A FIB-SEM in-situ tensile fatigue testing method for metal materials

Abstract

The present invention discloses a FIB-SEM in-situ tensile fatigue testing method for metal materials, which relates to the field of metal performance testing and includes the following steps: Step 1, placing a sample block on the sample stage of the SEM, selecting appropriate grains based on the EBSD results of the sample block, and finding the corresponding position under the FIB viewing angle; Step 2, using the FIB to cut at the selected position, cutting the sample block into two parts: a matrix block and a microblock, and a manipulator driving the microblock away from the matrix block; Step 3, removing the matrix block from the sample stage, and placing a carrier block on the sample stage, fixing the microblock on the carrier block; Step 4, processing the fixed microblock into a sample shape; Step 5, removing the sample stage, and placing the sample stage on the loading platform of the in-situ mechanical testing platform to perform a tensile fatigue test. This method can be used to carry out research on the microscopic tensile fatigue behavior of metal materials under the FIB-SEM system.

Description

Technical Field

[0001] The present invention relates to the field of metal performance testing, and in particular to a FIB-SEM in-situ tensile fatigue testing method for metal materials. Background Art

[0002] The introduction of in-situ mechanical testing technology has made it possible to study the correlation between the microscopic deformation and damage mechanisms of materials and load effects. Compared to CCD and AFM, SEM has the advantages of fast imaging speed, contact-free testing, high and continuously adjustable magnification (tens to hundreds of thousands of times), relatively loose imaging working distance requirements, and vacuum chamber dimensions that can meet in-situ testing requirements. Therefore, in-situ mechanical testing technology under SEM monitoring has received special attention. In 2004, Uchic et al. published an article in Science, in which they first used FIB-SEM technology to produce nickel single crystal micropillars and studied the scale effect of their plastic deformation under uniaxial compression. Small-scale testing can select specific microstructures to measure mechanical properties, has higher precision, more uniform stress / strain fields, can directly measure yield strength, and study the mechanism of dislocation motion. Therefore, it has attracted great interest among researchers. However, existing technologies are mainly distributed in FIB-SEM in-situ compression tests and TEM fatigue tests. It is difficult to perform mechanical strength tests on flat microstructures with existing technologies, and they all use a single load mode, making it impossible to achieve in-situ tensile fatigue tests. In other words, there is a lack of a universal and efficient FIB-SEM in-situ tensile fatigue test method. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a FIB-SEM in-situ tensile fatigue testing method for metal materials, which can be used to study the microscopic tensile fatigue behavior of metal materials under a FIB-SEM system.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a FIB-SEM in-situ tensile fatigue testing method for metal materials, comprising the following steps:

[0006] Step 1: Place the sample block on the SEM sample stage, select appropriate grains based on the EBSD results of the sample block, and find the corresponding position under the FIB perspective;

[0007] Step 2: Using a FIB to cut at a selected location, the sample block is cut into a matrix block and a microblock. One end of the microblock is connected to the matrix block. The microblock is fixed to a manipulator by Pt deposition. The connection between the microblock and the matrix block is then cut using the FIB. The manipulator moves the microblock away from the matrix block.

[0008] Step 3: Remove the substrate block from the sample stage and place a carrier block on the sample stage. The manipulator moves the microblock until it contacts the carrier block. The microblock is fixed to the carrier block by Pt deposition. The connection between the manipulator and the microblock is then cut using FIB, and the manipulator is removed.

[0009] Step 4: Processing the fixed microblock into a specimen shape, using FIB to process the upper portion of the microblock into an I-shape to obtain a fatigue specimen, wherein the fatigue specimen includes a base fixedly connected to the load block and an I-shaped specimen disposed on the base;

[0010] Step 5. Remove the sample stage and place it on the loading table of the in-situ mechanical testing platform. The loading head of the in-situ mechanical testing platform is provided with a prefabricated groove that matches the structure of one end of the I-shaped specimen. Place the in-situ mechanical testing platform in the SEM. After vacuuming, adjust the position of the loading table so that the I-shaped specimen is engaged with the prefabricated groove of the loading head, and then perform a tensile fatigue test. After completing the tensile fatigue test, use SEM to observe the slip deformation and fracture morphology of the I-shaped specimen.

