Method for preparing TA15 titanium alloy thin-wall component through electron beam selective forming technology

Abstract

The invention belongs to the technical field of metal materials, and particularly relates to a method for preparing a TA15 titanium alloy thin-wall component through an electron beam selective forming technology. The method comprises the following steps that TA15 titanium alloy powder is prepared through a gas atomization method; the method comprises the following steps: constructing a three-dimensional model of a required TA15 titanium alloy thin-wall component, slicing the three-dimensional model to obtain a plurality of layers of slice files, and importing printing paths corresponding to the slice files into electron beam selective melting equipment; in a vacuum environment, a substrate of the electron beam selective melting equipment is preheated in stages; and TA15 titanium alloy powder is spread on the preheated base plate, scanning treatment is conducted in sequence according to the printing path of each layer of slices, and the TA15 titanium alloy thin-wall component is obtained. The TA15 titanium alloy thin-wall component prepared through the method is good in surface quality, refined in structure and uniform in component, and the TA15 titanium alloy thin-wall component is good in forming quality and high in density and has the excellent performance of high toughness and high strength.

Description

Technical Field

[0001] The invention belongs to the technical field of metal materials, and in particular relates to a method for preparing a TA15 titanium alloy thin-walled component by electron beam selective forming technology. Background Art

[0002] TA15 titanium alloy belongs to the near-α-type titanium alloy TA15, which has higher room temperature and high temperature strength, fracture toughness, fatigue limit, stress resistance, corrosion resistance and welding performance. It can work for a long time at 500℃, and the instantaneous working temperature can reach 800℃, and the working life can reach 6000 hours at 450℃. With its excellent performance, it is widely used in the aerospace industry.

[0003] Traditional forming methods mainly include casting, forging and extrusion. Electron beam selective forming is a new type of powder bed additive manufacturing technology. The full name of electron beam selective forming is Elecron Beam Selective Melting, or EBSM in English. EBSM manufactures three-dimensional metal parts by scanning with an electron beam, melting powder materials and depositing them layer by layer. Due to the high power of the electron beam and the high energy absorption rate of the material to the electron beam, EBSM technology has the characteristics of high efficiency and low thermal stress, and is suitable for the forming and manufacturing of refractory and high-performance metal materials such as titanium alloys and titanium-aluminum-based alloys.

[0004] At present, EBSM technology has achieved the forming of difficult-to-form metal materials such as lightweight metal materials, medium entropy alloys, Ti-Al high-temperature alloys, and refractory and difficult-to-weld metal materials. By adjusting appropriate process parameters, the density of metals and alloys formed by EBSM technology can reach 100%. In the prior art, the TA15 low-alloy steel produced by EBSM technology has almost no porosity in its microstructure, and its microstructure is martensite with high hardness; the TC4 titanium-based alloy manufactured by EBSM technology has comparable strength and elongation with the best titanium forging products under appropriate process parameters. Compared with traditional casting and forging forming methods, EBSM technology can be used as a new manufacturing method to form TA15 thin-walled components. However, the wall thickness of the thin-walled structure is thin, and the heat dissipation is fast during the forming and cooling process, which accelerates the solidification rate of the thin-walled complex TA15 titanium alloy formed by EBSM. Therefore, it is necessary to solve the problems of sudden curvature and ultra-thin wall thickness and easy deformation in the preparation process of thin-walled components, so as to obtain TA15 thin-walled structural parts with excellent performance. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing TA15 titanium alloy thin-walled components by electron beam selective forming technology.

[0006] The first object of the present invention is to provide a method for preparing TA15 titanium alloy thin-walled components by electron beam selective forming technology, comprising the following steps:

[0007] S1. TA15 titanium alloy powder was prepared by gas atomization method.

