Preparation method of high-strength and high-toughness TC6 titanium alloy forgings

Abstract

The application belongs to the technical field of non-ferrous metal processing, and relates to a preparation method of a TC6 titanium alloy high-strength and high-toughness forging, wherein step heating is adopted in the beta forging process, the heat preservation time of the alloy above the phase transition point is shortened, and full heat penetration is achieved, the heat preservation temperature above the phase transition point is reasonably selected, grain growth caused by excessively high heat preservation temperature or excessively long heat preservation time is avoided, and uniform and fine alloy grain refinement is realized. In the forming forging process, the sheet layer alpha phase morphology regulation in the net basket organization is realized by controlling the elongation deformation amount of the blank, and then the reasonable matching of the strength and toughness is obtained. In the heat treatment process, the air cooling rate after the first reheating treatment is controlled, the number of metastable phases of the alloy is controlled, and then the number of precipitated strengthening phases during the second low-temperature heat preservation is controlled, and the improvement of the plasticity of the alloy is realized. The prepared forging has a great improvement in the fracture toughness compared with the TC6 titanium alloy duplex structure forging, and provides a solid mechanical property foundation for the wide application of the forging in structural parts.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal processing technology and relates to a method for preparing TC6 titanium alloy high-strength and high-toughness forgings. Background Technology

[0002] Titanium alloys, due to their low density and high specific strength, are gradually replacing other metallic materials in the manufacture of aerospace structural components. TC6 titanium alloy is a martensitic α+β two-phase titanium alloy with excellent comprehensive properties, its nominal composition being Ti-6Al-1.5Cr-2.5Mo-0.5Fe-0.3Si. This alloy possesses excellent comprehensive properties, including good room temperature and high temperature mechanical properties, and fatigue life. Through controlled forging and heat treatment processes, a good match of mechanical properties can be achieved. Therefore, TC6 titanium alloy with its two-phase microstructure can operate continuously at 400℃~450℃ and can be widely used in the manufacture of compressor discs and blades. Current application research has found that TC6 titanium alloy with a basket-like microstructure exhibits a good match of room temperature tensile strength, plasticity, and fracture toughness, with a fracture toughness K0... IC Stable at ≥70MPa·m 1 / 2 These forgings can be used in the manufacture of aerospace structural components, further reducing component weight and becoming one of the effective ways to reduce the weight of aerospace vehicles. Therefore, TC6 titanium alloy forgings, with their high strength and high toughness, are gradually becoming one of the main materials selected for the manufacture of aerospace structural components.

[0003] In the preparation of high-strength and high-toughness TC6 titanium alloy forgings, room-temperature plasticity and fracture toughness are extremely sensitive to hot working parameters. Improper parameter settings will prevent a good match between room-temperature plasticity and fracture toughness. The design of the forming deformation amount in the two-phase region after deformation in the single-phase region is crucial. If the forming deformation amount in the two-phase region is too large, the lamellar α-phase in the basketweave microstructure will be highly fragmented, leading to a decrease in fracture toughness. Conversely, if the forming deformation amount in the two-phase region is too small, the lamellar α-phase in the basketweave microstructure will be less fragmented, resulting in low room-temperature tensile plasticity of the alloy. To obtain alloy forgings with a good match between room-temperature plasticity and fracture toughness, on the one hand, it is necessary to determine the appropriate forming deformation amount in the single-phase region and subsequently the two-phase region according to performance requirements; on the other hand, it is necessary to control the cooling rate after solution treatment during alloy heat treatment according to strength and toughness requirements to obtain the best solution treatment effect, and then control the precipitation of strengthening phases during subsequent aging processes to obtain the desired mechanical properties.

