Aluminum alloy plate strip and preparation method thereof

Abstract

The invention provides an aluminum alloy plate strip and a preparation method thereof. The aluminum alloy plate strip is prepared from the following elements in percentage by mass: 4.5 to 7.5 percent of Mg element, 0.08 to 0.18 percent of Fe element, 0.02 to 0.06 percent of Si element, 0.1 to 0.6 percent of Mn element, 0.01 to 0.06 percent of Ti element, less than or equal to 0.15 percent of inevitable impurities and the balance of Al element, the tensile strength of the aluminum alloy plate strip is larger than or equal to 330 MPa, the yield strength of the aluminum alloy plate strip is larger than or equal to 230 MPa, and the elongation of the aluminum alloy plate strip is larger than or equal to 12%. The aluminum alloy plate strip is not cracked after being bent by 90 degrees and 180 degrees. The aluminum alloy plate strip has excellent strength and forming performance, and can meet the technical requirements of mobile phones, tablet middle plates and the like on the strength and forming performance of aluminum alloy materials.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to an aluminum alloy plate and strip material and a preparation method thereof. Background Art

[0002] High-strength, high-alloy, ultra-thin electronic backplane is a new product with high added value, which can be used in mobile phones and tablet midplanes, etc., and has broad market application prospects. However, this product requires excellent mechanical properties of high strength and good plasticity, excellent plate shape and high surface quality, so it is difficult to produce.

[0003] 5 series aluminum alloy is widely used in the production of mobile phones and tablet middle plates due to its light weight, high strength and good corrosion resistance. Adding a high proportion of Mg element to high Mg aluminum alloy can significantly improve the strength of aluminum alloy plate and strip. The processing of the middle plate generally adopts the stamping process, which can make the 5 series aluminum alloy middle plate have good formability and dimensional accuracy, and also meet the material performance requirements of the internal structure of the mobile phone. However, the biggest problem at present is that the 5 series aluminum alloy with high Mg content has a large amount of precipitated phases due to the high Mg content, which leads to uneven precipitation during the heat treatment process, resulting in stamping cracking of aluminum alloy plate and strip, which seriously restricts the application and development of aluminum alloy in this field. Therefore, the technical development of aluminum alloy plate and strip in this application scenario mainly focuses on further improving its forming performance under the premise of ensuring the strength of aluminum alloy plate and strip, so as to meet the product requirements of crack-free plate and strip during the stamping process. Summary of the invention

[0004] The main purpose of the present invention is to provide an aluminum alloy plate and strip and a preparation method thereof, so as to solve the problem in the prior art that the aluminum alloy plate and strip is prone to cracking during the stamping process.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided an aluminum alloy plate and strip, which comprises the following elements, in mass percentage: 4.5-7.5% Mg element, 0.08-0.18% Fe element, 0.02-0.06% Si element, 0.1-0.6% Mn element and 0.01-0.06% Ti element, the total of inevitable impurities is ≤0.15%, and the balance is Al element; the tensile strength of the aluminum alloy plate and strip is ≥330MPa, the yield strength of the aluminum alloy plate and strip is ≥230MPa, and the elongation of the aluminum alloy plate and strip is ≥12%; the aluminum alloy plate and strip does not crack after being bent at 90° and 180°.

[0006] Furthermore, the aluminum alloy sheet and strip comprises the following elements, in percentage by mass: 5.0-6.0% of Mg, 0.12-0.15% of Fe, 0.03-0.05% of Si, 0.2-0.4% of Mn and 0.02-0.04% of Ti, the total of unavoidable impurities is ≤0.15%, and the balance is Al.

[0007] Furthermore, the mass ratio of the Mg element to the Mn element is 15 to 28:1; and / or the mass ratio of the Fe element to the Si element is 3 to 5:1.

[0008] Furthermore, the area ratio of the AlMg phase in the aluminum alloy sheet and strip is 9-12%, and / or the size of the AlMg phase in the aluminum alloy sheet and strip is 0.5-72 μm.

[0009] Furthermore, the thickness of the aluminum alloy plate and strip is 0.1 to 0.5 mm.

[0010] Furthermore, the tensile strength of the aluminum alloy sheet and strip is 340-370 MPa, the yield strength of the aluminum alloy sheet and strip is 260-280 MPa, and the elongation of the aluminum alloy sheet and strip is 12-14%.

