High-toughness impact-resistant titanium alloy and preparation method thereof

Abstract

The invention belongs to the technical field of titanium alloy component design and processing, and particularly relates to a high-toughness impact-resistant titanium alloy and a preparation method thereof. The high-toughness impact-resistant titanium alloy is prepared from the following elements in percentage by mass: 3.9%-4.8% of Al, 3.7%-4.6% of Mo, 2.0%-2.8% of V, 3.2%-4.3% of Nb and the balance of Ti and inevitable impurity elements, and the total percentage is 100%. According to the high-strength and high-toughness impact-resistant titanium alloy and the preparation method thereof, alloy components are optimized, beta-crossing forging and strengthening and toughening heat treatment are combined, the structure form of a basket is regulated, and an alpha phase and a beta phase are subjected to coordinated deformation, so that the high-strength and high-toughness impact-resistant titanium alloy with excellent strength, fracture toughness and impact performance is obtained, and the strength and toughness matching of the high-strength and high-toughness impact-resistant titanium alloy is superior to those of existing alloys such as TC4, TC4-ELI and Ti-80; the method has a wide application prospect in the fields of deep diving equipment, aerospace and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of titanium alloy composition design and processing, and particularly relates to a high-strength and high-toughness impact-resistant titanium alloy and a preparation method thereof. BACKGROUND

[0002] Titanium and titanium alloys have become indispensable key structural materials in the fields of aerospace, weapon equipment and marine engineering due to their small density, high specific strength, good toughness, corrosion resistance and high-temperature resistance, etc.

[0003] With the development of modern industrial equipment towards high performance, long service life and high reliability, more stringent requirements are put forward for the comprehensive mechanical properties of titanium alloys, especially in extreme service environments, the materials need to have high strength, high toughness and excellent impact resistance at the same time.

[0004] However, as the strength of titanium alloys increases, the toughness and impact resistance usually decrease. In the development of high-strength and high-toughness titanium alloys, the existing technology mainly realizes the balance of properties by adding multiple elements and controlling the microstructure through heat treatment and mechanical treatment. For example, patent application CN114752811A discloses a high-aluminum, high-molybdenum and high-zirconium ultra-high-strength and high-toughness titanium alloy with good additive manufacturing performance and a preparation method thereof. In this titanium alloy, the contents of molybdenum and zirconium are as high as 12.5%. The high alloying level not only significantly increases the smelting difficulty, but also leads to a sharp decrease in plasticity, which seriously restricts the processing and forming ability and engineering application prospect. At the same time, the titanium alloy contains a large amount of silicon element, which helps to improve the thermal stability and strength to a certain extent, but easily forms brittle silicides, resulting in a decrease in impact toughness, which is difficult to meet the requirements of the application scene with high impact toughness. SUMMARY

[0005] In order to solve the technical problem that the existing titanium alloy cannot balance the strength, toughness and impact resistance, the application provides a high-strength and high-toughness impact-resistant titanium alloy and a preparation method thereof. Based on the phase interface regulation strategy of "low mismatch-multiple scale coordination", the alloy composition and process are optimized to realize the low mismatch design of the α / β phase interface, and the net basket microstructure is regulated by combining cross-beta forging and strengthening and toughening heat treatment, so that the α phase and β phase can deform well, and the comprehensive mechanical properties of the alloy are changed.

[0006] The first object of the application is to provide a preparation method of a high-strength and high-toughness impact-resistant titanium alloy, which comprises the following steps: By mass percentage, high-strength, high-toughness, and impact-resistant titanium alloys are composed of the following elements: Al 3.9%–4.8%, Mo 3.7%–4.6%, V 2.0%–2.8%, Nb The alloy composition is 3.2%–4.3%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the phase interface mismatch degree δ between the α phase and the β matrix in the high-strength, tough, and impact-resistant titanium alloy is ≤5%. According to the elemental composition of the high-strength, tough, and impact-resistant titanium alloy, the raw materials are melted to prepare an ingot; the ingot is forged to obtain a forging; the forging is subjected to cross-β forging to obtain a basket structure, resulting in a forging blank; the forging blank is annealed in a two-phase region at 800℃–860℃ to form a basket structure containing primary lamellar α phase and β matrix, and then aged at 500℃–620℃ to form a basket structure containing primary lamellar α phase, nanoscale secondary α phase, and residual β phase, thus obtaining a high-strength, tough, and impact-resistant titanium alloy.