[0004] To address these challenges, it is necessary to redesign and optimize the alloy forging production process based on conventional forging techniques, thereby broadening the technological window for alloy forging preparation. Developing accurate forging process routes and deformation parameters, and adopting appropriate forging methods, is one of the key technologies for obtaining high-strength, high-toughness TC6 titanium alloy forgings. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing TC6 titanium alloy high-strength and high-toughness forgings. The forgings prepared by this method have good uniformity of microstructure and properties and are suitable for industrial production.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The preparation method of this TC6 titanium alloy high-strength and high-toughness forging is as follows: initial forging → intermediate forging → β forging → forming forging → heat treatment; wherein,

[0008] The β forging specifically involves heating the billet A obtained from intermediate forging to 20°C–60°C above the phase transformation point using a stepped heating method and holding it at that temperature for a specified time T3. After exiting the furnace, the billet A is forged with a deformation of more than 20%. After forging, it is air-cooled to obtain billet B.

[0009] The forming forging specifically involves heating the billet B obtained by β forging to 30°C to 60°C below the phase transformation point and holding it at that temperature for a specified time T4. After being taken out of the furnace, the billet B is forged, and the deformation amount is no more than 30%. After forging, it is air-cooled to obtain an intermediate forging.

[0010] The heat treatment specifically involves: performing double annealing on the intermediate forging obtained by forming and forging; the first annealing temperature is 870℃~920℃, and the forging is held at this temperature until it is fully heated, and then air-cooled after being taken out of the furnace; the second annealing temperature is 550℃~600℃, and the forging is held at this temperature for 2h~5h, and then air-cooled after being taken out of the furnace, to obtain a TC6 titanium alloy high-strength and high-toughness forging.

[0011] Furthermore, the specified time T3 = D3 × (0.3 ~ 0.6), where D3 is the minimum diameter of billet A in mm and T3 is in min; the specified time T4 = D4 × (0.6 ~ 0.8), where D4 is the minimum diameter of billet B in mm and T4 is in min.

[0012] Furthermore, the forging process specifically includes:

[0013] Titanium alloy ingots are selected and held at 100℃~250℃ above the phase transformation point for a specified time T1; the titanium alloy ingots are subjected to multiple upsetting and drawing forging to obtain the first billet, which is then air-cooled after forging; wherein, a furnace reheating method is used between the forging and drawing forging, the deformation amount of a single pass is controlled between 20% and 40%, and the cumulative deformation amount of each forging is greater than 60%.

[0014] Furthermore, the specified time T1 = D1 × (0.45 ~ 0.8), where D1 is the minimum size of the titanium alloy ingot in mm, and T1 is in min.

[0015] Furthermore, the intermediate forging specifically includes:

[0016] First, the first billet obtained after forging is subjected to 3 to 5 upsetting and drawing forging cycles (heating temperature distributed in the order of above, below, and above the phase transformation point) at temperatures ranging from 20°C to 200°C above the phase transformation point to 20°C to 70°C below the phase transformation point, to obtain the second billet. After forging, it is air-cooled or water-cooled. During the cycles, a reheating method is used between the cycles, and the deformation amount per pass is controlled between 30% and 50%. The cumulative deformation amount per pass is greater than 70%. The last cycle is held at 30°C to 70°C above the phase transformation point and then forged, with a cumulative deformation amount greater than 60%.

[0017] Then, the second billet is subjected to 3 to 5 heat treatments and forging at 30°C to 80°C below the phase transformation point, with a specified heat treatment time T2, followed by air cooling; wherein, the deformation amount per pass is controlled between 20% and 40%, and the cumulative deformation amount per heat treatment is greater than 40%; after forging, billet A is obtained for β forging.

[0018] Furthermore, the specified time T2 = D2 × (0.6 ~ 0.8), where D2 is the minimum diameter of the second billet in mm, and T2 is in min.

[0019] Furthermore, the cross-sectional shape of the second billet is square or octagonal to ensure uniform deformation of all parts of the second billet.

