An ultrahigh-strength pure metal and a method for producing the same

Abstract

The application provides an ultrahigh-strength pure metal and a preparation method thereof, and relates to the technical field of high-performance metal materials. The preparation method of the ultrahigh-strength pure metal provided by the application takes a nano pure metal powder as an initial raw material, and then forms a small block with a size of dozens of microns through high-pressure welding to form a dense pure metal without adding any alloy element. The pressure is a very pure regulation and control means, which can realize extreme strengthening of the nano metal without introducing any impurities. The pressure can effectively inhibit the grain boundary sliding of the nanocrystalline, can compact the nano metal powder to a certain extent, and can avoid grain coarsening, so that the deformation mechanism of the metal itself is activated, including various crystal defects such as full dislocation, partial dislocation, twinning, stacking fault and the like. The multiple types of defects interact with each other, generate strain fields and superimpose on each other, hinder the movement of dislocations, and then bring about strong work hardening and extreme strengthening, so that the pure metal finally realizes ultrahigh strength.

Description

Technical Field

[0001] This application relates to the field of high-performance metallic materials technology, and in particular to an ultra-high strength pure metal and its preparation method. Background Technology

[0002] Metals are widely used in daily life, and strengthening them is of great significance in engineering. Achieving ultra-high strength in metals has always been a goal. For structural materials, strength is one of their most important performance indicators. Strength refers to a material's ability to resist plastic deformation and fracture, and can be expressed by the amount of stress a material can withstand under given conditions. Strengthening metals can be approached from two aspects: one is to increase their theoretical strength (by increasing the bonding force between atoms) and to obtain 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, and grain boundaries. These defects hinder dislocation movement and significantly improve the metal's strength. The latter approach is usually the most effective method for improving metal strength in engineering, and optimal performance is generally achieved through a combination of strengthening methods.

[0003] A common metal strengthening method is grain refinement, based on the dislocation pile-up theory. A key concept in this theory is that grain boundaries, as proposed by Mott et al., are dislocation sources. 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 dislocation emission rate. After nucleation, dislocations begin to move, from one side of the grain to the other, at which point the grain boundary acts on the dislocation. The grain size effect was first proposed by Hall and Petch et al. when studying the yield strength of steel and iron as a function of grain size, and they proposed the famous Hall-Petch relationship (i.e., the smaller the size, the higher the strength of the material).

[0004] Twin strengthening is also a method of great interest, and in recent years, twin strengthening phenomena have been found in copper, cubic boron nitride, and diamond. By introducing nanoscale twins into polycrystalline materials, plastic deformation can be modulated, thereby strengthening the material. The excess energy at twin boundaries is about an order of magnitude lower than that at grain boundaries, thus twins can exist stably at a smaller scale. Many methods exist for fabricating twinned materials, such as electrodeposition, sputtering deposition, plastic deformation, recrystallization, and phase transformation.

[0005] Electrodeposition methods can be used to prepare nanocrystalline or nanotwinned metals, and high-strength metals can be achieved by utilizing grain refinement and twinning strengthening. Equal channel angle extrusion (ECAP) or high pressure torsion (HPT) can refine grains to prepare nanocrystalline metals. However, these techniques still have some limitations, 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 both high yield strength and high work hardening rate simultaneously.

[0006] Even when metals with extremely fine grain sizes are fabricated, a softening effect is inevitable (the metal's strength begins to decrease when the grain size is below 10 nanometers, i.e., the inverse Hall-Petch relationship). This is mainly due to grain boundary instability, where grain boundary slip begins to dominate deformation. Traditional understanding suggests that materials possess an ideal strength E / 10 (E is the Young's modulus of the material). Generally, the strength of nanometals does not exceed E / 80, metallic glasses do not exceed E / 50, and the maximum strength achievable through conventional methods is approximately E / 20. That is, the upper limit of strength achievable solely through grain refinement is approximately E / 80; further refinement leads to a softening effect. To address the problem of grain boundary instability, alloying can usually stabilize the grain boundaries, but this approach introduces alloying elements (which are typically expensive), sacrificing 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 cannot accommodate many dislocations. Improving strain hardening still faces the following problems: 1) High-strength materials will have reduced strain hardening capacity; 2) Significantly improving the strain hardening performance of high-strength metallic materials at room temperature is still difficult to achieve; 3) Lowering the temperature can improve strain hardening, and engineered spatial heterogeneous nanostructures with gradients, bimodal grain sizes, and multiple phases can exhibit additional strain hardening. However, low-temperature strain hardening often only maintains itself in the small plastic strain stage (<5%).

