Ultrahigh-strength pure metal and preparation method thereof

Abstract

The invention provides ultrahigh-strength pure metal and a preparation method thereof, and relates to the technical field of high-performance metal materials. According to the preparation method of the ultra-high-strength pure metal, the nanometer pure metal powder serves as an initial raw material and then is welded into small blocks with the size of dozens of micrometers through high pressure, compact pure metal is formed, no alloy element needs to be added, pressure is a very pure regulation and control means, and the preparation process is simple. And no impurity is introduced while extreme strengthening of the nano metal is realized. The pressure can effectively inhibit grain boundary slippage of nanocrystals, can compact nano metal powder to a certain extent, and avoids grain coarsening at the same time, so that a deformation mechanism of metal is activated, multiple crystal defects including full dislocation, offset dislocation, twin crystal, stacking dislocation and the like are included, the multiple types of defects interact to generate strain fields and are mutually overlapped, and therefore, the deformation of the nanocrystals is inhibited. And dislocation movement is hindered, so that strong work hardening and extreme strengthening are brought, and finally, pure metal achieves ultrahigh strength.

Description

Technical Field

[0001] The present application relates to the technical field of high-performance metal materials, and in particular to an ultra-high-strength pure metal and a preparation method thereof. Background Art

[0002] Metals are widely used in daily life. The strengthening of metals is of great significance to the engineering field. The ultra-high strength of metals has always been the goal pursued by people. For structural materials, strength is one of its important performance indicators. Strength refers to the ability of a material to resist plastic deformation and fracture, which can be expressed by the stress that the material can withstand under given conditions. The strengthening of metals can be started from two aspects. One is to improve its theoretical strength (increase the bonding force between atoms) and produce perfect crystals, such as extremely small whiskers; the other is to introduce a large number of crystal defects, such as point defects, dislocations, second phase particles, grain boundaries, etc. These defects will hinder the movement of dislocations and significantly improve the strength of metals. Usually the latter approach is an effective method to improve the strength of metals in engineering. People generally use comprehensive strengthening methods to achieve optimal performance.

[0003] A common method of metal strengthening is grain refinement, and its main principle is the dislocation pile-up theory. An important concept of this theory is that grain boundaries are dislocation sources, as proposed by Mott and others. Later, transmission electron microscopy also observed grain boundary emission dislocations (including full dislocations and partial dislocations), and the higher the grain boundary defect density, the greater the rate of dislocation emission. After the dislocation nucleates, it begins to move from one side of the grain to the other, so at this time the grain boundary will act on the dislocation. The grain size effect was first proposed by Hall and Petch et al. when they studied the change of yield strength of steel and iron with grain size, and proposed the famous Hall-Petch relationship (that is, the smaller the size, the higher the strength of the material).

[0004] Twin strengthening is also a method that people are very interested in. In recent years, twin strengthening has been found in copper, cubic boron nitride and diamond. Nanoscale twins are introduced into polycrystalline materials to adjust plastic deformation and strengthen the material. The excess energy of twin boundaries is about an order of magnitude lower than that of grain boundaries, so twins can exist stably at a smaller scale. There are many ways to make materials with twins, such as electrodeposition, sputtering deposition, plastic deformation, recrystallization and phase transformation.

[0005] Electrodeposition is used to prepare nanocrystalline metals or nanotwinned metals. High-strength metals can be achieved by using fine grain strengthening and twin strengthening. Equal channel angular pressing (ECAP) or high pressure torsion (HPT) can refine grains to prepare nanometals. However, these technologies still have some shortcomings, including but not limited to: 1) It is difficult to obtain extremely refined metals (grain size less than 20 nanometers); 2) It is difficult to achieve high yield strength and high work hardening rate at the same time.

[0006] Even if metals with extremely fine grain sizes are prepared, the softening effect is inevitable (when the grain size is less than 10 nanometers, the metal strength begins to decrease, that is, the inverse Hall-Petch relationship), mainly because the grain boundaries are unstable and grain boundary sliding begins to dominate the deformation. Traditional cognition shows that there is an ideal strength E / 10 for materials (E is the Young's modulus of the material). Generally, the strength of nanometals does not exceed E / 80, and that of metallic glasses does not exceed E / 50. The maximum strength obtained by traditional means is about E / 20. That is, the upper limit strength of strengthening only through fine grains is about E / 80, and further refinement will cause a softening effect. For the problem of unstable grain boundaries, the grain boundaries can usually be stabilized by alloying, but this approach introduces alloying elements (usually more expensive) and sacrifices the purity of the metal.

