A v-modified ti2alnab-based alloy and a preparation method thereof

Abstract

The application discloses a V-modified Ti2AlNb-based alloy and a preparation method thereof, and belongs to the technical field of Ti2AlNb-based alloy preparation. The alloy comprises 21-23% of Al, 22-24% of Nb, 1.5-2.5% of V, and the balance of Ti and inevitable impurities in percentage by atom; the structure of the alloy is composed of O phase and B2 phase ultrafine grains, the average grain size is less than 1 mu m, and a high-density dislocation is distributed in the matrix; the yield strength at room temperature is greater than 1300 MPa, the tensile strength is greater than 1500 MPa, and the fracture elongation is not less than 5%. The preparation method comprises the following steps: mixing elements, melting and obtaining an alloy ingot; homogenizing the ingot in a B2 single-phase region; and cold rolling the homogenized ingot to obtain a plate. In the application, the V element partially replaces the Nb element, the cold working performance of the alloy is improved, the alloy plate with ultra-high strength and good plasticity can be obtained through a simple cold rolling process, hot working and subsequent heat treatment are not needed, the production cycle is short, and the manufacturing cost is low.

Description

Technical Field

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

[0002] With the rapid development of the aerospace industry in recent years, higher requirements have been placed on the high-temperature performance and lightweighting of high-temperature materials operating in harsh high-temperature environments. Among commonly used metallic materials, titanium alloys are widely used in the aerospace field due to their lower density, higher specific strength, and superior creep resistance compared to nickel-based superalloys. However, with the design of new-generation engines raising turbine inlet temperatures to 600°C or even higher, traditional high-temperature titanium alloys experience a sharp deterioration in high-temperature oxidation resistance and a significant decrease in creep strength when operating at temperatures above 600°C for extended periods, highlighting performance bottlenecks. This limitation has spurred the exploration of new materials with higher specific strength and superior high-temperature load-bearing capacity. Adding a large amount of Al to titanium alloys can form TiAl-based intermetallic compounds (such as γ-Al). TiAl, α2 Ti3Al) significantly improves the alloy's oxidation resistance and high-temperature strength, but the poor ductility and toughness of TiAl-based alloys limit their development.

[0003] In 1988, Banerjee et al. discovered in their research on Ti3Al-based alloys that adding a large amount of Nb to Ti3Al alloys would form Ti2AlNb-based alloys with better plasticity, dominated by the O phase. Ti2AlNb-based alloys exhibit high specific strength and high specific elastic modulus, excellent high-temperature creep resistance and oxidation resistance between 650 and 850 °C, and their density is significantly lower than that of nickel-based superalloys. They are considered one of the most promising lightweight high-temperature structural materials for applications in the 650–850 °C range. However, their preparation process heavily relies on complex thermomechanical processing techniques (such as forging and high-temperature rolling) and has a narrow heat treatment process window, resulting in drawbacks such as cumbersome process flow and high manufacturing costs. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a V-modified Ti2AlNb-based alloy and its preparation method, which significantly improves the processing performance of Ti2AlNb-based alloy plates, enabling Ti2AlNb-based alloys to possess ultra-high strength and good plasticity without complex hot working and heat treatment.

[0005] This invention is achieved through the following technical solution: A V-modified Ti2AlNb-based alloy comprises, by atomic percentage, 21%–23% Al, 22%–24% Nb, 1.5%–2.5% V, with the balance being Ti and unavoidable impurities.

[0006] Preferably, the microstructure of the alloy consists of an O phase and a B2 phase, with the O and B2 phases exhibiting an ultrafine grain distribution and an average grain size of less than 1 μm.

[0007] Preferably, the O phase has an ordered orthogonal structure, the B2 phase has an ordered body-centered cubic structure, the O phase and the B2 phase are uniformly distributed in a two-phase manner, the volume fraction of the O phase is 40%~60%, and the volume fraction of the B2 phase is 40%~60%.

[0008] Preferably, the Ti2AlNb-based alloy has a room temperature yield strength of 1300~1400MPa, a tensile strength of 1500~1600MPa, and a fracture elongation of 5%~9%.

[0009] A method for preparing a V-modified Ti2AlNb-based alloy includes the following steps: Step 1: Mix Al, Nb, V and Ti by atomic percentage and then melt them to obtain an alloy ingot; Step 2: Homogenize the alloy ingot in the B2 single-phase region to obtain a uniform B2 phase structure. Step 3: Cold rolling is performed on the homogenized alloy ingot to break down and refine the B2 phase structure and form ultrafine grains of O and B2 phases to obtain Ti2AlNb-based alloy.

