Characterization method of polycrystalline material interface orientation

Abstract

The invention discloses a characterization method of polycrystalline material interface orientation, and belongs to the technical field of crystallography and material characterization. According to the method, etching is carried out after a protective layer is deposited on a target interface by using a focused ion beam, scanning images of a sample surface and an etching surface are collected, and an included angle between interface traces on the sample surface and the etching surface and a sample coordinate system is measured. And after the measured included angle of one surface is subjected to manual tilt correction, the normal direction of the interface is calculated by utilizing the outer product of the trace direction vectors on the surface of the sample and the etching surface. According to the method, the sample does not need to be rotated for multiple times, and all required data can be obtained only through single scanning, so that the characterization efficiency is greatly improved, the method is suitable for large-scale automatic interface orientation measurement, and powerful technical support is provided for research on a polycrystalline material micromechanism.

Description

Technical Field

[0001] The invention relates to the technical field of crystallography and material characterization, and in particular to a method for characterizing the interface orientation of a polycrystalline material. Background Art

[0002] Polycrystalline materials usually contain a large number of interfaces, such as grain boundaries, twin boundaries and phase boundaries. The orientation of these interfaces has an important influence on the microstructural evolution, chemical properties and mechanical properties of the materials. Accurate characterization of interface orientation is not only the basis for studying the deformation, phase transition and microscopic mechanism of polycrystalline materials, but also has important significance for predicting the evolution of material organization, optimizing mechanical properties, solving material failure problems and guiding material design and preparation.

[0003] At present, compared with traditional grain boundary orientation characterization methods (such as continuous cross-section method, two-surface trace method, three-dimensional reconstruction method and stereology method), the method based on focused ion beam (FIB) etching to characterize interface orientation has higher flexibility. It can combine multiple characterization methods such as electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), energy dispersive spectrum analysis (EDS) in the same device to perform directional analysis on grain boundaries with specific characteristics.

[0004] The traditional FIB characterization process usually includes the following steps: (1) establish a three-dimensional sample coordinate system on the sample surface; (2) place the sample in a dual-beam focused ion beam-scanning electron microscope (FIB-SEM), adjust the sample stage to a horizontal position, find the target interface and rotate it horizontally to be parallel to the Y-axis of the electron microscope coordinate system, and manually record the rotation angle; then keep the target interface parallel to the Y-axis of the electron microscope coordinate system and move the target interface to the center of the electron microscope view; (3) rotate the sample stage around the X-axis of the electron microscope coordinate system so that the sample surface is perpendicular to the focused ion beam, and use The focused ion beam is deposited and etched on the sample surface corresponding to the target interface to form an etched surface perpendicular to the sample surface; (4) The etched surface is scanned by an electron beam to obtain the angle between the interface trace of the target interface on the etched surface and the Z axis of the sample coordinate system. After correcting the angle, the normal vector of the target interface is calculated using the angle. The outer product of the normal vector of the target interface and the sample rotation matrix is ​​the normal vector of the target interface in the sample coordinate system; (5) Finally, the sample stage is rotated to a horizontal position, and steps (2)-(4) are repeated to characterize other interfaces. This process not only requires multiple adjustments to the sample stage angle and manual positioning of the target grain boundary, but also requires manual recording of the rotation data, which results in cumbersome operations and a long experimental cycle, making it difficult to meet the needs of large-scale, efficient interface orientation characterization.

