Titanium alloy based on electron gun scanning oscillation and additive manufacturing method thereof

Abstract

The invention relates to titanium alloy based on electron gun scanning oscillation and an additive manufacturing method thereof, and belongs to the technical field of metal additive manufacturing. According to the titanium alloy additive manufacturing method, after titanium alloy powder is subjected to vacuum degassing, electron beam additive manufacturing is conducted, the scanning track is a circular track or a sine curve track, the oscillation frequency and amplitude are controlled, and the titanium alloy is prepared. The titanium alloy prepared through the method has low porosity and high tensile strength and ductility, and anisotropy is remarkably reduced. The porosity of the titanium alloy is 0.5% or below, the tensile strength is 1000 MPa or above, the ductility is 12% or above, and the anisotropy is smaller than 5%.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing technology, and in particular to a titanium alloy based on electron gun scanning oscillation and its additive manufacturing method. Background Technology

[0002] Titanium alloys possess high strength and excellent corrosion resistance, making them widely used in high-end manufacturing equipment. Electron beam additive manufacturing (EBM) is the primary method for titanium alloy production. EBM offers advantages such as vacuum environment protection (reducing oxidation) and the ability to achieve high preheating temperatures (reducing thermal stress). However, the electron beam scanning process in EBM, which uses a fixed trajectory, results in several defects in the titanium alloy: for example, high defect rates, insufficient mechanical properties or significant anisotropy, and interlayer and intralayer property differences reaching 10–15%, impacting service reliability. Summary of the Invention

[0003] Based on the above analysis, the present invention aims to provide a titanium alloy based on electron gun scanning oscillation and its additive manufacturing method, which reduces the defect rate, improves mechanical properties and reduces anisotropy.

[0004] On the one hand, the present invention provides a titanium alloy additive manufacturing method based on electron gun scanning oscillation, wherein titanium alloy powder is vacuum degassed and then subjected to electron beam additive manufacturing, the scanning trajectory is a circular trajectory or a sine curve trajectory, and the oscillation frequency and amplitude are controlled to obtain titanium alloy.

[0005] Furthermore, the oscillation frequency is 500–1500 Hz, and the amplitude is 0.1–0.5 mm.

[0006] Furthermore, for titanium alloys with a wall thickness ≤ 0.6 mm, the scanning trajectory is a sinusoidal curve; for titanium alloys with a wall thickness > 0.6 mm, the scanning trajectory is a circular trajectory.

[0007] Furthermore, the titanium alloy powder has a particle size of 53–106 μm and a sphericity of ≥90%; after vacuum degassing, the hydrogen content in the titanium alloy powder is controlled to be ≤3 ppm.

[0008] Furthermore, in the electron beam additive manufacturing process, the electron gun power is 3-6kW, the accelerating voltage is 50-60kV, and the scanning speed is 600-1200mm / s.

[0009] Furthermore, the ratio of amplitude to layer thickness is 3 to 5:1.

[0010] Furthermore, preheating is required before each electron beam additive manufacturing process, with a preheating temperature of 600–800°C.

[0011] Furthermore, the grades of titanium alloys are TC4 and TA15.

[0012] Furthermore, the titanium alloy has a porosity of less than 0.5%, a tensile strength of more than 1000 MPa, an elongation of more than 12%, and an anisotropy of less than 5%.

[0013] On the other hand, the present invention provides a titanium alloy based on electron gun scanning oscillation, which is prepared by the titanium alloy additive manufacturing method described in the present invention.

[0014] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0015] 1. This invention incorporates high-frequency oscillations into the electron beam additive manufacturing process, transforming the existing linear scanning trajectory into a circular or sinusoidal trajectory. By controlling the oscillation frequency and amplitude, the microstructure and mechanical properties of titanium alloys can be significantly improved. The titanium alloy prepared by this invention exhibits low porosity, high tensile strength and elongation, and significantly reduced anisotropy. The porosity of the titanium alloy is below 0.5%, the tensile strength is above 1000 MPa, the elongation is above 12%, and the anisotropy is <5%.

