A metastable beta titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced omega phase transformation induced plasticity and a method of making the same

Abstract

The application provides a metastable beta titanium alloy combining gap oxygen solid solution strengthening and stress-induced omega phase transformation induced plasticity and a preparation method thereof. The titanium alloy comprises 18-20% of V, 0.15-0.4% of O and the balance of Ti and trace amounts of impurity elements in terms of mass percentage. The preparation method comprises the steps of vacuum arc melting, vacuum homogenization annealing, hot rolling, cold rolling and vacuum solid solution heat treatment. The titanium alloy provided by the application improves the solid solution strengthening effect by introducing the gap oxygen element, and on the other hand, by regulating the deformation mechanism, the stress-induced omega phase transformation is used to excite the phase transformation induced plasticity effect, so that the high yield strength and high work hardening capacity are obtained. The yield strength of the titanium alloy provided by the application is more than 500 MPa, the tensile strength is more than 784 MPa, and meanwhile, the titanium alloy still has excellent plasticity and work hardening capacity, and can be potentially applied to new aero-engine gearboxes, landing gears and hydraulic system components.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy materials technology, specifically relating to a metastable β titanium alloy that combines interstitial oxygen solid solution strengthening and stress-induced ω phase transformation-induced plasticity, and its preparation method. Background Technology

[0002] Titanium alloys possess advantages such as high specific strength and good corrosion resistance. Their application in aerospace structural components can achieve significant structural weight reduction, which is beneficial to improving aircraft maneuverability and fuel efficiency. In recent years, metastable β-titanium alloys exhibiting transformation-induced plasticity (TRIP) and / or twinning-induced plasticity (TWIP) effects have attracted widespread attention. Numerous studies have shown that by controlling the stability of the β matrix and introducing TRIP and / or TWIP effects into metastable β-titanium alloys, the work hardening ability and plasticity of these alloys can be significantly improved. However, it is worth noting that the TRIP effect in most metastable β-titanium alloys is triggered by stress-induced β→α'' martensitic phase transformation. Due to the low critical shear stress of the β→α'' martensitic phase transformation, these alloys begin to undergo nonlinear deformation at very low strength levels (generally below 400 MPa), severely limiting their engineering applications.

[0003] Obviously, if stress-induced β→ω phase transformation with higher critical shear stress and the same ability to excite the TRIP effect can be introduced into metastable β titanium alloys, and interstitial oxygen elements with significant solid solution strengthening effect can be added to further increase its critical shear stress, the disadvantage of low critical stress for nonlinear deformation of existing TRIP titanium alloys can be overcome. Thus, it is expected that higher strength can be obtained while retaining the excellent plasticity and work hardening ability of TRIP titanium alloys. Summary of the Invention

[0004] Considering that most TRIP titanium alloys begin to undergo nonlinear deformation at very low strength levels (generally below 400 MPa), severely limiting their engineering applications, developing a metastable β-titanium alloy that significantly enhances solid solution strengthening by utilizing interstitial oxygen elements while simultaneously exhibiting stress-induced β→ω phase transformation-induced plasticity is a key approach to solving this problem. This type of titanium alloy has potential applications in new aero-engine gearboxes, landing gear, and hydraulic system components.

[0005] When designing the composition of metastable β-titanium alloys, including but not limited to controlling the content of the main alloying element V and other alloying elements within a specific range, the atoms on the {112} surface of the β matrix can easily undergo deformation along the β matrix. <111> The directional shift causes stress-induced β→ω phase transformation in the alloy. The formation of the stress-induced ω phase inhibits the stress-induced β→α'' martensitic phase transformation at lower critical shear stresses, while effectively blocking dislocation slip and activating the TRIP effect. Therefore, it can significantly improve the strength and work hardening ability of the corresponding alloy. In addition, adding an appropriate amount of oxygen to metastable β titanium alloys improves the alloy's strength level without completely suppressing the TRIP / TWIP effect, and therefore does not significantly reduce the alloy's plasticity and work hardening ability.

