Hypoeutectic aluminum-silicon alloy composite alterant and preparation method thereof

Abstract

The invention discloses a hypoeutectic aluminum-silicon alloy composite alterant and a preparation method thereof, and aims to solve the technical problems that thick flaky eutectic silicon and dendritic primary alpha-Al exist in an as-cast structure of a current hypoeutectic aluminum-silicon alloy composite alterant, so that the mechanical property is low, and the structure needs to be optimized through modification treatment. The main component comprises 75-85% by mass of Al; 2.5%-4.0% of Sr in parts by mass; the mass part of Ba is 0.8%-1.5%; the mass part of Ti is 1.2%-2.0%; the mass part of Nb is 0.5%-1.0%; the mass part of RE is 0.3%-0.8%; and the mass part of Y is 0.2%-0.5%. The composite alterant can promote eutectic silicon to realize shape transformation from a sheet shape to a fiber shape, the uniformity of an alloy microstructure is remarkably improved, primary alpha-Al grains are refined into isometric crystals through a multi-heterogeneous nucleation mechanism, the grain size is accurately controlled within the range of 25-35 microns, and the grain size is controlled within the range of 25-35 microns. And meanwhile, the mechanical properties of the alloy in different directions can be more balanced, and performance fluctuation caused by uneven structures is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of composite modifier technology, specifically to a hypoeutectic aluminum-silicon alloy composite modifier and its preparation method. Background Technology

[0002] Lightweight hypoeutectic Al-Si alloys are widely used in the production of automotive wheels, engine blocks, cylinder heads, and aerospace components. However, in traditionally cast hypoeutectic Al-Si alloys, the eutectic Si in the solidification structure is distributed in coarse, needle-like forms on the alloy matrix. The cutting effect of these coarse, needle-like eutectic Si on the matrix and the sharp points of the eutectic Si cause localized stress concentration under load, resulting in a significant reduction in the mechanical properties of hypoeutectic Al-Si alloys and severely limiting their application in the automotive and aerospace fields. Improving the mechanical properties of the alloy, especially its plasticity, is crucial for the industrial application of hypoeutectic Al-Si alloys. Currently, the industrial application of hypoeutectic Al-Si alloys utilizes chemical modification methods, which require no equipment investment or modification, and are widely used due to their low cost and good modification effects.

[0003] In the process of developing this invention, the inventors discovered that at least the following problems remain unresolved in the existing technology: Hypoeutectic aluminum-silicon alloys are widely used in automobile wheel hubs, engine blocks, electronic housings, and other fields due to their low density, good casting performance, and low cost. However, their as-cast microstructure contains coarse lamellar eutectic silicon and dendritic primary α-Al, resulting in low mechanical properties, requiring modification treatment to optimize the microstructure. Therefore, a new technical solution needs to be designed to address these issues. Summary of the Invention

[0004] The purpose of this invention is to provide a hypoeutectic aluminum-silicon alloy composite modifier and its preparation method, in order to solve the technical problem that the current hypoeutectic aluminum-silicon alloy composite modifier has coarse lamellar eutectic silicon and dendritic primary α-Al in its as-cast microstructure, resulting in low mechanical properties, and requires optimization of the microstructure through modification treatment.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a hypoeutectic aluminum-silicon alloy composite modifier and its preparation method, the main components of which include Al (75%-85% by mass), Sr (2.5%-4.0% by mass), Ba (0.8%-1.5% by mass), Ti (1.2%-2.0% by mass), Nb (0.5%-1.0% by mass), RE (0.3%-0.8% by mass), and Y (0.2%-0.5% by mass).

[0006] In a preferred embodiment of the present invention, the hypoeutectic aluminum-silicon alloy composite modifier mainly comprises Al (75% by mass), Sr (2.5% by mass), Ba (0.8% by mass), Ti (1.2% by mass), Nb (0.5% by mass), RE (0.3% by mass), and Y (0.2% by mass).

