A method for preparing a high-strength aluminum-lithium alloy

Abstract

A preparation method of a high-strength aluminum-lithium alloy, the method comprising: subjecting an aluminum-lithium-antimony alloy with a thickness of 25-55 mm to medium-temperature rolling at 200-220 DEG C, applying a pulse current to the aluminum-lithium-antimony alloy during the rolling to complete electroplastic forming; cooling the material after the electroplastic forming to -100 to -120 DEG C to perform multi-pass ultra-low-temperature rolling; the single-pass deformation of the ultra-low-temperature rolling being 10-18%, and the total deformation being 25-35%, to complete ultra-low-temperature plastic deformation; heating the material after the ultra-low-temperature plastic deformation to 90-130 DEG C to perform multi-pass medium-low-temperature rolling; the single-pass deformation of the medium-low-temperature rolling being 10-15%, and the total deformation being 45-65%, to complete medium-low-temperature plastic deformation; again cooling the material after the medium-low-temperature plastic deformation to -100 to -120 DEG C to perform single-pass ultra-low-temperature rolling; subjecting the obtained material to low-temperature aging treatment and air cooling to room temperature to obtain the high-strength aluminum-lithium alloy.

Description

Technical Field

[0001] This invention belongs to the field of plastic manufacturing of aluminum-lithium-antimony alloys, and specifically relates to a method for preparing high-strength aluminum-lithium alloys. Background Technology

[0002] Aluminum-lithium alloys, with their advantages of being lightweight, high-strength, and corrosion-resistant, have become the preferred material for next-generation aerospace structural components such as wings, beams, and fuselage plates. Currently, aluminum-lithium alloys are typically prepared using traditional casting, powder metallurgy, and spray forming methods. However, due to the high surface activity of lithium, it is prone to oxidation during casting, and significant burn-off occurs during the preparation process, resulting in low material utilization and increased manufacturing costs. Furthermore, aluminum-lithium alloys prepared by powder metallurgy and spray forming exhibit numerous pores and discontinuous second phases at grain boundaries, leading to lower finished product performance that fails to meet application requirements.

[0003] Arc additive manufacturing, a novel technology with high deposition rates, is being applied to the preparation of aluminum-lithium alloys. However, aluminum-lithium alloy additive manufacturing faces the challenge of uncontrollable performance control. Currently, aluminum-lithium alloys prepared using arc additive manufacturing technology have a tensile strength of approximately 200-500 MPa and an elongation of approximately 5-12%. After solution treatment and aging, the strength can reach 400-550 MPa. However, in the aerospace field, the performance requirements for aluminum-lithium alloys are becoming increasingly stringent, such as tensile strength ≥600 MPa and hardness ≥150 HV. Due to the limitations of arc additive manufacturing technology and the material characteristics of aluminum-lithium alloys, the finished aluminum-lithium alloys inevitably contain problems such as porosity, coarse grains, and eutectic phase agglomeration, resulting in lower material performance that cannot meet application requirements. In addition, common 2-series and 7-series aluminum-lithium alloys contain alloying elements such as Cu, Zn, and Mg, and their aluminum-copper, aluminum-zinc, and aluminum-zinc-magnesium eutectic phases are brittle, which is not conducive to subsequent secondary forming processes such as traditional hot rolling and hot forging. Based on this, rare earth elements are added to aluminum-lithium alloys to improve the tensile strength and yield strength of the alloy through the solid solution strengthening effect. However, how to further improve the ultimate tensile strength after adding rare earth elements is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing high-strength aluminum-lithium alloy, which combines small deformation electroplastic forming, ultra-low temperature plastic forming, medium temperature plastic forming and heat treatment to prepare an aluminum-lithium alloy with significantly improved ultimate tensile strength.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a high-strength aluminum-lithium alloy includes the following steps:

[0007] Step 1: The aluminum-lithium-antimony alloy with a thickness of 25-55mm is subjected to medium-temperature rolling at 200-220℃. During the rolling process, pulse current is applied to the advancing and pushing sides of the aluminum-lithium-antimony alloy to complete the electro-plastic forming.

