High-toughness rare earth aluminum alloy and preparation method thereof

Abstract

The invention discloses a high-toughness rare earth aluminum alloy and a preparation method thereof, and relates to the technical field of aluminum alloys. In the process of gradually solidifying the melt, an axial static magnetic field and a low-frequency vertical electric field are applied, electromagnetic stirring is used in combination, then a static and dynamic combined control mode can be formed in the melt by using a mechanism of combining two-stage cooling, multi-physical field coupling and electromagnetic stirring, and the effects of refining grains and reducing segregation are achieved; according to the two-stage cooling, the cooling rate is regulated and controlled by stages, growth of primary crystal grains can be inhibited, uniform precipitation of a second phase can be promoted, and therefore the effects of further refining the crystal grains and improving the toughness of the aluminum alloy are achieved. And secondly, chromium is deposited on the surface of the aluminum alloy in a gradient mode through a low-temperature magnetron sputtering method, the aluminum-aluminum chromium-chromium gradient structure can prevent the coating from cracking or stripping, the oxidation process of the aluminum alloy is slowed down through a chromium film, and therefore the aluminum alloy stably plays a role. The prepared aluminum alloy has the effects of high toughness and high performance stability.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and specifically to a high-toughness rare-earth aluminum alloy and a preparation method thereof. Background Art

[0002] In the early 20th century, aluminum alloys were widely used in the fields of aerospace, transportation, etc. due to their light weight and high strength. However, with the improvement of industrial requirements, the strength, heat resistance and corrosion resistance of traditional aluminum alloys gradually cannot meet the requirements of extreme environments. Scientists began to try to improve their performance by adding trace elements, and rare-earth elements (such as lanthanum, cerium, yttrium, etc.) became ideal choices due to their unique electronic structures and chemical activities. The introduction of rare-earth elements began in the mid-20th century. Researchers found that rare-earth elements can refine the grains of aluminum alloys, inhibit the influence of impurity elements, and significantly improve the mechanical properties and high-temperature stability of the alloys. In addition, rare-earth elements can combine with impurities in aluminum to reduce the formation of brittle phases and improve the processing performance.

[0003] During the preparation of high-toughness rare-earth aluminum alloys, coarse grains and composition segregation are key problems affecting performance stability. Coarse grains will reduce the strength and toughness of the material, while composition segregation will lead to uneven microstructures and affect the overall performance of the material. These problems usually stem from improper temperature control, uneven stirring during the melting and cooling processes, and unreasonable addition methods of rare-earth elements. To solve these problems, multi-physical field coupling and optimized melting processes can be adopted, and at the same time, through reasonable surface treatment processes, to further improve the performance stability of the material. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-toughness rare-earth aluminum alloy and a preparation method thereof to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solution: A preparation method of a high-toughness rare-earth aluminum alloy, comprising the following preparation steps:

[0006] (1) Under nitrogen protection, add pure aluminum ingots into an intermediate-frequency induction furnace for melting. Melt at 720 - 740 °C for 20 - 30 min, add zinc ingots, manganese ingots, magnesium ingots, copper ingots and rare-earth metals, turn on the electromagnetic stirring device and stir at a frequency of 30 - 40 Hz for 10 - 20 min, and then carry out refining and slag skimming treatments to obtain an aluminum alloy melt;

[0007] (2) Under nitrogen protection, the melt obtained in step (1) is poured into a preheated mold at a speed of 1.2 - 1.6 m / min for double-stage cooling. Water cooling is used as the primary cooling method, cooling at a rate of 40 - 50 °C / min for 4 - 6 min to 620 - 630 °C, and then air cooling is used as the secondary cooling method, cooling at a rate of 8 - 10 °C / min for 10 - 16 min to 510 - 530 °C. During the process, an axial static magnetic field of 0.25 - 0.35 T and a low-frequency vertical electric field of 15 - 25 Hz and 0.5 - 1.0 A / cm 2 are applied, and stirring is carried out at an electromagnetic stirring frequency of 5 - 15 Hz for 10 - 20 min to obtain an aluminum alloy casting;