[0020] Furthermore, the TC6 titanium alloy high-strength and high-toughness forging has a room temperature tensile strength Rm ≥ 930 MPa, a room temperature tensile elongation A ≥ 8%, and a room temperature fracture toughness K. IC ≥70MPa·m 1 / 2 .

[0021] Furthermore, the cross-sectional dimensions (diameter of a circle or thickness of a square) of the TC6 titanium alloy high-strength and high-toughness forging are between 70mm and 400mm.

[0022] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0023] 1) During the intermediate forging process, based on the principle of repeated recrystallization of alloys to refine grains, the process route (two-stage intermediate forging) is optimized. Through the optimization of heating temperature, deformation amount and deformation method, as well as the precise control of heating and forging parameters, a uniform alloy billet A is obtained.

[0024] 2) Step heating is used in the β forging process to shorten the holding time of the alloy above the phase transformation point and ensure sufficient heat penetration. The holding temperature above the phase transformation point is reasonably selected to avoid grain growth caused by excessively high holding temperature or excessively long holding time, thereby achieving uniform and refined alloy grains.

[0025] 3) During the forming and forging process, the morphology of the lamellar α phase in the basket structure is controlled by controlling the elongation deformation of the billet, thereby obtaining a reasonable match between strength and toughness.

[0026] 4) During the heat treatment process, by controlling the air cooling rate after the first heat treatment, the amount of metastable phase formed in the alloy can be controlled, thereby controlling the amount of strengthening phase precipitated during the second low-temperature holding, thus improving the plasticity of the alloy.

[0027] In summary, this invention, through the control of microstructure morphology and precipitated strengthening phases throughout the entire preparation process, can achieve a reasonable balance between room temperature strength and toughness of forgings, ensuring that the prepared forgings have a room temperature tensile strength Rm ≥ 930 MPa, a room temperature tensile elongation A ≥ 8%, and a room temperature fracture toughness K. IC ≥70MPa·m 1 / 2 The remaining properties meet the requirements and can satisfy the stringent requirements of aerospace and other industries for the high strength and toughness of this alloy forging, making it suitable for industrial production. Attached Figure Description

[0028] 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.

[0029] 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.

[0030] Figure 1 A schematic diagram of the manufacturing process for the TC6 titanium alloy high-strength and high-toughness forgings provided by this invention;

[0031] Figure 2 Metallographic sampling location diagrams of the TC6 titanium alloy high-strength and high-toughness forgings provided by the present invention; wherein, (a) is the edge, (b) is at 1 / 2R, and (c) is the core;

[0032] Figure 3(a) is a low-magnification microstructure of the head forging provided in Embodiment 1 of the present invention, and Figure 3(b) is a low-magnification microstructure of the head forging at 1 / 2R provided in Embodiment 1 of the present invention;

[0033] Figure 4 This is a microstructure image of the head forging at 1 / 2R provided in Embodiment 1 of the present invention;

[0034] Figure 5(a) is a low-magnification microstructure of the head forging provided in Embodiment 2 of the present invention, and Figure 5(b) is a low-magnification microstructure of the head forging at 1 / 2R provided in Embodiment 2 of the present invention;

[0035] Figure 6(a) is a low-magnification microstructure of the tail forging provided in Embodiment 2 of the present invention, and Figure 6(b) is a low-magnification microstructure of the tail forging at 1 / 2R provided in Embodiment 2 of the present invention;

[0036] Figure 7(a) is a microstructure diagram of the edge of the head forging provided in Embodiment 2 of the present invention, Figure 7(b) is a microstructure diagram of the head forging at 1 / 2R provided in Embodiment 2 of the present invention, and Figure 7(c) is a microstructure diagram of the core of the head forging provided in Embodiment 2 of the present invention.

[0037] Figure 8(a) is a microstructure diagram of the edge of the tail forging provided in Embodiment 2 of the present invention, Figure 8(b) is a microstructure diagram of the tail forging at 1 / 2R provided in Embodiment 2 of the present invention, and Figure 8(c) is a microstructure diagram of the core of the tail forging provided in Embodiment 2 of the present invention. Detailed Implementation

[0038] Exemplary embodiments will now be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0039] 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.

