A high-thermal-conductivity tungsten material toughened by coupling of soft Cu phase and Y2O3 hard particles and a preparation method thereof

Abstract

The application provides a high-thermal-conductivity tungsten material toughened and strengthened by coupling of soft Cu phase and Y2O3 hard particles and a preparation method, and belongs to the technical field of powder metallurgy engineering. First, a CuY precursor alloy is prepared by arc melting technology, and the alloy is atomized and powdered, and then is mixed with industrial pure tungsten powder as raw materials, and is dosed based on the nominal composition of the target tungsten alloy sintered body; then, the mixture is subjected to high-energy ball milling to obtain a mixed and uniform composite powder; finally, the composite powder is subjected to hot-pressing sintering to obtain a bulk tungsten-based composite material in which a soft Cu phase is precipitated at the grain boundary and Y2O3 hard particles are uniformly and dispersedly distributed. The application can obtain a tungsten-based composite material toughened and strengthened by coupling of a soft Cu phase and Y2O3 dispersed hard particles, and the introduction of the soft Cu phase can significantly improve the low-temperature plastic deformation ability of the high product and improve the thermal conductivity, thereby providing a new idea for developing high-strength and high-thermal-conductivity tungsten materials with high thermal conductivity and excellent mechanical properties.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of powder metallurgy, and relates to a high-thermal-conductivity tungsten material toughened and strengthened by coupling of soft Cu phases and Y2O3 hard particles and a preparation method. BACKGROUND

[0002] The tungsten-based material with high melting point can still maintain high strength at 1500 DEG C, and simultaneously has characteristics such as good thermal conductivity, a high sputtering threshold and low tritium retention, and has wide application in fields such as aerospace, national defense and nuclear fusion devices.

[0003] The ductile-to-brittle transition temperature of pure tungsten is about 200-400℃, which is a brittle material at room temperature. The recrystallization temperature of pure tungsten in the processing state is about 1200-1300℃, and in a high heat load service environment, the surface temperature can reach 2000℃, causing recrystallization and deterioration of strength and plasticity. Tungsten-based composites, including WK alloys, carbide, and oxide dispersion strengthened tungsten, can significantly increase the recrystallization temperature, but cannot improve the room temperature plasticity of the material. Y2O3 has good thermal and chemical stability and is an important strengthening phase for dispersion-strengthened tungsten materials. Through hydrogen sintering and high-energy rate forging processes, Southwest Institute of Physics Lianyouyun et al. obtained W-Y2O3 alloy with a density of 99.3%, and its room temperature tensile strength was only 480 MPa; they further obtained W-Y2O3 rod with a diameter of 12 mm through four passes of rotary forging process, and the room temperature tensile strength can be increased to 1.25 GPa (Tang Y, Lianyouyun, Feng F, et al. Effect of deuterium plasma pre-irradiation on thermal shock resistance of W-Y2O3 alloy [J]. Nuclear Fusion and Plasma Physics, 2019, 39(2): 151-157.). Tianjin University Ma Zongqing et al. obtained bulk W-Y2O3 alloy with a thickness of 2.3 mm through wet chemical method combined with hydrogen sintering and hot rolling, and the tensile strength of the material at 150℃ can reach 1.17 GPa (Li L, Dong Z, Ma Z, et al. Ultrahigh strength and toughness in W-Y2O3 alloy with bimodal and lamellar structures [J]. Materials Research Letters, 2023, 11(6): 439-445.). Existing experiments show that Y2O3 hard particles can effectively improve the strength and hardness of tungsten materials, but are not conducive to the improvement of room temperature and low temperature plasticity of the material. During tensile process, stress concentration is easily generated at the junction of Y2O3 hard particles and tungsten matrix, inducing cracks and causing brittle intergranular fracture. It is particularly important to note that the presence of Y2O3 oxide particles with poor thermal conductivity will seriously affect the thermal conductivity of the material (Lv Y, Fan Y, Zhao S, et al. The microstructure evolution, damage behavior and failure analysis of fine-grained W-Y2O3 composites under high transient thermal shock [J]. International Journal of Refractory Metals and Hard Materials, 2022, 107: 105905-1-12.).

[0004] Tungsten heavy alloys are multiphase composites with tungsten as the matrix (mass fraction of tungsten is usually ≥80wt.%) and metals with lower melting point than tungsten (such as Ni-Fe, Ni-Co, Ni-Cu, etc.) as the second phase distributed at the grain boundaries. This kind of composite structure can effectively improve the plastic deformation ability of tungsten materials at room temperature or low temperature (corresponding to room temperature to the ductile-brittle transition temperature of pure tungsten) while maintaining the special properties of the tungsten matrix. This kind of material is generally prepared by liquid phase sintering. Due to the dissolution-precipitation of tungsten particles during sintering, the matrix particle size is coarsened (20-60μm), resulting in deterioration of material strength (German R.M., Sintered tungsten heavy alloys: Review of microstructure, strength, densification, and distortion[J], International Journal of Refractory Metals and Hard Materials, 2022, 108: 105940-1-12.).