[0008] (3) The aluminum alloy casting obtained in step (2) is subjected to solution treatment, followed by aging treatment after rapid cooling. After air cooling to room temperature, an aluminum alloy substrate is obtained;

[0009] (4) The aluminum alloy substrate obtained in step (3) is ultrasonically cleaned at a frequency of 25 Hz for 15 - 20 min and then hung in the cavity of a magnetron device. The cavity is evacuated to 5×10 -4 Pa and nitrogen is introduced at a rate of 5 - 10 L / min. Under water-cooled conditions, the temperature of the substrate is controlled at 80 °C. Using low-temperature magnetron sputtering, a pure aluminum target is sputtered at a radio frequency power of 1.6 - 2 kW and a target current of 4 - 6 A for 15 - 25 min to make the aluminum layer thickness reach 50 - 150 nm. Subsequently, an aluminum-chromium composite target is sputtered at a radio frequency power of 2.4 - 2.8 kW and a target current of 4 - 6 A for 30 - 50 min to make the mixed layer thickness reach 50 - 150 nm. Then, a pure chromium target is sputtered at a radio frequency power of 3.2 - 4 kW and a target current of 5 - 6 A for 4 - 5 h to make the chromium layer thickness reach 100 - 300 nm, obtaining a high-toughness rare-earth aluminum alloy.

[0010] Further, the aluminum alloy melt in step (1) contains the following elements by weight percentage: Zn: 3.05 - 3.93%, Mn: 1.15 - 1.6%, Mg: 1.66 - 2.38%, Cu: 1.4 - 1.55%, Ce: 1.21 - 1.48%, La: 1.39 - 1.65%, Y: 0.6 - 0.9%, and the balance is Al.

[0011] Further, the specific steps of refining and slag skimming treatment in step (1): Ar and Cl2 are mixed at a volume fraction of 85:15 and introduced into the melt at a rate of 10 - 15 L / min. An electromagnetic stirring device is used to stir at a frequency of 10 Hz for 10 min, and then left standing for 5 min. A vacuum slag skimming device is used to remove the surface scum.

[0012] Further, the temperature of the preheated mold in step (1) is 250 °C, the diameter is 250 mm, and the height is 400 mm.

[0013] Further, in the step (2), the axial static magnetic field is generated by applying a direct current electromagnetic coil along the Z-axis direction of the mold.

[0014] Further, in the step (2), the low-frequency vertical electric field is generated by applying a current along the Z-axis direction of the mold by a graphite electrode.

[0015] Further, the specific steps of the solution treatment in the step (3) are as follows: Under nitrogen protection, the aluminum alloy casting obtained in the step (2) is transferred into a box-type resistance furnace and kept warm at 505 - 520 °C for 2 - 3 h.

[0016] Further, the rapid cooling method in the step (3) is water cooling, and it is cooled at a cooling rate of 100 - 120 °C / min for 3 - 4 min to 110 - 130 °C.

[0017] Further, the specific preparation steps of the aging treatment in the step (3) are as follows: Under nitrogen protection, it is kept warm at 110 - 130 °C for 40 - 48 h.

[0018] Further, the aluminum-chromium composite target in the step (4) is prepared by mixing Al and Cr in a mass ratio of 9:1.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0020] The present invention uses Cu, Mg, Mn, Zn, and Al as the main components of the aluminum alloy, and uses Ce, Y, and La as rare earth alloying elements to prepare a high-toughness rare earth aluminum alloy. During the continuous casting process, a magnetic field, an electric field, and electromagnetic stirring are applied, and then the surface treatment of the aluminum alloy is carried out, so as to achieve the effects of high toughness and performance stability.

