A dual-phase metastable β titanium alloy with a three-state structure and a preparation method thereof

Abstract

The present invention discloses a dual-phase metastable β titanium alloy with a three-state structure and a preparation method, which belongs to the technical field of titanium alloy materials. The dual-phase metastable β titanium alloy is a matrix and contains a micron-sized spherical α phase with a volume fraction of 2-5%, a submicron-sized rod-shaped α phase with a volume fraction of 8-10%, and a nano-sized needle-shaped α phase with a volume fraction of 30-35%. During the preparation process, a continuous double solid solution treatment method is used to regulate the precipitation of the rod-shaped α phase, and finally, the needle-shaped secondary α phase is precipitated through a low-temperature aging treatment. The preparation method is simple and easy, and avoids the precipitation of harmful grain boundary α phase. The α phase content is controllable and has a large temperature range window for regulating the α phase, which is conducive to maintaining stability and consistency of the mechanical performance indicators of the three-state structure titanium alloy produced in engineering. The three-state structure titanium alloy and its preparation method have high value and broad prospects for further promoting the application of titanium alloys in the fields of aerospace, energy industry, etc., which have extremely high service performance requirements for high strength and high plasticity.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy materials, in particular to a dual-phase metastable beta titanium alloy with a three-state structure and a preparation method thereof. Background Art

[0002] Titanium and its alloys have attracted widespread attention across various industries due to their exceptional properties, including high specific strength, good age-hardenability, and excellent corrosion resistance. High-strength titanium alloys such as Ti-1023, Ti-6554, Ti-5553, and Ti-55531 typically exhibit yield strengths of approximately 1200–1300 MPa after aging, and their forgings have been successfully used in key components such as aircraft landing gear and connecting rods. For metastable β / α+β titanium alloys, α-precipitation strengthening is the most effective strengthening method. The introduction of α-precipitates significantly increases the density of the phase interface, distorting the surrounding lattice and thereby increasing the resistance to dislocation glide. These α-precipitates act as additional barriers to dislocation motion and exhibit remarkable strengthening effects. However, they still face a significant strength-ductility trade-off. A key challenge is overcoming the deformation incompatibility between adjacent heterogeneous phases, particularly between the soft α phase and the hard β matrix, i.e., the α / β phase interface. This is because the interface can cause local stress concentration through dislocation accumulation, leading to incompatible plastic deformation, accelerating the initiation of micropores and cracks, and sharply reducing the ductility of the alloy.

[0003] To cope with increasingly demanding operating environments, researchers have attempted to improve the mechanical properties of metastable β / α+β titanium alloys by appropriately adjusting the size, morphology, and distribution of the α phase through various thermomechanical processes. Several microstructures have been proposed, including equiaxed, basketweave, Widmanstätten, duplex, and trimodal structures. The trimodal structure, consisting of equiaxed α grains, rod-shaped α grains, and acicular α grains, combines the advantages of both equiaxed and basketweave structures. However, conventional processes require forging near the phase transformation point, resulting in a narrow forging temperature window, making microstructure control more difficult. Furthermore, the multiple, complex heat treatment processes required make it difficult to completely avoid the harmful precipitation of α phase at grain boundaries, severely hindering the widespread application of the trimodal microstructure in titanium alloys. Therefore, developing and improving multiple heat treatment processes to expand the solution-aging temperature window and facilitate precise control of the alloy's microstructure, morphology, phase content, and size in industrial production, maximize the mechanical properties and industrial application potential of trimodal titanium alloys, and have become urgent challenges in industrial production. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a dual-phase metastable β-titanium alloy with a three-state structure and a preparation method. The metastable β-titanium alloy rationally regulates the structure through a series of heat treatment processes, significantly improves its mechanical properties, and achieves a balance between high strength and good plasticity of the alloy.

[0005] The present invention is achieved through the following technical solutions:

[0006] The invention discloses a dual-phase metastable beta titanium alloy with a three-state structure. The dual-phase metastable beta titanium alloy takes beta phase as matrix and contains 2-5% volume fraction of micron-scale spherical alpha phase, 8-10% volume fraction of submicron-scale rod-shaped alpha phase and 30-35% volume fraction of nanometer-scale needle-shaped alpha phase.

