Preparation Method of Dual-Scale Ceramic Particle Co-Reinforced Aluminum Matrix Composite

Abstract

A dual-scale ceramic particle co-reinforced aluminum matrix composite and its preparation method. Nanoceramic particles and micron-sized AlMgScZr alloy powder are subjected to ball milling and dispersion treatment to obtain composite powder with nanometer particles uniformly coated on aluminum spheres. Then, micron-sized ceramic particles are mixed evenly with the above composite powder to obtain dual-scale particle co-reinforced aluminum matrix composite powder. A three-dimensional geometric model of the target part is established, and the model is sliced and the process is designed for subsequent laser forming. Using the laser additive manufacturing technology, according to the sliced data in step 3), the aluminum matrix composite powder is subjected to selective laser melting and solidification layer by layer to obtain the dual-scale ceramic particle co-reinforced aluminum matrix composite. The process of the present invention is simple and reasonable, breaking through the existing levels of the reinforcement phase content and elastic modulus of laser additive manufactured aluminum matrix composites, and solving the problems of many solidification defects and poor laser additive manufacturing quality of aluminum matrix composites reinforced with single-scale particles with high volume fractions.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser additive manufacturing of aluminum matrix composites, and relates to a preparation method of a dual-scale ceramic particle co-reinforced aluminum matrix composite based on laser additive manufacturing. Background Art

[0002] Aluminum matrix composites (AMCs) have the advantages of high specific strength, high specific modulus, wear resistance, and dimensional stability, and are key materials indispensable for the rapid development of fields such as aerospace, weaponry, and electronic packaging. The traditional preparation process is to first prepare a billet through methods such as powder metallurgy or casting, and then through cold / hot deformation and machining to finally make a component. The related processes are cumbersome, the production cycle is long, and the loss of raw materials is large. At the same time, the poor plastic deformation ability and high cutting processing difficulty of AMCs lead to very high precision processing difficulty and processing cost of AMCs structural parts, seriously restricting the application and development of AMCs.

[0003] In recent years, the laser additive manufacturing technology of AMCs has gradually become a research hotspot. This method can realize the integrated forming preparation from metal powder to workpiece, and has the advantages of being unrestricted by structure, highly designable, short production cycle, and powder recyclability. It is a green, efficient, and intelligent material preparation technology, which can not only improve the forming efficiency of AMCs parts, but also solve the problem of difficult processing and forming of traditional AMCs.

[0004] The existing research on laser additive manufacturing of AMCs mainly focuses on in-situ reactions or externally added nano-particle reinforcements. On the one hand, a small amount of nano-particles will not reduce the fluidity and powder spreading effect of the aluminum powder itself, and can continue the good laser forming quality of aluminum alloys. On the other hand, ceramic particles can increase the laser absorption rate of aluminum alloys and refine the grain size as heterogeneous nucleation sites, which is beneficial to the control of solidification microstructure. However, there is a strong van der Waals force between nano-particles themselves, resulting in their easy agglomeration, which creates the characteristic of generally low reinforcement content in nano-phase reinforced AMCs, most of which are below 5 vol.%. In the patent "7XXX series in-situ aluminum matrix composite powder for laser additive manufacturing and preparation" with the application number 201810107789.9, by using the molten salt method, the in-situ reaction of KBF4, K2TiF6 and Al can obtain nano-TiB2 reinforced AMCs with a maximum mass fraction of 10%. The elastic modulus of AMCs is positively correlated with the addition amount of ceramic particles. 10 wt.% of ceramic particles is still far from enough to increase the elastic modulus of AMCs to the level of titanium alloys or even steel materials. Therefore, in addition to nano-reinforcement particles, it is very necessary to develop micron-particle reinforced laser additive AMCs that are easy to disperse. However, it should be noted that compared with nano-particles, micron-particles have a more obvious hindering effect on the flow of liquid metal, and are more likely to cause defects such as pores and cracks due to untimely solidification feeding. On the other hand, the contact area between micron-particles and the Al matrix is larger, and it is more difficult to fully wet the interface. Poor interface bonding will seriously affect the strength and plasticity of the composite material.

