Aluminum alloy composite sheet, Al-Mg-Si aluminum alloy and casting method thereof

Abstract

The application provides an aluminum alloy composite plate, an Al-Mg-Si aluminum alloy and a casting method thereof. The aluminum alloy composite plate comprises a first barrier layer, a core material layer and a second barrier layer in sequence. The core material layer comprises the following alloy components in percentage by weight: Si: 0.3-0.7%, Mg: 0.6-1.1%, Fe: 0.25-0.7%, Cu: 0.05-0.5%, Zr: 0.02-0.1%, and Ti: 0.01-0.1%. After aging, the Si and Mg elements in the core material layer exist in the state of beta'' strengthening phase, beta' strengthening phase and beta phase. The aluminum alloy composite plate provided by the application can balance the requirements of casting forming property and stamping forming property, has high strength, and has wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy composite sheet technology, and in particular to an aluminum alloy composite sheet, an Al-Mg-Si aluminum alloy, and a casting method thereof. Background Technology

[0002] Aluminum and aluminum alloys possess high specific strength, good machinability, and corrosion resistance, making them among the most widely used materials in various industries seeking lightweight solutions. AlMn series aluminum alloys, with their excellent thermal conductivity, corrosion resistance, and machinability, are widely used in heat transfer applications. Currently, the most typical aluminum alloy heat transfer material grade is AA3003, with main components of Mn: 1.0-1.5wt%, Si: 0.3-0.6wt%, Fe: 0.5-0.8wt%, Cu: 0.05-0.2wt%. In the O state, its yield strength is 35-50 MPa, tensile strength is 95-135 MPa, and elongation is 17-25%.

[0003] However, most aluminum alloy materials currently used in heat transfer applications are primarily used as functional components for heat exchange and transfer, without providing structural support. With the increasing demands for low-carbon, environmentally friendly, and lightweight development in the new energy sector, the manufacturing industry urgently needs functional components with higher strength to fulfill certain structural functions. Therefore, the strength requirements for aluminum alloy heat transfer materials are gradually increasing. Furthermore, most aluminum heat transfer structural components require processing such as stamping or blow molding, which also places certain demands on the material's plasticity. Based on these considerations, higher-strength aluminum alloy heat transfer materials are needed in the heat transfer field to reduce the amount of structural components used, achieving lightweighting and reducing carbon emissions.

[0004] Currently, the main strengthening methods for AlMn series aluminum alloys include deformation strengthening, dispersion strengthening, and grain refinement strengthening. Among these, dispersion strengthening has limited effectiveness, while deformation strengthening cannot meet processing requirements. The preparation process for grain refinement materials is often complex and significantly reduces the material's plasticity. CN116005042A addresses this by adding strengthening elements such as Cu and Mg to traditional AlMn alloys, and by alloying Bi with Mg to form nano-sized Mg3Bi2 precipitates. This effectively pins dislocations and improves alloy strength, achieving a tensile strength of 140-155 MPa in the O-state. The rapid development of the new energy field has also placed higher demands on the strength of aluminum alloy heat transfer materials.

[0005] CN114670510A discloses an aluminum alloy composite sheet, which sequentially comprises an outer barrier layer, a core layer, an intermediate barrier layer, and a skin layer. The core layer is made of 6-series aluminum alloy, wherein the mass percentage of Si and Mg elements in the 6-series aluminum alloy is at least 0.49 wt% of Mg2Si (theoretically), and also contains 0.2-0.3 wt% excess Si; the 6-series aluminum alloy contains ≤0.4 wt% Cu; the 6-series aluminum alloy contains ≤0.6 wt% Mn; and the Si and Mg elements in the core layer exist primarily in the strengthening phases β" and β'. The aluminum alloy composite plate provided by this invention exhibits excellent mechanical properties, casting formability, and stamping formability, making it suitable for use as a high-performance next-generation aluminum alloy composite material for heat exchangers. The inventors discovered that increasing the Fe element in the Al-Mg-Si alloy system can improve the casting formability of 6XXX alloys and their modified alloys, such as CN114670510A. However, this application does not mention improvements to the alloy's casting formability, nor does it limit the amount of Fe added. Furthermore, it was found that in systems with excess Si, the amount of Fe affects the type of aluminum-iron-silicon phase formed, thus influencing stamping formability.

[0006] Therefore, it is urgent to develop an aluminum alloy sheet material with high strength and excellent casting and stamping properties for use in the field of heat transfer. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides an aluminum alloy composite sheet that improves the casting formability of the aluminum alloy composite sheet while giving it excellent stamping formability.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides an aluminum alloy composite sheet, the aluminum alloy composite sheet comprising, in sequence, a first barrier layer, a core material layer, and a second barrier layer; the core material layer comprises, by weight percentage, the following alloy components: Si: 0.3~0.7%, Mg: 0.6~1.1%, Fe: 0.25~0.7%, Cu: 0.05~0.5%, Zr: 0.02~0.1%, Ti: 0.01~0.1%.

[0010] The Si content in the core material layer of the present invention is controlled to be 0.3~0.7%, for example, it can be 0.3%, 0.4%, 0.5%, 0.58%, 0.6%, 0.61%, 0.66% or 0.7%, preferably 0.55~0.65%, more preferably 0.55~0.63%, and most preferably 0.6~0.62%.

[0011] It is worth noting that silicon (Si) can improve the fluidity of the alloy casting process and enhance the post-weld strength of the material. According to the technical inspiration disclosed in CN114670510A, when Si and Mg are in a specific theoretical excess Si ratio, they can form β″ and β′ magnesium-silicon reinforcing phases, which can effectively improve the strength of the material. However, the inventors found that when the Si content is higher than 0.7% and the Fe content is higher than 0.5%, especially when the Si content is higher than the Fe content, the relatively high concentration of Si and Fe can trigger the formation of skeletal or lath-like hard and brittle phases in the alloy, severely reducing the toughness of the material. This results in poor ductility before brazing aging, which is detrimental to stamping and leads to a high scrap rate in stamping. This invention further proposes further restrictions on Si and Fe elements based on the technology in CN114670510A to improve the stamping formability of the material. In the core material of this invention... Under alloying elements, after aging, Si and Mg elements in the core layer mainly exist in the states of β″ strengthening phase, β' strengthening phase, and β phase. Although β″ and β′ phases have better strengthening effects than β phase, if the Si element content is adjusted to be at least 0.2wt% excess based on Mg2Si, the Si element concentration may be too high. When more Fe element is added to the system to improve casting formability, for example, preferably more than 0.5wt% Fe element, the presence of high Si element is detrimental to stamping formability. Therefore, a small reduction in Si element content to control the Si element content at 0.3~0.7% results in the magnesium silicon phase in the core layer system being mainly β″, β', and β phases. Although there is a certain loss in strength, it can balance the requirements of casting formability and stamping formability.

