Rare earth aluminum alloy with three-dimensional interpenetrating framework and preparation method of rare earth aluminum alloy

Abstract

The invention belongs to the technical field of aluminum alloy additive manufacturing, and particularly relates to a rare earth aluminum alloy with a three-dimensional interpenetrating framework and a preparation method of the rare earth aluminum alloy. A laser powder bed melting additive manufacturing technology is adopted, ultrafine and uniform distribution of eutectic phases in the hypereutectic Al-Ce alloy is achieved, a nanoscale continuous grid structure is constructed, and therefore the hypereutectic Al-Ce alloy with a three-dimensional interpenetrating framework is successfully prepared. The tensile strength range of the prepared alloy in a printing state is 509-534 MPa, the tensile strength range of the prepared alloy after peak aging is 556-573 MPa, the conditioned yield strength range is 449-474 MPa, the ductility is not lower than 5%, and meanwhile the alloy has excellent forming performance and isotropic mechanical performance. The alloy material can be widely applied to the field of high-performance additive manufacturing of metal components with complex structures.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy additive manufacturing technology, specifically relating to rare earth aluminum alloys with a three-dimensional interpenetrating skeleton and their preparation method. Background Technology

[0002] With the development of aerospace, advanced transportation, energy equipment, and the low-altitude economy, the performance requirements for lightweight, high-temperature, and high-strength structural materials are increasingly demanding. Aluminum alloys, due to their low density, high specific strength, good processing properties, and recyclability, are widely used in aerospace, automotive, and electronic packaging fields. However, traditional aluminum alloys (such as the 2XXX and 7XXX series) rely on precipitation strengthening mechanisms to achieve high strength, but their strengthening phases are prone to coarsening or transformation above 150 °C, leading to a significant decrease in high-temperature strength and creep performance, making it difficult to meet the service requirements of medium- and high-temperature components. Furthermore, due to the extremely low solid solubility and extremely slow diffusion coefficient of Ce in the Al matrix, researchers have recently proposed using Al-Ce eutectic alloys to construct thermally stable intermetallic compounds to overcome the thermal stability bottleneck of traditional precipitation strengthening systems.

[0003] In as-cast alloys, Ce and Al can form a maze-like submicron-sized α-Al / Al structure. 11 Ce3 eutectic lamellar structure exhibits excellent resistance to coarsening at high temperatures, and the higher the Ce content in the alloy, the higher the volume fraction of this lamellar structure. Although as-cast hypereutectic Al-Ce alloys generally exhibit higher strength, hardness, and wear resistance than eutectic or hypoeutectic alloys due to their higher second-phase volume fraction, large primary phases form in the microstructure under conventional casting conditions. This is because, during the casting of hypereutectic Al-Ce alloys, Al... 11 Ce3, as a small planar growth phase, preferentially grows on specific crystal planes (such as low index planes), usually exhibiting angular geometric shapes (such as plates, polyhedra, etc.). Due to its slow cooling rate, its size increases rapidly during solidification, resulting in significant anisotropy, weak bonding with the matrix, and the formation of fatal defects such as pores and microcracks during cooling. This reduces the material's plasticity, severely impairs the overall forming, and limits the application of this type of alloy in high-performance structural components.

[0004] While existing casting or deformation heat treatment processes can partially improve the microstructure, they often struggle to simultaneously balance the thermal stability of a high volume fraction of the second phase with the plasticity of the aluminum matrix. Summary of the Invention

