阅读说明：本技术 一种激光增材制造双相钛合金的热处理方法 (Heat treatment method for manufacturing double-phase titanium alloy through laser material increase ) 是由 陈超越 王江 任忠鸣 汪蔚 赵睿鑫 徐松哲 帅三三 胡涛 于 2021-08-16 设计创作，主要内容包括：本发明提供了一种激光增材制造双相钛合金的热处理方法,属于增材制造双相钛合金热处理技术领域。本发明提供的增材制造双相钛合金的热处理方法,包括以下步骤：(1)采用增材制造工艺制备双相钛合金坯体；(2)将所述步骤(1)得到的双相钛合金坯体在磁场中进行时效处理,得到双相钛合金。本发明在时效处理过程中施加磁场,利用磁场无接触地影响热处理过程,以达到在双相钛合金中形成等轴初生α相和篮网状β相双态组织的目标,进而提高合金的塑性,且提高了获得双态组织热处理的效率。实施例的结果显示,本发明制备的双相钛合金硬度≥300HV,极限抗拉强度≥850MPa,延伸率≥10％,断裂韧性(K-(IC))≥70MPa·m～(1/2)。(The invention provides a heat treatment method for manufacturing a dual-phase titanium alloy through laser additive manufacturing, and belongs to the technical field of heat treatment of the dual-phase titanium alloy through the laser additive manufacturing. The invention provides a heat treatment method for additive manufacturing of a dual-phase titanium alloy, which comprises the following steps: (1) preparing a dual-phase titanium alloy blank by adopting an additive manufacturing process; (2) and (2) carrying out aging treatment on the dual-phase titanium alloy blank obtained in the step (1) in a magnetic field to obtain the dual-phase titanium alloy. The invention applies a magnetic field in the aging treatment process, and utilizes the magnetic field to influence the heat treatment process in a non-contact way so as to achieve the aim of forming the equiaxed primary alpha-phase and basket-net-shaped beta-phase dual-state structure in the dual-phase titanium alloy, thereby improving the plasticity of the alloy and improving the heat treatment efficiency for obtaining the dual-state structure. The results of the examples show that the hardness of the dual-phase titanium alloy prepared by the invention is more than or equal to 300HV, and the ultimate tensile strengthDegree is not less than 850MPa, elongation is not less than 10%, fracture toughness (K) IC )≥70MPa·m 1/2 。)

1. A heat treatment method for additive manufacturing of a dual phase titanium alloy, comprising the steps of:

(1) preparing a dual-phase titanium alloy blank by adopting an additive manufacturing process;

(2) and (2) carrying out aging treatment on the dual-phase titanium alloy blank obtained in the step (1) in a magnetic field to obtain the dual-phase titanium alloy.

2. The heat treatment method according to claim 1, wherein the additive manufacturing process in the step (1) is a laser additive manufacturing process or an electron beam additive manufacturing process.

3. The thermal processing method of claim 2, wherein the laser additive manufacturing process is a selective laser melting process or a direct laser energy deposition process.

4. The heat treatment method according to claim 1, wherein the prealloyed powder used in the laser additive manufacturing process in the step (1) is a spherical or near-spherical dual phase titanium alloy powder.

5. The heat treatment method according to claim 4, wherein the pre-alloyed powder has a particle size distribution in a range of 15 to 150 μm, and an average particle size of 50 to 100 μm.

6. The heat treatment method according to claim 1, wherein the magnetic field in the step (2) is a static magnetic field, and the intensity of the static magnetic field is 0.5 to 4.5T.

7. The heat treatment method according to claim 1 or 6, wherein the direction of the magnetic field in step (2) is parallel or perpendicular to the baseline of the forming direction of the dual-phase titanium alloy blank in step (1).

8. The heat treatment process of claim 1, wherein the temperature of the aging treatment in step (2) is below the beta transus temperature T of the dual phase titanium alloy blank_βAnd the time of aging treatment is 1-4 h.

9. The heat treatment method according to claim 1 or 8, wherein the temperature of the aging treatment in the step (2) is 600 to 950 ℃.

