Aluminum-silicon alloy and heat treatment method and application thereof

Abstract

The invention provides an aluminum-silicon alloy and a heat treatment method and application thereof. The invention relates to an aluminum-silicon alloy, which comprises the following components in percentage by weight: 5.5 to 8 percent of Si, more than 0 and less than or equal to 0.15 percent of Mg, 0.5 to 0.9 percent of Cu, 0.2 to 0.4 percent of Mn, more than 0 and less than 0.3 percent of Fe, and the balance of A1 and inevitable impurities. By adjusting the components of the aluminum-silicon alloy and innovating the heat treatment process, the mechanical properties of the aluminum-silicon alloy treated by the heat treatment process are as follows: the tensile strength is greater than or equal to 220MPa, the yield strength is greater than or equal to 120MPa, the overall elongation is greater than or equal to 20%, the farthest-end elongation is greater than or equal to 15%, and the balance of strength and plasticity is realized. The method is suitable for the field of integrated casting of automobile lightweight structural parts, aerospace precision parts and the like with high requirements for the ductility, and has remarkable industrial application value.

Description

Technical Field

[0001] This disclosure relates to the field of aluminum alloy materials technology, and in particular to an aluminum-silicon alloy and its heat treatment method and application. Background Technology

[0002] In the automotive lightweighting and aerospace fields, integrated die casting technology is widely used due to its high efficiency and high precision. Aluminum-silicon alloys (such as ZL101 and ZL114) are commonly used die casting materials, but they have significant defects before heat treatment: the overall elongation is low (usually around 10%), and the elongation at the farthest part of the casting (such as the thin-walled area of ​​complex structural parts) is only 3% to 6%, which cannot meet the requirements for high plasticity. In addition, conventional heat treatment processes in existing technologies (such as T6 treatment) can improve strength, but they will lead to a decrease in elongation, while T1 treatment (stress-relief annealing) has limited performance improvement, and the effect of T4 treatment (solution treatment + natural aging) cannot reach the ideal state due to the limitations of material composition.

[0003] In existing aluminum-silicon alloy composition designs, while Mg enhances strength by forming the Mg2Si strengthening phase, the precipitation of this phase reduces the material's plasticity. Fe, as an impurity element, if present in excessive amounts, will generate acicular B-A15FeSi phases, worsening elongation. Furthermore, traditional solution treatments often employ a single high-temperature, long-duration holding process, which easily leads to coarsening of the eutectic silicon. Additionally, the selection of quenching temperature and aging method is not optimized for elongation.

[0004] Therefore, how to significantly improve the elongation of aluminum-silicon alloys, especially the elongation at the far end of castings, while maintaining strength through composition adjustment and heat treatment process innovation has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This disclosure provides an aluminum-silicon alloy, its heat treatment method, and its application, to at least solve one of the technical problems existing in the prior art.

[0006] In a first aspect, this application provides an aluminum-silicon alloy, which, by weight percentage, comprises: Si: 5.5%-8%, Mg: greater than 0 and less than or equal to 0.15%, Cu: 0.5%-0.9%, Mn: 0.2%-0.4%, Fe: greater than 0 and less than 0.3%, with the balance being Al and unavoidable impurities.

[0007] In one embodiment, the total amount of unavoidable impurities is less than 0.5%.

[0008] In one embodiment, the Mg content is 0.05%-0.15%; the Cu content is 0.6%-0.8%; the Mn content is 0.25%-0.35%; and the Fe content is 0.1%-0.25%.

[0009] In one embodiment, the aluminum-silicon alloy further includes one of Sr and Sb. And Ce: 0.02%-0.15% and La: 0.02%-0.15%; among which, Sr: 0.1%-0.3% and Sb: 0.1%-0.3%.

[0010] In one embodiment, the Sr content is 0.1%-0.2%, the Sb content is 0.1%-0.2%, the Ce content is 0.05%-0.1%, and the La content is 0.05%-0.1%.

[0011] Secondly, this application provides a heat treatment method for the aforementioned aluminum-silicon alloy, the heat treatment comprising: Step 1), the aluminum-silicon alloy is heated to 480°C over 1-2 hours; Step 2), raise the temperature to 538℃ in 50-70 minutes and keep it at that temperature for 5 hours; Step 3), quench at 80℃ and leave at room temperature for ≥24 hours.

