An ordered phase reinforced titanium alloy casting and a preparation method and application thereof

Abstract

This application discloses an ordered phase-strengthened titanium alloy casting, its preparation method, and its application. The preparation method involves vacuum melting titanium alloy raw materials to obtain a molten titanium alloy, which is then poured into a preheated casting mold. After pouring, a segmented slow cooling process is employed: the first stage involves furnace cooling to 800-1000℃; the second stage involves continued cooling at a rate of 1-3℃ / min, with isothermal holding at 550-650℃ for 0.5-2 hours; and the third stage involves furnace cooling to room temperature. The casting is then subjected to shaping, hot isostatic pressing, solution treatment, and aging treatment to obtain the titanium alloy casting. This application, through the synergistic effect of segmented slow cooling and hot isostatic pressing, reduces defect sensitivity while preserving the ordered phase strengthening mechanism, enabling the casting to achieve good strength and plasticity matching under both room temperature and high temperature conditions, thereby improving the yield.

Description

Technical Field

[0001] This application belongs to the field of titanium alloy processing technology, specifically relating to an ordered phase-strengthened titanium alloy casting, its preparation method, and its application. Background Technology

[0002] Aero engines are developing towards higher thrust-to-weight ratios, lighter weight, and longer lifespans. Complex thin-walled titanium alloy castings are key structural components. Ti-Al-Sn ternary ordered phase reinforced titanium alloys can synergistically improve the lightweight and high-temperature resistance of castings. However, ordered phase reinforced titanium alloys face severe casting challenges. Directly applying traditional investment casting processes can easily lead to casting quality defects, failing to meet the requirements for high-quality production.

[0003] Currently, key structural components for aero-engines are mostly manufactured using titanium alloy investment casting. To overcome the performance bottlenecks of traditional materials, novel Ti-Al-Sn ternary ordered phase reinforced titanium alloys, represented by Ti8AlSn and Ti4AlSn2, have been developed, exhibiting excellent high-temperature strength and creep resistance. While the introduction of ordered phases into these alloys improves high-temperature performance, it also introduces inherent casting defects: the intrinsic brittleness of the ordered phases significantly reduces the room-temperature and mid-temperature plasticity of the alloys, making them highly susceptible to hot cracking during solidification shrinkage; the ordered phases are highly sensitive to the cooling rate, and improper temperature control can easily lead to the formation of coarse grains, resulting in microstructural degradation; traditional titanium alloy investment casting processes are mainly designed for conventional titanium alloys and do not fully consider the high brittleness, narrow process window, and phase transformation sensitivity of these alloys. Directly applying these processes can lead to problems such as casting cracking and insufficient performance, making it difficult to achieve stable mass production of high-quality castings. Summary of the Invention

[0004] This application addresses the technical problems of hot cracking, microstructure deterioration, and brittle fracture during casting and solidification of Ti-Al-Sn ordered phase reinforced titanium alloys due to the high intrinsic brittleness and strong sensitivity to cooling rate of the ordered phase. It provides an ordered phase reinforced titanium alloy casting, its preparation method, and its application.

[0005] To achieve the above objectives, this application adopts the following technical solution: The first aspect of this application provides a method for preparing ordered phase-strengthened titanium alloy castings, comprising the following steps: S1. Vacuum melt the titanium alloy raw material to obtain a titanium alloy liquid, and then pour it into a preheated casting mold shell. S2. After casting, a segmented slow cooling process is adopted, specifically: The first stage involves cooling the furnace to 800~1000℃; The second stage continues cooling at a cooling rate of 1~3℃ / min, and isothermal residence is carried out in the range of 550~650℃ for 0.5~2h; The third stage involves cooling the furnace to room temperature. S3. The casting is subjected to shaping, hot isostatic pressing, solution treatment and aging treatment in sequence to obtain the titanium alloy casting.

[0006] Furthermore, the hot isostatic pressing treatment is carried out at a temperature of 30~60℃ below the β phase transition point, a pressure of 120~180MPa, and a holding time of 2~4h.

[0007] Furthermore, the solution treatment temperature is 10~40℃ below the β phase transition point, and the holding time is 1~4h; the aging temperature is 600℃~750℃, and the holding time is 10~20h.

[0008] Furthermore, the titanium alloy liquid is cast using a centrifugal casting method with a centrifugal speed of 250~300 r / min.

