Method for preparing high-toughness TC11 titanium alloy thick forged plate based on quasi-beta forging

Abstract

The application belongs to the technical field of non-ferrous metal processing, and particularly relates to a method for preparing high-toughness TC11 titanium alloy thick forged plate based on quasi-beta forging. Since TC11 titanium alloy has poor hardenability and it is difficult to realize the uniformity of thick forged plate structure, in order to fully tap the application potential of TC11 titanium alloy structural parts, the application involves the control and optimization of four stages of uniform two-phase material, quasi-beta forging, two-phase zone forming forging and overall heat treatment; the thickness of the TC11 titanium alloy thick forged plate prepared by using the application ranges from 50mm to 200mm, and after overall heat treatment, the impact toughness and fracture toughness and other damage tolerance properties of the forged plate are significantly improved on the premise of not significantly reducing the strength, which fully proves the application potential of TC11 titanium alloy in the field of structural parts, and provides detailed accumulation and reference for the application of TC11 titanium alloy in structural parts.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal processing technology, and relates to the processing of thick titanium alloy forging plates, specifically to a method for preparing high-toughness TC11 titanium alloy thick forging plates based on quasi-β forging. Background Technology

[0002] The nominal composition (mass fraction, %) of TC11 titanium alloy is Ti-6.5Al-3.5Mo-1.5Zr-0.3Si. It belongs to the (α+β) two-phase heat-resistant titanium alloy category and is a typical high-alumina equivalent martensitic titanium alloy designed for long-term operation at 500℃. Due to its high specific strength and excellent high-temperature resistance, it is widely used in components such as compressor disks for aero-engines. With the development of my country's aerospace technology, the demand for large and complex TC11 alloy forgings is increasing, further promoting the application and development of TC11 titanium alloy.

[0003] The application of TC11 titanium alloy is mainly based on conventional forging of two-phase biphasic and equiaxed microstructures. These microstructures offer advantages such as high room temperature strength, good plasticity, and good stability in high-temperature service environments. However, their damage tolerance properties, such as resistance to fatigue crack propagation and fracture toughness, are relatively poor. With the expanding application range of titanium alloy products in the aerospace industry, especially for certain titanium alloy products used under high-stress, high-temperature, and long-term operating conditions, the damage tolerance of conventionally forged products has become significantly limited. Therefore, developing microstructures and processes targeting high resistance to fatigue crack propagation and fracture toughness to achieve a comprehensive balance of strength and toughness in TC11 titanium alloy products has received significant attention.

[0004] Currently, the main methods for achieving microstructures with high resistance to fatigue crack propagation and fracture toughness are based on quasi-β forging and overall β heat treatment. However, for TC11 titanium alloy thick forged plates, quasi-β forging and heat treatment present the following challenges: ① TC11 titanium alloy has poor hardenability, and the performance fluctuates due to differences in temperature distribution between the material surface and core during heating and cooling processes when preparing thick forged plates; ② When preparing TC11 titanium alloy thick forged plates, it is necessary to control the heating temperature and holding time above the phase transformation point. Therefore, forging above the phase transformation point cannot be performed frequently, and for thick forged plates, controlling the uniformity of the forged microstructure is crucial. The preparation of TC11 titanium alloy thick forged plates is relatively difficult; ③ In the preparation of TC11 titanium alloy thick forged plates, the selection and matching of hot deformation temperature and deformation amount directly affect the size of β grains, grain boundaries and the morphology of secondary α phase, as well as the performance after heat treatment. Therefore, accurate identification and control of hot deformation parameters are crucial for the preparation of TC11 titanium alloy thick forged plates; ④ The overall heat treatment of TC11 titanium alloy thick forged plates is a key step that determines the performance of the finished product. It is necessary not only to consider the poor hardenability of TC11 titanium alloy itself, but also to take into account the recrystallization characteristics of α phase and β phase at different temperatures, so as to ensure that the performance difference of the thick forged plate at different positions and directions is within a reasonable range.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing high-toughness TC11 titanium alloy thick forging plates based on quasi-β forging, aiming to achieve high fatigue crack propagation resistance and fracture toughness of TC11 titanium alloy thick forging plates while retaining high strength.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing high-toughness TC11 titanium alloy thick forged plates based on quasi-β forging includes the following steps:

[0009] Step 1: Prepare well-equiaxed two-phase materials through a short-process forging technique;

[0010] Step 2: Perform quasi-β forging;

[0011] Step 3: Perform α and β two-phase region forming forging;

[0012] Step 4: Perform overall near-β solution heat treatment and aging heat treatment.

