A method for preparing a biomimetic interlocking isomeric titanium alloy based on laser directed energy deposition technology

Abstract

The application discloses a method for preparing a bionic interlocking heterogeneous titanium alloy based on a laser directional energy deposition technology, and the method comprises the following steps: alternately depositing TC4 titanium alloy powder and TC18 titanium alloy powder on a titanium alloy substrate according to a preset scanning strategy by using the laser directional energy deposition technology, and constructing a bionic interlocking heterogeneous structure; the bionic interlocking heterogeneous structure is a fish scale-shaped interlocking unit designed according to the interlocking structure of a beetle sheath wing, and the interlocking effect in multiple directions is realized by alternately switching the deposition materials between layers and between channels. The titanium alloy prepared by the method has a significant increase in mechanical properties under the dual effects of the bionic interlocking heterogeneous structure and material synergistic strengthening, the tensile strength is greater than or equal to 1300 MPa, and the elongation after fracture is greater than or equal to 15%, and the performance is significantly better than that of the existing single titanium alloy and simple layered structure titanium alloy, and the titanium alloy can fully meet the use requirements in a high-load environment.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy additive manufacturing technology, specifically to a method for preparing biomimetic interlocking heterogeneous titanium alloys based on laser directional energy deposition technology. Background Technology

[0002] Additive manufacturing, also known as 3D printing, is an advanced manufacturing technology that uses computer-aided design of three-dimensional model data to construct physical objects from discrete materials through layer-by-layer manufacturing and stacking. Laser-directed energy deposition (LDED) technology, as an important branch of additive manufacturing, uses a laser to act on raw materials such as metal powder / filament materials and the surface of a substrate, causing them to melt and form a molten pool. After natural cooling, the deposited area achieves a metallurgical bond with the substrate. It possesses significant technical advantages: minimal thermal impact on the substrate material during the forming process, avoiding changes to the original mechanical properties and material characteristics of the substrate; low coating layer dilution rate, high material utilization; easy integration with automated equipment, and wide range of applications; and ample development space for multi-material hybrid forming, thus finding widespread use in the manufacturing field.

[0003] In the field of titanium alloy additive manufacturing, TC4 (composed of Ti-6Al-4V) and TC18 (composed of Ti-5Al-5Mo-5V-1Cr-1Fe) are two commonly used titanium alloy materials. However, both have performance limitations and struggle to balance strength and ductility: TC4's microstructure is dominated by acicular α′ martensite, exhibiting high strength and hardness, but poor ductility; TC18's microstructure consists of columnar β grains, exhibiting excellent ductility, but lower strength and hardness. Although the microstructure of both materials can be controlled through subsequent heat treatment to optimize performance, the inherent properties of the materials themselves make it difficult to overcome the trade-off between strength and ductility, thus failing to meet the application requirements of specific scenarios.

[0004] Layered structures are widely used in titanium alloy fabrication due to the layer-by-layer processing characteristics of laser-directed energy deposition (LDED). The mechanical heterogeneity of the coexistence of hard and soft layers in these structures leads to asynchronous deformation of each layer under stress, triggering a heterogeneous deformation strengthening effect. The core mechanism does not rely on a single strengthening method; rather, to ensure strain continuity at the interface, the system generates a large number of geometrically necessary dislocations, resulting in long-range internal stresses, which in turn increase flow stress and enhance work hardening capacity. However, relying solely on layered structures limits the potential for improving material properties, making it difficult to achieve a synergistic optimization of high strength and high ductility / toughness.

[0005] Existing technologies draw on the superior toughening strategies and multi-scale design paradigms of biomaterials found in nature to develop high-performance heterogeneous biomimetic metallic materials, attempting to improve the overall mechanical properties of titanium alloys through the design of special structures. For example, Chinese invention patent CN114713846A discloses a heterogeneous biomimetic structural design and its directional energy deposition additive manufacturing method; however, the structure designed in this patent can only achieve structural interlocking in one direction, resulting in a less than significant improvement in the expected mechanical properties.

