Shot blasting method for strengthening mechanical property of laser additive manufacturing titanium-based composite material

Abstract

The invention relates to a shot peening method for strengthening the mechanical property of a laser additive manufacturing titanium-based composite material, which comprises the following steps of: performing single-pass shot peening on the surface of the titanium-based composite material under the conditions that the air pressure is 0.1-0.25 MPa and the shot peening time is 3-10 minutes, and removing residual shots on the surface of the titanium-based composite material after the shot peening is finished, the tensile strength of the reinforced titanium-based composite material at the room temperature is improved by 50-100 MPa from 1152.76 MPa in an initial printing state. According to the shot blasting treatment provided by the invention, residual compressive stress is introduced by bombarding the metal surface through small particles, the surface structure is subjected to plastic deformation, grains on the outermost surface are remarkably refined, and the mechanical property of the titanium-based composite material manufactured by laser additive manufacturing is effectively improved at low cost.

Description

Technical Field

[0001] The present invention relates to the field of metal matrix composites, and particularly to the field of manufacturing titanium matrix composites by laser additive manufacturing. Background Art

[0002] Titanium matrix composites have high specific modulus, high specific strength, good high-temperature resistance and corrosion resistance, and have broad application prospects in the fields of aerospace, transportation, biomedicine, etc. Laser additive manufacturing technology can greatly shorten the manufacturing cycle and improve the efficiency of product R & D and production. Therefore, the application field of titanium matrix composites can be further expanded by using laser additive manufacturing technology. However, the laser additive manufacturing process is a rapid non-equilibrium solidification process with a large temperature gradient, generating a columnar crystal structure, which affects the mechanical properties of titanium matrix composites. Therefore, in order to improve the mechanical properties of laser additive manufactured titanium matrix composites, it is very necessary to find a post-treatment process.

[0003] Shot peening is a surface modification technology that introduces residual compressive stress to enhance its mechanical properties by bombarding the metal surface with small particles. It has the advantages of simple operation, low cost, and being unrestricted by the shape and position of parts, and is widely used to improve the mechanical strength, wear resistance, fatigue resistance, and corrosion resistance of metal parts. Shot peening is not only used to improve its fatigue life, but also can cause plastic deformation and refine the grain size. Therefore, shot peening can be used to improve the microstructure of laser additive manufactured titanium matrix composites and enhance the mechanical properties of titanium matrix composites.

[0004] At present, the research on strengthening the mechanical properties of laser additive manufactured titanium matrix composites mainly focuses on the preparation methods of laser additive manufactured titanium matrix composites and the research on the mechanical properties of traditional titanium alloys by shot peening. The Chinese invention patent with the publication number: CN113061779A and the publication date: December 31, 2021 discloses an additive manufacturing method of nanoparticle-reinforced titanium matrix composites based on electron beam selective melting. The electron beam selective melting technology under high vacuum and in-situ stress relief annealing conditions is used to obtain titanium matrix composites, and surface sandblasting treatment is carried out by post-treatment. However, it only studies how to prepare titanium matrix composites and does not study the influence of post-treatment on the mechanical properties of titanium matrix composites.

[0005] Reference 1 "M. Kahlin, H. Ansell, D. Basu, et al. Improved fatigue strength of additively manufactured Ti6Al4V by surface post processing[J]. International Journal of Fatigue, 2020, 134: 105497." points out that surface post-processing can improve the mechanical properties and fatigue strength of additively manufactured Ti6Al4V titanium alloy, but the maximum tensile strength is only 1108 MPa. How to further improve the mechanical properties of additively manufactured titanium matrix composites needs further research.

[0006] At present, most of the research on shot peening treatment focuses on the mechanical properties of traditional titanium alloys, and there is relatively little research on the mechanical properties of composites. In addition, the shot peening treatment parameters for laser additive manufactured titanium matrix composites still need to be explored through experiments. Moreover, inappropriate shot peening treatment parameters cannot achieve the purpose of strengthening the mechanical properties of laser additive manufactured titanium matrix composites by shot peening treatment. Summary of the Invention

