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

Abstract

The application discloses a kind of high tough impact-resistant titanium alloy and preparation method, application, belong to titanium alloy component design and processing technical field.The titanium alloy includes: Al 4.2%~4.8%, Mo 1.8%~2.2%, V 1.0%~1.2%, Nb 7.3%~7.9% by mass percentage, and the balance is Ti and inevitable impurities.After the above component design, it makes that α / β phase interface mismatch degree δ≤4.5%.The application is based on the "low mismatch phase interface multiscale α phase coordination" regulation idea, utilizes low mismatch α / β phase interface coordination deformation, improves alloy toughness, improves strength by nanometer secondary α phase dispersion precipitation, can realize the synergistic promotion of titanium alloy high strength, high toughness and impact resistance simultaneously, successfully overcome existing structural titanium alloy strength-fracture toughness, strength-impact performance inverted relationship.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy composition design and processing technology, specifically relating to a high-strength, high-toughness, and impact-resistant titanium alloy, its preparation method, and its applications. Background Technology

[0002] Titanium alloys, due to their high specific strength, excellent corrosion resistance, good high-temperature performance, and outstanding biocompatibility, have become the preferred material for key structural components in aerospace, marine engineering, weaponry, and biomedicine. With the increasing demands for lightweight and high reliability in high-end equipment, titanium alloys need to maintain high strength while possessing good plasticity, fracture toughness, and impact toughness—that is, achieving a synergistic improvement in strength and toughness. However, existing conventional titanium alloys and most high-strength titanium alloys generally suffer from the technical challenge of "inverted strength-fracture-toughness" and "inverted strength-impact performance": after increasing strength through traditional alloying methods, the alloy's plasticity, fracture toughness, and impact energy often decrease significantly, making it difficult to meet the stringent requirements of high damage tolerance and impact resistance for deep-sea equipment and critical aerospace components; traditional titanium alloys have a large α / β phase interface mismatch, which easily leads to elastic strain and dislocation pile-up at the phase interface, resulting in stress concentration and early crack initiation, limiting the development of plasticity and toughness; although existing titanium alloys have good room-temperature plasticity, the matching level of strength and toughness is poor, and the impact resistance is still insufficient. Therefore, how to significantly improve fracture toughness and impact toughness while maintaining high strength, and break the inverse relationship between strength and toughness, has become a core technical problem that urgently needs to be solved. Summary of the Invention

[0003] To address the technical bottleneck of the difficulty in synergistically improving the strength, toughness, and impact resistance of existing titanium alloys, this invention provides a high-strength, high-toughness, and impact-resistant titanium alloy, its preparation method, and its applications. This invention employs a novel approach of "low mismatch interface - multi-scale α-phase synergy" control. By optimizing the alloy composition and preparation process, a low-mismatch α / β phase interface is constructed. Combined with forging and toughening heat treatment, the microstructure characteristics are controlled, enabling efficient and coordinated deformation of the α and β phases, thereby significantly improving the alloy's overall mechanical properties.

[0004] The first objective of this invention is to provide a high-strength, high-toughness, and impact-resistant titanium alloy, which, by mass percentage, is composed of the following elements: Al 4.2%–4.8%, Mo 1.8%–2.2%, V 1.0%–1.2%, Nb 7.3%–7.9%, with the balance being Ti and unavoidable impurity elements, totaling 100%.

[0005] In a preferred embodiment of the present invention, the high-strength, high-toughness, and impact-resistant titanium alloy, by mass percentage, comprises the following elements: Al 4.5%, Mo 2.0%, V 1.1%, Nb 7.6%, with the balance being Ti and unavoidable impurity elements. This high-strength, high-toughness, and impact-resistant titanium alloy with the Ti-4.5Al-2Mo-1.1V-7.6Nb composition further achieves a low mismatch design at the α / β phase interface, with a calculated mismatch degree δ as low as 3.91%.

[0006] More preferably, in the high-strength, high-toughness, and impact-resistant titanium alloy, the Al equivalent is <5.0% and the Mo equivalent is 4.5% to 6.0%.

[0007] As a preferred embodiment of the present invention, the microstructure of the high-strength, tough and impact-resistant titanium alloy is a multi-scale structure, including primary lamellar α phase, nanoscale secondary α phase and residual β phase, and the phase interface mismatch degree δ between the α phase and the β phase is ≤4.5%.

