Aluminum alloy for four doors and two covers of new energy automobile and preparation method of aluminum alloy

Abstract

The invention discloses an aluminum alloy for four doors and two covers of a new energy automobile and a preparation method of the aluminum alloy, and relates to the technical field of aluminum alloys, and the aluminum alloy comprises the following chemical components in percentage by mass: less than or equal to 0.20% of silicon, less than or equal to 0.35% of iron, less than or equal to 0.15% of copper, 0.20-0.50% of manganese, 4.0-5.0% of magnesium, less than or equal to 0.10% of chromium, less than or equal to 0.25% of zinc, 0.10% of titanium, 0.30-0.45% of zirconium, less than or equal to 0.35% of rare earth components and the balance of aluminum. The preparation method comprises the working procedures of smelting, refining, degassing, casting, saw cutting, surface milling, heat treatment, rolling and the like. By adjusting the chemical components, the proportion and the preparation process, the prepared aluminum alloy has higher tensile strength, yield strength and elongation at break compared with an existing medium-strength 5182 alloy, and the mechanical property of an aluminum alloy material is remarkably improved; and the alloy also has the advantages of small density, high hardness, good corrosion resistance, good stamping performance, easiness in welding forming and the like, and the safety performance of the current lightweight new energy automobile and the protectiveness to people in the automobile can be greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy materials, and specifically relates to an aluminum alloy for four doors and two hoods of new energy vehicles and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of the demand for automotive lightweighting and the new energy vehicle industry, the demand and requirements for automotive profiles have been continuously increasing. Different from traditional vehicles, new energy vehicles use batteries as a power drive. Affected by factors such as battery weight and driving range limitations, lightweight materials are most favored in the design and material selection of new energy vehicles. Among them, aluminum alloy profiles have become the focus of research and development in the automotive industry and new material enterprises due to their short development cycle, low mold cost, and arbitrary structural changes, making aluminum alloy materials the preferred material for automotive lightweighting. Currently, 5182 aluminum is mainly used for the four doors and two hoods of new energy vehicles. 5182 aluminum belongs to the Al-Mg series alloy material, with low density, high hardness, good corrosion resistance, good stamping performance, and easy welding and forming. Although 5182 aluminum has good deformability and can absorb impact force well when subjected to external impact, protecting the driver and passengers to a large extent, the mechanical strength of 5182 aluminum is not high and is at a medium strength level. Summary of the Invention

[0003] Aiming at the deficiencies in the prior art, an object of the present invention is to provide an aluminum alloy material and its preparation process, which is based on the 5182 aluminum alloy material. By improving the chemical composition formula and preparation process, while taking into account other excellent properties of the original material, the strength of the material is further enhanced to improve the safety performance of lightweight new energy vehicles.

[0004] To achieve the above object, the aluminum alloy described in the present application contains the following chemical components by mass percentage:

[0005] Silicon ≤ 0.20%, iron ≤ 0.35%, copper ≤ 0.15%, manganese 0.20% - 0.50%, magnesium 4.0% - 5.0%, chromium ≤ 0.10%, zinc ≤ 0.25%, titanium 0.10%, zirconium 0.30% - 0.45%, rare earth components ≤ 0.35%, and the balance is aluminum.

[0006] Further, the ratio of the zinc content to the copper content is 5:3.

[0007] Further, the ratio of the zirconium content to the titanium content is (3 - 4.5):1.

[0008] Further, the rare earth components are yttrium and erbium, and the mass ratio of yttrium to erbium is 3:2.

[0009] Furthermore, the tensile strength of the aluminum alloy is ≥ 338 MPa, the yield strength is ≥ 265 MPa, and the elongation rate is ≥ 15%.

