A processing method for improving the number density of dispersed phases of 6061 aluminum alloy

Abstract

The application relates to a processing method for improving the dispersion phase number density of 6061 aluminum alloy, which comprises the following steps: (1) casting; (2) homogenization annealing; (3) after the homogenization annealing, the sample is subjected to a multi-pass hot rolling and cold rolling process; (4) hot rolling; (5) cold rolling, wherein the final total reduction rate of the hot rolling and the cold rolling is 75%-95%; (6) low-temperature pretreatment: the rolled alloy plate is kept at 250-290 DEG C for 5-10 h; (7) solid solution treatment: the alloy after the low-temperature pretreatment is heated to 520-540 DEG C and kept for 1-3 h, and then is immediately water-quenched; (8) aging treatment: the artificial aging treatment is carried out within 5 minutes after the quenching, the aging temperature is 165-185 DEG C, and the keeping time is 2-12 h. The processing method solves the problem of the insufficient dispersion phase number density of the 6061 aluminum alloy under the traditional homogenization annealing process, and solves the problems of the complicated process and the high energy consumption caused by the multi-stage homogenization annealing process for improving the dispersion phase number density.

Description

Technical Field

[0001] This invention relates to a processing method for increasing the dispersed phase number density of 6061 aluminum alloy. Background Technology

[0002] Aluminum alloys, with their excellent specific strength, corrosion resistance, and good adaptability to welding processes, have been widely used in modern transportation equipment, engineering machinery, and the manufacture of key structural components. Among them, high-strength aluminum alloys in the Al-Mg-Si system (such as alloy 6061) are widely used in applications requiring high safety and durability, such as rail transit car bodies, lightweight automotive components, ship structures, and cryogenic pressure vessels, due to their excellent mechanical properties and weldability.

[0003] The performance of this type of aluminum alloy ultimately depends on its complete processing chain, typically requiring coordinated control of multiple processes such as melting, casting, deformation processing, and heat treatment to achieve the desired microstructure and comprehensive performance. To optimize the alloy's service behavior, transition elements such as Mn and Cr are often added to 6061 alloy. Existing research shows that these elements precipitate as fine, dispersed phases during homogenization (solubilization). These dispersed phase particles exhibit a significant pinning effect, effectively inhibiting grain boundary migration and hindering grain coarsening during recrystallization. Furthermore, they can interact with dislocations, positively impacting key performance indicators such as plasticity and fatigue life. Therefore, improving the number density of dispersed phases through process control has become crucial for further exploring the performance potential of this alloy series.

[0004] To improve the number density of dispersed phases in 6xxx series alloys, there are already patents that disclose the methods for achieving this. Currently, the main methods used in the industry are to introduce other microalloying elements besides Mn and Cr or to use a complex three-stage homogenization annealing process.

[0005] For example, in the scheme of patent CN117867423A, by introducing dispersed phase forming elements (transition metal elements such as Mn, Cr, Zr, and Sc) and trace amounts of Sn, and employing a two-stage homogenization heat treatment process, a large amount of uniform precipitation of dispersed phases is promoted. If elements other than common Mn and Cr are introduced to increase the number density of dispersed phases, this will inevitably cause difficulties in alloy recycling.

[0006] For example, patents CN118207488A and CN117737620A disclose a three-stage uniform annealing method to improve the dispersed phase number density in 6xxx series aluminum alloys containing Mn and Cr. However, this three-stage uniform annealing method will lead to the complexity of heat treatment, increase the difficulty of heat treatment, and increase the energy consumption of heat treatment. Summary of the Invention

[0007] This invention addresses the aforementioned problems by providing a processing method to improve the dispersed phase density of 6061 aluminum alloy. This method solves the problem of insufficient dispersed phase density in 6061 aluminum alloy after solution treatment and aging. Without introducing other microalloying elements or affecting alloy recycling, this invention develops a low-temperature pretreatment process before solution treatment. This relatively simple process effectively improves the dispersed phase density of 6061 aluminum alloy without requiring adjustments to the alloy composition or the use of a complex three-stage homogenization annealing method, thus simplifying the overall process and reducing energy consumption.

