A heat-resistant eutectic Al-Si alloy material and a preparation method thereof

Abstract

This application discloses a heat-resistant eutectic Al-Si alloy material, which is obtained by adding strengthening elements Cu, Mg, Ni and microalloying elements Ti, Sc, and Zr to a eutectic Al-Si alloy and then subjecting it to ultrasonic treatment during the alloy solidification process. This application also provides a method for preparing the heat-resistant eutectic Al-Si alloy material. By controlling the formation of a nano-scale high-temperature stable precipitate phase, the thermomechanical fatigue performance and service performance of the Al-Si alloy material are improved; this addresses the technical problem that excessive Cu and Ni additions increase the volume fraction of intermetallic phases in the alloy microstructure, leading to increased brittleness and a mismatch between low-temperature plasticity and high-temperature strength, which is detrimental to the alloy's insufficient thermomechanical fatigue life during service.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy material preparation technology, specifically to a heat-resistant eutectic Al-Si alloy material and its preparation method. Background Technology

[0002] With the rapid development of national construction, the important role of heavy machinery in the national economy and defense industry is becoming increasingly prominent, such as ships, tractors, tanks, and large transport vehicles. These machines often require both lightweight construction and high mobility, which places higher demands on the power density, combustion pressure, and wear resistance of internal combustion engines. Cast Al-Si alloys, due to their excellent casting properties, high specific strength, good wear resistance, and low coefficient of thermal expansion, have been widely used in high-temperature components such as engine pistons and cylinder heads. However, the harsh high-temperature service conditions cause pistons to endure more complex cyclic mechanical and thermal stresses. In particular, the piston combustion chamber throat area often fails due to thermomechanical fatigue damage. Multi-scale phase damage and thermomechanical fatigue of Al-Si alloys remain the most significant limiting factors for piston service life, and improving the high-temperature thermomechanical fatigue life of piston aluminum alloys is a key technical challenge. Traditional Al-Si alloys can no longer meet the stringent service requirements of high-power-density internal combustion engines, leading to increasing demand and research on new heat-resistant Al-Si alloys both domestically and internationally. Currently, a common method is to add transition elements (Ni, Cu, Mg, Mn, etc.) to Al-Si alloys to form precipitates with good thermal stability and high-temperature strength, thereby improving their mechanical properties at high temperatures. The typical microstructure of this alloy includes micron-scale primary phases (α-Al matrix, primary Si, eutectic Si, Mg2Si, and intermetallic compounds such as AlCuNi, AlTiCe, and AlFeMnNi) and nano-scale precipitates (GP zone, θ(Al2Cu), θ′, and θ″ phases, etc.).

[0003] The increase in Ni content significantly improves the thermal stability of the Cu-rich phase, and the formed ε-Al3Ni, δ-Al3CuNi, and γ-Al7Cu4Ni phases can improve the high-temperature strength of the alloy (Materials Science and Engineering A527(2010)7132-7137). However, with the increase of Ni content, although the tensile properties are improved, the fatigue strength shows a trend of first increasing and then decreasing (Materials Science and Engineering: A706(2017)27-37). This is because although a high proportion of precipitated phases can improve the high-temperature strength of the alloy, it will also aggravate thermomechanical fatigue damage, thereby reducing the service life (Materials 11(8)(2018)1300). At present, the content of elements such as Si, Ni, and Cu in the alloy has exceeded 20%, and the negative effects such as the reduction in fatigue life caused by precipitated phases have begun to emerge. Chinese invention patent CN101463440B discloses an aluminum-based composite material for pistons and its preparation method, which simultaneously achieves phosphorus modification treatment and AlP particle reinforcement. However, for multi-component Al-Si alloys, a large number of precipitates can cause the agglomeration of strengthening phase particles, leading to fatigue cracks. Chinese invention patent CN110079711B proposes to improve the strength and elongation of the alloy through high-pressure casting. Although high-pressure casting can refine the grains and improve casting defects, coarse precipitates are still difficult to avoid and become the main factor affecting fatigue life. Improving the morphology of precipitates through microalloying and casting process adjustment is an effective way to further improve the mechanical properties of the alloy. Patent CN110284030B discloses an ultrasonic-assisted casting device and a method for manufacturing aluminum-lithium alloys. This method can effectively improve the uniformity of the ingot structure and suppress the formation of coarse grains. However, for heat-resistant Al-Si alloys, although ultrasonic treatment can significantly improve low-temperature strength and toughness, it has limited effect on high-temperature strength. In particular, when the temperature exceeds 350°C, it will cause a decrease in strength (Journal of Alloys and Compounds 712(2017)277-287). Adjusting the distribution of θ-Al2Cu nanoprecipitate phase can improve the thermomechanical fatigue life of Al-Si alloys during cycling at 50℃-150℃. However, as the temperature increases further, the strengthening effect of θ-Al2Cu will gradually weaken. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the purpose of this application is to provide a heat-resistant eutectic Al-Si alloy material, which improves the thermomechanical fatigue performance and service performance of Al-Si alloy material by regulating the formation of a nano-high temperature stable precipitate phase; and solves the technical problem that excessive addition of Cu and Ni elements increases the volume fraction of intermetallic chemical phases in the alloy microstructure, leading to increased brittleness and mismatch between low-temperature plasticity and high-temperature strength, which is detrimental to the insufficient thermomechanical fatigue life of the alloy during service.

