High-thermal-conductivity easy-to-shape 6-series aluminum alloy plate and preparation method thereof

Abstract

The invention provides a high-thermal-conductivity easy-to-form 6-series aluminum alloy plate and a preparation method thereof. The 6-series aluminum alloy plate comprises the following components in percentage by weight: 0.25-0.5% of Mg, 0.2-0.5% of Si, less than or equal to 0.20% of Fe, less than or equal to 0.10% of Cu, less than or equal to 0.10% of Mn, less than or equal to 0.10% of Zn, less than or equal to 0.05% of Ti and the balance of Al and impurities, has a short rod-shaped beta phase and a Cube texture, has the length of 20-50nm and the diameter of 1-3nm, and the volume content of the Cube texture is less than or equal to 20%. By optimizing alloy components, precipitated phase scattering is reduced, meanwhile, fine short-rod-shaped beta phases and the low Cube texture content are dispersed, the aluminum alloy can have the high heat conductivity, the high strength and the good forming performance by being further combined with grains of the specific size, and the aluminum material subjected to anodic oxidation treatment is small in surface color difference and high in glossiness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy materials, in particular to a high-thermal-conductivity and easy-to-form 6-series aluminum alloy plate and a preparation method thereof. BACKGROUND

[0002] With the rapid improvement of the computing power of high-end notebook computers (such as AIPC, i.e., artificial intelligence personal computer), the heat dissipation performance of the device has become a core bottleneck restricting its stability and service life. Research shows that 55% of electronic device failures are caused by high temperature, and the component failure rate increases exponentially with temperature, i.e., the system reliability decreases by 50% for every 10℃ increase in operating temperature. The current mainstream notebook computer appearance structure adopts a 5-series aluminum alloy, which has good anodizing effect and formability, but its thermal conductivity is about 130-150 W / (m·K), which is difficult to meet the high heat dissipation demand of high-end notebook computers.

[0003] The thermal conductivity of a 6-series aluminum alloy (such as 6061 and 6063) can reach 180-200 W / (m·K), but its traditional processing technology (such as CNC processing, i.e., computer numerical control processing) has a contradiction between strength and formability, i.e., high thermal conductivity requires reducing the content of precipitated phases, which means that the strength needs to be sacrificed; high strength requires increasing aging precipitation, which means that the formability will decrease. Moreover, the traditional 6-series profile relies on CNC processing, which has low material utilization rate (<50%), high carbon emission, and complex process and high cost. Therefore, the existing 6-series aluminum alloy plate has a contradiction between thermal conductivity, strength and formability, which is difficult to meet the requirements of high-end notebook computers. SUMMARY

[0004] The main purpose of the present application is to provide a high-thermal-conductivity and easy-to-form 6-series aluminum alloy plate and a preparation method thereof, so as to solve the problem that the existing 6-series aluminum alloy plate is difficult to have high thermal conductivity, high strength and good formability.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a high-thermal-conductivity and easy-to-form 6-series aluminum alloy plate is provided, which comprises, by weight percentage, Mg 0.25-0.5%, Si 0.2-0.5%, Fe≤0.20%, Cu≤0.10%, Mn≤0.10%, Zn≤0.10%, Ti≤0.05%, the balance being Al and unavoidable impurity elements, the content of a single impurity being ≤0.05%, and the total impurity content being ≤0.15%; the 6-series aluminum alloy plate has short rod-shaped β" phases and Cube texture, the length of the short rod-shaped β" phases being 20-50 nm, the diameter being 1-3 nm, and the volume content of the Cube texture being ≤20%.

[0006] Further, the 6-series aluminum alloy plate comprises Mg 0.35-0.45%, Si 0.25-0.3%, Fe≤0.10%, Cu≤0.01%, Mn≤0.01%, Zn≤0.03%, Ti≤0.05%, the balance of Al and inevitable impurities, the content of each impurity≤0.05%, and the total content of impurities≤0.15%; and / or the length of the short rod-shaped β" phase is 20-40 nm, and the diameter is 1-2 nm.

[0007] Further, in the 6-series aluminum alloy plate, the weight ratio of Mg and Si is (1.0-1.8):1.

[0008] Further, in the 6-series aluminum alloy plate, the volume percentage of the short rod-shaped β" phase is 0.2-0.5 vol.%; and / or the weight percentage of Mg in the short rod-shaped β" phase is 50-70 wt.%.

[0009] Further, in the 6-series aluminum alloy plate, the average grain size is 40-60 μm.

[0010] Further, the thermal conductivity of the 6-series aluminum alloy plate is 190-215 W / (m·K); and / or the tensile strength of the 6-series aluminum alloy plate is 220-250 MPa; and / or the yield strength of the 6-series aluminum alloy plate is 170-205 MPa; and / or the elongation of the 6-series aluminum alloy plate is 13-15%; and / or after anodizing, the color difference ΔE of the 6-series aluminum alloy plate is ≤0.2, and the glossiness Gu is 8-20.

[0011] According to another aspect of the present application, a method for preparing the high-thermal-conductivity and easy-to-form 6-series aluminum alloy plate is provided, comprising the following steps: step S1, alloy raw materials are melted and cast according to the component ratio to obtain an aluminum alloy ingot; step S2, the aluminum alloy ingot is subjected to homogenization heat treatment to obtain a homogenized ingot; step S3, the homogenized ingot is subjected to hot rolling to obtain a hot-rolled plate, and then the hot-rolled plate is subjected to cold rolling to obtain a cold-rolled plate; and step S4, the cold-rolled plate is sequentially subjected to solid solution treatment and stepwise aging treatment to obtain the high-thermal-conductivity and easy-to-form 6-series aluminum alloy plate; the stepwise aging treatment comprises sequentially performed first aging treatment and second aging treatment, the temperature increasing rate of the first aging treatment is greater than that of the second aging treatment, and the temperature of the first aging treatment is lower than that of the second aging treatment.

