A method for preparing a high thermal conductivity component of copper-chromium-niobium alloy based on green laser SLM

Abstract

The present application discloses a method for preparing a high thermal conductivity component of copper-chromium-niobium alloy based on green laser SLM, which relates to the technical field of copper-chromium-niobium alloy. The method includes the following steps: pretreating the copper-chromium-niobium alloy powder; laying the pretreated copper-chromium-niobium alloy powder on a substrate, and performing selective laser melting printing with a green laser, and setting printing parameters with at least two different energy densities in a layered energy gradient control manner for layered printing to form a pore structure with a continuously gradient distribution of porosity, thereby obtaining a prefabricated part; wherein, the wavelength of the green laser is 500nm - 550nm, and the spot diameter is 15μm - 30μm; heat-treating the prefabricated part to obtain a high thermal conductivity component. The present application prepares a copper-chromium-niobium alloy component through the green laser SLM process, and adopts a layered energy density gradient control technology to systematically solve the problems of high reflectivity, limited structure, insufficient performance, etc. in the additive manufacturing of copper-based alloys.

Description

Technical Field

[0001] This application relates to the technical field of copper-chromium-niobium alloys, and particularly relates to a method for preparing high-thermal-conductivity components of copper-chromium-niobium alloys based on green laser SLM. Background Art

[0002] Due to its excellent high-temperature mechanical properties and conductivity, copper-chromium-niobium alloys are widely used in high-thermal-conductivity complex components required for scenarios such as heat-dissipating electronic heat sinks, combustion chamber linings in aerospace, high-power IGBT heat dissipation modules, heat sinks for 5G base stations, and nuclear reactor heat exchangers. Selective laser melting (SLM) technology is a technology for manufacturing solid parts by layer-by-layer printing. Currently, in the process of preparing copper-chromium-niobium alloys using SLM technology, the following problems usually exist: (1) High reflectivity and low energy efficiency. The reflectivity of copper to traditional infrared lasers (wavelength 1064 nm) exceeds 90%, and the absorption rate is only 5%-10%. To achieve powder melting, traditional SLM relies on ultra-high-power lasers (≥800 W), which will result in more than 60% energy loss. Moreover, high-power lasers are prone to cause violent fluctuations in the molten pool, thereby forming defects such as pores and lack of fusion (porosity > 5%). At the same time, local overheating makes the oxygen content of the material exceed 1000 ppm, significantly reducing the conductivity (<70% IACS); (2) Insufficient complex structure forming ability. Traditional SLM processes are limited by a large spot diameter (60 μm - 70 μm) and a wide molten pool (200 μm - 300 μm), making it difficult to precisely control complex structure parts such as thin walls (<100 μm) and microchannels (pore diameter < 200 μm). The forming accuracy is limited, and subsequent finishing treatment is required, resulting in a 3 - 5-fold increase in cost. In addition, pore-forming agents need to be added or the scanning strategy needs to be adjusted to achieve a porous structure, but the pore distribution is random (connectivity rate < 50%), and interface stress concentration makes it difficult to balance high porosity and thermal properties (for example, when the porosity is 30%, the thermal conductivity is less than 200 W / m·K); (3) Process complexity. In the existing technology, graphene is added to improve the laser absorption rate, but additional processes (mixing, dispersion, drying) are introduced, resulting in a 40% - 60% increase in material cost. Moreover, nanoparticles are prone to agglomeration, which will affect the tissue uniformity. The entire process flow is very long and it is difficult to meet the requirements of rapid manufacturing. Based on this, there is an urgent need for a copper alloy additive manufacturing technology that can take into account high thermal conductivity, integrated forming of complex structures (such as microchannels, honeycomb structures), and low-cost manufacturing. Summary of the Invention

[0003] The main purpose of this application is to provide a method for preparing high-thermal-conductivity components of copper-chromium-niobium alloys based on green laser SLM, aiming to solve the technical problems of low laser absorption rate of copper-based materials and difficult integrated forming of complex structures in traditional SLM processes.

[0004] To achieve the above object, the present application proposes a method for preparing a high thermal conductivity component of copper-chromium-niobium alloy based on green laser SLM, comprising the following steps:

[0005] Pre-treat the copper-chromium-niobium alloy powder;

[0006] Lay the pre-treated copper-chromium-niobium alloy powder on a substrate, and perform selective laser melting printing using a green laser. Set the printing parameters of at least two layers with different energy densities by a layered energy gradient control method, and perform layered printing to form a pore structure with a continuously gradient distribution of porosity, obtaining a pre-processed part; wherein, the wavelength of the green laser is 500nm - 550nm, and the spot diameter is 15μm - 30μm;

[0007] Heat-treat the pre-processed part to obtain a high thermal conductivity component.

