Thermomechanical treatment method for improving obdurability and shape of Al-Cu-Mg alloy plate

Abstract

The invention discloses a thermomechanical treatment method for improving the obdurability and the plate shape of an Al-Cu-Mg alloy plate. The thermomechanical treatment method comprises the following steps: (1) carrying out pre-stretching treatment on a deformed plate; (2) carrying out single-stage or graded solid solution heat treatment on the pre-stretched plate, wherein the final solid solution heat treatment temperature is T1; (3) cooling the plate subjected to solid solution treatment to a temperature T2 at an average cooling rate V1, and then cooling the plate from T2 to a room temperature at an average cooling rate V2; (4) the quenched plate is subjected to cold deformation treatment after being placed at the room temperature; and (5) the plate subjected to cold deformation treatment is subjected to pre-stretching treatment, and then natural aging is conducted under the room temperature condition. According to the method, the Al-Cu-Mg alloy plate is subjected to pre-stretching, solid solution heat preservation, graded controlled cooling quenching, room temperature standing, cold deformation, pre-stretching and natural aging treatment, and the Al-Cu-Mg alloy can obtain an ideal obdurability matching relation on the premise of controlling residual stress and the plate shape.

Description

Technical Field

[0001] The invention relates to a thermomechanical treatment method for strengthening and toughening an Al-Cu-Mg alloy, and in particular to a thermomechanical treatment method for improving the toughness and shape of an Al-Cu-Mg alloy plate, belonging to the technical field of thermomechanical treatment of metal materials. Background Art

[0002] Al-Cu-Mg series high-strength aluminum alloy is a typical aluminum alloy that is widely used at present. It has low density, high strength, good machining performance, high corrosion resistance, high damage tolerance, good stress corrosion resistance, good fatigue performance and other excellent comprehensive properties. It is widely used in aerospace, rail transportation, automobiles and ships, home building materials, food hygiene, packaging and printing and other fields. Especially in the aviation field, Al-Cu-Mg series alloys have the characteristics of high damage tolerance, making them important structural materials in the aviation field. After being machined in the form of plates, the products are widely used in high damage tolerance design parts such as aircraft skins, trims and beam webs.

[0003] In order to meet the increasingly stringent requirements of aviation aircraft for material performance, Al-Cu-Mg alloy manufacturers have carried out a lot of research work from the aspects of adjusting alloy composition, improving alloy metallurgical quality, improving alloy plastic deformation processing methods, optimizing alloy heat treatment process and micro-alloying. Patent CN 112626401B discloses a 2xxx series aluminum alloy and its preparation method. By adjusting the ratio of main and micro alloy elements and controlling the content of impurity elements, the alloy matrix obtains a relatively fine and dispersed strengthening structure, thereby improving the strength of the alloy to a certain extent. Patent CN114737144B discloses a 2324 aluminum alloy homogenization heat treatment method. By slowly heating the alloy ingot at the melting temperature of the low melting point eutectic phase, the effect of temperature on the dissolution of the eutectic phase is fully utilized. Under the premise of ensuring that the ingot is not over-burned, the dissolution of the low melting point eutectic phase is accelerated, and the time rate of the homogenization heat treatment of the aluminum alloy ingot is effectively saved. Patent CN 112974747B discloses a method for improving the metallurgical quality of large-sized 2000 series aluminum alloy ingots. Patent CN114672678B discloses a method for preparing large round ingots of Al-Cu-Mg aluminum alloy, which obtains a casting method of large-sized round ingots with ideal metallurgical quality by applying external field treatment to the aluminum liquid during casting and accurately controlling the parameters of the casting process. Patent CN 115323294B discloses a strong plastic deformation method of Al-Cu-Mg alloy, which improves the mechanical properties of alloy thin plates by strong plastic deformation rolling. Patent document CN105734469A discloses a method for improving the damage tolerance performance of Al-Cu-Mg alloy, which achieves the purpose of improving the damage tolerance of Al-Cu-Mg alloy plates by solid solution + water quenching + cold rolling deformation + artificial aging of alloy plates. The above patents focus on either optimizing the design of alloy composition, or improving the metallurgical quality of alloy ingots, or improving the mechanical properties of Al-Cu-Mg alloys by plastic deformation rolling.

