Thermal field assisted laser additive manufacturing high-radiation-resistance tungsten-based composite material and integral forming method thereof

Abstract

The invention provides a thermal field assisted laser additive manufacturing high-radiation-resistance tungsten-based composite material and an integral forming method thereof. The tungsten-based composite material is composed of TiC ceramic particles, rare earth oxide Y2O3 and metal W. W powder and nano TiC and Y2O3 powder are mixed through a ball milling process to obtain tungsten composite powder, and the tungsten composite powder is formed through a thermal field assisted laser additive manufacturing process. In the additive manufacturing process, due to the high thermal conductivity, tungsten has the high solidification speed, large residual stress is generated, and cracks are generated. And a beam of laser is added to assist the thermal field, so that the cooling speed of tungsten in the forming process can be reduced, and the forming performance of tungsten is improved. And meanwhile, due to the addition of the second-phase particles, grains are effectively refined, the ductile-brittle transition temperature of tungsten is reduced, the brittleness of tungsten is improved, the radiation resistance of tungsten is remarkably improved, and the requirement for material-function integration of the tungsten-based composite material is met.

Description

Technical Field

[0001] The present invention belongs to the field of radiation-resistant materials, and specifically relates to a thermal field assisted laser additive manufacturing method for a highly radiation-resistant tungsten-based composite material and an integrated forming method thereof. Background Art

[0002] Controlled thermonuclear fusion is one of the clean energy sources that can solve the energy crisis of mankind. The Tokamak, which uses a strong magnetic field to confine high-temperature plasma, is the most promising device to achieve controlled thermonuclear fusion reactions. The use conditions of the device materials, especially the divertor materials facing the plasma wall, are extremely harsh and need to withstand high heat loads and bombardment of high-temperature plasma. Metal tungsten (W) is considered to be the most promising plasma material for nuclear fusion devices due to its unique physical and chemical properties, such as high melting point, high density, excellent strength and hardness, good thermal conductivity, excellent radiation shielding ability and structural stability. Due to long-term exposure to the irradiation environment of high-temperature plasma, tungsten materials still have problems such as radiation embrittlement, resulting in surface cracks, surface blistering, local melting and other damage, which in turn affects the service performance and service life of the material. In addition, due to the high ductile-brittle transition temperature (DBTT) and low recrystallization temperature (RCT) of tungsten, it is easy to cause low-temperature embrittlement and recrystallization embrittlement, which limits its application in fusion reactors.

[0003] In order to improve the toughness and high-temperature stability of tungsten, alloying elements are usually added to alloy tungsten, or carbides and oxides are added to produce dispersion strengthening. At the same time, studies have found that increasing the grain boundary and interface density of irradiation defects and implanted ions is an effective way to improve the radiation resistance of materials. Adding second-phase particles can pin dislocations, hinder grain boundary movement, and inhibit grain growth, thereby increasing the grain boundary area, improving its mechanical properties, and showing better radiation resistance. At present, most tungsten-based composites are based on single-phase reinforcement, but with the improvement of modern industry's requirements for material performance, there are more stringent requirements for the radiation resistance of plasma tungsten-based composites. Multiphase reinforced tungsten-based composites can combine the advantages of two added phases to synergistically improve the radiation resistance of tungsten-based composites.

[0004] However, the traditional sintering method cannot completely melt the tungsten powder. There are problems such as uneven distribution of the strengthening phase in the tungsten powder and segregation at the grain boundaries, resulting in low density of the formed sample. At the same time, due to the high brittleness of tungsten, traditional powder sintering technology is difficult to form complex components. Laser additive manufacturing technology can achieve complete melting of refractory metals such as W, Ta, Mo, etc., providing a new path for the formation of complex components. However, due to the good thermal conductivity of tungsten, tungsten solidifies rapidly during the laser additive manufacturing process, resulting in a large temperature gradient, causing cracks and holes in the formed components, which not only affects its mechanical properties, but also has poor radiation resistance.

[0005] Therefore, there is an urgent need to develop a method that enables formed components to have both high density and mechanical properties and high radiation resistance to achieve the material-function integration requirements of tungsten. Summary of the invention

[0006] Purpose of the invention: The technical problem to be solved by the present invention is to provide a thermal field assisted laser additive manufacturing method for highly radiation-resistant tungsten-based composite materials and a design method in view of the deficiencies in the prior art.