[0009] Furthermore, the casting shell is preheated to 500~600 ℃ and held at that temperature for 4~8 h.

[0010] Furthermore, the vacuum degree for vacuum melting of titanium alloy raw materials is ≤1×10⁻⁶. -2 Pa.

[0011] The second aspect of this application provides an ordered phase-strengthened titanium alloy casting, prepared according to the above-described method for preparing ordered phase-strengthened titanium alloy castings. By mass percentage, the composition of the titanium alloy includes: Al content of 4%~20%, Sn content of 4%~35%, W content ≤10%, Nb, Si, C, Zr, Mo, and B content of ≤4%, with the balance being Ti and unavoidable impurity elements.

[0012] The ordered phases dispersed in the matrix of the titanium alloy casting include one or both of the Ti8AlSn phase and Ti4AlSn2 phase.

[0013] Furthermore, by mass percentage, the titanium alloy contains: 5%~6% Al, 8.5%~15% Sn, ≤5% W, and ≤4% Nb, Si, C, Zr, Mo, and B, with the balance being Ti and unavoidable impurity elements.

[0014] Furthermore, at room temperature, the titanium alloy casting has a tensile strength ≥1180 MPa, a yield strength ≥1070 MPa, and an elongation ≥3.6%; at 650°C, the tensile strength ≥650 MPa, the yield strength ≥520 MPa, and the elongation ≥11.5%.

[0015] Furthermore, the internal porosity of the titanium alloy casting is ≤0.1%, with no macroscopic hot cracks or microcracks, and the microstructure is lamellar or lath-like, with an average lath width of 1~10 μm.

[0016] A third aspect of this application provides an application of the ordered phase-reinforced titanium alloy casting as described above, wherein the titanium alloy casting is used in high-temperature load-bearing structural components of an aero-engine.

[0017] Compared with the prior art, this application has the following beneficial effects: The method provided in this application involves allowing the casting to cool naturally in the furnace at a high temperature after casting, then actively slowing the cooling rate once it enters the intermediate temperature range, while simultaneously incorporating an isothermal residence period within the alloy's plasticity temperature range, and finally cooling it to room temperature in the furnace. This controlled cooling method effectively releases the thermal and phase transformation stresses accumulated during solidification, helping the casting smoothly pass through the brittle temperature range most prone to cracking and suppressing the formation of hot cracks. Simultaneously, the gentle cooling rate prevents abnormal grain growth, ensuring the uniformity of the microstructure. Subsequent hot isostatic pressing, solution treatment, and aging processes not only densify the casting microstructure and eliminate internal porosity but also regulate the structure of the ordered strengthening phases, thereby effectively enhancing the performance of the titanium alloy casting.

[0018] The ordered phase-reinforced titanium alloy castings prepared by the above method in this application, through optimization of the proportions of key elements such as aluminum, tin, tungsten, and silicon, form a uniformly distributed ordered reinforcing phase of Ti8AlSn or Ti4AlSn2 in the titanium matrix. The prepared titanium alloy castings exhibit a tensile strength of not less than 1180 MPa and a yield strength of not less than 1070 MPa at room temperature, while maintaining an elongation of over 3.6%. At a high temperature of 650 ℃, the tensile strength still reaches over 650 MPa, the yield strength exceeds 520 MPa, and the elongation is not less than 11.5%. Furthermore, the porosity inside the casting can be controlled below 0.1%, with no macroscopic hot cracks or microcracks, meeting the performance requirements of high-quality castings.

