Aluminum-silicon alloy sr modification method and system based on multi-mode synergistic regulation

Abstract

The present application relates to a kind of Sr modification method and system based on multi-mode synergistic regulation of aluminum-silicon alloy, solve the melt aspiration tendency big, modification gestation period long, eutectic silicon limited refining effect problem existing in present Sr modification.It is related to the method includes: after aluminum-silicon alloy raw material is melted, refining, Al-Sr intermediate alloy is added to carry out modification treatment;Alloy liquid is poured into mould, when solidification enters eutectic reaction temperature interval, simultaneously start high-frequency mechanical vibration and at least one controlled thermal cycle, wherein the frequency of high-frequency mechanical vibration is 20-100Hz, thermal cycle includes the temperature of alloy heating area is recovered to higher than eutectic temperature but lower than liquidus temperature in 5-30 seconds, after heat preservation, continue to cool;After complete solidification, obtain aluminum-silicon alloy casting.The present application realizes the nanometer refinement of eutectic silicon phase by the synergistic effect of vibration and thermal cycle, while effectively inhibiting aspiration tendency, significantly improve the mechanical properties of alloy.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy melting and solidification control technology, and in particular to a method and system for Sr modification of aluminum-silicon alloys based on multi-mode synergistic regulation. Background Technology

[0002] Aluminum-silicon alloys are widely used in lightweight manufacturing fields such as aerospace and automotive due to their excellent casting and mechanical properties. Strontium (Sr), as a commonly used long-lasting modifier in aluminum-silicon alloys, can effectively improve the morphology and distribution of eutectic silicon, thereby enhancing the overall performance of the alloy.

[0003] Existing Sr modification techniques for aluminum-silicon alloys mainly refine the eutectic silicon by adding Al-Sr master alloys during the smelting process. For example, patent CN108796317A discloses a semi-solid extrusion cast aluminum alloy and its preparation method, which involves subjecting the melt to 50Hz mechanical vibration treatment in the temperature range of 650-680℃ to obtain a semi-solid slurry. Patent CN109822079A proposes a metal melt treatment method combining power ultrasound and mechanical vibration, applying ultrasound and mechanical vibration simultaneously under heat preservation conditions to improve the microstructure.

[0004] However, the above technical solutions still fail to accurately match the nucleation and growth stages of eutectic silicon during the solidification process of aluminum-silicon alloys, making it difficult to achieve nanoscale refinement of eutectic silicon under conventional casting conditions. At the same time, existing methods lack targeted solutions to problems such as increased melt gas absorption tendency and long modification incubation period caused by Sr modification, resulting in easy porosity defects in castings and limited improvement in mechanical properties. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a method and system for Sr modification of aluminum-silicon alloys based on multi-mode synergistic regulation, so as to solve at least one of the technical problems in the prior art, such as large melt gas absorption tendency, long modification incubation period, and limited eutectic silicon refinement effect.

[0006] On one hand, embodiments of the present invention provide a method for Sr modification of Al-Si alloys based on multi-mode synergistic regulation, comprising the following steps: S1. After melting the Al-Si alloy raw material, it is refined and degassed. S2. Add Al-Sr master alloy to the refined melt, stir evenly and keep warm; S3. Pour the alloy liquid treated in S2 into the mold. When the alloy solidifies and enters the eutectic reaction temperature range, simultaneously start high-frequency mechanical vibration and at least one controlled thermal cycle. The frequency of the high-frequency mechanical vibration is 20-100 Hz. The controlled thermal cycle includes raising the temperature of the alloy heating area to a temperature higher than the eutectic temperature but lower than the liquidus temperature within 5-30 seconds, holding it at that temperature, and then continuing to cool it. S4. After the alloy has completely solidified, the Al-Si alloy casting is obtained.

[0007] Furthermore, the refining and degassing temperature in S1 is 720-760℃.

[0008] Furthermore, the amount of Sr added in S2 is 0.01%-0.05% of the total mass of the melt.

[0009] Furthermore, the high-frequency mechanical vibration described in S3 is achieved by a vibrator installed on the mold, and the vibration mode is selected from continuous vibration or pulse vibration; the controlled thermal cycle is achieved by a programmable movable induction heating coil or a focused infrared radiation device.