[0005] The present application successfully introduces a soft Cu phase with high electrical conductivity and thermal conductivity into the W-Y2O3 oxide dispersion strengthened tungsten material by using a special Cu-Y alloy as a precursor, realizes the complementary performance advantages of W-Y2O3 and tungsten heavy alloy materials, and obtains a W-Y2O3 material with high thermal conductivity that is toughened and strengthened by the synergistic effect of a soft Cu phase at the grain boundary and hard Y2O3 particles. The low-temperature plastic deformation ability and thermal conductivity of the existing W-Y2O3 material can be significantly improved. The composite powder of tungsten and Cu-Y alloy is prepared by high-energy ball milling, and Y2O3 particles are formed in-situ at the grain boundaries and inside the grains by absorbing free oxygen in the tungsten powder during the subsequent sintering process, realizing uniform dispersion of the oxide. The Cu element is segregated and precipitated at the grain boundaries by diffusion. Compared with single oxide dispersion strengthened tungsten alloy, the coupling strengthening of the grain boundary pure Cu and Y2O3 dispersed particles brings the following performance breakthroughs: on the basis of ensuring the refinement of the structure, the improvement of the material density and the strength, the existence of the grain boundary Cu soft phase improves the overall thermal conductivity of the material, and inhibits the intergranular cracking, improving the low-temperature plasticity of the material. It is a new type of tungsten-based material with high thermal conductivity and good matching of strength and plasticity. SUMMARY

[0006] In order to overcome the problems of room temperature brittleness and insufficient thermal conductivity in the existing oxide dispersion strengthened tungsten material, the application provides a kind of high thermal conductivity tungsten material with soft Cu phase improving thermal conductivity and low temperature plasticity and hard Y2O3 particles dispersedly distributed for synergistic strengthening, and a preparation method thereof, which can solve the problems of the current W-Y2O3 type dispersion strengthened tungsten material, including (1) large thermal conductivity reduction (generally more than 20% lower than pure tungsten at room temperature, see the above-mentioned literature); (2) grain boundary brittleness caused by impurity elements such as oxygen in the matrix tungsten; (3) intergranular cracking easily occurring at the junction of W / Y2O3 hard particles; and (4) low sintered material density caused by initial compaction density.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is:

[0008] A preparation method of a high thermal conductivity tungsten material with soft Cu phase and Y2O3 hard particle coupling strengthening, the preparation method first prepares a CuY precursor alloy by arc melting technology, atomizes and grinds it to powder, and then uses it as raw material together with industrial pure tungsten powder; then, it is placed in anhydrous ethanol medium environment for high-energy ball milling to obtain a mixed and uniform composite powder; finally, the composite powder is used for hot-pressing sintering to obtain a bulk tungsten-based composite material with soft Cu phase precipitated at the grain boundary and Y2O3 hard particles uniformly and dispersedly distributed. Specifically, it includes the following steps:

[0009] First, preparing Cu x Y 100-x alloy powder;

[0010] Step 1.1, using industrial pure Cu and Y metal as raw materials, preparing a precursor alloy with atomic percentage composition of Cu x Y 100-x (x=80~60, atomic percentage), melting the alloy ingot with uniform composition by using a general non-consumable vacuum arc melting furnace, and the mass loss rate of the precursor alloy before and after melting is not more than 5 parts per thousand.

[0011] Step 1.2, crushing the alloy ingot and putting it into a gas atomization powdering device for atomization and powdering: heating it by medium frequency induction to completely melt it, and spraying and cooling it by using atomization technology to obtain spherical particle powder with a particle size of 3~40 μm, which is sieved and used, i.e. Cu x Y 100-x alloy powder is obtained. In the atomization and powdering process, the atomization gas is industrial pure argon, the spraying pressure is 3~10 MPa, and the nozzle aperture of the flow guide rod of the gas atomization powdering device is 1~2 mm.

[0012] Second, preparing W+Cu x Y 100-x composite powder;

[0013] Step 2.1, commercially available industrial pure tungsten powder (median particle size 4.2 μm) was chosen as the base material, and the Cu x Y 100-x alloy powder as the additive, the mixture was prepared by weighing and mixing, and the composition of the mixture was W + (0.8-1.5 wt.%) Cu x Y 100-x , and the nominal composition of the corresponding target alloy was W-(0.42-1.11 wt.%) Cu-(0.21-0.72 wt.%) Y. In the target material, Cu is the source of pure Cu soft phase, and Y provides components for in-situ formation of Y2O3 hard particles.

[0014] Step 2.2, the mixture in step 2.1 was loaded into a ball mill tank with grinding balls (ball-to-material ratio 5:1-10:1), and high-energy ball milling was carried out in anhydrous ethanol medium. The rotation speed of the ball mill was 400-500 rpm, and the ball milling time was 20-30 h. After ball milling, the powder was taken out and vacuum dried to obtain a composite powder with a median particle size of 0.5-2.0 μm.

[0015] Step 3.1, the composite powder obtained in the second step was placed into a vacuum hot-pressing sintering furnace for hot-pressing sintering to prepare a W-(0.42-1.11 wt.%) Cu-(0.21-0.72 wt.%) Y bulk material, i.e. a high thermal conductivity tungsten material. In the hot-pressing sintering process of step 3.1, the preloading pressure of the billet was 30 MPa, the vacuum degree during sintering was 3×10 -2 Pa, and the hot-pressing sintering process mainly experienced two stages: the sintering temperature of the first stage was 1400-1500℃, and the holding time was 60 min; the sintering temperature of the second stage was 1700-1800℃, and the holding time was 2-4 h, and the pressure of both stages was 60 MPa.