[0012] In one embodiment, in step 1), the aluminum-silicon alloy is heated to 480°C over a period of 1 hour and 40 minutes. Step 2) involves heating the temperature to 538°C in 1 hour and maintaining the temperature for 5 hours.

[0013] In one embodiment, before performing step 1), the aluminum-silicon alloy is pretreated to remove the oxide layer on its surface.

[0014] In one embodiment, the pretreatment is to sandblast the aluminum-silicon alloy surface with Al2O3 with a particle size of 80-120 mesh.

[0015] Thirdly, this application provides the application of aluminum-silicon alloys treated by the aforementioned heat treatment method in lightweight automotive structural components or aerospace parts.

[0016] Compared with the prior art, the advantages of this application are as follows: 1) The aluminum-silicon alloy of this application, by controlling the Si content in the range of 5.5% to 8%, can effectively balance the strength and plasticity of the alloy, so that the integrated casting product has sufficient strength to withstand working loads while also having a certain degree of plasticity to cope with possible deformation. The low Mg content design of this application can effectively reduce the precipitation of Mg2Si strengthening phase, which avoids its negative impact on elongation, so that the alloy has good plasticity in the casting state, and leaves a large space for plasticity improvement in subsequent heat treatment processes. Cu and Mn form Al2Cu and AlMnSi phases, which are uniformly distributed in the grain boundaries and within the grains, achieving a weak strengthening effect and avoiding excessive strength improvement at the expense of plasticity. Limiting the Fe content to less than 0.3% can effectively reduce the formation of needle-like β-Al5FeSi impurity phases. With the reduction of Fe content, the continuity of the alloy matrix is ​​improved, internal defects are reduced, so that the stress can be more uniformly distributed when the alloy is subjected to external forces, thereby improving the comprehensive mechanical properties of the alloy, including strength, plasticity and toughness.

[0017] 2) The aluminum-silicon alloy of this application also has the effect of adding Sr or Sb, as well as Ce and La. Sr and Sb can both play a role in modifying eutectic silicon, while Ce and La can refine the grain structure. Together with Sr or Sb, they make the overall properties of the alloy, such as elongation, better.

[0018] 3) This application achieves a balance between strength and plasticity by adjusting the composition of the aluminum-silicon alloy and innovating the heat treatment process. The aluminum-silicon alloy treated with this heat treatment process exhibits mechanical properties such as tensile strength ≥220MPa, yield strength ≥120MPa, overall elongation ≥20%, and maximum elongation ≥15%. It is suitable for integrated casting applications requiring high elongation, such as lightweight automotive structural components and precision aerospace parts, and has significant industrial application value.

[0019] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0020] The above and other objects, features, and advantages of this disclosure will become readily apparent from the following detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings. Several embodiments of this disclosure are illustrated in the drawings by way of example and not limitation, in which: In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0021] Figure 1 A schematic diagram of the farthest end of the integrated die-cast part according to an embodiment of this disclosure is shown; Figure 2 The stress-strain curves of the aluminum-silicon alloys after heat treatment according to Embodiments 1-3 of this disclosure are shown. Figure 3 A metallographic image of the aluminum-silicon alloy after heat treatment according to Embodiment 1 of this disclosure is shown. Detailed Implementation

[0022] To make the objectives, features, and advantages of this disclosure more apparent and understandable, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0023] In a first aspect, this application provides a high elongation aluminum-silicon alloy (i.e., "aluminum-silicon alloy") for integrated casting, which, by weight percentage, comprises: Si: 5.5%-8%, Mg: greater than 0 and less than or equal to 0.15%, Cu: 0.5%-0.9%, Mn: 0.2%-0.4%, Fe: greater than 0 and less than 0.3%, with the balance being Al and unavoidable impurities.

[0024] Si, as the main alloying element, forms an Al-Si eutectic structure, improving fluidity. The Si content is controlled within the range of 5.5% to 8%, a result verified through extensive experiments and actual production. When the Si content is below 5.5%, although the alloy exhibits good plasticity, the insufficient formation of the Al-Si eutectic structure significantly impacts its strength, making it difficult to meet the mechanical performance requirements of integrated casting products in practical use. Conversely, when the Si content exceeds 8%, excessive eutectic silicon phases appear in the alloy. These eutectic silicon phases exist in the matrix as coarse needle-like or blocky structures, which can fracture the matrix, leading to a sharp decrease in plasticity. Under significant external forces, this can result in brittle fracture, also detrimental to product use. Therefore, by controlling the Si content within this range, a good balance between the alloy's strength and plasticity can be achieved, ensuring that the integrated casting product possesses sufficient strength to withstand working loads while also maintaining a certain level of plasticity to cope with potential deformation.

