Tungsten-based high-entropy alloy and preparation method thereof

Abstract

The invention relates to the technical field of high-entropy alloy materials, in particular to a tungsten-based high-entropy alloy and a preparation method thereof.The preparation method comprises the following steps that W powder and auxiliary powder are mixed and ball-milled to obtain mixed powder, the auxiliary raw materials are three or more of Mo powder, Ta powder, Nb powder, Fe powder, Ni powder and Co powder, in the mixed powder, the atomic percent of the W powder is 25%-55%, and the atomic percent of the Co powder is 25%-55%; in the auxiliary raw material powder, the atomic percent of each kind of metal powder is 10%-30%, and the sum of the W powder and the auxiliary raw material powder is 100%; and the mixed powder is subjected to spark plasma sintering under the vacuum condition, the tungsten-based high-entropy alloy is obtained, and various multi-phase tungsten-based high-entropy alloys with high compactness and excellent mechanical properties are prepared through different tungsten-based high-entropy alloy component design and adjustment of spark plasma sintering parameters.

Description

Technical Field

[0001] The present invention relates to the technical field of high entropy alloy materials, and in particular to a tungsten-based high entropy alloy and a preparation method thereof. Background Art

[0002] Tungsten alloy is an alloy material based on tungsten, usually with other metal elements as binders, such as nickel, iron, copper, etc. This alloy has the characteristics of high density, high melting point, good mechanical properties and thermal stability. Due to its excellent high temperature stability and mechanical properties, tungsten alloy is often used in the manufacture of rocket engine nozzles, thermal protection systems, etc. Due to its high density and hardness, tungsten alloy is widely used in the military field, usually used as armor-piercing cores, armor materials, etc.

[0003] As a multi-principal alloy, high entropy alloy breaks through the design concept of single principal element of traditional alloys, and embodies excellent properties different from traditional alloys, especially in extreme environments such as high temperature, high pressure, and high strain rate. The high strength and high hardness of high entropy alloys are exactly what tungsten alloys for bullets need. The severe lattice distortion of high entropy alloys will increase the scattering of phonons and electrons, thereby reducing thermal conductivity, and easily produce adiabatic shear bands during high-speed penetration. Moreover, under dynamic loads, dislocation movement can overcome the resistance caused by lattice distortion, continue to harden, and improve strength without sacrificing plasticity, showing good impact resistance. Therefore, high entropy alloys have excellent penetration self-sharpening characteristics and impact resistance, which can effectively improve penetration capability.

[0004] At present, high entropy alloys are generally prepared by traditional powder metallurgy sintering technology. However, the alloys prepared by traditional powder metallurgy sintering technology have low density and poor mechanical properties. At the same time, the preparation process has problems such as long sintering cycle and high energy consumption. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a tungsten-based high entropy alloy and a preparation method thereof. The present invention uses a spark plasma sintering process to change the spark plasma sintering process parameters, change the tungsten alloy composition and powder particle size, and sinter to prepare a variety of tungsten-based high entropy alloys with excellent mechanical properties.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for preparing a tungsten-based high entropy alloy comprises the following steps:

[0008] The W powder is mixed with the auxiliary raw material powder and ball-milled to obtain a mixed powder, wherein the auxiliary raw material powder is three or more of Mo powder, Ta powder, Nb powder, Fe powder, Ni powder and Co powder. In the mixed powder, the atomic percentage of W powder is 25% to 55%, and in the auxiliary raw material powder, the atomic percentage of each metal powder is 10% to 30%, respectively. The total of W powder and the auxiliary raw material powder is 100%.

[0009] The mixed powder is subjected to spark plasma sintering to obtain a tungsten-based high entropy alloy, wherein the sintering temperature is 1100°C to 2000°C.

[0010] The present invention mixes three or more of Mo powder, Ta powder, Nb powder, Fe powder, Ni powder and Co powder with W powder, ball mills to obtain a mixed powder, and performs spark plasma sintering on the mixed powder to obtain a tungsten-based high-entropy alloy. By designing different tungsten-based high-entropy alloy components and adjusting the spark plasma sintering temperature, a tungsten-based high-entropy alloy sample with high density and low porosity can be obtained. A higher sintering temperature will cause the interstitial phase to overflow and the alloy composition to change. A lower sintering temperature will cause the alloy porosity to increase and the density to decrease. The method of the present invention is simple in process operation, the material sintering time is short, and the molding effect is good.

[0011] In a preferred embodiment of the present invention, the sintering pressure is 20 MPa to 40 MPa, and the adjustment of the sintering pressure will directly affect the density of the alloy.

[0012] In a preferred embodiment of the present invention, the sintering holding time is 5 min to 30 min. Different holding times can affect the phase structure of the alloy, thereby affecting the microstructure and mechanical properties of the alloy.

[0013] The present invention changes the sintering result by changing the sintering pressure and the sintering holding time in conjunction with the sintering temperature. Different holding times can affect the phase structure of the alloy, thereby affecting the organization and mechanical properties of the alloy. The adjustment of the sintering pressure will directly affect the density of the alloy, thereby preparing a tungsten-based high-entropy alloy with high density and excellent comprehensive performance.

[0014] In a preferred embodiment of the present invention, the heating rate is 50°C / min to 100°C / min, the heating rate is 100°C / min when the temperature is 0-1000°C, and the heating rate is 50°C / min when the temperature is above 1000°C.

[0015] In a preferred embodiment of the present invention, the ball milling speed is 200 r / min to 300 r / min, and the ball milling time is 8 h to 16 h.