[0004] For Al-Cu-Mg alloy plates, although the above method can improve the strength and damage tolerance of the alloy, it fails to take into account the high level of residual stress that is easily formed inside the plate due to the warping or wavy plate shape before solution treatment, single-stage quenching and subsequent cold deformation treatment, which in turn has an adverse effect on the product's performance improvement, yield rate and subsequent machinability. Therefore, how to ensure that Al-Cu-Mg alloy plates have ideal strength, toughness and regular plate shape, reduce the residual stress inside the product, and improve the processing yield rate of the plate is a difficult problem that needs to be solved in the development of new deformation heat treatment processes for Al-Cu-Mg alloy plates. Summary of the invention

[0005] The object of the present invention is to provide a deformation heat treatment method for improving the strength, toughness and plate shape of an Al-Cu-Mg alloy plate, which can enable the Al-Cu-Mg alloy plate to have ideal strength and toughness, as well as a regular plate shape and lower residual stress.

[0006] To achieve the above purpose, the present invention mainly adopts the following technical solutions: A thermomechanical treatment method for improving the strength, toughness and shape of an Al-Cu-Mg alloy plate mainly comprises the following steps: (1) Pre-stretching the deformed sheet material by 0.5% to 4%; (2) The pre-stretched plate is subjected to single-stage or graded solution heat treatment, the heating rate during the heat treatment process is 10℃ / min≤V0≤15℃ / min, and the final solution heat treatment temperature is 480℃≤T1≤510℃; after 2~4h of insulation treatment, the plate is immediately subjected to graded controlled cooling water quenching treatment, and is cooled from T1 temperature point to T2 at an average cooling rate V1, where 60℃ / s≤V1≤80℃ / s, 160℃≤T2≤200℃; then cooled from T2 temperature point to room temperature at an average cooling rate V2, where 3℃ / s≤V2≤12℃ / s, and the quenching transfer time of the alloy plate is ≤4s; (3) The quenched plate is placed at room temperature for 1h≤t1≤4h; (4) subjecting the parked plate to a cold deformation treatment with a deformation amount of 6% to 15%; (5) subjecting the cold-deformed plate to a pre-stretching deformation treatment with a pre-stretching amount of 1% to 5%; (6) The pre-stretched plate is subjected to natural aging treatment at room temperature for a period of 4 days ≤ t2 ≤ 10 days until the performance is stable.

[0007] Preferably, in step (1), the pre-stretching amount of the deformed sheet is 1% to 4%, more preferably 1% to 3%.

[0008] Preferably, in step (2), the deformed Al-Cu-Mg alloy is placed in an air circulation furnace and heated to the final solution heat treatment temperature for solution heat treatment, and the temperature error is ±1.5°C. The furnace heating heating rate is 10°C / min≤V0≤14°C / min, and more preferably 11°C / min≤V0≤13°C / min.

[0009] Preferably, in step (2), the final solution heat treatment temperature of the plate is 490°C≤T1≤510°C, preferably 490°C≤T1≤500°C, and more preferably 495°C≤T1≤500°C.

[0010] Preferably, in step (2), the solution heat treatment holding time of the plate is 3 to 4 hours.

[0011] Preferably, in step (2), 70℃ / s≤V1≤80℃ / s, 160℃≤T2≤190℃, and 3℃ / s≤V2≤11℃ / s; more preferably, 70℃ / s≤V1≤80℃ / s, 160℃≤T2≤180℃, and 3℃ / s≤V2≤9℃ / s. Further preferably, 75℃ / s≤V1≤80℃ / s, 160℃≤T2≤170℃, and 3℃ / s≤V2≤7℃ / s.

[0012] Preferably, in step (2), after the solid solution heat preservation treatment of the plate is completed, a graded controlled cooling water quenching treatment is immediately carried out, and the quenching transfer time is ≤3s, and the quenching method can be spray quenching. More preferably, the quenching transfer time is ≤2s.

[0013] Preferably, in step (3), the plate is placed at room temperature after the quenching treatment, and the placement time is 1h≤t1≤2h.

[0014] Preferably, in step (4), the cold deformation amount of the plate after being parked during cold deformation treatment is 9-12%, more preferably 10-12%, and the cold deformation method can be cold rolling.

[0015] Preferably, in step (5), the pre-stretching deformation of the plate is performed using a pre-stretching machine, and the pre-stretching deformation amount is 1% to 4%, more preferably 1.0 to 2.5%.

[0016] Preferably, in step (6), the natural aging time of the pre-stretched plate is 4 days ≤ t2 ≤ 8 days. More preferably, the natural aging time is 5 days ≤ t2 ≤ 7 days.

