Fine-grain cast aluminum-copper alloy prepared based on rare earth composite refiner Al-Ti-B-RE and preparation method of fine-grain cast aluminum-copper alloy

Abstract

The invention belongs to the technical field of aluminum alloys, and particularly discloses a fine-grain cast aluminum-copper alloy prepared based on a rare earth composite refiner Al-Ti-B-RE and a preparation method of the fine-grain cast aluminum-copper alloy. The rare earth composite refiner Al-Ti-B-RE is prepared from the following components in percentage by mass: 3.5 to 6.5 percent of Ti, 0.5 to 2.5 percent of B, 2.1 to 9.0 percent of RE and the balance of Al and impurity elements, the fine grain cast aluminum-copper alloy prepared on the basis of the rare earth composite refiner Al-Ti-B-RE comprises the following components in percentage by mass: 3.50 to 6.50 percent of Cu, 0.20 to 0.40 percent of Mn, 0.30 to 0.55 percent of Si, 0.80 to 1.50 percent of Mg, 0.01 to 0.15 percent of Fe, 0.02 to 0.20 percent of Ti, 0.004 to 0.15 percent of B, 0.005 to 0.35 percent of RE and the balance of Al and impurity elements. According to the method, the composite refiner Al-Ti-B-RE is used for replacing a traditional Al-Ti-B refiner, and alloy component optimization is combined, so that effective refinement of aluminum-copper alloy grains is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloys, and in particular to a fine-grained cast aluminum-copper alloy prepared based on a rare earth composite refiner Al-Ti-B-RE and a preparation method thereof. Background Art

[0002] Al-Cu alloys have become indispensable metal materials in the aviation field due to their high specific strength, excellent fracture resistance, excellent fatigue resistance, good heat resistance and strong corrosion resistance. The excellent mechanical properties of aluminum-copper alloys are mainly due to the ability to precipitate Al2Cu through heat treatment. In order to further improve the mechanical properties of Al-Cu alloys, we use grain refiners to refine the grain size and structure of aluminum-copper alloys.

[0003] Grain refinement is an important means to improve the toughness of aluminum alloys. It can improve strength and plasticity at the same time. In addition, grain refinement can also reduce the solidification defects of the alloy and improve the casting performance of the alloy. Therefore, the research on grain refinement has important practical significance. At present, the commonly used refiner is Al-5Ti-1B refiner, but Al-Ti-B refiner still has some problems, such as TiB2 particles are easy to aggregate and precipitate, which affects the grain refinement effect. Therefore, the development of more efficient refiners has important research and practical significance.

[0004] The present invention takes aluminum-copper alloy as the object, and adds rare earth composite refiner Al-Ti-B-RE during the smelting process. After the aluminum-copper alloy is refined by the rare earth composite refiner Al-Ti-B-RE, the grain size is significantly reduced, thereby developing a fine-grained aluminum-copper alloy. Summary of the invention

[0005] The present invention provides a fine-grained cast aluminum-copper alloy prepared based on a rare earth composite refiner Al-Ti-B-RE and a preparation method thereof, wherein the element content of the rare earth composite refiner Al-Ti-B-RE is optimized, and the optimal element content and the optimal addition amount in the alloy are designed.

[0006] In order to achieve the above object, the specific technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a rare earth composite refiner Al-Ti-B-RE and a fine-grained cast aluminum-copper alloy prepared based on the rare earth composite refiner Al-Ti-B-RE. The rare earth composite refiner Al-Ti-B-RE comprises the following components by mass fraction: Ti 3.5-6.5%, B 0.5-2.5%, RE 2.1-9.0%, and the remainder is Al and impurity elements, and the total mass percentage of the impurity elements is less than or equal to 0.50%. The fine-grained cast aluminum-copper alloy prepared based on the rare earth composite refiner Al-Ti-B-RE includes the following components in mass fraction: Cu 3.50-6.50%, Mn 0.20-0.40%, Si0.30-0.55%, Mg 0.80-1.50%, Fe0.01-0.15%, Ti 0.02-0.20%, B 0.004-0.15%, RE 0.005-0.35%, and the remainder is Al and impurity elements, and the total mass percentage content of the impurity elements is less than or equal to 0.50%.

