Aluminum alloy and preparation method thereof

Abstract

The present invention belongs to the technical field of aluminum alloys, and relates to an aluminum alloy and a preparation method thereof. The aluminum alloy, taking the aluminum alloy as 100%, comprises the following components in mass percentage: Si content is 8.5% to 10.5%, Fe content is 0 to 0.65%, Cu content is 0 to 0.3%, Mn content is 0 to 0.25%, Mg content is 1.0% to 1.5%, Zn content is 0 to 0.3%, Pb content is 0 to 0.05%, Ti content is 0 to 0.03%, Sr content is 0 to 0.045%, Ce content is 0.001% to 0.04%, and the remainder is Al and other elements, and the total amount of other elements is less than 0.1%. The aluminum alloy has excellent mechanical properties, good thermal conductivity, excellent corrosion resistance and casting forming properties.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloys, and in particular relates to an aluminum alloy and a preparation method thereof. Background Art

[0002] Aluminum and its alloys are important industrial raw materials, which are widely used in aerospace, machinery, electronics, shipbuilding and chemical industries. Die-cast aluminum alloys have the advantages of high manufacturing efficiency, near net shape, good surface quality, etc. They are particularly suitable for large-scale, fast-paced industrial manufacturing and are widely used in automobile, communication, electronics, home appliances and other industries.

[0003] Die-cast aluminum alloys are widely used in the fields of communications, electronics, and transportation, and are mainly used to produce thin-walled shell parts. In order to meet the needs of thin-walled, lightweight, high-strength and casting production of parts, higher and higher requirements are put forward for the casting fluidity and mechanical properties of aluminum alloys. At present, the most commonly used casting aluminum alloy is Al-Si series casting aluminum alloy, among which ADC12 casting aluminum alloy is widely used, which usually contains more than 9.6% to 12.0% Si element, so it has good casting fluidity and meets the casting process requirements. However, the mechanical properties of the product body of Al-Si series casting aluminum alloy after die-casting are general, with a tensile strength between 200 and 330 MPa, a yield strength between 120 and 190 MPa, and a thermal conductivity between 90 and 110 W / (m·K), which cannot meet the requirements of aluminum alloy die-casting products with high comprehensive mechanical and thermal conductivity properties. Summary of the invention

[0004] In view of the problem that existing die-casting aluminum alloys cannot take into account casting performance, mechanical properties and thermal conductivity at the same time, the present invention provides a die-casting aluminum alloy and a preparation method thereof.

[0005] In order to solve the above technical problems, on the one hand, an embodiment of the present invention provides an aluminum alloy, which includes the following components in percentage by mass, based on 100% of the aluminum alloy:

[0006] The Si content is 8.5% to 10.5%, the Fe content is 0 to 0.65%, the Cu content is 0 to 0.3%, the Mn content is 0 to 0.25%, the Mg content is 1.0% to 1.5%, the Zn content is 0 to 0.3%, the Pb content is 0 to 0.05%, the Ti content is 0 to 0.03%, the Sr content is 0 to 0.045%, the Ce content is 0.001% to 0.04%, and the balance is Al and other elements, and the total amount of other elements is less than 0.1%.

[0007] Optionally, the aluminum alloy comprises the following element components, taking 100% as the aluminum alloy:

[0008] The Si content is 8.5% to 10.5%, the Fe content is 0.06% to 0.65%, the Cu content is 0.05% to 0.2%, the Mn content is 0.08% to 0.25%, the Mg content is 1.0% to 1.5%, the Zn content is 0 to 0.30%, the Pb content is 0 to 0.05%, the Ti content is 0 to 0.03%, the Sr content is 0.01% to 0.045%, the Ce content is 0.005% to 0.04%, and the balance is Al and other elements, and the total amount of other elements is less than 0.1%.

[0009] Optionally, the mass percentage contents of Sr and Ce satisfy 0.015%≤Sr+Ce≤0.07%.

