Sr, La and Ti composite modified refined hypoeutectic aluminum-silicon alloy and preparation method thereof

Abstract

The invention discloses a Sr, La and Ti composite modified refined hypoeutectic aluminum-silicon alloy and a preparation method thereof, and relates to the technical field of metal materials. The preparation method comprises the following steps: S1, heating an aluminum-silicon alloy ingot until the aluminum-silicon alloy ingot is completely molten, and introducing argon for refining treatment to obtain alloy liquid; s2, a modifier containing Sr is added and stirred, then a modifier containing La is added and stirred, and finally a refiner containing Ti is added and stirred; and S3, the alloy liquid is cast, and an aluminum-silicon alloy casting is obtained. By means of Sr, La and Ti composite modification and refinement, eutectic silicon in the hypoeutectic aluminum-silicon alloy can be changed into a fine fiber shape from a thick sheet shape, the long modification effect is maintained, meanwhile, Sr air suction is avoided, and the pinhole defect of a casting is reduced. A compound formed by the added Ti element can serve as a nucleation mass point of alpha-Al to play a role in refining, a rare earth La compound separated out firstly in the solidification process can pin a grain boundary, and the mechanical property of the hypoeutectic aluminum-silicon alloy is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal material processing, and in particular to a Sr, La, Ti composite modified and refined hypoeutectic aluminum-silicon alloy and a preparation method thereof. Background Art

[0002] Aluminum-silicon alloys are widely used in aerospace, automobile manufacturing, electronic equipment and many other fields due to their good casting properties, mechanical properties, processing characteristics and low cost. However, in aluminum-silicon alloys that have not been modified, the silicon phase is usually in the form of coarse flakes or needles, which will seriously split the matrix when subjected to external loads, causing local stress concentration and reducing the mechanical properties and cutting performance of the alloy. Therefore, modifying aluminum-silicon alloys to refine their structure is one of the key technologies to improve the comprehensive performance of aluminum-silicon alloys.

[0003] At present, the commonly used modifiers are sodium (Na), strontium (Sr), rare earth elements (such as La, Ce, Y, etc.). Sodium salt has good modification effect and fast onset, but it is easy to decay, the modification effect is unstable, and it pollutes the environment, so it has been gradually eliminated. The modification effect of Sr is equivalent to that of sodium salt, and it has a long aging time and good remelting property, but it absorbs hydrogen severely; the modification effect of rare earth elements is also limited, and the cost is relatively high. It can be seen that a single modifier has many shortcomings. The development of an efficient composite modification method is of great significance to improving the quality and performance of aluminum silicon alloys. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a Sr, La, Ti composite modified and refined aluminum-silicon alloy and a preparation method thereof, so as to solve the problems existing in the existing aluminum-silicon alloy modification treatment and obtain an aluminum-silicon alloy with fine and uniform structure and excellent mechanical properties.

[0005] The technical solution of the present invention is as follows: A first aspect of the present invention provides a method for refining a hypoeutectic aluminum-silicon alloy by composite modification of Sr, La and Ti, comprising the following steps: S1. After heating the aluminum-silicon alloy ingot until it is completely melted, introducing argon gas for refining treatment to obtain alloy liquid; S2, adding a modifier containing Sr into the alloy liquid and stirring, then continuing to add a modifier containing La into the alloy liquid and stirring, and finally adding a refiner containing Ti into the alloy liquid and stirring; S3, casting the alloy liquid treated in step S2 to obtain an aluminum-silicon alloy casting.

[0006] Preferably, in step S1, the heating temperature is 720°C-760°C, and the refining treatment time is 10-15 minutes.

[0007] Preferably, in step S2, the amount of Sr added is 0.02%-0.06% of the total mass of the aluminum-silicon alloy ingot, the amount of La added is 0.1%-0.3% of the total mass of the aluminum-silicon alloy ingot, and the amount of Ti-containing refiner added is 0.2~0.6% of the total mass of the aluminum-silicon alloy ingot.

