A method for additive manufacturing of titanium alloy

Abstract

The present application provides a method for additive manufacturing of titanium alloys, which belongs to the field of additive manufacturing technology. The method for additive manufacturing of titanium alloys comprises: forming an additive structure on the surface of a titanium alloy substrate by a laser additive method, and rolling the additive structure. The laser additive powder comprises titanium alloy powder and iron powder, and the mass fraction of the iron powder is 2.8 to 3.3 wt%. The method for additive manufacturing of titanium alloys of the present application adds iron powder to the laser additive powder, and cooperates with the rolling process after the corresponding laser additive manufacturing, so that the additive manufactured titanium alloy has high strength and toughness. Among them, part of the β phase structure will be retained inside the alloy structure at room temperature, and the addition of iron powder can increase the supercooling degree of the alloy during the cooling process, refine the grains and microstructure, and further roll the additive structure, which can increase the dislocation density of the titanium alloy and improve the density of the titanium alloy. The combination of the two improves the toughness of the additive manufactured titanium alloy structure.

Description

Technical Field

[0001] The present application relates to the field of additive manufacturing technology, and in particular to a method for additive manufacturing of titanium alloys. Background Art

[0002] Titanium alloys, with their low density, high specific strength, and excellent heat and corrosion resistance, have broad applications in aerospace, automotive, and mold manufacturing. Additive manufacturing integrates computer-aided design, numerical control, and rapid prototyping technologies, enabling rapid mold-free prototyping of complex structural parts, significantly reducing production cycles and costs. However, laser-additive titanium alloys form larger columnar primary β grains and coarse α lath microstructures, and the microstructure is not fully dense, significantly impacting the toughness of laser-additive titanium alloys. Summary of the Invention

[0003] The present application provides a method for additively manufacturing titanium alloys, which can improve the toughness of titanium alloys obtained by laser additive manufacturing.

[0004] The embodiment of the present application is implemented as follows:

[0005] In a first aspect, the present application example provides a method for additive manufacturing of titanium alloys, comprising: forming an additive structure on the surface of a titanium alloy substrate using a laser additive method, and rolling the additive structure.

[0006] The laser additive powder comprises titanium alloy powder and iron powder, and the mass fraction of the iron powder is 2.8-3.3wt%.

[0007] In the above technical solution, the method of additive manufacturing of titanium alloys of this application adds iron powder to the laser additive powder and cooperates with the corresponding rolling process after laser additive manufacturing, so that the additively manufactured titanium alloy has high strength and toughness. Among them, the alloy structure will retain part of the β phase structure at room temperature, and the addition of iron powder can increase the supercooling of the alloy during the cooling process, refine the grains and microstructure, and further roll the additive structure to increase the dislocation density of the titanium alloy and improve the density of the titanium alloy. The combination of the two improves the toughness of the additively manufactured titanium alloy structure.

[0008] In combination with the first aspect, in a first possible example of the first aspect of the present application, the rolling force of the above-mentioned rolling is 5 to 20 kN.

[0009] In combination with the first aspect, in a second possible example of the first aspect of the present application, the titanium alloy powder is TC4 alloy powder.

[0010] In combination with the first aspect, in a third possible example of the first aspect of the present application, the titanium alloy powder is a spherical particle powder.

[0011] In combination with the first aspect, in a fourth possible example of the first aspect of the present application, the diameter of the titanium alloy powder is 50 to 200 μm.

[0012] In combination with the first aspect, in a fifth possible example of the first aspect of the present application, the iron powder is a spherical particle powder.

[0013] In combination with the first aspect, in a sixth possible example of the first aspect of the present application, the diameter of the iron powder is 50 to 150 μm.

[0014] In combination with the first aspect, in a seventh possible example of the first aspect of the present application, the laser power during the laser additive process is 500-1800W.

[0015] Optionally, during the laser additive manufacturing process, the laser beam presents a uniform heat source distribution.

