Powder material additive manufacturing method, system and apparatus using cooling medium circulation

Abstract

The invention relates to a powder material additive manufacturing method, system and equipment applying cooling medium circulation, and the method comprises the steps that a geometric model of a target component is subjected to slicing and / or zoning analysis, so that at least one cooling area comprising at least one part of the target component is obtained, and an independent cooling medium control loop is arranged for each cooling area; according to the at least one cooling area and in combination with real-time temperature distribution and / or a process target, a preset periodic pulse thermal disturbance mode with cooling medium scouring frequency and flow velocity is distributed for the at least one cooling area and is applied to an energy beam scanning process; and when the energy beam scans to the cooling area on the forming base station, the corresponding cooling medium control loop is switched to the matched periodic pulse thermal disturbance mode. The heat accumulated by the forming base station is guided out in a targeted mode, the cooling rate of the formed part and the interior of a molten pool is increased, then the solidification microstructure is refined, and the mechanical property of the formed three-dimensional component is improved.

Description

Technical Field

[0001] The present application relates to the field of additive manufacturing technology, and more particularly to an additive manufacturing method for powder materials using a cooling medium circulation, a cooling medium circulation device, an additive manufacturing apparatus, and an electronic device. Background Art

[0002] In the powder material additive manufacturing process, through the interaction between an energy beam and the powder material, the powder material undergoes an instantaneous melting process from solid state to liquid state, and then a solidification process from liquid state to solid state. Under program control, the melting and solidification processes are precisely regulated so that the powder material is stacked layer by layer to finally form a three-dimensional component with a complex shape. Therefore, powder material additive manufacturing is an advanced forming technology that combines the rapid solidification mechanism with the forming of complex structures and even large-sized components.

[0003] In the current existing powder material additive manufacturing process, since the melting and solidification of each layer apply a new thermal cycle to the already formed area of the lower layer, heat accumulates layer by layer and is transferred to the substrate material, forming a temperature gradient from top to bottom, causing the entire component to maintain a relatively high temperature level during the deposition process. However, in actual processing, due to the long heat conduction path and limited heat dissipation efficiency, the temperature of the forming base often gradually increases, resulting in an obvious overall heat accumulation phenomenon in the forming area. In this case, the cooling rate is significantly reduced, the solidification conditions of the molten pool deteriorate. If the heat is not dissipated in time, not only will the temperature of the forming base continue to rise, breaking the original temperature gradient, but it will also interfere with the flow and solidification behavior inside the molten pool, leading to grain coarsening and a decline in mechanical properties.

[0004] Therefore, how to efficiently dissipate the accumulated heat in a timely manner during the forming process has become one of the key factors affecting the forming quality of powder material additive manufacturing. On the one hand, rapid and effective heat dissipation helps to maintain a large temperature gradient and cooling rate, promotes the formation of fine grains, and refines the microstructure, thereby enhancing the strength and toughness of the component. On the other hand, reasonably regulating the heat flow path and heat dissipation mechanism can effectively control the heat affected zone of each layer during the deposition process, reduce residual stress and thermal deformation, and improve the forming accuracy and structural integrity.

[0005] The evolution of the microstructure is affected by various factors, among which the key ones are the local solidification conditions in the molten pool and the overall temperature field distribution of the formed body under the action of continuous thermal cycles. These two factors are not only affected by the heat input parameters but also restricted by the heat storage effect and the heat dissipation ability. If the heat is not dissipated in time, not only will the temperature of the forming base continue to rise, breaking the original temperature gradient and causing the cooling rate to decrease, but it will also interfere with the flow and solidification behavior inside the molten pool, resulting in coarse microstructure and ultimately affecting the mechanical properties of the formed three-dimensional component. Summary of the Invention

[0006] The present application provides a powder material additive manufacturing method, system and equipment using cooling medium circulation, which can adopt a pulsed circulation mode of the cooling medium to provide a cooling medium with a matching cooling medium flushing frequency and flow rate for each cooling area of the forming base, and specifically export the heat accumulated in the forming base to increase the temperature gradient and cooling rate inside the formed part and the molten pool, thereby refining the solidification microstructure and improving the mechanical properties of the formed three-dimensional component.

[0007] In a first aspect, the present application provides a powder material additive manufacturing method using cooling medium circulation, the method comprising: performing slicing and / or zoning analysis on the geometric model of the target component to obtain at least one cooling area including at least a part of the target component and setting an independent cooling medium control loop for each cooling area; allocating a preset periodic pulsed thermal disturbance mode with a cooling medium flushing frequency and flow rate for the at least one cooling area according to the at least one cooling area in combination with the real-time temperature distribution and / or process target; and applying the periodic pulsed thermal disturbance mode to the energy beam scanning process, so that when the energy beam scans to the cooling area on the forming base, the corresponding cooling medium control loop is switched to the matching periodic pulsed thermal disturbance mode.

[0008] In an optional scheme of the first aspect, when slicing the geometric model of the target component, the method comprises: obtaining at least one cooling area including at least one layer of the target component according to the layered data of the target component after slicing and setting an independent cooling medium control loop for each layer of cooling area.

[0009] In an optional scheme of the first aspect, during energy beam scanning, the method comprises:

[0010] According to the number of layers of the target component scanned by the energy beam, switching the cooling medium control loop corresponding to the cooling area of the number of layers of the target component to the matching periodic pulsed thermal disturbance mode.

[0011] In an optional scheme of the first aspect, the periodic pulsed thermal disturbance mode includes a transition thermal disturbance mode between at least two cooling areas or a composite thermal disturbance mode formed by stacking at least two cooling areas.

[0012] In an alternative embodiment of the first aspect, when allocating a preset periodic pulsed thermal disturbance mode with a cooling medium flushing frequency and flow rate, the method includes: reconstructing the temperature distribution of the cooling region based on the collected real-time temperature distribution data using a two-dimensional transient heat conduction equation; establishing a periodic heat flux model coupled with the molten pool boundary according to the characteristics of the generated pulsed cooling medium; establishing a grain growth perturbation model of the grain refinement rate with respect to temperature perturbation and gradient according to the periodic heat flux model; constructing a preset optimization function, and updating the pulse parameters in real time to maximize the grain refinement rate within a limited time and / or space range.

[0013] In an alternative embodiment of the first aspect, when reconstructing the temperature distribution of the cooling region, the method includes: defining a two-dimensional transient heat conduction equation and simulating the energy beam input using a two-dimensional Gaussian distribution heat source; defining the cooling boundary conditions for applying the pulsed cooling medium; discretizing the two-dimensional region into grids and setting the spatial and time step sizes, and then assigning an initial temperature value; calculating the position of the energy beam heat source; updating the cooling boundary conditions; updating the temperature value using the explicit finite difference method; and outputting the temperature distribution.

[0014] In an alternative embodiment of the first aspect, when establishing the periodic heat flux model, the method includes: applying a time-varying heat transfer boundary to the cooling surface of the molten pool; calculating the Reynolds number and the convective heat transfer coefficient equation according to the change in the flow rate of the cooling medium to generate the instantaneous heat transfer coefficient of the cooling medium; calculating the cooling heat flux at each moment according to the instantaneous heat transfer coefficient and the temperature of the cooling medium; and applying the cooling heat flux at each moment as a Neumann boundary to the heat conduction equation to update the temperature value using the explicit finite difference method.

[0015] In an alternative embodiment of the first aspect, when establishing the grain growth perturbation model, the method includes: establishing a refinement differential equation for the growth rate of the refinement rate and introducing a perturbation enhancement function; obtaining the temperature distribution; calculating the cooling rate and the temperature gradient; calculating the perturbation enhancement function according to the flushing frequency and flow rate of the cooling medium; solving the refinement differential equation to generate the grain refinement rate; and outputting the equiaxed grain ratio field.

