A high-toughness aluminum-scandium alloy material and its preparation method

Abstract

This invention relates to the field of alloy materials technology, specifically to a high-toughness aluminum-scandium alloy material and its preparation method. This invention overcomes the problem of poor toughness in high-toughness aluminum-scandium alloy materials. The composition includes aluminum, zinc 5.5%-7.4%, magnesium 0.6%-1.4%, copper 0.8%-1.8%, manganese 0.1%-0.6%, zirconium 0.05%-0.26%, scandium 0.03%-0.05%, rare earth elements 0.05%-0.26%, silicon 0.06%-0.11%, and crystal phase regulating elements 0.05%-0.15%. By synergistically forming vacancy-solute atom complexes with trace amounts of Sn and Si, combined with high-temperature melting, special refining, and gradient heat treatment processes, the resulting high-toughness aluminum-scandium alloy material achieves ultra-high toughness while maintaining high strength, making it suitable for impact-absorbing structural components in aerospace and military industries.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, specifically to a high-toughness aluminum-scandium alloy material and its preparation method. Background Technology

[0002] 7000 series Al-Zn-Mg-Cu aluminum alloys are key structural materials in the aerospace field. To achieve higher specific strength, current technologies often involve adding trace amounts of scandium to form a dispersed strengthening phase. However, scandium-containing 7-series aluminum alloys still have significant drawbacks in practical applications: In pursuit of ultimate strength, existing alloys often result in coarse and continuous precipitates at grain boundaries, leading to severe grain boundary softening. When aerospace components are subjected to impact, intergranular fracture is highly likely, making it difficult to balance impact toughness and elongation. Furthermore, traditional high-performance aluminum alloys often incorporate the precious metal silver to promote precipitation, but this is costly and increases stress corrosion susceptibility. While existing technologies have attempted to introduce low-melting-point elements for microalloying, the unclear compositional synergy logic leads to segregation during casting, making it difficult to lock in the ideal solid solution state.

[0003] Chinese patent CN106636787B discloses a high-toughness die-cast aluminum alloy with Si: 8.5%-10.5% and Cu: 2.5%-4.5%. This technology optimizes the microstructure by adding rare earth element cerium and aluminum-titanium-boron modifiers. However, this alloy belongs to the aluminum-silicon casting alloy system. Although it has good fluidity, its matrix strength is far lower than that of the 7-series super-hard aluminum alloys used in aerospace. Moreover, its toughness improvement mainly relies on the modification of eutectic silicon, which cannot solve the problem of brittle fracture caused by grain boundary softening in aerospace load-bearing components under high stress. CN110885941B discloses a high-toughness aluminum alloy material with Si: 10%-13%, Fe: 0.8%-1%, and Cu: 2.5%-3.2%, which improves its performance by controlling the Fe content and adding Cr. However, in actual research, it was found that when facing the requirement of high damage tolerance for aerospace aluminum alloys, this solution lacks the synergistic control of the precipitation kinetics of trace elements such as Sc and Zr and low-melting-point elements such as Sn and In, resulting in insufficient nucleation density of strengthening phases. While achieving ultra-high strength, the elongation and impact toughness of the material still have considerable room for improvement.

[0004] To this end, a high-toughness aluminum-scandium alloy material and its preparation method are proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a high-toughness aluminum-scandium alloy material and its preparation method. The high-toughness aluminum-scandium alloy material comprises the following components by mass percentage: zinc 6.8%-7.6%, magnesium 0.7%-1.3%, copper 0.8%-1.5%, manganese 0.3%-0.6%, zirconium 0.10%-0.15%, scandium 0.11%-0.20%, lanthanum 0.012%-0.024%, cerium 0.028%-0.056%, silicon 0.08%-0.14%, titanium 0.06%-0.10%, crystal phase regulating elements 0.05%-0.15%, iron <0.1%, with the balance being aluminum; the mass ratio of lanthanum to cerium is 3:7. This invention solves the technical problems of insufficient elongation, poor impact energy absorption, and weak resistance to long-term stress corrosion cracking in existing aerospace 7-series aluminum alloys under high strength conditions by introducing trace amounts of Sn and slightly excess Si to form vacancy-solute atom complexes, combined with high-temperature melting, special refining, and gradient heat treatment processes. The high-toughness aluminum alloy of this invention achieves a tensile strength of 556 MPa and an elongation after fracture of 18.2%, representing an elongation increase of approximately 85.7% compared to existing aerospace 7075-T651 alloys. It also achieves an impact energy of 42.6 J and a folding angle exceeding 175°. This meets the stringent requirements of the aerospace and military industries for structural components with a tensile strength greater than 540 MPa and an elongation greater than 17%.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a high-toughness aluminum-scandium alloy material, which is composed of the following elements by mass percentage: zinc 5.5%-7.4%, magnesium 0.6%-1.4%, copper 0.8%-1.8%, manganese 0.1%-0.6%, zirconium 0.05%-0.26%, scandium 0.03%-0.05%, rare earth elements 0.05%-0.26%, silicon 0.06%-0.11%, titanium 0.06%-0.12%, crystal phase regulating elements 0.01%-0.05%, iron <0.12%, and the balance being aluminum; The crystal phase control element is selected from one of tin, indium, silver, and antimony; The preparation method is as follows: pure aluminum ingots, alloys, pure magnesium ingots, and pure zinc ingots are sequentially added and heated to melt in a graphite crucible. The melting is carried out by electromagnetic stirring, and a crystal phase control alloy is added to obtain a molten alloy. High-purity nitrogen gas is blown into the molten alloy through a graphite gas pipe, and a refining agent and aluminum-based alloy are added at a controlled rate for chemical refining. The round ingot substrate is obtained by vertical wet well casting and forced extreme cooling with circulating cold water. The round ingot substrate is subjected to two-stage homogenization, quenching, and gradient aging treatment to prepare a high-toughness aluminum-scandium alloy material. The alloys are aluminum-copper alloys, aluminum-manganese alloys, aluminum-silicon alloys, aluminum-zirconium alloys, and aluminum-scandium alloys.

