A method for preparing Ti2AlNb alloy by laser melting deposition

Abstract

The present invention discloses a method for preparing Ti2AlNb alloy by laser melting deposition, belonging to the field of additive manufacturing. The method comprises the following steps: Step S1, drying powder: undrying the Ti2AlNb alloy powder; Step S2, cleaning the substrate: manually polishing the substrate in the same direction with sandpaper, then removing oil stains and oxide layers on the substrate with a laser cleaner; Step S3, argon protection: filling an argon environment chamber with high-purity argon protective gas; Step S4, preheating the substrate; Step S5, printing: the powder feeding system uses a coaxial feeding system to feed the Ti2AlNb alloy powder, while the laser beam reciprocates relative to the substrate. Process parameters include: laser power of 800-1400 J / s, laser scanning speed of 6-10 mm / s, laser spot diameter of 2-3 mm, powder carrier gas flow rate of 0.8-1.5 L / min, powder feeding rate of 0.03-0.10 g / s, laser body energy density of 0.5-100 g / min, and protective gas flow rate of 15-45 L / min. The method of the present invention can be used to prepare parts with complex shapes, expand the application range of Ti2AlNb alloys, and provide new solutions for the aerospace field.

Description

Technical Field

[0001] The invention relates to a method for preparing Ti2AlNb alloy by laser melting deposition, and belongs to the technical field of additive manufacturing. Background Art

[0002] With the rapid development of aerospace technology, the performance requirements for high-temperature structural materials are becoming increasingly higher, especially for core engine component structural materials. There is an urgent need to improve the high-temperature service performance of materials while further reducing weight. Ti2AlNb intermetallic compounds, as an aerospace engine structural material with excellent creep resistance, high-temperature oxidation resistance and high specific strength, have emerged.

[0003] Traditional Ti2AlNb alloy preparation methods include smelting, forging, and powder metallurgy. Defects such as composition segregation and porosity are prone to occur during the smelting ingot preparation process. The preparation of high-quality ingots is difficult, with low material utilization and high cost, requiring subsequent forging to achieve the desired performance. Powder metallurgy includes processes such as hot pressing and spark plasma sintering. Although this process has advantages such as a short process flow, high material utilization, fine and uniform structure, and controllable composition, the forming size and preparation cost of the parts are limited by the size of the furnace and the furnace loading method. Furthermore, the difficulty of this technology lies in the large shrinkage and deformation of the powder, the easy leakage of the package under high temperature and high pressure, and the difficulty in accurately controlling the size.

[0004] Compared to the low efficiency and high cost of the above traditional preparation methods, additive manufacturing technology, as a new processing method, has the advantages of high material utilization, short manufacturing cycle, and high structural complexity, providing a new approach for the preparation of Ti2AlNb-based alloys. At present, research on additive manufacturing of Ti2AlNb alloys has made some progress, but some problems still exist, such as the easy occurrence of composition segregation and uneven structure during the preparation process, which affect the performance of the alloy. In addition, the control of process parameters during the preparation process also directly affects the forming quality and performance of the alloy. Therefore, how to optimize the process parameters of additive manufacturing and improve the performance of the alloy is a technical problem that needs to be solved. Summary of the Invention

[0005] The present invention improves some problems existing in the current additive manufacturing of Ti2AlNb alloy and proposes a method for preparing Ti2AlNb alloy by laser melting deposition.

[0006] The present invention provides a method for preparing Ti2AlNb alloy by laser melting deposition, comprising the following steps:

[0007] Step S1, drying powder: drying Ti2AlNb alloy powder;

[0008] Step S2, substrate cleaning: first manually polish the substrate in the same direction with sandpaper, and then use a laser cleaning machine to remove oil stains and oxide layers on the substrate;

[0009] Step S3, argon protection: filling the argon environment box with high-purity argon protection gas, controlling the oxygen content in the argon environment box to be less than 50ppm and the water content to be less than 0.01ppm;

[0010] Step S4, preheating the substrate: heating the substrate so that the substrate is maintained at 300-500° C.;

[0011] Step S5, printing: the powder feeding system adopts coaxial feeding of Ti2AlNb alloy powder, and the laser beam moves back and forth relative to the substrate. The process parameters include: laser power of 800-1400 J / s, laser scanning speed of 6-10 mm / s, laser spot diameter of 2-3 mm, high-purity argon as the powder carrier gas, powder carrier gas flow rate of 0.8-1.5 L / min, powder feeding rate of 0.03-0.10 g / s, laser body energy density of The protective gas of the argon environment box is high-purity argon, and the protective gas flow rate is 15~45L / min.