[0007] The purpose of the present invention is to avoid the deficiencies of the prior art and provide a shot peening method that can effectively and low-costly strengthen the mechanical properties of laser additive manufactured titanium matrix composites.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A shot peening method for strengthening the mechanical properties of laser additive manufactured titanium matrix composites, comprising the following steps: Take the titanium matrix composite obtained by laser additive manufacturing and cool it to room temperature, and then perform shot peening treatment on the two opposite X-Z planes of the titanium matrix composite. Specifically: Perform single-pass shot peening on the surface of the titanium matrix composite under the conditions of an air pressure of 0.1 - 0.25 MPa and a shot peening time of 3 - 10 min. After the shot peening treatment is completed, remove the residual shot on the surface of the titanium matrix composite, and the strengthened titanium matrix composite with a room temperature tensile strength increased by 50 - 100 MPa from the initial printed state of 1152.76 MPa can be obtained; Among them, the distance from the spray gun to the surface of the titanium matrix composite is 250 - 350 mm, and the angle with the surface of the titanium matrix composite is 45 - 90°. The moving speed of the single-pass shot peening spray gun is 1 - 3 mm / s, the shot flow rate ejected by the spray gun is 7 - 10 Kg / min, and the shot diameter is 0.2 - 1.4 mm.

[0009] Furthermore, it also includes: Prepare a metallographic specimen of the strengthened titanium matrix composite material, quantify the thickness of the plastic deformation layer where the surface layer structure undergoes plastic deformation, and conduct a room-temperature tensile property test on the laser additive manufacturing titanium matrix composite material specimen after shot peening treatment to obtain the measurement results of the room-temperature mechanical properties of the titanium matrix composite material before and after shot peening treatment, which are used to judge the strengthening degree of the mechanical properties of the titanium matrix composite material.

[0010] Furthermore, obtain the metallographic specimen by wire cutting method, with a cutting speed of 0.05 - 0.1 mm / min. After grinding and polishing the metallographic specimen, place it in anhydrous ethanol and ultrasonically vibrate and clean it for 10 - 15 min, and then dry it to obtain a metallographic specimen with a smooth surface. Then, observe the thickness of the plastic deformation layer using SEM, use backscattered electron imaging, and then calibrate the thickness of the plastic deformation layer using image processing software, quantifying at intervals of 5 - 10 µm. At the same time, under each shot peening parameter condition, quantify 5 - 10 SEM pictures.

[0011] Furthermore, in the laser additive manufacturing in step one, the laser power is 1800 - 2100 W, the powder feeding rate is 8 - 10 g / min, the scanning rate is 4 - 8 mm / s, the spot diameter is 3 - 6 mm, and the overlapping rate is 30 - 70%. The titanium matrix composite material made by the laser additive manufacturing has a length of 50 - 100 mm, a width of 3 - 20 mm, and a height of 10 - 35 mm.

[0012] Furthermore, in step one, pure titanium is used as the substrate during laser additive manufacturing, and the substrate is preheated to 100 - 300 °C before laser additive manufacturing to prevent excessive stress caused by too fast initial cooling rate. At the same time, after laser additive manufacturing, use electrical discharge wire cutting method to separate the titanium matrix composite material from the substrate, and ultrasonically clean it with anhydrous ethanol for 10 - 15 min to remove the oil stain and bonded powder on the surface of the titanium matrix composite material.

[0013] Furthermore, during the laser additive manufacturing process in step one, high-purity argon is introduced to keep the oxygen content in the laser additive manufacturing below 0.05%.

[0014] Furthermore, process the tensile specimen of the strengthened titanium matrix composite material, and at least take 3 - 5 tensile specimens under different tensile conditions, and take the average value as the room-temperature tensile property under the shot peening parameters.

[0015] Furthermore, at air pressures of 0.1 MPa, 0.15 MPa, 0.2 MPa, and 0.25 MPa, 3 - 5 titanium matrix composite material specimens after shot peening treatment are obtained to measure the room-temperature tensile strength of the shot peening treatment under different air pressures.

[0016] Further, the projectiles are cast steel shots or carbon steel shots, and ultrasonic cleaning is carried out with absolute ethanol after shot peening to remove the residual projectiles on the surface.

[0017] Further, the titanium matrix composite material uses Ti65, Ti55 or Ti6242 as the titanium alloy matrix, and the reinforcing phase is 0.5 - 2.5 vol.% of added TiB whiskers, particles or TiC particles.

