7xxx series rare earth aluminum alloy and preparation method thereof

Abstract

The invention provides a 7xxx series rare earth aluminum alloy and a preparation method thereof.The 7xxx series rare earth aluminum alloy comprises main alloy elements including 8.8%-9.4% of Zn, 2.0%-2.8% of Mg and 1.0%-1.5% of Cu and has the characteristic of high alloying; the high-alloying 7xxx series rare earth aluminum alloy with the tensile strength (Rm) larger than or equal to 650 MPa, the yield strength (Rp0.2) larger than or equal to 620 MPa and the ductility (A) larger than or equal to 5% is obtained by adding Sc and Tm rare earth elements and through the preparation method of the high-alloying 7xxx series rare earth aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of high-end Al-Zn-Mg-Cu wrought aluminum alloy materials, specifically to a 7xxx series rare earth aluminum alloy and its preparation method. Background Technology

[0002] 7xxx series aluminum alloys are aluminum alloys with Zn as the main alloying element, including Al-Zn-Mg and Al-Zn-Mg-Cu series alloys. Some alloys also contain small amounts of Mn, Cr, Zr, V, Ag, Ti, etc., and belong to heat-treatable wrought aluminum alloys. Currently, this series of aluminum alloys is usually cast using semi-continuous casting. However, semi-continuous casting has obvious "three-crystal zone" defects, namely fine-grained zone, columnar crystal zone, and coarse-grained zone, which leads to obvious microstructure and composition segregation problems in the ingots after semi-continuous casting. To solve the above problems, plastic deformation is adopted, that is, by rolling, extrusion, or forging, to obtain alloy materials with uniform microstructure and composition, thereby eliminating microstructure and composition segregation problems and meeting the requirements of alloy materials.

[0003] Currently, there are nearly 80 types of 7xxx series aluminum alloys commonly used, mainly Al-Zn-Mg-Cu alloys, accounting for about 74.3% of the total. Due to their high specific strength and hardness, good corrosion resistance and high plasticity, Al-Zn-Mg-Cu alloys have become the most important structural materials and are widely used in aviation, aerospace, shipbuilding, nuclear industry and weaponry.

[0004] However, with the development of science and technology, the demand for high-strength aluminum alloy materials is becoming increasingly urgent. Currently, the main way to improve the strength of alloys is to increase the content of the main alloying elements, but this inevitably brings certain challenges to casting. For example, ingots prepared by high alloying are prone to cracking in the traditional semi-continuous casting process, and also have serious problems such as microstructure and compositional segregation. Therefore, the cooling intensity is reduced in the semi-continuous casting process to ensure ingot formation. However, this operation results in coarse grains and severe segregation in the ingots. Even after subsequent plastic deformation treatment, the resulting alloy materials still have defects such as uneven composition, coarse grains, and low performance, which affect the development of high alloying materials and thus their application.

[0005] It is evident that providing a high-strength, high-alloy 7xxx series aluminum alloy is of great significance. Summary of the Invention

[0006] In view of this, the present invention provides a 7xxx series rare earth aluminum alloy and its preparation method. In this aluminum alloy, the main alloying elements are Zn: 8.8-9.4%, Mg: 2.0-2.8%, and Cu: 1.0-1.5%, which has the characteristics of high alloying. With the addition of Sc and Tm rare earth elements and the preparation method of the present invention, a high alloying 7xxx series rare earth aluminum alloy with tensile strength (Rm) ≥650MPa, yield strength (Rp0.2) ≥620MPa, and elongation (A) ≥5% is obtained.

[0007] The technical solution of the present invention is as follows: A 7xxx series rare earth aluminum alloy comprises the following components by weight percentage: Zn: 8.8-9.4%, Mg: 2.0-2.8%, Cu: 1.0-1.5%, Mn≤0.05%, Fe≤0.10%, Zr: 0.10-0.25%, Sc≤0.20%, Tm≤0.10%, Si≤0.10%, Ti: 0.05-0.10%, Cr≤0.05%, balance Al; Zn and Mg are the main strengthening elements in Al-Zn-Mg-Cu alloys, and the MgZn2 phase formed is the main strengthening phase. Within the ratio range of this invention (i.e., Zn / Mg is 3-5), the higher the Zn and Mg content, the more MgZn2 phase precipitates, and the higher the Rm and Rp0.2 of the alloy. However, when Zn / Mg > 5, it will lead to uneven phase distribution, resulting in severe segregation of the alloy structure, thereby reducing the alloy's deformation capacity, and also affecting the alloy's fracture toughness and SCC resistance. Therefore, in this invention, while ensuring casting performance, a Zn / Mg ratio of 3-5 and a Zn content of 8.8-9.4% are selected to improve the tensile properties of the alloy. Cu forms a sulfur phase (Al2CuMg) with Mg and Al. When the Cu content is 1.0-1.5% and the Zn / Mg ratio is 3-5, the sulfur phase and the MgZn2 phase work together to strengthen the alloy, further improving the Rm and Rp0.2. However, when the Cu content is less than 1.0%, the amount of sulfur phase is insufficient, and the strengthening effect is limited. When the Cu content exceeds 1.5%, the fracture toughness and stress corrosion resistance of the alloy deteriorate sharply. Therefore, this invention selects a Cu content of 1.0-1.5% to ensure the alloy has excellent corrosion resistance while maintaining its strength. Elongation depends on the uniformity and toughness of the alloy structure. When Mg: 2.0-2.8% and Cu: 1.0-1.5%, the precipitation of grain boundary embrittlement phase can be avoided, ensuring good plasticity. When Mg > 2.8% and Cu: 1.0-1.5%, a large number of residual phases will be formed, leading to a decrease in elongation.

