Aluminum alloy and preparation method thereof, welded joint and aluminum alloy component

Abstract

The invention relates to an aluminum alloy and a preparation method thereof, a welded joint and an aluminum alloy component. The aluminum alloy comprises, by mass, 5.5%-8% of Si, 0.8%-2% of Cu, 0.01%-0.2% of Zn, 0.2%-0.8% of Sn, 0.1%-0.6% of Mn, 0 < = Mg < 0.1%, 0-0.2% of Ti, 0 < = Fe < 0.3%, 0.01%-0.1% of Sr, less than 0.15% of rare earth elements and the balance Al. The aluminum alloy is excellent in toughness and weldability and can be used for die-casting forming.

Description

Technical Field

[0001] The invention relates to the technical field of automobile materials, and in particular to an aluminum alloy and a preparation method thereof, a welding joint and an aluminum alloy component. Background Art

[0002] In recent years, as people's demand for energy saving and endurance of automobiles continues to increase, lightweighting of vehicle body equipment has become a focus of industry attention as an important method to achieve this demand. Aluminum alloy materials are widely used in vehicle body structures due to their low density and high specific strength.

[0003] With the continuous development of advanced die-casting technology, the manufacturing of integrated large-scale complex thin-walled structural parts has attracted much attention. Advanced die-casting aluminum alloy materials have become a research hotspot as the basis for supporting the development of die-casting structural parts. The development of large die-casting parts has achieved the reduction and integration of body structures, but they still need to be fixedly connected with surrounding parts through welding. Ensuring the quality of die-casting aluminum alloy welded joints is the key to their application.

[0004] Due to the complex high-pressure casting technology of die-cast aluminum alloy materials, there are many factors that affect the material performance. The base material performance of the die-cast aluminum materials currently obtained is relatively excellent, but the mechanical properties of the welded joints are poor, and it is difficult to ensure the quality of the welded joints. Therefore, the welded joints become the weak points of large die-castings and cannot meet the use requirements. Summary of the invention

[0005] Based on this, it is necessary to provide an aluminum alloy with excellent toughness and weldability and a preparation method thereof, a welded joint and an aluminum alloy component.

[0006] In a first aspect of the present application, an aluminum alloy is provided, which comprises the following element composition, calculated by mass percentage: Si 5.5%~8%, Cu 0.8%~2%, Zn 0.01%~0.2%, Sn 0.2%~0.8%, Mn 0.1%~0.6%, 0≤Mg<0.1%, Ti 0~0.2%, 0≤Fe<0.3%, Sr 0.01%~0.1%, rare earth elements <0.15%, and the balance is Al element.

[0007] The above-mentioned aluminum alloy of the present application can improve the elongation of the aluminum alloy by regulating the element content and element composition of the aluminum alloy, reducing the content of components that are not conducive to the weldability of the material, and increasing or adding components that are conducive to the weldability of the material. High elongation can improve the weldability of the die-cast aluminum alloy and surrounding structural parts, and while improving the weldability of the aluminum material, it can still ensure its good casting performance and mechanical properties, thereby obtaining an aluminum alloy with excellent comprehensive performance that can be used for die castings.

[0008] In some of the embodiments, the element composition is as follows, by mass percentage: Si 5.5%~7.5%, Cu 0.8%~1.5%, Zn 0.08%~0.2%, Sn 0.3%~0.8%, Mn 0.2%~0.5%, Mg 0~0.05%, Ti 0~0.2%, Fe 0~0.2%, Sr 0.05%~0.1%, rare earth elements 0.05%~0.1%, and the balance is Al element.

[0009] In some of the embodiments, the element composition is as follows, calculated by mass percentage: Si 6%~7%, Cu 0.8%~1.2%, Zn 0.08%~0.15%, Sn 0.4%~0.5%, Mn 0.2%~0.5%, 0≤Mg<0.05%, Ti 0~0.2%, Fe 0~0.2%, Sr 0.05%~0.1%, rare earth elements 0.05%~0.1%, and the balance is Al element.

