Method for preparing hydrogenated and dehydrogenated / spherical TC4 titanium alloy composite powder through laser directional energy deposition

Abstract

The invention discloses a preparation method for hydrogenation dehydrogenation / spherical TC4 titanium alloy composite powder through laser directional energy deposition, and relates to the technical field of titanium alloy manufacturing. The preparation method specifically comprises the following steps that hydrogenated and dehydrogenated TC4 titanium alloy powder is subjected to vacuum heating annealing and screening pretreatment; the spherical TC4 titanium alloy powder is subjected to acid pickling or mechanical activation pretreatment after being screened; and the two kinds of pretreated powder are mixed in proportion, and the TC4 titanium alloy product is prepared through laser directional energy deposition and gradient aging heat treatment. The TC4 titanium alloy product with a unique microstructure and excellent comprehensive performance is prepared through regulation and control of the spherical TC4 titanium alloy powder and the hydrogenated and dehydrogenated TC4 titanium alloy powder in combination with the synergistic effect of the laser directional energy deposition technology and the gradient aging heat treatment technology, and the TC4 titanium alloy product is suitable for low-cost and high-performance manufacturing of force bearing components and biological materials.

Description

Technical Field

[0001] This invention relates to a method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition, belonging to the field of titanium alloy manufacturing technology. Background Technology

[0002] Laser-directed energy deposition (L-DED) technology for titanium alloys has become an important choice for manufacturing complex components due to its high degree of freedom in forming, excellent material utilization, and light weight. However, current processes generally use pure spherical TC4 powder as raw material, which is mainly prepared through plasma rotating electrode method or gas atomization process, resulting in generally high costs and significantly restricting the large-scale application of titanium materials. Although attempts have been made to introduce low-cost hydrogenated dehydrogenated (HDH) TC4 powder, its irregular morphology, poor flowability, and high oxygen content (typically >0.25wt%) make it prone to defects such as unstable molten pool, porosity >5%, and weakened interlayer bonding when directly used in L-DED, failing to meet the performance requirements of load-bearing components.

[0003] The existing technology using a simple mixture of spherical titanium alloy powder and HDH powder has significant limitations due to the failure to address the dual bottlenecks of powder compatibility and process matching: First, the lack of oxygen increment control pretreatment for HDH powder leads to increased material brittleness after deposition; second, the use of traditional spherical powder process parameters (power <2kW, speed >10mm / s) results in insufficient HDH powder fusion, leading to unmelted inclusions and microcracks; third, the ambiguous mixing ratio range (e.g., density drops sharply to 95% when >30 vol.% HDH powder) causes a decrease in component fatigue strength of more than 30%. In summary, the industry urgently needs a preparation process for TC4 titanium alloy powder to solve the problem of conflicting raw material costs and mechanical properties. Therefore, this invention, through the regulation of spherical titanium alloy TC4 powder and hydrogenated / dehydrogenated TC4 titanium alloy powder, combined with the preparation process and utilizing their synergistic effect, prepares TC4 titanium alloy products that significantly reduce the amount of spherical TC4 titanium alloy powder used while maintaining excellent mechanical properties. Summary of the Invention

[0004] One objective of this invention is to provide a method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition, specifically including the following steps: (1) The hydrogenated dehydrogenated TC4 titanium alloy powder is placed in a vacuum device (preferably a vacuum furnace) to be evacuated and heated, and then annealed under a protective atmosphere (preferably 99.99% high-purity argon). After that, it is sieved to obtain the pretreated hydrogenated dehydrogenated TC4 titanium alloy powder.

[0005] (2) The spherical TC4 titanium alloy powder is sieved and then acid-washed or mechanically activated to obtain pretreated spherical TC4 titanium alloy powder.

[0006] (3) The pretreated hydrogenated and dehydrogenated TC4 titanium alloy powder and the pretreated spherical TC4 titanium alloy powder were mixed evenly in proportion to obtain a mixed powder. The mixed powder was then subjected to laser directional energy deposition and gradient aging heat treatment in sequence (the process curve of gradient aging heat treatment is shown in Figure 1). Figure 1 As shown in the figure, the TC4 titanium alloy product was obtained.

[0007] Preferably, the annealing conditions in step (1) are: annealing at 600-800℃ for 1-3 hours; and the particle size range of the hydrogenated and dehydrogenated TC4 titanium alloy powder after sieving is 10-150 μm.

[0008] Preferably, the particle size range of the spherical TC4 titanium alloy powder after sieving in step (2) is 10-150 μm.

[0009] Preferably, the specific steps of pickling in step (2) are as follows: prepare a mixed acid aqueous solution containing 10% hydrofluoric acid (HF) and 30% nitric acid (HNO3) by mass percentage, pickle the surface of the sieved spherical TC4 titanium alloy powder, then ultrasonically clean it three times with water, and finally heat it at 80°C and 1×10⁻⁶ ℃. -2 Vacuum dried for 24 hours under Pa conditions.

[0010] Preferably, the specific steps of the mechanical activation are as follows: spherical TC4 powder is mechanically activated using a planetary ball mill. The spherical TC4 powder is placed in a ball milling jar at a ball-to-powder ratio of 10:1 (filling rate 35%). Argon gas is introduced into the ball milling jar for atmosphere protection. The ball milling is performed at 200 rpm clockwise for 50 min, stopped for 10 min, then at 200 rpm counterclockwise for 50 min, stopped for 10 min, then at 200 rpm clockwise for 50 min, stopped for 10 min, for a total duration of 3 hours. The ball-milled powder is then sieved to obtain spherical TC4 powder with a mesh size ≤45.

