High-Fe-content die-casting aluminum alloy and preparation method thereof

Abstract

The invention belongs to the technical field of aluminum alloys, and particularly relates to a high-Fe-content die-casting aluminum alloy and a preparation method thereof. The aluminum alloy is composed of the following elements of, by mass, 10.0%-13.0% of Si, 0.4%-0.65% of Mg, 0.55%-0.65% of Fe, 0.15%-0.25% of Mn, 0.01%-0.05% of Sr, 0.01%-0.5% of RE and the balance Al and inevitable impurities, and the RE is selected from mixed rare earth of Ce and La. The aluminum alloy has high toughness, high heat conductivity and high plasticity and is particularly suitable for die-casting forming, the tensile strength of a prepared die casting is 350-420 MPa, the yield strength is 220-300 MPa, the elongation is 5-12%, the heat conductivity coefficient is 140-160 W / (m.k), and the aluminum alloy is suitable for being applied to the fields of automobiles, communication or mobile phones and the like on a large scale.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum alloys, and particularly relates to a high-Fe-content die-casting aluminum alloy and a preparation method thereof. BACKGROUND

[0002] With the transformation of the automobile industry towards electrification and intelligence, lightweight technology has become the core path to improve energy efficiency and range. Integrated die-casting technology has become an important development direction for automobile manufacturing due to its high manufacturing efficiency and significant lightweight effect. However, this technology has strict requirements for material performance, especially high-strength and high-toughness die-casting aluminum alloys that are free of heat treatment. In addition, with the large-scale and high-power development of 5G communication base stations, the requirements for castings have gradually developed from high thermal conductivity to high thermal conductivity and high strength to achieve efficient heat dissipation and lightweight of the castings.

[0003] The traditional AlSi10MnMg(Fe) alloy is widely used due to its excellent casting performance and mechanical properties, but it has strict limitations on the Fe content (usually ≤0.25%), otherwise harmful needle-shaped β-AlFeSi phases will be formed, significantly reducing the performance of the alloy. In addition, the Fe content in recycled aluminum is high, which limits its application in high-end alloys. The existing technology improves the morphology of iron-rich phases by adding Mn, Sr or rare earth (RE), but the modification effect of a single element is limited, and it is difficult to achieve high strength and toughness and high Fe content resistance at the same time. SUMMARY

[0004] In order to overcome at least one of the technical problems existing in the prior art, one of the purposes of the present application is to provide an aluminum alloy. The present application significantly improves the morphology of iron-rich phases and eutectic silicon in the aluminum alloy by optimizing the composition of the aluminum alloy, and realizes excellent mechanical properties and thermal conductivity under high Fe content (0.4~0.65%).

[0005] The second purpose of the present application is to provide a preparation method of the aluminum alloy.

[0006] The third purpose of the present application is to provide the application of the above-mentioned aluminum alloy in the fields of automobiles, 5G communication or mobile phones.

[0007] In order to achieve the above-mentioned purposes, the technical solution adopted by the present application is as follows: The first aspect of the present application provides an aluminum alloy, which is composed of the following mass percentages of elements: Si 10.0~13.0%, Mg 0.4~0.65%, Fe 0.55~0.65%, Mn 0.15~0.25%, Sr 0.01~0.05%, RE 0.01~0.5%, the balance being Al and unavoidable impurities, and RE is selected from mixed rare earth of Ce and La.

[0008] In some embodiments of the present application, the RE is a mixed rare earth of Ce and La in any ratio; in some preferred embodiments of the present application, the RE is a mixed rare earth of Ce and La in a mass ratio of 1: (0.8-4).

[0009] In some embodiments of the present application, the mass ratio of Ce and La is any value selected from the group consisting of 1:0.8, 1:1.0, 1:1.2, 1:1.4, 1:1.5, 1:1.6, 1:1.8, 1:2.0, 1:2.2, 1:2.4, 1:2.5, 1:2.6, 1:2.8, 1:3.0, 1:3.2, 1:3.4, 1:3.5, 1:3.6, 1:3.8, 1:4.0 or a range value formed by any two of them.

[0010] In some embodiments of the present application, the aluminum alloy is a die-casting aluminum alloy.