[0016] After the hot-pressing sintering process is completed, the sintered body is cooled to room temperature with the furnace, and then taken out to observe the density, phase composition, microstructure, and performance. It is found that the present application obtains a high-density, high-thermal-conductivity tungsten material which is toughened and strengthened by the synergistic effect of the grain boundary Cu soft phase and Y2O3 dispersed hard particles. The density of the material is more than 99.0%; the thermal conductivity of the material at room temperature is greater than 150 W / m·K (the thermal conductivity of pure tungsten is about 172 W / m·K, and the thermal conductivity of the existing W-Y2O3 at room temperature is generally 20% lower than that of pure tungsten, as shown in the above-mentioned literature), and the thermal conductivity value is closer to that of pure tungsten as the temperature increases, and is basically the same as that of pure tungsten at 500℃ or above; the tensile strength of the tungsten-based composite material at room temperature is greater than 1000 MPa, and the tensile strength and elongation at 200℃ are more than 850 MPa and 7.0% respectively, which are significantly better than those of pure tungsten under the same conditions (pure tungsten has no tensile plasticity at a temperature lower than 300℃, and the tensile strength at room temperature and at 200℃ is 511 MPa and 673 MPa respectively).

[0017] A high-thermal-conductivity tungsten material which is toughened and strengthened by the synergistic effect of a soft Cu phase and Y2O3 hard particles, wherein the high-thermal-conductivity tungsten material is based on W+Cu x Y 100-x The composite powder is obtained by ordinary hot-pressing sintering, and the W+Cu x Y 100-x The composite powder is obtained by ordinary hot-pressing sintering, and the W+Cu x Y 100-x The precursor alloy powder is mixed according to a specific proportion and then formed by high-energy ball milling. The high-toughness, high-thermal-conductivity tungsten material has the following organizational characteristics: the Cu element is segregated at the tungsten grain boundary and exists in the form of pure Cu soft phase particles; the Y element absorbs free oxygen in the tungsten powder to form Y2O3 particles which are dispersedly distributed in the tungsten matrix at the intragranular and grain boundary positions.

[0018] Further, the high-thermal-conductivity tungsten material can be further processed by subsequent plastic processing (such as hot rolling, high-energy rate forging, etc.) to further regulate the morphology and distribution of the pure Cu and Y2O3 in the high-thermal-conductivity tungsten material and optimize the toughening and strengthening effect. This provides a new method for powder metallurgy to manufacture high-thermal-conductivity tungsten material with excellent strength and plasticity matching in the future.

[0019] The present application has the following beneficial effects:

[0020] (1) The present application is based on a special Cu x Y 100-x precursor alloy, and a W+Cu x Y 100-x composite powder is prepared; based on this, the soft Cu particles are successfully introduced into the W-Y2O3 material by using conventional hot-pressing sintering technology, and a tungsten-based composite material which is toughened and strengthened by the synergistic effect of the grain boundary Cu soft phase and Y2O3 dispersed hard particles is obtained.

[0021] (2) The introduction of soft Cu phase not only significantly improves the plastic deformation ability of high-strength W-Y2O3 material at low temperature, but also significantly improves the thermal conductivity of high-strength W-Y2O3 material due to the excellent electrical conductivity and thermal conductivity of Cu.

[0022] (3) The special Cu x Y 100-x The precursor alloy is liquefied during sintering and reacts with impurities in the tungsten matrix: Y elements can absorb free oxygen in tungsten powder to form oxides in situ at grain boundaries and in grains, realizing uniform distribution of oxides, having multiple effects of dispersion strengthening, fine-grain strengthening and purifying grain boundaries; and Cu elements are precipitated in the form of pure Cu phase at tungsten grain boundaries, improving the grain boundary bonding strength and the mechanical properties, transient thermal shock resistance and other properties of the material due to the high thermal conductivity and high ductility of Cu, and ensuring the high thermal conductivity of the tungsten-based composite material. This provides a new idea for developing high-strength high-thermal-conductivity tungsten materials with excellent mechanical properties. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The synchrotron X-ray diffraction spectrum of the W-0.70wt.%Cu-0.40wt.%Y sintered body material obtained in Example 1.

[0024] Figure 2 The microstructure morphology (backscattered electron image) of the W-0.70wt.%Cu-0.40wt.%Y sintered body obtained in Example 1.

[0025] Figure 3 The uniaxial tensile curve of the W-0.70wt.%Cu-0.40wt.%Y sintered body material obtained in Example 1 at 200°C (where the dotted line is the engineering stress-strain curve of pure tungsten under the same conditions for reference comparison).

[0026] Figure 4 The thermal conductivity value comparison curve of the W-0.70wt.%Cu-0.40wt.%Y sintered body obtained in Example 1 and the reference pure tungsten at different temperatures. DETAILED DESCRIPTION

[0027] The specific preparation process and effects of the present application are further described below through five examples.

