A method of producing a cast aluminium alloy

Abstract

The application discloses a preparation method of cast aluminum alloy and belongs to the technical field of alloys. The application can refine grains, promote the more uniform aluminum alloy liquid, reduce segregation, obviously improve the purity of the aluminum alloy liquid, and make the modification agent disperse more uniformly in the aluminum alloy liquid by adding a composite refining agent and a compound modification agent in steps, wherein, Al-Sr intermediate alloy is first added to modify eutectic silicon, so that the eutectic silicon is changed from flaky to fine fibrous, Al-5Ti-1B and nano CeO are added after a period of time, the grain growth is inhibited, and the agglomeration is reduced, and the grain refinement and the morphology optimization of eutectic silicon are realized by the synergistic effect, so that the uniform microstructure is formed. Then, through multi-stage solid solution treatment, the intracrystalline structure can be stabilized, and subsequent aging precipitation is promoted, so that finer, more uniform and dispersed strengthening phases are obtained, and the cast alloy can achieve the balance between mechanical properties and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of alloy technology, and more specifically, to a method for preparing cast aluminum alloys. Background Technology

[0002] Aluminum alloys possess excellent electrical and thermal conductivity. Compared to steel, copper alloys, and titanium alloys, they have a relatively low density and exhibit good plasticity, non-magnetic properties, low elastic modulus, and a tendency to form a dense oxide film on their surface, resulting in excellent corrosion resistance. Cast aluminum alloys, in particular, possess excellent casting properties, allowing for the mass production of various parts according to application requirements, part shapes, dimensional accuracy, and mechanical properties. The matrix of cast aluminum alloys is Al, with Si, Cu, Mg, and Zn as the main alloying elements, and Mn, Fe, Ni, and Ti as the main third-order additives. Each chemical composition significantly influences the alloy's mechanical properties, casting properties, and machinability. Currently, cast aluminum alloys are classified into four categories: Al-Si, Al-Cu, Al-Mg, and Al-Zn. Cast Al-Si-Mg alloys are an important branch of Al-Si alloys. Mg, as the third additive element, not only improves the alloy's fluidity and casting performance, but also acts as a major strengthening element. After solution treatment and aging, it forms the Mg2Si phase, significantly improving the alloy's mechanical properties. However, with increasing Mg content, while strength increases, plasticity decreases. This is because the eutectic Si phase in the microstructure coarsens with increasing Mg content. Therefore, it is necessary to add other trace elements to adjust the alloy composition to obtain the appropriate microstructure and desired mechanical properties. Al-Cu alloys can also be heat-treated for strengthening and have higher mechanical properties than Al-Si alloys. However, Al-Cu alloys have a wider crystallinity range, poorer casting performance, and the addition of large amounts of Cu exacerbates corrosion. Achieving a balance between strength, toughness, and corrosion resistance is difficult. In addition, during the casting process, traditional methods are used to modify eutectic silicon. However, traditional modifiers are prone to burn-out, rapid decay of modification effect, and easy generation of porosity (such as Sr), which affects the stability of the modification effect. Defects such as porosity, shrinkage porosity, and oxide inclusions can become stress concentration sources and significantly reduce the mechanical properties of the alloy.

[0003] There are also many existing technologies for improving cast aluminum alloys. For example, Chinese invention patent CN118531268A discloses a high-strength and high-toughness cast Al-Mg alloy and its preparation method. This invention uses an extrusion casting method to prepare the alloy and utilizes the residual heat of pressure casting for quenching, thereby improving the alloy's strength and toughness. This invention is only applicable to the extrusion casting method, which limits the alloy's forming methods. Furthermore, the alloy cannot be strengthened by heat treatment, resulting in limited strength improvement and failing to enhance corrosion resistance. Another example is Chinese invention patent CN117802364B, which discloses a high-strength and high-ductility extrusion cast aluminum alloy and its preparation method, relating to the field of aluminum alloys and their preparation. The aluminum alloy is composed of the following components by mass percentage: 6.5-7.5% Si, 0.25-0.45% Mg, 0.08-0.12% Ti, 0.01-0.03% Sr, Fe≤0.15%, with the remainder being Al and impurities. This solution refines α-Al grains and eutectic Si phases by scientifically designing the composition and preparation process of extruded aluminum alloys, thereby improving the purity of the aluminum alloy melt, eliminating the harm of hydrogen pores and inclusions to strength and plasticity, and solving the problem of mutual constraint between strength and plasticity. At the same time, it improves the strength and plasticity of extruded aluminum alloys, but its corrosion resistance still needs to be improved. Summary of the Invention

