High-toughness die-casting aluminum alloy for new energy automobile and preparation method of high-toughness die-casting aluminum alloy

Abstract

The invention relates to a high-toughness die-casting aluminum alloy for a new energy automobile and a preparation method of the high-toughness die-casting aluminum alloy, and belongs to the technical field of die-casting aluminum alloys. The preparation method of the high-toughness die-casting aluminum alloy for the new energy automobile comprises the following steps that after a 5-series aluminum alloy and an intermediate alloy are heated and molten, impurities are removed, and a molten alloy is obtained; performing pore-free pressure casting on the molten alloy to obtain a prefabricated aluminum alloy; and after the prefabricated aluminum alloy is subjected to high-temperature heat treatment, cooling heat treatment and normal-temperature cooling, the high-toughness die-casting aluminum alloy is obtained. According to the invention, the Mn and Zr elements are added to effectively refine crystal grains, air holes of a die casting are eliminated through a specific oxygenating die casting process, the aluminum alloy is compact in structure and free of blistering in high-temperature solid solution treatment, and the mechanical property of the alloy can be improved by adding the Mn and Zr elements for recrystallization and combining with ultrafine crystal grains of the oxygenating die casting process and large and coarse crystal grains of the Mg element; coarse grains keep deformability, superfine grains keep high strength, and the macroscopic mechanical property of the material is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of die-cast aluminum alloys and relates to a high-strength and toughness die-cast aluminum alloy for new energy vehicles and a preparation method thereof. Background Art

[0002] Aluminum alloy, as a non-ferrous metal structural material currently widely used in industrial production, occupies an irreplaceable position in many fields with its unique performance advantages. The most notable feature of this material is its low density, which makes it lighter than many other metal materials of the same volume, making it easy to reduce the overall weight of the product. At the same time, the strength of aluminum alloy is relatively high, which ensures that it can still maintain good structural integrity when subjected to a certain pressure or load. In addition, it has excellent plasticity and can be easily processed into various required profiles and structures to meet different industrial production needs.

[0003] In addition, aluminum alloy has a series of properties that are difficult to match with other metal materials. It has excellent electrical and thermal conductivity, which makes it excellent in application scenarios such as electronic equipment and heat dissipation systems. Its corrosion resistance is also quite outstanding, and it can maintain a long service life even in harsh environments, so it is widely used in industries that require high durability. It is precisely because of these comprehensive properties that aluminum alloy has been widely used in high-tech fields such as aviation and aerospace, as well as in the automotive and chemical industries.

[0004] As new energy vehicles emerge and enter a new stage of development, lightweight has become an important indicator for new energy vehicle manufacturing. In order to meet this indicator, automakers are forced to find and adopt suitable lightweight materials on a large scale. Judging from the current use of materials used in car bodies, aluminum alloy has become a very potential application material due to its excellent lightweight properties.

[0005] The aluminum alloy parts currently used in the car body mainly include some stampings, castings and extrusions. The application of aluminum alloy plates for the car body is mainly concentrated on 5-series and 6-series aluminum alloys, and a small number of 7-series aluminum alloys are also used. The application of these aluminum alloy materials not only effectively reduces the weight of the car body, but also ensures the stability and safety of the car body structure, making an important contribution to the performance improvement of new energy vehicles.

[0006] In order to obtain high-quality aluminum alloy stamping products, it is of vital importance to accurately select the appropriate forming process based on the inherent characteristics of the material to improve the overall performance of the stamping products. In recent years, experts and scholars in the academic circles at home and abroad have proposed a variety of innovative ideas and advanced processes to solve the forming problems of aluminum alloys, among which the most eye-catching ones include hot forming, superplastic forming and high pressure forming.

[0007] Although aluminum alloys exhibit superior plasticity in high temperature environments, their strength characteristics are correspondingly weakened. As the temperature gradually increases, the deformation resistance of the material is significantly reduced, which provides feasibility for the stamping of complex precision parts. However, in the process of applying hot forming technology to the production of aluminum alloy parts, local areas are prone to significant thickness thinning, accompanied by the risk of necking and even fracture, which poses a severe challenge to ensuring the structural strength of key parts. The root of this problem is that aluminum alloys are significantly affected by temperature factors during the hot forming process, and their internal structure undergoes recovery and recrystallization, resulting in the alloy material lacking sufficient strain strengthening ability. Summary of the invention

