Method for improving mechanical property of titanium alloy plate and product

Abstract

The invention discloses a method for improving mechanical properties of a titanium alloy plate and a product, and belongs to the technical field of titanium alloy forging.The method comprises the following steps that a titanium alloy cast ingot is heated and subjected to upsetting and drawing cogging, then single-phase-region rapid small-deformation forging is conducted in a drawing-out mode, air cooling is conducted after drawing-out forging is conducted every time, and the titanium alloy plate is obtained; and finally, the titanium alloy plate is obtained through one-way rolling and annealing treatment. According to the method, through beta-phase region rapid small-deformation forging and whole-course air cooling, a specific structure is obtained, and the fracture toughness and the mechanical property of the Ti80 plate are improved. The normal mechanical property of the plate meets the requirement, and the transverse and rolling direction performance is obviously superior to that of a plate prepared through a traditional technology. And the preparation method is simple and convenient to popularize and apply.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium alloy forging, and in particular relates to a method and a product for improving the mechanical properties of a titanium alloy plate. Background Art

[0002] Ti80 titanium alloy (Ti-6Al-3Nb-2Zr-1Mo) is a near-alpha titanium alloy characterized by high strength, toughness, high pressure resistance, and corrosion resistance. This alloy is suitable for a wide range of applications, including deep-sea equipment, shipbuilding, marine engineering, military protection, and aerospace, and is particularly well-suited for critical structural components in extreme environments. Ti80 titanium alloy excels in applications such as marine protection, resisting seawater corrosion and withstanding high hydrostatic pressure. Its excellent overall mechanical properties enable it to meet the demands of long-term use in complex operating conditions. Compared to traditional materials, Ti80 significantly improves safety and reliability while reducing structural weight.

[0003] Currently, more stringent requirements are placed on the fracture toughness and impact resistance of Ti80 titanium alloy materials. Especially under extreme load conditions, instantaneous impact may cause severe plastic deformation or even fracture failure of the material, directly affecting the structural integrity and safety performance of the equipment, and posing a major challenge to engineering applications.

[0004] In existing technology, Ti80 titanium alloy sheets produced in practice exhibit significant differences in mechanical properties, such as fracture toughness and impact resistance, between manufacturers of the same model. Traditional material research approaches yield Ti80 sheets with good isotropy and excellent mechanical properties, but significantly lack fracture toughness and impact resistance.

[0005] Therefore, how to provide a preparation method for Ti80 titanium alloy plate that can significantly improve the fracture toughness and impact resistance of the plate while ensuring excellent mechanical properties and meeting standards is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention proposes a method and product for improving the mechanical properties of titanium alloy plates.

[0007] To achieve the above objectives, the present invention provides the following technical solutions: A method for improving the mechanical properties of a titanium alloy plate comprises the following steps: The titanium alloy ingot is heated and drawn into a blank, and then drawn into a blank by rapid small deformation forging in the single-phase region. After each drawing and forging, it is cooled by air cooling, and finally subjected to unidirectional rolling and annealing treatment to obtain a titanium alloy plate.

[0008] Beneficial effects: the present application makes the beta grain flatten through the way of fast small deformation elongation forging in the beta phase region, and makes the crystal orientation distribution of the material present directional arrangement, and obtains the organization presenting layer characteristics (the organization morphology and the crystal orientation both have significant directionality), the thickness of the titanium alloy plate prepared through the above steps and the single layer thickness of the layer organization are between 1200:5~1200:10, which can effectively improve the fracture toughness of the material, compared with the traditional preparation method, the titanium alloy plate provided by the present application can better resist the severe plastic deformation or even fracture failure caused by the instantaneous impact load when encountering the impact load, and significantly enhances the survivability and impact resistance of the used product.

[0009] In addition, the material is cooled in the whole process by the way of air cooling, which avoids the situation that the plasticity of the material is reduced due to the martensite generated by fast cooling and the poor mechanical properties of the material due to the coarse lamellar structure generated by slow cooling. The air cooling makes the material present fine lamellar structure after single-phase forging, and the material presents the uniform distribution characteristics of dense ellipsoidal alpha grains after two-phase forging, which improves the mechanical properties of the material.