[0008] Optionally, the mass percentage of chromium element in the copper-chromium-niobium alloy powder is 3.0wt% - 4.0wt%, and the mass percentage of niobium element is 2.0wt% - 3.0wt%.

[0009] Optionally, the particle size of the copper-chromium-niobium alloy powder is 15μm - 53μm, the loose bulk density is 4.0g / cm 3 - 5.0g / cm 3 , and the fluidity ≤ 25s / 50g.

[0010] Optionally, the step of pre-treating the copper-chromium-niobium alloy powder includes:

[0011] After passing the copper-chromium-niobium alloy powder through a sieve with 180 - 200 meshes, dry it in a vacuum environment or an inert atmosphere at 80℃ - 150℃ for 2h - 4h, so that the gas content of the copper-chromium-niobium alloy powder < 100ppm.

[0012] Optionally, in the step of laying the pre-treated copper-chromium-niobium alloy powder on the substrate, the powder laying thickness is 0.03mm - 0.08mm, and the scanning speed is 600mm / s - 1200mm / s.

[0013] Optionally, before the step of laying the pre-treated copper-chromium-niobium alloy powder on the substrate, it further includes:

[0014] Grind and sandblast the substrate to make the surface roughness Ra of the substrate ≤ 3.2μm.

[0015] Optionally, in the step of setting the printing parameters of at least two layers with different energy densities by a layered energy gradient control method and performing layered printing to form a pore structure with a continuously gradient distribution of porosity, it includes:

[0016] Set the printing parameters of three different energy densities respectively, and perform layer-by-layer printing in sequence according to the dense layer, the transition layer and the core layer to form a pore structure with a continuously gradient distribution of porosity;

[0017] Among them, the printing parameters of the dense layer include: the laser power is 300W - 400W, the scanning speed is 800mm / s - 1200mm / s, and the scanning spacing is 0.04mm - 0.09mm;

[0018] The printing parameters of the transition layer include: the laser power is 200W - 300W, the scanning speed is 500mm / s - 800mm / s, and the scanning spacing is 0.04mm - 0.09mm;

[0019] The printing parameters of the core layer include: the laser power is 100W - 200W, the scanning speed is 200mm / s - 500mm / s, and the scanning spacing is 0.04mm - 0.09mm.

[0020] Optionally, the porosity of the dense layer is 0.5% - 3.0%, the porosity of the transition layer is 10.0% - 20.0%, and the porosity of the core layer is 20.0% - 30.0%.

[0021] Optionally, in the layered energy gradient control method, the scanning process adopts strip filling or checkerboard filling.

[0022] Optionally, the step of heat-treating the prefabricated part to obtain a high thermal conductivity component includes:

[0023] Vacuum heat-treat the prefabricated part, the heat treatment temperature is 600°C - 900°C, and the holding time is 3h - 7h.

[0024] This application has at least the following beneficial effects:

[0025] This application prepares copper chromium niobium alloy components through the green laser SLM process. By precisely melting copper alloy powder with a small spot of green laser, high-efficiency melting of copper alloy at low power is achieved, overcoming the problem of high reflectivity of copper, increasing the laser absorption rate of copper-based alloys to about 40%, and avoiding element volatilization caused by traditional high-power infrared laser printing (≥1000W). The thermal conductivity of the prepared copper chromium niobium alloy components is ≥350W / (m·K), which is more than 35% higher than that of the traditional infrared laser process (thermal conductivity ≤280W / (m·K)); and the electrical conductivity is ≥80% IACS (International Annealed Copper Standard), which is 14% higher than that of the traditional infrared laser process (electrical conductivity <70% IACS), significantly reducing the Joule heat loss during the operation of electronic devices; and based on the characteristics of the low power (100W - 400W) of the green laser in this application, the oxygen content of the prepared high-thermal conductivity components can be controlled below 500ppm, avoiding the deterioration of conductivity caused by the relatively high oxygen content in the traditional high-power laser (oxygen content >1000ppm); and this application adopts a hierarchical energy density gradient control technology for pore connectivity design and heat dissipation structure optimization. By coordinating the laser power and printing speed, the local pore distribution of the printed parts is precisely regulated. A dense layer is formed near the surface of the radiator to improve strength, and a high porosity is maintained in the core to optimize the heat exchange area. By smoothly regulating the interlayer porosity, the problem of interlayer interface stress concentration is effectively avoided, and a continuous gradient pore structure from the dense layer to the core layer is achieved. The microhardness of the heat-treated high-thermal conductivity components is ≥HB110, which is 50% higher than that of traditional cast copper alloys (HB60 - HB80), meeting the wear resistance and heat dissipation requirements of high-load heat dissipation components; and the green laser spot diameter in this application is 15μm - 30μm. The width of the molten pool can be precisely controlled within 30μm - 80μm by the small-spot laser, thereby improving the forming accuracy of the parts, supporting the processing of thin-walled structures with a thickness of 60μm - 100μm, breaking through the limit of the traditional SLM process (minimum forming size ≥200μm), and eliminating the need for subsequent finishing processing, saving processing costs. Thus, the problems of high reflectivity, structural limitations, and insufficient performance in the additive manufacturing of copper-based alloys are systematically solved, providing an efficient, low-cost, and high-precision solution for heat dissipation components of high-power devices. Brief Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0027] Figure 1Flow chart of the method for preparing a high thermal conductivity component of copper-chromium-niobium alloy based on green laser SLM according to the embodiments of the present application.

