Ti2AlNb / ti-48al-2cr-2nb composite material blade and preparation method thereof

Abstract

The disclosure provides a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade and a preparation method thereof, and belongs to the technical field of alloy material preparation. The preparation method comprises the following steps: Ti-48Al-2Cr-2Nb powder and Ti2AlNb powder are respectively prepared by adopting a rotating electrode powdering method and a whole-process oxygen content integrated control technology; the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder are uniformly mixed to form mixed powder; the mixed powder is laid on a substrate layer by layer by adopting an EBM forming process, the mixed powder is fused by an electronic beam in a layer-by-layer scanning mode to form a printed blade workpiece, and a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade is obtained. According to the disclosure, the Ti2AlNb powder and the Ti-48Al-2Cr-2Nb powder are doped, and the Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade is obtained by adopting an electron beam printing forming process, and the high-temperature tensile strength and yield strength of the blade are better than those of an undoped sample.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of alloy material preparation, and particularly relates to a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade and a preparation method thereof. BACKGROUND

[0002] With the continuous progress of the aviation industry, the working environment of the aero-engine is increasingly complex, and higher requirements are put forward for the energy consumption, service life and performance of the aero-engine. Among them, the engine blade has very high requirements on the mechanical properties of the material, and at present, high-temperature alloys are mainly used, such as titanium aluminum alloy, nickel-based alloy, etc. Among them, TiAl alloy is expected to replace Ni-based alloy as aero-engine low-pressure turbine blade material in the service environment of medium and high temperature (600-900℃) due to its low density, high specific strength and specific modulus, and excellent high-temperature oxidation resistance, creep resistance and fatigue resistance.

[0003] However, TiAl alloy is brittle at room temperature, which leads to great difficulty in processing, poor room temperature damage tolerance and short service life, which limits further engineering application. In addition, the structure and shape of the engine blade are complex, and it is difficult to obtain fine full lamellar structure by traditional forming methods. When TiAl alloy blades are formed by using current technical means, there are still problems to varying degrees, for example, the TiAl alloy blades formed by using laser melting deposition technology have problems such as difficulty in controlling O element and N element in the forming environment, large residual stress of the formed sample, etc.; the surface quality and microstructure of the TiAl alloy blades formed by using electron beam selective melting (EBM) additive manufacturing technology are poor, and there are problems such as powder blowing, insufficient density and loss of Al element, especially when the sample surface is about 90° to the building direction, different organizational morphology will appear along the forming direction, leading to uneven organization and reduced mechanical properties, poor room temperature plasticity. SUMMARY

[0004] The present disclosure aims to at least solve one of the technical problems existing in the prior art, and provides a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade and a preparation method thereof.

[0005] The present disclosure provides a preparation method of a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade, which comprises the following steps:

[0006] Ti-48Al-2Cr-2Nb powder and Ti2AlNb powder are prepared by a rotating electrode powdering method through full-process oxygen content integrated control technology;

[0007] The Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder are uniformly mixed to obtain a mixed powder.

[0008] The mixed powder is laid on a substrate layer by layer by using the EBM forming process, and the mixed powder is fused layer by layer by using electron beam scanning to obtain a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade.

[0009] Optionally, the oxygen content of the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder is less than 700 ppm; and / or,

[0010] The Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder are spherical and have a particle size range of 15-150 μm.

[0011] Optionally, the mass ratio of the Ti2AlNb powder to the Ti-48Al-2Cr-2Nb powder is (10-30):(70-90).

[0012] Optionally, the mixed powder is laid on a substrate layer by layer by using the EBM forming process, and the mixed powder is fused layer by layer by using electron beam scanning to obtain a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade, comprising:

[0013] The vacuum forming chamber maintains a vacuum degree of not more than 5×10 -2 Pa, the substrate is preheated by using electron beam, and the mixed powder is coated on the substrate;

[0014] The mixed powder is heated by using electron beam, the printing temperature is controlled by using temperature gradient control and real-time dynamic heat compensation control, the mixed powder is selectively fused according to the cross-sectional information of the blade to form a cladding layer, the cladding layer is observed in real time to adjust the process of the defective part, and then the cladding layer without defects is subjected to conformal heat treatment;

[0015] The mixed powder is cladded on the substrate layer by layer for multiple times to form a printed workpiece, and the Ti2AlNb / Ti-48Al-2Cr-2Nb blade is obtained by further machining the printed workpiece.

[0016] Optionally, the preheating temperature of the substrate preheated by using electron beam is 1000-1150℃, and the time is 10-30 min.

[0017] Optionally, in the process of fusing the mixed powder by using electron beam, the scanning path is 45°, the scanning path is rotated by 90° between each layer, the electron beam current is 12.5-14.5 mA, the scanning speed is 3.5-4.5 m / s, and the thickness of the single-layer cladding layer of the mixed powder is 40-60

[0018] μm.

[0019] Optionally, the printing temperature is 1250-1350℃, and the time is 1-3h.

[0020] Optionally, the density of the Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade is 97.0-99.6%.

