A method for preparing fine-grained near-alpha high-temperature titanium alloy

Abstract

The present invention belongs to the technical field of alloy materials, and specifically relates to a method for preparing a fine-grained near-α high-temperature titanium alloy. The method for preparing a fine-grained near-α high-temperature titanium alloy comprises the following steps: (1) filling alloy powder onto a construction platform of an SLM processing device and starting SLM processing; during SLM processing, the laser power is 260-380W, the scanning speed is 1000-1500mm / s, and the scanning spacing is 0.05-0.15mm; the alloy powder is a mixture of Ti60 alloy powder, boron powder, and iron powder; (2) the product obtained by SLM processing is subjected to stress relief treatment, solid solution treatment, and aging treatment in sequence; the temperatures of the stress relief treatment and the aging treatment are independently selected from 600-1000°C, the temperature of the solid solution treatment is 1000-1300°C, and the temperature of the solid solution treatment is greater than the temperature of the stress relief treatment and greater than the temperature of the aging treatment. By adjusting and controlling the laser power, scanning speed, and scanning spacing during the SLM processing and combining a reasonable and effective heat treatment process, an alloy material with a density better than 99.95% is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy materials, and in particular relates to a method for preparing a fine-grained near-alpha high-temperature titanium alloy. Background Art

[0002] With the rapid development of the aerospace industry, the performance requirements for related metals and alloys are becoming increasingly stringent. Titanium alloys, resistant to temperatures up to 600°C, are ideal materials for manufacturing components such as blades and disks for aircraft engines and spacecraft due to their excellent specific strength, corrosion resistance, and high-temperature resistance. The basketweave structure in high-temperature titanium alloys, composed of acicular α and β phases, exhibits higher strength than other microstructures when deformed at 800-900°C. This is because the numerous fine acicular α phase grain boundaries within the basketweave structure act as barriers to mobile dislocations, maintaining the material's strength even at high temperatures. The grains are relatively uniform, spherical or polyhedral, with a distinct orientation distribution and uniform grain size. This structure exhibits excellent plasticity and toughness, demonstrating outstanding high-temperature mechanical properties and low temperature sensitivity. Furthermore, the flow stress of the basketweave structure is largely unaffected by temperature when deformed around 600°C, demonstrating excellent thermal stability. These properties give the basketweave structure significant advantages in high-temperature titanium alloys, particularly in the manufacture of components requiring high-temperature performance in aerospace and other fields.

[0003] Traditional casting and forging processes face numerous limitations when manufacturing complex-shaped high-temperature titanium alloy components, such as high equipment costs, low material utilization, and long manufacturing cycles. Selective laser melting (SLM), an emerging additive manufacturing technology, can precisely control material deposition to produce complex-shaped components with high material utilization and short manufacturing cycles. However, the use of high-temperature titanium alloy Ti60 in additive manufacturing of large components at 600°C is still in its exploratory stages. The printing process easily forms a strong texture, resulting in coarse grains and affecting the overall performance of the material. Furthermore, traditional alloy heat treatment processes often fail to fully eliminate the rapid solidification structure and residual stresses generated during additive manufacturing, easily forming Widmanstätten microstructures and resulting in poor basketweave microstructure uniformity, further limiting the improvement of alloy performance. Therefore, optimization and exploration of the forming and heat treatment processes of alloy materials are necessary. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing fine-grained near-α high-temperature titanium alloy in response to the above technical problems. By controlling the internal structure of the titanium alloy through appropriate SLM processing parameters and heat treatment process, an alloy material with better mechanical properties is obtained.

[0005] The method for preparing a fine-grained near-α high-temperature titanium alloy in the technical solution of the present invention comprises the following steps:

[0006] (1) Filling the alloy powder onto the building platform of the SLM processing equipment and starting the SLM processing; during the SLM processing, the laser power is 260~380W, the scanning speed is 1000~1500mm / s, and the scanning spacing is 0.05~0.15mm; the alloy powder is a mixture of Ti60 alloy powder, boron powder and iron powder;

[0007] (2) The product obtained by SLM processing is subjected to stress relief treatment, solution treatment and aging treatment in sequence; the temperatures of stress relief treatment and aging treatment are independently selected from 600~1000℃, the temperature of solution treatment is 1000~1300℃, and the temperature of solution treatment is greater than the temperature of stress relief treatment and the temperature of aging treatment.