[0004] Therefore, in order to solve the above-mentioned technical problems, the present invention provides a method for preparing cast aluminum alloy, the specific technical solution of which is as follows: A method for preparing a cast aluminum alloy, the method comprising the following steps: S1. Melting and Composition Control: Under a protective atmosphere, industrial pure aluminum, aluminum-silicon master alloy, aluminum-copper master alloy, pure magnesium ingot, and aluminum-manganese master alloy are added to a melting furnace and heated for melting. The chemical composition of the alloy liquid is adjusted to obtain aluminum alloy liquid. S2. Composite Refining and Modification Treatment: The aluminum alloy liquid is cooled, a composite refining agent is added for rotary spray refining, and after refining, it is allowed to stand. Then, a modifier is added for modification treatment. S3. Ultrasonic Field Assisted Casting: The aluminum alloy liquid treated in step S2 is heated and poured into a casting mold for casting. During the solidification process, ultrasonic vibration with a frequency of 20kHz~40kHz and a power of 1kW~2kW is applied to the aluminum alloy liquid until the aluminum alloy liquid is completely solidified to obtain an ingot; S4. Multi-stage solution treatment: The ingot is subjected to solution treatment, and the solution treatment process is as follows: first, the temperature is raised to 530℃~545℃ at a heating rate of 5℃ / min~8℃ / min, and the first-stage solution treatment is performed for 4h~6h; then, the temperature is lowered to 480℃~490℃ at a heating rate of 3℃ / min~5℃ / min, and the second-stage solution treatment is performed for 1h~2h; and then the ingot is quenched in water to room temperature. S5. Aging treatment is performed on the water-quenched ingot.

[0005] Furthermore, in step S1, the temperature for the heating and melting process is 720℃~760℃.

[0006] Further, in step S1, the chemical composition of the alloy liquid is adjusted as follows: by mass percentage, Si 6.5~8.5%, Mg 1.2~2.3%, Cu 0.1~0.5%, Ti 0.1~0.2%, Sr 0.01~0.15%, Mn 0.4~0.6%, Fe ≤ 0.12%, with the balance being Al and unavoidable impurities.

[0007] Furthermore, in step S2, the temperature is lowered to 700℃~720℃.

[0008] Further, in step S2, the composite refining agent is obtained by mixing Na2SiF6 and C2Cl6 in a mass ratio of (1~3):1; The amount of the composite refining agent added accounts for 0.1-0.3% of the total mass of the aluminum alloy liquid; The rotary jet refining process is carried out at a speed of 400 r / min to 500 r / min for a duration of 10 min to 15 min.

[0009] Further, in step S2, the deteriorating agent is composed of component A and component B in a mass ratio of (1~3):(1~5), and component A and component B need to be added separately, with an interval of 10min~20min between additions.

[0010] Further, in step S2, component A is an Al-Sr master alloy, component B is a mixture of Al-5Ti-1B master alloy and CeO, and the mass ratio of Al-5Ti-1B master alloy to CeO is (3~7):1.

[0011] Furthermore, the CeO has a particle size of 20 μm to 100 μm.

[0012] Further, in step S3, the heating treatment is performed at a heating rate of 3℃ / min to 5℃ / min to 740℃ to 750℃.

[0013] Furthermore, in step S3, the aging treatment temperature is 155℃~165℃, and the time is 6h~8h.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention optimizes the preparation method by adding ultrasonic field assistance. The cavitation effect breaks up growing dendrites, increases the number of crystal nuclei, helps refine grains, promotes a more uniform aluminum alloy melt, and reduces segregation. Furthermore, it promotes the escape of microbubbles from the aluminum alloy melt, effectively inhibiting the formation of casting shrinkage porosity and helping to reduce casting defects.

