An aluminum alloy with synergistic addition of scandium and scandia and a method of making the same

Abstract

The application relates to the technical field of metal materials, and discloses an aluminum alloy with synergistically added scandium and scandium oxide and a preparation method thereof, which comprises the following steps: a casting method of an Al-4.5Cu-0.3Mg aluminum alloy, adding Sc and Sc2O3 in the Al-4.5Cu-0.3Mg aluminum alloy matrix; under high-purity argon protection and high vacuum, mixing the aluminum alloy matrix with Sc and Sc2O3, and carrying out homogenization treatment after smelting; carrying out primary and secondary aging treatment on the alloy after solid solution; carrying out low-temperature aging treatment and short-time high-temperature aging precipitation to prepare the alloy. The aluminum alloy has the advantages that the high-temperature performance and stability of the cast aluminum alloy are remarkably improved through synergistically added scandium and scandium oxide, the grain is refined and the structure is optimized compared to single addition; the alloy has good tensile strength, yield strength and plasticity after thermal exposure, Al3Sc precipitated phases are formed, the distribution of scandium is more uniform, and the high-temperature performance and stability of the alloy are improved.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials, and specifically relates to the performance improvement of aluminum alloy materials, specifically an aluminum alloy with synergistic addition of scandium and scandium oxide and its preparation method. Background Technology

[0002] With the rapid development of high-tech fields such as aerospace, automotive, and defense equipment, higher demands are being placed on material performance, especially lightweighting and high-temperature resistance, which have become key objectives in material design. Aluminum alloys, due to their low density, high specific strength, and excellent corrosion resistance, are widely used in fields with stringent lightweighting requirements. However, traditional Al-Cu cast aluminum alloys (such as Al-4.5Cu-0.3Mg) still face challenges in high-temperature environments. In particular, their main strengthening phase, θ'-Al2Cu, is prone to instability under long-term high-temperature conditions, leading to incoherence and precipitation of the θ'-Al2Cu phase. This results in softening of the alloy structure, grain growth, and a decrease in creep resistance, severely affecting the high-temperature strength and service life of Al-Cu cast aluminum alloys.

[0003] To address the high-temperature stability issue of Al-Cu cast aluminum alloys, researchers have proposed various modification schemes, such as adding transition metals (e.g., titanium, zirconium) or rare earth elements (e.g., scandium, lanthanum), to increase the alloy's thermal stability and creep resistance. Among these, scandium, as a rare earth element, has attracted attention due to its unique strengthening effect. Scandium can form Al3Sc nanoprecipitates in the aluminum alloy matrix. These precipitates are coherent with the aluminum matrix and can effectively suppress grain coarsening and phase structure changes under high-temperature conditions, thereby improving the alloy's high-temperature strength, heat resistance, and creep resistance. The formation of Al3Sc nanoprecipitates not only refines the grains but also improves the material's stability in high-temperature environments by hindering dislocation movement and reducing grain boundary sliding.

[0004] However, at higher temperatures, the addition of scandium alone still faces the problems of uneven distribution of Al3Sc nanoprecipitates and partial desolvation, which limits the effect of high-temperature strengthening.

[0005] Studies have found that adding Sc alone to Al-Cu cast aluminum alloys (especially Al-Cu cast aluminum alloys with Cu content greater than 4wt%) not only easily forms the W phase (Al2CuMg), causing a sharp decrease in plasticity, but also consumes strengthening elements (solid-dissolved Cu and Sc). Furthermore, due to the uneven composition during the addition process, a large number of coarse primary Al3Sc are easily generated during the casting process (coarse Al3Sc has no strengthening effect). Moreover, the grains grow uncontrollably during subsequent heat treatment, ultimately leading to a significant deterioration in the mechanical properties of the alloy.

[0006] To address the aforementioned problems, this invention proposes an aluminum alloy with synergistic addition of scandium and scandium oxide, and its preparation method. Summary of the Invention

[0007] To address the problem that adding scandium alone to Al-Cu cast aluminum alloys can lead to grain coarsening due to compositional segregation and the formation of coarse primary Al3Sc, which in turn promotes the precipitation of W phase, consumes a large amount of dissolved Cu and Sc elements, resulting in a reduction in the number of strengthening phases, insufficient high-temperature stability, and limiting the high-temperature strengthening effect, this invention provides an aluminum alloy with synergistic addition of scandium and scandium oxide and its preparation method.

