High-strength damage-resistant 2xxx series aluminum alloy

Abstract

A high-strength damage-resistant 2xxx series aluminum alloy, and a preparation method therefor and the use thereof. The aluminum alloy comprises the following components: Cu: 4.5-5.5%, Mg: 0.5-1.2%, Mn: 0.2-0.5%, Ag: 0.65-1.2%, Fe<0.1%, Si<0.1%, Zr: 0.05-0.1%, and the balance of Al and inevitable impurities, wherein the content of each inevitable impurity is less than 0.05%, the total content of the impurities is less than 0.1%, and the weight ratio of Cu to Mg is 5-10. In the aluminum alloy, the proportions of the main microalloying elements are optimized; and in the provided Al-Cu-Mg-Ag-Mn-Zr-system alloy, all the elements cooperate with each other, forming a strengthening phase with an Ω phase as a dominant phase, and due to the formation of the phase, the alloy has both a high strength and high damage resistance.

Description

High strength and damage resistance 2xxx series aluminum alloys

[0001] This application claims priority to Chinese patent application 202411438302.7, filed on October 15, 2024. The entire contents of the aforementioned Chinese patent application are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of 2xxx series aluminum alloy technology, specifically to a high-strength and damage-resistant 2xxx series aluminum alloy, and more specifically to a high-strength and damage-resistant 2xxx series aluminum alloy, its preparation method and application. Background Technology

[0003] With the rapid development of the aerospace industry, the comprehensive performance requirements for aircraft structural materials are becoming increasingly stringent. These requirements include excellent fatigue damage resistance, outstanding corrosion resistance, and superior heat resistance. Against this backdrop, aluminum alloys, due to their lightweight, high strength, and good machinability, remain one of the indispensable main structural materials in the aerospace field. In particular, Al-Cu-Mg aluminum alloys, as part of the 2xxx series, not only possess high specific strength but also exhibit good heat resistance and high fatigue damage resistance. These properties have led to the widespread application of Al-Cu-Mg aluminum alloys in the aerospace field. They can be processed through various techniques such as casting, deformation, and heat treatment to meet the specific performance requirements of different components.

[0004] The 2X24 aluminum alloy series is a heat-treated strengthened aluminum alloy belonging to the Al-Cu-Mg system. It is renowned for its excellent room-temperature tensile properties, fatigue resistance, and good pressure processing and machining properties, enabling the manufacture of various types of products. They are among the most commonly used skin materials in the aerospace field. Internationally, 2124, 2224, 2324, 2424, and 2524 series alloys have been developed. Over time, the development of 2X24 series alloys has evolved from initial requirements focused solely on static strength to comprehensive requirements encompassing damage tolerance, fatigue crack propagation rate, fracture toughness, and corrosion resistance. This evolution reflects the increasing demands and higher performance requirements for aerospace materials.

[0005] Within this family, 2024 aluminum alloy is widely used in military and civilian aircraft due to its lower strength and good ductility. 2524 aluminum alloy, on the other hand, is developed from 2024 by reducing the content of impurity elements iron and silicon. This improvement gives 2524 alloy significant advantages in damage resistance, fatigue resistance, and corrosion resistance, making it particularly suitable for producing large, integral components, and thus considered an ideal aircraft skin material.

[0006] The continuous advancements in the aerospace industry have placed increasingly higher demands on the performance of aluminum alloy materials, particularly in terms of static strength, damage tolerance, and corrosion resistance. To meet these requirements, Al-Cu-Mg-Ag alloys have emerged. Based on traditional Al-Cu-Mg alloys, the addition of trace amounts of silver significantly improves the material's strength, heat resistance, and damage tolerance. Since the introduction of the KO-1 alloy in 1962, this alloy system has undergone continuous optimization and innovation. In the 1980s, the Polmear team developed a new Al-Cu-Mg-Ag heat-resistant alloy with a yield strength as high as 520 MPa, based on the 2219 alloy. Subsequently, through fine-tuning the composition of the 2519 aluminum alloy, two alloys, C415 and C416, were developed. They achieved significant improvements in heat resistance, but still needed further improvement in damage tolerance.

[0007] In 1999, a commercially available Al-Cu-Mg-Ag alloy was launched, registered as grade 2039. Building upon this, two new heat-resistant and damage-resistant aluminum alloys, 2040 and 2139, were launched in 2003 and 2004, respectively. The 2040 alloy improves heat resistance by increasing the Mn content, but may sacrifice some damage tolerance. The 2139 alloy, on the other hand, improves damage tolerance by reducing the Mn and Mg content, but its tensile strength decreases to approximately 480 MPa.

