A high-density tungsten-tantalum-nickel-titanium alloy and its preparation method
By adding nickel-titanium alloy powder to tungsten powder and tantalum powder as the bonding phase, controlling the proportion and adopting vacuum sintering and cold isostatic press forming processes, the problem of the generation of intermetallic compounds in tungsten alloys is solved, and a high-density tungsten-tantalum nickel-titanium alloy is prepared, which improves the strength and toughness of the alloy and broadens the application range.
Patent Information
- Application Number
- CN202311126530.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-04
- Publication Date
- 2025-08-01
- Estimated Expiration
- 2043-09-04
AI Technical Summary
After the existing tungsten alloy system is added with tantalum, the matrix phase will form a large number of intermetallic compounds with tantalum, which will reduce the solid solubility of tantalum and the hard and brittle phase will greatly reduce the alloy performance.
By adding an appropriate amount of nickel-titanium alloy powder to the tungsten powder and tantalum powder as the bonding phase, the proportion of tungsten, tantalum, and nickel-titanium alloy powder is controlled, and vacuum sintering and cold isostatic pressing molding are adopted to avoid the formation of intermetallic compounds and achieve the ideal strengthening of tantalum elements on tungsten alloys.
High density tungsten tantalum nitinol alloys were prepared at lower sintering temperatures, which avoided the formation of intermetallic compounds, improved the strength and toughness of the alloys, and broadened the application range.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the field of tungsten alloy preparation, and particularly relates to a high-density tungsten tantalum nickel titanium alloy, a preparation method thereof, and an application thereof. Background Art
[0002] Tungsten heavy alloy is a two-phase material, which combines a body-centered cubic (BCC) tungsten phase with a binder phase and contains transition metals. This alloy provides an excellent combination of high density, strength, stiffness, and good corrosion resistance, and is therefore widely used in industrial and military applications such as radiation shielding, counterweights, and kinetic energy penetrators. With the development of technology, these demands have put forward higher requirements for both the strength and toughness of tungsten alloys.
[0003] There are several ways to improve the properties of tungsten alloys, including solid solution strengthening, dispersion strengthening, and second-phase strengthening. The addition of some elements can effectively improve the properties of tungsten alloys. Tantalum, like tungsten, belongs to the body-centered cubic (BCC) structure and can be infinitely solid-solved with tungsten. The ordered phase formed in the tungsten tantalum solid solution can change the symmetric nuclear structure of tungsten, increase the mobility of dislocations, and improve the properties of tungsten particles. At the same time, the addition of tantalum can reduce the solubility of tungsten in the binder phase, playing a role in fine grain strengthening. Moreover, tantalum has the characteristics of high melting point, high density, and high ductility, and is widely used to reduce the ductile-brittle transition temperature of martensitic steel, making it an ideal strengthening element for tungsten.
[0004] In the current tungsten alloy systems (W-Ni-Fe, W-Ni-Cu), after adding tantalum element, a large number of intermetallic compounds are formed between the matrix phase and the tantalum element. These intermetallic compounds not only consume the tantalum element, reducing the solid solubility of the tantalum element in tungsten particles, but also most of the intermetallic compounds are hard and brittle phases, greatly reducing the alloy properties. Summary of the Invention
[0005] Aiming at the problems in the prior art that the tantalum element cannot achieve an ideal strengthening behavior for tungsten alloys and the matrix phase will form a large number of intermetallic compounds with the tantalum element. The first object of the present invention is to provide a high-density tungsten tantalum nickel titanium alloy, which greatly reduces the sintering temperature of the tungsten tantalum alloy and avoids the formation of intermetallic compounds by adding an appropriate amount of nickel titanium alloy powder as the binder phase to tungsten powder and tantalum powder. At the same time, by balancing the amounts of tungsten and tantalum elements, the alloy can achieve an ideal strengthening behavior of the tantalum element for tungsten alloys.
[0006] The second object of the present invention is to provide a preparation method of a high-density tungsten tantalum nickel titanium alloy, which can prepare the tungsten tantalum nickel titanium alloy at a lower sintering temperature, has the advantages of simple process flow, short production cycle, etc., and is suitable for industrial production.
