阅读说明：本技术 一种石墨烯增强fcc类高熵合金的制备方法 (Preparation method of graphene-reinforced FCC (fluid catalytic cracking) high-entropy alloy ) 是由 董龙龙 夏洪勇 刘跃 张伟 卢金文 霍望图 李亮 张于胜 周廉 于 2020-06-16 设计创作，主要内容包括：本发明公开了一种石墨烯增强FCC类高熵合金的制备方法,该方法包括：一、采用气雾化法制备FCC类高熵合金粉末；二、将FCC类高熵合金粉末球磨处理后干燥；三、将经干燥后的FCC类高熵合金粉末与石墨烯纳米片混合后进行球磨处理得到复合粉末；四、将复合粉末进行放电等离子烧结,随炉冷却后得到石墨烯增强FCC类高熵合金。本发明采用短时高能球磨,使得FCC类高熵合金粉末形成多尺度层片结构并产生细小纳米晶,结合低能球磨使石墨烯纳米片完整且均匀分散在层片结构之间,制备得到多尺度晶粒的石墨烯增强FCC类高熵合金,有效增强了强化作用,实现了强塑性的良好匹配。(The invention discloses a preparation method of a graphene reinforced FCC (fluid catalytic cracking) high-entropy alloy, which comprises the following steps: firstly, preparing FCC high-entropy alloy powder by adopting a gas atomization method; secondly, drying the FCC high-entropy alloy powder after ball milling treatment; mixing the dried FCC high-entropy alloy powder with graphene nanosheets, and performing ball milling treatment to obtain composite powder; and fourthly, performing discharge plasma sintering on the composite powder, and cooling along with the furnace to obtain the graphene reinforced FCC high-entropy alloy. According to the invention, the short-time high-energy ball milling is adopted, so that FCC high-entropy alloy powder forms a multi-scale lamellar structure and generates fine nano-crystals, and graphene nano-sheets are completely and uniformly dispersed among the lamellar structures by combining with the low-energy ball milling, so that the multi-scale-grain graphene reinforced FCC high-entropy alloy is prepared, the reinforcement effect is effectively enhanced, and the good matching of strong plasticity is realized.)

1. A preparation method of a graphene-reinforced FCC (fluid catalytic cracking) high-entropy alloy is characterized by comprising the following steps of:

step one, preparing raw material powder: preparing FCC high-entropy alloy powder by adopting a gas atomization method;

step two, short-time high-energy ball milling: adding the FCC high-entropy alloy powder prepared in the step one into a planetary ball mill for ball milling treatment, and then drying; the rotation speed of the ball milling treatment is 300 r/min-500 r/min, and the time is 5 min-30 min;

step three, low-energy ball milling: mixing the dried FCC high-entropy alloy powder and the graphene nanosheets, and then putting the mixture into a planetary ball mill for ball milling treatment to obtain composite powder; the rotating speed of the ball milling treatment is 50 r/min-200 r/min, and the time is 20 min-60 min;

step four, sintering and forming: and (3) loading the composite powder obtained in the third step into a graphite die, then placing the graphite die into a furnace chamber of a discharge plasma sintering furnace for discharge plasma sintering, and cooling along with the furnace to obtain the graphene reinforced FCC high-entropy alloy.

2. The method for preparing the graphene reinforced FCC (fluid catalytic cracking) high-entropy alloy as claimed in claim 1, wherein the component of the FCC high-entropy alloy powder in the first step is CoCrFeNiCu or CoCrFeNiMn.

3. The method for preparing the graphene reinforced FCC (fluid catalytic cracking) high-entropy alloy as claimed in claim 1, wherein the particle size of the FCC high-entropy alloy powder in the first step is 120-325 meshes.

4. The preparation method of the graphene reinforced FCC (fluid catalytic cracking) high-entropy alloy as claimed in claim 1, wherein the ball milling tank and the grinding balls adopted in the ball milling treatment in the step two are made of stainless steel, the diameters of the grinding balls are 8mm, 5mm and 2mm, the mass ratio of the three grinding balls is 3:2:1, and the ball-to-material ratio is (15-50): 1, ball milling treatment is alternately carried out by stopping the ball milling for 10min every 5min, and ethanol is added as a process control agent in the ball milling treatment process.

