A rare earth-containing aluminum alloy refiner and method of use thereof

Abstract

This invention discloses a rare earth-containing aluminum alloy refining agent and its application method. The aluminum alloy refining agent is composed of aluminum powder, titanium powder, carbon powder, copper oxide powder and yttrium oxide powder, and the molar ratio of aluminum, titanium, carbon, copper oxide and yttrium oxide is (2.0~6.0):(0.5~1.5):(0.5~1.5):(0.2~1.5):(0.01~0.2). The application method includes: step (1) ball milling and mixing aluminum powder, titanium powder, carbon powder, copper oxide powder and yttrium oxide powder to obtain mixed raw material powder; step (2) pressing the mixed raw material powder into shape and drying to obtain aluminum alloy refining agent block; step (3) pressing the dried aluminum alloy refining agent block into aluminum alloy melt for high-temperature self-propagating reaction; step (4) casting using near liquidus temperature casting method to obtain aluminum alloy ingot with significantly refined grain structure. This invention can achieve a fine and uniform equiaxed crystal structure comparable to that of rapid solidification under conventional casting conditions. In-situ particles can also serve as reinforcing phases, playing a role in dispersion strengthening.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy refining agents. Specifically, it relates to a rare earth-containing aluminum alloy refining agent and its method of use. Background Technology

[0002] With the global energy structure transformation, transportation equipment, such as new energy vehicles, rail transit, and aircraft, is facing rigid demands for improved energy efficiency and extended range. Aluminum alloys, due to their excellent properties such as low density and high specific strength, have become a preferred material for lightweighting, and their application rate in key components such as vehicle bodies, chassis, and battery packs continues to rise. However, the contradictory relationship between the strength and ductility of aluminum alloys (i.e., the bottleneck problem of strength-toughness imbalance) prevents them from meeting the increasingly high requirements for the comprehensive performance of aluminum alloys in various applications. While various strengthening methods such as solid solution strengthening, work hardening, and second-phase strengthening improve the strength of aluminum alloys, they come at the cost of sacrificing some ductility. Only fine-grained strengthening not only improves the strength of the alloy but also slightly improves its ductility.

[0003] Patent CN 119571127 A discloses an aluminum-based composite material reinforced with rare earth-modified in-situ reinforcing particles and its preparation method. This patent uses Al powder, TiO2 powder, C powder, and Y2O3 powder as reinforcing phase raw materials, adding them to an aluminum alloy for in-situ reaction to generate reinforcing particles. The average grain size of the final aluminum-based composite material can be refined to 45-68 μm. However, due to the extremely poor wettability of C in molten aluminum alloys, it is difficult to completely react with TiO2 powder to form TiC. Furthermore, due to residual oxygen in TiO2, a TiC-O solid solution is formed, which is detrimental to improving the overall performance of the aluminum alloy.

[0004] Therefore, it is particularly important to develop high-quality and easy-to-use aluminum alloy refining agents. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to provide a rare earth-containing aluminum alloy refining agent and its application method, which can achieve a fine and uniform equiaxed crystal structure comparable to that of rapid solidification under conventional casting conditions. The in-situ particles can also serve as a reinforcing phase, playing a role in dispersion strengthening.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A rare earth-containing aluminum alloy refining agent is composed of aluminum powder, titanium powder, carbon powder, copper oxide powder, and yttrium oxide powder, wherein the molar ratio of aluminum, titanium, carbon, copper oxide, and yttrium oxide is (2.0~6.0):(0.5~1.5):(0.5~1.5):(0.2~1.5):(0.01~0.2); for example: 2.8:1:1.2:0.3:0.043, 3.5:1:1.2:1.0:0.1285, 5.4:1:1.2:1.0:0.1185, 2.8:1:1.2:0.4:0.045. If the proportion of aluminum in a rare-earth-containing aluminum alloy refining agent is too high, it will affect the contact area between reactants such as titanium, carbon, copper oxide, and yttrium oxide, resulting in insufficient reaction during the subsequent high-temperature self-propagating reaction. If the proportion of aluminum is too low, the subsequent high-temperature self-propagating reaction will be too violent, potentially causing splashing. If the proportions of titanium and carbon are too high or too low, they may not react completely or produce too few TiC particles, failing to achieve the desired refining effect. If the proportion of copper oxide is too high, the reaction will produce too much alumina (alumina's refining effect is not as good as TiC) and too little TiC, affecting the overall refining effect of the refining agent. If the proportion of copper oxide is too low, the heat generated by its thermal explosion reaction with aluminum will not be sufficient to promote the complete reaction of Ti and C, thus affecting the continuation of the self-propagating reaction. In addition, too little yttrium oxide will not achieve the desired effect, while too much will have negative effects. This invention controls the molar ratio of aluminum, titanium, carbon, copper oxide, and yttrium oxide in the aluminum alloy refining agent within the aforementioned range. This allows the components to interact and cooperate with each other in the subsequent high-temperature self-propagating reaction, resulting in a more thorough and gradual reaction process. This generates submicron-sized TiC and Al2O3 particles (both spherical in shape), without large-sized Al3Ti phase. Furthermore, the number and distribution of the generated in-situ particles reach an ideal state, thereby fully leveraging its refining effect on aluminum alloys.