[0007] The third object of the present invention is to provide an application of a high-density tungsten-tantalum-nickel-titanium alloy. Using it as a raw material in radiation shielding, counterweights, and the gyro outer rotor body of a large-caliber kinetic penetrator can greatly extend its service life.
[0008] To achieve the above technical object, the present invention provides a preparation method of a high-density tungsten-tantalum-nickel-titanium alloy. The method is to mix tungsten powder, tantalum powder, and nickel-titanium alloy powder to obtain a mixed powder, compact the mixed powder to obtain a green compact, and sinter it in a vacuum environment to obtain the product.
[0009] As a preferred solution, the mass ratio of the tungsten powder, tantalum powder, and nickel-titanium alloy powder is (108 - 162):(18 - 72):(15 - 25).
[0010] The key to the preparation method of the present invention is that tungsten and tantalum added belong to the body-centered cubic structure and can achieve infinite solid solution. At the same time, the ordered phase formed in the tungsten-tantalum solid solution can change the symmetric nuclear structure of tungsten, increase the mobility of dislocations, and improve the plasticity of tungsten particles. At the same time, the addition of tantalum can reduce the solubility of tungsten in the matrix phase, hinder the dissolution and precipitation process of tungsten particles, refine the tungsten particles, and play a role in fine-grain strengthening. And the inventor found that the dosages of tungsten powder, tantalum powder, and nickel-titanium alloy powder need to be strictly controlled within the scope of the present invention to achieve the solution strengthening of tantalum on tungsten; adding too much tantalum powder has no positive effect on the overall strength. During the sintering process, the oxidation of tantalum will generate tantalum pentoxide particles, causing brittle fracture of the alloy. And by adding an appropriate amount of nickel-titanium alloy powder in the alloy, it can be used as a binder phase to greatly reduce the sintering temperature of the tungsten-tantalum alloy, reducing the process difficulty and energy consumption. The dosage of the nickel-titanium alloy powder has a direct impact on the microstructure of the prepared finished alloy. If the dosage of the nickel-titanium alloy powder is too high, it will lead to too much liquid phase, causing the collapse of the finished alloy; while too little dosage will make the dissolution and precipitation process of tungsten particles in the sintering process insufficient, and the tungsten particles will agglomerate, reducing the toughness of the alloy. In addition, due to the very low binding energy between nickel and titanium, they will not form intermetallic compounds with tantalum, and both have good solubility in tungsten and can form a dense and high-content tungsten alloy with tungsten. Therefore, after fully mixing the tungsten powder, tantalum powder, and nickel-titanium alloy powder in the present invention, and then further compacting them into a dense green compact and combining with the sintering process, it can greatly reduce the sintering temperature of the tungsten-tantalum alloy while achieving the ideal strengthening behavior of tantalum on the tungsten alloy.
[0011] Further preferably, the mass ratio of the tungsten powder, tantalum powder, and nickel-titanium alloy powder is (108 - 126):(54 - 72):(15 - 20).
[0012] The inventor found that performing the preliminary weighing work in a vacuum glove box can effectively reduce the oxidation of titanium during the mixing process and improve the tissue uniformity of the alloy.
[0013] As a preferred solution, in the nickel-titanium alloy powder, the mass ratio of nickel to titanium is (45-55):(45-55). In the nickel-titanium alloy powder of the present invention, the ratio of nickel to titanium has a direct influence on the properties and sintering temperature of the alloy. By adjusting the ratio of nickel to titanium within the scope of the present invention, the alloy of the present invention can be sintered densely at a temperature higher than 1300 °C. Moreover, the inventor found that only by using nickel-titanium alloy powder in the technical solution of the present invention can the occurrence of component segregation be effectively avoided. If elemental powders of nickel and titanium are used to make the alloy, Ni3Ti with a hexagonal structure will be generated, and this hexagonal structure cannot produce a good interfacial match with the body-centered cubic structure of tungsten grains, thereby leading to a decrease in alloy properties. Further preferably, the mass ratio of nickel to titanium is (50-55):(45-50).