5. The method for preparing the graphene reinforced FCC (fluid catalytic cracking) high-entropy alloy as claimed in claim 1, wherein the drying device in the second step is a vacuum drying oven, the drying temperature is 60-100 ℃, the drying time is 10-20 h, and the vacuum degree is-1 × 10^-1MPa。

6. The preparation method of the graphene reinforced FCC (fluid catalytic cracking) high-entropy alloy as claimed in claim 1, wherein the thickness of the graphene nanoplatelets in step three is 5nm to 20 nm; the mass of the graphene nanosheet is 0.1-10% of the total mass of the FCC high-entropy alloy powder and the graphene nanosheet.

7. The preparation method of the graphene reinforced FCC (fluid catalytic cracking) high-entropy alloy as claimed in claim 1, wherein the ball milling tank and the milling balls adopted in the ball milling treatment in the third step are both made of agate materials, the diameter of the milling balls is 2-8 mm, and the ball-to-material ratio is (3-5): 1.

8. the method for preparing the graphene reinforced FCC (fluid catalytic cracking) high-entropy alloy as claimed in claim 1, wherein the step four of the spark plasma sintering comprises vacuumizing a furnace chamber to a vacuum degree of-1 × 10^-2And (2) under the pressure of 25-60 MPa, firstly heating to 600-800 ℃ at the speed of 50-100 ℃/min, preserving the heat for 2-5 min, and then heating to 900-1150 ℃ at the speed of 100-150 ℃/min, preserving the heat for 5-15 min.

Technical Field

The invention belongs to the technical field of composite material preparation, and particularly relates to a preparation method of a graphene reinforced FCC (fluid catalytic cracking) high-entropy alloy.

Background

The high-entropy alloy has the characteristics of good strength, plasticity, corrosion resistance, high-temperature softening resistance, low elastic modulus, soft magnetism, high resistivity and the like, and is suitable for manufacturing tools and dies with higher requirements, ultrahigh building refractory frameworks, high-frequency communication devices, golf heads and the like. Compared with the traditional heat-resistant steel and nickel-based high-temperature alloy, the VNdMoTaW high-entropy alloy has better temperature-bearing capacity; the corrosion resistance of the CoCrFeNiCu high-entropy alloy in a NaCl solution is more excellent than that of 304 stainless steel; FeCoNiCrMn shows excellent low-temperature performance at ultralow temperature and the like. Therefore, the high-entropy alloy material is a new material with compounding, diversification and multifunction. The high-entropy alloy material composed of the 3d transition group elements has good plasticity, but has low strength, and the application of the high-entropy alloy material in high-end fields is greatly limited.

Graphene is used as a novel two-dimensional stable material, has a unique structure, has excellent conductivity, thermal conductivity, ultrahigh strength and good toughness and rigidity, is a reinforcing phase of an ideal composite material, and simultaneously improves the strength, high-temperature performance and the like of the material. However, the current reports are almost all researches on graphene in composite materials such as metal matrix, ceramic matrix, polymer matrix and the like, for example, the literature (CARBON 164(2020) (272) 286) reports the influence of graphene and graphite on the structure performance of titanium alloy in comparison, and the mechanical property of the titanium alloy matrix can be obviously improved by the graphene.

At present, the method for improving the strength of the FCC (face-centered cubic lattice) type high-entropy alloy is usually to add alloy elements such as Al, Ti, Mo and the like (material report, 2019, 33: 1169-. Patents CN110004348A and CN110172629A both disclose methods of preparing high-entropy alloy powder by mechanical alloying high-energy ball milling, adding graphene, and sintering to synthesize a graphene-reinforced high-entropy alloy composite material, but due to long-time mechanical alloying, the pollution is severe in the ball milling process, the strength is not significantly improved, and the plasticity of the material is poor; in addition, in the patents CN107675061A and CN110578104A, the carbon powder or ceramic particles are added during the melting process to prepare the high-entropy alloy-based composite material, so that the melting components are easily uneven, the size is limited, and the carbon powder is unevenly dispersed and M7C3 brittle and hard carbide is easily generated during the casting process due to the low density of the carbon powder, so that the material performance is reduced. Therefore, under the condition of ensuring enough engineering plasticity, how to improve the strength of the FCC high-entropy alloy is the next development direction of the high-entropy alloy material.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a method for preparing a graphene-reinforced FCC-type high-entropy alloy, aiming at the above-mentioned deficiencies of the prior art. According to the method, the short-time high-energy ball milling is adopted, so that the FCC high-entropy alloy powder forms a multi-scale lamellar structure and generates fine nano-crystals, the graphene nano-sheets are completely and uniformly dispersed among the lamellar structures by combining with the low-energy ball milling, the graphene reinforced FCC high-entropy alloy with the multi-scale grains is prepared, the reinforcing effect is effectively enhanced, and the good matching of strong plasticity is realized.