[0021] Optionally, the tensile strength of the Ti2AlNb / Ti-48Al-2Cr-2Nb blade at room temperature in the transverse direction is 806-939.5MPa, the tensile strength at room temperature in the longitudinal direction is 695-790.1MPa, the tensile strength at high temperature in the transverse direction is 690-876.4MPa, and the tensile strength at high temperature in the longitudinal direction is 670-791.9MPa.

[0022] In another aspect of the present disclosure, a Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade is provided, which is prepared by the preparation method described above.

[0023] The present disclosure provides a Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade and a preparation method thereof. The preparation method comprises: preparing Ti-48Al-2Cr-2Nb powder and Ti2AlNb powder by a rotating electrode powdering method through full-process oxygen content integrated control technology; uniformly mixing the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder to form a mixed powder; and using an EBM forming process to lay the mixed powder on a substrate layer by layer, and melting the mixed powder layer by layer by means of electron beam scanning to obtain a Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade. The present disclosure effectively fuses the Ti2AlNb powder and the Ti-48Al-2Cr-2Nb powder, and realizes accurate material forming by using the EBM forming process, which is conducive to preparing a composite blade with excellent performance. The high-temperature tensile strength and yield strength of the composite blade doped with Ti2AlNb are better than those of the undoped sample. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A flowchart of the preparation method of the Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade of the specific embodiment of the present disclosure is shown in the figure;

[0025] Figure 2 A microstructure morphology of a 10wt.% Ti2AlNb doped sample of Example 1 of the present disclosure is shown in the figure;

[0026] Figure 3 A phase distribution of a 10wt.% Ti2AlNb doped sample of Example 1 of the present disclosure is shown in the figure;

[0027] Figure 4 Room temperature tensile stress-strain curve for the 10 wt.% doped Ti2AlNb specimen of Example 1 of the present disclosure;

[0028] Figure 5 High temperature tensile stress-strain curve for the 10 wt.% doped Ti2AlNb specimen of Example 1 of the present disclosure;

[0029] Figure 6 Microstructure morphology for the 20 wt.% doped Ti2AlNb specimen of Example 2 of the present disclosure;

[0030] Figure 7 Phase distribution for the 20 wt.% doped Ti2AlNb specimen of Example 2 of the present disclosure;

[0031] Figure 8 Room temperature tensile stress-strain curve for the 20 wt.% doped Ti2AlNb specimen of Example 2 of the present disclosure;

[0032] Figure 9 High temperature tensile stress-strain curve for the 20 wt.% doped Ti2AlNb specimen of Example 2 of the present disclosure;

[0033] Figure 10 Microstructure morphology for the 30 wt.% doped Ti2AlNb specimen of Example 3 of the present disclosure;

[0034] Figure 11 Phase distribution for the 30 wt.% doped Ti2AlNb specimen of Example 3 of the present disclosure;

[0035] Figure 12 Room temperature tensile stress-strain curve for the 30 wt.% doped Ti2AlNb specimen of Example 3 of the present disclosure;

[0036] Figure 13 High temperature tensile stress-strain curve for the 30 wt.% doped Ti2AlNb specimen of Example 3 of the present disclosure;

[0037] Figure 14 Metallograph of EBM formed Ti-48Al-2Cr-2Nb alloy of Comparative Example 1 of the present disclosure;

[0038] Figure 15 Phase distribution of different regions of EBM formed Ti-48Al-2Cr-2Nb alloy of Comparative Example 1 of the present disclosure; where (a) upper, (b) middle, (c) lower;

[0039] Figure 16Tensile stress-strain curves of EBM formed Ti-48Al-2Cr-2Nb alloy for Comparative Example 1 of the present disclosure; wherein (a) room temperature longitudinal tensile curve; (b) room temperature transverse tensile curve; (c) 650°C longitudinal tensile curve; (d) 650°C transverse tensile curve. DETAILED DESCRIPTION

[0040] In order for those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present disclosure.

[0041] As shown in the drawings, Figure 1 An aspect of the present disclosure provides a preparation method S100 of a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade, which specifically comprises the following steps S110-S130:

[0042] S110, Ti-48Al-2Cr-2Nb powder and Ti2AlNb powder are prepared by full-process oxygen content integrated control technology through a rotating electrode powdering method.

[0043] Specifically, high-purity Ti, Al, Cr, and Nb metal raw materials are selected to ensure the purity of the final powder, and the raw materials are prepared according to the corresponding atomic ratio, and the raw materials are dried to remove water and other impurities adsorbed on the surface of the raw materials, so as to avoid the introduction of additional oxygen in the subsequent preparation process; then, the raw materials are placed in a water-cooled copper crucible, and 2 times of consumable melting is carried out under vacuum or high-purity inert gas (such as argon) protection, 1 time of induction melting is carried out to prevent the reaction between the metal and oxygen in the air, and the melting temperature is generally 1700-1900°C; during the melting process, the alloy composition is homogenized by stirring and other methods to ensure that each element is uniformly distributed in the alloy. After melting, high-purity and homogeneous Ti-48Al-2Cr-2Nb alloy rods and Ti2AlNb alloy rods are prepared by high-speed centrifugal casting, and the alloy rods obtained by melting are precisely machined to process them into alloy electrode round rods that meet the requirements; Ti-48Al-2Cr-2Nb powder and Ti2AlNb powder are prepared by using a rotating plasma powdering device, wherein, during the powdering process, the alloy electrode round rod is rotated at a speed of 3000-50000 rpm by a rotating control shaft, and the oxygen content of the prepared powder is controlled to be below 700ppm under the condition of argon protection.

