Method for preparing beryllium-tungsten alloy through hot isostatic pressing method

Abstract

The invention belongs to the technical field of beryllium alloys, and particularly relates to a method for preparing a beryllium-tungsten alloy through a hot isostatic pressing method. According to the method, gas atomization method pre-alloying, two times of ball milling and multi-stage hot isostatic pressing are combined, the problem of uniformity of multiple components is solved, the strength, toughness and high-temperature stability of the beryllium-tungsten alloy are improved at the same time through collaborative design of the functional additive and the binding phase, and the prepared beryllium-tungsten alloy is uniform in component. Grain boundary diffusion dominated densification is realized through segmented gradient heating and heat preservation of hot isostatic pressing, and various properties of the beryllium-tungsten alloy are improved through synergistic modification of the technical means.

Description

Technical Field

[0001] The present invention belongs to the field of beryllium alloy materials, and particularly relates to a method for preparing beryllium-tungsten alloy by hot isostatic pressing. Background Art

[0002] Beryllium-rich alloys have excellent properties, which have attracted wide attention. Technicians have developed beryllium alloys such as Be 12 Ti (melting point about 1550 °C), Be 12 V (melting point about 1650 °C), etc. Tungsten has excellent properties such as high melting point (3410 °C), high density (19.35 g·cm -3 ), high hardness, low coefficient of thermal expansion, low vapor pressure, etc., and is a low-activation element. Therefore, it is of great significance to attempt to prepare beryllium-tungsten alloy. Tungsten has a high melting point, a low linear expansion coefficient, excellent resistance to fusion welding and erosion; beryllium has high stiffness, low density, high elastic modulus, high specific heat, high thermal conductivity and low linear thermal expansion coefficient. Therefore, beryllium and its composites can be used in airborne and aerospace structures, high-performance engines and brakes, and electronic components for thermal performance and vibration damping. Beryllium and its composites can also be used in a variety of different applications, including hypersonic aircraft, computer components, optical devices for space and ground systems, satellite structures, and solar collectors. However, the mutual solubility of tungsten and beryllium is poor, the atomic sizes do not match, the melting point differences are large, and the diffusion rates are different. Therefore, it is difficult to prepare beryllium-tungsten alloy with excellent comprehensive properties by conventional methods, which is also the reason why there are many reports on beryllium alloys and tungsten alloys, but few reports on the preparation process of beryllium-tungsten alloy.

[0003] The hot isostatic pressing (HIP) process is to place the product in a closed container, apply equal pressure in all directions to the product, and apply high temperature at the same time. Under the action of high temperature and high pressure, the product is sintered and densified. Hot isostatic pressing is an indispensable means for the production of high-performance materials and the development of new materials; it can directly form powder. The powder is loaded into a sheath (similar to the role of a mold), and the sheath can be made of metal or ceramic (low-carbon steel, Ni, Mo, glass, etc.), and then nitrogen or argon is used as the pressurizing medium to directly heat and pressurize the powder for sintering and forming; or the formed castings (such as shrinkage porosity castings of aluminum alloy, titanium alloy, superalloy, etc.) are subjected to hot densification treatment. After hot isostatic pressing treatment, the castings can reach 100% densification, improving the overall mechanical properties of the castings.

[0004] CN116024473A reports a beryllium-tungsten alloy with high temperature, high toughness and high neutron multiplication rate, and lists various methods for preparing the beryllium-tungsten alloy. For example, the hot isostatic pressing method is adopted. After the raw metal powders are mixed, they are filled into a metal cladding and sealed by high vacuum soldering, and then hot isostatically pressed into an ingot with a pressure of 100-1000 MPa, a temperature of 700-1300 °C, and a time of 0.5-6 h. However, in fact, according to the hot isostatic pressing process conditions of this patent, a beryllium-tungsten alloy with excellent properties cannot be obtained. Because the density and atomic size of Be and W are very different, the interatomic diffusion is difficult, and it is difficult to form a uniform bonding interface. Hot isostatic pressing eliminates the internal defects of the alloy through high temperature and high pressure, but the plastic deformation ability of Be and W is very different, resulting in the difficulty of hot isostatic pressing to play its characteristics. Summary of the Invention

