Coaxial six-laser-fuse equiaxed structure titanium alloy and additive preparation method thereof

Abstract

The invention discloses an additive preparation method of coaxial six-laser-fuse equiaxed structure titanium alloy. The equiaxed structure titanium alloy is prepared from titanium alloy wires through coaxial six-laser-fuse additive preparation. The laser power of the coaxial six-laser fuse wire is 700 to 1000 W; the wire feeding speed is 10-20 mm / s; the moving speed is 20-30 m / s; the interlayer temperature control temperature ranges from 150 DEG C to 450 DEG C; the scanning interval is 0.12 mm; the interlayer thickness is 1.2 mm; and the preheating temperature of the substrate is 80-120 DEG C. According to the coaxial six-laser-fuse equiaxed structure titanium alloy additive preparation technology, the obtained material has a thin equiaxed crystal structure, high ductility, high critical stress and excellent strength and plasticity performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal materials, and particularly relates to a coaxial six-laser-fused equiaxed microstructure titanium alloy and an additive manufacturing method thereof. BACKGROUND

[0002] As an alpha+beta dual-phase titanium alloy, the Ti alloy doped with Al and V elements has high specific strength, good fatigue resistance, excellent corrosion resistance and biocompatibility, is known as the most popular titanium alloy, and is widely used in the fields of aerospace, automobile industry, chemistry and biomedical treatment. However, the inherent high strength and low thermal conductivity of the titanium alloy result in poor cutting performance, and the titanium alloy is not suitable for traditional subtractive manufacturing methods. The rapidly developing additive manufacturing becomes the preferred method for manufacturing high-performance titanium alloys.

[0003] The laser directed energy deposition technology was first developed in the United States in the 1990s, and is an advanced manufacturing technology developed on the basis of laser cladding technology. The technology uses high-energy-density laser as a heat source, and melts the powder or wire material sent synchronously according to the predetermined processing path, so as to realize the direct additive manufacturing of metal parts. Compared with the powder-based directed energy deposition, the laser wire technology has the advantages of low cost, high deposition rate and high material utilization rate, and shows great potential in the preparation of large components.

[0004] However, the laser wire technology also has the following deficiencies in the preparation of titanium alloys: the titanium alloy prepared by the laser wire technology has a coarse columnar crystal as the main matrix due to repeated heating between layers, which further leads to poor mechanical properties and obvious anisotropy of mechanical properties in different directions. In addition, the traditional transverse wire feeding is prone to bending due to uneven heating of the wire. Furthermore, the consistency of the printing layer in each direction cannot be guaranteed due to the influence of the wire feeding position and angle. SUMMARY

[0005] This section aims to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, abstract and title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0006] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0007] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art, and to provide an additive manufacturing method of a coaxial six-laser-fused equiaxed microstructure titanium alloy.

[0008] To solve the above technical problems, the present application provides the following technical solutions, including,

[0009] After preheating the substrate, adjust the equipment parameters, and use the coaxial six-laser wire melting process to prepare equiaxed structure titanium alloy by laser wire melting additive manufacturing of titanium alloy wire;

[0010] The coaxial six-laser wire melting process, wherein the linear heat input Q is 50-60 J / mm; the ratio N of the wire feeding speed to the printing speed is 1.6-2.0.

[0011] As a preferred scheme of the additive manufacturing method of the coaxial six-laser wire melting equiaxed structure titanium alloy, the substrate comprises TC4 titanium alloy.

[0012] As a preferred scheme of the additive manufacturing method of the coaxial six-laser wire melting equiaxed structure titanium alloy, the preheating temperature is 80-120℃.

[0013] As a preferred scheme of the additive manufacturing method of the coaxial six-laser wire melting equiaxed structure titanium alloy, the titanium alloy wire comprises, in mass percentage,

[0014] Al: 5-7%, V: 3-4.5%, C: 0.07-0.12, Fe: 0.05-0.12%, and the rest is titanium.

[0015] As a preferred scheme of the additive manufacturing method of the coaxial six-laser wire melting equiaxed structure titanium alloy, the diameter of the titanium alloy wire is 0.8-2.4 mm.

[0016] As a preferred scheme of the additive manufacturing method of the coaxial six-laser wire melting equiaxed structure titanium alloy, the preparation method of the titanium alloy wire comprises weighing raw material powder according to the formula, vacuum melting, multi-pass hot forging to break down into a titanium alloy rod with a diameter of 3-10 mm; further drawing at room temperature to gradually reduce the diameter, and finally preparing a titanium alloy wire with a diameter of 0.8-2.4 mm.