[0005] To overcome the defects of hypereutectic Al-Ce alloys in traditional casting processes, such as coarse microstructure, strong anisotropy, and poor plasticity, this invention provides a novel hypereutectic Al-Ce alloy powder and a preparation method that achieves the construction of a three-dimensional continuous interpenetrating nanoscale mesh structure through LPBF additive manufacturing process. This allows the alloy to maintain a high second-phase volume fraction and high-temperature stability while obtaining high strength, good plasticity, and excellent formability.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing a rare-earth aluminum alloy with a three-dimensional interpenetrating framework, comprising the following steps: Step 1: Weigh a certain amount of high-purity aluminum, Al-20Ce master alloy, Al-2Sc master alloy and Al-5Zr master alloy and mix them to obtain raw materials. Heat the raw materials to melt them, then add a certain amount of Mg powder, cast them into shape and cool them to obtain a pre-made ingot. Step 2: The preformed ingot is made into powder to obtain hypereutectic Al-Ce alloy powder; Step 3: Mix a certain amount of hypereutectic Al-Ce alloy powder with a certain amount of nano-ceramic particles to obtain aluminum alloy composite powder; Step 4: The aluminum alloy composite powder is processed into a bulk material using laser powder bed melting technology to obtain a rare earth aluminum alloy with a three-dimensional interpenetrating skeleton.

[0007] As a preferred embodiment of the above technical solution, in step one, the raw material is placed in a crucible and melted at 600-1000 °C, then held at 850 °C for 15-30 min to ensure uniform composition. The temperature is then lowered to 680±5 °C, Mg powder is added, and the mixture is allowed to stand for 3-4 min to ensure complete melting and uniform distribution of the Mg powder. The temperature is then raised again to 760±5 °C, and a refining agent is added for refining for 5-10 min. Surface slag is removed. After refining, nitrogen gas is introduced for vacuum degassing for 10-15 min, and a covering agent is applied to the surface to prevent oxidation. Finally, the mixture is cast at a melt temperature of 740±5 °C and air-cooled to obtain a pre-formed ingot. The refining agent can be a chlorine-free and fluorine-free aluminum alloy refining agent (such as the Na3AlF6–KCl system), and the covering agent can be an environmentally friendly NaCl-KCl-Na3AlF6 system covering agent, or other commonly used refining / covering agents in the field.

[0008] As a preferred embodiment of the above technical solution, in step two, the pre-formed ingot is placed in a gas atomization powder-making device to produce hypereutectic Al-Ce alloy powder, which is then vacuum-packed for later use. The pre-formed ingot is placed in the crucible of the gas atomization powder-making device and melted under argon protection. It is heated to 800-1000 ℃ and held for 90 min to ensure complete melting and uniform composition. The melt flows out through a nozzle and is atomized into tiny droplets under the action of a high-pressure argon jet. The droplets rapidly solidify into powder during flight, with the atomization pressure set to 6 MPa. Subsequently, the atomized particles are collected and classified by an airflow sorting system, sieved to 15-53 μm. During the gas atomization process, the alloy powder forms a metastable fine eutectic structure, providing a nucleation basis for the subsequent microstructure reconstruction and three-dimensional interpenetrating mesh construction in the LPBF (laser-to-bed powder melting) process.

[0009] As a preferred embodiment of the above technical solution, the hypereutectic Al-Ce alloy powder has a particle size of 15-53 μm, and the chemical composition of the hypereutectic Al-Ce alloy powder, by mass percentage, includes Ce: 13-16 wt.%, Mg: 0.5-2 wt.%, Sc: 0.2-0.5 wt.%, Zr: 0.2-0.5 wt.%, with the balance being Al and unavoidable impurities (not exceeding 0.1 wt.%).

[0010] As a preferred embodiment of the above technical solution, hypereutectic Al-Ce alloy powder and nano-ceramic particles are placed in a vacuum drying oven and dried at 80-120 °C for 4-12 hours to remove surface-adsorbed moisture, oxygen, and other volatile impurities. Next, they are placed on an ultrasonic vibration table for pre-dispersion treatment. The ultrasonic frequency is controlled within the range of 20-40 kHz, the power is 200-400 W, and the vibration time is 60-80 min to effectively break up powder agglomeration and promote the initial adsorption of nanoparticles on the powder surface. Subsequently, the ultrasonically treated mixture is transferred to a V-shaped mixer and mixed at a speed of 30-50 rpm for 4-8 hours to obtain aluminum alloy composite powder. Further uniform dispersion of nanoparticles and alloy powder is achieved through mechanical shearing and rolling. This synergistic dispersion process can significantly improve the uniformity of the ceramic reinforcing phase distribution and the interfacial bonding state in the powder system, ensuring that nanoparticles can stably exist in the grain boundary or interdendritic region during the subsequent LPBF process, thereby effectively inhibiting grain coarsening, improving thermal stability, and enhancing the high-temperature strength and creep resistance of the material.

