Cast aluminum alloy, preparation method therefor and use thereof

Abstract

The present invention relates to a high temperature-resistant cast aluminum alloy, a preparation method therefor and a use thereof, belonging to the technical field of aluminum alloys. The elemental composition and mass percentages thereof in the high temperature-resistant cast aluminum alloy of the present invention are as follows: Si: 1%-10%, Cu: 0.1%-4%, Mg: 0.05%-0.5%, Fe: 0.05%-0.3%, Ti: 0.01%-0.3%, Mn: 0.1%-0.5%, Cr: 0.01%-0.6%, V: 0.02%-0.2%, Sn: 0.02%-0.2%, Sc: 0.02%-0.2%, Hf: 0.02%-0.2%, Er: 0.02%-0.2%, and the balance being unavoidable impurities and Al; the microstructure of the high-temperature resistant cast aluminum alloy comprises a submicron precipitate phase and / or a nano precipitate phase. By means of controlling the alloy composition, proportioning and preparation method, and reasonably configuring parameters for heat treatment and aging treatment, while simultaneously obtaining one or more high temperature-resistant coarsened precipitate phases of submicron and nanometer size having specific compositions, dimensions and characteristics, the strength of the aluminum alloy in high-temperature environments is effectively improved, and the high temperature resistance of the aluminum alloy is enhanced.

Description

A cast aluminum alloy and its preparation method and application Technical Field

[0001] The present invention belongs to the technical field of aluminum alloys, and in particular relates to a high-temperature resistant cast aluminum alloy and a preparation method and application thereof. Background Art

[0002] Cast aluminum-silicon alloys have attracted widespread attention due to their low density, high specific strength, excellent casting properties, and superior overall performance. They are currently used in industries such as shipbuilding, machinery, aviation, aerospace, weapons, and automobiles, particularly in the preparation and production of components such as pistons, cylinder blocks, cylinder liners, and connecting rods for automotive engines. However, driven by increased efficiency and stricter emission standards for combustion engines, engines need to further increase combustion pressures, which means that the operating temperature of combustion engines will exceed 250°C. Existing cast heat-resistant aluminum-silicon alloys are increasingly unable to meet the growing high-temperature performance requirements of automotive engines.

[0003] High-temperature-resistant cast aluminum alloys currently face several major challenges: First, the existing alloy structure contains a large number of precipitates with poor thermal stability. These phases gradually grow and lose their precipitation strengthening effect at high temperatures, making it difficult to control the structure to suppress the large-scale appearance of these precipitates. Second, it is difficult to balance the alloy's casting performance and mechanical properties. Third, it is difficult to balance the alloy's room-temperature performance and high-temperature performance. Therefore, developing or optimizing a cast heat-resistant aluminum alloy that can be used normally in high-temperature environments is a key issue that needs to be addressed urgently.

[0004] Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a high-temperature resistant cast aluminum alloy and its preparation method and application, which significantly improve the mechanical properties of the cast aluminum alloy at high temperatures.

[0006] A first object of the present invention is to provide a high-temperature resistant cast aluminum alloy, wherein the element composition and mass percentage of the high-temperature resistant cast aluminum alloy are: Si 1%-10%, Cu 0.1%-4%, Mg 0.05%-0.5%, Fe 0.05%-0.3%, Ti 0.01%-0.3%, Mn 0.1%-0.5%, Cr 0.01%-0.6%, V 0.02%-0.2%, Sn 0.02%-0.2%, Sc 0.02%-0.2%, Hf0.02%-0.2%, Er 0.02%-0.2%, and the balance is other inevitable impurities and Al; the microstructure of the high-temperature resistant cast aluminum alloy includes submicron precipitates and / or nano-precipitates.

[0007] Furthermore, the element composition and mass percentage of the high-temperature resistant cast aluminum alloy are: Si 1%-6%, Cu 0.5%-4%, Mg 0.2%-0.5%, Fe 0.1%-0.2%, Ti 0.1%-0.2%, Mn 0.2%-0.5%, Cr 0.1%-0.6%, V 0.1%-0.2%, Sn 0.1%-0.2%, Sc 0.1%-0.2%, Hf0.1%-0.2%, Er0.1%-0.2%, other unavoidable impurities 0-0.15%, and the rest is Al.

[0008] In one embodiment of the present invention, the size of the submicron precipitated phase is 50nm-300nm; the size of the nano precipitated phase is 20nm-100nm.

[0009] In one embodiment of the present invention, after the submicron precipitate phase or nano-precipitate phase is kept at 100° C.-400° C. for 1 h-30 h, the increase in size ratio is less than 10%.

