Powder metallurgy full-sheet high-strength beta titanium alloy and preparation process thereof

Abstract

The invention relates to the technical field of titanium alloy powder metallurgy, in particular to a powder metallurgy full-sheet high-strength beta titanium alloy and a preparation technology thereof.The preparation technology comprises the steps that Ti55541 alloy powder is prepared, and the Ti55541 alloy powder is formed by mixing coarse powder and fine powder; the Ti55541 alloy powder is put into a sheath, and then degassing and seal welding are carried out; performing hot isostatic pressing treatment on the sheath filled with the powder to obtain a workpiece; and removing the sheath outside the workpiece to obtain the target alloy. According to the method, the hot isostatic pressing near-net forming process is adopted, densification and aging treatment is completed on the powder, a workpiece with a fine and uniform microstructure is obtained, and compared with the process limitation of'primary forging-finish forging-heat treatment 'in the prior art, the mechanical property of the target alloy is remarkably improved, meanwhile, the production period can be effectively shortened, the machining amount is reduced, and the raw material utilization rate is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy powder metallurgy, and in particular to a powder metallurgy full-lamellar high-strength beta titanium alloy and a preparation process thereof. Background Art

[0002] Ti55541 titanium alloy offers advantages such as low density, high strength, and excellent corrosion resistance. After heat treatment, the alloy's fracture toughness remains on par with conventional high-strength alloys, but its static strength is higher and its hardenability is improved. This makes it a new metastable β-titanium alloy with the highest strength among existing titanium alloy aerospace structural materials.

[0003] At present, Ti55541 is mainly produced by forging process. However, due to the defects of titanium alloy such as high strength, poor deformation ability, severe cold work hardening, strong springback, easy cracking, easy sticking to the mold, etc., forging is prone to produce poor product quality, high material consumption, high labor intensity, low production efficiency, high scrap rate and high cost, which cannot meet the application needs of special fields such as aviation and aerospace.

[0004] In view of this, the present application proposes a production process for preparing high-strength metastable β titanium alloy by hot isostatic pressing. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention proposes a preparation process for powder metallurgy full-lamellar high-strength β titanium alloy. By adjusting and optimizing the hot isostatic pressing process, titanium alloy formed parts with uniform structure and excellent performance are prepared.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a preparation process of a powder metallurgy full-lamellar high-strength β titanium alloy, comprising the following steps:

[0008] S1. Prepare Ti55541 alloy powder, wherein the Ti55541 alloy powder is formed by mixing coarse powder and fine powder;

[0009] S2, after Ti55541 alloy powder is put into the package, degassing and sealing welding is carried out;

[0010] S3, hot isostatic pressing the bag filled with powder in S2 to obtain a product;

[0011] S4. Remove the outer sheath of the workpiece to obtain the target alloy.

[0012] Specifically, in S1, the chemical composition of the Ti55541 alloy powder is as follows by mass percentage: Mo: 4.5% to 5.5%, V: 4.5% to 5.5%, Cr: 5.0% to 6.5%, Al: 3.7% to 5.0%, Nb: 0.75% to 1.25%, Fe≤0.15%, Si≤0.15%, O≤0.07%, C≤0.005%, N≤0.004%, H≤0.002%, and Ti as the balance.

[0013] Specifically, in S1, the Ti55541 alloy powder has a sphericity of ≥95%, a fluidity of 17s / 50g to 23s / 50g, and a hollow powder rate of <0.1%.

[0014] Specifically, in S1, the particle size of the coarse powder is in the range of 90 μm to 150 μm, the particle size of the fine powder is in the range of 45 μm to 75 μm, and the mass proportion of the coarse powder in the Ti55541 alloy powder is 40% to 60%.

[0015] Specifically, in S3, the process of hot isostatic pressing treatment is: first, the temperature is increased to 800℃~880℃ at a heating rate of 5℃ / min~15℃ / min, the pressure is increased to 100MPa~200MPa with the temperature, and the temperature is kept at this temperature for 0.5h~5h; then, the temperature is reduced to 450℃~550℃ at a cooling rate of 5℃ / min~15℃ / min, and the temperature is kept at this temperature for 1h~10h; finally, the temperature is reduced to 80℃~100℃ before being taken out of the furnace.

[0016] Specifically, the temperature reduction process adopts argon air cooling.

[0017] Specifically, in S2, the shape of the sheath is designed according to the shape of the target alloy.

[0018] Specifically, in S2, the package needs to be shot blasted before being filled with powder.

[0019] The present invention also provides a powder metallurgy full-lamellar high-strength β titanium alloy, which is prepared by the above-mentioned preparation process.