[0005] To solve the above problems, the technical solution adopted in this application is as follows:

[0006] A heat-resistant eutectic Al-Si alloy material is obtained by adding strengthening elements Cu, Mg, Ni and microalloying elements Ti, Sc and Zr to a eutectic Al-Si alloy and then subjecting it to ultrasonic treatment during the alloy solidification process.

[0007] As a further preferred embodiment, the heat-resistant eutectic Al-Si alloy material described in this application comprises a micron-sized precipitate phase, a θ-Al2Cu nano-precipitate phase, and an Al3(Sc, Zr) reinforcing phase; wherein the mass percentage of the micron-sized precipitate phase in the alloy is 10-15%, the mass percentage of the θ-Al2Cu nano-precipitate phase in the alloy is 1%-2%, and the mass percentage of the Al3(Sc, Zr) reinforcing phase in the alloy is 0.4%-1.0%.

[0008] As a further preferred embodiment, the micron-sized precipitated phase described in this application is one or more of AlMnSi, AlFeMn, AlFeMnSi, Mg2Si, AlCuNi, AlTiCe, and AlFeMnN.

[0009] As a further preferred embodiment, the heat-resistant eutectic Al-Si alloy material described in this application has the following composition by mass percentage: Si 12%-13%, Cu 3-3.5%, Ni 2.5-3%, Mg 0.5-1%, Mn 0.3-0.5%, Zn 0.2%, Fe 0.2%, Ce 0.2%, Ti 0.2%-0.3%, Zr 0.2%, Sc 0.2%, with the balance being Al.

[0010] As a further preferred embodiment, the ultrasonic treatment described in this application has a power of 1.5 to 3 kW, a treatment time of 60 to 120 s, and an ultrasonic field treatment temperature of 520 to 560 ℃.

[0011] This application also provides a method for preparing a heat-resistant eutectic Al-Si alloy material, including...

[0012] Melting: Pure aluminum is placed in a crucible preheated to the first preset temperature and heated until melted. Then, Al-Si master alloy is added and the temperature is raised to the second preset temperature to melt the master alloy completely. Then, master alloys Al-Cu, Al-Ni, Al-Mn, and Al-Fe are added. After they are completely melted, the temperature is raised to the third preset temperature and master alloys Al-Zr, Al-Ti, and Al-Sc are added and held at the third preset temperature. Then, the temperature is lowered to the fourth preset temperature, and pure Mg and pure Zn wrapped in Al foil are added and pressed into the molten metal. After they are completely melted, the temperature is raised to the fifth preset temperature, and a modifier is added to obtain the melt.

[0013] Refining: After the above melt cools down to the sixth preset temperature, add the degassing agent, stir evenly and let stand. When the melt temperature rises back to the fifth preset temperature, remove the surface slag to complete the alloy refining.

[0014] Ultrasonic treatment: The preheated ultrasonic amplitude transformer is inserted into the refined melt, and an ultrasonic field is applied to the alloy during the solidification process of the melt to perform ultrasonic treatment, thereby obtaining an alloy ingot.

[0015] Water-cooled quenching: The above alloy ingot is heated to the seventh preset temperature and held for solution treatment, then water-cooled quenching, and cooled after holding to obtain heat-resistant eutectic Al-Si alloy material.

[0016] As a further preferred embodiment, the first preset temperature described in this application is 300-350℃, the second preset temperature is 735-745℃, the third preset temperature is 770-790℃, the fourth preset temperature is 690-710℃, the fifth preset temperature is 745-755℃, the sixth preset temperature is 725-735℃, and the seventh preset temperature is 490℃-520℃.

[0017] As a further preferred embodiment, the modifier described in this application is a phosphate modifier, and its addition amount is 0.6-1.5% of the total mass of the alloy.

[0018] As a further preferred embodiment, the ultrasonic field treatment temperature described in this application is 520-560℃, the treatment time is 60-120s, and the applied power is 1.5kW-3kW.

