1. CrCoNi-Al with heterostructure₂O₃A nanocomposite characterized by: the microstructure of the material is a heterostructure consisting of two areas of a coarse crystal area CG and a super fine crystal area UFG, and the super fine crystal area is formed by 2.5-5% of nano Al by mass fraction₂O₃Grains and superfine crystal matrix of Cr, Co and Ni in equal atomic ratio, in which there is Al dispersed homogeneously in the superfine crystal area₂O₃The nano particles are nano annealing twin crystals traversing CrCoNi matrix grains; the coarse crystal area is matrix of crystal grains formed by Cr, Co and Ni with equal atomic ratio, and the content of the coarse crystal area is 10-30 wt%.

2. CrCoNi-Al for preparing the heterostructure of claim 1₂O₃A method of preparing a nanocomposite characterised by the steps of:

step 1, pre-grinding coarse grains: adding Cr, Co and Ni powder with equal atomic ratio into a stainless steel tank in an operation box protected by high-purity argon, adding a stainless steel ball and absolute ethyl alcohol with the mass of 2-3 wt% of the powder as a process control agent, finally installing the sealed stainless steel ball milling tank on an omnibearing planetary ball mill, and performing positive and negative bidirectional rotation at the speed of 300-;

the grain size of the original powder Cr, Co and Ni is less than or equal to 48 mu m, alpha-Al₂O₃The particle size of the nano powder is 30-50 nm;

step 2, homogenizing CrCoNi-Al₂O₃High-energy ball milling of composite powder: al with the component of 2.5-5 wt% is put in an operation box protected by high-purity argon₂O₃Respectively and sequentially adding the nano powder and Cr, Co and Ni powder with equal atomic ratio into a stainless steel tank, adding stainless steel balls and alcohol with the mass of 2-3 wt% of the powder as a process control agent, finally installing the sealed stainless steel ball milling tank on an omnibearing planetary ball mill, and performing forward and reverse bidirectional rotation at the speed of 300-400rpm at room temperature for 50-55h to prepare the uniformly mixed CrCoNi-Al₂O₃Composite powder as UFG in the ultra-fine grain region of the isomeric intermediate entropy alloy-based composite material;

step 3, coarse/fine grain blending: in a high-purity argon protection operation box, 0-30 wt% of coarse grain powder obtained in the step 2 and CrCoNi-Al obtained in the step 3 are mixed₂O₃Adding the composite fine grain powder into a stainless steel tank, adding stainless steel balls and 2-3 wt% of alcohol in the powder quality as a process control agent, finally installing the sealed stainless steel ball milling tank on an omnibearing planetary ball mill, and performing positive and negative bidirectional rotation at the speed of 300 plus and 400rpm for 10-15h at room temperature to uniformly mix coarse and fine grains to obtain the mesoentropy alloy-based composite material powder with the heterostructure;

step 4, die filling and cold pressing: firstly, stacking a circle of graphite paper with the size consistent with that of the inner wall of a graphite mould on the inner wall of the graphite mould, then loading the powder of the heterostructure mid-entropy alloy-based composite material into the graphite mould in an operation box protected by high-purity argon, stacking the graphite paper on the upper end and the lower end, then mounting a graphite pressure head, and finally performing cold pressing compaction by using the pressure of 15-20 MPa;

and 5, vacuum hot-pressing sintering: placing the graphite mould filled with the composite powder into a vacuum hot-pressing furnace, and sintering the graphite mould into a block body through vacuumizing, heating, heat preservation and pressure maintaining; the sintering process is that the sintering is finished under the conditions of 1000-1100 ℃/30-50MPa of temperature and pressure preservation for 30-60min under the oxygen-free environment, and then the mould is taken out after the furnace is cooled to the room temperature;

step 6,Demolding: demoulding after sintering is finished to obtain corresponding heterostructure CrCoNi-Al₂O₃A nanocomposite material.

3. The method of claim 2, wherein: the purity of the original powder Cr, Co and Ni is more than or equal to 99.5 wt%.

4. The method of claim 2, wherein: the alpha-Al₂O₃The purity of the nano powder is more than or equal to 99.8 wt%.

5. The method of claim 2, wherein: the ball-material ratio in ball milling in the steps 1 to 3 is 10:1-15: 1.

Background

Cantor and Yeh in 2004 proposed a high entropy alloy concept based on near equal atomic ratios of multiple principal elements. The appearance of the novel alloy mainly designed by the configuration entropy breaks through the design concept of the traditional alloy mainly designed by 1 or 2 elements. Because a plurality of main elements exist under the nearly equal atomic ratio (5-35%), the high-entropy alloy shows four unique effects, namely a high-entropy effect, a delayed diffusion effect, a lattice distortion effect and a cocktail effect. The high-entropy alloy has wide application prospect in the field of structural materials due to unique components, microstructures and adjustable and controllable performance.

