A method and apparatus for preparing a porous metal material with controllable micrometer-scale pore structure

Abstract

The application discloses a kind of porous metal material preparation method and equipment with controllable micron pore structure, belong to functional material preparation field.For the insufficient designability of pore and matrix damage problem caused by the severe removal process of the limited arrangement of sacrificial template in prior art, a method combining additive manufacturing and selective corrosion is proposed, comprising: S1 using metal powder as raw material, embedding sacrificial metal wire through 3D printing simultaneously, and obtaining a blank by stress relief annealing;S2 the blank is sintered again to form an open hole material by complex corrosion;S3 the porous material is treated by hot isostatic pressing or plasma spraying to obtain a high-strength product.The method realizes precise forming through piezoelectric ceramic driving and infrared temperature measurement closed-loop feedback, and the corrosion selectivity is greater than 500:1 by using complexing agents such as tetrasodium ethylenediaminetetraacetate, which realizes three-dimensional controllable preparation of micron pores without damaging the matrix, with small pore size deviation and high compressive strength, and is suitable for aerospace, biomedical and other fields.

Description

Technical Field

[0001] This invention belongs to the field of functional materials preparation, and particularly relates to a method for preparing porous metal materials with controllable micron-scale pore structure through a combination of additive manufacturing and selective etching. Background Technology

[0002] Porous metallic materials are a class of metallic materials containing a large number of pores. They possess significant characteristics such as low density, high specific surface area, good thermal conductivity, and energy absorption capacity, and are widely used in aerospace, biomedicine, energy conversion, filtration and separation, environmental remediation, and many other fields. Their structural characteristics and physical properties can be customized by controlling porosity, pore size, pore morphology, and connectivity to meet functional requirements under different operating conditions.

[0003] Currently, the main methods for preparing porous metallic materials include powder metallurgy, sacrificial template method, foam replication method, gas foaming method, and a combination of phase transformation and tape casting method. However, these traditional processes suffer from problems such as uneven pore distribution, difficulty in precisely controlling pore size, and poor structural stability, which limit the further application of materials in high-end equipment and functional integration fields. Especially in applications requiring micron-level controllable pore structures, traditional processes struggle to combine customized structures with precision manufacturing.

[0004] In the preparation of porous metals, conventional processes such as powder metallurgy and tape casting have long been relied upon. These processes are based on the physical mechanisms of powder deposition and interlayer pressing, and while the technical routes are mature, they inherently limit the three-dimensional designability of the pore structure. Existing technologies focus on indirectly controlling the pore size through powder particle size or tape layer thickness, making it difficult to accurately arrange the pore-forming template in three-dimensional space. Furthermore, they are limited by the severity of material removal methods (strong acids, strong alkalis, or high-temperature oxidation), making it impossible to achieve non-destructive forming of micron-level fine pores.

[0005] Correspondingly, this patent application establishes a novel technical route that combines additive manufacturing with the simultaneous embedding of sacrificial metal wires and selective complexation corrosion. Through process innovation, it adapts the physical mechanism of simultaneous molding of high-melting-point sacrificial metal wires and low-melting-point matrix powders. During the 3D printing process, the process parameters are controlled to melt the matrix metal powder while keeping the sacrificial metal wires solid and unmelted. The mature metal wire drawing process is used to achieve precise control of the shape (circular, rectangular, square, triangular, etc.) and size of the sacrificial metal wires. Finally, the sacrificial metal wires are removed by selective corrosion, forming a controllable pore structure in situ that is consistent with the shape and size of the metal wires. At the same time, the chemical selectivity of the complexing agent and the metal ion coordination dissolution achieves efficient removal of the sacrificial metal wires.

[0006] Specifically, traditional sacrificial template methods often employ strong acids, strong alkalis, or high-temperature oxidation to remove the template material. These methods inevitably cause chemical corrosion or physical damage to the metal matrix while removing the template material, leading to problems such as decreased matrix strength, altered pore morphology, and the introduction of impurities. This problem is particularly prominent when preparing micron-scale fine porous structures. For example, when using strong acids such as hydrochloric acid or nitric acid for corrosion, the corrosion rate of 316L stainless steel matrix can reach approximately 0.5 mm / year, resulting in a significant decrease in compressive strength exceeding 30%.

[0007] In addition, the method proposed by the University of Science and Technology of China to prepare porous metal by combining phase transformation and multilayer casting (see CN105648255A) uses sacrificial slurry to remove the skin layer and sponge layer obtained by the phase transformation method, and obtains an open straight pore structure after reduction sintering. However, it uses graphite or starch powder as sacrificial material and removes it by high-temperature calcination. This method has problems such as low interlayer bonding strength, pores that can only be connected along the interlayer direction, and the inability to design pores with arbitrary orientation in three-dimensional space. Moreover, the high-temperature calcination process will oxidize the surface of the metal matrix and leave carbon residues that block the pores, making it difficult to accurately control the specific pore size in the range of 20 micrometers to 100 micrometers.

[0008] Therefore, considering the importance of better controlling the pore structure for porous metal casting, as well as the shortcomings of existing technologies such as insufficient structural designability, easy damage to the matrix, and inaccurate pore size control, it is of great significance to develop a porous metal preparation process with short production cycle, low production cost, controllable pore structure, and avoidance of matrix damage. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing porous metal materials with micron-level pores that can be precisely and controllably prepared in three-dimensional space without damaging the structural integrity of the metal matrix. This method overcomes the limitations of pore designability and the inability to simultaneously address matrix damage caused by the limited spatial arrangement of the sacrificial template and the harshness of the removal process in the prior art.

[0010] To achieve the above objectives, the present invention provides a method for preparing porous metallic materials with controllable micron-level pore structure, comprising the following steps: S1: Using metal powder as raw material, a preliminary blank is printed through 3D printing manufacturing process. Simultaneously and precisely control the embedding of sacrificial metal wire (metal powder is printed to form a shape that wraps the sacrificial metal wire), and the preliminary blank containing the sacrificial metal wire is stress-relief annealed to obtain the blank body. The sacrificial metal wire and the (matrix) metal powder have significantly different melting points. The significant difference means that there is a temperature difference between the melting points of the sacrificial metal wire and the matrix metal powder that is sufficient to achieve simultaneous molding and selective removal. The sacrificial metal wire and the (base) metal powder have significantly different melting points. Significant difference means that there is a temperature difference between the melting points of the sacrificial metal wire and the base metal powder that is sufficient to achieve simultaneous forming (the base metal powder melts while the sacrificial metal wire does not melt) and selective removal. Specifically, significant difference means that the melting point of the sacrificial metal wire is more than 250°C higher than that of the base metal powder, preferably more than 500°C higher. For example, when the base is stainless steel powder, titanium or titanium alloy is selected as the sacrificial metal wire, and when the base is magnesium alloy powder, stainless steel is selected as the sacrificial metal wire.

