Ta15 titanium alloy with tri-modal organization, and preparation method and application thereof, and method for improving strength-ductility matching of ta15 titanium alloy

Abstract

This invention relates to a TA15 titanium alloy with a trimodal microstructure, its preparation method and application, and a method for improving the strength-ductility matching of TA15 titanium alloy. The preparation method includes the following steps: S100. Heat treatment: heating the TA15 titanium alloy to a temperature 10℃~40℃ below the β transformation point, holding at that temperature, and cooling to obtain the heat-treated TA15 titanium alloy; S200. Hot rolling deformation: hot rolling the heat-treated TA15 titanium alloy, with the hot rolling temperature within the α+β two-phase region temperature range, to obtain a TA15 titanium alloy with a bimodal microstructure; S300. Short-time annealing: annealing the TA15 titanium alloy with the bimodal microstructure to obtain a TA15 titanium alloy with a trimodal microstructure. The method of the invention has the advantages of low cost, strong operability, and wide applicability, providing a way to prepare trimodal microstructures in other near-α type titanium alloys to further improve the mechanical properties of near-α type titanium alloy materials.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy processing technology, specifically to a TA15 titanium alloy with a trimodal microstructure, its preparation method and application, and a method for improving the strength-plasticity balance of TA15 titanium alloy. Background Technology

[0002] TA15 titanium alloy is a near-alpha type titanium alloy with high Al equivalent. Due to its excellent specific strength, good corrosion resistance, and thermal stability, it is widely used in the manufacture of critical components such as welded structural parts, load-bearing structural parts, and large integral parts in the aerospace field. With the rapid development of aerospace technology, the service environment of structural components is becoming increasingly harsh, placing more stringent requirements on the comprehensive mechanical properties of TA15 titanium alloy, especially the synergistic matching of high strength and high ductility (i.e., strength-ductility matching). Existing TA15 titanium alloy materials and their preparation processes are no longer sufficient to fully meet these increasingly demanding performance requirements.

[0003] For near-alpha titanium alloys, their microstructure is the core factor determining the alloy's strength and plasticity. Typically, equiaxed alpha phases and β matrix phases impart good plasticity, while fine acicular alpha phases contribute to improved strength. Therefore, precisely controlling the content, size, and morphology of the equiaxed alpha, acicular alpha, and β phases in the alloy to achieve synergistic optimization of strength and plasticity is a critical engineering problem that urgently needs to be solved in this field.

[0004] Common microstructures in titanium alloys include equiaxed, Widmanstätten, and bimodal structures. Equiaxed structures, primarily composed of equiaxed α phases, exhibit high elongation and fracture toughness, but relatively low strength, and the grains tend to coarsen at high temperatures. Widmanstätten structures consist of coarse primary β grains and their internally arranged parallel α lamellae; while possessing high strength, their elongation is significantly lower. Bimodal structures contain both equiaxed α phases and β-transformation bundles composed of acicular α phases, thus exhibiting a good balance between strength and ductility. However, as the equiaxed α phase content increases in bimodal structures, the alloy strength gradually decreases, and obtaining this structure often requires precise and complex deformation and heat treatment processes, resulting in a narrow process window and posing significant challenges to industrial production control.

[0005] In industrial production, the mainstream processes for microstructure control of near-α titanium alloys include β heat treatment, near-β heat treatment, α+β heat treatment, and conventional annealing. However, β heat treatment and near-β heat treatment processes easily lead to the formation of coarse Widmanstätten structures in the alloy, significantly impairing the material's plasticity. Although α+β heat treatment and conventional annealing processes can form equiaxed α phases, they tend to cause grain coarsening, making it difficult for the alloy to meet strength requirements.

[0006] Furthermore, there are existing reports on the preparation of tri-phase microstructures (i.e., three-peak microstructures) in titanium alloys. For example, Chinese patent CN103205662A discloses a pure heat treatment process that combines near-β temperature holding with water cooling and two-phase region holding with furnace cooling to obtain a tri-phase microstructure composed of equiaxed α, lamellar α, and β transformation microstructures in near-α titanium alloys. However, this method is a pure heat treatment route, lacking a plastic deformation stage, and has shortcomings such as limited grain refinement effect, long process cycle, and the need for precise control of cooling rate. Moreover, the flexibility of adjusting the obtained microstructure and properties needs to be further improved.

