High-toughness die-casting aluminum alloy and preparation method thereof

Abstract

The invention relates to the field of metal materials, in particular to a high-strength and high-toughness die-casting aluminum alloy and a preparation method thereof.The high-strength and high-toughness die-casting aluminum alloy comprises, by weight, 4.0%-4.5% of magnesium, 1.8%-2.6% of silicon, 0.5%-2.0% of iron, 0.3%-1.2% of manganese, 0.3%-1.2% of chromium, 0.5%-3.0% of zinc and the balance aluminum and inevitable impurities; the sum of the weight percentages of manganese and chromium is greater than or equal to the weight percentage of iron. The problems that an existing die-casting aluminum magnesium alloy is low in strength, difficult to regenerate and high in process cost can be solved, and certain strength and toughness can still be guaranteed while the high iron content is achieved.

Description

Technical Field

[0001] The present invention relates to the field of metal materials, and particularly to a high-strength and tough die-cast aluminum alloy and a preparation method thereof. Background Art

[0002] Lightweighting is an important way to reduce energy consumption and emissions and increase the driving range of automobiles. Aluminum-magnesium alloys have the advantages of low density, high specific strength, good corrosion resistance and formability. In addition, their good surface quality and gloss are suitable for manufacturing automotive exterior parts. However, the low strength of aluminum-magnesium alloys limits their use in body safety structural parts. Therefore, how to improve the strength of aluminum-magnesium alloys is a key issue. On the other hand, bauxite resources in China are relatively scarce, and more than 50% of bauxite depends on imports. The production of aluminum ingots for remelting, the raw material for preparing aluminum alloys by electrolytic aluminum, is a high-energy-consuming and highly polluting process. Therefore, the recycling and utilization of aluminum scraps is the future development trend.

[0003] In response to the above requirements, there are still several problems in the development and application of aluminum-magnesium alloys. First, the strength of existing die-cast aluminum-magnesium alloys is generally low, and the tensile strength usually does not exceed 280 MPa. Although some high-strength die-cast aluminum-magnesium alloys have relatively high tensile strength (300 - 400 MPa) and elongation (12 - 14%), the iron content in this alloy is strictly limited to 0.01 - 0.02%. Therefore, it is impossible to use aluminum scraps with a high iron content as raw materials for production, which greatly increases the material cost. Second, existing die-cast aluminum-magnesium alloys need to undergo 2 - 3 hours of artificial aging to achieve a better combination of strength and toughness. A typical die-cast Al-Mg-Si-Mn alloy needs to undergo artificial aging treatment at 250 °C for 3 h to make the yield strength reach 200 - 240 MPa, the tensile strength reach 340 - 380 MPa, and the elongation reach 10 - 13%. However, the high temperature and long aging holding time greatly increase the energy consumption cost and are not conducive to industrial production. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-strength and tough die-cast aluminum alloy and a preparation method thereof, which can solve the problems of low strength, difficulty in recycling and high process cost of existing die-cast aluminum-magnesium alloys, and can still ensure certain strength and toughness while having a high iron content.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a high-strength and tough die-casting aluminum alloy, which comprises the following components by weight percentage: 4.0% - 4.5% of magnesium, 1.8% - 2.6% of silicon, 0.5% - 2.0% of iron, 0.3% - 1.2% of manganese, 0.3% - 1.2% of chromium, 0.5% - 3.0% of zinc, and the balance is aluminum and unavoidable impurities; the sum of the weight percentages of manganese and chromium is greater than or equal to the weight percentage of iron.

[0007] Further, it further comprises the following components by weight percentage: 0.01% - 0.1% of tin and 0.01% - 0.1% of copper; the sum of the weight percentages of the tin and copper is ≤ 0.1%.

[0008] In a second aspect, the present invention provides a preparation method of a high-strength and tough die-casting aluminum alloy, which comprises the following steps:

[0009] Step 1: Heat the remelted aluminum ingot and the recycled aluminum alloy containing Fe impurity elements to melt, and then add auxiliary additives to obtain a melt; the auxiliary additives include at least one of magnesium, manganese, chromium, and zinc; the melt comprises the following components by weight percentage: 4.0% - 4.5% of magnesium, 1.8% - 2.6% of silicon, 0.5% - 2.0% of iron, 0.3% - 1.2% of manganese, 0.3% - 1.2% of chromium, 0.5% - 3.0% of zinc, and the balance is aluminum and unavoidable impurities; the sum of the weight percentages of manganese and chromium is greater than or equal to the weight percentage of iron;

[0010] Step 2: Refine and degas the melt, skim off the oxide inclusions after standing, and then adjust the temperature of the melt to 685°C - 700°C for die-casting to obtain a high-strength and tough die-casting aluminum alloy.

