Ceramic-reinforced bi-graded composite material based on laser melting deposition and method for manufacturing thereof

Abstract

The application provides a preparation method of a ceramic-reinforced double-gradient composite material based on laser melting deposition, mixed powder is sent through a multi-cylinder powder feeder and additive manufacturing is carried out in a protective atmosphere environment, and the printing process comprises the following processes: printing deposition is carried out in a layer-by-layer growth manner; wherein from the first layer to the nth layer, the particle size of ceramic particles in the mixed powder used for printing between layers changes in a multi-stage gradient from microns to nanometers; between adjacent layers, the particle size of ceramic particles in the mixed powder used for the lower layer is greater than or equal to the particle size of ceramic particles in the mixed powder used for the upper layer; when the particle size of ceramic particles in the mixed powder used for printing between layers is the same, the mass proportion of ceramic particles in the mixed powder changes in a continuous gradient; the above printing process is repeated until a workpiece is obtained; through the change of composition and the change of mismatch degree between layers, the continuous organization and the gradient change of the composition of the material are realized, and the double-gradient composite reinforcement of the material is realized.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and more specifically to a ceramic-reinforced dual-gradient composite material based on laser melting deposition and its preparation method. Background Technology

[0002] In the 1980s, Japanese scholars Masayuki Niino and others proposed the concept of Functionally Gradient Materials (FGMs). These materials achieve gradient changes in properties and functions through continuous variations in composition, structure, physical properties, and chemical properties, adapting to the demands of different service environments. With the development of science and technology, gradient materials and their unique properties have broad application prospects in various fields.

[0003] There are many methods for preparing gradient materials, including traditional methods such as centrifugal casting, powder pressing and sintering, and vapor deposition, all of which have certain limitations. Additive manufacturing (AM) builds solid parts by layering powder or filaments based on a three-dimensional model, effectively overcoming structural and material limitations. It boasts a short design-development-manufacturing cycle and saves on mold costs, earning it the reputation of a future "transformative" technology. Organically combining additive manufacturing with functional gradient design is of great significance for improving structural performance.

[0004] Currently, most laser additive manufacturing technologies applied to graded materials can only produce single-grade functional materials and structures with multiple material components, or structures with homogeneous properties and single-gradient variations. For example, Chinese patent CN104190930A discloses a laser additive manufacturing method for homogeneous functionally graded materials and structures. This method maps different functions to different temperatures, applies different temperatures as boundary conditions to different parts of a 3D model, calculates the heat conduction equation of the model using the 3D finite element method to obtain the internal temperature gradient distribution, extracts and slices the surface set to obtain a scanning path with gradient laser parameters, and inputs this path into a laser 3D printer to additively manufacture a homogeneous functionally graded structure. However, this method can only calculate the temperature field of homogeneous materials. Since heterogeneous materials have different functional temperatures, temperature cannot be used as a boundary condition, limiting the application of dissimilar metal functionally graded materials.

[0005] Chinese patent CN109590472A discloses a gradient material printing method based on coaxial powder feeding. The method sets process parameters according to the requirements of the part to be formed, including the number of powder feeders, the powder ratio for each slice layer and different regions within each slice layer, scanning speed, laser power, and spot diameter. This allows for the customization of the gradient material's composition distribution as required, and the mixing of different materials within the same structure to print complex-shaped gradient materials. However, the gradient materials printed using this method still require subsequent annealing to release thermal stress and increase material ductility and toughness, thus failing to fully control performance.

[0006] Therefore, it is of great significance to find a laser additive manufacturing method with dual gradient changes in both structure and composition. Summary of the Invention

[0007] The purpose of this invention is to address the current limitations of additive manufacturing, which can only produce multi-component gradient functional materials and structures or homogeneous structures with gradually changing properties. This invention proposes a ceramic-reinforced dual-gradient composite material based on laser melting deposition and its preparation method. By adding ceramic reinforcing particles to the alloy and changing the composition and mismatch degree layer by layer, the continuous microstructure and gradient composition of the ceramic-reinforced composite material are achieved, thereby realizing dual-gradient composite reinforcement of additively manufactured functionally gradient materials.

