Ultrahigh-strength Al-Mg-Si-Cu series aluminum alloy material and preparation method thereof

Abstract

The invention discloses an ultrahigh-strength Al-Mg-Si-Cu series aluminum alloy material and a preparation method thereof. The ultrahigh-strength Al-Mg-Si-Cu series aluminum alloy material is prepared from the following chemical components in percentage by mass: 1.2 to 2.0 percent of Mg, 1.0 to 1.5 percent of Si, 0.5 to 1.5 percent of Cu and the balance of Al and inevitable impurities. According to the ultrahigh-strength Al-Mg-Si-Cu series aluminum alloy material, alloy components are designed, the process is reasonably optimized, and peak aging treatment is carried out after cold rolling solution treatment and water quenching, so that the ultrahigh-strength Al-Mg-Si-Cu series aluminum alloy material has excellent plasticity while having ultrahigh strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy, more particularly, to an ultra-high-strength Al-Mg-Si-Cu series aluminum alloy material and a preparation method thereof. BACKGROUND

[0002] With the increasing requirements of safety regulations for automobile collision safety, especially the protection of cab members, the strength level of materials for vehicle body safety structure is also increasingly high. Since the ultra-high-strength 6xxx series aluminum plate has the characteristics of high specific strength, good corrosion resistance and easy welding, it has become the focus of development of automobile aluminum plates. However, the existing 6xxx aluminum alloy is mostly in the medium-high strength range, so it is urgent to develop a new type of ultra-high-strength 6xxx series aluminum alloy plate suitable for industrial production.

[0003] The 6xxx series aluminum alloy commonly used for automobile body plate at present is mainly AA6111, AA6016 and AA6022, which has a low yield strength of 290-300 MPa in the peak aging state. Therefore, it is necessary to further develop 6xxx series aluminum alloy with ultra-high strength through composition optimization and process control. In recent years, the composition design and optimization of new 6xxx series aluminum alloy have made some progress. With the increase of Mg and Si main alloying phase elements, the addition of solid solution strengthening and synergistic strengthening elements Zn and Cu, and the addition of dispersion and fine-grain micro-alloying elements Mn or Zr, the yield strength of the existing typical high-strength 6xxx series aluminum alloy, such as AA6056 and AA6069 alloy, reaches 315-400 MPa in the peak aging state. However, the above-mentioned alloy is mainly in the form of extruded rod, and there is a blank in the research of plate, which limits its application in the field of automobile plate. Therefore, considering the need for ultra-high-strength aluminum alloy plate in the lightweight design of the transportation field, the new 6xxx series aluminum alloy needs to be processed into a plate by the existing industrialized plate preparation process, and it also needs to have good plasticity under the premise of having ultra-high yield strength.

[0004] In view of the above, it is urgent to develop an aluminum alloy material with ultra-high strength and good plasticity and a preparation method thereof, which can solve the problem that the existing commercial 6xxx series aluminum alloy plate has low strength and cannot meet the lightweight design and safety requirements in the future transportation field. SUMMARY

[0005] In view of the defects in the prior art, the purpose of the present application is to provide an ultra-high-strength Al-Mg-Si-Cu series aluminum alloy material and a preparation method thereof. By designing the alloy composition and reasonably optimizing the process, the ultra-high-strength Al-Mg-Si-Cu series aluminum alloy material has ultra-high strength and good plasticity after peak aging treatment after cold rolling and solid solution treatment and water quenching.

[0006] To achieve the above object, the present application adopts the following technical solutions:

[0007] The first aspect of the present application provides a super-high-strength Al-Mg-Si-Cu aluminum alloy material, comprising the following chemical components in percentage by mass: Mg: 1.2-2.0 wt.%, Si: 1.0-1.5 wt.%, Cu: 0.5-1.5 wt.%, and the rest being Al and inevitable impurities.

[0008] Preferably, it further comprises the following chemical components: Zn: 0.15-0.5 wt.%, Mn: 0.2-0.4 wt.%, Ti: 0.05-0.1 wt.%, and Fe≤0.5 wt.%.

[0009] Preferably, it has the following performance: yield strength: 350-370 MPa, tensile strength≥400 MPa, and elongation after fracture≥14.5%.

