High-toughness 6XXX series aluminum alloy forge piece and preparation method thereof

Abstract

The invention discloses a high-toughness 6XXX series aluminum alloy forge piece and a preparation method thereof.The preparation method comprises the steps that firstly, an aluminum alloy round billet ingot is subjected to homogenization treatment and then peeled, and a peeled aluminum alloy blank is obtained; performing isothermal variable-speed hot forging on the aluminum alloy blank, and cooling to obtain an aluminum alloy forge piece; the aluminum alloy forge piece is subjected to solution treatment, cooling and aging treatment; the aluminum alloy round billet comprises the following element components in percentage by mass: 0.6 to 1.2 weight percent of Mg, 0.8 to 1.3 weight percent of Si, 0.4 to 0.6 weight percent of Cu, 0.4 to 1.0 weight percent of Mn, less than or equal to 0.3 weight percent of Cr, less than or equal to 0.3 weight percent of Mo, less than or equal to 0.15 weight percent of Fe, less than or equal to 0.10 weight percent of Ti, less than or equal to 0.15 weight percent of other impurities and the balance of Al. According to the 6XXX series aluminum alloy forge piece and the preparation method thereof, through optimization design of alloy components and combination of the preparation method, high-density and evenly-distributed submicron-level dispersed phases and nanometer-level precipitated phases are formed in the forge piece structure, meanwhile, a small-size recrystallization structure is obtained, and the strength and toughness of the 6XXX series aluminum alloy forge piece are remarkably improved through the synergistic effect of the microstructures.

Description

Technical Field

[0001] This invention relates to the field of metallic materials technology, specifically to a high-strength and high-toughness 6XXX series aluminum alloy forging and its preparation method. Background Technology Aluminum alloys have become one of the preferred materials for automotive lightweighting due to their high strength, good corrosion resistance, and recyclability, with 6XXX series aluminum alloys being the most widely used. As load-bearing structural components in automobiles, 6XXX series forgings need to possess both strength and toughness. However, during the production process, the microstructure of 6XXX series aluminum alloy forgings is quite sensitive to deformation temperature and strain rate. Improper process control can easily lead to recrystallization, resulting in uneven deformation microstructure and severely reducing the strength and toughness of the alloy. Domestic and foreign research institutions and enterprises have conducted some research on improving the strength and toughness of aluminum alloy forgings and have published some new research results.

[0002] Patent publication number CN117181973B discloses a This is a method for preparing free forgings of aluminum alloys. The method involves homogenizing the treated aluminum alloy... The aluminum alloy ingots were subjected to variable temperature forging, solution treatment, cryogenic treatment, cold compression treatment and aging treatment in sequence, and finally an aluminum alloy forging was obtained that improved the differences in the transverse, longitudinal and high-dimensional properties of high-strength aluminum alloy free forgings.

[0003] The patent with authorization publication number CN111945086B discloses a forging method to improve the anisotropy of 6XXX aluminum alloy forgings. The preparation method first performs high-temperature forging, then low-temperature forging, followed by solution treatment and subsequent cold deformation. By improving the recrystallization degree of 6XXX aluminum alloy forgings, the difference in strength and toughness between the longitudinal, transverse and high-axis directions of the forgings is reduced, thereby improving the strength and comprehensive mechanical properties of 6XXX free forgings.

[0004] The above methods can improve the uniformity of the alloy structure to a certain extent, thereby improving the strength and toughness of the alloy. However, variable temperature forging requires secondary heat preservation of the billet, which results in high industrial costs and is not suitable for large-scale forging production. Therefore, providing a high-strength and high-toughness 6XXX series aluminum alloy forging that can improve the uniformity of the microstructure and enhance the strength and toughness of 6XXX series alloys without temperature variation, and its preparation method, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength and high-toughness 6XXX series aluminum alloy forging and its preparation method. The preparation method of this invention is simple and yields aluminum alloys with high strength and toughness.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing high-strength and high-toughness 6XXX series aluminum alloy forgings includes the following steps: Step 1: Homogenize the aluminum alloy round billet and then cool it to room temperature; Step 2: Peel the aluminum alloy round billet from Step 1 to obtain the peeled aluminum alloy billet. Step 3: The aluminum alloy billet is subjected to isothermal variable speed hot forging, and then cooled to room temperature to obtain an aluminum alloy forging; Step 4: The aluminum alloy forging is subjected to solution treatment, cooled to room temperature, and aged in sequence to obtain the final product.

