Additive manufacturing method of TiAl alloy material with three-dimensional overlapped net microstructure

Abstract

The invention relates to the technical field of metal material manufacturing, in particular to an additive manufacturing method of a TiAl alloy material with a three-dimensional net stacking microstructure, which comprises the following steps: preheating a forming substrate to a set temperature, and preserving heat; according to a preset scanning path, TiAl alloy powder laid on a forming substrate layer by layer is scanned, and fixed-point scanning melting of a low-energy scanning area and a high-energy scanning area is correspondingly conducted on the TiAl alloy powder laid on the forming substrate layer by layer through a continuous electron beam and a continuous electron beam superposed pulse electron beam, the TiAl alloy material with the three-dimensional overlapped net microstructure is obtained; wherein the scanning speed is greater than or equal to 1000mm / s. The additive manufacturing method of the TiAl alloy material with the three-dimensional overlapped net microstructure aims at solving the problem of how to improve the high strength and the high crack propagation resistance of the TiAl alloy material at the same time.

Description

Technical Field

[0001] This invention relates to the field of metal material manufacturing technology, and specifically to an additive manufacturing method for TiAl alloy materials with a three-dimensional stacked microstructure. Background Technology

[0002] Electron beam selective melting additive manufacturing is a novel manufacturing technology that is very suitable for processing brittle materials. The TiAl alloy parts developed using this technology have already been applied in the aerospace field.

[0003] Currently, the core components of electron beam selective melting (EPM) equipment are mainly a high-voltage power supply and an electron gun. The high-voltage power supply consists of an accelerating power supply, a cathode heating power supply, and a bias power supply, providing continuous electron beam output during the forming process. The high-voltage power supply typically uses an inverter circuit to convert 380V AC power into the required 60KV DC high voltage for the electron gun output. Pulsed electron beam selective melting technology modulates the beam current into a pulsed form for energy output. At the same average power, pulsed electron beam selective melting has a higher energy density and greater penetration capability compared to traditional continuous beam selective melting.

[0004] Most TiAl alloys currently in service have equiaxed or lamellar structures, and each type of alloy has its own advantages and disadvantages. TiAl alloys with equiaxed structures have higher strength but poorer resistance to crack propagation, while TiAl alloys with lamellar structures have the opposite properties.

[0005] Therefore, the inventors provide an additive manufacturing method for TiAl alloy materials with a three-dimensional stacked microstructure. Summary of the Invention

[0006] (1) Technical problems to be solved This invention provides an additive manufacturing method for TiAl alloy materials with a three-dimensional stacked microstructure, solving the technical problem of how to simultaneously improve the high strength and high crack propagation resistance of TiAl alloy materials.

[0007] (2) Technical solution This invention provides an additive manufacturing method for TiAl alloy materials with a three-dimensional stacked microstructure, comprising the following steps: Preheat the molded substrate to the set temperature and maintain that temperature. According to the preset scanning path, a continuous electron beam and a pulsed electron beam superimposed on the continuous electron beam are used to perform fixed-point scanning melting of TiAl alloy powder layered on the shaped substrate in the corresponding low-energy scanning region and high-energy scanning region, respectively, to obtain TiAl alloy material with a three-dimensional stacked microstructure; wherein, the scanning speed is ≥1000mm / s.

[0008] Further, according to a preset scanning path, a continuous electron beam and a pulsed electron beam are used to perform point-to-point scanning melting of the TiAl alloy powder layered on the shaped substrate in corresponding low-energy and high-energy scanning regions, respectively, to obtain a TiAl alloy material with a three-dimensional stacked microstructure. Specifically: The continuous electron beam is used to perform low-energy scanning melting on all forming regions, and the continuous electron beam is superimposed with the pulsed electron beam to perform scanning melting on the high-energy scanning region, so as to obtain a grid-like energy input mode and obtain the TiAl alloy material with a three-dimensional grid microstructure.

[0009] Furthermore, a composite bias power supply device is used to achieve simultaneous output of the continuous electron beam and the pulsed electron beam. The composite bias power supply device includes a pulse bias circuit and an isolation switch located at the output terminal of the pulse bias circuit. The isolation switch is used to switch the pulse bias.

