A high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy and its preparation method

Abstract

The present invention discloses a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy, its composition and the content of each element: Cu: 13.0 - 15.0%; Si: 5.0 - 7.0%; Zn: 0.1 - 0.5%; Mg: 0.1 - 0.5%; Sr: 0.05 - 0.3%; the balance is Al. The present invention also discloses the above-mentioned melting and preparation process: melting the aluminum alloy at high temperature, performing melt treatment on the modification elements, alloying treatment with multiple trace elements, refining and slag removal, and casting and forming. The preparation process of the Al-Cu-Si series die-casting aluminum alloy of the present invention is simple and easy to implement, the addition amount of alloying elements is easy to control, the comprehensive performance effect is remarkable, the industrial production cost is low, and it has wide applicability. The present invention uses Sr modification elements to improve the morphology and distribution of eutectic Si and Al2Cu phases, and gives play to the strengthening effect of alloying of Mg and Zn trace elements, solves the problem of the contradiction between the thermal conductivity and mechanical properties of the alloy, realizes the double improvement of the thermal conductivity and mechanical properties of the Al-Cu-Si series die-casting aluminum alloy, and obtains a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy for encapsulation devices used in communication equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of cast aluminum alloys, and particularly relates to a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy and a preparation method thereof. Background Art

[0002] With the rapid development of electronic communication technology, the high-speed, large-capacity and low-latency 5G communication network gradually replaces the 4G network. The packaging devices for communication equipment put forward higher requirements for the thermal conductivity of materials to ensure and improve the service life and working stability of products. Pure aluminum and aluminum alloys for conduction (such as: 1xxx series) have relatively high thermal conductivity, but their relatively low mechanical properties cannot meet the requirements for strength and stiffness during the assembly of packaging devices; 6xxx series aluminum alloys are commonly used in the heat dissipation field, and products are generally prepared by extrusion and CNC machining. Existing packaging devices often have a thin-wall heat sink structure, and the 6xxx series aluminum alloys with poor fluidity restrict their application in the direction of die-casting integrated molding. Therefore, it is urgent to develop an aluminum alloy with good thermal conductivity and suitable for large-scale die-casting production.

[0003] In recent years, domestic research has been carried out on the composition design and preparation methods of high-thermal-conductivity aluminum alloys. Chinese Patent Application CN110144499A discloses a die-casting aluminum alloy for a 5G communication base station housing and a preparation method thereof. The invention controls the Si content to be 9.0-12.0%, the Zn content to be 4.5-6.5%, the Mg content to be 0.3-0.65%, the Fe content to be 0.5-0.8%, the Mn content to be 0.3-0.5%, and the Ti content to be 0.08-0.15% to obtain a die-casting aluminum alloy with high strength and high thermal conductivity, and having good casting performance and self-quenching performance. The thermal conductivity of its preferred composition alloy can reach 146.5 W / (m·K), and the yield strength and tensile strength can reach 250 MPa and 310 MPa respectively. However, the Zn content is relatively high, reducing the hot cracking resistance of the alloy and being disadvantageous to the forming performance of the thin-wall position during the actual die-casting process.

[0004] Chinese Patent Application for Invention CN109306413A discloses a high-strength and high-thermal-conductivity die-cast aluminum alloy material, its preparation method and application. In this method, the Si content is controlled to be 8.0 - 10.0%, the Mg content is 1.5 - 3.5%, the Fe content is 0.06 - 0.5%, and the Sr content is 0.005 - 0.05%. By adding an appropriate amount of strengthening element Mg to the Al-Si alloy with excellent casting performance and strictly controlling impurity elements such as Fe, Cu, Mn, Cr, V, and Ti, the synchronous improvement of the thermal conductivity and mechanical properties of the alloy is achieved. Its comprehensive performance is superior to conventional aluminum alloys such as ADC12 and A380, and it can be applied to products with complex shapes and high requirements for thermal conductivity and mechanical properties, such as communication chassis and mobile phone middle plates. However, a high content of Mg element has an adverse effect on the die-casting forming performance of the alloy.