[0007] In a preferred embodiment of the present invention, the hypoeutectic aluminum-silicon alloy composite modifier mainly comprises 80% Al by mass; 3% Sr by mass; 1.2% Ba by mass; 1.6% Ti by mass; 0.8% Nb by mass; 0.5% RE by mass; and 0.3% Y by mass.

[0008] As a preferred embodiment of the present invention, the preparation method of the hypoeutectic aluminum-silicon alloy composite modifier includes the following steps: a. First, the selected raw materials are placed into a vacuum induction furnace for melting; b. After step a is completed, the smelted alloy melt is subjected to gas atomization powdering treatment; c. After step b is completed, the prepared powder is loaded into the mold, and then the mold is placed on a hydraulic press for pressure cold pressing to obtain the molded body; d. After step c is completed, the molded body is placed in a vacuum sintering furnace for sintering. After cooling to room temperature in the furnace, the composite modifier is removed from the furnace.

[0009] In a preferred embodiment of the present invention, step a, which involves placing the selected raw materials into a vacuum induction furnace for melting, includes the following steps: First, select 99.99% industrial pure Al blocks, 99.95% Sr granules, 99.9% Ba blocks, 99.95% Ti wire, 99.9% Nb flakes, 99.9% La-Ce mixed rare earth (2:1), and 99.95% Y flakes, and weigh them precisely according to the reference ratio; Next, the Al block was placed in a graphite crucible, then loaded into a vacuum induction furnace, and evacuated to a vacuum level of ≤5×10⁻⁶. -3 Pa, heat to 780-820℃; after Al is completely melted, add high melting point Ti wire and Nb sheet in sequence, keep warm for 15 min; then add Sr particles and Ba block, keep warm for 10 min; finally add RE and Y, stir for 5 min to ensure uniform composition.

[0010] In a preferred embodiment of the present invention, the specific steps of gas atomization powdering treatment of the smelted alloy melt in step b are as follows: the smelted alloy melt (temperature 760-780℃) is introduced into the atomization chamber through a guide tube, and 3-5MPa high-pressure Ar gas is introduced. The gas flow breaks the melt into fine droplets, which are then rapidly cooled in the Ar atmosphere to form spherical powder of 50-150μm.

[0011] In a preferred embodiment of the present invention, the guide tube has a diameter of 5 mm, the Ar gas purity is 99.999%, and it is rapidly cooled in an Ar atmosphere at a cooling rate of 10. 3 -10 4 ℃ / s.

[0012] In a preferred embodiment of the present invention, in step c, the pressure of the hydraulic press used to cold press the powder in the mold is 200-250 MPa, and the holding time is 5 min.

[0013] In a preferred embodiment of the present invention, the vacuum sintering furnace in step d is evacuated to a vacuum level of ≤1×10⁻⁶. - 3 Pa, heat to 580-620℃, and hold for 2 hours.

[0014] In a preferred embodiment of the present invention, the RE is a mixture of La and Ce, where La:Ce = 2:1.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The composite modifier of this invention can promote the morphological transformation of eutectic silicon from lamellar to fibrous, with the fibrous size controlled to <1μm, significantly improving the uniformity of the alloy's microstructure. Through multiple heterogeneous nucleation mechanisms, it refines the primary α-Al grains into equiaxed grains, with the grain size precisely controlled within the range of 25-35μm. At the same time, it can make the mechanical properties of the alloy more balanced in different directions, effectively reducing the performance fluctuations caused by the inhomogeneity of the structure. Furthermore, with its special deoxidation purification and adsorption agglomeration functions, it significantly reduces the cutting effect of inclusions on the alloy matrix, improving the purity and reliability of the alloy.

