Neutron and gamma ray integrated aluminum-based nuclear shielding material and preparation method thereof

Abstract

The invention discloses a neutron and gamma ray integrated aluminum-based nuclear shielding material. The aluminum-based nuclear shielding material comprises, by mass, 1%-10% of boron carbide, 5%-30% of high-entropy alloy powder and 60%-94% of aluminum alloy powder. The invention further discloses a preparation method of the aluminum-based nuclear shielding material. The preparation method comprises the steps that firstly, boron carbide, high-entropy alloy powder and aluminum alloy powder are mixed and then subjected to ball milling; step 2, crushing; 3, cold pressing and hot pressing sintering; and 4, hot rolling and solid solution aging heat treatment. According to the neutron and gamma ray integrated aluminum-based nuclear shielding material, the gamma ray shielding efficiency and the mechanical property of the aluminum-based nuclear shielding material are improved by introducing the high-entropy alloy powder, the neutron and gamma ray integrated aluminum-based nuclear shielding material high in shielding efficiency and excellent in comprehensive mechanical property is obtained, and the neutron and gamma ray integrated aluminum-based nuclear shielding material is suitable for the technical fields of small reactors, movable reactors, nuclear submarines and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear materials, and in particular relates to a neutron and gamma ray integrated aluminum-based nuclear shielding material and a preparation method thereof. Background Art

[0002] With the modular development of nuclear reactors, their weight and volume are greatly restricted, and higher requirements are placed on reactor shielding materials. Nuclear reactors are mainly irradiated by neutrons and gamma rays during operation. The shielding materials currently used in China, such as lead-boron polyethylene and boron steel, cannot meet the shielding requirements well due to their insufficient structural strength and low shielding efficiency. Therefore, it is urgent to optimize the composition and preparation process of existing shielding materials, improve and enhance their shielding performance while ensuring the mechanical properties of the structure, reduce the overall cost, expand the application field, and promote the industrialization process.

[0003] In order to make the shielding material have the dual functions of shielding neutrons and gamma rays, on the one hand, it is necessary to increase the content of neutron shielding components such as Cd, B, Gd and other elements in the composite shielding material to improve the material's shielding performance against neutrons; on the other hand, it is also necessary to significantly increase the proportion of heavy metal elements to improve the material's shielding performance against gamma rays. Aluminum-based composite materials are currently widely used in various fields of industry and life. Among them, aluminum-based boron carbide composite materials have outstanding advantages such as light weight, high strength, good corrosion resistance, high thermal conductivity, and stable neutron absorption. They have been widely used in the field of spent fuel storage and transportation. Introducing gamma-ray shielding components into aluminum-based boron carbide composite materials can make the material have both neutron and gamma-ray shielding properties.

[0004] The Chinese invention patent "Aluminum-based composite material and preparation method for shielding high-dose gamma rays and thermal neutrons" (Announcement No. CN109402477B) has a shielding effect on high-dose gamma rays and thermal neutrons by adding 75% to 90% tungsten and 0.5% to 3% boron to the aluminum-based composite material. The Chinese invention patent "Aluminum-based composite material for nuclear reactors that shield neutrons and gamma rays and preparation method" (Announcement No. CN105803267B) has developed an aluminum-based composite material with certain mechanical strength and excellent resistance to nuclear reactor neutron and gamma ray irradiation by adopting an isostatic pressing method. The aluminum-based composite material includes 20% to 70% tungsten and 1% to 10% boron carbide. However, the above patents all use tungsten as a gamma-ray shielding component, which has low shielding efficiency and is difficult to meet the requirements of small modular nuclear reactors for nuclear shielding materials. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and provide an integrated aluminum-based nuclear shielding material for neutrons and gamma rays. The aluminum-based nuclear shielding material effectively improves the gamma-ray shielding efficiency of the aluminum-based nuclear shielding material by adding a high entropy alloy as a gamma-ray shielding component, making it suitable for modular nuclear reactors, and solving the problem that the shielding efficiency of traditional shielding materials is low and it is difficult to meet the requirements of small modular nuclear reactors for nuclear shielding materials.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a neutron and gamma-ray integrated aluminum-based nuclear shielding material, characterized in that the aluminum-based nuclear shielding material comprises the following components in mass percentage: 1%~10% boron carbide, 5%~30% high entropy alloy powder, and 60%~94% aluminum alloy powder.