[0028] Example 1 (W-0.70wt.%Cu-0.40wt.%Y material)

[0029] (1) First step, preparation of Cu 71 Y 29 alloy powder;

[0030] Step 1.1, using industrial pure Cu (purity > 99.99%) and Y metal (purity > 99.9%) as raw materials, the atomic percentage composition of Cu 71 Y 29 alloy was prepared, which was placed in a water-cooled copper crucible of a non-consumable vacuum arc melting furnace, vacuumed to 6 x 10 - 3 Pa, and 0.01 MPa of industrial pure Ar gas was filled to carry out non-consumable arc melting, and the working current of the melting was 300 A; the alloy was repeatedly melted up and down for 4 times to obtain a Cu 71 Y 29 alloy ingot, and the mass loss of the alloy before and after melting was about three ten-thousandths.

[0031] Step 1.2, the Cu 71 Y 29 alloy ingot was crushed and put into a graphite crucible to carry out atomization powdering: the Cu 71 Y 29 alloy was completely melted by medium-frequency induction heating, and was sprayed out and cooled by using atomization technology, the spraying pressure of the atomization gas was 5 MPa, the nozzle aperture of the flow guide rod was 2 mm, spherical powder material was obtained, the particle size was 10-25 μm, and the powder was reserved after screening.

[0032] (2) the second step, preparing W+Cu 71 Y 29 composite powder;

[0033] Step 2.1, using industrial pure tungsten powder (particle size 4.2 μm) and Cu 71 Y 29 powder (obtained in step 1.2, particle size 18-23 μm, screened by a 600-800 mesh screen) as raw materials, the W+1.1wt.%Cu 71 Y 29 composite powder (corresponding to the target alloy with a nominal composition of W-0.70wt.%Cu-0.40wt.%Y) was prepared by weighing and compounding. After mixing the powder and balls (ball-to-powder ratio 5:1), the mixture was loaded into a ball mill tank in an anhydrous ethanol medium environment, high-energy ball milling was carried out for 25 h, and the ball mill speed was 450 rpm. The milled powder was taken out and dried in a vacuum drying oven to obtain a composite powder with a median particle size of 2.0 μm.

[0034] (3) the third step, vacuum hot-pressing sintering to prepare a W-0.70wt.%Cu-0.40wt.%Y sintered body;

[0035] Step 3.1, about 500 g of the composite powder obtained in step two was poured into a graphite mold, which was placed in a vacuum hot-pressing sintering furnace, vacuumed to 3 x 10 -2Pa, and pre-pressurized at 30 MPa, then heated to 1450℃ at a rate of 10℃ / min and held for 60 min, and then heated to 1800℃ and held for 3 h. The pressure in the two sintering stages was 60 MPa. After sintering, the sample was cooled to room temperature in the furnace and taken out for observation.

[0036] The density of the sintered W-0.70wt.%Cu-0.40wt.%Y sample was measured by the Archimedes method and was found to be 99.2%. The synchrotron radiation X-ray diffraction (SR-XRD) spectrum of the sintered sample is shown in Fig. 1, in which the strong diffraction peaks are from the body-centered cubic tungsten matrix (corresponding to the standard diffraction spectrum No. 97-015-1760), and the remaining low-intensity diffraction peaks can be identified by the face-centered cubic pure Cu phase (PDF#04-001-2764) and the face-centered cubic Y2O3 phase (PDF#97-015-1760), indicating that the main phase of the obtained sintered material matrix is body-centered cubic tungsten, with a certain amount of pure Cu and Y2O3 precipitated phases. Figure 1 The microstructure and morphology of the sintered sample are shown in Fig. 2. As can be seen, near-circular particles of different sizes are dispersed in the grain boundaries and inside the grains, with sizes of 0.2-3 μm. Combined with the composition analysis and SR-XRD detection results, it can be known that it corresponds to Y2O3 (white arrows in Fig. 2); similarly, it is confirmed that the larger particles appearing at the grain boundaries are pure Cu phases, with sizes of 2-3 μm (black arrows in Fig. 2). The above results show that the bulk tungsten-based composite material with soft Cu phases precipitated at the grain boundaries and uniformly and dispersedly distributed Y2O3 hard particles has been successfully prepared by the present application. Figure 2 Figure 2 Figure 2

[0037] Further performance test results show that the uniaxial tensile fracture strength of the tungsten-based new material obtained by the present application at room temperature is 1120 MPa, and has excellent low-temperature plasticity and heat conduction capacity. Fig. 3 shows the tensile engineering stress-strain curve of the W-0.70wt.%Cu-0.40wt.%Y sintered sample at 200°C, in which the experimental data of the pure tungsten reference sample under the same experimental conditions are also given. The results show that the uniaxial tensile strength and elongation of the sintered sample at 200°C are 900 MPa and 8.3%, respectively, while the pure tungsten is brittlely broken without plastic deformation when the loading stress reaches 673 MPa at 200°C. Figure 3 Figure 4 ​​​​The curve of the thermal conductivity of the W-0.70wt.%Cu-0.40wt.%Y sintered body sample with temperature is given. The thermal conductivity of the sample at room temperature is slightly lower than that of pure tungsten, which is 164 W / m·K (the thermal conductivity of the single W-0.4wt.%Y material without Cu phase separation measured under the same conditions is only 120 W / m·K at room temperature); the thermal conductivity value of the material is closer to that of pure tungsten as the temperature rises, and the measured thermal conductivity value is basically the same as that of pure tungsten above 500°C.

