A non-stick die-cast aluminum alloy and its preparation method

Abstract

This invention relates to a non-stick die-cast aluminum alloy, the composition of which, by weight percentage, is: Si: 7.5-9.5%, Cu: 2.0-4.2%, Zn: 1.5-2.5%, Sb: 1.1-2.7%, with the balance being Al and unavoidable impurities, wherein [Cu] / [Sb] = 1.02-2.13, [Zn] / [Sb] = 0.74-1.88, and [Cu], [Sb], and [Zn] represent the proportions of Cu, Sb, and Zn in the die-cast aluminum alloy, respectively. The preparation method of this non-stick die-cast aluminum alloy, by mass percentage, includes the following steps: S1, melting to obtain an aluminum alloy liquid of the corresponding composition; S2, preheating the die-casting mold to 150-250℃, while controlling the vacuum degree of the die-casting cavity below 10kPa; S3, adjusting the temperature of the aluminum alloy liquid to 650-700℃, performing die casting, controlling the injection pressure of the die-casting machine to 40-150MPa, the injection speed to 1.0-5.0m / s, and demolding after holding the pressure for 1-5 minutes after die casting.

Description

Technical Field

[0001] This invention relates to a non-stick die-casting aluminum alloy, which has high mechanical and thermal conductivity properties. This aluminum alloy does not stick to the mold during the die-casting process, resulting in good product quality and high yield. This invention also provides a method for preparing the above-mentioned non-stick die-casting aluminum alloy. The non-stick die-casting aluminum alloy of this invention can be widely used in 3C product shells and frames, vehicle parts, aerospace parts, etc. Background Technology

[0002] Aluminum alloys, characterized by low density, high strength, and high thermal conductivity, are widely used in 3C products, aerospace, transportation, and other fields. With industrial advancements and product iterations, the shapes and structures of various components are becoming increasingly complex, demanding ever higher forming precision. Due to these technological requirements, die casting of aluminum alloys has become the primary forming process for high-precision, complex aluminum alloy parts.

[0003] In production practice, it has been found that traditional die-cast aluminum alloys have serious sticking problems. Since die-cast parts are usually complex in size and structure, have high precision and quality requirements, and are usually thin-walled, sticking defects greatly affect the precision and yield of products, resulting in high production costs of die-cast aluminum alloy materials.

[0004] As is widely recognized in the industry, Fe can effectively alleviate the sticking problem in die-cast aluminum alloys. However, the addition of Fe also brings new problems: it leads to the formation of coarse iron-rich intermetallic compounds, also known as "iron-rich phases," in the aluminum alloy. These coarse iron-rich phases drastically deteriorate the mechanical and thermal conductivity of die-cast aluminum alloys. To avoid the formation of these coarse iron-rich phases, rapid quenching of the melt or the addition of modifying elements such as Na, Ca, and Sr are necessary. Subsequent heat treatment can also be used to further refine them. However, rapid quenching, modification treatment, or subsequent heat treatment undoubtedly increase the process threshold, leading to a narrowing of the process window and making it difficult to effectively control process costs.

[0005] Based on this, the present invention aims to provide a die-cast aluminum alloy material with excellent mechanical properties, thermal conductivity and non-stick properties. Summary of the Invention

[0006] This invention provides a non-stick die-cast aluminum alloy with high mechanical and thermal properties. This aluminum alloy does not stick to the mold during the die-casting process, resulting in high product quality and high yield. It can be widely used in 3C product housings and frames, transportation vehicle parts, aerospace parts, etc.

[0007] The technical objective of this invention is achieved through the following means.

[0008] A non-stick die-cast aluminum alloy, characterized in that: the composition of the die-cast aluminum alloy by weight percentage is: Si: 7.5-9.5%, Cu: 2.0-4.2%, Zn: 1.5-2.5%, Sb: 1.1-2.7%, with the balance being Al and unavoidable impurities, wherein [Cu] / [Sb]=1.02-2.13, [Zn] / [Sb]=0.74-1.88, and [Cu], [Sb], and [Zn] represent the mass percentage content of Cu, Sb, and Zn in the die-cast aluminum alloy, respectively.

[0009] The role of each element in the die-cast aluminum alloy of this invention is described below.

