A composite dispersion strengthened tungsten alloy and its preparation method

Abstract

The present invention belongs to the field of alloy manufacturing, and specifically relates to a composite dispersion-strengthened tungsten alloy and a preparation method thereof. The invention comprises the following steps: reducing a tungsten-containing compound with a rare earth compound, K2SiO3, Al(NO3)3, and a KCl solution through hydrogen reduction to obtain a mixed alloy powder containing W-K and rare earth oxides; then pressing, sintering, and thermoplastic processing the mixed alloy powder containing W-K and rare earth oxides to obtain a composite dispersion-strengthened tungsten alloy; the invention comprises the following steps: micro-doping rare earth oxides into the W-K alloy, combining the pinning effect of oxide nanoparticles and K bubbles at different temperature sections (1200°C to 1600°C, 1600°C to 1900°C) during sintering, thereby inhibiting grain boundary diffusion and grain growth, making the temperature range for inhibiting recrystallization of the W alloy wider, and obtaining a W alloy with uniform structure and an average grain size of 2.46 to 3.31 μm; and after thermoplastic processing, a W alloy with excellent comprehensive performance is prepared, and the tensile strength can reach 1373 MPa.

Description

Technical Field

[0001] The present invention belongs to the field of alloy manufacturing, and in particular relates to a composite dispersion strengthened tungsten alloy and a preparation method thereof. Background Art

[0002] Tungsten, with its high melting point, high sputtering threshold, high thermal conductivity, and low tritium retention, is considered the most promising plasma-facing material (PFM) for future fusion reactors. Currently, pure tungsten has been selected for the first wall and divertor materials of the International Thermonuclear Experimental Reactor (ITER) and the Hefei Institutes of Physical Science's Institute of Plasma Physics for the Experimental Superconducting Tokamak (EAST). However, pure tungsten as a PFM still faces numerous challenges, including low-temperature brittleness due to its high ductile-to-brittle transition temperature (DBTT) (approximately 300-500°C), high-temperature embrittlement due to its low recrystallization temperature (RCT) (approximately 1300°C), and neutron-induced embrittlement.

[0003] A lot of work has been done internationally to improve the properties of tungsten and tungsten alloys, using a variety of methods including solid solution strengthening, dispersion strengthening, fiber strengthening, and fine grain strengthening. Among them, dispersion strengthening has received extensive research, mainly including K doping and rare earth oxide doping.

[0004] K-doped tungsten alloys primarily draw upon the strengthening mechanism of doped tungsten filaments. Through doping with K, Al, Si, and other materials, K evaporates during sintering, forming potassium bubbles. These evaporated potassium bubbles break into smaller ones during processing, inhibiting grain boundary diffusion and grain growth. Patent (CN109321796A) utilizes this mechanism to dope with one or more of the following: rare earth oxides, tungsten powder, or tungsten carbide. After mixing, silicon-aluminum-potassium-tungsten powder is obtained. This powder is then cold-pressed, sintered, and hot-worked to produce a bulk WK alloy with excellent mechanical properties. Patent (CN104164579), based on the potassium bubble strengthening theory, successfully produces small-sized tungsten blocks with nano-potassium bubbles through spark plasma sintering, exhibiting excellent mechanical properties and thermal shock resistance. Foreign fusion material researchers have studied K-doped tungsten plates with a K content of 60 to 220 ppm and found that at a temperature of about 1560°C, potassium aluminum silicate in the K-doped tungsten alloy begins to decompose and produce K bubbles. When the temperature is higher (1900°C), the K element in the potassium aluminum silicate in the alloy material is basically completely decomposed, and most of the K bubbles are pinned to the grain boundaries. As the temperature gradually increases, the number of K bubbles gradually increases. When the temperature is raised to 1900-2300°C, its effect on inhibiting the diffusion of grain boundaries and the growth of grains is most significant. When the temperature continues to rise to above 2300°C, the movement of metal atoms intensifies and the K bubble pinning effect gradually weakens.

