High-strength high-toughness plasticity neutron absorption plate and manufacturing method thereof

Abstract

The application discloses a kind of high-strength high-tough plasticity neutron absorption plate and its manufacturing method, belong to neutron absorption material field, the method is by mixing the aluminum powder of different thickness to regulate the content of mixed grain structure in neutron absorption material matrix and nano Al2O3 reinforcing phase, the amorphous Al2O3 of aluminum powder surface layer can effectively hinder the fusion between different aluminum powder grains and grow, so that the grain size distribution characteristics of mixed particle size aluminum powder can be retained after forming processing, form mixed grain structure in Al2O3 / B4C / Al neutron absorption material.The control of specific surface area and oxygen content of mixed particle size aluminum powder can ensure that sufficient content of in-situ nano Al2O3 is introduced, which can pin the grain boundary at high temperature, effectively inhibit grain growth and significantly improve the high-temperature mechanical strength of neutron absorption material.The mixed grain structure designed in the neutron absorption material can take advantage of the high strength of fine-grained grains and the high plasticity of coarse-grained grains.

Description

Technical Field

[0001] This invention relates to a high-strength, high-toughness, and ductile neutron absorbing plate and its manufacturing method, belonging to the field of neutron absorbing materials. Background Technology

[0002] Aluminum-based boron carbide (B4C / Al) composites possess high specific strength, low density, high thermal conductivity, and excellent neutron absorption, making them ideal neutron absorbing materials. Among them, B4C / Al neutron absorbing materials reinforced with nano-ceramic particles exhibit excellent high-temperature mechanical strength and can be applied to spent fuel dry storage containers and transport containers. However, while existing nano-ceramic particle-reinforced B4C / Al neutron absorbing materials possess high strength, they suffer from poor plasticity and impact toughness, failing to simultaneously possess excellent high-temperature strength and plasticity. In fact, the higher the strength, the worse the plasticity, making even the material's molding and processing extremely difficult. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention provides a high-strength, high-toughness and plasticity neutron absorbing plate and its manufacturing method. The plate obtained has both high strength at high temperature and good toughness and plasticity.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] In a first aspect, this application provides a method for manufacturing a high-strength, high-toughness, and ductile neutron-absorbing plate, comprising the following steps:

[0006] Aluminum powder of varying coarseness is mixed to obtain aluminum powder with a mixed particle size; the specific surface area of ​​the mixed particle size aluminum powder is ≥1.5 m². 2 / g, oxygen content ≥1.0wt%;

[0007] Boron carbide particles are mixed with the aluminum powder of the mixed particle size to obtain a composite powder.

[0008] The composite powder is pressed into a blank;

[0009] The billet is sintered in two stages to obtain an ingot; the temperature of the first stage sintering is 370℃~420℃, and the temperature of the second stage sintering is 510℃~540℃.

[0010] The billet is subjected to hot extrusion to obtain an extruded thick plate; the hot extrusion temperature is 450℃~500℃, the extrusion ratio is 10:1~20:1, and the extrusion speed is 2mm / s~8mm / s.

[0011] The extruded thick plate is subjected to high strain rate hot rolling to obtain the high-strength, high-toughness, and high-plasticity neutron absorbing plate; the total hot rolling reduction is 30%~60%, the number of rolling passes is 2~6, the temperature is 400℃~450℃, and the rolling speed is 20m / min~50m / min.

[0012] The method for manufacturing a high-strength, high-toughness, and high-plasticity neutron absorbing plate provided in this application can produce a plate with good toughness and plasticity, and high strength at high temperatures. Microscopically, micron-sized B4C particles are uniformly distributed in the matrix, and in-situ nano-Al2O3 particles are distributed at the grain boundaries and within the grains of the matrix. The matrix is ​​a mixed grain structure composed of a large number of fine grains and some coarse grains, and at the same time, it contains a high-density stacking fault structure within the matrix grains.

[0013] Furthermore, the raw material aluminum powder includes fine aluminum powder with an average particle size of 1.1μm to 1.5μm and other aluminum powders with even larger particle sizes. The in-situ nano-Al2O3 particles give the plate high strength at high temperatures. The nano-Al2O3 reinforcing phase distributed at the grain boundaries and within the grains can pin and strengthen the grain boundaries at high temperatures, effectively inhibiting grain growth and significantly improving the high-temperature mechanical strength of the neutron absorbing material.