[0010] In some embodiments, the rare earth element includes at least one of La, Sc and Ce.

[0011] In some embodiments, the rare earth elements include La and Ce, and the mass ratio of La to Ce is 1:1.

[0012] In some of these embodiments, the sum of other elements is less than 0.35% by weight.

[0013] In a second aspect of the present application, a method for preparing an aluminum alloy is provided, comprising the following steps:

[0014] Providing raw materials according to the composition of the aluminum alloy provided in the first aspect of the present application;

[0015] Mixing and smelting the raw materials to obtain a molten metal;

[0016] The metal melt is cast to obtain an aluminum alloy.

[0017] In some of the embodiments, the casting is performed by high-pressure die casting, and the high-pressure die casting includes the following conditions: the temperature of the molten metal is 660°C~680°C, the high-speed filling speed of the injection molding machine is 3.0m / s~7.0m / s, the low-speed filling speed of the injection molding machine is 0.2m / s~0.4m / s, the die casting pressure is 30MPa~80MPa, and the vacuum degree of the mold cavity is 10KPa~20KPa.

[0018] In a third aspect of the present application, a welding joint is provided, which is made by a welding process using the aluminum alloy provided in the second aspect of the present application.

[0019] In a fourth aspect of the present application, an aluminum alloy component is provided, comprising the aluminum alloy of the second aspect of the present application and at least one of the welded joints of the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a metallographic structure photograph of the base material obtained in Example 1 of the present invention;

[0021] Figure 2 is a low-magnification full-view photograph of the welded joint obtained in Example 1 of the present invention;

[0022] Figure 3 is a metallographic structure photograph of the welded joint prepared in Example 1 of the present invention;

[0023] Figure 4 This is a metallographic structure photograph of the parent material prepared in Comparative Example 1 of the present invention;

[0024] Figure 5 This is a low-magnification full-view photograph of the welded joint prepared in Comparative Example 1 of the present invention;

[0025] Figure 6 This is a metallographic photograph of the welded joint prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0026] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0028] "Scope" disclosed in the present application can be limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or excluding end values, and any end value can be included or not included independently, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 listed, and if the maximum range values ​​3,4 and 5 are also listed, the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0029] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0030] In the present application, "plurality", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0031] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0032] Those skilled in the art will appreciate that, in the methods of each embodiment or example, the order in which each step is written does not mean a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) can be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0033] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0034] In this application, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0035] The high-pressure casting technology of die-cast aluminum alloy materials is complex, and there are many factors that affect the material properties. The technicians of this application found that the researchers focused on the casting molding and substrate performance, and therefore did not realize the problem of poor mechanical properties of the welded joints. In fact, although the substrate performance of die-cast aluminum materials is relatively excellent, defects such as dense pores and cracks are easily formed at the welded joints, and there will also be problems such as increased joint brittleness and intergranular corrosion tendency, which will affect its mechanical properties, making it difficult to ensure the quality of the welded joints and making them weak points, and unable to meet the use requirements.

[0036] Therefore, when designing material composition, traditional technicians focus on the ratio of element content that is beneficial to casting and substrate performance, and often ignore the content of elements that are beneficial to improving weldability. Therefore, they do not consider whether there is a high content of elements that are harmful to weldability in die-cast aluminum alloy materials, and they do not think of adding relevant elements to improve the weldability of the material.

[0037] An embodiment of the present application provides an aluminum alloy, which includes the following element composition, calculated by mass percentage: 5.5%~8%, Cu 0.8%~2%, Zn 0.01%~0.2%, Sn 0.2%~0.8%, Mn 0.1%~0.6%, 0≤Mg<0.1%, Ti 0~0.2%, 0≤Fe<0.3%, Sr 0.01%~0.1%, rare earth elements <0.15%, and the balance is Al element.

