A laser shock micro-nano structure morphology control method based on micro-bubble morphology in a constraint layer

Abstract

The application provides a laser impact micro-nano structure form control method based on micro-bubble form in a constraint layer, laser energy distribution is changed by controlling the bubble form in the constraint layer, and then the surface relief micro-nano structure form of the laser impact area is adjusted. The method comprises a work platform, a plate, an absorbing layer, a constraint layer and a laser system from bottom to top. When there is a single constraint layer, micro-bubbles are dissolved in the water constraint layer and the water flow speed is adjusted, or the stretching degree of the glass thin plate during preparation is changed to adjust the micro-bubble form; when there are multiple constraint layers, the glass thin plate containing elliptical micro-bubbles or the K9 glass pipeline containing deionized water with a certain flow speed and micro-nano scale bubbles is used as the constraint layer, and on this basis, two or more constraint layers are stacked at multiple angles to further control the surface relief micro-nano structure form. The material surface micro-nano structure is realized in the case of no mold, and the method has the advantages of high efficiency and wide adaptability.

Description

Technical Field

[0001] This invention belongs to the field of laser manufacturing technology, and specifically relates to a method for controlling the morphology of laser-shocked micro / nano structures based on the microbubble morphology in the constraint layer, that is, using pulsed lasers to realize the fabrication of micro / nano structures with single or multi-directional distribution in the shock region. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] There are various methods for preparing micro / nano structures on material surfaces, which can be broadly classified into two categories: "top-down" and "bottom-up." Ion beam etching, laser etching, and wet etching belong to the "top-down" method. Their advantages include the ability to obtain ideal topological structures with relatively high precision and to prepare porous materials that inherit the original morphology. However, their disadvantages include material waste and limited preparation conditions. Physical / chemical vapor deposition, molecular beam deposition, and chemical / electrochemical reduction methods belong to the "bottom-up" method. These methods enable atoms, molecules, and other particles to self-assemble into micro / nano structures through weak interactions. Their advantages include material savings and control over morphology and material thickness. However, their disadvantages include complex and time-consuming preparation processes and difficult synthesis.

[0004] In applications requiring large-scale fabrication of micro / nano structures, one common method is imprinting using micro / nano-scale templates. Commonly used micro / nano-scale templates are typically fabricated using dry or wet etching methods, and are primarily made of silicon or other hard materials such as quartz. However, after numerous imprinting cycles, these templates wear down and eventually become unusable. Furthermore, high-resolution and large-area molds are difficult to fabricate and expensive. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for controlling the morphology of laser-shocked micro / nanostructures based on the microbubble morphology within a confined layer. During laser-shock processes using water or glass as the confined layer, surface-protruding micro / nanostructures with different morphological characteristics can be formed within the laser-shocked region of the material surface. Based on the influence of the morphology, orientation, concentration, and flow direction of elliptical microbubbles within the confined layer on the gas morphology, this invention guides the laser energy distribution by controlling the bubble morphology within the confined layer, constructing confined layers with different bubble distribution states, thereby adjusting the surface-protruding micro / nanostructure morphology of the laser-shocked region.

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

[0007] A first aspect of the present invention provides a method for controlling the morphology of laser-shocked micro / nano structures based on the morphology of microbubbles in a constraint layer, comprising:

[0008] The surface of the material to be processed is treated to make it smooth;

[0009] An absorber layer and at least one constraint layer are sequentially coated onto the material to be processed to obtain a composite board, wherein micro- and nano-scale bubbles are uniformly distributed in the medium of the constraint layer.

[0010] The composite material is subjected to laser impact using a pulsed laser to form micro-nano structures on the material surface.

[0011] This invention relates to a technique for directly controlling the morphology of micro / nano structures on the surface of metallic materials using laser shock lithography. Compared with various methods for preparing micro / nano structures mentioned above, this invention represents a novel approach to micro / nano structure fabrication, eliminating the need for templates and relying solely on the laser shock force effect. Furthermore, this invention offers advantages such as simultaneously introducing surface strengthening effects on metals, high processing efficiency, and high material utilization.

