Harmonic structure Mo-Si-B alloy and preparation method thereof

Abstract

According to the Mo-Si-B alloy with the harmonic structure and the preparation method of the Mo-Si-B alloy with the harmonic structure, the distribution state, the volume fraction and the grain size of all phases of the Mo-Si-B alloy can be accurately controlled through the method, and units with the large size, the medium size and the small size are distributed in a harmonic structure characteristic mode; further, good effects of back stress strengthening, crack passivation and the like are generated by utilizing a multi-stage size unit structure, so that the obdurability of the alloy is improved, meanwhile, a passivation layer is assisted to quickly grow at a high temperature, and the excellent high-temperature oxidation resistance of the alloy is kept. The strength, toughness and oxidation resistance of the alloy can be synergistically improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder metallurgy, and in particular relates to a harmonic structure Mo-Si-B alloy. The present invention also relates to a preparation method of the harmonic structure Mo-Si-B alloy. Background Art

[0002] As core strategic materials in key sectors such as aviation, aerospace, petrochemicals, and energy, the development of superalloys plays a crucial role in modern industrial and technological progress. As aircraft engines evolve toward higher thrust-to-weight ratios, higher flow rates, and higher inlet temperatures, combustion chamber temperatures and pressures continue to rise, necessitating the development of new structural materials capable of stable service above 1200°C. Mo-Si-B alloy, with its high melting point near 2000°C and excellent high-temperature creep and oxidation resistance, has become a key candidate for the next generation of superalloys.

[0003] Among Mo-Si-B alloys, those composed of three phases, α-Mo, Mo₃Si, and Mo₅SiB₂, exhibit excellent overall properties. Their microstructure is characterized by dispersed Mo₃Si and Mo₅SiB₂ particles within a continuous α-Mo matrix. However, the alloy's low room-temperature fracture toughness limits its widespread application. In this system, while the metallic α-Mo phase possesses relatively good ductility and toughness, it suffers from insufficient high-temperature oxidation resistance and readily oxidizes to volatile MoO₃ in air above 700°C. Meanwhile, Mo₃Si and Mo₅SiB₂, while exhibiting lower room-temperature toughness, possess excellent high-temperature strength and creep resistance. Furthermore, they can oxidize at high temperatures to form a borosilicate glass phase with oxidation resistance and self-healing properties. This discrepancy in properties leads to a key contradiction: increasing the volume fraction of the α-Mo phase to improve the alloy's room-temperature toughness results in a significant decrease in oxidation resistance. This contradiction has become a focus of research for both domestic and international researchers.

[0004] Research has shown that the size and distribution of the α-Mo phase significantly influence the mechanical properties of Mo-Si-B alloys. For example, when α-Mo forms a continuous, micron-sized structure, it can better exert toughening effects such as crack capture and crack bridging, thereby improving the alloy's fracture toughness. Conversely, when α-Mo forms a continuous, fine, submicron / nanoscale structure, it can better exert its grain refinement strengthening effect, enhancing the alloy's strength. Similarly, when the intermetallic compounds Mo3Si and Mo5SiB2 form micron-sized coarse grains, they exhibit excellent stability at high temperatures and enhance the alloy's high-temperature strength and creep resistance. When they form a dispersed, submicron / nanoscale, fine-grained structure, they rapidly form a continuous borosilicate glass layer at high temperatures, improving the alloy's oxidation resistance.

[0005] Ameyama et al. proposed a dual-scale structural design approach, consisting of numerous evenly dispersed independent core-shell structural units. Each core-shell unit exhibits a characteristic microstructure characterized by a submicron / nanoscale fine grain structure (the "shell") encapsulating a micron-scale coarse grain (the "core"). Due to the uniform distribution of the tiny core-shell structural units, the material exhibits isotropic properties and excellent stability. In particular, it can significantly improve the coordination of coarse and fine grain deformation, achieving a strengthening and toughening effect. Therefore, developing a multi-level, multi-scale structural design for multiphase Mo-Si-B alloys is expected to simultaneously achieve excellent mechanical properties and oxidation resistance, accelerating the industrialization and application of the alloy. Summary of the Invention

[0006] The purpose of the present invention is to provide a harmonic structure Mo-Si-B alloy, which can synergistically improve the strength, toughness and oxidation resistance of the alloy.

[0007] Another object of the present invention is to provide a method for preparing a harmonic structure Mo-Si-B alloy. This method can accurately control the distribution state, volume fraction and grain size of each phase of the Mo-Si-B alloy, so that large, medium and small size units are distributed in a harmonic structure characteristic. The multi-level size unit structure is then used to produce good effects such as back stress strengthening and crack passivation to improve the strength and toughness of the alloy, while helping the passivation layer to grow rapidly at high temperatures, thereby maintaining the alloy's excellent high-temperature oxidation resistance.

[0008] The first technical solution adopted by the present invention is that the harmonic structure Mo-Si-B alloy includes large, medium and small size units composed of three phases of α-Mo, Mo3Si and Mo5SiB2. Each unit includes 10-15% large size units, 15-30% medium size units, and 55-75% small size units in terms of volume fraction; the large size and medium size units are evenly distributed in a large number of continuous small size units, and in each size unit, each phase includes 40-70% α-Mo, 15-30% Mo3Si, and 15-35% Mo5SiB2 in terms of volume fraction.

[0009] The first technical solution of the present invention is also characterized in that: The large-size unit size is 20-30μm, the medium-size unit size is 10-15μm, and the small-size unit size is ≤5μm. In each unit, the α-Mo phase grain size is 2-5μm, the Mo3Si phase particle size is 0.5-2μm, and the Mo5SiB2 phase particle size is 0.5-2μm.

[0010] The second technical solution adopted by the present invention is a method for preparing a harmonic structure Mo-Si-B alloy, which is specifically implemented according to the following steps: Step 1. Weigh the raw materials, and weigh 93%-97% of molybdenum powder, 2.5%-4.8% of silicon powder, and 0.5%-2.2% of boron powder according to mass fraction, with the total mass of the above components being 100%; Step 2: ball-milling the molybdenum powder, silicon powder and boron powder weighed in step 1 to obtain a mixed powder, and then mechanically alloying the mixed powder; Step 3, pressing the powder mechanically alloyed in step 2 into a cylindrical compact; Step 4, calcining the compact obtained in step 3; Step 5: polish the surface of the blank calcined in step 4 and then perform arc melting; Step 6: polishing the surface of the smelted alloy ingot obtained in step 5, performing ultrasonic cleaning, and crushing it into powder; Step 7: The powder crushed in step 6 is subjected to multi-stage screening to obtain powders of various particle sizes; Step 8: Select coarse, medium, and fine powders from the various particle sizes obtained in step 7, and weigh them according to the following mass fractions: 10-15% coarse powder, 15-30% medium powder, and 55-75% fine powder, and then ball mill and mix them; Step 9: hot-pressing and sintering the mixed powder obtained in step 8 to obtain a harmonic structure Mo-Si-B alloy.

[0011] The second technical solution of the present invention is also characterized in that: In step 1, the purity of molybdenum powder is ≥99.9%, the particle size of molybdenum powder is ≤6.5μm, the purity of silicon powder is ≥99.99%, the particle size of silicon powder is <50μm; the purity of boron powder is ≥99.9%, the particle size of boron powder is <50μm; In the ball milling mixing process in step 2, a ball mill made of either agate or polyurethane is used, and the grinding balls used are made of agate or zirconia. An argon atmosphere is introduced into the ball mill, and the air pressure is 0.3MPa-0.6MPa. During mixing, the ball-to-material ratio is 1-2:1, the ball mill speed is 300-400r / min, and the ball milling time is 6-8h. In the mechanical alloying process, the ball mill and the grinding balls used are both made of tungsten carbide to achieve a multi-element alloying effect. The ball milling time is 10-15h, the ball-to-material ratio is 5-10:1, the ball mill speed is 180r / min-250r / min, and an argon atmosphere is introduced into the ball mill, and the air pressure is 0.3MPa-0.6MPa.

[0012] The pressure during the powder pressing process in step 3 is 25 MPa to 37 MPa; The calcination in step 4 adopts a two-step heating method: the first step is to heat up to 1200-1400℃ at 8-10℃ / min and keep warm for 0.5-1h; the second step is to heat up to 1400-1600℃ at 8-10℃ / min and keep warm for 2-3h. The vacuum degree during the calcination process is ≤8×10 - 3 Pa.

[0013] The arc current during arc melting in step 5 is 800-900A, and high-purity argon is introduced as a protective gas. After each melting is completed, the sample is turned over and melted again, and a total of 6-8 melting times are performed.

[0014] In step 6, the ultrasonic cleaning time is 10-30 minutes, and the cleaning medium is anhydrous ethanol; the crushing process adopts two-step crushing: the first step uses a sealed jaw crusher and a roller crusher to crush, respectively, to obtain particles with a particle size of ≤3 mm; the second step uses ball milling, and the ball mill and grinding balls are both made of tungsten carbide, the ball-to-material ratio is 5-10:1, the rotation speed is 150r / min-220r / min, the crushing time is 6-10h, and an argon atmosphere is introduced into the ball mill with an air pressure of 0.3MPa-0.6MPa.

