A high-strength, high-plasticity, and high-work-hardening titanium alloy prepared by laser powder bed melting, its preparation method, and its application.

Abstract

This invention discloses a laser powder bed melting method for producing a high-strength, high-plasticity, and high-work-hardening titanium alloy, along with its application. The method involves mixing two titanium alloy powders with different Mo equivalents in a specific mass ratio to form a mixed powder. This mixed powder is then placed in a laser powder bed melting device, which, following the slicing path and process parameters of a three-dimensional model, forms the titanium alloy layer by layer. The resulting titanium alloy exhibits a microstructure comprising hexagonal martensite α′ and orthorhombic martensite α′′. In a preferred embodiment, the titanium alloy, without heat treatment, achieves a yield strength ≥950 MPa, a tensile strength ≥1250 MPa, an elongation ≥14%, and a work-hardening capacity ≥250 MPa. This demonstrates a comprehensive performance of high strength, high plasticity, and excellent work-hardening capacity, meeting the requirements for forming complex-shaped titanium alloy components and demanding high mechanical properties. It is particularly suitable for applications in aerospace, automotive, and marine industries.

Description

Technical Field

[0001] This invention belongs to the field of laser powder bed melting technology, and relates to a high-strength, high-plasticity, and high-work-hardening titanium alloy for laser powder bed melting, its preparation method, and its application. Background Technology

[0002] In recent years, additive manufacturing technology has gradually gained widespread attention, surpassing traditional manufacturing technologies, due to its significant advantages in the rapid prototyping of complex components. As one of the core additive manufacturing technologies, laser powder bed melting (LPBF) technology, with its high forming accuracy, high density, and high strength, has shown great potential in aerospace, medical, mold making, and consumer electronics fields. Titanium alloys, with their low density, high specific strength, excellent corrosion resistance, and good biocompatibility, have become key materials in these fields. Titanium alloys are difficult to machine using traditional methods, and the formation of high-performance titanium alloys using laser powder bed melting technology has become an important research direction.

[0003] The extremely high cooling rate (10) during laser powder bed melting process 5 ~10 7 The microstructure of near-α type (e.g., TA15) and α+β type titanium alloys (e.g., TC4) formed by the temperature (℃ / s) is usually acicular martensitic α′ structure. This structure endows titanium alloys with significantly higher strength than the forged or cast state, but it also leads to problems such as insufficient plasticity (elongation is usually less than 10%, with most studies reporting 6~8%) and poor work hardening ability. Low plasticity may cause cracking during the forming process of laser powder bed molten components, especially large-sized meter-scale components, as well as rapid strength decline after heat treatment. Low work hardening ability makes titanium alloys have poor energy absorption capacity during service. These mechanical property characteristics of high strength, low plasticity and poor work hardening ability have greatly limited the application of such titanium alloys in aerospace, automotive, marine and other fields.

[0004] Existing research on improving the plasticity of LPBF titanium alloys mainly focuses on process parameter optimization and composition modification. However, the effects of process optimization are limited, with plasticity typically increasing by only about 10%, making further improvement difficult. Moreover, the strength decreases while plasticity is improved. Regarding composition modification, common methods include doping TC4 with other powders (such as 316L stainless steel powder) or adjusting the Al content. However, these methods have significant limitations:

[0005] (1) Limited improvement in plasticity: The doping modifier (such as 316L) is extremely sensitive to the amount of doping. Low doping may induce a brittle ω phase, leading to a sharp deterioration in plasticity. Although appropriate doping can simultaneously improve tensile strength, plasticity, and work hardening ability, the optimal elongation is only about 9% (published in Science in 2021), with limited improvement. It is worth noting that the mixing of the two powders is not a simple superposition of properties; their interaction leads to a more complex microstructure. For example, although 316L itself has excellent plasticity, increasing its doping amount cannot linearly or continuously improve plasticity and work hardening ability. The effect of improving plasticity is very limited. In fact, some materials with good plasticity, when incorporated into titanium alloy powder, cannot play a role in improving plasticity.

