A refining and strengthening agent, its preparation method and application

Abstract

This invention provides a refining-strengthening agent, its preparation method, and its application, belonging to the field of aluminum alloy technology. The refining-strengthening agent provided by this invention comprises the following components by mass percentage: 5-15% nano-ceramic particles, 1-3% rare earth elements, 1-3% Zr, and the balance Al; the nano-ceramic particles include ZrB2, TiB2, and Al2O3. In this invention, the nano-ceramic particles ZrB2, Al2O3, and TiB2 can act as heterogeneous nucleation cores for α-Al within aluminum grains, pinning grain boundaries and hindering grain boundary migration. During deformation, they also impede dislocation movement, simultaneously forming fine recrystallized grains, thereby improving the refining and strengthening effects. The addition of rare earth elements enables the nanoparticles to achieve both refining and strengthening effects. The combination of Zr and rare earth elements provides excellent anti-coarsening properties, thus enabling the refining-strengthening agent to exhibit good strengthening effects at both high and room temperatures.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy technology, specifically relating to a refining and strengthening agent, its preparation method, and its application. Background Technology

[0002] Aluminum alloys, due to their high strength, high toughness, low density, and high specific stiffness, are widely used in structural components for aerospace, rail transportation, ships, and new energy vehicles. With the increasing energy crisis and growing concern for environmental pollution, the need for lightweight structural components is becoming more urgent. Adding grain refiners and strengthening agents can effectively refine the grain structure of aluminum alloys; simultaneously, the nanophase within the grain refiner can act as a strengthening phase to enhance the strength of the aluminum alloy.

[0003] Currently, grain refiners and strengthening agents for aluminum alloys typically employ single particles or single rare earth elements to refine the grains. However, with the increasing demand for higher performance in aluminum alloys, these grain refiners and strengthening agents are no longer sufficient. Therefore, improving the grain refinement effect of grain refiners and strengthening agents has become a pressing technical challenge in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a refining and strengthening agent, its preparation method, and its application. The refining and strengthening agent provided by this invention has a significant refining and strengthening effect on aluminum alloys.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a refining-strengthening agent comprising the following components by mass percentage: 5-15% nano-ceramic particles, 1-3% rare earth elements, 1-3% Zr, and the balance Al;

[0007] The nano-ceramic particles include ZrB2, TiB2, and Al2O3.

[0008] Preferably, the mass ratio of ZrB2, TiB2 and Al2O3 is 1:1:1.

[0009] Preferably, the particle size of ZrB2 and Al2O3 is independently 20-80 nm; the particle size of TiB2 is 40-100 nm.

[0010] Preferably, the rare earth element includes at least one of Er, Sc, Y, and Ce.

[0011] Preferably, when the rare earth elements are Er, Sc, and Y, the mass ratio of Er, Sc, and Y is 1:1:1.

[0012] This invention also provides a method for preparing the refining-strengthening agent described in the above technical solution, comprising the following steps:

[0013] (1) The reactants, aluminum melt and Al-Al2O3 preform are mixed and synthesized in situ, and then slag is formed to obtain a mixed melt; the reactants are K2ZrF6, K2TiF6 and KBF4;

[0014] (2) The mixed melt obtained in step (1), zirconium master alloy and rare earth master alloy are mixed and rare earth microalloying is carried out to obtain composite melt;

[0015] (3) The composite melt obtained in step (2) is sequentially cast and plastically deformed to obtain a refining-strengthening agent.

[0016] Preferably, the temperature for in-situ synthesis in step (1) is 850–900°C, and the time for in-situ synthesis is 25–30 min.

[0017] Preferably, the in-situ synthesis in step (1) and the rare earth microalloying in step (2) are carried out under electromagnetic and ultrasonic field conditions.

[0018] Preferably, the power of the electromagnetic field is 15-20kW, and the power of the ultrasonic field is 15-20kW.

[0019] The present invention also provides the application of the refining-strengthening agent described in the above technical solution or the refining-strengthening agent prepared by the preparation method described in the above technical solution in aluminum alloys.

