High-strength and high-toughness die-casting aluminum alloy as well as preparation method and application thereof

Abstract

The invention discloses a high-strength and high-toughness die-casting aluminum alloy and a preparation method and application thereof, and relates to the technical field of aluminum alloy materials. The aluminum alloy comprises, by mass, 11.5%-14.5% of Si, 2.5%-4.0% of Cu, 0.65%-1.2% of Mg, 0.5%-0.8% of Mn, 0.75%-1.25% of Ni, 0.8%-1.5% of Fe, 0.01%-0.1% of P, 0.02%-0.06% of Ca and the balance Al and inevitable impurities, and the total mass of the inevitable impurities is smaller than or equal to 0.25%. By optimizing the proportion of all the elements of the die-casting aluminum alloy, the die-casting aluminum alloy has good flowability and die-casting forming capacity when being in a liquid state, and the formed die-casting aluminum alloy material has the characteristics of high toughness, high strength and high hardness, has good comprehensive performance in a normal-temperature state and a high-temperature state and is suitable for large-scale production. And the method can adapt to high-performance development of vehicle engines.

Description

Technical Field

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

[0002] As people's living standards and environmental awareness improve, the importance of energy consumption is gradually increasing. With the rapid development of vehicles such as cars and motorcycles in recent years, their energy consumption, such as the consumption of steel materials, is increasing. Steel materials are heavy and the production process is more polluting. Aluminum alloy, as a lightweight alloy material, can replace steel materials and be used in some components of vehicles such as cars and motorcycles to achieve lightweighting of vehicles such as cars and motorcycles.

[0003] Since Al-Si alloy melt has good fluidity, it is widely used in die-casting to form engine cylinder blocks, cylinder heads and various housing parts of automobiles and motorcycles. It is currently the most widely used die-cast aluminum alloy. However, with the improvement of the performance of vehicles such as automobiles and motorcycles, the performance requirements for vehicle engines are gradually increasing, and the engines are required to have higher power. This puts higher requirements on the room temperature and high temperature performance of the aluminum alloy used to cast the cylinder block and cylinder head of the engine. Therefore, how to improve the strength, toughness and hardness of die-cast aluminum alloys at room temperature and high temperature is one of the problems that need to be solved in this field.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide a high-strength and high-toughness die-cast aluminum alloy and a preparation method and application thereof, which can improve the strength, toughness and hardness of the die-cast aluminum alloy at room temperature and high temperature.

[0006] The present invention is achieved in that:

[0007] In the first aspect, the present invention provides a high-strength and high-toughness die-cast aluminum alloy, which includes, by mass percentage, Si: 11.5-14.5%, Cu: 2.5-4.0%, Mg: 0.65-1.2%, Mn: 0.5-0.8%, Ni: 0.75-1.25%, Fe: 0.8-1.5%, P: 0.01-0.1%, Ca: 0.02-0.06%, and the rest is Al and unavoidable impurities, and the total mass of the unavoidable impurities is ≤0.25%.

[0008] In a second aspect, the present invention provides a method for preparing a die-cast aluminum alloy as described in any of the aforementioned embodiments, comprising smelting raw materials of Si, Cu, Mg, Mn, Ni, Fe and Al in proportion to obtain a first melt, adding a raw material of P to the first melt for a first metamorphism and refining to obtain a second melt, adding a raw material of Ca to the second melt for a second metamorphism to obtain a third melt, and performing T5 heat treatment after die-casting the third melt.

[0009] In a third aspect, the present invention provides a die-cast aluminum alloy as in any one of the aforementioned embodiments or a die-cast aluminum alloy obtained by the preparation method as in any one of the aforementioned embodiments for improving the strength, toughness, hardness or high temperature performance of a component.

