Method for homogenizing TiAl alloy structure in additive manufacturing

Abstract

The invention relates to the technical field of metal material additive manufacturing, in particular to an additive manufacturing TiAl alloy structure homogenization method. According to the method, 1.5 at.%-2.5 at.% of an Al element is added into a TiAl alloy for compensation, then TiAl alloy powder is prepared, electron beam selective melting printing is carried out, short-time circulating heat treatment is carried out after hot isostatic pressing treatment is carried out, the temperature in the short-time circulating heat treatment process is 5-20 DEG C higher than T alpha / (alpha + gamma), and heat preservation is carried out for 3-10 min; according to the method, the problem of non-uniform structure of the TiAl alloy formed by SEBM is synergistically solved by compensating the content of Al element and a short-time circulating heat treatment process, a uniform and fine lamellar structure can be obtained without a complicated process parameter optimization process, the size of a lamellar cluster is smaller than 100 microns and is far lower than that of a lamellar cluster prepared by conventional heat treatment, and the method is suitable for large-scale production. The room-temperature tensile strength of the alloy is at least improved by 150MPa, and the tensile strength at 750 DEG C is at least improved by 80MPa. The process method is simple and high in adaptability, and can be widely applied to additive manufacturing of the TiAl alloy.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology for metallic materials, and specifically to a method for homogenizing the microstructure of TiAl alloys through additive manufacturing. Background Technology

[0002] Currently, TiAl alloys are mainly prepared using traditional processes such as casting and hot working. However, inherent defects generated during casting are difficult to completely eliminate through subsequent processes, and the narrow hot working window leads to high difficulty in process control and low yield, severely restricting its further engineering applications. Selective Electron Beam Melting (SEBM), as an emerging additive manufacturing technology, can achieve near-net-shape forming of complex thin-walled components, effectively avoiding cumbersome subsequent machining and plastic forming processes. This technology integrates advantages such as high vacuum, high preheating temperature, high forming efficiency, and rapid solidification. The rapid solidification characteristic unique to additive manufacturing technology is conducive to the formation of fine-grained structures, thereby improving the overall performance of the material. Therefore, SEBM technology shows great application potential in the preparation of high-performance TiAl alloy components with complex thin-walled structures and is one of the key technologies to promote the engineering application of this alloy, attracting widespread attention.

[0003] In electron beam additive manufacturing, the high vacuum environment exacerbates the volatilization of low-melting-point elements such as Al, leading to a unique banded, heterogeneous microstructure in the electron beam additive TiAl alloy. This heterogeneous structure consists of alternating coarse γ-grained bands and fine (γ+α2) bimorphic bands, essentially classified as a near-γ structure. Such structures exhibit insufficient high-temperature strength and creep resistance. Therefore, subsequent heat treatment is necessary to control the microstructure, aiming to transform it into a lamellar structure and thus endow the TiAl alloy with excellent high-temperature mechanical properties.

[0004] During the SEBM preparation of TiAl alloys, the aforementioned banded non-uniform microstructure is easily formed. This non-uniform microstructure significantly affects the phase transformation behavior during subsequent heat treatment. When using conventional α single-phase annealing, the segregation of Al elements in the non-uniform microstructure leads to different phase transformation behaviors in different regions. α / (α+γ) Phase transition point differences—coarse γ-grained bands with high Al content exhibit higher phase transition points, while fine (γ+α2) bimorphic bands with low Al content show lower phase transition points. This difference in phase transition points leads to significant differences in the kinetic behavior of lamellar structures in different regions during coarsening. However, due to the Tg in low Al regions… α / (α+γ)At lower temperatures, when the heat treatment temperature significantly exceeds the phase transformation point, it induces rapid growth of the α phase, causing coarsening of the lamellar structure in the low-Al region. This coarsening process negates the inherent fine-grain advantage of additive manufacturing, significantly weakening the room-temperature plasticity of the material; moreover, existing methods for controlling the formation of non-uniform TiAl alloys using SEBM are complex and have poor adaptability.