[0011] S2: The green body is sintered a second time to further strengthen the metallurgical bond between the matrix powders. Combined with selective corrosion process, the sacrificial metal wires are removed, the metal powder forming structure is retained, and a porous material with open pore characteristics is formed.

[0012] The 3D printing manufacturing process in step S1 is preferably a powder bed fusion metal 3D printing process, including but not limited to laser powder bed fusion process; the sacrificial metal wire includes but is not limited to pure titanium, magnesium and their alloys; the synchronous and precise control embedding is achieved through a precision wire feeding mechanism; the selective corrosion process in step S2 is preferably complexation corrosion, electrochemical corrosion or other mild corrosion methods that cause little damage to the substrate.

[0013] Stress-relief annealing is used to eliminate residual thermal stress generated during 3D printing and prevent deformation or cracking of the blank during subsequent sintering; secondary sintering is used to strengthen the metallurgical bond between matrix powders and improve material strength.

[0014] The prior art document CN105648255A adopts a casting-phase inversion-high temperature calcination route, with graphite or starch powder layers as sacrificial materials, which cannot achieve precise three-dimensional spatial arrangement, and the high temperature calcination will oxidize the matrix and leave residual carbon to block the channels; the present invention overcomes the above defects by combining additive manufacturing and selective etching.

[0015] The 3D printing manufacturing process uses a 3D printer (i.e., a selective laser melting device, preferably an SLM 280HL device). The synchronous and precise control of embedding the sacrificial metal wire in step S1 is achieved by a precision filament feeding mechanism mounted on the 3D printer. The precision filament feeding mechanism includes a piezoelectric ceramic actuator. An infrared temperature measurement system is configured on the 3D printer in conjunction with the precision filament feeding mechanism. Piezoelectric ceramic actuators are used to convert control signals into micro-displacement outputs, driving sacrificial metal wires to be fed into the molten pool of a 3D printer with a positioning accuracy of ±3μm (the molten pool refers to the liquid metal region that is formed instantaneously when the laser beam scans the metal powder bed in selective laser melting). The infrared temperature measurement system is used to monitor the molten pool temperature in real time and feed the temperature signal back to the control system. The control system dynamically adjusts the laser power of 3D printing according to the preset process temperature threshold, so that the molten pool temperature is maintained within the process range where the base metal powder melts and is formed and the sacrificial metal wire is formed. This ensures the stable and synchronous forming of the sacrificial metal wire and the metal powder, as well as the feasibility of subsequent selective etching to remove the sacrificial metal wire. The temperature measurement range of the infrared temperature measurement system is 400℃-1600℃, and the temperature measurement accuracy is ±5℃.

[0016] The piezoelectric ceramic actuator achieves micron-level precision filament feeding through the inverse piezoelectric effect of the piezoelectric ceramic; the infrared temperature measurement system has a response time of 10μs-25μs; the precision filament feeding mechanism is integrated with the 3D printer, and the laser power is adjusted by the control system based on the feedback signal from the infrared temperature measurement system. The precision filament feeding mechanism is integrated with the 3D printer (i.e., a laser powder bed forming device), and the laser power is adjusted by the control system based on the feedback signal from the infrared temperature measurement system.

[0017] The "preset process temperature threshold" includes the following two types of control objectives: 1. Upper limit threshold of surface temperature of sacrificial wire.

[0018] For titanium wire (melting point approximately 1668℃), the preset threshold is ≤800℃ (degrees Celsius). This threshold is set based on the following conditions: under laser power of 80W-150W and scanning speed of 1500mm / s-3000mm / s, it ensures that only micro-melting occurs on the surface of the titanium wire to form a metallurgical bond with the substrate, while the wire core remains solid, avoiding the melting of the entire wire which could lead to pore blockage or an excessively thick interfacial reaction layer (greater than 2μm).

[0019] For magnesium wire (melting point approximately 650°C), the preset threshold should be lower than its melting point, typically controlled at ≤600°C (achieved in Example 4 by combining a laser power of 100W and a scanning speed of 2000mm / s) to prevent the low-melting-point magnesium wire from completely melting and diffusing in the molten pool.

[0020] 2. Dynamic setting curve for molten pool temperature.

[0021] The control system is not based on a single fixed temperature value, but rather on a dynamic setting curve that varies with scanning speed and powder / filament coupling state. This curve is determined as follows: Feedforward: Wire feed rate (mm / min), used to predict the thermal shock when the sacrificial wire enters the molten pool; Feedback adjustment: The infrared temperature measurement system monitors the molten pool temperature in real time (response time 10μs-25μs). When the molten pool temperature deviates from the set curve, the laser power is adjusted within ≤60μs to keep the molten pool temperature within the process range where the base metal powder is fully melted (greater than 1400℃ for 316L stainless steel) and the sacrificial metal wire is adapted for forming (less than or equal to 800℃ for titanium wire).

[0022] The aforementioned thresholds are executed in real time through the PI control algorithm or LPV-MPC control algorithm of the closed-loop feedback system to ensure synchronous and stable molding of powder and filament.

[0023] The high positioning accuracy (±3μm) of the piezoelectric ceramic actuator ensures the precise arrangement of the sacrificial metal wire in three-dimensional space, providing a prerequisite for precise control of micron-level pores; the high accuracy (±5℃) and fast response (10μs-25μs) of the infrared temperature measurement system ensure real-time monitoring of the molten pool temperature, providing a data foundation for closed-loop control; the two work together to solve the problem of molten pool stability when high-melting-point sacrificial metal wire and low-melting-point matrix powder are formed simultaneously, such as the combination of high-melting-point titanium wire (melting point about 1668℃) and low-melting-point stainless steel powder (melting point about 1400℃), or high-melting-point stainless steel wire (melting point about 1400℃) and low-melting-point magnesium alloy powder (melting point about 650℃), avoiding defects such as channel blockage or molten pool instability caused by the melting of sacrificial metal wire (the matrix metal powder melts but the sacrificial metal wire does not melt during simultaneous forming).

[0024] Those skilled in the art know that piezoelectric ceramics can be used for precision driving and infrared thermometry can be used for temperature monitoring, but integrating the two into a powder bed melting device and coordinating their control for the synchronous powder-filament forming process is not a conventional technical means.

[0025] The selective corrosion process described in step S2 employs a complex corrosion system, which contains a complexing agent selected from at least one of ethylenediaminetetraacetic acid tetrasodium, citric acid, tartaric acid, or their salts, with a concentration of 0.01 mol / L to 0.1 mol / L (determined based on the balance between the corrosion rate required for complete removal of the sacrificial metal wire and the substrate protection requirements).

