2GPa ultrahigh-strength titanium alloy and preparation method thereof

Abstract

The invention relates to a 2GPa ultrahigh-strength titanium alloy, which comprises the following chemical components in percentage by weight: 5.0-7.0% of Al, 5.0-7.0% of Cu, 5.0-7.0% of Ni, 5.0-7.0% of Ti, and the balance of Ti. 3.0 to 5.0 parts of V; 3.0 to 7.0 parts of Cu; 1.2 to 2.8 parts of Ni; 0.2 to 1.8 parts of Co; 0.3 to 0.7 percent of Si; 0.15 to 0.35 part of O; and the balance of Ti. The preparation method of the 2GPa ultrahigh-strength titanium alloy comprises the following steps: smelting by adopting a consumable electrode vacuum furnace, and then forging a blank at the temperature of 1000 DEG C or above, so as to obtain the 2GPa ultrahigh-strength titanium alloy. According to the 2GPa ultrahigh-strength titanium alloy, equipment, a mold and a preparation process are simple; the microscopic structure of the 2GPa ultrahigh-strength titanium alloy is a multiphase core-shell nanostructure with the alpha grain size of 220-450 nm, the yield strength of the 2GPa ultrahigh-strength titanium alloy is 1450-2020 MPa, the tensile strength of the 2GPa ultrahigh-strength titanium alloy is 1490-2030 MPa, the ductility of the 2GPa ultrahigh-strength titanium alloy is 4-13%, and the U port impact energy of the 2GPa ultrahigh-strength titanium alloy is 6-20 J / cm < 2 >.

Description

Technical Field

[0001] The present invention relates to the technical field of the design, preparation and application of 2GPa ultra-high strength titanium alloy materials, and particularly relates to a 2GPa ultra-high strength titanium alloy and a preparation method thereof. Background Art

[0002] With the high strength, low density, excellent corrosion resistance and good biocompatibility of titanium alloys, they are widely used in important fields such as aerospace, biomedicine, petrochemical industry, automotive industry and marine engineering. With the rapid development of economic technology in recent years, it is necessary to develop new titanium alloy materials with higher strength, plasticity and toughness.

[0003] Existing studies have shown that refining the grain size can improve the strength of metal materials. At present, the preparation of ultrafine-grained metal materials is mainly achieved by severe plastic deformation (SPD) methods. Common severe plastic deformation methods include equal-channel angular pressing (ECAP), accumulative roll bonding (ARB), multi-directional forging (MF) and high-pressure torsion (HPT), etc. These methods all rely on high-power equipment and expensive molds, and the size of the prepared materials is also small, which cannot meet the needs of large-scale industrial production.

[0004] However, when the grain size of titanium alloy is refined to the nanoscale (below 100nm), the further refinement of the grain size has limited effect on the improvement of the material strength, so it is difficult for its strength to break through 2GPa. This is because in nanocrystalline metal materials, the high density of interfaces reduces the stability of the interfaces. At this time, the strength of the grain boundaries is lower than that of the grain interior. Refining the grain size means that the increase in the number of interfaces will cause the strength of the material to decrease. By adding alloying elements to form a multiphase core-shell nanostructure along the grain boundaries to strengthen the grain boundaries, it is expected to solve this problem and further improve the strength of titanium alloys.

[0005] Based on the above background, it is urgent to develop an ultra-high strength titanium alloy with ultrafine-grained structure and its low-cost and large-scale preparation method, so as to improve the comprehensive mechanical properties of titanium alloys and lay a new foundation for the further development of the titanium industry. Summary of the Invention

[0006] The present invention provides a 2GPa ultra-high strength titanium alloy. The key technology is that, by weight percentage, the chemical composition and its weight percentage of this titanium alloy meet the following requirements:

[0007] Al: 5.0 - 7.0; V: 3.0 - 5.0; Cu: 3.0 - 7.0; Ni: 1.2 - 2.8; Co: 0.2 - 1.8; Si: 0.3 - 0.7; O: 0.15 - 0.35; the balance is Ti.