[0008] In this invention, Zr exists in the form of Al3Zr and is coherent with the matrix; during the homogenization process, a secondary precipitated Al3Zr dispersed phase can be formed, which can play a role in dispersion strengthening on the one hand, and strongly inhibit the recrystallization of the alloy during hot working on the other hand, while reducing the quenching sensitivity of the alloy. In this invention, the Zr content is 0.10-0.25%. The main purpose of Ti is to refine the as-cast microstructure and increase the recrystallization temperature. In this invention, the Ti content is 0.05-0.10%. In this invention, two rare earth elements, Sc and Tm, are introduced into 7xxx series aluminum alloys. The difference in their atomic radii forms a core-shell structure (Al3Sc core + Al3Tm shell), which inhibits recrystallization and strengthens the alloy. Therefore, while improving high-temperature stability, it also inhibits recrystallization and promotes fine-grain strengthening, thereby enhancing the toughness of high-alloy aluminum alloys. Specifically, Sc ≤ 0.20%, and Tm ≤ 0.10%. Fe and Si readily form coarse, Fe-rich phases that are difficult to eliminate during homogenization and exhibit extreme brittleness. During deformation, these phases act as crack initiation sites, severely reducing the alloy's deformability. Furthermore, they affect the alloy's fracture toughness. Therefore, the Fe and Si contents are strictly controlled in aerospace materials, with Fe ≤ 0.10% and Si ≤ 0.10%. Mn and Cr elements can inhibit recrystallization, but excessive content can easily form coarse blocky phases, which seriously affect the material properties. Therefore, in order to avoid the formation of large brittle Mn / Cr-rich phases, the Mn / Cr content is reduced as much as possible in this invention. In this invention, Mn ≤ 0.05% and Cr ≤ 0.05%.

[0009] The above-mentioned method for preparing 7xxx series rare earth aluminum alloys uses melt impact printing for ingot casting, and the printing device used in the melt impact method... It includes a liquid supply system, a motion system, a jet system, a cooling system, and an intelligent control system; The liquid supply system is connected to the jet system, and the motion system is connected to the cooling system. The jet system, motion system, and cooling system are all located in a sealed chamber, while the liquid supply system is located outside the sealed chamber. The liquid supply system includes a liquid reservoir, a heating jacket is provided outside the liquid reservoir, and a temperature sensor is provided inside the liquid reservoir. The temperature sensor is connected to a temperature controller. The liquid reservoir is used to store high-temperature alloy melt, and the heating jacket is used to heat the melt to keep the melt within a certain temperature. The jet system includes a liquid guide tube, one end of which is connected to a liquid reservoir, and the other end is equipped with a nozzle, which is used for high-temperature melt jetting to achieve the melt impact process. The motion system is a three-axis motion platform, including a lifting device and a translation device. The translation device is located on the top of the lifting device and can reciprocate horizontally on the top of the lifting device. The cooling system includes cooling water pipes and a cooling platform connected to the cooling water pipes; The cooling platform is fixed on the translation device; Driven by the reciprocating motion of the translation device, the cooling platform can reciprocate to obtain a printing ingot of a certain length; Driven by the lifting device, the cooling system can move up and down; the distance between the cooling platform and the nozzle can be controlled to obtain a certain height of printing ingot while ensuring the impact effect; During cooling, cooling water is injected into the cooling platform through pipelines, and the cooling water cools the cooling platform to achieve cooling of the ingot printed on the cooling platform. The intelligent control system includes a PLC controller, which is connected to a temperature controller, a printing atmosphere controller, a jet pressure controller, a lifting device controller, a translation device controller, and a water flow controller. The melt impact printing process is fully and intelligently controlled through an intelligent control system.