[0010] Preferably, the melting in step 1 is carried out under inert gas protection through multiple vacuum melting processes, with electromagnetic stirring activated during the melting process.

[0011] Preferably, the induction current of the vacuum melting is 460~500A. After the alloy is completely melted, it is held for 3~4 minutes and cooled to obtain an ingot. Then the ingot is flipped over and melted for at least 2 more times. After turning on the electromagnetic stirring, it is melted for at least 5 more times.

[0012] Preferably, the homogenization process in step 2 includes: heating the alloy ingot to 1100℃~1150℃ and holding it for 1~1.5 hours, and then cooling it after holding.

[0013] Preferably, the cooling method is water cooling. Preferably, the cold rolling in step 3 is carried out at room temperature, with a total deformation of 87% to 89% and a reduction of 2% to 3% of the total thickness per pass.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: This application discloses a V-modified Ti2AlNb-based alloy, whose composition is designed to partially replace Nb with V. By atomic percentage, it contains 21%–23% Al, 22%–24% Nb, 1.5%–2.5% V, with the balance being Ti. V and Nb belong to the same group (VB) in the periodic table and have similar atomic radii, which helps stabilize the B2 phase structure. Simultaneously, the addition of V reduces the stacking fault energy of the alloy, making dislocations easier to multiply and accumulate during cold rolling, thus providing the microstructure conditions for subsequent large plastic deformation. In terms of performance, the alloy sheet exhibits a room temperature yield strength greater than 1300 MPa, a tensile strength greater than 1500 MPa, and a fracture elongation of not less than 5%. Currently, the room temperature mechanical properties of most Ti2AlNb-based alloys are concentrated in the range of yield strength 900–1100 MPa and fracture elongation 3%–10%. The alloy in this application significantly exceeds this range in terms of strength, while maintaining plasticity within existing levels, breaking through the bottleneck of traditional Ti2AlNb-based alloys where strength and plasticity are difficult to balance. In terms of process, this alloy composition does not require hot rolling, forging or other hot working processes, nor does it require subsequent heat treatment. High-performance plates can be obtained through a simple cold rolling process, which greatly shortens the production cycle and significantly reduces manufacturing costs. It has significant application value in the field of high-temperature structural components for aerospace. Attached Figure Description

[0015] 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.

[0016] Figure 1 The BC and Ph plots of the EBSD after the high-temperature homogenization of the Ti2AlNb-based alloy of this invention are shown. Figure 2 These are room temperature tensile curves of different embodiments of the Ti2AlNb-based alloy of the present invention; Figure 3 This is a comparison diagram of the mechanical properties of the Ti2AlNb-based alloy and the Ti2AlNb alloy of this invention; Figure a shows a comparison between yield strength and tensile strength, and Figure b shows a comparison between elongation at break and tensile strength. Figure 4 This is a diagram showing the EBSD phase distribution of the Ti2AlNb-based alloy after cold rolling. Detailed Implementation

[0017] 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, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0019] Ti2AlNb-based alloys are complex multiphase alloy systems. Different elemental modifications significantly affect the transformation temperature, morphology, distribution, quantity of precipitated phases, and alloy properties. This application aims to reduce alloy density, simplify the preparation process, and improve the overall mechanical properties of the alloy. It involves alloy composition design and optimization to prepare a suitable Ti2AlNb-based alloy. The specific methods are as follows: A V-modified Ti2AlNb-based alloy, comprising, by atomic percentage, 21-23% Al, 22-24% Nb, 1.5-2.5% V, with the balance being Ti and other unavoidable impurities.

[0020] The microstructure of the V-modified Ti2AlNb-based alloy consists of O and B2 phases. Both phases exhibit an ultrafine grain distribution with an average grain size of less than 1 μm, and the matrix contains a high density of dislocations. The O phase has an ordered orthorhombic structure and is the main strengthening phase of the alloy; the B2 phase has an ordered body-centered cubic structure and is the matrix phase. The two phases are uniformly distributed in a biphasic manner, with the O phase accounting for 40%–60% of the volume and the B2 phase accounting for 40%–60% of the volume.