[0010] Furthermore, the acceleration of the high-frequency mechanical vibration described in S3 is 1-5 times the acceleration due to gravity.

[0011] Furthermore, the controlled thermal cycle described in S3 has a temperature rise range of 5-30°C, a holding time of 5-60 seconds, and a cycle count of 2-4 times; the temperature rise range refers to the difference in holding temperature between two adjacent thermal cycles.

[0012] Furthermore, the temperature rise in each thermal cycle in S3 decreases progressively.

[0013] On the other hand, embodiments of the present invention propose a system for implementing the above-described method, comprising: Smelting and refining unit; The mold unit is equipped with a vibrator and a temperature sensor. The heat cycle generating unit is used to locally heat the alloy inside the mold; The intelligent control unit receives signals from the temperature sensor in real time and dynamically adjusts the start-up, shutdown, power, and operating sequence of the exciter and the thermal cycling unit accordingly.

[0014] Furthermore, this embodiment of the invention also proposes an aluminum-silicon alloy casting prepared by the above-described method, wherein the average size of the eutectic silicon phase of the aluminum-silicon alloy casting is ≤120nm, the pinhole degree of the casting is less than grade 1, the room temperature tensile strength of the alloy is above 400MPa, and the elongation is above 10%.

[0015] Furthermore, the average size of the eutectic silicon phase is 100-150 nm.

[0016] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1) By introducing controlled thermal cycling while simultaneously engaging high-frequency mechanical vibration, a dual refining mechanism of "physical fragmentation + thermal melting" is generated within the eutectic reaction temperature range. The aluminum-silicon alloy treated by the method of this invention can have its average eutectic silicon phase size refined to below 120 nm, which is far superior to the micron-scale structure of conventional Sr modification processes, significantly improving the strength-ductility balance of the alloy.

[0017] 2) The acoustic flow effect generated by high-frequency vibration accelerates the merging and rising of bubbles in the melt. Combined with the disturbance of the solidification front by thermal cycling, it creates a dynamic solidification environment unfavorable to gas precipitation and retention. The pinhole degree of the castings produced by this invention is less than grade 1, and no obvious pores are observed in the low magnification structure, solving the problem that traditional Sr modification processes easily lead to gas absorption in the melt, resulting in pinhole defects in the castings.

[0018] 3) High-frequency vibration promotes rapid and uniform diffusion of Sr elements, while thermal cycling breaks the continuous structure of the grown eutectic silicon. The synergistic effect of these two factors allows the modification effect to manifest rapidly during solidification. The resulting castings have a room temperature tensile strength of not less than 400 MPa, for example, 418~425 MPa, and an elongation of not less than 10%, for example, 11%~12%, achieving a simultaneous improvement in strength and plasticity. This meets the application requirements of high-performance aluminum-silicon alloy castings in aerospace, automotive, and other fields.

[0019] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0020] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0021] Figure 1 This is a flowchart illustrating the implementation of multi-mode collaborative processing in an embodiment of the present invention.

[0022] Figure 2 This is a transmission electron microscope (TEM) image of the eutectic silicon phase of the aluminum-silicon alloy casting obtained in Example 1 of the present invention.

[0023] Figure 3 The image shows the eutectic silicon phase metallographic structure of the aluminum-silicon alloy casting obtained in Comparative Example 1.

[0024] Figure 4The image shows the eutectic silicon phase metallographic structure of the aluminum-silicon alloy casting obtained in Comparative Example 2.

[0025] Figure 5 This is a low-magnification microstructure photograph of the aluminum-silicon alloy casting obtained in Example 1 of the present invention.

[0026] Figure 6 This is a low-magnification microstructure photograph of the aluminum-silicon alloy casting obtained in Comparative Example 1.

[0027] Figure 7 This is a schematic diagram of the structure of an aluminum-silicon alloy Sr modification system based on multi-mode synergistic regulation, provided in an embodiment of the present invention.