[0011] In some embodiments of the present application, the mass percentage of Si is any value selected from the group consisting of 10%, 10.2%, 10.4%, 10.6%, 10.8%, 11%, 11.2%, 11.4%, 11.6%, 11.8%, 12%, 12.2%, 12.4%, 12.6%, 12.8%, 13% or a range value formed by any two of them. According to the Al-Si phase diagram, the present application selects eutectic Al-Si alloy, i.e. the Si content is near 12.6wt.%, specifically 10-13%.

[0012] In some embodiments of the present application, the mass percentage of Mg is any value selected from the group consisting of 0.4%, 0.42%, 0.44%, 0.45%, 0.46%, 0.48%, 0.5%, 0.52%, 0.54%, 0.55%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.65% or a range value formed by any two of them.

[0013] In some embodiments of the present application, the mass percentage of Fe is any value selected from the group consisting of 0.55%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.65% or a range value formed by any two of them.

[0014] In some embodiments of the present application, the mass percentage of Mn is any value selected from the group consisting of 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25% or a range value formed by any two of them.

[0015] In order to solve the problem of alloy sticking to the mold in the process of die casting of the aluminum alloy in the application, the application adopts the combination of Fe+Mn. Through thermodynamic phase diagram calculation, the formation temperature of the iron-rich phase under different Fe and Mn contents is determined, and the content of Mn and Fe is optimized in combination with the influence law of Mn and Fe on the heat conduction performance of the Al-Si alloy. The adverse effect of Fe on the heat conduction performance of the Al-Si alloy is far lower than that of Mn, so the alloy composition is designed as Fe-based and Mn-assisted, that is, the content of Fe is 0.55-0.65%, and the content of Mn is 0.15-0.25%, so that the aluminum alloy can still have high mechanical properties and heat conduction performance under high iron content.

[0016] In some embodiments of the application, the mass percentage of Sr is any one of 0.01%, 0.02%, 0.03%, 0.04%, 0.05% or a range value formed by any two of them.

[0017] In some embodiments of the application, the mass percentage of RE is any one of 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.10%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20%, 0.22%, 0.24%, 0.26%, 0.28%, 0.30%, 0.32%, 0.34%, 0.36%, 0.38%, 0.40%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5% or a range value formed by any two of them.

[0018] In some embodiments of the application, the mass percentage of the inevitable impurities is ≤0.2%; in some embodiments of the application, the mass percentage of the inevitable impurities is any one of 0%, 0.02%, 0.04%, 0.06%, 0.08%, 0.10%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20% or a range value formed by any two of them.

[0019] In some embodiments of the application, the total mass percentage of Mn and Fe in the aluminum alloy is 0.75-0.85%; in some embodiments of the application, the total mass percentage of Mn and Fe in the aluminum alloy is any one of 0.75%, 0.76%, 0.77%, 0.78%, 0.79%, 0.80%, 0.81%, 0.82%, 0.83%, 0.84%, 0.85% or a range value formed by any two of them.

[0020] In some embodiments of the application, the Sr and RE are added in the form of an Al-Sr-RE composite modifier. In the preparation of the aluminum alloy, the Sr and RE are added in the form of an Al-Sr-RE composite modifier.

[0021] In some embodiments of the present application, the Al-Sr-RE composite modifier contains Al4Sr phase and Al 11 RE3 phase.

[0022] In some embodiments of the present application, Sr and RE are mutually soluble.

[0023] In order to achieve high strength and toughness of the aluminum alloy, in one aspect of the present application, an Al-Sr-RE composite modifier is introduced to improve the plasticity of the alloy by deeply modifying the morphology of eutectic silicon and iron-rich phase, and to provide plasticity guarantee for the casting; on the other hand, the content of the strengthening element Mg is significantly increased to obtain high strength and toughness aluminum alloy material.

[0024] In some embodiments of the present application, the tensile strength of the aluminum alloy is 350-420 MPa; in some embodiments of the present application, the tensile strength of the aluminum alloy is any one of 350 MPa, 360 MPa, 370 MPa, 380 MPa, 390 MPa, 400 MPa, 410 MPa, 420 MPa or a range value formed by any two of them.