[0008] Step 2: The material that has been electro-plasticized is air-cooled to 50-85℃, and then cooled to -100 to -120℃ for multiple passes of ultra-low temperature rolling; the deformation amount of a single pass of ultra-low temperature rolling is 10-18%, and the total deformation amount is 25-35%, thus completing the ultra-low temperature plastic deformation.

[0009] Step 3: The material that has undergone ultra-low temperature plastic deformation is heated to 90-130℃ and subjected to multiple passes of medium-low temperature rolling; the deformation amount per pass of the medium-low temperature rolling is 10-15%, and the total deformation amount is 45-65%, thus completing the medium-low temperature plastic deformation.

[0010] Step 4: The material that has undergone medium-low temperature plastic deformation is cooled again to -100 to -120°C for single-pass ultra-low temperature rolling;

[0011] Step 5: Perform low-temperature aging treatment on the material obtained in Step 4 and air-cool it to room temperature to obtain the high-strength aluminum-lithium alloy.

[0012] In one embodiment, the composition of the aluminum-lithium-antimony alloy is:

[0013] Li: 0.8-3.2%, Sb: 0.1-0.3%, Zn: 2.8-4.0%, Mg: 1.3-2.3%, balance Al.

[0014] In one embodiment, by weight, in step 1, before medium-temperature rolling, the aluminum-lithium-antimony alloy is first subjected to a strengthening solution treatment at 538-545℃ for 0.5-1.5h, then water quenched, and then immediately placed in an aging furnace at 150-180℃ for 4-6h aging treatment.

[0015] In one embodiment, the deformation per pass of the medium-temperature rolling is 5-8%, and the total deformation is 15-20%.

[0016] In one embodiment, the amplitude of the pulse current is 1000-2500A, the frequency is 50-200Hz, and the duty cycle is 5-12%.

[0017] In one embodiment, step 2 involves spraying liquid nitrogen onto the rolls and alloy surface during the cryogenic rolling process. The spraying volume is controlled by a four-way valve, with the flow rate adjusted to a range of 1.0-4.5 L / min based on the thickness and volume of the rolled material.

[0018] In one embodiment, in step 4, the deformation amount of cryogenic rolling is 5-15%.

[0019] In one embodiment, step 4 involves storing the material that has undergone cryogenic rolling in a cryogenic chamber at -50 to -100°C.

[0020] In one embodiment, step 5 involves placing the material that has undergone ultra-low temperature rolling into an aging furnace at 80-120°C for low-temperature aging treatment, with an aging holding time of 10-60 hours.

[0021] In one embodiment, an infrared temperature measuring device is installed on the discharge side of the rolling mill, and the alarm temperature is set to 530°C. When the measured temperature exceeds the set temperature, the rolling mill will issue an alarm and stop working.

[0022] The Al-Li-Sb alloy used in this invention has an initial tensile strength of about 170-250 MPa. After using the heat treatment technology in this invention, its tensile strength can reach more than 400 MPa. After using the composite heat treatment and plastic forming technology of this invention, the ultimate tensile strength of the material is increased to more than 700 MPa, an increase of more than 200%. Attached Figure Description

[0023] Figure 1 This is a schematic diagram comparing the initial properties of the billet with the properties of the high-strength aluminum-lithium alloy prepared by this invention. Detailed Implementation

[0024] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0025] This invention discloses a composite heat treatment and plastic forming method for preparing high-strength aluminum-lithium alloys. By adding a small amount of the rare earth element antimony to the aluminum-lithium alloy, the method improves the solid solution strengthening effect of the alloy and regulates its corrosion resistance and high-temperature stability through antimony, while also enhancing the material's heat treatment sensitivity and aging strengthening effect. Specifically, the method of this invention includes the following steps:

[0026] Step 1: Take the Al-Li-Sb alloy prepared using arc additive manufacturing technology and place it in a resistance furnace for strengthening solution treatment. Heat the furnace to 538-545℃ and hold for 0.5-1.0 h. After reaching the set temperature, remove it and water quench it to room temperature, with a water quenching transfer time of less than 5 s. This step improves the solute solubility and removes internal stress through strengthening solution treatment, resulting in a stable billet material.

