Aluminum alloy and preparation method thereof, box for packaging battery, battery, and electrical device

Abstract

This application relates to an aluminum alloy and its preparation method, a casing for battery encapsulation, a battery, and an electrical device. The aluminum alloy comprises the following components by mass percentage: Si 0.51-0.59; Fe ≤ 0.20; Cu 0.16-0.23; Mn ≤ 0.03; Mg 0.52-0.59; Cr ≤ 0.03; Zn ≤ 0.03; Ti ≤ 0.05; rare earth elements 0.11-0.15; other unavoidable impurities ≤ 0.10; and the balance being Al. By controlling the Si, Mg, and Cu contents within the above ranges, the aluminum alloy achieves both high strength and extrusion performance. Simultaneously, the addition of 0.11-0.15 wt.% rare earth elements refines and improves the alloy microstructure, which is beneficial for toughening the alloy and thus improving its extrusion performance.

Description

Technical Field

[0001] This application relates to an aluminum alloy and its preparation method, a casing for encapsulating batteries, a battery, and an electrical device. Background Technology

[0002] In recent years, with the development of lithium-ion rechargeable battery technology, lithium-ion rechargeable batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant advancements in lithium-ion rechargeable batteries, higher requirements have been placed on the extrusion performance of the casings used to package the batteries. Summary of the Invention

[0003] The purpose of this application is to provide an aluminum alloy and its preparation method, a casing for encapsulating batteries, a battery, and an electrical device.

[0004] The embodiments of this application are implemented as follows:

[0005] In a first aspect, embodiments of this application provide an aluminum alloy, which, by mass percentage, comprises the following components:

[0006] Si 0.51-0.59; Fe≤0.20; Cu 0.16-0.23; Mn≤0.03; Mg 0.52-0.59; Cr≤0.03; Zn≤0.03; Ti≤0.05; Rare earth elements 0.11-0.15; Other unavoidable impurities ≤0.10; Balance Al.

[0007] This application presents an aluminum alloy formulation in which the Si content is strictly controlled between 0.51 wt.% and 0.59 wt.% and the Mg content between 0.52 wt.% and 0.59 wt.%, respectively, to enhance precipitation strengthening and thus improve the alloy's basic mechanical properties, resulting in high strength and high extrusion performance. Simultaneously, the Cu content is controlled at 0.16 wt.% to 0.23 wt.%, which is beneficial for improving both solid solution strengthening and precipitation strengthening, further enhancing the product's mechanical properties. Furthermore, the addition of 0.11 wt.% to 0.15 wt.% of rare earth elements refines and improves the alloy's microstructure, promoting toughness and consequently improving its extrusion performance. Therefore, the aforementioned aluminum alloy achieves both high strength and high extrusion performance; its application in the production of battery casings can improve extrusion performance, reduce extrusion difficulty, and increase extrusion efficiency.

[0008] Furthermore, the aforementioned aluminum alloy formula strictly controls the Mn and Cr content to below 0.03 wt.%, greatly reducing the formation of supersaturated solid solutions in the alloy and thus reducing the quenching sensitivity of the aluminum alloy. Applying this formula to the production of battery casings can reduce the difficulty of the quenching process, reduce uneven distribution of residual stress generated during quenching, reduce profile deformation, and improve the yield rate.

[0009] In some alternative implementations, Si 0.52-0.58; Fe ≤0.20; Cu 0.17-0.22; Mn ≤0.03; Mg 0.53-0.54; Cr ≤0.03; Zn ≤0.03; Ti ≤0.05; rare earth elements 0.12-0.14; other unavoidable impurities ≤0.10; balance Al.

[0010] The above aluminum alloy formula, by further strictly controlling the addition of Mg and Si elements, can further improve the alloy strength and extrusion performance. Further controlling the addition of Cu elements can further improve the alloy strength. Further controlling the addition of rare earth elements can improve the extrusion performance of the alloy. Thus, the alloy has high strength, low quenching sensitivity, and excellent extrusion performance, making it the most valuable for industrial applications.

[0011] In some alternative implementations, the mass ratio of Mg to Si is 0.881-1.157.

[0012] Controlling the Mg / Si mass ratio between 0.881 and 1.157 can enable aluminum alloys to achieve excellent extrusion performance and strength.

[0013] In some alternative implementations, the rare earth element includes at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, or Y.

[0014] In some alternative implementations, the rare earth element is La.

[0015] Rare earth element La is the cheapest among the 17 rare earth elements, making it both economical and practical while improving material performance.

[0016] In some alternative implementations, when other unavoidable impurities include multiple elements by mass percentage, the percentage of a single element is ≤0.03.

[0017] Controlling the content of a single impurity element to ≤0.03% helps avoid the aggregation of a single element and is beneficial to the overall performance of aluminum alloys.

[0018] In some alternative implementations, the aluminum alloy meets the following condition under air-cooled quenching conditions, where the cooling intensity of air-cooled quenching is 5°C / s:

[0019] (a) The tensile strength of aluminum alloy is ≥290 MPa;

[0020] (b) The yield strength of the aluminum alloy is ≥260MPa;

[0021] (c) The elongation after fracture of aluminum alloy is ≥9%.

[0022] In the above technical solution, the cooling intensity of air-cooled quenching is 5℃ / s. The higher the quenching cooling intensity, the higher the above properties.