[0008] This invention is achieved using the following techniques:

[0009] This invention provides a method for preparing an aluminum alloy by synergistic addition of scandium and scandium oxide, comprising the following steps: including a method for casting an Al-4.5Cu-0.3Mg aluminum alloy, wherein Sc (scandium) and Sc2O3 (scandium oxide) are added to the Al-4.5Cu-0.3Mg aluminum alloy matrix, wherein the amount of Sc added is 0.1~0.6wt% and the amount of Sc2O3 added is 0.3~3wt%.

[0010] Among them, Sc is the active scandium source, and the preferred addition amount is 0.3~0.6wt%; Sc2O3 is the heterogeneous nucleating agent and scandium slow-release source, and the preferred addition amount is 1~3wt%. The two work together to form a synergistically reinforced composite nano-precipitation structure, ensuring that scandium and scandium oxide form a stable nano-scale precipitate phase in the Al-4.5Cu-0.3Mg aluminum alloy matrix, thereby enhancing the alloy's resistance to high-temperature softening and creep.

[0011] Specifically, it includes the following steps:

[0012] a. Smelting

[0013] Sc is alloyed with Al to form an Al-Sc pre-alloy. This pre-alloy is then tested under high-purity argon protection and high vacuum conditions (vacuum degree less than or equal to 3 × 10⁻⁶). -3 Pa, Al-Sc pre-alloy, Al-4.5Cu-0.3Mg aluminum alloy matrix and Sc2O3 are mixed and melted three times at 800℃ using a water-cooled copper crucible, and magnetic stirring is used to ensure uniform dispersion of components and uniform distribution of scandium and scandium oxide to reduce the introduction of impurities, so as to obtain an alloy with synergistic oxide addition.

[0014] b. Homogenization treatment

[0015] The alloy with synergistic oxide addition obtained in step a was kept at 475°C for 12 hours to promote the diffusion of solute elements, eliminate microsegregation, ensure the uniformity of microstructure, and obtain an alloy with homogeneous composition.

[0016] c. Primary solution treatment

[0017] The alloy with homogenized composition is heated to 505℃ and held for 6~10 hours. Slow heating promotes the dissolution and diffusion of low melting point elements, avoids grain coarsening, and lays the foundation for the uniform distribution of precipitates.

[0018] d. Secondary solution treatment

[0019] The alloy undergoing primary solution treatment is rapidly heated to 525℃ and held for 2-6 hours. This short-term high temperature activates the reaction between Sc2O3 and the Al-4.5Cu-0.3Mg aluminum alloy matrix, ensuring that as much Sc2O3 as possible dissolves into the Al-4.5Cu-0.3Mg aluminum alloy matrix without causing overheating of the matrix. This achieves maximum Sc2O3 dissolution and active release, resulting in a solution-treated alloy.

[0020] The primary and secondary solution treatments employ a controlled heating rate and short-term high-temperature holding method to enable the rapid solution of Sc and the Sc2O3 interfacial reaction to proceed in synergy. This promotes the maintenance of Al3Sc nano-precipitates at the nanoscale and their uniform distribution within the Al-4.5Cu-0.3Mg aluminum alloy matrix, thereby achieving structural stability under long-term service.

[0021] e. Two-level timeliness processing

[0022] The first step is low-temperature aging treatment: the solution-treated alloy is aged at 180~200℃ for 8~24 hours. Preferably, the first step of low-temperature aging treatment is carried out at 185℃ to form a stable Al3Sc precipitation template;

[0023] The second step is high-temperature aging treatment: The temperature is raised to 250~400℃ for 2~6 hours to promote the growth of Al3Sc precipitates, forming a stable nano-precipitate structure, inhibiting PFZ (segregation band) formation, and obtaining a composite strengthened microstructure. Preferably, the second step of high-temperature aging treatment is carried out at 380℃ to form stable Al3Sc nano-precipitates and θ'-Al2Cu phases, obtaining an aluminum alloy with synergistic addition of scandium and scandium oxide. The Al3Sc nano-precipitates and θ'-Al2Cu phases generated after aging treatment effectively strengthen the Al-4.5Cu-0.3Mg aluminum alloy matrix, enabling the obtained aluminum alloy with synergistic addition of scandium and scandium oxide to maintain high strength and resist softening under high-temperature conditions.

