A method for preparing an aluminum alloy plate by a gradient cryogenic extrusion and rolling composite forming process

Abstract

The present application belongs to the field of aluminum alloy forging, and relates to a method for preparing an aluminum alloy plate through a gradient cryogenic extrusion-rolling combined forming process. The method comprises the following steps: step 1, carrying out three-stage coordinated pretreatment on a blank; step 2, carrying out gradient cryogenic plastic forming on the blank after the three-stage coordinated pretreatment to obtain a rolled piece, wherein the gradient cryogenic plastic forming comprises gradient cryogenic extrusion preforming and cryogenic multi-pass rolling; and step 3, carrying out three-stage directional cryogenic aging treatment on the rolled piece to obtain an aluminum alloy plate.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy forging and relates to a method for preparing aluminum alloy sheets using a gradient cryogenic extrusion composite forming process. Background Technology

[0002] In traditional 2000 series aluminum alloy sheet manufacturing processes, its high strength is often accompanied by problems such as poor formability and significant anisotropy. Especially in high-end applications such as aerospace, higher requirements are placed on the uniformity of the sheet texture, interfacial bonding strength, and comprehensive mechanical properties. In existing technologies, although conventional hot-rolling-cold-rolling processes can achieve a certain degree of performance control, they are prone to grain coarsening and paint brush line defects, and the redundancy of the process leads to low efficiency.

[0003] While existing cryogenic treatment technologies can refine grains (e.g., cryogenic asynchronous rolling can optimize the ultrafine grain structure of aluminum alloys), their gradient coupling mechanism with the rolling process is not yet perfect, resulting in the incomplete release of the cryogenic strengthening effect. Therefore, there is an urgent need for a composite forming process that integrates gradient cryogenic strengthening and dynamic texture control to overcome the current technological bottlenecks. Summary of the Invention

[0004] Purpose of the invention: To provide a method for preparing aluminum alloy sheets using a gradient cryogenic extrusion composite forming process, which improves the strength of the sheet while reducing forming energy consumption, thereby achieving efficient and energy-saving preparation of high-strength aluminum alloy sheets.

[0005] The technical solution of this invention is:

[0006] A method for preparing aluminum alloy sheets using a gradient cryogenic extrusion composite forming process includes:

[0007] Step 1: Perform three-stage synergistic pretreatment on the billet;

[0008] Step 2: The billet after the three-stage co-processing pretreatment is subjected to gradient cryogenic plastic forming to obtain the rolled part. The gradient cryogenic plastic forming includes gradient cryogenic extrusion preforming and cryogenic multi-pass rolling.

[0009] Step 3: Perform three-stage directional cryogenic aging treatment on the rolled part to obtain aluminum alloy sheet.

[0010] Furthermore, in step 1, the three-stage synergistic pretreatment is as follows: homogenization treatment → solution treatment → cryogenic phase change treatment.

[0011] Furthermore, the homogenization treatment was: 490℃×18 h + water quenching.

[0012] Furthermore, the solution treatment was performed at 470℃ for 2 hours followed by water quenching.

[0013] Furthermore, the cryogenic pretreatment is as follows: -196℃×2 h + gradient rewarming to -50℃, with the gradient being -196℃→-150℃→-100℃→-50℃.

[0014] Furthermore, gradient cryogenic extrusion preforming includes:

[0015] a) Pre-cool the aluminum alloy billet and extrusion die to -196℃ and hold for 30~60 minutes;

[0016] b) During the extrusion process, the billet temperature gradient is controlled by liquid nitrogen injection from -196℃ at the inlet to -150℃ at the outlet. The extrusion speed is 1~3 mm / s and the extrusion ratio is 20:1~35:1 to obtain a preformed sheet with a thickness of 2~15 mm.

[0017] Furthermore, the flow divider of the extrusion die adopts an asymmetric gradient design, with the inlet diameter being 15% to 30% larger than the outlet diameter.

[0018] Furthermore, the temperature gradient of the inner wall of the extrusion die cavity is -196℃ at the inlet to -150℃ at the outlet, and the inner wall is coated with a CrAlN coating, and the friction coefficient of the extrusion die is ≤0.08.

[0019] Furthermore, the gradient cryogenic rolling of preformed plates includes:

[0020] a) Transfer the preformed sheet to the rolling mill, pre-cool the rolls to -150°C, and maintain the sheet surface temperature at -120°C for the first pass and -80°C for the last pass using a segmented temperature control device.

[0021] b) Perform multi-pass rolling, with a single-pass deformation of 5% to 30% and a total deformation of 70% to 90%.

