Preparation method of bionic interpenetrating Ti2AlNb / TiAl-based composite material

Abstract

A method for preparing a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material is provided, belonging to the technical field of titanium-aluminum intermetallic compound-based composite material preparation. This method utilizes a selective laser melting process to additively manufacture a three-dimensional continuous Ti2AlNb reinforcement skeleton to weaken the anisotropy of the mechanical properties of traditional fiber-reinforced composite materials and laminated materials, achieving a good match between strength and plasticity and toughness in multiple directions. The method is more convenient to operate, significantly improves efficiency, and can effectively control the volume fraction of the reinforcement and its arrangement in the matrix, achieving three-dimensional interconnectivity between the reinforcement and the matrix. A biomimetic interpenetrating Ti2AlNb / TiAl-based composite material with an excellent combination of strength, plasticity, and toughness is then prepared through hot pressing and sintering, providing a new approach to breaking the bottleneck in the application of TiAl in hot-end components of aerospace propulsion systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of titanium-aluminum intermetallic compound-based composite materials, and specifically relates to a method for preparing a bionic interpenetrating Ti2AlNb / TiAl-based composite material. A three-dimensional continuous structure Ti2AlNb reinforcement is manufactured by selective laser melting and then vacuum hot pressing and sintering to prepare a bionic interpenetrating Ti2AlNb / TiAl-based composite material with high strength, high plasticity and high fracture toughness. Background Art

[0002] TiAl-based alloys have low density (approximately 3.9 to 4.3 g / cm 3 ), high specific modulus, high creep resistance and excellent oxidation resistance, so it is considered to be the only candidate material to replace nickel-based high-temperature alloys in the range of 700-800 ℃. Currently, the 4822 alloy (Ti-48Al-2Cr-2Nb, at.%) developed by GE has been successfully used in GEnx due to its excellent mechanical properties. TM The low-pressure turbine blades of the engine. However, the low room temperature fracture toughness of TiAl alloys has always been the biggest bottleneck in their development. The room temperature fracture toughness of TiAl alloys modified by alloying is still generally lower than 30 MPa·m 1 / 2 However, the room temperature elongation is limited and the service temperature is lower than 700 ℃, which seriously restricts the application of TiAl alloys in the complex thermal shock environment in the hypersonic field. Therefore, the composite toughening and plasticization of TiAl alloys have received more and more attention.

[0003] Research has shown that discontinuously reinforced TiAl-based composites, such as particles, whiskers, or short fibers, have broad application prospects due to their advantages such as low cost, simple preparation process, ease of secondary processing, and isotropic properties. However, discontinuous reinforcements tend to cluster in the matrix material, leading to stress concentration, which in turn causes fracture failure and reduces the toughness of the material (L.Xiang, F. Wang, J. Zhu, et. al. Mechanical properties and microstructure of Al2O3 / TiAl in situ composites doped with Cr2O3[J]. Materials Science and Engineering A, 2011, 528(9): 3337-3341).

[0004] Compared to discontinuous reinforcements, continuous fibers have great potential for improving the toughness of TiAl alloys (Y.Zhou, DL Sun, Q. Wang, et. al. Effect of fabrication parameters on the microstructure and mechanical properties of unidirectional Mo-fiber reinforced TiAl matrix composites[J]. Materials Science and Engineering A, 2013, 575: 21-29). However, the fiber arrangement in currently developed TiAl-based composites is highly directional, resulting in severe anisotropy in mechanical properties and high dispersion (cv value).

[0005] In recent years, laminated TiAl-based composites have developed rapidly, achieving a significant improvement in the toughness of materials in one direction, but the anisotropy of mechanical properties has become increasingly prominent, and the interface reaction delamination phenomenon is prominent (DH Li, BB Wang, LSLuo, et. al. The interface structure and its impact on the mechanical behavior of TiAl / Ti2AlNb laminated composites[J]. Materials Science andEngineering A, 2021, 827: 142095).

[0006] This shows that although composite design is an effective way to significantly improve the mechanical properties of TiAl alloys, it is still urgent to further improve the fracture toughness of the material and weaken the anisotropy of the mechanical properties of traditional fiber-reinforced composites and laminated materials. Therefore, it is necessary to design a new type of TiAl-based composite material that can improve the fracture toughness of the composite material on the one hand and achieve a good match between strength and plasticity in multiple directions on the other hand. Summary of the Invention

[0007] The present invention addresses the following technical issues: providing a method for preparing a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material. Addressing the low room-temperature fracture toughness of TiAl alloys, the present invention utilizes a selective laser melting process to additively manufacture a three-dimensional continuous Ti2AlNb reinforcement skeleton. This mitigates the anisotropy of mechanical properties found in traditional fiber-reinforced composites and laminates, achieving a well-matched balance of strength and plasticity in multiple directions. Hot-pressing sintering then yields a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material with an excellent combination of strength, plasticity, and toughness. This approach provides a new approach for overcoming the bottleneck in the application of TiAl in hot-end components of aerospace propulsion systems.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for preparing a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material utilizes a selective laser melting process to additively manufacture a three-dimensional continuous Ti2AlNb reinforcement skeleton, thereby reducing the anisotropy of mechanical properties in conventional fiber-reinforced composite materials and laminated materials, thereby achieving a good match between strength and plasticity and toughness in multiple directions. The biomimetic interpenetrating Ti2AlNb / TiAl-based composite material with an excellent combination of strength, plasticity, and toughness is then prepared through hot pressing and sintering.

[0010] The Ti2AlNb reinforcement used in selective laser melting is composed of 22-25 at.% Al and 20-30 at.% Nb, with the balance being Ti. The TiAl matrix is ​​composed of 45-48 at.% Al, 1-3 at.% Cr, and 2-5 at.% Nb, with the balance being Ti. All the above components are expressed in atomic percentages.

[0011] The method for preparing bionic interpenetrating Ti2AlNb / TiAl-based composite materials is specifically divided into two parts:

[0012] (1) Preparation of three-dimensional continuous structure Ti2AlNb reinforcement by selective laser melting. The specific process is as follows:

[0013] Step 1: Powder preparation and pretreatment

[0014] Weighing raw materials according to the above alloy composition, mixing the weighed raw materials uniformly and then smelting them into a master alloy ingot, processing the obtained master alloy ingot into straight alloy rods, and then preparing Ti2AlNb alloy powder by plasma rotating electrode atomization method, and drying the powder for later use;

[0015] Step 2: Create a 3D model

[0016] First, the stl model file of the three-dimensional continuous structure Ti2AlNb reinforcement was constructed using Unigraphics NX software, and then imported into Materialise Magics software for slicing. The determined specific parameters of the three-dimensional model were imported into the Mlab cusing R device.

[0017] Step 3: Powder laying and atmosphere treatment in the forming tank

[0018] The substrate is sandblasted; first, Ti2AlNb alloy powder is loaded into the liftable powder supply cylinder; then the forming cylinder of the equipment is evacuated to make the atmosphere in the forming cylinder meet the requirements;

[0019] Step 4: Set the forming process parameters

[0020] The selective laser melting forming process parameters include laser power, scanning speed, scanning spacing and powder layer thickness;

[0021] Step 5: Selective laser melting

[0022] After setting the forming process parameters, after each layer of powder is laid, the laser beam selectively melts the area according to the slice data of the 3D model; then the base plate in the forming cylinder descends to a layer thickness, the scraper spreads the powder again, and the laser re-melts the newly laid powder area, and this process is repeated until the sample is formed;

[0023] After the sample has cooled, it is cut from the substrate, ultrasonically cleaned, and dried for later use, completing the selective laser melting preparation of the three-dimensional continuous structure Ti2AlNb reinforcement.