[0016] In an alternative embodiment of the first aspect, when updating the pulse parameters in real time, the method includes: constructing a preset optimization function according to the grain refinement model; using a preset optimization strategy to search for the optimal cooling medium flushing frequency and flow rate to update the pulse parameters; and outputting the updated pulse parameters as a control signal to the corresponding cooling medium control loop.

[0017] In an alternative embodiment of the first aspect, the method further includes: slicing and / or partitioning the geometric model of the target component to obtain at least one cooling zone including at least a part of the target component, and setting an independent cooling medium control loop for each cooling zone; allocating a preset periodic pulsed thermal disturbance pattern with cooling medium flushing frequency, flow rate, and flow direction to the at least one cooling zone based on the at least one cooling zone in combination with the real-time temperature distribution and / or process target; and applying the periodic pulsed thermal disturbance pattern to the energy beam scanning process, so that when the energy beam scans to the cooling zone on the forming substrate, the corresponding cooling medium control loop is switched to the matching periodic pulsed thermal disturbance pattern.

[0018] In an alternative embodiment of the first aspect, the cooling medium control loop includes a cooling medium pulse parameter control loop and a cooling medium flow direction control loop.

[0019] In a second aspect, the present application provides a cooling medium circulation device for additive manufacturing of powder materials, including: a forming substrate provided with at least one cooling circulation channel; at least one pulsed pump connected to the at least one cooling circulation channel for driving the cooling medium to achieve a periodic pulsed thermal disturbance pattern; a temperature monitoring unit arranged in the forming chamber and the forming substrate for collecting real-time temperature data; and a control unit connected to and controlling the at least one pulsed pump and the temperature monitoring unit to execute the above-mentioned powder material additive manufacturing method using a cooling medium circulation.

[0020] In a third aspect, the present application provides a cooling medium circulation device for additive manufacturing of powder materials, including:

[0021] a forming substrate provided with a plurality of cooling circulation channels; a variable flow guiding unit arranged in the plurality of cooling circulation channels for realizing dynamic change of the cooling medium direction; at least one pulsed pump connected to the plurality of cooling circulation channels for driving the cooling medium to achieve a periodic pulsed thermal disturbance pattern; a temperature monitoring unit arranged in the forming chamber and the forming substrate for collecting real-time temperature data; and a control unit connected to and controlling the variable flow guiding unit, the pulsed pump, and the temperature detection unit to execute the above-mentioned powder material additive manufacturing method using a cooling medium circulation.

[0022] In a fourth aspect, the present application provides an additive manufacturing device including the cooling medium circulation device of any one of the above.

[0023] Fifth aspect, the present application provides an electronic device, including: at least one processor; at least one memory; the at least one memory is coupled to the at least one processor and is configured to store instructions executed by the at least one processor, and when the instructions are executed by the at least one processor, the electronic device is caused to execute the method according to any one of the above.

[0024] It should be understood that the above general description and the following detailed description are only exemplary and do not limit the present application. Description of the Drawings

[0025] The drawings incorporated herein and forming a part of the specification illustrate one or more embodiments of the present application and are used in conjunction with the description to explain the principles of the present application and to enable those of ordinary skill in the relevant art to make and use the present application.

[0026] Figure 1 It is a schematic structural diagram of an exemplary base with a cooling cycle channel formed according to some embodiments of the present application.

[0027] Figure 2 It is a scanning schematic diagram of an exemplary powder material additive manufacturing using a cooling medium cycle according to some embodiments of the present application.

[0028] Figure 3 It is a comparative schematic diagram of the apparent quality of a three-dimensional component according to some embodiments of the present application; wherein, ① is a three-dimensional component formed without using a cooling medium cycle, and ② is a three-dimensional component formed after using a cooling medium cycle.

[0029] Figure 4 It is a comparative schematic diagram of the microstructure of a three-dimensional component according to some embodiments of the present application. Among them, ① is an OM micrograph of a three-dimensional component formed without using a cooling medium cycle, ② is an OM micrograph of a three-dimensional component formed using a cooling medium cycle, ③ is an SEM electron micrograph of a three-dimensional component formed without using a cooling medium cycle, and ④ is an SEM electron micrograph of a three-dimensional component formed using a cooling medium cycle.

[0030] Figure 5 It is a comparative schematic diagram of the mechanical properties of a three-dimensional component according to some embodiments of the present application.

[0031] Figure 6 It is a scanning schematic diagram of an exemplary powder material additive manufacturing with a sliced layered cooling medium cycle according to some embodiments of the present application.

[0032] Figure 7 It is a scanning schematic diagram of an exemplary powder material additive manufacturing with a zoned cooling medium cycle according to some embodiments of the present application.

[0033] Figure 8 It is a schematic cross-sectional view of an exemplary sliced and layered forming base with a variable flow guiding unit according to some embodiments of the present application.

[0034] Figure 9 It is a schematic scan view of an exemplary powder material additive manufacturing with adjacent layer cooling medium circulation according to some embodiments of the present application.

[0035] Figure 10 It is a schematic scan view of an exemplary powder material additive manufacturing with cross-layer cooling medium circulation according to some embodiments of the present application.

[0036] Figure 11 It is a schematic cross-sectional view of an exemplary partitioned forming base with a variable flow guiding unit according to some embodiments of the present application.

[0037] Figure 12 It is a schematic scan view of an exemplary powder material additive manufacturing with adjacent area cooling medium circulation according to some embodiments of the present application.

[0038] Figure 13 It is a schematic scan view of an exemplary powder material additive manufacturing with cross-area cooling medium circulation according to some embodiments of the present application.

[0039] Figure 14 It is a schematic frame view of an exemplary electronic device according to some embodiments of the present application.

[0040] Description of reference numerals in the accompanying drawings of the specification:

[0041] 1. Optical path unit, 2. Forming base, 3. Electronic device, 4. Three-dimensional component, 20. Cooling medium, 21. Cooling medium control loop, 21a. Cooling medium control loop I, 21b. Cooling medium control loop II, 21c. Cooling medium control loop III, 21d. Cooling medium control loop IV, 21e. Cooling medium control loop V, 22. Cooling circulation channel, 23. Variable flow guiding unit, 200. Cooling area, 200a. Area I, 200b. Area II, 200c. Area III, 200d. Area IV, 200e. Area V, 301. Memory, 302. Processor, 303. Communication interface. Detailed implementation manners

[0042] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more complete and comprehensive, and will fully convey the concept of the example embodiments to those skilled in the art. The features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of this application.

[0043] The embodiments of this application are not limited to a specific type of additive manufacturing and can be applied to various additive manufacturing processes based on powder materials, including Laser-Directed Energy Deposition (L-DED), Laser Powder Bed Fusion (LPBF), Electron Beam Melting (EBM), Selective Laser Melting (SLM), Selective Laser Sintering (SLS), and other additive manufacturing processes that use powder as the forming material and an energy beam (such as a laser beam, ion beam, or electron beam, etc.) as the energy source. The "powder material" described generally refers to the base material for forming a three-dimensional component, which is in a granular form and allows for differences in morphology, particle size, and size distribution. In a preferred embodiment, a metal powder system is used, covering typical engineering materials such as stainless steel, aluminum alloy, titanium alloy, nickel-based alloy, cobalt-based alloy, copper, and copper alloys; in other alternative embodiments, it can also be extended to ceramic-based, polymer-based, or composite powder systems.