[0007] Preferably, the aluminum alloy round billet contains the following elemental composition by mass percentage: Mg: 0.6-1.2 wt.%, Si: 0.8-1.3 wt.%, Cu: 0.4-0.6 wt.%, Mn: 0.4-1.0 wt.%, Cr≤0.3 wt.%, Mo≤0.3 wt.%, Fe≤0.15 wt.%, Ti≤0.10 wt.%, other impurities ≤0.15 wt.%, and the balance is Al.

[0008] Preferably, the mass fractions of Mg and Si satisfy: Si = Mg + 0.2 wt.%; and the mass fractions of Mn, Cr and Mo satisfy: Mo + Cr ≤ Mn.

[0009] This invention first regulates the contents of Mg, Si, and Cu to ensure Si = Mg + 0.2 wt.%. The excess Si not only compensates for Si loss during casting but also significantly increases the supersaturation of solute atoms in the matrix, thereby greatly stimulating the nucleation driving force of the coherent strengthening phase β″ (Mg5Si6), causing it to precipitate in an extremely high-density, nanoscale morphology. Simultaneously, the added Cu atoms participate in the formation of the quaternary metastable strengthening phase Q′ (typical chemical formula Al3Cu2Mg9Si7). The β″ phase is completely coherent with the aluminum matrix, generating a strong lattice distortion strain field around it, while the Q′ phase is usually semi-coherent with the matrix, exhibiting superior thermal stability. During deformation, the presence of these two precipitated phases allows dislocations to pass through them via shearing and bypassing mechanisms, significantly increasing the resistance to dislocation movement, macroscopically manifested as a significant enhancement of the alloy's mechanical properties. Based on this, the microalloying composition of Mn, Cr, and Mo is also regulated. The mass of Mn, Cr, and Mo in the alloy satisfies the condition: Cr + Mo ≤ Mn. During solidification, due to the different distribution behaviors of Mn, Cr, and Mo, Mn segregates along grain boundaries, while Cr and Mo segregate within the grains. The synergistic addition of these three elements improves the precipitation density and uniformity of the Al(Mn, Cr, Mo)Si dispersed phase in the matrix during homogenization, thereby significantly reducing the proportion of non-precipitated regions of the dispersed phase. This effectively enhances the pinning force of the Al(Mn, Cr, Mo)Si dispersed phase on subgrain boundaries during hot forging and subsequent solution treatment, thus suppressing abnormal grain growth during subsequent hot forging and solution treatment. Through isothermal variable speed three-pronged forging process, combined with the grain boundary pinning effect of the dispersed phase, the recrystallized grain size was successfully controlled within 30-100 μm, and the recrystallization ratio was reduced to below 40%, thereby significantly improving the uniformity and stability of the deformed structure and synergistically enhancing the strength and toughness of the alloy.

[0010] Preferably, in step one, the homogenization treatment conditions are: temperature of 500-560℃, holding time of 5-10h, heating rate of 3-10℃ / min, and cooling rate of 10-20℃ / min.

[0011] Preferably, in step two, the aluminum alloy round billet from step one is peeled off using a hot peeling machine.

[0012] Preferably, the isothermal variable speed hot forging of the aluminum alloy billet specifically involves the free forging of the aluminum alloy billet using a three-stage forging and three-stage drawing process.

[0013] Preferably, in step three, the aluminum alloy billet is subjected to isothermal variable speed hot forging using a forging machine. The hot forging process is an upsetting and drawing process, which includes: firstly, heating the aluminum alloy billet to 450-530°C and performing two upsetting and drawing operations, with a forging speed of 45-70 mm / s and a single upsetting and drawing deformation of 55%-70%; then performing a third upsetting and drawing operation, with a forging speed of 10-30 mm / s and an upsetting and drawing deformation of 55%-70%, and the cooling rate is 50-150°C / s.

