Heat-insulating flexible composite substrate for metal additive manufacturing and application method of heat-insulating flexible composite substrate

Abstract

The invention provides a heat insulation flexible composite substrate for metal additive manufacturing and an application method of the heat insulation flexible composite substrate, and relates to the technical field of additive manufacturing. The composite substrate comprises a metal upper substrate and a heat insulation lower substrate which are detachably connected. The upper substrate is provided with through transverse and longitudinal array cavities or a periodic cell element structure, and the upper substrate is filled with a thermal insulation material, so that the thermal conductivity and the rigidity are reduced; the lower substrate is made of a low-heat-conductivity material and blocks vertical heat flow; the upper substrate can deform relative to the lower substrate to realize slow release of thermal stress. Through heat-force cooperative regulation and control, the temperature gradient is reduced, the high-temperature environment of a forming area is maintained, stress in-situ release is promoted, residual stress and hot cracks are effectively restrained, and the forming quality of the alloy difficult to weld is improved.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, specifically relating to a heat-insulating flexible composite substrate for metal additive manufacturing and its application method. Background Technology

[0002] High-energy-density additive manufacturing (AM) technologies—including laser powder bed melting (LPBF), electron beam melting (EBM), and directed energy deposition (DED)—enable the rapid fabrication of complex metal components by locally melting materials layer by layer. However, these processes are inherently characterized by "high energy density + rapid melting and solidification + rapid cooling," resulting in the formation of up to 10... 5 -10 6 Temperature gradient of K / m and 10 4 -10 6 The cooling rate is K / s. Under continuous thermal cycling and substrate constraint, the deposited layer is prone to significant thermal stress, phase transformation stress, and mechanical constraint stress, which accumulate over time, leading to microstructure embrittlement, stress concentration, and crack initiation and propagation. This problem is particularly pronounced for difficult-to-weld materials, such as nickel-based superalloys with high γ′ content (IN738, CM247LC, Rene80, etc.), TiAl alloys, and high-strength aluminum alloys. These alloys generally exhibit wide solidification temperature ranges, significant elemental segregation, and easy formation of grain boundary liquid films. Under the rapid solidification conditions of high-energy beam AM, they are more prone to hot and cold cracking, thus limiting their forming quality and engineering applications.

[0003] Currently, high-energy beam AM (Ampere) equipment mostly uses monolithic metal substrates. Due to their high thermal conductivity and high rigidity, the deposited material is strongly constrained during cooling and shrinkage, making it difficult to release residual stress. Although various suppression measures have been implemented, such as substrate preheating, scanning strategy optimization, material composition control, and heat treatment, they generally still face problems such as high energy consumption, complex processes, limited applicability, or insufficient suppression effect. Given the increasing demand for high-performance, difficult-to-weld alloy components in aerospace, energy, and power industries, developing more efficient and universally applicable crack-resistant technologies is particularly crucial. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a thermally insulating flexible composite substrate for metal additive manufacturing and its application method, so as to solve the problems of residual stress accumulation and hot cracking caused by high temperature gradient and rigid substrate constraints in the prior art, and is especially suitable for high-quality forming of difficult-to-weld alloys.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A thermally insulating flexible composite substrate for metal additive manufacturing includes an upper substrate and a lower substrate that are detachably connected. The upper substrate has cavities or periodic cell structures arranged in a horizontal and vertical array, the cavities or gaps penetrating the upper substrate and filled with a first heat-insulating material; the upper substrate is a metal plate. The lower substrate is a support structure made of a second heat-insulating material; The upper substrate can deform or move relative to the lower substrate.

[0006] A further improvement of the present invention is that: Preferably, the cross-section of the cavity is rectangular, circular, elliptical, or triangular.

[0007] Preferably, the cell structure is a grid-like structure formed by an array of geometric units.

[0008] Preferably, the cross-section of the grid in the cell structure is rectangular, quadrilateral, or hexagonal.

[0009] Preferably, the first heat-insulating material is any one or more of heat-insulating powder, ceramic flakes, or lightweight heat-resistant materials, wherein the density of the lightweight heat-resistant material is less than 1.0 g / cm³. 3 Thermal conductivity less than 0.5 W·m -1 ·K -1 .