[0025] In some embodiments of the present application, the yield strength of the aluminum alloy is 220-300 MPa; in some embodiments of the present application, the yield strength of the aluminum alloy is any one of 220 MPa, 230 MPa, 240 MPa, 250 MPa, 260 MPa, 270 MPa, 280 MPa, 290 MPa, 300 MPa or a range value formed by any two of them.

[0026] In some embodiments of the present application, the elongation of the aluminum alloy is 5-12%; in some embodiments of the present application, the elongation of the aluminum alloy is any one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or a range value formed by any two of them.

[0027] In some embodiments of the present application, the thermal conductivity of the aluminum alloy is 140-160 W / (m·k); in some embodiments of the present application, the thermal conductivity of the aluminum alloy is any one of 140 W / (m·k), 142 W / (m·k), 144 W / (m·k), 146 W / (m·k), 148 W / (m·k), 150 W / (m·k), 152 W / (m·k), 154 W / (m·k), 156 W / (m·k), 158 W / (m·k), 160 W / (m·k) or a range value formed by any two of them.

[0028] In some embodiments of the present application, the aluminum alloy contains iron-rich phase with an average equivalent diameter of ≤3 μm; In some embodiments of the present application, the aluminum alloy contains eutectic silicon with an average equivalent diameter of ≤ 1 μm.

[0029] A second aspect of the present application provides a method for preparing the aluminum alloy of the first aspect of the present application, comprising the steps of: melting and mixing an aluminum source, a silicon source, an iron source, and a manganese source, refining, then adding a magnesium source and an Al-Sr-RE composite modifier for modification treatment to obtain an aluminum alloy melt; casting the aluminum alloy melt, then water quenching, and then heat treating to obtain the aluminum alloy.

[0030] In the present application, the water quenching serves to inhibit the precipitation of Mg-containing phases and reduce the formation of coarse Mg2Si, thereby reducing the adverse effects of the coarse Mg2Si on the strength and plasticity of the castings. The preparation method of the present application obtains a high Mg concentration supersaturated solid solution through the water quenching step during casting, and uniformly precipitates through heat treatment (i.e. artificial aging), thereby obtaining an aluminum alloy with high strength and toughness and high thermal conductivity.

[0031] In addition, the present application uses Al-Sr-RE to cooperate with Mg to modify and refine the second phase structure, and to refine the structure of the die casting alloy, i.e. by adding a trace amount of Al-Sr-RE, high-activity Sr, RE, and Sr / RE atomic clusters are formed, which are adsorbed on the solid-liquid interface to inhibit the nucleation and growth of the second phase, thereby achieving the purpose of refining the structure. In combination with the rapid cooling (i.e. water quenching) during casting, the possibility of the formation of coarse AlSi(SrRE) phases from Sr, RE, and Al, Si, etc. is reduced, the uniform dispersibility of the Sr and RE elements is improved, and the modification effect is improved.

[0032] In some embodiments of the present application, the aluminum source includes at least one of an aluminum alloy, pure aluminum, and recycled aluminum.

[0033] In some embodiments of the present application, the silicon source includes at least one of pure silicon and silicon-aluminum intermediate alloy.

[0034] In some embodiments of the present application, the iron source includes at least one of pure iron and aluminum-iron intermediate alloy.

[0035] In some embodiments of the present application, the manganese source includes at least one of pure manganese and aluminum-manganese intermediate alloy.

[0036] In some embodiments of the present application, the magnesium source includes at least one of pure magnesium and magnesium-aluminum intermediate alloy.

[0037] The aluminum alloy in the application has the characteristics of wide raw material source and low cost, the alloy elements are all high-abundance and low-price elements, Sr is the most expensive element in the alloy, the unit price of which is about 60 yuan / kg, but the addition amount is less than 0.05%, and the cost per ton is about 30 yuan. The price of La / Ce mixed rare earth is about 21 yuan / kg, which is basically the same as that of industrial pure aluminum, and the price of single Ce or La is about 26 yuan / kg. The recycled aluminum material with high Fe content can be selected as the alloy raw material, and the price decreases with the increase of the Fe content. When the Fe content is 0.6%, the price is 20-30% lower than that of the original aluminum, and after deducting the burning loss and process cost, 1500 yuan per ton can be saved. In addition, the use of recycled aluminum reduces carbon emissions. According to 50% waste, about 6 tons of carbon emissions can be reduced per ton.