[0019] As a further preferred embodiment, the degassing agent described in this application is C2Cl6, and its addition amount is 1.2-1.8% of the alloy mass.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. The heat-resistant eutectic Al-Si alloy material described in this application adds strengthening elements Cu, Mg, Ni and microalloying elements Ti, Sc, Zr to the eutectic Al-Si alloy. The alloy material is obtained by ultrasonic treatment during the solidification process of the alloy. The micron-sized precipitates in the alloy are adjusted to increase nucleation points, improve the microstructure and reduce defects, and improve the low-temperature toughness W0. At the same time, combined with microalloying, a nano-high-temperature stable precipitate phase is formed, which increases the matrix's ability to resist creep damage and improves the high-temperature fatigue cracking index β of the alloy.

[0022] 2. The heat-resistant eutectic Al-Si alloy material described in this application increases the intrinsic fatigue toughness W0 (improving defects and inhomogeneous structure) and the high-temperature fatigue cracking index β (increasing the high-temperature stable phase of the matrix) at lower temperatures, thereby improving service shortcomings and increasing the thermomechanical fatigue life of the alloy throughout the entire service temperature range.

[0023] 3. This application also provides a method for preparing a heat-resistant eutectic Al-Si alloy material. The preparation method improves the size and morphology of the micron-sized primary phase through ultrasonic treatment, and also has a significant grain-refining effect, thereby improving room temperature plasticity.

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0025] Figure 1 The images show the changes in precipitated phases and grains after ultrasonic treatment in the embodiments of this application; where a represents the size and morphology of the precipitated phases in the alloy of Comparative Example 1; b represents the size and morphology of the precipitated phases in the alloy of Example 1; c represents the EBSD grain size of the alloy of Comparative Example 1; d represents the EBSD grain size of the alloy of Example 1; e represents the changes in the primary Si size distribution in Comparative Example 1 and Example 1; and f represents the changes in the grain size distribution in Comparative Example 1 and Example 1.

[0026] Figure 2 This is an Al3(Sc, Zr) strengthening phase diagram formed in the alloy described in the embodiments of this application.

[0027] Figure 3 This is a schematic diagram of thermal strain and thermomechanical fatigue loading of an alloy. Figure 4 The intensity changes at different temperatures for Example 1 (AC) and Example 1 (UT).

[0028] Figure 5 The images represent the tissue damage behavior after thermomechanical fatigue in Comparative Example 1 and Example 1; where a represents the crack morphology after fatigue failure in Comparative Example 1; b represents the three-dimensional XRT image of the crack after fatigue failure in Comparative Example 1; c represents the crack morphology after fatigue failure in Example 1; and d represents the three-dimensional XRT image of the crack after fatigue failure in Example 1.

[0029] Figure 6 This is a comparison chart of thermomechanical fatigue life between Comparative Example 1 (AC) and Example 1 (UT). Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] The term "comprising" and other equivalent descriptive terms used in the specification and claims of this application are intended to cover a non-exclusive inclusion, which includes both the contents explicitly described in the specification and claims and steps or units that are not described in the specification and claims but are inherent in the product, method or structure.

[0032] This application provides a heat-resistant eutectic Al-Si alloy material, obtained by adding strengthening elements Cu, Mg, Ni and microalloying elements Ti, Sc, and Zr to a eutectic Al-Si alloy, followed by ultrasonic treatment during alloy solidification. Increasing intrinsic fatigue toughness W0 (improving defect and inhomogeneous microstructure) and increasing the high-temperature fatigue cracking index β (increasing the high-temperature stable phase of the matrix) at lower temperatures is beneficial for improving thermomechanical fatigue life throughout the entire service temperature range. Simultaneously increasing the crack propagation resistance W0 and the damage index can improve the fatigue resistance of the material, but the changes in these two parameters usually exhibit a significant inverse relationship, making simultaneous improvement difficult. Therefore, in the embodiments of this application, adding high-temperature strengthening elements can improve the high-temperature stability of the alloy; ultrasonic treatment is used during the solidification process of the alloy to adjust the micron-sized precipitates in the alloy, increase nucleation points, improve the microstructure and reduce defects, and improve the low-temperature toughness W0; during the research process, it was found that the refinement of the micron-sized precipitates caused by the increase of the phase interface would aggravate the damage to the matrix interface at high temperature. This application can form a nano-high-temperature stable precipitate phase by adding microalloying metal, which can increase the matrix's ability to resist creep damage and improve the high-temperature fatigue cracking index β of the alloy. Ultimately, it can simultaneously improve the intrinsic fatigue toughness W0 and the high-temperature fatigue cracking index β at low temperatures, thereby extending the thermomechanical fatigue life of the alloy material under service temperature cycling conditions.

