Aluminum alloy material and preparation method and application thereof

Abstract

The invention discloses an aluminum alloy material and a preparation method and application thereof, and relates to the technical field of aluminum alloy materials, and the aluminum alloy material comprises the following element components by mass percent: 5.5-6.5% of Zn; 2.8% to 3.2% of Mg; cu: 1.0%-1.3%; 0.12% to 0.18% of Zr; 0.08% to 0.12% of Sc; 0.02% to 0.04% of Ti; and Al: the balance. The preparation method of the aluminum alloy material comprises the steps of smelting, casting, homogenizing, multi-pass hot rolling, intermediate annealing, solution treatment, aging treatment and the like. The problems that an existing superplastic aluminum alloy is high in forming temperature and large in energy consumption, strength and plasticity after forming are difficult to consider at the same time, grain size control is unstable, and consequently the surface quality of a formed part is poor are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy materials, and in particular to an aluminum alloy with excellent superplastic forming ability and high mechanical properties and a preparation method thereof. Background Art

[0002] With the rapid development of industries such as aerospace, automobiles, and electronics, the demand for aluminum alloy components with complex shapes and excellent mechanical properties is growing. Traditional aluminum alloy forming processes, such as casting and forging, have many limitations when manufacturing complex-shaped components, such as low forming accuracy, low material utilization, and large subsequent processing volume. Superplastic forming technology is a forming method that makes the material have extremely high ductility under specific conditions, and can produce components with complex shapes and high precision. However, the superplastic forming temperature of traditional aluminum alloys is high (usually ≥500℃), the mechanical properties after forming are insufficient (such as tensile strength ≤600MPa), and the coarse grains can easily lead to forming defects. In existing technologies, rare earth elements are added to refine the grains, but the cost is high and the process is complicated; other solutions use a high zinc content design, which improves the strength but significantly reduces the ductility. The present invention achieves the unification of low-temperature (≤450°C) superplastic forming (elongation ≥800%) and high strength and toughness after forming (tensile strength ≥680MPa, elongation ≥10%) through component optimization and process coordinated regulation. Summary of the Invention

[0003] In response to the defects in the prior art, the purpose of the present invention is to provide a superplastic forming aluminum alloy material and a preparation method thereof, aiming to solve the problems of the existing superplastic aluminum alloy, such as high forming temperature, high energy consumption, difficulty in balancing strength and plasticity after forming, and unstable grain size control, which leads to poor surface quality of the formed parts.

[0004] In order to achieve the above-mentioned object, the superplastic forming aluminum alloy material proposed by the present invention comprises the following elemental components in percentage by mass:

[0005] Zn (zinc): 5.5% to 6.5%;

[0006] Mg (magnesium): 2.8% to 3.2%;

[0007] Cu (copper): 1.0% to 1.3%;

[0008] Zr (zirconium): 0.12% to 0.18%;

[0009] Sc (scandium): 0.08% to 0.12%;

[0010] Ti (titanium): 0.02% to 0.04%;

[0011] Fe (iron) + Si (silicon): ≤ 0.10%;

[0012] Al (aluminum): balance.

[0013] In the present invention's formulation, Zn can form a MgZn2 strengthening phase with Mg and reduce superplastic flow stress. When the zinc content in the present invention is less than 5.5%, insufficient solid solution strengthening may result. When the zinc content in the present invention is greater than 6.5%, coarse intermetallic compounds are likely to form, leading to a decrease in plasticity.

[0014] In the formulation of the present invention, Mg, on the one hand, synergistically enhances aging strengthening with Zn, and on the other hand, can improve the corrosion resistance of the alloy. In the present invention, when the Mg content is too high (>3.5%), it may lead to deterioration of hot workability, and when it is too low (<2.5%), insufficient aging strengthening may occur.

[0015] In the present invention's formulation, Cu serves two functions: first, it inhibits high-temperature grain boundary sliding cracking; second, it improves high-temperature stability. When the copper content exceeds 1.5%, excessive and coarse Al2Cu phases may form, significantly reducing the alloy's toughness and plasticity. When the copper content is less than 1.0%, insufficient grain boundary strength may result, leading to reduced mechanical properties.

[0016] In the present invention's formulation, Zr not only forms Al3Zr nanoparticles (≤50nm) with Al, pinning grain boundaries but also inhibiting recrystallization. Zr has a low solid solubility in Al (0.18% is the limit), and excessive Zr may form coarse particles, affecting alloy properties.