[0011] As a preferred embodiment of the above technical solution, the nano-ceramic particles are NbB2, ZrB2 or TiB2, the size of the nano-ceramic particles is 50-100nm, and the mass percentage of nano-ceramic particles in the aluminum alloy composite powder is 0.6-8wt.%.

[0012] As a preferred embodiment of the above technical solution, in step four, aluminum alloy composite powder is placed in an LPBF device to prepare bulk material under an argon protective atmosphere: 6061 aluminum alloy is selected as the component substrate, which is fixed on a liftable worktable and preheated to 160 ℃. After the printing chamber is evacuated, it is filled with high-purity argon. Printing begins when the oxygen content is below 1000 ppm. The process parameters are set as follows: laser power is 335 W, scanning speed is 2000 mm / s, layer thickness is 30 μm, scanning spacing is 0.1 mm, and a short straight-line scanning strategy with interlayer rotation of 67° is adopted to reduce heat accumulation and anisotropy. After forming, the sample is allowed to cool naturally, and then the sample is kept at 300 ℃ for 1 h and then air-cooled (peak aging treatment). Finally, a rare earth aluminum alloy with a three-dimensional interpenetrating skeleton is obtained. During peak aging treatment, Sc and Zr atoms precipitate from the supersaturated solid solution to form Al3(Sc,Zr) dispersed nano-precipitates, which effectively suppress high-temperature microstructure coarsening and dislocation climb, further improving the strength and thermal stability of the alloy.

[0013] Rare earth aluminum alloys with a three-dimensional interpenetrating skeleton are prepared by the above-described method.

[0014] As a preferred embodiment of the above technical solution, the rare earth aluminum alloy comprises an α-Al matrix and Al... 11 Ce3 eutectic phase, α-Al matrix and Al 11 The Ce3 eutectic phase forms a continuous, interconnected three-dimensional nanogrid structure at the microscale. This nanogrid structure resembles a root-like interlaced structure, periodically distributed and deeply embedded within the aluminum matrix, forming a spatially interconnected grid. This microstructure construction results in a fine-grained matrix structure reinforced by a continuous nano-eutectic network, achieving a synergy of high strength and good plasticity at the macroscale.

[0015] The beneficial effects of this invention are: The alloy prepared by this invention maintains good plasticity while achieving a tensile strength of approximately 570 MPa, which is about 73.7% higher than that of conventional cast hypereutectic Al-Ce alloys (approximately 150 MPa) reported in existing literature. This performance improvement stems from the synergistic effect of the multi-scale strengthening mechanism brought about by the three-dimensional continuous and interpenetrating nanogrid structure, including the restriction of dislocation movement and stress dispersion effect of the nanogrid, thereby achieving a synergistic improvement in strength and plasticity.

[0016] This invention utilizes laser powder bed fusion additive manufacturing technology to bond α-Al matrix with Al 11A continuous, interpenetrating nanoscale network structure is formed between the Ce3 eutectic phases, with a network channel width of approximately 14 nm and an average network unit size of approximately 197 nm, which is significantly superior to the discrete or discontinuous eutectic networks reported in previous studies. This three-dimensional continuous, interpenetrating structure not only improves the load transfer efficiency and interfacial bonding strength of the alloy, but also effectively suppresses crack initiation and propagation, ensuring the isotropic macroscopic mechanical properties and long-term thermal stability.

