Method for multi-dimensional uniform deformation of micro-nano structure

Abstract

The invention discloses a method for multi-dimensional uniform deformation of a micro-nano structure, belongs to the technical field of advanced material processing and manufacturing, and solves the problems of product structure distortion and out-of-control precision of a nano-scale structure caused by low shrinkage rate and non-uniform sintering process densification in the prior art. The method comprises the following steps: uniformly mixing matrix powder, an activator and a morphology stabilizer to obtain a mixture, and carrying out micro-injection molding on the mixture to obtain a pre-amplified micro-nano structure; performing segmented degreasing on the pre-amplified micro-nano structure, performing gradient sintering, and performing hot isostatic pressing treatment to obtain a multi-dimensional uniformly-deformed micro-nano structure; wherein the matrix powder comprises metal powder and / or ceramic powder, the activating agent is eutectic alloy with the melting point smaller than or equal to 200 DEG C, and the morphology stabilizing agent is rare earth metal oxide and / or transition metal oxide. The invention has the advantages of high shrinkage rate, uniform shrinkage and high mechanical strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of advanced material processing and manufacturing technology, in particular to a method for multi-dimensional uniform deformation of micro-nano structures. BACKGROUND

[0002] Powder metallurgy is a traditional process for manufacturing parts by compacting and sintering metal or ceramic powders. However, in the field of micro-nano scale manufacturing, this process faces severe challenges and cannot meet the stringent requirements of high-precision structures for shape fidelity and performance consistency.

[0003] Firstly, the sintering shrinkage rate of traditional powder metallurgy process is generally low (usually <20%), which cannot achieve high magnification and uniform reduction from macroscopic preform to micro-nano feature size. This leads to loss of dimensional accuracy when manufacturing micro-nano structures, severely limiting their application in micro-electro-mechanical systems (MEMS), micro medical devices, etc.

[0004] Secondly, due to factors such as uneven powder packing density, anisotropy of sintering driving force, and uncontrolled grain boundary migration, non-uniform densification occurs during sintering, causing significant structural distortion with anisotropic shrinkage deviation usually >5%. This distortion can directly lead to problems such as failure of micro-gear meshing, blockage of micro-channels, or drift of sensor signals.

[0005] In recent years, although methods combining additive manufacturing (such as 3D printing) with sintering technology have emerged for shaping complex three-dimensional structures, there are still fundamental defects at the micro-nano scale: ① The printing resolution limit and sintering shrinkage superposition make it extremely difficult to control nanoscale precision; ② Abnormal grain coarsening and increased interface defects (pores, micro-cracks) during high-temperature sintering severely degrade the mechanical properties of the structure.

[0006] Therefore, existing powder metallurgy and additive manufacturing-sintering technologies still cannot break through the multiple technical bottlenecks of low shrinkage, high uniformity, and nanoscale precision control, and there is an urgent need to develop a new high-precision manufacturing method that can achieve multi-dimensional uniform deformation of micro-nano structures. SUMMARY

[0007] In view of the above, the present application aims to provide a method for multi-dimensional uniform deformation of micro-nano structures, which at least solves one of the following problems: (1) the traditional powder metallurgy process cannot achieve more than 50% ultra-high magnification uniform reduction due to low shrinkage rate and non-uniform densification during sintering process, leading to structural distortion; (2) the thermal decomposition of the polymer matrix is contaminated by the shrinkage of the polymer in the traditional powder metallurgy process, and the large loss of the polymer will cause structural shrinkage or even collapse, affecting the dimensional accuracy and structural integrity of the product; (3) the existing 3D printing combined with sintering technology has precision loss control, grain coarsening, and interface defects at the nanoscale.

[0008] The object of the present application is mainly achieved by the following technical solutions.

[0009] The first aspect of the present application provides a method for uniform deformation of micro-nano structures in multiple dimensions, the method comprising:

[0010] S1, uniformly mixing a base powder, an activator and a morphology stabilizer to obtain a mixture, and micro-injection molding the mixture to obtain a pre-amplified micro-nano structure;

[0011] S2, after segmenting and debinding the pre-amplified micro-nano structure, performing gradient sintering and hot isostatic pressing treatment to obtain a micro-nano structure with uniform deformation in multiple dimensions;

[0012] The base powder includes metal powder and / or ceramic powder, the activator is a eutectic alloy with a melting point ≤200℃, and the morphology stabilizer is a rare earth metal oxide and / or a transition metal oxide.

[0013] Further, in step S1, the content of the base powder in the mixture is 88-94wt%, the content of the activator is 3-8wt%, and the content of the morphology stabilizer is 1-5wt%.

[0014] Further, the base powder includes large-size powder and small-size powder, the average particle size of the large-size powder is 120-200nm, and the average particle size of the small-size powder is <120nm.

[0015] Further, the large-size powder accounts for 70-80% of the total mass of the base powder, and the small-size powder accounts for 20-30% of the total mass of the base powder.

[0016] Further, the metal powder is selected from stainless steel powder, noble metal powder or transition metal powder.

[0017] Further, the ceramic powder is selected from at least one of Al2O3, SiC, Si3N4 and SiO2.

[0018] Further, the average particle size of the base powder is 50-200nm.

