A method for improving the comprehensive performance of copper materials based on multi-field composite technology

Abstract

This invention discloses a method for improving the comprehensive performance of copper materials based on multi-field composite irradiation. The method employs a specific continuous / pulsed composite laser to irradiate the surface of the copper material. First, a high-energy continuous laser melts the copper material, which more readily absorbs laser energy. Then, a high-repetition-rate laser acts on the molten pool, inducing cavitation and stirring the molten pool. This process generates high temperature and pressure within the molten pool, achieving grain refinement. The resulting microstructure exhibits a grain size gradient structure with a diameter of 1–50 μm and a certain thickness, leading to a surface strength increase of over 50% and a significant improvement in the overall performance of the copper material. Furthermore, this method directly strengthens the original substrate, making it green, safe, and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of laser modification processing technology, specifically to a method for improving the comprehensive performance of copper materials based on multi-field composite processing. Background Technology

[0002] Copper and copper alloys have excellent mechanical, electrical, and thermal conductivity properties, and are widely used in aerospace, rail transportation, energy and power, microelectronics, and even defense industries.

[0003] However, with the rapid advancement of industrial technology, copper and its alloys face increasingly stringent environmental requirements. Particularly in the field of shipbuilding and marine engineering, as a core component, copper materials must withstand the increasingly severe erosion and corrosion challenges brought about by the ever-increasing load capacity and speed of ships. Furthermore, in high-speed rail systems, electrical energy is converted into driving power via pantographs located on the roof of the carriages. With the continuous breakthroughs in high-speed rail operating speeds, higher requirements are placed on the conductor materials used for power transmission, demanding superior conductivity, excellent flexibility, and outstanding strength. Based on these application needs, a large number of exploratory studies have emerged focusing on the modification of high-performance copper and its alloys.

[0004] Surface treatment technology, as an advanced process, commonly includes electroplating, vapor deposition, and laser cladding. This technology optimizes performance while maintaining the inherent properties of the substrate material, thereby improving overall material performance, effectively extending its service life, or expanding its application areas. However, electroplated coatings often have poor adhesion to the substrate, leading to peeling under specific service conditions. Vapor deposition also faces challenges such as low adhesion strength and limited deposition thickness. Laser cladding, when used with copper-based materials, often suffers from limited material selection due to the material's poor wettability, and copper's low laser absorption rate makes remelting difficult. Summary of the Invention

[0005] To address the problems existing in the background technology, the present invention provides a method for improving the comprehensive performance of copper materials based on multi-field composite technology. This method uses multi-field laser strengthening technology to directly strengthen the original substrate, which can significantly improve the comprehensive performance of copper materials, such as hardness and tensile properties. It does not require the addition of cladding materials to the original substrate, nor does it require consideration of the bonding strength between the electroplated coating or deposition layer and the substrate.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for improving the overall performance of copper materials based on multi-field composite, comprising the following steps:

[0008] A laser irradiation surface treatment is performed on copper materials, wherein the laser used for the laser irradiation surface treatment is a composite laser of continuous laser and pulsed laser;

[0009] The copper material is metallic copper or a copper alloy;

[0010] The power of the continuous laser in the composite laser is 1500W to 3000W, and the power of the pulsed laser is 250W to 500W.

[0011] The depth of the surface strengthening layer of copper material ranges from 0.01 to 4 mm, and the grain size of the surface strengthening layer shows a gradient decreasing structure from the surface to the interior, with the grain size ranging from 1 to 50 μm.

[0012] Specifically, in the composite laser, the wavelength of the continuous laser is 1080nm and the wavelength of the pulsed laser is 1064nm. During laser processing, the focal points of the continuous laser and the pulsed laser remain concentric.

[0013] Furthermore, for copper materials with a thickness ranging from 1 to 10 mm, the power of the continuous laser in the composite laser is 1500W to 2000W, the power of the pulsed laser is 250W to 350W, and the depth of the surface strengthening layer is 0.01 to 0.5 mm. Within the above laser range, thermal warping deformation of the thin material can be avoided. Specifically, the continuous laser acts as a pre-energy source, using its high power (upper limit of 2000W to prevent overheating) to irradiate the copper surface. Based on the heat conduction principle of laser-material interaction, the high reflectivity of copper can be overcome, promoting rapid melting of the surface to form a shallow molten pool. After melting, the absorptivity of copper increases, allowing for efficient energy injection. However, excessively high power (>2000W) will increase the total heat input at this thickness, leading to residual stress accumulation and thin plate warping. Subsequently, the pulsed laser (power 250W to 350W) intervenes in the molten pool, inducing cavitation and stirring effects, which amplifies the temperature gradient and high-pressure field within the molten pool, thereby ensuring that the depth of the surface strengthening layer is within a suitable range.

[0014] For copper materials with a thickness ranging from 11 to 20 mm, the power of the continuous laser in the composite laser system is 1800 W to 2500 W, and the power of the pulsed laser is 300 W to 400 W, with a surface strengthening layer depth of 0.04 to 2 mm. The initial continuous laser power of 1800 W provides higher energy flux and extends the depth of the heat-affected zone. Based on an energy balance model, this laser power can overcome the high reflectivity and thermal diffusion of copper, forming a medium-depth molten pool; the upper limit of 2500 W prevents overheating leading to evaporation or plasma shielding. The medium thickness can withstand higher heat input without easily warping because the increased volume disperses residual stress. The pulsed laser power is correspondingly increased to 300 W to 400 W, enhancing cavitation impact intensity and stirring force, promoting a more uniform high-temperature and high-pressure distribution within the molten pool, further accelerating the cooling rate, and increasing undercooling, leading to a decrease in nucleation work and an increase in nucleation rate, achieving gradient grain refinement from the surface inwards.

