7000 series aluminum alloy and preparation method and application thereof

Abstract

The invention discloses 7000 series aluminum alloy and a preparation method and application thereof, and relates to the technical field of aluminum alloy. The aluminum alloy comprises Al and the following components in percentage by mass: 6%-7% of Zn; 2.5%-4% of Mg; cu: 0.2%-0.7%; 0.05% to 0.2% of Mn; less than or equal to 0.05% of Cr; ti < = 0.1%; zr < = 0.1%; less than or equal to 0.15% of Si; fe is less than or equal to 0.15%. The aluminum alloy has high strength, high corrosion resistance and excellent anodic oxidation performance, and is suitable for the field of 3C electronic products or automobiles. The invention further provides a preparation method and application of the aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, specifically to a 7000 series aluminum alloy, its preparation method, and its application. Background Technology

[0002] Aluminum alloys possess significant advantages such as lightweight, high strength, excellent thermal conductivity, and superior processing and forming properties, making them widely used in the manufacture of structural components. 7000 series aluminum alloys (such as 7075 and 7050) exhibit ultra-high strength and low density. Their excellent specific strength and comprehensive mechanical properties make them widely used in aerospace, automotive, and high-end sporting goods industries. In recent years, their outstanding mechanical properties and high structural reliability have led to rapid expansion into the 3C electronics field, making them an ideal choice for high-performance load-bearing structural components such as laptop casings and smartphone frames.

[0003] However, to achieve ultra-high strength and hardness, 7000 aluminum alloys typically require high levels of Zn and Cu. While this enhances the heat treatment strengthening effect, it also significantly reduces the material's corrosion resistance, especially in systems with high Zn and Cu content. Specifically, this manifests as increased stress corrosion sensitivity and exacerbated intergranular corrosion, severely impacting the surface finish of subsequent anodizing processes, including film uniformity, colorability, and decorative properties, making it difficult to meet the high appearance and stability requirements of 3C electronic products.

[0004] While high Cu content can promote the formation of stable strengthening phases and enhance the properties of alloys after heat treatment, the Al-Cu phase formed at high temperatures during extrusion has a high melting point and is prone to creating hard and brittle regions during the cooling stage. This increases the risk of hot cracking and die wear, significantly reducing production efficiency and increasing the difficulty of extrusion molding. During the anodizing stage, Zn promotes enhanced local electrochemical activity and, together with microscopic defects (such as precipitated phases), induces selective dissolution, leading to uncontrolled oxide film thickness uniformity, decreased film integrity, and ultimately deterioration of corrosion resistance.

[0005] Therefore, it is necessary to develop 7000 series alloys with better overall performance to overcome the limitations of existing materials in terms of strength and corrosion resistance, so as to better meet the practical application needs of high-performance structural materials. Summary of the Invention

[0006] This invention provides a 7000 series aluminum alloy that combines high strength, high corrosion resistance and excellent anodizing performance. It is suitable for the casings and accessories of 3C electronic products, and can also be used in the field of lightweight automotive components.

[0007] This invention also provides a method for preparing the 7000 series aluminum alloy.

[0008] The present invention also provides applications of the 7000 series aluminum alloy.

[0009] Specifically, embodiments of the present invention relate to a 7000 series aluminum alloy, comprising Al and the following components by mass percentage:

[0010] Zn: 6%-7%;

[0011] Mg: 2.5%-4%;

[0012] Cu: 0.2%-0.7%;

[0013] Mn: 0.05%-0.2%;

[0014] Cr ≤ 0.05%;

[0015] Ti≤0.1%;

[0016] Zr≤0.1%;

[0017] Si≤0.15%;

[0018] Fe ≤ 0.15%.

[0019] According to a first aspect of the present invention, a 7000 series aluminum alloy has at least the following beneficial effects:

[0020] In 7000 series aluminum alloys, Zn, Mg, and Cu are the three core elements that construct the alloy's strength system, jointly determining the alloy's mechanical properties through their respective contributions and synergistic effects. Zn combines with Mg to form the metastable precipitate phase η' (which eventually transforms into the η phase MgZn2). These nanoscale precipitates are the alloy's primary strengthening source, significantly hindering dislocation movement. Mg is an indispensable component of the η' / η phase, and its content directly affects the volume fraction and precipitation density of the strengthening phase, ensuring the formation of a high-density precipitate network. Cu plays multiple roles: it not only provides significant solid solution strengthening but also participates in the formation of Cu-containing strengthening phases (such as the S phase or dissolves into the η phase to form a quaternary phase). More importantly, it significantly improves the thermal stability of the η phase, inhibits its coarsening, and maintains strength under high-temperature or over-aging conditions.