[0016] 2. This invention targets hypoeutectic aluminum-silicon alloys with a Si content of 7 wt.%. After treatment with this composite modifier, the room temperature tensile strength is increased to ≥320 MPa through the synergistic effects of eutectic silicon morphology optimization, grain refinement, and inclusion control. By finely controlling the microstructure, the strength is significantly improved while effectively balancing the relationship between strength and toughness, giving the alloy good plastic deformation ability, making it less prone to brittle fracture under complex stress conditions. Furthermore, after treatment with this composite modifier, the wear resistance of the alloy surface is significantly enhanced. More importantly, the uniformity of the alloy hardness is greatly improved, ensuring the stability and consistency of product quality and meeting the stringent requirements of precision machining and surface treatment. Attached Figure Description

[0017] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a flowchart illustrating the preparation process of the hypoeutectic aluminum-silicon alloy composite modifier of the present invention. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0019] This invention provides a technical solution: a hypoeutectic aluminum-silicon alloy composite modifier and its preparation method, the main components of which include Al (75%-85% by mass), Sr (2.5%-4.0% by mass), Ba (0.8%-1.5% by mass), Ti (1.2%-2.0% by mass), Nb (0.5%-1.0% by mass), RE (0.3%-0.8% by mass), and Y (0.2%-0.5% by mass).

[0020] Furthermore, the hypoeutectic aluminum-silicon alloy composite modifier mainly comprises Al (75% by mass), Sr (2.5% by mass), Ba (0.8% by mass), Ti (1.2% by mass), Nb (0.5% by mass), RE (0.3% by mass), and Y (0.2% by mass).

[0021] Furthermore, the hypoeutectic aluminum-silicon alloy composite modifier mainly comprises 80% Al by mass; 3% Sr by mass; 1.2% Ba by mass; 1.6% Ti by mass; 0.8% Nb by mass; 0.5% RE by mass; and 0.3% Y by mass.

[0022] Furthermore, the preparation method of the hypoeutectic aluminum-silicon alloy composite modifier includes the following steps: a. First, the selected raw materials are placed into a vacuum induction furnace for melting; b. After step a is completed, the smelted alloy melt is subjected to gas atomization powdering treatment; c. After step b is completed, the prepared powder is loaded into the mold, and then the mold is placed on a hydraulic press for pressure cold pressing to obtain the molded body; d. After step c is completed, the molded body is placed in a vacuum sintering furnace for sintering. After cooling to room temperature in the furnace, the composite modifier is removed from the furnace.

[0023] Furthermore, step a, which involves placing the selected raw materials into a vacuum induction furnace for melting, includes the following steps: First, select 99.99% industrial pure Al blocks, 99.95% Sr granules, 99.9% Ba blocks, 99.95% Ti wire, 99.9% Nb flakes, 99.9% La-Ce mixed rare earth (2:1), and 99.95% Y flakes, and weigh them precisely according to the reference ratio; Next, the Al block was placed in a graphite crucible, then loaded into a vacuum induction furnace, and evacuated to a vacuum level of ≤5×10⁻⁶. -3 Pa, heat to 780-820℃; after Al is completely melted, add high melting point Ti wire and Nb sheet in sequence, keep warm for 15 min; then add Sr particles and Ba block, keep warm for 10 min; finally add RE and Y, stir for 5 min to ensure uniform composition.

[0024] Furthermore, the specific steps of gas atomization powdering treatment of the smelted alloy melt in step b are as follows: the smelted alloy melt (temperature 760-780℃) is introduced into the atomization chamber through a guide tube, and 3-5MPa high-pressure Ar gas is introduced. The gas flow breaks the melt into fine droplets, which are then rapidly cooled in the Ar atmosphere to form spherical powder of 50-150μm.

[0025] Furthermore, the guide tube has a diameter of 5 mm, the Ar gas purity is 99.999%, and it is rapidly cooled in an Ar atmosphere at a cooling rate of 10. 3 -10 4 ℃ / s.

[0026] Furthermore, in step c, the pressure applied by the hydraulic press to the powder in the mold is 200-250 MPa, and the holding time is 5 minutes.