[0017] This invention successfully prepared hypereutectic Al-Ce alloy powder (with a synergistic ratio of Ce, Mg, Sc, and Zr), significantly improving the forming window width and printing stability of the alloy in additive manufacturing. This alloy is less prone to hot cracking, voids, and spheroidization defects under LPBF additive manufacturing technology, exhibiting excellent process repeatability and dimensional accuracy. Under the same process parameters, this material can be stably formed under different forming paths, layer thicknesses, and scanning angles, enabling near-net-shape forming of complex components, and possessing high process robustness and design freedom. Attached Figure Description

[0018] Figure 1 This is a contrast image of the surface morphology of the rare earth aluminum alloy powder in Example 1 under a scanning electron microscope; Figure 2 It is a superimposed image of the electron backscatter diffraction pattern of rare earth aluminum alloy in Example 1 with contrast and grain outline; Figure 3 This is a bright-field image of the rare-earth aluminum alloy in Example 1 under a transmission electron microscope; Figure 4 This is the engineering stress-engineering strain curve of the rare earth aluminum alloy in Example 1; Figure 5 This is the large-sized thin-walled sample formed from rare earth aluminum alloy in Example 1; Figure 6 These are cross-sectional views of the preform and contrast images of its surface morphology under a scanning electron microscope; Figure 7 It is the engineering stress-engineering strain curve of the precast ingot. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 Step 1: Weigh 7.95 kg (preferred) of high-purity aluminum, 67.5 kg (preferred) of Al-20Ce master alloy, 17.5 kg (preferred) of Al-2Sc master alloy, and 5.2 kg (preferred) of Al-5Zr master alloy, mix them to obtain raw materials, place the raw materials in a crucible, melt them at 1000 ℃, raise the temperature to 850 ℃ and hold for 30 min to ensure uniform composition. Then cool to 680±5 ℃, add 1.85 kg (preferred) of Mg powder, let stand for 4 min to allow the Mg powder to completely melt and be evenly distributed. After heating to 760±5 ℃ again, a certain amount of refining agent Na3AlF6–KCl was added and refined for 10 min. Surface slag was removed. After refining, nitrogen gas was introduced for vacuum degassing for 15 min. A certain amount of covering agent NaCl-KCl-Na3AlF6 was added to prevent oxidation. Finally, the ingot was cast at a melt temperature of 740±5 ℃ and air-cooled to obtain a pre-formed ingot (this pre-formed ingot serves as Comparative Example 1).

[0021] Step 2: Place the preform ingot into a gas atomization powder-making device to produce hypereutectic Al-Ce alloy powder. Vacuum package the hypereutectic Al-Ce alloy powder for later use. The preform ingot is placed in the crucible of the gas atomization device and melted under argon protection. Heating to 1000 ℃ and holding for 90 min ensures complete melting and homogeneous composition. The melt flows out through a nozzle and is atomized into tiny droplets under the action of a high-pressure argon jet. The droplets rapidly solidify into powder during flight. The gas atomization pressure is set to 6 MPa. Subsequently, the atomized particles are collected and classified by an airflow separation system, sieved to 15-53 μm.

[0022] Step 3: 4 kg of hypereutectic Al-Ce alloy powder and 60 g (preferably) of nano-ceramic particles NbB2 were placed in a vacuum drying oven and dried at 120°C for 12 hours to remove surface-adsorbed moisture, oxygen, and other volatile impurities. Next, the powder was placed on an ultrasonic vibration table for pre-dispersion treatment. The ultrasonic frequency was controlled within the range of 20-40 kHz, the power was 400 W, and the vibration time was 80 min to effectively break up powder agglomerations and promote the initial adsorption of nanoparticles on the powder surface. Subsequently, the ultrasonically treated mixture was transferred to a V-shaped mixer and mixed at 50 rpm for 8 h to obtain aluminum alloy composite powder. The surface morphology contrast of this aluminum alloy composite powder under a scanning electron microscope is as follows: Figure 1 As shown.

[0023] Step 4: Place the aluminum alloy composite powder in an LPBF device (Easy Plus 3D EP-M150) and prepare bulk materials under an argon protective atmosphere. Select 6061 aluminum alloy as the component substrate, fix it on a liftable worktable and preheat it to 160°C. After evacuating the printing chamber, fill it with high-purity argon. Start printing when the oxygen content is below 1000 ppm. The process parameters are set as follows: laser power is 335 W, scanning speed is 2000 mm / s, layer thickness is 30 μm, scanning interval is 0.1 mm, and a short straight-line scanning strategy with interlayer rotation of 67° is adopted to reduce heat accumulation and anisotropy. After forming, allow the sample to cool naturally, and then keep it at 300°C for 1 hour before air cooling. Finally, a rare earth aluminum alloy with a three-dimensional interpenetrating skeleton is obtained.