[0038] In some embodiments of the application, the melting and mixing is carried out by stirring and mixing with an electromagnetic or mechanical rotor to improve the temperature and composition uniformity of the melt.

[0039] In some embodiments of the application, the refining is carried out by introducing a refining agent into the carrier gas.

[0040] In some embodiments of the application, the refining time is 15-20 min.

[0041] In some embodiments of the application, the refining is assisted by mechanical rotor or electromagnetic stirring.

[0042] In some embodiments of the application, the inert gas is high-purity inert gas.

[0043] In some embodiments of the application, the heat treatment temperature is 160-200℃; in some embodiments of the application, the heat treatment temperature is any one of 160℃, 170℃, 180℃, 190℃, 200℃ or a range value formed by any two of them.

[0044] In some embodiments of the application, the heat treatment time is 2-6h; in some embodiments of the application, the heat treatment time is any one of 2h, 3h, 4h, 5h, 6h or a range value formed by any two of them.

[0045] In some embodiments of the application, the step of melting and mixing the aluminum source, silicon source, iron source and manganese source is: heating the aluminum source and part of the silicon source to 760-850℃ for melting and mixing, then sequentially adding the iron source, manganese source and the remaining silicon source at 730-750℃ for melting and mixing. In the preparation of the melt, the silicon source is added in two times, and the melt can be cooled.

[0046] In some embodiments of the present application, the melting mixing temperature of the aluminum source and part of the silicon source is any one of 760℃, 770℃, 780℃, 790℃, 800℃ or a range formed by any two of them.

[0047] In some embodiments of the present application, the melting mixing temperature of the iron source, the manganese source and the remaining silicon source is any one of 730℃, 735℃, 740℃, 745℃, 750℃ or a range formed by any two of them.

[0048] In some embodiments of the present application, the step of modification treatment is: adding a magnesium source and an Al-Sr-RE composite modifier and stirring, and then standing for 20-60 min.

[0049] In some embodiments of the present application, the preparation method further comprises a step of degassing and filtering the melt; the step is located after the modification treatment step and before the casting step.

[0050] In some embodiments of the present application, the degassing step is degassing by a rotating degassing device.

[0051] In some embodiments of the present application, the filtering is filtering by a filtering device.

[0052] In some embodiments of the present application, the casting is die casting.

[0053] In some embodiments of the present application, the casting is first cast into a shape, and then cast into a shape after melting.

[0054] The third aspect of the present application provides the application of the aluminum alloy of the first aspect of the present application in the field of automobiles, 5G communication or mobile phones.

[0055] The beneficial effects of the present application are: the aluminum alloy in the present application has high strength and toughness and high thermal conductivity, and at the same time has high plasticity, and can be die cast into a shape, specifically: the tensile strength is 350-420 MPa, the yield strength is 220-300 MPa, the elongation is 5-12%, the thermal conductivity is 140-160 W / (m·k), and it can be widely used in the fields of automobiles, 5G communication or mobile phones, etc.

[0056] In addition, the aluminum alloy in the present application is optimized by component design and Al-Sr-RE composite modifier, which promotes the refinement of the structure and the improvement of the performance of the aluminum alloy, and the die-casting aluminum alloy obtained has a structure composed of iron-rich phases with an average equivalent diameter of not more than 3μm and eutectic silicon with an average equivalent diameter of not more than 1μm. In addition, the highest tolerance of Fe content of the aluminum alloy in the present application is increased to 0.65%, which can be used for the use of recycled aluminum. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 SEM images and element distribution maps of Al-Sr-RE in the examples.

[0058] Figure 2 alloy structure map of the aluminum alloy in Example 1.

[0059] Figure 3 alloy structure map of the aluminum alloy in Comparative Example 1. DETAILED DESCRIPTION

[0060] The specific implementation of the present application is further described in detail below in conjunction with the drawings and examples, but the implementation and protection of the present application are not limited thereto. It should be noted that if the following processes are not specifically described in detail, they can be implemented or understood by those skilled in the art with reference to the prior art. If the reagents or instruments used are not marked with the manufacturer, they are conventional products that can be purchased on the market.

