Method for inhibiting laser processing damage of heterogeneous material

Abstract

The invention discloses a method for inhibiting laser processing damage of a heterogeneous material, which comprises the following steps: a processed material is immersed in an auxiliary liquid, so that the processed part of the processed material is fully infiltrated by the auxiliary liquid, the processed material is a solid heterogeneous material, and under the central wavelength of used laser, the room temperature complex refractive index of the processed material is n1, the effective complex refractive index of the auxiliary liquid at the working temperature is n2, and n1 and n2 meet matching conditions; and the machined material is subjected to laser subtractive machining, and the residual auxiliary liquid is removed after machining is completed. By selecting proper auxiliary liquid and applying optical parameters matched with the auxiliary liquid, binary interaction of the laser and the heterogeneous material is converted into interaction of the laser, the heterogeneous material and the auxiliary liquid, so that comprehensive effects of stray light suppression, micro-stripping effect of a thermal damage area caused by laser-induced cavitation, suppression of a heat affected area by liquid cooling and the like are achieved; and the processing quality of the heterogeneous material is obviously improved.

Description

Technical Field

[0001] The present application relates to the technical field of laser processing, and in particular to a method for suppressing damage in laser processing of inhomogeneous materials. Background Art

[0002] Heterogeneous materials such as porous materials, fiber-reinforced or toughened composite materials are widely used in load-bearing structures, thermal control and fluid control products, electromagnetic products, etc. in the fields of aerospace, weapons and equipment, rail transportation, etc. due to their unique material organization and material properties. In the process of forming part structures, these materials are almost inevitably faced with the processing of structures such as contour surfaces, holes, cavities or grooves, which are generally processed by traditional manufacturing methods such as cutting / grinding. In recent years, laser processing technology has begun to be widely studied and applied due to its advantages such as material universality, no contact stress, and suitability for cross-scale processing. In particular, ultrashort pulse lasers (also known as ultrafast lasers) are expected to become a powerful tool for high-quality processing of heterogeneous materials due to their potential capabilities such as low thermal processing damage.

[0003] One of the biggest drawbacks of laser processing is the inevitable thermal damage during processing, which is true for almost all materials. For heterogeneous materials such as porous materials, fiber-reinforced or toughened composite materials, both theoretical and practical explorations have shown that compared with homogenized materials, due to the multi-component or (and) heterogeneous characteristics of heterogeneous materials, the laser beam propagating inside the material is very likely to have obvious scattering. The emergence of the scattering phenomenon not only diverts the energy of the mainstream beam that was originally in deterministic refractive propagation, resulting in a decrease in processing capacity, but also because the scattered light intensity often has the "sub-threshold" (i.e. low energy) characteristics, it can often only be used to modify the material to create thermal damage, but cannot be used for deformation (deformation requires higher energy than the threshold), which directly causes heterogeneous materials to be prone to prominent processing damage and poor quality consistency in the processing area. The inherent particularity of the heterogeneous material organization makes it very easy to have the above-mentioned processing quality problems even if it is directly processed by lasers with low thermal processing effects such as femtosecond lasers and picosecond lasers.

[0004] Therefore, it is necessary to develop a simple, low-cost, low-damage, high-consistency processing method for heterogeneous material structures. By utilizing some special processes of laser-material interaction generated by some extreme characteristics of ultrafast lasers, the processing quality problems caused by direct laser processing of heterogeneous materials, including ultrafast lasers, can be fundamentally suppressed. Summary of the invention

[0005] The present application provides a method for suppressing damage during laser processing of heterogeneous materials, the purpose of which is to achieve damage suppression during ultrafast laser processing of heterogeneous materials by filling liquid into the processed parts of the heterogeneous materials.

[0006] In a first aspect, a method for suppressing laser processing damage of inhomogeneous materials is provided, comprising:

[0007] Step S1: Immerse the processed material in the auxiliary liquid so that the processed material is fully infiltrated by the auxiliary liquid at the processed part, wherein the processed material is a solid inhomogeneous material, and at the central wavelength of the laser used, the room temperature complex refractive index of the processed material is n1, the effective complex refractive index of the auxiliary liquid at the working temperature is n2, the room temperature complex refractive index of air is n3, and the auxiliary liquid satisfies:

[0008] Step S2: performing laser subtractive processing on the material to be processed, and cleaning the residual auxiliary liquid after the processing is completed.