[0014] Preferably, in step four, the conditions for the solution treatment are: a temperature of 520–560°C, a holding time of 1–3 h, and a cooling rate of 50–150°C / s; the conditions for the aging treatment are: an aging temperature of 150–200°C, and a holding time of 5–10 h.

[0015] Preferably, the volume fraction of dispersed phase in the microstructure of the aluminum alloy round billet after the homogenization treatment exceeds 2%, and the average size of the dispersed phase is 50-200 nm.

[0016] Preferably, the recrystallization size in the microstructure of the aluminum alloy forging after the solution treatment is 30-100µm, the recrystallization ratio is ≤40%, and the average spacing between recrystallized grains is 100-300µm. The volume fraction of precipitates in the microstructure of the aluminum alloy forgings after the aging treatment exceeds 3%, and the average size of the precipitates is 10-60 nm.

[0017] High-strength and high-toughness 6XXX series aluminum alloy forgings prepared by the preparation method described above.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a high-strength and high-toughness 6XXX series aluminum alloy forging and its preparation method. The high-strength and high-toughness aluminum alloy forging prepared by this invention has added multiple elements such as Mg, Si, Cu, Mn, Cr, Mo, and Fe to its alloy composition, and further optimized the content of alloying elements and adjusted the process conditions during preparation to enable each element and the deformed structure to play a synergistic role, thereby improving the strength and toughness of the aluminum alloy. The synergistic effect of aging precipitates and an appropriate amount of recrystallized structure is achieved to achieve a synergistic improvement in strength and toughness. Among them, the precipitates (such as β″ and Q′ phases) effectively hinder dislocation movement through the cutting and bypassing mechanism, providing significant strength enhancement to the alloy. At the same time, the proportion of recrystallized structure is controlled below 40%, and its equiaxed morphology and low dislocation density characteristics promote uniform plastic deformation and delay necking formation, thereby effectively improving the elongation and toughness of the alloy. The synergistic effect of the two significantly enhances toughness while maintaining high strength, comprehensively improving the mechanical properties of the alloy, and is suitable for applications such as automotive structural parts. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings in this description are merely embodiments of the present invention.

[0020] Figure 1 This is a TEM image of the diffuse phase in Example 1; Figure 2 EBSD analysis of tissue after solution treatment in Example 1; Figure 3 This is a TEM image of the precipitated phase after aging treatment in Example 1; Figure 4 The stretch curve after aging treatment in Example 1 is shown. Detailed Implementation

[0021] Embodiments of the present invention are described below, examples of which are shown in the accompanying drawings. The embodiments described with reference to the drawings are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention. Example

[0022] A method for preparing a high-strength, high-toughness 6XXX series aluminum alloy includes the following steps: Step 1: According to the alloy composition of Mg 0.6%, Si 0.8%, Cu 0.4wt.%, Mn 0.4wt.%, Cr 0.1wt.%, Mo 0.1wt.%, Fe 0.05wt.%, Ti 0.03wt.%, other impurities ≤0.15wt.%, and the balance being the mass fraction of Al, the raw materials are batched, smelted, and cast into ingots to obtain aluminum alloy round billets. The aluminum alloy round billets are then homogenized at a temperature of 500℃ for 5 hours at a heating rate of 3℃ / min. Finally, the aluminum alloy round billets are cooled to room temperature at a cooling rate of 10℃ / min. Step 2: The aluminum alloy round billet from Step 1 is peeled off using a hot peeling machine to obtain the peeled aluminum alloy billet. Step 3: The aluminum alloy billet is subjected to isothermal variable speed hot forging. First, the aluminum alloy billet is heated to 450℃, and then free forging is carried out in a three-stage forging process. The forging speed of the first two forging and drawing processes is 45mm / s, and the deformation amount of each forging and drawing process is 55%. Then, the final forging and drawing process is carried out, and the forging speed is reduced to 10mm / s, with a deformation amount of 55% per forging and drawing process. After hot forging, the billet is rapidly cooled to room temperature at a cooling rate of 50℃ / s to obtain the aluminum alloy forging. Step 4: The aluminum alloy forgings are subjected to solution treatment and aging treatment. Specifically, the solution treatment temperature is 520℃ and the holding time is 1 hour. The aluminum alloy forgings after solution treatment are immediately cooled to room temperature at a cooling rate of 50℃ / s. The forgings after solution treatment are immediately subjected to aging treatment at a temperature of 150℃ and a holding time of 5 hours, finally obtaining high-strength and high-toughness 6XXX series aluminum alloy forgings.