[0025] This application employs a low Mg content design, which effectively reduces the precipitation of the Mg2Si strengthening phase. This avoids its negative impact on elongation, resulting in good plasticity in the as-cast state. Furthermore, it preserves significant potential for plasticity enhancement during subsequent heat treatment. During heat treatment, appropriate process parameters can be adjusted to allow a small amount of Mg to dissolve more uniformly into the matrix, or to promote the precipitation of the Mg2Si strengthening phase in a finer, more dispersed manner. This improves the alloy's strength without excessively compromising plasticity, achieving a good balance between strength and plasticity.

[0026] Cu and Mn form Al2Cu and AlMnSi phases, which are uniformly distributed at grain boundaries and within grains, achieving a weak strengthening effect and avoiding excessive strength increase at the expense of plasticity.

[0027] Controlling the Fe content to greater than 0 and less than 0.3% effectively reduces the formation of needle-like β-Al5FeSi impurity phases. As the Fe content decreases, the continuity of the alloy matrix improves, internal defects decrease, and stress is more evenly distributed when the alloy is subjected to external forces, thereby improving the alloy's overall mechanical properties, including strength, plasticity, and toughness.

[0028] For example, the total amount of unavoidable impurities is less than 0.5%. Controlling the total amount of unavoidable impurities to <0.5% can minimize the interference of these impurities on the alloy properties, ensure the stability and consistency of the alloy properties, and make the produced integrated casting products reliable in quality.

[0029] For example, the Si content can be 5.5%, 6%, 6.5%, 7%, 7.5%, 8.0%, or any value between adjacent values. The Mg content can be 0.05%, 0.1%, 0.15%, or any value between adjacent values. The Cu content can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or any value between adjacent values. The Mn content can be 0.2%, 0.3%, 0.4%, or any value between adjacent values. The Fe content can be 0.1%, 0.15%, 0.2%, 0.25%, or any value between adjacent values.

[0030] Preferably, the Mg content is 0.05%-0.15%; the Cu content is 0.6%-0.8%; the Mn content is 0.25%-0.35%; and the Fe content is 0.1%-0.25%.

[0031] In one embodiment, the aluminum-silicon alloy further includes one of Sr and Sb. And Ce: 0.02%-0.15% and La: 0.02%-0.15%; among which, Sr: 0.1%-0.3% and Sb: 0.1%-0.3%.

[0032] Both Sr and Sb can modify eutectic silicon. Sr atoms adsorb at the eutectic silicon growth interface, interfering with the ordered arrangement of silicon atoms and inhibiting their directional growth, transforming the eutectic silicon from coarse needle-like or blocky structures into fine, dispersed fibrous or granular structures. Sb, on the other hand, alters the growth pattern of the eutectic silicon, hindering its growth and achieving a refining effect. The refining of eutectic silicon by Sr and Sb reduces the cutting effect of the eutectic silicon on the matrix, resulting in a more uniform stress distribution under load and significantly improving the alloy's plasticity.

[0033] As rare earth elements, Ce and La accumulate at grain boundaries during alloy solidification, increasing nucleation sites and inhibiting grain growth, thus refining the grain structure. Simultaneously, they can chemically react with harmful impurities such as S and P in the alloy, forming high-melting-point compounds. These compounds float to the liquid surface and are removed, achieving the purpose of purifying the alloy. Ce and La refine grains, increase grain boundary area, hinder crack propagation, and also help improve the alloy's plasticity and elongation. Working together with Sr or Sb, they further enhance the overall elongation and other properties of the alloy.

[0034] When Ce and La coexist, the Ce content is 0.02%–0.15%, and the La content is 0.02%–0.15%. At this ratio, the synergistic effect of Ce and La is maximized. In the alloy, they jointly increase nucleation sites, inhibit grain growth, and achieve more significant grain refinement. Simultaneously, they can fully react with harmful impurities, purifying the alloy without introducing new impurity phases due to excessive amounts of these elements, thus comprehensively improving the alloy's overall performance.