10. A dual phase titanium alloy produced by the heat treatment method according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of heat treatment for additive manufacturing of a dual-phase titanium alloy, in particular to a heat treatment method for laser additive manufacturing of the dual-phase titanium alloy.

Background

The titanium alloy has the advantages of high specific strength, good corrosion resistance, high thermal strength and the like, and is widely applied to the fields of aerospace, medical treatment, chemical industry and the like, such as preparation of compressor disks and blades of aircraft engines, 3D printing of artificial bones and teeth and the like. According to the molybdenum equivalent of alloying elements in the titanium alloy and the room temperature tissue type, the titanium alloy can be divided into a plurality of types such as alpha type, alpha + beta double-phase type, beta type and the like, wherein the alpha + beta double-phase type titanium alloy has the comprehensive characteristics of equiaxial alpha and lamellar beta tissues, can be subjected to heat treatment strengthening and has excellent comprehensive performance. However, the titanium alloy has more alloying elements and more activity of titanium, so that the traditional titanium alloy processing technology is difficult, for example, forged forgings are easy to generate defects such as segregation, forging cracks and the like, the casting performance is low, the welding combination among the castings is difficult, and the casting cracking tendency is high.

At present, 3D printing of metal as a novel additive manufacturing process different from the traditional material reduction processing process becomes a research hotspot. And because of the excellent weldability of the titanium alloy, the titanium alloy is very suitable for 3D printing of metal, is widely applied to the field of additive manufacturing, and the printed performance can reach or even exceed the level of a forged piece. However, due to the large cooling speed in the additive manufacturing process, the room temperature structure of the dual-phase titanium alloy is usually a needle-shaped or fine lath martensite structure, the material has large internal stress and high hardness and strength, but the plasticity is poor, and the strength and the plasticity are not sufficiently matched, so that it is necessary to convert the printed dual-phase titanium alloy structure into a uniform dual-phase structure through a heat treatment process so as to improve the plasticity of the dual-phase titanium alloy structure.

The traditional heat treatment process for obtaining the titanium alloy with the duplex structure usually combines multiple annealing and multiple aging, although the heat treatment mode can improve the plasticity of the titanium alloy with the duplex structure to different degrees according to different temperatures, time and cooling rates, the plasticity of the titanium alloy is still not ideal enough for the titanium alloy with the duplex structure which is severe in service environment, and the heat treatment mode for obtaining the duplex structure needs to be carried out at T_βThe efficiency is lower due to the multiple heating and cooling nearby. Therefore, there is a need for an efficient heat treatment method that can improve the efficiency of obtaining a bimodal structure.

Disclosure of Invention

The invention aims to provide a heat treatment method for manufacturing a dual-phase titanium alloy by laser additive manufacturing, and the dual-phase titanium alloy provided by the invention has higher hardness and plasticity and more reasonable proportion of strength and plasticity.

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

the invention provides a heat treatment method for additive manufacturing of a dual-phase titanium alloy, which comprises the following steps:

(1) preparing a dual-phase titanium alloy blank by adopting an additive manufacturing process;

(2) and (2) carrying out aging treatment on the dual-phase titanium alloy blank obtained in the step (1) in a magnetic field to obtain the dual-phase titanium alloy.

Preferably, the additive manufacturing process in the step (1) is a laser additive manufacturing process or an electron beam additive manufacturing process.

Preferably, the laser additive manufacturing process is a selective laser melting process or a direct laser energy deposition process.

Preferably, the prealloyed powder used in the laser additive manufacturing process in the step (1) is spherical or approximately spherical dual-phase titanium alloy powder.

Preferably, the particle size distribution range of the pre-alloy powder is 15-150 mu m, and the average particle size of the pre-alloy powder is 50-100 mu m.

Preferably, the magnetic field in the step (2) is a static magnetic field, and the strength of the static magnetic field is 0.5-4.5T.

Preferably, the direction of the magnetic field in the step (2) is parallel or perpendicular to the forming direction baseline of the dual-phase titanium alloy blank in the additive manufacturing process in the step (1).

Preferably, the temperature of the aging treatment in the step (2) is lower than the beta transformation temperature T of the dual-phase titanium alloy blank_βAnd the time of aging treatment is 1-4 h.