[0033] As a further preferred embodiment, in some embodiments of this application, the heat-resistant eutectic Al-Si alloy material comprises micron-sized precipitates (one or more of AlMnSi, AlFeMn, AlFeMnSi, Mg2Si, and AlCuNi, AlTiCe, AlFeMnNi), θ-Al2Cu nano-precipitates, and Al3(Sc, Zr) reinforcing phases; wherein the mass percentage of the micron-sized precipitates in the alloy is 10%-15%, the mass percentage of the θ-Al2Cu nano-precipitates in the alloy is 1%-2.0%, and the mass percentage of the Al3(Sc, Zr) reinforcing phases in the alloy is 0.4%-1%. The average grain size of the heat-resistant eutectic Al-Si alloy material is 400-500 μm.

[0034] In the above scheme, among the microalloying elements, Sc achieves microalloying through the segregation behavior at the original precipitate interface. By causing an excess of solute at the Gibbsian interface, it significantly reduces the interfacial energy between the precipitate and the matrix, thereby effectively suppressing the coarsening behavior of the precipitate. However, Al3Sc precipitates typically require aging temperatures above 300℃, significantly higher than the precipitation temperatures of traditional precipitate strengthening phases. This inevitably leads to severe coarsening or dissolution of most traditional precipitate strengthening phases simultaneously. Therefore, using Sc alone as a microalloying metal is insufficient for improving the alloy's strength and high-temperature resistance. The addition of Zr can slow down the softening process caused by over-aging, significantly improving the alloy's thermal stability. Ti can dissolve in the Al3Sc phase, displacing Sc atoms to form Al3(Sc, Ti). The addition of titanium can enhance the alloy's modification effect and reduce the alloy's critical concentration. Therefore, in the embodiments of this application, Ti, Sc, and Zr composite microalloying is used. Ti and Zr partially replace the Sc atoms of Al3Sc particles, preventing the growth of Al3Sc particles and making these particles smaller. These small, dispersed Al3Sc particles are more effective as nucleation cores for the α phase, thereby increasing the number of particles in the solution and making the grain refinement effect of Al-Si alloy more significant.

[0035] As a further preferred embodiment, in some embodiments of this application, the heat-resistant eutectic Al-Si alloy material has the following composition by mass percentage: Si 12%-13%, Cu 3-3.5%, Ni 2.5-3%, Mg 0.5-1%, Mn 0.3-0.5%, Zn 0.1-0.2%, Fe ≤ 0.2%, Ce ≤ 0.2%, Ti 0.2%-0.3%, Zr 0.1-0.2%, Sc ≤ 0.2%, with the balance being Al.

[0036] This application also provides a method for preparing a heat-resistant eutectic Al-Si alloy material, including...

[0037] Melting: Pure aluminum is placed in a crucible preheated to the first preset temperature and heated until melted. Then, Al-Si master alloy is added and the temperature is raised to the second preset temperature to melt the master alloy completely. Then, master alloys Al-Cu, Al-Ni, Al-Mn, and Al-Fe are added. After they are completely melted, the temperature is raised to the third preset temperature and master alloys Al-Zr, Al-Ti, and Al-Sc are added and held at the third preset temperature. Then, the temperature is lowered to the fourth preset temperature, and pure Mg and pure Zn wrapped in Al foil are added and pressed into the molten metal. After they are completely melted, the temperature is raised to the fifth preset temperature, and a modifier is added to obtain the melt.

[0038] Refining: After the above melt cools down to the sixth preset temperature, add the degassing agent, stir evenly and let stand. When the melt temperature rises back to the fifth preset temperature, remove the surface slag to complete the alloy refining.

[0039] Ultrasonic treatment: The preheated ultrasonic amplitude transformer is inserted into the refined melt, and an ultrasonic field is applied to the alloy during the solidification process of the melt to perform ultrasonic treatment, thereby obtaining an alloy ingot.

[0040] Water-cooled quenching: The above alloy ingot is heated to the seventh preset temperature and held for solution treatment, then water-cooled quenching, and cooled after holding to obtain heat-resistant eutectic Al-Si alloy material.

[0041] In the embodiments of this application, an intermediate alloy is used when preparing the heat-resistant eutectic Al-Si alloy material. The intermediate alloy can reduce the melting temperature and shorten the melting time of the alloy; on the other hand, it can reduce furnace loss and improve the actual yield of alloying elements. In addition, using an intermediate alloy can also increase the uniformity of the smelting elements.

[0042] As a further preferred embodiment, the first preset temperature described in this application is 300-350℃, the second preset temperature is 735-745℃, the third preset temperature is 770-790℃, the fourth preset temperature is 690-710℃, the fifth preset temperature is 745-755℃, the sixth preset temperature is 725-735℃, and the seventh preset temperature is 490℃-520℃.

[0043] As a further preferred embodiment, the modifier described in this application is a phosphate modifier, and its addition amount is 0.6-1.5% of the total mass of the alloy.