[0040] See Figure 1 As shown, this invention provides a method for preparing a high-strength, high-toughness TC6 titanium alloy forging. The process flow of the preparation method is as follows: initial forging → intermediate forging → β forging → forming forging → heat treatment; wherein,

[0041] The β forging specifically involves heating the billet A obtained from intermediate forging to 20°C–60°C above the phase transformation point using a stepped heating method and holding it at that temperature for a specified time T3. After exiting the furnace, the billet A is forged with a deformation of more than 20%. After forging, it is air-cooled to obtain billet B.

[0042] The forming forging specifically involves heating the billet B obtained by β forging to 30°C to 60°C below the phase transformation point and holding it at that temperature for a specified time T4. After being taken out of the furnace, the billet B is forged, and the deformation amount is no more than 30%. After forging, it is air-cooled to obtain an intermediate forging.

[0043] The heat treatment specifically involves: performing double annealing on the intermediate forging obtained by forming and forging; the first annealing temperature is 870℃~920℃, and the forging is held at this temperature until it is fully heated, and then air-cooled after being taken out of the furnace; the second annealing temperature is 550℃~600℃, and the forging is held at this temperature for 2h~5h, and then air-cooled after being taken out of the furnace, to obtain a TC6 titanium alloy high-strength and high-toughness forging.

[0044] Furthermore, the specified time T3 = D3 × (0.3 ~ 0.6), where D3 is the minimum diameter of billet A in mm and T3 is in min; the specified time T4 = D4 × (0.6 ~ 0.8), where D4 is the minimum diameter of billet B in mm and T4 is in min.

[0045] Furthermore, the forging process specifically includes:

[0046] Titanium alloy ingots are selected and held at 100℃~250℃ above the phase transformation point for a specified time T1; the titanium alloy ingots are subjected to multiple upsetting and drawing forging to obtain the first billet, which is then air-cooled after forging; wherein, a furnace reheating method is used between the forging and drawing forging, the deformation amount of a single pass is controlled between 20% and 40%, and the cumulative deformation amount of each forging is greater than 60%.

[0047] Furthermore, the specified time T1 = D1 × (0.45 ~ 0.8), where D1 is the minimum size of the titanium alloy ingot in mm, and T1 is in min.

[0048] Furthermore, the intermediate forging specifically includes:

[0049] First, the first billet obtained after forging is subjected to 3 to 5 upsetting and drawing forging cycles (heating temperature distributed in the order of above, below, and above the phase transformation point) at temperatures ranging from 20°C to 200°C above the phase transformation point to 20°C to 70°C below the phase transformation point, to obtain the second billet. After forging, it is air-cooled or water-cooled. During the cycles, a reheating method is used between the cycles, and the deformation amount per pass is controlled between 30% and 50%. The cumulative deformation amount per pass is greater than 70%. The last cycle is held at 30°C to 70°C above the phase transformation point and then forged, with a cumulative deformation amount greater than 60%.

[0050] Then, the second billet is subjected to 3 to 5 heat treatments and forging at 30°C to 80°C below the phase transformation point, with a specified heat treatment time T2, followed by air cooling; wherein, the deformation amount per pass is controlled between 20% and 40%, and the cumulative deformation amount per heat treatment is greater than 40%; after forging, billet A is obtained for β forging.

[0051] Furthermore, the specified time T2 = D2 × (0.6 ~ 0.8), where D2 is the minimum diameter of the second billet in mm, and T2 is in min.

[0052] Furthermore, the cross-sectional shape of the second billet is square or octagonal to ensure uniform deformation of all parts of the second billet.

[0053] Furthermore, the TC6 titanium alloy high-strength and high-toughness forging has a room temperature tensile strength Rm ≥ 930 MPa, a room temperature tensile elongation A ≥ 8%, and a room temperature fracture toughness K. IC≥70MPa·m 1 / 2 .

