Ti2AlNb-based alloy for casting and preparation method

Abstract

The invention discloses a Ti2AlNb-based alloy for casting and a preparation method thereof, relates to the technical field of Ti2AlNb-based alloys, and aims to solve the problems that an existing TiAlNb-based alloy component system is limited by alloy component design, and high-content Nb elements can cause poor mold filling capacity, solidification segregation and coarse structure of the alloy during casting, so that the casting quality is poor. The Ti2AlNb-based alloy for casting, disclosed by the invention, comprises the following components in percentage by atom: 23 to 26 percent of aluminum, 20 to 23 percent of niobium, 0.5 to 1.5 percent of molybdenum, 0.5 to 1.5 percent of zirconium, 0.2 to 0.5 percent of silicon and the balance of titanium and less than 0.2 percent of impurities. In the Ti2AlNb-based alloy, the atomic ratio of the niobium element and the atomic ratio of the molybdenum element are shown in the specification.

Description

Technical Field

[0001] This invention relates to the field of Ti2AlNb-based alloy technology, and more specifically, to a Ti2AlNb-based alloy for casting and its preparation method. Background Technology

[0002] With the development of aerospace technology, the harsh and extreme hot service environments have placed higher demands on the high-temperature performance and weight reduction of hot-end service materials for aerospace applications. As the design of new-generation engines pushes turbine inlet temperatures to 600°C and even higher, the high-temperature oxidation resistance of traditional high-temperature titanium alloys deteriorates sharply, and creep strength decreases significantly, highlighting performance bottlenecks. This performance limitation has spurred the exploration of new materials with higher specific strength and excellent high-temperature load-bearing capacity. To overcome this bottleneck, research has shifted its focus to the exploration of intermetallic compounds with higher order. TiAl-based intermetallic compounds have better oxidation resistance and high-temperature strength; however, the inherent room-temperature brittleness and low damage tolerance of γ-TiAl alloys limit their application in critical load-bearing components.

[0003] Ti2AlNb-based intermetallic compounds exhibit advantages such as high specific strength and high specific elastic modulus, strong high-temperature creep resistance and oxidation resistance in the 650-700℃ range, and their density is significantly lower than that of nickel-based superalloys, making them one of the most promising lightweight high-temperature structural materials for application in the 750-850℃ range. Existing research mainly focuses on wrought alloys, whose preparation process heavily relies on complex ingot metallurgy and thermomechanical processing, resulting in drawbacks such as long process flow, low material utilization, high manufacturing costs, and difficulty in forming complex thin-walled components. Existing compositional systems (such as Ti-22Al-25Nb) are limited by alloy composition design; high Nb content often leads to poor filling ability, solidification segregation, and coarse microstructure when the alloy is used in casting, a highly efficient near-net-shape forming process. Furthermore, high Nb content also reduces the alloy's high-temperature oxidation resistance. Summary of the Invention

[0004] The purpose of this invention is to provide a Ti2AlNb-based alloy for casting and its preparation method, addressing the technical problems of existing TiAlNb-based alloy compositions being limited by alloy design, where high Nb content leads to poor filling ability, solidification segregation, coarse microstructure, and decreased high-temperature oxidation resistance during casting. In view of this, the invention achieves this through the following solution.

[0005] In a first aspect, the present invention provides a Ti2AlNb-based alloy for casting, comprising, by atomic percentage: Aluminum 23-26%, niobium 20-23%, molybdenum 0.5-1.5%, zirconium 0.5-1.5%, silicon 0.2-0.5%, with the balance being titanium and impurities less than 0.2%; In the Ti2AlNb-based alloy, the relationship between the atomic ratio of niobium and molybdenum is as follows: ; in, Indicates the atomic ratio of niobium. This indicates the atomic ratio of molybdenum.