[0035] Preferably, the Sr content is 0.1%-0.2%, the Sb content is 0.1%-0.2%, the Ce content is 0.05%-0.1%, and the La content is 0.05%-0.1%.

[0036] Secondly, this application provides a heat treatment method for the above-mentioned aluminum-silicon alloy, the heat treatment comprising: Step 1), heat the aluminum-silicon alloy to 480℃ over 1-2 hours; Step 2), raise the temperature to 538℃ in 50-70 minutes and keep it at that temperature for 5 hours; Step 3), quench at 80℃ and leave at room temperature for ≥24 hours.

[0037] The heat treatment method in this application employs a step-by-step heating process. For example, in step 1), the pre-heating to 480℃ causes some of the strengthening phases to initially melt, such as some small, unstable strengthening phases. This step makes the distribution of the strengthening phases in the alloy more uniform, creating favorable conditions for the subsequent full dissolution of the Si phase and promotion of its spheroidization at higher temperatures. Without this pre-heating stage, directly heating the alloy to a higher temperature may cause a large amount of strengthening phases to melt rapidly in a short period of time, resulting in uneven microstructure and even defects such as overheating, affecting the alloy's properties.

[0038] For example, in step 2), the temperature of 538℃ is close to the melting point of the Al-Si eutectic. At this temperature, the Si phase in the alloy begins to dissolve completely. Since the morphology of the Si phase in the alloy has a significant impact on the alloy's properties, within this temperature range, through atomic diffusion and migration, the Si phase gradually transforms from its original irregular shape to a spherical shape, i.e., a spheroidization process occurs. The purpose of holding at this temperature for 5 hours is to ensure the homogenization of the microstructure, allowing the Si phase to fully dissolve and spheroidize, and to achieve a uniform distribution of composition and microstructure within the alloy. During the holding process, atoms have sufficient time to diffuse, causing the composition and microstructure of different regions in the alloy to gradually become more consistent, reducing the inhomogeneity of the microstructure. The complete dissolution and spheroidization of the Si phase, as well as the homogenization of the microstructure, have a significant effect on improving the mechanical properties of the alloy. The spheroidized Si phase has a greatly reduced cutting effect on the matrix, allowing stress to be transmitted more evenly when the alloy is under stress, reducing stress concentration points, and thus improving the alloy's plasticity and toughness. At the same time, the homogenization of the structure also helps to improve the strength uniformity of the alloy, so that the alloy can exhibit more consistent mechanical properties in various parts, which is beneficial to the reliability of integrated casting products in actual use.

[0039] For example, in step 3), quenching is performed at a water temperature of 80℃, which is lower than the conventional quenching temperature. A lower quenching temperature avoids excessive thermal and structural stresses during rapid cooling of the alloy. At high temperatures, the alloy's microstructure is unstable; rapid cooling, due to differences in cooling rates in different parts, can easily generate significant internal stresses, which may lead to deformation or even cracking. A water temperature of 80℃ allows the alloy to cool at a relatively gentle rate, reducing the generation of internal stresses. Allowing the alloy to stand at room temperature for ≥24 hours constitutes a natural aging process. During this process, solute atoms within the alloy undergo segregation and precipitation, further stabilizing the microstructure and improving the alloy's strength and hardness through an aging strengthening mechanism, while maintaining a certain degree of plasticity.

[0040] For example, in step 1), heating the aluminum-silicon alloy to 480°C over 1-2 hours means that the aluminum-silicon alloy needs to be heated to 480°C within 1-2 hours. Preferably, in step 1), the aluminum-silicon alloy is heated to 480°C over 1 hour and 40 minutes.

[0041] Preferably, in step 2), the temperature is increased to 538°C in 1 hour and kept at that temperature for 5 hours.

[0042] In one embodiment, before performing step 1), the aluminum-silicon alloy is pretreated to remove the oxide layer on its surface.

[0043] For example, the pretreatment involves sandblasting the surface of the aluminum-silicon alloy with Al2O3 with a particle size of 80-120 mesh.

[0044] Physical pretreatment steps to remove the oxide layer from the alloy surface help expose a pure metal matrix. During subsequent heat treatment, atomic diffusion and migration are smoother, and processes such as the dissolution, spheroidization, and homogenization of the strengthening phase can proceed more effectively, contributing to improved alloy performance. It also removes impurities adhering to the alloy surface, reducing defects and performance degradation caused by these impurities.

