阅读说明：本技术 一种静磁场下3D打印γ-TiAl合金的方法及其装置 (Method and device for 3D printing of gamma-TiAl alloy in static magnetic field ) 是由 王江 任忠鸣 陈超越 曹庭玮 帅三三 胡涛 玄伟东 李传军 于 2021-01-11 设计创作，主要内容包括：本发明提供了一种静磁场下3D打印γ-TiAl合金的方法,按照γ-TiAl合金成型件的三维立体数据对预合金粉末进行3D打印,得到γ-TiAl合金；所述3D打印在静磁场中进行。本发明制备γ-TiAl合金时施加外部磁场来获取致密高性能的γ-TiAl合金,外部磁场可以进一步改善合金内部的组织形态,减少残余应力,获得更高的力学性能,减少后续热处理可能会带来的开裂风险；采用3D打印技术制备γ-TiAl合金具有柔性高,材料利用率高,生产周期短等特点,并且γ-TiAl合金中的凝固组织细小。实施例的结果显示,本发明制备的γ-TiAl合金的抗拉强度＞560MPa,硬度＞420HV,延伸率为0.5～0.8％。(The invention provides a method for 3D printing of gamma-TiAl alloy in a static magnetic field, which comprises the following steps of 3D printing prealloy powder according to three-dimensional data of a gamma-TiAl alloy forming part to obtain gamma-TiAl alloy; the 3D printing is performed in a static magnetic field. According to the invention, an external magnetic field is applied to obtain the dense high-performance gamma-TiAl alloy when the gamma-TiAl alloy is prepared, the internal structure of the alloy can be further improved by the external magnetic field, the residual stress is reduced, the higher mechanical property is obtained, and the cracking risk possibly brought by the subsequent heat treatment is reduced; the gamma-TiAl alloy prepared by adopting the 3D printing technology has the characteristics of high flexibility, high material utilization rate, short production period and the like, and the solidification structure in the gamma-TiAl alloy is fine. The results of the examples show that the tensile strength of the gamma-TiAl alloy prepared by the invention is more than 560MPa, the hardness is more than 420HV, and the elongation is 0.5-0.8%.)

1. A method for 3D printing gamma-TiAl alloy in static magnetic field, 3D printing prealloy powder according to three-dimensional data of a gamma-TiAl alloy forming part to obtain gamma-TiAl alloy; the 3D printing is performed in a static magnetic field.

2. The method of claim 1, wherein the direction of the static magnetic field is perpendicular to the direction of 3D printing.

3. The method according to claim 1, wherein the static magnetic field is a steady magnetic field, and the static magnetic field has a strength of 0.3 to 0.5T.

4. The method according to claim 1, wherein the parameters of the 3D printing are: the laser scanning speed is 3-8 mm/s, the laser power is 800-1200W, the powder feeding speed is 3-10 g/min, and the powder feeding air carrying capacity is 5-10L/min.

5. The method of claim 1, wherein the pre-alloyed powder is a spherical or near-spherical titanium-aluminum alloy powder, the pre-alloyed powder having a particle size distribution ranging from 53 μm to 150 μm and an average particle size ranging from 75 μm to 90 μm.

6. The method according to claim 1, wherein the 3D printing is performed under a protective atmosphere having an oxygen content of less than 50 ppm.

7. A device for 3D printing of gamma-TiAl alloy in a static magnetic field is characterized in that a laser cladding head of the device is provided with a magnet device.

8. The apparatus of claim 7, wherein the magnet means comprises two static magnets or two electromagnets; the two static magnets or the two electromagnets are oppositely arranged on two sides of a nozzle of the laser cladding head.

9. The apparatus of claim 7, comprising: the device comprises a substrate heating device, a titanium alloy substrate, a magnet device, a laser, a powder feeder, a laser cladding head, a water cooling system, a numerical control system and a gas circulation system;

the substrate heating device, the titanium alloy substrate and the laser cladding head are positioned in the forming cavity; the running system of the numerical control system is positioned inside the forming cavity, and the operating platform of the numerical control system is positioned outside the forming cavity;

the laser cladding head is fixed on a traveling system of the numerical control system; the powder feeder is communicated with the laser cladding head through a powder feeding pipeline; the laser is connected with the laser cladding head through an optical fiber; and the water cooling system is connected to the laser cladding head through a pipeline.