[0010] The ingot is prepared using the melt impact method, and the process is as follows: S1, Place the melt in the reservoir and keep the melt warm; S2, control the melt temperature at 695-720℃, the injection pressure at 30-45kPa; the nozzle diameter at 1.0-1.5mm, and the distance between nozzles at 3-5mm; S3 controls the translation device to reciprocate at a speed of 40-150 mm / s to obtain the required ingot length. Based on the distance between the cooling platform and the nozzle, the lifting device is automatically adjusted to pull down at a constant value of 570-600mm to obtain the required ingot height while ensuring the same impact effect during the printing process. S4, during the printing process, control the cooling water flow rate to 300-450L / min, and after printing, control the cooling water flow rate to 150-300L / min; After printing, the high-alloy ingot has a large internal stress. The water flow rate is reduced to reduce the temperature difference between the surface and core of the printed ingot, thereby ensuring that the ingot does not crack due to thermal stress. The preparation method of the above-mentioned 7xxx series rare earth aluminum alloys is as follows: (1) Batching: Batching is carried out according to the chemical composition and weight percentage of the alloy; (2) Smelting: First, add aluminum ingots. When the temperature rises to 780±3℃, add Mg ingots, Zn ingots, pure copper, 10% Al-Zr master alloy, 2% Al-Sc master alloy and 10% Al-Tm master alloy. After the alloy is fully melted, refine the liquid metal at a refining temperature of 720±3℃. Then degas the metal. At the same time, add Al-5Ti-B master alloy at a ratio of 1-1.5‰. After degassing, allow the metal to stand for 15-20 minutes to obtain a high-temperature melt. (3) Printing ingots using the melt impact method; (4) Heat treatment of the ingot SS1, High-temperature heat treatment Three-stage heat treatment is carried out at a heating rate of 40℃ / h: Level 1: 320-370℃ × 3-8h; Level 2: 465-471℃ × 15-30h; Level 3: 473-475℃×12-30h; after the heat preservation is completed, quenching treatment should be carried out immediately, and the quenching transfer time should be ≤15s; The first stage of heat treatment not only relieves stress but also precipitates a large amount of rare earth Sc and Tm dispersed phases, which play a role in inhibiting recrystallization and dispersion strengthening. The main purpose of the second-stage heat treatment is to eliminate the low-melting-point eutectic α(Al)+T phase in the alloy, and to allow Zn, Mg, and Cu atoms to diffuse into the aluminum matrix and be evenly distributed. The third stage of heat treatment mainly involves high-temperature solution treatment. SS2, Low-temperature heat treatment: The quenched ingots are subjected to low-temperature heat treatment at a temperature of 118-125℃ for 15-30 hours.

[0011] Preferably, in step (2), Tm is added as a 10% Al-Tm master alloy.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: The method of this invention solves the problem of casting cracking in high-alloy 7xxx series aluminum alloys. Through the proportioning and preparation method of this invention, a high-alloy 7xxx series aluminum alloy with a grain size of 45-60μm is obtained. This high-alloy 7xxx series aluminum alloy has a tensile strength ≥650MPa, a yield strength ≥620MPa, and an elongation ≥5% without deformation. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the printing device of the present invention.

[0015] Figure 2 The images show the grain structure of the printed ingots of Examples 1-3 and Comparative Examples 1-5.

[0016] Figure 3 SEM images (100 μm) of the second phase microstructure of the printed ingots of Examples 1-3 and Comparative Examples 1-5.

[0017] Figure 4 The image shows a SEM image (2 μm) of the second phase structure of the ingot from Example 1.

