A kind of die-casting aluminum alloy and its preparation method and application

Abstract

The present invention discloses a die-cast aluminum alloy and a preparation method and application thereof, and belongs to the technical field of metal materials. The die-cast aluminum alloy provided by the present invention is composed of the following components in mass percentage: 10.5-13% Si, 0.4-0.8% Fe, 0-0.45% Mn, 0.25-0.45% Mg, 0.06-0.1% Ti, 0.05-0.12% Zr, 0.005-0.01% B, 0.015-0.03% Sr, and the remainder is impurity elements and Al; the sum of the mass percentages of Mn and Fe is 0.7-0.9%. The present invention is based on Al-Si alloy, designs a higher Fe content, and prepares a die-cast aluminum alloy with good casting formability and high strength and toughness through the composition optimization design of the main alloy components of Si, Fe, and Mg and the trace elements of Ti, B, Sr, Zr, and Mn.

Description

Technical Field

[0001] The invention belongs to the technical field of metal materials, and in particular relates to a die-casting aluminum alloy and a preparation method and application thereof. Background Art

[0002] New energy vehicles are the main development direction of future vehicles, but the weight of the power system is 10-30% higher than that of the traditional engine system. The increase in vehicle weight leads to increased energy consumption. Therefore, it is imperative to make new energy vehicles lightweight.

[0003] In recent years, die-casting integrated molding technology has become one of the effective ways to achieve lightweight automobiles, but the corresponding materials cannot be improved by traditional high-temperature heat treatment (including T5, T6) to improve their strength, and it is urgent to develop non-heat treatment / free high-strength and toughness die-casting aluminum alloy materials. CN116287890A discloses a high-strength and toughness, high welding performance, free heat treatment high-pressure casting aluminum alloy and its properties and preparation method. The alloy contains Si 7-13%, Fe 0.08-1%, Mn 0.1-2%, V 0.05-0.8%, Zr 0.05-0.3%, Cu 0.1-0.5%, Cr 0.05-0.4%, Ni 0.05-0.5%, Ti 0.05-0.2%, Sc 0.05-0.3%, Mo 0.05-0.5%, Hf 0.05-0.3%, Zn<2%. The tensile strength, yield strength and elongation of the castings prepared by high pressure casting are 270-300MPa, 110-130MPa and 8-13% respectively. CN117210729A discloses a heat-treatment-free cast aluminum alloy for making battery trays, which contains 8.0-10.0% Si; 0.1-0.25% Fe; 0.3-0.4% Mn; 0.05-0.15% Cr; 0.05-0.4% Mg; 0.05-0.15% V; 0.1-0.2% Ti; 0.05-0.15% Zr; 0.01-0.03% Sr; 0.03-0.07% Nb. After low pressure casting, the yield strength, tensile strength and elongation of the alloy are higher than 90MPa, 180MPa and 8.0% respectively. CN116752018A discloses a heat-treatment-free die-casting aluminum alloy material, which includes: Si8.5-10.0%, Fe≤0.15, Cu 2.0-2.5%, Mg 1.0-1.5%, Zn 1.5-2.0%, Ti 0.1-0.3%, Sr0.02-0.07%, Zr 0.03-0.06%, Mn 0.3-0.6%, Mo content of 0.02-0.03%, and the balance of Al. The bulk properties of the prepared vacuum die-casting aluminum alloy material include: yield strength of more than 220MPa, tensile strength of more than 330MPa, and elongation of more than 2.3%.

[0004] Among the above alloys, the alloy materials disclosed in CN116287890A and CN117210729A are traditional heat-treatment-free materials, and their yield strength is low, which is not conducive to the lightweighting of automobile components; the alloy disclosed in CN116752018A has high strength, but poor plasticity, and has a high copper content and a low Fe content, and the alloy cost is high. Summary of the invention

[0005] In order to overcome at least one of the problems existing in the above-mentioned prior art, one of the objectives of the present invention is to provide a die-casting aluminum alloy having both good casting formability and high strength and toughness.

[0006] A second object of the present invention is to provide a method for preparing the above-mentioned die-cast aluminum alloy.