[0045] In this application, the aluminum-silicon alloy treated by this heat treatment process achieves mechanical properties with a tensile strength ≥220MPa, a yield strength ≥120MPa, an overall elongation ≥20%, and an elongation at the furthest end ≥15%, thus achieving a balance between strength and plasticity. It is suitable for integrated casting applications requiring high elongation, such as lightweight automotive structural components and precision aerospace parts, and has significant industrial application value.

[0046] For example, such as Figure 1 As shown, Figure 1 The diagram shows a schematic of the integrated die-cast part obtained by using the aluminum-silicon alloy ratio and heat treatment method of this application when used in automotive structural parts. The arrow in the diagram indicates the farthest end of the automotive structural part product.

[0047] Therefore, aluminum-silicon alloys treated by the above heat treatment method can be used in lightweight automotive structural components or precision aerospace parts.

[0048] The present application will be further described in detail below with reference to specific embodiments: Example 1 (a) An aluminum-silicon alloy, comprising, by weight percentage, Si: 6.5%, Mg: 0.1%, Cu: 0.7%, Mn: 0.3%, Fe: 0.2%, with the balance being Al and unavoidable impurities (total less than 0.5%).

[0049] The aluminum-silicon alloy is generally prepared using existing processes, including alloy composition preparation: accurately weighing raw materials with a Si content of 6.5%, Mg content of 0.1%, Cu content of 0.7%, Mn content of 0.3%, and Fe content of 0.2% by weight, with the balance being Al and unavoidable impurities (total unavoidable impurities < 0.5%). For example, to prepare 100 kg of alloy, 6.5 kg of Si, 0.1 kg of Mg, 0.7 kg of Cu, 0.3 kg of Mn, and 0.2 kg of Fe are required, with the remainder being Al and a small amount of impurities.

[0050] Melting process: The above raw materials are placed in a melting furnace and melted under an argon protective atmosphere to prevent metal oxidation. The melting temperature is controlled at 720-750℃, and electromagnetic stirring technology is used with a stirring speed set at 300-400 r / min. Continuous stirring ensures uniform mixing of all components to obtain a homogeneous alloy melt.

[0051] (ii) A heat treatment method for aluminum-silicon alloy, comprising the following steps: Step A) Pretreatment step: Select Al2O3 with a particle size of 80-120 mesh to perform sandblasting on the aluminum-silicon alloy to remove the oxide layer on the alloy surface, so that the pure metal matrix is ​​exposed on the alloy surface, which facilitates the diffusion and migration of atoms in the subsequent heat treatment steps. Step B) Heat treatment step: Step 1): The pretreated aluminum-silicon alloy is slowly heated to 480℃ over 1 hour and 40 minutes to allow some of the strengthening phases to initially melt, promote uniform distribution of the strengthening phases, and create favorable conditions for the subsequent full dissolution and spheroidization of the Si phase. Step 2): Next, the temperature is increased to 538℃ over 1 hour and held at this temperature for 5 hours. At this point, the Si phase in the alloy is fully dissolved and spheroidized, and the internal composition and microstructure of the alloy reach a uniform distribution. Step 3): Quenching is performed at a water temperature of 80℃. Compared with the conventional quenching temperature, this temperature allows the alloy to cool at a relatively gentle rate, reducing the generation of thermal stress and structural stress. After quenching, the alloy is placed at room temperature for ≥24 hours for natural aging, which allows solute atoms inside the alloy to segregate and precipitate, further stabilizing the structure, improving the strength and hardness of the alloy, while maintaining good plasticity.

[0052] The aluminum-silicon alloy after heat treatment in Example 1 was tested for performance according to the following standards: Performance Testing: Standard tensile specimens were prepared according to GB / T228.1 "Metallic Materials - Tensile Testing - Part 1: Test Method at Room Temperature". Tensile tests were performed on the specimens using an electronic universal testing machine to measure their tensile strength, yield strength, and elongation. The microstructure of the alloy was observed using a metallographic microscope to detect grain size and microstructure uniformity. The results showed that Example 1 had a tensile strength of 220 MPa, a yield strength of 131 MPa, an overall elongation of 20%, and an elongation at the furthest point of 16%.

[0053] Example 2 An aluminum-silicon alloy, by weight percentage, comprises: 5.5% Si, 0.15% Mg, 0.5% Cu, 0.2% Mn, 0.15% Fe, with the balance being Al and unavoidable impurities (total unavoidable impurities < 0.5%).