[0006] Based on the above considerations, this invention addresses the problem of low critical stress for nonlinear deformation in existing TRIP titanium alloys by providing a metastable β titanium alloy that combines interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity, as well as its preparation method.

[0007] Specifically, the first aspect of the present invention provides a metastable β titanium alloy that combines interstitial oxygen solid solution strengthening and stress-induced ω phase transformation-induced plasticity. The elemental composition and mass percentage of the titanium alloy are: 18%~20%V, 0.15%~0.4%O, with the balance being Ti and trace impurity elements.

[0008] As a further explanation of the present invention, the sum of 0.67 times the mass percentage of V element and 2.9 times the mass percentage of Fe element (substitutional impurity) in the titanium alloy is in the range of 10 to 13, so as to ensure that the titanium alloy can obtain 100% of the relatively unstable β phase after solution quenching in the β phase region temperature range.

[0009] As a further explanation of the present invention, the mass percentages of interstitial impurity elements H, N, and C in the titanium alloy are less than 0.01%, 0.055%, and 0.05%, respectively, to ensure that the atoms on the {112} plane involved in the stress-induced β→ω phase transformation of the titanium alloy are within acceptable limits. <111> The directional shift is not completely blocked by interstitial impurity atoms.

[0010] As a further illustration of the present invention, the titanium alloy is composed of 100% β phase, and stress-induced ω phase and {332} are generated during the plastic deformation stage. <113> Deformed twins.

[0011] A second aspect of the present invention provides a method for preparing the above-mentioned metastable β-titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity, comprising the following steps:

[0012] S1. Using pure Ti, pure V and pure TiO2 as raw materials, the finished ingot is obtained by vacuum arc melting.

[0013] S2. Vacuum homogenization annealing treatment is performed on the finished ingots;

[0014] S3. The ingot processed in S2 is hot rolled, and after hot rolling, it is water-cooled and quenched to room temperature. Then, the hot-rolled plate is cold rolled in multiple passes.

[0015] S4. The obtained cold-rolled sheet is subjected to vacuum solution heat treatment. After solution treatment, it is water-quenched to room temperature to complete the preparation of the alloy.

[0016] As a further explanation of the present invention, in S1, high-purity Ti, high-purity V and high-purity TiO2 with a purity of not less than 99.95% are used as raw materials, and the ingredients are proportioned according to the mass percentage of each element; vacuum arc melting is carried out in a vacuum arc melting furnace, and the furnace is kept in a vacuum state throughout the melting process; vacuum arc melting is repeated 3 to 5 times, and after each melting is completed, the alloy ingot is flipped over for the next melting.

[0017] As a further explanation of the present invention, in S2, the obtained finished ingot is placed in a vacuum with a degree higher than 3.5 × 10⁻⁶. - 4 In an environment of Pa, it is kept at 1050℃ for more than 12 hours, and then cooled to room temperature with the furnace.

[0018] As a further explanation of the present invention, in S3, the ingot processed in S2 is first placed in a vacuum with a degree higher than 3.5 × 10⁻⁶. -4 In an environment of Pa, the furnace is heated and held at 900℃ for more than 30 minutes for thorough heating. Then, a two-roll strip mill is used for one-pass rolling with a deformation of 40% to 60%. After hot rolling, the hot-rolled sheet is water-cooled and quenched to room temperature. Then, at room temperature, a two-roll strip mill is used to roll the hot-rolled sheet in multiple passes, with the roll pressure in each pass not exceeding 0.3 mm and the total deformation being 60% to 70%.

[0019] As a further explanation of the present invention, in S4, the cold-rolled sheet obtained in S3 is subjected to a vacuum degree higher than 1×10⁻⁶. -3 It is heated in an environment of Pa at 830℃~900℃ for 30 minutes, and then water-quenched to room temperature.