[0011] Preferably, in step one, an area of ​​the sample block is selected in the SEM for EBSD analysis, and the FIB and SEM are aligned so that the same position is observed from the perspectives of the SEM and FIB. Then, from the perspective of the FIB, a small-flux ion beam is selected to scan the surface of the sample block. After scanning, the surface of the sample block exhibits different contrasts, and the grains and grain boundaries can be observed from the perspective of the FIB, thereby clarifying the grain orientation of the sample block and finding the corresponding position from the perspective of the FIB.

[0012] Preferably, in step 2, the position of the initial sample block is selected, and a large-beam ion beam is used to cut the surrounding area of ​​the initial sample block, and the connection at the lower left corner is retained; the sample stage is lowered and tilted, and a long-focal-length beam is used to cut through the bottom of the initial sample block along the length direction to form the microblock, and the lower left corner of the microblock is connected to the substrate block; the sample stage is returned to a horizontal state, the manipulator is moved to contact the microblock, and the microblock and the manipulator are fixed together at the contact point by Pt deposition.

[0013] Preferably, in step 2, an initial sample block with a length of 25 μm and a width of 15 μm is selected, the cutting depth of the surrounding area of ​​the initial sample block is 8 to 12 μm, the tilt angle of the sample stage is 60°, and the cross section of the microblock is trapezoidal.

[0014] Preferably, in step three, the microblock is reshaped so that the bottom surface of the microblock is horizontal; the manipulator is moved so that the bottom surface of the microblock contacts the prefabricated notch of the carrier block, and one side of the microblock is fixed to the carrier block by Pt deposition; the connection between the manipulator and the microblock is cut using FIB, and the manipulator is removed; the carrier block is rotated 180°, and the other side of the microblock is fixed to the carrier block by Pt deposition.

[0015] Preferably, in step three, the depth of the prefabricated notch is 1-2 μm, and both the prefabricated notch and the prefabricated groove are processed by FIB.

[0016] Preferably, in step four, the carrier block is rotated 90°, and the end of the microblock away from the carrier block is cut using FIB; then the carrier block is rotated 90° to return to a horizontal state, and a target area is deposited above the microblock by a Pt deposition method; then, the end of the microblock away from the carrier block is continued to be cut to form a rectangular plate with reference to the target area using FIB; the carrier block is rotated 90° again, and the rectangular plate is processed using FIB to obtain the I-shaped specimen.

[0017] Preferably, in step 4, the width of the target area is 1 μm, and the deposition thickness is 0.2-0.8 μm; the voltage of Pt deposition is 30 kV, and the current is 100 pA; and the thickness of the rectangular plate is 0.5 μm.

[0018] Preferably, in step 4, the widths of the upper and lower ends of the I-shaped sample are both 6-7 μm, the width of the middle portion is 0.6-1 μm, the height is 8 μm, and the thickness is 0.5 μm.

[0019] Preferably, in step five, the tensile fatigue test is performed in a stress-controlled manner, with a stress ratio of 0.3 and a loading cycle of 12 seconds.

[0020] Compared with the prior art, the present invention has achieved the following technical effects:

[0021] The present invention discloses a FIB-SEM in-situ tensile fatigue testing method for metal materials. The method comprises the following steps: using SEM microscopic imaging to observe a specific area in real time in a FIB-SEM dual-beam system; selecting appropriate grains according to EBSD analysis results of the material to be tested; finding corresponding positions under the FIB viewing angle; cutting out microblocks at the selected positions; transferring the microblocks by a robot; fixing the microblocks on a carrier block; processing the shape of the fatigue specimen; the fatigue specimen comprising a base fixedly connected to the carrier block and an I-shaped specimen arranged on the base; removing the sample stage and placing the sample stage on a loading table of an in-situ mechanical testing platform; providing a prefabricated groove on the loading head of the in-situ mechanical testing platform that matches the structure of one end of the I-shaped specimen; engaging the I-shaped specimen with the prefabricated groove of the loading head; and performing a tensile fatigue test under the SEM viewing angle. The present invention can perform in-situ tensile fatigue testing on microscopic plate-like parts with specific grain structures. Through innovations in specimen design and preparation methods, in-situ tensile fatigue testing is provided, and in-situ tensile and compressive fatigue testing can also be realized, that is, composite loading forms such as in-situ tensile fatigue / tensile and compressive fatigue are realized, and it has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 Schematic diagram of step 1 in the FIB-SEM in-situ tensile fatigue testing method for metal materials provided by the present invention;