[0008] It should be noted that the present invention adopts plasma rotating electrode technology to prepare TA15 titanium alloy powder formed by electron beam selection. The full name of plasma rotating electrode technology in English is Plasma rotating electrode process, which is abbreviated as PREP in English. PREP has unparalleled advantages over other powder making technologies in preparing spherical metal powders with ultra-low interstitial element content, and the prepared metal powder has the advantages of easy control of spherical metal powder composition, good sphericity, and no hollow spheres and powder adhesion. PREP uses high-temperature plasma generated by DC arc as a heat source to melt the consumable electrode made of raw metal, and the centrifugal force generated by the high-speed rotation of the consumable electrode is used to throw out the molten liquid film to form droplets, which are atomized and solidified into spherical powders in an inert atmosphere. Under the centrifugal force generated by high-speed rotation, the molten liquid film quickly flows to the edge of the rod, and is broken and dispersed into fine droplets. Subsequently, the droplets are spheroidized and condensed into spherical powders in an inert gas due to surface tension during flight. Different electron gun powers will cause partial melting of the alloy powder, and the size of the fine droplets dispersed into them will be inconsistent, resulting in different compositions and size distributions of the formed spherical powders. The composition and size of the alloy powders during the printing process under different process parameters will affect the subsequent printing of thin-walled components. In order to select suitable powders for printing thin-walled components, the present invention changes the melting temperature by controlling the electron gun power of PREP, thereby obtaining alloy powders with different alloy composition. Preferably, the electron gun power of the atomization method is 110kW to 130kW.

[0009] When the drying temperature is too high and the drying time is short, the surface of the alloy powder is easily too dry while the inside is still moist, resulting in uneven drying; when the drying temperature is too low, the alloy powder is easily too wet, which affects the subsequent forming effect of thin-walled components. Preferably, the drying temperature is 40°C to 80°C and the drying time is 20min to 40min.

[0010] Preferably, the sieve mesh particle size is 50 μm to 100 μm to avoid blowing during the printing process due to the particle size being too large.

[0011] S2. Construct the required 3D model of TA15 titanium alloy thin-walled component, import it into slicing software, obtain slicing file, and import the slicing file into electron beam selective melting equipment.

[0012] It should be noted that in the process of drawing and processing parts, each printed part must be spaced 2mm apart to avoid printing failure due to excessive heat during the printing process. The present invention is to form thin-walled components with thin walls. When constructing the required TA15 titanium alloy thin-walled component three-dimensional model, the thickness of the three-dimensional model is less than or equal to 2.5mm.

[0013] S3. Preheating the substrate of the electron beam selective melting equipment in a vacuum environment.

[0014] It should be noted that before vacuuming the powder bed chamber in the electron beam selective melting equipment, first remove the oil, dust and other attachments on the substrate surface, and level the substrate and fill the powder in the molding chamber in the electron beam selective melting equipment. Then vacuumize. Since the high-speed rotation of molecules may cause mechanical damage or overheating, the life of the pump will be shortened; and when the vacuum pump speed is too low, it may not be able to reach the required vacuum degree or flow, resulting in reduced work efficiency or inability to complete the task. Therefore, during the vacuum treatment, the speed of the vacuum pump is 60,000 r / min, and the speed of the electron gun molecular pump is 72,000 r / min. When the vacuum degree reaches 8×10 -1 Then fill in the protective gas for 4 minutes, turn on the power to 60KV, and focus the electron beam after the voltage stabilizes.

[0015] The present invention uses a defocused current to preheat the substrate in a chessboard cycle, and monitors the substrate temperature in real time through a thermocouple attached to the center of the bottom of the substrate. The staged preheating of the substrate is an important process in electron beam selective melting, which can reduce thermal stress, volatilize volatile components, and protect the surface coating of the substrate to ensure the quality and stability of the melting process. At the same time, the substrate is preheated to ensure that a better stability phenomenon can occur in the early stage of printing. Preferably, the preheating process of the substrate is: in the first stage, it is preheated to 100°C with a current of 5mA, and then preheated to 240°C~260°C with a current of 10mA and kept warm for 5min~10min; in the second stage, it is preheated to 590°C~610°C with a current of 15mA and kept warm for 5min~10min; in the third stage, it is preheated to 740°C~840°C with a current of 20mA and kept warm for 5min~10min.