[0008] A method for using a rare earth-containing aluminum alloy refining agent includes the following steps:

[0009] Step (1): Ball mill and mix aluminum powder, titanium powder, carbon powder, copper oxide powder and yttrium oxide powder evenly to obtain the mixed raw material powder of the above rare earth aluminum alloy refining agent; use a powder mixer or ball mill to mix the powder to ensure that the raw material powders are evenly mixed and fully contacted.

[0010] Step (2): Press the mixed raw material powder into shape to obtain aluminum alloy refining agent block; wrap the aluminum alloy refining agent block with aluminum foil and dry it;

[0011] Step (3): Press the dried aluminum alloy refining agent block into the aluminum alloy melt for a high-temperature self-propagating reaction to generate the required in-situ particles in the aluminum alloy melt.

[0012] Step (4): After the aluminum alloy melt has reacted, it is stirred appropriately and cooled to a certain temperature. Then, the melt is purified. When the melt temperature drops to near the liquidus temperature of the alloy, near-liquidus casting is used to obtain an aluminum alloy ingot with uniform and fine equiaxed crystal structure.

[0013] This invention selects yttrium oxide powder mixed with aluminum powder, titanium powder, carbon powder, and copper oxide powder to prepare a refining agent, instead of lanthanum oxide, which is also a rare earth oxide of the lanthanide series. This is because when the refining agent prepared by mixing lanthanum oxide with aluminum powder, titanium powder, carbon powder, and copper oxide powder is used to optimize the microstructure of aluminum-magnesium-zinc alloys, even if the ratio of each refining agent raw material component and the processing conditions of the aluminum alloy material are optimized, the final aluminum alloy material not only has relatively large-sized in-situ particle reinforcing phases, but also contains large-sized (tens of micrometers) rare earth phases. These rare earth phases are not suitable as nucleating agents and reinforcing phases, and will affect the overall performance of the aluminum alloy material.

[0014] Furthermore, compared to lanthanum oxide, yttrium oxide exhibits several advantages: yttrium oxide has a cubic (Ia-3) crystal structure, maintaining a stable cubic structure from room temperature to high temperatures without phase transformation, which is beneficial for sintering and densification; while lanthanum oxide's crystal structure is unstable at high temperatures, remaining hexagonal at room temperature but transforming into a cubic phase at temperatures above 600°C, a phase transformation that can lead to volume changes. Yttrium oxide also demonstrates extremely high stability in molten metals, with a melting point as high as 2430°C, one of the highest among rare earth oxides (second only to Lu₂O₃), making it suitable for extreme high-temperature applications. During room temperature storage, yttrium oxide is more stable, while lanthanum oxide readily hydrates to form La(OH)₃ when exposed to air, requiring special storage. Therefore, using Al-Ti-C-CuO-Y₂O₃ as a refining agent, the pressed aluminum alloy refining agent block is stable during room temperature storage and preheating, and is not prone to hydration; during high-temperature reactions, it is less susceptible to phase transformation, which is beneficial for preparing high-quality as-cast aluminum alloys.

[0015] The Al-Ti-C-CuO-Y2O3 refining agent of this invention uses titanium powder instead of the commonly used titanium dioxide powder as the titanium source because: Since Al2O3 has a semi-coherent interface with the Al matrix, while TiC has a coherent interface with the Al matrix, the latter's lattice matching relationship is superior to the former, meaning TiC has a better refining effect on aluminum alloy materials than Al2O3; for the Al-TiO2-C-Y2O3 system, TiO2 provides Ti and O atoms, and the amounts of Al2O3 and TiC generated are "bound" proportionally, resulting in low adjustability; furthermore, C has extremely poor wettability in molten aluminum alloys, easily leading to incomplete reaction between TiO2 and C; moreover, since the reaction between TiO2 and C needs to proceed stepwise, the reaction process generates CO gas, and the prepared cast aluminum alloy will also exhibit porosity problems due to CO escape. Most importantly, TiC generated by TiO2 carburization often forms a TiC-O solid solution due to residual oxygen, and the presence of this solid solution will seriously affect the plasticity of aluminum alloys.

[0016] This invention, based on the Al-TiO2-C-Y2O3 system refining agent, replaces TiO2 with titanium powder and adds copper oxide powder to form an Al-Ti-C-CuO-Y2O3 refining agent. This agent offers high adjustability in the amounts of Al2O3 and TiC generated. By controlling the proportion of yttrium oxide added, the wettability of C in molten aluminum alloys can be effectively improved. Adding a specific amount of CuO utilizes the heat released from the thermal explosion reaction between CuO and Al to promote the full reaction of Ti and C, thereby generating as much TiC as possible with better refining effect (without CuO, the heat generated by the reaction of Ti and C is insufficient under conventional casting conditions to support the complete self-propagating reaction, leading to insufficient TiC generation, increased byproducts, and affecting the refining effect). Furthermore, the localized high-temperature environment generated by the thermal explosion reaction between CuO and Al promotes the decomposition of byproducts generated during the Ti and C reaction, effectively preventing the formation of TiC-O solid solution. The Cu generated by the thermal explosion reaction between CuO and Al can be incorporated into the matrix as an alloying element, which is beneficial for optimizing the alloy strength of aluminum alloy materials. In addition, the reaction between Ti and C is a direct diffusion reaction, so there will be no porosity problem caused by CO escaping during the TiC formation process.