[0014] As a preferred solution, the tungsten powder is spherical powder with an average particle size of 3-5 μm and a purity of ≥99.8%; the tantalum powder is spherical powder with an average particle size of 10-35 μm and a purity of ≥99.5%; the nickel-titanium alloy powder is spherical powder with an average particle size of 15-53 μm and a purity of ≥99.9%. All raw materials used in the present invention are spherical powders because spherical powders have the highest specific surface area under the same mass and can provide the highest sintering activity. At the same time, using fine spherical powders can reduce the sintering temperature and increase the diffusion between elements.
[0015] As a preferred solution, the mixing is carried out in a three-dimensional mixer for 8-10 h. By mixing in a three-dimensional mixer, tungsten-tantalum-nickel-titanium powder with uniform mixing can be obtained.
[0016] As a preferred solution, the method of pressing and forming is cold isostatic pressing. In the present invention, a reliable dense green compact is obtained by using cold isostatic pressing.
[0017] As a preferred solution, the process of cold isostatic pressing is as follows: gradually increase the cold isostatic pressure to 250-350 MPa at a rate of 25-30 MPa / min, maintain the pressure for 8-10 min, and then reduce the pressure to 0 MPa at a rate of 5-10 MPa / min. In the technical solution of the present invention, if the pressure value of cold isostatic pressing is too low, the powder cannot be formed, and if the pressure value is too high, cracks will be generated inside.
[0018] As a preferred solution, the vacuum degree during sintering is ≤10 -3 Pa; since titanium is easily oxidized, it is necessary to strictly control the vacuum degree during the sintering process of tungsten-tantalum-nickel-titanium alloy to avoid oxidation during the sintering process.
[0019] As a preferred solution, the sintering process is as follows: heating at a heating rate of 8 - 15 °C / min to 800 - 850 °C, holding for 20 - 40 min, then heating at a heating rate of 5 - 10 °C / min to 1300 - 1400 °C, holding for 120 - 150 min; then cooling at a cooling rate of 5 - 10 °C / min to 1000 - 1100 °C and holding for 180 - 300 min; finally cooling at a cooling rate of 10 - 15 °C / min to room temperature. The technical solution of the present invention promotes the formation of sintering necks between tungsten particles and forms a connecting bone between tungsten particles by first heating the alloy powder to 800 - 850 °C. On the other hand, it can stabilize the temperature in the furnace, and the holding time at the sintering temperature in the first stage is short, which can ensure that the tungsten particles do not grow excessively. By further increasing the sintering temperature to 1300 - 1400 °C, a large amount of nickel-titanium alloy liquid phase can be formed to reduce the sintering temperature while realizing the solid solution of tungsten and tantalum. Then holding at 1000 - 1100 °C can effectively stabilize the alloy structure. If the heating and cooling rates are not within the scope of the present invention, liquid phase splashing will occur, resulting in a large loss of the bonding phase.
[0020] The present invention also provides a high-density tungsten tantalum nickel titanium alloy obtained by the above preparation method.
[0021] As a preferred solution, the tungsten tantalum nickel titanium alloy is composed of a tungsten tantalum solid solution alloy matrix and a NiTi bonding phase, without the formation of intermetallic compounds, and the particle size of the alloy matrix is ≤ 20 μm.
[0022] The present invention also provides an application of the high-density tungsten tantalum nickel titanium alloy. Using it as a raw material in radiation shielding, counterweight, and the gyro outer rim rotor body of a large-caliber kinetic penetrator can not only greatly improve its service life but also significantly broaden the application range of tantalum alloys.
[0023] Compared with the prior art, the present invention has the following beneficial effects:
[0024] 1) In the alloy system of the present invention, using tantalum powder improves the strength of tungsten particles; and by using Ni-Ti instead of the traditional bonding phase, not only the performance of the bonding phase is improved, but also the formation of metal intermediate phases is avoided, enabling the tungsten tantalum nickel titanium alloy composition to achieve the ideal strengthening behavior of tantalum element on tungsten alloy at a relatively low sintering temperature.