[0018] Figure 1 In the middle, 101-liquid reservoir, 102-melt, 201-liquid guide pipe, 202-nozzle, 203-nozzle, 301-lifting device, 302-translation device, 401-cooling water pipeline, 402-cooling platform, 5-control cabinet. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0020] Printing apparatus for use in melt 102 impact method It includes a liquid supply system, a motion system, a jet system, a cooling system, and an intelligent control system; The liquid supply system is connected to the jet system, and the motion system is connected to the cooling system. The jet system, motion system, and cooling system are all located in a sealed chamber, while the liquid supply system is located outside the sealed chamber. The liquid supply system includes a liquid reservoir 101, a heating jacket is provided outside the liquid reservoir 101, and a temperature sensor is provided inside the liquid reservoir 101. The temperature sensor is connected to a temperature controller. The liquid reservoir 101 is used to store high-temperature alloy melt 102, and the heating jacket is used to heat the melt 102 to keep the melt 102 within a certain temperature. The heating jacket and temperature sensor are existing technologies and will not be described in detail here. The jet system includes a liquid guide tube 201, one end of which is connected to a liquid reservoir 101, and the other end is equipped with a nozzle 202. The nozzle 202 is equipped with a nozzle 203 for spraying high-temperature melt 102, thereby realizing the impact process of melt 102. The motion system is a three-axis motion platform, including a lifting device 301 and a translation device 302. The translation device 302 is located on the top of the lifting device 301 and can reciprocate horizontally on the top of the lifting device 301. The cooling system includes a cooling water pipe 401 and a cooling platform 402 connected to the cooling water pipe 401; The cooling platform 402 is fixed on the translation device 302; Driven by the reciprocating motion of the translation device 302, the cooling platform 402 can reciprocate to obtain a printing ingot of a certain length; Driven by the lifting device 301, the cooling system can move up and down; the distance between the cooling platform 402 and the nozzle 203 is controlled to obtain a certain height of printing ingot while ensuring the impact effect; During cooling, cooling water is injected into the cooling platform 402 through pipelines. The cooling water cools the cooling platform 402, thereby cooling the ingot printed on the cooling platform 402. The intelligent control system includes a PLC controller installed in the control cabinet 5. The PLC controller is connected to a temperature controller, a printing atmosphere controller, a jet pressure controller, a lifting device 301 controller, a translation device 302 controller, and a water flow controller. Among them, the PLC controller, temperature controller, printing atmosphere controller, jet pressure controller, lifting device 301 controller, translation device 302 controller, and water flow controller are all existing technologies and will not be described in detail; inventors in the field can install them in the corresponding positions according to their needs. The intelligent control system fully and intelligently controls the impact printing process of the melt 102. The melt 102 first flows into the jet system through the liquid supply system, and then the jet system sprays the melt 102 onto the transport system. At the same time, the cooling system cools the sprayed melt 102, thereby producing a printed ingot.

[0021] Example 1 A 7xxx series rare earth aluminum alloy comprises the following components by weight percentage (design values): Zn: 9.4%, Mg: 2.7%, Cu: 1.4%, Fe: 0.10%, Zr: 0.12%, Sc: 0.20%, Tm: 0.10%, Si: 0.10%, Ti: 0.10%, Cr: 0.05%, balance Al; The preparation method of the above-mentioned 7xxx series rare earth aluminum alloys is as follows: (1) Batching: Batching is carried out according to the chemical composition and weight percentage of the alloy; (2) Smelting: First, add aluminum ingots. When the temperature rises to 780℃, add Mg ingots, Zn ingots, pure copper, 10% Al-Zr master alloy, 2% Al-Sc master alloy and 10% Al-Tm master alloy. After the alloy is fully melted, refine the liquid metal at 720℃. Then degas it. At the same time, add Al-5Ti-B master alloy at a ratio of 1.5‰. After degassing, let it stand for 15 minutes to obtain a high-temperature melt. (3) Using the above printing device, aluminum alloy ingots are printed using the melt impact method. The thickness of the ingot is 100 mm and the length is 1500 mm. The process is as follows: S1, Place the high-temperature melt in the liquid storage tank and keep the melt at a constant temperature; S2, control the melt temperature at 700℃, the injection pressure at 40kPa; the nozzle diameter is 1.5mm, and the distance between nozzles is 4mm; S3 controls the translation device to reciprocate at a speed of 50 mm / s; The lifting device automatically adjusts its downward movement based on a constant value of 570mm, according to the distance between the cooling platform and the nozzle. S4, During the printing process, the cooling water flow rate is controlled at 360L / min, and after the printing is completed, the cooling water flow rate is 200L / min; After printing, a 100mm thick ingot is obtained. The high-alloy ingot has large internal stress. The water flow rate is reduced to reduce the temperature difference between the surface and core of the printed ingot, thereby ensuring that the ingot does not crack due to thermal stress. (4) Heat treatment of the printed ingot. SS1, High-temperature heat treatment Three-stage heat treatment is carried out at a heating rate of 40℃ / h: Level 1: 350℃ × 5h; Level 2: 465℃×20h; Level 3: 475℃×24h; After the heat preservation is completed, the ingot is immediately placed in 80℃ hot water for quenching treatment, and the quenching transfer time is ≤15s; Remove the ingot after it has completely cooled. SS2, Low-temperature heat treatment: The quenched ingots are placed in a heat treatment furnace for enhanced heat treatment at 125°C for 24 hours. They are then removed and air-cooled to obtain the ingot product.