[0010] The present invention has the following beneficial effects:

[0011] The present invention provides a high-strength and high-toughness die-casting aluminum alloy, a preparation method and application thereof. By optimizing the ratio of each element of the die-casting aluminum alloy, the die-casting aluminum alloy has good fluidity and die-casting forming ability when in liquid state. The formed die-casting aluminum alloy material has the characteristics of high toughness, high strength and high hardness, has good comprehensive performance both at room temperature and at high temperature, and can adapt to the high-performance development of vehicle engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0013] Figure 1 This is a scanning electron microscope image of the high-strength and high-toughness die-cast aluminum alloy provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0015] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0016] In the first aspect, the present invention provides a high-strength and high-toughness die-cast aluminum alloy, which includes, by mass percentage, Si: 11.5-14.5%, Cu: 2.5-4.0%, Mg: 0.65-1.2%, Mn: 0.5-0.8%, Ni: 0.75-1.25%, Fe: 0.8-1.5%, P: 0.01-0.1%, Ca: 0.02-0.06%, and the rest is Al and unavoidable impurities, and the total mass of the unavoidable impurities is ≤0.25%.

[0017] In an optional embodiment, the composition includes Si: 12.4-14.3%, Cu: 3.1-4.0%, Mg: 0.75-0.90%, Mn: 0.60-0.75%, Ni: 0.95-1.10%, Fe:

[0018] 1.05~1.5%, P: 0.01~0.08%, Ca: 0.02~0.05%, the rest is Al and unavoidable impurities, and the total mass of unavoidable impurities is ≤0.25%.

[0019] Preferably, in terms of mass percentage, it includes Si: 13.0-14.3%, Cu: 3.1-3.4%, Mg: 0.82-0.85%, Mn: 0.63-0.65%, Ni: 0.98-1.08%, Fe: 1.10-1.15%, P: 0.01-0.05%, Ca: 0.03-0.05%, and the rest are Al and unavoidable impurities, and the total mass of unavoidable impurities is ≤0.25%.

[0020] Among them, the role of each element in the die-casting aluminum alloy of the present invention is as follows:

[0021] The Si content is in the range of 11.5-14.5%, preferably 12.4-14.3%, and more preferably 13.0-14.3%, which can ensure that the aluminum alloy has good fluidity during die casting. At the same time, Si and Mg can react to precipitate Mg2Si particles, which has the effect of improving the strength and hardness of the aluminum alloy; the remaining Si in the aluminum alloy plays a role in further improving the strength and hardness of the alloy. When the Si content is lower than 11.5%, the amount of remaining Si in the aluminum alloy is small, and the effect on improving the strength and hardness of the aluminum alloy is limited. At the same time, the melt fluidity decreases, which is not conducive to die casting; when the Si content exceeds 14.5%, it is easy to produce more primary silicon under non-equilibrium solidification conditions, resulting in a decrease in the toughness of the die-cast aluminum alloy.

[0022] Cu plays a role in solid solution strengthening in the alloy. At the same time, it can react with Al during heat treatment to precipitate strengthening phases such as Al2Cu and Q-AlCuMgSi, thereby improving the strength and hardness of the aluminum alloy. When the mass fraction of Cu is lower than 2.5%, the strengthening effect of Cu is not obvious; when the mass fraction of Cu exceeds 4.0%, the amount of Al2Cu increases, and the toughness and corrosion resistance of the aluminum alloy decrease. Therefore, the content of Cu is in the range of 2.5-4.0%, preferably 3.1-4.0%, and more preferably 3.1-3.4%.

[0023] Mg reacts with other elements to form compounds such as Mg2Si and Al-Si-Mg-Cu, which can improve the strength and hardness of aluminum alloys. At the same time, due to the low density of Mg, it is beneficial to reduce the density of aluminum alloys. When the mass fraction of Mg is lower than 0.65%, the strengthening effect of Mg is weak; when the mass fraction of Mg exceeds 1.2%, the viscosity of the melt increases, and the number of defects such as inclusions in the casting increases. Therefore, the Mg content is in the range of 0.65-1.2%, preferably 0.75-0.90%, and more preferably 0.82-0.85%.

[0024] The Fe and Ni elements in the alloy can generate high temperature strengthening phases such as Al-Cu-Ni, Al-Cu-Mg-Fe-Mn-Ni-Si, and Al-Cu-Ni-Fe-Mn-Si in the alloy, which mainly play the role of improving the strength of the aluminum alloy under high temperature conditions.