[0016] The purpose of substrate preheating is to avoid powder blowing caused by too fast a temperature drop, and to consolidate the powder bed surface for printing ta15 titanium alloy thin-walled components. Due to the instability of electron beam forming, the current and time of substrate preheating are fluctuating. Preferably, the maximum current of substrate preheating is 48mA, and the average current of substrate preheating is 12mA~16mA; the minimum time of substrate preheating is 8s~18s, and the maximum time of substrate preheating is 16s~25s. In addition, powder printing will start when the total preheating time of substrate preheating is greater than the sum of the minimum preheating time and the maximum preheating time.

[0017] S4. Spread TA15 titanium alloy powder on the preheated substrate, and scan and process each layer of slices in sequence according to the printing path to obtain a TA15 titanium alloy thin-walled component.

[0018] It should be noted that during the scanning process, the energy density calculation is composed of the scanning power, scanning speed, scanning spacing and the thickness of each slice; the present invention fixes the scanning spacing and the thickness of each slice; preferably, the scanning spacing is 40μm to 60μm, and the thickness of each slice is 40μm to 60μm; more preferably, the scanning spacing is 50μm, and the thickness of each slice is 50μm; then the scanning power and scanning rate are adjusted to change the energy density calculation, thereby controlling the processing window of the energy density and obtaining a stable energy density formula. Preferably, the scanning power is 14mA to 16mA, and the scanning speed is 4m / s to 5m / s.

[0019] Preferably, the scanning strategy is to rotate the scanning directions of two adjacent passes by 180°, and rotate the plane scanning directions of two adjacent layers by 90°.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] The present invention prints TA15 titanium alloy thin-walled components by electron beam selective melting. The high-energy electron beam selective melting is performed under vacuum conditions, which can effectively prevent the entry of foreign gas during the printing process. The formed TA15 titanium alloy thin-walled components have good surface quality, refined structure and uniform composition. The present invention adjusts the process parameters from powder making to forming stage to form TA15 titanium alloy thin-walled parts, improves the uniformity of temperature distribution, and solves the problem of easy deformation and cracking of TA15 titanium alloy thin-walled components; spherical powders with different compositions and size distributions are obtained by regulating the power of the electron gun, so as to optimize suitable powders for printing thin-walled components; and then preheating and regulating the preheating temperature and time of the substrate in stages, and finally controlling the processing window of energy density by regulating the scanning power and scanning rate during the printing process, so as to obtain a stable energy density formula, so as to avoid the phenomenon of wall thickness deformation such as warping during the printing of thin-walled components, thereby obtaining TA15 titanium alloy thin-walled components with better strength and plasticity matching.

[0022] Compared with the traditional process, the method of the present invention can overcome various casting defects brought about by casting, low yield rate and the problems of complex forming structure being limited during forging; electron beam selective melting forming can realize in-situ heat treatment, and the formed TA15 titanium alloy thin-walled components have good forming quality, high density, and excellent properties of high toughness and high strength.

[0023] Compared with titanium alloy prepared by laser additive manufacturing, the present invention prints samples at a higher preheating temperature, which can effectively reduce residual stress and prevent defects such as cracking. It has vacuum conditions and can prevent high-temperature oxidation. Under appropriate process parameters and a faster cooling rate, a TA15 titanium alloy thin-walled component with uniform structure and near α can be obtained. It can provide process improvements for thin-walled component modules with the same structure, providing a good process parameter foundation for subsequent TA15 titanium alloy thin-walled components with different wall thicknesses. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The microscopic morphology and particle size distribution diagram of the TA15 titanium alloy powder prepared in Comparative Example 1 of the present invention; wherein (a) is the microscopic morphology diagram, and (b) is the particle size distribution diagram.

[0025] Figure 2 Surface density diagram of TA15 titanium alloy thin-walled components prepared according to Examples 1 to 9 of the present invention and Comparative Examples 1 and 6; wherein, (a) is Comparative Example 1, (b) is Comparative Example 2, (c) is Comparative Example 3, (d) is Comparative Example 4, (e) is Comparative Example 5, (f) is Comparative Example 6, (g) is Example 2, (h) is Example 1, (i) is Example 3, (j) is Example 4, (k) is Example 5, (l) is Example 6, (m) is Example 7, (n) is Example 8, and (o) is Example 9.