[0022] Example 2 A 7xxx series rare earth aluminum alloy comprises the following components by weight percentage (design values): Zn: 9.2%, Mg: 2.2%, Cu: 1.4%, Fe: 0.07%, Zr: 0.12%, Sc: 0.20%, Tm: 0.10%, Si: 0.09%, Ti: 0.10%, Cr: 0.03%, balance Al; The preparation method of the above-mentioned 7xxx series rare earth aluminum alloys is as follows: (1) Batching: Batching is carried out according to the chemical composition and weight percentage of the alloy; (2) Smelting: First, add aluminum ingots. When the temperature rises to 780℃, add Mg ingots, Zn ingots, pure copper, 10% Al-Zr master alloy, 2% Al-Sc master alloy and 10% Al-Tm master alloy. After the alloy is fully melted, refine the liquid metal at a refining temperature of 720℃. Then degas it. At the same time, add Al-5Ti-B master alloy at a ratio of 1‰. After degassing, allow it to stand for 15 minutes to obtain a high-temperature melt. (3) Using a printing device, aluminum alloy ingots are printed using the melt impact method. The ingots are 100mm thick and 1500mm long. The process is as follows: S1, Place the high-temperature melt in the liquid storage tank and keep the melt at a constant temperature; S2, control the melt temperature at 720℃, the injection pressure at 32kPa; the nozzle diameter is 1.5mm, and the distance between nozzles is 4mm; S3 controls the translation device to reciprocate at a speed of 50 mm / s; The lifting device automatically adjusts its downward movement based on a constant value of 570mm, according to the distance between the cooling platform and the nozzle. S4, During the printing process, the cooling water flow rate is controlled at 360 L / min, and after the printing is completed, the cooling water flow rate is 200 L / min; After printing, a 100mm thick ingot is obtained. The high-alloy ingot has large internal stress. The water flow rate is reduced to reduce the temperature difference between the surface and core of the printed ingot, thereby ensuring that the ingot does not crack due to thermal stress. (4) Heat treatment of the printed ingot. SS1, High-temperature heat treatment Three-stage heat treatment is carried out at a heating rate of 40℃ / h: Level 1: 350℃ × 5h; Level 2: 465℃×20h; Level 3: 475℃×24h; After the heat preservation is completed, the ingot is immediately placed in 80℃ hot water for quenching treatment, and the quenching transfer time is ≤15s; Remove the ingot after it has completely cooled. SS2, Low-temperature heat treatment: The quenched ingots were subjected to a strengthening heat treatment at 125°C for 24 hours, and then air-cooled to obtain the ingot product.

[0023] Example 3 A 7xxx series rare earth aluminum alloy comprises the following components by weight percentage (design values): Zn: 9.3%, Mg: 2.0%, Cu: 1.4%, Fe: 0.05%, Zr: 0.12%, Sc: 0.20%, Tm: 0.10%, Si: 0.10%, Ti: 0.10%, Cr: 0.01%, balance Al; The preparation method of the above-mentioned 7xxx series rare earth aluminum alloys is as follows: (1) Batching: Batching is carried out according to the chemical composition and weight percentage of the alloy; (2) Smelting: First, add aluminum ingots. When the temperature rises to 780℃, add Mg ingots, Zn ingots, pure copper, 10% Al-Zr master alloy, 2% Al-Sc master alloy and 10% Al-Tm master alloy. After the alloy is fully melted, refine the liquid metal at 720℃. Then degas it. At the same time, add Al-5Ti-B master alloy at a ratio of 1.5‰. After degassing, let it stand for 20 minutes to obtain a high-temperature melt. (3) Using a printing device, aluminum alloy ingots are printed using the melt impact method. The thickness of the aluminum alloy ingots is 100 mm and the length is 1500 mm. The process is as follows: S1, Place the high-temperature melt in the liquid storage tank and keep the melt at a constant temperature; S2, control the melt temperature at 720℃, the injection pressure at 32kPa; the nozzle diameter is 1.5mm, and the distance between nozzles is 4mm; S3 controls the translation device to reciprocate at a speed of 50 mm / s; The lifting device automatically adjusts its downward movement based on a constant value of 570mm, according to the distance between the cooling platform and the nozzle. S4, During the printing process, the cooling water flow rate is controlled at 360 L / min, and after the printing is completed, the cooling water flow rate is 200 L / min; After printing, a 100mm thick ingot is obtained. The high-alloy ingot has large internal stress. The water flow rate is reduced to reduce the temperature difference between the surface and the core of the ingot, thereby ensuring that the ingot does not crack due to thermal stress. (4) Heat treatment of aluminum alloy ingots SS1, High-temperature heat treatment Three-stage heat treatment is carried out at a heating rate of 40℃ / h: Level 1: 350℃ × 5h; Level 2: 465℃×20h; Level 3: 475℃×24h; After the heat preservation is completed, quenching treatment should be carried out immediately; After the high-temperature heat treatment, the ingot is immediately placed in 80℃ hot water for quenching. The transfer time should not exceed 15 seconds. After it is completely cooled, the aluminum alloy ingot is taken out. SS2, Low-temperature heat treatment: The quenched ingots were subjected to a strengthening heat treatment at 125°C for 24 hours, and then air-cooled to obtain the ingot product.