[0026] The sacrificial metal wire and the base metal powder form an interface reaction layer after secondary sintering. The interface reaction layer has a thickness of 0.5μm-2.0μm and can be disintegrated and removed by the complex corrosion system (e.g., disintegration, detachment, or dissolution).

[0027] The pH value of the complex corrosion system should be controlled between 8.5 and 9.5, and the corrosion temperature between 40℃ and 45℃. Ultrasonic treatment can be used as an adjunct, with an ultrasonic frequency of 40kHz and a power density of 0.5W / cm³. 2The interface reaction layer is mainly composed of a diffusion layer, containing interdiffusion products of the base metal and the sacrificial metal.

[0028] Complex corrosion systems utilize complexing agents to interact with sacrificial metal ions (Ti). 4+ Mg 2+ A stable, soluble complex is formed, continuously dissolving the sacrificial metal wire at a corrosion rate greater than 5 mm / year. Simultaneously, the 316L stainless steel substrate remains passivated in a weakly alkaline environment, with a corrosion rate less than 0.01 mm / year. The corrosion rate ratio of the two is greater than 500:1, achieving highly selective removal. The thickness of the interface reaction layer is controlled at 0.5 μm-2.0 μm (submicron level), ensuring both the metallurgical bonding strength between the sacrificial metal wire and the substrate during sintering and ensuring that it can be completely disintegrated and removed by the complex corrosion liquid, avoiding pore blockage and ensuring pore unobstructed flow.

[0029] The thickness of the interface reaction layer is 0.5μm-2.0μm (micrometers), determined based on the requirements of metallurgical bonding strength (thickness ≥0.5μm) and the requirements of removability of complex corrosion (thickness ≤2.0μm); the pH value is 8.5-9.5, determined based on the complexing effect of the complexing agent and the passivation stability of the substrate; the corrosion temperature is 40℃-45℃ (degrees Celsius), optimized based on the corrosion rate and the substrate protection effect.

[0030] Traditional strong acids (such as 1.0 mol / L HCl) have a corrosion rate of up to about 0.5 mm / year on 316L substrate, resulting in a strength decrease of more than 30%; the complex corrosion system of this invention has a corrosion rate of less than 0.01 mm / year on the substrate, and a strength retention rate of more than 95%.

[0031] The metal powder is a low-melting-point metal powder (preferably spherical 316L stainless steel powder with a particle size of 15μm-53μm); the sacrificial metal wire is a high-melting-point metal wire with a melting point 250°C or higher than that of the metal powder; specifically, when the metal powder is stainless steel, the sacrificial metal wire is titanium or a titanium alloy, and when the metal powder is a magnesium alloy, the sacrificial metal wire is stainless steel; the diameter of the sacrificial metal wire is 20μm-100μm.

[0032] The preferred particle size D50 of the metal powder is 25μm-30μm, and the oxygen content is less than 0.08%; the purity of the sacrificial metal wire is greater than 99.9%, and the tensile strength is ≥550MPa.

[0033] The particle size of 15μm-53μm (micrometers) is determined based on the requirements of powder flowability and laser melting characteristics in powder bed melting process; the diameter of the sacrificial metal wire of 20μm-100μm (micrometers) is determined by back-calculation based on the target pore size range and sintering expansion coefficient.

[0034] Example 1 used a titanium wire with a diameter of 40 μm, Example 2 used a titanium wire with a diameter of 60 μm, and Example 4 used a magnesium wire with a diameter of 50 μm. All of these examples successfully prepared porous materials with the expected pore size.

[0035] The secondary sintering in step S2 is divided into two stages. In the first stage, the temperature is raised to 250℃-340℃ and held for 1h-4h. In the second stage, the temperature is raised to 1280℃-1400℃ and held for 1h-4h. The heating and cooling rates are both 5℃ / min-10℃ / min. The final pore size d and the initial sacrificial wire diameter D satisfy the relationship d≈k×D, where k is the sintering expansion coefficient, and the value range is 1.05-1.25.

[0036] Step S2 is followed by a post-processing step S3: the porous metal material obtained after selective etching is cleaned with deionized water or ethanol, dried, and then post-processed using hot isostatic pressing or plasma spraying to obtain a porous metal product with high strength.

[0037] The hot isostatic pressing pressure is 200 MPa, and the holding time is 2 min; the first stage of heat preservation is used to eliminate the internal stress of printing, and the second stage of heat preservation is used to densify the matrix.

[0038] The first stage temperature (250℃-340℃) is determined based on the stress relief effect and to avoid premature diffusion of the sacrificial wire. The second stage temperature (1280℃-1400℃) is determined based on the densification temperature window of 316L stainless steel solid-state sintering. The holding time (1h-4h) is determined based on the billet size and densification requirements. The heating / cooling rate (5℃-10℃ / min) is determined based on the interface reaction control requirements. The sintering expansion coefficient (k) is an empirical parameter of 1.05-1.25, pre-calibrated based on a specific material combination (316L stainless steel-titanium / magnesium) and sintering process. The hot isostatic pressing pressure (200MPa) is determined based on the requirement to close residual pores while maintaining open pore connectivity.

[0039] The present invention also discloses an apparatus for implementing the preparation method, comprising a 3D printer as a laser powder bed forming device. The 3D printer is equipped with a precision filament feeding mechanism, a piezoelectric ceramic driver, an infrared temperature measurement system, and a closed-loop feedback control system. The precision filament feeding mechanism is used to synchronously embed sacrificial metal wires into the laser molten pool of metal powder. The infrared temperature measurement system is used to monitor the temperature of the molten pool in real time. The control system adjusts the laser power according to the temperature measurement signal of the infrared temperature measurement system to achieve synchronous forming of metal powder and sacrificial metal wires.

[0040] The laser powder bed forming equipment also includes a laser, a powder spreading system, and an inert gas protection system; the control system includes a controller and a power regulator, the controller receives the temperature signal from the infrared temperature measurement system, calculates the required laser power, and adjusts the laser output power within ≤60μs through the power regulator; the piezoelectric ceramic actuator includes a piezoelectric ceramic actuator and a wire feeding guide.

[0041] Response time: ≤60μs (microseconds) is determined based on the real-time requirements of molten pool temperature control and the performance of the laser power adjustment system.

[0042] The control system uses the wire feed rate as the feedforward quantity and combines it with the molten pool temperature feedback signal. It uses a PI control algorithm or an LPV-MPC control algorithm to calculate the laser power setpoint, so that the molten pool temperature tracks the dynamic set curve that changes with the scanning speed and the wire coupling state.