[0011] Preferably, the mixing conditions for the pretreated hydrogenated dehydrogenated TC4 titanium alloy powder and spherical TC4 titanium alloy powder in step (3) are: mixing for 0.5-2 hours at 100-300 rpm using a mixing device (such as a mixer).

[0012] Preferably, the composition of the mixed powder in step (3) includes 5-60% pretreated hydrogenated and dehydrogenated TC4 titanium alloy powder by mass percentage, and the remainder is pretreated spherical TC4 titanium alloy powder.

[0013] Preferably, the laser-directed energy deposition process in step (3) is performed under the following conditions: using an inert gas (such as 99.99% high-purity argon) as a protective gas, and depositing the laser at a power of 500-1000W, a scanning speed of 1-10mm / s, and a powder feeding rate of 8-12g / min.

[0014] Preferably, the gradient aging heat treatment conditions in step (3) are as follows: the mixed powder after laser directional energy deposition treatment is heated to 790-810℃ and kept at that temperature for 1-2 hours, then cooled to 490-510℃ and kept at that temperature for 3-5 hours, and then cooled.

[0015] Another object of the present invention is to provide a TC4 titanium alloy product prepared by the preparation method of the present invention.

[0016] Mechanism of the invention: The core mechanism of this invention lies in constructing a multi-scale synergistically strengthened structural system in TC4 titanium alloy through the synergistic regulation of raw material composition and preparation process. Its technical essence is reflected in the following synergistic mechanism: (1) The precise coordination of raw material ratio and process parameters forms a dynamic control mechanism for dislocation network construction. This network has both strengthening phase and plasticity coordination functions, effectively solving the problem of the inversion of strength and plasticity.

[0017] (2) Raw material purification and process atmosphere control constitute a dual synergistic barrier to suppress oxygen increment. By regulating oxygen active migration, the gradient distribution of impurity elements is controlled. This characteristic is crucial to the performance stability of key aerospace components.

[0018] (3) The multi-level synergistic strengthening mechanism of the present invention, from the atomic scale to the macroscopic scale, enables the material to maintain good plasticity while significantly improving its strength, thus realizing a true synergistic effect of strengthening and toughening.

[0019] The beneficial effects of this invention are: (1) This invention innovatively uses hydrogenated dehydrogenated (HDH) powder as an in-situ nucleation inducer to successfully construct a bimodal microstructure consisting of coarse β grains and fine α' martensite. In the β / α' phase interface region, by controlling the thermomechanical treatment parameters, the directional construction of a high-density dislocation network is achieved, thereby significantly improving the interfacial strengthening effect of the material, resulting in an overall oxygen content ≤0.18wt%; tensile strength ≥800MPa; and elongation ≥25%.

[0020] (2) Through the synergistic effect of the preparation process and raw material ratio control of the present invention, the prepared TC4 titanium alloy products have the same tensile strength and elongation as or even exceed the performance of spherical TC4 titanium alloy powder, and are suitable for low-cost and high-performance manufacturing of load-bearing components and biomaterials.

[0021] (3) The present invention can control the particle size range, distribution uniformity and flowability of titanium alloy powder and the performance of titanium alloy products by adjusting the process parameters (pretreatment, mixing ratio, laser directional energy deposition treatment, gradient aging heat treatment process parameters), and prepare titanium alloy components with different properties for application in powder metallurgy, laser selective melting, laser cladding, powder injection molding, and binder jet printing fields. Attached Figure Description

[0022] Figure 1 This is a process curve diagram of the gradient aging heat treatment of the present invention.

[0023] Figure 2 The image shows the metallographic structure of the mixed powder deposit prepared in Example 1.

[0024] Figure 3 The image shows the metallographic structure of the mixed powder deposit prepared in Example 2.

[0025] Figure 4 The image shows the metallographic structure of the spherical TC4 titanium alloy powder deposit prepared in Comparative Example 1.

[0026] Figure 5 The image shows the metallographic structure of the mixed powder deposit prepared in Comparative Example 2.

[0027] Figure 6 The image shows the metallographic structure of the mixed powder deposit prepared in Comparative Example 3.

[0028] Figure 7 The image shows the metallographic structure of the mixed powder deposit prepared in Comparative Example 4. Detailed Implementation

[0029] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0030] In the following embodiments, comparative examples and test examples of the present invention, if room temperature is involved, it specifically refers to 25±5℃.

[0031] Unless otherwise specified, all raw materials used in the following embodiments, comparative examples, and test examples of this invention are commercially available products. In the embodiments and comparative examples of this invention, unless otherwise specified, all chemical reagents were commercially available analytical grade. Spherical TC4 titanium alloy powder was prepared by gas atomization, plasma atomization, and rotating electrode; hydrogenated and dehydrogenated TC4 titanium alloy powder was obtained by crushing titanium alloy blocks, coarse TC4 titanium alloy powder, and titanium alloy scraps formed after cutting, followed by a hydrogenation-crushing-dehydrogenation process. The specifications and specific properties of each raw material are shown in Tables 1 and 2.