In order to solve the technical problems, the invention adopts the technical scheme that: a preparation method of a graphene-reinforced FCC (fluid catalytic cracking) high-entropy alloy is characterized by comprising the following steps of:

step one, preparing raw material powder: preparing FCC high-entropy alloy powder by adopting a gas atomization method;

step two, short-time high-energy ball milling: adding the FCC high-entropy alloy powder prepared in the step one into a planetary ball mill for ball milling treatment, and then drying; the rotation speed of the ball milling treatment is 300 r/min-500 r/min, and the time is 5 min-30 min;

step three, low-energy ball milling: mixing the dried FCC high-entropy alloy powder and the graphene nanosheets, and then putting the mixture into a planetary ball mill for ball milling treatment to obtain composite powder; the rotating speed of the ball milling treatment is 50 r/min-200 r/min, and the time is 20 min-60 min;

step four, sintering and forming: and (3) loading the composite powder obtained in the third step into a graphite die, then placing the graphite die into a furnace chamber of a discharge plasma sintering furnace for discharge plasma sintering, and cooling along with the furnace to obtain the graphene reinforced FCC high-entropy alloy.

Compared with the defect that the FCC high-entropy alloy powder prepared by directly sintering the FCC high-entropy alloy powder is not dense in structure and limited in performance in the prior art, the method firstly adopts an aerosol method to prepare the FCC high-entropy alloy powder, avoids the defects of pollution, non-uniform components and easy formation of amorphous state in the process of preparing the high-entropy alloy powder by conventional ball-milling mechanical alloying, then leads the FCC high-entropy alloy powder to form a multi-scale lamellar structure and generate fine nano crystals by short-time high-energy ball milling, and then mixes the nano crystals with the graphene nano sheets to carry out low-energy ball milling, improves the interface bonding performance of the graphene nano sheets and the matrix FCC high-entropy alloy powder, promotes the uniform dispersion of the graphene nano sheets in the FCC high-entropy alloy powder, and overcomes the problem that the graphene nano sheets and one original component in the FCC high-entropy alloy powder have serious interface reaction in the conventional mechanical alloying process, the strengthening effect is effectively exerted, and finally, rapid densification is realized by adopting spark plasma activation sintering, so that the graphene-reinforced FCC high-entropy alloy with good strong plasticity matching is obtained.

The preparation method of the graphene-reinforced FCC high-entropy alloy is characterized in that in the step one, the component of the FCC high-entropy alloy powder is CoCrFeNiCu or CoCrFeNiMn. The method is suitable for the commonly used FCC high-entropy alloy powder, and has wide application range and high application value.

The preparation method of the graphene reinforced FCC high-entropy alloy is characterized in that the particle size of the FCC high-entropy alloy powder in the first step is 120-325 meshes. The FCC high-entropy alloy powder with the optimal particle size is easy to form a multi-scale lamellar structure in the subsequent short-time high-energy ball milling process, thereby avoiding premature cold welding agglomeration, and simultaneously avoiding the defects that the gas content in the powder is too much to be beneficial to subsequent sintering and the block compactness is reduced due to the too large particle size of the FCC high-entropy alloy powder.

The preparation method of the graphene-reinforced FCC high-entropy alloy is characterized in that a ball milling tank and grinding balls adopted in the ball milling treatment in the step two are made of stainless steel, the diameters of the grinding balls are 8mm, 5mm and 2mm, the mass ratio of the three grinding balls is 3:2:1, and the ball-to-material ratio is (15-50): 1, ball milling treatment is alternately carried out by stopping the ball milling for 10min every 5min, and ethanol is added as a process control agent in the ball milling treatment process. The grinding balls with the optimized diameter and mass ratio are beneficial to the full dispersion and deformation of FCC high-entropy alloy powder; the optimized ball-material ratio shortens the time of forming a multi-scale lamellar structure by the FCC high-entropy alloy, and simultaneously avoids the defects of serious heat generation and powder pollution of a ball-milling tank; and the adoption of the preferable ball milling alternating process and the process control agent effectively avoids the serious pollution of powder due to the heating of the ball milling tank.