[0026] Figure 3 These are microstructural morphology images of the TA15 titanium alloy thin-walled component prepared in Example 1 of the present invention at different magnifications; wherein (a) is at 200 μm, and (b) is at 10 μm. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand that the technical solution of the present invention can be implemented, the present invention is further described below in conjunction with specific embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment provides a method for preparing TA15 titanium alloy thin-walled components using electron beam selective forming technology.

[0030] Step 1: Preparation of TA15 titanium alloy powder

[0031] A titanium alloy rod with a diameter of 50 mm was loaded into the plasma rotating electrode atomization powder making equipment, and a mixed gas was introduced for atomization powder making; wherein, the distance between the plasma gun and the electrode rod was 45 mm, the power was 110 kW, the atomization speed was 2.1 kg / min, and the pressure was 2 MPa. The melting temperature was 1800 °C, and the vacuum degree was 0.6×10 -3 MPa, and put it into a drying oven at 115℃~125℃ for use; the atomized alloy powder is dried, and the drying process is continuous drying, the continuous drying temperature is 60℃, and the time is 30min; and the dried alloy powder is sieved using mesh sieves with particle sizes of 50μm and 100μm in turn to obtain TA15 titanium alloy powder.

[0032] Step 2: Construct a 3D model of TA15 titanium alloy thin-walled components

[0033] The Materialise Magics software of Theron was used to build the 3D processing platform and the processing parts in sequence; the model size of the processing parts was 40mm×40mm×2.5mm. Then the SL-EBM BuildPrepare software was used to slice the 3D model of the processing parts to obtain data, and the data was used for path planning to generate an STL format file, and the STL format file was imported into the electron beam selective melting equipment; and the slice layer thickness during the electron beam forming process was set to 50μm.

[0034] Step 3: EBSM printing of TA15 titanium alloy thin-walled components

[0035] (3.1) Use a mesh sieve with a particle size of 100 μm to sieve the TA15 titanium alloy powder; fill the sieved TA15 titanium alloy powder into the printing chamber, select a stainless steel substrate with a size of 170 mm × 170 mm × 10 mm, mark the center and level the substrate; then evacuate the printing chamber, where the speed of the vacuum pump is 60000 r / min, the speed of the electron gun molecular pump is 72000 r / min, and when the vacuum degree reaches 8×10 -1 Then fill in the protective gas for 4 minutes and then turn on the power to 60KV.

[0036] (3.2) The powder in the printing chamber is passed onto the substrate in the melting chamber, and the substrate is preheated in a chessboard cycle using a defocused current in the melting chamber. The substrate temperature is monitored in real time by a thermocouple attached to the center of the bottom of the substrate. In the first stage, the powder is preheated to 100°C with a 5mA current, and then preheated to 240°C with a 10mA current and kept warm for 10 minutes. In the second stage, the powder is preheated to 590°C with a 15mA current and kept warm for 10 minutes. In the third stage, the powder is preheated to 740°C with a 20mA current and kept warm for 10 minutes.

[0037] (3.3) After the substrate reaches the target temperature, the powder box drops powder and the powder scraper scrapes the powder to spread the TA15 titanium alloy powder on the substrate to form a powder bed with a spreading thickness of 50μm; the electron beam begins to perform selective melting scanning on the powder bed to obtain a single-layer solid sheet; the above method is repeated in sequence along the scanning path until a single-layer solid sheet is stacked layer by layer and formed, and the formed part is cooled to 100°C and removed with the forming chamber to obtain a TA15 titanium alloy thin-walled component; wherein, the scanning power is 14mA, the scanning speed is 5m / s, the scanning spacing is 50μm, the beam spot defocus is -0.500V, and the beam spot size is 0.100mm; the scanning direction of two adjacent passes is rotated 180°, and the scanning direction of two adjacent layers is rotated 90°, and the powder removal amount is 0.1mm.