[0008] The further preferably claimed technical content is as follows: By weight percentage, the chemical composition and its weight percentage of the 2GPa ultra-high strength titanium alloy meet the following requirements:

[0009] Al: 6.3 - 6.7; V: 4.2 - 4.7; Cu: 5.5 - 6.5; Ni: 2.2 - 2.6; Co: 1.2 - 1.6; Si: 0.55 - 0.65; O: 0.27 - 0.33; the balance is Ti; the content of impurity elements in the alloy shall meet the corresponding requirements in the national standard of "Titanium and Titanium Alloy Grades and Chemical Compositions Table".

[0010] The 2GPa ultra-high strength titanium alloy is Ti6Al4V5Cu2Ni1Co0.5Si0.25O.

[0011] The present invention also claims the preparation method of the aforementioned 2GPa ultra-high strength titanium alloy, and its technical key is:

[0012] The preparation method of the 2GPa ultra-high strength titanium alloy meets the following requirements: The chemical composition and its weight percentage of the raw materials meet the following requirements: Al: 5.0 - 7.0; V: 3.0 - 5.0; Cu: 3.0 - 7.0; Ni: 1.2 - 2.8; Co: 0.2 - 1.8; Si: 0.3 - 0.7; O: 0.15 - 0.35; the balance is Ti;

[0013] Use a vacuum consumable furnace for melting, and then forge the billet at a temperature above 1000°C to obtain the 2GPa ultra-high strength titanium alloy.

[0014] The initial structure of the hot-rolled billet is a martensite structure with ultra-fine laths. Hot-roll this structure in the (α + β + Ti5Si3) three-phase region at 770 - 850°C to obtain a nano-ultra-fine grain structure.

[0015] The rolling deformation amount of the hot-rolled billet is not less than 70%.

[0016] Quench the forged billet after holding it at a temperature above 1000°C for 1 - 3 hours to obtain a fully martensite structure.

[0017] After solution quenching the rolled-deformed material at 830 - 880°C, age it at 480°C for 2 hours.

[0018] The further preferred requirements are: the rolling deformation temperature is 820 - 840°C, the rolling deformation amount is not less than 80%, and the solution treatment temperature after rolling is 860 - 880°C.

[0019] The microstructure is a multiphase core-shell nanostructure with α grain sizes ranging from 220 to 450 nm, having a yield strength of 1450 - 2020 MPa, a tensile strength of 1490 - 2030 MPa, an elongation of 4 - 13%, and a U-notch impact energy of 6 - 20 J / cm 2 .

[0020] The preparation method of the 2GPa ultra-high strength titanium alloy can refine the width of martensite laths after quenching and obtain ultrafine lath martensite structure by adding Cu, Ni, Co, Si, and O elements to traditional TC4 titanium alloy. Using the above-mentioned ultrafine lath martensite as the initial structure, hot rolling is carried out on its blank in the (α + β + Ti5Si3) three-phase region at 770 - 850 °C to obtain a nano-ultrafine grain structure. During the rolling process, the deformation degree is not less than 70%. After solution quenching the rolled material at 830 - 880 °C, aging is carried out at 480 °C for 2 h.

[0021] To develop a 2GPa ultra-high strength titanium alloy material, the present invention designs and prepares an ultrafine-grained Ti6Al4V5Cu2Ni1Co0.5Si0.25O titanium alloy with a multiphase core-shell nanostructure. It will use the nanocrystalline structure to enhance its strength and use the multiphase core-shell nanostructure distributed along the grain boundaries to strengthen the grain boundaries, further enhancing the strength of the nanocrystalline titanium alloy. To achieve the preparation of the above-mentioned ultrafine-grained structure, the present invention adds Cu, Si, Ni, Co, and O elements to traditional TC4 titanium alloy, conducts solution treatment in the β single-phase region, and by means of rapid cooling during quenching, makes Cu, Ni, Co, Si, and O elements supersaturatedly dissolve in the matrix, thereby causing strong lattice distortion. The self-adaptation of the lattice distortion finally enables the material to obtain an ultrafine lath martensite structure after quenching. Subsequently, hot rolling deformation is carried out on this ultrafine lath martensite structure in the (α + β + Ti5Si3) three-phase region at 770 - 850 °C. The strain energy and interface energy stored in the martensite structure will provide a powerful driving force for the dynamic recrystallization of the α phase, thus greatly increasing the dynamic recrystallization nucleation rate. At the same time, during the hot rolling process, martensite will decompose into α′ → α + β + Ti5Si3, and the decomposition products β / Ti5Si3 phases can pin α grains and inhibit the coarsening growth of dynamic recrystallization nuclei, enabling the material to obtain an ultrafine-grained structure after deformation. To further enhance the strength of the material, the present invention conducts solution quenching treatment on the rolled titanium alloy, causing a large amount of β phase, Ti2Cu phase, Ti2Ni phase, Ti2Co phase, and Ti5Si3 to precipitate along the α grain boundaries, improving the strength of the grain boundaries of the ultrafine-grained structure. Through this treatment process, a 2GPa ultra-high strength Ti6Al4V5Cu2Ni1Co0.5Si0.25O titanium alloy can be finally prepared.