[0010] Furthermore, the pulse bias power supply is always on during the processing.

[0011] Furthermore, the pulse bias circuit is composed of an independent bias base value generation circuit and a bias pulse generation circuit connected in series; wherein, When both the bias base value generation circuit and the bias pulse generation circuit are working, a pulse bias is generated to achieve the simultaneous output of the continuous electron beam and the pulsed electron beam.

[0012] Furthermore, the pulse bias circuit has the following two operating modes: When both the bias base value generation circuit and the bias pulse generation circuit output voltage, the output voltage U0 of the rectifier filter circuit is measured. Since the output voltage U1 of the bias base value generation circuit and the output voltage U2 of the bias pulse generation circuit are connected in series, and the two circuits are input in parallel by the same given signal, when the output voltage U1 of the bias pulse generation circuit decreases by the set voltage value... When U is reached, the corresponding U2 increases simultaneously. U, the bias voltage U0 = U1 + U2 measured at the output terminal is a stable and constant DC voltage; When the bias base value generating circuit has an output voltage and the output voltage of the bias pulse generating circuit is zero, since the output value of the bias pulse generating circuit is 0V, the output voltage of the rectifier filter circuit is the base value voltage output.

[0013] Furthermore, the disconnecting switch is a high-voltage MOSFET device.

[0014] Furthermore, when the isolating switch is open, the electron gun outputs the combined energy of the continuous electron beam and the pulsed electron beam; when the isolating switch is closed, the electron gun only outputs the continuous energy provided by the continuous electron beam.

[0015] Furthermore, the parameters of the continuous electron beam are: current 8-13mA, accelerating voltage 50-70kV, and scanning rate 1000-1500mm / s.

[0016] Furthermore, the parameters of the pulsed electron beam are: current 5-10mA, duty cycle 10%-20%.

[0017] (3) Beneficial effects In summary, this invention utilizes electron beam selective melting additive manufacturing to perform fixed-point rapid non-uniform scanning (i.e., mesh scanning with different melting energy inputs at different positions on the scanning plane) on the same melting plane, thereby achieving spatial mesh melting energy input and obtaining the desired three-dimensional mesh microstructure. This enables the development of TiAl alloy materials with a three-dimensional mesh microstructure. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of an additive manufacturing method for a TiAl alloy material with a three-dimensional overlay microstructure provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the scanning energy distribution during the additive manufacturing of a TiAl alloy material with a three-dimensional stacked microstructure, provided in an embodiment of the present invention. Figure 3(a) is a microstructure of a conventional TiAl alloy material; Figure 3(b) is a microstructure diagram of a TiAl alloy material with a three-dimensional overlay microstructure provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a pulse bias circuit provided in an embodiment of the present invention.

[0020] In the picture: 1-Low-energy scanning region; 2-High-energy scanning region; 3-Bias base circuit; 4-Bias pulse circuit. Detailed Implementation

[0021] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention, but should not be used to limit the scope of the present invention.

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] This invention provides an additive manufacturing method for TiAl alloy materials with a three-dimensional stacked microstructure. (See also...) Figure 1 The method may include the following steps: S100: Preheat the molded substrate to the set temperature and keep it warm.

[0025] Specifically, the set temperature is generally 1050℃, and the heat preservation time is 20 minutes.

[0026] S200. According to the preset scanning path, a continuous electron beam and a continuous electron beam superimposed with a pulsed electron beam are used to perform fixed-point scanning melting of the TiAl alloy powder layered on the forming substrate in the corresponding low-energy scanning area and high-energy scanning area, respectively, to obtain TiAl alloy material with a three-dimensional stacked microstructure; wherein, the scanning speed is ≥1000mm / s.