[0005] Upon investigation, in the Chinese patent "Preparation method of an interface-strengthened in-situ reinforced aluminum matrix composite based on laser additive manufacturing" with the application number 202210528945.5, the molten salt method is used to deposit zirconium elements on the surface of 4 - 6 μm boron particles, so that zirconium and aluminum undergo an interface reaction during laser heating to generate Al3Zr, achieving the effect of strengthening the interface between the reinforcement phase and the aluminum matrix. However, this process is very complex, and the potassium salts and sodium salts used are easily retained in the powder. More importantly, the addition content of the micron zirconium-coated boron particles disclosed in this patented technology is still lower than 8 wt.%. In addition, due to the different thermal expansion coefficients of ceramic particles and the Al matrix, during the solidification process of the molten pool, thermal stress will inevitably be generated around the micron-particles, increasing the solidification cracking tendency of AMCs and greatly increasing the difficulty of its laser forming. Therefore, simply using nano- or micron-particles as reinforcements cannot achieve the laser additive manufacturing of high volume fraction AMCs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a preparation method of a dual-scale ceramic particle co-reinforced aluminum matrix composite based on laser additive manufacturing, which has a simple process, is easy to operate, and the prepared material has good laser formability and a high elastic modulus.

[0007] The technical solution adopted by the present invention to solve the above technical problems is as follows: A preparation method of a dual-scale ceramic particle co-reinforced aluminum matrix composite based on laser additive manufacturing, which is characterized by including the following steps:

[0008] 1) Perform ball milling and dispersion treatment on low-volume fraction nano-ceramic particles and micron-sized AlMgScZr alloy powder to obtain composite powder with nano-particles uniformly coated on aluminum spheres;

[0009] 2) Mix high-volume fraction micron-sized ceramic particles with the composite powder prepared in step 1) evenly in a mechanical mixer to obtain dual-scale particle co-reinforced aluminum matrix composite powder suitable for laser additive manufacturing;

[0010] 3) Establish a three-dimensional geometric model of the target part, and perform slicing treatment and process design on the model for subsequent laser forming;

[0011] 4) Use laser additive manufacturing technology to perform selective laser melting and solidification layer by layer on the aluminum matrix composite powder obtained in step 2) according to the slicing data obtained in step 3) to obtain a dual-scale ceramic particle co-reinforced aluminum matrix composite.

[0012] Preferably, the average particle size of the nano-ceramic particles in step 1) is 20 - 200 nm, and the volume content is 2 - 5%. The ceramic particles are SiC, TiN, AlN, TiC or TiB2; the nano-ceramic particles need to be dried in an oven at 200 ± 10 °C for 2 ± 0.5 h before ball milling, and then ultrasonically vibrated for 20 ± 5 min to break up the agglomeration of the nano-particles themselves and reduce agglomeration.

[0013] Preferably, the average particle size of the micron-sized AlMgScZr alloy powder in step 1) is 15 - 53 μm. In terms of mass percentage, the composition of the micron-sized AlMgScZr alloy powder is: magnesium content is 3.0 - 5.5%, scandium content is 0.5 - 0.8%, zirconium content is 0.2 - 0.5%, manganese content is 0.3 - 0.8%, and the balance is aluminum and inevitable impurities.

[0014] Furthermore, the ball milling and dispersion treatment in step 1) is specifically as follows: Use a planetary ball mill to pre-disperse the nano-ceramic particles and the micron-sized AlMgScZr alloy powder under argon protection to obtain composite powder with nano-particles uniformly coated on AlMgScZr. The ball mill uses a stainless steel tank and stainless steel grinding balls, the diameter of the grinding balls is 5 - 7 mm, the ball-to-material ratio is 0.5:1 - 1:1, the ball milling method is a one-way continuous operation mode, and according to the content of the nano-ceramic particles, the ball milling speed range is 150 - 200 rpm, and the ball milling time is 1.5 - 2.5 h.

[0015] Preferably, the average size of the micron ceramic particles in step 2) is 5-20 μm, the volume content is 10-20%, the morphology is near equiaxed, the aspect ratio of the particles is ≤2.0, the ceramic particles are SiC, TiN, AlN, TiC or TiB2. When the dual-scale particles are matched, they can be the same type of ceramic phase or different types of ceramic phases.

[0016] Furthermore, the mechanical mixer in step 2) is a V-type mixer, using a stainless steel tank and stainless steel balls. The diameter of the steel balls is 5-7 mm, the ball-to-material ratio is 1:1, the rotation speed of the mixer is 30-50 rpm, and the mixing time is 6-8 h.

[0017] Furthermore, the three-dimensional geometric model in step 3) is constructed using three-dimensional modeling software. The slicing process and process design refer to converting the model into an STL file, then importing it into the slicing software for slicing, designing the printing parameters and strategies to obtain the two-dimensional layered cross-sectional data and processing path of the part, and importing this file into the laser additive manufacturing equipment to prepare for 3D printing and forming.