[0012] This invention relates to the control of the irregular protrusion shape at the bottom of the pit formed by laser shock, specifically involving height and aspect ratio. Height control is achieved through conventional laser shock process parameters. Based on the upper limit of the laser power density corresponding to the laser parameters selected for the laser shock strengthening process of the material to be processed, the parameters are set according to the principle that "higher laser power density leads to greater height." Aspect ratio control is achieved through the control of the bubble morphology and orientation of the constraint layer, or the superposition angle between multiple constraint layers, as provided in this invention.

[0013] To fabricate micro / nano structures of a specific shape on the surface of a sheet material using laser impact, the surface of the sheet material to be processed needs to be treated to make it smooth. The smoothing treatment methods include, but are not limited to, mechanical grinding and polishing. In some embodiments, the surface roughness of the material before laser impact does not exceed Ra0.01.

[0014] In some embodiments, the absorber layer is made of black paint, graphite, black tape, or metal foil. When a pulsed laser shines on the absorber layer, it ionizes to generate high-temperature, high-pressure plasma, which, under the induction of laser energy, generates a shock wave. This shock wave then acts as a driving force to induce high-strain-rate plastic deformation in the substrate, thus completing the laser impact test.

[0015] Furthermore, this application optimizes the morphology and medium of the bubble in the confinement layer. In some embodiments with better results, the confinement layer is a water confinement layer containing elliptical microbubbles, or a glass plate containing elliptical microbubbles.

[0016] Preferably, the thickness of the water-binding layer or the glass-binding layer is 0.2~3mm;

[0017] More preferably, the glass sheet is made of K9 glass, from which thin sheets are produced.

[0018] Furthermore, to achieve the desired micro / nano structure control effect, this invention also optimized the size of the micro / nano-scale bubbles within the confinement layer. Tests show that the size of the laser spot should be much larger than the size of the micro-bubbles within the confinement layer. The laser size is typically on the order of mm, while the size of the micro-bubbles within the confinement layer should be on the order of μm or nm. This ensures that the laser beam energy is not excessively consumed, thus inducing the formation of pits on the surface of the metal material. Therefore, in some superior embodiments, the diameter of the micro / nano-scale bubbles is 1~50 μm.

[0019] Furthermore, the present invention optimizes the combination method of multiple constraint layers, wherein the multiple constraint layers are at least two layers, and the constraint layers are stacked one on top of the other;

[0020] In some more specific implementations, the double (multi) constraint layer can be selected from two superimposed glass plates containing microbubbles, or two water constraint layers, or a double (multi) constraint layer composed of glass plates and a water curtain.

[0021] It should also be noted that when using glass laminates, a bubble-free liquid adhesive can be used directly for bonding.

[0022] Furthermore, the present invention optimizes the method for controlling the size of micro- and nano-scale bubbles in the constraint layer, including:

[0023] When using a single-layer water confinement layer, the elliptical bubble morphology in the confinement layer is controlled by adjusting the flow velocity of the water confinement layer.

[0024] In some more effective implementations, a deionized water curtain containing microbubbles is used as the confinement layer, and the morphology of the bubbles in the confinement layer is controlled by adjusting the flow velocity of the water confinement layer. When the water flow layer is stationary, the bubbles are standard spherical; when the water flow layer has a higher velocity, the bubbles will take on an elongated elliptical shape.

[0025] In some more effective embodiments, a water confinement layer containing micro- and nano-scale bubbles can also be prepared by applying deionized water with the same flow rate but different flow directions and containing micro- and nano-scale bubbles in a pipe.

[0026] More specifically, water-confined layers containing micro- and nano-scale bubbles can be prepared using a pressurized dissolved gas method. This involves using an air compressor to pressurize the water, causing the gas to dissolve in the water during agitation, resulting in a supersaturated state. The supersaturated dissolved gas water then flows through a release device, where it is instantly depressurized as it passes through a nozzle. The air in the water separates from the water, creating a cavitation effect that releases the supersaturated gas dissolved in the water as micro- and nano-scale bubbles. This ultimately forms deionized water free of impurities and containing relatively uniformly distributed micro- and nano-scale bubbles with a particle size of 1–50 μm.