[0007] Preferably, the dual-phase metastable β titanium alloy has the following properties: maximum yield strength of 1400 MPa, tensile strength greater than 1460 MPa, plastic elongation of 11%, and uniform elongation exceeding 4.5%.

[0008] Preferably, based on mass percentage, it includes 4-5% Al, 4-6% Mo, 6-8% V, 1-2% Cr, 1-2% Zr, and the balance is Ti and inevitable impurity elements.

[0009] A method for preparing a dual-phase metastable β titanium alloy with a three-state structure, comprising the following steps:

[0010] Step 1: Forging the metastable β titanium alloy in the β single phase region at 30 to 60° C. above the phase transformation point, and then water quenching to room temperature;

[0011] Step 2: forging the metastable β titanium alloy obtained in step 1 across the β single phase region at a phase transition point of -20 to +20° C., and then cooling to room temperature;

[0012] Step 3, subjecting the metastable β titanium alloy obtained in step 2 to a two-step solution treatment, and then water quenching to room temperature;

[0013] The temperature of the first solution treatment is higher than that of the second solution treatment;

[0014] Step 4: subjecting the metastable β titanium alloy obtained in step 3 to aging treatment at a temperature of 480-520° C. for 4-6 hours, and cooling to room temperature to obtain a dual-phase metastable β titanium alloy with a three-state structure.

[0015] Preferably, the phase transition point temperature is 800°C±5°C.

[0016] Preferably, the temperature of the first solution treatment in step 3 is 780-760°C, and the temperature of the second solution treatment is 740-720°C.

[0017] Preferably, the time for the first solution treatment in step 3 is 0.5-1 h, and the time for the second solution treatment is 2-4 h.

[0018] Preferably, the interval time between the two steps of solution treatment in step 3 is less than 0.5 min.

[0019] Preferably, the temperature of forging across the β single-phase region in step 2 is 780±5-820±5°C.

[0020] Preferably, the cooling method in step 2 is air cooling to room temperature.

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

[0022] The tri-modal, dual-phase metastable β titanium alloy proposed in this application has a β phase as its matrix and contains approximately 2-5% by volume of micron-sized spherical α phase, approximately 8-10% by volume of submicron-sized rod-shaped α phase, and approximately 30-35% by volume of nanometer-sized acicular α phase. Due to size effects and element distribution, the spherical α phase is relatively soft, the rod-shaped α phase has moderate hardness, and the acicular α phase is relatively hard. This alloy combines the plasticity of the micron-sized α phase with the strengthening of the nanometer-sized α phase, while the submicron-sized α phase provides both strengthening and plastic deformation coordination, thereby simultaneously improving the alloy's strength and plasticity.

[0023] Furthermore, the high-strength and high-plasticity dual-phase metastable β titanium alloy with this three-state structure becomes the Ti-Al-Mo-V-Cr-Zr system, which is a common element in high-strength titanium alloys, but exhibits more outstanding mechanical properties. Its yield strength can reach 1400MPa, the tensile strength exceeds 1460MPa, the plastic elongation is 11%, and the uniform elongation exceeds 4.5%, which are better than the mechanical properties of the alloy with the dual-state structure.

[0024] This application describes a method for preparing a dual-phase metastable β titanium alloy with a tri-modal microstructure. This method produces a spherical α phase after two forgings, then uses a continuous double solution treatment to control the precipitation of rod-shaped α phase. Finally, a low-temperature aging treatment is performed to precipitate a needle-shaped secondary α phase. This method is simple and easy to implement, avoids harmful grain boundary α phase precipitation, and provides a controllable α phase content within a wide temperature window for controlling the α phase. This method facilitates the stability and consistency of the mechanical properties of titanium alloys with a tri-modal microstructure in engineering production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a microstructure diagram of a metastable β titanium alloy with a tri-state structure prepared in Example 1 of the present invention;

[0027] Figure 2Comparison of tensile property curves of the metastable β titanium alloy with a ternary structure prepared in Example 1 of the present invention and a dual-state structure of the comparative example. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0030] A dual-phase metastable beta titanium alloy with a three-state structure comprises, by mass percentage, 4-5% Al, 4-6% Mo, 6-8% V, 1-2% Cr, 1-2% Zr, and the balance being Ti and unavoidable impurity elements.