[0008] The purpose of the present invention is to provide a high-strength and toughness die-casting aluminum alloy for new energy vehicles and a preparation method thereof. The present invention effectively refines the grains by adding Mn and Zr elements, eliminates the pores of the die-casting through a specific oxygenated die-casting process, and makes the aluminum alloy structure dense, and does not bubble during high-temperature solution treatment. The addition of Mn and Zr elements for recrystallization and the combination of the oxygenated die-casting process to produce ultrafine grains can improve the mechanical properties of the alloy with the large coarse grains of the Mg element, the coarse grains maintain deformation ability, the ultrafine grains maintain high strength, and the macroscopic mechanical properties of the material are improved; the combination of high-temperature heat treatment and low-temperature heat treatment is helpful to refine the grains and improve the uniformity of the aluminum alloy, and can effectively improve the mechanical properties of the aluminum alloy.

[0009] The purpose of the present invention can be achieved by the following technical solutions: A method for preparing a high-strength and toughness die-cast aluminum alloy for new energy vehicles, the preparation method comprising the following steps: 1) Heat and melt the 5 series aluminum alloy and the master alloy, remove impurities, and obtain a molten alloy; 2) performing pore-free die casting on the molten alloy to obtain a prefabricated aluminum alloy; 3) After the prefabricated aluminum alloy is subjected to high-temperature heat treatment, the temperature is reduced for heat treatment, and then cooled at room temperature to obtain a high-strength and toughness die-cast aluminum alloy; In step 1), the molten alloy includes 0.5% Mg, 4% Cu and 0.2% Zr by weight. The addition of Mn effectively prevents mold sticking and improves performance. The addition of Zr effectively refines the grains. In step 1), the impurity removal is to use hexachloroethane for degassing to remove surface oxide inclusions; In step 2), the parameters of the pore-free die casting are an oxygen atmosphere environment, a low speed of 0.25 m / s, a high speed of 2 m / s, a mold retention time of 10 s, a pouring temperature of 700°C, and a mold preheating temperature of 150°C; the oxygenated die casting process can effectively eliminate the pore problem in the die casting, so that the die casting has the characteristics of being heat-treatable, the microstructure of the alloy is denser, and its strength is significantly higher than that of conventional alloys, so that even during high-temperature solution treatment, the die casting will not have blistering, and by combining the recrystallization process after heat treatment, the combination of ultrafine grains and large coarse grains can significantly improve the mechanical properties of the alloy, among which the coarse grains help to maintain the deformation ability of the alloy, while the ultrafine grains help to maintain the high strength of the aluminum alloy.

[0010] In a preferred technical solution of the present invention, in step 1), the heating and melting is heating to 750-780°C until completely melted, then cooling to 650-700°C and keeping warm for 30 minutes.

[0011] As a preferred technical solution of the present invention, in step 1), the molten alloy is composed of the following raw materials in weight percentage: 13.5-13.8% Si, 5.7-5.73% Cu, 0.66-0.70% Zn, 0.86-0.89% Fe, 0.76-0.77% Mg, 0.220-0.234% Mn, 0.058-0.060% Pb, 0.2% Zr, and the balance Al and unavoidable impurities.

[0012] As a preferred technical solution of the present invention, in step 3), the high temperature heat treatment is carried out at a temperature of 300-320°C for 2.5-3.0h; in the solution of the present invention, in the above-mentioned insulation process, a suitable insulation time is adopted to avoid the problems of insufficient precipitation of the second phase and insufficient dislocation formation in the aluminum alloy material that may be caused by too long or too short insulation time, and can effectively and accurately control the size, quantity and number of dislocations of the second phase in the material to reach an ideal state, thereby ensuring that the plasticity and toughness of the material are not affected.

[0013] As a preferred technical solution of the present invention, the cooling heat treatment is to cool down to 180-210°C at a slow cooling rate and continue to keep warm for 30-45 minutes; in order to prevent the cooling rate from being too fast, resulting in cold shock inside the alloy, and then causing defects such as microcracks inside the material due to excessive local stress, a slow cooling measure is taken. If the cooling rate is too slow, the lattice shrinkage causes the elastic strain energy accumulated in the alloy microstructure to be low, and the number of dislocations formed is also small. These energies provide a relatively low driving force for the precipitation of the second phase during the subsequent heating process, which is not conducive to precipitation strengthening, thereby weakening the dislocation strengthening and precipitation strengthening effects.

[0014] As a preferred technical solution of the present invention, the cooling rate is 4-8°C / min.