[0010] The second aspect of the present application provides a preparation method of the super-high-strength Al-Mg-Si-Cu aluminum alloy material as described in the first aspect of the present application, comprising the following steps:

[0011] S1, obtaining a cold-rolled plate through alloy smelting, homogenization treatment, hot rolling, annealing and cold rolling treatment;

[0012] S2, water quenching the cold-rolled plate after solid solution treatment;

[0013] S3, peak aging treatment of the water-quenched cold-rolled plate to obtain a high-strength Al-Mg-Si-Cu aluminum alloy material.

[0014] Preferably, in the step S1, the raw materials for alloy smelting include high-purity aluminum, high-purity magnesium, Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Ti intermediate alloy, Al-Fe intermediate alloy and Al-Si intermediate alloy.

[0015] Preferably, in the alloy smelting process, after adding high-purity aluminum and heating to melt it, the melt is heated to 740-760℃, and then the intermediate alloy is added and kept at 760-780℃ for 20-40 min; after the intermediate alloy is melted, the melt is cooled to 720-760℃, and then high-purity magnesium and high-purity zinc are added and kept for 20-30 min; then a refining agent is added and kept at 720-740℃ for 15-25 min; then a slagging agent is added and kept at 730-750℃ for 10-20 min before slagging; finally, a refiner is added and kept for 2-6 min before casting the steel into an ingot.

[0016] Preferably, the refining agent is a sodium fluoride ionic refining agent, and its addition amount is 0.40 to 0.60 wt.% of the melt mass; the refining agent is an Al-Ti-B refining agent, and its addition amount is 0.01 to 0.06 wt.% of the melt mass.

[0017] Preferably, the casting temperature is 720–740°C.

[0018] Preferably, in step S1, the homogenization treatment involves holding the alloy smelting ingot at 540–560°C for 20–30 hours.

[0019] Preferably, in step S1, the hot rolling process involves heating the homogenized ingot to 540–560°C and holding it at that temperature for 1.5–3 hours before performing multi-pass rolling. Between every three passes, the ingot is held at 540–560°C for 15–30 minutes, and the total deformation during hot rolling is controlled to be 85%–94%.

[0020] Preferably, in step S1, the annealing process involves heating the hot-rolled plate obtained from the hot-rolling process to 380-420°C at a heating rate of 0.5-1.0°C / min and holding it at that temperature for 30-60 minutes.

[0021] Preferably, in step S1, the cold rolling process employs multi-pass rolling with a total reduction of ≥80%.

[0022] Preferably, in step S2, the solution treatment involves placing the cold-rolled sheet in a salt bath furnace and holding it at 560–570°C for 1.0–2.0 hours.

[0023] Preferably, in step S3, the cold-rolled sheet is quickly transferred to an aging furnace after water quenching for peak aging treatment, and the transfer time is less than 1 minute.

[0024] Preferably, in step S3, the peak aging process adopts a single-level aging or a two-level aging process;

[0025] The single-stage aging process involves aging at 160–185°C for 3–6 hours.

[0026] The two-stage aging process involves first pre-aging at 60–90°C for 12–24 hours, and then aging at 160–185°C for 1–3 hours.

[0027] This invention designs the composition of ultra-high strength Al-Mg-Si-Cu aluminum alloy materials, and the design principle of each chemical element is as follows:

[0028] Mg and Si are important components of the main strengthening phase, the β phase, and its metastable phase in the Al-Mg-Si-Cu alloy described in this invention. Increasing the content of Mg and Si can increase the volume fraction of the strengthening phase and improve the mechanical properties of the alloy. However, excessive addition of Mg and Si will reduce the ductility, hardening index, and bending performance of the sheet metal. In addition, the Mg / Si ratio of the alloy also has a significant impact on its mechanical properties. Excess Mg reduces the solubility of the β phase in the matrix, which is not conducive to the improvement of strength. Excess Si reduces the alloy's resistance to intergranular corrosion and is also prone to forming Al6(FeMnSi) impurity phase with Mg and Fe, which damages plasticity. Considering the above factors, the Mg / Si ratio of the alloy is set to 1.50, the Mg content is set to 1.2-2.0 wt.%, and the Si content is set to 1.0-1.5 wt.%.

