Polycrystalline diamond directional polishing method based on grain anisotropy regulation and control

Abstract

The invention discloses a polycrystalline diamond directional polishing method based on grain anisotropy regulation and control, and belongs to the technical field of superhard material precision machining and surface engineering. A positioning mark is prepared on the to-be-polished surface of polycrystalline diamond, crystallographic information is obtained, and a target polishing area is selected; then, multi-orientation micro-nano scratch testing is conducted on the target polishing area, an atomic scale model is established for simulation analysis, and the optimized polishing direction is determined based on the results of the multi-orientation micro-nano scratch testing and the atomic scale model; and the workpiece is fixed through a polishing clamp, and the target polishing area is polished in the optimized polishing direction. According to the method, the reason of the height difference between the polycrystalline diamond grains is revealed microcosmically, a theoretical basis is provided for eliminating the height difference between the grains, a polishing scheme is provided according to the anisotropic characteristics of the polycrystalline diamond, that is, the purpose of reducing the height difference between the grains is achieved by polishing along the easy polishing direction of the higher grains, and then the surface roughness is reduced; the directional polishing fixing clamp can effectively solve the problem that traditional polishing equipment cannot achieve directional polishing.

Description

Technical Field

[0001] This invention relates to the field of precision machining and surface engineering technology for superhard materials, and in particular to a method for directional polishing of polycrystalline diamond based on grain anisotropy control. Background Technology

[0002] Diamond possesses the highest thermal conductivity, extremely high hardness, and excellent chemical stability among known materials, making it an ideal heat dissipation substrate material for high-power electronic devices. Among these, polycrystalline diamond stands out due to its large size, low-cost fabrication, and high thermal conductivity (800~2000 W / (m²)). The ultra-high thermal conductivity of K) is significantly better than that of traditional substrate materials (such as SiC, whose thermal conductivity is less than 400 W / (m²)). K)) is an ideal material for heat dissipation substrates of high-power chips.

[0003] The surface roughness of polycrystalline diamond directly determines the interfacial heat transport efficiency. When the surface roughness increases from the atomic level to 100 nm, the interfacial thermal resistance increases by approximately two orders of magnitude. Therefore, an atomically smooth surface is crucial for ensuring the application of polycrystalline diamond in chip heat dissipation substrates. Unlike single-crystal diamond, the polished surface of polycrystalline diamond contains numerous grains and no longer maintains its single-crystal nature. In traditional polishing processes, the polishing motion direction is usually fixed or random, without considering the intrinsic strong mechanical anisotropy of diamond—that is, the material removal rate varies significantly between different crystal planes and orientations. This leads to inconsistent material removal rates between adjacent grains due to different orientations during polishing, ultimately forming a difficult-to-eliminate height difference between grains at the grain boundaries. This microscopic height difference is the core obstacle restricting the achievement of atomically smooth polycrystalline diamond surfaces.

[0004] Therefore, there is an urgent need for a polishing method that can reduce the height difference between polycrystalline diamond grains and thus reduce its surface roughness. Summary of the Invention

[0005] The purpose of this invention is to provide a method for directional polishing of polycrystalline diamond based on grain anisotropy control, so as to solve the problems in the background art.

[0006] To achieve the above objectives, the present invention provides a method for directional polishing of polycrystalline diamond based on grain anisotropy control, comprising the following steps: S1. Prepare positioning marks on the polycrystalline diamond surface to be polished, and use crystallographic characterization techniques to obtain crystallographic information within the marked area; based on the crystallographic information, select at least one group of areas containing adjacent grains and having a significant height difference as the target polishing area; S2. Perform multi-oriented micro- and nano-scratching tests on the target polishing area to obtain the material removal response under different scratch directions; establish an atomic-scale model with crystallographic information, and elucidate the generation mechanism and evolution law of the height difference between grains through scratch simulation; determine the optimized polishing direction based on the results of scratch testing and simulation. S3. Use a polishing jig with directional adjustment function to fix the polycrystalline diamond, and polish the target polishing area along the optimized polishing direction confirmed in S2.

[0007] Preferably, in S1, the crystallographic characterization technique is electron backscatter diffraction; the positioning mark is obtained by focused ion beam processing; and the height difference is obtained by atomic force microscopy.

[0008] Preferably, in S1, the crystallographic information includes grain shape, crystal face, and crystal orientation information.