[0044] At present, the evolution of the microstructure in additive manufacturing of powder materials is affected by various factors. Among them, two important factors determining the microstructure are, firstly, the local solidification conditions in the molten pool and, secondly, the temperature field in the deposited specimen under the action of thermal cycles. These two aspects are affected by the heat input on the one hand and determined by the ability to store and conduct heat on the other hand. At present, among the powder materials used in additive manufacturing of powder materials, powder materials such as titanium alloys, superalloys, stainless steels, and aluminum alloys are mainly used. For titanium alloys, the faster the solidification rate, the easier it is to obtain equiaxed grains or refined grains. For superalloys, stainless steels, 2-series (Al-Cu) and 7-series (Al-Zn-Mg-Cu) aluminum alloys, during the deposition process, the dendrites inside the alloy grow epitaxially along the deposition direction, and the growth direction of dendrites in local areas will change with the morphology of the molten pool and the scanning strategy. In addition, the liquid phase between dendrites in the alloy itself is not easily compensated during solidification and is extremely prone to cracking under the action of thermal stress, which greatly affects the forming quality and tensile properties. Moreover, even for alloys such as Al-Si alloys that are extremely easy to form, due to their low density, during the additive manufacturing of powder materials, the powder materials are prone to scattering when transported to the molten pool. At the same time, due to the relatively low melting point of aluminum alloys, they are not easily solidified in the molten pool, and the cladding layer is prone to semi-solid creep during the deposition process, resulting in defects in the apparent morphology and internal quality of the formed three-dimensional component 4.

[0045] In addition, during the additive manufacturing of powder materials, the energy beam emitted by the optical path unit 1 scans as a heat source along the planned path. At the same time, the powder materials are continuously fed, melted, form a molten pool and then solidify, and are stacked layer by layer to finally construct the target component. During the deposition process, a large amount of heat generated by the interaction between the energy beam and the powder materials is mainly transferred from the molten pool to the deposited part and the forming base 2 by means of heat conduction, forming a temperature gradient that decreases from top to bottom. However, in the actual forming process, due to the long heat conduction path and limited heat conduction efficiency, the heat is often not conducted in time, and the temperature of the forming base 2 gradually increases, resulting in obvious overall heat accumulation in the forming area. In this case, it affects the temperature field in the formed part and the molten pool during the forming process, resulting in a decrease in the cooling rate, leading to coarse microstructure and ultimately affecting the tensile mechanical properties of the formed three-dimensional component 4.

[0046] Therefore, referring to Figure 1 as shown, Figure 1The schematic structural diagram of an exemplary forming base with a cooling circulation channel according to some embodiments of the present application is shown. In some embodiments of the present application, in order to quickly export heat and reduce the heat accumulation phenomenon in the forming area, the present application relates to a cooling medium 20 circulation device for additive manufacturing of powder materials. Based on the existing additive manufacturing equipment, a cooling circulation channel 22 is provided in the forming base 2 and a circulating cooling medium 20 is introduced to timely export the heat generated during the forming process, increase the temperature gradient and cooling rate in the formed part and inside the molten pool. It can not only effectively improve the appearance and internal quality of the deposited specimen, but also increase the cooling rate inside the molten pool, so as to achieve the purpose of refining the microstructure, and further improve the strength and plasticity of the as-deposited specimen at the same time.

[0047] Among them, as long as the cooling medium 20 adopted in the present application can quickly export the heat of the forming base 2, it can be any form of fluid medium, including but not limited to liquid cooling medium 20, gas cooling medium 20 or liquid-solid combined cooling medium 20, which is specifically set by the designer according to actual needs. Exemplarily, for example, the liquid cooling medium 20 can adopt at least one of coolant, cooling oil, cooling water, etc. For example, the gas cooling medium 20 can adopt at least one of nitrogen, argon, helium, etc. For example, the liquid-solid combined cooling medium 20 can adopt at least one of phase change materials (such as paraffin) and liquid cooling media, solid carbon dioxide and liquid cooling media, etc.

[0048] Therefore, the cooling medium 20 circulation device for additive manufacturing of powder materials specifically involved at least includes a forming base 2, at least one pulse pump, a temperature monitoring unit and a control unit. The forming base 2 is provided with at least one cooling circulation channel 22. The at least one pulse pump is communicated with the at least one cooling circulation channel 22 for driving the cooling medium 20 to realize a periodic pulse heat disturbance mode in the cooling circulation channel 22. The temperature monitoring unit is arranged in the forming chamber and the forming base 2 of the additive manufacturing equipment for collecting real-time temperature data. The control unit is connected to and controls the at least one pulse pump and the temperature monitoring unit to execute the powder material additive manufacturing method involving the application of the cooling medium 20 circulation in the present application.

[0049] Specifically, when designing the cooling circulation channel 22 opened for the forming base 2, the cooling circulation channel 22 of the forming base 2 is stratified and / or partitioned according to the three-dimensional geometric model and scanning path of the target component, and different layer cooling regions 200 and / or different interval cooling regions 200 are divided in the whole forming base 2. Each cooling region 200 has an independent cooling circulation channel 22 and a cooling medium control loop 21. The independent cooling medium control loop 21 includes at least one pulse pump and a controller.

[0050] The number of the at least one pulsating pump is greater than or equal to the number of the cooling medium control loops 21, and the pulsating pump can be any form of pump as long as it can achieve the pulsating circulation of the cooling medium 20 in the cooling circulation channel 22, including but not limited to electromagnetic pulsating pumps, piezoelectric pulsating pumps, mechanical pulsating pumps, peristaltic pumps, etc., which are specifically set by the designer according to actual requirements.

[0051] The temperature monitoring unit can be any form of temperature monitoring device as long as it can obtain the temperature data of the forming area, including but not limited to infrared thermal imagers, multi-channel temperature recorders, temperature sensors distributed in each cooling area 200 of the forming chamber and the forming base 2, etc., which are specifically set by the designer according to actual requirements.

[0052] Thus, referring to Figure 2 as shown, Figure 2 Fig. shows a schematic scanning diagram of an exemplary application of a cooling medium circulation in powder material additive manufacturing according to some embodiments of the present application. When using the cooling medium 20 circulation device for powder material additive manufacturing involved in the present application to execute the powder material additive manufacturing method with the application of cooling medium 20 circulation, the specific process is as follows:

[0053] In the first step, the design of the forming base 2. During the additive manufacturing process, an alloy material that is the same as or has a similar composition to the powder material is usually selected as the forming base 2, and then the geometric model of the target component is sliced and / or partitioned to obtain at least one cooling area 200 including at least a part of the target component and set an independent cooling medium control loop 21 for each cooling area 200. Then, according to the aforementioned design requirements, several regular channels are opened in the forming base 2 as the cooling circulation channels 22 for the flow of the cooling medium 20, and then the inlets and outlets of each cooling circulation channel 22 are respectively connected to a conduit. The outer surface of the conduit is wrapped with tin foil to prevent the heat during the deposition process from burning the conduit. The other end of the conduit is connected to at least one pulsating pump of the corresponding cooling medium control loop 21. Referring to Figure 1 as shown, for example, an LZ104 aluminum alloy forming base 2 with a size of 200 mm × 200 mm × 20 mm (height) is selected. A 30-mm spacing is left on both sides of the long side, and 8 equally spaced holes with a diameter of 8 mm are dug out as the cooling circulation channels 22 for the flow of the cooling medium 20. The cooling circulation channels 22 are connected by a conduit. The outer surface of the conduit is wrapped with tin foil, and the conduit is fastened to the forming base 2 by threads.

