High-strength high-bending-performance t4p-state 6xxx series aluminum alloy plate and preparation method therefor

Abstract

The present disclosure relates to a T4P-state 6xxx series aluminum alloy plate and a preparation method therefor. The contents of chemical elements in the T4P-state 6xxx series aluminum alloy plate are: in percentage by mass, 0.5-1.0% of Mg, 0.60-1.2% of Si, 0.05-0.2% of Cu, 0.05-0.2% of Mn, Fe ≤ 0.4%, and the balance being Al and other inevitable impurities, wherein the content of a single inevitable impurity is less than or equal to 0.05%; and the contents of Mg and Si meet the following relational expressions: 0.7 ≤ Mg / Si ≤ 1.2 and 1.2% ≤ Mg + Si ≤ 1.8%. The T4P-state 6xxx series aluminum alloy plate of the present disclosure has both high strength and high bending (forming) performance. A T8x-state 6xxx series aluminum alloy plate obtained after simulated paint baking treatment can achieve the performance of a conventional T6-state 6xxx series aluminum alloy and can thus replace a conventional T6-state 6xxx series aluminum alloy plate for use in automobile parts and components having relatively high strength requirements, such as automobile structural members, thereby satisfying the automobile lightweight demand.

Description

A high-strength, high-bending performance T4P state 6xxx series aluminum alloy plate and its preparation method Technical Field

[0001] The present disclosure relates to an aluminum alloy plate and a preparation method thereof, and in particular to a T4P state 6xxx series aluminum alloy plate with high strength and high bending performance and a preparation method thereof. Background Art

[0002] With the continuous increase in automobile production and ownership, and the increasingly prominent problems of energy shortage and environmental pollution, under the constraints of the "dual carbon" goals of carbon peak and carbon neutrality, automobile lightweighting has become an important means for OEMs to reduce carbon emissions.

[0003] 6xxx series aluminum alloys are one of the important materials for lightweight automobiles because of their excellent specific strength, formability, corrosion resistance and bake hardening properties. As an aluminum alloy that can be strengthened by heat treatment, 6xxx series aluminum alloy sheets for automobile covering parts are generally supplied in T4P state after solution hardening, quenching, surface treatment and pre-aging treatment on a continuous annealing line to meet the high formability requirements of covering parts. T4P state aluminum sheets will undergo natural aging during natural storage, accompanied by increased yield strength and decreased formability, leading to problems such as increased rebound, drawing and flanging cracking when automobile factories are stamping parts. Therefore, most 6xxx series aluminum sheets are also pre-aged after solution hardening and quenching treatment on a continuous annealing line to improve the natural aging stability during storage and transportation. The yield strength of T4P state aluminum alloy sheets is usually required to be above 150MPa. When the strength is too high, it is usually accompanied by a deterioration of formability. Due to the short time for OEMs to apply paint, conventional 6xxx series aluminum alloys are usually in an under-aged state after being pre-stretched by 2%, heated to 185°C and kept warm for 20 minutes to simulate paint treatment. The yield strength is generally 200-250MPa.

[0004] With the vigorous development of new energy vehicles, automotive structural parts represented by power battery packs have traditionally been made of 6xxx series aluminum alloy sheets, which are extruded in a state with low solid solution strength and then subjected to artificial peak aging treatment to meet the strength and stiffness requirements of the battery pack assembly. The commonly used grades of 6xxx series aluminum alloy sheets mainly include 6063, 6005, 6061, 6082, etc. Multiple aluminum alloy sheet parts are welded together by CMT, stir friction welding, and MIG / TIG welding. Considering the low production efficiency of extruded sheets, the large number of parts, and the high connection cost, various automobile manufacturers have proposed the use of aluminum alloy sheets by cold stamping instead of sheet materials. Therefore, in order to meet the strength, stiffness, and forming performance requirements of automotive structural parts and safety parts such as power battery packs, higher requirements are placed on the performance of aluminum alloy sheets.

