Preparation method of high-strength and high-ductility aluminum-zinc-magnesium-lithium alloy

Abstract

A method for preparing a high-strength, high-ductility aluminum-zinc-magnesium-lithium alloy employs composite plastic forming. This method utilizes multi-pass, high-deformation, variable-temperature rolling technology to improve the solubility of solute elements, reduce the concentration of coarse, brittle phases, and enhance the recrystallization of the matrix. Simultaneously, the electroplastic effect under intermediate-temperature conditions promotes the interaction between deformation dislocations and drift electrons, reducing the energy required for dislocation activation and thus lowering the deformation stress. This composite process also increases the local strain of the material, promoting uniform deformation of the matrix during forming and further improving its elongation, ultimately producing a high-strength, high-ductility aluminum-lithium alloy for aerospace applications.

Description

Technical Field

[0001] This technology belongs to the field of aluminum-lithium alloy plastic manufacturing, and specifically relates to a method for preparing a high-strength and high-ductility aluminum-zinc-magnesium-lithium alloy. Background Technology

[0002] Aluminum-lithium alloys, due to their low density, excellent elastic modulus, high strength, and specific stiffness, have broad application prospects in aerospace, rail transportation, and other fields. However, current traditional aluminum-lithium structural component manufacturing methods, such as casting, have limitations such as long production cycles and low material utilization, which also increases manufacturing costs. Arc additive manufacturing, as a new technology with high deposition rates, is widely used in the preparation of metal alloys. However, aluminum-lithium alloy additive manufacturing faces serious challenges in performance control. Existing research shows that aluminum-lithium alloys prepared using arc additive manufacturing or traditional casting techniques have tensile strengths of approximately 200-500 MPa and elongation of 5-12%. After solution treatment and aging, the strength can reach 400-550 MPa. With the development of the aerospace industry, the strength requirements for aluminum-lithium alloys are becoming increasingly stringent, exceeding 650 MPa. However, at present, due to the melting of metal wires involved in arc additive manufacturing, and the high solidification shrinkage and thermal conductivity of aluminum-lithium alloys, as well as the tendency for hydrogen absorption during manufacturing, problems such as porosity, coarse grains, and brittle phase agglomeration inevitably arise. This results in components with low strength and plasticity, failing to meet the application requirements of the aerospace field. Furthermore, traditional hot rolling and hot forging processes offer limited improvements in the performance of additively manufactured aluminum-lithium alloys, still unable to meet the ever-increasing application demands. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing a high-strength and high-ductility aluminum-zinc-magnesium-lithium alloy, in order to solve the above problems and improve the strength and ductility of the aluminum-lithium alloy.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a high-strength, high-ductility aluminum-zinc-magnesium-lithium alloy includes the following steps:

[0006] Step 1: The aluminum-zinc-magnesium-lithium alloy is subjected to strengthening solution treatment, quenching and aging treatment in sequence;

[0007] Step 2: The solution-treated aged alloy material obtained in Step 1 is hot-rolled while a high-energy pulsed current is applied to the upper and lower rolls. The deformation per pass is 20-35%. The hot rolling is repeated until the total deformation is 50-60%, thus achieving electro-plastic forming.

[0008] Step 3: Air-cool the electro-plastic forming material to room temperature, and then perform deep cryogenic rolling, with a single-pass deformation of 5-15%. Repeat deep cryogenic rolling until the total deformation reaches 70-80%.

[0009] Step 4: The material that has completed deep cryogenic rolling is hot rolled again, while a high-energy pulse current is applied to the upper and lower rolls. The deformation amount is set to 8-15%. The hot rolling is repeated until the total deformation amount is 80-85%.

[0010] Step 5: The material obtained in Step 4 is subjected to medium-temperature rolling, with a single-pass deformation of 10-25%. The medium-temperature rolling is repeated until the total deformation is 85-95%.

[0011] Step 6: The material that has been rolled at medium temperature is subjected to low temperature aging treatment to obtain a high-strength and high-ductility aluminum-zinc-magnesium-lithium alloy.

