Electron beam selective melting forming method and equipment based on ion beam assistance

Abstract

The invention discloses an electron beam selective melting forming method and device based on ion beam assistance, and relates to the technical field of additive manufacturing. The method comprises the following steps: establishing a three-dimensional digital model of a to-be-printed part, and slicing and layering to obtain layered scanning data; under the vacuum condition, metal powder is spread on the preheated base plate according to the set thickness, and a powder bed is formed; according to the layered scanning data, scanning and melting the powder bed through electron beams, and forming an uneven molten pool surface on the powder bed; impact treatment is conducted on the surface of the molten pool through focused ion beams, meanwhile, the shape of the surface of the molten pool is monitored in real time, parameters of impact treatment of the focused ion beams are dynamically adjusted till the flat surface of the molten pool is formed, single-layer scanning melting is completed, and scanning melting is completed layer by layer till part printing is completed; and the printed part is subjected to in-situ powder cleaning and surface strengthening through a defocusing ion beam, and a finished part is obtained. According to the method, through combination of ion beam auxiliary treatment and real-time detection feedback, the problem of pore defects in traditional electron beam powder bed additive manufacturing is solved, and the metallurgical quality and the mechanical property are improved.

Description

Technical Field

[0001] This application relates to the field of additive manufacturing technology, and in particular to a method and apparatus for electron beam selective melting forming based on ion beam assistance. Background Technology

[0002] In the field of selective electron beam melting, gas-atomized metal powders are widely used due to their low cost and high sphericity. However, their hollow powder ratio is significantly higher than that of rotating electrode powders (for example, the hollow powder ratio of titanium alloy gas-atomized powder can reach 5%-15%). This is mainly because the gas (such as argon) trapped inside the hollow powder fails to escape from the molten pool during electron beam melting. Instead, it enters the molten pool and forms bubbles. These bubbles are subjected to Marangoni forces within the molten pool, constantly moving and colliding with each other, gradually growing larger. As the molten pool solidifies, the bubbles are pushed to the solid-liquid interface and may capture more gas. When the bubbles grow to a certain size, the buoyancy is greater than the Marangoni force, causing them to escape from the molten pool. However, not all bubbles escape before the molten pool solidifies. Due to the rapid solidification rate of the molten pool, some bubbles cannot escape in time and become trapped in the solidified metal, eventually forming micron to sub-millimeter level pore defects. Furthermore, because the surface of the molten pool exhibits a pitted morphology after cooling, when powder is re-layered onto these uneven surfaces, interlayer gaps exist between the subsequent powder layer and the solidified layer. When the powder bed is remelted, these interlayer gaps become channels for bubble escape, further exacerbating the porosity problem (see...). Figure 2 (As shown). The presence of voids directly affects the mechanical properties of printed parts. In the existing technology, electron beam remelting is the main means of eliminating these voids. By repeatedly scanning the electron beam, the voids in the previously constructed layer are eliminated by thermocapillary force. However, the repeated scanning process will cause violent fluctuations in the molten pool, which will lead to the generation of unfused voids. Summary of the Invention

[0003] The main objective of this application is to provide an electron beam selective melting forming method and apparatus based on ion beam assistance, which aims to solve the technical problem that existing electron beam selective melting forming methods are prone to producing hole defects.

[0004] To achieve the above objectives, this application proposes an ion beam-assisted electron beam selective melting forming method, comprising the following steps: S1. Establish a three-dimensional digital model of the part to be printed, and slice and layer it to obtain layered scanning data; S2. Under vacuum conditions, metal powder is spread on a preheated substrate to a set thickness to form a powder bed. S3. Based on the layered scanning data, the powder bed is melted by electron beam scanning to form an uneven molten pool surface on the powder bed; S4. The surface of the molten pool is impacted by a focused ion beam, while the morphology of the molten pool surface is monitored in real time, and the parameters of the focused ion beam impact treatment are dynamically adjusted until a flat molten pool surface is formed, thus completing single-layer scanning melting. S5. Repeat steps S2-S4 to complete the scanning and melting layer by layer until the part is printed. S6. The printed parts are cleaned and surface strengthened in situ using a defocused ion beam to obtain the finished parts.

[0005] Optionally, in the step of spreading metal powder to a preheated substrate at a set thickness under vacuum conditions to form a powder bed, the metal powder is titanium alloy TC4 powder with an average particle size of 30μm-105μm, a powder bed thickness of 80μm-120μm, and a vacuum condition of 1.0×10⁻⁶. -3 Pa-1.0×10 -4 Pa.