[0005] Chinese patent application CN1974814A discloses an "Al-Mg-Si-Cu alloy for automobiles and its processing technology." The Al-Mg-Si-Cu alloy has the following composition (by mass percentage): Mg: 0.4-2wt%, Si: 0.5-1.5wt%, Cu: 0.01-0.5wt%, Fe: 0.05-0.15wt%, Mn: 0.01-0.1wt%, Cr: 0-0.15wt%, Zn: 0-0.30wt%, and a Si-to-Mg ratio of 1.6-2.2:1. The processing steps of this Al-Mg-Si-Cu alloy include: homogenizing and annealing the ingot obtained by melting and casting at 450-600°C for 10-20 hours, then holding it at 400-550°C for 1-2 hours before hot rolling; after hot rolling, the plate is held at 280-560°C for 1-2 hours, followed by cold rolling; after cold rolling, it is held at 530-580°C for 1-2 hours for solution treatment. However, the yield strength and tensile strength of this aluminum alloy after the paint treatment are low, which does not meet the strength requirements of automotive structural parts. Moreover, the bending performance is not considered, which cannot be demonstrated in parts with relatively high bending performance requirements, such as battery pack structural parts.

[0006] Chinese patent application CN101935785A discloses a "High-Formability Aluminum Alloy for Automotive Body Panels." By adjusting the content and ratio of the main elements Si, Mg, and Cu, a 6xxx series aluminum alloy for automotive body panels with excellent formability is achieved. While this aluminum alloy exhibits high elongation and work hardening rate, its yield strength in the T4P state is less than 130 MPa, which does not meet the strength requirements of structural components such as automotive battery packs.

[0007] It can be seen that the improvement solutions for 6xxx series aluminum alloys in the prior art still have some shortcomings.

[0008] Summary of the Invention

[0009] In view of the above-mentioned defects and deficiencies in the art, the purpose of the present disclosure is to provide a T4P state 6xxx series aluminum alloy sheet with high strength and high bending performance and a preparation method thereof. The present disclosure optimizes the component system of the 6xxx series aluminum alloy and regulates the content and ratio of the main alloying elements Mg and Si to achieve 0.7≤Mg / Si≤1.2 and 1.2%≤Mg+Si≤1.8%. This allows the 6xxx series aluminum alloy cold-rolled sheet to undergo recrystallization before the fine β" and β' precipitates dissolve back during solution treatment. The pinning effect of the β" and β' precipitates relative to dislocations and grain boundaries is utilized to refine the recrystallized grain size, while increasing the cubic texture density in the recrystallized texture and avoiding the precipitation of precipitates at grain boundaries, thereby improving the strength and bending performance of the alloy.

[0010] On the one hand, the present disclosure provides a T4P state 6xxx series aluminum alloy plate. In addition to containing Al and inevitable impurities, the T4P state 6xxx series aluminum alloy plate further contains the following chemical components, calculated by mass percentage: Mg: 0.5-1.0%, Si: 0.60-1.2%, Cu: 0.05-0.2%, Mn: 0.05-0.2%, Fe≤0.4%; the content of a single inevitable impurity is ≤0.05%; the contents of Mg and Si satisfy the following relationship: 0.7≤Mg / Si≤1.2, 1.2%≤Mg+Si≤1.8%.

[0011] In a preferred embodiment, the T4P state 6xxx series aluminum alloy plate of the present disclosure comprises the following chemical components, calculated in percentage by mass: Mg: 0.5-1.0%, Si: 0.60-1.2%, Cu: 0.05-0.2%, Mn: 0.05-0.2%, Fe≤0.4%, and the balance being Al and unavoidable impurities.

[0012] In a preferred embodiment, the thickness of the T4P state 6xxx series aluminum alloy plate is 0.5 to 4 mm.

[0013] In addition, the present inventors have found through extensive research that specific α-Al grain orientation, grain size, and distribution of precipitated phases can further improve the tensile and bending properties of T4P state 6xxx series aluminum alloy sheets.

[0014] Therefore, in a preferred embodiment, the microstructure of the T4P tempered 6xxx aluminum alloy plate comprises fine equiaxed α-Al grains with a dominant cubic texture and precipitates uniformly distributed within the crystals. In a preferred embodiment, the precipitates include GB regions, β" phases, and Q' phases. In a preferred embodiment, the average grain size of the T4P tempered 6xxx aluminum alloy plate is 15-30 μm. In a preferred embodiment, the density of the cube texture of the T4P tempered 6xxx aluminum alloy plate is 10.0-15.0. In a preferred embodiment, the volume fraction of the cube texture of the T4P tempered 6xxx aluminum alloy plate is ≥15%.