The research on the early stage of the high-entropy alloy mostly focuses on the design of alloy components, and with the gradual and deep research on the high-entropy alloy, besides the regulation and control of the alloy components, more methods for optimizing the performance have been used, for example, the preparation of a high-entropy alloy-based composite material by introducing second-phase nanoparticles into the high-entropy alloy is one of the most common strengthening means.

However, in the search for high-entropy alloy-based composite materials, a common problem is encountered in that the ductility of the materials is impaired to some extent by the increase in yield strength of the materials. From the traditional strengthening and toughening mechanism, the contradiction between strengthening and toughening seems to be irresolvable from the root. The strengthening of the material is realized by blocking dislocation motion, while the toughening is realized by plastic deformation, stress concentration release and crack initiation delay in a mode of promoting the starting of a dislocation source and the like. In the continuous effort of overcoming the contradiction between strength and ductility of materials, researchers have proposed a new concept of isomeric materials in the last five years, and the materials have high strength while ensuring larger ductility. A heterogeneous material may be defined as a material having significant heterogeneity in intensity from one region to another. This intensity heterogeneity may be caused by microstructural heterogeneity, crystalline structural heterogeneity, or compositional heterogeneity. The material is divided into a bimodal structure, a trimodal structure, a non-uniform flake structure, a gradient structure, a harmonic structure, a laminated plate structure, dual-phase steel, a nano-domain structure, a nano-twin crystal and the like.

The formation of the heterostructure generates a soft region and a hard region in the material, the soft region enables the material to have enough plastic regions to passivate or deflect cracks, meanwhile, due to strain mismatch at the interface of the soft region and the hard region, the accumulation of geometrical necessary dislocation is generated, and heterogeneous deformation induced stress is introduced into the material, so that the prepared material has high strength and toughness. The rise of the heterogeneous materials provides a new idea for the strengthening and toughening development of the composite material.

In current research, heterostructures have been widely used in various nanostructured materials, such as Al, Mg, Cu, Ti, High Entropy Alloys (HEA), Medium Entropy Alloys (MEA), and the like. For example, in CN 110629059 a, "a isomeric high-entropy alloy material and a preparation method thereof", a isomeric high-entropy alloy having advantages of various materials is obtained by mixing and mechanically alloying two or more high-entropy alloy scraps having different grain refinement effects, and then performing pre-compaction, plastic deformation treatment, annealing treatment and other processes. However, the method needs further plastic deformation and heat treatment to realize the coarse/fine grain region, the process flow is complex, and the obtained alloy material has low strength and tensile strength lower than 1000 MPa.

Compared with the nano material, due to the introduction of the second phase hard particles, the design and realization of the heterostructure are more difficult, so that the heterostructure research in the nano composite material is less, and the preparation of the trimodal structure or the layered structure is mainly limited in substrates such as Al, Ti, Mg and the like. Such as patent CN 111376572A "preparation method of heterogeneous layered aluminum-based composite material" and patent CN 111408623A "preparation multiscale analysisThe method and the system for producing the nano heterogeneous magnesium alloy plate respectively adopt a multi-pass accumulative stack rolling or rolling hot rolling process to form a layered heterostructure in the composite material. However, both of the above processes are only suitable for the preparation of sheet materials. In patent CN 111961902A, "titanium-based composite material with heterogeneous structure, preparation method and application thereof", a titanium-based composite material with grain size and component double heterogeneous structure is introduced, which is composed of titanium or titanium alloy as a matrix and in-situ self-generated titanium carbide particles or titanium boride whiskers as a reinforcing phase, and a new method is provided for preparing the titanium-based composite material with heterogeneous structure. Compared with the titanium matrix adopted in the patent, the medium entropy alloy CrCoNi as the matrix material shows better obdurability. There is currently no heterostructure-related Al₂O₃Reports of nano-particle reinforced CrCoNi-based intermediate entropy alloy-based composite materials.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides a CrCoNi-Al heterostructure₂O₃The nano composite material and the preparation method solve the problem of the contradiction between the strength and the ductility of the high-entropy and medium-entropy alloy-based nano composite material.