[0006] Compared with existing technologies, in order to balance the mechanical and processing properties (mainly fluidity) of the Ti2AlNb-based alloy for casting in this invention, it is necessary to control the Nb (niobium) content to avoid being too high. Since a decrease in Nb content leads to a decline in the alloy's mechanical properties, a stronger β-strengthening element is added while reducing the Nb content to offset the adverse effects of the reduced Nb content. Specifically, the above technical solution uses Mo (molybdenum). As a strong β-strengthening element, the addition of a small amount of Mo is beneficial to the high-temperature performance of the alloy. The critical β concentration of Mo is 5.3 at.%, while that of Nb is 22.5 at.%, with a ratio of approximately 1:4. Therefore, a small amount of Mo is added according to the ratio of critical β concentrations to compensate for the impact of the reduced Nb content. At the same time, this substitution significantly reduces the proportion of Nb and improves the casting performance of the alloy. Furthermore, using the above-mentioned element ratios, compared to the traditional Ti-22Al-25Nb alloy, the Ti2AlNb-based alloy system increases the proportion of Al, increasing the alloy strength while lowering the melting point; simultaneously, it reduces the proportion of Nb, increasing the alloy's oxidation resistance, lowering the melting point, and improving its casting performance. The introduction of a small amount of Mo can compensate for the decrease in high-temperature performance caused by the reduction in Nb, but a large amount of Mo will lead to a sharp decrease in the alloy's plasticity. Therefore, it is necessary to control the amount of Mo added. Adding trace amounts of Si can reduce the melting point, melt viscosity, and surface tension of the Ti2AlNb-based alloy, comprehensively improving the casting performance of the Ti2AlNb-based alloy while increasing its strength. The addition of a small amount of Zr further enhances the alloy's oxidation resistance at high temperatures. Through the above-mentioned technical solutions of the present invention, the technical problems of existing TiAlNb-based alloy composition systems being limited by alloy composition design, high Nb content leading to poor mold filling ability, solidification segregation, and coarse microstructure during casting, as well as the decrease in high-temperature oxidation resistance of the alloy are solved.

[0007] Furthermore, the Ti2AlNb-based alloy for casting of the present invention comprises, by atomic percentage: 25% aluminum, 22% niobium, 1% molybdenum, 1% zirconium, 0.3% silicon, with the balance being titanium and less than 0.2% impurities.

[0008] Secondly, the present invention provides a method for preparing a Ti2AlNb-based alloy for casting, comprising: The alloy raw materials are selected based on the atomic percentage set for the Ti2AlNb-based alloy; After the alloy raw materials are mixed evenly, they are subjected to multiple vacuum melting processes to obtain an ingot.

[0009] Furthermore, in the preparation method of the Ti2AlNb-based alloy for casting of the present invention, the alloy raw materials include aluminum briquettes, grade 0 sponge titanium, NbTi master alloy, AlNb master alloy, sponge zirconium, TiMo master alloy, AlV master alloy and TiSi master alloy.

[0010] Furthermore, in the method for preparing the Ti2AlNb-based alloy for casting of the present invention, the step of uniformly mixing the alloy raw materials and then performing multiple vacuum melting processes to obtain an ingot includes: After the alloy raw materials are mixed evenly, they are placed in bulk into a water-cooled copper crucible induction levitation melting furnace. Open the argon cylinder valve and purge the gas before evacuating. Each time, evacuate to 20 Pa and then fill with argon. Repeat this operation three times. After the gas washing is completed, the smelting furnace is evacuated until the gas pressure inside the furnace is lower than the specified value. Then stop; after the vacuum is exhausted, argon gas is introduced to 5000Pa to maintain an argon atmosphere inside the furnace; Ingots are obtained through multiple vacuum melting processes.

[0011] Furthermore, in the method for preparing the Ti2AlNb-based alloy for casting of the present invention, during the process of obtaining the ingot through multiple vacuum meltings, the power supply is increased from 30kW each time, increasing by 30kW and maintaining for 1-2 minutes until the alloy raw materials are completely melted and the melt is stable. Then, the power is maintained for 10 minutes. The power is gradually reduced until the melt solidifies to obtain the ingot. After the ingot cools inside the copper crucible, it is taken out, turned over, and melted again. This process is repeated 2-3 times to obtain the Ti2AlNb-based alloy ingot. Attached Figure Description

[0012] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1This is a schematic diagram showing the flowability test results of the Ti2AlNb-based alloy prepared in Example 1 of the present invention; Figure 2 This is a schematic diagram showing the flowability test results of the Ti2AlNb-based alloy prepared in Comparative Example 1 of this invention. Figure 3 This is a schematic diagram showing the flowability test results of the Ti2AlNb-based alloy prepared in Comparative Example 2 of this invention. Detailed Implementation

[0013] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0014] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0015] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "Several" means one or more, unless otherwise explicitly specified.

[0016] Ti2AlNb-based intermetallic compounds exhibit advantages such as high specific strength and high specific elastic modulus, strong high-temperature creep resistance and oxidation resistance in the 650-700℃ range, and their density is significantly lower than that of nickel-based superalloys, making them one of the most promising lightweight high-temperature structural materials for application in the 750-850℃ range. Existing research mainly focuses on wrought alloys, whose preparation process heavily relies on complex ingot metallurgy and thermomechanical processing, resulting in drawbacks such as long process flow, low material utilization, high manufacturing costs, and difficulty in forming complex thin-walled components. Existing compositional systems (such as Ti-22Al-25Nb) are limited by alloy composition design; high Nb content often leads to poor filling ability, solidification segregation, and coarse microstructure when the alloy is used in casting, a highly efficient near-net-shape forming process. Furthermore, high Nb content also reduces the alloy's high-temperature oxidation resistance.