[0031] This high-strength, high-plasticity, dual-phase metastable β-titanium alloy with a triple-structure structure consists of a β-phase matrix and contains approximately 2-5% by volume of micron-sized spherical α-phase, approximately 8-10% by volume of submicron-sized rod-shaped α-phase, and approximately 30-35% by volume of nanometer-sized needle-shaped α-phase. This alloy simultaneously improves its strength and plasticity, exhibiting outstanding mechanical properties. Its yield strength reaches 1400 MPa, its tensile strength exceeds 1460 MPa, its plastic elongation is 11%, and its uniform elongation exceeds 4.5%, surpassing the mechanical properties of alloys with a dual-structure structure.

[0032] Correspondingly, the present application also provides a method for preparing a dual-phase metastable β titanium alloy with a three-state structure, comprising the following steps:

[0033] Step 1: Forging the Ti-Al-Mo-V-Cr-Zr metastable β titanium alloy obtained by arc melting at 30 to 60° C. above the phase transformation point in the β single phase region to refine the β grains, and then water-quenching to room temperature;

[0034] Step 2: The titanium alloy obtained in step 1 is heated again to a temperature of -20 to +20°C near the phase transition point and forged across the β single phase region to further refine the β grains. Due to the precipitation and fragmentation of the α phase at high temperature, some micron-sized spherical α precipitates are obtained, and then the alloy is air-cooled to room temperature.

[0035] Step 3: Place the titanium alloy obtained in step 2 in a box-type heat treatment furnace for 0.5-1 hour of solution treatment. Then, remove it from the box-type heat treatment furnace and quickly place it in another box-type heat treatment furnace at a lower temperature for 2-4 hours of solution treatment. During this period, the time of being exposed to air does not exceed 0.5 minutes. Then, water-cooled quenching is performed to room temperature. Due to the precipitation and growth of α phase at medium temperature, submicron-sized rod-shaped α precipitate phase is obtained, while the precipitation of α phase at grain boundaries is avoided.

[0036] Step 4: Place the titanium alloy obtained in step 3 in a heat treatment furnace at 480-520°C, keep it warm for 4-6 hours for aging treatment, and then air cool it to room temperature. Due to the dense nucleation and precipitation of the α phase, a nano-scale needle-shaped α precipitate phase is obtained, that is, a dual-phase metastable β titanium alloy with a three-state structure is obtained.

[0037] The phase transition temperature of the alloy is 800±5℃.

[0038] This Ti-Al-Mo-V-Cr-Zr titanium alloy undergoes two forging processes and, for the first time, uses a simple continuous dual high- and low-temperature solution treatment to control the microstructure of the high-strength titanium alloy, preventing the precipitation of α phase at grain boundaries. This results in a three-modal microstructure consisting of spherical α phase, rod-shaped α phase, and needle-shaped α phase. This organically combines the strengthening and toughening effects of α phases of varying scales and hardness to improve the strain compatibility of the α / β phase interface. This metastable β titanium alloy undergoes a series of heat treatment processes to rationally control its microstructure, significantly improving its mechanical properties and achieving a balance between high strength and good plasticity.

[0039] Example 1

[0040] A method for preparing a dual-phase metastable β titanium alloy with a three-state structure, comprising the following steps:

[0041] Step 1: Prepare metastable β titanium alloy.

[0042] 4% Al, 5% Mo, 8% V, 2% Cr, 1% Zr, and the balance Ti and inevitable impurity elements are mixed uniformly by mass and arc-melted to obtain a metastable β titanium alloy.