[0007] Preferably, the preparation method of the molten alloy is as follows: aluminum ingots are placed in a graphite crucible and heated to 780°C to melt. Al-Cu50, Al-Mn20 and Al-Si20 are added sequentially and stirred evenly. Al-Zr10 and Al-Sc2 are added to a medium-frequency induction melting furnace, followed by pure magnesium ingots and pure zinc ingots. The furnace is held at 800°C for 40 minutes. At 1000Hz-2500Hz, the induced current is used to promote the full solid solution of Sc and Zr atoms. The thermocouple indication of the silicon nitride protection tube is monitored, and the frequency is reduced to 1000-1500Hz. When the aluminum liquid cools down to 740°C, Al-Sn10 is added. Sn has a low melting point, and adding it at this temperature can significantly reduce the volatilization loss of Sn and inhibit its oxidation segregation at high temperatures. The molten alloy is obtained by melting.

[0008] Preferably, the preparation method of the molten alloy is as follows: Aluminum ingots are placed in a graphite crucible and heated to 780°C to melt. Al-Cu50, Al-Mn20, and Al-Si20 are added sequentially and stirred until homogeneous. Al-Zr10 and Al-Sc2 are then added to a medium-frequency induction melting furnace, followed by pure magnesium ingots and pure zinc ingots. The mixture is held at 815°C for 55 minutes. min, Induction current is used to promote the full solid solution of Sc and Zr atoms; the thermocouple indication of silicon nitride protection tube is monitored, the frequency is reduced to 1000-1500Hz, and Al-In10 is added when the aluminum liquid cools down to 730℃. In has a low melting point, and the lower addition temperature and subsequent rapid dissolution in 35 minutes can reduce oxidation melting.

[0009] Preferably, the preparation method of the molten alloy is as follows: aluminum ingots are placed in a graphite crucible and heated to 805°C to melt. Al-Cu50, Al-Mn20 and Al-Si20 are added sequentially and stirred evenly. Al-Zr10 and Al-Sc2 are added to a medium-frequency induction melting furnace, followed by pure magnesium ingots and pure zinc ingots. The furnace is held at 825°C for 35 minutes, and the induced current is used to promote the full solid solution of Sc and Zr atoms. The thermocouple indication of the silicon nitride protection tube is monitored, and the frequency is reduced to 1000-1500Hz. When the aluminum liquid cools down to 760°C, Al-Ag10 is added, and the molten alloy is obtained by melting.

[0010] Preferably, the preparation method of the molten alloy is as follows: aluminum ingots are placed in a graphite crucible and heated to 795°C to melt. Al-Cu50, Al-Mn20 and Al-Si20 are added sequentially and stirred evenly. Al-Zr10 and Al-Sc2 are added to a medium-frequency induction melting furnace, followed by pure magnesium ingots and pure zinc ingots. The electromagnetic stirring effect is used to ensure the uniform distribution of trace amounts of Sn. The furnace is held at 810°C for 45 minutes, and the induced current is used to promote the full solid solution of Sc and Zr atoms. The thermocouple indication of the silicon nitride protection tube is monitored, and the frequency is reduced to 1000-1500Hz. When the aluminum liquid cools to 760-770°C, Al-Sb10 is added, and high-frequency induction stirring at 2500Hz is used for 5-10 minutes to ensure complete Sb atomization and suppress oxide scale formation. Since Sb has a high melting point, the feeding temperature needs to be maintained above 760°C to ensure complete alloying. The molten alloy is obtained by melting.

[0011] The preferred chemical refining process is as follows: A graphite gas inlet tube is inserted deep into the bottom of the crucible, and high-purity nitrogen is continuously blown in at 755°C. Al-RE10 is added, followed by 2.2%-2.9% refining agent at a rate of 15-25 g / min. Refining is carried out for 35-50 minutes. If frequent large bubbles appear on the surface of the molten aluminum, accompanied by dense white smoke and splashing, it indicates that the feeding speed is too fast, and the feeding speed should be reduced. Al-Ti5B1 wire is added for grain refinement treatment, followed by standing for 35-60 minutes. This facilitates slag-liquid separation in the high-Mn system. During the refining process, RE and Sn work synergistically; Sn alters the diffusion activation energy of solute atoms, resulting in a finer and more uniform precipitation of the strengthening phase.

[0012] Preferably, the preparation process of the round ingot substrate is as follows: a 25kg sample is cast in a vertical wet well using a round ingot with a diameter of Φ100mm. The vertical wet well casting machine and the matching circulating water-cooled copper crystallizer are turned on, the circulating cooling water is adjusted, and the water pump pressure is adjusted to 0.30-0.45MPa to ensure that the ingot achieves forced extreme cooling from the edge to the center. The casting temperature is lowered to 675-705℃ to lock the Sn in solid solution state.