[0013] Specifically, step 1 includes:

[0014] Step 1.1: Forging the billet

[0015] Select 4-5 ton TC11 titanium alloy ingots with a diameter of Φ600mm-Φ750mm and a chemical composition conforming to GB / T3620.1. Heat the ingots to 50℃-180℃ above the phase transformation point and perform the first and second forging processes. The forging ratio is controlled between 1.4 and 1.8. The holding time is t1 = η1 × H, where H is the thickness of the forging plate and the heating coefficient η1 is 0.6-0.8. The hot material is recycled between the first and second forging processes. After forging, the ingots are air-cooled to obtain the billet.

[0016] Step 1.2, Low and high temperature cyclic forging

[0017] The billet is heated and held at a certain temperature, and then subjected to low-temperature and high-temperature cyclic forging for the third and fourth cycles to obtain the first intermediate billet. The low-temperature and high-temperature cyclic forging includes low-temperature forging below the phase transformation point and quasi-β-high-temperature forging above the phase transformation point. The low-temperature forging temperature is 20℃ to 40℃ below the phase transformation point, with a holding time t2 = η2 × H, where H is the forging plate thickness, and the heating coefficient η2 is 0.6 to 0.8. The high-temperature forging temperature is 30℃ to 80℃ above the phase transformation point, with a holding time t3 = η3 × H, where H is the forging plate thickness, and the heating coefficient η3 is 0.4 to 0.8. After each forging cycle, the billet is air-cooled.

[0018] Step 1.3: Forging of the α and β two-phase regions

[0019] The first intermediate billet is heated and held at a certain temperature, and then forged in the 5th and 6th forging cycles to obtain the second intermediate billet; wherein the heating temperature for each forging is T below the phase transformation point. β ~T β -50℃, holding time t4=η4×H, where H is the thickness of the forging plate, the heating coefficient η4 is 0.6~0.8; after each holding, straight drawing is performed, the drawing rate is ≤50mm / s, the forging ratio during each upsetting and drawing is controlled between 1.3 and 1.6, the final forging temperature is not lower than 800℃, and the billet is air-cooled after each forging is completed.

[0020] Specifically, the temperature of the quasi-β forging in step 2 is T. β To T β At temperatures above 35℃, the deformation ranges from 25% to 70%.

[0021] Specifically, step 2, the quasi-β forging, adopts a stepped heating forging method, specifically as follows:

[0022] The first-stage heating temperature is T. β -50℃~T β -30℃, holding time t5=η5×H, where H is the thickness of the forging plate, and the heating coefficient η5 is 0.4~0.6;

[0023] The second-stage heating temperature is T. β ~T β+35℃, heat preservation time t6=η6×H, heating coefficient η6 is 0.2~0.3.

[0024] Specifically, step 2, the quasi-β forging, is the 7th forging, and the overall forging time is controlled within 5 minutes; the deformation per pass is not greater than 1 / 3 of the total deformation, and the ratio of the feed amount d to the forging plate thickness H is between 1 / 2 and 2 / 3.

[0025] Specifically, the cooling method after the quasi-β forging is completed is either air cooling or water cooling.

[0026] Specifically, in step 3, the forging plate is directly heated to a temperature of T. β -50℃~T β -30℃, holding time t7=η7×H, where H is the thickness of the forging plate, the heating coefficient η7 is 0.6~0.8; the deformation of the α and β two-phase regions is 20%~40%, and air cooling is performed after forging.

[0027] Specifically, step 4, the near-β solution heat treatment, employs a stepped heating method, specifically as follows:

[0028] The first-stage heating temperature is T. β -100℃~T β -200℃, the holding time is t8=η8×H, where H is the thickness of the forging plate, and the heating coefficient η8 is 0.4~0.6;

[0029] The second-stage heating temperature is T. β -30℃~T β -10℃, holding time is t9=η9×H, heating coefficient η9 is 0.2~0.3; and after the near β heat treatment is completed, the forging plate is cooled by air cooling or air cooling.