[0008] After extensive research, the applicant found that Al-5Ti-B is a good refiner. However, if Al-5Ti-B is added in excess, the B in it will react with Sr to form SrB. 6 , reducing the deterioration effect of Sr. In order to achieve a good refinement effect, the present invention adds rare earth La together. The addition of La can preferentially react with B to form LaB 6 , inhibiting the reaction of Sr and B, thereby protecting the modification effect of Sr; on the other hand, by strictly controlling the addition amount of Al-5Ti-B to 0.2~0.6% of the total mass of the aluminum-silicon alloy ingot, it helps to reduce the reaction of B with La or Sr.

[0009] Preferably, the Sr-containing modifier is an Al-Sr master alloy, the La-containing modifier is an Al-La master alloy, and the Ti-containing refiner is an Al-5Ti-B master alloy.

[0010] Preferably, in step S2, the Al-Sr master alloy is an Al-10% Sr master alloy, and the Al-La master alloy is an Al-10% La master alloy.

[0011] Preferably, the specific steps of "adding a Sr-containing modifier to the alloy liquid for stirring" in step S2 include: After the Al-Sr master alloy is wrapped with aluminum foil, it is added into the alloy liquid at a temperature of 730° C.-740° C. and stirred for 5-8 minutes.

[0012] Preferably, the specific steps of "then continuing to add the La-containing modifier to the alloy liquid for stirring" in step S2 include: Continue to add the Al-La master alloy to the alloy liquid at a temperature of 740°C-760°C and stir for 5-8 minutes. Preferably, the specific steps of "finally adding a Ti-containing refiner to the alloy liquid for stirring" in step S2 include: Finally, the Al-5Ti-B master alloy is added into the alloy liquid and stirred for 5-8 minutes.

[0013] Preferably, in step S3, the alloy liquid treated in step S2 is cast at a temperature range of 720°C-740°C, and the casting method includes one of sand casting, metal mold casting and die casting.

[0014] Specifically, the preparation method of the Sr, La, Ti composite modified and refined aluminum-silicon alloy of the present invention comprises the following steps: 1. Raw material preparation A hypoeutectic aluminum-silicon alloy is prepared, and a modification and refinement agent containing Sr, La, and Ti is prepared, wherein Sr is added in the form of a block Al-Sr master alloy, La is added in the form of a block Al-La master alloy, and Ti is added in the form of a filamentary Al-5Ti-B master alloy, ensuring that the Sr content in the modifier is 0.02%-0.06% of the total mass of the alloy, the La content is 0.1%-0.3% of the total mass of the alloy, and the Al-5Ti-B master alloy addition amount is 0.2~0.6% of the total mass of the alloy.

[0015] 2. Melting Put the prepared hypoeutectic aluminum-silicon alloy into the graphite crucible of the resistance furnace or medium frequency induction furnace, heat it to 720℃-760℃, and after the raw materials are completely melted, use argon gas for refining to remove impurities and gases in the alloy liquid. The refining time is 10-15 minutes.

[0016] 3. Deterioration treatment First, the Al-Sr master alloy is wrapped with aluminum foil, added into the refined alloy liquid at a temperature of 730°C-740°C, and fully stirred for 5-8 minutes to make Sr evenly distributed in the alloy liquid and achieve initial modification.

[0017] Then, the Al-La master alloy is added to the alloy liquid to which Sr has been added at a temperature of 740°C-760°C, and stirring is continued to ensure that La is evenly dispersed in the alloy liquid and plays a modifying and refining role together with Sr. Finally, filamentous Al-5Ti-B is added to the melt and stirred sufficiently to ensure that Ti is evenly dispersed in the alloy liquid.

[0018] 4. Casting The alloy liquid after modification is cast in the temperature range of 720℃-740℃. Different casting processes such as sand casting, metal mold casting or die casting can be used to cast the alloy liquid into a pre-prepared mold to obtain an aluminum-silicon alloy casting of a desired shape.

[0019] The second aspect of the present invention provides a hypoeutectic aluminum-silicon alloy obtained by the above-mentioned preparation method. The hypoeutectic aluminum-silicon alloy casting prepared by the present invention has excellent mechanical properties such as strength, hardness and toughness.