[0023] Figure 1 This is a TEM image of the diffuse phase in Example 1. Figure 2 EBSD analysis of tissue after solution treatment in Example 1. Figure 3 This is a TEM image of the precipitated phase after aging treatment in Example 1. Figure 4 The stretch curve after aging treatment in Example 1 is shown. Example

[0024] A method for preparing a high-strength, high-toughness 6XXX series aluminum alloy includes the following steps: Step 1: According to the alloy composition of Mg 1.1%, Si 1.3%, Cu 0.6wt.%, Mn 1.0wt.%, Cr 0.3wt.%, Mo 0.3wt.%, Fe 0.05wt.%, Ti 0.03wt.%, other impurities ≤0.15wt.%, and the balance being the mass fraction of Al, the raw materials are batched, smelted, and cast into ingots to obtain aluminum alloy round billets. The aluminum alloy round billets are then homogenized at a temperature of 500℃ for 5 hours at a heating rate of 3℃ / min. Finally, the aluminum alloy round billets are cooled to room temperature at a cooling rate of 10℃ / min. Step 2: The aluminum alloy round billet from Step 1 is peeled off using a hot peeling machine to obtain the peeled aluminum alloy billet. Step 3: The aluminum alloy billet is subjected to isothermal variable speed hot forging. First, the aluminum alloy billet is heated to 450℃, and then free forging is carried out in a three-stage forging process. The forging speed of the first two forging and drawing processes is 45mm / s, and the deformation amount of each forging and drawing process is 55%. Then, the final forging and drawing process is carried out, and the forging speed is reduced to 10mm / s, with a deformation amount of 55% per forging and drawing process. After hot forging, the billet is rapidly cooled to room temperature at a cooling rate of 50℃ / s to obtain the aluminum alloy forging. Step 4: The aluminum alloy forgings are subjected to solution treatment and aging treatment. Specifically, the solution treatment temperature is 520℃ and the holding time is 1 hour. The aluminum alloy forgings after solution treatment are immediately cooled to room temperature at a cooling rate of 50℃ / s. The forgings after solution treatment are immediately subjected to aging treatment at a temperature of 150℃ and a holding time of 5 hours, finally obtaining high-strength and high-toughness 6XXX series aluminum alloy forgings. Example

[0025] A method for preparing a high-strength, high-toughness 6XXX series aluminum alloy includes the following steps: Step 1: The aluminum alloy round billet is prepared by batching, melting, and casting according to the alloy composition of Mg 0.8wt.%, Si 1.0%, Cu 0.5wt.%, Mn 0.7wt.%, Cr 0.2wt.%, Mo 0.15wt.%, Fe 0.05wt.%, Ti 0.03wt.%, other impurities ≤0.15wt.%, and the balance being the mass fraction of Al. The aluminum alloy round billet is then homogenized at a temperature of 530℃ for 7 hours at a heating rate of 6℃ / min. The aluminum alloy round billet is then cooled to room temperature at a cooling rate of 15℃ / min.

[0026] Step 2: The aluminum alloy round billet from Step 1 is peeled off using a hot peeling machine to obtain the peeled aluminum alloy billet.

[0027] Step 3: The aluminum alloy billet is subjected to isothermal variable speed hot forging. First, the aluminum alloy billet is heated to 490℃, and then free forging is carried out in a three-stage forging process. The forging speed of the first two forging and drawing stages is 55mm / s, and the deformation amount of each stage is 60%. Then, the final forging and drawing stage is carried out, and the forging speed is reduced to 20mm / s, with a deformation amount of 60% per stage. After hot forging, the billet is rapidly cooled to room temperature at a cooling rate of 100℃ / s to obtain the aluminum alloy forging. Step 4: The aluminum alloy forgings are subjected to solution treatment and aging treatment. Specifically, the solution treatment temperature is 540℃ and the holding time is 1.5h. The aluminum alloy forgings after solution treatment are immediately cooled to room temperature at a cooling rate of 100℃ / s. The forgings after solution treatment are immediately subjected to aging treatment at a temperature of 180℃ and a holding time of 7h, finally obtaining high-strength and high-toughness 6XXX series aluminum alloy forgings. Example