[0022] Different from the prior art, the titanium alloy provided by the present invention can prepare an ultrafine-grained and ultra-high-strength titanium alloy through conventional hot deformation without relying on high-power equipment and expensive molds.

[0023] The microstructure of the titanium alloy prepared by the present invention is a multiphase core-shell nanostructure with an α grain size of 220-450 nm, its yield strength is 1450-2020 MPa, the tensile strength is 1490-2030 MPa, the elongation is 4-13%, and the U-notch impact energy is 6-20 J / cm 2 。

[0024] The ultra-high-strength Ti6Al4V5Cu2Ni1Co0.5Si0.25O titanium alloy prepared by the present invention can be widely applied to many important fields such as aerospace, biomedicine, petrochemical industry, automobile industry and ocean engineering. Brief Description of the Drawings

[0025] Figure 1 SEM photograph of the titanium alloy forging blank after quenching in Example 7 of the present invention;

[0026] Figure 2 SEM photograph of the titanium alloy forging blank after quenching in Comparative Example 10 of the present invention;

[0027] Figure 3 SEM photograph of the titanium alloy in Example 7 of the present invention after hot rolling and solution treatment;

[0028] Figure 4 SEM photograph of the titanium alloy in Comparative Example 10 of the present invention after hot rolling. Detailed Description of the Invention

[0029] The present invention will be further described below in conjunction with the examples and the drawings of the specification, but is not limited thereto.

[0030] To make the purpose, technical solution and effect of the present application clearer and more definite, the following further describes the present application in detail with reference to the drawings and by way of examples.

[0031] A 2 GPa ultra-high-strength titanium alloy, the chemical composition of the titanium alloy is: Al: 5.0-7.0; V: 3.0-5.0; Cu: 3.0-7.0; Ni: 1.2-2.8; Co: 0.2-1.8; Si: 0.3-0.7; O: 0.15-0.35; the balance is Ti. The content of impurity elements in the alloy shall meet the corresponding requirements in the national standard of "Titanium and Titanium Alloy Grades and Chemical Composition Tables".

[0032] Please refer to Figures 1-2 , Figure 1 which is the SEM photograph of the titanium alloy forging blank after quenching in Example 5 of the present invention, Figure 2It is the SEM photograph of the titanium alloy forging blank after quenching in Comparative Example 10 of the present invention. It can be seen therefrom that by adding Cu, Ni, Co, Si, and O elements to the traditional TC4 titanium alloy, the size of the martensite laths after forging blank quenching can be reduced, and an ultrafine nanolath martensite structure can be obtained.

[0033] The structure after hot rolling is ultrafine nanocrystalline, and the β phase, Ti5Si3 phase, Ti2Ni phase, Ti2Co phase, and Ti2Cu phase are distributed along the grain boundaries.

[0034] The figure shows the structure of the titanium alloy after hot rolling and solution treatment in Example 7 of the present invention. It can be seen that the microstructure of the material is an ultrafine crystal structure, and a core-shell structure is formed at the α grain boundaries.

[0035] Figure 4 It is the SEM photograph of the titanium alloy after hot rolling in Comparative Example 10. It can be seen that the α grain size of the traditional TC4 titanium alloy after hot rolling is several micrometers, and the size of the β phase is also significantly larger than that of the titanium alloy provided by the present invention.