[0021] The room temperature yield strength of this V-modified Ti2AlNb-based alloy cold-rolled sheet is 1300~1400 MPa, the tensile strength is 1500~1600 MPa, and the elongation at break is 5%~9%. When the Al content in the alloy varies within the range of 21%~23%, the strength increases with increasing Al content, while the plasticity decreases. Compared with existing Ti2AlNb-based alloys, the alloy sheet of this application exhibits significantly improved yield strength and tensile strength while maintaining good plasticity, demonstrating excellent comprehensive mechanical properties.

[0022] This alloy partially replaces Nb with V. The addition of V lowers the stacking fault energy, making dislocations easier to multiply and accumulate during cold rolling, thus providing sufficient plastic deformation capacity for subsequent large deformation rolling. Simultaneously, the atomic radius of V is close to that of Nb, which stabilizes the B2 phase structure. Based on the V-modified composition, large plastic deformation of 87%–89% is achieved through repeated rolling with multiple passes of small deformation. This fully breaks down the original coarse B2 phase grains, forming ultrafine O and B2 phase grains with an average grain size of less than 1 μm, significantly increasing the grain boundary density. At the same time, a large number of dislocations introduced by cold rolling become entangled and accumulate within the grains, forming a high-density dislocation structure. The O and B2 phases are evenly distributed in a two-phase configuration, and the phase interface further hinders dislocation movement. The synergistic effect of grain refinement strengthening, dislocation strengthening, and phase boundary strengthening mechanisms allows the alloy to achieve ultra-high strength while maintaining good plasticity through coordinated deformation at the grain boundaries of the ultrafine grains, achieving a balance between strength and plasticity.

[0023] Correspondingly, this application also provides a method for preparing the V-modified Ti2AlNb-based alloy, including the following steps: Step 1: Mix Al, Nb, V and Ti by atomic percentage and then melt them to obtain an alloy ingot; Step 2: Homogenize the alloy ingot in the B2 single-phase region to form a uniform B2 phase structure. Step 3: The homogenized alloy ingot is cold rolled to break down and refine the B2 phase structure and form ultrafine grains of O and B2 phases, thus obtaining Ti2AlNb-based alloy sheet.

[0024] This preparation method strengthens the alloy through a combination of homogenization and cold rolling processes. Step 2 involves homogenizing the ingot in the B2 single-phase region to eliminate compositional segregation during melting and solidification, resulting in a uniform and singular B2 phase structure. This provides a uniform initial state for subsequent cold rolling, preventing inhomogeneity or cracking caused by local compositional differences. Step 3 involves directly cold rolling the homogenized ingot without hot rolling or forging. Large plastic deformation is achieved through multiple passes of small deformation rolling at room temperature, fully breaking down the original coarse B2 phase grains into ultrafine O and B2 phase grains with an average grain size of less than 1 μm, resulting in significant grain strengthening. Simultaneously, cold rolling introduces high-density dislocations, which accumulate and entangle within the grains, leading to dislocation strengthening. The O and B2 phases are evenly distributed in a two-phase configuration, and the phase interface effectively hinders dislocation slip, resulting in phase boundary strengthening. The synergistic effect of the three strengthening mechanisms (grain refinement, dislocation strengthening, and phase boundary strengthening) enables the alloy to achieve ultra-high strength without subsequent heat treatment, while the grain boundary coordination deformation capability of the ultra-fine grains retains good plasticity. This process eliminates the hot rolling, forging, and complex subsequent heat treatment steps required for the preparation of traditional Ti2AlNb-based alloys, simplifying the production process and reducing manufacturing costs.

[0025] In some embodiments, the process of mixing Al, Nb, V, and Ti by atomic percentage and then smelting to obtain an alloy ingot includes the following steps: After mixing the raw materials of each element according to atomic percentage, the mixture is subjected to multiple vacuum melting processes under inert gas protection. Electromagnetic stirring is activated during the melting process, and the alloy ingot is obtained by cooling after melting.

[0026] Specifically, high-purity titanium, high-purity aluminum, high-purity niobium, and high-purity vanadium are weighed according to atomic percentages and mixed evenly, and then placed in a non-consumable vacuum arc melting furnace; the arc melting furnace is evacuated, and gas is washed before evacuation. Each time, high-purity argon is introduced after evacuation to 5 Pa, and this operation is repeated three times. After the gas washing is completed, the electric arc melting furnace is evacuated until the gas pressure inside the furnace is less than 5 × 10⁻⁶. - Stop after reaching ³Pa, then fill with high-purity argon to maintain an argon atmosphere inside the furnace; then melt the alloy raw materials with an induction current of 460~500A. After the alloy is completely melted, continue to maintain the current for 3~4 minutes, and then cool to obtain an ingot; then flip the ingot over and continue melting. After melting at least twice, turn on the electromagnetic stirring and continue melting at least five times to ensure the uniformity of the composition. After melting, cool in a water-cooled copper crucible to obtain the alloy ingot.