[0010] Preferably, the titanium alloy is Ti80, wherein the metal elements include the following mass fractions of components: Al 5.5%~6.5%, Nb 2.5%~3.5%, Zr 1.5%~2.5%, Mo 0.5%~1.5%, and the balance is Ti and unavoidable impurities.

[0011] More preferably, the titanium alloy is obtained by mixing Ti, Al, Nb, Zr and Mo powders in a mass ratio of 88:6:3:2:1.

[0012] More preferably, the thickness of the titanium alloy ingot is 800~850mm.

[0013] Preferably, the titanium alloy ingot is prepared by 4 times of vacuum consumable arc melting, and the specific parameters of the 4 times of vacuum consumable arc melting are as follows: The current of the first time of vacuum consumable melting is 4kA~8kA, the vacuum degree is ≤5Pa, and the melting voltage is 25V~35V; The current of the second time of vacuum consumable melting is 8kA~12kA, the vacuum degree is ≤1Pa, and the melting voltage is 25V~35V; The current of the third time of vacuum consumable melting is 12kA~16kA, the vacuum degree is ≤0.8Pa, and the melting voltage is 25V~35V; The current of the fourth time of vacuum consumable melting is 16kA~25kA, the vacuum degree is ≤0.6Pa, and the melting voltage is 25V~35V.

[0014] Beneficial effects: 4 times vacuum self-consumption arc smelting improves the density and uniformity of ingot, reduces the inclusion content, eliminates defects, and improves the purity and toughness of the material.

[0015] Preferably, the upsetting and drawing breakdown temperature is 150-220 DEG C above the titanium alloy phase transition point, the final forging temperature is greater than or equal to 980 DEG C, and the total deformation is 50% of the thickness of the titanium alloy ingot.

[0016] More preferably, the upsetting and drawing breakdown temperature is 1200 DEG C, and the time is 8-10h.

[0017] More preferably, the thickness of the titanium alloy plate after upsetting and drawing breakdown is 400-425mm.

[0018] More preferably, air cooling is used after upsetting and drawing breakdown.

[0019] Beneficial effects: under the above conditions, the breakdown process can eliminate defects such as pores in the blank, and promote the refinement and homogenization of the structure. And, fast cooling is easy to generate martensite structure, which reduces the plasticity of the material, and slow cooling is easy to form coarse lamellar structure, which affects the mechanical properties of the material. Therefore, air cooling is used after upsetting and drawing breakdown to obtain fine lamellar structure.

[0020] Preferably, the temperature of the single-phase zone rapid small deformation forging is 100-180 DEG C above the titanium alloy phase transition point, and the final forging temperature is greater than or equal to 980 DEG C.

[0021] More preferably, the temperature of the single-phase zone rapid small deformation forging is 1120 DEG C, and the time is 4-6h.

[0022] Preferably, the number of single-phase zone rapid small deformation forging is twice, and the single reduction amount is not more than 25%, the single feeding time is not more than 5s, and the total deformation is not more than 25% of the thickness of the plate obtained in the previous step.

[0023] More preferably, the single feeding amount is 210-230mm, and the drawing length is about 3s / time.

[0024] More preferably, in the single-phase zone rapid small deformation forging, the thickness of the titanium alloy plate obtained after the first drawing is 300-320mm, and the thickness of the titanium alloy plate obtained after the second drawing is 225-240mm.

[0025] Beneficial effects: the drawing forging method in the application can inhibit the recrystallization process of the material, promote the flatness of the beta grains, obtain a layer band structure, and also use air cooling after forging to obtain a finer layer band lamellar structure.

[0026] Preferably, the number of single-phase zone rapid small deformation forging is twice, and the single reduction amount is not more than 25%, the single feeding time is not more than 5s, and the total deformation is not more than 25% of the thickness of the plate obtained in the previous step.

[0027] Beneficial effects: the forging method of texture control is adopted to flatten the beta grains, and the flattened beta structure is converted into lamellar alpha structure according to the Burgers orientation relationship.