[0006] In summary, the strength and ductility / toughness of titanium alloys prepared by existing additive manufacturing technologies still cannot meet the requirements of specific high-load environments. There is an urgent need for a new structural design and preparation method to ensure that titanium alloys have sufficient ductility / toughness while maintaining high strength, thereby achieving a significant improvement in comprehensive mechanical properties. Summary of the Invention

[0007] The purpose of this invention is to solve the technical problems of existing additive manufacturing technology in titanium alloys, such as the difficulty in synergistically optimizing strength and ductility / toughness, the limited improvement in mechanical properties of unidirectional interlocking structures, and the inability to meet the requirements of specific high-load environments. The invention provides a method for preparing biomimetic interlocking heterogeneous titanium alloys based on laser-directed energy deposition technology, so as to achieve synergistic improvement in high strength and high ductility / toughness of titanium alloys and improve their comprehensive mechanical properties.

[0008] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0009] A method for preparing biomimetic interlocking heterogeneous titanium alloys based on laser-directed energy deposition technology includes the following steps:

[0010] Using laser-directed energy deposition technology, two types of titanium alloy powders were alternately deposited on a titanium alloy substrate according to a preset scanning strategy to construct a biomimetic interlocking heterogeneous structure; the two types of titanium alloy powders were TC4 titanium alloy powder and TC18 titanium alloy powder.

[0011] The preset scanning strategy is as follows: The first layer deposits a first type of titanium alloy powder using a unidirectional scanning method with a channel spacing of 1.0-1.6 mm; the second layer rotates 90° clockwise and uses a unidirectional scanning method, first depositing a second type of titanium alloy powder with a channel spacing of 2.2-3.0 mm, then depositing the first type of titanium alloy powder with a channel spacing of 1.0-1.6 mm and a channel spacing of 2.2-3.0 mm; the third layer rotates 90° counterclockwise and uses a unidirectional scanning method, depositing the second type of titanium alloy powder with a channel spacing of 1.0-1.6 mm; the fourth layer rotates 90° clockwise and uses a unidirectional scanning method, first depositing the first type of titanium alloy powder with a channel spacing of 2.2-3.0 mm, then depositing the second type of titanium alloy powder with a channel spacing of 1.0-1.6 mm and a channel spacing of 2.2-3.0 mm. mm; the four layers are used as a cycle for repeated deposition, and the total number of titanium alloy powder deposited in each layer is the same, and the length of each deposition channel is the same.

[0012] This invention utilizes high-strength, low-plasticity TC4 titanium alloy powder and low-strength, high-plasticity TC18 titanium alloy powder to construct a composite system. Leveraging the complementary properties of these two materials, a synergistic effect is achieved. A scanning strategy ensures uniform distribution and tight interlocking of the two materials, allowing the hard and soft layers to mutually constrain and reinforce each other under stress. Furthermore, it overcomes the limitations of existing unidirectional interlocking structures by incorporating the multi-scale interlocking principle of beetle elytra, designing a four-layer cyclic scanning strategy to achieve three-dimensional staggered interlocking between layers and channels, forming fish-scale-like interlocking units. This structure not only mechanically constrains interlayer slippage but also… This invention stimulates a strong heterogeneous deformation strengthening effect, breaking the trade-off between strength and plasticity at the structural level and providing core support for synergistic performance optimization. In addition, this invention systematically optimizes various process parameters such as scanning strategy, laser parameters, powder characteristics, and substrate treatment to form a complete technical solution. The parameters are matched and support each other to ensure the precise forming and metallurgical bonding quality of the biomimetic interlocking heterogeneous structure, avoiding performance shortcomings caused by single parameter optimization, achieving deep coupling between process, structure, and performance, and ultimately breaking the performance limitations of single materials, significantly improving the comprehensive mechanical properties of titanium alloys.

[0013] Furthermore, the process parameters of the directional energy deposition technology are: laser power 800-1200 W, scanning speed 3-6 mm / s, defocusing amount -2.5 mm to -0.5 mm, powder feed rate 1.2-1.8 g / min, and lifting amount 0.4-0.6 mm.

[0014] Furthermore, the process includes a surface pretreatment step for the titanium alloy substrate prior to deposition.

[0015] Furthermore, the titanium alloy substrate is a TA2 titanium alloy substrate.

[0016] In a specific embodiment, the TA2 titanium alloy substrate is 100 mm × 100 mm × 8 mm.