[0022] Furthermore, step 3 specifically includes:

[0023] a) Incubate at -50℃ to -30℃ for 2 to 4 hours to suppress dislocation recovery;

[0024] b) Incubate at 80℃~100℃ for 8~24 h to induce GP zone formation;

[0025] c) Keep at 120℃~160℃ for 4~8 h to promote the precipitation of η' / η phase.

[0026] The beneficial effects of this application are as follows:

[0027] The method of this invention first employs a three-stage synergistic pretreatment technology (homogenization treatment → solution treatment → cryogenic phase transformation treatment), which eliminates internal segregation of the billet and releases residual stress through the synergistic effect of element diffusion homogenization and cryogenic-induced phase transformation. Subsequently, gradient cryogenic plastic forming is implemented using temperature-zone controlled forming technology (gradient cryogenic extrusion preforming from -196℃ to -120℃ → cryogenic multi-pass rolling at -80℃), which suppresses dynamic recovery while improving dislocation multiplication efficiency. Finally, a three-stage directional cryogenic aging process (-50℃ / 8h → -80℃ / 16h → -120℃ / 24h) is used to establish a directional growth mechanism in the GP zone and regulate the nanoprecipitation behavior of the η' / η strengthening phase. Compared to the traditional hot-rolling-cold-rolling process, this technology suppresses dislocation annihilation and increases work hardening rate through a cryogenic environment, thereby improving the strength of the sheet while reducing forming energy consumption, achieving efficient and energy-saving preparation of high-strength aluminum alloy sheets. Attached Figure Description

[0028] Figure 1 Process flow diagram of gradient cryogenic extrusion composite molding technology. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0030] In the description of this invention, it should be understood that the terms "center", "axial", "vertical", "upper", "lower", "upper end", "bottom end", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0031] This invention discloses a method for preparing high-performance aluminum alloy sheets using a gradient cryogenic extrusion-rolling composite forming process, belonging to the field of aluminum alloy material forming technology. First, a three-stage synergistic pretreatment technique is employed to achieve the synergistic effect of element diffusion homogenization and cryogenic-induced phase transformation, eliminating internal segregation in the billet and releasing residual stress. Subsequently, gradient cryogenic plastic forming is implemented, employing temperature-zone controlled forming technology (-196℃ to -120℃ gradient cryogenic extrusion preforming → -80℃ cryogenic multi-pass rolling), which suppresses dynamic recovery while improving dislocation multiplication efficiency. Finally, a three-stage directional cryogenic aging process (-50℃ / 8h → -80℃ / 16h → -120℃ / 24h) is used to establish a directional growth mechanism in the GP zone and regulate the nano-precipitation behavior of the η' / η strengthening phase. Compared to the traditional hot-rolling-cold-rolling process, this technology suppresses dislocation annihilation and increases work hardening rate through a cryogenic environment, thereby improving sheet strength while reducing forming energy consumption, achieving efficient and energy-saving preparation of high-strength aluminum alloy sheets.

[0032] The final product is a high-performance aluminum alloy sheet with grain refinement to below 150nm, tensile strength ≥550MPa, and elongation ≥12%. Compared with traditional processes, the strength is increased by 20%-40%, energy consumption is reduced, and it is particularly suitable for forming 2000 series aluminum alloy sheets.

[0033] like Figure 1 This invention provides a method for preparing aluminum alloy sheets using a gradient cryogenic extrusion composite forming process, for the preparation of high-performance aluminum alloy sheets, comprising:

[0034] Step 1: Perform three-stage synergistic pretreatment on the billet: homogenization treatment → solution treatment → cryogenic phase transformation treatment;

[0035] (1) Homogenization treatment: 490℃×18 h+water quenching;

[0036] (2) Solution treatment: 470℃×2 h + water quenching;

[0037] (3) Cryogenic pretreatment: -196℃×2 h + gradient reheat to -50℃ (gradient is -196℃→-150℃→-100℃→-50℃).

[0038] Step 2: The billet after the three-stage co-processing pretreatment is subjected to gradient cryogenic plastic forming to obtain the rolled part. The gradient cryogenic plastic forming includes gradient cryogenic extrusion preforming and cryogenic multi-pass rolling.

[0039] Gradient cryogenic extrusion preforming includes:

[0040] a) Pre-cool the aluminum alloy billet and extrusion die to -196℃ and hold for 30~60 minutes;

[0041] b) During the extrusion process, the billet temperature gradient is controlled by liquid nitrogen injection to be -196℃ (inlet) → -150℃ (outlet), the extrusion speed is 1~3 mm / s, and the extrusion ratio is 20:1~35:1 to obtain a preformed sheet with a thickness of 2~15 mm.

[0042] The flow channel of the cryogenic extrusion die adopts an asymmetric gradient design, with the inlet diameter being 15%~30% larger than the outlet diameter, and the temperature gradient of the inner wall of the die cavity being -196℃ (inlet) → -150℃ (outlet), and the inner wall is coated with a CrAlN coating (friction coefficient ≤0.08).