[0017] The present invention uses aluminum alloy materials prepared by rare earth-containing aluminum alloy refining agents as raw castings without any processing. A non-vacuum melting method is selected, and the rare earth-containing aluminum alloy refining agents undergo a high-temperature self-propagating reaction in the aluminum alloy melt. The generated in-situ particles are directly generated in the aluminum alloy melt and have a coherent or semi-coherent interface with the matrix. The interface is free from contamination and has strong bonding ability. Under the action of thermal explosion reaction, they are dispersed and distributed, which can not only refine the grain structure, but also act as a dispersed strengthening phase.

[0018] In the above-mentioned method of using the rare earth-containing aluminum alloy refining agent, in step (1), the particle size of the mixed raw material powder is 1~40μm (which is beneficial for obtaining fine in-situ particles in the reaction; if the particle size of the mixed raw material powder is too large, the size of the in-situ particles obtained in the reaction will also be large); the ball milling time is 30~90min. Specifically, the ball milling time is, for example, but not limited to, any one or any two of 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, and 90 min.

[0019] In the above-mentioned method of using rare earth-containing aluminum alloy refining agent, in step (2), the forming pressure is 12~18MPa (if the forming pressure is too low, it will not be able to form or the resulting aluminum alloy refining agent block will be too loose, the contact between the reactants will not be tight, affecting the full progress of the reaction, and after being placed in the aluminum alloy melt, the temperature of the aluminothermic reaction cannot act on the entire reaction system, and it will disperse; if the forming pressure is too high, the reaction process will not be able to uniformly disperse the generated particles in the melt), and the holding time is 90~150s; specifically, the forming pressure is, for example, but not limited to, any one or any two of 12 MPa, 14 MPa, 14.5 MPa, 15 MPa, 15.5 MPa, 16 MPa, 17 MPa, 18 MPa; the aluminum alloy refining agent block is a cylinder with a diameter of 20~30mm and a thickness of 5~8mm; specifically, the reactant powder and rare earth oxide mixed powder are pressed into a circular aluminum alloy refining agent block with a diameter of, for example, but not limited to, 20 mm, 22 mm, 24 mm, 26 mm. The thickness of the reactant powder and rare earth oxide mixed powder pressed into a circular aluminum alloy refining agent block is, for example, but not limited to, any one of, or any two of, 5 mm, 6 mm, 7 mm, 8 mm; during the drying process, the drying temperature is 100~200℃ and the drying time is 30~60min; the drying temperature is, for example, but not limited to, any one of, or any two of, 100, 120, 140, 160, 180, 200℃; the drying time is, for example, but not limited to, any one of, or any two of, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min;

[0020] In the above-mentioned method of using rare earth-containing aluminum alloy refining agent, in step (3), the amount of aluminum alloy refining agent block is 0.5~10 wt.% of the mass of the aluminum alloy melt (if the amount of aluminum alloy refining agent block is too small, its refining effect on the aluminum alloy will not be significant; if the amount of aluminum alloy refining agent is too large, it will lead to a significant decrease in the plasticity of the final prepared aluminum alloy); preferably 3~10 wt.%, the amount of aluminum alloy refining agent block is the mass fraction of the base aluminum alloy, for example, but not limited to 3.0 wt.%, 3.5 wt.%, 4.0 wt.%, 4.5 wt.%, 5.0 wt.%, 5.5 wt.%, 6.0 wt.%, 6.5 wt.%, 7.0 wt.%, 7.5 wt.%, 8.0 wt.%, 8.5 wt.%, 9.0 wt.%, 9.5 wt.%, 10.0 wt.%. wt.%; During the high-temperature self-propagating reaction, the temperature of the aluminum alloy melt is controlled at 900~950℃. At this temperature, the high-temperature self-propagating reaction rate of the aluminum alloy refining agent block is moderate, which can ensure the full reaction of each component and make the generated in-situ particles uniformly dispersed in the aluminum alloy melt, which is conducive to its full play of the refining effect on aluminum alloy.

[0021] In the above-mentioned method of using rare earth-containing aluminum alloy refining agent, in step (4), the aluminum alloy melt temperature is reduced to 700~800℃ for purification treatment, and then the temperature is further reduced to 650~680℃ for casting. Before casting, the casting metal mold is preheated to 100~150℃; after casting, it is air-cooled to room temperature. The casting temperature is, for example, but not limited to, any one or any two of 650℃, 660℃, 670℃, and 680℃; the metal mold preheating temperature is, for example, but not limited to, any one or any two of 100℃, 120℃, 140℃, and 150℃.

[0022] The above-mentioned method of using rare earth-containing aluminum alloy refining agent, in step (3), the method of preparing aluminum alloy melt is as follows: prepare alloy raw materials according to the design composition of the base aluminum alloy, and melt them at room temperature and pressure using a non-vacuum melting method to obtain aluminum alloy melt.