[0023] The proposed solution can achieve the above objectives under the condition that the cooling intensity of air-cooled quenching is 5℃ / s.

[0024] Achieving high strength under air-cooled quenching conditions can reduce deformation defects caused by uneven cooling of products under high quenching intensity conditions such as fog cooling and water cooling.

[0025] In addition, some products with relatively symmetrical structures can be quenched using mist cooling or water cooling, which will result in higher tensile strength, yield strength, and elongation after fracture.

[0026] Secondly, embodiments of this application provide a method for preparing an aluminum alloy, comprising:

[0027] Aluminum alloy rods are obtained by smelting according to the aluminum alloy composition content provided in the first aspect above.

[0028] The aluminum alloy rod is homogenized and then cooled.

[0029] In some alternative implementations, the homogenization process is kept at a temperature of 555°C to 575°C for 6 to 10 hours.

[0030] In some alternative implementations, the cooling process includes: cooling the aluminum alloy bar to less than 250°C with a strong airflow and then water cooling to room temperature.

[0031] Due to the superior extrudability of the above alloy formulation, the alloy can achieve high strength and good extrudability under the above homogenization treatment combined with cooling treatment, that is, while achieving high strength, good extrudability is retained.

[0032] In some alternative implementations, the wind speed of the strong wind is 180°C / h to 220°C / h.

[0033] In some alternative embodiments, the method for preparing the aluminum alloy also includes processing the cooled aluminum alloy rod into an aluminum alloy profile.

[0034] In some alternative embodiments, the cooled aluminum alloy bar is processed into an aluminum alloy profile, including:

[0035] The aluminum alloy bar is air-cooled and quenched, and then cut into profiles.

[0036] In some alternative implementations, the air-cooling quenching temperature is 500℃~530℃.

[0037] By adjusting the aluminum alloy formula, the aluminum alloy is made to have low quenching sensitivity, so it can be quenched under air-cooling conditions, which reduces the difficulty of quenching, reduces the uneven distribution of residual stress generated during quenching, reduces profile deformation, and improves the pass rate.

[0038] Thirdly, embodiments of this application provide a housing for encapsulating a battery, the housing comprising the aluminum alloy described in the second aspect above.

[0039] Fourthly, embodiments of this application provide a battery, which includes the housing provided in the third aspect for encapsulating the battery.

[0040] Fifthly, embodiments of this application provide an electrical device, which includes the battery provided in the fourth aspect. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0043] Figure 2 Exploded views of batteries provided for some embodiments of this application;

[0044] Figure 3 for Figure 2 The exploded view of the battery cell shown;

[0045] Figure 4 A partial structural schematic diagram of an electrode assembly provided in some embodiments of this application;

[0046] Figure 5 A schematic diagram of the tensile specimen provided for the tensile test in this application;

[0047] Figure 6 A schematic diagram of the structure of the prototype mold provided for the extrusion test of this application.

[0048] icon:

[0049] 1000 vehicles;

[0050] Battery 100; Controller 200; Motor 300;

[0051] Box body 10; First part 11; Second part 12; Storage space 13;

[0052] Battery cell 20; casing 21; electrode assembly 22; electrode terminals 23; pressure relief structure 24;

[0053] 211 housing; 212 cover; 221 positive electrode plate; 222 negative electrode plate; 223 separator;

[0054] Positive electrode current collector 2211; Positive electrode active material layer 2212;

[0055] Negative electrode current collector 2221; negative electrode active material layer 2222. Detailed Implementation

[0056] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0058] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0059] In the description of the embodiments of this application, the technical terms "inner" and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0060] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0061] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0062] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the height, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall height, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0063] Currently, the materials used for the casing of packaged batteries are typically 6061 aluminum alloy or 6082 aluminum alloy, but these materials often have the following problems:

[0064] 1. Relatively poor extrusion performance, difficult extrusion, slow extrusion speed, low extrusion production efficiency, and short die life;

[0065] 2. Alloys are highly sensitive to quenching and require water cooling or mist cooling quenching to ensure quenching strength. This can lead to uneven distribution of residual stress during quenching, causing profile deformation, such as flatness, bending and twisting in the length direction, which cannot meet the higher usage requirements of the product.

[0066] This application provides an aluminum alloy comprising the following components by weight percentage:

[0067] Si 0.51-0.59; Fe≤0.20; Cu 0.16-0.23; Mn≤0.03; Mg 0.52-0.59; Cr≤0.03; Zn≤0.03; Ti≤0.05; Rare earth elements 0.11-0.15; Other unavoidable impurities ≤0.10; Balance Al.

[0068] The aluminum alloy formulation of this application strictly controls the Mn and Cr content to below 0.03 wt.%, greatly reducing the formation of supersaturated solid solutions in the alloy and thus reducing the quenching sensitivity of the aluminum alloy. At the same time, the Si content is strictly controlled to be between 0.51 wt.% and 0.59 wt.%, and the Mg content to be between 0.52 wt.% and 0.59 wt.%, to improve the precipitation strengthening effect of the alloy, thereby improving the basic mechanical properties of the alloy and obtaining high strength and high extrusion performance. In addition, 0.11 wt.% to 0.15 wt.% of rare earth elements are added to the formulation to refine and improve the alloy microstructure, which is beneficial to the toughening of the alloy and thus to the extrusion performance of the aluminum alloy.