[0017] In the formulation of the present invention, Sc can cooperate with Zr to form Al3 (Sc, Zr) composite particles, refining the grains to 1-3 μm. However, Sc is expensive, and 0.08-0.12% can achieve the refining effect, which is the best cost-effectiveness.

[0018] In the present invention, Ti not only acts as a nucleating agent to refine the as-cast structure, but also assists the grain refining effect of Sc / Zr. If the Ti content in the present invention exceeds 0.05%, a TiAl3 brittle phase may be formed, affecting plasticity.

[0019] In the formulation of the present invention, Fe and Si are both impurity elements, and their content needs to be controlled below 0.10%. Excessive Fe / Si may form hard and brittle phases, and must be strictly limited to ensure formability.

[0020] The method for preparing a superplastic forming aluminum alloy proposed in the present invention mainly comprises the following steps:

[0021] S1. Prepare raw materials according to the recipe. The metal raw materials can be either elemental or master alloys, as long as the alloy composition obtained after smelting the added metal raw materials is within the above range. Preferably, the aluminum ingot is a high-purity industrial aluminum ingot with a purity of 99.9% or higher. Other metal raw materials can be high-purity industrial zinc ingots with a purity of 99.9% or higher, aluminum-magnesium master alloys, aluminum-copper master alloys, aluminum-zirconium master alloys, aluminum-scandium master alloys, or aluminum-titanium master alloys.

[0022] S2. Under argon protection, the above metal raw materials are melted using a three-stage melting process.

[0023] in:

[0024] First-stage smelting: smelt aluminum ingot, aluminum-zirconium master alloy and aluminum-scandium master alloy in sequence at 745-755°C and keep them warm for 2 hours to ensure that high-melting-point elements Zr and Sc are fully dissolved and diffused first;

[0025] Secondary smelting: melting aluminum-copper master alloy and aluminum-titanium master alloy at 715-725℃, and coordinating with electromagnetic stirring at a frequency of 20-30Hz to improve the uniformity of Cu and Ti distribution;

[0026] Three-stage smelting: smelting elemental zinc and aluminum-magnesium master alloy at 675-685℃, adding them in the low temperature section to reduce the volatilization loss of elements and improve the yield.

[0027] The above-mentioned step-by-step cooling is used to decompose the intermediate alloy step by step, reducing energy consumption while ensuring that Al3(Sc,Zr) nanoparticles fully nucleate in the high-temperature section and elements such as Cu / Mg diffuse at the atomic level in the low-temperature section, reducing component segregation and inhibiting grain growth; argon is used to isolate oxygen and avoid alloy burning.

[0028] S3. Cast the aluminum alloy melt into a mold preheated to 260-280°C using a semi-continuous casting process at a casting speed of 60-80 mm / min to produce an aluminum alloy ingot. Preheating reduces the temperature difference between the mold and the melt, preventing surface cold shut caused by rapid cooling. It also allows moisture on the mold surface to evaporate, reducing the subsurface porosity of the ingot. Maintaining a casting speed of 60-80 mm / min ensures a uniform temperature gradient during the cooling process, reducing thermal stress, cracks, and porosity.

[0029] S4. Homogenization treatment: heat the obtained ingot to 460-480℃ and keep it for 8 hours, then air cool it; then heat the ingot to 290-310℃ and keep it for 24 hours, then furnace cool it to room temperature. Among them, the first-level homogenization treatment can dissolve the coarse Al3(Sc,Zr) non-equilibrium phase formed in the ingot due to rapid solidification, promote the uniform distribution of solute elements such as Mg, Sc, and Zr, eliminate cast segregation, and break the interdendritic component segregation and inhibit the coarsening of the primary phase under the premise of avoiding excessive grain growth through the first-level high-temperature short-time treatment. The diffusion rate of Sc and Zr atoms is accelerated under the first-level high-temperature treatment, providing pre-diffusion conditions for subsequent low-temperature treatment and activating the diffusion channel. The second-level homogenization treatment can regulate the nucleation of nanophase, induce the uniform nucleation of Al3(Sc,Zr,Ti) composite precipitate phase in the Sc / Zr supersaturated solid solution (size ≤20nm), and use low-temperature and long-term treatment to control the distribution density of precipitate phase (≥1×10 22 / m 3 ), achieving the pinning effect strengthening effect, in which the precipitated phase interacts with the dislocations to form a stable dislocation wall structure, which inhibits the dynamic recrystallization during the subsequent hot working process.