[0013] Preferably, the two-stage homogenization process is as follows: the cooled round ingot substrate is treated at 340°C for 12 hours, then adjusted to 470°C at a rate of 5-10°C / min, and maintained for another 8 hours.

[0014] Preferably, the quenching process is as follows: the material obtained after the two-stage homogenization treatment is taken out and placed on a forced cold air platform. The quenching ingot should be placed on a bracket with a bottom grid to ensure that the cold air can blow on the sample from all directions from top to bottom 360°. The outlet wind speed should be controlled at 20-30m / s, the cooling rate should not be less than 30℃ / min, and the ingot should be cooled to room temperature of 28℃.

[0015] The preferred gradient aging process is as follows: the quenched material is transferred into a preheated aging furnace within 2 hours and aged at 100-110℃ for 10-18 hours. Since Sn has a strong ability to capture vacancies and nucleates very quickly, shortening the time can prevent excessive growth of the initial precipitated phase. Finally, the temperature is adjusted to 155-170℃ at a rate of 10℃ / min and maintained for 4-6 hours. Low-temperature final aging helps to maintain the Sn-induced nanoscale ultrafine structure, fundamentally solving the brittleness risk caused by grain boundary softening, and obtaining a high-toughness aluminum-scandium alloy material.

[0016] This invention also provides a high-toughness aluminum-scandium alloy material, the raw materials for which include pure aluminum ingots, pure magnesium ingots, pure zinc ingots, aluminum-copper master alloys, aluminum-manganese master alloys, aluminum-zirconium master alloys, aluminum-scandium master alloys, aluminum-rare earth master alloys, aluminum-silicon master alloys, aluminum-tin master alloys, aluminum-silver master alloys, aluminum-titanium-boron wires, and special refining agents.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The high-toughness aluminum alloy of the present invention improves tensile strength and elongation after fracture by effectively capturing vacancies with elements such as Sn / In and precisely controlling the distribution of precipitated phases. The elongation is improved compared with the existing conventional aerospace 7075-T651 material. The prepared high-toughness aluminum alloy material meets the stringent requirements of aerospace and military fields for structural components that require both high load-bearing capacity and ultra-high energy absorption toughness.

[0018] 2. For existing Al-Zn-Mg-Cu-Sc alloys, by introducing trace elements such as Sn and Si to form vacancy-solute atom complexes, the precipitation behavior is optimized, solving the problems of excessively long aging cycles and easy segregation of strengthening phases at grain boundaries in conventional Sc / Zr strengthened aluminum alloys. Without the need for extreme ultra-high temperature solid solution, the gradient aging process designed in this invention can induce dispersed and isolated nanoscale strengthening phases in a short time, thereby improving yield strength. This achieves simultaneous growth in strength and toughness while improving production efficiency.

[0019] 3. The alloy of the present invention has good damage tolerance and service safety. Experimental data shows that the impact energy of the alloy of the present invention reaches more than 41.2J, the folding angle can reach 174°-180° and no microcracks are generated, which solves the problem of uncontrolled failure such as explosion and splashing of traditional high-strength aluminum alloys during the collision process.

[0020] 4. This invention, through a combination of high-temperature smelting, special refining, and gradient heat treatment processes, coupled with the modification of grain boundaries by trace elements, significantly improves the chemical stability of the material under harsh environments. The alloy of this invention maintains a high stress intensity factor even after 700 hours of corrosion in a 3.5% NaCl solution. This not only solves the hidden danger of early stress corrosion cracking in aerospace aluminum alloys but also significantly reduces the crack propagation rate, extending the service life and maintenance cycle of components. Attached Figure Description

[0021] Figure 1 The tensile strength and yield strength test results of the high-toughness aluminum-scandium alloy materials produced in Examples 1-4 and Comparative Examples 1-4 of this invention; Figure 2 The corrosion resistance test results of the high-toughness aluminum-scandium alloy materials in Production Example 1 and Comparative Example 4 of the present invention are shown below. Figure 3 The image shows the metallographic structure of the high-toughness aluminum-scandium alloy material prepared in Example 1 of this invention at 50X. Figure 4 The metallographic structure of the high-toughness aluminum-scandium alloy material prepared in Example 1 of the present invention is shown at 100X. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Please see Figures 1 to 2 This invention provides a high-toughness aluminum-scandium alloy material and its preparation method, the technical solution of which is as follows: Production Example 1: The aluminum alloy material of this invention accelerates the crystal phase transformation by introducing Sn (tin) and supplementing it with trace amounts of Si (silicon) to form a vacancy-solute atom complex. Zn: 6.5%, Mg: 1.0%, Cu: 1.2%, Mn: 0.4%, Zr: 0.15%, Sc: 0.05%, RE(La / Ce): 0.12%, Sn: 0.03%, Si: 0.09%, Ti: 0.08%, Fe: 0.08%, balance Al.

[0024] S1 Raw Material Preparation and Preparation: The purity of the pure metal ingots is all >99.99%. Isostatic high-purity graphite crucibles with a volume >15L are selected, and their surfaces are pre-sprayed with boron nitride coating to prevent Sc and Zr from reacting with the container wall and introducing impurities. The raw materials to be used are 1.625kg pure zinc ingots, 0.25kg pure magnesium ingots, 0.6kg Al-Cu50, 0.5kg Al-Mn20, 0.375kg Al-Zr10, 0.625kg Al-Sc2, 0.30kg Al-RE10, 0.113kg Al-Si20, 0.075kg Al-Sn10, 0.40kg Al-Ti5B1 wire, and high-purity aluminum ingots, totaling 25kg. The amount of materials fed has been factored in to compensate for the burning loss of flammable elements.