[0007] Strain hardening is also a way to improve strength. It is generally believed that strain hardening mainly occurs in coarse-grained metals and is difficult to occur in nanocrystals because nanoscale grains can hardly accommodate many dislocations. There are still the following problems in improving strain hardening: 1) High-strength materials will reduce strain hardening capacity; 2) It is still difficult to significantly improve the strain hardening performance of high-strength metal materials at room temperature; 3) Lowering the temperature can improve strain hardening. Engineered spatial heterogeneous nanostructures containing gradients, bimodal grain sizes, and multiphases can show additional strain hardening. However, low-temperature strain hardening can often only be maintained at a small plastic strain stage (<5%).

[0008] For some extreme service environments, such as aircraft engine turbine blades (high temperature), submarine seabed work (high pressure), reactor first wall materials (strong irradiation, ultra-high temperature), etc., the performance requirements for materials are relatively high and the material performance needs to be continuously optimized. The existing methods of improving metal strength are difficult to meet. Summary of the invention

[0009] The purpose of this application is to provide an ultra-high strength pure metal and a preparation method thereof, aiming to solve the problem that the metal obtained by the existing metal strength improvement method cannot be used in extreme service environments.

[0010] To achieve the above objectives, the present application provides a method for preparing ultra-high strength pure metal, comprising: subjecting nano-metal powder to high pressure treatment at a pressure of 5 to 40 GPa to obtain ultra-high strength pure metal.

[0011] In some embodiments, the particle size of the nano metal powder is less than 40 nanometers.

[0012] In some embodiments, the particle size of the nano metal powder is less than 10 nanometers.

[0013] In some embodiments, the nano-metal powder is treated in a reducing atmosphere at 100° C. for 5 to 20 minutes; And / or, the nano metal powder is pre-pressed into sheets before the high pressure treatment.

[0014] In some embodiments, the high pressure processing device includes: a sample carrier and a diamond anvil, a closed cavity is formed between the sample carrier and the diamond anvil, the cavity is used to place the nano-metal powder, and pressure can be applied from both sides of the diamond anvil in the top direction to compress the cavity.

[0015] In some embodiments, the sample carrier is provided with a sample cavity penetrating through both sides of the sample carrier, and the diamond anvils are pressed against both sides of the sample carrier corresponding to the two ends of the sample cavity, and the diamond anvils and the sample cavity form the cavity body.

[0016] In some embodiments, the sample carrier includes a Kapton plastic sheet and a sealing gasket embedded in the Kapton plastic sheet, and a through hole penetrating the sealing gasket is disposed at the center of the sealing gasket, and the through hole is the sample cavity.

[0017] In some embodiments, the seal includes: an amorphous boron gasket; And / or, the thickness of the amorphous boron gasket is 100-120 microns.

[0018] The present application also provides an ultra-high strength pure metal, which is prepared by the above-mentioned method for preparing ultra-high strength pure metal.

[0019] In some embodiments, the strength of the ultra-high strength pure metal is E / 26~E / 12.3.

[0020] Compared with the prior art, the beneficial effects of this application include: The preparation method of ultra-high strength pure metal provided by the present application uses nano pure metal powder as the initial raw material, and then welds it into small blocks of tens of microns in size through high pressure to form dense pure metal, without adding any alloying elements. Pressure is a very pure means of regulation, which does not introduce any impurities while achieving extreme strengthening of nano metal. Pressure can effectively inhibit the grain boundary slip of nanocrystals, compact nano metal powder to a certain extent, and avoid grain coarsening, thereby activating the deformation mechanism of the metal itself, including various crystal defects such as full dislocation, partial dislocation, twin, stacking fault, etc. These multiple types of defects interact with each other, generate strain fields and superimpose each other, hinder the movement of dislocations, and then bring about strong work hardening and extreme strengthening, and finally make pure metal achieve ultra-high strength.