[0015] In step 7, the multi-stage screening process uses a vibrating screening machine equipped with an ultrasonic generator. The matching screens include 400 mesh, 600 mesh, 800 mesh, and 1000 mesh specifications. The screens are stacked from top to bottom in the order of 400 mesh, 600 mesh, 800 mesh, and 1000 mesh. The crushed powder is poured into the screen from the top. When the powder can pass through the 400 mesh but not the 600 mesh screen, the particle size D is screened out. 50 For powders of 20-30 μm, if they can pass through 600 mesh but not 800 mesh, the particle size D 50 When the powder of 15-20μm can pass through 800 mesh but not 1000 mesh, the particle size D 50 When the powder is 10-15μm and can pass through a 1000-mesh sieve, the particle size D 50 For powders of 3-5 μm, the total sieving time is 10-30 min.

[0016] In step 8, the particle size of the coarse powder is 20-30 μm, the particle size of the medium powder is 10-15 μm, and the particle size of the fine powder is 3-5 μm; during the ball milling mixing process, a ball mill jar made of either agate or polyurethane is used, the grinding balls are made of either agate or zirconia, an argon atmosphere is introduced into the ball mill jar, the air pressure is 0.3 MPa-0.6 MPa, during mixing, the ball-to-material ratio is 1-2:1, the ball mill speed is 300-400 r / min, and the ball milling time is 6-8 h.

[0017] During the hot pressing sintering in step 9, the powder is placed in a graphite mold for hot pressing sintering. The sintering process is as follows: first, the temperature is raised to 1200-1400°C at a rate of 8-10°C / min and kept at this temperature for 0.5-1h. After keeping this temperature for 0.5-1h, the pressure is applied to 38-60MPa. Then, the temperature is raised to 1600-1800°C at a rate of 8-10°C / min and kept at this temperature for 2-3h. After reaching 1600-1800°C, the pressure is maintained. During the sintering process, the vacuum degree is maintained at 6×10 -3 Pa to 1.5×10 -2 Between Pa.

[0018] The beneficial effect of the present invention is that the harmonic structure Mo-Si-B alloy contains large, medium and small size units all composed of α-Mo, Mo3Si and Mo5SiB2 three phases, and the large size and medium size units are dispersed in a continuous number of small size units. Such a harmonic structure characteristic organization composed of multi-level size units will give play to the advantages of each size unit: on the one hand, the multi-level unit coordinated deformation produces significant back stress strengthening, and on the other hand, the large size and medium size units passivate and bridge the cracks, thereby making the alloy synergistically improve strength and toughness. In addition, the characteristic organization of Mo3Si and Mo5SiB2 dispersed in the α-Mo matrix in each size unit will cause Mo3Si and Mo5SiB2 to be rapidly oxidized at high temperature to form a borosilicate glass phase, shorten the flow healing time, and ensure the alloy's good high temperature oxidation resistance. Such an organizational design can provide new ideas and technical support for the preparation of high-performance refractory metals and alloys based on powder metallurgy. Compared to methods for preparing heterogeneous structures using large plastic deformation, electrodeposition, thermal processing, and heat treatment, the present invention utilizes a composite process of mechanical alloying, smelting, crushing, screening, and powder sintering to precisely control the composition, volume fraction, and distribution of the multi-level units in the alloy, as well as the grain size, volume fraction, and distribution within each unit. This results in a harmonic structural structure with topological distribution characteristics, enabling multi-level controllable design of the alloy's microstructure and properties, avoiding problems such as segregation, unevenness, and high oxygen impurity content. The present method is easy to operate, low-cost, and requires minimal equipment, making it easy to implement on an industrial scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The preparation flow chart of harmonic structure Mo-Si-B alloy.

[0020] Figure 2 This is the X-ray diffraction pattern of the harmonic structure Mo-Si-B alloy prepared in Example 9.

[0021] Figure 3 This is a scanning electron microscope photograph of the harmonic structure Mo-Si-B alloy prepared in Example 9. DETAILED DESCRIPTION

[0022] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] The harmonic structure Mo-Si-B alloy of the present invention includes large, medium and small size units composed of three phases of α-Mo, Mo3Si and Mo5SiB2. Each unit includes 10-15% of large size units, 15-30% of medium size units and 55-75% of small size units in terms of volume fraction. The large size and medium size units are evenly distributed in a plurality of continuous small size units. In each size unit, each phase includes 40-70% of α-Mo, 15-30% of Mo3Si and 15-35% of Mo5SiB2 in terms of volume fraction.

[0024] The large-size unit size is 20-30μm, the medium-size unit size is 10-15μm, and the small-size unit size is ≤5μm. In each unit, the α-Mo phase grain size is 2-5μm, the Mo3Si phase particle size is 0.5-2μm, and the Mo5SiB2 phase particle size is 0.5-2μm.

[0025] The preparation method of the harmonic structure Mo-Si-B alloy of the present invention is as follows: Figure 1 As shown, please follow the steps below: Step 1. Weigh the raw materials, and weigh 93%-97% of molybdenum powder, 2.5%-4.8% of silicon powder, and 0.5%-2.2% of boron powder according to mass fraction, with the total mass of the above components being 100%; The purity of the molybdenum powder in step 1 is ≥99.9%, and the particle size of the molybdenum powder is ≤6.5 μm; the purity of the silicon powder is ≥99.99%, and the particle size of the silicon powder is <50 μm; the purity of the boron powder is ≥99.9%, and the particle size of the boron powder is <50 μm; Step 2: Place the molybdenum powder, silicon powder and boron powder weighed in step 1 into a planetary ball mill and mix them to obtain a mixed powder, and then mechanically alloy the mixed powder; In the ball milling mixing process in step 2, a ball mill made of either agate or polyurethane is used, and the grinding balls used are made of agate or zirconia. An argon atmosphere is introduced into the ball mill, and the air pressure is 0.3MPa-0.6MPa. During mixing, the ball-to-material ratio is 1-2:1, the ball mill speed is 300-400r / min, and the ball milling time is 6-8h. In the mechanical alloying process, the ball mill and the grinding balls used are both made of tungsten carbide to achieve a multi-element alloying effect. The ball milling time is 10-15h, the ball-to-material ratio is 5-10:1, the ball mill speed is 180r / min-250r / min, and an argon atmosphere is introduced into the ball mill, and the air pressure is 0.3MPa-0.6MPa.

[0026] Step 3: Place the powder mechanically alloyed in step 2 into a tableting die with a diameter of 30-40 mm and press it into a cylindrical green compact; The pressure during the powder pressing process in step 3 is 25 MPa to 37 MPa; The calcination in step 4 adopts a two-step heating method: the first step is to heat up to 1200-1400℃ at 8-10℃ / min and keep warm for 0.5-1h; the second step is to heat up to 1400-1600℃ at 8-10℃ / min and keep warm for 2-3h. The vacuum degree during the calcination process is ≤8×10 - 3 Pa.

[0027] Step 4: placing the compact obtained in step 3 into a vacuum resistance furnace for calcination; Step 5: polish the surface of the blank calcined in step 4 and then perform arc melting; The arc current during arc melting in step 5 is 800-900A, and high-purity argon is introduced as a protective gas. After each melting is completed, the sample is turned over and melted again, and a total of 6-8 melting times are performed.

[0028] Step 6: polishing the surface of the smelted alloy ingot obtained in step 5, performing ultrasonic cleaning, and crushing it into powder; In step 6, the ultrasonic cleaning time is 10-30 minutes, and the cleaning medium is anhydrous ethanol. The crushing process adopts two-step crushing: the first step uses a sealed jaw crusher and a roller crusher to crush, respectively, to obtain particles with a particle size of ≤3 mm; the second step uses ball milling, and the ball mill and grinding balls are both made of tungsten carbide, the ball-to-material ratio is 5-10:1, the rotation speed is 150r / min-220r / min, the crushing time is 6-10h, and an argon atmosphere is introduced into the ball mill with an air pressure of 0.3MPa-0.6MPa.

[0029] Step 7: The powder crushed in step 6 is subjected to multi-stage screening to obtain powders of various particle sizes; In step 7, the multi-stage screening process uses a vibrating screening machine equipped with an ultrasonic generator. The matching screens include 400 mesh, 600 mesh, 800 mesh, and 1000 mesh specifications. The screens are stacked from top to bottom in the order of 400 mesh, 600 mesh, 800 mesh, and 1000 mesh. The crushed powder is poured into the screen from the top. When the powder can pass through the 400 mesh but not the 600 mesh screen, the particle size D is screened out. 50 For powders of 20-30 μm, if they can pass through 600 mesh but not 800 mesh, the particle size D 50 When the powder of 15-20μm can pass through 800 mesh but not 1000 mesh, the particle size D 50 When the powder is 10-15μm and can pass through a 1000-mesh sieve, the particle size D 50For powders of 3-5 μm, the total sieving time is 10-30 min.