[0018] The beneficial effects of the present invention are as follows: The titanium matrix composite material produced by laser additive manufacturing has a large temperature gradient and generates a columnar crystal structure, which affects the mechanical properties of the material. The shot peening treatment provided by the present invention introduces residual compressive stress by bombarding the metal surface with small particles. The surface structure undergoes plastic deformation, and the grains at the outermost surface are significantly refined, effectively and at low cost improving the mechanical properties of the laser additive manufactured titanium matrix composite material. Description of the Drawings

[0019] Figure 1 It is the size and laser scanning strategy of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material in Example 1 of the present invention; Figure 2 It is the original microstructure photo of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material in Example 1 of the present invention without shot peening treatment; Figure 3 It is the thickness of the plastic deformation layer of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material in Example 1 of the present invention after shot peening treatment; Figure 4 It is the room temperature tensile stress - strain curve of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material in Example 1 of the present invention without shot peening treatment; Figure 5 It is the room temperature tensile stress - strain curve of the specimens of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material in Example 1 of the present invention after shot peening treatment at different air pressures when the shot peening time is 5 min.

[0020] Figure 6 It is the room temperature tensile stress - strain curve of the specimens of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material in Example 2 of the present invention without and after shot peening treatment at an air pressure of 0.25 MPa when the shot peening time is 10 min. Detailed Embodiments

[0021] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0022] The laser additive manufacturing process is a rapid non-equilibrium solidification process with a large temperature gradient, resulting in a columnar crystal structure, which affects the mechanical properties of the material. Therefore, in order to improve the mechanical properties of laser additive manufactured titanium matrix composites, it is very necessary to find a post-treatment process. Shot peening is a surface modification technology that introduces residual compressive stress by bombarding the metal surface with small particles to enhance mechanical properties. It has the advantages of simple operation, low cost, and being unrestricted by the shape and position of the parts, and is widely used to improve the mechanical strength, wear resistance, fatigue resistance, and corrosion resistance of metal parts. Shot peening is not only used to improve its fatigue life, but also can cause plastic deformation and refine the grain size. Therefore, shot peening can be used to improve the microstructure of laser additive manufactured titanium matrix composites and strengthen the mechanical properties of the material.

[0023] In order to achieve the above object, the present invention provides the following specific embodiments: Example 1: A shot peening method for strengthening the mechanical properties of laser additive manufactured titanium matrix composites, comprising the following steps: Step 1: Take a titanium matrix composite with Ti65, Ti55 or Ti6242 as the titanium alloy matrix and 0.5 - 2.5 vol.% of TiB whiskers, particles or TiC particles added as the reinforcing phase. Under the protection of high-purity argon, the oxygen content in the laser additive is maintained below 0.05%. With a laser power of 1800 - 2100W, a powder feeding rate of 8 - 10g / min, a scanning rate of 4 - 8mm / s, a spot diameter of 3 - 6mm, and an overlapping rate of 30 - 70%, perform laser additive manufacturing of the titanium matrix composite; At the same time, use pure titanium as the substrate and preheat the substrate to 100 - 300°C before laser additive manufacturing to prevent excessive stress caused by too fast initial cooling rate; Print a titanium matrix composite with a length of 50 - 100mm, a width of 3 - 20mm, and a height of 10 - 35mm.

[0024] Step 2: Use electrical discharge wire cutting to separate the titanium matrix composite obtained in Step 1 from the substrate, cool it to room temperature, and then perform ultrasonic cleaning with anhydrous ethanol for 10 - 15min to remove the oil stains and bonded powder on the surface of the titanium matrix composite.

[0025] Step 3: Perform shot peening on the opposite two X-Z planes of the titanium matrix composite processed in Step 2. Specifically: Under the conditions that the air pressure is 0.1 - 0.25 MPa and the shot peening time is 3 - 10 min, single-pass shot peening is carried out on the surface of the titanium matrix composite material. After the shot peening is completed, the residual shot on the surface of the titanium matrix composite material is removed, and the strengthened titanium matrix composite material with the room-temperature tensile strength increased by 50 - 100 MPa compared with the initial printed state of 1152.76 MPa is obtained; Among them, the distance from the spray gun to the surface of the titanium matrix composite material is 250 - 350 mm, and the angle with the surface of the titanium matrix composite material is 45 - 90°. The moving speed of the single-pass shot peening spray gun is 1 - 3 mm / s, the shot flow rate ejected by the spray gun is 7 - 10 Kg / min, and the shot diameter is 0.2 - 1.4 mm; The shot is cast steel shot or carbon steel shot, and after shot peening, ultrasonic cleaning is carried out with absolute ethanol to remove the residual shot on the surface.

