Printing and heat treatment process for additive manufacturing of Ti175 alloy

Abstract

The invention discloses a printing and heat treatment process of a special Ti175 alloy for additive manufacturing, and belongs to the technical field of titanium alloy machining, and the printing and heat treatment process comprises the following steps: S1, carrying out printing forming on Ti175 alloy powder by adopting 3D printing equipment; and S2, the component printed and formed in the step S1 is subjected to heat treatment within the temperature range of 950-1100 DEG C and then cooled to the room temperature. According to the printing and heat treatment process of the special Ti175 alloy for additive manufacturing, the density of the Ti175 alloy is improved through the printing process, the mechanical property of the alloy can be greatly regulated and controlled through the heat treatment process, the plasticity of the Ti175 alloy is optimized, and the room-temperature tensile strength and the elongation at break are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of titanium alloy processing, in particular to a printing and heat treatment process of Ti175 alloy special for additive manufacturing. BACKGROUND

[0002] With the replacement of generations of aeroengines, the use environment of titanium alloy is more severe, in particular, the use temperature of the centrifugal pump matched with a ramjet engine even exceeds 400 DEG C, and the traditional TC4 alloy has been difficult to meet the use demand, so it is imperative to develop a new type of high-temperature-resistant high-performance titanium alloy special for additive manufacturing.

[0003] The Ti175 alloy is a kind of alloy that can be used at 500-600 DEG C, and the component design of the traditional Ti175 alloy is mainly aimed at the forging process, since the additive manufacturing has the non-equilibrium physical metallurgy and thermal physical process of extremely fast heating / cooling, the adaptability of the alloy component in the additive manufacturing forming process still has many uncertainties, such as the burning loss of low-melting-point elements, the distribution uniformity of high-melting-point elements and the like. In addition, suitable printing process parameters are also the key to obtain high-quality parts. Therefore, for the Ti175 alloy special for additive manufacturing, the alloy additive manufacturing whole-process process development needs to be carried out. The printing quality of additive manufacturing is affected by multiple process parameters, and there is a coupling effect between the parameters, how to match the input process parameters and then optimize the quality of the additive manufacturing alloy component still needs in-depth research. SUMMARY

[0004] The application aims to provide a printing and heat treatment process of Ti175 alloy special for additive manufacturing, the printing process improves the density of the Ti175 alloy, the heat treatment process can greatly control the mechanical properties of the alloy, and the plasticity of the Ti175 alloy is optimized, the room temperature tensile strength and the elongation at break are improved.

[0005] To achieve the above-mentioned purpose, the application provides a printing and heat treatment process of Ti175 alloy special for additive manufacturing, which comprises the following steps: S1, using a 3D printing device to print and form Ti175 alloy powder; S2, heat treating the component printed and formed in S1 at 950-1100 DEG C, and then cooling to room temperature.

[0006] Preferably, in S1, the process parameters of printing and forming are as follows: laser power 170-180 W, scanning speed 1000-1500 mm / s, scanning interval 0.05-0.2 mm, and powder layer thickness 0.01-0.05 mm.

[0007] Preferably, in S2, the specific operation of heat treatment is as follows: first, heat the tube furnace to 20°C below the target temperature at a heating rate of 5-10°C / min, then place the cuboid part into the tube furnace, close the tube furnace, and introduce protective gas, then heat to the target temperature at a heating rate of 2-5°C / min, and hold for 0.5-2 hours.

[0008] Preferably, in S2, the protective gas is argon or nitrogen.

[0009] Preferably, in S2, the cooling method is one or more of air cooling, furnace cooling, and water quenching.