[0030] S5: Multi-pass hot rolling: The ingot is hot rolled at 380-440°C, with a deformation of 10-18% per pass and a total deformation of 80-85%, ultimately resulting in a 2-4mm thick plate. This multi-pass hot rolling process repeatedly crushes and refines coarse grains, forming a fine, uniform, equiaxed grain structure. This fine-grained structure significantly improves the material's strength and toughness. Furthermore, by properly controlling the deformation and rolling temperature per pass, dynamic recrystallization can be effectively promoted, allowing grains to continuously renucleate and grow during deformation, further optimizing the grain structure and enhancing the material's superplasticity.

[0031] S6, intermediate annealing: keep the hot-rolled plate at 400-420℃ for 2 hours and then air-cool it to room temperature. Intermediate annealing is used to release the internal stress generated by rolling and prevent cracking during subsequent processing.

[0032] S7: Solution treatment: Heat the plate to 460-480°C, hold for 1 hour, and then quickly water quench to room temperature. Solution treatment allows elements such as Zn / Mg / Cu to fully dissolve into the aluminum matrix, preparing for subsequent aging strengthening. Rapid water quenching can "freeze" the solution state. Furthermore, the technical parameters for rapid water quenching are: the quenching medium is deionized water at 20-25°C, the quenching method is double-sided high-pressure spraying, the water flow rate is controlled at 2.5-3.5m / s, the water pressure is 0.3-0.5MPa, and the transfer time is less than 5 seconds. Deionized water can prevent impurities from adhering to the plate surface and causing corrosion. Water temperatures below 20°C can easily cause quenching deformation, while temperatures above 25°C can lead to insufficient cooling speed. A flow rate below 2m / s can lead to uneven cooling, while a flow rate above 4m / s can easily damage the plate. A pressure below 0.3MPa may result in a residual steam film, while a pressure above 0.5MPa may cause plate deformation. A transfer time of less than 5 seconds can prevent the solid solution elements (Zn / Mg) from precipitating in the air.

[0033] S8, aging treatment

[0034] Pre-aging: Keep the plate at 110-130°C for 6 hours and air-cool. Pre-aging in the present invention can, firstly, promote the uniform nucleation of the precipitate phase. Pre-aging at a lower temperature can form a high-density nanoscale precipitate phase core in the supersaturated solid solution, providing uniformly distributed nucleation sites for subsequent final aging. Secondly, it can inhibit the natural aging effect, control the precipitation process in advance, and improve the stability of material properties. Thirdly, pre-aging can reduce internal stress. The low-temperature insulation process can partially release the residual stress generated by the workpiece during solution treatment or cold working, reducing the risk of deformation during subsequent high-temperature treatment.

[0035] Final aging: keep the plate at 160-180℃ for 8 hours and air-cool. The final aging in the present invention can firstly regulate the size and distribution of the precipitate phase. Final aging at a higher temperature can promote the appropriate growth of the fine precipitate phase formed in the pre-aging stage, optimize its size and spatial distribution, and make the precipitate phase more evenly dispersed in the matrix. Second, it can improve the comprehensive mechanical properties of the material. Final aging significantly improves the strength, hardness and creep resistance of the material by adjusting the volume fraction and interface structure of the precipitate phase. Third, it can stabilize the organization and performance. The high temperature section of the final aging can eliminate the metastable structure remaining in the pre-aging stage, so that the precipitate phase and the matrix reach a thermodynamic equilibrium state, thereby enhancing the performance stability of the material under high temperature or long-term use.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] Low-temperature superplastic forming capability: Sc / Zr / Ti synergistically refines grains to 1-3 μm, combined with Cu / Mg to inhibit high-temperature grain boundary sliding, achieving superplastic elongation ≥ 800% at 440-450°C, significantly reducing energy consumption and equipment loss;

[0038] High strength and toughness matching: After final aging, the size of the precipitated phase [MgZn2, Al3(Sc, Zr)] is ≤20nm, the volume fraction is ≥30%, the tensile strength is ≥680MPa, and the elongation is ≥10%. The comprehensive performance is better than that of traditional high-zinc aluminum alloys;

[0039] Cost optimization: The Sc content is only 0.08-0.12%, which reduces the cost by more than 40% compared with the rare earth addition solution. The three-stage smelting process increases the element yield to more than 98%, reducing raw material waste.