[0043] The feedforward is the real-time wire feeding speed of the piezoelectric ceramic actuator; the dynamic setting curve is preset according to the thermal properties (melting point, thermal conductivity, specific heat capacity) of the sacrificial metal wire and the matrix powder; the proportional coefficient and integral coefficient of the PI control algorithm are adjusted according to the thermal inertia of the molten pool; the LPV-MPC is a linear parameter variation model predictive control algorithm.

[0044] Feedforward: Wire feed rate (mm / min, millimeters per minute is determined based on the diameter of the sacrificial wire and the laser scanning speed); Control algorithm: PI control or LPV-MPC control, selected by design and determined according to the requirements of control accuracy and response speed.

[0045] The above control strategy is designed for the special working condition of "powder-filament synchronous molding", which is different from the constant power or simple temperature feedback control of traditional 3D printing.

[0046] The laser powder bed forming equipment has a laser power of 80W-150W, a scanning speed of 1500mm / s-3000mm / s, a scanning spacing of 0.05mm-0.08mm, a layer thickness of 20μm-40μm, and a volume energy density controlled at 60J / mm². 3 -150J / mm 3 .

[0047] The laser power is preferably 120W; the scanning speed is preferably 2000mm / s; the scanning spacing is preferably 0.06mm; the layer thickness is preferably 30μm; the volume energy density is calculated using the formula E=P / (v×s×h), where E is the volume energy density, P is the laser power, v is the scanning speed, s is the scanning spacing, and h is the layer thickness.

[0048] Laser power 80W-150W (watts) is determined based on powder melting requirements and sacrificial wire heat protection requirements; scanning speed 1500mm / s-3000mm / s (millimeters per second) is determined based on the balance between forming efficiency and melt pool stability; scanning spacing 0.05mm-0.08mm is determined based on laser spot diameter and overlap rate requirements; layer thickness 20μm-40μm (micrometers) is determined based on powder particle size and forming precision requirements; volume energy density 60J / mm². 3 -150J / mm 3 (Joules per cubic millimeter) was determined based on the dual objectives of sufficient matrix melting and control of interfacial reactions. The above parameter range was optimized to ensure sufficient matrix densification while minimizing interfacial reactions between the matrix and the sacrificial wire.

[0049] The present invention has the following advantages: By simultaneously embedding high-melting-point sacrificial metal wires in a 3D printing process, and leveraging their solid-state properties within a molten matrix environment, precise arrangement of the sacrificial wires in three-dimensional space is achieved. Since the sacrificial wires remain solid and do not melt during printing, their original shape, cross-sectional morphology, and spatial arrangement directly determine the final shape, size, and distribution of the pores. Furthermore, the mature wire drawing process ensures controllable shape and size, enabling micron-level precise and controllable fabrication of the pore structure and resolving the limitation on the spatial arrangement of the sacrificial template. Selective etching replaces traditional strong acid, strong alkali, or high-temperature oxidation removal methods, completely removing the sacrificial wires while avoiding chemical erosion or physical damage to the metal matrix, thus solving the problem of matrix damage caused by the harshness of the removal process. The synergistic effect of these two processes enables precise and controllable fabrication of micron-level pores in three-dimensional space without compromising the structural integrity of the metal matrix. The significant difference in melting points between the sacrificial metal wires and the metal powder ensures simultaneous forming and selective removal.

[0050] Spherical 316L stainless steel powder has good flowability and laser absorption rate, making it suitable for powder bed melting processes. The particle size of 15μm-53μm ensures laser melting effect and sintering densification. When the matrix is ​​stainless steel, high melting point titanium wire (melting point of about 1668℃) is selected, and when the matrix is ​​magnesium alloy, high melting point stainless steel wire is selected. Both meet the requirement that "the melting point of the sacrificial metal wire is higher than that of the matrix powder" and are less likely to form excessively thick and brittle intermetallic compounds, which is beneficial for subsequent selective corrosion removal. Since the wire drawing process is mature, its cross-sectional shape (circular, rectangular, square, triangular, etc.) and size (diameter 20μm-100μm) can be precisely controlled. Moreover, the wire remains solid and does not melt during the printing process. Therefore, the shape, distribution and size of the pores formed in situ after corrosion are highly consistent with the wire. Combined with the sintering expansion coefficient k=1.05-1.25, the final pore size can be precisely controlled at the micron level.

[0051] The two-stage sintering process not only achieved the densification requirement of a matrix relative density ≥96%, but also suppressed excessive diffusion between the sacrificial wire and the matrix by controlling the heating / cooling rate (5℃-10℃ / min), keeping the thickness of the interfacial reaction layer within the target range (0.5μm-2.0μm). The sintering expansion coefficient k (1.05-1.25) quantifies the squeezing / expansion effect of matrix densification shrinkage on the pores during sintering. By pre-calibrating the k value, the final pore diameter d can be accurately predicted and controlled by selecting the sacrificial wire diameter D, with the deviation controlled within ±20%, achieving quantitative controllability of the pore diameter. The post-processing steps improve the material strength while preserving the open pore characteristics.

[0052] The mathematical model d≈k×D breaks through the traditional technology's reliance on empirical control based solely on template size, achieving a leap from qualitative experience to quantitative control.

[0053] The device of this invention integrates high-precision wire feeding, real-time temperature measurement and closed-loop control functions, which solves the technical problem of "synchronous and precise control of embedded sacrificial metal wire" in the preparation method and provides hardware guarantee for the synchronous molding of powder and wire. By adjusting the laser power in real time through the control system, the temperature fluctuation of the molten pool caused by the sacrificial metal wire as a "cold source" is effectively dealt with, ensuring the stability and reliability of the molding process.

[0054] By introducing the wire feed rate as a feedforward, the control system can predict the thermal shock when the sacrificial wire enters the molten pool and adjust the laser power in advance, avoiding the lag of traditional systems that rely solely on temperature feedback. By employing high-bandwidth PI or LPV-MPC algorithms, rapid closed-loop control is achieved within a temperature measurement response time of 10μs-25μs and a power adjustment time of ≤60μs, ensuring the stability of the molten pool temperature and avoiding the defects of "spheroidization + unmelted wire".

[0055] By optimizing the laser thermal input parameters, the volume energy density was controlled at 60 J / mm². 3 -150J / mm 3 Within a relatively low range, the metal powder is fully melted while minimizing thermal shock and element interdiffusion to the sacrificial metal wire, resulting in an interfacial reaction layer thickness of less than 2 μm, which creates conditions for subsequent selective corrosion. Attached Figure Description

[0056] Appendix Figure 1 This is a process flow diagram of the present invention, with arrows indicating the process flow direction.

