A method for improving the thermal and electrical conductivity of low-silicon aluminum alloys

Abstract

The application belongs to the alloy field, and specifically discloses a method for improving the heat conduction and electric conduction performance of a low-silicon aluminum alloy, which comprises the following steps: firstly, mixing an aluminum alloy melt with rare earth, refining, then mixing with an Al-Sr-RE composite modifier, standing, then skimming slag, then adding a covering agent, degassing, filtering, and casting to obtain the aluminum alloy; RE in the Al-Sr-RE composite modifier is at least one of La and Ce; the aluminum alloy contains a transition metal. In the method, the rare earth and the Al-Sr-RE composite modifier are used for composite modification, compounds are formed with transition metals Ti, V, Mn and Cr, the existing form of the transition metal is changed, the solid solubility of the transition element is reduced, the morphology, size and distribution of the iron-rich phase are improved, and thus the electric conduction and heat conduction performance of the aluminum alloy is improved.

Description

Technical Field

[0001] This invention belongs to the field of alloys, and specifically relates to a method for improving the thermal and electrical conductivity of low-silicon aluminum alloys. Background Technology

[0002] Aluminum alloys possess high specific strength and specific stiffness, good processing and formability, excellent corrosion resistance, and superior thermal and electrical conductivity, making them widely used in various sectors of the national economy. In recent years, with the increasing power of 5G communications, automobiles, and electronic appliances, higher demands have been placed on the thermal and electrical conductivity of materials. Pure aluminum has good electrical and thermal conductivity, but its low strength (only tens of megapascals) limits its applications. Alloying is an effective method to improve alloy strength. By adding alloying elements such as Mg, Cu, and Zn, solid solution strengthening and second-phase strengthening are achieved, significantly improving the alloy's strength. However, the addition of any element will lead to lattice distortion, increasing the scattering of electrons in electrical / thermal conduction and reducing the alloy's electrical / thermal conductivity.

[0003] Studies have found that different elements have significantly different effects on the thermal and electrical conductivity of aluminum alloys. For example, transition elements such as Ti, Mn, Cr, and V have a greater impact on the thermal and electrical conductivity of aluminum alloys, while elements such as Fe, Zn, and Co have a smaller impact. This is related to the solid solubility of the elements in Al and their atomic radii; the greater the solid solubility and the greater the size difference, the greater the adverse effect. Therefore, reducing the content of transition elements or forming a second phase is crucial to improving the thermal and electrical conductivity of aluminum alloys. CN117587279A discloses a method for improving the thermal conductivity of 6XXX series aluminum alloys. This method mainly involves adding an appropriate amount of boron (B) and allowing the melt to settle, promoting the formation of high-density, high-temperature phases of V, Ti, and Cr transition elements with B, which are then removed through natural sedimentation. Simultaneously, an Al-Sr-RE composite modifier is used to coarse the grains and refine the iron-rich phase to improve electrical and thermal conductivity. CN118460892A discloses a high-Fe-content conductive wrought aluminum alloy and its preparation method. The alloy contains Mg: 0.45–0.6%; Si: 0.4–0.5%; Fe: 0.1–0.5%; La: 0.3–0.4%; B: 0.03–0.05%; Y: 0.05–0.08%; Sn: 0.03–0.06%; with the remainder being Al. By adding trace amounts of B, Y, La, and Sn, the alloy's conductivity and toughness are improved. B and Y mainly reduce impurities such as Mn, V, Cr, and Ti, while La modifies the iron-rich phase, and Sn mainly delays the precipitation of strengthening phases. Both of the above methods improve the conductivity of the alloy by removing impurities and modifying the second phase, but after adding B, static holding is required, which reduces production efficiency. At the same time, the melt at the bottom contains a high content of transition elements, which cannot be directly used for the preparation of high conductivity aluminum alloys, thus affecting the utilization rate of the alloy. Summary of the Invention

[0004] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide a method for improving the properties of aluminum alloys, which improves the thermal and electrical conductivity of aluminum alloys by changing the form in which transition elements exist.

[0005] The second objective of this invention is to provide an aluminum alloy.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a method for improving the properties of aluminum alloys, comprising the following steps:

[0008] First, the aluminum alloy melt is mixed with rare earth elements and refined. Then, it is mixed with Al-Sr-RE composite modifier, allowed to stand, and slag is removed. Then, a covering agent is added, and the mixture is degassed, filtered, and cast to obtain the aluminum alloy.