[0010] Si: Silicon is an element that improves the fluidity of die-cast aluminum alloys, and it is also an element that ensures the strength of the aluminum alloy of this invention. Too high a silicon content will lead to a decrease in elongation, while too low a silicon content will result in a decrease in strength. Furthermore, too low a silicon content will lead to a decrease in the fluidity of the liquid aluminum alloy, causing difficulties in the die-casting process. In this invention, the silicon content is controlled between 7.5% and 9.5%.

[0011] Cu: Adding copper to the die-cast aluminum alloy of the present invention can significantly improve its strength performance. Cu can form CuAl2 and be dissolved into the matrix to produce a strengthening effect. If the Cu content is too high, the elongation will decrease significantly, and if the Cu content is too low, the strength cannot be guaranteed. The Cu content of the present invention is controlled at 2.0-4.2%.

[0012] Zinc: Adding zinc to the die-cast aluminum alloy of the present invention can improve the fluidity of the aluminum melt and effectively improve the strength. However, while improving the strength of the die-cast aluminum alloy, zinc will reduce the thermal conductivity to a certain extent. In order to balance the strength and thermal conductivity, the present invention controls the amount of zinc added to be 1.5-2.5%. If the amount of zinc is too high, the thermal conductivity will deteriorate, and if the amount of zinc is too low, the strength will not meet the requirements of the invention.

[0013] Sb: Antimony is a crucial element for achieving the technical effects of this invention. The inventors discovered that adding a certain amount of Sb to the die-cast aluminum alloy of this invention's composition and synergistically controlling the ratio of Cu, Zn, and Sb within a certain range can avoid mold sticking defects during the die-casting process while ensuring the die-cast aluminum alloy possesses excellent mechanical and thermal conductivity properties. The Sb addition amount in the die-cast aluminum alloy of this invention is controlled at 1.1-2.7%.

[0014] As mentioned earlier, while adding Sb, it is necessary to synergistically control the Cu / Sb and Zn / Sb ratios to ultimately obtain a die-cast aluminum alloy that is free from sticking and maintains good mechanical properties (tensile strength, yield strength, elongation) and thermal conductivity. Although the specific mechanism is not yet clear, it is speculated that it should be related to the formation of Cu-Sb and Zn-Sb intermetallic compounds. After repeated research and exploration, the inventors of this invention finally determined the Cu, Zn, and Sb content ratios that can balance mechanical properties, thermal conductivity, and the absence of sticking defects: [Cu] / [Sb] = 1.02-2.13, [Zn] / [Sb] = 0.74-1.88.

[0015] Based on the composition design of this invention, particularly the addition of Sb and the control of the proportions of Cu, Zn, and Sb, the sticking defect during the die-casting process is effectively avoided while ensuring the mechanical and thermal conductivity properties of the die-cast aluminum alloy. This eliminates the need for traditional processes that rely on adding large amounts of Fe to solve the sticking problem, and avoids the performance degradation of the die-cast aluminum alloy caused by Fe addition. Furthermore, the die-casting production process does not require strictly controlled high cooling rates, no modification treatment during smelting, and no subsequent heat treatment. Therefore, the die-cast aluminum alloy composition design of this invention is simple, the production process is simple, and the process cost is low.

[0016] As a further description of the technical solution of the present invention, the die-cast aluminum alloy of the present invention includes Cu-Sb intermetallic compounds and Zn-Sb intermetallic compounds. As a non-limiting description, the Cu-Sb intermetallic compounds include Cu3Sb and Cu2Sb intermetallic compounds; as a non-limiting description, the Zn-Sb intermetallic compounds include ZnSb intermetallic compounds.

[0017] As an example, the die-cast aluminum alloy of the present invention has the following mechanical properties: ① room temperature tensile strength of 305 MPa or more, preferably 320 MPa or more, more preferably 335 MPa or more; ② room temperature yield strength of 195 MPa or more, preferably 210 MPa or more, more preferably 230 MPa or more; ③ room temperature elongation of 6.6% or more, preferably 7.3% or more, more preferably 8.0% or more.

[0018] As an example, the die-cast aluminum alloy of the present invention has the following thermal conductivity: the thermal conductivity of the die-cast aluminum alloy of the present invention reaches 160 W / m·K, preferably 175 W / m·K or more, and more preferably 180 W / m·K or more.

[0019] As one of the significant features of the die-cast aluminum alloy of the present invention, the die-cast aluminum alloy of the present invention, through the design and matching of the composition, especially the control of the amount of Sb added and the matching of the proportions of Cu, Zn and Sb, does not have the defect of sticking to the mold after die casting.