[0012] Further, in step S4, the temperature increasing rate of the first aging treatment is 15-50 ℃ / h; and / or the temperature of the first aging treatment is 120-130 ℃; and / or the temperature increasing rate of the second aging treatment is 1-3 ℃ / h, preferably 1.5-2.5 ℃ / h; and / or the temperature of the second aging treatment is 140-170 ℃, preferably 155-165 ℃; and / or the holding time of the second aging treatment is 10-20 h.

[0013] Further, in step S2, the heating rate of the homogenization treatment is 50-120℃ / h, the temperature is 550-570℃, and the holding time is 6-24h; and / or in step S3, the starting rolling temperature of the hot rolling is 420-480℃, and the finishing rolling temperature is 280-320℃; and / or the single pass reduction rate of the hot rolling is 15-50%, and the number of passes with a single pass reduction rate of 40-50% is not less than 3 passes; and / or the thickness of the hot rolled plate is 3-7mm; and / or the single pass reduction rate of the cold rolling is 20-40%; and / or the thickness of the cold rolled plate is 0.3-2.0mm.

[0014] Further, in step S4, the heating rate of the solution treatment is 3-15℃ / s, the solution temperature is 490-540℃, and the holding time is 20-60s; and / or after the solution treatment and before the step aging treatment, the material is cooled to room temperature using water cooling, water mist cooling or air cooling, and the cooling speed is 10-20℃ / s.

[0015] By applying the technical solution of the present application, the content of Mg, Si elements and impurities in the plate is controlled by optimizing the alloy composition, the scattering of precipitated phase is reduced, the thermal conductivity of the aluminum alloy plate is significantly improved, and the risk of thermal failure is significantly reduced. At the same time, the aluminum alloy plate under this composition also has a specific shape and size of dispersed fine short rod-shaped β" phase and a low Cube texture content, which can solve the contradiction between the thermal conductivity, strength and formability of the aluminum alloy, so that the aluminum alloy has high thermal conductivity and high strength, while having good forming performance, no cracks and orange peel defects after bending, small color difference and high gloss on the surface of the aluminum material after anodic oxidation treatment, suitable for high-end notebook computer plate high heat dissipation demand application scenarios, while ensuring good surface quality and low manufacturing cost. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application. The present application is not limited by the accompanying drawings.

[0017] Figure 1 A 90° bending photo of the high-thermal-conductivity easy-to-form 6-series aluminum alloy plate according to Example 1 of the present application is shown;

[0018] Figure 2 A 90° bending photo of the 6-series aluminum alloy plate according to Comparative Example 1 is shown; DETAILED DESCRIPTION

[0019] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0020] Terminology:

[0021] Weight percentage: the percentage of the mass of a certain alloy component in the total mass of the alloy.

[0022] Texture: in the process of crystal formation, such as the cold and hot processing and plastic forming of metal materials, the grains in the polycrystal will be arranged in order along certain directions, showing more or less statistical uneven distribution, that is, the phenomenon of gathering arrangement in certain directions and thus the orientation probability in these directions significantly increases, which is called preferred orientation or texture. Typical textures in the aged 6 series aluminum alloy sheet are as follows: P(011)

[122] , Cube(011)

[100] , Brass(011)

[211] , Goss(011)

[100] , Q(013)

[231] .

[0023] As described in the background of the present application, there is a problem in the prior art that the 6 series aluminum alloy sheet is difficult to balance high thermal conductivity, high strength and good formability. In order to solve the above problem, in a typical embodiment of the present application, a high-thermal-conductivity and easy-to-form 6 series aluminum alloy sheet is provided, which comprises, by weight percentage, Mg 0.25-0.5%, Si 0.2-0.5%, Fe≤0.20%, Cu≤0.10%, Mn≤0.10%, Zn≤0.10%, Ti≤0.05%, the balance being Al and unavoidable impurity elements, the content of a single impurity being≤0.05%, and the total impurity content being≤0.15%; the 6 series aluminum alloy sheet has short rod-shaped β" phase and Cube texture, the length of the short rod-shaped β" phase being 20-50 nm, the diameter being 1-3 nm, and the volume content of the Cube texture being≤20%.

[0024] Mg and Si are the main strengthening elements in the 6 series aluminum alloy, which can form β" strengthening phase (precursor of Mg2Si). When Mg is less than 0.25% and Si is less than 0.2%, the number of strengthening phase β" phase is small, resulting in low alloy strength; when Mg is higher than 0.5% and Si is higher than 0.5%, the density of precipitated phase β" phase will increase, but the thermal conductivity and forming performance will be significantly reduced. The content of Mg and Si elements in the above range can generate an appropriate amount of short rod-shaped β" phase, and too long β" phase may form intragranular or grain boundary segregation, increase the grain boundary strength, and reduce the ductility and formability of the material; and too short β" phase may not be able to effectively strengthen the material, so that the aluminum alloy sheet can balance the thermal conductivity, strength and formability.

[0025] The aggregation of Cube texture easily leads to the existence of anodic oxidation stripes. By controlling the content of Cube texture in the above range, the adverse effects of this texture can be effectively reduced, the surface quality of the material is improved, and the isotropy of the material is improved, and the forming performance of the plate in different directions is improved. At the same time, the lower Cube texture content helps to reduce the segregation at the grain boundary, reduce the anisotropy of the grain, and thus reduce the scattering effect of the thermal conductivity, and improve the thermal conductivity of the material.

[0026] Fe is a main impurity element, which is easy to form intermetallic compounds (such as Al5FeSi) with Al and Si, consumes part of Si, reduces the generation amount of Mg2Si, and affects the thermal conductivity; Cu is a trace element, which has a certain effect on improving strength, but has an adverse effect on forming performance, and reduces the corrosion resistance of the material; Mn element also has an adverse effect on forming performance; Zn is an impurity element, so the above elements need to be controlled in the above range; Ti mainly serves the purpose of refining the as-cast structure, and its content is below 0.05wt%.

