High damage tolerance high oxygen titanium alloy and preparation method thereof

Abstract

The application belongs to the technical field of titanium alloy material preparation, and more particularly relates to a high-damage-tolerance high-oxygen titanium alloy and a preparation method thereof. The high-damage-tolerance high-oxygen titanium alloy contains, in terms of mass percentage of elements, Al 5.0-7.0%, V 2.5-5.0%, O 0.2-0.6%, C≤0.02%, N≤0.01%, H≤0.01%, Si≤0.01% and Fe≤0.08%, and the balance is Ti and inevitable impurity elements, wherein the total amount of the impurity elements is less than 0.05%. The blank is subjected to induction suspension smelting to obtain a finished product ingot. The finished product ingot is subjected to vacuum homogenization annealing treatment, and then subjected to multi-temperature multi-direction forging, low-temperature rolling and heat treatment to obtain the high-damage-tolerance high-oxygen titanium alloy, realizing the synergistic optimization of high strength and good plasticity under the condition of high oxygen content, having good damage tolerance performance, and proving that the process and component control scheme have significant practical value.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy material preparation technology, and more specifically relates to a high-damage-tolerant high-oxygen titanium alloy and its preparation method. Background Technology

[0002] Titanium alloys, with their high specific strength and corrosion resistance, have become key structural materials in high-value-added fields such as aerospace. For next-generation applications, material research continues to pursue even higher strength, but also faces challenges such as balancing strength and toughness, and controlling interstitial / impurity elements.

[0003] Given that structural components are mostly used for long-term service, damage tolerance is crucial: it's essential to avoid embrittlement caused by increased strength, and also to prevent early fracture induced by impurities. Oxygen is often considered a key factor leading to "oxygen embrittlement." On the other hand, oxygen is also a highly efficient and economical solid solution strengthening element for enhancing the strength of titanium alloys. How to achieve synergistic optimization of strength and damage tolerance by fully utilizing the strengthening effect of oxygen while suppressing the decrease in toughness and crack propagation resistance through synergistic design of composition, process, and microstructure (such as optimizing hot working paths and heat treatment regimes) has become a core issue and important direction in current research and engineering applications of high-strength titanium alloys.

[0004] There are roughly two approaches to treating dissolved oxygen (O) in titanium alloys: one is to remove oxygen as much as possible, controlling the oxygen content to ≤0.15 wt.% during the ingot or powder preparation stage and avoiding secondary oxygen absorption in subsequent processing; the other is to actively utilize the solid solution strengthening effect of oxygen, increasing the oxygen content to ≥0.2 wt.% or even higher, and obtaining a microstructure that balances strength, toughness and damage tolerance through alloying, thermomechanical processing and heat treatment.

[0005] However, both approaches have unavoidable engineering drawbacks. For the "oxygen removal" approach, achieving extremely low oxygen content requires high vacuum, multiple remelting processes, high-purity raw materials, and strict end-to-end contamination control. This not only significantly increases raw material and preparation costs but also greatly affects batch-to-batch stability due to furnace lining, atmosphere, and equipment condition. At scale, localized oxygen reabsorption and performance dispersion are prone to occur. Low-temperature deformation processes adopted to avoid subsequent oxygen absorption increase flow stress, exacerbate mold wear, and slow down cycle time, leading to high processing difficulty, long cycles, and high overall costs. Previously, the industry has repeatedly encountered such bottlenecks when expanding size and batch size, making it difficult to establish a mass production window that is both low-cost and highly consistent.

[0006] Conversely, the "oxygen-utilizing" approach also faces key obstacles in terms of mechanism and process. While oxygen, as an interstitial element, can significantly strengthen the α phase through solid solution, it reduces ductility and fracture toughness, easily inducing microcrack nucleation and early cracking at microstructural discontinuities such as inclusions / phase boundaries, and exacerbating deformation inhomogeneity and dynamic strain aging risks during two-phase processing. To counteract embrittlement, existing methods often involve adding β-stabilizing elements or employing multi-element microalloying, but this increases density and cost, alters phase transformation kinetics, and narrows the controllable process window. On the other hand, to obtain acceptable lamellar scale, phase volume fraction, and connectivity, multiple thermomechanical couplings and cyclic heat treatments are often required, resulting in long processes, strong parameter coupling, and sensitivity to equipment and geometry, leading to insufficient repeatability and engineering robustness. More importantly, existing "high-oxygen" practices often rely on high-cost methods such as powder metallurgy or additive manufacturing for precise oxygen control and microstructure regulation, but these approaches still have uncertainties in terms of size limitations, anisotropy, and internal defect control, making it difficult to meet the general engineering needs of large-size structural components. The common root cause of the above problems lies in the fact that, on the one hand, it is difficult to simultaneously and stably control the "total amount and spatial distribution of oxygen" to avoid embrittlement caused by local enrichment; on the other hand, the synergistic window of microstructure and properties is narrow, and the balance of strength, toughness and crack propagation resistance places demands on the synergistic precision and repeatability of thermomechanical-heat treatment that exceed conventional manufacturing capabilities. These are also practical difficulties that have been repeatedly encountered in previous attempts. Summary of the Invention

