TiB2 / 7075Al composite material and laser additive manufacturing method thereof

Abstract

The invention belongs to the technical field of additive manufacturing, and particularly relates to a TiB2 / 7075Al composite material and a laser additive manufacturing method thereof. In order to solve the problems that in laser additive manufacturing of the 7075 aluminum alloy, hot cracks are prone to occurring, residual stress is large, grains are coarse, performance defects exist and the like, TiB2 particles are added into the 7075 aluminum alloy, laser additive manufacturing is assisted through cooperation of high-frequency pulse current and ultrasonic waves, by means of the method, the performance of a structural part can be improved, and the performance of the structural part can be improved. And the application range of the laser additive manufacturing technology in the fields of aerospace and the like can be expanded.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and particularly relates to a TiB2 / 7075Al composite material and a laser additive manufacturing method thereof. Background Art

[0002] In the field of aerospace, 7075 aluminum alloy is widely used in various components due to its excellent mechanical properties and machining performance, especially in the manufacture of complex curved surface structures. Specifically, 7075 aluminum alloy is used to manufacture key components such as aircraft skins, fuselage frames, girders, propellers, fuel tanks, panels, and landing gear struts, as well as important components such as engine devices, main components, and turntables of space launch vehicles. However, traditional processing methods such as casting and forging have long production cycles, large material waste, and may lead to non-uniform and coarsened material microstructure and properties.

[0003] In recent years, laser additive manufacturing technology has received extensive attention due to its unique advantages. This technology can directly use powder materials to manufacture parts with complex geometric shapes, which not only greatly shortens the production cycle but also reduces material waste. More importantly, this technology can ensure that the processed parts have uniform microstructure and refined grains. In addition, laser additive manufacturing technology can also achieve fine control of the microstructure, thereby obtaining excellent mechanical properties. This technology has been widely applied in the manufacture of materials such as nickel-based and iron-based.

[0004] Applying laser additive manufacturing technology to 7075 aluminum alloy can overcome the disadvantages of traditional processing methods and achieve efficient and energy-saving production. However, due to the low laser absorption rate, high thermal conductivity, easy oxidation, large solidification range, high cooling rate, and high heat input of 7075 aluminum alloy, the following problems will occur in the laser additive manufacturing of 7075 aluminum alloy: (1) Prone to hot cracks: 7075 aluminum alloy has a high melting point and poor thermal conductivity, making it prone to hot cracks during the laser additive manufacturing process.

[0005] (2) Large residual stress: During the laser additive manufacturing process, due to rapid heating and cooling, large residual stress will be generated in 7075 aluminum alloy parts, affecting their mechanical properties.

[0006] (3) Coarse grains: During the laser additive manufacturing process, the grains of 7075 aluminum alloy are prone to coarsening, affecting its mechanical properties.

[0007] (4) Performance defects: During the laser additive manufacturing process, 7075 aluminum alloy parts are prone to defects such as pores and cracks, affecting their surface quality and corrosion resistance. Summary of the Invention

[0008] The present invention provides a TiB2 / 7075Al composite material and a laser additive manufacturing method therefor. The present invention adds TiB2 particles to 7075 aluminum alloy, and synergistically assists in laser additive manufacturing of structural parts (composite materials) through high-frequency pulsed current and ultrasonic waves. By this method, not only can the performance of the structural parts be improved, but also the application scope of laser additive manufacturing technology in the fields of aerospace and the like can be expanded.

[0009] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a laser additive manufacturing method for a TiB2 / 7075Al composite material, comprising the following steps: Step 1: Using 7075 aluminum alloy powder and TiB2 particles as raw materials, and fully mixing and homogenizing the 7075 aluminum alloy powder and TiB2 particles by high-energy ball milling to obtain a binary mixed powder of 7075 aluminum alloy and TiB2; Step 2: Drying the binary mixed powder of 7075 aluminum alloy and TiB2 obtained in Step 1; Step 3: Connecting the positive and negative electrodes of a high-frequency pulsed power supply to both ends of a substrate respectively, connecting an ultrasonic controller to an ultrasonic vibrator, and arranging the ultrasonic vibrator below the substrate; before printing starts, first turn on the high-frequency pulsed power supply to apply high-frequency pulsed current to preheat the substrate, and after printing starts, adjust the high-frequency pulsed power supply, turn on the ultrasonic controller, and use the ultrasonic vibrator to apply ultrasonic waves; Step 4: Using laser additive manufacturing technology to print the binary mixed powder of 7075 aluminum alloy and TiB2 after drying treatment in Step 2 along a preset path to form a three-dimensional part; Step 5: Grinding and cleaning the three-dimensional part in Step 4 to obtain the TiB2 / 7075Al composite material.

