TiB / TC4 titanium-based composite material based on selective laser melting and preparation method of TiB / TC4 titanium-based composite material

Abstract

The invention provides a TiB / TC4 titanium-based composite material based on selective laser melting and a preparation method of the TiB / TC4 titanium-based composite material, and relates to the technical field of metal additive manufacturing and titanium-based composites.The preparation method comprises the steps that TC4 titanium alloy powder serves as a matrix, TiB2 ceramic particles are introduced into the TC4 titanium alloy powder, and the TiB / TC4 titanium-based composite material is obtained; in the selective laser melting process, TiB2 and a titanium matrix are induced to be subjected to an in-situ reaction through the high-energy laser effect, a TiB reinforced phase is generated, and therefore the TiB / TC4 titanium-based composite material which is refined in structure, high in density and excellent in comprehensive performance is obtained. Through verification, uniform distribution of a TiB reinforcement phase in a matrix can be realized by reasonably controlling process parameters such as laser power, scanning speed and scanning spacing, and the hardness, wear resistance and corrosion resistance of the material are remarkably improved; the method is stable in process, high in controllability and suitable for integrated forming of the titanium-based component of the complex structure.

Description

Technical Field

[0001] This invention relates to the fields of metal additive manufacturing and titanium-based composite materials, and particularly to a titanium-based composite material and its preparation method that generates a TiB reinforcing phase in situ in a TC4 titanium alloy matrix by selective laser melting technology. Background Technology

[0002] TC4 titanium alloy is widely used in aerospace, high-end equipment manufacturing, and biomedical fields due to its high specific strength, good corrosion resistance, and excellent comprehensive mechanical properties. However, with the increasing complexity of service environments and the growing demand for high performance, the service stability of traditional TC4 titanium alloy under friction and wear conditions and its long-term reliability in corrosive media have gradually become insufficient. In particular, its hardness and wear resistance are difficult to meet the requirements when subjected to complex loads or harsh environments.

[0003] To improve the overall performance of TC4 titanium alloy, existing technologies typically employ methods that introduce ceramic reinforcing phases to prepare titanium-based composites. However, in conventional preparation processes or additive manufacturing processes involving the direct addition of reinforcing phases, problems such as poor interfacial bonding between the reinforcing phase and the matrix, uneven distribution of the reinforcing phase, and increased forming defects easily arise, thus affecting the stability and reliability of the material properties. Especially under rapid melting and solidification processes such as selective laser melting (SLM), the added reinforcing particles are prone to agglomeration or incomplete reaction, limiting further improvements in the composite material's performance.

[0004] Therefore, how to achieve in-situ generation of the reinforcing phase during selective laser melting and forming, and obtain a uniform and stable microstructure while ensuring the forming density, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention proposes a TiB / TC4 titanium-based composite material based on selective laser melting and its preparation method, in order to solve the problems in conventional preparation processes or additive manufacturing processes with direct external reinforcement phases, which lead to poor interfacial bonding between the reinforcement phase and the matrix, uneven distribution of the reinforcement phase, and an increase in forming defects. In particular, under rapid melting and solidification processes such as selective laser melting, the externally added reinforcement particles are prone to agglomeration or incomplete reaction.

[0006] In a first aspect, the present invention provides a method for preparing TiB / TC4 titanium-based composite materials based on selective laser melting, the method comprising: Step S1: Weigh TC4 titanium alloy powder and TiB2 powder according to the set ratio, place the two powders in a mixing tank for mechanical mixing, and obtain TiB2 / TC4 composite powder. Step S2: Pre-treat the TiB2 / TC4 composite powder and place the pre-treated powder into the powder supply system of the selective laser melting equipment; Step S3: Selective laser melting equipment is used to lay TiB2 / TC4 composite powder layer by layer and perform laser scanning to obtain TiB / TC4 composite material specimens; Step S4: Use wire cutting technology to cut the TiB / TC4 composite material specimen formed by selective laser melting from the substrate.

[0007] Furthermore, in step S1, the stirring speed in the mixing tank is 100~300 r / min, and the stirring time is 4~6h.

[0008] Further, in step S1, the mass fraction of TiB2 particles in the composite powder is 1~3 wt%; the particle size of the TC4 titanium alloy powder is 15~53 μm; and the particle size of the TiB2 powder is 3~5 μm.