[0010] In one embodiment of the present invention, after the submicron precipitate phase or nano-precipitate phase is kept at 100° C.-400° C. for 1 h-30 h, the interface relationship with the alloy matrix is ​​coherent and / or semi-coherent.

[0011] In one embodiment of the present invention, the submicron precipitated phase is selected from a submicron precipitated phase containing one or more elements of Al, Fe, Mn, Cr, V and Sc, for example, it can be a submicron precipitated phase such as Al3Sc, Al4(Cr,Mn), Al(MnCrFe)Si, Al(FeMn)Si, etc.

[0012] In one embodiment of the present invention, the nano-precipitated phase is selected from the nano-precipitated phase containing one or more elements of Al, Sc, Hf and Er, for example, it can be Al3Er, Al3(Er,Hf) and other nano-precipitated phases; and / or, the nano-precipitated phase is selected from the nano-precipitated phase containing one or more elements of Al, Cu, Mg, Si and Sc, for example, it can be θ-Al2Cu, Q-Al5Cu2Mg8Si6, Al(Si,Sc) and other nano-precipitated phases.

[0013] A second object of the present invention is to provide a method for preparing the high-temperature resistant cast aluminum alloy, comprising the following steps:

[0014] S1. After drying the raw materials, add them into a melting furnace in the form of pure metal or master alloy, heat and melt them, and stir them evenly to obtain an aluminum alloy melt;

[0015] S2. Under a protective atmosphere, the aluminum alloy melt described in step S1 is mixed with a refining agent to be refined, degassed and impurity removed;

[0016] S3, casting, solution heat treatment and aging treatment are performed on the aluminum alloy melt refined in S2 to obtain a high-temperature resistant cast aluminum alloy.

[0017] In one embodiment of the present invention, in S1, the drying temperature is 100°C-500°C; the heating and melting temperature is 700°C-800°C; and the stirring time is 5 min-15 min.

[0018] In one embodiment of the present invention, in S2, the refining agent is hexachloroethane gas.

[0019] In one embodiment of the present invention, in S3, the solution heat treatment is divided into three stages: the temperature of the first stage is 200°C-350°C, and the time is 1h-5h; the temperature of the second stage is 400°C-470°C, and the time is 1h-6h; the temperature of the third stage is 480°C-535°C, and the time is 1h-6h;

[0020] The aging treatment is divided into two stages. The temperature of the first stage is 140° C.-190° C., and the time is 1 hour-20 hours. The temperature of the second stage is 200° C.-230° C., and the time is 0.5 hour-2 hours.

[0021] The third object of the present invention is to provide an application of the high-temperature resistant cast aluminum alloy in automobile engines.

[0022] The technical solution of the present invention has the following advantages over the prior art:

[0023] (1) The high-temperature resistant cast aluminum alloy described in the present invention improves the high-temperature performance of the aluminum alloy by mainly introducing micron-level high-temperature resistant phases at the grain boundaries to improve the tensile properties of the aluminum alloy at high temperatures. By controlling the alloy composition, proportions, and preparation methods, and rationally setting the heat treatment and aging treatment parameters, one or more submicron-level and nanometer-level high-temperature resistant coarsened precipitation phases of certain composition, size, and characteristics are simultaneously obtained, effectively improving the strength of the aluminum alloy in high-temperature environments and enhancing the high-temperature resistance of the aluminum alloy. This effectively improves the low strength of cast aluminum alloys at high temperatures and meets the growing demand for high-temperature performance in the automotive engineering field.

[0024] (2) The high-temperature resistant cast aluminum alloy described in the present invention has a tensile strength greater than 250 MPa when kept at 200°C for more than 10 hours, a tensile strength greater than 129 MPa when kept at 300°C for more than 10 hours, and a tensile strength greater than 85 MPa when kept at 400°C for more than 10 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0026] FIG1 is a microstructure diagram of the cast aluminum alloy prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0028] In the present invention, unless otherwise defined, technical and scientific terms used herein have the same meanings as commonly understood by one skilled in the art to which the present invention belongs.

[0029] In the present invention, unless stated otherwise, the term "and / or" used in the present invention includes any and all combinations of one or more of the associated listed items.

[0030] In the present invention, unless otherwise stated, the experimental methods used in the examples of the present invention are conventional methods unless otherwise stated, and the materials, reagents, etc. used are all commercially available unless otherwise stated.

[0031] In the present invention, unless otherwise stated, when the terms "comprise" and / or "include" are used in the specification of the present invention, they indicate the existence of the described features, integers, steps, operations, raw materials or components, but do not exclude the existence or addition of one or more other features, integers, steps, operations, raw materials, components or their combinations.