[0016] 2. This invention controls the oscillation frequency to be 500–1500 Hz and the amplitude to be 0.1–0.5 mm. The electron beam can melt the titanium alloy powder more uniformly, reducing porosity and incomplete fusion defects. The resulting titanium alloy has low porosity, thereby improving the density and service reliability of the titanium alloy.

[0017] 3. This invention automatically selects a sine curve or circular trajectory based on the titanium alloy wall thickness (≤0.6mm or >0.6mm), and combines preheating (600~800℃) and powder control (particle size 53~106μm, hydrogen content ≤3ppm) to improve forming quality and titanium alloy performance, reduce interlayer and intralayer performance differences, and make the manufacturing process more stable.

[0018] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0019] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0020] Figure 1 The image shows the metallographic structure of the titanium alloy obtained in Example 1.

[0021] Figure 2The image shows the metallographic structure of the titanium alloy obtained in Comparative Example 1. Detailed Implementation

[0022] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0023] Titanium alloys possess high strength and excellent corrosion resistance, making them widely used in high-end manufacturing equipment. Electron beam additive manufacturing (EBM) is the primary method for titanium alloy production. EBM offers advantages such as vacuum environment protection (reducing oxidation) and the ability to achieve high preheating temperatures (reducing thermal stress). However, the electron beam scanning process in EBM, which uses a fixed trajectory, results in several defects in the titanium alloy: for example, high defect rates, insufficient mechanical properties or significant anisotropy, and interlayer and intralayer property differences reaching 10–15%, impacting service reliability.

[0024] Therefore, the present invention provides a titanium alloy additive manufacturing method based on electron gun scanning oscillation, wherein titanium alloy powder is vacuum degassed and then subjected to electron beam additive manufacturing, the scanning trajectory is a circular trajectory or a sine curve trajectory, and the oscillation frequency and amplitude are controlled to obtain titanium alloy.

[0025] Compared with existing technologies, this invention adds high-frequency oscillation during the electron beam additive manufacturing process, changing the existing linear scanning trajectory to a circular or sinusoidal trajectory, and controlling the oscillation frequency and amplitude, which can significantly improve the microstructure and mechanical properties of titanium alloys. The titanium alloy prepared by this invention exhibits low porosity, high tensile strength and elongation, and significantly reduced anisotropy. The porosity of the titanium alloy is below 0.5%, the tensile strength is above 1000 MPa, the elongation is above 12%, and the anisotropy is <5%.

[0026] Specifically, the oscillation frequency is 500–1500 Hz, and the amplitude is 0.1–0.5 mm.

[0027] It should be noted that in this invention, the oscillation frequency is strictly controlled between 500 and 1500 Hz. If the frequency is too low, the stirring effect of the molten pool will be insufficient, failing to effectively break dendrites and promote gas escape, resulting in poor printing quality, increased porosity, and reduced performance. If the frequency is too high, it may exceed the response limit of the electron gun deflection coil, leading to trajectory distortion and instability, and introducing new defects. At the same time, an excessively high frequency may cause the heat input to be too dispersed, which is not conducive to the formation of a stable molten pool.

[0028] The oscillation frequency of this invention can be 500Hz, 600Hz, 700Hz, 800Hz, 900Hz, 1000Hz, 1100Hz, 1200Hz, 1300Hz, 1400Hz or 1500Hz.

[0029] Preferably, the oscillation frequency is 800–1200 Hz.

[0030] This invention controls both the oscillation frequency and the amplitude. If the amplitude is too small, the stirring area is limited to the center of the molten pool, having limited effect on the edges and interlayer bonding, resulting in low bonding strength. If the amplitude is too large, it may "break" the molten pool, disrupting the forming continuity, or it may entrain surrounding uncooked cold powder into the molten pool, forming incomplete fusion defects and reducing the performance of the titanium alloy. Therefore, the amplitude of this invention is 0.1–0.5 mm.

[0031] The amplitude of the present invention can be 0.1mm, 0.2mm, 0.3mm, 0.4mm or 0.5mm.

[0032] Specifically, for titanium alloys with a wall thickness ≤ 0.6 mm, the scanning trajectory is a sinusoidal curve; for titanium alloys with a wall thickness > 0.6 mm, the scanning trajectory is a circular trajectory.