[0069] Furthermore, the aluminum alloy provided in this application, through adjustment of the aluminum alloy formula, yields a high-strength, low-quenching-sensitivity, and high-extrusion-performance extruded aluminum alloy. This alloy exhibits high T6 mechanical properties under air-cooled quenching conditions, reducing quenching difficulty, minimizing uneven distribution of residual stress generated during quenching, reducing profile deformation, and improving the yield rate. Simultaneously, its good extrusion performance meets the requirements of industrial production, improving extrusion production efficiency and yield, thereby significantly reducing processing costs.

[0070] The T6 state mentioned above represents the heat treatment state, which is the same as the conventional T6 state treatment method for 6061 aluminum alloy. This state generally includes medium-thick plate quenching, medium-thick plate slicing, stretching, aging treatment, sawing, polishing, and packaging. The entire production cycle is about 10 days. After solution heat treatment, no cold working is required, and straightening and leveling can be performed, but this will not affect the mechanical properties.

[0071] The battery casing provided in this application includes the aforementioned aluminum alloy. Casings made of this aluminum alloy have higher strength and better extrusion performance.

[0072] The battery provided in this application includes the aforementioned housing, and the battery has higher strength and higher compressibility.

[0073] This application provides an electrical device, including the aforementioned battery.

[0074] For ease of explanation, the following embodiments use a lithium-ion battery according to an embodiment of this application as an example.

[0075] See Figure 1 , Figure 1This is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0076] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0077] In this application, battery 100 can refer to a physical module including a single battery cell, or it can be a single physical module including multiple battery cells 20 to provide higher voltage and capacity. Battery 100 can be in the form of a battery module or battery pack. Battery 100 may include a housing 10 for encapsulating one or more battery cells 20. Housing 10 can prevent liquids or other foreign objects from affecting the charging or discharging of battery cells 20.

[0078] See Figure 2 , Figure 2 The exploded view of a battery 100 provided in some embodiments of this application shows that the battery 100 includes a housing 10 and battery cells 20, with the battery cells 20 housed within the housing 10. In the battery 100, there can be one or more battery cells 20. If there are multiple battery cells 20, they can be connected in series, parallel, or a combination thereof. A combination thereof means that multiple battery cells 20 can be connected in both series and parallel connections. Multiple battery cells 20 can be directly connected in series, parallel, or a combination thereof, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, multiple battery cells 20 can first be connected in series, parallel, or a combination thereof to form modules, and then these modules can be connected in series, parallel, or a combination thereof to form a whole, which is then housed within the housing 10. The battery 100 may also include other structures; for example, multiple battery cells 20 can be electrically connected through a busbar component to achieve parallel, series, or combination connections of the multiple battery cells 20.

[0079] Each battery cell 20 can be a lithium-ion battery, such as a secondary battery or a primary battery; it can also be a lithium-sulfur battery, a sodium-ion battery or a magnesium-ion battery, but is not limited to these.

[0080] See Figure 3 , Figure 3 for Figure 2 The diagram shows an exploded view of a single battery cell 20. A single battery cell 20 refers to the smallest unit that makes up the battery 100. A single battery cell 20 may include a housing 21, an electrode assembly 22, and an electrolyte, with the electrode assembly 22 and electrolyte both housed within the housing 21.

[0081] The outer casing 21 may include a housing 211 and a cover 212. The housing 211 is an assembly that fits with the cover 212 to form an internal sealed space for the battery cell 20, wherein the formed sealed space can accommodate the electrode assembly 22, electrolyte, and other components. The cover 212 is a component that covers the opening of the housing 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover 212 may be adapted to the shape of the housing 211 to fit the housing 211, and the cover 212 may also be provided with functional components such as electrode terminals 23 and pressure relief structures 24. A sealing ring may be provided between the opening of the housing 211 and the cover 212 to achieve a seal between the housing 211 and the cover 212.

[0082] The housing 211 and cover 212 can be of various shapes and sizes, such as cuboids, cylinders, and hexagonal prisms. Specifically, the shapes of the housing 211 and cover 212 can be determined according to the specific shape and size of the electrode assembly 22. The materials of the housing 211 and cover 212 can be various, such as, but not limited to, metals like copper, iron, aluminum, stainless steel, and aluminum alloys. The materials of the sealing ring can be various, such as, but not limited to, materials resistant to electrolyte corrosion, high toughness, and fatigue resistance, such as PP (polypropylene), PC (polycarbonate), and PET (polyethylene terephthalate). A plating layer can be formed on the outer surface of the housing 211, and the plating layer material can be various, such as, but not limited to, corrosion-resistant materials like Ni and Cr.

[0083] See Figure 4 The electrode assembly 22 may consist of a positive electrode 221, a negative electrode 222, and a separator 223. The separator 223 is located between the positive electrode 221 and the negative electrode 222 and serves as an separator. The electrode assembly 22 may be a wound structure or a stacked structure, and the embodiments of this application are not limited thereto.

[0084] See Figure 4 The positive electrode 221 includes a positive current collector 2211 and a positive active material layer 2212. Taking a lithium-ion battery cell 20 as an example, the material of the positive current collector 2211 can be aluminum. The positive active material layer 2212 includes a positive active material.

