High-strength aluminum alloy for 3c electronic products and method for manufacturing the same

Abstract

The application provides a high-strength aluminum alloy for 3C electronic products and a preparation method thereof, which comprises six steps of smelting, refining, casting forming, homogenization treatment, quenching and aging. The preparation process of the aluminum alloy is optimized by strictly reducing the content of Fe and Cu, improving the atomic ratio of Mg and Si, guaranteeing the synergistic effect of Al, Mg and Si, and promoting the uniform and stable precipitation of the strengthening phase. The coarse G.P. zone formed after the aluminum alloy is quenched and stored at room temperature can be avoided, the demand for high dispersion of the strengthening phase is met, and the mechanical properties of the aluminum alloy are significantly improved. The yield strength of the aluminum alloy is 288 MPa-305 MPa, the tensile strength is 302 MPa-313 MPa, the precision range of the accessory after the aluminum alloy is processed into 3C product accessories is ±0.009 mm-±0.02 mm, the surface color difference value ΔE of the accessory after anodic oxidation is 0.31-0.45, and the tolerance fluctuation rate and the color difference fluctuation rate are both lower than 7%. The aluminum alloy does not need to add expensive metals, the crystal phase structure is uniform, has high strength and high plasticity, is easy to popularize and implement, and can meet the processing requirements of 3C electronic products and ultra-high-precision medical devices.

Description

Technical Field

[0001] This application belongs to the field of metallurgical technology, specifically relating to a high-strength aluminum alloy for 3C electronic products and its preparation method. Background Technology

[0002] In existing technologies, aluminum alloys, due to their low density, good plasticity, and excellent specific strength, have become the core lightweight material for structural components (frames, brackets, and custom-shaped internal components) and exterior components (shells and decorative panels) of 3C products, providing key support for product lightweighting and portability, and effectively improving user experience and market competitiveness. However, as 3C products rapidly develop towards thinner, lighter, stronger, and more precise designs (dimensional tolerance ±0.03mm), mainstream 6-series aluminum alloys have significant performance shortcomings and are unable to meet the ever-increasing production demands.

[0003] In existing technologies, 6-series aluminum alloys mainly rely on Mg and Si elements for strengthening. However, the Mg and Si ratios in existing alloys are not ideal, and the processing technology cannot meet the requirements for highly uniform dispersion of strengthening phases in aluminum alloys. This not only easily leads to unstable precipitation of strengthening phases, significantly reducing the mechanical properties of finished aluminum alloys, but also exhibits a significant "suspension effect." When quenched aluminum alloys are left at room temperature before aging, the strengthening phases in the aluminum alloy precipitate prematurely, forming coarse GP regions. This will cause stress concentration zones to form inside the aluminum alloy, which will have a huge negative impact on the subsequent aging of the aluminum alloy, significantly reducing its mechanical properties.

[0004] Furthermore, due to imperfections in the dispersion distribution of the strengthening phase in existing aluminum alloys, the uniformity of the matrix and strengthening phases in aluminum alloys is low. During processing, the surface specifications of aluminum alloys are reduced, which will also affect the processing of subsequent 3C product accessories. For example, during CNC machining, the precision of extruded products will be significantly reduced, and the cumulative error fluctuation of components will require operators to frequently adjust the CNC machining equipment. During anodizing, the uniformity of the oxide film on the surface of aluminum alloys is reduced, and there is a high color difference after anodizing.

[0005] Therefore, there is an urgent need to develop a new type of aluminum alloy with a highly refined and uniform internal crystal structure, low production cost, and that meets the processing requirements of ultra-high precision 3C electronic products. Summary of the Invention

[0006] This application aims to address the following technical problems in the prior art: poor Mg and Si element ratios and processing techniques in 6-series aluminum alloys, resulting in unstable precipitation of strengthening phases, low uniformity of the matrix and strengthening phases, inability to meet the requirement of highly uniform dispersion of the strengthening phase, and the formation of coarse GP zones after quenching and room temperature resting followed by aging, which significantly reduces the mechanical properties of the aluminum alloy; furthermore, when processed into 3C product components, the finished product precision fluctuates greatly, the color difference fluctuates greatly after anodizing, the oxide film adhesion strength decreases, and it is difficult to meet the technical problems of the thinness, high strength, and precision requirements of 3C products. Therefore, this application proposes a high-strength aluminum alloy for 3C electronic products.

[0007] In order to solve the technical problems raised in this application, this application also proposes a method for preparing high-strength aluminum alloy for 3C electronic products.

[0008] In order to solve the technical problems raised in this application, this application also proposes an application of high-strength aluminum alloy for 3C electronic products.

[0009] This application adopts the following approach: a method for preparing a high-strength aluminum alloy for 3C electronic products, comprising the following steps:

[0010] Melting: Aluminum source, silicon source, iron source, copper source, manganese source, magnesium source, chromium source, zinc source, and titanium source are added sequentially to a high-frequency induction melting furnace. The mixture is stirred for 30-50 minutes at 740℃-760℃ and an electromagnetic stirring frequency of 200Hz-500Hz. During the stirring process, samples are taken from the high-frequency induction melting furnace at regular intervals for analysis to control the various components in the melt to be within the preset range. After stirring is completed, the first melt is obtained.

[0011] Refining: Add the refining agent (Al-5Ti-1B) and the refining agent (hexachloroethane refining agent) to the first melt in sequence, and let it stand for 20-30 minutes to remove gas and slag (hydrogen content ≤0.12mL / 100gAl) to obtain the second melt;

[0012] Casting: The second melt is transferred to a casting machine and a semi-continuous casting process is adopted. Under the conditions of casting speed of 80 mm / min and cooling water pressure of 0.3 MPa-0.5 MPa, the second melt is cast into aluminum material of preset size and specifications.