[0008] In 2013, to address the pressure design requirements of fifth-generation advanced fighter jets such as the F-22 and F-35 for their fuselage skin and pressure chamber bulkheads, Alcoa developed a new Al-Cu-Mg-Ag alloy, registered as grade 2029. The 2029-T8 clad aluminum sheet exhibits superior performance while maintaining a crack propagation rate comparable to alloy 2524: a yield strength of 380 MPa, a tensile strength exceeding 421 MPa, and a plane stress fracture toughness exceeding 104 MPa·m. 1 / 2 It is far superior to the level of alloy 2524.

[0009] To further enhance the overall performance of Al-Cu-Mg-Ag alloys, numerous research teams have recently explored the possibility of composite microalloying with Ag elements. Shyam's research shows that adding Sc to Al-Cu-Mg-Ag alloys can induce an in-situ phase transformation in the Cu-rich phase (Al₂Cu) at a high temperature of 400℃. During this process, Sc atoms diffuse and occupy interstitial sites in the Ω phase, forming a new V phase (Sc₂AlSi₂). This new phase not only maintains high density but also significantly enhances its thermal stability, resulting in excellent strength and creep resistance at 400℃.

[0010] Xia Yage et al.'s research focused on the effect of Zr on the properties of Al-Cu-Mg-Ag alloys. They found that the addition of Zr can effectively refine the alloy's grains, thereby improving the alloy's mechanical properties at room temperature, including tensile strength, yield strength, and elongation. However, the addition of Zr also increases the grain boundary area, leading to more severe grain boundary slip under high temperature and high stress conditions, thus weakening the alloy's creep resistance.

[0011] Despite significant progress in the field of composite microalloying, most research focuses on improving individual alloy properties, such as strength or high-temperature performance, without comprehensively considering how to further enhance the overall material properties through integrated strengthening and toughening mechanisms. Future research needs to explore this area more deeply to achieve a comprehensive improvement in alloy properties.

[0012] With the development of larger and longer-life aircraft, more stringent requirements have been placed on the structural weight reduction and service life of new aerospace aluminum alloys. Higher specific strength and higher damage tolerance are important directions for the future development of aerospace aluminum alloy materials. Al-Cu-Mg-Ag alloys, due to their unique properties, are considered important candidates for future aerospace aluminum alloy material development. How to achieve the optimal microstructure matching mode to improve the overall performance of Al-Cu-Mg-Ag alloys through scientific major and micro-elements design and processing technology control is a problem that urgently needs to be solved for Al-Cu-Mg-Ag aluminum alloys, and also a pressing need for the development of the aerospace field. Summary of the Invention

[0013] The main objective of this invention is to provide a high-strength, damage-resistant 2xxx series aluminum alloy, its preparation method, and its application, so as to solve the problem that aerospace aluminum alloys in the prior art are difficult to have both high specific strength and high damage tolerance.

[0014] To achieve the above objectives, according to one aspect of the present invention, a high-strength, damage-resistant 2xxx series aluminum alloy is provided. The aluminum alloy comprises, by weight percentage: Cu: 4.5–5.5%, Mg: 0.5–1.2%, Mn: 0.2–0.5%, Ag: 0.65–1.2%, Fe < 0.1%, Si < 0.1%, Zr: 0.05–0.1%, with the balance being Al and unavoidable impurities, each unavoidable impurity < 0.05%, and total impurities < 0.1%; wherein the weight ratio of Cu to Mg is 5–10.

[0015] Furthermore, by weight percentage, the aluminum alloy composition includes: Cu: 4.8–5.2%, Mg: 0.6–0.9%, Mn: 0.2–0.5%, Ag: 0.7–1.0%, Fe < 0.1%, Si < 0.1%, Zr: 0.05–0.08%, with the balance being Al and unavoidable impurities, each unavoidable impurity < 0.05%, and total impurities < 0.1%; wherein the weight ratio of Cu to Mg is 6–8.

[0016] Furthermore, the weight ratio of Ag to Mg is 1 to 1.5; and / or the sum of the weight percentages of Fe and Si is <0.15%.

[0017] Furthermore, in the 2xxx series aluminum alloy, the volume fraction of the Ω phase is 4-6%; and / or the volume fraction of the S phase is <1%; and / or the volume fraction of the θ phase is <1%; preferably, the ratio of the volume of the Ω phase to the sum of the volumes of the S phase and the θ phase is >5.

[0018] According to another aspect of the present invention, a method for preparing the above-mentioned high-strength and damage-resistant 2xxx series aluminum alloy is provided, comprising the following steps: Step S1, mixing, melting, refining and casting the raw materials in sequence according to the component ratio to obtain an aluminum alloy ingot; Step S2, subjecting the aluminum alloy ingot to homogenization annealing and cooling in sequence to obtain a homogenized ingot; Step S3, subjecting the homogenized ingot to heating and processing in sequence to obtain a processed sheet; Step S4, subjecting the processed sheet to solution treatment and quenching in sequence to obtain a quenched sheet; Step S5, subjecting the quenched sheet to pre-deformation and aging treatment in sequence to obtain a 2xxx series aluminum alloy.