[0007] The purpose of this invention is to provide a high-damage-tolerant high-oxygen titanium alloy and its preparation method, so as to solve the problems existing in the prior art.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] One of the technical solutions of this invention: provides a high-damage-tolerance high-oxygen titanium alloy, comprising, by elemental mass percentage:

[0010] Al 5.0-7.0%, V 2.5-5.0%, O 0.2-0.6%, C≤0.02%, N≤0.01%, H≤0.01%, Si≤0.01% and Fe≤0.08%, with the balance being Ti and unavoidable impurity elements, wherein the total amount of impurity elements is less than 0.05%.

[0011] The second technical solution of this invention provides a method for preparing a high-damage-tolerant high-oxygen titanium alloy, comprising the following steps:

[0012] Prepare raw materials according to the elemental ratio of the high-damage-tolerance high-oxygen titanium alloy mentioned above.

[0013] The raw material is pressed into a mold using a layered pressing method to prepare a billet. After the billet is dried, it is subjected to induction suspension melting to obtain a finished ingot.

[0014] The finished ingot is subjected to vacuum homogenization annealing, followed by multi-temperature multi-directional forging, low-temperature rolling and heat treatment to obtain the high-damage-tolerance high-oxygen titanium alloy.

[0015] Furthermore, the raw materials include sponge titanium, aluminum briquettes, vanadium source, and rutile titanium dioxide.

[0016] Optionally, the vanadium source may include an aluminum-vanadium alloy and / or vanadium blocks.

[0017] Furthermore, the lower part of the blank is made of lightweight material, and the upper part is made of heavy material.

[0018] Furthermore, the drying temperature is 80-120℃, and the time is 40-80 minutes.

[0019] Furthermore, the induction levitation melting step includes:

[0020] The dried billet is placed in a vacuum induction levitation melting furnace, and the vacuum level of the melting furnace is maintained at 2-4 × 10⁻⁴. -2 The furnace is protected by argon and initially preheated at 50KW, then adjusted to 170KW. After the billet melts, the power is reduced back to 150KW. The melt is suspended and stirred for no less than 90s (to improve the uniformity of composition). This melting process is repeated at least three times. After melting, the furnace is cast and the riser is removed to obtain the finished ingot.

[0021] Optionally, the preheating time is 1 hour.

[0022] Furthermore, the vacuum homogenization annealing treatment is carried out at a temperature of 1000-1050℃ for 2-3.5 hours.

[0023] Furthermore, the multi-temperature multi-directional forging step includes:

[0024] The temperature of the β phase region of the ingot was determined by differential thermal analysis (DTG).

[0025] In the first forging, the finished ingot, which has undergone vacuum homogenization annealing, is heated to 30-50°C above the β phase temperature and held for 60-90 minutes. After heating, the ingot is forged, with a total deformation of 20-40%.

[0026] In the second forging, when the ingot cools to 20-50°C below the β phase temperature, the ingot is forged again, with a total deformation of 20-40%. Then it is naturally air-cooled to room temperature, completing the multi-temperature multi-directional forging.

[0027] The heat treatment regime for titanium alloys needs to be designed based on their phase transformation points. The addition of oxygen will cause changes in the phase region distribution of titanium alloys. Therefore, the phase transformation temperature of the ingot needs to be determined by methods such as DTG.

[0028] If the specified deformation amount is not achieved after multi-temperature multi-directional forging, then the multi-temperature multi-directional forging process is repeated.