[0028] Figure label: 1. Melting and refining unit; 2. Mold unit; 3. Vibrator; 4. Temperature sensor; 5. Heat circulation generating unit; 6. Intelligent control unit; 7. Induction heating coil; 8. Focused infrared radiation device. Detailed Implementation

[0029] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0030] Aluminum-silicon alloys are widely used in aerospace, automotive, and other industries due to their excellent casting and mechanical properties. Strontium (Sr), as the most commonly used long-lasting modifier for aluminum-silicon alloys, can effectively improve the morphology of eutectic silicon. However, its application faces technical bottlenecks such as increased melt gas absorption tendency, long modification incubation period, and difficulty in achieving deep nanoscale microstructure. To address these issues, this invention proposes a multi-mode synergistic regulation method and system for Sr modification of aluminum-silicon alloys. Through the synchronous synergistic effect of high-frequency mechanical vibration and controlled thermal cycling, a dual refinement mechanism of "physical fragmentation + thermal melting" is achieved at the critical stages of eutectic nucleation and growth, while effectively suppressing gas absorption tendency and significantly improving alloy performance.

[0031] On one hand, a specific embodiment of the present invention discloses a method for Sr modification of aluminum-silicon alloys based on multi-mode synergistic regulation, such as... Figure 1 As shown, it includes the following steps: S1. After melting the aluminum-silicon alloy raw material, it is refined and degassed. S2. Add aluminum-strontium master alloy to the refined melt, stir evenly, and then keep it at a constant temperature; S3. Pour the alloy liquid treated in S2 into the mold. When the alloy solidifies and enters the eutectic reaction temperature range (the arrival of this temperature range is identified and determined by the data collected in real time by the intelligent control unit 6 from the temperature sensor 4), simultaneously start high-frequency mechanical vibration and at least one controlled thermal cycle. The frequency of the high-frequency mechanical vibration is 20-100 Hz. The controlled thermal cycle includes raising the temperature of the alloy heating area to a temperature higher than the eutectic temperature but lower than the liquidus temperature within 5-30 seconds, holding it at that temperature, and then continuing to cool it. S4. After the alloy has completely solidified, an aluminum-silicon alloy casting is obtained.

[0032] It should be noted that the "eutectic reaction temperature range" mentioned in step S3 refers to the temperature range in which the eutectic transformation occurs during the solidification process of the aluminum-silicon alloy. For hypoeutectic aluminum-silicon alloys (such as A356), this range is usually between the liquidus temperature and the eutectic temperature. The "synchronous start-up" refers to the simultaneous application of high-frequency mechanical vibration and controlled thermal cycling in time, rather than their sequential application.

[0033] In practice, the aluminum-silicon alloy raw material is first heated in a melting furnace to a certain temperature above the liquidus (720-760℃) to completely melt it. Then, it undergoes refining and degassing to remove gases and inclusions from the melt. After refining, an aluminum-strontium master alloy is added to the melt for Sr modification treatment. After stirring evenly, the mixture is held at this temperature for a certain time (30-60 minutes) to ensure the Sr element is fully dissolved and evenly distributed. The modified alloy liquid is poured into a mold preheated to a certain temperature. While the alloy liquid cools to the eutectic reaction temperature range, a high-frequency mechanical vibration device and a thermal circulation generator are simultaneously activated. The high-frequency mechanical vibration is transmitted to the mold and the internal alloy liquid through the vibrator, generating periodic disturbances; the thermal circulation unit rapidly heats the alloy inside the mold locally, causing the temperature to rise briefly before continuing to cool. After the alloy has completely solidified, it is demolded to obtain an aluminum-silicon alloy casting with a refined microstructure.

[0034] Compared with existing technologies, the method provided in this embodiment generates a dual refinement mechanism of "physical fragmentation + thermal melting" within the eutectic reaction temperature range by simultaneously applying high-frequency mechanical vibration and controlled thermal cycling. On the one hand, the dendrite fragmentation effect and acoustic flow effect generated by high-frequency vibration promote the rapid diffusion and homogenization of Sr elements, shortening the modification incubation period; on the other hand, thermal cycling causes the already grown eutectic silicon tips to remelt, breaking their continuous structure. The synergistic effect of these two factors allows the average size of the eutectic silicon phase to be refined to below 120 nm, which is far superior to the micron-scale structure of conventional Sr modification processes, significantly improving the strength-ductility matching of the alloy.