[0009] Further, the chemical composition of the TC4 titanium alloy powder in step S1 includes, by mass percentage: Al 5.5~6.75wt%, V 3.5~4.5wt%, Fe≤0.3wt%, C≤0.08wt%, N≤0.05wt%, H≤0.015wt%, O≤0.8~0.15wt%, with the remainder being Ti.

[0010] Furthermore, the pretreatment of TiB2 / TC4 composite powder in step S2 involves loading the TiB2 / TC4 composite powder into an oven for drying. The temperature of the oven is 120~150℃, and the drying time is 4~6h.

[0011] Furthermore, the process parameters for selective laser melting in step S3 include: laser power 200~300 W, scanning speed 1000~1300 mm / s, and scanning spacing 0.08~0.10 mm.

[0012] Furthermore, the layer-by-layer forming step in step S3 is as follows: (1) Set the scanning rotation increment to 90° and use the circular scanning mode; (2) The laser beam scans the substrate surface to perform single sintering scanning; (3) Repeat step (2) by layering until TiB / TC4 composite material specimens are obtained.

[0013] Furthermore, the substrate is a titanium TC4 titanium alloy substrate.

[0014] Secondly, the present invention also provides a TiB / TC4 titanium matrix composite material based on selective laser melting, comprising a TC4 titanium alloy as a matrix; and a TiB reinforcing phase dispersed in the matrix, wherein the TiB reinforcing phase is formed by the reaction of TiB2 particles with the in-situ generated titanium matrix during selective laser melting, and is embedded in the matrix in a fibrous morphology to form a continuous metallurgical bonding interface with the matrix.

[0015] Compared with the prior art, the present invention has the following advantages: 1. This invention, by adding an appropriate amount of TiB2 ceramic particles to TC4 titanium alloy powder, induces an in-situ reaction during selective laser melting (SLM) to generate a finely dispersed TiB reinforcing phase, significantly refining the grain size of the formed material and improving the uniformity and density of the microstructure. The high energy density and rapid solidification characteristics of SLM effectively suppress the generation of forming defects, reduce porosity, and decrease the heat-affected zone and residual stress level. The prepared TiB / TC4 titanium-based composite material exhibits superior microhardness, wear resistance, and corrosion resistance compared to TC4 titanium alloy without TiB2. This composite material achieves good comprehensive performance without subsequent overall heat treatment, and the process is relatively simplified, making it suitable for additive manufacturing and engineering applications of complex titanium-based components. Preferably, the TiB2 addition amount is 3.0 wt% of the TC4 titanium alloy powder. Further increases in the addition amount can lead to unreacted particles and porosity defects, adversely affecting material properties, demonstrating the sensitivity of TiB2 addition amount to microstructure and property control.

[0016] 2. This invention introduces TiB2 particles during selective laser melting and induces them to undergo an in-situ reaction, thereby generating a TiB reinforcing phase in the TC4 titanium alloy matrix. The reinforcing phase and the matrix form a good metallurgical bonding interface, effectively avoiding the problem of insufficient interfacial bonding force of the external reinforcing phase.

[0017] 3. The in-situ generated TiB reinforcing phase is distributed in the interior of the titanium alloy matrix in the form of fibers or short rods, which plays a significant role in refining and strengthening the matrix structure, thereby improving the hardness and wear resistance of the material.

[0018] 4. Selective laser melting technology has the characteristics of high energy density and rapid solidification, which makes the obtained TiB / TC4 titanium-based composite material have high forming density, good microstructure uniformity and high material performance stability.

[0019] 5. The preparation method of the present invention has controllable process parameters and good repeatability, and is suitable for the integrated forming of complex titanium-based components, with good engineering application prospects.

[0020] Based on the implementation methods provided in the above aspects, this application can be further combined to provide more implementation methods. Attached Figure Description

