Method for eliminating beta segregation defect of in-situ alloying additive manufacturing titanium alloy

Abstract

The invention discloses a method for eliminating the beta segregation defect of an in-situ alloying additive manufacturing titanium alloy, which is characterized in that in-situ alloying additive manufacturing is carried out by adding a certain amount of Fe element, and Fe is utilized to promote the formation of a nearly equiaxed microstructure and the grain refinement, so that the strength of the titanium alloy is enhanced. Meanwhile, through rapid heat treatment, elements in the alloy are more uniformly distributed, composition segregation is reduced, formation of acicular martensite is inhibited, a microstructure is optimized, the plasticity of the material is improved, and finally synergistic improvement of the strength and plasticity of the titanium alloy is achieved; and the problem of grain growth caused by long-time heat treatment is avoided, the production cost is reduced, the production efficiency is improved, and large-scale popularization and application are easier.

Description

Technical Field

[0001] This application relates to the fields of metal material processing and additive manufacturing technology, and in particular to a method for eliminating beta segregation defects in in-situ alloying additive manufacturing of titanium alloys. Background Technology

[0002] Titanium alloys, due to their high strength, low density, good corrosion resistance, and high-temperature performance, are widely used in aerospace, automotive manufacturing, biomedicine, and many other fields. With technological advancements, the complexity of shapes and performance requirements for titanium alloy parts are constantly increasing, making traditional processing techniques insufficient. Additive manufacturing technology, as an emerging manufacturing method, enables the direct fabrication of complex-shaped parts, bringing new opportunities for titanium alloy processing. In-situ alloying additive manufacturing technology has unique advantages in titanium alloy processing; by adding alloying elements during the additive manufacturing process, the performance of titanium alloys can be effectively improved. However, in the in-situ alloying additive manufacturing of titanium alloys, beta spots (segregation defects) are prone to occur, severely affecting the performance and quality of the printed material. The presence of beta spots leads to inhomogeneous internal structure of the material, reducing its strength, plasticity, and fatigue properties, thus limiting the application of in-situ alloying additive manufacturing of titanium alloys in high-end fields.

[0003] Currently, the common methods for treating beta spots (segregation defects) in in-situ alloying additive manufacturing of titanium alloys mainly involve extending the heat treatment time or employing complex multi-step heat treatment processes. While extending the heat treatment time can improve elemental segregation to some extent, it increases production costs, reduces production efficiency, and may even lead to grain growth, affecting the overall properties of the material. Complex multi-step heat treatment processes require precise control of parameters such as temperature, time, and cooling rate at each step, placing high demands on equipment and operators, and are complex to operate, making large-scale application difficult. These shortcomings of existing technologies urgently necessitate a new, efficient, simple, and effective method to eliminate beta spots. Summary of the Invention

[0004] This invention discloses a method for eliminating beta segregation defects in in-situ alloying additive manufacturing of titanium alloys, thereby solving any of the existing and other potential problems.

[0005] To achieve the above objectives, the technical solution of this invention is: a method for eliminating beta segregation defects in in-situ alloyed additive manufacturing of titanium alloys. This method involves adding a certain amount of Fe element for in-situ alloying, utilizing Fe to promote the formation of a near-equiaxed microstructure and grain refinement, thereby enhancing the strength of the titanium alloy. Simultaneously, rapid heat treatment ensures a more uniform distribution of elements in the alloy, reducing compositional segregation, suppressing the formation of acicular martensite, optimizing the microstructure, and improving the material's plasticity, thus achieving a synergistic improvement in both the strength and plasticity of the titanium alloy. Furthermore, the method specifically includes the following steps: S1) Weigh the matrix powder and Fe powder according to the design ratio, mix the weighed powders, and then place the mixed powder in a vacuum drying oven for drying to obtain mixed alloy powder; S2) The mixed alloy powder obtained in S1) is printed using DED or SLM technology to obtain titanium alloy parts; S3) The titanium alloy parts obtained in S2) are subjected to rapid heat treatment, held at a certain temperature for a period of time, and then quickly placed in water for quenching and cooling.