[0035] Furthermore, in S1, considering that excessively low refining and degassing temperatures will lead to increased melt viscosity and decreased refining efficiency, while excessively high temperatures will exacerbate melt oxidation and gas absorption, the refining and degassing temperature is controlled at 720-760℃, for example, 720℃, 730℃, 740℃, 750℃, and 760℃.

[0036] Furthermore, in step S2, considering that too low a strontium (Sr) addition would result in insufficient degradation, while too high a addition would not only increase costs but also potentially lead to over-degradation, forming coarse Sr-containing compounds, the strontium (Sr) addition is controlled to be 0.01%-0.05% of the total melt mass, for example, 0.01%, 0.02%, 0.025%, 0.03%, 0.04%, and 0.05% of the total melt mass.

[0037] Furthermore, the high-frequency mechanical vibration described in S3 is achieved through a vibrator mounted on the mold, with the vibration mode selected from continuous vibration or pulse vibration. Continuous vibration mode is suitable for scenarios requiring continuous disturbance to promote uniform diffusion of elements; pulse vibration mode (e.g., 50% duty cycle) can reduce energy consumption and equipment load while ensuring vibration effect. The specific selection can be based on a comprehensive consideration of factors such as alloy composition and casting wall thickness.

[0038] The controlled thermal cycle is achieved through a programmable movable induction heating coil 7 or a focused infrared radiation device 8, such as... Figure 7 As shown. The induction heating coil 7 and the focused infrared radiation device 8 are respectively arranged on the outer side / periphery of the mold unit 2. By locally and rapidly heating the outer wall of the mold or the surface of the alloy melt, the temperature of the alloy heating area is restored and maintained. Induction heating has the characteristics of fast heating speed and concentrated energy, and is suitable for scenarios that require precise local heating; the focused infrared radiation device has a simple structure and is easy to arrange, and is suitable for scenarios that require high flexibility in heating position.

[0039] Furthermore, the controlled thermal cycle involves a temperature rise of 5-30°C (e.g., 5°C, 10°C, 15°C, 20°C, 25°C, 30°C), a holding time of 5-60 seconds (e.g., 5 seconds, 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds), and 2-4 cycles (e.g., 2, 3, 4). The temperature rise refers to the height of temperature recovery in the heated area. If the temperature rise is too small, it will be difficult to effectively melt the already grown eutectic silicon tip; if the temperature rise is too large, it may lead to excessive remelting of the solidified structure, thus damaging the uniformity of the structure. The holding time is controlled within the range of 5-60 seconds to ensure sufficient thermal cycling while avoiding grain coarsening due to excessive holding time. The 2-4 cycle number allows for continuous intervention of eutectic silicon growth through multiple thermal disturbances without significantly extending the process cycle.

[0040] Furthermore, the acceleration of the high-frequency mechanical vibration described in step S3 is 1-5 times the gravitational acceleration g (e.g., 1g, 2g, 3g, 5g). Vibration acceleration reflects the intensity of the vibration. If the acceleration is too low, the resulting dendrite fragmentation and acoustic flow effects will be insufficient; if the acceleration is too high, it may lead to mold damage or molten alloy splashing. Controlling the acceleration within the range of 1-5g can achieve good microstructure refinement while ensuring equipment safety.

[0041] Furthermore, the processing window for high-frequency mechanical vibration and controlled thermal cycling in step S3 is dynamically determined and controlled by an intelligent control system based on the temperature change rate or eutectic platform characteristic points on the melt cooling curve, to ensure that the intervention occurs during the critical stages of eutectic nucleation and growth.

[0042] Aluminum-silicon alloys with different compositions, pouring temperatures, and mold temperatures exhibit varying cooling profiles during solidification. By monitoring the melt temperature in real time using temperature sensors, the intelligent control system automatically identifies the starting point of the eutectic reaction temperature range based on extracted cooling profile characteristics (such as temperature change rate, eutectic plateau temperature, or duration), and triggers vibration and thermal circulation devices at the optimal time to achieve precise matching of process parameters. This intelligent dynamic control effectively addresses the uncertainties caused by melt state fluctuations in actual production, improving process stability and repeatability.