[0030] Specifically, in step 4, after the near-β solution heat treatment, the temperature of the forging plate is reduced to 530℃±30℃ by air cooling or air cooling, and then aging heat treatment is performed for 6 to 8 hours, followed by air cooling; when matching the aging temperature, it should be ensured that the difference between the solution temperature and the aging temperature is not less than 400℃.

[0031] Specifically, the thickness of the forged plate is 50mm to 200mm.

[0032] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0033] This invention establishes a complete process for preparing high-toughness TC11 titanium alloy thick forged plates. First, a billet forging process is performed. Then, a short-process preparation technology using low-high cycles is employed to obtain a refined and uniform intermediate billet. Next, by rationally setting key process parameters for quasi-β forging and two-phase region forming forging, including heating temperature, deformation amount, and uniform deformation distribution, a TC11 titanium alloy thick forged plate with a uniform microstructure is obtained. Finally, through overall near-β heat treatment and aging to control phase content, morphology, and strength matching, a large-size TC11 titanium alloy forged plate (50mm ≤ thickness ≤ 200mm) with a basketweave microstructure is obtained. This forged plate achieves high fatigue crack propagation resistance and fracture toughness while retaining high strength. A standardized process and control points for the complete preparation of TC11 titanium alloy forged plates are established. The forged plate after overall heat treatment significantly improves damage tolerance properties such as impact toughness and fracture toughness without reducing strength, fully demonstrating the application potential of TC11 titanium alloy in structural components and providing detailed technical accumulation and reference for its application in structural components. Attached Figure Description

[0034] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a diagram showing the sampling locations of the forged plate mechanical specimens in Examples 1 and 2 of the present invention;

[0037] Figure 2 These are microstructure images of different locations in the middle of the forged plate in Embodiment 1 of the present invention;

[0038] Figure 3 These are microstructure images of different locations in the middle of the forged plate in Embodiment 2 of the present invention;

[0039] Figure 4 This is a flowchart of the method for preparing high-toughness TC11 titanium alloy thick forging plate based on quasi-β forging according to the present invention. Detailed Implementation

[0040] Exemplary embodiments will now be described in detail, with examples illustrated in the accompanying drawings. The embodiments described below do not represent all embodiments consistent with the present invention. Rather, they are merely examples of methods consistent with some aspects of the invention as detailed in the appended claims.

[0041] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0042] Example 1

[0043] This embodiment provides a method for preparing high-toughness TC11 titanium alloy thick forged plates based on quasi-β forging. TC11 titanium alloy with a phase transformation point of 1015℃ is used to prepare forged plates with dimensions of 200mm × 600mm × 1500mm. The specific steps are as follows:

[0044] Step 1: Forging the billet

[0045] Step 1.1: The first heating temperature of the forged plate is 1200℃, and after holding for 480 minutes, it is subjected to 2 upsetting and 2 drawing, with the forging ratio controlled at 1.6. The forged size is 650×L octagonal. The hot material after forging is returned to the furnace for the second heating. The heating temperature of the second heating is 1120℃, and after holding for 420 minutes, it is subjected to 2 upsetting and 2 drawing, with the forging ratio controlled at 1.6. The forged size is 600×L octagonal. The final forging temperature is controlled above 850℃. The forged material is cooled by air cooling to obtain the billet.

[0046] Step 1.2: The billet undergoes low-high temperature cyclic forging. The specific process is as follows: the heating temperature for the third forging is 970℃, and after holding for 420 minutes, it is upsetting and drawing once; then the heating temperature for the fourth forging is 1060℃, and after holding for 300 minutes, it is upsetting and drawing twice. The specifications after the fourth forging are all octagonal 750×L (in the high-temperature forging, the height of the intermediate billet is reduced to increase the drawing ratio of the two-phase zone). The forging ratio of each forging is controlled at 1.5, and the final forging temperature is controlled above 800℃; after each forging, it is cooled by air cooling.

[0047] Step 1.3: The intermediate billet for the two-phase forging process is an octagonal 750×L billet. It undergoes two forging passes (4 steps) to fully break down and refine the microstructure. The fifth forging pass is heated to 970℃ and held for 480 minutes before direct drawing. After two forging steps, the billet size is 550×L. The forging ratio for each forging pass is controlled at 1.55. The sixth forging pass is heated to 970℃ and held for 350 minutes before upsetting. The forged billet size is a flat square 420×600×L billet, with a forging ratio controlled at 1.45. The final forging temperature for both passes is controlled above 800℃. After each forging pass, air cooling is used for cooling.