[0006] Furthermore, the Fe powder in S1) has a mass percentage of 1.2-5%, with the remainder being matrix powder and unavoidable impurities.

[0007] Furthermore, the matrix powder is Ti powder or TC4 powder with a particle size of 15-53 micrometers; the Fe powder has a particle size of 0.1-10 micrometers.

[0008] Furthermore, the specific process of powder mixing and drying in S1) is as follows: the powder mixing equipment is a three-dimensional swing mixer, the medium is [missing information], the rotation speed is 40-100 rpm, and the powder mixing time is 2.5-3.5 h; The drying temperature is 65-75℃, and the drying time is 7-9 hours.

[0009] Furthermore, the specific parameters of the DED technology in S2) are: laser power of 600-1000W, scanning speed of 6-15mm / s, and powder tray rotation speed of 0.2-0.6r / min.

[0010] Furthermore, the specific parameters of the SLM technology in S2) are: laser power of 70-200W, scanning strategy of checkerboard scanning or rotational scanning, and powder layer thickness of 20-50μm.

[0011] Furthermore, in step S3), the heat treatment temperature is 800°C, and the holding time is 20s - 5min.

[0012] A titanium alloy, which is prepared by the above method.

[0013] The principle of this invention is as follows: Iron exhibits an anomalous rapid diffusion phenomenon in titanium alloys. In the additive manufacturing process, micron-sized iron powder is used for in-situ alloying to introduce small-sized beta segregation defects. A short heat treatment time allows iron to diffuse from the beta segregation into the surrounding matrix, eliminating beta segregation, reducing stress concentration during deformation, and restoring the plastic deformation capacity of the in-situ alloyed Ti-Fe alloy.

[0014] Physical phenomena occurring during short-time heat treatment: (1) The beta-phase stable Fe element is enriched in the beta spot, exceeding its solubility. During the rapid heat treatment process, Fe diffuses from the high-concentration beta spot into the surrounding titanium matrix to achieve an equilibrium low-concentration state, thereby reducing the size of the beta spot and weakening stress concentration. The deformation process is more uniform, and the plasticity is improved.

[0015] (2) At the nanoscale, supersaturated Fe is also enriched in the lamellar α-titanium grains. During rapid heat treatment, Fe also diffuses from the nanoscale lamellar α-titanium grains to the interlamellar region, forming a thin β phase. This reduces the solid solution strengthening effect of Fe in the α phase and lowers the yield strength of the alloy.

[0016] The beneficial technical effects of this invention are as follows: By adopting the above technical solution, the method of this invention, through the addition of Fe element for in-situ alloying, can promote the formation of near-equiaxed microstructure and grain refinement, enhance the strength of titanium alloy, and effectively eliminate segregation defects, thereby improving the uniformity of the internal structure of the material. Furthermore, it is simple to operate, shortens the heat treatment time, avoids grain growth problems caused by prolonged heat treatment, reduces production costs, improves production efficiency, and is easier to promote and apply on a large scale. Attached Figure Description

[0017] To more clearly illustrate the specific methods in the embodiments of the present invention, the relevant performance or data involved in the embodiments will be briefly described below using the accompanying drawings. The drawings below are only some results involved in the embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative changes.

[0018] Figure 1 This is a flowchart of the method for eliminating beta segregation defects in in-situ alloying additive manufacturing of titanium or titanium alloys according to the present invention.

[0019] Figure 2 A schematic diagram comparing the performance of the printed titanium alloy and the titanium alloy after heat treatment according to the present invention.

[0020] Figure 3 This is a schematic diagram of titanium powder and iron powder before they have been processed.

[0021] Figure 4 This is an electron microscope schematic diagram of the iron content in the printed titanium alloy and the titanium alloy after heat treatment according to the present invention.