[0011] Further, the recycled aluminum alloy containing Fe impurity elements in Step 1 is at least one of Al-Mg series recycled aluminum alloy, Al-Si series recycled aluminum alloy, and Al-Zn-Si series recycled aluminum alloy.

[0012] Further, the yield strength of the high-strength and tough die-casting aluminum alloy obtained in Step 2 is 165 MPa - 185 MPa, the tensile strength is 270 MPa - 300 MPa, and the elongation is 10% - 16%.

[0013] Further, the auxiliary additives in Step 1 further include tin and copper;

[0014] The melt comprises the following components by weight percentage: 4.0% to 4.5% of magnesium, 1.8% to 2.6% of silicon, 0.5% to 2.0% of iron, 0.3% to 1.2% of manganese, 0.3% to 1.2% of chromium, 0.5% to 3.0% of zinc, 0.01% to 0.1% of tin, 0.01% to 0.1% of copper, and the balance is aluminum and unavoidable impurities; the sum of the weight percentages of tin and copper ≤ 0.1%.

[0015] Further, the method further comprises: Step Three, performing artificial aging treatment on the high-strength and high-toughness die-cast aluminum alloy obtained in Step Two, setting the aging temperature to 180°C to 240°C, and setting the holding time to 10 min to 60 min.

[0016] Further, the yield strength of the high-strength and high-toughness die-cast aluminum alloy after artificial aging treatment is 180 MPa to 240 MPa, the tensile strength is 300 MPa to 380 MPa, and the elongation is 9% to 14%.

[0017] The present invention has the following unexpected beneficial effects:

[0018] 1. The content of iron element in the high-strength and high-toughness die-cast aluminum alloy of the present invention is controlled at 0.5% to 2.0%, and its main source is the common impurity element in recycled aluminum. The relatively high iron content range is beneficial to increasing the usage ratio of recycled aluminum and further reducing the material cost. However, the iron element will form harmful Al 13 Fe4 phase, and this second phase usually presents needle flakes or blocks, reducing the plasticity of the alloy. Therefore, 0.3% to 1.2% of manganese and 0.3% to 1.2% of chromium are added to the high-strength and high-toughness die-cast aluminum alloy, and the sum of the weight percentages of manganese and chromium elements is greater than or equal to the weight percentage of the iron element, thereby forming α-Al(Fe,Cr)Si phase and α-Al(Fe,Mn)Si phase with less influence on plasticity to replace the harmful Al 13 Fe4 phase. At the same time, adding manganese and chromium elements has higher efficiency than adding them separately, reducing the total addition amount of manganese and chromium and the total amount of iron-rich phase formation, which is beneficial to ensuring the plasticity of the die-cast aluminum alloy. Furthermore, the problems of low strength, difficulty in recycling, and high process cost of the existing die-cast aluminum-magnesium alloy are solved. While having a high iron content, it can still ensure a certain strength and toughness.

[0019] 2. In the high-strength and high-toughness die-casting aluminum alloy of the present invention, the content of magnesium element is controlled at 4.0% - 4.5%, and the content of silicon element is controlled at 1.8% - 2.6%. Most of the magnesium forms β-Mg2Si phase with silicon, which plays a strengthening effect, and part of the magnesium element dissolves in α-Al in the form of solid solution atoms, playing a solid solution strengthening effect. The content of zinc element in the high-strength and high-toughness die-casting aluminum alloy is controlled at 0.5% - 3.0%. The purpose is to enrich at the grain boundary and form a transition phase η-MgZn2, which forms a coherent or semi-coherent interface with the aluminum matrix, providing a strengthening effect.

[0020] 3. The high-strength and high-toughness die-casting aluminum alloy of the present invention also includes 0.01% - 0.1% of tin and 0.01% - 0.1% of copper by weight percentage; the sum of the weight percentages of tin and copper ≤ 0.1%. Adding tin and copper simultaneously can more effectively inhibit the natural aging of die-castings during storage, and promote the nucleation of β' precipitate phase during subsequent artificial aging, greatly shortening the artificial aging time, reducing the aging temperature, enabling the alloy to achieve the best strengthening effect after short-term artificial aging, and reducing the energy consumption cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It shows a schematic diagram of the microstructure morphology of the high-strength and high-toughness die-casting aluminum alloy described in the embodiment of the present invention.