[0021] There is a strong synergistic strengthening effect between Zn and Mg, and their ratio is crucial, as it determines the kinetics and density of η' phase precipitation. An inappropriate ratio can lead to low efficiency or the formation of harmful phases. Zn and Cu, on the other hand, have a relationship of both competitive solid solution and synergistic strengthening. Cu dissolving into the η phase can greatly improve its resistance to coarsening, stabilize high strength, and inhibit the formation of harmful T phases.

[0022] When developing ultra-high yield strength 7000 series aluminum alloys, Zn, Mg, and Cu require precise proportioning and synergistic design: Zn, as the strength foundation, provides the core material basis for forming the high-density strengthening phase η' / η(MgZn2); Mg, as a synergistic element, maximizes the volume fraction and density of the precipitated phase by optimizing the Zn / Mg ratio, forming an intragranular precipitation network that supports high strength, while simultaneously controlling grain boundary precipitation to suppress the formation of wide precipitate-free zones. Cu has a solid solution strengthening effect and, by forming a Cuη-containing phase with higher thermal stability, suppresses phase coarsening during aging or service, improving aging stability and stress corrosion resistance, enabling the alloy to possess extremely high yield strength under T6 or T77 heat treatment.

[0023] Excessive Zn, Mg, and Cu content can lead to a series of problems: high Zn / Mg content tends to accumulate at grain boundaries, forming electrochemically active η phases, which are prone to intergranular corrosion and stress cracking in humid environments; high Cu content causes CuO inclusions in the anodic oxide film, resulting in uneven coloring (dark spots, streaks) and decreased corrosion resistance; coarse η phases or iron-containing phases can also cause appearance defects such as "snowflake patterns" on the oxide film. Simultaneously, the brittle phases enriched at grain boundaries significantly reduce fracture toughness (KIC < 25 MPa·m). 1 / 2 The product's resistance to drop impacts is weakened, making it prone to brittle fracture.

[0024] In 7000 series aluminum alloys, Fe and Si are considered harmful impurity elements, tending to form coarse, brittle AlFeSi intermetallic compound phases. These hard and brittle phases significantly impair the material's machinability (e.g., cutting performance) and toughness (e.g., fracture toughness), and can also cause porosity in the anodizing film, affecting the film's uniformity, gloss, and protective properties (e.g., corrosion resistance, wear resistance). Therefore, the Fe and Si content must be strictly controlled.

[0025] In summary, to meet the combined requirements of high strength, excellent anodizing quality, and good corrosion resistance for 3C electronic products, it is necessary to appropriately reduce the content of Zn, Mg, and Cu in the alloy design and achieve the optimal balance of overall performance through composition optimization design.

[0026] According to one embodiment of the present invention, the mass ratio of Zn to Mg is 1.80-2.62.

[0027] According to one embodiment of the present invention, the aluminum alloy comprises Al and the following components by mass percentage:

[0028] Zn: 6.2%-6.80%;

[0029] Mg: 2.6%-3.4%;

[0030] Cu: 0.22%-0.52%;

[0031] Mn: 0.05%-0.15%;

[0032] Cr ≤ 0.01%;

[0033] Ti: 0.005%-0.02%;

[0034] Zr: 0.005%-0.02%;

[0035] Si≤0.08%;

[0036] Fe ≤ 0.10%.

[0037] According to one embodiment of the present invention, the mass ratio of Zn to Mg is 2-2.6, for example, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5 or 2.6.

[0038] According to one embodiment of the present invention, the total mass percentage of Si and Fe is ≤0.15%, for example ≤0.1%.

[0039] According to one embodiment of the present invention, the 7000 series aluminum alloy has a yield strength ≥590MPa and a hardness ≥190Hv.

[0040] According to a preferred embodiment of the present invention, the 7000 series aluminum alloy has a yield strength ≥600MPa and a hardness ≥200Hv.

[0041] According to a preferred embodiment of the present invention, the 7000 series aluminum alloy has a yield strength ≥610MPa and a hardness ≥200Hv.

[0042] According to a preferred embodiment of the present invention, the 7000 series aluminum alloy has a yield strength ≥630MPa and a hardness ≥200Hv.

[0043] The second aspect of the present invention relates to a method for preparing the 7000 series aluminum alloy, comprising the following steps: mixing the components, followed by melting, casting, homogenization treatment, extrusion molding, online quenching, primary deformation treatment, artificial aging, and secondary deformation treatment to obtain the aluminum alloy.