[0030] Step 8: Select coarse, medium, and fine powders from the various particle sizes obtained in step 7, and weigh them according to the following mass fractions: 10-15% coarse powder, 15-30% medium powder, and 55-75% fine powder, and then ball mill and mix them; In step 8, the particle size of the coarse powder is 20-30 μm, the particle size of the medium powder is 10-15 μm, and the particle size of the fine powder is 3-5 μm; during the ball milling mixing process, a ball mill jar made of either agate or polyurethane is used, the grinding balls are made of either agate or zirconia, an argon atmosphere is introduced into the ball mill jar, the air pressure is 0.3 MPa-0.6 MPa, during mixing, the ball-to-material ratio is 1-2:1, the ball mill speed is 300-400 r / min, and the ball milling time is 6-8 h.

[0031] Step 9: hot-pressing and sintering the mixed powder obtained in step 8 to obtain a harmonic structure Mo-Si-B alloy.

[0032] During the hot pressing sintering in step 9, the powder is placed in a graphite mold for hot pressing sintering. The sintering process is as follows: first, the temperature is raised to 1200-1400°C at a rate of 8-10°C / min and kept at this temperature for 0.5-1h. After keeping this temperature for 0.5-1h, the pressure is applied to 38-60MPa. Then, the temperature is raised to 1600-1800°C at a rate of 8-10°C / min and kept at this temperature for 2-3h. After reaching 1600-1800°C, the pressure is maintained. During the sintering process, the vacuum degree is maintained at 6×10 -3 Pa to 1.5×10 -2 Between Pa.

[0033] Example 1 The harmonic structure Mo-Si-B alloy of the present invention includes large, medium and small size units composed of three phases of α-Mo, Mo3Si and Mo5SiB2. Each unit includes 10-15% of large size units, 15-30% of medium size units and 55-75% of small size units in terms of volume fraction. The large size and medium size units are evenly distributed in a plurality of continuous small size units. In each size unit, each phase includes 40-70% of α-Mo, 15-30% of Mo3Si and 15-35% of Mo5SiB2 in terms of volume fraction.

[0034] Example 2 The harmonic structure Mo-Si-B alloy of the present invention includes large, medium and small size units composed of three phases of α-Mo, Mo3Si and Mo5SiB2. Each unit includes 10% large size units, 15% medium size units and 75% small size units in terms of volume fraction. The large size and medium size units are evenly distributed in a plurality of continuous small size units. In each size unit, each phase includes 70% α-Mo, 15% Mo3Si and 15% Mo5SiB2 in terms of volume fraction.

[0035] The large-size unit is 20μm, the medium-size unit is 15μm, and the small-size unit is ≤5μm. In each unit, the α-Mo phase grain size is 5μm, the Mo3Si phase particle size is 2μm, and the Mo5SiB2 phase particle size is 2μm.

[0036] Example 3 The harmonic structure Mo-Si-B alloy of the present invention includes large, medium and small size units composed of three phases of α-Mo, Mo3Si and Mo5SiB2. Each unit includes 15% large size units, 30% medium size units and 55% small size units in terms of volume fraction. The large size and medium size units are evenly distributed in a plurality of continuous small size units. In each size unit, each phase includes 40% α-Mo, 30% Mo3Si and 30% Mo5SiB2 in terms of volume fraction.

[0037] The large-size unit is 30μm, the medium-size unit is 10μm, and the small-size unit is ≤5μm. In each unit, the α-Mo phase grain size is 5μm, the Mo3Si phase particle size is 0.5μm, and the Mo5SiB2 phase particle size is 0.5μm.

[0038] Example 4 The harmonic structure Mo-Si-B alloy of the present invention includes large, medium and small size units composed of three phases of α-Mo, Mo3Si and Mo5SiB2. Each unit includes 15% large size units, 20% medium size units and 65% small size units in terms of volume fraction. The large size and medium size units are evenly distributed in a plurality of continuous small size units. In each size unit, each phase includes 50% α-Mo, 20% Mo3Si and 30% Mo5SiB2 in terms of volume fraction.

[0039] The large-size unit is 25μm, the medium-size unit is 12μm, and the small-size unit is ≤5μm. In each unit, the α-Mo phase grain size is 3μm, the Mo3Si phase particle size is 1.5μm, and the Mo5SiB2 phase particle size is 1.5μm.

[0040] Example 5 The preparation method of the harmonic structure Mo-Si-B alloy of the present invention is as follows: Figure 3 As shown, please follow the steps below: Step 1. Weigh the raw materials, and weigh 93%-97% of molybdenum powder, 2.5%-4.8% of silicon powder, and 0.5%-2.2% of boron powder according to mass fraction, with the total mass of the above components being 100%; Step 2: Place the molybdenum powder, silicon powder and boron powder weighed in step 1 into a planetary ball mill and mix them to obtain a mixed powder, and then mechanically alloy the mixed powder; Step 3: Place the powder mechanically alloyed in step 2 into a tableting die with a diameter of 30-40 mm and press it into a cylindrical green compact; Step 4: placing the compact obtained in step 3 into a vacuum resistance furnace for calcination; Step 5: polish the surface of the blank calcined in step 4 and then perform arc melting; Step 6: polishing the surface of the smelted alloy ingot obtained in step 5, performing ultrasonic cleaning, and crushing it into powder; Step 7: The powder crushed in step 6 is subjected to multi-stage screening to obtain powders of various particle sizes; Step 8: Select coarse, medium, and fine powders from the various particle sizes obtained in step 7, and weigh them according to the following mass fractions: 10-15% coarse powder, 15-30% medium powder, and 55-75% fine powder, and then ball mill and mix them; Step 9: hot-pressing and sintering the mixed powder obtained in step 8 to obtain a harmonic structure Mo-Si-B alloy.

[0041] Example 6 The preparation method of the harmonic structure Mo-Si-B alloy of the present invention is as follows: Figure 3 As shown, please follow the steps below: Step 1: Weigh the raw materials, and weigh 97% molybdenum powder, 2.5% silicon powder, and 0.5% boron powder according to the mass fraction, and the total mass of the above components is 100%; The purity of the molybdenum powder in step 1 is ≥99.9%, and the particle size of the molybdenum powder is ≤6.5 μm; the purity of the silicon powder is ≥99.99%, and the particle size of the silicon powder is <50 μm; the purity of the boron powder is ≥99.9%, and the particle size of the boron powder is <50 μm; Step 2: Place the molybdenum powder, silicon powder and boron powder weighed in step 1 into a planetary ball mill and mix them to obtain a mixed powder, and then mechanically alloy the mixed powder; In the ball milling mixing process in step 2, a ball mill made of either agate or polyurethane is used, and the grinding balls used are made of agate or zirconia. An argon atmosphere is introduced into the ball mill at a pressure of 0.3 MPa. During mixing, the ball-to-material ratio is 1:1, the ball mill speed is 300 r / min, and the ball milling time is 6 h. In the mechanical alloying process, the ball mill and grinding balls used are both made of tungsten carbide to achieve a multi-element alloying effect. The ball milling time is 10 h, the ball-to-material ratio is 5:1, the ball mill speed is 250 r / min, and an argon atmosphere is introduced into the ball mill at a pressure of 0.6 MPa.

[0042] Step 3: Place the powder mechanically alloyed in step 2 into a φ30 mm tableting die and press it into a cylindrical green compact; The pressure during the powder pressing process in step 3 is 37 MPa; The calcination in step 4 adopts a two-step heating method: the first step is to heat up to 1400℃ at 10℃ / min and keep it for 0.5h; the second step is to heat up to 1600℃ at 8℃ / min and keep it for 2h. The vacuum degree during the calcination process is ≤8×10 -3 Pa.

[0043] Step 4: placing the compact obtained in step 3 into a vacuum resistance furnace for calcination; Step 5: polish the surface of the blank calcined in step 4 and then perform arc melting; The arc current during arc melting in step 5 is 800 A, and high-purity argon is introduced as a protective gas. After each melting is completed, the sample is turned over and melted again, and a total of 6 meltings are performed.

[0044] Step 6: polishing the surface of the smelted alloy ingot obtained in step 5, performing ultrasonic cleaning, and crushing it into powder; In step 6, the ultrasonic cleaning time is 30 minutes, and the cleaning medium is anhydrous ethanol; the crushing process adopts two-step crushing: the first step uses a sealed jaw crusher and a roller crusher to crush, respectively, to obtain particles with a particle size of ≤3 mm; the second step uses ball milling, and the ball mill and grinding balls are both made of tungsten carbide, the ball-to-material ratio is 5:1, the rotation speed is 180 r / min, the crushing time is 10 hours, and an argon atmosphere is introduced into the ball mill at a pressure of 0.6 MPa.

[0045] Step 7: The powder crushed in step 6 is subjected to multi-stage screening to obtain powders of various particle sizes; In step 7, the multi-stage screening process uses a vibrating screening machine equipped with an ultrasonic generator. The matching screens include 400 mesh, 600 mesh, 800 mesh, and 1000 mesh specifications. The screens are stacked from top to bottom in the order of 400 mesh, 600 mesh, 800 mesh, and 1000 mesh. The crushed powder is poured into the screen from the top. When the powder can pass through the 400 mesh but not the 600 mesh screen, the particle size D is screened out.50 When the powder of 30μm can pass through 600 mesh but not 800 mesh, the particle size D 50 When the powder of 20μm can pass through 800 mesh but not 1000 mesh, the particle size D 50 When the powder of 15μm can pass through 1000 mesh sieve, the particle size D 50 For a powder of 5 μm, the total sieving time is 30 min.