[0013] Homogenization: The prepared aluminum material is transferred to a continuous homogenizing furnace and homogenized at 530℃-550℃ for 4-5 hours. After cooling to room temperature, the homogenized aluminum material is obtained.

[0014] Quenching: The homogenized aluminum material is heated to 510℃-520℃ and then transferred to a hot extruder. It is extruded at a die temperature of 480℃-490℃. After extrusion, the homogenized aluminum material is cooled by a water mist cooling device to 170℃-180℃ to obtain quenched aluminum material.

[0015] Aging: The prepared quenched aluminum material is transferred to a hot air circulating aging furnace, held at 170℃-180℃ for 8-9 hours and then naturally cooled to room temperature to obtain a high-strength aluminum alloy for 3C electronic products.

[0016] In some feasible embodiments, the homogenization process includes a heating stage, a holding stage, and a cooling stage;

[0017] The heating stage involves raising the aluminum material from room temperature to 535℃-545℃, with a corresponding heating rate of 4.5℃ / min-5℃ / min.

[0018] The heat preservation stage involves heat preservation of the aluminum material at 535℃-545℃ for 4-5 hours.

[0019] The cooling stage involves cooling the aluminum material from 535℃-545℃ to room temperature, with a corresponding cooling rate of 20℃ / s-50℃ / s.

[0020] The cooling stage uses cooling water to cool the aluminum material, with a flow rate of 50L / min-60L / min.

[0021] In some feasible embodiments, during the quenching process, the water mist flow rate is 25L / min-30L / min, and the water mist cooling rate is 15℃ / s-25℃ / s.

[0022] In existing technologies, rapid cooling or even cryogenic (liquid nitrogen) is often used to cool aluminum alloys during homogeneous cooling and quenching to prevent the premature precipitation of the strengthening phase after full solidification. However, in actual implementation, although rapid cooling / cryogenic cooling can keep the strengthening phase in a solid solution state, excessive temperature changes result in large residual stress inside the aluminum alloy, which can easily lead to grain distortion. During subsequent aging, the strengthening phase is greatly affected by temperature and tends to coarsen explosively at the grain interface. Microscopically, this will severely deteriorate the uniformity of the aluminum alloy's crystal structure. Macroscopically, although the aluminum alloy has high strength, its plasticity is significantly reduced, and there are many stress concentration points inside the aluminum alloy, which cannot meet the processing requirements of high-precision components.

[0023] This application employs a gentle cooling process (20℃ / s-50℃ / s) that differs from commonly used techniques in the field, avoiding rapid cooling. This ensures that solute atoms are fully dissolved while preventing grain distortion during rapid cooling, laying the foundation for the precipitation of a uniform strengthening phase during subsequent aging.

[0024] In some feasible embodiments, during the aging process, the temperature fluctuation of the hot air circulating aging furnace is defined as X, wherein X satisfies the following relationship: ±1℃≤X≤±2.5℃.

[0025] In some feasible embodiments, during the cooling phase and water mist cooling process, the Mg2Si reinforced phase approaches a supersaturated solid solution state.

[0026] To address the technical problems raised in this application, this application also provides a high-strength aluminum alloy for 3C electronic products, which is prepared by the above-mentioned method for preparing high-strength aluminum alloy for 3C electronic products. By mass percentage, the aluminum alloy comprises the following components: Si 0.43%-0.51%, Fe 0.02%-0.15%, Cu 0.01%-0.08%, Mn 0.01%-0.05%, Mg 0.57%-0.65%, Cr 0.01%-0.05%, Zn 0.01%-0.03%, Ti 0.05%-0.07%, with the remainder being Al and other unavoidable impurity elements, the total amount of which is ≤0.01%.

[0027] For example, the mass percentage of Si can be selected from any value between 0.43% and 0.51% (accurate to two decimal places). Further, the mass percentage of Si is not limited to 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, 0.50%, or 0.51%, or any two of the above values ​​as endpoints. The mass percentage of Mg includes, but is not limited to, 0.57%, 0.58%, 0.59%, 0.60%, 0.61%, 0.62%, 0.63%, 0.64%, or 0.65%, or any two of the above values ​​as endpoints. The mass percentage of Fe includes, but is not limited to, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, or any two of the above values ​​as endpoints. The mass percentage of Cu includes, but is not limited to, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, or any two of the above values ​​as endpoints.

[0028] In some feasible embodiments, the aluminum alloy comprises an α-Al matrix phase and a Mg2Si strengthening phase dispersed within the α-Al matrix phase.

[0029] In some feasible embodiments, the total amount of Mg2Si strengthening phase in the aluminum alloy grains is defined as Z, and the amount of Mg2Si strengthening phase on the α-Al matrix grain boundaries is defined as Y. Z and Y satisfy the following relationship: 89.8%≤(ZY) / Z≤94.3%.

[0030] In some feasible embodiments, the atomic ratio of Mg to Si in the aluminum alloy is 1.60-1.73.

[0031] For example, the atomic ratio of Mg to Si (retaining two decimal places) is 1.61, 1.62, 1.63, 1.64, 1.65, 1.66, 1.67, 1.68, 1.69, 1.70, 1.71, 1.72, 1.73, or any two of the above point values ​​as endpoints.

[0032] In some feasible embodiments, the grain size of the aluminum alloy is 12μm-17μm, and the grain size difference is 3μm-5μm;

[0033] In the aluminum alloy, the grain size of the Mg2Si strengthening phase is 0.4μm-0.8μm, and the distance between two adjacent Mg2Si strengthening phase grains is 1μm-5μm.

[0034] In the aluminum alloy, the average three-dimensional distribution density of the Mg2Si strengthening phase within a single grain is 2.4 × 10⁻⁶. 7 pcs / mm 3 -3.9×10 7 pcs / mm 3 ;

[0035] In the aluminum alloy, the number of Mg2Si strengthening phases in a single grain is 33-84.