[0005] To solve the problem that it is difficult to prepare a beryllium-tungsten alloy with good performance by the hot isostatic pressing method in the prior art, the present invention provides a method for preparing a beryllium-tungsten alloy by the hot isostatic pressing method. By improving the hot isostatic pressing process and adding trace active elements during the preparation of the beryllium-tungsten alloy to promote interface bonding; through two-stage long-time high-energy ball milling treatment, the various materials are better mixed and pre-mechanically alloyed, which is convenient for the subsequent hot isostatic pressing treatment at a gradient temperature, realizing densification dominated by grain boundary diffusion, densifying the powder, better forming a uniformly distributed alloy, and improving the toughness and strength of the material. To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a beryllium-tungsten alloy by the hot isostatic pressing method, comprising the following steps:

[0007] (S1) 70-80 parts by mass of beryllium rods and 2-4 parts by mass of titanium rods are prepared into a beryllium-titanium pre-alloy by gas atomization;

[0008] (S2) Under an inert atmosphere, the beryllium-titanium pre-alloy, 15-20 parts by mass of tungsten powder, and 3-5 parts by mass of Al-Si alloy powder are subjected to the first high-energy ball milling to obtain powder A; powder A and 0.5-1 part by mass of nano-molybdenum powder, 2-4 parts by mass of nano-nickel powder, and 0.7-1.1 parts by mass of LaB6 nano-particles are subjected to the second high-energy ball milling to obtain powder B;

[0009] (S3) The powder B is filled into a metal jacket, evacuated and then sealed by soldering;

[0010] (S4) The sealed metal jacket is placed in a hot isostatic pressing device, and hot isostatic pressing treatment is carried out at 1100-1250 °C and 120-200 MPa for 4-6 h, then the temperature is increased by 100-150 °C and kept warm for 3-5 h, cooled to 300-500 °C and kept warm for 1-2 h, and naturally cooled to room temperature, and the metal jacket is removed to obtain the beryllium-tungsten alloy.

[0011] Further, in step (S1), in the gas atomization method, the beryllium rod and the titanium rod are melted into a liquid state in a high-frequency induction furnace, and are impacted by high-pressure inert gas, and the liquid metal is granulated and cooled to obtain a beryllium-titanium pre-alloy; the inert gas is argon and / or nitrogen, and the flow rate of the inert gas is 50-100 L·s -1 , the pressure of the inert gas is 4-8 MPa, and the working temperature of the high-frequency induction furnace is 1700-1900 °C.

[0012] Furthermore, the diameters of the beryllium rod and the titanium rod are 10-20 mm. The beryllium rod and the titanium rod are melted in a high-frequency induction furnace to become a liquid state, and are sprayed out through an atomization nozzle. The liquid metal is impacted by inert gas with a certain gas flow rate under high pressure, so that the liquid metal is granulated. After cooling, sieving is carried out to obtain spherical beryllium-titanium pre-alloy with a particle size of 50-200 μm. Since titanium is relatively active, it is difficult to find a suitable crucible for the preparation of titanium alloy. The present invention adopts a gas spraying method without a crucible to prepare the beryllium-titanium pre-alloy first, which solves the problem of no suitable crucible due to the high activity of titanium during alloy preparation; on the other hand, metallic beryllium is toxic, and directly using beryllium powder to prepare an alloy has a safety hazard. The highly active titanium rod and beryllium rod are used to prepare the beryllium-titanium pre-alloy by the gas atomization method, which can reduce the toxicity and oxidation problems of beryllium in the process; the fluidity of the beryllium-titanium pre-alloy powder is more suitable for high-energy ball milling.

[0013] Further, in step (S2), the inert atmosphere is nitrogen and / or argon; the rotation speed of the first high-energy ball milling is 500-600 rpm, and the ball milling time is 10-20 h. In the first ball milling, the high-speed ball milling provides sufficient energy to complete mechanical alloying; the rotation speed of the second high-energy ball milling is 200-300 rpm, and the ball milling time is 10-20 h. When ball milling, the size of the grinding balls is 3-5 mm, the material of the grinding balls is tungsten carbide, which can reduce the introduction of impurities, and the ball-to-material ratio is 10-20:1.

