Preparation method of hypoeutectic high-strength heat-resistant aluminum-silicon alloy

Abstract

The invention discloses a preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy, and relates to a preparation method of a high-strength heat-resistant aluminum-silicon alloy. The invention aims to solve the technical problem that the mechanical property, especially the mechanical property at the high temperature of 350 DEG C, of the existing cast hypoeutectic aluminum-silicon alloy is poor. A basic framework of the material is formed by a hypoeutectic Ai-Si component, and degassing and deslagging are performed through a multi-stage smelting process, mechanical stirring, an ultrasonic field, a temperature field and an argon field; the extrusion casting process is adopted to determine and improve the material basic performance, and the material performance can be further strengthened through the heat treatment process; and fine grain strengthening, solid solution strengthening, second phase strengthening and dislocation strengthening ensure excellent mechanical properties of the material at room temperature and high temperature. The room-temperature performance of the hypoeutectic high-strength heat-resistant aluminum-silicon alloy provided by the invention can reach 395 MPa, the high-temperature performance at 350 DEG C can reach 100-118 MPa, and the hypoeutectic high-strength heat-resistant aluminum-silicon alloy has a relatively good application prospect.

Description

Technical Field

[0001] The present invention relates to a preparation method of a high-strength heat-resistant aluminum-silicon alloy. Background Art

[0002] Traditional steel heat-resistant components have a large density, which does not meet the requirements of energy conservation, emission reduction and lightweight. High-strength heat-resistant aluminum alloys have a stable microstructure and excellent high-temperature mechanical properties, and are widely used in the production and manufacturing of key components such as aerospace, automotive manufacturing, and weaponry. Existing components such as pistons and generators must maintain a certain strength at 300 °C and ensure their stability. Traditional heat-resistant aluminum alloys contain elements such as Si, Cu, and Mg, but their precipitation strengthening phases Mg2Si, Al2Cu, and Al2MgCu are extremely prone to coarsening when the temperature is higher than 180 - 200 °C, seriously reducing the mechanical properties of the material. Currently, the mechanical properties of cast hypoeutectic aluminum-silicon alloys, especially the high-temperature mechanical properties at 350 °C, are limited. Summary of the Invention

[0003] The present invention aims to solve the technical problem of the poor mechanical properties of currently cast hypoeutectic aluminum-silicon alloys, especially the poor high-temperature mechanical properties at 350 °C, and provides a preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy.

[0004] The preparation method of the hypoeutectic high-strength heat-resistant aluminum-silicon alloy of the present invention is carried out according to the following steps:

[0005] 1. Weigh pure aluminum and a plurality of master alloys according to the mass fractions of each metal element in the aluminum-silicon alloy;

[0006] The mass fractions of each metal element in the aluminum-silicon alloy are as follows: aluminum is 82% - 87%, silicon is 5% - 8%, copper is 2% - 6%, nickel is 0.5% - 2%, titanium is 0.05% - 0.5%, strontium is 0.05% - 0.1%, manganese is 0 - 1%, magnesium is 0 - 1%, gadolinium is 0 - 0.5%, ytterbium is 0 - 0.5%, zirconium is 0 - 0.5%;

[0007] In the composition of each element of the material of the present invention, except for the matrix elements of the aluminum alloy, the content of other alloy elements also needs to be strictly controlled. On the one hand, a small content of alloy elements results in insufficient skeleton strength of the material matrix; on the other hand, a large content of alloy elements will form coarse second phases, which are prone to form brittle regions. The transition metal elements Ni, Mn, Ti, and Zr selected in the present invention have a slow diffusion rate during the solidification of the aluminum alloy and can have better high-temperature stability in a high-temperature environment. Alloy elements such as Al7Cu4Ni, Al3Ni, and Al3Zr have a slow growth rate and good deformation resistance in the room-temperature and high-temperature service environments.