[0009] In combination with the first aspect, in certain implementations of the first aspect, the microstructure of the processed material is that at the interface between the laser and the material, the material satisfies at least one of the following items: the porosity is between 20% and 95% and at least one dimension of the characteristic pore size is distributed in the range of 5μm to 1mm; at the interface between the laser and the material, the roughness of the processed material is distributed in the range of Ra5μm to Ra100μm.

[0010] In combination with the first aspect, in certain implementations of the first aspect, solid particles are added to the auxiliary liquid in addition to the liquid itself as the main component. The solid particles are used to adjust the effective complex refractive index of the auxiliary liquid at the working temperature. After the solid particles are added, the auxiliary liquid is a mixture with flow properties.

[0011] In conjunction with the first aspect, in certain implementations of the first aspect, the solid particles satisfy at least one of the following:

[0012] The solid particles include at least one of silicon nanoparticle powder and NaCl particles;

[0013] The average particle size of the solid particles after dissolving into the liquid as the main component is smaller than the minimum pore characteristic size value of the processed material;

[0014] The average particle size of the solid particles after dissolving into the liquid as the main component is smaller than the value of the roughness Ra of the machined section of the machined material.

[0015] In conjunction with the first aspect, in certain implementations of the first aspect, the matching relationship between the processed material and the auxiliary liquid satisfies:

[0016] In combination with the first aspect, in certain implementations of the first aspect, in step S2, after laser subtractive processing of the material to be processed, if the processing quality does not meet the requirements, jump to step S1 and reselect a new auxiliary liquid for processing until the processing quality meets the requirements.

[0017] In combination with the first aspect, in certain implementations of the first aspect, at the central wavelength of the laser used, the effective complex refractive index of the newly selected auxiliary liquid at the working temperature is n4, satisfying:

[0018] In combination with the first aspect, in certain implementations of the first aspect, the pulse flux F of the processing pulse laser in step S2 satisfies: F is greater than the processing threshold F0 of the processed material removal, and F>F th ;

[0019] F th =(A×E2-B)×t p k

[0020] In the formula, F th is the single pulse processing threshold of the auxiliary liquid, E2 is the bandgap width of the auxiliary liquid at the working temperature, t p is the duration of a single pulse, k, A and B are dimensionless constants, where k is 0.25-0.35; A is 0.80-1.20 J / (cm 2 ·ps 0.3 ·eV); the value of B is 1.00~1.55J / (cm 2 ·ps 0.3 ).

[0021] In combination with the first aspect, in certain implementations of the first aspect, the laser used is a pulsed laser and the duration of a single pulse is t p <100ps.

[0022] In combination with the first aspect, in certain implementations of the first aspect, the bandgap width E1 of the processed material satisfies 0≤E1≤13.5eV, and the auxiliary liquid is a fluid with a bandgap width E2≥2.0eV at the working temperature.

[0023] In a second aspect, a laser processing device is provided, wherein the laser processing device is used to execute the laser processing damage method as described in any one of the implementations of the first aspect.

[0024] Compared with the prior art, the solution provided by this application includes at least the following beneficial technical effects:

[0025] (1) The present invention provides a method for suppressing damage in laser processing of heterogeneous materials. The method adopts optical reflection principles such as Fresnel's law and the idea of ​​refractive index matching to reduce the energy reflection of the laser beam at the interface of the heterogeneous material-auxiliary liquid, thereby producing an effect similar to that of laser processing of conventional materials (i.e., homogenized materials) in the heterogeneous material: the binary interaction between the laser and the heterogeneous material under conventional practices is transformed into a three-way interaction among the laser, the heterogeneous material, and the auxiliary liquid, so as to achieve stray light suppression, which creates favorable conditions for suppressing the production of thermal damage zones at the edge of the structure caused by stray light; at the same time, by applying an irradiation intensity higher than its processing threshold energy to the auxiliary liquid, the liquid generates cavitation bubbles through phase change, and the instantaneous local strong mechanical peeling effect generated by the subsequent rupture of the cavitation bubbles further achieves the removal of the thermal damage zone at the edge of the structure; in addition, the liquid also creates powerful conditions for suppressing the diffusion of the heat-affected zone. Therefore, the present method is a method with clear principles and effective measures that significantly improves the processing quality compared with direct dry processing.