[0010] Preferably, the second thermal insulation material is ceramic or has a thermal conductivity of less than 0.5 W·m. - ¹·K - ¹ Composite materials.

[0011] Preferably, a third heat insulation material is provided at the lower part of the lower substrate, and the third heat insulation material is heat insulation cotton or aerogel.

[0012] Preferably, the upper substrate and the lower substrate are connected by a connecting structure, which allows the upper substrate to move or deform relative to the lower substrate.

[0013] Preferably, the connection structure is a mortise and tenon structure, bolt, buckle, groove or adhesive.

[0014] A method for applying the above-mentioned heat-insulating flexible composite substrate for metal additive manufacturing includes the following steps: S1, providing a metal plate and a second heat insulation material, processing the metal plate into the shape of a designed upper substrate, and processing the second heat insulation material into the shape of a designed lower substrate; S2, the upper substrate and the lower substrate are connected by a connection structure that allows for slight thermal deformation of the upper substrate; S3, fill the upper substrate with a first heat-insulating material to obtain the heat-insulating flexible composite substrate; S4, Place the heat-insulating flexible composite substrate on the forming platform of the LPBF equipment and level it; S5, metal powder is laid on the heat-insulating flexible composite substrate and printed layer by layer.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a thermally insulated flexible composite substrate for metal additive manufacturing. By incorporating an upper metal substrate with arrayed cavities filled with a first thermal insulation material, the heat conduction rate and local structural stiffness are reduced, enabling the substrate to possess controlled flexible deformation capabilities, thereby alleviating stress concentration caused by thermal expansion and contraction. Combined with a lower substrate composed of a second thermal insulation material, vertical heat conduction to the equipment platform is blocked, improving the temperature stability of the forming zone, extending the high-temperature holding time, and reducing the temperature gradient. The design of detachable upper and lower substrates that allow relative deformation further realizes stress relief during thermal cycling. This composite substrate, through the introduction of a thermal insulation layer, a split upper and lower structure, and deformable grooves, can simultaneously act from both thermal and mechanical control dimensions: the thermal insulation material reduces heat flow and mitigates the thermal gradient; the split structure and flexible grooves significantly reduce substrate stiffness, weaken mechanical constraints, and achieve stress relief. This thermo-mechanical synergistic control mechanism enables the composite substrate to effectively improve the temperature and stress field distribution in the deposition zone, reduce crack sensitivity, and improve the forming quality of difficult-to-weld alloys in various high-energy beam AM processes. This invention provides a new technical approach to metal additive manufacturing by achieving thermal management and flexible constraint through structured substrate design. The invention also offers the following advantages: (1) Effectively reduce the temperature gradient in the printing area, thereby reducing the accumulation of thermal stress and residual stress level from the source.

[0016] (2) A stable in-situ high-temperature softening environment is formed, so that the stress can be released continuously and naturally under high temperature conditions.

[0017] (3) Vertical array slots reduce the local stiffness of the metal substrate, achieve a controllable weak constraint effect, and significantly suppress crack generation.

[0018] (4) Significantly reduces the risk of material cracking and greatly improves the forming success rate of materials such as difficult-to-weld high-temperature alloys.

[0019] (5) Reduce heat loss, reduce the overall preheating requirements of the equipment and laser energy consumption, and achieve higher energy efficiency and energy saving and emission reduction.

[0020] (6) Reduce the thermal shock and mechanical load on the equipment during long-term high-temperature cycling, and significantly extend the service life of key components of LPBF. Attached Figure Description