[0007] In order to achieve the above technical objectives, the present invention will adopt the following technical solutions:

[0008] A method for integrally forming a highly radiation-resistant tungsten-based composite material by thermal field-assisted laser additive manufacturing, comprising the following steps:

[0009] (1) ball milling nano-TiC ceramic powder, Y2O3 rare earth oxide and W powder under inert gas protection to prepare tungsten-based composite powder; in the tungsten-based composite powder, the mass fraction of W powder is 98wt.%, and the mass ratio of nano-TiC ceramic powder to Y2O3 rare earth oxide is 1:3 to 3:1;

[0010] (2) placing the tungsten-based composite powder mixed in step (1) into a forming cavity of a laser powder bed melting forming device, and introducing argon gas as a protective gas;

[0011] (3) Establishing a three-dimensional geometric model of the part and importing it into the slicing software for layered slicing processing to discretize it into a series of two-dimensional slicing data, which are saved and imported into the laser powder bed fusion forming equipment;

[0012] (4) The laser powder bed fusion forming equipment uses the thermal field assisted laser additive manufacturing technology according to the two-dimensional slice data imported in step (3) to melt and solidify the tungsten-based composite powder in the forming cavity layer by layer to obtain a thermal field assisted laser additive manufacturing tungsten-based composite material with high radiation resistance.

[0013] Preferably, in the tungsten-based composite powder prepared in step (1), the mass fraction of the TiC ceramic powder is 0-2wt.%, the average particle size is 50-100nm, and the purity is greater than 99.5%; the mass fraction of the Y2O3 rare earth oxide is 0-2wt.%, the average particle size is 50-100nm, and the purity is greater than 99.5%; the average particle size of the W powder is 5-25μm, and the purity is greater than 99.5%.

[0014] Preferably, in step (1), nano-TiC ceramic powder and Y2O3 rare earth oxide are ball-milled and mixed in a mass ratio of 3:1, 1:1 or 1:3 by a planetary ball mill under inert gas protection, the ball-to-material ratio is 2:1, the ball milling speed is 250 rpm, and the ball milling time is 2 h.

[0015] Preferably, in step (4), the thermal field assisted laser additive manufacturing forming uses two laser beams in the laser scanning forming process, corresponding to the first and second laser beams; wherein: the first laser beam is used to melt the tungsten-based composite powder, and the second laser beam in situ assists the first laser beam to melt the tungsten-based composite powder to form a thermal field to control the solidification rate of the tungsten-based composite powder.

[0016] Preferably, in step (4), the solidification rate satisfies:

[0017]

[0018] Where: K represents the solidification rate coefficient; α represents the thermal diffusion coefficient; T in it represents the temperature field; P1 is the power of the first laser beam; A1 is the effective area of ​​the first laser beam; P2 is the power of the second laser beam; A2 is the effective area of ​​the second laser beam; V s1 represents the scanning speed of the first laser beam; V s2 represents the scanning speed of the second laser beam; a1 represents the scanning speed V of the first laser beam s1 The linear influence coefficient on the solidification speed; a2 represents the scanning speed V of the second laser beam s2 The linear influence coefficient on the solidification speed; β represents the influence coefficient of the interaction between the scanning speed of the second and second laser beams on the solidification speed; γ represents the scanning speed V of the first laser beam s1 The nonlinear influence coefficient of the solidification speed is: δ represents the nonlinear influence coefficient of the scanning speed of the second laser beam on the solidification speed; μ is the material solidification characteristic constant; Δt is the interval time between the two laser beams; b is the influence coefficient of the laser interval time on the solidification speed; τ is the nonlinear influence coefficient of the laser interval time on the solidification speed.

[0019] Preferably, in step (4), during the laser forming process of the laser powder bed fusion forming equipment, the process parameters of the first laser beam are: laser power of 200-450 W, laser scanning speed of 200-600 mm / s, spot diameter of 70 μm, scanning spacing of 50 μm, powder layer thickness of 30 μm, scanning strategy of checkerboard scanning, and inter-layer rotation of 67 degrees.

[0020] Preferably, in step (4), the process parameters of the second laser beam are: laser power of 225 W, scanning speed of 450 mm / s, the interval time between the two laser beams is set to 0.06 seconds, the laser spot diameter is 60 μm, and the scanning interval is 40 μm; the powder layer thickness is 20 μm, the scanning strategy is checkerboard scanning, and the inter-layer rotation is 67 degrees.

[0021] Another technical purpose of the present invention is to provide a thermal field assisted laser additive manufacturing of highly radiation-resistant tungsten-based composite materials, which is made using the above-mentioned integrated forming method of the thermal field assisted laser additive manufacturing of highly radiation-resistant tungsten-based composite materials.