[0040] Organization uniformity: Multi-stage homogenization treatment makes the composition segregation rate less than 3% and the precipitated phase density ≥1×10 22 / m 3 , the standard deviation of grain size after hot rolling is ≤0.5μm, avoiding forming defects. DETAILED DESCRIPTION

[0041] The specific embodiments of the present invention will be further described below in conjunction with examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0042] Example 1

[0043] This embodiment 1 discloses an aluminum alloy material for superplastic forming, comprising the following elemental components in percentage by mass:

[0044] Zn: 5.5%, Mg: 2.8%, Cu: 1.0%, Zr: 0.12%, Sc: 0.08%, Ti: 0.02%, Fe+Si: ≤ 0.10%, and Al: balance.

[0045] Based on the above-mentioned formula composition of the superplastic forming aluminum alloy, this embodiment 1 proposes a preparation method of the superplastic forming aluminum alloy, comprising the following steps:

[0046] S1. Prepare materials. The raw materials include: industrial aluminum ingots and industrial zinc ingots with a purity of 99.9%, aluminum-magnesium master alloys, aluminum-copper master alloys, aluminum-zirconium master alloys, aluminum-scandium master alloys, and aluminum-titanium master alloys.

[0047] S2. melting the metal raw materials under argon protection;

[0048] First stage smelting: smelt aluminum ingot, aluminum-zirconium master alloy and aluminum-scandium master alloy in sequence at 745℃ and keep warm for 2h;

[0049] Secondary smelting: melting aluminum-copper master alloy and aluminum-titanium master alloy at 715°C with electromagnetic stirring at a frequency of 20-30 Hz;

[0050] Three-stage smelting: smelting elemental zinc and aluminum-magnesium master alloy at 675℃.

[0051] S3. Casting the aluminum alloy melt into a mold preheated to 260° C. using a semi-continuous casting process at a casting speed of 60 mm / min to obtain an aluminum alloy ingot.

[0052] S4, homogenization treatment, heating the obtained ingot to 460 ° C. and keeping it at this temperature for 8 hours, followed by air cooling; then heating the ingot to 290 ° C. and keeping it at this temperature for 24 hours, and then cooling it to room temperature;

[0053] S5. Multi-pass hot rolling: hot rolling the ingot at 380-440°C, with a deformation of 10-18% per pass and a total deformation of 80%, to obtain a 3mm thick plate. The specific hot rolling passes, deformation and rolling temperature are shown in Table 1 below:

[0054] Table 1

[0055]

[0056]

[0057] S6: Intermediate annealing: keep the hot-rolled plate at 400°C for 2 hours and air-cool it to room temperature.

[0058] S7: Solution treatment: Heat the plate to 460°C for 1 hour, then rapidly water quench to room temperature. The technical parameters for rapid water quenching are: quenching medium: deionized water at 21±1°C, quenching method: double-sided high-pressure spraying, water flow rate controlled at 2.5m / s, water pressure at 0.3MPa, and transfer time of 4 seconds.

[0059] S8, aging treatment

[0060] Pre-aging: keep the plate at 110℃ for 6 hours and air cool.

[0061] Final aging: keep the plate at 160℃ for 8 hours and air cool.

[0062] Example 2

[0063] This embodiment 2 discloses an aluminum alloy material for superplastic forming, comprising the following elemental components in percentage by mass:

[0064] Zn: 6.0%, Mg: 2.0%, Cu: 1.15%, Zr: 0.15%, Sc: 0.10%, Ti: 0.03%, Fe+Si: ≤ 0.10%, and Al: balance.

[0065] Based on the above-mentioned formula composition of the superplastic forming aluminum alloy, this embodiment 2 proposes a preparation method of the superplastic forming aluminum alloy, comprising the following steps:

[0066] S1. Prepare materials. The raw materials include: industrial aluminum ingots and industrial zinc ingots with a purity of 99.9%, aluminum-magnesium master alloys, aluminum-copper master alloys, aluminum-zirconium master alloys, aluminum-scandium master alloys, and aluminum-titanium master alloys.

[0067] S2. melting the metal raw materials under argon protection;

[0068] First stage smelting: smelt aluminum ingot, aluminum-zirconium master alloy and aluminum-scandium master alloy in sequence at 750℃ and keep warm for 2h;

[0069] Secondary smelting: melting aluminum-copper master alloy and aluminum-titanium master alloy at 720°C with electromagnetic stirring at 30Hz;

[0070] Three-stage smelting: smelting elemental zinc and aluminum-magnesium master alloy at 680℃.