[0014] Furthermore, relative to the fine aluminum powder, "other coarser aluminum powders" include medium aluminum powder with an average particle size of 2.0 μm to 7.5 μm and / or coarse aluminum powder with an average particle size of 7.5 μm to 15 μm, wherein the oxygen content of both the medium aluminum powder and the coarse aluminum powder is 0.3 wt% to 0.8 wt%. The medium aluminum powder, or the coarse aluminum powder, or both, form a coarse-grained portion in the microstructure after calcination. This coarse-grained portion gives the material good plasticity, which is more conducive to the formation of high-density stacking faults in subsequent processes.

[0015] Furthermore, in the raw aluminum powder, by mass, the fine aluminum powder accounts for 75% to 90%, the medium aluminum powder accounts for 8% to 25%, and the coarse aluminum powder accounts for 0% to 3%.

[0016] Furthermore, in the composite powder, by mass, the mixed particle size aluminum powder accounts for 85%~92%, and the boron carbide particles account for 8%~15%.

[0017] Furthermore, the boron carbide particles are nuclear-grade boron carbide with an average particle size of 1 μm to 25 μm. Nuclear-grade boron carbide refers to boron carbide with an atomic percentage (10B / B) of 19.60% to 20.00% of the 10B isotope.

[0018] Furthermore, the density of the billet is 85%~95%. The billet can be pressed by cold isostatic pressing, hot isostatic pressing, or uniaxial hot pressing.

[0019] Furthermore, the sintering time for the first stage is 12h~16h, and the sintering time for the second stage is 2h~12h. During the sintering stage, the temperature is between 510℃ and 540℃, which falls within the transformation temperature range of amorphous Al2O3 to crystalline γAl2O3. By strictly controlling the sintering time, the partial transformation of amorphous Al2O3 to crystalline Al2O3 is promoted, while maintaining the matrix grain size and preventing a decrease in strength, thus improving the plasticity and processing performance of the billet.

[0020] Preferably, during the hot extrusion process, the temperature is 480℃~500℃, the extrusion ratio is 10:1, and the extrusion speed is 2.5mm / s~4mm / s.

[0021] Secondly, this application provides a high-strength, high-toughness, and ductile neutron absorbing plate, manufactured according to the method for producing such a plate described in the first aspect. The plate comprises: 1.0 wt% to 2.0 wt% Al₂O₃, 8.0 wt% to 15.0 wt% B₄C, and the remainder being aluminum. In the microstructure of this plate, the matrix is ​​a mixed grain structure consisting of fine grains and some coarse grains, with uniform distribution of fine and coarse grains and a large number of high-density stacking faults within the crystals. In-situ nano-Al₂O₃ reinforcing phases are distributed at the grain boundaries and within the grains, while B₄C particles are uniformly distributed within the matrix. The in-situ nano-Al₂O₃ has a size of 10 nm to 100 nm, exhibiting a coexistence of nanosheets and particles; the fine grain size is 300 nm to 1.0 μm, and the coarse grain size is 1.0 μm to 20 μm, with the coarse grains accounting for 10% to 30% of the total grain volume of the matrix.

[0022] The beneficial effects of this invention are as follows: This invention regulates the mixed grain structure and the content of nano-Al2O3 reinforcing phase in the Al2O3 / B4C / Al neutron absorber matrix by mixing aluminum powders of varying coarseness. The amorphous Al2O3 on the surface of the aluminum powder effectively hinders the fusion and growth of different aluminum powder grains, allowing the grain size distribution characteristics of the mixed-size aluminum powder to be retained after molding and processing, thus forming a mixed grain structure in the Al2O3 / B4C / Al neutron absorber. Controlling the specific surface area and oxygen content of the mixed-size aluminum powder ensures the introduction of sufficient in-situ nano-Al2O3, which can pin and strengthen grain boundaries at high temperatures, effectively inhibiting grain growth and significantly improving the high-temperature mechanical strength of the neutron absorber. The mixed grain structure designed in the neutron absorber can leverage the advantages of high strength in fine grains and high plasticity in coarse grains.

[0023] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0024] Figure 1 This is the electron micrograph of the plate material prepared in Example 1, showing the coexistence of sheet-like and granular nano-alumina.

[0025] Figure 2 This is the electron micrograph of the stacking fault state inside the grains in the plate material prepared in Example 1.

[0026] Figure 3 yes Figure 2 Inverse Fourier transform diffraction spot at the center frame.

[0027] Figure 4 This is a macroscopic photograph of the extruded thick plate in Example 2.