[0026] Example 2: The same as Example 1, except that it further includes preparing a metallographic specimen of the strengthened titanium matrix composite material, quantitatively measuring the thickness of the plastic deformation layer where the surface layer structure undergoes plastic deformation, and conducting a room-temperature tensile property test on the metallographic specimen to obtain the measurement results of the room-temperature mechanical properties of the titanium matrix composite material before and after shot peening, which are used to judge the strengthening degree of the mechanical properties of the titanium matrix composite material; The metallographic specimen is obtained by wire cutting method, the cutting speed is 0.05 - 0.1 mm / min. After the metallographic specimen is polished, it is placed in absolute ethanol and ultrasonically vibrated and cleaned for 10 - 15 min and then dried to obtain a metallographic specimen with a smooth surface; Then, SEM is used to observe the thickness of the plastic deformation layer, backscattered electron imaging is used, and then, image processing software is used to calibrate the thickness of the plastic deformation layer, which is quantified at every 5 - 10 µm. At the same time, under each shot peening parameter condition, 5 - 10 SEM pictures are quantified.

[0027] Example 3: The same as Example 1, except that it further includes machining the tensile specimen of the strengthened titanium matrix composite material, and at least 3 - 5 tensile specimens are taken under different tensile conditions, and the average value is taken as the room-temperature tensile property under the shot peening parameters.

[0028] Example 4: The same as Example 1, except that it further includes obtaining 3 - 5 specimens of the titanium matrix composite material after shot peening under the air pressures of 0.1 MPa, 0.15 MPa, 0.2 MPa, and 0.25 MPa, which are used to measure the room-temperature tensile strength of the titanium matrix composite material after shot peening under different air pressures.

[0029] As Figure 1-6 shown, in order to further illustrate the technical solution and technical effect of the present invention, the following examples are provided, Example 1: As Figure 1As shown, a method for the mechanical properties of titanium matrix composites using shot peening enhanced laser additive manufacturing includes the following steps: Step 1: Prepare 1.0 vol.% TiBw / Ti65 composite materials using laser deposition technology. As Figure 1 shown, a single pass is used to fabricate a 65×15×5 mm 3 thin-walled wall of 1.0 vol.% TiBw / Ti65 composite material. Figure 1 In this case, during the additive manufacturing process, the reference point at the printing start position is point O. The X and Y axes refer to the directions within the build plane, which are horizontal directions and are also called in-layer directions, while the Z axis is the direction perpendicular to the build plane, which is the vertical direction and is also called the build direction. Then, the X-Z plane is the plane corresponding to the X and Z axes, and this plane is called the side section or XZ plane, while the XY plane is the transverse section.

[0030] Use pure titanium as the substrate. Before laser additive manufacturing, it must be preheated to 100 - 300 °C to prevent excessive stress caused by too fast initial cooling rate. After laser additive manufacturing, the sample is cooled to room temperature, and the sample is separated from the substrate using electrical discharge wire cutting method, and ultrasonically cleaned with absolute ethanol for 10 - 15 min to remove surface oil stains and part of the adhered powder. The laser process parameters used include: laser power of 2000 W, powder feeding rate of 9 g / min, scanning rate of 6 mm / s, spot diameter of 5 mm, and overlapping rate of 50%.

[0031] Step 2: Perform shot peening on the 1.0 vol.% TiBw / Ti65 composite material prepared by the laser deposition technology in step 1 on two opposite X-Z planes. First, place the sample in the equipment cavity, adjust the distance between the spray gun and the sample surface to 300 mm, use tools to make the angle between the spray gun and the sample 90°, set the moving rate of the spray gun for shot peening treatment to 2 mm / s, the shot flow rate to 9 Kg / min, the shot peening time to 5 min, and the air pressure to four groups of parameters of 0.1 MPa, 0.15 MPa, 0.2 MPa, and 0.25 MPa, with 3 samples under each group of shot peening parameters. After shot peening, ultrasonically clean with absolute ethanol for 15 min to remove the residual cast steel shots on the surface; Step 3: Obtain the metallographic specimens of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material after shot peening by wire cutting to quantify the thickness of the plastically deformed layer. Obtain the metallographic specimens of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material in the shot peened state by wire cutting with a cutting speed of 0.07 mm / min. Grind and polish the metallographic specimens, place them in absolute ethanol for ultrasonic vibration cleaning for 10 - 15 min, and then dry them to obtain the metallographic specimens of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material with a smooth surface. Observe the thickness of the plastically deformed layer by SEM and use backscattered electron imaging. Use Image-Pro Plus software to calibrate the plastically deformed layer, quantify it every 5 µm, and quantify 5 SEM images under each shot peening parameter.