[0027] In this embodiment of the invention, the aluminum-lithium-antimony alloy has the following composition by weight: Li: 0.8-3.2%, Sb: 0.1-0.3%, and may also contain Zn: 2.8-4.0%, Mg: 1.3-2.3%, with the balance being Al.

[0028] This step selects Al-Li-Sb alloys prepared using arc additive manufacturing technology because traditional casting methods for preparing aluminum-lithium alloys are prone to oxidation during casting due to the high surface activity of lithium. This results in numerous internal pores and inclusions, leading to poor material performance. Furthermore, severe lithium burn-off during the preparation process results in low material utilization, increasing manufacturing costs. In contrast, aluminum-lithium alloys prepared by powder metallurgy and spray forming exhibit numerous pore defects and discontinuous second phases at grain boundaries, resulting in lower finished product performance that fails to meet application requirements.

[0029] Step 2: Place the material in an aging furnace at 150-180℃ for aging treatment. After reaching the set temperature, keep it at that temperature for 4-6 hours. After reaching the set temperature, remove the material and air cool it to room temperature to ensure that the elements, structure and properties of different composite gold materials are more uniform.

[0030] Step 3: After step 2, the solution-treated aged alloy material is obtained. It is then cut to a thickness of 25-55 mm and placed in a resistance furnace, heated to 200-220℃, and held for 30-60 minutes. Alternatively, an Al-Li-Sb alloy with a thickness of 25-55 mm can be used directly in step 1 to achieve the same effect.

[0031] Step 4: After removing the material, place it in a rolling mill for medium-temperature rolling. The deformation amount is set to 5-8%. After the rolls bite into the alloy material, apply pulsed current simultaneously to the material's advancing and pushing sides. The pulsed current amplitude is 1000-2500A, the frequency is 50-200Hz, and the duty cycle is 5-12%. The pulsed current is provided by a pulse power supply with a constant temperature mode. In this step, electroplastic deformation with a small deformation amount can reduce the dislocation kinetic energy of the material, improve the material's ductility, and minimize the loss of material strength.

[0032] Step 5: After completing the electroforming process in Step 4, air-cool the material to 50-85℃. The purpose of this step is to allow partial dislocation recovery during air cooling, reducing residual stress within the material and facilitating subsequent cryogenic deformation. If rapid cooling is used, the material will have a higher dislocation density and greater deformation resistance, making it more prone to edge cracking during subsequent cryogenic deformation.

[0033] Step 6: Place the air-cooled material directly into a -100 to -120°C cryogenic chamber for 20-45 minutes to cool it down. Obviously, any other feasible cooling method can also be adopted.

[0034] Step 7: After the material is removed, it is immediately transferred to the rolling mill for ultra-low temperature plastic deformation. The transfer time is less than 5 seconds, and the deformation amount of a single pass is 10-18%.

[0035] Furthermore, in order to reduce the temperature rise effect generated during the plastic deformation process of the material, liquid nitrogen spraying treatment is required on the rolls and alloy surface during the ultra-low temperature rolling process. The spraying volume is controlled by a four-way valve, and the flow rate is adjusted from 1.0 to 4.5 L / min according to the thickness and volume of the rolled material.

[0036] Step 8: Repeat steps 6 and 7 until the total deformation of the material is 25-35%. Through multiple passes of cryogenic rolling, the internal pores of the material can be healed and the accumulation of dislocations inside the material can be improved, thus providing sufficient power for subsequent heat treatment and deformation treatment.