[0007] A third object of the present invention is to provide an application of the above die-cast aluminum alloy in the automotive field.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] The first aspect of the present invention provides a die-casting aluminum alloy, which is composed of the following components in mass percentage: 10.5-13% Si, 0.4-0.8% Fe, 0-0.45% Mn, 0.25-0.45% Mg, 0.06-0.1% Ti, 0.05-0.12% Zr, 0.005-0.01% B, 0.015-0.03% Sr, and the remainder is impurity elements and Al; the sum of the mass percentages of Mn and Fe is 0.7-0.9%.

[0010] The present invention is based on Al-Si alloy and is designed with a higher Fe content, which is conducive to using recycled aluminum with a high Fe content as a raw material to achieve aluminum recycling. First, select the Al-Si alloy system to ensure the excellent casting formability of the alloy; second, increase the upper limit of the Fe content to ensure the demoulding property of the alloy and the high Fe scrap ratio, and through thermodynamic calculations, combine the Mn element to regulate the formation temperature of the iron-rich phase, optimize the morphology of the iron-rich phase, and reduce its harm to plasticity. Specifically, when the Si content is designed to be high, the Fe content is high, while the Mn content is low, and vice versa; thirdly, design a medium content of Mg to obtain higher strength without significantly reducing the plasticity of the alloy; finally, add trace elements of Ti, B, Sr, Zr, and Mn to regulate the alloy structure and properties, specifically: add trace amounts of Ti and B elements, and appropriately increase the Ti content to avoid the formation of TiB2 particles and reduce the toxic effect of Zr on grain refinement; the role of Sr is to modify eutectic silicon and improve the plasticity and strength of the alloy; the role of Zr is to form metastable coherent Al3Zr (L12), which plays a role in precipitation strengthening. Through the above composition optimization design, the casting forming performance and strength of the alloy are ensured, combined with the multi-element micro-alloying design, the alloy structure is optimized, the plasticity of the alloy is improved, and a die-casting aluminum alloy product with good casting formability and high strength and toughness is prepared.

[0011] In the composition of the die casting aluminum alloy, non-limiting examples of the mass percentage of Si are 11%, 11.5%, 12% or 12.5%.

[0012] In the composition of the die casting aluminum alloy, non-limiting examples of the mass percentage of Fe are 0.5%, 0.6%, 0.7% or 0.75%.

[0013] In the composition of the die casting aluminum alloy, non-limiting examples of the mass percentage of Mn are 0.1%, 0.2%, 0.3% or 0.4%.

[0014] In the composition of the die casting aluminum alloy, a non-limiting example of the sum of the mass percentages of Mn and Fe is 0.75%, 0.78%, 0.8%, 0.85% or 0.88%.

[0015] In the composition of the die casting aluminum alloy, non-limiting examples of the mass percentage of Mg are 0.3%, 0.35%, 0.4% or 0.42%.

[0016] In the composition of the die casting aluminum alloy, non-limiting examples of the mass percentage of Ti are 0.07%, 0.08%, 0.09% or 0.095%.

[0017] In the composition of the die casting aluminum alloy, non-limiting examples of the mass percentage of Zr are 0.07%, 0.09%, 0.1% or 0.11%.

[0018] In the composition of the die casting aluminum alloy, non-limiting examples of the mass percentage of B are 0.006%, 0.007%, 0.008% or 0.009%.

[0019] In the composition of the die casting aluminum alloy, non-limiting examples of the mass percentage of Sr are 0.018%, 0.02%, 0.022%, 0.025% or 0.028%.

[0020] Preferably, in the composition of the die-cast aluminum alloy, the mass percentage of impurity elements is less than 0.5%; further preferably, in the impurity elements, the mass percentage of a single impurity element is less than 0.1%.

[0021] Preferably, Ti is added in the form of Al-Ti binary master alloy.

[0022] Preferably, B is added in the form of Al-B binary master alloy.

[0023] The addition form of Ti and B will affect the strength and plasticity of the alloy. When using Al-Ti-B ternary master alloy (such as Al-5Ti-1B), the strength and plasticity of the alloy will decrease. However, when Ti and B are added separately, the strength and plasticity of the alloy are significantly improved.

[0024] Preferably, the tensile strength of the die-cast aluminum alloy is 300-350 MPa.

[0025] Preferably, the yield strength of the die-cast aluminum alloy is 180-250 MPa.

[0026] Preferably, the elongation of the die-cast aluminum alloy is 8-15%.

[0027] Preferably, the die-casting aluminum alloy contains spherical eutectic silicon grains.