[0014] Further, in step (S2), the particle size of the Al-Si alloy powder is 1-5 μm, and the Si content is 12-16 wt%; the particle size of the LaB6 nanoparticles is 100-300 nm, and the sizes of the nano-molybdenum powder and the nano-nickel powder are independently 50-200 nm.

[0015] The inventors found that the introduction of Al-Si alloy powder is crucial for the performance of the products of the present invention. We believe that the Al-Si alloy powder plays a multi-functional role: firstly, the in-situ reaction between beryllium and aluminum is induced under the high-temperature conditions of hot isostatic pressing to form Be-Al intermetallic compounds; secondly, during the high-energy ball milling process, it is possible to form a Be-Al-Si ternary phase. The presence of Be-Al intermetallic compounds / Be-Al-Si ternary phase is beneficial to improving the interfacial properties; secondly, at the initial stage of hot isostatic pressing, the Al-Si alloy powder melts rapidly, and the formed liquid phase promotes the diffusion and densification of high-melting-point substances, enhances the interfacial compatibility of beryllium-titanium and tungsten particles, and plays a role similar to "lubrication". However, the Al-Si alloy powder needs to be added during the first ball milling, otherwise the performance of the final product beryllium-tungsten alloy will deteriorate. The possible reason is that the density difference between the beryllium-titanium pre-alloy and tungsten powder is too large, and it is necessary to rely on the Al-Si alloy powder as a buffer medium to reduce the delamination phenomenon and increase the contact area between each other. If the Al-Si alloy powder is added during the second ball milling, the density difference gradient cannot be effectively alleviated, and delamination is likely to occur; or the contact area between the Al-Si alloy and beryllium-titanium and tungsten decreases, and the liquid phase distribution is uneven during the subsequent hot isostatic pressing process, the interfacial bonding is weakened, pores or structural defects are generated, and the performance of the beryllium-tungsten alloy is weakened.

[0016] During the second ball milling, LaB6 nanoparticles are added as grain boundary strengtheners and are dispersed in the matrix. The grain growth is inhibited through the pinning effect, the grains are refined, and the interfacial bonding is enhanced, improving the room temperature strength and fracture toughness of the alloy; nano-molybdenum powder and nano-nickel powder are also added during the second ball milling; molybdenum dissolves in the tungsten matrix, refining the grains and increasing the strength; nickel enhances the ductility of the bonding phase and improves the toughness of the alloy.

[0017] The ball milling of the present invention is carried out in stages to avoid the delamination problem when materials with different particle sizes or densities are mixed. The ductility of molybdenum powder and nickel powder improves the toughness of the beryllium-tungsten alloy and also improves the compatibility between beryllium and tungsten. However, the molybdenum powder and nickel powder need to be of nanoscale size and are added during the second ball milling to maximize the performance of the beryllium-tungsten alloy. The LaB6 nanoparticles are also added during the second ball milling to prevent agglomeration or structural damage caused by long-term mechanical action during the first ball milling.

[0018] Furthermore, the purity of all materials ≥ 99.99%, the single metal impurity ≤ 5 ppm, and the total metal impurity ≤ 20 ppm.

[0019] Furthermore, in step (S3), the metal jacket is a stainless steel or tantalum or its alloy jacket, which is evacuated and then sealed by welding;

[0020] Furthermore, in step (S4), in step (3) in the hot isostatic pressing equipment, the heating rate is 1-20 °C / min; the cooling rate is 1-10 °C / min.

[0021] Furthermore, in step (S4), during the hot isostatic pressing process, it is kept at a temperature of 1150 - 1200 °C for 4 - 6 h, then after the temperature is increased by 120 - 150 °C, it is kept at the elevated temperature for 3 - 4 h, and then cooled down to 400 - 500 °C and kept at this temperature for 1 - 2 h.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The present invention combines gas atomization pre - alloying, two - stage ball milling, and multi - stage hot isostatic pressing, solving the problem of multi - component composition uniformity. Through the synergistic design of functional additives and binder phases, the strength, toughness, and high - temperature stability of beryllium - tungsten alloy are improved simultaneously. The prepared beryllium - tungsten alloy has a high density and uniform composition. Through the gradient heating and heat preservation in stages during hot isostatic pressing, densification dominated by grain - boundary diffusion is achieved; the toughness of the material is improved by adding titanium, molybdenum, and nickel - based superalloy powders; Al - Si alloy powder is incorporated into the beryllium - tungsten matrix, and the in - situ reaction between beryllium and aluminum is induced under the high - temperature conditions of hot isostatic pressing to generate Be - Al intermetallic compounds, which are used as reinforcement phases to enhance the strength of the material. LaB6 nanoparticles are added to inhibit grain - boundary migration, refine grains, and simultaneously improve the high - temperature stability and properties of the material; the present invention synergistically modifies the above - mentioned technical means to improve the various properties of beryllium - tungsten alloy. Description of the Drawings