[0018] Finally, the specific process of laser additive manufacturing and forming in step 4) is as follows: Using the laser additive manufacturing technology based on powder bed powder spreading, the pre-mixed composite powder in step 2) is placed in the powder chamber, and argon and nitrogen are introduced to ensure that the oxygen content in the equipment is lower than 100 ppm. According to the layered slicing data in step 3), the powder spreading blade spreads a layer of powder onto the 6061Al substrate, and the substrate is pre-heated to 160±10°C in advance. The laser selectively melts the powder according to the predetermined scanning path, and the target part is obtained by layer-by-layer melting and solidification. The process parameters of laser additive manufacturing are: laser power 250-350 W, scanning speed 600-1000 mm / s, spot diameter less than 100 μm, scanning spacing 110-130 μm, powder spreading layer thickness 20-40 μm, and the scanning strategy is zonal island scanning.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] 1. The low-ball-to-material ratio and low-speed ball milling process is used to uniformly coat the low-volume fraction of nano-ceramic particles on the surface of micron-sized lMgScZr alloy powder, maximizing the retention of the good sphericity and powder fluidity of the original aluminum powder, making the composite powder suitable for the laser additive manufacturing process. Compared with the in-situ self-generated nano-TiB2 reinforcement phase by the molten salt method disclosed in the previous patent, the ball milling method of the present invention is not limited by the type of reinforcement phase, has a simple operation process, low cost, and is more suitable for large-scale production.

[0021] 2. Through the mechanical mixing process, a high volume fraction of micron ceramic particles is continuously introduced to fully utilize the performance advantages of the high elastic modulus of ceramic particles, obtaining a uniformly mixed dual-scale particle-reinforced AlMgScZr composite powder, which is finally formed by laser additive manufacturing. The structural design of the dual-scale ceramic particle co-reinforcement realizes the laser additive manufacturing of high elastic modulus aluminum matrix composites, solving the problems of many solidification defects and poor laser additive manufacturing quality of high volume fraction single-scale particle-reinforced aluminum matrix composites.

[0022] 3. The prepared aluminum matrix composite has a structure co-reinforced by low-content nanoparticles and high-content micron particles. The dual-scale ceramic particles can significantly improve the elastic modulus of the material, making it reach the level of titanium alloys or even steels, meeting the performance requirements of lightweight structural components. According to the ratio of micron / nano dual-scale particle content, the elastic modulus range of the laser additive manufactured aluminum matrix composite is 92 - 105 GPa.

[0023] The present invention fully utilizes the functions of nanoparticles in regulating the solidification structure and relieving stress concentration, as well as the characteristics of micron particles being easy to disperse. The micron / nano ceramic particles cooperate with each other, avoiding both the problem of agglomeration of reinforcement phases in nanoparticle-reinforced aluminum matrix composites and the problem of many solidification defects in micron particle-reinforced aluminum matrix composites during laser forming. The process is simple and easy to operate. The obtained dual-scale ceramic particle co-reinforced aluminum matrix composite has good laser forming quality, few metallurgical defects, and a relative density of over 99.5%. It breaks through the reinforcement phase content and elastic modulus level of existing laser additive manufactured aluminum matrix composites, enabling the integrated forming of complex components, and has broad application prospects in the fields of aerospace, weaponry, etc. Description of the Drawings

[0024] Figure 1 It is a scanning photograph of the nano-TiC particle-coated micron AlMgScZr alloy powder in Example 1 of the present invention;

[0025] Figure 2 It is a scanning photograph of the micron / nano dual-scale TiC particle-reinforced AlMgScZr composite material powder in Example 1;

[0026] Figure 3 It is a macroscopic view of the sample block of the dual-scale particle co-reinforced aluminum matrix composite prepared in Example 1 after removing the oxide skin;

[0027] Figure 4 It is an optical micrograph of the deposition cross-section of the dual-scale particle co-reinforced aluminum matrix composite sample prepared in Example 1;

[0028] Figure 5 It is a transmission photograph of the dual-scale particle co-reinforced aluminum matrix composite sample prepared in Example 1;

[0029] Figure 6 Macrograph of the specimen block after removing the oxide skin of the micron single-scale particle-reinforced aluminum matrix composite prepared in Comparative Example 1;

[0030] Figure 7 Scanning photograph of the 10 vol.% nano-TiC particle and AlMgScZr alloy composite powder in Comparative Example 3;

[0031] Figure 8 Macrograph of the laser formed specimen block of the TiC / AlMgScZr composite material prepared in Comparative Example 3. Specific Embodiments

[0032] The present invention will be further described in detail below in conjunction with the embodiments with reference to the drawings.