[0012] Optionally, after step S5, the following steps are further included:

[0013] Step S6, solution treatment: heating in the furnace at a heating rate of 10-20°C / min to 900-1000°C, keeping the temperature for 2-3 hours, and then air cooling to room temperature;

[0014] Step S7, aging treatment: heating in the furnace at a heating rate of 10-20°C / min to 760-860°C, keeping the temperature for 6-8h, and then air cooling to room temperature.

[0015] Optionally, in step S1, the particle size of the Ti2AlNb alloy powder is in the range of 45 to 150 μm, wherein the gas content O≤0.12%, N≤0.03%, and H≤0.005%.

[0016] Optionally, in step S1, the drying treatment is performed at a temperature ranging from 80 to 120° C. and for a time ranging from 2 to 4 hours.

[0017] Optionally, in step S3, high-purity argon protective gas is filled into the argon environment box for 3 to 4 hours, and the protective gas flow rate is 15 to 45 L / min.

[0018] Optionally, in step S3, the oxygen content in the argon environment box is lower than 20 ppm.

[0019] Optionally, in step S5, the laser body energy density is

[0020] Optionally, in steps S3 to S5, the high-purity argon gas has an Ar value ≥ 99.999%.

[0021] Optionally, in step S6, the heating rate is 15°C / min, the temperature is raised to 950°C, and the temperature is kept at this temperature for 2.5 hours.

[0022] Optionally, in step S7, the heating rate is 15°C / min, the temperature is raised to 810°C, and the temperature is kept for 7 hours.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] (1) When preparing large and complex parts, compared with conventional deformation followed by machining, the preparation method of the present invention has a short preparation cycle, greatly improves material utilization, and reduces the cost of the finished product by about 65%;

[0025] (2) The preparation method of the present invention can directly obtain Ti2AlNb alloy materials with good morphology, no obvious defects, and smooth surface, and can be used to prepare parts with complex shapes, thus expanding the application range of Ti2AlNb alloys and providing a new solution for the preparation of high-temperature structural materials in the aerospace field;

[0026] (3) The preparation method of the present invention can obtain a Ti2AlNb alloy with uniform composition distribution and fine structure, thereby improving the comprehensive mechanical properties of the alloy, especially the room temperature elongation exceeding 20%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 This is a morphology diagram of the Ti2AlNb alloy powder used in the present invention;

[0029] Figure 2 This is a macroscopic structural photo of a single wall of Ti2AlNb material prepared by the present invention;

[0030] Figure 3 This is the room temperature tensile property curve of the deposited Ti2AlNb alloy of the present invention;

[0031] Figure 4 is a SEM image of the microstructure of the deposited Ti2AlNb alloy of the present invention;

[0032] Figure 5This is the room temperature tensile property curve of the Ti2AlNb alloy after heat treatment of the present invention;

[0033] Figure 6 This is the tensile property curve of the heat-treated Ti2AlNb alloy at 650°C;

[0034] Figure 7 is a SEM image of the microstructure of the Ti2AlNb alloy after heat treatment of the present invention;

[0035] Figure 8 The morphology of the Ti22Al25Nb alloy powder used in Examples 1 to 3;

[0036] Figure 9 This is the SEM image of the microstructure of the Ti22Al25Nb alloy after heat treatment in Example 2.

[0037] Figure 10 This is the room temperature tensile property curve of the Ti22Al25Nb alloy after heat treatment in Example 2;

[0038] Figure 11 This is the tensile property curve of the Ti22Al25Nb alloy after heat treatment at 650°C in Example 2. DETAILED DESCRIPTION

[0039] In order to make the invention purpose, technical solution and beneficial technical effect of the present invention clearer, the present invention is described in detail below with reference to specific embodiments. It should be understood that the embodiments described in this specification are only for explaining the present invention and are not intended to limit the present invention.

[0040] Laser metal deposition (LMD), also known as laser direct manufacturing (LDM) or laser directed energy deposition (L-DED), is a direct energy deposition process that uses a gas jet to deposit metal powder onto a substrate. A laser heat source then melts a thin layer of metal powder in a controlled manner to form a molten pool. The molten pool solidifies to form a deposited layer, which is then sprayed with powder to melt again. This process is repeated several times to form the final printed part. LMD equipment primarily consists of a laser, a powder delivery system, and an argon atmosphere chamber.