[0024] Figure 2 Schematic diagram of step 2 in the FIB-SEM in-situ tensile fatigue testing method for metal materials provided by the present invention;

[0025] Figure 3 Schematic diagram of step 3 in the FIB-SEM in-situ tensile fatigue testing method for metal materials provided by the present invention;

[0026] Figure 4 Schematic diagram of step 4 in the FIB-SEM in-situ tensile fatigue testing method for metal materials provided by the present invention;

[0027] Figure 5 Schematic diagram of step five in the FIB-SEM in-situ tensile fatigue testing method for metal materials provided by the present invention;

[0028] Figure 6 This is a diagram of the slip deformation and fracture morphology of an I-shaped specimen in the FIB-SEM in-situ tensile fatigue testing method for metal materials provided by the present invention.

[0029] Explanation of the accompanying symbols: 1. Initial sample block; 2. Microblock; 3. Loading block; 4. Base; 5. Intermediate trapezoidal block; 6. Target area; 7. Rectangular plate; 8. I-shaped sample; 9. Loading platform; 10. Loading head; 11. Loading drive unit; 12. Sample stage. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] The purpose of the present invention is to provide a FIB-SEM in-situ tensile fatigue testing method for metal materials, which can be used to study the microscopic tensile fatigue behavior of metal materials under a FIB-SEM system.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] like Figures 1-6 As shown, this embodiment provides a FIB-SEM in-situ tensile fatigue testing method for metal materials, comprising the following steps:

[0034] Step 1: Place the sample block on the sample stage 12 of the SEM, select appropriate grains based on the EBSD results of the sample block, and find the corresponding position under the FIB perspective; the sample block in this embodiment is made of metal material and is fixed on the sample stage 12 using conductive gel.

[0035] Step 2: Use FIB to cut at the selected position, cutting the sample block into two parts: the substrate block and the microblock 2. One end of the microblock 2 is connected to the substrate block. The microblock 2 is fixed to the robot by Pt deposition. Then, the FIB is used to cut the connection between the microblock 2 and the substrate block, and the robot drives the microblock 2 away from the substrate block.

[0036] Step 3: Remove the substrate block from the sample stage 12 and place the carrier block 3 on the sample stage 12. The robot drives the microblock 2 to move and then contact the carrier block 3. The microblock 2 is fixed on the carrier block 3 by Pt deposition. Then, the connection between the robot and the microblock 2 is cut using FIB, and the robot is removed. In this embodiment, the carrier block 3 is made of metal material and is fixed on the sample stage 12 using conductive gel.

[0037] Step 4: Process the fixed microblock 2 into a sample shape. Use FIB to process the upper part of the microblock 2 into an I-shape to obtain a fatigue specimen. The fatigue specimen includes a base 4 fixedly connected to the load block 3 and an I-shaped specimen 8 set on the base 4.

[0038] Step 5: Remove the sample stage 12 and place it on the loading platform 9 of the in-situ mechanical testing platform. The sample stage 12 is installed on one side of the loading platform 9 so that the I-shaped specimen 8 is placed horizontally. Specifically, the sample stage 12 includes a disc and a cylinder arranged on one side of the disc. The object block 3 is fixed to the other side of the disc through a conductive gel. A circular hole for inserting the cylinder is provided on one side of the loading platform 9. A threaded hole is provided on the top surface of the loading platform. The threaded hole is perpendicular to the circular hole and connected to each other. The cylinder of the sample stage 12 is inserted into the circular hole, and the bolt is installed in the threaded hole. The bolt and the circular hole are fixed together. The columns are perpendicular to each other, and one end of the bolt is tightened on the cylinder, thereby realizing the installation of the sample table 12 on the loading platform 9; the loading head 10 of the in-situ mechanical testing platform is provided with a prefabricated groove that matches the structure of one end of the I-shaped sample 8, and the loading platform 9 can move in three axes, thereby ensuring that the loading head 10 and the I-shaped sample 8 are coaxially aligned; the in-situ mechanical testing platform is set in the SEM, and after vacuuming, the position of the loading platform 9 is adjusted to make the I-shaped sample 8 fit into the prefabricated groove of the loading head 10, and then the tensile fatigue test is carried out; after the tensile fatigue test is completed, Figure 6 As shown, the slip deformation and fracture morphology of the I-shaped sample 8 were observed using SEM.