Preferably, the temperature of the aging treatment in the step (2) is 600-950 ℃.

The invention provides the dual-phase titanium alloy prepared by the heat treatment method in the technical scheme.

The invention provides a heat treatment method for additive manufacturing of a dual-phase titanium alloy, which comprises the following steps: preparing a dual-phase titanium alloy blank by adopting an additive manufacturing process; and carrying out aging treatment on the dual-phase titanium alloy blank in a magnetic field to obtain the dual-phase titanium alloy. According to the invention, the magnetic field is applied in the aging treatment process, and the heat treatment process is influenced in a non-contact manner by the magnetic field, so that the aim of forming the equiaxial primary alpha-phase and basket-net-shaped beta-phase dual-state structure in the dual-phase titanium alloy is achieved, the plasticity of the alloy is further improved, and the heat treatment efficiency for obtaining the dual-state structure is improved. The results of the examples show that the hardness of the dual-phase titanium alloy prepared by the heat treatment method provided by the invention is more than or equal to 300HV, the ultimate tensile strength is more than or equal to 850MPa, the elongation is more than or equal to 10 percent, and the fracture toughness (K) is_IC)≥70MPa·m^1/2。

Drawings

FIG. 1 is an electron micrograph of the microstructure of dual phase titanium alloy blanks prepared in example 1 and comparative example 3;

FIG. 2 is an electron micrograph of the microstructure of the dual phase titanium alloy prepared in example 1;

FIG. 3 is an electron micrograph of the microstructure of the dual phase titanium alloy blanks prepared in example 2 and comparative example 4;

FIG. 4 is an electron micrograph of the microstructure of the dual phase titanium alloy prepared in example 2;

FIG. 5 is an electron micrograph of the microstructure of the dual phase titanium alloy billet prepared in example 3;

FIG. 6 is an electron micrograph of the microstructure of the dual phase titanium alloy prepared in example 3;

FIG. 7 is an electron micrograph of the microstructure of the dual phase titanium alloy prepared in comparative example 1;

FIG. 8 is an electron micrograph of the microstructure of the dual phase titanium alloy prepared in comparative example 2;

FIG. 9 is an electron microscope image of prealloyed powder used in the preparation of examples 1-3 of the present invention and comparative examples 1-4;

fig. 10 is a schematic view showing the relationship between the static magnetic field applied when the dual-phase titanium alloy is produced according to the present invention and the baseline of the forming direction of the dual-phase titanium alloy blank in the additive manufacturing process.

Detailed Description

The invention provides a heat treatment method for additive manufacturing of a dual-phase titanium alloy, which comprises the following steps:

(1) preparing a dual-phase titanium alloy blank by adopting an additive manufacturing process;

(2) and (2) carrying out aging treatment on the dual-phase titanium alloy blank obtained in the step (1) in a magnetic field to obtain the dual-phase titanium alloy.

The invention adopts an additive manufacturing process to prepare a dual-phase titanium alloy blank.

In the invention, the prealloying powder used in the laser additive manufacturing process is preferably spherical or approximately spherical dual-phase titanium alloy powder, and more preferably spherical titanium alloy powder; the pre-alloyed powder preferably comprises a TC-series titanium alloy, more preferably Ti-6 Al-4V; the particle size distribution range of the pre-alloy powder is preferably 15-150 mu m, more preferably 35-100 mu m, and the average particle size of the pre-alloy powder is preferably 50-100 mu m, more preferably 60-90 mu m. In the invention, the prealloyed powder is preferably dried before use, the drying temperature is preferably 50-200 ℃, more preferably 100 ℃, and the drying time is preferably 1-4 hours, more preferably 2 hours. 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. The invention limits the shape and the grain diameter of the prealloyed powder in the range, and can improve the mechanical property of the two-phase titanium alloy blank.

In the present invention, the preparation of the dual-phase titanium alloy blank is preferably performed under a protective atmosphere, preferably argon or helium, more preferably argon. In the present invention, the oxygen content in the protective atmosphere is preferably less than 500ppm, more preferably less than 200 ppm. The invention prepares the biphase titanium alloy blank under the protective atmosphere, and can prevent the pre-alloyed powder from being oxidized in the preparation process.

