Preparation method of in-situ reaction aluminum oxide nanoparticle reinforced aluminum-based boron carbide composite material

Abstract

The invention relates to a preparation method of an in-situ reaction aluminum oxide nanoparticle reinforced aluminum-based boron carbide composite material. The preparation method comprises the following steps: carrying out low-speed ball-milling deformation flaking on aluminum powder to obtain flaky aluminum powder, and controlling the oxygen content in a ball-milling atmosphere to form an oxide film nano layer on the surface of the powder to obtain nano oxidized flaky aluminum powder; then, high-speed ball milling is carried out, so that an oxidation film nano layer is broken and is dispersed and distributed in a crystal or a crystal boundary, high-speed ball milling and cold welding granulation are carried out, and aluminum oxide nano particle reinforced aluminum-based composite powder is obtained; and finally, uniformly mixing with boron carbide micron particles, compacting, sintering and carrying out deformation processing to prepare the aluminum-based boron carbide composite material. According to the preparation method, an oxidation film nano layer is obtained through in-situ oxidation, aluminum oxide nano particles are obtained after high-speed ball milling and crushing, the nano particles are evenly distributed and dispersed, interface bonding is good, the method is simple and controllable, and the method is suitable for large-scale and low-cost preparation; the aluminum-based boron carbide composite material can be used for neutron absorption application scenes such as spent fuel storage and transportation and post-treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aluminum matrix composite material preparation, and particularly relates to a preparation method of in-situ reaction aluminum oxide nanoparticle reinforced aluminum matrix boron carbide composite material. BACKGROUND

[0002] In recent years, with the increasing attention of the state to energy saving and environmental protection, nuclear energy as a high-efficiency clean energy has attracted much attention. The development of nuclear energy and the application of nuclear technology will inevitably produce a large amount of spent fuel. Spent fuel contains a large amount of radioactive elements, has a certain neutron emission rate, and is accompanied by strong alpha and gamma radioactivity, and emits heat. The treatment of spent fuel has become a new problem. Spent fuel currently has two technologies of wet storage and dry storage. Among them, dry storage is to place spent fuel in a protective grid made of neutron absorbing material, and to pass protective gas in the grid, which is more economical and safe than wet storage.

[0003] Dry storage of spent fuel requires a material that can absorb thermal neutrons. Boron isotope 10B has strong capture ability for thermal neutrons. Boron will not produce harmful elements after contacting thermal neutrons, and the secondary radiation energy is low. In addition, there is a large amount of boron in nature, which makes it suitable as a neutron absorbing element.

[0004] The boron carbide microparticles have large neutron capture cross section, wide capture spectrum, strong absorption capacity, and advantages of low density, high melting point, high hardness, high elastic modulus, and good wear resistance, which make them suitable as neutron absorbing materials. However, they have defects of high brittleness, poor plasticity, poor oxidation resistance, and low sintering temperature, so they cannot be used as single structure materials in the field of neutron protection. Aluminum has good engineering properties of low density and easy processing, and is an excellent matrix material in composite materials. After dispersing boron carbide particles as a strengthening phase into an aluminum matrix to form an aluminum matrix boron carbide composite material, the density of aluminum alloy (2.7 g / cm 3 ) is similar to that of boron carbide (2.52 g / cm 3 ), and the powders of aluminum alloy and boron carbide can be easily mixed uniformly, so that they have neutron absorption capacity, low thermal expansion coefficient, high toughness and high strength, to meet the requirements of high-density storage of spent fuel, and can be applied to the storage and protection field of spent fuel.