[0010] Therefore, the above-mentioned printing and heat treatment process for additive manufacturing of Ti175 alloy has the following beneficial effects: (1) Due to the rapid cooling characteristics of L-PBF printing, the deposited Ti175 alloy exhibits extremely high work hardening properties, with a yield strength of approximately 850 MPa, a tensile strength of up to 1250 MPa, and a fracture elongation of up to 15%. (2) The mechanical properties of the alloy can be greatly controlled by heat treatment optimization. The Ti175 alloy achieves a good balance of strength and plasticity. The room temperature tensile strength of the alloy can reach 1125 MPa and the elongation at break can reach 16%. At 550℃ high temperature tensile test, the alloy strength can reach 876 MPa and the elongation at break can reach 25%.

[0011] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0012] Figure 1 This is a Micro-CT image of the deposited Ti175 alloy, which is a Ti175 alloy for additive manufacturing according to the present invention, and is obtained through printing and heat treatment process. Figure 2 This is a metallographic diagram of a Ti175 alloy deposited in the additive manufacturing process of the present invention, which involves printing and heat treatment of a Ti175 alloy for additive manufacturing. Figure 3 This is a metallographic diagram of the Ti175 alloy after heat treatment in Example 1 of the printing and heat treatment process of a special Ti175 alloy for additive manufacturing according to the present invention. Figure 4 This is a metallographic diagram of the Ti175 alloy after heat treatment in Example 2 of the printing and heat treatment process of a special Ti175 alloy for additive manufacturing according to the present invention. Figure 5 This is a metallographic diagram of the Ti175 alloy after heat treatment in Example 3 of the printing and heat treatment process of a special Ti175 alloy for additive manufacturing according to the present invention. Figure 6This invention describes the printing and heat treatment process of a special Ti175 alloy for additive manufacturing. The SEM microstructures of the deposited Ti175 alloy and the Ti175 alloys after different heat treatments in Examples 1-3 are shown. Figure 7 This is a wire-cut dog-bone shaped sheet stretching dimension diagram of a printing and heat treatment process for a Ti175 alloy for additive manufacturing according to the present invention. Figure 8 This invention relates to a printing and heat treatment process for a special Ti175 alloy for additive manufacturing, showing the tensile stress-strain curves of deposited Ti175 alloy and heat-treated Ti175 alloy at room temperature, 400°C, and 550°C. Figure 9 This invention describes the tensile properties of a Ti175 alloy deposited at different deposition heights after sampling using a printing and heat treatment process for a Ti175 alloy specifically designed for additive manufacturing. Figure 10 This invention compares the mechanical properties of various high-temperature titanium alloys (laser additive and forged) and L-PBF-printed Ti175 alloys using a special additive manufacturing process for Ti175 alloy. Detailed Implementation

[0013] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0014] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0015] Example 1 A printing and heat treatment process for a Ti175 alloy specifically for additive manufacturing includes the following steps: S1. Using a BLT-S210 metal 3D printing equipment, Ti175 alloy powder is printed into a cuboid with dimensions of 15mm×25mm×10mm. The printing process parameters are: laser power 175W, scanning speed 1400mm / s, scanning spacing 0.1mm, and powder layer thickness 0.03mm.

[0016] S2. First, heat the tube furnace to 940℃ at a heating rate of 10℃ / min. Then, place the cuboid part obtained in S1 into the tube furnace, close the tube furnace, and introduce 99.99% argon gas as a protective gas. Heat to 960℃ at a heating rate of 2℃ / min and hold for 1 hour. After holding, remove the cuboid part and place it on a heat-insulating tile to cool naturally to room temperature.

[0017] Example 2 A printing and heat treatment process for a Ti175 alloy specifically for additive manufacturing includes the following steps: S1. Using a BLT-S210 metal 3D printing equipment, Ti175 alloy powder is printed into a cuboid with dimensions of 15mm×25mm×10mm. The printing process parameters are: laser power 175W, scanning speed 1400mm / s, scanning spacing 0.1mm, and powder layer thickness 0.03mm.

