Titanium alloy component and preparation method thereof based on powder metallurgy-isothermal forging

Abstract

The invention belongs to the technical field of titanium alloy preparation, and particularly discloses a titanium alloy component and a preparation method thereof based on powder metallurgy-isothermal forging.The preparation method comprises the steps that titanium powder and intermediate alloy powder are evenly mixed, and mixed powder is obtained; the mixed powder is subjected to cold isostatic pressing forming, and a green body sample is obtained; the green body sample is subjected to vacuum sintering, and a titanium alloy sintered ingot is obtained; the titanium alloy sintered ingot is pre-forged and then subjected to isothermal forging forming, and a titanium alloy forge piece is obtained; and the titanium alloy forge piece is subjected to heat treatment to obtain the titanium alloy component. According to the method, powder metallurgy is combined with two-step forging forming, the titanium alloy component which is small in grain size, high in homogeneity and high in performance can be obtained, and the method is suitable for low-cost, large-scale and efficient production of the titanium alloy component.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy preparation technology, and more specifically, relates to a titanium alloy component and its preparation method based on powder metallurgy-isothermal forging. Background Technology

[0002] Titanium alloys possess advantages such as high specific strength, excellent high-temperature resistance, good corrosion resistance, good fatigue performance, and good fracture toughness, making them of great significance in aerospace, marine, and chemical industries. Traditional high-performance titanium alloy components are typically produced using a casting-forging process, but this method has the following limitations: 1. High risk of component segregation: Element segregation is prone to occur during the casting process, requiring repeated remelting to improve uniformity, which leads to a significant increase in production costs; 2. Coarse grain structure: The grain size of cast titanium alloy is relatively large, and its mechanical properties are difficult to meet the requirements of high-end equipment. Multiple pre-forging processes are required before forging to refine the grains. Therefore, the process is complicated, the production cycle is long, and the manufacturing cost is further increased. 3. The isothermal forging process is very sensitive to process parameters, and the forging window is narrow, which can easily lead to unstable performance.

[0003] Therefore, there is an urgent need for a low-cost, highly homogeneous, and high-performance method for preparing titanium alloy components. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a titanium alloy component and its preparation method based on powder metallurgy-isothermal forging, with the aim of achieving low-cost preparation of high homogeneous and high-performance titanium alloy components.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for preparing titanium alloy components based on powder metallurgy-isothermal forging is proposed, comprising the following steps: S1. Mix titanium powder and intermediate alloy powder evenly to obtain mixed powder; S2. The mixed powder is cold isostatically pressed to form a green sample. S3. Vacuum sinter the green sample to obtain a titanium alloy sintered ingot; S4. The titanium alloy sintered ingot is first pre-forged and then isothermal forged to obtain titanium alloy forgings. S5. Heat treat the titanium alloy forgings to obtain titanium alloy components.

[0006] As a further preferred option, in step S4, the pre-forging temperature is 10°C to 60°C below the phase transformation point.

[0007] As a further preferred option, in step S4, the isothermal forging temperature is 80°C below the phase transformation point to 60°C above the phase transformation point, followed by air cooling after forging.

[0008] As a further preferred option, in step S4, the isothermal forging temperature is 20°C to 60°C above the phase transformation point.

[0009] As a further preferred option, in step S4, the temperature is maintained for 0.5h to 3h before pre-forging and isothermal forging, respectively.

[0010] As a further preferred option, in step S2, the cold isostatic pressure is 150MPa to 800MPa, and the pressure holding time is 800s to 1800s.

[0011] As a further preferred option, in step S3, the sintering temperature is 1000℃~1500℃, and the holding time is 2h~6h.

[0012] As a further preferred option, in step S5, the heat treatment adopts a solution-aging process. The solution process involves holding at 750℃~850℃ for 3h~5h and then quenching; the aging process involves holding at 550℃~650℃ for 6h~12h and then air cooling.

[0013] As a further preferred embodiment, the titanium powder has an oxygen content of <1000ppm, a hydrogen content of <500ppm, and a particle size of <150μm; the intermediate alloy powder has an oxygen content of <1000ppm and a particle size of <150μm.

[0014] According to another aspect of the present invention, a titanium alloy component is provided, which is prepared by the above-mentioned titanium alloy component preparation method based on powder metallurgy-isothermal forging.

[0015] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages: 1. This invention employs a two-step forging process combined with powder metallurgy. The sintered ingot prepared by powder metallurgy has the advantages of high homogeneity and fine grains. Moreover, the presence of residual pores inhibits grain growth during the forging process. Furthermore, forging further improves the microstructure and completely closes the pores of the ingot, ultimately obtaining a titanium alloy component with fine grains, high homogeneity, and high performance.