[0039] like Figure 1 As shown, in step 1, an area of ​​the sample block is selected in the SEM for EBSD analysis, and the FIB and SEM are aligned so that the same position is observed from the perspectives of the SEM and FIB. Then, from the perspective of the FIB, a small-flow ion beam is selected to scan the surface of the sample block. Since grains with different grain orientations have different resistance to the ion beam, the thinning effect under the action of the ion beam is also different. Therefore, the surface of the sample block after scanning shows different contrasts. The grains and grain boundaries can be observed from the perspective of the FIB, thereby clarifying the grain orientation of the sample block and finding the corresponding position from the perspective of the FIB.

[0040] like Figure 2As shown, in step 2, the position of the initial sample block 1 is selected, and the cutting area around the initial sample block 1 is drawn in the SmartFIB operating system, and the system is allowed to execute the cutting command. The area around the initial sample block 1 is cut with a large beam ion beam, and the connection at the lower left corner is retained. The purpose is to prevent the initial sample block 1 from sliding when the bottom of the sample is subsequently cut through; the sample stage 12 is lowered and tilted, and a long focal length beam is used to cut through the bottom of the initial sample block 1 along the length direction to form a microblock 2. The lower left corner of the microblock 2 is connected to the substrate block, that is, the microblock 2 only retains the cantilever on the left side connected to the substrate block, while ensuring the strength, optimizing the efficiency of the subsequent transfer steps; then the microblock 2 needs to be removed from the substrate block, so that the sample stage 12 returns to a horizontal state, the manipulator is moved to contact the microblock 2, and the microblock 2 and the manipulator are fixed together at the contact point by Pt deposition. After the deposition is completed, the connection between the microblock 2 and the substrate block is cut, and the manipulator connected to the microblock 2 is slowly lifted and returned to a safe position.

[0041] In this specific embodiment, in step 2, an initial sample block 1 with a length of 25 μm and a width of 15 μm is selected, the cutting depth of the surrounding area of ​​the initial sample block 1 is 8 to 12 μm, the inclination angle of the sample stage 12 is 60°, and the cross section of the microblock 2 is trapezoidal.

[0042] like Figure 3 As shown, in step three, microblock 2 is reshaped so that the bottom surface of microblock 2 is horizontal; the manipulator is moved so that the bottom surface of microblock 2 contacts the prefabricated notch of microblock 3, which matches the structure of microblock 2. One side of microblock 2 is fixed to microblock 3 by Pt deposition; the connection between the manipulator and microblock 2 is cut using FIB, and the manipulator is removed; microblock 3 is rotated 180°, and the other side of microblock 2 is fixed to microblock 3 by Pt deposition. It should be noted that the rotation of microblock 3 in this step is achieved by the sample stage 12 driving its rotation.

[0043] In this specific embodiment, in step three, the depth of the prefabricated notch is 1-2 μm, and both the prefabricated notch and the prefabricated groove are processed by FIB.

[0044] like Figure 4As shown, in step 4, the microblock 2 is kept in a vertical state in the initial state, and the carrier block 3 is rotated 90° so that the microblock 2 is converted to a horizontal state. The end of the microblock 2 away from the carrier block 3 is cut by FIB, and both sides of the end of the microblock 2 away from the carrier block 3 are cut so that the end forms an intermediate trapezoidal block 5, so that the width of the intermediate trapezoidal block 5 is the same as the maximum width of the final I-shaped sample 8. Specifically, the unprocessed end of the microblock 2 close to the carrier block 3 is the base 4; then the carrier block 3 is rotated 90° to return to the horizontal state, and a target area 6 is deposited above the microblock 2 by the Pt deposition method, thereby effectively protecting the area where the sample is finally formed, that is, depositing above the intermediate trapezoidal block 5. A target area 6 is a rectangular area, so that the length of the rectangular area is the same as the width of the intermediate trapezoidal block 5, and the width of the rectangular area is greater than the thickness of the final I-shaped sample 8; then, referring to the target area 6 and using FIB, the end of the microblock 2 away from the carrier block 3 is further cut to form a rectangular plate 7, that is, the intermediate trapezoidal block 5 deposited with the target area 6 is cut into a rectangular plate 7, so that the thickness of the rectangular plate 7 is the same as the thickness of the final I-shaped sample 8; the carrier block 3 is rotated 90° again, so that the microblock 2 is converted to a horizontal state, and the rectangular plate 7 is processed by FIB, and a small beam of ion beam is selected to cut both sides of the rectangular plate 7 to process the transition section and the notch to obtain the I-shaped sample 8. It should be noted that the rotation of the carrier block 3 in this step is achieved by driving it to rotate by the sample stage 12. The method in this embodiment provides an efficient preparation process for micrometer-scale I-shaped samples 8 with high sample precision and high success rate.