[0025] S2 melting and high-temperature alloying: Aluminum ingots are placed in a graphite crucible and heated to 780℃ to melt. Al-Cu50, Al-Mn20 and Al-Si20 are added sequentially and stirred evenly. Al-Zr10 and Al-Sc2 are added to a medium-frequency induction melting furnace, followed by pure magnesium ingots and pure zinc ingots. The electromagnetic stirring effect is used to ensure the uniform distribution of trace amounts of Sn. The furnace is held at 800℃ for 40 minutes, and the induced current is used to promote the full solid solution of Sc and Zr atoms. The thermocouple indication of the silicon nitride protection tube is monitored. When the aluminum liquid cools down to 740℃, Al-Sn10 is added, and the molten alloy is obtained. S3 Chemical Refining - Promoting Crystal Phase Transformation: A graphite gas-conducting tube is inserted deep into the bottom of the crucible, and high-purity nitrogen is continuously blown in at 730℃. Al-RE10, i.e., an aluminum-based alloy, is added, and a 2.5% concentration of refining agent is added at a rate of 15 g / min. Refining is carried out for 40 min, followed by the addition of Al-Ti5B1 wire for grain refinement treatment, and the mixture is allowed to stand for 50 min. During the refining process, RE and Sn work synergistically. Sn changes the diffusion activation energy of solute atoms, resulting in a finer and more uniform precipitation of the strengthening phase. S4 Physical Cooling: Using a Φ100mm diameter round ingot, a 25kg sample is cast in a vertical wet well. The vertical wet well casting machine and the matching circulating water-cooled copper crystallizer are turned on, the circulating cooling water is adjusted, and the water pump pressure is adjusted to 0.3MPa to ensure that the ingot achieves forced extreme cooling from the edge to the center. The casting temperature is lowered to 680℃ to lock the Sn solid solution state. S5 gradient heat treatment: Treat at 340℃ for 12 hours, then adjust to 470℃ at a rate of 10℃ / min and maintain for another 8 hours. After the treatment, remove the sample and place it on a forced cooling air platform. The quenched ingot should be placed on a bracket with a bottom grid to ensure that the cold air can blow on the sample from all directions (360°). The outlet air velocity should be controlled at 20 m / s, and the cooling rate should be 30℃ / min. Cool the ingot to room temperature (28℃). Within 2 hours, transfer it to an aging furnace preheated to 100℃ and treat at 100℃ for 10 hours. Due to Sn's strong ability to capture vacancies, nucleation is extremely fast. Shortening the treatment time can prevent excessive growth of the initial precipitated phase. Finally, adjust to 155℃ at a rate of 10℃ / min and maintain for 4 hours. Low-temperature final aging helps maintain the Sn-induced nanoscale ultrafine structure, fundamentally solving the brittleness risk caused by grain boundary softening, and obtaining a high-toughness aluminum-scandium alloy material.

[0026] The refining agent has a mass ratio of 45% MgCl2, 30% KCl, 15% Na3AlF6 and 10% mixed rare earth fluorides. The above raw materials are dried in an oven at 200°C for 4 hours to remove physical water, and then mixed and ground in a ball mill to below 100 mesh. The mixture is then sealed, dried and stored. The mixed rare earth fluoride is REF3.

[0027] Metallographic observation was performed on the material obtained in Example 1, and its microstructure is as follows: Figure 3 (50X) and Figure 4 As shown in (100X). As can be seen from the figure, the alloy grains prepared by the process of the present invention are uniform, and the strengthening phase is visible in a dispersed and isolated state within the grains at different magnifications. No obvious coarse precipitates or continuous low-melting-point brittle films were found at the grain boundaries.

[0028] In this example, the content of Mn and Zr was increased to pin dislocations through a high-density dispersed phase, while the In element was responsible for guiding the strengthening phase to be uniformly distributed within the crystal. See Production Example 2 for details. Zn: 5.5%, Mg: 1.4%, Cu: 1.0%, Mn: 0.6%, Zr: 0.26%, Sc: 0.03%, RE(La / Ce): 0.26%, ln: 0.01%, Si: 0.06%, Ti: 0.06%, Fe: 0.05%, balance Al.

[0029] S1 Raw Material Preparation and Preparation: Select an isostatic high-purity graphite crucible with a volume >15L. Its surface is pre-sprayed with boron nitride coating to prevent Sc and Zr from reacting with the container wall and introducing impurities. The raw materials to be used are 1.375kg pure zinc ingot, 0.35kg pure magnesium ingot, 0.5kg Al-Cu50, 0.75kg Al-Mn20, 0.65kg Al-Zr10, 0.375kg Al-Sc2, 0.65kg Al-RE10, 0.025kg Al-In10, 0.075kg Al-Si20, 0.30kg Al-Ti5B1 wire, and high-purity aluminum ingot, totaling 25kg. The amount of materials fed has been factored in to compensate for the burning loss of flammable elements.