[0010] Further, in Step 1, the particle size range of the 7075 aluminum alloy powder is 5 μm to 25 μm, and the particle size range of the TiB2 particles is 1 μm to 3 μm.

[0011] Still further, in Step 1, fully mixing and homogenizing the 7075 aluminum alloy powder and TiB2 particles by high-energy ball milling specifically includes: Set the mass fraction of TiB2 particles to 1% and the mass fraction of 7075 aluminum alloy powder to 99%. Install the ball milling tank containing the mixed powder of 7075 aluminum alloy powder and TiB2 particles on a planetary ball mill and fix it tightly. Carry out high-energy ball milling for powder mixing. The ball milling medium is stainless steel. The powder mixing time is 32 - 48 h, the rotational speed of the ball mill is 1200 - 2000 r / min, and the ball-to-powder ratio is 5:1. After powder mixing, the TiB2 powder is dispersedly distributed and completely embedded inside the surface layer of the 7075 aluminum alloy powder, obtaining a binary mixed powder of 7075 aluminum alloy and TiB2.

[0012] Furthermore, the drying treatment in step 2 is vacuum drying. The vacuum degree of vacuum drying is <5 Pa, the temperature is 120 - 140 °C, and the time is 2 - 3 h.

[0013] Furthermore, before the start of printing in step 3, first turn on the high-frequency pulse power supply to apply a high-frequency pulse current to preheat the substrate. After the start of printing, adjust the high-frequency pulse power supply and turn on the ultrasonic controller to apply ultrasonic waves using an ultrasonic oscillator. Specifically: Before the start of printing, first turn on the high-frequency pulse power supply to apply a high-frequency pulse current. Set the current intensity to 400 - 600 A, the pulse frequency to 10 - 15 kHz, and keep the power on for 10 seconds to preheat the substrate. After the start of printing, adjust the high-frequency pulse power supply, adjust the current intensity to 300 - 500 A, that is, the current intensity is reduced by 100 A, and the pulse frequency is 10 - 12 kHz, that is, the pulse frequency is reduced by 0 - 3 kHz. Turn on the ultrasonic controller and use the ultrasonic oscillator to apply ultrasonic waves with a frequency of 15 - 30 kHz.

[0014] Furthermore, in step 4, using the laser additive manufacturing technology, print the binary mixed powder of 7075 aluminum alloy and TiB2 after the drying treatment in step 2 along a preset path to form a three-dimensional part. Specifically: Weigh the binary mixed powder of 7075 aluminum alloy and TiB2 after the drying treatment in step 2 by weight and place it inside the laser additive manufacturing equipment. The process parameters of laser additive manufacturing are as follows: Laser power: 1500 - 4000 W; Scanning speed: 300 - 800 mm / s; Printing layer thickness: 50 μm; Printing rotation angle: 60°; The protective gas is argon, and the flow rate is 20 L / min.

[0015] Furthermore, in step 5, grind and clean the three-dimensional part in step 4. Specifically: Place the three-dimensional part obtained in Step 4 on a steel flat plate, and successively polish the periphery and surface with sandpapers of 400 mesh, 800 mesh, 1000 mesh, and 1500 mesh. After polishing, polish it with a polishing machine, and then clean it with an ultrasonic cleaning machine. The ultrasonic frequency is 28KHz - 40KHz, and the cleaning duration is 2 - 4 minutes.

[0016] In a second aspect, the present invention also provides a TiB2 / 7075Al composite material prepared by a method of laser additive manufacturing of TiB2 / 7075Al composite material.