[0028] Figure 5 This is a macroscopic photograph of the final sheet material obtained in Example 2.

[0029] Figure 6 This is a macroscopic photograph of the extruded thick plate in Comparative Example 3. Detailed Implementation

[0030] To address the problem of inverted strength and toughness / plasticity in existing high-temperature structural and functional integrated B4C / Al neutron absorbing materials, this invention provides a high-strength, high-toughness / plasticity neutron absorbing plate (actually a high-temperature comprehensive performance nano-Al2O3-reinforced B4C / Al neutron absorbing material), and proposes a simple manufacturing method suitable for the industrial production of large-size plates.

[0031] The specific steps of this method are as follows:

[0032] S1: Mix raw aluminum powder of different coarse and fine sizes to obtain aluminum powder with mixed particle size.

[0033] The aluminum powder shall be mixed according to the following mass percentages: 75%–90% fine aluminum powder with an average particle size of 1.1 μm–1.5 μm, 8%–25% medium aluminum powder with an average particle size of 2.0 μm–7.5 μm, and 0%–3% coarse aluminum powder with an average particle size of 7.5 μm–15 μm. The oxygen content of the fine aluminum powder shall be 1.1 wt%–1.3 wt%, and the oxygen content of the coarse aluminum powder shall be 0.3 wt%–0.8 wt%. The mixture shall be mechanically mixed until homogeneous, and the specific surface area of ​​the mixed aluminum powder shall be ≥1.5 m². 2 / g, the oxygen content of the mixed particle size aluminum powder is ≥1.0wt%.

[0034] S2: Boron carbide particles are mixed with aluminum powder of mixed particle size to obtain composite powder.

[0035] Prepare the raw materials according to the following mass percentages: 85%~92% aluminum powder with a mixed particle size, and 8%~15% nuclear-grade boron carbide particles with an average particle size of 1μm~25μm (the atomic percentage of 10B isotope (10B / B) should be 19.60%~20.00%). Mix them evenly using a mechanical mixing method.

[0036] S3: Press the composite powder into a blank.

[0037] Compression molding can be performed using methods such as cold isostatic pressing, hot isostatic pressing, or uniaxial hot pressing, with a blank density of 85% to 95%.

[0038] S4: The billet is obtained by sintering the billet in two stages.

[0039] The first sintering temperature is 370℃~420℃, and the sintering time is 12h~16h; the second sintering temperature is 510℃~540℃, and the sintering time is 2h~12h.

[0040] S5 performs hot extrusion treatment on the billet to obtain extruded thick plates.

[0041] The hot extrusion temperature is 450℃~500℃, the extrusion ratio is 10:1~20:1, and the extrusion speed is 2mm / s~8mm / s. Preferably, the extrusion temperature is 480℃~500℃, the preferred extrusion ratio is 10:1, and the preferred extrusion speed is 2.5mm / s~4mm / s.

[0042] S6: High strain rate hot rolling is performed on the extruded thick plate to obtain a neutron absorbing plate with high strength, high toughness and plasticity.

[0043] The total hot rolling reduction is 30%~60%, the number of rolling passes is 2~6, the temperature is 400℃~450℃, and the rolling speed is 20m / min~50m / min.

[0044] In step S1, by controlling the specific surface area and oxygen content of the aluminum powder, coarse and fine aluminum powders are mixed in a specific ratio to prepare aluminum powder with a certain specific surface area and oxygen content, which can ensure the content of nano-alumina reinforcing phase in the neutron absorbing material. At the same time, the design of mixed-size aluminum powder can ultimately obtain a mixed grain structure in the neutron absorbing material structure.

[0045] In step S4, the first stage of low-temperature sintering primarily removes chemically bonded water; the second stage of high-temperature sintering primarily promotes the transformation of continuous amorphous Al2O3 into crystalline Al2O3. The temperature range of 510℃ to 540℃ represents the rapid transformation temperature from amorphous to crystalline Al2O3. By strictly controlling the temperature and time, Al2O3 is in a partially transformed state where nanosheets and particles coexist. The regulation of nano-alumina in the Al2O3 / B4C / Al neutron absorber material during the sintering stage can maintain the high mechanical strength of aluminum-based boron carbide while improving the plasticity and machinability of the ingot, providing favorable preconditions for the hot extrusion and hot rolling deformation processes in steps S5 and S6.