[0043] Step 2: forging the Ti-Al-Mo-V-Cr-Zr metastable β titanium alloy at 835° C. in the β single phase region to refine the β grains, and then water-quenching to room temperature;

[0044] Step 3: The titanium alloy obtained in step 2 is heated to 810° C. again forged across the β single-phase region to further refine the β grains. Due to the precipitation and fragmentation of the α phase at high temperature, some micron-sized spherical α precipitates are obtained, and then air-cooled to room temperature;

[0045] Step 4: Place the titanium alloy obtained in Step 3 in a 780°C box-type heat treatment furnace for 1 hour of solution treatment. Then remove it from the box-type heat treatment furnace and quickly place it in another 740°C box-type heat treatment furnace for 2 hours of solution treatment, during which it is exposed to air for about 15 seconds. Then, water-cooled and quenched to room temperature, submicron-sized rod-shaped α precipitates are obtained due to the precipitation and growth of α phase at the medium temperature.

[0046] Step 5: Place the titanium alloy obtained in step 4 in a heat treatment furnace at 500°C, keep it warm for 6 hours for aging treatment, and then air-cool it to room temperature. Due to the dense nucleation and precipitation of the α phase, a nano-scale needle-shaped α precipitate phase is obtained, that is, a dual-phase metastable β titanium alloy with a three-state structure is obtained.

[0047] The microstructure of the prepared dual-phase metastable β titanium alloy with three-state structure is as follows Figure 1 As shown in Figure 1, the titanium alloy microstructure contains about 2% volume fraction of spherical primary α phase with an average diameter of about 0.76μm, about 8% volume fraction of submicron rod-shaped α phase with an average width of about 0.30μm, and about 30% volume fraction of nanometer-sized needle-shaped α phase with an average width of about 37nm. The room temperature tensile properties of this dual-phase metastable β titanium alloy were tested in accordance with the requirements of GB / T228.1-2010 standard. The tensile properties curve is shown in Figure 1. Figure 2 , the tensile strength R of the alloy mechanical properties was measured m The yield strength R is 1462MPa. 0.2 The elongation at break is 1392MPa and the elongation at break is A f The uniform elongation is 11.7%. u It is 5.2%, see Table 1.

[0048] Example 2

[0049] A method for preparing a dual-phase metastable β titanium alloy with a three-state structure, comprising the following steps:

[0050] Step 1: Prepare metastable β titanium alloy.

[0051] 5% Al, 6% Mo, 7% V, 1% Cr, 2% Zr, and the balance Ti and inevitable impurity elements are mixed uniformly by mass and arc-melted to obtain a metastable β titanium alloy.

[0052] Step 2: forging the Ti-Al-Mo-V-Cr-Zr metastable β titanium alloy at 850° C. in the β single phase region to refine the β grains, and then water-quenching to room temperature;

[0053] Step 3: The titanium alloy obtained in step 1 is heated to 820° C. again forged across the β single-phase region to further refine the β grains. Due to the precipitation and fragmentation of the α phase at high temperature, some micron-sized spherical α precipitates are obtained, and then air-cooled to room temperature;

[0054] Step 4: Place the titanium alloy obtained in Step 3 in a 770°C box-type heat treatment furnace for 0.5 hours of solution treatment. Then, remove it from the box-type heat treatment furnace and quickly place it in another 730°C box-type heat treatment furnace for 3 hours of solution treatment, during which it is exposed to air for about 10 seconds. Then, water-cooled and quenched to room temperature, submicron-sized rod-shaped α precipitates are obtained due to the precipitation and growth of α phase at the medium temperature.

[0055] Step 5: Place the titanium alloy obtained in step 4 in a heat treatment furnace at 480°C, keep it warm for 6 hours for aging treatment, and then air-cool it to room temperature. Due to the dense nucleation and precipitation of the α phase, a nano-scale needle-shaped α precipitate phase is obtained, that is, a dual-phase metastable β titanium alloy with a three-state microstructure is obtained.

[0056] The titanium alloy microstructure contains about 4% volume fraction of spherical primary α phase with an average diameter of about 0.69μm, about 10% volume fraction of submicron rod-shaped α phase with an average width of about 0.30μm, and about 35% volume fraction of nanometer needle-shaped α phase with an average width of about 27nm. The room temperature tensile properties of this dual-phase metastable β titanium alloy were tested in accordance with the requirements of GB / T228.1-2010 standard. The tensile properties curve is shown in Figure 2 , the tensile strength R of the alloy mechanical properties was measured m The yield strength R is 1469MPa. 0.2 The elongation at break is 1408MPa and the elongation at break is A f The uniform elongation is 11.0%, u It is 4.6%, see Table 1.