[0038] The above-mentioned aluminum alloy of the present application can improve the elongation of the aluminum alloy by regulating the element content and element composition of the aluminum alloy, reducing the content of components that are not conducive to the weldability of the material, and increasing or adding components that are conducive to the weldability of the material. High elongation can improve the weldability of the die-cast aluminum alloy and surrounding structural parts, and while improving the weldability of the aluminum material, it can still ensure its good casting performance and mechanical properties, thereby obtaining an aluminum alloy with excellent comprehensive performance that can be used for die castings.

[0039] Specifically, the aluminum alloy of the present application improves the fluidity of the material, reduces the number of casting pores and improves the elongation of the material by regulating the content of Si element in the material matrix, without affecting the casting performance of the material; reduces the content of Zn and Mg elements in the material matrix, reduces the hard phase and reduces the brittleness of the material, and improves the welding performance; controls the content of Cu element in the material to improve the thermal conductivity and other properties of the material, and reduces the risk of welding cracks; improves the weldability of the material by adding Sn element to the material, and improves the strength and corrosion resistance of the welded joint; and improves the toughness of the matrix by adding a small amount of rare earth elements such as Ce and Sc to the material. In this way, by regulating the synergistic effect of each element, the aluminum alloy has excellent casting performance (strength and toughness will not be significantly reduced), and solves the problem of poor weldability of traditional die-cast aluminum alloy materials and insufficient quality stability of welded joints.

[0040] Compared with the Si element mass percentage of 8% to 12% in most die-cast aluminum alloys, the aluminum alloy of the present invention reduces the content of Si element in the material composition, which can reduce the number of hard strengthening phases in the structure, improve the fluidity of the material, reduce the number of casting defects inside the material, and improve the elongation of the material to a certain extent. It can improve the weldability of the die-cast aluminum alloy material, improve the quality of the joint, and have little effect on the casting performance of the material. As an example, in the aluminum alloy, Si can be 5.5%, 5.7%, 6%, 6.4%, 6.5%, 6.6%, 7%, 7.2%, 7.5%, 8%, or within the range of any two of the above point values ​​as end values. Further, in the aluminum alloy, Si can be 5.5% to 7.5% by mass percentage.

[0041] The aluminum alloy of the present invention increases the content of Cu element in the material composition. Properly increasing the content of Cu element can improve the thermal conductivity and thermal expansion coefficient of the material, reduce the generation of thermal cracks during casting and welding, improve the welding performance of the material, and offset the strength loss caused by the reduction of the content of elements such as Si and Mg. However, too high a Cu element content will lead to a higher hardness in the heat-affected zone of the material weld, increase the risk of cracks and pores, and control the Cu element content within the above range.

[0042] As an example, in the aluminum alloy, Cu can be 0.8%, 0.9%, 1%, 1.3%, 1.5%, 1.6%, 1.8%, 2%, or within a range consisting of any two of the above point values ​​as end values. Further, in the aluminum alloy, Cu can be 0.8% to 1.5% by mass.

[0043] The aluminum alloy of the present invention reduces the content of Mg and Zn in the material composition. Mg and Zn are the main alloying elements for improving the strength of the material, but the hard phase formed by them has a great adverse effect on the weldability of the cast aluminum material, the weld is brittle, and defects such as cracks are easily generated, which affects the weldability of the material. Since the appropriate Zn content helps to improve the fluidity of the material during the casting process, the Zn content is controlled within the above range, and the Mg element, as a component that is not conducive to the weldability of the material, needs to be controlled at a lower level.

[0044] As an example, in the aluminum alloy, Zn can be 0.01%, 0.05%, 0.08%, 0.1%, 0.13%, 0.15%, 0.2%, or within a range consisting of any two of the above point values ​​as end values. Further, in the aluminum alloy, Zn is 0.08% to 0.2% by mass.