[0054] Second step: Place the formed abutment 2 after punching into the forming chamber of the additive manufacturing equipment for mating installation. Fix it with the clamping device and connect the conduit outward to the pulse pump of the fluid medium. Turn on the pulse pump of the fluid medium so that the cooling circulation channel 22 is filled with the circulating fluid medium. After the airtightness inspection of the cooling circulation channel 22 is completed, turn off the pulse pump of the fluid medium. Among them, to avoid the conduit part being burned by high temperature, an iron plate with a side length of 500 mm × 500 mm can be placed in the forming area of the formed abutment 2 to transfer the temperature transmitted during the forming of the three-dimensional component 4 through the iron plate at intervals.

[0055] Third step: Preparation of the powder material. Before additive manufacturing, dry the powder material with a powder drying oven, usually at 120°C / 3h. For energy beam additive manufacturing, the powder material particles are usually screened in the size range of 40μm - 170μm.

[0056] Fourth step: After the formed abutment 2 is installed and fixed, use a glass cover and plastic film to hermetically seal the forming chamber and fill the forming chamber with an inert gas (argon / helium). When the oxygen content in the chamber is reduced to less than 100 ppm, additive manufacturing can be carried out.

[0057] Fifth step: Put the dried AlSi10Mg alloy powder material with a particle size of 47μm - 165μm into the powder bin, turn on the synchronous powder feeding device, and check the powder feeding path.

[0058] Sixth step: In the preparation process of additive manufacturing forming, turn on the pulse pump of the fluid medium so that the cooling circulation channel 22 is filled with the cooling medium 20. When all equipment such as the formed abutment 2, the powder feeding device of the additive manufacturing equipment, and the optical path unit 1 are in a stable and reliable state, according to the scanning strategy in the program, carry out energy beam additive manufacturing; among them, before additive manufacturing, compile the scanning program, check the energy beam path, and set the forming parameters. For different alloy systems, the specific parameters used are different, but the general parameter range is: energy beam power 100 W - 3000W; scanning speed 5 mm / s - 100mm / s; energy beam diameter 1 mm - 5mm; overlap rate 30% - 80%; lift amount 0.05 mm - 2mm; scanning strategy is forward / backward reciprocating scanning; powder feeding amount 1 g / min - 10g / min; gas flow rate 1 L / min - 20L / min.

[0059] Exemplarily, for example, the process parameters for using aluminum alloy powder material are as follows:

[0060] Table 1: Process parameters for direct energy deposition forming of aluminum alloy powder material

[0061]

[0062] Step 7: Conduct additive manufacturing of aluminum alloy powder materials. During manufacturing, according to at least one cooling area 200 and in combination with the real-time temperature distribution and / or process target, assign a preset periodic pulse thermal disturbance mode with the flushing frequency and flow rate of the cooling medium 20 to the at least one cooling area 200, and then apply this periodic pulse thermal disturbance mode to the energy beam scanning process. When the energy beam scans to the cooling area 200 on the forming base, switch its corresponding cooling medium control loop 21 to the matching periodic pulse thermal disturbance mode, and provide the cooling medium 20 of the corresponding periodic pulse thermal disturbance mode for each cooling area 200 of the forming base 2 in real time.

[0063] Step 8: After the additive manufacturing is completed and the target component is printed, turn off the powder feeding device and the optical path unit 1. At the same time, the cooling medium 20 and the inert gas still need to operate. After the temperature of the forming base 2 drops to room temperature, turn off the pulse pump of the fluid medium and the inert gas valve, open the forming chamber, clean the forming chamber and the forming base 2, remove the clamping device, take down the forming base 2 and the target component, and use a wire electrical discharge machining machine to cut the target component from the forming base 2. And inside the target component, use a wire electrical discharge machining machine to cut samples for metallographic structure observation and mechanical tensile experiments.

[0064] Step 9: Use sandpaper, polishing liquid, etching liquid, etc. to conduct metallographic treatment on the surface of the samples for microstructure observation by an optical microscope (OM) and a scanning electron microscope (SEM). Then use a universal mechanical testing machine to conduct quasi-static axial tensile experiments at room temperature.

[0065] Reference Figures 3 to 5 shown in Figure 3 shows a comparative schematic diagram of the apparent quality of a three-dimensional component according to some embodiments of the present application. Figure 3 ① in is a three-dimensional component 4 formed without using the cooling medium 20 in a cycle. Figure 3 ② in is a three-dimensional component 4 formed after using the cooling medium 20 in a cycle; Figure 4 shows a comparative schematic diagram of the microstructure of a three-dimensional component according to some embodiments of the present application. Figure 4 ① in is an OM micrograph of a three-dimensional component 4 formed without using the cooling medium 20 in a cycle. Figure 4 ② in is an OM micrograph of a three-dimensional component 4 formed after using the cooling medium 20 in a cycle. Figure 4 ③ in is an SEM micrograph of a three-dimensional component 4 formed without using the cooling medium 20 in a cycle. Figure 4 ④ in is an SEM micrograph of a three-dimensional component 4 formed after using the cooling medium 20 in a cycle; Figure 5A comparative schematic diagram of the mechanical properties of an exemplary three-dimensional component according to some embodiments of the present application is shown. By adopting the above technical solution, the forming base 2 is passed through the circulating cooling medium 20, and the accumulated heat generated by the melting of the energy beam in the forming area and its adjacent areas can be continuously and effectively exported during the forming process, significantly reducing the influence of heat input on the local overheating of the molten pool, and then significantly refining the microstructure of the formed three-dimensional component 4, improving the appearance and internal quality of the three-dimensional component 4, and improving the tensile mechanical properties.

[0066] In some examples of the present application, when allocating a preset periodic pulse thermal disturbance mode with a cooling medium flushing frequency and flow rate, according to the collected real-time temperature distribution data, the temperature distribution of the cooling region 200 is reconstructed using the two-dimensional instantaneous heat conduction equation; according to the characteristics of the generated pulsed cooling medium 20, a periodic heat flux model coupled with the molten pool boundary is established; according to the periodic heat flux model, a grain growth disturbance model of the grain refinement rate with temperature disturbance and gradient is established; a preset optimization function is constructed to update the pulse parameters in real time so that the grain refinement rate is maximized within a limited time and / or space range; thus, a periodic pulse thermal disturbance mode with corresponding pulse parameters is allocated to each cooling region 200 in combination with the real-time temperature distribution and / or process target, so as to control the cooling medium control loop 21 of the cooling region 200 to execute the corresponding working mode.

[0067] Among them, the pulse parameters include the flushing frequency and flow rate of the cooling medium 20. The flushing frequency of the cooling medium 20 is adjustable from 0.1 to 10 Hz, the pulse pressure is adjustable from 0 to 1.5 MPa, the pulse flow rate is adjustable from 100 to 6000 mL / min, the pulse waveform includes at least one of trapezoidal wave, sine wave, square wave, convex character wave, etc., and the set temperature range of the cooling medium 20 is -40°C to 160°C; and each cooling region 200 can adopt the same periodic pulse thermal disturbance mode of the flushing frequency and flow rate of the cooling medium 20, or can adopt different periodic pulse thermal disturbance modes of the flushing frequency and flow rate of the cooling medium 20, which are specifically set by the designer according to actual needs.