[0021] Figure 1 This is a side view of the composite substrate assembly structure; Figure 2 This is a top view of the upper substrate, which has a circular cavity. Figure 3 This is a top view of the upper substrate, which has a rectangular cavity. Figure 4 A schematic diagram of a cellular structure with gaps; Figure 5 A schematic diagram of a hexagonal cellular structure; Figure 6 This is a schematic diagram of the heat insulation layer / heat insulation powder material on the upper substrate; Figure 7 This is a schematic diagram of the metal grooved substrate structure. Figure 8 This is a schematic diagram of the groove structure of the lower substrate heat insulation substrate; Figure 9 This is a three-dimensional schematic diagram of the composite substrate. Figure 10 This is a schematic diagram of the LPBF printing process for a conventional substrate; Figure 11 A schematic diagram of the LPBF printing process for designing a substrate; Figure 12 This is a schematic diagram showing the temperature history of the center of the upper surface of a conventional substrate and a designed substrate. Figure 13 This is a schematic diagram showing the temperature history of the center of the lower surface of a conventional substrate and a designed substrate. Figure 14 This is a schematic diagram comparing the temperature field changes during the printing process of conventional and designed substrates. Figure 15 This is a schematic diagram comparing the stress field changes during the printing process of conventional and designed substrates.

[0022] Among them, 1. upper substrate; 2. lower substrate; 3. cavity; 4. gap; 5. cellular structure; 6. first thermal material. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings: Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0024] See Figure 1 The first aspect of the present invention discloses a heat-insulating flexible composite substrate for metal additive manufacturing, comprising an upper substrate 1 and a lower substrate 2 that are detachably connected. The upper substrate 1 has cavities 3 or periodic cell structures 5 arranged in a horizontal and vertical array. The cavities 3 or gaps 4 penetrate the upper substrate 1 and are filled with a first heat-insulating material 6. The upper substrate 1 is a metal plate. The lower substrate 2 is a support structure made of a second heat-insulating material; The upper substrate 1 can deform or move relative to the lower substrate 2.

[0025] This invention provides a thermally insulated flexible composite substrate that improves the temperature and stress field distribution in the forming area through a thermo-mechanical synergistic regulation mechanism. Its core lies in reconstructing the traditional rigid integral substrate into an upper and lower split structure, and combining local stiffness adjustment and heat flow path control methods to achieve an adaptive response to the thermal expansion / contraction behavior during the printing process.

[0026] The upper substrate 1, serving as a platform directly supporting the formed part, is made of metal to ensure good thermal conductivity stability and structural strength. It contains cavities 3 or periodic cell structures 5 arranged regularly along the transverse and longitudinal directions. These structures penetrate the thickness direction of the upper substrate 1, forming through-holes or gaps 4, and are filled with a first thermal insulation material 6. These cavities or cell structures not only alter the continuity of the upper substrate and reduce local structural stiffness, giving it a certain elastic deformation capacity when heated, thus alleviating stress concentration caused by thermal expansion and contraction, but also, the filling first thermal insulation material further weakens the downward heat transfer, slowing down the heat flow rate in the vertical direction, helping to maintain a high and stable temperature environment in the forming area. The upper substrate 1 is a metal plate, which can be made of materials with sufficient thermal stability and mechanical strength, such as stainless steel, tool steel, titanium alloy, or nickel-based high-temperature alloy. The cavities 3 or gaps 4 are arranged in an array along the transverse and longitudinal directions. The cavity 3 or gap 4 is filled with a first heat-insulating material 6. The filling method can be completed by vibration compaction, vacuum injection or pre-embedding, etc., to ensure that the material is densely filled in the cavity and does not fall off. The lower substrate 2 is a support structure made of a second heat-insulating material. Its main function is to act as a heat flow blocking layer to prevent heat from being quickly dissipated from the upper substrate to the forming platform of the equipment.

[0027] join Figure 2 and Figure 3 In some embodiments of the present invention, the cross-section of the cavity 3 is rectangular, circular, elliptical, triangular, or other regular or irregular shapes. The selection of each cross-sectional shape needs to comprehensively consider processing feasibility, heat conduction suppression effect, and structural stability. It should be understood that the specific cross-sectional shape of the cavity 3 can be adjusted according to actual conditions.

[0028] In the above structure, the upper substrate 1 undertakes the forming task and provides controllable flexibility. Its internal cavity structure and filling material together realize local stiffness modulation and lateral / longitudinal thermal resistance improvement. The lower substrate 2 is used for vertical thermal isolation to build a stable high-temperature background environment. The detachable connection between the two enables the entire composite substrate to achieve stress relief during multiple rounds of thermal loading.

