阅读说明：本技术 面向中子防护的铝基碳化硼结构的增材制造方法 (Additive manufacturing method of aluminum-based boron carbide structure facing neutron protection ) 是由 宋长辉 李玉龙 杨永强 刘峰 陈杰 刘夏杰 黄文有 于 2020-07-03 设计创作，主要内容包括：本发明公开了一种面向中子防护的铝基碳化硼结构的增材制造方法,包括下述步骤：将铝合金实体结构通过拓扑优化再设计为点阵结构,并通过激光选区熔化技术对其进行制造成形；所述点阵结构为内部为具有一定孔隙率的多孔结构,而外部轮廓封闭,但留有碳化硼粉末填充口；将细小的碳化硼粉末灌入铝合金点阵结构中；将铝合金点阵结构的碳化硼粉末填充口通过激光选区熔化技术进行再增材,从而使再增材后的铝合金点阵结构外部轮廓实体完整。本发明将增材制造结构成形自由度高的特点应用到防中子辐射铝基碳化硼材料的成形制造中,弥补了防中子辐射铝基碳化硼材料的传统制造方法无法成形异性结构,中子吸收材料空间分布防护效能低且有漏缝的缺陷。(The invention discloses a material increase manufacturing method of an aluminum-based boron carbide structure for neutron protection, which comprises the following steps: the aluminum alloy solid structure is redesigned into a lattice structure through topological optimization, and is manufactured and formed through a selective laser melting technology; the lattice structure is a porous structure with certain porosity inside, the outline of the lattice structure is closed, and a boron carbide powder filling port is reserved; pouring fine boron carbide powder into the aluminum alloy lattice structure; and (3) performing re-material increase on the boron carbide powder filling port of the aluminum alloy lattice structure by a selective laser melting technology, so that the solid of the external outline of the re-material increased aluminum alloy lattice structure is complete. The invention applies the characteristic of high forming freedom degree of an additive manufacturing structure to the forming manufacturing of the neutron radiation prevention aluminum-based boron carbide material, and overcomes the defects that the traditional manufacturing method of the neutron radiation prevention aluminum-based boron carbide material cannot form an anisotropic structure, the space distribution protection efficiency of a neutron absorption material is low, and leaks exist.)

1. The additive manufacturing method of the aluminum-based boron carbide structure facing neutron protection is characterized by comprising the following steps:

forming a complex aluminum alloy lattice structure, redesigning an aluminum alloy solid structure into the lattice structure through topological optimization, and manufacturing and forming the lattice structure through a selective laser melting technology; the lattice structure is a porous structure with certain porosity inside, and the outer contour is a solid body with a boron carbide powder filling port left;

filling boron carbide powder, namely filling fine boron carbide powder into the aluminum alloy lattice structure to enable the boron carbide powder to fill the pores in the aluminum alloy lattice structure;

sealing the aluminum alloy lattice structure, and performing re-material increase on a boron carbide powder filling port of the aluminum alloy lattice structure through a selective laser melting technology, so that the solid of the external outline of the re-material increased aluminum alloy lattice structure is complete, and the boron carbide powder is completely sealed inside.

2. The additive manufacturing method of the neutron-protection-oriented aluminum-based boron carbide structure according to claim 1, wherein the step of redesigning the aluminum alloy solid structure into a lattice structure through topological optimization specifically comprises:

according to the neutron protection application environment requirement, the shielding material of the neutron protection is subjected to shape construction, the shape topology optimization and the lattice structure density design are carried out by means of finite element analysis stress condition and neutron radiation intensity, and according to the stress distribution condition and places with large stress, the requirements on the shape thickness and the lattice density are high, so that the larger stress is borne, and the strength and rigidity requirements are met; for the places with dense neutron radiation, the appearance thickness is reduced, the lattice density is reduced, and a larger space is reserved for the neutron absorbing material boron carbide.