[0024] Figure 1 is the metallographic diagram of the beryllium - tungsten alloy prepared in Example 1.

[0025] Figure 2 is the metallographic diagram of the beryllium - tungsten alloy prepared in Comparative Example 1.

[0026] Figure 3 is the metallographic diagram of the beryllium - tungsten alloy prepared in Comparative Example 2.

[0027] Figure 4 is the metallographic diagram of the beryllium - tungsten alloy prepared in Comparative Example 3.

[0028] Figure 5 is the metallographic diagram of the beryllium - tungsten alloy prepared in Comparative Example 4.

[0029] Figure 6 is the metallographic diagram of the beryllium - tungsten alloy prepared in Comparative Example 5. Detailed Embodiments

[0030] The present invention will be further described below in conjunction with specific embodiments, but it is not limited to the content in the specification. Unless otherwise specified, the "parts" mentioned in the embodiments of the present invention are all parts by mass. The reagents used are all commercially available reagents in the art.

[0031] Example 1

[0032] Dosage of each raw material: 77 parts by mass of beryllium rods (diameter 20 mm), 3.1 parts by mass of titanium rods (diameter 20 mm), 20 parts by mass of tungsten powder, 4 parts by mass of Al-Si alloy powder (Si content 14.3 wt%), 0.8 parts by mass of nano molybdenum powder (D50 = 190 nm), 2.8 parts by mass of nano nickel powder (D50 = 150 nm), 0.9 parts by mass of LaB6 nano particles (D50 = 280 nm).

[0033] (S1) The beryllium rods and titanium rods are heated to 1900 °C in a high-frequency induction furnace until the beryllium rods and titanium rods are in a molten state. The molten beryllium liquid and molten titanium liquid are impacted by high-pressure argon gas to turn the molten liquid into small droplets, which solidify during flight. A beryllium-titanium pre-alloy with a particle size of about 100 μm is prepared by gas atomization method. The argon gas pressure is 5 MPa and the argon gas flow rate is 80 L·s -1 ;

[0034] (S2) Under an argon atmosphere, the beryllium-titanium pre-alloy particles, tungsten powder, and Al-Si alloy powder obtained in step (S1) are subjected to the first high-energy ball milling. The grinding balls are made of tungsten carbide, with a size of 3 mm, a ball-to-material ratio of 20:1, a rotation speed of 600 rpm, and a ball milling time of 16 h. After the first high-energy ball milling is completed, powder A is obtained; Powder A is mixed evenly with nano molybdenum powder (D50 = 190 nm), nano nickel powder (D50 = 150 nm), and LaB6 nano particles (D50 = 280 nm), and then subjected to the second ball milling. The grinding balls are made of tungsten carbide, with a size of 3 mm, a ball-to-material ratio of 20:1, a rotation speed of 300 rpm, and a ball milling time of 10 h. After the second high-energy ball milling is completed, powder B is obtained;

[0035] (S3) The powder B is loaded into a tantalum-molybdenum alloy metal sheath, evacuated and then sealed by welding;

[0036] (S4) The sealed metal sheath is placed in a hot isostatic pressing equipment, heated to 1150 °C at a rate of 10 °C / min, pressurized to 160 MPa with high-purity argon gas, and heat isostatic pressing treatment is carried out for 5 h. Then, it is heated to 1300 °C at a heating rate of 2 °C / min and kept warm for another 3 h. It is cooled at a cooling rate of 5 °C / min to 400 °C and kept warm for 2 h, and then naturally cooled to room temperature. The metal sheath is removed to obtain a beryllium-tungsten alloy.