[0008] This invention also provides a method for preparing the high-strength, high-toughness, and impact-resistant titanium alloy, comprising the following steps: According to the elemental composition of high-strength, tough, and impact-resistant titanium alloy, the raw materials are smelted and ingots are prepared. The ingot is forged to obtain a basket structure, thus obtaining a forged billet; The forged billet is solution treated in the two-phase region to form a basketweave microstructure containing primary lamellar α phase and β matrix, and then aged to form a multi-scale microstructure containing primary lamellar α phase, nanoscale secondary α phase and residual β phase, thus obtaining the high-strength, tough and impact-resistant titanium alloy.

[0009] In a preferred embodiment of the present invention, the ingot is forged in the β single-phase region at 150°C to 200°C above the phase transformation point. The forged billet is heated to 940°C to 970°C and held for 90 to 120 minutes, and then subjected to two upsetting and two drawing forgings with a forging ratio of 4 to 6. The billet after the second forging is heated to 920°C to 950°C and held for 90 to 120 minutes, and then subjected to drawing forging with a forging ratio of 3 to 5. After forging, the billet is water-cooled to obtain a basket web structure and thus a forged billet.

[0010] More preferably, the phase transformation point of the ingot is 910℃±10℃. This phase transformation point is determined by metallographic method.

[0011] In a preferred embodiment of the present invention, the solution treatment temperature is 840℃~880℃, and the holding time is 1 hour~2.5 hours. By changing the solution temperature 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.

[0012] In a preferred embodiment of the present invention, the aging treatment temperature is 480℃~620℃, and the holding time is 4 hours~6 hours. 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.

[0013] In a preferred embodiment of the present invention, the smelting is carried out by three vacuum self-consuming arc smelting processes, the solution treatment is followed by air cooling, and the aging treatment is followed by air cooling.

[0014] The present invention also provides an application of the high-strength, high-toughness, and impact-resistant titanium alloy described above in the manufacture of aerospace components or deep-sea equipment components.

[0015] The design principle of this invention, a high-strength, tough, and impact-resistant titanium alloy, is as follows: To achieve the aforementioned goals of "low mismatch and high strength and toughness," this invention constructs a Ti-Al-Mo-V-Nb pentagonal alloy system by adding low-mismatch Nb, medium-mismatch Mo, and V elements to the Ti-Al binary alloy. Al acts as the α-phase stabilizing element, primarily strengthening the α-phase through solid solution. Mo, Nb, and V act as β-phase stabilizing elements, primarily strengthening and stabilizing the β-phase through solid solution. Mo and V together refine the grains and enhance the solid solution strengthening effect, resulting in an alloy with both high strength and good plasticity. Nb and Mo stabilize the β-phase, refine the α-lamellae, reduce interfacial mismatch and interfacial energy, decrease dislocation slip resistance, and improve room temperature plasticity. This invention accurately calculates the lattice parameters and mismatch degrees of the α and β phases in Ti-Al-Mo-V-Nb pentagonal alloys with different component ratios using Pandat thermodynamic software and EMTO-CPA first-principles calculations.

[0016] This invention achieves a synergistic improvement in the strength and toughness of titanium alloys through composition design and microstructure control: First, by constructing a low mismatch α / β phase interface, the interfacial elastic strain energy and dislocation pile-up are reduced, dislocation crossing of the phase interface is promoted, interfacial stress is relieved, crack initiation is inhibited, and the plasticity and toughness of the alloy are improved; Second, nanoscale fine and dispersed secondary α phases are introduced into the β matrix, which significantly improve the strength of the alloy by hindering dislocation movement and generating precipitation strengthening, ultimately achieving synergistic optimization of strength and toughness.

[0017] This invention employs air cooling after heat treatment, rather than other cooling methods, based on the following principles: The moderate cooling rate provided by air cooling can suppress the continuous precipitation of secondary α phase at β grain boundaries, while simultaneously promoting high-density, dispersed nucleation of secondary α phase within β grains, resulting in nanoscale secondary α lamellae. Slow cooling conditions result in less undercooling, providing sufficient nucleation and growth time for phase transformation during heat treatment, promoting the full growth of the secondary α phase and leading to its coarsening. Conversely, rapid cooling, due to its faster cooling rate, results in a higher supersaturation of the β phase, leading to the precipitation of fine secondary α phases during subsequent aging. Simultaneously, high-temperature rapid cooling retains a large number of crystal defects (such as vacancies, dislocations, and subgrain boundaries) within the alloy. These defects can serve as non-uniform nucleation sites for the secondary α phase during aging, effectively increasing the nucleation rate. This results in finer and more numerous secondary α precipitates. The large amount of dispersed secondary α phase leads to stress concentration in the microstructure, thus reducing resistance to deformation and decreasing the alloy's plasticity.