[0006] Optionally, in the step of spreading metal powder to a set thickness on a preheated substrate under vacuum conditions to form a powder bed, the substrate is preheated to 100°C-200°C by a defocused electron beam, the scanning current of the defocused electron beam is 25mA-35mA, and the scanning speed is 8m / s-12m / s.

[0007] Optionally, in the step of melting the powder bed by electron beam scanning to form an uneven molten pool surface on the powder bed, the powder bed is melted by focused electron beam scanning, wherein the beam spot diameter of the focused electron beam is 50μm-150μm, the focused beam current is 15mA-25mA, the scanning speed is 1m / s-3m / s, and the scanning spacing is 80μm-120μm.

[0008] Optionally, in the step of impacting the molten pool surface with a focused ion beam, simultaneously monitoring the morphology of the molten pool surface in real time, and dynamically adjusting the parameters of the focused ion beam impact treatment until a smooth molten pool surface is formed, the parameter adjustment range of the focused ion beam is: voltage 80V-120V, current 8mmA-12mmA, current density 5mA / cm². 2 -15mA / cm 2 The scanning speed is 5m / s-15m / s.

[0009] Optionally, in the step of performing in-situ powder removal and surface strengthening of the printed parts using a defocused ion beam, the voltage of the defocused ion beam is 900V-1100V, the current is 0.8mmA-1.2mmA, and the current density is 5mA / cm². 2 -15mA / cm 2 .

[0010] This application also proposes an ion beam-assisted electron beam selective melting and forming apparatus for implementing the above-mentioned ion beam-assisted electron beam selective melting and forming method, wherein the melting and forming apparatus includes: A vacuum forming chamber, wherein a worktable is provided inside the vacuum forming chamber for supporting the substrate; A powder supply mechanism, located in the vacuum forming chamber and connected to the worktable, is used to spread metal powder onto the substrate. An electron beam emission focusing and scanning device is disposed at the top of the vacuum forming chamber, and the scanning range of the electron beam emission focusing and scanning device covers the forming area on the worktable; An ion beam emission focusing scanning device is disposed at the top of the vacuum forming chamber. The scanning range of the ion beam emission focusing scanning device is the same as that of the electron beam emission focusing scanning device. The ion beam emission focusing scanning device is capable of emitting focused ion beams and defocused ion beams. A detection feedback device, which is electrically connected to the ion beam emission focusing scanning device, is used to acquire morphology data of the molten pool surface in real time. The controller is electrically connected to the electron beam emission focusing scanning device, the ion beam emission focusing scanning device, and the detection feedback device, respectively, and is used to control the electron beam emission focusing scanning device to emit an electron beam, and to respond to the morphology data of the detection feedback device and adjust the parameters of the ion beam emission focusing scanning device.

[0011] Optionally, the electron beam emission focusing scanning device has a preheating mode and a scanning melting mode; The preheating mode is to preheat the substrate by emitting a defocused electron beam; The scanning melting mode involves scanning and melting metal powder by emitting a focused electron beam.

[0012] Optionally, the ion beam emission focusing scanning device can dynamically switch between focusing mode and defocusing mode; When the ion beam emission focusing scanning device switches to focusing mode, it emits a focused ion beam to impact the surface of the molten pool. When the ion beam emission focusing scanning device switches to defocus mode, it emits a defocused ion beam to perform powder removal and strengthening treatment on the surface of the part.