[0020] Another technical objective of this invention is to provide a method for preparing the non-stick die-cast aluminum alloy described in this invention, specifically: S1, melting to obtain an aluminum alloy liquid of the corresponding composition; S2, preheating the die-casting mold to 150-250℃, while controlling the vacuum degree of the die-casting cavity below 10kPa; S3, adjusting the temperature of the aluminum alloy liquid to 650-700℃, performing die casting, controlling the injection pressure of the die-casting machine to 40-150MPa, the injection speed to 1.0-5.0m / s, and demolding after holding the pressure for 1-5 minutes after die casting.

[0021] The non-stick die-cast aluminum alloy prepared by the method of this invention is widely used in the shells and frames of 3C products (such as mobile phones, laptops, tablets, etc.), parts of transportation vehicles (such as automobiles, high-speed trains, etc.), aerospace parts, etc. Because the non-stick die-cast aluminum alloy of this invention has a simple composition design, excellent mechanical and thermal properties, and does not stick to the mold during the die-casting process, it ensures high performance and high finished product qualification rate. The process steps are simple, the process cost is low, and the competitive advantage is obvious.

[0022] The dimensions of the aluminum alloy products obtained by die casting according to this invention are not specifically limited, meaning they are suitable for manufacturing any aluminum alloy parts that can be produced by conventional die casting processes. It should be particularly noted that, because the die-cast aluminum alloy of this invention does not stick to the mold during die casting, its process and cost advantages are even more pronounced when manufacturing high-precision, thin-walled, and complex parts.

[0023] The present invention has the following beneficial effects.

[0024] To avoid sticking defects, the die-cast aluminum alloy of this invention adopts a different technical route than existing technologies by adding Fe. Instead of adding Fe, which easily forms coarse iron-rich phases, this invention adds a certain amount of Sb and synergistically controls the content relationship between Sb, Cu, and Zn. The resulting die-cast aluminum alloy does not have sticking defects and has outstanding mechanical and thermal properties. The production process is simple and the product yield is high, which has the dual advantages of performance and cost. It can be widely used in the production of various die-cast aluminum alloy parts. Detailed Implementation

[0025] To enable those skilled in the art to fully understand the technical solution and beneficial effects of the present invention, the following detailed explanation is provided in conjunction with specific experimental examples.

[0026] According to the composition in Table 1, the aluminum alloy liquid was smelted, the die-casting mold was preheated to 185℃, the vacuum degree of the die-casting cavity was controlled at 5kPa, and then the aluminum alloy liquid temperature was controlled at 660℃ for die casting. The injection pressure of the die-casting machine was 60MPa, the injection speed was 1.5m / s, and the mold was demolded after holding the pressure for 150s after the die casting was completed. The aluminum alloy sample obtained by die casting was a thin-walled plate with dimensions of 200mm*200mm*2mm.

[0027] The die-cast plates were then subjected to performance testing and defect observation. Elongation, tensile strength, and yield strength at room temperature were tested according to GB / T 228.1-2021 "Metallic materials, tensile testing—Part 1: Test at room temperature," and thermal conductivity was tested according to GB / T 22588-2008 "Measuring thermal diffusivity or thermal conductivity by flash method." For each die-cast plate sample, sticking defects were observed; the presence of sticking defects was marked with "×," and the absence of sticking defects was marked with "〇." The test and observation results are recorded in Table 2.

[0028] Table 1. Composition of each die-cast aluminum alloy (in mass percentage, %, balance Al).

[0029]

[0030] Table 2. Performance test results and observation results of sticking defects of various die-cast aluminum alloys.

[0031]

[0032] The following analysis will be conducted in conjunction with Tables 1 and 2.

[0033] The composition, Cu / Sb, and Zn / Sb of the die-cast aluminum alloys in tests 1-8 in Table 1 all meet the requirements of this invention. As shown in Table 2, the elongation at room temperature of the die-cast aluminum alloys in tests 1-8 can all reach over 6.6%, the room temperature tensile strength can reach over 305 MPa, the room temperature yield strength can reach over 195 MPa, and the thermal conductivity can reach over 160 W / m·K. They possess good mechanical and thermal properties, and no sticking was observed after die casting of the thin slab, indicating good demolding and no die-casting sticking problem. Tests 1-8 are embodiments of this invention.

