Laser composite additive manufacturing method and application of high-toughness TiAl-based alloy

Abstract

The invention discloses a laser composite additive manufacturing method and application of a high-toughness TiAl-based alloy, and the method comprises the following steps: forming TiAl4822 powder by adopting a laser melting deposition technology to form a front alloy layer of the TiAl-based alloy; after the deposited front alloy layer is cooled and solidified, Nb powder is laid on the surface of the front alloy layer, light-transmitting quartz glass is pressed on the Nb powder in a covering mode, then single high-peak-intensity pulse laser penetrates through the quartz glass, the Nb powder is mechanically embedded into the front alloy layer through the laser shock effect, and Nb is dispersed and distributed on the TiAl base body in the form of an elementary substance; the laser shock process is repeated to improve the content and distribution uniformity of the elementary substance Nb in the TiAl matrix; and the laser melting deposition process and the pulse laser shock process are interacted layer by layer and are repeated in sequence until the size of the prepared high-toughness TiAl-based alloy meets the requirement. The high-strength and high-toughness TiAl-based alloy prepared through the method has good strength and toughness and high-temperature performance.

Description

Technical Field

[0001] This invention relates to the field of 3D printing of composite materials, specifically to a laser composite additive manufacturing method and application of a high-strength and high-toughness TiAl-based alloy. Background Technology

[0002] TiAl-based alloys are lightweight, high-temperature structural materials. Due to their low density, high specific strength, and excellent high-temperature oxidation resistance, they are widely considered the most promising new high-temperature alloy materials after nickel-based alloys. These alloys offer significant weight reduction advantages in aerospace, gas turbines, and automotive engines, improving overall efficiency while maintaining high-temperature strength and durability. However, TiAl-based alloys exhibit insufficient ductility and poor plasticity at room temperature, making them prone to brittle fracture during forming, processing, and use. This limits their widespread application in the manufacture of complex components and under harsh service conditions. Overall, TiAl-based alloys combine the advantages of lightweight and high-temperature performance, but their inherent poor room-temperature plasticity has become a key bottleneck restricting their further engineering applications.

[0003] To improve the room-temperature ductility of TiAl-based alloys, existing technologies typically involve adding nitrogen (Nb) to enhance their toughness and ductility. Nb can form strengthening phases at grain boundaries or in the matrix of TiAl alloys, effectively inhibiting crack initiation and propagation, thereby alleviating room-temperature brittleness and improving ductility and crack resistance to some extent. However, the amount of Nb added must be strictly controlled. Excessive Nb can easily dissolve into the TiAl matrix and form brittle phases, limiting further improvements in ductility and potentially negatively impacting the alloy's formability and machinability. Therefore, although Nb addition plays a role in improving the toughness of TiAl alloys, its application still faces the challenges of metal solid solution strengthening and balancing machinability, limiting the alloy's widespread adoption in the manufacture of complex components and engineering applications.

[0004] The main challenges currently facing TiAl-based alloys are: on the one hand, their room temperature plasticity is difficult to improve significantly; on the other hand, although the addition of Nb can strengthen the alloy and increase its strength, traditional hot forming technology makes it easy for excessive Nb to form a brittle phase with the matrix solid solution, which inhibits the improvement of plasticity. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides a laser composite additive manufacturing method and application for high-strength and high-toughness TiAl-based alloys. The prepared TiAl-based alloys not only possess the advantages of traditional TiAl alloys, such as low density, high specific strength, high elastic modulus, and resistance to high-temperature creep, but also exhibit good strength, toughness, and high-temperature performance at room temperature, which can meet their application requirements in the fields of new energy vehicles, drones, aerospace, and humanoid robots.

[0006] The first objective of this invention is to provide a laser composite additive manufacturing method for high-strength and high-toughness TiAl-based alloys.

[0007] The second objective of this invention is to provide a high-strength and high-toughness TiAl-based alloy.

[0008] The third objective of this invention is to provide an application of a high-strength and high-toughness TiAl-based alloy.

