Efficient laser directed energy deposition of large-grained tc4 titanium alloy and method of making

Abstract

The application discloses a kind of high-efficiency laser directional energy deposition large-grained TC4 titanium alloy and preparation method thereof, belong to laser additive manufacturing technical field.For the bottleneck that deposition efficiency is low in prior art when laser directional energy deposition TC4 titanium alloy, large-grained powder is difficult to obtain high-performance workpiece, the application adopts the large-grained TC4 powder with particle size range of 250-355 μm, laser directional energy deposition is carried out under inert gas protection, and the key process parameters are as follows: laser power 8000W, powder feeding rate 62g / min, scanning speed 1000mm / min.The application realizes complete melting and efficient deposition of large-grained powder by ultra-high power laser input, and the deposition efficiency is improved by more than 50%, and the key indicators such as tensile property and plasticity fully reach the forging standard.The application significantly improves production efficiency, reduces powder cost and material waste, and is especially suitable for rapid preparation of large titanium alloy structural parts.

Description

Technical Field

[0001] This invention belongs to the field of laser additive manufacturing technology, specifically relating to a highly efficient laser-directed energy deposition method for large-particle-size TC4 titanium alloy and its preparation method. Background Technology

[0002] Currently, TC4 titanium alloy is the most widely used titanium alloy in the industrial field worldwide. TC4 titanium alloy is the most typical (α+β) type dual-phase titanium alloy. It has a very low density, close to half that of steel, while its strength is comparable to structural steel and cemented carbide, meeting the requirements of aerospace. At the same time, TC4 titanium alloy also has wide applications in biomedical materials, marine and chemical materials due to its high corrosion resistance and excellent biocompatibility.

[0003] Laser Directed Energy Deposition (LDED), as an advanced additive manufacturing technique, can achieve near-net-shape forming of complex structural parts, significantly shortening the manufacturing cycle and reducing costs. However, existing LDED technologies generally face a contradiction between deposition efficiency and the mechanical properties of the parts when preparing TC4 alloys. On the one hand, increasing deposition efficiency requires increasing laser power, resulting in a larger molten pool volume and a greater likelihood of defects such as porosity, which adversely affects the performance of the deposited parts. On the other hand, to obtain dense, high-performance deposited parts, existing technologies typically tend to use small-particle-size powders (such as 75-180 μm or 75-250 μm) and combine them with medium-power laser parameters for slow deposition. While this ensures high density, the deposition efficiency is extremely low, failing to meet the manufacturing requirements of large structural parts.

[0004] Furthermore, during the preparation of TC4 powder, large-particle-size powder (particle size greater than 250μm) is inevitably present. However, due to the difficulty in completely melting it with existing processes, it is screened out, resulting in serious material waste. Moreover, the heat input required to melt large-particle-size powder is much higher than that for small-particle-size powder. Conventional power laser equipment (e.g., 3000-5000W) cannot provide sufficient energy density to completely melt it, easily leading to incomplete fusion defects caused by "unmelted powder core." This makes it difficult for the tensile properties, plasticity, and other key mechanical properties of the finished product to meet forging standards. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a highly efficient laser-directed energy deposition method for large-particle-size TC4 titanium alloy and its preparation method. This invention addresses the technical bottlenecks in the prior art, such as low deposition efficiency and difficulty in obtaining high-performance parts from large-particle-size powder during laser-directed energy deposition of TC4 titanium alloy. The invention aims to achieve efficient and high-quality deposition of large-particle-size TC4 powder through a specific combination of high-power parameters, enabling the mechanical properties of the parts to fully meet forging standards, while significantly improving production efficiency and reducing material waste.

