Method for producing high-strength 7xxx-series aluminum alloy coil stock for consumer electronics and applications

Abstract

The present application relates to the technical field of metal plastic working, in particular to a high-strength 7xxx series aluminum alloy coil profile for consumer electronic products and a preparation method and application thereof. The chemical composition of the aluminum alloy coil profile is as follows: Zn: 6.2-8.2%, Mg: 2.0-2.8%, Cu: 0.1-0.5%, Mn: 0.01-0.05%, Cr: 0.01-0.05%, Zr: 0.08-0.20%, Y: 0.10-0.25%, Si: ≤0.05%, Fe: ≤0.08%, and the rest is Al and inevitable impurities. The present application solves the problems of poor welding performance, large color difference on the anodized surface, insufficient brightness and low yield strength of the existing 7xxx series aluminum alloy by optimizing the alloy component ratio and cooperating with the customized whole-process process. The prepared material has excellent mechanical properties, the yield strength is more than 550 MPa, the welding performance is excellent, the surface after anodization is high in brightness and uniform, and the processing adaptability is good. The coil profile can be widely applied to appearance parts of consumer electronic products such as smart phones and smart wearable devices, and meets the needs of product lightness and high performance.

Description

Technical Field

[0001] This invention relates to the field of metal plastic processing technology, specifically to a high-strength 7xxx series aluminum alloy coil profile for consumer electronics products, its preparation method, and its application. Background Technology

[0002] As consumer electronics products rapidly develop towards thinner, lighter, and higher-performance designs, their exterior components not only need to meet the basic requirements of lightweight and aesthetics, but also face increasingly stringent standards regarding the mechanical strength, surface finish, and precision machining adaptability of materials. Among these, yield strength, as a core mechanical performance indicator, directly determines the deformation resistance and impact resistance of exterior components, and is crucial for ensuring the structural stability of high-end consumer electronics products.

[0003] Currently, the mainstream material for exterior components of consumer electronics products is 6xxx series aluminum alloy. This series of aluminum alloys uses magnesium and silicon as the main alloying elements, and achieves performance improvement by forming the Mg2Si strengthening phase. It has good processability and corrosion resistance, and the cost is controllable, so it is widely used in low- and mid-range consumer electronics products. However, due to its alloy composition and strengthening mechanism, the yield strength of 6xxx series aluminum alloys is generally low. Even after optimization treatment, its yield strength is still difficult to meet the stringent structural strength requirements of high-end consumer electronics products, becoming a major bottleneck restricting the performance upgrade of exterior components in high-end products.

[0004] 7xxx series aluminum alloys, with zinc and magnesium as the main strengthening elements, possess superior mechanical strength compared to 6xxx series aluminum alloys due to their excellent solid solution strengthening and precipitation strengthening effects. Theoretically, they can perfectly meet the high-strength requirements of high-end consumer electronics product exterior components, making them a highly promising alternative material in this field. However, 7xxx series aluminum alloys produced using conventional manufacturing processes have many technical defects, severely limiting their large-scale application in consumer electronics product exterior components: on the one hand, their weldability is poor, prone to problems such as weld hot cracking and reduced joint strength, making it difficult to meet the requirements of integrated processing of exterior components; on the other hand, their anodized surfaces are prone to large color differences and insufficient brightness, failing to meet the decorative requirements of consumer electronics product exterior components.

[0005] In addition, 7xxx series aluminum alloy coils produced by traditional manufacturing processes still suffer from poor compositional uniformity and insufficient microstructure refinement, resulting in significant room for improvement in yield strength. This makes it difficult to meet the core requirements of precision machining and dimensional stability for the appearance components of consumer electronics products. In the prior art, such as the production method of 7xxx series aluminum alloy narrow strip for consumer electronics products disclosed in CN119406960B, the alloy composition of the disclosed 7075 aluminum alloy is: Si content 0.08-0.09%, Fe content 0.1-0.2%, Cu content 1.6-1.8%, Mn content 0.1-0.2%, Mg content 2.5-2.8%, Cr content 0.2-0.3%, Zn content 5.5-6%, Ti content 0.07-0.09%. After the aluminum alloy melt is processed by rapid cooling continuous casting, homogenization treatment, continuous expansion extrusion, residual heat rolling, coiling, cold rolling and intermediate annealing, the tensile strength of the product is 572MPa, the hardness Hv is 188, and the yield strength is only 503MPa. This still cannot fully meet the dual requirements of high strength and high surface quality for the appearance parts of high-end consumer electronics products.

[0006] In summary, current aluminum alloy materials used in the exterior components of consumer electronics products have significant technical shortcomings: 6xxx series aluminum alloys lack sufficient strength, while 7xxx series aluminum alloys suffer from poor weldability, unsatisfactory surface finish, and a need to improve yield strength. Furthermore, existing similar products (7xxx series aluminum alloy coil profiles used in consumer electronics) have not effectively addressed these issues. Therefore, developing a 7xxx series aluminum alloy coil profile with high yield strength, excellent anodized surface properties, and good processing adaptability has become a key issue in meeting the technical requirements of high-end consumer electronics product exterior components. Summary of the Invention

[0007] (a) Technical problems to be solved In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a high-strength 7xxx series aluminum alloy coil profile for consumer electronics products and its preparation method. The invention mainly improves the alloy strength, weldability and anodized surface quality by optimizing the alloy chemical composition ratio of 7xxx series aluminum alloy materials. On this basis, further optimization of process parameters is carried out to prepare 7xxx series aluminum alloy coil profiles with high yield strength and excellent anodized surface performance, which better meets the technical requirements of the appearance parts of consumer electronics products and fills the gap in the prior art.