[0009] The first objective of this invention can be achieved by adopting the following technical solution: A laser composite additive manufacturing method for high-strength and high-toughness TiAl-based alloys, the method comprising: S1: TiAl4822 powder and Nb powder were dried separately in a vacuum drying oven; the purity of both TiAl4822 powder and Nb powder was above 99.9%; the average particle size of TiAl4822 powder was 40~150μm; the chemical composition of TiAl4822 powder was: Al 32.4~33.6wt.%, Cr 2.4~2.8wt.%, Nb 4.5~5.1wt.%, O≤0.0 8 wt.%, C≤0.02 wt.%, N≤0.02 wt.%, H≤0.005 wt.%, Fe≤0.10 wt.%, Ni≤0.05 wt.%, balance Ti; the average particle size of Nb powder is 0.5~1 μm; the chemical composition of Nb powder is: Nb≥99.9 wt.%, O≤0.065 wt.%, C≤0.02 wt.%, N≤0.01 wt.%, H≤0.005 wt.%; S2: Adjust the distance between the heating induction coil and the substrate so that the substrate can be effectively heated by the skin effect; add the dried TiAl4822 powder and high-purity Nb powder to the coaxial powder feeding system respectively; wherein, the substrate is heated to a temperature of 300~600℃; the substrate is a TC4 alloy plate; S3: Laser melting deposition technology is used to melt and deposit dried TiAl4822 powder onto the substrate surface according to a preset trajectory to form a multi-layer single-layer cladding coating as a pre-alloy layer for TiAl-based alloys; inert gas is continuously introduced throughout the preparation process to form a positive pressure protective environment; S4: After the single-layer cladding coating cools and solidifies, Nb powder is laid on its surface; a three-axis robotic arm is used to press a transparent quartz glass onto the Nb powder, and then a single high peak intensity pulsed laser is used to mechanically and uniformly embed the Nb powder into the pre-alloy layer of the TiAl-based alloy through laser shock strengthening, so as to ensure that the Nb element is dispersed in the TiAl-based alloy in the form of elemental rather than solid solution; by repeating the laser shock process multiple times, the content of elemental Nb in the TiAl-based alloy and its distribution uniformity are improved; S5: Repeat steps S3 and S4 to achieve layer-by-layer interaction between laser melting deposition and pulsed laser shock processes, and repeat this process until the dimensions of the prepared high-strength and tough TiAl-based alloy meet the requirements.

[0010] Preferably, a fiber laser is used to laser melt and deposit the dried TiAl4822 powder onto the substrate surface; wherein the laser melting deposition process parameters are: laser power of 1200~1600W, scanning speed of 1000~2000mm / s, spot diameter of 1500~3000μm, overlap rate of 30~70%, and layer thickness of 35~50μm.

[0011] Preferably, a nanosecond laser is used to mechanically and uniformly embed Nb powder into the pre-alloy layer of the TiAl-based alloy; wherein the laser shock process parameters are: laser power of 10~100W, pulse repetition frequency of 1~20kHz, pulse width of 5~30ns, scanning speed of 1~100mm / s, and overlap rate of 30~70%.

[0012] Preferably, coaxial powder feeding is used to uniformly spray and lay each layer of Nb powder with a thickness of 30~50μm on the surface of the single-layer cladding coating. The three-axis robotic arm adjusts its motion trajectory and Z-axis position in real time according to the surface height of the TiAl-based alloy after cooling and the powder thickness. Then, a high-flatness quartz glass sheet is accurately positioned and covered on the Nb powder layer, and a uniform surface pressure of 0.1~0.3MPa is applied to achieve appropriate compression so that the quartz sheet and the powder layer are fully bonded, forming a rigid quartz glass constraint layer for the powder absorption layer. After each layer is laser-shocked, the three-axis robotic arm automatically compensates for the height change in the Z-axis direction to ensure that the laser focus remains consistent with the quartz glass surface in subsequent cycles.

[0013] More preferably, the Nb powder feeding rate is 4~10 g / min, and the inert protective gas flow rate is 5~10 L / min.