[0021] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, with the same or corresponding reference numerals denoteing the same or corresponding parts, wherein: Figure 1 This is a forming diagram of TC4 titanium alloy prepared based on selective laser melting technology in an embodiment of the present invention; Figure 2 Figure (a) shows the SEM morphology of TC4 titanium alloy powder; Figure (b) shows the SEM morphology of TiB2 powder. Figure 3 Figures (a1-a4) show the microstructure of SLM-formed samples with different TiB2 additions before corrosion; Figures (b1-b4) show the microstructure of the vertical cross-section of SLM-formed samples with different TiB2 additions; Figures (c1-c4) show the microstructure of the horizontal cross-section of SLM-formed samples with different TiB2 additions. Figure 4 Figures (a1-a4) show the high-magnification microstructure of the vertical cross-section of SLM-formed specimens with different TiB2 addition amounts; Figures (b1-b4) show the high-magnification microstructure of the horizontal cross-section of SLM-formed specimens with different TiB2 addition amounts; Figures (c1-c4) show the low-magnification microstructure of the vertical cross-section of SLM-formed specimens with different TiB2 addition amounts. Figure 5 X-ray diffraction patterns of SLM-formed samples with different TiB2 addition amounts; Figure 6 Microhardness test results of SLM-formed specimens with different TiB2 addition amounts; Figure 7 Friction coefficient variation curves for SLM-formed samples with different TiB2 addition amounts; Figure 8 Wear patterns of SLM-formed specimens with different TiB2 addition amounts; Figure 9 SLM wear morphology images for different TiB2 addition amounts; Figure 10 Polarization curves of SLM-formed samples with different TiB2 addition amounts in 3.5% NaCl solution; Figure 11 This is a flowchart illustrating the preparation of TiB / TC4 composite materials based on selective laser melting technology in an embodiment of the present invention. Detailed Implementation

[0022] The exemplary embodiments disclosed in this application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0023] Selective Laser Melting (SLM) is an additive manufacturing technology based on the layer-by-layer melting of metal powder using a high-energy laser. This technology features high energy density, rapid cooling rate, and high forming accuracy, enabling rapid solidification and forming of metallic materials, which is beneficial for obtaining fine solidification structures and high forming density. However, research shows that single TC4 titanium alloys still suffer from insufficient hardness and wear resistance under complex service conditions such as friction, wear, and corrosion. Simply relying on process parameter control is insufficient to fundamentally improve its overall performance; therefore, it is necessary to introduce new strengthening mechanisms from the perspective of material system design.

[0024] TiB2 ceramic particles possess characteristics such as high melting point, high elastic modulus, and good chemical stability, making them a commonly used reinforcing phase precursor in the preparation of titanium-based composites. Previous studies have shown that under high-energy laser irradiation, TiB2 can undergo an in-situ reaction with the titanium matrix to generate a TiB reinforcing phase. The resulting TiB fiber structure can strengthen and refine the microstructure during solidification, thereby significantly improving the mechanical properties of titanium alloys. However, the in-situ formation mechanism of TiB under the typical rapid melting and solidification process of selective laser melting (SLM) and its systematic control over the microstructure and properties of TC4 titanium alloys still require further refinement.

[0025] This invention provides a TiB / TC4 titanium-based composite powder material based on selective laser melting, wherein the titanium-based composite powder comprises TC4 titanium alloy powder and TiB2 ceramic particles; the content of the TiB2 ceramic particles is 1wt%~3wt% of the TC4 titanium alloy powder.

[0026] Optionally, the particle size of the TC4 titanium alloy powder is 15-53 μm; the particle size of the TiB2 ceramic particles is 3-5 μm.

[0027] Optionally, the chemical composition of the TC4 titanium alloy powder by mass percentage includes: Al 5.5~6.75 wt%, V 3.5~4.5 wt%, Fe≤0.30 wt%, C≤0.08 wt%, N≤0.05 wt%, H≤0.015 wt%, O≤0.20 wt%, with the remainder being Ti.

[0028] like Figure 11 As shown, the present invention also provides a method for preparing TiB / TC4 titanium-based composite materials based on selective laser melting, comprising the following steps: Step S1: Weigh TC4 titanium alloy powder and TiB2 ceramic particles according to the set ratio, place the two powders in a mixing tank for mechanical mixing, and obtain TiB2 / TC4 composite powder. Step S2: Pre-treat the TiB2 / TC4 composite powder and place the pre-treated powder into the powder supply system of the selective laser melting equipment; Step S3: Selective laser melting equipment is used to lay TiB2 / TC4 composite powder layer by layer and scan it with laser. Under the action of high-energy laser, the powder is locally melted and in-situ reaction occurs to obtain TiB / TC4 titanium-based composite material specimens. Step S4: After the molding is completed, the prepared TiB / TC4 titanium-based composite material specimen is removed from the molded substrate.

[0029] Optionally, the mechanical mixing speed in step S1 is 100–300 r / min, and the mixing time is 4–6 h.

[0030] Optionally, the pretreatment in step S2 includes drying the TiB2 / TC4 composite powder at a temperature of 120–150 °C for 4–6 h.

[0031] Optionally, the process parameters for selective laser melting in step S3 include: laser power of 200-300 W, scanning speed of 1000-1300 mm / s, and scanning spacing of 0.08-0.10 mm.