[0005] Chinese Invention Patent CN112522648A discloses a process method for improving the thermal conductivity of die-cast aluminum alloy. By applying a heat treatment process to the aluminum alloy sample obtained by vacuum die-casting, the heating temperature is 200 - 300 °C, and the heat treatment time is 2 - 4 h. This heat treatment process can effectively eliminate phenomena such as lattice distortion, point defects, and line defects existing inside the product, improve the internal continuity of the product, and thus improve the thermal conductivity of the product. However, the cost of vacuum die-casting is relatively high, and ordinary high-pressure die-casting causes a large number of pores inside the product, and problems such as bulging will occur in the subsequent heat treatment, seriously affecting the appearance and dimensional accuracy of the die-cast product.

[0006] The above-mentioned patented technologies all involve the composition design and preparation methods of high-strength and high-thermal-conductivity die-cast Al-Si-based aluminum alloys, which have good thermal conductivity and mechanical properties and can meet die-casting forming at the same time. However, high contents of Mg and Zn elements have an adverse effect on the die-casting forming performance of the alloy, are prone to generate casting defects, seriously affect the product quality and die life, increase the manufacturing cost of the product, and limit the industrial application scope of these alloys in packaging devices for communication equipment. Summary of the Invention

[0007] The purpose of the present invention is to provide a high-strength and high-thermal-conductivity Al-Cu-Si-based die-cast aluminum alloy to solve the technical problem of poor performance of die-cast alloys in the prior art, which can improve the morphology and distribution of eutectic Si phase and Al2Cu phase, and can be a die-cast alloy with both high strength and high thermal conductivity.

[0008] A high-strength and high-thermal-conductivity Al-Cu-Si-based die-cast aluminum alloy is made of the following components by mass percentage: Cu: 13.0 - 15.0%, Si: 5.0 - 7.0%, Zn: 0.1 - 0.5%, Mg: 0.1 - 0.5%, Sr: 0.05 - 0.3%, and the balance is Al.

[0009] A preparation method of a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy, comprising the following steps:

[0010] S1: Melting the aluminum alloy: Design the alloy composition according to the performance requirements, use industrial pure Al, Al-50Cu and Al-20Si master alloys as raw materials, formulate and melt the aluminum alloy according to the target composition; after all the alloy is melted, stir it to make its composition uniform, obtain an aluminum alloy melt, and keep it static and insulated.

[0011] S2: Melt treatment with modification elements: Skim the dross on the surface of the aluminum alloy melt, add Al-10Sr master alloy to the aluminum alloy melt melted in step S1 for melting, and then stir to obtain a modified aluminum alloy melt, and keep it static and insulated.

[0012] S3: Trace element alloying: Skim the dross on the surface of the modified aluminum alloy melt, add one or both of pure Mg and pure Zn to the aluminum alloy melt in step S2 for micro-alloying treatment, stir thoroughly until the melt composition is uniform, and keep it static and insulated.

[0013] S4: Melt refining and slag removal: Add a refining agent and a slag removal agent to the melt in step S3 for refining and slag removal, keep it static and insulated for 10 min; after slag removal, take it out of the furnace and cast it into a mold to obtain an Al-Cu-Si series die-casting aluminum alloy casting.

[0014] Furthermore, the melting temperature described in steps S1 and S2 is 700 - 720 °C, and the stirring time is 5 - 20 min.

[0015] Furthermore, the static insulation time described in steps S1 and S2 is 10 - 30 min.

[0016] Furthermore, the micro-alloying treatment temperature described in step S3 is 680 - 700 °C, and the stirring time is 5 - 20 min.

[0017] Furthermore, the static insulation time described in step S3 is 30 - 120 min.

[0018] Furthermore, in step S4, the refining agent and the slag removal agent are added by nitrogen gas blowing method.

[0019] Furthermore, the refining agent and the slag removal agent are proportioned at 1:1 and mixed evenly.

[0020] Furthermore, the total addition amount of the refining agent and the slag removal agent is 1% of the melt weight.

[0021] Furthermore, when adding the refining agent and the slag removal agent, the temperature is controlled at 680 - 690 °C and the time is 5 - 15 min.