[0012] In one embodiment, in step 1, the aluminum-zinc-magnesium-lithium alloy is manufactured using arc additive manufacturing 3D printing technology, and its composition by weight is:

[0013] Zn: 3.8-6.0%, Mg: 1.8-2.8%, Li: 0.5-2.0%, Cu: 1.3-1.8%, balance Al.

[0014] In one embodiment, step 1, the strengthening solution treatment conditions are: 530-541℃, holding for 1-1.5h; the quenching treatment conditions are: cooling water quenching, transfer time less than 5s; the aging treatment conditions are: aging furnace at 200-220℃, 4-6h.

[0015] In one embodiment, the hot rolling temperature in steps 2 and 4 is 200-230°C.

[0016] In one embodiment, step 2 involves cutting the solution-aged alloy material to a thickness of 30-50 mm, then heating it to 470°C, holding it at that temperature for 30-60 minutes, cooling it to 200-230°C, and then hot rolling it.

[0017] In one embodiment, the parameters of the high-energy pulse current in steps 2 and 4 are: pulse current amplitude 1200-3000A, frequency 50-200Hz, and duty cycle 5-15%.

[0018] In one embodiment, in step 3, the temperature of cryogenic rolling is -190 to -50°C.

[0019] In one embodiment, in step 5, the temperature of the medium-temperature rolling is 100-150°C.

[0020] In one embodiment, after the intermediate temperature rolling is completed in step 5, the material is stored in a low-temperature chamber at -80 to -50°C.

[0021] In one embodiment, the conditions for the low-temperature aging treatment in step 6 are: aging furnace at 60-150℃ for 20-45 hours.

[0022] The principle of this invention is as follows:

[0023] A composite plastic forming method is employed, utilizing multi-pass, large-deformation, variable-temperature rolling technology to enhance the solubility of solute elements, reduce the concentration of coarse, brittle phases, and improve the recrystallization of the matrix. Simultaneously, the electroplastic effect under intermediate-temperature conditions promotes the interaction between deformation dislocations and drift electrons, reducing the energy required for dislocation activation and thus lowering the deformation stress. This composite process also increases local strain, promoting uniform deformation of the matrix during forming and further improving elongation, ultimately producing a high-strength, high-ductility aluminum-lithium alloy for aerospace applications. Currently, there are no research reports, either domestically or internationally, on the preparation of high-performance aluminum-lithium alloys using composite multi-pass, large-deformation, variable-temperature rolling technology combined with electroplastic forming technology.

[0024] Compared with the blanks produced by arc-assisted additive manufacturing, the aluminum-zinc-magnesium-lithium alloy produced by the method of this invention has an increased ultimate tensile strength of 50-70% and an increased elongation at break of 100-200%. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the rolling process of the present invention.

[0026] Figure 2 This is a schematic diagram comparing the performance of the material obtained by the preparation method of this invention with that of the material obtained by the existing process.

[0027] Among them: 1-frame, 2-drive roller, 3-ceramic insulator, 4-upper roll, 5-drive shaft insulating block, 6-pulse power supply, 7-rolled material, 8-lower roll, 9-temperature measuring instrument. Detailed Implementation

[0028] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0029] This invention discloses a method for preparing aluminum-zinc-magnesium-lithium alloys using a combination of temperature-dependent plastic forming and electro-plastic forming. The steps are described below:

[0030] Step 1: The aluminum-zinc-magnesium-lithium alloy is subjected to strengthening solution treatment, quenching and aging treatment in sequence.

[0031] Specifically, in this embodiment of the invention, an aluminum-zinc-magnesium-lithium alloy manufactured using arc additive manufacturing 3D printing technology is used. This alloy has a Zn content of 3.8-6.0%, a Mg content of 1.8-2.8%, a Li content of 0.5-2.0%, a Cu content of 1.3-1.8%, and the balance being Al. It undergoes a strengthening solution treatment at 530-541℃ for 1-1.5 hours, followed by a cooling water quenching treatment with a transfer time of less than 5 seconds. The alloy is then placed in an aging furnace at 200-220℃ for 4-6 hours of aging treatment, and finally cooled to room temperature in the furnace. These treatment steps ensure more uniform performance across different sample groups.

