A method for preparing a low-oxygen heterostructure tungsten-based composite material

Abstract

The application relates to a preparation method of a low-oxygen heterogeneous structure tungsten-based composite material, and relates to the technical field of tungsten-based composite material preparation. W powder, Ti powder, TiB2 powder and WC hard alloy balls are loaded into a ball mill tank for ball milling; then a two-step sintering method is adopted to prepare W-Ti-TiB2 tungsten-based composite material with high hardness and low oxygen content. The relative density of the prepared W-Ti-TiB2 tungsten-based composite material reaches 92.0% or more, and the microhardness value is 425-530 HV, which is superior to that of pure tungsten material (microhardness 360-420 HV). The oxygen content (20-80 ppm) of the prepared new heterogeneous structure W-Ti-TiB2 tungsten-based composite material is lower than that of pure tungsten (70-180 ppm) prepared by the same process and W-Ti-TiB2 tungsten-based composite material (150-380 ppm) prepared by the same process but with different powder loading sequences.

Description

Technical Field

[0001] This invention relates to the field of tungsten-based composite material preparation technology, specifically to a method for preparing a low-oxygen heterostructure tungsten-based composite material. Background Technology

[0002] Tungsten is a high-density, high-melting-point body-centered cubic metal with high hardness, strong wear resistance, and strong chemical stability, making it widely used in defense, military, and industrial production. However, studies have reported that oxygen segregation at grain boundaries reduces the binding force of tungsten grain boundaries, deteriorates its mechanical properties, and limits its applications. Pure tungsten exhibits significant brittleness at room temperature, with a ductile-brittle transition temperature (DBTT) of approximately 400℃ and a recrystallization temperature of approximately 1200℃. As a candidate material for the first plasma-facing wall of future fusion reactors, tungsten will experience irradiation embrittlement, surface spalling, and recrystallization embrittlement under these service conditions (high temperature, high flux deuterium, helium ion bombardment, etc.), thus requiring materials with a good balance of strength and toughness and a high recrystallization temperature. To develop tungsten-based composite materials with good strength-toughness synergy, researchers at home and abroad have enhanced the strength of tungsten alloys by adding alloying elements and second-phase particles, and combined this with subsequent large plastic deformation to improve the material's ductility and toughness. Large deformation leads to a significant increase in grain boundary density, and the material's plasticity shifts from dislocation-controlled plasticity to grain boundary-controlled plasticity. Therefore, researchers considered adding grain boundary cohesion enhancers to tungsten-based materials to remove oxygen, a brittle element at grain boundaries, and further improve the grain boundary bonding force of the materials.

[0003] Currently, research reports indicate that heterogeneous structural material design is an effective means to achieve a synergistic improvement in strength and toughness of metal matrix composites. The design of heterogeneous structural materials is widely applied both domestically and internationally to face-centered cubic (FCC) and hexagonal close-packed (HPC) metals, with further in-depth research on improving the strength-toughness balance of body-centered cubic (BCC) metals. In recent years, researchers have improved the ductility and fracture resistance of tungsten by adding dispersed nano-second phases and reducing grain size through mechanical ball milling. Mechanical ball milling is an effective method for designing the structure of metal matrix composites, capable of controlling the desired structure and properties, and is particularly suitable for preparing nanomaterials. However, during mechanical ball milling, powder surface oxidation causes oxygen segregation at grain boundaries during sintering, leading to performance degradation. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a low-oxygen heterostructure tungsten-based composite material. The technical problem to be solved is to prepare W-Ti-TiB2 tungsten-based composite material by optimizing the ball milling and sintering process, so as to significantly improve the hardness of the tungsten-based composite material and reduce its oxygen content.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a low-oxygen heterostructure tungsten-based composite material includes the following steps:

[0007] Step 1: Powdering

[0008] W powder, Ti powder, TiB2 powder, and WC cemented carbide balls were loaded into a ball mill jar, and then an appropriate amount of anhydrous ethanol, a process control agent, was added to the mixed powder. The ball mill jar was purged with argon and the ball milling parameters were set: the ball milling speed was 100-150 rpm and the ball milling time was 6-18 h. The slurry after ball milling was dried to obtain W-Ti-TiB2 composite powder.

[0009] Based on the mass percentage of the mixed powders, the proportion of Ti powder is 0-1.0%, the proportion of TiB2 powder is 0-1.0%, and the remainder is W powder. The proportions of Ti and TiB2 powders are not set to 0.