[0019] Further, the eutectic alloy is selected from a eutectic Sn-Bi alloy or a eutectic In-Bi alloy.

[0020] Further, the average particle size of the eutectic alloy is ≤100nm.

[0021] Further, the morphology stabilizer is selected from at least one of Y2O3, ZrO2, CeO2 and La2O3.

[0022] Further, the morphology stabilizer has an average particle size of 20-50 nm.

[0023] Further, in the step S2, the segmental debinding includes a first debinding and a second debinding.

[0024] Further, the first debinding is performed at a temperature of 200-350 DEG C for 0.5-2 h.

[0025] Further, the second debinding is performed at a temperature of 400-500 DEG C for 0.5-2 h.

[0026] Further, the gradient sintering includes a first sintering, a second sintering and a third sintering.

[0027] Further, the first sintering is performed at a temperature of 600-800 DEG C for 1-3 h.

[0028] Further, the second sintering is performed at a temperature of 850-950 DEG C for 1-2 h.

[0029] Further, the third sintering is performed at a temperature of 1050-1200 DEG C for 1-2 h.

[0030] Further, the ratio of the holding time of the first sintering to the holding time of the second sintering plus the holding time of the third sintering is 0.2-0.8.

[0031] Further, in the step S2, the hot isostatic pressing is performed at a temperature of 800-1200 DEG C under a pressure of 100-200 MPa for 2-4 h in the presence of a protective gas.

[0032] The second aspect of the present application provides a micro-nano structure prepared by the method of the first aspect.

[0033] The third aspect of the present application provides an application of the micro-nano structure of the second aspect in electronic structures or aerospace materials.

[0034] Compared with the prior art, the present application can achieve at least one of the following beneficial effects:

[0035] (1) The present application avoids the anisotropic deviation caused by the thermal shrinkage of the polymer binder in the matrix powder by the segmental debinding process, directly obtains a high-density metal / ceramic product, avoids the pollution caused by the thermal decomposition of the polymer matrix, and avoids the structural shrinkage or even collapse caused by the large loss of the polymer, which affects the size accuracy and structural integrity of the product. The anisotropic deviation of the product obtained by the method is not greater than 3.5%, and can be as low as 1% or less.

[0036] (2) The present application realizes ultra-high magnification, high precision, and multi-dimensional uniform deformation from a macroscopic preform to a micro-nano final product by utilizing the synergistic effect among the base powder, the activator, and the morphology stabilizer, specifically, taking the nano bimodal base powder as the basis, relying on the nano activator of eutectic composition to provide strong and uniform densification power in the medium temperature range, and simultaneously applying precise grain boundary pinning control in the high temperature range with the help of the nano morphology stabilizer, the three functions are mutually restricted and complementary, and the ultra-high magnification, high precision, and multi-dimensional uniform deformation from a macroscopic preform to a micro-nano final product are realized, while ensuring that the anisotropy deviation is not more than 3.5%, the shrinkage is more than 50%, and the micro-nano structure bending strength is reduced due to grain coarsening.

[0037] (3) The method of the present application can realize ultra-high shrinkage uniform deformation (more than 50%) while ensuring that the bending strength is more than 820 MPa (up to 1350 MPa), the fracture toughness is as high as 12.8 MPa·m1 / 2, the raw material utilization rate is high, and high-cost materials such as photocuring resin are not needed, thereby realizing low-cost and large-scale production.

[0038] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and attained by means of the instrumentalities particularly pointed out in the written description and the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0039] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principles of the application.

[0040] Figure 1 Three-dimensional morphology reconstruction map of the structure prepared for Example 1. DETAILED DESCRIPTION

[0041] The preferred embodiments of the present application will be specifically described below in conjunction with the drawings, wherein the drawings constitute a part of the present application and are used to illustrate the principles of the embodiments of the present application.

[0042] The traditional powder metallurgy process is difficult to realize ultra-high magnification uniform reduction (more than 50%) due to low shrinkage (usually <20%) and sintering densification distortion (anisotropy deviation >5%), and the existing 3D printing combined with sintering technology faces the bottleneck of nano-scale precision loss of control, grain coarsening, and interface defects, which seriously restricts the performance of high-precision metal / ceramic micro-structure.

[0043] Therefore, the first aspect of the present application provides a method for uniform deformation of micro-nano structures in multiple dimensions, the method comprising:

[0044] S1, uniformly mixing a base powder, an activator and a morphology stabilizer to obtain a mixture, and micro-injection molding the mixture to obtain a pre-amplified micro-nano structure;

[0045] S2, after segmenting and debinding the pre-amplified micro-nano structure, performing gradient activation sintering and hot isostatic pressing to obtain a micro-nano structure with uniform deformation in multiple dimensions;

[0046] The base powder includes metal powder and / or ceramic powder, the activator is a eutectic alloy with a melting point of ≤200℃, and the morphology stabilizer is a rare earth metal oxide and / or a transition metal oxide.

[0047] In the present application, the activator is selected from a eutectic alloy with a melting point of not more than 200℃, which can realize low-temperature melting and ensure mixing with the base powder and the morphology stabilizer in the molten state, and penetrate into the gaps between the base powder particles through capillary force, dissolve the surface oxides of the base powder, form atomic diffusion channels, and more easily penetrate into the grain boundaries of the base powder, so that the subsequent sintering is carried out at a lower temperature, which is beneficial to realize uniform shrinkage while ensuring high shrinkage rate and reducing anisotropy deviation.

