A heat-resistant wrought aluminum alloy with a high rare earth content and a preparation method thereof

Abstract

The present invention relates to a wrought heat-resistant aluminum alloy with a high rare earth content and a preparation method thereof. The alloy consists of the following components in mass percentage: Ce 5.0 - 15.0%, Mg 1.0 - 5.0%, Zn 0.05 - 5.0%, Zr 0.05 - 0.2%, Y 0.05 - 0.15%, and the balance is Al. The preparation method is as follows: according to the designed alloy component ratio, each component is weighed, and an ingot is obtained through melting and casting, and then an isothermal homogenization treatment and a hot extrusion treatment are carried out to obtain the alloy. The present invention uses low-cost rare earth cerium as the main alloying element, and through microalloying of Mg, Zn, Zr, Y and a hot deformation process, a wrought heat-resistant aluminum alloy with a high rare earth content is obtained. This alloy has high strength under medium and high temperature long-term thermal exposure, maintains good thermal stability, and the preparation process is simple and can realize industrial production.

Description

Technical Field

[0001] The present invention relates to a high rare earth content wrought heat-resistant aluminum alloy and a preparation method thereof; it belongs to the field of non-ferrous metal materials. Background Art

[0002] Aluminum alloys are widely used in fields such as aerospace, transportation, and weaponry. However, the sharp decline in mechanical properties of aluminum alloys during service at medium and high temperatures restricts their further application; for example, the existing 2618 (Al-Cu-Mg series wrought heat-resistant alloy) aluminum alloy has a room temperature tensile strength of 426 MPa, but the tensile strength is only 150 MPa after 100 h of thermal exposure at 250 °C; the 2219 (Al-Cu series wrought heat-resistant alloy) aluminum alloy has a room temperature tensile strength of 450 MPa, but the tensile strength is only 200 MPa after 100 h of thermal exposure at 300 °C. Therefore, an important development goal of aluminum alloys is to improve the heat resistance at 200 - 400 °C.

[0003] China is rich in rare earth resources, among which the storage of cerium element ranks first among rare earth elements, and the price is 80 - 100 times lower than that of other key rare earths (such as scandium); moreover, the Al-Ce alloy designed based on the eutectic reaction of Al and Ce at 642 °C has good castability and heat resistance, which makes the Al-Ce alloy a candidate material for high-temperature automotive and aerospace applications. Czerwinski et al. (Materials Science and Engineering: A, 2021, 0921 - 5093) conducted experiments on Al-Ce binary alloys and compared the results with the commonly used A380 (Al-Si-Cu series) alloy and found that the Al-Ce binary system maintains superior mechanical properties in the range of 200 - 400 °C. However, the existing as-cast binary Al-Ce eutectic alloy has poor mechanical properties at room temperature, simple composition design, lack of solutes in the aluminum matrix, and a large number of primary coarse intermetallic compounds are not conducive to load transfer, resulting in stress concentration and microcracks, significantly reducing the mechanical properties.

[0004] Therefore, based on the above technical background, the wrought heat-resistant aluminum alloys prepared by the prior art are difficult to meet the application and industrialization requirements at medium and high temperatures. How to reduce the material production cost and prepare aluminum alloys with high room temperature mechanical properties and high thermal stability is a technical problem to be solved urgently at present. Summary of the Invention

[0005] Aiming at the differences from the prior art, the first object of the present invention is to provide a high rare earth content wrought heat-resistant aluminum alloy with good room temperature strength, high strength under long-term thermal exposure at medium and high temperatures, and good thermal stability. The aluminum alloy provided by the present invention can meet the requirements for application in medium and high temperature environments in fields such as aerospace.

[0006] The second object of the present invention is to provide a method for preparing a wrought heat-resistant aluminum alloy with a high rare earth content.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A wrought heat-resistant aluminum alloy with a high rare earth content according to the present invention, by mass percentage, consists of the following components: Ce 5.0 - 15.0%, Mg 1.0 - 5.0%, Zn 0.05 - 5.0%, Zr 0.05 - 0.2%, Y 0.05 - 0.15%, and the balance is Al.

