A high-strength and high-toughness tungsten-based composite material and its preparation method

Abstract

The present invention discloses a high-strength and high-toughness tungsten-based composite material and a preparation method thereof, belonging to the technical field of composite material preparation. The high-strength and high-toughness tungsten-based composite material provided by the present invention comprises a multi-endpoint-like reticular structure, nano-particles and a matrix material; the multi-endpoint-like reticular structure contains main branch fibers, branch fibers and bridging fibers; in the multi-endpoint-like reticular structure, adjacent main branch fibers are connected to each other through bridging fibers, and the branch fibers are distributed on the main branch fibers; the nano-particles include non-magnetic nano-particles and magnetic nano-particles, and are all uniformly distributed in the multi-endpoint-like reticular structure; the matrix material is tungsten powder. Through the combination of main branch fibers, branch fibers and bridging fibers, a stable and firm multi-endpoint-like reticular structure is formed, and through the synergistic effect with the nano-particles, multi-level toughening is achieved, so that the synthesized tungsten-based composite material can effectively resist the formation and propagation of cracks while bearing a large stress.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material preparation, and specifically relates to a high-strength and high-toughness tungsten-based composite material and a preparation method thereof. Background Art

[0002] Tungsten (W) is a material with a high atomic number and is widely used in many fields such as energy, aerospace, national defense, military, automotive industry, and medical machinery due to its high density (19.35 g / cm 3 ), high melting point (3412 °C), high hardness, excellent corrosion resistance, and electrical and thermal conductivity. In the energy field, tungsten is one of the most promising materials for plasma-facing materials in nuclear fusion reactors. However, the brittleness of tungsten materials is an obvious defect. The ductile-to-brittle transition temperature (DBTT) is one of the indicators to measure the brittleness and toughness of tungsten and tungsten-based materials, which refers to the temperature at which tungsten materials change from ductile fracture to brittle fracture. For tungsten, this temperature is relatively high because tungsten itself is a metal with a body-centered cubic (BCC) structure. The electronic structure, characteristics of atomic bonds, and lattice resistance of the dislocation stress field of BCC metals determine the room-temperature brittleness of tungsten. In addition, the recrystallization brittleness and irradiation embrittlement of tungsten severely limit the application of tungsten materials in service environments such as irradiation and high temperature.

[0003] At present, there are mainly two effective methods to improve the toughness of tungsten materials: internal toughening method and external toughening method. The internal toughening method mainly improves the plasticity of tungsten itself by adding alloying elements (such as rhenium, molybdenum, copper, etc.), second-phase particles or refining tungsten grains. However, due to the high strength of tungsten itself and its sensitivity to impurities, and in the service environment of high heat load, recrystallization is likely to occur. Therefore, the effect of using the internal toughening method alone is not obvious; the external toughening method toughens by adding ductile phases such as fibers and layered materials to the tungsten matrix, which is called fiber toughening and layered toughening. The layered toughened tungsten matrix composite material generally composits some ductile metal foils, such as titanium foil, vanadium foil, tantalum foil and copper foil, etc. with tungsten foil by methods such as rolling welding and diffusion bonding to form a multi-layer structure and a dissimilar metal phase interface structure. The toughening phases of fiber toughening include metal fibers, carbon fibers and tungsten fibers. However, at present, the fiber toughening still has defects such as low density of the composite material, poor interfacial bonding degree, and easy appearance of micropores and cracks in the composite material, which affect the overall performance of the tungsten matrix composite material. For example, the Chinese patent with the authorized announcement number CN112442643 B discloses a layered fiber toughened tungsten matrix composite material and its preparation method. The composite material includes alternately laminated tungsten matrix layers and titanium foil and tungsten fiber mesh toughening layers, and the layered fiber toughened tungsten matrix composite material is obtained after spark plasma sintering under vacuum conditions. However, the tungsten matrix composite material prepared by this method lacks an interface between the collective layer and the toughening layer, which is not conducive to improving the fracture dissipation energy. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the current tungsten matrix composite material still has problems of insufficient strength and toughness. The purpose is to provide a high-strength and high-toughness tungsten matrix composite material and its preparation method, which can improve the brittleness of the tungsten matrix composite material and enhance the toughness of tungsten.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] A high-strength and high-toughness tungsten matrix composite material, comprising a multi-endpoint mesh-like structure, nano-particles and a matrix material. The multi-endpoint mesh-like structure includes main branch fibers, branch fibers and bridging fibers; in the multi-endpoint mesh-like structure, adjacent main branch fibers are connected to each other by bridging fibers, and the branch fibers are distributed on the main branch fibers; the nano-particles include non-magnetic nano-particles and magnetic nano-particles, both of which are uniformly distributed in the multi-endpoint mesh-like structure; the matrix material is tungsten powder.