[0045] In this specific embodiment, in step 4, the length of the target area 6 is 6 μm, the width of the target area 6 is 1 μm, and the deposition thickness is 0.2-0.8 μm; the voltage of Pt deposition is 30 kV, and the current is 100 pA; the thickness of the rectangular plate 7 is 0.5 μm.

[0046] The size and morphology of the fatigue specimen have undergone multiple experimental iterations to avoid problems such as bending and uneven thickness at the tensile end of the specimen due to insufficient strength. In this specific embodiment, in step four, the width of the upper and lower ends of the I-shaped specimen 8 is 6-7 μm, the width of the middle part is 0.6-1 μm, the height is 8 μm, and the thickness is 0.5 μm.

[0047] Before performing the tensile fatigue test in step five, the dimensions of the I-shaped specimen 8 are measured. The width, thickness, and related defect dimensions of the I-shaped specimen 8 are observed and measured using a SEM.

[0048] like Figure 5As shown, in step five, the equipment used for the in-situ fatigue test is the HysitronPicoIndenter 88 in-situ mechanical testing platform (PI-88 for short) developed by Bruker. The maximum load that the equipment can apply is 10mN, the load accuracy is 0.4μN, the maximum displacement of the loading head 10 is 5μm, and the displacement accuracy is <1nm. During the test, the fatigue specimen is mounted on the loading platform 9 on the left through the sample stage 12, and the load is applied by the loading head 10 mounted on the right. The diamond loading head used in this experiment is a flat indenter with a taper of 60° and a cone head diameter of 20μm. Its Young's modulus is 1140GPa and its Poisson's ratio is 0.07. Before the start of the experiment, the sample stage 12 with the load block 3 and the fatigue specimen and the loading head 10 are mounted on the in-situ mechanical testing platform and placed in the SEM. After evacuation, the load and displacement of the loading head 10 are calibrated using software. The loading platform 9 is then moved close to the loading head 10 at a low magnification. The loading platform 9 is slowly adjusted to align the fatigue specimen with the loading head 10. The loading head 10 is then driven by the loading drive unit 11 to conduct a tensile fatigue test. Tensile and compressive fatigue tests can also be performed based on actual test requirements. The tensile fatigue test is conducted using stress control, with a stress ratio of 0.3 and a loading cycle of 12 seconds.

[0049] It can be seen that in this embodiment, in-situ tensile fatigue testing can be performed on microscopic plate-like parts with specific grain structures. Through the innovation of specimen design and preparation methods, in-situ tensile fatigue testing is provided, and in-situ tensile and compressive fatigue testing can also be realized, that is, composite loading forms such as in-situ tensile fatigue / tensile and compressive fatigue are realized, which has a wide range of applicability. Through the flexible use of the FIB-SEM system, a set of efficient and general microscopic specimen structures and preparation methods are designed, with few process steps, high processing precision, and excellent repeatability. This method can study the tensile fatigue damage mechanism and defect characteristics of materials with specific structures (such as twin boundaries, phase boundaries, and grain boundaries) or specific orientations at the micron scale, and provide an in-situ testing means for the study of fatigue mechanical properties and damage deformation mechanisms of materials under cyclic loading at room temperature.