[0019] This application applies the aforementioned ordered phase-strengthened titanium alloy castings to high-temperature load-bearing structural components of aero-engines. The resulting castings, with their high strength, good plasticity, and excellent creep resistance maintained at high temperatures, effectively address the industry pain points of existing high-temperature load-bearing structural components, such as easy creep deformation and short service life. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1High-magnification image of the as-cast microstructure of the titanium alloy casting prepared in Example 1 of this application; Figure 2 High-magnification image of the as-cast microstructure of the titanium alloy casting prepared in Example 2 of this application; Figure 3 The image shows the macroscopic morphology of the solidified alloy that fractured when segmented slow cooling and isothermal holding were not used in Comparative Example 1. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] Novel titanium alloys reinforced by the Ti-Al-Sn ternary ordered phase, represented by Ti8AlSn and Ti4AlSn2, are important candidate materials for achieving synergistic improvement in casting lightweight and high-temperature performance due to their excellent high-temperature strength and creep resistance. However, while the introduction of ordered phases significantly improves high-temperature performance, it also brings severe casting technology challenges. First, ordered phases are intrinsically brittle, causing a sharp drop in plasticity in the alloy from room temperature to intermediate temperature, making it highly susceptible to hot cracking during solidification shrinkage. Second, ordered phases are highly sensitive to cooling rates; improper temperature control can lead to the formation of coarse columnar crystals or inhomogeneous precipitates, severely degrading mechanical properties. Furthermore, traditional titanium alloy investment casting processes are mainly designed for conventional titanium alloys and do not fully consider the high brittleness, narrow process window, and phase transformation sensitivity of ordered phase-reinforced titanium alloys. Direct application of these processes can easily lead to problems such as casting cracking, microstructural degradation, and substandard performance.

[0024] Based on this, the method for preparing ordered phase-strengthened titanium alloy castings provided in this application is applicable to titanium alloys with the following composition (by mass percentage): Al content 4%~20%, Sn content 4%~35%, W content ≤10%, Nb, Si, C, Zr, Mo, and B content all ≤4%, with the balance being Ti and unavoidable impurity elements, wherein one or two ordered strengthening phases, namely Ti8AlSn phase and Ti4AlSn2 phase, are dispersed in the matrix. The specific preparation steps are as follows: S1. Vacuum melt the titanium alloy raw material to obtain a titanium alloy liquid, and then pour it into a preheated casting mold shell. S2. After casting, a segmented slow cooling process is adopted: the first stage is to cool with the furnace to 800~1000℃; the second stage is to continue cooling at a cooling rate of 1~3℃ / min, and to hold at an isothermal temperature of 550~650℃ for 0.5~2h; the third stage is to cool with the furnace to room temperature. S3. The casting is subjected to shaping, hot isostatic pressing, solution treatment and aging treatment in sequence to obtain the titanium alloy casting.

[0025] This application employs a segmented slow cooling process with isothermal dwell steps in the high-brittleness temperature range of the alloy to fully release thermal stress and phase transformation stress during solidification, enabling the casting to safely pass through the brittle range and effectively suppressing the generation of hot cracks. The hot isostatic pressing process, slightly below the β phase transformation point, closes the internal micropores while avoiding grain coarsening. Combined with solution treatment and aging processes, the ordered phase structure is rationally controlled, achieving a good strength-plasticity match for titanium alloy castings under both room temperature and high temperature conditions.

[0026] In some specific embodiments of this application, the preparation of the casting shell in S1 specifically involves preparing a wax model and a gating system wax model based on a three-dimensional digital model of the casting using 3D printing or mold pressing. After assembling the wax models into a module, a surface layer, a transition layer, and a back layer slurry are applied sequentially. After drying, dewaxing, and high-temperature firing, a high-strength casting shell is obtained. The prepared casting shell is preheated to 500~600℃ and held at that temperature for 4~8 hours to ensure uniform temperature inside and outside the shell, avoiding thermal shock cracks caused by excessive temperature differences during pouring.

[0027] In some specific embodiments of this application, a vacuum induction levitation melting furnace or a vacuum consumable electrode solidification furnace is used to vacuum melt titanium alloy raw materials, and the vacuum degree is controlled at ≤1×10 during the melting process. -2 Pa prevents alloy oxidation and gas absorption. After the furnace charge is completely melted and the composition is uniform, it is held at a temperature for 3-8 minutes to remove gas and impurities. Then, the titanium alloy liquid is cast by centrifugal casting, with the centrifugal speed controlled at 250-300 r / min. Centrifugal force is used to improve the filling capacity of the alloy liquid and ensure the complete forming of complex thin-walled parts.

