Method for improving size stability of fine-grain 6061 aluminum alloy
By combining high-temperature coarse grain formation, thermal cycling, and deep cryogenic fine grain formation, a heterogeneous structure of fine-grained soft region and coarse-grained hard region is formed, which solves the problem of improving the dimensional stability and mechanical properties of fine-grained 6061 aluminum alloy, and realizes efficient and simple material improvement, which is suitable for industrial production.
Patent Information
- Application Number
- CN202511869198.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-11
- Publication Date
- 2026-02-17
AI Technical Summary
Existing technologies cannot simultaneously improve the dimensional stability characterization index, microstructure stability, and reduce macroscopic residual stress of fine-grained 6061 aluminum alloy. Conventional heat treatment methods have limited effects and may adversely affect other properties, failing to meet the high requirements of precision inertial instruments.
A combination of high-temperature coarsening, thermal cycling, and cryogenic fine crystallization processes is employed to form a heterogeneous structure of fine-grained soft regions and coarse-grained hard regions by alternating or sequentially performing these processes. Thermal cycling is used to promote the formation of high-density dislocations and age-induced precipitation, thereby reducing residual stress.
It significantly improves the dimensional stability and mechanical properties of fine-grained 6061 aluminum alloy, simplifies the operation process, is suitable for industrial production, is environmentally friendly, does not affect subsequent processing performance, and shortens the production cycle.
Smart Images
Figure CN121538583A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for improving the dimensional stability of aluminum alloys. Background Technology
[0002] With the continuous breakthroughs in modern technology in fields such as aerospace, the demands on the performance of inertial devices have reached new heights. This requires materials to possess not only low density, high strength, high stiffness, and good fatigue resistance, but also excellent dimensional stability under various service environments. As the core of the guidance system, precision inertial instruments such as gyroscopes directly determine the overall performance of the inertial navigation system. However, these precision instruments face multiple challenges in complex and variable service environments, such as hot standby, frequent start-stop, and high-speed flight, including constant temperature, thermal shock, and external loads. This can easily lead to microplastic deformation of internal components, thus affecting the accuracy of the instruments. The long-term stability of instrument accuracy is still heavily constrained by the intrinsic properties of the materials, i.e., their inherent characteristics. These intrinsic properties, such as inherent defects in the microstructure, the presence of second-phase particles, grain size and distribution, and the material's texture, all directly affect the dimensional stability of the material. Adding to the complexity, when these precision instrument materials are exposed to variable external environments, such as varying stress fields, temperature fluctuations, and the long-term effects of time, the accuracy performance of the instruments is eroded.
[0003] To ensure high dimensional stability of components, one approach is material selection, specifically choosing materials with excellent dimensional stability and other properties. Another approach is to improve the dimensional stability of inertial equipment, which can be achieved through dimensional stabilization treatment. This is generally achieved through the following aspects: (1) improving the indicators of dimensional stability, such as micro-yield strength, micro-creep resistance, and stress relaxation limit; (2) improving the stability of the microstructure, including micro-defects, second phase, grain size, and texture; and (3) reducing macroscopic residual stress.
[0004] However, most current dimensional stabilization processes struggle to simultaneously meet all the aforementioned requirements. Conventional heat treatment methods in China, such as ordinary annealing and normalizing, have limited effectiveness in improving material dimensional stability. These methods primarily focus on improving certain fundamental properties of the material, such as hardness and toughness, but their improvement on dimensional stability is not comprehensive or significant. They cannot simultaneously address multiple aspects, including improving dimensional stability indicators (such as micro-yield strength, micro-creep resistance, and stress relaxation limit), improving microstructure stability (including micro-defects, second phase, grain size, and texture), and reducing macroscopic residual stress. Furthermore, these conventional heat treatment methods often improve one aspect while potentially negatively impacting others, failing to meet the high requirements for material dimensional stability in precision inertial instruments.