[0020] This invention provides a grain refiner / strengthener comprising the following components by mass percentage: 5-15% nano-ceramic particles, 1-3% rare earth elements, 1-3% Zr, and the balance Al; the nano-ceramic particles include ZrB2, TiB2, and Al2O3. In this invention, the nano-ceramic particles ZrB2, Al2O3, and TiB2 can act as heterogeneous nucleation sites for α-Al within aluminum grains, pinning grain boundaries and hindering grain boundary migration. During deformation, they impede dislocation movement and simultaneously form fine recrystallized grains, thereby improving toughness and enhancing the grain refinement and strengthening effects. The addition of rare earth elements allows more nanoparticles to contribute to the grain refinement and strengthening effects. The combination of Zr and rare earth elements provides excellent anti-coarsening properties, resulting in good strengthening effects of the grain refiner / strengthener at both high and room temperatures. Experimental results show that when the grain refiner / strengthener provided by this invention is applied to aluminum alloys, the size of the cast and extruded grains is significantly reduced, and the yield strength and elongation of the aluminum alloy are greatly improved. Attached Figure Description

[0021] Figure 1 SEM image of the refining-strengthening agent prepared in Example 1;

[0022] Figure 2This is a diagram of the as-cast microstructure of the aluminum alloy in Application Example 2. Detailed Implementation

[0023] This invention provides a refining-strengthening agent comprising the following components by mass percentage: 5-15% nano-ceramic particles, 1-3% rare earth elements, 1-3% Zr, and the balance Al;

[0024] The nano-ceramic particles include ZrB2, TiB2, and Al2O3.

[0025] The refining-strengthening agent provided by this invention, by mass percentage, comprises 5-15% nano-ceramic particles; the nano-ceramic particles comprise ZrB2, TiB2, and Al2O3; the preferred mass ratio of ZrB2, TiB2, and Al2O3 is 1:1:1; the particle size of ZrB2 and Al2O3 is independently preferably 20-80 nm; the preferred particle size of TiB2 is 40-100 nm. In this invention, the nano-ceramic particles ZrB2, Al2O3, and TiB2 can act as heterogeneous nucleation cores for α-Al within aluminum grains, pinning grain boundaries and hindering grain boundary migration, thus impeding dislocation movement during deformation and improving toughness, thereby enhancing the refining and strengthening effects. By limiting the content of nano-ceramic particles within the above-mentioned range, this invention can further improve the refining and strengthening effects.

[0026] In one embodiment, the mass percentage of the nano-ceramic particles can be 6-10%, or even 7-8%; the particle size of ZrB2 and Al2O3 can independently be 30-60 nm, or even 40-50 nm; the particle size of TiB2 can be 50-90 nm, or even 60-80 nm. In this invention, multi-sized particles can exert the size strengthening effect of different ceramic particles.

[0027] The refining-strengthening agent provided by this invention, by weight percentage, further includes 1-3% rare earth elements; preferably, the rare earth elements include at least one of Er, Sc, Y, and Ce. In this invention, rare earth elements enable more nanoparticles to achieve refining and strengthening effects; limiting the content of rare earth elements within the above-mentioned range further improves the refining and strengthening effects.

[0028] In one implementation, the rare earth element can be any two, three, or four of Er, Sc, Y, and Ce; the mass percentage of the rare earth element can be 1%, 1.3%, 1.5%, 1.8%, 2%, 2.5%, or 3%.

[0029] In this invention, when the rare earth elements are Er, Sc, and Y, the preferred mass ratio of Er, Sc, and Y is 1:1:1.

[0030] The grain refiner and strengthening agent provided by this invention further includes 1-3% Zr by mass percentage. As one embodiment, the mass percentage of Zr can be 1-1.5%, or 1.8-3%. In this invention, Zr can significantly refine grains, thereby improving the grain refinement and strengthening effect.

[0031] The refining and strengthening agent provided by this invention, by weight percentage, also includes the balance Al. In this invention, Al is a matrix element.

[0032] In this invention, the nano-ceramic particles ZrB2, Al2O3, and TiB2 can act as heterogeneous nucleation cores of α-Al within aluminum grains. They can pin grain boundaries, hindering grain boundary migration and dislocation movement during deformation, thereby improving toughness and enhancing the refining and strengthening effects. The addition of rare earth elements enables more nanoparticles to achieve the refining and strengthening effects. The addition of Zr can significantly refine the grains, thereby improving the refining and strengthening effects.

[0033] In this invention, the nano-ceramic particles are resistant to high temperatures, and the combination of rare earth and Zr elements has good anti-coarsening ability (below 400℃), so that the refining-strengthening agent has excellent strengthening effect at both high temperature and room temperature.