[0008] (II) Technical Solution In a first aspect, the present invention provides a high-strength 7xxx series aluminum alloy coil profile for consumer electronics products, the chemical composition of which, by weight percentage, is: Zn: 6.2-8.2%, Mg: 2.0-2.8%, Cu: 0.1-0.5%, Mn: 0.01-0.05%, Cr: 0.01-0.05%, Zr: 0.08-0.20%, Y: 0.10-0.25%, Si: ≤0.05%, Fe: ≤0.08%, with the remainder being Al and unavoidable impurities.

[0009] Compared with the aluminum alloy product scheme of the prior patent application CN119406960B, the chemical composition of the high-strength 7xxx series aluminum alloy coil profile of the present invention has been adjusted as follows: the metal elements Y and Zr have been introduced, the content of Zn has been increased, and the content of metal elements such as Cu, Mn, Si, Fe, and Cr has been reduced.

[0010] In the high-strength 7xxx series aluminum alloy coil profile designed in this invention, the roles of each alloying element are explained as follows: Zr: It refines grain size and reduces the quenching sensitivity of the alloy, ensuring the strengthening effect of subsequent heat treatment processes; Y: Rare earth element Y can play a role in modification, refining and purification and alloying, effectively refining the alloy structure, reducing the porosity of the billet, while improving the strength, weldability and fatigue life of the alloy, and improving the surface quality of anodized. Zn and Mg: As core strengthening elements, they form strengthening phases such as MgZn2, which are the main source of high strength in alloys. This invention precisely controls the ratio of Zn to Mg to ensure the full precipitation and uniform distribution of the strengthening phase. Cu: can improve the strength, plasticity and stress corrosion resistance of alloys, and improve the processing performance defects of alloys with high Zn / Mg ratios; Mn and Cr: refine grains by generating dispersed phases, hinder dislocation migration, and improve the microstructure stability of the alloy; Si and Fe: As impurity elements, their content is strictly controlled to avoid the formation of brittle phases and coarse compounds, prevent the formation of banded structures after subsequent processing, and ensure the surface properties and processing compatibility of the alloy.

[0011] Secondly, the present invention provides a method for preparing high-strength 7xxx series aluminum alloy coil profiles for consumer electronics products, wherein alloy raw materials are prepared according to the chemical composition of the aforementioned high-strength 7xxx series aluminum alloy coil profiles, and the preparation method includes the following steps performed sequentially: (1) Horizontal casting process: During the casting process, 0.25-0.35wt% of granular refining agent is added in combination with argon gas for refining and degassing; online degassing and filtration purification are carried out when the melt is released; 0.12-0.20% of aluminum-titanium-carbon-boron refining agent is added to the flow channel for grain refinement; the casting speed is controlled at 400-600mm / min and the cooling water temperature is controlled at 20-35℃; (2) Homogenization process: The coiled rod prepared by the horizontal casting process is subjected to segmented homogenization process. The process parameters are: first, keep it at 450-460℃ for 4-8 hours, then raise the temperature to 470-482℃ and keep it for 10-16 hours; after the heat preservation is completed, cool it with the furnace to 210-230℃, and then remove it from the furnace and air cool it. The cooling rate is controlled to be ≤30℃ / h throughout the process. (3) Surface peeling process: The oxide scale is removed from the surface of the homogenized casting rod; (4) Hot rolling process: The stripped cast bar is rolled into a coil profile close to the target size by hot rolling process. The deformation ratio of hot rolling is 10-16. (5) Solution treatment process: The hot rolled coil is subjected to multi-stage solution treatment. The process parameters are: first, keep it at 445-455℃ for 110-130 min, then raise the temperature to 480-488℃ and keep it for 80-100 min; after the heat preservation is completed, the coil is quickly immersed in warm water at 40-60℃ for quenching treatment within 10 seconds. (6) Artificial aging process: The coil profile after solution quenching is subjected to segmented artificial aging treatment. The process parameters are: first, keep it at 115-125℃ for 12-21 hours, and then raise the temperature to 160-170℃ and keep it for 220-260 minutes.

[0012] According to a preferred embodiment of the present invention, the aluminum alloy melt is formed into a coiled rod with a diameter of 35-42 mm by a horizontal casting process; in the surface peeling process, the peeling depth is controlled to be 2-7 mm.

[0013] According to a preferred embodiment of the present invention, in the horizontal casting process, an online degassing box is used for degassing during melt release, and a tubular filter is used for online filtration and purification. The granular refining agent used in the horizontal casting process consists of a composite salt system of magnesium chloride, sodium chloride, and potassium chloride; the titanium-carbon-boron refining agent consists of Ti 2.0-10.0wt%, C 0.1-1.0wt%, B 0.1-1.0wt%, with the balance being Al and unavoidable impurities.