[0006] To achieve the above objectives, the present invention employs the following technical solution: A method for preparing TC4 titanium alloy by laser-directed energy deposition, comprising: S1, TC4 titanium alloy spherical powder with a particle size range of 250μm to 355μm was selected as the deposition raw material; S2, In an inert gas protective environment, a laser is used to heat the substrate to form a molten pool, and the TC4 titanium alloy spherical powder is simultaneously transported to the molten pool for multi-layer stacking and forming. After cooling, TC4 titanium alloy with laser-directed energy deposition is obtained. The laser power is 7900-8100W, the powder feeding rate is 60-65g / min, and the scanning speed is 900-1100mm / min.

[0007] A further improvement of the present invention is that: Preferably, in step S2, the inert gas is argon, and the oxygen content in the forming chamber is controlled below 100 ppm.

[0008] Preferably, in S2, during the conveying process of TC4 titanium alloy spherical powder, the powder-carrying gas flow rate is 10L / min, the spot diameter is 8mm, and the deposition layer thickness is 1.2mm.

[0009] Preferably, in S1, the TC4 titanium alloy spherical powder is vacuum dried before deposition.

[0010] Preferably, the vacuum drying conditions are: drying at 120°C for 2 hours in an electrically heated vacuum drying oven.

[0011] Preferably, the large TC4 titanium alloy spherical powder comprises, by mass percentage: O 0.1768%, N 0.004%, H 0.0003%, C 0.0225%, S 0.0086%, Al 6.35%, V 4.12%, Fe 0.12%, with the balance being Ti.

[0012] Preferably, the substrate is a TC4 titanium alloy rolled sheet, and its surface is polished, cleaned and dried before deposition.

[0013] Preferably, in S2, during the multi-layer stacking process, the interlayer rotation angle is 45° and the interlayer overlap rate is 50%.

[0014] Preferably, in S2, after deposition is completed, the resulting TC4 titanium alloy is cooled in the furnace.

[0015] A laser-directed energy deposition TC4 titanium alloy prepared by any one of the above preparation methods, wherein the room temperature tensile properties of the TC4 titanium alloy workpiece satisfy the following: tensile strength ≥ 895 MPa, yield strength ≥ 825 MPa, and elongation after fracture ≥ 8%.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for efficiently preparing titanium alloy workpieces with mechanical properties reaching forging-grade standards using large-particle-size TC4 titanium alloy powder via laser-directed energy deposition. This method achieves efficient and high-quality deposition of large-particle-size powder through a specific combination of high-power parameters, enabling the finished workpieces to fully meet forging standards in terms of mechanical properties, significantly improving production efficiency and reducing material waste. This invention has the following advantages: (1) Existing laser-directed energy deposition (EDA) processes for TC4 titanium alloy typically employ laser power in the range of 3000-5000W, combined with small-diameter powders of 75-180μm or 75-250μm, and deposition is carried out at a relatively low powder feed rate (usually 20-25g / min) and scanning speed. In pursuit of higher deposition efficiency, this invention breaks through the paradigm of "low power, fine powder, and low speed". For TC4 powders with large particle sizes of 250-355μm, a high-power laser of 7900-8100W and a high powder feed rate of 60-65g / min are used. Under these operating conditions, high power requires a larger scanning speed to ensure the cooling of the molten pool, while large-diameter powders and a large powder feed rate require a slower scanning speed to ensure complete melting of the powder and reduce defects such as incomplete fusion. This invention employs a scanning speed of 900-1100 mm / min for laser-directed energy deposition (LDED), adapting to high-power, large-particle-size, and high-powder-feed conditions to improve production efficiency while ensuring key indicators such as strength and plasticity meet forging standards. This invention significantly improves production efficiency, reduces powder costs and material waste, and is particularly suitable for the rapid fabrication of large titanium alloy structural components.

[0017] (2) By precisely controlling the powder-carrying gas flow rate to 10L / min, the continuity and uniformity of large-particle-size powder delivery can be ensured, while avoiding excessive disturbance to the molten pool or entrainment of ambient gas due to excessive airflow, thereby minimizing porosity. At the same time, controlling the oxygen content in the forming chamber to below 100ppm effectively suppresses the oxidation reaction of titanium alloy at high temperatures and reduces the formation of oxide inclusion defects.