[0038] Example 2

[0039] This embodiment provides a method for preparing TA15 titanium alloy thin-walled components using electron beam selective forming technology.

[0040] The difference between this embodiment and embodiment 1 is:

[0041] In this embodiment, the substrate preheating is divided into three stages: in the first stage, it is preheated to 100°C with a current of 5mA, and then preheated to 240°C with a current of 10mA and kept warm for 5 minutes; in the second stage, it is preheated to 590°C with a current of 15mA and kept warm for 5 minutes; in the third stage, it is preheated to 740°C with a current of 20mA and kept warm for 5 minutes.

[0042] Example 3

[0043] This embodiment provides a method for preparing TA15 titanium alloy thin-walled components using electron beam selective forming technology.

[0044] The difference between this embodiment and embodiment 1 is:

[0045] In this embodiment, the substrate preheating is divided into three stages: in the first stage, it is preheated to 100°C with a current of 5mA, and then preheated to 260°C with a current of 10mA and kept warm for 5 minutes; in the second stage, it is preheated to 610°C with a current of 15mA and kept warm for 5 minutes; in the third stage, it is preheated to 840°C with a current of 20mA and kept warm for 5 minutes.

[0046] Example 4

[0047] This embodiment provides a method for preparing TA15 titanium alloy thin-walled components using electron beam selective forming technology.

[0048] The difference between this embodiment and embodiment 1 is:

[0049] In this embodiment, the substrate preheating is divided into three stages: in the first stage, it is preheated to 100°C with a current of 5mA, and then preheated to 260°C with a current of 10mA and kept warm for 10 minutes; in the second stage, it is preheated to 610°C with a current of 15mA and kept warm for 10 minutes; in the third stage, it is preheated to 840°C with a current of 20mA and kept warm for 10 minutes.

[0050] Example 5

[0051] This embodiment provides a method for preparing TA15 titanium alloy thin-walled components using electron beam selective forming technology.

[0052] The difference between this embodiment and embodiment 1 is:

[0053] In this embodiment, the scanning power of the scanning process is 14 mA and the scanning speed is 4 m / s.

[0054] Example 6

[0055] This embodiment provides a method for preparing TA15 titanium alloy thin-walled components using electron beam selective forming technology.

[0056] The difference between this embodiment and embodiment 1 is:

[0057] The scanning power of the scanning process in this embodiment is 15mA and the scanning speed is 4m / s

[0058] Example 7

[0059] This embodiment provides a method for preparing TA15 titanium alloy thin-walled components using electron beam selective forming technology.

[0060] The difference between this embodiment and embodiment 1 is:

[0061] In this embodiment, the scanning power of the scanning process is 16 mA and the scanning speed is 4 m / s.

[0062] Example 8

[0063] This embodiment provides a method for preparing TA15 titanium alloy thin-walled components using electron beam selective forming technology.

[0064] The difference between this embodiment and embodiment 1 is:

[0065] In this embodiment, the scanning power of the scanning process is 15 mA and the scanning speed is 5 m / s.

[0066] Example 9

[0067] This embodiment provides a method for preparing TA15 titanium alloy thin-walled components using electron beam selective forming technology.

[0068] The difference between this embodiment and embodiment 1 is:

[0069] In this embodiment, the scanning power of the scanning process is 16 mA and the scanning speed is 5 m / s.

[0070] Comparative Example 1

[0071] This comparative example provides a method for preparing TA15 titanium alloy thin-walled components using electron beam selective forming technology.

[0072] Step 1: Preparation of TA15 titanium alloy powder

[0073] A titanium alloy rod with a diameter of 50 mm was loaded into the plasma rotating electrode atomization powder making equipment, and a mixed gas was introduced for atomization powder making; wherein, the distance between the plasma gun and the electrode rod was 45 mm, the power was 110 kW, the atomization speed was 2.1 kg / min, and the pressure was 2 MPa. The melting temperature was 1800 °C, and the vacuum degree was 0.6×10 -3 MPa, and put it into a drying oven at 115°C to 125°C for use; then use mesh sieves with particle sizes of 50μm and 100μm to sieve the dried alloy powder in turn to obtain TA15 titanium alloy powder.