[0036] In the aluminum alloy, the volume fraction of the Mg2Si strengthening phase within a single grain is 0.22%-0.43%.

[0037] In order to solve the technical problems raised in this application, this application also provides an application of a high-strength aluminum alloy for 3C electronic products, which is used to process 3C electronic products or precision medical devices;

[0038] During the process of machining the aluminum alloy into metal components using CNC machining technology, the tolerance level of the metal components is ±0.009mm-±0.02mm, the tolerance fluctuation rate is 6%-7%, and the color difference ΔE range after batch anodizing is 0.31-0.45, with a color difference fluctuation rate of 5%-6%.

[0039] Specifically, it is used to process any one of the following: laptop shell bezel, laptop chip support frame, laptop screen back panel, laptop internal support beam, mobile phone metal mid-frame, mobile phone front and rear frame, smartwatch shell, heat dissipation module shell, heat dissipation module pipeline, mobile phone camera mounting bracket, drone bracket, battery pack internal bracket, and CNC medical device metal parts.

[0040] Compared with the prior art, this application has the following beneficial effects:

[0041] This application provides a high-strength aluminum alloy for 3C electronic products, its preparation method, and its application. The method includes six steps: melting, refining, casting, homogenization, quenching, and aging. By strictly reducing the content of Fe and Cu, increasing the atomic ratio of Mg and Si, and optimizing the aluminum alloy preparation process, the synergistic effect of Al, Mg, and Si is ensured, promoting the uniform and stable precipitation of the strengthening phase. This avoids the formation of coarse GP zones after room temperature storage following quenching, meeting the requirement for highly dispersed strengthening phases and significantly improving the mechanical properties of the aluminum alloy. The yield strength of this aluminum alloy is 288MPa-305MPa, and the tensile strength is 302MPa-313MPa. After processing into 3C product parts, the precision range of the parts is ±0.009mm-±0.02mm, and the surface color difference value after anodizing is 0.31-0.45. This aluminum alloy does not require the addition of expensive metals, has a highly uniform crystal phase distribution, can simultaneously meet the processing requirements of 3C electronic products and ultra-high precision medical devices, possesses the advantages of high strength and high plasticity, has low implementation cost, and is easy to promote and implement. Attached Figure Description

[0042] Figure 1 These are the crystal phase diagrams of the aluminum alloys prepared in Examples 1-3 of this application;

[0043] Figure 2 This is a crystal phase structure diagram of the aluminum alloy prepared in Examples 1-3 of this application at another magnification;

[0044] Figure 3 This is a crystal phase diagram of the aluminum alloy prepared in Comparative Example 1 of this application;

[0045] Figure 4 This is a crystal phase diagram of the aluminum alloy prepared in Comparative Example 2 of this application;

[0046] Figure 5 This is a crystal phase diagram of the aluminum alloy prepared in Comparative Example 3 of this application;

[0047] Figure 6 This is a crystal phase diagram of the aluminum alloy prepared in Comparative Example 4 of this application;

[0048] Figure 7This is the color difference fluctuation curve of 50 finished mobile phone shell frames continuously processed according to the processing technology in Examples 1-3 and Comparative Examples 1-4 in Test 4 of this application;

[0049] Figure 8 This is the tolerance fluctuation curve of 50 finished mobile phone shell frames continuously processed according to the processing technology in Examples 1-3 and Comparative Examples 1-4 in Test 5 of this application. Detailed Implementation

[0050] Combination Figures 1 to 8 The content shown further illustrates the technical solution proposed in this application. Example 1

[0051] (1) A method for preparing high-strength aluminum alloys for 3C electronic products, comprising the following steps:

[0052] Melting: Aluminum source, silicon source, iron source, copper source, manganese source, magnesium source, chromium source, zinc source, and titanium source are added sequentially to the high-frequency induction melting furnace according to the alloy composition shown in Table 1. The mixture is stirred for 30 minutes at 740℃ and an electromagnetic stirring frequency of 200Hz. During the stirring process, samples are taken from the high-frequency induction melting furnace at regular intervals for analysis to control the various components in the melt to be within the preset range. After the stirring is completed, the first melt is obtained.

[0053] Refining: Add the refining agent and the refining agent to the first melt in sequence, and let it stand for 20 minutes to remove gas and slag, and then the second melt is obtained.

[0054] Casting: The second melt is transferred to a casting machine and a semi-continuous casting process is adopted. Under the conditions of casting speed of 80 mm / min and cooling water pressure of 0.3 MPa, the second melt is cast into aluminum material of preset size and specifications.

[0055] Homogenization: The prepared aluminum material is transferred to a continuous homogenizing furnace and homogenized at 530°C for 4 hours. After cooling to room temperature, the homogenized aluminum material is obtained.

[0056] The homogenization process includes a heating stage, a holding stage, and a cooling stage.

[0057] The heating stage involves raising the aluminum material from room temperature to 535°C, with a corresponding heating rate of 4.5°C / min.

[0058] The heat preservation stage involves heat preservation of the aluminum material at 535℃ for 4 hours.

[0059] The cooling stage involves cooling the aluminum material from 535°C to room temperature, with a corresponding cooling rate of 20°C / s.

[0060] The cooling stage uses cooling water to cool the aluminum material at a flow rate of 50L / min.

[0061] Extrusion and quenching: The homogenized aluminum material prepared is heated to 510℃ and then transferred to a hot extrusion press. It is extruded at a die temperature of 480℃. After extrusion, the homogenized aluminum material is cooled by a water mist cooling device. After cooling to 170℃, a quenched aluminum material with a width of 88mm and a thickness of 8.2mm (which can be adjusted according to actual processing requirements) is obtained.