[0016] In a preferred embodiment of the present invention, during ball milling, the ball-to-material mass ratio is 3 to 10:1.

[0017] In a preferred embodiment of the present invention, the particle size of W powder is 15 microns to 53 microns, the particle size of Nb powder is 15 microns to 53 microns, the particle size of Ta powder is 15 microns to 53 microns, and the particle sizes of Co powder, Fe powder, Nb powder and Ni powder are all less than 10 microns.

[0018] In a preferred embodiment of the present invention, the purity of the raw material powder is ≥99.9%.

[0019] Another object of the present invention is to provide a tungsten-based high entropy alloy prepared by any of the methods described above.

[0020] In a preferred embodiment of the present invention, the tungsten-based high entropy alloy has a density of 95.1% to 99.07%, a compressive strength of 1710 MPa to 2835 MPa, and a compressive strain of 2.9% to 6.1%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention proposes a tungsten-based high entropy alloy prepared based on a spark plasma sintering process. Three or more of Mo powder, Ta powder, Nb powder, Fe powder, Ni powder and Co powder are mixed with W powder and ball-milled to obtain a mixed powder. The mixed powder is spark plasma sintered to obtain a tungsten-based high entropy alloy. By designing different tungsten-based high entropy alloy components and adjusting the spark plasma sintering temperature, a tungsten-based high entropy alloy sample with high density and low porosity can be obtained. A higher sintering temperature will cause the interstitial phase to overflow and the alloy composition to change. A lower sintering temperature will cause the alloy porosity to increase and the density to decrease. The method of the present invention is simple to operate, the material sintering time is short, and the molding effect is good.

[0023] 2. The present invention proposes a tungsten-based high-entropy alloy prepared based on a spark plasma sintering process and a preparation method thereof. The sintering result is changed by changing the sintering pressure and the sintering holding time in conjunction with the sintering temperature. Different holding times can affect the phase structure of the alloy, thereby affecting the microstructure and mechanical properties of the alloy. The adjustment of the sintering pressure will directly affect the density of the alloy, thereby preparing a tungsten-based high-entropy alloy with high density and excellent comprehensive performance.

[0024] 3. The present invention proposes a tungsten-based high entropy alloy prepared by spark plasma sintering process and a preparation method thereof, specifically: firstly, the single substance powder is mixed evenly, and then the powder is quickly sintered into a block by a spark plasma sintering furnace to obtain a tungsten-based high entropy alloy. By using the spark plasma sintering process, by changing the composition of the tungsten-based high entropy alloy, sintering process parameters, etc., a variety of tungsten-based high entropy alloys with different compositions, different structures and mechanical properties are prepared. The prepared tungsten-based high entropy alloy has excellent mechanical properties, and the actual measured density exceeds 11.5g / cm3 The lowest density can reach more than 95%, the highest density can reach more than 99%, the highest compressive strength exceeds 2.8Gpa, and the highest compression strain can reach 25%. From a process perspective, the preparation process is fast, the production cycle is short, the operation is simple, and it is easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the microstructure of the WFeNiMo multiphase tungsten-based high entropy alloy prepared in Example 1 of the present invention.

[0026] Figure 2 This is the compressive stress-strain curve of the WFeNiMo multiphase tungsten-based high entropy alloy prepared in Example 1 of the present invention.

[0027] Figure 3 The microstructure of the WMoTaNb multiphase tungsten-based high entropy alloy prepared in Example 2 of the present invention.

[0028] Figure 4 This is a microstructure picture of the WMoNbCo multiphase tungsten-based high entropy alloy prepared in Example 3 of the present invention.

[0029] Figure 5 This is the compressive stress-strain curve of the WMoNbCo multiphase tungsten-based high entropy alloy prepared in Example 3 of the present invention.

[0030] Figure 6 This is a microstructure picture of the WFeNiCo multiphase tungsten-based high entropy alloy prepared in Example 4 of the present invention.

[0031] Figure 7 This is the compressive stress-strain curve of the WFeNiCo multiphase tungsten-based high entropy alloy prepared in Example 4 of the present invention.

[0032] Figure 8 This is a picture of the mold of the WMoNbCo multiphase tungsten-based high entropy alloy prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The following is a detailed description of the technical solutions in the embodiments of the present invention in combination with the preferred embodiments and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that all professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0035] Spark plasma sintering technology, referred to as SPS, is an advanced powder metallurgy technology that uses pulsed current to pass through powder materials to achieve rapid sintering. This technology can significantly improve the density of the material and complete the sintering process in a shorter time, thereby reducing energy consumption and improving production efficiency. The principle of spark plasma sintering is that during the SPS process, the powder is loaded into a graphite mold and then a direct current or pulse current is applied. When the current passes through the powder, an instantaneous high temperature is generated between the particles, causing local melting and discharge phenomena. In addition to the current, a certain axial pressure is also applied to help the contact and bonding between the powder particles and promote the densification of the material. Due to the action of the pulsed current, the heating rate is very fast and the required sintering temperature can be reached within a few minutes. Similarly, the cooling rate is also very fast, which helps to form a special microstructure. The following are the advantages of the spark plasma sintering process: 1. Rapid sintering: SPS can complete the sintering process in a short time, significantly shortening the production cycle. 2. High density: It is possible to prepare materials close to the theoretical density, which is critical for many high-performance applications. 3. Microstructure control: Due to rapid heating and cooling, a unique microstructure can be obtained, which is beneficial to improve material properties. 4. Low energy consumption: Compared with traditional sintering methods, SPS consumes less energy. 5. Wide range of applications: Applicable to various types of powder materials, including metals, ceramics and composite materials. 6. Easy to operate: The whole process is easy to control and adjust, suitable for industrial production.

