7xxx-series aluminum alloy for large-size ingot under homogenizing annealing and slow cooling conditions and method of manufacturing

Abstract

This invention discloses a 7XXX series aluminum alloy for large-size ingots under homogenized annealing and slow cooling conditions and its manufacturing method. The alloy comprises, by mass percentage: Zn: 5.0%–5.5%, Mg: 2.1%–2.5%, Cu: 1.1%–1.7%, Mn: 0.2%–0.45%, Cr: 0.18%–0.3%, Zr: 0.08%–0.15%, Ti: ≤0.1%, Fe: ≤0.3%, Si: ≤0.2%; wherein the total content of Mg+Cu is 3.5–4.1 wt%, and the total content of Mn+Cr is not less than 0.4% wt%. This invention solves the problems of coarse CuMg phase precipitation and insufficient mechanical properties of plates during the homogenization and slow cooling of large-size 7XXX series ingots by optimizing the element ratio and combining it with dry well semi-continuous casting, two-stage homogenization annealing and slow cooling, multi-pass hot rolling + cold rolling, solution treatment and aging process. The homogenization annealing cooling rate of this invention can be as low as 100℃ / h, suppressing the precipitation of coarse S phase without rapid cooling, and is suitable for the production of large-size ingots. The resulting plates have a yield strength ≥480MPa, tensile strength ≥570MPa, and elongation ≥13%. The process is simple and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of processing and production technology of high-strength 7XXX series wrought aluminum alloys, specifically to 7XXX series aluminum alloys for large-size ingots under homogenized annealing and slow cooling conditions and their manufacturing method. Background Technology

[0002] Al-Zn-Mg-Cu (7xxx series) alloys are ultra-high strength aluminum alloys widely used in the manufacture of structural components for rail transit vehicles, automobiles, ships, and 3C electronic products. Their production process involves multiple complex steps, including melting, casting, homogenization annealing, deformation, solution treatment, and aging. Homogenization annealing, as a key heat treatment step in aluminum alloy processing, effectively eliminates casting stress, improves segregation defects in the as-cast structure, and controls the state of microalloying elements such as Mn and Cr, thereby enhancing the material's processing performance and final overall properties. With the increasing demand for lightweighting in aerospace, rail transportation, and other fields, aluminum alloy components are becoming increasingly larger. With the increasing demand for large-size, high-strength and high-toughness 7XXX round ingots due to integrated development, the cooling rate is usually slow during the homogenization annealing process because of the large size of the casting or to prevent deformation. During this process, elements in the aluminum matrix that have been dissolved back during the holding stage will precipitate again, affecting the subsequent microstructure and properties. Among them, the negative impact of S-Al2CuMg phase precipitation is more obvious, as it consumes solute atoms and is difficult to dissolve back during the solid solution stage. Therefore, it is of great significance to design and develop new alloy materials and processes to control the precipitation behavior of S-Al2CuMg phase during the homogenization annealing cooling stage, thereby improving the final properties of the alloy.

[0003] For example, Chinese patent CN115261688A discloses a hot-formed 7-series aluminum alloy material and its manufacturing method. The specific process includes alloy composition design, three-stage homogenization process, reasonable hot rolling pass matching, and double-stage continuous annealing process. Among them, the three-stage homogenization annealing process is: (350-420)℃ / (4-10)h + (450-465)℃ / (20-40)h + (470-475)℃ / (4-10)h. After homogenization, the ingot is rapidly cooled at a rate of 150℃ / h or higher to control the precipitation of coarse second phase during the cooling process.