[0022] The beneficial effects of the present invention compared with the prior art are as follows:

[0023] 1. The present invention uses Cu, Si, Sr, Mg, Zn, and Al as the main raw materials. Among them, the Cu element has a certain solid solubility in the aluminum matrix, but its influence on the thermal conductivity of the alloy is much smaller than that of transition elements such as Mn, Cr, and V. Moreover, the Cu element is a good strengthening element. After solution aging treatment, fine and dispersed Al2Cu phases will precipitate uniformly in the aluminum matrix, achieving a good strengthening effect.

[0024] 2. Si in the present invention can improve the fluidity of the aluminum alloy and reduce the linear shrinkage rate. The Si content in the present invention is controlled to be 5.0 - 7.0%, which can ensure that the alloy has good casting performance while preventing the decline of thermal conductivity while ensuring the mechanical properties of the alloy.

[0025] 3. Sr in the present invention can effectively refine the morphology and distribution of eutectic Si phase in the as-cast alloy, transforming it from thick plate-like to fine fibrous. The refinement of the eutectic Si phase can simultaneously improve the thermal conductivity and mechanical properties of the alloy. The addition amount of Sr element in the present invention is controlled to be 0.05 - 0.3%, which can ensure the comprehensive performance of the alloy while improving the modification effect of Si.

[0026] 4. Mg in the present invention is beneficial to the improvement of the mechanical properties and casting performance of the aluminum alloy. The trace amount of Mg element mainly exists in a solid solution form. When Si and Zn elements exist in the melt, the Mg element will undergo a metallurgical reaction with them to form Mg2Si and MgZn2 phases, both of which are high-quality strengthening phases. They interact with dislocations, hinder the movement of dislocations, and significantly improve the mechanical properties of the alloy. Moreover, the formation of intermetallic compounds can reduce the solid solution amount of solute elements in the aluminum matrix, thereby weakening the scattering effect of solute atoms on electrons and phonons, and promoting the improvement of the thermal conductivity of the alloy. Zn can improve the mechanical properties of the alloy through the interaction between solid solution atoms and dislocations, and has a relatively small influence on the thermal conductivity of the aluminum alloy.

[0027] 5. In the present invention, Mg and Zn are used for trace element alloying. Among them, through a synergistic reaction between Mg and Zn, high-quality MgZn2 strengthening phases can be generated, playing a role of dispersion strengthening, and thus significantly improving the mechanical properties of the alloy. Moreover, when alloy elements exist in the form of the second phase, their influence on the thermal conductivity of the alloy is relatively small.

[0028] 6. The alloy designed by the present invention successfully solves the problem of the mutual contradiction between the mechanical properties and thermal conductivity of the aluminum alloy for communication equipment. By adding an appropriate amount of modification element Sr, the morphology and distribution of eutectic Si and Al2Cu phases are effectively improved, realizing the dual improvement of mechanical properties and thermal conductivity. After Sr modification and microalloying with Zn and Mg, the best thermal conductivity is as high as 127 W / (m·K), the yield strength reaches 175 MPa, the tensile strength reaches 346 MPa, and the elongation is 5.2%. A die-cast aluminum alloy with both high thermal conductivity and high strength can be obtained, fully meeting the dual requirements of mechanical and thermal properties for the packaging devices used in communication equipment.

[0029] 7. The preparation operation of the alloy system involved in the present invention is simple and easy to perform, the addition amount is easy to control, the formula is streamlined and optimized. By reasonably designing the dosage ratio, high performance can still be maintained, the cost is reduced. Using multi-element composite microalloying treatment, no pollutants are discharged, the operating process is simple, the elements of the alloy system used are low in cost, and the comprehensive performance is excellent. Brief Description of the Drawings

[0030] Figure 1 It is the XEM diagram of Example 1 of the present invention.

[0031] Figure 2 It is the XRD diffraction diagram of Example 1 of the present invention. Detailed Embodiments

[0032] Before further describing the specific embodiments of the present invention, it should be understood that the protection scope of the present invention is not limited to the following specific embodiments; it should also be understood that the terms used in the embodiments of the present invention are for the purpose of describing specific embodiments, rather than limiting the protection scope of the present invention.