[0010] Furthermore, the preparation method of the aluminum alloy is generally carried out according to the following steps:

[0011] Prepare the aluminum alloy raw materials according to the ratio, melt the other raw materials except the rare earth components at a temperature of 720 - 735 °C, and perform electromagnetic stirring for 35 min; after stirring, skim the slag, let it stand for 15 min after skimming the slag, introduce a ternary mixed gas of nitrogen - chlorine - carbon monoxide into the melting furnace as a refining agent to refine the aluminum liquid for 10 min. The ternary mixed gas of nitrogen - chlorine - carbon monoxide is introduced in a selective jetting manner. The purity of nitrogen and chlorine is above 98%. The refining temperature is 710 °C - 725 °C, and the vacuum in the furnace is raised to 0.05 MPa. During refining, electromagnetic stirring is carried out and the surface scum is removed, and an online filtration of the aluminum liquid is carried out using a double - stage foam ceramic filter plate;

[0012] Add the rare earth components into the furnace, the melting temperature is 785 °C - 805 °C, carry out electromagnetic stirring for about 15 min, and keep warm for 20 min after stirring;

[0013] Transport the aluminum liquid to the crystallizer for semi - continuous casting, the casting temperature is 710 °C - 720 °C, and the casting speed is 60 mm / min to obtain an aluminum alloy flat ingot;

[0014] Saw and mill the aluminum alloy flat ingot, then first heat it to 460 °C - 475 °C at a rate of 150 °C / h and keep warm for 12 - 14 h, and then air - cool; then heat it to 350 °C - 410 °C at a rate of 120 °C / h and keep warm for 3 - 5 h, and then water - cool; then heat it to 350 °C - 420 °C at a rate of 100 °C / h. When the finished product thickness is greater than or equal to 8 mm, keep warm for at least 45 min. When the finished product thickness is less than 8 mm, keep warm for at least 35 min; air - cool; finally heat it to 250 - 300 °C at a rate of 80 °C / h; keep warm for 1.5 h, and air - cool;

[0015] Hot continuous rolling is carried out when discharging from the furnace to a hot - rolled slab stock of 7 - 9 mm. The starting rolling temperature is 485 °C - 505 °C, and the final rolling temperature is 275 - 295 °C; the hot - rolled slab stock is cold - continuously rolled through two passes, and the final rolling temperature is controlled at 160 °C - 180 °C; the cold - rolled sheet is annealed, the annealing temperature is 325 °C - 335 °C, and the holding time is 3.5 h.

[0016] Furthermore, the volume ratio of each gas component in the ternary mixed gas of nitrogen - chlorine - carbon monoxide is 7:2:1.

[0017] Furthermore, the porosity of the double - stage foam ceramic filter plate is 30 / 50 PPI.

[0018] Furthermore, after the aluminum liquid flows into the crystallizer through the shunt trough, a low-frequency electromagnetic field is applied. The low-frequency electromagnetic frequency range is 50 Hz, and the intensity is 6000 AT.

[0019] Furthermore, the length of the flat ingot saw head is set at 120 - 150 mm, the milling amount on the large surface of the flat ingot is 7 - 9 mm, and the single-side milling amount on the small surface is 10 - 12 mm.

[0020] Compared with the prior art, the embodiments of the present application have at least the following beneficial effects:

[0021] Based on the 5182 aluminum alloy, in the first embodiment of the present application, by adding Zr element and limiting the content ratio between it and Ti [(3 - 4.5):1]; second, by limiting the content ratio of Zn to Cu (5:3); third, by adding rare earth elements and limiting its components to yttrium and erbium (further limiting the content ratio of the two to 3:2, and the total amount is less than or equal to 0.35%); fourth, through the optimization and improvement of the alloy preparation process (including but not limited to temperature control parameters, refining process, casting parameters, hot rolling and cold rolling parameters, and heat treatment parameters), the aluminum alloy prepared in the embodiments of the present application has higher tensile strength, yield strength, and elongation at break compared with the existing medium-strength 5182 alloy, significantly improving the mechanical properties of the aluminum alloy material. Moreover, this alloy of the present invention also has the advantages of low density, high hardness, good corrosion resistance, good stamping performance, and easy welding and forming. Combining the improvement of the material mechanical strength, it can not only be applied to the four doors and two covers of new energy vehicles, greatly improving the safety performance of current lightweight new energy vehicles and the protection of vehicle occupants, but also can be widely applied to other fields according to requirements. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art.

