T4P-state 6xxx series aluminum alloy plate with high strength and high bending performance and preparation method of T4P-state 6xxx series aluminum alloy plate

Abstract

The high-strength and high-bending-performance T4P-state 6xxx series aluminum alloy plate comprises the following components in percentage by mass: 0.5-1.0% of Mg, 0.6-1.2% of Si, 0.05-0.2% of Cu, 0.05-0.2% of Mn, less than or equal to 0.4% of Fe and the balance of Al and other inevitable impurities or trace elements, Mg / Si is more than or equal to 0.7 and less than or equal to 1.2, and Mg + Si is more than or equal to 1.2% and less than or equal to 1.8%. The preparation method comprises the following steps: 1) homogenization treatment; 2) hot rolling and coiling. 3) cold rolling; (4) solid solution heat treatment; (5) rapid quenching; and (6) pre-aging treatment. The obtained 6xxx series aluminum alloy plate has high strength and high forming performance, the T6 state performance of a traditional 6xxx series aluminum alloy can be achieved after 2% pre-stretching and 185 DEG C baking for 20 min (T8x state), and therefore the 6xxx series aluminum alloy plate replaces a traditional T6 state 6xxx series aluminum alloy profile, is used for automobile structural parts and other automobile parts with the high strength requirement at high efficiency and low cost, and meets the requirement for automobile light weight.

Description

Technical Field

[0001] The present invention relates to the field of aluminum alloy plates and their manufacturing, and in particular to a high-strength, high-bending performance T4P state 6xxx series aluminum alloy plate and a preparation method thereof. Background Art

[0002] With the continuous increase in automobile production and ownership, accompanied by the increasing prominence of energy shortages and environmental pollution problems, under the constraints of the "dual carbon" goals of carbon peak and carbon neutrality, automobile lightweighting has become an important means for carbon emission reduction for various OEMs. 6xxx series aluminum alloys are one of the important materials for automobile lightweighting because of their excellent specific strength, forming performance, corrosion resistance and baking hardening performance. As a heat-treatable and strengthened aluminum alloy, 6xxx series aluminum alloy sheets for automobile covering parts are generally supplied in the T4P state after solid solution, quenching, surface treatment and pre-aging treatment on the continuous withdrawal line to meet the high formability requirements of the covering parts. The yield strength in the T4P state is generally required to be ≤150MPa. When the strength is too high, it is usually accompanied by deterioration of the forming performance. Because the OEM's painting and baking time is short, conventional 6xxx series aluminum alloys are usually in an under-aged state after 2% pre-stretching and baking at 185℃ for 20min (T8x state) for simulated baking, and the yield strength is generally 200-250MPa.

[0003] With the vigorous development of new energy vehicles, automotive structural parts represented by power battery packs used to use 6xxx series aluminum alloy profiles, which were extruded in a state with low solid solution strength, and then artificially aged at peak aging to meet the strength and stiffness requirements of the battery pack assembly. The aluminum alloy profile grades used are mainly 6063, 6005, 6061, 6082, etc., and multiple aluminum alloy profile parts are welded by CMT, stir friction welding and MIG / TIG welding. Considering the low production efficiency of extruded profiles, the large number of parts and the high connection cost, various automobile factories have proposed the use of aluminum alloy sheets by cold stamping instead of profiles. 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.

[0004] Chinese patent CN1974814A discloses "an Al-Mg-Si-Cu alloy for automobiles and its processing technology". The alloy composition is (in 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 the ratio of Si content to Mg content in the alloy is 1.6~2.2:1. The processing steps of the Al-Mg-Si-Cu alloy include: homogenizing and annealing the ingot obtained by melting and casting at 450-600°C for 10-20 hours, and then hot rolling after keeping it at 400-550°C for 1-2 hours; after hot rolling, the plate is kept at 280-560°C for 1-2 hours, followed by cold rolling; after cold rolling, it is kept at 530-580°C for 1-2 hours for solution treatment. The yield strength of this aluminum alloy after baking paint is ≥160MPa, and the tensile strength is ≥280MPa, so it does not meet the strength requirements of automotive structural parts, and does not involve bending performance, and cannot be reflected in the applicability of parts with relatively high bending performance requirements such as battery pack structural parts.