[0045] The aluminum alloy of the present invention adds the Sn element in the above content range to the material composition, which can improve the heat resistance and corrosion resistance of the material, and the material strength is also improved to a certain extent, greatly improving the weldability of the material, reducing the generation of defects such as weld pores and cracks, and has little effect on the casting performance of the material. As an example, in the aluminum alloy, Sn can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or within the range formed by any two of the above point values ​​as end values. Further, in the aluminum alloy, Sn is 0.3%~0.8% by mass.

[0046] As an example, in the aluminum alloy, Mn can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, or within a range consisting of any two of the above point values ​​as end values, by mass percentage. Further, in the aluminum alloy, Mn is 0.2% to 0.5%, by mass percentage.

[0047] As an example, in the aluminum alloy, Mg can be 0, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or a range consisting of any two of the above point values ​​as end values. Further, in the aluminum alloy, Mg is 0-0.05% by mass; further, it can be 0.01%-0.05%.

[0048] As an example, in the aluminum alloy, Ti can be 0, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, or within a range consisting of any two of the above point values ​​as end values, by mass percentage. Further, in the aluminum alloy, Ti is 0-0.2%, or 0.1%-0.2%.

[0049] As an example, in the aluminum alloy, Fe can be 0, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, or any two of the above points as end values. Further, in the aluminum alloy, Fe is 0-0.2% by mass, or Fe≤0.15%; further, it can be 0.1%-0.15%.

[0050] As an example, in the aluminum alloy, Sr can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, or within a range consisting of any two of the above point values ​​as end values. Further, in the aluminum alloy, Sr is 0.05% to 0.1% by mass.

[0051] As an example, in the aluminum alloy, the rare earth element can be 0, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, or a range consisting of any two of the above point values ​​as end values. Further, in the aluminum alloy, the rare earth element is ≤0.1% by mass; further optionally, the rare earth element is 0.05%~0.1%.

[0052] In some of the embodiments, the element composition is as follows, calculated by mass percentage: Si 5.5%~7.5%, Cu 0.8%~1.5%, Zn 0.08%~0.2%, Sn 0.3%~0.8%, Mn 0.2%~0.5%, Mg 0~0.05%, Ti 0~0.2%, Fe 0~0.2%, Sr 0.05%~0.1%, rare earth elements 0.05%~0.1%, and the balance is Al element.

[0053] In some of the embodiments, the element composition is as follows, calculated by mass percentage: Si 6%~7%, Cu 0.8%~1.2%, Zn 0.08%~0.15%, Sn 0.4%~0.5%, Mn 0.2%~0.5%, 0≤Mg<0.05%, Ti 0~0.2%, Fe 0~0.2%, Sr 0.05%~0.1%, rare earth elements 0.05%~0.1%, and the balance is Al element.

[0054] In some embodiments, the rare earth element includes at least one of La, Sc and Ce. The aluminum alloy of the present invention adds rare earth elements such as La and Sc in the above content range to the material composition, which can purify the melt and reduce the hydrogen content in the aluminum liquid; when Sc is added, a non-uniform nucleation phenomenon with Al3Sc particles as the core can be formed, which can refine the grains of the material matrix, improve the strength and toughness of the material, improve the strength and toughness loss caused by the above composition adjustment, and make the material have excellent comprehensive performance.

[0055] Furthermore, the rare earth elements include La and Ce. Furthermore, the mass ratio of La to Ce is 1:1.

[0056] In some of these embodiments, the sum of other elements is less than 0.35% by weight.

[0057] An embodiment of the present application further provides a method for preparing an aluminum alloy, comprising the following steps S10 to S30:

[0058] S10. Providing raw materials according to the composition of the above-mentioned aluminum alloy.