[0005] Since dry storage racks lack cooling water, the overall structure needs stronger heat dissipation capabilities to prevent heat accumulation and material softening. Using high-strength structural materials (such as stainless steel) for support would reduce heat dissipation and increase weight. Therefore, aluminum-based boron carbide composite materials for dry storage racks need to possess neutron absorption capabilities, room temperature strength, high temperature strength, high plasticity, and creep resistance. Compared to traditional heat-resistant aluminum alloys, aluminum-based composites using nano-ceramic phases as reinforcement exhibit superior stability at high temperatures. The nano-ceramic reinforcement phase can pin dislocations and grain boundaries in the aluminum matrix, hindering grain growth and improving mechanical properties. Common reinforcement phases include TiC, AlN, Al2O3, and TiB2. Among these, Al2O3 is the most commonly used reinforcement due to its low density, abundant resources, good strength and chemical stability, good wettability with the matrix, and the absence of harmful interfacial products. However, directly adding Al2O3 nano-reinforcing phases through methods such as powder metallurgy will encounter problems such as poor wettability between the Al2O3 nano-reinforcing phase and the aluminum matrix, and easy agglomeration. For example, the Institute of Metal Research, Chinese Academy of Sciences, prepared Al2O3 nano-reinforced aluminum matrix composites through an Al-La2O3 reaction system. The Al2O3 nanoparticles were mainly distributed along the grain boundaries, and micron-sized Al particles were inevitably introduced. 11 La3+ makes it difficult for its room temperature strength to exceed 400 MPa (Zhou, C. et al. Mater. Charact. 188, 111887, 2022). Shandong University prepared Al2O3-reinforced aluminum matrix composites by an additive method. However, the size of Al2O3 is generally larger than 500 nm, making it difficult to improve its number density and thus its room temperature strength is difficult to exceed 350 MPa (Li, M. et al. Compos. Commun. 47, 101860, 2024). It is evident that Al2O3-reinforced aluminum matrix composites prepared by the above methods generally have poor performance, requiring a novel strategy to improve the mechanical properties of the composites. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a method for preparing an in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material. The prepared composite material contains alumina nanoparticles with an average size not exceeding 50 nm, distributed both within the aluminum matrix and at grain boundaries. This method not only meets the requirements for neutron absorption applications but also exhibits excellent high-temperature mechanical properties. The preparation process includes the following steps: The objective of this invention can be achieved through the following methods: This invention provides a method for preparing an in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material, comprising the following steps: S1. The aluminum matrix powder is ball-milled at low speed. During the low-speed ball milling process, oxygen or oxygen-containing gas is intermittently introduced to oxidize the aluminum matrix powder in situ, thereby obtaining aluminum matrix powder I. S2. The obtained aluminum-based powder I is subjected to high-speed ball milling to obtain aluminum-based powder II; S3. Mix the obtained aluminum-based powder II with boron carbide micron particles, and then ball-mill to obtain mixed powder III; S4. The obtained mixed powder III is subjected to compaction, heat preservation, sintering and hot extrusion to obtain alumina nanoparticle reinforced aluminum-based boron carbide composite material.

[0007] In one embodiment of the present invention, in step S1, the aluminum matrix includes one or more of pure aluminum, 1-series aluminum alloys, 2-series aluminum alloys, 5-series aluminum alloys, 6-series aluminum alloys, and 7-series aluminum alloys. The particle size of the aluminum matrix powder is 1μm to 100μm.

[0008] In one embodiment of the present invention, in step S1, the rotation speed of the low-speed ball mill is 100 rpm to 200 rpm, and the time is 4 h to 24 h. The low-speed ball milling is carried out under an inert atmosphere.

[0009] In one embodiment of the present invention, in step S1, the intermittent introduction of oxygen-containing gas specifically involves: ball milling for 1-2 hours, followed by introducing oxygen or oxygen-containing gas to oxidize the Al powder for 10 minutes to 1 hour, and then continuing ball milling after oxidation. The Al powder is oxidized by introducing oxygen or oxygen-containing gas at least four times. The mass fraction of alumina generated by the in-situ reaction is 0.5% to 8%. The oxygen-containing gas is one of air or a nitrogen-oxygen mixture.

[0010] The direct addition method of Al2O3 cannot avoid the problem of agglomeration. The original Al2O3 film produced by ball milling oxidation in this invention has a thinner film thickness, and smaller Al2O3 particles can be generated in subsequent processes.

[0011] In one embodiment of the present invention, in step S1, the grinding balls used in the low-speed ball mill are hard balls, including one or more of alumina, zirconium oxide, silicon carbide, zirconium silicate, tungsten carbide, agate, quartz, high-chromium alloy, carbon steel, bearing steel, and stainless steel grinding balls. The grinding aids include one or more of stearic acid, mineral oil, palm oil, polyethylene glycol, and alcohol.

[0012] In one embodiment of the present invention, in step S2, the high-speed ball mill rotates at a speed of 300 rpm to 500 rpm for a time of 1 h to 4 h. The high-speed ball milling is performed under an inert atmosphere.

[0013] As one embodiment of the present invention, in the aluminum-based powder II obtained in step S2, the average size of the alumina nanoparticles reacted in situ is no greater than 50 nm.

