Laser powder bed fusion composite impact strengthening method and device based on temperature field positioning
Patent Information
- Application Number
- CN202611546619.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-10-08
- Publication Date
- 2026-11-03
AI Technical Summary
Laser powder bed melting technology is prone to internal defects such as porosity and lack of fusion during the layer-by-layer melting process. Furthermore, the high temperature gradient and cooling rate introduce residual stress, which limits its application in high-performance load-bearing components.
By monitoring the temperature field distribution, ultrafast lasers are used to perform impact strengthening in the target temperature range. Combined with the melting and forming of continuous lasers, real-time strengthening is achieved in layer-by-layer processing, avoiding subsequent processing.
It improves processing efficiency, reduces porosity and residual stress, enhances the overall performance of components, and ensures stable strengthening effects at different locations.
Smart Images
Figure CN123024898A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of metal powder processing technology, specifically to a laser powder bed melting composite impact strengthening method and equipment based on temperature field positioning. Background Technology
[0002] Laser powder bed melting, also known as selective laser melting, is a high-precision metal additive manufacturing technology capable of integrally forming complex structures and high-performance components. It offers great design freedom, theoretically enabling the manufacture of arbitrarily complex structures and complex internal structures that are difficult to process using traditional methods. It is suitable for high-end manufacturing fields such as aerospace and biomedicine. However, during the layer-by-layer melting process, the instability of the molten pool can easily lead to internal defects such as porosity and incomplete fusion. Furthermore, the extremely high temperature gradient and cooling rate can introduce significant residual stress, inducing deformation or even cracking of parts, severely limiting its application in high-performance load-bearing components. Summary of the Invention
[0003] To address the aforementioned problems, this application proposes a laser powder bed melting composite impact strengthening method based on temperature field positioning, comprising: The three-dimensional model of the target component to be processed is sliced to obtain the cross-sectional data of each layer, and the current processing layer is constructed based on the cross-sectional data; Repeat the following steps until all processing layers are determined to be formed, resulting in the finished target component: For the current processing layer, a continuous laser is used as a heat source, and the material to be processed in the current processing layer is melted and shaped according to a preset scanning strategy; Monitor the temperature field distribution of the current processing layer, identify the target spatial location in the current processing layer whose temperature is within a preset target temperature range based on the temperature field distribution, and control the ultrafast laser to act on the target spatial location to implement the impact strengthening operation; After determining the current processing layer is formed, a next processing layer is superimposed on the current processing layer based on the cross-sectional data, and the next processing layer is used as the new current processing layer.
[0004] This application provides a laser powder bed fusion composite impact strengthening device based on temperature field positioning, the device comprising: At least one processor; And, a memory communicatively connected to the at least one processor; The memory stores instructions that can be executed by the at least one processor, which are executed by the at least one processor to enable the at least one processor to perform a laser powder bed melt composite impact strengthening method based on temperature field positioning as described above.
[0005] This application provides a non-volatile computer storage medium storing computer-executable instructions, wherein the computer-executable instructions are configured as follows: A laser powder bed fusion composite impact strengthening method based on temperature field positioning, as described in any of the preceding items.
[0006] The laser powder bed fusion composite impact strengthening method based on temperature field positioning proposed in this application can bring the following beneficial effects: By monitoring the temperature field distribution during the melt forming process in real time, the target location requiring impact strengthening can be directly located based on the actual temperature field distribution. This allows for precise matching of different strengthening requirements, ensuring that different components and locations can achieve stable and consistent strengthening effects. Simultaneously, impact strengthening is completed during the layer-by-layer processing of melt forming, eliminating the need for secondary processing after the component is formed as a whole. This improves processing efficiency while ensuring the strengthening effect. It can also simultaneously improve the microstructure and mechanical properties of the component during the forming process, reducing defects such as porosity and residual stress, and enhancing the overall performance of the formed component. Attached Figure Description
[0007] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 A schematic flowchart of a laser powder bed fusion composite impact strengthening method based on temperature field positioning provided in this application embodiment; Figure 2 A schematic diagram of the enhanced mode in the first working mode provided in the embodiments of this application; Figure 3 A schematic diagram of continuous laser melting and temperature monitoring in the second working mode provided in the embodiments of this application; Figure 4 A schematic diagram of ultrafast laser shock enhancement in the second working mode provided in this application embodiment; Figure 5 A schematic diagram of continuous laser melting and temperature monitoring in the third working mode provided in the embodiments of this application; Figure 6 A schematic diagram of ultrafast laser shock blasting in the third working mode provided in an embodiment of this application; Figure 7 This is a schematic diagram of a laser powder bed melting composite impact strengthening device based on temperature field positioning, provided as an embodiment of this application.
[0008] Among them, 1. Continuous laser, 2. Temperature measuring device, 3. Central controller, 4. Ultrafast laser, 5. Continuous laser action position, 6. Target temperature range position, 7. Raw material powder, 8. Current processing layer, 9. Powder spreading device, 10. Molten part, 11. Substrate. Detailed Implementation
[0009] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0010] The technical solutions provided by the various embodiments of this application are described in detail below with reference to the accompanying drawings.
[0011] like Figure 1 As shown in the embodiments of this application, the laser powder bed fusion composite impact strengthening method based on temperature field positioning includes: S101: Slice the 3D model of the target component to be processed to obtain the cross-sectional data of each layer, and construct the current processing layer based on the cross-sectional data.
[0012] The 3D model of the target component to be processed is sliced. Slicing refers to discretizing the 3D digital model of the target component along the height direction according to a set layer thickness (usually 30 to 50 micrometers), decomposing the 3D model into 2D cross-sectional data. Each layer of cross-sectional data records the geometric shape and size information of the component's cross-section at that layer's height. Through the cross-sectional data, the area within the current processing layer that needs to be melted and formed can be clearly identified. By slicing, the additive manufacturing problem of complex 3D components can be transformed into a layer-by-layer stacking 2D forming problem, providing an accurate processing benchmark for subsequent layer-by-layer scanning and melting.