[0008] The first aspect of this invention relates to a method for preparing a ceramic-reinforced dual-gradient composite material based on laser melting deposition, comprising:

[0009] Alloy powder is mixed with ceramic particles of different particle sizes to obtain multi-level mismatched mixed powder; wherein the particle size of the ceramic particles varies in a multi-level gradient, and in mixed powders with ceramic particles of the same particle size, the mass proportion of ceramic particles in the mixed powder varies in a continuous gradient.

[0010] The mixed powder is fed through a multi-tube powder feeder and additively manufactured in a protective atmosphere. The printing process includes the following steps:

[0011] The printing deposition of each layer is completed by growing layer by layer, with each layer corresponding to a preset laser power and scanning spacing.

[0012] Among them, from the first layer to the nth layer, the particle size of the ceramic particles in the mixed powder used for printing between layers varies in multiple levels from micrometers to nanometers; between adjacent layers, the particle size of the ceramic particles in the mixed powder used in the lower layer is greater than or equal to the particle size of the ceramic particles in the mixed powder used in the upper layer.

[0013] When the ceramic particles in the mixed powder used for printing between layers have the same particle size, the mass proportion of ceramic particles in the mixed powder changes in a continuous gradient.

[0014] Repeat the above layer-by-layer growth printing process until the workpiece is printed and a shaped part is obtained.

[0015] In an optional embodiment, the ceramic particles account for 0–5 wt.% of the mass percentage in the mixed powder.

[0016] In an optional embodiment, the particle size range of the ceramic particles of different particle size grades is 1-100 μm grade powder and 1-50 nm grade powder.

[0017] In an optional implementation, the particle size range is used to apply the printing deposition to complete the first to nth layers respectively.

[0018] In an optional embodiment, the alloy powder is a Ti-6Al-4V titanium alloy with an average particle size of 53-150 μm.

[0019] In an optional implementation, during the printing deposition process of the first to nth layers, the laser power and scanning spacing are set according to the type of ceramic reinforcing phase and alloy.

[0020] The second aspect of the present invention relates to a ceramic-reinforced dual-gradient composite material prepared by the aforementioned method.

[0021] In an optional embodiment, the ceramic-reinforced dual-gradient composite material is formed by printing layers 1 to n, corresponding to the formation of multiple micron-scale mixed powder layers and multiple nano-scale powder layers, wherein the grain size of the multiple micron-scale mixed powder layers and multiple nano-scale powder layers decreases layer by layer.

[0022] A third aspect of the present invention relates to an aircraft landing gear using the aforementioned ceramic-reinforced dual-gradient composite material.

[0023] As can be seen from the above technical solutions of the present invention, the method for preparing ceramic-reinforced dual-gradient composite materials based on laser melting deposition proposed in this invention introduces ceramic particles and designs the particle size mismatch and mixing ratio of ceramic particles and alloy powder. By adopting the idea of ​​additive manufacturing layer by layer, and through layer-by-layer composition changes and particle size mismatch changes, the continuous microstructure and gradient controllable changes of the composition of the ceramic-reinforced composite material are achieved, thereby realizing dual-gradient composite reinforcement of additively manufactured functionally graded materials.

[0024] Different amounts of ceramic reinforcing particles increase the number of nucleation sites during laser melting deposition solidification. The more nucleation sites there are, the higher the nucleation efficiency of the alloy material and the more obvious the finer grain formation. However, too many ceramic reinforcing particles can increase the brittleness of the material. Therefore, this invention introduces ceramic reinforcing particle components with different particle sizes to achieve a mismatch between the particle size of the ceramic reinforcing particles and the metal powder in micron-sized ceramic-reinforced-micron-metal powder and nano-sized ceramic-reinforced-micron-metal powder. The smaller the ceramic reinforcing particles, the better their contact with the metal powder surface. Combined with the continuous gradient change in the content of ceramic reinforcing particles, the more ceramic reinforcing particles there are, the more nucleation sites there will be during alloy solidification, ultimately leading to a finer grain formation of the ceramic-reinforced-micron-metal powder. By controlling the ceramic reinforcing particle components and the particle size of the ceramic particles, the microstructure and composition can be controlled by a dual gradient. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the toner feeding and printing system provided in an embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of the microstructure of the ceramic-reinforced dual-gradient composite material provided in the embodiments of the present invention.