[0024] The mechanism of this method is as follows:

[0025] This method introduces scandium oxide to further enhance the dispersion of scandium in the Al-4.5Cu-0.3Mg aluminum alloy matrix. During the melting process, scandium oxide aggregates at the triple grain boundaries and acts as heterogeneous nucleation sites, effectively promoting grain refinement. In the melting process, scandium oxide not only plays a controlling role in the early stages of grain growth but also ensures the reduction of grain size in Al-Cu cast aluminum alloys during casting, especially at high temperatures. It helps suppress high-temperature grain growth and plays a crucial role in grain refinement. This grain refinement effect helps improve the alloy's strength, thereby enhancing its mechanical properties and stability in high-temperature environments.

[0026] During the smelting process, scandium oxide reacts with the Al-4.5Cu-0.3Mg aluminum alloy matrix, releasing scandium and providing a stable scandium source. The addition of scandium oxide also increases the solubility of scandium in the Al-4.5Cu-0.3Mg aluminum alloy matrix, promoting the uniform distribution of Sc and forming a stable solid solution in the Al-4.5Cu-0.3Mg aluminum alloy matrix, thus forming nanoscale Al3Sc nanoprecipitates. At high temperatures, the Al3Sc nanoprecipitates can be uniformly distributed in the Al-4.5Cu-0.3Mg aluminum alloy matrix, further suppressing grain coarsening and dislocation slip, and improving the microstructure stability of the alloy. This enhances the high-temperature stability and creep resistance of the aluminum alloy with synergistic addition of scandium and scandium oxide.

[0027] Furthermore, the addition of scandium oxide significantly improves grain boundary stability by increasing the interfacial energy of the grain boundaries. This makes the grain boundaries more robust at high temperatures and reduces grain boundary slip caused by temperature increases. More importantly, scandium oxide effectively prevents the formation of coarse Al₂Cu phases, which cause inhomogeneity at high temperatures in aluminum alloy grain boundaries, resulting in precipitation bands and performance degradation. The addition of scandium oxide reduces the formation of PFZ and optimizes the microstructure of aluminum alloys with synergistic scandium and scandium oxide addition, thereby significantly improving softening resistance and creep resistance.

[0028] This synergistic effect not only significantly improves the heat resistance under high-temperature environments and demonstrates excellent mechanical properties, but also enhances the long-term service stability of aluminum alloys with synergistic addition of scandium and scandium oxide. It is widely applicable to high-temperature applications in aerospace, automotive industry and military equipment, meeting the stringent requirements for lightweight and high-temperature resistant materials.

[0029] The present invention also provides an aluminum alloy with synergistic addition of scandium and scandium oxide prepared by a method for synergistic addition of scandium and scandium oxide.

[0030] Preferably, the aluminum alloy matrix includes uniformly distributed nano-sized Al3Sc precipitates and Sc2O3 particles distributed at the grain boundaries. The aluminum alloy with synergistic addition of scandium and scandium oxide has excellent microstructure stability and mechanical properties under high-temperature service conditions. After 100 hours of heat exposure at 300°C, the tensile strength retention rate is greater than 90%.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This application provides an aluminum alloy with synergistic addition of scandium (Sc) and scandium oxide, and its preparation method. By synergistically adding scandium (Sc) and scandium oxide (Sc2O3), firstly, a Cu / Mg enrichment layer is formed in the Al-4.5Cu-0.3Mg aluminum alloy, using Sc2O3 as a heterogeneous nucleation site. This reduces the Cu content in the matrix and inhibits the formation of the harmful W phase (which drastically reduces plasticity and consumes dissolved Cu and Sc), thus avoiding plasticity loss due to Al2Cu phase coarsening. Secondly, when Sc2O3 is uniformly dispersed, it provides a semi-coherent interface, allowing Sc to preferentially nucleate at the interface, forming Al3Sc nano-precipitates with uniform and diffuse distribution. Therefore, the synergistic addition of scandium and scandium oxide not only solves the plasticity loss caused by PFZ formation and W phase formation but also increases the Al3Sc precipitation ratio, improving heat resistance and enabling the alloy material to maintain both high strength and good plasticity after high-temperature exposure. The synergistic strengthening mechanism of scandium and scandium oxide provides a new solution for the design of high-temperature stability of alloy materials.

