A method for additive manufacturing of in-situ titanium matrix composite based on laser remelting assistance

Abstract

The application belongs to the technical field of titanium-based composite materials, and particularly relates to an in-situ self-grown titanium-based composite material additive manufacturing method based on laser remelting assistance, which comprises the following steps: S1. composite powder preparation: titanium alloy matrix powder is mixed with precursor powder to obtain a composite powder; S2. printing and remelting forming: printing: under the protection of an inert atmosphere, a first set of laser parameters is used to scan and melt the current powder layer to form a current fused layer; remelting: after the printing and scanning of the current fused layer are completed, a second set of laser parameters is used to perform at least one remelting scanning on the current fused layer; S3. repeating step S2, layer by layer accumulation, until the forming of the entire three-dimensional entity is completed, and the application utilizes laser remelting assistance to control the molten pool behavior and promote the complete reaction of the precursor, so that the density and mechanical properties of the material can be improved.

Description

Technical Field

[0001] This invention belongs to the field of titanium-based composite material technology, specifically relating to an in-situ self-generated titanium-based composite material additive manufacturing method based on laser remelting assistance. Background Technology

[0002] Titanium matrix composites (TMCs) have significant application value in aerospace, high-end equipment, and other fields due to their excellent specific strength, high-temperature resistance, and corrosion resistance. In-situ self-generation methods can generate uniformly distributed, interfacially bonded reinforcing phases within the matrix through chemical reactions, providing an effective approach for preparing high-performance titanium matrix composites. Laser powder bed fusion (L-PBF), as a precision additive manufacturing technology, offers the possibility of direct near-net-shape forming of complex titanium matrix composite parts; its layer-by-layer melting and rapid solidification characteristics help refine grains and suppress the coarsening of the reinforcing phase.

[0003] However, in the preparation of TMCs using refractory compounds (such as Mo2C, CrB2, LaB6, YB6, B4C, TiB2, etc.) as precursors via L-PBF, the high melting point of the precursors and the harsh reaction kinetics with the titanium alloy matrix mean that, under conventional process parameters, insufficient energy input or a short molten pool duration can easily lead to incomplete melting and reaction of the precursors, resulting in unreacted particles remaining in the matrix. These residual precursor particles disrupt the continuity of the matrix, becoming stress concentration points and potential crack initiation sites, severely degrading the material's density, fatigue performance, toughness, and overall reliability. Although adjusting parameters such as printing laser power and scanning speed can improve the reaction degree to some extent, this often comes at the expense of other factors. Increasing the energy input to promote the reaction can easily cause molten pool overheating, spattering, and spheroidization, leading to a decrease in density.

[0004] Therefore, ensuring the complete reaction of the precursor without compromising the molding quality is a key technical bottleneck in the preparation of high-performance TMCs by L-PBF. Summary of the Invention

[0005] To address the problems in the prior art, this invention provides an additive manufacturing method for in-situ self-generated titanium-based composite materials based on laser remelting assistance. This method is used for laser powder bed melting to form in-situ self-generated titanium-based composite materials. It utilizes laser remelting assistance to regulate the behavior of the molten pool and promote the complete reaction of the precursor, thereby improving the density and mechanical properties of the material.

[0006] The technical problem solved by this invention is achieved by the following technical solution:

[0007] The present invention aims to provide an additive manufacturing method for in-situ self-generated titanium-based composite materials based on laser remelting assistance, comprising the following steps:

[0008] S1. Composite Powder Preparation: Mix titanium alloy matrix powder with precursor powder to obtain composite powder; S2. Printing and Remelting: Printing: Under inert atmosphere protection, use the first set of laser parameters to scan and melt the current powder layer to form the current fused layer; Remelting: After completing the printing scan of the current fused layer, use the second set of laser parameters to perform at least one remelting scan of the current fused layer; S3. Repeat step S2, layer by layer, until the entire three-dimensional solid is formed.