[0028] The realization of the purpose of the present application, functional features and advantages will be further described in conjunction with the embodiments with reference to the accompanying drawings. Specific embodiments

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0030] In view of the technical problems existing in the prior art, embodiments of the present application provide a method for preparing a high thermal conductivity component of copper-chromium-niobium alloy based on green laser SLM, as Figure 1 shown, including the following steps:

[0031] S1. Pretreat the copper-chromium-niobium alloy powder.

[0032] In the specific implementation process, during pretreatment, the copper-chromium-niobium alloy powder is sieved through a 180-mesh to 200-mesh sieve to remove agglomerated particles and ultrafine powders, control the particle size distribution range of the copper-chromium-niobium alloy powder, and then dried in a vacuum environment or inert atmosphere at 80°C - 150°C for 2h - 4h to make the gas content of the copper-chromium-niobium alloy powder < 100 ppm.

[0033] The present application controls the gas content < 100 ppm (the gas content of traditional undried powder can reach 300 ppm - 500 ppm), which can significantly reduce the pore defects during printing (reduce the porosity from more than 5% to less than 1%), and combined with heat treatment in an inert atmosphere (such as argon), it can avoid copper oxidation at high temperatures (oxygen content < 500 ppm), thereby ensuring a conductivity ≥ 80% IACS.

[0034] Specifically, the mass percentage of chromium element in the copper-chromium-niobium alloy powder is 3.0 wt% - 4.0 wt%, and the mass percentage of niobium element is 2.0 wt% - 3.0 wt%.

[0035] The particle size of the copper-chromium-niobium alloy powder is 15 μm - 53 μm, and the loose bulk density is 4.0 g / cm 3 - 5.0 g / cm 3 , and the fluidity ≤ 25 s / 50 g. The particle size distribution is concentrated in 15 μm - 53 μm, which can reduce the instability of the molten pool caused by the difference in particle size (such as lack of fusion or spatter), and 4.0 g / cm 3 - 5.0 g / cm 3The loose packing density can be adapted to the SLM powder spreading layer thickness (0.03 mm - 0.08 mm) to ensure powder spreading uniformity (with layer thickness deviation < 5%). The fluidity of the copper-chromium-niobium alloy powder after sieving is ≤ 25 s / 50 g (the fluidity test standard is the time for 50 g of powder to pass through a standard funnel), which can avoid uneven powder accumulation caused by agglomeration during powder spreading.

[0036] S2. Grind and sandblast the substrate to make the surface roughness Ra of the substrate ≤ 3.2 μm; coat the pre-treated copper-chromium-niobium alloy powder on the substrate, and use green laser for selective laser melting printing. Set the printing parameters of at least two layers with different energy densities by means of hierarchical energy gradient control, and perform hierarchical printing to form a pore structure with a continuously gradient distribution of porosity to obtain a pre-processed part; wherein, the wavelength of the green laser is 500 nm - 550 nm, and the spot diameter is 15 μm - 30 μm.

[0037] This application uses a green laser with a wavelength of 500 nm - 550 nm, which has a higher compatibility with copper-based materials. The absorption rate of copper-based materials in the 500 nm - 550 nm band is about 40%, which is significantly higher than the absorption rate of traditional infrared lasers (1064 nm) (about 5%). Moreover, it can also reduce the laser power to 300 W - 400 W (the traditional SLM laser power ≥ 800 W), thereby reducing energy loss and oxidation risk. And the conventional SLM technology is limited by a large spot diameter of 60 μm - 70 μm, and the formed wide molten pool is prone to adhesion of unmelted powder particles, resulting in ineffective control of the surface roughness and porosity of the formed part, and great difficulty in optimizing the surface quality. It is difficult to machine complex micro-channel structures. While the spot diameter of this application is 15 μm - 30 μm, which can support a micron-level molten pool (width 30 μm - 80 μm), thus realizing high-precision printing of thin walls (60 μm - 100 μm) and micro-channels (pore diameter < 200 μm).