[0010] Step 2: Suppression

[0011] The W-Ti-TiB2 composite powder obtained in step 1 is loaded into a mold, and then the mold is placed in a tablet press. The powder is pressed under a pressure of 400-600 MPa for 3-5 minutes to obtain a W-Ti-TiB2 tungsten alloy green block.

[0012] Step 3: Pre-sintering

[0013] The W-Ti-TiB2 tungsten alloy bulk blank obtained in step 2 was placed in a tube furnace. After the furnace cavity was evacuated, hydrogen gas was introduced. Then, the temperature was increased to 1000℃ at 10℃ / min, and then increased to 1300~1400℃ at 5℃ / min and held for 0.5~2h. After the holding was completed, the temperature was reduced to room temperature at 5℃ / min to obtain a low-density W-Ti-TiB2 tungsten alloy bulk blank.

[0014] Step 4: Sintering

[0015] The low-density W-Ti-TiB2 tungsten alloy block obtained in step 3 was placed in the furnace chamber of a Joule heating device. After the furnace chamber was evacuated, argon gas was introduced. Then, the temperature was rapidly increased from room temperature to 1900℃ and held for 2 hours. The heating time was 1-3 minutes. After the holding time was completed, the furnace was cooled to room temperature to obtain the high-density W-Ti-TiB2 tungsten alloy block.

[0016] As a preferred technical solution of the present invention, in the preparation method:

[0017] The W powder used in step 1 has a particle size of 0.5 μm, the Ti powder has a particle size >300 mesh and a purity ≥99.99%, and the TiB2 powder has a particle size <15 μm and a purity ≥99.5%.

[0018] The diameter of the WC cemented carbide balls used in step 1 is 6-8 mm, and the amount added is 300-500% of the mass of the mixed powder.

[0019] The amount of anhydrous ethanol added as the process control agent in step 1 is 100-120% of the mass of the mixed powder.

[0020] In step 1, the argon gas pressure introduced into the ball mill jar is 0.01–0.02 MPa.

[0021] In step 1, the slurry after ball milling is placed in a drying oven and dried at 60-80℃ for 6-8 hours to obtain W-Ti-TiB2 composite powder.

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

[0023] 1. Mechanical ball milling makes it easier to control the material structure and prepare multi-element powders. This invention uses mechanical ball milling to obtain W-Ti-TiB2 composite powder and uses a two-step sintering method to prepare W-Ti-TiB2 tungsten-based composite material with high hardness and low oxygen content.

[0024] 2. The novel heterostructured W-Ti-TiB2 tungsten-based composite material obtained by ball milling W, Ti, and TiB2 powders simultaneously and then sintering them in two steps can be obtained. The W-Ti-TiB2 tungsten-based composite material prepared by this invention has a relative density of over 92.0% and a microhardness value of 425-530 HV, which is superior to that of pure tungsten material (microhardness 360-420 HV). The oxygen content (20-80 ppm) of the novel heterostructured W-Ti-TiB2 tungsten-based composite material prepared by this invention is lower than that of pure tungsten prepared by the same process (70-180 ppm) and W-Ti-TiB2 tungsten-based composite material prepared by different powder loading sequences under the same process (150-380 ppm). Attached Figure Description

[0025] Figure 1 The images show SEM images of the W-Ti-TiB2 tungsten-based composite powders prepared in Example 1 and Comparative Example 1. Specifically, a and b are SEM images of the W-Ti-TiB2 composite powder (Comparative Example 1) obtained by ball milling Ti powder and TiB2 powder first, and then ball milling them together with W powder, at different magnifications; c and d are SEM images of the W-Ti-TiB2 composite powder (Example 1) obtained by ball milling W powder, Ti powder, and TiB2 powder simultaneously, at different magnifications.

[0026] Figure 2 The image shows the metallographic structure of the W-Ti-TiB2 tungsten-based composite material obtained after sintering in Example 1. Wherein, a, b, c, and d represent magnifications of 50x, 100x, 200x, and 1000x, respectively.