Technical scheme

CrCoNi-Al with heterostructure₂O₃A nanocomposite characterized by: the microstructure of the material is a heterostructure consisting of two areas of a coarse crystal area CG and a super fine crystal area UFG, and the super fine crystal area is formed by 2.5-5% of nano Al by mass fraction₂O₃Grains and superfine crystal matrix of Cr, Co and Ni in equal atomic ratio, in which there is Al dispersed homogeneously in the superfine crystal area₂O₃The nano particles are nano annealing twin crystals traversing CrCoNi matrix grains; the coarse crystal area is matrix of crystal grains formed by Cr, Co and Ni with equal atomic ratio, and the content of the coarse crystal area is 10-30 wt%.

CrCoNi-Al for preparing the heterostructure₂O₃A method of preparing a nanocomposite characterised by the steps of:

step 1, pre-grinding coarse grains: adding Cr, Co and Ni powder with equal atomic ratio into a stainless steel tank in an operation box protected by high-purity argon, adding a stainless steel ball and absolute ethyl alcohol with the mass of 2-3 wt% of the powder as a process control agent, finally installing the sealed stainless steel ball milling tank on an omnibearing planetary ball mill, and performing positive and negative bidirectional rotation at the speed of 300-;

the grain size of the original powder Cr, Co and Ni is less than or equal to 48 mu m, alpha-Al₂O₃The particle size of the nano powder is 30-50 nm;

step 2, homogenizing CrCoNi-Al₂O₃High-energy ball milling of composite powder: al with the component of 2.5-5 wt% is put in an operation box protected by high-purity argon₂O₃Respectively and sequentially adding the nano powder and Cr, Co and Ni powder with equal atomic ratio into a stainless steel tank, adding stainless steel balls and alcohol with the mass of 2-3 wt% of the powder as a process control agent, finally installing the sealed stainless steel ball milling tank on an omnibearing planetary ball mill, and performing forward and reverse bidirectional rotation at the speed of 300-400rpm at room temperature for 50-55h to prepare the uniformly mixed CrCoNi-Al₂O₃Composite powder as UFG in the ultra-fine grain region of the isomeric intermediate entropy alloy-based composite material;

step 3, coarse/fine grain blending: in a high-purity argon protection operation box, 0-30 wt% of coarse grain powder obtained in the step 2 and CrCoNi-Al obtained in the step 3 are mixed₂O₃Adding the composite fine grain powder into a stainless steel tank, adding stainless steel balls and 2-3 wt% of alcohol in the powder quality as a process control agent, finally installing the sealed stainless steel ball milling tank on an omnibearing planetary ball mill, and performing positive and negative bidirectional rotation at the speed of 300 plus and 400rpm for 10-15h at room temperature to uniformly mix coarse and fine grains to obtain the mesoentropy alloy-based composite material powder with the heterostructure;

step 4, die filling and cold pressing: firstly, stacking a circle of graphite paper with the size consistent with that of the inner wall of a graphite mould on the inner wall of the graphite mould, then loading the powder of the heterostructure mid-entropy alloy-based composite material into the graphite mould in an operation box protected by high-purity argon, stacking the graphite paper on the upper end and the lower end, then mounting a graphite pressure head, and finally performing cold pressing compaction by using the pressure of 15-20 MPa;

and 5, vacuum hot-pressing sintering: placing the graphite mould filled with the composite powder into a vacuum hot-pressing furnace, and sintering the graphite mould into a block body through vacuumizing, heating, heat preservation and pressure maintaining; the sintering process is that the sintering is finished under the conditions of 1000-1100 ℃/30-50MPa of temperature and pressure preservation for 30-60min under the oxygen-free environment, and then the mould is taken out after the furnace is cooled to the room temperature;

step 6, demolding: demoulding after sintering is finished to obtain corresponding heterostructure CrCoNi-Al₂O₃A nanocomposite material.

The purity of the original powder Cr, Co and Ni is more than or equal to 99.5 wt%.

The alpha-Al₂O₃The purity of the nano powder is more than or equal to 99.8 wt%.

The ball-material ratio in ball milling in the steps 1 to 3 is 10:1-15: 1.