[0021] First, the cooling and forming process of continuous casting is used. During the gradual solidification of the melt, an axial static magnetic field and a low-frequency vertical electric field are applied, and electromagnetic stirring is used at the same time. Then, double-stage cooling is used. The axial static magnetic field can inhibit macroscopic deflection, reduce the temperature gradient, promote the formation of equiaxed crystals, and increase the nucleation rate. The low-frequency vertical electric field can induce periodic vibration of the melt, promote compositional homogenization, enhance micro-mixing, and inhibit the growth of coarse columnar crystals. This mechanism of multi-physical field coupling combined with electromagnetic stirring can form a "static-dynamic combination" control mode in the melt, achieving the effects of refining grains and reducing segregation. Double-stage cooling can control the cooling rate in stages. The combination of rapid cooling and slow cooling can not only inhibit the growth of primary grains but also promote the uniform precipitation of the second phase, thus further refining grains and improving the toughness of the aluminum alloy.

[0022] Secondly, a chromium gradient is deposited on the surface of the aluminum alloy by means of low-temperature magnetron sputtering. First, a layer of pure aluminum is deposited on the surface of the aluminum alloy, followed by a layer of aluminum-chromium alloy mixed layer, and finally a dense chromium film is deposited. This gradient structure of aluminum-aluminum chromium-chromium significantly reduces the interfacial stress between the chromium film and the aluminum alloy, effectively alleviates the stress concentration phenomenon, enhances the adhesion strength, avoids coating cracking or peeling, and the low-temperature magnetron sputtering technology prevents the change of internal grains and tissue structure of the aluminum alloy due to high temperature. The gradient-deposited chromium film slows down the oxidation process of the aluminum alloy, so that the aluminum alloy can play a role stably for a long time. Specific embodiments

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the scope of protection of the present invention.

[0024] Example 1

[0025] (1) Under nitrogen protection, pure aluminum ingots are added to an intermediate-frequency induction furnace for melting. Melting is carried out at 720 °C for 20 min. 3.05% Zn, 1.15% Mn, 1.66% Mg, 1.4% Cu, 1.39% La, 1.21% Ce, 0.6% Y are added by weight percentage, and the balance is Al. The electromagnetic stirring device is turned on and stirred at a frequency of 30 Hz for 10 min. Ar and Cl2 are mixed at a volume fraction of 85:15 and introduced into the melt at a rate of 10 L / min. The electromagnetic stirring device is used to stir at a frequency of 10 Hz for 10 min, and then left to stand for 5 min. The surface scum is removed using a vacuum slag removal device to obtain an aluminum alloy melt;

[0026] (2) Under nitrogen protection, the melt obtained in step (1) is poured into a preheated mold at a speed of 1.2 m / min for two-stage cooling. Water cooling is used as the first-stage cooling method and cooled to 620 °C at a rate of 40 °C / min, and then air cooling is used as the second-stage cooling method and cooled to 510 °C at a rate of 8 °C / min. During the process, an axial static magnetic field of 0.25 T and a low-frequency vertical electric field of 15 Hz and 0.5 A / cm 2 are applied, and stirred at an electromagnetic stirring frequency of 5 Hz for 10 min to obtain an aluminum alloy casting;

[0027] (3) Under nitrogen protection, the aluminum alloy casting obtained in step (2) is transferred to a box-type resistance furnace, kept at 505 °C for 2 h, water cooling is used as the cooling method, cooled to 110 °C at a cooling rate of 100 °C / min, kept warm for 40 h, and air-cooled to room temperature to obtain an aluminum alloy substrate;

[0028] (4) The aluminum alloy substrate obtained in step (3) was ultrasonically cleaned at a frequency of 25 Hz for 15 min and then hung in the cavity of the magnetron equipment. The cavity was evacuated to 5×10 -4 Pa and nitrogen was introduced at a rate of 5 L / min. Under water-cooled conditions, the substrate temperature was controlled at 80 °C. Using low-temperature magnetron sputtering, a pure aluminum target was sputtered at a radio frequency power of 1.6 kW and a target current of 4 A for 15 min to make the aluminum layer thickness reach 50 nm. Subsequently, an aluminum-chromium composite target was sputtered at a radio frequency power of 2.4 kW and a target current of 4 A for 30 min to make the mixed layer thickness reach 50 nm. Then, a pure chromium target was sputtered at a radio frequency power of 3.2 kW and a target current of 5 A for 4 h to make the chromium layer thickness reach 100 nm, thus obtaining a high-toughness rare-earth aluminum alloy.