[0007] The design principle of this invention, a high-strength, tough, and impact-resistant titanium alloy, is as follows: This invention achieves a synergistic improvement in the strength and toughness of titanium alloys through microstructure control. The intrinsic mechanism of strengthening and toughening of titanium alloys is mainly based on the interaction between phase interfaces and dislocations: On the one hand, by constructing α / β phase interfaces with low mismatch, the elastic strain energy and dislocation pile-up density at the interface are effectively reduced. This facilitates the smooth passage of dislocations along cylindrical or basal slip systems through the phase interface, thereby significantly reducing the stress at the α / β phase interface, delaying crack initiation, and improving the plasticity and toughness of the titanium alloy. On the other hand, the introduction of fine, dispersed nanoscale secondary α phases into the β matrix can effectively hinder the movement of matrix dislocations, producing a significant precipitation strengthening effect, thereby improving the strength of the alloy.

[0008] To achieve the aforementioned goals of "low mismatch and high strength and toughness," this invention, based on a Ti-Al binary alloy, incorporates low-mismatch Nb and medium-mismatch Mo and V elements, constructing a Ti-Al-Mo-V-Nb pentagonal alloy system. Al, as the α-phase stabilizing element, primarily functions to strengthen the α-phase through solid solution. Mo, Nb, and V, as β-phase stabilizing elements, primarily function to strengthen and stabilize the β-phase through solid solution. Furthermore, this invention accurately simulates and calculates the lattice parameters and mismatch degrees of the α and β phases under different component ratios using Pandat thermodynamic software and EMTO-CPA first-principles calculations. Preferably, by mass percentage, the high-strength, high-toughness, and impact-resistant titanium alloy comprises the following elements: Al 4.2%–4.8%, Mo 3.7%–4.3%, V 2.0%–2.4%, Nb 3.7%–4.3%, with the balance being Ti and unavoidable impurity elements. More preferably, the high-strength, high-toughness, and impact-resistant titanium alloy is composed of the following elements by mass percentage: Al 4.5%, Mo 4.0%, V 2.2%, and Nb 4.0%. Under this Ti-4.5Al-4Mo-2.2V-4Nb composition, the high-strength, high-toughness, and impact-resistant titanium alloy achieves a low mismatch design at the α / β phase interface, with a calculated mismatch degree δ as low as 4.16%.

[0009] Preferably, in the high-strength, high-toughness, and impact-resistant titanium alloy, the Al equivalent is <6.0%, and the Mo equivalent is 6.0% to 7.5%.

[0010] Preferably, the specific method of the trans-β forging is as follows: The forging is deformed in the β single-phase region at 20°C to 40°C above the phase transformation point and the deformation ends in the α+β two-phase region at 20°C to 50°C below the phase transformation point. The deformation amount in the α+β two-phase region is controlled to be 30% to 40%. After forging, the forging is water-cooled to room temperature to obtain a basket structure and a forging billet.

[0011] The phase transformation point of the ingot was determined to be 890℃±10℃ by metallographic analysis, and then forging was performed. Preferably, the forging method is as follows: the ingot is forged at 150℃~200℃ above the phase transformation point, then forged again at 100℃~160℃ above the phase transformation point, and finally forged again at 60℃~100℃ above the phase transformation point.

[0012] Preferably, the annealing temperature is 800℃~860℃, and the holding time is 0.5 hours~1.5 hours; after the holding time, air cooling is used. By changing the annealing temperature and cooling rate in the two-phase region, the content, size, and morphology of the primary α phase in the basketweave structure can be controlled, and its low mismatch interface can be used to coordinate deformation, ensuring plasticity and toughness.

[0013] Preferably, the aging treatment temperature is 500℃~620℃, and the holding time is 4 hours~6 hours; after the holding time, air cooling is used. By adjusting the process parameters of low-temperature aging, the size and precipitation amount of the secondary α phase are controlled, and its dispersed distribution is used to effectively hinder dislocation movement, thereby significantly improving the strength.

[0014] A second objective of this invention is to provide a high-strength, high-toughness, and impact-resistant titanium alloy prepared by the above-described method.