[0027] Figure 3 This is a microstructure diagram of the ceramic-reinforced dual-gradient composite material obtained in Example 1 of the present invention.

[0028] Figure 4 This is a microstructure diagram of the material obtained in Comparative Example 1 of this invention.

[0029] Figure 5 This is a microstructure diagram of the material obtained in Comparative Example 2 of this invention. Detailed Implementation

[0030] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0031] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described below in more detail, can be implemented in any of a number of ways.

[0032] Additive manufacturing has many bottlenecks in metallurgical structure, such as uneven structure, columnar crystal structure, and significant defects such as thermal deformation cracking. The addition of ceramic reinforcing particles can promote the generation of non-spontaneous nucleation and refine the grains.

[0033] Based on this, the present invention proposes a method for achieving dual gradient changes in the microstructure and composition of ceramic reinforced composite materials based on laser melting deposition. By continuously varying the content of ceramic reinforcing particles, a dual continuous gradient structure is constructed by mismatching the particle sizes of ceramic reinforcing particles of different sizes with those of metal powder, thereby achieving dual continuous gradient changes in microstructure and composition.

[0034] The microstructure-composition dual gradient refers to the gradient of grain size in the microstructure, such as the gradient change of columnar crystals, coarse crystals, equiaxed crystals, and fine crystals, which is a primary gradient; and the different contents of ceramic reinforcing phase components with different particle sizes in composite materials, where the particle size of the ceramic reinforcing phase shows a gradient from micrometers to nanometers in the mixed powder, for example, starting from 100 μm, decreasing sequentially to 50 μm, 10 μm, 100 nm, 50 nm, and 10 nm, and under the same particle size conditions, the mass proportion of the ceramic reinforcing phase shows a continuous gradient change, which is a secondary gradient.

[0035] The proportion of ceramic particles affects the composition and nucleation efficiency of composite materials, thereby affecting their additive manufacturing metallurgical structure. Therefore, we establish the variation law of microstructure gradient and composition gradient under the coupling effect between the proportion of micro / nano ceramic particles and ceramic mismatch characteristics, and establish the correlation among the three.

[0036] An embodiment of the present invention provides a method for preparing ceramic-reinforced dual-gradient composite materials based on laser melting deposition, comprising:

[0037] Alloy powder is mixed with ceramic particles of different particle sizes to obtain multi-level mismatched mixed powder; wherein the particle size of the ceramic particles varies in a multi-level gradient, and in mixed powders with ceramic particles of the same particle size, the mass proportion of ceramic particles in the mixed powder varies in a continuous gradient.

[0038] The mixed powder is fed through a multi-tube powder feeder and additively manufactured in a protective atmosphere. The printing process includes the following steps:

[0039] The printing deposition of each layer is completed by growing layer by layer, with each layer corresponding to a preset laser power and scanning spacing.

[0040] Among them, from the first layer to the nth layer, the particle size of the ceramic particles in the mixed powder used for printing between layers varies in multiple levels from micrometers to nanometers; between adjacent layers, the particle size of the ceramic particles in the mixed powder used in the lower layer is greater than or equal to the particle size of the ceramic particles in the mixed powder used in the upper layer.

[0041] When the ceramic particles in the mixed powder used for printing between layers have the same particle size, the mass proportion of ceramic particles in the mixed powder changes in a continuous gradient.

[0042] Repeat the above layer-by-layer growth printing process until the workpiece is printed and a shaped part is obtained.

[0043] In an optional embodiment, the ceramic particles account for 0–5 wt.% of the mass percentage in the mixed powder.