The preparation method of the graphene-reinforced FCC high-entropy alloy is characterized in that in the second step, the drying equipment is a vacuum drying oven, the drying temperature is 60-100 ℃, the drying time is 10-20 hours, and the vacuum degree is-1 ×10^{- 1}MPa. The vacuum drying parameters avoid the oxidation of FCC high-entropy alloy powder after ball milling treatment, and ensure the stable and rapid volatilization of ethanol.

The preparation method of the graphene reinforced FCC high-entropy alloy is characterized in that the thickness of the graphene nanosheet in the third step is 5-20 nm; the mass of the graphene nanosheet is 0.1-10% of the total mass of the FCC high-entropy alloy powder and the graphene nanosheet. The graphene nanosheet with the optimal lamella thickness has fewer structural defects, is easy to disperse in FCC (fluid catalytic cracking) high-entropy alloy powder, reduces the cost of raw materials, and is beneficial to enhancing the strengthening effect.

The preparation method of the graphene-reinforced FCC high-entropy alloy is characterized in that in the third step, the ball milling tank and the milling balls adopted in the ball milling treatment are made of agate materials, the diameter of the milling balls is 2-8 mm, and the ball-to-material ratio is (3-5): 1. the ball milling tank and the milling balls made of the preferable materials are beneficial to reducing powder pollution; the grinding ball-to-ball material ratio with the optimal diameter is beneficial to uniformly dispersing and attaching the graphene nanosheets to the surface of FCC (fluid catalytic cracking) high-entropy alloy powder, and the damage to the graphene nanosheet structure is avoided.

The preparation method of the graphene-reinforced FCC (fluid catalytic cracking) high-entropy alloy is characterized in that the discharge plasma sintering process in the fourth step is that the furnace chamber is vacuumized to the vacuum degree of-1 × 10^-2And (2) under the pressure of 25-60 MPa, firstly heating to 600-800 ℃ at the speed of 50-100 ℃/min, preserving the heat for 2-5 min, and then heating to 900-1150 ℃ at the speed of 100-150 ℃/min, preserving the heat for 5-15 min. The process of the spark plasma sintering is firstly increased to a low-temperature region at a low temperature rise rate, so that gas attached to the surface of the composite powder has enough time to escape sufficiently, the compactness of the graphene reinforced FCC high-entropy alloy is improved, and then the temperature is increased to the high-temperature region at a high temperature rise rate, so that the heating time of the high-temperature region is shortened, and the growth of crystal grains of the graphene reinforced FCC high-entropy alloy is limited.

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

1. the invention carries out short-time high-energy ball milling on FCC high-entropy alloy powder prepared by an aerosol method, so that the FCC high-entropy alloy powder forms a multi-scale lamellar structure and generates fine nanocrystals, the lamellar structure provides higher plasticity in the tension process, the fine nanocrystals provide higher strength, the formation of a multi-scale grain reinforcing material after sintering is ensured, and good matching of strong plasticity is realized.

2. According to the invention, the FCC high-entropy alloy powder subjected to short-time high-energy ball milling is mixed with the graphene nanosheets and subjected to low-energy ball milling, so that the graphene nanosheets are coated and attached between the lamellar structures, the structural integrity of the graphene nanosheets and the distribution uniformity in the FCC high-entropy alloy powder are ensured, the unique two-dimensional structure of graphene is fully exerted, the strengthening effect is realized, and the mechanical property of the FCC high-entropy alloy reinforced by the graphene is further improved.

3. The invention adopts short-time high-energy ball milling to effectively reduce the impurity pollution in the FCC high-entropy alloy powder and improve the quality of the graphene reinforced FCC high-entropy alloy.

4. The preparation method disclosed by the invention is simple to operate, low in energy consumption, high in universality, suitable for various FCC (fluid catalytic cracking) high-entropy alloy powders and easy for industrial production.

The technical solution of the present invention is further described in detail by the accompanying drawings and examples.

Drawings

FIG. 1 is an SEM image of a graphene reinforced CoCrFeNiCu high-entropy alloy prepared in example 1 of the invention.

FIG. 2 is an SEM image of a ball-milled CoCrFeNiCu high-entropy alloy powder of comparative example 1 of the invention.

FIG. 3 is a tensile stress-strain curve of the graphene-reinforced CoCrFeNiCu high-entropy alloy prepared in example 1 of the invention and the CoCrFeNiCu high-entropy alloys prepared in comparative examples 1-2.

Detailed Description