[0008] For certain extreme service environments, such as aircraft engine turbine blades (high temperature), submarine underwater operations (high pressure), and reactor first wall materials (strong radiation, ultra-high temperature), the performance requirements of materials are relatively high, and the performance of materials needs to be continuously optimized. Existing methods for improving metal strength are difficult to meet these requirements. Summary of the Invention

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

[0010] To achieve the above objectives, this application provides a method for preparing ultra-high strength pure metal, comprising: subjecting nano-metal powder to high pressure treatment at a pressure of 5~40 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 or below for 5 to 20 minutes.

[0014] And / or, the nano-metal powder is pre-pressed into sheets before undergoing the high-pressure treatment.

[0015] In some embodiments, the high-pressure processing apparatus includes a sample carrier and a diamond anvil cell, wherein a closed cavity is formed between the sample carrier and the diamond anvil cell, the cavity being used to hold the nano-metal powder, and pressure applied from both sides of the diamond anvil cell toward the anvil cell can compress the cavity.

[0016] In some embodiments, the sample carrier is provided with a sample cavity that extends through both sides of the sample carrier, and the diamond anvil cell abuts against both sides of the sample carrier at the two ends corresponding to the sample cavity, and the diamond anvil cell and the sample cavity form the cavity.

[0017] In some embodiments, the sample carrier includes a Kapton plastic sheet and a sealing gasket embedded in the Kapton plastic sheet, wherein the sealing gasket has a through hole at its center, which is the sample cavity.

[0018] In some embodiments, the sealing gasket includes: an amorphous boron gasket;

[0019] And / or, the thickness of the amorphous boron gasket is 100-120 micrometers.

[0020] This application also provides an ultra-high strength pure metal, which is prepared by the above-described method for preparing ultra-high strength pure metal.

[0021] In some embodiments, the strength of the ultra-high strength pure metal is E / 26 to E / 12.3.

[0022] Compared with the prior art, the beneficial effects of this application include:

[0023] The method for preparing ultra-high strength pure metal provided in this application uses nano-pure metal powder as the initial raw material, and then welds it into small blocks of tens of micrometers in size under high pressure to form a dense pure metal. No alloying elements need to be added. Pressure is a very pure control method that achieves extreme strengthening of nano-metal without introducing any impurities. Pressure can effectively suppress grain boundary slip of nanocrystals, compact the nano-metal powder to a certain extent, and avoid grain coarsening. This activates the metal's own deformation mechanism, including various crystal defects such as full dislocations, off-center dislocations, twins, and stacking faults. These various types of defects interact, generate strain fields, and superimpose each other, hindering the movement of dislocations, thereby bringing about strong work hardening and extreme strengthening, ultimately enabling the pure metal to achieve ultra-high strength.

[0024] The strengthening effect of ultra-high strength pure metals provided in this application (up to approximately E / 12.3) surpasses any traditional strengthening method. The maximum strength of 3nm nickel reaches E / 20, with a work hardening rate of 2.3 GPa at 1% lattice strain; the maximum strength of 8nm nickel is E / 26, with a work hardening rate of 1.9 GPa at 1% lattice strain. The strengthening method mentioned in this application overcomes the challenge of simultaneously achieving high yield strength and high work hardening rate. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0026] Figure 1 This is a schematic diagram of the high-pressure in-situ radial X-ray diffraction device of this application;

[0027] Figure 2 This is a top view of the sample carrier of this application;

[0028] Figure 3 This is a pressure distribution diagram inside the 9 nm palladium sample chamber during the high-pressure processing of Example 1;

[0029] Figure 4 Figure 1 shows the intensity characterization results of ultra-high strength pure metal samples based on synchrotron X-ray diffraction technology for Examples 1 to 3 and Comparative Examples 1 to 2.