[0013] Optionally, the detection feedback device includes a laser scanner, which generates morphological data of the molten pool surface in real time and feeds it back to the ion beam emission focusing scanning device through the controller. The beneficial effects of this application include: This application introduces a focused ion beam into electron beam powder bed additive manufacturing. After each layer of powder melts, the surface of the molten pool cools rapidly. The focused ion beam has a large kinetic energy. By continuously impacting the surface of the molten pool with the high kinetic energy of the focused ion beam, it can promote the escape of bubbles in the molten pool and improve the surface roughness, greatly reducing the pits on the surface of the molten pool. The gap between the subsequent powder layer and the solidified layer becomes very small. When the subsequent powder layer melts, the bubbles generated cannot move downwards, causing the bubbles to be discharged upwards. This effectively reduces the interlayer gas residue caused by surface pits, thereby avoiding the generation of interlayer unfused pore defects. This application utilizes a focused ion beam to continuously bombard the uneven surface of a molten pool, causing micro-regional plastic deformation and inducing grain refinement on the molten pool surface. This results in a denser surface layer, suppressing the generation of reheating cold cracks. Then, a defocused ion beam is used to perform in-situ treatment on the surface of the formed part. The defocused ion beam removes residual powder from the surface through the sputtering effect, and the impact of the defocused ion beam on the part surface can induce dislocation proliferation. Thus, residual powder removal and surface densification are achieved simultaneously, resulting in better metallurgical quality of the part, making it less prone to deformation. Furthermore, it eliminates the need to transfer to external equipment, saving process time and costs. This application uses a detection feedback device to collect three-dimensional morphology data of the molten pool surface in real time, analyze the surface roughness, and transmit the detection data to the controller. The controller dynamically adjusts the focusing ion beam parameters according to the detection data, thereby ensuring the effect of improving the surface morphology of the interlayer molten pool. At the same time, the electron beam emission focusing scanning device and the ion beam emission focusing scanning device are integrated in the same vacuum forming chamber, sharing the scanning path and control system, and realizing efficient collaborative work. This application solves the problem of porosity defects in traditional electron beam powder bed additive manufacturing by combining ion beam-assisted processing with real-time detection feedback. Compared with traditional electron beam remelting process, the molten pool is more stable, avoiding molten pool fluctuations and incomplete fusion defects caused by electron beam remelting, improving the surface quality of parts, and achieving the improvement of metallurgical quality and mechanical properties. It is suitable for manufacturing high-performance metal parts in the aerospace field. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0015] Figure 1 This is a flowchart of the electron beam selective melting and forming method based on ion beam assistance described in the embodiments of this application; Figure 2This is a schematic diagram illustrating the generation of pore defects in the electron beam powder bed of gas-atomized powder as described in the embodiments of this application; Figure 3 This is a schematic diagram of the internal structure of the melting and forming equipment described in the embodiments of this application; Figure 4 This is a schematic diagram of the cross-section of the focused electron beam scanning component as described in the embodiments of this application; Figure 5 This is a schematic diagram of a focused ion beam scanning molten pool cross-section as described in an embodiment of this application; Figure 6 This is a schematic diagram illustrating the defocusing ion beam used for powder removal and surface strengthening of parts according to an embodiment of this application.

[0016] Figure label: 1-Vacuum forming chamber; 2-Worktable; 3-Powder supply mechanism; 4-Electron beam emission focusing scanning device; 5-Ion beam emission focusing scanning device; 6-Detection feedback device.

[0017] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0019] To address the technical problems existing in the prior art, embodiments of this application provide a method for selective electron beam melting and forming based on ion beam assistance, such as... Figure 1 As shown, it includes the following steps: S1. Establish a three-dimensional digital model of the part to be printed, and slice and layer it to obtain layered scanning data.

[0020] S2. Under vacuum conditions, metal powder is spread onto a preheated substrate to a set thickness to form a powder bed.

[0021] In the specific implementation process, in the step of spreading metal powder to a preheated substrate to form a powder bed at a set thickness, the metal powder is titanium alloy TC4 powder with an average particle size of 30μm-105μm, a powder bed thickness of 80μm-120μm, and a vacuum condition of 1.0×10⁻⁶. -3 Pa-1.0×10 -4 Pa.

[0022] Specifically, the substrate is preheated to 100°C-200°C by a defocused electron beam, the scanning current of the defocused electron beam is 25mA-35mA, and the scanning speed is 8m / s-12m / s.

[0023] S3, such as Figure 4 As shown, based on the layered scanning data, the powder bed is melted by electron beam scanning, forming an uneven molten pool surface on the powder bed.

[0024] In the specific implementation process, the powder bed is melted by scanning with a focused electron beam. The diameter of the focused electron beam is 50μm-150μm, the focused beam current is 15mA-25mA, the scanning speed is 1m / s-3m / s, and the scanning spacing is 80μm-120μm.

[0025] Specifically, when the beam spot diameter is small and the beam current is high, the energy is highly concentrated, which can form a deep and narrow molten pool, ensuring that the powder is completely melted and reducing incomplete fusion defects; when the beam spot diameter is large and the beam current is low, the energy distribution is more uniform, forming a shallow and wide molten pool, which is suitable for thin-walled structures or low heat input requirements; by flexibly adjusting the beam spot diameter and scanning speed, it can be adapted to the geometry of different parts (such as complex cavities and thin-walled structures).