[0005] In addition, although modern dual-beam electron microscope equipment is equipped with automatic micro-nano processing programs, the existing FIB characterization process still relies mainly on manual operation and cannot achieve fully automatic measurement of interface orientation. This technical bottleneck not only limits the comprehensive statistical analysis of the interface orientation of polycrystalline materials, but also hinders the in-depth understanding of the evolution of material microstructures, deformation mechanisms and failure behaviors. Therefore, the development of an efficient and automated interface orientation characterization method has important scientific significance and application value. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a method for characterizing the interface orientation of polycrystalline materials, so as to solve the problems of the existing method for characterizing interface orientation, such as complicated operation, long experimental cycle, and difficulty in meeting the needs of large-scale and efficient interface orientation characterization.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for characterizing the interface orientation of a polycrystalline material comprises the following steps:

[0009] (1) Establishing a sample coordinate system XYZ on the surface of a smooth polycrystalline sample; making the Z axis perpendicular to the sample surface, and the X axis and Y axis parallel to the sample surface and perpendicular to each other;

[0010] (2) placing the sample in a dual-beam focused ion beam-scanning electron microscope, rotating the electron microscope sample stage so that the sample surface is perpendicular to the focused ion beam, and using the focused ion beam to sequentially deposit a protective layer and etch on the sample surface portion corresponding to the target interface to form an etched surface perpendicular to the sample surface;

[0011] (3) using an electron beam to simultaneously scan and image the sample surface and the etched surface, and based on the scanned image, measuring the angle α between the interface trace of the target interface on the sample surface and the X-axis and the angle β' between the interface trace of the target interface on the etched surface and the Z-axis, and performing a tilt correction on β' to obtain a corrected angle β;

[0012] (4) Calculate the direction vector v of the interface trace of the target interface on the sample surface based on α and β 1 and the direction vector v of the interface trace of the target interface on the etched surface 2 , v 1 and v 2 The outer product of is the target interface normal vector n in the sample coordinate system, thereby completing the characterization of the interface orientation of the polycrystalline material.

[0013] Further, in step (3), the correction formula for the angle between the interface trace of the target interface on the etched surface and the Z axis is:

[0014] β=atan((tan(β') / cos(θ))×sin(θ))

[0015] θ is the rotation angle of the electron microscope sample stage in step (2).

[0016] Furthermore, in step (4), v 1 and v 2 The expression is:

[0017] v 1 =(cos(α),sin(α),0)

[0018] v 2 =(-sin(β),0,cos(β)).

[0019] Furthermore, in step (2), when depositing the protective layer, the ion beam current is 20 kV / 240 pA; when etching, the ion beam current is 20 kV / 4 nA.

[0020] Furthermore, when characterizing different target interfaces of the same sample, after the characterization of the previous target interface is completed, the sample is translated on the sample stage and steps (2)-(4) are repeated to characterize the next target interface until the characterization of all target interfaces is completed.

[0021] Furthermore, in step (3), when scanning with an electron beam, the electron beam is not parallel to any of the sample surface and the etched surface, and the interface trace orientation of the target interface on the sample surface and the etched surface is simultaneously obtained through a single scan. The direction of the electron beam is not parallel to any of the sample surface and the etched surface, because once the electron beam is parallel to a certain surface, the surface will appear as a line in the scanned image, and the interface trace on the surface cannot be observed.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention provides a method for characterizing the interface orientation of polycrystalline materials. The method synchronously obtains the interface trace data of the target interface on the sample surface and the etched surface through a single scan, and then obtains the interface trace vector of the target interface on the sample surface and the etched surface by combining the angle measurement and tilt correction algorithm. Finally, the interface normal vector is directly obtained by the outer product operation of the interface trace vector. Compared with the traditional FIB characterization technology, the present invention does not need to adjust the sample stage multiple times and manually record the horizontal rotation angle, nor does it need to manually locate the target interface (i.e., move the target interface back to the center of the electron microscope view), which greatly simplifies the operation steps and improves the accuracy and efficiency of interface orientation characterization.