[0074] Step 2: Construct a 3D model of TA15 titanium alloy thin-walled components

[0075] The Materialise Magics software of Theron was used to build the 3D processing platform and the processing parts in sequence; the model size of the processing parts was 40mm×40mm×2.5mm. Then the SL-EBM BuildPrepare software was used to slice the 3D model of the processing parts to obtain data, and the data was used for path planning to generate an STL format file, and the STL format file was imported into the electron beam selective melting equipment; and the slice layer thickness during the electron beam forming process was set to 50μm.

[0076] Step 3: EBSM printing of TA15 titanium alloy thin-walled components

[0077] (3.1) Use a mesh sieve with a particle size of 100 μm to sieve the TA15 titanium alloy powder; fill the sieved TA15 titanium alloy powder into the printing chamber, select a stainless steel substrate with a size of 170 mm × 170 mm × 10 mm, mark the center and level the substrate; then evacuate the printing chamber, where the speed of the vacuum pump is 60000 r / min, the speed of the electron gun molecular pump is 72000 r / min, and when the vacuum degree reaches 8×10 -1 Then fill in the protective gas for 4 minutes and then turn on the power to 60KV.

[0078] (3.2) The powder in the printing chamber is passed onto the substrate in the melting chamber, and the substrate is directly preheated to 700°C in the melting chamber.

[0079] (3.3) After the substrate reaches the target temperature, the powder box drops powder and the powder scraper scrapes the powder to spread the TA15 titanium alloy powder on the substrate to form a powder bed with a spreading thickness of 50μm; the electron beam begins to perform selective melting scanning on the powder bed to obtain a single-layer solid sheet; the above method is repeated in sequence along the scanning path until a single-layer solid sheet is stacked layer by layer and formed, and the formed part is cooled to 100°C and removed with the forming chamber to obtain a TA15 titanium alloy thin-walled component; wherein, the scanning power is 14mA, the scanning speed is 5m / s, the scanning spacing is 50μm, the beam spot defocus is -0.500V, and the beam spot size is 0.100mm; the scanning direction of two adjacent passes is rotated 180°, and the scanning direction of two adjacent layers is rotated 90°, and the powder removal amount is 0.1mm.

[0080] Comparative Example 2

[0081] The difference between this comparative example and comparative example 1 is:

[0082] In this comparative example, the power of the plasma gun in preparing TA15 titanium alloy powder is 120 kW.

[0083] Comparative Example 3

[0084] The difference between this comparative example and comparative example 1 is:

[0085] In this comparative example, the power of the plasma gun in preparing TA15 titanium alloy powder is 130 kW.

[0086] Comparative Example 4

[0087] The difference between this comparative example and comparative example 1 is:

[0088] In the preparation of TA15 titanium alloy powder in this comparative example, the atomized alloy powder was dried at a temperature of 40° C. for 20 min.

[0089] Comparative Example 5

[0090] The difference between this comparative example and comparative example 1 is:

[0091] In the present comparative example, in the preparation of TA15 titanium alloy powder, the atomized alloy powder was dried at a temperature of 60° C. and a drying time of 30 min.

[0092] Comparative Example 6

[0093] The difference between this comparative example and comparative example 1 is:

[0094] In the present comparative example, in the preparation of TA15 titanium alloy powder, the atomized alloy powder was dried at a temperature of 80° C. and a drying time of 40 min.

[0095] Table 1 is the composition table of TA15 titanium alloy powder of Comparative Examples 1 to 3 at different electron gun powers. It can be seen from Table 1 that with the increase of electron gun power, the proportions of Mo, Fe, Si, C and O elements gradually decrease.