[0029] Furthermore, the low-temperature rolling step includes:

[0030] After removing the oxide scale from the ingot that has undergone multi-temperature and multi-directional forging, it is heated to 450-550℃ and held for 60 minutes. Then, it is rolled in multiple passes, with a deformation of 10-15% per pass. After each pass, it is returned to the furnace and held for 10-50 minutes. The total deformation is not less than 70%.

[0031] Furthermore, the heat treatment step includes:

[0032] The low-temperature rolled plate is solution treated at 920-950℃ for 1-2 hours, water-quenched, and then aged at 450-500℃ for 4-6 hours.

[0033] The present invention discloses the following technical effects:

[0034] This invention incorporates vacuum homogenization annealing treatment into oxygen-containing titanium alloy ingots before thermomechanical processing. This process homogenizes the distribution of oxygen elements, which tend to accumulate at grain boundaries, thereby resolving the uneven distribution of micro-stress during subsequent hot processing and achieving uniformity in the hot-processed microstructure.

[0035] In the thermomechanical forging stage (multi-temperature multi-directional forging), this invention employs a combination of β single-phase region processing (above / below the β transformation temperature) and α / β two-phase region forging. The good machinability of the β phase region is utilized to achieve the expected deformation amount, while the α precipitation tendency of the two-phase region is utilized to more fully break down the microstructure, achieve equiaxed structure, and facilitate grain breakage and microstructure transformation during the subsequent gradual decrease of the forging billet temperature. This ensures that the grains are fully refined and broken down in the subsequent low-temperature rolling stage.

[0036] This invention employs an α single-phase rolling process in the thermomechanical rolling stage to increase the temperature of the forging billet, thereby improving machinability and promoting equiaxing during the rolling process. The solution aging heat treatment of this invention can ensure sufficient control over the thermomechanical structure, ultimately obtaining a fine biphase structure with a grain size of about 10 μm, thus achieving the predetermined performance target. Attached Figure Description

[0037] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0038] Figure 1 This is a schematic diagram of the preparation process of the high-damage-tolerance high-oxygen titanium alloy of the present invention.

[0039] Figure 2 The microstructure of the high-damage-tolerant high-oxygen titanium alloy prepared in Example 1.

[0040] Figure 3 The elemental distribution diagram is shown for the finished ingot of Example 1 after vacuum homogenization annealing.

[0041] Figure 4 This is a microstructure photograph after multi-temperature multi-directional forging in Example 1.

[0042] Figure 5 Mechanical properties of high-damage-tolerant oxygen-titanium alloys prepared in Examples 1-3. Detailed Implementation

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0045] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0046] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0047] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0048] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.

[0049] Unless otherwise specified, room temperature and normal temperature in the specific embodiments of this invention refer to 20-30℃.

[0050] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0051] In some specific embodiments, the present invention provides a hot working manufacturing method for high-damage-tolerant high-oxygen titanium alloys, the steps of which include:

[0052] S1. According to the elemental mass percentage: Al 5.0-7.0%, V 2.5-5.0%, O 0.2-0.6%, C≤0.02%, N≤0.01%, H≤0.01%, Si≤0.01%, and Fe≤0.08%, with the balance being Ti and unavoidable impurity elements, wherein the total amount of impurity elements is less than 0.05%, prepare sponge titanium, aluminum briquettes, vanadium blocks (or aluminum-vanadium alloys), and rutile titanium dioxide as raw materials;

[0053] S2. The blank is formed by pressing it in a mold using a layered pressing method. The lower part of the material is lightweight and the upper part is heavy material. The blank diameter is smaller than the crucible diameter. Then, it is pretreated in a drying oven at 80-120℃ for 40-80 minutes to completely remove residual moisture from the raw materials.

[0054] S3. Place the dried billet from step S2 into the water-cooled copper crucible of a vacuum induction levitation melting furnace, maintaining the furnace vacuum at 2-4 × 10⁻⁴. -2 The furnace was protected with argon charge and initially preheated at 50KW for 60 minutes. Then, the power was increased to 170KW and maintained until the billet was completely melted. After melting, the power was reduced to 150KW and the melt was suspended and stirred for at least 90 seconds to improve the uniformity of composition. To ensure the quality of the alloy, the melting process was repeated three times. After the final melting was completed, the molten metal was poured into a steel mold for casting to form a preliminary ingot. The riser was removed to obtain the finished ingot.

[0055] S4. Vacuum homogenization annealing treatment is performed on the finished ingots at a temperature of 1000-1050℃ for 2-3.5 hours.