[0044] In an optional embodiment, the particle size range of the ceramic particles of different particle size grades is 1-100 μm grade powder and 1-50 nm grade powder.

[0045] In an optional implementation, the particle size range is used to apply the printing deposition to complete the first to nth layers respectively.

[0046] In an optional embodiment, the alloy powder is a Ti-6Al-4V titanium alloy with an average particle size of 53-150 μm.

[0047] In an optional implementation, during the printing deposition process of the first to nth layers, the laser power and scanning spacing are set according to the type of ceramic reinforcing phase and alloy.

[0048] In another exemplary embodiment of the present invention, a ceramic-reinforced dual-gradient composite material prepared by the aforementioned method is provided.

[0049] In an optional embodiment, the ceramic-reinforced dual-gradient composite material is formed by printing layers 1 to n, corresponding to the formation of multiple micron-scale mixed powder layers and multiple nano-scale powder layers, wherein the grain size of the multiple micron-scale mixed powder layers and multiple nano-scale powder layers decreases layer by layer.

[0050] In another exemplary embodiment of the present invention, an aircraft landing gear using the aforementioned ceramic-reinforced dual-gradient composite material is also provided. Aircraft landing gear is subjected to extreme temperatures, high stresses, extreme frictional damage, drastic temperature changes, and dynamic loading. The functionally graded composite material of the present invention can meet the requirements for withstanding ultra-high temperatures, high-temperature impacts, high-temperature fatigue, and providing thermal stress mitigation and sound absorption.

[0051] In an exemplary embodiment of the present invention, a mixed powder of Ti-6Al-4V titanium alloy (particle size 53-150μm) and B4C particles of different sizes and proportions is proposed, wherein the B4C particles include nano-sized powder (50nm) and micro-sized powder (100μm); under the same particle size conditions, the mass percentage of B4C particles in the mixed powder is 3wt.% and 5wt.% respectively.

[0052] like Figure 1The system shown for preparing ceramic-reinforced dual-gradient composite materials, during the printing process, uses a 5-cylinder powder feeder 1 to mix B4C particles of different sizes and proportions with titanium alloy powder, and then feeds the powder into the printing process according to a predetermined sequence. This allows for the printing of a layered structure without changing the powder. The printed titanium alloy microstructure is shown in the figure. Figure 2 As shown, the grain size increases gradually from bottom to top.

[0053] Figure 1 In the diagram, number 2 represents the mixed powder, and number 3 represents the molten pool.

[0054] Based on the above description, in Figure 1 Based on the system shown, the exemplary printing process of titanium alloys by additive manufacturing using powders of different particle sizes and proportions is as follows:

[0055] Example 1

[0056] (1) B4C powders of different proportions (50nm, 100μm) were mixed with TC4 powders of 53-150μm to prepare (a) 3wt.% 100μm B4C-TC4, (b) 5wt.% 100μm B4C-TC4, (c) 3wt.% 50nm B4C-TC4, and (d) 5wt.% 50nm B4C-TC4 mixed powders. The powders were placed in a vacuum drying oven and dried for 4 hours. After drying, they were placed in a powder mixer and mixed thoroughly for 8 hours. The four mixed powders (a, b, c, and d) were placed in the four powder feeding buckets of the powder feeder. At the same time, the powder feeding process was set up, and argon gas was introduced for atmosphere protection while the powder was being fed.

[0057] (2) Use the four B4C-TC4 mixed powders (a)(b)(c)(d) in (1) to print additive manufacturing components, establish a three-dimensional model of the part, perform layer slicing on the three-dimensional model, set the printing program of the four slices to correspond to the four different mixed powders, ensure that the powder feeding amount of the powder feeding equipment is 8.0g / min, and control the oxygen content below 200ppm.

[0058] The LMD laser power is 1500W, the scanning speed is 10mm / s, the scanning spacing is 1.6mm, the printing layer thickness is 0.5mm, and the printed part has dimensions of 30mm×30mm×16mm.