[0014] According to a preferred embodiment of the present invention, the amount of particle refining agent added during the casting process is 0.3%; the amount of titanium-carbon-boron refining agent added in the flow channel is 0.15wt%.

[0015] According to a preferred embodiment of the present invention, the process parameters for the homogenization process are as follows: first, heat at 455°C for 4-8 hours, then heat to 480°C and heat for 10-16 hours; after the heat treatment is completed, cool with the furnace to 230°C, and then remove from the furnace and air cool, with the cooling rate controlled at ≤30°C / h throughout the process.

[0016] According to a preferred embodiment of the present invention, in the hot rolling process, the thickness of the coil profile that is close to the target size is the target thickness H ± 0.02 mm, and its width is the target width ± 0.10 mm.

[0017] The target thickness H of aluminum alloy coil profiles for consumer electronics products is set according to the final finished product thickness requirements of downstream consumer electronics product appearance parts, with a conventional range of 0.8-3.0mm (to meet the requirements of subsequent cold rolling processes to reduce the finished product thickness to ≤0.5mm); the target width W is adapted to the specifications of consumer electronics product appearance parts, with a conventional range of 40-300mm, which can be flexibly adjusted according to actual product requirements.

[0018] Preferably, the hot rolling process includes: hot rolling a cast bar with a diameter of 35-42mm through 8-12 passes to obtain a (4-7)mm×(10-15)mm plate or a rod with a diameter of 10-12mm.

[0019] According to a preferred embodiment of the present invention, the process parameters of the solution treatment process are as follows: first, heat at 450°C for 120 minutes, then heat to 485°C and heat for 90 minutes; after the heat treatment is completed, the coil profile is immersed in warm water at 40-60°C for quenching treatment within 10 seconds.

[0020] According to a preferred embodiment of the present invention, the process parameters for the artificial aging process are as follows: first, heat at 120°C for 20 hours, then heat to 165°C and heat for 240 minutes.

[0021] In the horizontal casting process, by controlling the casting speed and cooling water temperature, the billet structure is made uniform and free of obvious defects. In the homogenization process, the segmented heat preservation mode can effectively eliminate casting stress, make alloy elements uniformly distributed, and reduce component segregation. In the surface peeling process, by controlling the peeling amount to a certain thickness, the oxide layer, defect layer and impurity enrichment layer on the surface of the cast rod can be effectively removed, ensuring the surface purity and flatness of the raw materials for subsequent processing, while ensuring the effective utilization rate of the raw materials.

[0022] In the hot continuous rolling process, large deformation (deformation ratio 10-16) refines the grains, forming a uniform rolled microstructure and improving the mechanical properties and processing adaptability of the alloy. The hot continuous rolling is a multi-pass continuous rolling process with intervals ranging from a few tenths of a second to several seconds between passes. Under the action of large deformation, the second-phase particles in the alloy material break down and become more uniformly distributed, significantly increasing the PSN nucleation sites and the DDRX ratio, while simultaneously refining the recrystallized grains.

[0023] In the solution treatment process, rapid quenching (immersing the coiled profile in warm water at 40-60°C for quenching within 10 seconds) is used to allow strengthening elements such as Zn, Mg, and Cu to fully dissolve into the Al matrix, forming a supersaturated solid solution, which provides conditions for subsequent aging strengthening.

[0024] The artificial aging process allows fine, dispersed strengthening phases (such as GP zones and η' phases) to precipitate in the supersaturated solid solution, significantly improving the alloy's strength while ensuring good plasticity and surface stability.

[0025] Thirdly, the present invention provides a high-strength 7xxx series aluminum alloy coil profile for consumer electronics products, which is prepared by any of the above-described methods.

[0026] Fourthly, the present invention relates to the application of the high-strength 7xxx series aluminum alloy coil profiles in the processing and manufacturing of exterior parts (covers, frames, etc.) for consumer electronic products such as smartphones, smart TVs, smart wearable devices, or tablet computers.

[0027] (III) Beneficial Effects The solution of the present invention has the following technical effects (I) Alloy composition optimization This invention achieves the following technical effects by precisely optimizing the chemical composition ratio of 7xxx series aluminum alloys, compared to existing 7xxx series aluminum alloys used in consumer electronics: by introducing Y and Zr elements, increasing Zn content, and reducing Cu, Mn, Si, Fe, and Cr content. 1. Significantly improved strengthening effect: The precise ratio of core strengthening elements Zn (6.2-8.2%) and Mg (2.0-2.8%) can fully form strengthening phases such as MgZn2, laying the foundation for the high strength of the alloy; at the same time, the introduction of Zr element effectively refines the grains, reduces the quenching sensitivity of the alloy, ensures the strengthening efficiency of subsequent heat treatment, and further enhances the strength potential of the alloy.

[0028] 2. Improvement of alloy structure and surface quality: The introduction of rare earth element Y plays a role in modification, refining and purification, effectively refining the alloy structure, reducing the porosity of the billet, and reducing structural defects; the content of impurity elements such as Si (≤0.05%) and Fe (≤0.08%) is strictly controlled to avoid the formation of brittle phases and coarse compounds, and to prevent the formation of banded structures in subsequent processing, thus providing a compositional basis for improving the surface quality of anodizing.