[0022] Beneficial effects:

[0023] (1) The TiC ceramic particles and rare earth oxide Y2O3 particles used in the present invention are multi-phase reinforced tungsten-based composite materials. The TiC ceramic particles and rare earth oxide Y2O3 particles themselves can achieve a good strengthening effect on tungsten. Y2O3 can reduce the ductile-brittle transition temperature of W, reduce its room temperature brittleness, effectively inhibit the migration of W grain boundaries, refine and stabilize W grains, inhibit the formation of cracks and pores during the forming process, and improve its strength and toughness. However, nano Y2O3 itself is prone to agglomeration and is difficult to achieve uniform dispersion on the surface of tungsten powder. The addition of nano TiC ceramic particles can disperse the agglomerated nano Y2O3 particles during the powder mixing process, so that the two-phase nano particles are evenly coated on the surface of the spherical tungsten powder. TiC particles have good compatibility with tungsten, similar thermal expansion coefficients, and high strength and hardness, which can improve the high-temperature strength of tungsten to a certain extent. The addition of these two phases of nano particles at the same time plays a role of dispersion strengthening, can pin dislocations, inhibit the movement of grain boundaries, effectively refine grains, increase the area of ​​grain boundaries, and improve the plasticity, toughness and radiation resistance of the tungsten-based composite material.

[0024] (2) The present invention adopts the addition of TiC ceramic particles and rare earth oxide Y2O3 particles in different proportions to determine the forming properties of tungsten-based composite materials in different proportions, and at the same time determine the two-phase particles that play a major role in improving the mechanical properties and radiation resistance of the tungsten-based composite materials.

[0025] (3) The present invention uses an additional laser beam to assist the thermal field in the forming process of the tungsten-based composite material, slowing down the solidification rate during the forming process, inhibiting the generation of pores and cracks in the formed sample, improving the density of the formed sample, and overcoming the problem of low density of tungsten formed by laser additive manufacturing. At the same time, the laser used for thermal field assistance can play a role in crushing grains, refining the grain size, and further improving the comprehensive performance of the tungsten-based composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and other advantages of the present invention will become more clear.

[0027] Figure 1 Print detailed flow chart for samples

[0028] Figure 2 SEM image of W-1%Y2O3-1%TiC powder prepared in Example 1.

[0029] Figure 3 This is the SEM image of W-2% Y2O3 powder prepared in Comparative Example 1.

[0030] Figure 4 This is an optical microscopy image of the sample prepared in Example 1.

[0031] Figure 5 This is the optical microscopy morphology image of the sample prepared in Example 2.

[0032] Figure 6 This is the optical microscopy morphology image of the sample prepared in Example 2 after corrosion.

[0033] Figure 7 This is an optical microscopy image of the sample prepared in Example 3.

[0034] Figure 8 This is the optical microscopy morphology image of the sample after corrosion prepared in Comparative Example 1.

[0035] Fig. 9 Optical microscopic morphology image of the sample after corrosion prepared for comparative example 2

[0036] Fig.10 This is a graph showing the laser absorptivity of the samples measured in Example 4.

[0037] Fig.11 The compressive stress-strain curves of the samples prepared in Example 1, Example 2, Example 3 and Comparative Example 2.

[0038] Fig.12 This is the relationship between the energy of He ion implantation and the damage depth.

[0039] Fig.13 The nuclear energy loss and electronic energy loss of the samples prepared in Example 2 for He ions with different energies.

[0040] Fig.14 Atomic displacement damage and He ion retention concentration distribution of the sample prepared in Example 2 for He ions. DETAILED DESCRIPTION

[0041] The following embodiments are used to further describe the technical problems and methods to be solved by the present invention.

[0042] In the following embodiments, the TiC content used is 0-2wt.%, the Y2O3 content is 0-2wt.%, and the rest is tungsten powder. The particle size distribution range of the TiC ceramic powder used is 50-100mm, and the purity is greater than 99%. The particle size distribution range of the Y2O3 rare earth oxide particles used is 50-100nm, and the purity is greater than 99%. The particle size distribution range of the W powder used is 5-25μm, and the purity is greater than 99%.

[0043] Example 1

[0044] In the W-TiC-Y2O3 composite material with high radiation resistance in this embodiment, the composition of each element in terms of mass percentage is as follows: W-1wt.% TiC-1wt.% Y2O3, with the remainder being W.

