Additive Manufacturing In-Situ Strengthening Method

Abstract

The present invention provides an in-situ strengthening method for additive manufacturing, comprising the following steps: S1: determining the microstructure and residual stress requirements required for different locations of the component based on the use requirements of the component, determining the manufacturing and strengthening processes for each location of the component, and obtaining manufacturing process parameters and path parameters; S2: using a surface light source laser as a continuous laser, and performing beam shaping on the surface light source laser so that the light spot becomes a hollow shape; S3: using the continuous laser to melt a metal powder material layer to obtain an annular molten pool, and forming an inner solidification region inside the annular molten pool; S4: applying at least one pulsed laser to the inner solidification region; S5: scanning with a pulsed laser following the continuous laser, and strengthening the prepared metal deposition layer below the annular molten pool by the pulsed laser; S6: repeating steps S3-S5, processing layer by layer. In this method, the strengthening region is located below the annular molten pool, which can avoid recrystallization and annealing of the material during the melting process.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to an additive manufacturing in-situ strengthening method. Background Art

[0002] Additive manufacturing (AM) is a 3D printing technology that uses a computer to control the movement of a high-energy beam to achieve melting or sintering. This technology directly manufactures complex parts by melting and stacking them layer by layer. It offers advantages such as high forming freedom, low material consumption, and suitability for customized designs. Therefore, it is widely used in aerospace, automotive, medical device, and other fields, becoming one of the advanced manufacturing technologies that countries are competing to develop. However, due to the high cooling rate, high stress, and the dominant top-to-bottom temperature gradient, AM currently suffers from internal defects such as pores and cracks that are difficult to eliminate, the formation of large columnar crystals, and the generation of tensile stress on the surface. Furthermore, directly forming complex structures makes it difficult to strengthen individual components.

[0003] In order to solve the above problems, a variety of in-situ strengthening methods for additive manufacturing have attracted much attention in recent years. CN117551952A discloses a scanning strip ultra-high frequency laser shot peening strengthening method for nickel-based high-temperature alloys. This method requires the formation of a water constraint layer on the surface of the material first, which is difficult to achieve for additive manufacturing using powders, wires and high environmental requirements. CN114985767B discloses a method for metal additive manufacturing using composite laser shock and laser annealing, which uses a pulsed laser followed by a continuous laser to achieve the strengthening of additively manufactured parts. However, this method still requires a mask and a loss layer, and a smaller molten pool has a poor effect on the shock wave constraint effect, and the strengthening area is in a shallower forming layer. The remelting depth during additive manufacturing is generally 2-5 times the layer thickness, which is greater than the depth of the above-mentioned strengthening layer. Therefore, the strengthening layer will be melted or annealed by the next layer of additive manufacturing molten pool, losing the strengthening effect.

[0004] Looking at the above related technologies, the mechanical properties of metal parts obtained by metal additive manufacturing need to be improved. Summary of the Invention

[0005] In order to overcome the problems existing in the related art, the present invention provides an in-situ strengthening method for additive manufacturing, which aims to solve the problem of poor strengthening effect caused by the pulsed laser strengthening layer being remelted or annealed by the next forming layer in additive manufacturing.

[0006] The object of the present invention is to provide an additive manufacturing in-situ strengthening method, comprising the following steps:

[0007] S1: According to the use requirements of the parts, determine the microstructure and residual stress requirements of different parts, determine the manufacturing and strengthening processes of each part, and obtain the manufacturing process parameters and path parameters;

[0008] S2: Using the surface light source laser as a continuous laser, the surface light source laser is beam shaped to make the light spot into a hollow shape;

[0009] S3: using a continuous laser to melt the metal powder material layer to obtain an annular molten pool of a desired size, wherein an inner solidification region is formed inside the annular molten pool;

[0010] S4: applying at least one pulsed laser beam to the inner coagulation area;