[0024] Comparative Example 1 The traditional method for casting a 100mm ingot involves the following preparation process: (1) Ingredients: Ingredients were prepared according to the alloy chemical composition and weight percentage of Example 2; (2) Smelting: Same as in Example 2; Tm is added as a 10% Al-Tm master alloy; (3) Semi-continuous casting The casting process follows traditional casting methods to obtain semi-continuous casting ingots with a diameter of 100 mm and a cooling water flow rate of 1300 L / min. (4) Heat treatment of round ingots SS1, High-temperature heat treatment Three-stage heat treatment is carried out at a heating rate of 40℃ / h: Level 1: 350℃ × 5h; Level 2: 465℃×20h; Level 3: 475℃×24h; after the heat preservation is completed, quenching treatment should be carried out immediately. After the high-temperature heat treatment, the round ingot is immediately placed in 80℃ hot water for quenching. The transfer time should not exceed 15 seconds. After it is completely cooled, the round ingot is taken out. SS2, Low-temperature heat treatment: The quenched round ingots were subjected to a strengthening heat treatment at 125°C for 24 hours, and then removed and air-cooled.

[0025] Comparative Example 2 A 7xxx series rare earth aluminum alloy comprises the following components by weight percentage (design values): Zn: 8.8%, Mg: 3.0%, Cu: 1.4%, Fe: 0.07%, Zr: 0.12%, Sc: 0.20%, Tm: 0.10%, Si: 0.09%, Ti: 0.10%, Cr: 0.03%, balance Al; The preparation method of the above-mentioned 7xxx series rare earth aluminum alloys is as follows: (1) Batching: Batching is carried out according to the chemical composition and weight percentage of the alloy; (2) Smelting: Same as step (2) in Example 2; (3) Same as step (3) in Example 2; (4) Same as step (4) in Example 2; to obtain the ingot product.

[0026] Comparative Example 3 A 7xxx series rare earth aluminum alloy comprises the following components by weight percentage (design values): Zn: 8.8%, Mg: 1.8%, Cu: 1.4%, Fe: 0.07%, Zr: 0.12%, Sc: 0.20%, Tm: 0.10%, Si: 0.09%, Ti: 0.10%, Cr: 0.03%, balance Al; The preparation method of the above-mentioned 7xxx series rare earth aluminum alloys is as follows: (1) Batching: Batching is carried out according to the chemical composition and weight percentage of the alloy; (2) Smelting: Same as step (2) in Example 2; (3) Same as step (3) in Example 2; (4) Same as step (4) in Example 2; to obtain the ingot product.

[0027] Comparative Example 4 A 7xxx series rare earth aluminum alloy comprises the following components by weight percentage (design values): Zn: 9.4%, Mg: 3.0%, Cu: 1.4%, Fe: 0.07%, Zr: 0.12%, Sc: 0.20%, Tm: 0.10%, Si: 0.09%, Ti: 0.10%, Cr: 0.03%, balance Al; The preparation method of the above-mentioned 7xxx series rare earth aluminum alloys is as follows: (1) Batching: Batching is carried out according to the chemical composition and weight percentage of the alloy; (2) Smelting: Same as step (2) in Example 2; (3) Same as step (3) in Example 2; (4) Same as step (4) in Example 2; to obtain the ingot product.

[0028] Comparative Example 5 A 7xxx series rare earth aluminum alloy comprises the following components by weight percentage (design values): Zn: 9.4%, Mg: 1.8%, Cu: 1.4%, Fe: 0.07%, Zr: 0.12%, Sc: 0.20%, Tm: 0.10%, Si: 0.09%, Ti: 0.10%, Cr: 0.03%, balance Al; The preparation method of the above-mentioned 7xxx series rare earth aluminum alloys is as follows: (1) Batching: Batching is carried out according to the chemical composition and weight percentage of the alloy; (2) Smelting: Same as step (2) in Example 2; (3) Same as step (3) in Example 2; (4) Same as step (4) in Example 2; to obtain the ingot product.

[0029] The statistical results of ingot preparation in Examples 1-3 and Comparative Examples 1-5 are shown in Table 1 below: Table 1 Statistical analysis of casting results

[0030] The elemental content in the ingots of Examples 1-3 and Comparative Examples 1-5 was detected, and the results are shown in Table 2 below: Table 2. Elemental composition of aluminum alloy ingots

[0031] The as-cast OM microstructure of the ingots of Examples 1-3 and Comparative Examples 1-5 was analyzed, and the results are shown in Table 3 and 4. Figure 1 ,as follows: Table 3. Results of Omniform Detection of Aluminum Alloy Ingots in As-cast State

[0032] The mechanical properties of the ingots from Examples 1-3 and Comparative Examples 1-5 were tested, and the results are shown in Table 4 and... Figure 2 ,as follows: Table 4. Test results of mechanical properties of aluminum alloy ingots

[0033] Based on the above test results, it can be seen that: (1) Under the same conditions, the alloy properties obtained by melt impact technology are higher than those obtained by semi-continuous casting. (2) Zn: 8.8-9.4%, Mg: 2.0-2.8%, Cu: 1.0-1.5%, Mn≤0.05%, Fe≤0.10%, Zr: 0.10-0.25%, Sc≤0.20%, Tm≤0.10%, Si≤0.10%, Ti: 0.05-0.10%, Cr≤0.05%, balance Al; this is the optimal composition range for this patent. (3) The 7xxx series rare earth aluminum alloy of the present invention can obtain a material with tensile strength ≥650MPa, yield strength ≥620MPa and elongation ≥5% without deformation.