[0061] The SEM images of Al-Sr-RE in the examples of the present application are tested by scanning electron microscopy, as shown in (a) of FIG. 1, and then the element distribution maps of Al-Sr-RE are tested, as shown in (b)-(f) of FIG. 1. Figure 1 Figure 1 It can be seen from FIG. 1 that the coarse long needle-shaped iron-rich phase in Al-Sr-RE is Al4Sr, and the Chinese script-shaped eutectic structure is Al 11 RE3, RE is Ce and La, and Sr and La, Ce are mutually solid-soluble. Figure 1

[0062] Example 1 This example provides a high-Fe-content die-casting aluminum alloy, which is composed of the following alloy components in mass percentage: Si 10.50%, Fe 0.60%, Mg 0.44%, Mn 0.25%, Sr 0.023%, Ce 0.015%, La 0.012%, impurity elements 0.13%, and the balance being Al.

[0063] This example provides a preparation method of a high-Fe-content die-casting aluminum alloy, which comprises the following steps: (1) Melting: high-Fe-content aluminum alloy raw materials and Si raw materials are added to a melting furnace, and the temperature is raised to 760°C. After the raw materials are melted, the chemical composition of the melt is tested by sampling.

[0064] (2) Component adjustment: according to the measured composition and the designed composition, the types and weights of the added raw materials are obtained by a raw material ratio calculation software, and then raw materials except for Mg, Al-Sr-RE composite modifier are added. The feeding sequence is Fe agent, Mn agent, and Si agent in order, and the melt is stirred by electromagnetic stirring to improve the temperature and composition uniformity of the melt.

[0065] ​​(3) Refining: The temperature of the melt is controlled by regulating the heating power of the feeding process, so that the temperature of the melt after composition adjustment is 730°C. Then, 0.2% of the melt mass of commercially available refining agent is introduced into the melt as a carrier of high-purity argon, the refining time is 15 minutes, and the melt is stirred by a mechanical rotor; (4) Modification: After refining, an appropriate amount of Mg and Al-8Sr-6Ce-4La composite modifier (in the composite modifier, the mass percentage of Sr is 8%, the mass percentage of La is 4%, the mass percentage of Ce is 6%, and Al is the balance) is added, and the stirring device is started at the same time. After standing for 30 minutes, the composition is sampled and confirmed; according to the measured composition, the second composition adjustment is carried out to make the melt composition consistent with the target aluminum alloy composition.

[0066] (5) Casting: A rotary degassing and filtering device is provided in the runner, and the melt is injected into the ladle after passing through the runner to supply the die casting equipment directly. The die casting method is used to obtain the casting, and the obtained casting is quickly water quenched to inhibit the precipitation of Mg-containing phase.

[0067] (6) Heat treatment: The die casting is subjected to artificial aging heat treatment, and the aging temperature is 160°C and the time is 4h, thereby obtaining the high Fe content die casting aluminum alloy in this example.

[0068] Example 2 This example provides a high Fe content die casting aluminum alloy, which is composed of the following mass percentage of alloy composition: Si 11.5%, Fe 0.60%, Mg 0.65%, Mn 0.22%, Sr 0.015%, Ce 0.01%, La 0.015%, impurity elements 0.10%, and the balance is Al.

[0069] This example provides a method for preparing a high Fe content die casting aluminum alloy, which includes the following steps: (1) Melting: The high Fe content aluminum alloy raw material and Si raw material are added to the melting furnace, and the temperature is raised to 850°C. After the raw materials are melted, the chemical composition of the melt is tested by sampling.

[0070] (2) Composition adjustment: According to the measured composition and the designed composition, the type and weight of the added raw materials are obtained by a raw material ratio calculation software. Then, the raw materials except Mg, Al-Sr-RE composite modifier are added, the feeding sequence is Fe agent, Mn agent, and Si agent in order, and the melt is stirred by a mechanical rotor to improve the temperature and composition uniformity of the melt.