[0011] The pulse laser is arranged at at least one of the inner coagulation region, the front edge of the inner coagulation region and the rear edge of the inner coagulation region;

[0012] S5: The pulse laser scans following the continuous laser, and while preparing the metal deposition layer of the current layer, the pulse laser strengthens the prepared metal deposition layer below the annular molten pool;

[0013] When the current metal deposition layer is formed, the bottom of the molten pool is at least one layer thick higher than the bottom of the molten pool when the previous layer is formed. Therefore, the previous layer cannot be remelted when the current layer is formed. The range of influence of the residual heat of forming is smaller than the strengthening range, which is conducive to reducing annealing.

[0014] S6: Repeat steps S3-S5, processing layer by layer to obtain the required parts.

[0015] In a preferred technical solution of the present invention, the metal deposition layer includes a structural edge area, a transition area and a central area arranged in sequence from the outside to the inside;

[0016] When forming the structural edge area of ​​the component, the pulse laser acting on the edge of the inner solidification area is moved into the inner solidification area by a first preset distance, and the pulse laser generates shock wave strengthening and compressive stress;

[0017] When forming the transition zone of the component, the pulsed laser acting on the edge of the inner solidification area is moved outward of the inner solidification area by a second preset distance. The pulsed laser generates a shock wave to break the columnar crystals to achieve fine grain strengthening and improve the strength and hardness of the material.

[0018] When forming the central area of ​​the component, pulse laser is not used or the energy parameters of the pulse laser are reduced to reduce the degree of columnar crystal breakage, so that the columnar crystal is transformed from long columnar crystal to short columnar crystal, so that the central area has better toughness and ductility.

[0019] In a preferred technical solution of the present invention, the first preset distance is 50-200 μm;

[0020] The second preset distance is 0 to 100 μm.

[0021] In a preferred technical solution of the present invention, if the surface light source laser is composed of multiple point light source lasers, when forming the central area of ​​the component, the laser energy on the side opposite to the scanning direction needs to be reduced.

[0022] In a preferred technical solution of the present invention, after the metal deposition layer of the current layer is prepared, it is necessary to first lay a metal powder material layer on the metal deposition layer, and then perform laser additive manufacturing.

[0023] In a preferred embodiment of the present invention, when more than one pulsed laser beam is provided, the spacing between adjacent pulsed laser beams is an integer multiple of half a wavelength. The shock waves generated by the pulsed light have a uniform phase difference. As the phase difference gradually increases at a certain angle in space, it forms a plane wave that propagates at a specific angle, thereby controlling the propagation direction of the shock wave in the material.

[0024] In a preferred technical solution of the present invention, when preparing the first metal deposition layer, only continuous laser is used, and pulsed laser is not used.

[0025] In a preferred technical solution of the present invention, the process parameters include continuous laser parameters and pulsed laser parameters;

[0026] The continuous laser parameters include at least spot shape, spot size and power;

[0027] The pulse laser parameters include at least single pulse energy, repetition frequency, pulse width, spot size and number of pulse spots.

[0028] Exemplarily, the shape of the continuous laser spot is rectangular, elliptical, circular, triangular, spindle-shaped or arc-shaped; the size of the hollow area inside the spot of the continuous laser is 100 μm-7.8 mm, the power is 500-10000 W, and the spot size is 0.1-8 mm.

[0029] Exemplarily, the single pulse energy is 5 μJ-20 mJ, the repetition frequency is 10-2000 kHz, the pulse width is 1 fs-5 ns, the spot size is 10-50 μm, and the number of pulse spots is 1-10.

[0030] In a preferred technical solution of the present invention, the pulse laser acts at a position 0-3000 μm away from the edge of the inner coagulation area.

[0031] When the pulse laser is located inside the edge of the inner solidification zone, the material explodes, and the generated shock wave strengthens the material below the molten pool. The shock wave transmitted to the surrounding and upward parts is transmitted to the annular molten pool. Since the molten pool is liquid and cannot be compressed, the annular molten pool has a restraining and reflecting effect on the shock wave. The shock wave enters the material below the molten pool and strengthens the area about 30 to 1000 μm away from the current forming surface.