[0045] (1) According to the material ratio, 98g of pure tungsten powder, 1g of nano-TiC powder, and 1g of nano-Y2O3 powder were weighed and put into a ball mill, with a ball-to-material ratio of 2:1, a ball milling time of 2h, a rotation speed of 250rpm, and a rest of 5 minutes every 15 minutes during the ball milling process to obtain a tungsten-based composite powder of W-1wt.%TiC-1wt.%Y2O3. The SEM image of the tungsten-based composite powder is shown in FIG. Figure 2 As shown, it can be seen that the tungsten-based composite powder maintains good sphericity and the second phase is evenly distributed.

[0046] (2) The obtained tungsten-based composite powder was placed in a vacuum drying oven, the drying temperature was set to 80° C., the drying time was set to 8 hours, and after the vacuum drying was completed, the powder was taken out.

[0047] (3) Establish a three-dimensional geometric model of the part, set the laser processing parameters, determine the scanning strategy, and then import the model into the slicing software for layered slicing processing, so that the three-dimensional entity is discretized into a series of two-dimensional data, which are saved and imported into the laser powder bed fusion forming equipment.

[0048] (4) The laser process parameters used for printing were set as follows: laser power of 195 W, scanning speed of 350 mm / s, scanning spacing of 40 μm, powder thickness of 20 μm, and a checkerboard scanning strategy with 67-degree interlayer rotation to avoid stress concentration; the laser power used for thermal field assistance was 225 W, and the scanning speed was 450 mm / s.

[0049] (5) The tungsten-based composite powder dried in step (2) is used for laser powder bed fusion forming, and the 316 stainless steel substrate is fixed in the forming cavity of the laser powder bed equipment and leveled, and then argon gas is introduced into the forming cavity as a protective gas to reduce the oxygen content in the forming cavity to 80 ppm. Then the laser is turned on, and the laser beam scans the slice area line by line according to a pre-designed scanning path. After the laser beam scans one line, the laser used for thermal field assistance will scan immediately according to the pre-set scanning path to reduce the temperature gradient and relieve residual stress until the sample is printed.

[0050] The second laser beam in-situ assists the first laser beam in melting the tungsten-based composite powder to form a thermal field to control the solidification rate of the tungsten-based composite powder. The relationship between the following physical quantities needs to be considered.

[0051] Heat conduction equation: The heat conduction process can be described by the heat conduction equation:

[0052]

[0053] Where Q represents the heat provided by the laser beam, α represents the thermal diffusion coefficient, and T represents the temperature field.

[0054] Relationship between laser power and temperature:

[0055]

[0056] Where: P1 is the power of the first laser beam; P2 is the power of the second laser beam; A1 and A2 are the action areas of the first and second laser beams respectively.

[0057] Solidification rate: The solidification rate is related to the temperature gradient, supercooling and scanning speed, and can be expressed as:

[0058]

[0059] Where K is the solidification rate coefficient; is the temperature gradient along the solidification direction; f(V s1 , V s2 ) is a function used to express the effect of scanning speed on solidification speed, V s1 Indicates the scanning speed of the first laser beam; V s2 represents the scanning speed of the second laser beam; f(Δt) represents the influence function of the interval time between the first laser beam and the second laser beam on the solidification speed.

[0060] Among them, the function f(V s1 , V s2 ) can be defined as:

[0061] f(V s1 ,V s2 )=1+a1·V s1 +a2·V s2 +β·V s1 ·V s2 +γ·V s1 2 +δ·V s2 2

[0062] Where: a1 represents the scanning speed V of the first laser beam s1 The linear influence coefficient on the solidification speed; a2 represents the scanning speed V of the second laser beam s2 The linear influence coefficient on the solidification speed; β represents the influence coefficient of the interaction between the scanning speed of the second and second laser beams on the solidification speed; γ represents the scanning speed V of the first laser beam s1The nonlinear influence coefficient on the solidification speed, δ, represents the nonlinear influence coefficient of the scanning speed of the second laser beam on the solidification speed.

[0063] The function f(Δt) can be defined as:

[0064] f(Δt)=μ·(1+bΔt) τ

[0065] μ is the material solidification characteristic constant; Δt is the interval between two laser beams, and the present invention fixes the time to 0.06S; a is the influence coefficient of the laser interval on the solidification speed; τ is the nonlinear influence coefficient of the laser interval on the solidification speed.