[0009] Preferably, in S1, the target polishing area is a grain group consisting of two adjacent grains.

[0010] Preferably, in step S2, the multi-orientation micro / nano scratch test is performed using an atomic force microscope, and the scratch direction covers a certain angular range.

[0011] Preferably, in S2, the specific modeling method for the atomic-scale model includes: (1) Use modeling software to establish an initial crystal plane model; (2) Use Atomsk software based on the Thiessen polygon algorithm to rotate and merge the initial crystal plane model to obtain the grain group model of the required crystal plane orientation; (3) Delete some atoms to make the grain group model obtain the height difference between grains.

[0012] Preferably, in step S2, the principle for determining the optimized polishing direction is to select a scratch direction that can relatively increase the removal rate of higher grain material in the target polishing area and effectively reduce the height difference.

[0013] Preferably, in step S3, the polishing fixture with orientation adjustment function can rotate the fixed polycrystalline diamond around its normal direction to align it with the optimized polishing direction.

[0014] Preferably, the polishing fixture includes a rotating assembly for mounting the workpiece and adjusting the angle, and a fixed base for docking with external polishing equipment.

[0015] The present invention also provides a directional polishing system for implementing the above-described polishing method, comprising: The characterization module, used to perform sample characterization in step S1, includes at least an electron backscatter diffractometer for crystallographic orientation analysis and an atomic force microscope for morphology and height difference measurement. The analysis and decision module, used to execute step S2, includes at least an atomic force microscope subsystem for scratch testing, software for atomic-scale modeling and simulation, and software for determining the optimized polishing direction based on test and simulation data (the software type is given in the specific embodiment). An execution module is used to perform step S3, and it includes at least a polishing fixture and a chemical mechanical polishing device.

[0016] Preferably, step S2 is implemented using the molecular modeling software MaterialsStudio and Atmosk software to simulate the scratching process of abrasive particles on the surfaces of adjacent grains with height differences.

[0017] Therefore, the polycrystalline diamond directional polishing method based on grain anisotropy control of the present invention has the following beneficial effects: (1) Combining atomic force microscopy scratch experiments with molecular dynamics simulations, and applying them directly to the study of the height difference generation mechanism of specific grain groups, reveals from a physical perspective that the mismatch between the polishing direction and the anisotropic removal rate is the fundamental reason for the height difference between adjacent grains; this transforms the determination of the polishing direction from an empirical choice to a scientific decision based on microscopic mechanisms.

[0018] (2) By developing a dedicated rotatable directional polishing fixture, the optimized polishing direction determined in step S2 for a specific grain group can be accurately reproduced in the macroscopic polishing process, realizing a precise closed loop from microscopic analysis to macroscopic execution, and solving the problem that traditional polishing equipment cannot perform precise directional polishing.