[0026] (2) The present invention provides a method for suppressing damage in laser processing of heterogeneous materials. By quantifying the pulse flux F of the pulsed laser required to be applied to liquids with different pulse widths and different bandgap widths, a quantitative guarantee is provided for utilizing the liquid to generate subsequent phase changes and cavitation bubbles through nonlinear ionization. At the same time, in response to different processing quality requirements, the present invention provides semi-quantitative guidance for refractive index matching, and the present invention provides a liquid selection strategy with flexible and adjustable optional auxiliary liquid types to ensure the feasibility of refractive index matching. Therefore, the present invention is a method for improving the processing quality of heterogeneous materials with reliable method, simple calculation and strong adjustability.

[0027] (3) Compared with the conventional direct laser processing method, the method for suppressing damage in laser processing of heterogeneous materials provided by the present invention can improve the processing quality only by increasing the input of auxiliary liquid consumables, so it is a simple and economical method. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is a flow chart of a method for suppressing laser processing damage of inhomogeneous materials.

[0029] Figure 2 This is a diagram showing the effect of processing porous polyimide using the present invention.

[0030] Figure 3 The effect diagram of processing porous polyimide before using the present invention. DETAILED DESCRIPTION

[0031] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] The present invention provides a method for suppressing laser processing damage of heterogeneous materials, and the specific steps are as follows.

[0033] Step S1: Immerse the processed material in the auxiliary liquid so that the processed material is fully infiltrated by the auxiliary liquid at the processed part, wherein the processed material is a solid inhomogeneous material, and at the central wavelength of the laser used, the room temperature complex refractive index of the processed material is n1, the effective complex refractive index of the auxiliary liquid at the working temperature is n2, the room temperature complex refractive index of air is n3, and the auxiliary liquid satisfies: The amount of auxiliary liquid can be determined by whether the processed part can be immersed in the auxiliary liquid.

[0034] Step S2: performing laser subtractive processing on the material to be processed, and cleaning the residual auxiliary liquid after the processing is completed.

[0035] In some embodiments. In some embodiments, the microstructure of the processed material is that at the interface between the laser and the material, the material satisfies at least one of the following: the porosity is between 20% and 95% and at least one dimension of the pore characteristic size is distributed in the range of 5μm to 1mm; at the interface between the laser and the material, the roughness of the processed material is distributed in the range of Ra5μm to Ra100μm.

[0036] In some embodiments, solid particles may be added to the auxiliary liquid in addition to the liquid itself, and the solid particles are used to adjust the effective complex refractive index of the auxiliary liquid at the working temperature. After adding the solid particles, the auxiliary liquid is a mixture with fluid properties. The solid particles may be, for example, silicon nanoparticle powder, NaCl particles, etc.

[0037] Furthermore, the average particle size of the solid particles satisfies at least one of the following: after the added solid particles are dissolved in the liquid as the main component, the average particle size of the solid particles is less than the minimum pore characteristic size value of the processed material; after the added solid particles are dissolved in the liquid as the main component, the average particle size of the solid particles is less than the value of the roughness Ra of the machined section of the processed material. For example, the characteristic pore size of the processed material includes the length, width, and height of the pore. Assuming that the size of the pore in a certain direction is the smallest, then this size corresponds to the size value of the minimum pore characteristic of the processed material. For another example, if the roughness Ra of the machined section of the processed material is Ra10μm, then the average particle size of the solid particles is less than 10μm.