[0009] The wrought heat-resistant aluminum alloy with a high rare earth content provided by the present invention uses low-cost rare earth cerium (Ce) as the main alloying element, and in addition, appropriate strengthening elements (Mg, Zn) and thermal stability elements (Zr, Y) are added. Among them, the main alloying element Ce will form a high-thermal-stability Al 11 Ce3 structure to obtain high heat resistance; the addition of Mg and Zn contents is to improve the precipitation strengthening and solid solution strengthening effects, which have an obvious strengthening effect on the matrix and help to obtain high mechanical properties. Zr is easy to form a metastable phase of Al3Zr with an L12 structure with Al, which has a low misfit degree and is difficult to transform from the metastable transition phase to the stable phase, thereby enhancing the high-temperature heat resistance of the alloy; Y can form nano-precipitates including Al3X, Al3(X1, X2) or even Al3(X1, X2, X3) with Al. The dispersed compounds formed by Zr, Y and Al can reduce the grain size of the alloy and improve the room temperature and high temperature strength of the alloy. At the same time, the addition of Mg, Zn, Zr and Y can reduce the growth rate of the primary Al 11 Ce3 compound, thereby making it refined. Under the synergistic effect of the above components, the wrought heat-resistant aluminum alloy with a high rare earth content provided by the present invention has a room temperature strength greater than 250 MPa and has a high strength under medium and high temperature long-term thermal exposure, and maintains good thermal stability.

[0010] A wrought heat-resistant aluminum alloy with a high rare earth content according to the present invention, by mass percentage, consists of the following components: Ce 10.5 - 15.0%, Mg 2.3 - 5.0%, Zn 1 - 5.0%, Zr 0.11 - 0.2%, Y 0.1 - 0.15%, and the balance is Al.

[0011] A wrought heat-resistant aluminum alloy with a high rare earth content according to the present invention, by mass percentage, consists of the following components: Ce 10.5 - 11%, Mg 2.3 - 2.9%, Zn 1 - 4.9%, Zr 0.11 - 0.12%, Y 0.1 - 0.11%, and the balance is Al.

[0012] A preparation method of a high-rare-earth-content deformed heat-resistant aluminum alloy. Pure Al, Al-Ce master alloy, pure Mg, Al-Zr master alloy, Al-Y master alloy, and pure Zn are weighed according to the designed aluminum alloy component ratio and melted to obtain a molten alloy liquid. The molten alloy liquid is poured into a mold to crystallize into an ingot, and the ingot is subjected to isothermal homogenization treatment and hot extrusion treatment in sequence to obtain the product.

[0013] The Al-Ce alloy prepared by this process method uses low-cost rare-earth Ce as the main alloying element. By regulating the contents of the main element (Ce), strengthening elements (Mg, Zn), and thermal stability elements (Zr, Y), and coordinating the isothermal homogenization treatment process and hot extrusion process conditions, a deformed heat-resistant aluminum alloy with excellent room-temperature mechanical properties is obtained. Such aluminum alloys prepared have high strength and good thermal stability under medium and high-temperature long-term thermal exposure. The preparation process provided by the present invention is simple and can be industrially produced.

[0014] As a preferred scheme, the melting process is as follows: Pure Al and Al-Ce master alloy are heated and melted at 780 - 850 °C; then the temperature is lowered to 730 - 780 °C, and pure Mg, Al-Zr master alloy, Al-Y master alloy, and pure Zn are added. After the alloy is completely melted, it is stirred, and then C2Cl6 is added to the melt and argon is filled for composite degassing and slag removal treatment to obtain a molten alloy liquid.

[0015] As a preferred scheme, after the molten alloy liquid is statically held at 730 - 780 °C for 5 - 30 min, it is poured into a mold to crystallize into an ingot.