[0021] The strengthening effect of ultra-high strength pure metal provided by this application (up to about E / 12.3) exceeds any traditional strengthening means. The maximum strength of 3 nanometer nickel reaches E / 20, and the work hardening rate under 1% lattice strain reaches 2.3 GPa; the maximum strength of 8 nanometer nickel is E / 26, and the work hardening rate under 1% lattice strain reaches 1.9 GPa. The strengthening method mentioned in this application overcomes the problem that high yield strength and high work hardening rate cannot be achieved at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0023] Figure 1 This is a schematic structural diagram of the high-pressure in-situ radial X-ray diffraction device of the present application; Figure 2 A schematic top view of the sample carrier of the present application; Figure 3 This is a diagram showing the pressure distribution inside the cavity of a 9-nanometer palladium sample during the high pressure treatment process of Example 1; Figure 4 The sample strength characterization result diagram of ultra-high strength pure metal of Examples 1 to 3 and Comparative Examples 1 to 2 based on synchrotron radiation X-ray diffraction technology; Figure 5 This is a characterization diagram of internal defects of the ultra-high strength pure metal of Example 1; Figure 6 This is a characterization diagram of internal defects of the ultra-high strength pure metal of Example 2; Figure 7 are atomic strain diagrams of ultra-high strength pure metals of Example 1 and Comparative Example 1; Figure 8 Figure 2 is a graph showing the work hardening rate of nickel with different grain sizes.

[0024] Reference numerals: 100 - high pressure treatment device; 10 - sample carrier; 11 - sample chamber; 12 - support plate; 13 - seal; 20 - diamond anvil; 30 - chamber; 40 - X-ray light source. DETAILED DESCRIPTION

[0025] As used herein: "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0026] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0027] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0028] In these examples, parts and percentages are by mass unless otherwise indicated.

[0029] "Mass parts" refers to the basic unit of measurement for expressing the mass ratio of multiple components. 1 part can represent any unit mass, such as 1g or 2.689g. If we say that the mass parts of component A are a parts and the mass parts of component B are b parts, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it means that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It should not be misunderstood that, unlike the mass parts, the sum of the mass parts of all components is not limited to 100 parts.

[0030] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0031] The present application provides a method for preparing ultra-high strength pure metal, comprising: subjecting nano-metal powder to high-pressure treatment, the pressure of which is 5~40 GPa, for example, 5GPa, 10GPa, 15GPa, 20GPa, 25GPa, 30GPa, 35GPa, 40 GPa or any value between 5~40 GPa, to obtain ultra-high strength pure metal.

[0032] The preparation method of ultra-high strength pure metal provided by the present application uses nano pure metal powder as the initial raw material, and then welds it into small blocks of tens of microns in size through high pressure to form dense pure metal, without adding any alloying elements. Pressure is a very pure means of regulation, which does not introduce any impurities while achieving extreme strengthening of nano metal. Pressure can effectively inhibit the grain boundary slip of nanocrystals, compact nano metal powder to a certain extent, and avoid grain coarsening, thereby activating the deformation mechanism of the metal itself, including various crystal defects such as full dislocation, partial dislocation, twin, stacking fault, etc. These multiple types of defects interact with each other, generate strain fields and superimpose each other, hinder the movement of dislocations, and then bring about strong work hardening and extreme strengthening, and finally make pure metal achieve ultra-high strength.

[0033] Generally speaking, coarse-grained metals have a strong work hardening phenomenon during deformation, and metals above 100 nanometers can show a certain work hardening effect at low temperatures. However, metals of a few nanometers are very brittle at room temperature and basically have no work hardening phenomenon. The present application can make nanometals show a strong work hardening phenomenon at room temperature through high-pressure deformation, and its work hardening rate is much higher than that of coarse-grained metals. The preparation method of the present application is simple and low-cost, and effectively solves the weaknesses of pure metals of a few nanometers in softening and lack of work hardening, so that its maximum strength approaches the ideal strength. The preparation method of the present application is universal for nanometals, and similar extreme strengthening has been achieved in nano nickel, gold and stainless steel.

[0034] In some embodiments, the particle size of the nano metal powder is less than 40 nanometers.