[0004] However, the existing 7XXX series aluminum alloy materials and their preparation methods for large-size ingots under the conditions of homogenization annealing and slow cooling have the following defects when in operation: The existing three-stage homogenization annealing process, because it includes a low-temperature stage, increases the process complexity and production cycle to a certain extent. The published three-stage homogenization heat treatment method must adopt a faster cooling rate in order to suppress the precipitation of coarse phases, so it is difficult to apply to large-size ingots or conditions of homogenization and slow cooling. In view of this, the present invention develops a 7xxx series aluminum alloy material for large-size ingots that can be used under homogenization annealing and slow cooling conditions. At the same time, a matching homogenization heat treatment method and plate processing method are developed, which enable the alloy to achieve slow cooling in the homogenization annealing cooling stage and suppress the precipitation of coarse S phase. Finally, the plate prepared by this method exhibits good comprehensive mechanical properties. Summary of the Invention

[0005] The purpose of this invention is to provide a 7XXX series aluminum alloy for large-size ingots under homogenized annealing and slow cooling conditions and its manufacturing method, so as to solve the problem of severe precipitation of coarse S-Al2CuMg phase in large-size 7XXX series alloy ingots under homogenized annealing heat treatment and slow cooling conditions, and to solve the problem of insufficient comprehensive mechanical properties of 7XXX series alloy rolled plates after aging treatment under homogenized annealing and slow cooling conditions.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A 7XXX series aluminum alloy material for large-size ingots under homogenized annealing and slow cooling conditions comprises, by mass percentage: Zn: 5.0%–5.5%, Mg: 2.1%–2.5%, Cu: 1.1%–1.7%, Mn: 0.2%–0.45%, Cr: 0.18%–0.3%, Zr: 0.08%–0.15%, Ti: ≤0.1%, Fe: ≤0.3%, Si: ≤0.2%; wherein the total content of Mg+Cu is 3.5–4.1 wt%, and the total content of Mn+Cr is not less than 0.4% wt%.

[0007] A method for manufacturing large-size ingots of 7XXX series aluminum alloy under homogenized annealing and slow cooling conditions, comprising the following steps in sequence: melting and casting, homogenized annealing, rolling, solution treatment, and aging treatment. S1. Melting and casting: Semi-continuous casting combined with dry well casting process is adopted, and alloy melt is prepared according to the mass percentage. The melt after degassing and slag removal is semi-continuous direct cooling casting. During casting, the scraper is turned on to prevent the cooling water from contacting the ingot. The cooling water is evacuated in advance to form dry well casting conditions. After casting, the ingot is water cooled for 10 to 60 seconds, the water supply is stopped, and the ingot is left to cool in the well for 1 to 2 hours before being hoisted. S2. Homogenization Annealing: After heating the ingot, it undergoes two-stage heat preservation, followed by slow cooling to room temperature. The homogenization annealing employs a two-stage heat preservation process: first, the temperature is raised to 460–470℃ and held for 2–12 hours, then raised to 480–485℃ and held for 10–18 hours. During the cooling process, the cooling rate can be as low as 100℃ / h. Combined with specific component ratios and two-stage homogenization, slow cooling at 100℃ / h can still suppress the precipitation of coarse S-Al2CuMg phases, meeting the industrial requirements for deformation prevention and slow cooling production of large-size ingots. S3. Rolling: The homogenized ingot is heated to 410-450℃ and held for 20-40 minutes, then hot-rolled in 3-5 passes. The first pass has a reduction of 30%-50%, and the total hot-rolling reduction is 55%-70%. After cooling to below 60℃, it is cold-rolled in 2-4 passes, with a total cold-rolling reduction of 10%-30%. After hot rolling and cold rolling, the final sheet has a total reduction of 65%-90%. The homogenized annealed ingot is then hot-rolled and cold-rolled to produce sheet metal. S4. Solution treatment: Heat the rolled plate to 460℃-470℃ at a heating rate of 2-10℃ / min, hold for 1-2 hours, and then water quench. S5. Aging treatment: The quenched plate is transferred into an aging furnace within 5 minutes for heat treatment, and aged at 110℃-130℃ for 20-30 hours to obtain the final aluminum alloy material; this aging process can precipitate a large number of nano-scale strengthening phases.