[0032] Table 1 Table 2 Example 1 A method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition specifically includes the following steps: (1) Place the hydrogenated and dehydrogenated TC4 titanium alloy powder in a vacuum furnace and evacuate it to 1×10⁻⁶. -2 Pa, then heated to 750℃ and annealed for 2 hours in a 99.99% high-purity argon atmosphere; the annealed hydrogenated dehydrogenated TC4 titanium alloy powder was then vibrated and sieved using a gradient sieve of 1800 mesh (10μm sieve diameter) + 100 mesh (150μm sieve diameter) and an elliptical trajectory (3mm major axis / 1.2mm minor axis) vibration mode to obtain pretreated hydrogenated dehydrogenated TC4 titanium alloy powder with an oxygen content ≤2500ppm and a particle size range of 10-150μm.

[0033] (2) Spherical TC4 titanium alloy powder was vibrated and sieved using a gradient screen of 1800 mesh (10 μm sieve diameter) + 100 mesh (150 μm sieve diameter) and an elliptical trajectory (3 mm major axis / 1.2 mm minor axis) vibration mode to obtain spherical TC4 titanium alloy powder with a particle size range of 10-150 μm. The sieved spherical TC4 titanium alloy powder was surface-washed with a mixed acid aqueous solution containing 10% hydrofluoric acid and 30% nitric acid to remove the oxide layer and oil stains. After acid washing, it was ultrasonically cleaned three times with deionized water and subjected to 1×10 at 80℃. -2 Vacuum drying under Pa conditions for 24 hours yielded spherical TC4 titanium alloy powder with an oxygen content ≤1200ppm after pretreatment.

[0034] (3) The pretreated hydrogenated dehydrogenated TC4 titanium alloy powder and the pretreated spherical TC4 titanium alloy powder were mixed in a mixer at a speed of 250 rpm for 2 hours to form a mixed powder. The mixed powder included 5% of the pretreated hydrogenated dehydrogenated TC4 titanium alloy powder by mass percentage, and the remainder was the pretreated spherical TC4 titanium alloy powder. The mixed powder was loaded into a powder feeding tank and laser-directed energy deposition was performed on the mixed powder under a 99.99% high-purity argon atmosphere with a laser power of 700W, a scanning rate of 8mm / s, and a powder feeding rate of 10g / min to obtain a mixed powder deposit. The mixed powder deposit was heated to 800℃ at a heating rate of 5℃ / min and held for 1 hour, and then cooled to 500℃ at a cooling rate of 10℃ / min and held for 4 hours. After cooling, the TC4 titanium alloy product was obtained.

[0035] The TC4 titanium alloy product prepared in this embodiment was subjected to density testing, mechanical property testing, and cost analysis to comprehensively analyze its application performance. The specific methods are as follows: Density testing method: (1) Weigh the dry sample in air (mair).

[0036] (2) Immerse the sample in liquid (anhydrous ethanol) and weigh its apparent mass (mliquid).

[0037] (3) Calculate the actual density of TC4 titanium alloy products according to ρactual = mair / (mair - mliquid × ρliquid) to evaluate density (density = ρactual / ρtheoretical).

[0038] Mechanical property testing methods: Measure the diameter and gauge length (L0) of the specimen and calculate its cross-sectional area (S0). Clamp the specimen in the fixture with its axis aligned with the center of the fixture. Fix the extensometer in the gauge length section. Use a universal testing machine equipped with a high-precision load sensor to preload a small amount of tensile force onto the specimen to eliminate gaps. Set the loading rate, then stretch the specimen and collect data according to the set loading frequency until the specimen breaks. Record the maximum load (F). max And measure the gauge length (L) after the break. u Then, the tensile strength (R) of the specimen is calculated according to the formula. m The formulas for calculating elongation (A) and elongation (A) are as follows: R m =F max / S0 A=(L u -L0) / L0×100% Cost analysis methods: The manufacturing difficulty and process cost of spherical TC4 powder are relatively high. Therefore, the cost is closely related to the amount of hydrogenated dehydrogenated TC4 powder and spherical TC4 powder added. The manufacturing cost is analyzed by the mixing ratio of spherical TC4 powder and hydrogenated dehydrogenated TC4 powder.

[0039] Oxygen content test: The oxygen content of TC4 titanium alloy deposits after aging treatment was determined using an oxygen, nitrogen, and hydrogen analyzer.

[0040] The TC4 titanium alloy product prepared in this embodiment was subjected to density, mechanical properties, and oxygen content tests, and its metallographic structure was observed. The tests showed that the TC4 titanium alloy product prepared in this embodiment had a density of 99.1%, a tensile strength of 865 MPa, an elongation of 20.2%, and an oxygen content of 0.16% by mass. The metallographic structure of the TC4 titanium alloy product prepared in this embodiment (e.g., ...) is shown in the image. Figure 2 As shown, the TC4 titanium alloy product consists of β-crystalline regions and acicular martensite regions, exhibiting good microstructure density and an average grain size of 56 μm. It possesses excellent application performance. This is due to the vacuum annealing pretreatment of the hydrogenated dehydrogenated TC4 titanium alloy powder, coupled with the doping and compounding of spherical TC4 titanium alloy powder and the hydrogenated dehydrogenated TC4 titanium alloy powder, and the synergistic effect of the laser-directed energy deposition technology and gradient aging heat treatment. Cost calculation of the TC4 titanium alloy product prepared in this embodiment shows that its cost is 71.8% of that of the pure spherical TC4 titanium alloy product, demonstrating a cost advantage.