[0005] Chinese patent CN101935785B discloses "a high-formability aluminum alloy for automobile body panels". By adjusting the content and ratio of the main elements Si, Mg, and Cu, a 6xxx series aluminum alloy for automobile body panels with excellent formability is obtained. However, although this patent has a high elongation and work hardening rate, the T4P state yield strength is lower than 130MPa, which does not meet the strength requirements of structural parts such as automotive battery packs.

[0006] It can be seen that the improvement schemes for 6xxx series aluminum alloys in the prior art still have some shortcomings. Summary of the invention

[0007] The present invention aims to provide a high-strength, high-bending performance T4P state 6xxx series aluminum alloy plate and a preparation method thereof, wherein the T4P state 6xxx series aluminum alloy plate has a yield strength of 155-200MPa, a tensile strength of 240-300MPa, an elongation of ≥20%, a 90-degree bending radius of ≤0.3mm when the plate thickness is 0.5-1mm; a 90-degree bending radius of ≤0.3t when the plate thickness is 1-4mm, t is the plate thickness, in mm; after 2% pre-stretching and baking at 185°C for 20min (T8x The yield strength of the aluminum alloy sheet in the T8x state is 300-350 MPa, and the tensile strength is 350-400 MPa. The present invention enables the 6xxx series aluminum alloy sheet to have both high strength and high formability, and can realize large-scale industrial production. After 2% pre-stretching and baking at 185°C for 20 minutes (T8x state), the performance of the traditional 6xxx series aluminum alloy T6 state can be achieved, thereby replacing the traditional T6 state 6xxx series aluminum alloy profiles, and being used efficiently and at low cost for automotive components with high strength requirements such as automotive structural parts, thereby meeting the further demand for lightweight automobiles.

[0008] To achieve the above object, the technical solution of the present invention is:

[0009] A high-strength, high-bending performance T4P state 6xxx series aluminum alloy plate, whose chemical composition mass percentage is: Mg: 0.5-1.0%, Si: 0.6-1.2%, Cu: 0.05-0.2%, Mn: 0.05-0.2%, Fe≤0.4%, the rest includes Al and other inevitable impurities or trace elements, the content of a single inevitable impurity or trace element is ≤0.05%, and it is necessary to simultaneously meet the following conditions: 0.7≤Mg / Si≤1.2, 1.2%≤Mg+Si≤1.8%.

[0010] Furthermore, the remainder is Al and other inevitable impurities or trace elements.

[0011] The microstructure of the T4P state 6xxx series aluminum alloy plate of the present invention is α-Al fine equiaxed grains dominated by cubic texture + precipitation phases uniformly distributed in the grains, 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%.

[0012] The yield strength of the T4P state 6xxx series aluminum alloy plate of the present invention is: 155-200MPa, the tensile strength is: 240-300MPa, the elongation is ≥20%, and the 90-degree bending radius is ≤0.3mm when the plate thickness is 0.5-1mm; when the plate thickness is 1-4mm, the 90-degree bending radius is ≤0.3t, where t is the plate thickness, unit is mm.

[0013] The aluminum alloy sheet of the present invention has a yield strength of 300-350 MPa and a tensile strength of 350-400 MPa in the T8x state after being pre-stretched by 2% and baked at 185° C. for 20 minutes.

[0014] In the composition design of the aluminum alloy sheet of the present invention:

[0015] Mg, Si: Mg and Si are the main strengthening elements of 6xxx aluminum alloys. After the solution quenching treatment of the continuous annealing line, atomic clusters can be formed in the T4P state, and β" strengthening precipitation phases can be formed during the baking artificial aging treatment, which significantly improves the strength of 6xxx aluminum alloys. The present invention controls the Mg content to 0.5-1.0%, the Si content to 0.6-1.2%, and controls 1.2%≤Mg+Si≤1.8% to form enough β" precipitation phases and β' precipitation phases, refine the recrystallized grains, and increase the cubic texture density in the recrystallized structure. If Mg+Si is less than 1.2%, sufficient β' and β" phases cannot be precipitated in the hot rolling process, and there are not enough β" precipitation phases and β' precipitation phases in the first stage of the solution treatment to pin the dislocations and grain boundaries. The recrystallized grain size refinement degree is low, and at the same time, the cubic texture density in the recrystallized texture is low, resulting in poor bending performance in the T4P state. At the same time, not enough atomic clusters and precipitated phases can be precipitated in the T4P state and during baking, resulting in low strength. When Mg+Si>1.8%, Mg2Si or Si precipitated phases are easily precipitated at the grain boundaries, which seriously deteriorates the bending performance of the T4P state.