[0038] Example 2 (W-0.42wt.%Cu-0.38wt.%Y material) 60 Y 40 alloy powder;

[0039] Step 1.1, using industrial pure Cu (purity > 99.99%) and Y metal (purity > 99.9%) as raw materials, the atomic percentage composition of Cu 60 Y 40 alloy is prepared, which is placed in a water-cooled copper crucible of a non-consumable vacuum arc melting furnace, vacuumized to 6×10 - 3 Pa, and 0.01 MPa of industrial pure Ar gas is filled to carry out non-consumable arc melting, and the working current of the melting is 300 A; the alloy is repeatedly melted up and down for 4 times to obtain a Cu 60 Y 40 alloy ingot, and the mass loss of the alloy before and after melting is about 5 parts per thousand.

[0040] Step 1.2, the Cu 60 Y 40 alloy ingot is crushed and put into a graphite crucible, and the Cu 60 Y 40 alloy is completely melted by medium-frequency induction heating, and is sprayed out by using atomization technology, the atomization gas spraying pressure is 3 MPa, the nozzle aperture of the flow guide rod is 1.5 mm, and the spherical powder with a particle size of 5-30 μm is obtained, which is sieved and reserved.

[0041] (2) Second step, preparation of W+Cu 60 Y 40 composite powder;

[0042] Step 2.1, using industrial pure tungsten powder (particle size 4.2 μm) and Cu 60 Y 40 powder with a particle size of 13-23 μm obtained in step 1.2 as raw materials, weighing and preparing W+0.8wt.%Cu 60 Y 40The composite powder (corresponding to the target alloy with nominal composition of W-0.42wt.%Cu-0.38wt.%Y) was loaded into a ball mill pot with grinding balls and ball-to-powder ratio of 7:1, and high-energy ball milling was carried out in ethanol medium for 20h at a rotation speed of 500rpm. The W+Cu 60 Y 40 composite powder was obtained with a median particle size of 2.0μm.

[0043] (3) Third step, vacuum hot-pressing sintering to prepare W-0.42wt.%Cu-0.38wt.%Y sintered body;

[0044] Step 3.1, 500g of the composite powder obtained in step 2.1 was put into a graphite mold and placed in a vacuum hot-pressing sintering furnace, pre-pressed at 30MPa, vacuumed to 3×10 -2 Pa, then heated to 1400℃ for 60min, and then heated to 1800℃ for 2h. The pressure during sintering was 60MPa. Finally, the sample was cooled to room temperature and taken out for observation.

[0045] The density of the W-0.42wt.%Cu-0.38wt.%Y sintered body was 99.0% measured by drainage method. The results of SR-XRD and scanning electron microscopy analysis showed that the matrix of the sintered body was body-centered cubic tungsten, and pure Cu phase and Y2O3 particles were generated on the matrix. The Y2O3 particles were dispersed and uniformly distributed in the intragranular and grain boundary of the tungsten grains, with a size of 0.2-2μm; the pure Cu phase particles were slightly larger, with a size of 1-2μm, and were only precipitated at the tungsten grain boundaries. The mechanical and thermal conductivity test results showed that the room temperature uniaxial tensile strength of the W-0.42wt.%Cu-0.38wt.%Y sample was 1200MPa, and the uniaxial tensile strength and elongation at 200℃ were 950MPa and 7.0% respectively; the room temperature thermal conductivity value was 156W / m·K; the thermal conductivity value changed with temperature in a similar trend to that of the material of Example 1.

[0046] Example 3 (W-0.59wt.%Cu-0.21wt.%Y material)

[0047] (1) First step, preparation of Cu 80 Y 20 alloy powder;

[0048] Step 1.1, industrial pure Cu (purity >99.99%) and Y metal (purity >99.9%) were used as raw materials to prepare Cu 80 Y 20 alloy with an atomic percentage composition of Cu -3Pa, non-consumable arc melting was carried out under the protection of 0.01 MPa pure Ar gas, and the melting working current was 300 A; the Cu 80 Y 20 The alloy ingot was broken and placed in a graphite crucible, and was completely melted by medium-frequency induction heating, and was sprayed to prepare powder by using atomization technology, the spraying pressure of the atomizing gas was 10 MPa, the nozzle aperture of the flow guide rod was 1 mm, 3-30 μm spherical powder was obtained, and the powder was used after screening.

[0049] Step 1.2, Cu 80 Y 20 The alloy ingot was broken and placed in a graphite crucible, and was completely melted by medium-frequency induction heating, and was sprayed to prepare powder by using atomization technology, the spraying pressure of the atomizing gas was 10 MPa, the nozzle aperture of the flow guide rod was 1 mm, 3-30 μm spherical powder was obtained, and the powder was used after screening.