[0016] As a preferred scheme, the mold is one of a steel mold or a copper mold.

[0017] As a preferred scheme, the temperature of the isothermal homogenization treatment is 430 - 500 °C, preferably 450 - 500 °C, and the time of the isothermal homogenization treatment is 8 - 24 h. Through the isothermal homogenization treatment, a homogenized ingot is obtained.

[0018] As a preferred scheme, the temperature of the hot extrusion treatment is 400 - 460 °C, and the extrusion ratio is 5 - 20.

[0019] After the Al-Ce alloy prepared by this process method undergoes subsequent heat treatment and hot working, the room-temperature strength reaches above 250 MPa and good thermal stability is maintained.

[0020] The characteristics of the present invention:

[0021] The present invention adopts smelting casting and heat treatment hot working processes, uses low-cost rare earth cerium (Ce) as the main alloying element, and obtains a deformed heat-resistant aluminum alloy with excellent room temperature mechanical properties by regulating the contents of the main element (Ce), strengthening elements (Mg, Zn) and heat stability elements (Zr, Y), the isothermal homogenization heat treatment process, and the hot extrusion process conditions. The obtained aluminum alloy has high strength under medium and high temperature long-term heat exposure and maintains good thermal stability. The preparation process is simple and can realize industrial production. Specific embodiments

[0022] Comparative example 1

[0023] A typical A380 aluminum-silicon-copper heat-resistant alloy is used, with its composition being Al-8.3Si-3.2Cu-0.3Mn-0.1Mg-0.05Ni-0.04Ti. The raw materials are added in the forms of pure aluminum, industrial pure magnesium, Al-Si master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Ni master alloy, and Al-Ti master alloy, etc. After melting at 780 - 800 °C, the alloy is poured into a steel mold at a pouring temperature of 730 °C. After the ingot alloy is homogenized at 500 °C for 6 h, it is aged at 170 °C for 5 h. The test results of its mechanical properties are shown in Table 1.

[0024] Comparative example 2

[0025] A typical 2XXX series 2618 aluminum-copper-magnesium deformed heat-resistant alloy is used, with its composition being Al-4.6Cu-0.5Mg-0.6Ag-0.35Mn-0.1Zr. The raw materials are added in the forms of pure aluminum, industrial pure magnesium, pure silver, Al-Cu master alloy, Al-Mn master alloy, and Al-Zr master alloy, etc. After melting and casting the alloy, the ingot alloy is homogenized at 420 °C for 6 h + 515 °C for 6 h, and then rolled into a thin plate about 1.5 mm thick at 470 °C. The thin plate is solution-treated at 515 °C for 6 h and quenched to room temperature in water, and then aged at 165 °C for 2 h. The test results of its mechanical properties are shown in Table 1.

[0026] Comparative example 3

[0027] A typical aluminum-cerium heat-resistant alloy is used, with its composition being Al-15Ce. The raw materials are added in the forms of pure aluminum and Al-Ce master alloy, etc. After melting, the above aluminum alloy is left standing for 30 min at 780–800 °C and then poured into a steel mold at a pouring temperature of 730 °C. The isothermal homogenization heat treatment time of the ingot at 500 °C is 24 h, and it is hot-extruded at 460 °C with an extrusion ratio of 5. The test results of its mechanical properties are shown in Table 1

[0028] Comparative example 4

[0029] The components of the alloy and their weight percentages are Al-5Ce-1Mg. The preparation method is as follows: (1) Weigh each component according to the designed alloy composition ratio. Use an electric resistance furnace to melt pure Al and Al-Ce master alloy at 850°C; then cool down to 750°C and add pure Mg. After the alloy is completely melted, stir, then add C2Cl6 to the melt and fill with argon for composite degassing and slag removal treatment to obtain a molten alloy liquid; (2) Keep the molten alloy liquid obtained in step (1) standing and heat-insulating at 730°C for 20 min, then pour it into a copper mold to crystallize into an ingot; (3) Perform isothermal homogenization heat treatment on the ingot obtained in step (2), the heat treatment temperature is 500°C, and after heat-insulating for 8 h, a homogenized ingot is obtained; (4) Perform hot extrusion treatment on the homogenized ingot obtained in step (3), the extrusion temperature is 460°C, and the extrusion ratio is 5. The test results of its mechanical properties are shown in Table 1.