[0028] In some specific embodiments of this application, after casting in step S2, a segmented slow cooling process is adopted. By controlling the cooling path, stress is released and the generation of hot cracks is suppressed, as follows: First stage: After casting, the alloy is cooled to 800~1000℃ in the furnace. During this stage, the alloy is in the high temperature plastic zone, and the cooling rate is fast, which will not cause cracks and can shorten the production cycle. The second stage involves continuing cooling at a slow rate of 1~3℃ / min, followed by an isothermal hold of 0.5~2h in the 550~650℃ range. This temperature range is the high brittleness zone of the alloy, and the isothermal hold can fully release the thermal stress and phase transformation stress generated during solidification, allowing the casting to safely pass through the brittle zone and inhibiting the initiation and propagation of hot cracks. Third stage: After the isothermal holding period, the furnace is cooled to room temperature to avoid residual stress concentration caused by rapid cooling.

[0029] In some specific embodiments of this application, the cooled titanium alloy casting is first subjected to shaping treatment: the ceramic shell on the surface of the casting is removed by mechanical vibration or high-pressure air jetting, the gate, riser and process allowance are removed by electrical discharge wire cutting, and the deformed parts are cold straightened to ensure that the dimensional accuracy of the casting meets the design requirements.

[0030] The shaped titanium alloy castings are then subjected to hot isostatic pressing (HIP). Specifically, the castings are placed in a HIP furnace at a temperature controlled at 30–60°C below the β phase transformation point, with a pressure of 120–180 MPa and a holding time of 2–4 hours. This process promotes the closure of internal defects such as micropores and shrinkage porosity without causing grain coarsening, reducing the internal porosity to below 0.1% and improving the uniformity of the microstructure.

[0031] Finally, solution treatment and aging are performed. Specifically, the solution treatment temperature is controlled at 10~40℃ below the β phase transformation point, and the solution is held for 1~4 hours followed by air cooling to obtain a uniform supersaturated solid solution. Then, aging treatment is performed at 600℃~750℃, held for 10~20 hours, and then air cooled to promote the uniform dispersion and precipitation of the ordered phase, achieving a good balance between strength and plasticity. After treatment, the castings undergo surface sandblasting, polishing, and non-destructive testing to ensure that the surface and internal quality meet the requirements.

[0032] The titanium alloy castings prepared by the above method have the following properties at room temperature: tensile strength ≥1180 MPa; yield strength ≥1070 MPa; elongation ≥3.6%; tensile strength ≥650 MPa; yield strength ≥520 MPa; elongation ≥11.5% at 650℃; internal porosity ≤0.1%; no macroscopic hot cracks or microcracks; and microstructure is lamellar or lath-like, with an average lath width of 1~10 μm.

[0033] The titanium alloy castings obtained in this application are used in high-temperature load-bearing structural components of aero engines, including integral bladed disks, intermediate casings, and turbine rear casings, providing key material support for the development of high thrust-to-weight ratio aero engines.

[0034] The present application will be further described in detail below with reference to specific embodiments and accompanying drawings. The specific embodiments described below are only used to further illustrate the present application and are not intended to limit the scope of protection of the present application.

[0035] Unless otherwise defined, all terms used below shall be interpreted in accordance with their meaning as commonly understood by those skilled in the art. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this application may be obtained commercially or prepared by existing methods.

[0036] Example 1 The titanium alloy casting used in this embodiment has the following composition by mass percentage: Ti 6Al The metallographic determination of 12Sn-2.8W-0.5Si-0.05C showed that its β-phase transformation point was 1160℃.

[0037] S1. Based on the three-dimensional digital model of the casting, wax models and gating system wax models are prepared using 3D printing photosensitive resin. After assembling the modules, a surface layer, transition layer, and back layer are sequentially applied. After drying, dewaxing, and firing, a ceramic shell for the casting is obtained. The ceramic shell is preheated to 550℃ and held for 6 hours. A vacuum induction levitation melting furnace is used, with a vacuum degree ≤5×10⁻⁶. -3 Titanium alloy raw materials are smelted under Pa conditions. After the alloy liquid is completely melted, it is kept at a temperature of 5 minutes and then centrifuged and cast at a centrifugal speed of 300 r / min.

[0038] S2, after casting, adopts a segmented slow cooling process, specifically: First stage: Cooling in the furnace to 950℃; Second stage: appropriately increase the furnace temperature and reduce the cooling rate, continue cooling at a cooling rate of 2℃ / min, and hold at 580℃ for 2 hours isothermally to fully release thermal stress and phase transformation stress; Third stage: After the isothermal holding period, the furnace is cooled to room temperature.