[0015] For copper materials with a thickness ranging from 21 to 30 mm, the power of the continuous laser in the composite laser system is 2500 W to 3000 W, and the power of the pulsed laser is 400 W to 500 W, with a surface strengthening layer depth of 1.5 to 4 mm. As the thickness increases, the heat diffusion path lengthens, and low power (<2500 W) is insufficient to accumulate enough energy to form a deep molten pool, resulting in a shallow surface refinement. Therefore, the continuous laser power is initially increased to 2500 W to generate a strong thermal effect and increase the molten pool volume. An upper limit of 3000 W is used to avoid overheating that could cause material evaporation or microscopic defects. The pulsed laser power is increased to 400 W to 500 W to further enhance cavitation impact and stirring effects, generating a stronger high-temperature and high-pressure field. This promotes a uniform distribution of the deep temperature gradient, accelerates the cooling rate, and dramatically increases the nucleation rate. Furthermore, high-frequency vibration breaks up the grains, achieving grain refinement.

[0016] Furthermore, the copper material has a multilayer structure, comprising a surface strengthening layer, a transition layer, and a substrate layer from top to bottom; the thickness of the transition layer is 1–100 μm, and its grain size ranges from 50–150 μm; the grain size of the substrate layer ranges from 150–500 μm.

[0017] The gradient multilayer structure formed after multi-field composite laser treatment of copper materials, through a design that gradually increases grain size from the surface to the interior, significantly improves its overall performance. The surface strengthening layer utilizes fine grains to increase grain boundary density, improving strength, hardness, and wear resistance; the transition layer acts as a buffer, alleviating the microscopic mismatch between the high surface strength and the high toughness of the matrix, reducing stress concentration and inhibiting crack propagation; the matrix layer retains a coarse-grained structure, ensuring the material's ductility and intrinsic toughness. This gradient structure optimizes stress distribution and energy dissipation, achieving a balance between strength and toughness, resulting in a significant improvement in surface strength, hardness, and tensile properties.

[0018] Preferably, before laser irradiation surface treatment, the copper material is subjected to surface cleaning treatment. The surface cleaning treatment method includes: polishing the surface of the copper material with sandpaper, then cleaning it with water and ethanol in sequence, and then drying it.

[0019] Furthermore, the pulsed laser repetition frequency is 20–40 kHz.

[0020] Furthermore, the laser head of the laser device used in the laser irradiation surface treatment is 15-20 mm away from the surface of the copper material, and the deflection angle relative to the surface of the copper material is 1-10°.

[0021] Furthermore, the linear scanning speed of the composite laser along the X-axis is 5000–10000 mm / s, and the movement speed along the Y-axis is 0.001–0.02 m / s.

[0022] Furthermore, the laser irradiation surface treatment is performed under an argon protective atmosphere.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Since copper has low absorption rates for all wavelengths of laser light, this invention uses a specific continuous / pulsed composite laser to irradiate the surface of the copper material. First, a high-energy continuous laser is used to melt the copper material. The molten copper material absorbs laser energy more easily. Then, a high-repetition-rate laser acts on the molten pool, causing cavitation and stirring the molten pool. In the above phenomenon, high temperature and high pressure are generated in the molten pool, thereby achieving grain refinement. This refines the grains on the surface of the copper material, forming a microstructure with a grain size gradient structure of 1-50 μm and a certain thickness. This results in an increase of more than 50% in the surface strength of the copper material and a significant improvement in its overall performance. Furthermore, this method directly strengthens the original substrate, making it green, safe, and environmentally friendly. Compared with existing electroplating, vapor deposition, and laser cladding surface treatment technologies, it does not require the addition of cladding materials or consideration of the bonding strength between the electroplated coating or deposited layer and the substrate.

[0025] (2) The method for improving the comprehensive performance of copper materials based on multi-field composite provided by the present invention adopts multi-field laser strengthening technology, which is easy to operate, not limited by the size of the parts, and has obvious grain refinement and performance improvement, and has a wide range of applications. Attached Figure Description

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0027] Figure 1 This is a schematic diagram of the structure of the laser device provided by the present invention;

[0028] Figure 2 Simulation images of copper materials under laser irradiation in Experimental Examples 1-3 and Comparative Example 1 provided for this invention;

[0029] Figure 3 Metallographic image of metallic copper enhanced by multi-field laser according to Embodiment 1 of the present invention;

[0030] Figure 4 Metallographic image of metallic copper enhanced by multi-field laser in Embodiment 2 of the present invention;

[0031] Figure 5 Metallographic image of metallic copper enhanced by multi-field laser in Example 3 of this invention;

[0032] Figure 6 Electron scanning microscope image of metallic copper enhanced by multi-field laser in Example 3 of this invention;

[0033] Figure 7 The statistical results of grain size of metallic copper after multi-field laser strengthening in Example 1 of this invention;

[0034] Figure 8 Statistical results of grain size of metallic copper as a comparative example provided by the present invention;

[0035] Figure 9 This is a schematic diagram of the equipment used for laser irradiation surface treatment provided by the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] This invention provides a method for improving the comprehensive performance of copper materials based on multi-field composite irradiation, or a method for improving the comprehensive strength and toughness of copper materials by using multi-field composite irradiation, comprising the following steps: performing laser irradiation surface treatment on the copper material, wherein the laser used for the laser irradiation surface treatment is a continuous / pulsed composite laser, so as to achieve surface strengthening and improvement of the comprehensive performance of the copper material.

[0038] That is, the surface of copper material is irradiated with a continuous / pulsed composite laser to refine the grains on the surface of copper material, forming a micro-morphology with a grain size gradient structure, thereby achieving surface strengthening and improvement of the overall performance of copper material.