[0035] Wherein, initial nano metal powder raw material can be directly chemically synthesized or refined from coarse crystal powder, and can also be purchased from the market. The particle diameter of nano metal powder is less than 40 nanometers, for example, can be 1 nanometer, 2 nanometers, 3 nanometers, 4 nanometers, 5 nanometers, 6 nanometers, 7 nanometers, 8 nanometers, 9 nanometers, 10 nanometers, 11 nanometers, 12 nanometers, 13 nanometers, 14 nanometers, 15 nanometers, 16 nanometers, 17 nanometers, 18 nanometers, 19 nanometers, 20 nanometers, 21 nanometers, 22 nanometers, 23 nanometers, 24 nanometers, 25 nanometers, 26 nanometers, 27 nanometers, 28 nanometers, 29 nanometers, 30 nanometers, 31 nanometers, 32 nanometers, 33 nanometers, 34 nanometers, 35 nanometers, 36 nanometers, 37 nanometers, 38 nanometers, 39 nanometers or any numerical value less than 40 nanometers, generally speaking, the particle diameter of nano metal powder is as small as possible.

[0036] The smaller the grains, the higher the proportion of grain boundaries, and the high pressure makes the grain boundaries a strengthening factor and avoids the softening effect.

[0037] In some embodiments, the particle size of the nano metal powder is less than 10 nanometers.

[0038] In some embodiments, the nano-metal powder is treated in a reducing atmosphere at 100° C. for 5 to 20 minutes to remove the surface oxide layer to achieve pure metal.

[0039] In some embodiments, the nano-metal powder is pre-pressed into sheets before the high-pressure treatment, in order to fill more sample in the sample cavity. If the nano-powder is directly loaded into the sample cavity, there are too many pores and the pressurization process can easily cause the sample to shrink, which may lead to shrinkage cavities and damage to the diamond anvil.

[0040] In some embodiments, see Figure 1 The high pressure treatment device 100 includes: a sample carrier 10 and a diamond anvil 20, a closed cavity 30 is formed between the sample carrier 10 and the diamond anvil 20, and the cavity 30 is used to place the nano-metal powder. Applying pressure from both sides of the diamond anvil 20 in the top direction can compress the cavity 30.

[0041] Figure 1 Here, σ1 and σ3 represent the axial and radial stress components of the sample, respectively.

[0042] In some embodiments, the sample carrier 10 is provided with a sample cavity 11 that passes through both sides of the sample carrier 10 , and the diamond anvil 20 is abutted against both sides of the sample carrier 10 corresponding to the two ends of the sample cavity 11 , and the diamond anvil 20 and the sample cavity 11 form the cavity body 30 .

[0043] In some embodiments, see Figure 2 The sample carrier 10 includes a support sheet 12 and a sealing pad 13 embedded in the support sheet 12 . A through hole penetrating the sealing pad 13 is disposed at the center of the sealing pad 13 . The through hole is the sample cavity 11 .

[0044] Among them, the support sheet 12 can be, for example, a Kapton plastic sheet. The Kapton plastic sheet is a polyimide (PI) film material produced by DuPont of the United States. The Kapton plastic sheet can maintain its performance at extreme temperatures, and can withstand a temperature range from -269°C to 400°C for a short time. The long-term use temperature can reach 230°C. It has strong chemical inertness, is insoluble in any known organic solvents, is tough, wear-resistant, and has good mechanical strength.

[0045] In some embodiments, the sealing gasket 13 comprises: an amorphous boron gasket, wherein the amorphous boron gasket is a mixture of amorphous boron powder and epoxy resin, and the shape of the amorphous boron gasket can be any shape, preferably a circle.

[0046] In some embodiments, the thickness of the amorphous boron gasket is 100-120 microns, for example, 100 microns, 105 microns, 110 microns, 115 microns, 120 microns, or any value between 100-120 microns.

[0047] In some embodiments, please refer to Figure 1 The high pressure treatment device 100 further includes: an X-ray light source 40 for generating X-rays to perform synchrotron radiation X-ray diffraction characterization on the ultra-high strength metal after the high pressure treatment.

[0048] The method for performing diffraction measurement on the high-pressure processing device 100 includes: placing a sample in a cavity 30 formed between diamond anvils 20 under normal pressure; establishing a coordinate origin and determining a diffraction center; positioning the sample at the diffraction center, applying pressure to the diamond anvil 20 so that the pressure in the cavity 30 reaches a set pressure value; turning on an X-ray light source 40 to emit X-rays toward the diffraction center, and using a detector to collect data for intensity characterization.