In the present invention, the preparation of the dual phase titanium alloy blank is preferably performed on a substrate, preferably a titanium alloy substrate, more preferably a dual phase titanium alloy substrate, most preferably a substrate of the same composition as the pre-alloyed powder. According to the invention, the substrate is preferably cleaned and preheated before the dual-phase titanium alloy blank is prepared, the cleaning is preferably carried out by adopting ethanol, and the preheating temperature is preferably 30-600 ℃, more preferably 300-500 ℃. According to the invention, the titanium alloy substrate is heated, so that the problem of overlarge internal stress caused by rapid cooling in the printing process can be prevented.

In the present invention, the additive manufacturing process is preferably a laser additive manufacturing process or an electron beam additive manufacturing process.

In the present invention, when the additive manufacturing process is a laser additive manufacturing process, the laser additive manufacturing process is preferably a selective laser melting process or a direct laser energy deposition process.

In the present invention, when the laser additive manufacturing process is a selective laser melting process, the parameters of the selective laser melting process are preferably: the laser scanning speed is 500-3000 mm/s, the laser power is 50-500W, the spot size is 10-200 μm, the layer thickness of the prealloyed powder is 10-100 μm, the oxygen content is lower than 500ppm, the substrate preheating temperature is 30-600 ℃, and more preferably: the laser scanning speed is 1000-2000 mm/s, the laser power is 100-300W, the spot size is 50-150 μm, the layer thickness of the prealloyed powder is 30-60 μm, the oxygen content is less than 200ppm, and the substrate preheating temperature is 300-500 ℃.

In the present invention, when the laser additive manufacturing process is a direct laser energy deposition process, the parameters of the direct laser energy deposition process are preferably: the powder feeding speed is 0.5-3 rpm, the powder feeding airflow is 2-20L/min, the shielding gas airflow is 5-25L/min, the oxygen content is lower than 1%, the laser power is 200-3000W, the laser scanning speed is 100-2000 mm/min, the spot size is 1-6 mm, the substrate preheating temperature is 30-600 ℃, and the preferable range is as follows: the powder feeding speed is 1-2 rpm, the powder feeding airflow is 5-15L/min, the shielding gas airflow is 10-20L/min, the oxygen content is lower than 0.5%, the laser power is 1000-2000W, the spot size is 2-4 mm, the substrate preheating temperature is 300-500 ℃, and the laser scanning speed is 500-1500 mm/min.

In the present invention, when the additive manufacturing process is an electron beam additive manufacturing process, the electron beam additive manufacturing process parameters are preferably: the thickness of the pre-alloyed powder is 10-200 μm, the diameter of the electron beam spot is 0.1-2 mm, the scanning speed is 1-20000 mm/s, the power of the electron beam is 100-5000W, the preheating temperature of the substrate is 300-500 ℃, the oxygen content is less than 500ppm, and more preferably: the thickness of the prealloying powder layer is 50-150 mu m, the diameter of an electron beam spot is 0.5-1.5 mm, the scanning speed is 100-10000 mm/s, the power of the electron beam is 1000-3000W, the preheating temperature of the substrate is 350-450 ℃, and the oxygen content is less than 200 ppm.

The invention limits the parameters of the additive manufacturing process within the range, can further improve the mechanical property of the dual-phase titanium alloy, and enables the mechanical property of the 3D printed dual-phase titanium alloy part to reach or even exceed the level of a forged piece.

After the dual-phase titanium alloy blank is prepared, the dual-phase titanium alloy blank is subjected to aging treatment in a magnetic field to obtain the dual-phase titanium alloy.