[0017] To address the aforementioned technical problems, in a first aspect, the present invention provides a Ti2AlNb-based alloy for casting, comprising, by atomic percentage: Aluminum 23-26%, niobium 20-23%, molybdenum 0.5-1.5%, zirconium 0.5-1.5%, silicon 0.2-0.5%, with the balance being titanium and impurities less than 0.2%; In the Ti2AlNb-based alloy, the relationship between the atomic ratio of niobium and molybdenum is as follows: ; in, Indicates the atomic ratio of niobium. This indicates the atomic ratio of molybdenum.

[0018] In the above-described technical solution, to balance the mechanical and processing properties (mainly fluidity) of the Ti2AlNb-based alloy for casting, the Nb (niobium) content needs to be controlled to avoid being too high. Since a decrease in Nb content leads to a decline in the alloy's mechanical properties, a stronger β-strengthening element is added while reducing the Nb content to offset the adverse effects of reduced Nb content. Specifically, the above technical solution uses Mo (molybdenum). As a strong β-strengthening element, a small amount of Mo is beneficial to the high-temperature performance of the alloy. The critical β concentration of Mo is 5.3 at.%, while that of Nb is 22.5 at.%, with a ratio of approximately 1:4. Therefore, a small amount of Mo is added according to the ratio of critical β concentrations to compensate for the decrease in Nb content. Simultaneously, this substitution significantly reduces the proportion of Nb, improving the alloy's casting performance. Furthermore, using the above-mentioned element ratios, compared to the traditional Ti-22Al-25Nb alloy, the Ti2AlNb-based alloy system increases the proportion of Al, increasing the alloy strength while lowering the melting point; simultaneously, it reduces the proportion of Nb, increasing the alloy's oxidation resistance, lowering the melting point, and improving its casting performance. The introduction of a small amount of Mo can compensate for the decrease in high-temperature performance caused by the reduction in Nb, but a large amount of Mo will lead to a sharp decrease in the alloy's plasticity. Therefore, it is necessary to control the amount of Mo added. Adding trace amounts of Si can reduce the melting point, melt viscosity, and surface tension of the Ti2AlNb-based alloy, comprehensively improving the casting performance of the Ti2AlNb-based alloy while increasing its strength. The addition of a small amount of Zr further enhances the alloy's oxidation resistance at high temperatures. Through the above-mentioned technical solutions of the present invention, the technical problems of existing TiAlNb-based alloy composition systems being limited by alloy composition design, high Nb content leading to poor mold filling ability, solidification segregation, and coarse microstructure during casting, as well as the decrease in high-temperature oxidation resistance of the alloy are solved.

[0019] For example, in the Ti2AlNb-based alloy for casting of the present invention, aluminum (Al) may be 23%, 25% or 26% by atomic percentage, niobium (Nb) may be 20%, 22% or 23%, molybdenum (Mo) may be 0.5%, 1% or 1.5%, zirconium (Zr) may be 0.5%, 1% or 1.5%, silicon (Si) may be 0.2%, 0.4% or 0.5%, and the balance is titanium (Ti) and impurities less than 0.2%.

[0020] Secondly, the present invention provides a method for preparing a Ti2AlNb-based alloy for casting, comprising: The alloy raw materials are selected based on the atomic percentage set for the Ti2AlNb-based alloy; After the alloy raw materials are mixed evenly, they are subjected to multiple vacuum melting processes to obtain an ingot.