[0038] In the specific implementation process, the powder spreading thickness is 0.03 mm - 0.08 mm, and the scanning speed is 600 mm / s - 1200 mm / s. The powder spreading thickness of 0.03 mm - 0.08 mm can ensure uniform powder spreading for each layer, reduce lack of fusion defects (porosity < 3%), and the layer thickness matches the spot diameter (spot diameter ≈ 2 - 3 times the layer thickness), ensuring the molten pool depth and interlayer bonding strength. And a moderate scanning speed (600 mm / s - 1200 mm / s) can balance energy input and molten pool stability, avoiding lack of fusion caused by too fast speed or element volatilization caused by too slow speed.

[0039] The method of controlling by hierarchical energy gradient is specifically as follows:

[0040] Set the printing parameters of three layers with different energy densities respectively, and perform hierarchical printing in sequence according to the dense layer, transition layer and core layer;

[0041] Among them, the printing parameters of the dense layer include: the laser power is 300W - 400W, the scanning speed is 800mm / s - 1200mm / s, and the scanning pitch is 0.04mm - 0.09mm;

[0042] The printing parameters of the transition layer include: the laser power is 200W - 300W, the scanning speed is 500mm / s - 800mm / s, and the scanning pitch is 0.04mm - 0.09mm;

[0043] The printing parameters of the core layer include: the laser power is 100W - 200W, the scanning speed is 200mm / s - 500mm / s, and the scanning pitch is 0.04mm - 0.09mm.

[0044] The dense layer realizes dense melting through fast scanning + high power to form a nearly pore-free surface layer, improving the surface hardness (HB≥110) and wear resistance of the component. Moreover, the short-time action of high power can reduce heat accumulation, making the oxygen content <500ppm (traditional process >1000ppm); the transition layer can alleviate the difference in thermal expansion coefficient between the dense layer and the core layer, reduce the stress concentration at the interlayer interface, and achieve a smooth transition of mechanical properties and heat dissipation performance; the core layer promotes the full melting of the powder through low power + slow scanning, avoiding defects such as unfused pores in the shape of spheres or honeycombs and reducing stress concentration.

[0045] Specifically, the scanning process adopts strip filling or checkerboard filling. Strip filling refers to a unidirectional scanning path, which is suitable for the rapid forming of the dense layer, reducing the turning time of the scanning head and improving the efficiency; checkerboard filling refers to zonal scanning (rotation angle 67°) to disperse heat accumulation, reduce residual stress, and avoid part warping.

[0046] Specifically, the porosity of the formed dense layer is 0.5% - 3.0%, the porosity of the transition layer is 10.0% - 20.0%, and the porosity of the core layer is 20.0% - 30.0%, thus forming a pore structure with a continuous gradient distribution of porosity.

[0047] The lower porosity of the dense layer can form a nearly pore-free surface layer to improve the surface hardness and wear resistance of the high thermal conductivity component. The medium porosity of the transition layer can reduce the stress concentration at the interlayer interface and achieve a smooth transition of porosity between the dense layer and the core layer. The high porosity of the core layer can increase the heat dissipation surface area. By combining the high-strength surface (dense layer) with the efficient heat dissipation core (core layer), the thermal conductivity is increased to 350W / (m·K), achieving a balance between heat dissipation efficiency and structural strength; and the gradient pore structure effectively avoids the problem of stress concentration at the interlayer interface and improves the fatigue life of the high thermal conductivity component.

[0048] S3. Heat-treat the pre-processed workpiece to obtain a high thermal conductivity component.

[0049] In the specific implementation process, vacuum heat-treat the pre-processed workpiece, the heat treatment temperature is 600°C - 900°C, and the holding time is 3h - 7h.

[0050] Since in the selective laser melting process, rapid melting and cooling will cause residual stress to accumulate inside the component, and holding at 600°C - 900°C for 3h - 7h, through atomic diffusion and dislocation recombination, the residual stress can be reduced to <50 MPa, reducing the risk of deformation and cracking of the high thermal conductivity component, and simultaneously improving the thermal conductivity and electrical conductivity, and further reducing the oxygen content.

[0051] The above technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

[0052] Example 1

[0053] A method for preparing a high thermal conductivity component of copper chromium niobium alloy based on green laser SLM includes the following steps;

[0054] Step 1: Material selection and pretreatment

[0055] Select CuCr4Nb2 powder prepared by gas atomization method, the composition includes: Cr 3.8 wt%, Nb 2.5 wt%, the balance is Cu and trace O (<0.05 wt%); the particle size distribution D50 = 32μm, D90 = 55μm; the loose bulk density is 4.5g / cm 3 , and the fluidity is 22s / 50g;

[0056] After sieving the copper chromium niobium alloy powder through a 200-mesh sieve, dry it in an argon atmosphere at 120°C for 3h to reduce the gas content of the copper chromium niobium alloy powder to 80 ppm.