[0020] The present invention mainly includes the following innovations: 1. Innovation of modifier combination (1) Multi-element synergistic effect: The combination of Sr, La and Ti overcomes the limitations of a single modifier. Sr, as a common aluminum-silicon alloy modifier, can effectively change the growth morphology of eutectic silicon, transforming it from coarse flakes or needles to fine forms such as fibers, thereby improving the mechanical properties of the alloy. The addition of La further plays a unique role. It can not only refine the grains itself, but also produce a synergistic effect with Sr, enhance the modification effect, and make the alloy structure more uniform and fine. Ti can refine the α-Al grains and improve the uniformity of the structure.

[0021] (2) Inhibition of the gas absorption effect: Sr has the disadvantage of absorbing hydrogen when used as a modifier, which will cause defects such as pores in the casting, affecting the quality and performance of the alloy. The addition of La can react chemically with the hydrogen in the melt, reduce the gas absorption effect caused by the addition of Sr, purify the melt, and thus improve the density and mechanical properties of the alloy. This is a major innovation of the present invention in solving practical production problems.

[0022] 2. Innovation of refinement mechanism (1) Increase in heterogeneous nucleation cores: Ti, as a commonly used grain refiner, can significantly refine aluminum alloys by introducing a large number of heterogeneous nucleation particles into the aluminum alloy melt. La has a strong surface chemical activity and can react with other elements in the alloy melt to form high-temperature particles, providing a large number of heterogeneous nucleation cores for the α-Al phase and refining the grains. At the same time, the fibrous eutectic silicon produced by Sr modification can also serve as heterogeneous nucleation particles for the α-Al phase, further promoting the refinement of the α-Al phase. This triple heterogeneous nucleation effect makes the grain refinement effect of the alloy more significant.

[0023] (2) Growth inhibition effect: La is easily adsorbed on the growth surface of α-Al and Si, inhibiting the growth of eutectic silicon. It works together with Sr to regulate the microstructure of the alloy from the two stages of nucleation and growth, making the eutectic silicon finer and more uniform. Compared with the traditional single modifier that only works in the nucleation stage, this is a new breakthrough in the modification mechanism.

[0024] 3. Innovations to improve performance (1) Improvement of comprehensive mechanical properties: Through the composite modification and refinement of Sr, La, and Ti, the grains of the aluminum-silicon alloy are significantly refined, and the morphology of eutectic silicon is optimized, thereby effectively improving the comprehensive mechanical properties of the alloy, such as strength, hardness, toughness, and wear resistance. This enables the alloy to better meet the demand for high-performance aluminum alloy materials in high-end fields such as aerospace and automobiles, and broadens the application range of aluminum-silicon alloys.

[0025] (2) Solving the poisoning problem: In aluminum-silicon alloys, when commonly used refiners such as B-containing refiners and Sr modifiers are added at the same time, B-Sr poisoning problems will occur, resulting in the failure of the Sr modification effect. However, the addition of La in the present invention can preferentially react with B to form LaB 6 , inhibiting the reaction between Sr and B, thereby protecting the modification effect of Sr, solving the poisoning problem that has long plagued the field of aluminum-silicon alloy modification and refinement, realizing refinement-modification integration, and improving the elongation of the alloy. This is another important innovation of this patent in terms of technological breakthrough.

[0026] 4. Innovation in process application (1) Simplify the production process: The use of Sr, La, and Ti composite modification and refinement agents can achieve refinement and modification treatment in the same smelting process, which greatly simplifies the production process, reduces production costs, improves production efficiency, and is conducive to large-scale industrial production.

[0027] (2) Precise control of composition: The present invention clarifies the mass percentage range of Sr and La, as well as the addition range of the refiner Al-5Ti-B, which can more accurately control the composition and structure of the alloy, ensure the stability and consistency of product quality, and provide reliable technical support for the production of high-performance aluminum-silicon alloys.