[0027] In some embodiments, the alloy ingot is homogenized in the B2 single-phase region, including: The alloy ingot is heated to 1100℃~1150℃ and held for 1~1.5 hours. After holding, it is cooled to obtain a uniform B2 phase structure.

[0028] The cooling method is water cooling.

[0029] Homogenization is performed in the B2 single-phase region by heating the alloy ingot to 1100℃~1150℃ and holding it for 1~1.5 hours. During the melting and solidification process, due to the different melting points and diffusion rates of various elements, dendritic segregation and regions of non-uniform composition exist inside the ingot. These local compositional differences can lead to inconsistent deformation resistance during subsequent cold rolling, easily causing cracks. When holding in the B2 single-phase region, the alloy is in a single B2 phase region with a high atomic diffusion rate. Elements such as Al, Nb, and V diffuse fully at high temperatures, eliminating the compositional segregation formed during solidification and making the composition of each region more uniform. Rapid cooling after holding can retain the uniform single-phase B2 structure to room temperature, providing an initial billet with uniform composition and structure for subsequent cold rolling.

[0030] In some embodiments, cold rolling of the homogenized alloy ingot includes: The homogenized alloy ingot is rolled multiple times at room temperature, with a total deformation of 87% to 89% and a reduction of 2% to 3% of the total thickness in each pass.

[0031] The cold rolling process is carried out at room temperature, and large plastic deformation of 87% to 89% of the total deformation is achieved by repeatedly rolling with small deformations in multiple passes. The reduction amount in each pass accounts for only 2% to 3% of the total thickness. Repeated rolling disperses the risk of cracking from a single large deformation to multiple passes, allowing the alloy to withstand high total deformation without fracture at room temperature.

[0032] During cold rolling, the original coarse B2 phase grains are thoroughly broken down under repeated rolling pressure, forming ultrafine O and B2 phase grains. The average grain size is refined to below 1 μm, and the grain boundary density increases significantly, resulting in a remarkable grain refinement strengthening effect. Simultaneously, the large deformation introduces a high density of dislocations, which entangle and accumulate within the grains, forming dislocation strengthening. The O phase, as an ordered orthogonal strengthening phase, is uniformly distributed with the B2 matrix phase in a two-phase configuration. The phase interface effectively hinders dislocation slip, resulting in phase boundary strengthening. The synergistic effect of these three strengthening mechanisms allows the alloy to achieve ultra-high strength without subsequent heat treatment, while the grain boundary coordination deformation capability of the ultrafine grains retains good plasticity, achieving a balance between strength and plasticity.

[0033] Example 1 A method for preparing a V-modified Ti2AlNb-based alloy plate includes the following steps: Step 1: Place high-purity titanium, high-purity aluminum, high-purity niobium, and high-purity vanadium (99.9% purity) into a non-consumable vacuum arc melting furnace according to the atomic percentages mentioned above, with high-purity niobium placed on the top layer; each element, by atomic percentage, includes 21% Al, 23% Nb, 2% V, with the balance being Ti and other unavoidable impurities.

[0034] Step 2: After placing the alloy raw materials into the furnace, evacuate the electric arc melting furnace. Open the high-purity argon cylinder valve and purge the gas before evacuation. Each time, evacuate to 5 Pa and then purge with high-purity argon, repeating this operation three times. After purging, evacuate the electric arc melting furnace until the furnace pressure is less than 5 × 10⁻⁶ Pa. 3 After Pa, stop, and after the vacuum is exhausted, introduce high-purity argon gas to maintain an argon atmosphere inside the furnace.

[0035] Step 3: Melt the alloy raw materials using an induction current of 480A. After the alloy is completely melted, maintain the current for 3 minutes. After cooling, obtain an ingot. Then, flip the ingot and continue melting. After melting ≥2 times, turn on the electromagnetic stirring and continue melting ≥5 times using the above parameters to ensure the uniformity of the composition. After melting, cool the ingot in a water-cooled copper crucible to obtain the alloy ingot.