[0020] As a further explanation of the present invention, in S4, the temperature of the solution heat treatment holding is based on obtaining an microstructure characterized by equiaxed β grains with an average grain size in the range of 50 μm to 150 μm.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] The metastable β-titanium alloy prepared in this invention combines interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity. Through rational control of the β-stabilizing element V and interstitial oxygen content, a stress-induced ω-phase transformation with a higher critical shear stress is introduced into the metastable β-titanium alloy, resulting in a strength enhancement while exhibiting the TRIP effect. This alloy achieves a yield strength exceeding 500 MPa, a tensile strength exceeding 784 MPa, and a fracture elongation exceeding 35%, with a yield strength ratio not exceeding 0.654 and a maximum work hardening rate exceeding 1700 MPa during the plastic deformation stage. It demonstrates excellent strength-plasticity matching and superior work hardening capability, and has potential applications in new aero-engine gearboxes, landing gear, and hydraulic system components. Attached Figure Description

[0023] Figure 1 These are backscattered electron images of the initial microstructure of the titanium alloys prepared in Examples 1-3 and Comparative Example 4 of this invention.

[0024] Figure 2 Examples of room temperature tensile engineering stress-engineering strain curves of titanium alloys prepared in Examples 1-3 and Comparative Example 4 of this invention.

[0025] Figure 3 Examples of room temperature tensile work hardening rate-true strain curves of titanium alloys prepared in Examples 1-3 and Comparative Example 4 of this invention.

[0026] Figure 4 These are electron backscatter diffraction images of the deformed microstructures of the titanium alloys prepared in Examples 1-3 and Comparative Example 4 of this invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0028] The main elemental composition and mass percentage of a metastable β-titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity are as follows: 19.26% V, 0.16% O, 0.002% H, 0.019% N, 0.014% C, 0.012% Fe, with the balance being Ti and unavoidable impurity elements.

[0029] The preparation method of this metastable β-titanium alloy, which combines interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity, includes the following steps:

[0030] S1. Using high-purity Ti (99.995%), high-purity V (99.95%), and high-purity TiO2 (99.99%) as raw materials, the finished ingot is obtained by vacuum arc melting. The melting is repeated 5 times. After each melting is completed, the alloy ingot is flipped over for the next melting.

[0031] S2. Place the obtained finished ingot under a vacuum of 3.5 × 10⁻⁶. -4 In an environment of Pa, it was homogenized at 1050℃ for 12 hours, and then cooled to room temperature in the furnace.

[0032] S3. Place the ingot treated in S2 under a vacuum of 3.5 × 10⁻⁶. -4 In an environment of Pa, the furnace temperature was increased and held at 900℃ for 30 minutes for thorough heating. Then, a single hot rolling pass was performed using a twin-roll strip mill, resulting in a total deformation of 40.93%. After hot rolling, the sheet was water-quenched to room temperature. Next, a multi-pass cold rolling pass was performed on the hot-rolled sheet using a twin-roll strip mill, with a roll reduction of 0.3 mm per pass, resulting in a total deformation of 67.86%.

[0033] S4. The cold-rolled sheet obtained in S3 is subjected to a vacuum degree of 1×10⁻⁶. -3 It is heated at 830℃ for 30 minutes in an environment of Pa, and then water-quenched to room temperature.

[0034] The initial microstructure of the titanium alloy prepared in this embodiment was characterized using scanning electron microscopy, as shown in the attached figure. Figure 1 As shown in the figure, the initial microstructure of the titanium alloy prepared in this embodiment is mainly characterized by equiaxed β-phase grains. No other structural phases were observed at the micrometer scale, and the average grain size was 104.2 ± 2.2 μm.

[0035] The mechanical properties of the titanium alloy prepared in this example were measured according to GB / T 228.1–2010 "Metallic materials, tensile testing—Part 1: Test at room temperature". Its stress-strain curves are attached. Figure 2 As shown in the attached figure, the work hardening rate curve is... Figure 3 As shown, the results indicate that its yield strength is 535 MPa, tensile strength is 784 MPa, elongation at break is 43%, yield strength ratio is 0.638, and the maximum work hardening rate in the plastic deformation stage reaches 1890 MPa.