[0041] Example 2 A method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition specifically includes the following steps: (1) Place the hydrogenated and dehydrogenated TC4 titanium alloy powder in a vacuum furnace and evacuate it to 1×10⁻⁶. -2 Pa, then heated to 750℃ and annealed for 2 hours in a 99.99% high-purity argon atmosphere; the annealed hydrogenated dehydrogenated TC4 titanium alloy powder was then vibrated and sieved using a gradient sieve of 1800 mesh (10μm sieve diameter) + 100 mesh (150μm sieve diameter) and an elliptical trajectory (3mm major axis / 1.2mm minor axis) vibration mode to obtain pretreated hydrogenated dehydrogenated TC4 titanium alloy powder with an oxygen content ≤2500ppm and a particle size range of 10-150μm.

[0042] (2) Spherical TC4 titanium alloy powder was vibrated and sieved using a gradient screen of 1800 mesh (10 μm sieve diameter) + 100 mesh (150 μm sieve diameter) and an elliptical trajectory (3 mm major axis / 1.2 mm minor axis) vibration mode to obtain spherical TC4 titanium alloy powder with a particle size range of 10-150 μm. The sieved spherical TC4 titanium alloy powder was surface-washed with a mixed acid aqueous solution containing 10% hydrofluoric acid and 30% nitric acid to remove the oxide layer and oil stains. After acid washing, it was ultrasonically cleaned three times with deionized water and subjected to 1×10 at 80℃. -2 Vacuum drying under Pa conditions for 24 hours yielded spherical TC4 titanium alloy powder with an oxygen content ≤1200ppm after pretreatment.

[0043] (3) The pretreated hydrogenated dehydrogenated TC4 titanium alloy powder and the pretreated spherical TC4 titanium alloy powder were mixed in a mixer at a speed of 250 rpm for 2 hours to form a mixed powder. The mixed powder included 10% of the pretreated hydrogenated dehydrogenated TC4 titanium alloy powder by mass percentage, and the remainder was the pretreated spherical TC4 titanium alloy powder. The mixed powder was loaded into a powder feeding tank and laser-directed energy deposition was performed on the mixed powder under a 99.99% high-purity argon atmosphere with a laser power of 700W, a scanning rate of 8mm / s, and a powder feeding rate of 10g / min to obtain a mixed powder deposit. The mixed powder deposit was heated to 800℃ at a heating rate of 10℃ / min and held for 1 hour, and then cooled to 500℃ at a cooling rate of 10℃ / min and held for 4 hours. After cooling, the TC4 titanium alloy product was obtained.

[0044] The TC4 titanium alloy product prepared in this embodiment was tested using the same methods as in Example 1. Its density, mechanical properties, and oxygen content were tested, and its metallographic structure was observed. The tests showed that the TC4 titanium alloy product prepared in this embodiment had a density of 99.3%, a tensile strength of 926 MPa, an elongation of 19.5%, and an oxygen content of 0.18% by mass. The metallographic structure of the TC4 titanium alloy product prepared in this embodiment (e.g., ...) is shown in the image. Figure 3 As shown in the figure, the microstructure of this TC4 titanium alloy product exhibits an increased content of acicular martensite and an average grain size of 62 μm, demonstrating excellent application performance. This is because the hydrogenated dehydrogenated TC4 titanium alloy powder of this invention undergoes vacuum annealing pretreatment, while spherical TC4 titanium alloy powder is doped and compounded with the hydrogenated dehydrogenated TC4 titanium alloy powder, and this is combined with the laser-directed energy deposition technology and gradient aging heat treatment of this invention. Cost calculation of the TC4 titanium alloy product prepared in this embodiment shows that its cost is only 61.5% of that of the pure spherical TC4 titanium alloy product, demonstrating a cost advantage.

[0045] Example 3 A method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition specifically includes the following steps: (1) Place the hydrogenated and dehydrogenated TC4 titanium alloy powder in a vacuum furnace and evacuate it to 1×10⁻⁶. -2 Pa, then heated to 600℃ and annealed for 3 hours in a 99.99% high-purity argon atmosphere; the annealed hydrogenated dehydrogenated TC4 titanium alloy powder was vibrated and sieved using a gradient sieve of 1800 mesh (10μm sieve diameter) + 100 mesh (150μm sieve diameter) and an elliptical trajectory (3mm major axis / 1.2mm minor axis) vibration mode to obtain pretreated hydrogenated dehydrogenated TC4 titanium alloy powder with an oxygen content ≤2500ppm and a particle size range of 10-150μm.

[0046] (2) Spherical TC4 titanium alloy powder was vibrated and sieved using a gradient screen of 1800 mesh (10 μm sieve diameter) + 100 mesh (150 μm sieve diameter) and an elliptical trajectory (3 mm major axis / 1.2 mm minor axis) vibration mode to obtain spherical TC4 titanium alloy powder with a particle size range of 10-150 μm; the sieved spherical TC4 titanium alloy powder was mechanically activated using a planetary ball mill, and the spherical TC4 powder was placed in the ball mill at a ball-to-material ratio of 10:1. In a jar (filling rate 35%), 99.99% high-purity argon gas was introduced into the ball mill tube for atmosphere protection. The ball mill was run at 200 rpm clockwise for 50 min, stopped for 10 min, then at 200 rpm counterclockwise for 50 min, stopped for 10 min, then at 200 rpm clockwise for 50 min, stopped for 10 min, for a total duration of 3 hours. The ball-milled powder was sieved to obtain spherical TC4 titanium alloy powder with a pretreated oxygen content ≤1200 ppm and a particle size ≤45 mesh.

