Cast aluminum alloy, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a cast aluminum alloy, and a preparation method therefor and a use thereof. The cast aluminum alloy comprises Al, Si, Cu, Mg, Mn, Ti, Cr, Sr, and inevitable impurities. The impurities include Fe and other impurities except Fe. During preparation, the components are mixed, melted, and then refined to prepare an aluminum alloy cast ingot, and the aluminum alloy cast ingot is then subjected to a solid solution treatment, a quenching cooling, and an aging treatment. The aluminum alloy of the present invention can have the characteristics of a simple formulation, a high tolerance to impurity elements, especially iron, a low thermal cracking property, and a high heat fatigue resistance. The aluminum alloy can satisfy the equivalent or even higher grade use of a large amount of high-quality recycled aluminum alloys, the aluminum alloy itself can also be recycled, thereby reducing carbon emission; furthermore, the aluminum alloy can also be used at a relatively high service temperature, the formulation is simple, and the raw material cost is relatively low.

Description

A cast aluminum alloy and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of cast aluminum alloys, and in particular to a renewable heat-resistant and high-fatigue aluminum-silicon alloy and a preparation method thereof, more particularly to a renewable heat-resistant and high-fatigue cast aluminum alloy with a low carbon equivalent suitable for working conditions under thermomechanical coupling, and specifically to a cast aluminum alloy and a preparation method and application thereof. Background Art

[0002] In recent years, with the development of the aerospace and automotive industries, the requirements for energy conservation and emission reduction have become increasingly stringent. Aluminum-silicon casting alloys have been widely used in transportation manufacturing due to their low density, excellent strength, good casting properties, wear resistance, and thermal conductivity. In particular, various engine housings, reducer housings, and accessory transmission housings, which serve as chassis components and power transmission components for aircraft, passenger cars, and commercial vehicles, are increasingly manufactured from aluminum-silicon casting alloys to achieve lightweighting. However, in practice, due to the complex and harsh operating environments faced by engines and the increasing power density, the next generation of materials for manufacturing engines and transmissions must not only withstand service temperatures of up to 250°C but also exhibit excellent fatigue properties.

[0003] Currently, Mg and Cu are commonly added to Al-Si alloys to improve room-temperature mechanical properties by forming Mg2Si, Al2Cu, Q phase and its metastable phase. These alloys include A356.2 alloy, A319 alloy, A380 alloy, ZL114A alloy, ZL702A alloy, etc. However, at higher service temperatures, the strengthening phase of these alloys rapidly coarsens and the high-temperature strength decreases significantly.

[0004] At the same time, compared to virgin aluminum ingots, the parallel use or even upgrade of renewable high-quality recycled aluminum with higher impurity element content can significantly reduce carbon emissions, meeting the development direction of green, low-carbon aluminum. Therefore, it is urgent to achieve the efficient utilization of renewable aluminum and improve the thermal stability and fatigue performance of cast aluminum alloys. However, current cast aluminum alloys have high requirements for impurity elements, such as Fe impurity content, which must be controlled at a low level. Otherwise, it is difficult to obtain good mechanical properties. This has caused problems for the parallel use or even upgrade of renewable high-quality recycled aluminum with higher impurity element content.

[0005] For example, invention patent application CN114774741A discloses a heat-resistant cast aluminum alloy whose impurity element content is no more than 0.12%, and the sum of other impurity elements is no more than 0.2%. This requirement for low impurity element content limits the use of high-quality recycled aluminum. Furthermore, the alloy relies solely on the addition of Al3Zr and Al3(ZrV) nano-scale heat-resistant phases, resulting in a limited variety of heat-resistant phases. Invention patent application JP5344527B2 improves the alloy's high-temperature performance by adding Fe and Ni to form Ni-rich compounds such as ε-Al3Ni, δ-Al3CuNi, γ-Al7Cu4Ni, and T-Al9FeNi. The presence of Ni in the Al-Si alloy neutralizes Fe and reduces the tendency to form iron-rich β-Al5FeSi needle-like phases. While the reticular and semi-reticular distributions contribute to the alloy's high-temperature strength, the formation of phases between Ni and Cu reduces the Cu content in the α-Al matrix, thereby reducing precipitation hardening. The presence of larger brittle phases also negatively impacts the alloy's fatigue strength. In general, the existing publicly available cast aluminum-silicon alloys cannot meet the requirements of high heat resistance and fatigue resistance. The types of heat-resistant phases are still relatively single, the number density is low, and the low impurity element content also limits the use of high-quality recycled aluminum.

[0006] In addition, the existing patent CN115261682B discloses a cast aluminum alloy and a preparation method thereof, wherein the matrix of the aluminum alloy includes one or more submicron-sized dispersed phases, and the grain boundaries of the aluminum alloy include one or more micron-sized second phases, wherein the size of the submicron-sized dispersed phases ranges from 20 to 1000 nm, and the composition includes any two or more of the elements Al, Fe, Mn, Cr, Zr, Mo, Ti, Cu, Ni, Co, Y, V, and Sc, and the number density of the submicron-sized dispersed phases is within 10 15 -10 20 / m 3range; the size range of the micron-sized second phase is between 1-20 μm, and the composition includes any two or more of the elements Al, Fe, Mn, Cr, Zr, Mo, Ti, Cu, Ni, Co, Y, V, and Sc; the composition of the aluminum alloy includes: Si 4-17%, Mg 0.1-1%, Fe 0.1-0.5%, Mn 0.1-0.5%, Cr 0.1-0.5%, Zr 0.1-0.5%, Mo 0.1-0.5%, Ti 0.1-0.5%, Cu 0.1-2%, Ni 0.1-1%, Co 0.1-0.5%, Y 0.1-0.5%, V 0.1-0.5%, Sc 0.1-0.5%, and the rest is Al. The patent suggests that aluminum alloys can have non-shear strengthening phases and high fatigue properties. However, referring to its formula, it can be seen that, first, its formula composition is complex, with at least 15 alloy components. The complexity of the composition leads to a narrow process window for the alloy, especially for sand castings and thick parts. Due to the slow cooling rate, primary multi-metallic compounds are easily formed, thereby damaging the alloy performance; second, it must also contain more expensive metals such as nickel, which is relatively expensive; third, it must include a variety of expensive rare earth elements for use in combination. It can be seen that the cast aluminum alloy in this patent is not only expensive to prepare, but also has a complex formula, which is not conducive to industrial application.

[0007] Summary of the Invention

[0008] The purpose of the present invention is to overcome one or more deficiencies in the prior art and to provide an improved cast aluminum alloy that combines a simple formula, high tolerance to impurity elements, especially iron, low hot cracking resistance, and high heat fatigue resistance. The alloy can not only meet the needs of the existing large amount of high-quality recycled aluminum alloys for equal or even upgraded use, but can also be recycled to reduce carbon emissions, and can also be used at higher service temperatures.

[0009] The present invention also provides a method for preparing the cast aluminum alloy.

[0010] The present invention also provides an application of the above-mentioned cast aluminum alloy in the preparation of automobile chassis structural parts, engines or transmission components. The automobile chassis structural parts, engines or transmission components may not only need to withstand a service temperature of up to 250°C, but also need to have good fatigue performance, which can be met by the cast aluminum alloy of the present invention.

[0011] In order to achieve the above object, a technical solution adopted by the present invention is:

[0012] A cast aluminum alloy comprising Al, Si, Cu, Mg, Mn, Ti and unavoidable impurities, in particular, the cast aluminum alloy further comprising Cr, Sr and X1, wherein X1 is Sn and / or In, and the impurities comprise Fe and other impurities except Fe;

[0013] The cast aluminum alloy comprises, in percentage by mass: Si 6.5%-8.5%, Cu 0.5%-2.0%, Mg 0.1%-0.5%, Mn 0.05%-0.4%, Cr 0.05%-0.3%, Ti 0.05%-0.3%, Sr 0.005%-0.04%, the content of the elements contained in X1 is independently 0.001%-0.2%, Fe is less than or equal to 0.5%, and the sum of other impurities other than Fe is not more than 0.2%. The Al content is adjusted so that the total amount of the aluminum alloy is 100%.

[0014] In the process of preparing the cast aluminum alloy, the various components are mixed, melted, and then refined, and then an aluminum alloy ingot is made, and the aluminum alloy ingot is subjected to a solid solution treatment, a quenching cooling, and an aging treatment; wherein the solid solution treatment is carried out at 250-550°C and in a multi-stage treatment, and the temperature between the multi-stage treatments increases in sequence according to the order of treatment. The multi-stage treatment is at least three-stage treatment, and the first solid solution treatment in the multi-stage treatment is carried out at 250-350°C.