[0023] In the above-mentioned method of using rare earth-containing aluminum alloy refining agent, in step (3), the following are the contents of the base aluminum alloy: magnesium mass fraction is 4.40~5.60 wt.%, zinc mass fraction is 2.40~3.60 wt.%, silicon mass fraction is less than or equal to 0.08 wt.%, iron mass fraction is less than or equal to 0.08 wt.%, manganese mass fraction is less than or equal to 0.08 wt.%, and the balance is aluminum and unavoidable impurities. Specifically, the Zn content of the base alloy, by weight percentage, is, for example, but not limited to, any one or any two of 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, and 3.6; the Mg content of the base alloy, by weight percentage, is, for example, but not limited to, any one or any two of 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, and 5.6.

[0024] In the above-mentioned method of using rare earth-containing aluminum alloy refining agent, in step (3), the melting temperature of the alloy raw material is 900~950℃, and the melting time is 20~40min. Specifically, the melting temperature is, for example, but not limited to, any one or any two of 900℃, 910℃, 920℃, 930℃, 940℃, and 950℃.

[0025] In the above-mentioned method of using rare earth-containing aluminum alloy refining agent, in step (1), the molar ratio of aluminum, titanium, carbon, copper oxide and yttrium oxide in the mixed raw material powder is 2.8:1:1.2:0.3:0.043; aluminum powder passes through a 700-mesh sieve, titanium powder passes through a 500-mesh sieve, carbon powder passes through a 500-mesh sieve, copper oxide powder passes through a 700-mesh sieve, and the average particle size of yttrium oxide powder is 1.0 μm; the ball milling mixing time is 60 min.

[0026] In step (2), the forming pressure is 16MPa and the holding time is 120s; the aluminum alloy refining agent block is a cylinder with a diameter of 20~30mm and a height of 5~8mm; during the drying process, the drying temperature is 150℃ and the drying time is 40min.

[0027] In step (3), the method for preparing the aluminum alloy melt is as follows: prepare alloy raw materials according to the designed composition of the base aluminum alloy, and melt them at room temperature and pressure using a non-vacuum melting method to obtain the aluminum alloy melt; in the base aluminum alloy: the mass fraction of magnesium is 5.0 wt.%, the mass fraction of zinc is 3.0 wt.%, the mass fraction of silicon is less than or equal to 0.08 wt.%, the mass fraction of iron is less than or equal to 0.08 wt.%, the mass fraction of manganese is less than or equal to 0.08 wt.%, and the balance is aluminum; the melting temperature of the alloy raw materials is 950℃, and the melting time is 30 min;

[0028] In step (3), the amount of aluminum alloy refining agent block is 8 wt.% of the mass of aluminum alloy melt, and the temperature of aluminum alloy melt is controlled at 950℃ during high-temperature self-propagating reaction;

[0029] In step (4), the aluminum alloy melt temperature is reduced to 700°C for purification treatment, and then the temperature is further reduced to close to the liquidus temperature of 650°C for casting. Before casting, the casting metal mold is preheated to 150°C; after casting, it is air-cooled to room temperature.

[0030] The high-strength, high-ductility aluminum alloy material prepared by the above method is used in the manufacture of transportation equipment parts.

[0031] The technical solution of the present invention achieves the following beneficial technical effects:

[0032] 1. This invention relates to a rare-earth-containing aluminum alloy refining agent and its application method. Based on an Al-Ti-C-CuO reaction system, rare-earth oxides (Y₂O₃) are added, and the proportions of each component are controlled to form a rare-earth-containing aluminum alloy refining agent. Utilizing the reactivity of rare earth elements, the reaction pathway of the high-temperature self-propagating reaction is affected, refining the reaction products and increasing the number of nucleating agents, resulting in a better microstructure refinement effect. Using the rare-earth-containing aluminum alloy refining agent of this invention, aluminum alloys with uniform and fine equiaxed grain structures can be prepared under normal pressure and room temperature conditions using conventional casting equipment. The degree of grain refinement is comparable to that of rapid solidification technology, meeting the high comprehensive performance requirements of related fields.

[0033] 2. The rare-earth-containing aluminum alloy refining agent and its application method of this invention utilize a high-temperature self-propagating reaction to generate in-situ particles with submicron-sized grains. These particles have a coherent or semi-coherent interface with the aluminum-magnesium-zinc alloy matrix. Under the action of the thermal explosion reaction of copper oxide and aluminum, the in-situ particles can exhibit a dispersed distribution in the melt. In the subsequent crystallization process, they not only promote nucleation but also hinder crystal growth, thereby producing a significant refining effect. Furthermore, the in-situ particles can also act as a dispersed strengthening phase to improve the overall performance of the aluminum alloy material. Therefore, the Al-Ti-C-CuO refining agent of this invention has a dual strengthening effect of grain refinement and dispersion strengthening, providing an economical and effective way to synergistically improve the strength and toughness of aluminum alloys.