[0036] Example 1

[0037] A method for preparing a WFeNiMo multiphase tungsten-based high entropy alloy comprises the following steps:

[0038] (1) Preparation of mixed powder for sintering: First, the composition of the multiphase tungsten-based high entropy alloy is designed, and the WFeNiMo multiphase tungsten-based high entropy alloy with equal atomic ratio is designed. The multiphase tungsten-based high entropy alloy is composed of four elements: W, Fe, Ni, and Mo, and the atomic ratio is 1:1:1:1. The mass fraction of each element in the multiphase tungsten-based high entropy alloy with this composition is calculated according to the atomic ratio. After determining the weight of the mixed powder, the single powder is weighed by an electronic balance. The purity of the raw materials used is ≥99.9%. The particle size of the tungsten powder used is 15 microns to 53 microns, the iron powder is carbonyl iron powder, the nickel powder is carbonyl nickel powder, and the particle size of the iron powder, nickel powder, and molybdenum powder are all below 10 microns. Pour the weighed single-substance powder into a 500mL nylon ball mill jar, add the corresponding weight of zirconia ball mill beads according to the weight of the powder and the ball-to-material mass ratio of 3:1, fix the ball mill jar on a planetary ball mill, and ball mill at a speed of 250r / min for 8h. After the ball milling is completed, use a sieve to sieve out the milled mixed powder.

[0039] (2) Sintering: Use a sintering mold with a diameter of 35 mm, spray a release agent on the pressure head and inner wall of the sintering mold, use an electronic balance to weigh the appropriate weight of the mixed powder, pour the mixed powder into the graphite mold, wrap the contact surface between the powder and the graphite mold with carbon paper, and wrap the outside of the mold with carbon felt to improve the insulation effect of the mold. Put the mold into the spark plasma sintering furnace, place the mold, evacuate for 15 minutes, apply a pressure of 30 MPa, set the sintering program, keep the temperature at 1100 ° C for 30 minutes, start sintering, cool with the furnace after sintering, open the furnace door to take samples, demold, and obtain WFeNiMo multiphase tungsten-based high entropy alloy.

[0040] Example 2

[0041] A method for preparing a WMoTaNb multiphase tungsten-based high entropy alloy comprises the following steps:

[0042] (1) Preparation of mixed powder for sintering: First, the composition of the multiphase tungsten-based high entropy alloy is designed, and the WMoTaNb multiphase tungsten-based high entropy alloy with equal atomic ratio is designed. The multiphase tungsten-based high entropy alloy is composed of four elements: W, Nb, Ta, and Mo, and the atomic ratio is 1:1:1:1. The mass fraction of each element in the multiphase tungsten-based high entropy alloy with the composition is calculated according to the atomic ratio. After determining the weight of the mixed powder, the single powder is weighed by an electronic balance. The purity of the raw materials used is ≥99.9%. The particle size of the tungsten powder and tantalum powder used is 15 microns to 53 microns, and the particle size of the niobium powder and molybdenum powder is less than 10 microns. The weighed single powder is poured into a nylon ball mill with a capacity of 500 mL. According to the weight of the powder, the corresponding weight of zirconia ball milling beads is added according to the ball-to-material mass ratio of 3:1. The ball mill is fixed to a planetary ball mill and ball milled at a speed of 250 r / min for 16 hours. After the ball milling is completed, the ball milled mixed powder is sieved out using a sieve.

[0043] (2) Sintering: Use a sintering mold with a diameter of 10 mm, spray a release agent on the pressure head and inner wall of the sintering mold, use an electronic balance to weigh the appropriate weight of the mixed powder, pour the powder into the graphite mold, wrap the contact surface between the powder and the graphite mold with carbon paper, and wrap the outside of the mold with carbon felt to improve the insulation effect of the mold. Put the mold into the spark plasma sintering furnace, place the mold, evacuate for 15 minutes, apply a pressure of 30 MPa, set the sintering program, keep the temperature at 1900 ° C for 10 minutes, and start sintering. After sintering, cool it with the furnace, open the furnace door to take samples, demold, and obtain WMoTaNb multiphase tungsten-based high entropy alloy.

[0044] Example 3

[0045] A method for preparing a WMoNbCo multiphase tungsten-based high entropy alloy comprises the following steps:

[0046] (1) Preparation of mixed powder for sintering: First, the composition of the multiphase tungsten-based high entropy alloy is designed, and a WMoNbCo multiphase tungsten-based high entropy alloy with an equiatomic ratio is designed. The multiphase tungsten-based high entropy alloy is composed of four elements: W, Nb, Co, and Mo, with an atomic ratio of 1:1:1:1. The mass fraction of each element in the multiphase tungsten-based high entropy alloy with the composition is calculated according to the atomic ratio. After determining the weight of the mixed powder, the single powder is weighed by an electronic balance, and the purity of the raw materials used is ≥99.9%. The particle size of the tungsten powder used is 1 micron to 3 microns, the particle size of the niobium powder is 15 microns to 53 microns, and the particle size of the cobalt powder and the molybdenum powder are both less than 10 microns. The weighed single powder is poured into a nylon ball mill with a capacity of 500 mL, and the corresponding weight of zirconia ball mill beads is added according to the weight of the powder and the ball-to-material ratio of 5:1. The ball mill was fixed to the planetary ball mill and ball milled at a speed of 250 r / min for 10 h. After the ball milling was completed, a sieve was used to sieve out the milled mixed powder.