[0018] S2. First, heat the tube furnace to 940℃ at a heating rate of 10℃ / min. Then, place the cuboid part obtained in S1 into the tube furnace, close the tube furnace, and introduce 99.99% argon gas as a protective gas. Heat to 960℃ at a heating rate of 2℃ / min and hold for 1 hour. After the holding period, cool the part with the furnace to below 860℃ and then remove the cuboid part and place it on a heat-insulating tile to cool naturally to room temperature.

[0019] Example 3 A printing and heat treatment process for a Ti175 alloy specifically for additive manufacturing includes the following steps: S1. Using a BLT-S210 metal 3D printing equipment, Ti175 alloy powder is printed into a cuboid with dimensions of 15mm×25mm×10mm. The printing process parameters are: laser power 175W, scanning speed 1400mm / s, scanning spacing 0.1mm, and powder layer thickness 0.03mm.

[0020] S2. First, heat the tube furnace to 940℃ at a heating rate of 10℃ / min. Then, put the cuboid part obtained in S1 into the tube furnace, close the tube furnace, and introduce 99.99% argon gas as a protective gas. Heat to 960℃ at a heating rate of 2℃ / min and hold for 1 hour. After the holding period, cool the part to below 300℃ with the furnace before taking it out.

[0021] Example 4 A printing and heat treatment process for a Ti175 alloy specifically for additive manufacturing includes the following steps: S1. Using a BLT-S210 metal 3D printing equipment, Ti175 alloy powder is printed into a cuboid with dimensions of 15mm×25mm×10mm. The printing process parameters are: laser power 175W, scanning speed 1400mm / s, scanning spacing 0.1mm, and powder layer thickness 0.03mm.

[0022] S2. First, heat the tube furnace to 990℃ at a heating rate of 10℃ / min. Then, put the cuboid part obtained in S1 into the tube furnace, close the tube furnace, and introduce 99.99% argon gas as a protective gas. Heat to 1010℃ at a heating rate of 2℃ / min and hold for 0.5h. After the holding period, take out the cuboid part and water cool it.

[0023] Test 1 The cuboid parts obtained in S1 of Examples 1-3 are consistent, and their alloys are in a deposited state. Therefore, the cuboid part obtained in S1 of Example 1 is used as a representative for testing. Samples of 8mm×8mm×8mm were taken from the cuboid part obtained in S1 of Example 1 and the heat-treated cuboid parts of Examples 1-3, respectively. The microstructure of the alloy was characterized by metallographic microscopy (OM, BX51M), scanning electron microscopy (SEM, CIQTEK-SEM3100), and energy dispersive spectroscopy (EDS).

[0024] Figure 1 The figure shows the Micro-CT morphology of the deposited Ti175 alloy. As can be seen from the figure, no obvious metallurgical defects were observed in the L-PBF-printed Ti175 alloy (the testing accuracy of Micro-CT can reach 10 μm), and the density of the alloy can reach 99.87%. Figures 2-5 The metallographic structures of the deposited Ti175 alloy and the Ti175 alloys after different heat treatments in Examples 1-3 are shown respectively. Figure 2 In the figures (a)-(d), the metallographic structures of the deposited Ti175 alloy at different magnifications are shown. Figure 3 In the figures (a)-(d), the metallographic structures of the Ti175 alloy after being held at 960℃ for 1 hour and then air-cooled are shown respectively. Figure 4 In Example 1, (a)-(d) show the metallographic structures of the Ti175 alloy after being held at 960℃ for 1 hour and then furnace cooled to 860℃. Figure 5 In the figures (a)-(d), the microstructures of the Ti175 alloy after furnace cooling at 960℃ for 1 hour in Example 1 are shown. Figure 2 As shown, due to the rapid cooling characteristics of L-PBF printing, the boundaries of the molten pool can be observed in the deposited Ti175 alloy, and fine needle-like α' martensite structures exist inside the molten pool. The α+β two-phase region temperature of the Ti175 alloy is approximately 880-985℃, and the alloy microstructure changes significantly after heat treatment. After holding at 960℃ for 1 hour and then air cooling, the Ti175 alloy exhibits a dual-state microstructure, namely primary coarse α laths and β phase transformation structures (secondary fine α laths + residual β phase), with primary α laths accounting for approximately 10.6% and β phase transformation structures accounting for approximately 89.4% (area percentage). Since 960℃ is closer to the β phase transformation temperature of the Ti175 alloy, the aspect ratio of the primary α phase is small, and some primary α laths exhibit a near-equiaxed morphology. Discontinuous α phases can be observed at the original β phase grain boundaries. When the alloy is heat-treated from 960℃ for 1 hour to 860℃ (see...), Figure 4 In the Ti175 alloy, the proportion of primary α-lamellae (coarse laths) is significantly increased, accounting for approximately 35.2%, while the proportion of β-phase transformation microstructure is approximately 64.8% (area percentage). The alloy microstructure after furnace cooling at 960℃ for 1 hour is as follows...Figure 5 As shown, the Ti175 alloy has a uniformly coarsened α-lamellae structure, with residual β phase at the α-lamellae interface.