[0013] After obtaining the cross-sectional data of each layer through slicing, the subsequent step is the actual construction stage of layer-by-layer additive manufacturing. It's important to note that slicing only discretizes the 3D model into 2D contour data. To transform this cross-sectional data into a solid component, the cross-sectional shape of each layer needs to be reproduced layer by layer in physical space. Therefore, the current processing layer needs to be constructed based on the cross-sectional data of the current layer. The current processing layer refers to the material being melted and fused by laser scanning during the layer-by-layer deposition manufacturing process, as well as the molten and solidified layer formed by it. It is the most basic manufacturing unit in the additive manufacturing process. After each layer is completed, it transforms from its previous state into a formed layer, becoming the base for the next layer.
[0014] The specific process for constructing the current processing layer is as follows: The powder spreading device uniformly spreads a layer of metal powder on the forming worktable or on the already formed layer. The metal powder can be any type of metal powder or a combination of multiple metal powders. The thickness of the powder layer is determined according to the layer thickness set during the slicing process, typically 30 to 50 micrometers. This thickness needs to match the laser energy penetration depth and the size of the molten pool to ensure that the newly spread powder layer can form a good metallurgical bond with the underlying formed layer. After the powder is spread, the powder layer spatially covers the entire area corresponding to the current layer cross-sectional data. At this time, a continuous laser is used as a heat source to melt and form the powder layer. Continuous laser, unlike pulsed laser, refers to a laser beam that continuously outputs laser energy without interruption during operation, providing a continuous and stable heat input to the powder material. In the embodiments of this application, the wavelength range of the continuous laser is 445 nanometers to 1080 nanometers, the power range is 50 watts to 4000 watts, and the scanning speed can reach up to 8 meters per second.
[0015] Repeat the following steps until all processing layers are determined to be formed, resulting in the finished target component: S102: For the current processing layer, using a continuous laser as a heat source, the material to be processed in the current processing layer is melted and shaped according to a preset scanning strategy.
[0016] When performing continuous laser melting and forming, a preset scanning strategy must be followed. The scanning strategy refers to the execution plan that guides the continuous laser to perform scanning actions on the powder layer surface, and it includes two parts: the scanning trajectory and laser parameters. The scanning trajectory defines the movement path and scanning sequence of the laser spot on the powder layer surface, i.e., which positions the laser beam passes through sequentially, in which direction it moves, and how the scanning tracks are arranged and overlapped. The scanning trajectory needs to be planned based on the geometry of the current layer cross-section data to ensure that the entire area inside the cross-section is scanned and covered while minimizing the total length of the scanning path and the number of turns, thereby improving forming efficiency. The laser parameters define the energy state and movement speed of the laser beam during its movement along the scanning trajectory, including laser power, scanning speed, and scanning spacing. These parameters collectively determine the laser energy density received by the powder material per unit area, thus affecting the melting temperature, melt pool size, cooling rate, and the density and mechanical properties of the final formed layer.
[0017] For the current processing layer, the continuous laser scans the layer line by line according to the above scanning strategy. After the laser energy is absorbed by the powder particles, the powder temperature rapidly rises above the melting point to form molten metal. The molten metal between adjacent scan tracks flows and merges under the drive of surface tension, forming a continuous molten pool region. Subsequently, the molten pool rapidly dissipates heat to the already formed layer below and the surrounding cold powder under the action of thermal conduction, and solidifies to form a solid thin layer with the same cross-sectional data profile as the current layer. After the current processing layer has completed scanning of all preset scan trajectories, the material to be processed in this layer has been melted and formed, becoming part of the already formed layer, providing a substrate for the powder laying and forming of the next layer.
[0018] S103: Monitor the temperature field distribution of the current processing layer, identify the target spatial location in the current processing layer whose temperature is within the preset target temperature range based on the temperature field distribution, and control the ultrafast laser to act on the target spatial location to implement the impact strengthening operation.
[0019] Ultrafast lasers are lasers capable of generating ultrashort pulses in the picosecond (10⁻¹² seconds), femtosecond (10⁻¹⁵ seconds), and even attosecond (10⁻¹⁸ seconds) range. They utilize the high-pressure shock waves induced by these ultrashort laser pulses to plastically deform materials, significantly improving material density, surface hardness, wear resistance, and fatigue resistance. Simultaneously, they introduce beneficial residual compressive stress, inhibiting crack propagation. The effectiveness of ultrafast laser shock strengthening is influenced not only by the laser's inherent process parameters but also primarily by the temperature state of the material being treated. This is similar to the classic concepts of cold forging, warm forging, and hot forging in traditional forging; that is, the material's physical properties differ at different temperatures, leading to varying shock strengthening effects. In the laser powder bed melting process, combined with temperature-guided ultrafast laser shock strengthening, different strengthening effects can be obtained according to requirements, achieving results similar to cold forging, warm forging, and hot forging in traditional forging processes. Therefore, this embodiment integrates a temperature monitoring device coaxially with an ultrafast laser shock strengthening head to form a coaxial system integrating temperature measurement and strengthening. This allows the temperature measuring device to track the scanning trajectory of the continuous laser in real time and obtain the temperature field distribution of the current processing layer during the melting and forming process. Based on this, according to the desired strengthening effect of the target component, such as high dislocation density, strong-plasticity matching, or high toughness, the target spatial position in the current processing layer with a temperature within a preset target temperature range is determined based on the temperature field distribution of the current processing layer. The central controller transmits the target spatial position to the scanning galvanometer of the ultrafast laser in real time, controlling the ultrafast laser to precisely point to the target spatial position to perform the shock strengthening operation. This prevents the ultrafast laser from blindly scanning a preset fixed trajectory, but instead dynamically follows the real-time changes in the temperature field, delivering its strengthening energy to the material position in the current processing layer that is within the target temperature range. It should be noted that the continuous laser and the ultrafast laser use the same scanning trajectory within the current processing layer, and the scanning range of the ultrafast laser covers the scanning trajectory of the continuous laser. The ultrafast laser can avoid optical path interference with the continuous laser through path planning.