[0007] Fiber toughening belongs to the external toughening method. Its basic principle is to utilize the high strength and high modulus characteristics of fibers to disperse and absorb the stress originally acting on the matrix material. Fibers can disperse the stress over a larger area, reduce stress concentration, and thus reduce the generation and propagation of cracks. After cracks are generated, the fibers will exert a certain closing pressure on the crack surface, which makes the cracks tend to close and hinders the opening and continuous extension of the cracks. Fibers in the tungsten-based composite can also change the propagation direction of cracks, playing a role in crack deflection. When cracks propagate and encounter fibers, due to the presence of fibers, the cracks cannot continue to expand linearly in the original direction. Fibers act like a barrier, forcing the cracks to change direction, making the propagation path of the cracks tortuous. The cracks need to overcome more obstacles and consume more energy, thereby improving the toughness of the material.

[0008] The main branch fibers, as the main load-bearing structure in the toughening unit, provide the basic strength and rigidity for the tungsten-based composite material. The main branch fibers bear most of the mechanical loads in the composite material, including tensile, compressive, and bending loads. The main branch fibers can effectively transfer various mechanical loads received from one end of the fiber to the other end, thus reducing local stress concentration. The branched fibers are distributed on the main branch fibers, forming a branched structure. This structure makes the propagation path of cracks more complex, so more energy is required to propagate the cracks, improving the fracture toughness of the material. The branched fibers can also play a bridging role near the crack tip to prevent the rapid propagation of cracks. Different branched structures are interconnected by bridging fibers, forming a multi-endpoint-like network structure. This not only significantly increases the complexity of the crack path, but the bridging fibers themselves can also provide an additional energy absorption mechanism, further enhancing the overall toughness of the tungsten-based composite material.

[0009] Nanoparticles have a huge specific surface area and can be filled into the voids between fibers. They can significantly improve the density of the tungsten-based composite material and also improve the bonding strength between tungsten fibers and the tungsten matrix. When the interfacial bonding strength between the fibers and the tungsten matrix is moderate, cracks can propagate along the interface between the fibers and the tungsten matrix. The fibers can undergo plastic deformation before fracture, thus absorbing a large amount of energy, and thus playing a toughening role. Nanoparticles can also prevent the propagation of cracks through the pinning effect.

[0010] Tungsten powder, as the matrix material, provides the basic physical and chemical properties of the tungsten-based composite material and is also the basis for the strength and hardness of the composite material.

[0011] Preferably, the main branch fibers are long tungsten fibers with a length of 10 - 50 mm, a diameter of 80 - 300 μm, and a mass ratio of 24 - 36%; the branched fibers are short tungsten fibers with a length of 1 - 3 mm, a diameter of 30 - 100 μm, and a mass ratio of 8 - 12%; the bridging fibers are alumina fibers with a fiber length of 16 - 28 mm, a diameter of 50 - 200 μm, and a mass ratio of 15 - 20%. Tungsten fibers are selected as the materials for the main branch fibers and the branched fibers because tungsten fibers do not require the introduction of other alloying elements, and the toughness of tungsten-based composites is improved by fully exerting the excellent properties of the fibers themselves. The main branch fibers selected are long tungsten fibers, and the branched fibers selected are short tungsten fibers. In the present invention, alumina fibers are selected as the bridging fibers. Alumina fibers also have excellent mechanical properties, including high strength and high modulus. These characteristics enable alumina fibers to effectively enhance the toughness and impact resistance of tungsten-based composites. Moreover, alumina fibers have extremely high chemical stability and thermal stability, with a melting point as high as 1840°C, and can be used at high temperatures of 1300 - 1400°C for a long time while maintaining their structure and properties, thereby improving the high-temperature resistance of tungsten-based composites. Compared with traditional metal materials, alumina fibers have a lower density, which helps to reduce the overall weight of tungsten-based composites.

[0012] Preferably, the nanoparticles are any one of Al2O3 nanoparticles, ZrC nanoparticles, and TiC nanoparticles; the particle size of the nanoparticles is 25 - 60 nm, and the mass ratio is 0.2 - 1.8%; the magnetic nanoparticles are nickel nanoparticles, and the particle size of the nickel nanoparticles is 10 - 20 nm, and the mass ratio is 0.1 - 0.5%.

[0013] Both Al2O3 nanoparticles and TiC nanoparticles have the characteristic of high hardness. They can be evenly dispersed in the toughening unit to form hard particles, reduce wear during the friction process, and significantly improve the hardness and wear resistance of tungsten-based composites. Al2O3 nanoparticles also have good thermal stability and can maintain their structure and function in a high-temperature environment, improving the high-temperature resistance of the composites. TiC nanoparticles can maintain good stability in a corrosive environment, thereby improving the corrosion resistance of the composites. ZrC nanoparticles have relatively high fracture toughness and are not prone to brittle fracture when the tungsten-based composites are subjected to external force impact. ZrC nanoparticles can also form a stable oxide layer under high-temperature conditions, thereby protecting the interior of the composites from further oxidation and extending the service life of the composites.