[0037] Step 9: Then place the sample in a heating furnace and heat it to 90-130℃, holding it at that temperature for 20-30 minutes. Obviously, any other feasible heating method can also be used.

[0038] Step 10: After removing the material, immediately transfer it to the rolling mill for medium-low temperature rolling. The transfer time should be less than 5 seconds, and the deformation per pass should be controlled at 10-15%. Install an infrared temperature measuring device on the discharge side of the rolling mill, and set the alarm temperature to 530℃. When the measured temperature exceeds the set temperature, the rolling mill will issue an alarm and stop working.

[0039] Step 11: Repeat steps 9 and 10 above until the total deformation is 45-65%. Through medium-temperature rolling, while ensuring stable and uniform deformation and refining the grains, it also achieves the effects of breaking down coarse and brittle phases, improving the dynamic recrystallization of the matrix, and increasing the internal vacancy density of the material.

[0040] Step 12: Place the alloy in a low-temperature chamber at -100 to -120°C for 30-45 minutes to cool it down. Obviously, any other feasible cooling method can also be adopted.

[0041] Step 13: Immediately transfer the alloy to a rolling mill for cryogenic rolling with a deformation of 5%. The purpose of this step is to introduce a large number of dislocations through cryogenic rolling, increase the dislocation and vacancy density inside the material, and strengthen the driving force for the precipitation of precipitated phases in the subsequent aging process. At the same time, cryogenic deformation further breaks down coarse grains and brittle grain boundary phases within the material, promoting the subsequent dynamic recrystallization process.

[0042] Step 14: After rolling, store the sample in a low-temperature chamber at -50 to -100°C. The purpose of this step is to preserve the internal lattice distortions and dislocations of the material to the greatest extent possible, and to reduce the weakening effect of natural aging on the material properties.

[0043] Step 15: Place the deformed alloy material in an aging furnace at 80-120℃ for aging treatment, with a holding time of 10-60 hours. After aging, air cool to room temperature. This low-temperature aging treatment promotes the precipitation of strengthening phases and further improves the material strength.

[0044] The following are specific embodiments of the present invention.

[0045] Example 1

[0046] A method for preparing a high-strength aluminum-lithium alloy includes the following steps:

[0047] Step 1: Take the Al-Li-Sb alloy manufactured by arc additive manufacturing, with the following composition: Li-1.2%, Sb-0.17%, Zn-3.1%, Mg-1.6%, and the balance being Al. Place it in a resistance furnace for strengthening solution treatment, heat it to 543℃ in the furnace and hold it for 1.0 h. After reaching the set temperature, remove it and water quench it to room temperature, with the water quenching transfer time being less than 5 s.

[0048] Step 2: Place the material in an aging furnace at 160℃ and heat it in the furnace for aging treatment. After reaching the temperature, keep it at that temperature for 4.5 hours. After reaching the temperature, take it out and air cool it to room temperature.

[0049] Step 3: Cut the solution-treated aged alloy material to a thickness of 25mm.

[0050] Step 4: Place the material in a resistance furnace and heat it to 200°C, then hold it at that temperature for 30 minutes.

[0051] Step 5: After the material is taken out, it is placed in the rolling mill for medium-temperature rolling. The deformation amount per pass is set to 6%. After the roll bites into the alloy material, a pulse current is applied to the material's forward and push-in sides at the same time. The pulse current amplitude is 1000-2500A, the frequency is 50-200Hz, and the duty cycle is 5-12%.

[0052] Step 6: Repeat steps 4 and 5 until the total deformation is 15%.

[0053] Step 7: After electro-plastic molding, air cool the material to 50°C.

[0054] Step 8: Then place the material in a -100℃ cryogenic chamber to cool it down for 30 minutes.