[0020] In one embodiment, while the continuous laser melts and shapes the current processing layer, the temperature measuring device also acquires infrared images of the current processing layer in real time. The temperature measuring device can be an infrared thermal imager. Since the temperature measuring device is coaxially integrated with the ultrafast laser processing head, the monitoring center of the temperature measuring device is always synchronized with the location of the continuous laser spot. Therefore, the infrared thermal imager can follow the scanning trajectory of the continuous laser and capture the infrared radiation signals of the molten zone and its surrounding heat-affected zone in real time.
[0021] During continuous acquisition by an infrared thermal imager, the original infrared image undergoes noise reduction processing to filter out noise interference. This embodiment employs a Fast Non-Local Means (FNLM) filter for noise reduction. For each pixel in the image, all pixel blocks with similar texture features to the surrounding neighborhood blocks are searched throughout the entire image. The original value of the pixel is replaced by a weighted average of the pixel values at corresponding positions within these similar pixel blocks. Since random noise in the image manifests as isolated, unrelated pixel value abrupt changes, while the actual temperature distribution information exhibits spatial continuity and structural repetition, the temperature gradient distribution of the molten pool and its heat-affected zone along the scanning trajectory is highly similar across different scanning tracks. Therefore, the FNLM filter can effectively preserve key spatial features such as the molten pool boundary and temperature zone contour in the temperature distribution image while suppressing noise. After noise reduction, the infrared image also needs to be interpolated to improve image resolution. This application employs a bicubic interpolation algorithm for interpolation processing. When calculating the grayscale value of a newly inserted pixel, this algorithm considers not only its four nearest neighbors but also the grayscale values of its surrounding 16 neighboring pixels (4×4 pixels in total), and performs a cubic polynomial weighted calculation based on the distance between each neighboring pixel and the interpolation point. Compared to the simpler bilinear interpolation, bicubic interpolation produces a smoother transition of grayscale values between pixels, effectively avoiding jagged edges and stepped color blocks in the interpolated image, thus obtaining a more refined and continuous temperature distribution image. After noise reduction and interpolation processing, the original infrared image is converted into a temperature distribution image with a higher signal-to-noise ratio and spatial resolution.
[0022] After obtaining the temperature distribution image, it is necessary to identify the pixel region containing the preset target temperature range. However, the temperature value of each pixel in the temperature distribution image is a continuously changing value. Directly extracting the spatial location of a temperature value within a specific temperature range from continuous values requires first determining the numerical boundaries of that temperature range. Therefore, this embodiment divides the temperature distribution image into multiple temperature ranges based on the material properties of the target component. Material properties include thermophysical parameters such as the melting point, recrystallization temperature, phase transition point, and thermal conductivity of the powder material used in the target component. These parameters collectively determine the thermodynamic state of the material within different temperature ranges.
[0023] The division of temperature zones follows the principle of combining the material's thermophysical properties with actual processing requirements. First, the temperature at which the material begins to melt is used as the highest temperature boundary, because areas above this temperature are in a molten liquid state, and impact strengthening cannot produce plastic deformation strengthening effects on liquid materials. Second, room temperature or the substrate preheating temperature is used as the lowest temperature boundary, because the temperature field in areas below this temperature is basically stable, the material's yield strength recovers to a high level, and shock waves are unlikely to drive significant dislocation movement. The temperature range between the highest and lowest temperature boundaries is divided into several continuous temperature zones according to preset temperature intervals. Taking TC4 titanium alloy as an example, its solidus temperature is approximately 1600 degrees Celsius, and the temperature distribution image can be divided into five temperature zones: 50℃-600℃, 600℃-700℃, 700℃-800℃, 800℃-900℃, and 900℃-1500℃.
[0024] Each temperature range corresponds to a different physical meaning. By discretizing the temperature field into a finite number of temperature ranges, the originally continuous temperature distribution is transformed into discrete temperature intervals with clear physical meanings, each corresponding to a specific thermodynamic state of the material. Based on this, according to the preset type of strengthening effect required for the current processing layer, the target temperature interval is determined from the multiple temperature ranges defined above. The type of strengthening effect refers to the strengthening effect that the user expects to achieve in impact strengthening based on the mechanical performance requirements of the target component under service conditions, including cold forging effect, warm forging effect, and hot forging effect. Since the effect of ultrafast laser shock strengthening on materials essentially depends on the temperature state of the material at the moment of impact, by selecting different target temperature intervals, different strengthening effects can be obtained by utilizing the differences in the thermophysical state of the material at different temperatures under the same ultrafast laser shock energy input. After determining the target temperature interval, the coordinate information of all pixels in the current processing layer whose temperature falls within the target temperature interval can be extracted from the temperature distribution image, thereby determining the target spatial location.
[0025] In one embodiment, during the laser powder bed fusion composite ultrafast laser shock annealing process, the target spatial position changes in real time due to the real-time variation in temperature field distribution. Furthermore, the differences in the thermophysical properties of different materials lead to variations in the duration of the target spatial position change and the rate of temperature change. In the actual processing of laser powder bed fusion composite ultrafast laser shock annealing, the temperature measurement and positioning operations and the ultrafast laser shock annealing operations cannot be limited to a single execution coordination method. If a fixed execution coordination method is used, problems may arise such as the ultrafast laser's response speed failing to keep up with the rate of change in the target spatial position, or the temperature measurement signal being interfered with by the ultrafast laser plasma flash.