[0015] Compared with the prior art, the present invention has the following technical effects: This invention constructs a Ti-Al-Mo-V-Nb pentagonal alloy system by incorporating low-mismatch Nb, medium-mismatch Mo, and V elements into a Ti-Al binary alloy. Through low-mismatch α / β interface design and multi-scale phase interface control, the elastic strain and dislocation density at the phase interface are reduced, improving toughness. Furthermore, by combining cross-β forging and toughening heat treatment, the basketweave microstructure is optimized, allowing the primary α phase at the low-mismatch interface to deform in coordination with the β matrix, thus improving the alloy's ductility and toughness. Simultaneously, the fine, dispersed nanoscale secondary α phase effectively hinders dislocation movement, enhancing the alloy's strength. This invention solves the technical problem of existing titanium alloys where strength, toughness, and impact performance are difficult to balance simultaneously.

[0016] The high-strength, high-toughness, and impact-resistant titanium alloy prepared by this invention can achieve a yield strength of 840 MPa and a fracture toughness of 119 MPa·m. 1 / 2 It possesses a medium-strength, ultra-high-toughness impact resistance with an impact energy of 78 J; and a yield strength of 1057 MPa and a fracture toughness of 100 MPa·m. 1 / 2 With an impact energy of 37J, it boasts a high strength and toughness, and its strength and toughness are superior to existing alloys such as TC4, TC4-ELI, and Ti-80. It has broad prospects for application in deep-sea equipment, aerospace, and other fields. Attached Figure Description

[0017] Figure 1 The images show the microstructure of the high-strength, high-toughness, and impact-resistant titanium alloy prepared in Example 1 at different magnifications; where (a) is the microstructure at 2000x magnification, (b) is the microstructure at 15000x magnification, and (c) is the microstructure at 30000x magnification.

[0018] Figure 2 The experimental sample of high-strength, high-toughness, and impact-resistant titanium alloy prepared in Example 1 is shown in Figure (a) and the macroscopic fracture morphology is shown in Figure (b).

[0019] Figure 3The images show the microstructure of the high-strength, high-toughness, and impact-resistant titanium alloy prepared in Example 2 at different magnifications; where (a) is the microstructure at 2000x magnification, (b) is the microstructure at 15000x magnification, and (c) is the microstructure at 30000x magnification.

[0020] Figure 4 The experimental sample of high-strength, high-toughness, and impact-resistant titanium alloy prepared in Example 2 is shown in Figure (a) and the macroscopic fracture morphology (b).

[0021] Figure 5 The images show the microstructure of the high-strength, high-toughness, and impact-resistant titanium alloy prepared in Example 3 at different magnifications; where (a) is the microstructure at 2000x magnification, (b) is the microstructure at 15000x magnification, and (c) is the microstructure at 30000x magnification.

[0022] Figure 6 The experimental sample of high-strength, high-toughness, and impact-resistant titanium alloy prepared in Example 3 is shown in Figure (a) and the macroscopic fracture morphology (b).

[0023] Figure 7 The images show the microstructure of the high-strength, high-toughness, and impact-resistant titanium alloy prepared in Example 4 at different magnifications; where (a) is the microstructure at 2000x magnification, (b) is the microstructure at 15000x magnification, and (c) is the microstructure at 30000x magnification.

[0024] Figure 8 The experimental sample of high-strength, high-toughness, and impact-resistant titanium alloy prepared in Example 4 is shown in Figure (a) and the macroscopic fracture morphology (b).

[0025] Figure 9 The images show the microstructure of the high-strength, high-toughness, and impact-resistant titanium alloy prepared in Example 5 at different magnifications; where (a) is the microstructure at 2000x magnification, (b) is the microstructure at 15000x magnification, and (c) is the microstructure at 30000x magnification.

[0026] Figure 10 The experimental sample of high-strength, high-toughness, and impact-resistant titanium alloy prepared in Example 5 is shown in Figure (a) and the macroscopic fracture morphology (b).

[0027] Figure 11 The images show the microstructure of the high-strength, tough, and impact-resistant titanium alloy prepared in Example 6 at different magnifications; where (a) is the microstructure at 2000x magnification, (b) is the microstructure at 15000x magnification, and (c) is the microstructure at 30000x magnification.

