Method for reducing micropores after thermal deformation of additive 7050 aluminum alloy

Abstract

The invention discloses a method for reducing micropores after thermal deformation of an additive 7050 aluminum alloy, and relates to a method for reducing micropores after thermal deformation of an additive aluminum alloy. The invention aims to solve the problem that numerous micropores still exist in the existing additive aluminum alloy subjected to thermal deformation modification. The method comprises the following steps: 1, preparing the 7050 aluminum alloy by adopting an electric arc additive manufacturing technology; 2, heating and preserving heat; 3, hot compression; 4, vacuum heat treatment; and 5, heat treatment. The method is used for reducing the micropores after thermal deformation of the additive 7050 aluminum alloy.

Description

Technical Field

[0001] The invention relates to a method for reducing micropores in an additive aluminum alloy after thermal deformation. Background Art

[0002] At present, 7050 aluminum alloy is used in aerospace, railway transportation, automobile manufacturing and other fields due to its 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 structures. These defects limit their further application in various fields. Therefore, the researchers modified the additive aluminum alloy by introducing thermal deformation, which can close large-sized pores and unfused defects inside the aluminum alloy, while crushing the columnar crystals, refining the grains, improving segregation, and improving the mechanical properties.

[0003] However, after thermal deformation modification, there are still many micropores inside aluminum alloys. Studies have found that micropores are related to hydrogen content, and various defects inside aluminum alloys are easy to become hydrogen nucleation sites, such as the connection interface between the precipitate phase and the matrix. Therefore, reducing the hydrogen content and the number of precipitates inside 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 provide a method for reducing micropores in additive 7050 aluminum alloy after thermal deformation.

[0005] A method for reducing micropores in an additively manufactured 7050 aluminum alloy after thermal deformation is performed 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 10min to 20min to obtain the aluminum alloy after the heat treatment;

[0008] 3. The aluminum alloy after heat preservation is transferred to a press machine with a temperature of 470°C to 490°C, and hot-compressed to a deformation amount of 40% to 60% under the condition of a temperature of 470°C to 490°C. After reaching the deformation amount, the aluminum alloy is kept under pressure for 1min to 3min under the condition of a temperature of 470°C to 490°C, and finally cooled 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, and then the temperature is raised to 430°C to 460°C, and the temperature is 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 30min to 90min 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 dehydrogenation. Except for step 4 which requires vacuuming, other processes are carried out in an air atmosphere. The implementation steps are simple and only a short-time vacuum heat treatment is required. There is no need to adjust the additive and thermal deformation parameters, which simplifies the manufacturing process and has high flexibility.

[0013] 2. Compared with the existing additive-thermal deformation composite forming process, the present invention realizes uniform distribution of hydrogen elements through a short-time pressure holding operation during the hot compression process, and does not require 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-hot deformation composite forming process, the present invention removes the aluminum oxide layer on the surface of the 7050 aluminum alloy by grinding, making it easier for hydrogen to diffuse out of the material, and combines it with a short period of vacuum high-temperature treatment to greatly reduce the hydrogen content of the aluminum alloy, thereby significantly reducing the number of micropores, solving the problem that hydrogen in the aluminum alloy causes micropore nucleation and reduces 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 It is a schematic diagram of the process of reducing micropores after thermal deformation of additively manufactured 7050 aluminum alloy according to the present invention;

[0017] Figure 2 The 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;

[0018] Figure 3This is a comparison chart of the tensile properties 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 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, which 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 10min to 20min to obtain the aluminum alloy after the heat treatment;

[0022] 3. The aluminum alloy after heat preservation is transferred to a press machine with a temperature of 470°C to 490°C, and hot-compressed to a deformation amount of 40% to 60% under the condition of a temperature of 470°C to 490°C. After reaching the deformation amount, the aluminum alloy is kept under pressure for 1min to 3min under the condition of a temperature of 470°C to 490°C, and finally cooled 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, and then the temperature is raised to 430°C to 460°C, and the temperature is 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 30min to 90min 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 additional atmosphere for dehydrogenation. Except for step 4 which requires vacuuming, other processes are carried out in an air atmosphere. The implementation steps are simple and only a short-time vacuum heat treatment is required. There is no need to adjust additive and thermal deformation parameters, which simplifies the manufacturing process and has high flexibility.

[0027] 2. Compared with the existing additive-thermal deformation composite forming process, this embodiment achieves uniform distribution of hydrogen elements through a short-time pressure holding operation during the hot compression process, and does not require 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;

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

[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 implementation method 2: This implementation method is different from specific implementation method 1 in that: in step 1, 7050 aluminum alloy is prepared by arc additive manufacturing technology, which is specifically carried out in the following steps: CMT+ADV mode is adopted, and the walking speed is 5mm / s-10mm / s, the wire feeding speed is 5m / min-10m / min, the current is 70A-120A, the voltage is 10V-13V, and the wire feeding angle is 7°-10°. Others are the same as specific implementation method 1.

[0031] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: in step 3, the aluminum alloy after heat preservation is transferred to a press machine with a temperature of 470° C. to 490° C. for hot compression within 5 to 30 seconds. The rest is the same as specific implementation method 1 or 2.