[0034] This invention also provides a method for preparing the refining-strengthening agent described in the above technical solution, comprising the following steps:

[0035] (1) The reactants, aluminum melt and Al-Al2O3 preform are mixed and synthesized in situ, and then slag is formed to obtain a mixed melt; the reactants are K2ZrF6, K2TiF6 and KBF4;

[0036] (2) The mixed melt obtained in step (1), zirconium master alloy and rare earth master alloy are mixed and rare earth microalloying is carried out to obtain composite melt;

[0037] (3) The composite melt obtained in step (2) is sequentially cast and plastically deformed to obtain a refining-strengthening agent.

[0038] This invention does not impose any special restrictions on the source of the raw materials; commercially available products familiar to those skilled in the art can be used.

[0039] This invention involves mixing reactants, aluminum melt, and Al-Al2O3 preforms for in-situ synthesis, followed by slag formation to obtain a mixed melt. In this invention, the reactants and aluminum melt are used to synthesize high-hardness, high-modulus ZrB2 and TiB2 ceramic particles in situ, with the Al2O3 ceramic particles forming an Al-Al2O3 preform. The nano-ceramic particles ZrB2, Al2O3, and TiB2 can act as heterogeneous nucleation sites for α-Al within the grains, and can pin grain boundaries, hindering grain boundary migration and dislocation movement during deformation, thus improving toughness. Adding multiple ceramic particles overcomes the limitations imposed by single-particle content.

[0040] In this invention, the reactants are K2ZrF6, K2TiF6, and KBF4; the purity of the reactants is preferably ≥99.9%. This invention uses K2ZrF6, K2TiF6, and KBF4 to disrupt the oxide layer of the molten aluminum, allowing Al2O3 particles to be completely wetted into the molten aluminum after the Al-Al2O3 preform is melted.

[0041] In this invention, the temperature of the molten aluminum is preferably 850–900°C. As one embodiment, the temperature of the molten aluminum can be 860–890°C.

[0042] In this invention, the preferred method for preparing the Al-Al2O3 preform is as follows:

[0043] The oxide / calcined kaolin was mixed with aluminum powder and sintered to obtain Al-Al2O3 preforms.

[0044] In this invention, the oxide is preferably at least one of ZnO, SiO2, and TiO2; when the oxide is two of ZnO, SiO2, and TiO2, the mass ratio of the two oxides is preferably 1:1; when the oxide is three of ZnO, SiO2, and TiO2, the mass ratio of the three oxides is preferably 1:1:1; the purity of the oxide is preferably ≥99.9%; and the particle size of the oxide is preferably ≤100nm.

[0045] In this invention, the particle size of the calcined kaolin is preferably ≤2μm.

[0046] In this invention, the particle size of the aluminum powder is preferably 2 to 20 μm.

[0047] In this invention, the preferred mass ratio of oxide / calcined kaolin to aluminum powder is 1:(5-10). As one embodiment, the mass ratio of oxide / calcined kaolin to aluminum powder can be 1:6, 1:7, 1:8, 1:9, or 1:10.

[0048] In this invention, the mixing of the oxide / calcined kaolin and aluminum powder is preferably ball milling; the ball-to-material ratio in the ball milling is preferably (8-15):1; the ball milling speed is preferably 300-500 r / min; and the ball milling time is preferably 20-36 h. The ball milling method used in this invention ensures thorough mixing of the raw materials.

[0049] In one embodiment, the ball-to-material ratio in the ball milling mixture can be (9-12):1 or (10-11):1; the ball milling speed can be 400-450 r / min; and the ball milling time can be 24-32 h or 28-30 h.

[0050] In this invention, the sintering temperature is preferably 900–1000°C; the sintering time is preferably 90–150 min. As one embodiment, the sintering temperature can be 940–980°C; the sintering time can be 100–120 min, or even 110 min.

[0051] In this invention, the Al-Al2O3 preform is preferably ≤1cm 3 The small square.

[0052] In this invention, the preferred mass ratio of the reactant, aluminum melt, and Al-Al2O3 preform is 2:(5-9):1. As one embodiment, the mass ratio of the reactant, aluminum melt, and Al-Al2O3 preform can be 2:(6-8):1.

[0053] In this invention, the mixing of the reactants, aluminum melt, and Al-Al2O3 preform is preferably carried out by mixing the reactants and aluminum melt for 1-3 minutes before adding the Al-Al2O3 preform. This step-by-step addition of raw materials improves the degree of mixing.