[0027] It should be noted that, in this invention, the water is deionized water containing a certain volume and concentration of bubbles and having removed impurities such as calcium and magnesium ions.

[0028] When using a single-layer glass constraint layer, the morphology of elliptical bubbles in the constraint layer can be controlled by adjusting the degree of stretching during the customization of the thin glass sheet.

[0029] For multiple constraint layers, the present invention can control the micro-nano structure by superimposing each constraint layer at multiple angles. At this time, the shape and orientation of the microbubbles in each constraint layer are not exactly the same.

[0030] In some superior implementations, when all the multiple constraint layers are glass constraint layers, the microbubbles in each glass constraint layer have the same shape but are located in different orientations; (i.e., the elongation directions of the microbubbles are superimposed at different angles).

[0031] In some more effective implementations, when all the multiple constraint layers are water constraint layers, the water flow velocity in each water constraint layer is the same.

[0032] In some superior implementations, when the multilayer confinement layer consists of a glass confinement layer and a water confinement layer, the water flow rate in the water confinement layer remains constant, and the microbubbles in each glass confinement layer have the same shape but are located in different orientations.

[0033] Furthermore, the present invention optimizes the positional relationship when different constraint layers are stacked. In some embodiments, when the multilayer constraint layers are glass constraint layers and water constraint layers stacked, the glass constraint layer is located on the side further away from the surface of the material to be processed, so as to reduce costs and facilitate control of the thickness of the water constraint layer.

[0034] In some implementations, when all the multiple constraint layers are glass constraint layers, the thicker glass constraint layer is located on the side further away from the surface of the material to be processed.

[0035] In some implementations, when all multiple constraint layers are water constraint layers, the sheet material needs to be placed under a double water constraint layer and constructed by using two bubble-free K9 glass pipes to pass deionized water at a certain speed.

[0036] This application also optimizes the angle, power, and distribution of the laser beam, including:

[0037] In some embodiments, the laser beam is perpendicular to the surface of the material to be processed;

[0038] In some implementations, the power density of the pulsed laser is greater than 0.1 GW / cm². 2 The selection is based on the mechanical properties of the material to be processed, and the specific values ​​depend on the pulse width, spot size, and laser energy.

[0039] It should be noted that the higher the yield strength and other mechanical properties of the material to be processed, the greater the laser power density should be.

[0040] In some embodiments, the energy distribution of the pulsed laser beam emitted by the laser is detected and corrected, and the laser beam energy is adjusted to a flat-top distribution, that is, the laser energy is the same at all points within the laser spot range.

[0041] It should be noted that a flat-top energy distribution within a single beam can be achieved by adjusting the voltage. A laser beam is emitted onto black test paper, and the change in the degree of ablation on the black test paper surface is observed. If the color contrast of the white ablated areas on the black test paper surface is the same, then the laser beam energy is considered to have a flat-top distribution.

[0042] Furthermore, the area to be processed on the sheet metal is subjected to single-beam laser shock treatment. When the pulsed laser passes through the constraint layer, microbubbles within the constraint layer cause energy loss and absence in the flat-topped laser energy distribution, resembling bubble shapes. Through microscopic morphological observation of the laser-shocked area, the laser-shocked area on the sheet metal surface exhibits a surface-protruding micro / nano structure corresponding to the bubble shapes in a single constraint layer or the superimposed bubble shapes in double (multiple) constraint layers.

[0043] More specifically, including:

[0044] 1) Identify and process the raw material sheet, and ensure that the material surface is in a smooth state with low surface roughness;

[0045] 2) Select a single constraint layer containing elliptical microbubbles with different aspect ratios, or select double (multiple) constraint layers containing microbubbles of the same shape and stack them at different angles, and place them on the raw material board covered with the absorption layer.