[0034] 3. The rare earth-containing aluminum alloy refining agent of the present invention and its application method, under normal pressure and room temperature conditions, adopts a non-vacuum melting method, and uses a metal mold to cast aluminum alloy ingots with uniform and fine equiaxed crystal structure at a temperature close to the liquidus temperature of aluminum alloy. That is, it can be achieved under conventional processing conditions. The preparation method is simple and easy to implement, has no special requirements for equipment and environment, and the process flow is concise, which has the prospect of subsequent large-scale production and use.

[0035] 4. The Al-Ti-C-CuO-Y2O3 grain refiner used in this invention can be understood as a rare earth modified aluminum alloy grain refiner. It is made by adding a trace amount of rare earth yttrium oxide to the Al-Ti-C-CuO system. The added rare earth yttrium oxide not only participates in the high-temperature self-propagating reaction but also refines the reaction products, significantly increasing the nucleation sites and obtaining a better grain refinement effect. The addition of rare earth yttrium in the form of rare earth oxides in trace amounts can achieve a significant grain refinement effect with a small increase in cost. This reflects the special role of the active properties of rare earths in the field of grain refiners: further refining the size of ceramic particles generated by the reaction of the grain refiner.

[0036] 5. This invention employs an Al-Ti-C-CuO-Y2O3 refining agent system to refine Al-5Mg-3Zn (wt.%). By controlling its process parameters, submicron-sized TiC and micron-sized Al2O3 particles can be prepared, both of which are spherical. The added rare earth element Y exists around the TiC particles; the Cu element in the Al-Ti-C-CuO-Y2O3 refining agent system reacts with the original strengthening phase T-Mg of the matrix alloy. 32 (Al,Zn) 49 Combined to form Cu-containing T-Mg 32 (Al,Zn,Cu) 49 The phase, with a size ranging from nanometer to submicron, is circular / elliptical in shape. Under the same amount of aluminum alloy refining agent, the alloys prepared using the Al-Ti-C-CuO-Y2O3 refining agent system generally have higher hardness values ​​than those prepared using the Al-TiO2-C-Y2O3 refining agent system. Furthermore, the corrosion potential and corrosion current of the Al-5Mg-3Zn alloy prepared using the Al-Ti-C-CuO-Y2O3 refining agent system are significantly higher than those prepared using the Al-TiO2-C-Y2O3 refining agent system. Attached Figure Description

[0037] Figure 1 Flowchart of rare earth-containing aluminum alloy refining agent and its usage method in Embodiment 1 of the present invention;

[0038] Figure 2 Grain structure diagram of the Al-5Mg-3Zn aluminum alloy prepared in Example 1 of this invention;

[0039] Figure 3 Grain structure diagram of the Al-5Mg-3Zn aluminum alloy prepared in Example 2 of this invention;

[0040] Figure 4 Grain structure diagram of the Al-5Mg-3Zn aluminum alloy prepared in Comparative Example 1 of this invention;

[0041] Figure 5Morphology of TiC particles in Al-5Mg-3Zn aluminum alloy prepared in Example 1 of this invention;

[0042] Figure 6 Morphology of Al2O3 particles in Al-5Mg-3Zn aluminum alloy prepared in Example 1 of this invention;

[0043] Figure 7 TEM morphology and energy dispersive spectroscopy (EDS) results of TiC particles in Al-5Mg-3Zn aluminum alloy prepared in Example 1 of this invention;

[0044] Figure 8 TEM morphology and energy dispersive spectroscopy (EDS) results of another TiC particle in the Al-5Mg-3Zn aluminum alloy prepared in Example 1 of this invention;

[0045] Figure 9 TEM images of the precipitated phases in Al-5Mg-3Zn aluminum alloy prepared in Example 1 and Comparative Example 2 of this invention; in the figures, (a), (b), (c) and (d) correspond to Example 1; (e), (f), (g) and (h) correspond to Comparative Example 2;

[0046] Figure 10 Morphology and energy dispersive spectroscopy analysis of the second phase precipitated in Al-5Mg-3Zn aluminum alloy prepared in Example 1 of this invention. Detailed Implementation

[0047] Example 1

[0048] This embodiment describes a rare-earth-containing aluminum alloy refining agent and its application method, including the following steps:

[0049] Step (1): Place 3.777g aluminum powder, 2.394g titanium powder, 0.721g carbon powder, 1.193g copper oxide powder and 0.486g yttrium oxide powder in a ball mill and mix them evenly to obtain a mixed raw material powder; the molar ratio of Al, Ti, C, CuO and Y2O3 in the mixed raw material powder is 2.8:1:1.2:0.3:0.043; aluminum powder passes through a 700-mesh sieve, titanium powder passes through a 500-mesh sieve, carbon powder passes through a 500-mesh sieve, copper oxide powder passes through a 700-mesh sieve, and the average particle size of yttrium oxide powder is 1.0μm; the ball milling time is 60min;

[0050] Step (2): Press the mixed raw material powder under 16MPa for 120s to form a round aluminum alloy refining agent block with a diameter of 25 mm, a thickness of 7 mm, and a weight of 6 g. Wrap the aluminum alloy refining agent block with aluminum foil to isolate it from air and impurities and place it in a desiccator for later use. Place the aluminum alloy refining agent block in a box-type resistance furnace and dry it at 150℃ for 40 min to completely remove the moisture from the aluminum alloy refining agent block.