[0015] Another technical solution provided by the present invention is a cast aluminum alloy, comprising Al, Si, Cu, Mg, Mn, Ti and unavoidable impurities, particularly, the cast aluminum alloy further comprising Cr and Sr, and the impurities comprising Fe and other impurities except Fe;

[0016] The cast aluminum alloy comprises, in percentage by mass: Si 6.5%-8.5%, Cu 0.5%-2.0%, Mg 0.1%-0.5%, Mn 0.05%-0.4%, Cr 0.05%-0.3%, Ti 0.05%-0.3%, Sr 0.005%-0.04%, Fe less than or equal to 0.5%, and the sum of other impurities other than Fe is not more than 0.2%. The Al content is adjusted so that the total amount of the aluminum alloy is 100%.

[0017] In the process of preparing the cast aluminum alloy, the various components are mixed, melted, and then refined, and then an aluminum alloy ingot is made, and the aluminum alloy ingot is subjected to a solid solution treatment, a quenching cooling, and an aging treatment; wherein the solid solution treatment is carried out at 250-550°C and in a multi-stage treatment, and the temperature between the multi-stage treatments increases in sequence according to the order of treatment. The multi-stage treatment is at least three-stage treatment, and the first solid solution treatment in the multi-stage treatment is carried out at 250-350°C.

[0018] Another technical solution provided by the present invention is a cast aluminum alloy, comprising Al, Si, Cu, Mg, Mn, Ti and unavoidable impurities, particularly, the cast aluminum alloy further comprising Cr and Sr, and the impurities comprising Fe and other impurities except Fe;

[0019] Calculated in percentage by mass, the cast aluminum alloy comprises: Si 6.5%-8.5%, Cu 0.5%-2.0%, Mg 0.1%-0.5%, Mn 0.05%-0.4%, Cr 0.05%-0.3%, Ti 0.05%-0.3%, Sr 0.005%-0.04%, Fe is less than or equal to 0.5%, and the sum of other impurities except Fe is not more than 0.2%. The Al content is adjusted so that the total amount of the aluminum alloy is 100%.

[0020] According to some preferred aspects of the present invention, in the cast aluminum alloy, the ratio of the addition amount of Cu to the addition amount of Mg is 1.2-6.

[0021] According to some preferred aspects of the present invention, in terms of mass percentage, Mg accounts for 0.25%-0.5% in the cast aluminum alloy.

[0022] According to some preferred aspects of the present invention, in terms of mass percentage, Fe accounts for 0.1%-0.5% in the cast aluminum alloy.

[0023] According to some specific aspects of the present invention, the needle-shaped β-Fe phase in the alloy structure of the cast aluminum alloy accounts for less than 5% of the total area of ​​the Fe phase, and the needle-shaped β-Fe phase can even be completely eliminated.

[0024] According to some specific aspects of the present invention, during the solution treatment, the Cu-containing phase and the Mg-containing phase are dissolved into the α-Al matrix of the alloy structure, and the Q′ metastable phase is precipitated during the aging treatment;

[0025] After the solution treatment and before the aging treatment, the alloy structure of the intermediate includes an α-Al(Fe, Mn, Cr)Si dispersed phase.

[0026] In some embodiments of the present invention, the cast aluminum alloy further includes Zr, and after the solution treatment and before the aging treatment, the alloy structure of the intermediate includes a (Al, Si) 3 (Zr, Ti) dispersed phase.

[0027] According to some preferred aspects of the present invention, Zr accounts for 0.05%-0.3% in the cast aluminum alloy in terms of mass percentage.

[0028] In some embodiments of the present invention, the cast aluminum alloy further includes X2, and X2 is a combination of one or more selected from Mo, V, Y and Er.

[0029] According to some preferred aspects of the present invention, in the cast aluminum alloy, the content of the elements contained in X2 is independently 0.01%-0.3%, calculated as percentage by mass.

[0030] According to some preferred and specific aspects of the present invention, the solution treatment is performed at 250-540°C.

[0031] In some preferred embodiments of the present invention, the solution treatment comprises the following steps performed in sequence:

[0032] Primary solution treatment: keep warm at 250-350℃;

[0033] Secondary solution treatment: keep warm at 370-470℃;

[0034] Three-stage solution treatment: keep warm at 490-510℃;

[0035] Fourth-level solution treatment: keep warm at 520-540℃.

[0036] In some preferred embodiments of the present invention, the solution treatment comprises:

[0037] Primary solution treatment: heat the ingot from room temperature to 250-350°C at a heating rate of 1-10°C / min, and keep it at 250-350°C for 3-11 hours;

[0038] Secondary solution treatment: the alloy obtained by the primary solution treatment is heated from 250-350°C to 370-470°C at a heating rate of 1-10°C / min, and kept at 370-470°C for 3-13 hours;

[0039] Three-stage solution treatment: the alloy obtained by the two-stage solution treatment is heated from 370-470℃ to 490-510℃ at a heating rate of 1-10℃ / min, and then kept at 490-510℃ for 2-6h;

[0040] Four-stage solution treatment: The alloy obtained by the three-stage solution treatment is heated from 490-510°C to 520-540°C at a heating rate of 1-10°C / min, and then kept at 520-540°C for 2-12 hours.

[0041] According to some specific aspects of the present invention, the filling length of the cast aluminum alloy at 700° C. is greater than 645 mm.

[0042] According to some specific aspects of the present invention, after the aging treatment, the cast aluminum alloy has a tensile strength of more than 360 MPa at room temperature and an elongation after fracture of more than 7.5%.

[0043] According to some specific aspects of the present invention, after the aging treatment, under the test conditions of smooth specimen, stress ratio R of -1, and 10 million cycles, the fatigue strength of the cast aluminum alloy reaches above 100 MPa.

[0044] According to some preferred aspects of the present invention, the quenching cooling is cooling to room temperature in water within 30 seconds.

[0045] In some embodiments of the present invention, the aging treatment is performed at 140-200° C. Further, the aging treatment is performed at 140-200° C. for 1-18 hours.

[0046] Furthermore, in some embodiments of the present invention, the aging treatment is performed at 140-200° C. for 6-18 hours.

[0047] As is well known, the use of recycled aluminum will lead to an increase in the content of impurity elements in the alloy, especially Fe. The needle-shaped Fe phase formed after solidification will seriously split the matrix. The aluminum alloy formula of the present invention has the advantage of high tolerance to impurities, especially high tolerance to Fe. Therefore, in practice, in the cast aluminum alloy, some components including Al can be added by adding recycled aluminum alloy. The recycled aluminum alloy is a combination of one or more selected from Al-Si-Mg alloy, Al-Si-Cu alloy, Al-Si-Cu-Mg alloy, and Al-Mn alloy. In this way, not only can a large amount of high-quality recycled aluminum alloy be used at the same level or even upgraded, but it can also be recycled (i.e., regenerated) to reduce carbon emissions.

[0048] Another technical solution provided by the present invention is a method for preparing the above-mentioned cast aluminum alloy, the preparation method comprising:

[0049] The aluminum alloy ingot is prepared by mixing ingredients according to the composition, melting, refining, metamorphism and refinement, and then subjected to solution treatment, quenching cooling and aging treatment. The solution treatment is carried out at 250-550° C. and in multiple stages. The temperatures between the multiple stages increase in sequence according to the order of treatment. The multiple stages are at least three stages, and the first stage of the solution treatment is carried out at 250-350° C.

[0050] In some embodiments of the present invention, in the process of preparing the cast aluminum alloy, Al-Si-Mg, Al-Si-Cu, Al-Si-Cu-Mg, Al-Mn high-quality recycled aluminum alloy can be melted first, the surface slag can be removed, the composition mushroom sample can be cast, the composition can be measured, and the alloy composition can be adjusted to the target range using pure alloys or intermediate alloys of the corresponding elements. The alloy can be refined and deslagging, modified and refined, and allowed to stand for cooling to make an aluminum alloy ingot.

[0051] To further achieve the purpose of the present invention, preferably, the melting temperature of the Al-Si-Mg, Al-Si-Cu, Al-Si-Cu-Mg, and Al-Mn high-quality recycled aluminum alloys is controlled to be 730-760°C.

