A method for reducing micropores in 7050 aluminum alloy after thermal deformation

Abstract

A method for reducing micropores in 7050 aluminum alloy after thermal deformation is disclosed. This method addresses the problem of numerous micropores still existing in existing additive aluminum alloys after thermal deformation and modification. The method includes: 1. preparing 7050 aluminum alloy using arc additive manufacturing technology; 2. heating and heat preservation; 3. hot compression; 4. vacuum heat treatment; and 5. heat treatment. This method is used to reduce micropores in 7050 aluminum alloy after thermal deformation.

Description

Technical Field

[0001] The invention relates to a method for reducing micropores in additively manufactured aluminum alloys after thermal deformation. Background Art

[0002] At present, 7050 aluminum alloy is used in aerospace, railway transportation, and automobile manufacturing due to its advantages such as strong corrosion resistance, low density and high specific strength. Arc additive manufacturing obtains complex components by depositing and forming layer by layer according to a predetermined path. Arc additive manufacturing has the advantages of high deposition efficiency, good mechanical properties of formed components, and the ability to form complex parts. However, there are often various defects inside arc additively manufactured components, such as pores, unfused components, and uneven structure. These defects limit its further application in various fields. Therefore, researchers modified the additive aluminum alloy by introducing thermal deformation, which can close large-scale pores and unfused defects inside the aluminum alloy. At the same time, the columnar crystals are broken, the grains are refined, and the segregation is improved, thereby improving the mechanical properties.

[0003] However, even after thermal deformation, aluminum alloys still contain numerous micropores. Research has shown that micropores are related to hydrogen content, and various defects within aluminum alloys, such as the interface between precipitates and the matrix, easily serve as hydrogen nucleation sites. Therefore, reducing the hydrogen content and the number of precipitates within aluminum alloys is an effective way to reduce micropores. Summary of the Invention

[0004] The present invention aims to solve the problem that numerous micropores still exist inside the existing additive aluminum alloy after thermal deformation modification, and further provides a method for reducing micropores in the additive 7050 aluminum alloy after thermal deformation.

[0005] A method for reducing micropores in 7050 aluminum alloy after thermal deformation is carried out by the following steps:

[0006] 1. Using 7050 aluminum alloy wire as raw material, 7050 aluminum alloy was prepared by arc additive manufacturing technology;

[0007] 2. placing the 7050 aluminum alloy in a heat treatment furnace at a temperature of 470° C. to 490° C., and keeping the temperature at 470° C. to 490° C. for 10 to 20 minutes to obtain the aluminum alloy after the heat treatment;

[0008] 3. Transferring the aluminum alloy after heat preservation to a press at a temperature of 470℃~490℃, hot compressing it at a temperature of 470℃~490℃ until the deformation is 40%~60%. After reaching the deformation, maintaining the pressure at a temperature of 470℃~490℃ for 1min~3min, and finally cooling it to obtain the compressed aluminum alloy;

[0009] Fourth, the surface of the compressed aluminum alloy is polished, and then placed in a vacuum heat treatment furnace to evacuate the vacuum, and then heated to 430°C to 460°C, and kept at 430°C to 460°C for 3h to 5h, and finally cooled to obtain a vacuum heat-treated aluminum alloy;

[0010] 5. The vacuum heat-treated aluminum alloy is placed in a heat treatment furnace at 470°C to 490°C, kept warm for 30 minutes to 90 minutes at a temperature of 470°C to 490°C, and then cooled, thereby completing the method of reducing micropores in the additive 7050 aluminum alloy after thermal deformation.

[0011] The beneficial effects of the present invention are:

[0012] 1. Compared with the existing additive-thermal deformation composite forming process, the present invention does not require additional atmosphere for hydrogen removal. Except for step 4 which requires vacuuming, the rest of the process is carried out in an air atmosphere. The implementation steps are simple and only a short vacuum heat treatment is required. There is no need to adjust the additive and thermal deformation parameters, which simplifies the manufacturing process and increases flexibility.