[0038] In some embodiments, at the central wavelength of the laser used, the room temperature complex refractive index n1 of the processed material and the effective complex refractive index n2 of the auxiliary liquid at the working temperature must be matched as required, and the difference between the two satisfies the quantitative condition constraint of the following formula: It should be understood that in the above formula, when the requirements for processing damage and processing area quality consistency control are high, the smaller the value within the interval, the greater the value within the interval.

[0039] In some embodiments, in step S2, after the material to be processed is subjected to laser subtractive processing, if the processing quality does not meet the requirements, the process jumps to step S1 and reselects a new auxiliary liquid for processing until the processing quality meets the requirements; wherein, at the central wavelength of the laser used, the effective complex refractive index of the newly selected auxiliary liquid at the working temperature is n4, which satisfies:

[0040] In some embodiments, the laser used is a pulsed laser, and the duration of a single pulse is t p <100ps.

[0041] In some embodiments, the pulse flux F of the pulsed laser used for processing in step S2 is calculated based on F being greater than the processing threshold F0 for material removal and F>Fth, and F th (E2,t p )=(A×E2-B)×t p k In the formula, F th is the single pulse processing threshold of the auxiliary liquid, E2 is the bandgap width of the auxiliary liquid at the working temperature, t p is the single pulse duration, k, A and B are dimensionless constants.

[0042] F th (E2,t p )=(A×E2-B)×t p k The physical meaning is: the pulse laser processing threshold F of the auxiliary liquid th It is a linear function of the bandgap E2 of the auxiliary liquid at the working temperature and is proportional to the duration t of a single pulse of the applied pulsed laser. p to the power of 0.3.

[0043] Furthermore, k is a dimensionless constant typically ranging from 0.25 to 0.35 (e.g., 0.30), and constant A is typically ranging from 0.80 to 1.20 J / (cm 2 ·ps 0.3 ·eV)(A is, for example, 1.00 J / (cm 2 ·ps 0.3 ·eV)), the typical value of B is 1.00~1.55J / (cm 2 ·ps 0.3 )(B is, for example, 1.30 J / (cm 2 ·ps 0.3 )).

[0044] In some embodiments, the processing mentioned above includes the overall contour and local structure of the structure formed by subtractive processing methods such as laser cutting, milling, drilling, and etching.

[0045] In some embodiments, the band gap width E1 of the processed material satisfies 0≤E1≤13.5 eV.

[0046] The auxiliary liquid can be selected from a wide range of liquids, such as inorganic liquids such as water and liquid nitrogen, non-flammable and explosive organic solvents such as ethylene glycol, and colloids. In some embodiments, the auxiliary liquid is a fluid with a bandgap width of E2≥2.0 eV at the working temperature.

[0047] The present invention also provides a laser processing device, which is used to execute the laser processing damage method described above.

[0048] The present invention aims at the problems of prominent processing damage and poor processing consistency in direct dry processing of heterogeneous material structures by ultrafast laser in air or vacuum. By selecting a suitable auxiliary liquid and applying optical parameters matching therewith, the binary interaction between laser and heterogeneous material is transformed into a tripartite interaction among laser, heterogeneous material and auxiliary liquid, thereby achieving comprehensive effects such as stray light suppression, micro-peeling effect of thermal damage zone caused by laser-induced cavitation, and liquid cooling suppression of heat-affected zone, thereby achieving a significant improvement in the quality of heterogeneous materials compared with direct dry processing.

[0049] Example 1

[0050] A method for inhibiting laser processing damage of inhomogeneous materials, the specific steps are as follows: Figure 1 As shown,

[0051] Step 1: According to the laser center wavelength of the selected laser processing system, an auxiliary liquid is selected as the liquid to be filled into the processed part during the laser processing of the processed material, wherein the effective complex refractive index of the auxiliary liquid at the working temperature is n2 and the band gap width is E2, and the room temperature complex refractive index of the processed material is n1 and the band gap width is E1 as a reference,

[0052] The band gap width E1 of the processed material satisfies 0≤E1≤13.5eV; the auxiliary liquid is a fluid with a band gap width E2≥2.0eV at the working temperature; solid particles are allowed to be added to the liquid to form a mixture with flow properties to adjust the effective complex refractive index n2 of the auxiliary liquid, wherein the average particle size of the solid particles after dissolving in the liquid as the main component is smaller than the minimum pore characteristic size value of the processed material, or smaller than the value of the roughness Ra of the processed section of the processed material; the room temperature complex refractive index n1 of the processed material and the effective refractive index n2 of the auxiliary liquid at the working temperature must match as needed, and the difference between the two satisfies |(n1-n2) / (n1+n2) 2∈(0,0.04]] as the quantization condition constraint.

