast aluminum-silicon alloy raw material, the cast aluminum-silicon alloy raw material comprises: 7.0~9.0 wt% Si, 0.1~0.36 wt% Fe, 0.2~0.65 wt% Mn, 0.06~0.32 wt% Mg, 0.001~0.3 wt% Cu, 0.01~0.15 wt% Ti, 0.015~0.03 wt% Sr, 0.01~0.06 wt% M, wherein M is selected from one or more of Zr, Cr and V, and other impurity elements less than or equal to 0.06 wt% and the balance Al, and the contents of Mn, Fe and Si satisfy the following formula: 0.08Si + 0.2 ≥ Mn + Fe, and the average size of the Fe-rich phase in the microstructure of the cast aluminum-silicon alloy raw material is not greater than 40 μm.

[0016] Optionally, the microstructure of the cast aluminum-silicon alloy raw material does not contain primary α-AlFeMnSi phase; and / or, The Fe-rich phase is an α-AlFeMnSi phase, distributed within the eutectic silicon region, and mainly in the form of granules and short rods.

[0017] Optionally, in the cast aluminum-silicon alloy raw material, the Fe content is 0.18~0.3% by weight, the total Mn and Fe content is 0.6~0.75% by weight, and the weight ratio of Mn to Fe is (1~3):1.

[0018] Optionally, the average elongation of the cast aluminum-silicon alloy raw material in multiple tensile mechanical property tests is 7.9% to 8.9%, and the proportion of samples with an elongation of more than 6.0% is more than 95%.

[0019] A second aspect of this disclosure provides a method for preparing the cast aluminum-silicon alloy raw material described in the first aspect of this disclosure, the method comprising: S1. The aluminum-containing raw material is subjected to a first refining, a second refining and a third refining in sequence to obtain an alloy melt; The temperatures of the first refining, the second refining, and the third refining are gradually reduced. At least one of Si, Mn, Cu, Ti, Cr, Zr, and V raw materials is added in the second refining stage, and at least one of Mg and Sr raw materials is added in the third refining stage. S2. The alloy melt is cast into shape to obtain the cast aluminum-silicon alloy raw material.

[0020] Optionally, the aluminum-containing raw material includes recycled aluminum waste; the method further includes: before step S1, pre-treating the recycled aluminum waste, performing low-temperature smelting, and magnetic iron removal sequentially.

[0021] Optionally, in step S1, the conditions for the first refining include: a temperature of 760~780℃ and a time of 15~20min; The conditions for the second refining process include: a temperature of 740~760℃ and a time of 10~15min; The conditions for the third refining process include: a temperature of 730~750℃ and a time of 8~10 minutes.

[0022] Optionally, in step S2, the casting conditions include: the alloy melt temperature is 690~710℃, and the mold preheating temperature is 150~200℃.

[0023] A third aspect of this disclosure provides the application of the cast aluminum-silicon alloy raw material described in the first aspect of this disclosure in the preparation of automotive structural parts.

[0024] In a fourth aspect, this disclosure provides an automobile including structural components made from the cast aluminum-silicon alloy raw material described in the first aspect of this disclosure.

[0025] Through the above technical solution, the cast aluminum-silicon alloy raw material disclosed herein has significantly improved elongation and mechanical property stability, while also having excellent demolding processability, which can meet the application requirements of automotive structural parts for alloy materials in terms of high toughness and high reliability.