[0014] Nickel is a metal with good plasticity and toughness, good oxidation resistance, a melting point of about 1455 °C, and stable processing performance. After being added in the form of nanoparticles, it can relieve stress concentration to a certain extent and improve the fracture toughness of the composite material. Nickel nanoparticles can, under the action of a magnetic field, arrange their magnetic moments along with the change of the magnetic field, distribute between non-magnetic nanoparticles, and form micro-channels.

[0015] Preferably, the tungsten powder is in a spherical shape, with a particle size of 0.5 - 10 μm and a mass ratio of 29.7 - 52.7%. The spherical tungsten powder is selected in the present invention because it has good fluidity and compressibility, is easy to be evenly distributed; the gaps between spherical particles are small, which is beneficial to the preparation of a denser tungsten-based composite material; the contact points between spherical particles are fewer, reducing stress concentration during the sintering process and enabling a more uniform sintered body to be obtained.

[0016] The present invention also provides a method for preparing a high-strength and high-toughness tungsten-based composite material, as Figure 1 shown, which includes the following steps:

[0017] Step 1: Put the tungsten powder and nanoparticles into a ball mill under the protection of an inert gas for high-energy ball milling treatment;

[0018] Step 2: Place the main branch fibers, branch fibers, and bridging fibers in absolute ethanol for ultrasonic cleaning, and after vacuum drying; use the electrostatic spraying method to spray the branch fibers on the main branch fibers to form a dendritic structure;

[0019] Step 3: Put the dendritic structure and bridging fibers pretreated in Step 2 into a three-dimensional powder mixer for preliminary mixing to form a multi-endpoint-like network structure;

[0020] Step 4: Fill the tungsten powder and nanoparticles processed in Step 1 into the mold of the multi-endpoint-like network structure constructed in Step 3, and cold isostatically press it to be compacted to form a green body;

[0021] Step 5: Put the green body formed in Step 4 into a sintering furnace equipped with electromagnetic coils, and under variable magnetic field conditions, carry out vacuum sintering when reaching the set temperature, and demold after cooling to obtain a high-strength and high-toughness tungsten-based composite material.

[0022] Preferably, in the step 1, the inert gas is argon; the mass ratio of the grinding balls to the tungsten powder during ball milling is 5-35:1; the rotation speed of the ball mill is 260-640 r / min, and the ball milling time is 6-18 h. The present invention uses the high-energy ball milling method. Through the high-energy collision and shear force during ball milling, the agglomeration phenomenon between nanoparticles can be broken, so that the nanoparticles are evenly dispersed in the matrix of tungsten powder. During ball milling, the surfaces of the nanoparticles and tungsten powder will be mechanically activated, generating a large number of fresh surfaces, improving the surface activity of both, and thus enhancing the interfacial bonding force. Ball milling under the protection of argon can isolate oxygen and moisture, prevent the tungsten powder and nanoparticles from undergoing oxidation reactions during ball milling, and ensure the purity of the material.

[0023] Preferably, in the step 2, the ultrasonic cleaning time is 5-20 min; the vacuum drying time is 15-30 min; during the electrostatic spraying process, the voltage used is between 30 kV and 60 kV, and the spraying distance is 15-60 cm. Ultrasonic cleaning of the surfaces of tungsten fibers and alumina fibers can effectively remove grease, dust and other pollutants on the fiber surfaces; the ultrasonic action can also penetrate into the tiny gaps and cavities on the fiber surfaces to remove pollutants that are difficult to reach, and can remove the oxide layer on the fiber surfaces, making the fibers in a more active state. Electrostatic spraying uses the action of electrostatic force to spray branch fibers onto the main branch fibers. Due to the action of electrostatic force, the branch fibers can be evenly dispersed on the main branch fibers, avoiding the agglomeration phenomenon. Electrostatic spraying can achieve a good covering effect, ensuring the full coverage of the branch fibers on the main branch fibers.

[0024] Preferably, in the step 3, the mixing time is 3-5 h, and the mixing rotation speed is 100-300 r / min.

[0025] Preferably, in the step 4, cold isostatic pressing is carried out using a hydraulic press, and the cold pressing pressure is 150-300 MPa.

[0026] Preferably, in the step 5, the sintering pressure is 100-200 MPa, and the set temperature is 1000-1300 °C; the variable magnetic field is generated by an alternating current, the provided voltage is 220 V-380 V, the frequency is 300-600 Hz, and the time is 0.5-3 h. By changing the voltage and frequency of the electromagnetic coil, a variable magnetic field is generated, causing the magnetic nanoparticles in the composite material to change accordingly.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) The main branch fibers serve as the basic framework in the toughening unit. When the tungsten-based composite material is under stress, relying on the high strength and high modulus characteristics of the fibers themselves, the stress can be transmitted from one end to the other. Moreover, long tungsten fibers are selected as the main branch fibers, which can bear more loads, have a longer stress transmission path, and consume more energy.