[0046] In step S5, the extrusion temperature should be lower than the second-stage sintering temperature in step S4, that is, lower than the rapid transformation temperature of amorphous Al2O3 to crystalline Al2O3. This effectively avoids the complete transformation of amorphous Al2O3 to crystalline Al2O3 during the extrusion process, which would reduce grain boundary pinning efficiency and even lead to dynamic recrystallization and growth, resulting in a decline in the mechanical properties of the composite material. Simultaneously, selecting the highest possible hot extrusion temperature results in better billet fluidity and a better surface quality for the extruded thick plate, allowing it to be directly used for subsequent hot rolling, thus providing favorable preconditions for the deformation processing in step S6.

[0047] In step S6, the extruded thick plate is rolled under a large rolling reduction and a high rolling speed to improve toughness. The Al2O3 / B4C / Al neutron absorber material undergoes further large plastic deformation, forming a high-density stacking fault inside the Al2O3 / B4C / Al neutron absorber material matrix grains. This can further improve the strain hardening ability of the Al2O3 / B4C / Al neutron absorber material and delay necking and fracture.

[0048] Example 1

[0049] Fine aluminum powder with an average particle size of 1.3 μm, medium aluminum powder with an average particle size of 5.3 μm, and coarse aluminum powder with an average particle size of 10.7 μm were mixed in a mass ratio of 82:15:3 and mechanically mixed to obtain an average particle size D50 (D50 represents the particle size corresponding to a cumulative particle size distribution percentage of 50%) of 1.63 μm and a specific surface area of ​​1.72 m². 2Aluminum powder with a mixed particle size of / g and an oxygen content of 1.16wt.% was then mixed with nuclear-grade boron carbide powder with an average particle size of 7.5μm at a mass ratio of 90:10 to obtain a composite powder with uniformly dispersed boron carbide particles. The composite powder was then vacuum-dried at 180℃ for 4h to remove adsorbed moisture. The composite powder was then placed in a rubber cold-pressing sleeve, vacuumed, and cold isostatically pressed at 350MPa to obtain a blank with a density of 93%. The blank was then subjected to two-stage vacuum sintering: first, the temperature was raised to 420℃ and held for 12h, with the vacuum level reduced to 10. -2 At Pa, the temperature was further increased to 540℃ and held for 4 hours, then cooled in the furnace. Hot extrusion was performed at 500℃ with an extrusion ratio of 10:1 and an extrusion speed of 2.5 mm / s to obtain an extruded plate with a thickness of 30 mm. The extruded plate was rolled at a rolling temperature of 420℃ and a rolling speed of 50 m / min, with each pass requiring a 0.5 h holding time in the furnace, for a total of 3 passes to obtain a plate with a thickness of 15 mm. Finally, the plate was straightened. Samples of the plate obtained in Example 1 were taken to observe its microstructure, and inverse Fourier transform diffraction signals were collected. The results are as follows: Figure 1 , Figure 2 and Figure 3 As shown.

[0050] Comparative Example 1

[0051] The average particle size is 1.61 μm and the specific surface area is 1.30 m². 2 Aluminum powder with an oxygen content of 0.68 wt.% was directly mixed with nuclear-grade boron carbide powder with an average particle size of 7.5 μm at a mass ratio of 90:10, and mechanically mixed to obtain a composite powder with uniformly dispersed boron carbide particles. The composite powder was then vacuum-dried at 180℃ for 4 hours to remove adsorbed moisture. Subsequently, the composite powder was placed in a rubber cold-pressing sleeve, vacuum-sealed, and cold isostatically pressed at 350 MPa to obtain a blank with a density of 93%. The blank was then subjected to two-stage vacuum sintering: first, the temperature was raised to 420℃ and held for 12 hours, with the vacuum level reduced to 10. -2 At Pa, the temperature was further increased to 540℃ and held for 4 hours, then cooled in the furnace. Hot extrusion was performed at 500℃ with an extrusion ratio of 10:1 and an extrusion speed of 2.5 mm / s to obtain an extruded plate with a thickness of 30 mm. The extruded plate was then rolled at a rolling temperature of 420℃ and a rolling speed of 50 m / min, with each pass requiring a 0.5-hour furnace hold, for a total of 3 passes to obtain a plate with a thickness of 15 mm. Finally, the plate was straightened.