[0057] The diagram illustrates the core process chain of this patent, starting with the input of "metal powder" raw materials. A side arrow to the right of the "3D printing preform" step indicates "synchronous embedding of sacrificial metal wire," signifying that the embedding of the sacrificial metal wire occurs simultaneously with 3D printing. Subsequently, it undergoes four key processes: "stress relief annealing," "secondary sintering," "selective etching," and "cleaning, drying, and post-treatment," ultimately yielding the finished "porous metal material."

[0058] Appendix Figure 2 This is a schematic diagram illustrating the principle of powder bed molten metal 3D printing in this invention.

[0059] Appendix Figure 2 This demonstrates the principle of the powder bed molten metal 3D printing process used in this invention, and is a visual illustration of the core innovation of this invention: "synchronous and precise control of embedding sacrificial metal wires".

[0060] The "laser" located slightly above the center projects downwards in a yellow beam; the "piezoelectric wire feeder" on the left refers to a precision wire feeding mechanism using a piezoelectric ceramic actuator. There is also a sacrificial metal wire on the left. The bottom substrate is labeled "spherical 316L stainless steel powder".

[0061] Appendix Figure 2 The key process can be visualized as follows: the piezoelectric wire feeder precisely feeds the sacrificial metal wire into the molten pool area formed by the laser, the metal powder melts under the laser and encapsulates the sacrificial metal wire, and the infrared temperature measurement system monitors the molten pool temperature in real time, forming a closed-loop feedback control.

[0062] Appendix Figure 3 This is a schematic diagram illustrating the working principle of the preparation method of the present invention.

[0063] Appendix Figure 3 Different technical elements are distinguished by color-coded labels and are marked with numbers 1 to 6.

[0064] Mark "1" points to the yellow "sacrificial wire," representing the sacrificial material embedded in the matrix; Mark "2" points to the symmetrically arranged blue conical structures on both sides, representing the "inert gas nozzles" used to deliver protective gas; Mark "3" points to the cyan structures arranged at an angle on both sides, which are the laser emission units built into the SLM 280HL device (selective laser melting device, belonging to laser powder bed forming equipment, or 3D printer), used to emit a laser beam (marked 4) to melt the metal powder bed and form a molten pool for simultaneous molding. Mark "4" points to the red line sloping downwards in the center, representing the "laser beam"; Mark "5" points to the light gray layered structure at the bottom, representing the deposited material; Mark "6" points to the dark gray substrate at the bottom, representing the SLM 280HL device's build plate, serving as the basic support platform in the 3D printing process to support Mark "5" (the deposited material, i.e., the initial blank formed by layer-by-layer deposition). According to the embodiment, this substrate is preheated to 180°C or 200°C before the simultaneous deposition step to optimize the thermal field distribution and reduce the accumulation of thermal stress during the printing process. The core function of the substrate is to provide stable thermodynamic support during the 3D printing stage (the first half of step S1); it is a component of the equipment and does not participate in the material system composition. The "stress relief annealing" in step S1 applies to the already formed blank (i.e., marked 5), and it is not limited whether the blank is attached to the substrate during annealing. This process detail does not affect the scope of protection of this invention.

[0065] The marker "5" (deposited material) corresponds to the "prototype printed by 3D printing manufacturing process" in step S1, which is a three-dimensional solid structure composed of a matrix metal region formed by the laser melting and cooling of metal powder, and a sacrificial metal wire that is simultaneously embedded and wrapped. After the prototype is transformed into a blank by stress relief annealing, it enters step S2: the matrix bonding is strengthened by secondary sintering, and the sacrificial metal wire is removed by selective etching. Finally, the matrix skeleton formed by the melting and solidification of the original metal powder is retained, forming a porous metal material with open-pore characteristics.

[0066] The substrate (marked 6) is the basic platform for the formation of the deposited material (marked 5). The deposited material is deposited layer by layer on the surface of the substrate through a laser powder bed melting process to form a blank. The preheating temperature of the substrate (as a key process parameter, set to 180°C or 200°C in the embodiment) is used to optimize the thermal field distribution during the printing process, which helps to control the generation of residual thermal stress during the printing stage.

[0067] The deposited material (i.e., the "initial blank" mentioned in step S1) needs to be transformed into a blank through stress relief annealing, and then subjected to secondary sintering, selective corrosion and optional post-treatment in step S2 to finally form a porous metal product with open-pore characteristics.

[0068] Inert gas nozzle 2 corresponds to the actuator of the "inert gas protection system". This nozzle sprays high-purity argon or nitrogen into the forming chamber to form a stable laminar flow environment, effectively isolating oxygen, inhibiting oxidation of the molten metal pool, and helping to remove metal fumes and splashes during the printing process, providing a clean and protective atmosphere for the simultaneous melting and forming of powder and filament.

[0069] Appendix Figure 4 This is a schematic diagram of the pore formation mechanism of secondary sintering and selective corrosion in this invention. The evolution of pore structure before and after secondary sintering and selective corrosion is shown by comparison. The left-hand image shows a large array of solid black dots, representing the distribution of the sacrificial metal wire (pure titanium or magnesium) in the metal matrix before secondary sintering. The right-hand image shows an array of blue dots corresponding to the positions of the black dots on the left, representing the open-pore structure formed after the sacrificial metal wire is removed following secondary sintering and selective etching. The arrows between the two images, labeled "Secondary Sintering" and "Selective Etching," indicate the process conversion direction from left to right. The visual difference between the black and blue dots clearly demonstrates the technical principle of "sacrificial metal wire placement—removal—pore formation." This image visually proves that by controlling the diameter (20-100 μm) and arrangement of the sacrificial metal wire, the final pore size (d≈k×D, where k is the sintering expansion coefficient of 1.05 to 1.25) can be controlled at the micrometer level, achieving controllable design of the pore structure. Detailed Implementation

[0070] like Figures 1 to 4 As shown, the present invention provides a method for preparing porous metal materials with micron-level pores that can be precisely and controllably prepared in three-dimensional space without damaging the structural integrity of the metal matrix (i.e., a method for preparing porous metal materials with controllable micron-level pore structure), so as to overcome the limitations of pore designability and matrix damage caused by the limited space arrangement of the sacrificial template and the severity of the removal process in the prior art.

[0071] This embodiment employs a forming process combining powder bed molten metal 3D printing with selective etching. Using a precision wire feeding mechanism equipped with a laser powder bed forming equipment (preferably an SLM 280HL device), sacrificial metal wires are simultaneously embedded into the molten pool while the metal powder is melted layer by layer. Through stress-relief annealing, secondary sintering, and selective etching, a high-strength porous metal product with a three-dimensional interconnected pore structure is formed.