[0016] Optionally, the diameter of the spot formed by the laser beam during the laser additive process is 0.8 to 3.0 mm.

[0017] In combination with the first aspect, in an eighth possible example of the first aspect of the present application, a powder feeder is used to transfer laser additive powder, and the rotation speed of the powder feeder is 5 to 20 r / min.

[0018] Optionally, the movement rate of the laser head during the laser additive process is 500 to 2000 mm / min;

[0019] Optionally, the layer height during the laser additive process is 0.2 to 0.5 mm.

[0020] In combination with the first aspect, in a ninth possible example of the first aspect of the present application, the laser additive powder is pretreated before laser additive manufacturing, and the pretreatment includes drying.

[0021] Optionally, the drying temperature is 80-120° C., and the drying time is 240-300 min. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 This is a large-scale EBSD image of the titanium alloy structure obtained in Example 1 of the present application;

[0024] Figure 2This is a small-scale EBSD image of the titanium alloy structure obtained in Example 1 of the present application;

[0025] Figure 3 This is a large-scale EBSD image of the titanium alloy structure obtained in Comparative Example 1 of this application;

[0026] Figure 4 This is a small-scale EBSD image of the titanium alloy structure obtained in Comparative Example 1 of the present application;

[0027] Figure 5 This is a large-scale EBSD image of the titanium alloy structure obtained in Comparative Example 2 of this application;

[0028] Figure 6 This is a small-scale EBSD image of the titanium alloy structure obtained in Comparative Example 2 of this application;

[0029] Figure 7 This is a large-scale EBSD image of the titanium alloy structure obtained in Comparative Example 3 of this application;

[0030] Figure 8 This is a small-scale EBSD image of the titanium alloy structure obtained in Comparative Example 3 of the present application;

[0031] Figure 9 This is a three-dimensional X-ray image of the titanium alloy structure before rolling in Example 1 of the present application;

[0032] Figure 10 This is a three-dimensional X-ray image of the titanium alloy structure after rolling in Example 1 of the present application;

[0033] Figure 11 This is a comparison diagram of the tensile curves of the titanium alloy structure before and after rolling in Example 1 of the present application;

[0034] Figure 12 This is a comparison diagram of the tensile curves of the titanium alloy structure before and after rolling in Comparative Example 1 of the present application;

[0035] Figure 13 This is a comparison diagram of the tensile curves of the titanium alloy structure before and after rolling in Comparative Example 2 of this application;

[0036] Figure 14 This is a comparison diagram of the tensile curves of the titanium alloy structure before and after rolling in comparative example 3 of this application. DETAILED DESCRIPTION

[0037] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0038] The inventors have noted that laser-additive titanium alloys have poor toughness. Large columnar primary β grains and coarse α lath microstructures form in the laser-additive titanium alloys, and the structure is not fully dense, which greatly affects the toughness of the laser-additive titanium alloys.

[0039] To improve the low toughness of titanium alloys produced using laser additive manufacturing, the inventors discovered that when conventional TC4 titanium alloy is produced using the laser additive process, the structure is essentially entirely α-phase at room temperature. However, when the α-phase and β-phase each account for approximately half of the titanium alloy, the alloy exhibits excellent overall mechanical properties. Therefore, controlling the morphology and ratio of the α-phase and β-phase in titanium alloy additive manufacturing and reducing internal porosity defects are crucial for achieving high-strength and toughness alloys.

[0040] Based on the above considerations, the inventors conducted in-depth research and discovered that, for titanium alloys, Fe is a β-phase-forming element. This means that by adding iron powder to laser additive powder, the alloy structure can retain some β-phase at room temperature. Furthermore, the addition of iron powder can increase the alloy's undercooling during cooling, refine the grains and microstructure, and further rolling the additive structure can increase the titanium alloy's dislocation density and density. This combination of factors improves the toughness of the additively manufactured titanium alloy structure.