[0005] Rare earth oxides primarily include ThO2, La2O3, Y2O3, and Lu2O3. Among these, W-La2O3 alloys exhibit superior performance and have been extensively studied. The strengthening mechanism of W-La2O3 alloys is primarily due to La2O3 being uniformly distributed within the tungsten matrix and pinned to grain boundaries, inhibiting grain growth by hindering dislocation and grain boundary diffusion. Fusion researchers at home and abroad have extensively studied W with La2O3 contents ranging from 0.5% to 5%. They have found that La2O3 begins to inhibit grain diffusion at relatively low temperatures (less than 1200°C). Furthermore, they have found that the hardness of W doped with La2O3 is significantly enhanced when sintered at higher temperatures (1500-1650°C). While the hardness begins to decrease at temperatures above 1650°C, it remains higher than that of pure W samples.

[0006] From the above, it can be seen that the existing technology has poor ability to inhibit recrystallization in the medium and high temperature stage (1200-1600°C) of WK and the high temperature stage (1600-2300°C) of W-La2O3 alloy during sintering. Therefore, a composite dispersion-strengthened W alloy that inhibits recrystallization of W alloy and a preparation method thereof are needed in this field. Summary of the Invention

[0007] Based on the above problems, this solution aims to meet the requirements of fusion reactor operating conditions in all aspects of the performance of plasma-facing materials for fusion reactors, and aims to solve the problem in the background technology that the material performance deteriorates due to recrystallization of sintered WK at medium and high temperatures (1200-1600°C) and W-doped rare earth oxide alloys at high temperatures (1600-1900°C). By trace-doping rare earth oxides into the WK alloy, combined with the pinning effect of rare earth oxide nanoparticles and K bubbles in different temperature ranges (1200-1600°C and 1600-1900°C) during the sintering process of the alloy material, grain boundary diffusion and grain growth are inhibited, making the temperature range for inhibiting the recrystallization of the W alloy wider, obtaining a W alloy with a fine-grained structure, and thus improving the comprehensive performance of the material.

[0008] To this end, the first technical solution of the present application discloses a method for preparing a composite dispersion-strengthened tungsten alloy, comprising the following steps:

[0009] A tungsten-containing compound, a rare earth compound, K2SiO3, Al(NO3)3, and a KCl solution are reduced by hydrogen to obtain a mixed alloy powder containing WK ​​and rare earth oxides;

[0010] The mixed alloy powder containing WK ​​and rare earth oxide is pressed, sintered and thermoplastic processed to obtain composite dispersion strengthened tungsten alloy;

[0011] Wherein, the tungsten-containing compound is WO3 or ATM solution, and the rare earth compound is rare earth oxide or soluble rare earth nitrate.

[0012] Furthermore, the addition amounts of K2SiO3, Al(NO3)3, and KCl are calculated based on equivalent weights, wherein the K content is 0.0006-0.0022 wt.%, the Si content is 0.0006-0.0009 wt.%, and the Al addition amount is 0.00008-0.00013 wt.%.

[0013] Furthermore, when the rare earth compound is a rare earth oxide, it can be directly mixed with the tungsten-containing compound, K2SiO3, Al(NO3)3, and KCl solution and added, or it can be added after the tungsten-containing compound, K2SiO3, Al(NO3)3, and KCl solution are reduced with hydrogen.

[0014] Furthermore, the rare earth oxides include one or more of La2O3, Y2O3, CeO2, ZrO2 and Tb2O3, and the added amount thereof is 0.063 to 0.63 wt.% of the total mass of WO3.

[0015] Furthermore, the soluble rare earth nitrate includes any one of lanthanum nitrate (La(NO3)3), yttrium nitrate (Y(NO3)3), cerium nitrate (Ce(NO3)3), zirconium nitrate (Zr(NO3)3), and terbium nitrate (Tb(NO3)3), and the added amount thereof is calculated as 0.039-0.396 wt.% of WO3 or 0.037-0.37 wt.% of AMT based on equivalent weight.

[0016] Furthermore, the hydrogen reduction is a step-by-step temperature reduction, the temperature gradients are 300-600°C, 750-850°C, 900-1000°C, the holding time of each stage is 3-10h, and the hydrogen flow rate is 5-8m 3 / h.