[0015] The T4P state 6xxx series aluminum alloy plate disclosed herein has a yield strength of 155 to 200 MPa, a tensile strength of 240 to 300 MPa, and an elongation of ≥20%.

[0016] When the thickness of the T4P state 6xxx series aluminum alloy plate disclosed in the present invention is 0.5~1mm, the 90-degree bending radius of the plate is ≤0.3mm; when the thickness of the T4P state 6xxx series aluminum alloy plate disclosed in the present invention is 1~4mm, the 90-degree bending radius of the plate is ≤0.3t, where t is the plate thickness in mm.

[0017] On the other hand, the present disclosure provides a method for preparing T4P state 6xxx series aluminum alloy plate, comprising the following steps: 1) homogenization treatment; 2) hot rolling and coiling; 3) cold rolling; 4) solution heat treatment; 5) rapid quenching; 6) pre-aging treatment.

[0018] In a preferred embodiment, in step 1) of the method of the present disclosure, the homogenization treatment temperature is 535-575° C., and the treatment time is 4-20 h.

[0019] In a preferred embodiment, in step 2) of the method of the present disclosure, the rolling temperature is 520-575°C, and the coiling temperature is 280-360°C.

[0020] In a preferred embodiment, in step 2) of the method of the present disclosure, the total deformation amount of hot rolling is ≥90%.

[0021] In a preferred embodiment, in step 3) of the method of the present disclosure, the total cold rolling deformation is 50 to 90%.

[0022] In a preferred embodiment, in step 4) of the method of the present invention, a two-stage solution heat treatment is adopted: first, the cold-rolled sheet obtained in step 3) is heated to 380-430°C at a heating rate of 11-25°C / s and kept warm for 3-15s; then, it is heated to 540-580°C at a heating rate of 15-25°C / s and kept warm for 1-20s.

[0023] In a preferred embodiment, in step 5) of the method of the present disclosure, the plate after solution heat treatment is subjected to quenching treatment at a cooling rate of 80 to 120° C. / s for 1 to 10 seconds.

[0024] In a preferred embodiment, in step 5) of the method of the present disclosure, the plate after solution heat treatment is cooled to below 40° C. at a cooling rate of 80-120° C. / s.

[0025] In a preferred embodiment, in step 6) of the method of the present disclosure, the coiling temperature of the pre-aging treatment is 120-200° C., and the cooling rate is 0.04-0.1° C. / min.

[0026] This disclosure further optimizes the full-process production process of 6xxx aluminum alloys based on the optimized composition system of these alloys. By employing specific soaking, hot rolling, coiling, and cold rolling process conditions, this disclosure achieves a cold-rolled sheet with dispersed submicron-level β metastable precipitations and a deformed microstructure. Then, by combining specific two-stage solution heat treatment, quenching, and pre-aging treatment process parameters, the precipitation, dissolution behavior, and recrystallization process of precipitates such as the Mg2Si metastable phase are coupled and regulated, thereby promoting the precipitate phase to inhibit recrystallization nucleation and growth, thereby achieving the effect of refining the grains and increasing the cubic texture density in the recrystallization texture, avoiding the precipitation phase at the grain boundary, and obtaining equiaxed fine α-Al grains, a dominant cubic texture, an average grain size of 15 to 30 μm, a cubic texture density of 10.0-15.0, a cubic texture volume fraction ≥15%, and a high-strength, high-bend T4P state 6xxx series aluminum alloy sheet with precipitates uniformly distributed in the crystal.

[0027] On the other hand, the present disclosure provides a T8x state 6xxx series aluminum alloy plate, which is obtained by performing a simulated paint baking treatment on the T4P state 6xxx series aluminum alloy plate of the present disclosure, wherein the simulated paint baking treatment includes the steps of pre-stretching the T4P state 6xxx series aluminum alloy plate by 2% and then heating it to 185°C and keeping it warm for 20 minutes.

[0028] The yield strength of the T8x state 6xxx series aluminum alloy plate disclosed herein is 300-350 MPa, and the tensile strength is 350-400 MPa.