[0029] See Figure 4 and Figure 5 In some embodiments of the present invention, the cell structure 5 is a grid-like structure formed by an array of geometric units. The cell structure 5 refers to a porous or perforated structure with repeating geometric features arranged regularly in the transverse and longitudinal directions within the upper substrate 1, presenting an overall spatially periodically distributed grid shape. This structure, by constructing ordered void regions in the metallic material, increases the tortuosity of the heat flow path and weakens the vertical thermal conductivity without significantly sacrificing load-bearing capacity; simultaneously, it reduces the local structural stiffness, enabling the upper substrate to have a certain degree of deformation compliance when heated or cooled, thus alleviating stress concentration caused by temperature gradients.

[0030] Furthermore, the geometric units can be any closed or polygonal basic configuration, such as rectangular units, hexagonal honeycomb units, quadrilateral units, or other asymmetric units obtained through topology optimization. These units are arranged in an array with translational or rotational symmetry to form a macroscopically uniform yet microscopically heterogeneous structural feature. Mesh structures refer to connected networks formed by multiple interconnected or adjacent geometric units, which can be precisely formed on metal sheets using processes such as laser cutting, wire EDM, additive manufacturing, or micro-milling. It should be understood that the support wall thickness of the mesh can be adjusted according to actual conditions.

[0031] More preferably, the geometric unit has a hexagonal cross-section. The hexagonal grid cells simulate the honeycomb structure in nature, possessing high symmetry and an optimal areal density ratio, providing higher buckling strength and more uniform stress distribution with the same material usage. Its multi-directional load-bearing characteristics effectively alleviate stress accumulation in local hot spots, making it particularly suitable for additive manufacturing scenarios subjected to multi-directional thermal cycling loads. Furthermore, the hexagonal structure has continuous closed boundary connections, forming a stable mechanical network that helps maintain the overall planar stability of the upper substrate 1, preventing misalignment of the forming surface due to local collapse. This configuration can also maximize the filling area of ​​the thermal insulation material within a limited space, enhancing the lateral thermal barrier effect and slowing down the downward heat conduction rate.

[0032] In some embodiments of the present invention, the first heat insulation material 6 is any one or more of heat insulation powder, ceramic sheet or lightweight heat-resistant material.

[0033] The first thermal insulation material 6 can be made of thermal insulation powder, such as alumina, silica, or polycrystalline mullite fiber powder, which are inorganic powder materials with low thermal conductivity and good high-temperature stability. This type of material can fill the cavity 3 or gap 4 through vibration filling or airflow-assisted compaction, achieving seamless filling of complex geometric spaces, and is particularly suitable for cavity structures with irregular cross-sectional shapes or large depths. Due to the large number of micropores between the powder particles, multiple reflection and scattering paths are formed, significantly suppressing the heat conduction process. Simultaneously, it possesses a certain degree of compressive resilience during thermal expansion, allowing for minor local deformation and helping to release interfacial stress.

[0034] In addition, the first thermal insulation material 6 can also be made of ceramic sheets, such as sheet-like components made of zirconium oxide, boron nitride, or silicon carbide, with a thickness typically ranging from 0.1 to 2 mm. These sheets can be pre-cut to fit the cavity size before being embedded. Ceramic sheets possess excellent high-temperature resistance, chemical inertness, and mechanical integrity, and are not easily pulverized or degraded under long-term thermal cycling conditions, ensuring durable and reliable thermal insulation. Their planar structure also serves as a stress buffer layer, playing a sliding adjustment role during thermal expansion and contraction, reducing thermal mismatch stress between the metal matrix and the filler.

[0035] The lightweight thermally insulating material is an aerogel felt, porous ceramic block, foam glass, or microsphere-filled composite material, etc., which has both extremely low thermal conductivity and good flexibility, and its density is less than 1.0 g / cm³. 3 Thermal conductivity less than 0.5 W·m -1 ·K -1 It is used to block the downward heat transfer of the substrate and improve the heat preservation effect of the printing area.

[0036] The aforementioned materials can be used individually or combined to form a functionally graded structure, depending on the actual operating conditions. For example, high-temperature resistant ceramic sheets can be placed near the molten pool to resist instantaneous high-temperature impacts, while low-cost heat-insulating powder can be filled in the deeper cavities to extend the insulation time; alternatively, lightweight heat-insulating materials can be mixed with powder to form a graded insulation layer, balancing insulation efficiency and structural reliability. This multi-material synergistic design strategy enhances the applicability of the composite substrate to different material systems and different energy beam processes.