[0017] Furthermore, the pressing pressure is 180-220 MPa, and the holding time is 60-180 s.

[0018] Furthermore, the sintering temperature is 2000-2300° C., the holding time is 5-10 hours, and the atmosphere is hydrogen.

[0019] Furthermore, the thermoplastic processing is divided into high-speed forging, rotary forging or rolling process; wherein, the high-speed forging temperature is 1500-1700°C, and forging is performed after holding at 40-80°C, the forging pressure is 30-40MPa, the deformation per pass is 25-35%, and the final deformation is 70%-80%; the rotary forging temperature is 1400-1700°C, and the holding time is 50-70min, the deformation per pass is 28-30%, and the final deformation is 88-94%; the rolling temperature is 1350-1600°C, one hot rolling is adopted for blanking, and one hot two rolling or one hot three rolling is adopted subsequently, the roller spacing is reduced by 10-15% between passes, the holding time is 30-60min between passes, and the final deformation is 78-92%.

[0020] And, the composite dispersion strengthened tungsten alloy prepared according to the above preparation method.

[0021] The present invention has the following beneficial effects:

[0022] The present invention adopts a scheme of slightly doping La2O3 into the WK alloy, and combines the pinning effect of La2O3 nanoparticles and K bubbles in different temperature ranges (1200°C to 1600°C and 1600°C to 2300°C) during the sintering process of the alloy material to inhibit grain boundary diffusion and grain growth, thereby widening the temperature range for inhibiting the recrystallization of the W alloy and obtaining a W alloy with a fine-grained structure and an average grain size in the range of 2.46 to 3.31 μm.

[0023] Due to the pinning effect of La2O3 particles and K bubbles in the W-La2O3-K alloy, the grain boundary strength of the alloy is synergistically strengthened, and the mechanical properties of the material are significantly improved, with a tensile strength of up to 1373 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the metallographic diagram of the sintered W-0.05wt.%La2O3-K;

[0025] Figure 2 This is the metallographic diagram of the sintered W-0.1wt.%La2O3-K;

[0026] Figure 3 This is the metallographic diagram of the sintered W-0.2wt.%La2O3-K;

[0027] Figure 4 This is the metallographic diagram of the sintered W-0.5wt.%La2O3-K;

[0028] Figure 5 This is the metallographic diagram of the sintered W-0.2wt.%La2O3-K;

[0029] Figure 6 This is the metallographic phase diagram of sintered W-0.2wt.%Y2O3-K. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values ​​should be interpreted as being merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0032] To this end, the first embodiment of the present application discloses a method for preparing a composite dispersion strengthened tungsten alloy, comprising the following steps:

[0033] A tungsten-containing compound, a rare earth compound, K2SiO3, Al(NO3)3, and a KCl solution are reduced with hydrogen to obtain a mixed alloy powder containing WK ​​and rare earth oxides; the mixed alloy powder containing WK ​​and rare earth oxides is pressed, sintered, and thermoplastic processed to obtain a composite dispersion-strengthened tungsten alloy; wherein the tungsten-containing compound is WO3 or an ATM solution, and the rare earth compound is a rare earth oxide or a soluble rare earth nitrate.

[0034] In this embodiment, the mixed alloy powder includes WK and rare earth oxides, wherein WK is obtained by hydrogen reduction of a tungsten-containing compound with a K2SiO3, Al(NO3)3, and KCl solution, and the rare earth oxide is an actively added rare earth oxide or a soluble rare earth salt obtained by hydrogen reduction; therefore, when the rare earth compound is a rare earth oxide, it can be added before or after the tungsten-containing compound, K2SiO3, Al(NO3)3, and KCl solution are reduced with hydrogen; and when the rare earth compound is a soluble rare earth salt (such as a soluble rare earth nitrate), it needs to be added together with the tungsten-containing compound, K2SiO3, Al(NO3)3, and KCl solution before reduction.

