Method for refining aluminum alloy structure by adding rare earth-based alloy

Abstract

The invention discloses a method for refining an aluminum alloy structure by adding a rare earth-based alloy, the chemical general formula of the rare earth-based alloy is RExAlyMz, in the formula, x, y and z are atomic ratios, x is more than or equal to 13 and less than or equal to 18, y is more than or equal to 75 and less than or equal to 82, z is more than or equal to 5 and less than or equal to 10, and x + y + z is equal to 100; wherein RE is any one or more of La, Ce and Y, and M is Li and Mg; the rare earth-based alloy is cut into blocks after being subjected to induction melting and casting in sequence, then the blocks are packaged in an aluminum box, and through alloy density and structure control, the rare earth-based alloy only needs to be put into molten alloy in the casting process after aluminum alloy melting, it can be ensured that the rare earth-based alloy sinks to the middle in an aluminum alloy solution and then is gradually melted, and the alloy is completely melted. And a rare earth compound second-phase refined solidification structure is formed in the solidification process, so that the problems that the aluminum alloy structure is not uniform and thick during aluminum alloy casting are remarkably solved, and the mechanical property is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy casting and relates to a method for refining aluminum alloy structure by adding rare earth-based alloy. Background Art

[0002] A1-Si series cast aluminum alloys have excellent fluidity, low thermal expansion and contraction, good weldability and corrosion resistance, and are widely used in the fields of automobiles, electronics, communications, etc. However, during the casting process of A1-Si series alloys, A1 and Si will combine to form a binary eutectic, and the eutectic structure is in the form of coarse needles, which destroys the A1 matrix to a certain extent and causes stress concentration at the tip of the Si phase needle and some corners. During machining, the Si phase is prone to peeling, making the machined surface rough and uneven, which seriously affects the quality of the casting and reduces its performance. In order to improve the performance of A1-Si series alloys, A1-Si series alloys are usually subjected to modification.

[0003] Refining aluminum alloy grains by adding refiners during the casting process is an important method to improve its performance. However, the aluminum alloy refiners widely used in industry also have many problems in the grain refinement of Al-Si alloys. For example, the refiners are easily "poisoned" by Si elements, thus affecting the modification effect. Therefore, it is necessary to develop more efficient refiners suitable for the industrial production of cast aluminum alloys.

[0004] In addition to purifying the melt in aluminum alloys, rare earths also have a very obvious effect on the modification of eutectic silicon in Al-Si alloys, and have a significant refining effect on the α-Al matrix, which can significantly improve the mechanical properties of the alloy. However, because rare earths are extremely active, it is difficult to add rare earths under traditional casting processes, and the amount added is limited, which is not easy to control in actual production. Adding rare earth-containing intermediate alloys to aluminum alloys is an effective way to overcome the above problems. The composition of the intermediate alloy is an important factor affecting the modification effect, but it cannot be ignored that its addition method and its coordination with the intermediate alloy play a vital role in the addition efficiency, uniformity and modification effect.

[0005] Although there are related technologies about rare earth-containing master alloys, such as CN118703841A, CN117987692A, CN116287815A, and CN115433859B, the above technologies all add rare earth-containing master alloys during the smelting process. In practical applications, due to the very active nature of rare earths, there will be more losses during the smelting process, and a considerable amount of rare earth will be lost after oxidation during the casting process; and after the rare earth is added, a large amount of slag will be formed after multiple processes of smelting and casting. On the one hand, it is difficult to accurately control the actual amount of addition, and on the other hand, it also introduces an uneven slag phase, which deteriorates the organization and performance. For cast aluminum alloys, if a modifier master alloy can be added during the casting process, the amount of the modifier can be better controlled, and a better modification effect can be obtained at the same time. However, when adding a master alloy during the casting process, it is necessary to consider the influence of multiple factors such as the melting, combination, and distribution of the alloy. This has a synergistic and mutual influence relationship with the density, melting point, organization, and addition method of the master alloy. At present, there is no report on the technology that takes into account the composition, structure and addition method of the master alloy at the same time.