[0025] Figure 6 The SEM microstructures of the deposited Ti175 alloy and the heat-treated Ti175 alloy are shown. Figure 6 (a)-(b) are SEM images of the deposited Ti175 alloy. Similar to the metallographic structure of the Ti175 alloy, fine needle-like α' phases were observed in the deposited Ti175 alloy. Figure 6 (c)-(d) in the figure are Ti175 alloys that were held at 960℃ for 1 hour and then air-cooled. They contain primary coarse α laths and β phase transformation structures (secondary fine α laths + residual β phase). Figure 6 (e)-(f) in the figure are Ti175 alloys that were held at 960℃ for 1 hour and then furnace cooled to 860℃. When the alloy was furnace cooled from 960℃ to 860℃, the primary α phase in the alloy gradually increased and the β transformation structure decreased. Figure 6 (g)-(h) in the figure refers to Ti175 alloy that was held at 960℃ for 1 hour and then furnace cooled. The alloy that was furnace cooled at 960℃ consists of coarse α laths and residual β phase.

[0026] Test 2 Three tensile samples were taken from the cuboid obtained in S1 of Example 1 and the heat-treated cuboids in Examples 1-3, respectively. The tensile dimensions of the wire-cut dog-bone-shaped sheet are as follows: Figure 7 As shown. Before testing, the wire cutting marks on the sides and the oxide layer on the surface of the tensile specimens were ground off, and the width and thickness of the gauge length were measured and recorded. A Bairoe universal testing machine was used to perform mechanical tests on each group of tensile specimens, with the tensile rate set to 0.18 mm / min. Simultaneously, a video extensometer was used to record the deformation behavior mechanism of the tensile specimens.

[0027] The tensile stress-strain curves of deposited Ti175 alloy and heat-treated Ti175 alloy at room temperature, 400℃, and 550℃ are shown below. Figure 8 As shown in Table 1-3, Figure 8 (a) in the figure represents the stretching at room temperature. Figure 8 (b) shows the room temperature horizontal and vertical tensile tests on the deposited Ti175 alloy. Figure 8 (c) represents a stretch at 400℃. Figure 8(c) represents tensile testing at 550℃. The deposited Ti175 alloy exhibits extremely high work hardening properties at room temperature, exhibiting a double yield phenomenon. Analysis suggests this may be related to the presence of a metastable β phase in the deposited Ti175 alloy. During deformation, the alloy undergoes a phase transformation (TRIP effect), precipitating finer α' / α' phases, thus resulting in extremely high work hardening characteristics. Heat treatment significantly affects the mechanical properties of the alloy. After furnace cooling at 960℃ for 1 hour, the alloy exhibits extremely high ductility at room temperature, but its strength is relatively low (tensile strength 1093 MPa; elongation at break 21%). After air cooling at 960℃ for 1 hour, the alloy exhibits high strength but relatively low plasticity (tensile strength 1374 MPa; elongation at break 9.6%). After furnace cooling from 960℃ for 1 hour to 860℃ combined with air cooling heat treatment, the Ti175 alloy achieves a good balance between strength and plasticity, with a room temperature tensile strength of 1125 MPa and an elongation at break of 16%. At 400℃, the alloy achieves a tensile strength of 979 MPa and an elongation at break of 18.3%. At 550℃, the alloy achieves a tensile strength of 876 MPa and an elongation at break of 25.3%.