[0029] (2) The branched fibers are distributed on the main branch fibers by the electrostatic spraying method to form a dendritic structure. This structure makes the crack propagation path more complex and diverse, further dispersing and bearing stress; the branched fibers can also play a bridging role near the crack tip to prevent further crack propagation.

[0030] (3) The main branch fibers are interconnected by bridging fibers to form a more stable and robust multi-endpoint-like network structure. Alumina fibers have high strength and good thermal stability, which not only increase the connection between the main branch fibers but also provide an additional energy absorption mechanism. When the material is under stress, the bridging fibers can also transmit the load and play a bridging role during crack propagation, delaying the crack propagation. At lower temperatures, especially below 550 °C, the mass and volume of the alumina fibers will shrink rapidly, with a shrinkage rate higher than 85%. However, as the temperature further increases, this shrinkage trend will gradually weaken and remain stable at higher temperatures, thus generating certain voids around the alumina fibers. These voids can provide a good buffer space when the composite material is under stress, thereby consuming energy and improving toughness.

[0031] (4) Due to their high specific surface area and high surface energy, nanoparticles can serve as heterogeneous nucleation sites to promote grain refinement of the matrix material. Fine grains can improve the hardness and strength of the material; nanoparticles can prevent crack propagation through the pinning effect, thereby improving the fracture toughness of the material. When a crack encounters a nanoparticle, the particle will pin the crack tip like a nail, consuming more energy to expand the crack. By mixing magnetic nanoparticles and non-magnetic nanoparticles, the magnetic nanoparticles can continuously align their magnetic moments under a variable magnetic field, thus forming multiple micro-channels between the non-magnetic nanoparticles. When the tungsten-based composite material is under stress, the voids formed by these micro-channels can well absorb and consume part of the stress, not just disperse the stress. Moreover, the existence of the micro-channels provides additional space for the volume change caused by thermal expansion and contraction during high-temperature sintering and low-temperature cooling of the composite material, reducing the problem of internal stress concentration caused by thermal stress, improving the heat shock resistance of the composite material, and extending its service life. Description of the Drawings

[0032] Figure 1 is a flow chart for preparing a high-strength and high-toughness tungsten-based composite material. Detailed Embodiments

[0033] The technical solutions in the embodiments of the present invention will be described in detail below. The described embodiments are only partial embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention fall within the scope of protection of the present invention. The present invention will be further described below in conjunction with specific embodiments.

[0034] The experimental materials, reagents, etc. used in the following embodiments can be obtained from commercial channels without special instructions.

[0035] Example 1

[0036] This embodiment provides a high-strength and high-toughness tungsten-based composite material. The main branch fibers are tungsten fibers with a length of 32 mm and a diameter of 150 μm, and the mass ratio is 30%; the branch fibers are short tungsten fibers with a length of 2 mm and a diameter of 55 μm, and the mass ratio is 8%; the bridging fibers are alumina fibers with a length of 22 mm and a diameter of 120 μm, and the mass ratio is 16%; the non-magnetic nanoparticles are TiC with a particle size of 50 nm, and the mass ratio is 0.5%; the non-magnetic nanoparticles are nickel nanoparticles with a particle size of 15 nm, and the mass ratio is 0.2%; the particle size of the tungsten powder is 10 μm, and the mass ratio is 45.3%.

[0037] The specific preparation method is as follows:

[0038] Step 1: Put the tungsten powder, TiC nanoparticles and nickel nanoparticles into a ball mill under argon protection for high-energy ball milling; the mass ratio of the ball to the tungsten powder during ball milling is 15:1, the rotation speed of the ball mill is 360 r / min, and the ball milling time is 10 h;

[0039] Step 2: Place the long tungsten fibers, short tungsten fibers and alumina fibers in absolute ethanol for ultrasonic cleaning for 15 min and vacuum drying for 25 min; use the electrostatic spraying method to spray the short tungsten fibers on the long tungsten fibers to form a dendritic structure, with a voltage of 56 kV and a spraying distance of 32 cm;

[0040] Step 3: Put the dendritic structure and alumina fibers pretreated in Step 2 into a three-dimensional powder mixer for preliminary mixing for 5 h, with a mixing rotation speed of 200 r / min, to form a primary fiber network structure;

[0041] Step 4: Fill the tungsten powder, TiC nanoparticles and nickel nanoparticles treated in Step 1 into the mold of the primary fiber network constructed in Step 3, and use a hydraulic press to perform cold isostatic pressing with a cold pressing pressure of 200 MPa to compact it to form a green body;

[0042] Step 5: Place the green body formed in Step 4 into a sintering furnace equipped with electromagnetic coils. When the temperature reaches 1300 °C, turn on the alternating current with a voltage of 220 V and a frequency of 500 Hz, and conduct vacuum sintering. Apply uniform pressure up to 120 MPa and sinter for 2 h. After cooling, demold the sample to obtain a high-strength and high-toughness tungsten-based composite material.