[0010] Optionally, the content of Fe is 0.06% to 0.49%, and the content of Zn is 0 to 0.10%.

[0011] Optionally, the aluminum alloy does not contain La.

[0012] Optionally, the other elements include at least one of Cr and V.

[0013] Optionally, the die-cast aluminum alloy has a yield strength greater than or equal to 300 MPa, a tensile strength greater than or equal to 400 MPa, an elongation at break greater than or equal to 3%, and a thermal conductivity greater than or equal to 150 W / m·K.

[0014] In another aspect, the present invention provides a method for preparing the aluminum alloy as described above, comprising the following steps:

[0015] Weigh the required proportions of Al, Si, Fe, Cu, Mn, Zn, Mg, Ce, Pb, Ti and Sr according to the element ratio in the aluminum alloy;

[0016] Put pure Al into the melting furnace, heat it to 200-230°C, preheat it for 2-4 hours; then heat it to 750-760°C, keep it warm for 20-40 minutes, and obtain aluminum liquid;

[0017] Adding Si, Fe, Cu, Mn and Zn to the aluminum liquid to obtain a first melt;

[0018] adding Mg and an alloy containing Ce, Pb, Ti and Sr to the first melt at 700-740° C. to obtain a second melt;

[0019] Inert gas is introduced into the second melt to degas for 10 to 20 minutes, and then refined. After refining, the melt is allowed to stand for 10 to 120 minutes, and slag is removed to obtain an aluminum alloy melt. The aluminum alloy melt is kept warm at 700 to 720° C.;

[0020] The aluminum alloy melt is poured into an aluminum ingot mold to obtain an aluminum alloy ingot.

[0021] Optionally, after obtaining the aluminum alloy ingot, the aluminum alloy ingot is made into a thin plate die casting, and the thin plate die casting is subjected to a heat shaping process, wherein the heat shaping process is to heat the thin plate die casting at 250-280°C for 10-18s and then naturally place it for 40-48h.

[0022] Optionally, the thin plate die-casting is a die-cast aluminum alloy mobile phone mid-plate.

[0023] In the present invention, the alloying elements of the aluminum alloy are optimized to improve its strength, toughness and thermal conductivity to meet the requirements of the new generation of communications, electronics and other products for structural materials. The die-cast aluminum alloy has excellent casting performance, high strength, certain plasticity, good economy, and is particularly suitable for manufacturing structural parts for communications, electronics and other products. In addition, in the present invention, a dense oxide film is formed on the surface of the aluminum alloy by adding Ce, and this oxide film can effectively improve the corrosion resistance of the aluminum alloy. This is especially important for alloy materials that need to be used in corrosive environments. In addition, the Ce element can also significantly enhance the mechanical properties of Al-Si-Mg aluminum alloy. Since the radius of the Ce atom is larger than that of the Al atom, when Ce is dissolved in the α-Al matrix, a large lattice distortion will be generated in the matrix, thereby hindering dislocation movement and improving the strength of the aluminum alloy. The Ce element can form Al with Al 2 Ce intermetallic compounds are dispersed in the matrix, which further hinders the movement of dislocations and plays a precipitation strengthening effect. Furthermore, the role of Ce elements in Al-Si-Mg aluminum alloys can be further optimized by heat treatment of aluminum alloy ingots. Heat treatment can make the Ce element more evenly distributed in the alloy and promote the formation of precipitation phases, thereby further improving the mechanical properties and corrosion resistance of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a polarization curve diagram of a die-cast aluminum alloy mobile phone middle plate made of the aluminum alloy ingot prepared in Example 1 without passivation process;

[0025] Figure 2 This is a polarization curve diagram of a die-cast aluminum alloy mobile phone middle plate made from the aluminum alloy ingot prepared in Example 1 without the passivation process. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] The aluminum alloy provided in the embodiment of the present invention, taking the aluminum alloy as 100%, includes the following components in percentage by mass:

[0028] The Si content is 8.5% to 10.5%, the Fe content is 0 to 0.65%, the Cu content is 0 to 0.3%, the Mn content is 0 to 0.25%, the Mg content is 1.0% to 1.5%, the Zn content is 0 to 0.3%, the Pb content is 0 to 0.05%, the Ti content is 0 to 0.03%, the Sr content is 0 to 0.045%, the Ce content is 0.001% to 0.04%, and the balance is Al and other elements, and the total amount of other elements is less than 0.1%.