[0017] Furthermore, the surface pretreatment includes sandblasting and anhydrous ethanol cleaning. Sandblasting can remove impurities such as oxide scale and oil stains from the substrate surface, while increasing the surface roughness of the substrate and improving the laser absorption rate and the mechanical bonding force of the deposited layer; anhydrous ethanol cleaning can further remove residual dust and oil stains after sandblasting, preventing impurities from affecting the interlayer metallurgical bonding quality.

[0018] Furthermore, the process includes a pre-deposition step of baking the two titanium alloy powders. Baking effectively removes moisture and adsorbed gases from the powder, ensuring its flowability and purity.

[0019] Furthermore, the temperature of the powder drying process is 100-140 ℃, and the holding time is 1.5-2.5 h.

[0020] Furthermore, the particle size of the TC4 titanium alloy powder is 53-105 μm, and the particle size of the TC18 titanium alloy powder is 53-105 μm.

[0021] Furthermore, both the TC4 and TC18 titanium alloy powders are prepared by gas atomization, resulting in spherical powders with excellent sphericity. The spherical powders prepared by gas atomization exhibit excellent flowability, ensuring the stability and uniformity of the powder feeding process and preventing powder agglomeration that could lead to powder feeding interruptions or uneven deposition channels.

[0022] Furthermore, the track length can be 45-55 mm.

[0023] In a specific implementation, the preset scanning strategy is as follows: The first layer deposits TC18 titanium alloy powder using a unidirectional scanning method, with 19 passes deposited, a pass spacing of 1.3 mm, and a pass length of 48 mm. The second layer is scanned 90° clockwise using a unidirectional scanning method, first depositing TC4 titanium alloy powder with a pass spacing of 2.6 mm, depositing 10 passes with a pass length of 48 mm, then depositing TC18 titanium alloy powder with a 1.3 mm gap from the first pass of TC4 titanium alloy powder, continuing to deposit 9 passes with a pass spacing of 2.6 mm and a pass length of 48 mm. The third layer is scanned 90° counterclockwise using a unidirectional scanning method, depositing TC4 titanium alloy powder, with 19 passes deposited, a pass spacing of 1.3 mm, and a pass length of 48 mm. The fourth layer is scanned 90° clockwise using a unidirectional scanning method, first depositing TC18 titanium alloy powder with a pass spacing of 2.6 mm, depositing 10 passes with a pass length of 48 mm. mm, then deposit TC4 titanium alloy powder, with a spacing of 1.3 mm between it and the first TC18 titanium alloy powder, and continue to deposit 9 more layers, with a layer spacing of 2.6 mm and a layer length of 48 mm; the deposition is repeated in four layers as one cycle.

[0024] Furthermore, the biomimetic interlocking heterogeneity is a fish-scale-like interlocking unit designed based on the interlocking structure of beetle elytra. Multi-directional interlocking effects are achieved through alternating switching of deposition materials between layers and channels. The natural interlocking structure of beetle elytra possesses excellent mechanical transmission and constraint capabilities. This invention borrows from this design, enabling the TC4 hard layer and TC18 soft layer to form a fish-scale-like interlocking morphology. Compared to existing unidirectional interlocking structures, this design achieves stress transmission and deformation constraint in multiple directions, significantly improving structural stability and mechanical properties.

[0025] Furthermore, the prepared biomimetic interlocking heterogeneous titanium alloy has a tensile strength ≥1300 MPa and an elongation after fracture ≥15%; these performance indicators are significantly better than existing single titanium alloys and simple layered titanium alloys, and can fully meet the requirements of high load environments.

[0026] The superior performance of the biomimetic interlocking heterogeneous titanium alloy prepared by this invention stems from a multi-faceted synergistic strengthening mechanism: on the one hand, the unique biomimetic interlocking heterogeneity can effectively suppress interlayer slip and early localized deformation, delaying the occurrence of material necking and instability; on the other hand, the mechanical heterogeneity of the TC4 hard layer and the TC18 soft layer induces a significant strain gradient, which promotes the generation of a large number of geometrically necessary dislocations near the interface and forms a long-range internal stress field. The soft layer is strengthened by back stress, and the deformation capacity of the hard layer is optimized by forward stress, ultimately achieving a synergistic effect of heterogeneous deformation strengthening and mechanical interlocking strengthening.