[0043] Example 2

[0044] This example provides a high-strength and high-toughness tungsten-based composite material. The main branch fibers are long tungsten fibers with a length of 27 mm and a diameter of 120 μm, with a mass ratio of 28%; the branch fibers are short tungsten fibers with a length of 3 mm and a diameter of 50 μm, with a mass ratio of 10%; the bridging fibers are alumina fibers with a length of 28 mm and a diameter of 100 μm, with a mass ratio of 15%; the nanoparticles are TiC with a particle size of 60 nm, with a mass ratio of 0.6%; the non-magnetic nanoparticles are nickel nanoparticles with a particle size of 10 nm, with a mass ratio of 0.3%; the tungsten powder has a particle size of 3.5 μm, with a mass ratio of 46.1%.

[0045] The specific preparation method is as follows:

[0046] Step 1: Put tungsten powder, TiC nanoparticles, and nickel nanoparticles into a ball mill under argon protection for high-energy ball milling; the mass ratio of the ball to tungsten powder during ball milling is 25:1, the rotation speed of the ball mill is 260 r / min, and the ball milling time is 6 h;

[0047] Step 2: Place the long tungsten fibers, short tungsten fibers, and alumina fibers in absolute ethanol for ultrasonic cleaning for 5 min and vacuum drying for 15 min; use the electrostatic spraying method to spray the short tungsten fibers on the long tungsten fibers to form a branched structure with a voltage of 30 kV and a spraying distance of 15 cm;

[0048] Step 3: Put the pretreated branched structure and alumina fibers in Step 2 into a three-dimensional powder mixer for preliminary mixing for 3 h at a mixing rotation speed of 100 r / min to form a primary fiber network structure;

[0049] Step 4: Fill the tungsten powder, TiC nanoparticles, and nickel nanoparticles treated in Step 1 into the mold of the primary fiber network constructed in Step 3, and use a hydraulic press to perform cold isostatic pressing with a cold pressing pressure of 150 MPa to compact it and form a green body;

[0050] Step 5: Place the green body formed in Step 4 into a sintering furnace equipped with electromagnetic coils. When the temperature reaches 1000 °C, turn on the alternating current with a voltage of 300 V and a frequency of 300 Hz, and conduct vacuum sintering. Apply uniform pressure up to 100 MPa and sinter for 0.5 h. After cooling, demold the sample to obtain a high-strength and high-toughness tungsten-based composite material.

[0051] Example 3

[0052] This example provides a high-strength and high-toughness tungsten-based composite material. The main branch fibers are long tungsten fibers with a length of 50 mm and a diameter of 180 μm, and the mass ratio is 36%; the branched fibers are short tungsten fibers with a length of 1.5 mm and a diameter of 100 μm, and the mass ratio is 12%; the bridging fibers are alumina fibers with a length of 20 mm and a diameter of 200 μm, and the mass ratio is 20%; the nanoparticles are ZrC with a particle size of 35 nm, and the mass ratio is 1.8%; the non-magnetic nanoparticles are nickel nanoparticles with a particle size of 20 nm, and the mass ratio is 0.5%; the particle size of the tungsten powder is 0.5 μm, and the mass ratio is 29.7%.

[0053] The specific preparation method is as follows:

[0054] Step 1: Put the tungsten powder, ZrC nanoparticles and nickel nanoparticles into a ball mill under argon protection for high-energy ball milling; the mass ratio of the ball to the tungsten powder during ball milling is 35:1, the rotation speed of the ball mill is 640 r / min, and the ball milling time is 12 h;

[0055] Step 2: Place the long tungsten fibers, short tungsten fibers and alumina fibers in anhydrous ethanol and ultrasonically clean them for 20 min, and then vacuum dry them for 30 min; use the electrostatic spraying method to spray the short tungsten fibers on the long tungsten fibers to form a dendritic structure, with a voltage of 60 kV and a spraying distance of 60 cm;

[0056] Step 3: Put the dendritic structure and alumina fibers pretreated in Step 2 into a three-dimensional powder mixer for preliminary mixing for 4.5 h, with a mixing rotation speed of 300 r / min, to form a primary fiber network structure;

[0057] Step 4: Fill the tungsten powder, ZrC nanoparticles and nickel nanoparticles treated in Step 1 into the mold of the primary fiber network constructed in Step 3, and use a hydraulic press to perform cold isostatic pressing with a cold pressing pressure of 300 MPa to compact it and form a green body;

[0058] Step 5: Put the green body formed in Step 4 into a sintering furnace equipped with an electromagnetic coil. When the temperature reaches 1100 °C, turn on the alternating current, with a voltage of 380 V and a frequency of 600 Hz, and perform vacuum sintering, uniformly pressurize to 200 MPa, sinter for 3 h, and demold the sample after cooling to obtain the high-strength and high-toughness tungsten-based composite material.