[0059] The first layer was printed as (a) a 3wt.% 100μm B4C-TC4 mixed powder layer;

[0060] The second layer is (b) a 5wt.% 100μm B4C-TC4 mixed powder layer;

[0061] The third layer is a 3wt.% 50nm B4C-TC4 mixed powder layer;

[0062] The fourth layer is a (d) 5wt.% 50nm B4C-TC4 mixed powder layer;

[0063] The process of repeating abcdabcd… 8 times until printing is complete yields ceramic-reinforced composite material components with dual gradient changes in microstructure and composition.

[0064] (3) After the sealing and printing are completed, wait about 3 hours for the component to cool completely before opening the hatch and taking it out.

[0065] (4) Observe the microstructure of the component and measure its tensile and bending properties.

[0066] Example 2

[0067] (1) B4C powders (50nm, 100μm) with different proportions were mixed with TC4 powders of 53-150μm to prepare (a) 1wt.% 100μm B4C-TC4, (b) 3wt.% 100μm B4C-TC4, (c) 1wt.% 50nm B4C-TC4, and (d) 3wt.% 50nm B4C-TC4 mixed powders. The powders were dried in a vacuum drying oven for 4 hours. After drying, they were mixed thoroughly in a powder mixer for 8 hours. The four mixed powders (a, b, c, and d) were placed into the four powder feeding buckets of the powder feeder. At the same time, the powder feeding process was set up, and argon gas was introduced for atmosphere protection while the powder was being fed.

[0068] (2) Use the four B4C-TC4 mixed powders (a)(b)(c)(d) in (1) to print additive manufacturing components, establish a three-dimensional model of the part, perform layer slicing on the three-dimensional model, set the printing program of four slice layers corresponding to four different mixed powders, ensure that the powder feeding amount of the powder feeding equipment is 8.0g / min, and control the oxygen content below 200ppm.

[0069] The LMD laser power is 1500W, the scanning speed is 10mm / s, the scanning spacing is 1.6mm, the printing layer thickness is 0.5mm, and the printed part has dimensions of 30mm×30mm×16mm.

[0070] The first layer printed is (a) a 1 wt.% 100 μm B4C-TC4 mixed powder layer;

[0071] The second layer is (b) a 3wt.% 100μm B4C-TC4 mixed powder layer;

[0072] The third layer is (c) 1 wt.% 50 nm B4C-TC4 mixed powder layer;

[0073] The fourth layer is a (d) 3wt.% 50nm B4C-TC4 mixed powder layer;

[0074] The process of repeating abcdabcd… 8 times until printing is complete yields ceramic-reinforced composite material components with dual gradient changes in microstructure and composition.

[0075] (3) After the sealing and printing are completed, wait about 4 hours for the components to cool completely before opening the hatch and taking them out.

[0076] (4) Observe the microstructure of the component and measure its tensile and bending properties.

[0077] Example 3

[0078] (1) Mix 50nm, 10μm, 50μm, and 100μm B4C powder with 53-150μm TC4 powder to prepare (a) 1wt.% 100μm B4C-TC4, (b) 5wt.% 100μm B4C-TC4, (c) 1wt.% 50nm B4C-TC4, and (d) 5wt.% 50nm B4C-TC4. Place the powder in a vacuum drying oven and dry for 4 hours. After drying, place it in a powder mixer and mix thoroughly for 8 hours. Place the four mixed powders (a, b, c, and d) into the four powder feeding buckets of the powder feeder. At the same time, set up the powder feeding process and introduce argon gas for atmosphere protection while feeding the powder.

[0079] (2) Use the four B4C-TC4 mixed powders (a)(b)(c)(d) in (1) to print additive manufacturing components, establish a three-dimensional model of the part, perform layer slicing on the three-dimensional model, set the printing program of four slice layers corresponding to four different mixed powders, ensure that the powder feeding amount of the powder feeding equipment is 8.0g / min, and control the oxygen content below 200ppm.

[0080] The LMD laser power is 1500W, the scanning speed is 10mm / s, the scanning spacing is 1.6mm, the printing layer thickness is 0.5mm, and the printed part has dimensions of 30mm×30mm×16mm.