[0012] The Mg content in the core layer of this invention is controlled at 0.6-1.1%, for example, it can be 0.6%, 0.7%, 0.75%, 0.8%, 0.81%, 0.85%, 0.9%, 0.92%, 1.0%, or 1.1%, preferably 0.8-0.95%, more preferably 0.83-0.93%, and even more preferably 0.87-0.91%. In some preferred embodiments, the strength of the material after brazing and aging is still comparable to that of an alloy system that is essentially composed of β" and β' phases.

[0013] Besides forming the Mg₂Si reinforcing phase with Si, Mg can also dissolve in the matrix to provide solid solution strengthening. When the Mg content is below 0.6%, it is difficult to form a sufficient Mg₂Si reinforcing phase, resulting in insignificant strengthening. Excessive Mg content can lead to severe cracking during casting.

[0014] The Fe content in the core material layer of the present invention is controlled at 0.25~0.7%, for example, it can be 0.25%, 0.3%, 0.42%, 0.5%, 0.51%, 0.52%, 0.55%, 0.58%, 0.6%, 0.65% or 0.7%, preferably 0.5~0.62%, more preferably 0.52~0.59%, and even more preferably 0.54~0.58%.

[0015] Fe element improves casting formability. The addition amounts of Fe and Si are controlled to ensure that the eutectic phase formed is primarily granular α-Fe₂SiAl₈ eutectic phase and / or Fe₃Si₂Al₈. 12 The presence of a eutectic phase can enhance the strength and hardness of a material with minimal reduction in toughness. However, when the Fe content is too high, coarse and brittle AlFe intermetallic compounds easily form in the alloy, significantly reducing its stamping formability and corrosion resistance.

[0016] The Cu content in the core layer of this invention is controlled to be 0.05-0.5%, for example, it can be 0.05%, 0.07%, 0.08%, 0.1%, 0.13%, 0.14%, 0.16%, 0.18%, 0.20%, 0.21%, 0.30%, 0.33%, 0.35%, 0.40%, 0.45%, or 0.5%, etc., preferably 0.12-0.22%, more preferably 0.15-0.21%, and even more preferably 0.17-0.20%.

[0017] Besides its solid solution strengthening effect when dissolved in the matrix, Cu can also precipitate θ-Al₂Cu strengthening phases during aging, improving alloy strength. Furthermore, the addition of Cu promotes the aggregation of atomic clusters during pre-aging and inhibits the migration of Mg and Si solute atoms during natural aging. Experimental studies have shown that when the Cu content is below 0.05%, its effect is relatively small; when the Cu content is above 0.5%, it significantly increases the material's deformation resistance, reduces the plasticity and corrosion resistance of the aluminum alloy, lowers the alloy's melting point, increases the risk of cracking during casting, and may also cause overheating.

[0018] The Zr content in the core material layer of this invention is controlled to be 0.02~0.1%, for example, it can be 0.02%, 0.03%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%, etc.

[0019] Zr has low solid solubility in aluminum matrix. The addition of Zr can form dispersed Al3Zr particles in the matrix. During hot deformation, this can pin grain boundaries, inhibit recrystallization, and preserve the deformed structure of the alloy. During annealing after cold deformation, it can pin dislocations and grain boundaries, thereby hindering recrystallized grain growth and improving the material's plasticity. Zr possesses both dispersion strengthening and grain refinement strengthening effects. Furthermore, the addition of trace amounts of Zr can also prevent the formation of coarse intermetallic compounds.

[0020] The Ti content in the core material layer of this invention is controlled to be 0.01~0.1%, for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%, etc.

[0021] Ti can form Al3Ti particles with the Al matrix, promoting grain nucleation and refining the grain size. Furthermore, Ti dissolved in the matrix can transform pitting corrosion into layered general corrosion, extending corrosion penetration time and improving the material's corrosion life. However, excessively high Ti content can lead to the formation of coarse Al3Ti intermetallic compounds in the matrix, weakening the material's properties.

[0022] Preferably, the average size of the grains in the core material layer is 10~20μm, for example, it can be 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm or 20μm, etc., and the aspect ratio is 1.5~2.5, for example, it can be 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4 or 2.5, etc.

[0023] The present invention further preferably controls the average size of the grains in the core layer to 10~20μm and the aspect ratio to 1.5~2.5. This is achieved by adjusting the content ratio of elements to achieve the state where the average size of the grains is controlled at 10~20μm and the aspect ratio is 1.5~2.5. Studies have found that when the average size of the grains is too large, it will reduce the strength and plasticity of the material. When the average size of the grains is too small, it will increase the grain boundary area and have an adverse effect on the corrosion resistance of the material.

[0024] Preferably, the Fe element in the core layer is primarily in the α-Fe₂SiAl₈ eutectic phase and / or Fe₃Si₂Al₈ eutectic phase. 12 Eutectic phase.

[0025] Preferably, the core material layer further includes any one or a combination of at least two of Mn, Zn, Cr, Bi, Ni, or Sr, and the total weight percentage is ≤0.3%, for example, it can be 0.3%, 0.29%, 0.28%, 0.27%, 0.26%, 0.25%, 0.24%, 0.23%, 0.22%, 0.20%, 0.19%, 0.18%, 0.15%, 0.12%, 0.10%, 0.09%, 0.08%, or 0.07%, etc. Typical but non-limiting combinations among the above are the combination of Mn and Zn, the combination of Cr and Zn, the combination of Mn and Cr, the combination of Bi and Zn, the combination of Bi and Sr, the combination of Sr and Zn, the combination of Mn and Bi, etc.

[0026] Preferably, the content of Mn in the core material layer by weight percentage is ≤0.05%, for example, it can be 0.05%, 0.04%, 0.03%, 0.02% or 0.01%, etc., preferably ≤0.04%, more preferably ≤0.03%, and especially ≤0.02% or ≤0.01%.

[0027] Preferably, the Zn content in the core layer is ≤0.05% by weight, for example, it can be 0.05%, 0.04%, 0.03%, 0.02% or 0.01%, etc., preferably ≤0.04%, more preferably ≤0.03%, and especially ≤0.02% or ≤0.01%.