[0071] S3. Casting the aluminum alloy melt into a mold preheated to 270° C. using a semi-continuous casting process at a casting speed of 70 mm / min to obtain an aluminum alloy ingot.

[0072] S4, homogenization treatment, heating the obtained ingot to 470 ° C. and keeping it at this temperature for 8 hours, followed by air cooling; then heating the ingot to 300 ° C. and keeping it at this temperature for 24 hours, and then cooling it to room temperature;

[0073] S5. Multi-pass hot rolling: hot rolling the ingot at 380-440°C, with a deformation of 10-18% per pass and a total deformation of 82%, to obtain a 3mm thick plate. The specific hot rolling passes, deformation and rolling temperature are shown in Table 2 below:

[0074] Table 2

[0075] path Rolling temperature / ℃ Single pass deformation / % Cumulative deformation / % 1 435±2 18 18 2 425±2 16 34 3 415±2 14 48 4 405±2 12 60 5 395±2 12 72 6 385±2 10 82

[0076] S6, intermediate annealing, keeping the hot-rolled plate at 410°C for 2 hours and air-cooling to room temperature.

[0077] S7: Solution treatment: Heat the plate to 470°C for 1 hour, then rapidly water quench to room temperature. The technical parameters for rapid water quenching are: quenching medium: deionized water at 23±1°C, quenching method: double-sided high-pressure spraying, water flow rate controlled at 3.0m / s, water pressure at 0.4MPa, and transfer time of 4 seconds.

[0078] S8, aging treatment

[0079] Pre-aging: Keep the plate at 120℃ for 6 hours and air cool.

[0080] Final aging: keep the plate at 170℃ for 8 hours and air cool.

[0081] Example 3

[0082] This embodiment 3 discloses an aluminum alloy material for superplastic forming, comprising the following elemental components in percentage by mass:

[0083] Zn: 6.5%, Mg: 3.2%, Cu: 1.3%, Zr: 0.18%, Sc: 0.12%, Ti: 0.04%, Fe+Si: ≤ 0.10%, and Al: balance.

[0084] Based on the above-mentioned formula composition of the superplastic forming aluminum alloy, this embodiment 3 proposes a preparation method of the superplastic forming aluminum alloy, comprising the following steps:

[0085] S1. Prepare materials. The raw materials include: industrial aluminum ingots and industrial zinc ingots with a purity of 99.9%, aluminum-magnesium master alloys, aluminum-copper master alloys, aluminum-zirconium master alloys, aluminum-scandium master alloys, and aluminum-titanium master alloys.

[0086] S2. melting the metal raw materials under argon protection;

[0087] First stage smelting: smelt aluminum ingot, aluminum-zirconium master alloy and aluminum-scandium master alloy in sequence at 755℃ and keep warm for 2h;

[0088] Secondary smelting: melting aluminum-copper master alloy and aluminum-titanium master alloy at 725°C with electromagnetic stirring at a frequency of 20-30 Hz;

[0089] Three-stage smelting: smelting elemental zinc and aluminum-magnesium master alloy at 685℃.

[0090] S3. Casting the aluminum alloy melt into a mold preheated to 280° C. using a semi-continuous casting process at a casting speed of 80 mm / min to obtain an aluminum alloy ingot.

[0091] S4, homogenization treatment, heating the obtained ingot to 480 ° C. and keeping it at this temperature for 8 hours, followed by air cooling; then heating the ingot to 310 ° C. and keeping it at this temperature for 24 hours, and then cooling it to room temperature;

[0092] S5. Multi-pass hot rolling: hot rolling the ingot at 380-440°C, with a deformation of 10-18% per pass and a total deformation of 85%, to obtain a 3mm thick plate. The specific hot rolling passes, deformation and rolling temperature are shown in Table 3 below:

[0093] Table 3

[0094] path Rolling temperature / ℃ Single pass deformation / % Cumulative deformation / % 1 435±2 18 18 2 425±2 16 34 3 415±2 15 49 4 405±2 14 63 5 395±2 12 75 6 385±2 10 85

[0095] S6, intermediate annealing, keeping the hot-rolled plate at 420°C for 2 hours and air-cooling to room temperature.