[0017] Compared with the prior art, the present invention has the following advantages: 1. The present invention proposes a brand-new method for laser additive manufacturing of TiB2 / 7075Al composite material, which can realize short-cycle, high-precision, and high-performance continuous manufacturing of difficult-to-machine parts, meeting the major needs of modern industry.

[0018] 2. The addition of TiB2 particles inside the 7075 aluminum alloy powder in the present invention is based on the following theoretical bases: 1) TiB2 particles are an excellent reinforcing phase, and the dispersed TiB2 particles can significantly improve the mechanical properties of the matrix. 2) Considering the relatively high reflectivity of 7075 aluminum alloy powder, the addition of TiB2 particles can effectively improve the laser absorption rate of the mixed powder, inhibit nucleation and refine the microstructure, eliminate cracks and inhibit the generation of pores, thereby improving the formability and mechanical properties of the material.

[0019] 3. The use of high-frequency pulsed current for assistance in laser additive manufacturing in the present invention has the following effects: 1) For the substrate: In the present invention, the substrate is preheated by high-frequency pulsed current, which can improve the temperature uniformity of the substrate, thereby reducing the generation of thermal stress and thermal cracks. In addition, preheating can improve the melting performance of 7075 aluminum alloy, making it easier to interact with the laser, thereby improving the printing quality and accuracy. At the same time, preheating can also reduce the heat conduction loss during the printing process, improve the melting efficiency of the material, and accelerate the printing speed. 2) For the printed layer: In the present invention, high-frequency pulsed current can be used to achieve local annealing and recrystallization, thereby increasing the recrystallization ratio and mechanical properties of the TiB2 / 7075Al composite material. In addition, high-frequency pulsed current treatment can eliminate the first internal stress and the second internal stress inside the material of the printed layer, reducing the stress concentration phenomenon. 3) For the layer being printed: In the present invention, the printed layer is equivalent to the substrate during the printing process, forming a virtuous cycle. This design enables each layer of printing to have a good forming foundation, thereby improving the overall printing quality and efficiency.

[0020] 4. The present invention uses ultrasonic waves for assistance in laser additive manufacturing and has the following effects: 1) Ultrasonic waves can adjust the internal pressure gradient of the melt, thereby achieving control over the grain structure and distribution. This is because the high-frequency vibration of ultrasonic waves can generate pressure waves at the microscale, and these pressure waves can change the fluidity inside the melt, thereby affecting the formation and distribution of grains inside the composite material and the overall performance. 2) The introduction of ultrasonic waves can effectively inhibit the growth of columnar grains and promote the formation of equiaxed grains. This is because the high-frequency vibration of ultrasonic waves can break the temperature gradient in the melt, thereby inhibiting the growth of columnar grains. At the same time, this high-frequency vibration can also promote the formation of crystal nuclei in the melt, thereby promoting the formation of equiaxed grains. The above changes not only improve the microstructure of the TiB2 / 7075Al composite material, but also increase the density and mechanical properties of the TiB2 / 7075Al composite material, making the properties of the TiB2 / 7075Al composite material more uniform in all directions and reducing anisotropy. 3) The introduction of ultrasonic waves can weaken the texture of the TiB2 / 7075Al composite material, making the properties of the TiB2 / 7075Al composite material more uniform and stable. This is because the high-frequency vibration of ultrasonic waves can break the grain orientation in the melt, thereby weakening the texture of the TiB2 / 7075Al composite material. This change helps to improve the overall performance of the TiB2 / 7075Al composite material, and the parameters of the ultrasonic controller can be adjusted to make it more suitable for various complex application scenarios. 4) The introduction of ultrasonic waves can optimize the surface quality of the laser additive manufacturing finished product. By the high-frequency vibration of ultrasonic waves, the fluidity of the melt surface is changed, thereby improving the surface quality of the finished product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a scanning micrograph of 7075 aluminum alloy powder; Figure 2 is a scanning micrograph of TiB2 particles; Figure 3 is a scanning micrograph of the binary mixed powder; Figure 4 are the density and relative density test results of the TiB2 / 7075Al composite materials in Examples 1, 2, and 3; Figure 5 is the metallographic structure diagram of the TiB2 / 7075Al composite material in Example 1; Figure 6 is the metallographic structure diagram of the TiB2 / 7075Al composite material in Example 2; Figure 7 is the metallographic structure diagram of the TiB2 / 7075Al composite material in Example 3; Figure 8 are the nanoindentation microhardness diagrams of the TiB2 / 7075Al composite materials in Examples 1, 2, and 3. Detailed implementation manners