[0030] Figure 5 This is a characterization diagram of the internal defects of the ultra-high strength pure metal in Example 1;

[0031] Figure 6 This is a characterization diagram of the internal defects of the ultra-high strength pure metal in Example 2;

[0032] Figure 7Atomic strain diagrams of the ultra-high strength pure metals of Example 1 and Comparative Example 1;

[0033] Figure 8 This is a work hardening rate curve for nickel with different grain sizes.

[0034] Figure label:

[0035] 100-High pressure processing device; 10-Sample carrier; 11-Sample chamber; 12-Support sheet; 13-Sealing pad; 20-Diamond anvil; 30-Cavity; 40-X-ray source. Detailed Implementation

[0036] As used in this article:

[0037] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0038] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0039] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0040] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0041] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0042] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0043] This application provides a method for preparing ultra-high strength pure metal, comprising: subjecting nano-metal powder to high pressure treatment at a pressure of 5~40 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.

[0044] The method for preparing ultra-high strength pure metal provided in this application uses nano-pure metal powder as the initial raw material, and then welds it into small blocks of tens of micrometers in size under high pressure to form a dense pure metal. No alloying elements need to be added. Pressure is a very pure control method that achieves extreme strengthening of nano-metal without introducing any impurities. Pressure can effectively suppress grain boundary slip of nanocrystals, compact the nano-metal powder to a certain extent, and avoid grain coarsening. This activates the metal's own deformation mechanism, including various crystal defects such as full dislocations, off-center dislocations, twins, and stacking faults. These various types of defects interact, generate strain fields, and superimpose each other, hindering the movement of dislocations, thereby bringing about strong work hardening and extreme strengthening, ultimately enabling the pure metal to achieve ultra-high strength.

[0045] Generally, coarse-grained metals exhibit strong work hardening during deformation, and metals larger than 100 nanometers can show a certain work hardening effect at low temperatures. However, metals a few nanometers in size are brittle at room temperature and show virtually no work hardening. This application achieves strong work hardening of nanoscale metals at room temperature through high-pressure deformation, with a work hardening rate much higher than that of coarse-grained metals. The preparation method of this application is simple and low-cost, effectively solving the weaknesses of pure metals at the nanometer scale, such as softening and lack of work hardening, and bringing their maximum strength close to the ideal strength. The preparation method of this application is universally applicable to nanoscale metals, and similar extreme strengthening has also been achieved in nanoscale nickel, gold, and stainless steel.

[0046] In some embodiments, the particle size of the nano-metal powder is less than 40 nanometers.

[0047] The initial nano-metal powder raw materials can be obtained through direct chemical synthesis or by refining coarse-grained powders, or they can be purchased from the market. The particle size of the nano-metal powder is less than 40 nanometers, for example, it can be any value of 1 nanometer, 2 nanometer, 3 nanometer, 4 nanometer, 5 nanometer, 6 nanometer, 7 nanometer, 8 nanometer, 9 nanometer, 10 nanometer, 11 nanometer, 12 nanometer, 13 nanometer, 14 nanometer, 15 nanometer, 16 nanometer, 17 nanometer, 18 nanometer, 19 nanometer, 20 nanometer, 21 nanometer, 22 nanometer, 23 nanometer, 24 nanometer, 25 nanometer, 26 nanometer, 27 nanometer, 28 nanometer, 29 nanometer, 30 nanometer, 31 nanometer, 32 nanometer, 33 nanometer, 34 nanometer, 35 nanometer, 36 nanometer, 37 nanometer, 38 nanometer, 39 nanometer or less than 40 nanometers. Generally speaking, the smaller the particle size of the nano-metal powder, the better.

[0048] The smaller the grain size, the higher the proportion of grain boundaries. High pressure makes grain boundaries a strengthening factor and avoids the softening effect.

[0049] In some embodiments, the particle size of the nano-metal powder is less than 10 nanometers.

[0050] In some embodiments, the nano-metal powder is treated in a reducing atmosphere at 100°C or below for 5 to 20 minutes to remove the surface oxide layer and achieve the purpose of pure metal.