[0029] 3. Comprehensive performance enhancement: The synergistic effect of Y element with Zr, Cu, Mn, Cr and other elements not only improves the strength of the alloy, but also significantly improves the weldability and fatigue life of the alloy, solving the pain points of easy cracking and poor fatigue performance of traditional 7xxx series aluminum alloys; the precise control of Cu element (0.1-0.5%) improves the strength, plasticity and stress corrosion resistance, while improving the processing performance defects of alloys with high Zn / Mg ratio.

[0030] 4. Improved composition uniformity: The optimized composition ratio (especially the reduction of impurities and the content of some elements, and the introduction of refined element Y) reduces composition segregation during the casting process, providing compositional assurance for subsequent processing and performance stability.

[0031] (II) Preparation process of high-strength 7xxx series aluminum alloy coil profiles of the present invention This invention synergistically combines optimized alloy composition with customized end-to-end processes (horizontal casting, segmented homogenization, surface peeling, hot continuous rolling, and multi-stage solution aging) to achieve a deep match between composition, process, and performance. Compared to existing technologies, it produces the following comprehensive technical effects: 1. Significantly improved mechanical properties, especially yield strength: Through composition optimization and process synergy, the strengthening phases (GP zone, η' phase) in the alloy are finely dispersed and precipitated, while the grains are fully refined. The yield strength of the 7xxx series aluminum alloy coil profiles prepared in the end far exceeds that of existing similar products (comparative document yield strength 503MPa), meeting the stringent structural strength requirements of high-end consumer electronics product appearance components.

[0032] 2. Excellent surface performance of anodized materials: Optimized composition (low impurities, Y element modification) reduces the source of surface defects. Combined with full-process process control (grain refinement in horizontal casting, removal of defect layers by surface peeling, homogenization of microstructure in hot continuous rolling, and surface stability assurance through solution aging), the anodized coil profiles have no obvious color difference and good gloss, meeting the decorative requirements of exterior parts for consumer electronics products.

[0033] 3. Excellent processing adaptability and dimensional stability: The hot continuous rolling process (deformation ratio 10-16, multi-pass rolling) further refines the grains and forms a uniform rolling structure. Combined with the precise control of the target dimensions (thickness H±0.02mm, width W±0.10mm), the coil profile has good precision processing performance, is compatible with subsequent downstream processing processes such as cold rolling and finishing, and has small dimensional fluctuations and strong stability.

[0034] 4. High process stability and production feasibility: Segmented homogenization treatment effectively eliminates casting stress and ensures uniform distribution of alloying elements; rapid quenching (within 10 seconds) ensures that strengthening elements are fully dissolved into the Al matrix, guaranteeing the effect of aging strengthening; coordinated matching of parameters in each process reduces the defect rate in the production process, improves batch consistency of products, and is suitable for large-scale production.

[0035] 5. Balanced comprehensive performance: While improving yield strength and surface quality, it also takes into account the alloy's plasticity, weldability, fatigue life and stress corrosion resistance, which solves the technical contradiction of "difficulty in balancing high strength with machinability and surface quality" in existing 7xxx series aluminum alloys and fills the existing technological gap.

[0036] (III) Application of high-strength 7xxx series aluminum alloy coils The high-strength 7xxx series aluminum alloy coil profiles prepared by this invention are applied to the exterior parts (covers, frames, etc.) of consumer electronics products such as smartphones, smart TVs, smart wearable devices, and tablets, producing the following application-level technical effects: 1. Adapting to the demands for thinner, lighter, and higher-performance consumer electronics: The high strength (high yield strength) of the coil profiles effectively reduces the thickness of exterior components, enabling thinner and lighter designs while ensuring the components' resistance to deformation and impact, thus extending product lifespan. The excellent dimensional stability and precision machining adaptability allow for the fulfillment of complex shapes and high-precision dimensional requirements for exterior components. According to tests, the aluminum alloy coil profiles prepared by this invention have a yield strength greater than 550 MPa, a tensile strength exceeding 570 MPa, and a hardness (Hv) above 170, with a yield strength significantly higher than existing similar products.

[0037] 2. Enhance the appearance and competitiveness of consumer electronics products: The excellent anodized surface performance (no obvious color difference, high gloss and uniformity) can achieve diversified and high-quality appearance decoration effects, enhance the appearance and grade of products, differentiate them from existing products using 6xxx series or conventional 7xxx series aluminum alloys, and enhance the market competitiveness of products.

[0038] 3. Ensure the reliability of appearance components: The alloy has good welding performance, which can ensure that appearance components are not easily damaged, deformed or cracked during long-term use, daily bumps and knocks and assembly, thereby improving the overall quality and user experience of consumer electronics products.