[0032] Step 2: The solution-treated aged alloy material obtained in Step 1 is hot-rolled while a high-energy pulsed current is applied to the upper and lower rolls. The deformation per pass is 20-35%. The hot rolling is repeated until the total deformation is 50-60%, thus achieving electro-plastic forming.

[0033] This step utilizes the initial porosity defects within the high-temperature, high-deformation welded material to increase the solubility of solute elements, reduce the concentration of coarse, brittle phases, and enhance the material's plastic deformation capacity. Simultaneously, the electroplastic effect promotes the interaction between deformation dislocations and drifting electrons, reducing the energy required for dislocation activation and thus lowering deformation stress. The electromagnetic pulse effect can also improve the temperature uniformity of the matrix during hot rolling, reduce the temperature gradient in the microstructure, delay the phase transformation process, and introduce a stress relaxation effect, reducing residual stress generated by deformation, decreasing grain boundary slip resistance, regulating grain boundary plastic deformation behavior, and further refining the alloy grain size.

[0034] In this embodiment of the invention, the hot rolling temperature is set to 200-230℃. Specifically, the solution-aged alloy material can first be cut to a thickness of 30-50mm to reduce the effects of uneven temperature and uneven deformation along the thickness direction. It is then placed in a resistance furnace and heated to 470℃, held for 30-60 minutes, to perform secondary solution strengthening, promoting the maximum dissolution of solute elements such as Zn and Cu in the aluminum matrix. Finally, it is cooled in the furnace to 200-230℃. The reason for deforming the material at 200-230℃ in this step is to prevent overheating caused by the high temperature generated during the hot rolling process due to the application of electromagnetic pulses.

[0035] After the material reaches the specified temperature, it is placed in a rolling mill for single-pass hot rolling with a transfer time of less than 5 seconds and a deformation of 20-35%. Once the rolls engage the alloy material, a high-energy pulsed current is applied to both the upper and lower rolls simultaneously. This process is repeated until the total deformation reaches 50-60%, achieving the effect of thinning the sample while significantly improving the alloy's ductility.

[0036] For example, see reference Figure 1The rolling mill mainly consists of the following parts: frame 1, drive roll 2, upper roll 4, and lower roll 8. The upper roll 4 is driven by the drive roll 2. The surface of the drive roll 2 has a ceramic insulator 3. The drive shaft of the upper roll 4 has a drive shaft insulator 5. The pulse power supply 6 connects the upper roll 4 and the lower roll 8 and applies a high-energy pulse current to them. The upper roll 4 and the lower roll 8 perform the rolling process on the rolled material 7 under the set conditions. The temperature measuring instrument 9 monitors the temperature of the rolled material 7 in real time.

[0037] During hot rolling, a high-energy pulsed current is connected to the upper and lower rolls. The pulsed current amplitude is 1200-3000A, the frequency is 50-200Hz, and the duty cycle is 5-15%. The pulsed current is provided by a pulse power supply with a constant temperature mode. An infrared temperature measuring device is installed at the top of the mill outlet, with an alarm temperature set at 535-541℃. When the temperature exceeds the set temperature, the pulse power supply will issue an alarm and stop working. Ceramic insulating sheets are installed between the upper and lower rolls and the mill and drive shaft to prevent the pulsed current from being conducted to the mill, affecting the mill operation and the safety of the experimental personnel.

[0038] Step 3: Air-cool the electro-plastic forming material to room temperature, and then perform deep cryogenic rolling, with a single-pass deformation of 5-15%. Repeat deep cryogenic rolling until the total deformation is 70-80%.

[0039] The purpose of this step is to significantly increase the dislocation density of the material through cryogenic plastic deformation, thereby promoting the integrated control of deformation resistance and shape properties of aluminum-zinc-magnesium-lithium alloys during subsequent hot rolling and electromagnetic pulse forming processes.

[0040] Specifically, in this embodiment of the invention, after electroforming, the sample is first air-cooled to room temperature. Then, the sample is placed in a cryogenic chamber at -190 to -50°C for 30-60 minutes, removed, and quickly transferred to a rolling mill for single-pass cryogenic rolling. The transfer time is less than 5 seconds, and the deformation per pass is 5-15%. After single-pass rolling, the aluminum-lithium alloy is again placed in a -150°C cryogenic chamber for 30-60 minutes. This cryogenic process is repeated until the total deformation is 70-80%. During cryogenic rolling, the rolls and alloy are sprayed with liquid nitrogen to reduce the temperature rise caused by the plastic deformation process. The liquid nitrogen nozzle is connected to a liquid nitrogen tank, and the pipeline is equipped with an adjustable four-way valve. The liquid nitrogen spray rate is adjusted within the range of 0.8-5.0 L / min according to the material volume and thickness.