[0051] Step (3): Prepare alloy raw materials (75g in total) according to the designed composition of the base aluminum alloy (Al-5Mg-3Zn), and melt them at room temperature and pressure using a non-vacuum melting method to obtain aluminum alloy melt; during melting, first heat the crucible resistance furnace to a preheating temperature of 950℃, put the alloy raw materials into the graphite crucible, and place it in the preheated crucible resistance furnace to melt at a temperature of 950℃ for 30 minutes until the alloy raw materials melt.

[0052] In this embodiment, the base aluminum alloy contains: 5.0 wt.% magnesium, 3.0 wt.% zinc, less than or equal to 0.05 wt.% silicon, less than or equal to 0.05 wt.% iron, less than or equal to 0.05 wt.% manganese, and the balance is aluminum;

[0053] The dried aluminum alloy refining agent block is placed into the molten aluminum alloy using crucible tongs, and then completely pressed into the molten aluminum alloy using a graphite bell jar. The reaction system is ignited at a high temperature to carry out a high-temperature self-propagating reaction. After the reaction is completed, the aluminum alloy material melt is obtained. The preheating temperature of the aluminum alloy melt is controlled at 950℃ during the high-temperature self-propagating reaction. The reactants of the high-temperature self-propagating reaction are elemental metals or metal oxides, all of which participate in the high-temperature self-propagating reaction in the form of powder, which can ensure the full progress of the reaction. The thermal explosion reaction helps the uniform distribution of in-situ reaction product particles in the aluminum alloy melt.

[0054] Step (4): When the aluminum alloy melt is cooled to 700°C, it is purified by refining and degassing with pre-prepared hexachloroethane and removing the slag suspended on the surface of the melt. Then, when the temperature is cooled to close to the liquidus temperature of the aluminum alloy (650°C), it is cast using a metal mold (a steel mold preheated to 150°C). After casting, it is air-cooled to room temperature to obtain an aluminum alloy ingot with uniform and fine equiaxed crystal structure.

[0055] This embodiment employs a non-vacuum melting method. Rare earth refining agents undergo a high-temperature self-propagating reaction in the aluminum alloy melt. The resulting in-situ particles are directly dispersed within the aluminum alloy melt under the influence of a thermal explosion reaction. This not only refines the grain structure but also acts as a dispersed strengthening phase. The final aluminum alloy prepared in this embodiment is a raw casting without further processing. The in-situ particles and the matrix exhibit a coherent or semi-coherent interface relationship, with no interface contamination and strong bonding. Figure 2 As can be seen from the data, the aluminum alloy prepared in this embodiment has a fine equiaxed grain structure with an average grain size of nearly 40 μm.

[0056] Example 2

[0057] The only difference between this embodiment and embodiment 1 is that in step (1), 3.777g of aluminum powder, 2.394g of titanium powder, 0.721g of carbon powder, 1.591g of copper oxide powder and 0.508g of yttrium oxide powder are placed in a ball mill and ball-milled to mix evenly to obtain a mixed raw material powder; in the mixed raw material powder, the molar ratio of Al, Ti, C, CuO and Y2O3 is 2.8:1:1.2:0.4:0.045.

[0058] The other steps, process parameters, raw material sources, and equipment used are exactly the same as in Example 1.

[0059] from Figure 3 As can be seen from the data, the aluminum alloy material prepared in this embodiment has a fine equiaxed crystal structure with an average grain size of nearly 50 μm.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Examples 1 and 2 is that no aluminum alloy refining agent block was added, and the Al-5Mg-3Zn as-cast alloy was prepared by casting using the process equipment and parameter conditions of Example 1.

[0062] from Figure 4 As can be seen, the aluminum alloy grains prepared in this comparative example are equiaxed, but their size distribution range is large, with an average grain size of nearly 110 μm.

[0063] Comparing Comparative Example 1 with Examples 1 and 2, it can be seen that the aluminum alloy using the rare earth-containing aluminum alloy refining agent of the present invention has a more significant effect on grain structure optimization.

[0064] In summary, this invention can achieve the preparation and microstructure control of Al-5Mg-3Zn alloy by adding a rare earth-containing aluminum alloy refining agent and using a high-temperature self-propagating reaction. The rare earth-containing aluminum alloy refining agent used in this invention has a significant effect on optimizing the microstructure of Al-5Mg-3Zn alloy.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Example 1 is that in step (1), 4.212g of aluminum powder, 3.995g of titanium dioxide powder, 0.721g of carbon powder and 0.474g of yttrium oxide powder are placed in a ball mill and mixed evenly to obtain a mixed raw material powder; in the mixed raw material powder, the molar ratio of Al, TiO2, C and Y2O3 is 3.15:1:1.2:0.042.

[0067] The other steps, process parameters, raw material sources, and equipment used are exactly the same as in Example 1.

[0068] The aluminum alloy material prepared in this embodiment has a fine equiaxed grain structure with an average grain size of nearly 60 μm.