[0008] Preferably, the mass ratio of manganese to magnesium elements is 1:1 to control the size of the Alpha phase (Al6SiMnNiCu) and the size and proportion of the Mg2Si and Q phase (Al5Cu2Mg8Si6);

[0009] In the present invention, gadolinium, ytterbium, and zirconium elements are selectively added in a mass ratio of 1:1:1 to control the effective precipitation of Al3Zr(Gd, Yb) with L12, D0 22 and D0 23 structures. These phases have excellent high-temperature mechanical potential. At the same time, the solubility of these phases in aluminum alloys is limited. In order to better control their uniform and dispersed precipitation, their addition amounts should be strictly controlled to avoid abnormal growth of related phases and reduce the mechanical properties of the material;

[0010] In the present invention, the addition amounts of Sr and Ti elements are strictly controlled to achieve better modification and refinement of the alloy during the melting process and avoid the "poisoning" phenomenon caused by inappropriate contents;

[0011] The eutectic Si, AlCuNi (Al7Cu4Ni and Al3CuNi), Alpha (Al6MnSiCuNi), Q (Al5Cu2Mg8Si6), Mg2Si, and Al2CuMg precipitation phases at the micron scale and the eutectic Si, AlCuNi (Al7Cu4Ni and Al3CuNi), Alpha (Al6MnSiCuNi), Q (Al5Cu2Mg8Si6), Mg2Si, Al2CuMg, and Al3Zr(Gd, Yb) precipitation phases at the nanoscale and others synergistically improve the deformation resistance of the material through different scales;

[0012] II. Place the pure aluminum and master alloy weighed in Step I in a drying furnace for drying;

[0013] III. Place the graphite crucible in a resistance furnace for heating, and then coat the inner part of the crucible with a zinc oxide solution with a mass fraction of 20%;

[0014] IV. Place the pure aluminum weighed in Step I in the crucible of Step III, and then heat it up and melt it in the resistance furnace;

[0015] V. After the pure aluminum melts, add all the master alloy weighed in Step I, melt it at a high temperature and keep it warm;

[0016] VI. Stir with a graphite rod, and then simultaneously carry out melt purification in an argon gas field and an ultrasonic field;

[0017] VII. Cast the above molten aluminum alloy into an ingot by squeeze casting, and then carry out heat treatment to obtain a hypoeutectic high-strength heat-resistant aluminum-silicon alloy;

[0018] The heat treatment process is: multi-stage solution treatment + water quenching + aging + air cooling.

[0019] The present invention adopts the squeeze casting process, which can further improve the mechanical properties of the material at room temperature and 350 °C compared with gravity casting. A large number of stacking faults and dislocations can be formed during the forming process of squeeze casting. Combined with multi-scale second phases and nano-precipitates, it can better improve the deformation resistance of the material.

[0020] Through the microalloying of different alloying elements and the squeeze casting process in the present invention, dislocations, second phases, and nano-scale precipitates interact with each other. During the deformation process, the movement of dislocations stacks at grain boundaries and precipitate phases, significantly improving the mechanical properties of the material.

[0021] The present invention focuses on controlling the composition of the material. In addition to adding traditional alloying elements such as Si, Cu, and Mg, slow-diffusion elements of transition metals such as Ni, Mn, Ti, Zr, and rare earth elements such as Gd and Yb are also added. The addition of rare earth elements and transition elements can further improve the high-temperature mechanical properties of the material. By controlling the material composition, forming method, and heat treatment process, while ensuring the room-temperature mechanical properties of the material, the high-temperature properties of the material are improved. Its strengthening methods are: fine grain strengthening, dislocation strengthening, solid solution strengthening, second phase strengthening, etc. The squeeze casting and appropriate heat treatment process are adopted to further exert the room-temperature and high-temperature mechanical potential of the material, ensuring that the material can maintain high parameter indexes in both room-temperature and high-temperature environments.

[0022] The present invention uses a hypoeutectic Al-Si composition to form the basic framework of the material. Through multi-stage melting process, mechanical stirring, ultrasonic field, temperature field, and argon gas field for degassing and slag removal; the squeeze casting process is adopted to determine and improve the basic properties of the material, and the material properties can be further strengthened through the heat treatment process; fine grain strengthening, solid solution strengthening, second phase strengthening, and dislocation strengthening ensure excellent mechanical properties of the material at room temperature and high temperature. The room-temperature properties of the hypoeutectic high-strength heat-resistant aluminum-silicon alloy provided by the present invention reach 395 MPa, and the high-temperature properties at 350 °C reach 100 MPa - 118 MPa, having good application prospects. Description of the Drawings