[0050] (2) the second step, preparing W+Cu 80 Y 20 Composite powder;

[0051] Step 2.1, using industrial pure tungsten powder (particle size 4.2 μm) and Cu 80 Y 20 Powder with a particle size of 6.5-18 μm obtained in step 1.2 as raw materials, weighing and preparing a composite powder (corresponding to the target alloy with a nominal composition of W-0.59wt.%Cu-0.21wt.%Y) with a composition of W+0.8wt.%Cu 80 Y 20 , and the ball-to-powder ratio was 10:1, and high-speed ball milling was carried out in anhydrous ethanol for 30 h at a speed of 500 rpm. W+Cu 80 Y 20 Composite powder with a median particle size of 0.5 μm was obtained.

[0052] (3) the third step, vacuum hot-pressing sintering to prepare a W-0.59wt.%Cu-0.21wt.%Y sintered body;

[0053] Step 3.1, 500 g of the composite powder obtained in step 2.1 was placed in a graphite mold and placed in a vacuum hot-pressing sintering furnace, pre-pressed at 30 MPa, vacuumed to 3×10 -2 Pa, then heated to 1500℃ and kept for 60 min, then continuously heated to 1700℃ and kept for 4 h. The pressure during sintering was 60 MPa. Finally, the sample was cooled to room temperature, and was taken out for observation.

[0054] The density of the sintered body of W-0.42wt.%Cu-0.38wt.%Y measured by drainage method is 99.3%. The results of SR-XRD and scanning electron microscope analysis show that the sintered body matrix is body-centered cubic tungsten, and 0.5-1.5μm size pure Cu phase and 0.1-1μm size Y2O3 particles are generated on the tungsten grain. Among them, the Y2O3 particles are dispersed and uniformly distributed in the intracrystalline and grain boundary of the matrix grain, and the pure Cu phase particles only appear at the tungsten grain boundary. The mechanical and thermal conductivity test results show that the uniaxial tensile fracture strength of the W-0.42wt.%Cu-0.38wt.%Y sample at room temperature is 1030MPa, and the uniaxial tensile strength and elongation at 200°C are 850MPa and 9.8% respectively; the room temperature thermal conductivity value is 170W / m·K; the trend of the thermal conductivity with temperature change is similar to that of the material of Example 1.

[0055] Example 4 (W-0.78wt.%Cu-0.72wt.%Y material)

[0056] (1) First step, preparation of Cu 60 Y 40 alloy powder;

[0057] Step 1.1, using industrial pure Cu with purity >99.99% and Y metal with purity >99.9% as raw materials, preparing Cu 60 Y 40 alloy with atomic percentage composition of Cu -3 Pa, filling in 0.01MPa industrial pure Ar gas protection, carrying out non-consumable arc smelting, and the smelting working current is 300A; repeated smelting 4 times to obtain Cu 60 Y 40 alloy ingot with uniform composition, and the sample mass loss before and after smelting is about 5 parts per thousand.

[0058] Step 1.2, crushing the Cu 60 Y 40 alloy ingot and putting it into a graphite crucible, fully melting it by medium-frequency induction heating, and powdering by using atomization technology, the atomization gas spray pressure is 7MPa, the nozzle aperture of the flow guide rod is 2mm, obtaining spherical powder with particle size of 10-40μm, and the powder is used after screening.

[0059] (2) Second step, preparation of W+Cu 60 Y 40 composite powder;

[0060] Step 2.1, using industrial pure tungsten powder (particle size 4.2μm) and Cu 60 Y 40The powders are used as raw materials, weighed and formulated into W+1.5wt.%Cu 60 Y 40 The composite powders (corresponding to the target alloy with nominal composition of W-0.78wt.%Cu-0.72wt.%Y) are loaded into a ball mill tank together with the milling balls (ball-to-powder ratio of 8:1) and ball-milled in ethanol medium for 25h at a rotation speed of 400rpm. The W+Cu 60 Y 40 composite powders with a median particle size of 1.8μm are obtained.

[0061] (3) Third step, vacuum hot-pressing sintering to prepare W-0.78wt.%Cu-0.72wt.%Y sintered body;

[0062] Step 3.1, 500g of the composite powders obtained in Step 2.1 are placed into a graphite mold of a vacuum hot-pressing sintering furnace, preloaded at 30MPa, vacuumed to 3×10 -2 Pa, then heated to 1400℃ for 60min, and then continuously heated to 1800℃ for 2.5h. The pressure applied during the heat-sintering is 60MPa. Finally, the sample is furnace-cooled to room temperature and taken out for observation.

[0063] The density of the W-0.78wt.%Cu-0.72wt.%Y sintered body is 99.3% as measured by the drainage method. The results of SR-XRD and scanning electron microscope analysis show that the matrix of the sintered body is body-centered cubic tungsten, with pure Cu and Y2O3 phases formed thereon. The Y2O3 particles are dispersed and uniformly distributed in the tungsten grains at the intragranular and grain boundary sites, with a size of 0.5-2μm; the pure Cu phase particles are only visible at the tungsten grain boundaries, with a size of 1.5μm or so. The mechanical and thermal conductivity test results show that the uniaxial tensile fracture strength of the W-0.42wt.%Cu-0.38wt.%Y sample at room temperature is 1290MPa, and the uniaxial tensile strength and elongation thereof at 200℃ are 970MPa and 9.2% respectively; the thermal conductivity value at room temperature is 150W / m·K; and the thermal conductivity value thereof changes with temperature in a similar manner to that of the material of Example 1.