[0006] (2) Difficulty in achieving a balance between strength, plasticity, and work hardening ability: Starting from the selection of titanium alloy powder, reducing the Al content in TC4 raw material powder can increase the plasticity of titanium alloy to about 14%, but inevitably causes a significant reduction in yield strength (<900 MPa) and tensile strength (<1000 MPa). Similarly, although adding pure titanium powder to TC4 can improve plasticity, the strength is significantly reduced due to the formation of hexagonal martensite α′ with low alloy element content (≤5 wt.%), and its work hardening ability is poor. The difference between tensile strength and yield strength is usually less than 150 MPa.

[0007] In summary, existing technologies, whether through process adjustments or compositional modifications, struggle to simultaneously achieve high strength, high plasticity, and excellent work hardening capability in laser powder bed molten titanium alloys. The core challenge lies in the fact that existing modification strategies often sacrifice strength for improved plasticity, offering limited gains in work hardening capability. Furthermore, the microstructure evolution and performance response of the powder mixture system are highly complex and unpredictable, making control difficult and presenting significant technical bottlenecks. Summary of the Invention

[0008] Based on the shortcomings of existing technologies, this invention aims to provide a high-strength, high-plasticity, and high-work-hardening titanium alloy obtained by laser powder bed melting, its preparation method, and its applications. The titanium alloy provided by this invention possesses high strength, high plasticity, and excellent work-hardening ability, and its preparation process is simple and controllable, requiring no heat treatment. It has broad application prospects in the engineering field, can meet the forming requirements of complex-shaped titanium alloy components and high mechanical properties, and is particularly suitable for aerospace, automotive, and marine fields.

[0009] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0010] One aspect of this invention is to provide a high-strength, high-plasticity, and high-work-hardening titanium alloy obtained by laser powder bed melting. The alloy is composed of a mixture of titanium alloy powder I and titanium alloy powder II, which is then layer-by-layer formed in a laser powder bed melting apparatus. Titanium alloy powder I is an α or α+β type titanium alloy powder with an Al equivalent of 4-8 and a Mo equivalent of 0-4, such as TC4, TA15, TA19, TC11, etc. Titanium alloy powder II is an α+β type titanium alloy powder with an Al equivalent of 4-8 and a Mo equivalent of 4.5-9.0, such as TC17, TC19, etc. The mass fraction of titanium alloy powder II in the mixture is 30-70%. The microstructure of the titanium alloy includes hexagonal martensite α′ and orthorhombic martensite α′′. The titanium alloy has a yield strength ≥900 MPa, a tensile strength ≥1200 MPa, an elongation ≥10%, and a work-hardening capacity ≥200 MPa. MPa, or work hardening capacity, also known as strain hardening capacity, refers to the intrinsic property of a metallic material where its strength and hardness significantly increase with the amount of deformation during plastic deformation. Work hardening capacity is measured by subtracting yield strength from tensile strength, while plasticity is measured by elongation. Compared to conventional TC4 titanium alloys, this invention utilizes a compounding concept of two titanium alloy powders with different Mo equivalents to control the microstructure of the titanium alloy, forming a mixed structure of hexagonal martensite α′ and orthorhombic martensite α′′. This mixed structure helps to enhance the synergistic effect of strength, plasticity, and work hardening properties. The titanium alloy provided by this invention differs from existing technologies in composition and structure, representing a new product with significantly improved key performance compared to existing technologies, further meeting the application needs of aerospace, automotive, consumer electronics, and marine fields. In particular, the titanium alloy provided by this invention can meet the manufacturing requirements of aircraft landing gear, aero-engine bladed disks, aero-engine compressor disks, and pressure hulls for deep-sea submersibles. It should be understood that the specific applications listed above are merely illustrative and are not intended to limit the scope of protection of this invention. Based on the high strength, high plasticity and high work hardening capacity of this titanium alloy, it is also suitable for the conventional application scenarios of additive manufacturing of titanium alloys, and is particularly suitable for the manufacture of titanium alloy components with complex shapes or higher requirements for mechanical properties.