[0033] It should be noted that for thin-walled titanium alloys with a wall thickness ≤ 0.6 mm, a sinusoidal trajectory is used. The electron beam moves along a continuous and smooth path, avoiding abrupt stops and heat accumulation at the endpoints, resulting in more uniform heat input. The wavy path itself has a certain degree of elasticity, which can better adapt to and release the thermal stress generated during the forming process, reducing warping or cracking of thin-walled parts due to stress concentration.

[0034] For thick-walled titanium alloys with a wall thickness greater than 0.6 mm, a circular trajectory is used. Within a larger scanning area, the circular trajectory can form a stable and symmetrical molten pool, which is beneficial for the wetting and spreading of the molten metal, thereby achieving a dense and defect-free fusion. At the same time, it helps to form a relatively uniform temperature distribution within the thicker cross-section, reducing internal stress caused by uneven cooling.

[0035] Specifically, the particle size of the titanium alloy powder is 53–106 μm, and the sphericity is ≥90%; after vacuum degassing, the hydrogen content in the titanium alloy powder is controlled to be ≤3 ppm.

[0036] Specifically, the temperature for vacuum degassing is 780–820℃.

[0037] It should be noted that by selecting powders with a specific particle size (53–106 μm) and high sphericity (>90%), the uniformity and high density of the powder layering are ensured, laying the foundation for forming a defect-free molten pool. The EBM process involves layer-by-layer powder layering in a vacuum. High-sphericity powder particles have low friction between them, allowing for smooth and uniform flow. If the powder has poor flowability, the powder layering will be uneven, leading to inconsistent layer thickness, which in turn causes uneven melting, defects, or even printing failure.

[0038] This invention controls the particle size of titanium alloy powder to be between 53 and 106 μm. Titanium alloy powder within this particle size range has a suitable "specific surface area" (total surface area per unit mass of powder). An excessively large specific surface area (too fine powder) or too small a specific surface area (too coarse powder) will affect the energy absorption and heat conduction of the electron beam, thereby affecting melting stability and molten pool morphology.

[0039] Strict vacuum degassing treatment controls the hydrogen content to ≤3ppm, eliminating the gas source that causes porosity to the greatest extent and effectively avoiding the "hydrogen embrittlement" phenomenon. This significantly improves the density and plasticity of the titanium alloy, thereby enhancing its strength and service reliability.

[0040] Specifically, in the electron beam additive manufacturing process, the electron gun power is 3 to 6 kW, the accelerating voltage is 50 to 60 kV, and the scanning speed is 600 to 1200 mm / s.

[0041] It should be noted that within this parameter window, the energy provided is sufficient to completely melt titanium alloy powder (such as TC4) without over-boiling or vaporizing. It can form a dimensionally stable molten pool of moderate depth, ensuring that the current layer of powder is completely melted and achieves good metallurgical bonding with the underlying layer.

[0042] The electron gun power of this invention can be 3kW, 3.5kW, 4kW, 4.5kW, 5kW, 5.5kW, or 6kW. If the power is higher than 6kW, the energy input is too high, which will cause the molten pool to overheat and splash (vaporize); at the same time, the excessive thermal gradient will generate huge thermal stress, which may cause the titanium alloy to crack or be severely deformed. If the power is lower than 3kW, the energy input is insufficient and the titanium alloy powder cannot be completely melted, forming unfused defects and porous structures. The bonding force between layers and between channels is extremely poor, and the overall strength of the resulting titanium alloy is poor.

[0043] The scanning speed of this invention can be 600 mm / s, 650 mm / s, 700 mm / s, 750 mm / s, 800 mm / s, 850 mm / s, 900 mm / s, 950 mm / s, 1000 mm / s, 1050 mm / s, 1100 mm / s, 1150 mm / s, or 1200 mm / s. If the scanning speed is greater than 1200 mm / s, the electron beam's time at a single point is too short, and heat cannot be conducted and accumulated in time, resulting in insufficient powder melting, producing unfused defects and a large number of pores. The molten pool is also shallow and narrow, making it impossible to achieve good interlayer bonding. If the scanning speed is less than 600 mm / s, the electron beam's residence time in local areas is too long, causing excessive energy accumulation. The molten pool is too deep, leading to element evaporation, spheroidization, and thermal stress concentration.