[0041] The present invention provides a method for preparing Ti2AlNb alloy by laser melting deposition, comprising the following steps:

[0042] Step S1, drying powder: putting Ti2AlNb alloy powder into a drying oven for drying;

[0043] Step S2, substrate cleaning: first manually polish the substrate in the same direction with sandpaper, and then use a laser cleaning machine to remove oil stains and oxide layers on the substrate;

[0044] Step S3, argon protection: filling the argon environment box with high-purity argon protection gas, controlling the oxygen content in the argon environment box to be less than 50ppm and the water content to be less than 0.01ppm;

[0045] Step S4, preheating the substrate: heating the substrate so that the substrate is maintained at 300-500° C.;

[0046] Step S5, printing: the powder feeding system uses a coaxial feeding method to feed Ti2AlNb alloy powder, while the laser beam performs a reciprocating motion relative to the substrate;

[0047] Step S6, solution treatment: heating in the furnace at a heating rate of 10-20°C / min to 900-1000°C, keeping the temperature for 2-3 hours, and then air cooling to room temperature;

[0048] Step S7, aging treatment: heating in the furnace at a heating rate of 10-20°C / min to 760-860°C, keeping the temperature for 6-8h, and then air cooling to room temperature.

[0049] Specifically, in step S1, the Ti2AlNb alloy powder is not prepared using gas atomization, plasma rotating electrode method, plasma atomization method, or plasma spheroidization method. The particle size range is 45 to 150 μm, and the gas content O is ≤ 0.12%, N is ≤ 0.03%, and H is ≤ 0.005%. The drying temperature range is 80 to 120°C, and the drying time is 2 to 4 hours. The drying process is to remove moisture from the powder, reduce adhesion between powder particles, and ensure good powder flowability. Figure 1 This is a morphology diagram of the Ti2AlNb alloy powder used in the present invention.

[0050] Specifically, in step S2, the substrate used is TC4 titanium alloy. In order to avoid poor bonding between the Ti2AlNb alloy deposited layer and the substrate, which may lead to deviations in the performance of the Ti2AlNb alloy or cracks along the bottom of the connection between the Ti2AlNb alloy and the substrate, before starting deposition, the substrate is manually polished in the same direction with sandpaper, and then the oil and oxide layer on the substrate are removed with a laser cleaning machine, thereby enhancing the bonding strength between the deposited layer and the substrate.

[0051] Specifically, in step S3, high-purity argon protective gas is filled into the argon environment box for 3 to 4 hours, the protective gas flow rate of the argon environment box is 15 to 45 L / min, and the purity of the high-purity argon gas Ar is ≥99.999%; the oxygen concentration in the argon environment box is dynamically measured using an oxygen content detector, and the oxygen content is controlled to be lower than 50 ppm, preferably lower than 20 ppm.

[0052] Specifically, in step S4, the substrate is preheated. Electric heating can be provided under the substrate, or a single thin layer of Ti2AlNb powder can be deposited on the surface of the TC4 substrate using a relatively small laser energy, so that the substrate temperature gradually increases to reduce the temperature difference in the argon environment box, thereby avoiding stress release caused by the sudden temperature rise during the printing process, which leads to cracking of the Ti2AlNb alloy. The relatively small laser energy means that the laser power is lower than the laser energy in normal production, which can meet the substrate preheating temperature requirements and prevent the deposited single thin layer of Ti2AlNb powder from cracking. For example, the laser power is 300-600 J / s, the laser scanning speed is 3-6 mm / s, the laser spot diameter is 2-3 mm, the powder carrier gas is high-purity argon, the powder carrier gas flow rate is 0.4-0.8 L / min, the powder feeding rate is 0.01-0.03 g / s, and the purity of the high-purity argon gas Ar is ≥99.999%.