[0054] The present invention does not have any special limitations on the operation of mixing the reactants, aluminum melt and Al-Al2O3 preform; any technical solution for preparing the mixture well known to those skilled in the art can be used.

[0055] In this invention, the preferred temperature for in-situ synthesis is 850–900°C; the preferred time for in-situ synthesis is 25–30 min; the preferred method for in-situ synthesis is to perform the synthesis under electromagnetic and ultrasonic field conditions; the preferred power of the electromagnetic field is 15–20 kW; and the preferred power of the ultrasonic field is 15–20 kW. Limiting the temperature and time of in-situ synthesis within the above ranges improves the degree of in-situ synthesis; applying electromagnetic and ultrasonic fields during the in-situ synthesis process generates nanoscale particles.

[0056] In one embodiment, the temperature of the in-situ synthesis can be 860–870°C; the time of the in-situ synthesis can be 26–28 min; the power of the electromagnetic field can be 16–18 kW; and the power of the ultrasonic field can be 16–18 kW.

[0057] The present invention does not impose any special limitations on the slag-forming operation; any operation well known to those skilled in the art can be used. The slag-forming operation of the present invention can remove excess elements, such as K, F, and Zn, from the refining-strengthening agent.

[0058] After obtaining the mixed melt, the present invention mixes the mixed melt, zirconium master alloy and rare earth master alloy, and performs rare earth microalloying to obtain a composite melt.

[0059] In this invention, the zirconium master alloy is preferably added in the form of an aluminum-zirconium master alloy; the aluminum-zirconium master alloy is preferably Al-10Zr.

[0060] In this invention, the rare earth master alloy is preferably a rare earth-aluminum master alloy; the rare earth-aluminum master alloy is preferably Al-20Er, Al-20Ce, Al-5Sc, or Al-10Y. In this invention, adding the rare earth elements as a rare earth master alloy prevents burn-off and facilitates proportioning. This invention does not impose specific limitations on the amount of rare earth master alloy used, as long as the content of rare earth elements in the refining-strengthening agent meets the requirements.

[0061] The present invention does not impose any special limitations on the operation of mixing the mixed melt, zirconium master alloy and rare earth master alloy, and any technical solution for preparing the mixed material well known to those skilled in the art can be used.

[0062] In this invention, the preferred temperature for rare earth microalloying is 700–750°C; the preferred time for rare earth microalloying is 10–20 min; the rare earth microalloying is preferably carried out under electromagnetic and ultrasonic field conditions; the preferred power of the electromagnetic field is 15–20 kW; and the preferred power of the ultrasonic field is 15–20 kW. Limiting the temperature and time of rare earth microalloying within the above ranges in this invention can improve the mixing degree between rare earth and nano-ceramic particles; the rare earth microalloying is carried out under electromagnetic and ultrasonic field conditions, where the electromagnetic field causes the melt to tumble, allowing for thorough mixing of rare earth and nano-ceramic particles, improving particle wettability, and enabling more nanoparticles to achieve a refining and strengthening effect.

[0063] In one embodiment, the temperature of rare earth microalloying can be 720–740°C; the time of rare earth microalloying can be 15–17 min; the power of the electromagnetic field can be 16–18 kW; and the power of the ultrasonic field can be 16–18 kW.

[0064] After obtaining the composite melt, the present invention sequentially casts and plastically deforms the composite melt to obtain a refining-strengthening agent.

[0065] The present invention does not impose any special limitations on the casting operation; any operation known to those skilled in the art can be used.

[0066] In this invention, the plastic deformation is preferably hot extrusion; the hot extrusion temperature is preferably 410℃~450℃; and the hot extrusion ratio is preferably (20~30):1. As one embodiment, the hot extrusion temperature can be 450℃, 440℃, 435℃, 430℃, 425℃, or 420℃; and the hot extrusion ratio can be 25:1, 26:1, 27:1, 28:1, 29:1, or 30:1.

[0067] In this invention, the refining-strengthening agent is preferably a thin plate or filament; the thickness of the thin plate is preferably ≤2mm; and the diameter of the filament is preferably ≤2mm.

[0068] This invention prepares a refining and strengthening agent for aluminum alloys through chemical composition design, in-situ synthesis of nanoparticles, and rare earth microalloying technology. This invention combines multi-component particle composite strengthening with multi-component rare earth microalloying technology, and applies electromagnetic and ultrasonic fields during the preparation process to prepare a refining and strengthening agent containing multiple nanophases. The aluminum alloy modified by the refining and strengthening agent obtains a fine grain structure, while improving the strength and plasticity of the aluminum alloy.