[0062] The water mist flow rate is 25 L / min, and the water mist cooling rate is 15 °C / s;

[0063] Aging: The prepared quenched aluminum material is transferred to a hot air circulating aging furnace, held at 170℃ for 8 hours and then naturally cooled to room temperature to obtain a high-strength aluminum alloy for 3C electronic products.

[0064] During the aging process, the temperature fluctuation X of the hot air circulating aging furnace satisfies the following relationship: ±1℃≤X≤±2.5℃.

[0065] (2) The preparation method of the laptop shell frame / mobile phone shell mid-frame includes the following steps:

[0066] CNC machining: After importing the preset laptop shell frame / mobile phone shell mid-frame drawing into the CNC machining equipment, the high-strength aluminum alloy used in 3C electronic products is transferred to the CNC machining equipment. After the CNC machining equipment completes the machining, 3C component A is obtained.

[0067] In the preset laptop shell frame drawing / mobile phone shell mid-frame drawing, the minimum thickness of the processing area is 1.573mm;

[0068] Degreasing treatment: Immerse 3C component A in an alkaline degreasing agent and keep it at a degreasing temperature of 55℃ for 10 minutes; after degreasing, wash and dry it with deionized water to obtain 3C component B.

[0069] The degreasing agent is prepared by mixing a 25 g / L sodium bicarbonate solution and a 6 g / L sodium hydroxide solution in a mass ratio of 1:1.

[0070] Neutralization treatment: 3C component B is transferred into a 6% (v / v) nitric acid solution and soaked at room temperature for 3 minutes; after neutralization, it is washed with deionized water and dried to obtain 3C component C.

[0071] Anodizing: The 3C component C is transferred to an anodizing tank containing a sulfuric acid solution with a concentration of 200 g / L. A lead plate is used as the cathode and the aluminum alloy component as the anode. The electrolyte temperature is 20℃ and the current density is 1.5 A / dm³. 2After oxidation for 30 minutes under the specified conditions, component D of type 3C is obtained.

[0072] Boiling water sealing: Immerse 3C component D in 100℃ deionized water (conductivity ≤10μS / cm) and keep it warm for 30 minutes to obtain the finished laptop shell frame / mobile phone shell mid-frame. Example 2

[0073] (1) A method for preparing high-strength aluminum alloys for 3C electronic products, comprising the following steps:

[0074] Melting: Aluminum source, silicon source, iron source, copper source, manganese source, magnesium source, chromium source, zinc source and titanium source are added sequentially to the high-frequency induction melting furnace according to the alloy composition shown in Table 1. Stir for 40 minutes at 750℃ and electromagnetic stirring frequency of 300Hz. During the stirring process, samples are taken from the high-frequency induction melting furnace at regular intervals for analysis to control the various components in the melt to be within the preset range. After the stirring is completed, the first melt is obtained.

[0075] Refining: Add the refining agent and the refining agent to the first melt in sequence, and let it stand for 25 minutes to remove gas and slag, and then the second melt is obtained.

[0076] Casting: The second melt is transferred to a casting machine and a semi-continuous casting process is adopted. Under the conditions of casting speed of 80 mm / min and cooling water pressure of 0.4 MPa, the second melt is cast into aluminum material of preset size and specifications.

[0077] Homogenization: The prepared aluminum material is transferred to a continuous homogenizing furnace and homogenized at 540°C for 4 hours. After cooling to room temperature, the homogenized aluminum material is obtained.

[0078] The homogenization process includes a heating stage, a holding stage, and a cooling stage.

[0079] The heating stage involves raising the aluminum material from room temperature to 540°C, with a corresponding heating rate of 4.5°C / min.

[0080] The heat preservation stage involves heat preservation of the aluminum material at 540℃ for 5 hours.

[0081] The cooling stage involves cooling the aluminum material from 540°C to room temperature, with a corresponding cooling rate of 30°C / s.

[0082] The cooling stage uses cooling water to cool the aluminum material at a flow rate of 55 L / min.

[0083] Extrusion and quenching: The homogenized aluminum material prepared is heated to 515℃ and then transferred to a hot extrusion press. It is extruded at a die temperature of 485℃. After extrusion, the homogenized aluminum material is cooled by a water mist cooling device. After cooling to 175℃, a quenched aluminum material with a width of 88mm and a thickness of 8.2mm is obtained.

[0084] The water mist flow rate is 27 L / min, and the water mist cooling rate is 20 °C / s;

[0085] Aging: The quenched aluminum material is transferred to a hot air circulating aging furnace, held at 175℃ for 8.5 hours and then naturally cooled to room temperature to obtain a high-strength aluminum alloy for 3C electronic products.

[0086] During the aging process, the temperature fluctuation X of the hot air circulating aging furnace satisfies the following relationship: ±1℃≤X≤±2.5℃.

[0087] (2) The preparation method of the laptop shell frame / mobile phone shell mid-frame includes the following steps:

[0088] CNC machining: After importing the preset laptop shell frame / mobile phone shell mid-frame drawing into the CNC machining equipment, the high-strength aluminum alloy used in 3C electronic products is transferred to the CNC machining equipment. After the CNC machining equipment completes the machining, 3C component A is obtained.

[0089] In the preset laptop shell frame drawing / mobile phone shell mid-frame drawing, the minimum thickness of the processing area is 1.573mm;

[0090] Degreasing treatment: Immerse 3C component A in an alkaline degreasing agent and keep it at a degreasing temperature of 55℃ for 10 minutes; after degreasing, wash and dry it with deionized water to obtain 3C component B.

[0091] The degreasing agent is prepared by mixing a 25 g / L sodium bicarbonate solution and a 6 g / L sodium hydroxide solution in a mass ratio of 1:1.

[0092] Neutralization treatment: 3C component B is transferred into a 6% (v / v) nitric acid solution and soaked at room temperature for 3 minutes; after neutralization, it is washed with deionized water and dried to obtain 3C component C.