[0043] For example, the processing window in step S3 is determined by monitoring the cooling curve of the melt in real time through a temperature sensor. When the cooling rate is lower than a preset threshold (e.g., 0.5℃ / s) for the first time, the intelligent control system determines that the melt has entered the eutectic nucleation stage and then triggers the synchronous start of high-frequency mechanical vibration and controlled thermal cycling.

[0044] Considering that different application scenarios may have different requirements for the degree of microstructure refinement, the controlled thermal cycling in step S3 can be performed 2-4 times, with the temperature rise gradually decreasing in each cycle. As the solidification process progresses, the remaining liquid phase gradually decreases, and the grown eutectic silicon framework gradually strengthens, thus reducing the intervention intensity required for subsequent thermal cycles. By gradually reducing the temperature rise, the continuous control of eutectic silicon growth by the thermal cycle is ensured, while avoiding excessive thermal intervention that could lead to microstructure coarsening.

[0045] For example, the temperature rise during the first thermal cycle is 20-30℃, the second is 10-20℃, the third is 5-10℃, and the fourth is controlled within 5℃.

[0046] On the other hand, the present invention provides a system for implementing the above-described method, such as... Figure 7 As shown, it includes: Smelting and refining unit 1; Mold unit 2 is equipped with a vibrator 3 and a temperature sensor 4; The heat cycle generating unit 5 is used for local heating of the alloy inside the mold; The intelligent control unit 6 receives the signal from the temperature sensor 4 in real time and dynamically adjusts the start-up, shutdown, power, and operating sequence of the exciter 3 and the thermal cycling unit 5 accordingly.

[0047] When the system is working: the melting and refining unit 1 completes the melting and refining degassing of the alloy; the alloy liquid after Sr modification treatment is poured into the mold unit 2; the temperature sensor 4 monitors the temperature change of the alloy in the mold in real time and transmits the signal to the intelligent control unit 6; the intelligent control unit 6 determines whether the eutectic reaction temperature range has been entered according to the preset process logic and real-time temperature data; when the triggering conditions are met, the intelligent control unit 6 simultaneously starts the vibrator 3 to generate high-frequency mechanical vibration and the thermal cycling unit 5 to locally heat the alloy; after the thermal cycling is completed, the intelligent control unit 6 controls the vibrator 3 and the thermal cycling unit 5 to stop working according to the temperature feedback; after the alloy is completely solidified, an aluminum-silicon alloy casting is obtained.

[0048] Specifically, the heat cycle generating unit 5 can be implemented using different heating methods. For example, the heat cycle generating unit 5 can be a programmable movable induction heating coil 7, which rapidly heats the alloy within the mold using electromagnetic induction; or it can be a focused infrared radiation device 8, which heats the alloy surface and subsurface layer through infrared radiation. Induction heating features fast heating speed and concentrated energy, making it suitable for scenarios requiring precise localized heating; the focused infrared radiation device has a simple structure and is easy to arrange, making it suitable for scenarios requiring high flexibility in heating position.

[0049] The aluminum-silicon alloy castings prepared by the above method have an average size of less than 120 nm for the eutectic silicon phase, a pinhole degree of less than grade 1, a room temperature tensile strength of not less than 400 MPa, and an elongation of not less than 10%.

[0050] Specifically, the pinholes are evaluated according to GB / T 10851-89 "Method for evaluating pinholes in aluminum alloy castings". Grade 1 pinholes refer to the fact that the number of pinholes per unit area in the low magnification structure of the casting is extremely small and the pore diameter is small, indicating that the casting has good density.

[0051] Furthermore, the average size of the eutectic silicon phase is 100-120 nm. Eutectic silicon phases within this size range can more effectively impede dislocation movement while avoiding stress concentration caused by excessively large particles, thus achieving a better strength-plasticity match.

[0052] The present invention will be described in more detail below through specific embodiments. These embodiments are merely descriptions of the best implementation of the invention and do not limit the scope of the invention in any way.