[0009] Furthermore, the first set of laser parameters includes printing laser power and printing scan spacing, and the second set of laser parameters includes remelting laser power and remelting scan spacing. The remelting laser power is greater than the printing laser power, and the remelting scan spacing is greater than the printing scan spacing.

[0010] Furthermore, the ratio of remelting laser power to printing laser power is 1.1-1.75:1.

[0011] Furthermore, the ratio of the remelting scan spacing to the printing scan spacing is 1.1-2.5:1.

[0012] Furthermore, the precursor powder has a mass fraction of 2.3 wt.%–4.6 wt.%.

[0013] Furthermore, when the mass fraction of the precursor powder is less than 3 wt.%, the remelting scan is performed once; when the mass fraction of the precursor powder is greater than or equal to 3 wt.%, at least two remelting scans with the same second set of laser parameters are performed.

[0014] Furthermore, the precursor powder is Mo2C.

[0015] This invention provides an in-situ self-generated titanium-based composite additive manufacturing method based on laser remelting assistance. After each layer is conventionally printed, a laser remelting scan with specific parameters is performed immediately. By creatively utilizing the synergistic effect of "increasing power to extend the high-temperature dwell time" and "expanding the scanning spacing to disperse heat input and stabilize the molten pool," precursor residues are completely eliminated without introducing new defects, resulting in titanium-based composite components with uniform microstructure and excellent performance.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0017] 1. Multiple heat inputs promote complete reaction: This invention employs multiple energy input modes of "printing + remelting" and "printing + double melting". The printing step completes the basic melting and shaping of the powder; the subsequent remelting step reheats the still high-temperature molten layer, significantly extending the total residence time of the molten pool at the high temperature required for the reaction. This provides more sufficient thermodynamic conditions for the complete melting of precursor particles and their in-situ chemical reaction with the titanium matrix (such as Mo2C + Ti → TiC + Mo).

[0018] 2. Synergistic Shape Control of "High Power + Large Spacing": Increasing laser power during remelting aims to raise the molten pool temperature and residence time, enhance Marangoni convection within the molten pool, and promote compositional homogenization and reaction kinetics. However, simply increasing power can easily lead to overheating and instability of the molten pool. This invention innovatively expands the remelting scanning spacing simultaneously. This reduces the thermal superposition effect between adjacent remelting channels, effectively disperses heat input, and avoids excessive local energy accumulation. As a result, while inputting higher total energy to promote the reaction, a stable and appropriate molten pool size is maintained, preventing defects such as keyholes, spatter, and spheroidization, and ensuring the geometric accuracy and internal density of the formed part. This synergistic mechanism is as follows: Figure 2 As shown.

[0019] 3. High versatility and compatibility: The core process parameters of this method (power enhancement ratio, spacing expansion factor) have a wide optimization window, enabling it to adapt to composite material systems with different precursor types and addition amounts (e.g., from 2.3 wt.% to 4.6 wt.%). The entire process requires no hardware modification to existing commercial L-PBF equipment; it can be implemented simply by editing the scanning strategy in the software, facilitating industrial-scale promotion.

[0020] 4. Significantly Improved Material Properties: By completely eliminating unreacted precursor residues (residual area fraction can be reduced to below 1%) and promoting in-situ generation of fine, dispersed reinforcing phases (such as TiC), the method of this invention can significantly improve the mechanical properties of materials, such as density, hardness, and tensile strength. Simultaneously, due to the reduction of micro-defects, the ductility and toughness of the material are also improved or effectively maintained, achieving a good balance between strength and toughness.

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the specification. Furthermore, in order to make the above contents, objectives, features and advantages of the present invention more obvious and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the printing and remelting scanning path used in an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram illustrating the mechanism by which the remelting process (high power + large spacing) of the present invention reduces precursor residue, promotes reaction, and stabilizes the molten pool.

[0024] Figure 3 This is a scanning electron microscope (SEM) image of the Ti-6Al-4V / Mo2C composite powder after ball milling and mixing in Example 1.