[0008] By adjusting the laser power, scanning speed, and scanning spacing, cracks and porosity defects during the forming process are avoided, ensuring good metallurgical bonding between each melt channel and between layers, significantly improving the density of the alloy material, thereby improving the material's mechanical properties and enhancing its application potential in harsh environments. Stress relief heat treatment can eliminate residual stress generated during the manufacturing process, solution treatment can fully dissolve the strengthening phases in the alloy and eliminate the rapidly solidified structure, and aging treatment can promote the nucleation and growth of precipitated phases. The three steps are carried out in sequence to optimize the microstructure and obtain a uniform basketweave structure, significantly improving the alloy's strength-ductility matching, thermal stability, and creep resistance, and reducing the possibility of performance degradation due to surface oxidation.

[0009] Furthermore, the chemical composition of the Ti60 alloy powder consists of the following components in mass percentage: Al 5.2-6.0%, Mo 0.2-1.0%, Sn 3.0-4.5%, Zr 2.5-4.0%, Si 0.2- 0.6%, Ta 0.2-1.5%, Nb 0.2-0.7%, C 0.02-0.08%, and the balance is Ti.

[0010] Preferably, the Ti60 alloy powder is pre-dried at 60-100° C. for 6-12 hours to remove moisture, and a screening device is used to remove impurities and large particles in the alloy powder.

[0011] Preferably, the particle size of the Ti60 alloy powder is 15-60 μm.

[0012] Furthermore, the mass of boron powder and iron powder is 0.005-0.02% of the mass of Ti60 alloy powder. Adding trace amounts of boron powder and iron powder to Ti60 alloy powder, introducing elements B and Fe, can provide heterogeneous nucleation sites, promote grain refinement, reduce the formation of columnar grains, help reduce the anisotropy of the alloy material, and improve its uniformity in different directions, which is crucial for improving the overall performance and reliability of components.

[0013] Furthermore, in step (1), the laser power during SLM processing is 280-350 W, the scanning speed is 1200-1400 mm / s, and the scanning spacing is 0.09-0.11 mm. Reasonable laser power, scanning speed, and scanning spacing can reduce the formation of texture, significantly refine the grains, help reduce the anisotropy of the material, improve its uniform performance in different directions, and improve the overall performance and reliability of the component.

[0014] Furthermore, in step (1), the thickness of the alloy powder filled onto the building platform of the SLM processing equipment is 30-60 μm.

[0015] Furthermore, in step (2), the temperature of the stress relief treatment is 700-900°C, and the time is 1-5 hours; the temperature of the solution treatment is 1000-1200°C, and the time is 1-5 hours; the temperature of the aging treatment is 600-800°C, and the time is 1-10 hours.

[0016] Furthermore, in step (2), the temperature of the solution treatment minus the temperature of the stress relief treatment is ≤ 200° C. By controlling the temperature of the heat treatment, it is possible to avoid the internal residual tensile stress exceeding the alloy strength due to excessive temperature gradient, thereby effectively controlling the generation of cracks.

[0017] The present invention also provides a fine-grained near-α high-temperature titanium alloy, which is prepared by the above-mentioned preparation method of the fine-grained near-α high-temperature titanium alloy.

[0018] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0019] (1) By adjusting and controlling the laser power, scanning speed, and scanning spacing during the SLM process, combined with a reasonable and effective heat treatment process, an alloy material with a density better than 99.95% was obtained, significantly improving its mechanical properties, thermal stability, and creep resistance.