[0019] Furthermore, in step S2, the homogenization annealing temperature is 450–550°C, and the time is 18–22 h.

[0020] Further, in step S3, the final heating temperature is 360–460°C, the holding time is 5–10 h; and / or the processing includes one or more of rolling, extrusion and forging.

[0021] Further, in step S4, the solution temperature is 480–540°C and the time is 2–1200 min; and / or the quenching includes spray quenching and / or immersion quenching; preferably, when the quenching is spray quenching, the quenching cooling rate is >500°C / min; preferably, when the quenching is immersion quenching, the quenching cooling rate is >600°C / min.

[0022] Further, in step S5, the aging includes natural aging and / or artificial aging; preferably, when the aging is natural aging, the aging time is ≥96h, and the total deformation of the pre-deformation is ≤2%; more preferably, the pre-deformation includes pre-stretching and / or straightening treatment; preferably, when the aging is artificial aging, the aging temperature is 150~250℃, the time is 5~20h, and the total deformation of the pre-deformation is 1~4%; more preferably, the pre-deformation includes pre-stretching.

[0023] According to another aspect of the present invention, the application of the above-mentioned high-strength and damage-resistant 2xxx series aluminum alloys is provided.

[0024] This invention optimizes the ratio of main and microalloying elements. In the Al-Cu-Mg-Ag-Mn-Zr alloy system provided, the elements synergistically cooperate to form a strengthening phase dominated by the Ω phase. The formation of this phase endows the alloy with both high strength and high damage resistance. In particular, by controlling the weight ratio of Cu to Mg within a specific range, this invention ensures the formation of a large amount of dispersed Ω phase while reducing the formation of the S phase, achieving an optimal matching mode of strengthening phases and thus effectively improving the material's damage resistance. In addition, by controlling impurity elements and other trace elements, this invention effectively reduces the adverse effects of coarse, insoluble compounds and dispersed phases on damage tolerance, thereby enabling 2xxx aluminum alloys to possess both high strength and high damage tolerance, providing a material selection basis for the structural weight reduction and long service life design of next-generation aircraft. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 shows a transmission electron microscope (TEM) microstructure of the 2xxx series aluminum alloy of Embodiment 1 of the present invention. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] As described in the background section of this invention, existing technologies suffer from the problem that aerospace aluminum alloys cannot simultaneously possess both high specific strength and high damage tolerance. To address this issue, in a typical embodiment of this invention, a high-strength, damage-resistant 2xxx series aluminum alloy is provided. By weight percentage, the aluminum alloy comprises: Cu: 4.5–5.5%, Mg: 0.5–1.2%, Mn: 0.2–0.5%, Ag: 0.65–1.2%, Fe < 0.1%, Si < 0.1%, Zr: 0.05–0.1%, with the balance being Al and unavoidable impurities, each unavoidable impurity < 0.05%, and total impurities < 0.1%; wherein the weight ratio of Cu to Mg is 5–10.

[0029] Through extensive experimentation, the inventors unexpectedly discovered that controlling the weight percentages and weight ratio of Cu and Mg in the alloy under the aforementioned conditions effectively suppresses the formation of the S phase (Al₂CuMg phase), thereby providing favorable conditions for the formation of a large quantity of dispersed Ω phase (Al₂Cu phase). In this invention, Mg and Ag interact in 2xxx series aluminum alloys to form atomic clusters, giving the Ω phase a nucleation advantage in competition with the θ phase (Al₂Cu phase), thus increasing the proportion and precipitation effect of the Ω phase. Based on the mechanism of interaction between the Ω phase and dislocations, this further enhances the damage resistance of the alloy. However, if the weight ratio of Cu to Mg is too high, it may lead to an excessively high proportion of the θ phase, which can easily result in poor strengthening and toughening effects of the material. If the ratio is too low, it may lead to an excessively high proportion of the S phase, which can easily reduce the damage resistance of the material. Therefore, this application limits the content of Cu and Mg, as well as their weight ratio, to the specific ranges mentioned above.

[0030] This invention also incorporates 0.65–1.2% Ag. Through extensive research and industrial application, the inventors discovered that the addition of Ag effectively strengthens the microstructure and promotes the formation of the Ω-phase-dominated strengthening phase in 2xxx series aluminum alloys. Within the aforementioned range, the formation of the Ω-phase exhibits a significant advantage. However, when the Ag content exceeds 1.2%, the total number of Ω-phase phases reaches its limit, and even further increases in Ag content have limited effect on improving the Ω-phase content. Insufficient Ag content may lead to inadequate formation of Mg atom clusters, affecting the number of Ω-phase nuclei. Therefore, this application limits the Ag content to the aforementioned specific range.