[0027] By optimizing the alloy composition to control the contents of Mg, Si elements and impurities in the plate, the present application significantly improves the thermal conductivity of the aluminum alloy plate and significantly reduces the risk of thermal failure. At the same time, the aluminum alloy plate under the above composition also has a specific shape and size of dispersed fine β" phase and a low Cube texture content, so that the aluminum alloy has high thermal conductivity and high strength, and at the same time has good forming performance and high surface quality, and the aluminum material has no cracks and orange peel defects after bending 180°, and the surface color difference is small and the gloss is high after anodic oxidation treatment, which meets the demand of high-end notebook computers and other 3C consumer electronic products.

[0028] Preferably, the 6-series aluminum alloy contains 0.3-0.45% Mg, 0.25-0.4% Si, and ≤0.15% Fe. Mg and Si form the main strengthening phase Mg2Si phase of the 6-series aluminum alloy in the aluminum alloy. In a preferred embodiment, the 6-series aluminum alloy plate contains 0.35-0.45% Mg, 0.25-0.3% Si, ≤0.10% Fe, ≤0.01% Cu, ≤0.01% Mn, ≤0.03% Zn, ≤0.05% Ti, and the balance of Al and unavoidable impurity elements, with the content of each impurity ≤0.05% and the total content of impurities ≤0.15%. When the contents of Mg and Si are controlled in the above preferred range, the formation of an appropriate amount of fine β" phase is promoted, which is more conducive to improving the strength of the material without significantly increasing the scattering effect of the thermal conductivity. In addition, the control of the contents of impurity elements such as Fe, Cu, Mn, Zn, and Ti can further reduce the formation of adverse secondary phases, thereby avoiding grain boundary segregation and micro-region segregation, refining the grains, enhancing the ductility and toughness of the material, and further improving the formability.

[0029] In a preferred embodiment, the length of the short rod-like β" phase is 20-40 nm and the diameter is 1-2 nm. When the size of the β" phase is controlled within the above preferred range, it can further effectively strengthen the alloy inside, and because of its extremely small size, the ability to scatter electrons is weakened, which can further reduce the obstruction to heat conduction, thereby improving the thermal conductivity.

[0030] In a preferred embodiment, in the 6-series aluminum alloy plate, the weight ratio of Mg and Si is (1.0-1.8): 1. At a specific Mg / Si ratio, the alloy can form an appropriate amount of β" phase, which has small size and moderate quantity, and can effectively improve the yield strength and tensile strength of the material, while reducing the grain growth and thermal conductivity caused by the large precipitation of β" phase. The uniform distribution and small size of the β" phase help to reduce the hardness of the alloy and improve its plasticity, so that the plate is not easy to crack during stamping, bending and other processing, thereby having good formability.

[0031] In the 6-series aluminum alloy, the morphology of the β" phase, especially its aspect ratio and content, has a direct impact on the thermal conductivity, strength and formability of the alloy. In a preferred embodiment, in the 6-series aluminum alloy plate, the volume percentage content of the short rod-like β" phase is 0.2-0.5 vol.%; and / or the weight percentage content of Mg in the short rod-like β" phase is 50-70 wt.%. Controlling the Mg content of the β" phase within the above range is conducive to its uniform distribution within the grain, avoiding the formation of too long or too short precipitates, and is conducive to improving the efficiency of the β" phase as a strengthening phase, while reducing the negative impact on thermal conductivity, thereby improving the strength while making the material have high thermal conductivity and good formability. Controlling the content of the β" phase within the above range can effectively improve the strength of the alloy while reducing the grain coarsening or the increase of grain boundary precipitates caused by excessive content, thereby reducing the ductility and toughness of the material. By optimizing the content of the β" phase, the best balance between strength and thermal conductivity can be achieved. The small and dispersed β" phase can improve the yield strength and tensile strength, and its small size can effectively reduce the scattering effect on heat conduction, maintaining the high thermal conductivity of the material.

[0032] Small grain size can improve the strength of the material by increasing the grain boundary area, but too small grain size can increase the grain boundary scattering, thereby reducing the thermal conductivity; too large grain size can lead to a decrease in the ability to resist plastic deformation, affecting the formability. In a preferred embodiment, the average grain size of the 6-series aluminum alloy plate is 40-60 μm. The above average grain size range is conducive to making the material have higher yield strength and tensile strength to meet the structural and strength requirements, while reducing the obstruction of the grain boundary to heat conduction, maintaining better thermal conductivity, and this size range helps to improve the ductility and bending performance of the plate, improving the formability of the material.

[0033] In a preferred embodiment, the 6-series aluminum alloy plate has a thermal conductivity of 190-215 W / (m·K); and / or the 6-series aluminum alloy plate has a tensile strength of 220-250 MPa; and / or the 6-series aluminum alloy plate has a yield strength of 170-205 MPa; and / or the 6-series aluminum alloy plate has an elongation of 13-15%; and / or the 6-series aluminum alloy plate has a color difference ΔE of ≤0.2 and a glossiness Gu of 8-20 after anodizing, preferably, the 6-series aluminum alloy plate has a color difference ΔE of ≤0.15 and a glossiness Gu of 16-20 after anodizing.

[0034] Based on the optimized alloy composition and the effect of fine β" strengthening phase, the 6-series aluminum alloy plate has a thermal conductivity in the above range, so that the plate can effectively dissipate the heat generated by high-power electronic devices and reduce the scattering effect in the heat conduction process; the yield strength and the elongation can reach the above range, so that the plate has sufficient strength to withstand the load and at the same time has good plastic deformation capacity. The thermal conductivity of the 6-series aluminum alloy plate of the present application is significantly higher than that of conventional 6-series aluminum alloy, and can be further improved by more than 33% based on the traditional high-thermal-conductivity aluminum alloy, i.e. 5-series aluminum alloy plate, thereby significantly reducing the risk of thermal failure of high-end notebook computers under high computing power. By controlling the content of impurity elements such as Fe, Cu, Mn, Zn, Ti, and combining the effect of β" strengthening phase, further combining the grain size and texture distribution, the generation of surface defects and the appearance of stripes of the aluminum alloy can be effectively inhibited, so that the anodizing color difference ΔE and glossiness Gu are controlled in the above range, and the surface quality of the plate is improved.