[0046] 3) Using pulsed laser-induced plasma shock waves as the deformation driving force, a laser shock surface processing device was built, and laser parameters were determined and adjusted;

[0047] 4) The laser beam is incident perpendicularly on the sheet material to perform single-beam laser impact treatment.

[0048] A second aspect of the present invention provides a material with a surface having a micro / nano structure prepared by the above-described method.

[0049] A third aspect of the present invention provides the application of the above-described method in the fabrication of micro / nano structures on material surfaces.

[0050] Beneficial effects of the present invention

[0051] (1) The method of the present invention utilizes the basic principle that the lack of laser energy distribution in laser shock causes the surface to be raised micro-nano structure. By adjusting the micro bubble morphology in a single constraint layer or the overlap angle between constraint layers, the actual laser energy distribution state received by the material to be processed is changed, thereby obtaining a micro-nano structure that is adapted to the micro bubble morphology in a single constraint layer or the superimposed bubble shape in a double (multiple) constraint layer.

[0052] (2) The method of the present invention can realize the preparation of surface protrusion micro-nano structures with different morphologies by the microbubble morphology in a single constraint layer or the overlap angle between double (multiple) constraint layers.

[0053] (3) The method of the present invention introduces surface strengthening effect while performing micro-nano manufacturing on the surface of the sheet material. The process is simple and the processing efficiency is high.

[0054] (4) The method of the present invention utilizes the laser shock force effect to perform high strain rate plastic deformation on the sheet material, and the absorption layer covers the surface of the sheet material, which will not cause ablation damage to the sheet material.

[0055] (5) The preparation method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0056] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0057] Figure 1 This is a schematic diagram of laser shock morphology control of micro / nano structures using a double-constrained glass sheet, where 1, laser system; 2, double-constrained glass sheet; 3, absorption layer; 4, substrate; and 5, working platform.

[0058] Figure 2 This is a schematic diagram of micro / nano structure morphology control using a double-constraint layer composed of upper and lower water curtains. 1. Laser system; 2. Upper and lower water constraint layers; 3. Absorption layer; 4. Plate material; 5. Working platform.

[0059] Figure 3 This is a schematic diagram of the material surface morphology.

[0060] Figure 4 This is a diagram of a device in a static state of a water-constrained layer; wherein, 1, laser, 2, constrained layer, 3, absorption layer, 4, target material, 5, water-blocking cavity, 6, microbubble generator, 7, water inlet valve, and 8, clamping device.

[0061] Figure 5This is a diagram of a device for the flow state of a water-constrained layer; wherein, 1, laser, 2, constrained layer, 3, absorption layer, 4, target material, 5, water inlet valve, 6, water pressure regulator, 7, microbubble generator, 8, water pump, and 9, clamping device.

[0062] Figure 6 This is a schematic diagram illustrating the principle of micro-protrusion shape changes caused by bubbles; where a is a schematic diagram of the pit formed by laser impact, b is a schematic diagram of the micro-protrusion shape caused by equiaxed bubbles when the constraint layer is stationary, c is a schematic diagram of the micro-protrusion shape caused by unequal-axis bubbles when the flow velocity of the constraint layer is low, and d is a schematic diagram of the micro-protrusion shape caused by unequal-axis bubbles when the flow velocity of the constraint layer is high; where 1 represents the bubble shape, 2 represents the cross-sectional shape of the micro-protrusion formed corresponding to the bubble shape, and 3 represents the three-dimensional shape of the micro-protrusion formed corresponding to the bubble shape. Detailed Implementation

[0063] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0064] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0065] Example 1

[0066] This embodiment provides a method for controlling the morphology of laser-shocked micro / nano structures based on the microbubble morphology in multi-constraint layers. For example... Figure 1 As shown, from top to bottom, the components are: 1. Laser system; 2. Glass sheet double constraint layer; 3. Absorption layer; 4. Plate material; 5. Working platform.