[0008] Furthermore, the fine-grained cast aluminum-copper alloy includes the following components in mass fraction: Cu 3.50-6.00%, Mn 0.20-0.35%, Si 0.30-0.50%, Mg 0.80-1.20%, Fe: 0.01-0.12%, Ti 0.02-0.20%, B 0.004-0.15%, RE 0.005-0.30%, and the balance is Al and impurity elements.

[0009] Furthermore, the rare earth composite refiner Al-Ti-B-RE comprises the following components in mass fractions: Ti 4.0-6.0%, B 0.5-2.0%, RE 2.1-8.5%, and the remainder is Al and impurity elements.

[0010] Furthermore, the rare earth composite refiner Al-Ti-B-RE is added to the aluminum-copper alloy in an amount of 0.10-2.00%, preferably 0.10-1.50%.

[0011] Furthermore, the rare earth includes at least one of La, Ce, Y, Pm, Er, Nd, and Sm.

[0012] In a second aspect, the present invention provides a method for preparing the fine-grained aluminum-copper alloy prepared based on the rare earth composite refiner Al-Ti-B-RE, comprising the following steps:

[0013] S1. Provide prefabricated raw materials of pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B-RE composite refiner, M includes Cu, Si, Fe, Mn; the component content of the Al-Ti-B-RE composite refiner is: Ti 3.5-6.5%, B 0.5-2.5%, RE 2.1-9.0%, the balance is Al and impurity elements, and the total mass percentage of the impurity elements is less than or equal to 0.50%; the mass proportion of each element in the prefabricated raw material based on 100 parts by mass of all the above prefabricated raw materials is: Cu 3.50-6.50%, Mn 0.20-0.40%, Si0.30-0.55%, Mg 0.80-1.50%, Fe 0.01-0.15%, Ti 0.02-0.20%, B 0.004-0.15%, RE 0.005-0.35%, the balance being Al and impurity elements, the sum of the mass percentages of the impurity elements being less than or equal to 0.50%;

[0014] S2. Before smelting, pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B-RE composite refiner are placed in a drying oven at a temperature of 150-250 ° C and dried for 1.5-2.5 hours for use;

[0015] S3. Adding a pure aluminum ingot into a smelting furnace, setting the furnace temperature to 720°C, and completely melting the aluminum ingot to obtain an aluminum melt;

[0016] S4. Adding aluminum-M master alloy and pure Mg to the aluminum melt in sequence to obtain an aluminum alloy melt.

[0017] S5. Raise the temperature of the aluminum alloy melt to 730°C-740°C, add a refining agent to the bottom of the melt, and stir the aluminum alloy melt for 5-10 minutes, and then let it stand for 5-10 minutes;

[0018] S6. After slagging, the temperature of the aluminum alloy melt is raised to 740°C-760°C, and an Al-Ti-B-RE rare earth composite refiner is added to the refined aluminum alloy melt, and the mixture is stirred for 3-5 minutes and then allowed to stand for 5-20 minutes;

[0019] S7. The furnace temperature is then lowered to 720°C-730°C, and the aluminum alloy melt is cast into a metal mold to obtain an aluminum-copper alloy containing rare earth.

[0020] Furthermore, the refining agent is a fluoride salt refining agent, such as MgF2, AlF3, etc., which can be one or more.

[0021] The present invention has the following beneficial effects:

[0022] (1) RE can inhibit the aggregation of TiB2 particles in Al-Ti-B. TiB2 has the lowest nucleation energy and is a very effective nucleating agent for aluminum. Therefore, the addition of RE is beneficial to the refining effect of the composite rare earth refiner Al-Ti-B-RE.

[0023] (2) Adding a small amount of RE to the Al-Ti-B refiner can form Ti2Al 20 RE phase, Ti2Al 20 There are 8 matching relationships between RE phase and Al phase, so Ti2Al 20 RE has a better nucleation effect than TiAl3, so a small amount of rare earth can improve the refining effect of the composite rare earth refiner Al-Ti-B-RE. As the amount of RE added to the Al-Ti-B refiner increases, RE can form Ti2Al on the surface of the TiAl3 phase. 20 RE phase, Ti2Al 20 The TiAl3 phase surrounded by RE phase also has a better nucleation effect.