[0059] Example 4

[0060] This embodiment provides a high-strength and high-toughness tungsten-based composite material. The main branch fibers are long tungsten fibers with a length of 10 mm and a diameter of 80 μm, and the mass ratio is 24%; the branched fibers are short tungsten fibers with a length of 1 mm and a diameter of 30 μm, and the mass ratio is 8%; the bridging fibers are alumina fibers with a length of 16 mm and a diameter of 50 μm, and the mass ratio is 15%. The nanoparticles are ZrC with a particle size of 25 nm, and the mass ratio is 0.2%; the non-magnetic nanoparticles are nickel nanoparticles with a particle size of 18 nm, and the mass ratio is 0.1%; the particle size of the tungsten powder is 2.5 μm, and the mass ratio is 52.7%.

[0061] The specific preparation method is as follows:

[0062] Step 1: Put the tungsten powder, ZrC nanoparticles and nickel nanoparticles into a ball mill under argon protection for high-energy ball milling; the mass ratio of the ball to the tungsten powder during ball milling is 5:1, the rotation speed of the ball mill is 460 r / min, and the ball milling time is 18 h;

[0063] Step 2: Place the long tungsten fibers, short tungsten fibers and alumina fibers in absolute ethanol for ultrasonic cleaning for 12 min and vacuum drying for 18 min; use the electrostatic spraying method to spray the short tungsten fibers on the long tungsten fibers to form a dendritic structure, with a voltage of 45 kV and a spraying distance of 26 cm;

[0064] Step 3: Put the dendritic structure and alumina fibers pretreated in Step 2 into a three-dimensional powder mixer for preliminary mixing for 3.5 h, with a mixing rotation speed of 220 r / min, to form a primary fiber network structure;

[0065] Step 4: Fill the tungsten powder, ZrC nanoparticles and nickel nanoparticles treated in Step 1 into the mold of the primary fiber network constructed in Step 3, and use a hydraulic press for cold isostatic pressing with a cold pressing pressure of 220 MPa to compact it to form a green body;

[0066] Step 5: Put the green body formed in Step 4 into a sintering furnace equipped with an electromagnetic coil. When the temperature reaches 1150 °C, turn on the alternating current, with a voltage of 360 V and a frequency of 560 Hz, and perform vacuum sintering, uniformly pressurize to 180 MPa, sinter for 1.5 h, and demold the sample after cooling to obtain the high-strength and high-toughness tungsten-based composite material.

[0067] Example 5

[0068] This embodiment provides a high-strength and high-toughness tungsten-based composite material. The main branch fibers are long tungsten fibers with a length of 40 mm and a diameter of 300 μm, and the mass ratio is 31%; the branch fibers are short tungsten fibers with a length of 2.2 mm and a diameter of 15 μm, and the mass ratio is 11%; the bridging fibers are alumina fibers with a length of 20 mm and a diameter of 160 μm, and the mass ratio is 18%; the nanoparticles are Al2O3 with a particle size of 36 nm, and the mass ratio is 1.5%; the non-magnetic nanoparticles are nickel nanoparticles with a particle size of 12 nm, and the mass ratio is 0.4%; the particle size of the tungsten powder is 1.6 μm, and the mass ratio is 38.1%.

[0069] The specific preparation method is as follows:

[0070] Step 1: Put the tungsten powder, Al2O3 nanoparticles and nickel nanoparticles into a ball mill under argon protection for high-energy ball milling; the mass ratio of the ball to the tungsten powder during ball milling is 28:1, the rotation speed of the ball mill is 380 r / min, and the ball milling time is 14 h;

[0071] Step 2: Place the long tungsten fibers, short tungsten fibers and alumina fibers in absolute ethanol for ultrasonic cleaning for 16 min and vacuum drying for 19 min; use the electrostatic spraying method to spray the short tungsten fibers on the long tungsten fibers to form a branched structure, with a voltage of 41 kV and a spraying distance of 32 cm;

[0072] Step 3: Put the branched structure and alumina fibers pretreated in Step 2 into a three-dimensional powder mixer for preliminary mixing for 4.2 h, with a mixing rotation speed of 260 r / min, to form a primary fiber network structure;

[0073] Step 4: Fill the tungsten powder, Al2O3 nanoparticles and nickel nanoparticles treated in Step 1 into the mold of the primary fiber network constructed in Step 3, and use a hydraulic press for cold isostatic pressing with a cold pressing pressure of 290 MPa to compact it and form a green body;

[0074] Step 5: Put the green body formed in Step 4 into a sintering furnace equipped with an electromagnetic coil. When the temperature reaches 1250 °C, turn on the alternating current, with a voltage of 250 V and a frequency of 460 Hz, and perform vacuum sintering, uniformly pressurize to 160 MPa, sinter for 2.5 h, and demold the sample after cooling to obtain the high-strength and high-toughness tungsten-based composite material.