[0051] In some embodiments, the high-pressure treatment is performed after the nano-metal powder is pre-pressed into sheets, in order to allow more sample to fill the sample cavity. If the nano-powder is directly loaded into the sample cavity, there will be 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.

[0052] In some embodiments, please refer to Figure 1 The high-pressure processing device 100 includes a sample carrier 10 and a diamond anvil cell 20, with a closed cavity 30 formed between the sample carrier 10 and the diamond anvil cell 20. The cavity 30 is used to place the nano-metal powder, and pressure is applied from both sides of the diamond anvil cell 20 toward the anvil cell to compress the cavity 30.

[0053] Figure 1 In this context, σ1 and σ3 represent the axial and radial stress components experienced by the sample, respectively.

[0054] In some embodiments, the sample carrier 10 is provided with a sample cavity 11 that extends through both sides of the sample carrier 10, and the diamond anvil cell 20 abuts against both sides of the sample carrier 10 at the two ends corresponding to the sample cavity 11, and the diamond anvil cell 20 and the sample cavity 11 form the cavity 30.

[0055] In some embodiments, please refer to Figure 2 The sample carrier 10 includes a support sheet 12 and a sealing pad 13 embedded in the support sheet 12. The sealing pad 13 has a through hole in the center, which is the sample cavity 11.

[0056] Among them, the support sheet 12 can be, for example, a Kapton plastic sheet. Kapton plastic sheet is a polyimide (PI) film material produced by DuPont. Kapton plastic sheet can maintain its performance at extreme temperatures, can withstand a temperature range from -269°C to 400°C for short periods, and can be used at temperatures up to 230°C for long periods. It has strong chemical inertness, is insoluble in any known organic solvent, is tough, wear-resistant, and has good mechanical strength.

[0057] In some embodiments, the sealing gasket 13 includes an amorphous boron gasket. The amorphous boron gasket is a mixture of amorphous boron powder and epoxy resin. The amorphous boron gasket can have any shape, but is preferably circular.

[0058] In some embodiments, the thickness of the amorphous boron gasket is 100-120 micrometers, for example, it can be any value between 100 micrometers, 105 micrometers, 110 micrometers, 115 micrometers, 120 micrometers or 100-120 micrometers.

[0059] In some embodiments, please continue reading Figure 1 The high-pressure treatment apparatus 100 also includes an X-ray source 40 for generating X-rays to perform synchrotron radiation X-ray diffraction characterization on the high-pressure treated ultra-high-strength metal.

[0060] The method for performing diffraction measurements using a high-pressure treatment apparatus 100 includes: placing a sample in a cavity 30 formed between diamond anvil cells 20 under normal pressure; establishing a coordinate origin and determining the diffraction center; positioning the sample at the diffraction center and applying pressure to the diamond anvil cells 20 to bring the pressure inside the cavity 30 to a set pressure value; turning on the X-ray source 40 to emit X-rays toward the diffraction center, and collecting data with a detector to characterize the intensity.

[0061] According to the radial diamond anvil cell X-ray diffraction theory, due to the axisymmetry of the diamond anvil cell, under high pressure, the stress at the center of the sample ( It can be decomposed into components along the axial direction ( ) and two equivalent radial components ( ), as shown below:

[0062] (1),

[0063] in This represents the normal stress component (which can be equivalent to hydrostatic pressure). ), This represents the shear stress component. The difference between the axial stress component and the radial stress component is called differential stress. (as attached) Figure 1 As shown), by The resulting strain increases continuously with increasing pressure, and an appropriate equation of state can be used for analysis. However, for... The resulting strain cannot be analyzed using state equations. According to Bragg's equations:

[0064] (2)

[0065] Where d is the inter-face spacing. The diffraction angle, Using the X-ray wavelength as an example, we can obtain the interplanar spacing (d-spacing) of different crystal planes by observing the positions of the XRD diffraction peaks. , The resulting strain can be expressed as:

[0066] (3)

[0067] in Under hydrostatic pressure Given the interplanar spacing of the crystal planes, we can reorganize formula (3) into the following expression:

[0068] (4)

[0069] in, It is the azimuth angle of the diffraction ring. .