[0037] In some embodiments of the present invention, the second thermal insulation material is ceramic or has a thermal conductivity of less than 0.5 W·m. - ¹·K -¹ Composite materials. The second thermal insulation material can be a ceramic material, such as inorganic non-metallic materials like alumina, mullite, silicon nitride, or silicon carbide. These materials have high melting points, low thermal conductivity, good chemical inertness, and thermal shock resistance, enabling them to operate stably for extended periods in high-temperature additive manufacturing environments and preventing structural failure due to material decomposition or softening. Alternatively, the second thermal insulation material can also be a composite material with significantly lower thermal conductivity than metallic materials, such as ceramic-polymer composites, ceramic fiber-reinforced composites, porous ceramic matrix composites, or aerogel-reinforced matrix materials. These materials can meet the thermal insulation requirements under different process temperature windows by adjusting the component ratios.

[0038] In some embodiments of the present invention, a third thermal insulation material, such as thermal insulation cotton or aerogel, is disposed on the lower part of the lower substrate 2. An additional functional thermal insulation layer with extremely low thermal conductivity is disposed on the surface of the existing lower substrate 2, which is composed of a second thermal insulation material, facing away from the upper substrate 1. This third thermal insulation material directly contacts the forming platform or support structure of the additive manufacturing equipment, serving as the final stage of thermal barrier during the printing process, effectively reducing heat loss to external equipment components. The third thermal insulation material is either thermal insulation cotton or aerogel, both of which are typical low-density, porous thermal insulation materials with excellent thermal insulation performance and a certain degree of flexibility.

[0039] In some embodiments of the present invention, the upper substrate 1 and the lower substrate 2 are connected by a connecting structure, which allows the upper substrate 1 to move or deform relative to the lower substrate 2. This connection method ensures the stability and assembly reliability of the overall structure, while allowing for minute displacements or local deformations during thermal cycling, thereby effectively releasing thermal stress caused by temperature changes and avoiding interface damage or structural failure due to stress concentration.

[0040] Furthermore, the connection structure can be implemented in different ways according to actual working conditions. For example, the structure can adopt mechanical interlocking connections, such as mortise and tenon structures, snap-fit, or slots. These structures achieve positioning and connection through shape matching, while retaining a certain amount of clearance to accommodate dimensional changes caused by thermal expansion and contraction. Fastener connections, such as bolts, can also be used, with space reserved for pre-tightening force adjustment or elastic gaskets set during assembly, so that the connection nodes have a certain degree of flexibility and buffering capacity. In addition, adhesive connections can also be used, selecting high-temperature adhesives with a certain degree of elasticity, such as silicone rubber or ceramic-based composite adhesives, which can provide sufficient bonding strength and can withstand micro-strain under temperature fluctuations without cracking.

[0041] A second aspect of the present invention discloses a method for applying the above-mentioned heat-insulating flexible composite substrate for metal additive manufacturing, comprising the following steps: S1, providing a metal plate and a second heat insulation material, processing the metal plate into the designed shape of the upper substrate 1, and processing the second heat insulation material into the designed shape of the lower substrate 2; such as Figure 7 and Figure 8 As shown.

[0042] S2, the upper substrate 1 and the lower substrate 2 are connected by a connection structure that allows for slight thermal deformation of the upper substrate 1; as shown in the example. Figure 9 As shown.

[0043] S3, fill the upper substrate 1 with the first heat-insulating material 6 to obtain the heat-insulating flexible composite substrate; as shown Figure 6 As shown.

[0044] In this embodiment, Figure 6 The first heat insulation material 6 is directly processed and can be directly placed in the upper substrate 1 and bonded to the upper substrate 1.

[0045] S4, Place the heat-insulating flexible composite substrate on the forming platform of the LPBF equipment and level it; S5, metal powder is laid on the heat-insulating flexible composite substrate and printed layer by layer.