[0052] Preferably, the refining and slagging is carried out by adding a universal refining agent using a rotary argon injection process.

[0053] Preferably, the refining agent is FL-228 type refining agent, and the addition amount of the refining agent is 0.05%-0.15% of the weight of the alloy melt.

[0054] Preferably, the refinement is performed using a TCB grain refiner, the addition amount of the refiner is 0.3%-0.8% of the weight of the alloy melt, and the modification is performed using an AlSr10 modifier, the addition amount of the modifier is 0.005%-0.04% of the weight of the alloy melt.

[0055] In some embodiments of the present invention, the method of preparing the cast aluminum alloy includes:

[0056] 1) High temperature melting of aluminum alloy: According to the composition ratio requirements of the raw materials, melt high-quality recycled aluminum alloys containing Al-Si-Mg, Al-Si-Cu, Al-Si-Cu-Mg, Al-Mn, etc., control the melting temperature to 730-760℃, and stir for 1-10 minutes until the composition is uniform;

[0057] 2) Cast the mushroom sample and calculate the mass of the corresponding alloy elements based on the test results;

[0058] 3) Alloying of aluminum alloy melt: scrape off the scum on the surface of the melt, add the pure alloy or master alloy of the corresponding element to the alloy melt prepared in step 1) (note that when adding pure Mg or selective X1, wrap it with aluminum foil to reduce burn-in loss), control the processing temperature to 720-730°C, stir for 1-10 minutes until the melt composition is uniform, continue casting the composition mushroom sample, and adjust the composition to the target range according to the test results;

[0059] 4) Melt refining and deslagging: The melt obtained in step 3) is refined and deslagging by adding a general refining agent using a rotary argon injection process. The treatment temperature is controlled at 705-715°C and the melt is allowed to stand for deslagging.

[0060] 5) Modification and refinement: First, add 0.005%-0.04% of AlSr10 modifier based on the weight of the alloy melt; let it stand, then add 0.3%-0.8% of TCB grain refiner based on the weight of the alloy melt, and skim the slag to obtain the target aluminum alloy melt;

[0061] 6) Casting: Aluminum alloy melt is cast;

[0062] 7) Solution treatment: The alloy obtained in step 6) is subjected to solution treatment, specifically comprising:

[0063] Primary solution treatment: heating the cast alloy from room temperature to 250-350°C at a heating rate of 1-10°C / min, and keeping it at 250-350°C for 3-11 hours;

[0064] Secondary solution treatment: the alloy obtained by the primary solution treatment is heated from 250-350°C to 370-470°C at a heating rate of 1-10°C / min, and kept at 370-470°C for 3-13 hours;

[0065] Three-stage solution treatment: the alloy obtained by the second-stage solution treatment is heated from 370-470℃ to 490-510℃ at a heating rate of 1-10℃ / min, and then kept at 490-510℃ for 2-6h;

[0066] Four-stage solid solution treatment: the alloy obtained by the three-stage solid solution is heated from 490-510℃ to 520-540℃ at a heating rate of 1-10℃ / min, and then kept at 520-540℃ for 2-12h;

[0067] Quenching cooling: The alloy obtained after the four-stage solid solution treatment was cooled to room temperature in water within 30 seconds;

[0068] Aging treatment: The alloy obtained after quenching is kept at 140-200℃ for 6-18h.

[0069] Preferably, in step 1) or 3), the stirring time is 2-3 minutes.

[0070] Preferably, in step 4) or 5), the standing time is 10-20 minutes.

[0071] Preferably, in step 6), the casting method of the casting molding is gravity casting or pressure casting.

[0072] Another technical solution provided by the present invention is a use of the above-mentioned cast aluminum alloy in the preparation of automobile chassis structural parts, engines or transmission components.

[0073] In the present invention, a multi-stage solution treatment method of at least three stages with temperatures increasing in sequence is adopted, which is conducive to the formation of Mg, Si, and Cu atomic clusters at relatively low temperatures. These clusters can serve as nucleation sites for α-type dispersed phases and Al3M (M can be Ti, Zr, V, Y, Er, etc.) type dispersed phases, thereby increasing the dispersivity of the dispersed phases. The increase in nucleation sites also reduces the size of the dispersed phases.

[0074] Then, under the gradually increasing relatively high temperature treatment, the nucleation and growth of the dispersed phase can be completed first, and a dispersed phase with a certain volume fraction and number density can be obtained. Then, the Cu-containing θ phase and Q phase can be further promoted to dissolve back to form a supersaturated solid solution, preparing for the subsequent precipitation of nano-strengthening phase during aging.

[0075] Ultimately, at the relatively highest temperature, the solid solubility of the Al matrix is ​​further increased, the elements are evenly distributed, the Si phase is promoted to spheroidize, the tearing effect of the long Si phase on the Al matrix is ​​reduced, the stress concentration is reduced, and the plasticity of the alloy is improved.

[0076] For example, in the preferred four-stage solution treatment process, the first-stage solution treatment can form Mg and Si atomic clusters, which can serve as nucleation sites for α-type dispersed phases and Al3M (M can be Ti, Zr, V, Y, Er, etc.) type dispersed phases, thereby increasing the dispersion of the dispersed phases. The increase in nucleation sites will also reduce the size of the dispersed phases.

[0077] Secondary solution treatment can promote the nucleation and growth of the dispersed phase, and obtain a dispersed phase with a certain volume fraction and number density;

[0078] The three-stage solution treatment can further promote the dissolution of Cu-containing θ phase and Q phase, forming a supersaturated solid solution to prepare for the subsequent precipitation of nano-strengthening phase during aging. The selection of solution temperature and time fully considers the incubation, nucleation and growth of the phase.

[0079] The fourth-stage solution treatment further increases the solubility of the Al matrix, homogenizes the element distribution, promotes Si spheroidization, reduces the tearing effect of the long Si phase on the Al matrix, reduces stress concentration, and thus improves the plasticity of the alloy. If the solution temperature is too high, the alloy may overheat. Considering the low temperature control accuracy of industrial furnaces, the upper limit is preferably set at 540°C.

[0080] In the present invention, quenching and cooling can maintain the vacancy concentration during solution treatment and obtain a supersaturated solid solution; aging treatment can promote the dispersion and precipitation of θ″ phase, θ′ phase and Q′ phase that are coherent or semi-coherent with the matrix, thereby further improving the room temperature / intermediate temperature strength of the alloy.

[0081] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0082] The present invention is based on the fact that the existing cast aluminum silicon alloys cannot meet the requirements of high heat resistance and fatigue, the types of heat-resistant phases are still relatively single, the number density is low, the low impurity element content limits the use of high-quality recycled aluminum, the formula is complex and the cost is high. After a large number of experimental studies, it was unexpectedly found that by adopting the Al-Si-Cu-Mg-Mn-Cr alloy system and controlling the addition amount of each component, a high tolerance to impurity elements, especially Fe, can be achieved. Not only can the Fe phase morphology be regulated from needle-shaped to block-shaped, but the adverse effects of the primary Fe phase can also be reduced. At the same time, the Fe element dissolved in the matrix is ​​converted into a beneficial dispersed phase through a solution treatment process, so that the alloy system of the present invention can use recycled ingots (80-90% of the ingots used in the present invention can come from secondary high-quality recycled materials, including A356 .2 alloy, A319 alloy, A380 alloy, ZL114A alloy, ZL702A alloy, etc.), which is suitable for the same level or even upgraded use of recycled ingots, saving costs; further, after adding Sn and / or In elements to the system, it can be found that they can diffuse rapidly and preferentially combine with vacancies, further increasing the nucleation density of the dispersed phase, making the dispersed phase more fine and evenly distributed, improving the heat resistance and mechanical properties, etc.; in particular, compared with the existing patent CN115261682B, after omitting most of the elements, especially expensive metals or rare earth elements, the present invention not only does not basically reduce the high-temperature strength and fatigue properties of the alloy, but also greatly improves the hot cracking resistance of the alloy. The reduction in hot cracking resistance is beneficial to the alloy forming of castings with complex shapes, in addition, it greatly saves costs and is suitable for industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] FIG1 is a metallographic structure diagram of the alloy of Comparative Example 1;

[0084] FIG2 is a metallographic structure diagram of the alloy of Example 1 of the present invention;

[0085] FIG3 is a diagram of the dispersed phase structure of the alloy of Example 1 of the present invention;