[0023] Figure 1 It is a graph of the mechanical property data of the ingots prepared with different material compositions and different forming methods in Test 1, Test 2, and their comparative tests at room temperature and 350 °C;

[0024] Figure 2 It is a distribution diagram of the phase composition before heat treatment and after the first heat treatment in Test 3;

[0025] Figure 3 It is the stress-strain curve of the aluminum alloy in Test 3 at 350 °C after the second heat treatment and the third heat treatment respectively. Specific Embodiment

[0026] Specific Embodiment 1: This embodiment is a preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy, and the specific steps are as follows:

[0027] I. Weigh pure aluminum and multiple master alloys according to the mass fractions of each metal element in the aluminum-silicon alloy;

[0028] The mass fractions of each metal element in the aluminum-silicon alloy are as follows: aluminum is 82% - 87%, silicon is 5% - 8%, copper is 2% - 6%, nickel is 0.5% - 2%, titanium is 0.05% - 0.5%, strontium is 0.05% - 0.1%, manganese is 0 - 1%, magnesium is 0 - 1%, gadolinium is 0 - 0.5%, ytterbium is 0 - 0.5%, zirconium is 0 - 0.5%;

[0029] II. Place the pure aluminum and master alloys weighed in step I in a drying furnace for drying;

[0030] III. Place the graphite crucible in a resistance furnace for heating, and then coat the inner part of the crucible with a zinc oxide solution with a mass fraction of 20%;

[0031] IV. Place the pure aluminum weighed in step I in the crucible of step III, and then heat it to melt in the resistance furnace;

[0032] V. After the pure aluminum melts, add all the master alloys weighed in step I, melt at high temperature and keep warm;

[0033] VI. Stir with a graphite rod, and then simultaneously carry out melt purification in an argon gas field and an ultrasonic field;

[0034] VII. Cast the above molten aluminum alloy into ingots by squeeze casting, and then carry out heat treatment to obtain a hypoeutectic high-strength heat-resistant aluminum-silicon alloy;

[0035] The heat treatment process is: multi-stage solution treatment + water quenching + aging + air cooling.

[0036] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that: the master alloys described in step I include: aluminum-silicon master alloy, with the mass proportion of silicon being 25% - 50%; aluminum-copper master alloy, with the mass proportion of copper being 25% - 50%; aluminum-nickel master alloy, with the mass proportion of nickel being 20%; aluminum-manganese master alloy, with the mass proportion of manganese being 10% - 20%; aluminum-magnesium master alloy, with the mass proportion of magnesium being 10% - 20%; aluminum-gadolinium master alloy, with the mass proportion of gadolinium being 10%; aluminum-ytterbium master alloy, with the mass proportion of ytterbium being 10%; aluminum-zirconium master alloy, with the mass proportion of zirconium being 10%; aluminum-titanium master alloy, with the mass proportion of titanium being 5%; aluminum-strontium master alloy, with the mass proportion of strontium being 10%. Others are the same as Specific Embodiment 1.

[0037] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that: in Step 2, the drying temperature is 180°C to 200°C, and the drying time is 2 h. Others are the same as Specific Embodiment 1 or 2.

[0038] Specific Embodiment 4: The difference between this embodiment and any one of Specific Embodiments 1 to 3 is that: in Step 3, the graphite crucible is placed in a resistance furnace and heated to 150°C to 180°C, and then a zinc oxide solution with a mass fraction of 20% is coated inside the crucible. Others are the same as any one of Specific Embodiments 1 to 3.

[0039] Specific Embodiment 5: The difference between this embodiment and Specific Embodiment 4 is that: in Step 4, the melting temperature of pure aluminum in the resistance furnace is 800°C to 950°C. Others are the same as Specific Embodiment 4.

[0040] Specific Embodiment 6: The difference between this embodiment and Specific Embodiment 5 is that: in Step 5, the melting temperature of the master alloy in the resistance furnace is 750 - 850°C. Others are the same as Specific Embodiment 5.

[0041] Specific Embodiment 7: The difference between this embodiment and Specific Embodiment 6 is that: in Step 6, the purification temperature of the melt is 730°C to 760°C; the graphite rod is first stirred clockwise 200 times, and then stirred counterclockwise 200 times; the argon degassing time is 100 s to 250 s, and the argon flow rate is 0.5 - 1 L / min; the ultrasonic frequency is 19 kHz to 20 kHz. Others are the same as Specific Embodiment 6.