[0036] The following will illustrate and explain the present application through several specific examples and comparative examples, but should not be used to limit the scope of the present application.

[0037] Examples: Examples 1 to 9 are Ti6Al4V5Cu2Ni1Co0.5Si0.25O alloys smelted according to the chemical composition ranges provided by the present invention, and the contents of Al, V, Cu, Si, and O elements are gradually increased, and the corresponding preparation processes are also appropriately adjusted within the technical parameters specified by the present invention.

[0038] Comparative Examples: The chemical composition of Comparative Example 1 is lower than the lower limit of the chemical composition range provided by the present invention, and the chemical composition of Comparative Example 9 is higher than the upper limit of the chemical composition range provided by the present invention. By comparing with Example 1 and Example 9 respectively, the influence of chemical composition on the microstructure and properties of the titanium alloy is illustrated. The quenching temperature of the forging blank in Comparative Example 2 is lower than the temperature specified by the present invention. By comparing with Example 2, the influence of the quenching temperature of the forging blank on the microstructure and properties of the titanium alloy is illustrated. The cooling method after solution treatment of the forging blank in Comparative Example 3 is not quenching as specified by the present invention, but furnace cooling. By comparing with Example 3, the influence of the cooling method after solution treatment of the forging blank on the microstructure and properties of the titanium alloy is illustrated. The rolling deformation temperature of Comparative Example 4 is higher than the upper limit specified by the present invention, and the rolling deformation temperature of Comparative Example 5 is lower than the lower limit specified by the present invention. By comparing with Example 4 and Example 5 respectively, the influence of rolling temperature on the microstructure and properties of the titanium alloy is illustrated. The rolling deformation amount of Comparative Example 6 is lower than the lower limit of the deformation amount specified by the present invention. By comparing with Example 6, the influence of the deformation amount on the microstructure and properties of the titanium alloy is illustrated. The material in Comparative Example 7 is not subjected to solution quenching treatment after rolling. By comparing with Example 7, the influence of solution quenching on the microstructure and properties of the titanium alloy is illustrated. Comparative Example 8 is not subjected to aging treatment after solution quenching. By comparing with Example 8, the influence of aging on the microstructure and properties of the titanium alloy is illustrated. Comparative Example 10 is a commercial TC4 titanium alloy. By comparing with Examples 1-9 of the present invention, the advantages of the microstructure and properties of the titanium alloy provided by the present invention are illustrated.

[0039] Table 1 Chemical Compositions and Preparation Processes of Materials in Examples and Comparative Examples

[0040]

[0041] The preparation processes of each example and comparative example are as follows:

[0042] Example 1: The ingot is subjected to cogging forging at 1000 °C, and then water quenched to room temperature after holding at 1000 °C for 1 hour to obtain a martensite blank. The martensite blank is hot rolled at 770 °C with a rolling deformation amount greater than 70%. The rolled material is solution treated at 830 °C for 1 hour and then water quenched, and then aged at 480 °C for 2 hours.

[0043] Example 2: The ingot is subjected to cogging forging at 1000 °C, and then water quenched to room temperature after holding at 1000 °C for 1 hour to obtain a martensite blank. The martensite blank is hot rolled at 780 °C with a rolling deformation amount greater than 70%. The rolled material is solution treated at 840 °C for 1 hour and then water quenched, and then aged at 480 °C for 2 hours.

[0044] Example 3: The ingot was subjected to cogging forging at 1050 °C, and then water quenched to room temperature after holding at 1050 °C for 2 hours to obtain a martensite blank. The martensite blank was hot rolled at 790 °C with a rolling reduction of more than 70%. The rolled material was solution treated at 850 °C for 1 hour and then water quenched, followed by aging at 480 °C for 2 hours.

[0045] Example 4: The ingot was subjected to cogging forging at 1050 °C, and then water quenched to room temperature after holding at 1050 °C for 2 hours to obtain a martensite blank. The martensite blank was hot rolled at 800 °C with a rolling reduction of more than 80%. The rolled material was solution treated at 860 °C for 1 hour and then water quenched, followed by aging at 480 °C for 2 hours.