[0059] In some embodiments, the raw materials include one or more of pure metals and aluminum-based master alloys. The pure metals described in step S10 include pure Al, pure Mg, pure Cu, pure Zn and pure Sn; the aluminum-based master alloys include: Al-20%Si alloy, Al-10%Mn alloy, Al-5%Ti alloy, Al-10%Sr alloy and rare earth Al-10%La alloy, Al-10%Sc alloy. Furthermore, the raw materials are nanopowders.

[0060] Furthermore, before performing step S20, preheating and drying are performed in a 180°C to 220°C insulation box.

[0061] S20, mixing and smelting the raw materials to obtain a molten metal.

[0062] It can be understood that the smelting step in step S20 includes refining, slag removal and degassing treatment, after which the metal melt is subjected to component detection to obtain a metal melt satisfying the above-mentioned element composition.

[0063] In some embodiments, during the refining process of the molten metal, inert argon or nitrogen is introduced, and a rotary degassing method is used to eliminate impurity gases in the molten metal. In this way, the number of pores in the matrix of the material after die-casting can be reduced, and the hydrogen content in the material can be reduced, reducing the risk of hydrogen-induced cracks in the material body and its welded joints, improving the weldability of the material, and ensuring the quality of the material welded joints.

[0064] In some embodiments, the step of mixing and smelting the raw materials comprises the following steps:

[0065] Firstly, a pure aluminum raw material is placed in a melting furnace for heating, and the temperature is controlled between 730°C and 760°C. Subsequently, Al-20%Si alloy, Al-10%Mn alloy, pure Cu, Fe agent, pure Zn and pure Sn alloy and other raw materials are added to the melting furnace respectively, the temperature in the furnace is maintained, and the molten metal is allowed to stand until all the raw materials are melted, and the surface scum is removed to obtain a molten metal 1;

[0066] The temperature of the smelting furnace is continued to be controlled between 720° C. and 750° C., and Al-5%Ti alloy and rare earth alloy such as Al-10%La alloy, Al-10%Sc alloy and other component raw materials are added to the metal melt 1, the temperature in the furnace is maintained and the metal melt is allowed to stand until all the raw materials are melted, and the melt is subjected to slag treatment to obtain the metal melt 2;

[0067] The temperature of the smelting furnace is controlled between 720° C. and 730° C., and the remaining Al-10% Sr alloy and pure Mg and other raw materials are added to the molten metal 2. The temperature in the furnace is maintained and the molten metal is allowed to stand until all the raw materials are melted, thereby obtaining a molten metal 3.

[0068] The metal melt 3 is sampled for chemical composition inspection. If the composition design requirements of the die-casting aluminum alloy material are met, subsequent refining, slag removal and degassing treatment are performed. If the conditions are not met, the alloy composition is further adjusted until a metal melt 4 that meets the requirements is obtained.

[0069] The metal melt 4 that meets the conditions is transferred to a new smelting furnace, and casting refining agent powder is added. It is refined using a rotary blowing device, and an inert gas such as argon or nitrogen is introduced. The gas flow rate is 20-30L / min, and the rotary degassing speed is about 580r / min. The refining temperature in the furnace is controlled between 680℃-720℃, and the refining time is 10min-15min. An aluminum alloy metal melt 5 that can be subjected to high-pressure die casting is obtained to proceed to step S30.

[0070] The preparation method of the above-mentioned aluminum alloy is to add the alloy raw materials into a smelting furnace in steps and in sequence to form a metal melt, and after each addition of the alloy raw materials for smelting, the alloy melt is allowed to stand and slag is removed to ensure the uniformity of the composition of the metal melt, and after the alloy raw materials are added, the composition is tested to ensure that the metal melt for subsequent die casting meets the composition design requirements of the present invention, so as to obtain a new type of die-casting aluminum alloy material with accurate alloy composition mass percentage and uniform structure.

[0071] S30, casting the metal melt to obtain an aluminum alloy.