[0019] (3) This method directly targets the “problem area” on the surface (i.e., the grain group with height difference). By polishing along the optimization direction, the height difference in the area is significantly reduced or even eliminated, laying the foundation for obtaining an ultra-smooth surface as a whole.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a flowchart of an embodiment of the present invention; Figure 2 This is a schematic diagram of a "Ⅲ" type positioning mark according to an embodiment of the present invention; Figure 3 The image shows the characterization results of the target polished area in an embodiment of the present invention, wherein (a) is the electron backscatter diffraction characterization image of the selected area, (b) is an enlarged image of the area in the red box in (a), (c) is the atomic force microscope morphology characterization image of the area corresponding to (b), and (d) is the characterization image of the height difference between grains. Figure 4This is a schematic diagram of multi-orientation scratch testing on a target grain group according to an embodiment of the present invention. (a) is an atomic force microscope morphology characterization diagram of the (014)-(234) grain group, and (b) is a local magnified view of the corresponding area in (a) and a schematic diagram of the directional scratch planning. Figure 5 This is a schematic diagram of an atomic-scale grain group model for molecular dynamics simulation according to an embodiment of the present invention, wherein (a) is a schematic diagram of a (011) unit cell model, (b) is a top view of the (014)-(234) grain group with a 0° scratch direction, and (c) is a front view of the (014)-(234) grain group with a 0° scratch direction; Figure 6 This is a schematic diagram of the molecular dynamics simulation of abrasive scratching process according to an embodiment of the present invention; Figure 7 The following are data curves related to the (014)-(234) grain groups obtained through scratch experiments and simulations in this embodiment of the invention. Among them, (a) is the scratch force-scratch distance curve in the 0° scratch direction measured by the experiment, (b) is the scratch force-scratch distance curve in the 0° scratch direction obtained by simulation, (c) is the scratch force-scratch direction curve in the five scratch directions statistically based on experimental data, and (d) is the scratch force-scratch direction curve in the five scratch directions statistically based on simulation data. Figure 8 The following is a diagram showing the results of a finer scratch test on another grain group based on the determined optimized polishing direction in an embodiment of the present invention; wherein, (a) is an electron backscatter diffraction characterization diagram of the selected area, (b) is an atomic force microscope morphology characterization diagram of the area in the red box in (a), (c) is a grain scratch force-scratching direction curve of (124), and (d) is a grain scratch force-scratching direction curve of (223). Figure 9 This is a schematic diagram showing the angular relationship between the optimized polishing direction of the sample surface and the baseline direction in an embodiment of the present invention; Figure 10 This is a schematic diagram of the fixing fixture in an embodiment of the present invention; Figure 11 The images shown are comparison diagrams of the height difference between grains before and after polishing in this embodiment of the invention; wherein, (a) is an atomic force microscope morphology characterization diagram of the selected area before polishing, (b) is a grain height difference characterization diagram of the selected grain group before polishing, (c) is an atomic force microscope morphology characterization diagram of the selected area after polishing, and (d) is a grain height difference characterization diagram of the selected grain group after polishing. Figure label: 1. Internal spline; 2. External spline; 3. Clamping bushing; 4. Base. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some embodiments of the present invention, but not all embodiments.

[0024] Example like Figure 1 As shown, this invention provides a method for directional polishing of polycrystalline diamond based on grain anisotropy control, comprising the following steps: S1. Positioning marks are prepared on the polycrystalline diamond surface to be polished, and crystallographic information within the marked areas is obtained using crystallographic characterization techniques. Based on the crystallographic information, at least one group of regions containing adjacent grains and having a significant height difference is selected as the target polishing area; specifically: 1) Preparation of positioning marks: Type III positioning marks were fabricated on the surface of the polycrystalline diamond sample using a focused ion beam, such as... Figure 2 As shown.

[0025] 2) Crystallographic information acquisition: Electron backscatter diffraction was used to analyze the area around the positioning marker within a 500×500μm region. 2 The region is scanned to obtain information on grain shape, crystal planes, and crystal orientations within that region, generating an electron backscattering diffraction characterization map corresponding to the selected region, such as... Figure 3 As shown in (a).

[0026] 3) Target grain group selection and height difference measurement: A grain group consisting of higher (014) and lower (234) grains was selected from the electron backscatter diffraction characterization region. For example... Figure 3 As shown in (b), the vertically upward crystal orientations of grains (014) and (234) are [17-41] and [-11-27], respectively. High-resolution morphological scanning of this grain group region was performed using atomic force microscopy, as shown in... Figure 3 As shown in (c), through analysis, the height difference between the two grains was extracted and measured to be 18.8 nm. Figure 3 As shown in (d).

[0027] S2. Perform multi-oriented micro / nano scratch tests on the target polishing area to obtain the material removal response under different scratch directions; establish an atomic-scale model to elucidate the generation mechanism and evolution law of intergranular height difference through scratch simulation; based on the results of scratch testing and simulation, determine the optimized polishing direction; specifically: 1) Multi-orientation micro / nano scratch testing: On a selected grain group, a directional scratch experiment was conducted using the scratch module of an atomic force microscope (AFM). With the vertically upward direction defined as 0°, five scratch paths were planned clockwise at 15° intervals (i.e., 0°, 15°, 30°, 45°, 60°) within the range of 0° to 60°. Each scratch should simultaneously pass through two grains in the grain group. Figure 4 As shown in (b), record the scratch force-displacement curves for each scratch direction.

[0028] 2) Atomic-scale modeling and simulation analysis: Based on the precise crystal plane and orientation information of the grain group obtained by electron backscatter diffraction, the corresponding atomic-scale model is constructed, as follows: First, an initial crystal model of a specific diamond crystal facet is created using the molecular modeling software MaterialsStudio (MS), such as... Figure 5 As shown in (a), the (011) crystal plane model is cut out, and its corresponding crystal orientations in the X and Y directions are

[100] and [01-1], respectively.