[0039] The copper material includes at least one of metallic copper and copper alloys.

[0040] The method for improving the comprehensive properties of copper materials based on multi-field composite technology provided by this invention can significantly improve the comprehensive properties of copper materials, such as hardness and tensile properties.

[0041] This method directly strengthens the original substrate. Compared with traditional vapor deposition technology, electroplating coating and laser cladding, it does not require the addition of cladding materials, nor does it require consideration of the bonding strength between the electroplated coating or deposited layer and the substrate. It is also green, safe and environmentally friendly.

[0042] This invention provides a method for improving the comprehensive performance of copper materials based on multi-field composite laser technology. This method employs multi-field laser strengthening technology, specifically a continuous / pulsed composite laser, which can refine grain size. Specifically, since copper has low absorption rates for all wavelengths of laser light, the multi-field modification technology developed in this invention first uses a high-energy continuous laser to melt the copper material. The molten copper more readily absorbs laser energy. Then, a high-repetition-rate laser acts on the molten pool, inducing cavitation and stirring the molten pool. This process generates high temperature and high pressure within the molten pool, thereby achieving grain refinement.

[0043] Furthermore, this invention employs multi-field laser strengthening technology, which is easy to operate, not limited by part size, significantly refines grains and improves performance, and has a wide range of applications.

[0044] In order to refine the grain size of copper materials and thus further improve their hardness and tensile properties, the present invention optimizes the parameters of the laser irradiation surface treatment as follows.

[0045] Copper's high reflectivity causes most of the laser energy to be reflected and unable to act on the copper surface, thus reducing the effectiveness of laser remelting in refining grains. However, when in a liquid state, copper's light absorption capacity improves significantly. Therefore, this invention utilizes dual-field composite technology, employing a larger pre-amplifier power to melt the copper surface and form a molten pool, thereby increasing laser absorption. Pulsed laser stirring is then applied to achieve grain refinement.

[0046] In some specific implementations, in order to ensure that the surface of the copper material melts and forms a micro-molten pool during laser irradiation, the pulsed laser is used to stir the molten pool, and the power of the continuous laser in the continuous / pulsed composite laser is 1500W to 3000W.

[0047] In some specific embodiments, the wavelength of the pulsed laser in the continuous / pulsed composite laser is 1064 nm.

[0048] In some specific implementations, in order to ensure grain refinement on the surface of the copper material, thereby improving its surface hardness and overall performance, the power of the pulsed laser in the continuous / pulsed composite laser is 250W to 500W.

[0049] The depth of the surface strengthening layer of the copper material ranges from 0.01 to 4 mm, and the grain size of the surface strengthening layer exhibits a gradient decreasing structure from the surface to the interior, with a grain size range of 1 to 50 μm. The copper material has a multilayer structure, comprising, from top to bottom, a surface strengthening layer, a transition layer, and a substrate layer; the thickness of the transition layer is 1 to 100 μm, and its grain size ranges from 50 to 150 μm; the grain size of the substrate layer ranges from 150 to 500 μm.

[0050] In some specific implementations, to ensure that continuous laser and pulsed laser act simultaneously on the surface of the copper material, the focal points of the continuous laser and the pulsed laser in the continuous / pulsed composite laser are kept concentric.

[0051] Specifically, for copper materials with a thickness range of 1 to 10 mm, the power combination of the composite laser should not be too high, because excessive heat input will cause thermal warping deformation of the copper material. The power of the continuous laser in the composite laser is 1500W to 2000W, the power of the pulsed laser is 250W to 350W, and the depth of the surface strengthening layer is 0.01 to 0.5 mm.

[0052] For copper materials with a thickness range of 11–20 mm, the power of the continuous laser in the composite laser is 1800 W–2500 W, the power of the pulsed laser is 300 W–400 W, and the depth of the surface strengthening layer is 0.04–2 mm.

[0053] For copper materials with a thickness range of 21–30 mm, the power of the continuous laser in the composite laser is 2500 W–3000 W, the power of the pulsed laser is 400 W–500 W, and the depth of the surface strengthening layer is 1.5–4 mm.

[0054] In some specific implementations, to ensure grain refinement on the surface of the copper material, thereby improving its surface hardness and overall performance, the pulse repetition frequency of the continuous / pulsed composite laser is 20–50 kHz. Here, the pulse repetition frequency refers to the number of pulses output by the laser per unit time.

[0055] In some specific implementations, to ensure grain refinement on the copper surface, thereby improving its surface hardness and overall performance, the distance between the laser head of the laser device used in the laser irradiation surface treatment and the copper surface is 15–20 mm; the deflection angle relative to the copper surface is 1°–10°. Here, the deflection angle relative to the copper surface refers to the angle between the laser beam and the copper surface. Copper is a highly reflective material, therefore it needs to be deflected at a certain angle relative to the laser beam to ensure that the laser does not reflect back into the laser head.

[0056] In some specific embodiments, to ensure that the copper material melts on its surface and forms a micro-molten pool during laser irradiation, and to allow the pulsed laser to stir the molten pool, the linear scanning speed of the continuous / pulsed composite laser along the X-axis is 5000–10000 mm / s; the speed of the continuous / pulsed composite laser along the Y-axis is 0.001–0.02 m / s. See also Figure 8 As shown, the equipment consists of a robot, a laser processing head, and a worktable. The laser processing head can output a line laser by moving the galvanometer inside the laser processing head. The laser laser is then mounted on the robot to achieve more complex and specific movements. The X-axis is the scanning direction of the galvanometer of the laser processing head, and the Y-axis is the movement direction of the robot.