[0052] Comparative Example 2:

[0053] Fine aluminum powder with an average particle size of 1.5 μm and medium aluminum powder with an average particle size of 2.0 μm were mixed at a mass ratio of 60:40 and mechanically mixed to obtain an average particle size D50 of 1.65 μm and a specific surface area of ​​1.4 m². 2 Aluminum powder with a mixed particle size of / g and an oxygen content of 0.98wt.% was mixed with nuclear-grade boron carbide powder with an average particle size of 7.5μm at a mass ratio of 90:10 and mechanically mixed to obtain a composite powder with uniformly dispersed boron carbide particles. The composite powder was vacuum dried at 180℃ for 4h to remove adsorbed moisture. The composite powder was then placed in a rubber cold pressing sleeve, vacuumed, and cold isostatically pressed at 350MPa to obtain a blank with a density of 93%. The blank was then subjected to two-stage vacuum sintering. First, the temperature was raised to 420℃ and held for 12h, and the vacuum degree was reduced to 10. -2 At Pa, the temperature was further increased to 540℃ and held for 4 hours, then cooled in the furnace. Hot extrusion was performed at 500℃ with an extrusion ratio of 10:1 and an extrusion speed of 2.5 mm / s to obtain an extruded plate with a thickness of 30 mm. The extruded plate was then rolled at a rolling temperature of 420℃ and a rolling speed of 50 m / min, with each pass requiring a 0.5-hour furnace hold, for a total of 3 passes to obtain a plate with a thickness of 15 mm. Finally, the plate was straightened.

[0054] Example 2

[0055] Fine aluminum powder with an average particle size of 1.4 μm and medium aluminum powder with average particle sizes of 2.0 μm and 5.3 μm were mixed at a mass ratio of 85:10:5 and mechanically mixed to obtain an average particle size D50 of 1.64 μm and a specific surface area of ​​1.5 m². 2 Aluminum powder with a mixed particle size of 1.05 wt.% and an oxygen content of 0.5 wt.% was mixed with nuclear-grade boron carbide powder with an average particle size of 7.5 μm at a mass ratio of 90:10 and mechanically mixed to obtain a composite powder with uniformly dispersed boron carbide particles. The composite powder was vacuum dried at 180℃ for 4 hours to remove adsorbed moisture. The composite powder was then placed in a rubber cold pressing sleeve, vacuumed, and cold isostatically pressed at 350 MPa to obtain a blank with a density of 93%. The blank was then subjected to two-stage vacuum sintering: first, the temperature was raised to 420℃ and held for 12 hours, with the vacuum level reduced to 10. -2 At Pa, the temperature was further increased to 510℃ and held for 12 hours, then cooled in the furnace. Hot extrusion was then performed at 500℃ with an extrusion ratio of 10:1 and an extrusion speed of 2.5 mm / s to obtain an extruded plate with a thickness of 30 mm. The macroscopic morphology is as follows. Figure 4 As shown. The extruded thick plate is rolled at a rolling temperature of 420℃ and a rolling speed of 50m / min. Each pass is held in the furnace for 0.5h, and the plate is rolled in 3 passes to a thickness of 15mm. Finally, the plate is straightened, and the final shape is as shown. Figure 5As shown.

[0056] Comparative Example 3

[0057] Fine aluminum powder with an average particle size of 1.4 μm and medium aluminum powder with average particle sizes of 2.0 μm and 5.3 μm were mixed at a mass ratio of 85:10:5 and mechanically mixed to obtain an average particle size D50 of 1.64 μm and a specific surface area of ​​1.5 m². 2 Aluminum powder with a mixed particle size of 1.05 wt.% and an oxygen content of 1.05 wt.% was mixed with nuclear-grade boron carbide powder with an average particle size of 7.5 μm at a mass ratio of 90:10. The mixture was mechanically mixed to obtain a composite powder with uniformly dispersed boron carbide particles. The composite powder was vacuum dried at 180℃ for 4 hours to remove adsorbed moisture. The composite powder was then placed in a rubber cold pressing sleeve, vacuum-sealed, and cold isostatically pressed at 350 MPa to obtain a blank with a density of 93%. The blank was then subjected to one-stage vacuum sintering, heated to 520℃ and held for 17 hours, and finally cooled in the furnace. Hot extrusion was performed at 420℃ with an extrusion ratio of 10:1 and an extrusion speed of 2.5 mm / s to obtain an extruded plate with a thickness of 30 mm. The macroscopic morphology is as follows. Figure 6 As shown. The extruded thick plate is surface treated and then rolled at a rolling temperature of 420℃ and a rolling speed of 50m / min. Each pass is held in the furnace for 0.5h, and the plate is rolled in 3 passes to a thickness of 15mm. Finally, the plate is straightened.