[0013] 2. Compared with the existing additive-thermal deformation composite forming process, the present invention achieves uniform distribution of hydrogen elements through a short-term pressure holding operation during the hot compression process, without the need for additional heat treatment steps, making the subsequent vacuum dehydrogenation effect more significant. It is suitable for aluminum alloy materials with powder and wire as additive raw materials and has a wide range of applications;

[0014] 3. Compared with the existing additive-thermal deformation composite forming process, the present invention removes the aluminum oxide layer on the surface of 7050 aluminum alloy by grinding, making it easier for hydrogen to diffuse out of the material. Combined with a short period of vacuum and high-temperature treatment, the hydrogen content of the aluminum alloy is greatly reduced, thereby significantly reducing the number of micropores. This solves the problem of hydrogen in the aluminum alloy causing micropore nucleation and reducing the mechanical properties of the material. It has high economic benefits and low implementation difficulty.

[0015] 4. Compared with the existing additive-thermal deformation composite forming process, the present invention optimizes its microstructure and significantly improves the mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the process of reducing micropores in 7050 aluminum alloy after thermal deformation;

[0017] Figure 2 SEM images of the additively manufactured 7050 aluminum alloy with reduced micropores after thermal deformation prepared in Example 1 and Comparative Experiments 1 to 3, a is for Comparative Experiment 3, b is for Comparative Experiment 2, c is for Comparative Experiment 1, and d is for Example 1;

[0018] Figure 3Comparison chart of tensile properties of additively manufactured 7050 aluminum alloy with reduced micropores after thermal deformation prepared in Example 1 and Comparative Experiments 1 to 3. A is Comparative Experiment 3, B is Comparative Experiment 2, C is Comparative Experiment 1, and D is Example 1. DETAILED DESCRIPTION

[0019] Specific implementation method 1, combined with Figure 1 Description: This embodiment is a method for reducing micropores in 7050 aluminum alloy after thermal deformation. It is carried out in the following steps:

[0020] 1. Using 7050 aluminum alloy wire as raw material, 7050 aluminum alloy was prepared by arc additive manufacturing technology;

[0021] 2. placing the 7050 aluminum alloy in a heat treatment furnace at a temperature of 470° C. to 490° C., and keeping the temperature at 470° C. to 490° C. for 10 to 20 minutes to obtain the aluminum alloy after the heat treatment;

[0022] 3. Transferring the aluminum alloy after heat preservation to a press at a temperature of 470℃~490℃, hot compressing it at a temperature of 470℃~490℃ until the deformation is 40%~60%. After reaching the deformation, maintaining the pressure at a temperature of 470℃~490℃ for 1min~3min, and finally cooling it to obtain the compressed aluminum alloy;

[0023] Fourth, the surface of the compressed aluminum alloy is polished, and then placed in a vacuum heat treatment furnace to evacuate the vacuum, and then heated to 430°C to 460°C, and kept at 430°C to 460°C for 3h to 5h, and finally cooled to obtain a vacuum heat-treated aluminum alloy;

[0024] 5. The vacuum heat-treated aluminum alloy is placed in a heat treatment furnace at 470°C to 490°C, kept warm for 30 minutes to 90 minutes at a temperature of 470°C to 490°C, and then cooled, thereby completing the method of reducing micropores in the additive 7050 aluminum alloy after thermal deformation.

[0025] The beneficial effects of this embodiment are:

[0026] 1. Compared with the existing additive-thermal deformation composite forming process, this embodiment does not require an additional atmosphere for hydrogen removal. Except for step 4, which requires vacuuming, the rest of the process is carried out in an air atmosphere. The implementation steps are simple and only a short vacuum heat treatment is required. There is no need to control the additive and thermal deformation parameters, which simplifies the manufacturing process and increases flexibility.

[0027] 2. Compared with the existing additive manufacturing-thermal deformation composite forming process, this embodiment achieves uniform distribution of hydrogen elements through a short-term pressure holding operation during the hot compression process, eliminating the need for additional heat treatment steps, making the subsequent vacuum dehydrogenation effect more significant. It is suitable for aluminum alloy materials using powder and wire as additive raw materials and has a wide range of applications.