[0057] Step 2: Substrate treatment and equipment configuration

[0058] Substrate: Use a 304 stainless steel substrate, the surface is sandblasted (the sand particle size is 50μm) and the roughness Ra = 1.2μm, preheat to 150°C to reduce thermal stress;

[0059] Equipment: Select an EOS M300-4 green laser SLM equipment, the laser wavelength is 532nm, the spot diameter is 20μm, and the powder layer thickness is 0.05mm.

[0060] Step 3: Layered printing strategy

[0061] Dense layer: The laser power is 380 W, the scanning speed is 1000mm / s, the scanning spacing is 0.06mm, to achieve high energy density printing of the near-surface dense layer, and the porosity is 1.5%;

[0062] Transition layer: Laser power is 250 W, scanning speed is 600 mm / s, scanning spacing is 0.06 mm, to achieve printing of the transition layer of the part with a relatively high energy density, and the porosity is 15%;

[0063] Core layer: Laser power is 150 W, scanning speed is 300 mm / s, scanning spacing is 0.06 mm, to achieve printing of high-porosity microchannels with a relatively high energy density, and the porosity is 25%; The scanning strategy is checkerboard filling.

[0064] After printing is completed, a pore structure with a continuous gradient distribution of porosity in the dense layer - transition layer - core layer is formed, and a pre-processed part is obtained.

[0065] Step 4: Post-processing and performance testing

[0066] Heat treatment: Place the pre-processed part in a vacuum furnace (vacuum degree ≤ 1×10 -3 Pa), heat it to 800 °C at a rate of 8 °C / min, hold for 5 h, and then cool it slowly to room temperature at a rate of 5 °C / min to obtain a high thermal conductivity component.

[0067] Perform performance testing on the high thermal conductivity component prepared in this example, and the test results are as follows:

[0068] Oxygen content: 420 ppm (measured by LECO oxygen and nitrogen analyzer);

[0069] Thermal conductivity: 365 W / (m·K) (measured by laser flash method with reference to ASTM E1461 standard);

[0070] Electrical conductivity: 82% IACS (measured by four-probe method);

[0071] Surface roughness: Ra = 5.8 μm (detected by white light interferometer);

[0072] Microhardness: HB118.

[0073] Example 2

[0074] A method for preparing a high thermal conductivity component of copper-chromium-niobium alloy based on green laser SLM, comprising the following steps;

[0075] Step 1: Material selection and preprocessing

[0076] Select CuCr4Nb2 powder prepared by gas atomization method, the composition includes: Cr 3.0 wt%, Nb 2.0 wt%, the balance is Cu and trace O (<0.05 wt%); The particle size distribution is D50 = 30 μm, D90 = 50 μm; The loose bulk density is 4.5 g / cm 3 , and the fluidity is 22 s / 50 g;

[0077] After passing the copper-chromium-niobium alloy powder through a 180-mesh sieve, it is dried in an argon atmosphere at 100 °C for 4 h to reduce the gas content of the copper-chromium-niobium alloy powder to 85 ppm.

[0078] Step 2: Substrate treatment and equipment configuration

[0079] Substrate: A 304 stainless steel substrate is used. After surface sandblasting (with sand particle size of 50 μm), the surface roughness Ra = 1.2 μm, and it is preheated to 150 °C to reduce thermal stress;

[0080] Equipment: An EOS M300-4 green laser SLM equipment is selected, with a laser wavelength of 532 nm, a spot diameter of 15 μm, and a powder spreading layer thickness of 0.03 mm.

[0081] Step 3: Layered printing strategy

[0082] Dense layer: The laser power is 300 W, the scanning speed is 800 mm / s, and the scanning spacing is 0.04 mm to achieve high-energy-density printing of the near-surface dense layer with a porosity of 0.5%;

[0083] Transition layer: The laser power is 200 W, the scanning speed is 500 mm / s, and the scanning spacing is 0.04 mm to achieve higher-energy-density printing of the part transition layer with a porosity of 10%;

[0084] Core layer: The laser power is 100 W, the scanning speed is 200 mm / s, and the scanning spacing is 0.04 mm to achieve higher-energy-density printing of the high-porosity microchannels with a porosity of 20%; The scanning strategy is checkerboard filling.

[0085] After printing is completed, a pore structure with a continuous gradient distribution of porosity in the dense layer-transition layer-core layer is formed to obtain a prefabricated part.

[0086] Step 4: Post-treatment and performance testing

[0087] Heat treatment: The prefabricated part is placed in a vacuum furnace (vacuum degree ≤ 1×10 -3 Pa), heated to 900 °C at a rate of 8 °C / min, held for 3 h, and then slowly cooled to room temperature at a rate of 5 °C / min to obtain a high thermal conductivity component.