[0085] Please continue reading Figure 2The housing 10 is used to accommodate the battery cell 20, and the housing 10 can have various structures. In some embodiments, the housing 10 may include a first part 11 and a second part 12, which overlap each other, and the first part 11 and the second part 12 together define a receiving space 13 for accommodating the battery cell 20. The second part 12 may be a hollow structure with one end open, and the first part 11 may be a plate-like structure, with the first part 11 covering the open side of the second part 12 to form a housing 10 with the receiving space 13; the first part 11 and the second part 12 may also both be hollow structures with one side open, with the open side of the first part 11 covering the open side of the second part 12 to form a housing 10 with the receiving space 13. Of course, the first part 11 and the second part 12 can be various shapes, such as cylinders, cuboids, etc.

[0086] In some embodiments of this application, the material of the housing 10 described above is aluminum alloy.

[0087] Furthermore, in some embodiments of this application, an aluminum alloy is provided, comprising the following components by weight percentage:

[0088] Si 0.51-0.59; Fe≤0.20; Cu 0.16-0.23; Mn≤0.03; Mg 0.52-0.59; Cr≤0.03; Zn≤0.03; Ti≤0.05; Rare earth elements 0.11-0.15; Other unavoidable impurities ≤0.10; Balance Al.

[0089] By adjusting the aluminum alloy formula, the above-mentioned aluminum alloy was obtained as an extruded aluminum alloy with high strength, low quenching sensitivity, and high extrusion performance.

[0090] Furthermore, in the above aluminum alloy formulation, the Mn and Cr contents are strictly controlled to be below 0.03 wt.% to greatly reduce the formation of supersaturated solid solutions in the alloy, thereby reducing the quenching sensitivity of the aluminum alloy.

[0091] When the content of Mn and Cr elements is higher than 0.03 wt.%, the quenching sensitivity of the alloy will be significantly increased. This is because during the solution treatment stage, alloying elements such as Mg and Si have high solubility in the Al matrix at high temperatures, forming a solid solution with aluminum as the matrix. Their solubility decreases as the temperature decreases. Therefore, after solution treatment and holding at high temperature, rapid cooling is required to form a metastable supersaturated solid solution.

[0092] Supersaturated solid solutions are unstable. When Mn and Cr are added to the alloy at concentrations higher than 0.03 wt.%, the resulting compounds (MnAl6, (FeMn)Al6, CrAl compounds, etc.) have relatively large particles. Mg and Si phases adhere to the surface of these compounds, which helps the nucleation of the equilibrium phase Mg2Si and provides a diffusion shortcut along the boundary, allowing it to precipitate and grow rapidly. The addition of Mn and Cr provides the conditions for precipitation and accelerates its decomposition. Therefore, a higher cooling rate is needed to reduce the premature precipitation and aggregation of the strengthening phase, thus increasing the alloy's quenching sensitivity.

[0093] As the quenching sensitivity of the alloy increases, a higher cooling rate and greater cooling intensity are required to ensure quenching strength. However, this leads to uneven distribution of residual stress generated during quenching, causing profile deformation, such as flatness issues, bending and twisting in the length direction. This type of aluminum alloy is unfavorable for battery casings, especially because uneven cooling of the side beam profiles can cause bending and twisting deformation, resulting in scrap and reduced yield.

[0094] Therefore, the above aluminum alloy formula strictly controls the Mn and Cr content to below 0.03 wt.% in order to obtain an aluminum alloy with low quenching sensitivity.

[0095] Furthermore, in the above aluminum alloy formulation, the Si content is strictly controlled at 0.51wt.%-0.59wt.% and the Mg content at 0.52wt.%-0.59wt.% to improve the precipitation strengthening effect of the alloy, thereby improving the basic mechanical properties of the alloy and obtaining high strength and high extrusion performance.

[0096] Si and Mg are the basic additive elements in the above aluminum alloy formulation. The content of Mg and Si affects the content of the precipitated strengthening phase Mg5Si6 in the alloy, which directly affects the basic strength of the alloy. If the content of the strengthening phase is too low, the performance will not meet the requirements, and if the content of the strengthening phase is too high, the strength will be too high, which will relatively reduce the extrusion performance of the alloy. In the above technical solution, the Mg5Si6 content is controlled at 0.307%-0.364%. At the same time, considering that the consumption of Si element by Fe element (Mn and Cr are not considered if they are below 0.03wt.%) in actual applications is 0.4*Fe content (forming AlFeSi phase), the above aluminum alloy formulation strictly controls the Si content at 0.51wt.%-0.59wt.% and the Mg content at 0.52wt.%-0.59wt.%, which can improve the precipitation strengthening effect of the alloy, thereby improving the basic mechanical properties of the alloy and obtaining high strength and high extrusion performance.

[0097] Furthermore, in the above aluminum alloy formulation, controlling the Cu content to be 0.16wt.%-0.23wt.% is beneficial to improving the solid solution strengthening and precipitation strengthening effects of the alloy, thereby further improving the mechanical properties of the product.

[0098] When atoms of another element dissolve in solid aluminum, a solid solution is formed. Some individual aluminum atoms are replaced by new atoms on the same crystal lattice. Aluminum is the "solvent," and the new atoms are the "solute" atoms. The solute atoms create a distorted region in the aluminum lattice, which hinders the plastic flow of aluminum atoms, making deformation difficult and thus increasing strength.