[0018] (3) This invention allows the use of large-particle-size (250-355μm) TC4 powder, which is cheaper, has better flowability, and is less prone to agglomeration. It effectively utilizes large-particle-size powder that is eliminated by screening in traditional processes, broadens the source of raw materials, significantly reduces the cost of powder preparation, and reduces material waste. In addition, the flowability of large-particle-size powder is better than that of small-particle-size powder, which can effectively reduce problems such as powder blockage and agglomeration during the powder feeding process, improve process stability, and is especially suitable for long-term continuous and rapid preparation of large titanium alloy structural parts.

[0019] (4) The TC4 titanium alloy workpiece prepared by the method of the present invention has room temperature tensile properties that meet the mechanical property requirements of GJB2744A-2007. Specifically, the tensile strength is ≥895MPa (measured up to 932.35MPa), the yield strength is ≥825MPa (measured up to 844.55MPa), and the elongation after fracture is ≥8% (measured up to 8.16%), achieving a good match between strength and plasticity. The high-power laser beam combined with a moderate scanning speed forms a uniform Widmanstätten structure and basketweave structure during the subsequent rapid solidification process. The α lath width is about 3.07μm, and the laths are uniform and do not change significantly. This fine microstructure is the key microstructural basis for the mechanical properties of the workpiece to reach the forging standard, enabling the workpiece to meet the forging standard and significantly reducing material waste. Attached Figure Description

[0020] Figure 1 This is a metallographic image (SEM) of the TC4 titanium alloy deposited sample prepared in Example 1 of the present invention.

[0021] Figure 2 This is a metallographic image (SEM) of the TC4 titanium alloy deposited sample prepared in Comparative Example 1 of this invention.

[0022] Figure 3 This is a metallographic image (SEM) of the TC4 titanium alloy deposited sample prepared in Comparative Example 2 of this invention.

[0023] Figure 4 The stress-strain curve of the TC4 titanium alloy prepared as a comparative example of this invention is shown. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings: To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0025] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0026] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0027] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0028] This invention discloses a method for preparing forging-grade titanium alloy workpieces by laser-directed energy deposition of large-particle-size TC4 powder, comprising the following steps: Step 1, Powder preparation: Select large-particle-size TC4 titanium alloy spherical powder with a particle size range of 250μm to 355μm as the deposition raw material, and perform vacuum drying treatment on the powder to ensure its flowability.

[0029] During the vacuum drying process, the powder is dried at 120°C for 2 hours in an electrically heated vacuum drying oven.

[0030] Step 2, Substrate Pretreatment: TC4 titanium alloy rolled sheet is selected as the deposition substrate, and its surface is polished, cleaned and dried to remove oil and oxide layer.

[0031] Step 3, laser-directed energy deposition: Under an inert gas protective environment, a high-power laser is used to heat the substrate, and the large-particle-size TC4 titanium alloy powder prepared in Step 1 is simultaneously transported to the molten pool for multi-layer deposition. The key process parameters for laser-directed energy deposition are set as follows: laser power of 7900-8100W, powder feeding rate of 60-65g / min, and scanning speed of 900-1100mm / min.

[0032] During the deposition process, argon is used as the inert gas, and the oxygen content in the forming chamber is controlled below 100 ppm.

[0033] During the deposition process, the powder flow rate for laser-directed energy deposition was 10 L / min, the spot diameter was 8 mm, and the deposition layer thickness was 1.2 mm.

[0034] After laser direct forming, a deposited state TC4 was obtained. Samples were taken from the deposited state TC4 using wire cutting, and the samples were then subjected to metallographic etching to observe their metallographic structure. The volume ratio of the metallographic etchant used for surface morphology observation was HF:HNO3:H2O=1:3:20, and the etching time was approximately 20s.

[0035] Step 4, Performance Testing: The deposited TC4 sample is processed into a standard tensile specimen, and its tensile properties are tested. The specimen used for performance testing in Step 4 is a room temperature plate-shaped tensile specimen with a parallel section dimension of 24 mm. The strain rate selected during testing is 0.001 s². -1 .