[0021] When using the above technical solution, the preparation method selects alloy raw materials according to the atomic percentage set for the Ti2AlNb-based alloy. When setting the atomic percentage of each element in the Ti2AlNb-based alloy, the Ti2AlNb-based alloy comprises, by atomic percentage: 23-26% aluminum, 20-23% niobium, 0.5-1.5% molybdenum, 0.5-1.5% zirconium, 0.2-0.5% silicon, with the balance being titanium and impurities less than 0.2%. Therefore, in order to balance the mechanical and processing properties (mainly fluidity) of the Ti2AlNb-based alloy, the Nb (niobium) content needs to be controlled to avoid being too high. Since a decrease in Nb content leads to a decrease in the alloy's mechanical properties, a stronger β-strengthening element than Nb is added while reducing the Nb content to offset the adverse effects of the reduced Nb content on the alloy. Specifically, the above technical solution uses Mo (molybdenum) element. As a strong β-strengthening element, the addition of a small amount of Mo is beneficial to the high-temperature performance of the alloy. The β-critical concentration of Mo is 5.3 at.%, while the β-critical concentration of Nb is 22.5 at.%, and their ratio is about 1:4. Therefore, a small amount of Mo is added according to the ratio of β-critical concentrations to compensate for the impact of the reduction of Nb element. At the same time, this substitution scheme will significantly reduce the proportion of Nb and improve the casting performance of the alloy. Furthermore, using the above-mentioned element ratios, compared to the traditional Ti-22Al-25Nb alloy, the Ti2AlNb-based alloy system increases the proportion of Al, increasing the alloy strength while lowering the melting point; simultaneously, it reduces the proportion of Nb, increasing the alloy's oxidation resistance, lowering the melting point, and improving its casting performance. The introduction of a small amount of Mo can compensate for the decrease in high-temperature performance caused by the reduction in Nb, but a large amount of Mo will lead to a sharp decrease in the alloy's plasticity. Therefore, it is necessary to control the amount of Mo added. Adding trace amounts of Si can reduce the melting point, melt viscosity, and surface tension of the Ti2AlNb-based alloy, comprehensively improving the casting performance of the Ti2AlNb-based alloy while increasing its strength; the addition of a small amount of Zr further enhances the alloy's oxidation resistance at high temperatures. For example, the above-mentioned alloy raw materials include aluminum briquettes, grade 0 sponge titanium, NbTi master alloy, AlNb master alloy, sponge zirconium, TiMo master alloy, AlV master alloy, and TiSi master alloy; in another example, the above-mentioned alloy raw materials may be one or more of aluminum briquettes, grade 0 sponge titanium, NbTi60 master alloy, AlNb70 master alloy, sponge zirconium, TiMo32 master alloy, AlV55 master alloy, and TiSi50 master alloy.

[0022] As one possible implementation, in the method for preparing the Ti2AlNb-based alloy for casting of the present invention, the step of uniformly mixing the alloy raw materials and then performing multiple vacuum melting processes to obtain an ingot includes: After the alloy raw materials are mixed evenly, they are placed in bulk into a water-cooled copper crucible induction levitation melting furnace. Open the argon cylinder valve and purge the gas before evacuating. Each time, evacuate to 20 Pa and then fill with argon. Repeat this operation three times. After the gas washing is completed, the smelting furnace is evacuated until the gas pressure inside the furnace is lower than the specified value. Then stop; after the vacuum is exhausted, argon gas is introduced to 5000Pa to maintain an argon atmosphere inside the furnace; Ingots are obtained through multiple vacuum melting processes.

[0023] By adopting the above technical solution, the oxygen content inside the melting furnace can be reduced as much as possible, preventing the alloy from reacting with oxygen during the melting process, which would lead to an increase in the impurity content inside the alloy and affect the alloy's performance.

[0024] As one possible implementation, in the method for preparing the Ti2AlNb-based alloy for casting of the present invention, during the process of obtaining the ingot through multiple vacuum melting processes, the power supply is increased from 30kW initially, increasing by 30kW each time and maintaining this increase for 1-2 minutes until the alloy raw materials are completely melted and the melt is stable. Then, the power is maintained for 10 minutes. The power is gradually reduced until the melt solidifies to obtain the ingot. After the ingot cools inside the copper crucible, it is removed, flipped, and melted again. This process is repeated 2-3 times to obtain the Ti2AlNb-based alloy ingot. Using the above technical solution ensures that the alloy composition is distributed as uniformly as possible, preventing unmelted blocks, macroscopic segregation, and other phenomena that could affect the performance of the finished product.

[0025] To better understand the present invention, the following specific embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0026] Unless otherwise specified, all raw materials used in the following examples are commercially available.

[0027] In the following examples, aluminum briquettes, grade 0 sponge titanium, NbTi60 master alloy, AlNb70 master alloy, sponge zirconium, TiMo32 master alloy, AlV55 master alloy, and TiSi50 master alloy are all commercially available raw materials.

[0028] Example 1 In a first aspect, this embodiment provides a Ti2AlNb-based alloy for casting, comprising, by atomic percentage: 24% aluminum, 21% niobium, 1% molybdenum, 1% zirconium, 0.5% silicon, and 52.5% titanium.