[0027] Figure 3 The image shows the fracture surface SEM image of the W-Ti-TiB2 tungsten-based composite material obtained after sintering in Example 1. Detailed Implementation

[0028] The preparation method of the low-oxygen heterostructure tungsten-based composite material of the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0029] Example 1:

[0030] The preparation method of the low oxygen content W-Ti-TiB2 tungsten-based composite material in this embodiment, wherein the ratio of W, Ti and TiB2 powder is 0.5% by mass of both Ti and TiB2 powder, with the remainder being W powder, includes the following steps:

[0031] 1. Powder preparation: W powder (0.5μm), Ti powder (>300 mesh, Aladdin, purity ≥99.99%), TiB2 powder (<15μm, Aladdin, purity ≥99.5%), and 7mm WC cemented carbide balls are simultaneously loaded into a ball mill jar. The WC cemented carbide balls account for 500% of the mass of the mixed powder. Then, an appropriate amount of anhydrous ethanol (C2H5OH, molecular weight 46.07) is added to the mixed powder as a process control agent, with the amount of anhydrous ethanol added being 120% of the mass of the mixed powder. The ball mill jar is then purged with argon at a pressure of 0.02MPa. The ball milling parameters are then set for ball milling (milling speed 150rpm, milling time 6h). The slurry after ball milling is placed in a drying oven and dried at 75℃ for 6h to obtain W-Ti-TiB2 composite powder.

[0032] 2. Pressing: Weigh 10g of the W-Ti-TiB2 composite powder obtained in step 1, put it into a mold with a diameter of 20mm, and then place the mold in a tablet press. Press the powder under a pressure of 500MPa for 3min30s to obtain the W-Ti-TiB2 tungsten alloy green block.

[0033] 3. Pre-sintering: The W-Ti-TiB2 tungsten alloy green billet obtained in step 2 is placed in a tube furnace. After the sintering furnace is evacuated, hydrogen gas is introduced. Then, the temperature is increased to 1000℃ at 10℃ / min, and then increased to 1300℃ at 5℃ / min and held for 2 hours. After the holding period, the temperature is decreased to room temperature at 5℃ / min to obtain a low-density W-Ti-TiB2 tungsten alloy block.

[0034] 4. Sintering: The low-density W-Ti-TiB2 tungsten alloy block obtained in step 3 is placed in the furnace chamber of the Joule heating equipment. After the furnace chamber is evacuated, argon gas is introduced. Then, the temperature is rapidly increased from room temperature to 1900℃ and held for 2 hours. The heating time is 3 minutes. After the holding time is completed, the furnace is cooled to room temperature to obtain the high-density W-Ti-TiB2 tungsten alloy block.

[0035] Comparative Example 1

[0036] The only difference between this comparative example and Example 1 is that Ti powder and TiB2 powder are ball-milled first, and then ball-milled with W powder. The ball milling process, as well as the pressing and sintering process, are exactly the same as in Example 1.

[0037] pass Figure 1 It can be seen that different ball milling mixing sequences can yield composite powders with different morphologies. Separate ball milling and mixing leads to agglomeration, which affects the diffusion of components during subsequent sintering and does not result in heterogeneous structures. Figure 2 , 3 As can be seen, a novel heterostructured W-Ti-TiB2 tungsten-based composite material can be obtained through the method of this invention. Metallographic and scanning electron microscopy revealed that the second phase is unevenly distributed in the tungsten matrix as slender rods. The main reason for the increased hardness of the heterostructured W-Ti-TiB2 tungsten-based composite material in this invention is the dominance of heterogeneous deformation-induced hardening (HDI).

[0038] The composite material sintered in this embodiment exhibits a novel heterogeneous structure (short fibrous distribution), which stabilizes the brittle element oxygen at the tungsten grain boundaries and reduces the dissolved oxygen content in the matrix material. The oxygen content is 30.8 ppm, lower than that of pure tungsten prepared using the same process (i.e., without adding Ti powder and TiB2 powder during ball milling, otherwise consistent with the example, the same below) (130.3 ppm) and the W-Ti-TiB2 tungsten-based composite material prepared using the same process but with a different powder loading order in Comparative Example 1 (166.7 ppm). The added second phase effectively hinders the growth of tungsten grains during sintering, thereby improving hardness. The hardness value is 450±8 HV, superior to that of pure tungsten material (microhardness 360~420 HV).