[0046] Example 5: The ingot was subjected to cogging forging at 1100 °C, and then water quenched to room temperature after holding at 1100 °C for 2 hours to obtain a martensite blank. The martensite blank was hot rolled at 810 °C with a rolling reduction of more than 80%. The rolled material was solution treated at 860 °C for 1 hour and then water quenched, followed by aging at 480 °C for 2 hours.

[0047] Example 6: The ingot was subjected to cogging forging at 1100 °C, and then oil quenched to room temperature after holding at 1100 °C for 2 hours to obtain a martensite blank. The martensite blank was hot rolled at 820 °C with a rolling reduction of more than 80%. The rolled material was solution treated at 860 °C for 1 hour and then water quenched, followed by aging at 480 °C for 2 hours.

[0048] Example 7: The ingot was subjected to cogging forging at 1150 °C, and then oil quenched to room temperature after holding at 1150 °C for 2 hours to obtain a martensite blank. The martensite blank was hot rolled at 830 °C with a rolling reduction of more than 80%. The rolled material was solution treated at 870 °C for 1 hour and then water quenched, followed by aging at 480 °C for 2 hours.

[0049] Example 8: The ingot was subjected to cogging forging at 1150 °C, and then oil quenched to room temperature after holding at 1150 °C for 2 hours to obtain a martensite blank. The martensite blank was hot rolled at 840 °C with a rolling reduction of more than 85%. The rolled material was solution treated at 880 °C for 1 hour and then water quenched, followed by aging at 480 °C for 2 hours.

[0050] Example 9: The ingot was subjected to cogging forging at 1150 °C, and then oil quenched to room temperature after holding at 1150 °C for 3 hours to obtain a martensite blank. The martensite blank was hot rolled at 850 °C with a rolling reduction of more than 85%. The rolled material was solution treated at 880 °C for 1 hour and then water quenched, followed by aging at 480 °C for 2 hours.

[0051] Comparative Example 1: The ingot was subjected to cogging forging at 1000 °C, and then held at 1000 °C for 1 hour and water-quenched to room temperature to obtain a martensite blank. The martensite blank was hot-rolled at 770 °C with a rolling reduction of more than 70%. The rolled material was solution-treated at 830 °C for 1 hour and then water-quenched, and then aged at 480 °C for 2 hours.

[0052] Comparative Example 2: The ingot was subjected to cogging forging at 1000 °C, and then held at 800 °C for 1 hour and water-quenched to room temperature to obtain a martensite blank. The martensite blank was hot-rolled at 780 °C with a rolling reduction of more than 70%. The rolled material was solution-treated at 840 °C for 1 hour and then water-quenched, and then aged at 480 °C for 2 hours.

[0053] Comparative Example 3: The ingot was subjected to cogging forging at 1050 °C, and then held at 1050 °C for 2 hours and slowly cooled in the furnace to room temperature. The blank was hot-rolled at 790 °C with a rolling reduction of more than 70%. The rolled material was solution-treated at 850 °C for 1 hour and then water-quenched, and then aged at 480 °C for 2 hours.

[0054] Comparative Example 4: The ingot was subjected to cogging forging at 1050 °C, and then held at 1050 °C for 2 hours and water-quenched to room temperature to obtain a martensite blank. The martensite blank was hot-rolled at 680 °C with a rolling reduction of more than 80%. The rolled material was solution-treated at 860 °C for 1 hour and then water-quenched, and then aged at 480 °C for 2 hours.

[0055] Comparative Example 5: The ingot was subjected to cogging forging at 1100 °C, and then held at 1100 °C for 2 hours and water-quenched to room temperature to obtain a martensite blank. The martensite blank was hot-rolled at 950 °C with a rolling reduction of more than 80%. The rolled material was solution-treated at 860 °C for 1 hour and then water-quenched, and then aged at 480 °C for 2 hours.

[0056] Comparative Example 6: The ingot was subjected to cogging forging at 1100 °C, and then held at 1100 °C for 2 hours and oil-quenched to room temperature to obtain a martensite blank. The martensite blank was hot-rolled at 820 °C with a rolling reduction of 40%. The rolled material was solution-treated at 860 °C for 1 hour and then water-quenched, and then aged at 480 °C for 2 hours.