[0069] The hardness and corrosion resistance of the Al-5Mg-3Zn as-cast aluminum alloys prepared in Example 1, Comparative Example 1, and Comparative Example 2 were tested. The results showed that the Brinell hardness of the Al-5Mg-3Zn as-cast aluminum alloys prepared in Example 1, Comparative Example 1, and Comparative Example 2 were 96.4 HBV, 78.6 HBV, and 89.3 HBV, respectively. Compared with Comparative Example 1, the corrosion potential and corrosion current density of the Al-5Mg-3Zn as-cast alloys prepared in Example 1 and Comparative Example 2 were increased to varying degrees, and the corrosion potential and corrosion current of the Al-5Mg-3Zn alloy prepared in Example 1 were significantly higher than those of the Al-5Mg-3Zn alloy prepared in Comparative Example 2.

[0070] Therefore, the Al-5Mg-3Zn alloy prepared in Example 1 exhibits superior mechanical and corrosion resistance properties compared to the Al-5Mg-3Zn alloy prepared in Comparative Example 2. To investigate the reasons for this excellent performance, a detailed analysis of the microstructure of the Al-5Mg-3Zn alloy prepared in Example 1 was conducted.

[0071] Figure 5 The microstructure of TiC particles in the alloy prepared in Example 1 is shown. The results show that the TiC particles generated by the in-situ reaction of the Al-Ti-C-CuO-Y2O3 refining agent system are spherical, with most having a diameter of about 500-600 nm. This is likely mainly due to the high temperature generated by the aluminothermic reaction and the combined effect of rare earth elements, which improves the wettability of carbon in the aluminum melt and promotes the complete reaction of the system.

[0072] Figure 6 The morphology of Al2O3 particles in the alloy prepared for Example 1 is shown in the figure. It can be seen from the figure that there are large TiC particles around the Al2O3 particles. It is believed that the Al2O3 is generated by the aluminothermic reaction between Al and CuO and a large amount of heat is released, which improves the wetting properties of C and Al.

[0073] from Figure 7 As can be seen, the TiC particles are approximately the same size but less than 1 μm, and are spherical. Surrounding the TiC particles are some Al₂O₃ particles, with a size similar to that of the TiC particles. From... Figure 8 As can be seen, the TiC particle size is approximately 500 nm, and the added rare earth element Y can be observed around the TiC particles. In this section, the TiC particle size is approximately 500 nanometers (nm), and the presence of added rare earth element Y is clearly visible around the TiC particles. The addition of these rare earth elements may have a certain impact on the formation and properties of TiC particles.

[0074] from Figure 9As can be seen from the figure, compared with Comparative Example 2, the size of the precipitated phase in the Al-5Mg-3Zn alloy prepared in Example 1 gradually decreases, while its shape changes from a long rod to an elliptical shape. Diffraction spot identification of the precipitated phases in Figures (b) and (f) shows the presence of the T'' / T' phase in the alloy. Furthermore, the precipitated phase of the alloy prepared in Example 1 contains trace amounts of Cu in addition to Al-5Mg-3Zn, while the precipitated phase of the alloy prepared in Comparative Example 2 contains only Al-5Mg-3Zn. The presence of Cu can significantly affect the microstructure evolution of the Al-5Mg-3Zn (wt.%) alloy; the GP region serves as the nucleation site for the T' phase, and the Cu-containing GP region has a higher number density, resulting in the formation of T-Mg... 32 (Al,Zn,Cu) 49 The precipitates are small and round, which is more beneficial to the improvement of the mechanical properties of the alloy.

[0075] Figure 10 Morphology and energy dispersive spectroscopy (EDS) analysis of the alloy precipitates prepared in Example 1. Figure 10 It is known that the T phase of the alloy contains Cu. The matrix alloy itself does not contain Cu. During the in-situ reaction of the Al-Ti-C-CuO-Y2O3 system within the Al-5Mg-3Zn (wt.%) aluminum alloy matrix to generate in-situ particles, the Al-CuO reaction releases a large amount of heat, igniting the high-temperature self-propagating reaction of the system and generating Al2O3 particles to further refine the alloy microstructure. The displaced Cu element interacts with the original strengthening phase T-Mg of the matrix alloy. 32 (Al,Zn) 49 Combined to form Cu-containing T-Mg 32 (Al,Zn,Cu) 49 Compared to the strengthening phases prepared in the Al-TiO2-C-Y2O3 system, the Cu-containing T-Mg phase is finer, more dispersed, and more circular / elliptical in shape, exhibiting a better promoting effect on alloy performance. 32 (Al,Zn,Cu) 49 The formation of the Cu-containing T-Mg phase will hinder the formation of the S phase in the alloy. The S phase, acting as a cathode phase, accelerates the corrosion and dissolution of the alloy in corrosive media. Therefore, under the preparation process parameters and alloy system of this invention, the Cu-containing T-Mg... 32 (Al,Zn,Cu) 49 The presence of the phase will be beneficial to improving the corrosion resistance of the alloy.

[0076] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A rare earth-containing aluminum alloy refining agent, characterized in that, It is composed of aluminum powder, titanium powder, carbon powder, copper oxide powder and yttrium oxide powder, and the molar ratio of aluminum, titanium, carbon, copper oxide and yttrium oxide is (2.8~6.0):(1.0~1.5):(1.2~1.5):(0.3~1.5):(0.043~0.2).