[0016] 2. Compared to traditional casting, powder metallurgy sintersulates below the melting point, achieving element homogenization through solid-state diffusion. This saves energy and reduces costs, while effectively avoiding compositional segregation and non-uniform regions like β-spots found in traditional casting processes, ensuring the uniformity of the sintered structure. Furthermore, the pinning effect of residual pores in powder metallurgy ingots effectively inhibits grain growth, resulting in significantly smaller grain sizes compared to traditional casting. Moreover, the presence of residual porosity makes it easier for grains to grow during pre-forging and isothermal forging, leading to stronger hot-forming capabilities.

[0017] 3. After powder metallurgy, a two-step forging process consisting of one-step pre-forging and one-step isothermal forging is employed. The forging temperature is designed, specifically pre-forging at 10~60℃ below the phase transformation point to introduce uniform deformation, further refine the β grains, and introduce high-density dislocations and substructures at the α / β interface. This provides stable recrystallization and phase transformation initiation conditions for subsequent isothermal forging, thereby enabling the acquisition of a basketweave structure or bimodal structure with fully broken α phase, fine grains, and uniform microstructure over a wide range of isothermal forging temperatures. Finally, high-performance titanium alloy components are obtained after heat treatment.

[0018] 4. Using low-cost, high-quality titanium powder with an oxygen content of less than 1000 ppm, oxygen is controlled from the source. Compared with titanium alloys prepared by the traditional mixed element method, the impurity element content is significantly reduced. After isothermal forging at different temperatures, good microstructure and strong performance stability are obtained. It is suitable for the industrial production of high-end titanium alloy equipment and can be used in cutting-edge fields such as aerospace and high-end equipment. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the microstructure and elemental distribution of the sintered blank according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the microstructure and elemental distribution of the forging in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the microstructure of the forging after heat treatment in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the tensile test results of the heat-treated part in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the microstructure and elemental distribution of the forging in Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of the microstructure of the forging after heat treatment in Embodiment 2 of the present invention; Figure 7 This is a schematic diagram of the tensile test results of the heat-treated part in Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of the microstructure and elemental distribution of the forging in Embodiment 3 of the present invention; Figure 9 This is a schematic diagram of the microstructure of the forging after heat treatment in Embodiment 3 of the present invention; Figure 10 This is a schematic diagram of the tensile test results of the heat-treated part in Embodiment 3 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0021] This invention provides a method for preparing titanium alloy components based on powder metallurgy-isothermal forging, comprising the following steps: S1. Mix titanium powder and intermediate alloy powder evenly to obtain mixed powder.

[0022] Specifically, low-cost titanium powders such as HDH titanium powder or PREP titanium powder are used. The titanium powder and intermediate alloy powder are weighed in a glove box according to the mass ratio, and then transferred to a mixer for a mixing process of 2 to 20 hours under argon protection to obtain uniformly mixed powder.

[0023] Furthermore, the titanium powder has an oxygen content of <1000 ppm, a hydrogen content of <500 ppm, and a particle size of <150 μm; the intermediate alloy powder has a particle size of <150 μm and an oxygen content of <1000 ppm.

[0024] S2. The mixed powder is cold isostatically pressed to form a green sample.

[0025] Furthermore, the mixed powder is filled and compacted in a cold isostatic pressing sleeve, then the sleeve is sealed and cold isostatically pressed into shape under a pressure of 150-800 MPa for a holding time of 800-1800 s to obtain a green sample; the green sample has a relative density ≥70% and a tensile strength ≥5 MPa.

[0026] S3. Vacuum sinter the green sample to obtain a titanium alloy sintered ingot.

[0027] Furthermore, the green sample was placed in a vacuum sintering furnace for vacuum sintering at a temperature of 1000–1500℃ for a holding time of 2–6 h to obtain a titanium alloy sintered ingot. During the sintering process, the vacuum was maintained below 1.0E-2 Pa. The sintered microstructure was Widmanstätten, with an average grain size of <150 μm and a density of ≥94%.

[0028] S4. The titanium alloy sintered ingot is first pre-forged and then isothermal forged to obtain titanium alloy forgings.

[0029] Furthermore, the titanium alloy sintered ingot is first pre-forged at a temperature 10-60°C below the phase transformation point to further refine the grains; then it undergoes isothermal forging at a temperature 80°C below the phase transformation point to 60°C above the phase transformation point, followed by air cooling to obtain a titanium alloy forging. This forging achieves complete densification (density > 99.9%), and the lath-like α-phase in the original Widmanstätten structure is fully broken down. Preferably, isothermal forging is performed at a temperature 20-60°C above the phase transformation point to obtain better fracture toughness, while also reducing flow stress and extending die life; this is the optimal isothermal forging temperature range.