[0025] 2) In the preparation method of the present invention, using nickel titanium alloy powder instead of traditional nickel, iron, copper and other elemental powders, adding the solid solution element tantalum using a three-dimensional mixer, and cold isostatic pressure molding; the designed alloy system successfully realizes the solid solution strengthening of tantalum element on tungsten alloy. The tantalum element does not react with the matrix and is consumed, nor is a brittle and hard intermetallic compound formed.
[0026] 3) In the preparation method of the present invention, by improving the sintering process and using a two-step sintering method combined with the design of the composition, a tungsten-tantalum-nickel-titanium alloy with high density (density ≥ 97.6%) and an average particle size of 2 - 20 μm is obtained without sacrificing tantalum elements. Through the fine-grain strengthening of the tungsten alloy by tantalum elements, the obtained finished product has a small and narrow particle size range, and within a further optimized range, it can reach 2 - 12 μm.
[0027] 4) The high-density tungsten-tantalum-nickel-titanium alloy provided by the present invention can be used in radiation shielding, counterweights, and gyro outer rotor bodies of large-caliber kinetic penetrators, warships, tanks, etc., greatly broadening the application of tantalum alloys. Description of the Drawings
[0028] Figure 1 It is the original morphology diagrams of the tungsten element powder and tantalum element powder used in Example 1, where Figure 1 (a) is the morphology diagram of tantalum powder, Figure 1 (b) is the morphology diagram of tungsten powder; it can be seen from the figures that both the tantalum powder and tungsten powder used in the present invention are spherical powders.
[0029] Figure 2 It is the morphology of the tungsten-tantalum-nickel-titanium alloy obtained by using Example 1, Example 2, Example 3, and Example 4 at different magnification ratios; where Figure 2 (a) is the morphology of the tungsten-tantalum-nickel-titanium alloy prepared in Example 1, Figure 2 (b) is the morphology of the tungsten-tantalum-nickel-titanium alloy prepared in Example 2, Figure 2 (c) is the morphology of the tungsten-tantalum-nickel-titanium alloy prepared in Example 3, Figure 2 (d) is the morphology of the tungsten-tantalum-nickel-titanium alloy prepared in Example 4. It can be seen from the figures that the overall morphology of the alloy is uniform, no intermediate phase is observed, and at the same time, it can be seen from the particle size distribution diagram in the figures that as the content of tantalum elements increases, the grains gradually become smaller, showing an obvious effect of fine-grain strengthening.
[0030] Figure 3 It is the atomic probe result analysis of the tungsten-tantalum-nickel-titanium alloy obtained in Example 1. It can be seen from the spectrum that all tantalum elements are dissolved in tungsten particles, producing solid solution strengthening of tungsten particles, and no metal intermetallic compounds are formed and consumed with nickel or titanium.
[0031] Figure 4 It is the scanning and transmission electron microscope analysis of the tungsten-tantalum-nickel-titanium alloy obtained in Example 1. It can be seen from the results of the transmission electron microscope that the bonding phase is the martensite phase of the NiTi alloy.
[0032] Figure 5 It is the alloy morphology of Comparative Example 1. It can be observed from the figure that the tungsten particles do not become regular spheres, indicating that the liquid-phase sintering did not proceed smoothly.