[0072] In some embodiments, the casting is performed by high-pressure die casting. Further, the high-pressure die casting includes the following conditions: the temperature of the molten metal is 660°C to 680°C, the high-speed filling speed of the injection molding machine is 3.0m / s to 7.0m / s, the low-speed filling speed of the injection molding machine is 0.2m / s to 0.4m / s, the die casting pressure is 30MPa to 80MPa, and the vacuum degree of the mold cavity is 10KPa to 20KPa.

[0073] Traditional die-cast materials have low elongation and need to be improved through subsequent heat treatment processes to ensure their connectability and realize production applications. The above-mentioned aluminum alloy in the present application regulates the elemental composition and matrix structure so that it does not require heat treatment after casting, that is, it has good elongation without sacrificing too much strength. Therefore, the preparation process of the above-mentioned aluminum alloy in the present application does not require a heat treatment process, which can simplify the process flow and reduce defects such as pores and cracks that may be caused by the heat treatment process.

[0074] The aluminum alloy prepared by the above preparation method has good weldability. It is a high-strength and tough die-cast aluminum alloy without heat treatment. Under normal temperature conditions, the tensile strength is above 280MPa, the yield strength is above 130MPa, and the elongation is above 10%. The metallographic structure is uniform, and it has both excellent weldability and casting performance. The high strength of the material can meet the performance requirements of common die-cast aluminum alloy structural parts, and the high elongation can improve the weldability of the die-cast aluminum alloy and the surrounding structural parts. The material has excellent weldability, the joint has no obvious defects and has high strength.

[0075] An embodiment of the present application further provides a welding joint, which is made by using the above-mentioned aluminum alloy through a welding process.

[0076] One embodiment of the present application also provides an aluminum alloy component, comprising at least one of the above-mentioned aluminum alloy and the above-mentioned welding joint.

[0077] In some embodiments, the aluminum alloy component is formed by die casting using the above aluminum alloy to obtain a die-cast aluminum alloy component. Further, the die-cast aluminum alloy component includes a welded joint formed by welding.

[0078] In order to make the purpose, technical solutions and advantages of the present invention more concise and clear, the present invention is described with the following specific embodiments, but the present invention is by no means limited to these embodiments. The embodiments described below are only preferred embodiments of the present invention, which can be used to describe the present invention and cannot be understood as limiting the scope of the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0079] In order to better illustrate the present invention, the present invention is further described below in conjunction with the embodiments. The following are specific embodiments.

[0080] Example 1

[0081] This embodiment provides a high-strength and toughness die-cast aluminum alloy that is free of heat treatment and has good weldability, and the preparation method thereof is as follows:

[0082] (1) The mass percentage of the element composition of the aluminum alloy of this embodiment is shown in Table 1 below: 6.6086.

[0083] Among them, the raw materials of alloy element components are pure metals such as pure Al, pure Mg, pure Cu, pure Zn and pure Sn; aluminum-based intermediate alloys such as Al-Si alloy, Al-Mn alloy, Al-Ti alloy, Al-Sr alloy and rare earth Al-La alloy, Al-Sc alloy.

[0084] (2) The aluminum alloy of this embodiment is prepared according to the following steps and parameters.

[0085] According to the alloy element composition, the above raw materials are preheated and dried in a 180℃ insulation box for 30 minutes. Then the pure aluminum raw material is melted in a smelting furnace, the furnace temperature is controlled at 750℃, and Al-Si alloy, Al-Mn alloy, pure Cu, Fe agent (pure Fe), pure Zn and pure Sn raw materials are added in sequence, left to stand for 5 minutes and slag is removed, and then the furnace temperature is adjusted to 730℃, and Al-Ti, Al-La, Al-Sc and other raw materials are added in sequence. After smelting, the furnace temperature is adjusted to 720℃, Al-Sr alloy and pure Mg raw materials are added, and the obtained metal melt is sampled for component detection, and adjustments are made according to the component detection results.