[0036] Step 4: Perform high-temperature homogenization treatment on the alloy ingot, hold at 1100℃ (B2 single-phase region) for 1 hour, and then water cool after the holding period is completed.

[0037] Homogeneous tissues such as Figure 1 As shown, heat preservation in the B2 single-phase region results in the alloy being composed of large-sized, uniform B2 phase grains.

[0038] Step 5: Cut the homogenized ingot into 16mm thick blocks using wire cutting, remove the surface oxide layer, and then roll them.

[0039] The initial rolling thickness was 16 mm. The reduction in pressure per pass was approximately 2% (0.3 mm) of the initial thickness. The final rolling thickness was approximately 1.5–2 mm, with a total deformation of approximately 87%–89%. Near the final stage, the reduction in pressure per pass could be appropriately reduced to prevent alloy cracking due to large single-pass deformation in the later stages.

[0040] Example 2 A method for preparing a V-modified Ti2AlNb-based alloy plate includes the following steps: Step 1: Place high-purity titanium, high-purity aluminum, high-purity niobium, and high-purity vanadium (99.9% purity) into a non-consumable vacuum arc melting furnace according to the atomic percentages mentioned above, with high-purity niobium placed on the top layer; each element, by atomic percentage, includes 22% Al, 23% Nb, 2% V, with the balance being Ti and other unavoidable impurities.

[0041] Step 2: After placing the alloy raw materials into the furnace, evacuate the electric arc melting furnace. Open the high-purity argon cylinder valve and purge the gas before evacuation. Each time, evacuate to 5 Pa and then purge with high-purity argon, repeating this operation three times. After purging, evacuate the electric arc melting furnace until the furnace pressure is less than 5 × 10⁻⁶ Pa. 3 After Pa, stop, and after the vacuum is exhausted, introduce high-purity argon gas to maintain an argon atmosphere inside the furnace.

[0042] Step 3: Melt the alloy raw materials using an induction current of 480A. After the alloy is completely melted, maintain the current for 3 minutes. After cooling, obtain an ingot. Then, flip the ingot and continue melting. After melting ≥2 times, turn on the electromagnetic stirring and continue melting ≥5 times using the above parameters to ensure the uniformity of the composition. After melting, cool the ingot in a water-cooled copper crucible to obtain the final ingot.

[0043] Step 4: Perform high-temperature homogenization treatment on the alloy ingot, hold at 1100℃ (B2 single-phase region) for 1 hour, and then water cool after the holding period is completed.

[0044] Homogeneous tissues such as Figure 1 As shown, heat preservation in the B2 single-phase region results in the alloy being composed of large-sized, uniform B2 phase grains.

[0045] Step 5: Cut the homogenized ingot into 16mm thick blocks using wire cutting, remove the surface oxide layer, and then roll them.

[0046] The initial rolling thickness was 16 mm. The reduction in pressure per pass was approximately 2% (0.3 mm) of the initial thickness. The final rolling thickness was approximately 1.5–2 mm, with a total deformation of approximately 87%–89%. Near the final stage, the reduction in pressure per pass could be appropriately reduced to prevent alloy cracking due to large single-pass deformation in the later stages.

[0047] Example 3: A method for preparing V-modified Ti2AlNb-based alloy cold-rolled sheet, comprising the following steps: Step 1: High-purity titanium, high-purity aluminum, high-purity niobium, and high-purity vanadium with a purity of 99.9% are placed in a non-consumable vacuum arc melting furnace according to the above atomic percentages, with high-purity niobium placed on the top layer; wherein each element, by atomic percentage, includes 23% Al, 23% Nb, 2% V, with the balance being Ti and other unavoidable impurities.

[0048] Step 2: After placing the alloy raw materials into the furnace, evacuate the electric arc melting furnace. Open the high-purity argon cylinder valve and purge the gas before evacuation. Each time, evacuate to 5 Pa and then purge with high-purity argon, repeating this operation three times. After purging, evacuate the electric arc melting furnace until the furnace pressure is less than 5 × 10⁻⁶ Pa. 3After Pa, stop, and after the vacuum is exhausted, introduce high-purity argon gas to maintain an argon atmosphere inside the furnace.