[0039] Example 2:

[0040] The preparation method of the low oxygen content W-Ti-TiB2 tungsten-based composite material in this embodiment, wherein the ratio of W, Ti and TiB2 powder is 1.0% by mass of both Ti and TiB2 powder, with the remainder being W powder, includes the following steps:

[0041] 1. Powder preparation: W powder (0.5μm), Ti powder (>300 mesh, Aladdin, purity ≥99.99%), TiB2 powder (<15μm, Aladdin, purity ≥99.5%), and 7mm WC cemented carbide balls are simultaneously loaded into a ball mill jar. The WC cemented carbide balls account for 500% of the mass of the mixed powder. Then, an appropriate amount of anhydrous ethanol (C2H5OH, molecular weight 46.07) is added to the mixed powder as a process control agent, with the amount of anhydrous ethanol added being 100% of the mass of the mixed powder. The ball mill jar is then purged with argon at a pressure of 0.02MPa. The ball milling parameters are then set for ball milling (milling speed 150rpm, milling time 6h). The slurry after ball milling is placed in a drying oven and dried at 75℃ for 6h to obtain W-Ti-TiB2 composite powder.

[0042] 2. Pressing: Weigh 10g of the W-Ti-TiB2 composite powder obtained in step 1, put it into a mold with a diameter of 20mm, and then place the mold in a tablet press. Press the powder under a pressure of 600MPa for 3min to obtain the W-Ti-TiB2 tungsten alloy green block.

[0043] 3. Pre-sintering: The W-Ti-TiB2 tungsten alloy green billet obtained in step 2 is placed in a tube furnace. After the sintering furnace is evacuated, hydrogen gas is introduced. Then, the temperature is increased to 1000℃ at 10℃ / min, and then increased to 1350℃ at 5℃ / min and held for 1.5h. After the holding period, the temperature is reduced to room temperature at 5℃ / min to obtain a low-density W-Ti-TiB2 tungsten alloy block.

[0044] 4. Sintering: The low-density W-Ti-TiB2 tungsten alloy block obtained in step 3 is placed in the furnace chamber of the Joule heating equipment. After the furnace chamber is evacuated, argon gas is introduced. Then, the temperature is rapidly increased from room temperature to 1900℃ and held for 2 hours. The heating time is 3 minutes. After the holding time is completed, the furnace is cooled to room temperature to obtain the high-density W-Ti-TiB2 tungsten alloy block.

[0045] The composite material sintered in this embodiment exhibits a novel heterogeneous structure (short fibrous distribution), which stabilizes the brittle element oxygen at the tungsten grain boundaries and reduces the dissolved oxygen content in the matrix material to 55.9 ppm, lower than that of pure tungsten prepared using the same process (130.3 ppm) and W-Ti-TiB2 tungsten-based composite material prepared using the same process but with different powder loading sequences (259.9 ppm). The added second phase effectively hinders the growth of tungsten grains during sintering, thereby improving hardness to 480 ± 2 HV, superior to that of pure tungsten material (microhardness 360–420 HV).

[0046] Example 3:

[0047] The preparation method of the low oxygen content W-Ti-TiB2 tungsten-based composite material in this embodiment, wherein the ratio of W, Ti and TiB2 powder is 2.5% by mass of both Ti and TiB2 powder, with the remainder being W powder, includes the following steps:

[0048] 1. Powder preparation: W powder (0.5μm), Ti powder (>300 mesh, Aladdin, purity ≥99.99%), TiB2 powder (<15μm, Aladdin, purity ≥99.5%), and 8mm WC cemented carbide balls are simultaneously loaded into a ball mill jar. The WC cemented carbide balls account for 400% of the mass of the mixed powder. Then, an appropriate amount of anhydrous ethanol (C2H5OH, molecular weight 46.07) is added to the mixed powder as a process control agent, with the amount of anhydrous ethanol added being 120% of the mass of the mixed powder. The ball mill jar is then purged with argon at a pressure of 0.01MPa. The ball milling parameters are then set for ball milling (milling speed 150rpm, milling time 6h). The slurry after ball milling is placed in a drying oven and dried at 75℃ for 6h to obtain W-Ti-TiB2 composite powder.

[0049] 2. Pressing: Weigh 10g of the W-Ti-TiB2 composite powder obtained in step 1, put it into a mold with a diameter of 20mm, and then place the mold in a tablet press. Press the powder under a pressure of 600MPa for 3min30s to obtain the W-Ti-TiB2 tungsten alloy green block.