[0008] Preferably, the heating rate of the homogenization annealing is 4-10℃ / min; this heating rate can avoid thermal stress cracking of the ingot due to excessive heating, while ensuring uniform temperature inside and outside the ingot, ensuring sufficient homogenization of composition during subsequent double-stage heat preservation, and laying the microstructure foundation for suppressing S phase precipitation.

[0009] Preferably, the two-stage heat preservation process involves first heating to 460–470°C and holding for 2–12 hours, then heating to 480–485°C and holding for 10–18 hours. The first stage of heat preservation promotes the transformation of the low-melting-point eutectic phase into the S phase. The second stage of high-temperature heat preservation achieves full homogenization of the ingot and dissolves the coarse S phase. The two-stage heat preservation replaces the traditional three-stage heat preservation, simplifying the process and shortening the cycle.

[0010] Preferably, the hot rolling is a 3-5 pass rolling process: first, heating to 410-450℃ and holding for 20-40 minutes, the first pass reduction rate is 30%-50%, and the total hot rolling reduction rate is 55%-70%.

[0011] Preferably, the cold rolling is a 2-4 pass rolling process: after the ingot is cooled to below 60°C, it undergoes 2-4 passes of cold rolling, with a total cold rolling reduction of 10%-30%. After the final hot rolling + cold rolling, the total reduction of the sheet is 65%-90%.

[0012] Preferably, the solution treatment is as follows: heating to 460-470°C at a rate of 2-10°C / min, holding at that temperature for 1-2 hours, and then water-quenching; these solution parameters can fully re-dissolve the soluble phase and retain solute atoms; rapid water-quenching suppresses the precipitation of the second phase during the cooling process and provides sufficient solute for subsequent aging strengthening.

[0013] Preferably, the prepared aluminum alloy sheet has a yield strength ≥480MPa, tensile strength ≥570MPa, and elongation ≥13%; ultimately achieving good comprehensive mechanical properties of the alloy under the conditions of homogenized annealing and slow cooling of large-size ingots.

[0014] The present invention has the following beneficial effects: (1) The present invention has carried out synergistic design optimization of the main alloying elements Al, Zn, Mg and Cu and the microalloying elements Mn, Cr and Zr, laying the foundation for achieving excellent final mechanical properties of the alloy under homogenized cooling and slow cooling conditions.

[0015] (2) Compared with the existing three-stage homogenization heat treatment method, the two-stage homogenization annealing operation in this invention is simple and can suppress the precipitation of S phase under slow cooling conditions during annealing, thereby improving the mechanical properties of the final rolled plate. In contrast, the existing three-stage homogenization heat treatment method requires a faster cooling rate to suppress the precipitation of coarse phases, which makes it difficult to apply to large-size ingots. The cooling rate of this invention can be reduced to 100℃ / h, which meets the actual industrial needs of slow cooling under large-size ingots or specific processes, and can obtain good comprehensive mechanical properties. Attached Figure Description

[0016] Figure 1 This is an optical microstructure diagram of the alloy after two-stage homogenization annealing according to an embodiment of the present invention.

[0017] Figure 2 These are SEM and EDS images of the alloy after two-stage homogenization annealing in an embodiment of the present invention.

[0018] Figure 3 This is an optical microstructure diagram of the alloy after single-stage homogenization annealing, which is Comparative Example 1 of this invention.

[0019] Figure 4 The images shown are SEM and EDS spectra of the alloy after single-stage homogenization annealing in Comparative Example 1 of this invention.

[0020] Figure 5 This is an optical microstructure diagram of the alloy after double-stage homogenization annealing, which is Comparative Example 2 of this invention.

[0021] Figure 6 The images shown are SEM and EDS spectra of the alloy after two-stage homogenization annealing in Comparative Example 2 of this invention.

[0022] Figure 7 These are the XRD patterns of the alloys in the homogenized annealed state of the embodiments of the present invention, Comparative Example 1, and Comparative Example 2.