[0086] FIG4 is a diagram showing the mold filling test results of the alloy of Example 2 of the present invention;

[0087] FIG5 is a diagram showing the hot cracking test results of the alloy of Example 2 of the present invention;

[0088] FIG6 is a diagram of the dispersed phase structure of the alloy of Example 2 of the present invention;

[0089] FIG7 is a diagram of the dispersed phase structure of the alloy of Example 3 of the present invention;

[0090] FIG8 is a diagram of the dispersed phase structure of the alloy of Example 5 of the present invention;

[0091] FIG9 is a diagram of the dispersed phase structure of the alloy of Example 6 of the present invention;

[0092] FIG10 is a diagram showing the dispersed phase distribution of the alloy of Example 6 of the present invention;

[0093] FIG11 is a transmission electron microscope image of the dispersed phase of the alloy of Example 2 of the present invention;

[0094] FIG12 is a transmission electron microscope image (TEM image) of the strengthening phase of the alloy of Example 2 of the present invention. DETAILED DESCRIPTION

[0095] The main concepts of the present invention are: 1) Hypoeutectic Al-Si alloys have a narrow solid-liquid crystallization temperature range, good fluidity and shrinkage compensation, good casting properties and low production costs, and are almost free of casting cracks. They have a low thermal expansion coefficient, good corrosion resistance, good wear resistance and machinability, and are therefore widely used. Although Al-Si alloys have many advantages, their low strength and hardness limit their application in heat-resistant and high-fatigue castings. Furthermore, Mg is added to the alloy system. In practice, the solid solubility of Mg in the α-Al matrix is ​​0.34% at room temperature and 14.9% at the eutectic temperature. Therefore, the strength and hardness of the alloy can be improved by solid solution strengthening and aging strengthening. In the system of the present invention, Mg can form β(Mg2Si) and Q(Al5Cu2Mg8Si6) strengthening phases, which can significantly improve the strength of the alloy after solid solution treatment. However, excessive Mg content can cause serious oxidation and gas absorption in the alloy. When the Mg content is less than 0.6%, the strength increases with increasing Mg content, while the plasticity and toughness decrease. Practice has shown that the amount of Mg added to the aluminum-silicon alloy of the present invention cannot be too much. If the content is too high, a brittle phase Al3Mg2 will be formed, which will split the matrix and reduce the mechanical properties. The higher the silicon content, the lower the magnesium content of the alloy should be. The present invention controls the mass content of Mg to be no higher than 0.5% and no lower than 0.1%. At the same time, the present invention further adds Cu. The solubility of Cu in the Al matrix is ​​0.2% at room temperature, and the solid solubility is 5.65% at the eutectic temperature of 548°C. Due to the dissolution of larger Cu atoms, the Al solid solution produces severe lattice distortion, which hinders the dislocation. Movement, increasing the shear stress of slip movement, forming solid solution strengthening, and improving the strength of the alloy; in the alloy system of the present invention, it can form θ (Al2Cu) phase. During the solid solution treatment, Al2Cu dissolves into the α solid solution, and precipitates θ', θ" metastable phase or θ stable phase during the aging process. These strengthening phases can hinder the movement of dislocations, improve tensile strength, hardness, fatigue strength and high temperature strength. In particular, in the system of the present invention, in addition to generating strengthening phases Al2Cu and Mg2Si, it is also easy to form Al2CuMg, Q phase (Al5Cu2Mg8Si6), W phase (Al x The formation of these phases results in higher strength and heat resistance than other aluminum-silicon alloys. Further controlling the Cu and Mg content within the alloy yields a Q (Al5Cu2Mg8Si6 or Al4Mg5Si4Cu) strengthening phase, which exhibits superior strengthening effects compared to Al2Cu and Mg2Si. The Q phase is a quaternary alloy phase. Multicomponent alloys possess higher atomic bonding strength than binary alloys, and the presence of more elements contributes to improved heat resistance and high-temperature performance.

[0096] 2) Adding trace elements such as Mn, Cr, and Ti can form a large number density of blocky morphology of α-type dispersed phase and rod-shaped / plate-shaped Al3M (M can be Ti, etc.) type heat-resistant dispersed phase in the alloy. Studies have found that the strength of alloys containing transition metals depends to a large extent on the size and morphology of the intermetallic phase formed; Mn and Cr elements often have a low diffusion rate, so that the alloy still maintains the precipitation strengthening effect at high temperatures, and their solid solubility in the aluminum matrix is ​​very low. When added in excessive amounts, primary intermetallic compounds will inevitably form, and these intermetallic compounds are often detrimental to the mechanical properties of the alloy. Therefore, in the present invention, it is preferred to control the Mn content to 0.05%-0.4%, the Cr content to 0.05%-0.3%, and the Ti content to 0.05%-0.3%.

[0097] 3) Furthermore, in the present invention, Zr elements can be further added on the basis of the above, or X2 elements (selected from a combination of one or more of Mo, V, Y and Er) can be further added. These elements can also achieve the effect of precipitation strengthening of the alloy at high temperatures, so that a large number density of blocky morphology α-type dispersed phase and rod-shaped / plate-shaped Al3M type heat-resistant dispersed phase (M can further include Zr, V, Y, Er, etc.) are formed in the alloy, and the formation of primary metal compounds that are not conducive to mechanical properties can be reduced by controlling the addition amount.

[0098] The above scheme is further described below in conjunction with specific examples; it should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following examples; the implementation conditions adopted in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are generally the conditions in routine experiments.

[0099] Unless otherwise specified in the following examples, all raw materials were purchased from commercial sources or prepared by conventional methods in the art.

[0100] Comparative Example 1:

[0101] Comparative Example 1 uses the commonly used alloy A356.2+0.5% Cu for the casing of the accessory receiver currently in service.

[0102] The specific preparation steps include the following:

[0103] (1) The raw materials of this alloy are A356.2+0.5% Cu, a commonly used alloy for accessory receiver shells currently in service. The composition ratio by mass range is: Si: 6%-7.5%, Cu: 0.4%-0.6%, Mg: 0.30%-0.45%, Ti≤0.2%, Fe≤0.12%, Mn≤0.05%, Zn≤0.05%, and the balance is Al.

[0104] (2) The specific smelting steps of this alloy include:

[0105] The weighed A356.2 alloy and pure Cu wire were melted at a melting temperature of 720°C. After all the alloys were melted, they were stirred manually for 2 minutes to make the composition uniform, and then allowed to stand and heat for 10 minutes. The mushroom sample was cast. After the composition was qualified, the F-228 general refining agent was added to the alloy melt by rotary argon injection method for refining and slag removal. The amount of refining agent added was 0.15% of the weight of the alloy melt. After treatment, it was allowed to stand for 5 minutes, cooled to 700°C, and then slag was removed, and then cast. The casting process used was gravity casting, and the melt was cast into a metal mold preheated to 200°C to prepare the casting. The heat treatment process used for the ingot was: 535°C for 6 hours + water quenching + aging at 170°C for 8 hours. After cooling, samples were taken from the ingot for microstructure observation and performance testing.

[0106] The filling properties, hot cracking properties, and mechanical properties at room temperature and high temperature of the alloy prepared in this example are shown in Table 1.

[0107] Comparative Example 2:

[0108] Comparative Example 2 further increases the Cu and Mg contents.

[0109] The specific steps include the following:

[0110] (1) The raw materials of this alloy are A356.2+0.5% Cu, a commonly used alloy for accessory receiver shells currently in service. The composition ratio by mass range is: Si: 6.5%-7.5%, Cu: 0.9%-1.1%, Mg: 0.9%-1.1%, Ti≤0.2%, Fe≤0.12%, Mn≤0.05%, Zn≤0.05%, and the balance is Al.

[0111] (2) The specific smelting steps of this alloy include:

[0112] Weighed A356.2 alloy and pure Cu wire were melted at 720°C. Once fully melted, pure Mg blocks wrapped in aluminum foil were added and manually stirred for 2 minutes to homogenize the composition. The mixture was then allowed to stand for 10 minutes. A mushroom-shaped sample was cast. Once the composition was acceptable, the alloy melt was refined and deslagging was performed using a rotary argon injection method with F-228 general-purpose refining agent added externally. The refining agent was added in an amount of 0.15% by weight of the alloy melt. After treatment, the melt was allowed to stand for 5 minutes, cooled to 700°C, deslagging, and then cast. The casting process used was gravity casting, with the melt poured into a preheated 200°C metal mold to produce the casting. The ingots were heat treated as follows: 500°C for 4 hours, 535°C for 6 hours, water quenching, and aging at 170°C for 8 hours. After cooling, samples were taken from the ingots for microstructure observation and performance testing.