[0031] Furthermore, trace amounts of Mn and Zr are added as microalloying elements in this invention. The addition of Mn and Zr can refine the grain size of the material, improve its overall performance, and also help control the morphology and distribution of grain boundary eutectic phases (such as θ phase and S phase) in the ingot, thus facilitating microstructure control in subsequent heat treatment processes such as homogenization and solution treatment. However, if the Mn content is too high, it may lead to an increase in the size and quantity of the Mn-containing insoluble phase, thereby reducing damage tolerance. If the content is too low, it is difficult to effectively refine the grain size. Similarly, if the Zr content is too high, it may lead to an increase in the number of Zr-containing dispersed phases, reducing damage tolerance. If the content is too low, the effect of grain refinement is also limited. Therefore, this application specifically limits the weight percentage of Mn to 0.2–0.5% and the weight percentage of Zr to 0.05–0.1%.

[0032] In addition, the present invention limits the content of impurity elements such as Fe and Si. These impurity elements can form coarse insoluble phases (such as Al7Cu2Fe phase) during the ingot smelting process. These insoluble phases are difficult to eliminate in subsequent heat treatment processes, which will increase the crack nucleation sites and shorten the crack propagation distance, thereby seriously affecting the damage resistance of the finished product. Therefore, the content of such impurity elements in the present invention is limited to: Fe < 0.1 wt%, Si < 0.1 wt%.

[0033] In summary, this invention optimizes the ratio of main and microalloying elements. In the Al-Cu-Mg-Ag-Mn-Zr alloy system provided, the elements synergistically cooperate to form a strengthening phase dominated by the Ω phase. The formation of this phase endows the alloy with both high strength and high damage resistance. In particular, by controlling the weight ratio of Cu to Mg within a specific range, this invention ensures the formation of a large amount of dispersed Ω phase while reducing the formation of the S phase, achieving an optimal matching mode of strengthening phases and thus effectively improving the material's damage resistance. Furthermore, by controlling impurity elements and other trace elements, this invention effectively reduces the adverse effects of coarse, insoluble compounds and dispersed phases on damage tolerance, thereby enabling 2xxx aluminum alloys to possess both high strength and high damage tolerance.

[0034] Typical, but not limiting, aluminum alloy compositions may contain Cu by weight of 4.5%, 4.8%, 5%, 5.2%, 5.5%, or any two of these values; Mg by weight of 0.5%, 0.6%, 0.8%, 0.9%, 1%, 1.2%, or any two of these values; Cu to Mg weight ratios of 5, 6, 7, 8, 9, 10, or any two of these values; Mn by weight of 0.2%, 0.3%, 0.4%, 0.5%, or any two of these values; and Ag by weight of 0.65%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, or any two of these values.

[0035] To further optimize the control effect on the alloy structure, in a preferred embodiment, the aluminum alloy composition by weight percentage includes: Cu: 4.8-5.2%, Mg: 0.6-0.9%, Mn: 0.2-0.5%, Ag: 0.7-1.0%, Fe < 0.1%, Si < 0.1%, Zr: 0.05-0.08%, with the balance being Al and unavoidable impurities, each unavoidable impurity < 0.05%, and total impurities < 0.1%; wherein the weight ratio of Cu to Mg is 6-8.

[0036] To further suppress the formation of the S phase (Al₂CuMg phase) and increase the proportion of the Ω phase (Al₂Cu phase) in the alloy, in a preferred embodiment, the weight ratio of Ag to Mg is 1 to 1.5, specifically 1, 1.1, 1.2, 1.3, 1.4, 1.5, or any two of these values. Preferably, the weight ratio of Ag to Mg is 1 to 1.3. To further reduce the content of the refractory phase and thus more effectively improve the damage resistance of the alloy, in a preferred embodiment, the sum of the weight percentages of Fe and Si is <0.15%.

[0037] In a preferred embodiment, in the 2xxx series aluminum alloy, the volume fraction of the Ω phase is 4-6%, preferably 5-6%; and / or the volume fraction of the S phase is <1%, preferably <0.5%; and / or the volume fraction of the θ phase is <1%, preferably <0.5%; preferably, the ratio of the volume of the Ω phase to the sum of the volumes of the S and θ phases is >5. Alloys under the above conditions can better combine high strength and high damage tolerance. Typically, but not limitingly, the volume fraction of the Ω phase is 4%, 4.5%, 5%, 5.5%, 6%, or any two of these values.