[0014] Preferably, laser shock strengthening involves the surface Nb powder absorbing short-pulse laser shock to form a high-temperature, high-density plasma, which then rapidly expands to generate a high-pressure shock wave. Transparent quartz glass acts as a confinement layer, restricting the free expansion of the plasma, significantly enhancing the impact effect and duration. This effectively embeds the pre-laid Nb powder mechanically into the plastic zone of the TiAl-based alloy's pre-alloy layer, allowing Nb particles to be uniformly dispersed within the alloy in an elemental state, thus achieving a non-solid-solution, uniformly embedded structure.

[0015] More preferably, the mass fraction of elemental Nb particles is 20~40 wt.%; Nb is dispersed and embedded in the TiAl-based alloy in the form of elemental particles, and is distributed in the TiAl matrix in the form of a small amount of in-situ phase, thereby improving the plastic deformation capacity and fracture toughness.

[0016] Preferably, the inert gas is argon.

[0017] The second objective of this invention can be achieved by adopting the following technical solution: A high-strength and high-toughness TiAl-based alloy was prepared based on the above-mentioned laser composite additive manufacturing method.

[0018] The third objective of this invention can be achieved by adopting the following technical solution: Applications of a high-strength and high-toughness TiAl-based alloy: The high-strength and high-toughness TiAl-based alloy prepared by the above-mentioned laser composite additive manufacturing method is applied in the fields of new energy vehicles, drones, aerospace and humanoid robots.

[0019] The present invention has the following advantages over the prior art: (1) In this invention, laser metal deposition (LMD) is used to melt and deposit TiAl4822 powder onto a substrate. Then, laser shock peening (LSP) is used to uniformly embed high-purity Nb powder particles into the TiAl matrix through mechanical impact, so that Nb elements are dispersed in the alloy in elemental form, thereby significantly improving the toughness of the TiAl alloy. Among them, the mechanical cold working of the TiAl alloy layer and Nb elements can be completed in the same processing center, which is the key condition for realizing the integrated additive manufacturing of laser melting deposition and laser shock peening. It is the premise for obtaining high-strength and high-toughness TiAl-based alloys. By adjusting the powder ratio and laser process parameters, the uniform embedding and dispersion strengthening of Nb powder particles in the TiAl matrix can be achieved to achieve the optimal effect.

[0020] (2) The preparation process of this invention is simple, highly controllable, and has a high material utilization rate, which can effectively overcome the traditional γThe high strength and toughness of TiAl alloys is a major technical bottleneck due to their brittleness and susceptibility to fracture. The high-strength, high-toughness TiAl-based alloy prepared based on this invention not only possesses excellent strength and hardness but also exhibits significantly improved room-temperature fracture plasticity, making it suitable for manufacturing lightweight, high-performance, and complex structural components required in aerospace and other fields. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the pre-alloy layer for preparing TiAl-based alloys using LMD technology in Example 1 of the present invention; Figure 2 This is a schematic diagram of Nb powder being uniformly spread on the surface of the TiAl-based alloy pre-alloy layer in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of how Nb powder was cold-impact embedded into the pre-alloy layer of a TiAl-based alloy using LSP technology in Embodiment 1 of the present invention. Figure 4 This is a schematic diagram of the preparation of a TiAl-based alloy pre-alloy layer using LMD technology after cold embedding Nb powder into a TiAl-based alloy pre-alloy layer in Embodiment 1 of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be understood that the specific embodiments described are merely used to explain this application and are not intended to limit the scope of this application.

[0024] The original purity of TiAl4822 powder and Nb powder in all embodiments was above 99.9%. The TiAl4822 powder particles were spherical with an average particle size of 40~150μm. The chemical composition of TiAl4822 powder was: Al 32.4~33.6wt.%, Cr 2.4~2.8wt.%, Nb 4.5~5.1wt.%, O≤0.08wt.%, C≤0.02wt.%, N≤0.02wt.%, H≤0.005wt.%, Fe≤0.10wt.%, Ni≤0.05wt.%, with the balance being Ti. The Nb powder particles were spherical with an average particle size of 0.5~1μm. The chemical composition of Nb powder was: Nb≥99.9wt.%, O≤0.065wt.%, C≤0.02wt.%, N≤0.01wt.%, H≤0.005wt.%.