[0070] (5)

[0071] It is the polymerization shear modulus of the powder under Reuss (stress continuity model) conditions. It is the shear modulus under the Voigt (strain continuity model) condition. It is a constant factor between 0 and 1, determined by the proportion of strain calculated under Reuss and Voigt conditions. For the cubic crystal system, This can be expressed as:

[0072] (6)

[0073] in, It 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. Based on formula (4), we draw... Follow By performing linear fitting on the changing curve, the slope and intercept can be obtained. The intercept is... The slope is From this, we can obtain The value of . Then, according to formula (5), we can derive:

[0074] (7)

[0075] The angle brackets represent the average value of the physical quantity inside the brackets. In stress The shear modulus of powder crystals. Representing elastic anisotropy, for powder crystals that are approximately isotropic, , It is also 1. The previous equation (7) can be simplified to

[0076] (8)

[0077] According to the Mises yield criterion, the differential stress that a sample can withstand can be considered as the lower limit of its yield strength, that is... ,in This represents the yield strength of the sample.

[0078] Therefore, radial diamond anvil cell X-ray diffraction experiments can be performed using a synchrotron radiation source to characterize the yield strength and flow stress of the material after yielding.

[0079] This application also provides an ultra-high strength pure metal, which is prepared by the above-described method for preparing ultra-high strength pure metal.

[0080] The extreme strengthening of ultra-high strength pure metals in this application is a combined result of grain refinement and work hardening, which is difficult to achieve using traditional methods. The resulting ultra-high strength pure metal exhibits a strengthening effect of up to approximately E / 12.3, exceeding any traditional strengthening method. Under 40 GPa pressure treatment, the maximum strength of nano-nickel reached E / 20, the maximum strength of 9-nanometer palladium reached E / 12.3, and the work hardening rate at 1% lattice strain reached 2.3 GPa (3-nanometer nickel), overcoming the challenge of simultaneously achieving high yield strength and high work hardening rate.

[0081] In some embodiments, the strength of the ultra-high strength pure metal is E / 26 to E / 12.3, where E is the Young's modulus of the metal.

[0082] The strength of the ultra-high strength pure metal obtained in this application can be, for example, any value between E / 12.3, E / 15, E / 20, E / 23, E / 26 or E / 26~E / 12.3.

[0083] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0084] Example 1

[0085] (1) Initial sample preparation

[0086] The initial sample was 9 nanometers of palladium powder.

[0087] (2) High pressure treatment

[0088] Amorphous boron pads with a thickness of 100-120 micrometers are laser-cut into small circular pieces with a diameter of 500 micrometers. A hole with a diameter of 60 micrometers is drilled in the center of each small circular piece. The small circular piece with the hole is placed in a long strip of Kapton plastic support with an inner diameter slightly larger than 500 micrometers (approximately 510 micrometers). The Kapton plastic support with the perforated pad is placed in a diamond anvil cell, with the hole located in the exact center of the diamond. The powder is slightly pre-pressed into a sheet shape (the purpose is to initially densify the powder, which can be done using a tableting mold or a pair of flat, hard materials, by hand or a small hydraulic press, with very low pressure, such as less than 1 MPa), and then inserted into the hole of the pad, ensuring that the sample fills the entire hole. The pressure is then applied to approximately 40 GPa using a diamond anvil cell with a 300-micrometer mesa.

[0089] (3) Strength characterization

[0090] Characterized by synchrotron X-ray diffraction, the final maximum intensity obtained was approximately E / 12.3, such as... Figure 4 As shown; Internal defect characterization diagram as shown Figure 5 As shown, high-density deformation twins are visible.

[0091] Example 2

[0092] (1) Initial sample preparation

[0093] The initial sample was 3 nanometers of metallic nickel powder.

[0094] (2) High pressure treatment

[0095] Amorphous boron pads with a thickness of 100-120 micrometers were laser-cut into small circular pieces with a diameter of 500 micrometers. A hole with a diameter of 60 micrometers was drilled in the center of each small circular piece. The small circular pieces with holes were placed in a long strip of Kapton plastic support with an inner diameter slightly larger than 500 micrometers (approximately 510 micrometers). The Kapton plastic support with the perforated pads was then placed in a diamond anvil cell, with the hole positioned at the exact center of the diamond. The powder was slightly pre-pressed into a sheet shape and then inserted into the hole of the pad, ensuring that the sample filled the entire hole. A diamond anvil cell with a 300-micrometer mesa was used to apply pressure to 40 GPa.