[0029] Cu: Adding a portion of Cu to 6xxx series aluminum alloys can, on the one hand, introduce new strengthening phases—Q phase and its metastable phases, thereby improving alloy strength; on the other hand, it can improve the precipitation kinetics of β phase and its metastable phases during aging, shortening the peak aging treatment time. Therefore, high Cu content is currently added to typical medium and high strength 6xxx series aluminum alloys. In summary, the Cu content is set to: 0.5–1.5 wt.%.

[0030] Zn: Adding a small amount of Zn to 6xxx series alloys can improve the stability of Mg-Si clusters, promote the nucleation and precipitation of strengthening phases, and enhance aging response behavior and mechanical properties. However, with the increase of Zn content, the alloy will precipitate new strengthening phases -η phase and its metastable phases, resulting in an excess of Si. In summary, the Zn content is set to 0.15~0.5 wt.%.

[0031] Mn: Mn is a trace element in Al-Mg-Si-Cu alloys. Adding a small amount of Mn can promote the transformation of the Fe-rich phase (AlFeSi phase) from lath-like to spherical, improving the alloy's plasticity. However, excessive Mn will form a coarse, hard, and brittle Al6Mn phase, impairing plasticity. Furthermore, Mn and Cr will form an Al(Mn,Cr)Si dispersed phase with Si, reducing the Si content in the matrix and thus decreasing the alloy's age-hardening ability. Therefore, the Mn content is set at 0.2–0.4 wt.%.

[0032] Ti: In Al-Mg-Si alloys, trace amounts of Ti can act as heterogeneous nuclei, promoting grain nucleation and refining grain size. Therefore, trace amounts of Ti are introduced in this invention, with a content of 0.05–0.1 wt.%.

[0033] Fe: As a common impurity element in aluminum alloys, Fe has very low solid solubility in aluminum and readily forms coarse intermetallic compounds (such as AlFeMnSi), reducing the plasticity and bending properties of the sheet metal. Simultaneously, it consumes Si and Mn elements, further reducing alloy strength and impairing plasticity. Therefore, the Fe content should be controlled at ≤0.5 wt.%.

[0034] The beneficial effects of this invention are as follows:

[0035] 1. This invention, through the comprehensive design of main alloying elements such as Mg, Si, and Cu, as well as trace elements, achieves the synergistic precipitation of multiple strengthening phases (β phase and its metastable phase and Q phase and its metastable phase), introducing a multiphase strengthening effect and breaking through the strength limitations of existing commercial 6xxx series aluminum alloy plates. On the other hand, by introducing heterogeneous cores and dispersed phases, the alloy grain size is refined, the alloy plasticity is improved, and an excellent match between strength and plasticity is achieved.

[0036] 2. This invention optimizes the process by performing peak aging treatment after cold rolling solution treatment and water quenching. The resulting sheet has good surface quality and fine grain size, and possesses both ultra-high strength and good plasticity. It has certain guiding significance for the development, processing and application of ultra-high strength 6xxx series aluminum alloy automotive sheet.

[0037] 3. The ultra-high strength Al-Mg-Si-Cu series aluminum alloy prepared by this invention is easy to roll and deform, which can meet the rolling forming process requirements under industrial conditions. It solves the problem that the existing commercial 6xxx series aluminum alloy plates have low strength and cannot meet the lightweight design and safety requirements of the future transportation field, thus filling the gap in the existing ultra-high strength 6xxx series aluminum alloy plates. Attached Figure Description

[0038] Figure 1 This is a flowchart of the preparation method of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material of the present invention;

[0039] Figure 2 These are the particle size distribution diagrams of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in Example 1 of this invention; (a) is a grain morphology diagram, and (b) is the grain size distribution of the alloy.

[0040] Figure 3 It is a typical strengthening phase in the peak aging state of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in Example 1 of this invention. Detailed Implementation

[0041] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0042] The present invention provides an ultra-high strength Al-Mg-Si-Cu aluminum alloy material, comprising the following chemical composition by mass percentage: Mg: 1.2-2.0 wt.%, Si: 1.0-1.5 wt.%, Cu: 0.5-1.5 wt.%, with the remainder being Al and unavoidable impurities.