[0028] Preferably, the Cr content in the core material layer is ≤0.04% by weight, for example, it can be 0.04%, 0.03%, 0.035%, 0.025%, 0.02%, 0.015% or 0.01%, etc., preferably ≤0.035%, more preferably ≤0.025%, and particularly ≤0.02% or ≤0.01%.

[0029] Preferably, the content of Bi in the core material layer by weight percentage is ≤0.06%, for example, it can be 0.06%, 0.058%, 0.05%, 0.045%, 0.04%, 0.03%, 0.035%, 0.025%, 0.02%, 0.015%, or 0.01%, etc., preferably ≤0.055%, more preferably ≤0.05%, and particularly ≤0.045% or ≤0.035%.

[0030] Preferably, the Ni content in the core material layer is ≤0.07% by weight, for example, it can be 0.07%, 0.065%, 0.062%, 0.060%, 0.058%, 0.055%, 0.050%, 0.048%, 0.045%, or 0.040%, etc., preferably ≤0.065%, more preferably ≤0.05%, and particularly ≤0.045% or ≤0.035%.

[0031] Preferably, the content of Sr in the core material layer by weight percentage is ≤0.03%, for example, it can be 0.03%, 0.029%, 0.028%, 0.025%, 0.024%, 0.023%, 0.022%, 0.020%, 0.018% or 0.015%, etc., preferably ≤0.025%, more preferably ≤0.02%, and particularly ≤0.015% or ≤0.01%.

[0032] Preferably, the first barrier layer and the second barrier layer each independently comprise the following alloy components by weight percentage: Si: 0.3~0.6%, Mn: 0.2~0.7%, Fe: 0.1~0.35%, Ti: 0.01~0.1%.

[0033] The aluminum alloy composite plate of the present invention can be used in brazing with materials containing a brazing layer. The main function of the barrier layer is to prevent Mg elements from diffusing from the core material layer to the brazing layer during the brazing process, thereby avoiding the harmful effects caused by the reaction of Mg elements with the flux.

[0034] Wherein, Si: 0.3~0.6%, for example, can be 0.3%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.5%, 0.52%, 0.55%, 0.58% or 0.6%, etc., preferably 0.35~0.5%, more preferably 0.4~0.48%, and most preferably 0.43~0.45%.

[0035] The main role of silicon (Si) is to form a nanoscale AlMnSi dispersed phase with Mn, thereby exerting a dispersion strengthening effect. When the Si content is too low, the strengthening effect is not obvious, while too high a content will cause the melting point of the barrier layer to drop, resulting in overheating during the brazing process.

[0036] Mn: 0.2~0.7%, for example 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65% or 0.7%, preferably 0.4~0.62%, more preferably 0.43~0.6%, and most preferably 0.45~0.55%.

[0037] Mn is a major additive element in 3-series aluminum alloys. Its main functions are solid solution strengthening when dissolved into the matrix and dispersion strengthening when forming Mn-containing dispersed phases. Simultaneously, Mn can react with Fe and Si to form acicular or lamellar Al6FeMn phases and Al... 12The (Fe, Mn)3 phase reduces the brittleness of the Fe-rich phase and increases the hot workability of the material. Furthermore, Mn can reduce the solid solubility of Mg in the matrix, thereby preventing the diffusion of Mg into the core layer.

[0038] Fe: 0.1~0.35%, for example 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3% or 0.35%, preferably 0.1~0.25%, more preferably 0.12~0.2%, and most preferably 0.15~0.18%.

[0039] Fe can form some strengthening phases in aluminum-iron-silicon alloys and improve the weldability of the alloy. However, in 3-series aluminum alloys, high-Si, high-Fe systems tend to produce coarse, brittle phases, which reduce the toughness of the material and thus affect its machinability.

[0040] Ti: 0.01~0.1%, for example 0.01%, 0.02%, 0.023%, 0.025%, 0.028%, 0.03%, 0.03%, 0.035%, 0.04%, 0.05%, 0.07%, 0.08%, 0.09% or 0.1%, preferably 0.1~0.25%, more preferably 0.12~0.2%, and most preferably 0.15~0.18%.

[0041] Ti can form Al3Ti particles with the Al matrix, promoting grain nucleation and refining the grain size. Furthermore, Ti dissolved in the matrix can transform pitting corrosion into layered general corrosion, extending corrosion penetration time and improving the material's corrosion life. However, excessively high Ti content can lead to the formation of coarse Al3Ti intermetallic compounds in the matrix, weakening the material's properties.

[0042] Preferably, the average grain size in the first barrier layer and the second barrier layer is independently 20~50μm, for example, it can be 20μm, 22μm, 23μm, 24μm, 25μm, 28μm, 30μm, 32μm, 35μm, 40μm, 42μm, 45μm or 50μm, and the aspect ratio is independently 2.5~5, for example, it can be 2.5, 2.8, 3.0, 3.2, 3.5, 4.0, 4.5 or 5.

[0043] Preferably, the first barrier layer and the second barrier layer each independently include any one or at least two combinations of Zn, Mg, Cr, Cu, or Zr, and the total content by weight percentage is controlled to be ≤0.25%, for example, 0.25%, 0.24%, 0.23%, 0.22%, 0.21%, 0.20%, 0.19%, 0.15%, 0.14%, or 0.13%, etc. Typical but non-limiting combinations among the above are combinations of Zn and Mg, Cr and Mg, Zn and Cr, Cu and Mg, Zn and Cu, Zr and Mg, and Zn and Zr.

[0044] Preferably, the Zn content in the first barrier layer and the second barrier layer is independently ≤0.05% by weight, for example, it can be 0.05%, 0.045%, 0.04%, 0.035%, 0.03%, 0.028%, 0.027% or 0.02%, etc., preferably ≤0.04%, more preferably ≤0.03%, and particularly ≤0.02% or ≤0.01%.

[0045] Preferably, the content of Mg in the first barrier layer and the second barrier layer is independently ≤0.05% by weight, for example, it can be 0.05%, 0.045%, 0.04%, 0.035%, 0.03%, 0.028%, 0.027% or 0.02%, etc., preferably ≤0.04%, more preferably ≤0.03%, and particularly ≤0.02% or ≤0.01%.

[0046] Preferably, the Cr content in the first barrier layer and the second barrier layer is independently ≤0.05% by weight, for example, it can be 0.05%, 0.045%, 0.04%, 0.035%, 0.03%, 0.028%, 0.027% or 0.02%, etc., preferably ≤0.04%, more preferably ≤0.03%, and particularly ≤0.02% or ≤0.01%.