[0033] Example 1

[0034] A high-strength and high-thermal-conductivity Al-Cu-Si series die-cast aluminum alloy, characterized in that it is made of the following components by mass percentage: Cu: 14%, Si: 6%, Zn: 0.3%, Mg: 0.2%, Sr: 0.15%, and the balance is Al;

[0035] A preparation method of a high-strength and high-thermal-conductivity Al-Cu-Si series die-cast aluminum alloy, comprising the following steps:

[0036] S1: Melting the aluminum alloy: Using industrial pure Al, Al-50Cu and Al-20Si master alloys as raw materials, formulating according to the target composition and melting the aluminum alloy at 720 °C; after the alloy is completely melted, stirring for 10 min to make its composition uniform, obtaining an aluminum alloy melt, and standing for heat preservation for 30 min;

[0037] S2: Melt treatment with modifying elements: Skim the dross on the surface of the aluminum alloy melt, add Al-10Sr master alloy to the aluminum alloy melt melted in S1, melt it at 720 °C, then stir for 5 min to obtain the modified aluminum alloy melt, and keep it static and insulated for 10 min.

[0038] S3: Trace element alloying: Skim the dross on the surface of the modified aluminum alloy melt, add one or both of pure Mg and pure Zn to the aluminum alloy melt in S2, perform microalloying treatment at 700 °C, stir for 10 min until the melt composition is uniform, and keep it static and insulated for 60 min.

[0039] S4: Melt refining and slag removal: At 680 °C, use the nitrogen injection method to add 1% of the refining agent and slag removal agent based on the weight of the melt in the melt of S3, where the mass ratio of the refining agent to the slag removal agent is 1:1, mix evenly, perform refining and slag removal for 15 min, and keep it static and insulated for 10 min; After skimming the slag, take it out of the furnace and cast it into shape to obtain an Al-Cu-Si series die-cast aluminum alloy casting.

[0040] Example 2

[0041] A high-strength and high-thermal conductivity Al-Cu-Si series die-cast aluminum alloy, characterized in that it is made of the following components by mass percentage: Cu: 13%, Si: 7%, Zn: 0.1%, Mg: 0.5%, Sr: 0.05%, and the balance is Al.

[0042] A preparation method of a high-strength and high-thermal conductivity Al-Cu-Si series die-cast aluminum alloy, comprising the following steps:

[0043] S1: Melting aluminum alloy: Design the alloy composition according to the performance requirements, use industrial pure Al, Al-50Cu and Al-20Si master alloys as raw materials, prepare according to the target composition and melt the aluminum alloy at 700 °C; After all the alloy is melted, stir for 15 min to make its composition uniform, obtain the aluminum alloy melt, and keep it static and insulated for 20 min.

[0044] S2: Melt treatment with modifying elements: Skim the dross on the surface of the aluminum alloy melt, add Al-10Sr master alloy to the aluminum alloy melt melted in S1, melt it at 710 °C, then stir for 10 min to obtain the modified aluminum alloy melt, and keep it static and insulated for 20 min.

[0045] S3: Trace element alloying: Skim the dross on the surface of the modified aluminum alloy melt, add one or both of pure Mg and pure Zn to the aluminum alloy melt in S2, perform microalloying treatment at 690 °C, stir for 5 min until the melt composition is uniform, and keep it static and insulated for 90 min.

[0046] S4: Melt refining and slag removal: At 680 °C, using the nitrogen gas injection method, a refining agent and a slag removal agent with a total addition amount of 1% of the melt weight are added to the melt in S3. The mass ratio of the refining agent to the slag removal agent is 1:1. After mixing evenly, refine and remove slag for 5 minutes, and keep it static and heat-insulated for 10 minutes; After skimming the slag, take it out of the furnace and cast it into shape to obtain an Al-Cu-Si series die-casting aluminum alloy casting.