[0072] The precision wire feeding mechanism includes a piezoelectric ceramic driver, a transmission push rod, and a wire feeding guide assembly. The output end of the piezoelectric ceramic driver is fixedly connected to the transmission push rod, and is used to convert the control signal into a micro-displacement output to drive the sacrificial metal wire into the molten pool with a positioning accuracy of ±3μm. The laser powder bed forming equipment is also equipped with an infrared temperature measurement system (temperature range 400℃-1600℃, accuracy ±5℃) and a closed-loop feedback control system. The infrared temperature measurement system is used to monitor the molten pool temperature in real time. The closed-loop feedback control system uses the wire feed rate as the feedforward quantity, combined with the molten pool temperature feedback signal, and uses a PI control algorithm or an LPV-MPC control algorithm to calculate the laser power setpoint. The laser output power is adjusted within ≤60μs, so that the molten pool temperature tracks the dynamic set curve that changes with the scanning speed and the wire coupling state, thereby achieving stable synchronous forming of metal powder and sacrificial metal wire.

[0073] The process includes the following steps: S1: Using metal powder as raw material, a preliminary blank is printed using a 3D printing process. Simultaneously and precisely controlled embedding of sacrificial metal wires is performed, followed by stress-relief annealing of the preliminary blank containing the sacrificial metal wires to obtain the final blank. The 3D printing process is a powder bed fusion metal 3D printing process, with a laser power of 80W-150W, a scanning speed of 1500mm / s-3000mm / s, a scanning spacing of 0.05mm-0.08mm, a layer thickness of 20μm-40μm, and a volume energy density controlled at 60J / mm². 3 -150J / mm 3 The calculation formula is E=P / (v×s×h), where E is the volume energy density, P is the laser power, v is the scanning speed, s is the scanning interval, and h is the layer thickness. The sacrificial metal wire and the base metal powder have significantly different melting points (difference ≥250℃, preferably ≥500℃), and are selected from pure titanium or magnesium, with a diameter of 20μm-100μm. The stress-relieving annealing temperature is 250℃-350℃, the holding time is 1h-2h, and it is carried out under inert gas (nitrogen or argon) or vacuum protection.

[0074] S2: The blank is subjected to secondary sintering, combined with selective etching to remove the sacrificial metal wires, retaining the metal powder forming structure, forming a porous material with open-pore characteristics. The secondary sintering is divided into two stages. The first stage involves heating to 250℃-340℃ and holding for 1-4 hours to eliminate printing internal stress. The second stage involves heating to 1280℃-1400℃ (1150℃ for Ti-6Al-4V matrix) and holding for 1-4 hours to achieve matrix densification. The heating and cooling rates are both 5℃ / min-10℃ / min. The selective etching process uses a complex etching system containing at least one of the complexing agents: tetrasodium ethylenediaminetetraacetate, citric acid, tartaric acid, or their salts, at a concentration of 0.01mol / L-0.1mol / L, pH controlled at 8.5-9.5, and etching temperature at 40℃-45℃. Ultrasonic treatment (frequency 40kHz, power density 0.5W / cm³) can be used as an adjunct. 2 The sacrificial metal wire and the base metal powder form an interfacial reaction layer after secondary sintering, with the thickness strictly controlled between 0.5 μm and 2.0 μm. This reaction layer can be disintegrated and removed by the complex corrosion system. The final pore size d and the initial sacrificial metal wire diameter D satisfy the relationship d ≈ k × D, where k is the sintering expansion coefficient, with a value ranging from 1.05 to 1.25.

[0075] S3: The porous metal material obtained after secondary sintering is cleaned with deionized water or ethanol, dried, and then post-treated by hot isostatic pressing (pressure 200MPa, hold for 2min) or plasma spraying to obtain porous metal products with high strength.

[0076] The porous materials prepared by this method have an open porosity of 50%–70%, a pore size deviation controlled within ±20%, a compressive strength better than 200 MPa, and a three-dimensional pore connectivity of over 95%.

[0077] The SLM 280HL is an industrial-grade selective laser melting (SLM) system (also known as a 3D printer) manufactured by SLM Solutions, Germany. To achieve the technical goal of simultaneous implantation of sacrificial metal wires, a precision wire feeding mechanism is added to the SLM 280HL. This mechanism includes a piezoelectric ceramic actuator, a drive push rod, and a wire feeding guide assembly. The piezoelectric ceramic actuator is a well-known inverse piezoelectric effect precision displacement element (commercially available standard parts, such as the PI P-845 series standard parts). Its output end is fixedly connected to the drive push rod, converting the control signal into a micro-displacement output to drive the sacrificial metal wire into the molten pool with an accuracy of ±3μm. The selection of the piezoelectric ceramic actuator, the drive circuit, and the mechanical connection method are all conventional techniques in the field. The SLM 280HL is responsible for melting and forming the metal matrix, while the precision wire feeding mechanism is responsible for accurately feeding the sacrificial metal wire into the molten pool. Together, they achieve the synchronous forming of the metal matrix and the sacrificial metal wire, serving the technical goal of preparing porous metal materials with controllable micron-level pore structures.

[0078] In this invention, the control system is an inherent core component of the laser powder bed forming equipment. As a standardized additive manufacturing device, the laser powder bed forming equipment inherently includes a control system composed of a controller, power regulator, motion control module, etc. This control system is the core for realizing basic printing functions such as laser power adjustment, laser scanning motion, and powder spreading system linkage. Without this control system, the laser powder bed forming equipment cannot complete the basic metal powder melting and forming. This invention expands and adapts the inherent control system without adding a new independent control system. Instead, it integrates the temperature signal acquisition module of the infrared temperature measurement system and the wire feeding rate feedforward module of the precision wire feeding mechanism with the native control system of the laser powder bed forming equipment. This enables the original native control system, which only realized basic printing control, to have closed-loop control functions such as receiving molten pool temperature feedback, reading the wire feed rate feedforward, calculating laser power through the PI / LPV-MPC algorithm, and driving the laser to adjust the output power within ≤60μs, thus adapting to the special process requirements of the synchronous powder-wire forming of this invention. In practical terms, this control system is the main control system of the SLM 280HL equipment.

[0079] Compared with the prior art CN105648255A (phase transformation and multilayer casting combined method), the core advantages of this embodiment are: 1. It achieves precise three-dimensional spatial arrangement of sacrificial metal wires, breaking through the limitation of traditional processes where the channels can only be connected along the interlayer; 2. It adopts a complex corrosion system with a corrosion rate ratio >500:1, avoiding damage to the substrate caused by traditional strong acid corrosion (the corrosion rate of traditional HCl on 316L stainless steel substrate is ≈0.5mm / year, while that of this invention is <0.01mm / year, forming a selective comparison of greater than 500:1); 3. It eliminates the need for high-temperature calcination to remove sacrificial materials, avoiding substrate oxidation and carbon residue, and achieving higher pore size control accuracy (deviation ≤±20%); 4. Through closed-loop feedback control, it achieves synchronous powder-wire forming, with a pore connectivity rate >95% and superior mechanical properties.