[0016] Furthermore, the composition of the present invention is controlled to be 0.7≤Mg / Si≤1.2. After a large number of experimental verifications, when Mg / Si<0.7, the Si content is too high, which is easy to cause the precipitation of coarse Si precipitation phase at the grain boundary during solution quenching treatment, seriously deteriorating the bending performance of the T4P state. When Mg / Si>1.2, it is easy to cause the precipitation of coarse Mg2Si at the grain boundary during solution quenching treatment, and the precipitation rate of β" strengthening precipitation phase is slow during baking, which reduces the content of the precipitated phase in the baked state, thereby reducing the strength after baking.

[0017] Cu: Cu is added in the present invention to increase the baking hardening rate. The addition of Cu can form a Cu-containing precipitate phase during baking, thereby improving the performance after baking. However, when the Cu content is greater than 0.2%, the filiform corrosion performance of the material is easily deteriorated. Therefore, the present invention controls the Cu content to 0.05-0.2%.

[0018] Fe: Fe is an inevitable impurity element added to raw materials and waste materials during alloy smelting. If the Fe content is too high, a coarse iron-rich phase will be formed in the alloy during casting, which will deteriorate the forming and bending properties. Therefore, the present invention needs to strictly limit the Fe content and control the Fe content to ≤0.4%.

[0019] Mn: Adding Mn can reduce the harmful effects of Fe, but if the Mn content is too high, it will easily form a coarse second phase, which will deteriorate the bending performance. Therefore, the present invention controls the Mn content to 0.05-0.2%.

[0020] The present invention also provides a method for preparing a high-strength, high-bending performance T4P state 6xxx series aluminum alloy sheet, comprising the following steps:

[0021] 1) Homogenization

[0022] The ingot homogenization treatment temperature is 535-575°C and the treatment time is 4-20h;

[0023] 2) Hot rolling and coiling

[0024] The starting rolling temperature is 520-575°C, and the hot rolled coil is obtained by coiling after hot rolling, and the coiling temperature is 280-360°C;

[0025] 3) Cold rolling

[0026] The hot rolled coil is then cold rolled after the temperature drops to room temperature to obtain a cold rolled sheet;

[0027] 4) Solution heat treatment

[0028] A two-stage solution heat treatment is adopted, wherein the cold-rolled sheet is first heated to 380-430°C at a heating rate of 11-25°C / s, kept at this temperature for 3-15s, and then heated to 540-570°C at a heating rate of 15-25°C / s, kept at this temperature for 1-20s;

[0029] 5) Rapid quenching

[0030] The plate after solution treatment is quenched within 1 to 10 seconds, and the quenching cooling rate is 80 to 120 ° C / s;

[0031] 6) Pre-aging treatment and coiling

[0032] The quenched plate is heated to a coiling temperature in a pre-aging furnace for coiling, the coiling temperature is 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 T4P state 6xxx series aluminum alloy coil.

[0033] Preferably, in step 2), the total hot rolling deformation is ≥ 90%.

[0034] Preferably, in step 3), the total cold rolling deformation is 50 to 90%.

[0035] As a heat-treatable aluminum alloy, the main strengthening method of 6xxx series aluminum alloy is precipitation strengthening. 6xxx series aluminum alloy plates must undergo melting-hot rolling-cold rolling-solid solution-quenching treatment in aluminum processing plants to obtain T4P aluminum plates with excellent formability. T4P aluminum plates will undergo natural aging during natural storage, accompanied by increased yield strength and decreased formability, which leads to problems such as increased rebound, drawing and flanging cracking when stamping parts in automobile factories. Therefore, most 6xxx series aluminum plates must undergo pre-aging treatment after solution quenching treatment on the continuous annealing line to improve the natural aging stability during storage and transportation.

[0036] After extensive research, the inventors found that the tensile and bending properties of T4P state 6xxx series aluminum plates are closely related to the orientation, size and distribution of α-Al grains and precipitated phases.

[0037] Homogenization treatment is carried out before hot rolling of the ingot, and the temperature of the homogenization treatment is 535-575℃, and the homogenization treatment time is 4-20h. The coarse Mg2Si and excess Si soluble crystalline phases formed in the casting are fully dissolved back into the Al matrix, which is conducive to giving full play to the precipitation strengthening effect of Mg and Si atoms in the subsequent pre-aging treatment and artificial aging process such as baking. The insoluble iron-rich phase undergoes chain breaking, spheroidization, phase transformation, and eliminates casting internal stress and intracrystalline segregation, which is conducive to hot rolling plastic deformation. The homogenization treatment temperature is lower than 535℃, which is not conducive to the dissolution of the soluble crystalline phase and the transformation of the insoluble iron-rich phase. The homogenization treatment temperature is higher than 575℃, which is prone to overburning.