[0035] This embodiment discloses the following preferred addition and reaction methods: Method 1: tungsten oxide is mixed with K2SiO3, Al(NO3)3, and KCl solution, and hydrogenated to obtain WK powder; rare earth oxide is added to the WK powder, and mechanically mixed to obtain a mixed alloy powder of WK and rare earth oxide;

[0036] Method 2: Mix tungsten oxide with rare earth oxide and K2SiO3, Al(NO3)3, and KCl solution, and reduce them with hydrogen to obtain WK and rare earth oxide mixed alloy powder;

[0037] Method 3: Mix tungsten oxide, soluble rare earth nitrate, K2SiO3, Al(NO3)3, and KCl solution and reduce them with hydrogen to obtain WK and rare earth oxide mixed alloy powder;

[0038] Method 4: AMT solution, soluble rare earth nitrate, K2SiO3, Al(NO3)3, and KCl solution are mixed and reduced with hydrogen to obtain WK and rare earth oxide mixed alloy powder.

[0039] Among them, ATM solution is ammonium metatungstate (H 28 N6O 41 W 12 A mixed solution of ammonium metatungstate (AMT) and water, with an ammonium metatungstate concentration of 1.02 mol / L (at room temperature).

[0040] In a further embodiment, in the preparation of WK powder, the added amounts of K2SiO3, Al(NO3)3, and KCl are calculated based on equivalent K content of 0.0006-0.0022 wt.%, Si content of 0.0006-0.0009 wt.%, and Al addition of 0.00008-0.00013 wt.%.

[0041] In this embodiment, the rare earth oxides include but are not limited to La2O3, Y2O3, CeO2, ZrO2 and Tb2O3, and the addition amount thereof is 0.039-0.396 wt.% of WO3 or 0.037-0.37 wt.% of AMT based on the total mass of WK powder.

[0042] Furthermore, the soluble rare earth nitrate includes but is not limited to lanthanum nitrate (La(NO3)3), yttrium nitrate (Y(NO3)3), cerium nitrate (Ce(NO3)3), zirconium nitrate (Zr(NO3)3), and terbium nitrate (Tb(NO3)3), and the added amount thereof is calculated as 0.039-0.396 wt.% of WO3 or 0.037-0.37 wt.% of AMT based on equivalent weight.

[0043] In this embodiment, the hydrogenation reduction is a step-by-step temperature reduction, the temperature changes are 300-600 ° C, 700-850 ° C, 900-1000 ° C, the holding time of each stage is 3-10 hours, and the hydrogen flow rate is 5-8m 3 / h.

[0044] It should be noted that in the above reduction process, the reduction of tungsten oxide is divided into three steps: WO 2.9 →WO 2.72 →WO2→W, different temperatures represent different reduction steps. 300-600℃ is WO 2.9 →WO 2.72 The reduction process of WO is 700-850℃. 2.72 →WO2 reduction process; 900-1000°C is WO2→W reduction process. Furthermore, the pressing pressure is 180-220 MPa, and the holding time is 60-180 s.

[0045] Furthermore, the sintering temperature is 2000-2300° C., the holding time is 5-10 hours, and the atmosphere is hydrogen; and the relative density of the sintered material is greater than 95%.

[0046] Furthermore, the thermoplastic processing includes (high-speed forging, rotary forging and hot rolling), and any one of the three processes is selected during actual production; wherein, the high-speed forging temperature is 1500-1700°C, and forging is performed after holding at 40-80°C, the forging pressure is 30-40MPa, the pass deformation is 25-35%, and the final deformation is 70%-80%; the rotary forging temperature is 1400-1700°C, and the holding time is 50-70min, the pass deformation is 28-30%, and the final deformation is 88-94%; the hot rolling process temperature is 1350-1500°C, the first blanking adopts one hot one rolling, and subsequently adopts one hot two rolling or one hot three rolling, the roller spacing between rolling passes is reduced by 10-15% successively, and the final deformation is 78-92%.

[0047] It should be noted that during the thermoplastic processing, after each heating and forging, in order to eliminate residual stress, the forged material should be annealed at 1100-1250℃ for 20-50min.