[0006] Based on this, the present invention aims to provide a method for refining the structure of aluminum alloy by adding rare earth-based alloys. The method takes into account factors such as the composition, structure, density, etc. of the intermediate alloy, as well as the mutual influence between the adding methods, which can effectively improve the adding efficiency and is conducive to the chemical formation of a uniform second phase to obtain the optimization of the casting structure. Summary of the invention

[0007] In view of the above technical problems, the present invention aims to provide a method for refining the structure of aluminum alloy by adding rare earth-based alloys. The method obtains the rare earth-based alloy by induction melting and casting in sequence, cuts it into blocks, and then packages it in an aluminum box. It is put into the molten alloy during the casting process after the aluminum alloy is smelted to ensure that it gradually melts after sinking to the middle of the aluminum alloy solution, and forms a rare earth compound second phase to refine the solidification structure during the solidification process, thereby significantly improving the problem of uneven and coarse aluminum alloy structure when casting aluminum alloy, and then improving the mechanical properties.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for refining aluminum alloy structure by adding rare earth-based alloy, which is carried out in the following steps in sequence:

[0010] (1) High-purity metals with a purity higher than 99.9% are mixed according to the chemical composition, and induction smelting is performed under an inert atmosphere to prepare a rare earth-based alloy. After 3-5 times of tumbling smelting, the rare earth-based alloy is cast into a square or cylindrical ingot in a crucible at a temperature of 200-300° C., and the rare earth-based alloy is solidified to obtain a chemical composition formula of RE xAl y M z , wherein: x, y, z are atomic ratios, 13≤x≤18, 75≤y≤82, 5≤z≤10, x+y+z=100; the RE is any one or more of La, Ce, and Y, and M is Li and Mg;

[0011] Since RE, Li and Mg will be lost during the smelting process, 3-8wt.% RE and 5-10wt.% Li and Mg need to be added during the smelting process to supplement the burning loss;

[0012] The composition design and heat preservation casting treatment of the rare earth-based alloy in the present invention can make the rare earth-based alloy contain more than 40% Al 11 RE3-Al eutectic phase ensures complete melting at the casting temperature; at the same time, the rare earth-based alloy contains light metal elements such as Li and Mg to ensure that the melting point and density of the alloy are within a suitable range, thereby ensuring that the rare earth-based alloy can be completely melted during the aluminum alloy casting process, especially in the casting solution, the effect of melting and combining from the middle to the lower part of the ingot can be achieved, effectively improving the efficiency and effect of adding rare earth elements;

[0013] (2) grinding and cutting the surface of the rare earth-based alloy, placing it in a square or cylindrical box made of pure aluminum, evacuating the box, and sealing and packaging it by aluminum welding to obtain a block material;

[0014] In the present invention, pure aluminum is used to encapsulate the rare earth-based alloy, which can avoid the phenomenon that the rare earth elements are rapidly melted, slag-formed and floated when the rare earth-based alloy is directly added to the aluminum alloy solution, and it is difficult to form a metamorphic second phase in the melt; at the same time, the rare earth-based alloy can be gradually melted after sinking to the middle of the aluminum alloy solution, effectively increasing the addition amount;

[0015] (3) During the aluminum alloy casting process, the above-mentioned block material is put into the aluminum alloy solution, and the block material sinks to the middle of the solution and gradually melts. The block material is completely melted within 1-2 minutes, and a uniform aluminum alloy is obtained after solidification.

[0016] As a limitation of the method of the present invention for refining the structure of an aluminum alloy by adding a rare earth-based alloy, in step (1), the crucible is a silicon carbide or graphite crucible.

[0017] As another limitation of the method of the present invention for refining the structure of an aluminum alloy by adding a rare earth-based alloy, in step (1), the temperature of the induction melting is 1300-1400° C. and the melting time is 5-15 min.