[0028] A high-strength and high-toughness 6XXX series aluminum alloy and its preparation method, comprising the following steps: Step 1: According to the alloy composition of Mg 0.8wt.%, Si 1.0%, Cu 0.5wt.%, Mn 0.7wt.%, Cr 0.2wt.%, Mo 0.15wt.%, Fe 0.05wt.%, Ti 0.03wt.%, other impurities ≤0.15wt.%, and the balance being the mass fraction of Al, the raw materials are batched, smelted, and cast into ingots to obtain aluminum alloy round billets. The aluminum alloy round billets are then homogenized at a temperature of 560℃ for 10 hours at a heating rate of 10℃ / min. The aluminum alloy round billets are then cooled to room temperature at a cooling rate of 20℃ / min. Step 2: The aluminum alloy round billet from Step 1 is peeled off using a hot peeling machine to obtain the peeled aluminum alloy billet. Step 3: The aluminum alloy billet is subjected to isothermal variable speed hot forging. First, the aluminum alloy billet is heated to 490℃, and then free forging is carried out in a three-stage forging process. The forging speed of the first two forging and drawing stages is 55mm / s, and the deformation amount of each stage is 60%. Then, the final forging and drawing stage is carried out, and the forging speed is reduced to 20mm / s, with a deformation amount of 60% per stage. After hot forging, the billet is rapidly cooled to room temperature at a cooling rate of 100℃ / s to obtain the aluminum alloy forging. Step 4: The aluminum alloy forgings are subjected to solution treatment and aging treatment. Specifically, the solution treatment temperature is 540℃ and the holding time is 1.5h. The aluminum alloy forgings after solution treatment are immediately cooled to room temperature at a cooling rate of 100℃ / s. The forgings after solution treatment are immediately subjected to aging treatment at a temperature of 180℃ and a holding time of 7h, finally obtaining high-strength and high-toughness 6XXX series aluminum alloy forgings. Example

[0029] A high-strength and high-toughness 6XXX series aluminum alloy and its preparation method, comprising the following steps: Step 1: According to the alloy composition of Mg 0.8wt.%, Si 1.0%, Cu 0.5wt.%, Mn 0.7wt.%, Cr 0.2wt.%, Mo 0.15wt.%, Fe 0.05wt.%, Ti 0.03wt.%, other impurities ≤0.15wt.%, and the balance being the mass fraction of Al, the raw materials are batched, smelted, and cast into ingots to obtain aluminum alloy round billets. The aluminum alloy round billets are then homogenized at a temperature of 530℃ for 7 hours at a heating rate of 6℃ / min. The aluminum alloy round billets are then cooled to room temperature at a cooling rate of 15℃ / min. Step 2: The aluminum alloy round billet from Step 1 is peeled off using a hot peeling machine to obtain the peeled aluminum alloy billet. Step 3: The aluminum alloy billet is subjected to isothermal variable speed hot forging. First, the aluminum alloy billet is heated to 530℃, and then free forging is carried out in a three-stage forging process. The forging speed of the first two forging and drawing processes is 70mm / s, and the deformation amount of each forging and drawing process is 70%. Then, the final forging and drawing process is carried out, and the forging speed is reduced to 30mm / s, with a deformation amount of 70% per forging and drawing process. After hot forging, the billet is rapidly cooled to room temperature at a cooling rate of 150℃ / s to obtain the aluminum alloy forging. Step 4: The aluminum alloy forgings are subjected to solution treatment and aging treatment. Specifically, the solution treatment temperature is 540℃ and the holding time is 1.5h. The aluminum alloy forgings after solution treatment are immediately cooled to room temperature at a cooling rate of 100℃ / s. The forgings after solution treatment are immediately subjected to aging treatment at a temperature of 180℃ and a holding time of 7h, finally obtaining high-strength and high-toughness 6XXX series aluminum alloy forgings. Example