[0056] S5. The β phase temperature of the ingot is determined by differential thermal analysis (DTG). Then, the first forging is carried out. The finished ingot, which has been vacuum homogenized and annealed, is heated to 30-50°C above the β phase temperature and held for 60-90 minutes. After heating, the ingot is forged with a total deformation of 20-40%. Then, the second forging is carried out. When the ingot cools to 20-50°C below the β phase temperature, the ingot is forged again with a total deformation of 20-40%. Then, it is naturally air-cooled to room temperature to complete the multi-temperature multi-directional forging.

[0057] S6. After removing the oxide scale from the billet that has undergone multi-temperature and multi-directional forging, heat it to 450-550℃ and hold it for 60 minutes. Then, perform multi-pass rolling with a deformation of 10-15% per pass. After each pass, return it to the furnace and hold it for 10-50 minutes. The total deformation should not be less than 70%. After natural air cooling to room temperature, the rolled plate is obtained.

[0058] S7. The rolled plate is solution treated at 920-950℃ for 1-2 hours, water-quenched, and then aged at 450-500℃ for 4-6 hours. It is then naturally air-cooled to room temperature to obtain a high-oxygen titanium alloy with high damage tolerance.

[0059] Oxygen is an α-phase stabilizing element for titanium alloys, therefore different thermomechanical processing and heat treatment processes are required to achieve the desired processing results.

[0060] This invention offers an engineering pathway for "direct high-oxygen strengthening" of the widely used TC4 (Ti-6Al-4V) system. It achieves the target oxygen content and compositional uniformity under industrially feasible vacuum melting conditions. By combining multi-stage thermomechanical processing and multi-stage heat treatment, it allows for staged control of the morphology and connectivity of the α / β phases in the two-phase region. This results in the refinement and discontinuity of α-lamellae, the construction of appropriate β-phase channels, and the promotion of uniform oxygen distribution and the ordering of dislocations / substructures within the grains through staged heat treatment. This reduces local stress concentration and dynamic strain aging sensitivity from the source. Compared to existing technologies, this invention aims to maintain or improve damage tolerance under high oxygen conditions, reduce reliance on extremely low-oxygen raw materials and high alloying, avoid high-cost routes such as powder metallurgy / additive manufacturing, and achieve synergistic optimization of strength, toughness, and crack propagation resistance through reproducible conventional melting and thermomechanical-heat treatment processes. It also provides more robust engineering feasibility in terms of cost, scalability, and batch consistency. The above improvements directly address the prominent shortcomings of existing technologies, such as high oxygen control costs, narrow tissue regulation windows, and insufficient robustness for large-scale scaling. These are also the core problems and long-term challenges that the technical solutions of this invention application aim to solve.

[0061] This invention employs a three-stage thermomechanical processing method in the phase region to achieve the desired microstructure and performance targets of high-oxygen titanium alloys. It solves the problems that the addition of oxygen leads to a decrease in the hot working performance of titanium alloys, easy occurrence of crack defects, and insufficient and uneven microstructure fragmentation.

[0062] Currently, GB and industry standards require TC4 titanium alloys to have an oxygen content of less than 0.15 wt%. This invention adopts a higher oxygen content standard of 0.2 wt% to 0.6 wt%, providing a high-damage-tolerant high-oxygen titanium alloy, which offers a candidate material for the application of high-strength titanium alloy structural components.

[0063] Figure 1 This is a schematic diagram of the preparation process of the high-damage-tolerance high-oxygen titanium alloy of the present invention.

[0064] Example 1

[0065] The titanium alloy used in this embodiment is based on TC4 alloy, with oxygen element introduced as a strengthening method.

[0066] The preparation steps for high-damage-tolerant high-oxygen titanium alloys include:

[0067] S1. The target chemical composition of the alloy is: Al 6.0 wt%, V 4.0 wt%, O 0.4 wt%, Fe 0.05 wt%, C, N, H and Si each not exceeding 0.01 wt%, with the balance being Ti and unavoidable impurity elements (total impurity content less than 0.05 wt%).

[0068] Based on the target chemical composition of the alloy, high-purity sponge titanium, aluminum briquettes, vanadium blocks, and rutile high-purity titanium dioxide were selected as raw materials. After precise weighing and strict control of the proportion of each element, the mass ratio of sponge titanium: aluminum briquettes: vanadium blocks: titanium dioxide = 89:6:4:1.