[0026] Preferably, the scanning spacing is 100μm, which can balance forming efficiency and quality and reduce the forming time of a single layer.

[0027] S4, such as Figure 5 As shown, the surface of the molten pool is impacted by a focused ion beam, while the morphology of the molten pool surface is monitored in real time, and the parameters of the focused ion beam impact treatment are dynamically adjusted until a flat molten pool surface is formed, thus completing single-layer scanning melting.

[0028] Specifically, the parameters of the focused ion beam are adjustable within the following ranges: voltage 80V-120V, current 8mmA-12mmA, and current density 5mA / cm². 2 -15mA / cm 2 The scanning speed is 5m / s-15m / s.

[0029] For larger protrusions on the molten pool surface, increasing the voltage increases the kinetic energy of the focused ion beam, causing more intense plastic deformation and reducing surface roughness. When fine-tuning micro-protrusions on the molten pool surface is required, decreasing the voltage and using moderate ion beam energy avoids over-melting and secondary defects. High current density enhances micro-area flow on the molten pool surface, filling surface depressions; low current density is suitable for local fine-tuning and reducing the heat-affected zone; low-speed scanning extends the single-point action time, promoting molten pool surface leveling; high-speed scanning improves processing efficiency and is suitable for large-scale leveling. Through dynamic adjustment of focused ion beam parameters, efficient leveling of the molten pool surface morphology, significant suppression of porosity defects, and comprehensive improvement of metallurgical properties are achieved.

[0030] S5. Repeat steps S2-S4 to complete the scanning and melting layer by layer until the part is printed.

[0031] S6. The printed parts are cleaned and surface strengthened in situ using a defocused ion beam to obtain the finished parts.

[0032] In the specific implementation process, in the step of performing in-situ powder removal and in-situ strengthening of the printed parts using a defocused ion beam, the voltage of the defocused ion beam is 900V-1100V, the current is 0.8mmA-1.2mmA, and the current density is 5mA / cm². 2 -15mA / cm 2 .

[0033] The high kinetic energy of the defocused ion beam can effectively remove residual metal powder adhering to the surface of parts, resulting in extremely high powder removal efficiency. Furthermore, the energy of the defocused ion beam causes plastic deformation of the surface metal atoms, forming a high-density dislocation structure, which increases the microhardness of the part surface. At the same time, the defocused ion beam fills the microcracks on the part surface through a micro-area melting-solidification mechanism, further reducing the surface roughness of the part. Moreover, powder removal and strengthening can be achieved simultaneously in a single treatment without the need to switch equipment or processes, saving time and costs.

[0034] Embodiments of this application also provide an ion beam-assisted electron beam selective melting and forming apparatus for implementing the above-described ion beam-assisted electron beam selective melting and forming method, such as... Figure 3 As shown, the melting and forming equipment includes: Vacuum forming chamber 1, wherein a worktable 2 is provided inside the vacuum forming chamber 1 for supporting the substrate; A powder supply mechanism 3 is located inside the vacuum forming chamber 1 and is connected to the worktable 2, and is used to spread metal powder onto the substrate. An electron beam emission focusing and scanning device 4 is disposed on the top of the vacuum forming chamber 1, and the scanning range of the electron beam emission focusing and scanning device 4 covers the forming area on the worktable 2. An ion beam emission focusing scanning device 5 is disposed on the top of the vacuum forming chamber 1. The scanning range of the ion beam emission focusing scanning device 5 is the same as that of the electron beam emission focusing scanning device 4. The ion beam emission focusing scanning device 5 is capable of emitting focused ion beams and defocused ion beams. The detection feedback device 6 is electrically connected to the ion beam emission focusing scanning device 5 and is used to collect morphology data of the molten pool surface in real time. The controller is electrically connected to the electron beam emission focusing scanning device 4, the ion beam emission focusing scanning device 5, and the detection feedback device 6, respectively. The controller is used to control the electron beam emission focusing scanning device 4 to emit an electron beam, and to respond to the morphology data of the detection feedback device 6 and adjust the parameters of the ion beam emission focusing scanning device 5.