[0068] Thus, when reconstructing the temperature distribution of the cooling region 200 using the two-dimensional instantaneous heat conduction equation according to the collected real-time temperature distribution data, assuming that the geometric model analysis is a two-dimensional plane (x, y), the heating source is a scanning energy beam, which is expressed as a time-to-space distributed heat source, and the cooling is the boundary cooling flux caused by time change (which is caused by the pulsed cooling medium 20); the specific method includes:

[0069] According to the temperature distribution data collected by the temperature monitoring unit, the two-dimensional plane temperature field T(x, y, t) is obtained at each moment t and the two-dimensional transient heat conduction equation is defined: , where ρ is the material density, is the derivative of the temperature field with respect to time, is the second derivative of temperature with respect to spatial position x, is the second derivative of temperature with respect to spatial position y, c p c is the specific heat capacity of the material, T(x, y, t) is the temperature field at spatial positions x and y at time t, k is the thermal conductivity of the material, and Q(x, y, t) is the energy beam input heat source term, i.e., the heating heat flux density of the energy beam at spatial positions x and y at time t.

[0070] The scanning energy beam input heat source term is simulated using a two-dimensional Gaussian distribution heat source:

[0071] , where η is the energy beam absorption rate, P is the energy beam power, r is the energy beam radius, and (x0(t), y0(t)) are the scanning center coordinates of the heat source position varying with time.

[0072] The cooling boundary condition of the applied pulsed cooling medium 20 is defined. The cooling boundary condition is used to affect the overall temperature field change and reflect the influence of thermal disturbance. Among them, it is assumed that the molten pool cooling surface between the forming base 2 and the three-dimensional component 4 is y = 0, and the pulsed cooling boundary heat flux is applied on this surface:

[0073] , where h(t) is the pulsed heat transfer coefficient, which is controlled by the pulse of the cooling medium 20: , h0 is the cooling reference heat transfer coefficient, A is the pulsed disturbance flow velocity coefficient, f is the pulsed flushing frequency, T cool is the temperature of the cooling medium 20.

[0074] The two-dimensional forming area is discretized into grids and the spatial step sizes Δx, Δy and the time step size Δt are set. Then, the initial temperature is assigned, and the initial two-dimensional plane temperature field T(x, y, t) is set to room temperature.

[0075] Calculate the energy beam heat source position .

[0076] Update the .

[0077] Update the internal node temperature values using the explicit finite difference method; among them, the formula of the explicit finite difference method is:

[0078] , where,

[0079] , , where α x +α y ≤1 / 2, is the temperature at position (i, j) at time n, is the heat source at position (i, j) at time n, αx is the thermal diffusivity in the x - direction, α y is the thermal diffusivity in the y - direction, Δx is the spacing of the grid cell in the x - direction, and Δy is the spacing of the grid cell in the y - direction.

[0080] Output the two - dimensional planar temperature field T(x, y, t) at each time step.

[0081] When establishing the periodic heat flux model, the pulsed pump provides a periodically variable - speed cooling medium 20, whose cooling intensity is non - constant. The cooling medium 20 is transmitted to the molten pool substrate through the cooling circulation channel 22. The pulsed cooling medium 20 makes the heat transfer coefficient h(t) fluctuate periodically. Thus, the cooling behavior directly determines the thermal disturbance characteristics of the solidification boundary of the molten pool; the specific method includes:

[0082] Apply a heat transfer boundary that varies with time to the cooling surface of the molten pool: , where q cool (t) is the instantaneous cooling heat flux per unit area, and T s (t) is the instantaneous temperature of the cooling surface of the molten pool.

[0083] Calculate the Reynolds number and the convective heat transfer coefficient equation according to the change in the real - time flow rate of the cooling medium 20 to reconstruct the instantaneous heat transfer coefficient of the cooling medium 20: , where N u (t) is the Nusselt number, N u (t)=0.23*R e (t) 0.8 *P r (t) 0.4 ,

[0084] is the Reynolds number, reflecting the ratio of the fluid inertial force to the viscous force; is the Prandtl number, reflecting the ratio of thermal diffusion to momentum diffusion; D h is the diameter of the medium in the cooling circulation channel 22, v(t) is the flow rate of the cooling medium 20; ρ f is the density of the cooling medium 20, μ is the dynamic viscosity of the cooling medium 20, c p,f is the specific heat capacity of the cooling medium 20, k f is the thermal conductivity of the cooling medium 20.

[0085] Calculate the cooling heat flux at each moment according to the instantaneous heat transfer coefficient and the temperature of the cooling medium 20.

[0086] Apply the cooling heat flux at each moment as a Neumann boundary to the two - dimensional transient heat conduction equation to update the temperature value using the explicit finite - difference method; where, for the cooling boundary y = 0, there is:

[0087] , the equivalent form can be processed by differential approximation as follows:

[0088] , from which the boundary node temperature update formula is obtained as:

[0089] .

[0090] Among them, the thermal gradient fluctuation caused by periodic cooling thermal disturbance can be quantified as: , and this value can determine the solidification interface cooling rate .

[0091] Thus, when establishing the grain growth disturbance model, the thermal disturbance generates unsteady temperature fluctuations and stimulates grain fragmentation or turning. The temperature gradient and cooling rate jointly determine the grain growth direction. Therefore, the grain refinement rate can be used as an index to characterize the tissue uniformity; the specific methods include:

[0092] Establish a refinement differential equation for the growth rate of the refinement rate: , where G(t) is the temperature gradient, η(t) is the grain refinement rate, representing the proportion of the refined area; α is a material constant; m and n are empirical exponents. For example, m = 1 and n = 1 represent a linear influence; [1 - η(t)] can represent the proportion of the unrefined area. Moreover, when considering periodic thermal disturbance, the grain refinement rate is also affected by the flushing frequency and flow rate. Therefore, a disturbance enhancement function is introduced:

[0093] , thus, after coupling the disturbance enhancement function into the refinement differential equation, it becomes:

[0094] .

[0095] Furthermore, obtain the output temperature value from the heat conduction equation and calculate the cooling rate R(t) and temperature gradient:

[0096] , the gradient of the temperature field;

[0097] Calculate the disturbance enhancement function according to the flushing frequency and flow rate of the cooling medium 20; among them, when there is a spatial flow rate gradient in the cooling medium 20 or the pulse pump is a multi-point pulse control, the disturbance enhancement function can be extended to:

[0098] , where A(x, y) is the local flow rate and f(x, y) is the local flushing frequency, so as to reflect the influence of different thermal disturbances on different cooling regions 200 and further improve the local regulation ability of the equiaxed crystal region growth.

[0099] Solve the refinement differential equation to generate the grain refinement rate ; where the grain refinement ratio of each mesh is updated using the explicit finite difference method in parallel with the calculation of the internal node temperature values:

[0100] , is the value of the impulse perturbation enhancement function at n, is the cooling rate at position (i, j) when n, is the temperature gradient at position (i, j) when n.

[0101] Output equiaxed crystal ratio field: and grain refinement rate.

[0102] Therefore, when the pulse parameters are updated in real time, the flushing frequency and flow rate of the cooling medium 20 output by the pulse pump are dynamically adjusted by constructing a feedback control optimization function, so that the grain refinement rate is maximized within a limited time or space range, so as to adjust the grain refinement effect to the optimum and inhibit the growth of columnar grains; the specific method includes:

[0103] Construct a preset optimization function based on the grain refinement model: , that is, maximizing the integral of the grain refinement rate per unit time; where J(f,A) is the constructed optimization objective function to accumulate the grain refinement rate.

[0104] The preset optimization strategy is used to search for the optimal flushing frequency and flow rate of the cooling medium 20 to update the flushing frequency and flow rate of the cooling medium 20; wherein the preset optimization strategy includes but is not limited to existing optimization strategies such as gradient ascent, genetic algorithm, and reinforcement learning; for example, referring to the use of gradient ascent, the partial derivative can be obtained , the update strategy is:

[0105] , where γ is the step size.

[0106] The updated flushing frequency and flow rate of the cooling medium 20 are output as control signals to the corresponding cooling medium control loop 21 .