[0081] The first layer printed is (a) a 1 wt.% 100 μm B4C-TC4 mixed powder layer;

[0082] The second layer is (b) a 5wt.% 100μm B4C-TC4 mixed powder layer;

[0083] The third layer is (c) 1 wt.% 50 nm B4C-TC4 mixed powder layer;

[0084] The fourth layer is a (d) 5wt.% 50nm B4C-TC4 mixed powder layer;

[0085] The process of repeating abcdabcd… 8 times until printing is complete yields ceramic-reinforced composite material components with dual gradient changes in microstructure and composition.

[0086] (3) After the sealing and printing are completed, wait for the components to cool completely for about 3-4 hours before opening the hatch and taking them out.

[0087] (4) Observe the microstructure of the component and measure its tensile and bending properties.

[0088] Comparative Example 1

[0089] (1) Prepare B4C-TC4 mixed powder by mixing 3wt.% 50nm B4C powder with 53-150μm TC4 powder, and put the powder into a vacuum drying oven to dry for 4h. After drying, put it into a powder mixer to mix thoroughly for 8h. Put the mixed powder into the powder feeding bucket of the powder feeder, set the powder feeding process, and introduce argon gas for atmosphere protection while feeding the powder.

[0090] (2) Use B4C-TC4 mixed powder to print additive manufacturing components, establish a three-dimensional model of the part, perform layer slicing on the three-dimensional model, set the printing program of the slice layer, ensure that the powder feeding amount of the powder feeding equipment is 8.0g / min, the oxygen content is controlled below 200ppm, the laser power is 1500W, the scanning speed is 10mm / s, the scanning interval is 1.6mm, the printing layer thickness is 0.5mm, and print a part with a length, width and height of 30mm×30mm×16mm. Print 32 layers one by one until the printing is completed, and obtain a ceramic reinforced composite component without gradient change.

[0091] (3) After the sealing and printing are completed, wait about 3 hours for the component to cool completely before opening the hatch and taking it out.

[0092] (4) Observe the microstructure of the component and measure its tensile and bending properties.

[0093] Comparative Example 2

[0094] (1) Mix 100μm B4C powder with 53-150μm TC4 powder in different proportions to prepare (a) 1wt.% 100μm B4C-TC4, (b) 3wt.% 100μm B4C-TC4, and (c) 5wt.% 100μm B4C-TC4 mixed powders. Place the powders in a vacuum drying oven and dry for 4 hours. After drying, place them in a powder mixer and mix thoroughly for 8 hours. Place the three mixed powders (a, b, and c) into the three powder feeding buckets of the powder feeder. At the same time, set up the powder feeding process and introduce argon gas for atmosphere protection while feeding the powder.

[0095] (2) Use the three B4C-TC4 mixed powders (a), (b) and (c) in (1) to print additive manufacturing components, establish a three-dimensional model of the part, perform layer slicing on the three-dimensional model, set the printing program of four slice layers corresponding to three different mixed powders, ensure that the powder feeding amount of the powder feeding equipment is 8.0g / min, the powder feeding rate is 1.5RPm, and the oxygen content is controlled below 200ppm.

[0096] The LMD laser power is 1500W, the scanning speed is 10mm / s, the scanning pitch is 1.6mm, the printing layer thickness is 0.5mm, and the printed part is approximately 30mm×30mm×16mm in length, width and height.

[0097] The first layer printed is (a) a 1 wt.% 100 μm B4C-TC4 mixed powder layer;

[0098] The second layer is (b) a 3wt.% 100μm B4C-TC4 mixed powder layer;

[0099] The third layer is (c) a 5wt.% 100μm B4C-TC4 mixed powder layer;

[0100] The process of using abcabc… was repeated 11 times until printing was completed, resulting in a ceramic-reinforced composite component with a single-component gradient.

[0101] (3) After the sealing and printing are completed, wait about 4 hours for the components to cool completely before opening the hatch and taking them out.

[0102] (4) Observe the microstructure of the component and measure its tensile properties and other mechanical properties.