[0015] As a preferred technical solution of the present invention, the temperature of the heat treatment is lowered after the high-temperature heat treatment. The lower heat treatment temperature is conducive to the diffusion and distribution of the magnesium element, refines the grains and improves the uniformity of the aluminum alloy, and can effectively improve the strength and toughness of the aluminum alloy and reduce the segregation of the material.

[0016] As a preferred technical solution of the present invention, zirconium can improve the structure and performance of aluminum alloy by refining grains, inhibiting recrystallization, and improving the stability of precipitated phases. During the heat treatment process, higher heat treatment can promote the faster entry of Zr elements into the aluminum alloy, and the addition of Zr can promote the formation of Al-Zr precipitated phases in the aluminum alloy. These precipitated phases can improve the strength and hardness of the aluminum alloy. Lower heat treatment temperature is conducive to controlling the precipitation behavior of Zr elements and avoiding the formation of premature or coarse precipitated phases, thereby maintaining the microstructure and performance advantages of the alloy.

[0017] As a preferred technical solution of the present invention, magnesium can improve the specific strength and corrosion resistance of aluminum alloys. During the heat treatment process, the diffusion and distribution of magnesium will affect the microstructure and properties of the alloy. A lower heat treatment temperature helps to maintain a uniform distribution of magnesium in the alloy matrix, thereby optimizing the mechanical properties and corrosion resistance of the alloy.

[0018] Beneficial effects of the present invention: The present invention effectively refines the grains by adding Mn and Zr elements, eliminates the pores of the die-casting through a specific oxygenated die-casting process, and makes the Mn and Zr elements of the aluminum alloy compact, and does not bubble during high-temperature solution treatment. The ultrafine grains obtained by recrystallization by adding Mn and Zr elements and combining the oxygenated die-casting process can improve the mechanical properties of the alloy with the large coarse grains of Mg elements, the coarse grains maintain deformation ability, the ultrafine grains maintain high strength, and the macroscopic mechanical properties of the material are improved.

[0019] In addition, the combination of high temperature heat treatment and lower temperature heat treatment helps to refine the grains and improve the uniformity of the aluminum alloy, and can effectively improve the mechanical properties of the aluminum alloy. DETAILED DESCRIPTION

[0020] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0021] Example 1 A method for preparing a high-strength and toughness die-cast aluminum alloy for new energy vehicles, the preparation method comprising the following steps: 1) Heat and melt the 5 series aluminum alloy and the master alloy, remove impurities, and obtain a molten alloy; 2) performing pore-free die casting on the molten alloy to obtain a prefabricated aluminum alloy; 3) After the prefabricated aluminum alloy is subjected to high-temperature heat treatment, the temperature is reduced for heat treatment, and then cooled at room temperature to obtain a high-strength and toughness die-cast aluminum alloy; In step 1), the molten alloy comprises, by weight percentage, 0.5% Mg element, 4% Cu element and 0.2% Zr element; In step 1), the impurity removal is performed by degassing with hexachloroethane; In step 2), the parameters of the pore-free die casting are oxygen atmosphere, low speed of 0.25 m / s, high speed of 2 m / s, mold retention time of 10 s, pouring temperature of 700° C., and mold preheating temperature of 150° C.

[0022] In step 1), the heating and melting is heating to 750° C. until the mixture is completely melted, then cooling to 650° C. and keeping the temperature for 30 minutes.

[0023] In step 1), the molten alloy is composed of the following raw materials in weight percentage: 13.5% Si, 5.7% Cu, 0.66% Zn, 0.86% Fe, 0.76% Mg, 0.220% Mn, 0.058% Pb, 0.2% Zr, and the balance Al and unavoidable impurities.

[0024] In step 3), the high temperature heat treatment is to keep the temperature at 300°C for 2.5 hours; the cooling heat treatment is to cool the temperature to 180°C at a slow cooling rate and keep the temperature for 30 minutes; the cooling rate is 4°C / min.

[0025] Example 2 A method for preparing a high-strength and toughness die-cast aluminum alloy for new energy vehicles, the preparation method comprising the following steps: 1) Heat and melt the 5 series aluminum alloy and the master alloy, remove impurities, and obtain a molten alloy; 2) performing pore-free die casting on the molten alloy to obtain a prefabricated aluminum alloy; 3) After the prefabricated aluminum alloy is subjected to high-temperature heat treatment, the temperature is reduced for heat treatment, and then cooled at room temperature to obtain a high-strength and toughness die-cast aluminum alloy; In step 1), the molten alloy comprises, by weight percentage, 0.5% Mg element, 4% Cu element and 0.2% Zr element; In step 1), the impurity removal is performed by degassing with hexachloroethane; In step 2), the parameters of the pore-free die casting are oxygen atmosphere, low speed of 0.25 m / s, high speed of 2 m / s, mold retention time of 10 s, pouring temperature of 700° C., and mold preheating temperature of 150° C.