[0048] In the present application, the morphology stabilizer is selected from a rare earth metal oxide and / or a transition metal oxide, which can avoid hindering the subsequent sintering process, and avoid grain coarsening to reduce the bending strength of the micro-nano structure.

[0049] According to the present application, in step S1, the content of the base powder in the mixture is 88-94wt%, the content of the activator is 3-8wt%, and the content of the morphology stabilizer is 1-5wt%.

[0050] In the present application, if the content of the base powder in the mixture is greater than 94wt%, a continuous network cannot be formed, the subsequent sintering will mainly be slow solid-state diffusion, resulting in a significant reduction in shrinkage rate and the inability to achieve more than 50% ultra-high magnification reduction, and if it is less than 88wt%, the liquid phase formed by the activator will generate a huge capillary force on the base powder skeleton, causing the base powder blank to soften, deform or even collapse under its own gravity. Illustratively, the content of the base powder is 88wt%, 89wt%, 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, and a range composed of any two of the above values.

[0051] In the present application, if the content of the activator in the mixture is less than 3wt%, isolated molten droplets will be formed between the powder particles of the activator, which is not continuous enough, resulting in uneven bonding between the particles and uneven capillary force effect during the subsequent sintering process, ultimately leading to uneven local densification, causing different shrinkage rates in different regions, resulting in uneven overall size of the micro-nano structure, and even cracks. If it is greater than 8wt%, the excess molten liquid phase will form a thick liquid layer at the grain boundary, causing the grain boundary strength to collapse at high sintering temperature, resulting in incomplete subsequent sintering, forming too many pores and defects, affecting the densification degree of the micro-nano structure, and the overall shape of the green body collapses and deforms, the liquid phase is pumped to the surface to cause composition segregation and internal pores, and the grain boundary forms a continuous brittle film after cooling, resulting in a sharp drop in product toughness. Therefore, the content range is a technical key to achieving high uniformity shrinkage.

[0052] Exemplarily, the content of the activator can be 3wt%, 3.2wt%, 3.5wt%, 3.6wt%, 3.8wt%, 4wt%, 4.5wt%, 4.8wt%, 5wt%, 5.5wt%, 6wt%, 6.8wt%, 7wt%, 7.5wt%, 8wt%, and a range composed of any two of the above values.

[0053] In the present application, if the content of the morphology stabilizer in the mixture is less than 1wt%, it is not enough to provide effective grain boundary pinning force, and it cannot inhibit the abnormal growth of the grains at high temperature, which will lead to the size of the powder grains in the mixture being too large, grain coarsening, incomplete sintering densification, and the formation of more pores, and also reducing the hardness of the micro-nano structure; if it is greater than 5wt%, it will lead to: 1, the formation of a brittle phase, the product cracks, and the fracture toughness and impact resistance drop sharply; 2, the formation of a high-melting-point rigid skeleton, which seriously hinders the sintering densification process, resulting in a significant decrease in the relative density of the product; 3, the hard particle agglomerates become stress concentration points, accelerating fatigue failure. All of the above will cause the mechanical properties of the product to deteriorate comprehensively, and cannot meet the use requirements.

[0054] Exemplarily, the content of the morphology stabilizer can be 1wt%, 1.5wt%, 2wt%, 3wt%, 3.2wt%, 3.5wt%, 3.6wt%, 3.8wt%, 4wt%, 4.5wt%, 4.8wt%, 5wt%, and a range composed of any two of the above values.

[0055] According to some embodiments of the present application, in the base powder including large-size powder and small-size powder, the average particle size of the large-size powder is 120-200 nm, and the average particle size of the small-size powder is < 120 nm, preferably 120 nm > average particle size ≥ 50 nm, wherein the large-size powder accounts for 70-80% of the total mass of the base powder, for example 70%, 72%, 75%, 76%, 78%, 80%, and the small-size powder accounts for 20-30% of the total mass of the base powder, for example 20%, 22%, 25%, 26%, 28%, 30%.

[0056] In the present application, the average particle sizes and contents of the small-size powder and the large-size powder meet the above ranges respectively, which can achieve a bimodal distribution, fill the gaps of the large-size powder with the small-size powder, improve the density of the green body, and at the same time, increase the specific surface area of the green body, so as to improve the sintering driving force, make the sintering efficiency higher, and reduce the sintering cost, thereby improving the shrinkage rate of the structure and reducing the pore size. In the present application, it can be understood that the green body refers to the pre-amplified micro-nano structure obtained after micro-injection molding, which has not been subjected to debinding and sintering. If the average particle size of the small-size powder is less than 20 nm, agglomeration is easy to occur, which leads to uneven mixing. During sintering, the agglomerated particles are preferentially densified, which causes uneven local shrinkage, induces micro-cracks or pores, and reduces the mechanical properties of the final product. If the average particle size of the large-size powder is greater than 200 nm, the contact area between the particles is reduced, the diffusion path is lengthened, and the sintering densification driving force is insufficient, which reduces the uniform shrinkage rate. Exemplarily, the average particle size of the large-size powder is 120 nm, 125 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, and a range formed by any two of the above values. The average particle size of the small-size powder is 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 115 nm, and a range formed by any two of the above values.