[0096] Figure 1 The microscopic morphology and particle size distribution diagram of the TA15 titanium alloy powder prepared in the comparative example; wherein (a) is the microscopic morphology diagram, and (b) is the particle size distribution diagram. Figure 1 As shown in (a), the TA15 titanium alloy powder is spherical or nearly spherical in shape, with a smooth surface, and a small amount of extremely fine powder particles adhere to the surface of large powder particles. Figure 1 As shown in (b), the TA15 titanium alloy powder size shows a Gaussian distribution between 45 μm and 106 μm, with an average particle size of 70.66 μm, and D(10) and D(90) are 54.65 μm and 90.92 μm, respectively.

[0097] Figure 2 The surface density diagrams of TA15 titanium alloy thin-walled components prepared in Examples 1 to 9 and Comparative Examples 1 and 6 are shown; wherein (a) is Comparative Example 1, (b) is Comparative Example 2, (c) is Comparative Example 3, (d) is Comparative Example 4, (e) is Comparative Example 5, (f) is Comparative Example 6, (g) is Example 2, (h) is Example 1, (i) is Example 3, (j) is Example 4, (k) is Example 5, (l) is Example 6, (m) is Example 7, (n) is Example 8, and (o) is Example 9. Figure 2 As shown in the figure, with the optimization of process parameters, the number of micropores gradually decreased and the size was significantly refined. Finally, the optimal 2.5mm thin-walled sample surface only had a few nano-sized micropores, and the surface density was 99.94%. Under this process parameter, the heat input of the sample was relatively balanced during the printing process, the molten pool could be evenly spread, the density of the formed part was high, and the hole shape was approximately circular.

[0098] Due to the high cooling rate of the EBSM process, the microstructure and grain size obtained are finer. The formed TA15 titanium alloy is mostly epitaxially grown columnar crystals along the forming height direction, and the original β grain boundaries still exist. Figure 3 The microstructure morphology of the TA15 titanium alloy thin-walled component prepared in Example 1 at different magnifications; (a) is at 200 μm, and (b) is at 10 μm. Figure 3As shown in the figure, the TA15 titanium alloy thin-walled structure prepared by electron beam selective melting also has β columnar crystals growing along the printing direction. The growth direction of the β columnar crystals is perpendicular to the direction of heat flow. The internal structure of the β columnar crystals and the chessboard shape. Figure 3 As shown in (b), a large number of fine needle-shaped α' martensite can be observed from the distribution inside the β columnar crystal, forming a basket-like structure. The phenomenon of forming a basket-like structure is due to the fact that the electron beam in the EBSM forming process quickly moves away after the molten pool is formed, and the temperature gradient between the molten pool and the surrounding environment increases sharply, resulting in an increase in the solidification rate. When the cooling rate is greater than 410Ks -1 When the temperature is high, the atoms in the lattice move, causing almost all columnar β grains to transform into non-diffused α phase.

[0099] Mechanical properties test

[0100] The present invention conducts mechanical property tests on TA15 titanium alloy thin-walled components prepared in Examples 1 to 9 and Comparative Examples 1 to 6. The macroscopic mechanical properties are only tested for room temperature tensile testing. The tensile test is conducted in accordance with GB / T 228.1-2010, with a tensile rate of 3 mm / min, wherein the room temperature tensile test is conducted on an Instron 5569, and the tensile specimen size is 24 mm long and 4 mm in gauge length. The present invention takes 5 specimens of Examples 1 to 16, and uses a DK77 wire cutting machine to cut the bottom of the specimen. Before the experiment, the surface of the specimen is polished smooth with sandpaper to reduce surface defects during the cutting process and reduce the impact on the experimental results. The tensile properties and density of the specimen are then tested, and the average of the score measurement results of the 5 specimens of each embodiment is taken as the score measurement result of the embodiment.

[0101] Table 2 Mechanical properties data of TA15 titanium alloy thin-walled components prepared in Examples 1 to 9 and Comparative Examples 1 to 6.