[0050] 3. Pre-sintering: The W-Ti-TiB2 tungsten alloy green billet obtained in step 2 is placed in a tube furnace. After the sintering furnace is evacuated, hydrogen gas is introduced. Then, the temperature is increased to 1000℃ at 10℃ / min, and then increased to 1400℃ at 5℃ / min and held for 1 hour. After the holding period, the temperature is decreased to room temperature at 5℃ / min to obtain a low-density W-Ti-TiB2 tungsten alloy block.

[0051] 4. Sintering: The low-density W-Ti-TiB2 tungsten alloy block obtained in step 3 is placed in the furnace chamber of the Joule heating equipment. After the furnace chamber is evacuated, argon gas is introduced. Then, the temperature is rapidly increased from room temperature to 1900℃ and held for 2 hours. The heating time is 3 minutes. After the holding time is completed, the furnace is cooled to room temperature to obtain the high-density W-Ti-TiB2 tungsten alloy block.

[0052] The composite material sintered in this embodiment exhibits a novel heterogeneous structure (short fibrous distribution), which stabilizes the brittle element oxygen at the tungsten grain boundaries and reduces the dissolved oxygen content in the matrix material to 77.8 ppm, lower than that of pure tungsten prepared using the same process (130.3 ppm) and W-Ti-TiB2 tungsten-based composite material prepared using the same process but with different powder loading sequences (322.6 ppm). The added second phase effectively hinders the growth of tungsten grains during sintering, thereby improving hardness to 510 ± 5 HV, superior to that of pure tungsten material (microhardness 360–420 HV).

[0053] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a low-oxygen heterostructure tungsten-based composite material, characterized in that, Includes the following steps: Step 1: Powdering W powder, Ti powder, TiB2 powder, and WC cemented carbide balls were loaded into a ball mill jar, and then an appropriate amount of anhydrous ethanol, a process control agent, was added to the mixed powder. The ball mill jar was purged with argon and the ball milling parameters were set: the ball milling speed was 100-150 rpm and the ball milling time was 6-18 h. The slurry after ball milling was dried to obtain W-Ti-TiB2 composite powder. Based on the mass percentage of the mixed powders, the proportion of Ti powder is 0-1.0%, the proportion of TiB2 powder is 0-1.0%, and the remainder is W powder. The proportions of Ti and TiB2 powders are not set to 0. Step 2: Suppression The W-Ti-TiB2 composite powder obtained in step 1 is loaded into a mold, and then the mold is placed in a tablet press. The powder is pressed under a pressure of 400-600 MPa for 3-5 minutes to obtain a W-Ti-TiB2 tungsten alloy green block. Step 3: Pre-sintering The W-Ti-TiB2 tungsten alloy bulk blank obtained in step 2 was placed in a tube furnace. After the furnace cavity was evacuated, hydrogen gas was introduced. Then, the temperature was increased to 1000℃ at 10℃ / min, and then increased to 1300~1400℃ at 5℃ / min and held for 0.5~2h. After the holding was completed, the temperature was reduced to room temperature at 5℃ / min to obtain a low-density W-Ti-TiB2 tungsten alloy bulk blank. Step 4: Sintering The low-density W-Ti-TiB2 tungsten alloy block obtained in step 3 was placed in the furnace chamber of a Joule heating device. After the furnace chamber was evacuated, argon gas was introduced. Then, the temperature was rapidly increased from room temperature to 1900℃ and held for 2 hours. The heating time was 1-3 minutes. After the holding time was completed, the furnace was cooled to room temperature to obtain the high-density W-Ti-TiB2 tungsten alloy block.

2. The preparation method according to claim 1, characterized in that, The W powder used in step 1 has a particle size of 0.5 μm, the Ti powder has a particle size >300 mesh and a purity ≥99.99%, and the TiB2 powder has a particle size <15 μm and a purity ≥99.5%.

3. The preparation method according to claim 1, characterized in that, The diameter of the WC cemented carbide balls used in step 1 is 6-8 mm, and the amount added is 300-500% of the mass of the mixed powder.

4. The preparation method according to claim 1, characterized in that, The amount of anhydrous ethanol added as the process control agent in step 1 is 100-120% of the mass of the mixed powder.

5. The preparation method according to claim 1, characterized in that, In step 1, the argon gas pressure introduced into the ball mill jar is 0.01–0.02 MPa.

6. The preparation method according to claim 1, characterized in that, In step 1, the slurry after ball milling is placed in a drying oven and dried at 60-80℃ for 6-8 hours to obtain W-Ti-TiB2 composite powder.

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