A method for forming high-temperature resistant titanium alloys by selective laser melting

Abstract

This invention relates to the field of titanium alloy material preparation, and discloses a method for manufacturing high-temperature titanium alloys based on a molten tin bed. The method involves activating a laser selective melting (SLM) module to perform layer-by-layer, zoned scanning and shaping of pre-treated titanium alloy powder. Each layer first scans the contour buffer zone, then the main body area. Adjacent layers are scanned at a 67° angle. After each layer is shaped, in-situ full-coverage remelting is initiated within ≤0.3 seconds. After remelting, the molten tin bed module performs simultaneous isothermal heat treatment and fluid support on the current shaped-remelted layer using molten tin. After overall shaping, temperature-controlled cooling and post-processing yield the finished part. This invention combines a zoned strategy of "spiral scanning of the contour buffer zone + checkerboard scanning of the main body area," regional laser parameter control, in-situ laser remelting technology, and a high-temperature titanium alloy SLM manufacturing method that simultaneously achieves shaping and heat treatment. This method can precisely optimize the shaping quality of different areas, improve the density and overall performance of components, and does not significantly increase the shaping time.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy material preparation, and in particular to a high-temperature resistant titanium alloy laser selective melting forming method. Background Technology

[0002] Titanium alloys play an irreplaceable role in high-end equipment fields such as aerospace, shipbuilding, and medical applications due to their excellent specific strength, corrosion resistance, and high-temperature performance. High-temperature titanium alloys, in particular, exhibit excellent strength, creep resistance, and thermal stability at high temperatures. Additive manufacturing is a digital manufacturing technology that constructs three-dimensional solids by adding materials layer by layer. It enables near-net-shape forming of complex titanium alloy parts, becoming an important method for manufacturing high-end metal components such as titanium alloys. Among these, selective laser melting (SLM) is a mainstream metal additive manufacturing technology, producing parts with high density and mechanical properties approaching or even reaching the level of forgings. However, SLM manufacturing of titanium alloy parts suffers from problems such as high residual stress, significant performance anisotropy, strength-plasticity mismatch, and high surface roughness. For some components with special requirements, such as aero-engine blades and disks, the blade surface requires extremely high wear resistance and erosion resistance, while the blade root and core require extremely high fracture toughness and fatigue strength, which existing additive manufacturing methods cannot meet. Meanwhile, traditional SLM forming requires additional heat treatment processes such as annealing and solution treatment to improve the microstructure and eliminate stress, which not only prolongs the production cycle and increases manufacturing costs, but may also lead to a decrease in the dimensional accuracy of the components.

[0003] In the SLM process, traditional high-temperature titanium alloys (Ti-Al-Sn-Zr-Mo-Nb-W-Si alloys) suffer from two main problems: insufficient formability and inadequate high-temperature performance. Due to the extremely rapid cooling and large temperature gradient during SLM, high residual stress is generated, making them prone to hot cracking. Rapid solidification of the molten pool also leads to the formation of coarse columnar crystals, resulting in a pronounced directional mechanical property. Furthermore, their high-temperature strength is insufficient. To address these issues, elemental screening revealed that adding trace amounts of rare earth elements (such as yttrium Y) can improve the solidification structure, reduce defects, and enhance the formability of titanium alloys in SLM. Adding an appropriate amount of titanium (Ta) can improve high-temperature performance.

[0004] Related studies indicate that the partitioned scanning strategy significantly reduces residual stress and deformation, improves microstructure uniformity, and suppresses anisotropy. However, poor overlap, voids, or microcracks are prone to occur at the partition interfaces. Furthermore, compared to the strip scanning strategy, the partitioned scanning strategy has lower printing efficiency. The spiral scanning strategy helps to homogenize heat accumulation and thermal stress distribution, thereby significantly reducing warping and deformation of large or complex thin-walled structures. While spiral scanning performs excellently in terms of macroscopic deformation, it is inferior to other optimized strategies in terms of surface roughness or microstructure uniformity in certain directions. Although current research attempts to optimize forming effects using different scanning strategies, this only locally improves performance and cannot fundamentally solve the synergistic problems of temperature field inhomogeneity, porosity defects, and density improvement. Summary of the Invention