[0067] A laser impact testing platform was constructed. A 2mm*10mm*10mm plate sample was made from TC4 titanium alloy and subjected to a combination of mechanical grinding and chemical polishing to achieve a smooth surface with a roughness not exceeding Ra 0.006. A 100μm thick black 3M tape was then applied to the plate surface, which was then placed on a horizontal work platform. The tape application process on the metal surface was slow and deliberate to prevent air bubbles from forming.

[0068] In this example, a double-constrained layer is created by stacking custom-made 2mm glass sheets, with each glass sheet containing elliptical microbubbles of the same shape. The two glass sheets are placed at a 90° angle and, through a glass lamination process, a 4.1mm thick double-constrained glass sheet is finally obtained.

[0069] In this example, the laser shock wave is induced by an Nd:YAG laser system with a wavelength of 1064 mm, a frequency of 2 Hz, and a pulse width of 14 ns. The laser beam emitted by this system is incident perpendicularly on the surface of the substrate after passing through an optical lens, forming a circular laser beam spot with a diameter of 2 mm on the substrate surface, and the laser energy is 6 J. A flat-top energy distribution of the single laser beam is achieved by adjusting the voltage.

[0070] A clamping element is placed on top of the constraint layer to stabilize the relative positions of the sheet material, the absorption layer, and the constraint layer, completing the preparation work. Then, single-beam laser shock blasting is performed on the sheet material to be processed, and the microstructure of the sheet surface is observed using a laser confocal microscope. A schematic diagram is shown below. Figure 3 As shown.

[0071] Considering that the laser beam of some laser systems is perpendicular to gravity, a working platform perpendicular to the ground needs to be built. Clamping components are then used to sequentially fix the plate, absorption layer, and constraint layer onto the working platform, constructing a new work clamping system. The remaining steps are the same as described above. After adjusting the laser parameters and completing the preparations, laser shock treatment is performed.

[0072] Example 2

[0073] This embodiment provides another method for controlling the morphology of laser-shocked micro / nano structures based on the microbubble morphology in multi-constraint layers. For example... Figure 2 The components shown from top to bottom are: 1. Laser system; 2. Upper and lower water confinement layers; 3. Absorption layer; 4. Plate; 5. Working platform.

[0074] First, a working platform different from that in Example 1 is constructed. This platform must be placed parallel to the ground, and the laser beam must ultimately be incident perpendicularly on the surface of the sheet material. TC4 is still selected as the raw material for the sheet material, and a sheet material sample is prepared. The sheet material is also polished to make its surface smooth, with a surface roughness not exceeding Ra0.006. A 100μm thick layer of black 3M tape is used to cover its surface and fix it to the working platform as a constraint layer. During the application of the tape to the metal surface, slow operation is required to prevent air bubbles from forming.

[0075] The constraint layer in this example is as follows: Figure 2 As shown in the diagram, the upper and lower water-constrained layers are constructed by stacking custom-made K9 thin glass tubes vertically at a 90° angle. Each glass tube has a rectangular ring cross-section and carries deionized water containing micro- and nano-sized air bubbles at a flow rate of 2 m / s. The relatively uniform micro- and nano-sized air bubbles are generated using a pressurized dissolved air method, with their diameter controlled to be 10–20 μm.

[0076] Then, place clamping components on top of the constraint layer to stabilize the relative positions of the sheet material, the absorption layer, and the constraint layer, thus completing the preparation work.

[0077] In this example, the laser shock wave is induced by an Nd:YAG laser system with a wavelength of 1064 mm, a frequency of 2 Hz, and a pulse width of 14 ns. The laser beam emitted by this laser system is incident perpendicularly on the surface of the material after passing through an optical lens, forming a circular laser beam spot with a diameter of 2 mm on the surface of the material, and the laser energy is 6 J.

[0078] The correction of the laser beam energy distribution is consistent with the steps in Example 1. After preparation, the material to be processed is subjected to single-beam laser shock treatment, and the microstructure of the material surface is observed using a laser confocal microscope, as shown in the schematic diagram. Figure 3 As shown.