[0035] This application maintains a vacuum forming chamber 1 with a diameter of 1.0 × 10⁻⁶. -3 Pa-1.0×10 -4 A vacuum level of Pa is maintained to reduce metal powder oxidation and impurity interference, ensuring the stability of electron beam energy transfer and avoiding molten pool contamination. The powder supply mechanism 3 includes a mechanical scraper or powder spreading roller, which can uniformly spread metal powder on the substrate at a certain thickness and ensure the density of each powder layer, providing a uniform raw material distribution for subsequent melting. The electron beam emission focusing scanning device 4 preheats the substrate or scans the molten metal powder by emitting an electron beam. The ion beam emission focusing scanning device 5 impacts the molten pool surface by emitting a focused ion beam and performs in-situ scanning of the surface of the formed part by emitting a defocused ion beam. Powder removal and surface strengthening treatment; the detection feedback device 6 collects three-dimensional morphology data of the molten pool surface in real time, analyzes the surface roughness, and transmits the detection data to the controller. The controller dynamically adjusts the focused ion beam parameters emitted by the ion beam emission focusing scanning device 5 according to the detection data, thereby ensuring the improvement effect of the surface morphology of the interlayer molten pool. Moreover, the electron beam emission focusing scanning device 4 and the ion beam emission focusing scanning device 5 are integrated in the same vacuum forming chamber 1, sharing the scanning path and control system, realizing efficient collaborative work, thereby achieving the simultaneous improvement of surface quality and efficiency in electron beam selective melting forming technology.

[0036] As one possible implementation of this application, the electron beam emission focusing scanning device 4 has a preheating mode and a scanning melting mode; The preheating mode is to preheat the substrate by emitting a defocused electron beam; The scanning melting mode involves scanning and melting metal powder by emitting a focused electron beam.

[0037] Specifically, defocused electron beams can disperse energy over a larger area, avoiding local overheating and allowing the substrate temperature to rise uniformly to the preset value, thereby reducing the temperature gradient between the substrate and the molten pool and suppressing warping deformation; while focused electron beams have more concentrated energy, enabling rapid melting of powders. Through the synergistic operation of preheating mode and scanning melting mode, the forming accuracy and metallurgical quality of parts can be significantly optimized.

[0038] As one possible implementation of this application, the ion beam emission focusing scanning device 5 is capable of dynamically switching between focusing mode and defocusing mode; When the ion beam emission focusing scanning device 5 switches to the focusing mode, it emits a focused ion beam to impact the surface of the molten pool. When the ion beam emission focusing scanning device 5 switches to defocus mode, it emits a defocused ion beam to perform powder removal and strengthening treatment on the surface of the part, such as... Figure 6 As shown.

[0039] The focusing mode uses a focused ion beam to bombard the molten pool surface with high energy density, generating micro-area plastic deformation, causing bubbles to escape from the molten pool, reducing the surface roughness of the molten pool, and inducing dynamic recrystallization of grains, reducing microcracks and incomplete fusion defects. The defocusing mode uses a defocused ion beam to sputter and remove residual powder from the surface. The large beam spot can cover complex areas, resulting in high powder removal efficiency and improving the surface density and hardness of the parts. The ion beam emission focusing scanning device 5 achieves the dual goals of high-precision surface treatment of the molten pool and efficient powder removal and strengthening of parts by dynamically switching between focusing and defocusing modes. The focusing mode optimizes metallurgical quality, while the defocusing mode improves surface performance. The two work together to significantly reduce the defect rate of parts and improve efficiency.

[0040] As one possible implementation of this application, the detection feedback device 6 includes a laser scanner, which generates morphological data of the molten pool surface in real time and feeds it back to the ion beam emission focusing scanning device 5 through the controller.

[0041] The laser scanner can acquire three-dimensional point cloud data of the molten pool surface in real time, accurately measure its surface roughness, pore distribution and interlayer gap. For the detected pores or unfused areas, the controller automatically adjusts the parameters of the ion beam emission focusing scanning device 5 to perform local high-energy scanning until the defects are eliminated. Moreover, it only performs local strengthening on the detected defect areas, which shortens the single-layer processing time and improves the overall forming efficiency.

[0042] The technical solutions described above in this application will be explained in detail below with reference to specific embodiments.

[0043] Example 1 An ion beam-assisted electron beam selective melting forming method includes the following steps: Step 1: Model Building and Data Processing A three-dimensional digital model of the titanium alloy TC4 part was created using CAD software. Import the 3D digital model into the slicing software, set the layer thickness to 100μm, and obtain the layered scanning data of the part's cross-section.