[0048] Step 2, Quasi-β Forging:

[0049] The material is heated in a stepped manner. The first stage of heating is at 950℃, and the holding time is 210 minutes. Then, the temperature is raised to 1030℃ and held for 100 minutes before being taken out of the furnace for forging. In order to ensure that the intermediate billet is fully and uniformly deformed in this heating process, the forging is divided into three passes in sequence: 420×600×L flat billet, 350×W1×L1 flat billet, 300×W2×L2 flat billet, and 250×610×L3 flat billet. The feed amount for each pass is 200mm, 170mm, and 100mm respectively, depending on the thickness of the intermediate billet. The forging process is controlled to be completed within 5 minutes, and the billet is water-cooled after forging.

[0050] Step 3: The heating temperature for the two-phase region forming forging is 970℃, the holding time is 210min, the deformation in the two-phase region is controlled at 20%, and the forging billet is forged into a flat square of 210×610×L4 in 2 to 3 passes, and then air-cooled.

[0051] Step 4, overall near-β heat treatment and aging, is the key step to achieve the strength and toughness matching of TC11 titanium alloy forging plate. The heat treatment of the incoming forging billet adopts stepped heating. The first heating temperature is 850℃ and the holding time is 2h. Then, the temperature is raised to 980℃ in the furnace and held for 1h. After being taken out of the furnace, it is air-cooled to 530℃ and held for 6h. It is then air-cooled to room temperature and machined to obtain the required forging plate.

[0052] Example 2

[0053] This embodiment provides a method for preparing high-toughness TC11 titanium alloy thick forged plates based on quasi-β forging. TC11 titanium alloy with a phase transformation point of 1015℃ is used to prepare forged plates with dimensions of 150mm × 800mm × 2000mm. The specific steps are as follows:

[0054] Follow these steps to implement the procedure:

[0055] Step 1, Forging the billet:

[0056] Step 1.1: The first heating temperature of the forging plate is 1180℃, and after holding for 480 minutes, it is subjected to 2 upsetting and 2 drawing, with the forging ratio controlled at 1.5. The forged size is 700×L octagonal, and the plate is air-cooled after forging. The second heating temperature is 1100℃, and after holding for 450 minutes, it is subjected to 2 upsetting and 2 drawing, with the forging ratio controlled at 1.6. The forged size is 650×L octagonal, and the final forging temperature is controlled above 850℃. The forged material is cooled by air cooling to obtain the billet.

[0057] Step 1.2: The billet undergoes low-high temperature cyclic forging. The specific process is as follows: the heating temperature for the third forging is 980℃, held for 420 minutes, followed by one upsetting and one drawing; then the heating temperature for the fourth forging is 1080℃, held for 300 minutes, followed by two upsettings and one drawing. The specifications after the fourth forging are all Φ600 (in the high-temperature forging, the height of the intermediate billet is reduced to increase the drawing ratio in the two-phase zone). The forging ratio for each forging is controlled at 1.5, and the final forging temperature is controlled above 800℃. After each forging, air cooling is used for cooling.

[0058] Step 1.3: The intermediate billet for two-phase forging is Φ600. It is fully crushed and refined through two hot forging processes. The heating temperature for the fifth hot forging is 965℃, and after holding for 450 minutes, it is upset. The specifications after the first hot forging are 380×730×L (flat square). The forging ratio for each hot forging is controlled at 1.25. The heating temperature for the sixth hot forging is 965℃, and after holding for 350 minutes, it is straight drawn. The specifications after forging are 250×830×L (flat square). The forging ratio is controlled at 1.3. The final forging temperature for both hot forging processes is controlled above 800℃. After each hot forging process, air cooling is used for cooling.