[0035] The anodizing can be performed using conventional methods in the art, such as first performing pretreatment, including degreasing, chemical polishing, alkali etching, and black film stripping in sequence, then performing anodizing to form a porous aluminum oxide layer, and finally performing post-treatment, i.e. dyeing and sealing.

[0036] In another typical embodiment of the present application, a method for preparing the high-thermal-conductivity and easy-to-form 6-series aluminum alloy plate of the present application is also provided, comprising the following steps: step S1, melting and casting alloy raw materials according to the component ratio to obtain an aluminum alloy ingot; step S2, homogenizing the aluminum alloy ingot to obtain a homogenized ingot; step S3, hot rolling the homogenized ingot to obtain a hot-rolled plate, and then cold rolling to obtain a cold-rolled plate; step S4, sequentially performing solid solution treatment and stepwise aging treatment on the cold-rolled plate to obtain the high-thermal-conductivity and easy-to-form 6-series aluminum alloy plate; the stepwise aging treatment comprises sequentially performing first aging treatment and second aging treatment, the temperature rising rate of the first aging treatment is greater than that of the second aging treatment, and the temperature of the first aging treatment is lower than that of the second aging treatment.

[0037] Specifically, the alloy raw materials are first mixed according to the composition ratio, then melted and refined to ensure a uniform distribution of the alloy composition. The mixture is then cast into ingots using a semi-continuous casting machine. The resulting aluminum alloy ingots undergo homogenization heat treatment to eliminate compositional segregation and dissolve the soluble second phase, resulting in a homogenized ingot. The homogenized ingot is then hot-rolled to achieve an ideal grain size, yielding a hot-rolled sheet. This is followed by cold rolling to refine the sheet structure, enhance its strength, and maintain good thermal conductivity, resulting in a cold-rolled sheet. The cold-rolled sheet is then solution-treated to obtain fine grains, enabling the material to possess both high strength and good formability.

[0038] The obtained solution-treated sheet is subjected to a stepped aging treatment, including a first aging treatment and a second aging treatment performed sequentially. First, a rapid heating rate is followed by a low-temperature aging treatment, which promotes rapid atomic movement within the crystal lattice and facilitates the initial precipitation of a large number of fine β" phases. Then, without holding, a high-temperature aging treatment is performed immediately after an ultra-low-rate heating process. This process promotes the further growth of the β" phase to the optimal strengthening size and facilitates the uniform precipitation of fine strengthening phases, achieving a balance between high thermal conductivity and high strength, resulting in a high thermal conductivity, easily formable 6-series aluminum alloy sheet. The stepped aging process allows for the precipitation of a large number of dispersed fine β" strengthening phases, significantly improving the yield strength and elongation of the material. It enables crack-free 180° bending, overcoming the problem of stamping cracking in high-strength aluminum alloy sheets, and obtaining a material with high thermal conductivity and high strength, achieving synergistic optimization of strength and plasticity. This method can also reduce the Cube and Goss textures in the sheet, which have adverse effects on surface properties, effectively improving the surface quality of the sheet.

[0039] The sheet material prepared using the components and process provided by this invention has high thermal conductivity, strength and good formability. In addition, the preparation method is developed based on existing industrial equipment, the process has good batch operation capability, high production efficiency and low manufacturing cost.

[0040] In order to further improve the material strength while maintaining high thermal conductivity, and at the same time improve the stability and surface integrity of the sheet in stamping, bending and other processes by controlling grain refinement and texture components, and finally achieve a balance between high thermal conductivity, high strength and good formability, in a preferred embodiment, the heating rate of the first aging treatment is greater than the heating rate of the second aging treatment, and the difference is 14 to 25 °C / h.

[0041] In a preferred embodiment, in step S4, the heating rate of the first aging treatment is 15–50 °C / h; and / or the temperature of the first aging treatment is 120–130 °C; and / or the heating rate of the second aging treatment is 1–3 °C / h, preferably 1.5–2.5 °C / h; and / or the temperature of the second aging treatment is 140–170 °C, preferably 155–165 °C; and / or the holding time of the second aging treatment is 10–20 h. Under the above aging regime, the rapid heating of the first aging treatment is more conducive to improving thermal conductivity, and the low-temperature treatment within the above range can further promote the uniform distribution of the β" phase, increase the plasticity and toughness of the material, and facilitate molding. The slow heating and higher temperature of the second aging treatment are conducive to promoting the growth of the β" phase to improve the strength of the material. At the same time, the heating rate and temperature in this stage are conducive to controlling the size and distribution of the β" phase, reducing abnormal grain growth and the formation of unfavorable textures, and helping to maintain the high thermal conductivity and good formability of the material.

[0042] To promote the full transformation of the AlFeSi phase while further preventing grain growth, in a preferred embodiment, in step S2, the heating rate of the homogenization treatment is 50–120°C / h, the temperature is 550–570°C, and the holding time is 6–24h; and / or in step S3, the initial rolling temperature of hot rolling is 420–480°C, and the final rolling temperature is 280–320°C; and / or the single-pass reduction rate of hot rolling is 15–50%, and the number of passes with a single-pass reduction rate of 40–50% is not less than 3 passes, such as 3–5 passes; and / or the thickness of the hot-rolled plate is 3–7 mm; and / or the single-pass reduction rate of cold rolling is 20–40%; and / or the thickness of the cold-rolled plate is 0.3–2.0 mm. Strictly controlled hot rolling conditions help to form ideal grain sizes, improve the formability and surface finish of the sheet, and are suitable for precision stamping and bending processes. The absence of intermediate annealing and the lower hot rolling temperature can further suppress the number of cube textures and reduce anodized color difference and streaks.