[0033] Figure 6 The alloy morphology diagram and particle size distribution diagram of Comparative Example 2 Figure 6 (a) and Figure 6 (b) are the alloy morphology diagrams of Comparative Example 2 at different magnifications Figure 6 (c) is the particle size distribution diagram of the alloy of Comparative Example 2
[0034] Figure 7 The alloy morphology diagram of Comparative Example 3 Specific implementation mode
[0035] For a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solutions of the present invention will be described in detail below, but it should not be construed as a limitation on the implementable scope of the present invention
[0036] Example 1
[0037] A preparation method of a high-density tungsten-tantalum-nickel-titanium alloy, comprising the following steps:
[0038] Step 1: Obtain mixed powder using a three-dimensional mixer
[0039] In a vacuum glove box, take 108 g of tungsten powder with an average particle size of 3-5 microns and a purity greater than 99.8%; take 72 g of tantalum powder with an average particle size of 30 microns and a purity greater than 99.5%; take 20 g of nickel-titanium alloy powder with a nickel-titanium mass ratio of 55:45 and an average particle size of 20-30 microns and a purity greater than 99.9%. Put the above powders into a tungsten carbide mixing tank together. Take out the mixing tank from the vacuum glove box and put it into a three-dimensional mixer for 10 hours of mixing
[0040] Step 2: Obtain a green body using cold isostatic pressing
[0041] Put the mixed powder into a cold isostatic pressing sleeve. The sleeve is 100 mm high, 50 mm in diameter, and 2.5 mm thick in wall. The upper and lower rubber plugs are 50 mm in diameter and 45 mm in height. Put the sleeve into a cold isostatic pressing furnace, and gradually increase the cold isostatic pressing pressure to 250 MPa at a rate of 25 MPa / min, keep the pressure for 10 min, and then reduce the pressure to 0 Mpa at a rate of 5 MPa / min. Take out the sleeve to obtain a pressed green body
[0042] Step 3: Sintering of tungsten-tantalum-nickel-titanium alloy
[0043] The sintering process uses an AL-2000-MG high-vacuum heat treatment furnace of Sichuan Liye Technology Co., Ltd. During the sintering process, the vacuum degree in the furnace is maintained at 10 -3Below Pa; heat at a heating rate of 8 °C / min to 800 °C, hold for 20 min, then heat at a heating rate of 5 °C / min to 1300 °C, hold for 150 min; then cool at a cooling rate of 10 °C / min to 1000 °C and hold for 300 min; finally cool at a cooling rate of 10 °C / min to room temperature to obtain a tungsten-tantalum-nickel-titanium alloy.
[0044] The density of the tungsten-tantalum-nickel-titanium alloy prepared in this example is 97.6, and its particle size distribution diagram is as Figure 2 (a) shown, with the particle size distribution in the range of 2 - 12 μm.
[0045] Example 2
[0046] A method for preparing a high-density tungsten-tantalum-nickel-titanium alloy, comprising the following steps:
[0047] Step 1: Obtain mixed powder using a three-dimensional mixer
[0048] In a vacuum glove box, take 126 g of tungsten powder with an average particle size of 3 - 5 μm and a purity greater than 99.8%; take 54 g of tantalum powder with an average particle size of 30 μm and a purity greater than 99.5%; take 20 g of nickel-titanium alloy powder with a nickel-titanium mass ratio of 55:45 and an average particle size of 20 - 30 μm and a purity greater than 99.9%. Put the above powders together into a tungsten carbide mixing tank. Take out the mixing tank from the vacuum glove box and put it into a three-dimensional mixer for 10 hours of mixing.
[0049] Step 2: Obtain a green body using cold isostatic pressing, same as in Example 1;
[0050] Step 3: Sinter the tungsten-tantalum-nickel-titanium alloy, same as in Example 1.
[0051] The density of the tungsten-tantalum-nickel-titanium alloy prepared in this example is 97.9, and its particle size distribution diagram is as Figure 2 (b) shown, with the particle size distribution in the range of 4 - 19 μm. Compared with Example 1, it shows that when increasing the mass ratio of tungsten powder to tantalum powder (i.e., reducing the tantalum content in the alloy), the grain size of the finished product will become larger.
[0052] Example 3
[0053] A method for preparing a high-density tungsten-tantalum-nickel-titanium alloy, comprising the following steps:
[0054] Step 1: Obtain mixed powder using a three-dimensional mixer
[0055] In a vacuum glove box, 144 g of tungsten powder with an average particle size of 3 - 5 μm and a purity greater than 99.8% was taken; 36 g of tantalum powder with an average particle size of 30 μm and a purity greater than 99.5% was taken; 20 g of nickel-titanium alloy powder with a nickel-titanium mass ratio of 50:50 and an average particle size of 20 - 30 μm and a purity greater than 99.9% was taken. The above powders were put into a tungsten carbide mixing tank together. The mixing tank was taken out of the vacuum glove box and put into a three-dimensional mixer for 10 hours of mixing.