[0047] Example 3:

[0048] A high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy, characterized in that it is made of the following components by mass percentage: Cu: 15%, Si: 5%, Zn: 0.5%, Mg: 0.1%, Sr: 0.3%, and the balance is Al;

[0049] A preparation method of a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy, comprising the following steps:

[0050] S1: Melting aluminum alloy: Design the alloy composition according to the performance requirements. Using industrial pure Al, Al-50Cu and Al-20Si master alloys as raw materials, prepare according to the target composition and melt the aluminum alloy at 710 °C; After all the alloy is melted, stir for 5 minutes to make its composition uniform, obtain an aluminum alloy melt, and keep it static and heat-insulated for 30 minutes;

[0051] S2: Melt treatment with modification elements: Skim the scum on the surface of the aluminum alloy melt, add Al-10Sr master alloy to the aluminum alloy melt melted in S1 and melt it at 700 °C, then stir for 20 minutes to obtain a modified aluminum alloy melt, and keep it static and heat-insulated for 30 minutes;

[0052] S3: Trace element alloying: Skim the scum on the surface of the modified aluminum alloy melt, add one or both of pure Mg and pure Zn to the aluminum alloy melt in S2, and carry out micro-alloying treatment at 680 °C, stir for 20 minutes until the melt composition is uniform, and keep it static and heat-insulated for 120 minutes;

[0053] S4: Melt refining and slag removal: At 690 °C, using the nitrogen gas injection method, add a refining agent and a slag removal agent with a weight of 1% of the melt to the melt in S3. The mass ratio of the refining agent to the slag is 1:1. After mixing evenly, refine and remove slag for 10 minutes, and keep it static and heat-insulated for 10 minutes; After skimming the slag, take it out of the furnace and cast it into shape to obtain an Al-Cu-Si series die-casting aluminum alloy casting.

[0054] Example 4

[0055] A high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy, characterized in that it is made of the following components by mass percentage: Cu: 14%, Si: 6%, Zn: 0.3%, Mg: 0.3%, Sr: 0.15%, and the balance is Al;

[0056] A preparation method of a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy, comprising the following steps:

[0057] S1: Melting the aluminum alloy: Design the alloy composition according to the performance requirements. Using industrial pure Al, Al-50Cu and Al-20Si master alloys as raw materials, prepare according to the target composition and melt the aluminum alloy at 720 °C; after all the alloy is melted, stir for 20 min to make its composition uniform, obtain the aluminum alloy melt, and keep it static and insulated for 10 min;

[0058] S2: Melt treatment with modification elements: Skim the dross on the surface of the aluminum alloy melt, add Al-10Sr master alloy to the aluminum alloy melt melted in S1 and melt it at 700 °C, then stir for 15 min, obtain the modified aluminum alloy melt, and keep it static and insulated for 30 min;

[0059] S3: Trace element alloying: Skim the dross on the surface of the modified aluminum alloy melt, add one or both of pure Mg and pure Zn to the aluminum alloy melt in S2, and carry out micro-alloying treatment at 680 °C, stir for 15 min until the melt composition is uniform, and keep it static and insulated for 30 min;

[0060] S4: Melt refining and slag removal: At 690 °C, use the nitrogen injection method to add 1% of the refining agent and slag removal agent based on the weight of the melt in the melt in S3, with a ratio of 1:1, mix evenly, carry out refining and slag removal for 5 min, and keep it static and insulated for 10 min; After skimming the slag, take it out of the furnace and cast it into a mold to obtain an Al-Cu-Si series die-casting aluminum alloy casting.

[0061] Comparative Example 1

[0062] It is basically the same as Example 1, except that the content of Si is 3%, and the aluminum balance increases accordingly.

[0063] Comparative Example 2

[0064] It is basically the same as Example 1, except that the content of Si is 9%, and the aluminum balance decreases accordingly.

[0065] Comparative Example 3

[0066] It is basically the same as Example 1, except that the content of Sr is 0.01%, and the aluminum balance increases accordingly.

[0067] Comparative Example 4

[0068] It is basically the same as Example 1, except that the content of Sr is 0.4%, and the remaining amount of aluminum is reduced accordingly.

[0069] Comparative Example 5

[0070] It is basically the same as Example 1, except that the content of Mn is 0.05%, and the remaining amount of aluminum is increased accordingly.

[0071] Comparative Example 6

[0072] It is basically the same as Example 1, except that the content of Mn is 0.7%, and the remaining amount of aluminum is reduced accordingly.

[0073] Comparative Example 7

[0074] It is basically the same as Example 1, except that the content of Zn is 0.05%, and the remaining amount of aluminum is increased accordingly.

[0075] Comparative Example 8

[0076] It is basically the same as Example 1, except that the content of Zn is 0.7%, and the remaining amount of aluminum is reduced accordingly.