[0028] Figure 12The experimental sample of high-strength, high-toughness, and impact-resistant titanium alloy fracture toughness prepared in Example 6 is shown in Figure (a) and the macroscopic fracture morphology (b). Detailed Implementation

[0029] It should be noted that the strengthening and toughening of titanium alloys both originate from the interaction between dislocations and interfaces. Low-mismatch α / β interfaces can reduce the elastic strain and dislocation density at the phase interface, thereby facilitating the passage of dislocations along parallel slip systems through the α / β phase interface, reducing phase interface stress, and improving the alloy's fracture toughness. On the other hand, preparing multi-scale α lamellae can also enhance and toughen the alloy. Larger primary α phases can withstand more plastic deformation to ensure the alloy's ductility and toughness, while fine and dispersed secondary α phases can increase the α / β phase interface, reduce the β matrix dislocation slip length, and significantly improve the alloy's strength. Therefore, this invention proposes a new approach to low-mismatch, multi-scale phase interface control based on α / β phase interface stress, a key control factor affecting the fracture toughness of titanium alloys. Based on a Ti-Al binary alloy, low-mismatch Nb, medium-mismatch Mo, and V elements are added in combination. Using Pandat thermodynamic software and EMTO-CPA calculations, a low-mismatch multi-component α / β dual-phase titanium alloy composition design is achieved.

[0030] Meanwhile, to ensure better overall performance of the titanium alloy, this invention also optimizes the strength-toughness match of the titanium alloy by combining a reasonable hot working process with a toughening heat treatment. By combining the trans-β forging process with a toughening heat treatment, the microstructure of the basket is controlled, allowing the α and β phases to deform in a well-coordinated manner. This alters the overall mechanical properties of the alloy, overcomes the contradiction between strength and toughness in titanium alloys, and opens up a new path for the development of high-strength, high-toughness, and impact-resistant titanium alloys.

[0031] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0032] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0033] Example 1 A high-strength, high-toughness, and impact-resistant titanium alloy, by mass percentage, is composed of the following elements: Al 4.5%, Mo 4.0%, V 2.2%, Nb 4.0%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.21% and the Mo equivalent is 6.59%.

[0034] The preparation method of the high-strength, high-toughness, and impact-resistant titanium alloy is as follows: Step 1, Ingredients: Ingredients are prepared according to the elemental composition of the high-strength, tough and impact-resistant titanium alloy described above; wherein, Al is 99.9% pure Al, Mo is added with Ti-Mo master alloy, Nb is added with Ti-Nb master alloy, and V is added with Al-V master alloy.

[0035] Step 2, Melting: The Al block, Ti-Mo master alloy, Ti-Nb master alloy, and Al-V master alloy are mixed evenly, and then a melting electrode is prepared using a 200MN hydraulic press. Melting is carried out using a vacuum arc remelting furnace with a three-stage vacuum arc remelting method. First, the vacuum degree in the furnace is evacuated to 1×10⁻⁶. -2 ~1×10 -3 The arc was initiated using a low current of 50%–70% of the rated current. Subsequently, the current was gradually increased and transitioned to stable melting, maintaining current fluctuations ≤±5% to ensure uniform molten pool temperature and reduce compositional segregation. A homogeneous ingot was prepared through three vacuum arc melting processes, and the phase transformation point of the ingot was determined to be ~893℃ using metallographic methods.

[0036] Step 3, Forging: The ingot obtained in Step 2 is forged at 1040℃, then forged again at 990℃, and finally forged again at 950℃ to obtain the forging.

[0037] Step 4, β-forging: The forging obtained in Step 3 is subjected to β-forging. Deformation begins in the β single-phase region at a temperature of 915℃ and ends in the α+β two-phase region at a temperature of 870℃. The deformation amount in the α+β two-phase region is controlled to be ~30%. After forging, the forging is water-cooled to room temperature to obtain the forging billet.

[0038] Step 5, Toughening heat treatment: The forging billet obtained in step 4 is annealed in the two-phase region at 860℃, held for 1 hour and then air-cooled. Then, it is aged at 540℃, held for 5 hours and then air-cooled to obtain a high-strength, tough and impact-resistant titanium alloy.

[0039] Microstructure of high-strength, tough, and impact-resistant titanium alloys, such as Figure 1 As shown, the microstructure mainly consists of primary lamellar α phase, nanoscale secondary α phase, and residual β phase; the primary lamellar α phase corresponds to Figure 1 α p Nanoscale secondary α-corresponding Figure 1 α s Fracture toughness test samples and macroscopic fracture morphology of alloys after heat treatment are shown below. Figure 2 As shown.

[0040] Example 2 A high-strength, high-toughness, and impact-resistant titanium alloy, by mass percentage, is composed of the following elements: Al 4.2%, Mo 4.2%, V 2.0%, Nb 4.1%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.51% and the Mo equivalent is 6.58%.