[0044] As a further preferred embodiment, in some embodiments of this application, the power of the ultrasonic waves has a significant impact on the morphology and distribution of primary silicon and eutectic silicon. During the research, the inventors discovered that high-power ultrasonic waves significantly improve the morphology and distribution of primary silicon and eutectic silicon, making their morphology more rounded, especially significantly reducing their size, making their distribution more uniform, and significantly improving their grain size. Therefore, in some embodiments of this application, to improve the alloy's resistance to thermomechanical fatigue cracks, the power of the ultrasonic waves during the ultrasonic treatment is 1.5–3 kW. Furthermore, the ultrasonic treatment time is 60–120 s, and the ultrasonic field treatment temperature is 520–560 °C.

[0045] As a further preferred embodiment, the degassing agent described in this application is C2Cl6, and its addition amount is 1.2-1.8% of the alloy mass.

[0046] Example 1

[0047] This embodiment provides a heat-resistant eutectic Al-Si alloy material, which is prepared by the following method:

[0048] Weigh out industrial pure aluminum (99.99%), Al-Si master alloy, Al-50%Cu master alloy, industrial pure magnesium (99.99%), Al-10%Fe master alloy, Al-10%Ni master alloy, and Al-Zr, Al-Ti, and Al-Sc master alloys according to the mass percentages of 13%Si, 3.5%Cu, 3%Ni, 1%Mg, 0.5%Mn, 0.3%Ti, 0.2%Zn, 0.2%Fe, 0.2%Ce, 0.2%Zr, 0.2%Sc, and 77.7%Al. Pure aluminum, prepared in a specific ratio, is placed in a preheated crucible at 300-350℃ and heated to 720℃ to melt. Al-Si master alloy is then added, and the temperature is raised to 740℃. After complete melting, Al-Cu, Al-Ni, Al-Mn, and Al-Fe master alloys are added. After complete melting, the temperature is raised to 780℃, and Al-Zr, Al-Ti, and Al-Sc are added and held for 20 minutes. The temperature is then lowered to 700℃, and pure Mg and pure Zn wrapped in Al foil are added and pressed into the molten metal. After complete melting, the temperature is raised to 750℃, and 1% phosphate salt modifier is added and stirred thoroughly. Slag removal is then performed. Before slag removal, a small amount of covering agent should be evenly sprinkled onto the melt to separate the slag from the melt and reduce the amount of metal carried over. Slag removal should be smooth to prevent slag from being drawn into the melt. Slag removal should be as thorough as possible to avoid increasing the gas content of the melt due to floating slag, which could contaminate the molten metal. When the temperature drops to 730℃, add 1.5% C2Cl6, stir evenly, and let stand for 15 minutes. Once the melt temperature rises back to 750℃, remove surface slag to complete alloy refining. Insert an ultrasonic amplitude transformer preheated to 500℃ 20mm into the solution and apply ultrasonic treatment during the solidification of the alloy melt. The initial temperature is 550℃, the treatment time is 120s, and the ultrasonic power is 3kW. Heat the prepared alloy ingot to 490℃-520℃ for solution treatment, followed by water quenching. The alloy material undergoes heating and holding for aging treatment, then cools to room temperature, finally obtaining a heat-resistant eutectic Al-Si alloy material.

[0049] The average grain size of the aforementioned heat-resistant eutectic Al-Si alloy is 439.7 μm. The alloy material exhibits 1000-1200 thermomechanical fatigue cycles.

[0050] Example 2

[0051] This embodiment provides a heat-resistant eutectic Al-Si alloy material, which is prepared by the following method:

[0052] Weigh out industrial pure aluminum (99.99%), Al-Si master alloy, Al-50%Cu master alloy, industrial pure magnesium (99.99%), Al-10%Fe master alloy, Al-10%Ni master alloy, and Al-Zr, Al-Ti, and Al-Sc master alloys according to the mass percentages of 13%Si, 3.5%Cu, 3%Ni, 1%Mg, 0.5%Mn, 0.3%Ti, 0.2%Zn, 0.2%Fe, 0.2%Ce, 0.2%Zr, 0.2%Sc, and 77.7%Al. Pure aluminum, prepared in a specific ratio, is placed in a preheated crucible at 300-350℃ and heated to 720℃ to melt. Al-Si master alloy is then added, and the temperature is raised to 740℃. After complete melting, Al-Cu, Al-Ni, Al-Mn, and Al-Fe master alloys are added. After complete melting, the temperature is raised to 780℃, and Al-Zr, Al-Ti, and Al-Sc are added and held for 20 minutes. The temperature is then lowered to 700℃, and pure Mg and pure Zn wrapped in Al foil are added and pressed into the molten metal. After complete melting, the temperature is raised to 750℃, and 1% phosphate salt modifier is added and stirred thoroughly. Slag removal is then performed. Before slag removal, a small amount of covering agent should be evenly sprinkled onto the melt to separate the slag from the melt and reduce the amount of metal carried over. Slag removal should be smooth to prevent slag from being drawn into the melt. Slag removal should be as thorough as possible to avoid increasing the gas content of the melt due to floating slag, which could contaminate the molten metal. When the temperature drops to 730℃, add 1.5% C2Cl6, stir evenly, and let stand for 15 minutes. Once the melt temperature rises back to 750℃, remove surface slag to complete alloy refining. Insert an ultrasonic amplitude transformer preheated to 500℃ 20mm into the solution and apply ultrasonic treatment during the alloy melt solidification process. The initial temperature is 530℃, the treatment time is 120s, and the ultrasonic power is 3kW. Heat the prepared alloy ingot to 490℃-520℃ for solution treatment, followed by water quenching. The alloy material undergoes heating and holding for aging treatment, then cools to room temperature to finally obtain a heat-resistant eutectic Al-Si alloy material.