[0044] In some preferred embodiments, the prepared Ti-48Al-2Cr-2Nb powder and Ti2AlNb powder are spherical with a particle size ranging from 50 to 106 μm.

[0045] By adopting the oxygen content integrated control technology, the present embodiment can strictly control the oxygen content, effectively avoid the brittle phase caused by excessive oxygen content, and significantly improve the mechanical properties such as strength and toughness of the material.

[0046] S120, uniformly mixing the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder by using a powder mixing device to form a mixed powder.

[0047] In some preferred embodiments, the mass ratio of the Ti2A1Nb powder and the Ti-48Al-2Cr-2Nb powder is (10-30):(70-90). For example, 10:90, 20:80, 30:70, etc. That is, the doping amount of the Ti2A1Nb powder is 10-30%.

[0048] S130, forming a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade by using an EBM forming process.

[0049] Specifically, the vacuum forming chamber maintains a vacuum degree of not more than 5×10 -2 Pa, preheats the substrate by using an electron beam, the preheating temperature reaches 1000-1150℃, and the preheating time is 10-30 min; then, the mixed powder formed in step S120 is laid on the substrate layer by layer; the mixed powder is heated by using an electron beam, the printing temperature is controlled to be 1250-1350℃ under the conditions of temperature gradient control and real-time dynamic heat compensation, the time is 1-3 h, the laid mixed powder is selectively melted by using an electron beam in a layer-by-layer scanning manner according to the cross-sectional information of the blade, a cladding layer is formed; the cladding layer is observed in real time by using an electron microscope, the defective parts of the cladding layer are adjusted in real time, so as to realize cladding layer compensation printing repair, then the cladding layer without defects is subjected to conformal heat treatment; the mixed powder is repeatedly laid on the substrate layer by layer and cladded, a plurality of cladding layers are formed, and a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade printing workpiece is obtained, and the finished blade is obtained by further machining.

[0050] In some preferred embodiments, the preheating temperature of the substrate is preferably 1000°C, 1050°C, 1100°C, 1150°C, etc., and the preheating time is preferably 10 min, 20 min, 30 min, etc. By preheating the substrate, the alloy can have ductility and plasticity during forming, while reducing thermal stress and preventing the generation of thermal cracks. In addition, by preheating the substrate, the initial powder layer can be slightly melted, and the "blowing powder" phenomenon caused by the impact of the electron beam can be prevented.

[0051] In other preferred embodiments, the printing temperature can be preferably 1250°C, 1300°C, 1350°C, and the time can be preferably 1 h, 2 h, 3 h, etc. In the melting process of the mixed powder, the scanning path is 45°, the scanning path is rotated by 90° between each layer, the electron beam current is preferably 12.5-14.5 mA, for example, which can be further preferably 12.5 mA, 13 mA, 13.5 mA, 14 mA, 14.5 mA, etc., and the scanning speed is preferably 3.5-4.5 m / s, for example, which can be further preferably 3.5 m / s, 4.0 m / s, 4.5 m / s, etc. The thickness of the single layer of the mixed powder cladding layer is 40-60 μm, and the scanning layer thickness is 40-60 μm.

[0052] In electron beam melting (EBM) forming, by controlling the printing temperature through temperature gradient control and real-time dynamic heat compensation, the melting temperature conditions of each layer of the cladding layer powder can be ensured to be close, thereby ensuring the consistency of the microstructure, making the heating and cooling of each part of the cladding layer more uniform, and avoiding the generation of thermal stress due to large local temperature changes. Real-time dynamic heat compensation can adjust the heat input in a timely manner according to the actual temperature of the blade, further reducing the generation of thermal stress, which helps to prevent defects such as deformation and cracking of the blade, and improves the dimensional accuracy and shape accuracy of the blade. Secondly, through precise temperature gradient control and real-time dynamic heat compensation, the melting and solidification process of the powder can be optimized. Suitable temperature conditions can make the powder fully melt and fill into each pore, reduce the pore defects caused by incomplete melting or solidification shrinkage of the powder, and improve the density of the blade. Furthermore, a reasonable temperature gradient can form a larger temperature difference during solidification, thereby producing a higher cooling rate. According to the solidification theory, a higher cooling rate is beneficial to the refinement of the grains, and real-time dynamic heat compensation can ensure the stability of the cooling rate during the entire forming process, further promoting the refinement of the grains, and the refined grains can improve the mechanical properties such as strength and toughness of the material.

[0053] In addition, in electron beam melting (EBM) forming, the present embodiment adopts conformal heat treatment, which can adjust heat treatment process parameters in real time during or after forming to realize accurate control of microstructure and performance of the part, can optimize grain structure, promote phase transition, reduce deformation and residual stress, reduce the cooling speed of the solidification layer, avoid the formation of a temperature gradient gap, and at the same time promote the stability of the powder layer when the next powder is laid, without the need for post-processing and the like.