[0053] Step 2: Immerse the workpiece blank of the processed material in the auxiliary liquid in step 1 so that the processed part of the material is fully soaked by the auxiliary liquid. The amount of liquid is based on the amount that the processed part of the workpiece blank of the processed material can just be immersed in the auxiliary liquid.

[0054] Step 3: Set the pulse flux F of the pulsed laser for processing according to the proposed calculation formula, set all other light parameters and light trajectory parameters at the same time, and use the parameters for subtractive processing of the target structure of the processed material until all processing is completed; if the processing quality does not meet the requirements, jump to step 1) until the processing quality meets the requirements.

[0055] The pulse flux F of the pulsed laser used for processing is greater than the processing threshold F0 of the material being processed and F>F th Calculate, and have

[0056] F th (E2,t p )=(A×E2-B)×t p k

[0057] In the formula, F th is the single pulse processing threshold of the auxiliary liquid, E2 is the bandgap width of the auxiliary liquid at the working temperature, t p is the duration of a single pulse, k is a dimensionless constant with a typical value of 0.30, and the typical values ​​of constants A and B are 1.00 J / (cm 2 ·ps 0.3 ·eV)、1.30J / (cm 2 ·ps 0.3 ).

[0058] Step 4: Clean the auxiliary liquid remaining in the target workpiece as required. The auxiliary liquid can be discharged by evaporation effect by placing it naturally, or by accelerating the evaporation of the liquid by blowing air. Alternatively, ultrasonic cleaning can be used according to the processing quality control requirements, and then the evaporation effect can be used to clean the residual auxiliary liquid.

[0059] In Example 1, the processed material is porous polyimide, and its microstructure is a porous material with a porosity of about 80% and a pore characteristic size of 500 μm to 1 mm. The processing goal is to cut a square sheet of 100 mm × 100 mm from the sheet material by laser milling, and a number of rounded square through holes need to be processed on the square sheet.

[0060] The laser of CNC laser processing equipment can emit a Gaussian beam with a central wavelength of 1030nm. After being transmitted by the optical path and focused by the scanning processing head lens, it is projected onto the surface of the workpiece to generate a single pulse sequence with a single pulse duration of 0.8ps and an adjustable pulse frequency of 0.1MHz to 2MHz. The peak flux of the generated spatial Gaussian spot can reach up to 10J / cm 2 , press "1 / e 2 The focused spot diameter defined by the "Gaussian spot diameter" is about 60μm.

[0061] First, referring to the room temperature complex refractive index n1≈1.50+0×i of the matrix of the processed material (i.e., polyimide), its bandgap E1 is about 3.0eV, which satisfies the above constraint on "E1". Referring to the value of n1, we preliminarily consider using economical tap water as the auxiliary liquid. The complex refractive index of this water at a wavelength of 1030nm is about n2≈1.34+0×i, and the bandgap E2≈6.5eV at its working temperature (i.e., room temperature), which satisfies the above constraint on "E2≥2.0eV". At this time, the room temperature complex refractive index n1 of the processed material polyimide and the effective complex refractive index n2 of the auxiliary liquid at the working temperature must be matched as needed, and the difference between the two satisfies (n1-n2) / (n1+n2) 2 ≈0.0032∈(0,0.04]) is the quantization condition constraint.