[0028] 3. Compared with the existing additive-thermal deformation composite forming process, this embodiment removes the aluminum oxide layer on the surface of 7050 aluminum alloy by grinding, making it easier for hydrogen to diffuse out of the material. Combined with a short period of vacuum and high-temperature treatment, it greatly reduces the hydrogen content of the aluminum alloy, thereby significantly reducing the number of micropores. This solves the problem of hydrogen in the aluminum alloy causing micropore nucleation and reducing the mechanical properties of the material. It has high economic benefits and low implementation difficulty.

[0029] 4. Compared with the existing additive-thermal deformation composite forming process, this embodiment optimizes its microstructure and significantly improves the mechanical properties.

[0030] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that, in step 1, 7050 aluminum alloy is prepared using arc additive manufacturing technology. Specifically, the process is performed using the CMT+ADV mode, with a travel speed of 5 mm / s to 10 mm / s, a wire feed speed of 5 m / min to 10 m / min, a current of 70 A to 120 A, a voltage of 10 V to 13 V, and a wire feed angle of 7° to 10°. Other steps are the same as those in specific embodiment 1.

[0031] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that in step 3, the aluminum alloy after heat preservation is transferred to a press at a temperature of 470° C. to 490° C. for hot compression within 5 to 30 seconds. Other aspects are the same as specific embodiment 1 or 2.

[0032] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the pressing speed of the pressing head during the hot compression process in step 3 is 40 min / min to 60 mm / min. It is the same as specific embodiments 1 to 3.

[0033] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the cooling in step 3 is air cooling in air at a temperature of 10°C to 30°C, or cooling to 10°C to 30°C within 120min to 360min. Other steps are the same as specific embodiments 1 to 4.

[0034] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that in step 4, the surface of the compressed aluminum alloy is polished for 5 to 10 minutes and then placed in a vacuum heat treatment furnace for 5 to 10 minutes. Other aspects are the same as specific embodiments 1 to 5.

[0035] Specific embodiment 7: This embodiment differs from any one of the specific embodiments 1 to 6 in that: in step 4, the vacuum is pumped to a vacuum degree of 1.0×10 -3 Pa~3.0×10 -3 Pa. The rest is the same as the specific embodiments 1 to 6.

[0036] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the temperature is raised to 430° C. to 460° C. at a heating rate of 5° C. / min to 25° C. / min in step 4. The rest is the same as specific embodiments 1 to 7.

[0037] Specific embodiment 9: This embodiment differs from any one of specific embodiments 1 to 8 in that the cooling described in step 4 is performed by cooling to 10°C to 50°C in the furnace, or by transferring the mixture to water or oil at 10°C to 30°C within 2s to 10s for cooling. Other aspects are the same as specific embodiments 1 to 8.

[0038] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that the cooling in step 5 is performed in water or oil at a temperature of 10° C. to 30° C. for 2 to 10 seconds. Other aspects are the same as specific embodiments 1 to 9.

[0039] The following examples are used to verify the beneficial effects of the present invention:

[0040] Example 1:

[0041] A method for reducing micropores in 7050 aluminum alloy after thermal deformation is carried out by the following steps:

[0042] First, 7050 aluminum alloy wire was used as raw material, and arc additive manufacturing was performed using the CMT+ADV mode at a travel speed of 7 mm / s, a wire feeding speed of 6.5 m / min, a current of 98 A, a voltage of 11.6 V, and a wire feeding angle of 7° to 10° to prepare 7050 aluminum alloy.

[0043] 2. placing the 7050 aluminum alloy in a heat treatment furnace at a temperature of 480° C., and keeping the temperature at 480° C. for 15 minutes to obtain the aluminum alloy after the heat treatment;

[0044] 3. Within 10 seconds, transfer the aluminum alloy after heat preservation to a press at a temperature of 480°C. Under the conditions of a temperature of 480°C and a pressing speed of the ram of 50 mm / min, hot compress it to a deformation of 50%. After reaching the deformation, hold the pressure at 480°C for 2 minutes, and finally cool it in air at a temperature of 20°C to obtain the compressed aluminum alloy.