[0020] (2) Adding trace amounts of B and Fe elements to Ti60 alloy powder can provide heterogeneous nucleation sites, promote grain refinement, reduce the formation of columnar grains, help reduce the anisotropy of the alloy material, and improve its uniform performance in different directions, which is crucial to improving the overall performance and reliability of the components;

[0021] (3) Through reasonable SLM processing technology, the formation of texture can be reduced, the grain size can be significantly refined, which helps to reduce the anisotropy of the material, avoid cracks and pore defects during the forming process, ensure good metallurgical bonding between each layer of melt and between layers, and significantly improve the density of the alloy material, thereby improving the mechanical properties of the material and enhancing its application potential in harsh environments;

[0022] (4) Combining stress relief heat treatment, solution treatment and aging treatment can optimize the microstructure and obtain a uniform basketweave structure, significantly improving the strength-ductility matching, thermal stability and creep resistance of the alloy, and reducing the possibility of performance degradation due to surface oxidation;

[0023] (5) By adjusting the temperature of stress relief heat treatment, solution treatment and aging treatment, the internal residual tensile stress exceeding the alloy strength due to excessive temperature gradient is avoided, thereby effectively controlling the generation of cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a microstructure photograph of the fine-grained near-α high-temperature titanium alloy obtained in Example 1;

[0025] Figure 2 This is a microstructure photograph of the fine-grained near-α high-temperature titanium alloy obtained in Example 2. DETAILED DESCRIPTION

[0026] Below by specific embodiment and accompanying drawing, technical scheme of the present invention is further described explanation, it should be understood that specific embodiment described herein is only for helping to understand the present invention, is not used for specific limitation of the present invention.And accompanying drawing used herein, is only for better illustrating the disclosed content of the present invention, does not have limiting effect on protection scope.If no special instructions, the raw materials adopted in the embodiment of the present invention are all the raw materials commonly used in this area, and the method adopted in the embodiment is all the conventional method in this area.

[0027] The Ti60 alloy powder provided by Asia New Materials Co., Ltd. used in the following examples and comparative examples consists of the following components in percentage by mass: Al 5.5%, Mo 0.7%, Sn 3.7%, Zr 3.2%, Si 0.4%, Ta 1.1%, Nb 0.5%, C 0.05%, and the balance Ti. Example 1

[0028] The preparation method of the fine-grained near-α high-temperature titanium alloy of this embodiment includes the following steps:

[0029] (1) Ti60 alloy powder was dried at 80°C for 8 h to remove moisture, and then impurities and large particles in the powder were removed using screening equipment;

[0030] (2) The sieved titanium alloy powder was evenly mixed with 0.01% boron powder and 0.01% iron powder, and filled onto the construction platform of the SLM processing equipment with a layer thickness of 50 μm. The laser power was adjusted to 340 W, the scanning speed was set to 1350 mm / s, the scanning pitch was 0.09 mm, the laser spot size was 90 m, the scanning rotation angle was 67°, the shape of the molten pool and the energy distribution were controlled, and the SLM processing was started.

[0031] (3) The products obtained by SLM processing were subjected to stress relief treatment, solution treatment and aging treatment in sequence. The stress relief treatment was carried out at 850℃ for 2h, the solution treatment was carried out at 1035℃ for 2h, and the aging treatment was carried out at 700℃ for 5h. The microstructure of the obtained fine-grained near-α high-temperature titanium alloy is as follows: Figure 1 As shown, a large number of elongated α phases can be seen, some of which are arranged regularly. Example 2

[0032] The preparation method of the fine-grained near-α high-temperature titanium alloy of this embodiment includes the following steps:

[0033] (1) The titanium alloy powder was dried at 80°C for 8 hours to remove moisture, and then the impurities and large particles in the powder were removed using screening equipment;

[0034] (2) The sieved titanium alloy powder, 0.015% boron powder, and 0.01% iron powder were uniformly mixed and filled onto the construction platform of the SLM processing equipment with a layer thickness of 50 μm. The laser power was adjusted to 360 W, the scanning speed was set to 1360 mm / s, the scanning pitch was 0.10 mm, the laser spot size was 90 m, the scanning rotation angle was 67°, the shape of the molten pool and the energy distribution were controlled, and the SLM processing was started.