[0099] Al atom diameter 2.84*10- 1 nm, Cu atom diameter 2.52*10- 1 The atomic diameter difference is relatively large, the mismatch degree is -0.32, and Cu atoms have high solubility in the aluminum matrix at high temperature, with a maximum solubility of 5.67% at 550℃. Therefore, after Cu is added, a tensile stress zone is formed around Cu atoms, which distorts the aluminum matrix lattice, making deformation more difficult, thereby improving the solid solution strengthening effect.

[0100] In addition, similar to the mechanism of Mg2Si strengthening phase generated by Mg and Si, an appropriate amount of Cu can react with the primary α-Al phase in the alloy to form CuAl2 strengthening phase. During the aging process, second phase particles such as GP zone, coherent θ phase, semi-coherent θ' phase, and incoherent equilibrium phase θ are precipitated to strengthen the matrix.

[0101] The evolution of the precipitated phase during the aging process is as follows:

[0102] CuAl2 precipitation enhancement:

[0103] Solid solution → GP zone (Cu-rich phase aggregation) → coherent phase θ” → semi-coherent phase θ' → incoherent equilibrium phase θ

[0104] The θ” phase has the best strengthening effect. After aging, these strengthening phases are dispersed in the aluminum matrix and hinder the movement of dislocations through the dislocation pinning effect, thereby improving the strength.

[0105] On the other hand, Cu has a high electrode potential and is more sensitive to the corrosion resistance of alloys. It will reduce the corrosion resistance of materials. In addition, the market price of copper-aluminum master alloys is high, and adding too much will affect the economics of the formula.

[0106] Therefore, taking all factors into consideration, the Cu content in the above aluminum alloy formulation should be controlled at 0.16 wt.%-0.23 wt.%.

[0107] Furthermore, the addition of 0.11wt.%-0.15wt.% rare earth elements to the above aluminum alloy formulation refines and improves the alloy microstructure, which is beneficial to the toughening of the alloy and thus to the extrusion performance of the aluminum alloy.

[0108] Besides refining and purifying the melt during the metal casting stage, rare earth elements mainly improve the alloy structure and have a strong precipitation strengthening effect on dispersed rare earth compounds. Adding rare earth elements can improve the crack initiation location and propagation path during alloy fracture, which is beneficial to the toughening of the alloy and extrusion performance.

[0109] The above aluminum alloy formula ensures a certain strength and good extrusion performance by strictly controlling the amount of Mg and Si added. The strength of the alloy is further improved by adding an appropriate amount of Cu, and the extrusion performance is improved by adding an appropriate amount of rare earth elements. Thus, the alloy has high strength, low quenching sensitivity, and excellent extrusion performance, making it the most valuable for industrial applications.

[0110] Further optionally, in some embodiments of this application, the aluminum alloy comprises the following components by mass percentage: Si 0.52-0.58; Fe ≤ 0.20; Cu 0.17-0.22; Mn ≤ 0.03; Mg 0.53-0.58; Cr ≤ 0.03; Zn ≤ 0.03; Ti ≤ 0.05; rare earth elements 0.12-0.14; other unavoidable impurities ≤ 0.10; the balance being Al.

[0111] The above aluminum alloy formula, by further strictly controlling the addition ratio of Mg and Si elements, can further improve the alloy strength and extrusion performance. Further controlling the addition of Cu element can further improve the alloy strength. Further controlling the addition of rare earth elements can improve the extrusion performance of the alloy. Thus, the alloy has high strength, low quenching sensitivity, and excellent extrusion performance, making it the most valuable for industrial applications.

[0112] For example, in some embodiments of this application, the aluminum alloy formulation is as follows, by weight percentage:

[0113] Si 0.53, Fe≤0.20; Cu 0.18, Mn≤0.03, Mg 0.58, Cr≤0.03, Zn≤0.03; Ti≤0.05; rare earth elements 0.125, other unavoidable impurities ≤0.10; balance Al.

[0114] For example, in some embodiments of this application, the aluminum alloy formulation is as follows, by weight percentage:

[0115] Si 0.54, Fe≤0.20; Cu 0.18, Mn≤0.03, Mg 0.57, Cr≤0.03, Zn≤0.03; Ti≤0.05; rare earth elements 0.13, other unavoidable impurities ≤0.10; balance Al.

[0116] For example, in some embodiments of this application, the aluminum alloy formulation is as follows, by weight percentage:

[0117] Si 0.55, Fe≤0.20; Cu 0.19, Mn≤0.03, Mg 0.56, Cr≤0.03, Zn≤0.03; Ti≤0.05; rare earth elements 0.14, other unavoidable impurities ≤0.10; balance Al.

[0118] For example, in some embodiments of this application, the aluminum alloy formulation is as follows, by weight percentage:

[0119] Si 0.56, Fe≤0.20; Cu 0.20, Mn≤0.03, Mg 0.55, Cr≤0.03, Zn≤0.03; Ti≤0.05; rare earth elements 0.12, other unavoidable impurities ≤0.10; balance Al.