[0007] The above-mentioned neutron and gamma-ray integrated aluminum-based nuclear shielding material is characterized in that the high entropy alloy powder is one of TiZrNbTa, TiZrNbHf and TiZrNbTaHf, and the aluminum alloy powder is one of 2 series aluminum alloy powder, 5 series aluminum alloy powder, 6 series aluminum alloy powder and 7 series aluminum alloy powder.

[0008] The present invention adopts one of TiZrNbTa, TiZrNbHf and TiZrNbTaHf as the raw material of the aluminum-based nuclear shielding material. Since the above-mentioned high entropy alloy has high strength, hardness and plasticity, it will not cause a significant decrease in the plasticity of the material when added as second phase particles to the aluminum matrix; in addition, the elements contained in the above-mentioned high entropy alloy are all elements with high density, which is beneficial to improving the shielding performance of the aluminum-based nuclear shielding material against gamma rays.

[0009] The above-mentioned neutron and gamma-ray integrated aluminum-based nuclear shielding material is characterized in that the average particle size of the high entropy alloy powder is 10μm~100μm.

[0010] By setting the particle size of the high entropy alloy powder to 10 μm-100 μm, the present invention can avoid the difficulty in uniform dispersion and easy agglomeration of the high entropy alloy powder when the particle size is less than 10 μm; and avoid the high entropy alloy powder being larger than 100 μm, so that the prepared aluminum-based nuclear shielding material is easy to crack during the stretching process, thereby reducing the mechanical properties of the aluminum-based nuclear shielding material.

[0011] In addition, the present invention also discloses a method for preparing the above-mentioned neutron and gamma-ray integrated aluminum-based nuclear shielding material, characterized in that the preparation method comprises the following steps: Step 1: mixing boron carbide, high entropy alloy powder and aluminum alloy powder and then ball milling to obtain powder; Step 2, drying the powder obtained in step 1 and then crushing it; Step 3: cold pressing and hot pressing the powder material crushed in step 2 to obtain a composite material ingot; Step 4: hot rolling and solution aging heat treatment are performed on the composite material ingot obtained in step 3 to obtain an aluminum-based core shielding material.

[0012] The above-mentioned method for preparing a neutron and gamma-ray integrated aluminum-based nuclear shielding material is characterized in that the rotation speed of the ball mill in step one is 100r / min~350r / min, the time of the ball milling is 1h~7h, and the ball-to-material ratio of the ball milling is 10:1~20:1.

[0013] The above-mentioned method for preparing a neutron and gamma-ray integrated aluminum-based nuclear shielding material is characterized in that the drying time in step 2 is 12h~24h.

[0014] The above-mentioned method for preparing the integrated aluminum-based nuclear shielding material for neutrons and gamma rays is characterized in that the cold pressing pressure in step three is 200MPa~300MPa.

[0015] The present invention can avoid the disadvantage of powder molding due to too low pressure by setting the cold pressing pressure to 200MPa-300MPa, and when the pressure exceeds 300MPa, further increasing the pressure will not significantly increase the density of the material.

[0016] The above-mentioned method for preparing a neutron and gamma-ray integrated aluminum-based nuclear shielding material is characterized in that the temperature of the hot pressing sintering in step three is 550°C~620°C, the pressure of the hot pressing sintering is 20MPa~50MPa, and the holding time of the hot pressing sintering is 10min~60min.

[0017] The present invention sets the temperature of hot pressing sintering at 550°C-620°C. Since the melting point of aluminum alloy is about 660°C, the aluminum alloy will melt when the sintering temperature is too high, while it is difficult to form a sintering neck when the temperature is too low, which is not conducive to the densification of the material. The hot pressing sintering pressure is set at 20MPa-50MPa to avoid the difficulty in ensuring the density of the material when the pressure is lower than 20MPa, and when the pressure is higher than 50MPa, the density of the material will not increase significantly with the increase of the pressure.