[0039] S3. After cooling, the titanium alloy casting is subjected to a high-pressure air jet to remove the ceramic shell. The gate, riser, and process allowance are then removed using wire electrical discharge machining. Following this, hot isostatic pressing (HIP) is performed at a temperature controlled 45°C below the β-phase transformation point (i.e., 1115°C), a pressure of 160 MPa, and a holding time of 3 hours. Next, solution aging is carried out (solution temperature 20°C below the β-phase transformation point, holding for 2 hours followed by air cooling; aging temperature 620°C, time 12 hours). Finally, surface treatment and quality inspection are performed to obtain the titanium alloy casting.

[0040] The final microstructure of the titanium alloy casting is as follows: Figure 1As shown, the microstructure exhibits lamellar or lattice-like characteristics, with lath structures bundled along a certain orientation. These bundles of laths with different orientations interweave, and the average α-lamellae width is approximately 1–5 μm. Fine dot-like and short linear second-phase particles are dispersed throughout the matrix, mainly located at the lath interfaces and within the laths. No obvious continuous network of brittle phases, microcracks, or pore defects were observed. This microstructure indicates that after segmented slow cooling combined with hot isostatic pressing and solution aging treatment, the internal microstructure of the casting is relatively uniform, and the ordered strengthening phase is sufficiently dispersed and precipitated, which is beneficial for improving the strength-plasticity balance at room temperature and high temperature. Tensile properties were tested, and the results are shown in Table 1.

[0041] Table 1 Tensile properties of castings in Example 1

[0042] Example 2 The titanium alloy casting used in this embodiment has the following composition by mass percentage: Ti 5.75Al The metallographic determination of the β phase transition point of 8.5Sn-4.8W-0.4Si-0.06C is 1120℃. S1, preheat the ceramic mold shell to 600℃ and hold for 8 hours. Use a vacuum induction levitation melting furnace with a vacuum degree ≤5×10⁻⁶. -3 Titanium alloy raw materials are smelted under Pa conditions. After the alloy liquid is completely melted, it is kept at a temperature of 6 minutes and then centrifuged and cast at a centrifugal speed of 300 r / min.

[0043] S2, after casting, adopts a segmented slow cooling process, specifically: First stage: Cooling in the furnace to 850℃; Second stage: Appropriately increase the furnace temperature and reduce the cooling rate, continue cooling at a cooling rate of 2.5℃ / min, and hold at 620℃ for 1 hour isothermally to fully release thermal stress and phase transformation stress; Third stage: After the isothermal holding period, the furnace is cooled to room temperature.

[0044] S3. After cooling, the titanium alloy casting is subjected to a high-pressure air jet to remove the ceramic shell. The gate, riser, and process allowance are then removed using wire electrical discharge machining. Subsequently, hot isostatic pressing (HIP) is performed at a temperature controlled 50°C below the β-phase transformation point (i.e., 1070°C), a pressure of 140 MPa, and a holding time of 3 hours. Next, solution aging is carried out (solution temperature 40°C below the β-phase transformation point, time 1.5 hours; aging temperature 650°C, time 14 hours). Finally, surface treatment and quality inspection are performed to obtain the titanium alloy casting.

[0045] The final microstructure of the titanium alloy casting is as follows: Figure 2As shown, the microstructure exhibits distinct lamellar or lattice-like characteristics. The lamellar structures are bundled along a certain direction, with locally interwoven lamellar bundles of different orientations. The average α-lamellae width is approximately 5–9 μm. Fine dot-like and short linear secondary phases are visible in the matrix, diffusely precipitated along the lamellar interfaces and within the lamellar layers. No obvious pores, microcracks, or continuous network brittle phases were observed. This microstructure indicates that after segmented slow cooling, hot isostatic pressing, and solution aging treatment, the casting microstructure is relatively uniform, and the strengthening phase is relatively dispersed, which is beneficial for obtaining a good high-temperature strength and plasticity balance. Tensile properties were tested, and the results are shown in Table 2.

[0046] Table 2 Tensile properties of castings in Example 2

[0047] Example 3 The titanium alloy casting used in this embodiment has the following composition by mass percentage: Ti-6Al-12Sn-2.5W-0.5Si-0.05C, with the balance being Ti and unavoidable impurities. Its β phase transformation point was measured to be 1155℃ by metallographic method.