[0069] S2. The material is loaded into the mold using a layered pressing method to ensure that the density gradient gradually increases from bottom to top, which is beneficial to the uniformity of composition during the melting process. From bottom to top, the material consists of aluminum granules, vanadium blocks, rutile high-purity titanium dioxide, and high-purity sponge titanium. After pressing, the billet is placed in an oven at 80°C for 60 minutes to dry in order to remove the adsorbed moisture in the raw material and obtain the dried billet.

[0070] S3. Place the dried billet from step S2 into the water-cooled copper crucible of the vacuum induction levitation melting furnace, maintaining the furnace vacuum at 3×10⁻⁶. -2 Pa, and high-purity argon gas is introduced to achieve inert protection. Initially, it is preheated at 50KW for 60 min, then adjusted to 170KW and continued until the billet is completely melted. After the melt is formed, the power is adjusted to 150KW and stirring is maintained for 90 s to enhance the compositional uniformity of the alloy liquid. At the same time, in order to ensure the quality of the alloy and improve the uniformity of the microstructure and the consistency of the composition, the melting process is repeated three times. After the final melting is completed, the molten liquid is poured into a preheated steel mold to cool and solidify, forming a preliminary ingot. The riser is removed to obtain the finished ingot.

[0071] S4. Vacuum homogenization annealing treatment is performed on the finished ingot at a temperature of 1050℃ for 2 hours to eliminate macro segregation and promote uniform microstructure.

[0072] S5. The temperature of the β phase region of the ingot was determined to be about 980℃ by differential thermal analysis (DTG). The forging process was then divided into two stages: high temperature and medium temperature.

[0073] In the first forging, the finished ingot, which has undergone vacuum homogenization annealing, is heated to 1020℃ and held for 80 minutes. Then it is quickly transferred to an air hammer for forging, and the total deformation is controlled within 30%.

[0074] The second forging is carried out after the ingot cools naturally to 950°C. The total deformation is controlled at 30%, and then it is naturally air-cooled to room temperature to complete the multi-temperature and multi-directional forging.

[0075] S6. After removing the oxide scale from the ingot that has undergone multi-temperature and multi-directional forging, heat it to 550℃, hold it for 60 minutes, and then quickly transfer it to the rolling mill. The deformation amount of each pass is controlled between 10-15%. After each pass of rolling is completed, return it to the furnace for 20 minutes of heat preservation. The total deformation amount is controlled to be above 70%. After natural air cooling to room temperature, the rolled plate is obtained.

[0076] S7. The rolled plate is solution treated at 950℃ for 2 hours, then water-quenched to ensure the formation of fine β residual phase and α phase dispersion. Subsequently, it is aged at 500℃ for 4 hours to promote α phase precipitation strengthening. Then it is naturally air-cooled to room temperature to obtain a high-oxygen titanium alloy with high damage tolerance, denoted as TC4-0.4wt.%O.

[0077] Example 2

[0078] The titanium alloy used in this embodiment is based on TC4 alloy, with oxygen element introduced as a strengthening method.

[0079] The preparation steps for high-damage-tolerant high-oxygen titanium alloys include:

[0080] S1. The target chemical composition of the alloy is: Al 6.0 wt%, V 4.0 wt%, O 0.2 wt%, Fe 0.05 wt%, C, N, H and Si each not exceeding 0.01 wt%, with the balance being Ti and unavoidable impurity elements (total impurity content less than 0.05 wt%).

[0081] Based on the target chemical composition of the alloy, high-purity sponge titanium, aluminum briquettes, Al55V aluminum vanadium alloy, and rutile high-purity titanium dioxide were selected as raw materials. After precise weighing and strict control of the proportion of each element, the mass ratio of sponge titanium: aluminum briquettes: aluminum vanadium alloy: titanium dioxide = 89.5:2.7:7.3:0.5.

[0082] S2. The material is loaded into the mold using a layered pressing method to ensure that the density gradient gradually increases from bottom to top, which is beneficial to the uniformity of composition during the melting process. From bottom to top, the material consists of aluminum granules, Al55V aluminum vanadium alloy, rutile high-purity titanium dioxide, and high-purity sponge titanium. After pressing, the billet is placed in an oven at 80°C for 60 minutes to dry in order to remove the adsorbed moisture in the raw material and obtain the dried billet.