[0022] Figure 5 The following is a schematic diagram of the heat treatment stress-strain curve of a titanium alloy using TC4 and iron as raw materials in an embodiment of the method of the present invention; (a) SLM printing of TC4+3Fe alloy, (b) DED printing of TC4+3Fe alloy. Detailed Implementation

[0023] To better illustrate the characteristics of the present invention, the present invention will be further described below with reference to embodiments. It should be noted that the following content is illustrative of the present invention and not a limitation thereof, and the implementation of the present invention is not limited to the following methods.

[0024] This invention discloses a method for eliminating beta segregation defects in titanium alloys manufactured through in-situ alloying additive manufacturing. The method involves adding a certain amount of Fe element for in-situ alloying, utilizing Fe to promote the formation of near-equiaxed microstructures and grain refinement, thereby enhancing the strength of the titanium alloy. Simultaneously, rapid heat treatment ensures a more uniform distribution of elements in the alloy, reducing compositional segregation, suppressing the formation of acicular martensite, optimizing the microstructure, and improving the material's plasticity, achieving a synergistic improvement in both the strength and plasticity of the titanium alloy. Furthermore, the method specifically includes the following steps: S1) Weigh the matrix powder and Fe powder according to the designed ratio, mix the weighed powders, and then place the mixed powder in a vacuum drying oven for drying to obtain mixed alloy powder; the purpose is to improve the mechanical properties of the titanium matrix and reduce the development cost of titanium alloys. The Fe powder comprises 1.2-5% by mass, with the remainder being matrix powder and unavoidable impurities.

[0025] S2) The mixed alloy powder obtained in S1) is printed using DED or SLM technology to obtain titanium alloy parts; the printing process achieves in-situ alloying and improves the performance of titanium alloys. S3) The titanium alloy parts obtained in S2) are subjected to rapid heat treatment, held at a certain temperature for a period of time, and then quickly immersed in water for quenching and cooling. Figure 1 As shown.

[0026] Furthermore, the matrix powder is Ti powder or TC4 powder with a particle size of 15-53 micrometers; the Fe powder has a particle size of 0.1-10 micrometers. Furthermore, the specific process of powder mixing and drying in S1) is as follows: the powder mixing equipment is a three-dimensional oscillating mixer, the medium is [missing information], the rotation speed is [missing information], and the mixing time is 2.5-3.5h; The drying temperature is 65-75℃, and the drying time is 7-9 hours.

[0027] Furthermore, the specific parameters of the DED technology in S2) are: laser power of 600-1000W, scanning speed of 6-15mm / s, and powder tray rotation speed of 0.2-0.6r / min.

[0028] Furthermore, the specific parameters of the SLM technology in S2) are: laser power of 70-200W, scanning strategy of checkerboard scanning or rotational scanning, and powder layer thickness of 20-50μm.

[0029] Furthermore, in step S3), the heat treatment temperature is 600-900℃, and the holding time is 20s-5min.

[0030] Example 1: S1) Weigh the matrix powder TC4 powder and Fe powder according to the design ratio, mix the weighed powders, and then place the mixed powder in a vacuum drying oven for drying to obtain mixed alloy powder; The mixing equipment is a three-dimensional oscillating mixer, operating under inert gas protection, with a rotational speed of: The mixing time is 2.5 seconds. The drying temperature was 65℃, and the drying time was 7 hours. The Fe powder comprises 3% by mass, with the remainder being TC4 matrix powder and unavoidable impurities.

[0031] S2) The mixed alloy powder obtained in S1) is printed using DED technology to obtain titanium alloy parts; The specific process parameters are: laser power of 800W, scanning speed of 8mm / s, and powder tray rotation speed of 0.3r / min.

[0032] S3) The titanium alloy part obtained in S2) is heated to 600℃ and held at that temperature for 5 minutes, then quickly quenched in water. The resulting titanium alloy has equiaxed β-grain shapes with an average β-grain size of 139μm. The strength increases from 807.1MPa to 1102.5MPa, a 36.6% increase, and the material plasticity increases from 5.0% to 6.1%, a 22% increase. Figure 5 As shown in (b).