[0017] Compared with the prior art, the Al-Cu-Mg alloy plate strength, toughness and plate shape deformation heat treatment method of the present invention has the following advantages and beneficial effects: (1) By adding a pre-stretching process before the solution heat treatment, the optimal solution heat treatment system is designed, including the heating rate, solution temperature, controlled cooling quenching method and transfer time, which can improve the plate shape and help the low-melting-point eutectic phases in the alloy matrix, such as Al2CuMg and Al2Cu phases, to fully dissolve back into the matrix to form an ideal supersaturated solid solution, providing favorable conditions for the precipitation of strengthening phases during the aging process of the alloy. At the same time, by matching the appropriate cold deformation, pre-stretching deformation and natural aging parking time, the alloy can have room temperature strength that meets the requirements, better plate shape and lower residual stress without losing toughness.

[0018] (2) The method of the present invention is accurate, reliable, easy to operate, highly operable, and economical. It fully considers the characteristics of Al-Cu-Mg alloy plates, helps to improve the processing yield of Al-Cu-Mg alloy plates, and is conducive to large-scale industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of parameter process control in the deformation heat treatment method of the present invention.

[0020] Figure 2 This is a scanning electron microscope photograph of the microstructure of the alloy plate in Comparative Example 1.

[0021] Figure 3 This is a scanning electron microscope photograph of the microstructure of the alloy plate in Example 5. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments. It should be noted that the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of protection of the present invention.

[0023] Figure 1 The process flow diagram of the present invention is shown in FIG. During the deformation heat treatment process, the Al-Cu-Mg alloy sequentially undergoes the steps of pre-stretching of the deformed sheet, solution heat treatment, graded controlled cold water quenching, cold rolling deformation, pre-stretching deformation and natural aging parking. Figure 1 In the figure, V0 is the solution treatment heating rate, T1 is the solution treatment temperature, and after the solution treatment and insulation, the plate temperature drops from T1 to T2 at an average cooling rate of V1, and then drops from temperature point T2 to room temperature at an average cooling rate of V2.

[0024] Comparative Example 1 The chemical composition of the alloy is (by mass percentage, wt%): Cu: 4.5, Mg: 1.5, Mn: 0.5, Fe: 0.1, Ti: 0.1, Cr: 0.08, Zn: 0.1, Si: 0.08, impurity content (total) <0.15, and the rest is Al plate. The alloy ingot is subjected to homogenization annealing and hot rolling deformation to obtain a deformed alloy plate. During the solution treatment, the plate is heated to 480°C at a heating rate of 10°C / min and kept warm for 1h, and then a single-stage water quenching treatment is carried out, and the quenching transfer time is 5s, and then the plate is parked for natural aging at room temperature for 5 days.

[0025] Comparative Example 2 The chemical composition of the alloy is (by mass percentage, wt%): Cu: 4.0, Mg: 1.7, Mn: 0.6, Fe: 0.08, Ti: 0.05, Cr: 0.06, Zn: 0.15, Si: 0.05, impurity content (total) <0.15, and the rest is Al plate. The alloy ingot is subjected to homogenization annealing and hot rolling deformation to obtain a deformed alloy plate. During the solution treatment, the plate is heated to 490°C at a heating rate of 12°C / min and kept warm for 1h, and then subjected to a two-stage controlled cold water quenching treatment (V1=55°C / s, T2=210°C, V2=10°C / s), and the quenching transfer time is 7s. Subsequently, the quenched plate is quickly cold-rolled and deformed using a 400T controlled rolling and controlled cold precision rolling test machine, and the cold rolling deformation is 9%. Finally, the cold-rolled plate is parked for natural aging at room temperature for 4 days.

[0026] Comparative Example 3 The chemical composition of the alloy is (by mass percentage, wt%): Cu: 4.8, Mg: 1.3, Mn: 0.7, Fe: 0.12, Ti: 0.1, Cr: 0.07, Zn: 0.2, Si: 0.03, impurity content (total) <0.15, and the rest is Al plate. The alloy ingot is subjected to homogenization annealing and hot rolling deformation to obtain a deformed alloy plate. During the solution treatment, the plate is heated to 495°C at a heating rate of 11°C / min and kept warm for 2h, and then subjected to a two-stage controlled cooling water quenching treatment (V1=60°C / s, T2=190°C, V2=12°C / s), and the quenching transfer time is 3s. The plate is then parked at room temperature for 2h, and then the quenched plate is cold rolled using a 400T controlled rolling and controlled cooling precision rolling test machine, and the cold rolling deformation is 7%. Furthermore, the cold-rolled plate samples were pre-stretched and deformed using a tensile testing machine, with the pre-stretching amount controlled to be 1.5%. Finally, the pre-stretched plate samples were placed in a room temperature for natural aging for 5 days.