[0030] Comparative Example 5

[0031] The components of the alloy and their weight percentages are Al-5Ce-0.05Zn. The preparation method is as follows: (1) Weigh each component according to the designed alloy composition ratio. Use an electric resistance furnace to melt pure Al and Al-Ce master alloy at 850°C; then cool down to 750°C and add pure Mg. After the alloy is completely melted, stir, then add C2Cl6 to the melt and fill with argon for composite degassing and slag removal treatment to obtain a molten alloy liquid; (2) Keep the molten alloy liquid obtained in step (1) standing and heat-insulating at 730°C for 20 min, then pour it into a copper mold to crystallize into an ingot; (3) Perform isothermal homogenization heat treatment on the ingot obtained in step (2), the heat treatment temperature is 500°C, and after heat-insulating for 8 h, a homogenized ingot is obtained; (4) Perform hot extrusion treatment on the homogenized ingot obtained in step (3), the extrusion temperature is 460°C, and the extrusion ratio is 5. The test results of its mechanical properties are shown in Table 1.

[0032] Comparative Example 6

[0033] The components of the alloy and their weight percentages are Al-10Ce-0.2Zr-0.1Y. The preparation method is as follows: (1) Weigh each component according to the designed alloy composition ratio. Use an electric resistance furnace to melt pure Al and Al-Ce master alloy at 850°C; then cool down to 750°C and add pure Mg. After the alloy is completely melted, stir and then add C2Cl6 to the melt and fill with argon for composite degassing and slag removal treatment to obtain a molten alloy liquid; (2) Keep the molten alloy liquid obtained in step (1) static at 730°C for 20 minutes and then pour it into a copper mold to crystallize into an ingot; (3) Perform isothermal homogenization heat treatment on the ingot obtained in step (2). The heat treatment temperature is 500°C, and after holding for 8 hours, a homogenized ingot is obtained; (4) Perform hot extrusion treatment on the homogenized ingot obtained in step (3). The extrusion temperature is 460°C, and the extrusion ratio is 5. The mechanical property test results are shown in Table 1.

[0034] Example 1

[0035] The components of the alloy and their weight percentages are Al-5Ce-1Mg-0.05Zn-0.05Zr-0.05Y. The preparation method is as follows:

[0036] (1) Weigh each component according to the designed alloy composition ratio. Use an electric resistance furnace to melt pure Al and Al-Ce master alloy at 850°C; then cool down to 750°C and add pure Mg, Al-Zr master alloy, Al-Y master alloy and pure Zn. After the alloy is completely melted, stir and then add C2Cl6 to the melt and fill with argon for composite degassing and slag removal treatment to obtain a molten alloy liquid; (2) Keep the molten alloy liquid obtained in step (1) static at 730°C for 5 minutes and then pour it into a copper mold to crystallize into an ingot; (3) Perform isothermal homogenization heat treatment on the ingot obtained in step (2). The heat treatment temperature is 500°C, and after holding for 8 hours, a homogenized ingot is obtained; (4) Perform hot extrusion treatment on the homogenized ingot obtained in step (3). The extrusion temperature is 460°C, and the extrusion ratio is 5. The mechanical property test results are shown in Table 1.