[0048] The technical effects of the technical solution of this application will be further explained below with reference to specific embodiments.

[0049] Example 1

[0050] Preparation of WK powder: Tungsten oxide (WO3) and K2SiO3, Al(NO3)3, KCl solution are used as raw materials, with the K content ratio of 0.0001wt.%, Si content of 0.00007wt.%, and Al addition of 0.00009wt.%. After mixing, place it in a hydrogen furnace for reduction, heat it to 500℃ at 5℃ / min and keep it for 3h, then heat it to 800℃ at 2.5℃ / min and keep it for 8h, and finally heat it to 950℃ at 2℃ / min and keep it for 8h. The hydrogen flow rate is 6m 3 The average particle size of the WK powder obtained after drying and reduction is 0.7 μm.

[0051] Preparation of W-La2O3-K powder: Add 0.05 wt.% La2O3 powder to WK powder using alcohol as the milling medium. Mill the mixture using a wet mixing method at a speed of 40 rad / min for 24 hours. After milling, dry the mixture to obtain W-La2O3-K alloy powder (W-0.05 wt.% La2O3-K (100 ppm)).

[0052] The W-La2O3-K powder was poured into a rubber mold and pressed in an isostatic press with a pressure of 200 MPa and a holding time of 180 s. The compact was sintered in a medium frequency furnace at a sintering temperature of 2100 ° C in a hydrogen atmosphere with a hydrogen flow rate of 10 m 3 / h, holding time 6h, the density is 18.34g / m 3 (relative density is 95.02%), the diameter is 50.37mm, the height is 75.87mm, the metallographic diagram of the sintered material is as follows Figure 1 shown.

[0053] Among them, high-speed forging processing: the sintered blank is placed in a hydrogen furnace and heated to 1600℃, kept warm for 50 minutes, and the heated cylinder is forged 3 times using a high-speed hammer with a forging pressure of 40MPa. It is returned to the furnace and heated to 1600℃ and kept warm for 40 minutes between passes. After forging and shaping, a block tungsten alloy material with a relative density of 99.60%, a diameter of 83mm, and a thickness of 8.8mm is obtained.

[0054] Since the high temperature during sintering will cause some K to volatilize, the actual K content in the bulk tungsten alloy material prepared in this embodiment is 0.00008 wt.%.

[0055] Example 2

[0056] The alloy preparation process is the same as that of Example 1, except that the amount of La2O3 powder added is 0.1 wt.%.

[0057] The density is 18.38 g / m 3(relative density is 95.24%), the diameter of the sintered blank is 51.04mm, the height is 76.17mm, the metallographic diagram of the sintered blank is as follows Figure 2 shown.

[0058] The relative density of the forging billet is 99.71%, the diameter is 84 mm and the thickness is 8.7 mm.

[0059] Since the high temperature during sintering will cause a portion of K to volatilize, the actual K content in the bulk tungsten alloy material prepared in this embodiment is 0.00008 wt.% (82 ppm).

[0060] Example 3

[0061] The alloy preparation process is the same as that of Example 1, except that the amount of La2O3 powder added is 0.2 wt.%.

[0062] The density is 18.43 g / m 3 (relative density is 95.52%), the diameter is 51.04mm, the height is 76.64mm, the metallographic diagram of the sintered blank is as follows Figure 3 shown.

[0063] The relative density of the forging billet is 99.53%, the diameter is 84 mm and the thickness is 8.6 mm.

[0064] Since the high temperature during sintering will cause a portion of K to volatilize, the actual K content in the bulk tungsten alloy material prepared in this embodiment is 0.00008 wt.% (80 ppm).

[0065] Example 4

[0066] The alloy preparation process is the same as that of Example 1, except that the amount of La2O3 powder added is 0.5 wt.%.

[0067] The density is 18.42 g / m 3 (relative density is 95.45%), diameter 51.04mm, height 76.17mm, the metallographic diagram of the sintered material is as follows Figure 4 shown.

[0068] The relative density of the forging billet is 99.65%, the diameter is 84 mm and the thickness is 8.9 mm.