[0036] The deformed microstructure of the titanium alloy prepared in this embodiment was characterized by electron backscatter diffraction using scanning electron microscopy, as shown in the attached figure. Figure 4 As shown in the figure, stress-induced ω phase and {332} are generated during the deformation process of this alloy. <113> Deformed twins. Example 2

[0037] The main elemental composition and mass percentage of a metastable β-titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity are as follows: 19.10% V, 0.28% O, 0.002% H, 0.003% N, 0.013% C, 0.009% Fe, with the balance being Ti and unavoidable impurity elements.

[0038] The preparation method of this metastable β-titanium alloy, which combines interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity, includes the following steps:

[0039] S1. Using high-purity Ti (99.995%), high-purity V (99.95%), and high-purity TiO2 (99.99%) as raw materials, the finished ingot is obtained by vacuum arc melting. The melting is repeated 5 times. After each melting is completed, the alloy ingot is flipped over for the next melting.

[0040] S2. Place the obtained finished ingot under a vacuum of 3.5 × 10⁻⁶. -4 In an environment of Pa, it was homogenized at 1050℃ for 12 hours, and then cooled to room temperature in the furnace.

[0041] S3. Place the ingot treated in S2 under a vacuum of 3.5 × 10⁻⁶. -4 In an environment of Pa, the furnace temperature was increased and held at 900℃ for 30 minutes for thorough heating. Then, a single hot rolling pass was performed using a twin-roll strip mill, resulting in a total deformation of 55.14%. After hot rolling, the sheet was water-quenched to room temperature. Subsequently, the hot-rolled sheet was cold-rolled multiple times using a twin-roll strip mill, with a roll reduction of 0.3 mm per pass, resulting in a total deformation of 63.86%.

[0042] S4. The cold-rolled sheet obtained in S3 is subjected to a vacuum degree of 1×10⁻⁶. -3 It is heated to 875℃ for 30 minutes in an environment of Pa, and then water-quenched to room temperature.

[0043] The initial microstructure of the titanium alloy prepared in this embodiment was characterized using scanning electron microscopy, as shown in the attached figure. Figure 1 As shown in the figure, the initial microstructure of the titanium alloy prepared in this embodiment is mainly characterized by equiaxed β-phase grains. No other structural phases were observed at the micrometer scale, and the average grain size was 104.6 ± 1.6 μm.

[0044] The mechanical properties of the titanium alloy prepared in this example were measured according to GB / T 228.1–2010 "Metallic materials, tensile testing—Part 1: Test at room temperature". Its stress-strain curves are attached. Figure 2 As shown in the attached figure, the work hardening rate curve is... Figure 3As shown, the results indicate that its yield strength is 526 MPa, tensile strength is 797 MPa, elongation after fracture is 41%, yield strength ratio is 0.654, and the maximum work hardening rate in the plastic deformation stage reaches 2109 MPa.

[0045] The deformed microstructure of the titanium alloy prepared in this embodiment was characterized by electron backscatter diffraction using scanning electron microscopy, as shown in the attached figure. Figure 4 As shown in the figure, stress-induced ω phase and {332} are generated during the deformation process of this alloy. <113> Deformed twins. Example 3

[0046] The main elemental composition and mass percentage of a metastable β-titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity are as follows: 19.07% V, 0.37% O, 0.002% H, 0.051% N, 0.018% C, 0.009% Fe, with the balance being Ti and unavoidable impurity elements.

[0047] The preparation method of this metastable β-titanium alloy, which combines interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity, includes the following steps:

[0048] S1. Using high-purity Ti (99.995%), high-purity V (99.95%), and high-purity TiO2 (99.99%) as raw materials, the finished ingot is obtained by vacuum arc melting. The melting is repeated 5 times. After each melting is completed, the alloy ingot is flipped over for the next melting.

[0049] S2. Place the obtained finished ingot under a vacuum of 3.5 × 10⁻⁶. -4 In an environment of Pa, it was homogenized at 1050℃ for 12 hours, and then cooled to room temperature in the furnace.