[0058] Comparative Example 4

[0059] Fine aluminum powder with an average particle size of 1.4 μm and medium aluminum powder with average particle sizes of 2.0 μm and 5.3 μm were mixed at a mass ratio of 85:10:5 and mechanically mixed to obtain an average particle size D50 of 1.64 μm and a specific surface area of ​​1.5 m². 2 Aluminum powder with a mixed particle size of 1.05 wt.% and an oxygen content of 0.5 wt.% was mixed with nuclear-grade boron carbide powder with an average particle size of 7.5 μm at a mass ratio of 90:10 and mechanically mixed to obtain a composite powder with uniformly dispersed boron carbide particles. The composite powder was vacuum dried at 180℃ for 4 hours to remove adsorbed moisture. The composite powder was then placed in a rubber cold pressing sleeve, vacuumed, and cold isostatically pressed at 350 MPa to obtain a blank with a density of 93%. The blank was then subjected to two-stage vacuum sintering: first, the temperature was raised to 420℃ and held for 12 hours, with the vacuum level reduced to 10. -2At Pa, the temperature was further increased to 510℃ and held for 12 hours, then cooled in the furnace. Hot extrusion was performed at 500℃ with an extrusion ratio of 10:1 and an extrusion speed of 2.5 mm / s to obtain an extruded plate with a thickness of 30 mm. The extruded plate was then rolled at a rolling temperature of 420℃ and a rolling speed of 10 m / min, with each pass requiring a 0.5-hour holding time in the furnace. After 8 passes, a plate with a thickness of 15 mm was obtained, and finally, the plate was straightened.

[0060] The composite material sheets obtained from the above 6 sets of tests were subjected to tensile and impact performance tests in accordance with relevant national standards, and the results are shown in Table 1.

[0061] Table 1 Mechanical and impact properties of composite material sheets

[0062] Experiment number Tensile strength at 350℃ (MPa) Yield strength at 350℃ (MPa) Elongation at 350℃ (%) Impact energy at 300℃, kV2 (J) Example 1 116 109 7.5 11.0 Comparative Example 1 100 93 2.0 4.0 Comparative Example 2 98 92 4.5 6.5 Example 2 112 104 8.0 13.0 Comparative Example 3 118 110 4.5 3.0 Comparative Example 4 97 90 5.0 5.0

[0063] Test results show that the composite material prepared using the embodiment of this invention, compared with the comparative case, possesses higher high-temperature mechanical strength, better plasticity and impact toughness, and excellent sheet forming performance. (Refer to...) Figure 1 , Figure 1 The arrows indicate non-flaky alumina, while the dashed circles enclose crystalline granular alumina. This shows that the matrix structure of the material in the plate is a mixed grain structure composed of fine grains and some coarse grains, with a uniform distribution of fine and coarse grains. The Al2O3 size ranges from 10 nm to 100 nm, exhibiting a coexistence of nanosheets and granules. (Refer to...) Figure 2 , Figure 2 In the diagram, the white dashed lines represent grain boundaries. The inverse Fourier transform diffraction signal at the dashed box is collected as follows: Figure 3 It was confirmed that the crystal contained stacking faults, meaning that the locations indicated by the arrows were all stacking faults. This shows that the crystal contained a large number of high-density stacking faults, and the in-situ nano-Al2O3 reinforcing phase was distributed at the matrix grain boundaries and within the crystal.

[0064] Comparing the test results of Example 1 and Comparative Example 1, although the aluminum powder used in Comparative Example 1 was all relatively fine, with an average particle size smaller than that in Example 1, the aluminum powder was still not fine enough, and the pinning effect of alumina on grain boundaries was not strong enough, failing to effectively inhibit grain growth at high temperatures. While the tensile strength was higher, it was not as high as in Example 1. Furthermore, Comparative Example 1 lacked a coarser aluminum grain structure, and its toughness and plasticity were significantly inferior to those of Example 1. Compared to the uniform grain size structure of B4C / Al neutron absorber material reinforced with nanoparticles, the Al2O3 / B4C / Al neutron absorber material of this invention has a mixed grain structure and high-density stacking fault characteristics within the grains, thus exhibiting a better combination of strength and toughness-plasticity, resulting in excellent overall mechanical properties.