[0069] Since the high temperature during sintering will cause a portion of K to volatilize, the actual K content in the bulk tungsten alloy material prepared in this embodiment is 0.00008 wt.% (79 ppm).

[0070] Example 5

[0071] Preparation of W-La2O3-K powder: Tungsten oxide, La(NO3)3, K2SiO3, Al(NO3)3 and KCl solution were mixed in the following ratio: La(NO3)3 was 0.36wt.% of the total mass of tungsten oxide, K content was 0.0001wt.%, Si content was 0.00007wt.%, Al addition amount was 0.00009wt.%, and after mixing, it was placed in a hydrogen furnace for reduction, heated to 500℃ at 5℃ / min and kept warm for 3h, then heated to 800℃ at 2.5℃ / min and kept warm for 8h, and finally heated to 950℃ at 2℃ / min and kept warm for 8h. The hydrogen flow rate was 6m 3 The W-0.2 wt.% La2O3-K powder obtained after drying and reduction had an average particle size of 0.7 μm.

[0072] The W-La2O3-K powder was poured into a rubber mold and pressed in an isostatic press with a pressure of 200 MPa and a holding time of 180 s. The compact was sintered in a medium frequency furnace at a sintering temperature of 2100 ° C in a hydrogen atmosphere with a hydrogen flow rate of 10 m 3 / h, holding time 6h, the density is 18.41g / m 3 (relative density is 95.38%), the diameter of the sintered blank is 50.37mm, the height is 75.87mm, the metallographic diagram of the sintered blank is as follows Figure 5 shown.

[0073] Rotary forging: Place the sintered blank in a hydrogen furnace and heat it to 1600℃, keep it warm for 50 minutes, and use an air hammer to forge the heated sample to the appropriate diameter. Place the die of the corresponding forging size in the rotary forging machine, take out the heated bar, and place it in the rotary forging machine to forge half of the length. After forging, place it in a molybdenum wire furnace and heat it to 1550℃, and place it in the rotary forging machine to forge the other half. After multiple forging passes, the deformation of each pass is 28-30%. Between rolling passes, the material is returned to the furnace and heated to 1550℃ and kept warm for 50 minutes. The final deformation after forging is 87%. In order to eliminate residual stress, the forged material is annealed at 1100℃ for 20 minutes, and finally a tungsten alloy rod with a diameter of 8mm and a relative density of 99.84% is obtained.

[0074] Since the high temperature during sintering will cause a portion of K to volatilize, the actual K content in the bulk tungsten alloy material prepared in this embodiment is 0.00008 wt.% (81 ppm).

[0075] Example 6

[0076] Preparation of W-Y2O3-K powder: AMT solution, soluble rare earth nitrate, K2SiO3, Al(NO3)3, and KCl solution were mixed, with Y(NO3)3 being 0.32wt.% of the total mass of AMT, K content being 0.000074wt.%, Si content being 0.00005wt.%, and Al addition being 0.000064wt.%. After mixing, the mixture was placed in a hydrogen furnace for reduction, heated to 400℃ at 3℃ / min for 6h, then heated to 800℃ at 2℃ / min for 9h, and finally heated to 950℃ at 2℃ / min for 9h. The hydrogen flow rate was 6m 3 The W-0.2 wt.% Y2O3-K powder obtained after drying and reduction had an average particle size of 0.7 μm.

[0077] Preparation of sintered compact: The preparation process of sintered compact is the same as that of Example 2. The density is 18.40 g / cm 3 (relative density is 95.35%), length 187mm, width 147.04mm, thickness 35.5mm sintered blank. The metallographic diagram of the sintered material is as follows Figure 6 shown.

[0078] Rolling: The sintered billet is kept at 1500℃ for 60min and then hot rolled to open the billet. In the subsequent rolling process, the roller spacing between passes is reduced by 10% successively. After opening the billet, the temperature is lowered to 1400℃ and kept for 50min before rolling for one pass. After the plate is cooled after rolling, the sample is kept at 1400℃ for 50min and then rolled twice. After the plate is cooled after rolling, the plate is kept at 1300℃ for 50min and then rolled three times. After the plate is cooled after rolling, it is annealed at 1100℃ for 30min. Finally, a tungsten alloy plate with a deformation of 80.2%, a thickness of 7mm and a relative density of 99.78% is obtained.