[0015] 2. This invention effectively removes gaseous and non-metallic inclusions from molten aluminum alloy using composite refining agents and compound modifiers, significantly improving the purity of the molten aluminum alloy and further reducing defects such as porosity and inclusions. Furthermore, the step-by-step addition of modifiers ensures uniform dispersion in the molten aluminum alloy. First, an Al-Sr master alloy is added to modify the eutectic silicon, transforming it from a flake-like structure to a fine fibrous structure. After a period of time, Al-5Ti-1B and nano-CeO are added. Al-5Ti-1B acts as a highly efficient grain refiner, providing heterogeneous nucleation sites. The fine CeO particles serve as an additional nucleation substrate, adsorbing at grain boundaries and phase boundaries, inhibiting grain growth, and reducing the agglomeration of the modifiers. Overall, this produces a synergistic effect, achieving grain refinement of the α-Al matrix and morphological optimization of the eutectic silicon, together forming a uniform microstructure.

[0016] 3. This invention, through multi-stage solid solution treatment, can stabilize the intracrystalline structure and promote more thorough preparation for aging precipitation, thereby obtaining finer, more uniform, and more dispersed strengthening phases. Overall, the resulting cast alloy can achieve a balance between mechanical properties and corrosion resistance. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0019] A method for preparing a cast aluminum alloy according to one embodiment of the present invention includes the following steps: S1. Melting and Composition Control: Under a protective atmosphere, industrial pure aluminum, aluminum-silicon master alloy, aluminum-copper master alloy, pure magnesium ingot, and aluminum-manganese master alloy are added to a melting furnace and heated for melting. The chemical composition of the alloy liquid is adjusted to obtain aluminum alloy liquid. S2. Composite Refining and Modification Treatment: The aluminum alloy liquid is cooled, a composite refining agent is added for rotary spray refining, and after refining, it is allowed to stand. Then, a modifier is added for modification treatment. S3. Ultrasonic Field Assisted Casting: The aluminum alloy liquid treated in step S2 is heated and poured into a casting mold for casting. During the solidification process, ultrasonic vibration with a frequency of 20kHz~40kHz and a power of 1kW~2kW is applied to the aluminum alloy liquid until the aluminum alloy liquid is completely solidified to obtain an ingot; S4. Multi-stage solution treatment: The ingot is subjected to solution treatment, and the solution treatment process is as follows: first, the temperature is raised to 530℃~545℃ at a heating rate of 5℃ / min~8℃ / min, and the first-stage solution treatment is performed for 4h~6h; then, the temperature is lowered to 480℃~490℃ at a heating rate of 3℃ / min~5℃ / min, and the second-stage solution treatment is performed for 1h~2h; and then the ingot is quenched in water to room temperature. S5. Aging treatment is performed on the water-quenched ingot.

[0020] This invention optimizes the heating and cooling rates of the solution treatment, which helps to quickly reach the target temperature while avoiding overheating of the low-melting-point eutectic phase, and allows solute atoms to diffuse and adjust more fully in the secondary solution stage.

[0021] In one embodiment, in step S1, the temperature of the heating and melting process is 720°C to 760°C.

[0022] In one embodiment, in step S1, the chemical composition of the alloy liquid is adjusted as follows (by mass percentage): Si 6.5-8.5%, Mg 1.2-2.3%, Cu 0.1-0.5%, Ti 0.1-0.2%, Sr 0.01-0.15%, Mn 0.4-0.6%, Fe ≤0.12%, with the balance being Al and unavoidable impurities. The moderate Si content of this invention ensures good casting fluidity; the combination of Mg and Cu elements forms the main age-strengthening phases, such as Mg2Si and Al2Cu; the extremely low Fe content (≤0.12%) and sufficient Mn element allow Fe to combine with Mn to form a Chinese character-shaped or skeletal Al-(Fe, Mn)-Si phase, rather than the needle-like brittle β-Al5FeSi phase, greatly eliminating the harmful effects of Fe and ensuring the mechanical properties of the material.

[0023] In one embodiment, in step S2, the temperature is reduced to 700°C~720°C.

[0024] In one embodiment, in step S2, the composite refining agent is obtained by mixing Na2SiF6 and C2Cl6 in a mass ratio of (1~3):1; The amount of the composite refining agent added accounts for 0.1-0.3% of the total mass of the aluminum alloy liquid; The rotary jet refining process is carried out at a speed of 400 r / min to 500 r / min for a duration of 10 min to 15 min.