[0008] The present invention is constructed as follows, comprising the following steps: (1) Casting: 6061 aluminum alloy ingots are prepared by semi-continuous casting, the chemical composition of which is as follows by mass percentage: Mg 0.8%-1.2%, Si 0.4%-0.8%, Cu 0.15%-0.4%, Zn 0%-0.2%, Mn 0.05%-0.15%, Ti 0%-0.15%, Cr 0.05%-0.35%, Fe 0.1%-0.35%, with the balance being Al and unavoidable impurities; (2) Homogenization annealing: The ingots are heated to 520-555℃ at a heating rate of 4-10℃ / min and held for 4-10h. (3) After homogenization annealing, the sample is subjected to multiple hot rolling and cold rolling processes; (4) Hot rolling: the homogenized annealed ingot is hot rolled at 450-490℃, and the total reduction rate of hot rolling is 60%-67%; (5) Cold rolling: after the alloy is cooled to room temperature, it is cold rolled, and the total reduction rate of cold rolling is 15%-28%, and the final total reduction rate of hot rolling and cold rolling is 75%-95%; (6) Low temperature pretreatment: the rolled alloy plate is kept at 250-290℃ for 5-10h; (7) Solution treatment: the alloy after low temperature pretreatment is heated to 520-540℃ and kept for 1-3h, and water quenching is performed immediately after solution treatment; (8) Aging treatment: artificial aging treatment is performed within 5 minutes after quenching, the aging temperature is 165-185℃, and the temperature is kept for 2-12h.

[0009] Furthermore, in step (2), the homogenization annealing is a single-stage homogenization annealing, and there is no need to use a multi-stage homogenization annealing process.

[0010] Furthermore, in step (6), the temperature of the low-temperature pretreatment is 250-280℃.

[0011] Furthermore, in step (6), the heat preservation time for low temperature pretreatment is 8-10 hours.

[0012] Furthermore, in step (7), the solution treatment temperature is 525-535℃ and the holding time is 1-2h.

[0013] Furthermore, in step (8), the aging treatment temperature is 170-180℃ and the holding time is 6-10h.

[0014] Furthermore, after processing in steps (1) to (8), the number density of dispersed phases in the aged state of 6061 aluminum alloy reaches 1.7-1.9 per μm².

[0015] Furthermore, this processing method does not require the introduction of alloying elements other than Mn and Cr, and does not change the main composition of the alloy.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The processing method does not require the introduction of other micro-alloying elements besides Mn and Cr, does not change the main composition of the alloy, does not cause difficulties in alloy recycling, and is conducive to resource recycling; (2) It does not require the use of a complex three-stage homogenization annealing process, and only the traditional single-stage homogenization annealing process is used in the homogenization annealing process. However, the pretreatment before the solution treatment reduces the driving force of recrystallization and promotes the formation of the MgSi-containing second phase. These factors together promote the formation of high number density dispersed phases. The overall process flow is simple, reducing the complexity of the process and the difficulty of operation. (3) The low-temperature pretreatment process designed before the solution treatment has a temperature and time that are lower than the heating section of the multi-stage homogenization annealing, which significantly reduces the heat treatment energy consumption and achieves high efficiency and energy saving. (4) After treatment by the present invention, the number density of dispersed phases in the aged state of 6061 aluminum alloy can reach 1.7-1.9 per μm², which is comparable to the three-stage homogenization annealing process and far exceeds the 0.95 per μm² of the traditional no-pretreatment process, effectively improving the comprehensive mechanical properties of the alloy. Attached Figure Description