[0005] Existing methods for improving the dimensional stability of fine-grained 6061 aluminum alloys all have certain limitations and cannot meet the development needs of aluminum-based composite materials with high dimensional stability. Therefore, developing a method for improving the dimensional stability of fine-grained 6061 aluminum alloys that is efficient, low-cost, and easy to industrialize is of great significance. Currently, the main approach to improving the dimensional stability and material properties of fine-grained 6061 aluminum alloys is optimized thermal cycling. Thermal cycling involves repeatedly subjecting the material to high and low temperature environments, using an alternating temperature field to subject the material to thermal shock. This process not only leads to the formation of high-density dislocations but also promotes aging precipitation. Furthermore, the alternating hot and cold action allows the thermal stress generated within the material to interact with the residual stress, thereby reducing residual stress and effectively improving material properties. Compared to isothermal aging, this method has a shorter cycle time. However, the thermal cycling process is cumbersome and more complex to operate. Summary of the Invention
[0006] In order to improve the dimensional stability of 6061 aluminum alloy, this invention proposes a method for improving the dimensional stability of fine-grained 6061 aluminum alloy.
[0007] The method for improving the dimensional stability of fine-grained 6061 aluminum alloy according to the present invention is carried out according to the following steps: the 6061 aluminum alloy is subjected to several high-temperature coarsening treatments and several cold and hot cycle treatments. The high-temperature coarsening treatment and the cold and hot cycle treatment can be performed alternately or sequentially, and finally, deep cryogenic fine-graining treatment is performed.
[0008] The high-temperature coarse crystallization process is as follows: heating 6061 aluminum alloy to 350-530℃ and holding it at that temperature for 1 hour, and then cooling it in the air after the holding time is completed.
[0009] The hot and cold cycle treatment process is as follows: 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen; the heating temperature is 150-220℃ and the time is 2-8h; the liquid nitrogen cooling temperature is -196℃ and the time is 2-8h; the hot and cold cycle treatment is repeated 1-10 times.
[0010] The cryogenic treatment process is as follows: 6061 aluminum alloy is placed in liquid nitrogen and kept at that temperature for 1-20 hours, and then placed in air to return to room temperature.
[0011] The principle of this invention is as follows: After subjecting 6061 aluminum alloy to thermal cycling, high-temperature coarsening, and deep-crystallization, three grain regions emerge within the material: a large-sized coarse-grained soft region, a small-sized fine-grained hard region, and a medium-grained region. During deformation, the soft region undergoes plastic deformation first, while the hard region remains in the elastic deformation stage, leading to the accumulation of a large number of geometrically necessary dislocations at the two-phase interface to accommodate strain. This mechanism activates the multi-slip system, enabling the material to maintain stable deformation even at high strains. Specifically, dislocations on slip surfaces with high slip resistance interact to form immobile dislocations, which in turn induce dislocation entanglement and accumulation, significantly enhancing strain hardening capability. As strain increases, the dislocation density in the fine-grained region rapidly saturates, while the coarse-grained region, due to its larger intragranular space, can continuously absorb newly formed dislocations, delaying hardening saturation. Simultaneously, the strain incompatibility between grains of different sizes induces strong back stress hardening, the effect of which far exceeds that of a homogeneous microstructure. Furthermore, the thermal cycling treatment utilizes an alternating temperature field to subject the material to thermal shock, which not only leads to the formation of high-density dislocations but also promotes aging precipitation. Additionally, the alternating thermal and residual stresses within the material interact to reduce residual stress. The novel heterogeneous structure design of the three regions in this invention results in higher material stability, improving both mechanical properties and dimensional stability.
[0012] The beneficial effects of this invention are as follows:
[0013] 1. This invention uses a hot-cold cycle treatment method to improve the dimensional stability of fine-grained 6061 aluminum alloy materials. By first coarsening, then hot-cold cycle treatment, and finally deep cryogenic fine-graining treatment, a good heterogeneous design combining fine-grained soft regions and coarse-grained hard regions is obtained. It does not require operation under an inert atmosphere, the process is simple and convenient, and it is suitable for large-scale industrial production.