[0047] Preferably, the Cu content in the first barrier layer and the second barrier layer is independently ≤0.05% by weight, for example, it can be 0.05%, 0.045%, 0.04%, 0.035%, 0.03%, 0.028%, 0.027% or 0.02%, etc., preferably ≤0.04%, more preferably ≤0.03%, and particularly ≤0.02% or ≤0.01%.

[0048] Preferably, the Zr content in the first barrier layer and the second barrier layer is independently ≤0.05% by weight, for example, it can be 0.05%, 0.045%, 0.04%, 0.035%, 0.03%, 0.028%, 0.027% or 0.02%, etc., preferably ≤0.04%, more preferably ≤0.03%, and particularly ≤0.02% or ≤0.01%.

[0049] Preferably, the ratio of the thickness of the core material layer to the total thickness of the first barrier layer and the second barrier layer is 7:3 to 8:2, for example, it can be 7:3, 7.1:2.9, 7.2:2.8, 7.3:2.7, 7.4:2.6, 7.5:2.5, 7.6:2.4, 7.7:2.3, 7.8:2.4, 7.9:2.1 or 8:2, etc.

[0050] Preferably, the thickness ratio of the first barrier layer to the second barrier layer is 1:1 to 1:3, for example, it can be 1:1, 1:1.2, 1:1.5, 1:1.6, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.5, 1:2.8 or 1:3.0, etc.

[0051] Preferably, the total thickness of the aluminum alloy composite sheet is 0.6~3mm, for example, it can be 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.2mm, 1.5mm, 1.8mm, 2.0mm, 2.5mm, 2.8mm, 3.0mm, etc.

[0052] Secondly, the present invention provides an Al-Mg-Si aluminum alloy with high castability, wherein the Al-Mg-Si aluminum alloy comprises the following alloy components by weight percentage: Si: 0.3~0.7%, Mg: 0.6~1.1%, Fe: 0.25~0.7%.

[0053] The Si content is controlled at 0.3~0.7%, for example, it can be 0.3%, 0.4%, 0.5%, 0.58%, 0.6%, 0.61%, 0.66% or 0.7%, etc.

[0054] The Mg content is controlled at 0.6~1.1%, for example, it can be 0.6%, 0.7%, 0.75%, 0.8%, 0.81%, 0.85%, 0.9%, 0.92%, 1.0% or 1.1%, etc.

[0055] The Fe content is controlled at 0.25~0.7%, for example, it can be 0.25%, 0.3%, 0.42%, 0.5%, 0.51%, 0.52%, 0.55%, 0.58%, 0.6%, 0.65% or 0.7%, etc.

[0056] Preferably, the Al-Mg-Si aluminum alloy further comprises, by weight percentage, Cu: 0.05~0.5%, Zr: 0.02~0.1%, and Ti: 0.01~0.1%.

[0057] The Cu content is controlled at 0.05~0.5%, for example, it can be 0.05%, 0.07%, 0.08%, 0.1%, 0.13%, 0.14%, 0.16%, 0.18%, 0.20%, 0.21%, 0.30%, 0.33%, 0.35%, 0.40%, 0.45%, or 0.5%, etc.

[0058] The Zr content is controlled at 0.02~0.1%, for example, it can be 0.02%, 0.03%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%, etc.

[0059] The Ti content is controlled at 0.01~0.1%, for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%, etc.

[0060] Thirdly, the present invention provides a casting method for an Al-Mg-Si aluminum alloy with high castability, the casting method comprising the following steps:

[0061] (1) Batching: The Al-Mg-Si aluminum alloy material is batched according to a specific composition;

[0062] (2) Melting: Melt the materials prepared in step (1) at a temperature of 700℃~750℃;

[0063] (3) Casting: Casting is carried out at a temperature of 685℃~710℃ to obtain aluminum ingots;

[0064] The specific components include, by weight percentage: Si: 0.3~0.7%, Mg: 0.6~1.1%, Fe: 0.25~0.7%.

[0065] Typically, for 6XXX aluminum alloys like Al-Mg-Si and their modified alloys, the high magnesium content often increases the susceptibility to cracking during casting. Therefore, these alloys exhibit high hot cracking susceptibility (HCS) values ​​during casting, leading to frequent cracking of the ingots during solidification and a high scrap rate. Experiments have shown that introducing a relatively high amount of Fe into Al-Mg-Si alloys helps reduce the HCS value and improves the alloy's castability.

[0066] In step (2), the melting temperature is 700℃~750℃, for example, it can be 700℃, 705℃, 710℃, 715℃, 720℃, 725℃, 730℃, 735℃, 740℃, 745℃ or 750℃, etc.

[0067] The casting temperature in step (3) is 685℃~710℃, for example, it can be 685℃, 690℃, 695℃, 698℃, 700℃, 701℃, 702℃, 705℃, 708℃ or 710℃, etc.

[0068] Compared with the prior art, the present invention has at least the following beneficial effects:

[0069] (1) In Al-Mg-Si alloys, the introduction of high Fe content is beneficial to reducing the HCS value and improving the alloy's castability. On the other hand, existing technologies often require the addition of a large amount of Si to obtain high strength. When the Si content is higher than 0.7% and the Fe content is higher than 0.5%, especially when the Si content is higher than the Fe content, the relatively high concentration of Si and Fe will trigger the formation of skeletal or lath-like hard and brittle phases in the alloy, which will severely reduce the plasticity of the material. This will result in poor ductility of the material before brazing aging, which is not conducive to stamping and leads to a high scrap rate. The aluminum alloy composite plate of the present invention has a reasonable Si and Fe content, which can better utilize the advantages of Fe in casting formability, while avoiding its reduction in stamping formability. The HCS of the core material ingot used to prepare the aluminum alloy composite plate is 48-72; the yield strength of the aluminum alloy composite plate in the O state is 39-51 MPa, the tensile strength is 88-118 MPa, the elongation is ≥29.3%, and the cupping value is ≥9.39 mm; after brazing and artificial aging treatment, the yield strength of the O-state aluminum alloy composite plate is ≥126 MPa, the tensile strength is ≥177 MPa, and the elongation is ≥9.8%; the low strength and high elongation of the aluminum alloy composite plate before brazing are beneficial for stamping, and the strength of the material can be significantly improved by artificial aging after forming and brazing.

[0070] (2) The aluminum alloy plate core layer of the present invention has a certain fine grain strengthening effect. The grain morphology of the barrier layer is flat and long fiber, which is beneficial to prevent Mg element from diffusing outward from the core layer during the brazing process. Attached Figure Description

[0071] Figure 1 The grain morphology of the longitudinal section of the aluminum alloy composite plate prepared in Example 1 is shown.