[0046] In section S1, a metal plate with sufficient thickness and rigidity is selected as the upper substrate material of the composite substrate to ensure stable and reliable heat transfer during the printing process. The bottom surface C0 of the printing area CAD is designed as a slightly smaller area C2, so that the printing area completely covers the center and avoids contact with the edges, while reserving space for the arrangement of the groove structure and the heat insulation unit. This design ensures controlled heating of the component forming area and avoids uneven temperature caused by heat dissipation from the edges.

[0047] For example, vertically arranged array grooves are machined in a regular pattern in the printing area of ​​the upper substrate 1. The groove depth is about 5-15 mm and the groove gap width is about 1-3 mm. The cross-sectional dimensions of the support columns are 1×1 to 3×3 mm. 2 The groove structure extends through the thickness of the upper plate, forming periodic flexible units and reducing the local structural stiffness.

[0048] For example, ceramic or low thermal conductivity composite materials are selected as the lower substrate 2. The horizontal dimension of the bottom insulation layer depends on the size of the PBF-LB / PBF-EB device or the molded part (DED-LB / EB), and the thickness can be set as needed. The insulation board, as an important structural layer for blocking heat flow, effectively improves the temperature stability of the printed area. For higher thermal insulation requirements, an insulation cotton or aerogel pad layer can be added to the bottom of the lower substrate to further enhance insulation capabilities and reduce temperature gradients.

[0049] In S2, the connection methods include mortise and tenon structure, bolt pre-tightening fit clearance design, snap / slot sliding connection, elastic adhesive or combination connection.

[0050] For example, the upper and lower parts of the substrate are connected using a trapezoidal tenon joint structure to firmly connect the two substrate parts. The connection interface is designed to allow for slight slippage or local deformation, enabling the composite substrate to release thermal stress appropriately during heating and cooling, thus preventing substrate warping or cracking. Simultaneously, it ensures the rigidity and stability of the overall structure, allowing it to withstand repeated thermal cycling loads during the LPBF process.

[0051] In S3, filling methods include vibration compaction, negative pressure suction, scraping and filling, or pre-placed prefabricated components to ensure that there are no obvious gaps or bridging phenomena in the cavity. The groove can be filled with heat-insulating powder, ceramic sheets, or lightweight heat-insulating materials to form a deformable structure, thereby enhancing the heat preservation effect and limiting the downward loss of heat.

[0052] In S4, a leveling operation is performed to ensure that the upper surface of the upper substrate 1 is parallel to the laser scanning plane, so as to ensure that the thickness of each powder layer is consistent and the scanning trajectory is accurate.

[0053] Specifically, the assembled composite substrate is fixed onto the forming platform of the LPBF equipment, and the flatness of the substrate is adjusted to ensure that the printing area on the upper plate is precisely coaxial with the scanning system of the equipment. The contact state between the substrate and the platform is adjusted to allow the heat insulation structure to function fully, while avoiding local suspension that could lead to vibration or forming defects.

[0054] Based on the material properties, process parameters such as laser power, scanning speed, scanning strategy, and layer thickness are set, and printing is performed layer by layer. During the printing process, the groove array structure of the upper plate and the heat insulation layer of the lower plate work together: the groove structure reduces the heat conduction path and allows local deformation to release stress, while the heat insulation layer maintains a high-temperature environment in the printing area and reduces the temperature gradient. Through the above structure-thermal coupling design, in-situ heat preservation and thermal stress relief in the forming area are achieved, thereby reducing forming cracks and improving component quality.

[0055] The following is an illustration using a specific example.

[0056] Taking LPBF technology in high-energy beam additive manufacturing as an example, and using the simulation of a typical TC11 titanium alloy material as an example, this paper compares the changes in temperature and stress fields of conventional substrates and designed substrates in LPBF, and explains how the present invention avoids cracking of parts in LPBF through a composite substrate with a split upper and lower structure, heat insulation configuration and controllable deformation groove.