[0018] Compared with the prior art, the present invention has the following technical effects: This invention proposes a novel approach to controlling the low-mismatch phase interface. Based on a Ti-Al binary alloy, low-mismatch Nb, medium-mismatch Mo, and V elements are added to construct a Ti-Al-Mo-V-Nb pentagonal alloy system. The Mo content is moderate, and the alloy consists of a mixture of α (hexagonal close-packed) and β (body-centered cubic) phases. Mo primarily plays a solid solution strengthening role and participates in reducing the mismatch degree at the two-phase interface (δ≤4.5%), making the interface smoother and reducing stress concentration. The low-mismatch α / β interface design is achieved through thermodynamic calculations and EMTO-CPA first-principles calculations. Multi-scale microstructure control is achieved by combining this with strengthening and toughening heat treatment. After alloy forging, a solution aging treatment is performed. The solution treatment in the two-phase region (840~880℃) retains approximately 20~30% of the primary α phase at this temperature. The aging treatment (480~620℃) promotes the precipitation of nanoscale secondary α phases within the β-transformation microstructure. The low mismatch interface reduces the elastic strain and dislocation density at the phase interface. The primary α phase and β matrix at the low mismatch interface can better coordinate deformation, improving the plasticity and toughness of the alloy. At the same time, the fine and dispersed nano-secondary α phase in the multi-scale structure effectively hinders dislocation movement and improves the strength of the alloy. This solves the technical problem that existing titanium alloys still have difficulty in achieving a balance between strength, fracture toughness and impact toughness.

[0019] The high-strength, high-toughness, and impact-resistant titanium alloy prepared by this invention can achieve a yield strength of 949 MPa and a fracture toughness of 117 MPa·m. 1 / 2 It possesses a medium-strength, ultra-high-toughness impact resistance with an impact energy of 68J; and a yield strength of 952MPa and a fracture toughness of 114MPa·m. 1 / 2With an impact energy of 56J, it boasts high strength and toughness, and its strength and toughness are superior to existing alloys such as TC4-ELI and TB6. The alloy's comprehensive mechanical properties are also superior to existing Ti80 and TC4, making it suitable for the preparation of key components in aerospace, deep-sea equipment, and other applications. Attached Figure Description

[0020] 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 1500x magnification, (b) is the microstructure at 5000x magnification, and (c) is the microstructure at 15000x magnification.

[0021] 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).

[0022] Figure 3 The images show the microstructure of the high-strength, tough, and impact-resistant titanium alloy prepared in Example 2 at different magnifications; where (a) is the microstructure at 1500x magnification, (b) is the microstructure at 5000x magnification, and (c) is the microstructure at 15000x magnification.

[0023] Figure 4 The experimental sample of high-strength, high-toughness, and impact-resistant titanium alloy fracture toughness prepared in Example 2 is shown in Figure (a) and the macroscopic fracture morphology (b).

[0024] Figure 5 The images show the microstructure of the high-strength, tough, and impact-resistant titanium alloy prepared in Example 3 at different magnifications; where (a) is the microstructure at 1500x magnification, (b) is the microstructure at 5000x magnification, and (c) is the microstructure at 15000x magnification.

[0025] 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).

[0026] 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 1500x magnification, (b) is the microstructure at 5000x magnification, and (c) is the microstructure at 15000x magnification.

[0027] 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).

[0028] Figure 9The 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 1500x magnification, (b) is the microstructure at 5000x magnification, and (c) is the microstructure at 15000x magnification.

[0029] 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).

[0030] Figure 11 The results show the performance comparison between the titanium alloy prepared in Example 3 and Comparative Example 1 and existing alloys. Detailed Implementation

[0031] Based on the toughening concept of "low mismatch and multi-scale phase interface regulation", this invention provides the following specific implementation method: Using Pandat thermodynamic software and the EMTO-CPA calculation method, a Ti-Al-Mo-V-Nb pentagonal alloy system with a mismatch degree of about 4% at the α / β phase interface (β phase transformation point 910℃±10℃) was designed by selectively adding low mismatch element Nb and medium mismatch elements Mo and V into the Ti-Al matrix.