[0038] As described above, the 2xxx series aluminum alloys of this invention, with specific compositions, contain abundant Ω phases, which significantly improve the damage tolerance performance of the alloy while meeting the required strength. Specifically, in a preferred embodiment, the yield strength R of the 2xxx series aluminum alloy... p0.2 ≥400MPa, tensile strength R m ≥500 MPa, elongation ≥10%, plane stress fracture toughness K 1C ≥50MPa·m 1 / 2 Or, the plane fracture toughness Kapp ≥ 110 MPa·m 1 / 2 Crack propagation rate (ΔK = 33 MPa·m) 1 / 2 )≤3×10 -3 mm / c. The 2xxx series aluminum alloy of this invention, while possessing excellent crack propagation resistance, significantly improves the strength of traditional Al-Cu-Mg alloys, providing a material selection basis for the structural weight reduction and long service life design of next-generation aircraft.

[0039] In another typical embodiment of the present invention, a method for preparing the above-mentioned high-strength and damage-resistant 2xxx series aluminum alloy is also provided, comprising the following steps: Step S1, mixing, melting, refining and casting the raw materials in sequence according to the proportion to obtain an aluminum alloy ingot; Step S2, subjecting the aluminum alloy ingot to homogenization annealing and cooling in sequence to obtain a homogenized ingot; Step S3, subjecting the homogenized ingot to heating and processing in sequence to obtain a processed sheet; Step S4, subjecting the processed sheet to solution treatment and quenching in sequence to obtain a quenched sheet; Step S5, subjecting the quenched sheet to pre-deformation and aging treatment in sequence to obtain a 2xxx series aluminum alloy.

[0040] First, the raw materials are mixed, smelted, refined, and cast. This process effectively removes gases and impurities from the melt. Then, the resulting ingot undergoes homogenization annealing to eliminate compositional segregation and homogenize the elements, which is beneficial for improving the performance stability of the aluminum alloy. Next, heating and processing are performed to refine the aluminum alloy grains, resulting in plates of specific dimensions. Second, the plates are solution-treated to dissolve the soluble phases. Then, quenching is performed to ensure a uniform distribution of the quenched microstructure. The quenched plates are pre-deformed to eliminate residual stress within the alloy, resulting in a uniform and stable alloy microstructure. Finally, aging is performed to promote phase transformation within the alloy, improving its strength and hardness, thus obtaining the aforementioned 2xxx series aluminum alloy. Using the preparation method of this invention, the components in the 2xxx alloy with specific compositions can be made uniform and stable.

[0041] In a preferred embodiment, in step S2, the homogenization annealing temperature is 450–550°C, and the time is 18–22 hours. Under these conditions, atomic diffusion and phase transition processes can proceed more fully, resulting in a more uniform distribution of elements. Regarding the cooling rate, conventional parameters in this technical field can be used, and no particular limitation is made here.

[0042] In a preferred embodiment, in step S3, the final heating temperature is 360–460°C, and the holding time is 5–10 hours. Under these conditions, the alloy can have higher thermoplasticity, which is conducive to the smooth hot deformation of the alloy. Too low or too high a temperature may cause hot deformation, leading to an increased risk of processing cracks.

[0043] The processing technology of this invention can be achieved using conventional processes in this technical field. Through extensive experimental research and considering the specific composition of the alloy, the inventors optimized the parameters of each processing step. In a preferred embodiment, the processing includes one or more of rolling, extrusion, and forging. Preferably, when the processing is rolling, the rolling includes sequential hot rolling and cold rolling. The hot rolling has 10-15 passes, a total deformation of ≥50%, and a final thickness of 4-200 mm. The cold rolling has 3-5 passes, a total deformation of ≥30%, and a final thickness of 1-5 mm. Under these conditions, by controlling the hot and cold deformation, the material can obtain a more uniform and finer grain structure, and the alloy's strength, plasticity, and damage tolerance properties are better matched.

[0044] In a preferred embodiment, in step S4, the solution treatment temperature is 480–540°C, and the time is 2–1200 min. Under these conditions, the soluble phase in the alloy of the specific composition of the present invention can be fully dissolved, which is more conducive to improving the strength of the alloy. In addition, the crack propagation resistance of the alloy of the present invention can be further improved, which is more conducive to improving the damage tolerance performance of the alloy. However, if the temperature is too high, there is a risk of over-burning of the soluble phase, which will lead to the scrapping of the material; if the temperature is too low, the solute atoms may not be fully dissolved, and the effect of improving the strength and damage tolerance performance of the alloy will be limited.

[0045] To make the quenched microstructure of the alloy more uniform and further improve its strength and damage tolerance, in a preferred embodiment, the quenching includes spray quenching and / or immersion quenching; preferably, when the quenching is spray quenching, the cooling rate is >500℃ / min and the final temperature is 25-40℃; preferably, when the quenching is immersion quenching, the cooling rate is >600℃ / min and the final temperature is 25-40℃.