[0018] As a third limitation of the method of the present invention for refining the structure of an aluminum alloy by adding a rare earth-based alloy, in step (2), the thickness of the square or cylindrical box made of pure aluminum is 0.5-2 mm.

[0019] As a fourth limitation of the method of the present invention for refining the structure of an aluminum alloy by adding a rare earth-based alloy, in step (2), the side length or diameter of the square or cylindrical box made of pure aluminum is 5-10 cm.

[0020] As a fifth limitation of the method for refining the structure of an aluminum alloy by adding a rare earth-based alloy according to the present invention, in step (2), the density difference between the block and the aluminum alloy solution is 20-30 kg / m 3 .

[0021] In the present invention, the density difference between the block and the aluminum alloy solution is crucial, which will affect the melting point in the solution. If the density difference between the block and the aluminum alloy solution is greater than 30 kg / m 3 The second phase will sink faster and melt only when it sinks to the bottom, making it difficult to ensure that the entire solution undergoes chemical reactions and forms a second phase. If the density difference between them is less than 20 kg / m 3 This will cause the sinking speed to be too slow, melting at the top of the solution, forming scum and agglomerating, making it difficult to achieve the deterioration effect.

[0022] As a sixth limitation of the method for refining the structure of an aluminum alloy by adding a rare earth-based alloy according to the present invention, in step (3), the mass ratio of the block material to the aluminum alloy solution is (0.5-0.8):100.

[0023] The above technical solution of the present invention is taken as a whole, and each step is closely related and influences each other, which jointly determine the morphological characteristics and performance of the product.

[0024] The above technical solution has the following advantages or beneficial effects:

[0025] 1. The method provided by the present invention for refining the structure of aluminum alloy by adding rare earth-based alloy is simple and easy to operate, and the prepared rare earth-based alloy can be stored for a long time, and is suitable for optimizing the casting structure of aluminum alloy castings of different sizes.

[0026] 2. After the rare earth-based alloy prepared by the present invention is added to the aluminum alloy solution, a rare earth compound second phase refines the solidification structure, thereby significantly improving the problem of uneven and coarse aluminum alloy structure during casting, thereby improving the mechanical properties.

[0027] The invention is applicable to a method for refining aluminum alloy structure by adding rare earth-based alloy.

[0028] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a microstructure morphology diagram of the rare earth-based alloy prepared in Example 1 of the present invention;

[0030] Figure 2 These are the organizational morphology diagrams of the aluminum alloys prepared in Example 1 and Comparative Example 1 of the present invention, wherein: a is the organizational morphology diagram of the aluminum alloy prepared in Comparative Example 1, and b is the organizational morphology diagram of the aluminum alloy prepared in Example 1. DETAILED DESCRIPTION

[0031] The following embodiments are only some embodiments of the present invention, rather than all embodiments. Therefore, the detailed description in the embodiments of the present invention provided below is not intended to limit the scope of the present invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the protection scope of the present invention.

[0032] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments are all conventional methods in the art unless otherwise specified.

[0033] Example

[0034] Example 1

[0035] This embodiment provides a method for refining the structure of aluminum alloy by adding rare earth-based alloy, and the specific process and steps are as follows:

[0036] (1) High-purity metals La, Al, Mg, and Li with a purity of more than 99.9% are prepared according to the chemical composition La 13 Al 82 Mg3Li2 is prepared and induction smelted in an inert atmosphere. During the smelting process, 5wt% La, 5wt% Li and 10wt% Mg are added as burn-off supplements. The smelting temperature is 1300°C and the smelting time is 10min. After 3 times of turning over and smelting, the alloy is cast in a graphite crucible at a temperature of 250°C to obtain a rare earth-based alloy.