[0028] Preferably, the bite rate of the single-direction rolling is 0.8-1.2 m / s, and the feeding rate is 3-4 m / s.

[0029] More preferably, the temperature of the single-direction rolling is 20-50℃ below the phase transition point, and the temperature at the end of each fire is ≥850℃.

[0030] More preferably, the thickness of the slab after the first single-direction rolling is 120-140 mm; the thickness of the slab after the second single-direction rolling is 60-80 mm; the thickness of the slab after the third single-direction rolling is 30-45 mm; the thickness of the slab after the fourth single-direction rolling is 15-25 mm; the thickness of the slab after the fifth single-direction rolling is 8-15 mm; and the thickness of the slab after the sixth single-direction rolling is 4-8 mm.

[0031] More preferably, air cooling is used after each rolling, and the slab is cut after every two fires to avoid the slab being too long and failing to be single-direction rolled at the appropriate temperature in time.

[0032] Beneficial effects: by using a certain deformation amount at the appropriate temperature range, the number and uniformity of nucleation can be significantly improved while promoting the spheroidization of alpha grains, and air cooling is also used after rolling to control the growth rate of alpha grains, promote the uniformity of the structure, and ensure the mechanical properties of the slab.

[0033] Preferably, the temperature of the annealing treatment is 850-900℃, and the time is 2-6h.

[0034] More preferably, the slab rolled for two fires is heated for 4-6h, the slab rolled for 3-4 fires is heated for 3-4h, and the slab rolled for 5-6 fires is heated for 2-3h.

[0035] Beneficial effects: the time required for the center temperature of the slab to reach the required temperature is different for slabs of different thicknesses, so the heating time is different, and a too long heating time is equivalent to aging treatment, which can cause the precipitation of phases in the internal structure of the slab, resulting in a decrease in toughness. A higher rolling rate can easily cause a higher dislocation density in the slab, and annealing is beneficial to eliminating residual stress and reducing dislocation density.

[0036] A titanium alloy slab prepared by the above method, wherein the thickness of the titanium alloy slab and the single-layer thickness of the lamellar structure are in a ratio of 1200:5-1200:10.

[0037] Beneficial effect: in this proportion, the laminated structure can 'disperse' the stress transmission in the impact direction, and form a certain resistance to stress transmission.

[0038] Compared with the prior art, the present application has the following advantages and technical effects: The present application can make the beta grains flatten and the crystal orientation directional arrangement by rapid small deformation elongation forging in the beta phase region, obtain a laminated structure, the thickness of the plate and the thickness of the laminated structure is about 1200:5~1200:10, which can improve the fracture toughness, enhance the product survival and impact resistance. At the same time, the present application avoids the generation of martensite by fast cooling and the generation of coarse lamellar structure by slow cooling, so that the material after single-phase forging presents a fine lamellar structure, and the material after two-phase forging presents a dense and equiaxial alpha grain distribution, which improves the mechanical properties. Moreover, the normal mechanical properties of the Ti80 plate prepared by the present application are weaker than the transverse and rolling directions, but meet the industry requirements, and the mechanical properties in the transverse and rolling directions are significantly higher than those of the plate prepared by the traditional process, and the impact resistance is excellent, which can be applied to the protection field of marine vessels. In addition, the method provided by the present application is simple and convenient for popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0039] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the present application illustrated in the drawings and their descriptions are used to explain the present application and are not intended to limit the present application. In the drawings: Figure 1 SEM scanning electron micrograph of the Ti80 plate obtained in Example 1; Figure 2 EBSD image of the Ti80 plate obtained in Example 1; Figure 3 SEM scanning electron micrograph of the Ti80 plate obtained in Example 2; Figure 4 EBSD image of the Ti80 plate obtained in Example 2; Figure 5 SEM scanning electron micrograph of the Ti80 plate obtained in Comparative Example 1; Figure 6 EBSD image of the Ti80 plate obtained in Comparative Example 1; Figure 7 SEM scanning electron micrograph of the Ti80 plate obtained in Comparative Example 2; Figure 8 EBSD image of the Ti80 plate obtained in Comparative Example 2; Figure 9 SEM scanning electron micrograph of the Ti80 plate obtained in Comparative Example 3; Figure 10 EBSD image of the Ti80 plate obtained in Comparative Example 3. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be apparently and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0041] In order to make the above-mentioned objects, features and advantages of the present application more apparent and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0042] Unless otherwise specified, the raw materials in the embodiments of the present application are obtained by market purchase; In the embodiments of the present application, the raw materials of the Ti80 ingot are only weighed according to the proportion of Ti:Al:Nb:Zr:Mo=88:6:3:2:1, and it is actually difficult to perfectly achieve the doping according to the proportion. The mass fraction of the actual raw materials fluctuates within the following ranges: Al is 5.5%~6.5%, Nb is 2.5%~3.5%, Zr is 1.5%~2.5%, Mo is 0.5%~1.5%, and the balance is Ti and unavoidable impurities.