[0113] The filling properties, hot cracking properties, and mechanical properties at room temperature and high temperature of the alloy prepared in this example are shown in Table 1.

[0114] Comparative Example 3:

[0115] Comparative Example 3 uses a commonly used alloy for cylinder heads of currently used engines, with the alloy grade being ZL702A.

[0116] The specific steps include the following:

[0117] (1) The raw materials of this alloy are from the widely used ZL702A alloy, and its composition ratio by mass range is: Si: 6.0%-8.0%, Cu: 1.3%-1.8%, Mg: 0.3%-0.5%, Ti: 0.1%-0.25%, Fe≤0.25%, Mn≤0.15%, Zn≤0.05%, and the balance is Al;

[0118] (2) The specific smelting steps of this alloy include:

[0119] The weighed ZL702A alloy was melted at a melting temperature of 720°C. After all the alloys were melted, they were stirred manually for 2 minutes to make the composition uniform, and then allowed to stand and heat for 10 minutes. The F-228 general-purpose refining agent was added to the alloy melt by the rotary argon injection method for refining and slag removal. The amount of refining agent added was 0.15% of the weight of the alloy melt. After treatment, the alloy was allowed to stand for 5 minutes, cooled to 700°C, and then the slag was removed and then cast. The casting process used was gravity casting, in which the melt was cast into a metal mold preheated to 200°C to prepare castings. The heat treatment process used for the ingots was: 535°C for 6 hours + water quenching + aging at 170°C for 8 hours. After cooling, samples were taken from the ingots for microstructure observation and performance testing.

[0120] The filling properties, hot cracking properties, and mechanical properties at room temperature and high temperature of the alloy prepared in this example are shown in Table 1.

[0121] Example 1:

[0122] This example provides a cast aluminum alloy and a preparation method thereof. Calculated by mass percentage, the cast aluminum alloy contains: Si 7%, Cu 0.5%, Mg 0.4%, Mn 0.3%, Cr 0.2%, Ti 0.08%, Sr 0.02%, Fe 0.4%, Sn 0.05%, and the balance is Al and other inevitable impurities except Fe.

[0123] The preparation method of the cast aluminum alloy comprises:

[0124] 1) High-temperature melting of aluminum alloy: According to the composition ratio requirements of the raw material components, melt the high-quality recycled aluminum alloy composed of 30% Al-Si-Mg, 30% Al-Si-Cu, 30% Al-Si-Cu-Mg, and 10% Al-Mn, control the processing temperature to 760°C, and stir until the composition is uniform;

[0125] 2) Cast the mushroom sample and calculate the mass of the corresponding alloy elements based on the test results;

[0126] 3) Alloying of the aluminum alloy melt: Remove the scum from the melt surface and add the corresponding element's pure alloy or master alloy to the alloy melt prepared in step 1) (note that when adding pure Mg and Sn, wrap them in aluminum foil to reduce burnout). Control the processing temperature to 730°C and stir until the melt composition is uniform. Continue casting the composition mushroom sample and measure the alloy composition until the target composition is reached.

[0127] 4) Melt refining and deslagging: The melt obtained in step 3) was subjected to refining and deslagging by adding F-228 general refining agent to the melt by rotary argon injection, with the refining agent added in an amount of 0.15% by weight of the alloy melt. The treatment temperature was controlled to be 710° C., the argon flow rate was 20 L / min, the refining time was 20 min, and the slag was removed by standing.

[0128] 5) First, add 0.03% of the weight of the alloy melt as a modifier of AlSr10, let it stand for 10 minutes, then add 0.5% of the weight of the alloy melt as a grain refiner of TCB, and skim off the slag to obtain the target aluminum alloy melt;

[0129] 6) Casting: The melt is poured into a metal mold preheated to 200°C to prepare a casting;

[0130] 7) Solution treatment parameters are: 275℃ for 7h + 390℃ for 3h + 500℃ for 4h + 530℃ for 4h;

[0131] Quenching cooling: water quenching (cooled to room temperature in water within 30s);

[0132] Aging treatment: keep warm at 180℃ for 13h.

[0133] The filling property, hot cracking property, and mechanical properties of the alloy at room temperature and high temperature in Example 1 are shown in Table 1.

[0134] Example 2:

[0135] This example provides a cast aluminum alloy and a preparation method thereof. Calculated by mass percentage, the cast aluminum alloy contains: Si 7.5%, Cu 1.8%, Mg 0.35%, Mn 0.3%, Cr 0.2%, Ti 0.08%, Zr 0.1%, Sr 0.03%, Fe 0.3%, Sn 0.1%, and the balance is Al and other inevitable impurities except Fe.

[0136] The preparation method of the cast aluminum alloy comprises:

[0137] 1) High-temperature melting of aluminum alloy: According to the composition ratio requirements of the raw material components, melt the high-quality recycled aluminum alloy composed of 30% Al-Si-Mg, 30% Al-Si-Cu, 30% Al-Si-Cu-Mg, and 10% Al-Mn, control the processing temperature to 760°C, and stir until the composition is uniform;

[0138] 2) Cast the mushroom sample and calculate the mass of the corresponding alloy elements based on the test results;

[0139] 3) Alloying of the aluminum alloy melt: Remove the scum from the melt surface and add the corresponding element's pure alloy or master alloy to the alloy melt prepared in step 1) (note that when adding pure Mg and Sn, wrap them in aluminum foil to reduce burnout). Control the processing temperature to 730°C and stir until the melt composition is uniform. Continue casting the composition mushroom sample and measure the alloy composition until the target composition is reached.

[0140] 4) Melt refining and deslagging: The melt obtained in step 3) was subjected to refining and deslagging by adding F-228 general refining agent to the melt by rotary argon injection, with the refining agent added in an amount of 0.15% by weight of the alloy melt. The treatment temperature was controlled to be 710° C., the argon flow rate was 20 L / min, the refining time was 20 min, and the slag was removed by standing.

[0141] 5) First, add 0.03% of the weight of the alloy melt as a modifier of AlSr10, let it stand for 10 minutes, then add 0.5% of the weight of the alloy melt as a grain refiner of TCB, and skim off the slag to obtain the target aluminum alloy melt;

[0142] 6) Casting: The melt is poured into a metal mold preheated to 200°C to prepare a casting;

[0143] 7) Solution treatment parameters are: 275℃ for 7h + 390℃ for 10h + 500℃ for 4h + 530℃ for 4h;

[0144] Quenching cooling: water quenching (cooled to room temperature in water within 30s);

[0145] Aging treatment: keep warm at 180℃ for 13h.

[0146] The filling property, hot cracking property, and mechanical properties of the alloy at room temperature and high temperature in Example 2 are shown in Table 1.

[0147] Example 3:

[0148] This example provides a cast aluminum alloy and a preparation method thereof. Calculated by mass percentage, the cast aluminum alloy contains: Si 7.5%, Cu 1.8%, Mg 0.35%, Mn 0.3%, Cr 0.2%, Ti 0.08%, Zr 0.1%, Sr 0.03%, Fe 0.3%, Sn 0.1%, and the balance is Al and other inevitable impurities except Fe.

[0149] The preparation method of the cast aluminum alloy comprises:

[0150] 1) High-temperature melting of aluminum alloy: According to the composition ratio requirements of the raw material components, melt the high-quality recycled aluminum alloy composed of 30% Al-Si-Mg, 30% Al-Si-Cu, 30% Al-Si-Cu-Mg, and 10% Al-Mn, control the processing temperature to 760°C, and stir until the composition is uniform;

[0151] 2) Cast the mushroom sample and calculate the mass of the corresponding alloy elements based on the test results;

[0152] 3) Alloying of the aluminum alloy melt: Remove the scum from the melt surface and add the corresponding element's pure alloy or master alloy to the alloy melt prepared in step 1) (note that when adding pure Mg and Sn, wrap them in aluminum foil to reduce burnout). Control the processing temperature to 730°C and stir until the melt composition is uniform. Continue casting the composition mushroom sample and measure the alloy composition until the target composition is reached.