[0057] According to some embodiments of the present application, considering the need for excellent mechanical strength of the micro-nano structure, the metal powder is selected from stainless steel powder, noble metal powder or transition metal powder, and the ceramic powder is selected from at least one of Al2O3, SiC, Si3N4 and SiO2.

[0058] According to some embodiments of the present application, the eutectic alloy is selected from a eutectic Sn-Bi alloy or a eutectic In-Bi alloy.

[0059] In the present application, the eutectic alloy is selected from eutectic Sn-Bi alloy or eutectic In-Bi alloy, on the one hand, because the melting point is not greater than 200℃, a low melting point liquid phase can be formed in the sintering process, thereby reducing the sintering temperature, helping to reduce the energy consumption cost in the sintering process, and at the same time avoiding the performance decline of the micro-nano structure due to high-temperature sintering, reducing the uniformity of shrinkage, and at the same time improving the activity in the sintering process, promoting the diffusion and combination between the powder particles, on the other hand, the Sn-Bi eutectic alloy or the In-Bi eutectic alloy can dissolve the surface oxides of the matrix powder, and compared with the traditional activator (such as Cu-P alloy), the eutectic Sn-Bi alloy or the eutectic In-Bi alloy has a small wetting angle in the molten state, and is more easily penetrated into the grain boundary of the matrix powder to form an atomic diffusion channel to realize uniform shrinkage, thereby significantly improving the shrinkage rate of the micro-nano structure and reducing the anisotropy deviation.

[0060] According to some embodiments of the present application, the average particle size of the eutectic alloy is ≤100 nm, and if it is greater than 100 nm, it will cause local sintering to be unevenly present, some areas are over-sintered, and some areas are insufficiently sintered, forming pores and cracks, which affects the hardness of the micro-nano structure. Preferably, the average particle size of the activator is 20-100 nm. Exemplarily, the average particle size of the activator can be 20 nm, 25 nm, 30 nm, 40 nm, 50 nm, 55 nm, 60 nm, 68 nm, 70 nm, 75 nm, 80 nm, 90 nm, 100 nm, and a range composed of any two of the above values.

[0061] According to some embodiments of the present application, considering the reasons for improving the hardness and density of the micro-nano structure, the morphology stabilizer is selected from at least one of Y2O3, ZrO2, CeO2 and La2O3.

[0062] According to a particularly preferred embodiment of the present application, the morphology stabilizer is preferably a combination of zirconium dioxide and rare earth metal oxide. In this way, the composite stabilizing mechanism of the morphology stabilizer can be played, specifically, the rare earth metal oxide plays a grain boundary pinning effect to prevent grain boundary migration, ensure the micro-morphology of the structure, and improve the hardness, and at the same time, the zirconium dioxide improves the toughness of the micro-nano structure through phase transformation toughening, and the synergistic effect of the two can help to form Y-Al-O precipitates, effectively hinder the growth of the grains, thereby refining the grain size and improving the toughness and hardness of the micro-nano structure.

[0063] According to some embodiments of the present application, the average particle size of the morphology stabilizer is 20-50 nm, for example, 20 nm, 22 nm, 25 nm, 30 nm, 35 nm, 38 nm, 40 nm, 42 nm, 45 nm, 48 nm, 50 nm.

[0064] In the present application, the inventors found that the average particle size of the morphology stabilizer has an important influence on the final density of the micro-nano structure, specifically, if the average particle size of the morphology stabilizer is less than 20 nm, the production cost is relatively high, at the same time, it is difficult to disperse, and additional process steps are needed to prevent agglomeration, if it exceeds 50 nm, it will cause the interface between the particles to be not firm, forming interface defects, reducing the strength and toughness of the material, leading to uneven local densification during sintering, forming pores and cracks.

[0065] In the present application, the base powder, activator and morphology stabilizer synergistically improve the comprehensive performance of the final micro-nano structure, specifically: the base powder is bimodal distribution, the small size powder fills the gap of the large size powder, improves the density of the base powder, thereby improving the density of the green body, at the same time, the specific surface area of the green body is increased, the sintering driving force is significantly enhanced, and the high density of the base powder provides a basis for the uniform distribution and penetration of the activator, at the same time, the addition of the morphology stabilizer further inhibits grain growth, ensuring the uniformity of the sintering process and the high density of the final micro-nano structure. The low-temperature molten state of the activator enhances the capillary force, further accelerating the sintering process and improving the sintering efficiency, the morphology stabilizer significantly improves the fracture toughness of the material through grain boundary pinning and phase transformation toughening mechanism, at the same time, it inhibits grain growth, ensuring high strength and high toughness of the material.

[0066] According to the present application, in step S2, the segmented debinding includes first debinding and second debinding.