[0046] To enable the Ω phase to precipitate more uniformly and dispersedly, thereby further improving the strength and damage tolerance of the alloy, in a preferred embodiment, step S5 includes natural aging and / or artificial aging; preferably, when the aging is natural, the time is ≥96h, and the total deformation of the pre-deformation is ≤2%; more preferably, the pre-deformation includes pre-stretching and / or straightening treatment; preferably, when the aging is artificial, the aging temperature is 150~250℃, the time is 5~20h, and the total deformation of the pre-deformation is 1~4%; more preferably, the pre-deformation includes pre-stretching. The 2xxx series aluminum alloy of this invention, while possessing excellent crack propagation resistance, significantly improves the strength of traditional Al-Cu-Mg alloys, wherein the yield strength in the artificially aged state is at least 100MPa higher than that of the 2524-T3 alloy, while maintaining the same level of damage resistance as the 2524 alloy.

[0047] In order to more effectively avoid age hardening that could lead to excessive pre-deformation resistance or deformation defects, in a preferred embodiment, pre-deformation can be carried out online or offline, wherein the time interval between the completion of quenching and the completion of pre-deformation shall not exceed 6 hours.

[0048] In another typical embodiment of the present invention, the application of the aforementioned high-strength, damage-resistant 2xxx series aluminum alloy in the aerospace field is also provided. Through a comprehensive strengthening and toughening mechanism, the present invention enables the 2xxx series aluminum alloy to possess both high strength and high damage tolerance. When the 2xxx series aluminum alloy of the present invention is used in the aerospace field, the structure of aircraft and other equipment becomes lighter and has a longer service life.

[0049] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0050] Example 1

[0051] The composition ratio of 2xxx series aluminum alloys is shown in Table 1.

[0052] Step S1: According to the composition ratio of 2xxx series aluminum alloy, the raw materials are mixed, smelted and refined in sequence to remove gas and impurities, and then a flat ingot with a thickness of 400mm and a width of 1500mm is prepared under semi-continuous casting conditions.

[0053] Step S2: The ingot is homogenized at a temperature of 500℃ for 20 hours to obtain a homogenized ingot.

[0054] Step S3: Cool the homogenized ingot to 25°C. After milling, the ingot is heated in a furnace at 460°C for 10 hours, followed by 10 passes of rough rolling with a total deformation of 95%, and then 3 passes of hot finishing rolling with a total deformation of 60%, to obtain a hot-rolled plate with a thickness of 8 mm. The hot-rolled plate is then cold-rolled on a cold rolling mill for 5 passes with a total deformation of 75%, to obtain a cold-rolled sheet with a thickness of 2 mm.

[0055] Step S4: The cold-rolled sheet is subjected to solution treatment at 500℃ for 5 minutes, and then spray-quenched to 25℃ at a cooling rate of 200℃ / s to obtain quenched sheet.

[0056] Step S5: The obtained quenched plate is subjected to 2% pre-stretch deformation, followed by artificial aging at a temperature of 180℃ for 15 hours to obtain 2xxx series aluminum alloy in T8 state.

[0057] The transmission electron microscopy (TEM) microstructure of the obtained 2xxx series aluminum alloy is shown in Figure 1. Figure 1A shows the TEM microstructure of the 2xxx series aluminum alloy under dark-field imaging, which is marked with the Ω phase under the <111> band axis. Figure 1B shows the TEM microstructure of the 2xxx series aluminum alloy under dark-field imaging, which is marked with the S phase and θ phase under the abnormal axis. This alloy will be used to manufacture aircraft in the aerospace field.

[0058] Examples 2 to 12

[0059] The only difference from Example 1 is:

[0060] The composition ratios of 2xxx series aluminum alloys vary; see Table 1 for specific ratios.

[0061] Example 13

[0062] The only difference from Example 1 is:

[0063] The composition ratio of 2xxx series aluminum alloys is shown in Table 1.

[0064] Step S1: According to the composition ratio of 2xxx series aluminum alloy, the raw materials are mixed, smelted and refined in sequence to remove gas and impurities, and then a round ingot with a diameter of φ400mm is prepared under semi-continuous casting conditions.

[0065] Step S2: The ingot is homogenized at a temperature of 500℃ for 20 hours to obtain a homogenized ingot.

[0066] Step S3: Cool the homogenized ingot to 25°C. After peeling and sawing, the ingot is then heated in a furnace at 460°C for 10 hours, and then extruded into 150mm × 40mm extrusion strips on an extruder.

[0067] Step S4: The prepared extruded strip is subjected to solution treatment at 480℃ / 5h→500℃ / 2h, and then subjected to spray water quenching at a cooling rate of 800℃ / min to obtain quenched strip.

[0068] Step S5 involves subjecting the obtained quenched strip to 2% pre-stretch deformation, followed by artificial aging at a temperature of 180°C for 18 hours to obtain 2xxx series aluminum alloy, which is then used to manufacture aircraft in the aerospace field.

[0069] Examples 14 to 18

[0070] The only difference from Example 1 is:

[0071] The composition ratios of 2xxx series aluminum alloys vary; see Table 1 for specific ratios.