[0028] Preferably, the average particle size of the eutectic silicon is 0.2 to 5 μm; more preferably, it is 0.2 to 3 μm; and even more preferably, it is 0.2 to 1.5 μm.

[0029] The second aspect of the present invention provides a method for preparing the die-cast aluminum alloy described in the first aspect of the present invention, characterized in that it includes the following steps: melting the initial raw material containing each target component, performing a first refining, adjusting the content of Si, Fe, Mn, Zr, and Ti to the target content, performing a second refining, adjusting the content of Mg, B, and Sr to the target content, casting, and heat treating to obtain the die-cast aluminum alloy.

[0030] Preferably, the initial raw material contains alloy waste.

[0031] Preferably, the alloy scrap contains at least one element of Si, Fe, Mn or Mg.

[0032] Preferably, in the alloy waste, the sum of the mass percentages of Si, Fe, Mn and Mg elements is 99-99.9%, with non-limiting examples being 99.2%, 99.5% or 99.8%.

[0033] Preferably, the method of adjusting the content of the component is to add a regulating raw material; the regulating raw material includes at least one of a single substance, an intermediate alloy or a compound containing the component; further preferably, the regulating raw material includes a single substance, an intermediate alloy or a combination thereof containing the component.

[0034] In some specific embodiments of the present invention, the regulating raw material includes at least one of aluminum element, magnesium element, Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Zr master alloy, Al-B master alloy or Al-Sr master alloy.

[0035] Preferably, the melting temperature is 720-800°C.

[0036] Preferably, the temperature of the first refining is 720-740°C.

[0037] Preferably, the first refining time is 10 to 20 minutes.

[0038] Preferably, after the first refining and before adjusting the component content, heat preservation is performed, and the heat preservation time is preferably 15 to 30 minutes.

[0039] Preferably, the temperature of the second refining is 720-740°C.

[0040] Preferably, the second refining time is 10 to 20 minutes.

[0041] Preferably, the first refining and the second refining are carried out under the conditions of a refining agent and a protective gas.

[0042] Preferably, the refining agent comprises chloride, fluoride or a combination thereof; further preferably, the refining agent is selected from a combination of chloride and fluoride.

[0043] Preferably, the protective gas comprises at least one of nitrogen, argon or helium.

[0044] Preferably, the casting is specifically as follows: after the melt is allowed to stand for 15 to 30 minutes, the slag is removed and then casting is performed under the condition of a covering agent.

[0045] Preferably, the covering agent is selected from chlorides. The chlorides can protect the solution and facilitate casting.

[0046] Preferably, the heat treatment includes solution treatment and paint aging treatment.

[0047] Preferably, the temperature of the solution treatment is 350-450°C.

[0048] Preferably, the solution treatment time is 30 to 60 minutes.

[0049] Preferably, the temperature of the baking paint aging treatment is 190-210°C.

[0050] Preferably, the time for the baking paint aging treatment is 20 to 40 minutes.

[0051] The main purpose of heat treatment is to improve the morphology and distribution of the precipitated phase and regulate the performance of the casting product. The heat treatment process of the present invention mainly includes solid solution treatment and baking varnish aging treatment. The former is carried out immediately after the die casting is completed, and the residual heat of the casting is used for medium temperature insulation treatment, but the insulation time is short. Its main purpose is to precipitate metastable Al3Zr; while the baking varnish aging treatment is mainly to regulate the precipitation of Mg-Si phase, thereby regulating the strength and toughness of the die casting product.

[0052] The third aspect of the present invention provides an application of the die-casting aluminum alloy described in the first aspect of the present invention in the automotive field.

[0053] Preferably, the automobile is a lightweight automobile; further preferably, the lightweight automobile is a new energy automobile.

[0054] The beneficial effects of the present invention are as follows: the present invention is based on Al-Si alloy and designs a higher Fe content, which is conducive to using recycled aluminum with a high Fe content as raw material to achieve aluminum recycling. The casting forming performance and strength of the alloy are ensured by optimizing the composition of the main alloy components Si, Fe, and Mg and the trace elements Ti, B, Sr, Zr, and Mn. Combined with the multi-element microalloying design, the alloy structure is optimized, the plasticity of the alloy is improved, and a die-casting aluminum alloy with good casting formability and high strength and toughness is prepared, which has a wide range of applications in automobiles, especially in the field of lightweighting.