[0029] The 6xxx series aluminum alloy sheet disclosed herein has both high strength and high formability, and can be industrially mass-produced. Moreover, the T8x aluminum alloy sheet obtained after simulated paint treatment can achieve the performance of traditional T6 state 6xxx series aluminum alloy, thereby replacing traditional T6 state 6xxx series aluminum alloy sheet, and can be used efficiently and at low cost for automotive components with high strength requirements, such as automotive structural parts, to meet the demand for lightweight vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a microstructure photograph of the aluminum alloy plate of Example 1.

[0031] FIG2 is a microstructure photograph of the aluminum alloy plate of Example 1 observed under a transmission electron microscope. DETAILED DESCRIPTION

[0032] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0033] In this article, T4P state refers to the state of the plate after solution quenching + pre-aging treatment.

[0034] In this article, the T8x state refers to the state of the plate after being subjected to a simulated paint baking treatment (ie, pre-stretched by 2% and then heated to 185° C. and kept at this temperature for 20 minutes).

[0035] In this paper, the average grain size of aluminum alloy plates was measured by metallographic microscopy according to ASTM E112, the texture was determined by electron backscatter diffraction (EBSD) using scanning electron microscopy, and the precipitated phase was observed by transmission electron microscopy (TEM).

[0036] In this paper, the yield strength, tensile strength and elongation of aluminum alloy sheets were determined according to ASTM E8.

[0037] In this article, the 90-degree bending radius (limit bending radius) of aluminum alloy sheets is measured according to GBT 232-2010.

[0038] Herein, the cubic texture "dominates" means that the volume fraction of the cubic texture is 15% or more.

[0039] The design principles of the chemical elements of the aluminum alloy plate disclosed in the present invention are as follows:

[0040] Mg and Si: Mg and Si are the primary strengthening elements in 6xxx aluminum alloys. They can form atomic clusters in the T4P state after solution quenching treatment on a continuous annealing line, and form β"-strengthening precipitates during baking and artificial aging treatment, significantly improving the strength of 6xxx aluminum alloys. The inventors discovered through experimental research that by controlling the Mg content between 0.5 and 1.0%, the Si content between 0.6 and 1.2%, and controlling the ratio of 1.2% ≤ Mg + Si ≤ 1.8%, sufficient β" and β' precipitates can be formed, refining the recrystallized grains and increasing the cubic texture density in the recrystallized structure. If Mg + Si is less than 1.2%, sufficient β' and β" phases cannot be precipitated during the hot rolling process. In the first stage of solution treatment, there are insufficient β" and β' precipitates to pin dislocations and grain boundaries, resulting in a low degree of recrystallized grain size refinement and a low cubic texture density in the recrystallized texture, leading to poor bending performance in the T4P state. At the same time, not enough atomic clusters and precipitates can be precipitated in the T4P state and during baking, resulting in lower strength. When Mg+Si>1.8%, Mg2Si or Si precipitates are easily precipitated at the grain boundaries, seriously deteriorating the bending performance of the T4P state.

[0041] In addition, the present disclosure also controls the Mg and Si contents to satisfy 0.7≤Mg / Si≤1.2. Extensive experiments have shown that when Mg / Si < 0.7, the Si content is too high, which can easily lead to the precipitation of coarse Si precipitates at grain boundaries during solution quenching, severely deteriorating the bending properties of the T4P state. When Mg / Si > 1.2, coarse Mg2Si precipitates easily at grain boundaries during solution quenching, slowing the precipitation rate of the β" strengthening precipitate during baking, reducing the content of the precipitate in the baked state and, consequently, the strength after baking.

[0042] Cu: Cu is added to the present invention to increase the bake hardening rate. The addition of Cu can form Cu-containing precipitates during baking, thereby improving post-baked properties. However, when the Cu content exceeds 0.2%, the filiform corrosion resistance of the material is easily deteriorated. Therefore, the present invention controls the Cu content to 0.05-0.2%.

[0043] Fe: Fe is an unavoidable impurity element added to raw materials and scrap during alloy smelting. Excessive Fe content can lead to the formation of coarse, iron-rich phases during alloy casting, impairing formability and bending properties. Therefore, the present disclosure requires a strict Fe content limit of 0.4% or less.

[0044] Mn: Adding Mn can reduce the harmful effects of Fe. However, excessive Mn content can easily form a coarse secondary phase, deteriorating bending performance. Therefore, this disclosure limits the Mn content to 0.05-0.2%.