[0025] In one embodiment, in step S2, the degrading agent is composed of component A and component B in a mass ratio of (1~3):(1~5), and component A and component B need to be added separately with an interval of 10 min~20 min between additions.

[0026] In one embodiment, in step S2, component A is an Al-Sr master alloy, component B is a mixture of Al-5Ti-1B master alloy and CeO, and the mass ratio of Al-5Ti-1B master alloy to CeO is (3~7):1.

[0027] In one embodiment, the CeO particle size is 20 μm to 100 μm.

[0028] In one embodiment, the amount of the modifier added accounts for 0.1%-0.5% of the total mass of the aluminum alloy liquid.

[0029] In one embodiment, in step S3, the heating treatment is performed at a heating rate of 3°C / min to 5°C / min to 740°C to 750°C.

[0030] In one embodiment, in step S3, the aging treatment temperature is 155℃~165℃ and the time is 6h~8h.

[0031] Through process optimization, the above scheme can achieve a balance between strength and corrosion resistance in cast aluminum alloys.

[0032] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0033] Example 1: A method for preparing a cast aluminum alloy includes the following steps: S1. Melting and Composition Control: Under a protective atmosphere, industrial pure aluminum, aluminum-silicon master alloy, aluminum-copper master alloy, pure magnesium ingot and aluminum-manganese master alloy are added to the melting furnace and heated to 740°C for melting treatment. The chemical composition of the alloy liquid is adjusted to obtain aluminum alloy liquid. The chemical composition of the alloy liquid is adjusted as follows: by mass percentage, Si 7.1%, Mg 1.8%, Cu 0.3%, Ti 0.1%, Sr 0.03%, Mn 0.5%, Fe 0.08%, with the balance being Al and unavoidable impurities; S2. Composite refining and modification treatment: The aluminum alloy liquid is cooled to 700℃, and a composite refining agent accounting for 0.2% of the total mass of the aluminum alloy liquid is added for rotary blowing refining. The rotary blowing refining speed is 400 r / min, and the time is 15 min. After refining, the mixture is allowed to stand, and then a modifier accounting for 0.4% of the total mass of the aluminum alloy liquid is added for modification treatment; The composite refining agent is obtained by mixing Na2SiF6 and C2Cl6 in a mass ratio of 2:1. The deteriorating agent consists of component A and component B in a mass ratio of 2:3, and component A and component B need to be added separately with an interval of 15 minutes between additions. Component A is an Al-Sr master alloy, and component B is a mixture of Al-5Ti-1B master alloy and CeO with a particle size of 50μm, wherein the mass ratio of Al-5Ti-1B master alloy to CeO is 5:1; S3. Ultrasonic field assisted casting: The aluminum alloy liquid treated in step S2 is heated to 740°C at a heating rate of 5°C / min and introduced into a casting mold. During the pouring and solidification process, ultrasonic vibration with a frequency of 20kHz and a power of 1kW is applied to the aluminum alloy liquid until the aluminum alloy liquid is completely solidified to obtain an ingot; S4. Multi-stage solution treatment: The ingot is subjected to solution treatment, and the solution treatment process is as follows: first, the temperature is raised to 530°C at a heating rate of 6°C / min for a first-stage solution treatment for 5 hours, then the temperature is lowered to 490°C at a heating rate of 5°C / min for a second-stage solution treatment for 1 hour, and then the ingot is quenched in water to room temperature; S5. The water-quenched ingot is subjected to aging treatment at a temperature of 160℃ for 8 hours.