[0055] More specifically, compared with the prior art, the present invention has the following advantages:

[0056] 1. Ensure the casting performance and strength of the alloy by designing the main components of the alloy, Si, Fe and Mg. First, select the Al-Si alloy system to ensure the excellent casting formability of the alloy; second, increase the upper limit of the Fe content to ensure the demoulding property and high Fe scrap ratio of the alloy, and through thermodynamic calculations, combine the Mn element to regulate the formation temperature of the iron-rich phase, optimize the morphology of the iron-rich phase, and reduce its harm to plasticity. Specifically, when the Si content is designed to be high, the Fe content is high, while the Mn content is low, and vice versa; finally, design a medium content of Mg to obtain higher strength without significantly reducing the plasticity of the alloy.

[0057] 2. By controlling the trace elements Ti, B, Sr, Zr and Mn in the alloy, the alloy structure and properties are regulated, the alloy structure is optimized, and the plasticity of the alloy is improved. First, a trace amount of Ti and B elements are added, and the Ti content is appropriately increased to avoid the formation of TiB2 particles and reduce the toxic effect of Zr on grain refinement; secondly, the role of Sr is to modify eutectic silicon, and Sr is used to improve the plasticity and strength of the alloy; finally, the role of Zr is to form metastable coherent Al3Zr (L12), and Zr is used to play a role in precipitation strengthening.

[0058] 3. Through the design of heat treatment process, the morphology and distribution of precipitation phase are improved, and the performance of casting products is regulated. The heat treatment process mainly includes short-time high-temperature heat treatment and paint aging. The former is carried out immediately after the die-casting is completed, and the residual heat of the casting is used for medium-temperature insulation treatment, but the insulation time is short. Its main purpose is to precipitate metastable Al3Zr; while the paint aging treatment is mainly to regulate the precipitation of Mg-Si phase, thereby regulating the strength and toughness of the die-casting product.

[0059] 4. The present invention can use a certain proportion of waste aluminum as the initial raw material, does not contain rare elements, has a low alloy cost, and has good low-carbon and green manufacturing characteristics, and the obtained alloy has good casting formability and toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is the metallographic spectrum of the die-cast aluminum alloy in Example 1 of the present invention in the gravity casting state.

[0061] Figure 2 This is the metallographic spectrum of the die-cast aluminum alloy after the heat treatment of Example 1 of the present invention.

[0062] Figure 3 This is the tensile curve of the die-cast aluminum alloy after the heat treatment of Example 1 of the present invention. DETAILED DESCRIPTION

[0063] The content of the present invention is further described in detail below through specific examples. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the principles set forth in the present invention all belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific data exemplified below. The raw materials, reagents or devices used in the following examples and comparative examples, unless otherwise specified, can all be obtained from conventional commercial sources, or can be obtained by existing known methods.

[0064] It should be noted that in the following embodiments and comparative examples, the refining agents used are chlorides and a small amount of fluorides; the covering agent is a chloride used to protect the melt; the method for adjusting the content of the component is to add a regulating raw material, and the regulating raw material is selected from a single substance or a binary master alloy containing the component, specifically aluminum, magnesium, Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Zr master alloy, Al-B master alloy and Al-Sr master alloy.

[0065] Example 1

[0066] A die-casting aluminum alloy consisting of the following components in percentage by mass:

[0067] Si 12.5%, Mg 0.45%, Fe 0.80%, Mn 0.10%, Zr 0.08%, Ti 0.08%, B 0.01%, Sr 0.018%, and the balance is impurity elements and Al.

[0068] The preparation process of the die-cast aluminum alloy is as follows:

[0069] (1) Ingredients: The Si content is the priority design basis. The raw materials are waste materials with a fixed composition and containing one or more elements of Si, Fe, Mn, and Mg (the total mass of the aforementioned elements accounts for 99.5% of the waste materials) and industrial pure aluminum, pure magnesium, Al-Si, Al-Mn, Al-Ti, Al-Zr, Al-B, and Al-Sr master alloys. The addition ratio of various raw materials is determined according to the target composition.

[0070] (2) Melting: First add the raw materials with high melting point and not easy to burn into the furnace, turn on the fire to melt, and raise the temperature to 760℃.