[0022] To further elaborate on the technical solution of the present invention, the present invention will be further described below through embodiments. Embodiment 1

[0023] A laser additive manufacturing method for a TiB2 / 7075Al composite material in this embodiment includes the following steps: Step 1: Using 7075 aluminum alloy powder and TiB2 particles as raw materials, and fully mixing the 7075 aluminum alloy powder and TiB2 particles evenly by high-energy ball milling to obtain a binary mixed powder of 7075 aluminum alloy and TiB2; The particle size range of the 7075 aluminum alloy powder is 5μm - 25μm, and the particle size range of the TiB2 particles is 1μm - 3μm.

[0024] The specific method of fully mixing the 7075 aluminum alloy powder and TiB2 particles evenly by high-energy ball milling is as follows: Set the mass fraction of TiB2 particles to 1% and the mass fraction of 7075 aluminum alloy powder to 99%. Install the ball milling tank filled with the mixed powder of 7075 aluminum alloy powder and TiB2 particles on a planetary ball mill and fix it tightly. Perform high-energy ball milling for powder mixing. The ball milling medium is stainless steel, the powder mixing time is 48h, the rotation speed of the ball mill is 1500r / min, the ball-to-material ratio is 5:1. After powder mixing, the TiB2 powder is diffusely distributed and completely embedded inside the surface layer of the 7075 aluminum alloy powder, obtaining a binary mixed powder of 7075 aluminum alloy and TiB2.

[0025] Step 2: Perform drying treatment on the binary mixed powder of 7075 aluminum alloy and TiB2 obtained in Step 1; The drying treatment is vacuum drying. The vacuum degree of vacuum drying is <5Pa, the temperature is 120°C, and the time is 2h. After drying, take it out and set it aside.

[0026] Step 3: Connect the positive and negative electrodes of the high-frequency pulse power supply to both ends of the substrate respectively. Connect the ultrasonic controller to the ultrasonic vibrator, and the ultrasonic vibrator is arranged under the substrate; before printing starts, first turn on the high-frequency pulse power supply to apply a high-frequency pulse current, set the current intensity to 500A, the pulse frequency to 15kHz, and keep the power on for 10 seconds to preheat the substrate. After printing starts, adjust the high-frequency pulse power supply, adjust the current intensity to 400A, the pulse frequency to 10kHz, turn on the ultrasonic controller, and use the ultrasonic vibrator to apply ultrasonic waves with a frequency of 20kHz; Step 4: Using laser additive manufacturing technology, print the binary mixed powder of 7075 aluminum alloy and TiB2 after drying treatment in Step 2 along a preset path to form a three-dimensional part; Specifically: Weigh 1000 g of the binary mixed powder of 7075 aluminum alloy and TiB2 after drying treatment in Step 2 according to the amount, and place it inside the laser additive manufacturing equipment. The process parameters of laser additive manufacturing are as follows: Laser power: 2000 W; Scanning speed: 500 mm / s; Printing layer thickness: 50 μm; Printing rotation angle: 60°; The protective gas is argon, and the flow rate is 20 L / min.

[0027] Step 5: Grind and clean the three-dimensional part in Step 4 to obtain the TiB2 / 7075Al composite material; Specifically: Place the three-dimensional part in Step 4 on a steel flat plate, and successively grind the periphery and surface with sandpapers of 400 mesh, 800 mesh, 1000 mesh, and 1500 mesh. After grinding, polish it with a polishing machine, and then clean it with an ultrasonic cleaning machine. The ultrasonic frequency is 30 KHz, and the cleaning duration is 3 min. Example 2

[0028] The difference between this example and Example 1 is that in Step 3, only high-frequency pulsed current assistance is applied.