[0017] As a preferred scheme of the additive manufacturing method of the coaxial six-laser wire melting equiaxed structure titanium alloy, the coaxial six-laser wire melting process, wherein the interlayer cooling temperature is 200-300℃; the protective atmosphere for interlayer cooling is argon, and the gas flow rate for interlayer cooling is 15-20 L / min.

[0018] As a preferred scheme of the additive manufacturing method of the coaxial six-laser wire melting equiaxed structure titanium alloy, the coaxial six-laser wire melting process, wherein the laser power is 700-1000 W; the printing speed is 10-20 mm / s; the wire feeding speed is 20-30 m / s; the scanning pitch is 0.12 mm; and the interlayer height is 1.2 mm.

[0019] As a preferred scheme of the additive preparation method of the coaxial six-laser-fused equiaxed structure titanium alloy, in the coaxial six-laser-fused process, the laser power is 800 W, the printing speed is 15 mm / s, the wire feeding speed is 27 mm / s, the interlayer temperature control temperature is 200 DEG C, the substrate preheating temperature is 100 DEG C, the scanning interval is 0.12 mm, and the interlayer thickness is 1.2 mm.

[0020] Therefore, another object of the present application is to overcome the deficiencies in the prior art and provide a coaxial six-laser-fused equiaxed structure titanium alloy, which has the following characteristics:

[0021] (i) the average equiaxed crystal grain size in the alloy matrix structure is less than 420 μm;

[0022] (ii) the tensile strength at room temperature is greater than 840 MPa;

[0023] (iii) the elongation after fracture at room temperature is greater than 17%

[0024] The present application has the following advantages:

[0025] (1) The coaxial six-laser-fused equiaxed structure titanium alloy provided by the present application has fine equiaxed crystal structure, high elongation and high critical stress, excellent strength and plasticity, and small anisotropy of mechanical properties.

[0026] (2) The equiaxed structure titanium alloy prepared by the present application has fine equiaxed crystal structure, high density, good mechanical properties and other excellent properties. For the equiaxed structure titanium alloy obtained by the present application, the average equiaxed crystal grain size in the alloy matrix structure is less than 420 μm, the tensile strength is greater than 840 MPa, and the elongation after fracture is greater than 17%. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor. Among them:

[0028] Figure 1 It is the grain structure metallographic phase diagram of the equiaxed structure titanium alloy obtained in embodiment 1 of the present application;

[0029] Figure 2 It is the tensile stress-strain curve diagram of the equiaxed structure titanium alloy obtained in embodiment 1 of the present application;

[0030] Figure 3 It is the grain structure metallographic phase diagram of the equiaxed structure titanium alloy obtained in embodiment 2 of the present application;

[0031] Figure 4 Tensile stress-strain curve of the equiaxed structure titanium alloy obtained in Example 2 of the present application;

[0032] Figure 5 Grain structure metallograph of the equiaxed structure titanium alloy obtained in Comparative Example 1 of the present application;

[0033] Figure 6 Tensile stress-strain curve of the equiaxed structure titanium alloy obtained in Comparative Example 1 of the present application;

[0034] Figure 7 Grain structure metallograph of the equiaxed structure titanium alloy obtained in Comparative Example 2 of the present application;

[0035] Figure 8 Tensile stress-strain curve of the equiaxed structure titanium alloy obtained in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0036] In order to make the above objectives, features and advantages of the present application more apparent, the specific embodiments of the present application will be described in detail below with reference to the description and embodiments.

[0037] In the following description, a lot of specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can be practiced in other manners different from those described herein, and those skilled in the art can make similar generalization without departing from the spirit and scope of the present application, therefore, the present application is not limited to the specific embodiments disclosed below.

[0038] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. The "in one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments.

[0039] The raw materials used in the present application are all commercially available without special instructions.

[0040] Linear heat input Wherein P is power, V p is printing speed; the ratio of wire feeding speed to printing speed Wherein V w is wire feeding speed, V p is printing speed.

[0041] The material prepared in the embodiments of the present application is subjected to mechanical property test according to the following method:

[0042] First, the prepared material sample is cut into thin bone-shaped tensile specimens. Then, a tensile test is performed using an Instron 8820 machine, which is equipped with appropriate clamps to ensure the stability of the sample during the test.

[0043] During the test, the Instron machine records the applied tensile force, and the MTS Advantage video extensometer records the deformation of the sample. The test should be conducted at room temperature to ensure that no external factors affect the test results. The test is stopped when the sample is destroyed, and key parameters such as maximum tensile strength, yield strength, and elongation after fracture are recorded.