[0054] Melting and heat treatment methods: The operation process is the same as in Example 1, including melting conditions, selection of pretreatment methods, and parameter settings for each step of heat treatment.

[0055] The performance of the heat-treated aluminum-silicon alloy of Example 2 was tested according to the same testing standards and methods. The results showed that the tensile strength of Example 2 was 228 MPa, the yield strength was 120 MPa, the overall elongation was 21%, and the elongation at the farthest end was 15%.

[0056] Example 3 An aluminum-silicon alloy, by weight percentage, comprises: 8.0% Si, 0.05% Mg, 0.9% Cu, 0.4% Mn, 0.25% Fe, with the balance being Al and unavoidable impurities (total unavoidable impurities < 0.5%).

[0057] Melting and heat treatment methods: Same as in Example 1.

[0058] The performance of the heat-treated aluminum-silicon alloy of Example 3 was tested. The test results showed that the tensile strength of Example 3 was 232 MPa, the yield strength was 126 MPa, the overall elongation was 25.5%, and the elongation at the farthest end was 17%.

[0059] Example 4 An aluminum-silicon alloy, by weight percentage, comprises: 6.5% Si, 0.1% Mg, 0.7% Cu, 0.3% Mn, 0.2% Fe, 0.2% Sr, 0.1% Ce, and 0.05% La, with the balance being Al and unavoidable impurities, wherein the total amount of unavoidable impurities is <0.5%.

[0060] Melting and heat treatment methods: Same as in Example 1.

[0061] The performance of the heat-treated aluminum-silicon alloy of Example 4 was tested. The test results showed that the tensile strength of Example 4 reached more than 220 MPa, the yield strength reached more than 131 MPa, the overall elongation was ≥20%, and the elongation at the farthest end was ≥16%.

[0062] Example 5 An aluminum-silicon alloy, by weight percentage, comprises: 5.5% Si, 0.15% Mg, 0.5% Cu, 0.2% Mn, 0.15% Fe, 0.1% Sb, 0.05% Ce, and 0.05% La, with the balance being Al and unavoidable impurities, the total amount of unavoidable impurities being <0.5%.

[0063] Melting and heat treatment methods: Same as in Example 1.

[0064] The performance of the heat-treated aluminum-silicon alloy of Example 5 was tested. The test results showed that the tensile strength of Example 5 was ≥220MPa, the yield strength was ≥120MPa, the overall elongation was ≥20%, and the elongation at the farthest end was ≥15%.

[0065] Comparative Example 1 (using a high-Mg alloy) (a) An alloy comprising, by weight percentage: 9.5% Si, 0.5% Mg, 1.2% Cu, 0.1% Mn, 0.2% Fe, with the balance being Al and unavoidable impurities.

[0066] Alloy smelting: The smelting process is the same as in Example 1.

[0067] (ii) The heat treatment method of the alloy adopts the conventional T6 heat treatment process, namely, holding at 540℃ for 10h, then quenching at 60℃ in water, and artificial aging at 180℃ for 2h.

[0068] The properties of the alloy after heat treatment in Comparative Example 1 will be tested.

[0069] Performance testing: Tested according to the same testing standards, the results showed that the tensile strength of Comparative Example 1 was 240 MPa, the yield strength was 130 MPa, the overall elongation was 10%, and the elongation at the farthest end was 8%.

[0070] Comparative Example 2 (a) An alloy having the same composition as in Example 1, namely, Si content of 6.5%, Mg content of 0.1%, Cu content of 0.7%, Mn content of 0.3%, Fe content of 0.2%, with the balance being Al and unavoidable impurities.

[0071] Smelting: The smelting process is the same as in Example 1.

[0072] (ii) The heat treatment method of the alloy is the conventional T6 process (holding at 540℃ for 10h, quenching at 60℃ in water, and artificial aging at 180℃ for 2h).

[0073] The properties of the alloy after heat treatment in Comparative Example 2 will be tested.

[0074] The results showed that the tensile strength of Comparative Example 2 was 225 MPa, the yield strength was 123 MPa, the overall elongation was 14%, and the elongation at the farthest end was 10%.

[0075] Comparative Example 3 (a) An alloy having the same composition as in Example 4, namely, a Si content of 6.5%, a Mg content of 0.1%, a Cu content of 0.7%, a Mn content of 0.3%, a Fe content of 0.2%, and the addition of 0.2% Sr, 0.1% Ce and 0.05% La, with the balance being Al and unavoidable impurities.