[0059] Step 2, Quasi-β Forging:

[0060] The material is heated in a stepped manner. The first stage of heating is 950℃, and the holding time is 210 minutes. Then, the temperature is raised to 1035℃ and held for 100 minutes before being taken out of the furnace for forging. In order to ensure that the intermediate billet is fully and uniformly deformed in this heat, the forging is divided into 3 passes in sequence: flat square 250×830×L, flat square 210×W2×L2, flat square H×800×L3, and flat square 170×820×L4. The feed amount for each pass is 200mm, 150mm, 100mm, and 80mm respectively, depending on the thickness of the intermediate billet. The forging process is controlled to be completed within 5 minutes, and the billet is water-cooled after forging.

[0061] Step 3: The heating temperature for the two-phase region forming forging is 965℃, the holding time is 210min, the deformation in the two-phase region is controlled at 20%, and the forging billet is forged into a flat square of 160×810×L4 in 2 to 3 passes, and then air-cooled.

[0062] Step 4, overall near-β heat treatment and aging, is the key step to achieve the strength and toughness matching of TC11 titanium alloy forging plate. The heat treatment of the incoming forging billet adopts stepped heating. The first heating temperature is 900℃ and the holding time is 80min. Then, the temperature is raised to 985℃ in the furnace and held for 50min. After being taken out of the furnace, it is air-cooled to 530℃ and held for 6h. It is then air-cooled to room temperature and machined to obtain the required forging plate.

[0063] Through the forging methods described in Examples 1 and 2 above, a TC11 titanium alloy forged plate (thickness ≤ 200 mm) with a uniform basket structure can be obtained. This forged plate can achieve high fatigue crack propagation resistance and fracture toughness of TC11 titanium alloy forged plate without significantly reducing plasticity. Based on this, a standardized process for the entire preparation of TC11 titanium alloy forged plate has been formed, which fully demonstrates the application potential of TC11 titanium alloy in the field of structural components and provides detailed accumulation and reference for its application in structural components.

[0064] The following analysis was performed on the forged plates prepared in Examples 1 and 2 above:

[0065] I. Mechanical Properties

[0066] Mechanical property analysis was performed on the forged plate with dimensions of 200 mm (thickness) × 600 mm (length) × 1500 mm (width) prepared in Example 1. Samples were taken from the ends and middle portion of the forging blank for analysis, as shown in the sampling diagram below. Figure 1 As shown, typical mechanical properties are shown in Tables 1 and 2:

[0067] Table 1. Room temperature tensile properties of the forging billet at different locations at the end and middle of Example 1.

[0068]

[0069] Table 2 Impact energy, fracture toughness, and fatigue crack propagation properties at different locations at the end and middle of the forging billet in Example 1

[0070]

[0071] Mechanical property analysis was performed on the forged plate with dimensions of 150 mm (thickness) × 800 mm (length) × 2000 mm (width) prepared in Example 2. Samples were taken from the ends and middle of the forged plate for analysis. The sampling diagram was consistent with that in Example 1. Typical mechanical properties are shown in Tables 3 and 4.

[0072] Table 3. Room temperature tensile properties of the forging blank at different locations at the end and middle of Example 2.

[0073]

[0074] Table 4. Impact energy, fracture toughness, and fatigue crack propagation properties at different locations at the end and middle of the forging billet in Example 2.

[0075]

[0076] According to the data in Tables 1 to 4, after overall heat treatment, the mechanical properties of the forged plates in Examples 1 and 2 at different positions of the ends and middle are improved by more than 50% and the fracture toughness is improved by more than 30% compared with the conventional bimodal structure of TC11, while the strength and plasticity are comparable. The resistance to fatigue crack propagation is also significantly improved. This shows that the forged plates prepared by the present invention have excellent damage tolerance properties.

[0077] II. Microstructural Analysis

[0078] Example 1 shows a 200mm × 600mm × 1500mm TC11 titanium alloy forged plate, such as... Figure 2 As shown; and the microstructure of the 150mm×800mm×2000mm forged plate of Example 2 was observed, as shown. Figure 3 As shown, the high-magnification microstructure at different locations of the forging plate all exhibits a basketweave structure, the α phase at the grain boundaries is fully broken, and the microstructure at different locations is relatively uniform.

[0079] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for preparing high-toughness TC11 titanium alloy thick forged plates based on quasi-β forging, characterized in that, Includes the following steps: Step 1: Prepare well-equiaxed two-phase materials through a short-process forging technique; Step 1.1, Forging: Heat the TC11 titanium alloy ingot to 50℃~180℃ above the phase transformation point and perform the first and second forging. The forging ratio is controlled between 1.4 and 1.