[0049] According to the radial diamond anvil X-ray diffraction theory, due to the axial symmetry of the diamond anvil, under high pressure, the stress at the center of the sample ( can be decomposed into components along the axial direction ( ) and two equivalent radial components ( ), as follows: (1) in represents the normal stress part (equivalent to the hydrostatic pressure, ), Represents the shear stress part. The difference between the axial stress component and the radial stress component is called differential stress. (As attached Figure 1 ), by The strain caused by the pressure increases continuously, and a suitable state equation can be used to analyze it. The resulting strain cannot be analyzed by the equation of state. According to the Bragg equation: , (2) Where d is the interplanar distance, is the diffraction angle, is the wavelength of X-rays used. Through the position of XRD diffraction peaks, we can obtain the interplanar spacing (d-spacing) of different crystal planes. , The resulting strain can be expressed as: , (3) in is the hydrostatic pressure Under the lattice plane spacing, we can organize formula (3) into the following expression: , (4) in, is the diffraction ring azimuth, .

[0050] , (5) is the aggregate shear modulus of the powder under Reuss (stress continuum model) conditions, is the shear modulus under Voigt (strain continuum model) conditions, is a constant factor between 0 and 1, which is determined by the weight of the strain calculated under Reuss and Voigt conditions. For the cubic system, It can be expressed as: , (6) in, is the material flexibility constant, For FCC crystals, the crystal planes (111), (200), and (220) correspond to The values ​​are 1 / 3, 0 and 1 / 4 respectively. According to formula (4), we draw Follow The slope and intercept can be obtained by linear fitting the curve of the change. , the slope is , from which we can get Then according to formula (5), it can be deduced that: (7) The angle brackets represent the average value of the physical quantity in the brackets. For stress Shear modulus of powder crystal. represents elastic anisotropy. For nearly isotropic powder crystals, , is also 1. The above equation (7) can be simplified to , (8) According to the Mises yield criterion, the differential stress that a sample can support can be regarded as the lower limit of its yield strength, that is, ,in is the yield strength of the sample.

[0051] Therefore, radial diamond anvil cell X-ray diffraction experiments can be carried out with the help of synchrotron radiation source to characterize the yield strength of the material and the flow stress after yield.

[0052] The present application also provides an ultra-high strength pure metal, which is prepared by the above-mentioned method for preparing ultra-high strength pure metal.

[0053] The extreme strengthening of the ultra-high strength pure metal of this application is the result of comprehensive strengthening of fine grain strengthening and work hardening, which are difficult to combine by traditional means. The strengthening effect of the ultra-high strength pure metal obtained is up to about E / 12.3, which exceeds any traditional strengthening means. Under 40 GPa pressure treatment, the maximum strength of nano nickel reaches E / 20, the maximum strength of 9 nano palladium reaches E / 12.3, and the work hardening rate under 1% lattice strain reaches 2.3 GPa (3 nano nickel), overcoming the problem that high yield strength and high work hardening rate cannot be achieved at the same time.

[0054] In some embodiments, the strength of the ultra-high strength pure metal is E / 26~E / 12.3, where E is the Young's modulus of the metal.

[0055] The strength of the ultra-high strength pure metal obtained in the present application can be, for example, E / 12.3, E / 15, E / 20, E / 23, E / 26 or any value between E / 26 and E / 12.3.

[0056] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0057] Example 1 (1) Initial sample preparation The initial sample was 9 nanometer palladium powder.

[0058] (2) High pressure treatment Use a 100-120 micron thick amorphous boron gasket, cut it into a small disc with a diameter of 500 microns by laser, and drill a hole with a diameter of 60 microns in the center of the small disc; place the small disc with a hole in a long supporting Kapton plastic sheet with an inner diameter slightly larger than 500 microns (about 510 microns); place the Kapton plastic sheet embedded with the gasket with a hole in the diamond anvil so that the hole is located in the center of the diamond; pre-press the powder slightly into a sheet (the purpose is to make the powder initially densified, which can be done with the help of a tabletting mold or a pair of flat hard materials, and can be loaded by hand pressure or a small hydraulic press. The pressure can be very low, such as within 1MPa), and then put it into the hole of the gasket to ensure that the sample fills the entire hole; use a 300-micron table diamond anvil to press it to about 40 GPa.

[0059] (3) Strength characterization The maximum intensity finally obtained by synchrotron X-ray diffraction is about E / 12.3, such as Figure 4 As shown; the internal defect characterization diagram is as follows Figure 5 As shown, high density of deformation twins can be seen.

[0060] Example 2 (1) Initial sample preparation The initial sample was 3 nanometer nickel powder.