[0024] (II) Preparation of biomimetic interpenetrating Ti2AlNb / TiAl-based composite materials. The specific process is as follows:

[0025] Step 6: Design of reinforcement volume fraction in composite material

[0026] Based on the three-dimensional model designed in step 2, the theoretically calculated reinforcement volume fraction is 10-30 vol.%;

[0027] Step 7: Powder filling and cold pressing

[0028] The prepared three-dimensional continuous structure Ti2AlNb skeleton was placed in a cylindrical graphite mold. The volume of TiAl powder required to fill the gap of the three-dimensional continuous structure was calculated according to the volume fraction of the reinforcement phase. Then, m=ρ×(πr 2 ×hV r ) formula can be used to calculate the mass of TiAl powder required for hot pressing and sintering. The weighed TiAl powder is loaded into a mold and cold pressed to obtain a bionic interpenetrating Ti2AlNb / TiAl powder compact.

[0029] Step 8: Hot Pressing and Sintering Process

[0030] The bionic interpenetrating Ti2AlNb / TiAl compact was vacuum sintered at 1050-1250 ℃ and 45 MPa pressure for 1 h. After the hot pressing process, the sample was cooled to room temperature with the furnace to prepare a bionic interpenetrating Ti2AlNb / TiAl-based composite material with a diameter of 50 mm and a height of 10 mm.

[0031] In the above step 1, the alloy powder particle size is selected to be 15 to 53 μm.

[0032] In the above step 2, the slice thickness of the three-dimensional model is 0.025 mm.

[0033] In the above step 3, the substrate used is made of pure titanium;

[0034] When evacuating the forming cylinder of the equipment, high-purity argon is used to dilute and discharge the oxygen in the forming cylinder and the circulation pipeline until the oxygen content in the forming cylinder is lower than 400 ppm; by adjusting the position of the forming cylinder and the powder supply cylinder, the top layer of powder in the powder supply cylinder, the upper surface of the substrate in the forming cylinder and the lower surface of the scraper are made flush.

[0035] In step 4 above, the process parameters are as follows: laser power 70-100 W, scanning speed 600-1100 mm / s, scanning spacing 0.06 mm, and powder layer thickness 0.025 mm; the laser scanning strategy is checkerboard scanning, and the scanning direction between adjacent layers is rotated 90°, that is, the laser scanning direction angle increases by 90° after each layer is printed.

[0036] In the above step 7, the cold pressing pressure is 5-10 MPa and the holding time is 10-30 min;

[0037] In order to avoid the reaction between TiAl alloy powder and graphite mold during hot pressing and sintering, yttrium oxide slurry is applied to the upper and lower pressing heads of the mold and the positions in contact with the powder, and then the powder is loaded after drying.

[0038] The TiAl alloy powder selected is plasma rotating electrode atomized powder, and the main particle size is concentrated in the range of 60 to 120 μm;

[0039] Formula m=ρ×(πr 2 ×hV r ), m—mass of TiAl powder g; ρ—density of TiAl alloy g / cm 3 ; r—radius of the mold used (mm); h—height of the three-dimensional continuous structure Ti2AlNb reinforcement (mm); V r—Volume fraction of reinforcement.

[0040] In step 8 above, the hot pressing sintering process is a staged heating and pressurizing process. First, the sintering temperature is kept at 600°C and 1000°C for 10 minutes each, and the pressure is maintained at 25 MPa under this condition to remove the included gas in the graphite mold. Then, vacuum sintering is carried out at 1050-1250°C and 45 MPa for 1 hour, and the pressure is increased to 45 MPa.

[0041] The sintering process must ensure that the oxygen content is less than 200 ppm and the heating rate is 5-10 ° C / min;

[0042] The theoretical density of the bionic interpenetrating Ti2AlNb / TiAl-based composite material is calculated according to the following formula:

[0043]

[0044] In the formula are the theoretical density and volume fraction of the reinforcement and matrix in the composite material, respectively; the theoretical density of the Ti2AlNb reinforcement and TiAl alloy used are 5.3 g / cm 3 、3.9 g / cm 3 .

[0045] The advantages of the present invention compared with the prior art are:

[0046] 1. This solution uses a three-dimensional continuous structure Ti2AlNb reinforcement to toughen the TiAl matrix to further improve the fracture toughness of the composite material. Solving the strong anisotropy problem of the composite material is a new idea of ​​the present invention. At present, there is no precedent for the preparation of such a three-dimensional continuous structure Ti2AlNb reinforcement. The present invention uses selective laser melting to prepare a three-dimensional continuous structure Ti2AlNb reinforcement. By rationally regulating the forming process parameters, including laser power of 70 to 100 W, scanning speed of 600 to 1100 mm / s, scanning spacing of 0.06 mm, powder layer thickness of 0.025 mm, laser scanning strategy of chessboard scanning, and rotation of the scanning direction between adjacent layers by 90°, a three-dimensional continuous structure Ti2AlNb reinforcement with good structural continuity, uniform size, no defects and a density of up to 99% is finally obtained;

[0047] 2. This proposal fabricates a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material through selective laser melting additive manufacturing of Ti2AlNb reinforcements followed by hot pressing and sintering. This additive manufacturing approach to produce a three-dimensional continuous Ti2AlNb reinforcement eliminates the traditional process of preparing a preform for continuous fiber-reinforced TiAl-based composites. This makes the process more convenient and significantly improves efficiency. It also allows for effective control of the reinforcement volume fraction and its arrangement within the matrix, achieving three-dimensional interconnectivity between the reinforcement and matrix. By rationally regulating the hot pressing and sintering parameters, including the hot pressing temperature, the thickness of the interfacial reaction layer and the types of reactants can be controlled, resulting in a dense biomimetic interpenetrating composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a flow chart of the present invention;

[0049] Figure 2 Schematic diagram of modeling of the three-dimensional continuous structure Ti2AlNb reinforcement in the present invention;

[0050] Figure 3 This is a scanning image of the three-dimensional continuous structure Ti2AlNb reinforcement in the present invention;

[0051] Figure 4 The relationship between the density of the three-dimensional continuous structure Ti2AlNb reinforcement and the forming process parameters in the present invention;

[0052] Figure 5 This is the X-ray diffraction pattern of the bionic interpenetrating Ti2AlNb / TiAl-based composite material obtained in Example 3 of the present invention;

[0053] Figure 6 This is a scanning image of the bionic interpenetrating Ti2AlNb / TiAl-based composite material obtained in Example 5 of the present invention. DETAILED DESCRIPTION

[0054] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0055] See also Figure 1-6 , details the embodiments of the present invention.

[0056] Example 1

[0057] To address the low room-temperature fracture toughness of TiAl alloys, this paper designs a biomimetic interpenetrating Ti2AlNb / TiAl-based composite. Using selective laser melting to additively manufacture a three-dimensional continuous Ti2AlNb reinforcement skeleton, followed by hot-pressing and sintering, the resulting biomimetic interpenetrating Ti2AlNb / TiAl-based composite exhibits an excellent combination of strength, ductility, and toughness. This approach offers a new approach to addressing the bottleneck in the application of TiAl in hot-end components of aerospace propulsion systems.

[0058] The Ti2AlNb alloy used for selective laser melting in the present invention consists of 22 at.% Al and 25 at.% Nb, with the balance being Ti. The TiAl matrix consists of 48 at.% Al, 2 at.% Cr, and 2 at.% Nb, with the balance being Ti. All percentages are in atomic percentage.