[0032] Figure 2 This is the original microstructure photo of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material without shot peening. Figure 2 It can be concluded that the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material specimen without shot peening is composed of lamellar α phase, β phase, and TiBw.

[0033] Figure 3 This is the thickness of the plastically deformed layer of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material after shot peening; the surface layer structure of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material after shot peening undergoes plastic deformation. The α lamellae in the area near the surface are bent, and the grains are significantly refined at the outermost surface. When the shot peening time is 5 min, the thickness of the plastically deformed layer increases with the increase of air pressure. This is because as the air pressure increases, the initial kinetic energy of the shot gradually increases, thereby enhancing the energy when the shot bombards the metal surface, making the surface structure deformation more severe. At the same time, the depth of the area affected by the shot bombardment expands, causing the deeper layer structure to deform. Among them, when the air pressure is 0.25 MPa, the α lamellae in the plastically deformed layer area are elongated and distributed in a streamline shape, and the severe plastic deformation is serious, resulting in a slight decrease in the tensile strength compared to the specimen with an air pressure of 0.2 MPa.

[0034] Step 4: Conduct room temperature tensile property tests on the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material specimens without shot peening and shot peened with four groups of air pressures. Conduct room temperature tensile property tests on an Instron 3382 electronic universal testing machine. Take the average value of three specimens in each group as the tensile value of the specimen to obtain the room temperature mechanical properties of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material without shot peening and after shot peening.

[0035] As Figure 4 shown in the room temperature tensile stress-strain curve of the 1.0 vol.% TiBw / Ti65 composite material prepared by laser additive manufacturing without shot peening, the yield strength of the titanium matrix composite material without shot peening is 1039.84 MPa, the tensile strength is 1152.76 MPa, and the elongation is 3.76%.

[0036] Attached Figure 5 is the room temperature tensile stress-strain curve of the samples of the 1.0 vol.% TiBw / Ti65 composite material prepared by laser additive manufacturing after shot peening under different air pressures when the shot peening time is 5 min.

[0037] Table 1 Tensile properties of the 1.0 vol.% TiBw / Ti65 composite material in Example 1

[0038] From Figure 4 , Figure 5 and the analysis of Table 1, it can be seen that the strength of the samples of the 1.0 vol.% TiBw / Ti65 composite material prepared by laser additive manufacturing after shot peening has been improved.

[0039] When the air pressure is 0.25 MPa and the treatment time is 5 min, the yield strength of the sample is 929.33 MPa, which is 10.63% lower than that of the non-shot peened sample, the tensile strength is 1166.61 MPa, which is 1.2% higher than that of the non-shot peened sample, and the elongation is 4.02%; When the air pressure is 0.2 MPa and the treatment time is 5 min, the yield strength of the sample is 1100.65 MPa, which is 5.85% higher than that of the non-shot peened sample, the tensile strength is 1238.15 MPa, which is 7.41% higher than that of the non-shot peened sample, and the elongation is 3.41%, which is 9.31% lower than that of the non-shot peened sample; When the air pressure is 0.15 MPa and the treatment time is 5 min, the yield strength of the sample is 984.87 MPa, which is 5.27% lower than that of the non-shot peened sample, the tensile strength is 1175.48 MPa, which is 2.0% higher than that of the non-shot peened sample, and the elongation is 4.38%, which is 16.49% higher than that of the non-shot peened sample; When the air pressure is 0.1 MPa and the treatment time is 5 min, the yield strength of the sample is 1038.03 MPa, which is 0.17% lower than that of the non-shot peened sample, the tensile strength is 1203.97 MPa, which is 4.44% higher than that of the non-shot peened sample, and the elongation is 3.55%, which is 5.59% lower than that of the non-shot peened sample; As can be seen from the above results, when the shot peening parameters are 0.2 MPa - 5 min, the strength of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material sample increases most significantly. After shot peening the laser additive manufactured titanium matrix composite material, the tensile strength increases by 40 - 100 MPa, achieving the purpose of strengthening the mechanical properties of the laser additive manufactured titanium matrix composite material by using the shot peening method, and having good application prospects.