[0069] The refining and strengthening agent prepared by the preparation method provided by this invention has a significant refining and strengthening effect on aluminum alloys due to the presence of multiple dispersed nanophases. It can significantly refine various series of aluminum alloys and improve the strength and toughness of various aluminum alloys. The grain size of the as-cast structure of aluminum alloys refined by the refining agent is ≤50μm, and the grain size of 2xxx series, 6xxx series, and 7xxx series aluminum alloys after plastic deformation is ≤10μm.

[0070] The present invention also provides the application of the refining-strengthening agent described in the above technical solution or the refining-strengthening agent prepared by the preparation method described in the above technical solution in aluminum alloys.

[0071] The present invention does not impose any special limitations on the application of the refining-strengthening agent in aluminum alloys; any application operation known to those skilled in the art can be used.

[0072] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0073] Example 1

[0074] The refining and strengthening agent consists of the following mass percentages: 6% nano-ceramic particles, 3% rare earth elements, 3% Zr, and the balance Al;

[0075] The nano-ceramic particles are ZrB2, TiB2, and Al2O3; the mass ratio of ZrB2, TiB2, and Al2O3 is 1:1:1.

[0076] The particle size of ZrB2 is 50 nm, the particle size of Al2O3 is 45 nm, and the particle size of TiB2 is 96 nm.

[0077] The rare earth element is Er;

[0078] The preparation method of the refining-strengthening agent includes the following steps:

[0079] (1) Pure aluminum was melted in an electromagnetic induction heating furnace and heated to 860℃. Reactants with a purity ≥99.9% were added to the aluminum melt and mixed for 2 min. Al-Al2O3 preforms were then added. Electromagnetic stirring and ultrasound were started, and in-situ synthesis was carried out for 30 min. After slag formation, a mixed melt was obtained. The reactants were K2TiF6, K2ZrF6 and KBF4 powders, and the mass ratio of K2TiF6, K2ZrF6 and KBF4 powders was 1:1:2. The mass ratio of aluminum melt, reactants and Al-Al2O3 preforms was 5:2:1. The power of the electromagnetic field was 15kW and the power of the ultrasonic field was 15kW.

[0080] The Al-Al2O3 preform is prepared by ball milling ZnO and aluminum powder, sintering at 950℃ for 120 min, and then cutting into pieces ≤1cm. 3 Small cubes were used to obtain Al-Al2O3 preforms; wherein, the purity of ZnO was ≥99.9% and the particle size was ≤30nm; the particle size of aluminum powder was 3μm; the mass ratio of ZnO to aluminum powder was 1:5; the ball-to-material ratio of the ball milling mixture was 10:1, the ball milling speed was 450r / min, and the ball milling time was 24h.

[0081] (2) Add Al-10Zr and Al-20Er to the mixed melt obtained in step (1), and perform rare earth micro-alloying under electromagnetic and ultrasonic field conditions at 730℃ for 18 min to obtain a composite melt; wherein, the power of the electromagnetic field is 15kW; the power of the ultrasonic field is 15kW.

[0082] (3) The composite melt obtained in step (2) is cast at a melt temperature of 720°C and then hot extruded to obtain a refining-strengthening agent; wherein the hot extrusion temperature is 420°C and the extrusion ratio is 30:1.

[0083] Figure 1 The image shows the SEM image of the refining-strengthening agent prepared in Example 1.

[0084] from Figure 1 As can be seen, the bright white part consists of ceramic particles, with various particles mixed together.

[0085] Application Example 1

[0086] 20 kg of AA6111 aluminum alloy was added to a graphite crucible and melted. Then, 3 wt.% of the refining and strengthening agent prepared in Example 1 was added. The electromagnetic stirring was turned on and the mixture was kept at 750℃ for 20 min. The mixture was then refined and poured into a mold preheated to 200℃. The mixture was homogenized at 560℃ for 20 h and then hot-extruded at 435℃ with an extrusion ratio of 26:1. After solution treatment at 550℃ for 3 h and aging at 175℃ for 5 h, samples were taken for testing and observation. The microstructure and mechanical properties (test standard: GB / T228.1-2021, tensile test, 3 samples were tested, and the average value of the results was taken, with a tensile rate of 1 mm / s) are shown in Table 1.

[0087] Comparative Application Example 1

[0088] The difference from Application Example 1 is that the refinement-strengthening agent is omitted, while other conditions remain the same.