[0059] The method for preparing the biomimetic interpenetrating Ti2AlNb / TiAl-based composite material proposed in the present invention is specifically divided into two parts:

[0060] (1) Preparation of three-dimensional continuous structure Ti2AlNb reinforcement by selective laser melting. The specific process is as follows:

[0061] Step 1: Powder preparation and pretreatment.

[0062] The Ti2AlNb alloy composition used was Ti-22Al-25Nb (at.%). Raw materials were weighed according to the alloy composition, mixed uniformly, and then smelted into a master alloy ingot. The resulting master alloy ingot was processed into straight alloy bars, which were then prepared into alloy powder using a plasma rotating electrode atomization method.

[0063] The obtained powder was cleaned and sieved to obtain a powder with a particle size of 15 to 53 μm. The powder was placed in a vacuum drying oven and dried at a temperature of 80°C for 10 hours.

[0064] Step 2: Create a 3D model.

[0065] First, Unigraphics NX software is used to construct the stl model file of the three-dimensional continuous structure Ti2AlNb reinforcement. The three-dimensional continuous structure model used in the above steps is shown in the figure below. Figure 2 As shown, the model has a diameter of 50 mm and a height of 10 mm. It was then sliced ​​in Materialise Magics software, with each layer having a uniform thickness of 0.025 mm, for a total of 400 layers. Finally, the determined 3D model slicing parameters were imported into the Mlab cusing R device.

[0066] Step 3: Spreading powder and treating the atmosphere in the forming tank.

[0067] Remove the scraper from the Mlab cusing R additive equipment, clean it with anhydrous ethanol, dry it, and then install it into the equipment; sandblast the substrate and install it into a freely liftable forming cylinder. The substrate used in the above steps is a pure titanium substrate with a size of 90 mm × 90 mm × 10 mm.

[0068] First, the Ti-22Al-25Nb powder prepared in step 1 is loaded into the liftable powder supply cylinder, and the equipment hatch is closed. Then, the equipment forming cylinder is evacuated, and high-purity argon is used to dilute and exhaust the oxygen in the forming cylinder and the circulation pipeline until the oxygen content in the forming cylinder is less than 400 ppm. Finally, by adjusting the position of the forming cylinder and the powder supply cylinder, the top layer of powder in the powder supply cylinder, the upper surface of the substrate in the forming cylinder, and the lower surface of the scraper are aligned.

[0069] Step 4: Set the forming process parameters.

[0070] The selective laser melting process parameters include laser power, scanning speed, scanning pitch, and powder layer thickness. In this embodiment, the laser power is 70 W, the scanning speed is 600 mm / s, the scanning pitch is 0.06 mm, and the powder layer thickness is 0.025 mm. The laser scanning strategy is a checkerboard scanning strategy, with the scanning direction rotating 90° between adjacent layers. That is, the laser scanning direction angle increases by 90° after each layer is printed.

[0071] Step 5: Selective laser melting.

[0072] After setting the forming process parameters, after each layer of powder is laid, the laser beam selectively melts the area based on the slice data of the 3D model. The baseplate in the forming cylinder then descends by the thickness of the layer, and the scraper spreads the powder again. The laser then selectively melts the newly laid powder, and this process is repeated until the sample is formed.

[0073] After the sample is cooled, it is cut from the substrate, ultrasonically cleaned, and dried for later use, completing the selective laser melting preparation of the three-dimensional continuous structure Ti2AlNb reinforcement.

[0074] (II) Preparation of biomimetic interpenetrating Ti2AlNb / TiAl-based composite materials. The specific process is as follows:

[0075] Step 6: Design of the reinforcement volume fraction in the composite material.

[0076] Based on the three-dimensional model designed in step 2, theoretical calculation shows that the volume fraction of the reinforcement is 28.3 vol.%.

[0077] Step 7: Powder filling and cold pressing.

[0078] The prepared three-dimensional continuous structure Ti2AlNb skeleton was placed in a cylindrical graphite mold. According to the volume fraction of the reinforcement phase, the volume of TiAl powder required to fill the gaps in the three-dimensional continuous structure was calculated to be 14.06 cm 3 , and then use m=ρ×(πr 2 ×hV r ) formula can be used to calculate that the mass of Ti-48Al-2Cr-2Nb (at.%) powder required for hot pressing sintering is 54.83 g. The weighed TiAl powder is loaded into a mold and cold pressed to produce a bionic interpenetrating Ti2AlNb / TiAl powder compact.

[0079] In the above formula, m is the mass of TiAl powder (g); ρ is the density of TiAl alloy (g / cm 3 ); r—radius of the mold used (mm); h—height of the three-dimensional continuous structure Ti2AlNb reinforcement (mm); V r —Volume fraction of reinforcement.

[0080] The cold pressing pressure selected in the above steps is 10 MPa, and the holding time is 20 min.

[0081] In order to avoid the reaction between TiAl alloy powder and graphite mold during hot pressing and sintering, yttrium oxide slurry is applied to the upper and lower pressing heads of the mold and the positions in contact with the powder, and then the powder is filled after drying.

[0082] The TiAl alloy powder selected above is plasma rotating electrode atomized powder, and the main particle size is concentrated in the range of 60 to 120 μm.

[0083] Step 8: Hot pressing and sintering process.

[0084] The biomimetic interpenetrating Ti2AlNb / TiAl compact was vacuum sintered at 1150°C and 45 MPa for 1 hour. The hot pressing sintering process involved a staged heating and pressurization process. First, the sintering temperatures were maintained at 600°C and 1000°C for 10 minutes each, while maintaining a pressure of 25 MPa under these conditions to remove gas inclusions from the graphite mold. The compact was then vacuum sintered at 1150°C and 45 MPa for 1 hour, with the pressure then increased to 45 MPa. After the hot pressing process, the sample was cooled to room temperature in the furnace, resulting in a biomimetic interpenetrating Ti2AlNb / TiAl-based composite with a diameter of 50 mm and a height of 10 mm.

[0085] The sintering process must ensure that the oxygen content is less than 200 ppm and the heating rate is 10 ° C / min.

[0086] The theoretical density of the bionic interpenetrating Ti2AlNb / TiAl-based composite material can be calculated according to the following formula:

[0087]

[0088] In the formula are the theoretical density and volume fraction of the reinforcement and matrix in the composite material, respectively. The theoretical density of the Ti2AlNb reinforcement and TiAl alloy used are 5.3 g / cm 3 、3.9 g / cm 3 The calculated theoretical density of the biomimetic interpenetrating Ti2AlNb / TiAl matrix composite material is 4.30 g / cm 3 .

[0089] The density of the biomimetic interpenetrating Ti2AlNb / TiAl-based composite material prepared in this embodiment is 99.9%.

[0090] Example 2

[0091] To address the low room-temperature fracture toughness of TiAl alloys, this paper designs a biomimetic interpenetrating Ti2AlNb / TiAl-based composite. Using selective laser melting to additively manufacture a three-dimensional continuous Ti2AlNb reinforcement skeleton, followed by hot-pressing and sintering, the resulting biomimetic interpenetrating Ti2AlNb / TiAl-based composite exhibits an excellent combination of strength, ductility, and toughness. This approach offers a new approach to addressing the bottleneck in the application of TiAl in hot-end components of aerospace propulsion systems.

[0092] The Ti2AlNb alloy used for selective laser melting in the present invention consists of 22 at.% Al and 25 at.% Nb, with the balance being Ti. The TiAl matrix consists of 48 at.% Al, 2 at.% Cr, and 2 at.% Nb, with the balance being Ti. All percentages are in atomic percentage.