[0043] In a specific embodiment, the ultra-high strength Al-Mg-Si-Cu aluminum alloy material further includes the following chemical composition: Zn: 0.15-0.5 wt.%, Mn: 0.2-0.4 wt.%, Ti: 0.05-0.1 wt.%, Fe ≤ 0.5 wt.%.

[0044] The aforementioned ultra-high strength Al-Mg-Si-Cu aluminum alloy material meets the following performance requirements: yield strength of 350-370 MPa, tensile strength ≥400 MPa, and elongation after fracture ≥14.5%. This ultra-high strength Al-Mg-Si-Cu aluminum alloy material possesses both ultra-high strength and good plasticity, significantly superior to existing 6xxx series aluminum alloy sheets for automobiles. This ultra-high strength Al-Mg-Si-Cu aluminum alloy material can be used in automobile sheet manufacturing, is easy to roll and deform, and can meet the requirements of rolling forming processes under industrial conditions, filling the gap in existing ultra-high strength 6xxx series aluminum alloy sheets.

[0045] The preparation method of the above-mentioned ultra-high strength Al-Mg-Si-Cu aluminum alloy material includes the following steps:

[0046] S1 is a cold-rolled sheet obtained by alloy melting, homogenization treatment, hot rolling, annealing and cold rolling.

[0047] First, the raw materials used in alloy smelting include high-purity aluminum, high-purity magnesium, high-purity zinc, Al-Cu master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Fe master alloy and Al-Si master alloy, etc. Before smelting, the oxide scale on the surface of the raw materials is removed by a grinding wheel to reduce the introduction of too many impurities during the smelting process.

[0048] In the alloy smelting process, high-purity aluminum is added to a graphite crucible and placed in a pit-type resistance furnace for heating to melt. After the melt reaches 740–760°C, intermediate alloys such as Al-Cu, Al-Mn, Al-Ti, Al-Fe, and Al-Si are added and held at 760–780°C for 20–40 minutes. After the intermediate alloys have fully melted, the melt is cooled to 720–760°C, and high-purity magnesium and high-purity zinc are added and held for 20–30 minutes. Then, a refining agent is added and held at 720–740°C for 15–25 minutes. Next, a slag-removing agent is added and the melt is held at 730–750°C for 10–20 minutes before slag removal. Finally, a refining agent is added and the melt is held for 2–6 minutes before casting to obtain an ingot. The refining agent is sodium fluoride ionic refining agent, added at 0.40–0.60 wt.% of the melt mass; the refining agent is Al-Ti-B refining agent, for example, Al-5 wt.%Ti-1 wt.%B refining agent, added at 0.01–0.06 wt.% of the melt mass. The casting temperature at tapping is 720–740℃.

[0049] The homogenization process involves melting the alloy to obtain an ingot and holding it at 540–560°C for 20–30 hours. During this process, the ingot is placed in a medium-temperature furnace and heated from room temperature to 540–560°C at a heating rate of 0.5–1.0°C / min, and held at that temperature for 20–30 hours. After the holding period, the ingot is slowly cooled to room temperature along with the furnace.

[0050] Hot rolling involves heating the homogenized ingot to 540–560°C and holding it at that temperature for 1.5–3 hours, followed by multiple rolling passes. Between every three passes, the ingot is held at 540–560°C for 15–30 minutes, controlling the total deformation to be 85%–94%. Before hot rolling, the homogenized ingot is milled to improve surface quality, and then heated in a medium-temperature furnace. The rolled sheet is then cooled to room temperature in air, ultimately yielding a hot-rolled plate with a thickness of 5–6 mm.

[0051] Annealing involves heating the hot-rolled plate obtained from hot rolling to 380–420°C at a heating rate of 0.5–1.0°C / min and holding it at that temperature for 30–60 minutes.

[0052] Cold rolling is a process that involves multiple rolling passes with a total reduction of ≥80%, ultimately yielding a cold-rolled sheet with a thickness of 1–1.2 mm.

[0053] S2, after solution treatment, the cold-rolled sheet is water quenched; the solution treatment involves placing the cold-rolled sheet in a salt bath furnace and holding it at 560-570℃ for 1.0-2.0h.