[0041] The following is a detailed description of a method for additive manufacturing of titanium alloy according to an embodiment of the present application:

[0042] The present application also provides a method for additive manufacturing of titanium alloy, which comprises the following steps:

[0043] S1. Prepare laser additive powder

[0044] Titanium alloy powder and iron powder are mixed according to a proportion, and are evenly mixed by a ball milling method to obtain a mixed powder. The mixed powder is placed in a vacuum heating furnace and dried for later use.

[0045] The laser additive powder comprises titanium alloy powder and iron powder, and the mass fraction of the iron powder is 2.8-3.3wt%.

[0046] As an example, the mass fraction of the iron powder may be 2.8 wt%, 2.9 wt%, 3.0 wt%, 3.1 wt%, 3.2 wt% or 3.3 wt%.

[0047] Optionally, the laser additive powder consists of titanium alloy powder and iron powder, the mass fraction of the iron powder is 2.8-3.3wt%, and the mass fraction of the titanium alloy powder is 96.7-97.2wt%.

[0048] Optionally, the titanium alloy powder is TC4 alloy powder.

[0049] Optionally, the titanium alloy powder is a spherical particle powder.

[0050] Optionally, the diameter of the titanium alloy powder is 50-200 μm.

[0051] As an example, the diameter of the titanium alloy powder may be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 180 μm, 190 μm, or 200 μm.

[0052] Optionally, the iron powder is spherical granular powder.

[0053] Optionally, the diameter of the iron powder is 50-150 μm.

[0054] As an example, the diameter of the iron powder may be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, or 150 μm.

[0055] Optionally, the ball-to-material ratio during ball milling is 2 to 3:1.

[0056] As an example, the ball-to-material ratio during ball milling can be 2:1, 2.5:1 or 3:1.

[0057] Optionally, the ball milling powder mixing process is carried out under the protection of an inert gas, and the inert gas includes any one or more of helium, argon, xenon and nitrogen.

[0058] Optionally, the rotation speed of the ball milling powder mixing process is 300-350 r / min.

[0059] As an example, the rotation speed of the ball milling mixing process can be 300 r / min, 310 r / min, 320 r / min, 330 r / min, 340 r / min or 350 r / min.

[0060] Optionally, the ball milling time is 250 to 300 minutes.

[0061] As an example, the ball milling time may be 250 min, 260 min, 270 min, 280 min, 290 min or 300 min.

[0062] Optionally, the temperature of the vacuum heating furnace is 80-120°C.

[0063] As an example, the temperature of the vacuum heating furnace may be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or 120°C.

[0064] Optionally, the drying time of the mixed powder in the vacuum heating furnace is 240 to 300 minutes.

[0065] As an example, the drying time of the mixed powder in the vacuum heating furnace can be 240 min, 240 min, 240 min, 240 min, 240 min, 240 min, 240 min or 300 min.

[0066] S2. Pre-processing

[0067] The titanium alloy substrate was polished, cleaned with acetone and ethanol in sequence, and air-dried for later use.

[0068] Place the titanium alloy substrate on the workbench of the semiconductor laser additive system and use a clamp to basically fix the titanium alloy; add laser additive powder into the powder feeder and place the laser powder feeding head in the chamber; close the chamber door and exhaust the air inside the chamber with inert gas; set parameters such as the powder feeder speed, powder blowing flow rate, laser power, laser head movement rate, layer height, deposition width, and number of deposition layers.

[0069] Optionally, the thickness of the titanium alloy substrate is 30 to 50 mm.

[0070] As an example, the thickness of the titanium alloy substrate may be 30 mm, 35 mm, 40 mm, 45 mm, or 50 mm.

[0071] Optionally, after the inert gas exhausts the air inside the chamber, the concentration in the chamber is 0 to 3 ppm.

[0072] Optionally, the rotation speed of the powder feeder is 5 to 20 r / min.