[0072] Example 19

[0073] The only difference from Example 1 is:

[0074] The manufacturing process parameters for 2xxx series aluminum alloys are different.

[0075] Step S1: According to the composition ratio of the 2xxx series aluminum alloy in Example 1, the raw materials are mixed, smelted and refined in sequence to remove gas and impurities, and then a flat ingot with a thickness of 400 mm and a width of 1500 mm is prepared under semi-continuous casting conditions.

[0076] Step S2: The ingot is homogenized at a temperature of 450°C for 22 hours to obtain a homogenized ingot.

[0077] Step S3: Cool the homogenized ingot to 25°C. After milling, the ingot is heated in a furnace at 360°C for 10 hours, followed by 12 passes of rough rolling with a total deformation of 97%, and then 3 passes of hot finishing rolling with a total deformation of 60%, to obtain a hot-rolled plate with a thickness of 5 mm. The hot-rolled plate is then cold-rolled on a cold rolling mill with 3 passes of cold rolling deformation, with a total deformation of 60%, to obtain a cold-rolled plate with a thickness of 2 mm.

[0078] Step S4: The cold-rolled sheet is subjected to solution treatment at 480℃ for 1200 min, and then spray quenching treatment is performed at a cooling rate of 550℃ / h to obtain quenched sheet.

[0079] Step S5: The obtained quenched plate is subjected to 4% pre-stretch deformation, followed by artificial aging at a temperature of 150℃ for 20 hours to obtain 2xxx series aluminum alloy.

[0080] Example 20

[0081] The only difference from Example 1 is:

[0082] The manufacturing process parameters for 2xxx series aluminum alloys are different.

[0083] Step S1: According to the composition ratio of the 2xxx series aluminum alloy in Example 1, the raw materials are mixed, smelted and refined in sequence to remove gas and impurities, and then a flat ingot with a thickness of 400 mm and a width of 1500 mm is prepared under semi-continuous casting conditions.

[0084] Step S2: The ingot is homogenized at a temperature of 550°C for 18 hours to obtain a homogenized ingot.

[0085] Step S3: Cool the homogenized ingot to 30°C. After milling, the ingot is heated in a furnace at 460°C for 5 hours, followed by 10 passes of rough rolling with a total deformation of 95%, and then 3 passes of hot finishing rolling with a total deformation of 60%, to obtain a hot-rolled plate with a thickness of 8 mm. The hot-rolled plate is then cold-rolled on a cold rolling mill for 3 passes with a total deformation of 62.5%, to obtain a cold-rolled plate with a thickness of 3 mm.

[0086] Step S4: The cold-rolled sheet is subjected to solution treatment at 540℃ for 2 minutes, and then immersed in quenching at a cooling rate of 620℃ / h to obtain quenched sheet.

[0087] Step S5: The obtained quenched sheet is subjected to 1% pre-stretch deformation, followed by artificial aging at a temperature of 250℃ for 5 hours to obtain 2xxx series aluminum alloy.

[0088] Comparative Examples 1 to 4

[0089] The only difference from Example 1 is:

[0090] The composition ratios of 2xxx series aluminum alloys vary; see Table 1 for specific ratios.

[0091] Comparative ratios 5 to 8

[0092] The only difference from Example 13 is:

[0093] The composition ratios of 2xxx series aluminum alloys vary; see Table 1 for specific ratios.

[0094] The test results of the phase volume fraction, room temperature tensile properties, fracture toughness and crack propagation rate of the 2xxx series aluminum alloys prepared in the above embodiments and comparative examples are shown in Table 2.

[0095] Test method:

[0096] Volume fractions of Ω phase, S phase, and θ phase: Analyzed and calculated based on transmission electron microscopy (TEM) tissue images.

[0097] Yield strength, tensile strength, and elongation: Tested in accordance with GB / T228.1-2021.

[0098] Plane stress fracture toughness Kapp, crack propagation rate, plane strain fracture toughness K 1C The fatigue testing machine was used for the test.

[0099] Table 1

[0100] Table 2

[0101] Regarding the preparation methods of 2xxx alloy sheets, compared with Comparative Example 1, Examples 1 to 12 increased the content of Ag, thereby increasing the proportion of the Ω phase in the material and improving the overall strength and damage tolerance performance of the material. Compared with Comparative Example 2, Examples 1 to 12 effectively controlled the grain structure characteristics by adding trace amounts of Zr, thus improving the damage resistance of the alloy. Compared with Comparative Example 3, Examples 1 to 12 significantly improved the damage tolerance performance of the material by reducing the content of impurity elements such as Fe and Si. Compared with the conventional 2524 alloy shown in Comparative Example 4, Examples 1 to 12 simultaneously and significantly improved the strength and damage tolerance performance of the material by increasing the main alloying element Cu, adding the Ω phase forming element Ag, and setting a matching preparation process. Similarly, regarding the preparation methods of extruded materials of 2xxx alloy sheets, the comparative effects of Comparative Examples 5 to 8 and Examples 13 to 18 are similar to those of the above-mentioned 2xxx sheets, with Examples 13 to 18 obtaining extruded materials with higher strength and higher damage tolerance performance.