[0029] Secondly, this embodiment provides a method for preparing the above-mentioned Ti2AlNb-based alloy for casting, comprising: Step 1: Set the atomic percentages of the Ti2AlNb-based alloy to be prepared as follows: aluminum 24%, niobium 21%, molybdenum 1%, zirconium 1%, silicon 0.5%, and titanium 52.5%. Step 2: Based on the atomic percentage of the Ti2AlNb-based alloy to be prepared as set in Step 1, calculate the contents of grade 0 sponge titanium, NbTi60 master alloy, AlNb70 master alloy, sponge Zr, TiMo32 master alloy, AlV55 master alloy, and TiSi50 master alloy and prepare the materials accordingly. Since aluminum has a low melting point and is easily burned off during the smelting process, 0.2 wt% Al briquettes are added during the material preparation to compensate for the aluminum element loss caused by the alloy smelting process. Step 3: Mix the above raw materials evenly and put them into the water-cooled copper crucible induction levitation melting furnace. Turn on the switch of the high-purity argon gas cylinder and perform gas washing before drawing high vacuum. Each time, draw to 20Pa and then fill with high-purity argon gas. Repeat this operation three times. Step 4: After gas washing, evacuate the smelting furnace to a high vacuum until the furnace pressure is <5×10⁻⁶. -3 After Pa, stop, and after the vacuum is exhausted, high-purity argon gas is introduced to 5000Pa to maintain an argon atmosphere in the furnace. Step 5: Perform multiple vacuum melting processes to obtain an ingot. Specifically, during melting, the power supply starts from 30kW and increases by 30kW each time, maintaining the power for 2 minutes while observing the melt state. Once the raw material is completely melted and the melt is stable, maintain the power for 10 minutes. Then, gradually reduce the power until the melt solidifies to obtain an ingot. After the ingot has completely cooled inside the copper crucible, remove it, flip it over, and melt it again. Repeat this process twice to obtain a Ti2AlNb-based alloy ingot.

[0030] Furthermore, after the Ti2AlNb-based alloy ingot of this embodiment has been uniformly melted, please refer to... Figure 1 During the final melting process, after the alloy melt stabilized, it was cast into a fluidity test mold to obtain alloy fluidity data. Specifically, in the fluidity test, the filling length was determined using a spiral fluidity test model, and the length of the spiral line filled by the alloy melt was used as the fluidity evaluation index. The test results showed that, as... Figure 1 As shown, the melt flow length of the Ti2AlNb-based alloy prepared in this embodiment is 180 mm.

[0031] Furthermore, the antioxidant performance was evaluated, specifically by cutting an 8×8×4mm oxidation sample and conducting an oxidation experiment at 850℃. The weight gain after 50 and 100 hours of oxidation at 850℃ was measured. In this embodiment, the alloy showed a weight gain of 0.180 g / m³ after 50 hours of oxidation. 2 The weight gain after 100 hours of oxidation is 0.100 g / m³. 2 ·h.

[0032] Furthermore, the high-temperature mechanical properties were evaluated, specifically: the high-temperature tensile properties test was conducted at 650℃ with a tensile rate of 5 × 10⁻⁶. -4 s -1 The alloy in this embodiment has a tensile strength of 1090 MPa and an engineering strain of 12.1%.

[0033] Example 2 In a first aspect, this embodiment provides a Ti2AlNb-based alloy for casting, comprising, by atomic percentage: 23% aluminum, 21% niobium, 1% molybdenum, 0.5% zirconium, 0.3% silicon, and 54.2% titanium.

[0034] Secondly, this embodiment provides a method for preparing the above-mentioned Ti2AlNb-based alloy for casting, comprising: Step 1: Set the atomic percentages of the Ti2AlNb-based alloy to be prepared as follows: aluminum 23%, niobium 21%, molybdenum 1%, zirconium 0.5%, silicon 0.3%, and titanium 54.2%. Step 2: Based on the atomic percentage of the Ti2AlNb-based alloy to be prepared as set in Step 1, calculate the contents of grade 0 sponge titanium, NbTi60 master alloy, AlNb70 master alloy, sponge Zr, TiMo32 master alloy, AlV55 master alloy, and TiSi50 master alloy and prepare the materials accordingly. Since aluminum has a low melting point and is easily burned off during the smelting process, 0.2 wt% Al briquettes are added during the material preparation to compensate for the aluminum element loss caused by the alloy smelting process. Step 3: Mix the above raw materials evenly and put them into the water-cooled copper crucible induction levitation melting furnace. Turn on the switch of the high-purity argon gas cylinder and perform gas washing before drawing high vacuum. Each time, draw to 20Pa and then fill with high-purity argon gas. Repeat this operation three times. Step 4: After gas washing, evacuate the smelting furnace to a high vacuum until the furnace pressure is <5×10⁻⁶. -3 After Pa, stop, and after the vacuum is exhausted, high-purity argon gas is introduced to 5000Pa to maintain an argon atmosphere in the furnace. Step 5: Perform multiple vacuum melting processes to obtain an ingot. Specifically, during melting, the power supply starts from 30kW and increases by 30kW each time, maintaining the power for 1 minute while observing the melt state. Once the raw material is completely melted and the melt is stable, maintain the power for 10 minutes. Then, gradually reduce the power until the melt solidifies to obtain an ingot. After the ingot has completely cooled inside the copper crucible, remove it, flip it over, and melt it again. Repeat this process 3 times to obtain a Ti2AlNb-based alloy ingot.