[0039] The technical solution of this invention broadens the application scenarios of 7xxx series aluminum alloys, solves the application bottlenecks of traditional 7xxx series aluminum alloys in the appearance parts of consumer electronics products due to poor surface, difficult processing, and insufficient strength, promotes the replacement of 6xxx series aluminum alloys with 7xxx series aluminum alloys, and applies them to the field of appearance parts of high-end consumer electronics products, thereby achieving material upgrades and product performance upgrades. Attached Figure Description

[0040] Figure 1 SEM images of the sample prepared in Example 1 of this invention under different backscattered electron (BSE) modes. Detailed Implementation

[0041] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Example 1 This embodiment provides a method for preparing a high-strength 7xxx series aluminum alloy coil profile. The chemical composition of the aluminum alloy coil profile, by weight percentage, is: Zn: 6.8%, Mg: 2.4%, Cu: 0.3%, Mn: 0.03%, Cr: 0.03%, Zr: 0.14%, Y: 0.18%, Si: 0.03%, Fe: 0.06%, with the remainder being Al and unavoidable impurities. The preparation method steps are as follows: (1) According to the above chemical composition, the raw materials are put into the furnace for smelting, wherein the Y element is an Al-Y master alloy (Y content 5%) used to eliminate segregation, and aluminum alloy melt is obtained.

[0043] (2) Horizontal casting process: A 42mm diameter coiled casting rod is prepared by horizontal casting; during the casting process, 0.3% of granular refining agent is added in combination with argon gas for refining and degassing; when the melt is released, an online degassing box is used for degassing, and tubular filtration is used to purify the melt; 0.15% of aluminum-titanium-carbon-boron refining agent is added to the flow channel for grain refinement; the casting speed is controlled at 500mm / min, and the cooling water temperature is controlled at 20-35℃ to obtain the casting billet.

[0044] (3) Homogenization process: First, keep it at 455℃ for 6 hours, then raise the temperature to 480℃ and keep it for 13 hours; after the heat preservation is completed, cool it down to 230℃ with the furnace, and then take it out of the furnace and air cool it. The cooling rate is controlled at 25℃ / h throughout the process.

[0045] (4) Surface peeling process: control the peeling amount to 7mm.

[0046] (5) Hot rolling process: The target size is a narrow roll plate with a target size of 5mm×15mm and a deformation ratio between 10-16.

[0047] (6) Solution treatment process: First, keep it at 450℃ for 2 hours, then raise the temperature to 485℃ and keep it for 1.5 hours; after the heat preservation is completed, immerse the coil in 50℃ warm water for quenching within 10 seconds.

[0048] (7) Artificial aging process: The coiled profile after solution quenching is subjected to segmented artificial aging treatment. The process parameters are: first, heat at 120℃ for 20 hours, then heat up to 165℃ and heat for 4 hours. After the heat treatment is completed, the product is recorded as sample 1.

[0049] Example 2 This embodiment provides a method for preparing high-strength 7xxx series aluminum alloy coil profiles. The chemical composition of the aluminum alloy coil profiles, by weight percentage, is: Zn: 6.2%, Mg: 2.0%, Cu: 0.1%, Mn: 0.01%, Cr: 0.01%, Zr: 0.08%, Y: 0.10%, Si: 0.02%, Fe: 0.05%, with the remainder being Al and unavoidable impurities. The preparation method steps are as follows: (1) According to the above chemical composition, the raw materials are put into the furnace for smelting, wherein the Y element is an Al-Y master alloy (Y content 5%) used to eliminate segregation, and aluminum alloy melt is obtained.

[0050] (2) Horizontal casting process: 40mm diameter coiled rods are prepared by horizontal casting; during the casting process, 0.3% granular refining agent is added in combination with argon gas for refining and degassing; during the discharge, an online degassing box is used for degassing, combined with tubular filtration for purification; 0.15% aluminum-titanium-carbon-boron refining agent is added to the flow channel for grain refinement; the casting speed is controlled at 400mm / min, and the cooling water temperature is controlled at 20-35℃ to obtain the billet.

[0051] (3) Homogenization process: First, keep it at 455℃ for 4 hours, then raise the temperature to 480℃ and keep it for 10 hours; after the heat preservation is completed, cool it down to 230℃ with the furnace, and then take it out of the furnace and air cool it. The cooling rate is controlled at 28℃ / h throughout the process.

[0052] (4) Surface peeling process: control the peeling amount to 5mm.

[0053] (5) Hot rolling process: The target size is a narrow roll plate with a target size of 5mm×15mm and a deformation ratio between 10-16.

[0054] (6) Solution treatment process: The hot rolled coil is subjected to multi-stage solution treatment. The process parameters are: first, keep it at 450℃ for 2 hours, then raise the temperature to 485℃ and keep it for 1.5 hours; after the heat preservation is completed, immerse the coil in 40℃ warm water for quenching within 10 seconds.

[0055] (7) Artificial aging process: The coiled profile after solution quenching is subjected to segmented artificial aging treatment. The process parameters are: first, keep it at 120℃ for 20 hours, and then raise the temperature to 166℃ and keep it for 240 minutes. After the heat preservation is completed, the product is recorded as sample 2.

[0056] Example 3 This embodiment provides a method for preparing a high-strength 7xxx series aluminum alloy coil profile. The chemical composition of the aluminum alloy coil profile, by weight percentage, is: Zn: 7.6%, Mg: 2.8%, Cu: 0.5%, Mn: 0.05%, Cr: 0.05%, Zr: 0.20%, Y: 0.25%, Si: 0.05%, Fe: 0.08%, with the remainder being Al and unavoidable impurities. The preparation method steps are as follows: (1) According to the above chemical composition, the raw materials are put into the furnace for smelting, wherein the Y element is an Al-Y master alloy (Y content 5%) used to eliminate segregation, and aluminum alloy melt is obtained.