[0075] Example 6

[0076] This embodiment provides a high-strength and high-toughness tungsten-based composite material. The main branch fibers are long tungsten fibers with a length of 28 mm and a diameter of 220 μm, and the mass ratio is 25%; the branched fibers are short tungsten fibers with a length of 2.2 mm and a diameter of 85 μm, and the mass ratio is 11%; the bridging fibers are alumina fibers with a length of 24 mm and a diameter of 140 μm, and the mass ratio is 16%; the nanoparticles are Al2O3 with a particle size of 40 nm, and the mass ratio is 0.3%; the non-magnetic nanoparticles are nickel nanoparticles with a particle size of 16 nm, and the mass ratio is 0.15%; the particle size of the tungsten powder is 4.8 μm, and the mass ratio is 47.55%.

[0077] The specific preparation method is as follows:

[0078] Step 1: Put the tungsten powder, Al2O3 nanoparticles and nickel nanoparticles into a ball mill under argon protection for high-energy ball milling; the mass ratio of the ball to the tungsten powder during ball milling is 30:1, the rotation speed of the ball mill is 460 r / min, and the ball milling time is 17 h;

[0079] Step 2: Place the long tungsten fibers, short tungsten fibers and alumina fibers in absolute ethanol for ultrasonic cleaning for 8 min and vacuum drying for 24 min; use the electrostatic spraying method to spray the short tungsten fibers on the long tungsten fibers to form a branched structure, with a voltage of 38 kV and a spraying distance of 20 cm;

[0080] Step 3: Put the branched structure pretreated in Step 2 and the alumina fibers into a three-dimensional powder mixer for preliminary mixing for 3.8 h, with a mixing rotation speed of 1900 r / min, to form a primary fiber network structure;

[0081] Step 4: Fill the tungsten powder, Al2O3 nanoparticles and nickel nanoparticles treated in Step 1 into the mold of the primary fiber network constructed in Step 3, and use a hydraulic press to perform cold isostatic pressing with a cold pressing pressure of 1800 MPa to compact it and form a green body;

[0082] Step 5: Put the green body formed in Step 4 into a sintering furnace equipped with an electromagnetic coil. When the temperature reaches 1190 °C, turn on the alternating current, with a voltage of 290 V and a frequency of 470 Hz, and perform vacuum sintering, uniformly pressurize to 140 MPa, sinter for 0.8 h, and demold the sample after cooling to obtain the high-strength and high-toughness tungsten-based composite material.

[0083] Comparative Example 1

[0084] This comparative example provides a preparation method of a high-strength and high-toughness tungsten-based composite material. Except for the absence of branched fibers, the other steps are the same as those in Example 1.

[0085] Comparative Example 2

[0086] This comparative example provides a method for preparing a high-strength and high-toughness tungsten-based composite material. Except for not containing bridging fibers, the remaining steps are the same as those in Example 1.

[0087] Comparative Example 3

[0088] This comparative example provides a method for preparing a high-strength and high-toughness tungsten-based composite material. Except for not containing nanoparticles, the remaining steps are the same as those in Example 1.

[0089] Select the products prepared in Examples 1-6 and the products prepared in Comparative Examples 1-3 to conduct bending tests according to GB / T 232-2010 "Metallic Materials - Bend Test". The tensile strength and tensile strain results are shown in Table 1.

[0090] Table 1 Mechanical properties of tungsten-based composite materials in Examples 1-6 and Comparative Examples 1-3

[0091] Tensile strength (MPa) Tensile strain (%) Example 1 1530 3.06 Example 2 1260 2.56 Example 3 1158 1.97 Example 4 1196 2.47 Example 5 1023 1.34 Example 6 1206 1.85 Comparative Example 1 985 0.95 Comparative Example 2 873 0.71 Comparative Example 3 965 0.89

[0092] Tensile strength and tensile strain are important indicators for evaluating the mechanical properties of tungsten-based composite materials. Tensile strength refers to the maximum stress that the composite material can withstand during the tensile process. Tensile strain refers to the amount of deformation that occurs in the composite material during the tensile process, expressed as a percentage, and is used to reflect the plastic deformation ability of the composite material during the tensile process. It can be seen from Table 1 that the tensile strength of Examples 1-6 provided by the present invention is 1023-1530 MPa, which is significantly higher than that of Comparative Examples 1-3, which is 873-985 MPa. This shows that the tensile strength of the tungsten-based composite material containing the toughening unit composed of main branch fibers, branch fibers, bridging fibers and nanoparticles has been significantly improved and has higher strength. The highest tensile strain in the examples provided by the present invention is 3.06%, and the lowest is 1.34%. While the highest in the comparative examples is only 0.95%. The tensile strain values of the composite materials in the examples are significantly better than those in the comparative examples, indicating that the tungsten-based composite material containing the toughening unit composed of main branch fibers, branch fibers, bridging fibers and nanoparticles has better toughness and good microstructure, and can undergo greater plastic deformation during the deformation process of the tungsten-based composite material, thus having a higher tensile strain.