[0022] Figure 2 It shows a schematic diagram of the enrichment of the transition phase at the grain boundary of the high-strength and high-toughness die-casting aluminum alloy described in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Hereinafter, the embodiments of the present invention will be described with reference to the drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for explaining the present invention, rather than for limiting the protection scope of the present invention.

[0024] In one embodiment, the present invention provides a high-strength and high-toughness die-casting aluminum alloy, which includes the following components by weight percentage: 4.0% - 4.5% of magnesium, 1.8% - 2.6% of silicon, 0.5% - 2.0% of iron, 0.3% - 1.2% of manganese, 0.3% - 1.2% of chromium, 0.5% - 3.0% of zinc, and the balance is aluminum and unavoidable impurities; the sum of the weight percentages of manganese and chromium is greater than or equal to the weight percentage of iron.

[0025] In the high-strength and tough die-cast aluminum alloy of the present invention, the iron element content is controlled within 0.5% to 2.0%. Its main source is the common impurity element in recycled aluminum alloy. A relatively high iron content range is beneficial to increasing the usage ratio of recycled aluminum and further reducing the material cost. However, iron elements will form harmful Al 13 Fe4 phase. This second phase usually presents needle-like or massive shapes, reducing the plasticity of the alloy. Therefore, 0.3% to 1.2% of manganese and 0.3% to 1.2% of chromium are added to the high-strength and tough die-cast aluminum alloy, and the sum of the weight percentages of manganese and chromium elements is greater than or equal to the weight percentage of iron elements, thereby forming α-Al(Fe,Cr)Si phase and α-Al(Fe,Mn)Si phase with less influence on plasticity to replace the harmful Al 13 Fe4 phase. At the same time, adding manganese and chromium elements has higher efficiency than adding them separately, reducing the total addition amount of manganese and chromium and the total amount of iron-rich phase formation, which is beneficial to ensuring the plasticity of the die-cast aluminum alloy. Furthermore, it solves the problems of low strength, difficulty in recycling, and high process cost of existing die-cast aluminum-magnesium alloys. While having a high iron content, it can still ensure certain strength and toughness. See Figure 1 As shown, α-Al(Fe,Cr)Si phase and α-Al(Fe,Mn)Si are polygon structures and are relatively fine, and the matrix is α-Al, which is not prone to brittle fracture when stressed.

[0026] In the high-strength and tough die-cast aluminum alloy, the magnesium element content is controlled within 4.0% to 4.5%, and the silicon element content is controlled within 1.8% to 2.6%. Most of the magnesium forms β-Mg2Si phase, which plays a strengthening effect, and part of the magnesium element dissolves in α-Al in the form of solid solution atoms, playing a solid solution strengthening effect.

[0027] In the high-strength and tough die-cast aluminum alloy, the zinc element content is controlled within 0.5% to 3.0%, and the purpose is to enrich at the grain boundary. See Figure 2 As shown, η-MgZn2 only enriches at the grain boundary, and the others are α-Al(Fe,Cr)Si phase, α-Al(Fe,Mn)Si and α-Al matrix. The transition phase η-MgZn2 forms coherent or semi-coherent interfaces with the aluminum matrix, providing a strengthening effect.

[0028] As a preferred embodiment of the present invention, it further includes the following components by weight percentage: 0.01% to 0.1% of tin and 0.01% to 0.1% of copper; the sum of the weight percentages of tin and copper ≤ 0.1%. Adding tin and copper simultaneously can more effectively inhibit natural aging of die-castings during storage, and promote the nucleation of β' precipitate phase during subsequent artificial aging, greatly shortening the artificial aging time, reducing the aging temperature, enabling the alloy to achieve the best strengthening effect after short-term artificial aging, and reducing the energy consumption cost.

[0029] In one embodiment, the present invention provides a method for preparing a high-strength and tough die-cast aluminum alloy, which comprises the following steps:

[0030] Step 1, heating remelted aluminum ingots and recycled aluminum alloy containing Fe impurity elements to melting, and then adding auxiliary additives to obtain a melt; the auxiliary additives include at least one of magnesium, manganese, chromium and zinc; the melt comprises the following components by weight percentage: 4.0% - 4.5% of magnesium, 1.8% - 2.6% of silicon, 0.5% - 2.0% of iron, 0.3% - 1.2% of manganese, 0.3% - 1.2% of chromium, 0.5% - 3.0% of zinc, and the balance is aluminum and inevitable impurities; the sum of the weight percentages of manganese and chromium is greater than or equal to the weight percentage of iron;

[0031] Step 2, refining and degassing the melt, skimming off oxide inclusions after standing, and then adjusting the temperature of the melt to 685°C - 700°C for die-casting to obtain a high-strength and tough die-cast aluminum alloy.