[0030] Furthermore, the workpiece is held at a temperature of 30 min to 3 h before pre-forging and isothermal forging to ensure uniform workpiece temperature. The specific time is adjusted according to the workpiece thickness. If the temperature drop during each forging process is less than 100℃, it is permissible to remelt the workpiece.

[0031] S5. Perform post-forging heat treatment on the titanium alloy forging to obtain titanium alloy components.

[0032] Furthermore, the heat treatment adopts a solution-aging process. The solution process involves holding at 750℃~850℃ for 3h~5h and then quenching; the aging process involves holding at 550℃~650℃ for 6h~12h and then air cooling. The microstructure after heat treatment is a bimodal microstructure or a basketweave microstructure.

[0033] The following are specific examples: Example 1 The preparation method of TC17 titanium alloy components includes the following steps: (1) HDH titanium powder, AlMoCr master alloy powder, Sn powder and Zr powder are mixed in a glove box at a mass ratio of 83:13:2:2. After mixing, the powder is put into a mixer protected by high-purity argon gas for 24 hours.

[0034] (2) The mixed powder described in step (1) is transferred to a glove box protected by high-purity argon gas and placed in a cold isostatic pressing sleeve. The sleeve is then sealed and cold isostatic pressing is performed at a pressure of 300 MPa for a holding time of 1800 s to obtain a pressed green compact.

[0035] (3) The green blank described in step (2) is sintered in a vacuum sintering furnace. Before heating, ensure that the vacuum degree is higher than 1E-2Pa, the sintering temperature is 1400 ℃, and the holding time is 4 h to obtain the sintered green blank with the following microstructure: Figure 1 As shown, the microstructure is uniform. Elemental analysis of the sintered ingot is shown in Table 1, with oxygen content ~950 ppm and hydrogen content ~11 ppm.

[0036] Table 1. Element content of sintered ingots

[0037] (4) The TC17 sintered billet from step (3) is pre-forged at 60°C below its phase transformation point and isothermal forged at 20°C above its phase transformation point, followed by air cooling. The asphalt microstructure is as follows: Figure 2 As shown, the tissue composition is uniform.

[0038] (5) The forgings from step (4) are subjected to heat treatment. The heat treatment process is: 800℃, 4h WQ, 630℃, 8h AC. The final heat-treated microstructure is as follows: Figure 3 The image shows the mesh structure of a basket. The tensile test curve is shown below. Figure 4 As shown (tested three times), the tensile strength is 1152.36±6.37 MPa, the yield strength is 1109.84±4.23 MPa, the elongation after fracture is 12.97%±0.37%, and K... ⅠC The measured value was 74.33 ± 2.81 MPa·m 1 / 2 The powder metallurgy-forging technology route can reduce production costs by 20% compared to the casting-forging technology route.

[0039] Example 2 The preparation method of TC17 titanium alloy components includes the following steps: (1) HDH titanium powder, AlMoCr master alloy powder, Sn powder and Zr powder are mixed in a glove box at a mass ratio of 83:13:2:2. After mixing, the powder is put into a mixer protected by high-purity argon gas for mixing for 24 hours. (2) The mixed powder described in step (1) is transferred to a glove box protected by high-purity argon gas and placed in a cold isostatic pressing sleeve. The sleeve is then sealed and cold isostatic pressing is performed at a pressure of 300 MPa for a holding time of 1800 s to obtain a pressed green compact. (3) The green billet described in step (2) is sintered in a vacuum sintering furnace. Before heating, ensure that the vacuum degree is higher than 1E-2Pa, the sintering temperature is 1400 ℃, and the temperature is held for 4 h to obtain the sintered green billet.

[0040] (4) The TC17 sintered billet from step (3) is pre-forged at 60°C below its phase transformation point and isothermal forged at 60°C above its phase transformation point, followed by air cooling. The asphalt microstructure is as follows: Figure 5 As shown, the tissue composition is uniform.

[0041] (5) The forgings from step (4) are subjected to heat treatment. The heat treatment process is: 800℃, 4h WQ, 630℃, 8h AC. The final heat-treated microstructure is as follows: Figure 6 The image shows the mesh structure of a basket. The tensile test curve is shown below. Figure 7As shown, the tensile strength is 1158.22±7.86 MPa, the yield strength is 1109.71±6.41 MPa, the elongation after fracture is 13.40%±1.21%, and K... ⅠC The measured value was 73.05 ± 2.62 MPa·m. 1 / 2 It exhibits excellent performance and fully complies with the national standard GB / T 38915-2020. The powder metallurgy-forging technology route can reduce production costs by 20% compared to the casting-forging technology route.