[0088] Performance testing is carried out on the high thermal conductivity component prepared in this example, and the test results are as follows:

[0089] Oxygen content: 424 ppm (measured by a LECO oxygen and nitrogen analyzer);

[0090] Thermal conductivity:  355 W / (m·K) (measured by the laser flash method with reference to ASTM E1461 standard);

[0091] Conductivity: 78% IACS (measured by four-probe method);

[0092] Surface roughness: Ra = 5.9 μm (detected by white light interferometer);

[0093] Microhardness: HB116.

[0094] Comparative experiment

[0095] The control group used a conventional 1064nm infrared laser at 1000W power, without layering, and with all other printing parameters remaining the same. This yielded a highly thermally conductive component. Testing showed that, under the same parameters, the oxygen content reached 1100ppm, while the thermal conductivity was only 280W / (m·K).

[0096] Example 3

[0097] A method for preparing a copper-chromium-niobium alloy electric vehicle motor heat dissipation housing based on green laser SLM, comprising the following steps:

[0098] Step 1: Material selection and pretreatment

[0099] The CuCr4Nb2 powder prepared by gas atomization method includes: Cr 3.5wt%, Nb 2.8wt%, the balance is Cu and trace O (<0.05 wt%); the particle size distribution is D50=28μm, D90=52μm; the apparent density is 4.9g / cm 3 , fluidity is 23s / 50g;

[0100] The copper-chromium-niobium alloy powder was sieved through a 180-mesh sieve and then dried in a vacuum environment at 100° C. for 4 hours to reduce the gas content of the copper-chromium-niobium alloy powder to 90 ppm.

[0101] Step 2: Substrate processing and equipment configuration

[0102] Substrate: 304 stainless steel substrate, the surface is sandblasted (sand particle size 50μm) to a roughness of Ra = 1.0μm, and preheated to 180℃ to reduce thermal stress;

[0103] Equipment: EOS M300-4 green laser SLM equipment is selected, with a laser wavelength of 532nm, a spot diameter of 25μm, and a powder layer thickness of 0.06mm.

[0104] Step 3: Layered Printing Strategy

[0105] Dense layer: laser power 400 W, scanning speed 1200 mm / s, scanning spacing 0.09 mm, achieving high energy density printing of near-surface dense layer with a porosity of 3.0%;

[0106] Transition layer: Laser power is 300 W, scanning speed is 800 mm / s, scanning spacing is 0.09 mm. To print the transition layer of the part with a high energy density, the porosity is 20%.

[0107] Core layer: Laser power is 200 W, scanning speed is 500 mm / s, scanning spacing is 0.09 mm. To print high-porosity microchannels with a high energy density, the porosity is 30%. The scanning strategy is checkerboard filling.

[0108] After printing is completed, a pore structure with a continuous gradient distribution of porosity in the dense layer - transition layer - core layer is formed, and a pre-processed part is obtained.

[0109] Step 4: Post-processing and performance testing

[0110] Heat treatment: Place the pre-processed part in a vacuum furnace (vacuum degree ≤ 1×10 -3 Pa), heat it to 850 °C at a rate of 8 °C / min, hold for 6 h, and then slowly cool it to room temperature at a rate of 5 °C / min to obtain a heat dissipation housing for an electric vehicle motor.

[0111] After testing, the thermal resistance at the integrated flow channel interface of this solution is 0.01 K / W.

[0112] Comparative experiment

[0113] Control group: Use the traditional brazing process to prepare high-thermal-conductivity components for the heat dissipation housing of an electric vehicle motor. After testing, the thermal resistance at its flow channel interface is 0.05 K / W.

[0114] Due to the high heat load generated during the operation of the electric vehicle motor (local temperature > 200 °C), the thermal conductivity of the traditional aluminum heat dissipation housing is insufficient, and its thermal conductivity ≤ 200 W / (m·K), resulting in a 10% - 15% decrease in the motor efficiency. Using a copper-based heat dissipation housing can improve the heat dissipation efficiency, but the traditional casting process cannot achieve the integrated forming of the internal spiral cooling flow channel and requires multi-part brazing assembly, resulting in an increase in thermal resistance. However, the thermal resistance of the integrated flow channel in this embodiment is only 0.01 K / W.