[0044] To ensure the reliability of the test results, each material sample should be tested at least three times, and the average value is taken as the final mechanical property data.

[0045] Example 1

[0046] This example provides a method for preparing a coaxial six-laser wire equiaxed microstructure titanium alloy, specifically:

[0047] 1) Cold drawing: The titanium alloy rod with a diameter of 3-10 mm prepared by vacuum melting is drawn into a titanium wire with a diameter of 1.0 mm at room temperature using a tungsten carbide die.

[0048] 2) Preheating the substrate: The TC4 titanium alloy substrate is preheated to 100℃;

[0049] 3) Adjustment of equipment parameters: laser power 800W, printing speed 15mm / s, wire feeding speed 27mm / s, interlayer cooling temperature 200℃, scanning pitch 0.12mm, interlayer height 1.2mm, argon gas flow rate 15L / min. That is, the linear heat input Q is 53.3J / mm, and the ratio N of wire feeding speed to printing speed is 1.8.

[0050] 4) Coaxial six-laser wire preparation: The customized titanium alloy wire is used for laser wire preparation, and an equiaxed microstructure titanium alloy is obtained.

[0051] The obtained coaxial six-laser wire equiaxed microstructure titanium alloy has an average equiaxed grain size of 337μm in the alloy matrix structure, a tensile strength of 947MPa, an elongation after fracture of 18.4%, and a tensile strength anisotropy of 1.9%.

[0052] Example 2

[0053] The difference between this example and Example 1 is that the laser power is adjusted to 900W, that is, the linear heat input Q is 60J / mm, and the rest of the preparation process is the same as Example 1, and an equiaxed microstructure titanium alloy is prepared.

[0054] Example 3

[0055] The difference between this embodiment and embodiment 1 is that the laser power is adjusted to 750 W, that is, the linear heat input Q is 50 J / mm, and the rest of the preparation process is the same as that of embodiment 1, and an equiaxed structure titanium alloy is prepared.

[0056] The materials prepared in the above embodiments are tested for performance, and the comparison results with embodiment 1 are shown in Table 1.

[0057] Table 1

[0058] Example 1 Example 2 Example 3 Average equiaxed grain size (pm) 337 417 311 Tensile strength (MPa) 947 849 857 Elongation at break (%) 18.4 17.5 17.1 Tensile strength anisotropy (%) 1.9 0.3 2.9

[0059] As can be seen from the above table, adjusting the linear heat input Q has a significant effect on the performance of the equiaxed structure titanium alloy, because too low / high heat input will affect the fusion and thermal stress of the alloy. According to the results in the above table, the linear heat input Q in the present application is 53.3 J / mm, which can obtain the best technical effect.

[0060] Embodiment 4

[0061] The difference between this embodiment and embodiment 1 is that the wire feeding speed is adjusted to 24 m / s, that is, the ratio N of the wire feeding speed to the printing speed is 1.6, and the rest of the preparation process is the same as that of embodiment 1, and an equiaxed structure titanium alloy is prepared.

[0062] Embodiment 5

[0063] The difference between this embodiment and embodiment 1 is that the wire feeding speed is adjusted to 30 m / s, that is, the ratio N of the wire feeding speed to the printing speed is 2.0, and the rest of the preparation process is the same as that of embodiment 1, and an equiaxed structure titanium alloy is prepared.

[0064] The materials prepared in the above embodiments are tested for performance, and the comparison results with embodiment 1 are shown in Table 2.

[0065] Table 2

[0066] Example 1 Example 4 Example 5 Average equiaxed grain size (pm) 337 402 331 Tensile strength (MPa) 947 916 873 Elongation at break (%) 18.4 17.4 17.9 Tensile strength anisotropy (%) 1.9 2.3 2.7

[0067] As can be seen from the above table, adjusting the ratio N of the wire feeding speed to the printing speed has a significant effect on the performance of the equiaxed structure titanium alloy, because high wire feeding speed makes the un-melted wire material as a nucleation point for equiaxed crystal to promote grain nucleation. According to the results in the above table, the ratio N of the wire feeding speed to the printing speed in the present application is 1.8, which can obtain the best technical effect.

[0068] Comparative Example 1

[0069] The difference between this comparative example and embodiment 1 is that the laser power is adjusted to 700 W, that is, the linear heat input Q is 46.7 J / mm, and the rest of the preparation process is the same as that of embodiment 1, and an equiaxed structure titanium alloy is prepared.

[0070] Comparative Example 2

[0071] The present comparative example differs from Example 1 in that the laser power is adjusted to 1000 W, i.e. the linear heat input Q is 66.7 J / mm, and the rest of the preparation process is the same as Example 1. The titanium alloy prepared appears a large range of columnar crystal structure.