[0086] After meeting the elemental composition design requirements of the aluminum alloy of this embodiment, the molten metal is charged into a new furnace and the temperature is adjusted to 680°C, an aluminum alloy casting refining agent is added, and argon gas is introduced for rotary spray refining treatment. The argon gas flow rate is 20L / min, the spray head speed is 580r / min, and the refining time is 15min. Subsequently, the molten metal is allowed to stand for 5min and slag removal is performed to obtain the final molten metal for die casting.

[0087] The molten metal is poured into the injection chamber of the die-casting machine. The high-speed filling speed and low-speed filling speed of the injection molding machine are 5.0m / s and 0.4m / s respectively. The die-casting pressure is 60MPa, and the filling time is 0.05s. The length, width and height dimensions of the mold cavity are 100mm, 30mm and 3mm, and the vacuum degree is kept below 20KPa. The material is high-pressure die-casted into the parent material of the above dimensions.

[0088] (3) The base material obtained in step (2) is made into a welded joint.

[0089] The surface of the base material was laser cleaned and preheated at 180°C, and then 5356 welding wire was used to weld under the process parameters of welding current 127A and welding voltage 17.5V to obtain an arc welding joint (also called a welding joint).

[0090] Example 2

[0091] This embodiment provides a high-strength and toughness die-cast aluminum alloy that is free of heat treatment and has good weldability, and the preparation method thereof is as follows:

[0092] (1) The mass percentages of the alloying elements of the materials of this embodiment are shown in Table 1 below.

[0093] (2) The steps and parameters for preparing the aluminum alloy in this embodiment are the same as those in Example 1.

[0094] (3) The step of making the base material obtained in step (2) into a welded joint is the same as that in Example 1.

[0095] Embodiment 3~5

[0096] It is basically the same as Example 1, except that the element composition of the aluminum alloy is different, as shown in Table 1.

[0097] Comparative Examples 1 to 3

[0098] It is basically the same as Example 1, except that the element composition of the aluminum alloy is different, as shown in Table 1.

[0099] The mass percentages of the element components of the parent aluminum alloys of the specific embodiments and comparative examples provided by the present invention are shown in Table 1, wherein the mass ratio of La to Sc is 1:1.

[0100] Table 1

[0101]

[0102] The following is a performance test.

[0103] (1) The tensile strength, yield strength and elongation of the base materials prepared in each embodiment and comparative example were tested according to the test standard GB_T 228.1-2021. The results are shown in Table 2 below.

[0104] (2) The maximum tensile shear force test was performed on the welded joints prepared in each embodiment and comparative example, and the test standard was GB_T228.1-2021. The results are shown in Table 2 below.

[0105] Table 2

[0106]

[0107] As can be seen from Table 2, the tensile strength of the base material of Example 1 is 285 MPa, the yield strength is 128 MPa, and the elongation is 11%.

[0108] Figure 1 This is a metallographic structure photo of the parent material of Example 1. Figure 2 This is a low-magnification full-view photo of the welded joint obtained in Example 1. Figure 3 The metallographic structure photograph of the weld of the welded joint obtained in Example 1 is shown in FIG. Figures 1 to 3 It can be seen that the weld structure is fine and uniform, without obvious defects such as cracks and pores. The maximum tensile shear force that the welded joint can withstand is 11.54KN.

[0109] As can be seen from Table 2, the base material of Example 2 has a tensile strength of 292 MPa, a yield strength of 131 MPa, and an elongation of 10.5%. The same welding parameters are used to prepare the welded joint, and its maximum tensile shear force is 12.36 KN.

[0110] in, Figure 4 This is the metallographic structure photo of the parent material obtained in Comparative Example 1. Figure 5 This is a low-magnification full-view photo of the welded joint obtained in Comparative Example 1. Figure 6 This is a metallographic structure photograph of the weld obtained in Comparative Example 1, in which many defects such as cracks and pores can be seen.