[0029] Specifically: Before printing starts, turn on the high-frequency pulsed power supply to apply high-frequency pulsed current. Set the current intensity to 500 A, the pulse frequency to 15 kHz, and keep the power on for 10 seconds to preheat the substrate. After printing starts, adjust the high-frequency pulsed power supply, and adjust the current intensity to 400 A and the pulse frequency to 10 kHz. Example 3

[0030] The difference between this example and Example 1 is that in Step 3, only ultrasonic assistance is applied.

[0031] Specifically: After printing starts, turn on the ultrasonic controller and use the ultrasonic vibrator to apply ultrasonic waves with a frequency of 20 kHz. Example 4

[0032] A method for laser additive manufacturing of a TiB2 / 7075Al composite material in this example includes the following steps: Step 1: Use 7075 aluminum alloy powder and TiB2 particles as raw materials, and fully mix and homogenize the 7075 aluminum alloy powder and TiB2 particles by high-energy ball milling to obtain a binary mixed powder of 7075 aluminum alloy and TiB2; The particle size range of the 7075 aluminum alloy powder is 5 μm to 25 μm, and the particle size range of the TiB2 particles is 1 μm to 3 μm.

[0033] The 7075 aluminum alloy powder and TiB2 particles are fully and evenly mixed by high-energy ball milling, specifically as follows: Set the mass fraction of TiB2 particles to 1% and the mass fraction of 7075 aluminum alloy powder to 99%. Install the ball milling tank containing the mixed powder of 7075 aluminum alloy powder and TiB2 particles on a planetary ball mill and fix it tightly. Conduct high-energy ball milling for powder mixing. The ball milling medium is stainless steel, the powder mixing time is 32 h, the rotational speed of the ball mill is 1200 r / min, the ball-to-powder ratio is 5:1. After powder mixing, the TiB2 powder is dispersedly distributed and completely embedded inside the surface layer of the 7075 aluminum alloy powder, obtaining a binary mixed powder of 7075 aluminum alloy and TiB2.

[0034] Step 2, perform a drying treatment on the binary mixed powder of 7075 aluminum alloy and TiB2 obtained in Step 1; The drying treatment is vacuum drying. The vacuum degree of vacuum drying is <5 Pa, the temperature is 130 °C, and the time is 3 h. After drying, take it out and set it aside.

[0035] Step 3, connect the positive and negative electrodes of the high-frequency pulse power supply to both ends of the substrate respectively. Connect the ultrasonic controller to the ultrasonic vibrator, and set the ultrasonic vibrator below the substrate; Before starting printing, first turn on the high-frequency pulse power supply to apply a high-frequency pulse current, set the current intensity to 400 A, the pulse frequency to 10 kHz, and keep the power on for 10 seconds to preheat the substrate. After starting printing, adjust the high-frequency pulse power supply, adjust the current intensity to 300 A, the pulse frequency to 10 kHz, turn on the ultrasonic controller, and use the ultrasonic vibrator to apply ultrasonic waves with a frequency of 15 kHz; Step 4, use laser additive manufacturing technology to print the binary mixed powder of 7075 aluminum alloy and TiB2 after the drying treatment in Step 2 along a preset path to form a three-dimensional part; Specifically: Weigh 1000 g of the binary mixed powder of 7075 aluminum alloy and TiB2 after the drying treatment in Step 2 and place it inside the laser additive manufacturing equipment. The process parameters of laser additive manufacturing are as follows: Laser power: 1500 W; Scanning speed: 300 mm / s; Printing layer thickness: 50 μm; Printing rotation angle: 60°; The protective gas is argon, and the flow rate is 20 L / min.