[0011] In this invention, the Al equivalent is calculated as [Al]eq.=[Al]+0.17[Zr]+0.33[Sn]+10[O], and the Mo equivalent is calculated as [Mo]eq.=[Mo]+0.2[Ta]+0.28[Nb]+0.4[W]+0.67[V]+1.25[Cr]+1.25

[0012] [Ni]+1.7[Mn]+1.7[Co]+2.5[Fe], where [X] represents the mass fraction of element X in the alloy.

[0013] Preferably, the mass fraction of titanium alloy powder II in the mixed powder is 40-60%, and more specifically, the mass fraction of titanium alloy powder II is 40-45%, 45-50%, 55-50%, 55-60%, including but not limited to 40%, 45%, 50%, 55%, 60%, etc., and the mass fraction of titanium alloy powder II can exceed 50%.

[0014] Preferably, the high-strength, high-plasticity, and high-work-hardening titanium alloy is in a laser powder bed fused printing state. Without heat treatment, the titanium alloy exhibits a yield strength ≥950 MPa, tensile strength ≥1250 MPa, elongation ≥14%, and work-hardening capacity ≥250 MPa.

[0015] More preferably, the yield strength is ≥970 MPa, the tensile strength is ≥1270 MPa, the elongation is ≥15%, and the work hardening capacity is ≥270 MPa.

[0016] The second aspect of this invention provides a method for preparing a high-strength, high-plasticity, and high-work-hardening titanium alloy using laser powder bed melting. The method includes: mixing titanium alloy powder I and titanium alloy powder II to form a mixed powder; placing the mixed powder into a laser powder bed melting device; and using the laser powder bed melting device to form the titanium alloy layer by layer according to the slicing path of a three-dimensional model and process parameters. The titanium alloy powder I is an α or α+β type titanium alloy powder, with an Al equivalent of 4-8 and a Mo equivalent of 0-4. The titanium alloy powder II is an α+β type titanium alloy powder, with an Al equivalent of 4-8 and a Mo equivalent of 4.5-9.0. The mass fraction of the titanium alloy powder II is 30-70%. The scanning volume energy density in the process parameters is 28-55 J / mm². 3 The scanning volume energy density = laser power / (scanning speed × scanning spacing × layer thickness).

[0017] This invention creatively proposes to use two titanium alloy powders with different Mo equivalents as raw materials. The mixing ratio of the two powders can be controlled within a wide range. When mixing the two powders, following conventional thinking to select scanning volume energy density process parameters, it tends to form a structure dominated by one of the hexagonal martensite α′ or orthorhombic martensite α′′ phases. This invention designs and controls the formation of a mixed microstructure of hexagonal martensite α′ and orthorhombic martensite α′′. This mixed structure helps to enhance the synergistic effect of strength and plasticity, thus achieving high plasticity while achieving high strength. To obtain this structure, it is creatively proposed to use a scanning volume energy density that is different from the conventional range of existing technologies.

[0018] Preferably, the mass fraction of titanium alloy powder II in the mixed powder is 40-60%, and more specifically, the mass fraction of titanium alloy powder II is 40-45%, 45-50%, 55-50%, 55-60%, including but not limited to 40%, 45%, 50%, 55%, 60%, etc., and the mass fraction of titanium alloy powder II can exceed 50%.

[0019] Furthermore, in the process parameters, the laser power is 100~400 W, the scanning speed is 800~1600 mm / s, the scanning spacing is 60~180 μm, and the powder layer thickness is 20~60 μm.

[0020] Furthermore, the D10 particle size of both titanium alloy powder I and titanium alloy powder II is 15~25 μm, the D50 particle size is 30~40 μm, and the D90 particle size is 40~60 μm.