[0032] The present invention uses remelted aluminum ingots and recycled aluminum alloy containing Fe impurity elements as basic raw materials, which not only utilizes recycled aluminum resources and reduces production and manufacturing costs, but also can meet the requirement of iron content in the alloy composition by virtue of the iron element in the recycled aluminum. Adding auxiliary additives containing at least one of magnesium, manganese, chromium and zinc is to accurately adjust the melt composition to make it conform to the element ratio of the high-strength and tough die-cast aluminum alloy, ensuring that each element plays a specific role, such as magnesium and silicon forming a strengthening phase, and manganese and chromium improving the adverse effects brought by the iron element, etc.

[0033] Refining and degassing the melt can effectively remove the gas and impurities in the melt and improve the purity of the melt. Skimming off oxide inclusions after standing further ensures the quality of the alloy and reduces the negative impact of impurities on the alloy performance. This step is crucial for improving the strength and toughness of the alloy, avoiding defects inside the alloy caused by gas and impurities and affecting the quality of the final product.

[0034] Adjusting the temperature of the treated melt to 685°C - 700°C for die-casting, this temperature range is a process parameter verified by practice and suitable for die-casting and forming of this alloy. At this temperature, the melt has good fluidity and filling property, which can ensure the smooth progress of the die-casting process, enable the alloy to be formed into the required shape and size in the mold, and finally obtain a high-strength and tough die-cast aluminum alloy that meets the performance requirements.

[0035] As a preferred embodiment of the present invention, the recycled aluminum alloy containing Fe impurity elements in Step 1 is at least one of Al-Mg series recycled aluminum alloy, Al-Si series recycled aluminum alloy and Al-Zn-Si series recycled aluminum alloy.

[0036] From the perspective of composition, the Al-Mg series recycled aluminum alloy itself contains magnesium element, which is compatible with the magnesium element in the target high-strength and tough die-cast aluminum alloy, can provide part of the magnesium source, reduce the usage amount of additional magnesium additives, and the iron impurities it contains can provide the required iron element for the alloy. At the same time, other elements in the alloy may also have a certain synergistic effect on the final alloy properties. The Al-Si series recycled aluminum alloy is rich in silicon element, corresponding to the silicon content range in the target alloy, can provide silicon source for the alloy, and the iron impurities in it can meet the iron content requirement. Silicon element can form strengthening phases with elements such as magnesium in the alloy, which helps to improve the strength and toughness of the alloy. The Al-Zn-Si series recycled aluminum alloy contains zinc and silicon elements, can provide zinc source and silicon source for the target alloy. Zinc enriches at the grain boundary to form strengthening phases, silicon can participate in forming strengthening phases, and its iron impurities can also meet the iron content requirement. The combined action of various elements is beneficial to improving the comprehensive properties of the alloy.

[0037] From the perspectives of resource utilization and cost, these several kinds of recycled aluminum alloys are widely sourced in the market. Selecting them as raw materials for recycled aluminum alloys containing Fe impurity elements can make full use of existing recycled resources, reduce the dependence on primary aluminum resources, and conform to the concept of sustainable development. Using recycled aluminum alloy has a lower cost compared with raw materials such as pure aluminum. By reasonably selecting these several kinds of recycled aluminum alloys, the cost of preparing high-strength and tough die-cast aluminum alloy can be effectively reduced while ensuring the alloy properties, and the market competitiveness of the product can be improved.

[0038] From the perspective of process adaptability, these several kinds of recycled aluminum alloys have good compatibility with remelted aluminum ingots and other auxiliary additives during the melting process, can be evenly mixed with other components during the heating and melting process to form a melt with uniform composition, which is beneficial to the subsequent process and the stability of alloy properties. And after these several kinds of recycled aluminum alloys are processed through melting and other treatments, they perform well in terms of fluidity and formability in the die-casting process, can adapt to the die-casting temperature range of 685°C - 700°C, ensure the smooth progress of the die-casting process, and obtain high-quality high-strength and tough die-cast aluminum alloy products.