[0053] The average grain size of the aforementioned heat-resistant eutectic Al-Si alloy is 463 μm. The alloy material can withstand 800-900 thermomechanical fatigue cycles.

[0054] Example 3

[0055] This embodiment provides a heat-resistant eutectic Al-Si alloy material, which is prepared by the following method:

[0056] Weigh out industrial pure aluminum (99.99%), Al-Si master alloy, Al-50%Cu master alloy, industrial pure magnesium (99.99%), Al-10%Fe master alloy, Al-10%Ni master alloy, and Al-Zr, Al-Ti, and Al-Sc master alloys according to the mass percentages of 13%Si, 3.5%Cu, 3%Ni, 1%Mg, 0.5%Mn, 0.3%Ti, 0.2%Zn, 0.2%Fe, 0.2%Ce, 0.2%Zr, 0.2%Sc, and 77.7%Al. Pure aluminum, prepared in a specific ratio, is placed in a preheated crucible at 300-350℃ and heated to 720℃ to melt. Al-Si master alloy is then added, and the temperature is raised to 740℃. After complete melting, Al-Cu, Al-Ni, Al-Mn, and Al-Fe master alloys are added. After complete melting, the temperature is raised to 780℃, and Al-Zr, Al-Ti, and Al-Sc are added and held for 20 minutes. The temperature is then lowered to 700℃, and pure Mg and pure Zn wrapped in Al foil are added and pressed into the molten metal. After complete melting, the temperature is raised to 750℃, and 1% phosphate salt modifier is added and stirred thoroughly. Slag removal is then performed. Before slag removal, a small amount of covering agent should be evenly sprinkled onto the melt to separate the slag from the melt and reduce the amount of metal carried over. Slag removal should be smooth to prevent slag from being drawn into the melt. Slag removal should be as thorough as possible to avoid increasing the gas content of the melt due to floating slag, which could contaminate the molten metal. When the temperature drops to 730℃, add 1.5% C2Cl6, stir evenly, and let stand for 15 minutes. Once the melt temperature rises back to 750℃, remove surface slag to complete alloy refining. Insert an ultrasonic amplitude transformer preheated to 500℃ 20mm into the solution and apply ultrasonic treatment during the alloy melt solidification process. The initial temperature is 530℃, the treatment time is 120s, and the ultrasonic power is 2kW. Heat the prepared alloy ingot to 490℃-520℃ for solution treatment, followed by water quenching. The alloy material undergoes heating and holding for aging treatment, then cools to room temperature to finally obtain a heat-resistant eutectic Al-Si alloy material.

[0057] The average grain size of the aforementioned heat-resistant eutectic Al-Si alloy is 452 μm. The alloy material can withstand 600-800 thermomechanical fatigue cycles.

[0058] Comparative Example 1

[0059] This embodiment provides an Al-Si alloy material, which is prepared by weighing industrial pure aluminum (99.99%), Al-Si master alloy, Al 50% Cu master alloy, industrial pure magnesium (99.99%), Al-10% Fe master alloy, and Al 10% Ni master alloy according to the mass percentages of 13% Si, 3.5% Cu, 3% Ni, 1% Mg, 0.5% Mn, 0.3% Ti, 0.2% Zn, 0.2% Fe, and 77.7% Al. The pure aluminum prepared in a certain proportion is placed in a crucible preheated to 300-350℃ and heated to 720℃ to melt. Then, the Al-Si master alloy is added and the temperature is raised to 740℃. After complete melting, Al-Cu, Al-Ni, Al-Mn, and Al-Fe master alloys are added. After complete melting, the temperature is raised to 780℃ and held for 20 minutes. The temperature was then lowered to 700℃, and pure Mg and pure Zn wrapped in Al foil were added and pressed into the molten metal. After complete melting, the temperature was raised to 750℃, and 1% phosphate salt modifier was added and stirred evenly. Slag removal was then performed. Before slag removal, a small amount of covering agent should be evenly sprinkled onto the melt to separate the slag from the melt and reduce the amount of metal carried over. Slag removal should be smooth to prevent slag from being drawn into the melt. Slag removal should be as thorough as possible to avoid increasing the gas content of the melt due to floating slag, which would contaminate the molten metal. When the temperature dropped to 730℃, 1.5% C2Cl6 was added, stirred evenly, and allowed to stand for 15 minutes. The melt temperature was then raised back to 750℃, and surface slag was removed, completing the alloy refining process. The prepared alloy ingot was heated to 490℃-520℃ and held for solution treatment, followed by water quenching. The alloy material was then heated and held for aging treatment, and then cooled to room temperature to finally obtain the Al-Si alloy material.