[0153] 4) Melt refining and deslagging: The melt obtained in step 3) was subjected to refining and deslagging by adding F-228 general refining agent to the melt by rotary argon injection, with the refining agent added in an amount of 0.15% by weight of the alloy melt. The treatment temperature was controlled to be 710° C., the argon flow rate was 20 L / min, the refining time was 20 min, and the slag was removed by standing.

[0154] 5) First, add 0.03% of the weight of the alloy melt as a modifier of AlSr10, let it stand for 10 minutes, then add 0.5% of the weight of the alloy melt as a grain refiner of TCB, and skim off the slag to obtain the target aluminum alloy melt;

[0155] 6) Casting: The melt is poured into a metal mold preheated to 200°C to prepare a casting;

[0156] 7) Solution treatment parameters are: 4 hours at 500°C + 10 hours at 530°C;

[0157] Quenching cooling: water quenching (cooled to room temperature in water within 30s);

[0158] Aging treatment: keep warm at 180℃ for 13h.

[0159] The filling property, hot cracking property, and mechanical properties of the alloy at room temperature and high temperature in Example 3 are shown in Table 1.

[0160] Example 4:

[0161] This example provides a cast aluminum alloy and a preparation method thereof. Calculated by mass percentage, the cast aluminum alloy contains: Si 7%, Cu 0.5%, Mg 0.35%, Mn 0.2%, Cr 0.1%, Mo 0.1%, Zr 0.1%, Ti 0.1%, V 0.1%, Y 0.1%, Er 0.1%, Sr 0.02%, Fe 0.3%, and the balance is Al and other inevitable impurities except Fe.

[0162] The preparation method of the cast aluminum alloy comprises:

[0163] 1) High-temperature melting of aluminum alloy: According to the composition ratio requirements of the raw material components, melt the high-quality recycled aluminum alloy composed of 30% Al-Si-Mg, 30% Al-Si-Cu, 30% Al-Si-Cu-Mg, and 10% Al-Mn, control the processing temperature to 760°C, and stir until the composition is uniform;

[0164] 2) Cast the mushroom sample and calculate the mass of the corresponding alloy elements based on the test results;

[0165] 3) Alloying of the aluminum alloy melt: Remove the scum from the melt surface and add the corresponding element's pure alloy or master alloy to the alloy melt prepared in step 1) (note that when adding pure Mg, wrap it in aluminum foil to reduce burn-off). Control the processing temperature to 730°C and stir until the melt composition is uniform. Continue casting the composition mushroom sample and measure the alloy composition until the target composition is reached.

[0166] 4) Melt refining and deslagging: The melt obtained in step 3) was subjected to refining and deslagging by adding F-228 general refining agent to the melt by rotary argon injection, with the refining agent added in an amount of 0.15% by weight of the alloy melt. The treatment temperature was controlled to be 710° C., the argon flow rate was 20 L / min, the refining time was 20 min, and the slag was removed by standing.

[0167] 5) First, add 0.03% of the weight of the alloy melt as a modifier of AlSr10, let it stand for 10 minutes, then add 0.5% of the weight of the alloy melt as a grain refiner of TCB, and skim off the slag to obtain the target aluminum alloy melt;

[0168] 6) Casting: The melt is poured into a metal mold preheated to 200°C to prepare a casting;

[0169] 7) Solution treatment parameters are: 250℃ for 11h + 390℃ for 12h + 500℃ for 4h + 530℃ for 8h;

[0170] Quenching cooling: water quenching (cooled to room temperature in water within 30s);

[0171] Aging treatment: keep warm at 180℃ for 13h.

[0172] The filling property, hot cracking property, and mechanical properties of the alloy at room temperature and high temperature in Example 4 are shown in Table 1.

[0173] Example 5:

[0174] This example provides a cast aluminum alloy and a preparation method thereof. Calculated by mass percentage, the cast aluminum alloy contains: Si 8.5%, Cu 2.0%, Mg 0.5%, Mn 0.4%, Cr 0.2%, Mo 0.2%, Zr 0.15%, Ti 0.3%, V 0.1%, Y 0.1%, Er 0.1%, Sn 0.05%, Sr 0.03%, Fe 0.4%, and the balance is Al and other inevitable impurities except Fe.

[0175] The preparation method of the cast aluminum alloy comprises:

[0176] 1) High-temperature melting of aluminum alloy: According to the composition ratio requirements of the raw material components, melt the high-quality recycled aluminum alloy composed of 30% Al-Si-Mg, 30% Al-Si-Cu, 30% Al-Si-Cu-Mg, and 10% Al-Mn, control the processing temperature to 760°C, and stir until the composition is uniform;

[0177] 2) Cast the mushroom sample and calculate the mass of the corresponding alloy elements based on the test results;

[0178] 3) Alloying of the aluminum alloy melt: Remove the scum from the melt surface and add the corresponding element's pure alloy or master alloy to the alloy melt prepared in step 1) (note that when adding pure Mg and Sn, wrap them in aluminum foil to reduce burnout). Control the processing temperature to 730°C and stir until the melt composition is uniform. Continue casting the composition mushroom sample and measure the alloy composition until the target composition is reached.

[0179] 4) Melt Refining and Deslagging: The melt obtained in step 3) was subjected to refining and deslagging by adding F-228 general-purpose refining agent to the melt by rotary argon injection, with the refining agent added in an amount of 0.15% by weight of the alloy melt. The treatment temperature was controlled at 710° C., the argon flow rate was 20 L / min, the refining time was 20 min, and the slag was removed by standing.

[0180] 5) First, add 0.03% of the weight of the alloy melt as a modifier of AlSr10, let it stand for 10 minutes, then add 0.5% of the weight of the alloy melt as a grain refiner of TCB, and skim off the slag to obtain the target aluminum alloy melt;

[0181] 6) Casting: The melt is poured into a metal mold preheated to 200°C to prepare a casting;

[0182] 7) Solution treatment parameters are: 310℃ for 6h + 410℃ for 8h + 500℃ for 6h + 530℃ for 4h;

[0183] Quenching cooling: water quenching (cooled to room temperature in water within 30s);

[0184] Aging treatment: keep warm at 160℃ for 15h.

[0185] The filling property, hot cracking property, and mechanical properties of the alloy in Example 5 at room temperature and high temperature are shown in Table 1.

[0186] Example 6:

[0187] This example provides a cast aluminum alloy and a preparation method thereof. Calculated by mass percentage, the cast aluminum alloy contains: Si 7%, Cu 1.5%, Mg 0.35%, Mn 0.2%, Cr 0.2%, Mo 0.2%, V 0.1%, Y 0.1%, Er 0.1%, Sn 0.05%, In 0.05%, Sr 0.025%, Fe 0.5%, and the balance is Al and other inevitable impurities except Fe.

[0188] The preparation method of the cast aluminum alloy comprises:

[0189] 1) High-temperature melting of aluminum alloy: According to the composition ratio requirements of the raw material components, melt the high-quality recycled aluminum alloy composed of 30% Al-Si-Mg, 30% Al-Si-Cu, 30% Al-Si-Cu-Mg, and 10% Al-Mn, control the processing temperature to 760°C, and stir until the composition is uniform;

[0190] 2) Cast the mushroom sample and calculate the mass of the corresponding alloy elements based on the test results;

[0191] 3) Alloying of the aluminum alloy melt: Remove the scum from the melt surface and add the corresponding pure alloy or master alloy to the alloy melt prepared in step 1) (note that when adding pure Mg, Sn, and In, wrap them with aluminum foil to reduce burn-off). Control the processing temperature to 730°C and stir until the melt composition is uniform. Continue to cast the composition mushroom sample and measure the alloy composition until the target composition is adjusted.

[0192] 4) Melt refining and deslagging: The melt obtained in step 3) was subjected to refining and deslagging by adding F-228 general refining agent to the melt by rotary argon injection, with the refining agent added in an amount of 0.15% by weight of the alloy melt. The treatment temperature was controlled to be 710° C., the argon flow rate was 20 L / min, the refining time was 20 min, and the slag was removed by standing.

[0193] 5) First, add 0.03% of the weight of the alloy melt as a modifier of AlSr10, let it stand for 10 minutes, then add 0.5% of the weight of the alloy melt as a grain refiner of TCB, and skim off the slag to obtain the target aluminum alloy melt;

[0194] 6) Casting: The melt is poured into a metal mold preheated to 200°C to prepare a casting;

[0195] 7) Solution treatment parameters are: 290℃ for 6h + 430℃ for 8h + 490℃ for 3h + 530℃ for 6h;

[0196] Quenching cooling: water quenching (cooled to room temperature in water within 30s);

[0197] Aging treatment: keep warm at 170℃ for 10h.