[0057] In some specific embodiments, in order to ensure that the copper material is not oxidized during the laser surface treatment process, the laser irradiation surface treatment is carried out under an argon protective atmosphere.

[0058] In some specific embodiments, the argon gas flow rate is 10-20 L / min.

[0059] In some specific embodiments, the copper material undergoes a surface cleaning treatment before the laser irradiation surface treatment. The surface cleaning method includes: polishing the surface of the copper material with sandpaper to remove oxide film and oil stains; then performing a first rinse with deionized water to remove abrasive particles left by the sandpaper; followed by a second rinse with anhydrous ethanol to facilitate subsequent drying and prevent oxidation; and finally drying to remove the ethanol from the copper material surface.

[0060] In some specific embodiments, the drying temperature can be 60-80°C and the drying time can be 30-60 minutes, but it is not limited to these.

[0061] In some specific embodiments, the sandpaper includes 320-grit sandpaper, 600-grit sandpaper, and 1200-grit sandpaper, that is, the surface of the copper material is polished by sequentially using 320-grit sandpaper, 600-grit sandpaper, and 1200-grit sandpaper.

[0062] Multi-field laser surface strengthening of copper materials generally needs to be carried out under the above parameters. If the focal points of the continuous laser and the pulsed laser are not concentric, the pulsed laser will not be able to act on the molten pool, thus failing to refine the grains on the surface of the copper material. If the continuous laser power is too low or the scanning speed is too fast, the continuous laser energy will be insufficient, failing to form a micro-molten pool on the surface of copper and copper alloys, thus affecting the grain refinement effect of the pulsed laser on the surface of copper and copper alloys. If the pulsed laser energy is too low or the frequency is too low, the grain refinement effect on the surface of copper and copper alloys will be insignificant or non-existent, thus failing to improve the surface hardness and overall performance of copper and copper alloys. Therefore, selecting the above-mentioned continuous / pulsed composite laser experimental parameters for surface irradiation treatment of copper materials is beneficial to achieving surface grain refinement, realizing a microstructure with grain size gradient characteristics, and thus further improving the surface hardness, tensile strength, and other comprehensive properties of copper materials.

[0063] The laser device used in the laser irradiation surface treatment of this invention can be an existing device, such as... Figure 1 The diagram shows the results of the laser device. Continuous and pulsed laser beams, after passing through their respective beam expanders, are reflected by mirrors and then converge inside the laser head. The motion is then output through a galvanometer inside the laser head. A vision camera and an air blowing system are mounted on the off-axis of the laser head, used for real-time monitoring of the workpiece's movement and for removing impurities, respectively.

[0064] Secondly, this invention provides the application of the method for improving the comprehensive performance of copper materials based on multi-field composite in the preparation of copper products.

[0065] The method for improving the comprehensive properties of copper materials based on multi-field composite technology provided by this invention can significantly improve the surface hardness, tensile strength, and other comprehensive properties of copper materials. This is beneficial to the promotion and use of copper and its alloys, and the method for improving the comprehensive properties of copper materials based on multi-field composite technology has broad application prospects.

[0066] Copper products include, but are not limited to, materials, components, parts, devices, apparatuses, or equipment containing copper and its alloys.

[0067] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0068] Example 1

[0069] The method for improving the overall performance of copper materials based on multi-field composite technology provided in this embodiment includes the following steps:

[0070] (1) Surface cleaning treatment of metallic copper (T2 pure copper, thickness of 16mm): First, use 320 grit, 600 grit and 1200 grit sandpaper to polish the surface of metallic copper in turn. After polishing, use deionized water for the first cleaning, then use anhydrous ethanol for the second cleaning. Then put the metallic copper into a vacuum oven and dry it at 70℃ for 50min.

[0071] (2) Place the cleaned copper metal on the processing table for laser irradiation surface treatment. The equipment used for laser irradiation surface treatment is as follows: Figure 9 As shown. Before laser irradiation, the distance between the laser head of the laser device and the copper and metallic copper is adjusted to 18mm, and the deflection angle relative to the surface of the metallic copper is 5°; and the argon protective gas is turned on, with an argon flow rate of 10L / min.

[0072] The cleaned copper surface was subjected to continuous / pulsed composite laser irradiation to refine the surface grains, resulting in a microstructure with a grain size gradient. Specifically, the continuous and pulsed lasers in the continuous / pulsed composite laser were concentrically focused; the continuous laser power was 2500W; the pulsed laser power was 350W; the continuous laser wavelength was 1080nm; the pulsed laser wavelength was 1064nm; the pulsed laser repetition rate was 40kHz; the linear scanning speed along the X-axis was 8000mm / s; and the laser head movement speed along the Y-axis was 0.02m / s.

[0073] Example 2

[0074] The method for improving the comprehensive performance of copper materials based on multi-field composite laser provided in this embodiment is basically the same as that in Embodiment 1, except that the pulse laser power in the continuous / pulsed composite laser is replaced with 450W.

[0075] Example 3

[0076] The method for improving the comprehensive performance of copper materials based on multi-field composite laser provided in this embodiment is basically the same as that in Embodiment 1, except that the pulse laser power in the continuous / pulsed composite laser is replaced with 250W.

[0077] Example 4

[0078] The method for improving the overall performance of copper materials based on multi-field composite technology provided in this embodiment includes the following steps:

[0079] (1) Surface cleaning treatment of metallic copper (T2 pure copper, thickness of 16mm): First, use 320 grit, 600 grit and 1200 grit sandpaper to polish the surface of metallic copper in turn. After polishing, use deionized water for the first cleaning, then use anhydrous ethanol for the second cleaning. Then put the metallic copper into a vacuum oven and dry it at 70℃ for 50min.