[0062] In contrast, if the porous matrix of the processed material (i.e., polyimide) is not filled, that is, the filling material is air (i.e., n3≈1.0+0×i), then the difference between the two reflects that the local normal incidence reflectivity on the hole surface will be |(n1-n3) / (n1+n3) 2 ≈0.04: Although the critical value satisfies the condition of “∈(0,0.04]”, the value after filling is only |(n1-n2) / (n1+n2) 2 The reflectivity of ≈0.0032 is one order of magnitude larger. It is worth mentioning that during the laser irradiation of the processed material (i.e., polyimide), the initial complex refractive index will also change: referring to the relevant calculation simulation, the complex refractive index of polyimide can reach the instantaneous level of n1≈1.45+1.0×i. At this time, the interface reflectivity of the excited polyimide-excited water filled with water (water is also ionized by the laser and the complex refractive index also changes) is still significantly lower than the interface of polyimide-air without liquid filling (i.e., the filler is air). Therefore, it is reasonable to use the idea of ​​refractive index matching to reduce the energy reflection of the laser beam at the interface of inhomogeneous material-auxiliary liquid.

[0063] Next, immerse the blank of the processed material (i.e., polyimide) in the tap water selected in step 1, and make the processed part of the material fully soaked by the auxiliary liquid. The amount of water added is based on the amount of water that can just immerse the processed part of the blank in the water.

[0064] Again, the pulse flux F of the pulsed laser for processing is set according to the proposed calculation formula, and all other light parameters and light trajectory parameters are set at the same time, and the parameters are used for subtractive processing of the target structure of the processed material until all processing is completed. Finally, F = (5.0 ~ 10.0) J / cm 2 The pulse flux is used as the processing energy, and the laser milling parameters are filled in the kerf area according to the characteristics of the target structure.

[0065] The selection process of the pulse flux F of the pulsed laser for processing is as follows:

[0066] The pulse flux F of the pulse laser used for processing must be greater than the processing threshold F0 (F0 is about 1.6 J / cm 2 ) and F>F th Select, where the single pulse processing threshold F of water as the auxiliary liquid th According to the following rough estimate:

[0067] F th (E2,t p )=(A×E2-B)×t p k =(1.0×6.5-1.3)×0.8 0.3 ≈4.9J / cm 2

[0068] Where E2 is the bandgap width of water at working temperature, t p The duration of a single laser pulse, k is a dimensionless constant with a typical value of 0.30, and the typical values ​​of constants A and B are 1.00 J / (cm 2 ·ps 0.3 ·eV)、1.30J / (cm 2 ·ps 0.3 ).

[0069] Then, as a continuation of the previous step, the processing quality was checked. Through naked eye observation and optical microscopy, it was found that the use of water as the auxiliary liquid for porous polyimide processing at this laser wavelength and pulse width has good processing quality and meets the product design and manufacturing requirements. For example, by observing the processed cross section of a 100mm×100mm square piece with the naked eye, it was found that the color of the material in the cross section area only changed slightly, and the optical microscopy magnification observation was characterized (see Figure 2) found that the edge thermal damage layer thickness is only tens of microns. Since the quality requirements are met, there is no need to return to the initial step to adjust or replace the auxiliary liquid.

[0070] Finally, according to the processing requirements of the workpiece, the natural evaporation effect of water is used to achieve the discharge of water as an auxiliary liquid through natural placement.

[0071] In contrast, if the water in the specific embodiment of the present invention is not used as the auxiliary liquid in the porous polyimide processing process, while keeping all other light parameters and light trajectory parameters unchanged, the processed cross section is very likely to appear as follows: Figure 3 The "blackened" area is visible to the naked eye, and the distribution of the blackened area and the area close to the original color of the material is somewhat random, resulting in a "random mottled" state on the processed section. If you touch the processed section with your hand, it will appear to be "slag-dropping". This is consistent with Figure 2 The effect in the video is in sharp contrast.