[0054] S3 involves peak aging treatment of water-quenched cold-rolled sheets to obtain high-strength Al-Mg-Si-Cu aluminum alloy materials.

[0055] The water-quenched cold-rolled sheet is quickly transferred (transfer time less than 1 min) to an aging furnace for peak aging treatment. Peak aging treatment adopts single-stage aging or double-stage aging. Among them, single-stage aging is aging at 160-185℃ for 3-6 hours; double-stage aging is first pre-aging at 60-90℃ for 12-24 hours, and then aging at 160-185℃ for 1-3 hours.

[0056] This invention comprehensively designs the main alloying elements such as Mg, Si, and Cu, as well as trace elements, and optimizes the preparation process. While refining the grain size, it achieves the synergistic precipitation of multiple strengthening phases (β phase and its metastable phase and Q phase and its metastable phase), ultimately obtaining an ultra-high strength Al-Mg-Si-Cu aluminum alloy material. This breaks through the strength limitations of commercially available 6xxx series aluminum alloy sheets and also has good plasticity.

[0057] The following section provides a further introduction to the ultra-high strength Al-Mg-Si-Cu aluminum alloy material and its preparation method of the present invention, using specific examples.

[0058] The raw materials used in the following examples are: high-purity aluminum (99.99 wt.%), pure magnesium (99.99 wt.%), pure zinc (99.99 wt.%), Al-50 wt.% Cu master alloy, Al-10 wt.% Mn master alloy, Al-10 wt.% Ti master alloy, Al-20 wt.% Fe master alloy, and Al-20 wt.% Si master alloy. Al-5 wt.% Ti-1 wt.% B was selected as a grain refiner. A grinding wheel was used to remove the oxide scale from the surfaces of the high-purity aluminum and pure magnesium raw materials to reduce the introduction of excessive impurities during the smelting process. The composition of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in this embodiment is shown in Table 1. The raw materials were obtained as ingots through alloy smelting, followed by homogenization treatment in a medium-temperature furnace. Specifically, the ingots were placed in the medium-temperature furnace, and then heated from room temperature to 560°C at a rate of 0.5°C / min, followed by holding at that temperature for 24 hours. After holding, the ingots were slowly cooled to room temperature with the furnace. The homogenized ingots underwent milling to improve surface quality. During hot rolling, a medium-temperature furnace was used for heating, first raising the temperature to 560°C and holding for 2 hours before multi-pass rolling. The total deformation during hot rolling was ≥ 85% of the rolling process involves holding the sheet at 560℃ for 15 minutes between each pass. The rolled sheet is then cooled to room temperature in air to obtain a hot-rolled sheet with a thickness of 5 mm. The hot-rolled sheet is then annealed at 400℃ for 1 hour at a heating rate of 0.5℃ / min. The annealed sheet is then cold-rolled in multiple passes with a total reduction of 80% to obtain a cold-rolled sheet with a thickness of 1 mm. The cold-rolled sheet is then solution-treated in a salt bath furnace at 570℃ for 1.5 hours, followed by water quenching, and then transferred to an aging furnace within 1 minute.

[0059] Peak aging process can be any one of the following two:

[0060] Single-stage aging: aging at 160~185℃ for 3~16h.

[0061] Two-stage aging: Pre-aging at 80℃ for 12 hours, followed by aging at 160~185℃ for 1~3 hours.

[0062] When testing the alloy properties, tensile specimens were prepared in accordance with GB / T 228.1-2021, and the elongation after interruption was tested according to the method of this procedure.

[0063] Table 1. Composition (wt.%) of the ultra-high strength Al-Mg-Si-Cu aluminum alloy materials in the examples.