[0071] (3) Refining: By regulating the heating power of the charging process, the temperature of the melt is controlled, and the temperature of the melt after composition adjustment is 750°C. Then, high-purity argon is used as the carrier to introduce 0.2% of the commercially available refining agent by mass of the melt, and the refining time is 15 minutes, and the melt is stirred using an electromagnetic stirrer; (4) Modification treatment: After refining treatment, appropriate amounts of Mg and Al-6Sr-3Ce-6La composite modifier (in the composite modifier, the mass percentage of Sr is 6%, the mass percentage of Ce is 3%, the mass percentage of La is 6%, and Al is the balance) are added, and the stirring device is started at the same time. After standing for 15 minutes, the composition is sampled and confirmed; according to the measured composition, the second composition adjustment is carried out to make the melt composition consistent with the target aluminum alloy composition.

[0072] (5) Casting: A rotary degassing and filtering device is provided in the runner, and the melt is injected into the ladle after passing through the runner to supply the die casting equipment directly. The obtained castings are quickly water quenched to inhibit the precipitation of Mg-containing phases.

[0073] (6) Heat treatment: The die castings are subjected to artificial aging heat treatment at a temperature of 200°C for 2h to obtain the high Fe content die cast aluminum alloy in this example.

[0074] Example 3 This example provides a high Fe content die cast aluminum alloy, which is composed of the following mass percentage of alloy composition: Si 12.5%, Fe 0.65%, Mg 0.55%, Mn 0.15%, Sr 0.01%, Ce 0.005%, La 0.02%, impurity elements 0.13%, and the balance is Al.

[0075] This example provides a method for preparing a high Fe content die cast aluminum alloy, which includes the following steps: (1) Melting: The high Fe content aluminum alloy raw material and Si raw material are added to the melting furnace, and the temperature is raised to 850°C. After the raw materials are melted, the chemical composition of the melt is tested by sampling.

[0076] (2) Composition adjustment: According to the measured composition and the designed composition, the type and weight of the added raw materials are obtained by a raw material ratio calculation software. Then, raw materials other than Mg, Al-Sr-RE composite modifier are added, and the charging is successfully carried out in the order of Fe agent, Mn agent, and Si agent. The melt is stirred using an electromagnetic stirrer to improve the temperature and composition uniformity of the melt.

[0077] (3) Refining: By regulating the heating power of the charging process, the temperature of the melt is controlled, and the temperature of the melt after composition adjustment is 740°C. Then, high-purity argon is used as the carrier to introduce 0.3% of the commercially available refining agent by mass of the melt, and the refining time is 20 minutes, and the melt is stirred using an electromagnetic stirrer; (4) Modification: After refining, add appropriate amount of Mg and Al-5Sr-2Ce-8La composite modifier (in the composite modifier, the mass percentage of Sr is 5%, the mass percentage of Ce is 2%, the mass percentage of La is 8%, and Al is the balance), and start the stirring device at the same time. After standing for 20 minutes, sample and confirm the composition; according to the measured composition, make second composition adjustment to make the melt composition consistent with the target aluminum alloy composition.

[0078] (5) Casting: Set up rotary degassing and filtering device in the runner, and after the melt passes through the runner, introduce it into the ingot casting machine to cast into ingot; after remelting the ingot, use die casting method to prepare the casting, and then quickly water quench the casting to inhibit the precipitation of Mg-containing phase.

[0079] (6) Heat treatment: artificially age heat treat the die casting to obtain the high Fe content die casting aluminum alloy in this example.

[0080] Example 4 This example provides a high Fe content die casting aluminum alloy, which is composed of the following mass percentage of alloy composition: Si 13.0%, Fe 0.58%, Mg 0.40%, Mn 0.25%, Sr 0.05%, Ce 0.025%, La 0.01%, impurity elements 0.15%, and the balance is Al.

[0081] This example provides a method for preparing a high Fe content die casting aluminum alloy, which comprises the following steps: (1) Melting: Put high Fe content aluminum alloy raw materials and Si raw materials into the melting furnace, heat to 800℃, and after the raw materials are melted, test the chemical composition of the melt.