[0014] In one embodiment of the present invention, the mass fraction of boron carbide micron-sized particles in the mixed powder III obtained in step S3 is 5% to 30%. The particle size of the boron carbide particles ranges from 1 μm to 100 μm, and preferably from 5 μm to 20 μm.

[0015] In one embodiment of the present invention, in step S3, ball milling is performed under an inert atmosphere at a rotation speed of 50 rpm to 100 rpm for a time of 2 h to 8 h. Low-speed ball milling ensures uniform distribution of boron carbide micron-sized particles.

[0016] In one embodiment of the present invention, in step S4, the pressure of the compact forming is 200MPa~600MPa, and the holding time is 20s~600s.

[0017] In one embodiment of the present invention, in step S4, the temperature for heat preservation is 400°C and the time is 1h to 2h.

[0018] In one embodiment of the present invention, in step S4, the sintering temperature is 550℃~650℃ and the time is 1h~5h.

[0019] In one embodiment of the present invention, in step S4, the temperature of hot extrusion is 400°C to 500°C, and the extrusion speed is 1 mm / s to 10 mm / s.

[0020] The composite compact obtained by compact forming is first evacuated from the furnace to below the back vacuum level. The furnace is then heated to degas and remove the ball milling aids. The temperature is then raised to the sintering temperature for sintering. Afterward, the compact is cooled to room temperature in the furnace before being removed. During sintering, the back vacuum level is maintained above 10°C. -1 Pa is then subjected to hot extrusion to achieve densification and deformation, resulting in an aluminum nanoparticle-reinforced aluminum-based boron carbide composite material.

[0021] In the composite material prepared according to the above steps, the alumina nanoparticles generated by the in-situ reaction exist simultaneously at the grain boundaries and within the grains. The alumina nanoparticles inside the grains achieve dislocation strengthening by hindering dislocation movement; the alumina nanoparticles located at the grain boundaries pin the grain boundaries, inhibit grain boundary slip, and slow down the annihilation of dislocations at the grain boundaries.

[0022] This invention provides an application of the in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material obtained by the above preparation method in the preparation of spent fuel dry storage racks.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) During low-speed ball milling, the original aluminum powder is flaked, increasing the specific surface area and exposing a fresh metal surface. Then, air or an oxygen-containing nitrogen-oxygen mixture is introduced into the flaked aluminum powder to form a dense alumina film on the surface. By changing the ball milling time and oxidation times, the alumina content can be controlled and prepared in a controlled manner, with the mass fraction adjustable between 0.5% and 8%. Furthermore, the alumina film is broken by high-energy impact during high-speed ball milling, making it uniformly dispersed within the grains and at the grain boundaries, significantly refining the grain size of the matrix material. The interface between the alumina nano-reinforcing phase and the matrix is ​​clean, with no other interface products, exhibiting good interfacial bonding.

[0024] (2) By changing the sintering temperature and holding time, the transformation from alumina film to nanoparticles is achieved, and the shape and size of the reinforcing phase are controlled. The average diameter of the alumina nanoparticles is 10 nm to 50 nm. Therefore, by changing the size and shape of the reinforcing phase, the room temperature / high temperature mechanical properties of aluminum-based boron carbide composites can be precisely controlled.

[0025] (3) The alumina nanoparticles generated by the in-situ reaction exist simultaneously at the grain boundaries and within the grains. The alumina nanoparticles inside the grains achieve dislocation strengthening by hindering dislocation movement; the alumina nanoparticles located at the grain boundaries pin the grain boundaries, inhibit grain boundary sliding, and slow down the annihilation of dislocations at the grain boundaries. Attached Figure Description

[0026] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the structure of the in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material of the present invention.