[0018] The above-mentioned method for preparing a neutron and gamma-ray integrated aluminum-based nuclear shielding material is characterized in that the hot rolling temperature in step four is 350°C~500°C, the total deformation of the hot rolling is 50%~90%, and the deformation of each hot rolling is 5%~15%.

[0019] The present invention can eliminate defects such as pores inside the material by hot rolling, further improve the density of the material, and by setting the hot rolling temperature at 350°C to 500°C, it can avoid that the material has a large deformation resistance due to the rolling temperature being too low, and the material will melt when the temperature is too high; by controlling the total deformation amount and the deformation amount of each pass, the material can be fully deformed and the cracking of the material can be reduced.

[0020] The above-mentioned method for preparing a neutron and gamma-ray integrated aluminum-based nuclear shielding material is characterized in that the solution temperature of the solution aging heat treatment in step four is 525°C~540°C, the solution time of the solution aging heat treatment is 30min~120min, the aging temperature of the solution aging heat treatment is 160°C~180°C, and the aging time of the solution aging heat treatment is 6h~10h.

[0021] The present invention adopts a solution aging heat treatment to fully dissolve the alloying elements in the aluminum alloy powder into the aluminum matrix to obtain a supersaturated solid solution, and then slowly precipitates the dispersed nano-strengthening phase in the supersaturated solid solution, resulting in lattice distortion, which can significantly improve the strength and hardness of the aluminum alloy; by controlling the temperature and time of each stage in the solution aging heat treatment, it can ensure that the alloying elements are fully dissolved, avoid grain growth, and ensure that a large number of dispersed nano-precipitated phases can be precipitated in the aluminum matrix. For example, when the 6-series aluminum alloy powder is solid-solutioned, the Mg2Si phase can be fully dissolved in the matrix to form a supersaturated solid solution, thereby enhancing the strength and hardness of the material.

[0022] Compared with the prior art, the present invention has the following advantages: 1. The present invention adopts high entropy alloy as a gamma-ray shielding component, and can utilize the lattice distortion brought about by the multi-principal element effect of the high entropy alloy to shorten the range of photons in the aluminum-based nuclear shielding material, thereby improving the shielding efficiency of the aluminum-based nuclear shielding material against gamma rays; compared with aluminum-based shielding materials of the same volume or mass using tungsten as a shielding component, the aluminum-based nuclear shielding material of the present invention has higher shielding efficiency and is suitable for application in small modular reactors.

[0023] 2. In the present invention, the high entropy alloy is preferably a titanium-based high entropy alloy. The titanium-based high entropy alloy has a body-centered cubic structure, has high strength, hardness and relatively ideal plasticity. Adding the titanium-based high entropy alloy to the aluminum-based nuclear shielding material can serve as a reinforcing phase to enhance the strength, while having no significant effect on the plasticity of the aluminum-based nuclear shielding material.

[0024] 3. The present invention adopts titanium-based high entropy alloy instead of tungsten as the gamma-ray shielding component. Since the plasticity of titanium-based high entropy alloy is better than that of tungsten, the prepared aluminum-based nuclear shielding material has excellent plastic deformation ability, and it is not easy to produce cracks on the surface during subsequent extrusion, rolling and other processes, thus avoiding the cracking phenomenon of existing aluminum-based nuclear shielding materials during plastic deformation.

[0025] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a microstructure diagram of the aluminum-based nuclear shielding material prepared in Example 1 of the present invention.

[0027] Figure 2 This is a graph showing the tensile stress-strain test results of the aluminum-based nuclear shielding material prepared in Example 1 of the present invention.

[0028] Figure 3 The aluminum-based nuclear shielding material prepared in Example 1 of the present invention is Co 60 Ray shielding rate test chart. DETAILED DESCRIPTION

[0029] The aluminum-based nuclear shielding material of this embodiment is composed of the following components in percentage by mass: 3% boron carbide, 10% TiZrNbTa and 87% Al6061 powder, wherein the average particle size of TiZrNbTa is 25 μm.