[0082] (2) Composition adjustment: According to the measured composition and the designed composition, obtain the type and weight of the added raw materials through raw material ratio calculation software, then add raw materials except Mg, Al-Sr-RE composite modifier, the feeding order is Fe agent, Mn agent, Si agent in turn, and use mechanical rotor to stir the melt to improve the temperature and composition uniformity of the melt.

[0083] (3) Refining: Control the heating power of the feeding process to realize the temperature control of the melt, and promote the temperature of the composition-adjusted melt to be 735℃. Then, use high-purity argon as carrier to pass in 0.3% of commercially available refining agent by mass of the melt, and refine for 16 minutes, and use electromagnetic stirring of the melt; (4) Modification treatment: After refining treatment, a proper amount of Mg and Al-10Sr-6Ce-3La composite modifier (in the composite modifier, the mass percentage of Sr is 10%, the mass percentage of Ce is 6%, the mass percentage of La is 3%, and Al is the balance) is added, and at the same time, the stirring device is started, and after standing for 25 minutes, the composition is sampled and confirmed; according to the measured composition, the second composition adjustment is carried out to make the melt composition consistent with the target aluminum alloy composition.

[0084] (5) Casting: A rotary degassing and filtering device is arranged in the runner, and after the melt passes through the runner, it is introduced into an ingot casting machine to be cast into an ingot; after remelting of the ingot, a die casting method is used to prepare a casting, and then the casting is rapidly water quenched to inhibit the precipitation of Mg-containing phases.

[0085] (6) Heat treatment: The die casting is subjected to artificial aging heat treatment at an aging temperature of 190°C for 2.5h to obtain the high Fe content die casting aluminum alloy in this example.

[0086] Comparative Example 1 The difference between the high Fe content die casting aluminum alloy in this example and that in Example 1 is only that an equal amount of Al-Sr intermediate alloy is used instead of the Al-Sr-RE composite modifier in Example 1.

[0087] Comparative Example 2 The difference between the high Fe content die casting aluminum alloy in this example and that in Example 2 is only that the Mg content in the aluminum alloy is increased from 0.65% in Example 2 to 0.85%.

[0088] Comparative Example 3 The difference between the high Fe content die casting aluminum alloy in this example and that in Example 3 is only that the Mn content in the aluminum alloy is increased from 0.15% in Example 3 to 0.35%.

[0089] Comparative Example 4 The difference between the high Fe content die casting aluminum alloy in this example and that in Example 4 is only that the Mg content in the aluminum alloy is decreased from 0.40% in Example 4 to 0.30%.

[0090] Performance test: The microstructure of the die casting aluminum alloy prepared in Example 1 and Comparative Example 1 is tested by scanning electron microscopy, as shown in Figure 2 and Figure 3 . Figure 2 The white phase in the center is a Fe-rich phase, which is mainly composed of fine granular particles, further indicating that the aluminum alloy structure obtained in Example 1 is composed of Fe-rich phases with an average equivalent diameter of not more than 3μm and eutectic silicon with an average equivalent diameter of not more than 1μm. Figure 3The medium white phase is a Fe-rich phase, which is mainly composed of granular particles, but the particle diameter is increased by more than 20% compared with that of Example 1, and needle-like Fe-rich phases with a length of more than 10 μm appear, further indicating that the use of the Al-Sr-RE composite modifier for modification can significantly refine the particle diameter of the Fe-rich phase.

[0091] The die-cast aluminum alloys prepared in Examples 1-4 and Comparative Examples 1-4 were sampled, and then the mechanical properties and thermal conductivity of the samples were tested, wherein the tensile strength, yield strength and elongation were obtained by testing according to the test method recorded in GB / T 228.1-2021 “Metallic Materials-Tensile Testing-Part 1: Method of Test at Room Temperature”. Then the thermal conductivity of the aluminum alloy was tested according to the test method recorded in GB / T22588-2008 “Measurement of Thermal Diffusivity or Thermal Conductivity by Flash Method”. The performance data of the die-cast aluminum alloys in Examples 1-4 and Comparative Examples 1-4 are shown in Table 1.