[0054] The sample obtained by the present embodiment has high mechanical properties and good plasticity at room temperature, especially when the sample surface is about 90° to the building direction, the uniform microstructure morphology is presented along with the forming direction, the effective fusion of the two powders can be realized, the accurate forming of the material can be realized, and the composite material blade with excellent performance can be prepared.

[0055] In another aspect of the present disclosure, a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade is provided, and the preparation process of the blade is described above and will not be repeated here.

[0056] In the present embodiment, the Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade obtained based on the preparation method described above has a room temperature transverse tensile strength of 806-939.5 MPa, a room temperature longitudinal tensile strength of 695-790.1 MPa, a high temperature transverse tensile strength of 690-876.4 MPa, and a high temperature longitudinal tensile strength of 670-791.9 MPa. At the same time, the Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade obtained by the present embodiment also has high density.

[0057] The preparation method of the Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade will be further described below in combination with specific examples.

[0058] Example 1

[0059] The present example provides a preparation method of a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade, which includes the following steps:

[0060] S1, Ti-48Al-2Cr-2Nb powder and Ti2AlNb powder are prepared by a rotating electrode powdering method through full-process oxygen content integrated control technology. The oxygen content of the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder is 670 ppm, and the particle size range of the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder is 50-105 μm.

[0061] S2, the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder are mixed by using a powder mixing device to form a mixed powder. The content ratio of the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder is 90:10 respectively.

[0062] S3, the mixed powder is fused to form a printed workpiece by using an EBM forming process, and the Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade is obtained by machining.

[0063] Specifically, the vacuum degree in the vacuum forming chamber is kept not more than 5x10 -2 Pa, the substrate is preheated by using an electron beam, the preheating temperature is 1000℃, the preheating time is 10min, the mixed powder is coated on the substrate, the mixed powder is heated by using an electron beam, the printing temperature is controlled to be 1250℃ under the conditions of temperature gradient control and real-time dynamic heat compensation, the time is 1h, the scanning path is 45°, the scanning path is rotated by 90° between each layer, the electron beam current is 12.5mA, 13.5mA and 14.5mA respectively, the scanning speed is 3.5m / s, 4m / s and 4.5m / s respectively, the powder layer height of the fused layer is 50μm, a fused layer is formed by melting, the fused layer is observed in real time by using an electron microscope, the defect position of the fused layer is adjusted in real time, and then the fused layer without defects is subjected to conformal heat treatment. The mixed powder is fused on the substrate repeatedly to form a printed workpiece, and the Ti2AlNb / Ti-48Al-2Cr-2Nb blade is obtained by further machining the printed workpiece.

[0064] As shown in Table 1, when the electron beam current is 12.5mA and the scanning speed is 3.5m / s, the density of the blade obtained is 4.075g / cm 3 , and the density is 99.5%. When the electron beam current is 12.5mA and the scanning speed is 4m / s, the density of the blade obtained is 3.970g / cm 3 , and the density is 96.8%. When the electron beam current is 12.5mA and the scanning speed is 4.5 / s, the density of the blade obtained is 4.011g / cm 3 , and the density is 97.8%.

[0065] Further, with reference to Table 1, when the electron beam current is 13.5mA and the scanning speed is 3.5m / s, the density of the blade obtained is 4.087g / cm 3 , and the density is 99.6%. When the electron beam current is 13.5mA and the scanning speed is 4m / s, the density of the blade obtained is 4.061g / cm 3, the density of the blade is 4.078 g / cm 3 , the density is 99.4%.

[0066] Further, please refer to Table 1, when the electron beam current is 14.5 mA and the scanning speed is 3.5 m / s, the density of the blade is 4.015 g / cm 3 , the density is 97.9%. When the electron beam current is 14.5 mA and the scanning speed is 4 m / s, the density of the blade is 3.984 g / cm 3 , the density is 97.1%. When the electron beam current is 14.5 mA and the scanning speed is 4.5 m / s, the density of the blade is 3.945 g / cm 3 , the density is 96.2%.

[0067] According to the density and the density of the samples obtained under the above different parameters, it can be seen that the density of the samples obtained under the process conditions given in the embodiment is high, especially when the electron beam current is 12.5 mA and 13.5 mA and the scanning speed is 3.5 m / s, the density is high, which is 99.5% and 99.6% respectively.

[0068] Further, the microstructure morphology, phase distribution and tensile stress-strain curve of the composite blade are analyzed by taking the sample formed by the electron beam current of 12.5 mA and the scanning speed of 3.5 m / s as an example.

[0069] As shown in Figure 2 , the microstructure of the sample presents fine equiaxed structure and lamellar structure, and large white bright bands are interspersed between the fine equiaxed structure and lamellar structure.

[0070] As shown in Figure 3 and Table 2, the composite blade sample is mainly composed of γ phase, α2 phase, B2 phase and O phase, mainly with γ phase, the structure is more fine and the coarse strip-shaped structure is less and fine.

[0071] As shown in Figure 4 , the room temperature mechanical properties of the composite blade sample are as follows: the average tensile strength of the transverse sample is 909.3 MPa, and the average elongation is 0.78%; the average tensile strength of the longitudinal sample is 871.1 MPa, and the average elongation is 0.65%, the room temperature tensile strength and yield strength are good.