[0042] Specific Embodiment 8: The difference between this embodiment and Specific Embodiment 7 is that: in Step 7, the squeeze casting specific pressure is 320 MPa, and the pressure holding time is 30 s. Others are the same as Specific Embodiment 7.

[0043] Specific Embodiment 9: The difference between this embodiment and Specific Embodiment 8 is that: in Step 7, the process of multi - stage solution treatment is: keep warm at 500°C to 520°C for 2 h to 4 h, and then keep warm at 400°C to 490°C for 4 h to 6 h. Others are the same as Specific Embodiment 8.

[0044] Specific Embodiment 10: The difference between this embodiment and Specific Embodiment 9 is that: in Step 7, the aging temperature is 150°C to 250°C, and the aging time is 1 h to 10 h. Others are the same as Specific Embodiment 9.

[0045] The present invention is verified by the following tests:

[0046] Test 1: This test is a preparation method of a hypoeutectic high - strength heat - resistant aluminum - silicon alloy, and specifically is carried out according to the following steps:

[0047] 1. Weigh 1828.4 g of pure aluminum (99.96%), 392 g of Al-50Si master alloy, 224 g of Al-50Cu master alloy, 280 g of Al-10Ni master alloy, 56 g of Al-5Ti master alloy and 5.6 g of Al-10Sr master alloy;

[0048] 2. Place the pure aluminum and master alloys weighed in step 1 in a drying oven at 200 °C and dry for 2 h;

[0049] 3. Place the graphite crucible in an electric resistance furnace and heat it to 180 °C, then coat the inner part of the crucible with a zinc oxide solution with a mass fraction of 20%;

[0050] 4. Raise the temperature of the electric resistance furnace to 500 °C, place the pure aluminum weighed in step 1 in the crucible in step 3, then raise the temperature in the electric resistance furnace to 800 °C. After the pure aluminum melts, keep it warm for 20 min;

[0051] 5. Add the Al-50Si master alloy, Al-50Cu master alloy and Al-10Ni master alloy weighed in step 1 into the graphite crucible containing the molten aluminum in step 4, adjust the temperature to 780 °C. After the master alloys melt, adjust the temperature to 760 °C and keep it warm for 20 min; then add the Al-10Sr master alloy and Al-5Ti master alloy into the molten alloy, and keep it warm at 750 °C for 20 min;

[0052] 6. Stir with a graphite rod, stir clockwise 200 times first, then stir counterclockwise 200 times to avoid gas entrapment; then immerse the titanium alloy head of the ultrasonic device 15 cm into the aluminum alloy solution. At this time, the holding temperature is 750 °C, and argon is introduced into the aluminum alloy solution for degassing for 120 s at a flow rate of 1 L / min; at the same time, turn on the ultrasonic device with an ultrasonic frequency of 19.5 kHz, and turn off the ultrasonic device and stop introducing argon when the time reaches 120 s; after degassing, remove the impurities and scum floating on the surface of the aluminum liquid with a steel spoon coated with zinc oxide;

[0053] 7. Set the temperature of the electric resistance furnace at 730 °C and keep it warm for 30 min, raise the temperature of the squeeze casting die to 200 °C, then carry out casting. The squeeze casting specific pressure is 320 MPa and the pressure holding time is 30 s. Transfer the squeeze casting ingot to room temperature water for water quenching; the mass fractions of each metal element in the aluminum alloy melted this time are: Al - 87.8%, Si - 7%, Cu - 4%, Ni - 1%, Ti - 0.1%, Sr - 0.02%. The room temperature performance of the squeeze casting ingot is 237 MPa, and the high temperature performance at 350 °C is 64 MPa.

[0054] Experiment 2: The difference between this experiment and Experiment 1 is as follows: In step 1, 1688.4 g of pure aluminum (99.96%), 392 g of Al-50Si master alloy, 224 g of Al-50Cu master alloy, 280 g of Al-10Ni master alloy, 56 g of Al-5Ti master alloy, 5.6 g of Al-10Sr master alloy, 70 g of Al-20Mn master alloy, and 70 g of Al-20Mg master alloy were weighed;

[0055] The mass fractions of the respective metal elements in the aluminum alloy melted this time were Al-87.8%, Si-7%, Cu-4%, Ni-1%, Ti-0.1%, Sr-0.02%, Mg-0.5%, Mn-0.5%. The room temperature properties of the squeeze-cast ingot in step 7 were 270 MPa, and the high temperature properties at 350 °C were 101 MPa.