[0080] Example 1: Preparation of porous 316L stainless steel.

[0081] Compared with the above specific implementation methods, the characteristics of this embodiment lie in the selection of specific parameters and performance characterization data, which will be explained in detail below: Material preparation: Spherical 316L stainless steel powder with particle size D50=25μm and oxygen content <0.08% was selected as the matrix powder; high-purity titanium wire with diameter of 40μm, purity >99.9% and tensile strength ≥550MPa was selected as the sacrificial metal wire.

[0082] Simultaneous deposition: A precision wire feed mechanism was added to the SLM 280HL equipment. The laser power was set to 120W, the scanning speed to 2000mm / s, the scanning spacing to 0.06mm, and the layer thickness to 30μm. Based on this, the volume energy density was calculated to be 83.3J / mm³. The wire feed speed was 150mm / min, and the substrate preheating temperature was 180℃. The laser power was adjusted through a closed-loop feedback system to ensure that the titanium wire surface temperature was ≤800℃.

[0083] Vacuum diffusion sintering: Under a hydrogen atmosphere, the deposited sample is placed in a sintering furnace and heated to 1380℃ at a heating rate of 5℃ / min, held for 4 hours, and the gas pressure is controlled at -0.095MPa.

[0084] Selective etching: The sintered sample is immersed in an etching solution prepared with deionized water as the solvent. The solution contains 0.05 mol / L sodium ethylenediaminetetraacetate, 0.03 mol / L citric acid, and 0.02 mol / L tartaric acid. 0.3 vol% ammonia is added as a pH adjuster, maintaining the pH between 8.5 and 9.5. The etching temperature is 40 ± 5℃, the ultrasonic frequency is 40 kHz, and the power density is 0.5 W / cm³. 2 The etching time was 4 hours. After etching, the sample was ultrasonically cleaned with deionized water for 30 minutes and then dried.

[0085] Post-treatment strengthening: The etched sample was subjected to cold isostatic pressing at a pressure of 200 MPa for 2 min; an Al2O3 coating was deposited on the pore surface by plasma spraying; and finally, it was annealed at 650℃ in a hydrogen atmosphere.

[0086] Performance characterization: Porosity measured by the Archimedes method was 62.3%; mercury porosimetry showed that the pore size was mainly distributed between 35 μm and 45 μm, which closely matched the diameter of the sacrificial wire; the compressive strength measured by the compression test was 285 MPa, and the elastic modulus was 4.2 GPa; Micro-CT three-dimensional reconstruction images showed that the pore connectivity was >98%, and the permeability was 1.8 × 10⁻⁶. -12 m 2 .

[0087] Comparative Example 1: A sintered green body was prepared using the same materials and 3D printing and secondary sintering process as in Example 1. The sintered sample was then immersed in a 1.0 mol / L hydrochloric acid aqueous solution and etched at 40°C for 4 hours. The results showed that the corrosion rate of the 316L matrix was as high as 0.5 mm / year, and the compressive strength decreased by about 30%-40% (from 285 MPa to 170 MPa), proving that the matrix structure was severely damaged.

[0088] Example 1 uses the complexation corrosion of the present invention (EDTA-Na4 system), and the final compressive strength is 285 MPa; in contrast, Comparative Example 1 uses conventional strong acid corrosion (1.0 mol / L HCl), and the final compressive strength is reduced to 170 MPa (a decrease of about 30%-40%).

[0089] Example 2: Preparation of porous 316L stainless steel with different pore sizes.

[0090] The difference between this embodiment and Embodiment 1 is as follows: the diameter of the sacrificial metal wire is 60 μm; the laser power is 150 W, the scanning speed is 2500 mm / s, the scanning spacing is 0.07 mm, the layer thickness is 40 μm, and the volume energy density is 53.6 J / mm³; the wire feeding speed is 200 mm / min, the substrate preheating temperature is 200 °C; the second stage temperature of the secondary sintering is 1280 °C, and the holding time is 3 h; the concentration of tetrasodium ethylenediaminetetraacetate in the etching solution is 0.1 mol / L, the concentration of citric acid is 0.04 mol / L, the etching temperature is 45 ± 5 °C, and the etching time is 6 h.

[0091] Performance characterization: Open porosity is 58.7%; mercury porosimetry shows that the pore size is mainly distributed between 55 μm and 65 μm; compressive strength is 310 MPa, elastic modulus is 4.8 GPa; permeability is 2.1 × 10⁻⁶. -12 m 2 .

[0092] Example 3: Preparation of air bearing throttling plate.

[0093] The difference between this embodiment and Embodiment 1 is that the sacrificial metal wires are arranged orthogonally with a wire spacing of 150μm; the laser power is 130W and the scanning speed is 1800mm / s; the second stage of secondary sintering is held at a temperature of 3h; and the etching time is 3.5h.

[0094] Performance characterization: The open porosity is 60.5%; mercury porosimetry analysis shows that the pore size is concentrated between 38μm and 42μm, meeting the accuracy requirements of air bearings for micron-level throttling orifices; the compressive strength is 295MPa, and the elastic modulus is 4.5GPa; gas permeability testing shows uniform gas flow, with a permeability of 1.9×10⁻⁶. -12 m 2 It meets the application standards for throttling plates.

[0095] Example 4: Preparation of biomedical porous titanium alloy.

[0096] The difference between this embodiment and Embodiment 1 is as follows: the matrix powder used is Ti-6Al-4V powder with a particle size D50=30μm; the sacrificial metal wire is magnesium wire with a diameter of 50μm; the laser power is 100W, the scanning speed is 2000mm / s, and the scanning interval is 0.05mm; the second stage temperature of the secondary sintering is 1150℃ (based on the sintering characteristics of Ti-6Al-4V), and the holding time is 3h; 0.2vol% ammonia water is added to the etching solution as a pH adjuster, and the etching time is 3.5h.

[0097] Performance characterization: The open porosity is 65.2%, which is close to the porosity range of human bone; mercury porosimetry shows that the pore size is mainly distributed in the range of 48μm-52μm, which meets the requirements for bone tissue ingrowth; the compressive strength is 220MPa and the elastic modulus is 3.8GPa, which is well matched with cortical bone; the pore connectivity is >95% and the permeability is 2.3×10-12m2, which is conducive to the permeation of body fluids and cells.