[0037] Example 2

[0038] The components and their weight percentages of the alloy are Al-10Ce-2.5Mg-0.05Zn-0.12Zr-0.1Y. The preparation method comprises the following steps: (1) Weigh each component according to the designed alloy composition ratio of aluminum alloy. Use an electric resistance furnace to melt pure Al and Al-Ce master alloy at 780 °C; then cool down to 780 °C and add pure Mg, Al-Zr master alloy, Al-Y master alloy and pure Zn. After the alloy is completely melted, stir and then add C2Cl6 into the melt, and charge argon for composite degassing and slag removal treatment to obtain a molten alloy liquid; (2) Keep the molten alloy liquid obtained in step (1) standing and heat-insulating at 750 °C for 30 min, and then pour it into a steel mold to crystallize into an ingot; (3) Carry out isothermal homogenization heat treatment on the ingot obtained in step (2), the heat treatment temperature is 450 °C, and after heat-insulating for 24 h, a homogenized ingot is obtained; (4) Carry out hot extrusion treatment on the homogenized ingot obtained in step (3), the extrusion temperature is 440 °C, and the extrusion ratio is 10:1. The test results of its mechanical properties are shown in Table 1.

[0039] Example 3

[0040] The components and their weight percentages of the alloy are Al-10.5Ce-2.9Mg-1Zn-0.11Zr-0.1Y. The preparation method comprises the following steps: (1) Weigh each component according to the designed alloy composition ratio of aluminum alloy. Use an electric resistance furnace to melt pure Al and Al-Ce master alloy at 800 °C; then cool down to 750 °C and add pure Mg, Al-Zr master alloy, Al-Y master alloy and pure Zn. After the alloy is completely melted, stir and then add C2Cl6 into the melt, and charge argon for composite degassing and slag removal treatment to obtain a molten alloy liquid; (2) Keep the molten alloy liquid obtained in step (1) standing and heat-insulating at 730 °C for 20 min, and then pour it into a steel mold to crystallize into an ingot; (3) Carry out isothermal homogenization heat treatment on the ingot obtained in step (2), the heat treatment temperature is 480 °C, and after heat-insulating for 10 h, a homogenized ingot is obtained; (4) Carry out hot extrusion treatment on the homogenized ingot obtained in step (3), the extrusion temperature is 440 °C, and the extrusion ratio is 10. The test results of its mechanical properties are shown in Table 1.

[0041] Example 4

[0042] The components and their weight percentages of the alloy are Al-11Ce-2.4Mg-3.2Zn-0.12Zr-0.1Y. The preparation method comprises the following steps: (1) According to the designed alloy component ratio of aluminum alloy, weigh each component, and use an electric resistance furnace to melt pure Al and Al-Ce master alloy at 800 °C; then cool down to 750 °C and add pure Mg, Al-Zr master alloy, Al-Y master alloy and pure Zn. After the alloy is completely melted, stir and then add C2Cl6 to the melt, and fill argon for composite degassing and slag removal treatment to obtain a molten alloy liquid; (2) Keep the molten alloy liquid obtained in step (1) standing and heat-insulating at 750 °C for 15 min, and then pour it into a steel mold to crystallize into an ingot; (3) Carry out isothermal homogenization heat treatment on the ingot obtained in step (2), the heat treatment temperature is 480 °C, and after heat-insulating for 10 h, a homogenized ingot is obtained; (4) Carry out hot extrusion treatment on the homogenized ingot obtained in step (3), the extrusion temperature is 440 °C, and the extrusion ratio is 20. The test results of its mechanical properties are shown in Table 1.

[0043] Example 5

[0044] The components and their weight percentages of the alloy are Al-10.5Ce-2.3Mg-4.9Zn-0.12Zr-0.11Y. The preparation method comprises the following steps: (1) According to the designed alloy component ratio of aluminum alloy, weigh each component, and use an electric resistance furnace to melt pure Al and Al-Ce master alloy at 780 °C; then cool down to 750 °C and add pure Mg, Al-Zr master alloy, Al-Y master alloy and pure Zn. After the alloy is completely melted, stir and then add C2Cl6 to the melt, and fill argon for composite degassing and slag removal treatment to obtain a molten alloy liquid; (2) Keep the molten alloy liquid obtained in step (1) standing and heat-insulating at 750 °C for 20 min, and then pour it into a steel mold to crystallize into an ingot; (3) Carry out isothermal homogenization heat treatment on the ingot obtained in step (2), the heat treatment temperature is 460 °C, and after heat-insulating for 15 h, a homogenized ingot is obtained; (4) Carry out hot extrusion treatment on the homogenized ingot obtained in step (3), the extrusion temperature is 440 °C, and the extrusion ratio is 12. The test results of its mechanical properties are shown in Table 1.