[0115] Example 4

[0116] A method for preparing a copper-chromium-niobium alloy aerospace lightweight support component based on green laser SLM, comprising the following steps;

[0117] Step 1: Material selection and pretreatment

[0118] Select CuCr4Nb2 powder prepared by gas atomization method, the composition includes: Cr 4.0 wt%, Nb 3.0 wt%, the balance is Cu and trace O (< 0.05 wt%); the particle size distribution D50 = 35 μm, D90 = 53 μm; the loose bulk density is 5.0 g / cm 3, the fluidity is 25 s / 50 g;

[0119] After sieving the copper-chromium-niobium alloy powder through a 200-mesh sieve, it is dried in a vacuum environment at 100 °C for 4 h to reduce the gas content of the copper-chromium-niobium alloy powder to 90 ppm.

[0120] Step 2: Substrate treatment and equipment configuration

[0121] Substrate: A 304 stainless steel substrate is used. After surface sandblasting (with sand particle size of 50 μm), the surface roughness Ra = 1.0 μm, and it is preheated to 180 °C to reduce thermal stress;

[0122] Equipment: An EOS M300-4 green laser SLM equipment is selected, with a laser wavelength of 532 nm, a spot diameter of 25 μm, and a powder spreading layer thickness of 0.06 mm.

[0123] Step 3: Layered printing strategy

[0124] Dense layer: The laser power is 400 W, the scanning speed is 1100 mm / s, and the scanning spacing is 0.09 mm to achieve high-energy density printing of the near-surface dense layer with a porosity of 1.0%;

[0125] Transition layer: The laser power is 250 W, the scanning speed is 700 mm / s, and the scanning spacing is 0.09 mm to achieve high-energy density printing of the part transition layer with a porosity of 15%;

[0126] Core layer (porous area): The laser power is 100 W, the scanning speed is 200 mm / s, and the scanning spacing is 0.09 mm to achieve high-energy density printing of high-porosity microchannels with a porosity of 30%;

[0127] During this period, the temperature of the molten pool is continuously feedback by an infrared thermal imager. When the local temperature > 1450 °C is detected, the power is automatically reduced by 10%; and the scanning strategy is dynamically switched according to the geometric characteristics of the part (strip filling for the dense area and honeycomb filling for the porous area);

[0128] After printing, a pore structure with a continuous gradient distribution of porosity in the dense layer - transition layer - core layer is formed to obtain a prefabricated part.

[0129] Step 4: Post-treatment and performance testing

[0130] Heat treatment: The prefabricated part is placed in a vacuum furnace (vacuum degree ≤ 1×10 -3 Pa), heated to 850 °C at a rate of 8 °C / min, held for 6 h, and then slowly cooled to room temperature at a rate of 5 °C / min to obtain an aerospace lightweight support component.

[0131] The performance test results are as follows:

[0132] Density: 5.2 g / cm³ (40% weight reduction compared to solid structures);

[0133] Tensile strength: 420 MPa;

[0134] Thermal conductivity: 320 W / (m·K).

[0135] Since the thermal conductivity of the traditional aluminum honeycomb structure is ≤200 W / (m·K), and the tensile strength is <300 MPa, the lightweight support component prepared in this embodiment can increase the strength by 40%, improve the heat dissipation efficiency by 60%, and avoid the risk of failure at the connection interface of dissimilar materials.

[0136] In summary, this application prepares a copper-chromium-niobium alloy component through the green laser SLM process. By precisely melting the copper alloy powder with a small spot of green laser, it realizes the efficient melting of copper alloy at low power, overcomes the problem of high reflectivity of copper, increases the laser absorption rate of copper-based alloy to about 40%, and avoids the element volatilization caused by traditional infrared laser high-power printing (≥1000W). The thermal conductivity of the prepared copper-chromium-niobium alloy component is ≥350 W / (m·K), which is more than 35% higher than that of the traditional infrared laser process (thermal conductivity ≤280 W / (m·K)); and the electrical conductivity is ≥80% IACS (International Annealed Copper Standard), which is 14% higher than that of the traditional infrared laser process (electrical conductivity <70% IACS), significantly reducing the Joule heat loss during the operation of electronic devices; and based on the characteristics of the green laser low power (100W - 400W) of this application, the oxygen content of the prepared high thermal conductivity component can be controlled below 500 ppm, avoiding the deterioration of conductivity caused by the relatively high oxygen content (oxygen content >1000 ppm) of traditional high-power lasers; and this application adopts a hierarchical energy density gradient control technology to carry out pore connectivity design and heat dissipation structure optimization. By coordinating the laser power and printing speed, it precisely regulates the local pore distribution of the printed part, forms a dense layer near the surface of the radiator to increase the strength, maintains a high porosity in the core to optimize the heat exchange area, and effectively avoids the problem of interlayer interface stress concentration by smoothly regulating the interlayer porosity, realizing a continuous gradient pore structure from the dense layer to the core layer. The microhardness of the high thermal conductivity component after heat treatment is ≥HB110, which is 50% higher than that of traditional cast copper alloys (HB60 - HB80), meeting the wear resistance requirements and heat dissipation requirements of high-load heat dissipation components; and the green laser spot diameter of this application is 15μm - 30μm. Through the small spot laser, the molten pool width can be precisely controlled within 30μm - 80μm, thereby improving the part forming accuracy, supporting the processing of thin-walled structures with a thickness of 60μm - 100μm, breaking through the limit of the traditional SLM process (minimum forming size ≥200μm), and eliminating the need for subsequent finishing treatment, saving processing costs.

