High-strength Al-Si-Cu-Mg aluminum alloy and preparation method thereof

Abstract

The invention belongs to the field of aluminum alloys, and particularly relates to a high-strength Al-Si-Cu-Mg aluminum alloy and a preparation method thereof. The aluminum alloy is composed of the following elements of, by mass, 6.0%-8.0% of Si, 0.2%-0.8% of Mg, 3.0%-4.5% of Cu, 0.01%-0.05% of Sr, 0.02%-0.10% of RE, 0.015%-0.025% of B and the balance Fe. The total amount of impurity elements does not exceed 0.15%, and the balance is Al; the RE comprises at least one of Ce and La. After the aluminum alloy is subjected to T6 heat treatment, the tensile strength can reach 420-530 MPa, the yield strength can reach 350-480 MPa, the elongation can reach 2-12%, and the aluminum alloy is suitable for the fields with strict lightweight requirements such as automobile hubs, engine parts and aerospace structural parts.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aluminum alloys, and particularly relates to a high-strength Al-Si-Cu-Mg aluminum alloy and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for lightweight and high-performance materials in the automotive and aerospace industries, the development of high-strength cast aluminum alloys has become a research hotspot. Al-Si series alloys are widely used in structural part manufacturing due to their good castability, high specific strength, and corrosion resistance. However, traditional Al-Si-Mg alloys (such as A356 and A357) can only achieve a certain strength after T6 treatment, but still cannot meet the requirements of some high-load and high-fatigue applications.

[0003] To further improve the strength of the alloy, Cu and Mg elements are usually introduced to form Mg2Si and Al2Cu strengthening phases to enhance the matrix. However, high Cu content can lead to increased hot cracking tendency and decreased castability, and conventional modification treatment has limited effect on the refinement of eutectic silicon, affecting the plasticity of the alloy. Therefore, it is an urgent need in the field of lightweight materials to develop an Al-Si-Cu-Mg alloy with high strength, good plasticity, and excellent castability.

[0004] CN112941377A discloses a cast heat-resistant Al Si Cu Mg alloy containing Er, which forms 5-10 nm Al3Er through Er and three-stage solid solution treatment, improving the room temperature tensile and high temperature tensile properties of the alloy. However, the Cu content of this alloy is low, and the strength is low (270-380 MPa). CN120330545A discloses an Al Si Cu Mg series aluminum alloy, which includes: Si: 7.50%-12.50%; Mg: 0.35%-0.45%; Cu: 1.50%-3.50%; Mn: 0.25%-0.50%; Al Ti B: 0.05%-0.15%; Al RE: 0.01%-0.02%; Al Zr: 0.01%~0.02%; Fe: 0.10%~0.50%, by Mn modification to improve the morphology and mechanical properties of iron-rich phase, the tensile strength, yield strength and elongation of the casting are respectively: 280~325MPa, 190~250MPa and 3.2~8.1%. CN119392053A discloses a high strength and toughness high temperature resistant Al-Si-Cu-Mg series aluminum alloy, the main alloy components include: Si 6.5 9%, Fe≤0.2%, Cu 1.5 3.5%, Mn 0.1 0.5%, Mg 0.2 0.8%, Ti 0.05 0.2%, Sr 0 0.1%, RE 0 0.2%. By adding Al Ti B Sc, AI RE and Al Sr refines the structure, the prepared alloy has a room temperature tensile strength≥350MPa, yield strength≥300MPa, and elongation after fracture of 3.0 5.0%.

[0005] As shown above, the existing Al Si Cu Mg alloy has a room temperature tensile strength not more than 410MPa, and generally has the problem of low strength, which hinders the application of Al Si Cu Mg alloy in the field of automobile or aerospace. SUMMARY

[0006] In order to overcome at least one technical problem existing in the prior art, one of the purposes of the present application is to provide an aluminum alloy.

[0007] The second purpose of the present application is to provide a preparation method of the aluminum alloy.

[0008] The third purpose of the present application is to provide a product.