[0025] Mn can improve the thermal cracking tendency of aluminum alloys, and form multi-component compounds with Fe, Ni, etc. in aluminum alloys, and can transform the morphology of iron-containing compounds into spherical, blocky or rod-shaped, reducing the harmful effects of the morphology of iron-containing compounds on the toughness and other properties of aluminum alloys. When the mass fraction of Mn is lower than 0.5%, needle-like Al9Si2Fe2 and Al8FeMg3Si6 phases are formed in the aluminum alloy. These needle-like Fe-containing phases grow significantly with the increase of Fe content, which seriously reduces the toughness of the aluminum alloy; when the mass fraction of Mn is greater than 0.8%, the fluidity of the aluminum alloy decreases and the casting performance deteriorates. Therefore, the content of Mn is controlled within the range of 0.5-0.8%, preferably 0.60-0.75%, and more preferably 0.63-0.65%.

[0026] P and Ca can serve as the crystallization core of Si. Under die-casting conditions, primary silicon and eutectic silicon can be significantly refined, the morphology of the organization can be modified, the strength and toughness of the aluminum alloy can be improved, and the improvement of the toughness of the aluminum alloy is particularly obvious. When the mass fraction of P and Ca is too low, the modification effect is not obvious; when the mass fraction of P and Ca is higher than the above range provided by the present invention, the primary silicon and eutectic silicon in the organization will not be further refined. Therefore, the P content is controlled to be 0.01-0.1%, preferably 0.01-0.08%, and more preferably 0.01-0.05%; and the Ca content is 0.02-0.06%, preferably 0.02-0.05%, and more preferably 0.03-0.05%.

[0027] In an optional embodiment, the aluminum alloy has a tensile strength of ≥375 MPa, a yield strength of ≥330 MPa, an elongation after fracture of ≥10.5, and a hardness of ≥140 HB.

[0028] Preferably, the aluminum alloy has a tensile strength of 375 to 400 MPa, a yield strength of 330 to 360 MPa, an elongation after fracture of 10.5 to 13.5, and a hardness of 140 to 160 HB.

[0029] In a second aspect, the present invention provides a method for preparing a die-cast aluminum alloy as described in any of the aforementioned embodiments, comprising smelting raw materials of Si, Cu, Mg, Mn, Ni, Fe and Al in proportion to obtain a first melt, adding a raw material of P to the first melt for a first metamorphism and refining to obtain a second melt, adding a raw material of Ca to the second melt for a second metamorphism to obtain a third melt, and performing T5 heat treatment after die-casting the third melt.

[0030] If P and Ca are directly added to the alloy melt for smelting together with other raw materials, or P and Ca are added to the alloy melt at the same time for a single modification, a good modification effect cannot be achieved. The present invention effectively controls the size and distribution of silicon and iron-containing intermetallic compounds in the aluminum alloy by adding P for the first modification and then adding Ca for the second modification, so that the casting has excellent room temperature and high temperature mechanical properties after heat treatment.

[0031] The die-casting aluminum alloy provided by the present invention can be strengthened by T5 heat treatment while ensuring that the melt has good die-casting forming performance. After T5 heat treatment, the aluminum alloy has good room temperature and high temperature performance, and its performance parameters such as mechanical strength can meet the requirements of castings such as automobile and motorcycle cylinder blocks and cylinder heads.

[0032] Preferably, the time from the addition of P raw materials to the completion of die casting and the demolding of the casting does not exceed 3 hours.

[0033] In an optional embodiment, before the first metamorphism, the temperature of the first melt is 800-850° C., and the time of the first metamorphism is 15-30 min.

[0034] For example, the temperature of the first melt may be any value among 800° C., 810° C., 820° C., 830° C., 840° C. or 850° C., or a range between any two values ​​and any value within the range.

[0035] For example, the time of the first deterioration can be any value among 15 minutes, 20 minutes, 25 minutes or 30 minutes, or a range value between any two values ​​and any value within the range value.

[0036] In an optional embodiment, the refining includes adding a refining agent to the first melt and introducing an inert gas for refining, the refining time is 10 to 15 minutes, and the scum is removed.

[0037] For example, the refining time may be any value among 10 min, 11 min, 12 min, 13 min, 14 min or 15 min, or a range value between any two values ​​and any value within the range value.