[0053] Example 1 This embodiment provides a method for Sr modification of aluminum-silicon alloys based on multi-mode synergistic regulation, such as... Figure 1 As shown, the specific steps are as follows: S1. Melt the A356 aluminum-silicon alloy raw material at 740℃, and then pass argon gas through it for refining and degassing. The refining temperature is 740℃.

[0054] S2. Add Al-10Sr master alloy to the refined melt so that the amount of strontium added to the melt is 0.04% of the total mass. Stir evenly and then keep warm at 740℃ for 40 minutes.

[0055] S3. Pour the alloy liquid treated in S2 into the mold. When the temperature drops to 580℃ (the eutectic reaction temperature range), simultaneously initiate high-frequency mechanical vibration and controlled thermal cycling. The high-frequency mechanical vibration is achieved through a vibrator mounted on the mold, using a continuous vibration mode with a frequency of 50 Hz and an acceleration of twice the gravitational acceleration g. The controlled thermal cycling is achieved through a programmable movable induction heating coil, undergoing two thermal cycles. Each thermal cycle begins when the alloy temperature naturally cools to 580℃, and the temperature rise in the two thermal cycles decreases progressively, specifically as follows: First thermal cycle: The temperature of the alloy heating zone is raised from 580°C to 595°C within 15 seconds (temperature increase of 15°C), held at that temperature for 20 seconds, and then cooled. Second thermal cycle: After the alloy temperature naturally cools to 580℃, the temperature of the alloy heating area is raised from 580℃ to 585℃ within 15 seconds (temperature increase of 5℃), and held at that temperature for 20 seconds.

[0056] S4. After the alloy has completely solidified, an aluminum-silicon alloy casting is obtained.

[0057] Systems for implementing the above methods include, for example, Figure 7 As shown, it includes a melting and refining unit 1; a mold unit 2, which is equipped with a vibrator 3 and a temperature sensor 4; a thermal cycling generating unit 5, which is used to locally heat the alloy in the mold; and an intelligent control unit 6, which receives the signal from the temperature sensor 4 and controls the start-up, shutdown, power and operating sequence of the vibrator 3 and the thermal cycling generating unit 5 accordingly.

[0058] Example 2 This embodiment is basically the same as Embodiment 1, except that the parameters for multi-mode collaborative processing in S3 are different. Specifically: In S3, the high-frequency mechanical vibration adopts a pulse vibration mode (50% duty cycle), with a frequency of 20 Hz and an acceleration of 1g. The controlled thermal cycle is achieved through a focused infrared radiation device, and a total of 3 thermal cycles are performed. Each thermal cycle is initiated when the alloy temperature naturally cools to 580℃, and the temperature rise rate decreases progressively with each thermal cycle. Specifically: First thermal cycle: The temperature of the alloy heating zone is raised from 580°C to 595°C within 30 seconds (temperature increase of 15°C), and held at that temperature for 60 seconds; Second thermal cycle: After the alloy temperature naturally cools to 580℃, the temperature of the alloy heating area is raised from 580℃ to 590℃ within 30 seconds (temperature increase of 10℃), and held at that temperature for 60 seconds; The third thermal cycle: After the alloy temperature naturally cools to 580℃, the temperature of the alloy heating area is raised from 580℃ to 585℃ within 30 seconds (temperature increase of 5℃), and held at that temperature for 60 seconds.

[0059] The remaining steps and parameters are the same as in Example 1, and the aluminum-silicon alloy casting is finally obtained.

[0060] Example 3 This embodiment is basically the same as Embodiment 1, except that the parameters for multi-mode collaborative processing in S3 are different. Specifically: In S3, the high-frequency mechanical vibration adopts a continuous vibration mode with a frequency of 100 Hz and an acceleration of 5g. The controlled thermal cycle is achieved through a programmable movable induction heating coil, and a total of two thermal cycles are performed. Each thermal cycle is initiated when the alloy temperature naturally cools to 580℃, and the temperature rise in the two thermal cycles decreases successively, specifically as follows: First thermal cycle: The temperature of the alloy heating zone is raised from 580°C to 592°C within 5 seconds (temperature increase of 12°C), held at that temperature for 5 seconds, and then cooled. Second thermal cycle: After the alloy temperature naturally cools to 580℃, the temperature of the alloy heating area is raised from 580℃ to 586℃ within 5 seconds (temperature increase of 6℃), and held at that temperature for 5 seconds.