[0045] The preparation method of the T4P state 6xxx series aluminum alloy plate disclosed in the present invention includes the following steps: 1) homogenization treatment; 2) hot rolling and coiling; 3) cold rolling; 4) solution heat treatment; 5) rapid quenching; 6) pre-aging treatment.

[0046] In a preferred embodiment, a homogenization treatment is performed before hot rolling of the ingot, with the homogenization treatment temperature being 535-575°C and the homogenization treatment time being 4-20 hours. This allows the soluble crystalline phases, such as the coarse Mg2Si and excess Si, formed during casting to fully dissolve back into the Al matrix, which is beneficial for fully utilizing the precipitation strengthening effect of Mg and Si atoms during subsequent artificial aging processes such as pre-aging treatment and baking. The insoluble iron-rich phase undergoes chain scission, spheroidization, and phase transformation, and eliminates casting internal stress and intracrystalline segregation, thereby facilitating hot rolling plastic deformation. When the homogenization treatment temperature is lower than 535°C, it is not conducive to the dissolution of the soluble crystalline phase and the transformation of the insoluble iron-rich phase. When the homogenization treatment temperature is higher than 575°C, overburning is likely to occur.

[0047] In a preferred embodiment, the ingot after homogenization treatment is directly taken out of the furnace for hot rolling, the starting rolling temperature is 520-575°C, the total deformation of hot rough rolling and hot finish rolling is ≥90%, and the hot rolled coil is obtained by coiling after hot rolling, the coiling temperature is 280-360°C, and then cooled to room temperature. The hot rolling start temperature is 520-575°C to avoid the precipitation of coarse β-Mg2Si during the hot rolling process, which makes it difficult to dissolve back during the solution treatment. In order to fully crush the casting structure to obtain a deformed structure, it is necessary to control the hot rolling deformation to ≥90%. The hot rolling coiling temperature is 280-360°C to obtain fine and dispersed submicron β" and β' precipitation phases, avoiding the precipitation of coarse micron β-Mg2Si.

[0048] In a preferred embodiment, after the hot rolled coil temperature drops to room temperature, the hot rolled coil is cold rolled with a cold rolling deformation of 50-90%, thereby obtaining T4P state 6xxx series aluminum alloy cold rolled sheet with sufficient work hardening degree.

[0049] In a preferred embodiment, the cold-rolled plate is subjected to a two-stage solution heat treatment in a continuous annealing line air cushion furnace, firstly heating the plate to 380-430°C at a heating rate of 10-25°C / s and holding the temperature for 3-15s, so that the 6xxx series aluminum alloy cold-rolled plate undergoes recrystallization before the fine β" and β' precipitates dissolve back, and the pinning effect of the relative dislocations and grain boundaries of the β" precipitates and β' precipitates is utilized to refine the recrystallized grain size and at the same time increase the cubic texture density in the recrystallized texture; then heating the plate to 540-570°C at a heating rate of 15-25°C / s and holding the temperature for 1-20s, thereby obtaining a supersaturated solid solution with fine grain size in which Mg and Si atoms are fully dissolved.

[0050] In a preferred embodiment, the aluminum alloy plate undergoes a quenching treatment for 1 to 10 seconds after solution treatment in a continuous annealing line air cushion furnace, with a quenching cooling rate of 80 to 120°C / s. Too slow a cooling rate can easily lead to the precipitation of Si atomic clusters, Mg atomic clusters, and Mg-Si atomic clusters at grain boundaries, accompanied by the formation of non-precipitation zones at grain boundaries, which can easily cause bending cracking during the subsequent bending process.

[0051] In a preferred embodiment, the aluminum alloy sheet after solution treatment and quenching is pre-aged, coiled at a temperature of 120-200°C, then cooled to below 50°C at a cooling rate of 0.05-0.1°C / min, and then air-cooled to room temperature to obtain a finished sheet. By controlling the coiling temperature during the pre-aging treatment and the cooling process after coiling, the aluminum alloy material is brought to an under-aged state, resulting in incomplete precipitation of the precipitated phase, thereby controlling the strength of the material within a certain range. The resulting aluminum alloy material has both high strength and excellent formability (primarily bending performance).