[0027] The above-described technical solution of the present invention has the following beneficial effects:

[0028] 1. The titanium alloy prepared by this invention achieves a significant leap in mechanical properties under the dual effects of biomimetic interlocking heterogeneity and material synergistic strengthening. Its tensile strength is ≥1300 MPa and elongation after fracture is ≥15%. Compared with single TC4 titanium alloy (tensile strength 1100 MPa, elongation after fracture 5%), single TC18 titanium alloy (tensile strength 800 MPa, elongation after fracture 18%), and simple layered TC4 / TC18 titanium alloy (tensile strength 1250 MPa, elongation after fracture 13%), it successfully achieves a simultaneous breakthrough in strength and plasticity.

[0029] 2. The process parameters of this invention have been systematically optimized, exhibiting good repeatability and stability, ensuring product consistency during mass production. The laser-directed energy deposition technology employed is easy to integrate with automated equipment, has a wide range of applications, and allows for flexible adjustment of deposition size and cycle count according to actual needs, adapting to the application requirements of different scenarios. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the deposition sequence for preparing the biomimetic interlocking heterogeneous TC4 / TC18 titanium alloy in Example 1.

[0031] Figure 2 The diagram shows the interlocking structure of the elytra of an iron beetle (left) and the biomimetic interlocking heterostructure of the TC4 / TC18 titanium alloy of this invention (right).

[0032] Figure 3 The image shows the contrast of the biomimetic interlocking heterogeneous TC4 / TC18 titanium alloy prepared in Example 1 under backscattering mode in a scanning electron microscope.

[0033] Figure 4 A schematic diagram of the deposition sequence for preparing TC4 titanium alloy for Comparative Example 1.

[0034] Figure 5 A schematic diagram of the deposition sequence for preparing layered TC4 / TC18 titanium alloy for Comparative Example 3.

[0035] Figure 6 The engineering stress-strain curves are shown for the biomimetic interlocking heterogeneous TC4 / TC18 titanium alloy prepared in Example 1, the TC4 titanium alloy prepared in Comparative Example 1, the TC18 titanium alloy prepared in Comparative Example 2, and the layered TC4 / TC18 titanium alloy prepared in Comparative Example 3. Detailed Implementation

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0037] This invention provides a method for preparing biomimetic interlocking heterogeneous titanium alloys based on laser-directed energy deposition technology, comprising the following steps:

[0038] Using laser-directed energy deposition technology, two types of titanium alloy powders were alternately deposited on a titanium alloy substrate according to a preset scanning strategy to construct a biomimetic interlocking heterogeneous structure; the two types of titanium alloy powders were TC4 titanium alloy powder and TC18 titanium alloy powder.

[0039] The preset scanning strategy is as follows: The first layer deposits a first type of titanium alloy powder using a unidirectional scanning method with a channel spacing of 1.0-1.6 mm; the second layer rotates 90° clockwise and uses a unidirectional scanning method, first depositing a second type of titanium alloy powder with a channel spacing of 2.2-3.0 mm, then depositing the first type of titanium alloy powder with a channel spacing of 1.0-1.6 mm and a channel spacing of 2.2-3.0 mm; the third layer rotates 90° counterclockwise and uses a unidirectional scanning method, depositing the second type of titanium alloy powder with a channel spacing of 1.0-1.6 mm; the fourth layer rotates 90° clockwise and uses a unidirectional scanning method, first depositing the first type of titanium alloy powder with a channel spacing of 2.2-3.0 mm, then depositing the second type of titanium alloy powder with a channel spacing of 1.0-1.6 mm and a channel spacing of 2.2-3.0 mm. mm; the four layers are used as a cycle for repeated deposition, and the total number of titanium alloy powder deposited in each layer is the same, and the length of each deposition channel is the same.