[0027] Figure 2 Transmission electron microscope image of the in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material prepared in Example 1 of this invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0029] This invention relates to a method for preparing an aluminum-based boron carbide composite material reinforced with in-situ reacted alumina nanoparticles for neutron absorption. The aluminum-based boron carbide composite material comprises boron carbide micron-sized particles, alumina nanoparticles, and an aluminum matrix. The alumina nanoparticles generated by the in-situ reaction exist simultaneously at grain boundaries and within the grains. The alumina nanoparticles within the grains strengthen the composite by hindering dislocation movement; the alumina nanoparticles located at grain boundaries pin the grain boundaries, inhibit grain boundary slip, and slow down dislocation annihilation at the grain boundaries. This invention achieves excellent room-temperature and high-temperature mechanical properties by using boron carbide micron-sized particles to absorb neutrons and alumina nanoparticles to stabilize the grain structure. The preparation method employs powder metallurgy technology. First, aluminum powder is ball-milled at low speed to deform and sheet into flake-like aluminum powder (Powder I). The oxygen content in the ball-milling atmosphere is controlled to form a nano-oxide film layer on the surface of Powder I, resulting in nano-oxide flake-like aluminum powder (Powder II). Then, it is ball-milled at high speed to break up the oxide film nano-layer and disperse it within the grains or at the grain boundaries. The high-speed ball-milling time is extended to allow Powder II to be cold-welded and granulated, obtaining alumina nanoparticle-reinforced aluminum-based composite powder (Powder III). Finally, Powder III is uniformly mixed with boron carbide micron-sized particles, pressed, sintered, and deformed to prepare an aluminum-based boron carbide composite material. This preparation method obtains an oxide film nano-layer through in-situ oxidation and then breaks it up through high-speed ball milling to obtain alumina nanoparticles. The nanoparticles are uniformly distributed, dispersed, and have good interfacial bonding. The method is simple, controllable, and suitable for large-scale, low-cost preparation. The aluminum-based boron carbide composite material can be used in neutron absorption applications such as spent fuel storage, transportation, and reprocessing.

[0030] The present invention proposes a method for preparing an in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material, which is carried out according to the following steps: S1. Weigh aluminum matrix powder with a diameter of 5μm~40μm and place it in a planetary ball mill jar. The aluminum matrix can be one or more of pure aluminum, 1-series aluminum alloys, 2-series aluminum alloys, 5-series aluminum alloys, 6-series aluminum alloys, and 7-series aluminum alloys. Add grinding balls such as zirconium oxide or stainless steel. To prevent cold welding of the powder during ball milling, add an appropriate amount of stearic acid or alcohol as a ball milling aid. Control the ball milling speed at 100rpm~200rpm and conduct ball milling under a high-purity Ar atmosphere. The ball milling time is 4h~24h. Oxidize the Al powder by aeration in 1h~4h cycles for 10min~1h, thereby obtaining aluminum-based powder I. The mass fraction of alumina generated in situ is 5%~10%.

[0031] S2. The powder after low-speed ball milling is then subjected to high-speed ball milling, with the milling speed controlled at 200 rpm to 500 rpm, under a high-purity Ar atmosphere. The milling time is 1 h to 4 h to obtain aluminum-based powder II.

[0032] S3. Alumina-reinforced aluminum-based composite powder is mixed with boron carbide micron particles with a particle size range of 1μm to 500μm, wherein the mass fraction of boron carbide micron particles is 5% to 50%, and the boron carbide micron particles are uniformly distributed by low-speed ball milling. Ball milling is carried out under a high-purity Ar atmosphere at a speed of 50 rpm to 100 rpm for 4 h to 8 h to obtain mixed powder III.

[0033] S4. Press the above mixed powder into a compact at a pressure of 400MPa~600MPa and a holding time of 20s~60s to obtain a composite compact.

[0034] S5. Place the composite compact in a vacuum sintering furnace for sintering. First, evacuate the furnace to 10°C. -1 The temperature is below Pa, then the temperature is raised from room temperature to 400℃ and held for 1-2 hours to remove stearic acid and degas. Then the temperature is raised to the sintering temperature and held for 2-4 hours for sintering. The sintering temperature is 570℃-650℃. After cooling to room temperature in the furnace, the ingot is taken out to obtain the sintered billet.

[0035] S6. The sintered sample is held at 300°C~500°C and hot-extruded at a speed of 1mm / s~10mm / s to achieve densification of the composite material, ultimately obtaining an in-situ reacted alumina nanoparticle-reinforced aluminum-based boron carbide composite material. The average size of the in-situ reacted alumina nanoparticles in the composite material is less than 50nm, and they are distributed simultaneously within the aluminum matrix grains and at the grain boundaries. The structural schematic diagram is shown below. Figure 1 As shown.