[0047] (3) The pretreated hydrogenated dehydrogenated TC4 titanium alloy powder and the pretreated spherical TC4 titanium alloy powder were mixed in a mixer at a speed of 100 rpm for 1 h to form a mixed powder. The mixed powder consisted of 60% pretreated hydrogenated dehydrogenated TC4 titanium alloy powder by mass percentage, and the remainder was pretreated spherical TC4 titanium alloy powder. The mixed powder was loaded into a powder feeding tank and laser-directed energy deposition was performed on the mixed powder under a 99.99% high-purity argon atmosphere with a laser power of 500 W, a scanning rate of 1 mm / s, and a powder feeding rate of 8 g / min to obtain a mixed powder deposit. The mixed powder deposit was heated to 790℃ at a heating rate of 10℃ / min and held for 1.5 h, and then cooled to 490℃ at a cooling rate of 10℃ / min and held for 3 h. After cooling, the TC4 titanium alloy product was obtained.

[0048] The TC4 titanium alloy product prepared in this embodiment was tested using the same methods as in Example 1. Its density, mechanical properties, and oxygen content were tested, and its metallographic structure was observed. The tests showed that the TC4 titanium alloy product prepared in this embodiment had an increased content of acicular martensite in its microstructure, exhibiting excellent application performance. This is because the hydrogenated dehydrogenated TC4 titanium alloy powder of this invention underwent vacuum annealing pretreatment, and spherical TC4 titanium alloy powder was doped and compounded with the hydrogenated dehydrogenated TC4 titanium alloy powder, in conjunction with the laser-directed energy deposition technology and gradient aging heat treatment of this invention. Cost analysis of the TC4 titanium alloy product prepared in this embodiment showed that its cost was low, giving it a price competitive advantage.

[0049] Example 4 A method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition specifically includes the following steps: (1) Place the hydrogenated and dehydrogenated TC4 titanium alloy powder in a vacuum furnace and evacuate it to 1×10⁻⁶. -2 Pa, then heated to 800℃ and annealed for 1 hour in a 99.99% high-purity argon atmosphere; the annealed hydrogenated dehydrogenated TC4 titanium alloy powder was then vibrated and sieved using a gradient sieve of 1800 mesh (10μm sieve diameter) + 100 mesh (150μm sieve diameter) and an elliptical trajectory (3mm major axis / 1.2mm minor axis) vibration mode to obtain pretreated hydrogenated dehydrogenated TC4 titanium alloy powder with an oxygen content ≤2500ppm and a particle size range of 10-150μm.

[0050] (2) Spherical TC4 titanium alloy powder was vibrated and sieved using a gradient screen of 1800 mesh (10 μm sieve diameter) + 100 mesh (150 μm sieve diameter) and an elliptical trajectory (3 mm major axis / 1.2 mm minor axis) vibration mode to obtain spherical TC4 titanium alloy powder with a particle size range of 10-150 μm. The sieved spherical TC4 titanium alloy powder was surface-washed with a mixed acid aqueous solution containing 10% hydrofluoric acid and 30% nitric acid to remove the oxide layer and oil stains. After acid washing, it was ultrasonically cleaned three times with deionized water and subjected to 1×10 at 80℃. -2 Vacuum drying under Pa conditions for 24 hours yielded spherical TC4 titanium alloy powder with an oxygen content ≤1200ppm after pretreatment.

[0051] (3) The pretreated hydrogenated dehydrogenated TC4 titanium alloy powder and the pretreated spherical TC4 titanium alloy powder were mixed in a mixer at a speed of 300 rpm for 0.5 h to form a mixed powder. The mixed powder included 20% of the pretreated hydrogenated dehydrogenated TC4 titanium alloy powder by mass percentage, and the remainder was the pretreated spherical TC4 titanium alloy powder. The mixed powder was loaded into a powder feeding tank and laser-directed energy deposition was performed on the mixed powder under a 99.99% high-purity argon atmosphere with a laser power of 1000 W, a scanning rate of 10 mm / s, and a powder feeding rate of 12 g / min to obtain a mixed powder deposit. The mixed powder deposit was heated to 810℃ at a heating rate of 10℃ / min and held for 2 h, and then cooled to 510℃ at a cooling rate of 10℃ / min and held for 5 h. After cooling, the TC4 titanium alloy product was obtained.

[0052] The TC4 titanium alloy product prepared in this embodiment was tested using the same methods as in Example 1. Its density, mechanical properties, and oxygen content were tested, and its metallographic structure was observed. The tests showed that the TC4 titanium alloy product prepared in this embodiment had an increased content of acicular martensite in its microstructure, exhibiting excellent application performance. This is because the hydrogenated dehydrogenated TC4 titanium alloy powder of this invention underwent vacuum annealing pretreatment, and spherical TC4 titanium alloy powder was doped and compounded with the hydrogenated dehydrogenated TC4 titanium alloy powder, in conjunction with the laser-directed energy deposition technology and gradient aging heat treatment of this invention. Cost analysis of the TC4 titanium alloy product prepared in this embodiment showed that its cost was low, giving it a price competitive advantage.

[0053] Comparative Example 1 A method for preparing spherical TC4 titanium alloy powder laser-directed energy deposition material specifically includes the following steps: (1) Spherical TC4 titanium alloy powder was vibrated and sieved using a gradient screen of 1800 mesh (10 μm sieve diameter) + 100 mesh (150 μm sieve diameter) and an elliptical trajectory (3 mm major axis / 1.2 mm minor axis) vibration mode to obtain spherical TC4 titanium alloy powder with a particle size range of 10-150 μm. The sieved spherical TC4 titanium alloy powder was surface-washed with a mixed acid aqueous solution containing 10% hydrofluoric acid and 30% nitric acid to remove the oxide layer and oil stains. After acid washing, it was ultrasonically cleaned 3 times with deionized water and subjected to 1×10 at 80℃. -2 Vacuum drying under Pa conditions for 24 hours yielded spherical TC4 titanium alloy powder with an oxygen content ≤1200ppm after pretreatment.