[0030] The preparation method of the aluminum-based nuclear shielding material in this embodiment comprises the following steps: Step 1: Mix boron carbide, TiZrNbTa and Al6061 powders and place them in a planetary ball mill for 5 hours at a speed of 200 r / min to obtain a powder; the ball-to-powder ratio is 10:1; Step 2: Dry the powder obtained in step 1 for 12 hours and then crush it; Step 3: placing the powder crushed in step 2 in a steel mold for cold pressing at a pressure of 200 MPa, and then transferring it into a graphite mold for hot pressing and sintering at a temperature of 580° C. and a pressure of 35 MPa to obtain a composite material ingot; the hot pressing and sintering holding time is 30 min; Step 4: hot rolling the composite material ingot obtained in step 3 at a rolling temperature of 450°C, and then performing solid solution aging heat treatment to obtain an aluminum-based nuclear shielding material; the total hot rolling deformation is 50%, the hot rolling deformation per pass is 5%, the solid solution temperature of the solid solution aging heat treatment is 535°C, the solid solution time is 90min, the aging temperature is 175°C, and the aging time is 8h.

[0031] The TiZrNbTa in this embodiment can be replaced by TiZrNbHf or TiZrNbTaHf, and the Al6061 powder can also be replaced by one of the 2-series aluminum alloy powder, 5-series aluminum alloy powder and 7-series aluminum alloy powder other than the Al6061 powder.

[0032] The aluminum-based nuclear shielding material prepared in this embodiment was observed for its microstructure. Figure 1 As shown, boron carbide and TiZrNbTa are uniformly distributed in the aluminum-based core shielding material.

[0033] The aluminum-based nuclear shielding material prepared in this embodiment was subjected to a tensile stress-strain test, with the aluminum-based shielding material having a thickness of 30 mm as the sample. The results are as follows: Figure 2 As shown, the tensile strength of the aluminum-based nuclear shielding material is 420 MPa and the elongation is 4%, indicating that the aluminum-based nuclear shielding material has good mechanical properties.

[0034] The aluminum-based nuclear shielding material prepared in this embodiment was subjected to γ-ray (Co 60 The shielding rate test of the radiation) is as follows Figure 3 As shown, the aluminum-based core shielding material has a 60 The shielding rate of radiation increases with the increase of material thickness. When the thickness of the aluminum-based nuclear shielding material reaches 30 mm, the shielding rate is greater than 30%, indicating that the aluminum-based nuclear shielding material has excellent Co 60 Radiation shielding performance.

[0035] Example 2 The aluminum-based nuclear shielding material of this embodiment is composed of the following components in percentage by mass: 5% boron carbide, 5% TiZrNbTa and 90% Al2024 powder, wherein the average particle size of TiZrNbTa is 10 μm.

[0036] The preparation method of the aluminum-based nuclear shielding material in this embodiment comprises the following steps: Step 1: Mix boron carbide, TiZrNbTa and Al2024 powders and place them in a planetary ball mill for ball milling at a speed of 100 r / min for 1 hour to obtain a powder; the ball-to-powder ratio is 15:1; Step 2: Dry the powder obtained in step 1 for 18 hours and then crush it; Step 3: placing the powder crushed in step 2 in a steel mold for cold pressing at a pressure of 300 MPa, and then transferring it to a graphite mold for hot pressing and sintering at a temperature of 550° C. and a pressure of 35 MPa to obtain a composite material ingot; the hot pressing and sintering holding time is 30 min; Step 4: hot rolling the composite material ingot obtained in step 3 at a rolling temperature of 350°C, and then performing solid solution aging heat treatment to obtain an aluminum-based nuclear shielding material; the total hot rolling deformation is 70%, the hot rolling deformation per pass is 10%, the solid solution temperature of the solid solution aging heat treatment is 525°C, the solid solution time is 30min, the aging temperature is 160°C, and the aging time is 6h.

[0037] In this embodiment, the Al2024 powder can also be replaced by one of the 5-series aluminum alloy powder, 6-series aluminum alloy powder and 7-series aluminum alloy powder other than the Al2024 powder.

[0038] Example 3 The aluminum-based nuclear shielding material of this embodiment is composed of the following components in percentage by mass: 1% boron carbide, 5% TiZrNbHf and 94% Al5085 powder, wherein the average particle size of TiZrNbHf is 100 μm.