[0030] S2 melting and high-temperature alloying: Aluminum ingots are placed in a graphite crucible and heated to 780℃ to melt. Al-Cu50, Al-Mn20 and Al-Si20 are added sequentially and stirred evenly. Al-Zr10 and Al-Sc2 are added to a medium-frequency induction melting furnace, followed by pure magnesium ingots and pure zinc ingots. The furnace is held at 815℃ for 55 minutes, and the induced current is used to promote the full solid solution of Sc and Zr atoms. The thermocouple indication of the silicon nitride protection tube is monitored. When the aluminum liquid cools down to 730℃, Al-In10 is added to melt. S3 Chemical Refining - Promoting Crystal Phase Transformation: A graphite gas inlet tube is inserted deep into the bottom of the crucible, and high-purity nitrogen is continuously blown in at 735°C. Al-RE10 is added, and a 2.2% concentration of refining agent is slowly added. The refining process is carried out for 35 minutes, and then allowed to stand for 60 minutes. S4 Physical Cooling: Using a Φ100mm diameter round ingot, a 25kg sample is cast in a vertical wet well. The vertical wet well casting machine and the matching circulating water-cooled copper crystallizer are turned on, the circulating cooling water is adjusted, and the water pump pressure is adjusted to 0.35MPa to ensure that the ingot achieves forced extreme cooling from the edge to the center. The casting temperature is lowered to 675℃ to lock the Sn solid solution state. S5 gradient heat treatment: Treat at 340℃ for 12 hours, adjust to 470℃ at a rate of 10℃ / min, and continue to maintain for 8 hours. After the treatment, remove the sample and place it on a forced cooling air platform. The quenched ingot should be placed on a bracket with a bottom grid to ensure that the cold air can blow on the sample from all directions from top to bottom 360°. The outlet air velocity should be controlled at 20-30m / s, and the cooling rate should not be less than 30℃ / min. Cool the ingot to room temperature. Within 2 hours, transfer it to a preheated aging furnace and treat at 110℃ for 12 hours. Finally, adjust to 155℃ at a rate of 10℃ / min and maintain for 6 hours to obtain a high-toughness aluminum-scandium alloy material.

[0031] This example demonstrates how the combination of extremely low magnesium (Mg) and ultra-high scandium (Sc), along with Ag to suppress the rapid growth of precipitates, ensures that the material possesses extremely strong deformation capacity under impact. See Production Example 3 for details. Zn: 7.0%, Mg: 0.6%, Cu: 1.8%, Mn: 0.1%, Zr: 0.05%, Sc: 0.05%, RE(La / Ce): 0.05%, Ag: 0.04%, Si: 0.08%, Ti: 0.12%, Fe: 0.12%, balance Al and high-purity aluminum ingots (99.99%), total 25kg.

[0032] S1 Raw Material Preparation and Preparation: Select an isostatic high-purity graphite crucible with a volume >15L, and pre-spray boron nitride coating on its surface to prevent Sc and Zr from reacting with the container wall and introducing impurities; Prepare the following raw materials: 1.75kg pure zinc ingot, 0.15kg pure magnesium ingot, 0.90kg Al-Cu50, 0.125kg Al-Mn20, 0.125kg Al-Zr10, 0.625kg Al-Sc2, 0.125kg Al-RE10, 0.10kg Al-Ag10, 0.10kg Al-Si20, 0.60kg Al-Ti5B1 wire, and high-purity aluminum ingot, totaling 25kg. The amount of material added has been factored in to compensate for the burning loss of flammable elements.

[0033] S2 melting and high-temperature alloying: Aluminum ingots were placed in a graphite crucible and heated to 805℃ to melt. Al-Cu50, Al-Mn20, and Al-Si20 were added sequentially and stirred evenly. Al-Zr10 and Al-Sc2 were added to a medium-frequency induction melting furnace, followed by pure magnesium ingots and pure zinc ingots. The furnace was held at 825℃ for 35 minutes, and the induced current was used to promote the full solid solution of Sc and Zr atoms. The thermocouple indication of the silicon nitride protection tube was monitored. When the aluminum liquid cooled to 760℃, Al-Ag10 was added, and the alloy was melted to obtain a molten alloy. Ag significantly reduced the interfacial energy and guided the uniform distribution of the strengthening phase within the grain. S3 Chemical Refining - Promoting Crystal Phase Transformation: A graphite gas delivery tube is inserted deep into the bottom of the crucible, and high-purity nitrogen is continuously blown in at 750°C. Al-RE10 is added, and a refining agent with a concentration of 2.9% is slowly added. The refining process is carried out for 45 minutes, and then allowed to stand for 40 minutes. S4 Physical Cooling: Using a Φ100mm diameter round ingot, cast a 25kg sample in a vertical wet well. Turn on the vertical wet well casting machine and the matching circulating water-cooled copper crystallizer, adjust the circulating cooling water, and adjust the water pump pressure to 0.45MPa to ensure that the ingot achieves forced extreme cooling from the edge to the center, and lower the casting temperature to 695℃. S5 gradient heat treatment: The sample is treated at 340℃ for 12 hours, then adjusted to 470℃ at a rate of 10℃ / min and held for another 8 hours. After this, it is removed and placed on a forced-air cooling platform. The quenched ingot should be placed on a bracket with a bottom grid to ensure that the cold air can blow onto the sample from all directions (360°). The outlet air velocity should be controlled at 20-30 m / s, and the cooling rate should not be less than 30℃ / min. The ingot is then cooled to room temperature. Within 2 hours, it is transferred to a preheated aging furnace and treated at 100℃ for 18 hours. Due to Sn's strong ability to capture vacancies and its extremely rapid nucleation, shortening the treatment time can prevent excessive growth of the initial precipitated phase. Finally, the temperature is adjusted to 170℃ at a rate of 10℃ / min and held for 4 hours to obtain a high-toughness aluminum-scandium alloy material. Because Ag and Mg atoms have strong interactions, significantly promoting the formation of early GP zones, the first-stage aging at 100℃ aims to induce a large number of uniform nuclei, while the second-stage aging at 170℃ forces the strengthening phase to transform into a thermally stable metastable phase, fundamentally solving the stress corrosion risk of aerospace components.