[0026] Therefore, this application embodiment predefines multiple working modes, each corresponding to a specific coordination method between temperature measurement and positioning and impact strengthening, including differences such as whether the two are executed simultaneously, whether they are executed on the same processing layer, and whether the continuous laser participates in secondary heating. Before performing impact strengthening, the ultrafast laser needs to select a target working mode from the predefined multiple working modes based on the actual working conditions of the current processing layer, i.e., the duration of the target spatial position in the current processing layer. Then, based on the target working mode, the timing of the temperature measurement and positioning operation relative to the current processing layer is determined.
[0027] Specifically, the execution time required for an ultrafast laser to complete a single impact strengthening operation, and the duration of the target spatial position within the current processing layer, are determined. Duration refers to the time window from when the temperature at the target spatial position first enters the target temperature range until the temperature at that position decays below the lower boundary of the target temperature range. This duration is affected by the rate of temperature change, which is influenced by factors including the thermophysical properties of the material in the current processing layer, melting process parameters, and filling path. Thermophysical properties include thermal conductivity, specific heat capacity, and density. Lower thermal conductivity and higher specific heat capacity result in slower heat dissipation and a longer duration of the target spatial position, and vice versa. Melting process parameters include, but are not limited to, laser power, scanning speed, scanning spacing, and layer thickness. For example, when a higher scanning speed is used for melting, the interaction time between the continuous laser and the material being processed is shortened, the heat input per unit area decreases, the thermal cycle time experienced by the molten zone is shortened, and the corresponding cooling rate is accelerated. Consequently, the duration of the target spatial position within the target temperature range will be shortened, and vice versa. The filling path reflects the spatial configuration of the area to which the continuous laser scanning trajectory in the current processing layer belongs, such as the solid filling area, the contour boundary area, and the thin-walled structure area. The heat dissipation boundary conditions corresponding to different filling paths are significantly different, the temperature decay rate is different, and the duration will also be affected.
[0028] Based on the aforementioned influencing factors, the duration can be determined as follows: A transient temperature field model of the current processed layer during continuous laser melting is established based on the material thermophysical parameters of the current processed layer, combined with the melting process parameters and filling path. Based on the transient temperature field model, the temperature change curves of each spatial location of the current processed layer during continuous laser scanning are simulated. According to a preset target temperature range, the time difference between the temperature at that spatial location entering and leaving the target temperature range is extracted from the temperature change curves; this time difference is the duration.
[0029] Optionally, the duration can also be obtained by looking up a table in a pre-built process database or empirical model. For example, for a specific material system and combination of process parameters, temperature-time response curves under different scanning speeds and filling paths can be calibrated through preliminary temperature measurement experiments to establish a mapping relationship table between process parameters and duration. During actual processing, the central controller queries or interpolates to calculate the corresponding duration in real time based on the material properties and process parameters of the current processing layer.
[0030] If the duration of the continuous operation exceeds the execution duration, it indicates that during the melting process of the current processing layer, the time window within which the target spatial location is within the target temperature range is sufficient to support the ultrafast laser to complete the impact strengthening operation before the temperature decays to the lower limit of the target temperature range. In this case, the current working condition meets all the conditions for real-time synchronous processing, and the target working mode is determined to be the first working mode. The first working mode includes directly performing the impact strengthening operation in the current processing layer. That is, temperature measurement and positioning and ultrafast laser impact strengthening are performed synchronously in the same processing layer. The temperature measurement device follows the continuous laser scanning trajectory in real time to identify the position of the target temperature range and provides real-time feedback to the central controller. The central controller then commands the ultrafast laser to point to that position in real time to perform impact strengthening.
[0031] If the duration is not greater than the execution duration, it indicates that during the melting process of the current processing layer, the window time for the target spatial position to be within the target temperature range is insufficient to support the ultrafast laser to complete the impact strengthening operation before temperature decay. In this case, the similarity of the temperature fields between adjacent processed layers is further determined. It should be noted that the similarity of the temperature fields between adjacent layers refers to the degree of similarity in the temperature field distribution and temperature change patterns of adjacent layers that have previously completed melting and forming, under the same scanning strategy and laser parameters. In one implementation of this application, the temperature field similarity can be obtained by comparing the infrared temperature distribution images of two layers. After registering the temperature distribution images of adjacent processed layers, the similarity index between the temperature distribution images is calculated. The similarity index comprehensively considers the similarity of the two images in three dimensions: brightness, contrast, and structure. The closer the value is to 1, the more similar the temperature field distribution patterns of the two layers are.
[0032] If the temperature field similarity is greater than a preset threshold, it indicates that the temperature field distribution of adjacent processing layers is sufficiently similar under the current process conditions. In this case, the target working mode is determined to be the second working mode. The second working mode involves delaying the impact strengthening operation to adjacent already formed processing layers. In this mode, temperature measurement and positioning, along with ultrafast laser impact strengthening, are performed on different processing layers. During the continuous laser melting process of the current processing layer, the temperature measuring device continuously tracks the scanning trajectory to identify the target spatial position and stores it. The central controller generates control commands based on the stored target spatial position to execute impact strengthening with ultrafast laser in the subsequent layer or several layers. This allows the ultrafast laser to directly perform impact strengthening operations on adjacent already formed processing layers according to the stored target spatial position, without the need for further real-time temperature measurement and positioning. By coordinating temperature measurement at the current layer with strengthening at the current and lower layers, even when temperature measurement and ultrafast laser cannot operate simultaneously, the similarity of the temperature fields of adjacent layers allows for spatial allocation of temperature measurement and positioning, along with impact strengthening, to different processing layers. This avoids potential conflicts arising from simultaneous operation and ensures that each layer achieves impact strengthening based on temperature field positioning.