[0035] Furthermore, after the Ti2AlNb-based alloy ingot of this embodiment has been melted uniformly, it is poured into a fluidity test mold after the alloy melt has stabilized during the last melting process to obtain alloy fluidity data. Specifically, during the fluidity test, the fluidity filling length is tested using a spiral fluidity test model, and the length of the spiral line filled by the alloy melt is used as the fluidity evaluation index. The melt flow length of the Ti2AlNb-based alloy prepared in this embodiment is 172 mm.

[0036] Further, the antioxidant properties were evaluated, specifically by cutting an 8×8×4mm oxidation sample and conducting an oxidation experiment at 850℃. The weight gain after 50 and 100 hours of oxidation at 850℃ was measured. In this embodiment, the alloy showed a weight gain of 0.230 g / m² after 50 hours of oxidation. 2 The weight gain after 100 hours of oxidation was 0.160 g / m³. 2 ·h.

[0037] Furthermore, the high-temperature mechanical properties were evaluated, specifically: the high-temperature tensile properties test was conducted at 650℃ with a tensile rate of 5 × 10⁻⁶. -4 s -1 The alloy in this embodiment has a tensile strength of 1068 MPa and an engineering strain of 10.3%.

[0038] Example 3 In a first aspect, this embodiment provides a Ti2AlNb-based alloy for casting, comprising, by atomic percentage: 26% aluminum, 21.8% niobium, 0.8% molybdenum, 1.5% zirconium, 0.3% silicon, and 49.6% titanium.

[0039] Secondly, this embodiment provides a method for preparing the above-mentioned Ti2AlNb-based alloy for casting, comprising: Step 1: Set the atomic percentages of the Ti2AlNb-based alloy to be prepared as follows: aluminum 26%, niobium 21.8%, molybdenum 0.8%, zirconium 1.5%, silicon 0.3%, and titanium 49.6%. Step 2: Based on the atomic percentage of the Ti2AlNb-based alloy to be prepared as set in Step 1, calculate the contents of grade 0 sponge titanium, NbTi60 master alloy, AlNb70 master alloy, sponge Zr, TiMo32 master alloy, AlV55 master alloy, and TiSi50 master alloy and prepare the materials accordingly. Since aluminum has a low melting point and is easily burned off during the smelting process, 0.2 wt% Al briquettes are added during the material preparation to compensate for the aluminum element loss caused by the alloy smelting process. Step 3: Mix the above raw materials evenly and put them into the water-cooled copper crucible induction levitation melting furnace. Turn on the switch of the high-purity argon gas cylinder and perform gas washing before drawing high vacuum. Each time, draw to 20Pa and then fill with high-purity argon gas. Repeat this operation three times. Step 4: After gas washing, evacuate the smelting furnace to a high vacuum until the furnace pressure is <5×10⁻⁶. -3 After Pa, stop, and after the vacuum is exhausted, high-purity argon gas is introduced to 5000Pa to maintain an argon atmosphere in the furnace. Step 5: Perform multiple vacuum melting processes to obtain an ingot. Specifically, during melting, the power supply starts from 30kW and increases by 30kW each time, maintaining the power for 1 minute while observing the melt state. Once the raw material is completely melted and the melt is stable, maintain the power for 10 minutes. Then, gradually reduce the power until the melt solidifies to obtain an ingot. After the ingot has completely cooled inside the copper crucible, remove it, flip it over, and melt it again. Repeat this process 3 times to obtain a Ti2AlNb-based alloy ingot.

[0040] Furthermore, after the Ti2AlNb-based alloy ingot of this embodiment has been melted uniformly, it is poured into a fluidity test mold after the alloy melt has stabilized during the last melting process to obtain alloy fluidity data. Specifically, during the fluidity test, the fluidity filling length is tested using a spiral fluidity test model, and the length of the spiral line filled by the alloy melt is used as the fluidity evaluation index. The melt flow length of the Ti2AlNb-based alloy prepared in this embodiment is 165 mm.

[0041] Furthermore, the antioxidant performance was evaluated, specifically by cutting an 8×8×4mm oxidation sample and conducting an oxidation experiment at 850℃. The weight gain after 50 and 100 hours of oxidation at 850℃ was measured. In this embodiment, the alloy showed a weight gain of 0.220 g / m³ after 50 hours of oxidation. 2 The weight gain after 100 hours of oxidation is 0.120 g / m³. 2 ·h.