[0039] As a preferred implementation manner of the present invention, the yield strength of the high-strength and tough die-cast aluminum alloy obtained in the second step is 165 MPa - 185 MPa, which indicates that the alloy has good anti-plastic deformation ability. When subjected to external force, a certain stress level needs to be reached before irreversible plastic deformation begins, which enables it to withstand a certain degree of load without permanent deformation in practical applications and can be used for manufacturing components with certain requirements for structural stability.

[0040] The tensile strength of the high-strength and tough die-cast aluminum alloy obtained in step 2 is 270MPa to 300MPa, indicating that the alloy can withstand a large tensile force without breaking during the stretching process. A higher tensile strength means that the alloy has better reliability and safety when subjected to tensile force, and is suitable for occasions that need to withstand tensile loads, such as certain parts of automobiles, mechanical structural parts, etc.

[0041] The high-strength and toughness die-cast aluminum alloy obtained in step 2 has an elongation of 10% to 16%, indicating that the alloy has a certain plasticity. This allows the alloy to deform to a certain extent without breaking during processing, and can also absorb a certain amount of energy during use, avoiding brittle fracture due to sudden external forces, thereby increasing the toughness and reliability of the alloy.

[0042] Compared with some traditional die-cast aluminum alloys, this high-strength and tough die-cast aluminum alloy may have better comprehensive properties in terms of strength and plasticity. Some traditional aluminum alloys may have high strength but poor plasticity and are prone to brittle fracture; while others may have good plasticity but insufficient strength. Through reasonable composition design and preparation process, this alloy achieves a good balance between yield strength, tensile strength and elongation, making it more widely applicable in engineering applications.

[0043] As a preferred embodiment of the present invention, the auxiliary additives in step one also include tin and copper; the melt includes the following components by weight percentage: 4.0% to 4.5% magnesium, 1.8% to 2.6% silicon, 0.5% to 2.0% iron, 0.3% to 1.2% manganese, 0.3% to 1.2% chromium, 0.5% to 3.0% zinc, 0.01% to 0.1% tin, 0.01% to 0.1% copper, and the remainder is aluminum and unavoidable impurities; the sum of the weight percentages of tin and copper is ≤0.1%.

[0044] Adding tin and copper at the same time can more effectively inhibit the natural aging of die castings during storage, and promote the nucleation of β' precipitation phase in the subsequent artificial aging process, which greatly shortens the artificial aging time and reduces the aging temperature, so that the alloy can achieve the best strengthening effect after a short period of artificial aging and reduce energy consumption costs.

[0045] As a preferred embodiment of the present invention, the method further includes: step three, artificial aging treatment of the high-strength and toughness die-cast aluminum alloy obtained in step two, the aging temperature is set to 180°C to 240°C, and the insulation time is set to 10min to 60min.

[0046] The high-strength and tough die-cast aluminum alloy obtained in Step 2 already has a certain microstructure and property basis. Artificial aging treatment further optimizes the alloy properties on this basis. The grain structure and solid solution state formed during die-casting will affect the formation and distribution of precipitates during aging treatment. For example, if the grain refinement degree is better during die-casting, during aging treatment, precipitates may nucleate at more grain boundaries and dislocations and other defects, thereby improving the strengthening effect. After artificial aging treatment, the properties of the aluminum alloy are more stable and excellent, which can better meet the requirements of subsequent processing (such as machining, surface treatment, etc.), and can also show better properties in actual use, such as withstanding higher loads and having better wear resistance, etc., improving the quality and reliability of the product.

[0047] As a preferred embodiment of the present invention, the yield strength of the high-strength and tough die-cast aluminum alloy after artificial aging treatment is 180 MPa to 240 MPa, the tensile strength is 300 MPa to 380 MPa, and the elongation is 9% to 14%.

[0048] The yield strength is increased from 165 MPa to 185 MPa before artificial aging treatment to 180 MPa to 240 MPa, indicating that artificial aging treatment significantly enhances the alloy's ability to resist plastic deformation. This is because during the aging process, the supersaturated solid solution inside the alloy decomposes to form fine and dispersed precipitates, and these precipitates hinder the movement of dislocations, making the alloy start to undergo plastic deformation at a higher stress level, thereby increasing the yield strength.

[0049] The tensile strength is increased from 270 MPa to 300 MPa before artificial aging treatment to 300 MPa to 380 MPa, further illustrating the enhancing effect of artificial aging treatment on the alloy strength. More strengthening phases are formed and evenly distributed in the matrix during the aging process, increasing the alloy's ability to resist fracture during the tensile process and enabling it to withstand greater tensile force.