[0007] In summary, how to develop a simple, short-cycle, and precisely controllable deformation heat treatment method that integrates the content and morphology of equiaxed α phase, acicular α phase, and β phase to obtain a TA15 titanium alloy with a tri-peak microstructure that combines high strength and high plasticity remains a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0008] Therefore, it is necessary to provide a TA15 titanium alloy with a trimodal structure, its preparation method and application, and a method to improve the strength-plasticity matching of TA15 titanium alloy, aiming to solve the technical problems existing in the prior art.

[0009] To achieve the above objectives, the present invention provides a technical solution: A method for preparing TA15 titanium alloy with a trimodal microstructure includes the following steps: S100. Heat treatment: Heat the TA15 titanium alloy to 10℃-40℃ below the β transformation point, hold at that temperature, and then cool to obtain the heat-treated TA15 titanium alloy. S200. Hot rolling deformation: The heat-treated TA15 titanium alloy is hot rolled, and the hot pressing temperature is within the α+β two-phase temperature range to obtain a TA15 titanium alloy with a bimodal structure. S300. Short-time annealing: Annealing TA15 titanium alloy with bimodal structure to obtain TA15 titanium alloy with trimodal structure.

[0010] Preferably, in step S100, the heat preservation time is 0.5-2 hours.

[0011] Preferably, in step S100, the heating rate is 5℃ / min-15℃ / min.

[0012] Preferably, in step S200, the hot rolling process is performed by multi-pass unidirectional rolling, with a deformation of 12-15% per pass, and the hot rolling is repeated in the furnace for 2-10 minutes between passes.

[0013] Preferably, in step S200, the total deformation is 40%-60%.

[0014] Preferably, in step S300, the parameters for the annealing process are: Heat to 650℃-850℃ at a rate of 5℃ / min-15℃ / min, and anneal for 20 min-40 min.

[0015] This application also provides a TA15 titanium alloy with a trimodal structure.

[0016] Specifically, the TA15 titanium alloy has an ultimate tensile strength of 1096.5 MPa, a plasticity of 11.72%, and a strength-ductility product of 12850.98 MPa.

[0017] Preferably, the TA15 titanium alloy comprises the following chemical composition by weight percentage: Al 5.5%-7.0%; V 0.8%-2.5; Zr 1.0%-2.5%; Mo 0.5%-2.0%; Si 0.05%-0.15%; Fe 0-0.005%; The balance consists of Ti and impurities.

[0018] The present invention also provides an application of TA15 titanium alloy with a trimodal structure in the manufacture of aerospace structural components.

[0019] Specifically, the structural components include aircraft fuselage frames, wing connection joints, engine mounting brackets, or rocket body connection rings.

[0020] The present invention also provides a method for improving the strength-plasticity matching of TA15 titanium alloy, wherein the TA15 titanium alloy is subjected to hot rolling deformation and short-time annealing treatment steps, so that the TA15 titanium alloy obtains a three-peak structure composed of equiaxed α phase, acicular α phase and β phase.

[0021] Specifically, the TA15 titanium alloy is a forged TA15 titanium alloy bar, and the method is applicable to other near-α type titanium alloys.

[0022] The beneficial effects of this invention are: 1. The microstructure of TA15 titanium alloy is crucial in determining its tensile strength and plasticity, and titanium alloys often exhibit a strength-plasticity inversion problem. This invention achieves a uniform equiaxed microstructure in TA15 titanium alloy through heat treatment; a fine bimodal microstructure through hot rolling; precise control of the trimodal microstructure through annealing, resulting in a uniformly distributed and appropriately sized trimodal microstructure; and improved strength and plasticity of TA15 titanium alloy through a combination of hot rolling and short-time annealing. This synergistic improvement in strength and plasticity of near-α-type TA15 titanium alloy material results in excellent overall performance.