[0011] According to one aspect of the present invention, there is provided a method for preparing the above-mentioned aluminum alloy sheet and strip, the preparation method comprising: subjecting the raw materials corresponding to the aluminum alloy to smelting and semi-continuous casting, homogenization heat treatment, hot rolling, cold rolling, intermediate annealing and finished product annealing in sequence to obtain the aluminum alloy sheet and strip; wherein, precipitation annealing is performed after the intermediate annealing and before the finished product annealing, the temperature of the precipitation annealing is lower than the temperature of the intermediate annealing, and the temperature of the precipitation annealing is 140-200°C.

[0012] Furthermore, the temperature of the precipitation annealing is 150-180° C., and / or the holding time of the precipitation annealing is 3-10 hours.

[0013] Furthermore, the temperature of the intermediate annealing is 280-350° C., and / or the holding time of the intermediate annealing is 2-4 hours.

[0014] Furthermore, the temperature of the finished product annealing is 120-150° C., and / or the holding time of the finished product annealing is 2-4 hours.

[0015] By applying the technical solution of the present invention, the present application can significantly improve the strength of the aluminum alloy sheet and strip while reducing the density of the aluminum alloy sheet and strip to achieve the weight reduction effect by adding the Mg element, so that the aluminum alloy sheet and strip can have high strength performance, that is, tensile strength ≥330MPa, yield strength ≥230MPa. In addition, by controlling the content of the Mg element within the above range, the AlMg phase can be formed, thereby improving the formability of the aluminum alloy sheet and strip, that is, the elongation ≥12% and no cracking at 90° and 180° bending. Adding the Mn element can refine the grains, thereby further improving the strength of the aluminum alloy sheet and strip. The aluminum alloy sheet and strip of the present invention has excellent strength and formability, and can meet the technical requirements of mobile phones, tablet mid-plates, etc. for the strength and formability of aluminum alloy materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0017] Figure 1 The metallographic corrosion diagram of the aluminum alloy plate and strip in Example 1 of the present application is shown;

[0018] Figure 2 The metallographic corrosion diagram of the aluminum alloy plate and strip in Comparative Example 1 of the present application is shown;

[0019] Figure 3 The metallographic corrosion diagram of the aluminum alloy sheet and strip in Comparative Example 2 of the present application is shown. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] As analyzed in the background technology of this application, there is a problem in the prior art that aluminum alloy plates and strips are prone to cracking during the stamping process. In order to solve the above problem, this application provides an aluminum alloy plate and strip and a preparation method thereof.

[0022] In a typical embodiment of the present application, an aluminum alloy sheet and strip is provided, which includes the following elements, in mass percentage: 4.5-7.5% Mg element, 0.08-0.18% Fe element, 0.02-0.06% Si element, 0.1-0.6% Mn element, 0.01-0.06% Ti element, the total of unavoidable impurities ≤0.15% and the balance being Al element; the tensile strength of the aluminum alloy sheet and strip is ≥330MPa, the yield strength of the aluminum alloy sheet and strip is ≥230MPa, and the elongation of the aluminum alloy sheet and strip is ≥12%; the aluminum alloy sheet and strip does not crack after being bent at 90° and 180°.

[0023] The present application can significantly improve the strength of the aluminum alloy sheet and strip while reducing the density of the aluminum alloy sheet and strip to achieve the weight reduction effect by adding the Mg element, so that the aluminum alloy sheet and strip can have high-strength performance, that is, tensile strength ≥330MPa, and yield strength ≥230MPa. In addition, by controlling the content of the Mg element within the above range, the AlMg phase can be formed, thereby improving the formability of the aluminum alloy sheet and strip, that is, the elongation ≥12% and no cracking at 90° and 180° bending. Adding the Mn element can refine the grains, thereby further improving the strength of the aluminum alloy sheet and strip. The aluminum alloy sheet and strip of the present invention has excellent strength and formability, and can meet the technical requirements of mobile phones, tablet mid-plates, etc. for the strength and formability of aluminum alloy materials.