[0050] The elongation changes from 10% to 16% before artificial aging treatment to 9% to 14%, showing a slight decrease. This is because the formation of precipitates during the aging process will hinder the slip of dislocations to a certain extent, restricting the alloy's plastic deformation ability. However, even though the elongation decreases, it still remains in the range of 9% to 14%, indicating that while the alloy improves its strength, it still retains a certain amount of plasticity and does not become a brittle material, ensuring the comprehensive properties of the alloy.

[0051] Compared with other aluminum alloys or traditional materials that have not undergone similar aging treatments, this high-strength and tough die-cast aluminum alloy after artificial aging treatment has obvious advantages in terms of strength. Its relatively high yield strength and tensile strength make it more reliable when bearing loads and suitable for engineering application fields with high strength requirements, such as the manufacturing of key components in industries like automotive and aerospace. At the same time, its retained certain plasticity also enables it to have better adaptability during processing and use. Compared with some materials with high strength but poor plasticity, this alloy is less likely to undergo sudden brittle fracture when subjected to external force impact, thus having higher safety.

[0052] The following is an analysis and explanation with specific examples.

[0053] Example 1, a high-strength and tough die-cast aluminum alloy, which includes the following components by weight percentage: 4.0% magnesium (Mg), 1.8% silicon (Si), 0.5% iron (Fe), 0.3% manganese (Mn), 0.3% chromium (Cr), 0.5% zinc (Zn), 0.05% tin (Sn), 0.05% copper (Cu), and the balance is aluminum (Al) and unavoidable impurities.

[0054] The preparation method of this high-strength and tough die-cast aluminum alloy includes the following steps:

[0055] Step 1, heat the remelted aluminum ingot and the recycled aluminum alloy containing Fe impurity element to melting, and then add auxiliary additives to obtain a melt; the auxiliary additives include at least one of magnesium, manganese, chromium, and zinc; the melt includes the following components by weight percentage: 4.0% magnesium, 1.8% silicon, 0.5% iron, 0.3% manganese, 0.3% chromium, 0.5% zinc, 0.05% tin, 0.05% copper, and the balance is aluminum and unavoidable impurities. The recycled aluminum alloy containing Fe impurity element is Al-Mg series recycled aluminum alloy, Al-Si series recycled aluminum alloy, and Al-Zn-Si series recycled aluminum alloy.

[0056] Step 2, refine and degas the melt, skim off the oxide inclusions after standing for 30 min, and then adjust the melt temperature to 685 °C - 700 °C for die-casting to obtain the high-strength and tough die-cast aluminum alloy.

[0057] Step 3, perform artificial aging treatment on the high-strength and tough die-cast aluminum alloy obtained in Step 2, and the aging treatment process parameters include:

[0058] The first group: the aging temperature is set at 180 °C, and the holding time is set at 30 min.

[0059] The second group: the aging temperature is set at 200 °C, and the holding time is set at 30 min.

[0060] The third group: the aging temperature is set at 240 °C, and the holding time is set at 30 min.

[0061] The mechanical properties of the high-strength and high-toughness die-cast aluminum alloy obtained in Step 2 and the high-strength and high-toughness die-cast aluminum alloy after artificial aging treatment with three groups of different process parameters were measured respectively. The results are shown in Table 1.

[0062] Table 1 Mechanical Properties of High-Strength and High-Toughness Die-Cast Aluminum Alloy

[0063]

[0064] Example 2: A high-strength and high-toughness die-cast aluminum alloy, which comprises the following components by weight percentage: 4.5% of magnesium, 2.6% of silicon, 2.0% of iron, 1.1% of manganese, 1.2% of chromium, 2.9% of zinc, 0.05% of tin, 0.05% of copper, and the balance is aluminum and unavoidable impurities.

[0065] The preparation method of the high-strength and high-toughness die-cast aluminum alloy comprises the following steps:

[0066] Step 1: Heat the remelted aluminum ingot and the recycled aluminum alloy containing Fe impurity elements to melt, and then add auxiliary additives to obtain a melt; the auxiliary additives include at least one of magnesium, manganese, chromium, and zinc; the melt comprises the following components by weight percentage: 4.5% of magnesium, 2.6% of silicon, 2.0% of iron, 1.1% of manganese, 1.2% of chromium, 2.9% of zinc, 0.05% of tin, 0.05% of copper, and the balance is aluminum and unavoidable impurities. The recycled aluminum alloy containing Fe impurity elements is Al-Mg series recycled aluminum alloy, Al-Si series recycled aluminum alloy, and Al-Zn-Si series recycled aluminum alloy.