10. The apparatus of claim 9, wherein the laser is CO₂A gas laser, a YAG solid laser, a fiber laser, or a semiconductor laser.

Technical Field

The invention relates to the technical field of metal additive manufacturing, in particular to a method and a device for 3D printing of gamma-TiAl alloy in a static magnetic field.

Background

The gamma-TiAl alloy has excellent mechanical properties, excellent flame retardant property, low density and other characteristics, is a potential substitute material for manufacturing a novel low-pressure turbine engine, but is difficult to process by using a common processing and forming method due to low room temperature plasticity. The gamma-TiAl alloy obtained by traditional casting has a large structure and needs quenching and aging treatment, while the gamma-TiAl alloy is easy to be quenched and cracked during quenching, and the titanium aluminum alloy has the characteristics of poor cutting performance, blade damage and the like, so that the subtractive manufacturing of the titanium aluminum alloy consumes very high cost.

At present, the internal structure obtained by using the laser additive technology is mostly a fine near-rapid solidification structure, and the obtained gamma-TiAl alloy component also has mechanical properties comparable to that of a forged piece. However, since the room temperature plasticity of γ -TiAl alloys is poor, which makes stereolithography using laser difficult, γ -TiAl alloys prepared by conventional 3D printing devices are prone to crack from the bottom, even along the building direction to the top, which is a crack caused by excessive internal residual stress. In the existing reports, a high preheating temperature is mostly used for obtaining compact gamma-TiAl alloy during 3D printing, so that the process flow is increased, the production cost is increased, and meanwhile, the structure obtained by overhigh temperature is often similar to the gamma-TiAl alloy obtained by a selective area electron beam melting technology, so that the advantage of fine laser three-dimensional forming structure is lost.

Therefore, it is required to provide a method for preparing γ -TiAl alloy, which can change the solidification behavior of γ -TiAl alloy during the laser stereoforming process, thereby obtaining γ -TiAl alloy with good compactness and excellent performance.

Disclosure of Invention

The invention aims to provide a method and a device for 3D printing of gamma-TiAl alloy under a static magnetic field.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a method for 3D printing of gamma-TiAl alloy in a static magnetic field, which comprises the following steps of 3D printing prealloy powder according to three-dimensional data of a gamma-TiAl alloy forming part to obtain gamma-TiAl alloy; the 3D printing is performed in a static magnetic field.

Preferably, the direction of the static magnetic field is perpendicular to the direction of 3D printing.

Preferably, the static magnetic field is a steady magnetic field, and the strength of the static magnetic field is 0.3-0.5T.

Preferably, the parameters of the 3D printing are: the laser scanning speed is 3-8 mm/s, the laser power is 800-1200W, the powder feeding speed is 3-10 g/min, and the powder feeding air carrying capacity is 5-10L/min.

Preferably, the prealloyed powder is spherical or near-spherical titanium-aluminum alloy powder, the particle size distribution range of the prealloyed powder is 53-150 μm, and the average particle size is 75-90 μm.

Preferably, the 3D printing is performed under a protective atmosphere having an oxygen content of less than 50 ppm.

The invention provides a device for 3D printing of gamma-TiAl alloy in a static magnetic field.

Preferably, the magnet means comprises two static magnets or two electromagnets; the two static magnets or the two electromagnets are oppositely arranged on two sides of a nozzle of the laser cladding head.

Preferably, the apparatus for 3D printing γ -TiAl alloy comprises: the device comprises a substrate heating device, a titanium alloy substrate, a magnet device, a laser, a powder feeder, a laser cladding head, a water cooling system, a numerical control system and a gas circulation system;

the substrate heating device, the titanium alloy substrate and the laser cladding head are positioned in the forming cavity; the running system of the numerical control system is positioned inside the forming cavity, and the operating platform of the numerical control system is positioned outside the forming cavity;

the laser cladding head is fixed on a traveling system of the numerical control system; the powder feeder is communicated with the laser cladding head through a powder feeding pipeline; the laser is connected with the laser cladding head through an optical fiber; and the water cooling system is connected to the laser cladding head through a pipeline.