[0043] Rapid solution treatment can improve production efficiency, reduce energy consumption, and lower manufacturing costs, making it suitable for large-scale industrial production. In a preferred embodiment, in step S4, the heating rate of the solution treatment is 3–15 °C / s, the solution temperature is 490–540 °C, and the holding time is 20–60 s; and / or after the solution treatment and before the stepped aging treatment, the material is cooled to room temperature using water cooling, water mist cooling, or air cooling at a cooling rate of 10–20 °C / s to effectively suppress the formation of coarse precipitates, reduce scattering of precipitated phases in grain boundary regions, maintain the high thermal conductivity of the material, and avoid negative impacts on the plasticity of the material, thus helping to maintain good formability of the sheet. This invention uses online solution treatment and thin-plate stamping to replace thick-plate CNC machining, achieving a material utilization rate of >80% and reducing energy consumption by 50%, which can meet the high appearance standards and low-carbon manufacturing requirements of electronic products. Under the above-mentioned parameter conditions, Mg and Si are fully dissolved into the crystal lattice. The subsequent short holding time combined with high-speed cooling can promote the solid solution of the precipitated phase, so that the β" phase does not have time to form a stable large complex, but remains in a fine and dispersed state in the alloy matrix. The precipitated phase in this state can not only significantly improve the yield strength of the material, but also maintain the characteristic of easy forming of the plate due to its small size. Thus, while ensuring the strength of the alloy, its thermal conductivity and formability are not sacrificed.

[0044] Typical, but not limiting, 6-series aluminum alloy sheets contain, by weight percentage, Mg in the range of 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or any two of these values; Si in the range of 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or any two of these values; Fe in the range of 0.05%, 0.10%, 0.15%, 0.20%, or any two of these values; and Cu in the range of 0.005%, 0.01%, 0.02%, 0.05%. The content of Mn is 0.005%, 0.01%, 0.02%, 0.05%, 0.08%, 0.10%, or any two of these values; the content of Zn is 0.005%, 0.01%, 0.02%, 0.03%, 0.05%, 0.08%, 0.10%, or any two of these values; the content of Ti is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or any two of these values; and the balance is Al and unavoidable impurity elements.

[0045] Typical, but not limiting, weight ratios of Mg to Si are 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, or any two of these ratios.

[0046] Typical, but not limiting, short rod-shaped β" phases have lengths of 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, 32 nm, 35 nm, 38 nm, 40 nm, 42 nm, 45 nm, 48 nm, 50 nm or any two of these values, and diameters of 1 nm, 1.2 nm, 1.5 nm, 1.8 nm, 2 nm, 2.2 nm, 2.5 nm, 2.8 nm, 3 nm or any two of these values.

[0047] Typical, but not limiting, volume percentages of the short rod-shaped β phase are 0.2 vol.%, 0.25 vol.%, 0.3 vol.%, 0.35 vol.%, 0.4 vol.%, 0.45 vol.%, 0.5 vol.%, or any combination of two of these values.

[0048] In a typical but not limiting short rod-shaped β phase, the weight percentage of Mg is 50 wt.%, 52 wt.%, 55 wt.%, 58 wt.%, 60 wt.%, 62 wt.%, 65 wt.%, 68 wt.%, 70 wt.%, or any two of these values.

[0049] Typical, but not limiting, 6-series aluminum alloy sheets have an average grain size of 40μm, 42μm, 45μm, 48μm, 50μm, 52μm, 55μm, 58μm, 60μm or any two of these values, and a cube texture volume content of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, 18%, 20% or any two of these values.

[0050] Typically, but not limitingly, in step S4, the heating rate of the first aging treatment is a range of 15℃ / h, 20℃ / h, 25℃ / h, 30℃ / h, 35℃ / h, 40℃ / h, 45℃ / h, 50℃ / h or any two of these values, and the temperature is a range of 120℃, 122℃, 124℃, 126℃, 128℃, 130℃ or any two of these values.

[0051] Typically, but not limitingly, in step S4, the heating rate of the second aging treatment is a range of 1℃ / h, 1.2℃ / h, 1.5℃ / h, 1.8℃ / h, 2℃ / h, 2.2℃ / h, 2.5℃ / h, 2.8℃ / h, 3℃ / h, or any two of these values, and the temperature is a range of 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, or any two of these values.

[0052] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0053] Example 1

[0054] The preparation method of high thermal conductivity and easily formable 6-series aluminum alloy sheet includes the following steps:

[0055] Step S1: Mix the alloy raw materials according to the composition ratio in Table 1, melt and refine them at 740°C, and then cast them into aluminum alloy ingots using a semi-continuous casting machine.

[0056] Step S2: The aluminum alloy ingot is heated to 565°C in the furnace at a rate of 50°C / h and held for 8 hours to perform homogenization heat treatment and obtain a homogenized ingot.

[0057] Step S3: The homogenized ingot is hot-rolled to a thickness of 4 mm, with a single-pass reduction rate between 15% and 50%. The number of passes for hot rolling with a large reduction rate (40% to 50%) is 4. The initial rolling temperature is 430°C and the final rolling temperature is 310°C to obtain a hot-rolled plate. Then, the hot-rolled plate is cold-rolled to a thickness of 0.8 mm, with a single-pass reduction rate between 20% and 30% to obtain a cold-rolled plate.

[0058] Step S4: The cold-rolled sheet is subjected to solution treatment using online continuous annealing at a heating rate of 10℃ / s, a solution temperature of 505℃, and a holding time of 30s. It is then water-cooled to room temperature at a cooling rate of 12℃ / s to obtain the solution-treated sheet. The solution-treated sheet is first heated to 120℃ at a rate of 20℃ / h, and then immediately heated to 160℃ at a rate of 2℃ / h and held for 15h to perform a stepped aging treatment, thereby obtaining a high thermal conductivity and easily formable 6-series aluminum alloy sheet.