[0120] For example, in some embodiments of this application, the aluminum alloy formulation is as follows, by weight percentage:

[0121] Si 0.57, Fe≤0.20; Cu 0.21, Mn≤0.03, Mg 0.54, Cr≤0.03, Zn≤0.03; Ti≤0.05; rare earth elements 0.125, other unavoidable impurities ≤0.10; balance Al.

[0122] Furthermore, in some embodiments of this application, the mass ratio of Mg to Si is 0.881-1.157.

[0123] During aging, Si and Mg interact to precipitate second-phase particles such as the GP zone (Si-rich, Mg-rich phase aggregation), needle-like coherent phase β”, rod-like semi-coherent phase β’, and columnar coherent equilibrium phase β. After aging, these strengthening phases are dispersed in the aluminum matrix, hindering dislocation movement through dislocation pinning, thereby improving strength. The evolution of the precipitated phases during aging is as follows:

[0124] Mg2Si precipitation strengthening:

[0125] Solid solution → GP zone (Mg- and Si-rich phase aggregation) → needle-like coherent phase B” → rod-like semi-coherent phase β’ → columnar coherent equilibrium phase β

[0126] Among them, the acicular coherent phase β” has the best strengthening effect and is the most important strengthening precipitate in peak-aging alloys. Its chemical composition is Mg5Si6, with a Mg:Si mass ratio of 0.714:1. If the actual Mg / Si ratio in the alloy is lower than 0.714, then Si is excessive. Excess Si in the matrix is ​​prone to segregation at grain boundaries, reducing grain boundary bonding strength. It also easily causes stress concentration, becoming the source of crack initiation during deformation and reducing the plasticity of the alloy. Therefore, in the above aluminum alloy formulation, the designed Mg / Si mass ratio is higher than 0.714, that is, Mg is excessive. A certain amount of excess Mg helps to improve the thermal stability of the alloy. However, if there is too much excess Mg, this excess Mg does not have effective Si to combine with to form a strengthening precipitate, which will not only weaken the strengthening effect but also reduce the extrusion performance of the alloy.

[0127] The contents of Mg and Si jointly affect the extrusion performance and strength of aluminum alloys. As the Mg / Si ratio increases, the strain hardening index of the alloy increases, while the extrusion performance decreases. Through DOE (Design of Experiments) analysis, further optimization and control of the Mg / Si mass ratio between 0.881 and 1.157 can enable aluminum alloys to achieve excellent extrusion performance and strength.

[0128] Furthermore, in some embodiments of this application, the rare earth element includes at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, or Y.

[0129] Alternatively, in some embodiments of this application, the rare earth element is selected as La; La is the cheapest among the 17 rare earth elements, which can improve the material performance while being economical and practical.

[0130] Furthermore, in some embodiments of this application, when other unavoidable impurities in the aluminum alloy include multiple elements, the content of a single element is ≤0.03% by mass percentage.

[0131] Controlling the content of a single impurity element to ≤0.03% helps avoid the aggregation of a single element and is beneficial to the overall performance of aluminum alloys.

[0132] Furthermore, in some embodiments of this application, the aluminum alloy meets the following condition under air-cooled quenching conditions: the cooling intensity of air-cooled quenching is 5°C / s:

[0133] (a) The tensile strength of aluminum alloy is ≥290 MPa;

[0134] (b) The yield strength of the aluminum alloy is ≥260MPa;

[0135] (c) The elongation after fracture of aluminum alloy is ≥9%.

[0136] In the above technical solution, the cooling intensity of air-cooled quenching is 5℃ / s. The higher the quenching cooling intensity, the higher the above properties.

[0137] The proposed solution can achieve the above objectives under the condition that the cooling intensity of air-cooled quenching is 5℃ / s.

[0138] Achieving high strength under air-cooled quenching conditions can reduce deformation defects caused by uneven cooling of products under high quenching intensity conditions such as fog cooling and water cooling.

[0139] In addition, some products with relatively symmetrical structures can be quenched using mist cooling or water cooling, which will result in higher tensile strength, yield strength, and elongation after fracture.

[0140] Furthermore, in some embodiments of this application, the method for preparing the aluminum alloy includes:

[0141] Aluminum alloy rods are obtained by smelting according to the component content of the aluminum alloy provided in any of the foregoing embodiments.

[0142] The aluminum alloy rod is homogenized and then cooled.

[0143] Furthermore, in some embodiments of this application, the heat treatment temperature for homogenization is 555℃~575℃, and the heat treatment time is 6h-10h.

[0144] Further optionally, in some embodiments of this application, the heat treatment temperature for homogenization is 556℃~574℃, and the heat treatment time is 7h-9h.

[0145] For example, in some embodiments of this application, the heat preservation temperature for homogenization is 557°C, 558°C, 559°C, 560°C, 561°C, 562°C, 563°C, 564°C, 565°C, 566°C, 567°C, 568°C, 569°C, 570°C, 571°C, 572°C, 573°C, or 574°C.

[0146] For example, in some embodiments of this application, the above-mentioned heat preservation time is 7h, 8h or 9h.

[0147] Furthermore, in some embodiments of this application, the cooling process includes: cooling the aluminum alloy rod to less than 250°C using strong air and then water cooling to room temperature.

[0148] The aforementioned room temperature can be 10℃-40℃. Further alternatively, it can be 20℃-35℃.