[0067] In the present application, it can be understood that, in order to improve the processing performance and forming performance, a binder (such as polypropylene (PP), polyethylene (PE), polyoxymethylene (POM)) and a lubricant (such as paraffin wax and the like) are usually added to the base powder, and because the binder and the lubricant are easy to leave carbon impurities during sintering, these impurities will affect the purity and performance of the final product, in order to improve the subsequent sintering efficiency, reduce the impurities and porosity during sintering, and optimize the microstructure of the sintered body, the present application preferably adopts the segmented debinding mode to remove the binder and the lubricant, which can accurately and safely remove the polymer, avoid defects such as collapse and deformation, and thus obtain a pure powder sintered skeleton.

[0068] For example, the addition amount of the binder and the lubricant is the conventional amount in the art, for example, in the present application, the addition amount of the binder is 15-25% of the mixture, for example, 15%, 18%, 20%, 22%, 24%, 25%, and the addition amount of the lubricant is 60-70% of the mixture, for example, 60%, 62%, 65%, 68%, 70%.

[0069] According to an embodiment of the present application, the first debinding condition comprises: temperature of 200-350℃, for example, 200℃, 210℃, 250℃, 260℃, 280℃, 300℃, 320℃, 350℃, time of 0.5-2h, for example, 0.5h, 0.6h, 0.8h, 1h, 1.2h, 1.5h, 2h, the second debinding condition comprises: temperature of 400-500℃, for example, 400℃, 420℃, 450℃, 480℃, 500℃, time of 0.5-2h, for example, 0.5h, 0.6h, 0.8h, 1h, 1.2h, 1.5h, 2h.

[0070] In the present application, the first debinding condition meets the above range, which can effectively remove the binder, and the second debinding condition meets the above range, which can effectively remove the lubricant. In this way, the content of the binder and the lubricant in the mixture can be further reduced, and the performance of the micro-nano structure can be ensured.

[0071] According to an embodiment of the present application, the first sintering condition comprises: temperature of 600-800℃, for example, 600℃, 620℃, 650℃, 660℃, 680℃, 700℃, 720℃, 750℃, 800℃, holding time of 1-3h, for example, 0.5h, 0.6h, 0.8h, 1h, 1.2h, 1.5h, 2h, 2.5h, 3h, the second sintering condition comprises: temperature of 850-950℃, for example, 850℃, 860℃, 880℃, 900℃, 920℃, 950℃, holding time of 1-2h, for example, 1h, 1.2h, 1.5h, 2h, and the third sintering condition comprises: temperature of 1050-1200℃, for example, 1050℃, 1100℃, 1150℃, 1200℃, holding time of 1-2h, for example, 1h, 1.2h, 1.5h, 2h.

[0072] In the present application, the above three sintering conditions synergize with each other, the first sintering temperature is lower than the melting point of the activator, which can make the surface diffusion and recombination of the matrix powder, eliminate stress, and avoid the problem of low and uneven shrinkage caused by rapid rising to a higher temperature, the second sintering temperature makes the activator melt to form a liquid phase to fill the grain boundary and promote volume shrinkage, which provides a basis for uniform shrinkage of the subsequent micro-nano structure, realizes efficient densification of the main body shrinkage, and provides a high-density green body, and the third sintering temperature sintering the matrix powder, the morphology stabilizer ensures the micro stability of the product by inhibiting grain growth, finally densifies, inhibits grain growth, and improves the hardness and shrinkage rate of the micro-nano structure.

[0073] According to an embodiment of the present application, the holding time of the first sintering / (the holding time of the second sintering + the holding time of the third sintering) is 0.2-0.8. Exemplarily, the holding time of the first sintering / (the holding time of the second sintering + the holding time of the third sintering) is 0.2, 0.3, 0.4, 0.45, 0.5, 0.6, 0.7, 0.75, 0.8, and a range formed by any two of the above values, and preferably 0.4-0.8.

[0074] It should be noted that, by limiting the ratio of the holding time of the first sintering to the holding time of the second sintering + the holding time of the third sintering in the gradient sintering process to 0.2-0.8, the present application ensures the sufficiency of low-temperature surface diffusion, provides a uniform and stress-free reaction basis for subsequent liquid-phase densification, and at the same time avoids grain coarsening at high temperature and energy waste. This specific time ratio is a key process parameter for realizing ultra-high uniform shrinkage (anisotropy deviation < 3.5%) and high performance of micro-nano structures. Deviation from this ratio will result in defects such as structural distortion, insufficient densification, or grain coarsening.

[0075] According to an embodiment of the present application, in step S2, the conditions of the hot isostatic pressing treatment include: in the presence of a protective gas, the treatment temperature is 800-1200℃, for example, 800℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, the treatment pressure is 100-200MPa, for example, 100MPa, 105MPa, 110MPa, 120MPa, 150MPa, 180MPa, 200MPa, and the treatment temperature is 2-4h, for example, 2h, 2.5h, 3h, 3.5h, 4h.

[0076] In the present application, it can be understood that the protective gas is N2 or an inert gas, and preferably argon.

[0077] In the present application, the temperature and pressure of the hot isostatic pressing treatment meet the above ranges, which can significantly improve the density of the micro-nano structure and increase the shrinkage rate.