[0067] Step 2: Refine and degas the melt, skim off the oxide inclusions after standing for 30 min, and then adjust the temperature of the melt to 685 °C - 700 °C for die-casting to obtain the high-strength and high-toughness die-cast aluminum alloy.

[0068] Step 3: Perform artificial aging treatment on the high-strength and high-toughness die-cast aluminum alloy obtained in Step 2. The process parameters of the aging treatment include:

[0069] The first group: The aging temperature is set at 180 °C and the holding time is set at 50 min.

[0070] The second group: The aging temperature is set at 200 °C and the holding time is set at 50 min.

[0071] The third group: The aging temperature is set at 240 °C and the holding time is set at 50 min.

[0072] The mechanical properties of the high-strength and high-toughness die-cast aluminum alloy obtained in Step 2 and the high-strength and high-toughness die-cast aluminum alloy after artificial aging treatment with three groups of different process parameters were measured respectively. The results are shown in Table 2.

[0073] Table 2 Mechanical Properties of High Strength and Toughness Die Casting Aluminum Alloy

[0074]

[0075] Example 3: A high strength and toughness die casting aluminum alloy, which includes the following components by weight percentage: 4.2% magnesium, 2.2% silicon, 1.2% iron, 0.7% manganese, 0.6% chromium, 1.7% zinc, 0.04% tin, 0.03% copper, and the balance is aluminum and inevitable impurities.

[0076] The preparation method of the high strength and toughness die casting aluminum alloy includes the following steps:

[0077] Step 1: Heat the remelted aluminum ingot and the recycled aluminum alloy containing Fe impurity elements until they melt, and then add auxiliary additives to obtain a melt; the auxiliary additives include at least one of magnesium, manganese, chromium, and zinc; the melt includes the following components by weight percentage: 4.2% magnesium, 2.2% silicon, 1.2% iron, 0.7% manganese, 0.6% chromium, 1.7% zinc, 0.04% tin, 0.03% copper, and the balance is aluminum and inevitable impurities. The recycled aluminum alloy containing Fe impurity elements is Al-Mg series recycled aluminum alloy, Al-Si series recycled aluminum alloy, and Al-Zn-Si series recycled aluminum alloy.

[0078] Step 2: Refine and degas the melt, skim off the oxide inclusions after standing for 30 min, and then adjust the temperature of the melt to 685°C - 700°C for die casting to obtain the high strength and toughness die casting aluminum alloy.

[0079] Step 3: Perform artificial aging treatment on the high strength and toughness die casting aluminum alloy obtained in Step 2. The process parameters of the aging treatment include:

[0080] The first group: The aging temperature is set at 180°C and the holding time is set at 45 min.

[0081] The second group: The aging temperature is set at 200°C and the holding time is set at 45 min.

[0082] The third group: The aging temperature is set at 240°C and the holding time is set at 45 min.

[0083] Measure the mechanical properties of the high strength and toughness die casting aluminum alloy obtained in Step 2 and the high strength and toughness die casting aluminum alloy after artificial aging treatment with three groups of different process parameters respectively. The results are shown in Table 3.

[0084] Table 3 Mechanical Properties of High Strength and Toughness Die Casting Aluminum Alloy

[0085]

[0086] Example 4. A high-strength and tough die-cast aluminum alloy, which comprises the following components by weight percentage: 4.1% of magnesium, 2.0% of silicon, 0.8% of iron, 0.4% of manganese, 0.6% of chromium, 2.2% of zinc, 0.05% of tin, 0.05% of copper, and the balance is aluminum and inevitable impurities.

[0087] The preparation method of the high-strength and tough die-cast aluminum alloy comprises the following steps:

[0088] Step 1: Heat the remelted aluminum ingot and the recycled aluminum alloy containing Fe impurity elements to melting, and then add auxiliary additives to obtain a melt; the auxiliary additives include at least one of magnesium, manganese, chromium, and zinc; the melt comprises the following components by weight percentage: 4.1% of magnesium, 2.0% of silicon, 0.8% of iron, 0.4% of manganese, 0.6% of chromium, 2.2% of zinc, 0.05% of tin, 0.05% of copper, and the balance is aluminum and inevitable impurities. The recycled aluminum alloy containing Fe impurity elements is an Al-Mg series recycled aluminum alloy, an Al-Si series recycled aluminum alloy, and an Al-Zn-Si series recycled aluminum alloy.

[0089] Step 2: Refine and degas the melt, skim off the oxide inclusions after standing for 30 min, and then adjust the temperature of the melt to 685 °C - 700 °C for die-casting to obtain the high-strength and tough die-cast aluminum alloy.