[0034] This example utilizes the synergistic effect of Sb and trace amounts of Si to form a dispersed nano-Sb-Si phase, which protects the grain boundaries from weakening under high-temperature conditions. See Production Example 4 for details. Zn: 7.4%, Mg: 1.0%, Cu: 0.8%, Mn: 0.5%, Zr: 0.20%, Sc: 0.04%, RE(La / Ce): 0.20%, Sb: 0.05%, Si: 0.11%, Ti: 0.07%, Fe: 0.10%, balance Al.

[0035] S1 Raw Material Preparation and Preparation: Select an isostatic high-purity graphite crucible with a volume >15L. Its surface is pre-sprayed with boron nitride coating to prevent Sc and Zr from reacting with the container wall and introducing impurities. Prepare the following raw materials: 1.85kg pure zinc ingot, 0.25kg pure magnesium ingot, 0.40kg Al-Cu50, 0.625kg Al-Mn20, 0.50kg Al-Zr10, 0.50kg Al-Sc2, 0.50kg Al-RE10, 0.125kg Al-Sb10, 0.138kg Al-Si20, 0.35kg Al-Ti5B1 wire, and pure aluminum ingot, totaling 25kg. The amount of material added has been factored in to compensate for the burning loss of flammable elements.

[0036] S2 melting and high-temperature alloying: Aluminum ingots are placed in a graphite crucible and heated to 795℃ to melt. Al-Cu50, Al-Mn20 and Al-Si20 are added sequentially and stirred evenly. Al-Zr10 and Al-Sc2 are added to a medium-frequency induction melting furnace, followed by pure magnesium ingots and pure zinc ingots. The furnace is held at 810℃ for 45 minutes, and the induced current is used to promote the full solid solution of Sc and Zr atoms. The thermocouple indication of the silicon nitride protection tube is monitored. When the aluminum liquid cools down to 765℃, Al-Sb10 is added to melt and obtain a molten alloy. S3 Chemical Refining - Promoting Crystal Phase Transformation: A graphite gas inlet tube is inserted deep into the bottom of the crucible, and high-purity nitrogen is continuously blown in at 755°C. Al-RE10 is added, and a 2.5% concentration of refining agent is slowly added. The refining process is carried out for 50 minutes, and then allowed to stand for 35 minutes. Sb is easily introduced with trace amounts of oxides, so the refining time is extended. S4 Physical Cooling: Using a Φ100mm diameter round ingot, cast a 25kg sample in a vertical wet well. Turn on the vertical wet well casting machine and the matching circulating water-cooled copper crystallizer, adjust the circulating cooling water, and adjust the water pump pressure to 0.30MPa to ensure that the ingot achieves forced extreme cooling from the edge to the center, and lower the casting temperature to 705℃. S5 gradient heat treatment: Treat at 340℃ for 12 hours, adjust to 470℃ at a rate of 10℃ / min, and continue to maintain for 8 hours. After the treatment, remove the sample and place it on a forced cooling air platform. The quenching ingot should be placed on a bracket with a bottom grid to ensure that the cold air can blow on the sample from all directions from top to bottom 360°. The outlet air velocity should be controlled at 20-30 m / s, and the cooling rate should not be less than 30℃ / min. Cool the ingot to room temperature. Within 2 hours, transfer it to a preheated aging furnace and treat at 105℃ for 16 hours. Finally, adjust to 165℃ at a rate of 5℃ / min and maintain for 4.5 hours to obtain high-toughness aluminum-scandium alloy material.

[0037] Comparative Example 1: The Sn content in Example 1 was adjusted to 0.5%, while other production conditions remained unchanged.

[0038] Comparative Example 2: The two-stage homogenization and gradient aging in Example 1 were cancelled. In the homogenization stage, a single high-temperature homogenization treatment at 470°C for 20 hours was used, followed by furnace cooling. In the aging stage, a conventional single-stage high-temperature aging treatment at 175°C for 8 hours was used.

[0039] Comparative Example 3 uses Alcoa 7075-T651 aluminum alloy sheet for aerospace standard parts.

[0040] Comparative Example 4: Zn: 6.5%, Mg: 1.0%, Cu: 1.2%, Mn: 0.4%, Zr: 0.15%, RE(La / Ce): 0.12%, Si: 0.09%, Ti: 0.08%, Fe: 0.08%, balance Al.

[0041] S1 Raw Material Preparation and Preparation: Select an isostatic high-purity graphite crucible with a volume >15L, and pre-spray boron nitride coating on its surface to prevent Sc and Zr from reacting with the container wall and introducing impurities; prepare the raw materials to be used: pure aluminum ingots, pure zinc ingots, and pure magnesium ingots; alloys include Al-Cu50, Al-Mn20, Al-Zr10, Al-Sc2, Al-RE10, and Al-Ti5B1 wire.