[0033] First, the design mechanism of the present invention will be described:

[0034] In order to improve the laser additive manufacturing forming quality of high volume fraction particle-reinforced aluminum matrix composites, the present invention proposes a microstructure regulation method of co-reinforcement with dual-scale ceramic particles. Through the powder pretreatment means of combining ball milling and mechanical mixing, nano- and micron-scale ceramic particles with uniform dispersion are gradually introduced into spherical AlMgScZr alloy powder, and the composite powder is finally formed and prepared through optimized laser process parameters. The nano-particles are distributed on the surface of the aluminum powder, and their main function is to improve the laser formability of the material and regulate the solidification microstructure morphology. Nano-particles can effectively reduce the laser reflectivity, enabling the material to be densified under a relatively low laser energy density, and can also serve as heterogeneous nucleation sites in the molten pool, contributing to the formation of uniform and fine equiaxed crystals during the solidification process of the molten pool. The micron-scale ceramic particles are distributed in the gaps between the aluminum powders. By utilizing their easy dispersion characteristics, the shortcoming of the limited addition amount of nano-particles is compensated, and the comprehensive addition amount of the ceramic phase in the composite material is increased, so as to obtain an aluminum matrix composite material with a high elastic modulus to meet the performance requirements of lightweight structural parts in engineering applications. In addition, the nano-particles have a strong pinning effect on the grain boundaries, which can effectively improve the strength and stiffness of the aluminum matrix, reduce the thermal deformation difference between the matrix and the micron-scale ceramic particles, and relieve the thermal stress concentration in the near-interface region, thereby avoiding thermal stress cracking during the cooling process of the molten pool. Therefore, the micron / nano dual-scale ceramic particles have a synergistic effect, and finally the laser additive manufacturing of high volume fraction aluminum matrix composites can be realized.

[0035] Example 1

[0036] A preparation method of a dual-scale ceramic particle co-reinforced aluminum matrix composite based on laser additive manufacturing, the specific steps are as follows:

[0037] (1) Mix 2 vol.% nano-TiC particles with AlMgScZr alloy powder in a planetary ball mill rotating at 150 rpm for 1.5 h to obtain Nano-TiC / AlMgScZr composite powder. The scanning electron micrograph of the powder morphology is shown in Figure 1 . Before starting the ball milling, evacuate the ball milling tank and introduce argon for protection. The ball-to-powder ratio is 1:1. The average particle size of nano-TiC is 50 nm, and the average particle size of AlMgScZr alloy powder is 35 μm. The specific alloy element ratio is 4.5 wt.% Mg, 0.6 wt.% Sc, 0.4 wt.% Zr, 0.5 wt.% Mn, and the balance is Al.

[0038] (2) Continuously add 13 vol.% TiC particles with an average particle size of 7 μm to 2 vol.% Nano-TiC / AlMgScZr composite powder, and mix them in a V-type mechanical mixer rotating at 36 rpm for 7 h to obtain a uniformly mixed dual-scale TiC / AlMgScZr composite powder. The scanning electron micrograph of the powder morphology is shown in Figure 2 . The ball-to-powder ratio is 1:1, and the average particle size of micron-TiC is 7 μm.

[0039] (3) Use 3D CAD software in the computer to draw a cuboid model and a tensile part model with dimensions of 70 mm × 10 mm × 10 mm. After converting the model into an STL file, import it into the slicing software for slicing processing, design the printing parameters and strategies to obtain the two-dimensional layered cross-sectional data of the part, and import it into the selective laser melting equipment for subsequent printing and processing.

[0040] (4) Use laser additive manufacturing technology to prepare micron / nano dual-scale TiC particle-reinforced AlMgScZr composite materials. The model of the selective laser melting equipment is EOS M290, the substrate material is 6061Al, the preheating temperature of the substrate before forming is 160 °C, and argon and nitrogen are introduced to ensure that the oxygen content in the equipment is lower than 100 ppm. The powder layer thickness is 30 μm, the laser power is 260 W, the scanning speed is 800 mm / s, the spot diameter is 70 μm, the scanning spacing is 120 μm, and the scanning strategy is zonal island scanning.