[0024] In order to further improve the strength and formability of aluminum alloy plates and strips, in one embodiment of the present application, in order to further improve the synergistic effect between the elements, the above-mentioned aluminum alloy plates and strips preferably include the following elements, in terms of mass percentage: 5.0-6.0% Mg element, 0.12-0.15% Fe element, 0.03-0.05% Si element, 0.2-0.4% Mn element, 0.02-0.04% Ti element, the total of unavoidable impurities ≤0.15% and the balance being Al element.

[0025] In one embodiment of the present application, the mass ratio of the Mg element to the Mn element is 15 to 28:1; and / or the mass ratio of the Fe element to the Si element is 3 to 5:1.

[0026] It is preferred to control the mass ratio of Mg element to Mn element within the above range, which helps to improve the synergistic effect of Mg element and Mn element, thereby helping to improve the yield strength and tensile strength of the aluminum alloy sheet and strip, while having good crack resistance. It is preferred to control the mass ratio of Fe element to Si element within the above range, which helps to control the amount and size of AlFeSi phase, thereby helping to improve the formability of the aluminum alloy sheet and strip.

[0027] In one embodiment of the present application, the area ratio of the AlMg phase in the aluminum alloy plate and strip is 9-12%, and / or the size of the AlMg phase in the aluminum alloy plate and strip is 0.5-72 μm.

[0028] It is preferred to control the area ratio of the AlMg phase in the aluminum alloy sheet and strip within the above range, which helps to further improve the strength and formability of the aluminum alloy sheet and strip, thereby achieving the mechanical properties of the aluminum alloy sheet and strip within the above range and no cracking when bent at 90° and 180°, and thus better application in mobile phones, tablet mid-plates, etc.

[0029] In one embodiment of the present application, the thickness of the aluminum alloy plate strip is 0.1-0.5 mm.

[0030] It is preferred to control the thickness of the aluminum alloy plate and strip within the above range, which helps to achieve high strength while realizing the lightness and thinness of the aluminum alloy plate and strip, so as to be better applied to mobile phones, tablet mid-plates, etc.

[0031] In order to better meet the requirements of mobile phones, tablet mid-plates, etc. for the strength and formability of aluminum alloy materials, in one embodiment of the present application, the tensile strength of the aluminum alloy plate and strip is 340-370 MPa, the yield strength of the aluminum alloy plate and strip is 260-280 MPa, and the elongation of the aluminum alloy plate and strip is 12-14%.

[0032] In another typical embodiment of the present application, a method for preparing the above-mentioned aluminum alloy sheet and strip is provided, and the preparation method comprises: sequentially subjecting the raw materials corresponding to the aluminum alloy to smelting and semi-continuous casting, homogenization heat treatment, hot rolling, cold rolling, intermediate annealing and finished product annealing to obtain the aluminum alloy sheet and strip; wherein, precipitation annealing is performed after the intermediate annealing and before the finished product annealing, and the temperature of the precipitation annealing is lower than the temperature of the intermediate annealing, and the temperature of the precipitation annealing is 140 to 200°C.

[0033] The present application can promote the uniform and sufficient precipitation of the AlMg phase by regulating the cooling process after the intermediate annealing, that is, performing precipitation annealing, controlling the temperature of the precipitation annealing to be lower than the temperature of the intermediate annealing, and controlling the temperature of the precipitation annealing to be within the above range, so that the aluminum alloy sheet and strip have excellent forming properties, that is, the elongation is ≥12%, and there is no cracking when bending at 90° and 180°. Melting the raw materials corresponding to the aluminum alloy can make the Mg element fully dissolved in the matrix, thereby improving the strength of the aluminum alloy sheet and strip. Through homogenization heat treatment, the distribution of the Mg element can be further regulated to obtain a more uniform structure. The finished product annealing process can further improve the forming properties of the aluminum alloy sheet and strip, thereby meeting the requirements of the strength and forming properties of aluminum alloy materials for mobile phones, tablet mid-plates, etc.

[0034] In one embodiment of the present application, the temperature of precipitation annealing is 150-180°C, and / or the holding time of precipitation annealing is 3-10h; the temperature of intermediate annealing is 280-350°C, and / or the holding time of intermediate annealing is 2-4h.

[0035] It is preferred to control the temperature and holding time of precipitation annealing and intermediate annealing within the above range, which helps to form more evenly distributed AlMg phases, thereby further improving the formability of the aluminum alloy sheet and strip, and thus preventing the aluminum alloy sheet and strip from cracking when bent at 90° and 180°.