[0020] Specifically, the room temperature tensile strength of the β titanium alloy is greater than 1300 MPa, and the elongation after fracture is greater than 7.5%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention adopts a hot isostatic pressing near-net-shape forming process to complete the densification and aging treatment of the powder under specific conditions to obtain a product with a fine and uniform microstructure. Compared with the "initial forging-final forging-heat treatment" process limitation of the prior art, the present invention significantly improves the mechanical properties of the target alloy while effectively shortening the production cycle, reducing the processing volume, and improving the utilization rate of raw materials.

[0023] (2) The present invention uses Ti55541 titanium alloy powder with a particle size range of 90μm to 150μm and 45μm to 75μm as raw material. The combination of coarse and fine powders can increase the powder tap density, reduce the shrinkage of the sheath after hot isostatic pressing, and reduce the amount of materials used in the initial sheath production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a process flow chart for preparing the same;

[0025] Figure 2 This is a metallographic diagram of the Ti55541 alloy prepared in Example 1 of the present invention;

[0026] Figure 3 This is a metallographic image of the Ti55541 alloy prepared in Example 2 of the present invention;

[0027] Figure 4 This is a metallographic image of the Ti55541 alloy prepared in Example 3 of the present invention;

[0028] Figure 5 This is the metallographic image of the Ti55541 alloy prepared in Comparative Example 1. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] Example 1

[0031] refer to Figure 1 This embodiment proposes a preparation process of a powder metallurgy full-lamellar high-strength β titanium alloy, which specifically comprises the following steps:

[0032] S1. Prepare Ti55541 alloy powder for use by a plasma rotating electrode method. The process of preparing the Ti55541 alloy powder for use is as follows: first prepare fine powder, the fine powder being Ti55541 alloy powder with a particle size in the range of 45 μm to 75 μm; then prepare coarse powder, the coarse powder being Ti55541 alloy powder with a particle size in the range of 90 μm to 150 μm; finally, uniformly mix the fine powder and the coarse powder to form the Ti55541 alloy powder for use; the sphericity of the Ti55541 alloy powder for use is ≥95%, the fluidity is 17 s / 50 g, the hollow powder rate is <0.09%, the relative density is 0.67, and the mass proportion of the coarse powder in the Ti55541 alloy powder for use is 60%;

[0033] S2, putting the Ti55541 alloy powder to be used into the package, degassing it and sealing it with welding;

[0034] S3. The bag filled with powder in S2 is subjected to hot isostatic pressing to obtain a product; the specific process of the hot isostatic pressing is as follows: first, the temperature is raised to 800°C at a heating rate of 5°C / min, the pressure is increased to 200 MPa as the temperature increases, and the heat and pressure are maintained for 0.5h; then, the temperature is lowered to 450°C at a cooling rate of 5°C / min, and the heat and pressure are maintained for 10h; finally, argon is used to air-cool the bag to 80°C before taking the bag out of the furnace.

[0035] S4. Remove the outer sheath of the workpiece to obtain Ti55541 alloy.

[0036] In this embodiment, the chemical composition of the Ti55541 alloy powder to be used is as follows by mass percentage: Mo: 4.5%, V: 5.5%, Cr: 5.0%, Al: 5.0%, Nb: 1.25%, Fe: 0.14%, Si: 0.15%, O: 0.07%, C: 0.005%, N: 0.003%, H: 0.002%, and the balance is Ti;

[0037] refer to Figure 2 It can be seen that in the Ti55541 alloy prepared in this embodiment, the original β grain size is 37 μm, the α cluster size is 11 μm, and the α sheet thickness is 0.5 μm.

[0038] Example 2

[0039] This embodiment provides a preparation process for a powder metallurgy full-lamellar high-strength β titanium alloy, which specifically comprises the following steps:

[0040] S1. Prepare Ti55541 alloy powder for use by a plasma rotating electrode method. The process of preparing the Ti55541 alloy powder for use is as follows: first prepare fine powder, the fine powder being Ti55541 alloy powder with a particle size in the range of 45 μm to 75 μm; then prepare coarse powder, the coarse powder being Ti55541 alloy powder with a particle size in the range of 90 μm to 150 μm; finally, uniformly mix the fine powder and the coarse powder to form the Ti55541 alloy powder for use; the sphericity of the Ti55541 alloy powder for use is ≥96%, the fluidity is 19.9 s / 50 g, the hollow powder rate is <0.08%, the relative density is 0.69, and the mass proportion of the coarse powder in the Ti55541 alloy powder for use is 50%;