[0032] When the pulse laser is located outside the edge of the inner solidification zone, it can generate shock waves to break up the columnar crystals and transform them into equiaxed crystals.

[0033] In a preferred technical solution of the present invention, the continuous laser is composed of a beam of laser light with a large spot size or multiple beams of laser light with small spot sizes.

[0034] Exemplarily, the large spot size is 0.1-8 mm, and the small spot size is 0.1-2 mm.

[0035] The beneficial effects of the present invention are:

[0036] Through the simultaneous action of continuous laser on the hollow surface spot and pulsed laser on the inner solidification area, the annular molten pool formed by the continuous laser is used as a confining medium to constrain and reflect the shock wave formed by the pulsed laser, so that the shock wave acts on the material below the molten pool, thereby strengthening the material during manufacturing and avoiding recrystallization and annealing of the material during the melting process, thereby ensuring the strengthening effect, and ultimately achieving the purpose of reducing defects, refining the structure, increasing dislocation density, and thus improving the performance of additively manufactured parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the coordination between pulsed laser and single beam continuous laser.

[0038] Figure 2 It is a schematic diagram of the coordination between pulsed laser and multiple continuous laser beams.

[0039] Figure 3 It is a schematic diagram of the additive strengthening principle of continuous laser and pulsed laser.

[0040] Reference numerals:

[0041] 1. Continuous laser; 110. First continuous laser; 111. First molten pool; 120. Second continuous laser; 121. Second molten pool; 130. Third continuous laser; 131. Third molten pool; 140. Fourth continuous laser; 141. Fourth molten pool; 2. Annular molten pool; 3. Inner solidification zone; 4. Pulsed laser; 401. First pulsed laser; 402. Second pulsed laser; 403. Third pulsed laser; 5. Heat-affected zone; 6. Shock wave; 7. Shock wave propagation direction; 8. Focus; 9. Strengthening zone; 10. Metal powder material layer. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0043] Additive manufacturing (AM) is a 3D printing technology that uses a computer to control the movement of a high-energy beam to achieve melting or sintering. This technology directly manufactures complex parts by melting and stacking them layer by layer. It offers advantages such as high forming freedom, low material consumption, and suitability for customized designs. Therefore, it is widely used in aerospace, automotive, medical device, and other fields, becoming one of the advanced manufacturing technologies that countries are competing to develop. However, due to the high cooling rate, high stress, and the dominant top-to-bottom temperature gradient, AM currently suffers from internal defects such as difficult-to-eliminate pores and cracks, the tendency to form large columnar crystals, and the generation of tensile stress on the surface.

[0044] Example

[0045] In response to the above problems, this embodiment provides an in-situ strengthening method for additive manufacturing, which aims to solve the problem of poor strengthening effect caused by the pulsed laser strengthening layer being remelted or annealed by the next forming layer in additive manufacturing.

[0046] like Figure 1-3 As shown, an additive manufacturing in-situ strengthening method includes the following steps:

[0047] S1: According to the use requirements of the parts, determine the microstructure and residual stress requirements of different parts, determine the manufacturing and strengthening processes of each part, and obtain the manufacturing process parameters and path parameters;

[0048] S2: Using a surface light source laser as the continuous laser 1, the surface light source laser is beam shaped so that the light spot becomes a hollow shape;

[0049] S3: using a continuous laser 1 to melt the metal powder material layer 10 to obtain an annular molten pool 2 of a desired size, wherein an inner solidification region 3 is formed inside the annular molten pool 2;

[0050] S4: applying at least one pulsed laser beam 4 to the inner coagulation region 3;

[0051] The pulse laser 4 is set in at least one of the inner coagulation area 3, the front edge of the inner coagulation area 3 and the rear edge of the inner coagulation area 3;