[0061] The remaining steps and parameters are the same as in Example 1, and the aluminum-silicon alloy casting is finally obtained.

[0062] Comparative Example 1 This comparative example uses the traditional Sr modification method without applying any synergistic external field.

[0063] S1 and S2 are the same as in Example 1.

[0064] S3. The alloy liquid treated by S2 is poured directly into a metal mold preheated to 250°C at 740°C and allowed to cool and solidify naturally without any mechanical vibration or thermal cycling.

[0065] S4. Obtain aluminum-silicon alloy castings.

[0066] Comparative Example 2 This comparative example only applies mechanical vibration, without applying thermal cycling.

[0067] S1 and S2 are the same as in Example 1.

[0068] S3. Pour the alloy liquid treated in S2 into the mold. When the temperature drops to 580°C, apply mechanical vibration (frequency 50 Hz, acceleration 2g, continuous mode) with the same parameters as in Example 1, without performing thermal cycling treatment.

[0069] S4. Obtain aluminum-silicon alloy castings.

[0070] Comparative Example 3 This comparative example only applies thermal cycling, without applying mechanical vibration.

[0071] S1 and S2 are the same as in Example 1.

[0072] S3. Pour the alloy liquid treated in S2 into the mold. When the temperature drops to 580°C, apply only the same heat cycle treatment as in Example 1 (raise to 590°C, hold for 20 seconds, cycle twice), without applying mechanical vibration.

[0073] S4. Obtain aluminum-silicon alloy castings.

[0074] Comparative Example 4 This comparative example changes the order in which mechanical vibration and thermal cycling are applied, using a sequential application method.

[0075] S1 and S2 are the same as in Example 1.

[0076] S3. Pour the alloy liquid treated in S2 into the mold. When the temperature drops to 580°C, apply mechanical vibration with the same parameters as in Example 1. After the vibration treatment is completed and the melt temperature continues to drop to 570°C, apply thermal cycling treatment (with the same parameters as in Example 1).

[0077] S4. Obtain aluminum-silicon alloy castings.

[0078] Comparative Example 5 The number of thermal cycles in this comparative example exceeds the range defined by this invention.

[0079] S1 and S2 are the same as in Example 1.

[0080] S3. Pour the alloy liquid treated by S2 into the mold, and apply mechanical vibration and thermal cycling with the same parameters as in Example 1 at 580°C, but increase the number of thermal cycles to 6.

[0081] S4. Obtain aluminum-silicon alloy castings.

[0082] Characterization results and analysis The performance of the aluminum-silicon alloy castings prepared in Examples 1-3 and Comparative Examples 1-5 was tested, and the specific test results are shown in Table 1.

[0083] Table 1. Performance Comparison Table of Embodiments and Comparative Examples of the Invention

[0084] Figure 2 The image shows a transmission electron microscope (TEM) image of the eutectic silicon phase in the aluminum-silicon alloy casting obtained in Example 1. As can be seen from the image, the eutectic silicon phase is uniformly distributed in the form of fine particles. Figure 5 The image shows a low-magnification microstructure of the aluminum-silicon alloy casting obtained in Example 1. It can be seen that the casting has a dense microstructure and no obvious pinhole defects were found.

[0085] In contrast, the metallographic structure of the eutectic silicon phase in Comparative Example 1 ( Figure 3 The results show that the eutectic silicon is only partially spheroidized, and there is still obvious fibrous eutectic silicon with an average size of 3.2 μm, and its low-magnification microstructure ( Figure 6 The image shows obvious pinhole defects. Comparative Example 2: Metallographic structure of eutectic silicon phase (…) Figure 4 The results show that the eutectic silicon size was somewhat refined, but there were still many coarse silicon phases, with an average size of about 1.3 μm, failing to achieve nanoscale refinement. Comparative Example 3, which only applied thermal cycling, showed non-uniform eutectic silicon size, with an average size of about 800 nm and a small number of pinholes. Comparative Example 4, which used a sequential treatment method of vibration followed by thermal cycling, achieved an average eutectic silicon size of about 306 nm, which was better than the single treatment but still inferior to the simultaneous treatment example. Comparative Example 5, due to excessive thermal cycling, showed coarsening of the eutectic silicon, with irregular eutectic silicon particles and an average size of about 230 nm.