[0005] The purpose of this invention is to address the problems of high residual stress, high defect rate, insufficient density, poor formability, and insufficient high-temperature performance in the preparation of high-temperature titanium alloys by traditional laser selective melting. This invention proposes a method for additive manufacturing of high-temperature titanium alloys based on a molten tin bed, which involves laser selective melting, zone scanning, in-situ remelting, and simultaneous heat treatment. Through the synergistic technology of "zone scanning strategy + regional laser parameter control + in-situ laser remelting + simultaneous heat treatment in a molten tin bed," the method integrates forming, defect suppression, and performance enhancement, ultimately yielding high-performance titanium alloy finished parts.

[0006] The technical solution adopted in this invention is: a high-temperature resistant titanium alloy laser selective melting forming method, comprising an integrated device of a laser selective melting module, a molten tin bed module, a zoned scanning control unit, and a collaborative control module (e.g., Figure 1 Titanium alloy powder is prepared, and the titanium alloy powder and the titanium alloy substrate forming substrate of the laser selective melting module are pretreated. The collaborative control module sets the partitioning strategy and control parameters, starts the laser selective melting module, and performs layer-by-layer partitioning scanning and forming on the pretreated titanium alloy powder. Each layer first scans the contour buffer zone, and then scans the main body area. Adjacent layers are cross-scanned at 67°. After each layer is partitioned and formed, in-situ full-coverage remelting is started within ≤0.3s. After remelting, the molten tin bed module performs synchronous isothermal heat treatment and fluid support on the current forming-remelting layer through molten tin. After overall forming, temperature-controlled cooling and post-processing are performed to obtain the finished part.

[0007] The titanium alloy powder, by mass percentage, comprises: Al 2%-6%, Sn 1%-3%, Zr 0.5%-9%, Mo 0.5%-4%, Nb 0.3%-3%, W 0.1%-2%, Si 0.05%-0.4%, Ta 0.01%-0.2%, Y 0.01%-0.05%, with the balance being Ti and unavoidable impurities; the particle size of the titanium alloy powder is 15-53 μm.

[0008] The pretreatment includes vacuum drying of titanium alloy powder at 120-150℃ for 2-4 hours, annealing of the formed substrate at 800-900℃ for 1-2 hours, polishing to remove the surface oxide scale, and then immersing it in molten tin.

[0009] The partitioning strategy is to divide each forming surface into a contour buffer zone and a main body region. The contour buffer zone is an annular region offset inward by 1-3mm from the part cross-sectional contour, and the main body region is the region inside the contour buffer zone.

[0010] The control parameters include general forming, scanning parameters, in-situ remelting parameters, and molten tin control parameters. General forming includes: a spot diameter of 50-100 μm, a powder layer thickness of 20-50 μm, and an argon atmosphere in the forming chamber with an oxygen content controlled below 50 ppm. Scanning parameters include: spiral scanning in the contour buffer zone with a scanning interval of 90-110 μm; checkerboard scanning in the main area with a scanning interval of 80-100 μm; laser power of 180-250 W and scanning speed of 600-1000 mm / s in the contour buffer zone; and laser power in the main area... The parameters include: 280-350W, scanning speed 600-1000mm / s; in-situ remelting parameters include: remelting power of the contour buffer zone being 80%-90% of its forming power, remelting power of the main body area being 85%-95% of its forming power, remelting scanning speed being 120%-150% of the forming speed of the corresponding area, remelting scanning path coinciding with the forming path of the corresponding area, and path deviation ≤±5μm; the tin liquid control parameters include: tin liquid temperature 500-700℃; the tin liquid surface is kept stable by a mechanical stabilization mechanism, and the surface fluctuation amplitude is ≤±0.1mm.

[0011] The temperature control cooling includes furnace-in-the-furnace cooling with a cooling rate of 5-10℃ / min; the post-treatment includes high-pressure argon purging to remove residual powder and sandblasting at 0.4-0.6MPa pressure.