[0014] 2. This invention promotes the formation and aging precipitation of high-density dislocations inside fine-grained 6061 aluminum alloy materials through multiple hot and cold cycles, thereby more effectively improving the dimensional stability of the material and shortening the production cycle.
[0015] 3. This invention does not require complex equipment to precisely control high and low temperature cycling parameters. It can improve the dimensional stability of fine-grained 6061 aluminum alloy materials simply through optimized process steps.
[0016] 4. The fine-grained 6061 aluminum alloy material treated by this invention has improved dimensional stability compared to the untreated fine-grained 6061 aluminum alloy material.
[0017] 5. The present invention has low dependence on environmental conditions during operation, and does not require strict control of specific environmental parameters such as humidity, thereby reducing the impact of environmental fluctuations on material properties and improving the stability and consistency of the process.
[0018] 6. This invention is also applicable to improving the dimensional stability of other similar aluminum-based composite materials or improving the overall performance of aluminum-based composite materials.
[0019] 7. The method of the present invention is easy to combine with other subsequent processing techniques and will not adversely affect the subsequent processing performance of fine-grained 6061 aluminum alloy material, thus providing convenient conditions for further deep processing and diversified applications of the material.
[0020] 8. No harmful gases are generated during the preparation process of this invention, making it ecological, environmentally friendly, green, and healthy. Attached Figure Description
[0021] Figure 1 The image shows the dimensional changes of the fine-grained 6061 aluminum alloy material after thermal cycling in real time, as detected by Example 1.
[0022] Figure 2 This is a surface scan image of the fine-grained 6061 aluminum alloy material after processing in Example 1;
[0023] Figure 3 Comparison of the microstructure of the fine-grained 6061 aluminum alloy material after treatment in Example 1;
[0024] Figure 4 The image shows the dimensional changes of the fine-grained 6061 aluminum alloy material after cold and hot cycling, as detected in real time in Example 2. Detailed Implementation
[0025] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.
[0026] Specific Implementation Method 1: The method for improving the dimensional stability of fine-grained 6061 aluminum alloy in this implementation method is carried out according to the following steps: the 6061 aluminum alloy is subjected to several high-temperature coarsening treatments and several cold and hot cycle treatments. The high-temperature coarsening treatment and the cold and hot cycle treatment can be carried out alternately or sequentially. Finally, a deep cryogenic fine-graining treatment is performed.
[0027] The high-temperature coarse crystallization process is as follows: heating 6061 aluminum alloy to 350-530℃ and holding it at that temperature for 1 hour, and then cooling it in the air after the holding time is completed.
[0028] The hot and cold cycle treatment process is as follows: 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen; the heating temperature is 150-220℃ and the time is 2-8h; the liquid nitrogen cooling temperature is -196℃ and the time is 2-8h; the hot and cold cycle treatment is repeated 1-10 times.
[0029] The cryogenic treatment process is as follows: 6061 aluminum alloy is placed in liquid nitrogen and kept at that temperature for 1-20 hours, and then placed in air to return to room temperature.
[0030] 1. This embodiment uses a hot-cold cycle treatment method to improve the dimensional stability of fine-grained 6061 aluminum alloy material. By first coarsening, then hot-cold cycle treatment, and finally deep cryogenic fine-graining treatment, a good heterogeneous design combining fine-grained soft regions and coarse-grained hard regions is obtained. It does not require operation under an inert atmosphere, the process is simple and convenient, and it is suitable for large-scale industrial production.
[0031] 2. This embodiment promotes the formation of high-density dislocations and age precipitation inside the fine-grained 6061 aluminum alloy material through multiple hot and cold cycles, which can more effectively improve the dimensional stability of the material and shorten the production cycle.
[0032] 3. This implementation method does not require complex equipment to precisely control the high and low temperature cycle parameters. The dimensional stability improvement of fine-grained 6061 aluminum alloy material can be achieved simply through the optimized process steps.