[0040] The hard TC4 layer is mainly composed of acicular martensite α′ phase, with an average hardness of 375 HV; the soft TC18 layer is rich in β phase, with an average hardness of 290 HV. The interlayer interface formed by the two materials acts as a key bridge, stimulating strong microscale strain incompatibility, which in turn triggers a series of multi-scale synergistic strengthening effects. Under external load, plastic deformation occurs first in the softer TC18 layer, while the deformation of the hard TC4 layer is delayed, resulting in a significant strain gradient on both sides of the same interface. To coordinate this non-uniform deformation and maintain the overall continuity of the material, a large number of geometrically necessary dislocations (GNDs) are continuously generated and accumulated near the interface, eventually forming a high-density dislocation entanglement region. These GNDs are not only the direct carriers of microscopic strain gradients, but also the core source of long-range internal stress. They generate strong back stress, which acts in the opposite direction on the soft TC18 phase, effectively hindering the further movement of dislocations within it and achieving "hardening" of the soft phase. At the same time, the plastic flow of the soft phase generates positive stress on the hard phase, promoting the initiation and proliferation of dislocations in the TC4 hard phase and optimizing its deformation capacity. This back stress and positive stress, generated by the heterogeneous interface and in opposite directions, together constitute an endogenous heterogeneous deformation-induced stress field. This is the core physical essence of the material's additional strengthening, and the increase in macroscopic hardness is a direct manifestation of the significant strengthening effect of this stress field on the soft TC18 phase.

[0041] The biomimetic interlocking heterostructure designed in this invention not only achieves heterogeneous deformation strengthening through the heterogeneous deformation between different materials, but also introduces a mechanical interlocking effect under tensile load, thereby significantly improving the overall toughness and bonding strength of the interface. This structure can effectively restrict the relative movement of materials under tensile stress, while preventing interface cracking, ensuring that the titanium alloy achieves high strength without a significant decrease in plasticity, ultimately achieving a comprehensive improvement in the overall mechanical properties of the titanium alloy.

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0043] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0044] In the following examples, both TC4 and TC18 titanium alloy powders were prepared by gas atomization, and the powders were spherical with a particle size of 53-105 μm. Both TC4 and TC18 titanium alloy powders were dried in a high-temperature oven at 120 °C for 120 min to completely remove moisture adsorbed from the air.

[0045] In the following examples, given that titanium in titanium alloy powder has high chemical reactivity and is prone to oxidation reaction with oxygen in the air, which affects product performance, argon was used as a protective gas, powder delivery gas and collimation gas throughout the experiment to create an inert atmosphere, effectively isolate the sample from air and prevent oxidation during the preparation process.

[0046] Example 1

[0047] This invention provides a method for preparing biomimetic interlocking heterogeneous TC4 / TC18 titanium alloy based on laser-directed energy deposition technology, comprising the following steps:

[0048] (1) The TA2 titanium alloy substrate is subjected to sandblasting and anhydrous ethanol cleaning in sequence: Sandblasting can remove impurities such as oxide scale and oil stains on the substrate surface, and at the same time increase the surface roughness of the substrate, thereby improving its absorption rate of laser; Anhydrous ethanol cleaning can further remove residual impurities, avoid impurities from interfering with the subsequent deposition process and product quality, and ensure the bonding effect between the deposited layer and the substrate.

[0049] (2) First, start the KUKA robotic arm control center, laser, water cooling system and other related equipment. After the equipment is running stably, load the dried TC4 titanium alloy powder and TC18 titanium alloy powder into the corresponding powder feeding devices, and set the powder feeding rate to 1.5 g / min. After focusing and positioning on the TA2 titanium alloy substrate surface by using red guide light, turn on the powder feeding device, protective gas and collimation gas, and run the KUKA robotic arm's preset control program simultaneously to construct the biomimetic interlocking heterogeneous titanium alloy according to the following deposition sequence:

[0050] The first layer is deposited with TC18 titanium alloy powder using a unidirectional scanning method, with a total of 19 deposited layers, a layer spacing of 1.3 mm, and a layer length of 48 mm.

[0051] The second layer is scanned 90° clockwise using a unidirectional scanning method. First, TC4 titanium alloy powder is deposited with a lane spacing of 2.6 mm, for a total of 10 lanes, with a lane length of 48 mm. Then, TC18 titanium alloy powder is deposited with a spacing of 1.3 mm between it and the first TC4 titanium alloy powder lane, and 9 more lanes are deposited with a lane spacing of 2.6 mm and a lane length of 48 mm.

[0052] The third layer is scanned 90° counterclockwise and uses a unidirectional scanning method to deposit TC4 titanium alloy powder. There are 19 passes in total, with a pass spacing of 1.3 mm and a pass length of 48 mm.