[0033] If the material to be processed in the current processing layer is a heat-sensitive material, the operating mode is the third operating mode. The third operating mode includes performing shock strengthening after the current processing layer is melted and shaped and its temperature field is controlled. In this mode, the continuous laser melting and shaping operation is executed sequentially with the temperature measurement and positioning and ultrafast laser shock strengthening operations. The continuous laser first melts and shapes the current processing layer according to the first laser parameters. After melting and shaping, the continuous laser then heats the current processing layer according to the second laser parameters. During the heating process, the temperature measurement and positioning operation and the shock strengthening operation are performed simultaneously on the current processing layer. Specifically, the third operating mode completely decouples the continuous laser melting and shaping operation from the temperature measurement and positioning and ultrafast laser shock strengthening operations in time, executing them in two stages. The first stage is the melting and shaping stage, where the continuous laser melts and shapes the current processing layer along a preset scanning trajectory according to the first laser parameters. The first laser parameters are typically high-powered to ensure the powder is fully melted. During this process, neither the temperature measuring device nor the ultrafast laser operates. This is to avoid interference from the intense radiation of the molten pool on the temperature measuring signal and to avoid uncontrollable thermo-coupling effects of the ultrafast laser shock wave on the melting and solidification process. After the continuous laser completes all preset scanning trajectories of the current processing layer, the melting and forming stage ends, and the current processing layer has solidified into a dense solid layer, but its temperature is still at a level far above room temperature. The second stage is the heating and strengthening stage. The continuous laser switches to a second laser parameter and performs a heating scan on the solidified current processing layer along the same preset scanning trajectory. The second laser parameter has a lower power, providing only enough heat to raise the material temperature without causing melting. Since the power density of the second laser parameter is lower than the melting threshold, this heating scan only raises the material temperature on the scanning trajectory to the preset target temperature range without melting the material again. During the heating scan, the temperature measuring device follows the heating scan trajectory of the continuous laser in real time, monitors the temperature field on the scanning trajectory, identifies the spatial location of the preset target temperature range, and feeds it back to the central controller. The central controller commands the ultrafast laser to point to that spatial location and simultaneously perform the impact strengthening operation. By completely separating melt forming and impact strengthening in time, the third working mode eliminates the coupling interference of factors such as melt pool flow, drastic temperature gradient changes and solidification shrinkage during the melting process on the impact strengthening effect. This allows ultrafast lasers to perform impact strengthening under stable and controllable temperature field conditions, making it suitable for materials that are sensitive to thermal history and require precise control of the strengthening temperature window.
[0034] It should be noted that after determining the target working mode, further dynamic control of the ultrafast laser's movement speed during the impact strengthening process is required. The target spatial position is not stationary during continuous laser melting or secondary heating; rather, it moves continuously along the scanning trajectory as the laser spot advances. Simultaneously, as the material conducts heat to the surrounding cold substrate, the area covered by the target spatial position continuously shrinks, and its temperature continuously decreases. Therefore, if the ultrafast laser moves at a constant speed along the scanning trajectory, if the ultrafast laser's movement speed is too slow, the temperature at the location to be strengthened may have decayed below the preset range or shifted to another spatial position as the scan progresses. When the ultrafast laser reaches that position, the temperature is no longer within the target temperature range, causing the impact strengthening to act on the material at an unexpected temperature state, resulting in a strengthening effect deviating from the preset target. Furthermore, if the ultrafast laser's movement speed is too fast, it may exceed the dynamic response range of the scanning galvanometer or lead to insufficient laser energy density, affecting the impact strengthening effect. To address the aforementioned issues, this application determines the real-time velocity of the ultrafast laser at each spatial location based on the rate of change of the target's spatial position in the current processing layer and the rate of change of its temperature.
[0035] Specifically, during the real-time temperature monitoring of the current processing layer by the temperature measuring device, feature parameters of the target spatial location are continuously extracted from the infrared temperature distribution image. Each frame of the infrared temperature distribution image contains spatial distribution information of the target spatial location at the current moment, including the length of the corresponding temperature zone along the scanning direction, the width perpendicular to the scanning direction, the total area covered, and the temperature value corresponding to each pixel within that temperature zone. By comparing the changes in feature parameters between adjacent time frames, the size change rate (i.e., the rate of contraction of the temperature zone along its length and width directions per unit time) and the temperature change rate (i.e., the rate of decrease of the average or peak temperature within the temperature zone per unit time) of the target spatial location can be calculated. After these parameters are transmitted to the central controller, the central controller dynamically calculates the real-time motion speed required by the ultrafast laser at each spatial location based on the current size of the target spatial location, the remaining length of the scanning trajectory requiring impact enhancement, and the remaining available time from the current moment until the temperature at the target spatial location decays below the lower boundary of the preset range. For regions that contract and cool rapidly, the ultrafast laser needs to pass through at a high speed to complete the enhancement before the temperature zone disappears. For more stable regions that cool slowly, the ultrafast laser can appropriately reduce its speed to ensure sufficient impact time. Based on this, the central controller sends the calculated real-time speed command to the ultrafast laser's scanning galvanometer control system. By controlling the deflection angle, deflection speed, and deflection acceleration of the galvanometer motor, the ultrafast laser spot moves along a preset scanning trajectory at a real-time changing speed.
[0036] To ensure that the ultrafast laser accurately follows the dynamic temperature changes of the target spatial location during impact strengthening, real-time closed-loop control of the ultrafast laser's acceleration and velocity is required. The central controller pre-calculates the required deflection direction and amplitude of the ultrafast laser spot based on the spatial offset of the target spatial location between the current and next frames, and generates the drive signal for the galvanometer motor accordingly. When the target spatial location moves rapidly, the galvanometer deflection speed increases accordingly; when the target spatial location moves slowly or tends to stabilize, the galvanometer deflection speed decreases accordingly. Through this variable-speed control mechanism, the ultrafast laser remains spatially aligned with the target spatial location, ensuring that each frame of impact strengthening operation applies to materials at temperatures precisely within the target spatial location, until all target spatial locations within the target temperature range on all preset scanning trajectories of the current layer are completely covered by the ultrafast laser.