[0044] The method for preparing the 7000 series aluminum alloy according to the second aspect of the present invention has at least the following beneficial effects:

[0045] A synergistic process involving online quenching, primary deformation treatment, artificial aging, and secondary deformation treatment significantly enhances the strength and hardness of 7000 series aluminum alloys through multi-level materials science control. Specifically, online quenching maximizes the preservation of supersaturated solid solubility of Zn, Mg, and Cu in the α-Al matrix, avoiding residual stress; primary deformation treatment introduces high-density dislocations, breaking down coarse phases while providing non-uniform nucleation sites for subsequent aging, thus strengthening the work hardening effect; in the artificial aging stage, a pre-stored dislocation network accelerates the dispersed precipitation of nanoscale η' phase, dominating precipitation strengthening; finally, deformation treatment allows the newly formed dislocations to interact with the existing η' phase, enhancing dislocation strengthening while inducing secondary precipitation through the stress field, forming a "dislocation-precipitate phase" interlocking structure and promoting the transformation of the η' phase into the stable η phase.

[0046] Therefore, through the above-mentioned multi-stage processing and strengthening mechanism, the present invention can still endow the alloy with excellent high strength performance while reducing the amount of main strengthening elements such as Zn and Cu, and at the same time meet the stringent requirements of 3C electronic products for anodized appearance quality and corrosion resistance, thus achieving the optimal balance between the mechanical properties and appearance quality of the alloy material.

[0047] According to one embodiment of the present invention, the melting temperature is 710-780°C, for example, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C or 780°C.

[0048] According to one embodiment of the present invention, the melting temperature is 730-780°C.

[0049] According to one embodiment of the present invention, the melting temperature is 750-780°C.

[0050] According to one embodiment of the present invention, the casting process employs air-lubricated casting.

[0051] According to one embodiment of the present invention, the casting temperature is 680-740°C, for example, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C or 740°C.

[0052] According to one embodiment of the present invention, the casting temperature is 700-740°C.

[0053] According to one embodiment of the present invention, the homogenization process includes the following steps: performing a first-stage homogenization process at 450-490°C, and then performing a second-stage homogenization process at 510-550°C. As an example, the temperature of the first-stage homogenization process is, for example, 450°C, 460°C, 470°C, 480°C, or 490°C, and the temperature of the second-stage homogenization process is, for example, 510°C, 520°C, 530°C, 540°C, or 550°C.

[0054] According to one embodiment of the present invention, the time for the first-stage homogenization process is 5-15 hours, for example, 5 hours, 8 hours, 10 hours, 12 hours or 15 hours.

[0055] According to one embodiment of the present invention, the time for the first-stage homogenization process is 5-10 hours.

[0056] According to one embodiment of the present invention, the time for the second-stage homogenization process is 10-20 hours, for example, 10 hours, 12 hours, 15 hours, 18 hours or 20 hours.

[0057] According to one embodiment of the present invention, the time for the second-stage homogenization process is 15-20 hours.

[0058] According to one embodiment of the present invention, in the extrusion molding, the heating temperature is 460-530°C, and the die temperature is 400-460°C. For example, the heating temperature is 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, or 530°C, and the die temperature is 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, or 460°C.

[0059] According to one embodiment of the present invention, the extrusion speed of the extrusion molding is 1 to 3 m / min, for example, 1 m / min, 2 m / min or 3 m / min.

[0060] According to one embodiment of the present invention, the extrusion ratio of the extrusion molding is 30-60, for example, 30, 40, 50 or 60.

[0061] According to one embodiment of the present invention, the online quenching is performed by immersion cooling.

[0062] According to one embodiment of the present invention, the primary deformation treatment employs a cold stretching process, with a stretching amount of 5%-20%, for example, 5%, 8%, 10%, 12%, 15%, 18%, or 20%.

[0063] According to one embodiment of the present invention, the primary deformation treatment adopts a cold stretching process, and the stretching amount is 10%-20%.

[0064] Preferably, the stretching amount of the primary deformation treatment is 12%-18%, and more preferably 15%-18%.

[0065] According to one embodiment of the present invention, the temperature for artificial aging is 100-160°C, for example, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or 160°C.

[0066] According to one embodiment of the present invention, the temperature of the artificial aging is 100-140°C, for example, 100-130°C.

[0067] According to one embodiment of the present invention, the artificial aging time is 6-30 hours, for example, 6 hours, 8 hours, 12 hours, 15 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours or 30 hours.

[0068] According to one embodiment of the present invention, the artificial aging time is 20 to 30 hours.

[0069] According to one embodiment of the present invention, the secondary deformation treatment adopts a cold stretching process, and the stretching amount is 2%-8%, for example, 2%, 3%, 4%, 5%, 6%, 7% or 8%.

[0070] According to one embodiment of the present invention, the secondary deformation treatment adopts a cold stretching process, and the stretching amount is 3%-8%.