[0072] Figure 2 The image shows the distribution of the α-Fe2SiAl8 eutectic phase in the longitudinal section of the core material of the aluminum alloy composite plate prepared in Example 1.

[0073] Figure 3 The distribution of β-FeSiAl3 eutectic phase in the longitudinal section of the core material of the aluminum alloy composite plate prepared in Comparative Example 1 is shown.

[0074] Figure 4 The image shows the morphology of the aluminum alloy composite plate prepared in Example 1 after a cupping test. Detailed Implementation

[0075] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0076] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0077] Terms and Definitions

[0078] HCS value: The HCS value is an indicator of the hot cracking sensitivity of aluminum alloy materials during the casting process. The higher the HCS value, the more likely the material is to crack during the casting process.

[0079] Aspect ratio: Also known as aspect ratio, for grain testing, the aspect ratio is the ratio of the longest diameter passing through the inside of the grain to the longest diameter perpendicular to it. This parameter is often used to describe grain morphology.

[0080] Atom number ratio: refers to the ratio of the mass of each element in the precipitated phase to the relative atomic mass of that element.

[0081] Test method:

[0082] 1. HCS value: To evaluate the formability of Al-Mg-Si aluminum alloys with high castability, the HCS value was determined by referring to the HCS test method disclosed in Ghadir Razaz, Torbjörn Carlberg. Hot Tearing Susceptibility of AA3000 Aluminum Alloy Containing Cu, Ti, and Zr [J]. Metallurgical and Materials Transactions A, 2019, 50(8):3842-3854. After the prepared material was melted, it was poured into a constraint rod casting mold. After cooling, the sample was taken out, and the HCS value was calculated according to the crack location and crack condition.

[0083] 2. Elemental Content: The cast barrier layer aluminum ingot and core material aluminum ingot were cut into 40mm × 40mm × 10mm block samples using a saw. The surfaces were then polished successively with 80-grit and 240-grit sandpaper, and cleaned with alcohol to obtain samples for elemental content testing of the barrier layer and core material. The samples were then tested using a SPECTRO M10 direct-reading spectrometer (Germany), with three locations measured. The final elemental content result was the average of the elemental content at the three locations.

[0084] 3. Evaluation of Grain Size, Texture, and Microstructure: The high-strength aluminum alloy composite plate was cut into 20mm × 10mm samples. During mounting, the longitudinal section of the sample was used as the observation surface. Subsequently, grinding, polishing, and vibratory polishing were performed sequentially to obtain metallographic specimens with a core layer and a barrier layer. EBSD testing was then conducted using a Zeiss Sigma 300 field emission electron microscope equipped with an EBSD probe. After testing, data processing was performed using Aztec Crystal software, and its built-in data processing system was used to obtain data such as average grain size and grain aspect ratio.

[0085] 4. Magnesium-silicon precipitate types: The medium-high strength aluminum alloy composite plate was cut into 15mm×15mm pieces and then thinned by grinding with 400-grit, 800-grit, 1200-grit, and 2400-grit sandpaper in sequence. During the grinding process, it was ensured that the barrier layers on both sides were removed, and the resulting sample consisted only of the core material, with a final sample thickness of 70~100nm. Then, a disc punch was used to punch the sample into a projection sample with a diameter of 3mm. Subsequently, the transmission sample was thinned by electrolytic double-jet in a solution of 30vol% nitric acid + 70vol% methanol to complete the preparation of the transmission sample. The types and distribution of magnesium-silicon precipitates were observed using a TECNAI transmission electron microscope manufactured by FEI in the United States at a voltage of 200KV and a magnification of 2500~20000. At the same time, the composition of the precipitates was tested using EDS.

[0086] 5. Eutectic phase: After cutting the medium-high strength aluminum alloy composite plate into 20mm×10mm samples, the longitudinal section of the sample was used as the observation surface during mounting. Then, the sample was ground and polished in sequence to obtain a metallographic sample with a core material layer and a barrier layer. The distribution of the eutectic phase was observed at 500-100 magnification using a Sigma 300 field emission electron microscope manufactured by Zeiss in Germany. The composition of the eutectic phase was determined by combining EDS.

[0087] 6. Yield strength, tensile strength, and elongation: The mechanical properties of the prepared medium-high strength aluminum alloy composite plates and the medium-high strength aluminum alloy composite plates after simulated brazing and aging treatment were tested according to the methods disclosed in GB / T228.1-2010 "Metallic materials, tensile testing—Part 1: Test methods at room temperature". The testing instrument was a ZWICK universal testing machine. The tested indicators included yield strength, tensile strength, and elongation, which refer to the plastic extension strength (Rp0.2), tensile strength (Rm), and elongation after fracture (A50) in the test method, respectively. They are commonly referred to in the industry as yield strength, tensile strength, and elongation.

[0088] 7. Cupping value: The cupping test of the prepared medium and high strength aluminum alloy composite plate was carried out using the method disclosed in GB / T 4156-2007 "Erikson Cupping Test for Thin Plates and Strips of Metallic Materials". The testing equipment was the GBW-60Z microcomputer-controlled fully automatic cupping tester produced by Jinan Shangtai Test Instrument Co., Ltd.

[0089] The method for preparing the aluminum alloy composite plate in this invention includes the following steps:

[0090] (1) Batching: The core layer and barrier layer materials are batched according to their composition and weight percentage;

[0091] (2) Smelting: The materials prepared in step (1) are smelted at 700-750℃. The smelting process includes refining, removing impurities and degassing.

[0092] (3) Casting: Casting is carried out at 685-710℃ to obtain aluminum ingots; and the aluminum ingots are cut off, the tail is removed, and the surface is milled to remove the parts with uneven composition.

[0093] (4) Homogenization: After removing the skin, the aluminum ingot is placed in a muffle furnace for homogenization treatment for 8~15h at a temperature of 500~600℃. After homogenization, the aluminum ingot is placed in the air to cool to room temperature. The purpose of homogenization is mainly to remove residual stress, eliminate dendrite segregation, and fully dissolve the Mg2Si phase in the matrix.

[0094] (5) Hot rolling composite: First, the core material layer and the barrier layer are rolled to the target size thickness according to their composite ratio. The ratio of the thickness of the core material layer to the total thickness of the first barrier layer and the second barrier layer is 7:3~8:2, and the ratio of the thickness of the first barrier layer and the second barrier layer is 1:1~1:3. Then, the barrier layer and the core material layer are preheated in a muffle furnace and hot rolled composite. The preheating temperature is 450~500℃ and the holding time is 2~3h. For example, the total thickness of the composite material after hot rolling composite is 4~6mm.