[0064] Example 5 (W-1.11wt.%Cu-0.39wt.%Y material)

[0065] (1) First step, preparation of Cu 80 Y 20 alloy powders;

[0066] Step 1.1, industrial pure Cu (purity >99.99%) and Y metal (purity >99.9%) are used as raw materials, and the atomic percentage composition of the alloy is formulated as Cu 80 Y 20 , which is placed in a water-cooled copper crucible of a vacuum arc furnace, vacuumed to 6×10-3 Pa, non-consumable arc melting was carried out under the protection of 0.01 MPa pure Ar gas, and the melting working current was 300 A; the Cu 80 Y 20 The alloy ingot was broken and placed in a graphite crucible, and the alloy was completely melted by medium-frequency induction heating, and the powder was prepared by liquid atomization technology, the atomization gas spray pressure was 9 MPa, the guide rod nozzle aperture was 2 mm, the particle size of the spherical powder was 8-35 μm, and the powder was used after screening.

[0067] Step 1.2, Cu 80 Y 20 The alloy ingot was broken and placed in a graphite crucible, and the alloy was completely melted by medium-frequency induction heating, and the powder was prepared by liquid atomization technology, the atomization gas spray pressure was 9 MPa, the guide rod nozzle aperture was 2 mm, the particle size of the spherical powder was 8-35 μm, and the powder was used after screening.

[0068] (2) The second step, preparing W+Cu 80 Y 20 Composite powder;

[0069] Step 2.1, using industrial pure tungsten powder (particle size 4.2 μm) and Cu 80 Y 20 Powder with a particle size of 18-25 μm obtained in step 1.2 as raw materials, weighing and preparing a composite powder (corresponding to the target alloy with a nominal composition of W-1.11wt.%Cu-0.39wt.%Y) with a composition of W+1.5wt.%Cu 80 Y 20 , and the ball-to-material ratio was 8:1, and high-speed ball milling was carried out in anhydrous ethanol for 25 h at a speed of 450 rpm. A W+Cu 80 Y 20 Composite powder with a median particle size of 2.0 μm was obtained.

[0070] (3) The third step, vacuum hot pressing sintering to prepare W-1.11wt.%Cu-0.39wt.%Y sintered body;

[0071] Step 3.1, 500 g of the composite powder obtained in step 2.1 was placed in a graphite mold and placed in a vacuum hot pressing sintering furnace, pre-pressed at 30 MPa, vacuumed to 3×10 -2 Pa; then heated to 1500℃ and kept for 60 min; then continue to heat to 1800℃ and keep for 3h. The pressure during sintering was 60 MPa. Finally, the sample was cooled to room temperature and taken out for observation.

[0072] The density of the sintered body of W-1.11wt.%Cu-0.39wt.%Y measured by drainage method is 99.5%. The results of SR-XRD and scanning electron microscope analysis show that the sintered body matrix is body-centered cubic tungsten, and there are about 1-2 μm size of pure Cu phase and 0.8-1.5 μm size of Y2O3 particles on the tungsten grain. The Y2O3 particles are dispersed and uniformly distributed in the intracrystalline and grain boundary of the matrix grain, while the pure Cu phase particles only appear at the tungsten grain boundary. The mechanical and thermal conductivity test results show that the uniaxial tensile fracture strength of the W-1.11wt.%Cu-0.39wt.%Y sample at room temperature is 1050 MPa, and the uniaxial tensile strength and elongation at 200°C are 860 MPa and 10.1% respectively; the thermal conductivity value at room temperature is 168 W / m·K; and the trend of the thermal conductivity with temperature change is similar to that of the material of Example 1.

[0073] The above example results show that the present application is based on the special W+Cu x Y 100-x The composite powder is prepared into a W-Y2O3 composite material with uniform structure and high density by conventional vacuum hot pressing sintering technology, that is, the Cu element is distributed in the tungsten grain boundary in the form of pure Cu phase, and the Y element absorbs the free oxygen in the raw material powder to form oxides in situ at the grain boundary and intracrystalline, realizing the uniform and dispersed distribution of Y2O3 oxides in the tungsten matrix particles, and finally obtaining a high thermal conductivity tungsten-based material coupled by the soft Cu phase at the grain boundary and the dispersed Y2O3 hard particles.

[0074] The above examples only express the embodiments of the present application, but cannot be interpreted as the limitation of the scope of the present patent. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application.