[0093] The method for preparing the biomimetic interpenetrating Ti2AlNb / TiAl-based composite material proposed in the present invention is specifically divided into two parts:

[0094] (1) Preparation of three-dimensional continuous structure Ti2AlNb reinforcement by selective laser melting. The specific process is as follows:

[0095] Step 1: Powder preparation and pretreatment.

[0096] The Ti2AlNb alloy composition used was Ti-22Al-25Nb (at.%). Raw materials were weighed according to the alloy composition, mixed uniformly, and then smelted into a master alloy ingot. The resulting master alloy ingot was processed into straight alloy bars, which were then prepared into alloy powder using a plasma rotating electrode atomization method.

[0097] The obtained powder was cleaned and sieved to obtain a powder with a particle size of 15 to 53 μm. The powder was placed in a vacuum drying oven and dried at a temperature of 80°C for 10 hours.

[0098] Step 2: Create a 3D model.

[0099] First, Unigraphics NX software is used to construct the stl model file of the three-dimensional continuous structure Ti2AlNb reinforcement. The three-dimensional continuous structure model used in the above steps is shown in the figure below. Figure 2 As shown, the model has a diameter of 50 mm and a height of 10 mm. It was then sliced ​​in Materialise Magics software, with each layer having a uniform thickness of 0.025 mm, for a total of 400 layers. Finally, the determined 3D model slicing parameters were imported into the Mlab cusing R device.

[0100] Step 3: Spreading powder and treating the atmosphere in the forming tank.

[0101] Remove the scraper from the Mlab cusing R additive equipment, clean it with anhydrous ethanol, dry it, and then install it into the equipment; sandblast the substrate and install it into a freely liftable forming cylinder. The substrate used in the above steps is a pure titanium substrate with a size of 90 mm × 90 mm × 10 mm.

[0102] First, the Ti-22Al-25Nb powder prepared in step 1 is loaded into the liftable powder supply cylinder, and the equipment hatch is closed. Then, the equipment forming cylinder is evacuated, and high-purity argon is used to dilute and exhaust the oxygen in the forming cylinder and the circulation pipeline until the oxygen content in the forming cylinder is less than 400 ppm. Finally, by adjusting the position of the forming cylinder and the powder supply cylinder, the top layer of powder in the powder supply cylinder, the upper surface of the substrate in the forming cylinder, and the lower surface of the scraper are aligned.

[0103] Step 4: Set the forming process parameters.

[0104] The selective laser melting process parameters include laser power, scanning speed, scanning pitch, and powder layer thickness. In this embodiment, the laser power is 80 W, the scanning speed is 1000 mm / s, the scanning pitch is 0.06 mm, and the powder layer thickness is 0.025 mm. The laser scanning strategy is a checkerboard scanning strategy, with the scanning direction rotating 90° between adjacent layers. That is, the laser scanning direction angle increases by 90° after each layer is printed.

[0105] Step 5: Selective laser melting.

[0106] After setting the forming process parameters, after each layer of powder is laid, the laser beam selectively melts the area based on the slice data of the 3D model. The baseplate in the forming cylinder then descends by the thickness of the layer, and the scraper spreads the powder again. The laser then selectively melts the newly laid powder, and this process is repeated until the sample is formed.

[0107] After the sample is cooled, it is cut from the substrate, ultrasonically cleaned, and dried for later use, completing the selective laser melting preparation of the three-dimensional continuous structure Ti2AlNb reinforcement.

[0108] (II) Preparation of biomimetic interpenetrating Ti2AlNb / TiAl-based composite materials. The specific process is as follows:

[0109] Step 6: Design of the reinforcement volume fraction in the composite material.

[0110] Based on the three-dimensional model designed in step 2, theoretical calculation shows that the volume fraction of the reinforcement is 28.3 vol.%.

[0111] Step 7: Powder filling and cold pressing.

[0112] The prepared three-dimensional continuous structure Ti2AlNb skeleton was placed in a cylindrical graphite mold. According to the volume fraction of the reinforcement phase, the volume of TiAl powder required to fill the gaps in the three-dimensional continuous structure was calculated to be 14.06 cm 3 , and then use m=ρ×(πr 2 ×hV r ) formula can be used to calculate that the mass of Ti-48Al-2Cr-2Nb (at.%) powder required for hot pressing sintering is 54.83 g. The weighed TiAl powder is loaded into a mold and cold pressed to produce a bionic interpenetrating Ti2AlNb / TiAl powder compact.

[0113] In the above formula, m is the mass of TiAl powder (g); ρ is the density of TiAl alloy (g / cm 3 ); r—radius of the mold used (mm); h—height of the three-dimensional continuous structure Ti2AlNb reinforcement (mm); V r —Volume fraction of reinforcement.

[0114] The cold pressing pressure selected in the above steps is 10 MPa, and the holding time is 20 min.

[0115] In order to avoid the reaction between TiAl alloy powder and graphite mold during hot pressing and sintering, yttrium oxide slurry is applied to the upper and lower pressing heads of the mold and the positions in contact with the powder, and then the powder is filled after drying.

[0116] The TiAl alloy powder selected above is plasma rotating electrode atomized powder, and the main particle size is concentrated in the range of 60 to 120 μm.

[0117] Step 8: Hot pressing and sintering process.

[0118] The biomimetic interpenetrating Ti2AlNb / TiAl compact was vacuum sintered at 1150°C and 45 MPa for 1 hour. The hot pressing sintering process involved a staged heating and pressurization process. First, the sintering temperatures were maintained at 600°C and 1000°C for 10 minutes each, while maintaining a pressure of 25 MPa under these conditions to remove gas inclusions from the graphite mold. The compact was then vacuum sintered at 1150°C and 45 MPa for 1 hour, with the pressure then increased to 45 MPa. After the hot pressing process, the sample was cooled to room temperature in the furnace, resulting in a biomimetic interpenetrating Ti2AlNb / TiAl-based composite with a diameter of 50 mm and a height of 10 mm.

[0119] The sintering process must ensure that the oxygen content is less than 200 ppm and the heating rate is 10 ° C / min.

[0120] The theoretical density of the bionic interpenetrating Ti2AlNb / TiAl-based composite material can be calculated according to the following formula:

[0121]

[0122] In the formula are the theoretical density and volume fraction of the reinforcement and matrix in the composite material, respectively. The theoretical density of the Ti2AlNb reinforcement and TiAl alloy used are 5.3 g / cm 3 、3.9 g / cm 3 The calculated theoretical density of the biomimetic interpenetrating Ti2AlNb / TiAl matrix composite material is 4.30 g / cm 3 .

[0123] The density of the bionic interpenetrating Ti2AlNb / TiAl-based composite material prepared in the embodiment is 99.95%.

[0124] Example 3

[0125] To address the low room-temperature fracture toughness of TiAl alloys, this paper designs a biomimetic interpenetrating Ti2AlNb / TiAl-based composite. Using selective laser melting to additively manufacture a three-dimensional continuous Ti2AlNb reinforcement skeleton, followed by hot-pressing and sintering, the resulting biomimetic interpenetrating Ti2AlNb / TiAl-based composite exhibits an excellent combination of strength, ductility, and toughness. This approach offers a new approach to addressing the bottleneck in the application of TiAl in hot-end components of aerospace propulsion systems.

[0126] The Ti2AlNb alloy used for selective laser melting in the present invention consists of 22 at.% Al and 25 at.% Nb, with the balance being Ti. The TiAl matrix consists of 48 at.% Al, 2 at.% Cr, and 2 at.% Nb, with the balance being Ti. All percentages are in atomic percentage.