[0043] Preformed plate gradient cryogenic rolling includes:

[0044] a) The preformed sheet is transferred to the rolling mill, the rolls are pre-cooled to -150°C, and the surface temperature of the sheet is maintained at -120°C (first pass) → -80°C (last pass) by a segmented temperature control device.

[0045] b) Perform multi-pass rolling, with a single-pass deformation of 5% to 30% and a total deformation of 70% to 90%.

[0046] Step 3: Perform three-stage directional cryogenic aging treatment on the rolled part to obtain aluminum alloy sheet.

[0047] The rolled sheet undergoes a three-stage directional cryogenic aging process within the temperature range of -50℃ to 150℃, including the following steps:

[0048] a) Incubate at -50℃ to -30℃ for 2 to 4 hours to suppress dislocation recovery;

[0049] b) Incubate at 80℃~100℃ for 8~24 h to induce GP zone formation;

[0050] c) Keep at 120℃~160℃ for 4~8 h to promote the precipitation of η' / η phase.

[0051] The following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0052] Example 1

[0053] This embodiment provides a method for preparing high-performance aluminum alloy sheets using a gradient cryogenic extrusion composite forming process, including three-stage synergistic pretreatment of the billet, gradient cryogenic extrusion preforming, gradient cryogenic rolling of the preformed sheet, and three-stage directional cryogenic aging. Using commercially available 2024 aluminum alloy as raw material, the specific operating steps and process parameters are as follows:

[0054] 1. Three-stage synergistic pretreatment of billets, including the following steps:

[0055] (1) Homogenization treatment: 490℃×18 h+water quenching;

[0056] (2) Solution treatment: 470℃×2 h + water quenching;

[0057] (3) Cryogenic pretreatment: -196℃×2 h + gradient reheat to -50℃ (gradient is -196℃→-150℃→-100℃→-50℃).

[0058] 2. Gradient cryogenic extrusion preforming, including the following steps:

[0059] (1) Pre-cool the aluminum alloy billet and extrusion die to -196℃ and hold for 30 minutes;

[0060] (2) During the extrusion process, the billet temperature gradient is controlled by liquid nitrogen injection to be -196℃ (inlet) → -150℃ (outlet), the extrusion speed is 3 mm / s, the extrusion ratio is 20:1, and a preformed plate with a thickness of 6 mm is obtained.

[0061] 3. Preformed plate gradient cryogenic rolling:

[0062] (1) Transfer the preformed sheet to the rolling mill, pre-cool the rolls to -150°C, and maintain the surface temperature of the sheet at -120°C (first pass) → -80°C (last pass) through a segmented temperature control device.

[0063] (2) Perform multi-pass rolling, with a single pass deformation of 10% and a total deformation of 80%.

[0064] 4. Three-stage directional cryogenic aging: The rolled sheet undergoes three-stage directional cryogenic aging in the range of -50℃ to 150℃, including the following steps:

[0065] (1) Incubate at -50℃ for 2 h to suppress dislocation recovery;

[0066] (2) Incubate at 80℃ for 12 h to induce GP zone formation;

[0067] (3) Keep warm at 120℃ for 4 h to promote the precipitation of η' / η phase.

[0068] 5. The flow divider of the cryogenic extrusion die adopts an asymmetric gradient design, with the inlet end diameter being 20% ​​larger than the outlet end, and the temperature gradient of the inner wall of the die cavity being -196℃ (inlet) → -150℃ (outlet), and the inner wall is coated with a CrAlN coating (friction coefficient ≤0.08).

[0069] 6. The grain size of the rolled aluminum alloy sheet is ≤150 nm, the tensile strength is ≥550 MPa, the elongation is ≥12%, and the thickness direction hardness fluctuation is ≤2%.

[0070] 7. Applicable to 2000 series aluminum alloys.

[0071] Example 2

[0072] This embodiment provides a method for preparing high-performance aluminum alloy sheets using a gradient cryogenic extrusion composite forming process, including three-stage synergistic pretreatment of the billet, gradient cryogenic extrusion preforming, gradient cryogenic rolling of the preformed sheet, and three-stage directional cryogenic aging. Using commercially available 2024 aluminum alloy as raw material, the specific operating steps and process parameters are as follows:

[0073] 1. Three-stage synergistic pretreatment of billets, including the following steps:

[0074] (1) Homogenization treatment: 490℃×18 h+water quenching;

[0075] (2) Solution treatment: 470℃×2 h + water quenching;

[0076] (3) Cryogenic pretreatment: -196℃×2 h + gradient reheat to -50℃ (gradient is -196℃→-150℃→-100℃→-50℃).