Preferably, the laser is CO₂A gas laser, a YAG solid laser, a fiber laser, or a semiconductor laser.

The invention provides a method for 3D printing of gamma-TiAl alloy in a static magnetic field, which comprises the following steps of 3D printing prealloy powder according to three-dimensional data of a gamma-TiAl alloy forming part to obtain gamma-TiAl alloy; the 3D printing is performed in a static magnetic field. According to the invention, the dense high-performance gamma-TiAl alloy is obtained by applying an external magnetic field while preparing the gamma-TiAl alloy by using a 3D printing technology, the applied external magnetic field can further improve the internal structure of the alloy, reduce residual stress, obtain higher mechanical properties and reduce the cracking risk possibly brought by subsequent heat treatment; the gamma-TiAl alloy prepared by the 3D printing technology has the characteristics of high flexibility, high material utilization rate, short production period and the like, and the solidification structure in the gamma-TiAl alloy is very fine. The results of the examples show that the tensile strength of the gamma-TiAl alloy prepared by the method is higher than 560MPa, the hardness is higher than 420HV, and the elongation is 0.5-0.8%.

Drawings

FIG. 1 is a schematic view of a 3D printing apparatus of the present invention;

in the figure, 1 is a substrate heating device, 2 is a titanium alloy substrate, 3 is a magnet device, 4 is a laser, 5 is a powder feeder, 6 is a laser cladding head, 7 is a water cooling system, 8 is a numerical control system, 9 is a gas circulation system, and 10 is gamma-TiAl alloy;

FIG. 2 is an electron micrograph of prealloyed powder provided in accordance with the present invention;

FIG. 3 is a schematic representation of a sample of γ -TiAl alloy prepared in accordance with example 1 of the present invention;

FIG. 4 is a scanning electron micrograph of γ -TiAl alloy prepared according to example 1 of the present invention;

FIG. 5 is a sample plot of γ -TiAl alloys prepared in example 2 of the present invention;

FIG. 6 is a scanning electron micrograph of γ -TiAl alloy prepared in example 2 of the present invention.

Detailed Description

The invention provides a method for 3D printing of gamma-TiAl alloy in a static magnetic field, which is characterized in that 3D printing is carried out on prealloy powder according to three-dimensional data of a gamma-TiAl alloy molding part to obtain the gamma-TiAl alloy.

In the present invention, the composition of the γ -TiAl alloy is preferably Ti-48Al-2Cr-2Nb, Ti-46Al-5Nb-0.2B or Ti-46.5 Al-2.5V.

According to the invention, preferably, three-dimensional modeling software is used for drawing the stl file of the gamma-TiAl alloy formed part, subdivision software is used for carrying out two-dimensional segmentation on three-dimensional data of the gamma-TiAl alloy formed part, and the three-dimensional data is converted into two-dimensional graphic data and loaded into a 3D printing device.

In the present invention, the 3D printing is performed in a static magnetic field. In the present invention, the means for generating the static magnetic field is preferably a magnet means, and the magnet means preferably includes two static magnets or two electromagnets, more preferably two static magnets. In the present invention, the static magnetic field is preferably a steady magnetic field, and the intensity of the static magnetic field is preferably 0.3 to 0.5T, and more preferably 0.4T. In the present invention, the direction of the static magnetic field is preferably perpendicular to the direction of 3D printing. According to the invention, 3D printing is carried out in a magnetic field, the internal structure of the alloy can be further improved, the residual stress is reduced, higher mechanical properties are obtained, and the cracking risk possibly brought by subsequent heat treatment can be reduced.

In the invention, the laser scanning speed of the 3D printing is preferably 3-8 mm/s, more preferably 4-7 mm/s, and most preferably 5-6 mm/s; the laser power is preferably 800-1200W, more preferably 900-1100W, and most preferably 1000W; the powder feeding rate is preferably 3-10 g/min, more preferably 4-8 g/min, and most preferably 6-7 g/min; the powder conveying and gas carrying amount is preferably 5-10L/min, and more preferably 6-8L/min. The invention limits the 3D printing parameters in the range, and can further improve the mechanical property of the gamma-TiAl alloy.