[0093] Anodizing: The 3C component C is transferred to an anodizing tank containing a sulfuric acid solution with a concentration of 200 g / L. A lead plate is used as the cathode and the aluminum alloy component as the anode. The electrolyte temperature is 20℃ and the current density is 1.5 A / dm³. 2 After oxidation for 30 minutes under the specified conditions, component D of type 3C is obtained.

[0094] Boiling water sealing: Immerse 3C component D in deionized water at 100℃ (conductivity ≤10μS / cm) and keep it warm for 30 minutes to obtain the finished laptop shell frame / mobile phone shell mid-frame. Example 3

[0095] (1) A method for preparing high-strength aluminum alloys for 3C electronic products, comprising the following steps:

[0096] Melting: Aluminum source, silicon source, iron source, copper source, manganese source, magnesium source, chromium source, zinc source and titanium source are added sequentially to the high-frequency induction melting furnace according to the alloy composition shown in Table 1. The mixture is stirred for 50 minutes at 760℃ and electromagnetic stirring frequency of 500Hz. During the stirring process, samples are taken from the high-frequency induction melting furnace at regular intervals for analysis to control the various components in the melt to be within the preset range. After the stirring is completed, the first melt is obtained.

[0097] Refining: Add the refining agent and the refining agent to the first melt in sequence, and let it stand for 30 minutes to remove gas and slag, and then the second melt is obtained.

[0098] Casting: The second melt is transferred to a casting machine and a semi-continuous casting process is adopted. Under the conditions of casting speed of 80 mm / min and cooling water pressure of 0.5 MPa, the second melt is cast into aluminum material of preset size and specifications.

[0099] Homogenization: The prepared aluminum material is transferred to a continuous homogenizing furnace and homogenized at 545°C for 5 hours. After cooling to room temperature, the homogenized aluminum material is obtained.

[0100] The homogenization process includes a heating stage, a holding stage, and a cooling stage.

[0101] The heating stage involves heating the aluminum material from room temperature to 545°C, with a corresponding heating rate of 5°C / min.

[0102] The heat preservation stage involves heat preservation of the aluminum material at 545℃ for 5 hours.

[0103] The cooling stage involves cooling the aluminum material from 545°C to room temperature, with a corresponding cooling rate of 50°C / s.

[0104] The cooling stage uses cooling water to cool the aluminum material at a flow rate of 60L / min.

[0105] Extrusion and quenching: The homogenized aluminum material prepared is heated to 520°C and then transferred to a hot extrusion press. It is extruded at a die temperature of 490°C. After extrusion, the homogenized aluminum material is cooled by a water mist cooling device. After cooling to 180°C, a quenched aluminum material with a width of 88 mm and a thickness of 8.2 mm is obtained.

[0106] The water mist flow rate is 30 L / min, and the water mist cooling rate is 25 °C / s;

[0107] Aging: The prepared quenched aluminum material is transferred to a hot air circulating aging furnace, held at 180℃ for 9 hours and then naturally cooled to room temperature to obtain a high-strength aluminum alloy for 3C electronic products.

[0108] During the aging process, the temperature fluctuation X of the hot air circulating aging furnace satisfies the following relationship: ±1℃≤X≤±2.5℃.

[0109] (2) The preparation method of the laptop shell frame / mobile phone shell mid-frame includes the following steps:

[0110] CNC machining: After importing the preset laptop shell frame / mobile phone shell mid-frame drawing into the CNC machining equipment, the high-strength aluminum alloy used in 3C electronic products is transferred to the CNC machining equipment. After the CNC machining equipment completes the machining, 3C component A is obtained.

[0111] In the preset laptop shell frame drawing / mobile phone shell mid-frame drawing, the minimum thickness of the processing area is 1.573mm;

[0112] Degreasing treatment: Immerse 3C component A in an alkaline degreasing agent and keep it at a degreasing temperature of 55℃ for 10 minutes; after degreasing, wash and dry it with deionized water to obtain 3C component B.

[0113] The degreasing agent is prepared by mixing a 25 g / L sodium bicarbonate solution and a 6 g / L sodium hydroxide solution in a mass ratio of 1:1.

[0114] Neutralization treatment: 3C component B is transferred into a 6% (v / v) nitric acid solution and soaked at room temperature for 3 minutes; after neutralization, it is washed with deionized water and dried to obtain 3C component C.

[0115] Anodizing: The 3C component C is transferred to an anodizing tank containing a sulfuric acid solution with a concentration of 200 g / L. A lead plate is used as the cathode and the aluminum alloy component as the anode. The electrolyte temperature is 20℃ and the current density is 1.5 A / dm³. 2 After oxidation for 30 minutes under the specified conditions, component D of type 3C is obtained.

[0116] Boiling water sealing: Immerse 3C component D in deionized water at 100℃ (conductivity ≤10μS / cm) and keep it warm for 30 minutes to obtain the finished laptop shell frame / mobile phone shell mid-frame.

[0117] Comparative Example 1

[0118] Commercially available 6063 aluminum alloy of brand A (see Table 1 for specific alloy ratio) and 3C components made from this alloy using the same manufacturing process.

[0119] The homogenization process for this aluminum alloy is as follows: the aluminum material is kept at 540℃ for 5 hours and then allowed to cool naturally to room temperature.

[0120] The quenching process for this aluminum alloy is as follows: the aluminum material is cooled from 500℃ to room temperature using a large flow of cooling water at a cooling rate of 500℃ / s.

[0121] The aging process for this aluminum alloy is as follows: the aluminum material is kept at 190℃ for 8 hours and then naturally cooled to room temperature.

[0122] Comparative Example 2

[0123] Commercially available 6063 aluminum alloy of brand A (see Table 1 for specific alloy ratio) and 3C components made from this alloy using the same manufacturing process.