[0072] As shown in Figure 5As shown, the high-temperature mechanical properties of the composite blade sample at a high temperature of 650℃ are as follows: the average tensile strength of the transverse sample is 796.9 MPa, and the average elongation is 1.4%; the average tensile strength of the longitudinal sample is 801.2 MPa, and the average elongation is 1.27%.

[0073] Example 2

[0074] The present example provides a preparation method of a Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade, comprising the following steps:

[0075] S1, Ti-48Al-2Cr-2Nb powder and Ti2AlNb powder are prepared by a rotating electrode powdering method through full-process oxygen content integrated control technology. The oxygen content of the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder is 670 ppm, and the particle size range of the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder is 50-105 μm.

[0076] S2, the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder are mixed by a powder mixing device to form a mixed powder. The content ratio of the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder is 80:20.

[0077] S3, the mixed powder is cladded to form a printed workpiece by an EBM forming process, and a Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade is obtained by machining.

[0078] Specifically, the vacuum degree in the vacuum forming chamber is kept not more than 5×10 -2 Pa, the substrate is preheated by an electron beam, the preheating temperature is 1000℃, the preheating time is 10 min, the mixed powder is coated on the substrate, the mixed powder is heated by an electron beam, the printing temperature is controlled to be 1250℃ under the conditions of temperature gradient control and real-time dynamic heat compensation, the time is 1 h, the scanning path is 45°, the scanning path is rotated by 90° between each layer, the electron beam current is 12.5 mA, 13.5 mA and 14.5 mA respectively, the scanning speed is 3.5 m / s, 4 m / s and 4.5 m / s respectively, the powder layer height of the cladding layer is 50 μm, a layer of cladding layer is formed by melting, the cladding layer is observed in real time by using an electron microscope, the defect position of the cladding layer is adjusted in real time, and then the cladding layer without defects is subjected to conformal heat treatment. The mixed powder is repeatedly cladded on the substrate to form a printed workpiece, and the Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade is obtained by further machining the printed workpiece.

[0079] As shown in Table 1, when the electron beam current is 12.5 mA and the scanning speed is 3.5 m / s, the obtained blade density is 4.134 g / cm 3 , and the density is 97.9%. When the electron beam current is 12.5 mA and the scanning speed is 4 m / s, the obtained blade density is 4.109 g / cm 3 , and the density is 97.38%. When the electron beam current is 12.5 mA and the scanning speed is 4.5 / s, the obtained blade density is 4.155 g / cm 3 , and the density is 98.4%.

[0080] Further, with reference to Table 1, when the electron beam current is 13.5 mA and the scanning speed is 3.5 m / s, the obtained blade density is 4.169 g / cm 3 , and the density is 98.7%. When the electron beam current is 13.5 mA and the scanning speed is 4 m / s, the obtained blade density is 4.177 g / cm 3 , and the density is 98.9%. When the electron beam current is 13.5 mA and the scanning speed is 4.5 m / s, the obtained blade density is 4.098 g / cm 3 , and the density is 97.0%.

[0081] Further, with reference to Table 1, when the electron beam current is 14.5 mA and the scanning speed is 3.5 m / s, the obtained blade density is 4.088 g / cm 3 , and the density is 96.8%. When the electron beam current is 14.5 mA and the scanning speed is 4 m / s, the obtained blade density is 4.161 g / cm 3 , and the density is 98.5%. When the electron beam current is 14.5 mA and the scanning speed is 4.5 m / s, the obtained blade density is 4.089 g / cm 3 , and the density is 96.8%.

[0082] According to the density and density of the samples obtained under the above different parameters, it can be seen that the density of the samples obtained under the process conditions given in the embodiment is high, especially when the electron beam current is 12.5 mA, the scanning speed is 4.5 m / s, the electron beam current is 13.5 mA, the scanning speed is 3.5 m / s, the electron beam current is 13.5 mA, the scanning speed is 4 m / s, and the electron beam current is 14.5 mA, the scanning speed is 4 m / s. The density of each sample is more than 98%.

[0083] Further, the embodiment takes the sample formed by the electron beam current of 14.5 mA and the scanning speed of 4 m / s as an example to analyze the microstructure morphology, phase distribution and tensile stress-strain curve of the composite material blade. Further, the embodiment takes the sample formed by the electron beam current of 14.5 mA and the scanning speed of 4 m / s as an example to analyze the microstructure morphology, phase distribution and tensile stress-strain curve of the composite material blade.

[0084] As Figure 6 shown, the microstructure of the above-mentioned composite blade sample has a great change compared with the sample without doping and the sample of Example 1, and becomes mainly in the form of acicular structure and lamellar structure, the equiaxed structure is distributed between adjacent acicular or lamellar structures, the white band becomes smaller and is uniformly distributed in the lamellar structure, the average grain size increases to 65 μm, the strip-shaped structure disappears and is replaced by large lamellar groups.