[0079] Example 3

[0080] like Figure 4 As shown, a device for stabilizing a water-constrained layer includes a water-retaining cavity. The main function of the water-retaining cavity is to stabilize the water-constrained layer, at which point the air bubbles in the water are equiaxed standard spheres. Simultaneously, it ensures that the processed target material can be fixed within the water-retaining cavity using a clamping device.

[0081] The specific implementation method is as follows:

[0082] 1. Construct a pulsed laser shock material processing platform:

[0083] The platform requires a device including a pulsed laser emitter and a water-blocking cavity that is attached to the target material.

[0084] Simultaneously adjust the parameters of the laser shock equipment: the laser beam uses a 6 J pulsed laser with a pulse width of 14 ns, a pulse frequency of 2 Hz, and a flat-top energy distribution. A circular laser beam with a diameter of 2 mm is used.

[0085] 2. Detection and adjustment of pulsed laser energy distribution:

[0086] A laser beam is emitted onto black test paper, and the change in the degree of ablation on the surface of the black test paper is judged. When the color contrast of the white ablated areas on the surface of the black test paper is the same, the energy of the laser beam is considered to be uniformly distributed.

[0087] The steps of this invention do not limit the specific adjustment method of the laser energy distribution; the ultimate goal is to achieve a uniform distribution of laser energy at different positions within the beam.

[0088] 3. Target material pretreatment:

[0089] Nickel-based single-crystal superalloy was selected as the laser shock target. It was cut into 10 mm * 10 mm * 10 mm test blocks using wire cutting. After cutting, the surface was cleaned using ultrasonic cleaning. Then, mechanical grinding and polishing were used to maintain the surface roughness at Ra 0.005, and a 100 μm thick layer of black 3M tape was applied as an absorption layer.

[0090] 4. Set up as follows Figure 4 The constrained layer static device platform shown:

[0091] The pretreated target is placed into the water-blocking cavity and fixed to the bottom of the cavity using a clamping device. Deionized water rich in microbubbles is generated using a microbubble generator, and then the inlet valve is opened to introduce this water into the water-blocking cavity as a water confinement layer for laser impact. When the water curtain formed is approximately 2 mm thick on the workpiece surface, the inlet valve is closed, and the entire water-blocking cavity is held still for 30 seconds, controlling the flow rate of the water confinement layer to 0. In this step, the water curtain coverage area must be larger than the laser impact spot area.

[0092] The microbubble generator uses a Venturi-type hydrodynamic cavitation device, with a water tank pressure of 5.8 kPa and a circulation time of 5 min to generate water rich in microbubbles with a size of 50~150 μm.

[0093] 5. Perform laser shock treatment and observe the morphology of the bottom of the pits on the target surface after treatment:

[0094] This step involves adjusting the laser beam to be perpendicular to the material surface, maximizing its energy application to the metal surface. The treated metal surface will then exhibit equiaxed protrusions approximately 50 μm high and 100 μm in diameter.

[0095] Example 4

[0096] like Figure 5 As shown, a confined layer flow device is characterized by the following: the water confined layer has a certain flow velocity, and the air bubbles in the water are elongated ellipses with non-equiaxial shape.

[0097] The specific implementation method is as follows:

[0098] 1. Construct a pulsed laser shock material processing platform:

[0099] The platform requires the following devices: a pulsed laser emitter and its water inlet system.

[0100] Simultaneously adjust the parameters of the laser shock equipment: the laser beam uses a 4 J pulsed laser with a pulse width of 12 ns, a pulse frequency of 1 Hz, and a flat-top energy distribution. A circular spot laser beam with a beam diameter of 2 mm is used.

[0101] 2. Detection and adjustment of pulsed laser energy distribution:

[0102] A laser beam is emitted onto black test paper, and the change in the degree of ablation on the surface of the black test paper is judged. When the color contrast of the white ablated areas on the surface of the black test paper is the same, the energy of the laser beam is considered to be uniformly distributed.