[0054] (2) The pretreated spherical TC4 titanium alloy powder was loaded into a powder feeding tank and laser-directed energy deposition was performed on the pretreated spherical TC4 titanium alloy powder under a 99.99% high-purity argon atmosphere with a laser power of 700W, a scanning rate of 8mm / s, and a powder feeding rate of 10g / min to obtain a spherical TC4 titanium alloy powder deposit. The spherical TC4 titanium alloy powder deposit was heated to 800℃ at a heating rate of 10℃ / min and held for 1h, and then cooled to 500℃ at a cooling rate of 10℃ / min and held for 4h. After cooling, the TC4 titanium alloy product was obtained.

[0055] The TC4 titanium alloy product prepared in this comparative example was tested using the same methods as in Example 1. Its density, mechanical properties, and oxygen content were tested, and its metallographic structure was observed. The tests showed that the TC4 titanium alloy product prepared in this comparative example had a density of 99.5%, a tensile strength of 880 MPa, an elongation of 19.0%, and an oxygen content of 0.15% by mass. The metallographic structure of the TC4 titanium alloy product prepared in this comparative example (e.g., [image of metallographic structure]) is shown below. Figure 4 As shown in the figure, the microstructure of the TC4 titanium alloy product is a single β crystal with an average grain size of 75 μm. This is because the pretreated hydrogenated and dehydrogenated TC4 titanium alloy powder was not added to the comparative example as an in-situ seed crystal to induce the formation of a dual-scale grain structure, resulting in poor application performance of the TC4 titanium alloy product prepared in the comparative example.

[0056] Comparative Example 2 A method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition specifically includes the following steps: (1) Hydrogenated dehydrogenated TC4 titanium alloy powder was vibrated and sieved using a gradient screen of 1800 mesh (10 μm sieve diameter) + 100 mesh (150 μm sieve diameter) and an elliptical trajectory (3 mm major axis / 1.2 mm minor axis) vibration mode to obtain hydrogenated dehydrogenated TC4 titanium alloy powder with a particle size range of 10-150 μm.

[0057] (2) Spherical TC4 titanium alloy powder was vibrated and sieved using a gradient screen of 1800 mesh (10 μm sieve diameter) + 100 mesh (150 μm sieve diameter) and an elliptical trajectory (3 mm major axis / 1.2 mm minor axis) vibration mode to obtain spherical TC4 titanium alloy powder with a particle size range of 10-150 μm. The sieved spherical TC4 titanium alloy powder was surface-washed with a mixed acid aqueous solution containing 10% hydrofluoric acid and 30% nitric acid to remove the oxide layer and oil stains. After acid washing, it was ultrasonically cleaned three times with deionized water and subjected to 1×10 at 80℃. -2 Vacuum drying under Pa conditions for 24 hours yielded spherical TC4 titanium alloy powder with an oxygen content ≤1200ppm after pretreatment.

[0058] (3) The sieved hydrogenated dehydrogenated TC4 titanium alloy powder and the pretreated spherical TC4 titanium alloy powder are mixed in a mixer at a speed of 250 rpm for 2 hours to form a mixed powder. The mixed powder includes 10% of the sieved hydrogenated dehydrogenated TC4 titanium alloy powder by mass percentage, and the remainder is the pretreated spherical TC4 titanium alloy powder. The mixed powder is loaded into a powder feeding tank and laser-directed energy deposition is performed on the mixed powder under a 99.99% high-purity argon atmosphere with a laser power of 700W, a scanning rate of 8mm / s, and a powder feeding rate of 10g / min to obtain a mixed powder deposit. The mixed powder deposit is heated to 800℃ at a heating rate of 10℃ / min and held for 1 hour, and then cooled to 500℃ at a cooling rate of 10℃ / min and held for 4 hours. After cooling, the TC4 titanium alloy product is obtained.

[0059] The TC4 titanium alloy product prepared in this comparative example was tested using the same methods as in Example 1. Its density, mechanical properties, and oxygen content were tested, and its metallographic structure was observed. The tests showed that the TC4 titanium alloy product prepared in this comparative example had a density of 93.8%, a tensile strength of 702 MPa, an elongation of 9.2%, and an oxygen content of 0.33% by mass. The metallographic structure of the TC4 titanium alloy product prepared in this comparative example (e.g., [image of metallographic structure]) is shown below. Figure 5 As shown in the figure, the TC4 titanium alloy product has a high oxygen content, which makes it prone to fracture due to oxygen embrittlement. Furthermore, the porosity is 6%, which is due to the aggregation of unmelted HDH powder. This comparative example did not undergo powder pretreatment, resulting in a high oxygen content. Therefore, due to oxygen embrittlement, the material is more susceptible to cracking and failure, exhibiting lower tensile strength and elongation, leading to poor application performance of the TC4 titanium alloy product.

[0060] Comparative Example 3 A method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition specifically includes the following steps: (1) Place the hydrogenated and dehydrogenated TC4 titanium alloy powder in a vacuum furnace and evacuate it to 1×10⁻⁶. -2 Pa, then heated to 750℃ and annealed for 2 hours in a 99.99% high-purity argon atmosphere; the annealed hydrogenated dehydrogenated TC4 titanium alloy powder was then vibrated and sieved using a gradient sieve of 1800 mesh (10μm sieve diameter) + 100 mesh (150μm sieve diameter) and an elliptical trajectory (3mm major axis / 1.2mm minor axis) vibration mode to obtain pretreated hydrogenated dehydrogenated TC4 titanium alloy powder with an oxygen content ≤2500ppm and a particle size range of 10-150μm.