[0053] Specifically, in step S5, the powder feeding system can adopt coaxial four-way powder feeding, and the Ti2AlNb alloy powder is fed into the molten pool from four directions simultaneously during deposition. The printing process parameters include laser power of 800-1400 J / s, laser scanning speed of 6-10 mm / s, laser spot diameter of 2-3 mm, powder carrier gas of high purity argon, Ar of high purity argon ≥ 99.999%, powder carrier gas flow rate of 0.8-1.5 L / min, powder feeding rate of 0.03-0.10 g / s, laser body energy density GED of Preferred GED=P / (GVd 2 ), where P is the laser power in W (J / s); G is the powder feed rate in g / s; V is the laser scanning speed in mm / s; and d is the laser spot diameter in mm. The argon environmental chamber shielding gas is high-purity argon with an Ar content of ≥99.999% at a flow rate of 15 to 45 L / min.

[0054] It should be noted that laser power is one of the key control parameters in the LMD forming process. Laser power significantly influences the melting effect of the cladding layer. When the laser power is low, the molten pool surface receives less energy, the powder cannot be fully melted, and the printed part exhibits interlayer defects, which affects the final density and mechanical properties. When the laser power is high, the printed part will have larger grains and a coarser microstructure, which also affects the final mechanical properties. Only when the laser power is within the appropriate range can the melting efficiency during the forming process be improved, the depth and width of the cladding layer be increased, the porosity be reduced, the density be increased, a uniform and fine microstructure be obtained, and ultimately a printed part that meets the mechanical property requirements. Therefore, the present invention sets the laser power to 800-1400 J / s.

[0055] Compared with laser power, the effect of laser scanning speed on microstructure is more obvious. At low scanning speed, the interaction time between laser and powder is longer, the melting degree of substrate surface is higher, the deposited powder will produce a larger molten pool, which takes a long time to solidify and cool, and the grains and microstructure are relatively coarse; at high scanning speed, the solidification speed of the printed part is faster, the internal grains and microstructure are not fully diffused and transformed, and the surface roughness is higher; similarly, only an appropriate laser scanning speed can meet the requirements of high-quality prints, so the present invention sets the laser scanning speed to 6-10 mm / s.

[0056] Similar to laser scanning speed, the powder feed rate also affects the build rate and quality of printed parts to a certain extent. When the powder feed rate is too low, excess energy input causes the melt to have a high degree of superheat, resulting in defects similar to those at lower laser scanning speeds and lower forming efficiency. When the powder feed rate is too high, excess powder is not melted by the molten pool, and powder is deposited in the printed part, resulting in unfused defects. In addition, excessively high powder feed rates lead to material waste and increased costs. Therefore, the present invention sets the powder feed rate to 0.03-0.10 g / s.

[0057] Since the laser power, laser scanning speed and powder feeding rate have an inter-influence on the printing effect, the present invention uses the laser body energy density as a comprehensive and balanced process parameter, that is, not only the laser power, laser scanning speed and powder feeding rate are required to be within the specified range, but also the laser body energy density is required to be within the specified range. The laser body energy density controls the effective residence time of the laser on the powder as a whole and directly affects the molten pool temperature, cooling rate and final microstructure. Specifically, the present invention sets the laser body energy density to Preferred

[0058] Furthermore, during the printing process, the most basic printing path process is set, such as a single wall, and the most basic printing process parameters are set, as follows:

[0059] The scanning path for a single wall is a single-channel reciprocating cycle. The laser head moves from the origin in the single-channel direction with a laser scanning speed of 6-10mm / s. Light is emitted and powder is fed simultaneously. When the set single-channel length is reached, the laser head is lifted upward at a speed of 1.5-2mm / s and a lifting distance of 0.3-0.7mm. No powder is discharged during the lifting process. Subsequently, the laser head turns 180° and moves along a single channel that coincides with the original path but in the opposite direction. Light is emitted and powder is fed simultaneously. When the set single-channel length is reached, the laser head is lifted upward at a speed of 1.5-2mm / s and a lifting distance of 0.3-0.7mm. No powder is discharged during the lifting process. This constitutes one cycle. Repeat several cycles until the set number of printing layers is completed and the single-channel wall printing is completed.

[0060] Figure 2 This is a macroscopic structural photograph of a single wall of Ti2AlNb material prepared in the present invention.

[0061] In specific printing, when it comes to multi-step paths on the same layer, the radial overlap rate between adjacent single paths is 40% to 60%.

[0062] Figure 3 is the room temperature tensile property curve of the deposited Ti2AlNb alloy obtained in step S5 of the present invention, Figure 4 This is a SEM image of the microstructure of the deposited Ti2AlNb alloy obtained in step S5 of the present invention.