[0054] Furthermore, the cross-sectional dimensions (diameter of a circle or thickness of a square) of the TC6 titanium alloy high-strength and high-toughness forging are between 70 mm and 400 mm.

[0055] Example 1

[0056] This embodiment provides a method for preparing TC6 titanium alloy high-strength and high-toughness forgings, the specific steps of which are as follows:

[0057] Step 1, Forging the billet:

[0058] TC6 titanium alloy ingots were selected, and after sawing, each piece weighed approximately 960 kg. The alloy phase transformation point was 980℃. The TC6 titanium alloy ingots were heated to 1170℃ (190℃ above the phase transformation point) using a stepped heating method and held for 300 min. After being taken out of the furnace, they were subjected to two upsetting and drawing forging processes to obtain the first billet. The cumulative deformation was approximately 70%. After forging, the billet was air-cooled.

[0059] Step 2, Intermediate Forging:

[0060] Step 2.1: The first billet is subjected to one-pass upsetting and drawing forging at 60°C above the phase transformation point and 60°C below the phase transformation point, respectively. The deformation per pass is approximately 40%, and the cumulative elongation deformation per pass is approximately 80%. Reversed upsetting and drawing can be used during the forging process to fully break down the microstructure. After forging, the cross-section of the billet is octagonal, and it is water-cooled after forging.

[0061] Step 2.2: The billet after the above forging is subjected to three upsetting and drawing forgings within the range of 60℃ to 200℃ above the phase transformation point, with the holding temperature decreasing successively for each forging, and the holding time being 240min to 300min. The deformation per pass is about 40%, and the cumulative elongation deformation per forging is about 80%. Reversed upsetting and drawing can be adopted during the forging process to fully break down the structure. After forging, the second billet has an octagonal cross section and is water-cooled after forging.

[0062] Step 2.3: After grinding and removing surface cracks from the second billet obtained after the above five forging cycles, it is held at 945℃ (35℃ below the phase transformation point) for 390 minutes. After being taken out of the furnace, it is upset forging with a drawing deformation of 33%. The hot material is then returned to the furnace and held at a temperature of 60 minutes before being upset forging again. The deformation per pass is 33%, and the total drawing deformation is approximately 66%. After forging, it is air-cooled. After grinding and removing surface cracks from the second billet, it is held at 940℃ (35℃ below the phase transformation point) for 390 minutes. The first billet is held at 40℃ below the specified temperature for 390 minutes, then removed from the furnace and subjected to upsetting forging with a stretching deformation of 33%. After forging, the hot material is returned to the furnace and held at the specified temperature for 60 minutes before being subjected to upsetting forging again, with a single-pass deformation of 33% and a total stretching deformation of approximately 66%. After forging, the billet is air-cooled. The second billet is then ground to remove surface cracks, held at 940℃ for 390 minutes, and then subjected to stretching deformation with a deformation of 36%. After the deformation is completed, a billet A with an octagonal cross-section is obtained.

[0063] Step 3, β forging:

[0064] After the billet A obtained from intermediate forging is sawn into two equal parts, it is heated to 1000℃ (20℃ above the phase transformation point) by step heating and held for 160 minutes. After being taken out of the furnace, it is drawn and the deformation is about 36%. The cross-section of the billet B obtained after forging is octagonal. After the deformation is completed, it is air cooled.

[0065] Step 4, Forming and Forging:

[0066] The billet B is heated to 940℃ (40℃ below the phase transformation point) and held for 210 minutes. After being taken out of the furnace, it is drawn and the deformation is about 18%. The cross-section of the forged billet is octagonal. It is then shaped into a Ф290mm bar using an anvil and air-cooled after forming.