[0043] Unless otherwise specified, the room temperature or normal temperature in the embodiments of the present application refers to 25±3℃.

[0044] Embodiment 1 A preparation method of a 60mm Ti80 plate, comprising the following steps: (1) blanking and arc melting Ti, Al, Nb, Zr and Mo powders are weighed according to the proportion of 88:6:3:2:1, and are uniformly doped. The uniformly Ti-6Al-3Nb-2Zr-1Mo powder is made into an electrode block by using 4 times of vacuum consumable arc melting (VAR), and is subjected to 4 times of vacuum consumable arc melting to ensure the uniformity of the Ti80 ingot organization, so as to be made into a Ti-6Al-3Nb-2Zr-1Mo ingot (Ti80 ingot) with a thickness of 800mm; In the 4 times of vacuum consumable arc melting (VAR), the current of the first time of vacuum consumable melting is 4kA, and the vacuum degree is less than or equal to 5Pa; the current of the second time of vacuum consumable melting is 8kA, and the vacuum degree is less than or equal to 1Pa; the current of the third time of vacuum consumable melting is 12kA, and the vacuum degree is less than or equal to 0.8Pa; the current of the fourth time of vacuum consumable melting is 16kA, and the vacuum degree is less than or equal to 0.6Pa; the melting voltage in the process of the four times of vacuum consumable melting is all 25V; (2) breaking down Put the Ti80 ingot obtained in step (1) into an electric heating furnace, heat for 8h after the furnace temperature is stabilized to 1200℃, then adopt upsetting and drawing to open the ingot for one time, in which the final forging temperature is greater than or equal to 980℃, the total deformation is 50% of the thickness of the ingot, air cooling after forging, and the material is trimmed and surface ground, finally obtaining a one-time open-killed Ti80 slab with a thickness of 400mm.

[0045] (3) single-phase zone one fire Put the one-time open-killed Ti80 slab obtained in step (2) into an electric heating furnace, heat for 6h after the furnace temperature is stabilized to 1150℃, then adopt drawing to fast and small deformation forging, in which the final forging temperature is greater than or equal to 980℃, the single feeding amount is 280mm, the drawing rate is required to be 3s / time, the total deformation of the single-phase zone one fire drawing is 25% of the thickness of the one-time open-killed Ti80 slab, air cooling after forging, and the material is trimmed and surface ground, obtaining a one-fire Ti80 slab with a thickness of 300mm.

[0046] (4) single-phase zone two fire Put the one-fire Ti80 slab obtained in step (3) into an electric heating furnace, heat for 4h after the furnace temperature is stabilized to 1120℃, then adopt drawing to fast and small deformation forging, in which the final forging temperature is greater than or equal to 980℃, the single feeding amount is 210mm, the drawing rate is required to be about 3s / time, the total deformation of the single-phase zone two fire drawing is 25% of the thickness of the one-fire Ti80 slab, air cooling after forging, and the material is trimmed and surface ground, finally obtaining a two-fire Ti80 slab with a thickness of 225mm.