[0024] (3) The content of RE in the composite rare earth refiner Al-Ti-B-RE cannot be too high. When the content of RE in the composite rare earth refiner Al-Ti-B-RE is too high, the excess RE will react with Ti2Al 20 RE phase reaction generates a large amount of network Al4RE phase, thereby reducing the Ti2Al 20 RE phase nucleates particles, while the network Al4RE phase does not have a nucleation effect, so it is necessary to control the content of RE in the composite rare earth refiner Al-Ti-B-RE.

[0025] (4) A small amount of RE in Al-Cu alloy can reduce the hydrogen concentration and purify the melt to the maximum extent, reduce the introduction of oxidizing substances, reduce the viscosity of the alloy, thereby improving the fluidity of the alloy and improving the ability of the melt to fill the mold. In addition, RE induces the refinement of dendrites, reduces the dendrite width, promotes the dispersion of the second phase, delays the coherence of dendrites, and reduces the flow resistance of the melt. Excessive RE content will form clustered Al8Cu4RE phases precipitated along the grain boundaries during the solidification of the alloy. During the solidification process, intermetallic compounds are pushed to the solid-liquid interface. The presence of intermetallic compounds will lead to greater resistance to fluid flow, which may impair fluidity. Therefore, it is necessary to control the content of RE in Al-Ti-B-RE and the amount of Al-Ti-B-RE added.

[0026] (5) The addition of an appropriate amount of RE has a certain purification ability, which can reduce harmful metal inclusions and oxides in aluminum alloys, thereby playing a role in degassing and purifying the melt. The addition of RE can reduce the size of the Fe-rich phase in the structure, thereby reducing the influence of the Fe-rich phase on the mechanical properties.

[0027] (6) The addition of rare earth composite refiner Al-Ti-B-RE greatly refines the alloy grain size and the size of the second phase, ensuring the uniformity of the structure. Grain refinement leads to a decrease in the porosity and pore size of the aluminum alloy, thereby improving the mechanical properties of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is the microstructure of the alloy anode coating in Example 1 of the present invention.

[0030] Figure 2 This is the microstructure of the alloy anode coating of Comparative Example 1 of the present invention.

[0031] Figure 3 This is the scanning microstructure of the rare earth composite refiner in Example 1 of the present invention.

[0032] Figure 4 This is the scanning microstructure of the refiner in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of 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 intended to limit the present invention.

[0034] The inventors found that the TiB2 particles of the Al-Ti-B grain refiner tend to aggregate, which results in a decrease in its aluminum alloy refinement effect. The addition of rare earth RE can make the TiB2 particles more evenly distributed in the Al-Ti-B structure, thereby improving the non-uniform nucleation effect of the TiB2 particles. l20 RE phase, and Ti2Al 20 The lattice matching degree between RE phase and α-Al is good, so Ti2Al 20RE phase can also serve as an effective nucleation site for α-Al. Based on this, the present invention combines the optimization of alloy components and contents, so that the grain size of the aluminum-copper alloy is significantly reduced after being refined by the composite refiner Al-Ti-B-RE, the second phase in the structure is significantly refined, and the number of oxidation and metal inclusions in the structure is also reduced, which is beneficial to the improvement of mechanical properties and processing properties. In addition, the addition form of the composite refiner Al-Ti-B-RE of the present invention is also necessary. When Ti, B, and RE elements are added to the aluminum-copper alloy separately at the same content, the refining effect when the composite refiner Al-Ti-B-RE is added and the improvement level of the mechanical properties and processing properties of the alloy cannot be achieved.

[0035] The following is a method for preparing the aluminum alloy in combination with the embodiments and comparative examples, wherein the mass percentage of the impurity elements in each embodiment and comparative example is ≤0.50%. It will be understood by those skilled in the art that the preparation method described in the present invention is only an example, and any other suitable preparation method is within the scope of the present invention.

[0036] Example 1

[0037] A prefabricated raw material of pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B-RE composite refiner is provided, wherein M comprises Cu, Si, Fe and Mn, and the mass proportion of each element in the prefabricated raw material based on 100 parts by mass of all the above prefabricated raw materials is as follows: Cu: 5.50%, Mn: 0.30%, Si: 0.35%, Mg: 0.90%, Fe: 0.08%, Ti: 0.025%, B: 0.005%, Ce: 0.015%, and the balance is Al and impurity elements.