[0055] Step 9: After the material is removed, it is immediately transferred to the rolling mill for cryogenic plastic deformation. The transfer time is less than 5 seconds, and the deformation amount per pass is 14%. During the cryogenic rolling process, the rolls and alloy surface need to be sprayed with liquid nitrogen at a rate of 4.2 L / min.

[0056] Step 10: Repeat steps 8 and 9 until the total material deformation is 30%.

[0057] Step 11: Then place the sample in a heating furnace and heat it to 120°C, and keep it at that temperature for 25 minutes.

[0058] Step 12: After removing the material, immediately transfer it to the rolling mill for medium and low temperature rolling. The transfer time should be less than 5 seconds, and the deformation amount per pass should be controlled at 14%.

[0059] Step 13: Repeat steps 11 and 12 above until the total deformation is 60%.

[0060] Step 14: Place the alloy in a -100℃ low-temperature chamber for 30 minutes to cool it down.

[0061] Step 15: Immediately transfer the alloy to a rolling mill for cryogenic rolling with a deformation of 5%.

[0062] Step 16: After rolling, store the sample in a -100℃ low-temperature chamber.

[0063] Step 17: Place the deformed alloy material in an aging furnace at 120℃ for aging treatment. The aging holding time is 42 hours. After aging, air cool to room temperature.

[0064] The Al-Li-Sb alloy prepared by this method exhibits extremely high ultimate tensile strength. A comparison of the engineering stress-strain curves with those of the alloy billet prepared by arc additive manufacturing is shown below. Figure 1 Its tensile strength increased from 179MPa to 789MPa, an increase of up to 340%, and it also retained a high elongation at break (7.8%) while having high strength.

[0065] Example 2

[0066] A method for preparing a high-strength aluminum-lithium alloy includes the following steps:

[0067] Step 1: Take the Al-Li-Sb alloy manufactured by arc additive manufacturing, with the following composition: Li-2.2%, Sb-0.22%, Zn-3.6%, Mg-2.3%, and the balance being Al. Place it in a resistance furnace for strengthening solution treatment, heat it in the furnace to 545℃ and hold it at that temperature for 0.5h. After reaching the set temperature, remove it and water quench it to room temperature, with the water quenching transfer time being less than 5s.

[0068] Step 2: Place the material in an aging furnace at 180℃ and heat it in the furnace for aging treatment. After reaching the temperature, keep it at that temperature for 4 hours. After reaching the temperature, take it out and air cool it to room temperature.

[0069] Step 3: Cut the solution-treated aged alloy material to a thickness of 40mm.

[0070] Step 4: Place the material in a resistance furnace and heat it to 220°C, then hold it for 30 minutes.

[0071] Step 5: After the material is taken out, it is placed in the rolling mill for medium-temperature rolling. The deformation amount per pass is set to 8%. After the roll bites into the alloy material, a pulse current is applied to the material's forward and push-in sides at the same time. The pulse current amplitude is 1000-2500A, the frequency is 50-200Hz, and the duty cycle is 5-12%.

[0072] Step 6: Repeat steps 4 and 5 until the total deformation is 17%.

[0073] Step 7: After electro-plastic molding, air cool the material to 65°C.

[0074] Step 8: Then place the material in a -120℃ cryogenic chamber for 20 minutes to cool it down.

[0075] Step 9: After the material is removed, it is immediately transferred to the rolling mill for cryogenic plastic deformation. The transfer time is less than 5 seconds, and the deformation amount per pass is 17%. During the cryogenic rolling process, the rolls and alloy surface need to be sprayed with liquid nitrogen at a rate of 4.5 L / min.

[0076] Step 10: Repeat steps 8 and 9 until the total material deformation is 35%.

[0077] Step 11: Then place the sample in a heating furnace and heat it to 100°C, and keep it at that temperature for 25 minutes.

[0078] Step 12: After removing the material, immediately transfer it to the rolling mill for medium and low temperature rolling. The transfer time should be less than 5 seconds, and the deformation amount per pass should be controlled at 10%.