[0071] (3) First refining: After the raw materials are completely melted, high-purity argon gas containing a refining agent is blown into the melt for 20 minutes;

[0072] (4) Composition adjustment: After keeping warm for 20 minutes, remove the slag on the surface of the melt, take samples to test the melt composition, and adjust the content of elements such as Si, Fe, Mn, Zr, and Ti to meet the design requirements; then carry out the second refining, and the refining process is the same as the first time.

[0073] (5) Second feeding: After refining, quickly take samples to test the melt composition, add industrial pure Mg and Al-B, Al-Sr master alloys as needed, and turn on the electromagnetic stirring device at the bottom of the furnace to stir the melt for 1 min.

[0074] (6) Casting: After the melt is left to stand for 15 minutes, the slag is cleaned and then a layer of covering agent is sprinkled on. The melt flows into a heat preservation furnace through a flow channel equipped with an online rotating degassing box and a double-layer ceramic filter plate, and is directly supplied to the casting molding equipment or ingot production line to prepare aluminum alloy castings or ingots.

[0075] (7) Heat treatment: The prepared die castings are subjected to immediate short-term high-temperature solution treatment at a holding temperature of 400°C for 45 min; the baking varnish aging process is at 210°C for 30 min.

[0076] Example 2

[0077] A die-casting aluminum alloy consisting of the following components in percentage by mass:

[0078] Si 11.5%, Mg 0.35%, Fe 0.70%, Mn 0.15%, Zr 0.10%, Ti 0.10%, B 0.005%, Sr 0.025%, and the balance is impurity elements and Al.

[0079] The preparation process of the die-cast aluminum alloy is as follows:

[0080] (1) Ingredients: The Si content is the priority design basis. The raw materials are waste materials with a fixed composition and containing one or more elements of Si, Fe, Mn, and Mg (the total mass of the aforementioned elements accounts for 99.5% of the waste materials) and industrial pure aluminum, pure magnesium, Al-Si, Al-Mn, Al-Ti, Al-Zr, Al-B, and Al-Sr master alloys. The addition ratio of various raw materials is determined according to the target composition.

[0081] (2) Melting: First add the raw materials with high melting point and not easy to burn into the furnace, turn on the fire to melt, and raise the temperature to 780℃.

[0082] (3) First refining: After the raw materials are completely melted, high-purity argon gas containing a refining agent is blown into the melt for 15 minutes;

[0083] (4) Composition adjustment: After keeping warm for 10 minutes, remove the slag on the surface of the melt, take samples to test the melt composition, and adjust the content of elements such as Si, Fe, Mn, Zr, and Ti to meet the design requirements; then carry out the second refining, and the refining process is the same as the first time.

[0084] (5) Second feeding: After refining is completed, quickly take samples to test the melt composition, add industrial pure Mg and Al-B, Al-Sr master alloys as needed, and turn on the electromagnetic stirring device at the bottom of the furnace to stir the melt for 3 minutes.

[0085] (6) Casting: After the melt is left to stand for 30 minutes, the slag is cleaned and then a layer of covering agent is sprinkled on. The melt flows into a heat preservation furnace through a flow channel equipped with an online rotating degassing box and a double-layer ceramic filter plate, and is directly supplied to a casting molding equipment or an ingot production line to prepare aluminum alloy castings or ingots.

[0086] (7) Heat treatment: The prepared die castings are subjected to immediate short-term high-temperature solution treatment at a holding temperature of 450°C for 30 min; the baking varnish aging process is 200°C for 40 min.

[0087] Example 3

[0088] A die-casting aluminum alloy consisting of the following components in percentage by mass:

[0089] Si 10.5%, Mg 0.25%, Fe 0.40%, Mn 0.45%, Zr 0.05%, Ti 0.07%, B 0.008%, Sr 0.015%, and the balance is impurity elements and Al.

[0090] The preparation process of the die-cast aluminum alloy is as follows:

[0091] (1) Ingredients: The Si content is the priority design basis. The raw materials are waste materials with a fixed composition and containing one or more elements of Si, Fe, Mn, and Mg (the total mass of the aforementioned elements accounts for 99.5% of the waste materials), industrial pure aluminum, pure magnesium, Al-Si, Al-Mn, Al-Ti, Al-Zr, Al-B, and Al-Sr master alloys. The addition ratio of various raw materials is determined according to the target composition.

[0092] (2) Melting: First add the raw materials with high melting point and not easy to burn into the furnace, turn on the fire to melt, and raise the temperature to 750℃.