[0076] Melting process: Same as in Example 1.

[0077] (ii) The heat treatment method for this alloy is conventional T6 heat treatment, specifically including: Step 1): Keep warm at 540℃ for 10 hours. Step 2): Water quenching at 60℃. Step 3): Artificial aging at 180℃ for 2 hours.

[0078] The alloy of Comparative Example 3 after heat treatment was tested according to the same testing standards and methods as in Example 1. The results showed that the tensile strength of Comparative Example 3 was 235 MPa, the yield strength was 135 MPa, the overall elongation was <18%, and the elongation at the furthest end was <12%.

[0079] The performance test data of Examples 1-5 and Comparative Examples 1-3 are summarized in Table 1.

[0080] Table 1. Performance test data of aluminum-silicon alloys after heat treatment in Examples 1-5 and alloys after heat treatment in Comparative Examples 1-3.

[0081] Referring to Table 1, and through comparison and verification between Examples 1-5 and Comparative Examples 1-3, the aluminum-silicon alloys of this application, after heat treatment, exhibit tensile strength ≥220MPa, yield strength ≥120MPa, overall elongation ≥20%, and maximum elongation ≥15%, achieving a balance between strength and plasticity. Comparative Example 1 uses existing element ratios and conventional T6 heat treatment, resulting in poor plasticity; Comparative Example 2 uses the same element ratios as Example 1 but does not use the heat treatment method of this application, resulting in no significant performance improvement. Comparative Example 3 adds the same element ratios as Example 4 but uses conventional T6 treatment, yet the elongation is still unsatisfactory. Therefore, this application demonstrates significant advantages in improving the performance of aluminum-silicon alloys and has important application value in related integrated casting fields.

[0082] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this disclosure can be achieved, and this is not limited herein.

[0083] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0084] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. An aluminum-silicon alloy, characterized in that, The aluminum-silicon alloy comprises, by weight percentage, Si: 5.5%-8%, Mg: greater than 0 and less than or equal to 0.15%, Cu: 0.5%-0.9%, Mn: 0.2%-0.4%, Fe: greater than 0 and less than 0.3%, with the balance being Al and unavoidable impurities.

2. The aluminum-silicon alloy according to claim 1, characterized in that, The total amount of unavoidable impurities is less than 0.5%.

3. The aluminum-silicon alloy according to claim 1, characterized in that, The Mg content is 0.05%-0.15%; the Cu content is 0.6%-0.8%; the Mn content is 0.25%-0.35%; and the Fe content is 0.1%-0.25%.

4. The aluminum-silicon alloy according to claim 1, characterized in that, The aluminum-silicon alloy also includes one of Sr and Sb. And Ce: 0.02%-0.15% and La: 0.02%-0.15%; among which, Sr: 0.1%-0.3% and Sb: 0.1%-0.3%.

5. The aluminum-silicon alloy according to claim 4, characterized in that, The Sr content is 0.1%-0.2%, the Sb content is 0.1%-0.2%, the Ce content is 0.05%-0.1%, and the La content is 0.05%-0.1%.

6. The heat treatment method for aluminum-silicon alloy according to any one of claims 1-5, characterized in that, The heat treatment includes: Step 1), the aluminum-silicon alloy is heated to 480°C over 1-2 hours; Step 2), raise the temperature to 538℃ in 50-70 minutes and keep it at that temperature for 5 hours; Step 3), quench at 80℃ and leave at room temperature for ≥24 hours.

7. The heat treatment method according to claim 6, characterized in that, In step 1), the aluminum-silicon alloy is heated to 480°C over a period of 1 hour and 40 minutes. Step 2) involves heating the temperature to 538°C in 1 hour and holding it at that temperature for 5 hours.

8. The heat treatment method according to claim 6, characterized in that, Before performing step 1), the aluminum-silicon alloy is pretreated to remove the oxide layer on its surface.

9. The heat treatment method according to claim 8, characterized in that, The pretreatment involves sandblasting the surface of the aluminum-silicon alloy with Al2O3 with a particle size of 80-120 mesh.

10. The application of aluminum-silicon alloys treated by the heat treatment method according to any one of claims 6-9 in lightweight automotive structural components or aerospace parts.

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