In the present invention, the prealloyed powder is preferably spherical or near-spherical titanium-aluminum alloy powder, more preferably spherical titanium-aluminum alloy powder; the particle size distribution range of the pre-alloy powder is preferably 53-150 mu m, and more preferably 60-120 mu m; the average particle size of the prealloyed powder is preferably 75-90 μm, and more preferably 80-85 μm. The invention limits the shape and the grain diameter of the prealloy powder in the range, can further compact the structure of the gamma-TiAl alloy, and has higher tensile strength and hardness.

In the present invention, the prealloyed powder is preferably dried prior to use. The specific source of the prealloyed powder is not particularly limited in this invention and may be any commercially available product known to those skilled in the art.

In the present invention, the prealloyed powder is preferably printed on a titanium alloy substrate. In the present invention, the titanium alloy substrate is preferably a TC4 alloy; the thickness of the titanium alloy substrate is preferably 5-10 mm, and more preferably 6-8 mm. In the invention, the temperature of the titanium alloy substrate is preferably 300-600 ℃, and more preferably 400-500 ℃. According to the invention, the titanium alloy substrate is heated, so that the excessive internal stress caused by rapid cooling in the printing process can be prevented.

In the present invention, the 3D printing is preferably performed under a protective atmosphere, which is preferably argon or helium. In the present invention, the oxygen content in the protective atmosphere is preferably less than 50ppm, more preferably less than 40 ppm. The invention can perform 3D printing in a protective atmosphere, and can prevent the pre-alloy powder from being oxidized in the printing process.

The invention provides a device for 3D printing of gamma-TiAl alloy in a static magnetic field.

In the present invention, the magnet means preferably includes two static magnets or two electromagnets, and more preferably two static magnets. In one embodiment of the invention, the two static magnets or the two electromagnets are oppositely arranged at two sides of the nozzle of the laser cladding head. The magnet devices are arranged on two sides of the nozzle of the laser cladding head, so that the magnetic field effect on the prealloy powder in the printing process can be ensured to be the same, the internal structure of the alloy is further improved, the residual stress is reduced, and the mechanical property of the gamma-TiAl alloy is improved.

As shown in fig. 1, in an embodiment of the present invention, the apparatus for 3D printing γ -TiAl alloy includes a substrate heating apparatus 1, a titanium alloy substrate 2, a magnet apparatus 3, a laser 4, a powder feeder 5, a laser cladding head 6, a water cooling system 7, a numerical control system 8 and a gas circulation system 9;

the substrate heating device 1, the titanium alloy substrate 2 and the laser cladding head 6 are positioned in the forming cavity; the advancing system of the numerical control system 8 is positioned inside the forming cavity, and the operating platform of the numerical control system 8 is positioned outside the forming cavity;

the laser cladding head 6 is fixed on a traveling system of the numerical control system 8; the powder feeder 5 is communicated with the laser cladding head 6 through a powder feeding pipeline; the laser 4 is connected with a laser cladding head 6 through an optical fiber; and the water cooling system 7 is connected to the laser cladding head 6 through a pipeline.

In the present invention, the internal heating method of the substrate heating apparatus 1 is preferably resistance heating. In one embodiment of the present invention, the exterior of the substrate heating apparatus 1 is plated with a plating layer formed of a high-permeability barrier alloy. The invention can isolate the influence of static magnetic field on the substrate heating device 1 by plating the plating layer on the surface of the substrate heating device 1.

In the present invention, the substrate heating apparatus 1 preferably heats the titanium alloy substrate 2 by heat conduction, heat convection, or heat radiation.

In one embodiment of the invention, the magnet means 3 comprise two static magnets or two electromagnets, more preferably two static magnets; the two static magnets or the two electromagnets are oppositely arranged on two sides of a nozzle of the laser cladding head.

In one embodiment of the invention, the laser 4 is CO₂Gas laser, YAG solid laser, and fiber laserOr a semiconductor laser, more preferably a fiber laser or a semiconductor laser.

In one embodiment of the present invention, the powder feeder 5 feeds powder in a coaxial powder feeding manner or a lateral powder feeding manner; the carrier gas in the powder feeding is preferably argon.