[0034] In the embodiments and comparative examples of the present invention, the prior art will not be described again.

[0035] Comparative Example 6 7085 alloy, 7055 alloy and 7050 alloy are available. The composition of the alloying elements is shown in Table 5, as follows: Table 5 Alloy element composition

[0036] As can be seen from Table 5, the present invention differs from alloys 7050, 7055, and 7085 in terms of elemental composition, as follows: Firstly, regarding the main strengthening elements (Zn / Mg / Cu), the Zn content of this invention is significantly higher than that of 7050 alloy, 7055 alloy, and 7085 alloy, achieving high alloying; by precisely controlling the Cu content, corrosion resistance deterioration is avoided; and the Mg content is matched with Cu / Mg < 1 to suppress harmful S phase. Secondly, in terms of rare earth elements, this invention adds the rare earth elements Sc and Tm, and controls Sc≤0.20% and Tm≤0.10%; this invention introduces Sc+Tm for the first time to form a core-shell structure strengthening phase; Thirdly, in terms of refining / auxiliary elements, this invention has a higher Ti content and stricter Mn / Cr control, reducing brittle phases; in terms of impurity element control, the Fe and Si contents are controlled between 7055 and 7085, balancing process feasibility and performance. Using the method of Comparative Example 1, 100mm 7085 alloy ingots, 7055 alloy ingots, and 7050 alloy ingots were cast. The process is as follows: (1) Batching: Batching is carried out according to the alloy chemical composition and weight percentage in Table 5; (2) Smelting: Same as in Example 2; (3) Semi-continuous casting The casting process follows traditional casting methods to obtain semi-continuous casting ingots with a diameter of 100 mm and a cooling water flow rate of 1300 L / min. (4) Heat treatment of round ingots SS1, High-temperature heat treatment Three-stage heat treatment is carried out at a heating rate of 40℃ / h: Level 1: 400℃ × 10h; Level 2: 465℃×20h; Level 3: 475℃×24h; after the heat preservation is completed, quenching treatment should be carried out immediately. After the high-temperature heat treatment, the round ingot is immediately placed in 80℃ hot water for quenching. The transfer time should not exceed 15 seconds. After it is completely cooled, the round ingot is taken out. SS2, Low-temperature heat treatment: The quenched round ingots were subjected to a strengthening heat treatment at 125°C for 24 hours, and then removed and air-cooled.

[0037] The performance tests of the 7050, 7055, and 7085 alloy ingots prepared above, and the statistical results compared with the performance of the alloy of the present invention, are shown in Table 6 below: Table 6 Summary of Alloy Properties

[0038] Table 6 summarizes the test results of ingots from three batches of casting with different element ratios, showing the properties of 7050 alloy ingots, 7055 alloy ingots, and 7085 alloy ingots. As can be seen from Table 6, firstly, the method of this invention can solve the three-crystal zone defects produced by existing semi-continuous casting, refining the ingot grains to 42-48 μm (above 150 μm for 7050 alloy ingots, 7055 alloy ingots, and 7085 alloy ingots), without compositional segregation; secondly, the heat treatment process of this invention, in synergy with rare earth elements Sc and Tm, ensures uniform precipitation of the strengthening phase, eliminating the need for subsequent plastic deformation; and thirdly, this invention yields ingots with a high yield rate and no casting cracks. Its performance far surpasses that of traditional alloys without deformation, solving the problem of the contradiction between strength and toughness in existing technologies.