Advantageous effects

The invention provides a CrCoNi-Al with a heterostructure₂O₃The nanometer composite material is prepared through powder metallurgy process on Al₂O₃The nanometer particle reinforced CrCoNi entropy alloy base composite material is introduced with a heterostructure to prepare a material with a superfine crystal region (UFG), a coarse crystal region (CG), a nanometer twin crystal and a nanometer Al₂O₃Granular multi-scale heterogeneous composite materials. Ultra fine crystal grains and Al₂O₃The nano reinforcing phase ensures the high strength of the composite material, meanwhile, the coarse grains maintain the good plasticity of the composite material, and the geometry at the interface of the soft and hard regions must be dislocated and stacked to bring extra reinforcing effect. The invention provides a method for preparing a high-strength high-toughness high/medium-entropy alloy-based composite material, provides a new idea for developing a high-strength high-ductility high-entropy and medium-entropy alloy-based composite material, and promotes a heterostructure to be suitable for more material systems.

Compared with the prior art, the invention has the following advantages:

(1) the invention adopts the mechanical alloying and vacuum hot pressing sintering or discharge plasma sintering process to prepare the CrCoNi-Al₂O₃The isomeric composite material has simple preparation processThe method has the advantages of simple process, strong repeatability and strong applicability, and can be popularized to the production of other isomeric composite materials.

(2) The invention can obtain the Al with the microstructure consisting of a coarse crystal area (CG), an ultra-fine crystal area (UFG) and an ultra-fine crystal area which are uniformly dispersed and distributed in the ultra-fine crystal area₂O₃The multi-scale intermediate entropy alloy-based heterogeneous composite material is composed of nano particles and nano annealing twin crystals in the cross CrCoNi matrix grains, and the microstructure can be regulated and controlled by simply changing the proportion of coarse crystals and fine crystals.

(3) The isomeric CrCoNi-Al of the invention₂O₃The nano composite material has higher compressive yield strength and excellent plasticity. Isomeric CrCoNi-Al containing 20 wt% coarse grains₂O₃The compressive yield strength of the composite material is 1664MPa, and the breaking strain is 24.9%. Comparative uniform CrCoNi-Al₂O₃The yield strength of the nano composite material is kept at the same level, the fracture strain is improved by 58.6 percent, and the nano composite material shows excellent comprehensive mechanical properties.

Drawings

FIG. 1 is CrCoNi-Al₂O₃The result of X-ray diffraction (XRD) analysis of the isomeric composite material. The heterogeneous composite material mainly comprises a face-centered cubic (FCC) phase matrix and alpha-Al₂O₃Ceramic particles.

FIGS. 2(a), (b), (c) and (d) are CrCoNi-Al containing Coarse Grains (CG) in an amount of 0 wt%, 10 wt%, 20 wt% and 30 wt%, respectively₂O₃Scanning electron microscope pictures (SEM-BSE picture) of the heterogeneous composite material. The microstructure of the material is composed of a coarse grain region (CG) and nano Al which is uniformly dispersed₂O₃Ultra Fine Grain (UFG) composition of particles in which more Cr is formed in 30CG isomeric composite₂₃C₆A compound is provided.

Fig. 3(a) is a Transmission Electron Microscope (TEM) bright field image of a heterogeneous composite material containing 20 wt% Coarse Grains (CG), and fig. 3(b) is a schematic representation of the corresponding microstructure. The microstructure of the alloy shows typical CrCoNi-Al₂O₃The heterogeneous composite material consists of coarse grain region and superfine grain region, and has nanometer reinforcing phase particle (Al)₂O₃) Uniformly distributed in the superfine crystal matrixNanometer annealing twin crystals which traverse the whole crystal grains exist in the body, and the annealing twin crystals also exist in the coarse crystal grain matrix.

FIGS. 4(a), (b) and (c) are the coarse grain region (CG), the ultra-fine grain region (UFG) and the nano Al in the isomeric composite material containing 20 wt% Coarse Grain (CG), respectively₂O₃Size distribution statistical plot of particles. Wherein the coarse crystal region, the ultra-fine crystal region and the nano Al₂O₃The sizes of the particles are 557 +/-223 nm, 231 +/-81 nm and 87 +/-44 nm respectively.

FIG. 5 is CrCoNi-Al₂O₃The results of the property analysis of the nanocomposite, wherein (a) is Vickers hardness and (b) is a compressive engineering stress-strain curve. It can be seen that as the coarse crystalline phase content increases, the hardness value decreases first and then increases, the compressive yield strength is basically maintained at the level of a uniform composite material, but the fracture strain of the 20CG isomeric composite material is remarkably increased, the increase reaches 58.6%, and the optimal strong plasticity combination is shown.