[0057] The substrate size used in this study is 100×100×25mm. 3The groove depth is 10 mm, the groove gap width is 2 mm, the support column is 2×2 mm, and the bottom insulation layer has dimensions of 100×100×10 mm. 3 The grooves can be filled with insulating powder, ceramic flakes, or lightweight heat-resistant materials to enhance overall thermal insulation performance and inhibit heat conduction to the substrate. This groove array structure can generate slight elastic deformation under thermal stress cycling, achieving adaptive adjustment to thermal expansion and contraction, thereby reducing the mechanical constraint of the substrate on the formed part during printing. The upper and lower substrates are fixed to the LPBF forming platform by bolts and trapezoidal tenon joints, ensuring structural stability and good thermal insulation. The printed part size is 60×60×10 mm. 3 The specific printing process parameters are as follows: fiber laser power 230 W, scanning speed 1250 mm / s, layer thickness 40 μm, scanning spacing 110 μm, and spot diameter 100 μm. The simulation part uses an equivalent layer-by-layer activation strategy for thermal-stress field coupling calculations. Figure 10 and Figure 11 Schematic structures of conventional substrates and designed composite substrates during the LPBF process are given respectively.

[0058] During the printing process, the groove array structure of the upper substrate can absorb and mitigate the local deformation caused by thermal expansion, while the heat insulation plate of the lower substrate effectively blocks the conduction of heat to the platform, keeping the forming area at a high temperature and achieving in-situ heat preservation. Figure 12 and Figure 13 Simulation results of the temperature changes over time at the center of the upper and lower surfaces of a conventional substrate and a design substrate are presented. Looking at the upper surface temperature, the temperature change trends of the two substrates are basically the same, but the design substrate maintains a slightly higher temperature level throughout. However, the temperature changes at the center of the lower surface show significant differences: the conventional substrate experiences drastic temperature fluctuations and rapid heat dissipation during printing, while the heat-insulating substrate achieves a greater temperature rise and significantly prolongs the high-temperature holding time. Figure 14 and Figure 15 The temperature and stress field distributions of the two types of substrates were further compared. Conventional substrates exhibit a larger overall temperature gradient, making it difficult to maintain high temperatures in the printing area, leading to significant thermal stress concentration. In contrast, the designed substrate allows heat to be more concentrated near the forming area, resulting in higher temperature peaks and a wider high-temperature zone. This is mainly because the heat insulation plate and groove structure together weaken downward heat conduction, significantly increasing the temperature at the bottom of the component. Conversely, conventional substrates dissipate heat too quickly, causing the high-temperature zone to shrink and the temperature gradient to increase. The stress field comparison results also show that using a heat-insulated substrate significantly reduces stress concentration within the component. The heat-insulating structure effectively suppresses the formation and accumulation of residual stress by increasing the overall forming temperature, smoothing the temperature gradient, and improving the thermal cycling process, thereby reducing the risk of thermal cracking.

[0059] This invention proposes a thermally insulated deformable composite substrate for high-energy beam additive manufacturing, consisting of an upper substrate metal plate and a lower substrate heat insulation plate. Through the synergistic effect of "thermal conduction regulation and structural flexibility design," it effectively suppresses the accumulation of residual stress and cracking of difficult-to-weld alloys during the printing process. Vertical array grooves extending along the thickness direction are arranged in the upper metal plate, and these grooves can be filled with low thermal conductivity materials such as thermal insulation powder, ceramic flakes, or aerogel felt. The array grooves reduce the local structural stiffness of the metal plate, enabling controlled flexible deformation of the substrate during thermal expansion and contraction, thereby improving the deformation coordination with the formed part. Furthermore, the filling with heat insulation material weakens heat flow transfer and mitigates temperature gradient changes. The lower substrate heat insulation plate uses low thermal conductivity ceramics, foam insulation layers, or composite structures, or can be replaced by laying heat insulation cotton at the bottom of the platform. Its core function is to block vertical heat conduction, achieving in-situ insulation of the printing area and avoiding high temperature gradients caused by rapid heat dissipation. Meanwhile, the split-type structure further reduces the mechanical constraint of the substrate on the deposited layer, helping to alleviate uneven shrinkage during thermal cycling. Based on the aforementioned thermal coupling design, the substrate can achieve long-term heat preservation and thermal stress relief in the forming area, thereby effectively reducing cracks and improving component forming quality. By reducing the thermal gradient in the forming area, adjusting the substrate structural stiffness, and providing an in-situ high-temperature softening effect, residual stress accumulation and thermal cracking are effectively suppressed. This substrate achieves in-situ temperature control and reduces the mechanical constraint of the substrate during additive manufacturing during LPBF, thus effectively preventing component cracking. In summary, the introduction of the thermally insulated substrate design effectively blocks downward heat conduction, allowing the designed substrate to maintain a higher temperature during printing and extending the high-temperature duration during the cooling phase. This helps reduce the temperature gradient and thermal stress level, thereby effectively improving component quality and reducing cracks. It has significant engineering value and application significance in high-energy beam additive manufacturing.