In the present invention, the magnetic field is preferably a static magnetic field, more preferably a steady static magnetic field, and the intensity of the static magnetic field is preferably 0.5 to 4.5T, more preferably 1 to 4T, and even more preferably 2 to 3T. In the present invention, the magnetic field direction is preferably parallel to or perpendicular to the baseline of the forming direction of the dual-phase titanium alloy blank in the additive manufacturing process, and more preferably parallel to the baseline of the forming direction of the dual-phase titanium alloy blank in the additive manufacturing process. The method adopts the method of external magnetic field, can efficiently obtain the microstructure with fine crystal grains in the dual-phase titanium alloy for additive manufacturing, obviously improves the plasticity of the dual-phase titanium alloy, and leads the strength-plasticity proportion of the titanium alloy for additive manufacturing to be more reasonable.

In the present invention, the temperature of the aging treatment is preferably lower than the beta transus temperature T of the dual-phase titanium alloy blank_βMore preferably 600 to 950 ℃, and most preferably 700 to 800 ℃; the time of the aging treatment is preferably 1-4 h, and more preferably 2-3 h; the atmosphere of the aging treatment is preferably a protective atmosphere, and the protective atmosphere is preferably helium or argon, and more preferably argon. The invention controls the temperature of the aging treatment within the range, and can further improve the strength of the dual-phase titanium alloy; the titanium alloy can be prevented from being oxidized by aging treatment in a protective atmosphere.

After the aging treatment is finished, the invention preferably cools the aging treated product to obtain the dual-phase titanium alloy. In the present invention, the cooling is preferably furnace cooling or air cooling, and more preferably furnace cooling. The invention can prevent the increase of the internal stress of the dual-phase titanium alloy caused by too fast cooling speed by adopting the cooling mode.

The invention applies the magnetic field in the aging treatment process, and utilizes the magnetic field to influence the heat treatment process in a non-contact way so as to achieve the aim of forming the duplex structure in the dual-phase titanium alloy, thereby improving the plasticity of the alloy and improving the heat treatment efficiency for obtaining the duplex structure.

The invention provides the dual-phase titanium alloy prepared by the heat treatment method in the technical scheme. The dual-phase titanium alloy prepared by the invention has higher plasticity, is more reasonable in proportion to strength, and is not easy to crack in the welding process.

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

The heat treatment method for additive manufacturing of the dual-phase titanium alloy comprises the following steps:

(1) preparing a dual-phase titanium alloy blank by adopting a selective laser melting process;

the equipment model is ProX200 and is provided with a 300W optical fiber laser; the base plate is TC4 titanium alloy cleaned by ethanol, the prealloying powder is Ti-6Al-4V alloy powder, and the atom percentage content of the alloy powder is as follows: 6% of Al, 4% of V, and the balance of Ti and inevitable impurities, wherein the particle size distribution range of the alloy powder is 15-75 μm, and the D50 is 53 μm; putting the pre-alloyed powder into a vacuum oven, and baking for 2 hours at 100 ℃ to obtain dry pre-alloyed powder;

the specific operation of the selective laser melting process consists of the following steps:

1) drawing an stl file of a TC4 alloy formed part by using three-dimensional modeling software, performing two-dimensional segmentation on three-dimensional data of the alloy formed part by using segmentation software, 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;

2) preheating the substrate to 300 ℃, then placing the substrate into a forming chamber, closing the forming chamber, introducing argon into the chamber, reducing the oxygen content to be below 200ppm, and setting the 3D printing parameters as follows: the laser scanning speed is 1200mm/s, the laser power is 240W, the laser spot size is 75 microns, the layer thickness of the pre-alloyed powder is 30 microns, the printing interval is 50 microns, and a dual-phase titanium alloy blank is printed, wherein the dual-phase titanium alloy blank is a rod-shaped sample with the diameter of 10mm and the height of 40 mm;

(2) processing the dual-phase titanium alloy blank obtained in the step (1) into a rod-shaped sample with the diameter of 9mm and the length of 30mm, then placing the rod-shaped sample in an argon protective atmosphere and a static magnetic field for aging treatment, and then cooling the rod-shaped sample to room temperature along with a furnace to obtain the dual-phase titanium alloy; the intensity of the static magnetic field is 3T, the direction of the static magnetic field is parallel to the manufacturing direction of the laser melting process of the selected area in the step (1), the temperature of the aging treatment is 800 ℃, and the time of the aging treatment is 2 h.