[0023] Figure 8 These are the DSC spectra of the alloys in the homogenized annealed state of the embodiments of the present invention, Comparative Example 1, and Comparative Example 2.

[0024] Figure 9 This is a comparison chart of the mechanical properties of alloys in the embodiments of the present invention, Comparative Example 1, and Comparative Example 2.

[0025] Table 2 is a table of mechanical property data of alloys in the embodiments of the present invention, Comparative Example 1, and Comparative Example 2.

[0026] Figure 10 These are SEM and EDS images of the aged alloy sheet in an embodiment of the present invention.

[0027] Figure 11 The images shown are SEM and EDS spectra of the aged alloy sheet in Comparative Example 1 of this invention. Detailed Implementation

[0028] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0029] Example 1: In this embodiment, the alloy was prepared according to the following mass percentages: Zn 5.34%, Mg 2.45%, Cu 1.54%, Fe 0.26%, Mn 0.24%, Cr 0.20%, Si 0.14%, Zr 0.10%, Ti 0.05%. The balance consists of Al and unavoidable impurities. The alloy is produced using a semi-continuous casting method based on dry well casting. The process is as follows: the degassed and slag-removed melt is fed into the crystallizer through a flow channel to begin semi-continuous direct cooling casting. At this time, the scraper is turned on to block the outer surface of the ingot and prevent the cooling water from contacting the ingot. In addition, the cooling water is evacuated in advance to form dry well casting conditions, which can raise the ingot temperature, which is beneficial to the elimination of internal stress and the enhancement of plasticity, thereby avoiding crack formation. After casting, the ingot is first water-cooled for 10-60 seconds, and then the water supply is immediately stopped. The ingot is left to cool in the well for 1-2 hours. Finally, the ingot is lifted, and a 100×20×8.5mm sample is taken from the ingot for homogenization heat treatment experiments. The homogenization treatment process is shown in Table 1 (Example). The optical microstructure characterization after double-stage homogenization annealing is as follows. Figure 1 As shown, to further determine the second phase, scanning electron microscopy (SEM) and EDS characterization were performed, as follows: Figure 2 As shown, no coarse S phase was observed. Furthermore, to comprehensively analyze the precipitation behavior of S-Al2CuMg during the homogenization annealing cooling stage, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses were performed on the cooled alloy. Figure 7 and Figure 8As shown, no S-phase diffraction peaks were observed in the XRD pattern after furnace cooling, and no S-phase endothermic peaks were observed in the DSC curve. Therefore, the two-stage homogenization heating in this embodiment can suppress the precipitation of the S-phase during the slow cooling process of homogenization annealing. Subsequently, the homogenized alloy was heated to 430°C in the furnace and held for 30 minutes before undergoing the first hot rolling with a reduction of 4.2 mm, the second hot rolling with a reduction of 0.8 mm, and the third hot rolling with a reduction of 0.5 mm, resulting in a total hot rolling reduction of 64.7%. After cooling to room temperature, two cold rolling passes were performed, with a reduction of 0.8 mm in the first pass and 0.2 mm in the second pass. The final sample thickness was 2 mm, with a total reduction of approximately 76.5%.

[0030] Homogenization heat treatment number heating rate Homogenization heat treatment process parameters Cooling method Example 4℃ / min 465℃ / 8h + 480℃ / 12h Furnace cooling (100℃ / h) Comparative Example 1 4℃ / min 465℃ / 20h Furnace cooling (100℃ / h) Comparative Example 2 4℃ / min 465℃ / 8h + 480℃ / 12h Furnace cooling (100℃ / h) Table 1 Subsequently, the rolled sheet underwent solution treatment, specifically by heating the sample in a muffle furnace to 470°C at a rate of 10°C / min and holding it at that temperature for 1 hour. Finally, it was cooled to room temperature in water. The solution-treated sample was then subjected to aging treatment within 5 minutes at 120°C for 24 hours. The final mechanical properties of the sheet were as follows: Figure 9 As shown in Table 2, the microstructure of the aged alloy sheet was characterized by SEM and EDS, and the results are as follows. Figure 10 As shown, no obvious coarse S phase residues were observed in the aged alloy.