[0078] In the present application, it can be understood that the shrinkage rate meets the following equation:

[0079]

[0080] wherein γ sv is the solid-gas surface energy of the matrix powder, and the value range is 1.0-3.0J / m 2 ; d is the characteristic particle size of the matrix powder, in nm; V 活化is the volume fraction of activator; β is the liquid phase shrinkage coefficient, and the value range is 0.18-0.25; Q is the sintering activation energy, and the value range is 120000-280000 J / mol; t is the isothermal sintering time, and the value range is 1800-7200 s; R is the gas constant, and the value is 8.314 J / (mol·K); T is the absolute sintering temperature, and the value range is 1373-1473 K; e is the natural constant, and the value is 2.71828; K is the system comprehensive constant, and the value range is 0.18-0.25.

[0081] Wherein, the liquid phase shrinkage coefficient β is obtained based on the following formula:

[0082]

[0083] In the application, the shrinkage rate compensation coefficient is based on the matrix powder particle size distribution d50 and the volume fraction V of activator 活化 Dynamic optimization:

[0084] Sdesign=[1+0.25ln(d50 / 100)+0.15V 活化 ]×Strget.

[0085] Wherein, Sdesign is the design size of micro-nano structure, and Starget is the target size.

[0086] It can be understood that the design size is the size of the micro-nano structure before shrinkage, that is, the size of the pre-magnified micro-nano structure, and the target size refers to the size of the structure after shrinkage.

[0087] The second aspect of the application provides a micro-nano structure prepared by the method of the first aspect.

[0088] In the application, the shrinkage rate of the micro-nano structure is not less than 55%, the relative density is not less than 90%, the grain size is ≤500 nm, and the micro-nano structure has excellent shrinkage uniformity, and the three-axis shrinkage rate deviation of the micro-nano structure is not more than 1.5% through three-dimensional scanning test.

[0089] The third aspect of the application provides an application of the micro-nano structure of the second aspect in electronic structure or aerospace material.

[0090] The following specific examples and comparative examples are used to show the advantages of accurate control of parameters in the application.

[0091] In the following examples, the shrinkage rate is calculated according to the following formula:

[0092] Wherein, AL is the difference of size change before and after sintering, L0 is the size before sintering, wherein the size refers to the diameter of the graduation circle, each sample is measured 5 times to take the average value, and the optical three-dimensional topography method is used to measure.

[0093] The anisotropic deviation is measured by the following method: first, the optical three-dimensional topography is used to measure the sintered body in X, Y and Z three perpendicular directions after sintering, and the linear shrinkage rate of each axis is calculated by comparing with the corresponding size before sintering, and the anisotropic deviation average deviation is shown in Table 1.

[0094] The average grain size is measured by electron backscattering diffraction.

[0095] The bending strength is measured by three-point bending test.

[0096] The fracture toughness is measured by indentation method.

[0097] In the present application, unless otherwise specified, the examples and comparative examples are prepared by preparing pre-amplified micro-nano structures with a size of Φ4.5mm and then sintering.

[0098] Example 1

[0099] S1, 92g of 17-4PH stainless steel powder (wherein, large size particle size powder: 70wt% (64.4g), average particle size is 170nm, small size particle size powder: 30wt% (27.6g), average particle size is 80nm), 5g of Sn-Bi eutectic powder with an average particle size of 80nm (wherein, Sn content is 42%, Bi content is 58%), 2.2g of Y2O3 powder with an average particle size of 40nm, 0.8g of ZrO2 with an average particle size of 50nm, 22g of polypropylene, 13g of stearic acid, 65g of paraffin, a mixture is obtained by mixing, the mixture is heated to a molten state and then injected into a mold by an injection machine to obtain a pre-amplified micro-nano structure;

[0100] S2-1, the pre-amplified micro-nano structure is heated to 300℃ at 1℃ / min in N2, and the first debinding is carried out at 300℃ for 2h;

[0101] S2-2, the atmosphere is switched to a mixed gas of H2(5vol%) and N2, and then heated to 400℃ at 2℃ / min, and the second debinding is carried out at 400℃ for 1h;

[0102] S3, then the material is heated to 650℃ for first sintering, and heated for 1h, heated to 900℃ for second sintering, and heated for 0.5h, and then heated to 1150℃ for third sintering, and heated for 2h, wherein the heating time of the first sintering / (the heating time of the second sintering+the heating time of the third sintering) is 0.4.

[0103] S4, the sintered body obtained in step S3 is subjected to hot isostatic pressing treatment under argon at 1200°C and 100 MPa for 1 h to obtain a micro-nano structure with multi-dimensional uniform deformation.

[0104] Example 2

[0105] According to the method of Example 1, except that 92 g of the base powder contains 78 g of large-size powder with an average particle size of 160 nm, 14 g of small-size powder with an average particle size of 70 nm, 4.5 g of Sn-Bi eutectic powder, and 2.8 g of Y2O3 and 0.7 g of ZrO2 as the morphology stabilizer, the rest is the same as in Example 1.

[0106] Example 3

[0107] According to the method of Example 1, except that 92 g of the base powder contains 88 g of large-size powder with an average particle size of 230 nm and 4 g of small-size powder with an average particle size of 35 nm.

[0108] Example 4

[0109] According to the method of Example 1, except that the content of the stainless steel powder is 89 g, of which the large-size powder is 70 wt% with an average particle size of 170 nm and the small-size powder is 30 wt% with an average particle size of 80 nm, the content of the Sn-Bi eutectic powder is 8 g, the content of Y2O3 powder is 3.2 g, and the content of ZrO2 powder is 0.8 g. The other conditions are the same as in Example 1.