[0089] Table 1 shows the microstructure and mechanical properties of the refining-strengthening agent prepared in Example 1 before and after refining.

[0090]

[0091] As can be seen from Table 1, the grain size of aluminum alloy is significantly reduced after the addition of refining and strengthening agents, and the room temperature and high temperature mechanical properties of aluminum alloy are improved, giving aluminum alloy high strength and high toughness.

[0092] Example 2

[0093] The refining and strengthening agent consists of the following mass percentages: 6% nano-ceramic particles, 3% rare earth elements, 3% Zr, and the balance Al;

[0094] The nano-ceramic particles are ZrB2, TiB2, and Al2O3; the mass ratio of ZrB2, TiB2, and Al2O3 is 1:1:1.

[0095] The particle size of ZrB2 is 55 nm, the particle size of Al2O3 is 50 nm, and the particle size of TiB2 is 95 nm.

[0096] The rare earth elements are Er, Sc, and Y. ， The mass ratio of Er, Sc and Y is 1:1:1;

[0097] The preparation method of the refining-strengthening agent includes the following steps:

[0098] (1) Pure aluminum was melted in an electromagnetic induction heating furnace and heated to 850℃. Reactants with a purity ≥99.9% were added to the aluminum melt and mixed for 3 min. Al-Al2O3 preforms were then added. Electromagnetic stirring and ultrasound were started, and in-situ synthesis was carried out for 30 min. After slag formation, a mixed melt was obtained. The reactants were K2TiF6, K2ZrF6 and KBF4 powders, and the mass ratio of K2TiF6, K2ZrF6 and KBF4 was 1:1:2. The mass ratio of aluminum melt, reactants and Al-Al2O3 preforms was 6:2:1. The power of the electromagnetic field was 15kW. The power of the ultrasonic field was 15kW.

[0099] The Al-Al2O3 preform is prepared by ball milling the oxide and aluminum powder together, sintering at 1000℃ for 110 min, and then cutting it into pieces ≤1cm in size. 3 Small cubes were used to obtain Al-Al2O3 preforms; wherein the oxides were ZnO and SiO2; the mass ratio of ZnO to SiO2 was 1:1; the particle size of ZnO was 35 nm and the purity was ≥99.9%; the particle size of SiO2 was 75 nm and the purity was ≥99.9%; the particle size of aluminum powder was 2 μm; the mass ratio of oxides to aluminum powder was 1:5; the ball-to-material ratio for ball milling was 12:1, the ball milling speed was 500 r / min, and the ball milling time was 20 h;

[0100] (2) Add Al-10Zr, Al-5Sc, Al-10Y and Al-20Er to the mixed melt obtained in step (1), and perform rare earth micro-alloying under electromagnetic and ultrasonic field conditions at 720℃ for 18 min to obtain composite melt; wherein, the power of electromagnetic field is 15kW; the power of ultrasonic field is 15kW.

[0101] (3) The composite melt obtained in step (2) is cast at a melt temperature of 720°C and then hot extruded to obtain a refining-strengthening agent; wherein the hot extrusion temperature is 420°C and the extrusion ratio is 30:1.

[0102] Application Example 2

[0103] 20 kg of AA6111 aluminum alloy was added to a graphite crucible and melted. Then, 3 wt.% of the refining-strengthening agent prepared in Example 2 was added. Electromagnetic stirring was turned on, and the mixture was held at 750℃ for 20 min. The resulting product was then refined and poured into a mold preheated to 200℃. Homogenization was performed at 560℃ for 20 h, followed by hot extrusion at 420℃ with an extrusion ratio of 28:1. After solution treatment at 545℃ for 3 h and aging at 170℃ for 8 h, samples were taken for testing and observation. The microstructure and mechanical properties (test standard: GB / T228.1-2021, tensile test, 3 samples tested, average result taken, tensile rate 1 mm / s) are shown in Table 2. Microscopic images are shown below. Figure 2 As shown.

[0104] Comparative Application Example 2

[0105] The difference from Application Example 2 is that the refining-strengthening agent is omitted, while other conditions remain the same.

[0106] Table 2 shows the microstructure and mechanical properties of the refining-strengthening agent prepared in Example 2 before and after refining.

[0107]

[0108] From Table 2 and Figure 2 It can be seen that the addition of refining and strengthening agents significantly reduces the grain size of aluminum alloys and improves their room temperature and high temperature mechanical properties, giving them high strength and high toughness.