[0031] process Yield strength / MPa Tensile strength / MPa Elongation / % Example 484.9 578.7 13.9 Comparative Example 1 442.7 539.5 10.0 Comparative Example 2 446.8 543.2 9.9 Table 2 Comparative Example 1: The alloy composition and casting method are the same as in the examples. The homogenization heat treatment process is shown in Table 1 (Comparative Example 1), and the optical microstructure characterization is as follows: Figure 3 As shown, to further identify the second phase, SEM and EDS characterization were performed, as follows: Figure 4 As shown, coarse S phase was formed under the slow cooling conditions of homogenization annealing. Furthermore, to comprehensively analyze the precipitation behavior of S-Al2CuMg during the homogenization annealing cooling stage, XRD and DSC analyses were performed on the cooled alloy, as shown below. Figure 7 and Figure 8 As shown, diffraction peaks of the S phase also appeared in the XRD pattern, and obvious endothermic peaks of the S phase also appeared in the DSC curve. Therefore, the traditional single-stage homogenization process cannot suppress the precipitation of the S phase during slow cooling. Subsequently, the sample was subjected to hot rolling + cold rolling + solution treatment + aging (the specific process is consistent with the example). The final mechanical properties of the plate are as follows. Figure 9 As shown in Table 2, the microstructure of the aged alloy sheet was characterized by SEM and EDS, and the results are as follows. Figure 11 As shown, the coarse S phase exhibits a clear genetic effect and remains even after solution treatment and aging treatment.

[0032] Comparative Example 2: The industrial grade 7075 alloy was used, with the following composition: Zn 5.63%, Mg 2.57%, Cu 1.86%, Fe 0.25%, Mn 0.26%, Cr 0.20%, Si 0.16%, Ti 0.06%, and the balance being Al and unavoidable impurities. The alloy was produced using a semi-continuous casting method based on dry well casting. Samples measuring 100×20×8.5mm were taken from the ingot for homogenization heat treatment experiments. The homogenization treatment process is shown in Table 1 (Comparative Example 2). The optical microstructure characterization is as follows: Figure 5 As shown, to further identify the second phase, SEM and EDS characterization were performed, as follows: Figure 6 As shown, even with the two-stage homogenization process of this invention, coarse S-phase still forms under the slow cooling conditions of homogenization annealing. Meanwhile, in order to comprehensively analyze the homogenization annealing cooling stage... The precipitation behavior was investigated, and the cooled alloy was analyzed using XRD and DSC methods, such as... Figure 7 and Figure 8 As shown, S-phase diffraction peaks also appeared in the XRD pattern, and a clear S-phase pattern also appeared in the DSC curve. Endothermic peak Therefore, even after the two-stage homogenization process of this invention, the precipitation of the S phase during slow cooling of the 7075 alloy could not be suppressed. Subsequently, the sample underwent hot rolling + cold rolling + solution treatment + aging (the specific process is consistent with the example). The final mechanical properties of the plate are as follows: Figure 9 As shown in Table 2.