[0035] (3) The products obtained by SLM processing were subjected to stress relief treatment, solution treatment and aging treatment in sequence. The stress relief treatment was carried out at 900℃ for 2h, the solution treatment was carried out at 1050℃ for 2h, and the aging treatment was carried out at 750℃ for 5h. The microstructure of the obtained fine-grained near-α high-temperature titanium alloy is as follows: Figure 2 As shown, a large number of elongated α phases can be seen, some of which are regularly arranged. Example 3

[0036] The preparation method of the fine-grained near-α high-temperature titanium alloy of this embodiment includes the following steps:

[0037] (1) The titanium alloy powder was dried at 80°C for 8 hours to remove moisture, and then the impurities and large particles in the powder were removed using screening equipment;

[0038] (2) The sieved titanium alloy powder was evenly mixed with 0.01% boron powder and 0.015% iron powder, and filled onto the construction platform of the SLM processing equipment with a layer thickness of 50 μm. The laser power was adjusted to 350 W, the scanning speed was set to 1300 mm / s, the scanning pitch was 0.11 mm, the laser spot size was 90 m, the scanning rotation angle was 67°, the shape of the molten pool and the energy distribution were controlled, and the SLM processing was started;

[0039] (3) The products obtained by SLM processing were subjected to stress relief treatment, solution treatment and aging treatment in sequence. The stress relief treatment was carried out at 930℃ for 2h, the solution treatment was carried out at 1050℃ for 2h, and the aging treatment was carried out at 800℃ for 5h. Example 4

[0040] The only difference between this embodiment and embodiment 1 is that in step (2), the titanium alloy powder obtained by screening and 0.01% of boron powder by mass are mixed evenly, and filled onto the building platform of the SLM processing equipment with a layer thickness of 50 μm. The laser power is adjusted to 355 W, the scanning speed is set to 1350 mm / s, the scanning spacing is 0.09 mm, the laser spot size is 90 m, the scanning rotation angle is 67°, the shape of the molten pool and the energy distribution are controlled, and the SLM processing is started. Example 5

[0041] The only difference between this embodiment and embodiment 1 is that in step (2), the titanium alloy powder obtained by screening and 0.01% of the iron powder by mass are mixed evenly, and filled onto the building platform of the SLM processing equipment with a layer thickness of 50 μm. The laser power is adjusted to 355 W, the scanning speed is set to 1350 mm / s, the scanning spacing is 0.09 mm, the laser spot size is 90 m, the scanning rotation angle is 0°, the shape and energy distribution of the molten pool are controlled, and the SLM processing is started. Example 6

[0042] The only difference between this embodiment and embodiment 1 is that in step (2), the titanium alloy powder obtained by screening is evenly mixed with 0.01% by mass of boron powder and 0.05% by mass of iron powder, and the mixture is filled onto the building platform of the SLM processing equipment with a layer thickness of 50 μm. The laser power is adjusted to 355 W, the scanning speed is set to 1350 mm / s, the scanning pitch is 0.09 mm, the laser spot size is 90 m, the scanning rotation angle is 67°, the shape of the molten pool and the energy distribution are controlled, and the SLM processing is started. Example 7

[0043] The only difference between this embodiment and embodiment 1 is that in step (2), the titanium alloy powder obtained by screening, 0.50% by mass of boron powder, and 0.01% by mass of iron powder are mixed evenly, and filled onto the building platform of the SLM processing equipment with a layer thickness of 50 μm. The laser power is adjusted to 355 W, the scanning speed is set to 1350 mm / s, the scanning spacing is 0.09 mm, the laser spot size is 90 m, the scanning rotation angle is 67°, the shape of the molten pool and the energy distribution are controlled, and the SLM processing is started. Example 8