[0038] Preferably, the purpose of adding a refining agent for refining is to remove impurities and gases in the melt. The refining agent can be an existing refining agent, such as 5AB, 6AB or a block refining agent.

[0039] Preferably, the inert gas is nitrogen or argon with a purity of ≥99.99%.

[0040] In addition, it should be noted that the entire smelting process needs to be carried out in an inert atmosphere to avoid oxidation of the metal raw materials, reduce impurities in the melt, and ensure that the element content of the melt meets the requirements.

[0041] In an optional embodiment, the temperature of the second melt during the second metamorphism is 720-760° C., and the time of the second metamorphism is 3-5 min.

[0042] For example, the temperature of the second melt may be any one of 720° C., 730° C., 740° C., 750° C., or 760° C., or a range between any two values, or any value within the range.

[0043] For example, the time for the second deterioration can be any value among 3 minutes, 4 minutes or 5 minutes, or a range value between any two values ​​and any value within the range value.

[0044] Among them, the smelting, first metamorphism, refining and second metamorphism processes before die casting are all carried out in a melting furnace, which can melt the raw materials of each element into a melt and control the temperature of the melt. The third melt obtained after the second metamorphism is transferred from the melting furnace to the die casting equipment for die casting, and the casting is obtained after the die casting is completed.

[0045] In an optional embodiment, the die casting includes high pressure casting or low pressure casting, and the temperature of the third melt is adjusted to 700-760° C. before die casting.

[0046] For example, the temperature of the third melt may be any value of 700° C., 710° C., 720° C., 730° C., 740° C., 750° C. or 760° C., or a range between any two values ​​and any value within the range.

[0047] In an optional embodiment, the T5 heat treatment includes water quenching and aging treatment of the casting obtained by die casting, and the demolding temperature of the casting is 350-450°C.

[0048] For example, the ejection temperature of the casting may be any value among 350° C., 380° C., 400° C., 430° C. or 450° C., or a range between any two values ​​and any value within the range.

[0049] Preferably, the aging treatment temperature is 165-200° C., and the aging treatment time is 6-12 hours.

[0050] For example, the aging treatment temperature can be any value among 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C or 200°C, or a range between any two values, or any value within the range.

[0051] For example, the aging treatment time can be any value among 6h, 7h, 8h, 9h, 10h, 11h or 12h, or a range value between any two values ​​and any value within the range value.

[0052] In an optional embodiment, the raw material of Si includes aluminum-silicon master alloy or quick-dissolving silicon.

[0053] The raw materials of Cu include aluminum-copper master alloy or pure copper.

[0054] The raw material of Mn includes aluminum-manganese master alloy or manganese additive, wherein the manganese additive may be, for example, an additive with a manganese content of 70% or 80%.

[0055] The raw material of Mg is pure magnesium.

[0056] The raw material of Ni is pure nickel.

[0057] The raw material of Fe is aluminum-iron master alloy.

[0058] The raw material of P is phosphor copper master alloy.

[0059] The raw material of Ca is aluminum-calcium master alloy.

[0060] In a third aspect, the present invention provides a die-cast aluminum alloy as in any one of the aforementioned embodiments or a die-cast aluminum alloy obtained by the preparation method as in any one of the aforementioned embodiments for improving the strength, toughness, hardness or high temperature performance of a component.

[0061] Example 1

[0062] The present embodiment provides a high-strength and high-toughness die-cast aluminum alloy, whose element composition, measured by mass percentage, includes Si: 13.1%, Cu: 3.2%, Mg: 0.85%, Mn: 0.65%, Ni: 1.08%, Fe: 1.15%, P: 0.03%, Ca: 0.04%, and the rest is Al and unavoidable impurities, and the total mass of the unavoidable impurities is ≤0.25%.

[0063] This embodiment also provides a method for preparing the above-mentioned high-strength and high-toughness die-casting aluminum alloy, comprising the following steps:

[0064] S01. Smelting: pure aluminum ingots, aluminum-silicon master alloys, electrolytic copper, electrolytic nickel, aluminum-manganese master alloys, and aluminum-iron master alloys are added to a melting furnace in proportion and heated. After they are completely melted, magnesium ingots are added. After all materials are melted, they are stirred evenly to obtain a first melt.