[0041] S2, putting the Ti55541 alloy powder to be used into the package, degassing it and sealing it with welding;

[0042] S3. The bag filled with powder in S2 is subjected to hot isostatic pressing to obtain a product; the specific process of the hot isostatic pressing is as follows: first, the temperature is increased to 840°C at a heating rate of 10°C / min, the pressure is increased to 150MPa as the temperature increases, and the product is kept at this temperature and pressure for 3 hours; then, the temperature is decreased to 500°C at a cooling rate of 10°C / min, and the product is kept at this temperature and pressure for 5 hours; finally, the product is air-cooled to 90°C with argon gas and then taken out of the furnace.

[0043] S4. Remove the outer sheath of the workpiece to obtain Ti55541 alloy.

[0044] In this embodiment, the chemical composition of the Ti55541 alloy powder to be used is as follows by mass percentage: Mo: 5%, V: 4.5%, Cr: 6.0%, Al: 4.5%, Nb: 1.0%, Fe: 0.13%, Si: 0.13%, O: 0.05%, C: 0.004%, N: 0.002%, H: 0.001%, and the balance is Ti;

[0045] refer to Figure 3 It can be seen that in the Ti55541 alloy prepared in this embodiment, the original β grain size is 74 μm, the α cluster size is 18 μm, and the α sheet thickness is 0.8 μm.

[0046] Example 3

[0047] This embodiment provides a preparation process for a powder metallurgy full-lamellar high-strength β titanium alloy, which specifically comprises the following steps:

[0048] S1. Prepare Ti55541 alloy powder for use by a plasma rotating electrode method. The process of preparing the Ti55541 alloy powder for use is as follows: first prepare fine powder, the fine powder being Ti55541 alloy powder with a particle size in the range of 45 μm to 75 μm; then prepare coarse powder, the coarse powder being Ti55541 alloy powder with a particle size in the range of 90 μm to 150 μm; finally, uniformly mix the fine powder and the coarse powder to form the Ti55541 alloy powder for use; the sphericity of the Ti55541 alloy powder for use is ≥97%, the fluidity is 23 s / 50 g, the hollow powder rate is <0.08%, the relative density is 0.71, and the mass proportion of the coarse powder in the Ti55541 alloy powder for use is 60%;

[0049] S2, putting the Ti55541 alloy powder to be used into the package, degassing it and sealing it with welding;

[0050] S3. The bag filled with powder in S2 is subjected to hot isostatic pressing to obtain a product; the specific process of the hot isostatic pressing is as follows: first, the temperature is raised to 880°C at a heating rate of 15°C / min, the pressure is increased to 100 MPa as the temperature increases, and the heat and pressure are maintained for 5 hours; then, the temperature is lowered to 550°C at a cooling rate of 15°C / min, and the heat and pressure are maintained for 2 hours; finally, argon is used to air cool the bag to 100°C before taking the bag out of the furnace.

[0051] S4. Remove the outer sheath of the workpiece to obtain Ti55541 alloy.

[0052] In this embodiment, the chemical composition of the Ti55541 alloy powder to be used is as follows by mass percentage: Mo: 5.5%, V: 5.0%, Cr: 6.5%, Al: 3.7%, Nb: 0.75%, Fe: 0.12%, Si: 0.14%, O: 0.04%, C: 0.004%, N: 0.003%, H: 0.001%, and Ti as the balance.

[0053] refer to Figure 4 It can be seen that in the Ti55541 alloy prepared in this embodiment, the original β grain size is 104 μm, the α cluster size is 28 μm, and the α sheet thickness is 1.8 μm.

[0054] In the above embodiments, the shape of the can is designed according to the shape of the target alloy; before powder filling, the can needs to be shot blasted to remove the oxide layer and oil stains on the surface of the can.

[0055] Comparative Example 1

[0056] This comparative example provides a forging process of Ti55541, which specifically includes the following steps:

[0057] S1. The ingot is heated to 850℃ and kept at this temperature for 2 hours. The ingot is initially forged using a two-fire free forging process with a deformation of 40% in each fire. The ingot is then air-cooled after forging.

[0058] S2. Heat the forging in S1 to 780℃, and then complete the final forging in two passes, with a deformation of 30% in each pass, and air cool after forging.

[0059] S3. The forging obtained in S2 is solution treated at 870°C for 2 hours and then air-cooled, and then aged at 550°C for 4 hours and then air-cooled.