[0044] The only difference between this embodiment and embodiment 1 is that in step (3), the product obtained by SLM processing is subjected to stress relief treatment, solution treatment and aging treatment in sequence. The stress relief treatment is carried out at 800°C for 2 hours, the solution treatment is carried out at 1100°C for 2 hours, and the aging treatment is carried out at 700°C for 5 hours. Comparative Example 1

[0045] The only difference between this comparative example and Example 1 is that in step (2), the titanium alloy powder obtained by screening, 0.01% by mass of boron powder, and 0.01% by mass of iron powder are uniformly mixed, and filled onto the building platform of the SLM processing equipment with a layer thickness of 50 μm. The laser power is adjusted to 200 W, the scanning speed is set to 800 mm / s, the scanning spacing is 0.09 mm, the laser spot size is 90 m, the scanning rotation angle is 0°, the shape and energy distribution of the molten pool are controlled, and the SLM processing is started. Comparative Example 2

[0046] The only difference between this comparative example and Example 1 is that in step (2), the sieved titanium alloy powder and 0.01% boron powder and 0.01% iron powder are uniformly mixed, and filled onto the building platform of the SLM processing equipment with a layer thickness of 50 μm. The laser power is adjusted to 400 W, the scanning speed is set to 1600 mm / s, the scanning spacing is 0.09 mm, the laser spot size is 90 m, the scanning rotation angle is 0°, the shape and energy distribution of the molten pool are controlled, and the SLM processing is started. Comparative Example 3

[0047] The only difference between this comparative example and Example 1 is that (2) the titanium alloy powder obtained by screening is filled onto the building platform of the SLM processing equipment with a layer thickness of 50 μm, the laser power is adjusted to 355 W, the scanning speed is set to 1350 mm / s, the scanning spacing is 0.09 mm, the laser spot size is 90 m, the scanning rotation angle is 67°, the shape and energy distribution of the molten pool are controlled, and the SLM processing is started. Comparative Example 4

[0048] The only difference between this comparative example and Example 1 is that in step (3), the product obtained by SLM processing is subjected to stress relief treatment and solution treatment in sequence, the stress relief treatment is carried out by keeping the temperature at 850°C for 2 hours, and the solution treatment is carried out by keeping the temperature at 1035°C for 2 hours. Comparative Example 5

[0049] The only difference between this comparative example and Example 1 is that in step (3), the product obtained by SLM processing is subjected to stress relief treatment and aging treatment in sequence. The stress relief treatment is carried out by keeping the temperature at 850°C for 2 hours, and the aging treatment is carried out by keeping the temperature at 700°C for 5 hours. Comparative Example 6

[0050] The only difference between this comparative example and Example 1 is that in step (3), the product obtained by SLM processing is subjected to solution treatment and aging treatment in sequence, the solution treatment is carried out at 1035°C for 2 hours, and the aging treatment is carried out at 700°C for 5 hours.

[0051] Mechanical properties and creep resistance of the titanium alloys obtained in the above examples and comparative examples were tested. The high-temperature tensile strength and high-temperature elongation were tested at 600°C, and the creep deformation was evaluated under the conditions of 600°C / 400 MPa / 30 min (referring to GB / T 2039). The test results are shown in Table 1.

[0052] Table 1 Titanium alloy performance data

[0053] .