[0028] The present invention has at least one of the following beneficial effects: 1. The present invention can significantly refine the silicon phase structure in the aluminum-silicon alloy through the composite modification of Sr, La and Ti, transforming it from coarse flakes or needles to fine fibers, effectively improving the organizational structure of the alloy and improving the mechanical properties of the alloy such as strength, hardness and toughness.

[0029] 2. The composite modification and refinement method of the present invention has a more stable modification effect, which can effectively overcome the problem of easy decay of Sr modification; La can interact with other elements to inhibit some harmful reactions and also play the role of purifying the melt; Ti can refine α-Al grains and improve the fluidity and uniformity of the alloy. The three elements produce a synergistic effect and can more comprehensively improve the performance of aluminum-silicon alloys.

[0030] 3. The method of the present invention has simple process, is easy to operate and control, is suitable for the needs of large-scale industrial production, and can provide strong technical support for the wide application of aluminum silicon alloy in various fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1This is the cast metallographic image of the hypoeutectic aluminum-silicon alloy after composite modification and refinement of Sr, La, and Ti (separate addition) in Example 1, in which the light gray is the matrix α-Al phase and the dark gray is the eutectic silicon phase. It can be clearly seen that after composite modification and refinement, most of the eutectic silicon in the alloy is in the form of fine fibers, and a small part is in the form of fine blocks. Most of the α-Al in the alloy is in the form of equiaxes or ellipses, and a small part is in the form of dendrites.

[0032] Figure 2 This is a metallographic image of the cast state of the unmodified hypoeutectic aluminum-silicon alloy in Comparative Example 1. In the image, eutectic silicon appears in the form of thick long blocks, and α-Al appears in the form of thick dendrites.

[0033] Figure 3 This is the metallographic image of the cast state of the hypoeutectic aluminum-silicon alloy after Sr modification in Comparative Example 2. In the figure, the eutectic silicon modification effect is good, most of it is fine fiber, and a small part is fine block. However, most of the α-Al is coarse dendrite, and a small part is equiaxed.

[0034] Figure 4 This is the cast metallographic image of the hypoeutectic aluminum-silicon alloy after Sr and La composite modification and refinement in Example 3. The eutectic silicon modification effect is good in the figure, most of it is in fine fiber shape, a small part is in fine block shape. Most of the α-Al is in a relatively coarse equiaxed shape.

[0035] Figure 5 This is a metallographic image of the cast state of the hypoeutectic aluminum-silicon alloy after Sr and Ti composite modification and refinement in Example 4. In the figure, the eutectic silicon modification effect is relatively good, part of it is in the form of fine fibers, part of it is in the form of fine blocks. Most of the α-Al is in a relatively fine equiaxed shape.

[0036] Figure 6 This is a metallographic image of the cast state of the hypoeutectic aluminum-silicon alloy after Sr, La, and Ti were compositely modified and refined (added simultaneously) in Example 5. In the figure, the eutectic silicon modification effect is relatively good, with some parts in fine fiber shape and some in fine block shape. Most of the α-Al is in a relatively coarse equiaxed shape.

[0037] Figure 7 The scanned images of eutectic silicon in Example 1 and Comparative Example 3 are shown in FIG. (a) is Example 1, and (b) is Comparative Example 3. It can be seen that the eutectic silicon is more finely fibrous after being compositely modified by Sr, La, and Ti. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] Example 1 A method for preparing a Sr, La, Ti composite modified and refined hypoeutectic aluminum-silicon alloy casting comprises the following steps: 1. The raw material is ZL101 alloy, and 1000g of ZL101 alloy ingot is weighed. Prepare Al-10% Sr master alloy (i.e. Al-10Sr master alloy, added in an amount of 2g) with a Sr content of 0.02% (i.e. 0.2g) and Al-10% La master alloy (i.e. Al-10La master alloy, added in an amount of 10g) with a La content of 0.1% (i.e. 1g) as modifiers, and weigh Al-5Ti-B master alloy with a mass fraction of 0.6% (i.e. 6g) as a refiner.

[0040] 2. Place the ZL101 alloy ingot into the graphite crucible of the resistance furnace, heat it to 740°C, and after it is completely melted, introduce argon gas for refining treatment for 15 minutes.