[0027] Comparative Example 4 The chemical composition of the alloy is (by mass percentage, wt%): Cu: 4.2, Mg: 1.4, Mn: 0.4, Fe: 0.05, Ti: 0.12, Cr: 0.09, Zn: 0.18, Si: 0.07, impurity content (total) <0.15, and the rest is Al plate. The alloy ingot is subjected to homogenization annealing and hot rolling deformation to obtain a deformed alloy plate. The deformed plate is first pre-stretched by 2% before solution treatment, and then the plate is heated to 495℃ at a heating rate of 15℃ / min and kept warm for 2h, and then subjected to double-stage controlled cooling water quenching treatment (V1=65℃ / s, T2=155℃, V2=10℃ / s), and the quenching transfer time is 3s. The plate is then parked at room temperature for 10h, and then the quenched plate is cold-rolled and deformed using a 400T controlled rolling and controlled cooling precision rolling test machine, and the cold rolling deformation is 14%. Furthermore, the cold-rolled sheet samples were pre-stretched and deformed using a tensile testing machine, with the pre-stretching amount controlled to be 0.5%. Finally, the pre-stretched sheet samples were placed in a room temperature for natural aging for 3 days.

[0028] Example 1 The chemical composition of the alloy is (by mass percentage, wt%): Cu: 4.0, Mg: 1.7, Mn: 0.6, Fe: 0.08, Ti: 0.05, Cr: 0.06, Zn: 0.15, Si: 0.05, impurity content (total) <0.15, and the rest is Al. The alloy ingot is subjected to homogenization annealing and hot rolling deformation to obtain a deformed alloy plate. The deformed plate is first pre-stretched by 1.8% before solution treatment, and then the plate is heated to 495℃ at a heating rate of 11℃ / min and kept warm for 3h, and then subjected to double-stage controlled cooling water quenching (V1=70℃ / s, T2=180℃, V2=5℃ / s), and the quenching transfer time is 3s. The plate is then parked at room temperature for 1.5h, and then the quenched plate is cold-rolled and deformed using a 400T controlled rolling and controlled cooling precision rolling test machine, and the cold rolling deformation is 9%. Furthermore, the cold-rolled sheet samples were pre-stretched and deformed using a tensile testing machine, with the pre-stretching amount controlled at 1.7%. Finally, the pre-stretched sheet samples were placed in a room temperature for natural aging for 4.5 days.

[0029] Example 2 The chemical composition of the alloy is (by mass percentage, wt%): Cu: 4.6, Mg: 1.5, Mn: 0.3, Fe: 0.1, Ti: 0.07, Cr: 0.1, Zn: 0.1, Si: 0.04, impurity content (total) <0.15, and the rest is Al plate. The alloy ingot is subjected to homogenization annealing and hot rolling deformation to obtain a deformed alloy plate. The deformed plate is first pre-stretched by 4% before solution treatment, and then the plate is heated to 495℃ at a heating rate of 15℃ / min and kept warm for 4h, and then subjected to double-stage controlled cooling water quenching (V1=70℃ / s, T2=175℃, V2=12℃ / s), and the quenching transfer time is 4s. The plate is then parked at room temperature for 3h, and then the quenched plate is cold-rolled and deformed using a 400T controlled rolling and controlled cooling precision rolling test machine, and the cold rolling deformation is 12%. Furthermore, the cold-rolled sheet samples were pre-stretched and deformed using a tensile testing machine, with the pre-stretching amount controlled at 2.3%. Finally, the pre-stretched sheet samples were placed in a room temperature for natural aging for 5 days.