[0110] Example 5

[0111] According to the method of Example 1, except that the average particle size of the large-size powder in the stainless steel powder is 200 nm, the average particle size of the small-size powder is 110 nm, the average particle size of the Sn-Bi alloy powder is 40 nm, the average particle size of the morphology stabilizer Y2O3 is 40 nm, and the average particle size of ZrO2 is 35 nm.

[0112] Example 6

[0113] According to the method of Example 1, except that the holding time of the first sintering is 1.5 h and the holding time of the third sintering is 1.5 h. The holding time of the first sintering / (the holding time of the second sintering + the holding time of the third sintering) is 0.75.

[0114] Example 7

[0115] The method of Example 1 was followed, except that the holding time of the first sintering was 0.5 h and the holding time of the third sintering was 3 h. The holding time of the first sintering / (the holding time of the second sintering + the holding time of the third sintering) was 0.14.

[0116] Example 8

[0117] The method of Example 1 was followed, except that the morphology stabilizer was 3.8 g of Y2O3 powder without ZrO2. Other conditions were the same.

[0118] Example 9

[0119] The method of Example 1 was followed, except that the average particle size of the 92 g of stainless steel powder was 150 nm (monomodal distribution).

[0120] Example 10

[0121] The method of Example 1 was followed, except that the average particle size of the stainless steel powder was (270 nm for large size powder and 20 nm for small size powder), the average particle size of the Sn-Bi alloy powder was 150 nm, and the average particle size of the morphology stabilizer was 150 nm.

[0122] Comparative Example 1

[0123] The method of Example 1 was followed, except that the activating agent was replaced by a Cu-P alloy (92 wt% Cu and 8 wt% P, eutectic melting point 710°C) with the same average particle size.

[0124] Comparative Example 2

[0125] The method of Example 1 was followed, except that the morphology stabilizer was replaced by Al2O3 with the same average particle size.

[0126] Comparative Example 3

[0127] The method of Example 1 was followed, except that no activating agent was added and the 17-4PH stainless steel powder was 97 g.

[0128] Comparative Example 4

[0129] The method of Example 1 was followed, except that no morphology stabilizer was added and the 17-4PH stainless steel powder was 95 g.

[0130] Comparative Example 5

[0131] S1, 300 g of 17-4PH stainless steel powder (average particle size 30 μm, monomodal distribution) and 65 g of paraffin wax (not separated from the powder) were mixed uniformly, and the mixture was formed into a green body by unidirectional die pressing (pressure 600 MPa).

[0132] S2, debinding at 450℃ for 2 hours under hydrogen atmosphere, then directly sintering at 1280℃ for 4 hours to obtain a sintered part;

[0133] S3, the sintered part needs to be machined, and the 17-4PH is subjected to solution treatment + aging hardening (H900 state) according to GB / T 122-2007.

[0134] Comparative Example 6

[0135] According to the method of Example 1, except that the content of the stainless steel powder is 82g, the content of the Sn-Bi eutectic powder is 12g, and the content of the Y2O3 powder is 1g + the content of the ZrO2 powder is 0.5g. Other conditions are the same.

[0136] Test Example

[0137] The micro-nano structures prepared in the examples and comparative examples are tested, and the results are shown in Table 1.

[0138]

[0139] Note: the numerical value of the anisotropic deviation is an absolute value

[0140] In order to further illustrate that the structure prepared by the method according to the present application shrinks uniformly and does not cause distortion of the product structure, further experiments are carried out on the samples of Example 1 and Comparative Example 5:

[0141] Detection equipment: laser scanning confocal microscope or optical three-dimensional topography instrument.

[0142] Comparative Example 5: the distance deviation (Radial Runout) between the center of the structure circle and the reference center is 8.5μm, and the pressure angle (Pressure Angle) deviation is >2°.

[0143] Example 1: the distance deviation (Radial Runout) between the center of the structure circle and the reference center is reduced to 0.8μm, the pressure angle (Pressure Angle) deviation is <0.2°, and there is no obvious distortion.

[0144] Comparing Example 1 and Example 3, due to too many large particles and partial agglomeration of small particles, the powder bulk density is low. The obtained product has increased three-axis shrinkage deviation, and the relative density is only 95.1% after further testing. In Comparative Example 7, due to insufficient low-temperature surface diffusion and too long high-temperature time, the grains are significantly coarsened (≈1.2μm), and the uneven shrinkage leads to an increase in the deviation to 2.5%.

[0145] The green density of Comparative Example 9 is low due to the lack of high packing density of bimodal distribution. The sintering shrinkage is obviously uneven, the three-axis deviation increases, and the middle of the product appears a shrinkage depression. It proves that bimodal distribution is crucial to uniform shrinkage. In Comparative Example 10, the average particle size of the activator and stabilizer is too large, resulting in functional failure. The liquid phase is uneven, the grain is severely coarsened (> 2 μm), and the densification is incomplete (density 94.5%).