Detailed Description

The invention will now be further described with reference to the following examples and drawings:

the invention prepares the CrCoNi-Al with a heterostructure₂O₃A nanocomposite material. The microstructure of the material mainly comprises two regions of a coarse grain region (CG) and an ultra-fine grain region (UFG), wherein Al is uniformly dispersed in the ultra-fine grain region₂O₃Nanoparticles and nano-annealed twins across the CrCoNi matrix grains. The coarse crystal area is a matrix of larger crystal grains formed by Cr, Co and Ni with equal atomic ratio, and the fine crystal area is formed by nano Al with the mass fraction of 2.5-5%₂O₃Particles and an ultrafine crystal matrix formed by Cr, Co and Ni with equal atomic ratio. The coarse and ultra-fine grained regions constitute a so-called heterostructure. In the isomeric composite material, the content of the coarse crystalline regions is selected to be 10 to 30 wt.%.

The preparation process mainly comprises coarse grain matrix powder and Al₂O₃Mechanical alloying of uniformly distributed fine-grained composite powder of CrCoNi (coarse grain pre-milling, homogeneous CrCoNi-Al)₂O₃High-energy ball milling of composite powder, blending of coarse and fine grains), die filling and cold pressing, vacuum hot pressing sintering or discharge plasmaSintering the daughter, and the like. The specific process comprises the following steps:

(1) starting powder material

The purity of original powder Cr, Co and Ni is more than or equal to 99.5 wt%, the particle size is less than or equal to 48 mu m, alpha-Al₂O₃The purity of the nano powder is more than or equal to 99.8 wt%, and the particle size is 30-50 nm.

(2) Pre-grinding of coarse grains

Weighing Cr, Co and Ni powder with equal atomic ratio in an operation box protected by high-purity argon, adding the Cr, Co and Ni powder into a stainless steel tank, adding a stainless steel ball (ball-to-material ratio is 10:1-15:1) and absolute ethyl alcohol with the mass of 2-3 wt% of the powder as a process control agent (preventing the powder from being cold welded on the tank body and the stainless steel ball), finally installing the sealed stainless steel ball milling tank on an omnibearing planetary ball mill, and performing forward and reverse bidirectional rotation at the speed of 300 plus and minus 400rpm for 10-15h at room temperature, so that the CrCoNi powder is preliminarily alloyed after being pre-milled and is used as a coarse grain region (CG) of the isomeric entropy alloy-based composite material.

(3) Homogeneous CrCoNi-Al₂O₃High energy ball mill for composite powder

Al with the component of 2.5-5 wt% is put in an operation box protected by high-purity argon₂O₃The nanometer powder and the Cr, Co and Ni powder with equal atomic ratio are respectively added into a stainless steel tank (Al)₂O₃The nano particles are directly added into the mixed powder of Cr, Co and Ni before ball milling, which is beneficial to hard Al₂O₃Embedding the particles into a metal matrix with good plasticity through a ball milling process so as to enable the particles to be uniformly dispersed and distributed in the matrix), adding stainless steel balls (the ball-material ratio is 10:1-15:1) and alcohol with the powder quality of 2-3 wt% as process control agents (preventing the powder from being cold-welded on a tank body and the stainless steel balls), finally installing a sealed stainless steel ball milling tank on an all-directional planetary ball mill, and performing forward and reverse bidirectional rotation at the speed of 300-400rpm at room temperature for 50-55h to prepare the uniformly mixed CrCoNi-Al₂O₃Composite powder as Ultra Fine Grain (UFG) region of a isomeric isentropic alloy based composite.

(4) Coarse/fine grain blending

Step (2) of setting the composition to 0 to 30 wt% in a high purity argon protected operation boxThe obtained coarse grain powder and the CrCoNi-Al obtained in the step (3)₂O₃And sequentially adding the composite fine grain powder into a stainless steel tank, adding a stainless steel ball (ball-to-material ratio is 10:1-15:1) and 2-3 wt% of alcohol based on the mass of the powder as a process control agent (preventing the powder from being cold-welded on the tank body and the stainless steel ball), finally installing the sealed stainless steel ball milling tank on an all-directional planetary ball mill, and performing forward and reverse bidirectional rotation at the speed of 300 plus 400rpm for 10-15 hours at room temperature to uniformly mix coarse and fine grains to obtain the intermediate entropy alloy based composite material powder with the heterostructure.