[0034] Example 2: A method for preparing a cast aluminum alloy includes the following steps: S1. Melting and Composition Control: Under a protective atmosphere, industrial pure aluminum, aluminum-silicon master alloy, aluminum-copper master alloy, pure magnesium ingot and aluminum-manganese master alloy are added to the melting furnace and heated to 740°C for melting treatment. The chemical composition of the alloy liquid is adjusted to obtain aluminum alloy liquid. The chemical composition of the alloy liquid is adjusted as follows: by mass percentage, Si 7.2%, Mg 1.8%, Cu 0.5%, Ti 0.2%, Sr 0.03%, Mn 0.6%, Fe 0.09%, with the balance being Al and unavoidable impurities; S2. Composite refining and modification treatment: The aluminum alloy liquid is cooled to 700℃, and a composite refining agent accounting for 0.2% of the total mass of the aluminum alloy liquid is added for rotary blowing refining. The rotary blowing refining speed is 500 r / min, and the time is 15 min. After refining, the mixture is allowed to stand, and then a modifier accounting for 0.3% of the total mass of the aluminum alloy liquid is added for modification treatment; The composite refining agent is obtained by mixing Na2SiF6 and C2Cl6 in a mass ratio of 2:1. The deteriorating agent consists of component A and component B in a mass ratio of 2:3, and component A and component B need to be added separately with an interval of 20 minutes between additions. Component A is an Al-Sr master alloy, and component B is a mixture of Al-5Ti-1B master alloy and CeO with a particle size of 50μm, wherein the mass ratio of Al-5Ti-1B master alloy to CeO is 5:1; S3. Ultrasonic field assisted casting: The aluminum alloy liquid treated in step S2 is heated to 745°C at a heating rate of 5°C / min and introduced into a casting mold. During the pouring and solidification process, ultrasonic vibration with a frequency of 22kHz and a power of 1.1kW is applied to the aluminum alloy liquid until the aluminum alloy liquid is completely solidified to obtain an ingot; S4. Multi-stage solution treatment: The ingot is subjected to solution treatment, and the solution treatment process is as follows: first, the temperature is raised to 540°C at a heating rate of 5°C / min for a first-stage solution treatment of 4h, then the temperature is lowered to 480°C at a heating rate of 5°C / min for a second-stage solution treatment of 1.5h, and then water quenched to room temperature; S5. The water-quenched ingot is subjected to aging treatment at a temperature of 160℃ for 8 hours.

[0035] Example 3: A method for preparing a cast aluminum alloy includes the following steps: S1. Melting and composition control: Under a protective atmosphere, industrial pure aluminum, aluminum-silicon master alloy, aluminum-copper master alloy, pure magnesium ingot and aluminum-manganese master alloy are added to the melting furnace and heated to 720℃~760℃ for melting treatment. The chemical composition of the alloy liquid is adjusted to obtain aluminum alloy liquid. The chemical composition of the alloy liquid is adjusted as follows: by mass percentage, Si 7.2%, Mg 1.9%, Cu 0.5%, Ti 0.2%, Sr 0.04%, Mn 0.6%, Fe 0.08%, with the balance being Al and unavoidable impurities; S2. Composite refining and modification treatment: The aluminum alloy liquid is cooled to 700℃, and a composite refining agent accounting for 0.2% of the total mass of the aluminum alloy liquid is added for rotary blowing refining. The rotary blowing refining speed is 500 r / min and the time is 15 min. After refining, it is allowed to stand, and then a modifier accounting for 0.3% of the total mass of the aluminum alloy liquid is added for modification treatment; The composite refining agent is obtained by mixing Na2SiF6 and C2Cl6 in a mass ratio of 2:1. The deteriorating agent consists of component A and component B in a mass ratio of 2:3, and component A and component B need to be added separately with an interval of 20 minutes between additions. Component A is an Al-Sr master alloy, and component B is a mixture of Al-5Ti-1B master alloy and CeO with a particle size of 50μm, wherein the mass ratio of Al-5Ti-1B master alloy to CeO is 5:1; S3. Ultrasonic field assisted casting: The aluminum alloy liquid treated in step S2 is heated to 740°C at a heating rate of 5°C / min and introduced into a casting mold. During the pouring and solidification process, ultrasonic vibration with a frequency of 21kHz and a power of 1.2kW is applied to the aluminum alloy liquid until the aluminum alloy liquid is completely solidified to obtain an ingot; S4. Multi-stage solution treatment: The ingot is subjected to solution treatment, and the solution treatment process is as follows: first, the temperature is raised to 545°C at a heating rate of 5°C / min for a first-stage solution treatment for 5 hours, then the temperature is lowered to 485°C at a heating rate of 5°C / min for a second-stage solution treatment for 1 hour, and then the ingot is quenched in water to room temperature. S5. The water-quenched ingot is subjected to aging treatment at a temperature of 165℃ for 6.5 hours.