[0036] In one embodiment of the present application, the temperature of the finished product annealing is 120-150° C., and / or the holding time of the finished product annealing is 2-4 hours.

[0037] It is preferred to control the annealing temperature and holding time of the finished product within the above range, which helps to further homogenize the structure, thereby helping to further regulate the strength and formability of the aluminum alloy sheet and strip so that it can be better used in mobile phones, tablet mid-plates, etc.

[0038] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.

[0039] Example 1

[0040] In terms of mass percentage, the aluminum alloy raw material includes the following elements: 5.9% Mg, 0.14% Fe, 0.04% Si, 0.3% Mn, 0.03% Ti, and the balance is Al. The above aluminum alloy raw materials are sequentially smelted and semi-continuously cast, homogenized heat treated, hot rolled and cold rolled. After cold rolling to a thickness of 0.7 mm, intermediate annealing is performed at a temperature of 330°C and a holding time of 3 hours. During the cooling process after the intermediate annealing, a precipitation annealing at 190°C is performed with a holding time of 3 hours, followed by continued cold rolling to a thickness of 0.5 mm. Finally, a finished product annealing at 150°C is performed with a holding time of 3 hours to obtain an aluminum alloy sheet and strip with a thickness of 0.5 mm.

[0041] Example 2

[0042] In terms of mass percentage, the aluminum alloy raw material includes the following elements: 7.5% Mg, 0.18% Fe, 0.06% Si, 0.6% Mn, 0.06% Ti, and the balance is Al. The above aluminum alloy raw materials are sequentially smelted and semi-continuously cast, homogenized heat treated, hot rolled and cold rolled. After cold rolling to a thickness of 0.6 mm, intermediate annealing is performed at a temperature of 305°C and a holding time of 3 hours. During the cooling process after the intermediate annealing, a precipitation annealing at 175°C is performed for a holding time of 3 hours, followed by cold rolling to a thickness of 0.4 mm. Finally, a finished product annealing at 130°C is performed for a holding time of 3 hours to obtain an aluminum alloy sheet and strip with a thickness of 0.4 mm.

[0043] Example 3

[0044] In terms of mass percentage, the aluminum alloy raw material includes the following elements: 4.5% Mg, 0.08% Fe, 0.02% Si, 0.1% Mn, 0.01% Ti, and the balance is Al. The above aluminum alloy raw materials are sequentially smelted and semi-continuously cast, homogenized heat treated, hot rolled and cold rolled. After cold rolling to a thickness of 0.3 mm, intermediate annealing is performed at a temperature of 350°C and a holding time of 4 hours. During the cooling process after the intermediate annealing, a precipitation annealing at 180°C is performed for a holding time of 5 hours, followed by cold rolling to a thickness of 0.1 mm. Finally, a finished product annealing at 120°C is performed for a holding time of 2 hours to obtain an aluminum alloy sheet and strip with a thickness of 0.1 mm.

[0045] Example 4

[0046] The difference from Example 1 is that, in terms of mass percentage, the aluminum alloy raw material includes the following elements: 7.5% of Mg, 0.13% of Fe, 0.04% of Si, 0.3% of Mn, 0.03% of Ti, and the balance is Al. The balance is Al, and an aluminum alloy sheet and strip is finally obtained.

[0047] Example 5

[0048] The difference from Example 1 is that the temperature of precipitation annealing is 180° C., the holding time of precipitation annealing is 3 h, and finally an aluminum alloy sheet and strip is obtained.

[0049] Example 6

[0050] The difference from Example 1 is that the precipitation annealing temperature is 160° C., the precipitation annealing holding time is 3 h, and finally an aluminum alloy sheet and strip is obtained.

[0051] Example 7

[0052] The difference from Example 1 is that the intermediate annealing temperature is 280° C., the intermediate annealing holding time is 4 hours, and finally an aluminum alloy sheet and strip is obtained.

[0053] Example 8

[0054] The difference from Example 1 is that the intermediate annealing temperature is 350° C., the intermediate annealing holding time is 2 h, and finally an aluminum alloy sheet and strip is obtained.

[0055] Example 9

[0056] The difference from Example 1 is that the intermediate annealing temperature is 250° C., the intermediate annealing holding time is 1 h, and finally an aluminum alloy sheet and strip is obtained.