[0023] Figure 1 It is a line graph showing the change of the aluminum alloy strength values in Examples 1 - 5 and Comparative Examples 1 - 6 in the test examples of the present application. Detailed Embodiments

[0024] The following further describes the specific embodiments of the present invention in combination with the embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0025] The embodiments of the present application disclose an aluminum alloy for the four doors and two hoods of new energy vehicles and its preparation method, aiming to solve the problem that the mechanical strength of the four doors and two hoods of new energy vehicles made of existing 5182 aluminum materials is not high. The aluminum alloy in the embodiments of the present application contains the following chemical components by mass percentage:

[0026] Silicon ≤ 0.20%, iron ≤ 0.35%, copper ≤ 0.15%, manganese 0.20% - 0.50%, magnesium 4.0% - 5.0%, chromium ≤ 0.10%, zinc ≤ 0.25%, titanium 0.10%, zirconium ≤ 0.45%, rare earth elements ≤ 0.35%, and the balance is aluminum.

[0027] It should be noted that: the addition of silicon in the embodiments of the present application can improve the fluidity of the alloy in the molten state, but excessive silicon will reduce the plasticity of the aluminum material. The silicon content in the embodiments of the present application is controlled within the above range, and the fluidity of the aluminum alloy meets the die-casting requirements and can form a Mg2Si strengthening phase with magnesium, which helps to improve the mechanical properties of the aluminum alloy.

[0028] The addition of iron in the embodiments of the present application can play a strengthening role. Specifically, it forms high-density and fine-sized Al-Fe and Al-Fe-Mn with Al and Mn, and can improve the welding performance of the aluminum alloy for the welding operation in the manufacturing and assembly process of new energy vehicles.

[0029] The addition of copper in the embodiments of the present application can form a solid solution phase with aluminum. The precipitated Al2Cu phase is dispersed on the grain boundaries of the aluminum alloy. This precipitated phase is a strengthening phase, which can improve the strength and toughness of the aluminum alloy. However, when the Cu content is too high, it will instead affect the elongation at break of the aluminum alloy. Therefore, the Cu content in the embodiments of the present application is not higher than 0.15%; and the CuZn combined phase formed by Cu and Zn can effectively improve the mechanical strength of the alloy.

[0030] The addition of manganese in the embodiments of the present application can be dissolved into the aluminum alloy matrix to play a strengthening role. At the same time, it can also inhibit the grain growth of primary Si and α-Al, so that the primary silicon content is dispersed among the grains, playing a dispersion strengthening role, thereby improving the strength and toughness of the aluminum alloy in the embodiments of the present application. Among them, most of the Mn will segregate to the grain boundaries of the aluminum alloy and combine with Fe to form needle-shaped AlFeMnSi phases, thereby improving the overall strength of the aluminum alloy. However, the Mn content cannot be too much or too little. It is just right to control it within 0.2% - 0.5% in this embodiment. If the Mn is excessive, the large number of needle-shaped structures formed will cause the splitting of the aluminum alloy matrix, and then the toughness of the aluminum alloy will be reduced, unable to meet the toughness requirements of the four doors and two hoods of new energy vehicles.

[0031] In the embodiments of the present application, magnesium is the main component in the aluminum alloy of the embodiments of the present application (the component content is controlled at 4.0%-5.0%). Its addition can improve the strength of the aluminum material. When Mg element is added to the Al-Si alloy, Mg can form a stable Mg2Si compound with Si, and this compound can greatly improve the mechanical properties of the aluminum material. However, excessive Mg will reduce the plasticity of the material. The solubility of Mg itself in the aluminum alloy is relatively limited, and the precipitation rate is not ideal enough. If too much Mg is added to the aluminum alloy, excess phases will be formed between the grains, which will instead reduce the strength at the grain boundaries and make the alloy brittle.

[0032] In the embodiments of the present application, the addition of chromium can improve the alloy strength and the ability to resist stress corrosion cracking. However, excessive Cr will form coarse intermediate compounds with other elements Mn, Fe, and Ti in the alloy, reducing the formability of the alloy. In the embodiments of the present application, the Cr content is controlled below 0.10%. Among them, chromium forms intermetallic compounds such as (CrFe)Al7 and (CrMn)Al12 in aluminum, hindering the nucleation and growth process of recrystallization, having a certain strengthening effect on the alloy, and can improve the alloy toughness and reduce the sensitivity to stress corrosion cracking.