[0009] The fourth purpose of the present application is to provide the application of the above-mentioned aluminum alloy or the preparation method of the above-mentioned aluminum alloy in the field of automobile or aerospace.

[0010] In order to achieve the above-mentioned purposes, the technical scheme adopted by the present application is: The first aspect of the present application provides an aluminum alloy consisting of the following mass percentages of elements: Si 6.0~8.0%, Mg 0.2~0.8%, Cu 3.0~4.5%, Sr 0.01~0.05%, RE 0.02~0.10%, B 0.015~0.025%, Fe<0.2%, the total amount of impurity elements is not more than 0.15%, and the balance is Al; The RE includes at least one of Ce and La.

[0011] In some embodiments of the present application, the mass percentage of Si is any one of 6%, 6.2%, 6.4%, 6.5%, 6.6%, 6.8%, 7.0%, 7.2%, 7.4%, 7.5%, 7.6%, 7.8%, 8.0% or a range value formed by any two of them.

[0012] In some embodiments of the present application, the mass percentage of Mg is any one of 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or a range value formed by any two of them.

[0013] In some embodiments of the present application, the mass percentage of Cu is any one of 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5% or a range value formed by any two of them.

[0014] In some embodiments of the present 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.

[0015] In some embodiments of the present application, the mass percentage of RE is any one of 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1% or a range value formed by any two of them.

[0016] In some embodiments of the present application, the mass percentage of B is any one of 0.015%, 0.016%, 0.017%, 0.018%, 0.019%, 0.02%, 0.021%, 0.022%, 0.023%, 0.024%, 0.025% or a range value formed by any two of them.

[0017] In some embodiments of the present application, the mass percentage of Fe is any one of 0%, 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.19%, 0.199% or a range formed by any two of them.

[0018] In some embodiments of the present application, the Sr and RE are added in the form of Al-Sr-RE.

[0019] In some embodiments of the present application, the B is added in the form of Al-B.

[0020] In some embodiments of the present application, the tensile strength of the aluminum alloy after T6 heat treatment is 420-530 MPa.

[0021] In some embodiments of the present application, the yield strength of the aluminum alloy after T6 heat treatment is 350-480 MPa.

[0022] In some embodiments of the present application, the elongation of the aluminum alloy after T6 heat treatment is 2-12%.

[0023] In some embodiments of the present application, the average particle size of eutectic silicon in the aluminum alloy after T6 heat treatment is not more than 3 μm; in some embodiments of the present application, the average particle size of eutectic silicon in the aluminum alloy after T6 heat treatment is any one of 0.1 μm, 0.5 μm, 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm or a range formed by any two of them; in some embodiments of the present application, the average particle size of eutectic silicon in the aluminum alloy after T6 heat treatment is 0.5-3 μm.

[0024] Secondly, the second aspect of the present application provides a preparation method of the aluminum alloy of the first aspect of the present application, comprising the following steps: melting and mixing the raw materials to obtain an aluminum alloy melt; casting the aluminum alloy melt to form a casting; subjecting the casting to T6 heat treatment to obtain the aluminum alloy; the T6 heat treatment is: first holding at a first-stage solid solution temperature, then holding at a second-stage solid solution temperature, and then performing artificial aging treatment after cooling; the first-stage solid solution temperature is lower than the second-stage solid solution temperature.

[0025] In some embodiments of the present application, the first-stage solid solution temperature is 490-530℃; in some embodiments of the present application, the first-stage solid solution temperature is any one of 490℃, 500℃, 510℃, 520℃, 530℃ or a range formed by any two of them.

[0026] In some embodiments of the present application, the holding time at the first-stage solid solution temperature is 3-6h; in some embodiments of the present application, the holding time at the first-stage solid solution temperature is any one of 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h or a range formed by any two of them.

[0027] In some embodiments of the present application, the second-stage solid solution temperature is 535-555℃; in some embodiments of the present application, the second-stage solid solution temperature is any one of 535℃, 540℃, 545℃, 550℃, 555℃ or a range formed by any two of them.