[0041] The preparation method of the high-strength, high-toughness, and impact-resistant titanium alloy is as follows: Step 1, Ingredients: Ingredients are prepared according to the elemental composition of the high-strength, tough, and impact-resistant titanium alloy described above; wherein, Al is 99.9% pure Al block, Mo is added with Ti-Mo master alloy, Nb is added with Ti-Nb master alloy, and V is added with Al-V master alloy.

[0042] Step 2, Melting: The Al block, Ti-Mo master alloy, Ti-Nb master alloy, and Al-V master alloy are mixed evenly, and then a smelted electrode is prepared. Three melting processes are performed using a vacuum arc remelting furnace. First, the vacuum level inside the furnace is evacuated to 1×10⁻⁶. -2 ~1×10 -3 The arc was initiated using a low current of 50%–70% of the rated current. Subsequently, the current was gradually increased and transitioned to stable melting, maintaining current fluctuations ≤±5% to ensure uniform molten pool temperature and reduce compositional segregation. Finally, a homogeneous ingot was prepared through three vacuum arc melting processes, and the phase transformation point of the ingot was determined to be ~890℃ using metallographic methods.

[0043] Step 3, Forging: The ingot obtained in Step 2 is forged at 1060℃, then forged again at 1010℃, and finally forged again at 970℃ to obtain the forging.

[0044] Step 4, β-forging: The forging obtained in Step 3 is subjected to β-forging. Deformation begins in the β single-phase region at a temperature of 920℃ and ends in the α+β two-phase region at a temperature of 860℃. The deformation amount in the α+β two-phase region is controlled to be ~35%. After forging, the forging is cooled to room temperature by water to obtain a basket structure and a forging billet.

[0045] Step 5, Toughening heat treatment: The forging billet obtained in step 4 is annealed in the two-phase region at 830℃, held for 1 hour and then air-cooled. Then, it is aged at 540℃, held for 5 hours and then air-cooled to obtain a high-strength, tough and impact-resistant titanium alloy.

[0046] Microstructure of high-strength, tough, and impact-resistant titanium alloys, such as Figure 3 As shown, the microstructure mainly consists of primary lamellar α phase, nanoscale secondary α phase, and residual β phase; the primary lamellar α phase corresponds to Figure 3 α p Nanoscale secondary α-corresponding Figure 3α s The fracture toughness test samples and macroscopic fracture morphology of the alloy after heat treatment are shown below. Figure 4 As shown.

[0047] Example 3 A high-strength, high-toughness, and impact-resistant titanium alloy, by mass percentage, is composed of the following elements: Al 4.2%, Mo 3.9%, V 2.3%, Nb 3.8%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.31% and the Mo equivalent is 6.54%.

[0048] The preparation method of the high-strength, high-toughness, and impact-resistant titanium alloy is as follows: Step 1, Ingredients: Ingredients are prepared according to the elemental composition of the high-strength, tough, and impact-resistant titanium alloy described above; wherein, Al is 99.9% pure Al block, Mo is added with Ti-Mo master alloy, Nb is added with Ti-Nb master alloy, and V is added with Al-V master alloy.

[0049] Step 2, Melting: The Al block, Ti-Mo master alloy, Ti-Nb master alloy, and Al-V master alloy are mixed evenly, and then a smelted electrode is prepared. Three melting processes are performed using a vacuum arc remelting furnace. First, the vacuum level inside the furnace is evacuated to 1×10⁻⁶. -2 ~1×10 -3 The arc was initiated using a low current of 50%–70% of the rated current. Subsequently, the current was gradually increased and transitioned to stable melting, maintaining current fluctuations ≤±5% to ensure uniform molten pool temperature and reduce compositional segregation. Finally, a homogeneous ingot was prepared through three vacuum arc melting processes, and the phase transformation point of the ingot was determined to be ~895℃ using metallographic methods.

[0050] Step 3, Forging: The ingot obtained in Step 2 is forged at 1080℃, then forged again at 1030℃, and finally forged again at 970℃ to obtain the forging.

[0051] Step 4, β-forging: The forging obtained in Step 3 is subjected to β-forging. Deformation begins in the β single-phase region at a temperature of 930℃ and ends in the α+β two-phase region at a temperature of 865℃. The deformation amount in the α+β two-phase region is controlled to be ~35%. After forging, the forging is cooled to room temperature by water to obtain a basket structure and a forging billet.