[0127] The method for preparing the bionic interpenetrating Ti2AlNb / TiAl-based composite material in this embodiment is specifically divided into two parts:

[0128] (1) Preparation of three-dimensional continuous structure Ti2AlNb reinforcement by selective laser melting. The specific process is as follows:

[0129] Step 1: Powder preparation and pretreatment.

[0130] The Ti2AlNb alloy composition used was Ti-22Al-25Nb (at.%). Raw materials were weighed according to the alloy composition, mixed uniformly, and then smelted into a master alloy ingot. The resulting master alloy ingot was processed into straight alloy bars, which were then prepared into alloy powder using a plasma rotating electrode atomization method.

[0131] The obtained powder was cleaned and sieved to obtain a powder with a particle size of 15 to 53 μm. The powder was placed in a vacuum drying oven and dried at a temperature of 80°C for 10 hours.

[0132] Step 2: Create a 3D model.

[0133] First, Unigraphics NX software is used to construct the stl model file of the three-dimensional continuous structure Ti2AlNb reinforcement. The three-dimensional continuous structure model used in the above steps is shown in the figure below. Figure 2 As shown, the model has a diameter of 50 mm and a height of 10 mm. It was then sliced ​​in Materialise Magics software, with each layer having a uniform thickness of 0.025 mm, for a total of 400 layers. Finally, the determined 3D model slicing parameters were imported into the Mlab cusing R device.

[0134] Step 3: Spreading powder and treating the atmosphere in the forming tank.

[0135] Remove the scraper from the Mlab cusing R additive equipment, clean it with anhydrous ethanol, dry it, and then install it into the equipment; sandblast the substrate and install it into a freely liftable forming cylinder. The substrate used in the above steps is a pure titanium substrate with a size of 90 mm × 90 mm × 10 mm.

[0136] First, the Ti-22Al-25Nb powder prepared in step 1 is loaded into the liftable powder supply cylinder, and the equipment hatch is closed. Then, the equipment forming cylinder is evacuated, and high-purity argon is used to dilute and exhaust the oxygen in the forming cylinder and the circulation pipeline until the oxygen content in the forming cylinder is less than 400 ppm. Finally, by adjusting the position of the forming cylinder and the powder supply cylinder, the top layer of powder in the powder supply cylinder, the upper surface of the substrate in the forming cylinder, and the lower surface of the scraper are aligned.

[0137] Step 4: Set the forming process parameters.

[0138] The selective laser melting process parameters include laser power, scanning speed, scanning pitch, and powder layer thickness. In this embodiment, the laser power is 100 W, the scanning speed is 600 mm / s, the scanning pitch is 0.06 mm, and the powder layer thickness is 0.025 mm. The laser scanning strategy is a checkerboard scanning pattern, with the scanning direction rotating 90° between adjacent layers. That is, the laser scanning direction angle increases by 90° after each layer is printed.

[0139] Step 5: Selective laser melting.

[0140] After setting the forming process parameters, after each layer of powder is laid, the laser beam selectively melts the area based on the slice data of the 3D model. The baseplate in the forming cylinder then descends by the thickness of the layer, and the scraper spreads the powder again. The laser then selectively melts the newly laid powder, and this process is repeated until the sample is formed.

[0141] After the sample is cooled, it is cut from the substrate, ultrasonically cleaned, and dried for later use, completing the selective laser melting preparation of the three-dimensional continuous structure Ti2AlNb reinforcement.

[0142] (II) Preparation of biomimetic interpenetrating Ti2AlNb / TiAl-based composite materials. The specific process is as follows:

[0143] Step 6: Design of the reinforcement volume fraction in the composite material.

[0144] Based on the three-dimensional model designed in step 2, theoretical calculation shows that the volume fraction of the reinforcement is 28.3 vol.%.

[0145] Step 7: Powder filling and cold pressing.

[0146] The prepared three-dimensional continuous structure Ti2AlNb skeleton was placed in a cylindrical graphite mold. According to the volume fraction of the reinforcement phase, the volume of TiAl powder required to fill the gaps in the three-dimensional continuous structure was calculated to be 14.06 cm 3 , and then use m=ρ×(πr 2 ×hV r ) formula can be used to calculate that the mass of Ti-48Al-2Cr-2Nb (at.%) powder required for hot pressing sintering is 54.83 g. The weighed TiAl powder is loaded into a mold and cold pressed to produce a bionic interpenetrating Ti2AlNb / TiAl powder compact.

[0147] In the above formula, m is the mass of TiAl powder (g); ρ is the density of TiAl alloy (g / cm 3 ); r—radius of the mold used (mm); h—height of the three-dimensional continuous structure Ti2AlNb reinforcement (mm); V r —Volume fraction of reinforcement.

[0148] The cold pressing pressure selected in the above steps is 10 MPa, and the holding time is 20 min.

[0149] In order to avoid the reaction between TiAl alloy powder and graphite mold during hot pressing and sintering, yttrium oxide slurry is applied to the upper and lower pressing heads of the mold and the positions in contact with the powder, and then the powder is filled after drying.

[0150] The TiAl alloy powder selected above is plasma rotating electrode atomized powder, and the main particle size is concentrated in the range of 60 to 120 μm.

[0151] Step 8: Hot pressing and sintering process.

[0152] The biomimetic interpenetrating Ti2AlNb / TiAl compact was vacuum sintered at 1250°C and 45 MPa for 1 hour. The hot pressing sintering process involved a staged temperature increase and pressure increase. First, the compact was held at 600°C and 1000°C for 10 minutes each, while maintaining a pressure of 25 MPa under these conditions to remove gas inclusions from the graphite mold. The compact was then vacuum sintered at 1250°C and 45 MPa for 1 hour, with the pressure then increased to 45 MPa. After the hot pressing process, the sample was cooled to room temperature in the furnace, resulting in a biomimetic interpenetrating Ti2AlNb / TiAl-based composite with a diameter of 50 mm and a height of 10 mm.

[0153] The sintering process must ensure that the oxygen content is less than 200 ppm and the heating rate is 10 ° C / min.

[0154] The theoretical density of the bionic interpenetrating Ti2AlNb / TiAl-based composite material can be calculated according to the following formula:

[0155]

[0156] In the formula are the theoretical density and volume fraction of the reinforcement and matrix in the composite material, respectively. The theoretical density of the Ti2AlNb reinforcement and TiAl alloy used are 5.3 g / cm 3 、3.9 g / cm 3 The calculated theoretical density of the biomimetic interpenetrating Ti2AlNb / TiAl matrix composite material is 4.30 g / cm 3 .

[0157] The density of the bionic interpenetrating Ti2AlNb / TiAl-based composite material prepared in the embodiment is 99.98%.

[0158] Example 4

[0159] To address the low room-temperature fracture toughness of TiAl alloys, this paper designs a biomimetic interpenetrating Ti2AlNb / TiAl-based composite. Using selective laser melting to additively manufacture a three-dimensional continuous Ti2AlNb reinforcement skeleton, followed by hot-pressing and sintering, the resulting biomimetic interpenetrating Ti2AlNb / TiAl-based composite exhibits an excellent combination of strength, ductility, and toughness. This approach offers a new approach to addressing the bottleneck in the application of TiAl in hot-end components of aerospace propulsion systems.

[0160] The Ti2AlNb alloy used for selective laser melting in the present invention consists of 22 at.% Al and 25 at.% Nb, with the balance being Ti. The TiAl matrix consists of 48 at.% Al, 2 at.% Cr, and 2 at.% Nb, with the balance being Ti. All percentages are in atomic percentage.