[0111] It can be seen from the performance data, metallographic blocking photos and low-magnification overall photos in the table that the aluminum alloy material in the embodiment of the present invention has a finer structure and better uniformity than the aluminum alloy material in the common comparison example, and its strength is slightly reduced, but the aluminum alloy material in the embodiment has better comprehensive mechanical properties of strength and toughness.

[0112] The welding joints of the aluminum alloy material in the embodiment of the present application have fewer defects, while the welding joints of the aluminum alloy material in the comparative example have significantly more porosity defects. The material in the embodiment of the present application can bear a greater shear force, which shows that the aluminum alloy material in the embodiment of the present application has better weldability.

[0113] Compared with the common die-cast aluminum materials in the comparative example, the new die-cast aluminum alloy in the embodiment of the present invention has excellent weldability while meeting the high strength and toughness requirements during use, avoiding the connection area between the die-cast aluminum alloy and the surrounding structural parts from becoming a weak point, and solving the problem that the practical application of traditional cast aluminum materials is limited due to poor weldability.

[0114] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims, and the description and drawings can be used to interpret the content of the claims.

Claims

1. An aluminum alloy, characterized in that: Calculated by mass percentage, the element composition includes the following: Si 5.5%~8%, Cu0.8%~2%, Zn 0.01%~0.2%, Sn 0.2%~0.8%, Mn 0.1%~0.6%, 0≤Mg<0.1%, Ti 0~0.2%, 0≤Fe<0.3%, Sr 0.01%~0.1%, rare earth elements<0.15%, and the balance is Al element.

2. The aluminum alloy according to claim 1, characterized in that Calculated by mass percentage, the element composition includes the following: Si 5.5%~7.5%, Cu 0.8%~1.5%, Zn 0.08%~0.2%, Sn 0.3%~0.8%, Mn 0.2%~0.5%, Mg 0~0.05%, Ti0~0.2%, Fe 0~0.2%, Sr 0.05%~0.1%, rare earth elements 0.05%~0.1%, and the balance is Al element.

3. The aluminum alloy according to claim 1, characterized in that Calculated by mass percentage, the element composition includes the following: Si 6%~7%, Cu 0.8%~1.2%, Zn 0.08%~0.15%, Sn 0.4%~0.5%, Mn 0.2%~0.5%, 0≤Mg<0.05%, Ti 0~0.2%, Fe 0~0.2%, Sr 0.05%~0.1%, rare earth elements 0.05%~0.1%, and the balance is Al element.

4. The aluminum alloy according to any one of claims 1 to 3, characterized in that The rare earth element includes at least one of La, Sc and Ce.

5. The aluminum alloy according to any one of claims 1 to 3, characterized in that The rare earth elements include La and Ce, and the mass ratio of La to Ce is 1:

1.

6. The aluminum alloy according to any one of claims 1 to 3, characterized in that The sum of other elements is less than 0.35% by mass.

7. A method for preparing an aluminum alloy, characterized in that: The steps include: Providing a raw material according to the composition of the aluminum alloy according to any one of claims 1 to 6; Mixing and smelting the raw materials to obtain a molten metal; The metal melt is cast to obtain an aluminum alloy.

8. The method for preparing an aluminum alloy according to claim 7, characterized in that: The casting molding adopts high-pressure die-casting molding, and the high-pressure die-casting includes the following conditions: the temperature of the metal melt is 660°C~680°C, the high-speed filling speed of the injection molding machine is 3.0m / s~7.0m / s, the low-speed filling speed of the injection molding machine is 0.2m / s~0.4m / s, the die-casting pressure is 30MPa~80MPa, and the vacuum degree of the mold cavity is 10KPa~20KPa.

9. A welding joint, characterized in that: A welded joint is prepared by a welding process using the aluminum alloy described in any one of claims 1 to 6.

10. An aluminum alloy component, characterized in that: Includes at least one of the aluminum alloy according to any one of claims 1 to 6 and the welded joint according to claim 9.

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