[0103] The steps of this invention do not limit the specific adjustment method of the laser energy distribution; the ultimate goal is to achieve a uniform distribution of laser energy at different positions within the beam.

[0104] 3. Target pretreatment:

[0105] 6061 aluminum alloy was selected as the laser shock target material. It was mechanically cut into 10 mm * 10 mm * 1 mm plates. After cutting, the 10 mm * 1 mm surface was cleaned as the surface to be processed. Then, mechanical grinding and chemical polishing were used to maintain the surface roughness at Ra 0.001. After ultrasonic cleaning, a 100 μm thick layer of black 3M tape was applied as an absorption layer.

[0106] 4. Set up as follows Figure 5 The constrained layer flow device platform shown:

[0107] The pretreated target material is fixed to the laser using a clamping device. Deionized water rich in microbubbles is generated using a microbubble generator. The water pressure regulator and pump are then turned on to control the flow rate of the water confinement layer at 80-150 mm / s. The inlet valve is then opened to introduce the water into the target surface as a water confinement layer for laser impact, forming a water curtain approximately 2 mm thick on the target surface. The area covered by this water curtain must be larger than the area of ​​the laser impact spot.

[0108] The microbubble generator uses a Venturi-type hydrodynamic cavitation device, with a water tank pressure of 6.9 kPa and a circulation time of 5 min to produce water rich in microbubbles with a size of 3~70 μm.

[0109] 5. Perform laser shock treatment and observe the morphology of the bottom of the pits on the target surface after treatment:

[0110] This step involves adjusting the laser beam to be perpendicular to the material surface, maximizing its energy application to the metal surface. The treated metal surface will then exhibit micro-protrusions with a height of approximately 20 μm, a particle size of 5–50 μm, and an aspect ratio of approximately 1.2.

[0111] Example 5

[0112] In this embodiment, the constraint layer material is changed from water to glass.

[0113] 1. Construct a pulsed laser shock material processing platform:

[0114] The platform requires the following devices: a pulsed laser emitter and its water inlet system.

[0115] Simultaneously adjust the parameters of the laser shock equipment: the laser beam uses a 5 J pulsed laser with a pulse width of 12 ns, a pulse frequency of 1 Hz, and a flat-top energy distribution. A circular laser beam with a diameter of 2 mm is used.

[0116] 2. Detection and adjustment of pulsed laser energy distribution:

[0117] A laser beam is emitted onto black test paper, and the change in the degree of ablation on the surface of the black test paper is judged. When the color contrast of the white ablated areas on the surface of the black test paper is the same, the energy of the laser beam is considered to be uniformly distributed.

[0118] The steps of this invention do not limit the specific adjustment method of the laser energy distribution; the ultimate goal is to achieve a uniform distribution of laser energy at different positions within the beam.

[0119] 3. Target pretreatment:

[0120] 6061 aluminum alloy was selected as the laser shock target material. It was mechanically cut into 10 mm * 10 mm * 1 mm plates. After cutting, the 10 mm * 1 mm surface was cleaned as the surface to be processed. Then, mechanical grinding and chemical polishing were used to maintain the surface roughness at Ra 0.001, and ultrasonic cleaning was performed.

[0121] Black paint is selected as the absorbent layer. The black paint is evenly sprayed onto the lower surface of the prepared opaque glass, and this lower surface is in contact with and pressed against the upper surface of the metal material.

[0122] 4. The device consists of a glass confinement layer and a black paint absorption layer.

[0123] A glass with a thickness of 2 mm and containing elongated elliptical bubbles with a size of 5-150 μm was prepared. Bubbles within the glass are easier to shape and their shape can be modified, without being limited to perfectly round bubbles. Black paint was then used as the absorption layer. The black paint was uniformly sprayed onto the lower surface of the prepared opaque glass, which was then pressed firmly against the target surface.