[0041] The total content of ceramic particles in the aluminum matrix composite material prepared by this example is 15 vol.%, the relative density is 99.81%, the forming quality is good, there are no pores and cracks. The macroscopic photograph of the formed specimen is shown in Figure 3 , the micron-TiC particles are evenly distributed. The metallographic photograph is shown in Figure 4 , most of the nano-TiC particles are distributed at the grain boundaries and a small amount are distributed inside the grains. The transmission electron micrograph is shown in Figure 5 . In the as-built state without heat treatment, the elastic modulus of the material is 92.5 GPa, the tensile strength and elongation at break are 356 MPa and 10.5% respectively.

[0042] Example 2

[0043] A preparation method of a dual-scale ceramic particle co-reinforced aluminum matrix composite based on laser additive manufacturing is as follows:

[0044] (1) Mix 3 vol.% nano-TiB2 particles and AlMgScZr alloy powder in a planetary ball mill with a rotation speed of 150 rpm for 2 h to obtain Nano-TiB2 / AlMgScZr composite powder. Before starting the ball milling, evacuate the ball milling tank and introduce argon for protection. The ball-to-powder ratio is 1:1. The average particle size of nano-TiB2 is 50 nm, and the average particle size of AlMgScZr alloy powder is 35 μm. The specific alloy element ratio is 4.5 wt.% Mg, 0.6 wt.% Sc, 0.4 wt.% Zr, 0.5 wt.% Mn, and the balance is Al. The nano-ceramic particles are dried in an oven at 200 °C for 2 h before ball milling, and then ultrasonically oscillated for 20 min.

[0045] (2) Continuously add 17 vol.% TiC particles with an average particle size of 10 μm to 3 vol.% Nano-TiB2 / AlMgScZr composite powder, and mix them in a V-type mechanical mixer with a rotation speed of 36 rpm for 8 h to obtain a uniformly mixed dual-scale particle-reinforced aluminum matrix composite powder. The ball-to-powder ratio is 1:1, and the average particle size of micron TiC is 10 μm.

[0046] (3) Use 3D CAD software in a computer to draw a cuboid model and a tensile part model with dimensions of 70 mm × 10 mm × 10 mm. After converting the model into an STL file, import it into a slicing software for slicing processing, design the printing parameters and strategies, obtain the two-dimensional layered cross-section data of the part, and import it into a selective laser melting equipment for subsequent printing and processing.

[0047] (4) Use laser additive manufacturing technology to prepare a micron / nano dual-scale particle-reinforced AlMgScZr composite material. The model of the selective laser melting equipment is EOS M290, the substrate material is 6061Al, the preheating temperature of the substrate before forming is 160 °C, and argon and nitrogen are introduced to ensure that the oxygen content in the equipment is lower than 100 ppm. The powder layer thickness is 30 μm, the laser power is 300 W, the scanning speed is 1000 mm / s, the spot diameter is 70 μm, the scanning spacing is 120 μm, and the scanning strategy is zonal island scanning.

[0048] The total content of ceramic particles in the aluminum matrix composite prepared by this embodiment is 20 vol.%, the relative density is 99.67%, the forming quality is good, and there are no pores and cracks. In the as - heat - treated state, the elastic modulus of the material is 101.5 GPa, and the tensile strength and elongation at break are 326 MPa and 6.5% respectively.

[0049] Example 3

[0050] A preparation method of a dual - scale ceramic particle co - reinforced aluminum matrix composite based on laser additive manufacturing, the specific steps are as follows:

[0051] (1) Mix 5 vol.% nano - TiB2 particles with AlMgScZr alloy powder in a planetary ball mill with a rotation speed of 150 rpm for 2.5 h to obtain Nano - TiB2 / AlMgScZr composite powder. Before the ball milling starts, evacuate the ball milling tank and introduce argon for protection. The ball - to - powder ratio is 1:1. The average particle size of nano - TiB2 is 100 nm, and the average particle size of AlMgScZr alloy powder is 40 μm. The specific alloy element ratio is 4.5 wt.% Mg content, 0.6 wt.% Sc content, 0.4 wt.% Zr content, 0.5 wt.% Mn content, and the balance is Al. The nano - ceramic particles are dried in an oven at 200 °C for 2 h before ball milling, and then ultrasonically oscillated for 20 min.