[0026] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0027] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a scanning electron microscope image of the cast aluminum-silicon alloy of Example 1; Figure 2 Here is a scanning electron microscope image of the cast aluminum-silicon alloy of Example 2; Figure 3 Here is a scanning electron microscope image of the cast aluminum-silicon alloy of Example 3; Figure 4 Here is a scanning electron microscope image of the cast aluminum-silicon alloy of Example 4; Figure 5 Here is a scanning electron microscope image of the cast aluminum-silicon alloy of Example 5; Figure 6 Here is a scanning electron microscope image of the cast aluminum-silicon alloy of Example 6; Figure 7 Here is a scanning electron microscope image of the cast aluminum-silicon alloy of Example 7; Figure 8 A scanning electron microscope image of the cast aluminum-silicon alloy of Comparative Example 1. Figure 9 A scanning electron microscope image of the cast aluminum-silicon alloy of Comparative Example 2. Figure 10 Selected area electron diffraction pattern of Fe-rich phase in cast aluminum-silicon alloy of Comparative Example 2 using transmission electron microscopy. Figure 11 The image shows a scanning electron microscope image of the cast aluminum-silicon alloy of Comparative Example 3. Detailed Implementation

[0028] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0029] In a first aspect, this disclosure provides a cast aluminum-silicon alloy raw material, wherein, based on the total weight of the cast aluminum-silicon alloy raw material, the cast aluminum-silicon alloy raw material comprises: 7.0~9.0 wt% Si (silicon), 0.1~0.36 wt% Fe (iron), 0.2~0.65 wt% Mn (manganese), 0.06~0.32 wt% Mg (magnesium), 0.001~0.3 wt% Cu (copper), and 0.01~0.15 wt% Ti (titanium). The raw material contains 0.015 to 0.03% by weight of Sr (strontium), 0.01 to 0.06% by weight of M, where M is selected from one or more of Zr (zirconium), Cr (chromium) and V (vanadium), less than or equal to 0.06% by weight of other impurity elements and the balance of Al (aluminum), and the contents of Mn, Fe and Si satisfy the following formula: 0.08Si + 0.2 ≥ Mn + Fe, and the average size of the Fe-rich phase in the microstructure of the cast aluminum-silicon alloy raw material is not greater than 40 μm.

[0030] This disclosure, by controlling the content of each element in the alloy raw material, especially by adjusting the total content of Mn and Fe according to the Si content, can suppress the formation of coarse primary α-AlFeMnSi phase, improve the uniformity of microstructure, and make the alloy raw material have significantly improved alloy elongation and mechanical property stability, while also having excellent demolding processability.

[0031] The Fe-rich phase is used to characterize the iron-containing intermetallic compound crystals formed in the later stage of the alloy solidification process. In one specific embodiment, the Fe-rich phase can be an α-AlFeMnSi phase, distributed within the eutectic silicon region, and its microstructure is mainly granular and / or short rod-shaped. The Fe-rich phase does not exhibit a needle-like structure or contains small needle-like phases, which helps to reduce the initiation source of internal cracks and local stress concentration under load, thereby improving elongation and mechanical property stability.

[0032] The average size of the Fe-rich phase can be adjusted within a certain range not exceeding 40 μm. In one specific embodiment, the average size of the Fe-rich phase can be 30.2~38.7 μm. When the average size of the Fe-rich phase is within the above range, it is beneficial to further improve the elongation and mechanical property stability.

[0033] In one specific embodiment, the microstructure of the cast aluminum-silicon alloy raw material does not contain the primary α-AlFeMnSi phase, that is, in the early stage of the solidification and cooling stage of the alloy, large-sized iron-manganese-silicon intermetallic compounds do not precipitate out in the melt before the α-Al matrix.

[0034] By controlling the total content and relative ratio of Mn and Fe in the alloy raw materials, it is beneficial to suppress the formation of coarse primary α-AlFeMnSi phase, regulate the crystallization path of Fe-rich phase, promote the complete transformation of the originally needle-like β-AlFeSi phase into α-AlFeMnSi phase, and optimize the demolding process.