[0030] A high-strength and high-toughness 6XXX series aluminum alloy and its preparation method, comprising the following steps: Step 1: According to the alloy composition of Mg 1.1%, Si 1.3%, Cu 0.6wt.%, Mn 1.0wt.%, Cr 0.3wt.%, Mo 0.3wt.%, Fe 0.05wt.%, Ti 0.03wt.%, other impurities ≤0.15wt.%, and the balance being the mass fraction of Al, the raw materials are batched, smelted, and cast into ingots to obtain aluminum alloy round billets. The aluminum alloy round billets are then homogenized at a temperature of 560℃ for 10 hours at a heating rate of 10℃ / min. Finally, the aluminum alloy round billets are cooled to room temperature at a cooling rate of 20℃ / min. Step 2: The aluminum alloy round billet is peeled off using a hot peeling machine to obtain the peeled aluminum alloy billet. Step 3: The aluminum alloy billet is subjected to isothermal variable speed hot forging. First, the aluminum alloy billet is heated to 530℃, and then free forging is carried out in a three-stage forging process. The forging speed of the first two forging and drawing processes is 70mm / s, and the deformation amount of each forging and drawing process is 70%. Then, the final forging and drawing process is carried out, and the forging speed is reduced to 30mm / s, with a deformation amount of 70% per forging and drawing process. After hot forging, the billet is rapidly cooled to room temperature at a cooling rate of 150℃ / s to obtain the aluminum alloy forging. Step 4: The aluminum alloy forgings are subjected to solution treatment and aging treatment. Specifically, the solution treatment temperature is 560℃ and the holding time is 3h. The aluminum alloy forgings after solution treatment are immediately cooled to room temperature at a cooling rate of 150℃ / s. The forgings after solution treatment are immediately subjected to aging treatment at a temperature of 200℃ and a holding time of 5h, finally obtaining high-strength and high-toughness 6XXX series aluminum alloy forgings. Example

[0031] A high-strength and high-toughness 6XXX series aluminum alloy and its preparation method, comprising the following steps: Step 1: According to the alloy composition of Mg 1.1%, Si 1.3%, Cu 0.6wt.%, Mn 1.0wt.%, Cr 0.3wt.%, Mo 0.3wt.%, Fe 0.05wt.%, Ti 0.03wt.%, other impurities ≤0.15wt.%, and the balance being the mass fraction of Al, the raw materials are batched, smelted, and cast into ingots to obtain aluminum alloy round billets. The aluminum alloy round billets are then homogenized at a temperature of 560℃ for 10 hours at a heating rate of 10℃ / min. Finally, the aluminum alloy round billets are cooled to room temperature at a cooling rate of 20℃ / min. Step 2: The aluminum alloy round billet is peeled off using a hot peeling machine to obtain the peeled aluminum alloy billet. Step 3: The aluminum alloy billet is subjected to isothermal variable speed hot forging. First, the aluminum alloy billet is heated to 450℃, and then free forging is carried out in a three-stage forging process. The forging speed of the first two forging and drawing processes is 45mm / s, and the deformation amount of each forging and drawing process is 55%. Then, the final forging and drawing process is carried out, and the forging speed is reduced to 10mm / s, with a deformation amount of 55% per forging and drawing process. After hot forging, the billet is rapidly cooled to room temperature at a cooling rate of 50℃ / s to obtain the aluminum alloy forging. Step 4: The aluminum alloy forgings are subjected to solution treatment and aging treatment. Specifically, the solution treatment temperature is 560℃ and the holding time is 3h. The aluminum alloy forgings after solution treatment are immediately cooled to room temperature at a cooling rate of 150℃ / s. The forgings after solution treatment are immediately subjected to aging treatment at a temperature of 200℃ and a holding time of 5h, finally obtaining high-strength and high-toughness 6XXX series aluminum alloy forgings.

[0032] The high-strength and high-toughness aluminum alloys in the embodiments of the present invention were characterized by microstructure and performance testing, and the results are shown in Table 1. The volume fraction of dispersed phases in different alloys was 2.5%–3.2%, and the average size was 103–143 nm. The recrystallization ratio in the microstructure of different alloys after solution treatment was 28%–40%, and the average recrystallization size was 30–76 µm. The volume fraction of precipitated phases after aging treatment in different alloys was 3.3%–4.1%, and the average size was 30–58 µm. The yield strength of different alloys was 400–418 MPa, the elongation was 416–432 MPa, and the elongation was 15.6–21.7%.