[0027] Furthermore, in step d, the vacuum sintering furnace is evacuated to a vacuum level of ≤1×10⁻⁶. -3 Pa, heat to 580-620℃, and hold for 2 hours.

[0028] Furthermore, the RE is a mixture of La and Ce, with La:Ce = 2:1.

[0029] Example 1 The hypoeutectic aluminum-silicon alloy composite modifier mainly comprises Al (75% by mass), Sr (2.5% by mass), Ba (0.8% by mass), Ti (1.2% by mass), Nb (0.5% by mass), RE (0.3% by mass), and Y (0.2% by mass).

[0030] The preparation steps are as follows: a. First, the selected raw materials are placed into a vacuum induction furnace for melting, including the following steps: First, select 99.99% industrial pure Al blocks, 99.95% Sr granules, 99.9% Ba blocks, 99.95% Ti wire, 99.9% Nb flakes, 99.9% La-Ce mixed rare earth (2:1), and 99.95% Y flakes, and weigh them accurately according to the reference ratio; Next, the Al block was placed in a graphite crucible, then loaded into a vacuum induction furnace, and evacuated to a vacuum level of ≤5×10⁻⁶. -3Pa, heat to 780-820℃; after Al is completely melted, add high melting point Ti wire and Nb sheet in sequence, keep warm for 15 min; then add Sr granules and Ba block, keep warm for 10 min; finally add RE and Y, stir for 5 min to ensure uniform composition. b. After step a is completed, the molten alloy is subjected to gas atomization powdering treatment. Specifically, the molten alloy (temperature 760-780℃) is introduced into the atomization chamber through a guide tube, and high-pressure Ar gas at 3-5MPa is introduced. The gas flow breaks the melt into fine droplets, which are then rapidly cooled in the Ar atmosphere to form spherical powders of 50-150μm. The guide tube diameter is 5mm, the Ar gas purity is 99.999%, and the powder is rapidly cooled in the Ar atmosphere at a cooling rate of 10. 3 -10 4 ℃ / s; c. After step b is completed, the prepared powder is loaded into the mold, and then the mold is placed on a hydraulic press for pressure cold pressing. The pressure of cold pressing is 200-250MPa, and the holding time is 5min to obtain the molded body. d. After step c is completed, place the molded body into a vacuum sintering furnace for sintering, and evacuate the vacuum to ≤1×10⁻⁶. -3 Pa, heat to 580-620℃, hold for 2 hours, cool to room temperature with the furnace, and then remove the composite modifier from the furnace.

[0031] Example 2 The hypoeutectic aluminum-silicon alloy composite modifier mainly comprises 80% Al by mass; 3% Sr by mass; 1.2% Ba by mass; 1.6% Ti by mass; 0.8% Nb by mass; 0.5% RE by mass; and 0.3% Y by mass.

[0032] The preparation steps are as follows: a. First, the selected raw materials are placed into a vacuum induction furnace for melting, including the following steps: First, select 99.99% industrial pure Al blocks, 99.95% Sr granules, 99.9% Ba blocks, 99.95% Ti wire, 99.9% Nb flakes, 99.9% La-Ce mixed rare earth (2:1), and 99.95% Y flakes, and weigh them accurately according to the reference ratio; Next, the Al block was placed in a graphite crucible, then loaded into a vacuum induction furnace, and evacuated to a vacuum level of ≤5×10⁻⁶. -3 Pa, heat to 780-820℃; after Al is completely melted, add high melting point Ti wire and Nb sheet in sequence, keep warm for 15 min; then add Sr granules and Ba block, keep warm for 10 min; finally add RE and Y, stir for 5 min to ensure uniform composition. b. After step a is completed, the molten alloy is subjected to gas atomization powdering treatment. Specifically, the molten alloy (temperature 760-780℃) is introduced into the atomization chamber through a guide tube, and high-pressure Ar gas at 3-5MPa is introduced. The gas flow breaks the melt into fine droplets, which are then rapidly cooled in the Ar atmosphere to form spherical powders of 50-150μm. The guide tube diameter is 5mm, the Ar gas purity is 99.999%, and the powder is rapidly cooled in the Ar atmosphere at a cooling rate of 10. 3 -10 4 ℃ / s; c. After step b is completed, the prepared powder is loaded into the mold, and then the mold is placed on a hydraulic press for pressure cold pressing. The pressure of cold pressing is 200-250MPa, and the holding time is 5min to obtain the molded body. d. After step c is completed, place the molded body into a vacuum sintering furnace for sintering, and evacuate the vacuum to ≤1×10⁻⁶. -3 Pa, heat to 580-620℃, hold for 2 hours, cool to room temperature with the furnace, and then remove the composite modifier from the furnace.