[0005] Therefore, developing an effective method to achieve uniform microstructure in additively manufactured TiAl alloys has become a critical issue that urgently needs to be addressed in this field. Summary of the Invention

[0006] This invention addresses the issue of achieving microstructure homogenization in additively manufactured TiAl alloys. It proposes a method for achieving microstructure homogenization in TiAl alloys, which solves the problems of complex process control and poor adaptability in additive manufacturing of TiAl alloys, and improves the mechanical properties of TiAl alloys. Currently, no related research or invention patents have been published domestically or internationally.

[0007] To achieve the above objectives, this invention proposes a method for homogenizing the microstructure of TiAl alloys through additive manufacturing, comprising the following steps: S1. Add 1.5 at.%~2.5 at.% Al element to TiAl alloy by atomic percentage to prepare TiAl alloy ingot after Al element compensation; S2. The TiAl alloy ingot is atomized by plasma rotating electrode to prepare TiAl alloy powder, which is then screened to obtain TiAl alloy powder for later use. S3. The TiAl alloy powder is subjected to electron beam selective melting printing, wherein the substrate preheating temperature is 1100℃~1250℃. S4. The printed TiAl alloy is subjected to hot isostatic pressing to obtain a dense TiAl alloy. S5. Short-time cycle heat treatment; the TiAl alloy after hot isostatic pressing is then subjected to T... α / (α+γ) The process involves heating at 5°C-20°C for 3-10 minutes, cooling to room temperature, and repeating this cycle 3-8 times to obtain a TiAl alloy with uniform and fine lamellar clusters, the lamellar cluster size being <100μm. α / (α+γ) This is the transition temperature from the α single-phase region to the α+γ two-phase region.

[0008] Preferably, in step S2, the particle size of the screened powder is 45μm~150μm.

[0009] Preferably, in step S3, during the electron beam selective melting printing process, the powder layer thickness is 50μm~90μm, the electron beam scanning speed is 3000mm / s~4500mm / s, the electron beam current is 9mA~10mA, the scanning spacing is 0.1mm, and the accelerating voltage is 60kV.

[0010] Preferably, in step S4, during the hot isostatic pressing process, the temperature is 1200℃~1300℃, the pressure is 140MPa~200MPa, the holding time is 2h~6h, and the furnace is cooled to room temperature.

[0011] Preferably, in step S5, the lamellar cluster size of the TiAl alloy is 15μm-60μm.

[0012] Preferably, in step S5, the cooling method is air cooling or oil cooling.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention addresses the issue of microstructure inhomogeneity in SEBM-formed TiAl alloys through a combination of Al content compensation and short-time cyclic heat treatment. It achieves a uniform and fine lamellar structure without requiring complex process parameter optimization, with lamellar cluster sizes less than 100 μm, significantly smaller than those obtained through conventional heat treatment. The fine and uniform lamellar structure regulated by short-time cyclic heat treatment exhibits excellent mechanical properties, with room temperature elongation typically exceeding 1.0%, room temperature tensile strength increased by at least 150 MPa, and tensile strength at 750°C increased by at least 80 MPa. Compared to methods that adjust process parameters to eliminate microstructure inhomogeneity, the short-time cyclic heat treatment process is simple, highly adaptable, and widely applicable to additive manufacturing of TiAl alloys. Attached Figure Description

[0014] Figure 1 This is a microstructure diagram of the deposited TiAl alloy after electron beam selective melting in Example 1 of the present invention.

[0015] Figure 2 This is a microstructure diagram of the TiAl alloy after hot isostatic pressing in Example 1 of the present invention.

[0016] Figure 3 This is a microstructure diagram of the TiAl alloy after short-time cyclic heat treatment in Example 1 of the present invention.