[0050] S3. Place the ingot treated in S2 under a vacuum of 3.5 × 10⁻⁶. -4 In an environment of Pa, the furnace temperature was increased and held at 900℃ for 30 minutes for thorough heating. Then, a single hot rolling pass was performed using a twin-roll strip mill, resulting in a total deformation of 40.60%. After hot rolling, the sheet was water-quenched to room temperature. Subsequently, the hot-rolled sheet was cold-rolled multiple times using a twin-roll strip mill, with a roll reduction of 0.3 mm per pass, resulting in a total deformation of 67.63%.

[0051] S4. The cold-rolled sheet obtained in S3 is subjected to a vacuum degree of 1×10⁻⁶. -3 It is heated to 860℃ for 30 minutes in an environment of Pa, and then water-quenched to room temperature.

[0052] The initial microstructure of the titanium alloy prepared in this embodiment was characterized using scanning electron microscopy, as shown in the attached figure. Figure 1As shown in the figure, the initial microstructure of the titanium alloy prepared in this embodiment is mainly characterized by equiaxed β-phase grains. No other structural phases were observed at the micrometer scale, and the average grain size was 103.8 ± 1.3 μm.

[0053] The mechanical properties of the titanium alloy prepared in this example were measured according to GB / T 228.1–2010 "Metallic materials, tensile testing—Part 1: Test at room temperature". Its stress-strain curves are attached. Figure 2 As shown in the attached figure, the work hardening rate curve is... Figure 3 As shown, the results indicate that its yield strength is 596 MPa, tensile strength is 839 MPa, elongation after fracture is 36%, yield strength ratio is 0.635, and the maximum work hardening rate in the plastic deformation stage reaches 1720 MPa.

[0054] The deformed microstructure of the titanium alloy prepared in this embodiment was characterized by electron backscatter diffraction using scanning electron microscopy, as shown in the attached figure. Figure 4 As shown in the figure, stress-induced ω phase and {332} are generated during the deformation process of this alloy. <113> Deformed twins.

[0055] Comparative Example 4

[0056] The main elemental composition and mass percentage of the titanium alloy provided in this comparative example are: 12.14%Mo, 0.042%O, 0.0008%H, 0.003%N, 0.021%Fe, with the balance being Ti and unavoidable impurity elements.

[0057] The preparation method of this alloy includes the following steps:

[0058] S1, using high-purity Ti with a purity of 99.99% and high-purity TiMo with a purity of 99.95%. 32 Using intermediate alloy as raw material, finished ingots are obtained by vacuum arc melting. The melting process is repeated 5 times. After each melting is completed, the alloy ingot is flipped over for the next melting.

[0059] S2. Place the obtained finished ingot under a vacuum of 3.5 × 10⁻⁶. -4 In an environment of Pa, it was homogenized at 1050℃ for 12 hours, and then cooled to room temperature in the furnace.

[0060] S3. Place the ingot treated in S2 under a vacuum of 3.5 × 10⁻⁶. -4In an environment of Pa, the furnace temperature is increased and held at 900℃ for 30 minutes for thorough heating. Then, a single hot rolling pass is performed using a twin-roll strip mill, with a total deformation of 50%. After hot rolling, the sheet is water-quenched to room temperature. Finally, a multi-pass cold rolling pass is performed on the hot-rolled sheet using a twin-roll strip mill, with a roll reduction of 0.3 mm per pass and a total deformation of 35%.

[0061] S4. The cold-rolled sheet obtained in S3 is subjected to a vacuum degree of 1×10⁻⁶. -3 It is heated to 905℃ for 30 minutes in an environment of Pa, and then water-quenched to room temperature.

[0062] The initial microstructure of the titanium alloy prepared in this comparative example was characterized using scanning electron microscopy, as shown in the attached figure. Figure 1 As shown in the figure, the initial microstructure of the titanium alloy prepared in this comparative example is mainly characterized by equiaxed β-phase grains. No other structural phases were observed at the micrometer scale, and the average grain size was about 100 μm.

[0063] The mechanical properties of the titanium alloy prepared in this comparative example were measured according to GB / T 228.1–2010 "Metallic materials, tensile testing—Part 1: Test at room temperature". The engineering stress-strain curves are attached. Figure 2 As shown in the attached figure, the work hardening rate curve is... Figure 3 As shown, the results indicate that its yield strength is 480 MPa, tensile strength is 682 MPa, elongation at break is 53%, yield strength ratio is 0.704, and the maximum work hardening rate in the plastic deformation stage reaches 2128 MPa.