[0036] Example 1 S1. Weigh pure aluminum powder with a diameter of 1 μm and place it in a planetary ball mill jar. Add zirconia grinding balls. To prevent cold welding of the powder during ball milling, add an appropriate amount of stearic acid as a ball milling aid. Control the ball milling speed at 100 rpm and ball mill under a high-purity Ar atmosphere. The ball milling time is 4 hours. In 1-hour cycles, oxidize the Al powder with air for 10 minutes to obtain aluminum-based powder I. The mass fraction of alumina (30 nm) generated by the in-situ reaction is 1.5%.

[0037] S2. The powder after low-speed ball milling is then subjected to high-speed ball milling at a speed of 300 rpm under a high-purity Ar atmosphere. The milling time is 1 hour to obtain aluminum-based powder II.

[0038] S3. Alumina-reinforced aluminum-based composite powder was mixed with boron carbide micron particles with a particle size range of 1 μm, the mass fraction of which was 5%. The boron carbide micron particles were then uniformly distributed by low-speed ball milling. Ball milling was carried out under a high-purity Ar atmosphere at a speed of 50 rpm for 2 hours to obtain mixed powder III.

[0039] S4. Press the above mixed powder into a compact at a pressure of 200 MPa and a holding time of 20 s to obtain a composite compact.

[0040] S5. Place the composite compact in a vacuum sintering furnace for sintering. First, evacuate the furnace to 10°C. -1 The temperature is below Pa, then the temperature is raised from room temperature to 400℃ and held for 1 hour to remove stearic acid and degas. Then the temperature is raised to the sintering temperature and held for 2 hours for sintering. The sintering temperature is 550℃. After cooling to room temperature in the furnace, the ingot is taken out to obtain the sintered billet.

[0041] S6. The sintered billet is kept at 400℃ and hot extruded at a speed of 1mm / s to achieve densification of the composite material, and finally obtains an in-situ reactive alumina nanoparticle reinforced aluminum-based boron carbide composite material.

[0042] The in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material prepared in this embodiment is shown in the transmission electron microscope image below. Figure 2 As shown, the tensile strength at room temperature is 312 MPa and the elongation is 15.1%, while the tensile strength at 300℃ is 126 MPa and the elongation is 8.6%.

[0043] Example 2 S1. Weigh pure aluminum powder with a diameter of 100 μm and place it in a planetary ball mill jar. Add stainless steel grinding balls. To prevent cold welding of the powder during ball milling, add an appropriate amount of alcohol as a ball milling aid. Control the ball milling speed at 200 rpm and conduct ball milling under a high-purity Ar atmosphere. The ball milling time is 24 hours. Oxidize the Al powder by aeration in 1-hour cycles for 1 hour each time, thereby obtaining aluminum-based powder I. The mass fraction of alumina generated in the in-situ reaction is 5%.

[0044] S2. The powder after low-speed ball milling is then subjected to high-speed ball milling at a speed of 500 rpm under a high-purity Ar atmosphere. The milling time is 4 hours to obtain aluminum-based powder II.

[0045] S3. Alumina-reinforced aluminum-based composite powder was mixed with boron carbide micron particles with a particle size range of 100 μm, the mass fraction of which was 30%. The boron carbide micron particles were then uniformly distributed by low-speed ball milling. Ball milling was carried out under a high-purity Ar atmosphere at a speed of 100 rpm for 8 hours to obtain mixed powder III.

[0046] S4. Press the above mixed powder into a compact at a pressure of 600 MPa and a holding time of 600 s to obtain a composite compact.

[0047] S5. Place the composite compact in a vacuum sintering furnace for sintering. First, evacuate the furnace to 10°C. -1 The temperature is below Pa, then the temperature is raised from room temperature to 400℃ and held for 2 hours to remove stearic acid and degas. Then the temperature is raised to the sintering temperature and held for 4 hours for sintering. The sintering temperature is 650℃. After cooling to room temperature in the furnace, the ingot is taken out.

[0048] S6. The sintered sample is kept at 500℃ and hot-extruded at a speed of 10mm / s to achieve densification of the composite material, and finally obtains an in-situ reactive alumina nanoparticle reinforced aluminum-based boron carbide composite material.

[0049] The in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material prepared in this embodiment has a tensile strength of 589 MPa and an elongation of 6.3% at room temperature, and a tensile strength of 362 MPa and an elongation of 4.2% at 300°C.