[0149] Due to the low quenching sensitivity of the above alloy formulation, the alloy can achieve high strength and good extrusion performance under the above homogenization treatment combined with cooling treatment, that is, while achieving high strength, good extrusion performance is retained.

[0150] Furthermore, in some embodiments of this application, the cooling process includes cooling the aluminum alloy rod to room temperature using a strong airflow.

[0151] Furthermore, in some embodiments of this application, the wind speed of the strong wind is 180°C / h to 220°C / h.

[0152] For example, the wind speeds of strong winds are: 180℃ / h, 190℃ / h, 200℃ / h, 210℃ / h, and 220℃ / h.

[0153] Furthermore, in some embodiments of this application, the method for preparing aluminum alloy further includes processing the cooled aluminum alloy rod into an aluminum alloy profile.

[0154] Furthermore, in some embodiments of this application, the aluminum alloy bar after cooling is processed into an aluminum alloy profile, including:

[0155] The aluminum alloy bar is air-cooled and quenched, and then cut into profiles.

[0156] Furthermore, in some embodiments of this application, the air-cooled quenching temperature is 500℃-530℃.

[0157] Further optionally, in some embodiments of this application, the air-cooled quenching temperature is 501℃-529℃.

[0158] For example, in some embodiments of this application, the air-cooled quenching temperature is 505°C, 510°C, 515°C, 520°C, or 525°C.

[0159] The following specific embodiments are provided to better illustrate this application.

[0160] Examples 1-9

[0161] An aluminum alloy is provided, the formula of which is shown in Table 1.

[0162] Comparative Examples 1-4

[0163] An aluminum alloy is provided, the formula of which is shown in Table 1.

[0164] Table 1 Aluminum alloy formulation (wt.%)

[0165]

[0166]

[0167] Preparation of Aluminum Alloys

[0168] (1) Prepare the raw materials according to the formulas of each embodiment or comparative example;

[0169] (2) The raw materials are melted, refined, degassed, deslag removed and cast to obtain aluminum alloy rods;

[0170] (3) After homogenizing the aluminum alloy rod, cool it. The homogenization process is held at a temperature of 565℃ for 8 hours. The cooling process is to cool it to <250℃ with strong air and then water-cool it to room temperature or directly cool it to room temperature with strong air.

[0171] (4) The aluminum alloy rod is heated, extruded, quenched in an online strong wind, stretched and straightened, and sawn to obtain aluminum profiles. The quenching temperature is 520℃.

[0172] (5) Artificial aging treatment is performed on aluminum profiles to obtain high-strength aluminum profiles.

[0173] [Aluminum Alloy Performance Testing]:

[0174] 1. Tensile test

[0175] Test Method: The test specimens for each embodiment or comparative example were processed according to GB / T 16865-2013 "Specimens and Methods for Tensile Testing of Wrought Aluminum, Magnesium and Their Alloys". The test specimens were processed into standard tensile specimens, and the dimensions and shape of the standard tensile specimens are as follows. Figure 5 As shown.

[0176] During testing, a Sansi CMT5504 50KN tensile testing machine was used at room temperature. Under the same conditions, each example or comparative example was subjected to tensile testing with five specimens, and the average value of the five specimens was used as the experimental data.

[0177] Yield strength, tensile strength, and elongation after fracture are obtained by reading experimental data from the equipment.

[0178] The test results are shown in Table 2.

[0179] 2. Compression test

[0180] (1) Trial production machine: 2200T, extrusion cylinder diameter

[0181] (2) Prototype mold: HP19 project side beam (e.g.) Figure 6 ), cross-sectional area 1440.92mm 2 The extrusion ratio is 24.27.

[0182] (3) Test aluminum rods: Samples prepared for each embodiment or comparative example: Aluminum rods;

[0183] (4) Extrusion process parameters

[0184] ① Compressed length: 30mm

[0185] ② Mold temperature: 485℃, holding time: 5h

[0186] ③ Aluminum rod temperature: 490℃ at the head and 470℃ at the tail (the starting temperature of the ignition rod is increased by 10℃).

[0187] ④ Extrusion speed: 1.8 mm / s

[0188] ⑤ Quenching temperature: 500℃

[0189] ⑥ Quenching method: Strong air cooling (100% airflow at the top and bottom, and 30% airflow at the left and right sides)

[0190] ⑦ Quenching temperature: ≤200℃

[0191] ⑧ Extrusion length: 15m, elongation: 0.9% (elongation length 130mm)

[0192] ⑨ Sawing the head and tail: The guide rod is scrapped directly, and the remaining head is cut ≥2m, and the tail is cut ≥2m.

[0193] ⑩ Aging scheme: Samples are aged at 175℃ for 8 hours, while fixed-length samples are temporarily left unaged.

[0194] The device reads the extrusion pressure of each embodiment or comparative sample.

[0195] The extrusion performance of each embodiment and comparative example was characterized using extrusion breakthrough pressure.

[0196] The lower the extrusion pressure, the better the extrusion performance.

[0197] The test results are shown in Table 2.