[0029] Preferably, the aluminum alloy comprises the following element components, taking 100% as the aluminum alloy:

[0030] The Si content is 8.5% to 10.5%, the Fe content is 0.06% to 0.65%, the Cu content is 0.05% to 0.2%, the Mn content is 0.08% to 0.25%, the Mg content is 1.0% to 1.5%, the Zn content is 0 to 0.30%, the Pb content is 0 to 0.05%, the Ti content is 0 to 0.03%, the Sr content is 0.01% to 0.045%, the Ce content is 0.005% to 0.04%, and the balance is Al and other elements, and the total amount of other elements is less than 0.1%.

[0031] In this embodiment, the present invention optimizes the alloying elements of the aluminum alloy to improve its strength, toughness and thermal conductivity to meet the requirements of the new generation of communications, electronics and other products for structural materials. The die-cast aluminum alloy has excellent casting performance, high strength, certain plasticity, good economy, and is particularly suitable for manufacturing structural parts for communications, electronics and other products. In addition, in the present invention, a dense oxide film is formed on the surface of the aluminum alloy by adding Ce. This oxide film can effectively improve the corrosion resistance of the aluminum alloy. This is especially important for alloy materials that need to be used in corrosive environments. In addition, the Ce element can also significantly enhance the mechanical properties of Al-Si-Mg aluminum alloy. Since the radius of the Ce atom is larger than that of the Al atom, when Ce is dissolved in the α-Al matrix, a large lattice distortion will be generated in the matrix, thereby hindering dislocation movement and improving the strength of the aluminum alloy. The Ce element can form Al with Al. 2 Ce intermetallic compounds are dispersed in the matrix, which further hinders the movement of dislocations and plays a precipitation strengthening effect. Furthermore, the role of Ce elements in Al-Si-Mg aluminum alloys can be further optimized by heat treatment of aluminum alloy ingots. Heat treatment can make the Ce element more evenly distributed in the alloy and promote the formation of precipitation phases, thereby further improving the mechanical properties and corrosion resistance of the alloy.

[0032] Mg and Si form Mg 2 The Si phase is dissolved in α-aluminum during the die-casting process and is dispersed strengthened after aging precipitation. As the Mg content increases, the tensile strength gradually increases and the elongation gradually decreases. However, when the Mg content exceeds a certain range, the welding performance gradually deteriorates. The present invention effectively guarantees the yield strength of the alloy material by adjusting the Mg content within 1.0% to 1.5%, so that the yield strength of the material can reach more than 300Mpa. For this aluminum alloy material with similar other element compositions, if the Mg content is lower than 1.0wt%, the yield strength of the material will be lower than 300Mpa; if the Mg content is higher than 1.5%, the elongation of the material will be lower than 3%.

[0033] Solid solution of Cu in aluminum alloy can improve the fluidity, tensile strength and hardness of the alloy, but reduce corrosion resistance and plasticity. The present invention effectively guarantees the yield strength and elongation of the alloy material by adjusting the Cu content to ≤0.2%. Preferably, the Cu content is 0.15%.