[0042] Furthermore, the high-temperature mechanical properties were evaluated, specifically: the high-temperature tensile properties test was conducted at 650℃ with a tensile rate of 5 × 10⁻⁶. -4 s -1 The alloy in this embodiment has a tensile strength of 1072 MPa and an engineering strain of 8.7%.

[0043] Comparative Example 1 This comparative example provides a method for preparing a Ti-22Al-25Nb alloy, including: Step 1: Set the atomic percentage of the Ti-22Al-25Nb alloy to be prepared as follows: aluminum 22%, niobium 25%, and the remainder titanium; Step 2: Based on the atomic percentage of the Ti-22Al-25Nb alloy to be prepared as set in Step 1, calculate the contents of NbTi60 master alloy, AlNb70 master alloy and Al bead and prepare the materials accordingly. Since aluminum has a low melting point and is easily burned off during the smelting process, 0.2wt% of Al bead is added during the preparation to compensate for the aluminum loss caused by the alloy smelting process. Step 3: Mix the above raw materials evenly and put them into the water-cooled copper crucible induction levitation melting furnace. Turn on the switch of the high-purity argon gas cylinder and perform gas washing before drawing high vacuum. Each time, draw to 20Pa and then fill with high-purity argon gas. Repeat this operation three times. Step 4: After gas washing, evacuate the smelting furnace to a high vacuum until the furnace pressure is <5×10⁻⁶. -3 After Pa, stop, and after the vacuum is exhausted, high-purity argon gas is introduced to 5000Pa to maintain an argon atmosphere in the furnace. Step 5: Perform multiple vacuum melting processes to obtain an ingot. Specifically, during melting, the power supply starts from 30kW and increases by 30kW each time, maintaining the power for 1 minute while observing the melt state. Once the raw material is completely melted and the melt is stable, maintain the power for 10 minutes. Then, gradually reduce the power until the melt solidifies to obtain an ingot. After the ingot has completely cooled inside the copper crucible, remove it, flip it over, and melt it again. Repeat this process 3 times to obtain a Ti2AlNb-based alloy ingot.

[0044] Furthermore, after the Ti-22Al-25Nb alloy ingot of this comparative example was uniformly melted, it was cast into a fluidity test mold during the final melting process once the alloy melt had stabilized, thus obtaining alloy fluidity data. Specifically, during the fluidity test, a spiral fluidity test model was used for casting experiments, and the length of the spiral line filled by the alloy melt was used as the fluidity evaluation index. The test results are shown in [reference needed]. Figure 2 The Ti-22Al-25Nb alloy prepared in this comparative example had a melt flow length of 121 mm. The tensile strength of the Ti-22Al-25Nb alloy prepared in this comparative example was tested to be 963 MPa, with an engineering strain of 5.3%. The weight gain of the Ti-22Al-25Nb alloy in this comparative example after 50 hours of oxidation was 0.380 g / m³. 2 The weight gain after 100 hours of oxidation was 0.310 g / m³. 2 The antioxidant properties of this material are far inferior to those of the examples described above.

[0045] Comparative Example 2 The preparation method of the Ti2AlNb-based alloy provided in this comparative example is basically the same as that in Example 1. The difference is that in step 1 of this comparative example, the atomic percentage of the Ti2AlNb-based alloy is: Al 24%, Nb 25%, Zr 1%, Si 0.5%, Ti 49.5%, and Mo is not added; in step 2, TiMo master alloy is not used.

[0046] After the alloy ingot of this comparative example has been melted evenly, during the last melting process, once the alloy melt has stabilized, it is poured into the fluidity test mold to obtain alloy fluidity data.

[0047] Furthermore, a flowability test was conducted, specifically: the melt flow length of the alloy in this comparative example was 150 mm (e.g., Figure 3 As shown in the figure, it is 24% higher than the Ti-22Al-25Nb alloy of Comparative Example 1, but the improvement is smaller than that of Example 1.

[0048] Further, the antioxidant properties were evaluated, specifically by cutting an 8×8×4mm oxide sample and conducting an oxidation experiment at 850℃. The weight gain after 50 and 100 hours of oxidation at 850℃ was measured. The alloy in this comparative example showed a weight gain of 0.180 g / m² per unit area after 50 hours of oxidation. 2 The weight gain per unit area after 100 hours of oxidation is 0.130 g / m². 2 •h, slightly inferior to Example 1.

[0049] Furthermore, a high-temperature mechanical property evaluation was conducted, specifically: high-temperature tensile property testing was performed at 650℃ with a tensile rate of 5 × 10⁻⁶. -4 s -1 The alloy in this comparative example has a tensile strength of 1080 MPa and an engineering strain of 11.5%, which is basically equivalent to that of Example 1.