[0025] Example 1: The laser composite additive manufacturing method for high-strength and tough TiAl-based alloys provided in this embodiment specifically includes the following steps: S1: Place TiAl4822 powder and Nb powder separately in a vacuum drying oven to dry.

[0026] In this embodiment, TiAl4822 powder with an average particle size of 95 μm and Nb powder with an average particle size of 0.8 μm were selected. The chemical composition (wt.%) of TiAl4822 powder is: Al 33%, Cr 2.5%, Nb 4.6%, O 0.06%, C 0.015%, N 0.015%, H 0.002%, Fe 0.07%, Ni 0.04%, with the balance being Ti; the chemical composition (wt.%) of submicron purity Nb powder is: Nb 99.92%, O 0.06%, C 0.01%, N 0.006%, and H 0.004%.

[0027] In a vacuum drying oven at 80°C, under vacuum conditions (<10 -2 Dry TiAl4822 powder and high-purity Nb powder for 8 hours in a protective atmosphere of Pa or high-purity argon, respectively, to obtain dry TiAl4822 powder and high-purity Nb powder.

[0028] S2: TC4 alloy is selected as the substrate. After cleaning and drying the surface with acetone solution, it is placed in an inert gas protection chamber and filled with argon to form a protective gas atmosphere.

[0029] The substrate surface is first cleaned and dried with acetone solution, and then placed in an inert gas protection chamber and filled with argon to form a protective atmosphere.

[0030] The substrate has a thickness of 20mm and a size of 100×100mm.

[0031] S3: Adjust the distance between the induction heating coil and the substrate surface so that the substrate can be effectively heated by the skin effect; add the dried TiAl4822 powder and high-purity Nb powder to the coaxial powder feeding system respectively.

[0032] In this embodiment, the substrate is heated to 500°C.

[0033] S4: TiAl4822 powder is sprayed onto the surface of TC4 substrate using a coaxial powder feeding method. Laser melting deposition technology is used to melt and deposit TiAl4822 powder according to a preset trajectory, so that the molten alloy powder can be rapidly solidified and crystallized to form multiple single-layer cladding coatings as a pre-alloy layer for TiAl-based alloys. Inert gas is continuously introduced throughout the laser composite additive manufacturing process to form a positive pressure protective environment.

[0034] In this embodiment, a YLS4000 IPG fiber laser is used for laser deposition fabrication. The laser power is 1200W, the spot diameter is 2000μm, and the overlap rate is 50%. TiAl4822 powder is sprayed onto the TC4 substrate surface using a coaxial powder feeding method at a scanning speed of 1200mm / s and irradiated to form a local molten pool. The powder then rapidly solidifies to form a TiAl-based alloy pre-alloy layer with a thickness of 50μm. The powder mass flow rate of the powder feeding nozzle is 8g / min, argon is used as the powder transport gas, and the protective gas flow rate is 8L / min. Argon is used as the inert gas.

[0035] S5: After the single-layer cladding coating to be deposited cools and solidifies, a layer of Nb powder is laid on its surface through a powder feeding nozzle. A three-axis robotic arm adjusts its trajectory and Z-axis height in real time according to the surface height of the cooled substrate and the powder thickness. A highly flat quartz glass sheet is then accurately positioned and placed on the powder layer, and a uniform surface pressure of 0.25 MPa is applied to achieve appropriate compaction, ensuring full adhesion between the quartz sheet and the powder layer, forming a rigid quartz glass constraint layer for the powder absorption layer. This constraint layer effectively suppresses the free expansion of plasma during laser pulse transmission, significantly enhancing the pressure and duration of the high-pressure shock wave. This allows Nb particles to be uniformly dispersed and embedded in the plastic region of the TiAl pre-alloy surface in an elemental state, achieving a non-solid-solution uniformly embedded structure, thereby obtaining a high-strength and high-toughness TiAl-based alloy. After each layer is laser-shocked, the three-axis robotic arm automatically compensates for changes in Z-axis height, ensuring that the laser focus remains consistent with the quartz surface in subsequent cycles.