[0029] Example 2

[0030] (1) Under nitrogen protection, pure aluminum ingots were added to an intermediate-frequency induction furnace for melting. Melting was carried out at 730 °C for 25 min. 3.51% Zn, 1.37% Mn, 2.01% Mg, 1.47% Cu, 1.35% Ce, 1.52% La, 0.75% Y were added by weight percentage, and the balance was Al. The electromagnetic stirring device was turned on and stirred at a frequency of 35 Hz for 15 min. Ar and Cl2 were mixed at a volume fraction of 85:15 and introduced into the melt at a rate of 15 L / min. The electromagnetic stirring device was used to stir at a frequency of 10 Hz for 10 min, and then left to stand for 5 min. The surface scum was removed using a vacuum slag removal device to obtain an aluminum alloy melt;

[0031] (2) Under nitrogen protection, the melt obtained in step (1) was poured into a preheated mold at a speed of 1.4 m / min for two-stage cooling. Water cooling was used as the first-stage cooling method and cooled at a rate of 45 °C / min to 625 °C. Then, air cooling was used as the second-stage cooling method and cooled at a rate of 9 °C / min to 520 °C. During the process, an axial static magnetic field of 0.3 T and a low-frequency vertical electric field of 20 Hz and 0.75 A / cm 2 were applied, and stirred at an electromagnetic stirring frequency of 10 Hz for 15 min to obtain an aluminum alloy casting;

[0032] (3) Under nitrogen protection, the aluminum alloy casting obtained in step (2) was transferred to a box-type resistance furnace and held at 515 °C for 2.5 h. Water cooling was used as the cooling method and cooled at a cooling rate of 110 °C / min to 120 °C. It was held at 120 °C for 44 h, and then air-cooled to room temperature to obtain an aluminum alloy substrate;

[0033] (4) The aluminum alloy substrate obtained in step (3) was ultrasonically cleaned at a frequency of 25 Hz for 20 min and then hung in the cavity of the magnetron equipment. The cavity was evacuated to 5×10 -4Pa was introduced with nitrogen at a rate of 10 L / min. Under water-cooling conditions, the substrate temperature was controlled at 80 °C. Pure aluminum target was sputtered by low-temperature magnetron sputtering with a radio frequency power of 1.8 kW and a target current of 5 A for 20 min to make the aluminum layer reach a thickness of 100 nm. Subsequently, an aluminum-chromium composite target was sputtered with a radio frequency power of 2.6 kW and a target current of 5 A for 40 min to make the mixed layer reach a thickness of 100 nm. Then, pure chromium target was sputtered with a radio frequency power of 3.6 kW and a target current of 5.5 A for 4.5 h to make the chromium layer reach a thickness of 200 nm, obtaining a high-toughness rare earth aluminum alloy.

[0034] Example 3

[0035] (1) Under nitrogen protection, pure aluminum ingots were added to an intermediate frequency induction furnace for melting. Melting was carried out at 740 °C for 30 min. 3.93% Zn, 1.6% Mn, 2.38% Mg, 1.55% Cu, 1.48% Ce, 1.65% La, 0.9% Y were added by weight percentage, and the balance was Al. The electromagnetic stirring device was turned on to stir at a frequency of 40 Hz for 20 min. Ar and Cl2 were mixed at a volume fraction of 85:15 and introduced into the melt at a rate of 15 L / min. The electromagnetic stirring device was used to stir at a frequency of 10 Hz for 10 min, and then left to stand for 5 min. The surface scum was removed using a vacuum slag removal device.