[0107] Therefore, the above-mentioned periodic pulse thermal disturbance control process is: obtain and reconstruct the temperature distribution of the cooling area 200 at the energy beam scanning position and calculate the corresponding cooling rate, temperature gradient and grain refinement rate, and then update the corresponding optimization objective function and generate the optimized cooling medium 20 flushing frequency and flow rate, and control the corresponding cooling medium control loop 21 to execute the optimized cooling medium 20 flushing frequency and flow rate, so as to export the heat accumulated in the cooling area 200 and improve the appearance and internal quality of the target component belonging to the area.

[0108] In some examples of the present application, when constructing a preset optimization function, an improved objective function may be constructed:

[0109] , where λ1 and λ2 are penalty coefficients for adjusting the scouring frequency and flow velocity to achieve a trade-off optimization between the grain refinement efficiency and energy consumption limit.

[0110] In some examples of the present application, when optimizing the pulse parameters, in order to prevent equipment damage or material quality degradation, dynamic constraints can be set: and , where f min is the minimum scouring frequency, f opt is the optimized scouring frequency, f max is the maximum scouring frequency, where A min is the minimum flow velocity, A opt is the optimized flow velocity, A max is the maximum flow velocity.

[0111] By adopting the above technical solution, a large number of equiaxed grains are generated in a large number of micro-regions in the three-dimensional component 4 through the periodic thermal perturbation mechanism, breaking the continuous growth path of columnar grains, and through the coupled regulation of the perturbation of the molten pool boundary layer and the heat flow distribution, the tissue refinement ability is improved, thereby improving the tissue homogenization and densification enhancement effect.

[0112] In some embodiments of the present application, when performing slice analysis on the geometric model of the target component, the geometric model of the target component is analyzed layer by layer. Thus, according to the layer data of the sliced target component, at least one cooling region 200 including at least one layer of the target component is obtained and an independent cooling medium control loop 21 is set for each layer of the cooling region 200. That is, a single layer of the cooling region 200 can be allocated to a single-layer target component, or multiple layers of the cooling region 200 can be allocated to a single-layer target component. A single layer of the cooling region 200 can be allocated to a multi-layer target component, or multiple layers of the cooling region 200 can be allocated to a multi-layer target component. Thus, after the slice analysis, the designer designs a single-layer or multi-layer stacked cooling circulation channel 22 for the forming base 2 according to the actual requirements and the above cooling region 200 division process.

[0113] Therefore, the powder material additive manufacturing method applying the circulation of the cooling medium 20 further includes:

[0114] Slice analysis is performed on the geometric model of the target component to obtain at least one cooling region 200 including at least one layer of the target component, and an independent cooling medium control loop 21 is set for each layer of the cooling region 200; according to at least one layer of the cooling region 200 and in combination with the real-time temperature distribution and / or process target, a preset periodic pulse thermal disturbance mode with the flushing frequency and flow rate of the cooling medium 20 is assigned to at least one layer of the cooling region 200; the periodic pulse thermal disturbance mode is applied to the energy beam scanning process, so that when the energy beam scans on the forming substrate, the cooling medium control loop 21 of the corresponding layer of the target component is switched to the matching periodic pulse thermal disturbance mode.

[0115] Reference Figure 6 shown in Figure 6 shows a scanning schematic diagram of powder material additive manufacturing with an exemplary slice-layered cooling medium cycle according to some embodiments of the present application. Exemplarily, for example, when performing slice analysis on the geometric model of the target component, four cooling circulation channels 22 and their corresponding cooling medium control loops 21 are assigned to the sliced target component, and the four cooling circulation channels 22 and their corresponding cooling medium control loops 21 are matched with the layering data of the target component, corresponding to four groups of layer families of the target component respectively. Each group of layer families can be a single-layer or multi-layer slice, thus divided into layer family I, layer family II, layer family III, and layer family IV, and the cooling medium control loop I21a matched with layer family I, the cooling medium control loop II21b matched with layer family II, the cooling medium control loop III21c matched with layer family III, and the cooling medium control loop IV21d matched with layer family IV.

[0116] When the energy beam scans and forms layer family I on the powder material laid on the forming substrate, the optimized flushing frequency and flow rate of the cooling medium 20 are generated according to the above periodic pulse thermal disturbance control process, and then a periodic pulse thermal disturbance mode matched with the cooling medium control loop I21a is generated according to the optimized pulse parameters, and further control the cooling medium control loop I21a to execute the corresponding periodic pulse thermal disturbance mode; and so on until the forming of the target component is completed.

[0117] In some embodiments of the present application, when performing partition analysis on the geometric model of the target component, the geometric model of the target component is subjected to partition analysis. Thus, according to the partition data of the sliced target component, at least one cooling region 200 including at least a part of the target component is obtained, and an independent cooling medium control loop 21 is set for each cooling region 200, that is, a single cooling region 200 can be assigned to a part of the target component, or multiple cooling regions 200 can be assigned to a part of the target component. Thus, after the partition analysis, the designer designs a single-zone or multi-zone superimposed cooling circulation channel 22 for the forming substrate 2 according to the actual requirements and the above cooling region 200 division process.

[0118] Accordingly, the powder material additive manufacturing method using the cooling medium 20 circulation further includes:

[0119] Performing a partition analysis on the geometric model of the target component to obtain at least one cooling region 200 including at least a part of the target component and setting an independent cooling medium control loop 21 for each cooling region 200; allocating a preset periodic pulse thermal disturbance mode with a cooling medium 20 flushing frequency and flow rate to at least one cooling region 200 according to at least one cooling region 200 in combination with the real-time temperature distribution and / or process target; applying the periodic pulse thermal disturbance mode to the energy beam scanning process, so that when the energy beam scans on the forming substrate, the cooling medium control loop 21 corresponding to the cooling region 200 where the energy beam is located is switched to the matching periodic pulse thermal disturbance mode.

[0120] Reference Figure 7 As shown, the figure shows a scanning schematic diagram of an exemplary partition cooling medium circulation for powder material additive manufacturing according to some embodiments of the present application. Exemplarily, for example, when performing a partition analysis on the geometric model of the target component, five cooling circulation channels 22 and their corresponding cooling medium control loops 21 are allocated to the partitioned target component, and the five cooling circulation channels 22 and their corresponding cooling medium control loops 21 are matched with the partition data of the target component, corresponding to five regions of the target component respectively, thus divided into region I 200a, region II 200b, region III 200c, region IV 200d and region V 200e, and the cooling medium control loop I 21a matching region I, the cooling medium control loop II 21b matching region II, the cooling medium control loop III 21c matching region III, the cooling medium control loop IV 21d matching region IV and the cooling medium control loop V 21e matching region V.

[0121] When the energy beam scans the forming region I 200a of the laid powder material on the forming substrate, an optimized cooling medium 20 flushing frequency and flow rate are generated according to the above periodic pulse thermal disturbance control process, and then a periodic pulse thermal disturbance mode matching the cooling medium control loop I 21a is generated according to the optimized pulse parameters, and further the cooling medium control loop I 21a is controlled to execute the corresponding periodic pulse thermal disturbance mode; and so on until the forming of the target component is completed.

[0122] In some embodiments of the present application, the periodic pulse thermal disturbance mode includes a transition thermal disturbance mode between at least two cooling regions 200.