[0065] S02. First modification: the first melt is heated to 830° C., and Cu—P master alloy is added to the first melt for first modification. The time for the first modification is 20 minutes.

[0066] S03, refining: refining agent and argon gas are introduced into the melt after the first modification treatment to perform degassing and deslagging operations. The refining time is 12 minutes. After the refining is completed, the scum is scraped off to obtain the second melt.

[0067] S04, second modification: controlling the temperature of the second melt to 740° C., adding Al—Ca master alloy to the second melt for second modification, the second modification time is 4 minutes, and obtaining a third melt.

[0068] S05. Die casting: The temperature of the third melt is controlled at 730-740° C., and then a 1000-ton die casting machine is used for die casting to obtain a casting, and the ejection temperature of the casting is 390-410° C.

[0069] S06, T5 heat treatment: the casting with a die temperature of 390-410°C is directly quenched in water; then aged at 185°C for 10 hours to obtain a high-strength and high-toughness die-cast aluminum alloy.

[0070] The high-strength and high-toughness die-cast aluminum alloy obtained in this embodiment was placed under a scanning electron microscope for observation, and the following Figure 1 The results are shown. Figure 1 It can be seen that after the high-strength and high-toughness die-cast aluminum alloy of this embodiment undergoes T5 aging heat treatment, the surface structure of the material is fine and uniform, without large particle inclusions, and the performance is better.

[0071] Examples 2 to 7 and Comparative Examples 1 to 4 also provide a high-strength and high-toughness die-cast aluminum alloy and a preparation method thereof, wherein the specific steps of the preparation method are the same as those of Example 1, the only difference being the composition and ratio of the elements, as shown in Table 1 for details.

[0072] Table 1 Element composition of die-cast aluminum alloy (wt%)

[0073] Si Cu Mg Mn Fe Ni P Ca Al Example 1 13.1 3.2 0.85 0.65 1.15 1.08 0.03 0.04 Bal. Example 2 14.3 3.3 0.82 0.64 1.12 0.98 0.03 0.04 Bal. Example 3 11.5 3.1 0.88 0.61 1.17 1.02 0.03 0.04 Bal. Example 4 13.3 3.8 0.81 0.64 1.08 1.01 0.03 0.04 Bal. Example 5 12.9 2.6 0.65 0.67 1.12 1.12 0.03 0.04 Bal. Example 6 12.4 2.8 0.77 0.51 1.25 1.08 0.03 0.04 Bal. Example 7 12.8 3.1 0.75 0.71 1.41 1.01 0.03 0.05 Bal. Comparative Example 1 15.6 2.7 0.88 0.53 1.41 1.15 0.03 0.05 Bal. Comparative Example 2 8.4 2.6 0.76 0.62 1.05 0.95 0.03 0.04 Bal. Comparative Example 3 12.8 3.1 0.85 0.75 1.82 0.98 0.03 0.04 Bal. Comparative Example 4 11.9 1.3 0.47 0.51 0.53 0.99 0.03 0.04 Bal.

[0074] Comparative Example 5

[0075] This comparative example provides a high-strength and high-toughness die-cast aluminum alloy, whose elemental composition is the same as that of Example 1, and the difference between the preparation method and Example 1 is that before refining, Cu-P and Al-Ca intermediate alloys are simultaneously added to the melt for a modification, and the modification time is 20 minutes.

[0076] Comparative Example 6

[0077] This comparative example provides a high-strength and high-toughness die-cast aluminum alloy, whose element composition is the same as that of Example 1, and the difference between the preparation method and Example 1 is that: Al-Ca master alloy is added in the first modification, and the modification time is 4 minutes. Cu-P master alloy is added in the second modification, and the modification time is less than 20 minutes.

[0078] Comparative Example 7

[0079] This comparative example provides a high-strength and high-toughness die-cast aluminum alloy, whose element composition is similar to that of Example 1, and the difference between the preparation method and Example 1 is that the amount of P added during the first metamorphism process is 0.005%; the amount of Ca added during the second metamorphism process is 0.01%.