[0029] Subsequently, using Atomsk software based on the Voronoi Tessellation algorithm, the initial crystal model was rotated and stitched together according to the orientation of the target grains to construct a bicrystalline or polycrystalline model containing grain boundaries. In this embodiment, the (011) crystal plane model was rotated to form a grain group model. The dimensions of the model in the X and Y directions are 100 nm and 24 nm, respectively, and the dimension of the higher grain in the grain group model in the Z direction is 10 nm. The 0° scratch direction model of the high grain (014)-low grain (234) grain group is as follows. Figure 5 As shown in (b) and (c), to ensure consistency between the MD simulation and the AFM scratch test, the grain boundary angle with the Y-axis in the 0° scratch direction model of the high-grain (014)-low-grain (234) grain group was set to 32°. The diamond probe tip radius used in the scratch test was 25nm, and the radius of the spherical diamond abrasive used in the simulation was 3nm. According to this ratio, the grain height difference in the experiment was scaled proportionally to the grain height difference in the model. Therefore, the grain height difference in the high-grain (014)-low-grain (234) grain group model was 2.256nm.

[0030] Finally, some atoms in the lower grains are removed, and an initial height difference proportional to the AFM measurement is introduced into the model; that is, some atoms in the (234) grains are removed so that the grain group model obtains the corresponding inter-grain height difference.

[0031] On the constructed grain set model, the scratching process of spherical diamond abrasive grains is simulated, such as... Figure 6As shown, both the grain model and the abrasive grains are divided into a Newtonian layer, an isothermal layer, and a stationary layer. The Newtonian layer is the interaction region between the grain model and the abrasive grains. The isothermal layer maintains a fixed temperature during the scratching process to absorb the generated heat. The velocity and force of the stationary layer are set to 0, fixing the grain model in place. The thickness of both the isothermal and stationary layers in the grain model is set to 1 nm, with the remaining portion being the Newtonian layer. In the abrasive grains, the radius of the stationary layer is 1 nm, the radius difference of the isothermal layer is 0.5 nm, and the remaining 1.5 nm radius difference is the Newtonian layer. The conjugate gradient method is used to minimize the energy of the model, and then the model is relaxed under the NVE ensemble. During the scratching simulation, both the Newtonian layer and the isothermal layer are set to the NVE ensemble. Periodic boundary conditions are selected for the X and Y directions of the grain model, and a stationary boundary condition is selected for the Z direction, with a time step of 1 fs. The Tersoff bond order potential is used to describe the interaction between CC atoms. The velocity of the abrasive grains along the X direction is set to 100 m / s. A fixed load of 4μN is applied to the abrasive grains in the Z direction, and the scratch distance is 80nm, of which the scratch distance on the first grain is 45nm.

[0032] Based on the simulation parameters that are comparable to those in the experiment, the simulated scratch force-distance curve can be obtained through simulation, and the movement of atoms, bond breaking and reconstruction during the scratching process can be visualized. This reveals the differences in material removal behavior under different scratch directions and the mechanism of height difference generation and evolution at the atomic scale.

[0033] By combining AFM scratch test data and molecular dynamics simulation results, the variation of scratch force (indirectly reflecting the difficulty of material removal) with direction was analyzed. The basic principle for determining the polishing direction is to select a scratch direction that can relatively increase the material removal rate of the higher grains in the target grain group, thereby making the heights of the two grains tend to be consistent.

[0034] In this embodiment, the scratch force-scratch distance curves for the scratch test and scratch simulation at the 0° scratch direction are as follows: Figure 7 As shown in (a) and (b), it can be seen that the scratching force of abrasive particles varies on different crystal planes. Statistical experimental and simulated scratching force-scratch direction curves are shown below. Figure 7As shown in (c) and (d), the scratching force exhibits significant anisotropy within the same crystal plane, consistent with experimental and simulation findings. The 30° scratching direction of the (234) grain exhibits the strongest scratching force compared to the other four directions, making the scratched material easier to remove ("soft" direction); while the 60° direction has the weakest scratching force, making the scratched material more difficult to remove ("hard" direction). In contrast, the 30° scratching direction of the (014) grain has a weaker scratching force, making material removal more difficult. Therefore, it can be inferred that polishing the (234) crystal plane along the 30° direction of the high-grain (014) - low-grain (234) grain group results in a much higher surface material removal rate than polishing the (014) crystal plane, which is the core reason for the 18.8 nm height difference between the two grains. Therefore, polishing along the "easy" scratching direction of the higher grain can effectively reduce the height difference between grains.