[0063] Specifically, in step S6 and step S7, the prepared Ti2AlNb alloy is subjected to solid solution treatment and aging treatment to eliminate residual stress, thereby regulating the structure of the Ti2AlNb alloy and improving the comprehensive properties of the alloy.

[0064] The density and mechanical properties of the heat-treated Ti2AlNb alloy were tested, and the density was above 96%. -4 / s, the room temperature tensile strength is above 950MPa, and the elongation can reach up to 20%; at a strain rate of 1×10 -3 / s, the tensile strength at 650℃ is above 685MPa and the elongation can reach up to 23%.

[0065] Figure 5 is the room temperature tensile property curve of the heat-treated Ti2AlNb alloy of the present invention, Figure 6 This is the tensile property curve of the heat-treated Ti2AlNb alloy at 650°C. Figure 7 This is an SEM image of the microstructure of the Ti2AlNb alloy after heat treatment of the present invention.

[0066] It should be noted that the present invention also carried out density and mechanical property tests on the deposited Ti2AlNb alloy obtained in step S5. The test results show that the density of the deposited Ti2AlNb alloy is above 96%, which is similar to the density of the Ti2AlNb alloy after heat treatment, indicating that the heat treatment process has little effect on the density of the Ti2AlNb alloy, or almost no effect.

[0067] Figure 3 The room temperature tensile performance curve of the deposited Ti2AlNb alloy of the present invention is obtained by Figure 5 Comparison of room temperature tensile properties curves of heat-treated Ti2AlNb alloys revealed that at a strain rate of 1×10 -4 / s, the yield strength of the deposited Ti2AlNb alloy at room temperature is equivalent to that of the heat-treated Ti2AlNb alloy, which is about 900MPa, indicating that the heat treatment process has little effect on the material in the elastic deformation stage, or almost no effect. However, compared with the tensile curve of the heat-treated Ti2AlNb alloy, the tensile curve of the deposited Ti2AlNb alloy has no strengthening stage, and directly enters the necking stage from the yield stage. Its yield strength is close to the tensile strength, which indicates that after the deposited Ti2AlNb alloy passes the yield stage, its internal crystal structure does not have the ability to actively adjust after plastic deformation. Its ability to resist deformation decreases with the increase of tension until the sample is broken. This indicates that the heat treatment process improves the ability of the material to actively adjust its internal crystal structure during plastic deformation. Heat treatment plays an important role in adjusting the microstructure, and its ability to resist deformation is enhanced. The maximum tensile strength is significantly higher than the yield strength.

[0068] Figure 4 The SEM image of the microstructure of the deposited Ti2AlNb alloy of the present invention shows that the Ti2AlNb structure is a B2 phase matrix with a very small amount of α2 phase at the grain boundaries. Figure 7 The SEM image of the microstructure of the Ti2AlNb alloy after heat treatment of the present invention shows that a fine needle-shaped O phase is precipitated in the B2 phase matrix, and a small amount of α2 phase is precipitated at the boundary. Existing literature reports that Ti2AlNb-based alloys with O+B2 phase have the best comprehensive mechanical properties. The intrinsic plasticity of the O phase is higher than that of the α2 phase. The α2 relative strength and plasticity of the grain boundary distribution are unfavorable, which easily leads to crack initiation at the grain boundary. It can be seen that the subsequent heat treatment reduces the α2 phase, and then reduces the α2 / α2 grain boundary, which is beneficial to the improvement of the alloy elongation and strength, which is also confirmed by the test results of the above-mentioned mechanical properties.

[0069] By comparing the mechanical properties and microstructure of the Ti2AlNb alloys as deposited and after heat treatment, it is shown that the Ti2AlNb alloys prepared by laser melting deposition must be heat treated to enhance and improve their mechanical properties, and that appropriate heat treatment process parameters such as those of the present invention must be formulated.

[0070] In summary, the preparation process of the present invention has a short cycle, high material utilization rate, and low production cost. When the method of the present invention is used to prepare large and complex parts, the near-net shape of additive printing requires machining treatment after the ordinary deformation process, which greatly improves the material utilization rate and reduces the cost by about 65%. The method of the present invention can prepare parts with complex shapes that meet various mechanical property requirements at room temperature and high temperature, expand the application range of Ti2AlNb alloy, and provide a new solution for the preparation of high-temperature structural materials in the aerospace field.