[0039] Based on the test results of the embodiments and comparative examples of this invention, as well as the 7050 alloy ingot, 7055 alloy ingot, and 7085 alloy ingot, it can be concluded that: This invention introduces Sc and Tm into 7xxx series aluminum alloys for the first time, forming a core-shell structure strengthening phase with an Al3Sc core and an Al3Tm shell. Figure 4 The grain size is refined to 42-48μm, and brittleness is avoided under the premise of high alloying (Zn 8.8-9.4%), so as to achieve a balance between high strength and high toughness. This invention employs melt impact casting, abandoning the traditional semi-continuous casting method. By controlling the injection pressure and cooling flow parameters, it solves the industry pain points of cracking and compositional segregation in high-alloy aluminum alloy casting. The ingot can achieve the performance without subsequent plastic deformation. In this invention, by controlling the composition and content of the main alloying elements, the formation of harmful S phase can be suppressed, and the content of impurities can be controlled to reduce brittle phases, while ensuring corrosion resistance, thereby achieving the goals of high strength, high corrosion resistance, and high plasticity. In this invention, a three-stage high-temperature heat treatment process is adopted, which forms a closed loop with melt impact casting and rare earth elements, and the strengthening phase is uniformly dispersed and precipitated. This allows the alloy to achieve a tensile strength of ≥650MPa and a yield strength of ≥620MPa without deformation processing, reaching the performance level of 7055 after traditional deformation processing, and significantly reducing production costs.

[0040] The rare earth alloy prepared by this invention has high strength and toughness, and is mainly used in aerospace load-bearing components, deep-sea exploration equipment, and the weapons industry.

[0041] Although the present invention has been described in detail with reference to preferred embodiments, it is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope of the claims.

Claims

1. A 7xxx-series rare earth aluminum alloy, characterized by, Comprising the following weight percentages of components: Zn: 8.8-9.4%, Mg: 2.0-2.8%, Cu: 1.0-1.5%, Mn≤0.05%, Fe≤0.10%, Zr: 0.10-0.25%, Sc≤0.20%, Tm≤0.10%, Si≤0.10%, Ti: 0.05-0.10%, Cr≤0.05%, the balance being Al.

2. The method of producing a 7xxx-series rare earth aluminum alloy according to claim 1, wherein The ingot is printed using a melt impact method, a printing device used in the melt impact method, It comprises a liquid supply system, a motion system, a jet system, a cooling system and an intelligent control system. The liquid supply system is connected with the jet system, and the motion system is connected with the cooling system, wherein the jet system, the motion system and the cooling system are located in a closed chamber, and the liquid supply system is located outside the closed chamber. The liquid supply system comprises a liquid storage tank, a heating jacket is arranged outside the liquid storage tank, and a temperature sensor is arranged inside the liquid storage tank, and the temperature sensor is connected with a temperature controller; The jet system comprises a liquid guide pipe, one end of the liquid guide pipe is connected with the liquid storage tank, and the other end is provided with a spray head, and a nozzle is arranged on the spray head; The motion system is a three-axis motion platform, comprising a lifting device and a translation device, the translation device is arranged on the top of the lifting device, and the translation device can reciprocate horizontally on the top of the lifting device; The cooling system comprises a cooling water pipeline and a cooling platform connected with the cooling water pipeline; The cooling platform is fixed on the translation device.

3. The method of producing a 7xxx-series rare earth aluminum alloy according to claim 2, wherein The ingot is prepared using the melt impact method, and the process is as follows: S1, the melt is placed in the liquid storage tank, and the melt is kept warm; S2, control the melt temperature to be 695-720℃, the jet pressure to be 30-45kPa; the nozzle diameter to be 1.0-1.5mm, and the distance between nozzles to be 3-5mm; S3, control the translation device to reciprocate at a speed of 40-150mm / s; According to the distance between the cooling platform and the nozzle, the lifting device is automatically adjusted to make a downward movement with a constant value of 570-600mm; S4, during the printing process, control the cooling water flow to be 300-450L / min, and after the printing is completed, the cooling water flow is 150-300L / min.

4. The method of producing a 7xxx-series rare earth aluminum alloy according to claim 3, wherein The process is as follows: (1) batching: batching according to the alloy chemical composition and weight percentage; (2) melting: first add aluminum ingot, when the temperature rises to 780±3℃, add Mg ingot, Zn ingot, pure copper, 10% Al-Zr intermediate alloy, 2% Al-Sc intermediate alloy and Al-Tm intermediate alloy, after the alloy is fully melted, refine the metal liquid, the refining temperature is 720±3℃, then degas, at the same time, add Al-5Ti-B intermediate alloy at a ratio of 1-1.5‰, after degassing, it should be fully static, the static time is 15-20min, and high temperature melt is obtained; (3) print the ingot using the melt impact method; (4) heat treatment of the ingot SS1, high temperature heat treatment Three-stage heat treatment at a temperature rising speed of 40℃ / h: First stage: 320-370℃×3-8h; Second stage: 465-471℃×15-30h; Third stage: 473-475℃ x 12-30h; immediately after the holding, quenching treatment is performed, quenching transfer time ≤15s; SS2, low temperature heat treatment: The ingot after the quenching treatment is subjected to low temperature heat treatment, heat treatment temperature 118-125℃, holding for 15-30h.

5. The method of producing a 7xxx-series rare earth aluminum alloy according to claim 4, wherein In step (2), Tm is added in the form of 10% Al-Tm intermediate alloy.

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