[0037] Example 2

[0038] Other conditions are the same as those in Example 1, except that the raw materials used are: 80 parts by mass of beryllium rods (diameter 20 mm), 4 parts by mass of titanium rods (diameter 20 mm), 15 parts by mass of tungsten powder, 3 parts by mass of Al-Si alloy powder (Si content 15.2 wt%), 1 part by mass of nano molybdenum powder (D50 = 190 nm), 4 parts by mass of nano nickel powder (D50 = 150 nm), 0.7 parts by mass of LaB6 nano particles (D50 = 280 nm).

[0039] Example 3

[0040] Other conditions are the same as those in Example 1, except that the raw materials used are: 70 parts by mass of beryllium rods (diameter 20 mm), 2 parts by mass of titanium rods (diameter 20 mm), 20 parts by mass of tungsten powder, 3 parts by mass of Al-Si alloy powder (Si content 13.6 wt%), 1 part by mass of nano-molybdenum powder (D50 = 190 nm), 4 parts by mass of nano-nickel powder (D50 = 150 nm), and 0.7 part by mass of LaB6 nano-particles (D50 = 280 nm).

[0041] Example 4

[0042] Other conditions are the same as those in Example 1, except that step (S4) is changed to: The metal cladding after sealing is placed in a hot isostatic pressing equipment, heated to 1200 °C at a rate of 10 °C / min, pressurized to 180 MPa with high-purity argon, and heat isostatic pressing treatment is carried out for 5 h. Then, it is heated to 1300 °C at a heating rate of 2 °C / min and kept warm for 4 h, cooled at a cooling rate of 5 °C / min to 500 °C and kept warm for 2 h, and then naturally cooled to room temperature. The metal cladding is removed to obtain a beryllium-tungsten alloy.

[0043] Comparative Example 1

[0044] (S1) 77 parts by mass of beryllium rods and 3.1 parts by mass of titanium rods are heated to 1900 °C in a high-frequency induction furnace. The beryllium rods and titanium rods are heated to a molten state. The molten beryllium liquid and molten titanium liquid are impacted by high-pressure argon to make the molten liquid into small droplets, and they solidify during flight. A beryllium-titanium pre-alloy with a particle size of about 100 μm is prepared by gas atomization method, with an argon gas pressure of 5 MPa and an argon gas flow rate of 80 L·s -1 ;

[0045] (S2) Under an argon atmosphere, the beryllium-titanium pre-alloy particles prepared in step (S1), 20 parts by mass of tungsten powder, 4 parts by mass of Al-Si alloy powder, 0.8 part by mass of nano-molybdenum powder (D50 = 190 nm), 2.8 parts by mass of nano-nickel powder (D50 = 150 nm), and 0.9 part by mass of LaB6 nano-particles (D50 = 280 nm) are mixed evenly and subjected to high-energy ball milling. The grinding balls are made of tungsten carbide, with a size of 3 mm, a ball-to-powder ratio of 20:1, a rotation speed of 500 rpm, and a ball milling time of 15 h to obtain a powder;

[0046] (S3) The powder is filled into a tantalum-molybdenum alloy metal cladding, evacuated and then sealed by welding;

[0047] (S4) The metal cladding after sealing is placed into a hot isostatic pressing equipment, heated to 1150 °C at a rate of 10 °C / min, pressurized with high-purity argon to 160 MPa, and heat isostatic pressing treatment is carried out for 5 h while maintaining the temperature. Then, it is heated to 1300 °C at a heating rate of 2 °C / min and kept warm for 3 h, cooled at a cooling rate of 5 °C / min to 400 °C and kept warm for 2 h, and then naturally cooled to room temperature. The metal cladding is removed to obtain a beryllium-tungsten alloy.

[0048] That is, compared with Example 1, in Comparative Example 1, only one ball milling is performed.