[0036] (2) Under nitrogen protection, the melt obtained in step (1) was poured into a preheated mold at a speed of 1.6 m / min for two-stage cooling. Water-cooling was used as the first-stage cooling method, cooling at a rate of 50 °C / min to 630 °C, and then air-cooling was used as the second-stage cooling method, cooling at a rate of 10 °C / min to 530 °C. During the process, an axial static magnetic field of 0.35 T and a low-frequency vertical electric field of 25 Hz and 1.0 A / cm 2 were applied, and stirring was carried out at an electromagnetic stirring frequency of 15 Hz for 20 min to obtain an aluminum alloy casting.

[0037] (3) Under nitrogen protection, the aluminum alloy casting obtained in step (2) was transferred to a box-type resistance furnace, held at 520 °C for 3 h, cooled at a cooling rate of 120 °C / min to 130 °C with water-cooling as the cooling method, held at 130 °C for 48 h, and then air-cooled to room temperature to obtain an aluminum alloy substrate.

[0038] (4) The aluminum alloy substrate obtained in step (3) was ultrasonically cleaned for 20 min at a frequency of 25 Hz and then hung in the cavity of the magnetron equipment. The cavity was evacuated to 5×10 -4Pa was introduced with nitrogen at a rate of 10 L / min. Under water-cooled conditions, the substrate temperature was controlled at 80 °C. Pure aluminum target was sputtered by low-temperature magnetron sputtering with a radio frequency power of 2 kW and a target current of 6 A for 25 min to make the aluminum layer thickness reach 150 nm. Subsequently, an aluminum-chromium composite target was sputtered with a radio frequency power of 2.8 kW and a target current of 6 A for 50 min to make the mixed layer thickness reach 150 nm. Then, a pure chromium target was sputtered with a radio frequency power of 4 kW and a target current of 6 A for 5 h to make the chromium layer thickness reach 300 nm, obtaining a high-toughness rare earth aluminum alloy.

[0039] Comparative Example 1

[0040] The difference between Comparative Example 1 and Example 2 lies in step (1). Step (1) was changed to: Under nitrogen protection, pure aluminum ingots were added to an intermediate frequency induction furnace for melting, melted at 730 °C for 25 min, and 3.05% Zn, 1.15% Mn, 1.66% Mg, 1.4% Cu, 1.21% Ce, 1.39% La, 0.6% Y were added by weight percentage, with the balance being Al. The electromagnetic stirring device was turned on to stir at a frequency of 35 Hz for 15 min. Ar and Cl2 were mixed at a volume fraction of 85:15 and introduced into the melt at a rate of 10 L / min. The electromagnetic stirring device was used to stir at a frequency of 10 Hz for 10 min, and then left to stand for 5 min. The surface dross was removed using a vacuum slag removal device to obtain an aluminum alloy melt; the remaining steps were the same as in Example 2.

[0041] Comparative Example 2

[0042] The difference between Comparative Example 2 and Example 2 lies in step (2). Step (2) was changed to: Under nitrogen protection, the melt obtained in step (1) was poured into a preheated mold at a speed of 1.2 m / min for two-stage cooling. Water cooling was used as the first-stage cooling method, cooled at a rate of 40 °C / min to 620 °C, and then air cooling was used as the second-stage cooling method, cooled at a rate of 8 °C / min to 510 °C. During the process, an axial static magnetic field of 0.25 T and a low-frequency vertical electric field of 15 Hz and 0.5 A / cm 2 were applied, and stirred at an electromagnetic stirring frequency of 5 Hz for 10 min to obtain an aluminum alloy casting; the remaining steps were the same as in Example 2.

[0043] Comparative Example 3

[0044] The difference between Comparative Example 3 and Example 2 lies in step (3). Step (3) was changed to: Under nitrogen protection, the aluminum alloy casting obtained in step (2) was transferred to a box-type resistance furnace, held at 505 °C for 2 h, water cooling was used as the cooling method, cooled at a cooling rate of 100 °C / min to 110 °C, held for 40 h, and air-cooled to room temperature to obtain an aluminum alloy substrate; the remaining steps were the same as in Example 2.