[0028] Table 1 Room temperature tensile data

[0029] Table 2 Tensile data at 400℃

[0030] Table 3 Tensile data at 550℃

[0031] Figure 8 (b) shows the comparison of tensile properties of deposited Ti175 alloy in the horizontal X direction and vertical Z direction. The specific data are shown in Table 4. The tensile strength in the two directions is comparable, but the plasticity (fracture elongation 10-12%) in the Z direction is slightly lower than that in the tensile sample in the X direction. Figure 9 The tensile properties of Ti175 alloy samples taken at different deposition heights are shown in the figure. As can be seen from the figure, the tensile properties of samples taken at different heights exhibit certain differences. The sample taken from the top has relatively low tensile plasticity, which is closely related to the microstructure at the top. In the alloy region at the top, due to the lack of cyclic heat treatment, the microstructure in this area exhibits a finer α-lamellae structure. This fine α-lamellae structure characteristic contributes to the reduction in alloy plasticity to some extent.

[0032] Table 4 Anisotropy of room temperature stretching

[0033] Figure 10 A comparison of the mechanical properties of various high-temperature titanium alloys (laser additive manufacturing and forged state) and L-PBF-printed Ti175 alloy is presented. Figure 10 Figures (a)-(c) show tensile properties at room temperature, 400℃, and 550℃, respectively. As can be seen from the figures, after heat treatment optimization, the room temperature tensile properties of the L-PBF-printed Ti175 alloy significantly outperform those of L-PBF-printed TC4, TA15, TC11, TC17, and TA32. At 400℃, this alloy is significantly stronger than L-PBF-printed TC17 and TC4, and also superior to forged TC4, TC17, and TA12A, with properties similar to those of forged Ti175 alloy. At 550℃, its performance is significantly better than that of forged TA15 and TA32 alloys.

[0034] Therefore, the present invention adopts the above-mentioned printing and heat treatment process for additive manufacturing of Ti175 alloy. The printing process improves the density of Ti175 alloy, and the heat treatment process can significantly control the mechanical properties of the alloy, optimize the plasticity of Ti175 alloy, and improve room temperature tensile strength and elongation at break.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A printing and heat treatment process of additive manufacturing of Ti175 alloy, characterized in that, The method comprises the following steps: S1, printing Ti175 alloy powder into a component by using a 3D printing device; S2, heat treating the component printed in S1 at 950-1100 ℃, and then cooling to room temperature.

2. The production method according to claim 1, characterized by, In S1, the process parameters for printing are as follows: laser power 170-180 W, scanning speed 1000-1500 mm / s, scanning interval 0.05-0.2 mm, and powder layer thickness 0.01-0.05 mm.

3. The preparation method according to claim 1, characterized in that, In S2, the specific operation of heat treatment is as follows: first, heating a tubular furnace to 20 ℃ below the target temperature at a heating rate of 5-10 ℃ / min, then putting the cuboid into the tubular furnace, closing the tubular furnace, and passing in a protective gas, heating to the target temperature at a heating rate of 2-5 ℃ / min, and keeping the temperature for 0.5-2 h.

4. The production method according to claim 3, characterized by, In S2, the protective gas is argon or nitrogen.

5. The preparation method according to claim 1, characterized in that, In S2, the cooling mode is one or more of air cooling, furnace cooling, and water quenching.

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