[0071] Another aspect of the present invention provides a casing for a 3C electronic product, comprising an aluminum alloy as described in the first aspect embodiment above.

[0072] The third aspect of this invention relates to the application of the 7000 series aluminum alloy in the manufacture of 3C electronic products or automotive parts. Specifically, this alloy can be widely used in the appearance structural components of 3C electronic products, such as mobile phone casings, mid-frames, and tablet back panels, as well as automotive body frames and other components with high requirements for lightweighting and mechanical performance.

[0073] In this article, the term "room temperature" refers to 23±2℃.

[0074] In this article, the numerical ranges mentioned all include the endpoint values ​​and cover any subranges within that range, such as the ranges obtained by arbitrarily combining the specifically listed numerical values.

[0075] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0076] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0077] Figure 1 Metallographic images (scale bar 100 μm) of the aluminum alloys prepared in Examples 1-9 and Comparative Examples 1-2.

[0078] Figure 2 Digital photographs showing the anodizing effect of the aluminum alloys prepared in Examples 1-9 and Comparative Examples 1-2. Detailed Implementation

[0079] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0080] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0081] Example 1

[0082] This example provides a 7000 series aluminum alloy, the composition of which is shown in Table 1, and the preparation steps are as follows:

[0083] S1 is prepared according to the element ratio and then smelted at 750℃. After refining and degassing, the melt is obtained.

[0084] S2 After the above melt is allowed to stand for 1 hour, it is then processed in a converter. After passing through an online degassing and filtration system, alloy round casting rods are obtained by air-slip casting, wherein the casting temperature is controlled at 700℃.

[0085] S3 performs a two-stage homogenization treatment on the above alloy round casting rod: the first stage homogenization temperature is 470℃ and the holding time is 5h, and the second stage homogenization temperature is 530℃ and the holding time is 15h.

[0086] S4 involves extruding and online quenching of homogenized aluminum rods to obtain extruded materials. The heating temperature of the aluminum rod is controlled at 480℃, the die temperature is controlled at 440℃, the extrusion speed is controlled at 2m / min, the extrusion ratio is 52, the discharge port temperature is controlled at 500℃, and the online quenching process uses water immersion cooling.

[0087] S5. The extruded profile that has been quenched online is cut into fixed-length materials according to the specified length and then subjected to cold stretching deformation (one-time deformation treatment) through a stretching machine. The stretching amount is 5% of the material length.

[0088] S6. The material after the first deformation treatment is artificially aged at 140℃ for 22 hours.

[0089] S7. After artificial aging, the material is cold-stretched again through a stretching machine (secondary deformation treatment), with a stretching amount of 3% of the total length of the material, to obtain 7000 series aluminum alloy.

[0090] Table 1

[0091]

[0092]

[0093] Note: Trace amounts of unavoidable impurities that may be introduced into the raw materials are not listed in the table, and the same applies below.

[0094] Example 2

[0095] This example provides a 7000 series aluminum alloy, the composition of which is shown in Table 1, and the preparation steps are as follows:

[0096] S1 is prepared according to the element ratio and then smelted at 750℃. After refining and degassing, the melt is obtained.

[0097] S2 After the above melt is allowed to stand for 1 hour, it is then processed in a converter. After passing through an online degassing and filtration system, alloy round casting rods are obtained by air-slip casting, wherein the casting temperature is controlled at 700℃.

[0098] S3 performs a two-stage homogenization treatment on the above alloy round casting rod: the first stage homogenization temperature is 470℃ and the holding time is 5h, and the second stage homogenization temperature is 530℃ and the holding time is 15h.

[0099] S4 involves extruding and online quenching of homogenized aluminum rods to obtain extruded materials. The heating temperature of the aluminum rod is controlled at 480℃, the die temperature is controlled at 440℃, the extrusion speed is controlled at 2m / min, the extrusion ratio is 52, the discharge port temperature is controlled at 500℃, and the online quenching process uses water immersion cooling.

[0100] S5. The extruded profile that has been quenched online is cut into fixed-length materials according to the specified length and then subjected to cold stretching deformation (one-time deformation treatment) through a stretching machine. The stretching amount is 5% of the material length.

[0101] S6. The material after the first deformation treatment is artificially aged at 140℃ for 22 hours.

[0102] S7. After artificial aging, the material is cold-stretched again through a stretching machine (secondary deformation treatment), with a stretching amount of 8% of the total length of the material, to obtain 7000 series aluminum alloy.

[0103] Example 3

[0104] This example provides a 7000 series aluminum alloy, the composition of which is shown in Table 1, and the preparation steps are as follows:

[0105] S1 is prepared according to the element ratio and then smelted at 750℃. After refining and degassing, the melt is obtained.