[0061] (2) High pressure treatment A 100-120 μm thick amorphous boron gasket is used, which is cut into a 500 μm diameter disc by laser, and a 60 μm diameter hole is drilled in the center of the disc. The disc with the hole is placed in a long supporting Kapton plastic sheet with an inner diameter slightly larger than 500 μm (about 510 μm). The Kapton plastic sheet embedded with the gasket with the hole is placed in the diamond anvil so that the hole is located in the center of the diamond. The powder is slightly pre-pressed into a sheet and then loaded into the hole of the gasket to ensure that the sample fills the entire hole. A 300 μm table diamond anvil is used to pressurize to 40 GPa.

[0062] (3) Strength characterization Characterized by synchrotron X-ray diffraction, the maximum intensity finally obtained was about E / 20, such as Figure 4 As shown; the internal defect characterization diagram is as follows Figure 6 As shown, complex and multi-type crystal defects can be seen, including full dislocation, partial dislocation, twins, etc.

[0063] Example 3 (1) Initial sample preparation The initial sample was 8 nanometer nickel powder.

[0064] (2) High pressure treatment A 100-120 μm thick amorphous boron gasket is used, which is cut into a 500 μm diameter disc by laser, and a 60 μm diameter hole is drilled in the center of the disc. The disc with the hole is placed in a long supporting Kapton plastic sheet with an inner diameter slightly larger than 500 μm (about 510 μm). The Kapton plastic sheet embedded with the gasket with the hole is placed in the diamond anvil so that the hole is located in the center of the diamond. The powder is slightly pre-pressed into a sheet and then loaded into the hole of the gasket to ensure that the sample fills the entire hole. A 300 μm table diamond anvil is used to pressurize to 40 GPa.

[0065] (3) Strength characterization The maximum intensity obtained by synchrotron X-ray diffraction is about E / 26, such as Figure 4 Shown in the upper right corner (green 8 nm Ni).

[0066] Example 4 (1) Initial sample preparation The initial sample was 20 nanometer nickel powder.

[0067] (2) High pressure treatment A 100-120 μm thick amorphous boron gasket is used, which is cut into a 500 μm diameter disc by laser, and a 60 μm diameter hole is drilled in the center of the disc. The disc with the hole is placed in a long supporting Kapton plastic sheet with an inner diameter slightly larger than 500 μm (about 510 μm). The Kapton plastic sheet embedded with the gasket with the hole is placed in the diamond anvil so that the hole is located in the center of the diamond. The powder is slightly pre-pressed into a sheet and then loaded into the hole of the gasket to ensure that the sample fills the entire hole. A 300 μm table diamond anvil is used to pressurize to 40 GPa.

[0068] Comparative Example 1 (1) Initial sample preparation The initial sample was 700 nanometers of palladium metal powder.

[0069] (2) High pressure treatment A 100-120 μm thick amorphous boron gasket is used, which is cut into a 500 μm diameter disc by laser, and a 60 μm diameter hole is drilled in the center of the disc. The disc with the hole is placed in a long supporting Kapton plastic sheet with an inner diameter slightly larger than 500 μm (about 510 μm). The Kapton plastic sheet embedded with the gasket with the hole is placed in the diamond anvil so that the hole is located in the center of the diamond. The powder is slightly pre-pressed into a sheet and then loaded into the hole of the gasket to ensure that the sample fills the entire hole. A 300 μm table diamond anvil is used to pressurize to 40 GPa.

[0070] (3) Strength characterization Characterized by synchrotron X-ray diffraction, the maximum intensity finally obtained was only E / 53, such as Figure 4 (700 nm Pd marked in red). The initial sample was not below 100 nanometers, so the strengthening effect was not obvious, indicating that the ultra-high strength of the metal is the result of the synergistic effect of fine grain strengthening + high pressure induced strain field superposition strengthening.

[0071] The atomic strain diagrams of the 9 nanometer metal palladium of Example 1 and the 700 nanometer metal palladium of Comparative Example 1 after high pressure deformation are shown in FIG. Figure 7 As shown, compared with 700 nanometers of palladium, the atomic strain inside 9 nanometers of palladium is greater, which is the key to its extreme strengthening.

[0072] Comparative Example 2 (1) Initial sample preparation The initial sample was 3 nanometer nickel powder.