[0035] In one specific embodiment, the Fe content in the cast aluminum-silicon alloy raw material can be less than 0.3% by weight, preferably 0.18-0.3% by weight, and the total Mn and Fe content can be 0.5-0.8% by weight, preferably 0.6-0.75% by weight, more preferably 0.6-0.70% by weight. Further, the weight ratio of Mn to Fe can be (1-6):1, including 3.5:1, 4:1, and preferably (1-3):1. When the weight ratio of Mn to Fe is within the above range, especially the preferred range, it is beneficial to promote the β-AlFeSi phase transformation and obtain a Fe-rich phase with a smaller average size.

[0036] In some specific embodiments, "7.0~9.0 wt%" includes 7.5 wt%, 7.9 wt%, 8.0 wt%, 8.2 wt%, 8.4 wt%, and 8.5 wt%; "0.2~0.65 wt%" includes 0.3 wt%, 0.35 wt%, 0.4 wt%, and 0.5 wt%; "0.06~0.32 wt%" includes 0.08 wt%, 0.1 wt%, 0.15 wt%, 0.25 wt%, and 0.3 wt%; "0.001~0.3 wt%" includes 0.005 wt%, 0.01 wt%, and 0.2 wt%; "0.01~0.15 wt%" includes 0.05 wt% and 0.08 wt%; "0.015~0.03 wt%" includes 0.02 wt% and 0.025 wt%; and "less than or equal to 0.06 wt%" includes 0.05 wt%, 0.04 wt%, and 0.03 wt%.

[0037] In one specific embodiment, Ni and / or Sm are not added to the cast aluminum-silicon alloy raw material. Ni and / or Sm may exist as impurities. Preferably, the cast aluminum-silicon alloy raw material does not contain Ni and / or Sm.

[0038] In one specific embodiment, the cast aluminum-silicon alloy raw material can be prepared from recycled aluminum scrap. The recycled aluminum scrap, also known as "recycled aluminum," typically includes waste generated during aluminum production or processing, and aluminum-containing products that have reached the end of their service life. Examples include machining waste, scrapped aluminum wheel hubs, engine housings, building templates, and aluminum wire. The recycled aluminum scrap can be a collection of the aforementioned various aluminum-containing recycled materials. The background elemental composition of this material collection is used to provide the metal matrix required for the target alloy formulation described above. There are no special restrictions on its initial elemental content; for example, it can be a mixture of various recycled aluminum scraps with significantly different compositions. Using the above raw materials helps reduce overall smelting energy consumption and greenhouse gas emissions, cuts raw material costs, and achieves high-performance, graded utilization of recycled aluminum.

[0039] The cast aluminum-silicon alloy raw material disclosed herein exhibits significantly improved elongation and mechanical property stability. Specifically, the average elongation of the cast aluminum-silicon alloy raw material in multiple (e.g., 5-10) tensile mechanical property tests can be 7.9%-8.9%, preferably 8.5%-8.9%, and the proportion of samples with an elongation of 6.0% or higher can be 95% or higher, preferably 99-100%. Meanwhile, the hardness and yield strength of the cast aluminum-silicon alloy raw material remain essentially unchanged.

[0040] The aluminum-silicon alloy raw material disclosed herein can be used directly by downstream casting and processing enterprises or remelted and formed. It is suitable for casting, die casting and other processes, and can be used in the manufacture of various load-bearing structural components that require high elongation and fatigue strength. In particular, it can meet the performance requirements of the automotive industry for structural components and is suitable for the production of lightweight, high toughness and high reliability structural components for new energy electric vehicles.

[0041] A second aspect of this disclosure provides a method for preparing the cast aluminum-silicon alloy raw material described in the first aspect of this disclosure, the method comprising: S1. The aluminum-containing raw material is subjected to a first refining, a second refining and a third refining in sequence to obtain an alloy melt; The temperatures of the first refining, the second refining, and the third refining are gradually reduced. At least one of Si, Mn, Cu, Ti, Cr, Zr, and V raw materials is added in the second refining stage, and at least one of Mg and Sr raw materials is added in the third refining stage. S2. The alloy melt is cast into a mold to obtain cast aluminum-silicon alloy raw material.