[0028] In some embodiments of the present application, the holding time at the second-stage solid solution temperature is 3-8h; in some embodiments of the present application, the holding time at the second-stage solid solution temperature is any one of 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h or a range formed by any two of them.

[0029] In some embodiments of the present application, the step of performing artificial aging treatment after cooling specifically comprises: cooling to 20-40℃ by water quenching, and then performing artificial aging treatment.

[0030] In some embodiments of the present application, the artificial aging temperature is 160-200℃; in some embodiments of the present application, the artificial aging temperature is any one of 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃, 200℃ or a range formed by any two of them.

[0031] In some embodiments of the present application, the artificial aging holding time is 4-12h; in some embodiments of the present application, the artificial aging holding time is any one of 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or a range formed by any two of them.

[0032] In some embodiments of the present application, the method of natural cooling in air is adopted after the artificial aging step.

[0033] In some embodiments of the present application, the temperature for the cast forming is 690-720℃; in some embodiments of the present application, the temperature for the cast forming is any one of 690℃, 695℃, 700℃, 705℃, 710℃, 715℃, 720℃ or a range formed by any two of them.

[0034] In some embodiments of the present application, the cast forming is performed by any one of gravity casting, low pressure casting, squeeze casting, differential pressure casting.

[0035] In some embodiments of the present application, the step of melting and mixing the raw materials is: heating the aluminum source, silicon source and copper source to 750-800℃ for melting and mixing, and then refining; then adding the magnesium source, Al-Sr-RE and Al-B for mixing to obtain the aluminum alloy melt. After refining, adding the magnesium source can reduce the burning loss of magnesium.

[0036] In some embodiments of the present application, the aluminum source is industrial pure aluminum ingot.

[0037] In some embodiments of the present application, the magnesium source is at least one of industrial pure magnesium ingot and aluminum-magnesium intermediate alloy.

[0038] In some embodiments of the present application, the silicon source includes at least one of silicon ingot and aluminum-silicon intermediate alloy.

[0039] In some embodiments of the present application, the copper source includes at least one of copper ingot and aluminum-copper intermediate alloy.

[0040] In some embodiments of the present application, when preparing the aluminum alloy melt, the melting temperature is any one of 750℃, 760℃, 770℃, 780℃, 790℃, 800℃ or a range formed by any two of them.

[0041] In some embodiments of the present application, the melting and mixing is performed by at least one of electromagnetic stirring and mechanical stirring.

[0042] In some embodiments of the present application, the refining is performed by introducing a carrier gas with a refining agent.

[0043] In some embodiments of the present application, the amount of the refining agent is 0.1-0.3% of the mass of the aluminum alloy melt.

[0044] In some embodiments of the present application, the carrier is at least one of nitrogen, argon or helium.

[0045] In some embodiments of the present application, the refining agent is a commercially available aluminum alloy refining agent.

[0046] In some embodiments of the present application, the preparation method further comprises the steps of sampling the test composition and adjusting the composition to the target composition; the step of sampling the test composition and adjusting the composition to the target composition is located after the step of adding the magnesium source, Al-Sr-RE and Al-B for mixing and before the step of casting forming.

[0047] The third aspect of the present application provides a product comprising the aluminum alloy of the first aspect of the present application or a component formed by the aluminum alloy of the first aspect of the present application. The product comprises an automobile wheel hub, an engine or an aerospace structure.

[0048] The fourth aspect of the present application provides an application of the preparation method of the aluminum alloy of the first aspect of the present application or the aluminum alloy of the second aspect of the present application in the field of automobiles or aerospace.

[0049] The aluminum alloy in the present application can significantly improve the strength and plasticity of the aluminum alloy while maintaining good casting performance by adjusting the composition of each element, specifically: after T6 heat treatment, the tensile strength of the aluminum alloy can reach 420-530 MPa, the yield strength can reach 350-480 MPa, the elongation can reach 2-12%, and the average particle size of eutectic silicon is not more than 3 μm, which is suitable for high-performance lightweight product fields such as automobile wheel hubs, engine components, aerospace structures, etc.