[0045] Fourth, the surface of the compressed aluminum alloy was polished for 8 minutes, and then placed in a vacuum heat treatment furnace for 10 minutes to evacuate the vacuum to 1.0×10 -3 Pa, then heated to 450°C at a heating rate of 10°C / min, and kept at 450°C for 4 hours, and finally cooled to room temperature within 1 hour to obtain a vacuum heat-treated aluminum alloy;

[0046] 5. The vacuum heat-treated aluminum alloy was placed in a heat treatment furnace at 480°C, kept at 480°C for 60 minutes, and then cooled in water at 20°C within 3 seconds to obtain an additive 7050 aluminum alloy with reduced micropores after thermal deformation.

[0047] Comparative Experiment 1: This comparative experiment differs from Example 1 in that the vacuum heat treatment furnace is replaced with a heat treatment furnace in step 4, and vacuuming is omitted; and the furnace cooling in step 4 is replaced with air cooling. Other differences are the same as Example 1.

[0048] Comparative Experiment 2: This comparative experiment differs from Example 1 in that Steps 2 and 3 are omitted. Other steps are the same as Example 1.

[0049] Comparative Experiment 3: This comparative experiment differs from Example 1 in that: Steps 2 and 3 are omitted; in Step 4, the vacuum heat treatment furnace is replaced with a heat treatment furnace, and vacuuming is omitted; and in Step 4, furnace cooling is replaced with air cooling. Other differences are the same as in Example 1.

[0050] Figure 2The following are SEM images of the additive 7050 aluminum alloy with reduced micropores after thermal deformation prepared in Example 1 and Comparative Experiments 1 to 3. a is Comparative Experiment 3, b is Comparative Experiment 2, c is Comparative Experiment 1, and d is Example 1. By comparing the effects of different embodiments, it was found that in Comparative Experiment 1, many micropores with high roundness were formed without vacuum dehydrogenation after hot compression and pressure holding, and the number of micropores was slightly reduced. In Comparative Experiment 2, the additive 7050 aluminum alloy was directly vacuum dehydrogenated, and the number of micropores was also reduced, but some large-sized micropores with irregular shapes still existed. In Example 1, the number of micropores after vacuum dehydrogenation after hot compression and pressure holding was the least. This is because holding pressure at high temperature can fully dissolve hydrogen into the matrix without forming micropores. Therefore, the vacuum dehydrogenation effect is better, the obtained structure is dense, the number of primary eutectic phases is significantly reduced, the strength and elongation are greatly improved, and the structure and defects are significantly improved.

[0051] Tensile performance test is carried out according to GB / T 228.1-2021 "Tensile tests on metallic materials - Part 1: Test methods at room temperature"; Figure 3 Comparison chart of tensile properties of additively manufactured 7050 aluminum alloy with reduced micropores after thermal deformation prepared in Example 1 and Comparative Experiments 1 to 3. A is Comparative Experiment 3, B is Comparative Experiment 2, C is Comparative Experiment 1, and D is Example 1. In comparative experiment three, the ultimate tensile strength of the material is 273.4 MPa, the yield strength is 228.7 MPa, and the elongation is 3.06%; in comparative experiment two, the ultimate tensile strength of the material is 416.9 MPa, the yield strength is 385.1 MPa, and the elongation is 4.57%; in comparative experiment one, the ultimate tensile strength of the material is 532.2 MPa, the yield strength is 460.3 MPa, and the elongation is 6.17%; in embodiment one, the ultimate tensile strength of the material is 588.4 MPa, the yield strength is 511.8 MPa, and the elongation is 8.04%. After hot compression + pressure holding + surface grinding + vacuum heat treatment, the ultimate tensile strength of the material is increased by 315 MPa compared with comparative experiment three, and the elongation is increased by 4.98%, and the strength and elongation are significantly improved.