[0057] Comparative Example 7: The ingot was subjected to cogging forging at 1150 °C, and then held at 1150 °C for 2 hours and oil-quenched to room temperature to obtain a martensite blank. The martensite blank was hot-rolled at 830 °C with a rolling reduction of more than 80%. Finally, the material was aged at 480 °C for 2 hours.

[0058] Comparative Example 8: The ingot was subjected to cogging forging at 1150 °C, and then held at 1150 °C for 2 hours and oil-quenched to room temperature to obtain a martensite blank. The martensite blank was hot-rolled at 840 °C with a rolling reduction of more than 85%. The rolled material was solution-treated at 880 °C for 1 hour and then water-quenched.

[0059] Comparative Example 9: The ingot was subjected to cogging forging at 1150 °C, and then oil quenched to room temperature after holding at 1150 °C for 3 hours to obtain a martensite blank. The martensite blank was hot rolled at 850 °C with a rolling deformation of more than 85%. The rolled material was solution treated at 880 °C for 1 hour and then water quenched, and then aged at 480 °C for 2 hours.

[0060] Comparative Example 10: The ingot was subjected to cogging forging at 1100 °C, and then water quenched to room temperature after holding at 1100 °C for 2 hours to obtain a martensite blank. The martensite blank was hot rolled at 900 °C with a rolling deformation of more than 80%.

[0061] Another supplementary description is as follows:

[0062] 1. Microstructure characterization: The microstructure of the material was characterized by a TESCAN scanning electron microscope (SEM). After the SEM test specimens were mechanically ground and polished, they were etched with Kroll etching solution for 20 s to observe their microstructure morphology. The experimental results are as Figures 1-2 shown. The microstructure of the material was characterized by a Talos F200x transmission electron microscope (TEM). After the TEM test specimens were manually thinned to 50 nm, they were chemically double thinned in a 10 vol.% HClO4 + 90 vol.% C2H5OH solution. The voltage during thinning was set at 25 V and the temperature was -25 °C. The experimental results are as Figures 3-4 shown.

[0063] 2. Mechanical property testing: According to the GBT228.1-2010 standard, standard cylindrical tensile specimens were processed. Subsequently, the room temperature tensile properties of the material were tested using an Instron 8872 tensile testing machine. The crosshead displacement rate of the tensile test was 0.5 mm / min, and the average value of 3 measurements was taken as the tensile property of the material. The tensile strength, yield strength, and elongation are shown in Table 2. According to the GB / T 229-2020 standard, U-notch impact specimens with dimensions of 10 × 10 × 55 mm were processed, and the impact toughness of the material was tested using a HIT450P impact testing machine. The final test results were given as the average value of 3 measurements, as shown in Table 2.

[0064] Table 2 Microstructural characteristics and mechanical properties of the materials in the examples and comparative examples

[0065]

[0066] As can be seen from the results in Table 2, Examples 1 to 9 are all multi-phase core-shell nano-ultrafine grain structures, and they all have relatively high strength. As the contents of Al, V, Cu, Si, and O elements increase, the yield strength σ s and tensile strength σb are significantly improved, while the elongation δ and impact toughness α k gradually decrease.

[0067] The contents of Al, V, Cu, Si, and O in Comparative Example 1 are all lower than the lower limits specified in the present invention, which results in relatively large grains and significantly lower yield strength and tensile strength of the material than those in Example 1 of the present invention. The contents of Al, V, Cu, Si, and O in Comparative Example 9 are all higher than the upper limits specified in the present invention, and both its strength and plastic toughness are lower than those in Comparative Example 9 of the present invention.

[0068] The quenching temperature of the forging blank in Comparative Example 2 is lower than the temperature specified in the present invention, and its structure is a duplex structure, rather than the multi-phase core-shell nano-ultrafine grain structure in Example 2 of the present invention. Therefore, both its yield strength and tensile strength are significantly lower than those in Example 2 of the present invention.

[0069] The cooling method after solution treatment of the forging blank in Comparative Example 3 is not quenching as specified in the present invention, but furnace cooling, which results in large grain size of the prepared material. Therefore, both its yield strength and tensile strength are significantly lower than those in Example 3 of the present invention.