[0033] Table 1

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing high-strength and high-toughness 6XXX series aluminum alloy forgings, characterized in that, Includes the following steps: Step 1: Homogenize the aluminum alloy round billet and then cool it to room temperature; Step 2: Peel the aluminum alloy round billet from Step 1 to obtain the peeled aluminum alloy billet. Step 3: The aluminum alloy billet is subjected to isothermal variable speed hot forging, and then cooled to room temperature to obtain an aluminum alloy forging; Step 4: The aluminum alloy forging is subjected to solution treatment, cooled to room temperature, and aged in sequence to obtain the product.

2. The method for preparing a high-strength and high-toughness 6XXX series aluminum alloy forging according to claim 1, characterized in that, The aluminum alloy round billet contains the following elemental composition by mass percentage: Mg: 0.6-1.2 wt.%, Si: 0.8-1.3 wt.%, Cu: 0.4-0.6 wt.%, Mn: 0.4-1.0 wt.%, Cr≤0.3 wt.%, Mo≤0.3 wt.%, Fe≤0.15 wt.%, Ti≤0.10 wt.%, other impurities ≤0.15 wt.%, and the balance is Al.

3. The method for preparing a high-strength and high-toughness 6XXX series aluminum alloy forging according to claim 2, characterized in that, The mass fractions of Mg and Si satisfy: Si = Mg + 0.2 wt.%; the mass fractions of Mn, Cr and Mo satisfy: Mo + Cr ≤ Mn.

4. The method for preparing a high-strength and high-toughness 6XXX series aluminum alloy forging according to claim 1, characterized in that, In step one, the homogenization conditions are: temperature of 500-560℃, holding time of 5-10h, heating rate of 3-10℃ / min, and cooling rate of 10-20℃ / min.

5. The method for preparing a high-strength and high-toughness 6XXX series aluminum alloy forging according to claim 1, characterized in that, In step two, the aluminum alloy round billet from step one is peeled off using a hot peeling machine.

6. The method for preparing a high-strength and high-toughness 6XXX series aluminum alloy forging according to claim 1, characterized in that, In step three, the aluminum alloy billet is subjected to isothermal variable speed hot forging using a forging machine. The hot forging process is an upsetting and drawing process. First, the aluminum alloy billet is heated to 450-530°C and then upsetting and drawing twice. The forging speed of the two upsetting and drawing processes is 45-70 mm / s, and the deformation amount of a single upsetting and drawing process is 55%-70%. Then, a third upsetting and drawing process is performed. The forging speed of the third upsetting and drawing process is 10-30 mm / s, and the deformation amount of the third upsetting and drawing process is 55%-70%. The cooling rate is 50-150°C / s.

7. The method for preparing a high-strength and high-toughness 6XXX series aluminum alloy forging according to claim 1, characterized in that, In step four, the conditions for the solution treatment are: a temperature of 520–560°C, a holding time of 1–3 h, and a cooling rate of 50–150°C / s; the conditions for the aging treatment are: an aging temperature of 150–200°C and a holding time of 5–10 h.

8. The method for preparing a high-strength and high-toughness 6XXX series aluminum alloy forging according to claim 4, characterized in that, The dispersed phase volume fraction in the aluminum alloy round billet after the homogenization treatment exceeds 2%, and the average size of the dispersed phase is 50-200 nm.

9. The method for preparing a high-strength and high-toughness 6XXX series aluminum alloy forging according to claim 7, characterized in that, The recrystallization size in the microstructure of the aluminum alloy forging after the solution treatment is 30-100µm, the recrystallization ratio is ≤40%, and the average spacing between recrystallized grains is 100-300µm. The aluminum alloy forgings after the aging treatment have a precipitate volume fraction of ≥3% and an average precipitate size of 10–60 nm.

10. High-strength and high-toughness 6XXX series aluminum alloy forgings prepared by the preparation method according to any one of claims 1 to 9.

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