[0033] Compared with the comparative examples, the strength and plasticity of the plates after aging treatment in the embodiments of the present invention were significantly improved, as shown in Table 2. The reason for the improvement in mechanical properties lies in the alloy composition design and process control, such as... Figures 1-4 As shown, compared to the traditional single-stage homogenization process (Comparative Example 1), the two-stage homogenization heat treatment (Example) significantly reduces the area of ​​the coarse second phase after slow cooling, under the same total homogenization time. Figure 2 It is evident that despite the slow cooling (100℃ / h), no coarse particles remained or precipitated in the matrix at this time. Mutually, Figure 7 XRD and Figure 8 DSC in The disappearance of the endothermic peak further verifies this, indicating that the alloy of the present invention and its paired two-stage homogenization process can suppress the precipitation of the S phase under slow cooling conditions. Therefore, as Figure 10 As shown, no obvious S phase residue remained in the matrix after solution treatment, thus improving the final mechanical properties of the plate. In contrast, in Comparative Example 1, the alloy of the present invention precipitated coarse S phase under the traditional single-stage homogenization slow cooling conditions. Figure 4 , Figure 7 and Figure 8All of these confirm this point. Therefore, this produces a significant genetic effect, leading to the residue of the S phase after solution treatment. Consequently, it causes the loss of solute atoms and ultimately results in lower overall mechanical properties of the sheet material. Furthermore, compared to the traditional 7075 alloy (Comparative Example 2), even with the two-stage homogenization process of this invention, it is impossible to completely suppress the coarse particles that appear during the slow cooling process of homogenization annealing. Precipitation of phase, see Figures 6-8 Therefore, the mechanical properties of the subsequent comparative examples in the aging state were also relatively low. In summary, to achieve good final mechanical properties of large-size ingots under slow cooling conditions, both composition design and process control are indispensable.

[0034] The working principle of this invention: The alloy composition of this invention is designed as follows: Zn: 5.0%~5.5%, Mg: 2.1%~2.5%, Cu: 1.1%~1.7%, Mn: 0.2%~0.45%, Cr: 0.18%~0.3%, Zr: 0.08%~0.15%, Ti: ≤0.1%, Fe: ≤0.3%, Si: ≤0.2%; wherein the total content of Mg+Cu is 3.5~4.1wt%, and the total content of Mn+Cr is not less than 0.4%wt.

[0035] The alloy is melted and cast using a semi-continuous casting method and a dry well casting process. The process is as follows: the degassed and slag-removed melt is fed into the crystallizer through a flow channel to begin semi-continuous direct cooling casting. At this time, the scraper is turned on to block the outer surface of the ingot and prevent the cooling water from contacting the ingot. In addition, the cooling water is evacuated in advance to create dry well casting conditions. This can raise the ingot temperature, which is beneficial for eliminating internal stress and enhancing plasticity, thereby avoiding crack formation. After casting, it is first water-cooled for 10-60 seconds, and then the water supply is immediately stopped. It is left to cool statically in the well for 1-2 hours. The ingot is then lifted and subjected to homogenization heat treatment. The temperature is raised to 460-470℃ at a rate of 4-10℃ / min and held for 2-20 hours. The temperature is then raised to 480-485℃ and held for 10-18 hours, followed by cooling to room temperature at a rate as low as 100℃ / h. After homogenization annealing, the sample is heated to 410-450℃ and held for 20-40 minutes before rolling. Hot rolling consists of 3-5 passes: the first pass reduction is 30%-50%, and the total hot rolling reduction is 55%-70%. Cold rolling consists of 2-4 passes: after the ingot cools to below 60℃, 2-4 cold rolling passes are performed, with a total cold rolling reduction of 10%-30%. After hot rolling and cold rolling, the total reduction rate of the plate is 65%-90%. Then, solution treatment is carried out, with the temperature raised to 460℃-470℃ at a rate of 2-10℃ / min, held for 1-2 hours, and then water-quenched. Within 5 minutes, the plate is transferred to an aging furnace for aging treatment at a temperature of 110℃-130℃ for 20-30 hours.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A 7XXX-series aluminum alloy material for large-size ingot under homogenization annealing and slow cooling, characterized by: The composition by mass percentage includes: Zn: 5.0%–5.5%, Mg: 2.1%–2.5%, Cu: 1.1%–1.7%, Mn: 0.2%–0.45%, Cr: 0.18%–0.3%, Zr: 0.08%–0.15%, Ti: ≤0.1%, Fe: ≤0.3%, Si: ≤0.2%; wherein the total content of Mg+Cu is 3.5–4.1 wt%, and the total content of Mn+Cr is not less than 0.4% wt%.