[0095] (6) Cold rolling: The hot-rolled sample is cold-rolled to the target thickness, for example, it can be cold-rolled to a finished thickness of 0.6~3.0m;

[0096] (7) Annealing: The sample obtained in step (6) is placed in a muffle furnace for annealing. The annealing temperature is 350~400℃ and the annealing time is 1~3h to obtain a medium-high strength aluminum alloy composite plate.

[0097] The annealed composite material was subjected to simulated brazing and aging treatment. The brazing temperature was 600~605℃, the brazing time was 3~10min, and the cooling method was air cooling. After cooling, the material was subjected to artificial aging treatment. The artificial aging temperature was 170~200℃, and the holding time was 1~18h.

[0098] In specific embodiments of the present invention, in Examples 1, 31-35 and Comparative Examples 1-2, the melting temperature in step (2) is 700℃; the casting temperature in step (3) is 685℃; the homogenization temperature in step (4) is 590℃ and the time is 9h; the preheating temperature in step (5) is 480℃ and the time is 2h, the core material and the barrier material are hot-rolled to the target size, and the total thickness of the composite material after hot rolling is 4mm; the annealing temperature in step (7) is 390℃ and the annealing time is 3h. The annealed composite material is subjected to simulated brazing at a temperature program of 600℃ for 10min, and then artificially aged at 170℃ for 18h.

[0099] In specific embodiments of the present invention, in Examples 2-13, the melting temperature of step (2) is 730℃; the casting temperature of step (3) is 700℃; the homogenization temperature of step (4) is 500℃ and the time is 15h; the preheating temperature of step (5) is 450℃ and the time is 2h, the core material and the barrier material are hot-rolled to the target size, and the total thickness of the composite material after hot rolling is 5mm; the annealing temperature of step (7) is 350℃ and the annealing time is 3h. The annealed composite material is subjected to simulated brazing at a temperature program of 605℃ for 3min, and then artificially aged at 200℃ for 1h.

[0100] In specific embodiments of the present invention, in Examples 14-30, the melting temperature of step (2) is 750℃; the casting temperature of step (3) is 710℃; the homogenization temperature of step (4) is 600℃ and the time is 8h; the preheating temperature of step (5) is 500℃ and the time is 3h, the core material and the barrier material are hot-rolled to the target size, and the total thickness of the composite material after hot rolling is 6mm; the annealing temperature of step (7) is 400℃ and the annealing time is 1h. The annealed composite material is subjected to simulated brazing at a temperature program of 602℃ for 5min, and then artificially aged at 180℃ for 5h.

[0101] Table 1 shows the composition of the core material layer, in wt%.

[0102] Table 1

[0103]

[0104] Table 2 shows the composition of the barrier layer, in wt%.

[0105] Table 2

[0106]

[0107] Table 3 shows the specific materials, composite ratio, and performance data of the aluminum alloy composite material before welding.

[0108] Table 3

[0109]

[0110] Table 4 shows the performance data of aluminum alloy composite materials after welding. Rp0.2 and Rm are in MPa, and A50 is in [missing information].

[0111] Table 4

[0112]

[0113] The following points can be observed from Tables 1 to 4:

[0114] (1) Castability of the core material layer

[0115] As can be seen from M1 to M18, the core material layer provided by the present invention reduces the Si element by a small amount and controls the Fe content within a specific range, so that the magnesium silicon phase in the core material layer system is basically β″ phase, β' phase and β phase, which improves the casting formability. Its HCS value is controlled between 48 and 72, and the casting formability is excellent.

[0116] Comparing M1 and M19, it can be seen that M19 has an Fe content of 0.20%, resulting in an HCS value of 156 and unqualified casting performance. In contrast, M1 has an Fe content of 0.57%, and with the same content of other elements, its HCS value is 60, indicating excellent casting performance. This shows that the present invention can improve casting performance by controlling the content of iron and Si elements to match.

[0117] (2) Stamping performance

[0118] As can be seen from Examples 1 to 35, the low strength and high elongation of the aluminum alloy composite plate provided by the present invention before brazing are both beneficial for stamping. Specifically, the cupping value of the aluminum alloy composite plate in the O state is ≥9.39mm.

[0119] Comparing Example 1 and Comparative Example 1, it can be seen that by adjusting the appropriate iron and silicon content in the core layer in Example 1, the morphology of the alloy composite plate obtained after cupping experiments is shown in the figure below. Figure 4 As shown in the figure, the alloy composite sheet in this embodiment exhibits excellent stamping performance and a large cupping value (9.95 mm). In Comparative Example 1, the core material contains 0.78% Si. Due to the excessively high content of iron and silicon, the relatively high concentration of Si and Fe triggers the formation of skeletal or lath-like hard and brittle phases in the alloy, significantly reducing the stamping performance of the core material. This ultimately results in a cupping value of 8.27 for Comparative Example 1. This demonstrates that the present invention can effectively ensure the stamping performance of the composite aluminum sheet by controlling the content of Si and Fe.

[0120] Furthermore, the grain morphology of the longitudinal section of the aluminum alloy composite plate obtained in Example 1 of this invention is as follows: Figure 1 As shown, from Figure 1 It can be seen that the average grain size obtained in Example 1 of the present invention is about 12.70 μm, and the aspect ratio of the grains is 2.1; the distribution of α-Fe2SiAl8 eutectic phase in the longitudinal section of the core material of the aluminum alloy composite plate prepared in this example is as follows. Figure 2 As shown, the β-FeSiAl3 eutectic phase distribution in the longitudinal section of the core material of the aluminum alloy composite plate obtained in Comparative Example 1 is as follows: Figure 3 As shown, comparison Figure 2 and Figure 3 It can be seen that the aluminum-iron-silicon eutectic phase in the aluminum alloy composite plate obtained in Example 1 of the present invention is basically the α-Fe2SiAl8 eutectic phase. This phase is short rod-shaped and has less impact on the stamping formability of the material compared with the hard and brittle strip-shaped β-FeSiAl3 eutectic phase formed in Comparative Example 1.