(5) Die filling and cold pressing

Firstly, stacking a circle of graphite paper with the size consistent with that of the inner wall of a graphite mould on the inner wall of the graphite mould, then loading the powder obtained in the step (4) into the graphite mould in an operation box protected by high-purity argon, stacking the graphite paper on the upper end and the lower end, then loading a graphite pressure head, and finally carrying out cold pressing compaction by using the pressure of 15-20 MPa.

(6) Vacuum hot pressing sintering

And (3) placing the graphite mould filled with the composite powder into a vacuum hot-pressing furnace, and sintering the graphite mould into a block body through vacuumizing, heating, heat preservation and pressure maintaining. The sintering process is that the sintering is finished under the conditions of 1000-1100 ℃/30-50MPa of temperature and pressure preservation for 30-60min under the oxygen-free environment, and then the mould is taken out after the furnace is cooled to the room temperature.

(7) Demoulding

Demoulding after sintering is finished to obtain corresponding heterostructure CrCoNi-Al₂O₃A nanocomposite material.

Example 1

(1) Weighing Cr, Co and Ni metal powder with equal atomic ratio in an operation box under the protection of high-purity argon, wherein the purity of the Cr, Co and Ni powder is more than or equal to 99.5 wt%, and the particle size is less than or equal to 48 mu m, then sequentially adding the powder, a stainless steel ball (ball-to-material ratio is 10:1) and absolute ethyl alcohol with the powder mass of 2.5 wt% into a stainless steel ball milling tank, finally installing the sealed stainless steel tank on an omnibearing planetary ball mill, and carrying out ball milling at the room temperature at the speed of 300rpm for 10h to obtain primarily alloyed CrCoNi powder, namely a coarse crystal grain region (CG).

(2) Weighing Cr, Co and Ni powder with equal atomic ratio and 5 wt% alpha in an operation box protected by high-purity argon-Al₂O₃Nano powder, wherein the purity of Cr, Co and Ni powder is more than or equal to 99.5 wt%, the particle size is less than or equal to 48 mu m, and Al₂O₃The purity of the powder is more than or equal to 99.8 wt%, and the particle size is 30-50 nm. Then sequentially adding the powder, stainless steel balls (ball-to-material ratio is 10:1) and absolute ethyl alcohol with the mass of 2.5 wt% of the powder into a stainless steel ball milling tank, finally installing the sealed stainless steel tank on an omnibearing planetary ball mill, and carrying out ball milling at the speed of 300rpm for 50h at room temperature to obtain the uniformly mixed CrCoNi-5 wt% Al₂O₃Composite powder, i.e., ultra fine grain regions (UFGs).

(3) Weighing 10 wt% of coarse grain powder obtained in the step (2) and the uniformly mixed CrCoNi-5 wt% Al obtained in the step (3) in an operation box protected by high-purity argon₂O₃And (2) compounding the powder, sequentially adding the powder, rust steel balls (ball-to-material ratio is 10:1) and alcohol with the mass of 2.5 wt% of the powder into a stainless steel tank ball milling tank, finally installing the sealed stainless steel tank on an omnibearing planetary ball mill, and carrying out ball milling at the speed of 300rpm for 10 hours at room temperature to obtain the isomeric medium-entropy alloy-based composite material powder with uniformly mixed coarse and fine grains.

(4) And (3) padding a circle of graphite paper with the size consistent with that of the inner wall on the inner wall of the graphite mould with the inner diameter of phi 30mm, then loading the powder obtained in the step (3) into the graphite mould in an operation box under the protection of high-purity argon, padding the graphite paper on the upper end and the lower end, then loading a graphite pressure head, and finally cold pressing by using the pressure of 15-20 MPa.

(5) And putting the graphite mould filled with the composite powder into vacuum hot-pressing sintering equipment, vacuumizing, preserving heat at the temperature of 1000 ℃ and under the pressure of 30MPa for 60min, finishing sintering, finally cooling the graphite mould to room temperature, taking out the mould, and demoulding to obtain the block heterogeneous composite material with the size of phi 30mm multiplied by 7 mm.