[0044] Step 2: Equipment preparation and substrate preheating The titanium alloy substrate is mounted on the worktable 2 of the vacuum forming chamber 1. The vacuum forming chamber 1 is then closed, and a vacuum of 1.0 × 10⁻⁶ is evacuated. -4 Pa; The controller controls the electron beam emission focusing scanning device 4 to switch to preheating mode, emitting a defocused electron beam with a scanning current of 30mA and a scanning speed of 10m / s to preheat the substrate to 150°C.

[0045] Step 3: Layer-by-layer forming Maintain the vacuum level in vacuum forming chamber 1 at 1.0 × 10⁻⁶. -4 Pa, the powder supply mechanism 3 evenly spreads spherical titanium alloy TC4 powder with an average particle size of 80μm on the preheated substrate, with a powder thickness of 100μm and a thickness error of ≤±5μm, to form a powder bed. The controller controls the electron beam emission focusing scanning device 4 to switch to scanning melting mode. Based on the layered scanning data, the focused electron beam is emitted to scan and melt the powder bed. The beam spot diameter of the focused electron beam is 100μm, the focused beam current is 20mA, the scanning speed is 2m / s, and the scanning interval is 100μm, forming an uneven molten pool surface on the powder bed. The controller switches the ion beam emission focusing scanning device 5 to focusing mode, emitting a focused ion beam to impact the surface of the molten pool. Simultaneously, the laser scanner in the detection feedback device 6 collects real-time morphological data of the molten pool surface, calculates the surface roughness Ra value, and feeds this data back to the ion beam emission focusing scanning device 5 in real-time via the controller. The ion beam emission focusing scanning device 5 dynamically adjusts the parameters of the focused ion beam based on the real-time detection data. The initial parameters of the focused ion beam are: voltage 100V, current 10mmA, and current density 10mA / cm². 2 The scanning speed is 10 m / s; When the surface roughness Ra of the molten pool is ≤ 5 μm, it is considered that a smooth molten pool surface has been formed, the focused ion beam emission is stopped, and the single-layer scanning melting is completed. Repeat the powder spreading, scanning melting and impact processing steps to complete the layer-by-layer melting and solidification of the part until the entire part is printed, and then let it cool naturally to below 50°C.

[0046] Step 4: In-situ powder removal and surface strengthening After the part is formed, the controller switches the ion beam emission focusing scanning device 5 to defocus mode, emitting a defocused ion beam to scan the entire surface of the part to remove residual powder and improve surface density. The voltage of the defocused ion beam is 1000V, the current is 1.0mmA, and the current density is 10mA / cm². 2 The finished parts are obtained.

[0047] Example 2 An ion beam-assisted electron beam selective melting forming method includes the following steps: Step 1: Model Building and Data Processing A three-dimensional digital model of the titanium alloy TC4 part was created using CAD software. Import the 3D digital model into the slicing software, set the layer thickness to 100μm, and obtain the layered scanning data of the part's cross-section.

[0048] Step 2: Equipment preparation and substrate preheating The titanium alloy substrate is mounted on the worktable 2 of the vacuum forming chamber 1. The vacuum forming chamber 1 is then closed, and a vacuum of 1.0 × 10⁻⁶ is evacuated. -4 Pa; The controller controls the electron beam emission focusing scanning device 4 to switch to preheating mode, emitting a defocused electron beam with a scanning current of 25mA and a scanning speed of 8m / s to preheat the substrate to 120°C.

[0049] Step 3: Layer-by-layer forming Maintain the vacuum level in vacuum forming chamber 1 at 1.0 × 10⁻⁶. -4 Pa, the powder supply mechanism 3 evenly spreads spherical titanium alloy TC4 powder with an average particle size of 65μm on the preheated substrate, with a powder thickness of 100μm and a thickness error of ≤±5μm, to form a powder bed. The controller controls the electron beam emission focusing scanning device 4 to switch to scanning melting mode. Based on the layered scanning data, the focused electron beam is emitted to scan and melt the powder bed. The beam spot diameter of the focused electron beam is 80μm, the focused beam current is 15mA, the scanning speed is 1m / s, and the scanning interval is 100μm, forming an uneven molten pool surface on the powder bed. The controller switches the ion beam emission focusing scanning device 5 to focusing mode, emitting a focused ion beam to impact the surface of the molten pool. Simultaneously, the laser scanner in the detection feedback device 6 collects real-time morphological data of the molten pool surface, calculates the surface roughness Ra value, and feeds this data back to the ion beam emission focusing scanning device 5 in real-time via the controller. The ion beam emission focusing scanning device 5 dynamically adjusts the parameters of the focused ion beam based on the real-time detection data. The initial parameters of the focused ion beam are: voltage 80V, current 8mmA, and current density 5mA / cm². 2 The scanning speed is 5 m / s; When the surface roughness Ra of the molten pool is ≤ 5 μm, it is considered that a smooth molten pool surface has been formed, the focused ion beam emission is stopped, and the single-layer scanning melting is completed. Repeat the powder spreading, scanning melting and impact processing steps to complete the layer-by-layer melting and solidification of the part until the entire part is printed, and then let it cool naturally to below 50°C.