[0052] (2) Continuously add 15 vol.% TiC particles with an average particle size of 15 microns to 5 vol.% Nano - TiB2 / AlMgScZr composite powder, and mix them with a V - type mechanical mixer with a rotation speed of 36 rpm for 8 h to obtain a uniformly mixed dual - scale particle - reinforced aluminum matrix composite powder. The ball - to - powder ratio is 1:1, and the average particle size of micron - sized TiC is 15 μm.

[0053] (3) Use 3D CAD software in the computer to draw a cuboid model and a tensile part model with dimensions of 70 mm×10 mm×10 mm. After converting the model into an STL file, import it into the slicing software for slicing processing, design the printing parameters and strategies, obtain the two - dimensional layered cross - section data of the part, and import it into the selective laser melting equipment for subsequent printing and processing.

[0054] (4) Use laser additive manufacturing technology to prepare a micron / nano dual - scale particle - reinforced AlMgScZr composite. The model of the selective laser melting equipment is EOS M290, the substrate material is 6061Al, the preheating temperature of the substrate before forming is 160 °C, and argon and nitrogen are introduced to ensure that the oxygen content in the equipment is less than 100 ppm. The powder layer thickness is 30 μm, the laser power is 300 W, the scanning speed is 800 mm / s, the spot diameter is 70 μm, the scanning pitch is 120 μm, and the scanning strategy is zonal island scanning.

[0055] The total content of ceramic particles in the aluminum matrix composite prepared by this example is 20 vol.%, the relative density is 99.76%, the forming quality is good, and there are no pores and cracks. In the as - heat - treated state, the elastic modulus of the material is 103.5 GPa, and the tensile strength and fracture elongation are 346 MPa and 5.4% respectively.

[0056] Comparative Example 1

[0057] This comparative example uses laser additive manufacturing technology to prepare a single - scale ceramic particle - reinforced aluminum matrix composite, including the following steps:

[0058] (1) 15 vol.% micron - sized SiC particles and AlMgScZr alloy powder are placed in a V - type mechanical mixer with a rotation speed of 36 rpm and mixed for 7 h to obtain a uniformly mixed SiC / AlMgScZr composite powder. The ball - to - powder ratio is 1:1, the average particle size of micron - sized SiC is 7 μm, the average particle size of AlMgScZr alloy powder is 35 μm, and the specific alloy element ratio is 4.5 wt.% Mg, 0.6 wt.% Sc, 0.4 wt.% Zr, 0.5 wt.% Mn, and the balance is Al.

[0059] (2) Use 3D CAD software in the computer to draw a cuboid model with dimensions of 70 mm×10 mm×10 mm. After the model is converted into an STL file, it is imported into the slicing software for slicing processing. Print parameters and strategies are designed to obtain the two - dimensional layered cross - section data of the part, which is then imported into the selective laser melting equipment for subsequent printing and processing.

[0060] (3) Use laser additive manufacturing technology to prepare SiC / AlMgScZr composite. The model of the selective laser melting equipment is EOS M290, the substrate material is 6061Al, the pre - heating temperature of the substrate before forming is 160 °C, argon and nitrogen are introduced to ensure that the oxygen content in the equipment is less than 100 ppm, the powder - laying layer thickness is 30 μm, the laser power is 260 W, the scanning speed is 800 mm / s, the spot diameter is 70 μm, the scanning spacing is 120 μm, and the scanning strategy is zonal island scanning.

[0061] The total content of ceramic particles in the aluminum matrix composite prepared by this comparative example is 15 vol.%, the relative density is 92.32%, the forming quality is extremely poor, cracks penetrate the strip - shaped specimen, and it is impossible to obtain specimens for measuring the mechanical properties of the elastic modulus. The macroscopic photograph of the formed specimen is as Figure 6 .

[0062] Comparative Example 2

[0063] This comparative example uses laser additive manufacturing technology to prepare a single - scale ceramic particle - reinforced aluminum matrix composite, including the following steps:

[0064] (1) 2 vol.% of nano-TiC particles and AlMgScZr alloy powder were placed in a planetary ball mill with a rotation speed of 150 rpm and mixed for 2 h to obtain Nano-TiC / AlMgScZr composite powder. The scanning electron micrograph of the powder morphology is as shown in Figure 1 . Before the ball milling started, the ball mill tank was evacuated and filled with argon for protection. The ball-to-powder ratio was 1:1. The average particle size of nano-TiC was 50 nm, and the average particle size of AlMgScZr alloy powder was 35 μm. The specific alloy element ratio was 4.5 wt.% of Mg, 0.6 wt.% of Sc, 0.4 wt.% of Zr, 0.5 wt.% of Mn, and the balance was Al.