[0198] The filling property, hot cracking property, and mechanical properties of the alloy in Example 6 at room temperature and high temperature are shown in Table 1.

[0199] Performance testing:

[0200] (1) The metallographic structure of the A356.2+0.5%Cu alloy of Comparative Example 1 is shown in FIG1 . The silicon phase is mostly in the form of fine particles of 1-3 μm, with a small amount of coarse particles of 5-10 μm at the edge. The Fe phase presents different forms, including needle-shaped and block-shaped. The needle-shaped Fe phase will seriously split the matrix and reduce the mechanical properties of the alloy.

[0201] (2) The metallographic structure of the cast aluminum alloy prepared in Example 1 is shown in FIG2 . The acicular Fe phase is essentially eliminated from the microstructure, leaving only the massive Fe phase, which is beneficial for improving the alloy's performance. The dispersed phase structure of the alloy is shown in FIG3 . It can be seen that a large number of bright white, fine, and dispersed phases are distributed within the crystals. This dispersed phase itself can serve as a strengthening phase and is beneficial for improving the deformation uniformity of the alloy, avoiding performance degradation caused by concentrated deformation. The present invention can significantly improve the high-temperature strength and fatigue strength of the alloy.

[0202] (3) The filling property test results of the cast aluminum alloy prepared in Example 2 are shown in FIG4 , and the hot cracking property test results are shown in FIG5 . It can be seen that the alloy has good filling property and hot cracking resistance, which is beneficial for the alloy to form complex-shaped castings. The submicron-scale dispersed phase structure of the cast aluminum alloy prepared in Example 2 is shown in FIG6 . A large number of bright white fine dispersed phases are also distributed in the crystal. The dispersed phase itself can serve as a strengthening phase and is beneficial for improving the deformation uniformity of the alloy. Through transmission electron microscopy analysis, it can be more clearly observed that a large number of Al3M dispersed phases (marked 1 in FIG11 ) and α-AlFeMnCrSi (marked 2 in FIG11 ) of different sizes are formed inside the α-Al grains. These phases are high-temperature thermally stable phases, which are beneficial for improving the heat resistance of the alloy. In addition, due to the pinning effect on dislocations, during fatigue loading, the accumulation of dislocations on the surface of weak positions is reduced, which significantly delays the initiation of fatigue cracks and improves the fatigue performance of the alloy. In addition to the submicron dispersed phase, a large number of Cu-containing nanoparticles (marked 3 in Figure 12) are precipitated in the α-Al grains. Compared with the conventional β" and β' phases, they have higher thermal stability, which not only effectively improves the static mechanical properties of the alloy, but also improves the high-temperature mechanical properties of the alloy.

[0203] (4) The submicron-scale dispersed phase structure of the cast aluminum alloy prepared in Example 3 is shown in FIG7 . The difference between Example 3 and Example 2 is basically the difference in the solid solution treatment process. Example 2 adopts the specific solid solution treatment process of the present invention, while Example 3 adopts the traditional solid solution treatment process. It can be seen that the number density of dispersed phase precipitation is significantly reduced by adopting the traditional solid solution treatment process. This shows that the solid solution treatment process of the present invention can greatly increase the number density of dispersed phase compared with the traditional solid solution treatment process, which is beneficial to improving the high temperature strength and fatigue strength of the alloy.

[0204] (5) The submicron dispersed phase structure of the cast aluminum alloy prepared in Example 5 is shown in FIG8 . It can be seen that the number density of the dispersed phase is further increased after further addition of Mo, V, Y, and Er elements.

[0205] (6) The submicron dispersed phase structure of the cast aluminum alloy prepared in Example 6 is shown in FIG9 , and the distribution of the dispersed phase is shown in FIG10 . It can be seen that the addition of Sn and In elements increases the number density of the dispersed phase and improves its distribution uniformity.

[0206] (7) The filling properties, hot cracking properties, and mechanical properties at room temperature and high temperature of the cast aluminum alloys prepared in Comparative Examples 1-3 and Examples 1-6 are shown in Table 1.

[0207] Among them: the filling test method: a single screw mold is used to test the fluidity, the mold temperature is 200℃, and the casting temperature is 700℃; the hot cracking test method: a hot cracking restraint rod mold is used to evaluate the hot cracking of the alloy, the mold temperature is 200℃, and the casting temperature is 730℃;

[0208] Test method for tensile strength at room temperature and high temperature: GB / T 228-2021; Test method for elongation at break at room temperature and high temperature: GB / T 228-2021;

[0209] Fatigue strength test method: GB / T 3075-2008.

[0210] Table 1

[0211] As shown in Table 1, although the commonly used alloy A356.2+0.5%Cu of the current accessory receiver shell of Comparative Example 1 has relatively good hot cracking resistance during casting, its processability, such as mold filling, is poor, especially its mechanical properties are insufficient;

[0212] Comparative Example 2 uses another commonly used alloy A356.2+0.5%Cu for accessory receiver shells in service. Its casting performance is not only poor overall, but its mechanical properties are also worse than those of Comparative Example 1.

[0213] Comparative Example 3 uses a common alloy for cylinder heads of currently used engines, with the alloy grade being ZL702A, and its comprehensive performance is the worst among all comparative examples and embodiments.

[0214] The present invention not only has better casting properties, but also has made significant progress in mechanical properties. At room temperature, the tensile strength can reach more than 365MPa, the elongation after fracture can reach more than 7.5%, and the fatigue strength is more than 105MPa; at the same time, it still has excellent mechanical properties at higher temperatures such as 150℃ and 250℃.

[0215] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

[0216] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

Claims

1. A cast aluminum alloy, the cast aluminum alloy comprising Al, Si, Cu, Mg, Mn, Ti and inevitable impurities, characterized in that, The cast aluminum alloy further includes Cr, Sr, and X1, where X1 is Sn and / or In, and the impurities include Fe and other impurities other than Fe; By mass percentage, in the cast aluminum alloy: Si is 6.5% - 8.5%, Cu is 0.5% - 2.0%, Mg is 0.1% - 0.5%, Mn is 0.05% - 0.4%, Cr is 0.05% - 0.3%, Ti is 0.05% - 0.3%, Sr is 0.005% - 0.04%, the content of each element contained in X1 is independently 0.001% - 0.2%, Fe is less than or equal to 0.5%, and the total of other impurities other than Fe is not more than 0.2%. Adjust the content of Al to make the total amount of this aluminum alloy 100%; In the process of preparing the cast aluminum alloy, each component is mixed and melted and then refined, and then made into an aluminum alloy ingot, and the aluminum alloy ingot is subjected to solution treatment, quenching and cooling, and aging treatment; among them, the solution treatment includes the following processes carried out in sequence: Primary solution treatment: Keep warm at 250 - 350 °C; Secondary solution treatment: Keep warm at 370 - 470 °C; Tertiary solution treatment: Keep warm at 490 - 510 °C; Quaternary solution treatment: Keep warm at 520 - 540 °C; In the cast aluminum alloy, its alloy structure includes α-type dispersed phases with a massive morphology, as well as θ″ phase, θ′ phase, and Q′ phase that are coherent or semi-coherent with the matrix. The α-type dispersed phases include α-Al(Fe,Mn,Cr)Si dispersed phases; Among them, the θ″ phase, θ′ phase, and Q′ phase that are coherent or semi-coherent with the matrix precipitate after aging treatment; After the aging treatment, the tensile strength of the cast aluminum alloy at room temperature is above 360 MPa, and the elongation after fracture is above 7.5%; After the aging treatment, under the test conditions: smooth specimen, stress ratio R is -1, and cycling for 10 million times, the fatigue strength of the cast aluminum alloy reaches above 100 MPa.

2. The cast aluminum alloy according to claim 1, characterized in that, In the cast aluminum alloy, the ratio of the addition amount of Cu to the addition amount of Mg is 1.2 - 6.

3. The cast aluminum alloy according to claim 1, characterized in that, By mass percentage, in the cast aluminum alloy, Mg accounts for 0.25% - 0.5%.

4. The cast aluminum alloy according to claim 1, characterized in that, By mass percentage, in the cast aluminum alloy, Fe accounts for 0.1% - 0.5%.

5. The cast aluminum alloy according to claim 4, wherein By mass percentage, in the cast aluminum alloy, Fe accounts for 0.3% - 0.5%.