[0032] Optionally, the layer-by-layer forming step in step S3 is as follows: (1) Set the laser scanning strategy and complete the single-layer powder spreading; (2) The laser beam scans the powder layer along the set path, so that the powder is fully melted and quickly solidified to form a single-layer shaped structure; (3) Repeat steps (1) and (2) by layering until TiB / TC4 titanium-based composite material specimens are obtained.

[0033] Optionally, the shaped substrate is a TC4 titanium alloy substrate.

[0034] Example 1 Control group: Selective laser melting forming of pure TC4 titanium alloy; Following the steps outlined above, TC4 titanium alloy powder with a particle size of 15–53 μm was selected. Its chemical composition is shown in Table 1. Selective laser melting (SLM) was used for sample preparation. During the forming process, a high-power fiber laser and an inert gas protection system were used to perform layer-by-layer melting on the TC4 titanium alloy substrate. After optimization, the main process parameters for SLM were: laser power 280 W, scanning speed 1200 mm / s, and scanning spacing 0.09 mm. The forming process was carried out under argon protection, with the oxygen content controlled below 10 ppm. TC4 titanium alloy specimens with a height of approximately 10 mm were prepared through a layer-by-layer stacking method. Figure 1 As shown, the surface has no obvious cracks, pores, or fissures, indicating that the forming quality is good under these parameters.

[0035] Table 1 shows the chemical composition (wt.%) of TC4. Example 2 The difference from Example 1 is that in this example, TC4 titanium alloy powder and TiB2 ceramic particles (particle size 3-5 μm) are mixed and mechanically homogenized to obtain TiB2 / TC4 composite powder. Selective laser melting is used to melt and form the composite powder layer by layer with TiB2 additions of 1wt%, 2wt%, and 3wt%, respectively. After forming, the specimen is removed from the substrate and its microstructure is characterized using scanning electron microscopy. The microstructure morphology of TiB / TC4 titanium-based composite material samples with different TiB2 additions based on selective laser melting is obtained, such as... Figure 4 As shown in the middle figure (a1-a4), its structure shows a transformation from fine needle-like TiB reinforcing phase to short rod-like phase and finally to cluster-like phase along the forming height direction. Figure 4Figures (b1-b4) show the microstructure of the horizontal cross-section. In Figure b1, the microstructure is mainly composed of densely packed α′ martensite with a Z-shaped distribution. A small number of dispersed β-phase particles, with nanoscale sizes, can be observed between some α′ martensite lamellae and near grain boundaries. When the TiB2 addition is 1 wt% (Figure b2), an in-situ generated TiB reinforcing phase can be observed in the matrix. This TiB reinforcing phase mainly exhibits nanoscale needle-like whisker morphology, distributed in the α′-Ti matrix, and shows a certain orientation along the laser scanning direction. Compared to the sample without TiB2, the matrix microstructure size is reduced. Simultaneously, the number of β-phase nanoparticles increases, while still maintaining a nanoscale distribution. When the TiB2 addition increases to 2 wt% (Figure b3), the number of TiB reinforcing phases further increases, and their morphology gradually changes from needle-like to a coexistence of needle-like and short rod-like structures, exhibiting an interwoven distribution in local areas. The matrix grain size further decreases under lower addition levels. The β-phase nanoparticles were more uniformly distributed in the matrix, and their quantity increased further compared to the 1 wt% condition. When the TiB2 addition was increased to 3 wt% (Figure b4), the TiB reinforcing phase formed a more obvious aggregated distribution in the matrix, constructing a continuous three-dimensional network structure. The β-phase nanoparticles still existed in a dispersed form between the α′ martensite and around the TiB reinforcing phase, and their quantity did not show a significant increasing trend compared to the 2 wt% condition. Compared with the TC4 titanium alloy sample without TiB2, the microstructure of the composite material was significantly refined, the grain size was reduced, and the microstructure distribution was more uniform. Figure 4 Figures (c1-c4) show the microstructure of samples obtained by selective laser melting (SLM) in the vertical cross-section under different TiB2 addition amounts. When the TiB2 addition amount is 1 wt% (Figure c2), a small number of small blocky particles can be observed in the matrix. These particles are irregular in shape and mostly distributed in an isolated form within the matrix. When the TiB2 addition amount increases to 2 wt% (Figure c3), the number of blocky particles increases compared to the 1 wt% condition, and the particle size shows an increasing trend. Some particles exhibit irregular contour characteristics at their edges and are mainly distributed in the molten pool boundary region. When the TiB2 addition amount is further increased to 3 wt% (Figure c4), the size of the blocky particles further increases, mainly existing in a blocky form, and a local core-shell structure agglomeration morphology can be observed.