[0053] The fourth layer is scanned 90° clockwise and uses a unidirectional scanning method. First, TC18 titanium alloy powder is deposited with a channel spacing of 2.6 mm, 10 channels are deposited, and the channel length is 48 mm. Then, TC4 titanium alloy powder is deposited with a spacing of 1.3 mm between it and the first channel of TC18 titanium alloy powder. Subsequently, 9 channels are deposited with a channel spacing of 2.6 mm and a channel length of 48 mm.

[0054] The above four layers constitute a complete sedimentary cycle, and the sedimentation sequence is as follows: Figure 1 As shown, deposition was performed cyclically. Seven cycles were conducted, resulting in a total of 28 layers, with a sample height of 14 mm. The processing parameters for the entire preparation process were set as follows: laser power 900 W, scanning speed 4 mm / s, defocusing amount -1 mm, and lifting amount 0.5 mm. After the control program was completed, a biomimetic interlocking heterogeneous titanium alloy was obtained.

[0055] The schematic diagram of the interlocking structure of the beetle elytra and the schematic diagram of the biomimetic interlocking heterostructure of the TC4 / TC18 titanium alloy of this invention are shown below. Figure 2 As shown, the left figure illustrates the microstructure of the elytra of a beetle (scale bar is 100 μm), where its naturally formed interlocking texture exhibits a typical multi-scale interlocking morphology; the right figure is a schematic diagram of the biomimetic interlocking heterostructure of the TC4 / TC18 titanium alloy of this invention. By simulating the interlocking principle of the beetle's elytra, hard TC4 and soft TC18 are arranged alternately in an interlocking manner to form an interlayer / channel interlocking structure similar to the texture of the elytra. This realizes the functional biomimicry of natural biological structures into artificial titanium alloy materials, providing structural support for improving the strength-plasticity synergy of titanium alloys.

[0056] The contrast image of the biomimetic interlocked isomeric TC4 / TC18 titanium alloy prepared in Example 1 under scanning electron microscopy backscatter mode is shown below. Figure 3 As shown in the figure, different gray areas correspond to TC4 and TC18 respectively. Through the contrast difference, it can be clearly observed that the two materials are arranged in an interlocking form, forming a continuous interlocking structure in both the horizontal and vertical directions. This intuitively presents the biomimetic interlocking heteromorphic morphology designed in this invention, verifies the effective replication of the interlocking structure of the beetle elytra by the preparation process, and also reflects the precise matching and tight combination between layers and channels.

[0057] Comparative Example 1

[0058] This invention provides a method for preparing TC4 titanium alloy based on laser-directed energy deposition technology, comprising the following steps:

[0059] (1) The TA2 titanium alloy substrate is subjected to sandblasting and anhydrous ethanol cleaning in sequence: Sandblasting can remove impurities such as oxide scale and oil stains on the substrate surface, and at the same time increase the surface roughness of the substrate, thereby improving its absorption rate of laser; Anhydrous ethanol cleaning can further remove residual impurities, avoid impurities from interfering with the subsequent deposition process and product quality, and ensure the bonding effect between the deposited layer and the substrate.

[0060] (2) First, start the KUKA robotic arm control center, laser, water cooling system and other related equipment. After the equipment is running stably, load the dried TC4 titanium alloy powder into the powder feeding device and set the powder feeding rate to 1.5 g / min. After the red guide light completes the focusing and positioning on the substrate surface, turn on the powder feeding device, protective gas and collimation gas, and run the KUKA robotic arm's preset control program simultaneously. During the deposition process, the first layer adopts a unidirectional scanning method, depositing 19 passes with a pass spacing of 1.3 mm and a pass length of 48 mm; the second layer rotates 90° clockwise and adopts a unidirectional scanning method, depositing 19 passes with a pass spacing of 1.3 mm and a pass length of 48 mm; these two layers constitute one deposition cycle, and the deposition sequence is as follows. Figure 4 As shown, the printing process was repeated cyclically. 14 cycles were performed, resulting in a total of 28 layers, with a sample height of 14 mm. The processing parameters for the entire fabrication process were set as follows: laser power 900 W, scanning speed 4 mm / s, defocusing amount -1 mm, and lifting amount 0.5 mm. After the control program completed its operation, a TC4 titanium alloy block was obtained.