[0083] S3. Place the dried billet from step S2 into the water-cooled copper crucible of the vacuum induction levitation melting furnace, maintaining the furnace vacuum at 3×10⁻⁶. -2 Pa, and high-purity argon gas is introduced to achieve inert protection. Initially, it is preheated at 50KW for 60 min, then adjusted to 170KW and continued until the billet is completely melted. After the melt is formed, the power is adjusted to 150KW and stirring is maintained for 90 s to enhance the compositional uniformity of the alloy liquid. At the same time, in order to ensure the quality of the alloy and improve the uniformity of the microstructure and the consistency of the composition, the melting process is repeated three times. After the final melting is completed, the molten liquid is poured into a preheated steel mold to cool and solidify, forming a preliminary ingot. The riser is removed to obtain the finished ingot.

[0084] S4. Vacuum homogenization annealing treatment is performed on the finished ingot at a temperature of 1000℃ for 3.5 hours to eliminate macrosegregation and promote uniform microstructure.

[0085] S5. The temperature of the β phase region of the ingot was determined to be about 980℃ by differential thermal analysis (DTG). The forging process was then divided into two stages: high temperature and medium temperature.

[0086] In the first forging, the finished ingot, which has undergone vacuum homogenization annealing, is heated to 1000℃ and held for 60 minutes. Then it is quickly transferred to an air hammer for forging, and the total deformation is controlled within 30%.

[0087] The second forging is carried out after the ingot cools naturally to 950°C. The total deformation is controlled at 30%, and then it is naturally air-cooled to room temperature to complete the multi-temperature and multi-directional forging.

[0088] S6. After removing the oxide scale from the billet that has undergone multi-temperature and multi-directional forging, heat it to 500℃, hold it for 60 minutes, and then quickly transfer it to the rolling mill. The deformation amount of each pass is controlled between 10-15%. After each pass of rolling is completed, return it to the furnace for 20 minutes of heat preservation. The total deformation amount is controlled to be above 70%. After natural air cooling to room temperature, the rolled plate is obtained.

[0089] S7. The rolled plate is solution treated at 950℃ for 1 hour, then water-quenched to ensure the formation of fine β residual phase and α phase dispersion. Subsequently, it is aged at 450℃ for 6 hours to promote α phase precipitation strengthening. Then it is naturally air-cooled to room temperature to obtain a high-damage-tolerance high-oxygen titanium alloy, denoted as TC4-0.2wt.%O.

[0090] Example 3

[0091] The titanium alloy used in this embodiment is based on TC4 alloy, with oxygen element introduced as a strengthening method.

[0092] The preparation steps for high-damage-tolerant high-oxygen titanium alloys include:

[0093] S1. The target chemical composition of the alloy is: Al 6.0 wt%, V 4.0 wt%, O 0.6 wt%, Fe 0.05 wt%, C, N, H and Si each not exceeding 0.01 wt%, with the balance being Ti and unavoidable impurity elements (total impurity content less than 0.05 wt%).

[0094] Based on the target chemical composition of the alloy, high-purity sponge titanium, aluminum briquettes, Al65V aluminum vanadium alloy, and rutile high-purity titanium dioxide were selected as raw materials. After precise weighing and strict control of the proportion of each element, the mass ratio of sponge titanium: aluminum briquettes: vanadium blocks: titanium dioxide = 59: 3: 4: 1.

[0095] S2. The material is loaded into the mold using a layered pressing method to ensure that the density gradient gradually increases from bottom to top, which is beneficial to the uniformity of composition during the melting process. From bottom to top, the material consists of aluminum briquettes, AlV65 aluminum vanadium master alloy, rutile titanium dioxide, and sponge titanium. After pressing, the billet is placed in an oven at 80°C for 60 minutes to dry in order to remove the adsorbed moisture in the raw material and obtain the dried billet.

[0096] S3. Place the dried billet from step S2 into the water-cooled copper crucible of the vacuum induction levitation melting furnace, maintaining the furnace vacuum at 3×10⁻⁶. -2 Pa, and high-purity argon gas is introduced to achieve inert protection. Initially, it is preheated at 50KW for 60 min, then adjusted to 170KW and continued until the billet is completely melted. After the melt is formed, the power is adjusted to 150KW and stirring is maintained for 90 s to enhance the compositional uniformity of the alloy liquid. At the same time, in order to ensure the quality of the alloy and improve the uniformity of the microstructure and the consistency of the composition, the melting process is repeated three times. After the final melting is completed, the molten liquid is poured into a preheated steel mold to cool and solidify, forming a preliminary ingot. The riser is removed to obtain the finished ingot.