[0109] Example 3

[0110] The refining-strengthening agent is composed of the following mass percentages: 10% nano-ceramic particles, 1.5% rare earth elements, 1.5% Zr, and the balance Al;

[0111] The nano-ceramic particles are ZrB2, TiB2, and Al2O3; the mass ratio of ZrB2, TiB2, and Al2O3 is 1:1:1.

[0112] The particle size of ZrB2 is 52 nm, the particle size of Al2O3 is 43 nm, and the particle size of TiB2 is 100 nm.

[0113] The rare earth element is Sc;

[0114] The preparation method of the refining-strengthening agent includes the following steps:

[0115] (1) Pure aluminum was melted in an electromagnetic induction heating furnace and heated to 860℃. Reactants with a purity ≥99.9% (K2TiF6, K2ZrF6 and KBF4 powders in a mass ratio of 1:1:2) were added to the aluminum melt and mixed for 2 min. Al-Al2O3 preforms were then added. Electromagnetic stirring and ultrasound were started, and in-situ synthesis was carried out for 30 min. After slag formation, a mixed melt was obtained. The reactants were K2TiF6, K2ZrF6 and KBF4 powders, and the mass ratio of K2TiF6, K2ZrF6 and KBF4 powders was 1:1:2. The mass ratio of aluminum melt, reactants and Al-Al2O3 preforms was 5:2:1. The power of the electromagnetic field was 15kW and the power of the ultrasonic field was 15kW.

[0116] The Al-Al2O3 preform is prepared by ball milling SiO2 and aluminum powder, sintering at 1000℃ for 150 min, and then cutting into pieces ≤1cm. 3 Small cubes were used to obtain Al-Al2O3 preforms; wherein, the purity of SiO2 was ≥99.9% and the particle size was ≤50nm; the particle size of aluminum powder was 2μm; the mass ratio of SiO2 to aluminum powder was 1:6; the ball-to-material ratio of ball milling was 9:1, the ball milling speed was 450r / min, and the ball milling time was 22h.

[0117] (2) Add Al-10Zr and Al-5Sc to the mixed melt obtained in step (1), and perform rare earth micro-alloying under electromagnetic and ultrasonic field conditions at 730℃ for 20 min to obtain composite melt; wherein, the power of electromagnetic field is 15kW; the power of ultrasonic field is 15kW.

[0118] (3) The composite melt obtained in step (2) is cast at a melt temperature of 725°C and then hot extruded to obtain a refining-strengthening agent; wherein the hot extrusion temperature is 420°C and the extrusion ratio is 30:1.

[0119] Application Example 3

[0120] 20 kg of AA6111 aluminum alloy was added to a graphite crucible and melted. Then, 3 wt.% of the refining-strengthening agent prepared in Example 3 was added. The electromagnetic stirring was turned on and the mixture was kept at 760℃ for 20 min. The mixture was then refined and poured into a mold preheated to 200℃. The mixture was homogenized at 460℃ for 20 h and then hot-extruded at 425℃ with an extrusion ratio of 28:1. After solution treatment at 555℃ for 3 h and aging at 173℃ for 7 h, samples were taken for testing and observation. The microstructure and mechanical properties (test standard: GB / T228.1-2021, tensile test, 3 samples were tested, and the average value of the results was taken, with a tensile rate of 1 mm / s) are shown in Table 3.

[0121] Comparative Application Example 3

[0122] The difference from Application Example 3 is that the refining-strengthening agent is omitted, while other conditions remain the same.

[0123] Table 3 shows the microstructure and mechanical properties of the refining-strengthening agent prepared in Example 3 before and after refining.

[0124]

[0125] As can be seen from Table 3, the grain size of aluminum alloy is significantly reduced after the addition of refining and strengthening agents, and the room temperature and high temperature mechanical properties of aluminum alloy are improved, giving aluminum alloy high strength and high toughness.

[0126] Comparative Example 1

[0127] The refining-strengthening agent consists of the following mass percentages: 5% nano-ceramic particles and the balance Al;

[0128] The nano-ceramic particles are ZrB2;

[0129] The particle size of the ZrB2 is 55 nm;

[0130] The preparation method of the refining-strengthening agent includes the following steps:

[0131] (1) Pure aluminum was melted in an electromagnetic induction heating furnace and heated to 850°C. Reactants with a purity ≥99.9% (K2ZrF6 and KBF4 powders in a mass ratio of 1:1) were added to the aluminum melt. Electromagnetic stirring and ultrasound were started, and in-situ synthesis was carried out for 28 minutes. After slag formation, a mixed melt was obtained. The mass ratio of aluminum melt to reactants was 6:2. The electromagnetic stirring power was 15kW, and the ultrasonic field power was 15kW.