[0061] Comparative Example 2

[0062] This invention provides a method for preparing TC18 titanium alloy based on laser-directed energy deposition technology, comprising the following steps:

[0063] (1) The TA2 titanium alloy substrate is subjected to sandblasting and anhydrous ethanol cleaning in sequence: Sandblasting can remove impurities such as oxide scale and oil stains on the substrate surface, and at the same time increase the surface roughness of the substrate, thereby improving its absorption rate of laser; Anhydrous ethanol cleaning can further remove residual impurities, avoid impurities from interfering with the subsequent deposition process and product quality, and ensure the bonding effect between the deposited layer and the substrate.

[0064] (2) First, start the KUKA robotic arm control center, laser, water cooling system and other related equipment. After the equipment is running stably, load the dried TC18 titanium alloy powder into the powder feeding device and set the powder feeding rate to 1.5 g / min. After focusing and positioning on the substrate surface with red guide light, turn on the powder feeding device, protective gas and collimation gas, and run the KUKA robotic arm's preset control program simultaneously. During the deposition process, the first layer adopts a unidirectional scanning method, depositing 19 channels with a channel spacing of 1.3 mm and a channel length of 48 mm. The second layer rotates 90° clockwise and adopts a unidirectional scanning method, depositing 19 channels with a channel spacing of 1.3 mm and a channel length of 48 mm. These two layers constitute one deposition cycle, and the printing is repeated. 14 cycles are performed, for a total of 28 layers, and the sample height is 14 mm. The processing parameters for the entire preparation process were set as follows: laser power 900 W, scanning speed 4 mm / s, defocusing amount -1 mm, and lifting amount 0.5 mm. After the control program was completed, a TC18 titanium alloy block was obtained.

[0065] Comparative Example 3

[0066] This invention provides a method for preparing layered TC4 / TC18 titanium alloy based on laser-directed energy deposition technology, comprising the following steps:

[0067] (1) The TA2 titanium alloy substrate is subjected to sandblasting and anhydrous ethanol cleaning in sequence: Sandblasting can remove impurities such as oxide scale and oil stains on the substrate surface, and at the same time increase the surface roughness of the substrate, thereby improving its absorption rate of laser; Anhydrous ethanol cleaning can further remove residual impurities, avoid impurities from interfering with the subsequent deposition process and product quality, and ensure the bonding effect between the deposited layer and the substrate.

[0068] (2) First, start the KUKA robotic arm control center, laser, water cooling system and other related equipment. After the equipment is running stably, load the dried TC4 titanium alloy powder and TC18 titanium alloy powder into the corresponding powder feeding devices, and set the powder feeding rate to 1.5 g / min. After focusing and positioning on the TA2 titanium alloy substrate surface by using red guide light, turn on the powder feeding device, protective gas and collimation gas, and run the KUKA robotic arm's preset control program simultaneously to build a layered titanium alloy structure according to the following deposition sequence:

[0069] The first layer is deposited with TC18 titanium alloy powder using a unidirectional scanning method, with a total of 19 deposited layers, a layer spacing of 1.3 mm, and a layer length of 48 mm.

[0070] The second layer is scanned 90° clockwise and uses a unidirectional scanning method to deposit TC4 titanium alloy powder. A total of 19 passes are deposited, with a pass spacing of 1.3 mm and a pass length of 48 mm.

[0071] The two layers described above constitute a complete sedimentary cycle, and the sedimentation sequence is as follows: Figure 5 As shown, deposition was performed cyclically. Fourteen cycles were conducted, resulting in a total of 28 layers, with a sample height of 14 mm. The processing parameters for the entire preparation process were set as follows: laser power 900 W, scanning speed 4 mm / s, defocusing amount -1 mm, and lifting amount 0.5 mm. After the control program completed its operation, a layered TC4 / TC18 titanium alloy structure was obtained.

[0072] Test case

[0073] Mechanical properties were tested on the biomimetic interlocking heterogeneous TC4 / TC18 titanium alloy prepared in Example 1, the TC4 titanium alloy prepared in Comparative Example 1, the TC18 titanium alloy prepared in Comparative Example 2, and the layered TC4 / TC18 titanium alloy prepared in Comparative Example 3. The testing method was as follows: uniaxial tensile tests were conducted on the titanium alloys at room temperature (20 ℃) ​​using a KPL Focal 100U2 mechanical testing machine. The tensile rate was 0.72 mm / min, and the strain was measured using an extensometer to obtain the tensile strength and elongation after fracture, among other mechanical property parameters. Three specimens were tested under each condition, and the average value was taken. The tensile dimensions of the specimens were 40 mm × 12 mm × 1.5 mm, with a gauge length of 12 mm and a width of 4 mm in the middle section.

