Detection method for improving dual-phase steel EBSD calibration rate

Abstract

The invention discloses a detection method for improving an EBSD calibration rate of dual-phase steel. The detection method comprises the following steps: (1) carrying out polishing pretreatment on a sample; (2) cleaning the surface of the sample; and (3) fixing the cleaned sample on a sample table by using a conductive adhesive, putting the sample table into a sample bin, vacuumizing, boosting the voltage, adjusting the working distance until an image is clear, optimizing a diffraction image, and then carrying out EBSD detection. The method is easy to operate, the definition of an image obtained when the sample is subjected to EBSD detection is guaranteed by combining multiple measures such as sample treatment and equipment parameter optimization, the calibration rate is high during EBSD detection and can be improved by 10% or above compared with a conventional calibration rate, the result is accurate, and the method is suitable for popularization.

Description

Technical Field

[0001] The present invention belongs to the technical field of research and characterization of the microstructure of metal materials, and in particular, to a detection method for improving the EBSD calibration rate of dual-phase steel. Background Art

[0002] Electron backscatter diffraction (EBSD) technology is an important tool for analyzing the microstructure of materials. It is widely used in the crystallographic research of materials such as metals, ceramics, and semiconductors, and can provide information about grain orientation, grain boundary characteristics, material phase distribution, etc. The calibration rate of EBSD technology, that is, the proportion of successfully obtaining diffraction patterns in each scan, is an important indicator to measure data quality and acquisition efficiency. When performing EBSD phase identification, the collected phase information (Kikuchi pattern) needs to be compared with the database. If the match is successful, calibration can be carried out, and then the composition and structure of the substance can be determined.

[0003] A high calibration rate means that more Kikuchi patterns are correctly identified, so as to more accurately understand the microstructure and texture of the material, and then analyze the properties and behaviors of the material. On the contrary, a low calibration rate will result in a large number of uncalibrated areas in the image, and the lack of information in these areas will seriously affect the analysis of the microstructure of the material.

[0004] Secondly, the calibration rate also affects the clarity and resolution of the image. In EBSD testing, the point-by-point scanning method makes the data of each pixel point crucial. If the calibration rate is low, then in some areas, the electron beam may not be accurately focused on the grains, resulting in inaccurate collected data, thus affecting the clarity and resolution of the image, and making it difficult to observe some important detailed features when analyzing the microstructure of the material.

[0005] However, in practical applications, due to the high strain fields of martensite or bainite in dual-phase steel samples spreading to the ferrite boundaries, the Kikuchi line patterns are blurred or distorted, and the calibration rate of EBSD often fails to reach the ideal level. A low calibration rate will lead to the lack of image information, affecting the reliability and efficiency of the analysis results of the microstructure of the material. Improving the EBSD calibration rate has become an important topic in current materials science research. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a detection method for improving the EBSD calibration rate of dual-phase steel with good effect.

[0007] To solve the above technical problem, the technical solution adopted by the present invention includes the following steps: (1) Pretreat the sample by polishing; (2) Clean the surface of the sample; (3) Fix the cleaned sample on the sample stage with conductive glue, place it in the sample chamber, evacuate the air, raise the voltage, adjust the working distance until the image is clear, and perform EBSD detection after optimizing the diffraction image.

[0008] Further, in the step (1), during the polishing pretreatment process, mechanical polishing is carried out first and then electrolytic polishing.

[0009] Further, in the step (3), the accelerating voltage should be raised to 15 kV; a 60-μm standard aperture is used, and the position of the sample stage is raised so that the sample surface is parallel to the scanning electron beam; a multi-phase calibration mode is used for detection.

[0010] Further, in the process of optimizing the diffraction image in the step (3): Select a position where the MAD at the image center ≤ 0.5 for optimization, adjust the exposure time of the detector, and accept the optimization if the MAD value becomes smaller; start EBSD detection after optimization.

[0011] Even further, the exposure time of the detector is controlled within 60 s.

[0012] The beneficial effects of adopting the above technical solutions are as follows: The operation of the present invention is simple. By combining various measures such as sample treatment and equipment parameter optimization, the clarity of the image obtained during EBSD detection of the sample is ensured. The calibration rate during EBSD detection is relatively high, which can be increased by more than 10% compared to the conventional calibration rate (about 70%), and the calibration rate can reach 85% or more. The results are accurate and suitable for popularization. Description of the Drawings

[0013] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0014] Figure 1 is the EBSD image photo obtained from the comparative example; Figure 2 is the EBSD image photo obtained from Example 1 of the present invention. Specific Embodiments

[0015] The detection method for improving the EBSD calibration rate of dual-phase steel includes the following steps: (1) Polishing pretreatment: Perform polishing pretreatment on the sample; the polishing pretreatment process is to first perform mechanical polishing to make the sample surface have no obvious scratches and remove the surface oxide layer; then perform electrolytic polishing to reduce the surface stress layer and amorphous layer and improve the calibration rate. The electrolytic polishing uses a perchloric acid alcohol solution with a mass concentration of 7%.