[0047] (5) rolling one fire Put the two-fire Ti80 slab obtained in step (4) into an electric heating furnace, heat for 4h after the furnace temperature is stabilized to 950℃, then adopt rolling to one-way rolling, in which the end temperature of each one-way rolling is greater than 850℃, the biting rate is 0.8m / s, and the feeding rate is 3m / s, air cooling after the one-fire rolling, and the material is trimmed and surface ground, obtaining a one-time one-way rolled Ti80 slab with a thickness of 120mm; (6) rolling two fire Repeat step (5), air cooling after the two-fire rolling, and the material is trimmed and surface ground, obtaining a two-time one-way rolled Ti80 slab with a thickness of 60mm; (7) annealing The Ti80 slab billet subjected to two-pass unidirectional rolling is placed in a heating furnace, heated at 850℃ for 4h for annealing treatment, and then air-cooled after annealing, to obtain the Ti80 plate. The thickness of the obtained titanium alloy plate and the single-layer thickness of the lamellar structure are 1200:10.

[0048] Example 2 A method for preparing a Ti80 plate with a thickness of 7mm includes the following steps: (1) blanking and arc melting Ti, Al, Nb, Zr and Mo powders are weighed according to a ratio of 88:6:3:2:1, mixed uniformly, and then subjected to 4 times of vacuum arc melting (VAR) to form an electrode block, and 4 times of vacuum arc melting is performed to ensure the uniformity of the Ti80 ingot structure, to form a Ti-6Al-3Nb-2Zr-1Mo ingot (Ti80 ingot) with a thickness of 850mm. In the 4 times of vacuum arc melting (VAR), the current of the first time of vacuum arc melting is 8kA, and the vacuum degree is less than or equal to 5Pa; the current of the second time of vacuum arc melting is 12kA, and the vacuum degree is less than or equal to 1Pa; the current of the third time of vacuum arc melting is 16kA, and the vacuum degree is less than or equal to 0.8Pa; the current of the fourth time of vacuum arc melting is 25kA, and the vacuum degree is less than or equal to 0.6Pa; the melting voltage of the four times of vacuum arc melting is 25V. (2) blooming The Ti80 ingot obtained in step (1) is placed in an electric heating furnace, and after the temperature in the furnace is stabilized at 1200℃, it is heated for 10h, and then the ingot is subjected to one-pass blooming by upsetting and drawing, in which the final forging temperature is greater than or equal to 980℃, the total deformation is 50% of the thickness of the ingot, and after forging, air cooling is performed, and the material is trimmed and surface ground, to obtain a one-pass bloomed Ti80 slab billet with a thickness of 425mm.

[0049] (3) one-pass single-phase forging The one-pass bloomed Ti80 slab billet obtained in step (2) is placed in an electric heating furnace, and after the temperature in the furnace is stabilized at 1150℃, it is heated for 8h, and then the Ti80 slab billet is subjected to rapid small deformation forging by elongation, in which the final forging temperature is greater than or equal to 980℃, the single feed amount is 300mm, the elongation rate requires elongation of 3s per time, the total deformation of the single-phase one-pass elongation forging is 25% of the thickness of the one-pass bloomed Ti80 slab billet, and after forging, air cooling is performed, and the material is trimmed and surface ground, to obtain a one-pass forged Ti80 slab billet with a thickness of 319mm.

[0050] (4) two-pass single-phase forging The one-fire forged Ti80 slab obtained in step (3) is placed in an electric heating furnace, and after the temperature in the furnace is stabilized to 1120 °C, heating is performed for 6 h. The slab is then forged again by elongation, and in this process, the final forging temperature is equal to or greater than 980 °C, the single feeding amount is 210 mm, and the elongation rate is about 3 s / time. The total deformation of the single-phase zone two-fire forging is 25% of the thickness of the one-fire forged Ti80 slab. After forging, air cooling is performed, and the material is trimmed and surface ground. A two-fire forged Ti80 slab with a thickness of 239 mm is finally obtained.