[0057] (2) Horizontal casting process: 38mm diameter coiled rods are prepared by horizontal casting; during the casting process, 0.3% granular refining agent is added in combination with argon gas for refining and degassing; during the discharge, an online degassing box is used for degassing, combined with tubular filtration for purification; 0.2% aluminum-titanium-carbon-boron refining agent is added to the flow channel for grain refinement; the casting speed is controlled at 600mm / min, and the cooling water temperature is controlled at 20-35℃ to obtain the billet.

[0058] (3) Homogenization process: First, keep it at 452℃ for 8 hours, then raise the temperature to 475℃ and keep it for 16 hours; after the heat preservation is completed, cool it down to 230℃ with the furnace, and then take it out of the furnace and air cool it. The cooling rate is controlled at 30℃ / h throughout the process.

[0059] (4) Surface peeling process: the amount of peeling is controlled to be 3mm.

[0060] (5) Hot rolling process: The target size is a narrow roll plate with a target size of 5mm×15mm and a deformation ratio between 10-16.

[0061] (6) Solution treatment process: First, keep it at 448℃ for 125 minutes, then raise the temperature to 483℃ and keep it at 483℃ for 1.5 hours, and immerse it in 60℃ warm water for quenching within 10 seconds.

[0062] (7) Artificial aging process: First, keep the product at 121℃ for 19.6 hours, then raise the temperature to 164℃ and keep it for 4 hours. After the heat treatment is completed, the product is recorded as sample 3.

[0063] Example 4 This embodiment provides a high-strength 7xxx series aluminum alloy coil profile for consumer electronics products. Its chemical composition, by weight percentage, is: Zn: 8.2%, Mg: 2.6%, Cu: 0.5%, Mn: 0.05%, Cr: 0.05%, Zr: 0.20%, Y: 0.25%, Si: 0.05%, Fe: 0.08%, with the remainder being Al and unavoidable impurities. The preparation method steps are as follows: (1) According to the above chemical composition, the raw materials are put into the furnace for smelting, wherein the Y element is an Al-Y master alloy (Y content 5%) used to eliminate segregation, and aluminum alloy melt is obtained.

[0064] (2) Horizontal casting process: 35mm diameter coiled rods are prepared by horizontal casting; during the casting process, 0.3% granular refining agent is added in combination with argon gas for refining and degassing; when the melt is released, an online degassing box is used for degassing, and tubular filtration is used to purify the melt; 0.2% aluminum-titanium-carbon-boron refining agent is added to the flow channel for grain refinement; the casting speed is controlled at 600mm / min, and the cooling water temperature is controlled at 20-35℃ to obtain the billet.

[0065] (3) Homogenization process: First, keep it at 455℃ for 7 hours, then raise the temperature to 483℃ and keep it for 12 hours; after the heat preservation is completed, cool it down to 225℃ with the furnace, and then take it out of the furnace and air cool it. The cooling rate is controlled at 30℃ / h throughout the process.

[0066] (4) Surface peeling process: the amount of peeling is controlled to be 3mm.

[0067] (5) Hot rolling process: The target size is a narrow roll plate with a target size of 5mm×15mm and a deformation ratio between 10-16.

[0068] (6) Solution treatment process: First, keep it at 450℃ for 2 hours, then raise the temperature to 485℃ and keep it for 1.5 hours; after the heat preservation is completed, immerse it in 60℃ warm water for quenching within 10 seconds.

[0069] (7) Artificial aging process: First, keep the product at 122℃ for 19.5 hours, then raise the temperature to 166℃ and keep it for 4 hours. After the heat treatment is completed, the product is recorded as sample 4.

[0070] like Figure 1The images shown are SEM scans of the sample prepared in Example 1 at different magnifications. (a) is a 500× SEM image of the sample, (b) is a 1000× SEM image, (c) is a 3000× SEM image of the sample, and (d) is a 10000× SEM image of the sample. The images reveal the characteristics of the second-phase particles: a large number of white / bright white particles are diffusely distributed in the matrix, with morphologies mainly equiaxed, short rod-shaped, and elliptical. The particles have a wide size distribution, ranging from approximately 0.5-1 μm for small particles to approximately 2-5 μm for large particles. The overall distribution is relatively uniform, with no obvious local agglomeration or segregation. The gray area represents the aluminum matrix, with uniform contrast and composition; a small number of black dot-like areas are common in 7xxx series cast / deformed materials.

[0071] The tensile strength, yield strength, and elongation (A) of the 7xxx series aluminum alloy coils in Examples 1-4 were tested. 50mm Mechanical properties such as % and Vickers hardness (HV) were measured. Nine test samples were taken from different parts of the coil profile for each sample, and the average value of the test results was taken. Finally, the test results of samples 1-4 are statistically summarized in Table 1.