[0034] In Table 1, the die-cast aluminum alloy composition of test numbers 9-20 does not meet the requirements of the present invention in terms of Cu content, Zn content, Sb content, Cu / Sb ratio, or Zn / Sb ratio. As can be seen from Table 2, at least one of its mechanical properties, thermal conductivity, or sticking defects fails to meet the requirements of the present invention. Therefore, test numbers 9-20 are comparative examples of the present invention.

[0035] The following is a detailed analysis of each comparative example.

[0036] Comparative Example 9 is a comparative example of Example 1. Under the premise that other components are the same, the Sb content is reduced. The reduced Sb content is still within the range required by the present invention, but Cu / Sb and Zn / Sb no longer meet the requirements of the invention. The results confirm that the die-cast aluminum alloy of Comparative Example 9 has a sticking problem, that is, the control of Cu / Sb and Zn / Sb plays an important role in avoiding sticking.

[0037] Comparative Example 10 is a comparative example of Example 2. Under the premise that other components are the same, the content of Sb is increased. The increased Sb content is still within the requirements of the present invention, but Cu / Sb and Zn / Sb no longer meet the requirements of the invention. The results confirm that the die-cast aluminum alloy of Comparative Example 10 has a sticking problem, that is, the control of Cu / Sb and Zn / Sb plays an important role in avoiding sticking.

[0038] Comparative Example 11 is a comparative example of Example 3. Under the premise that other components are the same, the Cu content is reduced. The reduced Cu content is still within the range required by the present invention, but the Cu / Sb no longer meets the requirements of the invention. The results show that the die-cast aluminum alloy of Comparative Example 11 has a sticking problem, that is, the control of Cu / Sb plays an important role in avoiding sticking.

[0039] Comparative Example 12 is a comparative example of Example 4. Under the premise that other components are the same, the Cu content is increased. The increased Cu content is still within the range required by the present invention, but the Cu / Sb no longer meets the requirements of the invention. The results show that the die-cast aluminum alloy of Comparative Example 12 has a sticking problem, that is, the control of Cu / Sb plays an important role in avoiding sticking.

[0040] Comparative Example 13 is a comparative example of Example 7. Under the premise that other components are the same, the Zn content is reduced. The reduced Zn content is still within the range required by the present invention, but the Zn / Sb no longer meets the requirements of the invention. The results confirm that the die-cast aluminum alloy of Comparative Example 13 has a sticking problem, that is, the control of Zn / Sb plays an important role in avoiding sticking.

[0041] Comparative Example 14 is a comparative example of Example 2. Under the premise that other components are the same, the content of Zn is increased. The increased Zn content is still within the requirements of the present invention, but the Zn / Sb no longer meets the requirements of the invention. The results confirm that the die-cast aluminum alloy of Comparative Example 14 has a sticking problem, that is, the control of Zn / Sb plays an important role in avoiding sticking.

[0042] Comparative Example 15 is a comparative example of Example 4. Under the premise that other components are the same, the Cu content is reduced. Although the Cu / Sb ratio still meets the requirements of the invention, the reduced Cu content is not within the scope of the requirements of the invention. The results show that although the die-cast aluminum alloy of Comparative Example 15 does not have the problem of sticking to the mold, the strength is insufficient due to the low Cu content, which cannot meet the requirements of the invention. That is, the control of Cu content plays an important role in obtaining excellent strength.

[0043] Comparative Example 16 is a comparative example of Example 8. Under the premise that other components are the same, the Cu content is increased. Although the Cu / Sb ratio still meets the requirements of the invention, the increased Cu content is not within the scope of the requirements of the invention. The results show that although the die-cast aluminum alloy of Comparative Example 16 does not have the problem of sticking to the mold, the elongation deteriorates due to the excessive Cu content, which cannot meet the requirements of the invention. The thermal conductivity also cannot meet the requirements of the invention. That is, the control of Cu content plays an important role in obtaining excellent elongation and thermal conductivity.

[0044] Comparative Example 17 is a comparative example of Example 6. Under the premise that other components are the same, the Zn content is reduced. Although the Zn / Sb ratio still meets the requirements of the invention, the reduced Zn content is not within the scope of the requirements of the invention. The results show that although the die-cast aluminum alloy of Comparative Example 17 does not have the problem of sticking to the mold, the strength is insufficient due to the low Zn content, which cannot meet the requirements of the invention. That is, the control of Zn content plays an important role in obtaining excellent strength.