[0056] Step 2: Obtain a green body using cold isostatic pressing
[0057] The mixed powder was put into a jacket for cold isostatic pressing. The jacket was 100 mm high, 50 mm in diameter, with a wall thickness of 2.5 mm, and the upper and lower rubber plugs were 50 mm in diameter and 45 mm in height. The jacket was put into a cold isostatic pressing furnace, and the cold isostatic pressing pressure was gradually increased to 300 MPa at a rate of 25 MPa / min, and the pressure was maintained for 10 min. Then the pressure was decreased to 0 MPa at a rate of 5 MPa / min. The jacket was taken out to obtain a pressed green body.
[0058] Step 3: Sintering of tungsten-tantalum-nickel-titanium alloy
[0059] During the sintering process, an AL-2000-MG high-vacuum heat treatment furnace from Sichuan Liye Technology Co., Ltd. was used. During the sintering process, the vacuum degree in the furnace was maintained below 10 -3 Pa; it was heated to 850 °C at a heating rate of 8 °C / min and held for 20 min, then heated to 1350 °C at a heating rate of 5 °C / min and held for 120 min; then cooled to 1000 °C at a cooling rate of 10 °C / min and held for 200 min; finally cooled to room temperature at a cooling rate of 10 °C / min to obtain tungsten-tantalum-nickel-titanium alloy.
[0060] The relative density of the tungsten-tantalum-nickel-titanium alloy prepared in this example was 97.6, and its particle size distribution diagram was as shown in Figure 2 (c), with the particle size distribution in the range of 3 - 16 μm. Compared with Example 2, in this example, the tantalum content in the alloy was further reduced, but at the same time, the titanium content in the nickel-titanium alloy powder, the cold isostatic pressing pressure, and the sintering temperature were increased. However, the grain size of its alloy was smaller than that of Example 2, indicating that the present invention utilized the synergistic effect of composition design and process to achieve the ideal strengthening behavior of tantalum element on tungsten alloy.
[0061] Example 4
[0062] A method for preparing a high relative density tungsten-tantalum-nickel-titanium alloy, comprising the following steps:
[0063] Step 1: Obtain mixed powder using a three-dimensional mixer
[0064] In a vacuum glove box, 162 g of tungsten powder with an average particle size of 3 - 5 μm and a purity greater than 99.8% was taken; 18 g of tantalum powder with an average particle size of 30 μm and a purity greater than 99.5% was taken; 20 g of nickel-titanium alloy powder with a nickel-titanium mass ratio of 55:45 and an average particle size of 20 - 30 μm and a purity greater than 99.9% were taken. The above powders were put into a tungsten carbide mixing tank together. The mixing tank was taken out of the vacuum glove box and put into a three-dimensional mixer for 10 hours of mixing.
[0065] Step 2: The same as Example 1 for obtaining the green body by cold isostatic pressing.
[0066] Step 3: The sintering of the tungsten-tantalum-nickel-titanium alloy was the same as that in Example 1.
[0067] The density of the tungsten-tantalum-nickel-titanium alloy prepared in this example was 97.8, and its particle size distribution diagram was as shown in Figure 2 (d), with the particle size distribution in the range of 4 - 20 μm. Compared with Example 2, it shows that when further increasing the mass ratio of tungsten powder to tantalum powder (i.e., reducing the tantalum content in the alloy), the grain size of the finished product will become larger.
[0068] Comparative Example 1
[0069] All other conditions of this comparative example were the same as those in Example 1, except that nickel element powder was used instead of nickel-titanium alloy powder: 20 g of nickel element powder with an average particle size of 20 μm and a purity greater than 99.8%.
[0070] The microscopic morphology of the material prepared in this comparative example was as shown in Figure 5 , and since the melting point of nickel element is relatively high, a liquid phase cannot be formed under the same sintering conditions, and the tungsten alloy cannot dissolve and precipitate, resulting in the failure of liquid phase sintering.