[0046] Step 8: Select coarse, medium, and fine powders from the various particle sizes obtained in step 7, and weigh them according to the following mass fractions: 10% coarse powder, 30% medium powder, and 60% fine powder, and then ball mill and mix them; In step 8, the particle size of the coarse powder is 30 μm, the particle size of the medium powder is 15 μm, and the particle size of the fine powder is 5 μm; during the ball milling mixing process, a ball mill jar made of either agate or polyurethane is used, and the grinding balls are made of either agate or zirconia. An argon atmosphere is introduced into the ball mill jar, and the air pressure is 0.6 MPa. During mixing, the ball-to-material ratio is 2:1, the ball mill speed is 400 r / min, and the ball milling time is 8 h.

[0047] Step 9: hot-pressing and sintering the mixed powder obtained in step 8 to obtain a harmonic structure Mo-Si-B alloy.

[0048] During the hot pressing sintering in step 9, the powder is placed in a graphite mold for hot pressing sintering. The sintering process is as follows: first, the temperature is raised to 1400°C at a rate of 10°C / min and kept at this temperature for 1 hour. After keeping at this temperature for 1 hour, the pressure is increased to 60 MPa. Then, the temperature is raised to 1800°C at a rate of 10°C / min and kept at this temperature for 3 hours. After reaching 1800°C, the pressure is maintained. During the sintering process, the vacuum degree is maintained at 1.5×10 -2 Pa.

[0049] Example 7 The preparation method of the harmonic structure Mo-Si-B alloy of the present invention is as follows: Figure 3 As shown, please follow the steps below: Step 1: Weigh the raw materials, and weigh 93% molybdenum powder, 4.8% silicon powder, and 2.2% boron powder according to the mass fraction, and the total mass of the above components is 100%; The purity of the molybdenum powder in step 1 is ≥99.9%, and the particle size of the molybdenum powder is ≤6.5 μm; the purity of the silicon powder is ≥99.99%, and the particle size of the silicon powder is <50 μm; the purity of the boron powder is ≥99.9%, and the particle size of the boron powder is <50 μm; Step 2: Place the molybdenum powder, silicon powder and boron powder weighed in step 1 into a planetary ball mill and mix them to obtain a mixed powder, and then mechanically alloy the mixed powder; In the ball milling mixing process in step 2, a ball mill made of either agate or polyurethane is used, and the grinding balls used are made of agate or zirconia. An argon atmosphere is introduced into the ball mill at a pressure of 0.6 MPa. During mixing, the ball-to-material ratio is 2:1, the ball mill speed is 400 r / min, and the ball milling time is 8 h. In the mechanical alloying process, the ball mill and grinding balls used are both made of tungsten carbide to achieve a multi-element alloying effect. The ball milling time is 15 h, the ball-to-material ratio is 10:1, the ball mill speed is 180 r / min, and an argon atmosphere is introduced into the ball mill at a pressure of 0.3 MPa.

[0050] Step 3: Place the powder mechanically alloyed in step 2 into a φ40 mm tableting die and press it into a cylindrical green compact; The pressure during the powder pressing process in step 3 is 25 MPa; The calcination in step 4 adopts a two-step heating method: the first step is to heat up to 1200℃ at 8℃ / min and keep it for 1h; the second step is to heat up to 1400℃ at 10℃ / min and keep it for 3h. The vacuum degree during the calcination process is ≤8×10 -3 Pa.

[0051] Step 4: placing the compact obtained in step 3 into a vacuum resistance furnace for calcination; Step 5: polish the surface of the blank calcined in step 4 and then perform arc melting; The arc current during arc melting in step 5 is 900 A, and high-purity argon gas is introduced as a shielding gas. After each melting is completed, the sample is turned over and melted again, and a total of 8 meltings are performed.

[0052] Step 6: polishing the surface of the smelted alloy ingot obtained in step 5, performing ultrasonic cleaning, and crushing it into powder; In step 6, the ultrasonic cleaning time is 20 minutes, and the cleaning medium is anhydrous ethanol; the crushing process adopts two-step crushing: the first step uses a sealed jaw crusher and a double-roll crusher to crush, respectively, to obtain particles with a particle size of ≤3 mm; the second step uses ball milling, and the ball mill and grinding balls are both made of tungsten carbide, the ball-to-material ratio is 10:1, the rotation speed is 220 r / min, the crushing time is 6 hours, and an argon atmosphere is introduced into the ball mill with an air pressure of 0.3 MPa.

[0053] Step 7: The powder crushed in step 6 is subjected to multi-stage screening to obtain powders of various particle sizes; In step 7, the multi-stage screening process uses a vibrating screening machine equipped with an ultrasonic generator. The matching screens include 400 mesh, 600 mesh, 800 mesh, and 1000 mesh specifications. The screens are stacked from top to bottom in the order of 400 mesh, 600 mesh, 800 mesh, and 1000 mesh. The crushed powder is poured into the screen from the top. When the powder can pass through the 400 mesh but not the 600 mesh screen, the particle size D is screened out.50 When the powder of 20μm can pass through 600 mesh but not 800 mesh, the particle size D 50 When the powder of 15μm can pass through 800 mesh but not 1000 mesh, the particle size D 50 When the powder of 10μm can pass through 1000 mesh sieve, the particle size D 50 For 3 μm powder, the total sieving time is 10 min.

[0054] Step 8: Select coarse, medium, and fine powders from the various particle sizes obtained in step 7, and weigh them according to the following mass fractions: 15% coarse powder, 15% medium powder, and 70% fine powder, and then ball mill and mix them; In step 8, the particle size of the coarse powder is 20 μm, the particle size of the medium powder is 10 μm, and the particle size of the fine powder is 3 μm; during the ball milling mixing process, a ball mill jar made of either agate or polyurethane is used, and the grinding balls are made of either agate or zirconia. An argon atmosphere is introduced into the ball mill jar, and the air pressure is 0.3 MPa. During mixing, the ball-to-material ratio is 1:1, the ball mill speed is 300 r / min, and the ball milling time is 6 h.

[0055] Step 9: hot-pressing and sintering the mixed powder obtained in step 8 to obtain a harmonic structure Mo-Si-B alloy.

[0056] During the hot pressing sintering in step 9, the powder is placed in a graphite mold for hot pressing sintering. The sintering process is as follows: first, the temperature is raised to 1200°C at a rate of 8°C / min and kept at this temperature for 0.5h. After keeping at this temperature for 0.5h, the pressure is applied to 38MPa. Then, the temperature is raised to 1600°C at a rate of 8°C / min and kept at this temperature for 2h. After that, the pressure is maintained at 1600°C. During the sintering process, the vacuum degree is maintained at 6×10 -3 Pa.

[0057] Example 8 The preparation method of the harmonic structure Mo-Si-B alloy of the present invention is as follows: Figure 3 As shown, please follow the steps below: Step 1: Weigh the raw materials, and weigh 95% molybdenum powder, 3% silicon powder, and 2% boron powder according to the mass fraction, with the total mass of the above components being 100%; The purity of the molybdenum powder in step 1 is ≥99.9%, and the particle size of the molybdenum powder is ≤6.5 μm; the purity of the silicon powder is ≥99.99%, and the particle size of the silicon powder is <50 μm; the purity of the boron powder is ≥99.9%, and the particle size of the boron powder is <50 μm; Step 2: Place the molybdenum powder, silicon powder and boron powder weighed in step 1 into a planetary ball mill and mix them to obtain a mixed powder, and then mechanically alloy the mixed powder; In the ball milling mixing process in step 2, a ball mill made of either agate or polyurethane is used, and the grinding balls used are made of agate or zirconia. An argon atmosphere is introduced into the ball mill at a pressure of 0.5 MPa. During mixing, the ball-to-material ratio is 1.5:1, the ball mill speed is 350 r / min, and the ball milling time is 7 h. In the mechanical alloying process, the ball mill and grinding balls used are both made of tungsten carbide to achieve a multi-element alloying effect. The ball milling time is 13 h, the ball-to-material ratio is 7:1, the ball mill speed is 200 r / min, and an argon atmosphere is introduced into the ball mill at a pressure of 0.4 MPa.

[0058] Step 3: Place the powder mechanically alloyed in step 2 into a φ35 mm tableting die and press it into a cylindrical green compact; The pressure during the powder pressing process in step 3 is 30 MPa; The calcination in step 4 was carried out in two steps: the first step was to heat up to 1300°C at 9°C / min and keep at this temperature for 0.8h; the second step was to heat up to 1500°C at 9°C / min and keep at this temperature for 2.5h. The vacuum degree during the calcination was ≤8×10 -3 Pa.

[0059] Step 4: placing the compact obtained in step 3 into a vacuum resistance furnace for calcination; Step 5: polish the surface of the blank calcined in step 4 and then perform arc melting; The arc current during arc melting in step 5 is 850 A, and high-purity argon gas is introduced as a protective gas. After each melting is completed, the sample is turned over and melted again, and a total of 7 melting times are performed.