[0080] (2) Place the cleaned copper metal on the processing table for laser irradiation surface treatment. Before laser irradiation, adjust the distance between the laser head of the laser device and the copper and the copper metal to 18 mm, and the relative deflection angle of the copper metal surface to 5°; and turn on the argon protective gas with an argon gas flow rate of 10 L / min.

[0081] The cleaned copper surface was subjected to continuous / pulsed composite laser irradiation to refine the surface grains, resulting in a microstructure with a grain size gradient. Specifically, the continuous and pulsed lasers in the continuous / pulsed composite laser were concentrically focused; the continuous laser power was 1800W; the pulsed laser power was 300W; the continuous laser wavelength was 1080nm; the pulsed laser wavelength was 1064nm; the pulsed laser repetition rate was 40kHz; the linear scanning speed along the X-axis was 8000mm / s; and the laser head movement speed along the Y-axis was 0.02m / s.

[0082] Example 5

[0083] The method for improving the overall performance of copper materials based on multi-field composite technology provided in this embodiment includes the following steps:

[0084] (1) Surface cleaning treatment of metallic copper (T2 pure copper, thickness of 16mm): First, use 320 grit, 600 grit and 1200 grit sandpaper to polish the surface of metallic copper in turn. After polishing, use deionized water for the first cleaning, then use anhydrous ethanol for the second cleaning. Then put the metallic copper into a vacuum oven and dry it at 70℃ for 50min.

[0085] (2) Place the cleaned copper metal on the processing table for laser irradiation surface treatment. Before laser irradiation, adjust the distance between the laser head of the laser device and the copper and the copper metal to 18 mm, and the relative deflection angle of the copper metal surface to 5°; and turn on the argon protective gas with an argon gas flow rate of 10 L / min.

[0086] The cleaned copper surface was subjected to continuous / pulsed composite laser irradiation to refine the surface grains, resulting in a microstructure with a grain size gradient. Specifically, the continuous and pulsed lasers in the continuous / pulsed composite laser were concentrically focused; the continuous laser power was 2000W; the pulsed laser power was 400W; the continuous laser wavelength was 1080nm; the pulsed laser wavelength was 1064nm; the pulsed laser repetition frequency was 40kHz; the linear scanning speed along the X-axis was 8000mm / s; and the laser head movement speed along the Y-axis was 0.02m / s.

[0087] Example 6

[0088] The method for improving the overall performance of copper materials based on multi-field composite technology provided in this embodiment includes the following steps:

[0089] (1) Surface cleaning treatment of metallic copper (T2 pure copper, thickness of 28mm): First, use 320 grit, 600 grit and 1200 grit sandpaper to polish the surface of metallic copper in turn. After polishing, use deionized water for the first cleaning, then use anhydrous ethanol for the second cleaning, and then put the metallic copper into a vacuum oven to dry at 70℃ for 50min.

[0090] (2) Place the cleaned copper metal on the processing table for laser irradiation surface treatment. Before laser irradiation, adjust the distance between the laser head of the laser device and the copper and the copper metal to 18 mm, and the relative deflection angle of the copper metal surface to 5°; and turn on the argon protective gas with an argon gas flow rate of 10 L / min.

[0091] The cleaned copper surface was subjected to continuous / pulsed composite laser irradiation to refine the surface grains, resulting in a microstructure with a grain size gradient. Specifically, the continuous and pulsed lasers in the continuous / pulsed composite laser were concentrically focused; the continuous laser power was 3000W; the pulsed laser power was 500W; the continuous laser wavelength was 1080nm; the pulsed laser wavelength was 1064nm; the pulsed laser repetition frequency was 40kHz; the linear scanning speed along the X-axis was 8000mm / s; and the laser head movement speed along the Y-axis was 0.02m / s.

[0092] Example 7

[0093] The method for improving the overall performance of copper materials based on multi-field composite technology provided in this embodiment includes the following steps:

[0094] (1) Surface cleaning treatment of metallic copper (T2 pure copper, thickness of 28mm): First, use 320 grit, 600 grit and 1200 grit sandpaper to polish the surface of metallic copper in turn. After polishing, use deionized water for the first cleaning, then use anhydrous ethanol for the second cleaning, and then put the metallic copper into a vacuum oven to dry at 70℃ for 50min.

[0095] (2) Place the cleaned copper metal on the processing table for laser irradiation surface treatment. Before laser irradiation, adjust the distance between the laser head of the laser device and the copper and the copper metal to 18 mm, and the relative deflection angle of the copper metal surface to 5°; and turn on the argon protective gas with an argon gas flow rate of 10 L / min.

[0096] The cleaned copper surface was subjected to continuous / pulsed composite laser irradiation to refine the surface grains, resulting in a microstructure with a grain size gradient. Specifically, the continuous and pulsed lasers in the continuous / pulsed composite laser were concentrically focused; the continuous laser power was 2500W; the pulsed laser power was 400W; the continuous laser wavelength was 1080nm; the pulsed laser wavelength was 1064nm; the pulsed laser repetition frequency was 40kHz; the linear scanning speed along the X-axis was 8000mm / s; and the laser head movement speed along the Y-axis was 0.02m / s.

[0097] Example 8

[0098] The method for improving the overall performance of copper materials based on multi-field composite technology provided in this embodiment includes the following steps:

[0099] (1) Surface cleaning treatment of metallic copper (T2 pure copper, thickness of 28mm): First, use 320 grit, 600 grit and 1200 grit sandpaper to polish the surface of metallic copper in turn. After polishing, use deionized water for the first cleaning, then use anhydrous ethanol for the second cleaning, and then put the metallic copper into a vacuum oven to dry at 70℃ for 50min.