[0079] Since the high temperature during sintering will cause a portion of K to volatilize, the actual K content in the bulk tungsten alloy material prepared in this embodiment is 0.00008 wt.% (78 ppm).

[0080] Comparative Example 1

[0081] Preparation of sintered blanks: Add 0.2wt.% La2O3 powder to commercial pure W powder (Xiamen Tungsten Co., Ltd.), use alcohol as the ball milling medium, and mix by wet mixing with ball milling. The ball milling tank rotates at a speed of 40rad / min and the ball milling time is 24h. After ball milling and drying, W-0.2wt.% La2O3 alloy powder is obtained. Pour the powder into a rubber mold and place it in an isostatic press to form the powder. The pressure is 200MPa and the holding time is 180s. Place the pressed blank in a medium frequency furnace for sintering. The sintering temperature is 2100℃, the atmosphere is hydrogen, and the hydrogen flow rate is 10m 3 / h, holding time 6h, the density is 18.37g / m 3 (relative density is 95.18%), sintered blank with a diameter of 53.62 mm and a height of 74.87 mm.

[0082] High-speed forging: Same as Example 1. After forging and shaping, a tungsten alloy block with a relative density of 99.55%, a diameter of 84.5 mm, and a thickness of 9 mm was obtained.

[0083] Comparative Example 2

[0084] Preparation of sintered blank: Preparation of sintered blank: Use blue tungsten oxide and K2SiO3, Al(NO3)3, KCl solution as raw materials, with the K content ratio of 0.0001wt.%, Si content of 0.00007wt.%, and Al addition of 0.00009wt.%. After mixing, place it in a hydrogen furnace for reduction, heat it to 500℃ at 5℃ / min and keep it for 3h, then heat it to 800℃ at 2.5℃ / min and keep it for 8h, and finally heat it to 950℃ at 2℃ / min and keep it for 8h. The hydrogen flow rate is 6m 3 / h. The average particle size of the powder obtained after drying and reduction is 2μm. The powder is poured into a rubber mold and is pressed in an isostatic press with a pressure of 200MPa and a holding time of 180s. The compact is sintered in a medium frequency furnace with a sintering temperature of 2100℃, a hydrogen atmosphere, and a hydrogen flow rate of 10m 3 / h, holding time 6h, the density is 18.34g / m 3 (relative density is 95.02%), a sintered blank with a diameter of 52.19 mm and a height of 75.24 mm.

[0085] High-speed forging: Same as Example 1. After forging and shaping, a tungsten alloy block with a relative density of 99.35%, a diameter of 84 mm, and a thickness of 9 mm was obtained.

[0086] Since the high temperature during sintering will cause a portion of K to volatilize, the actual K content in the bulk tungsten alloy material prepared in this embodiment is 0.00008 wt.% (78 ppm).

[0087] Comparative Example 3

[0088] Preparation of sintered compact: Commercial pure W powder (Xiamen Tungsten Co., Ltd.) was poured into a rubber mold and pressed in an isostatic press with a pressure of 200 MPa and a holding time of 180 s. The compact was sintered in an intermediate frequency furnace at a sintering temperature of 2100 °C in a hydrogen atmosphere with a hydrogen flow rate of 10 m 3 / h, holding time 6h, the density is 18.10g / m 3 (relative density is 93.5%), sintered blank with a diameter of 52.19 mm and a height of 75.24 mm.

[0089] The comparison of the average grain size and tensile strength of the bulk tungsten alloys prepared in Examples 1-6 and Comparative Examples 1-3 is shown in Table 1 below.