[0047] (2) Sintering: Use a sintering mold with a diameter of 20 mm, spray a release agent on the pressure head and inner wall of the sintering mold, use an electronic balance to weigh the appropriate weight of the mixed powder, pour the powder into the graphite mold, wrap the contact surface between the powder and the graphite mold with carbon paper, and wrap the outside of the mold with carbon felt to improve the insulation effect of the mold. Put the mold into the spark plasma sintering furnace, place the mold, evacuate for 15 minutes, apply a pressure of 30 MPa, set the sintering program, keep the temperature at 1200 ° C for 10 minutes, and start sintering. After sintering, cool it with the furnace, open the furnace door to take samples, demold, and obtain WMoNbCo multiphase tungsten-based high entropy alloy.

[0048] Example 4

[0049] A method for preparing a WFeNiCo multiphase tungsten-based high entropy alloy comprises the following steps:

[0050] (1) Preparation of mixed powder for sintering: First, the composition of the multiphase tungsten-based high entropy alloy is designed, and a WFeNiCo multiphase tungsten-based high entropy alloy with an equiatomic ratio is designed. The multiphase tungsten-based high entropy alloy is composed of four elements: W, Fe, Co, and Ni, with an atomic ratio of 1:1:1:1. The mass fraction of each element in the multiphase tungsten-based high entropy alloy with the composition is calculated according to the atomic ratio. After determining the weight of the mixed powder, the single powder is weighed by an electronic balance. The purity of the raw materials used is ≥99.9%. The particle size of the tungsten powder used is 1 micron to 3 microns, and the particle sizes of cobalt powder, iron powder, and nickel powder are all below 10 microns. Pour the weighed single powder into a nylon ball mill with a capacity of 500 mL, and add the corresponding weight of zirconia ball milling beads according to the weight of the powder and the ball-to-material ratio of 4:1. Fix the ball mill to a planetary ball mill and ball mill at a speed of 250 r / min for 10 hours. After the ball milling is completed, use a sieve to sieve out the ball-milled mixed powder.

[0051] (2) Sintering: Use a sintering mold with a diameter of 20 mm, spray a release agent on the pressure head and inner wall of the sintering mold, use an electronic balance to weigh the appropriate weight of the mixed powder, pour the powder into the graphite mold, wrap the contact surface between the powder and the graphite mold with carbon paper, and wrap the outside of the mold with carbon felt to improve the insulation effect of the mold. Put the mold into the spark plasma sintering furnace, place the mold, evacuate for 15 minutes, apply a pressure of 30 MPa, set the sintering program, keep the temperature at 1200 ° C for 10 minutes, and start sintering. After sintering, cool it with the furnace, open the furnace door to take samples, demold, and obtain WFeNiCo multiphase tungsten-based high entropy alloy.

[0052] Example 5

[0053] A method for preparing a WFeNiMo multiphase tungsten-based high entropy alloy comprises the following steps:

[0054] (1) Preparation of mixed powder for sintering: First, the composition of the multiphase tungsten-based high entropy alloy is designed, and a WFeNiMo multiphase tungsten-based high entropy alloy with an equiatomic ratio is designed. The multiphase tungsten-based high entropy alloy is composed of four elements: W, Fe, Ni, and Mo, with an atomic ratio of 1:1:1:1. The mass fraction of each element in the multiphase tungsten-based high entropy alloy with the composition is calculated according to the atomic ratio. After determining the weight of the mixed powder, the single powder is weighed by an electronic balance, and the purity of the raw materials used is ≥99.9%. The particle size of the tungsten powder used is 15 microns to 53 microns, the iron powder is carbonyl iron powder, and the nickel powder is carbonyl nickel powder. The particle size of the iron powder, nickel powder, and molybdenum powder is all below 10 microns. Pour the weighed single powder into a nylon ball mill with a capacity of 500 mL, and add the corresponding weight of zirconia ball mill beads according to the weight of the powder and the ball-to-material mass ratio of 5:1. The ball mill was fixed to the planetary ball mill and ball milled at a speed of 200 r / min for 16 h. After the ball milling was completed, a sieve was used to sieve out the milled mixed powder.

[0055] (2) Sintering: Use a sintering mold with a diameter of 35 mm, spray a release agent on the pressure head and inner wall of the sintering mold, use an electronic balance to weigh the appropriate weight of the mixed powder, pour the mixed powder into the graphite mold, wrap the contact surface between the powder and the graphite mold with carbon paper, and wrap the outside of the mold with carbon felt to improve the insulation effect of the mold. Put the mold into the spark plasma sintering furnace, place the mold, evacuate for 15 minutes, apply a pressure of 20 MPa, set the sintering program, keep the temperature at 1100 ° C for 5 minutes, start sintering, cool with the furnace after sintering, open the furnace door to take samples, demold, and obtain WFeNiMo multiphase tungsten-based high entropy alloy.

[0056] Example 6

[0057] A method for preparing a WFeNiMo multiphase tungsten-based high entropy alloy comprises the following steps:

[0058] (1) Preparation of mixed powder for sintering: First, the composition of the multiphase tungsten-based high entropy alloy is designed, and a WFeNiMo multiphase tungsten-based high entropy alloy with an equiatomic ratio is designed. The multiphase tungsten-based high entropy alloy is composed of four elements: W, Fe, Ni, and Mo, with an atomic ratio of 1:1:1:1. The mass fraction of each element in the multiphase tungsten-based high entropy alloy with the composition is calculated according to the atomic ratio. After determining the weight of the mixed powder, the single powder is weighed by an electronic balance, and the purity of the raw materials used is ≥99.9%. The particle size of the tungsten powder used is 15 microns to 53 microns, the iron powder is carbonyl iron powder, and the nickel powder is carbonyl nickel powder. The particle size of the iron powder, nickel powder, and molybdenum powder are all below 10 microns. Pour the weighed single powder into a nylon ball mill with a capacity of 500 mL, and add the corresponding weight of zirconia ball mill beads according to the weight of the powder and the ball-to-material mass ratio of 10:1. The ball mill was fixed to the planetary ball mill and ball milled at a speed of 300 r / min for 10 h. After the ball milling was completed, a sieve was used to sieve out the milled mixed powder.