[0033] Table 1 shows the data parameters for traditional hypoeutectic aluminum-silicon alloy composite modifiers:

[0034] Table 2 shows the data parameters for the hypoeutectic aluminum-silicon alloy composite modifier in Example 1:

[0035] Table 3 shows the data parameters of the hypoeutectic aluminum-silicon alloy composite modifier in Example 2:

[0036] In summary, based on the data comparison in Tables 1, 2, and 3, the composite modifier of this invention can promote the morphological transformation of eutectic silicon from lamellar to fibrous, with the fibrous size controlled to <1μm, significantly improving the uniformity of the alloy microstructure. Compared with the existing Sr modifier's 70% fibrous distribution rate, this scheme increases this indicator to 95%, greatly improving the dispersion strengthening effect of the eutectic silicon phase. The composite modifier of this invention refines primary α-Al grains into equiaxed grains through a multi-heterogeneous nucleation mechanism, with the grain size precisely controlled within the range of 25-35 μm. At the same time, the grain uniformity is increased from 60% to 84% of the existing Ti-B refining agent, making the mechanical properties of the alloy more balanced in different directions and effectively reducing the performance fluctuations caused by the inhomogeneity of the microstructure. The composite modifier of this invention, with its special deoxidation, purification, adsorption, and agglomeration functions, significantly reduces the O content in the melt to 20 ppm, shrinks the inclusion size to <1 μm, and reduces the number of inclusions by 60%, thereby significantly reducing the cutting effect of inclusions on the alloy matrix and improving the purity and reliability of the alloy.

[0037] This invention targets hypoeutectic aluminum-silicon alloys with a Si content of 7 wt.%. After treatment with this composite modifier, the room temperature tensile strength is increased to ≥320 MPa through the synergistic effect of eutectic silicon morphology optimization, grain refinement, and inclusion control. Compared with the tensile strength of ≤250 MPa in the prior art, this represents a significant increase of 28%, enabling the alloy to resist greater external forces when subjected to tensile loads and meeting the application requirements of high-strength structural components.

[0038] The composite modifier of this invention, through precise control of microstructure, significantly improves the strength while increasing the elongation of the alloy to ≥6.5%, an increase of up to 117%, effectively balancing the relationship between strength and toughness, giving the alloy good plastic deformation ability, and making it less prone to brittle fracture under complex stress conditions.

[0039] After treatment with this composite modifier, the alloy hardness is increased from 65-75HV in the existing technology to 85-95HV, which significantly enhances the wear resistance of the alloy surface. More importantly, the hardness fluctuation range is controlled within <5HV, which is much better than the fluctuation range of >10HV in the existing technology. This greatly improves the uniformity of the alloy hardness, ensures the stability and consistency of product quality, and meets the stringent requirements of precision machining and surface treatment.

[0040] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0041] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A hypoeutectic aluminum-silicon alloy composite modifier, characterized in that: The main components include Al (75%-85% by weight); Sr (2.5%-4.0% by weight); Ba (0.8%-1.5% by weight); Ti (1.2%-2.0% by weight); Nb (0.5%-1.0% by weight); RE (0.3%-0.8% by weight); and Y (0.2%-0.5% by weight).