[0161] The method for preparing the biomimetic interpenetrating Ti2AlNb / TiAl-based composite material proposed in this embodiment is specifically divided into two parts:

[0162] (1) Preparation of three-dimensional continuous structure Ti2AlNb reinforcement by selective laser melting. The specific process is as follows:

[0163] Step 1: Powder preparation and pretreatment.

[0164] The Ti2AlNb alloy composition used was Ti-22Al-25Nb (at.%). Raw materials were weighed according to the alloy composition, mixed uniformly, and then smelted into a master alloy ingot. The resulting master alloy ingot was processed into straight alloy bars, which were then prepared into alloy powder using a plasma rotating electrode atomization method.

[0165] The obtained powder was cleaned and sieved to obtain a powder with a particle size of 15 to 53 μm. The powder was placed in a vacuum drying oven and dried at a temperature of 80°C for 10 hours.

[0166] Step 2: Create a 3D model.

[0167] First, Unigraphics NX software is used to construct the stl model file of the three-dimensional continuous structure Ti2AlNb reinforcement. The three-dimensional continuous structure model used in the above steps is shown in the figure below. Figure 2 As shown, the model has a diameter of 50 mm and a height of 10 mm. It was then sliced ​​in Materialise Magics software, with each layer having a uniform thickness of 0.025 mm, for a total of 400 layers. Finally, the determined 3D model slicing parameters were imported into the Mlab cusing R device.

[0168] Step 3: Spreading powder and treating the atmosphere in the forming tank.

[0169] Remove the scraper from the Mlab cusing R additive equipment, clean it with anhydrous ethanol, dry it, and then install it into the equipment; sandblast the substrate and install it into a freely liftable forming cylinder. The substrate used in the above steps is a pure titanium substrate with a size of 90 mm × 90 mm × 10 mm.

[0170] First, the Ti-22Al-25Nb powder prepared in step 1 is loaded into the liftable powder supply cylinder, and the equipment hatch is closed. Then, the equipment forming cylinder is evacuated, and high-purity argon is used to dilute and exhaust the oxygen in the forming cylinder and the circulation pipeline until the oxygen content in the forming cylinder is less than 400 ppm. Finally, by adjusting the position of the forming cylinder and the powder supply cylinder, the top layer of powder in the powder supply cylinder, the upper surface of the substrate in the forming cylinder, and the lower surface of the scraper are aligned.

[0171] Step 4: Set the forming process parameters.

[0172] The selective laser melting process parameters include laser power, scanning speed, scanning pitch, and powder layer thickness. In this embodiment, the laser power is 90 W, the scanning speed is 800 mm / s, the scanning pitch is 0.06 mm, and the powder layer thickness is 0.025 mm. The laser scanning strategy is a checkerboard scanning strategy, with the scanning direction rotating 90° between adjacent layers. That is, the laser scanning direction angle increases by 90° after each layer is printed.

[0173] Step 5: Selective laser melting.

[0174] After setting the forming process parameters, after each layer of powder is laid, the laser beam selectively melts the area based on the slice data of the 3D model. The baseplate in the forming cylinder then descends by the thickness of the layer, and the scraper spreads the powder again. The laser then selectively melts the newly laid powder, and this process is repeated until the sample is formed.

[0175] After the sample is cooled, it is cut from the substrate, ultrasonically cleaned, and dried for later use, completing the selective laser melting preparation of the three-dimensional continuous structure Ti2AlNb reinforcement.

[0176] (II) Preparation of biomimetic interpenetrating Ti2AlNb / TiAl-based composite materials. The specific process is as follows:

[0177] Step 6: Design of the reinforcement volume fraction in the composite material.

[0178] Based on the three-dimensional model designed in step 2, theoretical calculation shows that the volume fraction of the reinforcement is 28.3 vol.%.

[0179] Step 7: Powder filling and cold pressing.

[0180] The prepared three-dimensional continuous structure Ti2AlNb skeleton was placed in a cylindrical graphite mold. According to the volume fraction of the reinforcement phase, the volume of TiAl powder required to fill the gaps in the three-dimensional continuous structure was calculated to be 14.06 cm 3 , and then use m=ρ×(πr 2 ×hV r ) formula can be used to calculate that the mass of Ti-48Al-2Cr-2Nb (at.%) powder required for hot pressing sintering is 54.83 g. The weighed TiAl powder is loaded into a mold and cold pressed to produce a bionic interpenetrating Ti2AlNb / TiAl powder compact.

[0181] In the above formula, m is the mass of TiAl powder (g); ρ is the density of TiAl alloy (g / cm 3 ); r—radius of the mold used (mm); h—height of the three-dimensional continuous structure Ti2AlNb reinforcement (mm); V r —Volume fraction of reinforcement.

[0182] The cold pressing pressure selected in the above steps is 10 MPa, and the holding time is 20 min.

[0183] In order to avoid the reaction between TiAl alloy powder and graphite mold during hot pressing and sintering, yttrium oxide slurry is applied to the upper and lower pressing heads of the mold and the positions in contact with the powder, and then the powder is filled after drying.

[0184] The TiAl alloy powder selected above is plasma rotating electrode atomized powder, and the main particle size is concentrated in the range of 60 to 120 μm.

[0185] Step 8: Hot pressing and sintering process.

[0186] The biomimetic interpenetrating Ti2AlNb / TiAl compact was vacuum sintered at 1200°C and 45 MPa for 1 hour. The hot pressing sintering process involved a staged heating and pressurization process. First, the sintering temperatures were maintained at 600°C and 1000°C for 10 minutes each, while maintaining a pressure of 25 MPa under these conditions to remove gas inclusions from the graphite mold. The compact was then vacuum sintered at 1200°C and 45 MPa for 1 hour, with the pressure then increased to 45 MPa. After the hot pressing process, the sample was cooled to room temperature in the furnace, resulting in a biomimetic interpenetrating Ti2AlNb / TiAl-based composite with a diameter of 50 mm and a height of 10 mm.

[0187] The sintering process must ensure that the oxygen content is less than 200 ppm and the heating rate is 10 ° C / min.

[0188] The theoretical density of the above-mentioned bionic interpenetrating composite material can be calculated according to the following formula:

[0189]

[0190] In the formula are the theoretical density and volume fraction of the reinforcement and matrix in the composite material respectively. The theoretical density of the Ti2AlNb reinforcement and TiAl alloy used above is 5.3 g / cm 3 、3.9 g / cm 3 The calculated theoretical density of the biomimetic interpenetrating Ti2AlNb / TiAl matrix composite material is 4.30 g / cm 3 .

[0191] The density of the bionic interpenetrating Ti2AlNb / TiAl-based composite material prepared in the embodiment is 99.97%.

[0192] Example 5

[0193] To address the low room-temperature fracture toughness of TiAl alloys, this paper designs a biomimetic interpenetrating Ti2AlNb / TiAl-based composite. Using selective laser melting to additively manufacture a three-dimensional continuous Ti2AlNb reinforcement skeleton, followed by hot-pressing and sintering, the resulting biomimetic interpenetrating Ti2AlNb / TiAl-based composite exhibits an excellent combination of strength, ductility, and toughness. This approach offers a new approach to addressing the bottleneck in the application of TiAl in hot-end components of aerospace propulsion systems.

[0194] In this embodiment, the Ti2AlNb alloy used for selective laser melting is composed of 22 at.% Al and 25 at.% Nb, with the balance being Ti. The TiAl matrix is ​​composed of 48 at.% Al, 2 at.% Cr, and 2 at.% Nb, with the balance being Ti. All percentages are in atomic percentage.