[0052] Example

[0053] The aluminum alloy plate and the preparation method thereof disclosed herein will be further explained and illustrated below in conjunction with specific embodiments. However, such explanation and illustration do not constitute an undue limitation to the technical solution disclosed herein.

[0054] Examples 1-6 and Comparative Examples 1-4

[0055] The aluminum alloy plates of Examples 1-6 were prepared by the following steps:

[0056] 1) Homogenization treatment;

[0057] 2) Hot rolling and coiling;

[0058] 3) Cold rolling;

[0059] 4) Solution heat treatment;

[0060] 5) Rapid quenching;

[0061] 6) Pre-aging treatment.

[0062] The comparative boards of Comparative Examples 1-4 were prepared using the same steps as above, with the only difference being the component contents and / or specific process parameters.

[0063] Table 1 lists the mass percentage content of each chemical element in the aluminum alloy plates of Examples 1-6 and the comparative plates of Comparative Examples 1-4. Table 2 lists the process parameters of the aluminum alloy plates of Examples 1-6 and the comparative plates of Comparative Examples 1-4.

[0064] Figure 1 shows a microstructure photograph of the aluminum alloy plate of Example 1, taken along a longitudinal cross-section, after being stored at room temperature for 7 days, followed by grinding, polishing, and anodic coating. As shown in Figure 1, the grains of the aluminum alloy plate of Example 1 are equiaxed and uniform in size from the surface to the core, with an average grain size of 23 μm.

[0065] Figure 2 shows a transmission electron microscope micrograph of the aluminum alloy plate of Example 1. As can be seen from Figure 2, the dispersed precipitates of the aluminum alloy plate of Example 1 are uniformly distributed within the crystals, and there are no precipitates at the grain boundaries.

[0066] The aluminum alloy plates of Examples 1-6 and the comparative plates of Comparative Examples 1-4 were sampled and subjected to performance tests. The obtained performance test results are listed in Table 3. The test process of the relevant properties is as follows:

[0067] Mechanical properties: With reference to ASTM E8 standard, the mechanical properties of the aluminum plates of the embodiments and comparative examples in the 90° direction were tested by tensile tests using an A50 gauge length.

[0068] 90-degree bending radius: Refer to GBT 232-2010, use different bending radii to test the 90-degree bending performance of samples taken in the 90-degree direction, and obtain the maximum bending radius.

[0069] It can be seen from Table 3 that after the aluminum alloy plates of Examples 1-6 were stored at room temperature for 7 days, the yield strength Rp in the tensile test perpendicular to the rolling direction was 0.2 The yield strength of the aluminum alloy sheets in Examples 1-6 is 155-200 MPa, the tensile strength is 240-300 MPa, the 90-degree bending radius is ≤0.3 mm for sheet thicknesses of 0.5-1 mm, and ≤0.3t for sheet thicknesses of 1-4 mm, where t represents the sheet thickness in mm. The aluminum alloy sheets of Examples 1-6 exhibit both high strength and excellent bending properties. The yield strength of the T8x aluminum alloy sheets obtained after simulated baking is 300-350 MPa, and the tensile strength is 350-400 MPa. These results demonstrate that the aluminum alloy sheets of Examples 1-6 have excellent age-hardening properties, meeting the performance requirements of high-strength, high-bending aluminum alloy sheets.

[0070] In contrast, Comparative Examples 1 and 3 had poor bending properties, and Comparative Examples 2 and 4 had poor bending properties and low strength.

[0071] All publications, patent applications, patents, and other references mentioned in this disclosure are incorporated by reference in their entirety.

[0072] Although the present disclosure has been illustrated and described with reference to certain preferred embodiments thereof, it should be understood by those skilled in the art that the above description is provided to further illustrate the present disclosure in conjunction with specific embodiments thereof, and that the present disclosure is not limited to these descriptions. Those skilled in the art may make various changes in form and detail, including simple deductions or substitutions, without departing from the spirit and scope of the present disclosure.

Claims

1. A T4P state 6xxx series aluminum alloy plate, wherein the T4P state 6xxx series aluminum alloy plate, in addition to Al and unavoidable impurities, further comprises the following chemical components in percentage by mass: Mg: 0.5-1.0%, Si: 0.60-1.2%, Cu: 0.05-0.2%, Mn: 0.05-0.2%, Fe≤0.4%; The content of a single unavoidable impurity is ≤ 0.05%; The contents of Mg and Si satisfy the following relationship: 0.7≤Mg / Si≤1.2, 1.2%≤Mg+Si≤1.8%.