[0060] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, "above" or "below" a second feature may include direct contact between the first and second features, or it may include contact between the first and second features not being in direct contact but through another feature between them.

[0061] In the description of this invention, the terms "above," "over," and "on top" for the first feature and the second feature include the first feature being directly above or diagonally above the second feature, or simply indicating that the first feature is at a higher horizontal level than the second feature.

[0062] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0063] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0064] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A thermally insulating flexible composite substrate for metal additive manufacturing, characterized in that, It includes a detachably connected upper substrate (1) and lower substrate (2); The upper substrate (1) has cavities (3) or periodic cell structures (5) arranged in a horizontal and vertical array. The cavities (3) or gaps (4) penetrate the upper substrate (1) and are filled with a first heat-insulating material (6). The upper substrate (1) is a metal plate. The lower substrate (2) is a support structure made of a second heat-insulating material; The upper substrate (1) can deform or move relative to the lower substrate (2).

2. The thermally insulating flexible composite substrate for metal additive manufacturing according to claim 1, characterized in that, The cross-section of the cavity (3) is rectangular, circular, elliptical or triangular.

3. The thermally insulating flexible composite substrate for metal additive manufacturing according to claim 1, characterized in that, The cell structure (5) is a grid-like structure formed by arrayed geometric units.

4. The thermally insulating flexible composite substrate for metal additive manufacturing according to claim 3, characterized in that, The cross-section of the grid in the cell structure (5) is rectangular, quadrilateral or hexagonal.

5. A thermally insulating flexible composite substrate for metal additive manufacturing according to claim 1, characterized in that, The first heat insulation material (6) is any one or more of heat insulation powder, ceramic flakes, or lightweight heat-insulating materials, wherein the density of the lightweight heat-insulating material is less than 1.0 g / cm³. 3 Thermal conductivity less than 0.5 W·m -1 ·K -1 .

6. The thermally insulating flexible composite substrate for metal additive manufacturing according to claim 1, characterized in that, The second thermal insulation material is ceramic or has a thermal conductivity of less than 0.5 W·m. - ¹·K - ¹ Composite materials.

7. A thermally insulating flexible composite substrate for metal additive manufacturing according to claim 1, characterized in that, The lower part of the lower substrate (2) is provided with a third heat insulation material, which is heat insulation cotton or aerogel.

8. The thermally insulating flexible composite substrate for metal additive manufacturing according to claim 1, characterized in that, The upper substrate (1) and the lower substrate (2) are connected by a connection structure, which enables the upper substrate (1) to move or deform relative to the lower substrate (2).

9. A thermally insulating flexible composite substrate for metal additive manufacturing according to claim 8, characterized in that, The connection structure can be a mortise and tenon joint, bolt, snap fastener, slot, or adhesive.

10. A method for applying the thermally insulating flexible composite substrate for metal additive manufacturing as described in claim 1, characterized in that, Includes the following steps: S1, providing a metal plate and a second heat insulation material, processing the metal plate into the shape of the designed upper substrate (1), and processing the second heat insulation material into the shape of the designed lower substrate (2); S2, the upper substrate (1) and the lower substrate (2) are connected by a connection structure that allows for slight thermal deformation of the upper substrate (1); S3, fill the upper substrate (1) with the first heat insulation material (6) to obtain the heat insulation flexible composite substrate; S4, Place the heat-insulating flexible composite substrate on the forming platform of the LPBF equipment and level it; S5, metal powder is laid on the heat-insulating flexible composite substrate and printed layer by layer.

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