[0037] In one embodiment, as the ultrafast laser moves along a preset scanning trajectory at a real-time speed, locations within the current processing layer that have already undergone impact strengthening by the ultrafast laser no longer require repeated monitoring and strengthening. Therefore, this strengthened location information is fed back to the central controller in real time, which then filters these locations out of the subsequent monitoring range of the temperature measuring device and the subsequent scanning range of the ultrafast laser. This avoids over-strengthening damage that may result from repeated strengthening of the same location, effectively reducing the unnecessary workload of the temperature measuring device and the ultrafast laser, and improving processing efficiency and process safety.
[0038] S104: After determining the current processing layer shape, the next processing layer is superimposed on the current processing layer based on the cross-sectional data, and the next processing layer is used as the new current processing layer.
[0039] This application embeds the impact strengthening operation into the melting and forming process of each processing layer. Specifically, after each layer completes powder spreading and continuous laser melting and forming, the aforementioned temperature measurement, positioning, and ultrafast laser shock strengthening operations are performed. In other words, after the current processing layer is formed, based on the cross-sectional data of the next layer, a new processing layer is superimposed on the current processing layer, and this next layer becomes the new current processing layer. Steps S102-S103 are repeated until all processing layers are formed and strengthened, resulting in the target component. Through this layer-by-layer cyclic processing method, each layer undergoes temperature-field-guided ultrafast laser shock strengthening before the temperature field has completely dissipated after melting and solidification, avoiding the limitation of traditional post-processing strengthening methods where the strengthening energy cannot penetrate the component surface to act on the interior. Since the impact strengthening of each layer is based on the real-time temperature field, different target temperature ranges can be selected to achieve cold forging, warm forging, or hot forging effects. Different strengthening effects can be obtained for each layer in the height direction of the target component, thereby achieving on-demand customization of mechanical properties along the three-dimensional space of the component.
[0040] The following are examples of each working mode.
[0041] like Figure 2 The diagram shows the strengthening mode under the first working mode. Using a TC4 titanium alloy component as the target component, the target titanium alloy component is 3D modeled and sliced into layers, each 40 μm thick. The continuous laser and ultrafast laser scanning trajectories are identical, both using a zigzag linear reciprocating scanning trajectory. For continuous laser 1, the wavelength is 1064 nm, with a power of 150 W, a scanning speed of 1000 mm / s, and a scanning interval of 80 μm. For ultrafast laser 4, the wavelength is 1030 nm, with a single pulse energy of 50 μJ, a pulse width of 200 fs, a repetition frequency of 2 kHz, a scanning speed of 1000 mm / s, and a scanning interval of 80 μm. A TC4 substrate 11 is installed and fixed, and raw material powder 7 (TC4 powder with a particle size of 15-53 μm) is filled in. The substrate preheating temperature is set to 150℃. High-purity constant-flow argon gas is introduced into the forming chamber for gas purging, controlling the oxygen concentration in the forming chamber to below 100 ppm. At the forming position, i.e., substrate 11, the powder is lowered by 40μm, and the powder spreading device 9 spreads 40μm thick powder at the forming position. The temperature measuring device 2 is coaxially mounted with the continuous laser 1 melting head to track the position of the molten pool in real time. The continuous laser 1 starts melting the powder according to the set scanning trajectory and laser parameters to perform the forming work. At the continuous laser action position 5, the temperature measuring device 2 starts working at the same time, collecting the infrared radiation information of the continuous laser melting zone in real time, obtaining the transient thermal response characteristic parameters during the continuous laser melting process. The infrared image of the melting zone is denoised using an FNLM filter and a bicubic interpolation algorithm to obtain the temperature field distribution of the melting zone. The melting zone is divided into five temperature ranges: 50-600℃, 600-700℃, 700-800℃, 800-900℃, and 900-1500℃. The 700-800℃ temperature range on the scanning trajectory is located, and the length, width, area, and temperature change rate characteristic parameters of the specified temperature range are extracted and synchronously fed back to the central controller 3. The central controller 3 adjusts the deflection angle, deflection speed, deflection acceleration, and deflection time of each mirror in the ultrafast laser head in real time, controlling the ultrafast laser 4 to aim at the target temperature range position 6 to perform impact strengthening. This ensures that the impact strengthening task is completed before the temperature decays to 700℃ or before the target temperature range is refreshed, until the ultrafast laser 4 follows the continuous laser to complete the preset scan of the current processing layer 8, resulting in the formed current processing layer 8. The molten portion 10 located below the current processing layer 8 is the formed processing layer that has completed composite impact strengthening. The above impact strengthening steps are repeated until all layers are completed, obtaining the target TC4 titanium alloy component.