[0033] 4. The fine-grained 6061 aluminum alloy material treated in this embodiment has improved dimensional stability compared to the untreated fine-grained 6061 aluminum alloy material.
[0034] 5. This implementation method has low dependence on environmental conditions during operation, does not require strict control of specific environmental parameters such as humidity, reduces the impact of environmental fluctuations on material properties, and improves the stability and consistency of the process.
[0035] 6. This embodiment is also applicable to improving the dimensional stability of other similar aluminum-based composite materials or improving the overall performance of aluminum-based composite materials.
[0036] 7. The method of this embodiment is easy to combine with other subsequent processing techniques and will not adversely affect the subsequent processing performance of fine-grained 6061 aluminum alloy material, thus providing convenient conditions for further deep processing and diversified applications of the material.
[0037] 8. This method produces no harmful gases during the preparation process, making it eco-friendly, environmentally friendly, and healthy.
[0038] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the average particle size of the 6061 aluminum alloy is 3-8 μm.
[0039] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the heat treatment state of the 6061 aluminum alloy is T6.
[0040] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the 6061 aluminum alloy is a cylinder with a diameter of 6mm and a height of 25mm. The cutting marks on the cylinder are removed by grinding equipment and polished to 5000 grit.
[0041] Specific Implementation Method 5: This implementation method differs from one of the specific implementation methods 1 to 4 in that the average particle size of the 6061 aluminum alloy is 4μm.
[0042] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the 6061 aluminum alloy is subjected to high-temperature coarse grain treatment, hot and cold cycle treatment, and deep cryogenic fine grain treatment in sequence.
[0043] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that: the 6061 aluminum alloy is subjected to a first hot and cold cycle treatment, a high-temperature coarse grain treatment, a second hot and cold cycle treatment, and a deep cold fine grain treatment in sequence.
[0044] Specific Implementation Method Eight: This implementation method differs from one of the specific implementation methods one to seven in that the high-temperature coarse crystallization process is as follows: 6061 aluminum alloy is heated to 350°C and held at that temperature for 1 hour. After the holding time is completed, it is placed in the air to cool.
[0045] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that the hot and cold cycle treatment process is as follows: a total of 10 hot and cold cycle treatments are performed. The 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen. The heating temperature is 150°C for 4 hours, and the liquid nitrogen cooling temperature is -196°C for 4 hours, for a total of 5 hot and cold cycle treatments. Then, the 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen. The heating temperature is 170°C for 4 hours, and the liquid nitrogen cooling temperature is -196°C for 4 hours, for a total of 5 hot and cold cycle treatments.
[0046] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the cryogenic treatment process is as follows: 6061 aluminum alloy is placed in liquid nitrogen and kept at a temperature of 10 hours, and then placed in air to recover to room temperature.
[0047] Example 1
[0048] The method for improving the dimensional stability of fine-grained 6061 aluminum alloy in this embodiment is as follows: the 6061 aluminum alloy is subjected to high-temperature coarsening treatment, hot and cold cycling treatment and deep cryogenic fine-graining treatment in sequence.
[0049] The average grain size of the 6061 aluminum alloy is 4 μm;
[0050] The heat treatment state of the 6061 aluminum alloy is T6.
[0051] The 6061 aluminum alloy is a cylinder with a diameter of 6mm and a height of 25mm. The cutting marks on the cylinder are removed by grinding equipment and polished to 5000 grit.
[0052] The high-temperature coarse crystallization process is as follows: heating 6061 aluminum alloy to 350°C and holding it at that temperature for 1 hour, and then cooling it in the air after the holding time is completed.
[0053] The hot and cold cycle treatment process is as follows: a total of 10 hot and cold cycle treatments are performed. The 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen. The heating temperature is 150℃ for 4 hours, and the liquid nitrogen cooling temperature is -196℃ for 4 hours, for a total of 5 hot and cold cycle treatments. Then, the 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen. The heating temperature is 170℃ for 4 hours, and the liquid nitrogen cooling temperature is -196℃ for 4 hours, for a total of 5 hot and cold cycle treatments.