[0024] 2. The method of the present invention is compatible with the FIB-SEM automated micro-nano processing system, supports batch interface continuous etching and data collection, has the potential for large-scale interface orientation measurement, and provides a standardized solution for high-throughput and high-precision characterization of interface orientation of polycrystalline materials, especially suitable for microscopic mechanism research in the fields of aerospace materials, semiconductor devices, etc. When the method of the present invention is used to characterize different grain boundaries of the same polycrystalline material, under the same experimental conditions and equipment, the characterization of 113 target interfaces can be successfully completed within 24 hours. However, the traditional FIB characterization method can only complete the characterization of 10 target interfaces within 24 hours. The efficiency of the method of the present invention is about ten times that of the traditional FIB characterization method. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the target interface, sample surface and etching surface after FIB etching according to the present invention;

[0026] Figure 2 Schematic diagram of the algorithm of the present invention: (a) interface scanning diagram after etching, (b) schematic diagram of interface trace correction on the etched surface, (c) schematic diagram of interface orientation calculation;

[0027] Figure 3 The material scans obtained after etching by the method of the present invention (a) and the conventional FIB etching method (b) in Example 1;

[0028] Figure 4 The material scans obtained after etching by the method of the present invention (a) and the conventional FIB etching method (b) in Example 2;

[0029] Figure 5 This is the distribution diagram obtained by large-scale characterization of 113 interfaces in Example 3; (a) and (b) are interface distribution diagrams after interface characterization at different positions of the same sample using the method of the present invention. DETAILED DESCRIPTION

[0030] The specific implementation modes of the present invention are further described in detail below in conjunction with specific examples.

[0031] 1. The present invention provides a method for characterizing the interface orientation of a polycrystalline material, comprising the following steps:

[0032] (1) Establishing a sample coordinate system XYZ on the surface of a smooth polycrystalline sample; making the Z axis perpendicular to the sample surface, and the X axis and Y axis parallel to the sample surface and perpendicular to each other;

[0033] (2) placing the sample in a dual-beam focused ion beam-scanning electron microscope (FIB-SEM), rotating the electron microscope sample stage around the X-axis of the electron microscope coordinate system so that the sample surface is perpendicular to the focused ion beam, the rotation angle is recorded as θ, and using the focused ion beam to sequentially deposit and etch a protective layer on the sample surface corresponding to the target interface to form an etched surface perpendicular to the sample surface;

[0034] (3) An electron beam is used to simultaneously scan and image the sample surface and the etched surface, and based on the scanned image, an angle α between the interface trace of the target interface on the sample surface and the X-axis and an angle β' between the interface trace of the target interface on the etched surface and the Z-axis are measured, and β' is tilt-corrected to obtain a corrected angle β; when scanning with an electron beam, the electron beam is not parallel to any surface of the sample surface and the etched surface, and the interface trace orientation of the target interface on the sample surface and the etched surface is simultaneously obtained through a single scan.

[0035] (4) Calculate the direction vector v of the interface trace of the target interface on the sample surface based on α and β 1 and the direction vector v of the interface trace of the target interface on the etched surface 2 , and its outer product is the normal vector n of the target interface in the sample coordinate system.

[0036] Figure 1 Schematic diagram of the target interface, sample surface and etching surface after FIB etching in the present invention; Figure 1 It can be seen that based on the method of the present invention, after FIB etching, the target interface intersects with the sample surface and the etched surface, and clear interface traces can be observed on both surfaces. Since both interface traces are located on the target interface, the three-dimensional orientation of the target interface can be directly derived by analyzing the spatial orientation relationship between the two in the sample coordinate system and combining the vector outer product calculation.

[0037] Figure 2 a is a scanning diagram of the interface after etching using the method of the present invention, such as Figure 2 As shown in a, the interface traces of the target interface can be observed on the sample surface and the etched surface respectively. According to the angle between the interface trace and the sample coordinate system, v can be obtained. 1 and v 2 :

[0038] v 1 =(cos(α),sin(α),0)

[0039] v 2 =(-sin(β),0,cos(β))

[0040] Among them, α is the angle between the interface trace of the target interface on the sample surface and the X-axis, and β is the angle between the interface trace of the target interface on the etched surface and the Z-axis after correction.