[0198] Table 2

[0199] Tensile strength / MPa Yield strength / MPa Elongation after fracture / % Breakthrough pressure / Bar Example 1 291 264 11.3 216 Example 2 303 273 11.8 212 Example 3 293 262 11.2 209 Example 4 295 261 10.9 211 Example 5 295 258 12.2 211 Example 6 298 266 10.8 212 Example 7 299 269 10.9 215 Example 8 299 270 11 214 Example 9 303 271 10.8 214 Comparative Example 1 292 256 10.5 254 Comparative Example 2 314 280 11 272 Comparative Example 3 257 239 11.3 210 Comparative Example 4 269 246 10.4 229 Comparative Example 5 273 252 8.6 240

[0200] The test results in Table 2 above show that:

[0201] The aluminum alloys in the embodiments of this application can simultaneously satisfy the following objectives:

[0202] (a) The tensile strength of aluminum alloy is ≥290 MPa;

[0203] (b) The yield strength of the aluminum alloy is ≥260MPa;

[0204] (c) The elongation after fracture of aluminum alloy is ≥9%.

[0205] (d) The extrusion breakthrough pressure of aluminum alloy is ≤216 Bar.

[0206] Comparative Examples 1-4 cannot simultaneously satisfy the objectives that the embodiments of this application aim to achieve.

[0207] The formulation of Comparative Example 1 is a commonly used 6061 aluminum alloy, which has a low yield strength and can be extruded to a pressure that far exceeds the target of this application; therefore, it cannot meet the requirements of this application.

[0208] Comparative Example 2 uses a commonly used 6082 aluminum alloy, whose extrusion pressure exceeds the target of this application and cannot meet the requirements of this application.

[0209] The formulation of Comparative Example 3 is a commonly used 6063 aluminum alloy, whose tensile strength and yield strength are far lower than the target of this application; it cannot meet the requirements of this application.

[0210] The formulations of Comparative Examples 4 and 5 are not aluminum alloys of this application, and their tensile strength and yield strength are lower than the target values ​​of this application; the elongation after fracture of Comparative Example 5 is also lower than the target of this application; neither Comparative Example 4 nor Comparative Example 5 can meet the requirements of this application; the extrusion pressure of Comparative Example 4 and Comparative Example 5 far exceeds the target of this application; therefore, they cannot meet the requirements of this application.

[0211] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. An aluminum alloy, characterized in that, The aluminum alloy comprises the following components by weight percentage: Si 0.51-0.59; Fe≤0.20; Cu 0.16-0.23; Mn≤0.03; Mg 0.52-0.59; Cr≤0.03; Zn≤0.03; Ti≤0.05; Rare earth elements 0.11-0.15; Other unavoidable impurities ≤0.10; Balance Al.

2. The aluminum alloy according to claim 1, characterized in that, The Si content is 0.52-0.58%; the Fe content is ≤0.20%; the Cu content is 0.17-0.22%; the Mn content is ≤0.03%; the Mg content is 0.53-0.58%; the Cr content is ≤0.03%; the Zn content is ≤0.03%; the Ti content is ≤0.05%; and the rare earth elements content is 0.12-0.14%. Other unavoidable impurities ≤ 0.10; balance Al.

3. The aluminum alloy according to claim 1, characterized in that, The mass ratio of Mg to Si is 0.881-1.

157.

4. The aluminum alloy according to claim 1, characterized in that, The mass ratio of Mg to Si is 0.897-1.

115.

5. The aluminum alloy according to any one of claims 1-3, characterized in that, The rare earth elements include at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, or Y.

6. The aluminum alloy according to any one of claims 1-3, characterized in that, The rare earth element is La.

7. The aluminum alloy according to any one of claims 1-3, characterized in that, When the other unavoidable impurities comprise multiple elements by mass percentage, the percentage of a single element is ≤0.03%.

8. The aluminum alloy according to any one of claims 1-3, characterized in that, The aluminum alloy, under air-cooled quenching conditions, meets the following condition, wherein the cooling intensity of the air-cooled quenching is 5℃ / s: (a) The tensile strength of the aluminum alloy is ≥290MPa; (b) The yield strength of the aluminum alloy is ≥260MPa; (c) The elongation after fracture of the aluminum alloy is ≥9%.

9. A method for preparing an aluminum alloy, characterized in that, include: Aluminum alloy rods are obtained by smelting according to the component content of the aluminum alloy as described in any one of claims 1-8. The aluminum alloy rod is homogenized and then cooled.

10. The method for preparing the aluminum alloy according to claim 9, characterized in that, The homogenization process is carried out at a temperature of 555℃ to 575℃ for 6 h to 10 h.

11. The method for preparing the aluminum alloy according to any one of claims 9-10, characterized in that, The method for preparing the aluminum alloy also includes processing the cooled aluminum alloy rod into an aluminum alloy profile.

12. The method for preparing the aluminum alloy according to claim 11, characterized in that, The process of processing the cooled aluminum alloy bar into aluminum alloy profiles includes: The aluminum alloy bar is subjected to air-cooling quenching and then cut into profiles.

13. The method for preparing the aluminum alloy according to claim 12, characterized in that, The air-cooled quenching temperature is 500℃~530℃.

14. A housing for encapsulating a battery, characterized in that, The casing for encapsulating the battery comprises the aluminum alloy as described in any one of claims 1-8; or the casing for encapsulating the battery comprises the aluminum alloy prepared by the method described in any one of claims 9-13.

15. A battery, characterized in that, The battery includes the housing for encapsulating the battery as described in claim 14.

16. An electrical appliance, characterized in that, The electrical device includes the battery as described in claim 15.

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