[0059] (2) Sintering: Use a sintering mold with a diameter of 35 mm, spray a release agent on the pressure head and inner wall of the sintering mold, use an electronic balance to weigh the appropriate weight of the mixed powder, pour the mixed powder into the graphite mold, wrap the contact surface between the powder and the graphite mold with carbon paper, and wrap the outside of the mold with carbon felt to improve the insulation effect of the mold. Put the mold into the spark plasma sintering furnace, place the mold, evacuate for 15 minutes, apply a pressure of 40 MPa, set the sintering program, keep the temperature at 1100 ° C for 20 minutes, start sintering, cool with the furnace after sintering, open the furnace door to take samples, demold, and obtain WFeNiMo multiphase tungsten-based high entropy alloy.

[0060] Example 7

[0061] A method for preparing a WFeNiMoNb tungsten-based high entropy alloy comprises the following steps:

[0062] (1) Preparation of mixed powder for sintering: First, the composition of the multiphase tungsten-based high entropy alloy is designed, and the WFeNiMoNb multiphase tungsten-based high entropy alloy with equal atomic ratio is designed. The multiphase tungsten-based high entropy alloy is composed of four elements: W, Fe, Ni, Mo, and Nb, and the atomic ratio is 1:1:1:1:1. The mass fraction of each element in the multiphase tungsten-based high entropy alloy with this composition is calculated according to the atomic ratio. After determining the weight of the mixed powder, the single powder is weighed by an electronic balance. The purity of the raw materials used is ≥99.9%. The particle size of the tungsten powder and niobium powder used is 15 microns to 53 microns, the iron powder is carbonyl iron powder, the nickel powder is carbonyl nickel powder, and the particle size of the iron powder, nickel powder, and molybdenum powder are all below 10 microns. Pour the weighed single-substance powder into a 500mL nylon ball mill jar, add the corresponding weight of zirconia ball mill beads according to the weight of the powder and the ball-to-material mass ratio of 3:1, fix the ball mill jar on a planetary ball mill, and ball mill at a speed of 250r / min for 8h. After the ball milling is completed, use a sieve to sieve out the milled mixed powder.

[0063] (2) Sintering: Use a 35 mm diameter sintering mold, spray a release agent on the sintering mold pressure head and inner wall, use an electronic balance to weigh the appropriate weight of the mixed powder, pour the mixed powder into the graphite mold, wrap the contact surface between the powder and the graphite mold with carbon paper, and wrap the outside of the mold with carbon felt to improve the mold insulation effect. Put the mold into the spark plasma sintering furnace, place the mold, evacuate for 15 minutes, apply a pressure of 30 MPa, set the sintering program, keep the temperature at 1100 ° C for 30 minutes, start sintering, cool with the furnace after sintering, open the furnace door to take samples, demold, and obtain WFeNiMoNb tungsten-based high entropy alloy.

[0064] The WFeNiMoNb tungsten-based high entropy alloy prepared in Example 7 has a density of 98.7%, a compressive strength of 1920 MPa, and a compressive strain of 19.8%.

[0065] Example 8

[0066] A method for preparing a WFeNiMoTaCo tungsten-based high entropy alloy comprises the following steps:

[0067] (1) Preparation of mixed powder for sintering: First, the composition of the multiphase tungsten-based high entropy alloy is designed, and the WFeNiMoTaCo tungsten-based high entropy alloy with equal atomic ratio is designed. The multiphase tungsten-based high entropy alloy is composed of four elements: W, Fe, Ni, Mo, Ta, and Co, and the atomic ratio is 1:1:1:1:1:1. The mass fraction of each element in the multiphase tungsten-based high entropy alloy with this composition is calculated according to the atomic ratio. After determining the weight of the mixed powder, the single powder is weighed by an electronic balance. The purity of the raw materials used is ≥99.9%. The particle size of the tungsten powder and tantalum powder used is 15 microns to 53 microns, the iron powder is carbonyl iron powder, the nickel powder is carbonyl nickel powder, and the particle size of the iron powder, nickel powder, molybdenum powder, and cobalt powder are all below 10 microns. Pour the weighed single-substance powder into a 500mL nylon ball mill jar, add the corresponding weight of zirconia ball mill beads according to the weight of the powder and the ball-to-material mass ratio of 3:1, fix the ball mill jar on a planetary ball mill, and ball mill at a speed of 250r / min for 8h. After the ball milling is completed, use a sieve to sieve out the milled mixed powder.

[0068] (2) Sintering: Use a sintering mold with a diameter of 35 mm, spray a release agent on the pressure head and inner wall of the sintering mold, use an electronic balance to weigh the appropriate weight of the mixed powder, pour the mixed powder into the graphite mold, wrap the contact surface between the powder and the graphite mold with carbon paper, and wrap the outside of the mold with carbon felt to improve the insulation effect of the mold. Put the mold into the spark plasma sintering furnace, place the mold, evacuate for 15 minutes, apply a pressure of 30 MPa, set the sintering program, keep the temperature at 1100 ° C for 30 minutes, start sintering, cool with the furnace after sintering, open the furnace door to take samples, demold, and obtain WFeNiMoTaCo tungsten-based high entropy alloy.