[0072] As a common method, the present invention provides a method for suppressing laser processing damage of heterogeneous materials, and proposes a liquid-assisted ultrafast laser processing method, and the physical mechanism behind it is clear: according to optical reflection principles such as Fresnel's law, the idea of ​​refractive index matching is used to reduce the energy scattering of the laser beam at the interface of the heterogeneous material-auxiliary liquid, thereby achieving an effect similar to laser processing of conventional materials (i.e., homogenized materials) in the heterogeneous material; at the same time, by applying key measures such as an irradiation intensity higher than its processing threshold energy to the auxiliary liquid, the liquid undergoes a phase change after nonlinear light absorption, generating cavitation bubbles, and the instantaneous local mechanical peeling effect generated by the rupture of the cavitation bubbles further achieves the reduction of the thermal damage zone at the edge of the structure; in addition, the liquid cooling mechanism also helps to suppress the generation process of the heat-affected zone. In general, the comprehensive mechanisms such as stray light suppression achieved through refractive index matching, micro-peeling of the thermal damage layer caused by laser-induced cavitation, and liquid cooling to suppress the heat-affected zone have achieved a method for improving the processing quality of heterogeneous materials with clear principles, reliable calculations, simple and effective measures, and strong adjustability compared to the direct dry processing adopted by the conventional method.

[0073] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A method for inhibiting laser processing damage of heterogeneous materials, characterized in that: include: Step S1: Immerse the processed material in the auxiliary liquid so that the processed material is fully infiltrated by the auxiliary liquid at the processed part, wherein the processed material is a solid inhomogeneous material, and at the central wavelength of the laser used, the room temperature complex refractive index of the processed material is n1, the effective complex refractive index of the auxiliary liquid at the working temperature is n2, the room temperature complex refractive index of air is n3, and the auxiliary liquid satisfies: Step S2: performing laser subtractive processing on the material to be processed, and cleaning the residual auxiliary liquid after the processing is completed.

2. The method according to claim 1, characterized in that The microstructure of the processed material is that at the interface between the laser and the material, the material satisfies at least one of the following: the porosity is between 20% and 95% and at least one dimension of the characteristic pore size is distributed in the range of 5μm to 1mm; at the interface between the laser and the material, the roughness of the processed material is distributed in the range of Ra5μm to Ra100μm.

3. The method according to claim 1, characterized in that In addition to the liquid itself as the main component, the auxiliary liquid also contains solid particles, which are used to adjust the effective complex refractive index of the auxiliary liquid at the working temperature. After adding the solid particles, the auxiliary liquid is a mixture with fluid properties.

4. The method according to claim 3, characterized in that The solid particles meet at least one of the following requirements: The solid particles include at least one of silicon nanoparticle powder and NaCl particles; The average particle size of the solid particles after dissolving into the liquid as the main component is smaller than the minimum pore characteristic size value of the processed material; The average particle size of the solid particles after dissolving into the liquid as the main component is smaller than the value of the roughness Ra of the machined section of the machined material.

5. The method according to claim 1, characterized in that The matching relationship between the processed material and the auxiliary liquid satisfies:

6. The method according to claim 1, characterized in that In step S2, after the material to be processed is subjected to laser subtractive processing, if the processing quality does not meet the requirements, jump to step S1 and reselect a new auxiliary liquid for processing until the processing quality meets the requirements.

7. The method according to claim 6, characterized in that At the central wavelength of the laser used, the effective complex refractive index of the newly selected auxiliary liquid at the working temperature is n4, which satisfies:

8. The method according to claim 1, characterized in that The pulse flux F of the pulse laser used for processing in step S2 satisfies: F is greater than the processing threshold F0 for removing the processed material, and F>F th ; F th =(A×E2-B)×t p k In the formula, F th is the single pulse processing threshold of the auxiliary liquid, E2 is the bandgap width of the auxiliary liquid at the working temperature, t p is the duration of a single pulse, k, A and B are dimensionless constants, where k is 0.25-0.35; A is 0.80-1.20 J / (cm 2 ·ps 0.3 ·eV); the value of B is 1.00~1.55J / (cm 2 ·ps 0.3 ).

9. The method according to claim 8, characterized in that The laser used is a pulsed laser and the duration of a single pulse is t p <100ps.

10. The method according to any one of claims 1 to 9, characterized in that The bandgap width E1 of the processed material satisfies 0≤E1≤13.5eV, and the auxiliary liquid is a fluid with a bandgap width E2≥2.0eV at the working temperature.

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