[0071] The following Examples 1 to 3 use Ti22Al25Nb alloy powder from the Ti2AlNb series alloys to specifically implement the method of the present invention. The Ti22Al25Nb alloy powder is not prepared by the plasma rotating electrode method, and the particle size range is 45 to 150 μm. The alloy powder has the following mass percentages: Al: 10.74%, Nb: 42.37%, gas content O: 0.066%, N: 0.003%, and H: 0.0039%. Figure 8 This is the morphology of the Ti22Al25Nb alloy powder used in Examples 1 to 3.

[0072] Example 1

[0073] A method for preparing Ti22Al25Nb alloy by laser melting deposition comprises the following steps:

[0074] Step S1, drying powder: putting Ti22Al25Nb alloy powder into a drying oven for drying;

[0075] The temperature range in the drying box is 80℃ and the drying time is 2h.

[0076] Step S2, substrate cleaning: first manually polish the substrate in the same direction with sandpaper, and then use a laser cleaning machine to remove oil stains and oxide layers on the substrate;

[0077] The substrate used is TC4 titanium alloy with a size of 150 mm × 150 mm × 20 mm.

[0078] Step S3, argon protection: high-purity argon protection gas is filled into the argon environment box for 3 hours, the argon environment box protection gas flow rate is 15L / min, and the oxygen content in the argon environment box is controlled to be lower than 50ppm and the water content is lower than 0.008ppm;

[0079] Step S4, preheating the substrate: heating the substrate so that the substrate is maintained at 300° C.;

[0080] The substrate preheating method is to use a small laser energy to deposit a single thin layer of Ti2AlNb powder on the surface of the TC4 substrate. The laser power is 300 J / s, the laser scanning speed is 3 mm / s, the laser spot diameter is 2 mm, the powder carrier gas is high-purity argon, the powder carrier gas flow rate is 0.4 L / min, and the powder feeding rate is 0.01 g / s.

[0081] Step S5, printing: the powder feeding system uses a coaxial feeding method to feed Ti2AlNb alloy powder, while the laser beam performs a reciprocating motion relative to the substrate;

[0082] Printing process parameters: laser power 800J / s, laser scanning speed 6mm / s, laser spot diameter 2mm, powder carrier gas is high-purity argon, the purity of high-purity argon Ar ≥ 99.999%, powder carrier gas flow rate 0.8L / min, powder feeding rate 0.067g / s, laser body energy density GED

[0083]

[0084] Step S6, solution treatment: heating in the furnace at a heating rate of 10°C / min to 900°C, keeping the temperature for 2 hours, and then air cooling to room temperature;

[0085] Step S7, aging treatment: heating in the furnace at a heating rate of 10°C / min to 860°C, keeping the temperature for 6 hours, and then air cooling to room temperature.

[0086] It should be noted that the above Figure 5 The room temperature tensile performance curve of the Ti2AlNb alloy after heat treatment is the room temperature tensile performance curve of the Ti22Al25Nb alloy after heat treatment in Example 1. Figure 6 The tensile performance curve of the Ti2AlNb alloy after heat treatment at 650°C is the tensile performance curve of the Ti22Al25Nb alloy after heat treatment at 650°C in Example 1. Figure 7 The SEM image of the microstructure of the Ti2AlNb alloy after heat treatment is the SEM image of the microstructure of the Ti22Al25Nb alloy after heat treatment in Example 1.

[0087] Table 1 shows the mechanical properties data of the Ti22Al25Nb alloy at room temperature and 650°C after heat treatment in Example 1.

[0088] Example 2

[0089] A method for preparing Ti22Al25Nb alloy by laser melting deposition comprises the following steps:

[0090] Step S1, drying powder: putting Ti22Al25Nb alloy powder into a drying oven for drying;

[0091] The temperature range in the drying box is 100°C and the drying time is 3 hours.

[0092] Step S2, substrate cleaning: first manually polish the substrate in the same direction with sandpaper, and then use a laser cleaning machine to remove oil stains and oxide layers on the substrate;

[0093] The substrate used is TC4 titanium alloy with a size of 150 mm × 150 mm × 20 mm.