[0092] Table 1 Performance test results of die-cast aluminum alloys

[0093] As can be seen from Table 1, by optimizing the composition of the aluminum alloy and Al-Sr-RE synergistic modification, an aluminum alloy die casting with good comprehensive mechanical properties is obtained, which has a tensile strength of 360-410 MPa, a yield strength of 230-270 MPa, an elongation of 10.5-14.2%, and a thermal conductivity of 140-155 W / (m·k). When the composition of the aluminum alloy exceeds the range defined in the present application, the mechanical properties or thermal conductivity will be significantly reduced, for example: compared with Example 1, after replacing Al-Sr-RE with Al-Sr in Comparative Example 1, the tensile strength, elongation and thermal conductivity of the casting are reduced by 6.7%, 44.0% and 11.4% respectively compared with Example 1. Compared with Example 2, the upper limit of the Mg content is increased in Comparative Example 2, and the tensile strength, yield strength, elongation and thermal conductivity of the casting are all reduced, among which the elongation and thermal conductivity are reduced by 66.7% and 13.6% respectively. Compared with Example 4, the Mg content is reduced in Comparative Example 4, and the plasticity and thermal conductivity of the prepared aluminum alloy are increased, but the tensile and yield strengths are reduced. Compared with Example 3, the Mn content is increased in Comparative Example 3, and the plasticity and thermal conductivity of the prepared aluminum alloy are significantly reduced, the Fe-rich phase is coarsened and the volume fraction is increased, which is because the increase of the solid solubility of Mn is the main reason for the decrease of the comprehensive mechanical properties.

[0094] The above describes the embodiments of the present application in detail, but the present application is not limited to the above-described embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. An aluminum alloy, characterized in that: The aluminum alloy is composed of the following elements by mass percentage: Si 10.0~13.0%, Mg 0.4~0.65%, Fe 0.55~0.65%, Mn 0.15~0.25%, Sr 0.01~0.05%, RE 0.01~0.5%, with the balance being Al and unavoidable impurities, and RE selected from a mixture of rare earth elements of Ce and La.

2. The aluminum alloy according to claim 1, characterized in that: The unavoidable impurities have a mass percentage of ≤0.2%.

3. The aluminum alloy according to claim 1, characterized in that: The Sr and RE are added in the form of an Al-Sr-RE composite modifier.

4. The aluminum alloy according to claim 3, characterized in that: The Al-Sr-RE composite modifier contains Al4Sr phase and Al 11 RE3 phase.

5. The aluminum alloy according to any one of claims 1 to 4, characterized in that: The aluminum alloy has at least one of the following characteristics: (a1) The tensile strength of the aluminum alloy is 350~420MPa; (a2) The yield strength of the aluminum alloy is 220~300MPa; (a3) The elongation of the aluminum alloy is 5~12%; (a4) The thermal conductivity of the aluminum alloy is 140~160 W / (m·K); (a5) The aluminum alloy contains an iron-rich phase with an average equivalent diameter ≤3μm; (a6) The aluminum alloy contains eutectic silicon with an average equivalent diameter ≤1μm.

6. The method for preparing the aluminum alloy according to any one of claims 1 to 5, characterized in that: Includes the following steps: Aluminum, silicon, iron, and manganese sources are melted, mixed, and refined. Then, magnesium source and Al-Sr-RE composite modifier are added for modification treatment to obtain aluminum alloy melt. The aluminum alloy melt is cast, then water-quenched, and then heat-treated to obtain the aluminum alloy.

7. The method for preparing the aluminum alloy according to claim 6, characterized in that: The heat treatment temperature is 160~200℃; and / or the heat treatment time is 2~6h.

8. The method for preparing the aluminum alloy according to claim 6, characterized in that: The step of melting and mixing the aluminum source, silicon source, iron source, and manganese source is as follows: the aluminum source and part of the silicon source are heated to 760~850℃ for melting and mixing, and then the iron source, manganese source, and the remaining silicon source are added in sequence and melted and mixed at 730~750℃.

9. The method for preparing the aluminum alloy according to claim 6, characterized in that: The casting is die casting; or, the casting is first cast into shape, then melted and die cast into shape.

10. The application of the aluminum alloy according to any one of claims 1 to 5 in the fields of automobiles, 5G communications or mobile phones.

Images