[0042] In step S1, the aluminum-containing raw material may include recycled aluminum waste. Further, the method may also include: before step S1, pre-treating the recycled aluminum waste, performing low-temperature smelting, and magnetic removal of iron in sequence.

[0043] The pretreatment may include waste sorting, crushing and washing steps. Through the above pretreatment, the composition of recycled aluminum waste with complex composition and different forms can be evaluated, proportioned and surface cleaned, the initial chemical composition boundary of raw materials can be controlled and the impurity content in raw materials can be reduced.

[0044] The aforementioned low-temperature smelting process allows for the preliminary melting of recycled aluminum waste, reducing the content of non-metallic inclusions and harmful substances such as oil in the raw materials. Specifically, the conditions for the low-temperature smelting may include a temperature of 630~650℃.

[0045] The magnetic iron removal process can further remove impurities from recycled aluminum after low-temperature smelting, reducing free iron impurities entrained in the raw materials. This can be achieved using commonly used magnetic equipment in the field. Specifically, the magnetic iron removal process may include: inserting the head of an electromagnetic rake into the bottom of the molten aluminum and moving it back and forth in an S-shaped path within the furnace to magnetically remove refractory aluminum-clad iron impurities, which are then removed and cleaned.

[0046] In step S1, the alloy melt is thoroughly cleaned and its composition is finely adjusted by performing three refining processes with gradually decreasing temperatures.

[0047] The first refining process is a high-temperature refining process, which can effectively strip and remove impurities such as aluminum dross from the raw materials. Specifically, the conditions for the first refining process may include: a temperature of 760~780℃ and a time of 15~20 minutes.

[0048] The temperature of the second refining process can be 10-30°C lower than that of the first refining process to achieve alloy homogenization. Specifically, the conditions for the second refining process may include a temperature of 740-760°C and a time of 10-15 minutes.

[0049] In the second refining stage, at least one of the following raw materials is added: Si, Mn, Cu, Ti, Cr, Zr, and V, to achieve alloy homogenization. The specific types and contents of the alloy raw materials can be adjusted according to actual needs. For example, the Si raw material can be 3303 industrial silicon, the Mn raw material can be pure manganese flakes, the Cu raw material can be an aluminum-copper master alloy, the Ti raw material can be an aluminum-titanium master alloy, the Cr raw material can be an aluminum-chromium master alloy, the Zr raw material can be an aluminum-zirconium master alloy, and the V raw material can be an aluminum-vanadium master alloy.

[0050] The temperature of the third refining process can be 10-30°C lower than that of the second refining process to avoid high-temperature burn-off of key metal elements, ensure the achievement of the target alloy ratio, and suppress the formation of the primary α-AlFeMnSi phase. Specifically, the conditions for the third refining process may include: a temperature of 730-750°C and a time of 8-10 minutes.

[0051] In the third refining stage, at least one of Mg and Sr raw materials is added to adjust the content of Mg and Sr elements. The specific types and contents of alloy raw materials can be adjusted according to actual needs. For example, the Mg raw material can be magnesium ingot, and the Sr raw material can be an aluminum-strontium master alloy.

[0052] After the above three-stage refining is completed, the refined melt can be allowed to stand for degassing and filtered to obtain the alloy melt.

[0053] In step S2, the casting process can be gravity casting. Specifically, the casting conditions may include: the alloy melt temperature is 690~710℃ and the mold preheating temperature is 150~200℃.

[0054] A third aspect of this disclosure provides the application of the cast aluminum-silicon alloy raw material described in the first aspect of this disclosure in the preparation of automotive structural parts.

[0055] The aforementioned cast aluminum-silicon alloy raw material can be used as a precast ingot to prepare automotive structural parts with specific load-bearing functions through casting and other processes, such as automotive chassis support parts, steering knuckles, and wheel hubs. This helps to significantly reduce manufacturing costs while ensuring that key load-bearing structural parts do not experience early fatigue fracture due to microscopic defects in the material.