[0051] (5) One-fire rolling The two-fire forged Ti80 slab obtained in step (4) is placed in an electric heating furnace, and after the temperature in the furnace is stabilized to 950 °C, heating is performed for 6 h. The slab is then unidirectionally rolled by rolling, and in this process, the end temperature of each fire of unidirectional rolling is greater than 850 °C, the bite-in rate is 0.8 m / s, and the feeding rate is 3 m / s. After one-fire rolling is completed, air cooling is performed, and the material is trimmed and surface ground. A one-fire unidirectional rolled Ti80 slab with a thickness of 135 mm is obtained. (6) Two-fire rolling Step (5) is repeated. After two-fire rolling is completed, air cooling is performed, and the material is trimmed and surface ground. A two-fire unidirectional rolled Ti80 slab with a thickness of 75 mm is obtained. (7) Three-fire rolling Step (6) is repeated. After three-fire rolling is completed, air cooling is performed, and the material is trimmed and surface ground. A three-fire unidirectional rolled Ti80 slab with a thickness of 40 mm is obtained. (8) Four-fire rolling Step (7) is repeated. After four-fire rolling is completed, air cooling is performed, and the material is trimmed and surface ground. A four-fire unidirectional rolled Ti80 slab with a thickness of 20 mm is obtained. (9) Five-fire rolling Step (8) is repeated. After five-fire rolling is completed, air cooling is performed, and the material is trimmed and surface ground. A five-fire unidirectional rolled Ti80 slab with a thickness of 12 mm is obtained. (10) Six-fire rolling Step (9) is repeated. After six-fire rolling is completed, air cooling is performed, and the material is trimmed and surface ground. A six-fire unidirectional rolled Ti80 slab with a thickness of 7 mm is obtained. (11) Annealing The six-fire unidirectional rolled Ti80 slab is placed in a heating furnace, heated at 900 °C for 3 h for annealing treatment, and then air cooled after annealing is completed. A Ti80 plate is obtained. The thickness of the obtained titanium alloy plate and the single-layer thickness ratio of the lamellar structure are 1200:5.

[0052] Comparative Example 1 Different from Example 1, steps (3) and (4) do not include rapid small deformation forging of the slab by means of elongation, which is a common forging process, and the remaining steps are the same as Example 1. Specifically, it includes the following steps: Steps (1) and (2) are the same as Example 1; (3) Single-phase zone first fire The first fire once-broken Ti80 slab obtained in step (2) is placed in an electric heating furnace, and after the furnace temperature is stabilized to 1150℃, it is heated for 6h, then the Ti80 slab is subjected to large deformation forging by means of elongation, and the total deformation of the single-phase zone first fire forging by means of elongation is 45% of the thickness of the first fire once-broken Ti80 slab. During this process, the final forging temperature is greater than or equal to 980℃, and after forging, air cooling is used, and the material is trimmed and surface ground, obtaining a first fire forged Ti80 slab with a thickness of 225mm.

[0053] (4) Single-phase zone second fire The first fire forged Ti80 slab obtained in step (3) is placed in an electric heating furnace, and after the furnace temperature is stabilized to 1120℃, it is heated for 4h, then the slab is subjected to large deformation forging by means of elongation again, and the total deformation of the single-phase zone first fire forging by means of elongation is 45% of the thickness of the first fire once-broken Ti80 slab. During this process, the final forging temperature is greater than or equal to 980℃, and after forging, air cooling is used, and the material is trimmed and surface ground, finally obtaining a second fire forged Ti80 slab with a thickness of 160mm.

[0054] (5) Rolling first fire The second fire forged Ti80 slab obtained in step (4) is placed in an electric heating furnace, and after the furnace temperature is stabilized to 950℃, it is heated for 6h, then the slab is subjected to unidirectional rolling, wherein the end temperature of each fire of unidirectional rolling is greater than 850℃, the biting rate is 0.8m / s, and the feeding rate is 3m / s. After the end of the first fire rolling, air cooling is used, and the material is trimmed and surface ground, obtaining a first fire unidirectional rolled Ti80 slab with a thickness of 100mm; (6) Rolling second fire Repeat step (5), after the end of the second fire rolling, air cooling is used, and the material is trimmed and surface ground, obtaining a second fire unidirectional rolled Ti80 slab with a thickness of 60mm; Steps (5)-(6) are similar to Example 1, and finally a Ti80 slab with a thickness of 60mm is obtained. The obtained titanium alloy plate has uniform structure.