[0041] Step 4: The material that has been cryogenically rolled is hot rolled again, while a high-energy pulse current is applied to the upper and lower rolls. The deformation is set to 8-15%. The hot rolling is repeated until the total deformation is 80-85%.

[0042] The purpose of this step is to further regulate the plastic deformation capacity of aluminum-zinc-magnesium-lithium alloys, remove residual porosity defects inside the welding material, promote the breakage and dispersion of coarse and concentrated brittle phases, refine the grains, and achieve a synergistic improvement in material strength and elongation.

[0043] Specifically, in this embodiment of the invention, the aluminum-lithium alloy is placed in a heating furnace and heated to 200-230°C, held for 20-30 minutes, and then placed in a rolling mill for hot rolling. The transfer time is less than 5 seconds, the deformation is set to 10%, and after the rolls bite into the alloy material, a high-energy pulse current is applied to the upper and lower rolls simultaneously.

[0044] Step 5: The material obtained in Step 4 is subjected to medium-temperature rolling, with a single-pass deformation of 10-25%. The medium-temperature rolling is repeated until the total deformation is 85-95%.

[0045] The purpose of this step is to generate a large number of defects such as dislocations and vacancies inside the material during the medium- and low-temperature deformation process, which promotes the precipitation of strengthening phases in the subsequent aging process; the medium- and low-temperature deformation causes some solute atoms to segregate and accumulate near grain boundaries or dislocations, which promotes the realization of the material's age hardening process; at the same time, it refines the grains and further improves the material's strength.

[0046] Specifically, in this embodiment of the invention, the material obtained in step 4 is placed in a heating furnace and heated to 100-150°C, held at that temperature for 20-30 minutes, and immediately transferred to a rolling mill for medium-temperature rolling. The transfer time is less than 5 seconds, and the deformation per pass is controlled at 10-25%. The above process is repeated until the total deformation is 85-95%. The alloy can be stored in a low-temperature chamber at -80 to -50°C to maximize the preservation of internal distortions and dislocations in the material and reduce the weakening effect of natural aging on the material's properties.

[0047] Step 6: The material that has been rolled at medium temperature is subjected to low temperature aging treatment to obtain a high-strength and high-ductility aluminum-zinc-magnesium-lithium alloy.

[0048] This step utilizes a low-temperature environment to reduce dislocation recovery and the static recovery and recrystallization processes within the material, promoting the precipitation of solute elements and forming a high-density, uniformly distributed fine reinforcing phase. This reinforcing phase can hinder crystal slip, improving the strength and hardness of the alloy, while its uniform distribution ensures good plasticity. Furthermore, the formation of the reinforcing phase involves dislocation movement and rearrangement, and the low-temperature environment slows down dislocation recovery, thus enhancing the age-hardening effect of the alloy.

[0049] Specifically, in this embodiment of the invention, the deformed aluminum-lithium alloy is placed in an aging furnace at 60-150℃ for low-temperature aging treatment, and the aging holding time is 20-45h. After aging is completed, the sample is taken out and air-cooled to room temperature.

[0050] To verify the effectiveness of the present invention, the following specific embodiments are provided.

[0051] Example 1

[0052] A method for preparing a high-strength, high-ductility aluminum-zinc-magnesium-lithium alloy includes the following steps:

[0053] Step 1: Take an aluminum-zinc-magnesium-lithium alloy prepared by arc additive manufacturing 3D printing technology. Its composition is: 5.8% Zn-2.5Mg-1.5Cu-0.2Cr-1.5Li-0.1Fe-0.1Mn-balance Al. Place it in a resistance furnace for strengthening solution treatment at 541℃, hold for 1.5h, quench with cooling water to room temperature, and transfer time is less than 5s.