[0059] Example 2

[0060] The difference from Example 1 is that the alloy composition of the 6-series aluminum alloy sheet is different, as detailed in Table 1.

[0061] Example 3

[0062] The difference from Example 1 is that in step S3, the homogenized ingot is hot-rolled to a thickness of 4 mm, with a single-pass reduction rate between 15% and 50%, and the number of passes for hot rolling with a large reduction rate (40% to 50%) is 5. The initial rolling temperature is 456°C, and the final rolling temperature is 300°C to obtain a hot-rolled plate. Then, the hot-rolled plate is cold-rolled to a thickness of 0.8 mm, with a single-pass reduction rate between 30% and 40%, to obtain a cold-rolled plate.

[0063] Example 4

[0064] The difference from Example 1 is that in step S3, the homogenized ingot is hot-rolled to a thickness of 4 mm, with a single-pass reduction rate between 15% and 50%, and the number of passes for hot rolling with a large reduction rate (40% to 50%) is 4. The initial rolling temperature is 430°C and the final rolling temperature is 310°C to obtain a hot-rolled plate. Then, the hot-rolled plate is cold-rolled to a thickness of 0.6 mm, with a single-pass reduction rate between 25% and 30% to obtain a cold-rolled plate.

[0065] Example 5

[0066] The difference from Example 1 is that in step S4, the cold-rolled sheet is subjected to solution treatment using online continuous annealing at a heating rate of 8°C / s, a solution temperature of 520°C, a holding time of 25s, and water cooling to room temperature at a cooling rate of 12°C / s to obtain a solution-treated sheet. The solution-treated sheet is first heated to 120°C at a rate of 20°C / h, and then immediately heated to 160°C at a rate of 2°C / h and held for 10h to perform a stepped aging treatment to obtain a 6-series aluminum alloy sheet.

[0067] Example 6

[0068] The difference from Example 1 is that in step S4, the cold-rolled sheet is subjected to solution treatment using online continuous annealing at a heating rate of 10°C / s, a solution temperature of 505°C, a holding time of 30s, and then water-cooled to room temperature at a cooling rate of 12°C / s to obtain the solution-treated sheet. The solution-treated sheet is then heated to 130°C at a rate of 15°C / h and immediately heated to 145°C at a rate of 1°C / h and held for 20h to perform a stepped aging treatment to obtain a 6-series aluminum alloy sheet.

[0069] Example 7

[0070] The difference from Example 1 is that in step S4, the cold-rolled sheet is subjected to solution treatment using online continuous annealing at a heating rate of 10°C / s, a solution temperature of 505°C, a holding time of 30s, and then water-cooled to room temperature at a cooling rate of 12°C / s to obtain the solution-treated sheet. The solution-treated sheet is first heated to 125°C at a rate of 25°C / h, and then immediately heated to 160°C at a rate of 2.5°C / h and held for 15h to perform a stepped aging treatment to obtain a 6-series aluminum alloy sheet.

[0071] Example 8

[0072] The difference from Example 1 is that in step S4, the cold-rolled sheet is subjected to solution treatment using online continuous annealing at a heating rate of 10°C / s, a solution temperature of 515°C, a holding time of 40s, and then water-cooled to room temperature at a cooling rate of 15°C / s to obtain the solution-treated sheet. The solution-treated sheet is first heated to 125°C at a rate of 30°C / h, and then immediately heated to 155°C at a rate of 1.5°C / h and held for 15h to perform a stepped aging treatment to obtain a 6-series aluminum alloy sheet.

[0073] Example 9

[0074] The difference from Example 1 is that in step S4, the cold-rolled sheet is subjected to solution treatment using online continuous annealing at a heating rate of 10℃ / s, a solution temperature of 515℃, a holding time of 40s, and then water-cooled to room temperature at a cooling rate of 15℃ / s to obtain a solution-treated sheet. The solution-treated sheet is first heated to 125℃ at a rate of 30℃ / h, and then immediately heated to 165℃ at a rate of 2.5℃ / h and held for 15h to perform a stepped aging treatment to obtain a 6-series aluminum alloy sheet.

[0075] Example 10

[0076] The difference from Example 1 is that in step S2, the aluminum alloy ingot is heated to 550°C at a rate of 50°C / h and held for 24 hours to perform homogenization heat treatment and obtain a homogenized ingot.

[0077] Example 11

[0078] The difference from Example 1 is that in step S2, the aluminum alloy ingot is heated to 570°C at a rate of 120°C / h and held for 6 hours to perform homogenization heat treatment and obtain a homogenized ingot.

[0079] Example 12

[0080] The difference from Example 1 is that in step S3, the homogenized ingot is hot-rolled to a thickness of 3 mm, with a single-pass reduction rate between 15% and 50%, and the number of passes for hot rolling with a large reduction rate (40% to 50%) is 3, with an initial rolling temperature of 420°C and a final rolling temperature of 280°C to obtain a hot-rolled plate; then the hot-rolled plate is cold-rolled to a thickness of 0.3 mm, with a single-pass reduction rate between 20% and 40%, to obtain a cold-rolled plate;

[0081] Example 13

[0082] The difference from Example 1 is that in step S3, the homogenized ingot is hot-rolled to a thickness of 7 mm, with a single-pass reduction rate between 15% and 50%, and the number of passes for hot rolling with a large reduction rate (40% to 50%) is 4. The initial rolling temperature is 480°C and the final rolling temperature is 320°C to obtain a hot-rolled plate. Then, the hot-rolled plate is cold-rolled to a thickness of 2.0 mm, with a single-pass reduction rate between 20% and 40% to obtain a cold-rolled plate.