[0023] 2. The present invention provides a method for obtaining a trimodal microstructure in TA15 titanium alloy through hot rolling and short-time annealing, which has the advantages of low cost, simple process and wide applicability.

[0024] 3. This invention provides a framework for preparing trimodal microstructures in other near-α type titanium alloys. Attached Figure Description

[0025] Figure 1 The image shown is a scanning electron microscope (SEM) image of the 950℃ hot-rolled TA15 titanium alloy annealed at 750℃ according to Example 1 of the present invention; where (b) is an enlarged view of (a) to show the morphology of the needle-like α phase. Figure 2 The image shown is a scanning electron microscope (SEM) image of the 950℃ hot-rolled TA15 titanium alloy annealed at 650℃ in Example 2 of the present invention; where (b) is an enlarged view of (a) to show the morphology of the needle-like α phase. Figure 3 The image shown is a scanning electron microscope (SEM) image of the 950℃ hot-rolled TA15 titanium alloy annealed at 850℃ in Example 3 of the present invention; where (b) is an enlarged view of (a) to show the morphology of the needle-like α phase. Figure 4 The image shown is a scanning electron microscope (SEM) image of the TA15 titanium alloy of Comparative Example 1 of the present invention after hot rolling at 950°C; where (b) is an enlarged view of (a) to show the morphology of the needle-like α phase. Figure 5 The figures are engineering stress-strain curves of Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0026] 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.

[0027] 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. Every smaller range between any stated value or intermediate value within a stated range, and 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.

[0028] 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 or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] 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 apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] 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.

[0031] Unless otherwise specified, "room temperature" as used in this invention refers to the range of 20–30°C.

[0032] Example 1

[0033] S100.TA15 titanium alloy heat treatment: First, raise the temperature of the muffle furnace from room temperature to 950℃. After the temperature stabilizes, put in the TA15 titanium alloy and hold it at that temperature for 1 hour. Then, air cool it to room temperature to obtain the heat-treated TA15 titanium alloy.

[0034] S200. Hot rolling treatment: The heat-treated TA15 titanium alloy is subjected to multi-pass unidirectional rolling. In the hot rolling process, the furnace temperature is first raised to 950℃ at a rate of 10℃ / s. After the temperature stabilizes, the TA15 titanium alloy is placed in the furnace and held for 10 min. Between passes, it is returned to the furnace for 5 min of holding. After rolling, it is air-cooled to room temperature. The rolling deformation is 50%.

[0035] S300. Annealing treatment: The hot-rolled TA15 titanium alloy was annealed by first raising the muffle furnace from room temperature to 750°C, then placing the hot-rolled TA15 titanium alloy in and holding it for 30 min, followed by air cooling to room temperature, to obtain a three-peak microstructure consisting of 9.63% equiaxed α phase (4.56 μm), 70.21% acicular α phase (0.22 μm) and 20.16% β phase.

[0036] Figure 1 This is a SEM image of the near-α type TA15 titanium alloy with a trimodal structure prepared in Example 1.

[0037] from Figure 1 As can be seen in (a), after hot rolling and short-time annealing, the microstructure of TA15 titanium alloy mainly consists of equiaxed α phase, acicular α phase, and β phase. Figure 1 As can be seen in (b), the needle-like α phase is slender and needle-like at this time.

[0038] The TA15 titanium alloy prepared in this embodiment has a tensile strength of 1096.5 MPa, a plasticity of 11.72%, and a strength-ductility product of 12850.98 MPa.

[0039] Example 2

[0040] S100.TA15 titanium alloy heat treatment: First, raise the temperature of the muffle furnace from room temperature to 950℃. After the temperature stabilizes, put in the TA15 titanium alloy and hold it at that temperature for 1 hour. Then, air cool it to room temperature to obtain the heat-treated TA15 titanium alloy.