[0012] The finished part has a density ≥99.8%, a microstructure consisting of uniform and fine lamellar structure or reinforcing phase, and an average grain size ≤5μm; the finished part has a tensile strength ≥1080MPa, an elongation after fracture ≥14.5%, a residual stress ≤55MPa, and a dimensional accuracy error ≤±0.01mm.

[0013] The laser selective melting module includes a laser emitter and a forming platform. The molten tin bed module includes a molten tin tank, a heating component, and a temperature detection component. The molten tin tank is set corresponding to the forming area of ​​the forming platform. The molten tin tank moves synchronously with the forming platform. The laser emitter is used to emit laser light to achieve powder melting and in-situ remelting. The forming platform is used to support the forming component. The heating component is used to heat the molten tin. The temperature detection component is used to monitor the temperature of the molten tin. The partition scanning control unit is used to set the partitions and corresponding scanning parameters. The collaborative control unit is electrically connected to the laser emitter, the forming platform, the heating component, and the partition scanning control unit to achieve parameter collaborative control.

[0014] The molten tin bed module also includes a heat insulation layer and a heat insulation layer. The heating component is a heating element, and the temperature detection component is a temperature sensor. The molten tin bath is made of high-temperature resistant ceramic material. The heating element is embedded in the side wall of the molten tin bath. The heat insulation layer is wrapped around the outside of the molten tin bath, and the heat insulation layer is set at the bottom of the molten tin bath. The temperature sensor is a platinum-rhodium thermocouple. The temperature sensor collects the temperature of the molten tin in real time and feeds it back to the collaborative control module. The molten tin is industrial pure tin with a purity of ≥99.9%, and is degassed under vacuum at 200-250℃ for 1-2 hours before use.

[0015] The beneficial effects of this invention are as follows: This invention combines the partitioning strategy of "contour buffer spiral scanning + main area checkerboard scanning", regional laser parameter control and in-situ laser remelting technology, and the high-temperature titanium alloy SLM manufacturing method that simultaneously realizes forming and heat treatment. It can accurately optimize the forming quality of different areas, significantly improve the density and comprehensive performance of components without significantly increasing the forming time, and has important engineering application value.

[0016] This invention innovatively employs a composite partitioning strategy of "67° cross-layer scanning + contour buffer spiral scanning + main area checkerboard scanning," combining regional laser parameter control with in-situ remelting technology, and synergistically heat-treating the molten tin bed to achieve integrated manufacturing from forming to finished product. The component density is increased to ≥99.8%, more than 2% higher than traditional SLM technology, effectively solving defects such as porosity and incomplete fusion. The 67° cross-layer scanning optimizes interlayer stress distribution, while the low-power, low-speed forming in the contour buffer ensures contour accuracy (dimensional error ≤ ±0.01mm). Appropriate power, low-speed forming in the main area generates a uniform and refined microstructure. Combined with the high thermal conductivity and high heat capacity of molten tin, residual stress is ≤55MPa, significantly suppressing deformation defects such as cracks and warping. In-situ remelting specifically fills defects in different areas, further improving the overall consistency of the component.

[0017] The combination of the fluid buoyancy support characteristics of molten tin and the forming stability of partitioned scanning can significantly reduce the number of mechanical supports for complex thin-walled structures (more than 75% less than traditional processes), reduce material consumption, avoid secondary deformation caused by support removal, and improve the surface quality and dimensional accuracy of finished parts.

[0018] The optimization of titanium alloy composition (including multi-element alloying of Al, Sn, Zr, Mo, Nb, W, Si, Ta, and Y) and the synergy of regional process parameters result in a uniform and fine lamellar structure or reinforcing phase in the finished part. At the same time, the addition of trace amounts of rare earth elements and appropriate amounts of Ta achieves a balance between performance and processability. The average grain size is ≤5μm, the tensile strength is ≥1080MPa, and the elongation after fracture is ≥14.5%. It has excellent strength and plasticity matching and is suitable for the needs of high-end fields such as aerospace.