Example 2

The temperature of the aging treatment in the step (2) was 900 ℃ and other conditions were the same as in example 1.

Example 3

The heat treatment method for additive manufacturing of the dual-phase titanium alloy comprises the following steps:

(1) preparing a dual-phase titanium alloy blank by adopting an electron beam additive manufacturing process;

the base plate is TC4 titanium alloy cleaned by ethanol, the prealloying powder is Ti-6Al-4V alloy powder, and the atom percentage content of the alloy powder is as follows: 6% of Al, 4% of V, and the balance of Ti and inevitable impurities, wherein the particle size distribution range of the alloy powder is 50-105 μm; putting the pre-alloyed powder into a vacuum oven, baking for 2 hours at 100 ℃ to obtain dry pre-alloyed powder, wherein the diameter of a beam spot of an electron beam is 1 mm;

the specific operation of the electron beam additive manufacturing process comprises the following steps:

1) using Magics data processing software to slice the model data, then customizing a printing procedure, and importing a printing file into an electron beam 3D printer control computer;

2) preheating the substrate to 300 ℃, then placing the substrate into a forming chamber, closing the forming chamber, introducing argon into the chamber, reducing the oxygen content to be below 200ppm, and setting the 3D printing parameters as follows: scanning speed of an electron beam is 1600mm/s, laser power is 3200W, the thickness of the prealloying powder layer is 90 mu m, powder feeding airflow is 7L/min, and protective airflow is 15L/min, and a two-phase titanium alloy blank is printed, wherein the two-phase titanium alloy blank is a rod-shaped sample with the diameter of 10mm and the height of 40 mm;

(2) processing the dual-phase titanium alloy blank obtained in the step (1) into a rod-shaped sample with the diameter of 9mm and the length of 30mm, then placing the rod-shaped sample in an argon protective atmosphere and a static magnetic field for aging treatment, and then cooling the rod-shaped sample to room temperature along with a furnace to obtain the dual-phase titanium alloy; the intensity of the static magnetic field is 1T, the direction of the static magnetic field is parallel to the manufacturing direction of the electron beam additive manufacturing process in the step (1), the temperature of the aging treatment is 650 ℃, and the time of the aging treatment is 2 h.

Comparative example 1

A dual phase titanium alloy was obtained in the same manner as in example 1 except that the static magnetic field was not applied.

Comparative example 2

A dual phase titanium alloy was obtained in the same manner as in example 2 except that the static magnetic field was not applied.

Comparative example 3

A dual phase titanium alloy billet obtained in example 1.

Comparative example 4

A dual phase titanium alloy billet obtained in example 3.

The mechanical properties of the dual phase titanium alloys prepared in examples 1 to 3 and comparative examples 1 to 4 are shown in table 1:

TABLE 1 mechanical Properties of the two-phase titanium alloys prepared in examples 1 to 3 and comparative examples 1 to 4

As can be seen from table 1, the heat treatment method provided by the present invention has a significant effect on the improvement of plasticity and fracture toughness of the dual-phase titanium alloy TC4, and compared with the dual-phase titanium alloy prepared in comparative example 1 without magnetic field treatment and comparative example 3 without magnetic field and aging treatment, the elongation of the dual-phase titanium alloy prepared in example 1 is respectively increased by 13.5% and 24.2%, the fracture toughness is respectively increased by 20.5% and 35.6%, and simultaneously the dual-phase titanium alloy has very high hardness and tensile strength; compared with the dual-phase titanium alloy prepared by the comparative example 2 without magnetic field treatment and the comparative example 3 without magnetic field and aging treatment, the dual-phase titanium alloy prepared by the example 2 has the advantages that the elongation is respectively improved by 21.6 percent and 55.8 percent, the fracture toughness is respectively improved by 26.6 percent and 55.5 percent, and simultaneously, the dual-phase titanium alloy has very high hardness and ultimate tensile strength; compared with the dual-phase titanium alloy prepared in the comparative example 4 without magnetic field and aging treatment, the dual-phase titanium alloy provided in the example 3 has the advantages that the elongation is improved by 25.6%, the fracture toughness is improved by 27.6%, and the dual-phase titanium alloy has high hardness and ultimate tensile strength; comparing the properties of the dual phase titanium alloys prepared in example 1 and example 2, it can be seen that the hardness and ultimate tensile strength of the dual phase titanium alloy are reduced with the increase of the aging treatment temperature, but the elongation and fracture toughness are greatly improved, which shows that the aging treatment under the action of the static magnetic field can improve the plasticity of the dual phase titanium alloy.