[0036] In this embodiment, argon gas is used as the powder transport gas through the powder feeding nozzle, so that each layer of Nb powder is uniformly laid on the surface of the TiAl pre-alloy layer with a compacted thickness of about 40 μm, and the powder mass flow rate is 6 g / min.

[0037] This embodiment uses a 532nm nanosecond laser with a laser power of 80W, a pulse repetition frequency of 15kHz, a pulse width of 20ns, and an overlap rate of 50%. The Nb powder is uniformly embedded into the TiAl-based alloy pre-layer at a scanning speed of 60mm / s. The laser spot focal point is coupled to the movement of a three-axis robotic arm, which rises an appropriate distance along the Z-axis after each layer is completed.

[0038] In this embodiment, high-purity submicron-sized Nb powder particles are uniformly embedded into the TiAl matrix via mechanical impact, allowing Nb to be dispersed in the alloy microstructure in elemental form. The dispersed Nb particles can regulate dislocation slip behavior at the microscale, promoting the synergistic activation of multi-orientation slip systems and significantly improving the plasticity of the TiAl-based alloy at room temperature. Simultaneously, Nb particles act as deflectors and passivators during crack propagation, complicating the crack propagation path and increasing fracture energy consumption, thereby enhancing the material's fracture toughness. Furthermore, the difference in thermal expansion coefficients between the Nb particles and the TiAl matrix creates a residual stress field at the interface, which can alter the dislocation slip mode of the matrix and effectively suppress brittle fracture. Moreover, the dispersed Nb particles can also hinder dislocation movement, inducing Orowan mechanisms such as dislocation bending or bypassing, thereby increasing the alloy's yield strength. Thus, while improving plasticity, the alloy maintains excellent strength and toughness.

[0039] In TiAl alloys, Nb significantly improves plasticity by controlling the microstructure and phase distribution. Adding Nb can promote… α 2 (ordered L10 structure) and γ The formation of (face-centered cubic) phases, which contribute to the formation of additional slip systems and suppress harmful phases (such as...) α - The brittle fracture path of the B2 phase and the refinement of grain structure effectively improve the room temperature plasticity and fracture toughness of the alloy. However, excessive Nb may delay recrystallization kinetics or lead to excessive coarsening of the interface phase, forming brittle Nb-rich phases (such as coarse aggregates of NbAl3) and reducing toughness; the solid solution Nb content and the proportion of elemental Nb in the TiAl-based alloy are the key to optimizing the plasticity of high-strength and high-toughness TiAl-based alloys.

[0040] Repeat steps S4 to S5, that is, sequentially perform the layer-by-layer interaction of laser melting deposition and pulsed laser shock processes until the dimensions of the high-strength and tough TiAl-based alloy prepared by laser composite additive manufacturing meet the requirements.

[0041] The entire preparation process of high-strength and high-toughness TiAl-based alloys can be found in [reference needed]. Figures 1-4 .

[0042] The high-strength and high-toughness TiAl-based alloy material prepared in this embodiment exhibits the following characteristics at room temperature: tensile strength of approximately 720 MPa and yield strength of approximately 650 MPa, demonstrating excellent load-bearing capacity; elongation of approximately 7% and reduction of area (Z) of approximately 10%, demonstrating high plasticity; and high-temperature strength of approximately 600 MPa at 700°C. Combined with its low density (approximately 4.4 g / cm³), this high-strength and high-toughness TiAl-based alloy material can be widely used in the manufacture of high-performance structural components in fields such as new energy vehicles, drones, aerospace, and humanoid robots.

[0043] Example 2: The laser composite additive manufacturing method for high-strength and tough TiAl-based alloys provided in this embodiment specifically includes the following steps: S1: Place TiAl4822 powder and Nb powder separately in a vacuum drying oven to dry.

[0044] In this embodiment, TiAl4822 powder with an average particle size of 95 μm and Nb powder with an average particle size of 0.8 μm were selected. The chemical composition (wt.%) of TiAl4822 powder is: Al 34%, Cr 2.5%, Nb 5%, O 0.07%, C 0.018%, N 0.018%, H 0.002%, Fe 0.05%, Ni 0.04%, with the balance being Ti; the chemical composition (wt.%) of submicron purity Nb powder is: Nb 99.92%, O 0.06%, C 0.01%, N 0.006%, and H 0.004%.