[0034] Mn can make Mg 5 Al 8 The compound is evenly precipitated to improve the corrosion resistance and welding performance of the aluminum alloy, and compensate for the weakening of welding performance caused by Mg; Fe is widely used in die-casting aluminum alloy materials as an element for demolding during die-casting, but the addition of Fe will form β-Al-Fe-Si phase in rod-shaped or needle-shaped during solidification. The rod-shaped or needle-shaped intermetallic compound will greatly affect the mechanical properties of the material, especially the elongation. In order to obtain high mechanical properties, the addition of Fe should be strictly controlled within the range of 0.06-0.65% to obtain the best mechanical properties and forming properties. Most of the Fe phase and Mn phase in the aluminum alloy dissolve into each other, so Mn can replace part of the Fe in the aluminum alloy and reduce the tendency of low-iron aluminum alloy to stick to the mold. Sr, as a modifier of aluminum-silicon alloy, can effectively refine the eutectic silicon in the casting process. The refinement of eutectic silicon is conducive to improving the toughness and thermal conductivity of the material.

[0035] In other specific embodiments, the Si content can be selected from 8.5%, 8.7%, 9.0%, 9.2%, 9.5%, 9.7%, 10% or 10.5%; the Fe content can be selected from 0, 0.06%, 0.1%, 0.14%, 0.18%, 0.22%, 0.26%, 0.30%, 0.34%, 0.38%, 0.42%, 0.45%, 0.5%, 0.54%, 0.58%, 0.62% or 0.65%; the Cu content can be selected from 0, 0.05%, 0. , 0.1%, 0.13%, 0.15%, 0.17%, 0.20%, 0.23%, 0.26% or 0.3%; the Mn can be selected from 0, 0.06%, 0.1%, 0.14%, 0.18%, 0.22% or 0.25%; the Mg can be selected from 1.0%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%; the Zn can be selected from 0, 0.06%, 0.1%, 0.14%, 0.18%, 0.22%, 0.26% or 0.30%. The Pb can be selected from 0, 0.005%, 0.01%, 0.02%, 0.03%, 0.04% or 0.05%. The Ti can be selected from 0, 0.005%, 0.01%, 0.02% or 0.03%. The Sr may be selected from 0.01%, 0.02%, 0.03%, 0.04% or 0.045%. The Ce may be selected from 0.005%, 0.01%, 0.014%, 0.018%, 0.022%, 0.026%, 0.030%, 0.034%, 0.037% or 0.04%.

[0036] It should be noted that in the die-cast aluminum alloy, each element does not act independently but has related effects. The increase or decrease of any element may lead to changes in the effects of other elements, thereby causing changes in the overall performance of the die-cast aluminum alloy.

[0037] In some embodiments, the mass percentage of Sr and Ce satisfies 0.015%≤Sr+Ce≤0.07%. When the Sr content is less than 0.01%, the refinement effect is not obvious. When the Sr content exceeds 0.03%, it will react with Ce to produce Sr 3 Ce compounds, while Sr 3 Ce has a poor thermal conductivity, which reduces the thermal conductivity of aluminum alloys. If the contents of Sr and Ce are reduced at the same time, so that the sum of their contents is less than 0.015%, the corrosion resistance and thermal conductivity of the alloy will be further reduced.

[0038] In some embodiments, the content of Fe is 0.06% to 0.49%, and the content of Zn is 0 to 0.10%. Adding the Fe element in the above range to the aluminum alloy can reduce the demolding difficulty of the aluminum alloy and reduce the erosion effect of the aluminum alloy on the mold. The Zn element can improve the fluidity of the aluminum alloy during the die-casting process. The existing aluminum alloy has the problem of poor machinability, and the melting point of the Zn element is relatively low. It is formed in a free state and distributed in the matrix in the aluminum alloy. By adding the Zn element in the above content range to the aluminum alloy, the softening and melting of the Zn element during cutting deformation is conducive to the formation of fine chips at the interface between the workpiece and the tool, reducing the friction between the tool and the aluminum alloy, and can effectively improve the cutting performance of the die-cast aluminum alloy, so that it has a richer molding structure.