[0086] From Table 1 and Figure 2-6 It can be seen that the eutectic silicon phase of Examples 1-3 of the present invention has an average size of 110-120 nm, a tensile strength of 418-425 MPa, an elongation of 11.0%-11.8%, and a pinhole degree of less than grade 1. The eutectic silicon phase of Comparative Examples 1-5 has an average size of 230 nm-3.2 μm, a tensile strength of 312-405 MPa, and an elongation of 4.3%-9.5%. Therefore, the comprehensive mechanical properties and microstructure refinement effect of the embodiments of the present invention are significantly better than those of the comparative examples.

[0087] In summary, the method and system of this invention can significantly refine the eutectic silicon phase and reduce the pinholes in castings, resulting in aluminum-silicon alloy castings with high strength and high plasticity. This invention is applicable to the production of high-performance aluminum-silicon alloy castings in aerospace, automotive, and other industries, and can significantly improve product quality and reliability.

[0088] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for Sr modification of Al-Si alloys based on multi-mode synergistic regulation, characterized in that, Includes the following steps: S1. After melting the Al-Si alloy raw material, it is refined and degassed. S2. Add Al-Sr master alloy to the refined melt, stir evenly and keep warm; S3. Pour the alloy liquid treated in S2 into the mold. When the alloy solidifies and enters the eutectic reaction temperature range, simultaneously start high-frequency mechanical vibration and at least one controlled thermal cycle. The frequency of the high-frequency mechanical vibration is 20-100 Hz. The controlled thermal cycle includes raising the temperature of the alloy heating area to a temperature higher than the eutectic temperature but lower than the liquidus temperature within 5-30 seconds, holding it at that temperature, and then continuing to cool it. S4. After the alloy has completely solidified, the Al-Si alloy casting is obtained.

2. The method according to claim 1, characterized in that, The refining and degassing temperature in S1 is 720-760℃.

3. The method according to claim 1, characterized in that, The amount of Sr added in S2 is 0.01%-0.05% of the total mass of the melt.

4. The method according to claim 1, characterized in that, The high-frequency mechanical vibration described in S3 is achieved by a vibrator installed on the mold, and the vibration mode is selected from continuous vibration or pulse vibration; the controlled thermal cycle is achieved by a programmable movable induction heating coil or a focused infrared radiation device.

5. The method according to claim 1, characterized in that, The acceleration of the high-frequency mechanical vibration described in S3 is 1-5 times the acceleration due to gravity.

6. The method according to claim 1, characterized in that, The controlled thermal cycle described in S3 has a temperature rise range of 5-30℃, a holding time of 5-60 seconds, and a cycle count of 2-4 times; the temperature rise range refers to the difference in holding temperature between two adjacent thermal cycles.

7. The method according to claim 6, characterized in that, In S3, the temperature rise rate decreases gradually with each thermal cycle.

8. A system for implementing the method according to any one of claims 1-7, characterized in that, include: Smelting and refining unit (1); The mold unit (2) is equipped with a vibrator (3) and a temperature sensor (4). The heat cycle generating unit (5) is used to locally heat the alloy inside the mold; The intelligent control unit (6) receives the signal fed back by the temperature sensor (4) in real time, and dynamically adjusts the start-up, shutdown, power and action sequence of the exciter (3) and the heat cycle generating unit (5) accordingly.

9. An aluminum-silicon alloy casting prepared by the method according to any one of claims 1-7, characterized in that, The average size of the eutectic silicon phase in the aluminum-silicon alloy casting is ≤120nm and the pinhole degree of the casting is less than grade 1.

10. The aluminum-silicon alloy casting according to claim 9, characterized in that, The average size of the eutectic silicon phase is 100-120 nm.

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