[0050] Step 4: In-situ powder removal and surface strengthening After the part is formed, the controller switches the ion beam emission focusing scanning device 5 to defocus mode, emitting a defocused ion beam to scan the entire surface of the part to remove residual powder and improve surface density. The voltage of the defocused ion beam is 900V, the current is 0.8mmA, and the current density is 8mA / cm². 2 The finished parts are obtained.

[0051] In summary, this application introduces a focused ion beam into electron beam powder bed additive manufacturing. After each powder layer melts, the molten pool surface cools rapidly. The focused ion beam possesses significant kinetic energy, and by continuously impacting the molten pool surface with this high kinetic energy, it promotes the escape of bubbles within the molten pool and improves surface roughness, greatly reducing pits on the molten pool surface. The gap between subsequent powder layers and the solidified layer becomes very small. When subsequent powder layers melt, the generated bubbles cannot move downwards, causing them to escape upwards. This effectively reduces interlayer gas residue caused by surface pits, thereby avoiding the generation of unfused interlayer pore defects. This application uses a focused ion beam to continuously impact the uneven molten pool surface, causing micro-regional plastic deformation and inducing grain refinement on the molten pool surface, making the surface layer denser and suppressing the generation of reheat cold cracks. Then, a defocused ion beam is used to perform in-situ treatment on the surface of the formed part. The defocused ion beam removes residual powder on the surface through the sputtering effect, and the impact of the defocused ion beam on the part surface can induce dislocation proliferation, thus simultaneously achieving residual... Powder removal and surface densification result in better metallurgical quality of parts, making them less prone to deformation and eliminating the need for transfer to external equipment, thus saving process time and costs. This application uses a detection feedback device to collect three-dimensional morphology data of the molten pool surface in real time, analyze surface roughness, and transmit the detection data to the controller. The controller dynamically adjusts the focused ion beam parameters based on the detection data, thereby ensuring the effect of improving the surface morphology of the interlayer molten pool. At the same time, the electron beam emission focusing scanning device and the ion beam emission focusing scanning device are integrated in the same vacuum forming chamber, sharing the scanning path and control system, achieving efficient collaborative work. This application solves the problem of porosity defects in traditional electron beam powder bed additive manufacturing by combining ion beam-assisted processing with real-time detection feedback. Compared with traditional electron beam remelting processes, the molten pool is more stable, avoiding molten pool fluctuations and incomplete fusion defects caused by electron beam remelting, improving the surface quality of parts, and achieving improvements in metallurgical quality and mechanical properties. It is suitable for manufacturing high-performance metal parts in the aerospace field.

[0052] The above description is merely an optional embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the inventive concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for selective electron beam melting and forming based on ion beam assistance, characterized in that, Includes the following steps: S1. Establish a three-dimensional digital model of the part to be printed, and slice and layer it to obtain layered scanning data; S2. Under vacuum conditions, metal powder is spread on a preheated substrate to a set thickness to form a powder bed. S3. Based on the layered scanning data, the powder bed is melted by electron beam scanning to form an uneven molten pool surface on the powder bed; S4. The surface of the molten pool is impacted by a focused ion beam, while the morphology of the molten pool surface is monitored in real time, and the parameters of the focused ion beam impact treatment are dynamically adjusted until a flat molten pool surface is formed, thus completing single-layer scanning melting. S5. Repeat steps S2-S4 to complete the scanning and melting layer by layer until the part is printed. S6. The printed parts are cleaned and surface strengthened in situ using a defocused ion beam to obtain the finished parts.