[0195] The method for preparing the biomimetic interpenetrating Ti2AlNb / TiAl-based composite material proposed in this embodiment is specifically divided into two parts:

[0196] (1) Preparation of three-dimensional continuous structure Ti2AlNb reinforcement by selective laser melting. The specific process is as follows:

[0197] Step 1: Powder preparation and pretreatment.

[0198] The Ti2AlNb alloy composition used was Ti-22Al-25Nb (at.%). Raw materials were weighed according to the alloy composition, mixed uniformly, and then smelted into a master alloy ingot. The resulting master alloy ingot was processed into straight alloy bars, which were then prepared into alloy powder using a plasma rotating electrode atomization method.

[0199] The obtained powder was cleaned and sieved to obtain a powder with a particle size of 15 to 53 μm. The powder was placed in a vacuum drying oven and dried at a temperature of 80°C for 10 hours.

[0200] Step 2: Create a 3D model.

[0201] First, Unigraphics NX software is used to construct the stl model file of the three-dimensional continuous structure Ti2AlNb reinforcement. The three-dimensional continuous structure model used in the above steps is shown in the figure below. Figure 2 As shown, the model has a diameter of 50 mm and a height of 10 mm. It was then sliced ​​in Materialise Magics software, with each layer having a uniform thickness of 0.025 mm, for a total of 400 layers. Finally, the determined 3D model slicing parameters were imported into the Mlab cusing R device.

[0202] Step 3: Spreading powder and treating the atmosphere in the forming tank.

[0203] Remove the scraper from the Mlab cusing R additive equipment, clean it with anhydrous ethanol, dry it, and then install it into the equipment; sandblast the substrate and install it into a freely liftable forming cylinder. The substrate used in the above steps is a pure titanium substrate with a size of 90 mm × 90 mm × 10 mm.

[0204] First, the Ti-22Al-25Nb powder prepared in step 1 is loaded into the liftable powder supply cylinder, and the equipment hatch is closed. Then, the equipment forming cylinder is evacuated, and high-purity argon is used to dilute and exhaust the oxygen in the forming cylinder and the circulation pipeline until the oxygen content in the forming cylinder is less than 400 ppm. Finally, by adjusting the position of the forming cylinder and the powder supply cylinder, the top layer of powder in the powder supply cylinder, the upper surface of the substrate in the forming cylinder, and the lower surface of the scraper are aligned.

[0205] Step 4: Set the forming process parameters.

[0206] The selective laser melting process parameters include laser power, scanning speed, scanning pitch, and powder layer thickness. In this embodiment, the laser power is 90 W, the scanning speed is 600 mm / s, the scanning pitch is 0.06 mm, and the powder layer thickness is 0.025 mm. The laser scanning strategy is a checkerboard scanning pattern, with the scanning direction rotating 90° between adjacent layers. That is, the laser scanning direction angle increases by 90° after each layer is printed.

[0207] Step 5: Selective laser melting.

[0208] After setting the forming process parameters, after each layer of powder is laid, the laser beam selectively melts the area based on the slice data of the 3D model. The baseplate in the forming cylinder then descends by the thickness of the layer, and the scraper spreads the powder again. The laser then selectively melts the newly laid powder, and this process is repeated until the sample is formed.

[0209] After the sample is cooled, it is cut from the substrate, ultrasonically cleaned, and dried for later use, completing the selective laser melting preparation of the three-dimensional continuous structure Ti2AlNb reinforcement.

[0210] (II) Preparation of biomimetic interpenetrating Ti2AlNb / TiAl-based composite materials. The specific process is as follows:

[0211] Step 6: Design of the reinforcement volume fraction in the composite material.

[0212] Based on the three-dimensional model designed in step 2, theoretical calculation shows that the volume fraction of the reinforcement is 28.3 vol.%.

[0213] Step 7: Powder filling and cold pressing.

[0214] The prepared three-dimensional continuous structure Ti2AlNb skeleton was placed in a cylindrical graphite mold. According to the volume fraction of the reinforcement phase, the volume of TiAl powder required to fill the gaps in the three-dimensional continuous structure was calculated to be 14.06 cm 3 , and then use m=ρ×(πr 2 ×hV r ) formula can be used to calculate that the mass of Ti-48Al-2Cr-2Nb (at.%) powder required for hot pressing sintering is 54.83 g. The weighed TiAl powder is loaded into a mold and cold pressed to produce a bionic interpenetrating Ti2AlNb / TiAl powder compact.

[0215] In the above formula, m is the mass of TiAl powder (g); ρ is the density of TiAl alloy (g / cm 3 ); r—radius of the mold used (mm); h—height of the three-dimensional continuous structure Ti2AlNb reinforcement (mm); V r —Volume fraction of reinforcement.

[0216] The cold pressing pressure selected in the above steps is 10 MPa, and the holding time is 20 min.

[0217] In order to avoid the reaction between TiAl alloy powder and graphite mold during hot pressing and sintering, yttrium oxide slurry is applied to the upper and lower pressing heads of the mold and the positions in contact with the powder, and then the powder is filled after drying.

[0218] The TiAl alloy powder selected above is plasma rotating electrode atomized powder, and the main particle size is concentrated in the range of 60 to 120 μm.

[0219] Step 8: Hot pressing and sintering process.

[0220] The biomimetic interpenetrating Ti2AlNb / TiAl compact was vacuum sintered at 1150°C and 45 MPa for 1 hour. The hot pressing sintering process involved a staged heating and pressurization process. First, the sintering temperatures were maintained at 600°C and 1000°C for 10 minutes each, while maintaining a pressure of 25 MPa under these conditions to remove gas inclusions from the graphite mold. The compact was then vacuum sintered at 1150°C and 45 MPa for 1 hour, with the pressure then increased to 45 MPa. After the hot pressing process, the sample was cooled to room temperature in the furnace, resulting in a biomimetic interpenetrating Ti2AlNb / TiAl-based composite with a diameter of 50 mm and a height of 10 mm.

[0221] The sintering process must ensure that the oxygen content is less than 200 ppm and the heating rate is 10 ° C / min.

[0222] The theoretical density of the above-mentioned bionic interpenetrating composite material can be calculated according to the following formula:

[0223]

[0224] In the formula are the theoretical density and volume fraction of the reinforcement and matrix in the composite material respectively. The theoretical density of the Ti2AlNb reinforcement and TiAl alloy used above is 5.3 g / cm 3 、3.9 g / cm 3 The calculated theoretical density of the biomimetic interpenetrating Ti2AlNb / TiAl matrix composite material is 4.30 g / cm 3 .

[0225] The density of the bionic interpenetrating Ti2AlNb / TiAl-based composite material prepared in the embodiment is 99.94%.

[0226] In summary, the present invention uses selective laser melting to prepare a three-dimensional continuous structure Ti2AlNb reinforcement. By rationally controlling the forming process parameters, including laser power of 70 to 100 W, scanning speed of 600 to 1100 mm / s, scanning spacing of 0.06 mm, powder layer thickness of 0.025 mm, laser scanning strategy of chessboard scanning, and 90° rotation of the scanning direction between adjacent layers, a three-dimensional continuous structure Ti2AlNb reinforcement with good structural continuity, uniform size, no defects and a density of up to 99% is finally obtained. The scanning diagram of the deposited three-dimensional continuous structure Ti2AlNb reinforcement is shown in the attached manual. Figure 3 , and the relationship between its density and forming process parameters is shown in the appendix of the manual. Figure 4 .