[0042] S2 melting and high-temperature alloying: aluminum ingots are placed in a graphite crucible and heated to 740℃ to melt. Al-Zr10 is added to a medium-frequency induction melting furnace and held at 750℃ for 45 minutes. The induced current is used to promote the full solid solution of Zr atoms. S3 Chemical Refining - Promoting Crystal Phase Transformation: A graphite gas guide tube is inserted deep into the bottom of the crucible to maintain the furnace temperature at 720℃-730℃. Pure zinc ingots, pure magnesium ingots, Al-Cu50, Al-Mn20, Al-RE10, and Al-Ti5B1 wire are added. A commercially available general-purpose chloride refining agent, 9RF, from Henan Aivens Metallurgical Materials Co., Ltd., is used. The mixture is manually stirred for 10 minutes using a conventional chloride refining agent, followed by slag removal. S4 Physical Cooling: Use a Φ100mm diameter round ingot to cast a 25kg sample in a vertical wet well. Turn on the vertical wet well casting machine and the matching circulating water-cooled copper crystallizer, adjust the circulating cooling water, and adjust the water pump pressure to 0.30MPa to ensure that the ingot achieves forced extreme cooling from the edge to the center, and lower the casting temperature to 700℃. S5 homogenization heat treatment: Adjust to 465℃ at a rate of 10℃ / min and continue to maintain for 24h. After the end, heat the cast rod to 420℃ for extrusion. After extrusion, air cool to room temperature. Within 2h, transfer it into a preheated aging furnace and treat at 120℃ for 24h. Air cool to room temperature to obtain high-toughness aluminum-scandium alloy material.

[0043] Mechanical properties of high-toughness aluminum-scandium alloy materials produced in different embodiments and comparative examples were tested according to GB / T228.1-2021. Samples were taken from the long axis of the extruded profile according to GB / T2975 and processed into circular cross-sectional proportional specimens (d0=5mm, L0=5d0=25mm). Testing was performed using an electronic universal testing machine. The test results are shown in Table 1 and... Figure 1 As shown.

[0044] Table 1 Mechanical test results of high-toughness aluminum-scandium alloy materials To evaluate the overall service performance of high-toughness aluminum-scandium alloy materials, the following properties were tested according to GB / T229, GB / T6398, and stress corrosion standards. The comprehensive test results for each group of service performance are as follows: Table 2. Test results of comprehensive service performance of high-toughness aluminum-scandium alloy materials As can be seen from the comparison between Production Example 1 and Comparative Example 1, when the Sn content is within the trace range defined in this application, the high binding energy of Sn with vacancies can significantly promote intracrystalline nucleation and form an extremely fine distribution of reinforcing phase, thereby enabling the tensile strength and elongation after fracture to meet the requirements of this application. However, when the Sn content is too high, the excessive Sn, due to its extremely low melting point, tends to undergo severe segregation at the grain boundaries during solidification and heat treatment, forming a low-melting-point brittle film. This makes the material prone to intergranular fracture when under stress, resulting in a sharp decrease in the elongation, impact energy, and folding angle of the extruded parts, and the toughness does not meet the requirements.

[0045] As can be seen from the comparison between Production Example 1 and Comparative Example 2, when the two-stage homogenization and gradient aging process designed in this application is adopted, the low-temperature pretreatment at 340℃ can fully stabilize the trace Sn, and the pre-aging at 100℃ utilizes the vacancy trapping effect of Sn to accelerate nucleation and prevent the coarsening of the strengthening phase. However, when a single high-temperature homogenization and conventional single-stage high-temperature aging are adopted, as in Comparative Example 2, due to the lack of the early nucleation process, the strengthening phase coarsens and precipitates at the grain boundaries, forming an obvious non-precipitate zone. This not only reduces the tensile strength and yield strength of the alloy, but also increases the fatigue crack propagation rate, making the overall service performance of the extruded component unable to meet the requirements.

[0046] A comparison of Production Examples 1-4 with Comparative Example 3 shows that while the existing standard 7075-T651 aluminum alloy possesses high static load strength, it lacks the nanoscale Al3(Sc,Zr) dispersed phase formed by Sc and Zr to suppress recrystallization, and it also lacks elements such as Sn and In to regulate the crystal phase. This results in coarse grain structure and dense grain boundary precipitates, leading to extremely low impact energy and fold angle of the extruded component under axial crushing or high-speed impact, resulting in poor energy absorption performance in actual aerospace service. Example 3 uses Ag instead of Sn, utilizing its unique microalloying effect in the 7-series alloys. Experimental data shows that although Ag is slightly more expensive than Sn, at extremely low addition levels, combined with the gradient heat treatment process of this invention, its fold angle and fracture toughness exhibit extremely high stability. This demonstrates that even in application scenarios where toxic elements must be avoided, this process system still possesses strong adaptability and advanced features.

[0047] A comparison of Production Example 1 and Comparative Example 4 shows that when Sn and Sc are missing, the precipitation driving force of the intragranular strengthening phase is significantly reduced. Because Comparative Example 4 uses a lower melting temperature and conventional refining and stirring process, the solid solution degree of Zr is insufficient, preventing the formation of a high-density dispersed pinned phase. This hinders the improvement of the tensile strength and yield strength of the extruded component, and in the stress corrosion environment, the uneven distribution of the grain boundary phase leads to... ISCC The reduced resistance means that the material's service stability cannot meet the requirements.