[0083] Example 14

[0084] The difference from Example 1 is that in step S4, the cold-rolled sheet is subjected to solution treatment using online continuous annealing at a heating rate of 3°C / s, a solution temperature of 490°C, a holding time of 60s, and water cooling to room temperature at a cooling rate of 10°C / s to obtain a solution-treated sheet. The solution-treated sheet is then heated to 120°C at a rate of 15°C / h and immediately heated to 140°C at a rate of 1°C / h and held for 20h to perform a stepped aging treatment to obtain a 6-series aluminum alloy sheet.

[0085] Example 15

[0086] The difference from Example 1 is that in step S4, the cold-rolled sheet is subjected to solution treatment using online continuous annealing at a heating rate of 15°C / s, a solution temperature of 540°C, a holding time of 20s, and then water-cooled to room temperature at a cooling rate of 20°C / s to obtain a solution-treated sheet. The solution-treated sheet is then heated to 130°C at a rate of 50°C / h and immediately heated to 170°C at a rate of 3°C / h and held for 10h to perform a stepped aging treatment to obtain a 6-series aluminum alloy sheet.

[0087] Examples 16 to 17

[0088] The difference from Example 1 is that the alloy composition of the 6-series aluminum alloy sheet is different, as detailed in Table 1.

[0089] Example 18

[0090] The difference from Example 1 is that in step S2, the aluminum alloy ingot is heated to 555°C at a rate of 50°C / h and held for 10h to perform homogenization heat treatment, thereby obtaining a homogenized ingot.

[0091] Comparative Examples 1 to 2

[0092] The difference from Example 1 is that the alloy composition of the 6-series aluminum alloy sheet is different, as detailed in Table 1.

[0093] Comparative Example 3

[0094] The difference from Example 1 is that in step S3, the final rolling temperature of hot rolling is 350°C.

[0095] Comparative Example 4

[0096] The difference from Example 1 is that in step S4, the heating rate of the solution treatment is 5°C / s, and the solution temperature is 550°C.

[0097] Comparative Example 5

[0098] The difference from Example 1 is that in step S4, the solution-treated board is heated to 180°C at a rate of 20°C / h and held for 6 hours.

[0099] Comparative Example 6

[0100] The difference from Example 1 is that in step S4, the solution-treated plate is first heated to 100°C at a rate of 5°C / h, and then immediately heated to 120°C at a rate of 0.5°C / h and held for 24 hours to obtain a 6-series aluminum alloy plate.

[0101] Comparative Example 7

[0102] The difference from Example 1 is that in step S4, the solution-treated plate is first heated to 150°C at a rate of 60°C / h, and then immediately heated to 180°C at a rate of 5°C / h and held for 8 hours to obtain a 6-series aluminum alloy plate.

[0103] Comparative Example 8

[0104] The difference from Example 1 is that in step S4, the solution-treated plate is first heated to 130°C at a rate of 25°C / h, and then immediately heated to 160°C at a rate of 25°C / h and held for 15 hours to obtain a 6-series aluminum alloy plate.

[0105] Comparative Example 9

[0106] The difference from Example 1 is that in step S4, the solution-treated plate is first heated to 100°C at a rate of 50°C / h, and then immediately heated to 120°C at a rate of 20°C / h and held for 15h to obtain a 6-series aluminum alloy plate.

[0107] Performance testing:

[0108] The composition of the aluminum alloys in the above embodiments and comparative examples is shown in Table 1, and the properties and microstructure characteristics are shown in Tables 2 and 3.

[0109] Thermal conductivity: Tested in accordance with national standard GB / T 22588-2008.

[0110] Tensile properties (including strength and elongation) and bending properties: tested in accordance with national standard GB / T 228.1-2010.

[0111] Anodizing performance: Tested in accordance with national standard GB / T 20503-2006.

[0112] Average grain size: Tested according to the national standard GB / T 6394-2017 "Method for determination of average grain size of metals".

[0113] Length, diameter, and cube texture volume content of the β phase: microscopic observation.

[0114] Table 1

[0115]

[0116]

[0117] Table 2

[0118]

[0119]

[0120] Table 3

[0121]

[0122]

[0123] See the photograph of the 90° bend of the 6-series aluminum alloy sheet in Example 1. Figure 1 Photograph of the 90° bend of the 6-series aluminum alloy sheet in Comparative Example 1 can be found in [link to Comparative Example 1]. Figure 2 It can be seen that the material of the present invention has good forming properties and no cracks or orange peel defects after bending.

[0124] In Comparative Example 1, the high Mg and Si content resulted in an excessively large β" phase size, leading to decreased thermal conductivity and bending cracks due to excessive strength. In Comparative Example 2, the high Mg and low Si content resulted in undesirable β" phase size and quantity, negatively impacting mechanical properties. In Comparative Example 3, the high hot rolling temperature resulted in coarse grains, an excessively large β" phase size, numerous cube and Goss textures, striations on the anodized surface, decreased formability, and orange peel appearance during stamping. In Comparative Example 4, the excessively high solution treatment temperature resulted in excessively large grains and an excessively large β" phase size, reducing the alloy's yield strength and formability. In Comparative Example 5, using a single-stage aging process, the excessively large β" phase size led to decreased sheet strength, elongation, and formability.

[0125] This invention optimizes the content of the main alloying elements Mg and Si, and the aging process to control the size of the β" phase. Through control of hot rolling and solution treatment processes, the material exhibits fine grain size and minimal cube texture. Under these microstructural characteristics, the aluminum alloy sheet possesses high thermal conductivity, ease of forming, good anodizing performance, and appropriate strength, making it suitable for high-end laptops. The finished aluminum alloy sheet obtained in the above embodiments has equiaxed grains, with average grain size and short rod-shaped β" phase size within suitable ranges. The grain orientation is diffusely and uniformly distributed, and the texture component has minimal cube texture. Based on these microstructural characteristics, the finished aluminum alloy sheet obtained in the above embodiments exhibits good thermal conductivity, high yield strength and tensile strength, while maintaining high elongation. It also has good formability; the surface is smooth and free of orange peel after a 90° bend, and free of cracks after a 180° bend, demonstrating excellent formability and suitability for stamping and bending processes. After anodizing, the surface is free of streaks, has minimal color difference, and high gloss. The finished aluminum alloy sheet obtained in the above embodiments combines high thermal conductivity, ease of forming, good anodizing performance, and appropriate strength, making it suitable for high-end laptops.