[0146] In Comparative Example 1, the melting point of Cu-P alloy is much higher than that of Sn-Bi eutectic alloy, the liquid phase generation temperature is too high, and the wettability difference is large. Before reaching its activation temperature, the sintering neck of the matrix powder has grown too much, and the densification dynamics decreases. The final product has low density (96%), uneven shrinkage (deviation 4.5%), and coarse grains (≈1.5 μm). It proves that a low-melting-point eutectic activator is the key to achieving low-temperature and uniform densification.

[0147] In Comparative Example 2, the chemical compatibility of Al2O3 with the 316L stainless steel matrix is poor, and it does not have the grain boundary purification effect of Y2O3. It forms a mechanical mixture at the grain boundary rather than a stable precipitated phase, and the pinning effect is weak. The final product has an abnormal grain growth of ≈1.8 μm at the high-temperature sintering stage, and the porosity is high due to the hindering of Al2O3 to densification, resulting in a significant decrease in mechanical properties. It proves that Y2O3 / ZrO2 composite stabilizer has an irreplaceable advantage in inhibiting grain growth and compatible densification.

[0148] In Comparative Example 3, the sintering process completely relies on solid-state diffusion, and the densification dynamics is severely insufficient. Even if the sintering time is extended and the temperature is increased, the final product has a very low shrinkage rate (about 18%), far from the expected size, and the relative density is only 92%, with a large number of connected pores and extremely low strength. It proves that the liquid phase sintering mechanism provided by the activator is a necessary condition for achieving ultra-high shrinkage and near-full densification.

[0149] In Comparative Example 4, the densification process is successfully completed under the action of the activator, and the shrinkage rate is close to the target (55%). However, due to the lack of substances to pin the grain boundaries, the grains are severely coarsened at the high-temperature third sintering stage, growing from nanoscale to microns (≈3-5 μm). Although the density is high, the coarse grains result in a significant decrease in hardness, strength, and toughness of the product, which is no different from traditional metallurgical products, losing the advantages of nanocrystalline materials. It proves that the morphology stabilizer is the key to obtaining a nanocrystalline structure and ensuring the final performance.

[0150] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements within the technical scope disclosed by the present application can be easily thought by those skilled in the art, which should be covered within the protection scope of the present application.

Claims

1. A method for uniform deformation of micro-nanostructures in multiple dimensions, comprising: The method comprises: S1, uniformly mixing a base powder, an activator and a morphology stabilizer to obtain a mixture, and micro-injection molding the mixture to obtain a pre-amplified micro-nano structure; S2, after segmenting and debinding the pre-amplified micro-nano structure, performing gradient sintering and hot isostatic pressing to obtain a multi-dimensional uniformly deformed micro-nano structure. The base powder comprises metal powder and / or ceramic powder, the activator is a eutectic alloy with a melting point ≤200℃, and the morphology stabilizer is a rare earth metal oxide and / or a transition metal oxide.

2. The method of claim 1, wherein, In step S1, the content of the base powder in the mixture is 88-94wt%, the content of the activator is 3-8wt%, and the content of the morphology stabilizer is 1-5wt%; And / or, the base powder comprises large-size powder and small-size powder, the average particle size of the large-size powder is 120-200nm, and the average particle size of the small-size powder is <120nm; And / or, the large-size powder accounts for 70-80% of the total mass of the base powder, and the small-size powder accounts for 20-30% of the total mass of the base powder.

3. The method of claim 1, wherein, The metal powder is selected from stainless steel powder, noble metal powder or transition metal powder; And / or, the ceramic powder is selected from at least one of Al2O3, SiC, Si3N4 and SiO2; And / or, the average particle size of the base powder is 50-200nm.

4. The method of claim 1, wherein, The eutectic alloy is selected from a eutectic Sn-Bi alloy or a eutectic In-Bi alloy; And / or, the average particle size of the eutectic alloy is ≤100nm.

5. The method of claim 1, wherein, The morphology stabilizer is selected from at least one of Y2O3, ZrO2, CeO2 and La2O3; And / or, the average particle size of the morphology stabilizer is 20-50nm.

6. The method of claim 1, wherein, In step S2, the segmenting and debinding comprises first debinding and second debinding; And / or, the conditions of the first debinding include a temperature of 200-350℃ and a time of 0.5-2h; And / or, the conditions of the second debinding include a temperature of 400-500℃ and a time of 0.5-2h.

7. The method of claim 1, wherein, The gradient sintering comprises first sintering, second sintering and third sintering; And / or, the conditions of the first sintering include a temperature of 600-800℃ and a holding time of 1-3h; And / or, the conditions of the second sintering include a temperature of 850-950℃ and a holding time of 1-2h; And / or, the conditions of the third sintering include a temperature of 1050-1200℃ and a holding time of 1-2h; And / or, the holding time of the first sintering / (the holding time of the second sintering + the holding time of the third sintering) is 0.2-0.

8.

8. The method of claim 7, wherein, In step S2, the conditions of the hot isostatic pressing include a processing temperature of 800-1200℃, a processing pressure of 100-200MPa and a processing time of 2-4h in the presence of a protective gas.

9. A micro-nano structure prepared by the method of any one of claims 1-8.

10. Use of the micro-nano structure of claim 9 in electronic devices or aerospace materials.

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