[0072] Table 1: Mechanical property test results of 7xxx series aluminum alloy coils in Examples 1-4

[0073] As shown in Table 1, the yield strength of the 7xxx series aluminum alloy coils prepared in Examples 1-4 is greater than 550 MPa, effectively improving the deformation resistance and impact resistance of the exterior components of consumer electronics products, and ensuring the structural stability of high-end consumer electronics products. Meanwhile, the high tensile strength and high yield strength of the material meet the core requirements of "lightweight and thin, high structural strength" for the exterior components of high-end consumer electronics products. Furthermore, the processing of exterior components (covers, frames, etc.) for consumer electronics products mostly employs CNC precision machining, with a small amount of stamping or bending. The elongation requirement is primarily to "meet the requirements of no cracking during forming and no deformation after processing," without excessively high elongation (excessive elongation can actually reduce material strength and is detrimental to the deformation resistance of the exterior components). Based on industry standards and existing technical practices, the elongation of aluminum alloys used for consumer electronics exterior components is typically required to be ≥7% to meet processing and usage requirements. These performance characteristics mainly stem from the optimization of the aluminum alloy composition (introduction of Y and Zr elements) and the processing technology (segmented aging and rapid quenching), ensuring the material's plasticity and processing stability.

[0074] Furthermore, the weldability and anodized surface properties of the samples from Examples 1-4 were tested using the following methods: 1. Welding performance test (1) Sample preparation: Cut samples from the coiled profiles obtained in Examples 1-4. Prepare 3 parallel samples for each set of examples. Grind the oxide scale and oil stains on the sample surface to ensure that the welding surface is clean.

[0075] (2) Welding process: Argon arc welding is adopted. The welding parameters are controlled as follows: welding current 100A, welding speed 120mm / min, argon flow rate 15L / min, welding joint is butt joint, gap 0.2-0.3mm, no filler material.

[0076] (3) Test items and judgment criteria: ① Weld hot crack test: After welding, the weld and heat-affected zone are observed by visual inspection and magnification (50x magnification) to determine whether hot cracks have occurred (longitudinal cracks and transverse cracks are considered unqualified); at the same time, the weld structure is observed by metallographic microscope, and the number and length of cracks are recorded to determine the crack sensitivity.

[0077] ② Welded joint strength test: The welded specimens are subjected to tensile tests (refer to GB / T 2651-2008 "Tensile Test Method for Welded Joints") to test the tensile strength of the welded joint and calculate the joint strength retention rate (joint tensile strength / substrate tensile strength × 100%). A retention rate ≥ 85% is considered to meet the integrated processing requirements of consumer electronics appearance parts.

[0078] 2. Anodized surface performance testing (1) Anodizing process: Samples from Examples 1-4 were subjected to degreasing (50°C, soaking in alkaline degreasing agent for 10 min), alkaline washing (40°C, soaking in 5wt% NaOH solution for 3 min), neutralization (soaking in 10% HNO3 solution for 1 min), and anodizing (sulfuric acid electrolyte concentration 180 g / L, temperature 20°C, current density 1.5 A / dm³). 2 The oxidation process was carried out for 30 minutes, followed by sealing (at 95°C with deionized water for 20 minutes) to obtain anodized samples (with an oxide film thickness of 10-15 μm, meeting the decorative requirements for consumer electronics exterior parts).

[0079] (2) Test items and judgment criteria: ① Color difference test: A colorimeter (model: CR-400) was used. According to GB / T 14161-2008 "Determination of color and color difference of board surface", the color difference ΔE of different areas (5 test points) of the same sample was tested. ΔE≤1.5 means there is no obvious color difference and meets the decorative requirements. At the same time, the color difference between different parallel samples was tested to ensure batch consistency.

[0080] ② Glossiness test: A gloss meter (model: HG60) was used to test the 60° specular gloss of the anodized surface, referring to GB / T 9754-2017 "Determination of 20°, 60° and 85° specular gloss of paint films without metallic pigments". A glossiness ≥80GU is considered to be excellent and meets the decorative requirements of consumer electronics appearance parts.

[0081] According to the above test method, the welding performance and anodized surface performance of samples 1-4 (corresponding to Examples 1-4) were tested. The average value of the test results of each group of parallel samples was taken. The specific results are shown in Table 2.

[0082] Table 2: Test results of welding and anodized surface properties of 7xxx series aluminum alloy coils in Examples 1-4

[0083] As shown in Table 2, the samples of Examples 1-4 of the present invention were all free of weld hot cracks, and the joint strength retention rate was ≥85%, which solved the problems of poor welding performance and reduced joint strength of existing 7xxx series aluminum alloys, and met the integrated processing requirements of appearance parts of consumer electronics products. Among them, Samples 3 and 4 of Examples 3-4 (with the upper limit of Y and Zr content) had low crack sensitivity and high joint strength retention rate, which precisely reflects the improving effect of Y element on welding performance.

[0084] In the above embodiments, the color difference ΔE of the anodized surface of all samples was ≤1.5, and the 60° mirror gloss was ≥80GU. There was no obvious color difference and the gloss was excellent, which met the decoration requirements of the appearance parts of consumer electronics products. Samples 3 and 4 had slightly better gloss than samples 1 and 2 due to their higher Y element content, which confirmed the effect of Y element on improving the quality of the anodized surface.