[0074] Test results are as follows Figure 6 As shown, the TC4 titanium alloy in Comparative Example 1 has high strength but weak plastic deformation capacity, and the curve quickly enters the descending segment; the TC18 titanium alloy in Comparative Example 2 has good plasticity but low strength; although the performance of the layered TC4 / TC18 titanium alloy in Comparative Example 3 is improved compared with the single material, the synergy between strength and plasticity is limited; while the curve of the biomimetic interlocking heterogeneous TC4 / TC18 titanium alloy in Example 1 not only shows a higher strength plateau, but also maintains a high stress level in the high deformation range where the engineering strain is close to 0.10, demonstrating the synergistic advantage of high strength and high plasticity, and verifying the optimization effect of the biomimetic interlocking structure on the comprehensive mechanical properties of titanium alloy.

[0075] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing biomimetic interlocking heterogeneous titanium alloys based on laser-directed energy deposition technology, characterized in that, Includes the following steps: Using laser-directed energy deposition technology, two types of titanium alloy powders were alternately deposited on a titanium alloy substrate according to a preset scanning strategy to construct a biomimetic interlocking heterogeneous structure; the two types of titanium alloy powders were TC4 titanium alloy powder and TC18 titanium alloy powder. The preset scanning strategy is as follows: The first layer deposits a first type of titanium alloy powder using a unidirectional scanning method with a channel spacing of 1.0-1.6 mm; the second layer rotates 90° clockwise and uses a unidirectional scanning method, first depositing a second type of titanium alloy powder with a channel spacing of 2.2-3.0 mm, then depositing the first type of titanium alloy powder with a channel spacing of 1.0-1.6 mm and a channel spacing of 2.2-3.0 mm; the third layer rotates 90° counterclockwise and uses a unidirectional scanning method, depositing the second type of titanium alloy powder with a channel spacing of 1.0-1.6 mm; the fourth layer rotates 90° clockwise and uses a unidirectional scanning method, first depositing the first type of titanium alloy powder with a channel spacing of 2.2-3.0 mm, then depositing the second type of titanium alloy powder with a channel spacing of 1.0-1.6 mm and a channel spacing of 2.2-3.0 mm. mm; the four layers are used as a cycle for repeated deposition, and the total number of titanium alloy powder deposited in each layer is the same, and the length of each deposition channel is the same.

2. The method according to claim 1, characterized in that, The process parameters of the directional energy deposition technology are: laser power 800-1200 W, scanning speed 3-6 mm / s, defocusing amount -2.5 mm to -0.5 mm, powder feed rate 1.2-1.8 g / min, and lifting amount 0.4-0.6 mm.

3. The method according to claim 1, characterized in that, The process prior to deposition also includes a surface pretreatment step for the titanium alloy substrate; the surface pretreatment includes sandblasting and anhydrous ethanol cleaning.

4. The method according to claim 1, characterized in that, The titanium alloy substrate is a TA2 titanium alloy substrate.

5. The method according to claim 1, characterized in that, The process also includes a baking step for the two titanium alloy powders before deposition.

6. The method according to claim 5, characterized in that, The powder drying process is carried out at a temperature of 100-140 ℃ and a holding time of 1.5-2.5 h.

7. The method according to claim 1, characterized in that, The particle size of the TC4 titanium alloy powder is 53-105 μm, and the particle size of the TC18 titanium alloy powder is 53-105 μm.

8. The method according to claim 1, characterized in that, Both the TC4 titanium alloy powder and the TC18 titanium alloy powder are prepared by gas atomization, and the powder geometry is spherical.

9. The method according to claim 1, characterized in that, The biomimetic interlocking heterogeneity is a fish-scale-shaped interlocking unit designed based on the interlocking structure of the elytra of a beetle.

10. The method according to claim 1, characterized in that, The prepared biomimetic interlocking heterogeneous titanium alloy has a tensile strength ≥1300 MPa and an elongation after fracture ≥15%.

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