[0124] 5. Perform laser shock treatment and observe the morphology of the bottom of the pits on the target surface after treatment:

[0125] This step involves adjusting the laser beam to be perpendicular to the material surface, maximizing its energy application to the metal surface. The treated target surface will then exhibit micro-protrusions with a height of approximately 30 μm, a particle size of 10–100 μm, and an aspect ratio of approximately 1.5.

[0126] It should be noted that this invention utilizes bubbles to consume laser beam energy. The size and shape of the bubbles affect the aspect ratio of the final protrusion, ultimately achieving control over the shape of the protrusion at the bottom of the pit. Specific embodiment 3 results analogy. Figure 6 In section b, the results of specific embodiment 4 are analogous. Figure 6 In the case of c, the results of specific embodiment 5 are analogous. Figure 6 d.

[0127] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the morphology of laser-shocked micro / nano structures based on the microbubble morphology in a constrained layer, characterized in that, include: The surface of the material to be processed is treated to make it smooth; An absorber layer and at least one constraint layer are sequentially coated onto the material to be processed to obtain a composite board, wherein micro- and nano-scale bubbles are uniformly distributed in the medium of the constraint layer. The composite material is subjected to laser impact blasting using a pulsed laser to form micro-nano structures on the surface of the material to be processed; the laser size is on the order of millimeters. The confinement layer is a water confinement layer containing elliptical micro-nano-scale bubbles, or a glass plate containing elliptical micro-nano-scale bubbles. When using a single-layer water confinement layer, the morphology of elliptical micro- and nano-scale bubbles in the confinement layer can be controlled by adjusting the flow velocity of the water confinement layer. Alternatively, when using a single-layer glass confinement layer, the morphology of elliptical micro / nano-scale bubbles in the confinement layer can be controlled by adjusting the degree of stretching during the customization of the thin glass sheet.

2. The laser shock morphology control method for micro / nano structures based on microbubble morphology in a constraint layer as described in claim 1, characterized in that, The surface roughness of the material to be processed before laser impact does not exceed Ra0.01; Alternatively, the absorbent layer may be made of black paint, graphite, black tape, or metal foil.

3. The laser shock morphology control method for micro / nano structures based on microbubble morphology in a constraint layer as described in claim 1, characterized in that, When using multiple constraint layers, the multiple constraint layers can be made by superimposing glass constraint layers and water constraint layers, or all multiple constraint layers can be glass constraint layers, or all multiple constraint layers can be water constraint layers.

4. The laser shock morphology control method for micro / nano structures based on microbubble morphology in a constraint layer as described in claim 1, characterized in that, When using multiple constraint layers, the micro-nano structure is controlled by stacking each constraint layer at multiple angles. The morphology and orientation of the micro-nano scale bubbles in each constraint layer are not completely the same. Alternatively, when all the multiple confinement layers are glass confinement layers, the micro- and nano-scale bubbles in each glass confinement layer have the same shape but are located in different orientations. Alternatively, when all multiple constraint layers are water constraint layers, the water flow velocity is the same in each water constraint layer; Alternatively, when the multilayer confinement layer consists of a glass confinement layer and a water confinement layer, the water flow rate in the water confinement layer remains constant, and the micro- and nano-scale bubbles in each glass confinement layer have the same shape but are located in different orientations.

5. The laser shock morphology control method for micro / nano structures based on microbubble morphology in a constraint layer as described in claim 1, characterized in that, When using a multi-layer constraint layer, where the multi-layer constraint layer consists of a glass constraint layer and a water constraint layer stacked together, the glass constraint layer is located on the side further away from the surface of the material to be processed. Alternatively, when all multiple constraint layers are glass constraint layers, the thicker glass constraint layer is located on the side further away from the surface of the material to be processed.

6. The laser shock morphology control method for micro / nano structures based on microbubble morphology in a constraint layer as described in claim 1, characterized in that, The laser beam is perpendicular to the surface of the material to be processed; Alternatively, the power density of the pulsed laser is greater than 0.1 GW / cm². 2 .

7. The application of the method according to any one of claims 1-6 in the fabrication of multidirectional distributed micro / nano structures.

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