(6) The 10CG isomeric composite material obtained by mechanical alloying and vacuum hot pressing sintering process mainly comprises FCC phase and alpha-Al₂O₃And (4) forming. The microstructure is composed of coarse grain region (CG) and nano Al uniformly dispersed₂O₃Fine grain region (UFG) composition of the particles, as shown in fig. 2 (b). 10CG isomeric CrCoNi-Al prepared by the process₂O₃The composite material has excellent comprehensive properties: hardness 517 + -14 HV, compressive yield strength 1711MPa, compressive fracture strength 2270MPa, and fracture strain 19.5%, as shown in FIG. 5. With homogeneous CrCoNi-5 wt% Al₂O₃Compared with the composite material, the 10CG isomeric composite material has the advantages that the hardness and the yield strength are slightly reduced due to the introduction of a coarse grain region, but the ductility is obviously improved.

Example 2

(1) Weighing Cr, Co and Ni powder with equal atomic ratio in an operation box under the protection of high-purity argon, wherein the purity of the Cr, Co and Ni powder is more than or equal to 99.5 wt%, and the particle size is less than or equal to 48 mu m, then sequentially adding the powder, stainless steel balls (ball-to-material ratio is 10:1) and alcohol with the powder quality of 2.5 wt% into a stainless steel ball milling tank, finally installing the sealed stainless steel tank on an omnibearing planetary ball mill, and carrying out ball milling at the room temperature at the speed of 300rpm for 10h to obtain primarily alloyed CrCoNi powder, namely a coarse grain region (CG).

(2) Weighing Cr, Co and Ni powder with equal atomic ratio and 5 wt% of alpha-Al in an operation box protected by high-purity argon₂O₃Nano powder, wherein the purity of Cr, Co and Ni powder is more than or equal to 99.5 wt%, the particle size is less than or equal to 48 mu m, and Al₂O₃The purity of the powder is more than or equal to 99.8 wt%, and the particle size is 30-50 nm. Then sequentially adding the powder, stainless steel balls (ball-to-material ratio is 10:1) and absolute ethyl alcohol with the mass of 2.5 wt% of the powder into a stainless steel ball milling tank, finally installing the sealed stainless steel tank on an omnibearing planetary ball mill, and carrying out ball milling at the speed of 300rpm for 50h at room temperature to obtain the uniformly mixed CrCoNi-5 wt% Al₂O₃Composite powder, i.e., ultra fine grain regions (UFGs).

(3) Weighing 20 wt% of coarse grain powder obtained in the step (2) and the uniformly mixed CrCoNi-5 wt% Al obtained in the step (3) in an operation box protected by high-purity argon gas₂O₃And (2) compounding the powder, sequentially adding the powder, rust steel balls (ball-to-material ratio is 10:1) and absolute ethyl alcohol accounting for 2.5 wt% of the mass of the powder into a stainless steel tank ball milling tank, finally installing the sealed stainless steel tank on an omnibearing planetary ball mill, and carrying out ball milling at the speed of 300rpm for 10 hours at room temperature to obtain the isomeric intermediate entropy alloy-based composite material powder with uniformly mixed coarse and fine grains.

(4) And (3) padding a circle of graphite paper with the size consistent with that of the inner wall on the inner wall of the graphite mould with the inner diameter of phi 30mm, then loading the powder obtained in the step (3) into the graphite mould in an operation box under the protection of high-purity argon, padding the graphite paper on the upper end and the lower end, then loading a graphite pressure head, and finally cold pressing by using the pressure of 15-20 MPa.

(5) And putting the graphite mould filled with the composite powder into vacuum hot-pressing sintering equipment, vacuumizing, preserving heat at the temperature of 1000 ℃ and under the pressure of 30MPa for 60min, finishing sintering, finally cooling the graphite mould to room temperature, taking out the mould, and demoulding to obtain the block heterogeneous composite material with the size of phi 30mm multiplied by 7 mm.

(6) The 20CG isomeric composite material obtained by mechanical alloying and vacuum hot pressing sintering process mainly comprises FCC phase and alpha-Al₂O₃The composition is shown in FIG. 1 and FIG. 2 (c). As can be seen from FIGS. 3 and 4, the microstructure of the 20CG isomeric composite material mainly comprises a coarse crystal region with the grain size of 557 +/-223 nm, a super-fine crystal region with the grain size of 231 +/-81 nm and nano Al with the grain size of 87 +/-44 nm₂O₃The grain composition, and annealing twin crystals which traverse the whole CrCoNi matrix grains exist in the matrix grains of the ultra-fine grain region and the coarse grain region. 20CG isomeric CrCoNi-Al prepared by the process₂O₃The composite material has excellent comprehensive properties: hardness 486 + -10 HV, compressive yield strength 1664MPa, compressive fracture strength 2610MPa, and fracture strain 24.9%, as shown in FIG. 5. The yield strength is basically kept at 0CG level, and the ductility is improved to 24.9%, and the result shows that the introduction of the isomeric structure effectively relieves the contradiction between strength and plasticity, so that the isomeric composite material has excellent strong plasticity compared with a uniform composite material.