[0049] Step 3: Melt the alloy raw materials using an induction current of 480A. After the alloy is completely melted, maintain the current for 3 minutes. After cooling, obtain an ingot. Then, flip the ingot and continue melting. After melting ≥2 times, turn on the electromagnetic stirring and continue melting ≥5 times using the above parameters to ensure the uniformity of the composition. After melting, cool the ingot in a water-cooled copper crucible to obtain the final ingot.

[0050] Step 4: Perform high-temperature homogenization treatment on the alloy ingot, hold at 1100℃ (B2 single-phase region) for 1 hour, and then water cool after the holding period is completed.

[0051] Homogeneous tissues such as Figure 1 As shown, heat preservation in the B2 single-phase region results in the alloy being composed of large-sized, uniform B2 phase grains.

[0052] Step 5: Cut the homogenized ingot into 16mm thick blocks using wire cutting, remove the surface oxide layer, and then roll them.

[0053] The initial rolling thickness was 16 mm. The reduction in pressure per pass was approximately 2% (0.3 mm) of the initial thickness. The final rolling thickness was approximately 1.5–2 mm, with a total deformation of approximately 87%–89%. Near the final stage, the reduction in pressure per pass could be appropriately reduced to prevent alloy cracking due to large single-pass deformation in the later stages.

[0054] Example 4 A method for preparing V-modified Ti2AlNb-based alloy cold-rolled sheet includes the following steps: Step 1: Mix 21% Al, 23% Nb, 2% V and the balance Ti by atomic percentage, place the mixture in a non-consumable vacuum arc furnace, and perform multiple vacuum melting processes under argon atmosphere protection. Electromagnetic stirring is activated during the melting process. After melting is completed, the mixture is cooled to obtain an alloy ingot.

[0055] Step 2: Homogenize the alloy ingot by holding it at 1150℃ in the B2 single-phase region for 1.5 hours. After holding, cool it with water to obtain a uniform B2 phase structure in the alloy ingot.

[0056] Step 3: Cold roll the homogenized alloy ingot with an initial rolling thickness of 16 mm. Perform multiple rolling passes at room temperature, with each pass reducing the thickness by 3% of the initial thickness. The total deformation is 87%~89%. Roll to a thickness of 1.5~2 mm to obtain Ti2AlNb-based alloy sheet.

[0057] Example 5 A method for preparing V-modified Ti2AlNb-based alloy cold-rolled sheet includes the following steps: Step 1: Mix 22% Al, 22% Nb, 1.5% V and the balance Ti by atomic percentage, place the mixture in a non-consumable vacuum arc melting furnace, and perform multiple vacuum meltings under argon atmosphere protection. Electromagnetic stirring is turned on during the melting process. After melting is completed, cool to obtain alloy ingots.

[0058] Step 2: Homogenize the alloy ingot by holding it at 1100℃ in the B2 single-phase region for 1 hour. After holding, cool it with water to obtain a uniform B2 phase structure in the alloy ingot.

[0059] Step 3: The homogenized alloy ingot is cold rolled with an initial rolling thickness of 16 mm. Multiple rolling passes are performed at room temperature, with each pass reducing the thickness by 2% of the initial thickness. The total deformation is 87%~89%, and the thickness is rolled to 1.5~2 mm to obtain Ti2AlNb-based alloy sheet.

[0060] Example 6 A method for preparing V-modified Ti2AlNb-based alloy cold-rolled sheet includes the following steps: Step 1: Mix 23% Al, 24% Nb, 2.5% V and the balance Ti by atomic percentage, place the mixture in a non-consumable vacuum arc furnace, and perform multiple vacuum melting processes under argon atmosphere protection. Electromagnetic stirring is activated during the melting process. After melting is completed, the mixture is cooled to obtain an alloy ingot.

[0061] Step 2: Homogenize the alloy ingot by holding it at 1150℃ in the B2 single-phase region for 1.5 hours. After holding, cool it with water to obtain a uniform B2 phase structure in the alloy ingot.

[0062] Step 3: Cold roll the homogenized alloy ingot with an initial rolling thickness of 16 mm. Perform multiple rolling passes at room temperature, with each pass reducing the thickness by 3% of the initial thickness. The total deformation is 87%~89%. Roll to a thickness of 1.5~2 mm to obtain Ti2AlNb-based alloy sheet.

[0063] See Figure 2 The figures show the tensile curves of the Ti2AlNb-based alloys prepared in Examples 1-3. It can be seen that... As the Al content increases, the alloy strength tends to increase, while the plasticity tends to decrease.