[0096] (3) Strength characterization

[0097] Characterized by synchrotron X-ray diffraction, the final maximum intensity obtained was approximately E / 20, such as Figure 4 As shown; Internal defect characterization diagram as shown Figure 6 As shown, complex and diverse crystal defects have emerged, including full dislocations, off-center dislocations, and twins.

[0098] Example 3

[0099] (1) Initial sample preparation

[0100] The initial sample was 8 nanometers of metallic nickel powder.

[0101] (2) High pressure treatment

[0102] Amorphous boron pads with a thickness of 100-120 micrometers were laser-cut into small circular pieces with a diameter of 500 micrometers. A hole with a diameter of 60 micrometers was drilled in the center of each small circular piece. The small circular pieces with holes were placed in a long strip of Kapton plastic support with an inner diameter slightly larger than 500 micrometers (approximately 510 micrometers). The Kapton plastic support with the perforated pads was then placed in a diamond anvil cell, with the hole positioned at the exact center of the diamond. The powder was slightly pre-pressed into a sheet shape and then inserted into the hole of the pad, ensuring that the sample filled the entire hole. A diamond anvil cell with a 300-micrometer mesa was used to apply pressure to 40 GPa.

[0103] (3) Strength characterization

[0104] Characterized by synchrotron X-ray diffraction, the final maximum intensity obtained was approximately E / 26, such as Figure 4 As shown in the upper right corner (green 8 nm Ni).

[0105] Example 4

[0106] (1) Initial sample preparation

[0107] The initial sample was 20 nanometers of metallic nickel powder.

[0108] (2) High pressure treatment

[0109] Amorphous boron pads with a thickness of 100-120 micrometers were laser-cut into small circular pieces with a diameter of 500 micrometers. A hole with a diameter of 60 micrometers was drilled in the center of each small circular piece. The small circular pieces with holes were placed in a long strip of Kapton plastic support with an inner diameter slightly larger than 500 micrometers (approximately 510 micrometers). The Kapton plastic support with the perforated pads was then placed in a diamond anvil cell, with the hole positioned at the exact center of the diamond. The powder was slightly pre-pressed into a sheet shape and then inserted into the hole of the pad, ensuring that the sample filled the entire hole. A diamond anvil cell with a 300-micrometer mesa was used to apply pressure to 40 GPa.

[0110] Comparative Example 1

[0111] (1) Initial sample preparation

[0112] The initial sample was 700 nanometers of palladium powder.

[0113] (2) High pressure treatment

[0114] Amorphous boron pads with a thickness of 100-120 micrometers were laser-cut into small circular pieces with a diameter of 500 micrometers. A hole with a diameter of 60 micrometers was drilled in the center of each small circular piece. The small circular pieces with holes were placed in a long strip of Kapton plastic support with an inner diameter slightly larger than 500 micrometers (approximately 510 micrometers). The Kapton plastic support with the perforated pads was then placed in a diamond anvil cell, with the hole positioned at the exact center of the diamond. The powder was slightly pre-pressed into a sheet shape and then inserted into the hole of the pad, ensuring that the sample filled the entire hole. A diamond anvil cell with a 300-micrometer mesa was used to apply pressure to 40 GPa.

[0115] (3) Strength characterization

[0116] Characterized by synchrotron X-ray diffraction, the maximum intensity finally obtained was only E / 53, such as Figure 4 (700 nm Pd is marked in red). The initial sample was not below 100 nm, so the strengthening effect was not obvious, indicating that the ultra-high strength of the metal is obtained by the synergistic effect of fine grain strengthening and high pressure induced strain field superposition.

[0117] Atomic strain diagrams of 9 nm palladium in Example 1 and 700 nm palladium in Comparative Example 1 after high-pressure deformation are shown below. Figure 7 As shown, compared to 700 nm palladium, 9 nm palladium has a greater degree of atomic strain, which is the key to its extreme strengthening.