[0067] Step 5, Heat Treatment:

[0068] After heating the billet to 890°C and holding it for 180 minutes, it was removed from the furnace, wrapped with asbestos, and air-cooled for 4 hours. After removing the asbestos, it was transferred to an indoor material rack for air-cooling. After air-cooling to room temperature, the billet was heated to 560°C, held for 240 minutes, and then air-cooled after being removed from the furnace.

[0069] The heat-treated billet can be machined into a single-length forging with a diameter of Ф280mm.

[0070] Example 2

[0071] This embodiment provides a method for preparing TC6 titanium alloy high-strength and high-toughness forgings, the specific steps of which are as follows:

[0072] Step 1, Forging the billet:

[0073] TC6 titanium alloy ingots were selected, and after sawing, each piece weighed approximately 960 kg. The alloy's phase transformation point was 980℃. The TC6 titanium alloy ingots were heated to 1170℃ (190℃ above the phase transformation point) in a stepped manner and held for 300 min. After being taken out of the furnace, they underwent two upsetting and drawing forging processes. The deformation per pass was approximately 30%, and the cumulative deformation was approximately 70%. After forging, the hot material was returned to the furnace and held at 1080℃ for 60 min. After being taken out of the furnace, it underwent reverse upsetting and drawing forging. The deformation per pass was approximately 30%, and the cumulative deformation was approximately 60%. After forging, it was air-cooled to obtain the first billet.

[0074] Step 2, Intermediate Forging:

[0075] Step 2.1: The first billet is subjected to one-pass upsetting and drawing forging at 40°C below the phase transformation point, and 190°C and 60°C above the phase transformation point, respectively. The deformation per pass is approximately 36%, and the cumulative elongation deformation per pass is 72%. Reversed upsetting can be used during the forging process to fully break down the microstructure. The second billet obtained after forging has an octagonal cross-section and is water-cooled after forging.

[0076] Step 2.2: Perform 3 to 5 heat treatments and forging on the second billet at a temperature of 30°C to 80°C below the phase transformation point.

[0077] After grinding to remove surface cracks, the second billet, after completing the above forging, is held at 945℃ (35℃ below the phase transformation point) for 390 minutes. After being taken out of the furnace, it is upset forging with a drawing deformation of 33%. The hot material is then returned to the furnace and held at the same temperature for 60 minutes before being upset forging again. The deformation per pass is 33%, and the total drawing deformation is about 66%. After forging, it is air-cooled.

[0078] After the second billet is polished to remove surface cracks, it is held at 940℃ (40℃ below the phase transformation point) for 390 minutes. After being taken out of the furnace, it is upset forging with a lengthening deformation of 33%. The hot material is then returned to the furnace and held at the temperature for 60 minutes before being upset forging again. The deformation per pass is 33%, and the total lengthening deformation is about 66%. After forging, it is air-cooled.

[0079] After the second billet is polished to remove surface cracks, it is held at 940℃ for 390 minutes. After being taken out of the furnace, it is stretched and deformed with a deformation amount of 36%. After the deformation is completed, billet A with an octagonal cross-section is obtained.

[0080] Step 3, β forging:

[0081] The billet A obtained from intermediate forging is heated to 1000℃ and held for 160 minutes using a stepped heating method. After being taken out of the furnace, it is drawn and the deformation is about 36%. The cross-section of the billet B obtained after forging is octagonal. After deformation, it is air-cooled.

[0082] Step 4, Forming and Forging:

[0083] The billet B is heated to 940℃ (40℃ below the phase transformation point) and held for 210 minutes. After being taken out of the furnace, it is drawn and the deformation is about 18%. The cross-section of the forged billet is octagonal. It is then shaped into a Ф290mm bar using an anvil and air-cooled after forming.

[0084] Step 5, Heat Treatment:

[0085] After heating the billet to 890°C and holding it for 180 minutes, it was removed from the furnace, wrapped with asbestos, and air-cooled for 4 hours. After removing the asbestos, it was transferred to an indoor material rack for air-cooling. After air-cooling to room temperature, the billet was heated to 560°C, held for 240 minutes, and then air-cooled after being removed from the furnace.