[0052] S5: The pulsed laser 4 scans following the continuous laser 1, and while preparing the metal deposition layer of the current layer, the pulsed laser 4 strengthens the prepared metal deposition layer below the annular molten pool 2;

[0053] When the current metal deposition layer is formed, the bottom of the molten pool is at least one layer thick higher than the bottom of the molten pool when the previous layer is formed. Therefore, the previous layer cannot be remelted when the current layer is formed. The range of influence of the residual heat of forming is smaller than the strengthening range, which is conducive to reducing annealing.

[0054] like Figure 3 As shown, the annular molten pool 2 formed by the continuous laser 1 is used as the confinement medium. When one or more pulsed lasers 4 act on the semi-solid area at the edge of the molten pool or the inner solidification area 3, a shock wave 6 is generated. The shock wave 6 propagates uniformly to the surrounding area (as shown in FIG. Figure 3 Reference number 7), when the shock wave 6 encounters the annular molten pool 2 formed by the continuous laser 1, which is in a liquid state and has a density different from that of a solid and cannot be compressed, the shock wave 6 cannot continue to propagate forward and is reflected and constrained by the annular molten pool 2, so that the shock wave 6 is reflected downward in the center. The annular molten pool 2 acts like a lens to converge the shock wave 6 to increase the strengthening depth, so that the shock waves 6 formed by the multiple pulsed lasers 4 intersect and form a focus 8 below the molten pool. That is, the action position of the generated shock wave 6 is located below the current layer of annular molten pool 2. When the current layer of metal deposition is formed, the bottom of the molten pool is at least one layer thicker than the bottom of the molten pool when the previous layer is formed, which can avoid being remelted or annealed by the next layer of molten pool;

[0055] like Figure 3 As shown, a continuous laser 1 acts on a metal powder material layer 10 to form an annular molten pool 2, an inner solidification zone 3 is formed inside the annular molten pool 2, and a heat-affected zone 5 (annealing zone) is formed in the annular molten pool 2. The edge of the inner solidification zone 3 can form fine equiaxed crystals and a large number of dislocations through laser shock strengthening to generate compressive stress. The pulsed light spot at the edge of the inner solidification zone 3 breaks the columnar crystals in the edge area into equiaxed crystals. The pulsed laser 4 in the inner solidification zone 3 generates a shock wave 6, which is reflected by the annular molten pool 2 and focused on the position below the molten pool.

[0056] As the molten pool and strengthening impact move with the continuous laser 1 and the pulsed laser 4, a strengthening zone 9 is formed which is much deeper than the molten pool and the heat-affected zone 5 (annealing zone), and the strengthening zone 9 generates compressive stress and increases strength.

[0057] S6: Repeat steps S3-S5, processing layer by layer to obtain the required parts.

[0058] In this method, the strengthening region 9 is located below the molten layer (annular molten pool 2), which can avoid recrystallization and annealing of the material during the melting process, thereby ensuring the strengthening effect, and ultimately achieving the purpose of reducing defects, refining the structure, increasing the dislocation density, and thus improving the performance of additively manufactured parts.

[0059] In practical applications, this method can adjust the strengthening parameters in real time during the manufacturing process according to the use requirements of the parts, realize the refinement of material structure, form pressure stress and dislocation according to the design requirements of the parts, and thus improve the material performance. This method is of great significance for the direct forming and heat treatment of high-performance complex parts in additive manufacturing.

[0060] In practical applications, by controlling the energy distribution within the spot of the continuous laser 1, a molten pool with different cross-sectional curvatures can be formed. Different molten pool curvatures can change the position where the shock wave 6 intersects below the molten pool.

[0061] In actual applications, infrared imaging, coaxial monitoring, and online ultrasonic testing are used during the forming and manufacturing process to monitor the size of the molten pool and the resulting shock waves in real time. These results are then compared against a database for real-time adjustments to ensure the forming and strengthening effects, and to control the distribution of microstructure and properties. Data is stored after each layer is formed, and the manufacturing data is obtained after the part is formed.