[0050] The present application can precipitate a large number of nanoscale β' (Mg-Si), β''(Mg-Si) and θ'(Al-Cu) etc. strengthening phases in the aging process through the synergistic effect of high Cu (3.0-4.5%) and Mg (0.2-0.8%), which has a coherent or semi-coherent relationship with the aluminum alloy matrix, significantly improving the strength of the aluminum alloy by hindering dislocation movement; through Al-Sr-RE deep modification of eutectic silicon, the eutectic silicon is transformed from coarse platelets to fine fibrous or granular, with an average diameter of the fiber not more than 3 μm, which is easy to melt and spheroidize; B refines the grains through Al-B eutectic reaction, and forms a synergistic effect with Al-Sr-RE to improve the elongation and toughness of the aluminum alloy.

[0051] The preparation method in the present application adopts double-stage solid solution treatment to promote the full dissolution and diffusion of each element in the aluminum alloy, and artificial aging treatment to control the precipitation behavior of the strengthening phase, thereby improving the comprehensive mechanical properties of the aluminum alloy; the aluminum alloy in the present application is suitable for various casting processes and has good industrial application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 The microstructure diagram of the Al-Si-Cu-Mg cast aluminum alloy in Example 1.

[0053] Figure 2 Microstructure chart of the Al-Si-Cu-Mg cast aluminum alloy in Comparative Example 1. DETAILED DESCRIPTION

[0054] The present application will be further described in conjunction with the accompanying 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.

[0055] Examples 1-4 each provide a high-strength Al-Si-Cu-Mg cast aluminum alloy, the chemical composition of which is shown in Table 1 below (the units in Table 1 are mass percent).

[0056] Table 1 Chemical composition of examples (%)

[0057] The high-strength Al-Si-Cu-Mg cast aluminum alloy in Examples 1-4 is prepared by a preparation method comprising the following steps: (1) Melting: industrial pure aluminum ingot, industrial pure magnesium, aluminum-silicon intermediate alloy, aluminum-copper intermediate, etc. are added to the melting furnace according to the proportion, heated to 750-800 ℃ (i.e. melting temperature), and the melt composition is made uniform by electromagnetic stirring; (2) Refining: high-purity argon or high-purity nitrogen is used as the carrier for refining, and 0.1-0.3% of the total mass of the melt is added as a refining agent; (3) Microstructure refinement: Mg, Al-Sr-RE composite modifier and Al-B grain refiner are added, and slight stirring is performed to promote homogenization; (3) Component adjustment: sample testing of components, fine-tuning to the qualified range; (4) Casting: the melt is transferred to a holding furnace, the pouring temperature is controlled at 690-720 ℃, and the castings are formed by gravity casting, low-pressure casting, extrusion casting or differential pressure casting process; the specific preparation process is shown in Table 2.

[0058] Table 2 Key preparation processes in the preparation method of the cast aluminum alloy of Examples 1-4

[0059] (5) Heat treatment: the castings are subjected to T6 heat treatment, including two steps of solid solution and artificial aging. Firstly, the solid solution treatment is carried out, and the process is as follows: holding at the first-stage solid solution temperature for t1; then, holding at the second-stage solid solution temperature for t2, and then water quenching to room temperature after the holding. Subsequently, the artificial aging is carried out, and the process is as follows: holding at the temperature T for t3; and then, cooling in air after the holding, to obtain the Al-Si-Cu-Mg cast aluminum alloy, wherein the specific values of the first-stage solid solution temperature, the second-stage solid solution temperature, T, t1, t2 and t3 in the preparation method of the cast aluminum alloy in examples 1-4 are recorded in Table 3.