[0054] The cryogenic treatment process is as follows: 6061 aluminum alloy is placed in liquid nitrogen and kept at that temperature for 10 hours, and then placed in air to return to room temperature.
[0055] The thermal cycling real-time online detection method was used for testing, and the dimensional stability of the material was measured by comparing the irreversible dimensional changes at room temperature (20℃). The thermal cycling real-time online detection method uses a thermal expansion instrument to apply cyclic temperature loads to the sample to simulate the external environmental temperature changes experienced by the part during service and storage. The thermal cycling real-time online detection method was used to test aluminum alloys with a program ranging from 20℃ to 150℃, and the program ran for a total of 27 hours. The irreversible dimensional changes obtained were processed and plotted to measure the dimensional stability of the material under thermal cycling service environment.
[0056] Figure 1 The image shows the dimensional changes of the fine-grained 6061 aluminum alloy material after thermal cycling in real time, as detected by Example 1. Figure 2 This is a surface scan image of the fine-grained 6061 aluminum alloy material after processing in Example 1; Figure 2 It can be seen that Mg and Si elements are aggregated at the grain boundary edges, which are Mg-Si precipitates after the treatment of 6061 aluminum alloy. At the same time, there are certain Al-Fe-Si phases precipitated in the grains, and a small amount of Cr and Ni are also present. Figure 3 The images show a comparison of the microstructure of the fine-grained 6061 aluminum alloy material after treatment in Example 1; where a is the original microstructure and b is the microstructure after treatment. Figure 3It can be seen that the small grain size can reach 3μm, while after treatment, a certain coarse grain distribution appears, with some coarse grain regions showing grains of about 40μm. The medium grain size in the medium region is between the two, which proves that the present invention has obtained the microstructure of three grain regions. The tensile strength of the fine-grained 6061 aluminum alloy material sample in the RD (rolling direction) direction after treatment in this embodiment is 404MPa, the elastic modulus is 71GPa, the elongation is 15.1%, and the average dimensional change of the material (the ratio of the dimensional change ΔL to the initial size H0) evaluated by online thermal cycling is 2.1×10 -6 The tensile strength of the sample in the ND (rolled plane normal) direction was 353 MPa, the elastic modulus was 71 GPa, and the elongation was 9.38%. The average dimensional change of the material during online thermal cycling evaluation was 1.2 × 10⁻⁶. -6 .
[0057] Example 2
[0058] The method for improving the dimensional stability of fine-grained 6061 aluminum alloy in this embodiment is as follows: the 6061 aluminum alloy is subjected to a first thermal cycling treatment, a high-temperature coarsening treatment, a second thermal cycling treatment, and a deep cryogenic fine-graining treatment in sequence.
[0059] The average grain size of the 6061 aluminum alloy is 4 μm;
[0060] The heat treatment state of the 6061 aluminum alloy is T6.
[0061] The 6061 aluminum alloy is a cylinder with a diameter of 6mm and a height of 25mm. The cutting marks on the cylinder are removed by grinding equipment and polished to 5000 grit.
[0062] The first thermal cycling process is as follows: a total of 4 thermal cycling treatments are performed. The 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen. The heating temperature is 150℃ for 4 hours, and the liquid nitrogen cooling temperature is -196℃ for 4 hours, for a total of 2 thermal cycling treatments. Then, the 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen. The heating temperature is 170℃ for 4 hours, and the liquid nitrogen cooling temperature is -196℃ for 4 hours, for a total of 2 thermal cycling treatments.
[0063] The high-temperature coarse crystallization process is as follows: heating 6061 aluminum alloy to 350°C and holding it at that temperature for 1 hour, and then cooling it in the air after the holding time is completed.
[0064] The second thermal cycling process is as follows: a total of 4 thermal cycling treatments are performed. The 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen. The heating temperature is 150℃ for 4 hours, and the liquid nitrogen cooling temperature is -196℃ for 4 hours, for a total of 2 thermal cycling treatments. Then, the 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen. The heating temperature is 170℃ for 4 hours, and the liquid nitrogen cooling temperature is -196℃ for 4 hours, for a total of 2 thermal cycling treatments.