[0038] The rare earth composite refiner Al-Ti-B-RE includes the following components in mass fractions: Ti: 5.1%, B: 1.1%, Ce: 3.1%, and the balance is Al and impurity elements.

[0039] Before smelting, pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B-RE composite refiner are placed in a drying oven at a temperature of 200° C. and dried for 2.0 hours for use.

[0040] Add pure aluminum ingots into a smelting furnace, set the furnace temperature to 720°C, and completely melt the aluminum ingots to obtain aluminum melt.

[0041] An aluminum alloy melt is obtained by sequentially adding aluminum-M master alloy Zn and pure Mg into the aluminum melt.

[0042] The temperature of the aluminum alloy melt was raised to 740°C, a refining agent was added to the bottom of the melt, and the aluminum alloy melt was stirred for 8 minutes and then allowed to stand for 8 minutes.

[0043] After slagging, the temperature of the aluminum alloy melt was raised to 750°C, and 0.5% by mass of Al-Ti-B-RE rare earth composite refiner was added to the refined aluminum alloy melt, and the mixture was stirred for 5 minutes and then allowed to stand for 10 minutes.

[0044] Subsequently, the furnace temperature is lowered to 725°C, and the aluminum alloy melt is cast into a metal mold to obtain a fine-grained cast aluminum-copper alloy containing rare earths. The addition of the rare earth composite refiner reduces the grain size of the alloy, and its grain size is smaller than that of the cast aluminum-copper alloy after refinement by the Al-Ti-B refiner in Comparative Example 1.

[0045] Example 2

[0046] A prefabricated raw material of pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B-RE composite refiner is provided, wherein M comprises Cu, Si, Fe and Mn, and the mass proportion of each element in the prefabricated raw material based on 100 parts by mass of all the above prefabricated raw materials is as follows: Cu: 5.20%, Mn: 0.25%, Si: 0.40%, Mg: 1.0%, Fe: 0.07%, Ti: 0.03%, B: 0.005%, La: 0.016%, and the balance is Al and impurity elements.

[0047] The rare earth composite refiner Al-Ti-B-RE includes the following components in mass fractions: Ti: 4.9%, B: 0.9%, La: 2.6%, and the balance is Al and impurity elements.

[0048] Before smelting, pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B-RE composite refiner are placed in a drying oven at a temperature of 200° C. and dried for 2.0 hours for use.

[0049] Add pure aluminum ingots into a smelting furnace, set the furnace temperature to 720°C, and completely melt the aluminum ingots to obtain aluminum melt.

[0050] An aluminum alloy melt is obtained by sequentially adding aluminum-M master alloy, pure Zn and pure Mg into an aluminum melt.

[0051] The temperature of the aluminum alloy melt was raised to 730°C, a refining agent was added to the bottom of the melt, and the aluminum alloy melt was stirred for 5 minutes and then allowed to stand for 5 minutes.

[0052] After slagging, the temperature of the aluminum alloy melt was raised to 750°C, and an Al-Ti-B-RE rare earth composite refiner with a mass fraction of 0.6% was added to the refined aluminum alloy melt, and the mixture was stirred for 5 minutes and then allowed to stand for 10 minutes.

[0053] Subsequently, the furnace temperature is lowered to 720°C, and the aluminum alloy melt is cast into a metal mold to obtain a fine-grained cast aluminum-copper alloy containing rare earths. The addition of the rare earth composite refiner reduces the grain size of the alloy, and its grain size is smaller than that of the cast aluminum-copper alloy refined by the Al-Ti-B refiner in Comparative Example 1.

[0054] Example 3

[0055] A prefabricated raw material of pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B-RE composite refiner is provided, wherein M comprises Cu, Si, Fe and Mn, and the mass proportion of each element in the prefabricated raw material based on 100 parts by mass of all the above prefabricated raw materials is as follows: Cu: 5.00%, Mn: 0.27%, Si: 0.42%, Mg: 0.9%, Fe: 0.08%, Ti: 0.04%, B: 0.008%, Er: 0.027%, and the balance is Al and impurity elements.