[0066] Combining the above relationships, a comprehensive expression for solidification rate can be obtained:

[0067]

[0068] Where: K represents the solidification rate coefficient; α represents the thermal diffusion coefficient; T in it represents the temperature field; P1 is the power of the first laser beam; A1 is the effective area of ​​the first laser beam; P2 is the power of the second laser beam; A2 is the effective area of ​​the second laser beam; V s1 represents the scanning speed of the first laser beam; V s2 represents the scanning speed of the second laser beam; a1 represents the scanning speed V of the first laser beam s1 The linear influence coefficient on the solidification speed; a2 represents the scanning speed V of the second laser beam s2 The linear influence coefficient on the solidification speed; β represents the influence coefficient of the interaction between the scanning speed of the second and second laser beams on the solidification speed; γ represents the scanning speed V of the first laser beam s1 The nonlinear influence coefficient on the solidification speed is: δ represents the nonlinear influence coefficient of the scanning speed of the second laser beam on the solidification speed; μ is the material solidification characteristic constant; Δt is the interval between the two laser beams, and the present invention fixes the time to 0.06S; a is the influence coefficient of the laser interval time on the solidification speed; τ is the nonlinear influence coefficient of the laser interval time on the solidification speed.

[0069] Note: Coefficients such as K, α, and μ can be obtained using material performance simulation software, and other linear influence coefficients are obtained through experimental fitting.

[0070] By adjusting the laser powers P1, P2 and the scanning speed Vs, the distribution of the temperature field T can be effectively controlled, thereby affecting the solidification speed Vc.

[0071] (6) After printing is completed, cool for 24 hours, then take it out of the forming cavity and separate the sample from the substrate using wire cutting. The obtained sample is tested for density, mainly using the Archimedes drainage method. At the same time, the tungsten-based composite block sample is ground, polished and corroded according to the standard metallographic sample preparation method. The pores and cracks on the surface of the sample are observed using a metallographic microscope. The obtained compression sample is tested for compression performance.

[0072] (7) Figure 4 Shown is the metallographic structure diagram of this embodiment, Fig.11 This is the compressive stress-strain curve of the sample in this embodiment, the ultimate compressive strength can reach 1135.4 MPa, and the elongation is 11.4%.

[0073] Example 2

[0074] In the W-TiC-Y2O3 composite material with high radiation resistance in this embodiment, the composition of each element in terms of mass percentage is as follows: W-1.5wt.%TiC-0.5wt.%Y2O3, with the remainder being W.

[0075] (1) According to the material ratio, 98g of pure tungsten powder, 1.5g of nano-TiC powder, and 0.5g of nano-Y2O3 powder were weighed and put into a ball mill with a ball-to-material ratio of 2:1. The ball milling time was 2h and the rotation speed was 250rpm. During the ball milling process, the ball milling was performed for 15 minutes with a rest period of 5 minutes to obtain a tungsten-based composite powder of W-1.5wt.%TiC-0.5wt.%Y2O3.

[0076] (2) The obtained tungsten-based composite powder was placed in a vacuum drying oven, the drying temperature was set to 80° C., the drying time was set to 8 hours, and after the vacuum drying was completed, the powder was taken out.

[0077] (3) Establish a three-dimensional geometric model of the part, set the laser processing parameters, determine the scanning strategy, and then import the model into the slicing software for layered slicing processing, so that the three-dimensional entity is discretized into a series of two-dimensional data, which are saved and imported into the laser powder bed fusion forming equipment.

[0078] (4) The laser process parameters used for printing were set as follows: laser power of 210 W, scanning speed of 400 mm / s, scanning spacing of 40 μm, powder thickness of 20 μm, and a checkerboard scanning strategy with 67-degree interlayer rotation to avoid stress concentration; the laser power used for thermal field assistance was 225 W, and the scanning speed was 450 mm / s.

[0079] (5) The tungsten-based composite powder dried in step (2) is used for laser powder bed fusion forming, and the 316 stainless steel substrate is fixed in the forming cavity of the laser powder bed equipment and leveled, and then argon gas is introduced into the forming cavity as a protective gas to reduce the oxygen content in the forming cavity to 80 ppm. Then the laser is turned on, and the laser beam scans the slice area line by line according to a pre-designed scanning path. After the laser beam scans one line, the laser used for thermal field assistance will scan immediately according to the pre-set scanning path to reduce the temperature gradient and relieve residual stress until the sample is printed.

[0080] (6) After printing, the sample was cooled for 24 hours and then removed from the forming cavity. The sample was separated from the substrate by wire cutting. The obtained sample was subjected to density test, mainly using the Archimedes drainage method. At the same time, the tungsten-based composite block sample was ground, polished and corroded according to the standard metallographic sample preparation method. The defects such as pores and cracks on the sample surface were observed using a metallographic microscope.