[0025] Figure 4 The image shows a comparison of backscattered electron (BSE) images and a statistical chart of the precursor residual area of ​​the sample without remelting and the sample after remelting treatment according to the present invention, under a low Mo2C addition amount (2.3 wt.%) in Example 1. Figure 5 This is a statistical comparison chart of the room temperature tensile mechanical properties (tensile strength and elongation after fracture) of the non-remelted sample and the remelted sample in Example 1.

[0026] Figure 6 This is a schematic diagram of the double remelting process strategy used in Example 2 for medium to high precursor addition levels. Figure 7 In Example 2, when the Mo2C addition amount was 3.45 wt.%, the samples without remelting and double-remelted samples were compared.

[0027] BSE image comparison and precursor residue statistics.

[0028] Figure 8 This is a comparison chart of the mechanical properties of the non-remelted sample and the double-remelted sample in Example 2.

[0029] Figure 9 In Example 3, when the Mo2C addition amount was 4.6 wt.%, the BSE images of the unremelted sample and the double-remelted sample were compared, and the precursor residue statistics were plotted. Figure 10 This is a comparison chart of the mechanical properties of the non-remelted sample and the double-remelted sample in Example 3. Detailed Implementation

[0030] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0031] In addition, unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be obtained by purchasing them from the market or prepared by existing methods.

[0032] A laser remelting-assisted in-situ self-generated titanium-based composite additive manufacturing method includes the following steps: S1. Composite powder preparation: Titanium alloy matrix powder and precursor powder are mechanically mixed according to a designed ratio to obtain…

[0033] S2. Layer-by-layer printing and remelting: S2.1 Under an inert atmosphere, the current powder layer is scanned and melted using the first set of laser parameters to form the current...

[0034] S2.2 After completing the printing and scanning of the current fused layer, immediately use the second set of laser parameters to scan the current fused layer.

[0035] The solidified layer undergoes at least one remelting scan; among which, the remelting laser power (P) in the second set of laser parameters remelt The laser power (P) in the first set of laser parameters is greater than the printing laser power in the first set. print ), and the remelting scan spacing (h) in the second set of laser parameters remelt The print scanning spacing (h) in the first set of laser parameters is greater than that in the first set of laser parameters. print S3. Repeat step S2, stacking layer by layer until the entire three-dimensional solid is formed; S4. Perform necessary post-processing and performance characterization on the obtained formed part.

[0036] The optimized remelting scan spacing (h) is adopted. remelt ) and printing scan spacing (h) print The ratio range of ) increases from 1:1 to 2.5:1. For example, when the printing scan pitch is 0.08 mm, the remelting scan pitch is correspondingly 0.08 mm to 0.20 mm. Correspondingly, the remelting laser power (P) remelt ) compared to printing laser power (P) print The W value was increased by 150%, from 280 W to 490 W. Among common refractory metal precursors such as Mo2C, CrB2, LaB6, YB6, B4C, and TiB2, Mo2C, with its relatively high melting point, was selected. When the precursor mass fraction exceeded 3%, the same remelting scan with identical parameters was performed twice or more on the same fused layer in step S2.2.

[0037] Example 1: Preparation of titanium-based composite material with low addition amount of Mo2C (2.3 wt.%).

[0038] This embodiment aims to verify the effectiveness of the method of the present invention at low precursor contents. S1. Preparation of composite powder:

[0039] Atomized Ti-6Al-4V powder (particle size range 15-53 μm) was selected as the matrix, and Mo2C powder (particle size 3-5 μm, purity 99.5%) was selected as the precursor. Mo2C was precisely weighed at a mass fraction of 2.3 wt.% and placed in a vacuum planetary ball mill. Under argon protection, the mixture was ball-milled at 200 rpm for 24 hours to ensure uniform adhesion of the precursor particles to the matrix powder surface. The morphology of the mixed powder is shown below. Figure 3 As shown. S2. Printing and Remelting: This invention uses the FF-M140C laser powder bed melting equipment manufactured by Jiangsu Meiguang Technology Co., Ltd., equipped with a 500 W fiber laser with a spot size of 100 μm. The forming chamber is filled with high-purity argon gas, and the oxygen content is controlled below 100 ppm. The formed cylindrical sample has a size of Φ6 mm × 6 mm.