[0049] Comparative Example 2

[0050] (S1) 77 parts by mass of beryllium powder, 3.1 parts by mass of titanium powder, 20 parts by mass of tungsten powder, and 4 parts by mass of Al-Si alloy powder are subjected to the first high-energy ball milling. The grinding balls are made of tungsten carbide, with a size of 3 mm, a ball-to-powder ratio of 20:1, a rotation speed of 600 rpm, and a ball milling time of 16 h. After the first high-energy ball milling, powder A is obtained; powder A is mixed evenly with 0.8 parts by mass of nano-molybdenum powder (D50 = 190 nm), 2.8 parts by mass of nano-nickel powder (D50 = 150 nm), and 0.9 parts by mass of LaB6 nano-particles (D50 = 280 nm), and then the second ball milling is carried out. The grinding balls are made of tungsten carbide, with a size of 3 mm, a ball-to-powder ratio of 20:1, a rotation speed of 300 rpm, and a ball milling time of 10 h. After the second high-energy ball milling, powder B is obtained.

[0051] (S2) Powder B is loaded into a tantalum-molybdenum alloy metal cladding, evacuated and then sealed.

[0052] (S3) The metal cladding after sealing is placed into a hot isostatic pressing equipment, heated to 1150 °C at a rate of 10 °C / min, pressurized with high-purity argon to 160 MPa, and heat isostatic pressing treatment is carried out for 5 h while maintaining the temperature. Then, it is heated to 1300 °C at a heating rate of 2 °C / min and kept warm for 3 h, cooled at a cooling rate of 5 °C / min to 400 °C and kept warm for 2 h, and then naturally cooled to room temperature. The metal cladding is removed to obtain a beryllium-tungsten alloy.

[0053] That is, compared with Example 1, in Comparative Example 2, the preparation of beryllium-titanium pre-alloy by gas spraying method in step (S1) is cancelled, and titanium powder and beryllium powder are directly used as raw materials and ball milled with other raw materials.

[0054] Comparative Example 3

[0055] Other conditions and operations are the same as those in Example 1, except that in step (S2), Al-Si alloy powder is not added.

[0056] Comparative Example 4

[0057] Other conditions and operations are the same as those in Example 1, except that in step (S2), LaB6 nano-particles are not added.

[0058] Comparative Example 5

[0059] Other conditions and operations were the same as those in Example 1, except that in step (S4), it was changed to: the sealed metal cladding was put into a hot isostatic pressing device, heated to 1300 °C at a rate of 10 °C / min, pressurized with high-purity argon to 160 MPa, heat isostatically pressed for 8 h while maintaining the temperature, cooled to 400 °C at a cooling rate of 5 °C / min and held for 2 h, and then naturally cooled to room temperature, and the metal cladding was removed to obtain a beryllium-tungsten alloy.

[0060] That is, compared with Example 1, in the hot isostatic pressing process of Comparative Example 5, it was a constant temperature instead of a gradient temperature treatment.

[0061] Figure 1 It is the metallographic diagram of the beryllium-tungsten alloy prepared in Example 1.

[0062] Figure 2 It is the metallographic diagram of the beryllium-tungsten alloy prepared in Comparative Example 1.

[0063] Figure 3 It is the metallographic diagram of the beryllium-tungsten alloy prepared in Comparative Example 2.

[0064] Figure 4 It is the metallographic diagram of the beryllium-tungsten alloy prepared in Comparative Example 3.

[0065] Figure 5 It is the metallographic diagram of the beryllium-tungsten alloy prepared in Comparative Example 4.

[0066] Figure 6 It is the metallographic diagram of the beryllium-tungsten alloy prepared in Comparative Example 5.

[0067] By comparing Figure 1 and Figures 2 to 6 , it can be seen that the beryllium-tungsten alloy prepared by the method of the embodiment of the present invention is more dense microscopically, has fewer defects, and smaller grain size, indicating that the mechanical properties of the alloy sample are more excellent.

[0068] Application Example

[0069] The beryllium-tungsten alloys prepared in the above examples and comparative examples were subjected to the following performance tests, and the results are shown in Table 1 below.

[0070] The test methods for tensile strength and yield strength refer to GB / T 228.2-2015; the test temperature is 600 °C.

[0071] The test method for elongation rate refers to GB / T 34505-2017.

[0072] The test method for elastic modulus refers to GB / T 22315-2008.