[0106] S2 After the above melt is allowed to stand for 1 hour, it is then processed in a converter. After passing through an online degassing and filtration system, alloy round casting rods are obtained by air-slip casting, wherein the casting temperature is controlled at 700℃.

[0107] S3 performs a two-stage homogenization treatment on the above alloy round casting rod: the first stage homogenization temperature is 470℃ and the holding time is 5h, and the second stage homogenization temperature is 530℃ and the holding time is 15h.

[0108] S4 involves extruding and online quenching of homogenized aluminum rods to obtain extruded materials. The heating temperature of the aluminum rod is controlled at 480℃, the die temperature is controlled at 440℃, the extrusion speed is controlled at 2m / min, the extrusion ratio is 52, the discharge port temperature is controlled at 500℃, and the online quenching process uses water immersion cooling.

[0109] S5. The extruded profiles that have been quenched online are cut into fixed-length materials according to the specified length, and then cold-stretched and deformed by a stretching machine, and cold-worked according to 5% of the length of the fixed-length material.

[0110] S6. The material after the first deformation treatment is artificially aged at 120℃ for 28 hours.

[0111] S7. After artificial aging, the material is cold-stretched again through a stretching machine, with a stretching amount of 8% of the total length of the material, to obtain 7000 series aluminum alloy.

[0112] Example 4

[0113] This example provides a 7000 series aluminum alloy, the composition of which is shown in Table 1, and the preparation steps are as follows:

[0114] S1 mixes the above components and melts them at 750°C. After refining and degassing, a melt is obtained.

[0115] S2 After the above melt is allowed to stand for 1 hour, it is then processed in a converter. After passing through an online degassing and filtration system, alloy round casting rods are obtained by air-slip casting, wherein the casting temperature is controlled at 700℃.

[0116] S3 homogenizes the above alloy round casting rods according to a two-stage homogenization process: the first stage homogenization temperature is 470℃ and the holding time is 5h; the second stage homogenization temperature is 530℃ and the holding time is 15h.

[0117] S4 involves extruding and online quenching of homogenized aluminum rods to obtain extruded materials. The heating temperature of the aluminum rod is controlled at 480℃, the die temperature is controlled at 440℃, the extrusion speed is controlled at 2m / min, the extrusion ratio is 52, the discharge port temperature is controlled at 500℃, and the online quenching process uses water immersion cooling.

[0118] S5. The extruded profile that has been quenched online is cut into fixed-length materials according to the specified length and then cold-stretched and deformed (one-time deformation treatment) by a stretching machine. The stretching amount is 15% of the material length.

[0119] S6. The material after the first deformation treatment is artificially aged at 130℃ for 26 hours.

[0120] S7. After artificial aging, the material is cold-stretched again through a stretching machine (secondary deformation treatment), with the stretching amount being 5% of the total length of the material, to obtain 7000 series aluminum alloy.

[0121] Example 5

[0122] This example provides a 7000 series aluminum alloy, the composition of which is shown in Table 1, and the preparation steps are as follows:

[0123] S1 is prepared according to the element ratio and then smelted at 750℃. After refining and degassing, the melt is obtained.

[0124] S2 After the above melt is allowed to stand for 1 hour, it is then processed in a converter. After passing through an online degassing and filtration system, alloy round casting rods are obtained by air-slip casting, wherein the casting temperature is controlled at 700℃.

[0125] S3 performs a two-stage homogenization treatment on the above alloy round casting rod: the first stage homogenization temperature is 470℃ and the holding time is 5h, and the second stage homogenization temperature is 530℃ and the holding time is 15h.

[0126] S4 involves extruding and online quenching of homogenized aluminum rods to obtain extruded materials. The heating temperature of the aluminum rod is controlled at 480℃, the die temperature is controlled at 440℃, the extrusion speed is controlled at 2m / min, the extrusion ratio is 52, the discharge port temperature is controlled at 500℃, and the online quenching process uses water immersion cooling.

[0127] S5. The extruded profile that has been quenched online is cut into fixed-length materials according to the specified length and then cold-stretched and deformed (one-time deformation treatment) by a stretching machine. The stretching amount is 18% of the material length.

[0128] S6. The material after the first deformation treatment is artificially aged at 130℃ for 26 hours.

[0129] S7. After artificial aging, the material is cold-stretched again through a stretching machine (secondary deformation treatment), with a stretching amount of 3% of the total length of the material, to obtain 7000 series aluminum alloy.