[0041] Figure 2 b is a schematic diagram of the interface trace correction on the etched surface. Figure 2 As shown in FIG. 2 , since the sample surface and the etched surface have different angles with the electron beam, this will cause the information in the scanned image to be distorted when it is projected onto the projection surface. Normally, the scanned image will be corrected according to the angle between the sample surface and the projection surface to obtain an image consistent with the actual sample surface. However, since the angle between the etched surface and the projection surface is different from that of the sample surface, the image of the etched surface will still have a large error, so the etched surface needs to be corrected twice. In the present invention, the correction formula for the angle β between the interface trace on the etched surface and the Z axis is:

[0042] β=atan((tan(β') / cos(θ))×sin(θ))

[0043] Where β' and β are the original angle and the corrected angle of the target interface trace on the etched surface relative to the Z-axis direction of the sample coordinate system, respectively. θ is the rotation angle of the electron microscope sample stage.

[0044] Figure 2 c is a schematic diagram of interface orientation calculation, such as Figure 2 As shown in c, the sample surface and the etched surface are perpendicular. According to the corrected angle, the direction vector of the interface trace of the target interface on the sample surface and the etched surface can be obtained, and the orientation vector n perpendicular to the target interface in the sample coordinate system can be calculated by its outer product:

[0045] n=v1×v2

[0046] Among them, v 1 and v 2 Represent the interface trace vectors of the target interface on the sample surface and the etched surface respectively.

[0047] 2. Embodiment

[0048] Example 1

[0049] Studies have shown that during the deformation twinning process of Ti-15Mo alloy, the twin interface is generally relatively straight, and the interface orientations at different positions in the same twin are basically the same. Therefore, this study selected the twin interface of Ti-15Mo alloy as the characterization target and compared the reliability of the method of the present invention and the traditional FIB etching method in measuring the interface orientation.

[0050] The method for characterizing the twin interface of the Ti-15Mo alloy provided in this embodiment comprises the following steps:

[0051] S1. Sample pretreatment

[0052] Firstly, the Ti-15Mo alloy was placed in a muffle furnace at 900°C for 1 hour and then quenched in water to obtain a Ti-15Mo alloy sample with a full β phase structure.

[0053] Subsequently, a compression specimen with a size of 9 mm × 6 mm × 6 mm was cut from the Ti-15Mo alloy sample and subjected to a strain test at a strain rate of 10 -3 s -1 A compression deformation test with a deformation amount of 2% was performed to form twins in the sample.

[0054] Next, the sample surface was polished with sandpaper of No. 400, 800, and 2000 in turn, and then the sample surface was electropolished to prepare a smooth sample surface. The polishing liquid was a mixed solution of 60% (v / v) methanol + 34% (v / v) n-butanol + 6% (v / v) perchloric acid, and the specific parameters of electropolishing were: voltage 30V, temperature -30℃, and time 30s.

[0055] S2. Interface Orientation Characterization

[0056] (1) Establish a sample coordinate system XYZ on the smooth sample surface, where the Z axis is perpendicular to the sample surface, and the X axis and Y axis are parallel to the sample surface and perpendicular to each other.

[0057] (2) Place the sample in a Zeiss Auriga FIB-SEM dual-beam electron microscope, then rotate the sample stage 54° around the X-axis of the electron microscope coordinate system so that the sample surface is perpendicular to the focused ion beam, and move the sample so that the target interface is within the observation window. The method for determining the target interface is as follows: by changing the magnification of the microscope, the position of the grain boundary can be observed, and a grain boundary to be studied is selected as the research object, and the determination of the target interface is completed.