[0100] (2) Place the cleaned copper metal on the processing table for laser irradiation surface treatment. Before laser irradiation, adjust the distance between the laser head of the laser device and the copper and the copper metal to 18 mm, and the relative deflection angle of the copper metal surface to 5°; and turn on the argon protective gas with an argon gas flow rate of 10 L / min.

[0101] The cleaned copper surface was subjected to continuous / pulsed composite laser irradiation to refine the surface grains, resulting in a microstructure with a grain size gradient. Specifically, the continuous and pulsed lasers in the continuous / pulsed composite laser were concentrically focused; the continuous laser power was 2800W; the pulsed laser power was 450W; the continuous laser wavelength was 1080nm; the pulsed laser wavelength was 1064nm; the pulsed laser repetition rate was 40kHz; the linear scanning speed along the X-axis was 8000mm / s; and the laser head movement speed along the Y-axis was 0.02m / s.

[0102] Example 9

[0103] The method for improving the overall performance of copper materials based on multi-field composite technology provided in this embodiment includes the following steps:

[0104] (1) Surface cleaning treatment of metallic copper (T2 pure copper, thickness of 7mm): First, use 320 grit, 600 grit and 1200 grit sandpaper to polish the surface of metallic copper in turn. After polishing, use deionized water for the first cleaning, then use anhydrous ethanol for the second cleaning, and then put the metallic copper into a vacuum oven to dry at 70℃ for 50min.

[0105] (2) Place the cleaned copper metal on the processing table for laser irradiation surface treatment. Before laser irradiation, adjust the distance between the laser head of the laser device and the copper and the copper metal to 18 mm, and the relative deflection angle of the copper metal surface to 5°; and turn on the argon protective gas with an argon gas flow rate of 10 L / min.

[0106] The cleaned copper surface was subjected to continuous / pulsed composite laser irradiation to refine the surface grains, resulting in a microstructure with a grain size gradient. Specifically, the continuous and pulsed lasers in the continuous / pulsed composite laser were concentrically focused; the continuous laser power was 1800W; the pulsed laser power was 300W; the continuous laser wavelength was 1080nm; the pulsed laser wavelength was 1064nm; the pulsed laser repetition rate was 40kHz; the linear scanning speed along the X-axis was 8000mm / s; and the laser head movement speed along the Y-axis was 0.02m / s.

[0107] Example 10

[0108] The method for improving the overall performance of copper materials based on multi-field composite technology provided in this embodiment includes the following steps:

[0109] (1) Surface cleaning treatment of metallic copper (T2 pure copper, thickness of 7mm): First, use 320 grit, 600 grit and 1200 grit sandpaper to polish the surface of metallic copper in turn. After polishing, use deionized water for the first cleaning, then use anhydrous ethanol for the second cleaning, and then put the metallic copper into a vacuum oven to dry at 70℃ for 50min.

[0110] (2) Place the cleaned copper metal on the processing table for laser irradiation surface treatment. Before laser irradiation, adjust the distance between the laser head of the laser device and the copper and the copper metal to 18 mm, and the relative deflection angle of the copper metal surface to 5°; and turn on the argon protective gas with an argon gas flow rate of 10 L / min.

[0111] The cleaned copper surface was subjected to continuous / pulsed composite laser irradiation to refine the surface grains, resulting in a microstructure with a grain size gradient. Specifically, the continuous and pulsed lasers in the continuous / pulsed composite laser were concentrically focused; the continuous laser power was 1500W; the pulsed laser power was 250W; the continuous laser wavelength was 1080nm; the pulsed laser wavelength was 1064nm; the pulsed laser repetition rate was 40kHz; the linear scanning speed along the X-axis was 8000mm / s; and the laser head movement speed along the Y-axis was 0.02m / s.

[0112] Example 11

[0113] The method for improving the overall performance of copper materials based on multi-field composite technology provided in this embodiment includes the following steps:

[0114] (1) Surface cleaning treatment of metallic copper (T2 pure copper, thickness of 7mm): First, use 320 grit, 600 grit and 1200 grit sandpaper to polish the surface of metallic copper in turn. After polishing, use deionized water for the first cleaning, then use anhydrous ethanol for the second cleaning, and then put the metallic copper into a vacuum oven to dry at 70℃ for 50min.

[0115] (2) Place the cleaned copper metal on the processing table for laser irradiation surface treatment. Before laser irradiation, adjust the distance between the laser head of the laser device and the copper and the copper metal to 18 mm, and the relative deflection angle of the copper metal surface to 5°; and turn on the argon protective gas with an argon gas flow rate of 10 L / min.

[0116] The cleaned copper surface was subjected to continuous / pulsed composite laser irradiation to refine the surface grains, resulting in a microstructure with a grain size gradient. Specifically, the continuous and pulsed lasers in the continuous / pulsed composite laser were concentrically focused; the continuous laser power was 2000W; the pulsed laser power was 350W; the continuous laser wavelength was 1080nm; the pulsed laser wavelength was 1064nm; the pulsed laser repetition rate was 40kHz; the linear scanning speed along the X-axis was 8000mm / s; and the laser head movement speed along the Y-axis was 0.02m / s.

[0117] Example 12

[0118] The method for improving the comprehensive performance of copper materials based on multi-field composite provided in this embodiment is basically the same as that in Embodiment 1, except that the repetition frequency of the pulse laser of the continuous / pulsed composite laser is 20kHz.

[0119] Example 13

[0120] The method for improving the comprehensive performance of copper materials based on multi-field composite provided in this embodiment is basically the same as that in embodiment 1. The difference is that the distance between the laser head of the laser device and the copper and the metallic copper is adjusted to 15mm, and the relative deflection angle to the surface of the metallic copper is 10°.