[0009] The RE in the Al-Sr-RE composite modifier is selected from at least one of La and Ce;

[0010] The aluminum alloy contains transition metals.

[0011] This invention utilizes rare earth microalloying and an Al-Sr-RE composite modifier for treatment. The purpose of rare earth microalloying is to leverage the high reactivity of rare earth elements to form multi-component compounds with transition elements such as Ti, V, Mn, and Cr, thereby reducing the solid solubility of these transition elements in Al. Without altering the beneficial properties of the transition elements to the alloy, the invention reduces their impact on the electrical and thermal conductivity of the aluminum alloy by changing their form. Unlike existing methods that use borylation, this invention, by introducing rare earth elements and an Al-Sr-RE composite modifier, eliminates the need to remove transition elements and avoids prolonged melt settling and liquid transfer to promote the precipitation of MB2 (M being V, Ti, Mn, Cr, etc.), offering advantages such as high efficiency and a shorter process.

[0012] In some embodiments of the present invention, the aluminum alloy contains no more than 1.5% Si by mass; in some embodiments of the present invention, the mass percentage of Si in the aluminum alloy is 0-1.5%; in some embodiments of the present invention, the mass percentage of Si in the aluminum alloy is any value or a range formed by any two of the following: 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, and 1.5%. Limiting the Si content aims to reduce RE consumption. When the alloy contains a certain amount of Si, it easily forms Al-Si-RE ternary compounds with La, Ce, etc., reducing the effective RE content and hindering the formation of compounds with transition elements, thus reducing the effect of RE addition.

[0013] In some embodiments of the present invention, the Al-Sr-RE composite modifier contains 4-10% Sr by mass, 5-20% RE by mass, and Al as the balance. The purpose of Al-Sr-RE composite modification is to improve the morphology and distribution of the iron-rich phase. The principle is to utilize the high reactivity of Sr and RE elements, and the formation of Al₄(SrRE) and Al₂O₃, where Sr and RE are mutually dissolved. 11 The (RESr)3 phase, which forms Sr and RE atom clusters upon dissolution, can adsorb onto the surface of the iron-rich phase and its nucleation particles, inhibiting the nucleation and growth of the iron-rich phase, improving the morphology, size and distribution of the iron-rich phase, thereby enhancing the mechanical properties of the alloy.

[0014] In some embodiments of the present invention, the mass percentage of Sr in the Al-Sr-RE composite modifier is any value of 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range formed by any two of these values.

[0015] In some embodiments of the present invention, the mass percentage of RE in the Al-Sr-RE composite modifier is any value or a range formed by any two of the following: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%.

[0016] In some embodiments of the present invention, the mass of the Al-Sr-RE composite modifier is 0.1% to 0.3% of the mass of the aluminum alloy melt; in some embodiments of the present invention, the mass of the Al-Sr-RE composite modifier is any value or a range formed by any two of 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, and 0.3% of the mass of the aluminum alloy melt.

[0017] In some embodiments of the present invention, the transition metal is selected from at least one of iron, cobalt, nickel, copper, zinc, chromium, manganese, vanadium, titanium, and zirconium; in some embodiments of the present invention, the transition metal is selected from at least one of iron, chromium, manganese, vanadium, and titanium.

[0018] In some embodiments of the present invention, the rare earth element is selected from at least one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium; in some embodiments of the present invention, the rare earth element is selected from at least one of lanthanum (La) and cerium (Ce). Compared with other rare earth elements, La and Ce have the advantages of readily available raw materials and low price.

[0019] In some embodiments of the present invention, the mass ratio of the rare earth element to the transition metal is (0.8–1.2):1; in some embodiments of the present invention, the mass ratio of the rare earth element to the transition metal is any value of 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, or a range formed by any two of these values. The amount of rare earth element added in the present invention is adjusted according to the content and type of transition metal in the aluminum alloy, but the total amount of rare earth element added does not exceed 0.1% of the total mass of the aluminum alloy melt.