[0097] S4. Vacuum homogenization annealing treatment is performed on the finished ingot at a temperature of 1050℃ for 3.5 hours to eliminate macrosegregation and promote uniform microstructure.

[0098] S5. The temperature of the β phase region of the ingot was determined to be about 985℃ by differential thermal analysis (DTG). The forging process was then divided into two stages: high temperature and medium temperature.

[0099] In the first forging, the finished ingot, which has undergone vacuum homogenization annealing, is heated to 1050℃ and held for 90 minutes. Then it is quickly transferred to an air hammer for forging, and the total deformation is controlled within 30%.

[0100] The second forging is carried out after the ingot cools naturally to 935°C. The total deformation is controlled at 30%, and then it is naturally air-cooled to room temperature to complete the multi-temperature and multi-directional forging.

[0101] S6. After removing the oxide scale from the ingot that has undergone multi-temperature and multi-directional forging, heat it to 550℃, hold it for 60 minutes, and then quickly transfer it to the rolling mill. The deformation amount of each pass is controlled between 10-15%. After each pass of rolling is completed, return it to the furnace for 20 minutes of heat preservation. The total deformation amount is controlled to be above 70%. After natural air cooling to room temperature, the rolled plate is obtained.

[0102] S7. The rolled plate is solution treated at 950℃ for 2 hours, then water-quenched to ensure the formation of fine β residual phase and α phase dispersion. Subsequently, it is aged at 500℃ for 6 hours to promote α phase precipitation strengthening. Then it is naturally air-cooled to room temperature to obtain a high-damage-tolerance high-oxygen titanium alloy, denoted as TC4-0.6wt.%O.

[0103] Test case

[0104] Figure 2 The microstructure of the high-damage-tolerant high-oxygen titanium alloy prepared in Example 1 is shown in the figure. As can be seen from the figure, its microstructure is a typical TC4 dual-state structure, consisting of primary α phase and β transformation structure, both of which are fine grains with a size of 10 μm.

[0105] Figure 3 The figure shows the elemental distribution of the finished ingot from Example 1 after vacuum homogenization annealing. As can be seen from the figure, vacuum homogenization annealing homogenizes the distribution of oxygen, which tends to aggregate at grain boundaries.

[0106] Figure 4 This is a microstructure photograph after multi-temperature multi-directional forging in Example 1.

[0107] Mechanical property testing:

[0108] To evaluate the mechanical properties of high-oxygen-content TC4 alloy, standardized tensile specimens were prepared according to the relevant GB / T 23604-2024 standard. Tensile testing was conducted at room temperature, with the strain rate strictly controlled at 10 °C. -3 The axial strain of the material is acquired in real time using a high-precision extensometer at a rate of / s to ensure the accuracy and repeatability of the strain measurement. The obtained stress-strain curves are used to analyze the material's yield behavior, tensile strength, and plasticity.

[0109] Figure 5 The mechanical properties of the high-damage-tolerance high-oxygen titanium alloys prepared in Examples 1-3 are shown in the figure. As can be seen from the figure, the maximum tensile strength of this high-oxygen titanium alloy is 1410 MPa, and the elongation at break is 7.94%. This alloy material achieves a synergistic optimization of high strength and good plasticity under high oxygen content (0.4 wt%) conditions, exhibiting excellent damage tolerance performance, proving that the described process and composition control scheme have significant practical value.