[0040] It shows that plastic deformation occurs in the surface structure of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material during shot peening. The grains at the outermost surface are significantly refined. The increase in air pressure makes the surface structure deformation more intense. At the same time, the increase in the depth of the area affected by the shot peening bombardment causes the metal in deeper layers to deform. However, intense plastic deformation is not conducive to the improvement of mechanical properties. When the air pressure is 0.2 MPa and the plastic deformation layer is 50 - 65 µm, the tensile strength of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material reaches 1238.15 MPa, indicating that the method of shot peening in the present invention realizes the strengthening of the laser additive manufactured titanium matrix composite material.

[0041] Example 2: The same as Example 1, except that this example includes the following steps: Step 1: Prepare a 1.0 vol.% TiBw / Ti65 composite material by using laser deposition technology, as Figure 1 shown to make a block-shaped 1.0 vol.% TiBw / Ti65 composite material of 70×15×15 mm 3 .

[0042] Use pure titanium as the substrate, and it must be preheated to 100 - 300 °C before laser additive manufacturing to prevent excessive stress caused by too fast initial cooling rate. After laser additive manufacturing, the sample is cooled to room temperature, and the sample is separated from the substrate by using electrical discharge wire cutting method, and ultrasonically cleaned with absolute ethanol for 15 min to remove the oil stain and part of the bonded powder on the surface. The laser process parameters used include: laser power of 2000 W, powder feeding rate of 9 g / min, scanning rate of 6 mm / s, spot diameter of 5 mm, and overlapping rate of 50%.

[0043] Step 2: Shot peening is carried out on the 1.0 vol.% TiBw / Ti65 composite material prepared by the laser deposition technology described in Step 1 with respect to two opposite X-Z planes. First, place the sample in the equipment cavity, adjust the distance between the spray gun and the sample surface to 300 mm, use tools to make the angle between the spray gun and the sample 90°, set the shot peening parameters: the moving speed of the spray gun is 2 mm / s, the shot flow rate is 9 Kg / min, the shot peening time is 10 min, and the air pressure is 0.25 MPa respectively. There are 3 samples under each set of shot peening parameters. After shot peening, ultrasonic cleaning is carried out with absolute ethanol for 15 min to remove the residual cast steel shots on the surface; Step 3: Room temperature tensile property tests are carried out on the as-deposited and shot-peened laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material specimens. The room temperature tensile property tests are carried out on an Instron 3382 electronic universal testing machine. The average value of three specimens in each group is taken as the tensile value of the specimen, and the room temperature mechanical properties of the as-deposited and shot-peened laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material are obtained.

[0044] As Figure 6 The room temperature tensile stress-strain curves of the as-deposited and shot-peened specimens of the laser additive manufactured 1.0 vol.% TiBw / Ti65 composite material with a shot peening time of 10 min and an air pressure of 0.25 MPa are obtained. It is found that the yield strength of the as-deposited bulk sample of the titanium matrix composite material is 1025.31 MPa, the tensile strength is 1126.80 MPa, and the elongation is 2.43%. The yield strength of the shot-peened bulk sample of the titanium matrix composite material is 995.89 MPa, the tensile strength is 1168.54 MPa, and the elongation is 2.86%. It shows that the method of shot peening in the present invention realizes the strengthening of the laser additive manufactured titanium matrix composite material.

[0045] The above are only the preferred examples of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A shot peening method for enhancing the mechanical properties of titanium-based composite materials manufactured by laser additive manufacturing, characterized in that: The following steps are involved: The titanium-based composite material obtained by laser additive manufacturing is cooled to room temperature, and then shot peening is performed on two opposite XZ surfaces of the titanium-based composite material, specifically: The surface of the titanium-based composite material is subjected to single-pass shot peening under the conditions of an air pressure of 0.1 to 0.25 MPa and a shot peening time of 3 to 10 minutes. After the shot peening is completed, the residual shot on the surface of the titanium-based composite material is removed to obtain a reinforced titanium-based composite material whose room temperature tensile strength is increased by 50 to 100 MPa from 1152.76 MPa in the initial printing state; Among them, the distance from the spray gun to the surface of the titanium-based composite material is 250-350 mm, and the angle with the surface of the titanium-based composite material is 45-90 degrees, the moving speed of the single-pass shot peening gun is 1-3 mm / s, the flow rate of the projectile sprayed by the spray gun is 7-10 kg / min, and the projectile diameter is 0.2-1.4 mm.