[0071] Comparative Example 2
[0072] The difference between this comparative example and Example 1 was only that the second heating rate during sintering was replaced with 15 °C / min, and the other conditions were the same.
[0073] The microscopic morphology of the material prepared in this comparative example was as shown in Figure 6 (a) and Figure 6 (b), its density was 97.2, as shown in Figure 6 (c), the grains became larger, and the particle size range was 4 - 16 μm. During the process, the inventor found that it would cause the generated liquid phase to splash, resulting in the loss of the bonding phase, and it was impossible to effectively reduce the sintering temperature of the tungsten-tantalum solid solution, and then it was impossible for tungsten particles to precipitate. At the same time, due to excessive residual thermal stress, the grains would crack.
[0074] Comparative Example 3
[0075] In this comparative example, 152 g of tungsten powder, 38 g of tantalum powder, and 10 g of nickel-titanium alloy powder were taken, and the remaining conditions were the same as those in Example 1.
[0076] The microtopography of the material prepared in this comparative example is as Figure 7 shown, and its relative density is 97.8. Compared with Example 1, when the amount of nickel-titanium alloy powder was reduced, during the process, the inventors found that due to too little liquid phase during the sintering process, the precipitation of tungsten particles was imperfect, and at the same time, tungsten particles would agglomerate, and the brittle connection between tungsten and tungsten would further reduce the alloy performance.
Claims
1. A preparation method of a high-density tungsten-tantalum-nickel-titanium alloy, characterized in that: Mix tungsten powder, tantalum powder and nickel-titanium alloy powder to obtain a mixed powder, press the mixed powder into a compact, and sinter it in a vacuum environment to obtain the product. The mass ratio of the tungsten powder, tantalum powder and nickel-titanium alloy powder is (108~162):(18~72):(15~25). In the nickel-titanium alloy powder, the mass ratio of nickel to titanium is (45~55):(45~55). The tungsten powder is spherical powder with an average particle size of 3~5 µm and a purity of ≥99.8%. The tantalum powder is spherical powder with an average particle size of 10~35 µm and a purity of ≥99.5%. The nickel-titanium alloy powder is spherical powder with an average particle size of 15~53 µm and a purity of ≥99.9%. The vacuum degree during sintering ≤ 10 -3 Pa; The sintering process is as follows: heat up at a heating rate of 8~15 °C / min to 800~850 °C, hold for 20~40 min, then heat up at a heating rate of 5~10 °C / min to 1300~1400 °C, hold for 120~150 min; then cool down at a cooling rate of 5~10 °C / min to 1000~1100 °C and hold for 180~300 min; finally cool down at a cooling rate of 10~15 °C / min to room temperature.
2. The preparation method of a high-density tungsten-tantalum-nickel-titanium alloy according to claim 1, wherein: The mixing is carried out in a three-dimensional mixer for 8~10 h. The method of pressing into a compact is cold isostatic pressing.
3. The preparation method of a high-density tungsten-tantalum-nickel-titanium alloy according to claim 1, wherein: The process of cold isostatic pressing is as follows: gradually increase the cold isostatic pressure to 250~350 MPa at a rate of 25~30 MPa / min, keep the pressure for 8~10 min, and then decrease the pressure to 0 MPa at a rate of 5~10 MPa / min.
4. A high-density tungsten-tantalum-nickel-titanium alloy, characterized in that: Obtained by the preparation method according to any one of claims 1~3.
5. A high-density tungsten tantalum nickel titanium alloy according to claim 4, characterized in that: The tungsten-tantalum-nickel-titanium alloy is composed of a tungsten-tantalum solid solution alloy matrix and a NiTi bonding phase, and no intermetallic compound is formed.
6. Use of the high-density tungsten-tantalum-nickel-titanium alloy according to claim 4 or 5, characterized in that: It is used as a raw material in radiation shielding, counterweight, and the gyro outer rim rotor body of a large-caliber kinetic penetrator.