[0055] It should be noted that, due to large deformation forging, the thickness of the plate in Comparative Example 1 cannot be exactly the same as that in Example 1, so the thickness of the plate rolled subsequently will also be reduced accordingly, but the overall processing technology is consistent with that of Example 1, i.e., the deformation amount, deformation rate and deformation temperature of single rolling of the plate are the same.

[0056] Comparative Example 2 Different from Example 1, in steps (3) and (4), air cooling is used after rapid small deformation forging, and the remaining steps are the same as those of Example 1. Specifically, the steps include the following steps: (3) Single-phase zone first fire The Ti80 plate blank in step (2) is placed in an electric heating furnace, and after the furnace temperature is stabilized to 1150℃, it is heated for 6h, and then the Ti80 plate blank is subjected to rapid small deformation forging by elongation, in which the final forging temperature is greater than or equal to 980℃, the single feeding amount is 280mm, the elongation rate is required to be elongated for 3s / time, the total deformation amount of the single-phase zone first fire elongation is 25% of the thickness of the first fire open blank Ti80 plate blank, and after forging, air cooling is used, and the material is trimmed and surface ground to obtain a first fire forged Ti80 plate blank with a thickness of 300mm.

[0057] (4) Single-phase zone second fire The first fire forged Ti80 plate blank obtained in step (3) is placed in an electric heating furnace, and after the furnace temperature is stabilized to 1120℃, it is heated for 4h, and then the plate blank is subjected to rapid small deformation forging by elongation, in which the final forging temperature is greater than or equal to 980℃, the single feeding amount is 210mm, the elongation rate is required to be elongated for about 3s / time, the total deformation amount of the single-phase zone second fire elongation is 25% of the thickness of the first fire forged Ti80 plate blank, and after forging, air cooling is used, and the material is trimmed and surface ground to obtain a second fire forged Ti80 plate blank with a thickness of 225mm.

[0058] Steps (5)-(7) are the same as those of Example 1, and finally a Ti80 plate blank with a thickness of 60mm is obtained. The microstructure of the obtained titanium alloy plate shows local lamellar characteristics, but the microstructure in most areas is still uniform.

[0059] Comparative Example 3 Different from Example 1, in steps (5) and (6), the bite rate of the rolling process is 0.5m / s, and the feeding rate is 2m / s, and in step (7), the heating time of annealing is 1.5h, and the remaining steps are the same as those of Example 1. Specifically, the steps include the following steps: Steps (1)-(4) are the same as those of Example 1; (5) Rolling first fire The forged Ti80 slab obtained in step (4) is placed in an electric heating furnace, and after the temperature in the furnace is stabilized to 950℃, heating is performed for 4h, and then the slab is unidirectionally rolled by rolling, wherein the end temperature of each rolling is greater than 850℃, the bite rate is 0.5m / s, the feeding rate is 2m / s, after the end of the first rolling, air cooling is performed, and the material is trimmed and surface ground, to obtain a Ti80 slab with a thickness of 120mm after the first unidirectional rolling; (6) Rolling the second time Step (5) is repeated, and after the end of the second rolling, air cooling is performed, and the material is trimmed and surface ground, to obtain a Ti80 slab with a thickness of 60mm after the second unidirectional rolling; (7) Annealing The Ti80 slab after the second unidirectional rolling is placed in a heating furnace, and annealing treatment is performed at 850℃ for 1.5h, and after the end of annealing, air cooling is performed, to obtain a Ti80 plate.