[0036] Example 3 The difference from Example 1 is that this example uses TC4 titanium alloy powder ( Figure 2 a) with TiB2 ceramic particles ( Figure 2b) The mixture was mechanically mixed and homogenized to obtain TiB2 / TC4 composite powder; the composite powder was then melted layer by layer using selective laser melting (SLM) to obtain TiB / TC4 titanium-based composite material specimens with TiB2 additions of 1 wt%, 2 wt%, and 3 wt%, respectively, prepared by SLM. Their macroscopic morphology and microstructure are as follows: Figure 4 As shown, when the TiB2 addition amount increases to 1 wt% ( Figure 4 c2) shows a small number of small, irregularly shaped residual TiB2 particles, mostly isolated. When the TiB2 content increases to 2 wt% ( Figure 4 c3), the number of residual TiB2 particles increased significantly, and the particle size showed an increasing trend. Some particles showed traces of dissolution reaction at their edges, exhibiting irregular shapes and mostly distributed at the interface of the molten pool, indicating that the melt failed to completely penetrate and react under high particle density. Further increasing the TiB2 addition to 3wt% ( Figure 4 (c4) The remaining TiB2 particles are larger, existing in a blocky form, and even showing a core-shell aggregate structure. These results indicate that TiB2 promotes grain refinement through heterogeneous nucleation of TiB synthesized in situ with TC4, forming a synergistic mechanism of grain refinement and grain boundary strengthening. X-ray diffraction (XRD) analysis is as follows: Figure 5 As shown, the test results indicate that, under the optimized process parameters, the X-ray diffraction patterns of the TC4 titanium alloy and titanium-based composite materials show that the TC4 alloy and titanium-based composite materials are mainly composed of the matrix phase, and each diffraction peak corresponds to the matrix phase. No other obvious diffraction peaks or obvious impurity phases were detected, indicating that under the above process parameters, the selective laser melting forming process can achieve stable forming of the material.

[0037] Then, the TiB / TC4 composite material was subjected to microstructure and performance testing, and observed by metallographic microscopy and scanning electron microscopy.

[0038] The results of the composite material hardness test are as follows Figure 6 As shown, the surface microhardness of the prepared TiB / TC4 titanium matrix composite coating is significantly higher than that of the TC4 titanium alloy without TiB2. Specifically, when the TiB2 addition is 3.0 wt%, the average microhardness of the composite reaches its highest level, exhibiting a significant hardness improvement. This performance improvement is mainly attributed to the multiple strengthening mechanisms introduced by the in-situ generated TiB reinforcing phase, including grain refinement strengthening, dispersion strengthening, and the reinforcing phase loading effect. On the one hand, the TiB reinforcing phase acts as a heterogeneous nucleation core, inhibiting grain growth and significantly refining the matrix structure. On the other hand, the uniformly distributed TiB reinforcing phase forms a good metallurgical bond with the α-Ti matrix, effectively distributing stress under external loads and improving the overall load-bearing capacity of the composite. The tribological test results of TiB / TC4 are shown below. Figure 7As shown. Figure 8 As shown, the 3.0 wt% TiB / TC4 composite coating exhibited the lowest wear rate, indicating a significant improvement in its wear resistance. The wear mechanism is that the mixed wear mechanism in TC4 titanium alloy, dominated by adhesive wear and abrasive wear, gradually shifts to a wear form dominated by slight cutting wear. This is mainly attributed to the continuous metallurgical bonding interface formed between the TiB reinforcing phase and the matrix, which significantly improves the overall hardness and resistance to plastic deformation of the coating. Simultaneously, the uniformly distributed hard TiB phase preferentially bears the external load during friction, effectively suppressing the plowing effect of abrasive particles on the matrix, thereby delaying the wear failure process. Figure 9 The wear morphology of TiB / TC4 composites with different TiB2 additions under the same experimental conditions is compared. Figure (a) shows the TC4 titanium alloy, Figure (b) shows the composite with 1 wt% TiB2 addition, Figure (c) shows the composite with 2 wt% TiB2 addition, and Figure (d) shows the composite with 3 wt% TiB2 addition. As can be seen from the figures, with the increase of TiB2 addition, the wear grooves of the coating become significantly shallower, and the degree of surface spalling and plastic deformation is significantly reduced. The electrochemical corrosion test results of the TiB / TC4 composites are as follows: Figure 10 As shown, the self-corrosion current density of the TiB / TC4 composite coating is significantly lower than that of the TC4 titanium alloy, while the charge transfer resistance is significantly improved, indicating that its corrosion resistance has been effectively improved. This performance improvement is mainly attributed to the introduction of the in-situ reinforcing phase of TiB, which significantly refines the matrix grains and improves the microstructure density, reducing corrosion-sensitive defects such as porosity and microcracks. At the same time, the dense and uniform microstructure facilitates the formation of a continuous and stable passivation film on the surface, reducing the diffusion rate of corrosive media into the matrix, thereby delaying the occurrence and development of the corrosion process.