[0094] Step S3, argon protection: high-purity argon protective gas is filled into the argon environment box for 3.5 hours, the argon environment box protective gas flow rate is 30 L / min, and the oxygen content in the argon environment box is controlled to be lower than 18 ppm and the water content is lower than 0.01 ppm;

[0095] Step S4, preheating the substrate: heating the substrate so that the substrate is maintained at 400° C.;

[0096] The substrate preheating method is to use a smaller laser energy to deposit a single thin layer of Ti2AlNb powder on the surface of the TC4 substrate. The laser power is 450J / s, the laser scanning speed is 5mm / s, the laser spot diameter is 2.5mm, the powder carrier gas is high-purity argon, the powder carrier gas flow rate is 0.6L / min, and the powder feeding rate is 0.02g / s.

[0097] Step S5, printing: the powder feeding system uses a coaxial feeding method to feed Ti2AlNb alloy powder, while the laser beam performs a reciprocating motion relative to the substrate;

[0098] Printing process parameters: laser power 1100 J / s, laser scanning speed 6 mm / s, laser spot diameter 2.5 mm, powder carrier gas is high-purity argon, the purity of high-purity argon Ar ≥ 99.999%, powder carrier gas flow rate 0.12 L / min, powder feeding rate 0.04 g / s, laser body energy density GED

[0099] Step S6, solution treatment: heating in the furnace at a heating rate of 15°C / min to 950°C, keeping the temperature for 2.5 hours, and then air cooling to room temperature;

[0100] Step S7, aging treatment: heating in the furnace at a heating rate of 15°C / min to 760°C, keeping the temperature for 8 hours, and then air cooling to room temperature.

[0101] Figure 9 This is the SEM image of the microstructure of the Ti22Al25Nb alloy after heat treatment in Example 2; Figure 10This is the room temperature tensile property curve of the Ti22Al25Nb alloy after heat treatment in Example 2. Figure 11 This is the tensile property curve of the Ti22Al25Nb alloy after heat treatment at 650°C in Example 2.

[0102] Table 1 shows the mechanical properties data of the Ti22Al25Nb alloy after heat treatment in Example 2 at room temperature and 650°C.

[0103] Example 3

[0104] A method for preparing Ti22Al25Nb alloy by laser melting deposition comprises the following steps:

[0105] Step S1, drying powder: putting Ti22Al25Nb alloy powder into a drying oven for drying;

[0106] The temperature range in the drying box is 120℃ and the drying time is 4h.

[0107] Step S2, substrate cleaning: first manually polish the substrate in the same direction with sandpaper, and then use a laser cleaning machine to remove oil stains and oxide layers on the substrate;

[0108] The substrate used is TC4 titanium alloy with a size of 150 mm × 150 mm × 20 mm.

[0109] Step S3, argon protection: high-purity argon protection gas is filled into the argon environment box for 3 hours, and the argon environment box protection gas flow rate is 15L / min, so that the oxygen content in the argon environment box is less than 15ppm and the water content is less than 0.008ppm;

[0110] Step S4, preheating the substrate: heating the substrate so that the substrate is maintained at 500° C.;

[0111] The substrate preheating method is to use a smaller laser energy to deposit a single thin layer of Ti2AlNb powder on the surface of the TC4 substrate. The laser power is 600 J / s, the laser scanning speed is 6 mm / s, the laser spot diameter is 3 mm, the powder carrier gas is high-purity argon, the powder carrier gas flow rate is 0.8 L / min, and the powder feeding rate is 0.03 g / s.

[0112] Step S5, printing: the powder feeding system uses a coaxial feeding method to feed Ti2AlNb alloy powder, while the laser beam performs a reciprocating motion relative to the substrate;

[0113] Printing process parameters: laser power 1400J / s, laser scanning speed 7mm / s, laser spot diameter 2mm, powder carrier gas is high-purity argon, the purity of high-purity argon Ar ≥ 99.999%, carrier gas flow rate 1.5L / min, powder feeding rate 0.035g / s, laser body energy density GED

[0114]

[0115] Step S6, solution treatment: heating in the furnace at a heating rate of 20°C / min to 1000°C, keeping the temperature for 3 hours, and then air cooling to room temperature;

[0116] Step S7, aging treatment: heating in the furnace at a heating rate of 20°C / min to 810°C, keeping the temperature for 7 hours, and then air cooling to room temperature.

[0117] Table 1 shows the mechanical properties data of the Ti22Al25Nb alloy at room temperature and 650°C after heat treatment in Example 3.