[0069] The WFeNiMoTaCo tungsten-based high entropy alloy prepared in Example 8 has a density of 98.5%, a compressive strength of 2045 MPa, and a compressive strain of 17.4%.

[0070] Example 9

[0071] A method for preparing a WFeNiMoTaCoNb tungsten-based high entropy alloy comprises the following steps:

[0072] (1) Preparation of mixed powder for sintering: First, the composition of the multiphase tungsten-based high entropy alloy is designed, and the WFeNiMoTaCoNb multiphase tungsten-based high entropy alloy with equal atomic ratio is designed. The multiphase tungsten-based high entropy alloy is composed of four elements: W, Fe, Ni, and Mo, and the atomic ratio is 1:1:1:1:1:1:1:1. The mass fraction of each element in the multiphase tungsten-based high entropy alloy with this composition is calculated according to the atomic ratio. After determining the weight of the mixed powder, the single powder is weighed by an electronic balance. The purity of the raw materials used is ≥99.9%. The particle size of the tungsten powder, niobium powder and tantalum powder used is 15 microns to 53 microns, the iron powder is carbonyl iron powder, the nickel powder is carbonyl nickel powder, and the particle size of the iron powder, nickel powder, molybdenum powder and cobalt powder is less than 10 microns. Pour the weighed single-substance powder into a 500mL nylon ball mill jar, add the corresponding weight of zirconia ball mill beads according to the weight of the powder and the ball-to-material mass ratio of 3:1, fix the ball mill jar on a planetary ball mill, and ball mill at a speed of 250r / min for 8h. After the ball milling is completed, use a sieve to sieve out the milled mixed powder.

[0073] (2) Sintering: Use a 35 mm diameter sintering mold, spray a release agent on the pressure head and inner wall of the sintering mold, use an electronic balance to weigh the appropriate weight of the mixed powder, pour the mixed powder into the graphite mold, wrap the contact surface between the powder and the graphite mold with carbon paper, and wrap the outside of the mold with carbon felt to improve the insulation effect of the mold. Put the mold into the spark plasma sintering furnace, place the mold, evacuate for 15 minutes, apply a pressure of 30 MPa, set the sintering program, keep the temperature at 1100 ° C for 30 minutes, start sintering, cool with the furnace after sintering, open the furnace door to take samples, demold, and obtain WFeNiMoTaCoNb tungsten-based high entropy alloy.

[0074] The WFeNiMoTaCoNb tungsten-based high entropy alloy prepared in Example 9 has a density of 97.9%, a compressive strength of 2204 MPa, and a compressive strain of 15.7%.

[0075] Comparative Example 1

[0076] A method for preparing a WMoNbCo multiphase tungsten-based high entropy alloy comprises the following steps:

[0077] (1) Preparation of mixed powder for sintering: First, the composition of the multiphase tungsten-based high entropy alloy is designed, and a WMoNbCo multiphase tungsten-based high entropy alloy with an equiatomic ratio is designed. The multiphase tungsten-based high entropy alloy is composed of four elements: W, Nb, Co, and Mo, with an atomic ratio of 1:1:1:1. The mass fraction of each element in the multiphase tungsten-based high entropy alloy with the composition is calculated according to the atomic ratio. After determining the weight of the mixed powder, the single powder is weighed by an electronic balance, and the purity of the raw materials used is ≥99.9%. The particle size of the tungsten powder used is 1 micron to 3 microns, the particle size of the niobium powder is 15 microns to 53 microns, and the particle size of the cobalt powder and the molybdenum powder are both less than 10 microns. The weighed single powder is poured into a nylon ball mill with a capacity of 500 mL, and the corresponding weight of zirconia ball mill beads is added according to the weight of the powder and the ball-to-material ratio of 5:1. The ball mill was fixed to the planetary ball mill and ball milled at a speed of 250 r / min for 10 h. After the ball milling was completed, a sieve was used to sieve out the milled mixed powder.

[0078] (2) Sintering: Use a sintering mold with a diameter of 42 mm, spray a release agent on the pressure head and inner wall of the sintering mold, use an electronic balance to weigh the appropriate weight of the mixed powder, pour the powder into the graphite mold, wrap the contact surface between the powder and the graphite mold with carbon paper, and wrap the outside of the mold with carbon felt to improve the insulation effect of the mold. Put the mold into the spark plasma sintering furnace, place the mold, evacuate for 15 minutes, apply a pressure of 30 MPa, set the sintering program, keep warm at 1250 ° C for 10 minutes, and start sintering. After sintering, cool it with the furnace, open the furnace door to take samples, demold, and obtain WMoNbCo multiphase tungsten-based high entropy alloy.

[0079] Results Analysis

[0080] The preparation conditions of the WFeNiMo multiphase tungsten-based high entropy alloy sample sintered by spark plasma at 1100°C in Example 1 of the present invention are as follows: use tungsten powder with a particle size of 15 microns to 53 microns, carbonyl iron powder, carbonyl nickel powder and molybdenum powder with a particle size less than 10 microns, and first use a planetary ball mill to mix the composite material powder evenly. Then put the mixed powder into a graphite mold, and use a spark plasma sintering furnace to quickly sinter the powder into a block. The sintering temperature is 1100°C, the holding time is 30 minutes, and the sintering pressure is 30Mpa to obtain a WFeNiMo multiphase tungsten-based high entropy alloy. The picture of the WFeNiMo multiphase tungsten-based high entropy alloy sample prepared by sintering is shown in the figure. Figure 1 As shown, the sample has a diameter of 35 mm and a height of 44 mm. The sample density is measured to be 99.04% according to the Archimedes drainage method. It can be seen that the WFeNiMo multiphase tungsten-based high entropy alloy prepared under this sintering process has a higher density.