6. The cast aluminum alloy according to claim 1, wherein In the alloy structure of the cast aluminum alloy, the acicular β-Fe phase accounts for 5% or less of the total area of the Fe phase.

7. The cast aluminum alloy according to claim 1, characterized in that, After the solution treatment and before the aging treatment, the alloy structure of the intermediate includes α-Al(Fe,Mn,Cr)Si dispersed phases.

8. The cast aluminum alloy according to claim 1, characterized in that, The cast aluminum alloy further includes Zr. After the solution treatment and before the aging treatment, the alloy structure of the intermediate includes (Al,Si)3(Zr,Ti) dispersed phases.

9. The cast aluminum alloy according to claim 8, characterized in that, By mass percentage, in the cast aluminum alloy, Zr accounts for 0.05% - 0.3%.

10. The cast aluminum alloy according to claim 1, characterized in that, The cast aluminum alloy further includes X2, and X2 is a combination of one or more selected from Mo, V, Y, and Er.

11. The cast aluminum alloy according to claim 10, wherein In the cast aluminum alloy, the contents of the elements contained in X2 are each independently 0.01% - 0.3% by mass percentage.

12. The cast aluminum alloy according to any one of claims 1-11, characterized in that, In the cast aluminum alloy, its alloy structure further includes rod / plate-shaped Al3M type dispersed phases, where M includes Ti; When the cast aluminum alloy further includes Zr, V, Y or Er, correspondingly, M further includes Zr, V, Y or Er.

13. The cast aluminum alloy according to claim 1, characterized in that, The filling length of the cast aluminum alloy at 700 °C is above 645 mm.

14. The cast aluminum alloy according to claim 1, wherein The quenching and cooling is to cool it to room temperature in water within 30 s.

15. The cast aluminum alloy according to claim 1, characterized in that, The aging treatment is to hold it at 140 - 200 °C for 1 - 18 h.

16. The cast aluminum alloy according to claim 1, wherein In the cast aluminum alloy, some components including Al are fed by adding recycled aluminum alloy, and the recycled aluminum alloy is a combination of one or more selected from Al-Si-Mg alloy, Al-Si-Cu alloy, Al-Si-Cu-Mg alloy, and Al-Mn alloy.

17. The preparation method of the cast aluminum alloy according to any one of claims 1-16, characterized in that, The preparation method includes: Weighing materials according to the composition, melting, refining, modifying, refining, and making an aluminum alloy ingot, and performing solution treatment, quenching and cooling, and aging treatment on the aluminum alloy ingot; among them, the solution treatment includes the following processes carried out in sequence: Primary solution treatment: holding at 250 - 350 °C; Secondary solution treatment: holding at 370 - 470 °C; Tertiary solution treatment: holding at 490 - 510 °C; Quaternary solution treatment: holding at 520 - 540 °C.

18. A cast aluminum alloy, the cast aluminum alloy includes Al, Si, Cu, Mg, Mn, Ti, Cr, Sr and inevitable impurities, the impurities include Fe and other impurities except Fe, and it is characterized in that: In the cast aluminum alloy by mass percentage: Si 6.5% - 8.5%, Cu 0.5% - 2.0%, Mg 0.1% - 0.5%, Mn 0.05% - 0.4%, Cr 0.05% - 0.3%, Ti 0.05% - 0.3%, Sr 0.005% - 0.04%, Fe is less than or equal to 0.5%, and the total of other impurities except Fe is not more than 0.2%, and the content of Al is adjusted to make the total amount of this aluminum alloy 100%; In the process of preparing the cast aluminum alloy, each component is mixed and melted and then refined, and then an aluminum alloy ingot is made. Solution treatment, quenching and cooling, and aging treatment are performed on the aluminum alloy ingot; among them, the solution treatment is carried out in four levels at 250 - 540 °C, and the temperatures between the four levels increase sequentially according to the order of treatment, and the primary solution treatment in the four-level treatment is carried out at 250 - 350 °C. During the primary solution treatment, Mg and Si atomic clusters can be formed and used as the nucleation sites of α-type dispersed phases.

19. A cast aluminum alloy, the cast aluminum alloy includes Al, Si, Cu, Mg, Mn, Ti, Cr, Sr and inevitable impurities, the impurities include Fe and other impurities except Fe, and it is characterized in that: In the cast aluminum alloy by mass percentage: Si 6.5%-8.5%, Cu 0.5%-2.0%, Mg 0.1%-0.5%, Mn 0.05%-0.4%, Cr 0.05%-0.3%, Ti 0.05%-0.3%, Sr 0.005%-0.04%, Fe is less than or equal to 0.5%, and the total sum of other impurities except Fe is not more than 0.2%. Adjust the content of Al to make the total amount of the aluminum alloy 100%; The preparation method of the cast aluminum alloy includes: mixing and melting each component and then refining, and then making an aluminum alloy ingot, and performing solution treatment, quenching and cooling, and aging treatment on the aluminum alloy ingot; wherein, the solution treatment includes the following processes carried out in sequence: Primary solution treatment: Keep the temperature at 250-350°C. During the primary solution treatment, Mg and Si atomic clusters can be formed and serve as the nucleation points of the α-type dispersion phase; Secondary solution treatment: Keep the temperature at 370-470°C; Tertiary solution treatment: Keep the temperature at 490-510°C; Quaternary solution treatment: Keep the temperature at 520-540°C.

20. The cast aluminum alloy according to claim 18 or 19, characterized in that: The implementation mode of the solution treatment includes: Primary solution treatment: Heat the aluminum alloy ingot from room temperature to 250-350°C at a heating rate of 1-10°C / min, and keep the temperature at 250-350°C for 3-11h; Secondary solution treatment: Heat the alloy obtained by the primary solution treatment from 250-350°C to 370-470°C at a heating rate of 1-10°C / min, and keep the temperature at 370-470°C for 3-13h; Tertiary solution treatment: Heat the alloy obtained by the secondary solution treatment from 370-470°C to 490-510°C at a heating rate of 1-10°C / min, and then keep the temperature at 490-510°C for 2-6h; Quaternary solution treatment: Heat the alloy obtained by the tertiary solution treatment from 490-510°C to 520-540°C at a heating rate of 1-10°C / min, and then keep the temperature at 520-540°C for 2-12h.

21. A cast aluminum alloy, the cast aluminum alloy includes Al, Si, Cu, Mg, Mn, Ti, Cr, Sr and inevitable impurities, the impurities include Fe and other impurities except Fe, and it is characterized in that: The cast aluminum alloy further includes Zr and X2, and the X2 is a combination of one or more selected from Mo, V, Y and Er; By mass percentage, in the cast aluminum alloy: Si 6.5% - 8.5%, Cu 0.5% - 2.0%, Mg 0.1% - 0.5%, Mn 0.05% - 0.4%, Cr 0.05% - 0.3%, Ti 0.05% - 0.3%, Zr 0.05% - 0.3%, Sr 0.005% - 0.04%, the content of the elements contained in X2 is independently 0.01% - 0.3%, Fe accounts for 0.3% - 0.5%, and the total sum of other impurities except Fe is not more than 0.2%. Adjust the content of Al to make the total amount of the aluminum alloy 100%; In the process of preparing the cast aluminum alloy, each component is mixed and melted and then refined, and then made into an aluminum alloy ingot. The aluminum alloy ingot is subjected to solution treatment, quenching and cooling, and aging treatment; wherein, the solution treatment is carried out at 250 - 540 °C and in four - stage treatment, the temperature between the four - stage treatments increases in sequence according to the order of treatment, and the first - stage solution treatment of the four - stage treatments is carried out at 250 - 350 °C. During the first - stage solution treatment, Mg and Si atomic clusters can be formed and used as the nucleation base points of the α - type dispersion phase and the Al3M - type dispersion phase, and M includes one or more combinations of Ti, Zr, V, Y, and Er.

22. Application of the cast aluminum alloy according to any one of claims 1 - 16, 18 - 21 under the working condition of thermo - mechanical coupling.

23. The application according to claim 22, characterized in that: The service temperature of the working condition of the thermo - mechanical coupling can reach 250 °C.

24. The application according to claim 22, wherein: Use the cast aluminum alloy according to any one of claims 1 - 16, 18 - 21 to prepare automotive chassis structural parts, engines or transmission devices, and apply them under the working condition of thermo - mechanical coupling.

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