[0036] The second aspect of this invention discloses a TC4 titanium alloy workpiece, wherein the room temperature tensile properties of the titanium alloy workpiece meet the following requirements: tensile strength ≥ 895 MPa, yield strength ≥ 825 MPa, and elongation after fracture ≥ 8%. The mechanical properties of the TC4 titanium alloy workpiece meet the mechanical property indicators of GJB2744A-2007.

[0037] The following description, in conjunction with specific embodiments, provides further details.

[0038] Example 1 This embodiment provides a method for preparing titanium alloy workpieces with properties meeting forging standards by laser-directed energy deposition of large-particle-size TC4 powder, including the following steps: (1) Select an annealed TC4 rolled plate with dimensions of 260mm×260mm×20mm as the base material. Before use, the surface is machined and cleaned with acetone to remove oil stains. The surface is ultrasonically cleaned for 15 minutes, rinsed with water, wiped with anhydrous ethanol and dried.

[0039] (2) The TC4 titanium alloy spherical powder was screened using a vibrating screen to select TC4 powder with a particle size distribution of 250-355μm. The TC4 powder contained, by mass percentage: O 0.1768%, N 0.004%, H 0.0003%, C 0.0225%, S 0.0086%, Al 6.35%, V 4.12%, Fe 0.12%, with the balance being Ti.

[0040] (3) The screened powder is dried in an electric vacuum drying oven. During drying, the TC4 titanium alloy powder is evenly scattered on the tray. The drying temperature is set to 120℃ and the drying time is 2h. After drying, the powder is cooled with the oven and then stored in a vacuum after cooling.

[0041] (4) A coaxial powder-feeding laser directional energy deposition equipment equipped with a high-power fiber laser is used. After the forming chamber is evacuated, it is filled with high-purity argon gas to reduce the oxygen content to below 100 ppm.

[0042] (5) Place the dried TC4 titanium alloy powder into the dual-cylinder powder feeder of the laser directional energy deposition equipment, set the rotation speed and measure the powder feeding rate per minute until the powder feeding rate per minute is 62g / min.

[0043] Using a coaxial powder feeding method with a laser power of 8000W, a scanning speed of 1000mm / min, a powder carrier gas flow rate of 10L / min, and a spot diameter of 8mm, TC4 titanium alloy sample blocks of 240mm×40mm×100mm were deposited layer by layer on the substrate in a direction perpendicular to the substrate. The layer thickness was controlled at approximately 1.2mm, the interlayer rotation angle was 45°, and the interlayer overlap rate was 50%.

[0044] (6) After deposition, the sample is cooled with the furnace.

[0045] (7) The deposited TC4 alloy was sampled by wire cutting and its surface morphology was analyzed and its performance was tested.

[0046] (8) The sample used for surface morphology analysis was first polished with sandpaper and then polished with SiO2 suspension. The sample surface was etched for 20s with metallographic etchant of HF:HNO3:H2O=1:3:20 and placed under a scanning electron microscope for tissue observation.

[0047] (9) Grind the upper and lower surfaces of the plate-shaped specimen used for performance testing until smooth, with no oxide scale or obvious wire cutting marks on the remaining surfaces. The strain rate during testing is 0.001 s. -1 .

[0048] The following are the test results for Example 1: (1) The surface morphology of the sample was observed, and the following results were obtained: Figure 1 The microstructure shown is uniform. The α-lamellae are approximately 22.79 μm long and 3.07 μm wide, with an aspect ratio of approximately 8.12. There are no obvious metallurgical defects. The microstructure exhibits a uniform Widmanstätten and basketweave structure without wide clusters.

[0049] (2) A tensile test was performed on the specimen, and the results are as follows: Figure 4 As shown, the sample has a yield strength of 844.55 MPa, a tensile strength of 932.35 MPa, and an elongation after fracture of 8.16%. All performance indicators fully meet and partially exceed the GJB2744A-2007 forging standard.