[0033] Example 2: S1) Weigh the matrix powder TC4 and Fe powder according to the design ratio, mix the weighed powders, and then place the mixed powder in a vacuum drying oven for drying to obtain mixed alloy powder. The Fe powder is 5% by mass, with the remainder being TC4 matrix powder and unavoidable impurities; The mixing equipment is a three-dimensional oscillating mixer, operating under inert gas protection, with a rotational speed of: The mixing time is 3.5 hours; The drying temperature was 75℃, and the drying time was 9 hours. S2) The mixed alloy powder obtained in S1) is printed using DED technology to obtain titanium alloy parts; The specific process parameters are: laser power of 800W, scanning speed of 8mm / s, and powder tray rotation speed of 0.3r / min.

[0034] S3) The titanium alloy part obtained in S2) is heated to 900℃ and held for 1.5 minutes. Then it is quickly immersed in water for quenching and cooling. The β grains in the resulting titanium alloy are equiaxed and have an average size of 122μm. The strength increases from 807.1MPa to 1301.7MPa, an increase of 36.6%. The material plasticity increases from 5.0% to 6.6%, an increase of 32.1%.

[0035] Example 3: S1) Weigh the matrix powder and Fe powder according to the design ratio, mix the weighed powders, and then place the mixed powder in a vacuum drying oven for drying to obtain mixed alloy powder; The Fe powder is 3% by mass, with the remainder being TC4 matrix powder and unavoidable impurities; The mixing equipment is a three-dimensional oscillating mixer, operating under inert gas protection, with a rotational speed of: The mixing time is 3.0 hours; The drying temperature is 70℃, and the drying time is 8 hours. S2) The mixed alloy powder obtained in S1) is printed using SLM technology to obtain titanium alloy parts; The specific process parameters are: laser power of 150W, scanning strategy of rotational scanning, scanning angle of 90°, and powder layer thickness of 40μm.

[0036] S3) The titanium alloy part obtained in S2) is heated to 800℃ and held at that temperature for 4 minutes, then quickly quenched in water. The resulting titanium alloy has equiaxed β grains with an average size of 122μm, a strength of 698.7MPa, and a material plasticity of 4.9%. Figure 5 As shown in (a) of the diagram.

[0037] Example 4: S1) Weigh the matrix powder and Fe powder according to the design ratio, mix the weighed powders, and then place the mixed powder in a vacuum drying oven for drying to obtain mixed alloy powder; The Fe powder comprises 5% by mass, with the remainder being Ti matrix powder and unavoidable impurities; The mixing equipment is a three-dimensional oscillating mixer, operating at a speed of 40 rpm under inert gas protection. The mixing time is 2.8 hours; The drying temperature was 68℃, and the drying time was 7.5 hours. S2) The mixed alloy powder obtained in S1) is printed using SLM technology to obtain titanium alloy parts; The specific parameters are: laser power 175W, scanning speed 1000mm / s, scanning strategy is checkerboard scanning, scanning angle is 90°, and powder layer thickness is 30μm.

[0038] S3) The titanium alloy part obtained in S2) is heated to 800℃, held at that temperature for 20 seconds, and then quickly immersed in water for quenching and cooling, resulting in a titanium alloy with a yield strength of 804MPa and a plasticity of 1.7%.

[0039] Example 5: S1) Weigh the matrix powder and Fe powder according to the design ratio, mix the weighed powders, and then place the mixed powder in a vacuum drying oven for drying to obtain mixed alloy powder; The Fe powder contains 1.1% by mass, with the remainder being Ti matrix powder and unavoidable impurities; the mixing equipment is a three-dimensional oscillating mixer, operating at a speed of 60 rpm under inert gas protection. The drying temperature was 73℃, and the drying time was 8.2 hours. S2) The mixed alloy powder obtained in S1) is printed using SLM technology to obtain titanium alloy parts; The specific parameters are: laser power 175W, scanning speed 1000mm / s, scanning strategy is checkerboard scanning, scanning angle is 90°, and powder layer thickness is 35μm.