[0085] As Figure 7 shown and shown in Table 2, compared with Example 1, the phase composition of the above-mentioned composite blade sample does not change, but the content of γ phase is significantly reduced, the phase content of the composite blade sample doped with 20 wt.% Ti2AlNb is shown in Table 2, the α2 phase and the B2 phase continue to increase, and the B2 phase and the α2 phase are uniformly distributed in the γ phase. Figure 7 It can be seen that the O phase mostly exists in the B2 phase and the α2 phase, and exists alone in the γ phase less, which is related to the phase transition of the Ti2AlNb powder in the EBM forming process.

[0086] As Figure 8 shown, the room temperature mechanical properties of the above-mentioned composite blade sample are as follows: the average tensile strength of the transverse sample is 939.5 MPa, and the average elongation is 0.82%; the average tensile strength of the longitudinal sample is 790.1 MPa, and the average elongation is 0.66%.

[0087] As Figure 9 shown, the high temperature (650℃) mechanical properties of the above-mentioned composite blade sample are as follows: the average tensile strength of the transverse sample is 876.4 MPa, and the average elongation is 2.3%; the average tensile strength of the longitudinal sample is 791.9 MPa, and the average elongation is 1.6%.

[0088] Example 3

[0089] The present example gives a preparation method of a Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade, which comprises the following steps:

[0090] S1, Ti-48Al-2Cr-2Nb powder and Ti2AlNb powder are prepared by a rotating electrode powdering method through full-process oxygen content integrated control technology. The oxygen content of the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder is 670 ppm, and the particle size range of the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder is 50-105 μm.

[0091] S2, mixing the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder by using a powder mixing device to form a mixed powder. The content ratio of the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder is 70:30 respectively.

[0092] S3, forming a printed workpiece by using an EBM forming process to fuse clad the mixed powder, and obtaining the Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade by machining.

[0093] Specifically, the vacuum degree in the vacuum forming chamber is kept not more than 5x10 -2 Pa, the substrate is preheated by using an electron beam, the preheating temperature is 1000℃, the preheating time is 10min, the mixed powder is coated on the substrate, the mixed powder is heated by using an electron beam, the printing temperature is controlled to be 1250℃ under the conditions of temperature gradient control and real-time dynamic heat compensation, the time is 1h, the scanning path is 45°, the scanning path is rotated by 90° between each layer, the electron beam current is 12.5mA, 13.5mA and 14.5mA respectively, the scanning speed is 3.5m / s, 4m / s and 4.5m / s respectively, the powder layer height of the cladding layer is 50μm, a cladding layer is formed by melting, the cladding layer is observed in real time by using an electron microscope, the defect position of the cladding layer is adjusted in real time, and then the cladding layer without defects is subjected to conformal heat treatment. The mixed powder is repeatedly fused clad on the substrate to form a printed workpiece, and the printed workpiece is further machined to obtain the Ti2AlNb / Ti-48Al-2Cr-2Nb blade.

[0094] As shown in Table 1, when the electron beam current is 12.5mA and the scanning speed is 3.5m / s, the density of the obtained blade is 4.278g / cm 3 , and the density is 98.4%. When the electron beam current is 12.5mA and the scanning speed is 4m / s, the density of the obtained blade is 4.184g / cm 3 , and the density is 96.3%. When the electron beam current is 12.5mA and the scanning speed is 4.5 / s, the density of the obtained blade is 4.221g / cm 3 , and the density is 97.1%.

[0095] Further, with reference to Table 1, when the electron beam current is 13.5mA and the scanning speed is 3.5m / s, the density of the obtained blade is 4.219g / cm 3 , and the density is 97.0%. When the electron beam current is 13.5mA and the scanning speed is 4m / s, the density of the obtained blade is 4.225g / cm 3, the density of the blade is 4.277 g / cm 3 , the density is 98.4%.

[0096] Further, referring to Table 1, when the electron beam current is 14.5 mA and the scanning speed is 3.5 m / s, the density of the blade is 4.221 g / cm 3 , the density is 97.1%. When the electron beam current is 14.5 mA and the scanning speed is 4 m / s, the density of the blade is 4.271 g / cm 3 , the density is 98.3%. When the electron beam current is 14.5 mA and the scanning speed is 4.5 m / s, the density of the blade is 4.268 g / cm 3 , the density is 98.2%.

[0097] According to the density and the density of the samples obtained under different parameters, it can be seen that the density of the samples obtained under the process conditions given in the embodiment is high, especially when the electron beam current is 12.5 mA and the scanning speed is 3.5 m / s, and the electron beam current is 13.5 mA and the scanning speed is 4.5 m / s, the density of each sample is the highest, which is 98.4%.

[0098] Further, the microstructure morphology, phase distribution and tensile stress-strain curve of the composite blade sample formed by the electron beam current of 12.5 mA and the scanning speed of 3.5 m / s are analyzed.

[0099] As shown in Figure 10 , compared with Examples 1 and 2, the average grain size of the above-mentioned composite blade sample is increased to more than 200 μm, and the white band is increased compared with the composite blade sample doped with 20 wt.% Ti2AlNb of Example 2.

[0100] As shown in Figure 11 and Table 2, the above-mentioned composite blade sample further reduces the γ phase, the sample is based on the B2 phase, the α2 phase is distributed in the B2 phase matrix in the form of dendritic, and the γ phase is distributed between the "branches" of the dendritic α2 phase, and the O phase is dispersedly distributed in the B2 phase matrix and the dendritic α2 phase, and there is still very little in the γ phase.