[0121] (3) Strength and plasticity

[0122] Comparing Example 1 and Comparative Example 2, it can be seen that the Si content in the core layer of Comparative Example 2 is only 0.25%, while the rest is the same as that of Example 1. However, the yield strength and tensile strength of Comparative Example 2 (Rp0.2 is 35 MPa, Rm is 80 MPa) before welding are both lower than those of Example 1 (Rp0.2 is 44 MPa, Rm is 103 MPa). After welding and aging treatment, the yield strength, tensile strength and elongation of Comparative Example 2 (Rp0.2 is 80 MPa, Rm is 151 MPa, A50 is 18.7%) are also lower than those of Example 1 (Rp0.2 is 165 MPa, Rm is 215 MPa, A50 is 12%). This shows that the present invention can further improve the strength of composite aluminum alloy sheet by controlling the Si content, while balancing the casting and stamping performance.

[0123] Comparing Examples 1 and 34-35, it can be seen that the content of each element in the core layer of Examples 34-35 is not within the preferred range. Under the condition that everything else is the same as in Example 1, the yield strength and tensile strength of the composite aluminum alloy sheet formed in Example 34 before welding (Rp0.2 is 39 MPa, Rm is 88 MPa) and after welding (Rp0.2 is 126 MPa, Rm is 177 MPa) are inferior to those in Example 1. The tensile strength A50 of the composite aluminum alloy sheet in Example 35 after welding and aging treatment is only 9.8%. This shows that by controlling the content of each element in the core layer within the preferred range, the present invention can further obtain a composite aluminum alloy sheet with excellent plasticity and strength.

[0124] Comparing Examples 1 and Examples 31-33, it can be seen that the composite ratio of the core layer to the barrier layer in Examples 31-33 is not within the preferred range, and the final strength after welding aging is lower than that in Example 1. This shows that by controlling the composite ratio within a specific range, the present invention can further improve the strength after welding aging.

[0125] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An aluminum alloy composite sheet, characterized in that, The aluminum alloy composite plate comprises, in sequence, a first barrier layer, a core material layer, and a second barrier layer; The core material layer comprises, by weight percentage, the following alloy components: Mg: 0.6%, Si: 0.3%, Fe: 0.25% or Mg: 0.8-0.95%, Si: 0.55-0.63%, Fe: 0.5-0.6% or Mg: 1.1%, Si: 0.7%, Fe: 0.7%; the Fe element in the core material layer exists primarily as the α-Fe2SiAl8 eutectic phase. The core material layer also includes the following alloy components by weight percentage: Cu: 0.05~0.5%, Zr: 0.02~0.1%, Ti: 0.01~0.1%; The average size of the grains in the core material layer is 10~20μm, and the aspect ratio is 1.5~2.

5.

2. The aluminum alloy composite sheet according to claim 1, characterized in that, The core material layer contains 0.55-0.63% Si, 0.5-0.58% Fe, and 0.8-0.91% Mg by weight percentage.

3. The aluminum alloy composite sheet according to claim 1, characterized in that, The core material layer contains 0.12 to 0.22% Cu by weight.

4. The aluminum alloy composite plate according to claim 3, characterized in that, The core material layer contains 0.15 to 0.21% Cu by weight.

5. The aluminum alloy composite plate according to claim 4, characterized in that, The core material layer contains 0.17 to 0.20% Cu by weight.

6. The aluminum alloy composite sheet according to any one of claims 1 to 5, characterized in that, The core material layer also includes any one or a combination of at least two of Mn, Zn, Cr, Bi, Ni or Sr, and the total weight percentage is ≤0.3%.

7. The aluminum alloy composite plate according to claim 6, characterized in that, The content of Mn in the core material layer is ≤0.05% by weight.

8. The aluminum alloy composite plate according to claim 7, characterized in that, The content of Mn in the core material layer is ≤0.04% by weight.

9. The aluminum alloy composite plate according to claim 8, characterized in that, The content of Mn in the core material layer is ≤0.03% by weight.

10. The aluminum alloy composite sheet according to claim 6, characterized in that, The Zn content in the core layer is ≤0.05% by weight.

11. The aluminum alloy composite sheet according to claim 10, characterized in that, The Zn content in the core layer is ≤0.04% by weight.

12. The aluminum alloy composite sheet according to claim 11, characterized in that, The Zn content in the core layer is ≤0.03% by weight.

13. The aluminum alloy composite sheet according to claim 6, characterized in that, The Cr content in the core layer is ≤0.04% by weight.

14. The aluminum alloy composite sheet according to claim 13, characterized in that, The Cr content in the core layer is ≤0.035% by weight.

15. The aluminum alloy composite sheet according to claim 14, characterized in that, The Cr content in the core layer is ≤0.025% by weight.

16. The aluminum alloy composite sheet according to claim 6, characterized in that, The content of Bi in the core material layer is ≤0.06% by weight.

17. The aluminum alloy composite sheet according to claim 16, characterized in that, The content of Bi in the core material layer is ≤0.055% by weight.

18. The aluminum alloy composite sheet according to claim 17, characterized in that, The content of Bi in the core material layer is ≤0.05% by weight.

19. The aluminum alloy composite sheet according to claim 6, characterized in that, The content of Ni in the core material layer is ≤0.07% by weight.

20. The aluminum alloy composite sheet according to claim 19, characterized in that, The content of Ni in the core material layer is ≤0.065% by weight.

21. The aluminum alloy composite sheet according to claim 20, characterized in that, The content of Ni in the core material layer is ≤0.05% by weight.

22. The aluminum alloy composite sheet according to claim 6, characterized in that, The content of Sr in the core material layer is ≤0.03% by weight.

23. The aluminum alloy composite sheet according to claim 22, characterized in that, The content of Sr in the core material layer is ≤0.025% by weight.

24. The aluminum alloy composite sheet according to claim 23, characterized in that, The content of Sr in the core material layer is ≤0.02% by weight.

25. The aluminum alloy composite sheet according to any one of claims 1 to 5, characterized in that, The first barrier layer and the second barrier layer each independently comprise the following alloy components by weight percentage: Si: 0.3~0.6%, Mn: 0.2~0.7%, Fe: 0.1~0.35%, Ti: 0.01~0.1%.

26. The aluminum alloy composite sheet according to claim 25, characterized in that, The average grain size in the first barrier layer and the second barrier layer is independently 20~50μm, and the aspect ratio is independently 2.5~5.

27. The aluminum alloy composite sheet according to claim 25, characterized in that, The Si content in the first barrier layer and the second barrier layer is independently 0.35~0.5% by weight.

28. The aluminum alloy composite sheet according to claim 27, characterized in that, The Si content in the first barrier layer and the second barrier layer is independently 0.4~0.48% by weight.

29. The aluminum alloy composite sheet according to claim 28, characterized in that, The Si content in the first barrier layer and the second barrier layer is independently 0.43~0.45% by weight.