[0079] Step 13: Repeat steps 11 and 12 above until the total deformation is 65%.

[0080] Step 14: Place the alloy in a -120℃ low-temperature chamber for 35 minutes to cool it down.

[0081] Step 15: Immediately transfer the alloy to a rolling mill for cryogenic rolling with a deformation of 15%.

[0082] Step 16: After rolling, store the sample in a -80℃ low-temperature chamber.

[0083] Step 17: Place the deformed alloy material in an aging furnace at 100℃ for aging treatment. The aging holding time is 50 hours. After aging, air cool to room temperature.

[0084] The Al-Li-Sb alloy prepared by this method also has a high ultimate tensile strength, which increases from 179 MPa to 758 MPa compared with the alloy billet manufactured by arc additive manufacturing.

[0085] Example 3

[0086] A method for preparing a high-strength aluminum-lithium alloy includes the following steps:

[0087] Step 1: Take the Al-Li-Sb alloy manufactured by arc additive manufacturing, with the following composition: Li-3.0%, Sb-0.25%, Zn-4.0%, Mg-1.3%, and the balance being Al. Place it in a resistance furnace for strengthening solution treatment, heat it to 538℃ in the furnace and hold it for 1.5 hours. After reaching the set temperature, remove it and water quench it to room temperature, with the water quenching transfer time being less than 5 seconds.

[0088] Step 2: Place the material in an aging furnace at 150℃ and heat it in the furnace for aging treatment. After reaching the temperature, keep it at that temperature for 6 hours. After reaching the temperature, take it out and air cool it to room temperature.

[0089] Step 3: Cut the solution-treated aged alloy material to a thickness of 55mm.

[0090] Step 4: Place it in a resistance furnace and heat it to 210℃, then keep it at that temperature for 45 minutes.

[0091] Step 5: After the material is taken out, it is placed in the rolling mill for medium-temperature rolling. The deformation is set to 5%. After the roll bites into the alloy material, a pulse current is applied to the material's forward and pushing sides at the same time. The pulse current amplitude is 1000-2500A, the frequency is 50-200Hz, and the duty cycle is 5-12%.

[0092] Step 6: Repeat steps 4 and 5 until the total deformation is 20%.

[0093] Step 7: After electro-plastic molding, air-cool the material to 85°C.

[0094] Step 8: Then place the material in a -105℃ cryogenic chamber for 40 minutes to cool it down.

[0095] Step 9: After the material is removed, it is immediately transferred to the rolling mill for cryogenic plastic deformation. The transfer time is less than 5 seconds, and the deformation amount per pass is 10%. During the cryogenic rolling process, the rolls and alloy surface need to be sprayed with liquid nitrogen at a rate of 4.5 L / min.

[0096] Step 10: Repeat steps 8 and 9 until the total material deformation is 25%.

[0097] Step 11: Then place the sample in a heating furnace and heat it to 130°C, and keep it at that temperature for 20 minutes.

[0098] Step 12: After removing the material, immediately transfer it to the rolling mill for medium and low temperature rolling. The transfer time should be less than 5 seconds, and the deformation amount per pass should be controlled at 12%.

[0099] Step 13: Repeat steps 11 and 12 above until the total deformation is 45%.

[0100] Step 14: Place the alloy in a -105℃ low-temperature chamber for 40 minutes to cool it down.

[0101] Step 15: Immediately transfer the alloy to a rolling mill for cryogenic rolling with a deformation of 10%.

[0102] Step 16: After rolling, store the sample in a -50℃ low-temperature chamber.

[0103] Step 17: Place the deformed alloy material in an aging furnace at 80℃ for aging treatment. The aging holding time is 60 hours. After aging, air cool to room temperature.