[0020] In some embodiments of the present invention, the mass of the rare earth element is 0.001 to 0.1% of the mass of the aluminum alloy melt; in some embodiments of the present invention, the mass of the rare earth element is any value or a range formed by any two of 0.001%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, and 0.10% of the mass of the aluminum alloy melt.

[0021] In some embodiments of the present invention, the settling time is 15 to 30 minutes; in some embodiments of the present invention, the settling time is any value or a range formed by any two of the following: 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, and 30 minutes.

[0022] In some embodiments of the present invention, the aluminum alloy melt is prepared by first placing an aluminum source and raw materials with a high melting point and that are not easily burned into a melting furnace, heating and melting them, and then refining them to adjust the aluminum alloy composition.

[0023] In some embodiments of the present invention, the refining step involves blowing the refining agent into the aluminum alloy melt using an inert gas carrier, then letting it stand for 15 to 30 minutes, and then removing the slag.

[0024] In some embodiments of the present invention, the inert gas is selected from at least one of nitrogen, argon, and helium.

[0025] A second aspect of the present invention provides an aluminum alloy obtained by processing it using the method for improving the properties of aluminum alloys described in the first aspect of the present invention.

[0026] In some embodiments of the present invention, the aluminum alloy of the present invention can be processed into wires, profiles, pipes, plates and castings by pressure processing methods such as rolling, extrusion, and drawing, or by methods such as die casting, gravity casting, and low-pressure casting.

[0027] The beneficial effects of the present invention are as follows: The method of the present invention uses rare earth and Al-Sr-RE composite modifier for composite modification. By forming compounds with transition metals such as Ti, V, Mn, and Cr, the existence form of transition metals is changed, the solid solubility of transition elements is reduced, and the morphology, size and distribution of iron-rich phase are improved, thereby improving the electrical and thermal conductivity of aluminum alloys. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope image of the aluminum alloy prepared in Example 1.

[0029] Figure 2 for Figure 1 Energy dispersive spectroscopy (EDS) and chemical composition analysis of the rare earth phase at the marked location.

[0030] Figure 3 This is a scanning electron microscope image of the aluminum alloy prepared in Comparative Example 1.

[0031] Figure 4 for Figure 3 Energy dispersive spectroscopy (EDS) and chemical composition analysis of the rare earth phase at the marked location. Detailed Implementation

[0032] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0033] The aluminum alloys used in the embodiments of the present invention are selected from 1050, 6101, and 8011 in GB / T 203190-2020 "Chemical Composition of Wrought Aluminum and Aluminum Alloys" and ZL205 alloy in GB / T 1173-2013 "Cast Aluminum Alloys". Their chemical composition and mass percentage of the composition are shown in Table 1.

[0034] Table 1. Chemical composition (wt.%) of the alloys used in the examples.

[0035]

[0036] Example 1

[0037] This example provides a method for improving the thermal and electrical conductivity of low-silicon aluminum alloys, the steps of which are as follows:

[0038] Step 1: Ingredients: Calculate the amount of raw materials to be added based on the composition of 6008 alloy.

[0039] Step 2: Melting: Place aluminum ingots and raw materials with high melting points and that are not easily burned into a melting furnace and heat them up to melt them.

[0040] Step 3: Furnace purification: Using high-purity argon gas (purity ≥ 99.9%) as a carrier, commercially available refining agent with a mass fraction of 0.12% of the melt is evenly blown into the melt. After standing for 15 minutes, the slag is removed.

[0041] Step 3: Composition Adjustment and Rare Earth Addition: Sample the melt for chemical composition testing, adjust the melt composition to ensure it meets specifications. Then add 0.06% Ce by mass of the melt.

[0042] Step 4: Second Refining and Composite Modification: The melt undergoes a second in-furnace refining process using high-purity argon as a carrier gas, through which a commercially available refining agent at a mass fraction of 0.03% of the melt is introduced. Immediately after refining, an Al-6Sr-6Ce composite modifier at a mass fraction of 0.5% of the melt is added. In the Al-6Sr-6Ce composite modifier, Sr accounts for 6% by mass, Ce accounts for 6% by mass, and Al is the balance.

[0043] Step 5: Casting: After the melt has been allowed to stand for 30 minutes, the slag is removed, and then a layer of covering agent is sprinkled on the surface of the aluminum melt; after degassing and filtration, the melt flows into the casting pan to prepare a semi-continuous casting rod.