[0056] Comparative tests were conducted on Experiment 1 and Experiment 2 respectively. The difference was that gravity casting was used instead of squeeze casting in step 7, and the others were the same as Experiment 1 and Experiment 2.

[0057] Figure 1 The figure shows the mechanical property data graphs of the ingots prepared with different material compositions and different forming methods at room temperature and 350 °C in the above experiments. GC in the figure is gravity casting, and SC is squeeze casting. The abscissa is the sample number. The 3rd sample corresponds to Experiment 1, and the 4th sample corresponds to Experiment 2. It can be seen that compared with gravity casting GC, squeeze casting SC can better exert the mechanical properties of the material at room temperature and 350 °C. After using squeeze casting and adopting microalloying of manganese and magnesium (corresponding to Experiment 2), the room temperature mechanical properties of the material reached approximately 275 MPa (the 4th sample), and the high temperature properties at 350 °C reached approximately 100 MPa (the 8th sample).

[0058] Experiment 3: The difference between this experiment and Experiment 1 is as follows: In step 1, 1049.4 g of pure aluminum (99.96%), 252 g of Al-50Si master alloy, 144 g of Al-50Cu master alloy, 180 g of Al-10Ni master alloy, 36 g of Al-5Ti master alloy, 3.6 g of Al-10Sr master alloy, 45 g of Al-20Mn master alloy, 45 g of Al-20Mg master alloy, 18 g of Al-10Zr master alloy, 18 g of Al-10Gd master alloy, and 18 g of Al-10Yb master alloy were weighed;

[0059] The mass fractions of the respective metal elements in the aluminum alloy melted this time are Al - 87.8%, Si - 7%, Cu - 4%, Ni - 1%, Ti - 0.1%, Sr - 0.02%, Mg - 0.5%, Mn - 0.5%, Zr - 0.1%, Gd - 0.1%, Yb - 0.1%. The room-temperature properties of the squeeze casting in Step 7 are 290 MPa, and the high-temperature properties at 350 °C are 106 MPa.

[0060] The aluminum alloy ingot obtained in Experiment 3 was subjected to the first heat treatment. The heat treatment process was as follows: First, solution treatment was carried out at a solution temperature of 480 °C for 8 h, followed by immediate water quenching; then aging treatment was carried out at an aging temperature of 180 °C for 8 h, followed by immediate air cooling. Figure 2 It is the phase composition distribution diagram before the heat treatment in Experiment 3 and after the first heat treatment. It can be seen that the sizes of the Si-containing phase and the precipitated phase are significantly reduced after the heat treatment.

[0061] The aluminum alloy ingot obtained in Experiment 3 was subjected to the second heat treatment. The heat treatment process was as follows: First, solution treatment was carried out at a solution temperature of 480 °C for 4 h, followed by immediate water quenching; then aging treatment was carried out at an aging temperature of 200 °C for 8 h, followed by immediate air cooling.

[0062] The aluminum alloy ingot obtained in Experiment 3 was subjected to the third heat treatment (multi-stage solution treatment). The heat treatment process was as follows: First, solution treatment was carried out at 500 °C for 2 h, then at 480 °C for 4 h, followed by water quenching; then aging treatment was carried out at 180 °C for 6 h, and finally air cooling. Its room-temperature mechanical properties are 380 MPa, and its high-temperature mechanical properties at 350 °C are 115 MPa.

[0063] Figure 3 It is the stress-strain curves of the aluminum alloy in Experiment 3 at 350 °C after the second heat treatment and the third heat treatment respectively. The black line corresponds to the second heat treatment, and the red line corresponds to the third heat treatment. It can be seen that the performance is better after the multi-stage solution treatment of the third heat treatment.

[0064] The room-temperature mechanical properties of traditional aluminum alloys are 270 MPa, and the high-temperature mechanical properties at 350 °C are 90 MPa. The room-temperature mechanical properties of the hypoeutectic high-strength heat-resistant aluminum-silicon alloy prepared by the present invention are 395 MPa, and the high-temperature mechanical properties at 350 °C are 118 MPa, with increases of 46.3% and 31% respectively.