[0041] 3. Wrap 2g of Al-10% Sr master alloy with aluminum foil, press it into the refined alloy liquid with a bell jar at 740℃, and stir for 5 minutes; then add 10g of Al-10% La master alloy into the alloy liquid and continue stirring for 5 minutes; add 6g of Al-5Ti-B master alloy into the alloy liquid and continue stirring for 5 minutes.

[0042] 4. The alloy liquid after modification is poured into a mold at 720°C to obtain an aluminum-silicon alloy casting.

[0043] The microstructure obtained is Figure 1 As shown in the figure, the microstructure of the casting is significantly refined, the eutectic silicon is well modified, most of it is in the form of fine fibers, and a small part is in the form of fine blocks. Most of the α-Al in the alloy is in the form of equiaxed or elliptical shapes, and a small part is in the form of dendrites.

[0044] Example 2 A method for preparing a Sr, La, Ti composite modified and refined hypoeutectic aluminum-silicon alloy comprises the following steps: 1. The raw material is ZL101 alloy, and 1000g of ZL101 alloy ingot is weighed. Prepare Al-10% Sr master alloy (i.e. Al-10Sr master alloy, added in an amount of 3g) with a Sr content of 0.03% (i.e. 0.3g) and Al-10% La master alloy (i.e. Al-10La master alloy, added in an amount of 20g) with a La content of 0.2% (i.e. 2g) as modifiers, and weigh Al-5Ti-B master alloy with a mass fraction of 0.4% (i.e. 4g) as a refiner.

[0045] 2. Place the ZL101 alloy ingot into the graphite crucible of the resistance furnace, heat it to 740°C, and after it is completely melted, introduce argon gas for refining treatment for 15 minutes.

[0046] 3. Wrap 3g of Al-10% Sr master alloy with aluminum foil, press it into the refined alloy liquid with a bell jar at 740℃, and stir for 5 minutes; then add 20g of Al-10% La master alloy into the alloy liquid and continue stirring for 5 minutes; add 4g of Al-5Ti-B master alloy into the alloy liquid and continue stirring for 5 minutes.

[0047] 4. The alloy liquid after modification is poured into a mold at 720°C to obtain an aluminum-silicon alloy casting.

[0048] Under this condition, a similar deterioration effect as in Example 1 can be achieved.

[0049] Example 3 A method for preparing a Sr, La, Ti composite modified and refined hypoeutectic aluminum-silicon alloy comprises the following steps: 1. The raw material is ZL101 alloy, and 1000g of ZL101 alloy ingot is weighed. Prepare Al-10% Sr master alloy (i.e. Al-10Sr master alloy, added in an amount of 4g) with a Sr content of 0.04% (i.e. 0.4g) and Al-10% La master alloy (i.e. Al-10La master alloy, added in an amount of 30g) with a La content of 0.3% (i.e. 3g) as modifiers, and weigh 0.2% (i.e. 2g) of Al-5Ti-B master alloy as a refiner.

[0050] 2. Place the ZL101 alloy ingot into the graphite crucible of the resistance furnace, heat it to 740°C, and after it is completely melted, introduce argon gas for refining treatment for 15 minutes.

[0051] 3. Wrap 4g of Al-10% Sr master alloy with aluminum foil, press it into the refined alloy liquid with a bell jar at 740℃, and stir for 5 minutes; then add 30g of Al-10% La master alloy into the alloy liquid and continue stirring for 5 minutes; add 2g of Al-5Ti-B master alloy into the alloy liquid and continue stirring for 5 minutes.

[0052] 4. The alloy liquid after modification is poured into a mold at 720°C to obtain an aluminum-silicon alloy casting.

[0053] Under this condition, a similar deterioration effect as in Example 1 can be achieved.

[0054] Comparative Example 1 This comparative example provides a method for preparing an aluminum-silicon alloy. Compared with Example 1, no Sr, La, and Ti are added for composite modification. The method specifically comprises the following steps: 1. The raw material is ZL101 alloy. Weigh 1000g ZL101 alloy ingot.