[0121] Example 14

[0122] The method for improving the comprehensive performance of copper materials based on multi-field composite provided in this embodiment is basically the same as that in embodiment 1. The difference is that the linear scanning speed of the continuous / pulsed composite laser along the X-axis is replaced with 5000 mm / s, and the laser head moves at a speed of 0.001 m / s along the Y-axis.

[0123] Example 15

[0124] The method for improving the comprehensive performance of copper materials based on multi-field composite provided in this embodiment is basically the same as that in Embodiment 1, except that metallic copper is replaced with Cu-Ni-Zn copper alloy.

[0125] Example 16

[0126] The method for improving the comprehensive performance of copper materials based on multi-field composite provided in this embodiment is basically the same as that in Embodiment 1, except that metallic copper is replaced with H68 copper alloy.

[0127] Comparative Example 1

[0128] The method for improving the overall performance of copper materials provided in this comparative example is basically the same as that in Example 1. The difference is that the laser device does not turn on the pulsed laser, but only uses continuous laser to perform laser irradiation surface treatment on the surface of the metallic copper.

[0129] Comparative Example 2

[0130] The method for improving the overall performance of copper materials provided in this comparative example is basically the same as that in Example 1. The difference is that the laser device does not turn on the continuous laser, but only uses pulsed laser to perform laser irradiation surface treatment on the surface of metallic copper.

[0131] Comparative Example 3

[0132] The method for improving the comprehensive performance of copper materials based on multi-field composite provided in this comparative example is basically the same as that in Example 1, except that the continuous laser power in the continuous / pulsed composite laser is 1000W and the pulsed laser power in the continuous / pulsed composite laser is 200W.

[0133] Comparative Example 4

[0134] The method for improving the comprehensive performance of copper materials based on multi-field composite laser provided in this comparative example is basically the same as that in Example 1, except that the continuous laser power in the continuous / pulsed composite laser is 3500W and the pulsed laser power in the continuous / pulsed composite laser is 550W.

[0135] Comparative Example 5

[0136] The method for improving the comprehensive performance of copper materials based on multi-field composite provided in this comparative example is basically the same as that in Example 1, except that: the pulse laser repetition frequency of the continuous / pulsed composite laser is 70kHz, the linear scanning speed of the continuous / pulsed composite laser along the X-axis is 3000mm / s, and the laser head moves at a speed of 0.05m / s along the Y-axis.

[0137] Experimental Example

[0138] Hardness and tensile tests were performed on the copper materials after laser irradiation surface treatment in each embodiment and each comparative example, and the results are shown in Table 1. Among them, the control example is metallic copper (T2 pure copper, thickness of 16 mm) without laser irradiation surface treatment, that is, the metallic copper (T2 pure copper) obtained after cleaning in step (1) of Example 1.

[0139] Table 1. Results of Hardness and Tensile Strength Tests

[0140]

[0141] As can be seen from Table 1 above, the multi-field laser irradiation of copper and copper alloys in the embodiments of the present invention has a better effect than any single mode of laser irradiation (Comparative Example 1 and Comparative Example 2), and can significantly improve the hardness and tensile properties of copper and copper alloys.

[0142] Meanwhile, comparing Example 1 and Comparative Examples 3-5, it can be seen that Example 1 uses appropriate parameters for a continuous / pulsed composite laser, which is beneficial to further improve the overall performance of copper and copper alloys.

[0143] In Comparative Example 3, when the continuous laser power is too low (1000W) and the pulsed laser power is insufficient (200W), copper material struggles to form a stable molten pool due to its high thermal conductivity and low solid-state absorptivity. On one hand, the heat input from the laser is insufficient. The continuous laser energy cannot overcome copper's high reflectivity and rapid heat dissipation, preventing the surface temperature from reaching the melting point, resulting in a shallow or discontinuous molten pool with a reinforcement layer depth of only 0.05 mm. On the other hand, the stirring effect of the pulsed laser fails. When the pulsed laser power is insufficient, the cavitation effect (high-pressure shock waves generated by bubble collapse) and the stirring effect of the molten pool are weak, failing to promote grain refinement.

[0144] In Comparative Example 4, when the continuous laser power is too high (3500W) and the pulsed laser power exceeds the limit (550W), excessive heat input causes turbulence and defects in the molten pool. First, the excessive laser input leads to uncontrolled molten pool flow, causing the keyhole effect to intensify metal evaporation and spatter, forming pores and microcracks. Second, the resulting thermal stress concentration leads to an excessively large temperature gradient, excessive Marangoni convection, and molten pool oscillation, resulting in fluctuations in melt depth. Finally, due to the excessively high pulsed power and the excessively large cavitation shock wave pressure, although the local undercooling increases, defects (such as pores) become stress concentration points, leading to abnormal grain growth and the coexistence of cracks.

[0145] The temperature field, flow field, and stress field of the dual-laser molten pool in Examples 1-3 and Comparative Example 1 under different laser irradiation were simulated and calculated. The results are as follows: Figure 2 As shown. Figure 2 As shown in (a) to (d), under laser irradiation, a molten pool with a high peak temperature is formed on the top of the copper material, and the peak temperature increases significantly with the introduction of pulsed laser. Furthermore, with the increase of pulse power, the temperature gradient along the x-direction of the molten pool surface gradually increases, and consequently, the surface tension gradient along the x-direction of the molten pool surface gradually increases, forming a high surface tension gradient region at the top of the molten pool, such as... Figure 2 As shown in (m)~(p). Generally speaking, the main driving force for molten pool flow is Marangoni convection, and the intensity of Marangoni convection can be characterized by the Marangoni number Ma as shown in equation (1). Its convection intensity is related to factors such as temperature gradient and surface tension gradient. However, the pulsed laser impact on the molten pool causes a high temperature gradient and a high surface tension difference in the molten pool, which further enhances Marangoni convection ( Figure 2(e)~(h)), and with the increase of pulsed laser power, the Marangoni convection velocity significantly increases ( Figure 2 (i)~(l)), thereby promoting the flow of the melt from the center of the melt pool to the edge of the melt pool, resulting in a more uniform temperature inside the melt pool and a reduction in the overall temperature gradient of the melt pool, thereby inhibiting the growth of columnar crystals and achieving equiaxed grains.