[0032] After the ingots with the above-mentioned composition are melted three times by vacuum self-consuming electric arc melting, the ingots are forged in the β single-phase region 150℃~200℃ above the phase transformation point. The billet after forging is heated to 940℃~970℃ and held for 90min~120min, and then subjected to two upsetting and two drawing forging with a forging ratio of 4~6. The billet after the second forging is heated to 920℃~950℃ and held for 90min~120min, and then subjected to drawing forging with a forging ratio of 3~5. After forging, the billet is water-cooled to obtain a basket structure and thus a forged billet.

[0033] Subsequently, heat treatment of the α+β two-phase region is carried out: solution treatment at 840~880℃ for 1 to 2.5 hours followed by air cooling, so that about 20% to 30% of the primary α phase is retained in the alloy (to coordinate plastic deformation). The primary α phase can increase crack propagation resistance and improve toughness. Then, aging treatment at 480~620℃ for 4 to 6 hours followed by air cooling is carried out to promote the precipitation of high-density, fine and dispersed secondary α lamellae in the β transformation structure, thereby significantly increasing the α / β phase interface, shortening the dislocation slip length, and finally forming a multi-scale structure with "low mismatch interface".

[0034] In this structure, the low mismatch interface effectively reduces the elastic strain and dislocation pile-up at the phase interface, which is conducive to the dislocation crossing the α / β interface along the parallel slip system, alleviating stress concentration and thus improving fracture toughness. Furthermore, the primary micron-scale α phase can deform in coordination with the β matrix, ensuring the plasticity and toughness of the alloy, while the secondary nanoscale α lamellae can effectively hinder dislocation movement and improve strength.

[0035] 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.

[0036] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0037] Example 1 A high-strength, high-toughness, and impact-resistant titanium alloy By mass percentage, the high-strength, high-toughness, and impact-resistant titanium alloy is composed of the following elements: Al 4.5%, Mo 2.1%, V 1.0%, Nb 7.7%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.34% and the Mo equivalent is 4.86%.

[0038] The preparation method of 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.

[0039] 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 consumable arc melting processes, and the phase transformation point of the ingot was determined to be ~908℃ using metallographic methods.

[0040] Step 3, Forging: The ingot obtained in Step 2 is forged at 1060℃. The billet after forging is heated to 940℃ and held for 90 minutes. It is then subjected to two upsetting and two drawing forgings with a forging ratio of 5. The billet after the second forging is heated to 930℃ and held for 120 minutes. It is then subjected to drawing forging with a forging ratio of 3. After forging, it is water-cooled to obtain a basket structure and a forged billet.

[0041] Step 4, Toughening heat treatment: The forging billet obtained in step 3 is solution treated at 878℃, held for 1 hour and then air-cooled. Then, it is aged at 520℃, held for 5 hours and then air-cooled to obtain a high-strength, tough and impact-resistant titanium alloy.

[0042] 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 The fracture toughness test samples and macroscopic fracture morphology of the alloy after heat treatment are shown in the figure. Figure 2 As shown.

[0043] Example 2 A high-strength, high-toughness, and impact-resistant titanium alloy By mass percentage, the high-strength, high-toughness, and impact-resistant titanium alloy is composed of the following elements: Al 4.6%, Mo 2.1%, V 1.0%, Nb 7.8%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.36% and the Mo equivalent is 4.83%.

[0044] The preparation method of 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.

[0045] 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 ~910℃ using metallographic methods.

[0046] Step 3, Forging: The ingot obtained in Step 2 is forged at 1060℃. The billet after forging is heated to 950℃ and held for 100 minutes. It is then subjected to two upsetting and two drawing forgings with a forging ratio of 5. The billet after the second forging is heated to 940℃ and held for 100 minutes. It is then subjected to drawing forging with a forging ratio of 4. After forging, it is water-cooled to obtain a basket structure and a forged billet.

[0047] Step 4, Toughening heat treatment: The forging billet obtained in step 3 is solution treated at 848℃, held for 1.5 hours and then air-cooled. Then, it is aged at 530℃, held for 5 hours and then air-cooled to obtain a high-strength, tough and impact-resistant titanium alloy.

[0048] 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 3 α s The fracture toughness test samples and macroscopic fracture morphology of the alloy after heat treatment are shown in the figure. Figure 4 As shown.