[0042] Example 3 The preparation method of TC17 titanium alloy components includes the following steps: (1) HDH titanium powder, AlMoCr master alloy powder, Sn powder and Zr powder are mixed in a glove box at a mass ratio of 83:13:2:2. After mixing, the powder is put into a mixer protected by high-purity argon gas for mixing for 24 hours. (2) The mixed powder described in step (1) is transferred to a glove box protected by high-purity argon gas and placed in a cold isostatic pressing sleeve. The sleeve is then sealed and cold isostatic pressing is performed at a pressure of 300 MPa for a holding time of 1800 s to obtain a pressed green compact. (3) The green billet described in step (2) is sintered in a vacuum sintering furnace. Before heating, ensure that the vacuum degree is higher than 1E-2Pa, the sintering temperature is 1400 ℃, and the temperature is held for 4 h to obtain the sintered green billet.

[0043] (4) The TC17 sintered billet from step (3) is pre-forged at 60°C below its phase transformation point and isothermal forged at 80°C below its phase transformation point, followed by air cooling. The asphalt microstructure is as follows: Figure 8 As shown, the tissue composition is uniform.

[0044] (5) The forgings from step (4) are subjected to heat treatment. The heat treatment process is: 800℃, 4h WQ, 630℃, 8h AC. The final heat-treated microstructure is as follows: Figure 9 As shown, this is a bimodal structure. The tensile test curve is as follows. Figure 10 As shown, the tensile strength is 1152.76±4.69 MPa, the yield strength is 1123.61±7.99 MPa, the elongation after fracture is 11.43%±0.86%, and K... ⅠC The measured value was 70.56 ± 2.87 MPa·m 1 / 2 It boasts excellent performance and fully complies with the national standard GB / T 38915-2020. The powder metallurgy-forging technology route can reduce production costs by 20% compared to the casting-forging technology route.

[0045] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing titanium alloy components based on powder metallurgy-isothermal forging, characterized in that, Includes the following steps: S1. Mix titanium powder and intermediate alloy powder evenly to obtain mixed powder; S2. The mixed powder is cold isostatically pressed to form a green sample. S3. Vacuum sinter the green sample to obtain a titanium alloy sintered ingot; S4. The titanium alloy sintered ingot is first pre-forged and then isothermal forged to obtain titanium alloy forgings. S5. Heat treat the titanium alloy forgings to obtain titanium alloy components.

2. The method for preparing titanium alloy components based on powder metallurgy-isothermal forging as described in claim 1, characterized in that, Step S4: The pre-forging temperature is 10℃~60℃ below the phase transformation point.

3. The method for preparing titanium alloy components based on powder metallurgy-isothermal forging as described in claim 2, characterized in that, Step S4: The isothermal forging temperature is 80°C below the phase transformation point to 60°C above the phase transformation point, followed by air cooling.

4. The method for preparing titanium alloy components based on powder metallurgy-isothermal forging as described in claim 3, characterized in that, Step S4: The isothermal forging temperature is 20°C to 60°C above the phase transformation point.

5. The method for preparing titanium alloy components based on powder metallurgy-isothermal forging as described in claim 1, characterized in that, Step S4: Hold the material at a temperature of 0.5h to 3h before pre-forging and isothermal forging.

6. The method for preparing titanium alloy components based on powder metallurgy-isothermal forging as described in claim 1, characterized in that, Step S2: The cold isostatic pressure is 150MPa to 800MPa, and the holding time is 800s to 1800s.

7. The method for preparing titanium alloy components based on powder metallurgy-isothermal forging as described in claim 1, characterized in that, Step S3: Sintering temperature is 1000℃~1500℃, holding time is 2h~6h.

8. The method for preparing titanium alloy components based on powder metallurgy-isothermal forging as described in claim 1, characterized in that, Step S5: The heat treatment adopts a solution-aging process. The solution process is to hold at 750℃~850℃ for 3h~5h and then quench; the aging process is to hold at 550℃~650℃ for 6h~12h and then air cool.

9. The method for preparing titanium alloy components based on powder metallurgy-isothermal forging as described in any one of claims 1-8, characterized in that, The titanium powder has an oxygen content of <1000ppm, a hydrogen content of <500ppm, and a particle size of <150μm; the intermediate alloy powder has an oxygen content of <1000ppm and a particle size of <150μm.

10. A titanium alloy component, characterized in that, The titanium alloy component was prepared using the powder metallurgy-isothermal forging method as described in any one of claims 1-9.

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