[0064] Alloy Mg Si Cu Zn Fe Mn Ti Al 1# 1.2 1.0 0.7 0.1 0.4 0.2 0.07 Balance 2# 1.5 1.0 0.7 0.1 0.4 0.2 0.07 Balance 3# 1.5 1.2 1.5 0.1 0.4 0.2 0.07 Balance 4# 1.8 1.3 0.7 0.1 0.4 0.2 0.07 Balance 5# 2.0 1.5 0.7 0.1 0.4 0.2 0.07 Balance

[0065] Example 1

[0066] The preparation method of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in this embodiment is as follows: The raw material with the composition of alloy 1# is prepared into a 1mm thick cold-rolled plate after alloy casting, homogenization treatment, hot rolling, annealing treatment and cold rolling; the cold-rolled plate is placed in a salt bath furnace for solution treatment, and after quenching, the plate is placed in an aging furnace for peak aging treatment within 1 minute. After aging at 170℃ for 12 hours, the ultra-high strength Al-Mg-Si-Cu aluminum alloy material is obtained. Tensile samples are taken along the rolling direction and the mechanical properties of the alloy are measured. The peak aging treatment process and alloy properties are shown in Table 2.

[0067] Example 2

[0068] The preparation method of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in this embodiment is as follows: The raw material with the composition of alloy 1# is prepared into a 1mm thick cold-rolled plate after alloy casting, homogenization treatment, hot rolling, annealing treatment and cold rolling; the cold-rolled plate is placed in a salt bath furnace for solution treatment, and after quenching, the plate is placed in an aging furnace for peak aging treatment within 1 minute. After aging at 185℃ for 3 hours, the ultra-high strength Al-Mg-Si-Cu aluminum alloy material is obtained. Tensile samples are taken along the rolling direction and the mechanical properties of the alloy are measured. The peak aging treatment process and alloy properties are shown in Table 2.

[0069] Example 3

[0070] The preparation method of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in this embodiment is as follows: The raw material with the composition of alloy 2# is prepared into a 1mm thick cold-rolled plate after alloy casting, homogenization treatment, hot rolling, annealing treatment and cold rolling; the cold-rolled plate is placed in a salt bath furnace for solution treatment, and after quenching, the plate is placed in an aging furnace for peak aging treatment within 1 minute. After aging at 170℃ for 12 hours, the ultra-high strength Al-Mg-Si-Cu aluminum alloy material is obtained. Tensile samples are taken along the rolling direction and the mechanical properties of the alloy are measured. The peak aging treatment process and alloy properties are shown in Table 2.

[0071] Example 4

[0072] The preparation method of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in this embodiment is as follows: The raw material with the composition of alloy 3# is prepared into a 1mm thick cold-rolled plate after alloy casting, homogenization treatment, hot rolling, annealing treatment and cold rolling; the cold-rolled plate is placed in a salt bath furnace for solution treatment, and after quenching, the plate is placed in an aging furnace for peak aging treatment within 1 minute. After aging at 170℃ for 10h, the ultra-high strength Al-Mg-Si-Cu aluminum alloy material is obtained. Tensile samples are taken along the rolling direction and the mechanical properties of the alloy are measured. The peak aging treatment process and alloy properties are shown in Table 2.

[0073] Example 5

[0074] The preparation method of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in this embodiment is as follows: The raw material with the composition of alloy 4# is prepared into a 1mm thick cold-rolled plate after alloy casting, homogenization treatment, hot rolling, annealing treatment and cold rolling; the cold-rolled plate is placed in a salt bath furnace for solution treatment, and after quenching, the plate is placed in an aging furnace for peak aging treatment within 1 minute. After aging at 170℃ for 12 hours, the ultra-high strength Al-Mg-Si-Cu aluminum alloy material is obtained. Tensile samples are taken along the rolling direction and the mechanical properties of the alloy are measured. The peak aging treatment process and alloy properties are shown in Table 2.

[0075] Example 6

[0076] The preparation method of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in this embodiment is as follows: The raw material with the composition of alloy 5# is prepared into a 1mm thick cold-rolled plate after alloy casting, homogenization treatment, hot rolling, annealing treatment and cold rolling; the cold-rolled plate is placed in a salt bath furnace for solution treatment, and after quenching, the plate is placed in an aging furnace for peak aging treatment within 1 minute. After aging at 170℃ for 12 hours, the ultra-high strength Al-Mg-Si-Cu aluminum alloy material is obtained. Tensile samples are taken along the rolling direction and the mechanical properties of the alloy are measured. The peak aging treatment process and alloy properties are shown in Table 2.