[0039] The preparation method of the aluminum-based nuclear shielding material in this embodiment comprises the following steps: Step 1: Mix boron carbide, TiZrNbHf and Al5085 powders and place them in a planetary ball mill for 7 hours at a speed of 350 r / min to obtain a powder; the ball-to-powder ratio is 20:1; Step 2: Dry the powder obtained in step 1 for 24 hours and then crush it; Step 3: placing the powder crushed in step 2 in a steel mold for cold pressing at a pressure of 250 MPa, and then transferring it to a graphite mold for hot pressing and sintering at a temperature of 550° C. and a pressure of 20 MPa to obtain a composite material ingot; the hot pressing and sintering holding time is 10 min; Step 4: hot rolling the composite material ingot obtained in step 3 at a rolling temperature of 500°C, and then performing solid solution aging heat treatment to obtain an aluminum-based nuclear shielding material; the total hot rolling deformation is 90%, the hot rolling deformation per pass is 15%, the solid solution temperature of the solid solution aging heat treatment is 540°C, the solid solution time is 120min, the aging temperature is 180°C, and the aging time is 10h.

[0040] In this embodiment, the Al5085 powder may also be replaced by one of the 2-series aluminum alloy powder, 6-series aluminum alloy powder and 7-series aluminum alloy powder other than the Al5085 powder.

[0041] Example 4 The aluminum-based nuclear shielding material of this embodiment is composed of the following components in percentage by mass: 10% boron carbide, 15% TiZrNbTaHf and 75% Al7075 powder, wherein the average particle size of TiZrNbTaHf is 50 μm.

[0042] The preparation method of the aluminum-based nuclear shielding material in this embodiment comprises the following steps: Step 1: Mix boron carbide, TiZrNbTaHf and Al7075 powders and place them in a planetary ball mill for 3 hours at a speed of 250 r / min to obtain a powder; the ball-to-powder ratio is 10:1; Step 2: Dry the powder obtained in step 1 for 12 hours and then crush it; Step 3: placing the powder crushed in step 2 in a steel mold for cold pressing at a pressure of 300 MPa, and then transferring it to a graphite mold for hot pressing and sintering at a temperature of 620° C. and a pressure of 50 MPa to obtain a composite material ingot; the hot pressing and sintering holding time is 60 min; Step 4: hot rolling the composite material ingot obtained in step 3 at a rolling temperature of 400°C, and then performing solid solution aging heat treatment to obtain an aluminum-based nuclear shielding material; the total hot rolling deformation is 80%, the hot rolling deformation per pass is 10%, the solid solution temperature of the solid solution aging heat treatment is 530°C, the solid solution time is 60min, the aging temperature is 170°C, and the aging time is 8h.

[0043] In this embodiment, the Al7075 powder can also be replaced by one of the 2 series aluminum alloy powder, 5 series aluminum alloy powder and 6 series aluminum alloy powder other than the Al7075 powder.

[0044] Example 5 The aluminum-based nuclear shielding material of this embodiment is composed of the following components in percentage by mass: 10% boron carbide, 30% TiZrNbTaHf and 60% Al6061 powder, wherein the average particle size of TiZrNbTaHf is 10 μm.

[0045] The preparation method of the aluminum-based nuclear shielding material in this embodiment comprises the following steps: Step 1: Mix boron carbide, TiZrNbTaHf and Al6061 powders and place them in a planetary ball mill for 5 hours at a speed of 200 r / min to obtain a powder; the ball-to-powder ratio is 10:1; Step 2: Dry the powder obtained in step 1 for 12 hours and then crush it; Step 3: placing the powder crushed in step 2 in a steel mold for cold pressing at a pressure of 200 MPa, and then transferring it into a graphite mold for hot pressing and sintering at a temperature of 600° C. and a pressure of 45 MPa to obtain a composite material ingot; the hot pressing and sintering holding time is 35 min; Step 4: hot rolling the composite material ingot obtained in step 3 at a rolling temperature of 450°C, and then performing a solution aging heat treatment to obtain an aluminum-based nuclear shielding material; the total hot rolling deformation is 80%, the hot rolling deformation per pass is 10%, the solution temperature of the solution aging heat treatment is 535°C, the time is 90min, the aging temperature is 175°C, and the time is 8h.