[0077] Comparative Example 9

[0078] The alloy material obtained by the method described in Example 1 of a kind of aluminum alloy and its preparation method and application in the Chinese invention patent (application number: CN201510849258.3) is adopted.

[0079] 1. Performance test experiment

[0080] The alloys prepared in Examples 1-4 and Comparative Example 1 were subjected to performance tests, including thermal conductivity [W / (m·K)], yield strength [Mpa], tensile strength [MPa], and elongation [%]. The data are shown in Table 1.

[0081] Table 1 Performance of each alloy in the comparative example and the example

[0082]

[0083]

[0084] Note: The improvement rate is calculated for the alloy in the same state.

[0085] As can be seen from Table 1, the thermal conductivities of Examples 1-5 are all above 123 W / (m·K), the yield strengths are all above 158 MPa, the tensile strengths are all above 325 MPa, and the elongations are all above 4.2%. From Figure 1 and Figure 2It can be seen that after the composite addition of Zn and Mg elements, the α-Al grains are further refined and the secondary dendrite arm spacing is significantly reduced. The XRD test results show that the composite addition of Zn and Mg elements to synthesize high-quality strengthening phase MgZn2 has a positive effect on the mechanical properties of the alloy.

[0086] In comparative examples 1-2, when the Si content is 3% and 9%, the yield strength of Example 1 is increased by 15% and 13% respectively; the tensile strength is increased by 15% and 11% respectively; and the elongation is increased by 44% and 38% respectively relative to Example 1-2.

[0087] This is because Si can improve the flow properties of aluminum alloys and reduce linear shrinkage, which can ensure that the alloy has good casting properties, and the tensile strength and hardness of the alloy increase with the increase of Si content. However, in the unmodified state, the eutectic Si phase mainly exists in the form of laths, which causes relatively serious scattering effects on the movement of electrons and phonons, resulting in a decrease in the thermal conductivity of the alloy. Therefore, the addition amount of Si element should not be too high. When the Si content of Comparative Example 2 is 9%, its thermal conductivity decreases significantly. Therefore, the present invention controls the Si content within the range of 5.0-7.0%, which can prevent the decrease in thermal conductivity while ensuring the mechanical properties of the alloy.

[0088] In Comparative Examples 3-4, when the Sr content is 0.01% and 0.4%, the thermal conductivity of Example 1 is increased by 5% and 3% respectively, the yield strength is increased by 15% and 12% respectively, the tensile strength is increased by 18% and 11% respectively, and the elongation is increased by 62% and 49% respectively.

[0089] This is because Sr can effectively refine the morphology and distribution of the eutectic Si phase in the cast alloy, transforming it from a coarse lath shape to a fine fiber shape. The refinement of the eutectic Si phase can simultaneously improve the thermal conductivity and mechanical properties of the alloy. The key to Sr-modified eutectic Si phase in aluminum alloys is the regulation of Sr content, modification temperature and holding time. If the Sr element content is too low, the modification effect on the eutectic Si phase is not ideal; if the Sr element content is too high, an over-modified structure is produced, and melt aspiration occurs, which is detrimental to the comprehensive performance of the alloy. Therefore, the present invention controls the addition amount of the Sr element to 0.05-0.3%, and in combination with the process of the present invention, it can improve the modification effect of Si while ensuring the comprehensive performance of the alloy.

[0090] In Comparative Examples 5-6, when the Mn content is 0.05% and 0.7%, the thermal conductivity of Example 1 is increased by 3% and 6% respectively, the yield strength is increased by 16% and 14% respectively, the tensile strength is increased by 12% and 11% respectively, and the elongation is increased by 44% and 30% respectively.

[0091] This is because Mg in the present invention is beneficial to improving the mechanical properties and casting properties of aluminum alloys. The trace-added Mg element mainly exists in a solid-solution form. When Si and Zn elements are present in the melt, the Mg element will undergo a metallurgical reaction with them to form Mg2Si and MgZn2 phases, both of which are high-quality strengthening phases. They interact with dislocations, hinder the movement of dislocations, and significantly improve the mechanical properties of the alloy. Moreover, the formation of intermetallic compounds can reduce the solid-solution amount of solute elements in the aluminum matrix, thereby weakening the scattering effect of solute atoms on electrons and phonons and promoting the improvement of the thermal conductivity of the alloy. However, with the increase in the Mn content, excessive MnO will be generated, which is not conducive to the alloy properties. The present invention controls the Mn content within 0.1-0.5%, which can ensure the overall performance of the alloy.