[0019] Industrial pure tin has stable chemical properties and does not react chemically with titanium alloys, thus avoiding contamination of finished parts. The molten tin can be reused. In-situ remelting requires no additional materials, making the process green and environmentally friendly. The integrated process eliminates the need for subsequent separate heat treatment, shortening the production cycle by more than 35%, making it suitable for industrial mass production of high-performance titanium alloy finished parts. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the device and molten tin bed module used in this invention; Figure 2 This is an organizational diagram of the finished product according to Embodiment 1 of the present invention; Figure 3 This is a stress-strain diagram of Embodiment 1 of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to specific embodiments.

[0022] Example 1 (Finished Titanium Alloy Part) The titanium alloy powder composition by mass percentage is: Al: 4%, Sn: 2%, Zr: 1%, Mo: 2%, Nb: 1%, W: 0.5%, Si: 0.1%, Ta: 0.5%, Y: 0.01%, with the balance being Ti and unavoidable impurities. The powder particle size is 30-45μm. The powder is vacuum dried at 135℃ for 3h.

[0023] The forming substrate is a TC4 titanium alloy substrate, which is annealed at 850℃ for 1.5h, and after the surface oxide scale is removed by polishing, it is mounted on the forming platform and immersed in molten tin.

[0024] The integrated device is a device that integrates a laser selective melting module, a molten tin bed module, a zoned scanning control unit, and a collaborative control module.

[0025] The laser selective melting module includes a laser emitter and a forming platform. The molten tin bed module includes a molten tin tank, a heating component, and a temperature detection component. The molten tin tank is set corresponding to the forming area of ​​the forming platform. The molten tin tank moves synchronously with the forming platform. The laser emitter is used to emit laser light to achieve powder melting and in-situ remelting. The forming platform is used to support the forming component. The heating component is used to heat the molten tin. The temperature detection component is used to monitor the temperature of the molten tin. The partition scanning control unit is used to set the partitions and corresponding scanning parameters. The collaborative control unit is electrically connected to the laser emitter, the forming platform, the heating component, and the partition scanning control unit to achieve parameter collaborative control.

[0026] Molten tin bed is a core component of a novel additive manufacturing technology that uses liquid tin as a carrier medium. It was first proposed and verified by Professor Lin Feng's team from the Department of Mechanical Engineering at Tsinghua University. This technology, known as Liquid Metal Assisted Powder Bed Laser Additive Manufacturing (LMA-LPBF), achieves dynamic thermal field control of the "local liquid surface-solidification interface" by stably floating metal powder on the surface of molten tin under laser action, significantly optimizing thermal management and microstructure evolution during the printing process.

[0027] In one embodiment, the molten tin bed module further includes a heat insulation layer and a heat insulation layer. The heating component is a heating element, the temperature detection component is a temperature sensor, the molten tin bath is made of high-temperature resistant ceramic material, the heating element is embedded in the side wall of the molten tin bath, the heat insulation layer is wrapped around the outside of the molten tin bath, and the heat insulation layer is set at the bottom of the molten tin bath. The temperature sensor is a platinum-rhodium thermocouple, and the temperature sensor collects the temperature of the molten tin in real time and feeds it back to the collaborative control module.

[0028] Add 99.9% pure industrial tin to the molten tin bath, degas under vacuum at 225°C for 1.5 hours, and then heat to 600°C and hold. Connect all components (including temperature sensors, etc.) through a collaborative control module and set the temperature feedback accuracy to ±5°C.