[0037] (2) The surface of the rare earth alloy was polished and then cut into square blocks with a side length of 10 cm, which were placed in a square box with a side length of 10 cm made of pure aluminum. The thickness of the pure aluminum box was 1 mm. The box was evacuated and sealed by aluminum welding to obtain a block. The density difference between the block and the aluminum alloy solution was adjusted to 30 kg / m by adjusting the gap in the box. 3 ;

[0038] (3) During the aluminum alloy casting process, the above-mentioned block material is put into the aluminum alloy solution, and the mass ratio of the block material to the aluminum alloy is 0.5:100. The block material sinks to the middle of the aluminum alloy solution and gradually melts. The block material is completely melted within 1-2 minutes. After solidification, a uniform aluminum alloy is obtained.

[0039] like Figure 1 , is a microstructure morphology diagram of the rare earth-based alloy prepared in Example 1. It can be seen from the figure that the microstructure of the rare earth-based alloy is uniform and contains 44% of RE-Al and Al eutectic phases.

[0040] Example 2

[0041] This embodiment provides a method for refining the structure of aluminum alloy by adding rare earth-based alloy, and the specific process and steps are as follows:

[0042] (1) High-purity metals La, Al, Mg, and Li with a purity of more than 99.9% are prepared according to the chemical composition La 18 Al 75 Mg4Li3 is prepared and induction smelted in an inert atmosphere. During the smelting process, 3wt% La, 10wt% Li and 5wt% Mg are added as burn-off supplements. The smelting temperature is 1320°C and the smelting time is 15min. After 5 times of turning over and smelting, the alloy is cast in a graphite crucible at a temperature of 200°C to obtain a rare earth-based alloy.

[0043] (2) The surface of the rare earth alloy was polished and then cut into square blocks with a side length of 8 cm, which were placed in a square box with a side length of 8 cm made of pure aluminum. The thickness of the pure aluminum box was 0.5 mm. The box was evacuated and sealed by aluminum welding to obtain a block. The density difference between the block and the aluminum alloy solution was adjusted to 20 kg / m by adjusting the gap in the box. 3 ;

[0044] (3) During the aluminum alloy casting process, the above-mentioned block material is put into the aluminum alloy solution, and the mass ratio of the block material to the aluminum alloy is 0.7:100. The block material sinks to the middle of the aluminum alloy solution and then gradually melts. The block material is completely melted within 1-2 minutes. After solidification, a uniform aluminum alloy is obtained.

[0045] Example 3

[0046] This embodiment provides a method for refining the structure of aluminum alloy by adding rare earth-based alloy, and the specific process and steps are as follows:

[0047] (1) High-purity metals La, Al, Mg, and Li with a purity of more than 99.9% are prepared according to the chemical composition La 14 Al 76Mg5Li5 is prepared and induction smelted in an inert atmosphere. During the smelting process, 8wt% La, 7wt% Li and 8wt% Mg are added as burn-off supplements. The smelting temperature is 1400°C and the smelting time is 5min. After 4 turns of smelting, the alloy is cast in a graphite crucible at a temperature of 300°C to obtain a rare earth-based alloy.

[0048] (2) The surface of the rare earth alloy was polished and then cut into square blocks with a side length of 5 cm, which were placed in a square box with a side length of 5 cm made of pure aluminum. The thickness of the pure aluminum box was 2 mm. The box was evacuated and sealed by aluminum welding to obtain a block. The density difference between the block B and the aluminum alloy solution was adjusted to 25 kg / m 3 ;

[0049] (3) During the aluminum alloy casting process, the above-mentioned block material is put into the aluminum alloy solution, and the mass ratio of the block material to the aluminum alloy is 0.8:100. The block material sinks to the middle of the aluminum alloy solution and gradually melts. The block material is completely melted within 1-2 minutes. After solidification, a uniform aluminum alloy is obtained.

[0050] Comparative Example

[0051] In order to explore the influence of different parameters on the performance of aluminum alloys prepared by the rare earth-based alloys and the rare earth-based alloys prepared by the present invention during the process of adding aluminum alloy solution, the following comparative experiments were conducted. The following comparative examples respectively prepared different rare earth-based alloys and adopted different aluminum alloy purification processes, as follows:

[0052] Comparative Example 1

[0053] This comparative example provides a method for preparing an aluminum alloy, wherein the aluminum casting alloy is remelted and then cast, and the rare earth-based alloy prepared by the present invention is not added during the casting.