[0102]

[0103] As shown in Table 2. The tensile strength of the TA15 titanium alloy thin-walled components prepared in Comparative Examples 1 to 3 are 1043MPa, 1032MPa and 895MPa, respectively. As the electron gun power increases, the melting temperature increases, the melting degree of the TA15 titanium alloy powder is different, and the tensile strength gradually decreases; and the molding density is 99.57%, 99.6% and 95.79%, respectively. When the electron gun power increases to 130kW, the density is also the lowest; preferably, the electron gun power of the gas atomization method is 110kW to 130kW. More preferably, the electron gun power of the gas atomization method is 110kW.

[0104] The maximum tensile strength of the thin-walled component prepared in Example 5 can reach 1136 MPa, but the elongation of the thin-walled component is poor, which is 10.7%; while the maximum tensile strength of the thin-walled component prepared in Example 1 with better strength-plasticity matching is 1100 MPa and the elongation is 13.2%. The forming process of the subsequent Example 1 of the present invention is used to form thinner thin-walled components.

[0105] Compared with the national standard requirements such as forging; the tensile strength σ b =930MPa~1130MPa, yield strength σ s >855MP and elongation δ>10%; the mechanical properties of the TA15 titanium alloy thin-walled components prepared by the present invention meet the requirements of ASTM rolled thin plates, most of the formed samples meet the requirements, and they have no obvious defects and are considered to meet the use standards.

[0106] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. If these modifications and variations of the present invention fall within the scope of the equivalent technology of the present invention, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing TA15 titanium alloy thin-walled components by electron beam selective forming technology, characterized in that: The following steps are involved: TA15 titanium alloy powder was prepared by gas atomization method; Construct the required 3D model of TA15 titanium alloy thin-walled components, slice the 3D model, obtain several layers of slice files, and import the printing path corresponding to the slice file into the electron beam selective melting equipment; In a vacuum environment, the substrate of the electron beam selective melting equipment is preheated in stages; Spread TA15 titanium alloy powder on the preheated substrate, and scan and process each layer of slices in sequence according to the printing path to obtain TA15 titanium alloy thin-walled components; The scanning power is 14mA-16mA, and the scanning speed is 4m / s-5m / s.

2. The method for preparing TA15 titanium alloy thin-walled components by electron beam selective forming technology according to claim 1, characterized in that: The thickness of the three-dimensional model is less than or equal to 2.5 mm.

3. The method for preparing TA15 titanium alloy thin-walled components by electron beam selective forming technology according to claim 1, characterized in that: The staged preheating process is as follows: in the first stage, the temperature is preheated to 100°C with a current of 5mA, and then preheated to 240°C to 260°C with a current of 10mA and kept warm for 5min to 10min; in the second stage, the temperature is preheated to 590°C to 610°C with a current of 15mA and kept warm for 5min to 10min; in the third stage, the temperature is preheated to 740°C to 840°C with a current of 20mA and kept warm for 5min to 10min.

4. The method for preparing TA15 titanium alloy thin-walled components by electron beam selective forming technology according to claim 1, characterized in that: The electron gun power of the gas atomization method is 110 kW to 130 kW.

5. The method for preparing TA15 titanium alloy thin-walled components by electron beam selective forming technology according to claim 1, characterized in that: The atomized TA15 titanium alloy powder is dried at a temperature of 40° C. to 80° C. for a time of 20 min to 40 min.

6. The method for preparing TA15 titanium alloy thin-walled components by electron beam selective forming technology according to claim 1, characterized in that: The scanning interval is 40 μm to 60 μm, and the thickness of each slice is 40 μm to 60 μm.

7. The method for preparing TA15 titanium alloy thin-walled components by electron beam selective forming technology according to claim 1, characterized in that: The scanning process is that the scanning directions of two adjacent passes are rotated by 180°, and the plane scanning directions of two adjacent layers are rotated by 90°.

8. The method for preparing TA15 titanium alloy thin-walled components by electron beam selective forming technology according to claim 1, characterized in that: The particle size of the TA15 titanium alloy powder is 45 μm to 106 μm.

9. A TA15 titanium alloy thin-walled component prepared by the method for producing a TA15 titanium alloy thin-walled component according to any one of claims 1 to 8.

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