[0038] The ingot after homogenization treatment is directly taken out of the furnace for hot rolling, the starting rolling temperature is 520-575℃, the total deformation of hot rough rolling and hot finishing rolling is ≥90%, and the hot rolled coil is obtained by coiling after hot rolling, the coiling temperature is 280-360℃, and then cooled to room temperature. The hot rolling starting temperature is 520-575℃ to avoid the precipitation of coarse β-Mg2Si during hot rolling, which makes it difficult to dissolve back during solution treatment. In order to fully crush the casting structure to obtain the deformed structure, it is necessary to control the hot rolling deformation to ≥90%. The hot rolling coiling temperature is 280-360℃ to obtain fine and dispersed submicron β" and β' precipitation phases to avoid the precipitation of coarse micron β-Mg2Si.

[0039] After the temperature of the hot rolled coil drops to room temperature, the hot rolled coil is cold rolled with a cold rolling deformation of 50-90% to obtain a T4P state 6xxx series aluminum alloy cold rolled sheet with sufficient work hardening degree.

[0040] The cold-rolled plate is subjected to a two-stage solution heat treatment in a continuous annealing line air cushion furnace. The temperature is firstly increased to 380-430°C at a heating rate of 10-25°C / s and kept at this 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. The pinning effect of the β" precipitates and β' precipitates on dislocations and grain boundaries is utilized to refine the recrystallized grain size and improve the cubic texture density in the recrystallized texture. Then, the temperature is increased to 540-570°C at a heating rate of 15-25°C / s and kept at this temperature for 1-20s, so as to obtain a supersaturated solid solution with fine grain size in which Mg and Si atoms are fully dissolved.

[0041] After the aluminum alloy plate completes the solution treatment in the continuous annealing line air cushion furnace, it is quenched within 1 to 10 seconds, and the quenching cooling rate is 80 to 120°C / s. A faster quenching cooling rate is used. If the cooling rate is too slow, it is easy to cause Si atomic clusters, Mg atomic clusters and Mg-Si atomic clusters to precipitate at the grain boundaries, accompanied by the formation of no precipitation zones at the grain boundaries, which is prone to bending cracking during the subsequent bending forming process.

[0042] After solution quenching, the aluminum alloy sheet is pre-aged, and the under-aging state is achieved by controlling the temperature and the cooling process after coiling, so that the precipitation phase is not completely precipitated, and the strength of the material is controlled within a certain range, so that the material has both high strength and good forming performance (here the bending performance is mainly emphasized). The coiling temperature of the heated aluminum alloy coil is 120-200°C, and then air-cooled to 50°C, with a cooling rate of 0.05-0.1°C / min, to obtain the T4P state 6xxx series aluminum alloy finished sheet.

[0043] Beneficial effects of the present invention:

[0044] The present invention optimizes the traditional 6xxx alloy component system, regulates the content and ratio of the main alloy elements Mg and Si, controls 0.7≤Mg / Si≤1.2, 1.2%≤Mg+Si≤1.8%, avoids the precipitation of precipitation phases at grain boundaries, ensures that enough β" precipitation phases and β' precipitation phases can be formed during solid solution, refines the recrystallized grains, increases the cubic texture density in the recrystallized structure, and thus improves the strength and bending performance of the alloy.

[0045] On the basis of component design, the present invention further optimizes the full-process production process of 6xxx series aluminum alloy, obtains a cold-rolled plate with dispersed submicron-level β metastable phase precipitation phase and deformation structure through soaking, hot rolling, coiling and cold rolling, and then combines the process parameters of two-stage solution heat treatment, quenching and pre-aging treatment to couple and regulate the precipitation, dissolution behavior and recrystallization process of precipitation phases such as Mg2Si metastable phase, thereby promoting the precipitation phase to inhibit recrystallization nucleation and growth, thereby achieving the effect of refining grains and improving the cubic texture density in the recrystallization texture, avoiding the precipitation phase from precipitating at the grain boundary, and obtaining equiaxed fine α-Al grains, cubic texture dominating, average grain size of 15 to 30 μm, cubic texture density of 10.0-15.0, cubic texture volume fraction of ≥15%, and T4P state high-strength and high-bend 6xxx series aluminum alloy plate with precipitation phase uniformly distributed in the crystal.