[0130] Example 6

[0131] This example provides a 7000 series aluminum alloy, the composition of which is shown in Table 1, and the preparation steps are as follows:

[0132] S1 is prepared according to the element ratio and then smelted at 750℃. After refining and degassing, the melt is obtained.

[0133] S2 After the above melt is allowed to stand for 1 hour, it is then processed in a converter. After passing through an online degassing and filtration system, alloy round casting rods are obtained by air-slip casting, wherein the casting temperature is controlled at 700℃.

[0134] S3 performs a two-stage homogenization treatment on the above alloy round casting rod: the first stage homogenization temperature is 470℃ and the holding time is 5h, and the second stage homogenization temperature is 530℃ and the holding time is 15h.

[0135] S4 involves extruding and online quenching of homogenized aluminum rods to obtain extruded materials. The heating temperature of the aluminum rod is controlled at 480℃, the die temperature is controlled at 440℃, the extrusion speed is controlled at 2m / min, the extrusion ratio is 52, the discharge port temperature is controlled at 500℃, and the online quenching process uses water immersion cooling.

[0136] S5. The extruded profile that has been quenched online is cut into fixed-length materials according to the specified length and then cold-stretched and deformed (one-time deformation treatment) by a stretching machine. The stretching amount is 18% of the material length.

[0137] S6. The material after the first deformation treatment is artificially aged at 100℃ for 30 hours.

[0138] S7. After artificial aging, the material is cold-stretched again through a stretching machine (secondary deformation treatment), with the stretching amount being 5% of the total length of the material, to obtain 7000 series aluminum alloy.

[0139] Example 7

[0140] This example provides a 7000 series aluminum alloy, the composition of which is shown in Table 1, and the preparation steps are as follows:

[0141] S1 is prepared according to the element ratio and then smelted at 750℃. After refining and degassing, the melt is obtained.

[0142] S2 After the above melt is allowed to stand for 1 hour, it is then processed in a converter. After passing through an online degassing and filtration system, alloy round casting rods are obtained by air-slip casting, wherein the casting temperature is controlled at 700℃.

[0143] S3 performs a two-stage homogenization treatment on the above alloy round casting rod: the first stage homogenization temperature is 470℃ and the holding time is 5h, and the second stage homogenization temperature is 530℃ and the holding time is 15h.

[0144] S4 involves extruding and online quenching of homogenized aluminum rods to obtain extruded materials. The heating temperature of the aluminum rod is controlled at 480℃, the die temperature is controlled at 440℃, the extrusion speed is controlled at 2m / min, the extrusion ratio is 52, the discharge port temperature is controlled at 500℃, and the online quenching process uses water immersion cooling.

[0145] S5 will artificially age the extruded profiles that have undergone online quenching at 150°C for 15 hours to obtain 7000 series aluminum alloy.

[0146] Example 8

[0147] This example provides a 7000 series aluminum alloy, the composition of which is shown in Table 1, and the preparation steps are as follows:

[0148] S1 is prepared according to the element ratio and then smelted at 750℃. After refining and degassing, the melt is obtained.

[0149] S2 After the above melt is allowed to stand for 1 hour, it is then processed in a converter. After passing through an online degassing and filtration system, alloy round casting rods are obtained by air-slip casting, wherein the casting temperature is controlled at 700℃.

[0150] S3 performs a two-stage homogenization treatment on the above alloy round casting rod: the first stage homogenization temperature is 470℃ and the holding time is 5h, and the second stage homogenization temperature is 530℃ and the holding time is 15h.

[0151] S4 involves extruding and online quenching of homogenized aluminum rods to obtain extruded materials. The heating temperature of the aluminum rod is controlled at 480℃, the die temperature is controlled at 440℃, the extrusion speed is controlled at 2m / min, the extrusion ratio is 52, the discharge port temperature is controlled at 500℃, and the online quenching process uses water immersion cooling.

[0152] S5. The extruded profile that has been quenched online is cut into fixed-length materials according to the specified length and then cold-stretched and deformed by a stretching machine, with the stretching amount being 18% of the material length.

[0153] S6. The deformed material is artificially aged at 100°C for 24 hours to obtain 7000 series aluminum alloy.

[0154] Example 9

[0155] This example provides a 7000 series aluminum alloy, the composition of which is shown in Table 1, and the preparation steps are as follows:

[0156] S1 is prepared according to the element ratio and then smelted at 750℃. After refining and degassing, the melt is obtained.

[0157] S2 After the above melt is allowed to stand for 1 hour, it is then processed in a converter. After passing through an online degassing and filtration system, alloy round casting rods are obtained by air-slip casting, wherein the casting temperature is controlled at 700℃.