[0073] (2) High pressure treatment A 250-micron-thick metal rhenium (Re) gasket was used, laser drilling was used to make the sample cavity diameter 50 microns, the diamond table was 150 microns, and 150 GPa ultrahigh pressure treatment was performed.

[0074] (3) Strength characterization The strength cannot be characterized by the method of the present application because most of the nickel powder has become an amorphous structure, which means that when the pressure exceeds the limit that the lattice can withstand, the crystal structure becomes unstable and turns into an amorphous structure.

[0075] Comparative Example 3 (1) Initial sample preparation The initial sample was 200 nanometer nickel powder.

[0076] (2) High pressure treatment A 100-120 μm thick amorphous boron gasket is used, which is cut into a 500 μm diameter disc by laser, and a 60 μm diameter hole is drilled in the center of the disc. The disc with the hole is placed in a long supporting Kapton plastic sheet with an inner diameter slightly larger than 500 μm (about 510 μm). The Kapton plastic sheet embedded with the gasket with the hole is placed in the diamond anvil so that the hole is located in the center of the diamond. The powder is slightly pre-pressed into a sheet and then loaded into the hole of the gasket to ensure that the sample fills the entire hole. A 300 μm table diamond anvil is used to pressurize to 40 GPa.

[0077] The work hardening rate curves of nickel with different grain sizes in Examples 2, 3, 4 and Comparative Example 3 are shown in FIG. Figure 8 As shown, the work hardening rate of 3 nanometer nickel under 1% lattice strain reaches 2.3 GPa; the work hardening rate of 8 nanometer nickel under 1% lattice strain reaches 1.9 GPa.

[0078] Therefore, the pressure range suitable for strengthening in this application is 5-40 GPa, and the particle size of the metal powder is less than 40 nanometers. The lower limit of pressure is to allow the material to undergo plastic deformation and produce the effect of inhibiting grain boundary sliding. If the pressure is too low, the effect of high pressure will not be reflected, and the effect will become similar to conventional fine grain strengthening.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0080] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the above claims, any one of the claimed embodiments may be used in any combination. The information disclosed in this background technology section is intended only to deepen the understanding of the overall background technology of the present application and should not be regarded as an admission or in any form of implication that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing ultra-high strength pure metal, characterized in that: include: Nanometal powders are subjected to high pressure treatment at a pressure of 5~40 GPa to obtain ultra-high strength pure metal.

2. The method for preparing ultra-high strength pure metal according to claim 1, characterized in that: The particle size of the nano metal powder is less than 40 nanometers.

3. The method for preparing ultra-high strength pure metal according to claim 2, characterized in that: The particle size of the nano metal powder is less than 10 nanometers.

4. The method for preparing ultra-high strength pure metal according to claim 1, characterized in that: The nano-metal powder is treated in a reducing atmosphere at 100° C. for 5 to 20 minutes; And / or, the nano metal powder is pre-pressed into sheets before the high pressure treatment.

5. The method for preparing ultra-high strength pure metal according to claim 1, characterized in that: The high pressure treatment device comprises: a sample carrier and a diamond anvil, wherein a closed cavity is formed between the sample carrier and the diamond anvil, and the cavity is used to place the nano metal powder. The cavity can be compressed by applying pressure from both sides of the diamond anvil toward the top.

6. The method for preparing ultra-high strength pure metal according to claim 5, characterized in that: The sample carrier is provided with a sample cavity which passes through both sides of the sample carrier. The two ends of the diamond anvil corresponding to the sample cavity are pressed against the two sides of the sample carrier. The diamond anvil and the sample cavity form the cavity body.

7. The method for preparing ultra-high strength pure metal according to claim 6, characterized in that: The sample carrier comprises a supporting sheet and a sealing pad embedded in the supporting sheet. A through hole penetrating the sealing pad is arranged at the center of the sealing pad, and the through hole is the sample cavity.

8. The method for preparing ultra-high strength pure metal according to claim 7, characterized in that: The sealing gasket comprises: an amorphous boron gasket; And / or, the thickness of the amorphous boron gasket is 100-120 microns.

9. An ultra-high strength pure metal, characterized in that: The ultra-high strength pure metal is prepared by the method for preparing the ultra-high strength pure metal according to any one of claims 1 to 8.

10. The ultra-high strength pure metal according to claim 9, characterized in that: The strength of the ultra-high strength pure metal is E / 26~E / 12.3.

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