[0042] In the second working mode, a GH4169 high-temperature nickel-based alloy component is used as the target component. The target high-temperature nickel-based alloy component is 3D modeled and sliced into layers, each 30μm thick. The continuous laser and ultrafast laser scanning trajectories are identical, both using a zigzag linear reciprocating scanning trajectory. The continuous laser wavelength is 1070 nm, with a power of 200 W, a scanning speed of 1500 mm / s, and a scanning interval of 90μm. The ultrafast laser wavelength is 1030 nm, with a single pulse energy of 60μJ, a pulse width of 300 fs, a repetition frequency of 3kHz, a scanning speed of 1500 mm / s, and a scanning interval of 90μm. A 304 stainless steel substrate 11 is installed and fixed, and raw material powder 7 (GH4169 powder with a particle size of 15-53μm) is filled in. The substrate 11 is preheated to 200℃, and high-purity constant-flow argon gas is introduced into the forming chamber for gas purging, controlling the oxygen concentration in the forming chamber to below 100 ppm. At the forming position, i.e., substrate 11, the height is lowered by 30μm, and the powder spreading device 9 spreads 30μm thick powder at the forming position. The continuous laser 1 begins to melt the powder according to the set scanning trajectory and laser parameters for forming. At the continuous laser action position 5, the temperature measuring device 2, coaxial with the continuous laser 1, starts working simultaneously, monitoring the temperature field along the continuous laser scanning trajectory in real time. Fast nonlocal mean filtering and bicubic interpolation are used to improve the infrared image resolution of the molten zone. The maximum temperature gradient is set as the molten pool boundary. After correcting the infrared image temperature distribution using the Stefan-Boltzmann law and the actual melting point of GH4169 high-temperature nickel-based alloy, the 500-600℃ temperature range on the scanning trajectory is located. The central controller 3 synchronously receives and stores the control commands for the ultrafast laser 4 to operate in the next layer, such as... Figure 3 As shown. The forming position descends 30 μm in height, and the powder spreading device 9 spreads a next layer of powder with a thickness of 30 μm at the forming position. (See diagram.) Figure 4 As shown, the molten portion 10 is the formed layer that has undergone composite impact strengthening. Continuous laser 1 begins melting the powder according to the set scanning trajectory and laser parameters to perform the forming process. Temperature measuring device 2 is not working. Ultrafast laser 4 performs impact strengthening on the target temperature range position 6 according to the central control command until ultrafast laser 4 follows the continuous laser to complete the preset scan of the current processed layer 8. The above strengthening operation is repeated until all layers are completed, obtaining the target GH4169 high-temperature nickel-based alloy component.
[0043] The third working mode is as follows: (1) Taking a certain NiTi shape memory alloy component as the target component, the target shape memory alloy component is three-dimensionally modeled and sliced into layers with a thickness of 50 μm. The continuous laser and ultrafast laser scanning trajectories are the same, and both use a zigzag straight reciprocating scanning trajectory. (2) The wavelength is selected as 1064 nm. The continuous laser is used for melting and forming according to the first laser parameters, with a power of 120 W, a scanning speed of 900 mm / s, and a scanning interval of 70 μm. The continuous laser is used for heating according to the second laser parameters, with a power of 50 W, a scanning speed of 1500 mm / s, and a scanning interval of 70 μm. The pulsed laser wavelength is 1030 nm, and the parameters are set as follows: single pulse energy of 30 μJ, pulse width of 500 fs, repetition frequency of 1 kHz, scanning speed of 1500 mm / s, and scanning interval of 70 μm. (3) Install and fix the NiTi shape memory alloy substrate 11 at the forming position, fill it with raw material powder 7, the raw material powder 7 is NiTi shape memory alloy powder, the powder particle size is 15-53μm, set the preheating temperature of the substrate 11 to 180℃, and introduce high-purity constant flow argon into the forming chamber for gas washing, and control the oxygen concentration in the forming chamber to below 50ppm. (4) At the forming position, i.e., the substrate 11, lower it by 50μm, and the powder spreading device 9 spreads 50μm thick powder at the forming position. (5) The continuous laser 1 starts to melt the powder according to the set scanning trajectory and the first laser parameters to carry out the forming work, and acts on the continuous laser action position 5 until the scanning of the current processing layer 8 is completed. The temperature measuring device 2 and the ultrafast laser 4 do not work. Figure 5 As shown. (6) The continuous laser 1 heats the area by setting the scanning trajectory and the second laser parameters, acting on the continuous laser action position 5. The temperature measuring device 2, which is installed on the same axis, starts working at the same time, and monitors the temperature field of the continuous laser scanning trajectory in real time. The resolution of the infrared image of the molten area is improved by using fast nonlocal mean filtering and bicubic interpolation. The maximum temperature gradient is set as the boundary of the molten pool. After correcting the infrared image temperature distribution by combining the Stefan-Boltzmann law and the actual melting point of GH4169 high-temperature nickel-based alloy, the temperature range of 400-500℃ on the scanning trajectory is located. The central controller 3 synchronously feeds back the command to the ultrafast laser 4 to aim at the target temperature range position 6 to perform the impact strengthening work until the ultrafast laser 4 follows the continuous laser to complete the preset scan of the current processing layer 8. The molten part 10 is the forming processing layer that has completed the composite impact strengthening, as shown. Figure 6 As shown.
[0044] The above are embodiments of the method proposed in this invention. Based on the same idea, some embodiments of this invention also provide devices and media corresponding to the above methods.
[0045] Figure 7 This is a schematic diagram of the structure of a laser powder bed melting composite impact strengthening device based on temperature field positioning, provided as an embodiment of the present invention. Figure 7 As shown, it includes: At least one processor; and, At least one processor-communication-connected memory; wherein, The memory stores instructions that can be executed by at least one processor, which enables the at least one processor to perform a laser powder bed melt composite impact strengthening method based on temperature field positioning as described above.
[0046] This invention provides a non-volatile computer storage medium storing computer-executable instructions, wherein the computer-executable instructions are configured as follows: A laser powder bed fusion composite impact strengthening method based on temperature field positioning, as described in any of the preceding items.
[0047] The various embodiments in this application are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device and medium embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the description of the method embodiments.
[0048] The devices and media provided in this application are one-to-one with the methods. Therefore, the devices and media also have similar beneficial technical effects as their corresponding methods. Since the beneficial technical effects of the methods have been described in detail above, the beneficial technical effects of the devices and media will not be repeated here.
[0049] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.
[0050] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.
[0051] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.
[0052] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.
[0053] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.
[0054] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.
[0055] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.
[0056] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0057] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.