[0158] S3 performs a two-stage homogenization treatment on the above alloy round casting rod: the first stage homogenization temperature is 470℃ and the holding time is 5h, and the second stage homogenization temperature is 530℃ and the holding time is 15h.

[0159] S4 involves extruding and online quenching of homogenized aluminum rods to obtain extruded materials. The heating temperature of the aluminum rod is controlled at 480℃, the die temperature is controlled at 440℃, the extrusion speed is controlled at 2m / min, the extrusion ratio is 52, the discharge port temperature is controlled at 500℃, and the online quenching process uses water immersion cooling.

[0160] S5. The extruded profiles that have been quenched online are cut into fixed lengths according to the specified lengths and then artificially aged at 150°C for 15 hours.

[0161] S6. After artificial aging, the material is cold-stretched by a stretching machine, with a stretching amount of 7% of the total length of the material, to obtain 7000 series aluminum alloy.

[0162] Comparative Example 1

[0163] An aluminum alloy comprising the following components by weight percentage:

[0164] Zn: 5.63%;

[0165] Mg: 2.74%;

[0166] Cu: 1.77%;

[0167] Mn: 0.15%;

[0168] Cr: 0.18%;

[0169] Ti: 0.01%;

[0170] Zr: 0.02%;

[0171] Fe: 0.12%;

[0172] Si: 0.08%;

[0173] The remaining material is Al.

[0174] The preparation steps of aluminum alloy are as follows:

[0175] S1 is prepared according to the element ratio and then smelted at 750℃. After refining and degassing, the melt is obtained.

[0176] S2 After the above melt is allowed to stand for 1 hour, it is then processed in a converter. After passing through an online degassing and filtration system, alloy round casting rods are obtained by air-slip casting, wherein the casting temperature is controlled at 700℃.

[0177] S3 performs a two-stage homogenization treatment on the above alloy round casting rod: the first stage homogenization temperature is 470℃ and the holding time is 5h, and the second stage homogenization temperature is 530℃ and the holding time is 15h.

[0178] S4 involves extruding and online quenching of homogenized aluminum rods to obtain extruded materials. The heating temperature of the aluminum rod is controlled at 480℃, the die temperature is controlled at 440℃, the extrusion speed is controlled at 2m / min, the extrusion ratio is 52, the discharge port temperature is controlled at 500℃, and the online quenching process uses water immersion cooling.

[0179] S5. The extruded profile that has been quenched online is artificially aged at 160°C for 8 hours to obtain the above-mentioned aluminum alloy.

[0180] Comparative Example 2

[0181] An aluminum alloy comprising the following components by weight percentage:

[0182] Zn content is 7.80%;

[0183] Mg content was 2.43%.

[0184] Cu content was 1.28%.

[0185] Mn: 0.05%;

[0186] Cr: 0.002%;

[0187] Ti: 0.005%;

[0188] Zr: 0.006%;

[0189] Fe: 0.08%;

[0190] Si: 0.06%;

[0191] The remaining material is Al.

[0192] The preparation steps of aluminum alloy are as follows:

[0193] S1 is prepared according to the element ratio and then smelted at 750℃. After refining and degassing, the melt is obtained.

[0194] S2 After the above melt is allowed to stand for 1 hour, it is then processed in a converter. After passing through an online degassing and filtration system, alloy round casting rods are obtained by air-slip casting, wherein the casting temperature is controlled at 700℃.

[0195] S3 performs a two-stage homogenization treatment on the above alloy round casting rod: the first stage homogenization temperature is 470℃ and the holding time is 5h, and the second stage homogenization temperature is 530℃ and the holding time is 15h.

[0196] S4 involves extruding and online quenching of homogenized aluminum rods to obtain extruded materials. The heating temperature of the aluminum rod is controlled at 480℃, the die temperature is controlled at 440℃, the extrusion speed is controlled at 2m / min, the extrusion ratio is 52, the discharge port temperature is controlled at 500℃, and the online quenching process uses water immersion cooling.

[0197] S5. The extruded profile that has been quenched online is subjected to a two-stage aging treatment: the first stage aging is carried out at 100℃ for 10 hours, and the second stage aging is carried out at 175℃ for 22 hours to obtain the above-mentioned aluminum alloy.

[0198] Performance testing:

[0199] Metallographic characterization was performed on the aluminum alloy samples prepared in Examples 1-9 and Comparative Examples 1-2, and the results are as follows: Figure 1 As shown in the figure. Figures (a) to (i) correspond to the grain structures of Examples 1 to 9, respectively, and (j) to (k) correspond to the grain structures of Examples 1 to 2, respectively. From... Figure 1 It can be seen that the alloys prepared in Examples 1 to 9 all exhibit a uniformly distributed recrystallized equiaxed crystal structure with regular grain morphology and uniform size. This indicates that the alloy composition and processing heat treatment conditions effectively promote uniform grain growth and obtain a stable microstructure. In contrast, the alloy samples prepared in Comparative Examples 1 and 2 show obvious inhomogeneity in grain structure, with large differences in grain size distribution and coarse grains in local areas, indicating that their composition or process parameters are not conducive to controlled recrystallization of grains.