[0039] In some embodiments, the aluminum alloy does not contain La. In Al-Si-Mg aluminum alloy, the amount of La added has a significant effect on the performance of the alloy. In general, adding La in an appropriate amount can refine the grains and improve the mechanical properties and casting properties of the alloy. However, in this embodiment, when the amount of La added exceeds 300ppm, LaAlSi intermetallic compounds will begin to form in the alloy. The formation of this compound will reduce the plasticity and processing properties of the alloy. At the same time, La, as a rare earth element, is relatively expensive, and excessive La content also increases the manufacturing cost of the alloy. In this embodiment, by avoiding the addition of lanthanum to enhance the stress and thermal conductivity of the aluminum alloy, the cost is saved while the plasticity and processing properties of the aluminum alloy are improved.

[0040] In some embodiments, the other elements include at least one of Cr and V. The other elements are impurity elements that are dissolved in the alloy to form impurity phases with elements in the aluminum alloy, reducing the thermal conductivity or mechanical properties of the alloy. This should be avoided by reducing impurities in the aluminum alloy as much as possible. In a preferred implementation, the aluminum alloy does not include the above-mentioned other elements.

[0041] In some embodiments, the die-cast aluminum alloy has a yield strength greater than or equal to 300 MPa, a tensile strength greater than or equal to 400 MPa, an elongation at break greater than or equal to 3%, and a thermal conductivity greater than or equal to 150 W / m·K.

[0042] An embodiment of the present invention further provides a method for preparing the aluminum alloy as described in the above embodiment, comprising the following steps: weighing Al, Si, Fe, Cu, Mn, Zn, Mg, Ce, Pb, Ti and Sr in required proportions according to the element ratio in the aluminum alloy;

[0043] Put pure Al into the melting furnace, heat it to 200-230℃, preheat it for 2-4h to eliminate moisture and other impurities in the Al agent; then heat it to 750-760℃, keep it warm for 20-40min to fully melt the Al agent and obtain aluminum liquid;

[0044] Adding Si, Fe, Cu, Mn and Zn to the aluminum liquid to obtain a first melt;

[0045] adding Mg and an alloy containing Ce, Pb, Ti and Sr to the first melt at 700-740° C. to obtain a second melt;

[0046] Inert gas is introduced into the second melt to degas for 10 to 20 minutes, and then refined. After refining, the melt is allowed to stand for 10 to 120 minutes, and slag is removed to obtain an aluminum alloy melt. The aluminum alloy melt is kept warm at 700 to 720° C. Specifically, before refining, the degassed second melt is deslagging and allowed to stand.

[0047] The aluminum alloy melt is poured into an aluminum ingot mold to obtain an aluminum alloy ingot.

[0048] The aluminum alloy raw material described in the present invention can be various pure metal ingots or alloy ingots containing Al, Zn, Mg, Cu, Fe, and Ce, without any particular limitation, as long as the mass percentage range of each component of the present invention can be obtained. The raw materials are purchased on the market, such as pure aluminum, pure zinc, pure magnesium, aluminum silicon alloy, aluminum manganese alloy, aluminum strontium alloy, aluminum cerium alloy, etc.

[0049] The aluminum alloy ingot prepared by the preparation method in this embodiment has Ce added thereto. Ce forms a dense oxide film on the surface of the aluminum alloy. This oxide film can effectively improve the corrosion resistance of the aluminum alloy, so that the corrosion resistance effect can be obtained without post-treatment of the surface.

[0050] In some embodiments, after obtaining the aluminum alloy ingot, the aluminum alloy ingot is made into a thin plate die casting, and the thin plate die casting is subjected to a hot shaping process, wherein the hot shaping process is to place the thin plate die casting naturally for 40-48 hours after hot shaping treatment at 250-280°C for 10-18s. The aluminum alloy ingot can further optimize the role of the Ce element in the Al-Si-Mg aluminum alloy through the hot shaping process. Hot shaping can make the Ce element more evenly distributed in the alloy, and at the same time can promote the formation of precipitation phases, thereby further improving the mechanical properties and corrosion resistance of the alloy.