2. The hypoeutectic aluminum-silicon alloy composite modifier according to claim 1, characterized in that: The main components include Al (75% by weight); Sr (2.5% by weight); Ba (0.8% by weight); Ti (1.2% by weight); Nb (0.5% by weight); RE (0.3% by weight); and Y (0.2% by weight).

3. The hypoeutectic aluminum-silicon alloy composite modifier according to claim 1, characterized in that: The main components include 80% Al by mass; 3% Sr by mass; 1.2% Ba by mass; 1.6% Ti by mass; 0.8% Nb by mass; 0.5% RE by mass; and 0.3% Y by mass.

4. The method for preparing a hypoeutectic aluminum-silicon alloy composite modifier according to claim 1, characterized in that: The preparation steps are as follows: a. First, the selected raw materials are placed into a vacuum induction furnace for melting; b. After step a is completed, the smelted alloy melt is subjected to gas atomization powdering treatment; c. After step b is completed, the prepared powder is loaded into the mold, and then the mold is placed on a hydraulic press for pressure cold pressing to obtain the molded body; d. After step c is completed, the molded body is placed in a vacuum sintering furnace for sintering. After cooling to room temperature in the furnace, the composite modifier is removed from the furnace.

5. The method for preparing a hypoeutectic aluminum-silicon alloy composite modifier according to claim 4, characterized in that: The step a of placing the selected raw materials into a vacuum induction furnace for melting includes the following steps: First, select 99.99% industrial pure Al blocks, 99.95% Sr granules, 99.9% Ba blocks, 99.95% Ti wire, 99.9% Nb flakes, 99.9% La-Ce mixed rare earth (2:1), and 99.95% Y flakes, and weigh them precisely according to the reference ratio; Next, the Al block was placed in a graphite crucible, then loaded into a vacuum induction furnace, and evacuated to a vacuum level of ≤5×10⁻⁶. -3 Pa, heat to 780-820℃; after Al is completely melted, add high melting point Ti wire and Nb sheet in sequence, keep warm for 15 min; then add Sr particles and Ba block, keep warm for 10 min; finally add RE and Y, stir for 5 min to ensure uniform composition.

6. The method for preparing a hypoeutectic aluminum-silicon alloy composite modifier according to claim 4, characterized in that: The specific steps of gas atomization powdering treatment of the smelted alloy melt in step b are as follows: the smelted alloy melt (temperature 760-780℃) is introduced into the atomization chamber through the guide tube, and 3-5MPa high-pressure Ar gas is introduced. The gas flow breaks the melt into fine droplets, which are then rapidly cooled in the Ar atmosphere to form spherical powder of 50-150μm.

7. The method for preparing a hypoeutectic aluminum-silicon alloy composite modifier according to claim 6, characterized in that: The guide tube has a diameter of 5 mm, and the Ar gas has a purity of 99.999%. It is rapidly cooled in an Ar atmosphere at a cooling rate of 10. 3 -10 4 ℃ / s.

8. The method for preparing a hypoeutectic aluminum-silicon alloy composite modifier according to claim 4, characterized in that: In step c, the hydraulic press applies a pressure of 200-250 MPa to the powder in the mold for cold pressing, and the pressure holding time is 5 minutes.

9. The method for preparing a hypoeutectic aluminum-silicon alloy composite modifier according to claim 4, characterized in that: In step d, the vacuum sintering furnace is evacuated to a vacuum level of ≤1×10⁻⁶. -3 Pa, heat to 580-620℃, and hold for 2 hours.

10. The method for preparing a hypoeutectic aluminum-silicon alloy composite modifier according to claim 1, characterized in that: The RE is a mixture of La and Ce, with La:Ce = 2:1.

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