[0029] Setting parameters: ① Zoning strategy: Based on the cross-sectional profile of the titanium alloy component, each forming surface is divided into a profile buffer zone and a main body region. The profile buffer zone is a ring-shaped area offset 2mm inward from the cross-sectional profile to ensure the accuracy of the component profile and surface quality; the main body region is the remaining area inside the profile buffer zone to ensure the internal density and uniformity of the component structure; ② General parameters: Spot diameter 75μm, powder layer thickness 35μm, argon atmosphere in the forming chamber, oxygen content 30ppm (argon gas keeps the oxygen content below 50ppm to prevent titanium alloy oxidation), 67° cross-scanning between adjacent layers to reduce interlayer stress accumulation; ③ Scanning parameters: Spiral scanning in the profile buffer zone, scanning interval 100μm; checkerboard scanning in the main body region, scanning interval 90μm to avoid local heat concentration; ④ Regional laser parameters: Profile buffer zone... The scanning speed is 800 mm / s (low scanning speed) in the contour area, reducing deformation and burrs caused by excessive heat input in the contour area; the scanning speed is 800 mm / s (scanning speed) in the main body area, ensuring sufficient powder melting and uniform structure, generating a microstructure that meets the mechanical performance requirements of the component; ⑤ Remelting parameters: Remelting is started 0.2s after forming. The remelting power in the contour buffer area is 198W (90% of forming power) and the speed is 960 mm / s (120% of forming speed). The remelting power in the main body area is 270W (90% of forming power) and the speed is 960 mm / s (120% of forming speed). The remelting path coincides with the forming path (the remelting scanning path coincides with the scanning path of the corresponding area of ​​the layer, with a deviation ≤ ±5μm). The secondary melting fills the pores and microcracks generated during the forming process, improving the overall density. After the equipment is started, the formed layer is immersed in molten tin after each layer is formed and remelted, and the liquid level fluctuation is controlled within ±0.08mm.

[0030] After the equipment is started, the laser melts the powder layer by layer according to the preset partitions and scanning paths: first, it scans the contour buffer zone (spiral scanning + low power and low speed), and then scans the main area (checkerboard scanning + appropriate power and appropriate speed). Adjacent layers maintain a 67° cross scanning direction, making the generated martensite distribution more dispersed and the size more refined. After each layer is scanned and formed, the collaborative control module immediately triggers the in-situ remelting program. The laser performs full-coverage remelting of the layer according to the regional remelting parameters, using the fluidity of the secondary molten pool to fill the pores and eliminate incomplete fusion defects, further refining the surface martensite. Within ≤0.2s after remelting, the molten tin comes into contact with the formed-remelted layer through fluid encapsulation. The high thermal conductivity of the molten tin (60W / m・K) achieves uniform isothermal heat treatment, refining the grains and releasing the thermal stress generated during forming and remelting. At the same time, it causes the metastable martensite to decompose, ultimately forming fine lamellar layers. The fluid characteristics of the molten tin provide buoyancy support, reducing the need for traditional mechanical support, which is especially suitable for complex thin-walled structures. The molten tin surface fluctuation is maintained at ≤±0.1mm by a mechanical stabilization mechanism to avoid affecting the forming and remelting accuracy. The next layer of powder is then applied, and the process of zonal scanning, parameter-based forming, in-situ remelting, and simultaneous heat treatment is repeated until the entire component is formed.

[0031] After forming, the component is cooled to room temperature in the furnace at 8℃ / min, residual powder is purged with high-pressure argon gas, and sandblasted at 0.5MPa pressure to obtain the finished titanium alloy part. Testing shows that the finished part has a density of 99.9%, an average grain size of 4.8μm, a residual stress of 40MPa, a tensile strength of 1100MPa, an elongation after fracture of 15.2%, and a dimensional accuracy error of ±0.008mm.

[0032] The tissue map prepared by this method ( Figure 2 ) and stress-strain diagrams ( Figure 3 As shown in the attached figure.

[0033] Example 2 (Finished Titanium Alloy Parts) The titanium alloy powder composition, by mass percentage, is: Al: 3%, Sn: 1.5%, Zr: 0.8%, Mo: 1.5%, Nb: 0.8%, W: 0.3%, Si: 0.08%, Ta: 0.8%, Y: 0.02%, with the balance being Ti and unavoidable impurities. The powder particle size is 15-35 μm. The powder was vacuum dried at 120℃ for 4 hours. A Ti-6Al-4V substrate was used for forming the powder, which was annealed at 800℃ for 2 hours, and then the surface oxide scale was removed before mounting.

[0034] The integrated device is the same as in Example 1. 99.9% pure industrial tin is added to the tin bath, and the tin is degassed under vacuum at 200°C for 2 hours, followed by heating to 650°C and holding at that temperature.