3. The additive manufacturing method of the neutron-protection-oriented aluminum-based boron carbide structure according to claim 1 or 2, wherein the lattice structure satisfies that the inclination angle of the hole rods in the forming growth direction is greater than 45 degrees, or the length of the hole rods is not more than 2 mm; the diameter of the hole rod exceeds 0.1mm, and the lattice structure has intercommunity, so that the boron carbide material can flow and be filled compactly; the lattice structure can be a regular octahedral structure and a special porous structure;

the lattice structure can be designed into a lattice structure with different pore densities of the outer layer and the inner layer according to requirements, can be graded, and can be a lattice structure with heterogeneous pore density so as to meet the requirement of radiation skid resistance.

4. The additive manufacturing method of the neutron-protection-oriented aluminum-based boron carbide structure according to claim 1, wherein the manufacturing and shaping steps are carried out by a selective laser melting technology, and specifically comprise the following steps:

firstly, paving aluminum-based material on a substrate, enabling laser to deflect through a vibrating mirror to realize beam radiation on the aluminum-based material, melting the aluminum-based material at a radiation part, and realizing the modeling of the aluminum-based material under the action of fast melting and fast setting;

the molding characteristic of the aluminum-based material is that the bottom surface and the side surface are sealed by a porous or sealed plate; the interior of the aluminum-based material is of an intercommunicated lattice structure;

after the selective laser melting passes through a layer of formed aluminum-based lattice structure, taking the substrate out of the equipment, and flowing out the powder remained in the lattice structure in an ultrasonic vibration mode;

at the moment, boron carbide particle materials are added, boron carbide particles with good fluidity flow into the lattice structure, and meanwhile, the boron carbide particles are compacted in an ultrasonic vibration mode.

5. The method for additive manufacturing of neutron-protection-oriented aluminum-based boron carbide structures according to claim 1, wherein the porosity is 500 μm to 5 mm.

6. The additive manufacturing method of an aluminum-based boron carbide structure facing neutron protection according to claim 1, wherein the porosity density of the porous structure is distributed with low external porosity and high internal porosity, and the porosity distribution is designed and shaped according to neutron radiation intensity.

7. The additive manufacturing method of a neutron-protection-oriented aluminum-based boron carbide structure according to claim 1, wherein the particle size of the boron carbide powder is from micron to nanometer; for the nanometer boron carbide powder material with poor flowing, the polyethylene material is coated, so that the particles become bigger, or the polyethylene material modified by polypropylene and rheological agent is mixed into the aluminum-based lattice structure under the heating condition.

8. The additive manufacturing method for the neutron-protection-oriented aluminum-based boron carbide structure according to claim 1, wherein the step of performing re-additive on the boron carbide powder filling port of the aluminum alloy lattice structure by a selective laser melting technology comprises the following specific steps:

the base plate and the aluminum-based lattice structure with boron carbide are placed into a selective laser melting device, aluminum-based powder materials are placed on the periphery of the aluminum-based lattice structure until a layer of materials can be uniformly placed on the upper layer, the newly covered aluminum-based powder materials are melted under the action of laser, and the aluminum-based lattice structure or a closed plate is formed on the upper layer, so that the whole structure is closed, and the distribution of the boron carbide materials is realized through the design and the forming of the aluminum-based lattice structure.

9. The method of additive manufacturing of a neutron protected, aluminum-based boron carbide structure according to claim 1, further comprising the steps of: and post-treating the formed aluminum-based boron carbide, further improving the service performance, and carrying out micro-deformation on the aluminum-based lattice structure under heating and pressurizing to further compact the aluminum-based lattice structure and the boron carbide.

10. The additive manufacturing method of the neutron-protection-oriented aluminum-based boron carbide structure is characterized in that the protective piece which is formed by melting in a selective laser area can be completed in a splicing mode, and the protection of a splicing port is well performed, so that boron carbide is completely covered and no leak exists.

Technical Field

The invention belongs to the technical field of additive manufacturing, and particularly relates to a method for additive manufacturing of an aluminum-based boron carbide structure for neutron protection.