2. A shot peening method for enhancing the mechanical properties of titanium-based composite materials manufactured by laser additive manufacturing according to claim 1, characterized in that: Also includes: A metallographic sample of the strengthened titanium-based composite material is prepared, the thickness of the plastic deformation layer where plastic deformation occurs in the surface structure is quantified, and the room temperature tensile property test of the shot peened laser additively manufactured titanium-based composite material sample is carried out to obtain the measurement results of the room temperature mechanical properties of the titanium-based composite material before and after shot peening, which are used to judge the degree of mechanical property strengthening of the titanium-based composite material.

3. A shot peening method for enhancing the mechanical properties of titanium-based composite materials manufactured by laser additive manufacturing according to claim 2, characterized in that: The metallographic sample is obtained by a wire cutting method at a cutting speed of 0.05 to 0.1 mm / min. After the metallographic sample is polished, it is placed in anhydrous ethanol for ultrasonic vibration cleaning for 10 to 15 minutes and then blown dry to obtain a metallographic sample with a smooth surface; Then, the thickness of the plastic deformation layer was observed by SEM, using backscattered electron imaging. Then, the thickness of the plastic deformation layer was calibrated by image processing software, with quantification at every 5 to 10 µm. At the same time, 5 to 10 SEM images were quantified under each shot peening parameter condition.

4. A shot peening method for enhancing the mechanical properties of titanium-based composite materials manufactured by laser additive manufacturing according to claim 1, characterized in that: In the step 1, the laser power during laser addition is 1800-2100W, the powder feeding rate is 8-10g / min, the scanning rate is 4-8mm / s, the spot diameter is 3-6mm, and the overlap rate is 30-70%; The titanium-based composite material manufactured by laser additive manufacturing has a length of 50 to 100 mm, a width of 3 to 20 mm, and a height of 10 to 35 mm.

5. A shot peening method for enhancing the mechanical properties of titanium-based composite materials manufactured by laser additive manufacturing according to claim 1, characterized in that: In the step 1, pure titanium is used as the substrate during laser material addition, and the substrate is preheated to 100-300° C. before laser material addition to prevent excessive initial cooling speed from causing large stress; At the same time, after laser additive manufacturing, the titanium-based composite material was separated from the substrate using electric spark wire cutting, and ultrasonic cleaning was performed using anhydrous ethanol for 10 to 15 minutes to remove oil stains and bonding powder on the surface of the titanium-based composite material.

6. A shot peening method for enhancing the mechanical properties of titanium-based composite materials manufactured by laser additive manufacturing according to claim 1, characterized in that: During the laser material addition process in step 1, high-purity argon gas is introduced to keep the oxygen content in the laser material addition below 0.05%.

7. A shot peening method for enhancing the mechanical properties of titanium-based composite materials manufactured by laser additive manufacturing according to claim 1, characterized in that: The tensile specimen of the strengthened titanium-based composite material is processed, and at least 3 to 5 tensile specimens are taken under different tensile conditions, and the average value is taken as the room temperature tensile property under the shot peening parameters.

8. The shot peening method for enhancing the mechanical properties of titanium-based composite materials manufactured by laser additive manufacturing according to claim 1, characterized in that: It also includes obtaining 3 to 5 titanium-based composite material samples after shot peening at the air pressure of 0.1 MPa, 0.15 MPa, 0.2 MPa, and 0.25 MPa, which are used to measure the room temperature tensile strength of the shot peening under different air pressures.

9. A shot peening method for enhancing the mechanical properties of titanium-based composite materials manufactured by laser additive manufacturing according to any one of claims 1 to 8, characterized in that: The shot is cast steel shot or carbon steel shot, and after shot peening, ultrasonic cleaning is performed using anhydrous ethanol to remove residual shot on the surface.

10. A shot peening method for enhancing the mechanical properties of titanium-based composite materials manufactured by laser additive manufacturing according to any one of claims 1 to 8, characterized in that: The titanium-based composite material uses Ti65, Ti55 or Ti6242 as a titanium alloy matrix, and the reinforcement phase is 0.5-2.5 vol.% of added TiB whiskers, particles or TiC particles.

Images