[0098] In this embodiment, the reason why the melting point of the sacrificial metal wire is lower than that of the matrix powder, but still conforms to the core design logic of the present invention, is as follows: From the perspective of the forming state: In Example 4, the laser power was set to 100W and the scanning speed to 2000mm / s. These process parameters were designed for Ti-6Al-4V powder (melting point 1600℃) to ensure that the matrix powder was fully melted. However, the melting point of magnesium wire is only 650℃. Because the laser energy is concentrated in the matrix powder area, the magnesium wire is in the heat-affected zone of the molten pool rather than the core area. Furthermore, the process parameters are precisely controlled (such as the substrate preheating to 180℃), so that the surface temperature of the magnesium wire does not reach the melting point and remains solid, thus meeting the core forming requirement of "powder melts but wire does not melt".

[0099] In terms of corrosion selectivity: the chemical properties of magnesium wire and Ti-6Al-4V matrix are significantly different. The corrosion rate of magnesium wire by complex corrosion system (EDTA-Na4, citric acid, etc.) is greater than 5 mm / year, while the corrosion rate of Ti-6Al-4V matrix is ​​almost zero. This can achieve selective removal of sacrificial metal wire without damaging the matrix structure.

[0100] From the perspective of the original design of the patent: the core is to achieve controllable porosity through "metal wire occupancy - corrosion removal". The melting point relationship between the metal wire and the substrate needs to be flexibly adapted in combination with material characteristics and process parameters, which is in line with the core logic. The material combination in Example 4 is based on the difference in characteristics and process compatibility between Ti-6Al-4V and magnesium. On the surface, it sacrifices the melting point of the metal wire being lower than that of the substrate powder, but still meets the core design logic of the present invention: "the wire does not melt during molding and can be removed during corrosion".

[0101] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing porous metallic materials with controllable micron-scale pore structure, characterized in that, Includes the following steps: S1: Using metal powder as raw material, a preliminary blank is printed through 3D printing manufacturing process. Simultaneously and precisely control the embedding of sacrificial metal wires, and the preliminary blank containing sacrificial metal wires is stress-relief annealed to obtain the blank body. The melting point of the sacrificial metal wire is higher than that of the base metal powder. The significant difference in melting points means that the difference is sufficient to achieve simultaneous molding, where the base metal powder melts while the sacrificial metal wire remains solid and does not melt, and subsequent selective removal. S2: The blank is sintered a second time, and the sacrificial metal wire is removed by selective etching process, while the metal powder forming structure is retained to form a porous material with open pore characteristics.

2. The method for preparing a porous metallic material with controllable micron-scale pore structure according to claim 1, characterized in that, The 3D printing manufacturing process uses a 3D printer. The synchronous and precise control of embedding the sacrificial metal wire in step S1 is achieved by a precision filament feeding mechanism mounted on the 3D printer. The precision filament feeding mechanism includes a piezoelectric ceramic actuator. An infrared temperature measurement system is configured on the 3D printer in conjunction with the precision filament feeding mechanism. Piezoelectric ceramic actuators are used to convert control signals into micro-displacement outputs, driving sacrificial wires to be fed into the molten pool of a 3D printer with a positioning accuracy of ±3μm. The infrared temperature measurement system is used to monitor the temperature of the molten pool in real time and feed the temperature signal back to the control system. The control system dynamically adjusts the laser power of 3D printing according to the preset process temperature threshold, so that the temperature of the molten pool is maintained in the process range where the base metal powder melts and the sacrificial metal wire is adapted and formed. The temperature measurement range of the infrared temperature measurement system is 400℃-1600℃, and the temperature measurement accuracy is ±5℃.

3. The method for preparing a porous metallic material with controllable micron-scale pore structure according to claim 1 or 2, characterized in that, The selective corrosion process described in step S2 employs a complexing corrosion system, which includes a complexing agent selected from at least one of ethylenediaminetetraacetic acid tetrasodium, citric acid, tartaric acid, or their salts, with a concentration of 0.01 mol / L to 0.1 mol / L. The sacrificial metal wire and the base metal powder form an interface reaction layer after secondary sintering. The interface reaction layer has a thickness of 0.5μm-2.0μm and can be disintegrated and removed by the complex corrosion system.

4. A method for preparing a porous metallic material with controllable micron-scale pore structure according to any one of claims 1-3, characterized in that, The metal powder is a low-melting-point metal powder, and the sacrificial metal wire is a high-melting-point metal wire with a melting point 250°C or higher than that of the metal powder; when the metal powder is stainless steel, the sacrificial metal wire is titanium or a titanium alloy; when the metal powder is a magnesium alloy, the sacrificial metal wire is stainless steel; the diameter of the sacrificial metal wire is 20μm-100μm.

5. A method for preparing a porous metallic material with controllable micron-scale pore structure according to any one of claims 1-4, characterized in that, The secondary sintering in step S2 is divided into two stages. In the first stage, the temperature is raised to 250℃-340℃ and held for 1h-4h. In the second stage, the temperature is raised to 1280℃-1400℃ and held for 1h-4h. The heating and cooling rates are both 5℃ / min-10℃ / min. The final pore size d and the initial sacrificial wire diameter D satisfy the relationship d≈k×D, where k is the sintering expansion coefficient, and the value range is 1.05-1.

25.

6. The method for preparing a porous metallic material with controllable micron-scale pore structure according to claim 5, characterized in that: Step S2 is followed by a post-processing step S3: the porous metal material obtained after selective etching is cleaned with deionized water or ethanol, dried, and then post-processed using hot isostatic pressing or plasma spraying to obtain a porous metal product with high strength.

7. An apparatus for implementing the preparation method according to any one of claims 1-5, characterized in that, The 3D printer, which serves as a laser powder bed forming device, is equipped with a precision filament feeding mechanism, a piezoelectric ceramic driver, an infrared temperature measurement system, and a closed-loop feedback control system. The precision filament feeding mechanism is used to synchronously embed sacrificial metal filaments into the laser molten pool of metal powder. The infrared temperature measurement system is used to monitor the temperature of the molten pool in real time. The control system adjusts the laser power according to the temperature measurement signal from the infrared temperature measurement system to achieve synchronous forming of metal powder and sacrificial metal filaments.

8. The device according to claim 6, characterized in that, The control system uses the wire feed rate as the feedforward quantity and combines it with the molten pool temperature feedback signal. It uses a PI control algorithm or an LPV-MPC control algorithm to calculate the laser power setpoint, so that the molten pool temperature tracks the dynamic set curve that changes with the scanning speed and the wire coupling state.

9. The device according to claim 6 or 7, characterized in that, The laser powder bed forming equipment has a laser power of 80W-150W, a scanning speed of 1500mm / s-3000mm / s, a scanning spacing of 0.05mm-0.08mm, a layer thickness of 20μm-40μm, and a volume energy density controlled at 60J / mm². 3 -150J / mm 3 .

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