[0081] (7) Figure 5 Shown is the metallographic structure diagram of this embodiment, Figure 6 This is a metallographic picture after etching of this embodiment. It is found that by using this method, the second laser beam can organize the originally grown columnar crystals and break them into equiaxed crystals. Fig.11 The compressive stress-strain curve of the sample in this embodiment shows that the ultimate compressive strength can reach 1363.5 MPa, the elongation is 14.7%, and the compressive strength reaches the highest.

[0082] Example 3

[0083] In the W-TiC-Y2O3 composite material with high radiation resistance in this embodiment, the composition of each element in terms of mass percentage is as follows: W-0.5wt.%TiC-1.5wt.%Y2O3, with the remainder being W.

[0084] (1) According to the material ratio, 98 g of pure tungsten powder, 0.5 g of nano-TiC powder, and 1.5 g of nano-Y2O3 powder were weighed and put into a ball mill with a ball-to-material ratio of 2:1. The ball milling time was 2 h and the rotation speed was 250 rpm. During the ball milling process, the ball milling was repeated for 15 minutes with a rest period of 5 minutes to obtain a tungsten-based composite powder of W-0.5wt.%TiC-1.5wt.%Y2O3.

[0085] (2) The obtained tungsten-based composite powder was placed in a vacuum drying oven, the drying temperature was set to 80° C., the drying time was set to 8 hours, and after the vacuum drying was completed, the powder was taken out.

[0086] (3) Establish a three-dimensional geometric model of the part, set the laser processing parameters, determine the scanning strategy, and then import the model into the slicing software for layered slicing processing, so that the three-dimensional entity is discretized into a series of two-dimensional data, which are saved and imported into the laser powder bed fusion forming equipment.

[0087] (4) The laser process parameters used for printing were set as follows: laser power of 240 W, scanning speed of 500 mm / s, scanning spacing of 40 μm, powder thickness of 20 μm, and a checkerboard scanning strategy with 67-degree interlayer rotation to avoid stress concentration; the laser power used for thermal field assistance was 225 W and the scanning speed was 450 mm / s.

[0088] (5) The tungsten-based composite powder dried in step (2) is used for laser powder bed fusion forming, and the 316 stainless steel substrate is fixed in the forming cavity of the laser powder bed equipment and leveled, and then argon gas is introduced into the forming cavity as a protective gas to reduce the oxygen content in the forming cavity to 80 ppm. Then the laser is turned on, and the laser beam scans the slice area line by line according to a pre-designed scanning path. After the laser beam scans one line, the laser used for thermal field assistance will scan immediately according to the pre-set scanning path to reduce the temperature gradient and relieve residual stress until the sample is printed.

[0089] (6) After printing, the sample was cooled for 24 hours and then removed from the forming cavity. The sample was separated from the substrate by wire cutting. The obtained sample was subjected to density test, mainly using the Archimedes drainage method. At the same time, the tungsten-based composite block sample was ground, polished and corroded according to the standard metallographic sample preparation method. The pores and cracks on the sample surface were observed using a metallographic microscope.

[0090] (7) Figure 7 Shown is the metallographic structure diagram of this embodiment, Fig.11 This is the compressive stress-strain curve of the sample in this embodiment, the ultimate compressive strength can reach 1205.9 MPa, and the elongation is 12.4%.

[0091] Example 4

[0092] The W-TiC-Y2O3 composite material with high radiation resistance in this embodiment is mainly composed of a composite material containing different proportions of reinforcing phases. The laser absorption rate of W-2wt.% TiC, W-0.5wt.% TiC-1.5wt.% Y2O3, W-1wt.% TiC-1wt.% Y2O3, W-1.5wt.% TiC-0.5wt.% Y2O3, W-2wt.% Y2O3 and pure tungsten powder were tested, which corresponds to the formability of the blocks formed in Example 1, Example 2, and Example 3.

[0093] As shown in Figure 10, the laser absorptivity of the composite powder with added reinforcing phase is higher than that of pure tungsten, and the laser absorptivity of the W-1.5wt.%TiC-0.5wt.%Y2O3 composite powder is higher than that of the other W-0.5wt.%TiC-1.5wt.%Y2O3 and W-1wt.%TiC-1wt.%Y2O3 composite powders. This is mainly due to the higher laser absorptivity of TiC powder. The higher the laser absorptivity of the powder, the higher the heat it absorbs, making the molten pool temperature higher, the powder can be completely melted, the liquid phase residence time is long, the melt flows fully, and the generation of irregular holes is reduced, which corresponds to the fewer holes on the surface of the sample obtained in Example 2 and the high density.