[0062] In a preferred technical solution of the present invention, the metal deposition layer includes a structural edge area, a transition area and a central area arranged in sequence from the outside to the inside;

[0063] When forming the structural edge area of ​​the component, the pulse laser 4 acting on the edge of the inner solidification area 3 is moved into the inner solidification area 3 by a first preset distance. The shock wave 6 generated by the pulse laser 4 impacts the columnar crystals in the molten pool, causing the columnar crystals to break into equiaxed crystals and solidify, thereby reducing the grain size in this area and improving the hardness and strength.

[0064] When forming the transition zone of the component, the pulse laser 4 acting on the edge of the inner solidification region 3 is moved outward of the inner solidification region 3 by a second preset distance so that the pulse laser 4 at the edge no longer directly acts on the inner solidification region 3, thereby reducing the intensity of the shock wave 6 and the degree of columnar crystal fragmentation, thereby transforming the columnar crystals from long columnar crystals to short columnar crystals while retaining a certain impact strengthening effect;

[0065] When forming the central area of ​​the component, pulse laser 4 is not used or the energy parameters of pulse laser 4 are reduced to reduce the degree of columnar crystal breakage, so that the columnar crystals are transformed from long columnar crystals to short columnar crystals, so that the central area has better toughness and ductility;

[0066] During the part forming process, different areas of the metal deposition layer are processed differently according to the part shape and application requirements to obtain a microstructure with columnar crystals and equiaxed crystals. The equiaxed crystal area is consistent with the part outline but the size gradually decreases, and columnar crystal structure is formed in the area between the equiaxed crystals, thus forming a multi-layer shell structure with alternating equiaxed crystals and columnar crystals. When the crack expands, it is difficult to pass through the short axis direction of the columnar crystal, and instead expands in the long axis direction of the columnar crystal, thereby preventing the crack from expanding into the interior of the material.

[0067] In a preferred technical solution of the present invention, the first preset distance is 50-200 μm;

[0068] The second preset distance is 0 to 100 μm.

[0069] In a preferred technical solution of the present invention, if the surface light source laser is composed of multiple point light source lasers, when forming the central area of ​​the component, in order to obtain better toughness and ductility in the central area, the laser energy on the side opposite to the scanning direction needs to be reduced.

[0070] In a preferred technical solution of the present invention, after the metal deposition layer of the current layer is prepared, it is necessary to first lay a metal powder material layer 10 on the metal deposition layer, and then perform laser additive manufacturing.

[0071] In a preferred technical solution of the present invention, when more than one pulse laser beam 4 is provided, the distance between the action positions of adjacent pulse laser beams 4 is an integer multiple of 1 / 2 wavelength.

[0072] In practical applications, the phase of each coherent pulse laser 4 is adjusted through the phased array principle, and the shock wave 6 generated by the pulse light has the same phase difference. Since the phase difference gradually increases at a certain angle in space, a plane wave propagating at a certain angle is formed, thereby controlling the propagation direction of the shock wave 6 in the material to achieve targeted strengthening of materials at different positions.

[0073] In a preferred technical solution of the present invention, when preparing the first metal deposition layer, only continuous laser 1 is used, and pulsed laser 4 is not used. After processing to a preset thickness (such as after processing 1-3 layers), when preparing the next metal deposition layer, continuous laser 1 is started to be used.

[0074] In a preferred technical solution of the present invention, the process parameters include continuous laser 1 parameters and pulsed laser 4 parameters;

[0075] The parameters of the continuous laser 1 include at least spot shape, spot size and power;

[0076] The parameters of the pulse laser 4 include at least single pulse energy, repetition frequency, pulse width, spot size and number of pulse spots.