[0123] Specifically, when the energy beam scans across the boundary between two regions, a transitional thermal disturbance zone is formed. In order to avoid cracks or structural discontinuity caused by a sudden change in temperature gradient, a step-by-step cooling intensity is introduced in the transitional region, that is, by adjusting the pulse parameters (such as the pulse parameters transitioning from Q1 in the first region to Q2 in the second region), a continuously changing thermal disturbance waveform is formed; specifically: , where x is the energy beam scanning position, x0 is the starting point of the transition zone, and L is the length of the transition zone; thus, by adjusting the difference between L and Q1 and Q2, transition disturbances with different flushing frequencies and flow rates can be obtained, which is conducive to the formation of a uniform and refined grain structure.

[0124] In some embodiments of the present application, the periodic pulse thermal disturbance pattern includes a composite thermal disturbance pattern formed by stacking at least two cooling regions 200 .

[0125] Specifically, multiple cooling areas 200 (such as the first area, the second area and the third area) are arranged in a spatial stacking manner, so that the energy beam molten pool passes through multiple areas with different pulse parameters in a periodic path during the processing, thereby generating a multi-parameter coupled thermal disturbance response. The stacking can be spatial overlap (such as multi-layer microchannel structure superposition) or time stacking (such as repeated staggered entry into different cooling areas during energy beam scanning), forming a composite superposition of thermal disturbances, which has a composite effect on the heat accumulation and grain evolution of the molten pool; illustratively, for example, the flushing frequency of the cooling medium 20 in the first area is f1, and the flushing frequency of the cooling medium 20 in the second area is f2. After superposition, the main disturbance frequency f = f1 + f2 is formed, and the pulse mode is constructed with the assistance of the energy beam scanning periodicity: , where A1 and A2 are the flow rate parameters of the first area and the second area respectively.

[0126] The periodic pulse thermal disturbance mode constructed by adopting the above technical solution can effectively promote grain refinement, improve organizational uniformity, and improve common thermal cracks and internal defects in the additive manufacturing process of powder materials.

[0127] refer to Figure 8 and Figure 11 As shown, Figure 8 A cross-sectional schematic diagram of an exemplary sliced ​​and layered forming base with a variable guide unit according to some embodiments of the present application is shown, Figure 11 A cross-sectional schematic diagram of an exemplary partitioned forming base with a variable guide unit according to some embodiments of the present application is shown. In some embodiments of the present application, the cooling medium 20 circulation device for powder material additive manufacturing of the present application also includes a variable guide unit 23, which is arranged in a plurality of cooling circulation channels 22 to achieve dynamic changes in the direction of the cooling medium 20.

[0128] Specifically, as long as the variable flow guiding unit 23 can achieve dynamic changes in the direction of the cooling medium 20, it can be any form of structure, including but not limited to at least one of a valve, an adjustable nozzle, a diverter, or a multi-channel switching device driven by an actuator; the number of variable flow guiding units 23 matches the number of cooling circulation channels 22. Through the variable flow guiding unit 23, each cooling circulation channel 22 can be connected, allowing the cooling medium 20 to circulate in several connected cooling circulation channels 22, further realizing real-time regulation of the thermal disturbance at the cooling boundary and the grain growth behavior, thereby inducing multi-directional equiaxed grain growth and suppressing the expansion of hot cracks along specific paths.

[0129] Reference Figure 9 and Figure 10 shown, Figure 9 shows a scanning schematic diagram of additive manufacturing of powder materials with an exemplary adjacent-layer cooling medium circulation according to some embodiments of the present application. Figure 10 shows a scanning schematic diagram of additive manufacturing of powder materials with an exemplary cross-layer cooling medium circulation according to some embodiments of the present application. When performing slicing analysis, the geometric model of the target component is analyzed layer by layer. Thus, according to the sliced layer data of the target component, at least one cooling region 200 including at least one layer of the target component is obtained, and an independent cooling medium control loop 21 is set for each layer of the cooling region 200. Furthermore, according to requirements, the cooling medium control loops 21 of adjacent layers or cross-layers can be connected through the variable flow guiding unit 23, so as to realize the circulation of the cooling medium 20 in the cooling medium control loops 21 of adjacent layers or cross-layers through the variable flow guiding unit 23. The adjacent layers can be two adjacent layers, or three or more adjacent layers; the cross-layers can be separated by one layer, or two or more layers, which are specifically set by designers according to actual requirements.

[0130] Reference Figure 12 and Figure 13 shown, Figure 12 shows a scanning schematic diagram of additive manufacturing of powder materials with an exemplary adjacent-region cooling medium circulation according to some embodiments of the present application. Figure 13The figure shows a schematic diagram of scanning for additive manufacturing of powder materials with an exemplary cross-region cooling medium circulation according to some embodiments of the present application. When performing zoning analysis, the geometric model of the target component is analyzed for zoning. Thus, according to the zoning data of the target component after slicing, at least one cooling region 200 including at least a part of the target component is obtained, and an independent cooling medium control loop 21 is set for each cooling region 200. Furthermore, according to requirements, the cooling medium control loops 21 in adjacent regions or across regions can be connected through a variable diversion unit 23, so as to realize the circulation of the cooling medium 20 in the cooling medium control loops 21 in adjacent regions or across regions through the variable diversion unit 23. The adjacent regions can be two adjacent regions, or three or more adjacent regions; the across regions can be separated by one region, or two or more regions, which is specifically set by the designer according to actual requirements.

[0131] In some embodiments of the present application, based on any one or more of the above embodiments, the temperature of the cooling medium 20 can also be set to be adjustable. When setting a periodic pulse thermal disturbance mode for the cooling region 200, the temperature parameter of the cooling medium 20 is introduced into the pulse parameters, so as to more accurately adjust the temperature of the forming base 2.

[0132] Specifically, after introducing the temperature parameter of the cooling medium 20, define , where T0 is the average temperature of the cooling medium 20, B is the temperature disturbance value, f T is the temperature disturbance frequency, is the phase difference between the temperature disturbance and the flow velocity disturbance, which is used to control the peak superposition and out-of-phase temperature reduction behaviors; and after introducing the temperature disturbance regulation factor, the enhancement function can be further extended to:

[0133] ,

[0134] where β is the response factor of the temperature disturbance to the grain growth disturbance; thus, the constructed optimization objective function is extended to:

[0135] , where λ1, λ2, and λ3 are the weight coefficients for adjusting the scouring frequency, flow velocity, and temperature of the cooling medium 20.

[0136] Thus, if the gradient ascent optimization strategy is adopted, an example is:

[0137] , ,

[0138] , where γ1, γ2, γ3, γ4, and γ5 are the step sizes.

[0139] By adopting the above technical solution, the temperature of the adjustable cooling medium 20 is set, not only the cooling intensity is controllable, but also the direction and magnitude of the local temperature gradient can be regulated, thereby affecting the grain orientation and refinement trend, and realizing the closed-loop optimization of multi-dimensional disturbance control.

[0140] In some embodiments, referring to Figure 14 as shown, Figure 14 FIG. shows a schematic framework diagram of an exemplary electronic device according to some embodiments of the present application. The electronic device 3 includes: a memory 301 and a processor 302, and a computer program that can run on the processor 302 is stored in the memory 301. When the processor 302 executes the computer program, the method in the above embodiments is implemented. The number of the memory 301 and the processor 302 can be one or more.

[0141] The electronic device 3 further includes: a communication interface 303, configured to communicate with external devices and perform data interaction and transmission.

[0142] If the memory 301, the processor 302, and the communication interface 303 are implemented independently, the memory 301, the processor 302, and the communication interface 303 can be connected to each other through a bus and complete communication with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For the sake of convenience of representation, Figure 14 only a thick line is shown in, but it does not mean that there is only one bus or one type of bus.

[0143] Optionally, in specific implementation, if the memory 301, the processor 302, and the communication interface 303 are integrated on a chip, the memory 301, the processor 302, and the communication interface 303 can complete communication with each other through an internal interface.