[0094] Example 5

[0095] The W-TiC-Y2O3 composite material with high radiation resistance in this embodiment is mainly composed of a composite material containing different proportions of reinforcing phases. SRIM software is used to simulate W-2wt.% TiC, W-0.5wt.% TiC-1.5wt.% Y2O3, W-1wt.% TiC-1wt.% Y2O3, W-1.5wt.% TiC-0.5wt.% Y2O3, W-2wt.% Y2O3 and pure tungsten to track the movement trajectory of each incident He ion inside the different composite materials and the recoil atoms formed, and the influence depth of 200keV He ions in different composite materials is compared, and the ion concentration distribution, energy loss and atomic displacement damage in the 200keV He ion W-1.5wt.% TiC-0.5wt.% Y2O3 composite material are calculated.

[0096] Fig.12 The damage depth of different materials after being irradiated with 200keV He ions. As the content of the reinforcing phase TiC increases, the damage depth of the composite material to He ions decreases, indicating that TiC can effectively capture He ions, reduce the generation of defects, reduce the accumulation of defects in the material, and improve the ability to resist radiation. This is mainly due to the formation of a solid solution of TiC in the tungsten matrix, which can enhance the lattice stability of tungsten and reduce the generation of defects (such as vacancies and dislocations) caused by radiation; the phase interface between TiC and tungsten can improve the radiation resistance of the material, making the material more stable under irradiation conditions, and the high hardness of TiC can improve the wear resistance of tungsten alloys and reduce damage under irradiation conditions.

[0097] Comparative Example 1

[0098] In this comparative example, a single Y2O3 powder is used as the reinforcement phase to prepare a tungsten-based composite powder, and laser powder bed melting is performed. Since laser additive manufacturing technology requires the use of tungsten powder materials with good sphericity and good fluidity as raw materials, and requires that nanopowders are evenly coated on the surface of spherical tungsten powders, this is conducive to obtaining uniform powder feeding and powder spreading effects. In this comparative example, the powder morphology is as follows Figure 3 As shown in FIG. 1 , although the Y2O3 particles are dispersed on the surface of the tungsten powder, serious agglomeration occurs, which reduces the sphericity and affects the performance of the formed sample. In this comparative example, the formed sample is polished and etched. Figure 8 As shown in the figure, it is found that the addition of Y2O3 can significantly improve the microstructure and refine the grains, mainly because Y2O3 forms oxide particles in the tungsten matrix. These particles act as strong obstacles and can effectively prevent the growth of grains. The presence of Y2O3 affects the diffusion behavior of atoms in tungsten, and promotes the formation of fine grains by changing the diffusion path and rate of atoms. The addition of Y2O3 can improve the thermal stability of tungsten, maintain a smaller grain size at high temperatures, and reduce grain coarsening caused by high temperatures. However, due to its severe agglomeration and low laser absorption rate of its powder, the temperature obtained under the same process parameters is lower, resulting in a large number of unmelted holes, resulting in a decrease in its density.

[0099] Comparative Example 2

[0100] This comparative example uses pure tungsten powder for laser powder bed fusion forming. During the forming process, the temperature gradient is large, there is a large residual stress, the density of the formed sample is low, there are obvious holes and long cracks, and there are coarse columnar crystals. This is mainly because the cooling rate of the molten pool is very fast during the laser additive manufacturing process. Tungsten has a high melting point, and rapid cooling will lead to rapid phase change, thus forming columnar crystals. This rapid solidification does not allow the grains to have enough time to be refined and homogenized, resulting in the formation of columnar crystals. Pure tungsten has no reinforcing phase as a nucleation point during the additive manufacturing process, which will only lead to the growth of more columnar crystals and increase the risk of crack formation. As shown in Figure 9, the density is reduced to about 94%, making its compression performance much lower than the compression strength of Example 1, Example 2, and Example 3. Fig.11 As shown, it only reaches 1005MPa, the elongation is 9.4%, and the radiation resistance is weakened.

Claims

1. A method for integrally forming a highly radiation-resistant tungsten-based composite material by thermal field-assisted laser additive manufacturing, characterized in that: The following steps are involved: (1) ball milling nano-TiC ceramic powder, Y2O3 rare earth oxide and W powder under inert gas protection to prepare tungsten-based composite powder; in the tungsten-based composite powder, the mass fraction of W powder is 98wt.%, and the mass ratio of nano-TiC ceramic powder to Y2O3 rare earth oxide is 1:3 to 3:1; (2) placing the tungsten-based composite powder mixed in step (1) into a forming cavity of a laser powder bed melting forming device, and introducing argon gas as a protective gas; (3) Establishing a three-dimensional geometric model of the part and importing it into the slicing software for layered slicing processing to discretize it into a series of two-dimensional slicing data, which are saved and imported into the laser powder bed fusion forming equipment; (4) The laser powder bed fusion forming equipment uses the thermal field assisted laser additive manufacturing technology according to the two-dimensional slice data imported in step (3) to melt and solidify the tungsten-based composite powder in the forming cavity layer by layer to obtain a thermal field assisted laser additive manufacturing tungsten-based composite material with high radiation resistance.