[0033] This invention maximizes the solution efficiency of scandium and the uniformity of the distribution of precipitated phases (Al3Sc nano-precipitates and θ'-Al2Cu phase) by precisely optimizing the addition amount of scandium and scandium oxide (0.1~0.6wt% scandium and 0.3~3wt% scandium oxide) and combining it with smelting, homogenization treatment, primary solution treatment, secondary solution treatment and two-stage aging treatment processes. This ensures that scandium and scandium oxide can synergistically form a stable heat-resistant composite phase structure at high temperature, overcoming the problem of unstable precipitated phases of single elements at high temperature, and significantly improving the high-temperature performance of the alloy. At the same time, the Cu content in the Al-4.5Cu-0.3Mg aluminum alloy matrix can be precisely controlled by the addition ratio of Sc2O3 combined with precise heat treatment process. Sc2O3 acts as a container for storing Cu, controlling the precipitation and growth process of the strengthening phase.

[0034] This invention effectively optimizes the distribution of scandium in the Al-4.5Cu-0.3Mg aluminum alloy matrix by introducing scandium oxide, promotes the formation of nanoscale Al3Sc nanoprecipitates, significantly enhances the stability of precipitates at grain boundaries, and inhibits grain coarsening and precipitate desolvation. This achieves long-term stability of aluminum alloys with synergistic addition of scandium and scandium oxide at high temperatures above 300°C, resulting in excellent performance of aluminum alloys with synergistic addition of scandium and scandium oxide under high-temperature service conditions.

[0035] The aluminum alloy with synergistic addition of scandium and scandium oxide obtained by this invention has both excellent high temperature resistance and lightweight properties, which can meet the demand for high-performance materials in high-temperature service fields such as aerospace, automobiles and military equipment. Attached Figure Description

[0036] Figure 1 This shows a metallographic micrograph from Example 2.

[0037] Figure 2 This represents a histogram showing the grain size distribution in Example 2.

[0038] Figure 3 This shows the metallographic micrograph of Comparative Example 1.

[0039] Figure 4 This represents the histogram of grain size distribution in Comparative Example 1.

[0040] Figure 5 This shows the metallographic micrograph of Comparative Example 2.

[0041] Figure 6 This represents the histogram of grain size distribution in Comparative Example 2.

[0042] Figure 7 This shows the metallographic micrograph of Comparative Example 3.

[0043] Figure 8 This represents the histogram of grain size distribution in Comparative Example 3.

[0044] Figure 9 This image shows the morphology of the precipitated phase in Example 2.

[0045] Figure 10 This shows the morphology of the precipitated phase in Comparative Example 1.

[0046] Figure 11 This shows the morphology of the precipitated phase in Comparative Example 2.

[0047] Figure 12 This shows the morphology of the precipitated phase in Comparative Example 3.

[0048] Figure 13 The image shows the TEM morphology of the precipitated phase in Example 2.

[0049] Figure 14 This is a TEM image of the PFZ region in Example 2.

[0050] Figure 15 The stress-strain curves of Example 2 and Comparative Examples 1-3 before heat exposure are shown.

[0051] Figure 16 The stress-strain curves of Example 2 and Comparative Examples 1-3 are shown after 100 hours of heat exposure.

[0052] Figure 17 This shows a SEM image of Example 2 before heat exposure.

[0053] Figure 18 This shows a SEM image of Example 2 after heat exposure. Detailed Implementation

[0054] The specific embodiments of the present invention will be described in detail below. Example 1

[0055] A method for preparing an aluminum alloy by synergistic addition of scandium and scandium oxide includes the following steps:

[0056] a. Smelting

[0057] Sc was alloyed with Al to prepare Al-0.3Sc pre-alloy. The Al-0.3Sc pre-alloy, Al-4.5Cu-0.3Mg aluminum alloy matrix, and Sc2O3 powder were mixed and subjected to a vacuum of 3×10⁻⁶. -3 Under the protection of Pa and high-purity argon, the melting was carried out three times with magnetic stirring at 800°C using a water-cooled copper crucible to ensure that Sc and Sc2O3 were fully dissolved and uniformly distributed, thus obtaining an alloy with synergistic oxide addition. The melt was then cast into ingots.

[0058] b. Homogenization treatment

[0059] The ingot obtained in step a was subjected to homogenization heat treatment at 475℃ for 12 hours to promote the diffusion of each alloying element in the Al-4.5Cu-0.3Mg aluminum alloy matrix, eliminate microsegregation, ensure the uniformity of the microstructure, and obtain an alloy with homogeneous composition.

[0060] c. Primary solution treatment

[0061] The alloy with homogenized composition is heated to 505℃ and held for 8 hours to achieve full solid solution of low-melting-point alloying elements (such as Cu and Mg), reduce primary phase residue, and lay the foundation for high-temperature treatment.