[0024] The density of this rare-earth aluminum alloy was determined to be 99.98% using the Archimedes displacement method. The contrast image and grain profile overlay of this rare-earth aluminum alloy are shown below. Figure 2 As shown, the average grain size of the printed alloy is 6.04 ± 4.5 μm.

[0025] The bright-field image of this rare-earth aluminum alloy under a scanning transmission electron microscope is as follows: Figure 3 As shown, the coarseness of the nanogrid is 14.32±0.15 nm, and the average size of the honeycomb unit formed by the nanogrid is 197.38±3.94 nm.

[0026] The engineering stress-strain curve of this rare earth aluminum alloy is shown in the figure below. Figure 4 As shown, the room temperature tensile strength of the alloy in the printed state is 527.71 MPa, the room temperature tensile strength after peak aging is 570.51 MPa, the conditional yield strength reaches 473.96 MPa, and the elongation is ≥5%.

[0027] Figure 5 This image shows a large-size, thin-walled sample of the rare-earth aluminum alloy. It can be seen that the printed sample did not exhibit obvious hot cracks, voids, or spheroidization defects. This demonstrates that the proposed preparation method exhibits excellent process repeatability and dimensional accuracy. Under the same process parameters, this material can be stably formed under different forming paths, layer thicknesses, and scanning angles, enabling near-net-shape forming of complex components. It possesses high process robustness and design freedom, exhibiting extremely high printing freedom and excellent forming performance.

[0028] Comparative Example 1 Using the preform obtained in step one of Example 1 as a comparative example, its cross-sectional view is as follows. Figure 6 As shown, its atomic number contrast image under a scanning electron microscope is as follows: Figure 6 As shown in the bottom left corner. It can be seen that, compared to... Figure 3In comparison, the as-cast structure of this rare earth aluminum alloy has a relatively coarse eutectic phase, with a large number of shrinkage cavities and microcracks, proving that the rare earth aluminum alloy prepared by this method has the advantages of a fine and uniform eutectic phase and high degree of freedom in forming.

[0029] Figure 7 The image shows a comparison of the engineering stress-engineering strain curves of the precast ingot. It can be seen that its tensile strength is 182 MPa, with an elongation of only 0.43%. In contrast, the alloy prepared by this method exhibits a tensile strength range of 509-534 MPa in the printed state, and after peak aging, its tensile strength ranges to 556-573 MPa, with a conditional yield strength range of 449-474 MPa and an elongation of not less than 5%.

[0030] It is worth mentioning that the technical features of the atomizing powder making device, LPBF equipment, etc. involved in this patent application should be regarded as prior art. The specific structure, working principle, and possible control methods and spatial arrangement of these technical features can be adopted using conventional choices in the field, and should not be regarded as the inventive point of this patent. This patent will not be further elaborated in detail.

[0031] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experimentation on the basis of the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a rare-earth aluminum alloy with a three-dimensional interpenetrating framework, characterized in that, It includes the following steps: Step 1: Weigh a certain amount of high-purity aluminum, Al-20Ce master alloy, Al-2Sc master alloy and Al-5Zr master alloy and mix them to obtain raw materials. Heat the raw materials to melt them, then add a certain amount of Mg powder, cast them into shape and cool them to obtain a pre-made ingot. Step 2: The preformed ingot is made into powder to obtain hypereutectic Al-Ce alloy powder; Step 3: Mix a certain amount of hypereutectic Al-Ce alloy powder with a certain amount of nano-ceramic particles to obtain aluminum alloy composite powder; Step 4: The aluminum alloy composite powder is processed into a bulk material using laser powder bed melting technology to obtain a rare earth aluminum alloy with a three-dimensional interpenetrating skeleton.