2. The one-piece forming method of thermal field assisted laser additive manufacturing of highly radiation-resistant tungsten-based composite materials according to claim 1, characterized in that: In the tungsten-based composite powder prepared in step (1), the mass fraction of the TiC ceramic powder is 0-2wt.%, the average particle size is 50-100nm, and the purity is greater than 99.5%; the mass fraction of the Y2O3 rare earth oxide is 0-2wt.%, the average particle size is 50-100nm, and the purity is greater than 99.5%; the average particle size of the W powder is 5-25μm, and the purity is greater than 99.5%.

3. The one-piece forming method of thermal field assisted laser additive manufacturing of highly radiation-resistant tungsten-based composite materials according to claim 1, characterized in that: In step (1), nano-TiC ceramic powder and Y2O3 rare earth oxide are ball-milled and mixed in a mass ratio of 3:1, 1:1 or 1:3 by a planetary ball mill under inert gas protection, the ball-to-material ratio is 2:1, the ball milling speed is 250 rpm, and the ball milling time is 2 h.

4. The one-piece forming method of thermal field assisted laser additive manufacturing of highly radiation-resistant tungsten-based composite materials according to claim 1, characterized in that: In step (4), the thermal field assisted laser additive manufacturing forming uses two laser beams in the laser scanning forming process, corresponding to the first and second laser beams; wherein: the first laser beam is used to melt the tungsten-based composite powder, and the second laser beam in situ assists the first laser beam to melt the tungsten-based composite powder to form a thermal field to control the solidification rate of the tungsten-based composite powder.

5. The one-piece forming method of thermal field assisted laser additive manufacturing of highly radiation-resistant tungsten-based composite materials according to claim 1, characterized in that: In step (4), the solidification rate satisfies: Where: K represents the solidification rate coefficient; α represents the thermal diffusion coefficient; T in it represents the temperature field; P1 is the power of the first laser beam; A1 is the effective area of ​​the first laser beam; P2 is the power of the second laser beam; A2 is the effective area of ​​the second laser beam; V s1 represents the scanning speed of the first laser beam; V s2 represents the scanning speed of the second laser beam; a1 represents the scanning speed V of the first laser beam s1 The linear influence coefficient on the solidification speed; a2 represents the scanning speed V of the second laser beam s2 The linear influence coefficient on the solidification speed; β represents the influence coefficient of the interaction between the scanning speed of the second and second laser beams on the solidification speed; γ represents the scanning speed V of the first laser beam s1 The nonlinear influence coefficient of the solidification speed is: δ represents the nonlinear influence coefficient of the scanning speed of the second laser beam on the solidification speed; μ is the material solidification characteristic constant; Δt is the interval time between the two laser beams; b is the influence coefficient of the laser interval time on the solidification speed; τ is the nonlinear influence coefficient of the laser interval time on the solidification speed.

6. The one-piece forming method of a high-radiation-resistant tungsten-based composite material manufactured by laser additive manufacturing assisted by a thermal field according to claim 1, characterized in that: In step (4), during the laser forming process of the laser powder bed fusion forming equipment, the process parameters of the first laser beam are: laser power of 200-450 W, laser scanning speed of 200-600 mm / s, spot diameter of 70 μm, scanning interval of 50 μm, powder layer thickness of 30 μm, scanning strategy of checkerboard scanning, and inter-layer rotation of 67 degrees.

7. The one-piece forming method of thermal field assisted laser additive manufacturing of highly radiation-resistant tungsten-based composite materials according to claim 6, characterized in that: In step (4), the process parameters of the second laser beam are: laser power is 225W, scanning speed is 450mm / s, the interval time between the two laser beams is set to 0.06 seconds, the laser spot diameter is 60μm, and the scanning interval is 40μm; the powder layer thickness is 20μm, the scanning strategy is chessboard scanning, and the inter-layer rotation is 67 degrees.

8. A thermal field assisted laser additive manufacturing of highly radiation resistant tungsten-based composite materials, characterized in that: The composite material is manufactured by the one-piece forming method of thermal field assisted laser additive manufacturing of highly radiation-resistant tungsten-based composite materials as described in claims 1 to 7.

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