[0017] Figure 4 This is a microstructure diagram of the TiAl alloy after conventional heat treatment in Comparative Example 2 of this invention. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0019] This invention proposes a method for homogenizing the microstructure of TiAl alloys in additive manufacturing, comprising the following steps: S1. Add 1.5 at.%~2.5 at.% Al element to TiAl alloy by atomic percentage to prepare TiAl alloy ingot after Al element compensation; Specifically, the strategy for compensating for Al in this invention is as follows: Al volatilization during electron beam additive manufacturing leads to the formation of non-uniform structures, resulting in uneven T values ​​in different regions. α / (α+γ) Differences in phase transition points exacerbate the difficulty of controlling tissue homogenization; therefore, Al element compensation is performed before electron beam selective melting printing, i.e., electron beam additive manufacturing.

[0020] S2. TiAl alloy powder is prepared by plasma rotating electrode atomization of TiAl alloy ingot and then screened to obtain TiAl alloy powder for later use. Specifically, the particle size of the powder screened in step S2 is 45μm~150μm.

[0021] S3. Electron beam selective melting printing is performed on TiAl alloy powder, wherein the substrate preheating temperature is preferably 1100℃~1250℃, for example, 1100℃, 1150℃, 1180℃, 1200℃, or 1250℃. Specifically, in the electron beam selective melting printing process in step S3, the powder layer thickness is preferably 50μm~90μm, for example, 50μm, 60μm, 70μm, 80μm, or 90μm; the electron beam scanning speed is preferably 3000mm / s~4500mm / s, for example, 3000mm / s, 3500mm / s, 3800mm / s, 4000mm / s, or 4500mm / s; the electron beam current is preferably 9mA~10mA, for example, 9mA, 9.5mA, or 10mA; the scanning spacing is 0.1mm; and the accelerating voltage is 60kV.

[0022] S4. Perform hot isostatic pressing on the printed TiAl alloy. Specifically, during the hot isostatic pressing process, the preferred temperature is 1200℃~1300℃, for example, 1200℃, 1250℃, 1280℃, or 1300℃; the preferred pressure is 140MPa~200MPa, for example, 140MPa, 150MPa, 160MPa, 170MPa, 180MPa, 190MPa, or 200MPa; and the preferred holding time is 2h~6h, for example, 2h, 3h, 4h, 5h, or 6h. After cooling to room temperature in the furnace, a dense TiAl alloy is obtained.

[0023] S5. Short-time cycle heat treatment; the TiAl alloy after hot isostatic pressing is subjected to a preferred T... α / (α+γ) + (5°C-20°C), for example, it can be T α / (α+γ) +5°C, T α / (α+γ) +10°C, T α / (α+γ) +15°C, T α / (α+γ) +20°C, hold for 3-10 minutes (e.g., 3, 5, 7, 9, or 10 minutes), then air-cool or oil-cool to room temperature. Cycle 3-8 times (e.g., 3, 5, 6, 7, or 8 times) to obtain a TiAl alloy with uniform and fine lamellar size <100 μm. α / (α+γ) This is the transition temperature from the α single-phase region to the α+γ two-phase region.

[0024] Specifically, after hot isostatic pressing, the holding temperature during the heat treatment process is higher than that in the high Al region. α / (α+γ) The process employs a strategy of short-time heat treatment and rapid cooling. On the one hand, short-time heat treatment prevents the rapid growth of the α phase in the low-Al region. On the other hand, rapid cooling forms a large number of non-equilibrium γ phases, which can delay the abnormal growth of the α phase in the low-Al region during repeated heating. Then, through multiple short-time cyclic heat treatments, sufficient time is provided for the high-Al region to complete the transformation from near-γ structure to lamellar structure, while effectively inhibiting the coarsening of lamellar structure in the low-Al region. Finally, a fine and uniform lamellar structure is obtained, with lamellar clusters ranging in size from 15 μm to 60 μm.

[0025] The present invention will be further described below with reference to the embodiments.

[0026] Example 1 The TiAl alloy used in this embodiment has a composition of Ti-45.5Al-4Nb-1Mo-0.1B (all atomic percentages). The specific steps to homogenize the alloy structure are as follows: Step 1: Prepare Ti-45.5Al-4Nb-1Mo-0.1B alloy ingot, add 1.5 at.%Al compensation, and finally prepare Ti-47Al-4Nb-1Mo-0.1B alloy ingot.