[0057] Example 10

[0058] The difference from Example 1 is that the temperature of the finished product annealing is 120° C., the holding time of the finished product annealing is 4 hours, and finally an aluminum alloy sheet and strip is obtained.

[0059] Embodiment 11

[0060] The difference from Example 1 is that the temperature of the finished product annealing is 100° C., the holding time of the finished product annealing is 1 hour, and finally an aluminum alloy sheet and strip is obtained.

[0061] Example 12

[0062] The difference from Example 1 is that the total mass of Mg element and Mn element is 6.2%, the mass ratio of Mg element to Mn element is 15:1, and finally an aluminum alloy sheet and strip is obtained.

[0063] Embodiment 13

[0064] The difference from Example 1 is that the total mass of Mg element and Mn element is 6.2%, the mass ratio of Mg element to Mn element is 28:1, and finally an aluminum alloy sheet and strip is obtained.

[0065] Embodiment 14

[0066] The difference from Example 1 is that the total mass of Fe element and Si element is 0.18%, the mass ratio of Fe element to Si element is 3:1, and finally an aluminum alloy sheet and strip is obtained.

[0067] Embodiment 15

[0068] The difference from Example 1 is that the total mass of Fe element and Si element is 0.18%, the mass ratio of Fe element to Si element is 5:1, and finally an aluminum alloy sheet and strip is obtained.

[0069] Comparative Example 1

[0070] The difference from Example 1 is that, during the cooling process after the intermediate annealing, a precipitation annealing at 240° C. is performed to finally obtain an aluminum alloy sheet and strip.

[0071] Comparative Example 2

[0072] The difference from Example 1 is that, during the cooling process after the intermediate annealing, a precipitation annealing at 220° C. is performed to finally obtain an aluminum alloy sheet and strip.

[0073] Comparative Example 3

[0074] The difference from Example 1 is that, in terms of mass percentage, the aluminum alloy raw material includes the following elements: 3% Mg element, 0.13% Fe element, 0.04% Si element, 0.3% Mn element, 0.03% Ti element, and the balance is Al element. The balance is Al element. Finally, an aluminum alloy sheet and strip is obtained.

[0075] Comparative Example 4

[0076] The difference from Example 1 is that, in terms of mass percentage, the aluminum alloy raw material includes the following elements: 8.5% of Mg, 0.13% of Fe, 0.04% of Si, 0.3% of Mn, 0.03% of Ti, and the balance is Al. Finally, an aluminum alloy sheet and strip is obtained.

[0077] Comparative Example 5

[0078] The difference from Example 1 is that the total mass of Mg element and Mn element is 6.2%, the mass ratio of Mg element to Mn element is 5:1, and finally an aluminum alloy sheet and strip is obtained.

[0079] Comparative Example 6

[0080] The difference from Example 1 is that the total mass of Fe element and Si element is 0.18%, the mass ratio of Fe element to Si element is 1:5, and finally an aluminum alloy sheet and strip is obtained.

[0081] Test Method

[0082] Metallographic test: After grinding and polishing, the sample was immersed in a 30% phosphoric acid solution for corrosion for 4 minutes, then observed and photographed with a metallographic microscope, and then measured with IPP (Image-Pro-Plus) software to obtain the area ratio of the AlMg phase.

[0083] Tensile strength, yield strength and elongation test: Tested in accordance with GB / T228.1-2021 "Metallic Materials-Tensile Tests Part 1: Room Temperature Test Method".

[0084] 90° and 180° bend test: The test was conducted according to ASTM B820-18 Standard Test Method for Bend Test for Determining the Formability of Copper and Copper Alloy Strip.

[0085] The aluminum alloy sheets and strips of the above embodiments and comparative examples were subjected to organizational characterization and performance testing, and the test results are shown in Table 1.

[0086] Table 1

[0087]

[0088]

[0089] in, Figure 1 is the metallographic corrosion diagram of the aluminum alloy strip in Example 1. Figure 1 It can be seen that there are a large number of AlMg phases in the aluminum alloy sheet and strip, which are small in size and evenly distributed.

[0090] Figure 2 This is the metallographic corrosion diagram of the aluminum alloy sheet and strip in Example 1. Figure 2 It can be seen that there are a large number of AlMg phases in the aluminum alloy sheet and strip, but the distribution is uneven, with more precipitation in the upper and lower surface layers and less precipitation in the core layer, forming an obvious bright band.