[0039] Table 2 Polarization parameters with different TiB2 addition amounts Example 4 The difference from Example 1 is that in this example, TC4 titanium alloy powder and TiB2 powder are mechanically mixed and homogenized at amounts of 1wt%, 2wt%, and 3wt%, respectively, to obtain a composite powder. Selective laser melting (SLM) is then used to melt and shape the composite powder layer by layer, resulting in a TiB / TC4 titanium-based composite material specimen prepared by SLM. Figure 3 The microstructures of samples formed by selective laser melting under different TiB2 addition amounts are shown in comparison. The images include the morphology of the uncorroded surface (a1-a4), the microstructure of the vertical cross section (b1-b4), and the microstructure of the horizontal cross section (c1-c4). Figure 3The middle figures (a1-a4) show the morphology of the uncorroded surface. The surface of the TC4 sample is generally dense, with only a few micropore defects observed. When the TiB2 addition amount is 1 wt%, a small number of dispersed undissolved TiB2 particles appear on the matrix surface. When the addition amount increases to 2 wt%, the number of undissolved TiB2 particles further increases, and the distribution density improves. When the addition amount is 3 wt%, both the size and number of undissolved TiB2 particles increase, and some particles exhibit localized aggregation characteristics. Figure 3 Figures (b1-b4) show the microstructure of the vertical cross-section. The TC4 sample exhibits obvious molten pool overlap and columnar crystal structure in the vertical cross-section, with β-columnar crystals visible growing along the construction direction. When the TiB2 addition is 1 wt%, dispersed blocky particles can be observed in the molten pool region and at the molten pool boundary. When the addition increases to 2 wt%, the number of blocky particles further increases, mainly distributed in the molten pool boundary region, with some particles showing a banded distribution along the molten pool contour. When the addition is 3 wt%, the blocky particles are more densely distributed near the molten pool boundary, and local aggregation occurs. Figure 3 The middle figures (c1-c4) show the microstructure of the horizontal cross-section. Sample TC4 exhibits a typical checkerboard-shaped molten pool scanning characteristic in the horizontal cross-section. When the TiB2 addition is 1 wt%, the scanning path is clearly discernible, and a small amount of particulate phase is distributed in the matrix. When the addition is 2 wt%, the number of particles further increases and shows a certain orientational distribution along the laser scanning path. When the addition is 3 wt%, the particles are more densely distributed in the scanning trajectory area, with a continuous distribution in some local areas. In summary, with the increase of TiB2 addition, the number of particulate phases in the sample gradually increases, and their distribution morphology in the uncorroded surface, vertical cross-section, and horizontal cross-section all show corresponding changes. Subsequently, the microstructure and properties of the composite material were tested using metallographic microscopy and scanning electron microscopy. The results show that when the TiB2 addition is 3.0 wt%, the number of TiB2 particles that have not undergone complete in-situ reaction in the composite material increases significantly, and particle agglomeration occurs in some areas, reducing the uniformity and density of the microstructure. Hardness testing of the composite material showed that the average microhardness of the composite surface was approximately 432 HV1, which was 0.78 times higher than that of the composite specimen without TiB2. This is mainly attributed to the fact that during the rapid solidification process of SLM, some boron atoms may not have enough time to completely form TiB, but instead remain supersaturated dissolved in the TC4 titanium matrix. As interstitial atoms, boron atoms produce strong lattice distortion and pinning dislocations, thus significantly increasing the hardness. Friction and wear testing of the TiB / TC4 composite material showed that the wear rate of the 3.0 wt% TiB / TC4 composite coating was approximately 333 mm. 3 / (N·m), which is 127 mm higher than that of materials without TiB2 addition. 3 / (N·m). The main reasons are twofold: firstly, with the increase in the amount of hard TiB2 particles added, the in-situ reacted TiB is distributed in the matrix, refining the grain size; secondly, the in-situ reacted TiB reinforcing phase bears the load and hinders dislocations, so the volumetric wear rate of the TiB / TC4 composite material is lower than that of the TC4 alloy specimen, further improving the wear resistance of the titanium-based composite material. Electrochemical corrosion test results of the TiB / TC4 composite material show that the self-corrosion potential E of the TC4 specimen is... corr The self-corrosion current density is -1.087V, i corr 4.48×10 -4 A / cm 2 As the amount of TiB2 added increases, E exhibits... corr Gradually increase, while i corr The trend is one of gradual decrease. When the TiB2 addition reaches 3%, E corr It reached its maximum value of -0.956V, while i corr Then it reaches the minimum value, which is 1.86 × 10. -4 A / cm 2 This indicates that the composite material specimen with this ratio exhibits the best corrosion resistance. The reason for this phenomenon is that the increased addition of TiB2 leads to a greater amount of TiB generated in situ from the TC4 matrix, resulting in higher chemical stability and making it less prone to chemical reaction in NaCl solution. The presence of TiB reduces the direct contact between the TC4 matrix and the corrosive medium, thus effectively hindering its penetration. From a microscopic perspective, TiB2 refines the grain size of the TC4 matrix, dilutes the chemical inhomogeneity at grain boundaries, promotes the formation of a stable passivation film, and facilitates the in-situ synthesis and uniform distribution of the hard TiB phase. This creates a continuous barrier that impedes the diffusion of corrosive media within the material, thereby improving corrosion resistance.