[0027] Step 2: Ti-47Al-4Nb-1Mo-0.1B alloy powder was prepared by plasma rotating electrode atomization, and Ti-47Al-4Nb-1Mo-0.1B alloy powder with a particle size of 45-150μm was screened out.

[0028] Step 3: Electron beam selective melting printing was used to create a small bulk sample of Ti-47Al-4Nb-1Mo-0.1B alloy, with dimensions of 12mm × 80mm × 70mm. The substrate preheating temperature was set to 1200℃, powder layer thickness to 90μm, scanning speed to 4000mm / s, electron beam current to 9.5mA, scanning spacing to 0.1mm, and accelerating voltage to 60kV. Compositional analysis showed that the actual composition of the deposited alloy was Ti-45.57Al-4.10Nb-1.10Mo-0.14B, within the error range of the nominal composition, meeting the compositional requirements. Further characterization revealed that the deposited microstructure was a non-uniform structure, characterized by alternating γ-coarse grain bands and (γ+α2) fine bimorphic grain bands. Figure 1 As shown.

[0029] Step 4: The small alloy bulk samples were subjected to hot isostatic pressing (HIP) at 1290℃ / 170MPa / 4h. This eliminated the "keyhole" and porosity defects of the deposited sample, resulting in a dense additive-manufactured Ti-45.5Al-4Nb-1Mo-0.1B alloy bulk sample. However, the inhomogeneity of the alloy microstructure was not eliminated, and the microstructure of the HIP state was as follows: Figure 2 As shown.

[0030] Step 5: Determine the T in the high Al region of the Ti-45.5Al-4Nb-1Mo-0.1B alloy using phase diagrams and metallographic methods. α / (α+γ) The temperature was 1320℃. Based on this, the small bulk samples of the Ti-45.5Al-4Nb-1Mo-0.1B alloy were subjected to the following heat treatment: at 1335℃ (i.e., T...). α / (α+γ) The mixture was held at 15°C for 5 minutes, then air-cooled to room temperature, and this heat treatment was repeated four times. After this short-cycle heat treatment, a fine and uniform lamellar structure was obtained, such as... Figure 3 As shown.

[0031] Mechanical property tests showed that the fine lamellar Ti-45.5Al-4Nb-1Mo-0.1B alloy prepared by short-time cyclic heat treatment had a room temperature tensile strength of 687 MPa, a fracture elongation of 1.1%, and a tensile strength of 650 MPa at 750℃.

[0032] Example 2 The TiAl alloy used in this embodiment has a composition of Ti-47Al-2Nb-2Cr (all atomic percentages). The specific steps to homogenize the alloy structure are as follows: Step 1: Prepare Ti-47Al-2Nb-2Cr alloy ingots, add 2.5 at.% Al compensation, and finally prepare Ti-47Al-2Nb-2Cr alloy ingots.

[0033] Step 2: Ti-47Al-2Nb-2Cr alloy powder was prepared by plasma rotating electrode atomization, and Ti-47Al-2Nb-2Cr alloy powder with a particle size of 45-150μm was screened out.

[0034] Step 3: Electron beam selective melting printing of Ti-47Al-2Nb-2Cr alloy low-pressure turbine blade blanks; the substrate preheating temperature was set to 1100℃, powder layer thickness to 50μm, scanning speed to 3000mm / s, electron beam current intensity to 9mA, scanning spacing to 0.1mm, and accelerating voltage to 60kV. Compositional analysis results showed that the actual composition of the deposited alloy was Ti-47Al-2Nb-2Cr, and the deviation from the nominal composition was within the error range, meeting the composition requirements. The deposited microstructure was a non-uniform structure, specifically characterized by alternating γ-coarse grain bands and (γ+α2) fine bimorphic grain bands along the printing direction.