[0051] The strengthening mechanism of the hot shaping process is: supersaturated solid solution (SSSS) - (Mg + Si) clusters / GP zone - metastable β "phase - metastable β 'phase - equilibrium β phase. (Mg + Si) clusters and GP zones are generally precipitated from the matrix in the early stage and play a certain strengthening role on the matrix. The cluster size is generally very small, about 1 to 2nm, spherical in shape, and completely coherent with the matrix. After the clusters and GP zones, the β "phase precipitates from the matrix, generally in a needle-like morphology, and is completely coherent with the Al matrix along its b-axis. β "plays a major role in strengthening the alloy. Its crystal structure is a C-centered monoclinic structure with a composition of Mg 5 Si 6 The β′ phase is a hexagonal close-packed (HCP) structure with Mg 1.7 The β phase has CaF 2 Type structure, the morphology is generally lamellar, it is the final equilibrium phase in the alloy, and its composition is Mg 2 Si. The size, quantity and distribution of the equilibrium phase in the alloy basically determine the macroscopic properties of the alloy. 2 The increase of Si content, Mg 2 The Si phase will first precipitate from the alloy in the form of a primary phase, playing the role of second phase particle reinforcement.

[0052] In some embodiments, the thin plate die casting is a die-cast aluminum alloy mobile phone mid-plate.

[0053] The present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0054] Examples and Comparative Examples

[0055] Table 1 shows the mass percentage (%) of the aluminum alloy components of various embodiments and comparative examples of the present invention. The total mass of the aluminum alloy is 100%, and the mass percentage of the remaining components except the components listed in Table 1 is Al.

[0056] Table 1

[0057]

[0058]

[0059] Example 1

[0060] This embodiment is used to illustrate the die-casting aluminum alloy and the preparation method thereof disclosed in the present invention, and includes the following steps:

[0061] Step 1: Weigh and prepare the raw materials according to the aluminum alloy composition shown in Table 1;

[0062] Step 2: Place pure aluminum ingots into the melting furnace, heat to 220°C, preheat for more than 2 hours, then heat to 755°C, keep warm for 20 minutes, so that the pure aluminum ingots are fully melted;

[0063] Step 3: Add Si, Mn, Zn, Cu, and Fe to the aluminum liquid obtained in step 2 and melt them in sequence to obtain a first melt. Then, lower the temperature to 710°C, add Mg, Pb, Sr, and Ce to the aluminum liquid and melt them to obtain a second melt;

[0064] Step 4: The second melt obtained in step 3 is kept warm for 20 minutes, fully stirred with a permanent magnetic stirrer, and the second melt is reheated to 740° C., refined by adding a refining agent, rotated to degas, and allowed to stand for 20 minutes to obtain an aluminum alloy melt, and the temperature of the aluminum alloy melt is adjusted to 710° C.;

[0065] Step 5: Pour the aluminum alloy melt obtained in step 4 into an aluminum ingot mold to obtain a high-strength, high-thermal-conductivity, and corrosion-resistant die-cast aluminum alloy ingot.

[0066] Specifically, the temperature of the molten aluminum alloy is controlled at 690-710°C, and a batch of mobile phone middle plate parts of the same model are produced using a 280-ton die-casting machine. The average wall thickness of the mobile phone middle plate is 0.5mm.

[0067] The mobile phone mid-plate is heat treated at 180°C for 48 hours.

[0068] Embodiments 2 to 13

[0069] Examples 2 to 13 are used to illustrate the aluminum alloy and the preparation method thereof disclosed in the present invention, and include most of the operating steps in Example 1, except that:

[0070] The aluminum alloy compositions shown in Examples 2 to 13 in Table 1 were used, and the other operating steps were the same as those in Example 1.