[0060] Table 3 Heat treatment parameters in the preparation method of the cast aluminum alloy in examples 1-4

[0061] As can be seen from Table 3, the solid solution time of the example with higher solid solution temperature is shorter; and the aging time required for the example with higher aging temperature is also shorter. The first-stage solid solution temperature in example 4 is lower, and the holding time t1 required is longer; while the second-stage solid solution temperature in example 2 is higher, and the solid solution of alloying elements can be completed in only 3h; the precipitation of the strengthening phase is closely related to the aging temperature, and the higher the temperature, the shorter the time required.

[0062] The present application sets 6 groups of comparative examples for examples 1-4, and the compositions and preparation processes of the comparative examples are different from those of the corresponding examples, and the specific differences are listed in Table 4. Among them, the difference between comparative example 1 and example 1 is only that: in the preparation of the Al-Si-Cu-Mg cast aluminum alloy, an equal amount of Al-Sr is used to replace the Al-Sr-RE composite modifier to improve the morphology and size of the eutectic silicon; the difference between comparative example 2 and example 2 is only that: in the preparation of the Al-Si-Cu-Mg cast aluminum alloy, no Al-B grain refiner is added; the difference between comparative example 3 and example 3 is only that: the content of copper in the Al-Si-Cu-Mg cast aluminum alloy is reduced to 2%, and the content ratio of other components remains unchanged except the content of aluminum. The difference between comparative example 4 and example 4 is only that: a single-stage solid solution process is used instead of the two-stage solid solution process in example 4, and the specific process is as follows: holding at 545℃ for 11h, and then water quenching to room temperature after the holding. Subsequently, the artificial aging is carried out, and the other steps are the same as those of example 4. The difference between comparative example 5 and example 3 is that the content of copper in the Al-Si-Cu-Mg cast aluminum alloy is increased to 6%, and the content ratio of other components remains unchanged except the content of aluminum. The difference between comparative example 6 and example 2 is that the content of magnesium in the Al-Si-Cu-Mg cast aluminum alloy is increased to 1.0%, and the content ratio of other components remains unchanged except the content of aluminum.

[0063] Table 4 Composition and key control process parameters of comparative examples

[0064] Performance test: The microstructure of the aluminum alloy in Example 1 and Comparative Example 1 was tested by microscope, as shown in Figure 1 and Figure 2 It can be seen from Figure 1 and Figure 2 that the eutectic silicon in the aluminum alloy in Example 1 is in the form of fine particles with an average particle size of about 2.5 μm and a maximum particle size of about 6 μm; while the eutectic silicon in Comparative Example 1 is in the form of particles and rods with an average particle size of about 3.8 μm (1.52 times that of Example 1) and a maximum length of rod of more than 15 μm (2.5 times that of Example 1).

[0065] The Al-Si-Cu-Mg cast aluminum alloy prepared in Examples 1-4 and Comparative Examples 1-6 was sampled, and then the room temperature mechanical properties of the sample were tested, and the test method referred to GB / T 228.1-2021 “Metallic Materials Tensile Test Part 1: Room Temperature Test Method”. The test results are shown in Table 5. In order to better evaluate the strength and toughness of the castings, the mass index was introduced, and the calculation formula was: . In the formula, A is the mass coefficient, which is 150 MPa; σb is the tensile strength, and EL is the elongation.

[0066] Table 5 Mechanical properties of examples and comparative examples

[0067] As can be seen from Table 5, the Al-Si-Cu-Mg cast aluminum alloy in Examples 1-4 has excellent mechanical properties, wherein the room temperature tensile strength is 450-525 MPa, the yield strength is 375-465 MPa, the elongation is 2.5-10%, and the mass index is 585-606. The specific analysis is as follows: Example 1 uses a high content of Cu (3.8%) and Mg (0.65%), and also uses RE (La and Ce), and the comprehensive mechanical properties of the castings are better; Example 2 uses a high content of Mg (0.8%) and a high content of Cu (4.2%), as well as Ce alone, and the mechanical properties are significantly improved in strength but decreased in plasticity; Example 3 uses a high content of Cu (4.5%), a low content of Mg (0.2%), and rare earth La, and the strength of the aluminum alloy is slightly reduced but the plasticity is significantly improved; Example 4 uses a moderate content of Mg (0.4%) and a low content of Cu (3.0%) and mixed rare earth, and the composition is balanced, and the comprehensive performance is better.