[0033] In the embodiments of the present application, the added zinc is effectively dissolved in α-Al to form a solid solution, playing a role in strengthening the mechanical properties of the aluminum alloy. At the same time, it can also improve the machining performance of the aluminum alloy and enhance the flow forming property of the aluminum alloy. However, when zinc is added to aluminum alone, the improvement of the strength of the aluminum alloy under deformation conditions is very limited, and there is also a tendency of stress corrosion cracking, thus restricting its application. Therefore, in the prior art, it is often added to the aluminum alloy in cooperation with Mg and Cu to form a strengthening phase, which has an obvious strengthening effect on the alloy, but the strengthening effect varies depending on the chemical composition and ratio.

[0034] In one embodiment of the present application, when the ratio of the Zn content to the Cu content is controlled at 5:3, the CuZn binding phase formed by Cu and Zn can effectively improve the mechanical strength of the aluminum alloy in the embodiments of the present application, and at the same time, can ensure that the aluminum alloy has a good elongation at fracture.

[0035] In the embodiments of the present application, adding Ti and Zr elements separately both has the effect of refining the grains of the aluminum alloy in the embodiments of the present application. Through a large number of experimental studies, the inventors of the present application found that when adding Ti and Zr simultaneously, and the ratio of the content of Zr to the content of Ti is (3 - 4.5):1, the grain refinement effect on the aluminum alloy in the embodiments of the present application is significantly better than that of adding them separately in equal amounts. This is because when Ti and Zr are added in combination, not only the Al3Zr and Al3Ti particles that exist when Ti and Zr are added separately act as nucleation sites, but also a large number of Al3(Ti,Zr) complex-phase nucleation cores are formed. These particles jointly promote the strong refinement of the grains, thereby improving the mechanical properties of the aluminum alloy. However, in the present application, the Ti content needs to be less than or equal to 0.10%, and the Zr content needs to be less than or equal to 0.45%.

[0036] In the embodiments of the present application, rare earth elements yttrium and erbium both provide heterogeneous nucleation during solidification, and are mainly distributed in the α(Al) phase, phase boundaries, grain boundaries, and segregation areas between dendrites of the aluminum alloy, making the dendritic structure and grains refined. In particular, it plays a strengthening role in the aluminum alloy of the present invention. Most of the yttrium and erbium segregate at the grain boundaries of the alloy, and the remaining part of the rare earth elements exists in the form of compounds (such as Al3Y, Al3Er, etc.), and are dispersed in the matrix, generating a dispersion strengthening effect. Through a large number of experimental studies, the inventors of the present application found that when the content of rare earth elements does not exceed 0.35%, and the mass ratio of yttrium to erbium in the rare earth elements is controlled at 3:2, the improvement effect of the mechanical strength of the aluminum alloy in the embodiments of the present application is the most significant.

[0037] In the embodiments of the present application, the aluminum alloy also includes inevitable impurities. Specifically, the content of a single element in the inevitable impurities does not exceed 0.01%, and the total content of the inevitable impurities does not exceed 0.15%. Since it is difficult to achieve 100% purity of the raw materials, and impurities are also likely to be introduced during the preparation process, the aluminum alloy usually contains inevitable impurities (such as B, Ca, Hf, etc.), but these inevitable impurities will not have too much negative impact on the aluminum alloy.

[0038] Example 1

[0039] This Example 1 discloses an aluminum alloy for the four doors and two covers of new energy vehicles, which contains the chemical components shown in Table 1 below:

[0040] Table 1: Chemical Composition of Aluminum Alloy in Example 1 (by mass percentage%)

[0041]

[0042]

[0043] Example 2

[0044] Example 2 discloses an aluminum alloy for the four doors and two hoods of new energy vehicles, which contains the chemical components in Table 2 below:

[0045] Table 2: Chemical Composition of Aluminum Alloy in Example 2 (by mass percentage%)

[0046] Serial Number Chemical Composition Content 1 Silicon Si 0.15％ 2 Iron Fe 0.30％ 3 Copper Cu 0.12％ 4 Manganese Mn 0.40％ 5 Magnesium Mg 4.75％ 6 Chromium Cr 0.08％ 7 Zinc Zn 0.20％ 8 Titanium Ti 0.10％ 9 Zirconium Zr 0.40％ 10 Rare Earth Components Composed of two elements, erbium (Er) and yttrium (Y), where Er is 0.18% and Y is 0.12% 9 Other Impurities ≤0.15％ 10 Aluminum Al Balance