[0036] Example 4: A method for preparing a cast aluminum alloy includes the following steps: S1. Melting and composition control: Under a protective atmosphere, industrial pure aluminum, aluminum-silicon master alloy, aluminum-copper master alloy, pure magnesium ingot and aluminum-manganese master alloy are added to the melting furnace and heated to 720℃~760℃ for melting treatment. The chemical composition of the alloy liquid is adjusted to obtain aluminum alloy liquid. The chemical composition of the alloy liquid is adjusted as follows: by mass percentage, Si 7.2%, Mg 1.9%, Cu 0.5%, Ti 0.2%, Sr 0.04%, Mn 0.6%, Fe 0.08%, with the balance being Al and unavoidable impurities; S2. Composite refining and modification treatment: The aluminum alloy liquid is cooled to 700℃, and a composite refining agent accounting for 0.2% of the total mass of the aluminum alloy liquid is added for rotary blowing refining. The rotary blowing refining speed is 500 r / min and the time is 15 min. After refining, it is allowed to stand, and then a modifier accounting for 0.3% of the total mass of the aluminum alloy liquid is added for modification treatment; The composite refining agent is obtained by mixing Na2SiF6 and C2Cl6 in a mass ratio of 2:1. The deteriorating agent consists of component A and component B in a mass ratio of 3:5, and component A and component B need to be added separately with an interval of 20 minutes between additions. Component A is an Al-Sr master alloy, and component B is a mixture of Al-5Ti-1B master alloy and CeO with a particle size of 50μm, wherein the mass ratio of Al-5Ti-1B master alloy to CeO is 4:1; S3. Ultrasonic field assisted casting: The aluminum alloy liquid treated in step S2 is heated to 740°C at a heating rate of 5°C / min and introduced into a casting mold. During the pouring and solidification process, ultrasonic vibration with a frequency of 21kHz and a power of 1.2kW is applied to the aluminum alloy liquid until the aluminum alloy liquid is completely solidified to obtain an ingot; S4. Multi-stage solution treatment: The ingot is subjected to solution treatment, and the solution treatment process is as follows: first, the temperature is raised to 545°C at a heating rate of 5°C / min for a first-stage solution treatment for 5 hours, then the temperature is lowered to 485°C at a heating rate of 5°C / min for a second-stage solution treatment for 1 hour, and then the ingot is quenched in water to room temperature. S5. The water-quenched ingot is subjected to aging treatment at a temperature of 165℃ for 6.5 hours.

[0037] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that in step S2 of Comparative Example 1, a single Al-Sr master alloy is added as a modifier, while the rest is the same as in Example 1.

[0038] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that in step S2 of Comparative Example 2, a single Al-5Ti-1B master alloy is added as a modifier, while the rest is the same as in Example 1.

[0039] Comparative Example 3: Compared with Example 1, Comparative Example 3 differs in that, in step S2 of Comparative Example 3, the modifier is obtained by mixing Al-Sr master alloy, Al-5Ti-1B master alloy and CeO in a mass ratio of 2:3:1, while the rest is the same as in Example 1.

[0040] Comparative Example 4: Compared with Example 1, Comparative Example 4 differs in that ultrasonic field assistance was not set in step S3, while the rest is the same as Example 1.

[0041] Comparative Example 5: Compared with Example 1, Comparative Example 5 differs in that, in step S4 of Comparative Example 5, the solution treatment process is as follows: the temperature is increased to 550°C at a heating rate of 8°C / min; the rest is the same as in Example 1.

[0042] The performance of the cast aluminum alloy samples prepared in Examples 1-4 and the cast aluminum alloy samples prepared in Comparative Examples 1-5 was tested, and the results are shown in Table 1 below.

[0043] Among them, the mechanical performance test references the standard GB / T6397-1985, and the anti-stripping corrosion performance references GBT22639-2008.