[0030] Example 3 The chemical composition of the alloy is (by mass percentage, wt%): Cu: 4.3, Mg: 1.8, Mn: 0.9, Fe: 0.02, Ti: 0.1, Cr: 0.06, Zn: 0.15, Si: 0.06, impurity content (total) <0.15, and the rest is Al plate. The alloy ingot is homogenized annealed and hot rolled to obtain a deformed alloy plate. The deformed plate is first pre-stretched by 2.3% before solution treatment, and then the plate is heated to 490℃ at a heating rate of 13℃ / min and kept warm for 2h, and then further heated to 495℃ and kept warm for 2h. After the insulation is completed, the plate is subjected to a double-stage controlled cold water quenching treatment (V1=80℃ / s, T2=175℃, V2=6℃ / s), and the quenching transfer time is 3s. The plate was then placed at room temperature for 2 hours before being cold-rolled and deformed by 7% using a 400T controlled rolling and controlled cooling precision rolling test machine. Furthermore, the cold-rolled plate samples were pre-stretched and deformed by a tensile testing machine, with the pre-stretching amount controlled at 1.9%. Finally, the pre-stretched plate samples were placed at room temperature for natural aging for 4 days.

[0031] Example 4 The chemical composition of the alloy is (by mass percentage, wt%): Cu: 4.7, Mg: 1.7, Mn: 0.6, Fe: 0.08, Ti: 0.05, Cr: 0.06, Zn: 0.15, Si: 0.05, impurity content (total) <0.15, and the rest is Al plate. The alloy ingot is homogenized annealed and hot rolled to obtain a deformed alloy plate. The deformed plate is first pre-stretched by 3.9% before solution treatment, and then the plate is heated to 490℃ at a heating rate of 10℃ / min and kept warm for 2h, and then further heated to 495℃ and kept warm for 2h. After the insulation is completed, the plate is subjected to a double-stage controlled cold water quenching treatment (V1=65℃ / s, T2=165℃, V2=10℃ / s), and the quenching transfer time is 3s. The plate was then parked at room temperature for 1.5 hours and then cold-rolled and deformed by 12% using a 400T controlled rolling and controlled cooling precision rolling test machine. Furthermore, the cold-rolled plate samples were pre-stretched and deformed using a tensile testing machine, with the pre-stretching amount controlled at 2.8%. Finally, the pre-stretched plate samples were parked at room temperature for natural aging for 3.5 days.

[0032] Example 5 The chemical composition of the alloy is (by mass percentage, wt%): Cu: 4.1, Mg: 1.6, Mn: 0.7, Fe: 0.09, Ti: 0.1, Cr: 0.09, Zn: 0.09, Si: 0.05, impurity content (total) <0.15, and the rest is Al plate. The alloy ingot is subjected to homogenization annealing and hot rolling deformation to obtain a deformed alloy plate. The deformed plate is first pre-stretched by 1.5% before solution treatment, and then the plate is heated to 495℃ at a heating rate of 12℃ / min and kept warm for 3h, and then further heated to 500℃ and kept warm for 1h. After the insulation is completed, the plate is subjected to a double-stage controlled cooling water quenching treatment (V1=75℃ / s, T2=170℃, V2=7℃ / s), and the quenching transfer time is 2s. The plate was then parked at room temperature for 2 hours and then subjected to cold rolling deformation treatment on the quenched plate using a 400T controlled rolling and controlled cooling precision rolling test machine, with a cold rolling deformation of 10%. Furthermore, the cold-rolled plate sample was pre-stretched using a tensile testing machine, with the pre-stretching amount controlled to 1.4%. Finally, the pre-stretched plate sample was parked at room temperature for natural aging for 4 days.

[0033] Example 6 The chemical composition of the alloy is (by mass percentage, wt%): Cu: 3.8, Mg: 1.4, Mn: 0.6, Fe: 0.1, Ti: 0.05, Cr: 0.08, Zn: 0.1, Si: 0.05, impurity content (total) <0.15, and the rest is Al plate. The alloy ingot is homogenized annealed and hot rolled to obtain a deformed alloy plate. The deformed plate is first pre-stretched by 3.2% before solution treatment, and then the plate is heated to 495℃ at a heating rate of 12℃ / min and kept for 2h, and then further heated to 500℃ and kept for 2h. After the insulation, the plate is subjected to a double-stage controlled cooling water quenching treatment (V1=75℃ / s, T2=175℃, V2=8℃ / s), and the quenching transfer time is 4s. The plate was then parked at room temperature for 2 hours and then subjected to cold rolling deformation treatment on the quenched plate using a 400T controlled rolling and controlled cooling precision rolling test machine, with a cold rolling deformation of 9%. Furthermore, the cold-rolled plate sample was pre-stretched using a tensile testing machine, with the pre-stretching amount controlled to 2.5%. Finally, the pre-stretched plate sample was parked at room temperature for natural aging for 4 days.