[0093] (3) First refining: After the raw materials are completely melted, high-purity argon gas containing a refining agent is blown into the melt for 10 minutes;

[0094] (4) Composition adjustment: After keeping warm for 20 minutes, remove the slag on the surface of the melt, take samples to test the melt composition, and adjust the content of elements such as Si, Fe, Mn, Zr, and Ti to meet the design requirements; then carry out the second refining, and the refining process is the same as the first time.

[0095] (5) Second feeding: After refining is completed, quickly take samples to test the melt composition, add industrial pure Mg and Al-B, Al-Sr master alloys as needed, and turn on the electromagnetic stirring device at the bottom of the furnace to stir the melt for 2 minutes.

[0096] (6) Casting: After the melt is left to stand for 20 minutes, the slag is cleaned and then a layer of covering agent is sprinkled on. The melt flows into a heat preservation furnace through a flow channel equipped with an online rotating degassing box and a double-layer ceramic filter plate, and is directly supplied to a casting molding equipment or an ingot production line to prepare aluminum alloy castings or ingots.

[0097] (7) Heat treatment: The prepared die castings are subjected to immediate short-term high-temperature solution treatment at a holding temperature of 350°C for 60 min; the baking varnish aging process is at 190°C for 30 min.

[0098] Example 4

[0099] A die-casting aluminum alloy consisting of the following components in percentage by mass:

[0100] Si 13.0%, Mg 0.30%, Fe 0.75%, Mn 0.12%, Zr 0.08%, Ti 0.08%, B 0.01%, Sr 0.018%, and the balance is impurity elements and Al.

[0101] The preparation process of the die-cast aluminum alloy is as follows:

[0102] (1) Ingredients: The Si content is the priority design basis. The raw materials are waste materials with a fixed composition and containing one or more elements of Si, Fe, Mn, and Mg (the total mass of the aforementioned elements accounts for 99.5% of the waste materials) and industrial pure aluminum, pure magnesium, Al-Si, Al-Mn, Al-Ti, Al-Zr, Al-B, and Al-Sr master alloys. The addition ratio of various raw materials is determined according to the target composition.

[0103] (2) Melting: First add the raw materials with high melting point and not easy to burn into the furnace, turn on the fire to melt, and raise the temperature to 760℃.

[0104] (3) First refining: After the raw materials are completely melted, high-purity argon gas containing a refining agent is blown into the melt for 10 minutes;

[0105] (4) Composition adjustment: After keeping warm for 30 minutes, remove the slag on the surface of the melt, take samples to test the melt composition, and adjust the content of elements such as Si, Fe, Mn, Zr, and Ti to meet the design requirements; then carry out the second refining, and the refining process is the same as the first time.

[0106] (5) Second feeding: After refining is completed, quickly take samples to test the melt composition, add industrial pure Mg and Al-B, Al-Sr master alloys as needed, and turn on the electromagnetic stirring device at the bottom of the furnace to stir the melt for 2 minutes.

[0107] (6) Casting: After the melt is left to stand for 25 minutes, the slag is cleaned and then a layer of covering agent is sprinkled on. The melt flows into a heat preservation furnace through a flow channel equipped with an online rotating degassing box and a double-layer ceramic filter plate, and is directly supplied to the casting molding equipment or ingot production line to prepare aluminum alloy castings or ingots.

[0108] (7) Heat treatment: The prepared die castings are subjected to immediate short-term high-temperature solution treatment at a holding temperature of 420°C for 40 min; the baking varnish aging process is at 200°C for 40 min.

[0109] Example 5

[0110] A die-casting aluminum alloy, which is different from Example 1 in that the composition of Example 5 does not contain the Mn element; other components and their contents and the preparation process of the alloy are the same as those of Example 1.

[0111] Comparative Example 1

[0112] A die-casting aluminum alloy, which is different from Example 1 in that the composition of Example 1 does not contain the Zr element; other components and their contents and the preparation process of the alloy are the same as those of Example 1.

[0113] Comparative Example 2

[0114] A die-casting aluminum alloy, which differs from Example 2 in that the Ti and B in Example 2 are added in the form of Al-5Ti-1B; the alloy composition and its content and the preparation process of the alloy are the same as those of Example 2.

[0115] Comparative Example 3

[0116] A die-casting aluminum alloy, which is different from Example 3 in that the content of component B in Example 3 is 0.015%; other components and their contents and the preparation process of the alloy are the same as those in Example 3.