[0061] (2) Spherical TC4 titanium alloy powder was vibrated and sieved using a gradient screen of 1800 mesh (10 μm sieve diameter) + 100 mesh (150 μm sieve diameter) and an elliptical trajectory (3 mm major axis / 1.2 mm minor axis) vibration mode to obtain spherical TC4 titanium alloy powder with a particle size range of 10-150 μm. The sieved spherical TC4 titanium alloy powder was surface-washed with a mixed acid aqueous solution containing 10% hydrofluoric acid and 30% nitric acid to remove the oxide layer and oil stains. After acid washing, it was ultrasonically cleaned three times with deionized water and subjected to 1×10 at 80℃. -2 Vacuum drying under Pa conditions for 24 hours yielded spherical TC4 titanium alloy powder with an oxygen content ≤1200ppm after pretreatment.

[0062] (3) The pretreated hydrogenated dehydrogenated TC4 titanium alloy powder and the pretreated spherical TC4 titanium alloy powder were mixed in a mixer at a speed of 250 rpm for 2 hours to form a mixed powder. The mixed powder included 10% of the pretreated hydrogenated dehydrogenated TC4 titanium alloy powder by mass percentage, and the remainder was the pretreated spherical TC4 titanium alloy powder. The mixed powder was loaded into a powder feeding tank and laser-directed energy deposition was performed on the mixed powder under a 99.99% high-purity argon atmosphere with a laser power of 400W, a scanning rate of 8mm / s, and a powder feeding rate of 10g / min to obtain a mixed powder deposit. The mixed powder deposit was heated to 800℃ at a heating rate of 10℃ / min and held for 1 hour, and then cooled to 500℃ at a cooling rate of 10℃ / min and held for 4 hours. After cooling, the TC4 titanium alloy product was obtained.

[0063] The TC4 titanium alloy product prepared in this comparative example was tested using the same methods as in Example 1. Its density, mechanical properties, and oxygen content were tested, and its metallographic structure was observed. The tests showed that the TC4 titanium alloy product prepared in this comparative example had a density of 94.5%, a tensile strength of 710 MPa, an elongation of 13.5%, and an oxygen content of 0.20% by mass. The metallographic structure of the TC4 titanium alloy product prepared in this comparative example (e.g., [image of metallographic structure]) is shown below. Figure 6 As shown in the figure, the TC4 titanium alloy product exhibits poor fusion between powder particles, low density, and numerous pores. In this comparative example, due to the low laser power, fusion between HDH powder and spherical powder failed, resulting in a material with a minimum tensile strength of 710 MPa and an elongation of 13.5%, indicating poor application performance of the TC4 titanium alloy product.

[0064] Comparative Example 4 A method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition specifically includes the following steps: (1) Place the hydrogenated and dehydrogenated TC4 titanium alloy powder in a vacuum furnace and evacuate it to 1×10⁻⁶. -2 Pa, then heated to 750℃ and annealed for 2 hours in a 99.99% high-purity argon atmosphere; the annealed hydrogenated dehydrogenated TC4 titanium alloy powder was then vibrated and sieved using a gradient sieve of 1800 mesh (10μm sieve diameter) + 100 mesh (150μm sieve diameter) and an elliptical trajectory (3mm major axis / 1.2mm minor axis) vibration mode to obtain pretreated hydrogenated dehydrogenated TC4 titanium alloy powder with an oxygen content ≤2500ppm and a particle size range of 10-150μm.

[0065] (2) Spherical TC4 titanium alloy powder was vibrated and sieved using a gradient screen of 1800 mesh (10 μm sieve diameter) + 100 mesh (150 μm sieve diameter) and an elliptical trajectory (3 mm major axis / 1.2 mm minor axis) vibration mode to obtain spherical TC4 titanium alloy powder with a particle size range of 10-150 μm. The sieved spherical TC4 titanium alloy powder was surface-washed with a mixed acid aqueous solution containing 10% hydrofluoric acid and 30% nitric acid to remove the oxide layer and oil stains. After acid washing, it was ultrasonically cleaned three times with deionized water and subjected to 1×10 at 80℃. -2 Vacuum drying under Pa conditions for 24 hours yielded spherical TC4 titanium alloy powder with an oxygen content ≤1200ppm after pretreatment.

[0066] (3) The pretreated hydrogenated dehydrogenated TC4 titanium alloy powder and the pretreated spherical TC4 titanium alloy powder were mixed in a mixer at a speed of 250 rpm for 2 hours to form a mixed powder. The mixed powder included 10% of the pretreated hydrogenated dehydrogenated TC4 titanium alloy powder by mass percentage, and the remainder was the pretreated spherical TC4 titanium alloy powder. The mixed powder was loaded into a powder feeding tank and laser-directed energy deposition was performed on the mixed powder under a 99.99% high-purity argon atmosphere with a laser power of 700W, a scanning rate of 8mm / s, and a powder feeding rate of 10g / min to obtain a mixed powder deposit. The mixed powder deposit was heated to 500℃ at a heating rate of 10℃ / min and held for 4 hours, and then cooled at a cooling rate of 10℃ / min to obtain the TC4 titanium alloy product.