[0065] Comparing the test results of Example 1, Comparative Example 1 and Comparative Example 2, Comparative Example 2 has a larger average particle size, the aluminum powder used is coarser than that of Comparative Example 1, and the plasticity is better than that of Comparative Example 1; however, the specific surface area of ​​the mixed particle size aluminum powder is not large enough, and the mechanical properties of the resulting plate are poor.

[0066] Comparing Example 2 and Comparative Example 3, the particle size of the mixed aluminum powder in Comparative Example 3 was the same as that in Example 2, but a one-stage vacuum sintering process was used. Although the material had higher strength, it had poor plasticity. Figure 4 As shown, the extruded thick plate obtained during the manufacturing process of Example 2 is smooth and flat; in contrast, Figure 6 In Comparative Example 3, the extruded thick plate obtained during the production process was bent and cracked in many places. Although the plate could be hot-rolled in the end, the yield was low, the quality rate was low, and the raw material consumption was high.

[0067] Compared with Example 2 and Comparative Example 4, the mixed particle size aluminum powder of Comparative Example 4 has the same specifications as that of Example 2, but a high strain rate was not used during the final hot rolling, so a high density stacking fault could not be formed, and the toughness of the plate was significantly lower than that of Example 2.

[0068] This invention uses high-oxygen-content industrial aluminum powder and nuclear-grade boron carbide particles as raw materials, and employs powder metallurgy combined with hot deformation processing to form a high-strength, high-toughness, and ductile neutron absorbing plate. By controlling the ratio of coarse to fine aluminum powder content and processing parameters, a high-strength, high-toughness, and ductile neutron absorbing material is prepared. It is essentially a high-temperature resistant, high-strength, and high-toughness Al₂O₃ / B₄C / Al neutron absorbing material. Its microstructure is characterized by uniform distribution of micron-sized B₄C particles in the matrix, and in-situ nano-Al₂O₃ particles distributed at the grain boundaries and within the grains. The matrix has a mixed grain structure composed of numerous fine grains and some coarse grains, and also contains a high-density stacking fault structure within the matrix grains.

[0069] The strengthening principle of this Al2O3 / B4C / Al neutron absorbing material is as follows: the nano-Al2O3 reinforcing phase distributed at the grain boundaries and within the grains can pin and strengthen the grain boundaries at high temperatures, effectively inhibiting grain growth and significantly improving the high-temperature mechanical strength of the neutron absorbing material. The mixed grain structure and high-density stacking fault structure designed in the neutron absorbing material, on the one hand, allow the non-uniformly distributed mixed grain structure to leverage the advantages of high strength in fine grains and high plasticity in coarse grains; on the other hand, the formation of high-density stacking faults within the grains further enhances the strain hardening ability of the neutron absorbing material, delaying necking and fracture.

[0070] In terms of raw material selection, this invention controls the mixed grain structure and the content of nano-Al2O3 reinforcing phase in the Al2O3 / B4C / Al neutron absorber matrix by controlling the specifications and ratios of coarse and fine aluminum powder raw materials. The amorphous Al2O3 on the surface of the aluminum powder can effectively hinder the fusion and growth between different aluminum powder grains, so that the grain size distribution characteristics of the mixed particle size aluminum powder can be retained after deformation processing, forming a mixed grain structure in the Al2O3 / B4C / Al neutron absorber. Controlling the specific surface area and oxygen content of the mixed particle size aluminum powder can ensure the introduction of a sufficient amount of in-situ nano-Al2O3, which has good thermal stability and is distributed at grain boundaries and within grains. At high temperatures, it can pin and strengthen grain boundaries, effectively inhibit grain growth, and significantly improve the high-temperature mechanical strength of the neutron absorber. The mixed grain structure designed in the neutron absorber can give full play to the advantages of high strength of fine grains and high plasticity of coarse grains.