[0035] Step 4: The alloy low-pressure turbine blade blank was subjected to hot isostatic pressing at 1300℃ / 140MPa / 2h. This eliminated the "keyhole" and porosity defects in the deposited sample, resulting in a dense additively manufactured Ti-47Al-2Nb-2Cr alloy low-pressure turbine blade blank. However, significant inhomogeneity still existed in the microstructure.

[0036] Step 5: Determine the T in the high Al region of the Ti-47Al-2Nb-2Cr alloy using phase diagrams and metallographic methods. α / (α+γ) The temperature is 1350℃. Based on this, the Ti-47Al-2Nb-2Cr alloy low-pressure turbine blade blank is subjected to the following heat treatment: at 1355℃ (i.e., T...). α / (α+γ) The sample was kept at 5°C for 10 minutes, then cooled to room temperature using oil cooling. This heat treatment was repeated 8 times. After a short cycle of heat treatment, a fine and uniform lamellar structure was obtained.

[0037] Mechanical property tests showed that the fine lamellar Ti-47Al-2Nb-2Cr alloy prepared by short-time cyclic heat treatment had a room temperature tensile strength of 642 MPa, a fracture elongation of 1.2%, and a tensile strength of 657 MPa at 650℃.

[0038] Example 3 In this embodiment, the TiAl alloy composition used is Ti-45Al-2Nb-2Mn-0.2B (all atomic percentages). The specific steps to homogenize the alloy structure are as follows: Step 1: Prepare Ti-45Al-2Nb-2Mn-0.2B alloy ingots, add 2 at.%Al compensation, and finally prepare Ti-45Al-2Nb-2Mn-0.2B alloy ingots.

[0039] Step 2: Ti-45Al-2Nb-2Mn-0.2B alloy powder was prepared by plasma rotating electrode atomization, and Ti-45Al-2Nb-2Mn-0.2B alloy powder with a particle size of 45-150μm was screened out.

[0040] Step 3: Electron beam selective melting printing of a Ti-45Al-2Nb-2Mn-0.2B alloy diffuser; the substrate preheating temperature was set to 1250℃, powder layer thickness to 50μm, scanning speed to 4500mm / s, electron beam current to 10mA, scanning spacing to 0.1mm, and accelerating voltage to 60kV. Compositional analysis results showed that the actual composition of the deposited alloy was Ti-45Al-2Nb-2Mn-0.2B, and the deviation from the nominal composition was within the error range, meeting the composition requirements. Microstructural observation showed that the deposited microstructure exhibited significant heterogeneity, displaying two different morphological characteristics.

[0041] Step 4: The alloy diffuser was subjected to hot isostatic pressing at 1200℃ / 200MPa / 6h. This eliminated the "keyhole" and pore defects in the deposited sample, resulting in a dense additively manufactured Ti-45Al-2Nb-2Mn-0.2B alloy diffuser. However, the internal non-uniformity of the microstructure remained significant.

[0042] Step 5: Determine the T in the high Al region of the Ti-45Al-2Nb-2Mn-0.2B alloy using metallographic methods. α / (α+γ) The temperature was 1300℃. Based on this, small bulk samples of the Ti-45Al-2Nb-2Mn-0.2B alloy were subjected to the following heat treatment: at 1320℃ (i.e., T...). α / (α+γ) The sample was held at 20°C for 3 minutes, then cooled to room temperature by air cooling, and the same heat treatment was repeated 3 times. After a short cycle of heat treatment, a fine and uniform lamellar structure was obtained.

[0043] Mechanical property tests showed that the fine-grained Ti-45Al-2Nb-2Mn-0.2B alloy prepared by short-time cyclic heat treatment had a room temperature tensile strength of 626 MPa, a fracture elongation of 1.3%, and a tensile strength of 591 MPa at 750℃.

[0044] Comparative Example 1 The TiAl alloy composition used in this comparative example is Ti-45.5Al-4Nb-1Mo-0.1B (all are atomic percentages).

[0045] In step 1, Al compensation is not performed, and the remaining steps are the same as in Example 1.