[0093] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A high-strength and high-toughness tungsten-based composite material, characterized in that, It includes a multi-endpoint-like network structure, nanoparticles, and a matrix material; the multi-endpoint-like network structure contains main branch fibers, branch fibers, and bridging fibers; in the multi-endpoint-like network structure, adjacent main branch fibers are interconnected by bridging fibers, and the branch fibers are distributed on the main branch fibers; the nanoparticles include non-magnetic nanoparticles and magnetic nanoparticles, both of which are uniformly distributed in the multi-endpoint-like network structure; the matrix material is tungsten powder; the main branch fibers are long tungsten fibers with a length of 10 - 50 mm, a diameter of 80 - 300 μm, and a mass ratio of 24 - 36%; the branch fibers are short tungsten fibers with a length of 1 - 3 mm, a diameter of 30 - 100 μm, and a mass ratio of 8 - 12%; the bridging fibers are alumina fibers with a fiber length of 16 - 28 mm, a diameter of 50 - 200 μm, and a mass ratio of 15 - 20%; the non-magnetic nanoparticles are any one of Al2O3 nanoparticles, ZrC nanoparticles, and TiC nanoparticles; the particle size of the nanoparticles is 25 - 60 nm, and the mass ratio is 0.2 - 1.8%; the magnetic nanoparticles are nickel nanoparticles, the particle size of the nickel nanoparticles is 10 - 20 nm, and the mass ratio is 0.1 - 0.5%; the tungsten powder is in a spherical shape, the particle size of the tungsten powder is 0.5 - 10 μm, and the mass ratio is 29.7 - 52.7%.

2. The preparation method of a high-strength and high-toughness tungsten-based composite material according to claim 1, characterized in that It includes the following steps: Step 1: Put the tungsten powder and nanoparticles into a ball mill under the protection of an inert gas for high-energy ball milling treatment; Step 2: Place the main branch fibers, branch fibers, and bridging fibers in anhydrous ethanol for ultrasonic cleaning, and after vacuum drying; use the electrostatic spraying method to spray the branch fibers on the main branch fibers to form a branched structure; Step 3: Put the branched structure and bridging fibers pretreated in Step 2 into a three-dimensional powder mixer for preliminary mixing to form a multi-endpoint-like network structure; Step 4: Fill the tungsten powder and nanoparticles treated in Step 1 into the mold of the multi-endpoint-like network structure constructed in Step 3, and cold isostatically press it to compact and form a green body; Step 5: Put the green body formed in Step 4 into a sintering furnace equipped with an electromagnetic coil, and when the set temperature is reached, carry out vacuum sintering under variable magnetic field conditions, and demold after cooling to obtain a high-strength and high-toughness tungsten-based composite material.

3. The preparation method of a high-strength and high-toughness tungsten-based composite material according to claim 2, wherein, In Step 1, the inert gas is argon; the mass ratio of the ball to the tungsten powder during ball milling is 5 - 35:1; the rotational speed of the ball mill is 260 - 640 r / min, and the ball milling time is 6 - 18 h.

4. The preparation method of a high-strength and high-toughness tungsten-based composite material according to claim 2, characterized in that, In Step 2, the ultrasonic cleaning time is 5 - 20 min; the vacuum drying time is 15 - 30 min; during the electrostatic spraying process, the voltage used is between 30 kV and 60 kV, and the spraying distance is 15 - 60 cm.

5. The preparation method of a high-strength and high-toughness tungsten-based composite material according to claim 2, characterized in that, In Step 3, the mixing time is 3 - 5 h, and the mixing rotational speed is 100 - 300 r / min.

6. The preparation method of a high-strength and high-toughness tungsten-based composite material according to claim 2, characterized in that, In Step 4, a hydraulic press is used for cold isostatic pressing, and the cold pressing pressure is 150 - 300 MPa.

7. The preparation method of a high-strength and high-toughness tungsten-based composite material according to claim 2, characterized in that, In the step 5, the sintering pressure is 100 - 200 MPa, the set temperature is 1000 - 1300 °C; the variable magnetic field is generated by an alternating current, the provided voltage is 220 V - 380 V, the frequency is 300 - 600 Hz, and the time is 0.5 - 3 h.

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