[0045] Comparative Example 18 is a comparative example of Example 1. Under the premise that other components are the same, the Zn content is increased. Although the Zn / Sb ratio still meets the requirements of the invention, the increased Zn content is not within the scope of the requirements of the invention. The results show that although the die-cast aluminum alloy of Comparative Example 18 does not have the problem of sticking to the mold, the elongation deteriorates due to the excessive Zn content, which cannot meet the requirements of the invention. The thermal conductivity also cannot meet the requirements of the invention. That is, the control of Zn content plays an important role in obtaining excellent elongation and thermal conductivity.

[0046] Comparative Example 19 is a comparative example of Example 5. Under the premise that other components are the same, the Sb content is reduced. Although Cu / Sb and Zn / Sb still meet the requirements of the invention, the reduced Sb content is not within the scope of the requirements of the invention. The results show that the die-cast aluminum alloy of Comparative Example 19 has a sticking problem, and due to the low Sb content, the strength is insufficient and cannot meet the requirements of the invention. That is, the control of Sb content plays an important role in obtaining excellent strength and avoiding sticking to the mold.

[0047] Comparative Example 20 is a comparative example of Example 7. Under the premise that other components are the same, the Sb content is increased. Although Cu / Sb and Zn / Sb still meet the requirements of the invention, the increased Sb content is not within the scope of the requirements of the invention. The results show that the die-cast aluminum alloy of Comparative Example 20 has a sticking problem. Furthermore, due to the excessive Sb content, the elongation deteriorates, and the thermal conductivity also decreases, which fails to meet the requirements of the invention. That is, the control of Sb content plays an important role in obtaining excellent elongation and thermal conductivity and avoiding sticking to the mold.

[0048] The comparison of the above embodiments and comparative examples clearly demonstrates that the die-cast aluminum alloy of the present invention, by controlling the reasonable Cu, Zn, and Sb contents and Cu / Sb and Zn / Sb ratios, can ensure excellent strength, elongation, and thermal conductivity. Furthermore, the die-cast aluminum alloy that meets the composition requirements of the present invention does not have a sticking problem during the die-casting process, which can greatly improve the yield and effectively control the process cost. It has the dual advantages of performance and cost, and is well applied in 3C products, transportation vehicles, aerospace and other parts, with obvious advantages.

[0049] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0050] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A non-stick die-cast aluminum alloy, characterized in that: The composition of the die-cast aluminum alloy by weight percentage is: Si: 7.5-9.5%, Cu: 2.0-4.2%, Zn: 1.54-2.5%, Sb: 1.1-2.7%, with the balance being Al and unavoidable impurities, wherein [Cu] / [Sb]=1.02-2.13, [Zn] / [Sb]=0.74-1.88, and [Cu], [Sb], and [Zn] represent the mass percentage content of Cu, Sb, and Zn in the die-cast aluminum alloy, respectively.

2. The non-stick die-cast aluminum alloy according to claim 1, characterized in that, The non-stick die-cast aluminum alloy includes Cu-Sb intermetallic compounds and Zn-Sb intermetallic compounds.

3. The non-stick die-cast aluminum alloy according to claim 2, characterized in that, The Cu-Sb intermetallic compounds include Cu3Sb and Cu2Sb intermetallic compounds.

4. The non-stick die-cast aluminum alloy according to claim 2, characterized in that, The Zn-Sb intermetallic compound includes the ZnSb intermetallic compound.

5. The non-stick die-cast aluminum alloy according to claim 1, characterized in that, The non-stick die-cast aluminum alloy has a room temperature tensile strength of 305 MPa or higher.

6. The non-stick die-cast aluminum alloy according to claim 1, characterized in that, The non-stick die-cast aluminum alloy has a room temperature yield strength of 195 MPa or higher.

7. The non-stick die-cast aluminum alloy according to claim 1, characterized in that, The thermal conductivity of the non-stick die-cast aluminum alloy reaches over 160 W / m·K.

8. The non-stick die-cast aluminum alloy according to claim 1, characterized in that, The non-stick die-cast aluminum alloy has a room temperature elongation of over 6.6%.

9. The method for preparing non-stick die-cast aluminum alloy according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Melting to obtain aluminum alloy liquid with the corresponding composition; S2. Preheat the die-casting mold to 150-250℃, and at the same time control the vacuum degree of the die-casting cavity below 10kPa; S3. Adjust the temperature of the aluminum alloy liquid to 650-700℃ and perform die casting. Control the injection pressure of the die casting machine to 40-150MPa and the injection speed to 1.0-5.0m / s. After die casting, hold the pressure for 1-5 minutes and then demold.

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