[0046] The actual composition of the alloy after electron beam selective printing in this comparative example is Ti-44.21Al-4.08Nb-1.05Mo-0.13B (at.%). The alloy without Al element compensation has a chemical composition that deviates significantly from the nominal composition after electron beam selective melting and forming, and cannot meet the usage requirements.

[0047] Comparative Example 2 The TiAl alloy composition used in this comparative example is Ti-45.5Al-4Nb-1Mo-0.1B (all are atomic percentages).

[0048] In step 5, conventional α-single-phase annealing is employed. The T-phase temperature of the high-Al region in the Ti-45.5Al-4Nb-1Mo-0.1B alloy is determined using phase diagrams and metallographic methods. α / (α+γ) The Ti-45.5Al-4Nb-1Mo-0.1B alloy bulk small samples were subjected to the following heat treatment at 1320℃: [Temperature not specified in the original text]. α / (α+γ) The sample was kept at 15°C for 60 minutes, and then cooled to room temperature using a furnace. The remaining steps were the same as in Example 1.

[0049] The microstructure of the alloy in this comparative example after α single-phase region annealing is as follows: Figure 4 As shown, compared to the microstructure diagram after short-time cyclic heat treatment in Example 1, the lamellar clusters in the low-Al region are larger.

[0050] Through mechanical property testing, the room temperature tensile strength of the alloy in this comparative example after α single-phase annealing was 527 MPa, which was about 160 MPa higher than that in Example 1. The room temperature elongation at break was 3.3%, which was twice that of Example 1. The tensile strength at 750°C was 575 MPa, which was 85 MPa higher than that of Example 1.

[0051] Comparative Example 3 The TiAl alloy composition used in this comparative example is Ti-47Al-2Nb-2Cr (all are atomic percentages).

[0052] In step 1, Al compensation is not performed; the remaining steps are the same as in Example 2.

[0053] The actual composition of the alloy in this comparative example after electron beam selective printing in step 3 is Ti-45.36Al-2.11Nb-2.06Cr; the alloy without added Al element compensation has a chemical composition that deviates significantly from the nominal composition after electron beam selective melting and forming, and cannot meet the usage requirements.

[0054] Comparative Example 4 The TiAl alloy composition used in this comparative example is Ti-47Al-2Nb-2Cr (all are atomic percentages).

[0055] In step 5, conventional α-single-phase annealing is employed. The T0 in the high-Al region of the Ti-47Al-2Nb-2Cr alloy is determined using phase diagrams and metallographic methods. α / (α+γ) The Ti-47Al-2Nb-2Cr alloy low-pressure turbine blade blank was subjected to the following heat treatment at 1350℃: α / (α+γ) The sample was kept at 5°C for 120 minutes, and then cooled to room temperature using a furnace. The remaining steps were the same as in Example 2.

[0056] Through mechanical property testing, the room temperature tensile strength of the alloy in this comparative example after α single-phase annealing was 477 MPa, which was about 165 MPa higher than that in Example 2. The room temperature elongation at break was 2.45%, which was doubled in Example 2. The tensile strength at 650°C was 567 MPa, which was increased by 90 MPa in Example 2.

[0057] Comparative Example 5 The TiAl alloy composition used in this comparative example is Ti-45Al-2Nb-2Mn-0.2B (all are atomic percentages).

[0058] In step 1, Al compensation is not performed, and the remaining steps are the same as in Example 3.

[0059] The actual composition of the alloy after electron beam selective printing in this comparative example is Ti-45Al-2Nb-2Mn-0.2B (at.%). The alloy without added Al element compensation has a chemical composition that deviates significantly from the nominal composition after electron beam selective melting and forming, and cannot meet the usage requirements.

[0060] Comparative Example 6 The TiAl alloy composition used in this comparative example is Ti-45Al-2Nb-2Mn-0.2B (all are atomic percentages).