2. The electron beam selective melting and forming method based on ion beam assistance according to claim 1, characterized in that, In the step of spreading metal powder to a preheated substrate at a set thickness under vacuum conditions to form a powder bed, the metal powder is titanium alloy TC4 powder with an average particle size of 30μm-105μm, a powder bed thickness of 80μm-120μm, and a vacuum condition of 1.0×10⁻⁶. -3 Pa-1.0×10 -4 Pa.

3. The electron beam selective melting and forming method based on ion beam assistance according to claim 1, characterized in that, In the step of spreading metal powder to a set thickness on a preheated substrate under vacuum conditions to form a powder bed, the substrate is preheated to 100°C-200°C by a defocused electron beam, the scanning current of the defocused electron beam is 25mA-35mA, and the scanning speed is 8m / s-12m / s.

4. The electron beam selective melting and forming method based on ion beam assistance according to claim 1, characterized in that, In the step of melting the powder bed by electron beam scanning to form an uneven molten pool surface on the powder bed, the powder bed is melted by focused electron beam scanning. The diameter of the focused electron beam spot is 50μm-150μm, the focused beam current is 15mA-25mA, the scanning speed is 1m / s-3m / s, and the scanning spacing is 80μm-120μm.

5. The electron beam selective melting and forming method based on ion beam assistance according to claim 1, characterized in that, In the step of impacting the molten pool surface with a focused ion beam, while simultaneously monitoring the morphology of the molten pool surface in real time and dynamically adjusting the parameters of the focused ion beam impact treatment until a smooth molten pool surface is formed, the parameter adjustment range of the focused ion beam is: voltage 80V-120V, current 8mmA-12mmA, current density 5mA / cm². 2 -15mA / cm 2 The scanning speed is 5m / s-15m / s.

6. The electron beam selective melting and forming method based on ion beam assistance according to claim 1, characterized in that, In the step of in-situ powder removal and surface strengthening of the printed parts using a defocused ion beam, the voltage of the defocused ion beam is 900V-1100V, the current is 0.8mmA-1.2mmA, and the current density is 5mA / cm². 2 -15mA / cm 2 .

7. An electron beam selective melting and forming apparatus based on ion beam assistance, characterized in that, For implementing the ion beam-assisted electron beam selective melting and forming method according to any one of claims 1-6, the melting and forming apparatus comprises: A vacuum forming chamber, wherein a worktable is provided inside the vacuum forming chamber for supporting the substrate; A powder supply mechanism, located in the vacuum forming chamber and connected to the worktable, is used to spread metal powder onto the substrate. An electron beam emission focusing and scanning device is disposed at the top of the vacuum forming chamber, and the scanning range of the electron beam emission focusing and scanning device covers the forming area on the worktable; An ion beam emission focusing scanning device is disposed at the top of the vacuum forming chamber. The scanning range of the ion beam emission focusing scanning device is the same as that of the electron beam emission focusing scanning device. The ion beam emission focusing scanning device is capable of emitting focused ion beams and defocused ion beams. A detection feedback device, which is electrically connected to the ion beam emission focusing scanning device, is used to acquire morphology data of the molten pool surface in real time. The controller is electrically connected to the electron beam emission focusing scanning device, the ion beam emission focusing scanning device, and the detection feedback device, respectively, and is used to control the electron beam emission focusing scanning device to emit an electron beam, and to respond to the morphology data of the detection feedback device and adjust the parameters of the ion beam emission focusing scanning device.

8. The electron beam selective melting and forming apparatus based on ion beam assistance according to claim 7, characterized in that, The electron beam emission focusing scanning device has a preheating mode and a scanning melting mode; The preheating mode is to preheat the substrate by emitting a defocused electron beam; The scanning melting mode involves scanning and melting metal powder by emitting a focused electron beam.

9. The electron beam selective melting and forming apparatus based on ion beam assistance according to claim 7, characterized in that, The ion beam emission focusing scanning device can dynamically switch between focusing and defocusing modes; When the ion beam emission focusing scanning device switches to focusing mode, it emits a focused ion beam to impact the surface of the molten pool. When the ion beam emission focusing scanning device switches to defocus mode, it emits a defocused ion beam to perform powder removal and strengthening treatment on the surface of the part.

10. The electron beam selective melting and forming apparatus based on ion beam assistance according to claim 7, characterized in that, The detection feedback device includes a laser scanner, which generates morphological data of the molten pool surface in real time and feeds it back to the ion beam emission focusing scanning device through the controller.

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