[0081] Example 1 The microstructure of the WFeNiMo multiphase tungsten-based high entropy alloy sample prepared by sintering is as follows Figure 1As shown in the figure, it can be seen that the WFeNiMo alloy prepared by sintering is composed of three phases. The white phase is tungsten particles, the gray phase is molybdenum-rich phase, and the black phase is iron-nickel-rich phase. The tungsten particles are body-centered cubic structures, which provide strength, and the FeNi-rich phase is face-centered cubic structures, which provide plasticity. Therefore, the WFeNiMo multiphase tungsten-based high entropy alloy sample has good strength and plasticity. The compressive stress-strain curve of the WFeNiMo multiphase tungsten-based high entropy alloy prepared in Example 1 is shown in Figure 2 As shown, the sample has a compressive strength of 1870 MPa and a compressive strain of 3.9%.

[0082] Figure 3 The microstructure of the WMoTaNb multiphase tungsten-based high entropy alloy prepared in Example 2 of the present invention. The preparation conditions are: using tungsten powder and niobium powder with a particle size of 15 microns to 53 microns, molybdenum powder and tantalum powder with a particle size of less than 10 microns, first use a planetary ball mill to mix the composite material powder evenly. Then the mixed powder is loaded into a graphite mold, and the powder is quickly sintered into a block using a spark plasma sintering furnace. The sintering temperature is 1900°C, the holding time is 10min, and the sintering pressure is 30Mpa to obtain a WMoTaNb multiphase tungsten-based high entropy alloy. The WMoTaNb multiphase tungsten-based high entropy alloy sample prepared by sintering has a diameter of 10mm and a height of 4mm. The sample density is measured to be 95.1% according to the Archimedes drainage method.

[0083] Example 2 The microstructure of the WMoTaNb multiphase tungsten-based high entropy alloy sample prepared by sintering is as follows Figure 3 As shown in the figure, it can be seen that the WMoTaNb multiphase tungsten-based high entropy alloy sample is mainly composed of three phases, among which the white phase is tungsten particles, the gray phase is molybdenum-niobium-rich phase, and the black phase is tantalum phase. The larger black phase is due to the larger particle size of the tantalum powder used in sintering.

[0084] Figure 4 This is a microstructure picture of the WMoNbCo multiphase tungsten-based high entropy alloy prepared in Example 3 of the present invention. The preparation conditions are: using tungsten powder and niobium powder with a particle size of 15 microns to 53 microns, molybdenum powder and cobalt powder with a particle size of less than 10 microns, first use a planetary ball mill to mix the composite material powder evenly. Then put the mixed powder into a graphite mold, and use a spark plasma sintering furnace to quickly sinter the powder into a block, the sintering temperature is 1200°C, the holding time is 10min, and the sintering pressure is 30Mpa to obtain a WMoNbCo multiphase tungsten-based high entropy alloy.

[0085] The WMoNbCo multiphase tungsten-based high entropy alloy sample prepared by sintering has a diameter of 42 mm and a height of 5 mm. The density of the sample measured by the Archimedes drainage method is 99.07%. It can be seen that the WMoNbCo multiphase tungsten-based high entropy alloy prepared by this sintering process has a higher density.

[0086] Example 3 The microstructure of the WMoNbCo multiphase tungsten-based high entropy alloy sample prepared by sintering is as follows Figure 4 As shown in the figure, it can be seen that the WMoNbCo multiphase tungsten-based high entropy alloy sample is mainly composed of three phases, namely white strip phase, black strip phase and gray phase. It can be known from EDS point scanning that the white strip phase is tungsten phase. Since the particle size of the tungsten powder used is small, the tungsten powder is deformed at high temperature to produce a white strip phase. The black strip phase is the niobium phase. Since the particle size of the niobium powder used is large and the melting point is too high, a black strip-shaped niobium phase appears. The gray phase is a cobalt-rich molybdenum phase generated by the reaction of low-particle-size cobalt powder and molybdenum powder. It can be seen from the organizational picture that the tungsten phase is distributed in the alloy in strips, providing strength to the alloy, so the sample has higher strength. The compressive stress-strain curve of the WMoNbCo multiphase tungsten-based high entropy alloy prepared in Example 3 is shown in Figure 3. Figure 5 As shown, the sample has a compressive strength of 2835 MPa and a compressive strain of 2.9%.

[0087] Figure 6 This is a microstructure picture of the WFeNiCo multiphase tungsten-based high entropy alloy prepared in Example 4 of the present invention. The preparation conditions are: using tungsten powder with a particle size of 15 microns to 53 microns, molybdenum powder, cobalt powder and iron powder with a particle size of less than 10 microns, first use a planetary ball mill to mix the composite material powder evenly. Then the mixed powder is loaded into a graphite mold, and the powder is quickly sintered into a block using a spark plasma sintering furnace. The sintering temperature is 1200°C, the holding time is 10min, and the sintering pressure is 30Mpa to obtain a WFeNiCo multiphase tungsten-based high entropy alloy. The WFeNiCo multiphase tungsten-based high entropy alloy sample prepared by sintering has a diameter of 15mm and a height of 5mm. The sample density is 97.10% measured according to the Archimedes drainage method.