[0080] Comparative Example 8

[0081] This comparative example provides a high-strength and high-toughness die-cast aluminum alloy, whose element composition is similar to that of Example 1, and the difference between the preparation method and Example 1 is that the amount of P added during the first metamorphism process is 0.15%; the amount of Ca added during the second metamorphism process is 0.1%.

[0082] Comparative Example 9

[0083] This comparative example provides a high-strength and high-toughness die-cast aluminum alloy, whose element composition is similar to that of Example 1, and the difference between the preparation method and Example 1 is that the second modification uses Sr to replace the Ca in Example 1 for modification, and the amount of Sr added is 0.03%.

[0084] Test Example 1

[0085] The high-strength and high-toughness die-casting aluminum alloys provided by Examples 1 to 7 and Comparative Examples 1 to 9 were subjected to performance tests, and the results shown in Tables 2 and 3 were obtained.

[0086] Among them, the test standards for room temperature tensile strength and yield strength in Table 2 refer to "GB / T16865-2013", the test standard for elongation after fracture refers to "GB / T16865-2013", and the hardness test standard refers to "GB / T231.1-2009".

[0087] The test standards for high temperature tensile strength, yield strength and elongation at break in Table 3 refer to GB / T228.2-2015.

[0088] Table 2 Properties of die-cast aluminum alloys at room temperature

[0089]

[0090]

[0091] Table 3 Properties of die-cast aluminum alloys at high temperatures

[0092]

[0093]

[0094]

[0095] As can be seen from Tables 2 and 3, the Si content of Comparative Example 1 is relatively high, so its elongation after fracture is significantly lower than that of the embodiment, proving that excessive Si content is prone to produce more primary silicon under non-equilibrium solidification conditions, resulting in a decrease in the toughness of the die-cast aluminum alloy. Due to the change in Si content, the overall ratio of the content of the elements inside the aluminum alloy changes, resulting in different degrees of decrease in the tensile strength and yield strength of the aluminum alloy at room temperature and high temperature, affecting the performance of the aluminum alloy.

[0096] The Si content of Comparative Example 2 is lower, so its tensile strength and yield strength at room temperature and high temperature are significantly lower than those of the embodiment, proving that the Si content is too low, resulting in a small amount of remaining Si in the aluminum alloy, which is not conducive to improving the strength of the aluminum alloy.

[0097] The Fe content of Comparative Example 3 is too high. Although the aluminum alloy obtained has a certain hardness at room temperature, the tensile strength, yield strength and elongation after fracture are significantly lower than those of the embodiment. Although a certain tensile strength can be guaranteed under high temperature conditions, the yield strength and elongation after fracture are not good, which affects the comprehensive performance of the aluminum alloy.

[0098] Comparative Example 4 reduces the element ratio of Cu, Mg and Fe at the same time, so the number of high-temperature strengthening phases formed by Cu, Mg and Fe is reduced, and the obtained aluminum alloy has better toughness at room temperature, but the strength and hardness are significantly reduced. After high-temperature treatment, the tensile strength and yield strength are significantly reduced, affecting the comprehensive performance of the aluminum alloy.

[0099] In Comparative Example 5, Cu-P and Al-Ca modifiers are added to the melt at the same time. P and Ca are in contact for a long time, which reduces the modification effect and leads to a decrease in mechanical properties, especially a greater impact on the elongation of the aluminum alloy.

[0100] In Comparative Example 6, Al-Ca intermediate alloy is first added for modification, and then Cu-P intermediate alloy is added for modification, which results in insufficient modification of primary silicon in the aluminum alloy, affecting the mechanical properties of the aluminum alloy.

[0101] The amount of Ca and P added to the aluminum alloy of Comparative Example 7 is low, the modification is insufficient, and the mechanical properties of the aluminum alloy are reduced.

[0102] Too much Ca and P are added to the aluminum alloy of Comparative Example 8, which easily causes melt air absorption, reduces the fluidity of the aluminum alloy, and easily causes defects such as pores and looseness in the casting, resulting in a decrease in the mechanical properties of the casting.

[0103] Comparative Example 9 uses Sr to modify eutectic silicon. Since Sr and P react easily, the modifying agent loses its modifying effect, causing the mechanical properties of the casting to decrease.