[0060] Step 6: polishing the surface of the smelted alloy ingot obtained in step 5, performing ultrasonic cleaning, and crushing it into powder; In step 6, the ultrasonic cleaning time is 20 minutes, and the cleaning medium is anhydrous ethanol; the crushing process adopts two-step crushing: the first step uses a sealed jaw crusher and a double-roll crusher to crush, respectively, to obtain particles with a particle size of ≤3 mm; the second step uses ball milling, and the ball mill and grinding balls are both made of tungsten carbide, the ball-to-material ratio is 8:1, the rotation speed is 200 r / min, the crushing time is 8 hours, and an argon atmosphere is introduced into the ball mill with an air pressure of 0.4 MPa.

[0061] Step 7: The powder crushed in step 6 is subjected to multi-stage screening to obtain powders of various particle sizes; In step 7, the multi-stage screening process uses a vibrating screening machine equipped with an ultrasonic generator. The matching screens include 400 mesh, 600 mesh, 800 mesh, and 1000 mesh specifications. The screens are stacked from top to bottom in the order of 400 mesh, 600 mesh, 800 mesh, and 1000 mesh. The crushed powder is poured into the screen from the top. When the powder can pass through the 400 mesh but not the 600 mesh screen, the particle size D is screened out.50 When the powder of 25μm can pass through 600 mesh but not 800 mesh, the particle size D 50 When the powder of 18μm can pass through 800 mesh but not 1000 mesh, the particle size D 50 When the powder of 12μm can pass through 1000 mesh sieve, the particle size D 50 For a powder of 4 μm, the total sieving time is 20 min.

[0062] Step 8: Select coarse, medium, and fine powders from the various particle sizes obtained in step 7, and weigh them according to the following mass fractions: 12% coarse powder, 25% medium powder, and 63% fine powder, and then ball mill and mix them; In step 8, the particle size of the coarse powder is 25 μm, the particle size of the medium powder is 12 μm, and the particle size of the fine powder is 4 μm; during the ball milling mixing process, a ball mill jar made of either agate or polyurethane is used, and the grinding balls are made of either agate or zirconia. An argon atmosphere is introduced into the ball mill jar, and the air pressure is 0.4 MPa. During mixing, the ball-to-material ratio is 1.5:1, the ball mill speed is 350 r / min, and the ball milling time is 7 h.

[0063] Step 9: hot-pressing and sintering the mixed powder obtained in step 8 to obtain a harmonic structure Mo-Si-B alloy.

[0064] During the hot pressing sintering in step 9, the powder is placed in a graphite mold for hot pressing sintering. The sintering process is as follows: first, the temperature is raised to 1300°C at a rate of 9°C / min and kept at this temperature for 0.8h. After keeping at this temperature for 0.8h, the pressure is applied at 45MPa. Then, the temperature is raised to 1700°C at a rate of 9°C / min and kept at this temperature for 2.5h. After that, the pressure is maintained at 1700°C. During the sintering process, the vacuum degree is maintained at 7×10 -3 Pa.

[0065] Example 9 The preparation method of the harmonic structure Mo-Si-B alloy of the present invention mainly comprises the following steps: Step 1, weigh the raw materials, that is, weigh 284.15g of molybdenum powder with a purity of ≥99.9% and a particle size of ≤6.5μm, 12.45g of silicon powder with a purity of ≥99.99% and a particle size of <50μm, and 3.40g of boron powder with a purity of ≥99.9% and a particle size of <50μm, the total of the above components being 100%.

[0066] Step 2: The molybdenum powder, silicon powder and boron powder weighed in step 1 are placed in a planetary ball mill for ball milling and mixing; the ball mill jar and the grinding balls used during ball milling are all made of agate, an argon atmosphere is introduced into the ball mill jar, the air pressure is 0.3 MPa, the ball-to-material ratio is 1:1, the ball mill speed is 300 r / min, and the effective time is 6 h; then the mixed powder is mechanically alloyed, the ball mill jar and the grinding balls used for mechanical alloying are all made of tungsten carbide, the ball milling time is 15 h, the ball-to-material ratio is 10:1, the ball mill speed is 220 r / min, an argon atmosphere is introduced into the ball mill jar, and the air pressure is 0.3 MPa.

[0067] Step 3: The powder mechanically alloyed in step 2 is placed in a φ30 mm tableting die and pressed into a cylindrical compact at a pressure of 25 MPa.

[0068] Step 4: Place the compact obtained in step 3 into a vacuum resistance furnace for calcination. The calcination is carried out by a two-step heating method: first, the temperature is raised to 1200°C at 8°C / min and kept at this temperature for 1 hour, then the temperature is raised to 1400°C at 8°C / min and kept at this temperature for 2 hours. The vacuum degree during the calcination process is ≤8×10 -3 Pa.

[0069] Step 5: After the surface of the blank calcined in step 4 is polished clean, arc melting is performed. The arc current is 900A, and high-purity argon is introduced as the protective gas. After each melting is completed, the sample is turned over and melted again, and a total of 6 meltings are performed.

[0070] Step 6: After the surface of the molten alloy ingot obtained in step 5 is polished clean, it is ultrasonically cleaned with anhydrous ethanol as a medium for 10 minutes, and then crushed into powder using a two-step method: first, a sealed jaw crusher and a double-roll crusher are used to crush it into particles with a particle size of ≤3 mm; then, ball milling is used for crushing, and the ball mill and grinding balls are both made of tungsten carbide, with a ball-to-material ratio of 5:1, a rotation speed of 220 r / min, a crushing time of 6 hours, and an argon atmosphere is introduced into the ball mill at a pressure of 0.3 MPa.

[0071] Step 7: The powder crushed in step 6 is screened in multiple stages using a vibrating screening machine equipped with an ultrasonic generator. The screens are stacked from top to bottom in the order of 400 mesh, 600 mesh, 800 mesh, and 1000 mesh. The crushed powder is poured into the screen from the top. When the powder can pass through the 400 mesh but not the 600 mesh screen, the particle size (D 50 ) In the 20-30μm powder; when it can pass through 600 mesh but not 800 mesh, the particle size (D 50 ) In the 15-20μm powder; when it can pass through 800 mesh but not 1000 mesh, the particle size (D 50 ) In the 10-15μm powder; when it can pass through a 1000 mesh sieve, the particle size (D 50) in the range of 3-5 μm. The total sieving time was 15 min, and powders of various particle sizes were obtained.

[0072] Step 8. From the various particle size powders obtained in step 7, select coarse, medium and fine powders with particle sizes of 20-30 μm, 10-15 μm and 3-5 μm, respectively, and weigh them according to mass fractions of 10%, 15% and 75%, and then perform ball milling. The ball mill jar and grinding balls are made of agate. Argon atmosphere is introduced into the ball mill jar, the air pressure is 0.3 MPa, the ball-to-material ratio is 1:1, the ball mill speed is 400 r / min, and the effective time is 6 hours.

[0073] Step 9: Place the mixed powder obtained in step 8 into a graphite mold for hot pressing and sintering. The sintering process is as follows: first, heat to 1200°C at 8°C / min and keep at this temperature for 1 hour, then heat to 1600°C at 8°C / min and keep at this temperature for 2 hours. After keeping at 1200°C, pressurize and maintain at 1600°C at a pressure of 40 MPa. The vacuum degree is maintained at 6×10 -3 Pa to 1.5×10 -2 Pa, and a harmonic structure Mo-Si-B alloy is obtained.

[0074] This harmonic Mo-Si-B alloy consists of large, medium, and small units, all composed of three phases: α-Mo, Mo3Si, and Mo5SiB2. Each unit, by volume, comprises 10% large units, 15% medium units, and 75% small units. The large and medium units are evenly distributed within a continuous network of small units. Within each unit, the phases, by volume, comprise 49% α-Mo, 27% Mo3Si, and 24% Mo5SiB2. The large units are approximately 25.0 μm in size, the medium units are approximately 11.6 μm, and the small units are approximately 4.5 μm. Within each unit, the average α-Mo grain size is 2.2 μm, the average Mo3Si particle size is 1.2 μm, and the average Mo5SiB2 particle size is 1.1 μm.

[0075] like Figure 2 and Figure 3 The hardness of the harmonic structure Mo-Si-B alloy is 1282HV and the room temperature indentation fracture toughness is 6.2 , the weight loss after oxidation at 1100℃ for 5h is 53.8mg / cm 2 .

[0076] Example 10 The preparation method of the harmonic structure Mo-Si-B alloy of the present invention mainly comprises the following steps: Step 1, weigh the raw materials, that is, weigh 286.65g of molybdenum powder with a purity of ≥99.9% and a particle size of ≤6.5μm, 10.20g of silicon powder with a purity of ≥99.99% and a particle size of <50μm, and 3.15g of boron powder with a purity of ≥99.9% and a particle size of <50μm, the total of the above components being 100%.

[0077] Step 2: The molybdenum powder, silicon powder and boron powder weighed in step 1 are placed in a planetary ball mill for ball milling and mixing; the ball mill jar and the grinding balls are made of agate during ball milling, an argon atmosphere is introduced into the ball mill jar, the air pressure is 0.4 MPa, the ball-to-material ratio is 2:1, the ball mill speed is 350 r / min, and the effective time is 7 h; then the mixed powder is mechanically alloyed, the ball mill jar and the grinding balls are made of tungsten carbide for mechanical alloying, the ball milling time is 14 h, the ball-to-material ratio is 9:1, the ball mill speed is 250 r / min, the ball mill jar is introduced into the argon atmosphere, and the air pressure is 0.4 MPa.