[0102] As can be seen from the above, compared with the comparative example, the Al-Cu-Mg-Ag-Mn-Zr alloy system provided by the embodiments of the present invention, through optimization of the main microalloying element ratio, exhibits synergistic cooperation among the elements, forming a strengthening phase dominated by the Ω phase. The formation of this phase endows the alloy with both high strength and high damage tolerance. Furthermore, it can be seen that when all process parameters are within the preferred range of the present invention, the 2xxx aluminum alloy exhibits even better strength and high damage tolerance.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-strength damage-tolerant 2xxx-series aluminum alloy, characterized in that, The aluminum alloy comprises, by weight percentage: Cu: 4.5–5.5%, Mg: 0.5–1.2%, Mn: 0.2–0.5%, Ag: 0.65–1.2%, Fe < 0.1%, Si < 0.1%, Zr: 0.05–0.1%, with the balance being Al and unavoidable impurities, each of which is < 0.05%, and total impurities < 0.1%. The weight ratio of Cu to Mg is 5 to 10.

2. The 2xxx aluminum alloy of claim 1, wherein The aluminum alloy comprises, by weight percentage: Cu: 4.8–5.2%, Mg: 0.6–0.9%, Mn: 0.2–0.5%, Ag: 0.7–1.0%, Fe < 0.1%, Si < 0.1%, Zr: 0.05–0.08%, with the balance being Al and unavoidable impurities, each of which is < 0.05%, and total impurities < 0.1%. The weight ratio of Cu to Mg is 6 to 8.

3. The 2xxx series aluminum alloy according to claim 1 or 2, characterized in that, The weight ratio of Ag to Mg is 1 to 1.

5.

4. The 2xxx series aluminum alloy according to claim 1 or 2, characterized in that, The sum of the weight percentages of Fe and Si is <0.15%.

5. The 2xxx aluminum alloy of claim 1 or 2, wherein In the 2xxx series aluminum alloys The volume fraction of the Ω phase is 4–6%; and / or The volume fraction of the S phase is <1%; and / or The volume fraction of the θ phase is <1%.

6. The 2xxx aluminum alloy of claim 5, wherein In the 2xxx series aluminum alloys The ratio of the volume of the Ω phase to the sum of the volumes of the S phase and the θ phase is greater than 5.

7. The method of producing a high-strength damage-tolerant 2xxx-series aluminum alloy according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1: Mix, melt, refine and cast the raw materials in sequence according to the component ratio to obtain aluminum alloy ingots; Step S2: The aluminum alloy ingot is subjected to homogenization annealing and cooling in sequence to obtain a homogenized ingot; Step S3: The homogenized ingot is heated and processed sequentially to obtain a processed plate. Step S4: The processed sheet material is subjected to solution treatment and quenching in sequence to obtain a quenched sheet material; Step S5: The quenched sheet is subjected to pre-deformation and aging treatment in sequence to obtain the 2xxx series aluminum alloy.

8. The production method according to claim 7, characterized by, In step S2 The homogenization annealing temperature is 450–550°C, and the time is 18–22 hours.

9. The production method according to claim 7 or 8, characterized by, In step S3 The final heating temperature is 360–460°C, and the holding time is 5–10 hours; and / or The processing includes one or more of rolling, extrusion, and forging.

10. The production method according to claim 7 or 8, characterized by, In step S4 The solution treatment temperature is 480–540°C, and the time is 2–1200 min; and / or The quenching includes spray quenching and / or immersion quenching.

11. The method of claim 10, wherein, In step S4 When the quenching is the spray quenching, the cooling rate of the quenching is >500℃ / min; When the quenching is the immersion quenching, the cooling rate of the quenching is >600℃ / min.

12. The production method according to claim 7 or 8, characterized by, In step S5 The time limit includes natural time limit and / or artificial time limit.

13. The method of claim 12, wherein, In step S5 When the aging is natural aging, the aging time is ≥96h, and the total deformation of the pre-deformation is ≤2%; the pre-deformation includes pre-stretching and / or straightening treatment.

14. The method of claim 12, wherein, In step S5 When the aging is artificial aging, the aging temperature is 150-250℃, the time is 5-20h, and the total deformation of the pre-deformation is 1-4%; the pre-deformation includes pre-stretching.

15. The application of the high-strength, damage-resistant 2xxx series aluminum alloy according to any one of claims 1 to 6 in the aerospace field.

Images