[0124] The homogenization process for this aluminum alloy is as follows: the aluminum material is kept at 540℃ for 5 hours and then cooled with a large flow of cooling water at a rate of 300℃ / s.

[0125] The quenching process for this aluminum alloy is as follows: the aluminum material is cooled from 500℃ to room temperature using a large flow of cooling water at a cooling rate of 400℃ / s.

[0126] Comparative Example 3

[0127] The difference between Comparative Example 3 and Example 3 is that the Mg / Si atomic ratio in the aluminum alloy was reduced from 1.71 to 1.3, the other components were adjusted accordingly, and the rest of the preparation process remained unchanged.

[0128] Comparative Example 4

[0129] The difference between Comparative Example 4 and Example 3 is that the homogenization process of the aluminum alloy is as follows: the aluminum material is kept at 540°C for 5 hours and then cooled with a large flow of cooling water at a cooling rate of 300°C / s.

[0130] The quenching process for this aluminum alloy is as follows: the aluminum material is cooled from 500℃ to room temperature using a large flow of cooling water at a cooling rate of 400℃ / s.

[0131] Table 1 Alloy composition table for Examples 1, 3 and Comparative Examples 1-4

[0132]

[0133] Note: The influence of unavoidable impurities is ignored in Table 1. The content of Al includes unavoidable impurities, and the content of unavoidable impurities meets the standard and is therefore negligible.

[0134] The aluminum alloys prepared in Examples 1-3 and the aluminum alloys mentioned in Comparative Examples 1-4 were subjected to the following tests:

[0135] Test 1: The tensile strength, yield strength, elongation after fracture, and Brinell hardness of the aluminum alloys prepared in Examples 1-3 and the aluminum alloys mentioned in Comparative Examples 1-4 were tested according to the provisions of GB / T 228.1-2021 and GB / T 231.1-2018, respectively.

[0136] Test 2: The surface roughness of 3C component A prepared in Examples 1-3 and Comparative Examples 1-4 was measured using the "pin contact method".

[0137] Among them, the "stylus method" uses a diamond stylus with a tip curvature radius of 2μm to slowly slide along the surface of the test piece. The vertical displacement of the diamond stylus is converted into an electrical signal by an electrical length sensor, and after amplification, filtering and calculation, the surface roughness value is indicated by a display instrument.

[0138] Test 3: The oxide film thickness and color difference of the finished mobile phone shell frames prepared in Examples 1-3 and Comparative Examples 1-4 were tested according to the provisions of GB / T 4957-2003 and GB / T 11186.3-1989, respectively.

[0139] Test 4: 50 finished mobile phone casing frames were continuously processed according to the processing technology in Examples 1-3 and Comparative Examples 1-4 respectively. The color difference of each finished mobile phone casing frame was tested according to the provisions of GB / T 11186.3-1989, and the color difference fluctuation curve was plotted.

[0140] Test 5: 50 finished mobile phone casing frames were continuously processed according to the processing technology in Examples 1-3 and Comparative Examples 1-4, and the tolerance of each finished mobile phone casing frame was measured by a coordinate measuring machine (CMM, measurement accuracy ≤ ±0.002mm), and the corresponding tolerance curve was plotted.

[0141] The measurement method for the finished tolerance of the mobile phone mid-frame is as follows: Select 3 measurement points evenly along the length of the mid-frame, record the actual size of each measurement point, calculate the average value of the 3 measurement points as the actual total length, and take the difference between the actual length and the design length (15.494cm) as the length processing tolerance.

[0142] Four wall thickness measuring points are evenly selected in the circumference of the middle frame. The actual size of each measuring point is recorded. The average value of the four measuring points is calculated as the actual total thickness. The difference between the actual thickness and the design thickness (1.573mm) is taken as the thickness processing tolerance.

[0143] Test 6: The aluminum alloys prepared in Example 3 and those mentioned in Comparative Examples 1-4 were transferred to a scanning electron microscope, and the crystal structure of each aluminum alloy was observed. The test results are shown in Table 2 below. Figures 1-8 As shown.

[0144] Table 2 Test Results Table for Tests 1-5

[0145]

[0146] Continued from Table 2

[0147]

[0148] From Table 2 and Figures 1-7 The test results show that in Examples 1-3, the aluminum alloy grain morphology is ultrafine equiaxed grain, with an average grain size of 14.8 μm. The average size of the Mg2Si strengthening phase is 0.5 μm, the average spacing between the Mg2Si strengthening phases is 3.7 μm, and the Mg2Si strengthening phase is spherically dispersed (e.g., Figures 1-2 (As shown by the black dots within the red circle), the average three-dimensional distribution density of the strengthening phase within the grain is 3.7 × 10⁻⁶. 7 pcs / mm 3 The average volume fraction of the Mg2Si strengthening phase is 0.4%. There is no grain boundary segregation or coarsening in the grains, no grain distortion, no microcracks, no harmful brittle phases, and the grain boundaries are clean and continuously and uniformly distributed in the grain boundaries.

[0149] In Comparative Example 1, the grains are coarse and uneven, with a grain size ranging from 82 μm to 96 μm. The grain distribution uniformity is poor, with an average size of 88.4 μm. Abnormal grain growth occurs in some areas. The size of the Mg2Si strengthening phase ranges from 20 μm to 35 μm, and there are irregular rod-shaped abnormal strengthening phases with low distribution uniformity. There are also a large number of aggregates at the grain boundaries (e.g., Figure 3 (As shown in the blue circle), the strengthening phase within the grains is sparse; the grain boundaries have a continuous distribution of many coarse and brittle phases (such as...). Figure 3 As shown in the red circle, there is obvious grain distortion and intragranular microcracks (such as...). Figure 3 (As shown in the yellow circle in the middle), residual internal stress is concentrated at the grain boundaries.