[0045] Example 6

[0046] The components of the alloy and their weight percentages are Al-15Ce-5Mg-5Zn-0.2Zr-0.15Y. The preparation method is as follows: (1) Weigh each component according to the designed alloy composition ratio of aluminum alloy. Use an electric resistance furnace to melt pure Al and Al-Ce master alloy at 850°C; then cool down to 740°C and add pure Mg, Al-Zr master alloy, Al-Y master alloy and pure Zn. After the alloy is completely melted, stir and then add C2Cl6 to the melt and fill with argon for composite degassing and slag removal treatment to obtain a molten alloy liquid; (2) Keep the molten alloy liquid obtained in step (1) standing and heat-insulating at 750°C for 20 min, and then pour it into a copper mold to crystallize into an ingot; (3) Perform isothermal homogenization heat treatment on the ingot obtained in step (2). The heat treatment temperature is 460°C, and after holding for 10 h, a homogenized ingot is obtained; (4) Perform hot extrusion treatment on the homogenized ingot obtained in step (3). The extrusion temperature is 400°C and the extrusion ratio is 8. The test results of its mechanical properties are shown in Table 1.

[0047] Table 1 Mechanical Properties of Examples and Comparative Examples

[0048]

[0049]

[0050] By comparing the performance parameter values of the examples and the comparative examples, it can be seen that: the high-rare-earth-content wrought heat-resistant aluminum alloy prepared by the present invention has excellent room temperature strength and also maintains good mechanical properties under medium and high temperature long-term heat exposure. It shows that through the interaction of alloy components and the synergistic effect of the process in the present invention, the alloy of the example has better room temperature mechanical properties and thermal stability than the alloy of the comparative example.

Claims

1. A preparation method of a heat-resistant wrought aluminum alloy with a high rare earth content, characterized in that: Pure Al, Al-Ce master alloy, pure Mg, Al-Zr master alloy, Al-Y master alloy, and pure Zn are taken according to the designed aluminum alloy component ratio. Pure Al and Al-Ce master alloy are heated and melted at 780 - 850 °C; then the temperature is lowered to 730 - 780 °C, and pure Mg, Al-Zr master alloy, Al-Y master alloy, and pure Zn are added. After the alloy is completely melted, it is stirred, and then C2Cl6 is added to the melt and argon is filled for composite degassing and slag removal treatment to obtain a molten alloy liquid. The molten alloy liquid is poured into a mold to crystallize into an ingot, and the ingot is successively subjected to isothermal homogenization heat treatment and hot extrusion treatment to obtain the product; The temperature of the isothermal homogenization heat treatment is 430 - 500 °C, and the time of the isothermal homogenization heat treatment is 8 - 24 h; The temperature of the hot extrusion treatment is 400 - 460 °C, and the extrusion ratio is 5 - 20; The described heat-resistant wrought aluminum alloy with a high rare earth content consists of the following components by mass percentage Composition: Ce 10.5 - 11%, Mg 2.3 - 2.9%, Zn 1 - 4.9%, Zr 0.11 - 0.12%, Y 0.1 - 0.11%, and the balance is Al.

2. The preparation method of a high rare earth content deformed heat-resistant aluminum alloy according to claim 1, characterized in that: After the molten alloy liquid is kept static and insulated at 730 - 780 °C for 5 - 30 min, it is poured into a mold to crystallize into an ingot.

3. The preparation method of a high rare earth content deformed heat-resistant aluminum alloy according to claim 1 or 2, characterized in that: The mold is one of a steel mold or a copper mold.

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