[0021] Furthermore, titanium alloy powder I and titanium alloy powder II are mixed by mechanical stirring, with the mixing equipment rotating at 20~150 rpm and the stirring time being 2~6 h.

[0022] Furthermore, a strip printing strategy is employed, with a strip width of 4-10 mm and a strip overlap spacing of -0.06-0.01 mm, where negative numbers indicate overlapping overlaps and positive numbers indicate gaps. The scanning method is a "Zig-Zag" zigzag scan, with an interlayer rotation angle of 67° or 90°. The preferred interlayer rotation angle is 90°. While 67° is commonly used in laser powder bed melting, in this invention, for two titanium alloy mixed powders with different Mo equivalents, a preferred interlayer rotation angle of 90° is used to better facilitate the formation of a mixed structure of hexagonal martensite α′ and orthorhombic martensite α′′.

[0023] Furthermore, the laser powder bed melting equipment prints under argon protection, and the oxygen content in the forming chamber is controlled below 1000 ppm.

[0024] Compared with the prior art, the beneficial effects of this invention are:

[0025] (1) A titanium alloy with high strength, high plasticity and excellent work hardening ability is provided. The titanium alloy provided by the present invention is different from the prior art in terms of composition and structure. It is a product with a new composition and structure. Compared with the prior art, its key performance is significantly improved. Specifically, the present invention introduces another α+β type (Al equivalent 4~8, Mo equivalent 4.5~9.0) titanium alloy powder into an α or α+β type (Al equivalent 4~8, Mo equivalent 0~4) titanium alloy powder through the concept of composite powder. By controlling the microstructure of the titanium alloy, a mixed structure including hexagonal martensite α′ and orthorhombic martensite α′′ is formed. This mixed structure helps to enhance the synergistic effect of strength-plasticity-work hardening performance. In the preferred embodiment, the titanium alloy has a yield strength ≥950 MPa, tensile strength ≥1250 MPa, elongation ≥14%, and work hardening ability ≥250 MPa without heat treatment. Its comprehensive performance is better than that of the prior art. Existing technologies do not disclose the solution to the problem of the inability to simultaneously achieve the desired strength, plasticity, and work hardening ability of titanium alloys by using a mixture of α or α+β (Al equivalent of 4~8, Mo equivalent of 0~4) titanium alloys and α+β (Al equivalent of 4~8, Mo equivalent of 4.5~9.0) titanium alloy powders. This invention proposes a solution and a new product, achieving unexpected technical effects and making a technical contribution to the existing technology.

[0026] (2) In the prior art, when α+β titanium alloy TC4 is mixed with other non-titanium alloys or pure titanium powder, in the formed microstructure, incompletely melted dopants, brittle ω phases, brittle eutectoids, or low-alloy-element-content hexagonal martensite α′ are easily formed, resulting in limited improvement in plasticity and failing to balance strength, plasticity, and work hardening ability. The present invention overcomes the above-mentioned problems of the prior art because the melting points of the two titanium alloy powders are not significantly different, and the Mo equivalent after mixing is less than 9.0. It is less likely to produce incompletely melted dopants, brittle ω phases, brittle eutectoids, or low-alloy-element-content hexagonal martensite α′.

[0027] (3) In the prior art, 316L is added to TC4. Although the plasticity of 316L is higher than 40%, the optimal elongation after mixing the two is reported to be only around 9%. This is mainly because the mixing of the two powders is not a simple superposition of properties, and the printing performance of the mixed powder cannot be easily predicted. The spatial element distribution after powder mixing is more complex. The interaction between the mixed powder and the laser involves complex melting, solidification and cooling processes. When the raw material ratio and process parameters do not have a clear directional selection, it is difficult to control to achieve excellent results. This invention provides a preparation method for obtaining a specific microstructure matching. When α or α+β type (Al equivalent of 4~8, Mo equivalent of 0~4) titanium alloy powder and α+β type (Al equivalent of 4~8, Mo equivalent of 4.5~9.0) titanium alloy powder are mixed, conventional approach to selecting process parameters tends to form a structure dominated by a single orthorhombic martensite α′′ or hexagonal martensite α′. This invention creatively controls the powder mixing ratio and laser process parameters, thereby controlling the composition of the molten pool micro-region and the corresponding temperature gradient, and regulating the mixed phase of orthorhombic martensite α′′ and hexagonal martensite α′′. This mixed phase of hexagonal martensite α′′ and orthorhombic martensite α′′ ultimately enables the titanium alloy to possess comprehensive mechanical properties of high strength, high plasticity and high work hardening ability.