8. The holding time is t1=η1×H and the heating coefficient η1 is 0.6~0.

8. Step 1.2, Low- and High-Temperature Cyclic Forging: The billet is heated and held at a certain temperature, and then subjected to the 3rd and 4th low- and high-temperature cyclic forging to obtain the first intermediate billet; wherein, the temperature of the low-temperature forging is 20℃ to 40℃ below the phase transformation point, the holding time is t2=η2×H, and the heating coefficient η2 is 0.6~0.8; the temperature of the high-temperature forging is 30℃ to 80℃ above the phase transformation point, the holding time is t3=η3×H, and the heating coefficient η3 is 0.4~0.8; after each forging, it is air-cooled. Step 1.3, Forging of the α and β two-phase regions: The first intermediate billet is heated and held at a certain temperature, and then forged in the 5th and 6th forging cycles to obtain the second intermediate billet; wherein, the heating temperature for each forging is T below the phase transformation point. β ~T β -50℃, holding time t4=η4×H, heating coefficient η4 is 0.6~0.8; after each holding, straight drawing is performed, the drawing rate is ≤50mm / s, the forging ratio during each upsetting and drawing is controlled between 1.3 and 1.6, the final forging temperature is not lower than 800℃, and the billet is air-cooled after each forging is completed; Step 2: Perform quasi-β forging on the second intermediate billet, wherein the quasi-β forging temperature is T. β To T β At temperatures above 35℃, the deformation ranges from 25% to 70%. Step 3: Perform α and β two-phase region forming forging; The forged plate is directly heated to a temperature of T. β -50℃~T β -30℃, holding time t7=η7×H, heating coefficient η7 is 0.6~0.8; deformation in the α and β two-phase regions is 20%~40%, and air cooling is performed after forging; Step 4: Perform overall near-β solution heat treatment and aging heat treatment to obtain a forged plate with the required thickness of 50mm~200mm; The near-β solution heat treatment employs a stepped heating process, specifically: The first-stage heating temperature is T. β -100℃~T β -200℃, the holding time is t8=η8×H, and the heating coefficient η8 is 0.4~0.6; The second-stage heating temperature is T. β -30℃~T β -10℃, holding time is t9=η9×H, heating coefficient η9 is 0.2~0.3; and after near-β heat treatment, the forging plate is cooled by air cooling or air cooling. After the near-β solution heat treatment, the temperature of the forging plate is reduced to 530℃±30℃ by air cooling or air cooling, and then subjected to aging heat treatment for 6~8 hours, followed by air cooling; when matching the aging temperature, the difference between the solution temperature and the aging temperature should be not less than 400℃; where H is the thickness of the forging plate.

2. The method for preparing high-toughness TC11 titanium alloy thick forged plates based on quasi-β forging according to claim 1, characterized in that, In step 1.1 of the forging process, a TC11 titanium alloy ingot with a capacity of 4 to 5 tons and a diameter of Φ600mm to Φ750mm is selected, and its chemical composition meets the requirements of GB / T3620.

1. The hot material is recycled between the first and second forging processes, and the billet is air-cooled after forging to obtain the billet.

3. The method for preparing high-toughness TC11 titanium alloy thick forged plates based on quasi-β forging according to claim 1, characterized in that, Step 2, the quasi-β forging, adopts a stepped heating forging method, specifically as follows: The first-stage heating temperature is T. β -50℃~T β -30℃, holding time t5=η5×H, where H is the thickness of the forging plate, and the heating coefficient η5 is 0.4~0.6; The second-stage heating temperature is T. β ~T β +35℃, heat preservation time t6=η6×H, heating coefficient η6 is 0.2~0.

3.

4. The method for preparing high-toughness TC11 titanium alloy thick forged plates based on quasi-β forging according to claim 1, characterized in that, The step 2 quasi-β forging is the 7th forging, and the overall forging time is controlled within 5 minutes; the deformation per pass is not greater than 1 / 3 of the total deformation, and the ratio of the feed amount d to the forging plate thickness H is between 1 / 2 and 2 / 3.

5. The method for preparing high-toughness TC11 titanium alloy thick forged plates based on quasi-β forging according to claim 4, characterized in that, The cooling method after the quasi-β forging is air cooling or water cooling.

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