[0050] Example 2 In this embodiment, the scanning speed is 900 mm / min, and the rest of the parts not involved are the same as in Embodiment 1.

[0051] Example 3 In this embodiment, the scanning speed is 1100 mm / min, and the rest of the parts not involved are the same as in Embodiment 1.

[0052] Example 4 In this embodiment, the laser power is 7900W, and the other parts not involved are the same as in Embodiment 1.

[0053] Example 5 In this embodiment, the laser power is 8100W, and the other parts not involved are the same as in Embodiment 1.

[0054] Example 6 In this embodiment, the powder feeding rate is 60 g / min, and the other parts not involved are the same as in Embodiment 1.

[0055] Example 7 In this embodiment, the powder feeding rate is 65 g / min, and the other parts not involved are the same as in Embodiment 1.

[0056] Comparative Example 1 This comparative example provides a method for laser-directed energy deposition of large-particle-size TC4 powder, including the following steps: (1) Select an annealed TC4 rolled plate with dimensions of 260mm×260mm×20mm as the base material. Before use, the surface is machined and cleaned with acetone to remove oil stains. The surface is ultrasonically cleaned for 15 minutes, rinsed with water, wiped with anhydrous ethanol and dried.

[0057] (2) The TC4 titanium alloy spherical powder was screened using a vibrating screen to select TC4 powder with a particle size distribution of 250-355μm. The TC4 powder contained, by mass percentage: O 0.1768%, N 0.004%, H 0.0003%, C 0.0225%, S 0.0086%, Al 6.35%, V 4.12%, Fe 0.12%, with the balance being Ti.

[0058] (3) The screened powder is dried in an electric vacuum drying oven. During drying, the TC4 titanium alloy powder is evenly scattered on the tray. The drying temperature is set to 120℃ and the drying time is 2h. After drying, the powder is cooled with the oven and then stored in a vacuum after cooling.

[0059] (4) A coaxial powder-feeding laser directional energy deposition equipment equipped with a high-power fiber laser is used. After the forming chamber is evacuated, it is filled with high-purity argon gas to reduce the oxygen content to below 100 ppm.

[0060] (5) Place the dried TC4 titanium alloy powder into the dual-cylinder powder feeder of the laser directional energy deposition equipment, set the rotation speed and measure the powder feeding rate per minute until the powder feeding rate per minute is 62g / min.

[0061] Using a coaxial powder feeding method with a laser power of 8000W, a scanning speed of 1700mm / min, a powder carrier gas flow rate of 10L / min, and a spot diameter of 8mm, TC4 titanium alloy sample blocks of 240mm×40mm×100mm were deposited layer by layer on the substrate in a direction perpendicular to the substrate. The layer thickness was controlled at approximately 1.2mm, the interlayer rotation angle was 45°, and the interlayer overlap rate was 50%.

[0062] (6) After deposition, the sample is cooled with the furnace.

[0063] (7) The deposited TC4 alloy was sampled by wire cutting and its surface morphology was analyzed and its performance was tested.

[0064] (8) The sample used for surface morphology analysis was first polished with sandpaper and then polished with SiO2 suspension. The sample surface was etched for 20s with metallographic etchant of HF:HNO3:H2O=1:3:20 and placed under a scanning electron microscope for tissue observation.

[0065] (9) Grind the upper and lower surfaces of the plate-shaped specimen used for performance testing until smooth, with no oxide scale or obvious wire cutting marks on the remaining surfaces. The strain rate during testing is 0.001 s. -1 .

[0066] The following are the test results for Comparative Example 1: (1) The surface morphology of the sample was observed, and the following results were obtained: Figure 2 The microstructure shown has α laths with a length of approximately 12.91 μm and a width of approximately 1.20 μm, resulting in an aspect ratio of 10.37. The lath width varies greatly within the grains, indicating significant microstructural defects. Additionally, the presence of large α clusters can negatively impact plasticity.