[0077] 2. Gradient cryogenic extrusion preforming, including the following steps:

[0078] (1) Pre-cool the aluminum alloy billet and extrusion die to -196℃ and hold for 30 minutes;

[0079] (2) During the extrusion process, the billet temperature gradient is controlled by liquid nitrogen injection to be -196℃ (inlet) → -150℃ (outlet), the extrusion speed is 3 mm / s, the extrusion ratio is 30:1, and a preformed sheet with a thickness of 4 mm is obtained.

[0080] 3. Preformed plate gradient cryogenic rolling:

[0081] (1) Transfer the preformed sheet to the rolling mill, pre-cool the rolls to -150°C, and maintain the surface temperature of the sheet at -120°C (first pass) → -80°C (last pass) through a segmented temperature control device.

[0082] (2) Perform multi-pass rolling, with a single-pass deformation of 8% and a total deformation of 90%.

[0083] 4. Three-stage directional cryogenic aging: The rolled sheet undergoes three-stage directional cryogenic aging in the range of -50℃ to 150℃, including the following steps:

[0084] (1) Incubation at -30℃ for 2 h to suppress dislocation recovery;

[0085] (2) Incubate at 100℃ for 12 h to induce GP zone formation;

[0086] (3) Keep warm at 160℃ for 4 h to promote the precipitation of η' / η phase.

[0087] 5. The flow divider of the cryogenic extrusion die adopts an asymmetric gradient design, with the inlet end diameter being 20% ​​larger than the outlet end, and the temperature gradient of the inner wall of the die cavity being -196℃ (inlet) → -150℃ (outlet), and the inner wall is coated with a CrAlN coating (friction coefficient ≤0.08).

[0088] 6. The grain size of the rolled aluminum alloy sheet is ≤150 nm, the tensile strength is ≥550 MPa, the elongation is ≥12%, and the thickness direction hardness fluctuation is ≤2%.

[0089] 7. Applicable to 2000 series aluminum alloys.

[0090] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing aluminum alloy sheets using a gradient cryogenic extrusion composite forming process, characterized in that, include: Step 1: Perform three-stage synergistic pretreatment on the billet; Step 2: The billet after the three-stage co-processing pretreatment is subjected to gradient cryogenic plastic forming to obtain the rolled part. The gradient cryogenic plastic forming includes gradient cryogenic extrusion preforming and cryogenic multi-pass rolling. Step 3: Perform three-stage directional cryogenic aging treatment on the rolled part to obtain aluminum alloy sheet.

2. The method according to claim 1, characterized in that, In step 1, the three-stage synergistic pretreatment is as follows: homogenization treatment → solution treatment → cryogenic phase change treatment.

3. The method according to claim 2, characterized in that, The homogenization process was: 490℃×18 h + water quenching.

4. The method according to claim 2, characterized in that, Solution treatment: 470℃×2 h + water quenching.

5. The method according to claim 2, characterized in that, The cryogenic pretreatment is as follows: -196℃×2 h + gradient reheating to -50℃, with the gradient being -196℃→-150℃→-100℃→-50℃.

6. The method according to claim 1, characterized in that, Gradient cryogenic extrusion preforming includes: a) Pre-cool the aluminum alloy billet and extrusion die to -196℃ and hold for 30~60 minutes; b) During the extrusion process, the billet temperature gradient is controlled by liquid nitrogen injection from -196℃ at the inlet to -150℃ at the outlet. The extrusion speed is 1~3 mm / s and the extrusion ratio is 20:1~35:1 to obtain a preformed sheet with a thickness of 2~15 mm.

7. The method according to claim 6, characterized in that, The flow divider of the extrusion die adopts an asymmetric gradient design, with the inlet diameter being 15% to 30% larger than the outlet diameter.

8. The method according to claim 6, characterized in that, The temperature gradient of the inner wall of the extrusion die cavity is -196℃ at the inlet and -150℃ at the outlet, and the inner wall is coated with CrAlN. The friction coefficient of the extrusion die is ≤0.

08.

9. The method according to claim 1, characterized in that, Preformed plate gradient cryogenic rolling includes: a) Transfer the preformed sheet to the rolling mill, pre-cool the rolls to -150°C, and maintain the sheet surface temperature at -120°C for the first pass and -80°C for the last pass using a segmented temperature control device. b) Perform multi-pass rolling, with a single-pass deformation of 5% to 30% and a total deformation of 70% to 90%.

10. The method according to claim 1, characterized in that, Step 3 specifically includes: a) Incubate at -50℃ to -30℃ for 2 to 4 hours to suppress dislocation recovery; b) Incubate at 80℃~100℃ for 8~24 h to induce GP zone formation; c) Keep at 120℃~160℃ for 4~8 h to promote the precipitation of η' / η phase.

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