[0104] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high strength and high toughness die-cast aluminum alloy, It is characterized in that Calculated by mass percentage, it includes Si: 11.5-14.5%, Cu: 2.5-4.0%, Mg: 0.65-1.2%, Mn: 0.5-0.8%, Ni: 0.75-1.25%, Fe: 0.8-1.5%, P: 0.01-0.1%, Ca: 0.02-0.06%, and the rest is Al and unavoidable impurities, and the total mass of the unavoidable impurities is ≤0.25%.

2. The die-cast aluminum alloy according to claim 1, It is characterized in that In terms of mass percentage, it includes Si: 12.4-14.3%, Cu: 3.1-4.0%, Mg: 0.75-0.90%, Mn: 0.60-0.75%, Ni: 0.95-1.10%, Fe: 1.05-1.5%, P: 0.01-0.08%, Ca: 0.02-0.05%, and the rest is Al and unavoidable impurities, and the total mass of the unavoidable impurities is ≤0.25%; Preferably, in terms of mass percentage, it includes Si: 13.0-14.3%, Cu: 3.1-3.4%, Mg: 0.82-0.85%, Mn: 0.63-0.65%, Ni: 0.98-1.08%, Fe: 1.10-1.15%, P: 0.01-0.05%, Ca: 0.03-0.05%, and the rest are Al and unavoidable impurities, and the total mass of the unavoidable impurities is ≤0.25%.

3. The die-cast aluminum alloy according to claim 1, It is characterized in that The tensile strength of aluminum alloy is ≥375MPa, the yield strength is ≥330MPa, the elongation after fracture is ≥10.5, and the hardness is ≥140HB; Preferably, the aluminum alloy has a tensile strength of 375 to 400 MPa, a yield strength of 330 to 360 MPa, an elongation after fracture of 10.5 to 13.5, and a hardness of 140 to 160 HB.

4. A method for preparing the die-cast aluminum alloy according to any one of claims 1 to 3, It is characterized in that The method comprises smelting raw materials of Si, Cu, Mg, Mn, Ni, Fe and Al in proportion to obtain a first melt, adding raw materials of P to the first melt for first metamorphism and refining to obtain a second melt, adding raw materials of Ca to the second melt for second metamorphism to obtain a third melt, and die-casting the third melt and then performing T5 heat treatment.

5. The preparation method according to claim 4, It is characterized in that Before the first metamorphism, the temperature of the first melt is 800-850° C., and the time of the first metamorphism is 15-30 minutes; Preferably, during the second metamorphosis, the temperature of the second melt is 720-760° C., and the time of the second metamorphosis is 3-5 min.

6. The preparation method according to claim 4, It is characterized in that The refining includes adding a refining agent to the first melt, introducing an inert gas for refining, the refining time is 10 to 15 minutes, and removing scum; Preferably, the inert gas is nitrogen or argon with a purity of ≥99.99%.

7. The preparation method according to claim 4, It is characterized in that The die casting includes high pressure casting or low pressure casting. Before the die casting, the temperature of the third melt is adjusted to 700-760°C.

8. The preparation method according to claim 4, It is characterized in that The T5 heat treatment includes water quenching and aging treatment of the casting obtained by die casting, and the mold ejection temperature of the casting is 350-450°C; Preferably, the aging treatment temperature is 165-200° C., and the aging treatment time is 6-12 hours.

9. The preparation method according to claim 4, It is characterized in that The raw material of Si includes aluminum silicon master alloy or quick-dissolving silicon; The raw material of Cu includes aluminum-copper master alloy or pure copper; The raw material of Mn includes aluminum-manganese master alloy or manganese additive; The raw material of Mg is pure magnesium; The raw material of Ni is pure nickel; The raw material of Fe is aluminum-iron master alloy; The raw material of P is phosphor copper master alloy; The raw material of Ca is aluminum-calcium master alloy.

10. Use of the die-casting aluminum alloy according to any one of claims 1 to 3 or the die-casting aluminum alloy prepared by the preparation method according to any one of claims 4 to 9 in improving the strength, toughness, hardness or high temperature performance of a component.

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