[0077] Exemplarily, the spot shape of the continuous laser 1 is rectangular, elliptical, circular, triangular, spindle-shaped or arc-shaped; the size of the hollow area inside the spot of the continuous laser 1 is 100μm-7.8mm, the power is 500-10000W, and the spot size is 0.1-8mm.

[0078] Exemplarily, the single pulse energy is 5 μJ-20 mJ, the repetition frequency is 10-2000 kHz, the pulse width is 1 fs-5 ns, the spot size is 10-50 μm, and the number of pulse spots is 1-10.

[0079] In a preferred technical solution of the present invention, the pulse laser 4 acts at a position 0-3000 μm away from the edge of the inner coagulation area 3 .

[0080] During additive processing, when the pulsed laser 4 is located on the inner side of the edge of the inner solidification zone 3, the material explodes, and the generated shock wave 6 strengthens the material below the molten pool. The shock wave 6 transmitted to the surrounding and upward directions is transmitted to the annular molten pool 2. Since the molten pool is liquid and cannot be compressed, the annular molten pool has a restraining and reflective effect on the shock wave 6. The shock wave 6 enters the material below the molten pool and strengthens the area about 30 to 1000 μm away from the current forming surface; at the same time, when the pulsed laser 4 is located on the outer side of the edge of the inner solidification zone 3, it can generate a shock wave 6 to break the columnar crystals and transform the columnar crystals into equiaxed crystals.

[0081] In a preferred technical solution of the present invention, the continuous laser 1 is composed of a beam of laser light with a large spot size or multiple beams of laser light with small spot sizes.

[0082] In a preferred technical solution of the present invention, the large spot size is 0.1-8 mm, and the small spot size is 0.1-2 mm.

[0083] For example, Figure 2 As shown, the continuous laser 1 is composed of multiple laser beams with small spot sizes;

[0084] A first continuous laser 110 with a small spot size (60-100 microns) and low power (20-300 W) is used to form a first molten pool 111 in front of the scanning direction;

[0085] On both sides of the rear of the first molten pool 111, a second continuous laser 120 and a third continuous laser 130 with a smaller spot size (60-100 microns) and lower power (20-500W) are used to form a second molten pool 121 and a third molten pool 131 respectively;

[0086] A fourth continuous laser 140 with a larger spot size (80-1000 μm) and a higher power (50-2000 W) is used to form a fourth molten pool 141 at the rear in the scanning direction, wherein one side of the fourth molten pool 141 is connected to the first molten pool 111 via the second molten pool 121, and the other side of the fourth molten pool 141 is connected to the first molten pool 111 via the third molten pool 131, thereby forming an annular molten pool 2 with an inner solidification area 3 in the middle.

[0087] During processing, the shock wave 6 formed by the first pulse laser 401 acting on the inner solidification area 3 will be reflected by the four molten pools and propagate downward, forming a large number of dislocations and generating compressive stress below the annular molten pool 2 (in the range of 100-5000μm from the forming surface). Since this depth is much greater than the action depth of the next layer of molten pool (50-200μm), the generated dislocations and compressive stress will not be remelted and annealed.

[0088] The second pulse laser 402 coherent with the first pulse laser 401 acts on a position in front of the annular molten pool at a distance from the first pulse laser 401 that is an integer multiple of the wavelength to form a coherent shock wave 6; by adjusting the phase of the second pulse laser 402, the direction of propagation of the shock wave 6 in the material can be adjusted. When scanning the edge of the part 0-5mm, the shock wave 6 can still propagate in a direction toward the edge, thereby achieving further strengthening of the edge material of the part.

[0089] A third pulsed laser 403 is applied to the edge of the rear molten pool. The explosion at the edge of the molten pool generates shockwave 6, which impacts the columnar crystals in the molten pool, breaking them into fine equiaxed crystals and solidifying them. Confined by the molten pool, shockwave 6 propagates downward, generating shockwave 6 in the already formed area. This increases the dislocation density in the material and creates compressive stress. Parts processed using this method exhibit high surface strength and excellent internal toughness and ductility. If cracks occur during use, they are difficult to propagate due to the high compressive stress and dislocation density, thereby improving the fatigue performance of the part.