[0200] Figure 2 These are digital photographs of the anodizing effects of the aluminum alloys prepared in Examples 1-9 and Comparative Examples 1-2 of this invention, wherein... Figure 2 In the examples (a) to (i), the terms correspond to Examples 1 to 9, respectively. Figure 2 In this context, (j) to (k) correspond to proportions 1 to 2, respectively. From... Figure 2 As can be seen, the extruded materials prepared in Examples 1-6 have a bright and clear surface after anodizing, with no appearance defects. The samples in Examples 7-9 have a normal surface gloss after anodizing, with no obvious appearance defects. The sample in Comparative Example 1 has a dull surface gloss, failing to meet the appearance requirements for 3C product casings. The sample in Comparative Example 2 has a dull surface gloss and obvious roughness and texture defects, also failing to meet the appearance requirements for 3C product casings.

[0201] The mechanical properties of the aluminum alloys prepared in Examples 1-9 and Comparative Examples 1-2 were tested, and the test results are shown in Table 2.

[0202] Tensile properties: The mechanical properties of the alloy were tested according to GB / T 228.1-2010 "Metallic materials, tensile testing—Part 1: Tensile testing at room temperature". Tensile specimens were sampled along the extrusion direction, with a size of 200*20mm, and machined into A50 specimens. The tensile test was conducted on a LEGEND 2382 universal testing machine, with an initial gauge length of 50mm and a tensile speed of 2mm / min.

[0203] Vickers hardness (Hv): Tested according to GB / T 4340.1-2024 "Metallic materials - Vickers hardness test - Part 1: Test method".

[0204] Table 2

[0205]

[0206] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A 7000 series aluminum alloy, characterized in that: Includes Al and the following components by mass percentage: Zn: 6%-7%; Mg: 2.5%-4%; Cu: 0.2%-0.7%; Mn: 0.05%-0.2%; Cr≤0.05％； Ti≤0.1%; Zr≤0.1％； Si≤0.15%; Fe ≤ 0.15%.

2. The 7000 series aluminum alloy according to claim 1, characterized in that: The mass ratio of Zn to Mg is 1.80-2.

62.

3. A 7000 series aluminum alloy according to claim 2, characterized in that: The aluminum alloy comprises Al and the following components by mass percentage: Zn: 6.2%-6.80%; Mg: 2.6%-3.4%; Cu: 0.22%-0.52%; Mn: 0.05%-0.15%; Cr≤0.01％； Ti: 0.005%-0.02%; Zr：0.005％-0.02％； Si≤0.08%; Fe ≤ 0.10%.

4. A 7000 series aluminum alloy according to claim 3, characterized in that: The mass ratio of Zn to Mg is 2-2.6; and / or the total mass percentage of Si and Fe is ≤0.15%.

5. A method for preparing a 7000 series aluminum alloy as described in any one of claims 1 to 4, characterized in that: Includes the following steps: The components are mixed and then subjected to melting, casting, homogenization, extrusion molding, online quenching, primary deformation treatment, artificial aging, and secondary deformation treatment to obtain the aluminum alloy.

6. The method according to claim 5, characterized in that: The melting temperature is 710-780℃; and / or the casting temperature is 680-740℃.

7. The method according to claim 5, characterized in that: The homogenization process includes the following steps: performing a first-stage homogenization process at 450-490℃, and then performing a second-stage homogenization process at 510-550℃. Optionally, the time for the first-stage homogenization process is 5-15 hours; Optionally, the second-stage homogenization process takes 10-20 hours.

8. The method according to claim 5, characterized in that: In the extrusion molding process, the heating temperature is 460-530℃, the die temperature is 400-460℃; and / or, the extrusion speed is 1-3 m / min; and / or, the extrusion ratio is 30-60.

9. The method according to claim 5, characterized in that: The primary deformation treatment employs a cold stretching process with a stretching amount of 5%-20%; and / or, the secondary deformation treatment employs a cold stretching process with a stretching amount of 2%-8%; and / or, the artificial aging temperature is 100-140℃; and / or, the artificial aging time is 6-30 hours.

10. The application of a 7000 series aluminum alloy as described in any one of claims 1 to 4 in the manufacture of 3C electronic products or automotive parts.

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