[0045] Comparative Example 4

[0046] The difference between Comparative Example 4 and Example 2 lies in step (4). Step (4) is changed to: After ultrasonic cleaning the aluminum alloy substrate obtained in step (3) for 15 min at a frequency of 25 Hz, hang it in the magnetron equipment cavity. The cavity is evacuated to 5×10 -4 Pa and nitrogen is introduced at a rate of 5 L / min. Under water-cooled conditions, control the substrate temperature at 80 °C. Use low-temperature magnetron sputtering to sputter a pure aluminum target with a radio frequency power of 1.6 kW and a target current of 4 A, deposit for 15 min to make the aluminum layer thickness reach 50 nm. Subsequently, sputter an aluminum-chromium composite target with a radio frequency power of 2.4 kW and a target current of 4 A, deposit for 30 min to make the mixed layer thickness reach 50 nm. Then, sputter a pure chromium target with a radio frequency power of 3.2 kW and a target current of 5 A, deposit for 4 h to make the chromium layer thickness reach 100 nm to obtain a high-toughness rare earth aluminum alloy; the remaining steps are the same as those in Example 2.

[0047] Effect Example

[0048] Table 1 below gives the performance analysis results of a high-toughness rare earth aluminum alloy and its preparation method using Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention.

[0049] Table 1

[0050]

[0051]

[0052] From the comparison of the experimental data of the elongation of the embodiment and the comparative example, it can be found that the present invention applies an axial static magnetic field and a low-frequency vertical electric field in the process of gradual solidification of the melt, and combines electromagnetic stirring at the same time. The static magnetic field suppresses melt turbulence, constrains the dislocation slip direction, and stabilizes the solid-liquid interface. The vertical electric field drives the directional migration of solute ions to offset the enrichment of solute elements at the solidification front and reduce the segregation index. At the same time, the shear flow of electromagnetic stirring breaks up the solute-rich melt. The three cooperate to form a "static-dynamic combination" convection mode. This flow can not only break up dendrites, but also promote the uniform distribution of heterogeneous nucleation cores. The total area of grain boundaries is increased to make the crack propagation path tortuous. The two-stage cooling controls the cooling rate in stages. The combination of rapid cooling and slow cooling can not only suppress the growth of primary grains but also promote the growth of secondary The uniform precipitation of phases can further refine the grains and improve the toughness of the aluminum alloy; from the comparison of the experimental data of tensile strength and yield strength of the embodiment and the comparative example, it can be found that the multi-physical field coupling optimizes the melt flow, refines the grains, reduces defects, and thus enhances the matrix properties of the material through electromagnetic stirring, and low-temperature magnetron sputtering forms a gradient chromium coating on the surface of the aluminum alloy. This coating not only increases the surface hardness, but also reduces stress concentration through the gradient structure and improves the overall strength. The hardness and wear resistance of chromium further enhance the surface properties of the aluminum alloy, so that the material exhibits higher yield strength and tensile strength when subjected to high stress. This combined method makes full use of the advantages of internal structure optimization and surface strengthening, and significantly improves the mechanical properties of the aluminum alloy.