[0061] In step 5, conventional α-single-phase annealing is employed. The T0 of the high-Al region in the Ti-45Al-2Nb-2Mn-0.2B alloy is determined using phase diagrams and metallographic methods. α / (α+γ)The Ti-45.5Al-4Nb-1Mo-0.1B alloy bulk small samples were subjected to the following heat treatment at 1300℃: 1320℃ (i.e., T... α / (α+γ) The sample was kept at 20°C for 45 minutes, and then cooled to room temperature using a furnace cooling method. The remaining steps were the same as in Example 1.

[0062] In the microstructure of the alloy after α single-phase annealing in this comparative example, the equiaxed γ phase in the low Al region rapidly transforms into lamellar structure; in the high Al region, some of the equiaxed γ phase does not completely transform into lamellar structure.

[0063] Through mechanical property testing, the room temperature tensile strength of the alloy in this comparative example after α single-phase annealing was 476 MPa, which was about 150 MPa higher than that in Example 3. The room temperature elongation at break was 1.56%, which was about 120% higher in Example 3. The tensile strength at 750°C was 511 MPa, which was 80 MPa higher in Example 3.

[0064] In summary, this application, through Al element compensation and short-time cyclic heat treatment, synergistically homogenizes the microstructure of TiAl alloy, obtaining a uniform and fine lamellar structure with lamellar clusters smaller than 100 μm. This increases the room temperature tensile strength of the alloy by at least 150 MPa and the 750℃ tensile strength by at least 80 MPa. Compared to methods that adjust process parameters to eliminate microstructure inhomogeneity, the short-time cyclic heat treatment process is simple, highly adaptable, and widely applicable to additive manufacturing of TiAl alloys.

[0065] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0066] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0067] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for homogenizing the microstructure of TiAl alloys in additive manufacturing, characterized in that, Includes the following steps: S1. Add 1.5 at.%~2.5 at.% Al element to TiAl alloy by atomic percentage to prepare TiAl alloy ingot after Al element compensation; S2. The TiAl alloy ingot is atomized by plasma rotating electrode to prepare TiAl alloy powder, which is then screened to obtain TiAl alloy powder for later use. S3. The TiAl alloy powder is subjected to electron beam selective melting printing, wherein the substrate preheating temperature is 1100℃~1250℃. S4. The printed TiAl alloy is subjected to hot isostatic pressing to obtain a dense TiAl alloy. S5. Short-time cycle heat treatment; the TiAl alloy after hot isostatic pressing is then subjected to T... α / (α+γ) The process involves heating at 5°C-20°C for 3-10 minutes, cooling to room temperature, and repeating this cycle 3-8 times to obtain a TiAl alloy with uniform and fine lamellar clusters, the lamellar cluster size being <100μm. α / (α+γ) This is the transition temperature from the α single-phase region to the α+γ two-phase region.

2. The method for homogenizing the microstructure of TiAl alloy in additive manufacturing according to claim 1, characterized in that, In step S2, the particle size of the screened powder is 45μm~150μm.

3. The method for homogenizing the microstructure of TiAl alloy in additive manufacturing according to claim 1, characterized in that, In step S3, during the electron beam selective melting printing process, the powder layer thickness is 50μm~90μm, the electron beam scanning speed is 3000mm / s~4500mm / s, the electron beam current is 9mA~10mA, the scanning spacing is 0.1mm, and the accelerating voltage is 60kV.

4. The method for homogenizing the microstructure of TiAl alloy in additive manufacturing according to claim 1, characterized in that, In step S4, during the hot isostatic pressing process, the temperature is 1200℃~1300℃, the pressure is 140MPa~200MPa, the pressure holding time is 2h~6h, and the furnace is cooled to room temperature.

5. The method for homogenizing the microstructure of TiAl alloy in additive manufacturing according to claim 1, characterized in that, In step S5, the lamellar cluster size of the TiAl alloy is 15μm-60μm.

6. The method for homogenizing the microstructure of TiAl alloy in additive manufacturing according to claim 1, characterized in that, In step S5, the cooling method is either air cooling or oil cooling.

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