[0050] This specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A FIB-SEM in-situ tensile fatigue testing method for metal materials, characterized in that: The following steps are involved: Step 1: Place the sample block on the SEM sample stage, select appropriate grains based on the EBSD results of the sample block, and find the corresponding position under the FIB perspective; Step 2: Using a FIB to cut at a selected location, the sample block is cut into a matrix block and a microblock. One end of the microblock is connected to the matrix block. The microblock is fixed to a manipulator by Pt deposition. The connection between the microblock and the matrix block is then cut using the FIB. The manipulator moves the microblock away from the matrix block. Step 3: Remove the substrate block from the sample stage and place a carrier block on the sample stage. The manipulator moves the microblock until it contacts the carrier block. The microblock is fixed to the carrier block by Pt deposition. The connection between the manipulator and the microblock is then cut using FIB, and the manipulator is removed. Step 4: Processing the fixed microblock into a specimen shape, using FIB to process the upper portion of the microblock into an I-shape to obtain a fatigue specimen, wherein the fatigue specimen includes a base fixedly connected to the load block and an I-shaped specimen disposed on the base; Step 5: Remove the sample stage and place it on the loading platform of an in-situ mechanical testing platform. The loading head of the in-situ mechanical testing platform is provided with a prefabricated groove that matches the structure of one end of the I-shaped specimen. The in-situ mechanical testing platform is placed in a SEM. After vacuuming, adjust the position of the loading platform so that the I-shaped specimen fits into the prefabricated groove of the loading head, and then perform a tensile fatigue test. After completing the tensile fatigue test, use an SEM to observe the slip deformation and fracture morphology of the I-shaped specimen. In step 1, an area of ​​the sample block is selected in the SEM for EBSD analysis. The FIB and SEM are aligned so that the same position is observed from the SEM and FIB perspectives. Then, a small-flux ion beam is used to scan the surface of the sample block from the FIB perspective. After scanning, the surface of the sample block exhibits different contrasts. Grains and grain boundaries can be observed from the FIB perspective, thereby clarifying the grain orientation of the sample block and finding the corresponding position from the FIB perspective. In step 2, the position of the initial sample block is selected, and a high-current ion beam is used to cut the surrounding area of ​​the initial sample block, while retaining the connection at the lower left corner. The sample stage is lowered and tilted, and a long-focal-length beam is used to cut through the bottom of the initial sample block along the length direction to form the microblock, and the lower left corner of the microblock is connected to the substrate block. The sample stage is returned to a horizontal state, and the manipulator is moved to contact the microblock. The microblock and the manipulator are fixed together at the contact point by Pt deposition. In step three, the microblock is reshaped so that its bottom surface is horizontal; the manipulator is moved so that the bottom surface of the microblock contacts the prefabricated notch of the carrier block, and one side of the microblock is fixed to the carrier block by Pt deposition; the connection between the manipulator and the microblock is cut using FIB, and the manipulator is removed; the carrier block is rotated 180°, and the other side of the microblock is fixed to the carrier block by Pt deposition; In step four, the carrier block is rotated 90°, and the end of the microblock away from the carrier block is cut using FIB; then the carrier block is rotated 90° to return to a horizontal state, and a target area is deposited above the microblock by Pt deposition; then, the end of the microblock away from the carrier block is continued to be cut to form a rectangular plate with reference to the target area using FIB; the carrier block is rotated 90° again, and the rectangular plate is processed using FIB to obtain the I-shaped specimen.

2. The FIB-SEM in-situ tensile fatigue testing method for metal materials according to claim 1, characterized in that: In step 2, an initial sample block with a length of 25 μm and a width of 15 μm is selected, the cutting depth of the surrounding area of ​​the initial sample block is 8-12 μm, the tilt angle of the sample stage is 60°, and the cross section of the microblock is trapezoidal.

3. The FIB-SEM in-situ tensile fatigue testing method for metal materials according to claim 1, characterized in that: In step three, the depth of the prefabricated notch is 1-2 μm, and both the prefabricated notch and the prefabricated groove are processed by FIB.

4. The FIB-SEM in-situ tensile fatigue testing method for metal materials according to claim 1, characterized in that: In step 4, the width of the target area is 1 μm, and the deposition thickness is 0.2-0.8 μm; the voltage of Pt deposition is 30 kV, and the current is 100 pA; and the thickness of the rectangular plate is 0.5 μm.

5. The FIB-SEM in-situ tensile fatigue testing method for metal materials according to claim 4, characterized in that: In step 4, the widths of the upper and lower ends of the I-shaped sample are both 6-7 μm, the width of the middle portion is 0.6-1 μm, the height is 8 μm, and the thickness is 0.5 μm.

6. The FIB-SEM in-situ tensile fatigue testing method for metal materials according to claim 1, characterized in that: In step five, the tensile fatigue test was performed using a stress-controlled method with a stress ratio of 0.3 and a loading cycle of 12 s.

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