[0073] As an example, the rotation speed of the powder feeder can be 5r / min, 6r / min, 7r / min, 8r / min, 9r / min, 10r / min, 11r / min, 12r / min, 13r / min, 14r / min, 15r / min, 16r / min, 17r / min, 18r / min, 19r / min or 20r / min.

[0074] Optionally, the powder blowing is an inert gas, and the gas flow rate of the inert gas is 10 to 20 L / min.

[0075] As an example, the gas flow rate of the inert gas may be 10 L / min, 11 L / min, 12 L / min, 13 L / min, 14 L / min, 15 L / min, 16 L / min, 17 L / min, 18 L / min, 19 L / min, or 20 L / min.

[0076] Optionally, the laser power is 500-1800W.

[0077] As an example, the laser power may be 500W, 600W, 700W, 800W, 900W, 1000W, 1100W, 1200W, 1300W, 1400W, 1500W, 1600W, 1700W, or 1800W.

[0078] Optionally, during the laser additive manufacturing process, the laser beam presents a uniform heat source distribution.

[0079] Optionally, the diameter of the spot formed by the laser beam during the laser additive process is 0.8 to 3.0 mm.

[0080] As an example, the diameter of the spot formed by the laser beam during the laser additive process can be 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm or 3.0 mm.

[0081] Optionally, the movement rate of the laser head is 500-2000 mm / min.

[0082] As an example, the movement rate of the laser head can be 500 mm / min, 600 mm / min, 700 mm / min, 800 mm / min, 900 mm / min, 1000 mm / min, 1100 mm / min, 1200 mm / min, 1300 mm / min, 1400 mm / min, 1500 mm / min, 1600 mm / min, 1700 mm / min, 1800 mm / min, 1900 mm / min or 2000 mm / min.

[0083] Optionally, the layer height is 0.2 to 0.5 mm.

[0084] As an example, the layer height may be 0.2 mm, 0.3 mm, 0.4 mm or 0.5 mm.

[0085] Optionally, the deposition width is 150 mm, and the number of deposition layers is set to 300 layers.

[0086] S3, Laser Additive Manufacturing

[0087] Move the laser powder feeder to the titanium alloy substrate, aligning the laser focus with the titanium alloy substrate. Align the laser powder feeder and laser focus positions. Run the laser deposition additive process to perform additive fabrication on the titanium alloy.

[0088] S4, rolling

[0089] After the additive structure is formed, the additive structure is rolled.

[0090] Optionally, the rolling force of the rolling is 5 to 20 kN.

[0091] As an example, the rolling force of the rolling may be 5 kN, 6 kN, 7 kN, 8 kN, 9 kN, 10 kN, 11 kN, 12 kN, 13 kN, 14 kN, 15 kN, 16 kN, 17 kN, 18 kN, 19 kN or 20 kN.

[0092] The following is a further detailed description of a method for additive manufacturing of titanium alloys according to the present application in conjunction with embodiments.

[0093] Example 1

[0094] The present invention provides a method for additive manufacturing of titanium alloys, which includes the following steps:

[0095] S1. Prepare laser additive powder

[0096] 3wt% iron powder and the remainder TC4 alloy powder were mixed according to a proportion and evenly mixed by ball milling to obtain a mixed powder. During the ball milling process, the ball-to-material ratio was 3:1. The ball mill was filled with argon gas, the rotation speed was 300 r / min, and the ball milling time was 270 min. The mixed powder was then placed in a vacuum heating furnace for drying at 100°C for 240 min.

[0097] The iron powder is a spherical particle powder with a diameter of 50 to 150 μm; the TC4 alloy powder is a spherical particle powder with a diameter of 50 to 150 μm.

[0098] S2. Pre-processing

[0099] A titanium alloy substrate with a size of 100 mm × 200 mm × 50 mm was used as the additive substrate. The oxide film on the surface of the titanium alloy substrate was removed by a grinder, and the titanium alloy substrate was cleaned with acetone and alcohol in turn, and then air-dried for use.