[0126] Furthermore, it can be seen that the overall effect is better when all process parameters are within the preferred range of the present invention.

[0127] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high thermal conductivity, easily formable 6-series aluminum alloy sheet, characterized in that, By weight percentage, the 6-series aluminum alloy sheet comprises 0.25–0.5% Mg, 0.2–0.5% Si, ≤0.20% Fe, ≤0.10% Cu, ≤0.10% Mn, ≤0.10% Zn, ≤0.10% Ti, with the balance being Al and unavoidable impurity elements, the content of a single impurity being ≤0.05%, and the total impurity content being ≤0.15%. The 6-series aluminum alloy sheet has short rod-shaped β" phases and a cube texture. The length of the short rod-shaped β" phases is 20–50 nm, and the diameter is 1–3 nm. The volume content of the cube texture is ≤20%.

2. The high thermal conductivity and easily formable 6-series aluminum alloy sheet according to claim 1, characterized in that, The 6-series aluminum alloy sheet comprises 0.35–0.45% Mg, 0.25–0.3% Si, ≤0.10% Fe, ≤0.01% Cu, ≤0.01% Mn, ≤0.01% Zn, ≤0.03% Ti, with the balance being Al and unavoidable impurity elements, with individual impurity content ≤0.05% and total impurity content ≤0.15%; and / or The short rod-shaped β" phase has a length of 20–40 nm and a diameter of 1–2 nm.

3. The high thermal conductivity and easily formable 6-series aluminum alloy sheet according to claim 1 or 2, characterized in that, In the 6-series aluminum alloy sheet, the weight ratio of Mg to Si is (1.0 to 1.8):

1.

4. The high thermal conductivity, easily formable 6-series aluminum alloy sheet according to any one of claims 1 to 3, characterized in that, In the 6-series aluminum alloy sheet, the volume percentage of the short rod-shaped β phase is 0.2–0.5 vol.%; and / or The short rod-shaped β phase contains 50–70 wt.% Mg.

5. The high thermal conductivity, easily formable 6-series aluminum alloy sheet according to any one of claims 1 to 4, characterized in that, The average grain size of the 6-series aluminum alloy sheet is 40–60 μm.

6. The high thermal conductivity, easily formable 6-series aluminum alloy sheet according to any one of claims 1 to 5, characterized in that, The thermal conductivity of the 6-series aluminum alloy sheet is 190–215 W / (m·K); and / or The tensile strength of the 6-series aluminum alloy sheet is 220–250 MPa; and / or The yield strength of the 6-series aluminum alloy sheet is 170–205 MPa; and / or The elongation of the 6-series aluminum alloy sheet is 13-15%; and / or After anodizing, the 6-series aluminum alloy sheet has a color difference ΔE ≤ 0.2 and a gloss Gu of 8 to 20.

7. The method for preparing high thermal conductivity and easily formable 6-series aluminum alloy sheet according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1: Melt and cast the alloy raw materials according to the composition ratio to obtain aluminum alloy ingots; Step S2: The aluminum alloy ingot is subjected to homogenization heat treatment to obtain a homogenized ingot. Step S3: The homogenized ingot is hot-rolled to obtain a hot-rolled plate, and then cold-rolled to obtain a cold-rolled plate; Step S4: The cold-rolled sheet is subjected to solution treatment and step-aging treatment in sequence to obtain the high thermal conductivity and easily formable 6-series aluminum alloy sheet. The stepped aging process includes a first aging process and a second aging process performed sequentially. The heating rate of the first aging process is greater than the heating rate of the second aging process, and the temperature of the first aging process is less than the temperature of the second aging process.

8. The method for preparing high thermal conductivity and easily formable 6-series aluminum alloy sheet according to claim 7, characterized in that, In step S4 The heating rate of the first aging treatment is 15–50 °C / h; and / or The temperature of the first aging treatment is 120–130°C; and / or The heating rate of the second aging treatment is 1–3 °C / h, preferably 1.5–2.5 °C / h; and / or The temperature for the second aging treatment is 140–170°C, preferably 155–165°C; and / or The heat preservation time for the second aging treatment is 10 to 20 hours.

9. The method for preparing high thermal conductivity and easily formable 6-series aluminum alloy sheet according to claim 7 or 8, characterized in that, In step S2, the homogenization treatment involves a heating rate of 50–120°C / h, a temperature of 550–570°C, and a holding time of 6–24h; and / or In step S3, the initial rolling temperature of the hot rolling is 420–480°C, and the final rolling temperature is 280–320°C; and / or The hot-rolled sheet has a single-pass reduction rate of 15-50%, and the number of passes with a single-pass reduction rate of 40-50% is not less than 3; and / or the thickness of the hot-rolled sheet is 3-7 mm; and / or The single-pass reduction rate of the cold rolling is 20-40%; and / or the thickness of the cold-rolled sheet is 0.3-2.0 mm.

10. The method for preparing high thermal conductivity and easily formable 6-series aluminum alloy sheet according to any one of claims 7 to 9, characterized in that, In step S4 The solution treatment has a heating rate of 3–15 °C / s, a solution temperature of 490–540 °C, and a holding time of 20–60 s; and / or After the solution treatment and before the stepped aging treatment, the material is cooled to room temperature using water cooling, water mist cooling or air cooling at a rate of 10-20°C / s.

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