[0044] Step 6: Processing and shaping: The cast rod is made into a heat sink using a hot extrusion process.

[0045] Example 2

[0046] This example provides a method for improving the thermal and electrical conductivity of low-silicon aluminum alloys, the steps of which are as follows:

[0047] Step 1: Ingredients: Calculate the amount of raw materials to be added based on the composition of 6101 alloy.

[0048] Step 2: Melting: Place aluminum ingots and raw materials with high melting points and that are not easily burned into a melting furnace and heat them up to melt them.

[0049] Step 3: Furnace purification: Using high-purity argon gas (purity ≥ 99.9%) as a carrier, commercially available refining agent accounting for 0.1% of the melt mass fraction is evenly blown into the melt. After standing for 20 minutes, the slag is removed.

[0050] Step 3: Composition Adjustment and Rare Earth Addition: Sample the melt for chemical composition testing, adjust the melt composition to ensure it meets specifications. Then add 0.05% La by mass of the melt.

[0051] Step 4: Second Refining and Composite Modification: The melt undergoes a second in-furnace refining process using high-purity nitrogen as a carrier gas, through which a commercially available refining agent at a mass fraction of 0.05% of the melt is introduced. Immediately after refining, an Al-8Sr-6Ce composite modifier at a mass fraction of 0.3% of the melt is added. In the Al-8Sr-6Ce composite modifier, Sr accounts for 8% by mass, Ce accounts for 6% by mass, and the balance is Al.

[0052] Step 5: Casting: After the melt has been allowed to stand for 20 minutes, the slag is removed, and then a layer of covering agent is sprinkled on the surface of the aluminum melt. After degassing and filtration, the melt flows into the casting pan and is continuously cast and rolled into aluminum rods.

[0053] Step 6: Processing and shaping: The aluminum rod is drawn into a wire with a diameter of 3mm using a drawing method.

[0054] Example 3

[0055] This example provides a method for improving the thermal and electrical conductivity of low-silicon aluminum alloys, the steps of which are as follows:

[0056] Step 1: Ingredients: Calculate the amount of raw materials to be added based on the composition of 1050 alloy.

[0057] Step 2: Melting: Place aluminum ingots and raw materials with high melting points and that are not easily burned into a melting furnace and heat them up to melt them.

[0058] Step 3: Furnace purification: Using high-purity nitrogen (purity ≥ 99.9%) as a carrier, commercially available refining agent with a mass fraction of 0.08% of the melt is evenly blown into the melt. After standing for 30 minutes, the slag is removed.

[0059] Step 3: Composition Adjustment and Rare Earth Addition: Sample the melt for chemical composition testing, adjust the melt composition to ensure it meets specifications. Then add 0.06% Ce and 0.02% La by mass fraction of the melt.

[0060] Step 4: Second Refining and Composite Modification: The melt undergoes a second in-furnace refining process using high-purity nitrogen as a carrier gas, through which a commercially available refining agent at a mass fraction of 0.08% of the melt is introduced. Immediately after refining, an Al-10Sr-4Ce-4La composite modifier at a mass fraction of 0.1% of the melt is added. In the Al-10Sr-4Ce-4La composite modifier, Sr accounts for 10% by mass, Ce for 4% by mass, La for 4% by mass, and Al is the balance.

[0061] Step 5: Casting: After the melt has been allowed to stand for 20 minutes, the slag is removed, and then a layer of covering agent is sprinkled on the surface of the aluminum melt; after degassing and filtration, the melt flows into the casting pan to prepare a semi-continuous casting rod.

[0062] Step 6: Processing and shaping: The base plate of the battery tray is made by hot extrusion.

[0063] Example 4

[0064] This example provides a method for improving the thermal and electrical conductivity of low-silicon aluminum alloys, the steps of which are as follows:

[0065] Step 1: Ingredients: Calculate the amount of raw materials to be added based on the composition of ZL205 alloy.

[0066] Step 2: Melting: Place aluminum ingots and raw materials with high melting points and that are not easily burned into a melting furnace and heat them up to melt them.

[0067] Step 3: Furnace purification: Using high-purity nitrogen (purity ≥ 99.9%) as a carrier, commercially available refining agent accounting for 0.10% of the melt mass fraction is evenly blown into the melt. After standing for 25 minutes, the slag is removed.