[0036] Step 5, polish and clean the three-dimensional part in Step 4 to obtain the TiB2 / 7075Al composite material; Specifically: Place the three-dimensional part in step 4 on a steel flat plate, and successively polish the periphery and surface with sandpapers of 400 mesh, 800 mesh, 1000 mesh, and 1500 mesh. After polishing, polish it with a polishing machine, and then clean it with an ultrasonic cleaner. The ultrasonic frequency is 28KHz, and the cleaning duration is 2 minutes. Example 5

[0037] A laser additive manufacturing method for TiB2 / 7075Al composite material in this example includes the following steps: Step 1: Use 7075 aluminum alloy powder and TiB2 particles as raw materials, and fully mix and homogenize the 7075 aluminum alloy powder and TiB2 particles by high-energy ball milling to obtain a binary mixed powder of 7075 aluminum alloy and TiB2. The particle size range of the 7075 aluminum alloy powder is 5μm - 25μm, and the particle size range of the TiB2 particles is 1μm - 3μm.

[0038] The specific method of fully mixing and homogenizing the 7075 aluminum alloy powder and TiB2 particles by high-energy ball milling is as follows: Set the mass fraction of TiB2 particles to 1%, and the mass fraction of 7075 aluminum alloy powder to 99%. Install the ball milling tank filled with the mixed powder of 7075 aluminum alloy powder and TiB2 particles on a planetary ball mill and fix it tightly, and perform high-energy ball milling for powder mixing. The ball milling medium is stainless steel, the powder mixing time is 40h, the rotational speed of the ball mill is 2000r / min, the ball-to-material ratio is 5:1. After powder mixing, the TiB2 powder is dispersed and completely embedded inside the surface layer of the 7075 aluminum alloy powder to obtain a binary mixed powder of 7075 aluminum alloy and TiB2.

[0039] Step 2: Perform drying treatment on the binary mixed powder of 7075 aluminum alloy and TiB2 obtained in step 1. The drying treatment is vacuum drying. The vacuum degree of vacuum drying < 5Pa, the temperature is 140°C, and the time is 2h. After drying, take it out and set it aside.

[0040] Step 3: Connect the positive and negative electrodes of the high-frequency pulse power supply to both ends of the substrate respectively, connect the ultrasonic controller to the ultrasonic vibrator, and set the ultrasonic vibrator below the substrate; before printing starts, first turn on the high-frequency pulse power supply to apply a high-frequency pulse current, set the current intensity to 600A, the pulse frequency to 13kHz, and keep the power on for 10 seconds to preheat the substrate. After printing starts, adjust the high-frequency pulse power supply, adjust the current intensity to 500A, the pulse frequency to 12 kHz, turn on the ultrasonic controller, and use the ultrasonic vibrator to apply ultrasonic waves with a frequency of 30 kHz. Step 4: Using laser additive manufacturing technology, print the binary mixed powder of 7075 aluminum alloy and TiB2 after the drying treatment in Step 2 along a preset path to form a three-dimensional part; Specifically: Weigh 1000 g of the binary mixed powder of 7075 aluminum alloy and TiB2 after the drying treatment in Step 2, and place it inside the laser additive manufacturing equipment. The process parameters of laser additive manufacturing are as follows: Laser power: 4000 W; Scanning speed: 800 mm / s; Printing layer thickness: 50 μm; Printing rotation angle: 60°; The protective gas is argon, and the flow rate is 20 L / min.

[0041] Step 5: Grind and clean the three-dimensional part in Step 4 to obtain the TiB2 / 7075Al composite material; Specifically: Place the three-dimensional part in Step 4 on a steel flat plate, and successively grind the periphery and surface with sandpapers of 400 mesh, 800 mesh, 1000 mesh, and 1500 mesh. After grinding, polish it with a polishing machine, and then clean it with an ultrasonic cleaner. The ultrasonic frequency is 40 KHz, and the cleaning duration is 3 min.

[0042] Perform scanning electron microscope inspection on the 7075 aluminum alloy powder, TiB2 particles, and the binary mixed powder formed by them involved in the above embodiments. The results are as Figures 1 to 3 shown. It can be clearly observed from Figures 1 to 3 that the mixing effect of the binary mixed powder is sufficient, the TiB2 particles are evenly distributed in it, and at the same time, the sphericity of the 7075 aluminum alloy powder is also good.