Claims

1. A method for producing a high thermal conductivity tungsten material which is strengthened and toughened by coupling of soft Cu phases and Y2O3 hard particles, characterized by, The preparation method comprises the following steps: firstly, a CuY precursor alloy is prepared by an arc melting technique, and the alloy is atomized to powder and mixed with industrial pure tungsten powder as raw materials; then, the mixture is ball milled in anhydrous ethanol medium to obtain a mixed and uniform composite powder; finally, the composite powder is hot-pressed and sintered to obtain a tungsten-based composite material in which soft Cu phase precipitates at grain boundaries and Y2O3 hard particles are uniformly and dispersedly distributed, i.e., a high-thermal-conductivity tungsten material. First, Cu x Y 100-x alloy powder; Step 1.1, using industrial pure Cu, Y metal as raw material, the atomic percentage composition of Cu x Y 100-x precursor alloy of x = 80 ~ 60, melt it into a homogeneous alloy ingot; Step 1.2, after the alloy ingot is broken, it is put into a gas atomization powder production device to be atomized and powdered, to obtain Cu x Y 100-x alloy powder; Second step, preparation of W+Cu x Y 100-x Composite powder; Step 2.1, using industrial pure tungsten powder as the base material, Cu x Y 100-x alloy powder as the additive, the mixture was prepared, and the composition of the mixture was W + (0.8-1.5 wt.%) Cu x Y 100-x , and the nominal composition of the corresponding target alloy was W - (0.42-1.11 wt.%) Cu - (0.21-0.72 wt.%) Y, wherein Cu was the source of pure Cu soft phase in the target material, and Y provided the component for in-situ formation of Y2O3 hard particles in the target material. Step 2.2, the mixture in step 2.1 was loaded into a ball mill tank with grinding balls, and the powder was taken out after high-energy ball milling in anhydrous ethanol medium, and vacuum drying to obtain W+Cu x Y 100-x Composite powder; Step 3.2, after the hot-pressing sintering process, the sintered body is cooled to room temperature in the furnace to obtain the high-thermal-conductivity tungsten material. Step 3.1, W+Cu x Y 100-x The composite powder is put into a vacuum hot-pressing sintering furnace to perform hot-pressing sintering, thereby obtaining a bulk material of W-(0.42-1.11 wt.%)Cu-(0.21-0.72 wt.%)Y; the hot-pressing sintering process mainly experiences two stages: the sintering temperature of the first stage is 1400-1500°C, and the sintering temperature of the second stage is 1700-1800°C. In step 1.1, a common non-consumable vacuum arc melting furnace is used to melt the alloy ingot with uniform composition, and the mass loss rate of the precursor alloy before and after melting is not more than 5 parts per thousand.

2. The method of claim 1, wherein the soft Cu phase and Y2O3 hard particles are coupled to strengthen and toughen the high thermal conductivity tungsten material. In step 2.2, the ball-to-material ratio of high-energy ball milling is 5:1-10:1, the ball milling speed is 400-500 rpm, and the ball milling time is 20-30 h.

3. The method of claim 1, wherein the soft Cu phase and Y2O3 hard particles are coupled to strengthen and toughen the high thermal conductivity tungsten material. In step 1.2, the alloy ingot is completely melted by medium-frequency induction heating, and is sprayed and cooled by using atomization technology to obtain spherical particle powder with a particle size of 3-40 μm, and Cu x Y 100-x The alloy powder is obtained by using industrial pure argon as the atomizing gas and by spraying at a pressure of 3-10 MPa in the atomization powder production process, and the guide rod nozzle aperture of the gas atomization powder production device is 1-2 mm.

4. The method of claim 1, wherein the soft Cu phase and Y2O3 hard particles are coupled to strengthen and toughen the high thermal conductivity tungsten material. The high-thermal-conductivity tungsten material is prepared by the preparation method of any one of claims 1-6, and the microstructure characteristics are that Cu element precipitates at tungsten grain boundaries in the form of pure Cu soft phase particles, Y element absorbs free oxygen in tungsten powder to form Y2O3 particles which are dispersedly distributed in the intragranular and grain boundary positions of the tungsten matrix.

5. The method of claim 1, wherein the soft Cu phase and Y2O3 hard particles are coupled to strengthen and toughen the high thermal conductivity tungsten material. In the step 2.2, W+Cu x Y 100-x The median particle size of the composite powder is 0.5-2.0 μm.

6. The method of claim 1, wherein the soft Cu phase and Y2O3 hard particles are coupled to strengthen and toughen the high thermal conductivity tungsten material. The preloading pressure of the blank in the hot-press sintering process of step 3.1 is 30 MPa, and the vacuum degree during sintering is 3x10 -2 Pa, and the hot-press sintering process mainly experiences two stages: the holding time of the first stage is 60 min; the holding time of the second stage is 2-4 h, and the pressure of both stages is 60 MPa.

7. A high thermal conductivity tungsten material coupled with strengthening of soft Cu phase and Y203 hard particles, characterized in that, The high-thermal-conductivity tungsten material has a density of more than 99.0%, a room temperature thermal conductivity of more than 150 W / m·K, and a room temperature tensile fracture strength of more than 1000 MPa.

8. The high thermal conductivity tungsten material of claim 7, wherein the soft Cu phase and Y2O3 hard particles are coupled to strengthen and toughen the material. The high-thermal-conductivity tungsten material is subjected to subsequent plastic processing to control the morphology and distribution of pure Cu and Y2O3 in the high-thermal-conductivity tungsten material, and to optimize the coupling toughening effect.

9. The high thermal conductivity tungsten material of claim 7, wherein the soft Cu phase and Y203 hard particles are coupled to strengthen and toughen the material. ​

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