[0060] In this embodiment, the chemical composition of the Ti55541 alloy powder to be used is as follows by mass percentage: Mo: 5.03%, V: 5.0%, Cr: 5.42%, Al: 4.28%, Nb: 0.97%, Fe: 0.021%, Si: 0.1%, O: 0.05%, C: 0.006%, N: 0.004%, H: 0.001%, and Ti as the balance.

[0061] refer to Figure 4 It can be seen that in the Ti55541 alloy prepared in this embodiment, the original β grain size is 161 μm, the α cluster size is 43 μm, and the α sheet thickness is 2.5 μm.

[0062] In order to better illustrate the beneficial effects of the present invention, the room temperature tensile strength and elongation after fracture of the Ti55541 alloys prepared in Examples 1-3 and Comparative Example 1 were tested with reference to GB / T 228.1-2021. The results are shown in Table 1:

[0063] Table 1 TC4 titanium alloy performance test results

[0064] performance Example 1 Example 2 Example 3 Comparative Example 1 Tensile strength Mpa 1378 1352 1302 1277 Elongation after break % 8.7 7.9 8.1 5.8

[0065] Depend on Figures 2 to 5 It can be seen from the data in Table 1 that the present invention can significantly improve the strength and plasticity of Ti55541 alloy and has very good promotion value.

[0066] The specific embodiments of the present invention are provided to enable those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be 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 present invention.

[0067] It should be understood that the present invention is not limited to the above description and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A process for preparing a powder metallurgy full-lamellar high-strength β titanium alloy, characterized in that: The following steps are involved: S1, preparing Ti55541 alloy powder, wherein the Ti55541 alloy powder is formed by mixing coarse powder and fine powder; S2, after Ti55541 alloy powder is put into the package, degassing and sealing welding is carried out; S3, hot isostatic pressing the bag filled with powder in S2 to obtain a product; S4. Remove the outer sheath of the workpiece to obtain the target alloy.

2. The process for preparing the powder metallurgy full-lamellar high-strength β titanium alloy according to claim 1, characterized in that: In S1, the chemical composition of the Ti55541 alloy powder is as follows by mass percentage: Mo: 4.5% to 5.5%, V: 4.5% to 5.5%, Cr: 5.0% to 6.5%, Al: 3.7% to 5.0%, Nb: 0.75% to 1.25%, Fe≤0.15%, Si≤0.15%, O≤0.07%, C≤0.005%, N≤0.004%, H≤0.002%, and Ti as the balance.

3. The process for preparing the powder metallurgy full lamellar high-strength β titanium alloy according to claim 1, characterized in that: In S1, the sphericity of the Ti55541 alloy powder is ≥95%, the fluidity is 17s / 50g to 23s / 50g, and the hollow powder rate is <0.1%.

4. The process for preparing the powder metallurgy full lamellar high-strength β titanium alloy according to claim 1, characterized in that: In S1, the particle size of the coarse powder is in the range of 90 μm to 150 μm, the particle size of the fine powder is in the range of 45 μm to 75 μm, and the mass proportion of the coarse powder in the Ti55541 alloy powder is 40% to 60%.

5. The process for preparing the powder metallurgy full lamellar high-strength β titanium alloy according to claim 1, characterized in that: In S3, the process of hot isostatic pressing treatment is: first, the temperature is increased to 800℃~880℃ at a heating rate of 5℃ / min~15℃ / min, the pressure is increased to 100MPa~200MPa as the temperature increases, and the temperature is kept at this temperature for 0.5h~5h; then, the temperature is reduced to 450℃~550℃ at a cooling rate of 5℃ / min~15℃ / min, and the temperature is kept at this temperature for 1h~10h; finally, the temperature is reduced to 80℃~100℃ before being taken out of the furnace.

6. The process for preparing the powder metallurgy full lamellar high-strength β titanium alloy according to claim 5, characterized in that: The temperature reduction process adopts argon air cooling.

7. The process for preparing a powder metallurgy full-lamellar high-strength β titanium alloy according to claim 1, characterized in that: In S2, the shape of the sheath is designed according to the shape of the target alloy.

8. The process for preparing the powder metallurgy full lamellar high-strength β titanium alloy according to claim 1, characterized in that: In S2, the bag needs to be shot blasted before powder is filled.

9. A powder metallurgy full lamellar high-strength β titanium alloy, characterized in that: The β titanium alloy is prepared by the preparation process according to any one of claims 1 to 8.

10. The powder metallurgy full lamellar high-strength β titanium alloy according to claim 9, characterized in that: The room temperature tensile strength of the beta titanium alloy is greater than 1300 MPa, and the elongation after fracture is greater than 7.5%.

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