[0150] In Comparative Example 2, the grains are relatively coarse, with a grain size range of 78 μm-89 μm and an average grain size of 82.6 μm. The grain distribution uniformity is poor. The size range of the Mg2Si strengthening phase is 18 μm-25 μm, with poor dispersion, and local abnormal enrichment phenomena occur (e.g., Figure 4 (As shown in the blue circle), there is slight grain distortion and microcracks (such as...) Figure 4 (As shown in the yellow circle).

[0151] In Comparative Example 3, the grain morphology is equiaxed, with a grain size ranging from 54 μm to 66 μm. The size of the Mg₂Si strengthening phase ranges from 11 μm to 17 μm, exhibiting poor dispersion uniformity. The average three-dimensional distribution density of the strengthening phase within the grain is 1.7 × 10⁻⁶. 5 pcs / mm 3 -1.1×10 6 pcs / mm 3 .

[0152] In Comparative Example 4, the grain morphology is equiaxed, with a grain size ranging from 46 μm to 50 μm. The size of the Mg₂Si strengthening phase ranges from 12 μm to 16 μm, and the average distribution density of the strengthening phase within the grain is 1.7 × 10⁻⁶. 6 pcs / mm 3 -4.6×10 6 pcs / mm 3 Mg2Si strengthening phases are enriched at grain boundaries (e.g.) Figure 6 As shown in the blue circle, the grains exhibit distortion and microcracks (such as...). Figure 6 (As shown in the yellow circle).

[0153] In Examples 1-3, the Mg / Si atomic ratio was 1.63-1.73, which is close to the theoretical atomic ratio of the Mg2Si phase. This can further approach the optimal precipitation range of the Mg2Si strengthening phase, significantly promoting the uniform nucleation and dispersion of the Mg2Si phase and significantly improving mechanical properties. In Comparative Examples 1, 2, and 3, the Mg / Si atomic ratio was too low, with a relative excess of Si and a relative deficiency of Mg, resulting in a reduction in the amount of Mg2Si phase precipitation, coarsening, and uneven distribution, which greatly weakened the strengthening effect. In Comparative Example 4, the Mg / Si atomic ratio was the same as in Example 3, but improper preparation process led to a deterioration in the distribution of the strengthening phase.

[0154] Furthermore, in Examples 1-3, the Fe content was strictly controlled to be ≤0.11% and Cu ≤0.05% to avoid the formation of coarse and brittle phases (Al3Fe, Al2Cu), reduce the cutting effect on the matrix, and ensure the uniformity of the microstructure. In Comparative Examples 1-2, the Fe content was 0.35% and the Cu content was 0.1%, which far exceeded the level of Example 3. A large amount of Al3Fe phase was continuously distributed along the grain boundaries, which not only reduced the plasticity (elongation after fracture was only 10.2-11.5%), but also destroyed the uniformity of the anodic oxide film formation (color difference ΔE=2.56-2.77).

[0155] In the existing technology, rapid cooling or even cryogenic cooling (liquid nitrogen) is often used in the homogeneous cooling process of aluminum alloys to prevent the premature precipitation of the strengthening phase after full solidification. However, in actual implementation, although rapid cooling / cryogenic cooling can keep the strengthening phase in a solid solution state, the excessive temperature change results in large residual stress inside the aluminum alloy, which can easily lead to grain distortion inside the aluminum alloy. During the subsequent aging process, the strengthening phase is greatly affected by temperature. During the aging process, the strengthening phase is prone to explosive coarsening at the grain interface, which will seriously deteriorate the uniformity of the aluminum alloy crystal structure at the microscopic level. At the macroscopic level, although the aluminum alloy has high strength, its plasticity is significantly reduced, and there are many stress concentration points inside the aluminum alloy, which cannot meet the processing requirements of high-precision parts.

[0156] In Examples 1-3, a gentle cooling process (20℃ / s-50℃ / s) was used during the homogenization process. This ensured that the solute atoms were fully dissolved and avoided grain distortion during rapid cooling, laying the foundation for the precipitation of a uniform strengthening phase during subsequent aging.

[0157] In Comparative Example 1, the natural cooling method is used during the homogenization process, which can easily lead to the premature precipitation of solute atoms to form a coarse phase. During the quenching process, the rapid cooling will cause residual internal stress and grain distortion, which will seriously deteriorate the crystal structure and alloy properties.

[0158] In Examples 1-3, a mild cooling method (15℃ / -25℃ / s) is used for quenching, which can effectively balance the solid solution saturation and internal stress. This not only avoids the explosive coarsening of the strengthening phase, but also avoids the generation of microcracks and ensures dimensional stability.

[0159] In Comparative Examples 2, 3, and 4, rapid cooling (400-500℃ / s) was used for quenching. The quenching rate was too fast, and the atomic diffusion of the aluminum alloy was completely suppressed. Although the strengthening phase would not precipitate prematurely, the grains were prone to distortion, the residual internal stress in the alloy was high, and microcracks existed inside the alloy. This not only reduced the plasticity of the aluminum alloy, but also led to large tolerance fluctuations after processing and significant color differences after anodizing. In actual implementation, the product qualification rate was reduced, which had a negative impact on continuous mass production.

[0160] In summary, this application eliminates the need for expensive alloying elements such as Zn and Zr. By optimizing the Mg / Si atomic ratio to be close to the theoretical atomic ratio of the Mg2Si phase, strictly controlling the content of Fe and Cu, overcoming the technical bias of rapid water cooling in existing technologies, and adopting a mild cooling homogenization and quenching process, it can significantly reduce harmful brittle phases (Al3Fe, Al2Cu) in aluminum alloys and significantly promote the uniform nucleation and dispersion of nanoscale Mg2Si phases. On the other hand, it can also balance the solid solution saturation and residual internal stress, ensuring the supersaturated solute atoms required for the precipitation of strengthening phases while avoiding grain distortion, microcracks, and the high temperature sensitivity of aluminum alloys during aging, as well as the explosive precipitation of strengthening phases. This balances the processing requirements of aluminum alloy strength and plasticity, and can effectively meet the processing needs of high-precision scenarios (3C electronic products, electronic precision medical devices).