[0054] Step 2: Place the alloy in an aging furnace at 200℃ for 6 hours of aging treatment, and then cool it to room temperature with the furnace.

[0055] Step 3: Cut the alloy material to a thickness of 45mm, place it in a resistance furnace and heat it to 470℃, hold it at that temperature for 60 minutes, and then cool it to 200℃ in the furnace.

[0056] Step 4: Take out the sample and place it in the rolling mill for single-pass hot rolling. The transfer time is less than 5 seconds and the deformation is set to 20%. After the rolls bite into the alloy material, apply a high-energy pulse current to the upper and lower rolls at the same time. The pulse current amplitude is 1200-3000A, the frequency is 50-200Hz, and the duty cycle is 5-15%.

[0057] Step 5: Repeat step 4 until the total rolling deformation reaches 60%, then air-cool the material to room temperature.

[0058] Step 6: Place the material in a -150℃ cryogenic chamber for 30-60 minutes.

[0059] Step 7: Remove the material and quickly transfer it to the rolling mill for single-pass cryogenic rolling. The transfer time is less than 5 seconds, and the single-pass rolling deformation is 10%. During the cryogenic rolling process, the rolls and alloy are sprayed with liquid nitrogen at a rate of 3.5 L / min.

[0060] Step 8: Repeat steps 6 and 7 until the total deformation is 75%.

[0061] Step 9: Place the aluminum-lithium alloy in a heating furnace and heat it to 200°C, then hold it at that temperature for 30 minutes.

[0062] Step 10: Remove the material and quickly transfer it to the rolling mill for hot rolling. The transfer time should be less than 5 seconds, and the deformation amount should be set to 10%. After the rolls bite into the alloy material, apply a high-energy pulse current to the upper and lower rolls at the same time.

[0063] Step 11: Repeat steps 9 and 10 until the total deformation is 80%.

[0064] Step 12: Place the sample in a heating furnace and heat it to 125°C, then keep it at that temperature for 25 minutes.

[0065] Step 13: Remove the material and immediately transfer it to the rolling mill for medium-temperature rolling. The transfer time should be less than 5 seconds, and the deformation amount per pass should be controlled at 15%.

[0066] Step 14: Repeat steps 12 and 13 until the total rolling deformation reaches 93%.

[0067] Step 15: Store the alloy in a -57°C low-temperature chamber.

[0068] Step 16: Place the aluminum-lithium alloy in a 100℃ aging furnace for low-temperature aging treatment. The aging holding time is 34 hours. After aging is completed, take out the sample and air-cool it to room temperature.

[0069] The aluminum-zinc-magnesium-lithium alloy prepared in Example 1 exhibits high ultimate tensile strength and ductility. Compared with the aged 3D-printed billet, its tensile strength increases from 525 MPa to 728 MPa, while maintaining high strength and a relatively high elongation at break (17.0%). Compared with the traditional hot-rolling aging process at 200-260℃, its tensile strength is increased by approximately 40%. Figure 2 .

[0070] Example 2

[0071] A method for preparing a high-strength, high-ductility aluminum-zinc-magnesium-lithium alloy includes the following steps:

[0072] Step 1: Take an aluminum-zinc-magnesium-lithium alloy prepared by arc additive manufacturing 3D printing technology. Its composition is: 4.3% Zn-2.2Mg-1.8Cu-0.2Cr-1.9Li-0.1Fe-0.1Mn-balance Al. Place it in a resistance furnace for strengthening solution treatment at 535℃, hold for 1.5h, quench with cooling water to room temperature, and transfer time is less than 5s.

[0073] Step 2: Place the alloy in an aging furnace at 220℃ for 4.5 hours of aging treatment, and then cool it to room temperature with the furnace.

[0074] Step 3: Cut the alloy material to a thickness of 45mm, place it in a resistance furnace and heat it to 470℃, hold it at that temperature for 40 minutes, and then cool it to 230℃ in the furnace.

[0075] Step 4: Take out the sample and place it in the rolling mill for single-pass hot rolling. The transfer time is less than 5 seconds and the deformation is set to 30%. After the rolls bite into the alloy material, apply a high-energy pulse current to the upper and lower rolls at the same time. The pulse current amplitude is 1200-3000A, the frequency is 50-200Hz, and the duty cycle is 5-15%.