[0103] Comparative Example 3

[0104] (1) Mix 3 wt.% of B4C powder with different particle sizes and TC4 powder with 53-150 μm to prepare (a) 3 wt.% 100 μm B4C-TC4 and (b) 3 wt.% 50 nm B4C-TC4 mixed powders. Place the powders in a vacuum drying oven and dry for 4 h. After drying, place them in a powder mixer and mix thoroughly for 8 h. Place the two mixed powders a and b into two powder feeding buckets of the powder feeder. At the same time, set the powder feeding process and introduce argon gas for atmosphere protection while feeding the powder.

[0105] (2) Use the three B4C-TC4 mixed powders (a) and (b) in (1) to print additive manufacturing components, establish a three-dimensional model of the part, perform layer slicing on the three-dimensional model, set the printing program of four slice layers corresponding to three different mixed powders, ensure that the powder feeding amount of the powder feeding equipment is 8.0g / min, the powder feeding rate is 1.5RPm, and the oxygen content is controlled below 200ppm.

[0106] The LMD laser power is 1500W, the scanning speed is 10mm / s, the scanning spacing is 1.6mm, the printing layer thickness is 0.5mm, and the printed part has dimensions of 30mm×30mm×16mm.

[0107] The first layer was printed as (a) a 3wt.% 100μm B4C-TC4 mixed powder layer;

[0108] The second layer is (b) a 3wt.% 50nm B4C-TC4 mixed powder layer;

[0109] The abab… cycle was repeated 16 times until printing was completed, resulting in a ceramic-reinforced composite component with a single-component gradient.

[0110] (3) After the sealing and printing are completed, wait about 4 hours for the components to cool completely before opening the hatch and taking them out.

[0111] (4) Observe the microstructure of the component and measure its tensile properties and other mechanical properties.

[0112] Microstructure characterization

[0113] Microstructure characterization was performed on samples of the alloy components obtained in Example 1 and Comparative Examples 1-2. The metallographic structure is as follows: Figure 3-5 As shown.

[0114] from Figure 3 As can be seen from the microstructure of the titanium-based composite material in Example 1, it exhibits a gradient distribution, with a large number of equiaxed grains and a small number of columnar grains. The equiaxed grains, to a certain extent, hinder the growth of columnar grains. There are precipitated TiC and TiB reinforcing phases at the grain boundaries. Furthermore, the grain characteristics of the mixed powder layers with different particle sizes are different. The grain size of the composite material varies with the particle size of the ceramic particles. The larger the particle size of the ceramic particles, the larger the grain size. Moreover, under the same particle size condition, the grain size varies with the mass ratio of the ceramic particle size. The higher the content of the ceramic particle size, the smaller the grain size.

[0115] like Figure 4 As shown, in Comparative Example 1, the microstructure of the component without a gradient change exhibits a relatively small degree of grain refinement, and penetrating columnar grains still exist; as... Figure 5 As shown in Comparative Example 2, the large difference in grain size due to the single-component gradient variation significantly affects the mechanical properties.

[0116] Performance testing

[0117] The tensile strength, elongation, and hardness of B4C-reinforced titanium matrix composites were obtained by testing Example 1 and Comparative Examples 1-3. The results are shown in the table below.

[0118]

[0119] Based on the above test results and the results of microstructure characterization, it can be seen that the tensile properties (tensile strength) of the B4C reinforced titanium matrix composite material with laser melting deposition structure and composition gradient changes are not significantly different from those of titanium matrix composite material without structural changes and titanium matrix composite material with single composition changes.

[0120] Among them, the room temperature plasticity (elongation) of Example 1 and Comparative Example 2 was significantly improved compared with Comparative Example 1, indicating that the gradient structure plays an important role in improving toughness and plasticity. The dual gradient structure of microstructure and composition formed by different powder particle sizes in Example 1 has a more significant improvement effect than that of a single gradient.

[0121] In addition, the hardness of different deposition layers of the titanium-based composite material with dual gradient changes varies greatly and is distributed in a gradient manner. The average microhardness is slightly improved compared with the titanium-based composite material without structural changes, while the hardness of the titanium-based composite material with single component gradient changes decreases significantly due to the large difference in grain size.