2. A method of manufacturing a 7XXX-series aluminum alloy material for a large-size ingot under homogenizing annealing and slow cooling conditions, characterized by: The process includes, in sequence, casting, homogenization annealing, rolling, solution treatment, and aging treatment. S1. Melting and casting: Semi-continuous casting combined with dry well casting process is adopted, and alloy melt is prepared according to the mass percentage. The melt after degassing and slag removal is semi-continuous direct cooling casting. During casting, the scraper is turned on to prevent the cooling water from contacting the ingot. The cooling water is evacuated in advance to form dry well casting conditions. After casting, the ingot is water cooled for 10 to 60 seconds, the water supply is stopped, and the ingot is left to cool in the well for 1 to 2 hours before being hoisted. S2. Homogenization Annealing: After heating the ingot, it undergoes two-stage heat preservation, followed by slow cooling to room temperature. The homogenization annealing adopts a two-stage heat preservation process: first, the temperature is raised to 460-470℃ and held for 2-12 hours, then raised to 480-485℃ and held for 10-18 hours. During the cooling process, the cooling rate can be as low as 100℃ / h. S3. Rolling: The homogenized ingot is heated to 410-450℃ and held for 20-40 minutes, then hot-rolled with a total reduction of 55%-70%. After cooling to below 60℃, it is cold-rolled with a total reduction of 10%-30%. After hot rolling and cold rolling, the final sheet material has a total reduction of 65%-90%. The homogenized annealed ingot is then hot-rolled and cold-rolled to produce sheet material. S4. Solution treatment: Heat the rolled plate to 460℃-470℃ at a heating rate of 2-10℃ / min, hold for 1-2 hours, and then water quench. S5. Aging treatment: The quenched plate is transferred into an aging furnace within 5 minutes for heat treatment, and aged at 110℃-130℃ for 20-30 hours to obtain the final aluminum alloy material.

3. The method of claim 2, wherein the 7XXX-series aluminum alloy material for a large-sized ingot under homogenization annealing and slow cooling conditions is characterized by: The heating rate for homogenization annealing is 4–10 °C / min.

4. The method of claim 2, wherein the 7XXX-series aluminum alloy material for a large-sized ingot under homogenization annealing and slow cooling conditions is characterized by: The two-stage heat preservation process involves first heating to 460–470°C and holding for 2–12 hours, then heating to 480–485°C and holding for 10–18 hours.

5. The method of making a 7XXX-series aluminum alloy material for large- ingot homogenization and annealing slow-cooling conditions according to claim 2, wherein: The first stage involves treatment at 465℃ for 8 hours, and the second stage involves treatment at 480℃ for 12 hours.

6. The method for manufacturing 7XXX series aluminum alloy materials for large-size ingots under homogenized annealing and slow cooling conditions according to claim 2, characterized in that: The hot rolling is carried out after heating to 420-450℃ and holding for 20-40 minutes. Except for the first pass, the reduction rate of each other pass is 10%-30%, and the total reduction rate of hot rolling is 55%-70%.

7. The method for manufacturing 7XXX series aluminum alloy materials for large-size ingots under homogenized annealing and slow cooling conditions according to claim 2, characterized in that: The cold rolling process consists of 2-4 passes: the ingot is cooled to below 60°C, the total cold rolling reduction is 10% to 30%, and the final plate has a total reduction of 65% to 90%.

8. The method for manufacturing 7XXX series aluminum alloy materials for large-size ingots under homogenized annealing and slow cooling conditions according to claim 2, characterized in that: The solution treatment is as follows: the temperature is increased to 460-470℃ at a rate of 2-10℃ / min, held for 1-2 hours, and then quenched by water cooling.

9. The method for manufacturing 7XXX series aluminum alloy materials for large-size ingots under homogenized annealing and slow cooling conditions according to claim 2, characterized in that: The prepared aluminum alloy sheet has a yield strength ≥480MPa, tensile strength ≥570MPa, and elongation ≥13%.

Images