In one embodiment of the present invention, the laser cladding head 6 is provided with a magnet arrangement 3.

In the invention, the substrate heating device 1, the titanium alloy substrate 2 and the laser cladding head 6 are positioned in a forming cavity; the advancing system of the numerical control system 8 is positioned inside the forming cavity, and the operating platform of the numerical control system 8 is positioned outside the forming cavity; the laser cladding head 6 is fixed on a traveling system of the numerical control system 8 and is controlled to move by inputting a program by an operation table; the powder feeder 5 is communicated with the laser cladding head 6 through a powder feeding pipeline and is used for conveying pre-alloyed powder to the laser cladding head 6, the laser 4 is used for generating laser beams and conveying the laser beams to the laser cladding head 6 through optical fibers, the laser cladding head 6 focuses the laser beams on the titanium alloy substrate 2 to form a molten pool, meanwhile, the pre-alloyed powder can be melted, and the water cooling system 7 is connected into the laser cladding head 6 through a pipeline to ensure that the working temperature of the water cooling system is normal; the magnet device 3 exerts a magnetic field perpendicular to the printing direction on the molten pool to influence the laser cladding preparation process of the TiAl alloy.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Preparation of titanium alloy substrate: selecting TC4 alloy as a substrate material, cutting the substrate material into plates, carrying out sand blasting treatment on the plates, and then cleaning the plates by using ethanol to obtain the titanium alloy substrate with a smooth and clean surface.

Preparation of prealloyed powder: the alloy powder of Ti-48Al-2Cr-2Nb is used, and the atomic percentage of the alloy powder is as follows: 48% of Al, 2% of Nb and 2% of Cr, the balance being Ti and inevitable impurities, 533ppm of O and 481ppm of N, the particle size distribution range of the alloy powder is 53-150 μm, and the D50 is 88.6 μm; and putting the prealloyed powder into a vacuum oven, and baking for 2 hours at 100 ℃ to obtain dry prealloyed powder.

The laser used in the 3D printing device is a 2000W optical fiber coupling semiconductor laser of Laserine company in Germany.

The method for 3D printing of the gamma-TiAl alloy comprises the following steps:

(1) putting the prealloyed powder into a powder feeder, and adjusting the powder feeding rate to be 3 g/min;

(2) using three-dimensional modeling software to draw a stl file of the gamma-TiAl alloy formed part, using subdivision software to perform two-dimensional segmentation on three-dimensional data of the gamma-TiAl alloy formed part, converting the three-dimensional data into two-dimensional graphic data and loading the two-dimensional graphic data into a numerical control system of a 3D printing device;

(3) placing a titanium alloy substrate on a substrate resistance heating device for heating, and heating the titanium alloy substrate to 400 ℃;

(4) adjusting the relative position of the laser cladding head and the substrate to focus the laser beam on the surface of the substrate;

(5) two static magnets are hung on a laser cladding head according to the mode that an N pole is opposite to an S pole, and the height of the two static magnets is adjusted to enable a molten pool to be located at the position of the maximum magnetic field intensity, wherein the magnetic field intensity is 0.3T;

(6) closing the forming chamber, introducing argon into the chamber, reducing the oxygen content to be below 50ppm, starting a water cooling system, and preparing to start a laser cladding process;

(7) the parameters for 3D printing are set as: the laser scanning speed is 3mm/s, the laser power is 800W, the powder feeding flow is 6L/min, and the lifting amount of the laser cladding head is 1 mm;

(8) opening a laser, melting a substrate by using a laser beam to form a molten pool with a certain size, and simultaneously conveying metal powder into the molten pool by using a coaxial powder feeding method, wherein a part of powder is melted above a focused laser beam to form metal droplets which fall into the molten pool, but the forming process is not influenced, and a laser cladding head travels according to a set scanning path to form a first cladding layer;

(9) starting a cladding process of a second layer immediately after the laser cladding head is lifted by 1mm, wherein the parameters of the process are consistent with those of the first layer;

(10) and (5) repeating the step (8) and the step (9) until a gamma-TiAl alloy molded part is obtained.