[0028] (4) The preparation process of this invention is simple and controllable, and the cost is low. Moreover, thanks to the excellent printing performance, the heat treatment step can be omitted in some applications, which can shorten the production cycle, reduce energy consumption, and achieve outstanding economic benefits. The prepared titanium alloy has excellent comprehensive mechanical properties such as high strength, high plasticity and excellent work hardening ability. Compared with the widely used TC4 titanium alloy, it significantly improves tensile strength and elongation while maintaining the same yield strength. It is particularly suitable for manufacturing complex components in aerospace, marine and other fields, effectively broadening the application range of high-performance titanium alloys. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the laser powder bed melting process for preparing high-strength, high-plasticity, and high-work-hardening titanium alloys according to the present invention.

[0030] Figure 2 SEM image of TC4 titanium alloy powder raw material in Example 1;

[0031] Figure 3 SEM image of TC19 titanium alloy powder raw material in Example 1;

[0032] Figure 4 The image shows the XRD pattern of the TC4+TC19 titanium alloy in Example 1. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0034] Example 1

[0035] TC4 (Al equivalent 6, Mo equivalent 2.68) powder and TC19 (Al equivalent 7.34, Mo equivalent 6.0) powder were mixed in a mechanical mixer at a 1:1 mass ratio (TC19 mass fraction 50%) for 4 hours at 28 rpm. The mixed powder was then dried in an oven at 100°C for 1 hour before use. Figure 2 SEM image of TC4 powder raw material. Figure 3 This is a SEM image of TC19 powder raw material.

[0036] A titanium alloy printing model was created using modeling software. This model was then converted into two-dimensional layer data using 3D-to-2D data conversion software. This two-dimensional slice data was then imported into the system of a laser powder bed melting equipment. The mixed powder was placed into the laser powder bed melting equipment, which, following the slicing path and process parameters of the 3D model, formed the titanium alloy layer by layer.

[0037] The forming process parameters were set as follows: laser power of 125 W, scanning speed of 1500 mm / s, scanning spacing of 65 μm, and powder layer thickness of 30 μm. The oxygen content in the forming chamber was maintained below 100 ppm. A strip strategy was adopted, with a strip width of 5 mm and a strip overlap spacing of -0.01 mm. The scanning volume energy density was 42.7 J / mm². 3 The scanning method is "Zig-Zag" zigzag scanning with an interlayer rotation angle of 90°. After laser powder bed melting and forming, printed titanium alloy is obtained.

[0038] Example 2

[0039] The difference between Example 2 and Example 1 lies in the laser process parameters; all other conditions remain unchanged. Specifically, the forming process parameters are set as follows: laser power of 150 W, scanning speed of 1250 mm / s, scanning spacing of 100 μm, and powder layer thickness of 30 μm. The oxygen content in the forming chamber is maintained below 100 ppm. A strip strategy is employed, with a strip width of 5 mm and a strip overlap spacing of -0.01 mm. The scanning volume energy density is 40 J / mm². 3 The scanning method is "Zig-Zag" zigzag scanning with an interlayer rotation angle of 90°. After laser powder bed melting and forming, printed titanium alloy is obtained.

[0040] Example 3

[0041] The difference between Example 3 and Example 1 is that the amount of TC19 powder incorporated is different; the amount of TC19 powder incorporated is 35%, while the other conditions remain unchanged.