[0027] Specifically, depending on the scan path, see [link / reference]. Figure 2A continuous electron beam is used to scan and melt the low-energy scanning region 1. Then, at a high-speed electron beam with a scanning speed of at least 1000 mm / s, within a region no larger than 100 mm × 100 mm, a pulsed electron beam is rapidly added to scan and melt the high-energy scanning region 2 using a continuous electron beam superposition pulsed electron beam scanning method. This achieves a mesh-like energy input mode, resulting in a TiAl alloy material with a three-dimensional mesh microstructure. Since the maximum currently achievable size of the three-dimensional mesh microstructure material is 100 mm × 100 mm, this region needs to be divided into multiple smaller sub-regions to further shorten the distance between the low-energy scanning region 1 and the high-energy scanning region 2 (to only a few millimeters). Then, a scanning speed of at least 1000 mm / s is used to achieve rapid fixed-point scanning.

[0028] Furthermore, a composite bias power supply device is employed to achieve simultaneous output of continuous and pulsed electron beams. This device includes a pulse bias circuit and an isolating switch located at the output of the pulse bias circuit, using the isolating switch to switch the pulse bias. The pulse bias power supply remains on throughout the processing, effectively avoiding response delays caused by the charging and discharging of the high-voltage power supply's own inverter circuit. The isolating switch is a high-voltage MOSFET device capable of withstanding 2000V and has a switching frequency of up to 200Hz, allowing for rapid power adjustment at the set scanning speed. During the scanning process, both the base bias power supply and the pulse bias power supply are always on. When the isolating switch module of the bias pulse circuit is on, the electron gun outputs a composite energy of continuous and pulsed beams; when the isolating switch module is off, the electron gun only outputs the base bias to provide continuous energy. This device utilizes the free and rapid switching of the pulse beam to achieve online adjustment of the energy source and energy level.

[0029] The parameters for the continuous electron beam are: current 8–13 mA, accelerating voltage 50–70 kV, and scanning rate 1000–1500 mm / s. The parameters for the pulsed electron beam are: current 5–10 mA and duty cycle 10%–20%.

[0030] As an optional implementation method, such as Figure 4 As shown, the pulse bias circuit is composed of an independent bias base value generation circuit 3 and a bias pulse generation circuit 4 connected in series; wherein, when both the bias base value generation circuit and the bias pulse generation circuit are working, a pulse bias is generated to realize the output of the pulsed electron beam.

[0031] Meanwhile, this pulse bias circuit has the following two operating modes: When both the bias base value generation circuit 3 and the bias pulse generation circuit 4 output voltage, the output voltage U0 of the rectifier filter circuit is measured. Since the output voltage U1 of the bias base value generation circuit 3 and the output value U2 of the bias pulse generation circuit 4 are connected in series, and the two circuits are input in parallel by the same given signal, when the output voltage U1 of the bias base value generation circuit 3 decreases by the set voltage value... When U is reached, the corresponding U2 increases simultaneously. U, the bias voltage U0 = U1 + U2 measured at the output terminal is a stable and constant DC voltage; When the bias base value generation circuit 3 has an output voltage and the output voltage of the bias pulse generation circuit 4 is zero, since the output value of the bias pulse generation circuit 4 is 0V, the output voltage of the rectifier filter circuit is the base value voltage output.

[0032] Example 1 Taking TiAl alloy materials with directional solidification characteristics as an example, its electron beam selective melting additive manufacturing method includes the following steps: 1) TiAl alloy powder of Ti-48Al-2Cr-2Nb was prepared by gas atomization; 2) Heat the molded substrate to 1050℃ and hold for 20 minutes; 3) Start the electron beam generator and control the electron beam current through a composite bias power supply. Perform grid scanning of TiAl alloy powder laid on the forming substrate at different energies according to a pre-set melting path. Use a continuous electron beam for continuous scanning and melting, and add pulsed electron beam scanning to the high-energy scanning area to increase energy input. The parameters of the continuous electron beam are: current 10mA, accelerating voltage 60kV, and scanning rate 1500mm / s; the parameters of the pulsed electron beam are: current 7mA and duty cycle 13%. 4) After melting is complete, TiAl alloy powder is continued to be laid to form the next layer.