[0062] d. Secondary solution treatment

[0063] The alloy undergoing primary solution treatment was rapidly heated to 525℃ and held for 4 hours to achieve maximum solid solution of Sc in the Al-Sc pre-alloy. At the same time, the interfacial reaction between Sc2O3 and the Al-4.5Cu-0.3Mg aluminum alloy matrix was activated, releasing active Sc and forming a uniform solid solution structure, thus obtaining the solution-treated alloy.

[0064] e. Two-level timeliness processing

[0065] The solution-treated alloy was held at 185℃ for 16 hours for the first step of low-temperature aging treatment to promote the formation of ultrafine Al3Sc precipitates, which served as templates for Al3Sc precipitation.

[0066] The temperature was then raised to 380℃ for a second high-temperature aging treatment for 1 hour, which allowed the Al3Sc nano-precipitates to grow and stabilize at high temperature, forming a coherent strengthening network. At the same time, θ'-Al2Cu phase was precipitated, achieving a composite strengthening effect. This yielded an aluminum alloy with synergistic addition of scandium and scandium oxide, with 0.3wt% of Sc and 1wt% of Sc2O3. Example 2

[0067] A method for preparing an aluminum alloy by synergistic addition of scandium and scandium oxide includes the following steps:

[0068] In this embodiment, the amount of Sc2O3 added was 3wt%, and the rest was exactly the same as in Example 1, so as to obtain an aluminum alloy with synergistic addition of scandium and scandium oxide, in order to explore the distribution of precipitated phases and thermal stability under high addition conditions. Comparative Example 1

[0069] A method for preparing an aluminum alloy includes the following steps:

[0070] In this comparative example, Sc and Sc2O3 were not added and were used as a blank control group. The remaining steps were completely consistent with those in Example 1 to obtain the aluminum alloy. Comparative Example 2

[0071] A method for preparing an aluminum alloy includes the following steps:

[0072] In this comparative example, Sc2O3 was not added, but only 0.3wt% of Sc was added. The remaining steps were completely consistent with those in Example 1 to obtain an aluminum alloy with only scandium addition, which was used to evaluate the strengthening effect of adding only Sc. Comparative Example 3

[0073] A method for preparing an aluminum alloy includes the following steps:

[0074] In this comparative example, no Sc was added, only 1 wt% Sc2O3 was added, and the remaining steps were completely consistent with those in Example 1, to obtain an aluminum alloy with only scandium oxide added, which was used to verify the strengthening effect of adding Sc2O3 alone.

[0075] I. Microscopic Observation

[0076] The overall microstructure of the alloys in Example 2 and Comparative Examples 1-3 was observed using a metallographic microscope, and the distribution and morphology of Al3Sc nano-precipitates and θ'-Al2Cu phases were observed using SEM (scanning electron microscopy).

[0077] The results show that, Figure 1 , 2 As shown, Example 2 exhibits a significant grain refinement effect, with the grain size of the as-cast alloy refined to below 10 μm. In the prior art, Al-Cu cast aluminum alloys can only maintain the grain size at 20~50 μm with the addition of grain refiners.

[0078] like Figures 3-8 As shown, compared with Comparative Example 1, the alloy grain size of Example 2 is significantly smaller, and the grains maintain good equiaxed grains. Comparing Comparative Examples 2 and 3 with Comparative Example 1, it can be observed that the alloy grain size of Comparative Examples 2 and 3 decreased by more than 50%, proving that the refining effect of adding Sc or Sc2O3 alone is limited; the grains only maintain a dendritic morphology, and the grains are coarse. Comparing Comparative Examples 2 and 3 with Example 2, the alloy grain size of Example 2 is significantly smaller, proving that in Example 2, the synergistic addition of Sc and Sc2O3 can overcome the limitations of single addition. The addition of Sc2O3 acts as a heterogeneous nucleation site during the melting process, promoting nucleation and increasing supercooling. Therefore, it can be proven that the present invention overcomes the poisoning phenomenon of traditional refining agents, achieving further refining.

[0079] like Figures 9-12 As shown, transmission electron microscopy was used to further observe and analyze the formation of Al3Sc nanoprecipitates and their stability under high temperature conditions.