[0067] (2) A tensile test was performed on the specimen, and the results are as follows: Figure 4 As shown, the sample had a yield strength of 835.51 MPa, a tensile strength of 915.27 MPa, and an elongation after fracture of 3.15%. Although the strength indicators basically met the forging standard, the significant increase in the aspect ratio of the α-plate and the non-uniform microstructure, along with the presence of defects in the microstructure, made these defects a preferred pathway for crack initiation and propagation, resulting in a significant decrease in plasticity and an elongation after fracture far below the 8% requirement of the forging standard.

[0068] Comparative Example 2 This comparative example provides a method for laser-directed energy deposition of large-particle-size TC4 powder.

[0069] (1) Select an annealed TC4 rolled plate with dimensions of 260mm×260mm×20mm as the base material. Before use, the surface is machined and cleaned with acetone to remove oil stains. The surface is ultrasonically cleaned for 15 minutes, rinsed with water, wiped with anhydrous ethanol and dried.

[0070] (2) The TC4 titanium alloy spherical powder was screened using a vibrating screen to select TC4 powder with a particle size distribution of 250-355μm. The TC4 powder contained, by mass percentage: O 0.1768%, N 0.004%, H 0.0003%, C 0.0225%, S 0.0086%, Al 6.35%, V 4.12%, Fe 0.12%, with the balance being Ti.

[0071] (3) The screened powder is dried in an electric vacuum drying oven. During drying, the TC4 titanium alloy powder is evenly scattered on the tray. The drying temperature is set to 120℃ and the drying time is 2h. After drying, the powder is cooled with the oven and then stored in a vacuum after cooling.

[0072] (4) A coaxial powder-feeding laser directional energy deposition equipment equipped with a high-power fiber laser is used. After the forming chamber is evacuated, it is filled with high-purity argon gas to reduce the oxygen content to below 100 ppm.

[0073] (5) Place the dried TC4 titanium alloy powder into the dual-cylinder powder feeder of the laser directional energy deposition equipment, set the rotation speed and measure the powder feeding rate per minute until the powder feeding rate per minute is 62g / min.

[0074] Using a coaxial powder feeding method with a laser power of 8000W, a scanning speed of 2400mm / min, a powder carrier gas flow rate of 10L / min, and a spot diameter of 8mm, the substrate was scanned layer by layer, and TC4 titanium alloy sample blocks of 240mm×40mm×100mm were deposited layer by layer in the direction perpendicular to the substrate. The layer thickness was controlled at about 1.2mm, the interlayer rotation angle was 45°, and the interlayer overlap rate was 50%.

[0075] (6) After deposition, the sample is cooled with the furnace.

[0076] (7) The deposited TC4 alloy was sampled by wire cutting and its surface morphology was analyzed and its performance was tested.

[0077] (8) The sample used for surface morphology analysis was first polished with sandpaper and then polished with SiO2 suspension. The sample surface was etched for 20s with metallographic etchant of HF:HNO3:H2O=1:3:20 and placed under a scanning electron microscope for tissue observation.

[0078] (9) Grind the upper and lower surfaces of the plate-shaped specimen used for performance testing until smooth, with no oxide scale or obvious wire cutting marks on the remaining surfaces. The strain rate during testing is 0.001 s. -1 .

[0079] The following are the test results for Comparative Example 2: (1) The surface morphology of the sample was observed, and the following results were obtained: Figure 3 The structure shown has the smallest α laths with no obvious defects, but the aspect ratio of α increases to 14.25, and it also exhibits Widmanstätten structure. The width of the α bundles is 25.56.

[0080] (2) A tensile test was performed on the specimen, and the results are as follows: Figure 4 As shown, the sample has a yield strength of 791.06 MPa, a tensile strength of 908.31 MPa, and an elongation after fracture of 6.68%.