Claims

1. A preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy, characterized in that The preparation method of hypoeutectic high-strength heat-resistant aluminum-silicon alloy is carried out according to the following steps: I. Weigh pure aluminum and multiple intermediate alloys respectively according to the mass fractions of each metal element in the aluminum-silicon alloy; The mass fractions of each metal element in the aluminum-silicon alloy are as follows: aluminum is 82% - 87%, silicon is 5% - 8%, copper is 2% - 6%, nickel is 0.5% - 2%, titanium is 0.05% - 0.5%, strontium is 0.05% - 0.1%, manganese is 0 - 1%, magnesium is 0 - 1%, gadolinium is 0 - 0.5%, ytterbium is 0 - 0.5%, zirconium is 0 - 0.5%; II. Place the pure aluminum and intermediate alloys weighed in step I in a drying furnace for drying; III. Place the graphite crucible in a resistance furnace for heating, and then coat the inner part of the crucible with a zinc oxide solution with a mass fraction of 20%; IV. Place the pure aluminum weighed in step I in the crucible of step III, and then heat it up to melt in the resistance furnace; V. After the pure aluminum melts, add all the intermediate alloys weighed in step I, melt at high temperature and keep warm; VI. Stir with a graphite rod, and then purify the melt simultaneously in an argon gas field and an ultrasonic field; VII. Cast the above molten aluminum alloy into ingots by squeeze casting, and then carry out heat treatment to obtain hypoeutectic high-strength heat-resistant aluminum-silicon alloy; The heat treatment process is: multi-stage solution treatment + water quenching + aging + air cooling.

2. The preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy according to claim 1, characterized in that The intermediate alloys mentioned in step I include: aluminum-silicon intermediate alloy, with the mass proportion of silicon being 25% - 50%; aluminum-copper intermediate alloy, with the mass proportion of copper being 25% - 50%; aluminum-nickel intermediate alloy, with the mass proportion of nickel being 20%; aluminum-manganese intermediate alloy, with the mass proportion of manganese being 10% - 20%; aluminum-magnesium intermediate alloy, with the mass proportion of magnesium being 10% - 20%; aluminum-gadolinium intermediate alloy, with the mass proportion of gadolinium being 10%; aluminum-ytterbium intermediate alloy, with the mass proportion of ytterbium being 10%; aluminum-zirconium intermediate alloy, with the mass proportion of zirconium being 10%; aluminum-titanium intermediate alloy, with the mass proportion of titanium being 5%; aluminum-strontium intermediate alloy, with the mass proportion of strontium being 10%.

3. The preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy according to claim 1, characterized in that The drying temperature in step II is 180°C - 200°C, and the drying time is 2h.

4. The preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy according to claim 1, characterized in that In step III, place the graphite crucible in a resistance furnace for heating at 150°C - 180°C, and then coat the inner part of the crucible with a zinc oxide solution with a mass fraction of 20%.

5. The preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy according to claim 1, characterized in that The melting temperature of pure aluminum in step IV in the resistance furnace is 800°C - 950°C.

6. The preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy according to claim 1, characterized in that The melting temperature of the intermediate alloys in step V in the resistance furnace is 750 - 850°C.

7. The preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy according to claim 1, characterized in that The purification temperature of the melt in step VI is 730°C - 760°C; the graphite rod stirs 200 times clockwise first, and then 200 times counterclockwise; the argon degassing time is 100s - 250s, and the argon flow rate is 0.5 - 1L / min; the ultrasonic frequency is 19kHz - 20kHz.

8. The preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy according to claim 1, characterized in that The squeeze casting specific pressure in step VII is 320MPa, and the pressure holding time is 30s.

9. The preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy according to claim 1, characterized in that The process of the multi-stage solution treatment mentioned in step VII is: keep warm at 500°C - 520°C for 2h - 4h, and then keep warm at 400°C - 490°C for 4h - 6h.

10. The preparation method of a hypoeutectic high-strength heat-resistant aluminum-silicon alloy according to claim 1, characterized in that The aging temperature mentioned in step VII is 150°C - 250°C, and the aging time is 1h - 10h.

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