[0032] Specific embodiment 4: This embodiment is different 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 described 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. The rest is the same as specific embodiments 1 to 4.

[0034] Specific embodiment 6: This embodiment is different 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. The rest is 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 evacuated 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: 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. The rest is the same as specific embodiments 1 to 7.

[0037] Specific embodiment 9: This embodiment is different from specific embodiments 1 to 8 in that the cooling described in step 4 is cooling to 10°C to 50°C with the furnace, or transferring to water or oil at 10 to 30°C for cooling within 2s to 10s. The rest is 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 described in step 5 is performed in water or oil at a temperature of 10° C. to 30° C. for 2s to 10s. The rest is the same as specific embodiments 1 to 9.

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

[0040] Embodiment 1:

[0041] A method for reducing micropores in an additively manufactured 7050 aluminum alloy after thermal deformation is performed by the following steps:

[0042] 1. Using 7050 aluminum alloy wire as raw material, CMT+ADV mode was adopted to perform arc additive manufacturing under the conditions of walking speed of 7 mm / s, wire feeding speed of 6.5 m / min, current of 98 A, voltage of 11.6 V and 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, the aluminum alloy after heat preservation is transferred to a press machine with a temperature of 480°C, and hot compressed to a deformation amount of 50% under the conditions of a temperature of 480°C and a pressing speed of the pressing head of 50mm / min. After reaching the deformation amount, the pressure is maintained at a temperature of 480°C for 2 minutes, and finally air-cooled 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 is placed in a heat treatment furnace at 480°C, kept at 480°C for 60 minutes, and then cooled in water at 20°C for 3 seconds to obtain an additive 7050 aluminum alloy with reduced micropores after thermal deformation.

[0047] Comparative Experiment 1: The difference between this comparative experiment and Example 1 is that in step 4, the vacuum heat treatment furnace is replaced by a heat treatment furnace, and vacuuming is cancelled; in step 4, furnace cooling is replaced by air cooling. The rest is the same as Example 1.

[0048] Comparative Experiment 2: This comparative experiment is different from Example 1 in that step 2 and step 3 are eliminated. The rest is the same as Example 1.

[0049] Comparative Experiment 3: The difference between this comparative experiment and Example 1 is that: Step 2 and Step 3 are eliminated; in Step 4, the vacuum heat treatment furnace is replaced by a heat treatment furnace, and vacuuming is eliminated; in Step 4, furnace cooling is replaced by air cooling. The rest is the same as Example 1.

[0050] Figure 2The SEM images of the additive 7050 aluminum alloy with reduced micropores after thermal deformation prepared for 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; the effects of different embodiments are compared and it is found that many micropores with high roundness are formed without vacuum dehydrogenation after hot compression and pressure holding in Comparative Experiment 1, and the number of micropores is slightly reduced; in Comparative Experiment 2, the additive 7050 aluminum alloy is directly vacuum dehydrogenated, and the number of micropores is also reduced, but there are still some large-sized micropores with irregular shapes. The number of micropores in vacuum dehydrogenation after hot compression and pressure holding in Example 1 is the least. This is because the pressure holding at high temperature can make the hydrogen element fully dissolved into the matrix without forming micropores, so the vacuum dehydrogenation effect is better, the obtained structure is dense, the number of primary eutectic phases is also significantly reduced, the strength and elongation are greatly improved, and the structure and defects are significantly improved.

[0051] The tensile properties 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 This is a comparison chart of the tensile properties 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 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 273.4MPa, the yield strength is 228.7MPa, and the elongation is 3.06%; in comparative experiment two, the ultimate tensile strength of the material is 416.9MPa, the yield strength is 385.1MPa, and the elongation is 4.57%; in comparative experiment one, the ultimate tensile strength of the material is 532.2MPa, the yield strength is 460.3MPa, and the elongation is 6.17%; in embodiment one, the ultimate tensile strength of the material is 588.4MPa, the yield strength is 511.8MPa, 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 315MPa 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 10min to 20min to obtain the aluminum alloy after the heat treatment; 3. The aluminum alloy after heat preservation is transferred to a press machine with a temperature of 470°C to 490°C, and hot-compressed to a deformation amount of 40% to 60% under the condition of a temperature of 470°C to 490°C. After reaching the deformation amount, the aluminum alloy is kept under pressure for 1min to 3min under the condition of a temperature of 470°C to 490°C, and finally cooled 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, and then the temperature is raised to 430°C to 460°C, and the temperature is 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 30min to 90min 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. A method for reducing micropores in 7050 aluminum alloy after thermal deformation according to claim 1, characterized in that In step one, 7050 aluminum alloy is prepared by arc additive manufacturing technology, which is specifically carried out in the following steps: CMT+ADV mode is used, and the process is carried out under the conditions of a walking speed of 5 mm / s to 10 mm / s, a wire feeding 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 feeding angle of 7° to 10°.

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

5. The method for reducing micropores in 7050 aluminum alloy after thermal deformation according to claim 1, characterized in that The cooling described 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, evacuate the vacuum to a 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 described in step 4 is cooling to 10°C to 50°C with 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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