[0047] Example 3

[0048] Example 3 discloses an aluminum alloy for the four doors and two hoods of new energy vehicles, which contains the chemical components in Table 3 below:

[0049] Table 3: Chemical Composition of Aluminum Alloy in Example 3 (by mass percentage%)

[0050] Serial Number Chemical Composition Content 1 Silicon Si 0.10％ 2 Iron Fe 0.25％ 3 Copper Cu 0.09％ 4 Manganese Mn 0.50％ 5 Magnesium Mg 4.5％ 6 Chromium Cr 0.05％ 7 Zinc Zn 0.15％ 8 Titanium Ti 0.10％ 9 Zirconium Zr 0.35％ 10 Rare Earth Components Composed of two elements, erbium (Er) and yttrium (Y), where Er is 0.15% and Y is 0.10% 9 Other Impurities ≤0.15％ 10 Aluminum Al Balance

[0051] Example 4

[0052] Example 4 discloses an aluminum alloy for the four doors and two hoods of new energy vehicles, which contains the chemical components in Table 4 below:

[0053] Table 4: Chemical Composition of Aluminum Alloy in Example 4 (by mass percentage%)

[0054]

[0055]

[0056] Example 5

[0057] Example 5 discloses an aluminum alloy for the four doors and two hoods of new energy vehicles, which contains the chemical components in Table 5 below:

[0058] Table 5: Chemical Composition of Aluminum Alloy in Example 5 (by mass percentage%)

[0059] Serial Number Chemical Composition Content 1 Silicon Si 0.15％ 2 Iron Fe 0.30％ 3 Copper Cu 0.15％ 4 Manganese Mn 0.25％ 5 Magnesium Mg 4.0％ 6 Chromium Cr 0.10％ 7 Zinc Zn 0.25％ 8 Titanium Ti 0.10％ 9 Zirconium Zr 0.40％ 10 Rare Earth Components Composed of two elements, erbium (Er) and yttrium (Y), where Er is 0.21% and Y is 0.14% 9 Other Impurities ≤0.15％ 10 Aluminum Al Balance

[0060] Example 6

[0061] Based on the aluminum alloys of the above Examples 1-5, Example 6 discloses a method for preparing an aluminum alloy, which includes the following steps:

[0062] According to the chemical composition formulations of the aluminum alloys in Examples 1 - 5, prepare the aluminum alloy raw materials according to the ratio. The raw materials include aluminum ingots, aluminum master alloy ingots, magnesium ingots, manganese agents, etc. Put the other raw materials except the rare earth components into an intermediate frequency induction furnace for melting. The melting temperature is 720 - 735°C, and electromagnetic stirring is carried out for 35 min; after stirring, skim the slag, let it stand for 15 min after skimming the slag, and introduce a ternary mixed gas of nitrogen - chlorine - carbon monoxide into the intermediate frequency induction furnace as a refining agent to refine the aluminum liquid for 10 min. The ternary mixed gas of nitrogen - chlorine - carbon monoxide is introduced in a selective jetting manner. The gas jetting makes the refining agent evenly distributed in the intermediate frequency induction furnace and facilitates the high - speed rotation of the rotor in the intermediate frequency induction furnace to break the bubbles. And the purity of the nitrogen and chlorine is above 98%. The temperature during refining is controlled at 710°C - 725°C, and the vacuum in the intermediate frequency induction furnace is raised to 0.05 MPa. During refining, electromagnetic stirring is carried out and the surface scum is removed. And the volume ratio of each gas component in the ternary mixed gas of nitrogen - chlorine - carbon monoxide is 7:2:1 [V(N2):V(Cl2):V(Co)]; the rotor speed is 400 - 500 r / min; and an online filtration of the aluminum liquid is carried out using a double - stage foam ceramic filter plate. The porosity of the double - stage foam ceramic filter plate is 30 / 50 PPI.