[0056] The rare earth composite refiner Al-Ti-B-RE includes the following components in mass fractions: Ti: 5.3%, B: 1.0%, Er: 3.4%, and the balance is Al and impurity elements.

[0057] Before smelting, pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B-RE composite refiner are placed in a drying oven at a temperature of 200° C. and dried for 2.0 hours for use.

[0058] Add pure aluminum ingots into a smelting furnace, set the furnace temperature to 720°C, and completely melt the aluminum ingots to obtain aluminum melt.

[0059] An aluminum alloy melt is obtained by sequentially adding aluminum-M master alloy, pure Zn and pure Mg into an aluminum melt.

[0060] The temperature of the aluminum alloy melt was raised to 730°C, a special refining agent for aluminum-magnesium alloy was added to the bottom of the melt, and the aluminum alloy melt was stirred for 10 minutes and then allowed to stand for 10 minutes.

[0061] After slagging, the temperature of the aluminum alloy melt was raised to 750°C, and 0.8% by mass of Al-Ti-B-RE rare earth composite refiner was added to the refined aluminum alloy melt, and the mixture was stirred for 5 minutes and then allowed to stand for 10 minutes.

[0062] Subsequently, the furnace temperature is lowered to 720°C, and the aluminum alloy melt is cast into a metal mold to obtain a fine-grained cast aluminum-copper alloy containing rare earths. The addition of the rare earth composite refiner reduces the grain size of the alloy, and its grain size is smaller than that of the cast aluminum-copper alloy refined by the Al-Ti-B refiner in Comparative Example 1.

[0063] Comparative Example 1

[0064] A prefabricated raw material of pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B refiner is provided, wherein M comprises Cu, Si, Fe and Mn, and the mass proportion of each element in the prefabricated raw material based on 100 parts by mass of all the above prefabricated raw materials is as follows: Cu: 4.80%, Mn: 0.26%, Si: 0.40%, Mg: 1.1%, Fe: 0.08%, Ti: 0.025%, B: 0.006%, and the balance is Al and impurity elements.

[0065] The refiner Al-Ti-B includes the following components in mass fractions: Ti: 5.1%, B: 1.2%, and the balance is Al and impurity elements.

[0066] Before smelting, pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B refiner are placed in a drying oven at a temperature of 200° C. and dried for 2.0 hours for use.

[0067] Add pure aluminum ingots into a smelting furnace, set the furnace temperature to 720°C, and completely melt the aluminum ingots to obtain aluminum melt.

[0068] An aluminum alloy melt is obtained by sequentially adding aluminum-M master alloy, pure Zn and pure Mg into an aluminum melt.

[0069] The temperature of the aluminum alloy melt was raised to 730°C, a special refining agent for aluminum-magnesium alloy was added to the bottom of the melt, and the aluminum alloy melt was stirred for 5 minutes and then allowed to stand for 5 minutes.

[0070] After slagging, the temperature of the aluminum alloy melt was raised to 750°C, and an Al-Ti-B refiner with a mass fraction of 0.5% was added to the refined aluminum alloy melt. The mixture was stirred for 5 minutes and then allowed to stand for 10 minutes.

[0071] The furnace temperature is then lowered to 720°C, and the aluminum alloy melt is cast into a metal mold to obtain a cast aluminum-copper alloy.

[0072] Examples 1-3 can all obtain uniform fine-grained structures, and the alloys have good mechanical properties and fluidity, among which Example 1 has the smallest grain size and the best refinement effect. Comparing the optical microstructures of the alloys of Example 1 and Comparative Example 1, as shown in FIG. Figure 1-2 As shown, it can be seen that the degree of grain refinement in Example 1 is significantly higher; comparing the scanning microstructures of the refiners in Example 1 and Comparative Example 1, as shown in FIG. Figure 3-4 As shown in the figure, it can be seen that compared with comparative example 1, the aggregation phenomenon of TiB2 particles in Example 1 is improved, and the core-shell TiAl3 formed by RE i2 Al 20 RE phase, all of which help to improve the grain refinement effect.