[0092] In Comparative Examples 7-8, when the Zn content was 0.05% and 0.7%, compared with Comparative Examples 7-8, the thermal conductivity of Example 1 did not increase significantly; the yield strength increased by 14% and 16% respectively; the tensile strength increased by 13% and 10% respectively; and the elongation increased by 41% and 33% respectively.

[0093] This is because Zn can improve the mechanical properties of the alloy through the interaction between solid-solution atoms and dislocations, and has relatively little influence on the thermal conductivity of aluminum alloys. However, when the Zn content is excessive, too many second phases with more structures and impurities will be generated, resulting in loose alloy structures and a decrease in mechanical properties. Therefore, the present invention controls the Zn content within 0.1-0.5%, which can ensure the mechanical properties of the alloy.

[0094] Compared with Comparative Example 1, the tensile strength of Example 1 increased by 9% and the elongation increased by 30%, showing a significant improvement in mechanical properties.

[0095] The above embodiments merely illustrate the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy, characterized in that: The invention is made of the following components in percentage by mass: Cu: 13.0-15.0%, Si: 5.0-7.0%, Zn: 0.1-0.5%, Mg: 0.1-0.5%, Sr: 0.05-0.3%, and the balance is Al.

2. A preparation method of a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy according to claim 1, characterized in that, The following steps are involved: S1: Melting aluminum alloy: designing alloy composition according to performance requirements, using industrial pure Al, Al-50Cu and Al-20Si master alloy as raw materials, preparing and melting aluminum alloy according to target composition; after all the alloy is melted, stirring to make the composition uniform, obtaining aluminum alloy melt, and keeping it still; S2: Melt treatment of modified elements: scrape off the scum on the surface of the aluminum alloy melt, add Al-10Sr master alloy to the aluminum alloy melt melted in step S1 to melt, stir, obtain the modified aluminum alloy melt, and let it stand to keep warm; S3: Trace element alloying: scrape off the scum on the surface of the aluminum alloy melt that has been modified, add one or both of pure Mg and pure Zn to the aluminum alloy melt in step S2, perform micro-alloying treatment, fully stir until the melt composition is uniform, and let it stand to keep warm; S4: melt refining and slag removal: add refining agent and slag removal agent to the melt of step S3, perform refining and slag removal, and keep the melt at room temperature for 10 minutes; remove the slag and then cast the melt to obtain Al-Cu-Si series die-cast aluminum alloy castings.

3. The preparation method of a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy according to claim 2, wherein: The melting temperature in steps S1 and S2 is 700-720° C., and the stirring time is 5-20 min.

4. The preparation method of a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy according to claim 2, characterized in that: The standing and heat preservation time described in steps S1 and S2 is 10 to 30 minutes.

5. The preparation method of a high-strength and high-thermal conductivity Al-Cu-Si series die-casting aluminum alloy according to claim 2, wherein: The microalloying treatment temperature in step S3 is 680-700° C., and the stirring time is 5-20 min.

6. The preparation method of a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy according to claim 2, characterized in that: The standing and heat preservation time described in step S3 is 30 to 120 minutes.

7. The preparation method of a high-strength and high-thermal conductivity Al-Cu-Si series die-casting aluminum alloy according to claim 2, characterized in that: In the step S4, the refining agent and the slag removal agent are added by nitrogen blowing.

8. The preparation method of a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy according to claim 2, characterized in that: The refining agent and the slag removal agent are mixed in a ratio of 1:1 and evenly mixed.

9. The preparation method of a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy according to claim 2, characterized in that: The total amount of the refining agent and the slag removal agent added is 1% of the weight of the melt.

10. The preparation method of a high-strength and high-thermal-conductivity Al-Cu-Si series die-casting aluminum alloy according to claim 2, characterized in that: When the refining agent and the slag removal agent are added, the temperature is controlled to be 680-690° C. and the time is 5-15 minutes.

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