[0048] Representative examples 1 and 4 were selected and subjected to accelerated corrosion tests to observe their stress intensity factor K. I The decay over time. Referring to GB / T15970.6-2007, standard compact tensile specimens were used, fatigue cracks were pre-induced, and a constant deformation loading method was employed. The specimens were immersed in a 3.5% NaCl solution, and an initial stress intensity factor was set. At fixed time points, specifically 100h, 200h, 400h, and 700h, the crack tip opening displacement or remaining load-bearing capacity was measured, and the critical stress intensity factor K at which the material can withstand stress without unstable propagation was calculated. ISCC The result is rounded to an integer, as shown below. Figure 2 As shown, the high-toughness aluminum-scandium alloy material prepared in Example 1 has good corrosion resistance.

[0049] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for preparing a high-toughness aluminum-scandium alloy material, characterized in that, By mass percentage, the constituent elements include: zinc 5.5%-7.4%, magnesium 0.6%-1.4%, copper 0.8%-1.8%, manganese 0.1%-0.6%, zirconium 0.05%-0.26%, scandium 0.03%-0.05%, rare earth elements 0.05%-0.26%, silicon 0.06%-0.11%, titanium 0.06%-0.12%, crystal phase control elements 0.05%-0.15%, iron less than 0.1%, and the balance being aluminum; The crystal phase control element is selected from one of tin, indium, silver and antimony; The preparation method is as follows: pure aluminum ingots, alloy, pure magnesium ingots, and pure zinc ingots are sequentially added to a graphite crucible and heated to melt. The melting is carried out by electromagnetic stirring, and a crystal phase control alloy is added to obtain a molten alloy. High-purity nitrogen gas is blown into the molten alloy through a graphite gas pipe, and a refining agent and aluminum-based alloy are added at a controlled rate for chemical refining. The round ingot substrate is obtained by vertical wet well casting and forced extreme cooling with circulating cold water. The round ingot substrate is subjected to two-stage homogenization, quenching, and gradient aging treatment to prepare the high-toughness aluminum-scandium alloy material. The alloys are aluminum-copper alloys, aluminum-manganese alloys, aluminum-silicon alloys, aluminum-zirconium alloys, and aluminum-scandium alloys.

2. The method for preparing the high-toughness aluminum-scandium alloy material according to claim 1, characterized in that, The mass ratio of zinc to magnesium in the constituent elements is 5.0-9.25; the mass ratio of magnesium to copper is 0.4-1.

5. The rare earth elements are composed of lanthanum and cerium, with lanthanum accounting for 0.012%-0.024% and cerium accounting for 0.028%-0.056% by mass percentage.

3. The method for preparing the high-toughness aluminum-scandium alloy material according to claim 1, characterized in that, The preparation method of the molten alloy is as follows: the pure aluminum ingot is placed in the graphite crucible and heated to 780°C to melt. The alloy is added to a medium-frequency induction melting furnace, along with the pure magnesium ingot and the pure zinc ingot. The mixture is held at 800-815°C for 40-55 minutes. When the aluminum melt cools to 740°C, the crystal phase regulating alloy is added and melted. The crystal phase regulating alloy is an aluminum-tin alloy. The aluminum-tin alloy contains 10% tin, with the balance being aluminum. The alloy consists of an aluminum-zirconium alloy, an aluminum-scandium alloy, the pure magnesium ingot, and the pure zinc ingot.

4. The method for preparing the high-toughness aluminum-scandium alloy material according to claim 3, characterized in that, When the molten aluminum cools to 730°C, the crystal phase control alloy is added and melted; the crystal phase control alloy is an aluminum-indium alloy; the aluminum-indium alloy contains 10% indium and the remainder is aluminum.

5. The method for preparing the high-toughness aluminum-scandium alloy material according to claim 3, characterized in that, When the aluminum liquid cools down to 760°C, the crystal phase control alloy is added and melted; the crystal phase control alloy is an aluminum-silver alloy, in which the silver content is 10% and the balance is aluminum.

6. The method for preparing the high-toughness aluminum-scandium alloy material according to claim 3, characterized in that, When the molten aluminum cools to 765°C, the crystal phase control alloy is added and melted; the crystal phase control alloy is an aluminum-antimony alloy, in which the antimony content is 10% and the balance is aluminum.

7. The method for preparing the high-toughness aluminum-scandium alloy material according to claim 1, characterized in that, The refining agent, by mass percentage, consists of 45% MgCl2, 30% KCl, 15% Na3AlF6 and 10% mixed rare earth fluorides; the amount of the refining agent is 2.2%-2.9%, and after adding the refining agent, the refining process lasts for 35-50 minutes. After adding aluminum-titanium-boron wire, the refining process is continued for 35-60 minutes.

8. The method for preparing the high-toughness aluminum-scandium alloy material according to claim 1, characterized in that, During the preparation of the round ingot substrate, the water pump pressure is 0.30-0.45 MPa, and the casting temperature is adjusted to 675-705℃. The conditions for the two-stage homogenization are: treatment at 340℃ for 12 hours, adjustment to 470℃ at a rate of 10℃ / min, and maintenance for another 8 hours. The conditions for the gradient aging treatment are: aging at 100-110℃ for 10-18 hours, adjustment to 155-170℃ at a rate of 5-10℃ / min, and maintenance for 4-6 hours.

9. A high-toughness aluminum-scandium alloy material, characterized in that, The high-toughness aluminum-scandium alloy material is prepared by the preparation method described in any one of claims 1-8; the raw materials for preparing the high-toughness aluminum-scandium alloy material include pure aluminum ingots, pure magnesium ingots and pure zinc ingots.

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