[0101] As shown in Figure 12 , the room temperature mechanical properties of the above-mentioned composite blade sample are as follows: the average tensile strength of the transverse sample is 851.1 MPa, and the average elongation is 0.59%; the average tensile strength of the longitudinal sample is 673.9 MPa, and the average elongation is 0.48%.

[0102] As shown in Figure 13The high-temperature (650℃) mechanical properties of the composite blade sample are as follows: the average tensile strength of the transverse sample is 941.1 MPa, and the average elongation is 3.3%; the average tensile strength of the longitudinal sample is 803.7 MPa, and the average elongation is 2.1%.

[0103] Comparative Example 1

[0104] The present example gives a preparation method of Ti-48Al-2Cr-2Nb blade, which comprises the following steps:

[0105] S1, Ti-48Al-2Cr-2Nb powder is prepared by a rotating electrode powdering method through full-process oxygen content integrated control technology. The oxygen content of the Ti-48Al-2Cr-2Nb powder is 670 ppm, and the particle size range of the Ti-48Al-2Cr-2Nb powder is 50-105 μm.

[0106] S2, the powder is cladded to form a printed workpiece by using an EBM forming process, and the Ti-48Al-2Cr-2Nb blade is obtained by machining.

[0107] Specifically, the vacuum degree in the vacuum forming chamber is kept not more than 5×10 -2 Pa, the substrate is preheated by an electron beam, the preheating temperature is 1000℃, the preheating time is 10 min, the mixed powder is coated on the substrate, the mixed powder is heated by an electron beam, the printing temperature is controlled to be 1250℃ under the conditions of temperature gradient control and real-time dynamic heat compensation, the time is 1 h, the scanning path is 45°, the scanning path is rotated by 90° between each layer, the electron beam current is 12.5 mA, the scanning speed is 3.5 m / s, the powder layer height of the cladding layer is 50 μm, a layer of cladding layer is formed by melting, the cladding layer is observed in real time by using an electron microscope, the defect position of the cladding layer is adjusted in real time, and then the cladding layer without defects is subjected to conformal heat treatment. The mixed powder is repeatedly cladded on the substrate to form a printed workpiece, and the Ti-48Al-2Cr-2Nb blade is obtained by further machining the printed workpiece.

[0108] As shown in Table 1, the density of the blade is 3.9175 g / cm 3 , and the compactness is 97.9%.

[0109] As shown in Table 1, the density of the blade is 3.9175 g / cm 3 , and the compactness is 97.9%. Figure 14 As shown in Table 1, the density of the blade is 3.9175 g / cm 3 , and the compactness is 97.9%. Figure 14 As shown in Table 1, the density of the blade is 3.9175 g / cm 3 , and the compactness is 97.9%.

[0110] As shown in Table 1, the density of the blade is 3.9175 g / cm 3 , and the compactness is 97.9%. Figure 15As shown in Table 3, the phase distribution in different regions of the EBM-formed Ti-48Al-2Cr-2Nb alloy is presented. The phase content in different regions of the EBM-formed Ti-48Al-2Cr-2Nb alloy is shown in Table 3. The lower part of the EBM-formed Ti-48Al-2Cr-2Nb alloy contains more B2 phase than the upper and middle parts.

[0111] like Figure 16 As shown, the EBM-formed Ti-48Al-2Cr-2Nb alloy exhibits an average tensile strength of 695.29 MPa parallel to the forming direction (longitudinal direction) at room temperature, but with very low elongation. This is attributed to the brittle nature of the B2 phase and the coarsening of the microstructure at room temperature, resulting in poor elongation. The average tensile strength perpendicular to the forming direction (transverse direction) is 806.05 MPa, with an average elongation of 2.10%. At high temperature (650 °C), the average tensile strength parallel to the forming direction (longitudinal direction) is 670.63 MPa, with an average elongation of 4.28%. At high temperature, the average tensile strength perpendicular to the forming direction (transverse direction) is 690.30 MPa, with an average elongation of 3.77%. At high temperature, the softening of the bimodal microstructure reduces the anisotropy of tensile properties in the tensile direction; that is, at 650 °C, the difference in properties between the longitudinal and transverse directions is relatively small.

[0112] In summary, based on Examples 1-3 and Comparative Example 1, it can be seen that due to the unique formation mechanism of the O phase, the O phase will only be formed in the B2 and α2 phases during the EBM forming process of materials with added Ti2AlNb powder. Since the content of the B2 and α2 phases formed by the original matrix Ti-48Al-2Cr-2Nb powder during the EBM forming process is very small, the distribution of the O phase in the Ti2AlNb / Ti-48Al-2Cr-2Nb composite material is mainly in the B2 and α2 phases, and its distribution in the γ phase of the original matrix Ti-48Al-2Cr-2Nb powder after EBM forming is extremely small.