[0045] TiAl4822 powder and high-purity Nb powder were placed in a vacuum drying oven and dried at 80°C in a vacuum environment (<10⁻²Pa) or a high-purity argon protective atmosphere for 10 hours to obtain dried TiAl4822 powder and high-purity Nb powder.

[0046] Steps S2 and S3 are largely the same as in Example 1, except that in step S3 the substrate is heated to 600°C.

[0047] S4: TiAl4822 powder is sprayed onto the surface of TC4 substrate using a coaxial powder feeding method. Laser melting deposition technology is used to melt and deposit TiAl4822 powder according to a preset trajectory, so that the molten alloy powder can be rapidly solidified and crystallized to form multiple single-layer cladding coatings as a pre-alloy layer for TiAl-based alloys. Inert gas is continuously introduced throughout the laser composite additive manufacturing process to form a positive pressure protective environment.

[0048] This embodiment uses a YLS4000 IPG fiber laser for laser deposition fabrication. The laser power is set at 1600W, the spot diameter is 2000μm, the overlap ratio is controlled at 60%, and the scanning speed is 1500mm / s. TiAl4822 powder is sprayed onto the surface of a TC4 substrate using a coaxial powder feeding method, followed by laser irradiation to form a localized molten pool. Rapid solidification then generates a TiAl-based alloy pre-alloy layer with a thickness of approximately 40μm. The powder mass flow rate from the powder feeding nozzle is 10g / min, argon is used as the powder transport gas, and the protective gas flow rate is 8L / min.

[0049] S5: First, using argon gas as the powder transport gas through a powder delivery nozzle, Nb powder is uniformly spread to the surface of the TiAl-based alloy pre-layer with a compacted thickness of approximately 40 μm. The powder mass flow rate is 8 g / min, and the protective gas flow rate is 8 L / min. Then, a three-axis robotic arm adjusts its motion trajectory and Z-axis height in real time based on the surface height of the cooled substrate and the powder thickness. A highly flat quartz glass sheet is precisely placed over the powder layer surface, and a uniform surface pressure of 0.15 MPa is applied to ensure full adhesion between the quartz glass and the powder layer, forming a rigid constraint layer for the powder absorption layer. Finally, a 532 nm nanosecond laser is used for laser shock, and the three-axis robotic arm movement is coupled through the laser beam focus to uniformly embed the Nb powder into the TiAl-based alloy pre-layer.

[0050] During laser pulse transmission, the quartz glass confinement layer effectively suppresses the free expansion of plasma, significantly enhancing the pressure and duration of the high-pressure shock wave. This allows Nb particles to be uniformly dispersed and embedded in the plastic region of the TiAl pre-alloy surface in an elemental state, forming a non-solid-solution uniformly embedded structure, thus achieving the preparation of a high-strength and high-toughness TiAl-based alloy. After each layer of laser shock is completed, the three-axis robotic arm automatically compensates for height changes in the Z-axis direction to ensure that the laser focus remains consistent with the quartz glass surface in subsequent cycles.

[0051] The laser power is 70W, the pulse repetition frequency is 25kHz, the pulse width is 15ns, the overlap rate is 50%, and the scanning speed is 60mm / s.

[0052] Repeat steps S4 to S5, that is, sequentially perform the layer-by-layer interaction of laser melting deposition and pulsed laser shock processes until the dimensions of the high-strength and tough TiAl-based alloy prepared by laser composite additive manufacturing meet the requirements.

[0053] The high-strength and high-toughness TiAl-based alloy material prepared in this example possesses comprehensive mechanical properties that combine high strength with good plasticity. At room temperature, the alloy exhibits a tensile strength of approximately 700 MPa and a yield strength of approximately 635 MPa, demonstrating excellent load-bearing capacity. The elongation is consistently around 7.5%, and the reduction of area (Z) reaches approximately 11.5%, showcasing good plasticity and toughness. At 700°C, the alloy material retains a high-temperature strength of approximately 650 MPa. Combined with its low density (approximately 4.7 g / cm³), this alloy material achieves an excellent strength-to-weight ratio while maintaining its mechanical properties, making it suitable for high-performance structural applications.