[0048] S1. Preheat the ceramic mold shell to 500℃ and hold for 4 hours. Vacuum induction melting furnace is used to melt the titanium alloy raw material, with the vacuum level controlled at ≤1×10⁻⁶ during the melting process. -2 Pa, after the alloy liquid is completely melted, keep it at the temperature for 5 minutes, and then cast it by centrifugal casting at a speed of 250 r / min.

[0049] S2, after casting, adopts a segmented slow cooling process, specifically: First stage: Cooling in the furnace to 1000℃; Second stage: The cooling rate is controlled at 1℃ / min by programmed temperature control, and the temperature is kept at 550℃ for 2 hours at an isothermal temperature. Third stage: After the isothermal holding period, the furnace is cooled to room temperature.

[0050] S3: After the casting cools, the ceramic shell is removed using mechanical vibration and high-pressure air jetting. The gate, riser, and process allowance are then removed by wire EDM. Following this, hot isostatic pressing (HIP) is performed at 1095°C (60°C below the β-phase transformation point) at a pressure of 120 MPa for 4 hours. After HIP, solution and aging treatments are carried out at 1115°C (40°C below the β-phase transformation point) for 2 hours followed by air cooling. Finally, aging treatment is performed at 600°C for 16 hours, followed by air cooling, resulting in an ordered phase-strengthened titanium alloy casting.

[0051] The tensile properties of the castings obtained in this embodiment are shown in Table 3. The microstructure is lamellar or lattice-like α+β structure. The lamellar structure is relatively uniform. Fine dot-like and short linear second phases are visible in the matrix. No obvious continuous network brittle phase, macroscopic hot cracks and microcracks are observed.

[0052] Table 3 Tensile properties of castings in Example 3

[0053] Example 4 The titanium alloy casting used in this embodiment has the following composition by mass percentage: Ti-5Al-15Sn-3.5W-0.5Si-0.05C-0.5Mo-0.02B, with the balance being Ti and unavoidable impurities. Its β phase transformation point was measured to be 1125℃ by metallographic method.

[0054] S1. Preheat the ceramic shell to 600℃ and hold for 8 hours. Vacuum melting of the titanium alloy raw material is performed using a vacuum consumable electrode solidification furnace or a vacuum induction levitation melting furnace, with the vacuum level controlled at ≤1×10⁻⁶ during the melting process. -2 Pa, after the alloy liquid is completely melted, it is kept at a temperature of 6 minutes, and then cast by centrifugal casting at a speed of 300 r / min.

[0055] S2, after casting, adopts a segmented slow cooling process, specifically: First stage: Cooling in the furnace to 800℃; Second stage: The cooling rate is controlled at 1℃ / min by programmed temperature control, and the temperature is kept at 650℃ for 2 hours at an isothermal temperature. Third stage: After the isothermal holding period, the furnace is cooled to room temperature.

[0056] S3: After the casting cools, the ceramic shell is removed by high-pressure air jetting, and the gate, riser, and process allowance are removed by wire EDM. Then, hot isostatic pressing (HIP) is performed at a temperature 30°C below the β phase transformation point (1095°C), a pressure of 180 MPa, and a holding time of 2 hours. Following HIP, solution and aging treatments are performed at a temperature 20°C below the β phase transformation point (1105°C), held for 1.5 hours, and then air-cooled. Finally, aging treatment is performed at 650°C, held for 14 hours, and then air-cooled, resulting in an ordered phase-strengthened titanium alloy casting.

[0057] The tensile properties of the castings obtained in this embodiment are shown in Table 4. The microstructure of the castings is a relatively uniform lamellar or lamellar α+β structure, with the lamellar bundles distributed in an interlaced orientation. Finely dispersed ordered reinforcing phases and a small amount of second phase are present in the matrix. No obvious coarse blocky brittle phases, shrinkage cavities, macroscopic hot cracks, or microcracks were observed. The internal porosity of the castings was measured to be 0.05%.

[0058] Table 4 Tensile properties of castings in Example 4

[0059] Comparative Example 1 The titanium alloy used in this comparative example has the same composition as that in Example 2. Except for the cooling process, all other steps are the same as in Example 2.

[0060] In this comparative example, after casting, a segmented slow cooling process is not used, nor is the alloy isothermally held in the 550~650℃ range. Instead, the solidified alloy is continuously cooled to room temperature with the furnace.