[0081] The results show that only Example 1 fully meets and partially exceeds the forging standard in terms of mechanical properties. In Example 1, the α-lamellae have a small aspect ratio and uniform structure, with good strength and plasticity matching. In Comparative Example 1, the strength meets the forging standard, but the aspect ratio of the α-lamellae increases and the structure is uneven. Defects are also present in the structure, which easily become preferential channels for crack initiation and propagation, resulting in a significant decrease in plasticity. In Comparative Example 2, the lamellae are the thinnest, and the structure has no obvious defects, but the aspect ratio of the α-lamellae is still increasing. While the performance has improved somewhat, it still does not meet the forging standard. In summary, Example 1 meets the forging standard, and the powder feeding rate is significantly improved. Without considering powder loss, the deposition efficiency is increased by approximately 50% compared to the original 5000W and by 54% compared to the original 3800W, significantly improving production efficiency.

[0082] Comparing the elongation after fracture of Example 1, Comparative Example 1, and Comparative Example 2, it can be found that the elongation is 8.16%, 3.15%, and 6.68%, respectively. Therefore, it can be seen that the scanning speed window is narrow for large-particle-size TC4 titanium alloy powder.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing TC4 titanium alloy by laser-directed energy deposition, characterized in that, include: S1, TC4 titanium alloy spherical powder with a particle size range of 250μm to 355μm was selected as the deposition raw material; S2, In an inert gas protective environment, a laser is used to heat the substrate to form a molten pool, and the TC4 titanium alloy spherical powder is simultaneously transported to the molten pool for multi-layer stacking and forming. After cooling, TC4 titanium alloy with laser-directed energy deposition is obtained. The laser power is 7900-8100W, the powder feeding rate is 60-65g / min, and the scanning speed is 900-1100mm / min.

2. The method for preparing TC4 titanium alloy by laser-directed energy deposition according to claim 1, characterized in that, In S2, the inert gas is argon, and the oxygen content in the forming chamber is controlled below 100 ppm.

3. The method for preparing TC4 titanium alloy by laser-directed energy deposition according to claim 1, characterized in that, In S2, during the conveying process of TC4 titanium alloy spherical powder, the powder-carrying gas flow rate is 10L / min, the spot diameter is 8mm, and the deposition layer thickness is 1.2mm.

4. The method for preparing TC4 titanium alloy by laser-directed energy deposition according to any one of claims 1-3, characterized in that, In S1, the TC4 titanium alloy spherical powder is vacuum dried before deposition.

5. The method for preparing TC4 titanium alloy by laser-directed energy deposition according to claim 4, characterized in that, The conditions for the vacuum drying process are: drying at 120°C for 2 hours in an electrically heated vacuum drying oven.

6. The method for preparing TC4 titanium alloy by laser-directed energy deposition according to claim 1, characterized in that, The TC4 titanium alloy spherical powder, by mass percentage, contains: O 0.1768%, N 0.004%, H 0.0003%, C 0.0225%, S 0.0086%, Al 6.35%, V 4.12%, Fe 0.12%, with the balance being Ti.

7. The method for preparing TC4 titanium alloy by laser-directed energy deposition according to claim 1, characterized in that, The substrate is a TC4 titanium alloy rolled plate, and its surface is polished, cleaned and dried before deposition.

8. The method for preparing TC4 titanium alloy by laser-directed energy deposition according to claim 1, characterized in that, In S2, during the multi-layer stacking process, the interlayer rotation angle is 45° and the interlayer overlap rate is 50%.

9. The method for preparing TC4 titanium alloy by laser-directed energy deposition according to claim 1, characterized in that, In S2, after deposition is complete, the resulting TC4 titanium alloy is cooled in the furnace.

10. A laser-directed energy deposition TC4 titanium alloy prepared by the preparation method according to any one of claims 1-9, characterized in that, The room temperature tensile properties of the TC4 titanium alloy workpiece meet the following requirements: tensile strength ≥ 895 MPa, yield strength ≥ 825 MPa, and elongation after fracture ≥ 8%.

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