[0057] Example 3

[0058] A method for preparing a dual-phase metastable β titanium alloy with a three-state structure, comprising the following steps:

[0059] Step 1: Prepare metastable β titanium alloy.

[0060] 4.6% of Al, 4% of Mo, 6% of V, 1.5% of Cr, 1.4% of Zr, and the balance of Ti and inevitable impurity elements are mixed uniformly by mass and arc-melted to obtain a metastable β titanium alloy.

[0061] Step 2: forging the Ti-Al-Mo-V-Cr-Zr metastable β titanium alloy at 860° C. in the β single phase region to refine the β grains, and then water-quenching to room temperature;

[0062] Step 3: The titanium alloy obtained in step 1 is heated to 780° C. again forged across the β single-phase region to further refine the β grains. Due to the precipitation and fragmentation of the α phase at high temperature, some micron-sized spherical α precipitates are obtained, and then air-cooled to room temperature;

[0063] Step 4: Place the titanium alloy obtained in Step 3 in a 760°C box-type heat treatment furnace for 0.7 hours of solution treatment. Then, remove it from the box-type heat treatment furnace and quickly place it in another 720°C box-type heat treatment furnace for 4 hours of solution treatment, during which it is exposed to air for about 30 seconds. Then, water-cooled and quenched to room temperature, submicron-sized rod-shaped α precipitates are obtained due to the precipitation and growth of α phase at the medium temperature.

[0064] Step 5: Place the titanium alloy obtained in step 4 in a heat treatment furnace at 520°C, keep it warm for 4 hours for aging treatment, and then air-cool it to room temperature. Due to the dense nucleation and precipitation of the α phase, a nano-scale needle-shaped α precipitate phase is obtained, that is, a dual-phase metastable β titanium alloy with a three-state microstructure is obtained.

[0065] Comparative Example

[0066] A metastable β titanium alloy obtained by arc melting comprises, by mass percentage, 4% Al, 5% Mo, 8% V, 2% Cr, 1% Zr, with the balance being Ti and unavoidable impurity elements. The alloy composition of this comparative example is the same as that of Example 1, differing only in the forging temperature and the continuous double heat treatment process. The preparation steps of this comparative example are as follows:

[0067] Step 1: forging the Ti-Al-Mo-V-Cr-Zr metastable β titanium alloy at 835° C. in the β single phase region to refine the β grains, and then water-quenching to room temperature;

[0068] Step 2: The titanium alloy obtained in step 1 is heated to 800° C. again and forged across the β single-phase region to further refine the β grains. Due to the precipitation and fragmentation of the α phase at high temperature, some micron-sized spherical α precipitates are obtained, and then air-cooled to room temperature.

[0069] Step 3: Place the titanium alloy obtained in step 2 in a heat treatment furnace at 500°C, keep it warm for 6 hours for aging treatment, and then air-cool it to room temperature. Due to the dense nucleation and precipitation of the α phase, a nano-scale needle-shaped α precipitate phase is obtained, that is, a dual-phase metastable β titanium alloy with a dual-state structure is obtained.

[0070] The microstructure of the titanium alloy contains about 10% volume fraction of spherical primary α phase with an average diameter of about 0.84μm, and about 30% volume fraction of nano-sized needle-shaped α phase with an average width of about 37nm. The room temperature tensile properties of the dual-phase metastable β titanium alloy were tested in accordance with the requirements of GB / T228.1-2010 standard. The tensile properties curve is shown in Figure 2 , the tensile strength R of the alloy mechanical properties was measured m The yield strength R is 1386MPa. 0.2 The elongation at break is 1352MPa and the elongation at break is A fThe uniform elongation is 6.7%. u It is 2.5%, see Table 1.