[0071] In terms of manufacturing process, this invention controls the sintering temperature, sintering time, and subsequent hot deformation temperature to ensure that the in-situ Al2O3 in the final microstructure exists in a coexisting state of nanosheets and particles, while simultaneously improving the formability of the sheet. During the sintering stage, the temperature is maintained within the transformation temperature range of 510℃ to 540℃ from amorphous Al2O3 to crystalline γAl2O3. Strict control of the sintering time promotes the partial transformation of amorphous Al2O3 to crystalline Al2O3 while maintaining the matrix grain size and preventing a decrease in strength, thus improving the plasticity and processing performance of the billet. During the hot deformation stage, the temperature remains below the transformation temperature of amorphous Al2O3 to crystalline γAl2O3, preventing further complete transformation of amorphous Al2O3 to crystalline Al2O3 and avoiding dynamic recrystallization growth and strength reduction in the matrix grains. Furthermore, thanks to the selection of raw materials and the temperature control in the preceding processes, the material exhibits good flowability during hot deformation processing, resulting in Al2O3 / B4C / Al neutron absorber material sheets with excellent surface quality and high yield. High-strain-rate hot rolling of Al2O3 / B4C / Al neutron absorbing materials, followed by rolling of thick extruded plates at high reduction and high rolling speed, further induces large plastic deformation in the Al2O3 / B4C / Al neutron absorbing materials. This process forms high-density stacking faults within the matrix grains of the Al2O3 / B4C / Al neutron absorbing materials, which can further improve the strain hardening ability of the Al2O3 / B4C / Al neutron absorbing materials and delay necking and fracture.

[0072] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0073] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for manufacturing a high-strength, high-toughness, and ductile neutron-absorbing plate, characterized in that, Includes the following steps: Aluminum powder of varying coarseness is mixed to obtain aluminum powder with a mixed particle size; the specific surface area of ​​the mixed particle size aluminum powder is ≥1.5 m². 2 / g, oxygen content ≥1.0wt%; Boron carbide particles are mixed with the aluminum powder of the mixed particle size to obtain a composite powder. The composite powder is pressed into a blank; The billet is sintered in two stages to obtain an ingot; the temperature of the first stage sintering is 370℃~420℃, and the temperature of the second stage sintering is 510℃~540℃. The billet is subjected to hot extrusion to obtain an extruded thick plate; the hot extrusion temperature is 450℃~500℃, the extrusion ratio is 10:1~20:1, and the extrusion speed is 2mm / s~8mm / s. The extruded thick plate is subjected to high strain rate hot rolling to obtain the high-strength, high-toughness, and high-plasticity neutron absorbing plate; the total hot rolling reduction is 30%~60%, the number of rolling passes is 2~6, the temperature is 400℃~450℃, and the rolling speed is 20m / min~50m / min.

2. The method for manufacturing the high-strength, high-toughness, and ductile neutron absorbing plate according to claim 1, characterized in that, The raw material aluminum powder includes fine aluminum powder with an average particle size of 1.1μm to 1.5μm, and the oxygen content of the fine aluminum powder is 1.1wt% to 1.3wt%.

3. The method for manufacturing the high-strength, high-toughness, and ductile neutron-absorbing plate according to claim 2, characterized in that, The raw aluminum powder also includes medium aluminum powder with an average particle size of 2.0μm to 7.5μm and / or coarse aluminum powder with an average particle size of 7.5μm to 15μm, wherein the oxygen content of the medium aluminum powder and the coarse aluminum powder is 0.3wt% to 0.8wt%.

4. The method for manufacturing the high-strength, high-toughness, and ductile neutron absorbing plate according to claim 3, characterized in that, By mass, the fine aluminum powder accounts for 75% to 90%, the medium aluminum powder accounts for 8% to 25%, and the coarse aluminum powder accounts for 0% to 3%.

5. The method for manufacturing the high-strength, high-toughness, and ductile neutron absorbing plate according to claim 1, characterized in that, The composite powder contains, by mass, 85% to 92% aluminum powder of mixed particle size and 8% to 15% boron carbide particles.

6. The method for manufacturing the high-strength, high-toughness, and ductile neutron-absorbing plate according to claim 1, characterized in that, The boron carbide particles are nuclear-grade boron carbide with an average particle size of 1 μm to 25 μm.

7. The method for manufacturing the high-strength, high-toughness, and ductile neutron absorbing plate according to claim 1, characterized in that, The density of the blank is 85%~95%.

8. The method for manufacturing the high-strength, high-toughness, and ductile neutron absorbing plate according to claim 1, characterized in that, The sintering time for the first stage is 12h~16h, and the sintering time for the second stage is 2h~12h.

9. The method for manufacturing the high-strength, high-toughness, and ductile neutron absorbing plate according to claim 1, characterized in that, During the hot extrusion process, the temperature is 480℃~500℃, the extrusion ratio is 10:1, and the extrusion speed is 2.5mm / s~4mm / s.

10. A high-strength, high-toughness, and high-plasticity neutron absorbing plate, characterized in that, It is manufactured according to the method for producing high-strength, high-toughness, and ductile neutron absorbing plates according to any one of claims 1 to 9.

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