[0100] Place the titanium alloy substrate on the workbench of the semiconductor laser additive system, and use a clamp to basically fix the titanium alloy; add laser additive powder into the powder feeder, and place the laser powder feeding head in the chamber; close the chamber door, and use argon to exhaust the air inside the chamber, and the concentration in the chamber is ≤3ppm; set the speed of the powder feeder to 12r / min, the powder blowing gas to argon, the powder blowing gas flow rate to 15L / min, the laser power to 1100W, the laser beam to a uniform heat source distribution, the diameter of the spot formed by the laser beam is 2.0mm, the laser head movement rate is set to 850mm / min, the layer height is 0.3mm, the deposition width is 150mm, and the number of deposition layers is set to 300 layers.

[0101] S3, Laser Additive Manufacturing

[0102] Turn on the laser guide spot, adjust the laser beam position to the edge of the titanium alloy substrate, and adjust the beam focus to the titanium alloy substrate surface. Run the laser deposition additive program to begin the titanium alloy mixed powder laser additive process.

[0103] S4, rolling

[0104] After the additive manufacturing process is completed, the obtained alloy is taken out and rolled with a rolling force set to 15 kN.

[0105] Comparative Example 1

[0106] The comparative example of the present application provides a method for additive manufacturing of titanium alloy, wherein the laser additive powder includes: TC4 alloy powder.

[0107] The C4 alloy powder is a spherical particle powder, and the diameter of the TC4 alloy powder is 50 to 150 μm.

[0108] The method for additive manufacturing of titanium alloy is the same as that in Example 1.

[0109] Comparative Example 2

[0110] The comparative example of the present application provides a method for additive manufacturing of titanium alloy, wherein the laser additive powder comprises: 1.5wt% iron powder and the balance TC4 alloy powder.

[0111] The iron powder is a spherical particle powder with a diameter of 50 to 150 μm; the TC4 alloy powder is a spherical particle powder with a diameter of 50 to 150 μm.

[0112] The method for additive manufacturing of titanium alloy is the same as that in Example 1.

[0113] Comparative Example 3

[0114] The comparative example of the present application provides a method for additive manufacturing of titanium alloy, wherein the laser additive powder comprises: 4wt% iron powder and the balance TC4 alloy powder.

[0115] The iron powder is a spherical particle powder with a diameter of 50 to 150 μm; the TC4 alloy powder is a spherical particle powder with a diameter of 50 to 150 μm.

[0116] The method for additive manufacturing of titanium alloy is the same as that in Example 1.

[0117] Test Example 1

[0118] The titanium alloy structures obtained in Example 1 and Comparative Examples 1 to 3 were observed. Figures 1 to 8 As shown, Figure 1 、 3 , 5 and 7 are 500 μm. Figure 2 、 4 , 6 and 8 are 100 μm; the titanium alloy structure before and after rolling in Example 1 was analyzed for internal voids, as shown in FIG. Figures 9-10 As shown; Test Example 2 respectively tested the mechanical properties of the titanium alloy structure of Example 1 and Comparative Examples 1 to 3 before and after rolling. Figures 11-14 As shown in Table 1, the proportions of α phase and β phase in the titanium alloy structures obtained in Example 1 and Comparative Examples 1 to 3 were respectively counted.

[0119] Table 1 The proportion of α phase and β phase in the titanium alloy structures obtained in Example 1 and Comparative Examples 1 to 3

[0120] project Fe content (wt%) α phase ratio (%) β phase ratio (%) Example 1 3 54.1 45.9 Comparative Example 1 0 98.6 1.4 Comparative Example 2 1.5 85.7 14.3 Comparative Example 3 4 8.2 91.8

[0121] As can be seen from Table 1, by comparing the proportions of α phase and β phase under different iron contents, it is found that when the Fe content in the laser additive powder is about 3wt%, the α phase and β phase can each account for about half, which can ensure that the alloy has the best comprehensive strength and toughness properties; when the Fe content in the laser additive powder is 0 or 1.5wt%, the α phase is ≥80%; when the Fe content in the laser additive powder is 4wt%, the β phase is ≥90%.