Claims

1. A method for reducing micropores in 7050 aluminum alloy after thermal deformation, characterized in that It is carried out in the following steps:

1. Using 7050 aluminum alloy wire as raw material, 7050 aluminum alloy was prepared by arc additive manufacturing technology; 2. placing the 7050 aluminum alloy in a heat treatment furnace at a temperature of 470° C. to 490° C., and keeping the temperature at 470° C. to 490° C. for 10 to 20 minutes to obtain the aluminum alloy after the heat treatment; 3. Transferring the aluminum alloy after heat preservation to a press at a temperature of 470℃~490℃, hot compressing it at a temperature of 470℃~490℃ until the deformation is 40%~60%. After reaching the deformation, maintaining the pressure at a temperature of 470℃~490℃ for 1min~3min, and finally cooling it to obtain the compressed aluminum alloy; Fourth, the surface of the compressed aluminum alloy is polished, and then placed in a vacuum heat treatment furnace to evacuate the vacuum, and then heated to 430°C to 460°C, and kept at 430°C to 460°C for 3h to 5h, and finally cooled to obtain a vacuum heat-treated aluminum alloy; 5. The vacuum heat-treated aluminum alloy is placed in a heat treatment furnace at 470°C to 490°C, kept warm for 30 minutes to 90 minutes at a temperature of 470°C to 490°C, and then cooled, thereby completing the method of reducing micropores in the additive 7050 aluminum alloy after thermal deformation.

2. The method for reducing micropores in 7050 aluminum alloy after thermal deformation according to claim 1 is characterized in that In step 1, 7050 aluminum alloy is prepared by arc additive manufacturing technology, which is specifically carried out in the following steps: using CMT+ADV mode, under the conditions of a walking speed of 5mm / s~10mm / s, a wire feeding speed of 5m / min~10m / min, a current of 70A~120A, a voltage of 10V~13V and a wire feeding angle of 7°~10°.

3. The method for reducing micropores in 7050 aluminum alloy after thermal deformation according to claim 1 is characterized in that In step 3, the aluminum alloy after heat preservation is transferred to a press with a temperature of 470° C. to 490° C. for hot compression within 5 seconds to 30 seconds.

4. The method for reducing micropores in 7050 aluminum alloy after thermal deformation according to claim 1 is characterized in that The pressing speed of the pressing head during the hot compression process in step 3 is 40 min / min to 60 mm / min.

5. The method for reducing micropores in 7050 aluminum alloy after thermal deformation according to claim 1, characterized in that The cooling in step 3 is air cooling in air at a temperature of 10°C to 30°C, or cooling to 10°C to 30°C within 120min to 360min.

6. The method for reducing micropores in 7050 aluminum alloy after thermal deformation according to claim 1, characterized in that In step 4, the surface of the compressed aluminum alloy is polished for 5 to 10 minutes, and then placed in a vacuum heat treatment furnace for 5 to 10 minutes.

7. The method for reducing micropores in 7050 aluminum alloy after thermal deformation according to claim 1, characterized in that In step 4, vacuum is drawn to a vacuum degree of 1.0×10 -3 Pa~3.0×10 -3 Pa.

8. The method for reducing micropores in 7050 aluminum alloy after thermal deformation according to claim 1, characterized in that In step 4, the temperature is increased to 430° C. to 460° C. at a heating rate of 5° C. / min to 25° C. / min.

9. The method for reducing micropores in 7050 aluminum alloy after thermal deformation according to claim 1, characterized in that The cooling in step 4 is cooling to 10°C to 50°C in the furnace, or transferring to water or oil at 10 to 30°C for cooling within 2s to 10s.

10. The method for reducing micropores in 7050 aluminum alloy after thermal deformation according to claim 1, characterized in that The cooling described in step 5 is cooling in water or oil at a temperature of 10° C. to 30° C. for 2 seconds to 10 seconds.

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