[0050] Example 3 S1. Weigh pure aluminum powder with a diameter of 30 μm and place it in a planetary ball mill jar. Add stainless steel grinding balls. To prevent cold welding of the powder during ball milling, add an appropriate amount of stearic acid as a ball milling aid. Control the ball milling speed at 135 rpm and conduct ball milling under a high-purity Ar atmosphere. The ball milling time is 12 h. At 2-hour intervals, oxidize the Al powder by aeration for 30 min, thereby obtaining aluminum-based powder I. The mass fraction of alumina generated in the in-situ reaction is 4%.

[0051] S2. The powder after low-speed ball milling is then subjected to high-speed ball milling at a speed of 375 rpm under a high-purity Ar atmosphere. The milling time is 2 hours to obtain aluminum-based powder II.

[0052] S3. Alumina-reinforced aluminum-based composite powder was mixed with boron carbide micron particles with a particle size range of 10 μm, the mass fraction of which was 15%. The boron carbide micron particles were then uniformly distributed by low-speed ball milling. Ball milling was carried out under a high-purity Ar atmosphere at a speed of 80 rpm for 8 hours to obtain mixed powder III.

[0053] S4. Press the above mixed powder into a compact at a pressure of 600 MPa and a holding time of 40 s to obtain a composite compact.

[0054] S5. Place the composite compact in a vacuum sintering furnace for sintering. First, evacuate the furnace to 10°C. -1 The temperature is below Pa, then the temperature is raised from room temperature to 400℃ and held for 2 hours to remove stearic acid and degas. Then the temperature is raised to the sintering temperature and held for 3 hours for sintering. The sintering temperature is 630℃. After cooling to room temperature in the furnace, the ingot is taken out to obtain the sintered billet.

[0055] S6. The sintered sample is kept at 400°C and hot-extruded at a speed of 5 mm / s to achieve densification of the composite material, and finally obtains an in-situ reactive alumina nanoparticle reinforced aluminum-based boron carbide composite material.

[0056] The in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material prepared in this embodiment has a tensile strength of 386 MPa and an elongation of 5.3% at room temperature, and a tensile strength of 152 MPa and an elongation of 3.4% at 300°C.

[0057] Example 4 S1. Weigh pure aluminum powder with a diameter of 20 μm and place it in a planetary ball mill jar. Add stainless steel grinding balls. To prevent cold welding of the powder during ball milling, add an appropriate amount of stearic acid as a ball milling aid. Control the ball milling speed at 100 rpm and conduct ball milling under a high-purity Ar atmosphere. The ball milling time is 8 hours. Oxidize the Al powder by aeration in 1-hour cycles for 10 minutes, thereby obtaining aluminum-based powder I. The mass fraction of alumina generated in the in-situ reaction is 3%.

[0058] S2. The powder after low-speed ball milling is then subjected to high-speed ball milling at a speed of 375 rpm under a high-purity Ar atmosphere. The milling time is 1 hour to obtain aluminum-based powder II.

[0059] S3. Alumina-reinforced aluminum-based composite powder was mixed with boron carbide micron particles with a particle size range of 100 μm, the mass fraction of which was 30%. The boron carbide micron particles were then uniformly distributed by low-speed ball milling. Ball milling was carried out under a high-purity Ar atmosphere at a speed of 50 rpm for 8 hours to obtain mixed powder III.

[0060] S4. Press the above mixed powder into a compact at a pressure of 500 MPa and a holding time of 60 s to obtain a composite compact.

[0061] S5. Place the composite compact in a vacuum sintering furnace for sintering. First, evacuate the furnace to 10°C. -1Below Pa, the temperature is then increased from room temperature to 400℃ and held for 2 hours to degas and remove stearic acid. Then, the temperature is increased to the sintering temperature and held for 2 hours for sintering. The sintering temperature is 600℃. o C. After cooling to room temperature in the furnace, the ingot is removed to obtain a sintered billet.

[0062] S6. The sintered sample is kept at 400℃ and hot-extruded at a speed of 5mm / s to achieve densification of the composite material, and finally obtains an in-situ reactive alumina nanoparticle reinforced aluminum-based boron carbide composite material.

[0063] The in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material prepared in this embodiment has a tensile strength of 551 MPa and an elongation of 5.3% at room temperature, and a tensile strength of 258 MPa and an elongation of 3.9% at 300°C.

[0064] Comparative Example 1 This comparative example provides an in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material. The preparation method is basically the same as that in Example 1, except that: Al powder and alumina (30 nm, mass fraction 0.5%) are mixed in equal proportions and then subjected to high-speed ball milling.