[0017] Figure 1 This is an observation diagram of the diffuse phase in Example 1 of the present invention under aging conditions; Figure 2 This is an observation diagram of the diffuse phase in Example 2 of the present invention under aging conditions; Figure 3 This is an observation diagram of the diffuse phase in Comparative Example 1 of the present invention under aging conditions; Figure 4 This is an observation diagram of the diffuse phase in Comparative Example 2 of the present invention under aging conditions; Figure 5 This is an observation diagram of the diffuse phase in Comparative Example 3 of the present invention under aging conditions; Figure 6 This is an observation diagram of the diffuse phase in Comparative Example 4 of the present invention under aging conditions; Figure 7 This is a comparison diagram of the diffuse phase number density of various embodiments and comparative examples of the present invention. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0019] In this embodiment, a processing method for improving the dispersed phase number density of 6061 aluminum alloy is provided, including the following steps: (1) Casting: 6061 aluminum alloy ingots are prepared by semi-continuous casting, and the chemical composition by mass percentage is: Mg 0.8%-1.2%, Si 0.4%-0.8%, Cu 0.15%-0.4%, Zn 0%-0.2%, Mn 0.05%-0.15%, Ti 0%-0.15%, Cr 0.05%-0.35%, Fe 0.1%-0.35%, with the balance being Al and unavoidable impurities; (2) Homogenization annealing: The ingot is heated to 520-555℃ at a heating rate of 4-10℃ / min and held for 4-10h. (3) After homogenization annealing, the sample is subjected to multiple hot rolling and cold rolling processes; (4) Hot rolling: the homogenized annealed ingot is hot rolled at 450-490℃, and the total reduction rate of hot rolling is 60%-67%; (5) Cold rolling: after the alloy is cooled to room temperature, it is cold rolled, and the total reduction rate of cold rolling is 15%-28%, and the final total reduction rate of hot rolling and cold rolling is 75%-95%; (6) Low temperature pretreatment: the rolled alloy plate is kept at 250-290℃ for 5-10h; (7) Solution treatment: the alloy after low temperature pretreatment is heated to 520-540℃ and kept for 1-3h, and water quenching is performed immediately after solution treatment; (8) Aging treatment: artificial aging treatment is performed within 5 minutes after quenching, the aging temperature is 165-185℃, and the temperature is kept for 2-12h.

[0020] In this embodiment of the invention, in step (2), the homogenization annealing is a single-stage homogenization annealing, and there is no need to use a multi-stage homogenization annealing process.

[0021] In this embodiment of the invention, in step (6), the temperature of the low-temperature pretreatment is 250-280°C.

[0022] In this embodiment of the invention, in step (6), the heat preservation time for low temperature pretreatment is 8-10 hours.

[0023] In this embodiment of the invention, in step (7), the solution treatment temperature is 525-535℃ and the holding time is 1-2h.

[0024] In this embodiment of the invention, in step (8), the aging treatment temperature is 170-180℃ and the heat preservation time is 6-10h.

[0025] In this embodiment of the invention, after processing in steps (1) to (8), the number density of dispersed phases in the aged state of 6061 aluminum alloy reaches 1.7-1.9 per μm².

[0026] In this embodiment of the invention, the processing method does not require the introduction of alloying elements other than Mn and Cr, and does not change the main composition of the alloy. Example

[0027] This embodiment uses 6061 aluminum alloy as the research object. The alloy is prepared according to the following mass percentages: Al-0.88Mg-0.71Si-0.28Cu-0.31Fe-0.1Mn-0.16Cr. The alloy is produced by semi-continuous casting, and the process flow is: casting aluminum ingot - hot rolling - cold rolling - low temperature pretreatment - solution treatment - aging. A 100×20×8mm sample is taken from the ingot and subjected to homogenization heat treatment at 550℃ for 10h. Then, the sample is heated to 480℃ in a muffle furnace and held for 30min before hot rolling. The first hot rolling reduction is 3mm, and the second reduction is 2mm. Finally, after cooling to room temperature, two cold rolling passes are performed, each with a reduction of 1mm. The final thickness of the sample is 1mm. Subsequently, the rolled plate is rolled at 250℃. o Pretreatment was performed for 10 hours under C, followed by 530... o Solution treatment with C for 1 hour. The solution-treated sample is then aged at 175℃ for 8 hours. The dispersed phase condition is as follows: Figure 1 As shown. Example

[0028] In this embodiment, the 6061 aluminum alloy composition, casting method, homogenization method, and rolling method are the same as in Embodiment 1. After rolling, the rolled sheet is heated to 280°C. o Pretreatment was performed for 8 hours under C, followed by 535... o Solution treatment at C for 1 hour. The solution-treated sample was then subjected to aging treatment, following the same process as in Example 1. The dispersed phase condition was as follows. Figure 2 As shown.