[0060] Technical effects: 1. Performance characterization The SEM scanning electron microscope images and EBSD images of the Ti80 slabs obtained in Examples 1-2 and Comparative Examples 1-3 are as shown in Figures 1-10 It can be seen that: the Ti80 plate obtained by the example of the present application presents obvious layer banding structure characteristics, and the thickness of the plate and the single layer thickness of the layer structure are between 1200:5~1200:10, and the plate obtained by the β single-phase region large deformation has uniform structure; the plate obtained by air cooling in each process step has the characteristics of local layer banding structure, but most of the regions are still uniform; the plate obtained by not increasing the rolling rate in the two-phase region (i.e. the bite rate is 0.5m / s, and the feeding rate is 2m / s) has sufficient dynamic recovery, larger grains, and smaller residual stress, so the annealing time is correspondingly reduced.

[0061] 2. Mechanical properties The mechanical properties of the Ti80 slabs obtained in Examples 1-2 and Comparative Examples 1-3 in the normal direction (ND), transverse direction (TD) and rolling direction (RD) are detected according to the GB / T228.1-2021 standard, and the impact toughness is detected by a drop hammer experiment, and a NI300C instrumented Charpy impact testing machine (which can simultaneously collect load-displacement curves, and is convenient for calculating energy distribution) is used, and the results are shown in Table 1: Table 1

[0062] As shown in Table 1, the mechanical properties of the Ti80 slabs obtained in the examples of the present invention in the normal direction (ND) are weaker than those in the transverse direction (TD) and rolling direction (RD). However, they meet industry requirements for mechanical properties of materials, and their mechanical properties in the TD and rolling directions are significantly higher than those of Ti80 sheets produced using conventional processes. Furthermore, the Ti80 slabs obtained in the examples of the present invention exhibit excellent impact toughness in the directions required for practical working conditions.

[0063] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for improving the mechanical properties of titanium alloy plates, characterized in that: The following steps are involved: The titanium alloy ingot is heated and formed into a blank by upsetting and drawing, and then a single-phase region rapid small deformation forging is performed by drawing. After each drawing and forging, air cooling is performed, and finally a titanium alloy plate is obtained by unidirectional rolling and annealing. The temperature of the upsetting and drawing process is 150-220°C above the phase transformation point of the titanium alloy, the final forging temperature is ≥980°C, and the total deformation is 50% of the thickness of the titanium alloy ingot; The temperature of the single-phase region rapid small deformation forging is 100-180°C above the phase transformation point of the titanium alloy, and the final forging temperature is ≥980°C; The single-phase region rapid small deformation forging is performed twice, with a single reduction not exceeding 25%, a single feed time not exceeding 5 seconds, and a total deformation not exceeding 25% of the thickness of the plate obtained in the previous step; The number of unidirectional rolling is 2-6 times, and the total deformation of a single fire is 40-45% of the thickness before deformation; The bite rate of the unidirectional rolling is 0.8-1.2 m / s, and the feed rate is 3-4 m / s.

2. The method for improving the mechanical properties of a titanium alloy sheet according to claim 1, characterized in that: The titanium alloy is Ti80.

3. The method for improving the mechanical properties of titanium alloy sheet according to claim 1, characterized in that: The titanium alloy ingot is prepared by four vacuum consumable arc melting processes, wherein the specific parameters of the four vacuum consumable arc melting processes are as follows: The current of the first vacuum consumable melting is 4kA~8kA, the vacuum degree is ≤5Pa, and the melting voltage is 25V~35V; The current of the second vacuum consumable melting is 8kA~12kA, the vacuum degree is ≤1Pa, and the melting voltage is 25V~35V; The current of the third vacuum consumable melting is 12kA~16kA, the vacuum degree is ≤0.8Pa, and the melting voltage is 25V~35V; The current of the fourth vacuum consumable melting is 16kA~25kA, the vacuum degree is ≤0.6Pa, and the melting voltage is 25V~35V.

4. The method for improving the mechanical properties of a titanium alloy sheet according to claim 1, wherein: The annealing treatment is performed at a temperature of 850-900° C. and for a time of 2-6 hours.

5. The titanium alloy sheet prepared by the method according to any one of claims 1 to 4, characterized in that: The ratio of the thickness of the titanium alloy plate to the thickness of a single layer of the layered structure is between 1200:5 and 1200:10.

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