[0055] 2. Place the ZL101 alloy ingot into the graphite crucible of the resistance furnace, heat it to 740°C, and after it is completely melted, introduce argon gas for refining treatment for 15 minutes.

[0056] 3. The refined alloy liquid is poured into a mold at 720°C to obtain an aluminum-silicon alloy casting.

[0057] The microstructure obtained under this condition is Figure 2 As shown, it can be seen that the unmodified eutectic silicon presents coarse flakes and the α-Al presents coarse dendrites.

[0058] Comparative Example 2 This comparative example provides a method for preparing an aluminum-silicon alloy. Compared with Example 1, only Sr is added for modification, and specifically comprises the following steps: 1. The raw material is ZL101 alloy, and 1000g ZL101 alloy ingot is weighed. Prepare Al-10%Sr master alloy (i.e. Al-10Sr master alloy, added in an amount of 2g) with Sr content of 0.02% (i.e. 0.2g) as a modifier.

[0059] 2. Place the ZL101 alloy ingot into the graphite crucible of the resistance furnace, heat it to 740°C, and after it is completely melted, introduce argon gas for refining treatment for 15 minutes.

[0060] 3. Wrap 2 g of Al-10% Sr master alloy with aluminum foil and press it into the refined alloy liquid at 740°C using a bell jar. Stir for 5 minutes.

[0061] 4. The alloy liquid after modification is poured into a mold at 720°C to obtain an aluminum-silicon alloy casting.

[0062] The microstructure obtained under this condition is Figure 3 As shown, it can be seen that after Sr modification, most of the eutectic silicon is in fine fiber shape, a small part is in fine block shape, most of the α-Al is still in coarse dendrite shape, and a small part is in equiaxed shape. Compared with Example 1, only Sr modification has a comparable modification effect on the eutectic silicon in the alloy, but the α-Al refinement effect is not as good as Example 1.

[0063] Comparative Example 3 This comparative example provides a method for preparing an aluminum-silicon alloy. Compared with Example 1, Sr and La are added for composite modification and refinement, which specifically includes the following steps: 1. The raw material is ZL101 alloy, and 1000g of ZL101 alloy ingot is weighed. Prepare Al-10%Sr master alloy (i.e. Al-10Sr master alloy, added in an amount of 2g) with a Sr content of 0.02% (i.e. 0.2g) and Al-10%La master alloy (i.e. Al-10La master alloy, added in an amount of 20g) with a La content of 0.2% (i.e. 2g) as modifiers.

[0064] 2. Place the ZL101 alloy ingot into the graphite crucible of the resistance furnace, heat it to 740°C, and after it is completely melted, introduce argon gas for refining treatment for 15 minutes.

[0065] 3. Wrap 2g of Al-10% Sr master alloy with aluminum foil and press it into the refined alloy liquid at 740℃ using a bell jar. Stir for 5 minutes. Then add 20g of Al-10% La master alloy into the alloy liquid and continue stirring for 5 minutes.

[0066] 4. The alloy liquid after modification is poured into a mold at 720°C to obtain an aluminum-silicon alloy casting.

[0067] The microstructure obtained under this condition is Figure 4 As shown in the figure, it can be seen that after the Sr and La composite modification and refinement, most of the eutectic silicon is in a fine fiber shape, a small part is in a fine block shape, and most of the α-Al is in a relatively coarse equiaxed shape. Compared with Example 1, the Sr and La composite modification and refinement has a comparable modification effect on the eutectic silicon in the alloy, but the refinement effect on the α-Al is not as good as that of Example 1.

[0068] Figure 7 (a) is a scanned image of eutectic silicon in Example 1, Figure 7 (b) Scanning image of eutectic silicon in Comparative Example 3. It can be seen that compared with the Sr and La composite modification, the eutectic silicon after Sr, La and Ti composite modification is more fine-grained and fibrous.