[0058] (3) Using a focused ion beam, a protective layer is deposited and etched on the sample surface corresponding to the target interface in sequence, forming an etched surface perpendicular to the sample surface; when depositing the protective layer, the ion beam current is 20kV / 240pA; when etching, the ion beam current is 20kV / 4nA. In this embodiment, when depositing the protective layer, a focused ion beam (FIB) is used to deposit a platinum (Pt) layer. The principle is: a high-energy ion beam (such as gallium ions, Ga + ) bombards the sample surface corresponding to the target interface, and at the same time sprays a metal organic precursor gas containing platinum (such as MeCpPtMe 3). The energy of the ion beam decomposes the precursor molecules, releasing platinum atoms that are deposited on the surface, while the organic components are converted into volatile byproducts that are removed by the vacuum system. By precisely controlling the scanning path of the ion beam, a platinum layer with nanometer-level precision is deposited layer by layer. Here, the purpose of depositing the protective layer is to ensure that the interface between the sample surface and the etched surface is well preserved during the subsequent etching process, thus presenting a complete right-angle shape.

[0059] (4) using an electron beam to simultaneously scan and image the sample surface and the etched surface, and based on the scanned images, respectively measuring the angle α between the interface trace of the target interface on the sample surface and the X-axis and the angle β' between the interface trace of the target interface on the etched surface and the Z-axis, and performing a tilt correction on β' to obtain a corrected angle β;

[0060] Figure 3 a is a scanning image of the target interface after etching obtained in this embodiment. From the scanning image, it can be measured that after tilt correction, α is 111.2°; β' is -4.1°, and after secondary correction, β is -5.6°.

[0061] (5) Calculate the direction vector v of the interface trace of the target interface on the sample surface based on α and β 1 and the direction vector v of the interface trace of the target interface on the etched surface 2 , and its outer product is the normal vector n of the target interface in the sample coordinate system.

[0062] According to α and β, we can get v 1 and v 2 :

[0063] v 1 =(cos(α),sin(α),0)=(-0.3616,0.9323,0)

[0064] v 2 =(-sin(β),0,cos(β))=(0.0976,0,0.9952)

[0065] The target interface normal can be expressed by the outer product vector of the above two vectors:

[0066] n=v 1 ×v 2 =(0.9279,0.3599,-0.0910)

[0067] In order to verify the reliability of the method for characterizing the interface orientation of the present invention, the traditional FIB etching method was used to characterize the same twin interface orientation.

[0068] The conventional FIB etching method for characterizing interface orientation includes the following steps:

[0069] (1) A sample coordinate system XYZ is established on the smooth surface of the Ti-15Mo alloy sample, where the Z axis is perpendicular to the sample surface, and the X axis and Y axis are parallel to the sample surface and perpendicular to each other.

[0070] (2) Place the sample into a Zeiss Auriga FIB-SEM dual-beam electron microscope and adjust the sample stage to a horizontal position to determine the target interface to be characterized. The determination method is as follows: by changing the magnification of the microscope, the position of the grain boundary can be observed. A grain boundary to be studied is selected as the research object, and the determination of the target interface is completed.

[0071] (3) Rotate the sample stage horizontally so that the target interface is parallel to the Y axis of the electron microscope coordinate system, and manually record the rotation angle; the rotation process in this experiment is: counterclockwise rotation of 339.4°, the rotation angle is recorded as α; then keep the target interface parallel to the Y axis of the electron microscope coordinate system and move the target interface to the center of the electron microscope view;

[0072] (4) Rotate the sample stage around the X-axis of the electron microscope coordinate system so that the sample surface is perpendicular to the focused ion beam. The rotation angle is denoted as θ. Use the focused ion beam to sequentially deposit and etch a protective layer on the sample surface corresponding to the target interface to form an etched surface perpendicular to the sample surface. During deposition, the ion beam current is 20 kV / 240 pA; during etching, the ion beam current is 20 kV / 4 nA.

[0073] (5) Scanning and imaging the etched surface with an electron beam, measuring the angle β' between the interface trace of the target interface on the etched surface and the Z axis of the sample coordinate system, and correcting β' to obtain β;

[0074] Figure 3 b is the scanning image of the etched surface obtained by the traditional method. It can be seen from the figure that the angle β' between the interface trace on the etched surface and the Z axis of the sample coordinate system is -6.2°. After correction, the actual angle β is -8.5°.