[0044] Table 1: Performance Test Results

[0045] Analysis of the data in Table 1 shows that, through process optimization, this invention effectively improves the mechanical properties and corrosion resistance of cast aluminum alloys by combining composite refining, composite modification, ultrasonic assistance, and multi-stage solid solution treatment. This achieves a balance between mechanical properties and corrosion resistance, meeting a wider range of application requirements. Compared to Example 1, Comparative Example 1, which added a single Al-Sr master alloy as a modifier, although it could not effectively improve the morphology of eutectic silicon, lacked the grain refinement effect of Al-5Ti-1B, resulting in greater refining, insufficient strength and toughness, and affecting corrosion resistance. Comparative Example 2 added a single Al-5Ti-1B master alloy as a modifier. Although Al-5Ti-1B refined the α-Al grains, it contained more lamellar eutectic silicon, leading to a decrease in the material's toughness and poorer corrosion resistance compared to the example. Comparative Example 3's modifier was obtained by mixing Al-Sr master alloy, Al-5Ti-1B master alloy, and CeO in a mass ratio of 2:3:1. Adding the composite modifier at once resulted in agglomeration, with lower dispersion and microstructure optimization compared to Example 1. The performance deteriorated; Comparative Example 4 did not have ultrasonic field assistance, and the lack of ultrasonic vibration led to coarse grains and increased defects, resulting in poorer mechanical properties and corrosion resistance compared to Example 1; In step S4 of Comparative Example 5, the solution treatment process was to heat to 550°C at a heating rate of 8°C / min, which resulted in insufficient precipitation of the strengthening phase, poorer grain boundary continuity than Example 1, and affected the subsequent aging treatment effect, resulting in poorer mechanical properties than Example 1, increased non-uniformity, and the formation of corrosion channels in the area near the grain boundaries, which also resulted in poorer corrosion resistance than Example 1.

[0046] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0047] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a cast aluminum alloy, characterized in that, The preparation method includes the following steps: S1. Melting and Composition Control: Under a protective atmosphere, industrial pure aluminum, aluminum-silicon master alloy, aluminum-copper master alloy, pure magnesium ingot and aluminum-manganese master alloy are added to a melting furnace, heated and melted, and the chemical composition of the alloy liquid is adjusted to obtain aluminum alloy liquid. The chemical composition of the alloy liquid is as follows (by mass percentage): Si 6.5~8.5%, Mg 1.2~2.3%, Cu 0.1~0.5%, Ti 0.1~0.2%, Sr 0.01~0.15%, Mn 0.4~0.6%, Fe ≤ 0.12%, with the balance being Al and unavoidable impurities. S2. Composite refining and modification treatment: The aluminum alloy liquid is cooled down, a composite refining agent is added for rotary spray refining, the refined liquid is allowed to stand, and then a modification agent is added for modification treatment. S3. Ultrasonic field assisted casting: The aluminum alloy liquid treated in step S2 is heated to 740℃~750℃ at a heating rate of 3℃ / min~5℃ / min, and then introduced into a casting mold. During the pouring and solidification process, ultrasonic vibration with a frequency of 20kHz~40kHz and a power of 1kW~2kW is applied to the aluminum alloy liquid until the aluminum alloy liquid is completely solidified to obtain an ingot. S4. Multi-stage solution treatment: The ingot is subjected to solution treatment, and the solution treatment process is as follows: first, the temperature is raised to 530℃~545℃ at a heating rate of 5℃ / min~8℃ / min, and the first-stage solution treatment lasts for 4h~6h; then, the temperature is lowered to 480℃~490℃ at a heating rate of 3℃ / min~5℃ / min, and the second-stage solution treatment lasts for 1h~2h; and then the ingot is quenched in water to room temperature. S5. Aging treatment is performed on the water-quenched ingot.

2. The preparation method according to claim 1, characterized in that, In step S1, the temperature for the heating and melting process is 720℃~760℃.

3. The preparation method according to claim 1, characterized in that, In step S2, the temperature is lowered to 700℃~720℃.

4. The preparation method according to claim 1, characterized in that, In step S2, the composite refining agent is obtained by mixing Na2SiF6 and C2Cl6 in a mass ratio of (1~3):1; The amount of the composite refining agent added accounts for 0.1-0.3% of the total mass of the aluminum alloy liquid; The rotary jet refining process is carried out at a speed of 400 r / min to 500 r / min for a duration of 10 min to 15 min.

5. The preparation method according to claim 1, characterized in that, In step S5, the aging treatment temperature is 155℃~165℃, and the time is 6h~8h.

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