[0054] It is understandable that high-strength and high-toughness TiAl-based alloys can also be prepared by using TiAl4822 powder and Nb powder with different particle sizes and chemical compositions in different embodiments, as well as by modifying other process parameters; therefore, this will not be elaborated further. The high-strength and high-toughness TiAl-based alloys prepared through multiple experiments exhibit tensile strengths of 700–720 MPa and yield strengths ranging from approximately 620–660 MPa at room temperature, demonstrating strong load-bearing capacity and excellent tensile strength. Compared to traditional… γ TiAl alloys, particularly high-strength and high-toughness TiAl-based alloys, exhibit elongation that can consistently reach 6%–8%, significantly improving their plasticity. Furthermore, the reduction of area (Z) of these high-strength and high-toughness TiAl-based alloys can reach 10–12%, demonstrating certain fracture plasticity, superior to conventional alloys. γ -TiAl alloy. At high temperatures (700~800°C), this high-strength and high-toughness TiAl-based alloy maintains a high-temperature strength of approximately 600 MPa or higher. Within the temperature range of 200°C to 600°C, the elongation of this high-strength and high-toughness TiAl-based alloy remains no less than 6%.

[0055] In summary, this invention utilizes a combination of laser melting deposition technology and laser shock peening technology to prepare high-strength and high-toughness TiAl-based alloys. These alloys not only possess the advantages of traditional TiAl alloys, such as low density, high specific strength, high elastic modulus, and resistance to high-temperature creep, but also exhibit excellent strength and toughness at room temperature and high-temperature performance. This invention uses laser shock peening technology to mechanically embed high-purity Nb powder into TiAl alloys. By controlling the laser parameters, the high-purity Nb powder embedded in the metal does not undergo solid solution formation with the TiAl alloy, thus preventing the formation of brittle metal compounds. Instead, the high-purity Nb powder particles are distributed in the TiAl matrix in the form of dispersed particles and a small amount of in-situ elemental phases, thereby improving the alloy's plasticity and meeting its application requirements in new energy vehicles, drones, aerospace, and humanoid robot technologies.

[0056] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A laser composite additive manufacturing method for high-strength and high-toughness TiAl-based alloys, characterized in that, The method includes: S1: TiAl4822 powder and Nb powder were dried separately in a vacuum drying oven; the purity of both TiAl4822 powder and Nb powder was above 99.9%; the average particle size of TiAl4822 powder was 40~150μm; the chemical composition of TiAl4822 powder was: Al 32.4~33.6wt.%, Cr 2.4~2.8wt.%, Nb 4.5~5.1wt.%, O≤0.0 8 wt.%, C≤0.02 wt.%, N≤0.02 wt.%, H≤0.005 wt.%, Fe≤0.10 wt.%, Ni≤0.05 wt.%, balance Ti; the average particle size of Nb powder is 0.5~1 μm; the chemical composition of Nb powder is: Nb≥99.9 wt.%, O≤0.065 wt.%, C≤0.02 wt.%, N≤0.01 wt.%, H≤0.005 wt.%; S2: Adjust the distance between the heating induction coil and the substrate to ensure that the substrate is heated efficiently through the skin effect; load the dried TiAl4822 powder and high-purity Nb powder into the coaxial powder feeding system respectively; wherein, the substrate is heated to a temperature of 300~600℃; the substrate is a TC4 alloy plate; S3: Laser melting deposition technology is used to melt and deposit dried TiAl4822 powder onto the substrate surface according to a preset trajectory to form a multi-layer single-layer cladding coating as a pre-alloy layer for TiAl-based alloys; inert gas is continuously introduced throughout the preparation process to form a positive pressure protective environment; S4: After the single-layer cladding coating cools and solidifies, Nb powder is laid on its surface; a three-axis robotic arm is used to press a transparent quartz glass onto the Nb powder, and then a single high peak intensity pulsed laser is used to mechanically and uniformly embed the Nb powder into the pre-alloy layer of the TiAl-based alloy through laser shock strengthening, so as to ensure that the Nb element is dispersed in the TiAl-based alloy in the form of elemental rather than solid solution; by repeating the laser shock process multiple times, the content of elemental Nb in the TiAl-based alloy and its distribution uniformity are improved; S5: Repeat steps S3 and S4 to achieve layer-by-layer interaction between laser melting deposition and pulsed laser shock processes, and repeat this process until the dimensions of the prepared high-strength and tough TiAl-based alloy meet the requirements.