[0227] The present invention prepares a bionic interpenetrating Ti2AlNb / TiAl-based composite material by means of selective laser melting additive manufacturing Ti2AlNb reinforcement-hot pressing sintering. The three-dimensional continuous structure Ti2AlNb reinforcement is prepared by additive manufacturing, which eliminates the process of preparing a preform of the traditional continuous fiber toughened TiAl-based composite material. The operation is more convenient, the efficiency is greatly improved, and the volume fraction of the reinforcement and the arrangement of the reinforcement in the matrix can be effectively controlled, thereby realizing the three-dimensional interconnection between the reinforcement and the matrix. By rationally regulating the hot pressing sintering parameters-hot pressing temperature, the thickness of the interface reaction layer and the type of reactants can be controlled to obtain a dense bionic interpenetrating composite material. The X-ray diffraction pattern of the bionic interpenetrating Ti2AlNb / TiAl-based composite material is shown in the attached manual. Figure 5 ; The scanning diagram of biomimetic interpenetrating Ti2AlNb / TiAl matrix composite material is shown in the appendix of the specification. Figure 6 .

[0228] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description. It is intended that all variations within the meaning and range of equivalents of the claims be embraced herein, and any reference signs in the claims should not be construed as limiting the claims to which they relate.

[0229] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material, characterized by: The Ti2AlNb reinforcement used in selective laser melting is composed of 22-25 at.% Al and 20-30 at.% Nb, with the balance being Ti. The TiAl matrix is ​​composed of 45-48 at.% Al, 1-3 at.% Cr, and 2-5 at.% Nb, with the balance being Ti. All the above components are expressed in atomic percentages. The method for preparing bionic interpenetrating Ti2AlNb / TiAl-based composite materials is specifically divided into two parts: (1) Preparation of three-dimensional continuous structure Ti2AlNb reinforcement by selective laser melting. The specific process is as follows: Step 1: Powder preparation and pretreatment Weighing raw materials according to the above alloy composition, mixing the weighed raw materials uniformly and then smelting them into a master alloy ingot, processing the obtained master alloy ingot into straight alloy rods, and then preparing Ti2AlNb alloy powder by plasma rotating electrode atomization method, and drying the powder for later use; Step 2: Create a 3D model First, the STL model file of the three-dimensional continuous structure Ti2AlNb reinforcement was constructed using Unigraphics NX software. Then, it was imported into Materialise Magics software for slicing. The determined specific parameters of the three-dimensional model were imported into the Mlabcusing R equipment. Step 3: Powder laying and atmosphere treatment in the forming tank The substrate is sandblasted; first, Ti2AlNb alloy powder is loaded into the liftable powder supply cylinder; then the forming cylinder of the equipment is evacuated to make the atmosphere in the forming cylinder meet the requirements; Step 4: Set the forming process parameters The process parameters of selective laser melting include laser power, scanning speed, scanning spacing and powder layer thickness; Step 5: Selective laser melting After setting the forming process parameters, after each layer of powder is laid, the laser beam selectively melts the area according to the slice data of the 3D model; then the base plate in the forming cylinder descends to a layer thickness, the scraper spreads the powder again, and the laser re-melts the newly laid powder area, and this process is repeated until the sample is formed; After the sample has cooled, it is cut from the substrate, ultrasonically cleaned, and dried for later use, completing the selective laser melting preparation of the three-dimensional continuous structure Ti2AlNb reinforcement. (II) Preparation of biomimetic interpenetrating Ti2AlNb / TiAl-based composite materials. The specific process is as follows: Step 6: Design of reinforcement volume fraction in composite material Based on the three-dimensional model in step 2, the theoretically calculated reinforcement volume fraction is 10-30 vol.%; Step 7: Powder filling and cold pressing The prepared three-dimensional continuous structure Ti2AlNb skeleton was placed in a cylindrical graphite mold, and the volume of TiAl alloy powder required to fill the gap of the three-dimensional continuous structure was calculated according to the volume fraction of the reinforcement phase. Then, m=ρ×(πr 2 ×hV r ) formula can be used to calculate the mass of TiAl alloy powder required for hot pressing and sintering. The weighed TiAl alloy powder is loaded into a mold and cold pressed to obtain a bionic interpenetrating Ti2AlNb / TiAl powder compact. Formula m=ρ×(πr 2 ×hV r ), m—mass of TiAl alloy powder g; ρ—density of TiAl alloy g / cm 3 ; r—radius of the mold used (mm); h—height of the three-dimensional continuous structure Ti2AlNb reinforcement (mm); V r — volume fraction of reinforcement; Step 8: Hot Pressing and Sintering Process The bionic interpenetrating Ti2AlNb / TiAl compact was vacuum sintered at 1050-1250 ℃ and 45 MPa pressure for 1 h. After the hot pressing process, the sample was cooled to room temperature with the furnace to prepare a bionic interpenetrating Ti2AlNb / TiAl-based composite material with a diameter of 50 mm and a height of 10 mm.

2. The method for preparing a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material according to claim 1, characterized in that: In the above step 1, the alloy powder particle size is selected to be 15 to 53 μm.

3. The method for preparing a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material according to claim 1, characterized in that: In the above step 2, the slice thickness of the three-dimensional model is 0.025 mm.

4. The method for preparing a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material according to claim 1, characterized in that: In the above step 3, the substrate used is made of pure titanium; When evacuating the forming cylinder of the equipment, high-purity argon is used to dilute and discharge the oxygen in the forming cylinder and the circulation pipeline until the oxygen content in the forming cylinder is lower than 400 ppm; by adjusting the position of the forming cylinder and the powder supply cylinder, the top layer of powder in the powder supply cylinder, the upper surface of the substrate in the forming cylinder and the lower surface of the scraper are made flush.

5. The method for preparing a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material according to claim 1, characterized in that: In step 4 above, the process parameters are as follows: laser power 70-100 W, scanning speed 600-1100 mm / s, scanning spacing 0.06 mm, and powder layer thickness 0.025 mm; the laser scanning strategy is checkerboard scanning, and the scanning direction between adjacent layers is rotated 90°, that is, the laser scanning direction angle increases by 90° after each layer is printed.

6. The method for preparing a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material according to claim 1, characterized in that: In the above step 7, the cold pressing pressure is 5-10 MPa and the holding time is 10-30 min; In order to avoid the reaction between TiAl alloy powder and graphite mold during hot pressing and sintering, yttrium oxide slurry is applied to the upper and lower pressing heads of the mold and the positions in contact with the powder, and then the powder is loaded after drying. The TiAl alloy powder selected is plasma rotating electrode atomized powder, and the main particle size is concentrated in the range of 60 to 120 μm.

7. The method for preparing a biomimetic interpenetrating Ti2AlNb / TiAl-based composite material according to claim 1, characterized in that: In step 8 above, the hot pressing sintering process is a staged heating and pressurizing process. First, the sintering temperature is kept at 600°C and 1000°C for 10 minutes each, and the pressure is maintained at 25 MPa under this condition to remove the included gas in the graphite mold. Then, vacuum sintering is carried out at 1050-1250°C and 45 MPa for 1 hour, and the pressure is increased to 45 MPa. The sintering process must ensure that the oxygen content is less than 200 ppm and the heating rate is 5-10 ° C / min; The theoretical density of the bionic interpenetrating Ti2AlNb / TiAl-based composite material is calculated according to the following formula: In the formula are the theoretical density and volume fraction of the reinforcement and matrix in the composite material, respectively; the theoretical density of the Ti2AlNb reinforcement and TiAl alloy used are 5.3 g / cm 3 、3.9 g / cm 3 .

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