[0096] S7: Solution treatment: Heat the plate to 480°C for 1 hour, then rapidly water quench to room temperature. The technical parameters for rapid water quenching are: quenching medium: deionized water at 24±1°C, quenching method: double-sided high-pressure spraying, water flow rate controlled at 3.5m / s, water pressure of 0.5MPa, and transfer time of 4 seconds.

[0097] S8, aging treatment

[0098] Pre-aging: keep the plate at 130℃ for 6 hours and air cool.

[0099] Final aging: keep the plate at 180℃ for 8 hours and air cool.

[0100] Example 4

[0101] Based on the aluminum alloy materials of Examples 1-3, this Example 4 discloses a superplastic forming process with the following technical parameters: process temperature 440-450°C, strain rate 2×10 -4 s -1 The air forming pressure is 2.0MPa, and after forming, it is directly water-cooled and aged (160℃×16h).

[0102] Comparative Example 1 (Traditional 7075 aluminum alloy)

[0103] Composition: Zn: 5.6%, Mg: 2.5%, Cu: 1.6%, Fe+Si: 0.15%, no Sc / Zr / Ti.

[0104] Process: Single-stage melting (720℃), conventional rolling, T6 aging.

[0105] Comparative Example 2 (Excess Sc / Zr)

[0106] Composition: Sc: 0.20%, Zr: 0.25%, and the rest is the same as in Example 2.

[0107] Process: Same as Example 2.

[0108] Comparative Example 3 (High Zn and Low Mg)

[0109] Composition: Zn: 7.0%, Mg: 2.0%, the rest is the same as Example 1

[0110] Process: Same as Example 1.

[0111] Comparative Example 4 (Simplified Homogenization Process)

[0112] Ingredients: Same as Example 1.

[0113] Process: Only one-stage homogenization (460° C.×8 h) is performed without the second-stage low-temperature treatment. The rest is the same as in Example 1.

[0114] Test example

[0115] The items or properties described in Table 4 below were tested for Examples 1-3 and Comparative Examples 1-4. The test method was as follows:

[0116] 1. Superplastic tensile properties: refer to GB / T 24172-2009 "Determination of tensile properties of metallic superplastic materials";

[0117] 2. Mechanical properties test: refer to GB / T 4338 "High temperature tensile test method for metallic materials";

[0118] 3. Microstructure analysis: Scanning electron microscope (SEM), transmission electron microscope (TEM) and other instruments are used to observe and analyze the microstructure.

[0119] Table 4:

[0120]

[0121]

[0122] By analyzing the test data in Table 4, we can conclude that:

[0123] The superplastic temperature (440-450°C) of the example samples is 50-60°C lower than that of the conventional 7075 aluminum alloy (500°C in comparative example 1), and the superplastic forming temperature is reduced by 10%-12%, thus achieving low-temperature and efficient forming.

[0124] The elongation of the examples (800-820%) was significantly higher than that of comparative example 1 (650%), and the superplastic elongation increased by 23%-26%. In particular, in comparative example 2 (excess Sc / Zr), the elongation dropped sharply to 560%, verifying the optimized ratio of 0.08-0.12% Sc and 0.12-0.18% Zr of the present invention.

[0125] The tensile strength of the samples in the examples (Examples 1-3) was ≥680 MPa, a 26% improvement over the conventional 7075 aluminum alloy (540 MPa in Comparative Example 1). The examples also maintained good ductility with an elongation ≥10%. While Comparative Example 3 (high Zn, low Mg) exhibited high tensile strength, its elongation was only 6%, demonstrating the critical role of Zn (5.5%-6.5%) and Mg (2.8%-3.2%) in ductility.

[0126] The addition of Sc / Zr / Ti composites refines the grain size to 1.5±0.3μm (SEM observation), which is 153% higher than the 3.8μm grains in comparative example 4 (simplified homogenization). The Al3(Sc,Zr) precipitation phase density reaches 1.2×10 22 / m 3(TEM statistics), compared with 8×10 21 / m 3 Increased by 50%.

[0127] The three-stage smelting process reduces the element segregation rate to ≤2.8% (EDS scanning), which is 63% lower than the 7.5% in the single-stage treatment of Comparative Example 4. The two-stage homogenization process reduces the standard deviation of the precipitate size distribution to ≤3nm, ensuring the uniformity of the pinning effect.