[0086] The heat-treated billet can be machined into a double-length forging with a diameter of Ф280mm.

[0087] Figure 1 This is a schematic diagram of the manufacturing process route for TC6 titanium alloy forgings provided by the present invention. Figure 1 It can be seen that the entire preparation process is divided into billet forging, intermediate forging, β forging, forming forging and heat treatment; and after the TC6 titanium alloy ingot is sawn and divided into materials, it is repeatedly heated, forged and ground to prepare alloy billet. After heat treatment, the billet is peeled and sawn to prepare alloy forging. Figure 2 This is a sampling location diagram for observing the microstructure of forgings, by... Figure 2 As can be seen, this invention involves taking metallographic samples from the edge, 1 / 2R, and core of the forging cross-section for microstructural observation and evaluation. Figures 3-8 show the low-magnification microstructure and microstructure of the TC6 titanium alloy forgings prepared in Examples 1 and 2. From Figures 3(a) and 3(b), 5(a) and 5(b), and 6(a) and 6(b), it can be seen that the low-magnification microstructure at the head and tail of the forging cross-section is uniform and fine, and the low-magnification microstructure at different locations is uniform and consistent. Figure 4 As can be seen, the microstructure of the forging is a basket webbing structure. As shown in Figures 7(a), 7(b), 7(c), 8(a), 8(b), and 8(c), the microstructure at different locations is uniform.

[0088] Comparative Example

[0089] Currently, there are two methods for preparing high-strength and high-toughness forgings of TC6 alloy: Method 1: forging is made by two-phase forging; Method 2: forging is made by single-phase forging.

[0090] To verify the effectiveness of the technical solution provided by this invention, room temperature mechanical properties were tested on the TC6 titanium alloy forgings prepared by methods one and two in Examples 1 and 2, respectively. The test results are detailed in Tables 1 to 4 below:

[0091] Table 1 shows the room temperature mechanical properties test results of the forgings obtained in Example 1.

[0092]

[0093] Table 2 shows the room temperature mechanical properties test results of the forgings obtained in Example 2.

[0094]

[0095] Table 3 shows the room temperature mechanical property test results of the forgings prepared by Comparative Method 1 (two-phase region forging).

[0096]

[0097]

[0098] Table 4 shows the room temperature mechanical property test results of the forgings prepared by Comparative Method 2 (single-phase region forging).

[0099]

[0100] As shown in Tables 3 and 4, the test results indicate that forgings produced by Method 1 using two-phase forging exhibit high fracture toughness K. IC Does not meet ≥70MPa.m 1 / 2； Method 2 uses single-phase forging to produce forgings, which have low room temperature tensile elongation and pose a risk of non-compliance.

[0101] As shown in Tables 1 and 2, the forgings prepared using the method provided by this invention completely solve the above problems, exhibiting a room temperature tensile strength Rm ≥ 930 MPa, a room temperature tensile elongation A ≥ 8%, and a room temperature fracture toughness K. IC ≥70MPa·m 1 / 2 The forgings exhibit good matching of room temperature tensile elongation and fracture toughness with sufficient allowances, and other properties meet standard requirements. They can satisfy the stringent requirements for high strength and toughness of the alloy forgings in aerospace and other industries, and are suitable for industrial production.

[0102] 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.

[0103] 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 present invention is limited only by the appended claims.