[0069] Comparative Example 4 This comparative example provides a method for preparing an aluminum-silicon alloy. Compared with Example 1, Sr and Ti are added for composite modification and refinement, which specifically includes the following steps: 1. The raw material is ZL101 alloy, and 1000g ZL101 alloy ingot is weighed. Prepare Al-10%Sr master alloy (i.e. Al-10Sr master alloy, added in an amount of 2g) with a Sr content of 0.02% (i.e. 0.2g) as a modifier, and weigh Al-5Ti-B master alloy with a mass fraction of 0.6% (i.e. 6g) as a refiner.

[0070] 2. Place the ZL101 alloy ingot into the graphite crucible of the resistance furnace, heat it to 740°C, and after it is completely melted, introduce argon gas for refining treatment for 15 minutes.

[0071] 3. Wrap 2g of Al-10% Sr master alloy with aluminum foil and press it into the refined alloy liquid at 740℃ using a bell jar. Stir for 5 minutes. Then add 6g of Al-5Ti-B master alloy into the alloy liquid and continue stirring for 5 minutes.

[0072] 4. The alloy liquid after modification is poured into a mold at 720°C to obtain an aluminum-silicon alloy casting.

[0073] The microstructure obtained under this condition is Figure 5 As shown, it can be seen that after Sr and Ti composite modification and refinement, the eutectic silicon part is in fine fiber shape, part is in fine block shape, and most of the α-Al is in a relatively fine equiaxed shape. Compared with Example 1, the amount of block eutectic silicon in the alloy is larger, and the modification effect is not as good as that of Example 1, but the refinement of α-Al is equivalent to that of Example 1. This is because when Al-10% Sr master alloy and Al-5Ti-B master alloy are added at the same time, B-Sr poisoning problem will occur, thereby causing the modification effect of Sr to fail.

[0074] Comparative Example 5 This comparative example provides a method for preparing a Sr, La, and Ti composite modified aluminum-silicon alloy. Compared with Example 1, Sr, La, and Ti are added simultaneously instead of sequentially, and specifically include the following steps: 1. The raw material is ZL101 alloy, and 1000g of ZL101 alloy ingot is weighed. Prepare Al-10% Sr master alloy (i.e. Al-10Sr master alloy, added in an amount of 2g) with a Sr content of 0.02% (i.e. 0.2g) and Al-10% La master alloy (i.e. Al-10La master alloy, added in an amount of 10g) with a La content of 0.1% (i.e. 1g) as modifiers, and weigh Al-5Ti-B master alloy with a mass fraction of 0.6% (i.e. 6g) as a refiner.

[0075] 2. Place the ZL101 alloy ingot into the graphite crucible of the resistance furnace, heat it to 740°C, and after it is completely melted, introduce argon gas for refining treatment for 15 minutes.

[0076] 3. Wrap 2g of Al-10% Sr master alloy with aluminum foil, add it into the alloy liquid together with 10g of Al-10% La master alloy and 6g of Al-5Ti-B master alloy, and stir for 15 minutes.

[0077] 4. The alloy liquid after modification is poured into a mold at 720°C to obtain an aluminum-silicon alloy casting.

[0078] The microstructure obtained under this condition is Figure 6 As shown, it can be seen that after Sr, La, and Ti are compositely modified and refined (added simultaneously), part of the eutectic silicon is in a fine fiber shape, part is in a fine block shape, and most of the α-Al is in a relatively coarse equiaxed shape. Compared with Example 1, the amount of blocky eutectic silicon in the alloy is relatively large, and the modification effect is not as good as that of Example 1, and the size of the equiaxed α-Al in the alloy is relatively large, and the refinement effect is not as good as that of Example 1. This is because when Al-10% Sr master alloy and Al-5Ti-B master alloy are added simultaneously, B-Sr poisoning problem will occur, thereby causing the modification effect of Sr to fail. Therefore, compared with the simultaneous addition of Sr, La, and Ti, the present invention adopts the method of adding Sr first, then La, and finally Ti for composite modification and refinement, which solves the poisoning problem, thereby improving the mechanical properties of silicon alloy such as strength, hardness, and toughness.