[0075] β=atan((tan(β') / cos(θ))×sin(θ))

[0076] (6) Use β to calculate the normal vector v of the target interface 3 , and according to the normal vector v 3 The normal vector n' of the target interface in the sample coordinate system is calculated using the rotation matrix T of the sample.

[0077] The algorithm is as follows:

[0078] After the sample stage is rotated horizontally, the normal vector of the target interface in the electron microscope coordinate system can be expressed as:

[0079] v 3=(cos(β),0,sin(β))=(0.9897,0,-0.1431)

[0080] The rotation matrix T of the sample can be expressed as:

[0081]

[0082] In the sample coordinate system, the normal vector n' of the target interface can be expressed as:

[0083] n'=v 3 T=(0.9258,0.3480,-0.1478)

[0084] The target interface normal vectors n and n' obtained by the above two methods are very close, and the slight difference mainly comes from the error of measuring the angle from the scan image, which verifies the accuracy and reliability of the method of the present invention.

[0085] Example 2

[0086] To further verify the accuracy of the method of the present invention, the interface orientation of another twin boundary of the same sample was characterized using the same experimental equipment, experimental parameters and experimental steps as in Example 1.

[0087] Figure 4 a shows a scanning diagram of the target interface obtained by the method of the present invention. In this figure, the angle α between the interface trace of the target interface on the sample surface and the X-axis is 61.3°, and the angle β' between the interface trace of the target interface on the etched surface and the Z-axis is 11.4°. After correction, the angle β between the interface trace on the etched surface and the Z-axis of the sample coordinate system is 15.5°.

[0088] The interface traces of the target interface on the sample surface and the etched surface are expressed by vectors as follows:

[0089] v 1 =(0.4802,0.8771,0)

[0090] v 2 =(-0.2672,0,0.9636)

[0091] The target interface normal can be expressed as the outer product vector of the above two vectors:

[0092] n=(0.8452,-0.4628,0.2344)

[0093] The twin interface described in this embodiment is characterized using a conventional FIB etching method, which is the same as the conventional FIB etching method described in Example 1, except that the angle of horizontal rotation of the sample stage is different, which is 29.4° counterclockwise.

[0094] After etching using the traditional FIB etching method, the scanned image of the etched surface is as follows: Figure 4 As shown in b, Figure 4 From b, it can be seen that the angle between the interface trace of the target interface on the etched surface and the Z-axis of the sample coordinate system is 13.2°, and the actual angle after correction is about 17.9°.

[0095] After the sample stage is rotated horizontally, the normal vector of the target interface can be expressed as:

[0096] v 3 =(cos(β),0,sin(β))=(0.9516,0,0.3074)

[0097] The rotation matrix T of the sample can be expressed as:

[0098]

[0099] The normal vector n' of the target interface in the sample coordinate system can be expressed as:

[0100] n'=v 3 T=(0.8290,-0.4671,0.3074)

[0101] The target interface normal vectors n and n' obtained by the above two methods are very close, and the slight difference mainly comes from the error of measuring the angle from the scan image, which verifies the accuracy and reliability of the method of the present invention.

[0102] Example 3

[0103] In order to verify the efficiency of the method of the present invention, a cubic sample with a side length of 4 mm was cut from an AZ31 magnesium alloy extruded rod. First, one side of the sample was polished in turn using 400, 800, and 2000 sandpapers to make its surface flat; then, electrolytic polishing was performed using a commercial ACII magnesium alloy polishing liquid, and the polishing parameters were set to a voltage of 20 V, a temperature of -30 ° C, and a time of 90 s. After polishing, a smooth AZ31 magnesium alloy sample was obtained.

[0104] Next, the processed sample was placed in a ZeissAuriga FIB-SEM dual-beam electron microscope. The sample stage was first rotated 70° around the X-axis of the electron microscope coordinate system, the target area was selected and an EBSD image was taken. The EBSD data was processed by AZtec software to obtain the grain boundary distribution map of the target area. Based on the grain boundary distribution map and the sample surface morphology, the target interface set to be characterized was selected.