[0035] Setting parameters: ① Zoning strategy: The contour buffer is offset inward by 1.5mm from the cross-sectional contour; ② General parameters: Spot diameter 80μm, powder layer thickness 30μm, argon atmosphere in the forming chamber, oxygen content 25ppm, 67° cross-scanning between adjacent layers; ③ Scanning parameters: Spiral scanning of the contour buffer, scanning interval 95μm; checkerboard scanning of the main area (grid size 5mm×5mm), scanning interval 85μm; ④ Regional laser parameters: Contour buffer power 200W, speed 700mm / s; Main area power 290W, speed 700mm / s; ⑤ Remelting parameters: Remelting is started 0.15s after forming, contour buffer remelting power 170W (85% forming power), speed 1050mm / s (150% forming speed), main area remelting power 256W (88% forming power), speed 1050mm / s (150% forming speed), remelting path coincides with forming path. Start the equipment. After each layer is formed and remelted, immerse the formed layer in molten tin, and control the molten tin level fluctuation within ±0.05mm.

[0036] After forming, the component was cooled to room temperature in the furnace at 6℃ / min, residual powder was purged with high-pressure argon gas, and sandblasted at 0.45MPa pressure to obtain the finished titanium alloy part. Test results showed that the finished part had a density of 99.8%, an average grain size of 4.2μm, a residual stress of 38MPa, a tensile strength of 1090MPa, an elongation after fracture of 14.8%, and a dimensional accuracy error of ±0.009mm.

[0037] Unless otherwise specified, the content of this embodiment is the same as that of Embodiment 1.

[0038] Example 3 (Complex Thin-Walled Titanium Alloy Finished Part) The titanium alloy powder composition by mass percentage is: Al: 5%, Sn: 2.5%, Zr: 1.5%, Mo: 3%, Nb: 2%, W: 1%, Si: 0.2%, Ta: 1.2%, Y: 0.01%, with the balance being Ti and unavoidable impurities. The powder particle size is 45-53 μm. The powder is vacuum dried at 150℃ for 2 hours. A Ti-6Al-4V substrate is used for forming the substrate, which is annealed at 900℃ for 1 hour, and the surface oxide scale is removed by polishing before mounting.

[0039] The integrated device is the same as in Example 1. 99.9% pure industrial tin is added to the tin bath, vacuum degassing is performed at 250°C for 1 hour, and then the temperature is raised to 550°C and maintained.

[0040] Setting parameters: ① Zoning strategy: The contour buffer is offset inward by 3mm from the cross-sectional contour; ② General parameters: Spot diameter 90μm, powder layer thickness 40μm, argon atmosphere in the forming chamber, oxygen content 20ppm, 67° cross scanning between adjacent layers; ③ Scanning parameters: Spiral scanning in the contour buffer, scanning interval 105μm; checkerboard scanning in the main area, scanning interval 95μm; ④ Regional laser parameters: Power 240W and speed 900mm / s in the contour buffer; Power 340W and speed 900mm / s in the main area; ⑤ Remelting parameters: Remelting is started 0.3s after forming, with a remelting power of 216W (90% forming power) and a speed of 1350mm / s (150% forming speed) in the contour buffer, and a remelting power of 317W (93% forming power) and a speed of 1350mm / s (150% forming speed) in the main area, with the remelting path coinciding with the forming path. Start the equipment. After each layer is formed and remelted, immerse the formed layer in molten tin, and control the molten tin level fluctuation within ±0.1mm.

[0041] After forming, the component is cooled to room temperature in the furnace at 10℃ / min, residual powder is purged with high-pressure argon gas, and sandblasting is performed at 0.6MPa pressure to obtain a complex thin-walled titanium alloy finished part. Test results show that the finished part has a density of 99.7%, an average grain size of 3.8μm, a residual stress of 48MPa, a tensile strength of 1085MPa, an elongation after fracture of 14.6%, and uses 80% less support structure compared to traditional processes, with a dimensional accuracy error ≤±0.01mm.

[0042] Unless otherwise specified, the content of this embodiment is the same as that of Embodiment 1.

[0043] Comparative Example 1 Titanium alloy components (with the same composition as in Example 1) were prepared using the conventional laser selective melting method. The pretreatment and general parameters were the same as in Example 1. A single cross-scan strategy (without partitioning or buffering) was adopted, and there was no in-situ remelting. After forming, the components were annealed at 600°C for 2 hours. The post-treatment was the same as in Example 1.