[0054] like Figure 2 , are the organizational morphology diagrams of the aluminum alloys prepared in Comparative Example 1 and Example 1, wherein: a is the organizational morphology diagram of the aluminum alloy prepared in Comparative Example 1, and b is the organizational morphology diagram of the aluminum alloy prepared in Example 1. It can be seen from the figure that, compared with Comparative Example 1, the macroscopic structure of the aluminum alloy obtained after adding the rare earth-based alloy in Example 1 is refined and more evenly distributed, while the formation of dendrites is reduced.

[0055] Comparative Example 2

[0056] This comparative example prepares a rare earth-based alloy similar to that of Example 1, except that in step (1), the crucible temperature during casting is 400°C.

[0057] Comparative Example 3

[0058] This comparative example prepares the same rare earth-based alloy as in Example 1, and provides an aluminum alloy refinement method similar to that in Example 1, except that, in step (3), the density difference between the block and the aluminum alloy is 10 kg / m 3 .

[0059] Comparative Example 4

[0060] This comparative example prepares the same rare earth-based alloy as in Example 1, and provides an aluminum alloy refinement method similar to that in Example 1, except that in step (3), the mass ratio of the block material to the aluminum alloy is 0.3:100.

[0061] Performance Testing

[0062] The hardness of the aluminum alloys prepared in Examples 1-3 and Comparative Examples 1-4 was tested, and the specific data are shown in the following table:

[0063]

[0064] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the claims of the present invention.

Claims

1. A method for refining aluminum alloy structure by adding rare earth-based alloy, characterized in that: Follow the steps below in order: (1) High-purity metals with a purity higher than 99.9% are mixed according to the chemical composition, and induction smelting is performed under an inert atmosphere to prepare a rare earth-based alloy. After 3-5 times of tumbling smelting, the rare earth-based alloy is cast into a square or cylindrical ingot in a crucible at a temperature of 200-300° C., and the rare earth-based alloy is solidified to obtain a chemical composition formula of RE x Al y M z , wherein: x, y, z are atomic ratios, 13≤x≤18, 75≤y≤82, 5≤z≤10, x+y+z=100; the RE is any one or more of La, Ce, and Y, and M is Li and Mg; (2) grinding and cutting the surface of the rare earth-based alloy, placing it in a square or cylindrical box made of pure aluminum, evacuating the box, and sealing and packaging it by aluminum welding to obtain a block material; (3) During the aluminum alloy casting process, the above-mentioned block material is put into the aluminum alloy solution, and the block material sinks to the middle of the solution and gradually melts. The block material is completely melted within 1-2 minutes, and a uniform aluminum alloy is obtained after solidification.

2. The method for refining aluminum alloy structure by adding rare earth-based alloy according to claim 1, characterized in that: In step (1), the crucible is a silicon carbide or graphite crucible.

3. The method for refining aluminum alloy structure by adding rare earth-based alloy according to claim 1, characterized in that: In step (1), the induction melting temperature is 1300-1400° C. and the melting time is 5-15 min.

4. The method for refining aluminum alloy structure by adding rare earth-based alloy according to claim 1, characterized in that: In step (2), the square or cylindrical box made of pure aluminum has a thickness of 0.5-2 mm.

5. The method for refining aluminum alloy structure by adding rare earth-based alloy according to claim 1, characterized in that: In step (2), the side length or diameter of the square or cylindrical box made of pure aluminum is 5-10 cm.

6. The method for refining aluminum alloy structure by adding rare earth-based alloy according to claim 1, characterized in that: In step (2), the density difference between the block and the aluminum alloy solution is 20-30 kg / m 3 .

7. The method for refining aluminum alloy structure by adding rare earth-based alloy according to claim 1, characterized in that: In step (3), the mass ratio of the block material to the aluminum alloy solution is (0.5-0.8):100.

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