[0090] This method can control the internal microstructure distribution of parts to form high-performance parts with a mixed microstructure. During the part forming process, the microstructure with a spacing of columnar and equiaxed crystals is designed based on the part's shape and application requirements. The equiaxed crystals conform to the part's contour but gradually decrease in size, while columnar crystals form between the equiaxed crystals. This results in a multilayered shell structure with alternating equiaxed and columnar crystals. Cracks propagate in the direction of the columnar crystals' short axes, preventing them from propagating through the material.

[0091] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values ​​should be interpreted as being merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0092] In the description of this application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, vertical, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of this application; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0093] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An additive manufacturing in-situ strengthening method, characterized in that: The following steps are involved: S1: According to the use requirements of the parts, determine the microstructure and residual stress requirements of different parts, determine the manufacturing and strengthening processes of each part, and obtain the manufacturing process parameters and path parameters; The process parameters include continuous laser parameters and pulsed laser parameters; The continuous laser parameters include at least spot shape, spot size and power; The pulse laser parameters include at least single pulse energy, repetition frequency, pulse width, spot size and number of pulse spots; S2: Using the surface light source laser as a continuous laser, the surface light source laser is beam shaped to make the light spot into a hollow shape; S3: using a continuous laser to melt the metal powder material layer to obtain an annular molten pool of a desired size, wherein an inner solidification region is formed inside the annular molten pool; S4: applying at least one pulsed laser beam to the inner coagulation area; The pulse laser is arranged at at least one of the inner coagulation region, the front edge of the inner coagulation region and the rear edge of the inner coagulation region; S5: The pulsed laser scans following the continuous laser. While preparing the metal deposition layer of the current layer, the pulsed laser strengthens the metal deposition layer prepared below the annular molten pool. When preparing the first metal deposition layer, only the continuous laser is used, without the pulsed laser. When the metal deposition layer of the current layer is formed, the bottom of the molten pool is at least one layer thickness higher than the bottom of the molten pool when the previous layer is formed; S6: Repeat steps S3-S5, processing layer by layer to obtain the required parts; The metal deposition layer includes a structural edge area, a transition area and a central area arranged in sequence from the outside to the inside; When forming the structural edge area of ​​the component, the pulsed laser acting on at least one of the front edge and the rear edge of the inner solidification area is moved into the inner solidification area by a first preset distance; the first preset distance is 50-200 μm; When forming the transition zone of the component, the pulse laser acting on at least one of the front edge and the rear edge of the inner solidification region is moved outward of the inner solidification region by a second preset distance; the second preset distance is 0-100 μm; When forming the center area of ​​the component, do not use pulsed laser or reduce the energy parameters of the pulsed laser.

2. The additive manufacturing in-situ strengthening method according to claim 1, characterized in that: If the surface light source laser is composed of multiple point light source lasers, the laser energy on the side opposite to the scanning direction needs to be reduced when forming the center area of ​​the component.

3. The additive manufacturing in-situ strengthening method according to claim 1, characterized in that: After preparing the metal deposition layer of the current layer, it is necessary to lay a metal powder material layer on the metal deposition layer before performing laser additive manufacturing.

4. The additive manufacturing in-situ strengthening method according to claim 1, characterized in that: When more than one pulse laser beam is provided, the distance between the action positions of adjacent pulse laser beams is an integer multiple of 1 / 2 wavelength.

5. The additive manufacturing in-situ strengthening method according to claim 1, characterized in that: The continuous laser is composed of a beam of laser light with a large spot size or multiple beams of laser light with a small spot size. The large spot size is 0.1-8 mm, and the small spot size is 0.1-2 mm.

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