[0040] In summary, the TiB / TC4 composite material prepared in this embodiment with a TiB2 addition of 3.0 wt% can generate TiB reinforcing phase in situ through selective laser melting. Compared with TC4 titanium alloy, the composite material has a hardness increase of more than 27.8%, a wear rate reduction to 0.78, and a corrosion resistance improvement of about 58%, fully demonstrating the superiority of the composite material of this invention.

[0041] The beneficial technical effects of this invention are as follows: The preferred TiB2 addition amount in this invention is 3.0 wt%. Excessive reinforcing phase content can lead to an increase in the number of pores and cracks in the formed product, a decrease in microstructure density, and consequently, a reduction in overall performance. This demonstrates the "critical content effect" of TiB2 addition amount in the selective laser melting forming process. In summary, by introducing an appropriate amount of TiB2 particles into TC4 titanium alloy-based powder and generating the TiB reinforcing phase through an in-situ reaction during selective laser melting, significant grain refinement of the formed composite material is achieved, improving microstructure uniformity and density. Simultaneously, the selective laser melting process features low heat input and high cooling rate, effectively suppressing the formation of defects such as pores and cracks, thereby obtaining a titanium-based composite material with excellent overall performance.

[0042] Increase the hardness of materials When the TiB2 addition amount was 3.0 wt%, the microhardness of the TiB / TC4 composite coating reached its maximum value, significantly higher than that of the titanium alloy without TiB2. This hardness improvement is mainly attributed to the synergistic effect of multiple strengthening mechanisms: on the one hand, the in-situ generated TiB reinforcing phase acts as a heterogeneous nucleation core during selective laser melting, significantly refining the matrix grains and producing a significant grain refinement strengthening effect; on the other hand, the fibrous TiB reinforcing phase forms a good metallurgical bond with the α-Ti matrix, which can effectively share stress under external load, producing dispersion strengthening and load transfer strengthening effects, thereby significantly improving the overall hardness of the composite coating.

[0043] Improve the wear resistance of materials The microhardness of the TiB / TC4 composite material prepared by SLM gradually increases with increasing TiB2 content. This is due to the synergistic effect of multiple strengthening mechanisms caused by the TiB reinforcing phase. The microhardness of the composite specimens with 1%, 2%, and 3% TiB2 content increased by 13.1%, 15.6%, and 27.8% respectively compared to the TC4 specimen. Both TC4 alloy and TiB / TC4 composite material exhibit composite wear mechanisms. Furthermore, one type of wear mechanism can induce other types, and multiple wear mechanisms can coexist. The TiB reinforcing phase generated by in-situ reaction directly bears the load, reduces matrix cutting, inhibits adhesive wear, and promotes the formation of a stable and wear-resistant tribooxide layer. Through extreme grain refinement and a significant hardening effect, it synergistically optimizes the wear resistance of the TC4 composite material. When the TiB2 content reaches 3 wt%, the wear rate and friction coefficient of the composite material are minimized, thus achieving optimal wear resistance.