[0118] Table 1 Mechanical properties of Ti22Al25Nb alloys at room temperature and 650℃ after heat treatment in Examples 1 to 3

[0119]

[0120] The data of Example 1 in Table 1 and Figure 5 、 Figure 6 、 Figure 7 Correspondingly, the data of Example 2 in Table 1 and Figure 9 、 Figure 10 、 Figure 11 Correspondingly, after Figure 7 and Figure 9 By comparison, it is obvious Figure 7 Compared with the needle-shaped O Figure 9 More, smaller and more uniform, Figure 7 The α2 grain boundaries in Figure 9 The more needle-like O phase there is, the fewer α2 grain boundaries there are, the better the plasticity is, and the higher the elongation is. This qualitative statement is consistent with the quantitative data shown in Table 1 that the elongation of Example 1 is more than twice that of Example 2.

[0121] As shown in Table 1, the Ti22Al25Nb alloys prepared by the present invention exhibit room temperature tensile strengths exceeding 950 MPa and elongations exceeding 8%, with the highest elongation exceeding 20%, after heat treatment. The tensile strength at 650°C exceeds 685 MPa, and the elongation exceeds 10%, with the highest elongation exceeding 23%. This embodiment reduces the cost of conventional post-deformation machining by approximately 65%.

[0122] The foregoing description is merely a specific embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any person skilled in the art will readily conceive of various equivalent modifications or substitutions within the technical scope disclosed herein, and such modifications or substitutions are intended to be encompassed within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection defined in the claims.

Claims

1. A method for preparing Ti2AlNb alloy by laser melting deposition, characterized in that: The following steps are involved: Step S1, drying powder: drying Ti2AlNb alloy powder; Step S2, substrate cleaning: first manually polish the substrate in the same direction with sandpaper, and then use a laser cleaning machine to remove oil stains and oxide layers on the substrate; Step S3, argon protection: filling the argon environment box with high-purity argon protection gas, controlling the oxygen content in the argon environment box to be less than 50ppm and the water content to be less than 0.01ppm; Step S4, preheating the substrate: heating the substrate so that the substrate is maintained at 300-500° C.; Step S5, printing: The powder feeding system uses coaxial feeding of Ti2AlNb alloy powder, and the laser beam moves back and forth relative to the substrate. The most basic printing path process is a single-pass reciprocating single-pass wall scanning path. The process parameters include: laser power of 800-1400 J / s, laser scanning speed of 6-7 mm / s, laser spot diameter of 2-3 mm, powder carrier gas of high purity argon, powder carrier gas flow rate of 0.8-1.5 L / min, powder feeding rate of 0.03-0.10 g / s, laser body energy density GED of The protective gas of the argon environment box is high-purity argon, and the protective gas flow rate is 15-45L / min; Step S6, solution treatment: heating in the furnace at a heating rate of 10-20°C / min to 900-1000°C, keeping the temperature for 2-3 hours, and then air cooling to room temperature; Step S7, aging treatment: heating in the furnace at a heating rate of 10-20°C / min to 760-860°C, keeping the temperature for 6-8h, and then air cooling to room temperature.

2. The method according to claim 1, characterized in that In the step S1, the particle size of the Ti2AlNb alloy powder is in the range of 45 to 150 μm, wherein the gas content O is ≤ 0.12%, N is ≤ 0.03%, and H is ≤ 0.005%.

3. The method according to claim 1, characterized in that In the step S1, the drying process is carried out at a temperature ranging from 80 to 120° C. and for a time ranging from 2 to 4 hours.

4. The method according to claim 1, wherein In step S3, high-purity argon protective gas is filled into the argon environment box for 3 to 4 hours, and the protective gas flow rate is 15 to 45 L / min.

5. The method according to claim 1, wherein In step S3, the oxygen content in the argon environment box is lower than 20 ppm.

6. The method according to claim 1, characterized in that In step S5, the laser volume energy density GED is 7. The method according to claim 1, characterized in that In the steps S3 to S5, the high-purity argon gas has an Ar concentration of ≥ 99.999%.

8. The method according to claim 1, characterized in that In step S6, the heating rate is 15°C / min, the temperature is raised to 950°C, and the temperature is kept for 2.5 hours.

9. The method according to claim 1, characterized in that In step S7, the heating rate is 15°C / min, the temperature is raised to 810°C, and the temperature is kept for 7 hours.

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