[0061] The results are as follows Figure 3 As shown, the resulting solidified alloy exhibited severe cracking and fragmentation, failing to yield a complete casting. Analysis suggests that without segmented slow cooling and isothermal holding, the thermal and structural stresses generated during solidification shrinkage and phase transformation were difficult to release in time, leading to crack initiation and propagation during cooling. Upon cooling to room temperature, due to the alloy's low plasticity, further fragmentation along existing cracks occurred during shell removal, extraction, or cleaning. Because of insufficient sample integrity, effective tensile specimens could not be fabricated, therefore tensile performance testing was not conducted. This comparative example demonstrates that segmented slow cooling and medium-temperature isothermal holding are key processes for ensuring the complete formation of ordered phase-strengthened titanium alloy castings and suppressing brittle cracking.

[0062] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the scope of the claims.

Claims

1. A method for preparing ordered phase-strengthened titanium alloy castings, characterized in that, Includes the following steps: S1. Vacuum melt the titanium alloy raw material to obtain a titanium alloy liquid, and then pour it into a preheated casting mold shell. S2. After casting, a segmented slow cooling process is adopted, specifically: The first stage involves cooling the furnace to 800~1000℃; The second stage continues cooling at a cooling rate of 1~3℃ / min, and isothermal residence is carried out in the range of 550~650℃ for 0.5~2h; The third stage involves cooling the furnace to room temperature. S3. The casting is subjected to shaping, hot isostatic pressing, solution treatment and aging treatment in sequence to obtain the titanium alloy casting.

2. The method for preparing ordered phase-strengthened titanium alloy castings according to claim 1, characterized in that, The hot isostatic pressing treatment is performed at a temperature of 30-60°C below the β phase transition point, at a pressure of 120-180 MPa, and for a holding time of 2-4 hours.

3. The method for preparing ordered phase-strengthened titanium alloy castings according to claim 1, characterized in that, The solution treatment temperature is 10~40℃ below the β phase transition point, and the holding time is 1~4h; the aging temperature is 600℃~750℃, and the holding time is 10~20h.

4. The method for preparing ordered phase-strengthened titanium alloy castings according to claim 1, characterized in that, The titanium alloy liquid is cast by centrifugation at a speed of 250~300 r / min.

5. The method for preparing ordered phase-strengthened titanium alloy castings according to claim 1, characterized in that, Preheat the casting mold to 500~600 ℃ and hold for 4~8 h.

6. The method for preparing ordered phase-strengthened titanium alloy castings according to claim 1, characterized in that, The vacuum degree for vacuum melting of titanium alloy raw materials is ≤1×10 -2 Pa.

7. A titanium alloy casting reinforced by an ordered phase, characterized in that, The titanium alloy casting with ordered phase strengthening is prepared according to any one of claims 1-6. The composition of the titanium alloy, by mass percentage, includes: Al content of 4%~20%, Sn content of 4%~35%, W content of ≤10%, Nb, Si, C, Zr, Mo and B content of ≤4%, and the balance being Ti and unavoidable impurity elements. The ordered phases dispersed in the matrix of the titanium alloy casting include one or both of the Ti8AlSn phase and Ti4AlSn2 phase.

8. The ordered phase-strengthened titanium alloy casting according to claim 7, characterized in that, The titanium alloy comprises, by mass percentage: 5% to 6% Al, 8.5% to 15% Sn, ≤5% W, and ≤4% Nb, Si, C, Zr, Mo, and B, with the balance being Ti and unavoidable impurity elements.

9. The ordered phase-strengthened titanium alloy casting according to claim 7, characterized in that, The titanium alloy casting has a tensile strength ≥1180 MPa and a yield strength ≥1070 MPa at room temperature. Elongation ≥3.6%; tensile strength ≥650 MPa at 650℃; yield strength ≥520 MPa; elongation ≥11.5%.

10. The ordered phase-strengthened titanium alloy casting according to claim 7, characterized in that, The titanium alloy casting has an internal porosity of ≤0.1%, no macroscopic hot cracks or microcracks, and a microstructure that is lamellar or lath-like with an average lath width of 1~10 μm.

11. An application of an ordered phase-strengthened titanium alloy casting according to any one of claims 7-10, characterized in that, The titanium alloy casting is used in high-temperature load-bearing structural components of aero engines.

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