[0070] The rolling deformation temperature in Comparative Example 4 is higher than the upper limit specified in the present invention, and the rolling deformation temperature in Comparative Example 5 is lower than the lower limit specified in the present invention. They both obtain a basket-weave structure after rolling deformation, so their yield strength and tensile strength are significantly lower than those in Example 4 and Example 5 of the present invention.

[0071] The rolling deformation amount in Comparative Example 6 is lower than the lower limit of the deformation amount specified in the present invention, so a lamellar structure is obtained after deformation, rather than the multi-phase core-shell nano-ultrafine grain structure of the present invention. Therefore, both its yield strength and tensile strength are significantly lower than those in Example 6 of the present invention.

[0072] The material in Comparative Example 7 is not subjected to solution quenching treatment after rolling. Although its structure is a multi-phase core-shell nano-ultrafine grain structure, its strength is significantly lower than that in Example 7 of the present invention.

[0073] The material in Comparative Example 8 is only subjected to solution quenching treatment after rolling and not aged. Although its structure is a multi-phase core-shell nano-ultrafine grain structure, its yield strength is significantly lower than that in Example 8 of the present invention.

[0074] Comparative Example 10 is a commercial TC4 titanium alloy, and its microstructure is an ultrafine grain structure. By comparing with Examples 1-9 of the present invention, it can be seen that the strength of the material provided by the present invention is significantly higher than that of the commercial ultrafine grain TC4 titanium alloy.

[0075] The above are only the embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present application.

Claims

1. A 2GPa ultra-high strength titanium alloy, characterized in that: The chemical composition and weight percentage of the titanium alloy meet the following requirements: Al：5.0～7.0； V: 3.0~5.0; Cu: 3.0~7.0; Ni: 1.2~2.8; Co: 0.2~1.8; Si: 0.3~0.7; O: 0.15~0.35; the balance is Ti.

2. The 2 GPa ultra-high strength titanium alloy according to claim 1, characterized in that: The chemical composition and weight percentage of the titanium alloy meet the following requirements: Al: 6.3~6.7; V: 4.2~4.7; Cu: 5.5~6.5; Ni: 2.2~2.6; Co: 1.2-1.6; Si: 0.55-0.65; O: 0.27-0.33; the balance is Ti; The 2GPa ultra-high strength titanium alloy is Ti6Al4V5Cu2Ni1Co0.5Si0.25O.

3. The method for preparing the 2GPa ultra-high strength titanium alloy according to claim 1, characterized in that: The preparation method of the 2GPa ultra-high strength titanium alloy meets the following requirements: The chemical composition and weight percentage of the raw materials meet the following requirements: Al: 5.0-7.0; V: 3.0~5.0; Cu: 3.0~7.0; Ni: 1.2~2.8; Co: 0.2~1.8; Si: 0.3~0.7; O: 0.15~0.35; the balance is Ti; The 2 GPa ultra-high strength titanium alloy is obtained by melting in a vacuum consumable furnace and then forging the blank at above 1000°C.

4. The method for preparing the 2GPa ultra-high strength titanium alloy according to claim 3, characterized in that: The initial structure of the hot-rolled billet is a martensitic structure with ultrafine laths, which is hot-rolled in the (α+β+Ti5Si3) three-phase region at 770-850°C to obtain a nano-ultrafine grain structure.

5. The method for preparing the 2 GPa ultra-high strength titanium alloy according to claim 4, characterized in that: The rolling deformation of the hot rolled billet is not less than 70%.

6. The method for preparing the 2 GPa ultra-high strength titanium alloy according to claim 3, 4 or 5, characterized in that: The forging blank is kept at above 1000°C for 1 to 3 hours and then quenched to obtain a full martensitic structure.

7. The method for preparing the 2 GPa ultra-high strength titanium alloy according to claim 6, characterized in that: The rolled and deformed material is solution quenched at 830-880°C and then aged at 480°C for 2 hours.

8. The method for preparing the 2 GPa ultra-high strength titanium alloy according to claim 6, characterized in that: The rolling deformation temperature is 820-840°C, the rolling deformation amount is not less than 80%, and the solution treatment temperature after rolling is 860-880°C.

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