[0046] The T4P state 6xxx series aluminum alloy sheet obtained by the present invention has high strength and high formability, and its yield strength reaches 155-200MPa, tensile strength is 240-300MPa, elongation is ≥20%, and the 90-degree bending radius is ≤0.3mm when the sheet thickness is 0.5-1mm, and the 90-degree bending radius is ≤0.3t when the sheet thickness is 1-4mm, where t is the sheet thickness in mm. After 2% pre-stretching + baking at 185°C for 20min (T8x state), the yield strength of the aluminum alloy sheet is 300-350MPa, and the tensile strength is 350-400MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a microstructure photograph of the aluminum alloy plate of Example 1 of the present invention.

[0048] Figure 2 This is a microstructure photograph of the aluminum alloy plate of Example 1 of the present invention observed under a transmission electron microscope. DETAILED DESCRIPTION

[0049] The present invention is further described below by way of embodiments and drawings, but this is not intended to limit the present invention. Those skilled in the art may make modifications or improvements based on the basic idea of ​​the invention, but as long as they do not deviate from the basic idea of ​​the invention, they are all within the scope of the present invention.

[0050] The mass percentages of chemical elements of the aluminum alloy plates used in the embodiments and comparative examples of the present invention are shown in Table 1. The process parameters of the embodiments and comparative examples are shown in Table 2, and the properties of the aluminum alloy plates obtained are shown in Table 3.

[0051] The aluminum alloy plate of Example 1 was placed at room temperature for 7 days, and samples were taken along the longitudinal section, and then ground, polished and anodic coated. The microstructure photographs observed under a polarizing microscope are shown in FIG. Figure 1 .Depend on Figure 1It can be seen that the grains are equiaxed and uniform in size from the surface to the core, with an average grain size of 23 μm.

[0052] Microstructure photographs observed under a transmission electron microscope Figure 2 As shown, from Figure 2 It can be seen that the dispersed precipitate phase is evenly distributed in the crystal, and there is no precipitate phase at the grain boundary.

[0053] Referring to the ASTM standard, the mechanical properties of the aluminum plates of the embodiments and comparative examples produced by various preparation processes in the 90° direction were tested by tensile test using the A50 gauge length.

[0054] Referring to GBT 232-2010, different bending radii were used to test the 90-degree bending performance of samples taken in the 90-degree direction, and the limit bending radius was obtained.

[0055] The mechanical properties test and the ultimate bending radius results of the aluminum alloy plates in Examples 1-6 and Comparative Examples 1-2 after different treatments and sampling at 90° are shown in Table 3, wherein the T4P state refers to the state of being parked at room temperature for 7 days after solid solution pre-aging, and T8x refers to the state after simulated baking paint (pre-stretching 2% and then heating to 185°C and keeping warm for 20 minutes).

[0056] 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, in the tensile property test perpendicular to the rolling direction, the yield strength Rp 0.2 The tensile strength is 240-300 MPa, the bending radius of 90 degrees is ≤0.3 mm when the plate thickness is 0.5-1 mm, and the bending radius of 90 degrees is ≤0.3 t when the plate thickness is 1-4 mm, where t is the plate thickness in mm. The alloy has high strength and high bending performance. The T8x yield strength after simulated baking is 300-350 MPa, and the tensile strength is 350-400 MPa, indicating that Examples 1-6 have excellent aging hardening performance and meet the performance requirements of high-strength and high-bending performance aluminum alloy plates.

[0057] In Comparative Example 1, Mg / Si is less than 0.7, which exceeds the Mg / Si composition ratio of the present invention, resulting in the precipitation of coarse Si particles at the grain boundaries during solution quenching, which seriously deteriorates the bending performance of the T4P state and results in a bending radius greater than 0.3t.

[0058] The Mg+Si content in Comparative Example 2 is less than the Mg+Si composition range of the present invention, resulting in insufficient precipitation of β" and β' precipitation phases in the hot rolling process, insufficient β" precipitation phases and β' precipitation phases for pinning dislocations and grain boundaries in the first stage of solution treatment, low degree of recrystallization grain size refinement, and low cubic texture density in the recrystallization texture, resulting in poor bending performance in the T4P state, with a bending radius of >0.3t. At the same time, insufficient atomic clusters and precipitation phases cannot be precipitated in the T4P state and during baking, resulting in lower strength.