[0110] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0111] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-damage-tolerance high-oxygen titanium alloy, characterized in that, By elemental mass percentage, it includes: Al 5.0 - 7.0%, V 2.5 - 5.0%, O 0.2 - 0.6%, C ≤ 0.02%, N ≤ 0.01%, H ≤ 0.01%, Si ≤ 0.01% and Fe ≤ 0.08%, and the balance is Ti and inevitable impurity elements, where the total amount of impurity elements is less than 0.05%; The preparation steps of the high - damage - tolerance high - oxygen titanium alloy include: Prepare raw materials according to the element ratio of the high - damage - tolerance high - oxygen titanium alloy described above; Press the raw materials into a blank in a mold by the layer pressing method, and after drying the blank, perform induction suspension melting to obtain a finished ingot; Perform vacuum homogenization annealing treatment on the finished ingot, and then perform multi - temperature multi - direction forging, cold rolling and heat treatment to obtain the high - damage - tolerance high - oxygen titanium alloy; The temperature of the vacuum homogenization annealing treatment is 1000 - 1050 °C, and the time is 2 - 3.5 h; The steps of the cold rolling include: After removing the oxide scale from the ingot blank after multi - temperature multi - direction forging, heat it to 450 - 550 °C, hold for 60 min, and then perform multi - pass rolling. The deformation amount per pass is 10 - 15%, and after each pass of rolling, heat it back in the furnace and hold for 10 - 50 min. The total deformation amount is not less than 70%; The steps of the multi - temperature multi - direction forging include: Determine the β - phase region temperature of the ingot by differential thermal analysis; The first forging: Heat the finished ingot after vacuum homogenization annealing to 30 - 50 °C above the β - phase region temperature, hold for 60 - 90 min, and perform forging on the ingot block after heating. The total deformation amount is 20 - 40%; The second forging: When the ingot cools to 20 - 50 °C below the β - phase region temperature, continue to forge the ingot. The total deformation amount is 20 - 40%, and then air - cool it naturally to room temperature to complete the multi - temperature multi - direction forging; The steps of the heat treatment include: Perform solid - solution treatment on the cold - rolled plate at 920 - 950 °C for 1 - 2 h, cool it by water quenching, and then perform aging treatment at 450 - 500 °C for 4 - 6 h.

2. A method for preparing a high-damage-tolerant high-oxygen titanium alloy, characterized in that the steps include... Include: Prepare raw materials according to the element ratio of the high - damage - tolerance high - oxygen titanium alloy described in claim 1; Press the raw materials into a blank in a mold by the layer pressing method, and after drying the blank, perform induction suspension melting to obtain a finished ingot; Perform vacuum homogenization annealing treatment on the finished ingot, and then perform multi - temperature multi - direction forging, cold rolling and heat treatment to obtain the high - damage - tolerance high - oxygen titanium alloy; The temperature of the vacuum homogenization annealing treatment is 1000 - 1050 °C, and the time is 2 - 3.5 h; The steps of the cold rolling include: After removing the oxide scale from the ingot blank after multi - temperature multi - direction forging, heat it to 450 - 550 °C, hold for 60 min, and then perform multi - pass rolling. The deformation amount per pass is 10 - 15%, and after each pass of rolling, heat it back in the furnace and hold for 10 - 50 min. The total deformation amount is not less than 70%; The steps of the multi - temperature multi - direction forging include: Determine the β - phase region temperature of the ingot by differential thermal analysis; In the first forging, the finished ingot, which has undergone vacuum homogenization annealing, is heated to 30-50°C above the β phase region temperature and held for 60-90 minutes. After heating, the ingot block is forged, with a total deformation of 20-40%. In the second forging, when the ingot cools to 20-50°C below the β phase temperature, the ingot is forged again, with a total deformation of 20-40%. Then it is naturally air-cooled to room temperature to complete the multi-temperature multi-directional forging. The heat treatment steps include: The low-temperature rolled plate is solution treated at 920-950℃ for 1-2 hours, water-quenched, and then aged at 450-500℃ for 4-6 hours.

3. The preparation method according to claim 2, characterized in that, The raw materials include sponge titanium, aluminum briquettes, vanadium source and rutile titanium dioxide; And / or, the lower part of the blank is a lightweight material and the upper part is a heavy material.

4. The preparation method according to claim 3, characterized in that, The vanadium source includes aluminum-vanadium alloy and / or vanadium blocks.

5. The preparation method according to claim 2, characterized in that, The drying temperature is 80-120℃, and the time is 40-80 minutes.

6. The preparation method according to claim 2, characterized in that, The steps of the induction suspension melting include: The dried billet is placed in a vacuum induction levitation melting furnace, and the vacuum level of the melting furnace is maintained at 2-4 × 10⁻⁴. -2 The process involves purging with argon for protection, initially preheating at 50kW, then adjusting to 170kW. After the billet melts, the power is reduced back to 150kW, and the melt is suspended and stirred for at least 90 seconds. This smelting process is repeated at least three times. After smelting, the billet is cast and the riser is removed to obtain the finished ingot.

Images