[0076] Step 5: Repeat step 4 until the total rolling deformation reaches 55%, then air-cool the material to room temperature.

[0077] Step 6: Place the material in a -50℃ cryogenic chamber for 60 minutes.

[0078] Step 7: Remove the material and quickly transfer it to the rolling mill for single-pass cryogenic rolling. The transfer time is less than 5 seconds, and the single-pass rolling deformation is 15%. During the cryogenic rolling process, the rolls and alloy are sprayed with liquid nitrogen at a rate of 3.5 L / min.

[0079] Step 8: Repeat steps 6 and 7 until the total deformation is 80%.

[0080] Step 9: Place the aluminum-lithium alloy in a heating furnace and heat it to 230°C, then hold it at that temperature for 20 minutes.

[0081] Step 10: Remove the material and quickly transfer it to the rolling mill for hot rolling. The transfer time should be less than 5 seconds, and the deformation amount should be set to 14%. After the rolls bite into the alloy material, apply a high-energy pulse current to the upper and lower rolls at the same time.

[0082] Step 11: Repeat steps 9 and 10 until the total deformation is 85%.

[0083] Step 12: Place the sample in a heating furnace and heat it to 150°C, then keep it at that temperature for 20 minutes.

[0084] Step 13: Remove the material and immediately transfer it to the rolling mill for medium-temperature rolling. The transfer time should be less than 5 seconds, and the deformation amount per pass should be controlled at 25%.

[0085] Step 14: Repeat steps 12 and 13 until the total rolling deformation reaches 95%.

[0086] Step 15: Store the alloy in a -80℃ low-temperature chamber.

[0087] Step 16: Place the aluminum-lithium alloy in a 120℃ aging furnace for low-temperature aging treatment. The aging holding time is 40 hours. After aging is completed, take out the sample and air-cool it to room temperature.

[0088] The aluminum-zinc-magnesium-lithium alloy prepared in Example 2 has high ultimate tensile strength and ductility. Compared with the aged 3D printed blank, its tensile strength is increased from 525MPa to 736MPa. It retains a high fracture elongation while having high strength.

[0089] Example 3

[0090] A method for preparing a high-strength, high-ductility aluminum-zinc-magnesium-lithium alloy includes the following steps:

[0091] Step 1: Take an aluminum-zinc-magnesium-lithium alloy prepared by arc additive manufacturing 3D printing technology. Its composition is: 4.9% Zn-2.8Mg-1.3Cu-0.1Cr-1.0Li-0.1Fe-0.1Mn-balance Al. Place it in a resistance furnace for strengthening solution treatment at 530℃, hold for 1.5h, quench with cooling water to room temperature, and transfer time is less than 5s.

[0092] Step 2: Place the alloy in an aging furnace at 210℃ for 5 hours of aging treatment, and then cool it to room temperature with the furnace.

[0093] Step 3: Cut the alloy material to a thickness of 30mm, place it in a resistance furnace and heat it to 470℃, hold it for 30 minutes, and then cool it to 210℃ in the furnace.

[0094] Step 4: Take out the sample and place it in the rolling mill for single-pass hot rolling. The transfer time is less than 5 seconds and the deformation is set to 27%. After the rolls bite into the alloy material, apply a high-energy pulse current to the upper and lower rolls at the same time. The pulse current amplitude is 1200-3000A, the frequency is 50-200Hz, and the duty cycle is 5-15%.

[0095] Step 5: Repeat step 4 until the total rolling deformation reaches 50%, then air-cool the material to room temperature.

[0096] Step 6: Place the material in a -190℃ cryogenic chamber for 35 minutes.

[0097] Step 7: Remove the material and quickly transfer it to the rolling mill for single-pass cryogenic rolling. The transfer time is less than 5 seconds, and the deformation amount of single-pass rolling is 5%. During the cryogenic rolling process, the rolls and alloy are sprayed with liquid nitrogen at a rate of 3.5 L / min.

[0098] Step 8: Repeat steps 6 and 7 until the total deformation is 70%.

[0099] Step 9: Place the aluminum-lithium alloy in a heating furnace and heat it to 210°C, then hold it at that temperature for 20 minutes.