[0071] Table 1 Metastable β titanium alloy performance test results of the embodiment and comparative example

[0072]

[0073] As can be seen from Table 1, Examples 1 and 2 of the present invention are dual-phase metastable β titanium alloys with a three-state structure. They have a tensile strength exceeding 1460 MPa, a yield strength approximately reaching 1400 MPa, an elongation at break exceeding 11%, and a uniform elongation exceeding 4.5%. The comparative example is a dual-phase metastable β titanium alloy with a two-state structure. Its tensile yield strength is 1352 MPa, its tensile strength is 1386 MPa, its elongation at break is only 6.7%, and its uniform elongation is a mere 2.5%.

[0074] Compared to the dual-phase metastable β titanium alloy with a dual-state structure in the comparative example, the dual-phase metastable β titanium alloy with a triple-state structure in Example 1 and Example 2 has a significant improvement in tensile strength and yield strength, while its plasticity has not suffered the expected loss, but has been greatly improved, including an increase of nearly 1 times in elongation at break and uniform elongation. The above results show that the high-strength and high-plasticity dual-phase metastable β titanium alloy with a triple-state structure of spherical α phase, rod-shaped α phase and needle-shaped α phase with different morphologies, different sizes and different hardnesses simultaneously obtains a triple-state structure of spherical α phase, rod-shaped α phase and needle-shaped α phase, while providing a strengthening effect and plastic deformation coordination, and simultaneously improving the alloy strength and improving the alloy plasticity. Therefore, the triple-state structure titanium alloy and its preparation method have high value and broad prospects for further promoting the application of titanium alloys in aerospace, energy industry and other fields with extremely high service performance requirements for high strength and high plasticity.

[0075] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a dual-phase metastable β titanium alloy with a three-state structure, characterized in that: The following steps are involved: Step 1: Forging the metastable β titanium alloy in the β single phase region at 30-60° C. above the phase transformation point, and then water quenching to room temperature; The metastable β titanium alloy comprises, by mass percentage, 4-5% Al, 4-6% Mo, 6-8% V, 1-2% Cr, 1-2% Zr, and the balance being Ti and unavoidable impurity elements; Step 2: forging the metastable β titanium alloy obtained in step 1 across the β single phase region at a phase transition point of -20°C to +20°C, and then cooling to room temperature; Step 3, subjecting the metastable β titanium alloy obtained in step 2 to a two-step solution treatment, and then water quenching to room temperature; The temperature of the first solution treatment is 780-760°C, and the temperature of the second solution treatment is 740-720°C; The temperature of the first solution treatment is higher than that of the second solution treatment; Step 4: subjecting the metastable β titanium alloy obtained in step 3 to aging treatment at a temperature of 480-520° C. for 4-6 hours, and cooling to room temperature to obtain a dual-phase metastable β titanium alloy with a three-state structure.

2. The method for preparing a dual-phase metastable β titanium alloy with a three-state structure according to claim 1, characterized in that: The phase transition point temperature is 800°C±5°C.

3. The method for preparing a dual-phase metastable β titanium alloy with a three-state structure according to claim 1, characterized in that: The time of the first solution treatment in step 3 is 0.5-1 h, and the time of the second solution treatment is 2-4 h.

4. The method for preparing a dual-phase metastable β titanium alloy with a three-state structure according to claim 1, characterized in that: The interval time between the two steps of solution treatment in step 3 is less than 0.5 min.

5. The method for preparing a dual-phase metastable β titanium alloy with a three-state structure according to claim 1, characterized in that: The temperature of the forging across the β single-phase region in step 2 is 780±5°C-820±5°C.

6. The method for preparing a dual-phase metastable β titanium alloy with a three-state structure according to claim 1, characterized in that: The cooling method described in step 2 is air cooling to room temperature.

7. A dual-phase metastable β titanium alloy with a three-state structure prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The dual-phase metastable beta titanium alloy takes beta phase as matrix and contains 2-5% volume fraction of micron-scale spherical alpha phase, 8-10% volume fraction of submicron-scale rod-shaped alpha phase and 30-35% volume fraction of nanometer-scale needle-shaped alpha phase.

8. The dual-phase metastable β titanium alloy with a triple structure according to claim 7, characterized in that: The performance of this dual-phase metastable β titanium alloy is a maximum yield strength of 1400MPa, a tensile strength greater than 1460MPa, a plastic elongation of 11%, and a uniform elongation of more than 4.5%.

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