2. The laser composite additive manufacturing method according to claim 1, characterized in that, A fiber laser was used to laser melt and deposit dried TiAl4822 powder onto the surface of a substrate. The laser melting deposition process parameters were as follows: laser power of 1200~1600W, scanning speed of 1000~2000mm / s, spot diameter of 1500~3000μm, overlap rate of 30~70%, and layer thickness of 35~50μm.

3. The laser composite additive manufacturing method according to claim 1, characterized in that, A nanosecond laser is used to mechanically and uniformly embed Nb powder into the pre-alloy layer of a TiAl-based alloy. The laser shock process parameters are as follows: laser power of 10~100W, pulse repetition frequency of 1~20kHz, pulse width of 5~30ns, scanning speed of 1~100mm / s, and overlap rate of 30~70%.

4. The laser composite additive manufacturing method according to claim 1, characterized in that, A coaxial powder feeding method is used to uniformly spray and lay each layer of Nb powder with a thickness of 30~50μm onto the surface of a single-layer cladding coating. The three-axis robotic arm adjusts its motion trajectory and Z-axis position in real time according to the surface height of the cooled TiAl-based alloy and the powder thickness. Then, a high-flatness quartz glass sheet is accurately positioned and covered on the Nb powder layer, and a uniform surface pressure of 0.1~0.3MPa is applied to achieve appropriate compression so that the quartz sheet and the powder layer are fully bonded, forming a rigid quartz glass constraint layer for the powder absorption layer. After each layer is laser-shocked, the three-axis robotic arm automatically compensates for changes in height in the Z-axis direction to ensure that the laser focus remains consistent with the quartz glass surface in subsequent cycles.

5. The laser composite additive manufacturing method according to claim 4, characterized in that, The Nb powder feeding rate is 4~10 g / min, and the inert protective gas flow rate is 5~10 L / min.

6. The laser composite additive manufacturing method according to claim 1, characterized in that, Laser shock strengthening involves the absorption of short-pulse laser shock by surface Nb powder to form high-temperature, high-density plasma, which then rapidly expands to generate a high-pressure shock wave. Transparent quartz glass acts as a confinement layer, restricting the free expansion of the plasma and significantly enhancing the impact effect and duration. This effectively embeds the pre-laid Nb powder into the plastic zone of the pre-alloy layer of the TiAl-based alloy, allowing Nb particles to be uniformly dispersed within the alloy in an elemental state, thus achieving a non-solid-solution, uniformly embedded structure.

7. The laser composite additive manufacturing method according to claim 6, characterized in that, The mass fraction of elemental Nb particles is 20~40 wt.%; Nb is dispersed and embedded in TiAl-based alloys in the form of elemental particles, and is also distributed in TiAl matrix in the form of a small amount of in-situ phase, thereby improving plastic deformation capacity and fracture toughness.

8. The laser composite additive manufacturing method according to any one of claims 1 to 7, characterized in that, The inert gas is argon.

9. A high-strength and high-toughness TiAl-based alloy, characterized in that, It was prepared based on the laser composite additive manufacturing method according to any one of claims 1 to 8.

10. An application of a high-strength and high-toughness TiAl-based alloy, characterized in that, Applications of high-strength and high-toughness TiAl-based alloys prepared by the laser composite additive manufacturing method according to any one of claims 1 to 8 in the fields of new energy vehicles, drones, aerospace and humanoid robot technology.

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