[0033] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0034] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. An additive manufacturing method for a TiAl alloy material with a three-dimensional stacked network microstructure, characterized in that, The method includes the following steps: Preheat the molded substrate to the set temperature and maintain that temperature. According to the preset scanning path, a continuous electron beam and a pulsed electron beam superimposed on the continuous electron beam are used to perform fixed-point scanning melting of TiAl alloy powder layered on the shaped substrate in the corresponding low-energy scanning region and high-energy scanning region, respectively, to obtain TiAl alloy material with a three-dimensional stacked microstructure; wherein, the scanning speed is ≥1000mm / s.

2. The additive manufacturing method for TiAl alloy material with a three-dimensional stacked network microstructure according to claim 1, characterized in that, The process involves using a preset scanning path, employing a continuous electron beam and a pulsed electron beam superimposed on the continuous electron beam to perform targeted scanning melting of TiAl alloy powder layered on the shaped substrate in corresponding low-energy and high-energy scanning regions, respectively, to obtain a TiAl alloy material with a three-dimensional network microstructure. Specifically: According to the scanning path, the continuous electron beam is used to perform low-energy scanning melting on the low-energy scanning region, and the continuous electron beam is superimposed with the pulsed electron beam to perform scanning melting on the high-energy scanning region, so as to obtain a grid-like energy input mode and obtain the TiAl alloy material with a three-dimensional grid microstructure.

3. The additive manufacturing method for TiAl alloy material with a three-dimensional stacked network microstructure according to claim 1, characterized in that, A composite bias power supply device is used to achieve the simultaneous output of the continuous electron beam and the pulsed electron beam. The composite bias power supply device includes a pulse bias circuit and an isolation switch located at the output terminal of the pulse bias circuit. The isolation switch is used to switch the pulse bias.

4. The additive manufacturing method for TiAl alloy material with a three-dimensional stacked network microstructure according to claim 3, characterized in that, The pulse bias power supply is always on during the processing.

5. The additive manufacturing method for TiAl alloy material with a three-dimensional stacked network microstructure according to claim 3, characterized in that, The pulse bias circuit is composed of an independent bias base value generation circuit and a bias pulse generation circuit connected in series; wherein... When both the bias base value generation circuit and the bias pulse generation circuit are working, a pulse bias is generated to achieve the simultaneous output of the continuous electron beam and the pulsed electron beam.

6. The additive manufacturing method for TiAl alloy material with a three-dimensional stacked network microstructure according to claim 5, characterized in that, The pulse bias circuit has the following two operating modes: When both the bias base value generation circuit and the bias pulse generation circuit output voltage, the output voltage U0 of the rectifier filter circuit is measured. Since the output voltage U1 of the bias base value generation circuit and the output value U2 of the bias pulse generation circuit are connected in series, and the two circuits are input in parallel by the same given signal, when the output voltage U1 of the base value circuit decreases by the set voltage value... When U is reached, the corresponding U2 increases simultaneously. U, the bias voltage U0 = U1 + U2 measured at the output terminal is a stable and constant DC voltage; When the bias base value generating circuit has an output voltage and the output voltage of the bias pulse generating circuit is zero, since the output value of the bias pulse generating circuit is 0V, the output voltage of the rectifier filter circuit is the base value voltage output.

7. The additive manufacturing method for TiAl alloy material with a three-dimensional stacked network microstructure according to claim 3, characterized in that, The disconnecting switch is a high-voltage MOSFET device.

8. The additive manufacturing method for TiAl alloy material with a three-dimensional stacked network microstructure according to claim 3, characterized in that, When the isolation switch is open, the electron gun outputs the combined energy of the continuous electron beam and the pulsed electron beam; when the isolation switch is closed, the electron gun only outputs the continuous energy provided by the continuous electron beam.

9. The additive manufacturing method for TiAl alloy material with a three-dimensional stacked network microstructure according to claim 1, characterized in that, The parameters of the continuous electron beam are: current 8-13mA, accelerating voltage 50-70kV, and scanning rate 1000-1500mm / s.

10. The additive manufacturing method for TiAl alloy material with a three-dimensional stacked network microstructure according to claim 1, characterized in that, The parameters of the pulsed electron beam are: current 5-10mA, duty cycle 10%-20%.

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