Background

The selective laser melting is a metal additive manufacturing technology which develops rapidly in recent years, can form aluminum alloy parts in any shapes, and has the advantages of good size precision, high surface quality and high density compared with other metal additive manufacturing technologies. The topological optimization lattice design is a structural design means in additive manufacturing, and can lighten a solid structure and finally change the solid structure into a porous structure formed by combining a plurality of unit body structures through a finite element idea. The lattice structure is characterized by light weight, high strength ratio and high specific rigidity. And brings various thermodynamic characteristics, the ultra-light structure of the lattice structure is suitable for being used in an anti-impact/explosion system or serving as a heat dissipation medium, a sound vibration and microwave absorption structure and a driving system.

Thermal neutrons, medium energy neutrons and fast neutrons are radiated in the spent fuel storage grillwork of the nuclear power plant. Generally, for intermediate and fast neutrons, the neutrons need to be moderated into thermal neutrons so that the thermal neutrons can be absorbed by the shielding material. The thermal neutron shielding material needs to have good thermal neutron absorption performance and mechanical performance. With the gradual development and maturity of aluminum-based composite materials, a novel aluminum-based boron carbide neutron absorbing material, namely a compact aluminum-based composite material formed by adding boron carbide (B4C) particles into an aluminum alloy matrix, appears in the last decade. The material has excellent mechanical property and neutron absorption property, and has low density and high thermal conductivity. In the nuclear fuel grillwork, neutron absorption materials are mainly functional materials, and a layer of stainless steel thin plate is fixed on the outer wall of a stainless steel grillwork unit to form a sandwich structure outside the nuclear fuel grillwork. With the requirements of improving the earthquake resistance of nuclear power plants and high-density storage and transportation of spent fuel, the novel aluminum-based boron carbide gradually replaces the traditional neutron absorption materials such as boron stainless steel to manufacture grillwork and transportation containers, and becomes the main scheme of nuclear power engineering design.

The traditional aluminum-based boron carbide manufacturing method is complex in manufacturing process, and compared with an additive manufacturing method, a complex-shaped structure cannot be formed. In order to apply the characteristic of high forming freedom degree of an additive manufacturing structure to the manufacturing of the aluminum-based boron carbide, the additive manufacturing method of the aluminum-based boron carbide structure facing neutron protection is provided.

Disclosure of Invention

The invention mainly aims to overcome the defects and shortcomings of the prior art, and provides an additive manufacturing method of an aluminum-based boron carbide structure for neutron protection.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a material increase manufacturing method of an aluminum-based boron carbide structure facing neutron protection, which comprises the following steps:

forming a complex aluminum alloy lattice structure, redesigning an aluminum alloy solid structure into the lattice structure through topological optimization, and manufacturing and forming the lattice structure through a selective laser melting technology; the lattice structure is a porous structure with certain porosity inside, and the outer contour is a solid body with a boron carbide powder filling port left;

filling boron carbide powder, namely filling fine boron carbide powder into the aluminum alloy lattice structure to enable the boron carbide powder to fill the pores in the aluminum alloy lattice structure;

sealing the aluminum alloy lattice structure, and performing re-material increase on a boron carbide powder filling port of the aluminum alloy lattice structure through a selective laser melting technology, so that the solid of the external outline of the re-material increased aluminum alloy lattice structure is complete, and the boron carbide powder is completely sealed inside.

As a preferred technical scheme, the step of redesigning the aluminum alloy solid structure into a lattice structure through topological optimization specifically comprises:

according to the neutron protection application environment requirement, the shielding material of the neutron protection is subjected to shape construction, the shape topology optimization and the lattice structure density design are carried out by means of finite element analysis stress condition and neutron radiation intensity, and according to the stress distribution condition and places with large stress, the requirements on the shape thickness and the lattice density are high, so that the larger stress is borne, and the strength and rigidity requirements are met; for the places with dense neutron radiation, the appearance thickness is reduced, the lattice density is reduced, and a larger space is reserved for the neutron absorbing material boron carbide.

According to the preferable technical scheme, the lattice structure meets the condition that the inclination angle of the hole rods in the forming growth direction is more than 45 degrees, or the length of the hole rods is not more than 2 mm; the diameter of the hole rod exceeds 0.1mm, and the lattice structure has intercommunity, so that the boron carbide material can flow and be filled compactly; the lattice structure can be a regular octahedral structure and a special porous structure;

the lattice structure can be designed into a lattice structure with different pore densities of the outer layer and the inner layer according to requirements, can be graded, and can be a lattice structure with heterogeneous pore density so as to meet the requirement of radiation skid resistance.