[0063] Add the rare earth components into the intermediate frequency induction furnace. The melting temperature is 785°C - 805°C, and electromagnetic stirring is carried out for about 15 min. After stirring, keep the temperature for 20 min;

[0064] Transport the obtained aluminum liquid to a crystallizer for semi - continuous casting. The casting temperature is 710°C - 720°C, and the casting speed is 60 mm / min to obtain an aluminum alloy flat ingot; and in the semi - continuous casting of this example, after the aluminum liquid flows into the crystallizer through a flow - dividing groove, a low - frequency electromagnetic field is applied. The low - frequency electromagnetic frequency range is 50 Hz, and the intensity is 6000 AT;

[0065] Saw and mill the surface of the aluminum alloy flat ingot. The length of the saw head of the flat ingot is set at 120 - 150 mm, the milling amount of the large surface of the flat ingot is 7 - 9 mm, and the single - side milling amount of the small surface is 10 - 12 mm; then first heat it at a rate of 150°C / h to 460°C - 475°C and keep the temperature for 12 - 14 h, and then air - cool; then heat it at a rate of 120°C / h to 350°C - 410°C and keep the temperature for 3 - 5 h, and then water - cool; then heat it at a rate of 100°C / h to 350°C - 420°C. When the thickness of the finished product is greater than or equal to 8 mm, keep the temperature for at least 45 min. When the thickness of the finished product is less than 8 mm, keep the temperature for at least 35 min; air - cool; finally heat it at a rate of 80°C / h to 250 - 300°C; keep the temperature for 1.5 h, and then air - cool.

[0066] Hot-rolled out, the hot-rolled slab stock is rolled to 7-9 mm, with the starting rolling temperature of 485°C - 505°C and the finishing rolling temperature of 275 - 295°C; the hot-rolled slab stock is cold-rolled in two passes, and the finishing rolling temperature is controlled at 160°C - 180°C; the cold-rolled sheet is annealed, with the annealing temperature of 325°C - 335°C and the holding time of 3.5 h.

[0067] Cutting the sheet, cutting the sheet on a cross-cutting machine according to the required specifications.

[0068] Comparative Example 1

[0069] Comparative Example 1 is 5182 aluminum alloy, which contains the chemical components shown in Table 6 below:

[0070] Table 6: Chemical Composition of 5182 Aluminum Material (by mass percentage%)

[0071]

[0072]

[0073] Comparative Example 2

[0074] The only difference between Comparative Example 2 and Example 1 is that:

[0075] The contents of copper and zinc are 0.15% and 0.20% respectively.

[0076] Comparative Example 3

[0077] The only difference between Comparative Example 3 and Example 2 is that:

[0078] The contents of copper and zinc are 0.12% and 0.25% respectively.

[0079] Comparative Example 4

[0080] The only difference between Comparative Example 4 and Example 3 is that:

[0081] The contents of zirconium and titanium are 0.35% and 0.15% respectively.

[0082] Comparative Example 5

[0083] The only difference between Comparative Example 5 and Example 4 is that:

[0084] The contents of zirconium and titanium are 0.3% and 0.05% respectively.

[0085] Comparative Example 6

[0086] The only difference between Comparative Example 6 and Example 5 is that:

[0087] The contents of yttrium and erbium are 0.15% and 0.15% respectively.

[0088] Test Example

[0089] The following performance tests were carried out on the aluminum alloys obtained in the above examples and comparative examples, and the test results are shown in Table 7 below:

[0090] Table 7: Test Data

[0091] Object Tensile Strength σb / MPa Condition Yield Strength σ0.2 / MPa Elongation δ5 / % Example 1 346 271 16 Example 2 342 270 16 Example 3 343 268 16 Example 4 338 265 15 Example 5 341 272 16 Comparative Example 1 175 80 15 Comparative Example 2 284 206 14 Comparative Example 3 277 199 14 Comparative Example 4 256 173 14 Comparative Example 5 260 188 15 Comparative Example 6 232 154 14

[0092] Combined with Table 7 and Figure 1 the characterized test data and content, it can be concluded that:

[0093] The performance of the aluminum alloy prepared in the embodiment of the present application is significantly better than that of the 5182 alloy on the existing market, and also better than other comparative examples set in the present application. By setting these comparative examples, it can be seen that if the content of each element component is not within the protection scope of the present application, or some components are outside the formula, or the ratio of certain two chemical components does not meet the requirements, the mechanical properties of the aluminum alloy cannot achieve the expected effect;

[0094] Compared with the 5182 alloy on the existing market, the tensile strength of the aluminum alloy prepared in the embodiment of the present application is increased by more than 93.14%, the yield strength is increased by more than 231.25%, and the elongation at break is increased by 1-2 percentage points, and the mechanical properties are significantly improved.