[0122] Depend on Figures 1 to 8 By comparison, it can be seen that with the addition of Fe, the original β phase grains are transformed from coarse columnar crystals to fine equiaxed crystals, the grain size is significantly reduced, and the α phase also becomes finer.

[0123] Depend on Figures 9-10 By comparison, the porosity inside the structure decreased from 0.62% to 0.29% before and after rolling, indicating that rolling significantly improved the density.

[0124] Depend on Figures 11-14By comparison, it can be seen that the improvement in strength and toughness is not obvious by simply adding Fe without rolling; the improvement in strength and toughness is also limited by simply rolling without adding Fe elements; but by the process of adding Fe and rolling, and when the Fe content in the laser additive powder is around 3wt%, the strength of the additively manufactured titanium alloy can exceed 1400MPa and the elongation can exceed 5%, achieving a significant improvement in the comprehensive strength and toughness of the titanium alloy.

[0125] In summary, the method of additive manufacturing of titanium alloys in this application adds iron powder to laser additive powder and combines it with the corresponding rolling process after laser additive manufacturing, so that the additively manufactured titanium alloy has high strength and toughness. Among them, part of the β-phase structure will be retained inside the alloy structure at room temperature, and the addition of iron powder can increase the supercooling of the alloy during the cooling process, refine the grains and microstructure, and further roll the additive structure to increase the dislocation density of the titanium alloy and improve the density of the titanium alloy. The combination of the two improves the toughness of the additively manufactured titanium alloy structure.

[0126] The foregoing description is merely a specific embodiment of the present application and is not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for additive manufacturing of titanium alloy, characterized in that: The method for additive manufacturing of titanium alloy comprises: forming an additive structure on the surface of a titanium alloy substrate by a laser additive method, and rolling the additive structure; The laser additive powder is composed of titanium alloy powder and iron powder, the mass fraction of the iron powder is 2.8-3.3wt%, and the mass fraction of the titanium alloy powder is 96.7-97.2wt%; The titanium alloy powder is TC4 alloy powder. The laser power during the laser additive process is 500~1800W. The diameter of the spot formed by the laser beam during the laser additive process is 0.8~3.0mm. A powder feeder is used to transfer the laser additive powder. The rotation speed of the powder feeder is 5~20r / min. The movement rate of the laser head during the laser additive process is 500~2000mm / min. The layer height during the laser additive process is 0.2~0.5mm.

2. The method for additive manufacturing of titanium alloy according to claim 1, characterized in that: The rolling force of the rolling is 5~20kN.

3. The method for additive manufacturing of titanium alloy according to claim 1, characterized in that: The titanium alloy powder is spherical particle powder.

4. The method for additive manufacturing of titanium alloy according to claim 3, characterized in that: The diameter of the titanium alloy powder is 50-200 μm.

5. The method for additive manufacturing of titanium alloy according to claim 1, characterized in that: The iron powder is spherical particle powder.

6. The method for additive manufacturing of titanium alloy according to claim 5, characterized in that: The diameter of the iron powder is 50-150 μm.

7. The method for additive manufacturing of titanium alloy according to claim 1, characterized in that: During the laser material addition process, the laser beam presents a uniform heat source distribution.

8. The method for additive manufacturing of titanium alloy according to claim 1, characterized in that: Before the laser material addition, the laser material addition powder is pretreated, and the pretreatment includes drying.

9. The method for additive manufacturing of titanium alloy according to claim 8, characterized in that: The drying temperature is 80~120℃ and the drying time is 240~300min.

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