2. The method for preparing a rare-earth aluminum alloy with a three-dimensional interpenetrating framework as described in claim 1, characterized in that, In step one, the raw material is placed in a crucible and melted at 600-1000 ℃, held at 850 ℃ for 15-30 min, then cooled to 680±5 ℃, Mg powder is added, and the mixture is allowed to stand for 3-4 min to allow the Mg powder to melt completely and distribute evenly. The temperature is then raised again to 760±5 ℃, and a refining agent is added for refining for 5-10 min. Surface slag is removed, and after refining, nitrogen gas is introduced for vacuum degassing for 10-15 min. A covering agent is then applied to the surface to prevent oxidation. Finally, the mixture is cast at a melt temperature of 740±5 ℃ and air-cooled to obtain a pre-formed ingot.

3. The method for preparing a rare-earth aluminum alloy with a three-dimensional interpenetrating framework as described in claim 1, characterized in that, In step two, the preformed ingot is placed in an air atomization powder making device, and hypereutectic Al-Ce alloy powder is made using the air atomization powder making device. The hypereutectic Al-Ce alloy powder is then vacuum packaged for later use.

4. The method for preparing a rare-earth aluminum alloy with a three-dimensional interpenetrating framework as described in claim 3, characterized in that, The hypereutectic Al-Ce alloy powder has a particle size of 15-53 μm, and its chemical composition, by mass percentage, is... It includes Ce: 13-16 wt.%, Mg: 0.5-2 wt.%, Sc: 0.2-0.5 wt.%, Zr: 0.2-0.5 wt.%, with the balance being Al and unavoidable impurities.

5. The method for preparing a rare-earth aluminum alloy with a three-dimensional interpenetrating framework as described in claim 1, characterized in that, In step three, the hypereutectic Al-Ce alloy powder and nano-ceramic particles are placed in a vacuum drying oven and dried at 80-120 ℃ for 4-12 hours. Then, they are placed on an ultrasonic vibration table for pre-dispersion treatment. The ultrasonic frequency is controlled in the range of 20-40 kHz, the power is 200-400 W, and the vibration time is 60-80 min. Subsequently, the ultrasonically treated mixture is transferred to a V-shaped mixer and mixed at a speed of 30-50 rpm for 4-8 h to obtain aluminum alloy composite powder.

6. The method for preparing a rare-earth aluminum alloy with a three-dimensional interpenetrating framework as described in claim 5, characterized in that, The nano-ceramic particles are NbB2, ZrB2 or TiB2, and the size of the nano-ceramic particles is 50-100 nm. The mass percentage of nano-ceramic particles in the aluminum alloy composite powder is 0.6-8 wt.%.

7. The method for preparing a rare-earth aluminum alloy with a three-dimensional interpenetrating framework as described in claim 1, characterized in that, In step four, aluminum alloy composite powder is placed in an LPBF device to prepare bulk material under an argon protective atmosphere. 6061 aluminum alloy is selected as the component substrate, which is fixed on a liftable worktable and preheated to 160 ℃. After the printing chamber is evacuated, it is filled with high-purity argon. Printing begins when the oxygen content is below 1000 ppm. The process parameters are set as follows: laser power is 335 W, scanning speed is 2000 mm / s, layer thickness is 30 μm, scanning spacing is 0.1 mm, and a short straight-line scanning strategy with interlayer rotation of 67° is adopted to reduce heat accumulation and anisotropy. After forming, the sample is allowed to cool naturally, and then the sample is kept at 300 ℃ for 1 h and then air-cooled. Finally, a rare earth aluminum alloy with a three-dimensional interpenetrating skeleton is obtained.

8. A rare-earth aluminum alloy with a three-dimensional interpenetrating skeleton, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

9. The rare-earth aluminum alloy with a three-dimensional interpenetrating skeleton as described in claim 8, characterized in that, The rare earth aluminum alloy comprises an α-Al matrix and Al 11 Ce3 eutectic phase, α-Al matrix and Al 11 The Ce3 eutectic phase forms a continuous and interconnected three-dimensional nanogrid structure at the microscale.

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