[0034] Example 7 The chemical composition of the alloy is (by mass percentage, wt%): Cu: 4.4, Mg: 1.3, Mn: 0.4, Fe: 0.05, Ti: 0.1, Cr: 0.05, Zn: 0.25, Si: 0.05, impurity content (total) <0.15, and the rest is Al plate. The alloy ingot is subjected to homogenization annealing and hot rolling deformation to obtain a deformed alloy plate. The deformed plate is first pre-stretched by 2.8% before solution treatment, and then the plate is heated to 500℃ at a heating rate of 12℃ / min and kept warm for 2.5h. After the insulation is completed, the plate is subjected to a double-stage controlled cold water quenching treatment (V1=60℃ / s, T2=170℃, V2=5℃ / s), and the quenching transfer time is 3s. The plate was then parked at room temperature for 2.5 hours and then cold-rolled and deformed by 11% using a 400T controlled rolling and controlled cooling precision rolling test machine. Furthermore, the cold-rolled plate samples were pre-stretched and deformed by a tensile testing machine, and the pre-stretching amount was controlled to be 1.6%. Finally, the pre-stretched plate samples were parked at room temperature for natural aging for 4.5 days.

[0035] Figure 2 The following is a scanning electron microscope photo of the microstructure of the alloy plate in Comparative Example 1. Figure 3The microstructure of the alloy plate in Example 5 is shown in the scanning electron microscope photo. After the solution treatment, the plate sample of Comparative Example 1 still has a large amount of second phase in the matrix that has not been dissolved back into the matrix. The second phase in the plate sample of Example 5 is fully dissolved back. Table 1 shows the mechanical properties comparison table of the Al-Cu-Mg alloy obtained in the above comparative examples and examples.

[0036] Table 1 Mechanical properties parameters of Al-Cu-Mg alloys in different comparative examples and examples

[0037] It can be seen from the alloy mechanical properties comparison table shown in Table 1: (1) The tensile strength and yield strength of the plate samples of the comparative example are relatively low, while the plate strength of the sample samples of the embodiment is relatively high, and although the elongation decreases after undergoing different degrees of cold deformation, the fracture toughness remains at the same level. It can be seen that the alloy obtained by the method of the present invention has both high strength performance and ideal fracture toughness.

[0038] (2) Specifically, the plate in Comparative Example 1 was not pre-stretched before solution quenching and no effective controlled cooling water quenching was performed during the solution quenching process, resulting in warping of the plate shape and rapid quenching cooling, which resulted in high residual stress in the plate. The plate in Comparative Example 2 was also not pre-stretched before solution quenching, and the plate shape eventually showed warping and wavy forms, and the subsequent cold rolling process aggravated the abnormality of the plate shape, making it more irregular. However, since controlled cooling and graded quenching were used during the quenching process, the internal residual stress level of the plate obtained in this comparative example was controlled to a certain extent compared with Comparative Example 1. Compared with Comparative Example 2, the plate in Comparative Example 3 was less than that in Comparative Example 2 during solution quenching. No pre-stretching treatment was performed before, but a pre-stretching process was added after the room temperature parking and cold rolling deformation. However, due to the serious irregular deformation of the plate shape in the early stage, the pre-stretching in the later stage was difficult to achieve the improvement of the overall plate shape; the plate in comparative example 4 adopted the method of pre-stretching before solid solution quenching + graded controlled cold quenching, so that the plate shape of the quenched plate was effectively controlled, but due to the long room temperature parking time, the rolling deformation resistance increased, the difficulty of the cold rolling process was increased, and the warping and wave of the plate shape were also aggravated. In order to regularize the plate shape, a large pre-stretching amount was used in the later process, which worsened the stress state of the material at the edge of the plate, resulting in cracking at the edge of the plate, and increasing the risk of stretching fragments. In comparison, the alloy plate obtained by the method of the present invention has undergone a more reasonable pre-stretching, controlled cold water quenching and room temperature parking treatment, which has achieved regular plate shape, improved the residual stress distribution inside the plate, reduced the residual stress level inside the plate, and achieved effective control of the residual stress inside the quenched plate, greatly improving the yield rate and machinability of the plate.