[0050] Comparative Example 3 The preparation method of the Ti2AlNb-based alloy provided in this comparative example is basically the same as that in Example 1. The difference is that the element content of the Ti2AlNb-based alloy in this comparative example has been adjusted. Specifically, the molybdenum content is 3% and the titanium content is 51.5%, while the rest are the same as in Example 1.

[0051] Testing revealed that the melt flow length of the Ti2AlNb-based alloy prepared in this comparative example was 96 mm, significantly shorter than that of the aforementioned examples. The weight gain of the Ti2AlNb-based alloy after 50 and 100 hours of oxidation at 850°C was also tested; the weight gain after 50 hours of oxidation was 0.260 g / m³. 2 The weight gain after 100 hours of oxidation was 0.210 g / m³. 2 •h; High-temperature tensile property tests were conducted at 650℃ with a tensile rate of 5×10⁻⁶.-4 s -1 The alloy in this comparative example has a tensile strength of 1140 MPa and an engineering strain of 4.7%.

[0052] Comparative Example 4 The preparation method of the Ti2AlNb-based alloy provided in this comparative example is basically the same as that in Example 1. The difference is that the element content of the Ti2AlNb-based alloy in this comparative example has been adjusted. Specifically, the molybdenum content is 0.5% and the titanium content is 53%, while the rest are the same as in Example 1.

[0053] The Ti2AlNb-based alloy prepared in this comparative example had a melt flow length of 170 mm. The weight gain of the Ti2AlNb-based alloy after 50 and 100 hours of oxidation at 850℃ was tested, with a weight gain of 0.200 g / m³ after 50 hours of oxidation. 2 The weight gain after 100 hours of oxidation was 0.140 g / m³. 2 •h; High-temperature tensile property tests were conducted at 650℃ with a tensile rate of 5×10⁻⁶. - 4 s -1 The alloy in this comparative example has a tensile strength of 1037 MPa and an engineering strain of 7.6%, which is lower than that of the above-mentioned embodiments.

[0054] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A Ti2AlNb-based alloy for casting, characterized in that, By atomic percentage, including: Aluminum 23-26%, niobium 20-23%, molybdenum 0.5-1.5%, zirconium 0.5-1.5%, silicon 0.2-0.5%, with the balance being titanium and impurities less than 0.2%; In the Ti2AlNb-based alloy, the relationship between the atomic ratio of niobium and molybdenum is as follows: ； in, Indicates the atomic ratio of niobium. This indicates the atomic ratio of molybdenum.

2. The Ti2AlNb-based alloy for casting according to claim 1, characterized in that, On an atomic percentage basis, it comprises: 25% aluminum, 22% niobium, 1% molybdenum, 1% zirconium, 0.3% silicon, with the balance being titanium and less than 0.2% impurities.

3. A method for preparing a Ti2AlNb-based alloy for casting, characterized in that, For preparing the Ti2AlNb-based alloy for casting as described in claim 1 or 2, comprising: The alloy raw materials are selected based on the atomic percentage set for the Ti2AlNb-based alloy; After the alloy raw materials are mixed evenly, they are subjected to multiple vacuum melting processes to obtain an ingot.

4. The method for preparing the Ti2AlNb-based alloy for casting according to claim 3, characterized in that, The alloy raw materials include aluminum briquettes, grade 0 sponge titanium, NbTi master alloy, AlNb master alloy, sponge zirconium, TiMo master alloy, AlV master alloy, and TiSi master alloy.

5. The method for preparing the Ti2AlNb-based alloy for casting according to claim 3, characterized in that, The process of uniformly mixing the alloy raw materials and then subjecting them to multiple vacuum melting processes to obtain an ingot includes: After the alloy raw materials are mixed evenly, they are placed in bulk into a water-cooled copper crucible induction levitation melting furnace. Open the argon cylinder valve and purge the gas before evacuating. Each time, evacuate to 20 Pa and then fill with argon. Repeat this operation three times. After the gas washing is completed, the smelting furnace is evacuated until the gas pressure inside the furnace is lower than the specified value. Then stop; after the vacuum is exhausted, argon gas is introduced to 5000Pa to maintain an argon atmosphere inside the furnace; Ingots are obtained through multiple vacuum melting processes.

6. The method for preparing the Ti2AlNb-based alloy for casting according to claim 5, characterized in that, In the process of obtaining the ingot through multiple vacuum meltings, the power supply is increased from 30kW each time, increasing by 30kW and maintaining for 1-2 minutes until the alloy raw material is completely melted and the melt is stable. Then, the power is maintained for 10 minutes. The power is gradually reduced until the melt solidifies to obtain the ingot. After the ingot cools inside the copper crucible, it is taken out, flipped, and melted again. This process is repeated 2-3 times to obtain the Ti2AlNb-based alloy ingot.

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