[0052] Step 5, Toughening heat treatment: The forging billet obtained in step 4 is annealed in the two-phase region at 800℃, held for 1 hour and then air-cooled. Then, it is aged at 540℃, held for 5 hours and then air-cooled to obtain a high-strength, tough and impact-resistant titanium alloy.

[0053] Microstructure of high-strength, tough, and impact-resistant titanium alloys, such asFigure 5 As shown, the microstructure mainly consists of primary lamellar α phase, nanoscale secondary α phase, and residual β phase; the primary lamellar α phase corresponds to Figure 5 α p Nanoscale secondary α-corresponding Figure 5 α s The fracture toughness test samples and macroscopic fracture morphology of the alloy after heat treatment are shown below. Figure 6 As shown.

[0054] Example 4 A high-strength, high-toughness, and impact-resistant titanium alloy, by mass percentage, is composed of the following elements: Al 4.3%, Mo 3.8%, V 2.2%, Nb 4.0%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.20% and the Mo equivalent is 6.61%.

[0055] The preparation method of the high-strength, high-toughness, and impact-resistant titanium alloy is as follows: Step 1, Ingredients: Ingredients are prepared according to the elemental composition of the high-strength, tough and impact-resistant titanium alloy mentioned above; wherein, Al is Al block with a purity of 99.9%, Mo is added with Ti-Mo master alloy, Nb is added with Ti-Nb master alloy, and V is added with Al-V master alloy. Step 2, Melting: The Al block, Ti-Mo master alloy, Ti-Nb master alloy, and Al-V master alloy are mixed evenly, and then a melting electrode is prepared using a 200MN hydraulic press. Melting is performed three times using a vacuum arc remelting furnace. First, the vacuum level inside the furnace is evacuated to 1×10⁻⁶. -2 ~1×10 -3 The arc was initiated using a low current of 50%–70% of the rated current. Subsequently, the current was gradually increased and transitioned to stable melting, maintaining current fluctuations ≤±5% to ensure uniform molten pool temperature and reduce compositional segregation. Finally, a homogeneous ingot was prepared through three vacuum arc melting processes, and the phase transformation point of the ingot was determined to be ~891℃ using metallographic methods.

[0056] Step 3, Forging: The ingot obtained in Step 2 is forged at 1080℃, then forged again at 1040℃, and finally forged again at 980℃ to obtain the forging.

[0057] Step 4, β-forging: The forging obtained in Step 3 is subjected to β-forging. Deformation begins in the β single-phase region at a temperature of 930℃ and ends in the α+β two-phase region at a temperature of 856℃. The deformation amount in the α+β two-phase region is controlled to be ~40%. After forging, the forging is water-cooled to room temperature to obtain a basket structure and a forging billet.

[0058] Step 5, Strengthening and toughening heat treatment: The forging billet obtained in step 4 was annealed in the two-phase region at 860℃, held for 1 hour and then air-cooled. Then, it was aged at 580℃, held for 5 hours and then air-cooled to obtain a high-strength, high-toughness, and impact-resistant titanium alloy.

[0059] Microstructure of high-strength, tough, and impact-resistant titanium alloys, such as Figure 7 As shown, the microstructure mainly consists of primary lamellar α phase, nanoscale secondary α phase, and residual β phase; the primary lamellar α phase corresponds to Figure 7 α p Nanoscale secondary α-corresponding Figure 7 α s Fracture toughness test samples and macroscopic fracture morphology of alloys after heat treatment are shown below. Figure 8 As shown.

[0060] Example 5 A high-strength, high-toughness, and impact-resistant titanium alloy, by mass percentage, is composed of the following elements: Al 4.5%, Mo 3.8%, V 2.3%, Nb 4.1%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.21% and the Mo equivalent is 6.60%.

[0061] The preparation method of the high-strength, high-toughness, and impact-resistant titanium alloy is as follows: Step 1, Ingredients: Ingredients are prepared according to the elemental composition of the high-strength, tough and impact-resistant titanium alloy mentioned above; wherein, Al is Al block with a purity of 99.99%, Mo is added with Ti-Mo master alloy, Nb is added with Ti-Nb master alloy, and V is added with Al-V master alloy. Step 2, Melting: The Al block, Ti-Mo master alloy, Ti-Nb master alloy, and Al-V master alloy are mixed evenly, and then a melting electrode is prepared using a 200MN hydraulic press. Melting is performed three times using a vacuum arc remelting furnace. First, the vacuum level inside the furnace is evacuated to 1×10⁻⁶. -2 ~1×10 -3 The arc was initiated using a low current of 50%–70% of the rated current. Subsequently, the current was gradually increased and transitioned to stable melting, maintaining current fluctuations ≤±5% to ensure uniform molten pool temperature and reduce compositional segregation. Finally, a homogeneous ingot was prepared through three vacuum arc melting processes, and the phase transformation point of the ingot was determined to be ~892℃ using metallographic methods.