Example 3

(1) Weighing Cr, Co and Ni powder with equal atomic ratio in an operation box under the protection of high-purity argon, wherein the purity of the Cr, Co and Ni powder is more than or equal to 99.5 wt%, and the particle size is less than or equal to 48 mu m, then sequentially adding the powder, stainless steel balls (ball-to-material ratio is 10:1) and alcohol with the powder quality of 2.5 wt% into a stainless steel ball milling tank, finally installing the sealed stainless steel tank on an omnibearing planetary ball mill, and carrying out ball milling at the room temperature at the speed of 300rpm for 10h to obtain primarily alloyed CrCoNi powder, namely a coarse grain region (CG).

(2) Weighing Cr, Co and Ni powder with equal atomic ratio and 5 wt% of alpha-Al in an operation box protected by high-purity argon₂O₃Nano powder, wherein the purity of Cr, Co and Ni powder is more than or equal to 99.5 wt%, the particle size is less than or equal to 48 mu m, and Al₂O₃The purity of the powder is more than or equal to 99.8 wt%, and the particle size is 30-50 nm. Then sequentially adding the powder, stainless steel balls (ball-to-material ratio is 10:1) and absolute ethyl alcohol with the mass of 2.5 wt% of the powder into a stainless steel ball milling tank, finally installing the sealed stainless steel tank on an omnibearing planetary ball mill, and carrying out ball milling at the speed of 300rpm for 50h at room temperature to obtain the uniformly mixed CrCoNi-5 wt% Al₂O₃Composite powder, i.e., ultra fine grain regions (UFGs).

(3) Weighing the coarse grain powder obtained in the step (2) with the components of 30 wt% and the CrCoNi-5 wt% Al uniformly mixed in the step (3) in an operation box protected by high-purity argon gas₂O₃And (2) compounding the powder, sequentially adding the powder, rust steel balls (ball-to-material ratio is 10:1) and absolute ethyl alcohol accounting for 2.5 wt% of the mass of the powder into a stainless steel tank ball milling tank, finally installing the sealed stainless steel tank on an omnibearing planetary ball mill, and carrying out ball milling at the speed of 300rpm for 10 hours at room temperature to obtain the isomeric intermediate entropy alloy-based composite material powder with uniformly mixed coarse and fine grains.

(4) And (3) padding a circle of graphite paper with the size consistent with that of the inner wall on the inner wall of the graphite mould with the inner diameter of phi 30mm, then loading the powder obtained in the step (3) into the graphite mould in an operation box under the protection of high-purity argon, padding the graphite paper on the upper end and the lower end, then loading a graphite pressure head, and finally cold pressing by using the pressure of 15-20 MPa.

(5) And putting the graphite mould filled with the composite powder into vacuum hot-pressing sintering equipment, vacuumizing, preserving heat at the temperature of 1000 ℃ and under the pressure of 30MPa for 60min, finishing sintering, finally cooling the furnace to room temperature, taking out the mould, and demoulding to obtain the block heterogeneous composite material with the size of phi 30mm multiplied by 7 mm.

(6) The 30CG isomeric composite material obtained by mechanical alloying and vacuum hot pressing sintering process mainly comprises FCC phase and alpha-Al₂O₃Composition, as shown in figure 1. Hardness of the composite material551. + -. 15HV, compressive yield strength 1645MPa, compressive breaking strength 2191MPa, strain at break 11.8%, as shown in FIG. 5. It can be seen that as the content of the coarse grain region (CG) increases, the yield strength of the isomeric composite material gradually decreases, while the strain at break increases and then decreases. The hardness of the 30CG isomeric composite material is improved, the fracture strain is reduced, and more Cr is generated₂₃C₆Carbon compounds (see dark gray phase in FIG. 2 (d)), Cr₂₃C₆The Vickers hardness of the carbide is up to 1650HV, so that the hardness of the 30CG isomeric composite material is improved; and much Cr₂₃C₆The carbon compound makes the region prone to stress concentration, resulting in reduced plasticity of the isomeric composite material.