[0041] S200. Hot rolling treatment: The heat-treated TA15 titanium alloy is subjected to multi-pass unidirectional rolling. In the hot rolling process, the furnace temperature is first raised to 950℃ at a rate of 10℃ / s. After the temperature stabilizes, the TA15 titanium alloy is placed in the furnace and held for 10 min. Between passes, it is returned to the furnace for 5 min of holding. After rolling, it is air-cooled to room temperature. The rolling deformation is 50%.

[0042] S300. Annealing treatment: The hot-rolled TA15 titanium alloy was annealed by first raising the muffle furnace from room temperature to 850°C, then placing the hot-rolled TA15 titanium alloy in and holding it for 30 min, followed by air cooling to room temperature, to obtain a three-peak microstructure consisting of 11.88% equiaxed α phase (5.32 μm), 68.98% acicular α phase (0.38 μm) and 19.14% β phase.

[0043] Figure 2 This is a SEM image of the near-α-type TA15 titanium alloy with a trimodal microstructure prepared in Example 2. From... Figure 2 As can be seen in (a), the content of equiaxed α phase increases significantly with increasing annealing temperature. Figure 2As shown in (b), after annealing at 850℃ for 30 min, the acicular α phase appears as short rods. Furthermore, the average size of both the equiaxed α phase and the acicular α phase gradually increases with increasing annealing temperature.

[0044] The TA15 titanium alloy prepared in this embodiment has a tensile strength of 1093.8 MPa, a plasticity of 10.29%, and a strength-ductility product of 11255.202 MPa.

[0045] Comparative Example 1 S100.TA15 titanium alloy heat treatment: First, raise the temperature of the muffle furnace from room temperature to 950℃. After the temperature stabilizes, put in the TA15 titanium alloy and hold it at that temperature for 1 hour. Then, air cool it to room temperature to obtain the heat-treated TA15 titanium alloy.

[0046] S200. Hot rolling treatment: The heat-treated TA15 titanium alloy is subjected to multi-pass unidirectional rolling. In the hot rolling process, the furnace temperature is first raised to 950℃ at a rate of 10℃ / s. After the temperature stabilizes, the TA15 titanium alloy is placed in the furnace and held for 10 min. Between passes, it is returned to the furnace for 5 min of holding. After rolling, it is air-cooled to room temperature. The rolling deformation is 50%.

[0047] Figure 3 This is a SEM image of the near-α-type TA15 titanium alloy with a bimodal microstructure prepared in this embodiment. (From...) Figure 3 As can be seen in (a), the microstructure of TA15 titanium alloy after hot rolling at 950℃ is mainly composed of equiaxed α phase and α bundle domain. At this time, the volume fraction and average size of the equiaxed α phase are 7.36% and 3.93 μm, respectively, and the volume fraction and average size of the acicular α phase are 69.24% and 0.17 μm, respectively.

[0048] The TA15 titanium alloy prepared in this comparative example has a tensile strength of 1170.0 MPa, a plasticity of 8.07%, and a strength-ductility product of 9441.9 MPa·.

[0049] Comparative Example 2: S100.TA15 titanium alloy heat treatment: First, raise the temperature of the muffle furnace from room temperature to 950℃. After the temperature stabilizes, put in the TA15 titanium alloy and hold it at that temperature for 1 hour. Then, air cool it to room temperature to obtain the heat-treated TA15 titanium alloy.

[0050] S200. Hot rolling treatment: The heat-treated TA15 titanium alloy is subjected to multi-pass unidirectional rolling. In the hot rolling process, the furnace temperature is first raised to 950℃ at a rate of 10℃ / s. After the temperature stabilizes, the TA15 titanium alloy is placed in the furnace and held for 10 min. Between passes, it is returned to the furnace for 5 min of holding. After rolling, it is air-cooled to room temperature. The rolling deformation is 50%.

[0051] S300. Annealing treatment: The hot-rolled TA15 titanium alloy was annealed by first raising the muffle furnace from room temperature to 650°C, then placing the hot-rolled TA15 titanium alloy in and holding it for 30 min, followed by air cooling to room temperature, to obtain a three-peak microstructure consisting of 7.84% equiaxed α phase (4.55 μm), 71.37% acicular α phase (0.09 μm) and 20.79% β phase.