[0039] The above description is only a more optimized specific implementation mode of the present invention, but it should be pointed out that the protection scope of the present invention is not limited thereto. Technical personnel in the relevant field should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the method of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A thermomechanical treatment method for improving the toughness and shape of an Al-Cu-Mg alloy sheet, characterized in that: The method mainly includes the following steps: (1) Pre-stretching the deformed sheet material by 0.5% to 4%; (2) The pre-stretched plate is subjected to single-stage or graded solution heat treatment, the heating rate during the heat treatment process is 10℃ / min≤V0≤15℃ / min, and the final solution heat treatment temperature is 480℃≤T1≤510℃; after 2~4h of insulation treatment, the plate is immediately subjected to graded controlled cooling water quenching treatment, and is cooled from T1 temperature point to T2 at an average cooling rate V1, where 60℃ / s≤V1≤80℃ / s, 160℃≤T2≤200℃; then cooled from T2 temperature point to room temperature at an average cooling rate V2, where 3℃ / s≤V2≤12℃ / s, and the quenching transfer time of the alloy plate is ≤4s; (3) The quenched plate is placed at room temperature for 1h≤t1≤4h; (4) subjecting the parked plate to a cold deformation treatment with a deformation amount of 6% to 15%; (5) subjecting the cold-deformed plate to a pre-stretching deformation treatment with a pre-stretching amount of 1% to 5%; (6) The pre-stretched plate is subjected to natural aging treatment at room temperature for a period of 4 days ≤ t2 ≤ 10 days until the performance is stable.

2. The thermomechanical treatment method according to claim 1, characterized in that: The heating rate during solution heat treatment is 10℃ / min≤V0≤14℃ / min; the final solution heat treatment temperature is 490℃≤T1≤510℃; the process parameters of graded controlled cold water quenching are: 70℃ / s≤V1≤80℃ / s, 160℃≤T2≤190℃, 3℃ / s≤V2≤11℃ / s; the room temperature parking time is 1h≤t1≤3h; the cold deformation of the plate after parking is 9~12%; the plate after cold deformation treatment is subjected to pre-stretching deformation treatment with a pre-stretching amount of 1%~4%; the natural aging time of the pre-stretched plate is 4 days≤t2≤8 days.

3. The thermomechanical treatment method according to claim 2, characterized in that: In the step (1), the pre-stretching amount of the deformed sheet is 1% to 3%.

4. The thermomechanical treatment method according to claim 2, characterized in that: In the step (2), the rate at which the plate is heated from room temperature to the final solution heat treatment temperature is 11°C / min≤V0≤13°C / min.

5. The thermomechanical treatment method according to claim 2, characterized in that: In the step (2), the final solution heat treatment temperature of the plate is 490°C ≤ T1 ≤ 500°C.

6. The thermomechanical treatment method according to claim 2, characterized in that: In the step (2), the solution heat treatment holding time of the plate is 3 to 4 hours.

7. The thermomechanical treatment method according to claim 2, characterized in that: In the step (2), 70°C / s≤V1≤80°C / s, 160°C≤T2≤180°C, and 3°C / s≤V2≤9°C / s.

8. The thermomechanical treatment method according to claim 2, characterized in that: In the step (2), the quenching transfer time of the plate is ≤3s.

9. The thermomechanical treatment method according to claim 2, characterized in that: In the step (3), the room temperature storage time of the quenched plate is 1h≤t1≤2h.

10. The thermomechanical treatment method according to claim 2, characterized in that: In the step (4), the parked plate is subjected to a cold deformation treatment with a deformation amount of 10-12%.

11. The thermomechanical treatment method according to claim 2, characterized in that: In the step (5), the plate after cold deformation is subjected to a pre-stretching deformation treatment with a pre-stretching amount of 1.0-2.5%.

12. The thermomechanical treatment method according to claim 2, characterized in that: In the step (6), the natural aging time of the pre-stretched plate is 5 days ≤ t2 ≤ 7 days.

13. The thermomechanical treatment method according to any one of claims 1 to 12, characterized in that: The components of the applicable Al-Cu-Mg alloy plate are as follows by mass percentage: Cu 0.7~6.5%, Mg 0.02~1.8%, Mn 0.10~1.2%, Fe0.07~1.4%, Ti 0.02~0.15%, Cr 0.05~0.10%, Zn 0.006~0.25%, Si 0.008~0.20%, the total impurity content is <0.15%, and the rest is Al.

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