[0042] Example 4

[0043] TA15 powder (Al equivalent 6.84, Mo equivalent 1.67) and TC19 powder (Al equivalent 7.34, Mo equivalent 6.0) were mixed in a mechanical mixer at a 1:1 mass ratio (TC19 mass fraction 50%) for 4 hours at 28 rpm. The mixed powder was then dried in an oven at 100°C for 1 hour before use.

[0044] A titanium alloy printing model was created using modeling software. This model was then converted into two-dimensional layer data using 3D-to-2D data conversion software. This two-dimensional slice data was then imported into the system of a laser powder bed melting equipment. The mixed powder was placed into the laser powder bed melting equipment, which, following the slicing path and process parameters of the 3D model, formed the titanium alloy layer by layer.

[0045] The forming process parameters were set as follows: laser power of 125 W, scanning speed of 1500 mm / s, scanning spacing of 65 μm, and powder layer thickness of 30 μm. The oxygen content in the forming chamber was maintained below 100 ppm. A strip strategy was adopted, with a strip width of 5 mm and a strip overlap spacing of -0.01 mm. The scanning volume energy density was 42.7 J / mm². 3 The scanning method is "Zig-Zag" zigzag scanning with an interlayer rotation angle of 90°. After laser powder bed melting and forming, printed titanium alloy is obtained.

[0046] Comparative Example 1

[0047] This comparative example uses only TC4 powder, and other conditions are the same as in Example 1. The mechanical properties of the printed titanium alloy obtained after laser powder bed melting and forming are: yield strength 990 MPa, tensile strength 1143 MPa, work hardening capacity 153 MPa, and elongation 8.9%.

[0048] Comparative Example 2

[0049] This comparative example uses only TC19 powder, and other conditions are the same as in Example 1. The mechanical properties of the printed titanium alloy obtained after laser powder bed melting and forming are: yield strength 658 MPa, tensile strength 1339 MPa, work hardening capacity 681 MPa, and elongation 10.7%.

[0050] Comparative Example 3

[0051] The amount of TC19 incorporated in this comparative example was different. TC4 and TC19 were mixed in a mechanical mixer at a mass ratio of 3:1 (TC19 mass fraction was 25%), at a speed of 28 rpm, for a total of 4 hours. The remaining conditions were the same as in Example 1.

[0052] The mechanical test results are: yield strength 1045 MPa, tensile strength 1222 MPa, elongation 11%, and work hardening capacity 177 MPa.

[0053] Comparative Example 4

[0054] Comparative Example 4 differs from Example 1 in that the laser process parameters are different, while other conditions remain unchanged. Specifically, the forming process parameters are set as follows: laser power of 180 W, scanning speed of 1200 mm / s, scanning spacing of 65 μm, and powder layer thickness of 30 μm. The oxygen content in the forming chamber is maintained below 100 ppm, a strip strategy is adopted, the strip width is 5 mm, and the strip overlap spacing is -0.01 mm. The bulk energy density is 76.9 J / mm². 3 The scanning method is "Zig-Zag" zigzag scanning with an interlayer rotation angle of 90°. After laser powder bed melting and forming, printed titanium alloy is obtained.

[0055] The microstructure of the titanium alloy in Comparative Example 4 is mainly hexagonal martensite α′, and its performance cannot meet the performance requirements of yield strength ≥900 MPa, tensile strength ≥1200 MPa, elongation ≥10%, and work hardening capacity ≥200 MPa in the embodiments of this invention. This is mainly due to the different thermal accumulation effect and cooling process in the conventional scanning volume energy density laser powder bed melting, which resulted in the failure to form a significant mixed phase of hexagonal martensite α′ and orthorhombic martensite α′′.