[0105] Then, the interface orientation characterization method described in step S2 of Example 1 was used to characterize the interface orientation of the selected target interfaces in turn. Finally, the characterization of 113 target interfaces was successfully completed within 24 hours, and the interface distribution was as follows: Figure 5 Under the same operating personnel and equipment conditions, the traditional FIB etching method for characterizing interface orientation can only characterize about 10 target interfaces within 24 hours, so the efficiency of the method of the present invention is about ten times that of the traditional method.

[0106] It should be noted that, when the present invention sequentially characterizes multiple interfaces of the same polycrystalline material, the operation can be completed by only translating the sample, without rotating the sample stage multiple times or manually locating the target interface position, while avoiding manual recording of the horizontal rotation angle.

[0107] In Example 1 and Example 2, the comparison of the characterization results of two interfaces with different orientations by the method of the present invention and the traditional FIB etching method for characterizing interface orientation shows that the interface normals obtained by the two methods are very close, verifying the accuracy and reliability of the method of the present invention in characterizing interface orientation. Example 3 further proves the high efficiency of the method in large-scale interface characterization.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A method for characterizing the interface orientation of a polycrystalline material, characterized in that: The following steps are involved: (1) Establishing a sample coordinate system XYZ on the surface of a smooth polycrystalline sample; making the Z axis perpendicular to the sample surface, and the X axis and Y axis parallel to the sample surface and perpendicular to each other; (2) placing the sample in a dual-beam focused ion beam-scanning electron microscope, rotating the electron microscope sample stage so that the sample surface is perpendicular to the focused ion beam, and using the focused ion beam to sequentially deposit a protective layer and etch on the sample surface portion corresponding to the target interface to form an etched surface perpendicular to the sample surface; (3) using an electron beam to simultaneously scan and image the sample surface and the etched surface, and based on the scanned image, measuring the angle α between the interface trace of the target interface on the sample surface and the X-axis and the angle β' between the interface trace of the target interface on the etched surface and the Z-axis, and performing a tilt correction on β' to obtain a corrected angle β; (4) Based on α and β, the direction vector v1 of the interface trace of the target interface on the sample surface and the direction vector v2 of the interface trace of the target interface on the etched surface are calculated respectively. The outer product of v1 and v2 is the normal vector n of the target interface in the sample coordinate system, thereby completing the characterization of the interface orientation of the polycrystalline material.

2. The method for characterizing the interface orientation of polycrystalline materials according to claim 1, characterized in that: In step (3), the correction formula for the angle between the interface trace of the target interface on the etched surface and the Z axis is: β=atan((tan(β') / cos(θ))×sin(θ)) θ is the rotation angle of the electron microscope sample stage in step (2).

3. The method for characterizing the interface orientation of polycrystalline materials according to claim 1, characterized in that: In step (4), the expressions of v1 and v2 are: v1=(cos(α),sin(α),0) v2=(-sin(β),0,cos(β)).

4. The method for characterizing the interface orientation of polycrystalline materials according to claim 1, characterized in that: In step (2), when depositing the protective layer, the ion beam current is 20kV / 240pA; when etching, the ion beam current is 20kV / 4nA.

5. The method for characterizing the interface orientation of polycrystalline materials according to claim 1, characterized in that: When characterizing different target interfaces of the same sample, after the characterization of the previous target interface is completed, the sample is translated on the sample stage and steps (2)-(4) are repeated to characterize the next target interface until the characterization of all target interfaces is completed.

6. The method for characterizing the interface orientation of polycrystalline materials according to claim 1, characterized in that: In step (3), when scanning with an electron beam, the electron beam is not parallel to any surface of the sample surface and the etched surface, and the interface trace orientation of the target interface on the sample surface and the etched surface is simultaneously obtained through a single scan.

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