[0062] Step 3, Forging: The ingot obtained in Step 2 is forged at 1070℃, then forged again at 1020℃, and finally forged again at 960℃ to obtain the forging.

[0063] Step 4, β-forging: The forging obtained in Step 3 is subjected to β-forging. Deformation begins in the β single-phase region at a temperature of 920℃ and ends in the α+β two-phase region at a temperature of 852℃. The deformation amount in the α+β two-phase region is controlled to be ~40%. After forging, the forging is cooled to room temperature by water to obtain a basket structure and a forging billet.

[0064] Step 5, Toughening heat treatment: The forging billet obtained in step 4 is annealed in the two-phase region at 860℃, held for 1 hour and then air-cooled. Then, it is aged at 580℃, held for 5 hours and then air-cooled to obtain a high-strength, tough and impact-resistant titanium alloy.

[0065] Microstructure of high-strength, tough, and impact-resistant titanium alloys, such as Figure 9 As shown, the microstructure mainly consists of primary lamellar α phase, nanoscale secondary α phase, and residual β phase; the primary lamellar α phase corresponds to Figure 9 α p Nanoscale secondary α-corresponding Figure 9 α s The fracture toughness test samples and macroscopic fracture morphology of the alloy after heat treatment are shown below. Figure 10 As shown.

[0066] Example 6 A high-strength, high-toughness, and impact-resistant titanium alloy, by mass percentage, is composed of the following elements: Al 4.3%, Mo 4.2%, V 2.0%, Nb 4.1%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.22% and the Mo equivalent is 6.49%.

[0067] The preparation method of the high-strength, high-toughness, and impact-resistant titanium alloy is as follows: Step 1, Ingredients: Ingredients are prepared according to the elemental composition of the high-strength, tough and impact-resistant titanium alloy mentioned above; wherein, Al is Al block with a purity of 99.9%, Mo is added with Ti-Mo master alloy, Nb is added with Ti-Nb master alloy, and V is added with Al-V master alloy. Step 2, Melting: The Al block, Ti-Mo master alloy, Ti-Nb master alloy, and Al-V master alloy are mixed evenly, and then a melting electrode is prepared using a 200MN hydraulic press. Melting is performed three times using a vacuum arc remelting furnace. First, the vacuum level inside the furnace is evacuated to 1×10⁻⁶. -2 - 1×10 -3 The arc was initiated using a low current of 50%–70% of the rated current. Subsequently, the current was gradually increased and transitioned to stable melting, maintaining current fluctuations ≤±5% to ensure uniform molten pool temperature and reduce compositional segregation. Finally, a homogeneous ingot was prepared through three vacuum arc melting processes, and the phase transformation point of the ingot was determined to be ~898℃ using metallographic methods.

[0068] Step 3, Forging: The ingot obtained in Step 2 is forged at 1050℃, then forged again at 990℃, and finally forged again at 950℃ to obtain the forging.

[0069] Step 4, β-forging: The forging obtained in Step 3 is subjected to β-forging. Deformation begins in the β single-phase region at a temperature of 910℃ and ends in the α+β two-phase region at a temperature of 863℃. The deformation in the two-phase region is controlled to be ~35%. After forging, the forging is cooled to room temperature to obtain a basket structure and a forging billet.

[0070] Step 5, Toughening heat treatment: The forging billet obtained in step 4 is annealed in the two-phase region at 860℃, held for 1 hour and then cooled in the furnace with the door open. Then, it is aged at 540℃, held for 5 hours and then air-cooled to obtain a high-strength, tough and impact-resistant titanium alloy.

[0071] Microstructure of high-strength, tough, and impact-resistant titanium alloys, such as Figure 11 As shown, the microstructure mainly consists of primary lamellar α phase, nanoscale secondary α phase, and residual β phase; the primary lamellar α phase corresponds to Figure 11 α p Nanoscale secondary α-corresponding Figure 11 α s The fracture toughness test samples and macroscopic fracture morphology of the alloy after heat treatment are shown below. Figure 12 As shown.