FIG. 1 is a microstructure of a dual phase titanium alloy billet prepared in example 1 and comparative example 3, and it can be seen from FIG. 1 that TC4 acicular martensite structure is produced for typical laser selective melting in the dual phase titanium alloy billet; fig. 2 shows the microstructure of the dual phase titanium alloy prepared in example 1, and it can be seen from fig. 2 that the microstructure of the dual phase titanium alloy is a typical dual phase structure, no significant β -phase grain boundary is observed, and a part of the primary α -phase has already begun to decompose to generate a spheroidization phenomenon, which indicates that aging treatment under a static magnetic field changes the microstructure of the dual phase titanium alloy.

FIG. 3 is a microstructure of a dual phase titanium alloy billet prepared in example 2 and comparative example 4, and it can be seen from FIG. 3 that TC4 acicular martensite structure is produced for typical laser selective melting in the dual phase titanium alloy billet; fig. 4 shows the microstructure of the dual-phase titanium alloy prepared in example 2, and it can be seen from fig. 4 that the microstructure of the dual-phase titanium alloy is a typical dual-phase structure, and no obvious β -phase grain boundary is observed, but the primary α -phase obviously generates a spheroidizing phenomenon, and the dual-phase structure also generates an obvious coarsening phenomenon, which indicates that the microstructure of the dual-phase titanium alloy is changed by aging treatment under a static magnetic field.

Fig. 5 is a microstructure of the dual phase titanium alloy billet prepared in example 3, and as can be seen from fig. 5, a typical electron beam additive manufacturing TC4 two phase α + β structure is within the dual phase titanium alloy billet; fig. 6 shows the microstructure of the dual phase titanium alloy prepared in example 3, and it can be seen from fig. 6 that the microstructure of the dual phase titanium alloy is obviously coarsened after the magnetic field and aging treatment, while it can be seen from the enlarged view of the selected area on the left side of fig. 6 that a finer lamellar α -structure is generated on a part of the β -phase, and the size of the primary α -phase is obviously enlarged and spheroidizing occurs.

Fig. 7 shows the microstructure of the dual-phase titanium alloy prepared in comparative example 1, and it can be seen from fig. 7 that the formed part of the dual-phase titanium alloy has a dense structure and few defects, the martensite structure is decomposed into a basket-shaped structure, and the microstructure is relatively fine.

Fig. 8 shows the microstructure of the dual-phase titanium alloy prepared in comparative example 2, and it can be seen from fig. 8 that the formed part of the dual-phase titanium alloy has a dense structure and few defects, the martensite structure is decomposed into a basket-shaped structure, and the microstructure is relatively fine.

From the results, the method provided by the invention can effectively obtain a coarsened basket structure and an equiaxial primary alpha phase in an original sample of a fine acicular martensite structure, so that the plasticity of the dual-phase titanium alloy prepared by the additive manufacturing process is obviously improved under the condition of not influencing the strength, and the good matching of the plasticity and the strength of the dual-phase titanium alloy is realized.

FIG. 9 is an electron microscope image of the prealloyed powder used in the preparation processes of examples 1-3 and comparative examples 1-4 of the present invention, and it can be seen from FIG. 9 that the prealloyed powder used in the present invention is a spherical or near-spherical dual phase titanium alloy powder.

Fig. 10 is a graph showing the relationship between the static magnetic field applied when the dual-phase titanium alloy is produced according to the present invention and the baseline of the forming direction of the dual-phase titanium alloy blank in the additive manufacturing process, and it can be seen from fig. 10 that the direction of the static magnetic field is parallel to or perpendicular to the baseline of the forming direction of the dual-phase titanium alloy blank in the additive manufacturing process.

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.