[0044] Specifically, the ratio of amplitude to layer thickness is 3 to 5:1.

[0045] It should be noted that in this invention, the amplitude needs to be much greater than the powder thickness. Due to the large amplitude, the oscillating electron beam not only melts the powder in the current layer but also partially remelts the solidified material of the previous layer directly below it. This not only provides a strong metallurgical bond but also facilitates gas escape and reduces defects such as porosity.

[0046] Specifically, preheating is required before each electron beam additive manufacturing process, with a preheating temperature of 600–800°C.

[0047] It should be noted that the primary function of preheating before electron beam printing is to cause the powder particles to slightly sinter and adhere together, forming a porous solid layer, thereby preventing the high-energy electron beam from blowing them apart. At the same time, preheating can reduce residual stress and deformation, and suppress hot cracking by reducing the cooling rate and temperature difference. It can also control the microstructure, create a uniform temperature field for subsequent melting, and promote the formation of equiaxed crystals.

[0048] Specifically, the titanium alloy grades are TC4 and TA15.

[0049] This invention provides a titanium alloy based on electron gun scanning oscillation, which is prepared by the additive manufacturing method described in this invention.

[0050] It should be noted that the titanium alloy prepared by this invention has low porosity, high tensile strength and elongation, and significantly reduced anisotropy. The titanium alloy has a porosity of less than 0.5%, a tensile strength of more than 1000 MPa, an elongation of more than 12%, and anisotropy of less than 5%.

[0051] To more clearly describe the present invention, the following embodiments and comparative examples are provided for further illustration.

[0052] Example 1

[0053] Titanium alloy powder: grade TC4, particle size 53~106μm, sphericity 95%, hydrogen content 2ppm after vacuum degassing at 800℃.

[0054] Electron beam additive manufacturing parameters: electron gun power is 4kW, accelerating voltage is 60kV, and scanning speed is 800mm / s.

[0055] The scanning trajectory is a sinusoidal curve (wall thickness ≤ 0.6 mm).

[0056] The oscillation frequency is 1000Hz, the amplitude is 0.3mm, and the powder layer thickness is 0.1mm (the ratio of amplitude to layer thickness is 3:1).

[0057] Preheating is required before printing each layer at a temperature of 700°C.

[0058] Example 2

[0059] The preparation process of Example 2 is largely the same as that of Example 1. The difference is that the titanium alloy powder in Example 2 is grade TC4, with a particle size of 53-106 μm, a sphericity of 92%, and a hydrogen content of 1.5 ppm after vacuum degassing.

[0060] Electron beam additive manufacturing parameters: electron gun power is 5kW, accelerating voltage is 50kV, and scanning speed is 1000mm / s.

[0061] The scanning trajectory is a circular trajectory (wall thickness > 0.6 mm).

[0062] The oscillation frequency is 800Hz, the amplitude is 0.4mm, and the powder layer thickness is 0.1mm (amplitude to layer thickness ratio 4:1).

[0063] Preheating is required before printing each layer at a temperature of 650°C.

[0064] Example 3

[0065] The preparation process of Example 3 is largely the same as that of Example 1. The difference is that the titanium alloy powder in Example 3 is grade TC4, with a particle size of 53-106 μm, a sphericity of 94%, and a hydrogen content of 2.5 ppm after vacuum degassing.

[0066] Electron beam additive manufacturing parameters: electron gun power is 3.5kW, accelerating voltage is 60kV, and scanning speed is 600mm / s.

[0067] The scanning trajectory is a circular trajectory (wall thickness > 0.6 mm).

[0068] The oscillation frequency is 1200Hz, the amplitude is 0.3mm, and the layer thickness is 0.1mm (the ratio of amplitude to layer thickness is 3:1).

[0069] Preheating is required before printing each layer at a temperature of 750°C.

[0070] Comparative Example 1

[0071] The preparation process of Comparative Example 1 is largely the same as that of Example 1, except that a fixed trajectory is used for scanning in Comparative Example 1, and the scanning trajectory is a straight line.