2. The method of using a rare earth-containing aluminum alloy refining agent as described in claim 1, characterized in that, Includes the following steps: Step (1): Ball mill and mix aluminum powder, titanium powder, carbon powder, copper oxide powder and yttrium oxide powder evenly to obtain the mixed raw material powder of the rare earth-containing aluminum alloy refining agent. Step (2): Press the mixed raw material powder into shape to obtain aluminum alloy refining agent block; wrap the aluminum alloy refining agent block with aluminum foil and dry it; Step (3): Press the dried aluminum alloy refining agent block into the aluminum alloy melt for a high-temperature self-propagating reaction to generate the required in-situ particles; Step (4): The reacted aluminum alloy melt is cast using a near-liquidothermal temperature casting method. After casting, an aluminum alloy with refined grain structure is obtained.

3. The method of using the rare earth-containing aluminum alloy refining agent according to claim 2, characterized in that, In step (1), the particle size of the mixed raw material powder is 1~40μm; the ball milling time is 30~90min.

4. The method of using the rare earth-containing aluminum alloy refining agent according to claim 2, characterized in that, In step (2), the forming pressure is 12~18MPa and the holding time is 90~150s; the aluminum alloy refining agent block is a cylinder with a diameter of 20~30mm and a thickness of 5~8mm; during the drying process, the drying temperature is 100~200℃ and the drying time is 30~60min.

5. The method of using the rare earth-containing aluminum alloy refining agent according to claim 2, characterized in that, In step (3), the amount of aluminum alloy refining agent block is 0.5~10wt.% of the mass of aluminum alloy melt; the temperature of aluminum alloy melt is controlled at 900~950℃ during high-temperature self-propagating reaction.

6. The method of using the rare earth-containing aluminum alloy refining agent according to claim 2, characterized in that, In step (4), the aluminum alloy melt temperature is reduced to 700~800℃ for purification treatment, and then the temperature is further reduced to 650~680℃ for casting. Before casting, the casting metal mold is preheated to 100~150℃; after casting, it is air-cooled to room temperature.

7. The method of using the rare earth-containing aluminum alloy refining agent according to claim 2, characterized in that, In step (3), the method for preparing the aluminum alloy melt is as follows: prepare alloy raw materials according to the design composition of the base aluminum alloy, and melt them at room temperature and pressure using a non-vacuum melting method to obtain the aluminum alloy melt.

8. The method of using the rare earth-containing aluminum alloy refining agent according to claim 7, characterized in that, In step (3), in the base aluminum alloy: the mass fraction of magnesium is 4.40~5.60 wt.%, the mass fraction of zinc is 2.40~3.60 wt.%, the mass fraction of silicon is less than or equal to 0.08 wt.%, the mass fraction of iron is less than or equal to 0.08 wt.%, the mass fraction of manganese is less than or equal to 0.08 wt.%, and the balance is aluminum.

9. The method of using the rare earth-containing aluminum alloy refining agent according to claim 7, characterized in that, In step (3), the melting temperature of the alloy raw materials is 900~950℃ and the melting time is 20~40min.

10. The method of using the rare earth-containing aluminum alloy refining agent according to any one of claims 2-9, characterized in that, In step (1), the molar ratio of aluminum, titanium, carbon, copper oxide and yttrium oxide in the mixed raw material powder is 2.8:1:1.2:0.3:0.043; aluminum powder passes through a 700-mesh sieve, titanium powder passes through a 500-mesh sieve, carbon powder passes through a 500-mesh sieve, copper oxide powder passes through a 700-mesh sieve, and the average particle size of yttrium oxide powder is 1.0 μm; the ball milling time is 60 min. In step (2), the forming pressure is 12~18MPa and the holding time is 120s; the aluminum alloy refining agent block is a cylinder with a diameter of 25mm and a height of 7mm; during the drying process, the drying temperature is 150℃ and the drying time is 40min. In step (3), the method for preparing the aluminum alloy melt is as follows: prepare alloy raw materials according to the designed composition of the base aluminum alloy, and melt them at room temperature and pressure using a non-vacuum melting method to obtain the aluminum alloy melt; in the base aluminum alloy: the mass fraction of magnesium is 5.0 wt.%, the mass fraction of zinc is 3.0 wt.%, the mass fraction of silicon is less than or equal to 0.08 wt.%, the mass fraction of iron is less than or equal to 0.08 wt.%, the mass fraction of manganese is less than or equal to 0.08 wt.%, and the balance is aluminum; the melting temperature of the alloy raw materials is 950℃, and the melting time is 30 min; In step (3), the amount of aluminum alloy refining agent block is 8 wt.% of the mass of the aluminum alloy melt; the temperature of the aluminum alloy melt is controlled at 950℃ during the high-temperature self-propagating reaction; In step (4), the aluminum alloy melt temperature is reduced to 700°C for purification treatment, and then the temperature is further reduced to 650°C for casting. Before casting, the casting metal mold is preheated to 150°C; after casting, it is air-cooled to room temperature.

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