[0035] To more accurately pinpoint the "polishable" direction of individual grains, a full-range scratch study from 0° to 360° can be conducted on individual grains (especially higher-grade grains) within a grain group. Based on... Figure 8 The electron backscattering diffraction pattern shown in (a) is used to characterize the grains of the low-grain (124) to high-grain (223) range. A directional scratch experiment was conducted, and the atomic force microscopy morphology of the selected grain groups is shown below. Figure 8 As shown in (b). The orientation scratch experiment involved scratching within a single grain in the range of 0° to 360°, with a crystal orientation interval of 45°. Nine scratch experiments were performed using an atomic force microscope along the directions of 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°, and 360°. The scratch results are shown below. Figure 8 As shown in (c) and (d), it can be seen that the scratching force of the higher grain (223) in the 90° direction is greater than that in other directions, making it an "easy" polishing direction. At this time, 90° is not an "easy" polishing direction for the lower grain (124). Therefore, the polishing experiment was carried out along the 90° direction of the (223) grain.

[0036] Combination Figure 7 and Figure 8 Analysis determined that polishing should be performed along the 90° direction of the higher grain (223). A linear mark was fabricated on the sample surface using a focused ion beam. This mark was used to determine the polishing direction during the experiment, establishing the angular relationship between the linear mark and the 90° direction of the (223) grain, as shown below. Figure 9 As shown, the angle between the 90° direction of the (223) grain and the linear mark is 135°.

[0037] S3. Fix the polycrystalline diamond sample using a polishing fixture with directional adjustment function, and polish the target polishing area along the optimized polishing direction confirmed in S2, specifically as follows: 1) Oriented Polishing Fixture: Design and fabricate a specialized polishing fixture with high-precision angle adjustment capabilities. The fixture includes a rotating assembly for mounting the workpiece and adjusting the angle, and a fixed base for docking with external polishing equipment. Specifically, as follows... Figure 10 As shown, the assembly includes a fixed base 4 for docking with external polishing equipment, and a rotating component comprising a clamping bushing 3, an internal spline 1, and an external spline 2. The base 4 mates with a square mounting bracket in the polishing equipment, thus requiring wire EDM to machine the square hole. Support is also needed for the clamping bushing 3, which is clamped to the base 4 using four M5 socket head cap screws and hexagonal nuts. The screw selection is based on the national standard GB / T912-2016. The base 4 is made of 45 steel, a material that combines strength and toughness, ease of machining, and low cost, making it suitable for the operating environment of the base 4. In addition to positioning itself with the base 4, the clamping bushing 3 also provides clamping force to the internal spline 1. Therefore, two "ear" structures are machined on the outer surface of the bushing, which are used with M6 socket head cap screws and hexagonal nuts according to GB / T912-2016 to clamp or release the bushing. When clamped, the internal spline 1 is fixed relative to the bushing. When relaxed, the inner spline 1 can rotate relative to the bushing. This function facilitates adjustment of the sample's orientation. Based on these functions, the clamping bushing 3 is made of 65Mn spring steel. This material has an extremely high elastic limit, meeting the elastic deformation required for bushing clamping. Furthermore, 65Mn spring steel possesses high strength and hardness, ensuring that the bushing's "ears" will not deform or wear when clamped by screws and nuts. The inner spline 1 is selected according to GB / T1144-2001. The outer spline 2 is a non-standard part based on GB / T1144-2001. The dimensions and tolerances of the number of teeth, major diameter, minor diameter, and key width of the inner and outer splines are designed according to national standards. This ensures that after the outer spline 2 mates with the inner spline 1, the outer spline 2 can slide up and down inside the inner spline 1 but cannot rotate due to the restriction of the inner spline 1. A blind hole is drilled on the upper surface of the outer spline 2 for adding weights or other counterweights to enhance the diamond polishing process. The lower end face of external spline 2 has a circular hole at its center, large enough to accommodate a PCD wafer. The depth of the hole is 60% of the wafer thickness, ensuring that the wafer does not detach from the fixture during polishing and that its surface can be polished. The internal and external splines are made of 40Cr, a material that, after tempering, possesses excellent plasticity, toughness, and strength, ensuring that the splines are resistant to brittle fracture. Furthermore, its high hardness reduces surface wear and pitting.