[0065] (2) A cuboid model with dimensions of 70 mm × 10 mm × 10 mm and a tensile part model were drawn using 3D CAD software on a computer. After the models were converted into STL files, they were imported into a slicing software for slicing processing. The printing parameters and strategies were designed to obtain the two-dimensional layered cross-sectional data of the parts, which were then imported into a selective laser melting equipment for subsequent printing and processing.

[0066] (3) TiC / AlMgScZr composite materials were prepared using laser additive manufacturing technology. The model of the selective laser melting equipment was EOS M290. The substrate material was 6061Al. Before forming, the preheating temperature of the substrate was 160 °C, and argon and nitrogen were introduced to ensure that the oxygen content in the equipment was lower than 100 ppm. The powder layer thickness was 30 μm, the laser power was 260 W, the scanning speed was 1000 mm / s, the spot diameter was 70 μm, the scanning spacing was 120 μm, and the scanning strategy was island scanning in zones.

[0067] For the aluminum matrix composite material prepared in this example, the total content of ceramic particles was 2 vol.%, the relative density was not less than 99.71%, the forming quality was good, and there were no pores and cracks. In the as-built state without heat treatment, the elastic modulus of the material was only 76.5 GPa, far lower than that of the composite materials in Examples 1 and 2. The tensile strength and elongation at break were 438 MPa and 15.5% respectively.

[0068] Comparative Example 3

[0069] In this comparative example, single-scale ceramic particle-reinforced aluminum matrix composite materials were prepared using laser additive manufacturing technology, including the following steps:

[0070] (1) 10 vol.% of nano-TiC particles and AlMgScZr alloy powder were placed in a planetary ball mill with a rotation speed of 200 rpm and mixed for 3 h to obtain Nano-TiC / AlMgScZr composite powder. The scanning electron micrograph of the powder morphology is as shown in Figure 7, too many nanoparticles agglomerate significantly, and even cause adhesion between aluminum powder particles. It is very difficult to achieve uniform dispersion of a high content of nanoparticles without destroying the sphericity of aluminum powder. Before starting ball milling, evacuate the ball milling tank and introduce argon for protection. The ball-to-powder ratio is 1:1. The average particle size of nano-TiC is 50 nm, and the average particle size of AlMgScZr alloy powder is 35 μm. The specific alloy element ratio is 4.5 wt.% of Mg, 0.6 wt.% of Sc, 0.4 wt.% of Zr, 0.5 wt.% of Mn, and the balance is Al.

[0071] (2) Use 3D CAD software in the computer to draw a cuboid model with dimensions of 70 mm × 10 mm × 10 mm. After converting the model into an STL file, import it into the slicing software for slicing processing. Design the printing parameters and strategies to obtain the two-dimensional layered cross-section data of the part, and import it into the selective laser melting equipment for subsequent printing and processing.

[0072] (3) Use laser additive manufacturing technology to prepare TiC / AlMgScZr composite materials. The model of the selective laser melting equipment is EOS M290, the substrate material is 6061Al, the preheating temperature of the substrate before forming is 160 °C, and argon and nitrogen are introduced to ensure that the oxygen content in the equipment is less than 100 ppm. The powder layer thickness is 30 μm, the laser power is 260 W, the scanning speed is 1000 mm / s, the spot diameter is 70 μm, the scanning spacing is 120 μm, and the scanning strategy is island scanning in zones.

[0073] The total content of ceramic particles in the aluminum matrix composite material prepared by this example is 10 vol.%, the relative density is 95.51%, the forming quality is poor, and it breaks during wire electrical discharge machining of the specimen (as Figure 8 ), and the elastic modulus and mechanical properties of the material cannot be measured.

[0074] From the data of the composite materials prepared in the above examples and comparative examples, it can be seen that the dual-scale ceramic particle co-reinforced aluminum matrix composite material prepared by the present invention has a relative density of more than 99.5%, good forming quality, no pores and cracks, breaks through the existing levels of the content of reinforcing phases and elastic modulus of laser additive manufacturing aluminum matrix composite materials, can realize the integrated forming of complex components, and solves the problems of many solidification defects and poor laser additive manufacturing quality of high volume fraction single-scale particle-reinforced aluminum matrix composite materials.