[0122] The ceramic-reinforced dual-gradient composite material of this invention fully utilizes the advantages of ceramic reinforcement and, based on the idea of ​​mismatched alloy powder particle size and layer-by-layer compositional variation in additive manufacturing, optimizes the microstructure through micro / nano particle size mismatch and different interlayer structural composition design. This achieves a controllable design of continuous microstructure and dual-gradient compositional variation in the titanium-based composite material microstructure, thus forming a new method for macroscopic structural design and manufacturing of ceramic particle-reinforced microstructure and dual-gradient compositional functional materials. By precisely controlling the construction of novel functional materials with microstructure-compositional dual-gradient variation layer by layer, the resulting composite material significantly improves the comprehensive performance of B4C-reinforced titanium-based composite materials. Combining the two not only effectively enhances its toughness and plasticity but also solves the bottleneck of matching strength and toughness in titanium-based composite materials, achieving dual-gradient composite reinforcement of additively manufactured functionally graded materials.

[0123] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for preparing ceramic-reinforced dual-gradient composite materials based on laser melting deposition, characterized in that, include: The alloy powder is mixed with ceramic particles of different particle sizes to obtain a multi-level mismatched mixed powder; wherein the particle size of the ceramic particles varies in a multi-level gradient, and the mass proportion of ceramic particles in the mixed powder with ceramic particles of the same particle size varies in a continuous gradient; the alloy powder is a Ti-6Al-4V titanium alloy with an average particle size of 53-150μm. The mixed powder is passed through a multi-cylinder powder feeder and laser melting deposition is performed in a protective atmosphere. The laser melting deposition process includes the following steps: The printing deposition of each layer is completed by growing layer by layer, with each layer corresponding to a preset laser power and scanning spacing. Among them, from the first layer to the nth layer, the particle size of the ceramic particles in the mixed powder used for printing between layers varies in multiple levels from micrometers to nanometers; between adjacent layers, the particle size of the ceramic particles in the mixed powder used in the lower layer is greater than or equal to the particle size of the ceramic particles in the mixed powder used in the upper layer. When the ceramic particles in the mixed powder used for printing between layers have the same particle size, the mass proportion of ceramic particles in the mixed powder changes in a continuous gradient. Repeat the above layer-by-layer growth printing process until the printing of the ceramic-reinforced dual-gradient composite material is completed, and the ceramic-reinforced dual-gradient composite material is obtained. Through printing from the 1st to the nth layer, multi-layer micron-scale mixed powder layers and multi-layer nano-scale powder layers are formed, and the grain size of the multi-layer micron-scale mixed powder layers and multi-layer nano-scale powder layers shows a decreasing trend layer by layer; The ceramic particles account for 0–5 wt.% of the mass of the mixed powder; the different particle size grades of the ceramic particles range from 1–100 μm to 1–50 nm.

2. The method for preparing ceramic-reinforced dual-gradient composite materials based on laser melting deposition according to claim 1, characterized in that, Based on the stated particle size range, the printing deposition applied to complete layers 1 through n is respectively.

3. The method for preparing ceramic-reinforced dual-gradient composite materials based on laser melting deposition according to claim 1, characterized in that, During the printing deposition process of the first to nth layers, the laser power and scanning spacing are set according to the type of ceramic reinforcing phase and alloy.

4. A ceramic-reinforced dual-gradient composite material prepared by the method described in any one of claims 1-3.

5. The ceramic-reinforced dual-gradient composite material according to claim 4, characterized in that, In the ceramic-reinforced dual-gradient composite material, through the printing of the first to the nth layers, multiple micron-scale mixed powder layers and multiple nano-scale powder layers are formed, and the grain size of the multiple micron-scale mixed powder layers and multiple nano-scale powder layers shows a decreasing trend layer by layer.

6. An aircraft landing gear using the ceramic-reinforced dual-gradient composite material of claim 4.

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