[0040] First set of laser parameters (i.e., printing parameters): Printing laser power P print = 280 W, printing and scanning speed V print = 800 mm / s, printing scan spacing H hatch = 0.08 mm, layer thickness t = 0.03 mm.

[0041] The second set of laser parameters (i.e., remelting parameters): Remelting laser power P remelt = 490 W (for P) print 1.75 times that of), remelting scan rate V remelt =910 mm / s, remelting scan interval H remelt = 0.20 mm (for H) hatch (2.5 times that of the previous method). See the scan path diagram. Figure 1 The process was strictly performed in a cyclical manner, following the sequence of "powder spreading → printing one layer → immediately remelting the layer," until the sample was formed. Comparative sample preparation: As a control, a set of "non-remelting" comparative samples were prepared under identical printing parameters without the remelting step. Microstructure and property characterization:

[0042] 1. Microstructure Analysis: The sample was axially sectioned and prepared using standard metallographic methods (grinding and polishing). The cross-section was observed using a scanning electron microscope (SEM) in backscattered electron (BSE) mode. Image analysis software (such as ImageJ) was used to quantitatively analyze the bright white unreacted Mo2C particles in the BSE images. The results are as follows: Figure 4 As shown, the residual area fraction of precursors in the unremelted sample was as high as 24.3%, while the residual area fraction of the sample treated by the method of the present invention dropped sharply to 0.5%, which directly demonstrates the excellent effect of the present invention in eliminating precursor residues.

[0043] 2. Mechanical property testing: Standard tensile specimens were prepared according to national standards and subjected to quasi-static tensile tests at room temperature. Results are as follows: Figure 5 As shown, compared with the sample without remelting, the sample prepared by the method of the present invention showed an increase in tensile strength from approximately 986±219 MPa to approximately 1306±42 MPa, an increase of approximately 32%; at the same time, the elongation after fracture increased from approximately 1.4±0.6% to approximately 5.7±2.0%, an increase of approximately 310%. This indicates that the present invention significantly improves the strength while greatly enhancing the plasticity of the material.

[0044] Example 2: Preparation by double remelting with moderate addition of Mo2C (3.45 wt.%)

[0045] This embodiment aims to verify the adaptability of the method of the present invention to higher precursor contents and to demonstrate the effect of the double remelting strategy. S1. Composite powder preparation: The steps are the same as in Example 1, except that the amount of Mo2C added is adjusted to 3.45 wt.%. S2. Printing and remelting: The printing parameters are exactly the same as in Example 1. The remelting strategy is adjusted to "double remelting": after each layer is printed, the same remelting parameters (P) as in Example 1 are used. remelt =490 W, H remelt =0.20 mm, V remelt =910mm / s), two consecutive remelting scans were performed. The scan path for the second remelting was the same as the first, but rotated 90° based on the first remelting to further homogenize the thermal field, as shown in the schematic diagram. Figure 6 As shown. Comparative sample preparation: no remelting, parameters same as Example 1. Microstructure and property characterization:

[0046] 1. Microstructural analysis: BSE observation and statistical results are as follows Figure 7 As shown, after two remeltings, the precursor residue was further controlled. Numerous fine, in-situ generated TiC particles were uniformly dispersed throughout the microstructure, with no obvious agglomeration observed.

[0047] 2. Mechanical property testing: Results are as follows Figure 8 As shown, the tensile strength of the double-remelted sample is significantly improved compared to the unremelted sample, mainly due to the reduction of residual defects and the increase in the number of reinforcing phases. Its elongation is lower than that of the remelted sample in Example 1, but still significantly better than the original sample without any remelting treatment. This indicates that for medium to high addition levels, the method of this invention can effectively ensure strength improvement and can meet higher reaction requirements through process adjustments (such as double remelting).