[0067] The TC4 titanium alloy product prepared in this comparative example was tested using the same methods as in Example 1. Its density, mechanical properties, and oxygen content were tested, and its metallographic structure was observed. The tests showed that the TC4 titanium alloy product prepared in this comparative example had a density of 98.2%, a tensile strength of 785 MPa, an elongation of 14.8%, and an oxygen content of 0.19% by mass. The metallographic structure of the TC4 titanium alloy product prepared in this comparative example (e.g., [image of metallographic structure]) is shown below. Figure 7 As shown in the figure, the microstructure of the TC4 titanium alloy product is significantly coarser than that of the gradient aging heat treatment product, with the β grains coarsening to 83μm and the tensile strength being lower. The application performance of the TC4 titanium alloy product is poor.

[0068] In summary, this invention achieves a density >99% by controllably mixing low-cost, dehydrogenated hydrogen (HDH) titanium alloy powder with high-performance, high-flowability spherical titanium alloy powder, and adapting the laser-directed energy deposition process parameters to solve the problem of insufficient fusion of the mixed powders. This results in titanium alloy components with unique microstructures, excellent comprehensive performance, and / or lower cost. The invention utilizes HDH powder as an in-situ seed crystal to induce the formation of a dual-scale grain structure (β-crystal region and acicular α' martensite region), and controls the oxygen content of the components to ≤0.18 wt% by suppressing oxygen increment through powder pretreatment. The resulting material achieves tensile strength and elongation reaching or even exceeding the performance of pure spherical powder with a HDH powder mass percentage of 10%, while reducing raw material costs. This invention shows promising application prospects in the low-cost, high-performance manufacturing of load-bearing components and biomaterials.

[0069] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition, characterized in that, Specifically, the following steps are included: (1) The hydrogenated dehydrogenated TC4 titanium alloy powder was placed in a vacuum device, vacuumed and heated, and annealed under a protective atmosphere. Then it was sieved to obtain the pretreated hydrogenated dehydrogenated TC4 titanium alloy powder. (2) The spherical TC4 titanium alloy powder is sieved and then pickled or mechanically activated to obtain pretreated spherical TC4 titanium alloy powder. (3) Mix the pretreated hydrogenated dehydrogenated TC4 titanium alloy powder and the pretreated spherical TC4 titanium alloy powder evenly according to the proportion to obtain mixed powder. Then, perform laser directional energy deposition treatment and gradient aging heat treatment on the mixed powder in sequence to obtain TC4 titanium alloy products.

2. The preparation method of hydrogenation-dehydrogenation / spherical TC4 titanium alloy composite powder by laser-directed energy deposition according to claim 1, characterized in that, The annealing conditions in step (1) are: annealing at 600-800℃ for 1-3 hours; the particle size range of the hydrogenated and dehydrogenated TC4 titanium alloy powder after sieving is 10-150μm.

3. The method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition according to claim 1, characterized in that, The particle size range of the spherical TC4 titanium alloy powder after sieving in step (2) is 10-150 μm.

4. The method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition according to claim 1, characterized in that, The specific steps of pickling in step (2) are as follows: Prepare a mixed acid aqueous solution containing 10% hydrofluoric acid and 30% nitric acid by mass percentage, pickle the surface of the sieved spherical TC4 titanium alloy powder, then ultrasonically clean it three times with water, and then perform pickling at 80℃ and 1×10 -2 Vacuum dried for 24 hours under Pa conditions.

5. The method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition according to claim 1, characterized in that, The specific steps of mechanical activation treatment in step (2) are as follows: spherical TC4 powder is mechanically activated using a planetary ball mill. The spherical TC4 powder is placed in a ball milling jar with a ball-to-material ratio of 10:1 and a filling rate of 35%. Argon gas is introduced into the ball milling jar for atmosphere protection. The ball milling is performed at a speed of 200 rpm for 50 min, stopped for 10 min, at a speed of 200 rpm for 50 min, stopped for 10 min, at a speed of 200 rpm for 50 min, stopped for 10 min, and then at a speed of 200 rpm for 50 min, stopped for 10 min, for a total duration of 3 hours. The spherical TC4 powder after ball milling is sieved to obtain spherical TC4 powder with a mesh size of ≤45.

6. The method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition according to claim 1, characterized in that, The mixing conditions for the pretreated hydrogenated dehydrogenated TC4 titanium alloy powder and spherical titanium alloy TC4 powder in step (3) are: mixing at 100-300 rpm for 0.5-2 hours using a mixing device.

7. The method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition according to claim 1, characterized in that, The mixed powder in step (3) comprises, by mass percentage, 5-60% pretreated hydrogenated dehydrogenated titanium alloy TC4 powder, with the remainder being pretreated spherical titanium alloy TC4 powder.

8. The method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition according to claim 1, characterized in that, The conditions for laser-directed energy deposition in step (3) are as follows: using inert gas as the protective gas, deposition is performed under the conditions of laser power of 500-1000W, scanning speed of 1-10mm / s, and powder feeding rate of 8-12g / min.

9. The method for preparing hydrogenated / dehydrogenated / spherical TC4 titanium alloy composite powder by laser-directed energy deposition according to claim 1, characterized in that, The conditions for gradient aging heat treatment in step (3) are as follows: heat the mixed powder after laser directional energy deposition treatment to 790-810℃ and keep it at that temperature for 1-2 hours, then cool it down to 490-510℃ and keep it at that temperature for 3-5 hours, and then cool it down.

10. The TC4 titanium alloy product prepared by the method according to any one of claims 1 to 9.

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