[0054] In Examples 1-3, alloy materials with a density of more than 99.80% are obtained by suitable SLM processing parameters and effective heat treatment process, showing excellent mechanical properties, thermal stability and creep resistance. In Example 4, the alloy powder comprises titanium alloy powder and boron powder without adding iron powder, and in Example 5, the alloy powder comprises titanium alloy powder and iron powder without adding boron powder, the effect of grain refinement is poor, the uniformity of the alloy material is low, and the mechanical properties are all poor. In Example 6, 0.01% boron powder by mass and 0.05% iron powder by mass of the titanium alloy powder are added, and in Example 7, 0.50% boron powder by mass of the titanium alloy powder and 0.01% iron powder by mass of the titanium alloy powder are added, and the dispersion uniformity in the alloy material system is reduced, resulting in low uniformity of the internal components of the alloy material, and poor mechanical properties and creep resistance. In Example 8, the temperature of the solution treatment is quite different from that of the stress relief treatment, and the internal residual tensile stress is large, which makes the performance of the alloy material poor. In Comparative Example 1, the stress during SLM processing is very low. The light power and scanning speed are small, the energy density of the alloy material becomes smaller, the density is reduced, and the performance of the alloy material deteriorates; in Comparative Example 2, the laser power and scanning speed during SLM processing are large, the energy density is low, the material porosity is large, and the mechanical properties are poor; in Comparative Example 3, only titanium alloy powder is used for SLM processing, and iron powder and boron powder are not added, the grain refinement effect deteriorates, the uniformity of the alloy material is low, the degree of anisotropy increases, and the mechanical properties deteriorate; Comparative Example 4 only performs stress relief treatment and solid solution treatment, and no aging treatment, which is not conducive to further nucleation and growth of alloy crystals, and the performance of the resulting titanium alloy deteriorates; Comparative Example 5 only performs stress relief treatment and aging treatment, and no solid solution treatment is performed. The internal phase distribution of the alloy material is uneven, and the organizational structure has different phases, which makes the performance of the resulting titanium alloy deteriorate; Comparative Example 6 only performs solid solution treatment and aging treatment, and no stress relief treatment is performed, and the residual stress generated in the manufacturing process cannot be effectively eliminated, resulting in excessive internal stress in the alloy, causing a decline in performance.

[0055] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the spirit of the present invention and are not intended to limit the manner in which the present invention is intended to be implemented. Persons skilled in the art may make various modifications, additions, or substitutions to the described embodiments, and it is not necessary or possible to provide a comprehensive list of all possible embodiments. However, any obvious changes or modifications arising from the essential spirit of the present invention remain within the scope of protection of the present invention, and interpreting them as any additional limitations would be contrary to the spirit of the present invention.

Claims

1. A method for preparing a fine-grained near-α high-temperature titanium alloy, characterized in that: The following steps are involved: (1) Filling the alloy powder onto the building platform of the SLM processing equipment with a thickness of 50-60 μm, and starting the SLM processing; during the SLM processing, the laser power is 280-350 W, the scanning speed is 1200-1400 mm / s, and the scanning interval is 0.09-0.11 mm; the alloy powder is a mixture of Ti60 alloy powder, boron powder and iron powder, and the mass of the boron powder and the iron powder is 0.005-0.02% of the mass of the Ti60 alloy powder; (2) The product obtained by SLM processing is subjected to stress relief treatment, solution treatment and aging treatment in sequence; the temperatures of stress relief treatment and aging treatment are independently selected from 600~1000℃, the temperature of solution treatment is 1000~1300℃, and the temperature of solution treatment is greater than the temperature of stress relief treatment and greater than the temperature of aging treatment, and the temperature of solution treatment minus the temperature of stress relief treatment is ≤200℃.

2. The preparation method according to claim 1, characterized in that The chemical composition of the Ti60 alloy powder consists of the following components in mass percentage: Al 5.2~6.0%, Mo 0.2~1.0%, Sn 3.0~4.5%, Zr 2.5~4.0%, Si 0.2~0.6%, Ta 0.2~1.5%, Nb 0.2~0.7%, C 0.02~0.08%, and the balance is Ti.

3. The preparation method according to claim 1 or 2, characterized in that The particle size of Ti60 alloy powder is 15~60μm.

4. The preparation method according to claim 1, characterized in that In step (2), the temperature of the stress relief treatment is 700-900°C, and the time is 1-5 hours; the temperature of the solution treatment is 1000-1200°C, and the time is 1-5 hours; the temperature of the aging treatment is 600-800°C, and the time is 1-10 hours.

5. A fine-grained near-alpha high-temperature titanium alloy, characterized in that: The method according to claim 1 is used to prepare the present invention.

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