[0029] Comparative Example 1: The composition, casting method, soaking method, and rolling method of the 6061 aluminum alloy in this comparative example are the same as those in Example 1. After rolling, it is subjected to a 10 o Heating rate increased to 535 °C / min o Solution treatment with C for 1 hour. Then, aging treatment is performed, following the same process as in Example 1, with the dispersed phase as shown. Figure 3 As shown.

[0030] Comparative Example 2: The composition and casting method of the 6061 aluminum alloy in this comparative example are the same as in Example 1. A sample of 100×20×8mm was taken from the ingot and subjected to 250°C testing.o C / 6h+400 o C / 6h+550 o A three-stage homogenization heat treatment of C / 8h was performed. This was followed by rolling, solution treatment, and aging, with the specific process identical to Comparative Example 1. The dispersed phase characteristics were as follows: Figure 4 As shown.

[0031] Comparative Example 3: The composition, casting method, soaking method, and rolling method of the 6061 aluminum alloy in this comparative example are the same as those in Example 1. After rolling, the rolled sheet is heated at 300°C. o Pretreatment was performed for 8 hours under C, followed by 535... o Solution treatment at C for 1 hour. The solution-treated sample was then subjected to aging treatment, following the same process as in Example 1. The dispersed phase condition was as follows. Figure 5 As shown.

[0032] Comparative Example 4: The composition, casting method, soaking method, and rolling method of the 6061 aluminum alloy in this comparative example are the same as those in Example 1. After rolling, the rolled sheet is heated to 235°C. o Pretreatment was performed for 10 hours under C, followed by 535... o Solution treatment at C for 1 hour. The solution-treated sample was then subjected to aging treatment, following the same process as in Example 1. The dispersed phase condition was as follows. Figure 6 As shown.

[0033] Compared with Comparative Examples 1, 3, and 4, the dispersed phase surface number density of Examples 1 and 2 of the present invention is improved. Specifically, Example 1 is essentially equivalent to Comparative Example 2, which employs a three-stage homogenization process. Figure 7 As shown. A common method to increase the number density of dispersed phases is three-stage homogenization annealing, which aims to increase the number density of dispersed phases during the homogenization annealing stage and inherit it into the final microstructure after aging. However, in this invention, the concept of controlling the dispersed phases during the initial homogenization annealing process is abandoned. Instead, only a traditional single-stage homogenization annealing process is used in the homogenization annealing process. However, the pretreatment performed before solution treatment reduces the driving force for recrystallization and promotes the formation of MgSi-containing second phases. These factors together promote the formation of high-number-density dispersed phases. Figure 7 As shown, in Examples 1 and 2 of the present invention, the dispersed phase number density reached 1.9 phases / µm, respectively. 2 and 1.7 per μm 2 Compared with the three-stage homogenization annealing process (Comparative Example 2), the concentration was 1.9 μm / µm. 2 Comparable to, and far higher than, the 0.95 particles / µm of traditional single-stage homogenization annealing without pretreatment. 2This is achieved by relying on the incomplete precipitation of the dispersed phase during the early homogenization annealing process. Therefore, single-stage homogenization annealing + pretreatment + solution treatment can significantly improve the number density of dispersed phases in 6061 aluminum alloy.