[0056] Technical effects and analysis of Examples 1 to 4: Microstructure and mechanical properties of the printed titanium alloy were tested. Figure 4The XRD pattern in Example 1 shows that the microstructure of the titanium alloy is a mixture of hexagonal martensite α′ and orthorhombic martensite α′′. For mechanical property testing, Examples 1 to 3 used a mixture of TC4 and TC19 powders, and Example 4 used a mixture of TA15 and TC19. The titanium alloys in Examples 1-4 all achieved yield strength ≥900 MPa, tensile strength ≥1200 MPa, elongation ≥10%, and work hardening capacity ≥200 MPa. This indicates that titanium alloys prepared by mixing titanium alloy powder I (α or α+β type titanium alloy powder, Al equivalent 4-8, Mo equivalent 0-4) and titanium alloy powder II (α+β type titanium alloy powder, Al equivalent 4-8, Mo equivalent 4.5-9.0) both achieved a mixed microstructure of hexagonal martensite α′ and orthorhombic martensite α′′ without heat treatment, thus realizing high strength, high plasticity, and high work hardening capacity. Examples 1 to 3 all used a mixture of TC4 and TC19 powders. Examples 1 and 2 showed better performance than Example 3. In Examples 1 and 2, by further optimizing the amount of TC19, the yield strength, tensile strength, and elongation were further improved. The titanium alloys in Examples 1 and 2 all achieved a yield strength ≥950 MPa, a tensile strength ≥1250 MPa, an elongation ≥14%, and a work hardening capacity ≥250 MPa. The mechanical test results of the preferred Example 1 were a yield strength of 981 MPa, a tensile strength of 1278 MPa, a work hardening capacity of 297 MPa, and an elongation of 15.8%.

[0057] Analysis of the technical effects of the examples and comparative examples: Table 1 shows the comparison of the mechanical properties of the preferred example 1, comparative examples 1 to 2, and preferred comparative example 3. Table 1 intuitively shows that in example 1, by compositing two titanium alloy powders with different Mo equivalents, compared with the TC4 titanium alloy in comparative example 1, the present invention, through the concept of composite powder, can significantly improve tensile strength, work hardening ability, and elongation while maintaining the same yield strength. Compared with the TC19 titanium alloy in comparative example 2, the present invention significantly improves yield strength and elongation. In comparative example 3, the mixing ratio of TC4 and TC19 powders is not within the scope of the present invention, achieving better strength and plasticity, but the work hardening ability is reduced compared with examples 1 to 3.

[0058] Table 1 Comparison of mechanical properties of the examples and comparative examples

[0059]

[0060] The above are merely preferred embodiments of the present invention and are 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 protection scope of the present invention.

Claims

1. A high-strength, high-plasticity, and high-work-hardening titanium alloy obtained by laser powder bed melting, characterized in that, A mixed powder composed of titanium alloy powder I and titanium alloy powder II is formed by layering the mixed powder in a laser powder bed melting device. The scanning volume energy density in the process parameters is 28~55 J / mm². 3 The laser power is 100~400 W, the scanning speed is 800~1600 mm / s, the scanning spacing is 60~180 μm, and the powder layer thickness is 20~60 μm; the titanium alloy powder I is α or α+β type titanium alloy powder, and the Al equivalent of the titanium alloy powder I is 4~8 and the Mo equivalent is 0~4; the titanium alloy powder II is α+β type titanium alloy powder, and the Al equivalent of the titanium alloy powder II is 4~8 and the Mo equivalent is 4.5~9.0; the mass fraction of titanium alloy powder II in the mixed powder is 30~70%; the microstructure of the high-strength, high-plasticity, and high-work-hardening titanium alloy includes hexagonal martensite α′ and orthorhombic martensite α′′; the yield strength of the titanium alloy is ≥900 MPa, the tensile strength is ≥1200 MPa, the elongation is ≥10%, and the work-hardening capacity is ≥200 MPa; The formula for calculating the Al equivalent is [Al]eq.=[Al]+0.17[Zr]+0.33[Sn]+10[O], and the formula for calculating the Mo equivalent is [Mo]eq.=[Mo]+0.2[Ta]+0.28[Nb]+0.4[W]+0.67[V]+1.25[Cr]+1.25[Ni]+1.7[Mn]+1.7[Co]+2.5[Fe]. The brackets [] around a given element represent the mass fraction of that element in the alloy.