[0043] Corrode the TiB2 / 7075Al composite materials obtained in Examples 1, 2, and 3 with a corrosion solution. The corrosion solution is composed of distilled water with a mass fraction of 95%, nitric acid with a mass fraction of 4%, and hydrofluoric acid with a mass fraction of 1%. Drop the corrosion solution on the surface of the TiB2 / 7075Al composite material and keep it for 70 s for corrosion. Next, wash the sample with clean water for 10 s. Then, further wash the sample with alcohol with a volume fraction of 75% for 2 s. Finally, dry the sample with a hair dryer.

[0044] Subsequent tissue analysis and hardness testing were carried out. The Archimedes drainage method was used to test the density of the TiB2 / 7075Al composite material. The test was conducted 5 times, and the maximum and minimum values were removed, and the average value was taken. The TiB2 / 7075Al composite material was placed under a metallurgical microscope to observe the distribution state of TiB2 and microscopic defects such as pores and cracks. Further, the morphology, quantity, and elemental distribution of internal microscopic defects were observed through a scanning electron microscope. Finally, the microhardness was measured by a nanoindentation tester.

[0045] Figure 4 Table 1 shows the density and densification test results of the TiB2 / 7075Al composite materials in Examples 1, 2, and 3. It can be seen that the density of the TiB2 / Al composite material in Example 2 is 2.68 g / cm 3 , and its densification is 94.04%; the density of the TiB2 / Al composite material in Example 3 is 2.71 g / cm 3 , and its densification is 95.09%. Under the action of ultrasonic waves, its densification is improved; the density of the TiB2 / 7075Al composite material in Example 1 is 2.79 g / cm 3 , and its densification is 97.89%. Under the synergistic action of high-frequency pulsed current and ultrasonic waves, its densification is significantly improved.

[0046] Figures 5 to 7 Figures 2, 3, and 4 are the metallographic structure diagrams of the TiB2 / 7075Al composite materials in Examples 1, 2, and 3 respectively. It can be seen that the surface cracks of the TiB2 / Al composite material in Example 2 are fewer and shallower, but the distribution of TiB2 particles is not uniform enough ( Figure 6 ); the TiB2 particles of the TiB2 / Al composite material in Example 3 are evenly distributed, but it has more and deeper cracks ( Figure 7 ); the TiB2 particles of the TiB2 / 7075Al composite material in Example 1 are evenly distributed, and the cracks are almost completely eliminated ( Figure 5 ).

[0047] Figure 8 Figure 5 is the nanoindentation microhardness diagram of the TiB2 / 7075Al composite materials in Examples 1, 2, and 3. It can be seen that the microhardness of the TiB2 / Al composite material in Example 2 is 2.109 GPa, the microhardness of the TiB2 / Al composite material in Example 3 is 2.258 GPa, which is enhanced compared with Example 2; the microhardness of the TiB2 / Al composite material in Example 1 is 2.660 GPa, which is significantly enhanced compared with Examples 2 and 3.

[0048] The main features and advantages of the present invention have been shown and described above. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

[0049] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A laser additive manufacturing method for TiB2 / 7075Al composite materials, characterized in that, It includes the following steps: Step 1: Using 7075 aluminum alloy powder and TiB2 particles as raw materials, and fully mixing the 7075 aluminum alloy powder and TiB2 particles evenly by high-energy ball milling to obtain a binary mixed powder of 7075 aluminum alloy and TiB2; Step 2: Drying the binary mixed powder of 7075 aluminum alloy and TiB2 obtained in Step 1; Step 3: Connecting the positive and negative electrodes of the high-frequency pulse power supply to both ends of the substrate respectively, connecting the ultrasonic controller to the ultrasonic vibrator, and setting the ultrasonic vibrator under the substrate; Before printing starts, first turn on the high-frequency pulse power supply to apply a high-frequency pulse current to preheat the substrate. After printing starts, adjust the high-frequency pulse power supply, turn on the ultrasonic controller, and use the ultrasonic vibrator to apply ultrasonic waves; Step 4: Using laser additive manufacturing technology to print the binary mixed powder of 7075 aluminum alloy and TiB2 after drying treatment in Step 2 along a preset path to form a three-dimensional part; Step 5: Grinding and cleaning the three-dimensional part in Step 4 to obtain the TiB2 / 7075Al composite material.