[0072] The material prepared in the above comparative example is tested for performance, and the comparison results with Example 1 are shown in Table 1.

[0073] Table 3

[0074] Example 1 Comparative Example 1 Comparative Example 2 Average grain size (pm) 337 310 550 Tensile strength (MPa) 947 862 814 Elongation at break (%) 18.4 5.5 18.3 Tensile strength anisotropy (%) 1.9 9.4 4.0

[0075] As can be seen from the above table, the linear heat input Q has a significant effect on the microstructure and performance of the titanium alloy. This is because too low heat input will cause uneven fusion and insufficient fusion, and too high heat input will produce high residual stress, and the wire is difficult to form un-melted fragments as equiaxed crystal nucleation points.

[0076] In summary, the coaxial six-laser wire equiaxed microstructure titanium alloy provided by the present application has fine equiaxed crystal structure, high elongation and high critical stress, excellent strength and plasticity, and small anisotropy of mechanical properties. The equiaxed microstructure titanium alloy prepared by the present application has fine equiaxed crystal structure, high density, good mechanical properties and other excellent properties. For the equiaxed microstructure titanium alloy obtained by the present application, the average equiaxed crystal grain size in the alloy matrix structure is less than 420 μm, the tensile strength is greater than 840 MPa, and the elongation after fracture is greater than 17%.

[0077] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. An additive manufacturing method for a coaxial six-laser fused wire equiaxed titanium alloy, characterized in that: include, After the substrate is preheated, the equipment parameters are adjusted, and the coaxial six-laser filament process is used to laser filament additive manufacturing of titanium alloy wire to obtain equiaxed titanium alloy. In the coaxial six-laser filament melting process, the linear heat input Q is 50-60 J / mm; the ratio N of the filament feed speed to the printing speed is 1.6-2.

0.

2. The additive manufacturing method for coaxial six-laser fused equiaxed titanium alloy as described in claim 1, characterized in that: The substrate comprises TC4 titanium alloy.

3. The additive manufacturing method for coaxial six-laser fused equiaxed titanium alloy as described in claim 1, characterized in that: The preheating temperature is 80–120°C.

4. The additive manufacturing method for coaxial six-laser fused wire equiaxed titanium alloy as described in claim 1, characterized in that: The titanium alloy wire, by weight percentage, comprises, Al: 5-7%, V: 3-4.5%, C: 0.07-0.12%, Fe: 0.05-0.12%, with the remainder being titanium.

5. The additive manufacturing method for coaxial six-laser fused wire equiaxed titanium alloy as described in claim 4, characterized in that: The diameter of the titanium alloy wire is 0.8 to 2.4 mm.

6. The additive manufacturing method for coaxial six-laser fused equiaxed titanium alloy as described in claim 4, characterized in that: The method for preparing the titanium alloy wire includes weighing raw material powder according to the formula, performing vacuum melting, hot forging in multiple passes to form titanium alloy rods with a diameter of 3 to 10 mm; further drawing at room temperature to gradually reduce the diameter, and finally preparing titanium alloy wire with a diameter of 0.8 to 2.4 mm.

7. The additive manufacturing method for coaxial six-laser fused wire equiaxed titanium alloy as described in claim 1, characterized in that: In the coaxial six-laser filament process, the interlayer cooling temperature is 200-300℃; the protective atmosphere for interlayer cooling is argon; and the gas flow rate for interlayer cooling is 15-20 L / min.

8. The additive manufacturing method for coaxial six-laser fused wire equiaxed titanium alloy as described in claim 1, characterized in that: The coaxial six-laser filament melting process includes a laser power of 700–1000W, a printing speed of 10–20 mm / s, a filament feeding speed of 20–30 m / s, a scanning spacing of 0.12 mm, and an interlayer height of 1.2 mm.

9. The additive manufacturing method for coaxial six-laser fused wire equiaxed titanium alloy as described in claim 1, characterized in that: The coaxial six-laser filament melting process includes a laser power of 800W, a printing speed of 15mm / s, a filament feeding speed of 27mm / s, an interlayer temperature control of 200℃, a substrate preheating temperature of 100℃, a scanning spacing of 0.12mm, and an interlayer thickness of 1.2mm.

10. A coaxial six-laser-fused equiaxed titanium alloy prepared by the method described in any one of claims 1 to 9, characterized in that: The alloy has the following properties: (i) The average equiaxed grain size in the alloy matrix is ​​<420 μm; (ii) Tensile strength at room temperature > 840 MPa; (iii) Elongation after fracture at room temperature > 17%.

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