2. The titanium alloy according to claim 1, characterized in that, The mass fraction of titanium alloy powder II in the mixed powder is 40-60%.

3. The titanium alloy according to claim 2, characterized in that, The titanium alloy has a yield strength ≥950 MPa, tensile strength ≥1250 MPa, elongation ≥14%, and work hardening capacity ≥250 MPa.

4. The titanium alloy according to any one of claims 1 to 3, characterized in that, The high-strength, high-plasticity, and high-work-hardening titanium alloy is in a laser powder bed fusion printing state and does not require heat treatment.

5. A method for preparing a high-strength, high-plasticity, and high-work-hardening titanium alloy using laser powder bed melting, characterized in that, The process includes the following steps: A mixed powder is formed by mixing titanium alloy powder I and titanium alloy powder II. This mixed powder is then placed in a laser powder bed melting device. Following the slicing path and process parameters of a three-dimensional model, the laser powder bed melting device forms the titanium alloy layer by layer. Titanium alloy powder I is an α or α+β type titanium alloy powder with an Al equivalent of 4-8 and a Mo equivalent of 0-4. Titanium alloy powder II is an α+β type titanium alloy powder with an Al equivalent of 4-8 and a Mo equivalent of 4.5-9.

0. The mass fraction of titanium alloy powder II in the mixed powder is 30-70%. The scanning volume energy density in the process parameters is 28-55 J / mm². 3 The process parameters include a laser power of 100-400 W, a scanning speed of 800-1600 mm / s, a scanning distance of 60-180 μm, and a powder layer thickness of 20-60 μm. The formula for calculating the Al equivalent is [Al]eq.=[Al]+0.17[Zr]+0.33[Sn]+10[O], and the formula for calculating the Mo equivalent is [Mo]eq.=[Mo]+0.2[Ta]+0.28[Nb]+0.4[W]+0.67[V]+1.25[Cr]+1.25[Ni]+1.7[Mn]+1.7[Co]+2.5[Fe]. The brackets [] around a given element represent the mass fraction of that element in the alloy.

6. The preparation method according to claim 5, characterized in that, The mass fraction of titanium alloy powder II in the mixed powder is 40-60%.

7. The preparation method according to any one of claims 5 to 6, wherein the D10 particle size of titanium alloy powder I and titanium alloy powder II is 15~25 μm, the D50 particle size is 30~40 μm, and the D90 particle size is 40~60 μm.

8. The preparation method according to any one of claims 5 to 6, characterized in that, Titanium alloy powder I and titanium alloy powder II are mixed by mechanical stirring, with the mixing equipment rotating at 20~150 rpm and the stirring time being 2~6 h.

9. The preparation method according to any one of claims 5-6, characterized in that, Strip printing is used, with a strip width of 4~10 mm; the strip overlap spacing is -0.06~0.01 mm, where negative numbers indicate overlapping overlaps and positive numbers indicate gaps. The laser scanning method is "Zig-Zag" zigzag scanning, and the interlayer rotation angle is 67° or 90°.

10. An application of a titanium alloy, characterized in that, The applications are in aerospace, automotive, consumer electronics, and marine fields, and the titanium alloy is the titanium alloy according to any one of claims 1 to 4, or the titanium alloy prepared by the preparation method according to any one of claims 5 to 9.

11. An application of a titanium alloy, characterized in that, The application is in the preparation of aircraft landing gear, aero-engine bladed disks, aero-engine compressor disks, and pressure hulls of deep-sea submersibles. The titanium alloy is the titanium alloy according to any one of claims 1 to 4, or the titanium alloy prepared by the preparation method according to any one of claims 5 to 9.

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