[0026] In step 1), the heating and melting is heating to 760° C. until it is completely melted, then cooling to 667° C. and keeping the temperature for 30 minutes.

[0027] In step 1), the molten alloy is composed of the following raw materials in weight percentage: 13.6% Si, 5.71% Cu, 0.67% Zn, 0.87% Fe, 0.763% Mg, 0.225% Mn, 0.0587% Pb, 0.2% Zr, and the balance Al and unavoidable impurities.

[0028] In step 3), the high temperature heat treatment is to keep the temperature at 307°C for 2.7 hours; the cooling heat treatment is to cool the temperature to 190°C at a slow cooling rate and keep the temperature for 35 minutes; the cooling rate is 5°C / min.

[0029] Example 3 A method for preparing a high-strength and toughness die-cast aluminum alloy for new energy vehicles, the preparation method comprising the following steps: 1) Heat and melt the 5 series aluminum alloy and the master alloy, remove impurities, and obtain a molten alloy; 2) performing pore-free die casting on the molten alloy to obtain a prefabricated aluminum alloy; 3) After the prefabricated aluminum alloy is subjected to high-temperature heat treatment, the temperature is reduced for heat treatment, and then cooled at room temperature to obtain a high-strength and toughness die-cast aluminum alloy; In step 1), the molten alloy comprises, by weight percentage, 0.5% Mg element, 4% Cu element and 0.2% Zr element; In step 1), the impurity removal is performed by degassing with hexachloroethane; In step 2), the parameters of the pore-free die casting are oxygen atmosphere, low speed of 0.25 m / s, high speed of 2 m / s, mold retention time of 10 s, pouring temperature of 700° C., and mold preheating temperature of 150° C.

[0030] In step 1), the heating and melting is heating to 770° C. until it is completely melted, then cooling to 683° C. and keeping the temperature for 30 minutes.

[0031] In step 1), the molten alloy is composed of the following raw materials in weight percentage: 13.7% Si, 5.72% Cu, 0.69% Zn, 0.88% Fe, 0.767% Mg, 0.229% Mn, 0.0593% Pb, 0.2% Zr, and the balance Al and unavoidable impurities.

[0032] In step 3), the high temperature heat treatment is to keep the temperature at 313°C for 2.8 hours; the cooling heat treatment is to cool the temperature to 200°C at a slow cooling rate and keep the temperature for 40 minutes; the cooling rate is 7°C / min.

[0033] Example 4 A method for preparing a high-strength and toughness die-cast aluminum alloy for new energy vehicles, the preparation method comprising the following steps: 1) Heat and melt the 5 series aluminum alloy and the master alloy, remove impurities, and obtain a molten alloy; 2) performing pore-free die casting on the molten alloy to obtain a prefabricated aluminum alloy; 3) After the prefabricated aluminum alloy is subjected to high-temperature heat treatment, the temperature is reduced for heat treatment, and then cooled at room temperature to obtain a high-strength and toughness die-cast aluminum alloy; In step 1), the master alloy includes 0.5% Mg element, 4% Cu element and 0.2% Zr element in terms of weight percentage of the molten alloy; In step 1), the impurity removal is performed by degassing with hexachloroethane; In step 2), the parameters of the pore-free die casting are oxygen atmosphere, low speed of 0.25 m / s, high speed of 2 m / s, mold retention time of 10 s, pouring temperature of 700° C., and mold preheating temperature of 150° C.

[0034] In step 1), the heating and melting is heating to 780° C. until the mixture is completely melted, then cooling to 700° C. and keeping the temperature for 30 minutes.

[0035] In step 1), the molten alloy is composed of the following raw materials in weight percentage: 13.8% Si, 5.73% Cu, 0.70% Zn, 0.89% Fe, 0.77% Mg, 0.234% Mn, 0.060% Pb, 0.2% Zr, and the balance Al and unavoidable impurities.