[0091] Figure 3 This is the metallographic corrosion diagram of the aluminum alloy sheet and strip in Example 2. Figure 3 It can be seen that there is a large amount of AlMg phase in the aluminum alloy sheet and strip, but the distribution is uneven, forming a bright band.

[0092] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0093] The present application can significantly improve the strength of the aluminum alloy sheet and strip while reducing the density of the aluminum alloy sheet and strip to achieve the weight reduction effect by adding the Mg element, so that the aluminum alloy sheet and strip can have high-strength performance, that is, tensile strength ≥330MPa, and yield strength ≥230MPa. In addition, by controlling the content of the Mg element within the above range, the AlMg phase can be formed, thereby improving the formability of the aluminum alloy sheet and strip, that is, the elongation ≥12% and no cracking at 90° and 180° bending. Adding the Mn element can refine the grains, thereby further improving the strength of the aluminum alloy sheet and strip. The aluminum alloy sheet and strip of the present invention has excellent strength and formability, and can meet the technical requirements of mobile phones, tablet mid-plates, etc. for the strength and formability of aluminum alloy materials.

[0094] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An aluminum alloy plate and strip, characterized in that: The aluminum alloy sheet and strip comprises the following elements in percentage by mass: 4.5-7.5% Mg, 0.08-0.18% Fe, 0.02-0.06% Si, 0.1-0.6% Mn, 0.01-0.06% Ti, the total of unavoidable impurities ≤ 0.15%, the balance being Al; The tensile strength of the aluminum alloy sheet and strip is ≥330MPa, the yield strength of the aluminum alloy sheet and strip is ≥230MPa, and the elongation of the aluminum alloy sheet and strip is ≥12%; the aluminum alloy sheet and strip does not crack after being bent at 90° and 180°.

2. The aluminum alloy sheet and strip according to claim 1, characterized in that: The aluminum alloy sheet and strip comprises the following elements in percentage by mass: 5.0-6.0% of the Mg element, 0.12-0.15% of the Fe element, 0.03-0.05% of the Si element, 0.2-0.4% of the Mn element, 0.02-0.04% of the Ti element, the total of inevitable impurities ≤0.15%, and the balance being Al element.

3. The aluminum alloy sheet and strip according to claim 1 or 2, characterized in that: The mass ratio of the Mg element to the Mn element is 15 to 28:1; and / or the mass ratio of the Fe element to the Si element is 3 to 5:

1.

4. The aluminum alloy sheet and strip according to any one of claims 1 to 3, characterized in that: The area ratio of the AlMg phase in the aluminum alloy plate and strip is 9-12%, and / or the size of the AlMg phase in the aluminum alloy plate and strip is 0.5-72 μm.

5. The aluminum alloy sheet and strip according to any one of claims 1 to 4, characterized in that: The thickness of the aluminum alloy plate and strip is 0.1-0.5 mm.

6. The aluminum alloy sheet and strip according to any one of claims 1 to 5, characterized in that: The tensile strength of the aluminum alloy plate and strip is 340-370 MPa, the yield strength of the aluminum alloy plate and strip is 260-280 MPa, and the elongation of the aluminum alloy plate and strip is 12-14%.

7. A method for preparing the aluminum alloy sheet or strip according to any one of claims 1 to 6, characterized in that: The preparation method comprises: sequentially performing smelting and semi-continuous casting, homogenization heat treatment, hot rolling, cold rolling, intermediate annealing and finished product annealing on raw materials corresponding to the aluminum alloy to obtain the aluminum alloy plate and strip; Wherein, precipitation annealing is performed after the intermediate annealing and before the final product annealing. The temperature of the precipitation annealing is lower than the temperature of the intermediate annealing, and the temperature of the precipitation annealing is 140-200°C.

8. The preparation method according to claim 7, characterized in that: The precipitation annealing temperature is 150-180° C., and / or the precipitation annealing holding time is 3-10 hours.

9. The preparation method according to claim 7 or 8, characterized in that: The temperature of the intermediate annealing is 280-350° C., and / or the holding time of the intermediate annealing is 2-4 hours.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The temperature of the finished product annealing is 120-150° C., and / or the holding time of the finished product annealing is 2-4 hours.

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