[0078] Step 3: The powder mechanically alloyed in step 2 is placed in a φ30 mm tableting die and pressed into a cylindrical compact at a pressure of 28 MPa.

[0079] Step 4: Place the compact obtained in step 3 into a vacuum resistance furnace for calcination. The calcination is carried out by a two-step heating method: first, the temperature is raised to 1200°C at 8°C / min and kept at this temperature for 0.8h, then the temperature is raised to 1400°C at 8°C / min and kept at this temperature for 2.5h. During the calcination process, the vacuum degree is ≤8×10 -3 Pa.

[0080] Step 5: After the surface of the blank calcined in step 4 is polished clean, arc melting is performed, the arc current is selected to be 850A, and high-purity argon is introduced as the protective gas. After each melting is completed, the sample is turned over and melted again, and a total of 7 meltings are performed.

[0081] Step 6: After the surface of the molten alloy ingot obtained in step 5 is polished clean, it is ultrasonically cleaned with anhydrous ethanol as a medium for 15 minutes, and then crushed into powder using a two-step method: first, a sealed jaw crusher and a double-roll crusher are used to crush it into particles with a particle size of ≤3 mm; then, ball milling is used for crushing, and the ball mill and grinding balls are both made of tungsten carbide, with a ball-to-material ratio of 5:1, a rotation speed of 200 r / min, a crushing time of 7 hours, and an argon atmosphere is introduced into the ball mill at a pressure of 0.4 MPa.

[0082] Step 7: The powder crushed in step 6 is screened in multiple stages using a vibrating screening machine equipped with an ultrasonic generator. The screens are stacked from top to bottom in the order of 400 mesh, 600 mesh, 800 mesh, and 1000 mesh. The crushed powder is poured into the screen from the top. When the powder can pass through the 400 mesh but not the 600 mesh screen, the particle size (D 50 ) In the 20-30μm powder; when it can pass through 600 mesh but not 800 mesh, the particle size (D50 ) In the 15-20μm powder; when it can pass through 800 mesh but not 1000 mesh, the particle size (D 50 ) In the 10-15μm powder; when it can pass through a 1000 mesh sieve, the particle size (D 50 ) in the range of 3-5 μm. The total sieving time was 20 min, and powders of various particle sizes were obtained.

[0083] Step 8. From the various particle size powders obtained in step 7, select coarse, medium and fine powders with particle sizes of 20-30 μm, 10-15 μm and 3-5 μm, respectively, and weigh them according to mass fractions of 12%, 20% and 68%, and then perform ball milling. The ball mill and grinding balls are made of agate. Argon atmosphere is introduced into the ball mill, the air pressure is 0.4 MPa, the ball-to-material ratio is 2:1, the ball mill speed is 350 r / min, and the effective time is 7 hours.

[0084] Step 9: Place the mixed powder obtained in step 8 into a graphite mold for hot pressing and sintering. The sintering process is as follows: first, heat to 1200°C at 8°C / min and keep at this temperature for 0.5h, then heat to 1700°C at 8°C / min and keep at this temperature for 2h. After keeping at 1200°C, pressurize and maintain at 1700°C at a pressure of 45MPa. The vacuum degree is maintained at 6×10 -3 Pa to 1.5×10 -2 Pa, and a harmonic structure Mo-Si-B alloy is obtained.

[0085] This harmonic-structured Mo-Si-B alloy consists of large, medium, and small units, all composed of three phases: α-Mo, Mo3Si, and Mo5SiB2. Each unit, by volume, comprises 12% large units, 20% medium units, and 68% small units. The large and medium units are evenly distributed within a continuous network of numerous small units. Within each unit, the phases, by volume, comprise 55% α-Mo, 25% Mo3Si, and 20% Mo5SiB2. The large units are approximately 28.0 μm in size, the medium units are approximately 13.2 μm, and the small units are approximately 4.7 μm. Within each unit, the average α-Mo grain size is 2.4 μm, the average Mo3Si particle size is 1.3 μm, and the average Mo5SiB2 particle size is 1.2 μm.

[0086] The hardness of the harmonic structure Mo-Si-B alloy is 1086HV and the room temperature indentation fracture toughness is 7.5 , the weight loss after oxidation at 1100℃ for 5h is 49.4mg / cm 2 .

[0087] Example 11 The preparation method of the harmonic structure Mo-Si-B alloy mainly includes the following steps: Step 1, weigh the raw materials, that is, weigh 289.85g of molybdenum powder with a purity of ≥99.9% and a particle size of ≤6.5μm, 7.87g of silicon powder with a purity of ≥99.99% and a particle size of <50μm, and 2.28g of boron powder with a purity of ≥99.9% and a particle size of <50μm, the total of the above components being 100%.

[0088] Step 2: The molybdenum powder, silicon powder and boron powder weighed in step 1 are placed in a planetary ball mill for ball milling and mixing; the ball mill jar and the grinding balls are made of agate during ball milling, an argon atmosphere is introduced into the ball mill jar, the air pressure is 0.5 MPa, the ball-to-material ratio is 1.5:1, the ball mill speed is 350 r / min, and the effective time is 8 h; then the mixed powder is mechanically alloyed, the ball mill jar and the grinding balls are made of tungsten carbide for mechanical alloying, the ball milling time is 14 h, the ball-to-material ratio is 8:1, the ball mill speed is 250 r / min, an argon atmosphere is introduced into the ball mill jar, and the air pressure is 0.5 MPa.

[0089] Step 3: The powder mechanically alloyed in step 2 is placed in a φ30 mm tableting die and pressed into a cylindrical compact at a pressure of 30 MPa.

[0090] Step 4: Place the compact obtained in step 3 into a vacuum resistance furnace for calcination. The calcination is carried out by a two-step heating method: first, the temperature is raised to 1200°C at a rate of 10°C / min and kept at that temperature for 1 hour, then the temperature is raised to 1400°C at a rate of 10°C / min and kept at that temperature for 2 hours. During the calcination process, the vacuum degree is ≤8×10 -3 Pa.

[0091] Step 5: After the surface of the blank calcined in step 4 is polished clean, arc melting is performed, the arc current is selected to be 850A, and high-purity argon is introduced as the protective gas. After each melting is completed, the sample is turned over and melted again, and a total of 8 melting times are performed.

[0092] Step 6: After the surface of the molten alloy ingot obtained in step 5 is polished clean, it is ultrasonically cleaned with anhydrous ethanol as a medium for 20 minutes, and then crushed into powder using a two-step method: first, a sealed jaw crusher and a double-roll crusher are used to crush it into particles with a particle size of ≤3 mm; then, ball milling is used for crushing, and the ball mill and grinding balls are both made of tungsten carbide, with a ball-to-material ratio of 5:1, a rotation speed of 200 r / min, a crushing time of 8 hours, and an argon atmosphere is introduced into the ball mill at a pressure of 0.5 MPa.

[0093] Step 7: The powder crushed in step 6 is screened in multiple stages using a vibrating screening machine equipped with an ultrasonic generator. The screens are stacked from top to bottom in the order of 400 mesh, 600 mesh, 800 mesh, and 1000 mesh. The crushed powder is poured into the screen from the top. When the powder can pass through the 400 mesh but not the 600 mesh screen, the particle size (D 50) In the 20-30μm powder; when it can pass through 600 mesh but not 800 mesh, the particle size (D 50 ) In the 15-20μm powder; when it can pass through 800 mesh but not 1000 mesh, the particle size (D 50 ) In the 10-15μm powder; when it can pass through a 1000 mesh sieve, the particle size (D 50 ) in the range of 3-5 μm. The total sieving time was 25 min, and powders of various particle sizes were obtained.

[0094] Step 8. From the various particle size powders obtained in step 7, select coarse, medium and fine powders with particle sizes of 20-30 μm, 10-15 μm and 3-5 μm, respectively, and weigh them according to mass fractions of 13%, 21% and 66%, respectively, and then perform ball milling. The ball mill jar and grinding balls are made of agate. Argon atmosphere is introduced into the ball mill jar, the air pressure is 0.5 MPa, the ball-to-material ratio is 1.5:1, the ball mill speed is 300 r / min, and the effective time is 8 hours.

[0095] Step 9: Place the mixed powder obtained in step 8 into a graphite mold for hot pressing and sintering. The sintering process is as follows: first, heat to 1200°C at 10°C / min and keep at this temperature for 1 hour, then heat to 1700°C at 10°C / min and keep at this temperature for 3 hours. After keeping at 1200°C, pressurize and maintain at 1700°C with a pressure of 50 MPa. The vacuum degree is maintained at 6×10 -3 Pa to 1.5×10 -2 Pa, and a harmonic structure Mo-Si-B alloy is obtained.