[0104] The Al-Li-Sb alloy prepared by this method also has a high ultimate tensile strength, which increases from 179 MPa to 721 MPa compared with the alloy billet manufactured by arc additive manufacturing.

Claims

1. A method for preparing a high-strength aluminum-lithium alloy, characterized in that, Includes the following steps: Step 1: Heat the aluminum-lithium-antimony alloy with a thickness of 25-55mm to 200-220℃ and perform medium-temperature rolling. During the rolling process, apply pulse current to the advancing and pushing sides of the aluminum-lithium-antimony alloy to complete the electro-plastic forming. Step 2: The material that has been electro-plasticized is air-cooled to 50-85℃, and then cooled to -100~-120℃ for multiple passes of ultra-low temperature rolling; the deformation amount of a single pass of ultra-low temperature rolling is 10-18%, and the total deformation amount is 25-35%, thus completing the ultra-low temperature plastic deformation. Step 3: The material that has undergone ultra-low temperature plastic deformation is heated to 90-130℃ and subjected to multiple passes of medium-low temperature rolling; the deformation amount per pass of the medium-low temperature rolling is 10-15%, and the total deformation amount is 45-65%, thus completing the medium-low temperature plastic deformation. Step 4: The material that has completed the medium-low temperature plastic deformation is cooled again to -100~-120℃ for single-pass ultra-low temperature rolling; Step 5: Perform low-temperature aging treatment on the material obtained in Step 4 and air-cool it to room temperature to obtain the high-strength aluminum-lithium alloy.

2. The method for preparing the high-strength aluminum-lithium alloy according to claim 1, characterized in that, The composition of the aluminum-lithium-antimony alloy, by weight, is as follows: Li: 0.8-3.2%, Sb: 0.1-0.3%, Zn: 2.8-4.0%, Mg: 1.3-2.3%, balance Al.

3. The method for preparing the high-strength aluminum-lithium alloy according to claim 1 or 2, characterized in that, In step 1, before medium-temperature rolling, the aluminum-lithium-antimony alloy is first subjected to a strengthening solution treatment at 538-545℃ and held for 0.5-1.5 hours, then water quenched, and then immediately placed in an aging furnace at 150-180℃ for aging treatment for 4-6 hours.

4. The method for preparing the high-strength aluminum-lithium alloy according to claim 1, characterized in that, The deformation per pass in the medium-temperature rolling process is 5-8%, and the total deformation is 15-20%.

5. The method for preparing the high-strength aluminum-lithium alloy according to claim 1 or 4, characterized in that, The amplitude of the pulse current is 1000-2500A, the frequency is 50-200Hz, and the duty cycle is 5-12%.

6. The method for preparing the high-strength aluminum-lithium alloy according to claim 1, characterized in that, In step 2, the rolls and alloy surfaces are sprayed with liquid nitrogen during the ultra-low temperature rolling process. The spraying volume is controlled by a four-way valve, and the flow rate is adjusted from 1.0 to 4.5 L / min according to the thickness and volume of the rolled material.

7. The method for preparing the high-strength aluminum-lithium alloy according to claim 1, characterized in that, In step 4, the deformation amount during cryogenic rolling is 5-15%.

8. The method for preparing the high-strength aluminum-lithium alloy according to claim 1 or 7, characterized in that, In step 4, the material that has undergone cryogenic rolling is stored in a cryogenic chamber at -50 to -100°C.

9. The method for preparing the high-strength aluminum-lithium alloy according to claim 1, characterized in that, In step 5, the material that has completed the ultra-low temperature rolling is placed in an aging furnace at 80-120℃ for low-temperature aging treatment, and the aging holding time is 10-60h.

10. The method for preparing the high-strength aluminum-lithium alloy according to claim 1, characterized in that, In step 3, an infrared temperature measuring device is installed on the discharge side of the rolling mill, and the alarm temperature is set to 530℃. When the measured temperature exceeds the alarm temperature, the rolling mill will issue an alarm and stop working.

Images