Claims

1. A fine-grained cast aluminum-copper alloy prepared based on a rare earth composite refiner Al-Ti-B-RE, characterized in that: The rare earth composite refiner Al-Ti-B-RE comprises the following components by mass fraction: Ti 3.5-6.5%, B 0.5-2.5%, RE 2.1-9.0%, and the remainder is Al and impurity elements, and the total mass percentage of the impurity elements is less than or equal to 0.50%; The fine-grained cast aluminum-copper alloy prepared based on the rare earth composite refiner Al-Ti-B-RE includes the following components in mass fraction: Cu 3.50-6.50%, Mn 0.20-0.40%, Si 0.30-0.55%, Mg0.80-1.50%, Fe 0.01-0.15%, Ti 0.02-0.20%, B 0.004-0.15%, RE 0.005-0.35%, and the remainder is Al and impurity elements, and the total mass percentage content of the impurity elements is less than or equal to 0.50%.

2. The fine-grained cast aluminum-copper alloy according to claim 1, characterized in that: The invention comprises the following components in mass fraction: Cu 3.50-6.00%, Mn 0.20-0.35%, Si 0.30-0.50%, Mg 0.80-1.20%, Fe: 0.01-0.12%, Ti 0.02-0.20%, B 0.004-0.15%, RE 0.005-0.30%, and the balance is Al and impurity elements.

3. The fine-grained cast aluminum-copper alloy according to claim 1, characterized in that: The rare earth composite refiner Al-Ti-B-RE comprises the following components in mass fractions: Ti 4.0-6.0%, B 0.5-2.0%, RE 2.1-8.5%, and the balance is Al and impurity elements.

4. The fine-grained cast aluminum-copper alloy according to claim 1 or 3, characterized in that: The rare earth composite refiner Al-Ti-B-RE is added in an amount of 0.10-2.00% in the aluminum-copper alloy.

5. The fine-grained cast aluminum-copper alloy according to claim 4, characterized in that: The rare earth composite refiner Al-Ti-B-RE is added in an amount of 0.10-1.50% in the aluminum-copper alloy.

6. The fine-grained cast aluminum-copper alloy according to claim 1, characterized in that: The rare earth includes at least one of La, Ce, Y, Pm, Er, Nd, and Sm.

7. A method for preparing a fine-grained cast aluminum-copper alloy based on a rare earth composite refiner Al-Ti-B-RE, comprising the following steps: S1. Provide prefabricated raw materials of pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B-RE composite refiner, M includes Cu, Si, Fe, Mn; the component content of the Al-Ti-B-RE composite refiner and the mass proportion of each element in the prefabricated raw material based on 100 parts by mass of all the above prefabricated raw materials are as shown in claim 1; S2. Before smelting, pure aluminum, pure magnesium, aluminum-M master alloy, refining agent and Al-Ti-B-RE composite refiner are placed in a drying oven at a temperature of 150-250 ° C and dried for 1.5-2.5 hours for use; S3. Adding a pure aluminum ingot into a smelting furnace, setting the furnace temperature to 720°C, and completely melting the aluminum ingot to obtain an aluminum melt; S4. Adding aluminum-M master alloy and pure Mg to the aluminum melt in sequence to obtain an aluminum alloy melt. S5. Raise the temperature of the aluminum alloy melt to 730°C-740°C, add a refining agent to the bottom of the melt, and stir the aluminum alloy melt for 5-10 minutes, and then let it stand for 5-10 minutes; S6. After slagging, the temperature of the aluminum alloy melt is raised to 740°C-760°C, and an Al-Ti-B-RE rare earth composite refiner is added to the refined aluminum alloy melt, and the mixture is stirred for 3-5 minutes and then allowed to stand for 5-20 minutes; S7. The furnace temperature is then lowered to 720°C-730°C, and the aluminum alloy melt is cast into a metal mold to obtain an aluminum-copper alloy containing rare earth.

8. The preparation method according to claim 7, characterized in that: The refining agent is a fluoride salt refining agent.

9. A rare earth composite refiner Al-Ti-B-RE suitable for preparing fine-grained cast aluminum-copper alloy, characterized in that: The invention comprises the following components by mass fraction: Ti 3.5-6.5%, B 0.5-2.5%, RE 2.1-9.0%, and the remainder is Al and impurity elements, wherein the total mass percentage of the impurity elements is less than or equal to 0.50%.

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