[0080] The results show that Example 2 formed uniformly distributed Al3Sc nanoprecipitates and θ'-Al2Cu phases. Sc2O3, as a semi-coherent structure with the matrix, acts as an attractive enrichment site for elements, temporarily storing excess Cu in the Al-4.5Cu-0.3Mg aluminum alloy matrix at the interface. Furthermore, its attraction to Sc further promotes the uniform distribution of Sc, enabling the uniform formation of Al3Sc around Sc2O3 during high-temperature aging, thus improving the segregation phenomenon of single additive elements and exhibiting equiaxed grains. In addition, Sc2O3 itself has a high elastic modulus and is a hard particle, therefore not only further refining the grains but also suppressing grain coarsening and precipitate desolvation through grain boundary pinning effect, significantly improving the alloy's high-temperature strength, heat resistance, and creep resistance.

[0081] Metallographic microscopy and TEM analysis revealed that the solubility of Scandium (Sc) was further enhanced after the addition of Sc2O3. This significantly improved the uniform distribution of Sc within the Al-4.5Cu-0.3Mg aluminum alloy matrix, promoting the formation of more uniform Al3Sc nano-precipitates, thereby enhancing the alloy's heat resistance and effectively improving its high-temperature stability and resistance to high-temperature softening. Furthermore, TEM analysis showed that Sc2O3 mainly aggregated at the triple grain boundaries in the alloy. This aggregation effect further enhanced the uniform distribution of Scandium in the Al-4.5Cu-0.3Mg aluminum alloy matrix, providing an ideal matrix for the formation of Al3Sc nano-precipitates and promoting the alloy's high-temperature stability. Through this microstructure regulation, the present invention exhibits excellent resistance to softening and creep at high temperatures.

[0082] like Figure 13 , 14 As shown, SEM was used to observe the alloy. The observation revealed that in Example 2, uniformly distributed Al3Sc nano-precipitates and θ'-Al2Cu phases were precipitated. Micron-sized spherical Sc2O3 particles were distributed at the grain boundaries, effectively pinning them and helping to maintain the grain structure of the material. This significantly suppressed grain growth at high temperatures, preventing coarsening and thus maintaining the mechanical properties of the alloy. The Sc2O3 particles within the grains were mostly irregular in shape, but their uniform distribution further increased the density of strengthening phases, resulting in improved strength.

[0083] The Al3Sc nano-precipitates and θ'-Al2Cu phases form a stable strengthening structure in the alloy. The Al3Sc nano-precipitates help improve the high-temperature strength and heat resistance of the alloy, while the θ'-Al2Cu phase improves the room-temperature strength and heat resistance of the alloy.

[0084] II. Tensile property testing before and after heat exposure

[0085] The tensile properties of Examples 2 and Comparative Examples 1-3 were tested under 300°C heat exposure. Figure 15 As shown, before heat exposure, the stress-strain curves of the alloys in Example 2 and Comparative Examples 1-3 exhibited similar morphologies. The tensile strength of Example 2 reached 300 MPa, and the elongation remained at 16%. This strength-plasticity match was significantly higher than that of alloys of the same composition.

[0086] like Figure 15 , 16As shown, comparing the comparative example before and after heat exposure with Example 2, the stress in Example 2 is significantly increased, indicating that the synergistic addition of Sc and Sc2O3 effectively improves high-temperature strength, and its performance is significantly better than that of the comparative example. Specifically, the tensile strength of Example 2 is increased by 15-20% and the yield strength is increased by 10-15% compared with Comparative Example 1, showing significant performance improvement.

[0087] Furthermore, Example 2 exhibited less plasticity change and higher ductility. This phenomenon indicates that the synergistic effect of Sc and Sc2O3 not only improved tensile strength but also effectively suppressed the coarsening of precipitates, reduced PFZ formation, and further enhanced resistance to softening and creep at high temperatures.

[0088] III. Tissue stability and resistance to softening

[0089] Tissue changes after high-temperature exposure were observed using SEM. Example 2 showed excellent tissue stability at high temperatures.

[0090] like Figure 16 As shown, after 100 hours of heat exposure at 300°C, Example 2 still maintained the highest strength with a plasticity loss rate of less than 10%, while the plasticity loss of Comparative Example 2, which was added alone, exceeded 50%. This indicates that synergistic addition not only maintains strength but also avoids plasticity loss caused by coarsening of precipitates. Softening under high-temperature conditions was significantly reduced; after 100 hours of exposure at 300°C, the θ'-Al2Cu phase remained stable, effectively suppressing grain coarsening and the dissolution of precipitates.