[0064] Figure 3 The figures show a comparison of the mechanical properties of Examples 1, 2, and 3 with other Ti2AlNb alloys. It can be seen that, compared with existing Ti2AlNb-based alloys, the alloy plates of this application have significantly improved yield strength and tensile strength while maintaining good plasticity, exhibiting excellent comprehensive mechanical properties.

[0065] Figure 4 The diagram shows the EBSD phase distribution after cold rolling in Example 2, where the O phase content is 50.8% and the B2 phase content is 49.1%, and the O and B2 phases are evenly distributed.

[0066] The preparation method of this application involves repeatedly rolling a homogenized alloy at room temperature using multiple passes with low deformation to prepare a Ti2AlNb alloy sheet with excellent mechanical properties. The sheet with an Al content of 21% (Example 1) exhibits a yield strength of 1391 MPa, a tensile strength of 1537 MPa, and an elongation at break of 8.1%; the sheet with an Al content of 22% (Example 2) exhibits a yield strength of 1365 MPa, a tensile strength of 1564 MPa, and an elongation at break of 7.5%; and the sheet with an Al content of 23% (Example 3) exhibits a yield strength of 1393 MPa, a tensile strength of 1601 MPa, and an elongation at break of 5.3%. Cold rolling introduces a large number of dislocations and makes the O and B2 phase grains very fine, significantly improving the alloy's strength. Furthermore, the alloy's strength increases with increasing Al content, while its plasticity decreases. Compared with existing methods for preparing Ti2AlNb-based alloys, this application can achieve high strength and good plasticity without complex hot working and heat treatment, providing a new approach for the preparation of Ti2AlNb-based alloys.

[0067] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A V-modified Ti2AlNb-based alloy, characterized in that, On an atomic percentage basis, it comprises 21%–23% Al, 22%–24% Nb, 1.5%–2.5% V, with the balance being Ti and unavoidable impurities.

2. The V-modified Ti2AlNb-based alloy according to claim 1, characterized in that, The microstructure of the alloy consists of O phase and B2 phase, which are distributed in an ultrafine grain pattern with an average grain size of less than 1 μm.

3. The V-modified Ti2AlNb-based alloy according to claim 2, characterized in that, The O phase has an ordered orthogonal structure, and the B2 phase has an ordered body-centered cubic structure. The O phase and the B2 phase are evenly distributed in a two-phase manner, with the O phase having a volume fraction of 40% to 60% and the B2 phase having a volume fraction of 40% to 60%.

4. The V-modified Ti₂AlNb-based alloy according to claim 1, characterized in that, The Ti2AlNb-based alloy has a room temperature yield strength of 1300~1400MPa, a tensile strength of 1500~1600MPa, and a fracture elongation of 5%~9%.

5. A method for preparing the V-modified Ti2AlNb-based alloy according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Mix Al, Nb, V and Ti by atomic percentage and then melt them to obtain an alloy ingot; Step 2: Homogenize the alloy ingot in the B2 single-phase region to obtain a uniform B2 phase structure. Step 3: Cold rolling is performed on the homogenized alloy ingot to break down and refine the B2 phase structure and form ultrafine grains of O and B2 phases to obtain Ti2AlNb-based alloy.

6. The method for preparing V-modified Ti2AlNb-based alloy according to claim 5, characterized in that, The melting process described in step 1 involves multiple vacuum melting processes under inert gas protection, with electromagnetic stirring activated during the melting process.

7. The method for preparing V-modified Ti2AlNb-based alloy according to claim 6, characterized in that, The induction current for vacuum melting is 460~500A. After the alloy is completely melted, it is held for 3~4 minutes and then cooled to obtain an ingot. The ingot is then flipped over and melted at least twice more. After turning on the electromagnetic stirring, it is melted at least five more times.

8. The method for preparing V-modified Ti2AlNb-based alloy according to claim 5, characterized in that, The homogenization process described in step 2 includes: heating the alloy ingot to 1100℃~1150℃ and holding it for 1~1.5 hours, followed by cooling.

9. The method for preparing V-modified Ti2AlNb-based alloy according to claim 5, characterized in that, The cooling method is water cooling.

10. The method for preparing V-modified Ti2AlNb-based alloy according to claim 5, characterized in that, The cold rolling described in step 3 is carried out at room temperature, with a total deformation of 87% to 89% and a reduction of 2% to 3% of the total thickness per pass.

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