[0132] (2) The mixed melt obtained in step (1) is cast at a melt temperature of 720°C and then hot extruded to obtain a refining-strengthening agent; wherein the hot extrusion temperature is 425°C and the extrusion ratio is 28:1.

[0133] Comparative Application Example 4

[0134] 20 kg of AA6111 aluminum alloy was added to a graphite crucible and melted. Then, 3 wt.% of the refining and strengthening agent prepared in Comparative Example 1 was added. The electromagnetic stirring and ultrasonic devices were turned on at a power of 15 kW and 15 kW respectively, and the reaction was carried out for 25 min. The mixture was then held at 750℃ for 20 min. Subsequently, it was refined with C2Cl6 at 750℃ and poured into a mold preheated to 200℃. Samples were taken to observe the as-cast microstructure. Homogenization treatment was then performed at 565℃ for 2.5 h, with an extrusion ratio of 25:1 and an extrusion temperature of 450℃. After solution treatment at 540℃ for 2 h and aging at 175℃ for 8 h, the microstructure and mechanical properties (test standard: GB / T228.1-2021, tensile test, 3 samples were tested, and the average value was taken, tensile rate 1 mm / s) are shown in Table 4.

[0135] Comparative Application Example 5

[0136] The difference from Comparative Application Example 4 is that the refining-strengthening agent is omitted, while other conditions remain the same.

[0137] Table 4 shows the microstructure and mechanical properties of the refining-strengthening agent prepared in Comparative Example 1 before and after refining.

[0138]

[0139] A comparison of Table 4 and Table 1 shows that the refining-strengthening agent provided by the present invention can significantly reduce the grain size of aluminum alloys and significantly improve the mechanical properties at room temperature and high temperature, possessing high strength and high toughness.

[0140] As can be seen from the above embodiments and comparative examples, the refining-strengthening agent provided by the present invention has a significant refining and strengthening effect on aluminum alloys.

[0141] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A refining-strengthening agent comprising the following components by mass percentage: 5-15% nano-ceramic particles, 1-3% rare earth elements, 1-3% Zr, and the balance Al; The nano-ceramic particles include ZrB2, TiB2, and Al2O3.

2. The refining-strengthening agent according to claim 1, characterized in that, The mass ratio of ZrB2, TiB2 and Al2O3 is 1:1:

1.

3. The refining-strengthening agent according to claim 1 or 2, characterized in that, The particle size of ZrB2 and Al2O3 is independently 20–80 nm; the particle size of TiB2 is 40–100 nm.

4. The refining-strengthening agent according to claim 1, characterized in that, The rare earth elements include at least one of Er, Sc, Y and Ce.

5. The refining-strengthening agent according to claim 4, characterized in that, When the rare earth elements are Er, Sc, and Y, the mass ratio of Er, Sc, and Y is 1:1:

1.

6. A method for preparing the refining-strengthening agent according to any one of claims 1 to 5, comprising the following steps: (1) The reactants, aluminum melt and Al-Al2O3 preform are mixed and synthesized in situ, and then slag is formed to obtain a mixed melt; the reactants are K2ZrF6, K2TiF6 and KBF4; (2) The mixed melt obtained in step (1), zirconium master alloy and rare earth master alloy are mixed and rare earth microalloying is carried out to obtain composite melt; (3) The composite melt obtained in step (2) is sequentially cast and plastically deformed to obtain a refining-strengthening agent.

7. The preparation method according to claim 6, characterized in that, The temperature for in-situ synthesis in step (1) is 850–900℃, and the time for in-situ synthesis is 25–30 min.

8. The preparation method according to claim 6, characterized in that, The in-situ synthesis in step (1) and the rare earth microalloying in step (2) are carried out under electromagnetic and ultrasonic field conditions.

9. The preparation method according to claim 8, characterized in that, The power of the electromagnetic field is 15-20 kW, and the power of the ultrasonic field is 15-20 kW.

10. The application of the refining-strengthening agent according to any one of claims 1 to 5 or the refining-strengthening agent prepared by the preparation method according to any one of claims 6 to 9 in aluminum alloys.

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