[0049] Example 3 A high-strength, high-toughness, and impact-resistant titanium alloy By mass percentage, the high-strength, high-toughness, and impact-resistant titanium alloy is composed of the following elements: Al 4.5%, Mo 2.0%, V 1.1%, Nb 7.6%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.41% and the Mo equivalent is 4.79%.

[0050] The preparation method of 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.

[0051] 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 ~912℃ using metallographic methods.

[0052] Step 3, Forging: The ingot obtained in Step 2 is forged at 1080℃. The billet after forging is heated to 945℃ and held for 120 minutes. It is then subjected to two upsetting and two drawing forgings with a forging ratio of 6. The billet after the second forging is heated to 935℃ and held for 120 minutes. It is then subjected to drawing forging with a forging ratio of 5. After forging, it is water-cooled to obtain a basket structure and a forged billet.

[0053] Step 4, Toughening heat treatment: The forging billet obtained in step 3 is solution treated at 848℃, held for 2.5h and then air-cooled. Then, it is aged at 570℃, held for 5h and then air-cooled to obtain a high-strength, tough and impact-resistant titanium alloy.

[0054] Microstructure of high-strength, tough, and impact-resistant titanium alloys, such as Figure 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 in the figure. Figure 6 As shown.

[0055] Example 4 A high-strength, high-toughness, and impact-resistant titanium alloy By mass percentage, the high-strength, high-toughness, and impact-resistant titanium alloy is composed of the following elements: Al 4.4%, Mo 2.0%, V 1.1%, Nb 7.5%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.35% and the Mo equivalent is 4.85%.

[0056] The preparation method of 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 -3The 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 ~909℃ using metallographic methods.

[0057] Step 3, Forging: The ingot obtained in Step 2 is forged at 1080℃. The billet after forging is heated to 960℃ and held for 100 minutes. It is then subjected to two upsetting and two drawing forgings with a forging ratio of 6. The billet after the second forging is heated to 940℃ and held for 100 minutes. It is then subjected to drawing forging with a forging ratio of 3. After forging, it is water-cooled to obtain a basket structure and a forged billet.

[0058] Step 4, Toughening heat treatment: The forging billet obtained in step 3 is solution treated at 848℃, held for 1 hour and then air-cooled. Then, it is aged at 610℃, held for 5 hours and then air-cooled to obtain a high-strength, tough 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 The fracture toughness test samples and macroscopic fracture morphology of the alloy after heat treatment are shown in the figure. Figure 8 As shown.

[0060] Example 5 A high-strength, high-toughness, and impact-resistant titanium alloy By mass percentage, the high-strength, high-toughness, and impact-resistant titanium alloy is composed of the following elements: Al 4.4%, Mo 2.1%, V 1.1%, Nb 7.9%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.38% and the Mo equivalent is 4.82%.

[0061] The preparation method of 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 ~911℃ using metallographic methods.

[0062] Step 3, Forging: The ingot obtained in Step 2 is forged at 1080℃. The billet after forging is heated to 955℃ and held for 90 minutes. It is then subjected to two upsetting and two drawing forgings with a forging ratio of 5. The billet after the second forging is heated to 945℃ and held for 90 minutes. It is then subjected to drawing forging with a forging ratio of 3. After forging, it is water-cooled to obtain a basket structure and a forged billet.

[0063] Step 4, Toughening heat treatment: The forging billet obtained in step 3 is solution treated at 878℃, held for 1 hour and then air-cooled. Then, it is aged at 550℃, held for 5 hours and then air-cooled to obtain a high-strength, tough and impact-resistant titanium alloy.

[0064] 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 in the figure. Figure 10 As shown.

[0065] Example 6 A high-strength, high-toughness, and impact-resistant titanium alloy By mass percentage, the high-strength, high-toughness, and impact-resistant titanium alloy is composed of the following elements: Al 4.8%, Mo 2.2%, V 1.2%, Nb 7.9%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.34% and the Mo equivalent is 4.86%.

[0066] The preparation method of 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.

[0067] 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 consumable arc melting processes, and the phase transformation point of the ingot was determined to be ~908℃ using metallographic methods.

[0068] Step 3, Forging: The ingot obtained in Step 2 is forged at 1060℃. The billet after forging is heated to 970℃ and held for 120 minutes. It is then subjected to two upsetting and two drawing forgings with a forging ratio of 5. The billet after the second forging is heated to 950℃ and held for 120 minutes. It is then subjected to drawing forging with a forging ratio of 3. After forging, it is water-cooled to obtain a basket structure and a forged billet.