[0095] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An aluminum alloy for four doors and two covers of new energy vehicles, characterized in that: Contains the following chemical components by mass percentage: Silicon ≤0.20%, iron ≤0.35%, copper ≤0.15%, manganese 0.20%~0.50%, magnesium 4.0%~5.0%, chromium ≤0.10%, zinc ≤0.25%, titanium 0.10%, zirconium 0.30%~0.45%, rare earth component ≤0.35%, and the balance aluminum.

2. The aluminum alloy according to claim 1, characterized in that The ratio of zinc content to copper content is 5:

3.

3. The aluminum alloy according to claim 1, characterized in that The ratio of zirconium content to titanium content is (3-4.5):

1.

4. The aluminum alloy according to claim 1, characterized in that The rare earth components are yttrium and erbium, and the mass ratio of yttrium to erbium is 3:

2.

5. The aluminum alloy according to claim 1, characterized in that The aluminum alloy has a tensile strength of ≥338 MPa, a yield strength of ≥265 MPa, and an elongation of ≥15%.

6. A method for preparing the aluminum alloy according to claim 1, characterized in that: The following steps are involved: Aluminum alloy raw materials are prepared according to the ratio, and other raw materials except rare earth components are smelted at a temperature of 720-735°C and electromagnetic stirring for 35 minutes; after stirring, slag is removed, and the slag is left to stand for 15 minutes, and nitrogen-chlorine-carbon monoxide ternary mixed gas is introduced into the smelting furnace as a refining agent to refine the aluminum liquid for 10 minutes, and the nitrogen-chlorine-carbon monoxide ternary mixed gas is introduced by selective jetting, the purity of the nitrogen and chlorine is above 98%, the refining temperature is 710°C-725°C, and the vacuum in the furnace is raised to 0.05MPa, electromagnetic stirring is performed during refining to remove the scum on the surface, and the aluminum liquid is filtered online using a double-stage foam ceramic filter plate; Add rare earth components into the furnace, the smelting temperature is 785℃~805℃, electromagnetic stirring is carried out for about 15 minutes, and the temperature is kept for 20 minutes after stirring; The aluminum liquid is transported to a crystallizer for semi-continuous casting at a casting temperature of 710°C to 720°C and a casting speed of 60 mm / min to obtain an aluminum alloy ingot; The aluminum alloy flat ingot is sawed and milled, and then heated to 460℃~475℃ at a rate of 150℃ / h, and kept warm for 12~14h, and air-cooled; then heated to 350℃~410℃ at a rate of 120℃ / h, and kept warm for 3~5h, and water-cooled; then heated to 350℃~420℃ at a rate of 100℃ / h, and kept warm for at least 45min when the thickness of the finished product is greater than or equal to 8mm, and kept warm for at least 35min when the thickness of the finished product is less than 8mm; air-cooled; finally heated to 250~300℃ at a rate of 80℃ / h; kept warm for 1.5h, and air-cooled; The hot rolled sheet is hot rolled out of the furnace, and the hot rolled sheet is rolled to 7-9 mm, wherein the starting rolling temperature is 485-505°C, and the final rolling temperature is 275-295°C; the hot rolled sheet is subjected to two passes of cold rolling, and the final rolling temperature is controlled at 160-180°C; the cold rolled sheet is annealed at 325-335°C and the holding time is 3.5h.

7. The preparation method according to claim 5, characterized in that: The volume ratio of each gas component in the nitrogen-chlorine-carbon monoxide ternary mixed gas is 7:2:

1.

8. The preparation method according to claim 5, characterized in that: The porosity of the dual-stage ceramic foam filter plate is 30 / 50 PPI.

9. The preparation method according to claim 5, characterized in that: After the aluminum liquid flows into the crystallizer through the diversion trough, a low-frequency electromagnetic field is applied, and the low-frequency electromagnetic field has a frequency range of 50 Hz and an intensity of 6000 AT.

10. The preparation method according to claim 5, characterized in that: The length of the flat ingot saw head is set at 120-150mm, the large face milling surface of the flat ingot is 7-9mm, and the small face single-side milling surface is 10-12mm.

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