[0090] Table 1 Composition and performance data of Examples and Comparative Examples

[0091]

[0092] Table 1 Average grain size of alloys prepared in Examples 1 to 6 and Comparative Examples 1 to 3 was measured with reference to the standard "GB / T6394-2017 Determination of average grain size of metals":

[0093] Table 1 The tensile strength and elongation test of Examples 1 to 6 and Comparative Examples 1 to 2 were tested with reference to the standard "GB / T 228.2-2015 Tensile tests on metallic materials Part 2: High temperature test methods", and the tensile test method was selected.

[0094] Result analysis: It can be seen from the data in Table 1 that in the sintered state, the alloys prepared in Examples 1 to 6 have smaller grain sizes than those in Comparative Examples 1 to 3; after thermoplastic processing, the alloys prepared in Examples 1 to 6 have higher tensile strength and better elongation than those in Comparative Examples 1 to 3.

[0095] The above embodiments are only preferred embodiments of the present application, and the scope of implementation of the present application is not limited thereto. The embodiments and features in the embodiments of the present invention can be arbitrarily combined with each other without conflict. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for preparing a composite dispersion strengthened tungsten alloy, characterized in that: The steps include: A tungsten-containing compound, a rare earth compound, K2SiO3, Al(NO3)3, and a KCl solution are reduced by hydrogen to obtain a mixed alloy powder containing WK ​​and rare earth oxides; The mixed alloy powder containing WK ​​and rare earth oxide is pressed, sintered and thermoplastic processed to obtain composite dispersion strengthened tungsten alloy; Wherein, the tungsten-containing compound is WO3 or AMT solution, and the rare earth compound is a rare earth oxide or a soluble rare earth nitrate; The amount of K2SiO3, Al (NO3) 3, KCl is calculated based on the equivalent K content of 0.0006 ~ 0.0022 wt.%, Si content of 0.0006 ~ 0.0009 wt.%, Al added in an amount of 0.00008 ~ 0.00013 wt.%; The rare earth oxide includes La2O3, Y2O3, CeO2, ZrO2 and Tb2O3 in one or more, which is added in an amount of 0.063 ~ 0.63wt.% of WO3; The soluble rare earth nitrate includes any one of lanthanum nitrate, yttrium nitrate, cerium nitrate, zirconium nitrate and terbium nitrate, and the addition amount thereof is 0.039-0.396 wt.% of WO3 or 0.037-0.37 wt.% of AMT according to equivalent weight.

2. The preparation method according to claim 1, characterized in that When the rare earth compound is a rare earth oxide, it can be directly mixed with the tungsten-containing compound, K2SiO3, Al(NO3)3, and KCl solution and added, or it can be added after the tungsten-containing compound, K2SiO3, Al(NO3)3, and KCl solution are reduced with hydrogen.

3. The preparation method according to claim 1, characterized in that: The hydrogen reduction was performed in a step-by-step temperature-increasing manner, with the temperature gradients being 300-600°C, 750-850°C, and 900-1000°C, respectively. The holding time for each stage was 3-10 hours, and the hydrogen flow rate was 5-8 m 3 / h.

4. The preparation method according to claim 1, characterized in that The pressing pressure is 180-220 MPa, and the holding time is 60-180 s.

5. The preparation method according to claim 1, characterized in that: The sintering temperature is 2000-2300° C., the holding time is 5-10 hours, and the atmosphere is hydrogen.

6. The preparation method according to claim 1, characterized in that: The hot plastic processing is divided into high-speed forging, rotary forging or rolling process; wherein, the high-speed forging temperature is 1500-1700°C, and forging is performed after holding for 40-80 minutes. The forging pressure is 30-40 MPa, the deformation per pass is 25-35%, and the final deformation is 70%-80%; the rotary forging temperature is 1400-1700°C, and the holding time is 50-70 minutes. The deformation per pass is 28-30%, and the final deformation is 88-94%; the rolling temperature is 1350-1600°C, and the blanking adopts one hot rolling, followed by one hot two rolling or one hot three rolling. The roller spacing is reduced by 10-15% between passes, and the holding time is 30-60 minutes between passes. The final deformation is 78-92%.

7. The composite dispersion strengthened tungsten alloy prepared according to any one of claims 1 to 6.

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