[0056] In a fourth aspect, this disclosure provides an automobile including structural components made from the cast aluminum-silicon alloy raw material described in the first aspect of this disclosure.

[0057] The present disclosure is further described in detail below through examples. All raw materials used in the examples are commercially available.

[0058] The methods for preparing aluminum alloys involved in the examples and comparative examples specifically include the following steps: (1) Based on the component ratio, recycled aluminum waste is batched and pretreated, then smelted at low temperature and subjected to magnetic iron removal; (2) The raw materials from step (1) are subjected to the following first refining, second refining and third refining in sequence, and after standing, degassing and filtering, the alloy melt is obtained: First refining: temperature 760~780℃, time 15~20min; Second refining: The temperature is 740~760℃, the time is 10~15min, and 3033 industrial silicon, pure manganese flakes, aluminum-copper master alloy, aluminum-titanium master alloy, aluminum-chromium master alloy, aluminum-zirconium master alloy and aluminum-vanadium master alloy are added. Third refining: temperature 730~750℃, time 8~10min, adding magnesium ingots and aluminum strontium master alloy; (3) Cast the alloy melt from step (2) into a mold. The temperature of the alloy melt is controlled at 690~710℃ and the mold preheating temperature is 180℃. Cast the alloy melt to be cast in step 1 to obtain a cast aluminum-silicon alloy.

[0059] In the following examples and comparative examples, the average size of the Fe-rich phase was calculated as follows: at least five non-overlapping fields of view (such as the top, middle, bottom, left, and right positions) were selected in the 200x magnification scanning electron microscope (SEM) image of the alloy sample. The maximum intercept data of the Fe-rich phase in all fields of view were extracted using image analysis software and sorted in descending order. The ten largest Fe-rich phases were selected and their arithmetic mean was calculated.

[0060] Example 1 The chemical composition of the cast aluminum-silicon alloy in this embodiment is shown in Table 1.

[0061] The scanning electron microscope (SEM) test results of the cast aluminum-silicon alloy are as follows: Figure 1As shown, the solidified structure of the alloy does not contain the primary α-AlFeMnSi phase. The α-AlFeMnSi phase is located in the eutectic silicon region and mainly appears as granules and short rods, with granules being the most abundant and having an average size of 30.2 μm.

[0062] Example 2 The chemical composition of the cast aluminum-silicon alloy in this embodiment is shown in Table 1.

[0063] The scanning electron microscope (SEM) test results of the cast aluminum-silicon alloy are as follows: Figure 2 As shown, the solidified structure of the alloy does not contain the primary α-AlFeMnSi phase. The α-AlFeMnSi phase is located in the eutectic silicon region and mainly appears as short rods and granules with an average size of 35.2 μm.

[0064] Example 3 The chemical composition of the cast aluminum-silicon alloy in this embodiment is shown in Table 1.

[0065] The scanning electron microscope (SEM) test results of the cast aluminum-silicon alloy are as follows: Figure 3 As shown, the solidified structure of the alloy does not contain the primary α-AlFeMnSi phase. The α-AlFeMnSi phase is located in the eutectic silicon region and is mainly granular and short rod-shaped. There is a small amount of small needle-like phase (which is less harmful than the large needle-like Fe-rich phase and the primary α-Al(Fe,Mn)Si phase), with an average size of 32.3 μm.

[0066] Example 4 The chemical composition of the cast aluminum-silicon alloy in this embodiment is shown in Table 1.

[0067] The scanning electron microscope (SEM) test results of the cast aluminum-silicon alloy are as follows: Figure 4 As shown, the solidified structure of the alloy does not contain the primary α-AlFeMnSi phase. The α-AlFeMnSi phase is located in the eutectic silicon region and is mainly granular and short rod-shaped. There is a small amount of small needle-like Fe-rich phase (relative to the large needle-like Fe-rich phase and the primary α-AlFeMnSi phase, this morphology is less harmful), with an average size of 36.2 μm.