[0053] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A preparation method of a high-toughness rare earth aluminum alloy, characterized in that It includes the following preparation steps: (1) Under nitrogen protection, add pure aluminum ingots into an intermediate frequency induction furnace for melting. Melt at 720 - 740 °C for 20 - 30 min, add zinc ingots, manganese ingots, magnesium ingots, copper ingots and rare earth metals, turn on the electromagnetic stirring device and stir at a frequency of 30 - 40 Hz for 10 - 20 min, and then carry out refining and slag skimming treatment to obtain an aluminum alloy melt; (2) Under nitrogen protection, the melt obtained in step (1) is poured into a preheated mold at a speed of 1.2 - 1.6 m / min for two-stage cooling. Water cooling is used as the primary cooling method, cooling at a rate of 40 - 50 °C / min for 4 - 6 min to 620 - 630 °C, and then air cooling is used as the secondary cooling method, cooling at a rate of 8 - 10 °C / min for 10 - 16 min to 510 - 530 °C. During the process, an axial static magnetic field of 0.25 - 0.35 T and a low-frequency vertical electric field of 15 - 25 Hz, 0.5 - 1.0 A / cm 2 are applied, and stirring is carried out at an electromagnetic stirring frequency of 5 - 15 Hz for 10 - 20 min to obtain an aluminum alloy casting; (3) Carry out solution treatment on the aluminum alloy casting obtained in step (2), perform aging treatment after rapid cooling, and air cool to room temperature to obtain an aluminum alloy substrate; (4) The aluminum alloy substrate obtained in step (3) is ultrasonically cleaned at a frequency of 25 Hz for 15 - 20 min and then hung in the magnetron equipment cavity. The cavity is evacuated to 5×10 -4 Pa and nitrogen is introduced at a rate of 5 - 10 L / min. Under water-cooled conditions, the substrate temperature is controlled at 80 °C. Using low-temperature magnetron sputtering, a pure aluminum target is sputtered at a radio frequency power of 1.6 - 2 kW and a target current of 4 - 6 A for 15 - 25 min to make the aluminum layer thickness reach 50 - 150 nm. Subsequently, an aluminum-chromium composite target is sputtered at a radio frequency power of 2.4 - 2.8 kW and a target current of 4 - 6 A for 30 - 50 min to make the mixed layer thickness reach 50 - 150 nm. Then, a pure chromium target is sputtered at a radio frequency power of 3.2 - 4 kW and a target current of 5 - 6 A for 4 - 5 h to make the chromium layer thickness reach 100 - 300 nm, thus obtaining a high-toughness rare-earth aluminum alloy.

2. The preparation method of a high-toughness rare earth aluminum alloy according to claim 1, characterized in that, The aluminum alloy melt in step (1) contains elements in the following weight percentages: Zn: 3.05 - 3.93%, Mn: 1.15 - 1.6%, Mg: 1.66 - 2.38%, Cu: 1.4 - 1.55%, Ce: 1.21 - 1.48%, La: 1.39 - 1.65%, Y: 0.6 - 0.9%, and the balance is Al.

3. The preparation method of a high-toughness rare earth aluminum alloy according to claim 1, characterized in that, The specific steps of the refining and slag skimming treatment in step (1): Mix Ar and Cl2 at a volume fraction of 85:15 and introduce them into the melt at a rate of 10 - 15 L / min. Use the electromagnetic stirring device to stir at a frequency of 10 Hz for 10 min, and then let it stand for 5 min and use a vacuum slag skimming device to remove the surface floating slag.

4. The preparation method of a high-toughness rare earth aluminum alloy according to claim 1, characterized in that The temperature of the preheated mold in step (1) is 250 °C, and its diameter is 250 mm and height is 400 mm.

5. The preparation method of a high-toughness rare earth aluminum alloy according to claim 1, characterized in that, In step (2), the axial static magnetic field is generated by applying a direct current electromagnetic coil along the Z-axis direction of the mold.

6. The preparation method of a high-toughness rare earth aluminum alloy according to claim 1, characterized in that, In step (2), the low-frequency vertical electric field is generated by applying a current along the Z-axis direction of the mold by a graphite electrode.

7. The preparation method of a high-toughness rare earth aluminum alloy according to claim 1, characterized in that, The specific steps of the solution treatment in step (3): Under nitrogen protection, transfer the aluminum alloy casting obtained in step (2) into a box-type resistance furnace and hold at 505 - 520 °C for 2 - 3 h.

8. The preparation method of a high-toughness rare earth aluminum alloy according to claim 1, characterized in that, The rapid cooling method in step (3) is water cooling, and it is cooled at a cooling rate of 100 - 120 °C / min for 3 - 4 min to 110 - 130 °C.

9. The preparation method of a high-toughness rare earth aluminum alloy according to claim 1, characterized in that The specific preparation steps of the aging treatment in step (3): Under nitrogen protection, hold at 110 - 130 °C for 40 - 48 h.

10. The preparation method of a high-toughness rare earth aluminum alloy according to claim 1, characterized in that, In step (4), the aluminum-chromium composite target is prepared from Al and Cr in a mass ratio of 9:1.

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