[0075] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a dual-scale ceramic particle co-reinforced aluminum matrix composite, characterized in that It includes the following steps: 1) Perform ball milling and dispersion treatment on nano-ceramic particles with a low volume fraction and micron-sized AlMgScZr alloy powder to obtain composite powder with nano-particles uniformly coated on aluminum spheres; The ball mill uses a stainless-steel tank and stainless-steel grinding balls. The diameter of the grinding balls is 5 - 7 mm, the ball-to-material ratio is 0.5:1 - 1:1, the ball milling method is a unidirectional continuous operation mode. According to the content of nano-ceramic particles, the ball milling speed range is 150 - 200 rpm, and the ball milling time is 1.5 - 2.5 h; 2) Mix high-volume-fraction micron-sized ceramic particles with the composite powder prepared in step 1) evenly in a mechanical mixer to obtain dual-scale particle co-reinforced aluminum matrix composite powder suitable for laser additive manufacturing; The mechanical mixer uses a stainless-steel tank and stainless-steel balls. The diameter of the steel balls is 5 - 7 mm, the ball-to-material ratio is 1:1, the rotation speed of the mixer is 30 - 50 rpm, and the mixing time is 6 - 8 h; 3) Establish a three-dimensional geometric model of the target part, and perform slicing processing and process design on the model for subsequent laser forming; 4) Use laser additive manufacturing technology to perform selective laser melting and solidification layer by layer on the aluminum matrix composite powder obtained in step 2) according to the sliced data obtained in step 3) to obtain dual-scale ceramic particle co-reinforced aluminum matrix composite material.

2. The preparation method according to claim 1, characterized in that: The average particle size of the nano-ceramic particles in step 1) is 20 - 200 nm, and the volume content is 2 - 5%. The ceramic particles are SiC, TiN, AlN, TiC or TiB2; the nano-ceramic particles need to be dried in an oven at 200 ± 10 °C for 2 ± 0.5 h before ball milling, and then ultrasonically vibrated for 20 ± 5 min.

3. The preparation method according to claim 1, characterized in that: The average particle size of the micron-sized AlMgScZr alloy powder in step 1) is 15 - 53 μm. By mass percentage, the composition of the micron-sized AlMgScZr alloy powder is: the magnesium content is 3.0 - 5.5%, the scandium content is 0.5 - 0.8%, the zirconium content is 0.2 - 0.5%, the manganese content is 0.3 - 0.8%, and the balance is aluminum and inevitable impurities.

4. The preparation method according to claim 1, characterized in that: The ball milling and dispersion treatment in step 1) is specifically: use a planetary ball mill to pre-disperse the nano-ceramic particles and micron-sized AlMgScZr alloy powder under argon protection to obtain composite powder with nano-particles uniformly coated on AlMgScZr.

5. The preparation method according to claim 1, characterized in that: The average size of the micron-sized ceramic particles in step 2) is 5 - 20 μm, and the volume content is 10 - 20%. The morphology is near equiaxed, and the aspect ratio of the particles ≤ 2.

0. The ceramic particles are SiC, TiN, AlN, TiC or TiB2. When the dual-scale particles are paired, they are of the same type of ceramic phase or different types of ceramic phases.

6. The preparation method according to claim 1, wherein: The mechanical mixer in step 2) is a V-type mixer.

7. The preparation method according to claim 1, characterized in that: The three-dimensional geometric model in step 3) is constructed using three-dimensional modeling software. The slicing processing and process design refer to converting the model into an STL file, then importing it into a slicing software for slicing processing, designing printing parameters and strategies to obtain the two-dimensional layered cross-sectional data and processing paths of the part, and importing this file into a laser additive manufacturing device to prepare for 3D printing and forming.

8. The preparation method according to claim 1, wherein: The specific process of laser additive manufacturing in step 4) is as follows: Using the laser additive manufacturing technology based on powder bed powder spreading, the composite powder pre-mixed evenly in step 2) is placed in the powder chamber, and argon and nitrogen are introduced to ensure that the oxygen content in the equipment is lower than 100 ppm. According to the layer slicing data in step 3), the powder spreading blade spreads a layer of powder onto the 6061Al substrate, and the substrate is preheated to 160 ± 10 °C in advance. The laser selectively melts the powder according to the predetermined scanning path, and the target part is obtained by the way of layer-by-layer melting and solidification. The process parameters of laser additive manufacturing are as follows: laser power 250 - 350 W, scanning speed 600 - 1000 mm / s, spot diameter less than 100 μm, scanning spacing 110 - 130 μm, powder spreading layer thickness 20 - 40 μm, and the scanning strategy is zonal island scanning.

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