[0072] The misfit degree of the high-strength, high-toughness, and impact-resistant titanium alloys prepared in Examples 1 to 6 was calculated. The misfit degree was calculated using the following formula:

[0073] in, For mismatch degree, These are the lattice parameters for the α phase; The lattice parameters for the β phase were obtained using transmission electron microscopy with selected electron diffraction and compared with first-principles calculations (EMTO-CPA). The results are shown in Table 1.

[0074] Table 1. Misfit degree of high-strength, high-toughness, and impact-resistant titanium alloys prepared in Examples 1 to 6 Table 1 shows that the calculated results of the mismatch degree of the high-strength, tough and impact-resistant titanium alloys prepared in Examples 1 to 6 are in good agreement with the measured values. The mismatch of the α / β phase interface in all examples is less than 4.5%, which is a low mismatch interface.

[0075] The tensile properties, fracture toughness, and impact toughness of the high-strength, high-toughness, and impact-resistant titanium alloys prepared in Examples 1 to 6 were tested according to GB / T 228.1-2010, GB / T 4161-2007, and GB / T 229-2020, respectively. The results are shown in Table 2. All mechanical properties listed above are average values ​​of test data from three parallel samples.

[0076] Table 2 Mechanical properties of high-strength, high-toughness, and impact-resistant titanium alloys prepared in Examples 1 to 6 As can be seen from Table 2, the high-strength, high-toughness, and impact-resistant titanium alloys prepared in Examples 1 to 6 all exhibit excellent matching of strength and fracture toughness at room temperature.

[0077] It should be noted that when numerical ranges are involved in this invention, it should be understood that the two endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described in this invention to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments, and all such changes and modifications fall within the scope of this invention.

[0078] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If these modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A method of producing a high toughness impact resistant titanium alloy, characterized by, The method comprises the following steps: The high-toughness impact-resistant titanium alloy is composed of the following elements in percentage by mass: Al 3.9%-4.8%, Mo 3.7%-4.6%, V 2.0%-2.8%, Nb 3.2%-4.3%, the balance of Ti and inevitable impurities, and the total is 100%; and the phase interface mismatch degree δ between the α phase and the β matrix in the high-toughness impact-resistant titanium alloy is ≤5%; The raw material is smelted according to the element composition of the high-toughness impact-resistant titanium alloy to prepare a ingot; The ingot is forged to obtain a forged piece; The forged piece is cross-β forged to obtain a net basket structure to obtain a forged blank; The forged blank is annealed in a two-phase zone to form a net basket structure containing primary lamellar α phase and β matrix, and then is aged to form a net basket structure containing primary lamellar α phase, nanometer secondary α phase and residual β phase, thereby obtaining the high-toughness impact-resistant titanium alloy.

2. The method of claim 1, wherein the high damage-tolerant impact-resistant titanium alloy is prepared by the steps of: The specific method of the cross-β forging is: The forged piece is deformed in the β single-phase zone 20-40 ℃ above the phase transition point, and is deformed in the α+β two-phase zone 20-50 ℃ below the phase transition point, and the deformation amount in the α+β two-phase zone is controlled to be 30%-40%, and the forged piece is water-cooled to room temperature after the forging is completed to obtain a net basket structure to obtain a forged blank.

3. The method of claim 1, wherein the high damage-tolerant impact-resistant titanium alloy is prepared by the steps of: The annealing temperature is 800-860 ℃, and the holding time is 0.5-1.5 hours.

4. The method of claim 1, wherein the high damage-tolerant impact-resistant titanium alloy is prepared by the steps of: The aging temperature is 500-620 ℃, and the holding time is 4-6 hours.

5. The method of claim 1, wherein the high damage-tolerant impact-resistant titanium alloy is prepared by the steps of: The forging method is as follows: the ingot is open-die forged at 150-200 ℃ above the phase transition point, then is two-fire forged at 100-160 ℃ above the phase transition point, and is three-fire forged at 60-100 ℃ above the phase transition point.

6. The method of producing a high tough impact resistant titanium alloy of claim 1, wherein, The phase transition point of the ingot is 890±10 ℃.

7. A high toughness impact resistant titanium alloy, characterized in that, The high-toughness impact-resistant titanium alloy is prepared by the method of any one of claims 1-6.

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