[0144] The embodiment of the present application provides a computer-readable storage medium, which stores a computer program, and when the program is executed by the processor 302, the method provided in the embodiment of the present application is implemented.

[0145] The embodiment of the present application further provides a chip, which includes a processor 302, configured to call and run an instruction stored in the memory 301 from the memory 301, so that a communication device installed with the chip executes the method provided in the embodiment of the present application.

[0146] An embodiment of the present application further provides a chip, including: an input interface, an output interface, a processor 302, and a memory 301. The input interface, the output interface, the processor 302, and the memory 301 are connected through an internal connection path. The processor 302 is configured to execute the code in the memory 301. When the code is executed, the processor 302 is configured to execute the method provided by the embodiment of the application.

[0147] It should be understood that the above-mentioned processor 302 may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc. It is worth noting that the processor 302 may be a processor 302 that supports the advanced reduced instruction set machine (ARM) architecture.

[0148] Further, the above-mentioned memory 301 may include a read-only memory and a random access memory, and may further include a non-volatile random access memory. The memory may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may include a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may include a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available. For example, static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchlink dynamic random access memory (SLDRAM), and direct rambus random access memory (DR RAM).

[0149] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions according to the present application are generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium.

[0150] As described above, the above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application can easily think of changes or substitutions, which should all be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims described above.

Claims

1. An additive manufacturing method for powder materials using a cooling medium circulation, characterized in that, The method includes: Performing slicing and / or zoning analysis on the geometric model of the target component to obtain at least one cooling region including at least a part of the target component and setting an independent cooling medium control loop for each cooling region; Allocating a preset periodic pulse thermal disturbance mode with a cooling medium flushing frequency and flow rate to the at least one cooling region according to the at least one cooling region and in combination with the real-time temperature distribution and / or process target; Applying the periodic pulse thermal disturbance mode to the energy beam scanning process, so that when the energy beam scans to the cooling region on the forming substrate, its corresponding cooling medium control loop is switched to the matching periodic pulse thermal disturbance mode.

2. The method according to claim 1, characterized in that, When slicing the geometric model of the target component, the method includes: According to the layered data of the target component after slicing, obtaining at least one cooling region including at least one layer of the target component and setting an independent cooling medium control loop for each layer of the cooling region.

3. The method according to claim 2, wherein When the energy beam scans, the method includes: According to the number of layers of the target component scanned by the energy beam, switching the cooling medium control loop corresponding to the cooling region of the number of layers of the target component to the matching periodic pulse thermal disturbance mode.

4. The method according to claim 1 or 3, characterized in that, The periodic pulse thermal disturbance mode includes a transition thermal disturbance mode between at least two cooling regions or a composite thermal disturbance mode formed by stacking at least two cooling regions.

5. The method according to claim 1, characterized in that, When allocating a preset periodic pulse thermal disturbance mode with a cooling medium flushing frequency and flow rate, the method includes: According to the collected real-time temperature distribution data, reconstructing the temperature distribution of the cooling region by using the two-dimensional transient heat conduction equation; Establishing a periodic heat flux model coupled with the molten pool boundary according to the characteristics of the pulsed cooling medium generated; Establishing a grain growth disturbance model of the grain refinement rate and temperature disturbance and gradient according to the periodic heat flux model; Constructing a preset optimization function and updating the pulse parameters in real time so that the grain refinement rate is maximized within a limited time and / or space range.

6. The method according to claim 5, wherein When reconstructing the temperature distribution of the cooling region, the method includes: Defining the two-dimensional transient heat conduction equation and simulating the energy beam input by using a two-dimensional Gaussian distribution heat source; Defining the cooling boundary condition for applying the pulsed cooling medium; Discretizing the two-dimensional region into grids and setting the space and time step sizes, and then assigning an initial temperature value; Calculating the position of the energy beam heat source; Updating the cooling boundary condition; Updating the temperature value by using the explicit finite difference method; Outputting the temperature distribution.

7. The method according to claim 6, wherein When establishing the periodic heat flux model, the method includes: Applying a time-varying heat transfer boundary to the cooling surface of the molten pool; Calculating the Reynolds number and the convective heat transfer coefficient equation according to the change of the cooling medium flow rate to generate the instantaneous heat transfer coefficient of the cooling medium; Calculating the cooling heat flux at each moment according to the instantaneous heat transfer coefficient and the cooling medium temperature; Applying the cooling heat flux at each moment as a Neumann boundary to the heat conduction equation to update the temperature value by using the explicit finite difference method.

8. The method according to claim 7, wherein When establishing the grain growth disturbance model, the method includes: Establishing a refinement differential equation for the growth rate of the refinement rate and introducing a disturbance enhancement function; Obtaining the temperature distribution; Calculating the cooling rate and temperature gradient; Calculate the disturbance enhancement function based on the flushing frequency and flow velocity of the cooling medium; Solve the refined differential equation to generate the grain refinement rate; Output the equiaxed crystal proportion field.

9. The method according to claim 8, wherein When the pulse parameters are updated in real time, the method includes: Construct a preset optimization function according to the grain refinement model; Use a preset optimization strategy to search for the optimal flushing frequency and flow velocity of the cooling medium to update the pulse parameters; Output the updated pulse parameters as a control signal to the corresponding cooling medium control loop.

10. The method according to claim 1 or 8, characterized in that The method further includes: Perform slicing and / or zoning analysis on the geometric model of the target component to obtain at least one cooling region including at least a part of the target component and set an independent cooling medium control loop for each cooling region; Allocate a preset periodic pulse thermal disturbance pattern with a flushing frequency, flow velocity, and flow direction of the cooling medium to the at least one cooling region according to the at least one cooling region in combination with the real-time temperature distribution and / or process target; Apply the periodic pulse thermal disturbance pattern to the energy beam scanning process, so that when the energy beam scans to the cooling region on the forming platform, switch its corresponding cooling medium control loop to the matching periodic pulse thermal disturbance pattern.

11. The method according to claim 10, wherein Wherein the cooling medium control loop includes a cooling medium pulse parameter control loop and a cooling medium flow direction control loop.

12. A cooling medium circulation device for additive manufacturing of powder materials, characterized in that, Includes: A forming platform provided with at least one cooling circulation channel; At least one pulse pump connected to the at least one cooling circulation channel for driving the cooling medium to achieve a periodic pulse thermal disturbance pattern; A temperature monitoring unit arranged in the forming chamber and the forming platform for collecting real-time temperature data; A control unit connected to and controlling the at least one pulse pump and the temperature monitoring unit to execute the method according to any one of claims 1 to 9.

13. A cooling medium circulation device for additive manufacturing of powder materials, characterized in that, Includes: A forming platform provided with a plurality of cooling circulation channels; A variable flow guiding unit arranged in the plurality of cooling circulation channels for realizing dynamic change of the cooling medium direction; At least one pulse pump connected to the plurality of cooling circulation channels for driving the cooling medium to achieve a periodic pulse thermal disturbance pattern; A temperature monitoring unit arranged in the forming chamber and the forming platform for collecting real-time temperature data; A control unit connected to and controlling the variable flow guiding unit, the pulse pump, and the temperature detection unit to execute the method according to any one of claims 10 to 11.

14. An additive manufacturing device, characterized in that, Includes the cooling medium circulation device according to claim 12 or 13.

15. An electronic device, characterized in that, Includes: At least one processor; At least one memory; The at least one memory is coupled to the at least one processor and is used for storing instructions executed by the at least one processor. When the instructions are executed by the at least one processor, the electronic device executes the method according to any one of claims 1 to 11.

Images