[0073] The test method for stress relaxation resistance refers to GB / T 39152-2020. After the alloy is stress-relaxed at 240°C for 100 h, the initial stress and the stress after 100 h are tested and calculated according to the following formula: R = (DELTA 0- DELTA t ) / DELTA0 * 100%, where DELTA0 represents the initial stress and DELTA t represents the stress after t hours (100 h).

[0074] Table 1 Performance of Beryllium-Tungsten Alloy

[0075]

[0076] It can be seen from Table 1 that the beryllium-tungsten alloy prepared by the preparation method of the present invention has excellent mechanical properties at high temperatures, excellent stress relaxation resistance and low ductile-brittle transition temperature.

Claims

1. A method for preparing beryllium-tungsten alloy by hot isostatic pressing, characterized in that, It includes the following steps: (S1) 70-80 parts by mass of beryllium rods and 2-4 parts by mass of titanium rods are used to prepare a beryllium-titanium pre-alloy by gas atomization method; (S2) Under an inert atmosphere, the beryllium-titanium pre-alloy, 15-20 parts by mass of tungsten powder, and 3-5 parts by mass of Al-Si alloy powder are subjected to the first high-energy ball milling to obtain powder A; powder A and 0.5-1 part by mass of nano-molybdenum powder, 2-4 parts by mass of nano-nickel powder, and 0.7-1.1 parts by mass of LaB6 nano-particles are subjected to the second high-energy ball milling to obtain powder B; (S3) The powder B is filled into a metal sheath, evacuated and then sealed by welding; (S4) The sealed metal sheath is placed in a hot isostatic pressing equipment, and heat isostatic pressing treatment is carried out at 1100-1250 °C and 120-200 MPa for 4-6 h, then the temperature is raised by 100-150 °C and continued to be kept warm for 3-5 h, cooled to 300-500 °C and kept warm for 1-2 h, and then naturally cooled to room temperature, and the metal sheath is removed to obtain a beryllium-tungsten alloy.

2. The method according to claim 1, characterized in that In step (S1), in the gas atomization method, the beryllium rod and the titanium rod are melted into a liquid state in a high-frequency induction furnace, and high-pressure inert gas is blown to granulate the liquid metal, followed by cooling to obtain a beryllium-titanium pre-alloy; the inert gas is argon and / or nitrogen, and the flow rate of the inert gas is 50 - 100 L·s -1 , the pressure of the inert gas is 4 - 8 MPa, and the working temperature of the high-frequency induction furnace is 1700 - 1900 °C.

3. The method according to claim 2, wherein The diameters of the beryllium rods and titanium rods are 10-20 mm; the obtained beryllium-titanium pre-alloy is spherical with a particle size of 50-200 μm.

4. The method according to claim 1, characterized in that In step (S2), the inert atmosphere is nitrogen and / or argon; the rotation speed of the first high-energy ball milling is 500-600 rpm, and the ball milling time is 10-20 h; the rotation speed of the second high-energy ball milling is 200-300 rpm, and the ball milling time is 10-20 h.

5. The method according to claim 4, wherein During ball milling, the size of the grinding balls is 3-5 mm, the material of the grinding balls is tungsten carbide, and the ball-to-material ratio is 10-20:

1.

6. The method according to claim 1, wherein In step (S2), the particle size of the Al-Si alloy powder is 1-5 μm, and the Si content is 12-16 wt%; the particle size of the LaB6 nano-particles is 100-300 nm, and the sizes of the nano-molybdenum powder and nano-nickel powder are independently 50-200 nm.

7. The method according to claim 1, characterized in that, The purity of all materials ≥99.99%, the single metal impurity ≤5 ppm, and the total metal impurity ≤20 ppm.

8. The method according to claim 1, characterized in that In step (S3), the metal sheath is a stainless steel or tantalum or its alloy sheath, evacuated and then sealed by welding.

9. The method according to claim 1, wherein In step (S4), in the hot isostatic pressing equipment, the heating rate of the metal sheath is 1-20 °C / min; the cooling rate is 1-10 °C / min.

10. The method according to claim 1, characterized in that, In step (S4), during the heat isostatic pressing process, it is kept warm at 1150-1200 °C for 4-6 h, the temperature is raised by 120-150 °C and then continued to be kept warm for 3-4 h, and cooled to 400-500 °C and kept warm for 1-2 h.

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