[0069] Step 4, Toughening heat treatment: The forging billet obtained in step 3 is solution treated at 840℃, held for 2.5h and then air-cooled. Then, it is aged at 480℃, held for 6h and then air-cooled to obtain a high-strength, tough and impact-resistant titanium alloy.

[0070] Example 7 A high-strength, high-toughness, and impact-resistant titanium alloy By mass percentage, the high-strength, high-toughness, and impact-resistant titanium alloy is composed of the following elements: Al 4.2%, Mo 1.8%, V 1.0%, Nb 7.3%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.34% and the Mo equivalent is 4.86%.

[0071] The preparation method of 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.

[0072] 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 -3The 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 consumable arc melting processes, and the phase transformation point of the ingot was determined to be ~908℃ using metallographic methods.

[0073] Step 3, Forging: The ingot obtained in Step 2 is forged at 1060℃. The billet after forging is heated to 940℃ and held for 100 minutes. It is then subjected to two upsetting and two drawing forgings with a forging ratio of 5. The billet after the second forging is heated to 920℃ and held for 100 minutes. It is then subjected to drawing forging with a forging ratio of 3. After forging, it is water-cooled to obtain a basket structure and a forged billet.

[0074] Step 4, Toughening heat treatment: The forging billet obtained in step 3 is solution treated at 880℃, held for 1 hour and then air-cooled. Then, it is aged at 620℃, held for 4 hours and then air-cooled to obtain a high-strength, tough and impact-resistant titanium alloy.

[0075] The misfit degree of the high-strength, high-toughness, and impact-resistant titanium alloys prepared in Examples 1 to 7 was calculated. The misfit degree was calculated as shown in equation (1), where a α and a β The lattice parameters of the two phases are shown in Table 1. The lattice parameters were obtained by selective electron diffraction using transmission electron microscopy (TEM) and compared with the results of first-principles calculations (EMTO-CPA).

[0076] (1) Table 1. Misfit degree of high-strength, high-toughness, and impact-resistant titanium alloys prepared in Examples 1 to 7 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 7 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.

[0077] The tensile properties, fracture toughness, and impact toughness of the high-strength, high-toughness, and impact-resistant titanium alloys prepared in Examples 1 to 7 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.

[0078] Table 2 Mechanical properties of the high-strength, high-toughness, and impact-resistant titanium alloys prepared in Examples 1 to 7 As can be seen from Table 2, the high-strength, high-toughness, and impact-resistant titanium alloys prepared in Examples 1 to 7 all exhibit excellent matching of strength and fracture toughness at room temperature.

[0079] Comparative Example 1 A titanium alloy, by mass percentage, is composed of the following elements: Al 4.5%, Mo 2.1%, V 1.0%, Nb 7.7%, with the balance being Ti and unavoidable impurity elements, totaling 100%; and the Al equivalent is 4.34% and the Mo equivalent is 4.86%.

[0080] The preparation method of titanium alloy is as follows: Step 1, Ingredients: Ingredients are prepared according to the elemental composition of the 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.

[0081] 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 consumable arc melting processes, and the phase transformation point of the ingot was determined to be ~908℃ using metallographic methods.

[0082] Step 3, Forging: The ingot obtained in Step 2 is forged at 1060℃. The billet after forging is heated to 940℃ and held for 100 minutes. It is then subjected to two upsetting and two drawing forgings with a forging ratio of 5. The billet after the second forging is heated to 930℃ and held for 100 minutes. It is then subjected to drawing forging with a forging ratio of 3. After forging, it is water-cooled to obtain a basket structure and a forged billet.

[0083] Step 4, Toughening heat treatment: The forging billet obtained in step 3 is solution treated at 878℃, held for 1 hour and then water cooled. Then, it is aged at 520℃, held for 5 hours and then air cooled to obtain titanium alloy.

[0084] The mechanical properties of the titanium alloy prepared in Comparative Example 1 were measured as follows: yield strength YS = 1145 MPa, tensile strength UTS = 1282 MPa, and elongation EI = 2.3%. Since this alloy has almost no plasticity, it cannot be used in practical applications.