[0060] The Al-Si alloy material obtained in this comparative example exhibits coarse, plate-like primary silicon and Al3(Ce,Ti) phases with sharp grain edges, a tendency to aggregate, and uneven microstructure. Furthermore, the grain size is relatively large, with an average size of 516 μm. Post-fatigue damage behavior is dominated by primary cracks and large-sized secondary cracks, which lead to crack merging. This indicates that the cracking and merging of large-sized precipitates significantly reduce the alloy's thermomechanical fatigue damage resistance, which is the main reason for its insufficient thermomechanical fatigue performance.

[0061] Comparative Example 2

[0062] This embodiment provides an Al-Si alloy material, which is prepared by weighing industrial pure aluminum (99.99%), Al-Si master alloy, Al-50%Cu master alloy, industrial pure magnesium (99.99%), Al-10%Fe master alloy, Al-10%Ni master alloy, and Al-Zr, Al-Ti-B, and Al-Sc master alloys according to the mass percentages of 13%Si, 3.5%Cu, 3%Ni, 1%Mg, 0.5%Mn, 0.3%Ti, 0.2%Zn, 0.2%Fe, 0.2%Ce, 0.2%Zr, 0.2%Sc, and 77.7%Al. Pure aluminum, prepared in a specific ratio, is placed in a preheated crucible at 300-350℃ and heated to 720℃ to melt. Al-Si master alloy is then added, and the temperature is raised to 740℃. After complete melting, Al-Cu, Al-Ni, Al-Mn, and Al-Fe master alloys are added. After complete melting, the temperature is raised to 780℃, and Al-Zr, Al-Ti, and Al-Sc are added and held for 20 minutes. The temperature is then lowered to 700℃, and pure Mg and pure Zn wrapped in Al foil are added and pressed into the molten metal. After complete melting, the temperature is raised to 750℃, and 1% phosphate salt modifier is added and stirred thoroughly. Slag removal is then performed. Before slag removal, a small amount of covering agent should be evenly sprinkled onto the melt to separate the slag from the melt and reduce the amount of metal carried over. Slag removal should be smooth to prevent slag from being drawn into the melt. Slag removal should be as thorough as possible to avoid increasing the gas content of the melt due to floating slag, which could contaminate the molten metal. When the temperature drops to 730℃, add 1.5% C2Cl6, stir evenly, and let stand for 15 minutes. Once the melt temperature rises back to 750℃, remove surface slag to complete alloy refining. Heat the prepared alloy ingot to 490℃-520℃ for solution treatment, then water-quench. The alloy material undergoes heating and holding for aging treatment, followed by cooling to room temperature to finally obtain the Al-Si alloy material.

[0063] Although the addition of a certain amount of Sc and Zr alloys improved the high-temperature strength of the alloy, it had no significant effect on the primary silicon. At this point, the material achieved 400-500 thermomechanical fatigue cycles.

[0064] Comparative Example 3

[0065] This embodiment provides an Al-Si alloy material, which is prepared by weighing industrial pure aluminum (99.99%), Al-Si master alloy, Al-50% Cu master alloy, industrial pure magnesium (99.99%), Al-10% Fe master alloy, and Al-10% Ni master alloy according to the mass percentages of 13% Si, 3.5% Cu, 3% Ni, 1% Mg, 0.5% Mn, 0.3% Ti, 0.2% Zn, 0.2% Fe, and 77.7% Al. The pure aluminum prepared in a certain proportion is placed in a crucible preheated to 300-350℃ and heated to 720℃ to melt. Then, the Al-Si master alloy is added and the temperature is raised to 740℃. After complete melting, Al-Cu, Al-Ni, Al-Mn, and Al-Fe master alloys are added. After complete melting, the temperature is raised to 780℃ and held for 20 minutes. The temperature was then lowered to 700℃, and pure Mg and pure Zn wrapped in Al foil were added and pressed into the molten metal. After complete melting, the temperature was raised to 750℃, and 1% phosphate modifier was added and stirred evenly. Slag removal was then performed. Before slag removal, a small amount of covering agent should be evenly sprinkled onto the melt to separate the slag from the melt and reduce the amount of metal carried over. Slag removal should be smooth to prevent slag from being drawn into the melt. Slag removal should be as thorough as possible to avoid increasing the gas content of the melt due to floating slag, which would contaminate the molten metal. When the temperature dropped to 730℃, 1.5% C2Cl6 was added, stirred evenly, and allowed to stand for 15 minutes. The melt temperature was then raised back to 750℃, and surface slag was removed, completing the alloy refining process. An ultrasonic amplitude transformer preheated to 500℃ was inserted 20mm into the solution, and ultrasonic treatment was applied during the solidification of the alloy melt. The initial temperature was 530℃, the treatment time was 60s, and the ultrasonic power was 1kW. The prepared alloy ingot was heated to 490℃-520℃ for solution treatment, followed by water quenching. The alloy material was then heated and held for aging treatment, and then cooled to room temperature to finally obtain the Al-Si alloy material.