2. The T4P state 6xxx series aluminum alloy plate as described in claim 1, comprising the following chemical components in percentage by mass: Mg: 0.5-1.0%, Si: 0.60-1.2%, Cu: 0.05-0.2%, Mn: 0.05-0.2%, Fe≤0.4%, and the balance is Al and unavoidable impurities.

3. The T4P state 6xxx series aluminum alloy sheet according to claim 1 or 2, wherein: The thickness of the T4P state 6xxx series aluminum alloy plate is 0.5-4 mm.

4. The T4P state 6xxx series aluminum alloy sheet according to any one of claims 1 to 3, wherein: The microstructure of the T4P state 6xxx series aluminum alloy plate is α-Al fine equiaxed grains dominated by cubic texture + precipitation phases uniformly distributed in the crystals, with an average grain size of 15 to 30 μm, a cubic texture density of 10.0 to 15.0, and a cubic texture volume fraction of ≥15%.

5. The T4P state 6xxx series aluminum alloy sheet according to any one of claims 1 to 4, wherein: The T4P state 6xxx series aluminum alloy sheet has a yield strength of 155-200 MPa, a tensile strength of 240-300 MPa, and an elongation of ≥20%. When the sheet thickness is 0.5-1 mm, the 90-degree bending radius of the T4P state 6xxx series aluminum alloy sheet is ≤0.3 mm. When the plate thickness is 1-4 mm, the 90-degree bending radius of the T4P state 6xxx series aluminum alloy plate is ≤0.3t, where t is the plate thickness in mm.

6. The T4P state 6xxx series aluminum alloy sheet according to any one of claims 1 to 5, wherein: The yield strength of the T8x state 6xxx series aluminum alloy plate obtained after the T4P state 6xxx series aluminum alloy plate is subjected to simulated paint treatment is 300-350 MPa, and the tensile strength is 350-400 MPa. The simulated paint baking treatment includes the steps of pre-stretching the T4P state 6xxx series aluminum alloy plate by 2%, heating it to 185° C. and keeping it warm for 20 minutes.

7. A method for preparing a T4P state 6xxx series aluminum alloy sheet according to any one of claims 1 to 6, comprising the following steps: 1) homogenization treatment, wherein the temperature of the homogenization treatment is 535-575° C. and the treatment time is 4-20 hours; 2) Hot rolling and coiling; 3) Cold rolling; 4) Solution heat treatment; 5) Rapid quenching; 6) Pre-aging treatment.

8. The method of claim 7, wherein: The method satisfies one or more of the following: In step 2), the rolling temperature is 520-575°C, and the coiling temperature is 280-360°C; In step 2), the total hot rolling deformation is ≥ 90%; In step 3), the total cold rolling deformation is 50 to 90%; In step 4), a two-stage solution heat treatment is adopted: first, the cold-rolled sheet obtained in step 3) is heated to 380-430°C at a heating rate of 11-25°C / s and kept at this temperature for 3-15s; then, it is heated to 540-580°C at a heating rate of 15-25°C / s and kept at this temperature for 1-20s; In step 5), the plate after solution heat treatment is quenched at a cooling rate of 80 to 120° C. / s for 1 to 10 seconds; and / or In step 6), the coiling temperature of the pre-aging treatment is 120-200°C, and then cooled to below 50°C at a cooling rate of 0.04-0.1°C / min, and then air-cooled to room temperature to obtain a T4P state 6xxx series aluminum alloy sheet.

9. A T8x state 6xxx series aluminum alloy plate, which is obtained by subjecting the T4P state 6xxx series aluminum alloy plate according to any one of claims 1 to 6 to a simulated paint baking treatment, wherein the simulated paint baking treatment comprises the steps of pre-stretching the T4P state 6xxx series aluminum alloy plate by 2% and then heating it to 185°C and keeping it warm for 20 minutes.

10. The T8x state 6xxx series aluminum alloy sheet according to claim 9, wherein: The yield strength of the T8x state 6xxx series aluminum alloy plate is 300-350 MPa, and the tensile strength is 350-400 MPa.

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