[0040] S3) The titanium alloy part obtained in S2) is heated to 800℃, held at that temperature for 60s, and then quickly immersed in water for quenching and cooling, resulting in a titanium alloy with a yield strength of 701MPa and a plasticity of 2.4%.

[0041] Example 6: S1) Weigh the matrix powder and Fe powder according to the design ratio, mix the weighed powders, and then place the mixed powder in a vacuum drying oven for drying to obtain mixed alloy powder; The Fe powder is 5% by mass, with the remainder being TC4 matrix powder and unavoidable impurities; The mixing equipment is a three-dimensional oscillating mixer, operating at a speed of 100 rpm under inert gas protection. The mixing time is 3.4 hours; The drying temperature was 68℃, and the drying time was 7.6 hours. S2) The mixed alloy powder obtained in S1) is printed using DED technology to obtain titanium alloy parts; Specific parameters are: laser power 200W, scanning strategy checkerboard scanning, scanning angle 90°, and powder layer thickness 30μm. S3) The titanium alloy part obtained in S2) is heated to 800℃, held at that temperature for 150s, and then rapidly immersed in water for quenching and cooling, resulting in a titanium alloy with a yield strength of 629MPa and a plasticity increased to 6.0%.

[0042] The above provides a detailed description of the method for eliminating beta segregation defects in in-situ alloying additive manufacturing of titanium or titanium alloys, as provided in the embodiments of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and its core ideas; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

[0043] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0044] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0045] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0046] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A method of eliminating beta segregation defects in in-situ alloyed additive manufactured titanium alloys, characterized in that, The method is in-situ alloying additive manufacturing by adding a certain amount of Fe element, using Fe to promote the formation of near-equiaxed microstructure and grain refinement, enhance the strength of titanium alloy, at the same time, through rapid heat treatment, make the elements in the alloy more evenly distributed, reduce the composition segregation, inhibit the formation of acicular martensite, optimize the microstructure, improve the plasticity of the material, finally realize the synergistic improvement of strength and plasticity of titanium alloy.

2. The method of claim 1, wherein, The method specifically comprises the following steps: S1) according to the design ratio, respectively weighing the base powder and Fe powder, mixing the weighed powder, and then placing the mixed powder in a vacuum drying box for drying to obtain a mixed alloy powder; S2) printing the mixed alloy powder obtained in S1) by using DED or SLM technology, thereby obtaining a titanium alloy part; S3) rapidly heat treating the titanium alloy part obtained in S2), and then rapidly placing it in water for quenching cooling after a certain holding time.

3. The method of claim 2, wherein, The mass percentage of Fe powder in S1) is 1.2-5%, and the rest is base powder and unavoidable impurities.

4. The method of claim 2, wherein, The base powder is Ti powder or TC4 powder, and the particle size is 15-53 microns; the particle size of Fe powder is 0.1-10 microns.

5. The method of claim 2, wherein, The specific process of powder mixing and drying in S1) is as follows: the mixing equipment is a three-dimensional swing mixer, the rotation speed is 40-100 rpm under the protection of inert gas, and the mixing time is 2.5-3.5 h; The drying temperature is 65-75℃, and the drying time is 7-9h.

6. The method of claim 2, wherein, The specific parameters of the laser direct energy deposition (DED) technology in S2) are as follows: the laser power is 600-1000 W, the scanning speed is 6-15 mm / s, and the powder disc rotation speed is 0.2-0.6 r / min.

7. The method of claim 2, wherein, The specific parameters of the selective laser melting (SLM) technology in S2) are as follows: the laser power is 70-200 W, the scanning strategy is chessboard scanning or rotary scanning, and the powder layer thickness is 20-50 microns.

8. The method of claim 2, wherein, The temperature of the heat treatment in S3) is 600-900℃, and the holding time is 20s-5min.

9. A titanium alloy, characterized by, The titanium alloy is prepared by the method according to any one of claims 1-8.

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