[0034] Unless otherwise stated, if any of the technical solutions disclosed in this invention specify a numerical range, then the disclosed numerical range is a preferred numerical range. Anyone skilled in the art should understand that the preferred numerical range is merely one among many feasible numerical values ​​that has a more obvious or representative technical effect. Because there are many numerical values, it is impossible to list them all. Therefore, this invention discloses only some numerical values ​​to illustrate the technical solutions of this invention. Furthermore, the numerical values ​​listed above should not constitute a limitation on the scope of protection of this invention.

[0035] Furthermore, if the present invention discloses or relates to mutually fixedly connected components or structural parts, then unless otherwise stated, a fixed connection can be understood as: a detachable fixed connection (e.g., using bolts or screws), or a non-detachable fixed connection (e.g., riveting, welding). Of course, mutually fixed connections can also be replaced by an integral structure (e.g., manufactured using a casting process) (except where it is obviously impossible to use an integral molding process).

[0036] In addition, unless otherwise stated, the terms used in any of the technical solutions disclosed in this invention to indicate positional relationships or shapes include states or shapes that are similar to, close to, or approximate with those states or shapes.

[0037] Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A processing method for increasing the dispersed phase number density of 6061 aluminum alloy, characterized in that, Includes the following steps: (1) Casting: 6061 aluminum alloy ingots were prepared by semi-continuous casting. The chemical composition by mass percentage was: Mg 0.8%-1.2%, Si 0.4%-0.8%, Cu 0.15%-0.4%, Zn 0%-0.2%, Mn 0.05%-0.15%, Ti 0%-0.15%, Cr 0.05%-0.35%, Fe 0.1%-0.35%, with the balance being Al and unavoidable impurities; (2) Homogenization annealing: The ingots were heated to 520-555℃ at a heating rate of 4-10℃ / min and held for 4-10h. (3) After homogenization annealing, the sample is subjected to multiple hot rolling and cold rolling processes; (4) Hot rolling: the homogenized annealed ingot is hot rolled at 450-490℃, and the total reduction rate of hot rolling is 60%-67%; (5) Cold rolling: after the alloy is cooled to room temperature, it is cold rolled, and the total reduction rate of cold rolling is 15%-28%, and the final total reduction rate of hot rolling and cold rolling is 75%-95%; (6) Low temperature pretreatment: the rolled alloy plate is kept at 250-290℃ for 5-10h; (7) Solution treatment: the alloy after low temperature pretreatment is heated to 520-540℃ and kept for 1-3h, and water quenching is performed immediately after solution treatment; (8) Aging treatment: artificial aging treatment is performed within 5 minutes after quenching, the aging temperature is 165-185℃, and the temperature is kept for 2-12h.

2. The processing method for increasing the dispersed phase number density of 6061 aluminum alloy according to claim 1, characterized in that, In step (2), the homogenization annealing is a single-stage homogenization annealing, and there is no need to use a multi-stage homogenization annealing process.

3. The processing method for increasing the dispersed phase number density of 6061 aluminum alloy according to claim 1, characterized in that, In step (6), the temperature of the low-temperature pretreatment is 250-280℃.

4. The processing method for increasing the dispersed phase number density of 6061 aluminum alloy according to claim 1, characterized in that, In step (6), the heat preservation time for low temperature pretreatment is 8-10 hours.

5. The processing method for increasing the dispersed phase number density of 6061 aluminum alloy according to claim 1, characterized in that, In step (7), the solution treatment temperature is 525-535℃ and the holding time is 1-2h.

6. The processing method for increasing the dispersed phase number density of 6061 aluminum alloy according to claim 1, characterized in that, In step (8), the aging treatment temperature is 170-180℃ and the holding time is 6-10h.

7. The processing method for increasing the dispersed phase number density of 6061 aluminum alloy according to claim 1, characterized in that, After processing in steps (1) to (8), the number density of dispersed phases in the aged state of 6061 aluminum alloy reaches 1.7-1.9 per μm².

8. The processing method for increasing the dispersed phase number density of 6061 aluminum alloy according to claim 1, characterized in that, This processing method does not require the introduction of alloying elements other than Mn and Cr, and does not change the main composition of the alloy.

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