[0077] Example 7

[0078] The preparation method of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in this embodiment is as follows: The raw material with the composition of alloy 2# is prepared into a 1mm thick cold-rolled plate after alloy casting, homogenization treatment, hot rolling, annealing treatment and cold rolling; the cold-rolled plate is placed in a salt bath furnace for solution treatment, and after quenching, the plate is placed in an aging furnace for peak aging treatment within 1 minute. After pre-aging at 80℃ for 12h, it is then subjected to a second-stage aging treatment at 170℃ / 3h to obtain the ultra-high strength Al-Mg-Si-Cu aluminum alloy material. Tensile samples are taken along the rolling direction and the mechanical properties of the alloy are measured. The peak aging treatment process and alloy properties are shown in Table 2.

[0079] Example 8

[0080] The preparation method of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in this embodiment is as follows: The raw material with the composition of alloy 2# is prepared into a 1mm thick cold-rolled plate after alloy casting, homogenization treatment, hot rolling, annealing treatment and cold rolling; the cold-rolled plate is placed in a salt bath furnace for solution treatment, and after quenching, the plate is placed in an aging furnace for peak aging treatment within 1 minute. After pre-aging at 80℃ for 12h, it is then subjected to a second-stage aging treatment at 185℃ / 1h to obtain the ultra-high strength Al-Mg-Si-Cu aluminum alloy material. Tensile samples are taken along the rolling direction and the mechanical properties of the alloy are measured. The peak aging treatment process and alloy properties are shown in Table 2.

[0081] Example 9

[0082] The preparation method of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in this embodiment is as follows: The raw material with the composition of alloy 3# is prepared into a 1mm thick cold-rolled plate after alloy casting, homogenization treatment, hot rolling, annealing treatment and cold rolling; the cold-rolled plate is placed in a salt bath furnace for solution treatment, and after quenching, the plate is placed in an aging furnace for peak aging treatment within 1 minute. After pre-aging at 80℃ for 12h, it is then subjected to a second-stage aging treatment at 170℃ / 1h to obtain the ultra-high strength Al-Mg-Si-Cu aluminum alloy material. Tensile samples are taken along the rolling direction and the mechanical properties of the alloy are measured. The peak aging treatment process and alloy properties are shown in Table 2.

[0083] Table 2 Mechanical properties of ultra-high strength Al-Mg-Si-Cu aluminum alloys prepared in the examples under peak aging.

[0084]

[0085] As shown in Examples 1-9, the cold-rolled sheets prepared by this invention through alloy casting, homogenization treatment, hot rolling, annealing, and cold rolling, after solution treatment and peak aging, exhibit yield strengths as high as 350-371 MPa, tensile strengths as high as 400-418 MPa, and elongation after fracture of 14.6%-17.1%, far exceeding those of existing commercially available AA6111, AA6016, and AA6022 aluminum alloy sheets. Furthermore, the hot-rolled and cold-rolled alloy sheets obtained during the preparation process have excellent surface quality. Figure 2 As shown in Figures (a) and (b), the grain size distribution of the ultra-high strength Al-Mg-Si-Cu aluminum alloy material is small, with an average grain size of 23.5 μm. Combined with... Figure 3As shown in Example 1, the ultra-high strength Al-Mg-Si-Cu aluminum alloy material in its peak aging state exhibits typical strengthening phases, including the β phase and its metastable phase, and the Q phase and its metastable phase. These strengthening phases enable the material to overcome the strength limitations of commercially available 6xxx series aluminum alloy sheets. Therefore, the ultra-high strength Al-Mg-Si-Cu aluminum alloy material prepared by this invention possesses excellent strength and a good balance of plasticity.

[0086] In summary, this invention, by optimizing the content of elements such as Mg, Si, Cu, Fe, Mn, and Ti, refines the grain size while achieving the synergistic precipitation of multiple strengthening phases (β phase and its metastable phase, and Q phase and its metastable phase), thus designing an ultra-high strength Al-Mg-Si-Cu aluminum alloy composition with high potential for strong mechanical properties. After rolling and deformation, the alloy involved in this invention exhibits good surface quality and fine grain size, possessing both ultra-high strength and good plasticity. This invention has certain guiding significance for the development, processing, and application of ultra-high strength 6xxx series aluminum alloy automotive sheet materials.