[0085] Meanwhile, the existing alloys TC4-ELI (Ti–6Al–4V), TB6 (Ti–10V–2Fe–3Al), Ti80 (Ti-6Al-3Nb-2Zr-1Mo), TC4 (Ti–6Al–4V), TC21 (Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.2Si), Ti-11V (Ti-8Al-1Mo-1V), Ti17 (Ti-5Al-2Sn-2Zr-4Mo-4Cr), and BT22 (Ti-5Al-5Mo-5V-1Cr-1Fe) were compared with the alloy provided in Example 3 of this invention (labeled as Ti-4.5Al-2Mo-1.1V-7.6Nb). The results are shown in Table 3. Figure 11 As shown.

[0086] Table 3 Comparison of Alloy Properties Table 3 shows that, at the same strength level, the Ti-4.5Al-2Mo-1.1V-7.6Nb alloy has higher fracture toughness. Figure 11 The diagram illustrates the strength-toughness distributions of various typical commercial and research titanium alloys. The blue dashed line represents the conventional performance range of existing titanium alloys, exhibiting a "strength-toughness inversion" relationship. The alloy prepared in this invention falls outside this conventional range, achieving a yield strength of 99–120 MPa while maintaining a yield strength of 800–952 MPa. 1 / 2 The high fracture toughness achieves synergistic optimization of strength and toughness.

[0087] 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.

[0088] 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 high-strength, high-toughness, and impact-resistant titanium alloy, characterized in that, The high-strength, high-toughness, and impact-resistant titanium alloy is composed of the following elements by mass percentage: Al 4.2%–4.8%, Mo 1.8%–2.2%, V 1.0%–1.2%, Nb 7.3%–7.9%, with the balance being Ti and unavoidable impurity elements.

2. The high-strength, high-toughness, and impact-resistant titanium alloy according to claim 1, characterized in that, The high-strength, high-toughness, and impact-resistant titanium alloy is composed of the following elements by mass percentage: Al 4.5%, Mo 2.0%, V 1.1%, Nb 7.6%, with the balance being Ti and unavoidable impurity elements.

3. The high-strength, high-toughness, and impact-resistant titanium alloy according to claim 1 or 2, characterized in that, The microstructure of the high-strength, tough, and impact-resistant titanium alloy is a multi-scale structure, including primary lamellar α phase, nanoscale secondary α phase and residual β phase, and the phase interface mismatch degree between the α phase and the β phase is δ≤4.5%.

4. A method for preparing the high-strength, high-toughness, and impact-resistant titanium alloy according to claim 1 or 2, characterized in that, Includes the following steps: According to the elemental composition of high-strength, tough, and impact-resistant titanium alloy, the raw materials are smelted and ingots are prepared. The ingot is forged to obtain a basket structure, thus obtaining a forged billet; The forged billet is solution treated in the two-phase region to form a basketweave microstructure containing primary lamellar α phase and β matrix, and then aged to form a multi-scale microstructure containing primary lamellar α phase, nanoscale secondary α phase and residual β phase, thus obtaining the high-strength, tough and impact-resistant titanium alloy.

5. The method for preparing the high-strength, high-toughness, and impact-resistant titanium alloy according to claim 4, characterized in that, The specific method of forging is as follows: The ingot is forged in the β single-phase region at 150℃~200℃ above the phase transformation point. The forged billet is heated to 940℃~970℃ and held for 90min~120min, and then subjected to two upsetting and two drawing forgings with a forging ratio of 4~6. The billet after the second forging is heated to 920℃~950℃ and held for 90min~120min, and then subjected to drawing forging with a forging ratio of 3~5. After forging, the billet is water-cooled to obtain a basket web structure and thus a forged billet.

6. The method for preparing the high-strength, high-toughness, and impact-resistant titanium alloy according to claim 5, characterized in that, The phase transformation point of the ingot is 910℃±10℃.

7. The method for preparing the high-strength, high-toughness, and impact-resistant titanium alloy according to claim 4, characterized in that, The solution treatment temperature is 840℃~880℃, and the holding time is 1 hour~2.5 hours.

8. The method for preparing the high-strength, high-toughness, and impact-resistant titanium alloy according to claim 4, characterized in that, The aging treatment temperature is 480℃~620℃, and the holding time is 4 hours~6 hours.

9. The method for preparing the high-strength, high-toughness, and impact-resistant titanium alloy according to claim 4, characterized in that, The smelting process employs three vacuum self-consuming arc smelting processes, followed by air cooling after the solution treatment and air cooling after the aging treatment.

10. The application of the high-strength, high-toughness, and impact-resistant titanium alloy according to any one of claims 1 to 3 in the manufacture of aerospace components or deep-sea equipment components.

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