[0046] The aluminum-based nuclear shielding materials prepared in Examples 1 to 5 were tested for mechanical properties, thermal neutron (neutron with energy of 0.025 eV) shielding properties, and gamma ray (Co 60) Shielding performance test, the test results are shown in Table 1.

[0047] Table 1 Performance test results of aluminum-based nuclear shielding materials prepared in Examples 1 to 5

[0048] It can be seen from Table 1 that the tensile strength of the aluminum-based nuclear shielding materials prepared in Examples 1 to 5 is not less than 405 MPa, and the elongation is not less than 3.5%; when the thickness of the aluminum-based nuclear shielding material is 30 mm, the thermal neutron shielding rate is not less than 99.63%, and the gamma-ray shielding rate is not less than 32.16%; in summary, the aluminum-based nuclear shielding material prepared by the present invention has good mechanical properties and excellent thermal neutron and gamma-ray shielding performance, which meets the performance requirements of shielding materials in the fields of small reactors, mobile reactors and nuclear-powered submarines.

[0049] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A neutron and gamma ray integrated aluminum-based nuclear shielding material, characterized in that: The aluminum-based nuclear shielding material comprises the following components in percentage by mass: 1% to 10% boron carbide, 5% to 30% high entropy alloy powder, and 60% to 94% aluminum alloy powder.

2. The neutron and gamma ray integrated aluminum-based nuclear shielding material according to claim 1, characterized in that: The high entropy alloy powder is one of TiZrNbTa, TiZrNbHf and TiZrNbTaHf, and the aluminum alloy powder is one of 2 series aluminum alloy powder, 5 series aluminum alloy powder, 6 series aluminum alloy powder and 7 series aluminum alloy powder.

3. The neutron and gamma ray integrated aluminum-based nuclear shielding material according to claim 1, characterized in that: The average particle size of the high entropy alloy powder is 10 μm to 100 μm.

4. A method for preparing the neutron and gamma ray integrated aluminum-based nuclear shielding material according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: Step 1: mixing boron carbide, high entropy alloy powder and aluminum alloy powder and then ball milling to obtain powder; Step 2, drying the powder obtained in step 1 and then crushing it; Step 3: cold pressing and hot pressing the powder material crushed in step 2 to obtain a composite material ingot; Step 4: hot rolling and solution aging heat treatment are performed on the composite material ingot obtained in step 3 to obtain an aluminum-based core shielding material.

5. The method for preparing a neutron and gamma-ray integrated aluminum-based nuclear shielding material according to claim 4, characterized in that: The rotation speed of the ball mill in step 1 is 100 r / min~350 r / min, the time of the ball milling is 1h~7h, and the ball-to-material ratio of the ball milling is 10:1~20:

1.

6. The method for preparing a neutron and gamma-ray integrated aluminum-based nuclear shielding material according to claim 4, characterized in that: The drying time in step 2 is 12h~24h.

7. The method for preparing a neutron and gamma-ray integrated aluminum-based nuclear shielding material according to claim 4, characterized in that: The cold pressing pressure in step 3 is 200MPa~300MPa.

8. The method for preparing a neutron and gamma ray integrated aluminum-based nuclear shielding material according to claim 4, characterized in that: The temperature of the hot pressing sintering in step 3 is 550° C. to 620° C., the pressure of the hot pressing sintering is 20 MPa to 50 MPa, and the holding time of the hot pressing sintering is 10 min to 60 min.

9. The method for preparing a neutron and gamma-ray integrated aluminum-based nuclear shielding material according to claim 4, characterized in that: The hot rolling temperature in step 4 is 350°C to 500°C, the total deformation of the hot rolling is 50% to 90%, and the deformation of each pass of the hot rolling is 5% to 15%.

10. The method for preparing a neutron and gamma ray integrated aluminum-based nuclear shielding material according to claim 4, characterized in that: The solution temperature of the solution aging heat treatment in step 4 is 525°C~540°C, the solution time of the solution aging heat treatment is 30min~120min, the aging temperature of the solution aging heat treatment is 160°C~180°C, and the aging time of the solution aging heat treatment is 6h~10h.

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