[0052] Figure 4 SEM image of the near-α-type TA15 titanium alloy with a trimodal microstructure prepared in this embodiment. Figure 2 As can be seen in (a), the content of the equiaxed α phase decreases significantly after the annealing temperature is reduced. Figure 2 As shown in (b), after annealing at 650℃ for 30 min, the acicular α phase appears as very fine needles. The size and volume fraction of both the equiaxed α phase and the acicular α phase have a significant impact on the strength and plasticity of TA15 titanium alloy.

[0053] The TA15 titanium alloy prepared in this comparative example has a tensile strength of 1183.7 MPa, a plasticity of 8.53%, and a strength-ductility product of 10096.961 MPa·.

[0054] Performance testing To test its mechanical properties, the TA15 titanium alloy treated in Example 1 and Comparative Example 1 was subjected to a room temperature tensile test.

[0055] Figure 5 The stress-strain diagrams for Example 1 and Comparative Example 1 after hot rolling and hot rolling + short-time annealing are shown.

[0056] from Figure 5 As can be seen, the elongation of TA15 titanium alloy increased by 45.23% after annealing, while the strength decreased by only 6.28%. This is because the size and volume fraction of equiaxed α phase and acicular α phase were controlled after annealing. The increase in the volume fraction and size of the equiaxed α phase both promoted the increase in elongation, while the finer acicular α phase allowed TA15 titanium alloy to retain high strength, ultimately achieving a good balance between strength and plasticity.

[0057] It should be noted that the specific parameters or reagents in the above embodiments are specific or preferred embodiments under the concept of the present invention, and not limitations thereof; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

Claims

1. A method for preparing a TA15 titanium alloy with a trimodal microstructure, characterized in that, Including the following steps: S100. Heat treatment: Heat the TA15 titanium alloy to 10℃~40℃ below the β transformation point, hold at the temperature, and then cool to obtain the heat-treated TA15 titanium alloy. S200. Hot rolling deformation: The heat-treated TA15 titanium alloy is hot rolled, and the hot pressing temperature is within the α+β two-phase temperature range to obtain a TA15 titanium alloy with a bimodal structure. S300. Short-time annealing: Annealing TA15 titanium alloy with bimodal structure to obtain TA15 titanium alloy with trimodal structure.

2. The preparation method according to claim 1, characterized in that, In step S100, the heat preservation time is 0.5-2 hours.

3. The preparation method according to claim 1, characterized in that, In step S100, the heating rate is 5℃ / min-15℃ / min.

4. The preparation method according to claim 1, characterized in that, In step S200, the hot rolling process is carried out by multi-pass unidirectional rolling, with a deformation of 12-15% per pass, and the heat treatment is carried out in the furnace for 2-10 minutes between passes.

5. The preparation method according to claim 4, characterized in that, In step S200, the total deformation is 40%-60%.

6. The preparation method according to claim 1, characterized in that, In step S300, the parameters for the annealing process are: Heat to 650℃-850℃ at a rate of 5℃ / min-15℃ / min, and anneal for 20 min-40 min.

7. A TA15 titanium alloy with a trimodal microstructure, characterized in that, It is prepared using the preparation method described in any one of claims 1-6.

8. The TA15 titanium alloy with a trimodal microstructure according to claim 7, characterized in that, The TA15 titanium alloy comprises the following chemical composition by weight percentage: Al 5.5%-7.0%； V 0.8%-2.5； Zr 1.0%-2.5； Mo 0.5%-2.0%; Si 0.05%-0.15%; Fe 0-0.005%; The balance consists of Ti and impurities.

9. The application of a TA15 titanium alloy with a trimodal microstructure as described in any one of claims 8-9 in the manufacture of aerospace structural components.

10. A method for improving the strength-ductility balance of TA15 titanium alloy, characterized in that, The TA15 titanium alloy is subjected to the hot rolling deformation and short-time annealing steps of the preparation method according to any one of claims 1-6, so that the TA15 titanium alloy obtains a three-peak structure composed of equiaxed α phase, acicular α phase and β phase.

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