[0146] (1)

[0147] In the formula: T is temperature; γ is surface tension; L is molten pool length; η is material viscosity; β is thermal diffusivity. Furthermore, the plasma shock wave caused by the pulsed laser leads to violent oscillations in the molten pool, further promoting heat transfer along the transverse and longitudinal directions, accelerating the cooling rate of melt solidification, and increasing undercooling. The critical nucleation work ΔG* is inversely proportional to the undercooling; as the undercooling ΔT increases, the critical nucleation work ΔG* gradually decreases, while the nucleation rate N gradually increases. Simultaneously, the high-frequency shock vibration of the pulsed laser causes dendrite breakage, providing more nucleation sites within the melt, thus contributing to equiaxed and refined grains.

[0148] Therefore, under the condition of fixed continuous laser power, by increasing the pulsed laser power to impact the molten pool and causing an increase in the surface temperature gradient of the molten pool, the Marangoni convection is enhanced. The plasma shock wave effect caused by the pulsed laser can accelerate the cooling rate of the melt solidification, reduce the critical nucleation work, and increase the nucleation rate, thereby enabling the control of grain morphology and size of laser additive copper alloys.

[0149] Furthermore, metallographic observations were performed on the multi-field laser-enhanced copper of Examples 1, 2, and 3, respectively, and the results are as follows: Figure 3 , Figure 4 and Figure 5 As shown. (Through) Figure 3 , Figure 4 and Figure 5 It can be seen that as the pulsed laser power in the continuous / pulsed composite laser increases, the grain refinement effect becomes more and more obvious, which is consistent with the simulation results.

[0150] also, Figure 6 This is a scanning electron microscope image of metallic copper enhanced by multi-field laser in Embodiment 3 of the present invention. From... Figure 6 It can be seen that the grain size decreases along a gradient from top to bottom, which may be due to grain refinement caused by the combined action of multiple laser fields.

[0151] Metallographic observation was performed on the copper alloy strengthened by multi-field laser in Example 1, and the surface grain size was measured, such as... Figure 7 The figure shows the statistical results of the grain size of metallic copper after multi-field laser strengthening in Example 1. Figure 8The figure shows the statistical results of the grain size of metallic copper in the comparative example. (The text abruptly ends here.) Figure 7 and Figure 8 As can be seen, the average grain size of the copper surface after multi-field laser strengthening in Example 1 is 2.99 micrometers, while the average grain size of the copper surface in the control example is 5.2 micrometers. This demonstrates that the method for improving the overall performance of copper materials based on multi-field composite technology provided by this invention refines the grain size.

[0152] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for improving the comprehensive performance of copper material based on multi-light field composite, characterized in that, The method comprises the following steps: The copper material is subjected to laser irradiation surface treatment to form a surface strengthening layer, wherein the laser used in the laser irradiation surface treatment is a composite laser of continuous laser and pulsed laser; The copper material is metal copper or copper alloy; The power of the continuous laser in the composite laser is 1500-3000 W, and the power of the pulsed laser is 250-500 W; The depth of the surface strengthening layer of the copper material ranges from 0.01 to 4 mm, the surface strengthening layer has a gradient reduction structure from the surface to the inside, and the grain size of the surface strengthening layer ranges from 1 to 50 μm; For a copper material with a thickness ranging from 1 to 10 mm, the power of the continuous laser in the composite laser is 1500-2000 W, the power of the pulsed laser is 250-350 W, and the depth of the surface strengthening layer is 0.01-0.5 mm; For a copper material with a thickness ranging from 11 to 20 mm, the power of the continuous laser in the composite laser is 1800-2500 W, the power of the pulsed laser is 300-400 W, and the depth of the surface strengthening layer is 0.04-2 mm; For a copper material with a thickness ranging from 21 to 30 mm, the power of the continuous laser in the composite laser is 2500-3000 W, the power of the pulsed laser is 400-500 W, and the depth of the surface strengthening layer is 1.5-4 mm; The copper material has a multi-layer structure, which comprises, from top to bottom, a surface strengthening layer, a transition layer and a base layer; the thickness of the transition layer is 1-100 μm, and the grain size thereof ranges from 50 to 150 μm; the grain size of the base layer ranges from 150 to 500 μm.

2. The method for synthesizing performance of multi-light-field composite copper material based on lifting according to claim 1, characterized in that, The repetition frequency of the pulsed laser is 20-40 kHz.

3. The method for synthesizing performance of copper material based on multi-light field composite according to claim 1 or 2, characterized in that, The distance between the laser head of the laser device used in the laser irradiation surface treatment and the surface of the copper material ranges from 15 to 20 mm, and the deflection angle relative to the surface of the copper material ranges from 1 to 10°.

4. The method for synthesizing performance of multi-light-field composite copper material based on lifting according to claim 1 or 2, characterized in that, The linear scanning speed of the composite laser along the X axis is 5000-10000 mm / s, and the movement speed along the Y axis is 0.001-0.02 m / s.

5. The method for synthesizing performance of multi-light field composite copper material based on lifting according to claim 1, characterized in that, The laser irradiation surface treatment is performed under an argon protective atmosphere.

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