[0071] Comparative Examples 1 to 6

[0072] Comparative Examples 1 to 6 are used to compare and illustrate the aluminum alloy and the preparation method thereof disclosed in the present invention, and include most of the operating steps in Example 1, except that:

[0073] The aluminum alloy compositions shown in Comparative Examples 1 to 6 in Table 1 were used, and other operation steps were the same as those in Example 1. Specifically, Comparative Example 1 was ADC12 aluminum alloy.

[0074] Performance Testing

[0075] The aluminum alloys prepared in the above examples and comparative examples were subjected to the following performance tests:

[0076] Aluminum alloy thermal conductivity λ (also known as "thermal conductivity") test method: Flash Method (sometimes also called laser method, laser flash method) is used to measure the thermal diffusion coefficient of the material, and DSC is used to measure the specific heat capacity of the material. The size requirements of the DSC sample are: 15-30 mg, generally made into a thin slice with a diameter of about 4 mm and a thickness of 0.4-0.8 mm. The bottom of the sample is flat, in good contact with the crucible, and the surface is clean and free of foreign matter; the real density of the material is measured by the drainage method, and the density is measured by the Archimedean method. The sample is required to be in block shape, without holes on the surface, and the weight does not exceed the range of the balance (220g), generally 1g to more than ten grams. The thermal conductivity of the sample can be calculated using the following formula.

[0077] λ T =α T ×C P ×ρ T

[0078] Where: T is the thermal conductivity of the material at temperature T, W / (m·K); α T is the thermal diffusivity of the material at temperature T, (mm) 2 / s;C P is the specific heat capacity of the material at temperature T, J / (g·K); ρ T Yes Material density, g / cm 3 .

[0079] The tensile strength, yield strength and elongation at break of the material were tested using GB / T 228.1-2010 Tensile test of metallic materials Part 1: Room temperature test method.

[0080] The aluminum alloy die-casting specimens prepared from the above components were tested for tensile properties using an electronic universal testing machine of model CMT5105, with a gauge length of 50 mm and a loading rate of 2 mm / min. The measurement data were recorded, and six specimens were tested at each recipe point, where the yield strength, tensile strength and elongation were the average values ​​of the six data. The relative standard deviation of the yield strength was the percentage ratio of the standard deviation of the six yield strength data to the average value, and the relative standard deviation of the tensile strength was the percentage ratio of the standard deviation of the six tensile strength data to the average value.

[0081] Corrosion resistance test method: GB / T24196-2009 Electrochemical test method for corrosion of metals and alloys - Constant potential and dynamic potential polarization measurement guide, GB / T40299-2021 Electrochemical measurement method for corrosion test of metals and alloys are used to test the corrosion resistance of the material.

[0082] Fill in the test results obtained above into Table 2.

[0083] Table 2

[0084]

[0085]

[0086] It can be seen from Table 2 that the high-strength, high-thermal-conductivity, corrosion-resistant die-cast aluminum alloy material of the present invention has the characteristics of excellent mechanical properties, good thermal conductivity, good corrosion resistance and casting formability, and simple heat treatment (thermal shaping) after die-casting into actual castings has mechanical properties with a yield strength exceeding 300MPa and thermal conductivity of 150W / (m·K). Therefore, the aluminum alloy of the present invention can be widely used in parts and components such as communications, electronics and transportation industries, while improving the mechanical properties, heat dissipation and corrosion resistance of the product. It can be seen from the test results of Examples 6-9 and Comparative Example 3 that with the increase of Ce content, the corrosion rate gradually slows down, but when the Ce content exceeds a certain range, the elongation at break of the product is significantly reduced, which further proves that when the Ce content is in the range of 0.001% to 0.04%, the aluminum alloy has the characteristics of excellent mechanical properties, good thermal conductivity, good corrosion resistance and casting formability.