[0087] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. An ultra-high strength Al-Mg-Si-Cu aluminum alloy material, characterized in that, It includes the following chemical components by mass percentage: Mg: 1.2–2.0 wt.%, Si: 1.0–1.5 wt.%, Cu: 0.5–1.5 wt.%, with the remainder being Al and unavoidable impurities.

2. The ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 1, characterized in that, It also includes the following chemical composition: Zn: 0.15–0.5 wt.%, Mn: 0.2–0.4 wt.%, Ti: 0.05–0.1 wt.%, Fe ≤ 0.5 wt.%.

3. The ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 2, characterized in that, Its performance meets the following requirements: yield strength of 350-370 MPa, tensile strength ≥400 MPa, and elongation after fracture ≥14.5%.

4. A method for preparing an ultra-high strength Al-Mg-Si-Cu aluminum alloy material as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1 is a cold-rolled sheet obtained by alloy melting, homogenization treatment, hot rolling, annealing and cold rolling. S2, cold-rolled sheet is solution treated and then water quenched; S3 involves peak aging treatment of water-quenched cold-rolled sheets to obtain high-strength Al-Mg-Si-Cu aluminum alloy materials.

5. The method for preparing ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 4, characterized in that, In step S1, the raw materials used for alloy smelting include high-purity aluminum, high-purity magnesium, high-purity zinc, Al-Cu master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Fe master alloy, and Al-Si master alloy.

6. The method for preparing ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 5, characterized in that, In the alloy smelting process, high-purity aluminum is added and heated to melt it. After the melt temperature reaches 740-760°C, an intermediate alloy is added and held at 760-780°C for 20-40 minutes. After the intermediate alloy melts, the melt temperature is lowered to 720-760°C, and then high-purity magnesium and high-purity zinc are added and held for 20-30 minutes. Then, a refining agent is added and held at 720-740°C for 15-25 minutes. Next, a slag-removing agent is added and held at 730-750°C for 10-20 minutes before slag removal. Finally, a refining agent is added and held for 2-6 minutes before casting to obtain an ingot.

7. The method for preparing ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 6, characterized in that, The refining agent is a sodium fluoride ionic refining agent, and its addition amount is 0.40 to 0.60 wt.% of the melt mass; the refining agent is an Al-Ti-B refining agent, and its addition amount is 0.01 to 0.06 wt.% of the melt mass.

8. The method for preparing ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 6, characterized in that, The casting temperature is 720–740℃.

9. The method for preparing ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 4, characterized in that, In step S1, the homogenization process involves melting the alloy to obtain an ingot and holding it at 540–560°C for 20–30 hours.

10. The method for preparing ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 4, characterized in that, In step S1, the hot rolling process involves heating the homogenized ingot to 540–560°C and holding it at that temperature for 1.5–3 hours before performing multiple rolling passes. Between each pass, the ingot is held at 540–560°C for 15–30 minutes, and the total deformation during hot rolling is controlled to be 85–94%.

11. The method for preparing ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 4, characterized in that, In step S1, the annealing process involves heating the hot-rolled plate obtained from the hot rolling process to 380-420°C at a heating rate of 0.5-1.0°C / min and holding it at that temperature for 30-60 minutes.

12. The method for preparing ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 4, characterized in that, In step S1, the cold rolling process employs multi-pass rolling with a total reduction of ≥80%.

13. The method for preparing ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 4, characterized in that, In step S2, the solution treatment involves placing the cold-rolled sheet in a salt bath furnace and holding it at 560–570°C for 1.0–2.0 hours.

14. The method for preparing ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 4, characterized in that, In step S3, the cold-rolled sheet is quickly transferred to an aging furnace after water quenching for peak aging treatment, with a transfer time of less than 1 minute.

15. The method for preparing ultra-high strength Al-Mg-Si-Cu aluminum alloy material according to claim 4, characterized in that, In step S3, the peak efficiency processing adopts single-level efficiency or two-level efficiency. The single-stage aging process involves aging at 160–185°C for 3–6 hours. The two-stage aging process involves first pre-aging at 60–90°C for 12–24 hours, and then aging at 160–185°C for 1–3 hours.

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