[0091] In summary, under appropriate addition amounts and aging conditions, this application significantly improves the high-temperature performance and stability of Al-Cu cast aluminum alloys through the synergistic addition of Sc and Sc2O3.

[0092] As shown in Figures 17 and 18, microstructural observations reveal that Sc2O3 aggregates at the triangular grain boundaries during melting and acts as a heterogeneous nucleation site to refine the grains. Simultaneously, during casting, it reacts with the Al-4.5Cu-0.3Mg aluminum alloy matrix, providing a stable scandium source and forming nanoscale Al3Sc nanoprecipitates, further refining the grains and enhancing the alloy's high-temperature stability. Furthermore, the addition of Sc2O3 effectively improves the uniformity of Sc distribution in the Al-4.5Cu-0.3Mg aluminum alloy matrix, reduces precipitate segregation, and optimizes the alloy's microstructural stability at high temperatures.

[0093] Tensile test results after heat exposure at 300℃ show that the aluminum alloy with synergistic addition of Sc and Sc2O3 exhibits higher tensile strength and yield strength under high-temperature conditions. Compared with comparative examples 1-3, the aluminum alloy with synergistic addition of Sc and Sc2O3 maintained better plasticity after heat exposure, indicating that the coarsening phenomenon of precipitated phases was effectively suppressed, thereby significantly improving the alloy's resistance to softening and creep, effectively extending the service life of the material in high-temperature environments, and prolonging its high-temperature service life.

[0094] Overall, the synergistic effect of Sc and Sc2O3 not only improves the high-temperature strength of Al-Cu cast aluminum alloys, but also enhances their long-term stability under high-temperature service conditions.

[0095] The scope of protection claimed by this invention is not limited to the specific embodiments described above. Moreover, for those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for producing an aluminum alloy to which scandium is synergistically added with scandium oxide, comprising a casting method of an Al-4.5Cu-0.3Mg aluminum alloy, characterized by, In an Al-4.5Cu-0.3Mg aluminum alloy matrix, Sc and Sc2O3 are added in coordination, the addition amount of Sc is 0.1-0.6wt%, and the addition amount of Sc2O3 is 0.3-3wt%, The method comprises the following steps: a, smelting Sc is alloyed with Al to prepare an Al-Sc pre-alloy, the Al-Sc pre-alloy, an Al-4.5Cu-0.3Mg aluminum alloy matrix and Sc2O3 are mixed under high-purity argon protection and high-vacuum conditions, and smelting is carried out three times at 800℃ to prepare an alloy with coordinated addition of oxides; b, homogenization treatment The alloy with coordinated addition of oxides prepared in step a is kept at 475℃ for 12 hours to prepare an alloy with uniform composition; c, primary solid solution treatment The alloy with uniform composition is heated to 505℃ and kept for 6-10 hours; d, secondary solid solution treatment The alloy after the primary solid solution treatment is rapidly heated to 525℃ and kept for 2-6 hours to prepare an alloy after solid solution; e, double-stage aging treatment The alloy after solid solution is subjected to low-temperature aging treatment at 180-200℃ for 8-24 hours to form stable Al3Sc precipitation templates; After being heated to 250-400℃, the alloy is subjected to aging treatment for 2-6 hours to prepare an aluminum alloy with coordinated addition of Sc and Sc2O3.

2. The method of claim 1, wherein the method comprises the steps of: (a) providing a molten aluminum alloy; (b) adding a scandium-containing additive to the molten aluminum alloy; (c) adding a scandia-containing additive to the molten aluminum alloy; and (d) solidifying the molten aluminum alloy. In step e, the first low-temperature aging treatment is carried out at 185℃, and the second heating aging treatment is carried out at 380℃.

3. The aluminum alloy with coordinated addition of Sc and Sc2O3 obtained by the preparation method of the aluminum alloy with coordinated addition of Sc and Sc2O3 according to claim 1.

4. The aluminum alloy of claim 3, wherein, The aluminum alloy comprises uniformly distributed nanoscale Al3Sc nano-precipitated phases and Sc2O3 particles distributed in grain boundaries in the matrix of the aluminum alloy.

5. An aluminium alloy according to claim 3 or 4, characterised in that, After being subjected to thermal exposure at 300℃ for 100 hours, the tensile strength retention rate of the aluminum alloy with coordinated addition of Sc and Sc2O3 is greater than 90%.

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