[0117] Comparative Example 4

[0118] A die-cast aluminum alloy, which differs from Example 4 in that Example 4 does not undergo short-time high-temperature solution treatment; the alloy composition and its content and other preparation processes of the alloy are the same as those of Example 1.

[0119] The die castings prepared from the alloys of Examples 1 to 5 and Comparative Examples 1 to 4 were selected, and their tensile mechanical properties were tested respectively according to GB / T 228.1-2021 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method". The results are shown in Table 1 below.

[0120] Table 1 Composition (in mass percentage) and mechanical properties of die-cast aluminum alloys of Examples 1 to 5 and Comparative Examples 1 to 4

[0121]

[0122] Table 1 is analyzed. From the comparison between Examples 1 to 5 and Comparative Examples 1 to 4, it can be seen that adding Zr is beneficial to improving the strength of the alloy without reducing the plasticity of the alloy; when Ti and B are added separately, the strength and plasticity of the casting are significantly improved compared with adding Al-5Ti-1B; too high B content is easy to poison the modification effect of Sr, and the elongation of the die casting is significantly reduced; high-temperature solution treatment is performed immediately after the die casting is formed, which is beneficial to the precipitation of hypoeutectic Al3Zr and is beneficial to improving the strength of the alloy; with the increase of Mg content, the tensile strength and yield strength of the casting are significantly improved.

[0123] The microstructure of the tissue obtained in Example 1 was analyzed. Figure 1 is the metallographic spectrum of the die-cast aluminum alloy of Example 1 in the gravity casting state; Figure 2 The metallographic spectrum of the die-cast aluminum alloy after the heat treatment of Example 1 is completed. Figure 1 It can be seen that the eutectic silicon (gray particles) obtained in Example 1 is evenly distributed, small in size, and highly spherical; the iron-rich phase (offwhite) is distributed in the Al-Si eutectic region, forming an Al-Si-(α-Fe) ternary eutectic in the shape of small Chinese characters. Figure 3 This is the tensile curve of the die-cast aluminum alloy after the heat treatment of Example 1, which shows that it has good tensile strength, yield strength and elongation.

Claims

1. A method for preparing a die-cast aluminum alloy, characterized in that: The following steps are involved: The initial raw materials containing the target components are melted, and the contents of Si, Fe, Mn, Zr and Ti are adjusted to the target contents. The contents of Mg, B and Sr are adjusted to the target contents by a second refining, and the casting and heat treatment are performed to obtain the die-casting aluminum alloy. The heat treatment includes solution treatment and paint aging treatment; The temperature of the solution treatment is 350-450°C; The solution treatment time is 30 to 60 minutes; The temperature of the baking varnish aging treatment is 190-210°C; The time of the baking varnish aging treatment is 20 to 40 minutes; The die-casting aluminum alloy is composed of the following components in mass percentage: 10.5-13% Si, 0.4-0.8% Fe, 0-0.45% Mn, 0.25-0.45% Mg, 0.06-0.1% Ti, 0.05-0.12% Zr, 0.005-0.01% B, 0.015-0.03% Sr, and the balance is Al and impurities; the sum of the mass percentages of Mn and Fe is 0.7-0.9%; The addition form of Ti is Al-Ti binary master alloy; the addition form of B is Al-B binary master alloy.

2. The preparation method according to claim 1, characterized in that: The tensile strength of the die-cast aluminum alloy is 300-350 MPa; And / or, the yield strength of the die-cast aluminum alloy is 180-250 MPa; And / or, the elongation of the die-cast aluminum alloy is 8-15%.

3. The preparation method according to claim 1, characterized in that: The die-casting aluminum alloy contains spherical eutectic silicon grains.

4. The preparation method according to claim 3, characterized in that: The average particle size of the eutectic silicon grains is 0.2-5 μm.

5. The preparation method according to claim 1, characterized in that: The initial raw materials contain alloy waste.

6. The preparation method according to claim 5, characterized in that: The alloy scrap contains at least one element of Si, Fe, Mn or Mg.

7. The preparation method according to claim 1, characterized in that: The melting temperature is 720-800°C; And / or, the temperature of the first refining is 720-740°C; And / or, the first refining time is 10 to 20 minutes; And / or, the temperature of the second refining is 720-740°C; And / or, the second refining time is 10 to 20 minutes.

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