[0059] In Comparative Example 3, the quenching cooling rate was too low after the two-stage solution treatment was adopted in the continuous annealing line, and the dissolved Mg and Si atoms precipitated Mg-Mg, Si-Si and Mg-Si atomic clusters at the grain boundaries, resulting in a significant deterioration in the bending performance of the T4P state plate, and the bending radius was greater than 0.2mm.

[0060] Comparative Example 4 did not adopt two-stage solid solution treatment, resulting in the T4P state plate having a cubic texture density of less than 10, a cubic texture component volume fraction of less than 15%, and a grain size of more than 30 μm, resulting in a T4P state yield strength of less than 155 MPa, a tensile strength of less than 240 MPa, and a bending radius of more than 0.1t, while a T8x state yield strength of less than 300 MPa and a tensile strength of less than 350 MPa.

[0061]

[0062]

[0063]

Claims

1. A high-strength, high-bending performance T4P state 6xxx series aluminum alloy plate, whose chemical composition mass percentage is: Mg: 0.5-1.0%, Si: 0.6-1.2%, Cu: 0.05-0.2%, Mn: 0.05-0.2%, Fe≤0.4%, the rest includes Al and other inevitable impurities or trace elements, the content of a single inevitable impurity or trace element is ≤0.05%, and it is necessary to simultaneously meet the following conditions: 0.7≤Mg / Si≤1.2, 1.2%≤Mg+Si≤1.8%.

2. The high-strength, high-bending performance T4P state 6xxx series aluminum alloy sheet according to claim 1, characterized in that: The rest is Al and other inevitable impurities or trace elements.

3. The high-strength, high-bending performance T4P state 6xxx series aluminum alloy sheet according to claim 1 or 2, characterized in that: 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 grains, 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%.

4. The high-strength, high-bending performance T4P state 6xxx series aluminum alloy sheet according to claim 1, 2 or 3, characterized in that: The yield strength of the T4P state 6xxx series aluminum alloy plate is 155-200MPa, the tensile strength is 240-300MPa, the elongation is ≥20%, and the 90-degree bending radius is ≤0.3mm when the plate thickness is 0.5-1mm; the 90-degree bending radius is ≤0.3t when the plate thickness is 1-4mm, where t is the plate thickness in mm.

5. The high-strength, high-bending performance T4P state 6xxx series aluminum alloy sheet according to claim 1, 2, 3 or 4, characterized in that: The aluminum alloy plate is pre-stretched by 2% and baked at 185° C. for 20 minutes, i.e., in the T8x state, the yield strength is 300-350 MPa and the tensile strength is 350-400 MPa.

6. The method for preparing a high-strength, high-bending-performance T4P-state 6xxx aluminum alloy sheet according to claims 1 to 5, characterized in that: The steps include: 1) Homogenization The ingot homogenization treatment temperature is 535-575°C and the treatment time is 4-20h; 2) Hot rolling and coiling The starting rolling temperature is 520-575°C, and the hot rolled coil is obtained by coiling after hot rolling, and the coiling temperature is 280-360°C; 3) Cold rolling The hot rolled coil is cooled to room temperature and then cold rolled to obtain a cold rolled sheet; 4) Solution heat treatment A two-stage solution heat treatment is adopted, wherein the cold-rolled sheet is first heated to 380-430°C at a heating rate of 11-25°C / s, kept at this temperature for 3-15s, and then heated to 540-570°C at a heating rate of 15-25°C / s, kept at this temperature for 1-20s; 5) Rapid quenching The plate after solution treatment is quenched within 1 to 10 seconds, and the quenching cooling rate is 80 to 120 ° C / s; 6) Pre-aging treatment The quenched plate is heated to a coiling temperature in a pre-aging furnace for coiling, the coiling temperature is 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 T4P state 6xxx series aluminum alloy coil.

7. The preparation method according to claim 6, characterized in that: In step 2), the total hot rolling deformation is ≥ 90%.

8. The preparation method according to claim 6, characterized in that: In step 3), the total cold rolling deformation is 50 to 90%.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The microstructure of the obtained T4P state 6xxx aluminum alloy plate is composed of α-Al fine equiaxed grains dominated by cubic texture + precipitation phases uniformly distributed in the grains, 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 ≥15%.

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