[0161] The embodiments provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a high-strength aluminum alloy for 3C electronic products, characterized in that, Includes the following steps: Melting: Aluminum source, silicon source, iron source, copper source, manganese source, magnesium source, chromium source, zinc source, and titanium source are added sequentially to a high-frequency induction melting furnace. The mixture is stirred for 30-50 minutes at 740℃-760℃ and an electromagnetic stirring frequency of 200Hz-500Hz. During the stirring process, samples are taken from the high-frequency induction melting furnace at regular intervals for analysis to control the various components in the melt to be within the preset range. After stirring is completed, the first melt is obtained. Refining: Add the refining agent and the refining agent to the first melt in sequence, and let it stand for 20-30 minutes to remove gas and slag, and then the second melt is obtained. Casting: The second melt is transferred to a casting machine and a semi-continuous casting process is adopted. Under the conditions of casting speed of 80 mm / min and cooling water pressure of 0.3 MPa-0.5 MPa, the second melt is cast into aluminum material of preset size and specifications. Homogenization treatment: The prepared aluminum material is transferred to a continuous homogenizing furnace and homogenized at 530℃-550℃ for 4-5 hours. After cooling to room temperature, the homogenized aluminum material is obtained. Quenching: The homogenized aluminum material is heated to 510℃-520℃ and then transferred to a hot extruder. It is extruded at a die temperature of 480℃-490℃. After extrusion, the homogenized aluminum material is cooled by a water mist cooling device to 170℃-180℃ to obtain quenched aluminum material. Aging: The quenched aluminum material is transferred to a hot air circulating aging furnace, held at 170℃-180℃ for 8-9 hours and then naturally cooled to room temperature to obtain a high-strength aluminum alloy for 3C electronic products. The high-strength aluminum alloy, by mass percentage, comprises the following components: Si 0.43%-0.46%, Fe 0.07%-0.09%, Cu 0.04%-0.05%, Mn 0.03%-0.04%, Mg 0.63%-0.65%, Cr 0.02%-0.04%, Zn 0.02%-0.03%, Ti 0.06%-0.07%, with the remainder being Al and other unavoidable impurity elements, the total amount of which is ≤0.01%. The aluminum alloy includes an α-Al matrix phase and a Mg2Si strengthening phase dispersed within the α-Al matrix phase. The atomic ratio of Mg to Si in the aluminum alloy is 1.63-1.71; The grain size of the aluminum alloy is 12μm-17μm, and the grain size difference is 3μm-5μm; In the aluminum alloy, the grain size of the Mg2Si strengthening phase is 0.4μm-0.8μm, and the distance between two adjacent Mg2Si strengthening phase grains is 1μm-5μm. In the aluminum alloy, the average three-dimensional distribution density of the Mg2Si strengthening phase within a single grain is 2.4 × 10⁻⁶. 7 pcs / mm 3 -3.9×10 7 pcs / mm 3 ; In the aluminum alloy, the number of Mg2Si strengthening phases in a single grain is 33-84; In the aluminum alloy, the volume fraction of the Mg2Si strengthening phase within a single grain is 0.22%-0.43%; The total amount of Mg2Si strengthening phase in aluminum alloy grains is defined as Z, and the amount of Mg2Si strengthening phase on α-Al matrix grain boundaries is defined as Y. Z and Y satisfy the following relationship: 89.8%≤(ZY) / Z≤94.3%.

2. The method for preparing a high-strength aluminum alloy for 3C electronic products according to claim 1, characterized in that, The homogenization process includes a heating stage, a holding stage, and a cooling stage. The heating stage involves raising the aluminum material from room temperature to 535℃-545℃, with a corresponding heating rate of 4.5℃ / min-5℃ / min. The heat preservation stage involves heat preservation of the aluminum material at 535℃-545℃ for 4-5 hours. The cooling stage involves cooling the aluminum material from 535℃-545℃ to room temperature, with a corresponding cooling rate of 20℃ / s-50℃ / s. The cooling stage uses cooling water to cool the aluminum material, with a flow rate of 50L / min-60L / min.

3. The method for preparing a high-strength aluminum alloy for 3C electronic products according to claim 1, characterized in that, During the quenching process, the water mist flow rate is 25L / min-30L / min, and the water mist cooling rate is 15℃ / s-25℃ / s.

4. The method for preparing a high-strength aluminum alloy for 3C electronic products according to claim 1, characterized in that, During the aging process, the temperature fluctuation of the hot air circulating aging furnace is defined as X, and X satisfies the following relationship: ±1℃≤X≤±2.5℃.

5. The method for preparing a high-strength aluminum alloy for 3C electronic products according to claim 2, characterized in that, During the cooling stage and water mist cooling process, the Mg2Si reinforced phase approaches a supersaturated solid solution state.

6. An application of a high-strength aluminum alloy for 3C electronic products, characterized in that, The aluminum alloy is prepared by any one of the methods for preparing a high-strength aluminum alloy for 3C electronic products according to any one of claims 1-5; The aluminum alloy is used to process any one of the following: laptop shell bezel, laptop chip support frame, laptop screen back panel, laptop internal support beam, mobile phone metal mid-frame, mobile phone front and rear frame, smartwatch shell, heat dissipation module shell, heat dissipation module pipeline, mobile phone camera mounting bracket, drone bracket, battery pack internal bracket, and CNC medical device metal parts.

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