[0096] This harmonic Mo-Si-B alloy consists of large, medium, and small units, all composed of three phases: α-Mo, Mo3Si, and Mo5SiB2. By volume, each unit comprises 13% large units, 21% medium units, and 66% small units. The large and medium units are evenly distributed within a continuous network of small units. Within each unit, the phases, by volume, comprise 66% α-Mo, 16% Mo3Si, and 18% Mo5SiB2. The large units are approximately 28.6μm in size, the medium units are approximately 14.4μm, and the small units are approximately 4.7μm. Within each unit, the average α-Mo grain size is 2.7μm, the average Mo3Si particle size is 1.5μm, and the average Mo5SiB2 particle size is 1.3μm.

[0097] The hardness of the harmonic structure Mo-Si-B alloy is 884HV and the room temperature indentation fracture toughness is 9.7 , the weight loss after oxidation at 1100℃ for 5h is 67mg / cm 2 .

[0098] Example 12 The preparation method of the harmonic structure Mo-Si-B alloy of the present invention mainly comprises the following steps: Step 1, weighing the raw materials, that is, weighing 281.98g of molybdenum powder with a purity of ≥99.9% and a particle size of ≤6.5μm, 13.89g of silicon powder with a purity of ≥99.99% and a particle size of <50μm, and 4.13g of boron powder with a purity of ≥99.9% and a particle size of <50μm, the total of the above components being 100%.

[0099] Step 2: The molybdenum powder, silicon powder and boron powder weighed in step 1 are placed in a planetary ball mill for ball milling and mixing; the ball mill jar and the grinding balls used during ball milling are all made of agate, an argon atmosphere is introduced into the ball mill jar, the air pressure is 0.6 MPa, the ball-to-material ratio is 2:1, the ball mill speed is 300 r / min, and the effective time is 8 hours; then the mixed powder is mechanically alloyed, the ball mill jar and the grinding balls used for mechanical alloying are all made of tungsten carbide, the ball milling time is 12 hours, the ball-to-material ratio is 10:1, the ball mill speed is 230 r / min, the ball mill jar is introduced into the argon atmosphere, and the air pressure is 0.6 MPa.

[0100] Step 3: The powder mechanically alloyed in step 2 is placed in a φ40 mm tableting die and pressed into a cylindrical compact at a pressure of 35 MPa.

[0101] Step 4: Place the compact obtained in step 3 into a vacuum resistance furnace for calcination. The calcination is carried out by a two-step heating method: first, heating to 1200°C at a rate of 10°C / min and holding for 0.5h, then heating to 1400°C at a rate of 10°C / min and holding for 2.5h. During the calcination process, the vacuum degree is ≤8×10 -3 Pa.

[0102] Step 5: After the surface of the blank calcined in step 4 is polished clean, arc melting is performed. The arc current is 900A, and high-purity argon is introduced as the protective gas. After each melting is completed, the sample is turned over and melted again, and a total of 6 meltings are performed.

[0103] Step 6: After the surface of the molten alloy ingot obtained in step 5 is polished clean, it is ultrasonically cleaned for 25 minutes using anhydrous ethanol as a medium, and then crushed into powder using a two-step method: first, a sealed jaw crusher and a double-roll crusher are used to crush it into particles with a particle size of ≤3 mm; then, ball milling is used for crushing, and the ball mill and grinding balls are both made of tungsten carbide, with a ball-to-material ratio of 5:1, a rotation speed of 190 r / min, a crushing time of 8 hours, and an argon atmosphere is introduced into the ball mill at a pressure of 0.6 MPa.

[0104] Step 7: The powder crushed in step 6 is screened in multiple stages using a vibrating screening machine equipped with an ultrasonic generator. The screens are stacked from top to bottom in the order of 400 mesh, 600 mesh, 800 mesh, and 1000 mesh. The crushed powder is poured into the screen from the top. When the powder can pass through the 400 mesh but not the 600 mesh screen, the particle size (D 50 ) In the 20-30μm powder; when it can pass through 600 mesh but not 800 mesh, the particle size (D 50 ) In the 15-20μm powder; when it can pass through 800 mesh but not 1000 mesh, the particle size (D 50 ) In the 10-15μm powder; when it can pass through a 1000 mesh sieve, the particle size (D 50 ) in the range of 3-5 μm. The total sieving time was 28 min, and powders of various particle sizes were obtained.

[0105] Step 8. From the various particle size powders obtained in step 7, select coarse, medium and fine powders with particle sizes of 20-30 μm, 10-15 μm and 3-5 μm, respectively, and weigh them according to mass fractions of 14%, 23% and 63%, and then perform ball milling. The ball mill jar and grinding balls are made of agate. Argon atmosphere is introduced into the ball mill jar, the air pressure is 0.6 MPa, the ball-to-material ratio is 2:1, the ball mill speed is 350 r / min, and the effective time is 7 hours.

[0106] Step 9: Place the mixed powder obtained in step 8 into a graphite mold for hot pressing and sintering. The sintering process is as follows: first, heat to 1200°C at 10°C / min and keep at this temperature for 0.5h, then heat to 1750°C at 10°C / min and keep at this temperature for 2h. After keeping at 1200°C, pressurize and maintain at 1750°C at a pressure of 55MPa. The vacuum degree is maintained at 6×10 -3 Pa to 1.5×10 -2 Pa, and a harmonic structure Mo-Si-B alloy is obtained.

[0107] This harmonic-structured Mo-Si-B alloy comprises large, medium, and small units, all composed of three phases: α-Mo, Mo3Si, and Mo5SiB2. Each unit, by volume, comprises 14% large units, 23% medium units, and 63% small units. The large and medium units are evenly distributed within a continuous network of numerous small units. Within each unit, the phases, by volume, comprise 43% α-Mo, 25% Mo3Si, and 32% Mo5SiB2. The large units are approximately 24.5μm in size, the medium units are approximately 10.4μm, and the small units are approximately 4.4μm. Within each unit, the average α-Mo grain size is 2.1μm, the average Mo3Si particle size is 1.1μm, and the average Mo5SiB2 particle size is 1.1μm.

[0108] The hardness of the harmonic structure Mo-Si-B alloy is 1342HV and the room temperature indentation fracture toughness is 5.7 , the weight loss after oxidation at 1100℃ for 5h is 26.2mg / cm 2 .

[0109] Example 13 The preparation method of the harmonic structure Mo-Si-B alloy of the present invention mainly comprises the following steps: Step 1, weigh the raw materials, that is, weigh 284.15g of molybdenum powder with a purity of ≥99.9% and a particle size of ≤6.5μm, 12.45g of silicon powder with a purity of ≥99.99% and a particle size of <50μm, and 3.40g of boron powder with a purity of ≥99.9% and a particle size of <50μm, the total of the above components being 100%.

[0110] Step 2: The molybdenum powder, silicon powder and boron powder weighed in step 1 are placed in a planetary ball mill for ball milling and mixing; the ball mill jar and the grinding balls used during ball milling are all made of agate, an argon atmosphere is introduced into the ball mill jar, the air pressure is 0.3 MPa, the ball-to-material ratio is 2:1, the ball mill speed is 400 r / min, and the effective time is 8 h; then the mixed powder is mechanically alloyed, the ball mill jar and the grinding balls used for mechanical alloying are all made of tungsten carbide, the ball milling time is 12 h, the ball-to-material ratio is 8:1, the ball mill speed is 220 r / min, an argon atmosphere is introduced into the ball mill jar, and the air pressure is 0.3 MPa.

[0111] Step 3: The powder mechanically alloyed in step 2 is placed in a φ40 mm tableting die and pressed into a cylindrical compact at a pressure of 37 MPa.

[0112] Step 4: Place the compact obtained in step 3 into a vacuum resistance furnace for calcination. The calcination is carried out by a two-step heating method: first, the temperature is raised to 1200°C at a rate of 10°C / min and kept at that temperature for 1 hour, then the temperature is raised to 1400°C at a rate of 10°C / min and kept at that temperature for 3 hours. The vacuum degree during the calcination process is ≤8×10 -3 Pa.

[0113] Step 5: After the surface of the blank calcined in step 4 is polished clean, arc melting is performed. The arc current is 900A, and high-purity argon is introduced as the protective gas. After each melting is completed, the sample is turned over and melted again, and a total of 7 melting times are performed.

[0114] Step 6: After the surface of the molten alloy ingot obtained in step 5 is polished clean, it is ultrasonically cleaned with anhydrous ethanol as a medium for 30 minutes, and then crushed into powder using a two-step method: first, a sealed jaw crusher and a double-roll crusher are used to crush it into particles with a particle size of ≤3 mm; then, ball milling is used for crushing, and the ball mill and grinding balls are both made of tungsten carbide, with a ball-to-material ratio of 5:1, a rotation speed of 180 r / min, a crushing time of 9 hours, and an argon atmosphere is introduced into the ball mill at a pressure of 0.3 MPa.

[0115] Step 7: The powder crushed in step 6 is screened in multiple stages using a vibrating screening machine equipped with an ultrasonic generator. The screens are stacked from top to bottom in the order of 400 mesh, 600 mesh, 800 mesh, and 1000 mesh. The crushed powder is poured into the screen from the top. When the powder can pass through the 400 mesh but not the 600 mesh screen, the particle size (D 50 ) In the 20-30μm powder; when it can pass through 600 mesh but not 800 mesh, the particle size (D 50 ) In the 15-20μm powder; when it can pass through 800 mesh but not 1000 mesh, the particle size (D 50 ) In the 10-15μm powder; when it can pass through a 1000 mesh sieve, the particle size (D 50 ) in the range of 3-5 μm. The total sieving time was 30 min, and powders of various particle sizes were obtained.