[0044] The test results showed that the component had a density of 96.6%, an average grain size of 27 μm, a residual stress of 200 MPa, a tensile strength of 790 MPa, an elongation after fracture of 7.2%, and a dimensional accuracy error of ±0.06 mm. The amount of support structure used was 3.4 times that of Example 1 of the present invention. All performance and forming quality were significantly lower than those of the titanium alloy finished product prepared by the present invention.

[0045] Comparative Example 2 Titanium alloy components (with the same composition as in Example 2) were prepared using the conventional laser selective melting method. The pretreatment and general parameters were the same as in Example 2. A checkerboard patterning strategy (without buffer) was adopted, and there was no in-situ remelting. After forming, the components were annealed at 600°C for 2 hours. The post-treatment was the same as in Example 2.

[0046] The test results showed that the component had a density of 97.6%, an average grain size of 24 μm, a residual stress of 175 MPa, a tensile strength of 830 MPa, an elongation after fracture of 8.2%, and a dimensional accuracy error of ±0.05 mm. The amount of support structure used was 3.2 times that of Example 1 of the present invention. All performance and forming quality were significantly lower than those of the titanium alloy finished product prepared by the present invention.

[0047] Comparative Example 3 The same titanium alloy powder and pretreatment with the same composition as in Example 1 were used. Traditional powder bed support was used. The laser parameters and scanning strategy were the same as in Example 1. No in-situ remelting was performed. After forming, traditional solution aging treatment was used (solution at 800℃ for 1 hour + aging at 500℃ for 4 hours). The post-treatment was the same as in Example 1.

[0048] The test results showed that the component had a density of 98.4%, an average grain size of 20 μm, a residual stress of 145 MPa, a tensile strength of 960 MPa, an elongation after fracture of 9.8%, and a dimensional accuracy error of ±0.04 mm. The amount of support structure used was three times that of Example 1 of the present invention. All performance and forming quality were significantly lower than those of the titanium alloy finished parts prepared by the present invention.

[0049] Comparative Example 4 The same titanium alloy powder and pretreatment with the same composition as in Example 1 were used. Traditional powder bed support was used. The laser parameters were the same as in Example 1. A single cross-scan strategy (no partition, no buffer) was adopted. In-situ remelting was used. The remelting parameters were the same as in Example 1. After forming, traditional solution aging treatment was used (solution at 800℃ for 1 h + aging at 500℃ for 4 h). The post-treatment was the same as in Example 1.

[0050] The test results showed that the component had a density of 98.1%, an average grain size of 22 μm, a residual stress of 158 MPa, a tensile strength of 950 MPa, an elongation after fracture of 9.2%, and a dimensional accuracy error of ±0.04 mm. The amount of support structure used was 3.1 times that of Example 1 of the present invention. All performance and forming quality were significantly lower than those of the titanium alloy finished product prepared by the present invention.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can be modified and varied in many ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for forming high-temperature resistant titanium alloy by selective laser melting, characterized in that: An integrated device comprising a laser selective melting module, a molten tin bed module, a partitioned scanning control unit, and a collaborative control module is constructed. Titanium alloy powder is prepared, and the titanium alloy powder and the titanium alloy substrate formed by the laser selective melting module are pretreated. The collaborative control module sets the partitioning strategy and control parameters, starts the laser selective melting module, and performs layer-by-layer partitioned scanning and forming on the pretreated titanium alloy powder. Each layer first scans the contour buffer zone, and then scans the main body area. Adjacent layers are cross-scanned at 67°. After each layer is partitioned and formed, in-situ full-coverage remelting is initiated within ≤0.3s. After remelting, the molten tin bed module performs synchronous isothermal heat treatment and fluid support on the current formed-remelted layer through molten tin. After overall forming, temperature-controlled cooling and post-processing are performed to obtain the finished part.