[0137] The above are only alternative embodiments of the present application, and do not limit the patent scope of the present application accordingly. Any equivalent structural transformation made by using the content of the specification and drawings of the present application under the inventive concept of the present application, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the present application.

Claims

1. A method for preparing a high thermal conductivity component of copper chromium niobium alloy based on green laser SLM, characterized in that, It includes the following steps: Pre-treat the copper-chromium-niobium alloy powder; Lay the pre-treated copper-chromium-niobium alloy powder on the substrate, and perform selective laser melting printing with green laser. Set the printing parameters of at least two layers with different energy densities by means of layered energy gradient control, and perform layered printing to form a pore structure with a continuously gradient distribution of porosity, so as to obtain a pre-processed part; wherein, the wavelength of the green laser is 500nm - 550nm, and the spot diameter is 15μm - 30μm; Heat-treat the pre-processed part to obtain a high thermal conductivity component; In the step of setting the printing parameters of at least two layers with different energy densities by means of layered energy gradient control and performing layered printing to form a pore structure with a continuously gradient distribution of porosity, it includes: Set the printing parameters of three layers with different energy densities respectively, and perform layered printing in sequence according to the dense layer, the transition layer and the core layer to form a pore structure with a continuously gradient distribution of porosity; Among them, the printing parameters of the dense layer include: laser power is 300W - 400W, scanning speed is 800mm / s - 1200mm / s, and scanning spacing is 0.04mm - 0.09mm; The printing parameters of the transition layer include: laser power is 200W - 300W, scanning speed is 500mm / s - 800mm / s, and scanning spacing is 0.04mm - 0.09mm; The printing parameters of the core layer include: laser power is 100W - 200W, scanning speed is 200mm / s - 500mm / s, and scanning spacing is 0.04mm - 0.09mm; The porosity of the dense layer is 0.5% - 3.0%, the porosity of the transition layer is 10.0% - 20.0%, and the porosity of the core layer is 20.0% - 30.0%.

2. The method for preparing a high thermal conductivity component of copper-chromium-niobium alloy based on green laser SLM according to claim 1, characterized in that The mass percentage of chromium element in the copper-chromium-niobium alloy powder is 3.0wt% - 4.0wt%, and the mass percentage of niobium element is 2.0wt% - 3.0wt%.

3. The method for preparing a high thermal conductivity component of copper-chromium-niobium alloy based on green laser SLM according to claim 1, wherein, The particle size of the copper-chromium-niobium alloy powder is 15μm - 53μm, and the apparent density is 4.0g / cm 3 - 5.0g / cm 3 , and the fluidity ≤ 25s / 50g.

4. The method for preparing a high thermal conductivity component of copper chromium niobium alloy based on green laser SLM according to claim 1, characterized in that, The step of pre-treating the copper-chromium-niobium alloy powder includes: After passing the copper-chromium-niobium alloy powder through a sieve with 180 - 200 meshes, dry it in a vacuum environment or inert atmosphere at 80℃ - 150℃ for 2h - 4h to make the gas content of the copper-chromium-niobium alloy powder < 100ppm.

5. The method for preparing a high thermal conductivity component of a copper-chromium-niobium alloy based on green laser SLM according to claim 1, wherein, In the step of laying the pre-treated copper-chromium-niobium alloy powder on the substrate, the powder laying thickness is 0.03mm - 0.08mm, and the scanning speed is 600mm / s - 1200mm / s.

6. The method for preparing a high thermal conductivity component of copper chromium niobium alloy based on green laser SLM according to claim 1, wherein Before the step of laying the pre-treated copper-chromium-niobium alloy powder on the substrate, it further includes: Grind and sandblast the substrate to make the surface roughness Ra of the substrate ≤ 3.2μm.

7. The method for preparing a high thermal conductivity component of copper chromium niobium alloy based on green laser SLM according to claim 1, characterized in that In the layered energy gradient control method, the scanning process adopts strip filling or checkerboard filling.

8. The method for preparing a high thermal conductivity component of copper chromium niobium alloy based on green laser SLM according to claim 1, characterized in that The step of heat-treating the pre-processed part to obtain a high thermal conductivity component includes: Perform vacuum heat treatment on the pre-processed part, the heat treatment temperature is 600℃ - 900℃, and the holding time is 3h - 7h.

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