[0085] In summary, the high-strength 7xxx series aluminum alloy coil profiles prepared by this invention can be widely used in the appearance structural components of consumer electronics products such as smartphones, smart wearable devices (e.g., smartwatches, smart bands), tablets, laptops, and smart TVs, including phone frames, tablet bezels, laptop casings, and smart TV bezels. This alloy coil profile not only possesses high strength, ensuring product structural stability, but also exhibits good processability and anodizing properties, making it suitable for the precision machining needs of consumer electronics product appearance components and possessing extremely high industrial application value.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions, or combinations of technical features in the above embodiments that do not conflict with each other, can be made in accordance with the manner described in the embodiments. These modifications, substitutions or combinations do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-strength 7xxx series aluminum alloy coil profile for consumer electronics products, characterized in that, Its chemical composition by weight percentage is as follows: Zn: 6.2-8.2%, Mg: 2.0-2.8%, Cu: 0.1-0.5%, Mn: 0.01-0.05%, Cr: 0.01-0.05%, Zr: 0.08-0.20%, Y: 0.10-0.25%, Si: ≤0.05%, Fe: ≤0.08%, with the remainder being Al and unavoidable impurities.

2. A method for preparing high-strength 7xxx series aluminum alloy coil profiles for consumer electronics products, characterized in that, The alloy raw materials are prepared according to the chemical composition of the high-strength 7xxx series aluminum alloy coil profile as described in claim 1, and the preparation method includes the following steps performed sequentially: (1) Horizontal casting process: During the casting process, 0.25-0.35wt% of granular refining agent is added in combination with argon gas for refining and degassing; online degassing and filtration purification are carried out when the melt is released; 0.12-0.20% of aluminum-titanium-carbon-boron refining agent is added to the flow channel for grain refinement; the casting speed is controlled at 400-600mm / min and the cooling water temperature is controlled at 20-35℃; (2) Homogenization process: The coiled rod prepared by the horizontal casting process is subjected to segmented homogenization process. The process parameters are: first, keep it at 450-460℃ for 4-8 hours, then raise the temperature to 470-482℃ and keep it for 10-16 hours; after the heat preservation is completed, cool it with the furnace to 210-230℃, and then remove it from the furnace and air cool it. The cooling rate is controlled to be ≤30℃ / h throughout the process. (3) Surface peeling process: The oxide scale is removed from the surface of the homogenized casting rod; (4) Hot rolling process: The stripped cast bar is rolled into a coil profile close to the target size by hot rolling process. The deformation ratio of hot rolling is 10-16. (5) Solution treatment process: The hot rolled coil is subjected to multi-stage solution treatment. The process parameters are: first, keep it at 445-455℃ for 110-130 min, then raise the temperature to 480-488℃ and keep it for 80-100 min; after the heat preservation is completed, the coil is quickly immersed in warm water at 40-60℃ for quenching treatment within 10 seconds. (6) Artificial aging process: The coil profile after solution quenching is subjected to segmented artificial aging treatment. The process parameters are: first, keep it at 115-125℃ for 12-21 hours, and then raise the temperature to 160-170℃ and keep it for 220-260 minutes.

3. The preparation method according to claim 2, characterized in that, The aluminum alloy melt is made into a coiled rod with a diameter of 35-42mm through a horizontal casting process; in the surface peeling process, the peeling depth is controlled to be 2-7mm.

4. The preparation method according to claim 2, characterized in that, In the horizontal casting process, an online degassing box is used to degas the melt during the discharge, and a tubular filter is used for online filtration and purification. The granular refining agent used in the horizontal casting process consists of a composite salt system of magnesium chloride, sodium chloride, and potassium chloride; the titanium-carbon-boron refining agent consists of Ti 2.0-10.0wt%, C 0.1-1.0wt%, B 0.1-1.0wt%, with the balance being Al and unavoidable impurities.

5. The preparation method according to claim 4, characterized in that, The amount of granular refining agent added during the casting process is 0.3%; the amount of titanium-carbon-boron refining agent added in the runner is 0.15wt%.

6. The preparation method according to claim 2, characterized in that, The process parameters for the homogenization process are as follows: first, hold at 455℃ for 4-8 hours, then raise the temperature to 480℃ and hold for 10-16 hours; after the holding period, cool with the furnace to 230℃, and then remove from the furnace and air cool, with the cooling rate controlled at ≤30℃ / h throughout the process.

7. The preparation method according to claim 2, characterized in that, In the hot rolling process, the thickness of the coil profile that is close to the target size is the target thickness H ± 0.02 mm, and its width is the target width ± 0.10 mm.

8. The preparation method according to claim 2, characterized in that, The hot rolling process includes: hot rolling a 35-42mm diameter cast bar through 8-12 passes to obtain a (4-7)mm×(10-15)mm plate or a 10-12mm diameter rod.

9. The preparation method according to claim 2, characterized in that, The process parameters for the solution treatment process are as follows: first, hold at 450℃ for 120 minutes, then raise the temperature to 485℃ and hold for 90 minutes; after the holding period, immerse the coiled profile in warm water at 40-60℃ for quenching within 10 seconds. The process parameters for the artificial aging process are: first, hold at 120℃ for 20 hours, then raise the temperature to 165℃ and hold for 240 minutes.

10. The high-strength 7xxx series aluminum alloy coil profiles for consumer electronics products prepared by the preparation method according to any one of claims 2-9, and their application in the processing and manufacturing of appearance parts for consumer electronics products such as smartphones, smart TVs, smart wearable devices or tablet computers.

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