[0068] Step 3: Composition Adjustment and Rare Earth Addition: Sample the melt for chemical composition testing, adjust the melt composition to ensure it meets specifications. Then add 0.03% Ce and 0.04% La by mass fraction of the melt.

[0069] Step 4: Second Refining and Composite Modification: The melt undergoes a second in-furnace refining process using high-purity nitrogen as a carrier gas, through which a commercially available refining agent at a mass fraction of 0.03% of the melt is introduced. Immediately after refining, an Al-8Sr-5Ce-5La composite modifier at a mass fraction of 0.15% of the melt is added. In the Al-8Sr-5Ce-5La composite modifier, Sr accounts for 8% by mass, Ce for 5% by mass, La for 5% by mass, and Al is the balance.

[0070] Step 5: Casting: After the melt has been allowed to stand for 25 minutes, the slag is removed, and then a layer of covering agent is sprinkled on the surface of the aluminum melt; after degassing and filtration, the melt flows into the casting pan to prepare the ingot.

[0071] Step 6: Shaping: The parts are gravity-cast using a remelting method.

[0072] Comparative Example 1

[0073] The method for improving the thermal and electrical conductivity of low-silicon aluminum alloys in this example differs from that in Example 1 only in that RE is not added in the third step of this example.

[0074] The third step in this example is to sample and test the chemical composition of the melt, adjust the melt composition, and ensure that the composition is qualified.

[0075] Comparative Example 2

[0076] The method for improving the thermal and electrical conductivity of low-silicon aluminum alloys in this example differs from that in Example 2 only in that Al-Sr-RE composite modifier is not added in step four of this example.

[0077] The fourth step in this example is to perform a second in-furnace refining of the melt, using high-purity nitrogen as a carrier to introduce a commercially available refining agent with a mass fraction of 0.05% of the melt.

[0078] Comparative Example 3

[0079] The method for improving the thermal and electrical conductivity of low-silicon aluminum alloys in this example differs from that in Example 3 only in that: in the third step of this example, an equal amount of B is used to replace RE, and in the fourth step, an equal amount of B is used to replace Al-Sr-RE.

[0080] The third step in this example is as follows: take a sample to test the chemical composition of the melt, adjust the melt composition to ensure that the composition is qualified. Then add B, which accounts for 0.08% of the melt mass fraction.

[0081] Step 4: The melt is refined a second time in the furnace. High-purity nitrogen is used as a carrier to introduce a commercially available refining agent with a mass fraction of 0.08% of the melt. After refining is completed, 0.1% of B is added.

[0082] Comparative Example 4

[0083] The method for improving the thermal and electrical conductivity of low-silicon aluminum alloys in this example differs from that in Example 4 only in that: in step four of this example, an equal amount of Al-5Ti-1B is used to replace the Al-Sr-RE in Example 4.

[0084] The fourth step in this example is as follows: The melt undergoes a second in-furnace refining process using high-purity nitrogen as a carrier gas, through which a commercially available refining agent at a mass fraction of 0.03% of the melt is introduced. Immediately after refining, an Al-5Ti-1B composite modifier at a mass fraction of 0.15% of the melt is added. In the Al-5Ti-1B composite modifier, Ti accounts for 5% of the mass, B accounts for 1% of the mass, and Al is the balance.

[0085] Comparative Example 5

[0086] The method for improving the thermal and electrical conductivity of low-silicon aluminum alloys in this example differs from that in Example 1 only in that RE is not added in step 3 and Al-Sr-RE is not added in step 4.

[0087] The third step in this example is to sample and test the chemical composition of the melt, adjust the melt composition, and ensure that the composition is qualified.

[0088] The fourth step in this example is to perform a second in-furnace refining of the melt, using high-purity nitrogen as a carrier to introduce a commercially available refining agent with a mass fraction of 0.03% of the melt.

[0089] Performance testing:

[0090] The electrical conductivity of the products prepared in Examples 1-4 and Comparative Examples 1-4 was tested respectively. The test method for electrical conductivity was as described in GB / T 3048.2-2007 "Test Methods for Electrical Properties of Wires and Cables Part 2: Test for Resistivity of Metallic Materials". The specific test results are shown in Table 2 below.