[0090] Step 3: Perform artificial aging treatment on the high-strength and tough die-cast aluminum alloy obtained in Step 2, and the aging treatment process parameters include:

[0091] The first group: The aging temperature is set at 180 °C, and the holding time is set at 45 min.

[0092] The second group: The aging temperature is set at 200 °C, and the holding time is set at 45 min.

[0093] The third group: The aging temperature is set at 240 °C, and the holding time is set at 45 min.

[0094] Measure the mechanical properties of the high-strength and tough die-cast aluminum alloy obtained in Step 2 and the high-strength and tough die-cast aluminum alloy after artificial aging treatment with three groups of different process parameters respectively. The results are shown in Table 4.

[0095] Table 4 Mechanical properties of the high-strength and tough die-cast aluminum alloy

[0096]

[0097] The above embodiments are only preferred embodiments given to fully illustrate the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention.

Claims

1. A high-strength and toughness die-cast aluminum alloy, characterized in that: The following components are included by weight percentage: 4.0% to 4.5% magnesium, 1.8% to 2.6% silicon, 0.5% to 2.0% iron, 0.3% to 1.2% manganese, 0.3% to 1.2% chromium, 0.5% to 3.0% zinc, and the balance is aluminum and unavoidable impurities; The sum of the weight percentages of manganese and chromium is greater than or equal to the weight percentage of iron.

2. The high-strength and toughness die-cast aluminum alloy according to claim 1, characterized in that: The following components are also included by weight percentage: 0.01% to 0.1% of tin and 0.01% to 0.1% of copper; The sum of the weight percentages of tin and copper is ≤0.1%.

3. A method for preparing a high-strength and toughness die-cast aluminum alloy, characterized in that: The steps include: Step 1, heating the remelted aluminum ingot and the recycled aluminum alloy including the Fe impurity element until they are melted, and then adding auxiliary additives to obtain a melt; the auxiliary additives include at least one of magnesium, manganese, chromium and zinc; the melt includes the following components by weight percentage: 4.0% to 4.5% magnesium, 1.8% to 2.6% silicon, 0.5% to 2.0% iron, 0.3% to 1.2% manganese, 0.3% to 1.2% chromium, 0.5% to 3.0% zinc, and the balance is aluminum and unavoidable impurities; the sum of the weight percentages of manganese and chromium is greater than or equal to the weight percentage of iron; Step 2: Refining and degassing the melt, removing oxide inclusions after standing, and then adjusting the melt temperature to 685°C~700°C for die casting to obtain a high-strength and toughness die-cast aluminum alloy.

4. The method for preparing a high-strength and toughness die-cast aluminum alloy according to claim 3, characterized in that: The recycled aluminum alloy including the Fe impurity element in the step 1 is at least one of an Al-Mg recycled aluminum alloy, an Al-Si recycled aluminum alloy, and an Al-Zn-Si recycled aluminum alloy.

5. The method for preparing a high-strength and toughness die-cast aluminum alloy according to claim 3, characterized in that: The high-strength and toughness die-cast aluminum alloy obtained in step 2 has a yield strength of 165MPa-185MPa, a tensile strength of 270MPa-300MPa, and an elongation of 10%-16%.

6. The method for preparing a high-strength and toughness die-cast aluminum alloy according to claim 3, characterized in that: The auxiliary additives in the step 1 also include tin and copper; The melt comprises the following components by weight percentage: 4.0% to 4.5% magnesium, 1.8% to 2.6% silicon, 0.5% to 2.0% iron, 0.3% to 1.2% manganese, 0.3% to 1.2% chromium, 0.5% to 3.0% zinc, 0.01% to 0.1% tin, 0.01% to 0.1% copper, and the remainder is aluminum and unavoidable impurities; the sum of the weight percentages of tin and copper is ≤0.1%.

7. The method for preparing a high-strength and toughness die-cast aluminum alloy according to claim 6, characterized in that: The method further includes: Step three, performing artificial aging treatment on the high-strength and toughness die-cast aluminum alloy obtained in step two, setting the aging temperature to 180° C. to 240° C., and setting the holding time to 10 min to 60 min.

8. The method for preparing a high-strength and toughness die-cast aluminum alloy according to claim 7, characterized in that: The yield strength of the high-strength and toughness die-cast aluminum alloy after artificial aging treatment is 180MPa~240MPa, the tensile strength is 300MPa~380MPa, and the elongation is 9%~14%.

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