[0068] ​The comparative example 1 uses the same amount of Al-Sr to replace the Al-Sr-RE composite modifier, the modification effect of Sr is reduced, and the comprehensive performance is reduced. The comparative example 2 does not use Al-B for grain refinement, and the comprehensive performance is reduced. The comparative example 3 reduces the Cu content, and the tensile strength and yield strength are both reduced; the comparative example 4 uses a single-stage solid solution process, and overburning structure appears in the casting, and the comprehensive mechanical properties are reduced. The comparative example 5 uses excessive Cu, the strength of the aluminum alloy is not obviously improved, but the plasticity is significantly reduced; the comparative example 6 uses excessive Mg, the strength is not significantly improved, but the plasticity and toughness are significantly reduced.

[0069] The above has made a detailed description on the embodiments of the present application, but the present application is not limited to the above-mentioned embodiments, and various changes can be made within the knowledge range possessed by the ordinary 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 by: consists of the following mass percentages of elements: Si 6.0-8.0%, Mg 0.2-0.8%, Cu 3.0-4.5%, Sr 0.01-0.05%, RE 0.02-0.10%, B 0.015-0.025%, Fe < 0.2%, the total amount of impurity elements is not more than 0.15%, and the balance is Al; The RE includes at least one of Ce and La.

2. The aluminum alloy of claim 1, wherein: The Sr and RE are added in the form of Al-Sr-RE. And / or, the B is added in the form of Al-B.

3. The aluminum alloy of claim 1 or 2, wherein: The aluminum alloy has at least one of the following characteristics after T6 heat treatment: (a1) the tensile strength of the aluminum alloy is 420-530 MPa; (a2) the yield strength of the aluminum alloy is 350-480 MPa; (a3) the elongation of the aluminum alloy is 2-12%; (a4) the average particle size of eutectic silicon in the aluminum alloy is not more than 3 μm.

4. The method of producing an aluminum alloy according to any one of claims 1 to 3, characterized by: comprising the following steps: melting and mixing raw materials to obtain an aluminum alloy melt; casting the aluminum alloy melt to form a casting; T6 heat treating the casting to obtain the aluminum alloy; the T6 heat treatment is: first heat preservation at a first-stage solid solution temperature, then heat preservation at a second-stage solid solution temperature, and artificial aging treatment after cooling; the first-stage solid solution temperature is lower than the second-stage solid solution temperature.

5. The method of making an aluminum alloy of claim 4, wherein: the first-stage solid solution temperature is 490-530℃; and / or, the heat preservation time at the first-stage solid solution temperature is 3-6h; and / or, the second-stage solid solution temperature is 535-555℃; and / or, the heat preservation time at the second-stage solid solution temperature is 3-8h.

6. The method of making an aluminum alloy of claim 4, wherein: the temperature of the artificial aging is 160-200℃; and / or, the heat preservation time of the artificial aging is 4-12h.

7. The method of making an aluminum alloy of claim 4, wherein: the temperature of the casting is 690-720℃; and / or, the casting is performed by any one of gravity casting, low-pressure casting, extrusion casting, and differential pressure casting.

8. The method of making an aluminum alloy of claim 4, wherein: the step of melting and mixing raw materials is: heating aluminum source, silicon source, and copper source to 750-800℃ for melting, then refining; and then adding magnesium source, Al-Sr-RE, and Al-B for mixing to obtain the aluminum alloy melt.

9. A product characterized by: comprising the aluminum alloy of any one of claims 1-3 or a component formed by the aluminum alloy of any one of claims 1-3; the product includes an automobile wheel hub, an engine, or an aerospace structural component.

10. Application of the preparation method of the aluminum alloy of any one of claims 1-3 or the aluminum alloy of any one of claims 4-8 in the field of automobiles or aerospace.

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