[0065] Comparative Example 2 This comparative example provides an in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material. The preparation method is basically the same as that in Example 1, except that: an equal amount of aluminum powder is added to boehmite sol (the alumina content is the same as that in Example 1) and stirred and dispersed. Then the boehmite sol is dried to obtain aluminum powder with a boehmite layer on the surface; then it is mixed with boron carbide micron particles.

[0066] Comparative Example 3 This comparative example provides an in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material. The preparation method is basically the same as that in Example 1, except that: the Al powder is directly ball-milled at low speed for 4 hours, and then oxidized by aeration for 40 minutes.

[0067] A single oxidation process produces a dense alumina film that prevents further oxidation, and even over a long period, a high alumina content cannot be introduced.

[0068] Comparative Example 4 This comparative example provides an in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material. The preparation method is basically the same as that in Example 1, except that the powder after low-speed ball milling is further ball milled at low speed (100 rpm, 1 h). Comparative Example 5 This comparative example provides an in-situ reactive alumina nanoparticle-reinforced aluminum-based boron carbide composite material. The preparation method is basically the same as that in Example 1, except that the low-speed ball milling speed is adjusted to 500 rpm.

[0069] High-speed ball milling cannot be used to flake Al powder directly, thus failing to increase the surface area.

[0070] The test performance is shown in Table 1: Table 1

[0071] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for producing in-situ reaction alumina nanoparticle reinforced aluminum matrix boron carbide composite material, characterized in that, The method comprises the following steps: S1, low-speed ball milling of aluminum matrix powder, intermittent filling of oxygen or oxygen-containing gas during low-speed ball milling, in-situ oxidation of aluminum matrix powder to obtain aluminum matrix powder I; S2, high-speed ball milling of the obtained aluminum matrix powder I to obtain aluminum matrix powder II; S3, mixing of the obtained aluminum matrix powder II with boron carbide microparticles, and ball milling to obtain mixed powder III; S4, green compact molding, heat preservation, sintering treatment, and hot extrusion processing of the obtained mixed powder III to obtain an aluminum oxide nanoparticle reinforced aluminum matrix boron carbide composite material.

2. The production method according to claim 1, characterized by, In step S1, the aluminum matrix comprises one or more of pure aluminum, 1-series aluminum alloy, 2-series aluminum alloy, 5-series aluminum alloy, 6-series aluminum alloy, and 7-series aluminum alloy matrix. And / or, the particle size of the aluminum matrix powder is 1 μm to 100 μm.

3. The preparation method according to claim 1, characterized in that, In step S1, the rotation speed of low-speed ball milling is 100 rpm to 200 rpm, and the time is 4 h to 24 h.

4. The method of claim 1, wherein, In step S1, the intermittent filling of oxygen-containing gas is as follows: after ball milling for 1 h to 4 h, oxygen or oxygen-containing gas is filled to oxidize the Al powder, the oxidation time is 10 min to 1 h, and after oxidation, the ball milling is continued.

5. The preparation method according to claim 1, characterized in that, The mass fraction of aluminum oxide generated by in-situ reaction is 0.5% to 8%.

6. The method of claim 1, wherein, In step S2, the rotation speed of high-speed ball milling is 200 rpm to 500 rpm, and the time is 1 h to 4 h.

7. The preparation method according to claim 1, characterized in that, In the mixed powder III obtained in step S3, the mass fraction of boron carbide microparticles is 5% to 30%; And / or, the particle size of the boron carbide particles is 1 μm to 100 μm.

8. The method of claim 1, wherein, In step S3, the ball milling is carried out under inert atmosphere protection, the ball milling rotation speed is 50 rpm to 100 rpm, and the ball milling time is 2 h to 8 h.

9. The method of claim 1, wherein, In step S4, the pressure for green compact molding is 200 MPa to 600 MPa, and the pressure holding time is 20 s to 600 s; The heat preservation temperature is 400°C, and the time is 1 h to 2 h; The sintering treatment temperature is 550°C to 650°C, and the time is 1 h to 5 h; The hot extrusion processing temperature is 400°C to 500°C, and the extrusion speed is 1 mm / s to 10 mm / s.

10. Use of an in-situ reaction aluminum oxide nanoparticle reinforced aluminum matrix boron carbide composite material obtained by the preparation method of claim 1 in the preparation of a spent fuel dry storage rack.

Images