[0048] Example 3: Preparation by double remelting with high addition of Mo2C (4.6 wt.%)

[0049] This embodiment aims to verify the process limits and effectiveness of the method of the present invention under high precursor content.

[0050] S1. Preparation of composite powder:

[0051] The steps are the same as in Example 1, except that the amount of Mo2C added is further increased to 4.6 wt.%.

[0052] S2. Printing and Remelting:

[0053] The process parameters and the "double remelting" strategy are exactly the same as in Example 2.

[0054] Preparation of control sample: No remelting, parameters are the same as in Example 1.

[0055] Organization and performance characterization:

[0056] 1. Microstructure analysis: Microstructure comparison, for example... Figure 9 As shown, even under harsh conditions with a precursor content as high as 4.6 wt.%, the double remelting process can still significantly reduce the residual amount of precursor, and the TiC reinforcing phase is well distributed.

[0057] 2. Mechanical property testing: Results are as follows Figure 10 As shown, the remelted sample exhibits higher tensile strength than the unremelted sample, continuing the advantage of this invention in improving material strength. Its elongation remains on the same order of magnitude as the unremelted sample, indicating that even with a high ceramic phase volume fraction, the process of this invention can still avoid a catastrophic decrease in material plasticity and maintain a basic level of toughness.

[0058] The above embodiments fully demonstrate that the laser remelting-assisted in-situ self-generated titanium-based composite additive manufacturing method provided by this invention creatively solves the core problem of precursor residue in the preparation of L-PBF materials by performing a "high-power, large-spacing" remelting scan after each layer is printed. Without excessively altering the existing production process, it achieves significant optimization of the material's microstructure and a comprehensive improvement in its overall mechanical properties, demonstrating clear innovation, significant practical value, and broad industrial application prospects.

[0059] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0060] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for in-situ self-generated titanium-based composite additive manufacturing based on laser remelting assistance, characterized in that, Includes the following steps: S1. Composite Powder Preparation: Titanium alloy matrix powder and precursor powder are mixed to obtain composite powder; S2. Printing and Remelting: Printing: Under the protection of an inert atmosphere, the current powder layer is scanned and melted using the first set of laser parameters to form the current molten layer; Remelting: After completing the printing scan of the current fused layer, use the second set of laser parameters to perform at least one remelting scan on the current fused layer; S3. Repeat step S2, stacking layer by layer until the entire three-dimensional solid is formed.

2. The method for in-situ self-generated titanium-based composite additive manufacturing based on laser remelting assistance as described in claim 1, characterized in that: The first set of laser parameters includes the printing laser power and the printing scan spacing. The second set of laser parameters includes the remelting laser power and the remelting scan spacing. The remelting laser power is greater than the printing laser power, and the remelting scan spacing is greater than the printing scan spacing.

3. The method for in-situ self-generated titanium-based composite additive manufacturing based on laser remelting assistance as described in claim 2, characterized in that: The ratio of remelting laser power to printing laser power is 1.1-1.75:

1.

4. The method for in-situ self-generated titanium-based composite additive manufacturing based on laser remelting assistance as described in claim 2, characterized in that: The ratio of remelting scan spacing to printing scan spacing is 1.1-2.5:

1.

5. The method for in-situ self-generated titanium-based composite additive manufacturing based on laser remelting assistance as described in claim 1, characterized in that: The precursor powder has a mass fraction of 2.3 wt.%–4.6 wt.%.

6. The method for in-situ self-generated titanium-based composite additive manufacturing based on laser remelting assistance as described in claim 5, characterized in that: When the mass fraction of the precursor powder is less than 3 wt.%, the remelting scan is performed once; when the mass fraction of the precursor powder is greater than or equal to 3 wt.%, at least two remelting scans with the same second set of laser parameters are performed.

7. The method for in-situ self-generated titanium-based composite additive manufacturing based on laser remelting assistance as described in claim 1, characterized in that: The precursor powder used is Mo2C.

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