[0088] Example 4 The microstructure of the WFeNiCo multiphase tungsten-based high entropy alloy sample prepared by sintering is as follows Figure 6 As shown in the figure, it can be seen that the alloy is mainly composed of two phases. From the EDS point scanning results, it is known that the white phase is the tungsten phase. Due to the small particle size of the tungsten powder used, the tungsten powder aggregated during the heating process. The black phase is the iron-nickel-cobalt phase. Since the iron-nickel-cobalt phase has low strength, good plasticity, and a large specific gravity, the alloy has low strength and good plasticity. Example 4 The compressive stress-strain curve of the WFeNiCo multiphase tungsten-based high entropy alloy prepared by sintering is shown in Figure 7 As shown, the sample has a compressive strength of 1710 MPa and a compressive strain of 6.1%.

[0089] Figure 8This is a picture of the mold of the WMoNbCo multiphase tungsten-based high entropy alloy prepared in Comparative Example 1 of the present invention. The preparation conditions are: use tungsten powder and niobium powder with a particle size of 15 microns to 53 microns, molybdenum powder and cobalt powder with a particle size of less than 10 microns, and first use a planetary ball mill to mix the composite material powder evenly. Then put the mixed powder into a graphite mold, and use a spark plasma sintering furnace to quickly sinter the powder into a block. The sintering temperature is 1250°C, the insulation time is 10 minutes, and the sintering pressure is 30Mpa to obtain a WFeNiCo multiphase tungsten-based high entropy alloy. Since the sintering temperature of WMoNbCo was increased, the mold overflowed due to the high temperature when sintering the WMoNbCo sample. Figure 8 This is the mold overflow situation when sintering WMoNbCo multiphase tungsten-based high entropy alloy at 1250℃, which means that the sintering temperature of 1250℃ is too high, and the sintering at 1100℃ is not dense enough. Due to the different alloy components and melting points, different elements may react during the sintering process to generate compounds with lower melting points. Therefore, the sintering temperature of WMoNbCo multiphase tungsten-based high entropy alloy is set to 1200℃.

[0090] In summary, the present invention proposes a multiphase tungsten-based high-entropy alloy prepared by spark plasma sintering process and a rapid preparation method thereof. Using the spark plasma sintering process, by changing the composition of the multiphase tungsten-based high-entropy alloy, sintering process parameters, etc., a variety of multiphase tungsten-based high-entropy alloys with different compositions, different structures and mechanical properties are prepared. The prepared multiphase tungsten-based high-entropy alloy has excellent mechanical properties, and its actual measured density exceeds 11.5g / cm 3 , the minimum density can reach more than 95%, and the maximum density can reach more than 99%. The maximum compressive strength exceeds 2.8Gpa, and the maximum compressive strain can reach 25%. However, due to the high melting point of tungsten-based high-entropy alloys, the density of tungsten-based high-entropy alloys prepared by traditional processes generally does not exceed 90%, and due to the low density of tungsten-based high-entropy alloys, they have many internal defects, resulting in low strength of tungsten-based high-entropy alloys prepared by traditional processes, the compressive strength generally does not exceed 1.5GPa, and the compressive strain generally does not exceed 10%. From a process point of view, the preparation process of the present invention has a fast preparation process, a short production cycle, simple operation, and is easy to promote and apply.

[0091] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0092] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the protection scope of the present invention and its equivalent technology, the present invention is also intended to include these changes and variations.

Claims

1. A method for preparing a tungsten-based high entropy alloy, characterized in that: The following steps are involved: Mixing W powder with auxiliary raw material powder and ball milling to obtain mixed powder, wherein the auxiliary raw material powder is three or more of Mo powder, Ta powder, Nb powder, Fe powder, Ni powder and Co powder, wherein the atomic percentage of W powder in the mixed powder is 25% to 55%, and the atomic percentage of each metal powder in the auxiliary raw material powder is 10% to 30%, and the total of W powder and auxiliary raw material powder is 100%; The mixed powder is subjected to spark plasma sintering under vacuum conditions to obtain a tungsten-based high entropy alloy, wherein the sintering temperature is 1100° C. to 2000° C.

2. The method for preparing a tungsten-based high entropy alloy according to claim 1, characterized in that: The sintering pressure is 20MPa~40MPa.

3. The method for preparing a tungsten-based high entropy alloy according to claim 1, characterized in that: The sintering holding time is 5min to 30min.

4. The method for preparing a tungsten-based high entropy alloy according to claim 1, characterized in that: The sintering heating rate is 50℃ / min~100℃ / min.

5. The method for preparing a tungsten-based high entropy alloy according to claim 1, characterized in that: The ball milling speed is 200 r / min to 300 r / min, and the ball milling time is 8 h to 16 h.

6. The method for preparing a tungsten-based high entropy alloy according to claim 1, characterized in that: The particle size of W powder is 15 microns to 53 microns, the particle size of Nb powder is 15 microns to 53 microns, the particle size of Ta powder is 15 microns to 53 microns, and the particle sizes of Co powder, Fe powder, Mo powder and Ni powder are all less than 10 microns.

7. The method for preparing a tungsten-based high entropy alloy according to claim 1, characterized in that: The purity of raw material powder is ≥99.9%.

8. The method for preparing a tungsten-based high entropy alloy according to claim 1, characterized in that: During ball milling, the ball-to-material mass ratio is 3 to 10:

1.

9. A tungsten-based high entropy alloy obtained by the method according to any one of claims 1 to 8.

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