[0044] Improve the corrosion resistance of materials In electrochemical corrosion experiments, corrosion pits typically occur around defects such as cracks and pores. The TiB reinforcing phase generated by in-situ reaction exhibits excellent interfacial bonding with the TC4 matrix, providing an ideal substrate for the formation of a continuous and dense TiO2 passivation film. This passivation film effectively hinders electrolyte penetration, thereby significantly improving the overall corrosion resistance of the composite material.

[0045] This invention demonstrates the preparation and application effects of composite powder materials through examples; the technical solution is not limited to the specific values ​​mentioned above, as long as it meets the scope of the claims, similar beneficial effects can be achieved; it can be seen that the TiB2 / TC4 composite powder material for selective laser melting technology provided by this invention has the advantages of simple structure, feasible preparation, and moderate cost, and by optimizing the amount of TiB2 added, it can significantly improve the microstructure and wear and corrosion resistance of nickel-based coatings, which has important practical value for selective laser melting processing and surface strengthening of high-end equipment parts.

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing TiB / TC4 titanium matrix composite based on selective laser melting, characterized in that, The preparation method includes: Step S1: Weigh TC4 titanium alloy powder and TiB2 powder according to the set ratio, place the two powders in a mixing tank for mechanical mixing, and obtain TiB2 / TC4 composite powder. Step S2: Pre-treat the TiB2 / TC4 composite powder and place the pre-treated powder into the powder supply system of the selective laser melting equipment; Step S3: Selective laser melting equipment is used to lay TiB2 / TC4 composite powder layer by layer and perform laser scanning to obtain TiB / TC4 composite material specimens; Step S4: Use wire cutting technology to cut the TiB / TC4 composite material specimen formed by selective laser melting from the substrate.

2. The method for preparing TiB / TC4 titanium matrix composite based on selective laser melting according to claim 1, characterized in that, The stirring speed in the mixing tank in step S1 is 100~300 r / min, and the stirring time is 4~6 h.

3. The method for preparing TiB / TC4 titanium-based composite material based on selective laser melting according to claim 1, characterized in that, The TiB2 particles in step S1 have a mass fraction of 1-3 wt% in the composite powder. The TC4 titanium alloy powder has a particle size of 15~53μm; the TiB2 powder has a particle size of 3~5μm.

4. The method for preparing TiB / TC4 titanium-based composite material based on selective laser melting according to claim 1, characterized in that, The chemical composition of the TC4 titanium alloy powder mentioned in step S1, by mass percentage, includes: Al 5.5~6.75wt%, V 3.5~4.5wt%, Fe≤0.3wt%, C≤0.08wt%, N≤0.05wt%, H≤0.015wt%, O≤0.8~0.15wt%, with the remainder being Ti.

5. The method for preparing TiB / TC4 titanium-based composite material based on selective laser melting according to claim 1, characterized in that, The pretreatment of TiB2 / TC4 composite powder in step S2 involves loading the TiB2 / TC4 composite powder into an oven for drying. The temperature of the oven is 120~150℃, and the drying time is 4~6h.

6. The method for preparing TiB / TC4 titanium-based composite material based on selective laser melting according to claim 1, characterized in that, The process parameters for selective laser melting in step S3 include: laser power 200~300 W, scanning speed 1000~1300 mm / s, and scanning spacing 0.08~0.10 mm.

7. The method for preparing TiB / TC4 titanium-based composite material based on selective laser melting according to claim 1, characterized in that, The layer-by-layer forming step in step S3 is as follows: (1) Set the scanning rotation increment to 90° and use the circular scanning mode; (2) The laser beam scans the substrate surface to perform single sintering scanning; (3) Repeat step (2) by layering until TiB / TC4 composite material specimens are obtained.

8. The method for preparing TiB / TC4 titanium-based composite material based on selective laser melting according to claim 7, characterized in that, The substrate is a titanium TC4 titanium alloy substrate.

9. A TiB / TC4 titanium-based composite material prepared by the preparation method described in claims 1-8, characterized in that, It includes a TC4 titanium alloy as the matrix; and a TiB reinforcing phase dispersed in the matrix. The TiB reinforcing phase is formed by the reaction of TiB2 particles with the in-situ generated titanium matrix during selective laser melting, and is embedded in the matrix in a fibrous form to form a continuous metallurgical bonding interface with the matrix.

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