[0128] The Sc dosage of 0.08-0.12% is 40-50% less than the conventional rare earth solution (0.15-0.25%). The three-stage smelting element yield is 98.2% (measured in Example 2), which is 3-6 percentage points higher than the traditional two-stage smelting (92-95%).

[0129] The superplastic forming temperature of 440°C matches the temperature tolerance of conventional die steel (≤450°C), which extends the life of the equipment. The direct aging process after forming (Example 4) saves the heat treatment process and shortens the production cycle.

[0130] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An aluminum alloy material, characterized in that: Contains the following elemental composition by mass percentage: Zn: 5.5%~6.5%; Mg: 2.8% to 3.2%; Cu: 1.0%~1.3%; Zr：0.12％～0.18％； Sc: 0.08%~0.12%; Ti: 0.02%~0.04%; Al: margin.

2. The aluminum alloy material according to claim 1, characterized in that The steel sheet contains the following element compositions in percentage by mass: Zn: 5.5%, Mg: 2.8%, Cu: 1.0%, Zr: 0.12%, Sc: 0.08%, Ti: 0.02%, and Al: the balance.

3. The aluminum alloy material according to claim 1, characterized in that The steel sheet contains the following element compositions in percentage by mass: Zn: 6.0%, Mg: 2.0%, Cu: 1.15%, Zr: 0.15%, Sc: 0.10%, Ti: 0.03%, and Al: the balance.

4. The aluminum alloy material according to claim 1, characterized in that The steel sheet contains the following element compositions in mass percentage: Zn: 6.5%, Mg: 3.2%, Cu: 1.3%, Zr: 0.18%, Sc: 0.12%, Ti: 0.04%, and Al: the balance.

5. A method for preparing the aluminum alloy material according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Prepare materials; S2. Melting the metal raw materials at a melting temperature of 675-755°C; S3, casting the aluminum alloy melt into a mold preheated to 260-280° C. using a semi-continuous casting process at a casting speed of 60-80 mm / min to obtain an aluminum alloy ingot; S4, homogenization treatment: heating the obtained ingot to 460-480°C for 8 hours, followed by air cooling; then heating the ingot to 290-310°C for 24 hours, and furnace cooling to room temperature; S5, multi-pass hot rolling, hot rolling the ingot at 380-440°C, with a deformation of 10-18% per pass and a total deformation of 80-85%, to finally obtain a 2-4 mm thick plate; S6, intermediate annealing, keeping the hot-rolled plate at 400-420°C for 2 hours, and air-cooling to room temperature; S7, solution treatment, heating the plate to 460-480℃ for 1 hour, and then quickly quenching it to room temperature; S8, aging treatment: Pre-aging: keep the plate at 110-130℃ for 6 hours, then air cool; Final aging: keep the plate at 160-180℃ for 8 hours and air cool.

6. The method for preparing the aluminum alloy material according to claim 5, wherein: The metal raw materials include: high-purity industrial aluminum ingots of 99.9% and above, high-purity industrial zinc ingots, aluminum-magnesium master alloys, aluminum-copper master alloys, aluminum-zirconium master alloys, aluminum-scandium master alloys, and aluminum-titanium master alloys.

7. The method for preparing the aluminum alloy material according to claim 6, wherein: The smelting comprises: First stage smelting: smelt aluminum ingot, aluminum-zirconium master alloy and aluminum-scandium master alloy in sequence at 745-755℃ and keep warm for 2h; Secondary smelting: melting aluminum-copper master alloy and aluminum-titanium master alloy at 715-725℃, with electromagnetic stirring at a frequency of 20-30Hz; Three-stage smelting: smelting elemental zinc and aluminum-magnesium master alloy at 675-685℃.

8. The method for preparing the aluminum alloy material according to claim 7, characterized in that: The smelting is carried out under the protection of an argon environment.

9. The method for preparing the aluminum alloy material according to claim 5, characterized in that: The rapid water quenching is as follows: the quenching medium is deionized water at 20-25°C, the quenching method is double-sided high-pressure spraying, the water flow rate is controlled at 2.5-3.5m / s, the water pressure is 0.3-0.5MPa, and the transfer time is less than 5 seconds.

10. Use of the aluminum alloy material according to any one of claims 1 to 4 in superplastic forming, characterized in that: The superplastic forming process is as follows: process temperature 440-450°C, strain rate 2×10 -4 s -1 The air forming pressure is 2.0 MPa, and the steel is directly water-cooled and aged after forming. The aging temperature is 160°C and the time is 16 hours.

Images