30. The aluminum alloy composite sheet according to claim 25, characterized in that, The content of Mn in the first barrier layer and the second barrier layer is independently 0.4~0.62% by weight.

31. The aluminum alloy composite sheet according to claim 30, characterized in that, The content of Mn in the first barrier layer and the second barrier layer is independently 0.43~0.6% by weight.

32. The aluminum alloy composite sheet according to claim 31, characterized in that, The content of Mn in the first barrier layer and the second barrier layer is independently 0.45~0.55% by weight.

33. The aluminum alloy composite sheet according to claim 25, characterized in that, The Fe content in the first barrier layer and the second barrier layer is independently 0.1~0.25% by weight.

34. The aluminum alloy composite sheet according to claim 33, characterized in that, The Fe content in the first barrier layer and the second barrier layer is independently 0.12~0.2% by weight.

35. The aluminum alloy composite sheet according to claim 34, characterized in that, The Fe content in the first barrier layer and the second barrier layer is independently 0.15~0.18% by weight.

36. The aluminum alloy composite sheet according to claim 25, characterized in that, The content of Ti in the first barrier layer and the second barrier layer is independently 0.1~0.25% by weight.

37. The aluminum alloy composite sheet according to claim 36, characterized in that, The content of Ti in the first barrier layer and the second barrier layer is independently 0.12~0.2% by weight.

38. The aluminum alloy composite sheet according to claim 37, characterized in that, The content of Ti in the first barrier layer and the second barrier layer is independently 0.15~0.18% by weight.

39. The aluminum alloy composite sheet according to any one of claims 1 to 5, characterized in that, The first barrier layer and the second barrier layer each independently include any one or at least two of Zn, Mg, Cr, Cu or Zr, and the total content is controlled to be ≤0.25% by weight.

40. The aluminum alloy composite sheet according to claim 39, characterized in that, The Zn content in the first barrier layer and the second barrier layer is independently ≤0.05% by weight.

41. The aluminum alloy composite sheet according to claim 40, characterized in that, The Zn content in the first barrier layer and the second barrier layer is independently ≤0.04% by weight.

42. The aluminum alloy composite sheet according to claim 41, characterized in that, The Zn content in the first barrier layer and the second barrier layer is independently ≤0.03% by weight.

43. The aluminum alloy composite plate according to claim 39, characterized in that, The content of Mg in the first barrier layer and the second barrier layer is independently ≤0.05% by weight.

44. The aluminum alloy composite sheet according to claim 43, characterized in that, The content of Mg in the first barrier layer and the second barrier layer is independently ≤0.04% by weight.

45. The aluminum alloy composite plate according to claim 44, characterized in that, The content of Mg in the first barrier layer and the second barrier layer is independently ≤0.03% by weight.

46. ​​The aluminum alloy composite sheet according to claim 39, characterized in that, The Cr content in the first barrier layer and the second barrier layer is independently ≤0.05% by weight.

47. The aluminum alloy composite sheet according to claim 46, characterized in that, The Cr content in the first barrier layer and the second barrier layer is independently ≤0.04% by weight.

48. The aluminum alloy composite sheet according to claim 47, characterized in that, The Cr content in the first barrier layer and the second barrier layer is independently ≤0.03% by weight.

49. The aluminum alloy composite sheet according to claim 39, characterized in that, The content of Cu in the first barrier layer and the second barrier layer is independently ≤0.05% by weight.

50. The aluminum alloy composite sheet according to claim 49, characterized in that, The content of Cu in the first barrier layer and the second barrier layer is independently ≤0.04% by weight.

51. The aluminum alloy composite sheet according to claim 50, characterized in that, The content of Cu in the first barrier layer and the second barrier layer is independently ≤0.03% by weight.

52. The aluminum alloy composite sheet according to claim 39, characterized in that, The Zr content in the first barrier layer and the second barrier layer is independently ≤0.05% by weight.

53. The aluminum alloy composite sheet according to claim 52, characterized in that, The Zr content in the first barrier layer and the second barrier layer is independently ≤0.04% by weight.

54. The aluminum alloy composite sheet according to claim 53, characterized in that, The Zr content in the first barrier layer and the second barrier layer is independently ≤0.03% by weight.

55. The aluminum alloy composite sheet according to any one of claims 1 to 5, characterized in that, The ratio of the thickness of the core layer to the total thickness of the first and second barrier layers is 7:3 to 8:

2.

56. The aluminum alloy composite sheet according to claim 55, characterized in that, The thickness ratio of the first barrier layer to the second barrier layer is 1:1 to 1:

3.

57. The aluminum alloy composite sheet according to claim 1, characterized in that, The total thickness of the aluminum alloy composite sheet is 0.6~3mm.

58. An Al-Mg-Si aluminum alloy with high castability, characterized in that, The Al-Mg-Si aluminum alloy comprises the following alloy components by weight percentage: Mg: 0.6%, Si: 0.3%, Fe: 0.25%; or Mg: 0.8-0.95%, Si: 0.55-0.63%, Fe: 0.5-0.6%; or Mg: 1.1%, Si: 0.7%, Fe: 0.7%. The Al-Mg-Si aluminum alloy, by weight percentage, also includes Cu: 0.05~0.5%, Zr: 0.02~0.1%, Ti: 0.01~0.1%; In the Al-Mg-Si aluminum alloy, Fe element mainly exists as the α-Fe2SiAl8 eutectic phase; The average grain size of the Al-Mg-Si aluminum alloy is 10~20μm, and the aspect ratio is 1.5~2.

5.

59. A casting method for an Al-Mg-Si aluminum alloy with high castability, characterized in that, The casting method includes the following steps: (1) Batching: The Al-Mg-Si aluminum alloy material is batched according to specific composition; (2) Melting: Melt the materials prepared in step (1) at a temperature of 700℃~750℃; (3) Casting: Casting is carried out at a temperature of 685℃~710℃ to obtain aluminum ingots; The specific components, by weight percentage, include Mg: 0.6%, Si: 0.3%, Fe: 0.25% or Mg: 0.8-0.95%, Si: 0.55-0.63%, Fe: 0.5-0.6% or Mg: 1.1%, Si: 0.7%, Fe: 0.7%; The specific components also include, by weight percentage, Cu: 0.05~0.5%, Zr: 0.02~0.1%, Ti: 0.01~0.1%; In the Al-Mg-Si aluminum alloy, Fe element mainly exists as the α-Fe2SiAl8 eutectic phase; The average grain size of the Al-Mg-Si aluminum alloy is 10~20μm, and the aspect ratio is 1.5~2.5.

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