[0072] Comparative Example 2

[0073] The preparation process of Comparative Example 2 is largely the same as that of Example 1, except that the oscillation frequency in Comparative Example 2 is low and the amplitude is high. The oscillation frequency is 300 Hz and the amplitude is 0.7 mm.

[0074] Comparative Example 3

[0075] The preparation process of Comparative Example 3 is largely the same as that of Example 1, except that the hydrogen content in Comparative Example 3 is 10 ppm.

[0076] Comparative Example 4

[0077] The preparation process of Comparative Example 4 is largely the same as that of Example 1. The difference is that in the electron beam additive manufacturing process of Comparative Example 4, the electron gun power is 8kW, the accelerating voltage is 60kV, and the scanning speed is 400mm / s.

[0078] Performance testing

[0079] The performance of the above embodiments and comparative examples was tested, and the test results are shown in Table 1.

[0080] Table 1 Performance Test Results

[0081]

[0082] As can be seen from Examples 1-3 and Comparative Examples 1-4, and with reference to Table 1, the present invention, by adding high-frequency oscillations during the electron beam additive manufacturing process, changes the existing linear scanning trajectory to a circular or sinusoidal trajectory, and controls the oscillation frequency and amplitude, which can significantly improve the microstructure and mechanical properties of titanium alloys. The titanium alloy prepared by the present invention exhibits low porosity, high tensile strength and elongation, and significantly reduced anisotropy. The porosity of the titanium alloy is below 0.5%, the tensile strength is above 1000 MPa, the elongation is above 12%, and the anisotropy is <5%.

[0083] Reference Figure 1 and Figure 2 , Figure 1 The image shows the metallographic structure of the titanium alloy obtained in Example 1. Figure 2 The image shows the metallographic structure of the titanium alloy obtained in Comparative Example 1. As can be seen from the image, the black pores are defects, which are significantly reduced in the titanium alloy obtained in this embodiment of the invention.

[0084] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for additive manufacturing of titanium alloys based on electron gun scanning oscillation, characterized in that, Titanium alloy powder is degassed under vacuum and then subjected to electron beam additive manufacturing. The scanning trajectory is either circular or sinusoidal, and the oscillation frequency and amplitude are controlled to obtain the titanium alloy.

2. The titanium alloy additive manufacturing method based on electron gun scanning oscillation according to claim 1, characterized in that, The oscillation frequency is 500–1500 Hz, and the amplitude is 0.1–0.5 mm.

3. The titanium alloy additive manufacturing method based on electron gun scanning oscillation according to claim 2, characterized in that, For titanium alloys with a wall thickness ≤ 0.6 mm, the scanning trajectory is a sinusoidal curve; for titanium alloys with a wall thickness > 0.6 mm, the scanning trajectory is a circular trajectory.

4. The titanium alloy additive manufacturing method based on electron gun scanning oscillation according to claim 1, characterized in that, The titanium alloy powder has a particle size of 53–106 μm and a sphericity of ≥90%; after vacuum degassing, the hydrogen content in the titanium alloy powder is controlled to be ≤3 ppm.

5. The titanium alloy additive manufacturing method based on electron gun scanning oscillation according to claim 1, characterized in that, In electron beam additive manufacturing, the electron gun power is 3-6kW, the accelerating voltage is 50-60kV, and the scanning speed is 600-1200mm / s.

6. The titanium alloy additive manufacturing method based on electron gun scanning oscillation according to claim 2, characterized in that, The ratio of amplitude to layer thickness is 3 to 5:

1.

7. The titanium alloy additive manufacturing method based on electron gun scanning oscillation according to claim 1, characterized in that, Preheating is required before each electron beam additive manufacturing process, with a preheating temperature of 600–800°C.

8. The titanium alloy additive manufacturing method based on electron gun scanning oscillation according to claim 1, characterized in that, The titanium alloy grades are TC4 and TA15.

9. The titanium alloy additive manufacturing method based on electron gun scanning oscillation according to claim 1, characterized in that, The titanium alloy has a porosity of less than 0.5%, a tensile strength of more than 1000 MPa, an elongation of more than 12%, and an anisotropy of less than 5%.

10. A titanium alloy based on electron gun scanning oscillation, characterized in that, The titanium alloy is prepared by the additive manufacturing method according to any one of claims 1-9.

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