[0066] At this point, the thermomechanical fatigue cycle count of the material reaches 400-500 cycles, and the improvement is still not significant.

[0067] The embodiments described in this application are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A heat-resistant eutectic Al-Si alloy material, characterized in that, Strengthening elements Cu, Mg, and Ni, and microalloying elements Ti, Sc, and Zr are added to a eutectic Al-Si alloy. The resulting alloy is obtained by ultrasonic treatment during solidification. Its composition, calculated as a percentage by mass, is as follows: Si 12%-13%, Cu 3-3.5%, Ni 2.5-3%, Mg 0.5-1%, Mn 0.3-0.5%, Zn 0.2%, Fe 0.2%, Ce 0.2%, Ti 0.2%-0.3%, Zr 0.2%, Sc 0.2%, with the balance being... Al; the ultrasonic treatment power is 1.5~3kw, the treatment time is 60~120s, and the ultrasonic field treatment temperature is 520-560℃; the alloy material comprises micron-sized precipitates, θ-Al2Cu nano-precipitates, and Al3 (Sc, Zr) reinforcing phases; wherein, the mass percentage of the micron-sized precipitates in the alloy is 30%-60%, the mass percentage of the θ-Al2Cu nano-precipitates in the alloy is 40%-70%, and the mass percentage of the Al3 (Sc, Zr) reinforcing phases in the alloy is 1%-10%.

2. The heat-resistant eutectic Al-Si alloy material according to claim 1, characterized in that, The micron-sized precipitated phase is one or more of AlMnSi, AlFeMn, AlFeMnSi, Mg2Si, AlCuNi, AlTiCe, and AlFeMnN.

3. A method for preparing a heat-resistant eutectic Al-Si alloy material as described in claim 1 or 2, characterized in that, include Melting: Pure aluminum is placed in a crucible preheated to the first preset temperature and heated until it melts. Then, Al-Si master alloy is added and the temperature is raised to the second preset temperature to melt the master alloy completely. Then, master alloys Al-Cu, Al-Ni, Al-Mn, and Al-Fe are added. After they are completely melted, the temperature is raised to the third preset temperature and master alloys Al-Zr, Al-Ti, and Al-Sc are added and held at the third preset temperature. Then, the temperature is lowered to the fourth preset temperature, and pure Mg and pure Zn wrapped in Al foil are added and pressed into the molten metal. After they are completely melted, the temperature is raised to the fifth preset temperature, and a modifier is added to obtain the melt. Refining: After the above melt cools down to the sixth preset temperature, add the degassing agent, stir evenly and let stand. When the melt temperature rises back to the fifth preset temperature, remove the surface slag to complete the alloy refining. Ultrasonic treatment: The preheated ultrasonic amplitude transformer is inserted into the refined melt. During the solidification process of the melt, an ultrasonic field is applied to the alloy for ultrasonic treatment. The ultrasonic treatment temperature is 520-560℃, the treatment time is 60-120s, and the applied power is 1.5kW-3kW to obtain an alloy ingot. Water-cooled quenching: The above alloy ingot is heated to the seventh preset temperature and held for solution treatment, then water-cooled quenching, and then cooled after holding to obtain heat-resistant eutectic Al-Si alloy material.

4. The preparation method according to claim 3, characterized in that, The first preset temperature is 300-350℃, the second preset temperature is 735-745℃; the third preset temperature is 770-790℃, the fourth preset temperature is 690-710℃, the fifth preset temperature is 745-755℃; the sixth preset temperature is 725-735℃; and the seventh preset temperature is 490℃-520℃.

5. The preparation method according to claim 3, characterized in that, The modifier is a phosphate modifier, and its addition amount is 0.6-1.5% of the total mass of the alloy.

6. The preparation method according to claim 3, characterized in that, The degassing agent is C2Cl6, and its addition amount is 1.2-1.8% of the alloy mass.

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