Claims
1. A laser powder bed fusion composite impact strengthening method based on temperature field positioning, characterized in that, The method includes: The three-dimensional model of the target component to be processed is sliced to obtain the cross-sectional data of each layer, and the current processing layer is constructed based on the cross-sectional data; Repeat the following steps until all processing layers are determined to be formed, resulting in the finished target component: For the current processing layer, a continuous laser is used as a heat source, and the material to be processed in the current processing layer is melted and shaped according to a preset scanning strategy; Monitor the temperature field distribution of the current processing layer, identify the target spatial location in the current processing layer whose temperature is within a preset target temperature range based on the temperature field distribution, and control the ultrafast laser to act on the target spatial location to implement the impact strengthening operation; After determining the current processing layer is formed, a next processing layer is superimposed on the current processing layer based on the cross-sectional data, and the next processing layer is used as the new current processing layer.
2. The laser powder bed fusion composite impact strengthening method based on temperature field positioning according to claim 1, characterized in that, Based on the temperature field distribution, the target spatial location in the current processing layer where the temperature falls within a preset target temperature range is identified, specifically including: Infrared images of the current processing layer during the continuous laser melting and forming process are collected in real time using a temperature measuring device. The infrared image is subjected to noise reduction and interpolation processing to obtain the temperature distribution image of the current processing layer; Based on the material properties of the target component, the temperature distribution image is divided into multiple temperature ranges; Based on the preset type of strengthening effect required for the current processing layer, a target temperature range is determined from the multiple temperature ranges, and a target spatial position in the current processing layer where the temperature falls within the target temperature range is determined; wherein, the strengthening effect type includes cold forging effect, warm forging effect, and hot forging effect.
3. The laser powder bed fusion composite impact strengthening method based on temperature field positioning according to claim 1, characterized in that, Before controlling an ultrafast laser to act on the target spatial location to perform a shock strengthening operation, the method further includes: Based on the duration of the target spatial position in the current processing layer, a target working mode is determined from a variety of preset working modes; According to the target working mode, determine the timing of the temperature measurement and positioning operation performed by the impact strengthening operation relative to the current processing layer.
4. The laser powder bed fusion composite impact strengthening method based on temperature field positioning according to claim 3, characterized in that, Based on the duration of the target spatial position in the current processing layer, a target working mode is determined from a variety of preset working modes, specifically including: Determine the execution time required for the ultrafast laser to complete the shock strengthening operation; Based on the thermophysical properties of the material, as well as the melting process parameters and filling path corresponding to the current processing layer, the duration of the target spatial position in the current processing layer is determined. If the duration is greater than the execution duration, the target working mode is determined to be the first working mode; the first working mode includes directly performing the impact strengthening operation on the current processing layer. Otherwise, determine the temperature field similarity between adjacent formed processing layers. If the temperature field similarity is greater than a preset threshold, determine the target working mode as the second working mode. The second working mode includes delaying the impact strengthening operation to be performed on the adjacent formed processing layer. If the material to be processed in the current processing layer is a heat-sensitive material, the target working mode is determined to be the third working mode; the third working mode includes performing an impact strengthening operation after the current processing layer is melted and formed and the temperature field is controlled.
5. The laser powder bed fusion composite impact strengthening method based on temperature field positioning according to claim 4, characterized in that, According to the target working mode, the timing of the execution of the impact strengthening operation relative to the temperature measurement and positioning operation of the current processing layer is determined, specifically including: When the target working mode is the first working mode, temperature measurement and positioning operations and impact strengthening operations are performed simultaneously on the current processing layer; When the target working mode is the second working mode, the spatial position obtained after performing temperature measurement and positioning operation on the current processing layer is stored, and the ultrafast laser is controlled to perform impact strengthening operation on the spatial position for the current processing layer and several processing layers located after the current processing layer. When the target working mode is the third working mode, the continuous laser is controlled to melt and form the current processing layer according to the first laser parameters. After the melting and forming is completed, the continuous laser is controlled to heat the current processing layer according to the second laser parameters. During the heating process, temperature measurement and positioning operations and impact strengthening operations are performed on the current processing layer simultaneously.
6. The laser powder bed fusion composite impact strengthening method based on temperature field positioning according to claim 1, characterized in that, The scanning strategy includes a scanning trajectory, wherein the continuous laser and the ultrafast laser use the same scanning trajectory within the current processing layer, and the scanning range of the ultrafast laser covers the scanning trajectory of the continuous laser.
7. The laser powder bed fusion composite impact strengthening method based on temperature field positioning according to claim 1, characterized in that, Controlling an ultrafast laser to act on the target spatial location to perform a shock enhancement operation specifically includes: The real-time velocity of the ultrafast laser at each spatial location is determined based on the rate of change of the size and the rate of change of the temperature of the target spatial location in the current processing layer. The ultrafast laser is controlled to move along a preset scanning trajectory according to the real-time motion speed, so that the ultrafast laser can complete the impact strengthening operation before the target space position experiences temperature decay or position change.
8. The laser powder bed fusion composite impact strengthening method based on temperature field positioning according to claim 7, characterized in that, Controlling the ultrafast laser to move along a preset scanning trajectory according to the real-time motion speed specifically includes: During the process of the ultrafast laser moving along the preset scanning trajectory at the real-time motion speed, the positions where the ultrafast laser has completed the impact strengthening operation are screened out from the monitoring range of the temperature measuring device and the subsequent scanning range of the ultrafast laser.
9. A laser powder bed fusion composite impact strengthening device based on temperature field positioning, characterized in that, The device includes: At least one processor; And, a memory communicatively connected to the at least one processor; The memory stores instructions that can be executed by the at least one processor, which are executed by the at least one processor to enable the at least one processor to perform a laser powder bed melting composite impact strengthening method based on temperature field positioning as described in any one of claims 1-8.
10. A non-volatile computer storage medium storing computer-executable instructions, characterized in that, The computer-executable instructions are set as follows: A laser powder bed fusion composite impact strengthening method based on temperature field positioning as described in any one of claims 1-8.