[0079] The aluminum-silicon alloy castings prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were solution treated at 540° C. for 4 h to 6 h and then aged at 165° C. for 6 h, and the mechanical properties were tested. The test method is as follows: According to the national standard GB / T 228.1-2021 "Tensile test of metallic materials Part 1: Room temperature test method", the alloy was processed into a standard tensile specimen and stretched on a universal electronic tensile testing machine (MTS, CMT5105) at a stretching rate of 2 mm / min.

[0080] The mechanical properties of the aluminum-silicon alloy ingots obtained in the above Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1: Table 1 It can be seen from Table 1 that the aluminum-silicon alloy castings prepared in Examples 1 to 3 have excellent tensile strength and elongation; and, by comparing the mechanical properties of the aluminum-silicon alloy castings prepared in Example 1 with those of Comparative Examples 1 to 5, it can be seen that the tensile strength and elongation of Example 1 are significantly better than those of Comparative Examples 1 to 5, which indicates that whether Sr, La, and Ti are used in synergistic modification and refinement treatment and the order of adding Sr, La, and Ti will affect the excellent tensile strength and elongation of the prepared aluminum-silicon alloy castings.

[0081] It can be seen from the above multiple embodiments that the method of Sr+La+Ti composite modification and refinement of aluminum-silicon alloy of the present invention can effectively improve the quality and performance of aluminum-silicon alloy, and shows good stability and adaptability under different alloy compositions and process conditions.

[0082] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a Sr, La, Ti composite modified and refined hypoeutectic aluminum-silicon alloy, characterized in that: The following steps are involved: S1. After heating the aluminum-silicon alloy ingot until it is completely melted, introducing argon gas for refining treatment to obtain alloy liquid; S2, adding a modifier containing Sr into the alloy liquid and stirring, then continuing to add a modifier containing La into the alloy liquid and stirring, and finally adding a refiner containing Ti into the alloy liquid and stirring; S3, casting the alloy liquid treated in step S2 to obtain an aluminum-silicon alloy casting.

2. The preparation method according to claim 1, characterized in that: In step S1, the heating temperature is 720°C-760°C, and the refining treatment time is 10-15 minutes.

3. The preparation method according to claim 1, characterized in that: In step S2, the amount of Sr added is 0.02%-0.06% of the total mass of the aluminum-silicon alloy ingot, the amount of La added is 0.1%-0.3% of the total mass of the aluminum-silicon alloy ingot, and the amount of the Ti-containing refiner added is 0.2~0.6% of the total mass of the aluminum-silicon alloy ingot.

4. The preparation method according to claim 1, characterized in that: In step S2, the Sr-containing modifier is an Al-Sr master alloy, the La-containing modifier is an Al-La master alloy, and the Ti-containing refiner is an Al-5Ti-B master alloy.

5. The method according to claim 4, characterized in that In step S2, the Al-Sr master alloy is an Al-10%Sr master alloy, and the Al-La master alloy is an Al-10%La master alloy.

6. The preparation method according to claim 4, characterized in that: The specific steps of "adding a Sr-containing modifier to the alloy liquid for stirring" in step S2 include: After the Al-Sr master alloy is wrapped with aluminum foil, it is added into the alloy liquid at a temperature of 730° C.-740° C. and stirred for 5-8 minutes.

7. The preparation method according to claim 4, characterized in that: The specific steps of "then continuing to add the La-containing modifier to the alloy liquid for stirring" in step S2 include: Continue to add the Al-La master alloy into the alloy liquid at a temperature of 740° C.-760° C. and stir for 5-8 minutes.

8. The method according to claim 4, characterized in that The specific steps of "finally adding a Ti-containing refiner to the alloy liquid for stirring" in step S2 include: Finally, the Al-5Ti-B master alloy is added into the alloy liquid and stirred for 5-8 minutes.

9. The preparation method according to claim 1, characterized in that: The specific steps of step S3 include: The alloy liquid treated in step S2 is cast at a temperature range of 720° C. to 740° C., and the casting method includes one of sand casting, metal mold casting and die casting.

10. A hypoeutectic aluminum-silicon alloy, characterized in that: The method is obtained by any one of claims 1 to 9.

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