[0100] Step 10: Remove the material and quickly transfer it to the rolling mill for hot rolling. The transfer time should be less than 5 seconds, and the deformation amount should be set to 8%. After the rolls bite into the alloy material, apply a high-energy pulse current to the upper and lower rolls at the same time.

[0101] Step 11: Repeat steps 9 and 10 until the total deformation is 83%.

[0102] Step 12: Place the sample in a heating furnace and heat it to 100°C, then keep it at that temperature for 230 minutes.

[0103] Step 13: Remove the material and immediately transfer it to the rolling mill for medium-temperature rolling. The transfer time should be less than 5 seconds, and the deformation amount per pass should be controlled at 10%.

[0104] Step 14: Repeat steps 12 and 13 until the total rolling deformation reaches 88%.

[0105] Step 15: Store the alloy in a -80℃ low-temperature chamber.

[0106] Step 16: Place the aluminum-lithium alloy in a 65℃ aging furnace for low-temperature aging treatment. The aging holding time is 45 hours. After aging is completed, take out the sample and air-cool it to room temperature.

[0107] The aluminum-zinc-magnesium-lithium alloy prepared in Example 3 has high ultimate tensile strength and ductility. Compared with the aged 3D printed blank, its tensile strength increased from 525MPa to 701MPa, the elongation at break was about 13.5%, and the material still retained high ductility.

Claims

1. A method for preparing a high-strength, high-ductility aluminum-zinc-magnesium-lithium alloy, characterized in that, Includes the following steps: Step 1: The aluminum-zinc-magnesium-lithium alloy is subjected to strengthening solution treatment, quenching, and aging treatment in sequence. The composition of the aluminum-zinc-magnesium-lithium alloy by weight is as follows: Zn: 3.8-6.0%, Mg: 1.8-2.8%, Li: 0.5-2.0%, Cu: 1.3-1.8%, balance Al; The conditions for strengthening solution treatment are: 530-541℃, holding for 1-1.5h; the conditions for quenching treatment are: cooling water quenching, transfer time less than 5s; the conditions for aging treatment are: aging furnace at 200-220℃, 4-6h. Step 2: The solution-treated aged alloy material obtained in Step 1 is hot-rolled at 200-230℃ while a high-energy pulsed current is applied to the upper and lower rolls. The deformation per pass is 20-35%. The hot rolling is repeated until the total deformation is 50-60%, thus achieving electro-plastic forming. Step 3: Air-cool the electro-plastic forming material to room temperature, and then perform cryogenic rolling, with a single-pass deformation of 5-15%, and repeat cryogenic rolling until the total deformation is 70-80%; the temperature of cryogenic rolling is -190 to -50℃. Step 4: The material that has undergone cryogenic rolling is hot-rolled again at 200-230℃, while a high-energy pulsed current is applied to the upper and lower rolls. The deformation is set to 8-15%. The hot rolling is repeated until the total deformation is 80-85%. In steps 2 and 4, the parameters of the high-energy pulsed current are: pulse current amplitude 1200-3000A, frequency 50-200Hz, and duty cycle 5-15%. Step 5: The material obtained in Step 4 is subjected to medium-temperature rolling, wherein the deformation per pass is 10-25%, and the medium-temperature rolling is repeated until the total deformation is 85-95%; wherein the temperature of medium-temperature rolling is 100-150℃. Step 6: The material that has been rolled at medium temperature is subjected to low-temperature aging treatment to obtain a high-strength and high-ductility aluminum-zinc-magnesium-lithium alloy. The conditions for low-temperature aging treatment are: aging furnace at 60-150℃ for 20-45 hours.

2. The method for preparing high-strength, high-ductility aluminum-zinc-magnesium-lithium alloy according to claim 1, characterized in that, In step 2, the solution-treated aged alloy material is cut to a thickness of 30-50 mm, then heated to 470°C, held for 30-60 min, cooled to 200-230°C, and then hot rolled.

3. The method for preparing high-strength, high-ductility aluminum-zinc-magnesium-lithium alloy according to claim 1, characterized in that, After the intermediate temperature rolling is completed in step 5, the material is stored in a low temperature chamber at -80 to -50°C.

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