[0064] The deformed microstructure of the titanium alloy prepared in this comparative example was characterized by electron backscatter diffraction using scanning electron microscopy, as shown in the attached figure. Figure 4 As shown in the figure, {332} is generated during the deformation of this alloy. <113> Deformation twins and stress-induced α² ​​martensite.

[0065] Compared to Examples 1-3, although the same preparation process was used, the composition of the titanium alloy described in Comparative Example 4 is not within the scope of protection of this application. This results in a significantly weaker solid solution strengthening effect and an inability to generate stress-induced ω-phase transformation-induced plasticity during deformation. Therefore, its nonlinear deformation critical stress is low, exhibiting a lower strength level.

[0066] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A metastable β-titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity, characterized in that, The elemental composition and mass percentage of the titanium alloy are: 18%~20% V, 0.15%~0.4% O, with the balance being Ti and trace impurity elements; the sum of 0.67 times the mass percentage of V and 2.9 times the mass percentage of the substitutional impurity Fe in the titanium alloy is in the range of 10~13; the titanium alloy is composed of 100% β phase, and stress-induced ω phase and {332} are generated during the plastic deformation stage. <113> Deformed twins.

2. The metastable β-titanium alloy as described in claim 1, combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity, is characterized in that... The mass percentages of interstitial impurity elements H, N, and C in the titanium alloy are less than 0.01%, 0.055%, and 0.05%, respectively.

3. A method for preparing a metastable β-titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Using pure Ti, pure V and pure TiO2 as raw materials, the finished ingot is obtained by vacuum arc melting. S2. Vacuum homogenization annealing treatment is performed on the finished ingots; S3. The ingot processed in S2 is hot rolled, and after hot rolling, it is water-quenched to room temperature. Then the hot-rolled plate is cold rolled in multiple passes. S4. The obtained cold-rolled sheet is subjected to vacuum solution heat treatment. After solution treatment, it is water-quenched to room temperature to complete the preparation of the alloy.

4. The method for preparing a metastable β-titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity as described in claim 3, characterized in that, In S1, the vacuum arc melting is repeated 3 to 5 times. After each melting is completed, the alloy ingot is flipped over for the next melting.

5. The method for preparing a metastable β-titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity as described in claim 3, characterized in that, In S2, the obtained finished ingot is placed in a vacuum with a degree higher than 3.5 × 10⁻⁶. -4 In an environment of Pa, it is kept at 1050℃ for more than 12 hours, and then cooled to room temperature with the furnace.

6. The method for preparing a metastable β-titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity as described in claim 3, characterized in that, In S3, the ingot processed in S2 is first placed in a vacuum with a degree higher than 3.5 × 10⁻⁶. -4 In an environment of Pa, the furnace is heated and held at 900℃ for more than 30 minutes for thorough heating. Then, a two-roll strip mill is used for one-pass rolling with a deformation of 40% to 60%. After hot rolling, the hot-rolled sheet is water-cooled and quenched to room temperature. Then, at room temperature, a two-roll strip mill is used to roll the hot-rolled sheet in multiple passes, with the roll pressure in each pass not exceeding 0.3 mm and the total deformation being 60% to 70%.

7. The method for preparing a metastable β-titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity as described in claim 3, characterized in that, In S4, the cold-rolled sheet obtained in S3 is subjected to a vacuum degree higher than 1×10⁻⁶. -3 It is heated in an environment of Pa at 830℃~900℃ for 30 minutes, and then water-quenched to room temperature.

8. The method for preparing a metastable β-titanium alloy combining interstitial oxygen solid solution strengthening and stress-induced ω-phase transformation-induced plasticity as described in claim 3, characterized in that, In S4, the temperature for solution heat treatment is set to obtain a microstructure characterized by equiaxed β grains with an average grain size in the range of 50 μm to 150 μm.

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