As a preferred technical solution, the step of manufacturing and shaping the material by the selective laser melting technology specifically comprises:

firstly, paving aluminum-based material on a substrate, enabling laser to deflect through a vibrating mirror to realize beam radiation on the aluminum-based material, melting the aluminum-based material at a radiation part, and realizing the modeling of the aluminum-based material under the action of fast melting and fast setting;

the molding characteristic of the aluminum-based material is that the bottom surface and the side surface are sealed by a porous or sealed plate; the interior of the aluminum-based material is of an intercommunicated lattice structure;

after the selective laser melting passes through a layer of formed aluminum-based lattice structure, taking the substrate out of the equipment, and flowing out the powder remained in the lattice structure in an ultrasonic vibration mode;

at the moment, boron carbide particle materials are added, boron carbide particles with good fluidity flow into the lattice structure, and meanwhile, the boron carbide particles are compacted in an ultrasonic vibration mode.

As a preferred technical scheme, the porosity is 500 mu m-5 mm.

As a preferred technical scheme, the pore density of the porous structure shows the distribution of low external pores and much internal pores, and the porosity distribution is designed and formed according to the neutron radiation intensity.

As a preferable technical solution, the particle size of the boron carbide powder is micrometer to nanometer; for the nanometer boron carbide powder material with poor flowing, the polyethylene material is coated, so that the particles become bigger, or the polyethylene material modified by polypropylene and rheological agent is mixed into the aluminum-based lattice structure under the heating condition.

As a preferred technical scheme, the step of performing re-additive on the boron carbide powder filling port with the aluminum alloy lattice structure by using a selective laser melting technology specifically comprises the following steps:

the base plate and the aluminum-based lattice structure with boron carbide are placed into a selective laser melting device, aluminum-based powder materials are placed on the periphery of the aluminum-based lattice structure until a layer of materials can be uniformly placed on the upper layer, the newly covered aluminum-based powder materials are melted under the action of laser, and the aluminum-based lattice structure or a closed plate is formed on the upper layer, so that the whole structure is closed, and the distribution of the boron carbide materials is realized through the design and the forming of the aluminum-based lattice structure.

As a preferable technical scheme, the method further comprises the following steps: and post-treating the formed aluminum-based boron carbide, further improving the service performance, and carrying out micro-deformation on the aluminum-based lattice structure under heating and pressurizing to further compact the aluminum-based lattice structure and the boron carbide.

As a preferred technical scheme, the protection part which is melted and formed in the selective laser area can be completed in a splicing mode, and the protection of the splicing interface is well covered by boron carbide and has no leak.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) compared with the traditional aluminum alloy boron carbide manufacturing method, the method applies the characteristic of high-freedom design of the structure of additive manufacturing to the manufacturing of aluminum-based boron carbide. The lattice structure has the characteristics of high quantification, high strength ratio and high specific rigidity, so that the use requirement of the aluminum alloy matrix can still be met after the aluminum alloy matrix topological lattice is designed, and boron carbide powder is filled in the aluminum alloy matrix topological lattice so as to achieve the purpose of neutron radiation prevention.

(2) The aluminum-based lattice structure can be a heteromorphic structure, meets various neutron radiation protection scenes, can finish large-area protection on large volume in a splicing mode, and has no leak after splicing.

(3) The aluminum-based lattice structure can be subjected to strength design under the condition of meeting the requirement of mechanical property according to an application scene, and meanwhile, the spatial pore gradient and the heterogeneous medium of the aluminum-based lattice can be measured and manufactured, so that the spatial position of the boron carbide material can be accurately placed and distributed, and various requirements of neutron radiation protection are met.

(4) The invention overcomes the defects of low content and low protection efficiency of the existing boron carbide material, can furthest improve the content of boron carbide, realizes the maximization of the protection efficiency and reduces the volume of the protection material.

Drawings

Fig. 1 is a flow chart of an additive manufacturing method of the present invention.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.