[0091] Table 2. Conductivity of the products obtained in Examples 1-4 and Comparative Examples 1-4

[0092]

[0093]

[0094] Comparing the data from Example 1 and Comparative Examples 1 and 5 in Table 2, it can be seen that in Example 1, the addition of RE and Al-Sr-RE, through their synergistic effect, increased the electrical conductivity of the alloy by 6.67% compared to Comparative Example 1 (Al-Sr-RE added alone), and by 7.3% compared to the base alloy in Comparative Example 5. Comparing the data from Example 2 and Comparative Example 2, it can be seen that in Example 2, the addition of RE and Al-Sr-RE, through their synergistic effect, increased the electrical conductivity of the alloy compared to Comparative Example 2 (RE-modified alloy only). The conductivity was increased by approximately 4.35%. Comparing the data from Example 3 and Comparative Example 3, it can be seen that after boronizing treatment in Example 3, the conductivity of the alloy increased from 54.01 IACS% before boronizing to 56.92 IACS. Furthermore, after adding RE and Al-Sr-RE in combination, the conductivity further increased to 57.45 IACS, representing increases of 6.37% and 0.93% compared to before and after boronizing, respectively. This indicates that the composite modification with RE and Al-Sr-RE significantly improves the conductivity of the alloy. Comparing the data from Example 4 and Comparative Example 4, it can be seen that the composite modifier composed of Al-Sr-RE and RE in Example 4 improved the conductivity of the modified alloy by 9.79% compared to the traditional Al-Ti-B refined alloy.

[0095] In addition, the microstructure and composition of the second phase in Example 1 and Comparative Example 1 were analyzed, specifically as follows: Figures 1-4 As shown. By Figures 1-4 It is known that when Al-Sr-RE and RE are added in combination, Ce can combine with elements such as Ti, V, Cr, and Mn to form multi-component compounds, reducing their solid solubility in aluminum alloys. However, when Al-Sr-RE is modified alone, its ability to capture Ti and Mn decreases. Therefore, the combined modification of rare earth microalloying and Al-Sr-RE modifiers is of great significance for expanding the application fields of alloys.

[0096] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for improving the properties of aluminum alloys, characterized in that: Includes the following steps: First, the aluminum alloy melt is mixed with rare earth elements and refined. Then, it is mixed with Al-Sr-RE composite modifier, allowed to stand, and slag is removed. Then, a covering agent is added, and the mixture is degassed, filtered, and cast to obtain the aluminum alloy. The RE in the Al-Sr-RE composite modifier is selected from at least one of La and Ce; The aluminum alloy contains transition metals.

2. The method for improving the properties of aluminum alloys according to claim 1, characterized in that: The aluminum alloy contains no more than 1.5% Si by mass.

3. The method for improving the properties of aluminum alloys according to claim 1, characterized in that: In the Al-Sr-RE composite modifier, the mass percentage of Sr is 4-10%, the mass percentage of RE is 5-20%, and Al is the balance.

4. The method for improving the properties of aluminum alloys according to claim 1 or 3, characterized in that: The mass of the Al-Sr-RE composite modifier is 0.1% to 0.3% of the mass of the aluminum alloy melt.

5. The method for improving the properties of aluminum alloys according to claim 1, characterized in that: The transition metal is selected from at least one of iron, cobalt, nickel, copper, zinc, chromium, manganese, vanadium, titanium, and zirconium.

6. The method for improving the properties of aluminum alloys according to claim 5, characterized in that: The mass ratio of the rare earth element to the transition metal is (0.8–1.2):

1.

7. The method for improving the properties of aluminum alloys according to claim 1, characterized in that: The mass of the rare earth element is 0.001 to 0.1% of the mass of the aluminum alloy melt.

8. The method for improving the properties of aluminum alloys according to claim 1, characterized in that: The settling time is 15 to 30 minutes.

9. The method for improving the properties of aluminum alloys according to claim 1, characterized in that: The refining step involves blowing the refining agent into the aluminum alloy melt using an inert gas carrier, then letting it stand for 15-30 minutes before removing the slag.

10. An aluminum alloy, characterized in that: The aluminum alloy is obtained by processing it using the method for improving the properties of aluminum alloys as described in any one of claims 1 to 9.

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