2. The method according to claim 1, characterized in that: The titanium alloy powder, by mass percentage, comprises: Al 2%-6%, Sn 1%-3%, Zr 0.5%-9%, Mo 0.5%-4%, Nb 0.3%-3%, W 0.1%-2%, Si 0.05%-0.4%, Ta 0.01%-0.2%, Y 0.01%-0.05%, with the balance being Ti and unavoidable impurities; the particle size of the titanium alloy powder is 15-53 μm.

3. The method according to claim 1, characterized in that: The pretreatment includes vacuum drying of titanium alloy powder at 120-150℃ for 2-4 hours, annealing of the formed substrate at 800-900℃ for 1-2 hours, polishing to remove the surface oxide scale, and then immersing it in molten tin.

4. The method according to claim 1, characterized in that: The partitioning strategy is to divide each forming surface into a contour buffer zone and a main body region. The contour buffer zone is an annular region offset inward by 1-3mm from the part cross-sectional contour, and the main body region is the region inside the contour buffer zone.

5. The method according to claim 4, characterized in that: The control parameters include general forming, scanning parameters, in-situ remelting parameters, and molten tin control parameters. General forming includes: a spot diameter of 50-100 μm, a powder layer thickness of 20-50 μm, and an argon atmosphere in the forming chamber with an oxygen content controlled below 50 ppm. Scanning parameters include: spiral scanning in the contour buffer zone with a scanning interval of 90-110 μm; checkerboard scanning in the main area with a scanning interval of 80-100 μm; laser power of 180-250 W and scanning speed of 600-1000 mm / s in the contour buffer zone; and laser power in the main area... The parameters include: 280-350W, scanning speed 600-1000mm / s; in-situ remelting parameters include: remelting power of the contour buffer zone being 80%-90% of its forming power, remelting power of the main body area being 85%-95% of its forming power, remelting scanning speed being 120%-150% of the forming speed of the corresponding area, remelting scanning path coinciding with the forming path of the corresponding area, and path deviation ≤±5μm; the tin liquid control parameters include: tin liquid temperature 500-700℃; the tin liquid surface is kept stable by a mechanical stabilization mechanism, and the surface fluctuation amplitude is ≤±0.1mm.

6. The method according to claim 1, characterized in that: The temperature control cooling includes furnace-in-the-furnace cooling with a cooling rate of 5-10℃ / min; the post-treatment includes high-pressure argon purging to remove residual powder and sandblasting at 0.4-0.6MPa pressure.

7. The method according to claim 1, characterized in that: The finished part has a density ≥99.8%, a microstructure consisting of uniform and fine lamellar structure or reinforcing phase, and an average grain size ≤5μm; the finished part has a tensile strength ≥1080MPa, an elongation after fracture ≥14.5%, a residual stress ≤55MPa, and a dimensional accuracy error ≤±0.01mm.

8. The method according to claim 1, characterized in that: The laser selective melting module includes a laser emitter and a forming platform. The molten tin bed module includes a molten tin tank, a heating component, and a temperature detection component. The molten tin tank is set corresponding to the forming area of ​​the forming platform. The molten tin tank moves synchronously with the forming platform. The laser emitter is used to emit laser light to achieve powder melting and in-situ remelting. The forming platform is used to support the forming component. The heating component is used to heat the molten tin. The temperature detection component is used to monitor the temperature of the molten tin. The partition scanning control unit is used to set the partitions and corresponding scanning parameters. The collaborative control unit is electrically connected to the laser emitter, the forming platform, the heating component, and the partition scanning control unit to achieve parameter collaborative control.

9. The method according to claim 8, characterized in that: The molten tin bed module also includes a heat insulation layer and a heat insulation layer. The heating component is a heating element, and the temperature detection component is a temperature sensor. The molten tin bath is made of high-temperature resistant ceramic material. The heating element is embedded in the side wall of the molten tin bath. The heat insulation layer is wrapped around the outside of the molten tin bath, and the heat insulation layer is set at the bottom of the molten tin bath. The temperature sensor is a platinum-rhodium thermocouple. The temperature sensor collects the temperature of the molten tin in real time and feeds it back to the collaborative control module. The molten tin is industrial pure tin with a purity of ≥99.9%, and is degassed under vacuum at 200-250℃ for 1-2 hours before use.

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