[0087] Figure 1 and Figure 2 In the figure, the red line is the polarization curve of the aluminum alloy measured, and the blue line is the fitting curve. Figure 1 and Figure 2 It can be seen that Figure 1 When the representative embodiment 1 is not subjected to the passivation process, the corrosion rate is significantly lower than that of the comparative example 1, which further proves that the aluminum alloy of this embodiment has strong corrosion resistance.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A die-cast aluminum alloy, characterized in that: Taking the aluminum alloy as 100%, the aluminum alloy includes the following components in percentage by mass: The content of Si is 8.5% to 10.5%, the content of Fe is 0.06% to 0.65%, the content of Cu is 0.05% to 0.3%, the content of Mn is 0.08% to 0.25%, the content of Mg is 1.0% to 1.5%, the content of Zn is 0.06% to 0.3%, the content of Pb is 0.005% to 0.05%, the content of Ti is 0% to 0.03%, the content of Sr is 0.01% to 0.045%, the content of Ce is 0.001% to 0.04%, and the balance is Al and other elements, and the total amount of other elements is less than 0.1%; the aluminum alloy does not contain La; The die-cast aluminum alloy has a yield strength greater than or equal to 300 MPa, a tensile strength greater than or equal to 400 MPa, a fracture elongation greater than or equal to 3%, and a thermal conductivity greater than or equal to 150 W / m·K.

2. The die-cast aluminum alloy according to claim 1, characterized in that: Taking the aluminum alloy as 100%, it includes the following element components: The Si content is 8.5%~10.5%, the Fe content is 0.06%~0.65%, the Cu content is 0.05%~0.2%, the Mn content is 0.08%~0.25%, the Mg content is 1.0%~1.5%, the Zn content is 0.06~0.30%, the Pb content is 0.005~0.05%, the Ti content is 0~0.03%, the Sr content is 0.01%~0.045%, the Ce content is 0.005%~0.04%, and the balance is Al and other elements. The total amount of other elements is less than 0.1%.

3. The die-cast aluminum alloy according to claim 2, characterized in that: The mass percentage contents of Sr and Ce satisfy 0.015%≤Sr+Ce≤0.07%.

4. The die-cast aluminum alloy according to claim 2, characterized in that: The Fe content is 0.06%~0.49%, and the Zn content is 0~0.10%.

5. The die-cast aluminum alloy according to claim 1, characterized in that: The other elements include at least one of Cr and V.

6. The method for preparing a die-cast aluminum alloy according to any one of claims 1 to 5, characterized in that: The following steps are involved: Weigh the alloy or metal ingot containing Al, Si, Fe, Cu, Mn, Zn, Mg, Ce, Pb, Ti and Sr in the required proportion according to the element ratio in the aluminum alloy; Put pure Al into the melting furnace, heat it to 200-230℃, preheat it for 2-4h; then heat it to 750-760℃, keep it warm for 20-40min, and obtain aluminum liquid; Adding Si, Fe, Cu, Mn and Zn to the aluminum liquid to obtain a first melt; adding Mg and an alloy containing Ce, Pb, Ti and Sr to the first melt at 700-740° C. to obtain a second melt; Inert gas is introduced into the second melt to degas for 10 to 20 minutes, and then refined. After refining, the melt is allowed to stand for 10 to 120 minutes, and slag is removed to obtain an aluminum alloy melt. The aluminum alloy melt is kept warm at 700 to 720°C. The aluminum alloy melt is poured into an aluminum ingot mold to obtain an aluminum alloy ingot.

7. The method for preparing a die-cast aluminum alloy according to claim 6, characterized in that: After obtaining the aluminum alloy ingot, the aluminum alloy ingot is made into a thin plate die casting, and the thin plate die casting is subjected to a heat shaping process. The heat shaping process is to heat the thin plate die casting at 250-280° C. for 10-18 seconds and then naturally place it for 40-48 hours.

8. The method for preparing a die-cast aluminum alloy according to claim 7, characterized in that: The thin plate die casting is a die-cast aluminum alloy mobile phone middle plate.

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