[0032] Example 1

[0033] The element composition and mass percentage of the high-temperature resistant cast aluminum alloy of the present invention are: Si 4.87%, Cu 1.23%, Mg 0.49%, Fe 0.10%, Ti 0.12%, Mn 0.30%, Cr 0.21%, V 0.11%, Sn 0.13%, Sc 0.11%, Hf 0.20%, Er 0.10%, other inevitable impurities 0-0.15%, and the rest is Al.

[0034] The preparation of high temperature resistant cast aluminum alloy specifically includes the following steps:

[0035] S1. Melting: Weigh the raw materials according to the designed composition and dry them in a furnace at 300°C. Add pure Al and Al-Si into the melting furnace and melt them at 720°C. After they are melted, add Al-Fe, Al-Ti, Al-Mn, Al-Cr, Al-V, Al-RE (Sc, Er, Hf) intermediate alloys and continue melting. Then add pure Mg, pure Cu and pure Sn. After they are completely melted, stir for 10 minutes to obtain a uniform aluminum alloy melt.

[0036] S2. Refining: Hexachloroethane gas is introduced into the aluminum alloy melt for refining at a gas flow rate of 0.1 L / min. The refining time is 12 min. After standing for 5 min, the slag is skimmed off to remove impurities.

[0037] S3. Forming: The refined aluminum alloy melt is subjected to gravity casting to obtain an aluminum alloy ingot; the aluminum alloy ingot is subjected to three-stage solid solution heat treatment and two-stage aging treatment to obtain a high-temperature resistant cast aluminum alloy; wherein, the first stage of the solid solution heat treatment is at a temperature of 300°C and a time of 2 hours; the second stage is at a temperature of 400°C and a time of 4 hours; the third stage is at a temperature of 500°C and a time of 2 hours; the first stage of the aging treatment is at a temperature of 150°C and a time of 10 hours, and the second stage is at a temperature of 200°C and a time of 1 hour.

[0038] The microstructure of the obtained cast aluminum alloy is shown in Figure 1. It can be seen from Figure 1 that submicron precipitates and nano-precipitates of different compositions and sizes exist in the cast aluminum alloy. The size range of the submicron precipitates is 80nm-300nm, including Al3Sc, Al(MnCrFe)Si, etc.; the size range of the nano-precipitates is 50nm-100nm, including θ-Al2Cu, Q-Al5Cu2Mg8Si6, etc.

[0039] After holding at high temperature for a certain period of time, it can be observed that these submicron precipitates and nano-precipitates still maintain a coherent or semi-coherent relationship with the interface of the alloy matrix. Subsequently, mechanical tests were performed on them, and the test results are shown in Table 1:

[0040] Table 1

[0041] It can be seen from Table 1 that the method of this embodiment can obtain an aluminum alloy material with high tensile strength under high temperature environment.

[0042] Example 2

[0043] The element composition and mass percentage of the high-temperature resistant cast aluminum alloy of the present invention are: Si 5.13%, Cu 2.08%, Mg 0.45%, Fe 0.11%, Ti 0.12%, Mn 0.32%, Cr 0.22%, V 0.10%, Sn 0.14%, Sc 0.11%, Hf 0.20%, Er 0.10%, other inevitable impurities 0-0.15%, and the rest is Al.

[0044] The preparation of high temperature resistant cast aluminum alloy specifically includes the following steps:

[0045] S1. Melting: Weigh the raw materials according to the designed composition and dry them in a furnace at 400°C. Add pure Al and Al-Si into the melting furnace and melt them at 730°C. After they are melted, add Al-Fe, Al-Ti, Al-Mn, Al-Cr, Al-V, Al-RE (Sc, Er, Hf) master alloys and continue melting. Then add pure Mg, pure Cu and pure Sn. After they are completely melted, stir for 12 minutes to obtain a uniform aluminum alloy melt.

[0046] S2. Refining: Hexachloroethane gas is introduced into the aluminum alloy melt for refining at a gas flow rate of 0.1 L / min. The refining time is 15 min. After standing for 6 min, the slag is skimmed off to remove impurities.

[0047] S3. Forming: The refined aluminum alloy melt is subjected to gravity casting to obtain an aluminum alloy ingot; the aluminum alloy ingot is subjected to three-stage solid solution heat treatment and two-stage aging treatment to obtain a high-temperature resistant cast aluminum alloy; wherein, the first stage of the solid solution heat treatment is at a temperature of 250°C for 3 hours; the second stage is at a temperature of 450°C for 3 hours; the third stage is at a temperature of 520°C for 4 hours; the first stage of the aging treatment is at a temperature of 140°C for 12 hours; and the second stage is at a temperature of 200°C for 1 hour.