[0118] Comparative Example 2

[0119] (1) Initial sample preparation

[0120] The initial sample was 3 nanometers of metallic nickel powder.

[0121] (2) High pressure treatment

[0122] A 250-micrometer-thick rhenium (Re) gasket was used, and laser drilling was used to make the sample cavity diameter 50 micrometers and the diamond stage 150 micrometers. The sample was then subjected to an ultra-high pressure treatment of 150 GPa.

[0123] (3) Strength characterization

[0124] Its strength cannot be characterized by the method of this application because most of the nickel powder becomes an amorphous structure, which indicates that when the pressure exceeds the limit that the lattice can withstand, the crystal structure becomes unstable and transforms into an amorphous structure.

[0125] Comparative Example 3

[0126] (1) Initial sample preparation

[0127] The initial sample was 200 nanometers of metallic nickel powder.

[0128] (2) High pressure treatment

[0129] Amorphous boron pads with a thickness of 100-120 micrometers were laser-cut into small circular pieces with a diameter of 500 micrometers. A hole with a diameter of 60 micrometers was drilled in the center of each small circular piece. The small circular pieces with holes were placed in a long strip of Kapton plastic support with an inner diameter slightly larger than 500 micrometers (approximately 510 micrometers). The Kapton plastic support with the perforated pads was then placed in a diamond anvil cell, with the hole positioned at the exact center of the diamond. The powder was slightly pre-pressed into a sheet shape and then inserted into the hole of the pad, ensuring that the sample filled the entire hole. A diamond anvil cell with a 300-micrometer mesa was used to apply pressure to 40 GPa.

[0130] The work hardening rate curves of nickel with different grain sizes in Examples 2, 3, 4 and Comparative Example 3 are shown in the figure. Figure 8 As shown, the work hardening rate of 3 nm nickel at 1% lattice strain reached 2.3 GPa; the work hardening rate of 8 nm nickel at 1% lattice strain reached 1.9 GPa.

[0131] Therefore, the suitable pressure range for strengthening in this application is 5-40 GPa, and the metal powder particle size is less than 40 nanometers. The lower pressure limit is to induce plastic deformation in the material and produce an effect that inhibits grain boundary slip. If the pressure is too low, the effect of high pressure will not be manifested, and it will become similar to the effect of conventional fine grain strengthening.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0133] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing an ultra-high strength pure metal, characterized in that, include: High-pressure treatment of nano-pure metal powder at a pressure of 20~40 GPa yields ultra-high strength pure metal. The ultra-high strength pure metal is nickel or palladium; The particle size of the nano-pure metal powder is less than 5 nanometers; The nano-pure metal powder is treated in a reducing atmosphere at 100°C or below for 5 to 20 minutes. The nano-pure metal powder is pre-pressed into sheets and then subjected to the high-pressure treatment. The strength of the ultra-high strength pure metal is E / 26 to E / 12.

3.

2. The method for preparing ultra-high strength pure metal according to claim 1, characterized in that, The high-pressure treatment device includes a sample carrier and a diamond anvil cell, with a closed cavity formed between the sample carrier and the diamond anvil cell. The cavity is used to place the nano-pure metal powder, and pressure is applied from both sides of the diamond anvil cell towards the anvil cell to compress the cavity.

3. The method for preparing ultra-high strength pure metal according to claim 2, characterized in that, The sample carrier has a sample cavity that extends through both sides of the sample carrier. The diamond anvil cell is supported on both sides of the sample carrier at the two ends of the sample cavity. The diamond anvil cell and the sample cavity form the cavity.

4. The method for preparing ultra-high strength pure metal according to claim 3, characterized in that, The sample carrier includes a support sheet and a sealing pad embedded in the support sheet. The sealing pad has a through hole in its center, which is the sample cavity.

5. The method for preparing ultra-high strength pure metal according to claim 4, characterized in that, The sealing gasket includes: an amorphous boron gasket; The thickness of the amorphous boron gasket is 100-120 micrometers.

6. A high-strength pure metal, characterized in that, It is prepared by the method for preparing ultra-high strength pure metal according to any one of claims 1 to 5.

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