[0116] Step 8. From the various particle size powders obtained in step 7, select coarse, medium and fine powders with particle sizes of 20-30 μm, 10-15 μm and 3-5 μm, respectively, and weigh them according to mass fractions of 15%, 25% and 60%, and then perform ball milling. The ball mill jar and grinding balls are made of agate. Argon atmosphere is introduced into the ball mill jar, the air pressure is 0.3 MPa, the ball-to-material ratio is 2:1, the ball mill speed is 400 r / min, and the effective time is 7.5 h.

[0117] Step 9: Place the mixed powder obtained in step 8 into a graphite mold for hot pressing and sintering. The sintering process is as follows: first, heat to 1200°C at 10°C / min and keep at this temperature for 1 hour, then heat to 1800°C at 10°C / min and keep at this temperature for 2 hours. After keeping at 1200°C, pressurize and maintain at 1800°C with a pressure of 60 MPa. During the sintering process, the vacuum degree is maintained at 6×10 -3 Pa to 1.5×10 -2 Pa, and a harmonic structure Mo-Si-B alloy is obtained.

[0118] This harmonic-structured Mo-Si-B alloy comprises large, medium, and small units, all composed of three phases: α-Mo, Mo3Si, and Mo5SiB2. Each unit, by volume, consists of 15% large units, 25% medium units, and 60% small units. The large and medium units are evenly distributed within a continuous network of numerous small units. Within each unit, the phases, by volume, comprise 48% α-Mo, 27% Mo3Si, and 25% Mo5SiB2. The large units are approximately 29.8μm in size, the medium units are approximately 14.8μm, and the small units are approximately 4.9μm. Within each unit, the average α-Mo grain size is 2.7μm, the average Mo3Si particle size is 1.5μm, and the average Mo5SiB2 particle size is 1.3μm.

[0119] The hardness of the harmonic structure Mo-Si-B alloy is 1112HV and the room temperature indentation fracture toughness is 7.4 , the weight loss after oxidation at 1100℃ for 5h is 36.4mg / cm 2 .

Claims

1. Harmonic structure Mo-Si-B alloy, characterized in that: It includes large, medium and small size units composed of three phases of α-Mo, Mo3Si and Mo5SiB2. Each unit, calculated by volume fraction, includes 10-15% large size units, 15-30% medium size units, and 55-75% small size units; the large size and medium size units are evenly distributed in a large number of continuous small size units. In each size unit, each phase, calculated by volume fraction, includes 40-70% α-Mo, 15-30% Mo3Si, and 15-35% Mo5SiB2.

2. The harmonic structure Mo-Si-B alloy according to claim 1, characterized in that: The size of large-size units is 20-30μm, the size of medium-size units is 10-15μm, and the size of small-size units is ≤5μm. In each unit, the grain size of α-Mo phase is 2-5μm, the particle size of Mo3Si phase is 0.5-2μm, and the particle size of Mo5SiB2 phase is 0.5-2μm.

3. A method for preparing a harmonic structure Mo-Si-B alloy, characterized in that: Please follow the steps below to implement it: Step 1. Weigh the raw materials, and weigh 93%-97% of molybdenum powder, 2.5%-4.8% of silicon powder, and 0.5%-2.2% of boron powder according to mass fraction, with the total mass of the above components being 100%; Step 2: ball-milling the molybdenum powder, silicon powder and boron powder weighed in step 1 to obtain a mixed powder, and then mechanically alloying the mixed powder; Step 3, pressing the powder mechanically alloyed in step 2 into a cylindrical compact; Step 4, calcining the compact obtained in step 3; Step 5: polish the surface of the blank calcined in step 4 and then perform arc melting; Step 6: polishing the surface of the smelted alloy ingot obtained in step 5, performing ultrasonic cleaning, and crushing it into powder; Step 7: The powder crushed in step 6 is subjected to multi-stage screening to obtain powders of various particle sizes; Step 8: Select coarse, medium, and fine powders from the various particle sizes obtained in step 7, and weigh them according to the following mass fractions: 10-15% coarse powder, 15-30% medium powder, and 55-75% fine powder, and then ball mill and mix them; Step 9: hot-pressing and sintering the mixed powder obtained in step 8 to obtain a harmonic structure Mo-Si-B alloy.

4. The method for preparing the harmonic structure Mo-Si-B alloy according to claim 3, characterized in that: The purity of the molybdenum powder in step 1 is ≥99.9%, and the particle size of the molybdenum powder is ≤6.5 μm; the purity of the silicon powder is ≥99.99%, and the particle size of the silicon powder is <50 μm; the purity of the boron powder is ≥99.9%, and the particle size of the boron powder is <50 μm; In the ball milling mixing process in step 2, a ball mill made of either agate or polyurethane is used, and the grinding balls used are made of agate or zirconia. An argon atmosphere is introduced into the ball mill, and the air pressure is 0.3MPa-0.6MPa. During mixing, the ball-to-material ratio is 1-2:1, the ball mill speed is 300-400r / min, and the ball milling time is 6-8h. In the mechanical alloying process, the ball mill and the grinding balls used are both made of tungsten carbide to achieve a multi-element alloying effect. The ball milling time is 10-15h, the ball-to-material ratio is 5-10:1, the ball mill speed is 180r / min-250r / min, and an argon atmosphere is introduced into the ball mill, and the air pressure is 0.3MPa-0.6MPa.

5. The method for preparing the harmonic structure Mo-Si-B alloy according to claim 3, characterized in that: The pressure during the powder pressing process in step 3 is 25 MPa to 37 MPa; The calcination in step 4 adopts a two-step heating method: the first step is to heat up to 1200-1400°C at 8-10°C / min and keep warm for 0.5-1h; the second step is to heat up to 1400-1600°C at 8-10°C / min and keep warm for 2-3h. The vacuum degree during the calcination process is ≤8×10 - 3 Pa.

6. The method for preparing the harmonic structure Mo-Si-B alloy according to claim 3, characterized in that: The arc current during arc melting in step 5 is 800-900A, and high-purity argon is introduced as a protective gas. After each melting is completed, the sample is turned over and melted again, and a total of 6-8 melting times are performed.

7. The method for preparing the harmonic structure Mo-Si-B alloy according to claim 3, characterized in that: In step 6, the ultrasonic cleaning time is 10-30 minutes, and the cleaning medium is anhydrous ethanol. The crushing process adopts two-step crushing: the first step uses a sealed jaw crusher and a roller crusher to crush, respectively, to obtain particles with a particle size of ≤3 mm; the second step uses ball milling, and the ball mill and grinding balls are both made of tungsten carbide, the ball-to-material ratio is 5-10:1, the rotation speed is 150 r / min-220 r / min, the crushing time is 6-10 hours, and an argon atmosphere is introduced into the ball mill, and the air pressure is 0.3 MPa-0.6 MPa.

8. The method for preparing the harmonic structure Mo-Si-B alloy according to claim 3, characterized in that: The multi-stage screening process in step 7 adopts a vibration screening machine equipped with an ultrasonic generator, and the matching screens include 400 mesh, 600 mesh, 800 mesh, and 1000 mesh specifications. The screens are stacked from top to bottom in the order of 400 mesh, 600 mesh, 800 mesh, and 1000 mesh. The crushed powder is poured into the screen from the top. When the powder can pass through the 400 mesh but not the 600 mesh screen, the particle size D is screened out. 50 For powders of 20-30 μm, if they can pass through 600 mesh but not 800 mesh, the particle size D 50 When the powder of 15-20μm can pass through 800 mesh but not 1000 mesh, the particle size D 50 When the powder is 10-15μm and can pass through a 1000-mesh sieve, the particle size D 50 For powders of 3-5 μm, the total sieving time is 10-30 min.

9. The method for preparing the harmonic structure Mo-Si-B alloy according to claim 3, characterized in that: In step 8, the particle size of the coarse powder is 20-30 μm, the particle size of the medium powder is 10-15 μm, and the particle size of the fine powder is 3-5 μm; during the ball milling mixing process, a ball mill jar made of either agate or polyurethane is used, the grinding balls are made of either agate or zirconia, an argon atmosphere is introduced into the ball mill jar, the air pressure is 0.3 MPa-0.6 MPa, during mixing, the ball-to-material ratio is 1-2:1, the ball mill speed is 300-400 r / min, and the ball milling time is 6-8 h.

10. The method for preparing the harmonic structure Mo-Si-B alloy according to claim 3, characterized in that: During the hot pressing sintering in step 9, the powder is placed in a graphite mold for hot pressing sintering. The sintering process is as follows: first, the temperature is raised to 1200-1400°C at a rate of 8-10°C / min and kept at this temperature for 0.5-1h. After keeping the temperature for 0.5-1h, the pressure is applied to 38-60MPa. Then, the temperature is raised to 1600-1800°C at a rate of 8-10°C / min and kept at this temperature for 2-3h. The pressure is maintained at 1600-1800°C. During the sintering process, the vacuum degree is maintained at 6×10 -3 Pa to 1.5×10 -2 Between Pa.

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