[0113] Secondly, compared with the undoped Ti2AlNb vane sample, the tensile strength of the Ti2AlNb doped composite vane sample is improved in both transverse and longitudinal directions, because the addition of Ti2AlNb powder increases the content of α2 phase and O phase in the composite, thereby improving the tensile strength of the composite. However, it can be found that the elongation of the doped sample is lower than that of the undoped sample, which is related to the B2 phase introduced by the EBM forming of the Ti2AlNb powder. Moreover, the elongation and tensile strength of the sample doped with 20wt.% Ti2AlNb are higher than those of the samples doped with 10wt.% and 30wt.% Ti2AlNb, which is also related to the size of the grains. When 10wt.% Ti2AlNb is doped, the coarse γ strip still exists, and there is obvious B2 phase segregation. When 20wt.% Ti2AlNb is doped, the γ strip disappears, and the B2 phase segregation is obviously reduced compared with the samples doped with 10wt.% and 20wt.% Ti2AlNb. When the microstructure is transformed into acicular structure, the microstructure of the sample doped with 20wt.% Ti2AlNb is finer than that of the sample doped with 30wt.% Ti2AlNb. Therefore, at room temperature, the composite vane doped with 20wt.% Ti2AlNb has the highest tensile strength and elongation due to the uniformity and relatively small size of the microstructure.

[0114] Further, the high-temperature tensile properties of the composite vane samples formed by the three doping amounts are further improved in tensile strength compared with the undoped sample, and with the increase of the doping amount, the high-temperature tensile strength and elongation increase, and after adding Ti2AlNb, the sample has an obvious yield stage, which indicates that the plasticity of the sample increases with the increase of the doping amount at high temperature. The tensile strength, yield strength and elongation of the sample doped with 30wt.% Ti2AlNb are higher than those of the other doping amounts at high temperature, which is related to the phase composition of the sample doped with 30wt.% Ti2AlNb. At this time, the B2 phase content in the phase composition of the sample is the highest. Because there are more slip twins in the B2 phase, the slip twin activity increases at high temperature, so that the B2 phase becomes a plastic phase, and the γ phase and O phase with high plasticity are uniformly distributed, so that the plasticity of the sample is greatly improved. Compared with the undoped sample mainly containing plastic γ phase, the composite vane sample doped with 30wt.% Ti2AlNb contains high α2 phase and O phase, and both of them have higher strength than γ phase at 650℃, so although the plasticity is not as good as that of the undoped γ-TiAl alloy, the high-temperature tensile strength is increased by 36% compared with the undoped sample.

[0115] Table 1 Density and density results of blade samples under different process parameters of examples 1-3

[0116]

[0117] Table 2 Phase content of blades under different process parameters of examples 1-3

[0118]

[0119] Table 3 Phase content of different regions of Ti-48Al-2Cr-2Nb alloy formed by EBM in comparative example 1

[0120]

[0121] The present disclosure provides a Ti2AlNb / Ti-48Al-2Cr-2Nb composite material blade and a preparation method thereof, and has the following beneficial effects compared with the prior art: the present disclosure forms a composite material blade by doping Ti2AlNb in Ti-48Al-2Cr-2Nb through an EBM forming process, effectively improves the surface quality, microstructure, density and high temperature performance of the sample, especially when the sample surface is about 90° to the building direction, the mechanical properties are effectively improved along with the forming direction, and the blowing phenomenon is reduced and the problems such as loss of Al element are avoided through process optimization.

[0122] It can be understood that the above embodiments are only exemplary embodiments adopted for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also considered to be within the protection scope of the present disclosure.

Claims

1. A method for preparing a Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade, characterized in that, The preparation method includes: Ti-48Al-2Cr-2Nb powder and Ti2AlNb powder were prepared by a rotating electrode powder preparation method using an integrated oxygen content control technology throughout the entire process; the mass ratio of Ti2AlNb powder to Ti-48Al-2Cr-2Nb powder ranged from (10-30):(70-90); The Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder were mixed evenly to obtain a mixed powder. The EBM forming process is employed, with the substrate preheated using an electron beam. Then, the mixed powder is layered onto the substrate, and melted by scanning each layer with an electron beam to obtain a Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade. The room temperature transverse tensile strength of the Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade is 806-939.5 MPa, and the room temperature longitudinal tensile strength is 695-790.1 MPa. When preheating the substrate with an electron beam, the vacuum forming chamber should maintain a vacuum level not exceeding 5 × 10⁻⁶. -2 Pa, the preheating temperature is 1000-1150℃, and the time is 10-30min; When melting the mixed powder by scanning layer by layer with an electron beam, the scanning path is 45°, the scanning path rotates 90° between each cladding layer, the electron beam current is 12.5-14.5mA, the scanning speed is 3.5-4.5m / s, the thickness of the single cladding layer of the mixed powder is 40-60μm, and the printing temperature is 1250-1350℃.

2. The preparation method according to claim 1, characterized in that, The oxygen content of the Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder is less than 700 ppm; and / or, The Ti-48Al-2Cr-2Nb powder and the Ti2AlNb powder are spherical with a particle size range of 15-150 μm.

3. The preparation method according to claim 1, characterized in that, The density of the Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade is 97.0-99.6%.

4. A Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade, characterized in that, The Ti2AlNb / Ti-48Al-2Cr-2Nb composite blade is prepared by the preparation method described in any one of claims 1 to 3.

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