[0068] Example 5 The chemical composition of the cast aluminum-silicon alloy in this embodiment is shown in Table 1.

[0069] The scanning electron microscope (SEM) test results of the cast aluminum-silicon alloy are as follows: Figure 5As shown, a large number of α-AlFeMnSi phases are located in the eutectic silicon region in the solidified structure of the alloy. They are mainly fine needle-like phases, with a small number of larger primary α-AlFeMnSi phases. This is because 0.08Si + 0.2 ≥ Mn + Fe in the alloy may have local segregation during the actual solidification process, resulting in the formation of primary α-AlFeMnSi phases at local locations with an average size of 38.7 μm.

[0070] Example 6 The chemical composition of the cast aluminum-silicon alloy in this embodiment is shown in Table 1.

[0071] The scanning electron microscope (SEM) test results of the cast aluminum-silicon alloy are as follows: Figure 6 As shown, a large number of α-AlFeMnSi phases are located in the eutectic silicon region in the solidified structure of the alloy, mainly in granular and short rod-shaped form, with a small number of larger primary α-AlFeMnSi phases. This is because in this alloy, 0.08Si+0.2≥Mn+Fe may have local segregation during the actual solidification process, resulting in the formation of primary α-AlFeMnSi phases at local locations, with an average size of 36.8μm.

[0072] Example 7 The chemical composition of the cast aluminum-silicon alloy in this embodiment is shown in Table 1.

[0073] The scanning electron microscope (SEM) test results of the cast aluminum-silicon alloy are as follows: Figure 7 As shown, a large number of α-AlFeMnSi phases are located in the eutectic silicon region in the solidified structure of the alloy, mainly in the form of granules and fine needles, with a small amount of larger primary α-AlFeMnSi. This is because in this alloy, 0.08Si+0.2≥Mn+Fe may have local segregation during the actual solidification process, resulting in the formation of primary α-AlFeMnSi phases at local locations, with an average size of 38.2 μm.

[0074] Comparative Example 1 The chemical composition of the cast aluminum-silicon alloy in this comparative example is shown in Table 1.

[0075] The scanning electron microscope (SEM) test results of the cast aluminum-silicon alloy are as follows: Figure 8 As shown, primary α-AlFeMnSi phases exist in the solidified structure of the alloy, and their distribution is uneven. A large amount of primary α-AlFeMnSi phases are enriched, mainly in the form of coarse skeletons, with a small amount of fine short rod / skeleton-like Fe-rich phases, with an average size of 76.7 μm.

[0076] Comparative Example 2 The chemical composition of the cast aluminum-silicon alloy in this comparative example is shown in Table 1.

[0077] The scanning electron microscope (SEM) test results of the cast aluminum-silicon alloy are as follows: Figure 9 As shown, the transmission electron microscopy (TEM) results of the Fe-rich phase in the eutectic region are as follows: Figure 10 As shown, the primary α-AlFeMnSi phase exists in the solidified structure of the alloy, and the Fe-rich phase in the eutectic part is the α-AlFeMnSi phase, which is mainly in the form of slender rods with an average size of 76.0 μm.

[0078] Comparative Example 3 The chemical composition of the cast aluminum-silicon alloy in this comparative example is shown in Table 1.

[0079] The scanning electron microscope (SEM) test results of the cast aluminum-silicon alloy are as follows: Figure 11 As shown, primary and secondary skeletal α-AlFeMnSi phases exist in the solidified structure of the alloy, and their distribution is uneven. There is local enrichment of primary α-AlFeMnSi phase, with an average size of 40.3 μm.