Example 2

Example 1 the temperature in step (3) was modified to 350 ℃, the magnetic field strength in step (5) was changed to 0.5T, and the parameters for 3D printing in step (7) were modified as follows: the laser scanning speed is 8mm/s, the laser power is 1200W, the powder feeding flow is 8L/min, the laser cladding head lifting amount is 1.5mm, and other conditions are the same as those of the embodiment 1.

Example 3

As shown in fig. 1, the apparatus for 3D printing γ -TiAl alloy provided in this embodiment includes a substrate heating apparatus 1, a titanium alloy substrate 2, a magnet apparatus 3, a laser 4, a powder feeder 5, a laser cladding head 6, a water cooling system 7, a numerical control system 8, and a gas circulation system 9;

a plating layer formed by high-permeability shielding alloy is arranged outside the substrate heating device 1;

the magnet device 3 comprises two static magnets which are oppositely arranged at two sides of a nozzle of the laser cladding head;

the laser 4 is a fiber laser;

the substrate heating device 1, the titanium alloy substrate 2 and the laser cladding head 6 are positioned in the forming cavity; the advancing system of the numerical control system 8 is positioned inside the forming cavity, and the operating platform of the numerical control system 8 is positioned outside the forming cavity;

the laser cladding head 6 is fixed on a traveling system of the numerical control system 8; the powder feeder 5 is communicated with the laser cladding head 6 through a powder feeding pipeline; the laser 4 is connected with a laser cladding head 6 through an optical fiber; and the water cooling system 7 is connected to the laser cladding head 6 through a pipeline.

Comparative example 1

The prealloyed powder used for the 3D printed γ -TiAl alloy without the application of a magnetic field was Ti48Al2Cr2Nb, the other conditions being the same as in example 1.

Comparative example 2

Ti48Al2Cr2Nb in its ordinary cast state.

The properties of the alloy molded articles prepared in examples 1 to 2 and comparative examples 1 to 2 are shown in Table 1:

TABLE 1 Properties of alloy molded articles prepared in examples 1 to 2 and comparative examples 1 to 2

	Tensile strength MPa	Elongation percentage%	Hardness HV
				Example 1	659	0.5	468
Example 2	564	0.8	421
				Comparative example 1	553	0.5	409
Comparative example 2	469	1.1	359

As can be seen from Table 1, the method provided by the invention is suitable for preparing gamma-TiAl alloy, has excellent mechanical properties, and reduces the tensile strength and the hardness to different degrees when preparing other alloys.

Fig. 1 is a schematic diagram of a 3D printing apparatus provided by the present invention. As can be seen from fig. 1, the magnet device 3 is disposed on the laser cladding head 6 and can move along with the movement of the laser cladding head 6, so as to ensure that the magnet device is always in a magnetic field during the printing process.

The prealloyed powder was subjected to electron microscopy and the results are shown in figure 2. As can be seen from FIG. 2, the prealloyed powder used in the invention is spherical or nearly spherical powder, and the mechanical properties of the gamma-TiAl alloy can be further improved.

FIG. 3 is a sample diagram of a γ -TiAl alloy molded part prepared in example 1 of the present invention, and it can be seen from FIG. 3 that the γ -TiAl alloy molded part prepared in example 1 of the present invention has a good appearance structure and no cracking phenomenon.

The γ -TiAl alloy molded article prepared in example 1 of the present invention was subjected to electron microscope scanning, and the result is shown in fig. 4. As can be seen from FIG. 4, the surface structure of the formed part of the gamma-TiAl alloy prepared in the embodiment 1 of the invention is compact and has few defects.

FIG. 5 is a sample diagram of a molded article of γ -TiAl alloy prepared in example 2 of the present invention, and it can be seen from FIG. 5 that the molded article of γ -TiAl alloy prepared in example 2 of the present invention has a good appearance structure and no cracking phenomenon.

The γ -TiAl alloy molded article prepared in example 2 of the present invention was subjected to electron microscope scanning, and the result is shown in fig. 6. As can be seen from FIG. 6, the surface structure of the formed part of the gamma-TiAl alloy prepared in the embodiment 1 of the invention is compact and has few defects.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.