[0065] The cryogenic treatment process is as follows: 6061 aluminum alloy is placed in liquid nitrogen and kept at that temperature for 10 hours, and then placed in air to return to room temperature.
[0066] The thermal cycling real-time online detection method was used for testing, and the dimensional stability of the material was measured by comparing the irreversible dimensional changes at room temperature (20℃). The thermal cycling real-time online detection method uses a thermal expansion instrument to apply cyclic temperature loads to the sample to simulate the external environmental temperature changes experienced by the part during service and storage. The thermal cycling real-time online detection method was used to test aluminum alloys with a program ranging from 20℃ to 150℃, and the program ran for a total of 27 hours. The irreversible dimensional changes obtained were processed and plotted to measure the dimensional stability of the material under thermal cycling service environment.
[0067] The tensile strength of the fine-grained 6061 aluminum alloy sample in the RD direction after treatment in this embodiment is 386 MPa, the elastic modulus is 71 GPa, the elongation is 14.9%, and the average dimensional change of the material during online evaluation of thermal cycling is 1.59 × 10⁻⁶. -6 The tensile strength of the sample in the ND direction was 333 MPa, the elastic modulus was 71 GPa, and the elongation was 8.9%. The average dimensional change of the material during online thermal cycling was 1.03 × 10⁻⁶. -6 .
[0068] Example 3
[0069] The method for improving the dimensional stability of fine-grained 6061 aluminum alloy in this embodiment is as follows: the 6061 aluminum alloy is subjected to high-temperature coarsening treatment, hot and cold cycling treatment and deep cryogenic fine-graining treatment in sequence.
[0070] The average grain size of the 6061 aluminum alloy is 4 μm;
[0071] The heat treatment state of the 6061 aluminum alloy is T6.
[0072] The 6061 aluminum alloy is a cylinder with a diameter of 6mm and a height of 25mm. The cutting marks on the cylinder are removed by grinding equipment and polished to 5000 grit.
[0073] The high-temperature coarse crystallization process is as follows: heating 6061 aluminum alloy to 350°C and holding it at that temperature for 1 hour, and then cooling it in the air after the holding time is completed.
[0074] The hot and cold cycle treatment process is as follows: a total of 10 hot and cold cycle treatments are performed. The 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen. The heating temperature is 170℃ for 4 hours, and the liquid nitrogen cooling temperature is -196℃ for 4 hours, for a total of 5 hot and cold cycle treatments. Then, the 6061 aluminum alloy is alternately heated and cooled with liquid nitrogen. The heating temperature is 200℃ for 4 hours, and the liquid nitrogen cooling temperature is -196℃ for 4 hours, for a total of 5 hot and cold cycle treatments.
[0075] The cryogenic treatment process is as follows: 6061 aluminum alloy is placed in liquid nitrogen and kept at that temperature for 10 hours, and then placed in air to return to room temperature.
[0076] The thermal cycling real-time online detection method was used for testing, and the dimensional stability of the material was measured by comparing the irreversible dimensional changes at room temperature (20℃). The thermal cycling real-time online detection method uses a thermal expansion instrument to apply cyclic temperature loads to the sample to simulate the external environmental temperature changes experienced by the part during service and storage. The thermal cycling real-time online detection method was used to test aluminum alloys with a program ranging from 20℃ to 150℃, and the program ran for a total of 27 hours. The data of the irreversible dimensional changes obtained were processed and plotted to measure the dimensional stability of the material under thermal cycling service environment.
[0077] The tensile strength of the fine-grained 6061 aluminum alloy sample in the RD direction after treatment in this embodiment is 311 MPa, the elastic modulus is 71 GPa, the elongation is 13.8%, and the average dimensional change of the material during online evaluation of thermal cycling is 1.98 × 10⁻⁶. -6 The tensile strength of the sample in the ND direction was 291 MPa, the elastic modulus was 71 GPa, and the elongation was 7.8%. The average dimensional change of the material during online thermal cycling was 2.4 × 10⁻⁶. -6 .