[0036] In step 3), the high temperature heat treatment is to keep the temperature at 320°C for 3.0 hours; the cooling heat treatment is to cool the temperature to 210°C at a slow cooling rate and keep the temperature for 45 minutes; the cooling rate is 8°C / min.

[0037] Comparative Example 1 Compared with Example 4, the difference in Comparative Example 1 is that the intermediate alloy does not contain the Zr element, and the other components, preparation steps and parameters are the same.

[0038] Comparative Example 2 Compared with Example 4, the difference in Comparative Example 2 is that the intermediate alloy does not contain Mg element, and the other components, preparation steps and parameters are the same.

[0039] Comparative Example 3 Compared with Example 4, the difference in Comparative Example 3 is that the parameters of the pore-free die-casting are a low speed of 0.25 m / s, a high speed of 2 m / s, a mold retention time of 10 s, a pouring temperature of 700°C, and a mold preheating temperature of 150°C; the remaining components, preparation steps and parameters are the same.

[0040] Comparative Example 4 Compared with Example 4, the difference of Comparative Example 4 is that no cooling heat treatment is performed, and the high-temperature heat treatment in step 3) is to keep the temperature at 320° C. for 225 minutes; the other components, preparation steps and parameters are the same.

[0041] Comparative Example 5 Compared with Example 4, Comparative Example 5 is different in that no high-temperature heat treatment is performed, and the heat treatment in step 3) is to continue to keep the temperature at 210° C. for 225 minutes; the other components, preparation steps and parameters are the same.

[0042] The mechanical properties of the aluminum alloys obtained in Examples 1-4 and Comparative Examples 1-5 were tested respectively, and the test results are shown in Table 1.

[0043] Table 1

[0044] From the test results in Table 1, it can be seen that compared with comparative examples 1-5, the mechanical properties of the aluminum alloys obtained in Examples 1-4 of the present invention are significantly better than those in comparative examples 1-5, and the aluminum alloys obtained in the present invention have the characteristics of high strength, toughness and compression.

[0045] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-strength and toughness die-cast aluminum alloy for new energy vehicles, characterized in that: The preparation method comprises the following steps: 1) Heat and melt the 5 series aluminum alloy and the master alloy, remove impurities, and obtain a molten alloy; 2) performing pore-free die casting on the molten alloy to obtain a prefabricated aluminum alloy; 3) After the prefabricated aluminum alloy is subjected to high-temperature heat treatment, the temperature is reduced for heat treatment, and then cooled at room temperature to obtain a high-strength and toughness die-cast aluminum alloy; In step 1), the molten alloy comprises, by weight percentage, 0.5% Mg element, 4% Cu element and 0.2% Zr element; In step 1), the impurity removal is performed by degassing with hexachloroethane; In step 2), the parameters of the pore-free die casting are oxygen atmosphere, low speed of 0.25 m / s, high speed of 2 m / s, mold retention time of 10 s, pouring temperature of 700°C, and mold preheating temperature of 150°C.

2. The method for preparing a high-strength and toughness die-casting aluminum alloy for new energy vehicles according to claim 1, characterized in that: In step 1), the heating and melting is heating to 750-780° C. until completely melted, then cooling to 650-700° C. and keeping the temperature for 30 minutes.

3. The method for preparing a high-strength and toughness die-casting aluminum alloy for new energy vehicles according to claim 1, characterized in that: In step 1), the molten alloy is composed of the following raw materials in weight percentage: 13.5-13.8% Si, 5.7-5.73% Cu, 0.66-0.70% Zn, 0.86-0.89% Fe, 0.76-0.77% Mg, 0.220-0.234% Mn, 0.058-0.060% Pb, 0.2% Zr, and the balance Al and unavoidable impurities.

4. The method for preparing a high-strength and toughness die-casting aluminum alloy for new energy vehicles according to claim 1, characterized in that: In step 3), the high temperature heat treatment is carried out at a temperature of 300-320° C. for 2.5-3.0 hours.

5. The method for preparing a high-strength and toughness die-casting aluminum alloy for new energy vehicles according to claim 1, characterized in that: The temperature reduction heat treatment is to reduce the temperature to 180-210° C. at a slow cooling rate and continue to keep the temperature for 30-45 minutes.

6. The method for preparing a high-strength and toughness die-casting aluminum alloy for new energy vehicles according to claim 5, characterized in that: The cooling rate is 4-8°C / min.

7. A high-strength and toughness die-casting aluminum alloy for new energy vehicles prepared by the preparation method according to any one of claims 1 to 6.

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