[0048] The microstructure of the resulting cast aluminum alloy contains submicron and nano-precipitates of different compositions and sizes. The size range of the submicron precipitates is 80nm-290nm, including Al3Sc, Al(MnCrFe)Si, etc.; the size range of the nano-precipitates is 30nm-90nm, including θ-Al2Cu, Q-Al5Cu2Mg8Si6, etc.

[0049] After holding at high temperature for a certain period of time, it can be observed that these submicron precipitates and nano-precipitates still maintain a coherent or semi-coherent relationship with the interface of the alloy matrix. Subsequently, mechanical tests were performed on them, and the test results are shown in Table 2:

[0050] Table 2

[0051] It can be seen from Table 2 that the method of this embodiment can obtain an aluminum alloy material with high tensile strength under high temperature environment.

[0052] Example 3

[0053] The element composition and mass percentage of the high-temperature resistant cast aluminum alloy of the present invention are: Si 4.11%, Cu 1.51%, Mg 0.35%, Fe 0.10%, Ti 0.15%, Mn 0.31%, Cr 0.20%, V 0.11%, Sn 0.12%, Sc 0.10%, Hf 0.19%, Er 0.11%, other inevitable impurities 0-0.15%, and the rest is Al.

[0054] The preparation of high temperature resistant cast aluminum alloy specifically includes the following steps:

[0055] S1. Melting: Weigh the raw materials according to the designed composition and dry them in a furnace at 400°C. Add pure Al and Al-Si into the melting furnace and melt them at 730°C. After they are melted, add Al-Fe, Al-Ti, Al-Mn, Al-Cr, Al-V, Al-RE (Sc, Er, Hf) master alloys, followed by pure Mg, pure Cu and pure Sn. After they are completely melted, stir for 15 minutes to obtain a uniform aluminum alloy melt.

[0056] S2. Refining: Hexachloroethane gas is introduced into the aluminum alloy melt for refining at a gas flow rate of 0.1 L / min. The refining time is 15 min. After standing for 8 min, the slag is skimmed off to remove impurities.

[0057] S3. Forming: The refined aluminum alloy melt is subjected to gravity casting to obtain an aluminum alloy ingot; the aluminum alloy ingot is subjected to three-level solid solution heat treatment and two-level aging treatment to obtain a high-temperature resistant cast aluminum alloy; wherein, the first level of solid solution heat treatment is at a temperature of 200°C and a time of 4 hours; the second level is at a temperature of 470°C and a time of 6 hours; the third level is at a temperature of 520°C and a time of 4 hours; the first level of aging treatment is at a temperature of 140°C and a time of 10 hours; the second level is at a temperature of 200°C and a time of 1 hour.

[0058] The microstructure of the obtained cast aluminum alloy is shown in Figure 3. It can be seen from Figure 3 that submicron precipitates and nano-precipitates of different compositions and sizes exist in the cast aluminum alloy. The size range of the submicron precipitates is 50nm-280nm, including Al3Sc, Al(MnCrFe)Si, etc.; the size range of the nano-precipitates is 20nm-80nm, including θ-Al2Cu, Q-Al5Cu2Mg8Si6, etc.

[0059] After holding at high temperature for a certain period of time, it can be observed that these submicron precipitates and nano-precipitates still maintain a coherent or semi-coherent relationship with the interface of the alloy matrix. Subsequently, mechanical tests were performed on them, and the test results are shown in Table 3:

[0060] Table 3

[0061] It can be seen from Table 3 that the method of this embodiment can obtain an aluminum alloy material with high tensile strength under high temperature environment.

[0062] Comparative Example 1

[0063] The element composition and mass percentage of the cast aluminum alloy are: Si 4.87%, Cu 1.23%, Mg 0.49%, Fe 0.10%, Ti 0.12%, other inevitable impurities 0-0.15%, and the rest is Al.

[0064] The preparation of cast aluminum alloy specifically includes the following steps:

[0065] S1. Melting: Weigh the raw materials according to the designed composition and dry them in a furnace at 300°C. Add pure Al and Al-Si into the melting furnace and melt them at 720°C. After they are melted, add Al-Fe and Al-Ti master alloys and continue melting. Then add pure Mg and pure Cu. After they are completely melted, stir for 10 minutes to obtain a uniform aluminum alloy melt.