Claims
1. A method of improving dimensional stability of a fine-grained 6061 aluminum alloy, characterized by: The method is performed according to the following steps: the 6061 aluminum alloy is subjected to several high-temperature coarse-grainizing treatments and several cold-heat cycle treatments, the high-temperature coarse-grainizing treatments and the cold-heat cycle treatments can be performed alternately or sequentially, and finally subjected to deep cold fine-grainizing treatment; The high-temperature coarse-grainizing treatment process is: the 6061 aluminum alloy is heated to 350-530 DEG C and kept for 1 h, and after the keeping, it is cooled in air; The cold-heat cycle treatment process is: the 6061 aluminum alloy is subjected to alternating heating treatment and liquid nitrogen cooling treatment; the heating treatment temperature is 150-220 DEG C, and the time is 2-8 h; the liquid nitrogen cooling treatment temperature is -196 DEG C, and the time is 2-8 h; the cold-heat cycle treatment is 1-10 times; The deep cold treatment process is: the 6061 aluminum alloy is kept in liquid nitrogen for 1-20 h, and then is placed in air to recover to room temperature.
2. The method of improving dimensional stability of a fine-grained 6061 aluminum alloy of claim 1, wherein: The average particle size of the 6061 aluminum alloy is 3-8 mu m.
3. The method of improving dimensional stability of a fine-grained 6061 aluminum alloy of claim 1, wherein: The heat treatment state of the 6061 aluminum alloy is T6 state.
4. The method of improving dimensional stability of a fine-grained 6061 aluminum alloy of claim 1, wherein: The 6061 aluminum alloy is a cylinder, the diameter is 6 mm, the height is 25 mm, the cutting marks on the cylinder are ground off by using a grinding device and polished to 5000 mesh.
5. The method of improving dimensional stability of a fine-grained 6061 aluminum alloy of claim 1, wherein: The average particle size of the 6061 aluminum alloy is 4 mu m.
6. The method of improving dimensional stability of a fine-grained 6061 aluminum alloy of claim 1, wherein: The 6061 aluminum alloy is sequentially subjected to high-temperature coarse-grainizing treatment, cold-heat cycle treatment and deep cold fine-grainizing treatment.
7. The method of improving dimensional stability of a fine-grained 6061 aluminum alloy of claim 1, wherein: The 6061 aluminum alloy is sequentially subjected to first cold-heat cycle treatment, high-temperature coarse-grainizing treatment, second cold-heat cycle treatment and deep cold fine-grainizing treatment.
8. The method of improving dimensional stability of a fine-grained 6061 aluminum alloy of claim 1, wherein: The high-temperature coarse-grainizing treatment process is: the 6061 aluminum alloy is heated to 350 DEG C and kept for 1 h, and after the keeping, it is cooled in air.
9. The method of improving dimensional stability of a fine-grained 6061 aluminum alloy of claim 1, wherein: The cold-heat cycle treatment process is: a total of 10 times of cold-heat cycle treatment is performed. The 6061 aluminum alloy is subjected to alternating heating treatment and liquid nitrogen cooling treatment, the heating treatment temperature is 150 DEG C, and the time is 4 h, the liquid nitrogen cooling treatment temperature is -196 DEG C, and the time is 4 h, and the cold-heat cycle treatment is 5 times; the 6061 aluminum alloy is subjected to alternating heating treatment and liquid nitrogen cooling treatment again, the heating treatment temperature is 170 DEG C, and the time is 4 h, the liquid nitrogen cooling treatment temperature is -196 DEG C, and the time is 4 h, and the cold-heat cycle treatment is 5 times.
10. The method of improving dimensional stability of a fine-grained 6061 aluminum alloy of claim 1, wherein: The deep cold treatment process is: the 6061 aluminum alloy is kept in liquid nitrogen for 10 h, and then is placed in air to recover to room temperature.