2. The laser additive manufacturing method of the TiB2 / 7075Al composite material according to claim 1, characterized in that, In Step 1, the particle size range of the 7075 aluminum alloy powder is 5μm - 25μm, and the particle size range of the TiB2 particles is 1μm - 3μm.

3. The laser additive manufacturing method of the TiB2 / 7075Al composite material according to claim 1, characterized in that, In Step 1, fully mixing the 7075 aluminum alloy powder and TiB2 particles evenly by high-energy ball milling is specifically as follows: Set the mass fraction of TiB2 particles to 1% and the mass fraction of 7075 aluminum alloy powder to 99%. Install the ball milling tank filled with the mixed powder of 7075 aluminum alloy powder and TiB2 particles on a planetary ball mill and fix it tightly. Perform high-energy ball milling for powder mixing. The ball milling medium is stainless steel, the powder mixing time is 32 - 48h, the rotational speed of the ball mill is 1200 - 2000r / min, the ball-to-material ratio is 5:

1. After powder mixing, the TiB2 powder is diffusely distributed and completely embedded inside the surface layer of the 7075 aluminum alloy powder to obtain a binary mixed powder of 7075 aluminum alloy and TiB2.

4. The laser additive manufacturing method of the TiB2 / 7075Al composite material according to claim 1, characterized in that, In Step 2, the drying treatment is vacuum drying. The vacuum degree of the vacuum drying is <5Pa, the temperature is 120 - 140°C, and the time is 2 - 3h.

5. The laser additive manufacturing method of the TiB2 / 7075Al composite material according to claim 1, characterized in that In Step 3, before printing starts, first turn on the high-frequency pulse power supply to apply a high-frequency pulse current to preheat the substrate. After printing starts, adjust the high-frequency pulse power supply, turn on the ultrasonic controller, and use the ultrasonic vibrator to apply ultrasonic waves, specifically as follows: Before printing starts, first turn on the high-frequency pulse power supply to apply a high-frequency pulse current, set the current intensity to 400 - 600A, the pulse frequency to 10 - 15kHz, and keep the power on for 10 seconds to preheat the substrate. After printing starts, adjust the high-frequency pulse power supply, adjust the current intensity to 300 - 500A, the pulse frequency to 10 - 12kHz, turn on the ultrasonic controller, and use the ultrasonic vibrator to apply ultrasonic waves with a frequency of 15 - 30kHz.

6. The laser additive manufacturing method of the TiB2 / 7075Al composite material according to claim 1, characterized in that, In Step 4, using laser additive manufacturing technology to print the binary mixed powder of 7075 aluminum alloy and TiB2 after drying treatment in Step 2 along a preset path to form a three-dimensional part, specifically as follows: Weigh the binary mixed powder of 7075 aluminum alloy and TiB2 after drying treatment in Step 2 according to the amount. Inside the laser additive manufacturing equipment, the process parameters of laser additive manufacturing are as follows: Laser power: 1500 - 4000 W; Scanning speed: 300 - 800 mm / s; Printing layer thickness: 50 μm; Printing rotation angle: 60°; The protective gas is argon with a flow rate of 20 L / min.

7. The laser additive manufacturing method of the TiB2 / 7075Al composite material according to claim 1, characterized in that, In Step 5, the three-dimensional part in Step 4 is polished and cleaned. Specifically: Place the three-dimensional part in Step 4 on a steel flat plate, and polish the periphery and surface successively with sandpapers of 400 mesh, 800 mesh, 1000 mesh, and 1500 mesh. After polishing, polish it with a polishing machine, and then clean it with an ultrasonic cleaner. The ultrasonic frequency is 28 KHz - 40 KHz, and the cleaning duration is 2 - 4 min.

8. The TiB2 / 7075Al composite material prepared by the laser additive manufacturing method of the TiB2 / 7075Al composite material according to any one of claims 1 - 7.

Images