[0066] S2. Refining: Hexachloroethane gas is introduced into the aluminum alloy melt for refining at a gas flow rate of 0.1 L / min. The refining time is 12 min. After standing for 5 min, the slag is skimmed off to remove impurities.

[0067] S3. Forming: The refined aluminum alloy melt is subjected to gravity casting to obtain an aluminum alloy ingot; the aluminum alloy ingot is subjected to three-stage solid solution heat treatment and two-stage aging treatment to obtain a high-temperature resistant cast aluminum alloy; wherein, the first stage of the solid solution heat treatment is at a temperature of 300°C and a time of 2 hours; the second stage is at a temperature of 400°C and a time of 4 hours; the third stage is at a temperature of 500°C and a time of 2 hours; the first stage of the aging treatment is at a temperature of 150°C and a time of 10 hours, and the second stage is at a temperature of 200°C and a time of 3 hours.

[0068] The test results are shown in Table 4.

[0069] Table 4

[0070] It can be seen from Table 4 that the aluminum alloy material obtained by the method of this comparative example has poor tensile strength under high temperature environment.

[0071] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A high temperature resistant cast aluminum alloy, characterized in that: The element composition and mass percentage of the high temperature resistant cast aluminum alloy are: Si 1%-10%, Cu 0.1%-4%, Mg 0.05%-0.5%, Fe 0.05%-0.3%, Ti 0.01%-0.3%, Mn 0.1%-0.5%, Cr 0.01%-0.6%, V 0.02%-0.2%, Sn 0.02%-0.2%, Sc 0.02%-0.2%, Hf 0.02%-0.2%, Er 0.02%-0.2%, and the balance is other inevitable impurities and Al; the microstructure of the high temperature resistant cast aluminum alloy includes submicron precipitated phases and / or nano precipitated phases.

2. The high temperature resistant cast aluminum alloy according to claim 1, characterized in that: The size of the submicron precipitated phase is 50nm-300nm; the size of the nano precipitated phase is 20nm-100nm.

3. The high temperature resistant cast aluminum alloy according to claim 1, characterized in that: After the submicron precipitated phase or the nano precipitated phase is kept at 100° C.-400° C. for 1 h-30 h, the increase range of the size ratio is less than 10%.

4. The high temperature resistant cast aluminum alloy according to claim 1, characterized in that: After the submicron precipitated phase or nano precipitated phase is kept at 100° C.-400° C. for 1 h-30 h, the interface relationship between the submicron precipitated phase and the alloy matrix is ​​coherent and / or semi-coherent.

5. The high temperature resistant cast aluminum alloy according to claim 1, characterized in that: The submicron precipitated phase is selected from submicron precipitated phases containing one or more elements of Al, Fe, Mn, Cr, V and Sc; The nano-precipitated phase is selected from the nano-precipitated phase containing one or more elements of Al, Sc, Hf and Er; and / or, the nano-precipitated phase is selected from the nano-precipitated phase containing one or more elements of Al, Cu, Mg, Si and Sc.

6. A method for preparing the high temperature resistant cast aluminum alloy according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. After drying the raw materials, add them into a smelting furnace in the form of pure metal or master alloy, heat and melt them, and stir them evenly to obtain an aluminum alloy melt; S2, under a protective atmosphere, mixing the aluminum alloy melt described in step S1 with a refining agent, and performing refining, degassing and impurity removal; S3, casting, solution heat treatment and aging treatment are performed on the aluminum alloy melt refined in S2 to obtain a high temperature resistant cast aluminum alloy.

7. The method for preparing a high temperature resistant cast aluminum alloy according to claim 6, characterized in that: In S1, the drying temperature is 100°C-500°C; the heating and melting temperature is 700°C-800°C; and the stirring time is 5min-15min.

8. The method for preparing a high temperature resistant cast aluminum alloy according to claim 6, characterized in that: In S2, the refining agent is hexachloroethane gas.

9. The method for preparing a high temperature resistant cast aluminum alloy according to claim 6, characterized in that: In S3, the solution heat treatment is divided into three stages, the temperature of the first stage is 200°C-350°C, and the time is 1h-5h; the temperature of the second stage is 400°C-470°C, and the time is 1h-6h; the temperature of the third stage is 480°C-535°C, and the time is 1h-6h; The aging treatment is divided into two stages. The temperature of the first stage is 140°C-190°C, and the time is 1h-20h; the temperature of the second stage is 200°C-230°C, and the time is 0.5h-2h.

10. Use of the high temperature resistant cast aluminum alloy according to any one of claims 1 to 5 in automobile engines.

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