[0038] 2) Polishing process execution: The polycrystalline diamond workpiece is mounted on the aforementioned directional polishing fixture, and the fixture is adjusted so that the surface of the workpiece to be polished is aligned with the surface of the fixture. Figure 9 The established correspondence is precisely aligned with the optimized polishing direction determined in step S2, so that the 90° direction of the (223) grains is consistent with the main polishing motion direction.

[0039] Secure the assembly with the workpiece and fixture to the worktable of a chemical mechanical polishing (CMP) or other polishing equipment.

[0040] Using a polishing slurry suitable for diamond polishing, and setting appropriate process parameters such as polishing pressure and polishing head speed, directional polishing is performed along a fixed optimized direction.

[0041] After polishing for a period of time, the workpiece can be removed, and the morphology of the original polished area can be measured again using AFM. The AFM images and line contours before and after polishing can be compared. Figure 11 As shown, it can be intuitively observed that the height difference between grains is significantly reduced, verifying the effectiveness of this method.

[0042] Therefore, this invention provides a directional polishing method for polycrystalline diamond based on grain anisotropy control, which reveals the cause of the height difference between polycrystalline diamond grains from a microscopic perspective, providing a theoretical basis for eliminating the height difference between grains. Unlike existing polishing techniques, this method proposes polishing along the "easier" polishing direction of higher grains based on the anisotropic characteristics of polycrystalline diamond to reduce the height difference between grains, thereby reducing surface roughness. The developed directional polishing fixture can effectively solve the problem that traditional polishing equipment cannot achieve directional polishing.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for directional polishing of polycrystalline diamond based on grain anisotropy regulation, characterized in that, The method comprises the following steps: S1, preparing a positioning mark on a polycrystalline diamond surface to be polished, and obtaining crystallographic information in the mark area by using a crystallographic characterization technique; Based on the crystallographic information, at least one group of regions containing adjacent grains and having height differences are selected as target polishing regions; S2, performing multi-orientation micro-nano scratch tests on the target polishing regions to obtain material removal responses under different scratch directions; An atomic scale model is established to clarify the generation mechanism and evolution law of the height difference between grains through scratch simulation; based on the results of scratch tests and simulation, the optimal polishing direction is determined; S3, fixing the polycrystalline diamond by using a polishing clamp with directional adjustment function, and polishing the target polishing regions along the optimal polishing direction determined in S2.

2. The method according to claim 1, wherein the method is characterized by: In S1, the crystallographic characterization technique is electron backscatter diffraction technology; the positioning mark is obtained by focused ion beam processing; and the height difference is obtained by atomic force microscope measurement.

3. The method of claim 1, wherein the method is a method of directional polishing of polycrystalline diamond based on the anisotropy of the crystal grains. In S1, the crystallographic information includes grain shape, crystal face and crystal direction information.

4. The method of claim 1, wherein the method is a method of directional polishing of polycrystalline diamond based on the anisotropy of the crystal grains. In S1, the target polishing region is a grain group composed of two adjacent grains.

5. The method of claim 1, wherein the method is a method of directional polishing of polycrystalline diamond based on the anisotropy of the crystal grains. In S2, the multi-orientation micro-nano scratch test is realized by atomic force microscope, and the scratch direction covers a certain angle range.

6. The method of claim 1, wherein the method is a method of directional polishing of polycrystalline diamond based on the anisotropy of the crystal grains. In S2, the principle for determining the optimal polishing direction is to select a scratch direction that can relatively increase the material removal rate of the higher grain in the target polishing region and effectively reduce the height difference.

7. The method of claim 1, wherein the method is a method of directional polishing of polycrystalline diamond based on the anisotropy of the crystal grains. In S3, the polishing clamp with directional adjustment function can rotate the fixed polycrystalline diamond around its normal direction to align the optimal polishing direction.

8. The method of claim 7, wherein the method is a method of directional polishing of polycrystalline diamond based on the anisotropy of the crystal grains. The polishing clamp comprises a rotating assembly for installing the workpiece and adjusting the angle, and a fixed base for interfacing with an external polishing device.

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