[0080] Table 1

[0081] Test case Mechanical properties of the cast aluminum-silicon alloys prepared in the examples and comparative examples were tested. The mechanical properties (mainly elongation and yield strength) were tested by room temperature tensile testing on a universal testing machine using an extensometer with a gauge length of 40 mm and a tensile rate of 1 mm / min. Ten tests were performed, and the average elongation was calculated. The sample pass rate (elongation ≥ 6%) was also statistically analyzed. Hardness was tested using a Vickers hardness tester. The test results are shown in Table 2.

[0082] Table 2

[0083] As can be seen from Table 2, the cast aluminum-silicon alloy disclosed herein has significantly improved elongation and mechanical property stability.

[0084] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0085] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0086] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A cast aluminum-silicon alloy raw material, characterized in that, Based on the total weight of the cast aluminum-silicon alloy raw material, the cast aluminum-silicon alloy raw material includes: 7.0~9.0 wt% Si, 0.1~0.36 wt% Fe, 0.2~0.65 wt% Mn, 0.06~0.32 wt% Mg, 0.001~0.3 wt% Cu, 0.01~0.15 wt% Ti, 0.015~0.03 wt% Sr, 0.01~0.06 wt% M, where M is selected from one or more of Zr, Cr and V, and other impurity elements less than or equal to 0.06 wt% and the balance Al. The contents of Mn, Fe and Si satisfy the following formula: 0.08Si + 0.2 ≥ Mn + Fe. The average size of the Fe-rich phase in the microstructure of the cast aluminum-silicon alloy raw material is not greater than 40 μm.

2. The cast aluminum-silicon alloy raw material according to claim 1, characterized in that, The microstructure of the cast aluminum-silicon alloy raw material does not contain primary α-AlFeMnSi phase; and / or, The Fe-rich phase is an α-AlFeMnSi phase, distributed within the eutectic silicon region, and mainly in the form of granules and short rods.

3. The cast aluminum-silicon alloy raw material according to claim 1, characterized in that, The cast aluminum-silicon alloy raw material contains 0.18-0.3% Fe by weight, 0.6-0.75% Mn by weight, and the weight ratio of Mn to Fe is (1-3):

1.

4. The cast aluminum-silicon alloy raw material according to any one of claims 1 to 3, characterized in that, The average elongation of the cast aluminum-silicon alloy raw material in multiple tensile mechanical property tests was 7.9% to 8.9%, and the proportion of samples with an elongation of more than 6.0% was more than 95%.

5. A method for preparing the cast aluminum-silicon alloy raw material according to any one of claims 1 to 4, characterized in that, The method includes: S1. The aluminum-containing raw material is subjected to a first refining, a second refining and a third refining in sequence to obtain an alloy melt; The temperatures of the first refining, the second refining, and the third refining are gradually reduced. At least one of Si, Mn, Cu, Ti, Cr, Zr, and V raw materials is added in the second refining stage, and at least one of Mg and Sr raw materials is added in the third refining stage. S2. The alloy melt is cast into shape to obtain the cast aluminum-silicon alloy raw material.

6. The method according to claim 5, characterized in that, The aluminum-containing raw material includes recycled aluminum waste; the method further includes: before step S1, pre-treating the recycled aluminum waste, performing low-temperature smelting and magnetic iron removal in sequence.

7. The method according to claim 5, characterized in that, In step S1, the conditions for the first refining include: a temperature of 760~780℃ and a time of 15~20min; The conditions for the second refining process include: a temperature of 740~760℃ and a time of 10~15min; The conditions for the third refining process include: a temperature of 730~750℃ and a time of 8~10 minutes.

8. The method according to claim 5, characterized in that, In step S2, the casting conditions include: the alloy melt temperature is 690~710℃, and the mold preheating temperature is 150~200℃.

9. The application of the cast aluminum-silicon alloy raw material according to any one of claims 1 to 3 in the preparation of automotive structural parts.

10. A car, characterized in that, Structural components made from the cast aluminum-silicon alloy raw material as described in any one of claims 1 to 3.

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