[0016] (2) Sample cleaning: Clean the sample surface to remove possible oil stains and impurities on the surface, preferably by ultrasonic cleaning.

[0017] (3) Fix the cleaned sample on the sample stage with conductive adhesive, place it in the sample chamber, and evacuate to 2×10 -5 MPa or less; raise the voltage to an acceleration voltage of 15 kV to avoid blurring of the EBSD image or reduction of the signal-to-noise ratio due to too high or too low voltage; switch the aperture to appropriately adjust the beam current intensity, and use a 60-μm standard aperture to balance the number of electrons emitted from the sample surface and the clarity of the diffraction pattern; raise the position of the sample stage to a working distance WD = 17 ± 0.3 mm to ensure that the sample surface is parallel to the scanning electron beam and optimize the clarity of the diffraction pattern; enable the "multi-phase calibration" mode and give priority to matching the ferrite phase; optimize the diffraction image, and the optimization process is as follows: adjust the exposure time of the detector to obtain a high-quality diffraction pattern, select a position with MAD ≤ 0.5 at the center of the image for optimization, adjust the exposure time of the detector within the range of 60 s, and accept the optimization if the MAD value of the selected position is observed to become smaller; repeat the above operation of optimizing the diffraction image 2 - 3 times, and then EBSD detection can be carried out.

[0018] Example 1: The detection method for improving the EBSD calibration rate of dual-phase steel is specifically described as follows.

[0019] (1) Cut the dual-phase steel sample into appropriate sizes and polish the sample; perform preliminary treatment on the surface of the polished sample by mechanical polishing to remove the surface oxide layer; electro-polish the sample surface with a 7% perchloric acid alcohol solution by mass concentration to reduce the surface stress layer and amorphous layer and improve the calibration rate.

[0020] (2) Ultrasonically clean the sample surface to remove possible oil stains and impurities on the surface.

[0021] (3) Fix the sample on the sample stage with conductive adhesive, place it in the sample chamber and evacuate to 2×10 -5 MPa or below, and the specific parameter selection for EBSD detection operation is as follows: Adjust the acceleration voltage to 15 kV to ensure that the electron beam can penetrate the sample and produce clear Kikuchi patterns. Raise the position of the sample stage to WD = 17 mm to ensure that the sample surface is parallel to the scanning electron beam. Use a 60-μm standard aperture to balance the number of electrons emitted from the sample surface and the clarity of the diffraction pattern. Select a position with an MAD value ≤ 0.5 at the center of the image for optimization, observe that the MAD value becomes smaller and then accept the optimization, and start detection after repeating the operation 3 times.

[0022] (4) The calibration rate during EBSD detection in this example is 85%.

[0023] Comparative Example 1: This comparative example uses the conventional operation method for EBSD detection, and the specific parameter selection for EBSD is as follows: Select a standard aperture of 60 μm, raise the voltage to 20 kV, adjust the working distance until the image is clear, ensure that the working distance is set within the range of 16.2 mm, and perform the detection after optimizing the diffraction pattern. The calibration rate during the EBSD detection of this comparative example was 73%.

[0024] As can be seen from the above, after adopting this method, the EBSD calibration rate of the sample has been significantly improved compared with that in the comparative example. Figure 1 is a photo of the EBSD image obtained from the comparative example, Figure 2 is a photo of the EBSD image obtained from Example 1 of the present invention. From Figure 1 、 2 it can be seen that the image quality of the EBSD image obtained by this method has been significantly improved, and the microscopic structure and texture characteristics of the material can be clearly observed.

Claims

1. A detection method for improving the EBSD calibration rate of dual-phase steel, characterized in that: It includes the following steps: (1) pre-polish the sample; (2) clean the surface of the sample; (3) fix the cleaned sample on the sample stage with conductive glue, put it into the sample chamber, evacuate the air, raise the voltage, adjust the working distance until the image is clear, and perform EBSD detection after optimizing the diffraction image.

2. The detection method for improving the EBSD calibration rate of duplex steel according to claim 1, characterized in that: In step (3), raise the voltage to an acceleration voltage of 15 kV; use a 60-μm standard aperture, raise the position of the sample stage to make the sample surface parallel to the scanning electron beam; perform detection in the multi-phase calibration mode.

3. The detection method for improving the EBSD calibration rate of duplex steel according to claim 1, wherein, The process of optimizing the diffraction image in step (3) is as follows: select a position with MAD ≤ 0.5 at the center of the image for optimization, adjust the exposure time of the detector, and accept the optimization if the MAD value is observed to become smaller; start EBSD detection after optimization.

4. The detection method for improving the EBSD calibration rate of duplex steel according to claim 3, characterized in that: The exposure time of the detector is controlled within 60 s.

5. A detection method for improving the EBSD calibration rate of duplex steel according to any one of claims 1-4, characterized in that: In step (1), the pre-polishing process first performs mechanical polishing and then electrolytic polishing.

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