Claims

1. A method for preparing a high-strength, high-toughness forging of TC6 titanium alloy, characterized in that, The process flow of the preparation method is as follows: billet forging → intermediate forging → β forging → forming forging → heat treatment; wherein, The intermediate forging process specifically involves the following steps: First, the first billet obtained after the initial forging is subjected to 3-5 upsetting and drawing forging cycles at temperatures ranging from 20°C to 200°C above the phase transformation point to 20°C to 70°C below the phase transformation point to obtain the second billet. After forging, the billet is air-cooled or water-cooled. Between forging cycles, a furnace reheating method is used, with the deformation per pass controlled between 30% and 50%, and the cumulative deformation per pass greater than 70%. The final forging cycle involves holding and forging at temperatures between 30°C and 70°C above the phase transformation point, with the cumulative deformation greater than 60%. Then, the second billet is subjected to 3-5 holding and forging cycles at temperatures between 30°C and 80°C below the phase transformation point for a specified holding time T2, followed by air cooling. The deformation per pass is controlled between 20% and 40%, and the cumulative deformation per pass greater than 40%. After forging, billet A is obtained for β forging. The β forging specifically involves heating the billet A obtained from intermediate forging to 20°C~60°C above the phase transformation point using a stepped heating method and holding it at that temperature for a specified time T3. After exiting the furnace, the billet A is forged with a deformation of more than 20%. After forging, it is air-cooled to obtain billet B. The forming forging specifically involves heating the billet B obtained by β forging to 30°C~60°C below the phase transformation point and holding it at that temperature for a specified time T4. After being taken out of the furnace, the billet B is forged, and the deformation amount is not greater than 30%. After forging, it is air-cooled to obtain an intermediate forging. The heat treatment specifically involves: performing double annealing on the intermediate forging obtained by forming forging; the first annealing temperature is 870℃~920℃, and the forging is held at this temperature until it is fully heated, and then air-cooled after being taken out of the furnace; the second annealing temperature is 550℃~600℃, and the forging is held at this temperature for 2h~5h, and then air-cooled after being taken out of the furnace, to obtain a TC6 titanium alloy high-strength and high-toughness forging. Wherein, the specified time T2 = D2 × (0.6~0.8), where D2 is the minimum diameter of the second billet in mm, and T2 is in min; the specified time T3 = D3 × (0.3~0.6), where D3 is the minimum diameter of billet A in mm, and T3 is in min.

2. The method for preparing the TC6 titanium alloy high-strength and high-toughness forging according to claim 1, characterized in that, The specified time T4 = D4 × (0.6~0.8), where D4 is the minimum diameter of billet B in mm, and T4 is in min.

3. The method for preparing the TC6 titanium alloy high-strength and high-toughness forging according to claim 1, characterized in that, The specific process of billet forging is as follows: Titanium alloy ingots are selected and held at 100℃~250℃ above the phase transformation point for a specified time T1; the titanium alloy ingots are subjected to multiple upsetting and drawing forging to obtain the first billet, which is then air-cooled after forging; wherein, a furnace reheating method is adopted between the forging and drawing forging, the deformation amount of a single pass is controlled between 20% and 40%, and the cumulative deformation amount of each forging is greater than 60%.

4. The method for preparing the TC6 titanium alloy high-strength and high-toughness forging according to claim 3, characterized in that, The specified time T1 = D1 × (0.45~0.8), where D1 is the minimum size of the titanium alloy ingot in mm, and T1 is in min.

5. The method for preparing the TC6 titanium alloy high-strength and high-toughness forging according to claim 1, characterized in that, The cross-sectional shape of the second billet is square or octagonal to ensure uniform deformation of all parts of the second billet.

6. The method for preparing the TC6 titanium alloy high-strength and high-toughness forging according to any one of claims 1 to 5, characterized in that, The TC6 titanium alloy high-strength and high-toughness forging has a room temperature tensile strength Rm ≥ 930 MPa, a room temperature tensile elongation A ≥ 8%, and a room temperature fracture toughness K. IC ≥70MPa·m 1 / 2 .

7. The method for preparing the TC6 titanium alloy high-strength and high-toughness forging according to any one of claims 1 to 5, characterized in that, The cross-sectional dimensions of the TC6 titanium alloy high-strength and high-toughness forgings are between 70mm and 400mm.

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