EBSD characterization method of deformation recrystallization fraction

Abstract

The EBSD characterization method comprises the following steps: S1, determining the size of a to-be-analyzed sample, and pretreating the surface of the to-be-analyzed sample; s2, placing the sample to be analyzed under a scanning electron microscope for observation, and selecting an area to be measured; s3, calibrating crystal orientation information by using an electron back scattering diffraction (EBSD) instrument; s4, analyzing and calibrating in Channel5 processing software to obtain an IPF graph, and analyzing the grain size; s5, recrystallization, recovery and non-recrystallization are distinguished according to the in-grain orientation difference distribution parameter GOS, a distribution diagram is formed, and the average grain size and the shape factor are calculated. According to the method, the recrystallization degree is represented according to the orientation difference distribution parameter GOS in the crystal grains, the recrystallization, recovery and non-recrystallization crystal integral numbers are given, and the average crystal grain size, the shape factor and the distribution characteristics of the average crystal grain size and the shape factor can be calculated.

Description

Technical Field

[0001] The invention relates to the technical field of material analysis and testing, and in particular to an EBSD characterization method for deformation recrystallization fraction. Background Art

[0002] The recrystallization structure fraction has a significant impact on the tensile strength, hardness and magnetic properties of cold-rolled steel sheets. Parameters such as alloying elements, annealing temperature and heating rate directly affect the deformation recrystallization process. Therefore, accurate characterization of recrystallization parameters can optimize process parameters and improve product quality. At present, the existing EBSD analysis of recrystallization requires large computational data, poor analysis results, and cannot simultaneously characterize the recrystallized grain information.

[0003] Patent CN202010810924.3 discloses an in-situ EBSD observation method for the evolution of micro-orientation of recrystallized grains in magnesium alloys. The method marks the sample area of ​​interest for EBSD analysis, removes the sample, anneals it, and re-prepares the sample. Find the area with the marked point in the analysis field of view, and then perform EBSD analysis to achieve in-situ observation of the recrystallization micro-orientation. It mainly solves the problem that magnesium alloys are difficult to observe in-situ EBSD due to the low calibration rate and inability to accurately locate due to surface stress layers, oxide layers, and contaminants. However, it does not give the volume fractions of recrystallization, recovery, and non-recrystallization, nor can it calculate the average grain size and shape factor and their distribution characteristics.

[0004] In summary, the existing technologies all have certain defects and shortcomings, and there is still room for further improvement and perfection. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide an EBSD characterization method for deformation recrystallization fraction, which can characterize the recrystallization degree according to the orientation difference distribution within the grains, and can not only give the recrystallized, recovered and non-recrystallized volume fractions, but also calculate their respective average grain size and shape factor and their distribution characteristics.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The present invention provides an EBSD characterization method for deformation recrystallization fraction, comprising the following steps:

[0008] S1. Determine the size of the sample to be analyzed and pre-treat the surface of the sample to be analyzed;

[0009] S2. Place the sample to be analyzed under a scanning electron microscope and select the area to be measured;

[0010] S3, use electron backscatter diffractometer EBSD to calibrate crystal orientation information;

[0011] S4, after parsing and calibration in Channel5 processing software, the IPF diagram is obtained and the grain size is analyzed;

[0012] S5. Distinguish recrystallization, recovery and non-recrystallization according to the intra-grain orientation difference distribution parameter GOS, form a distribution diagram and calculate the average grain size and shape factor.

[0013] Furthermore, in step S1, the sample size is: length 2-10 mm, width 2-10 mm, and thickness not exceeding 6 mm.

[0014] Furthermore, in step S1, the pretreatment includes: first grinding the analysis surface with coarse and fine sandpaper, then mechanically polishing the sample surface on a metallographic polishing machine, and finally removing the deformation layer formed on the sample surface during grinding and mechanical polishing by vibration polishing or electrolytic polishing.

[0015] Furthermore, the resolution rate of the sample after the pretreatment is above 90%.

[0016] Furthermore, in step S2, the working parameters of the scanning electron microscope are: acceleration voltage 20-25 kV, working distance 15-25 mm, aperture 60-120 microns, and the appropriate magnification is selected according to the characteristics of the sample.

[0017] Furthermore, in step S3, the calibration step length is set to 1 / 10-1 / 20 of the average grain size; the fluorescent screen intercepts the Kikuchi pattern in the analysis area point by point to obtain the orientation information surface distribution map.

[0018] Furthermore, in step S5, the GOS threshold value of the recrystallized grains is 1-2, the GOS threshold value of the recovery interval is 1-7, and the GOS threshold value of the non-recrystallized grains is greater than 5.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The EBSD characterization method of deformation recrystallization fraction proposed in the present invention characterizes the degree of recrystallization according to the distribution of intra-grain misorientation, not only giving the volume fractions of recrystallization, recovery, and non-recrystallization, but also being able to calculate the respective average grain size and shape factor and their distribution characteristics. This method is more accurate and scientific, filling the gap in detection in this regard, and can be effectively applied to detection and analysis practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the existing recrystallization fraction analysis results obtained based on orientation difference;

[0022] Figure 2 It is a schematic diagram of the GOS recrystallization fraction analysis results of the present invention;

[0023] Figure 3 for Figure 2 Schematic diagram of the volume fraction of recrystallized grains;

[0024] Figure 4 for Figure 2 Schematic diagram of the volume fraction of recovered grains;

[0025] Figure 5 for Figure 2 Schematic diagram of the volume fraction of unrecrystallized grains. DETAILED DESCRIPTION

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] The EBSD characterization method of deformation recrystallization fraction proposed in the present invention specifically comprises the following steps:

[0028] S1. First, determine that the length of the sample to be analyzed is 2-10mm, the width is 2-10mm, and the thickness does not exceed 6mm;

[0029] The surface of the sample to be analyzed is pretreated: first, the analysis surface is ground with coarse and fine sandpaper, then the sample surface is placed on a metallographic polishing machine and polished mechanically, and finally, the deformation layer formed on the sample surface during the grinding and mechanical polishing process is removed by vibration polishing or electrolytic polishing to ensure that the sample resolution rate is above 90%.

[0030] S2. Place the sample to be analyzed under a scanning electron microscope for observation, select the area to be measured, and use the following working parameters: acceleration voltage 20-25 kV, working distance 15-25 mm, aperture 60-120 microns. Select the appropriate magnification based on the sample characteristics.

[0031] S3. Use electron backscatter diffractometer EBSD to calibrate the crystal orientation information, and set the calibration step size to 1 / 10-1 / 20 of the average grain size; intercept the Kikuchi pattern in the analysis area point by point on the fluorescent screen to obtain the orientation information surface distribution map.

[0032] S4. After parsing and calibration in Channel5 post-processing software, the IPF diagram is obtained and the grain size is analyzed.

[0033] S5. According to the intra-grain orientation difference distribution parameter GOS, recrystallization, recovery and non-recrystallization are distinguished, a distribution diagram is formed and the average grain size and shape factor are calculated. The GOS parameter is adjusted to set a suitable threshold. Generally, the GOS threshold of recrystallized grains is 1-2, the GOS threshold of the recovery interval can be set between 1-7, and the GOS threshold of non-recrystallized grains is greater than 5.

[0034] The present invention will be further described below by specific examples:

[0035] An EBSD characterization method for deformation recrystallization fraction, taking the measurement of hypereutectoid steel grain boundary length as an example, the specific implementation process is as follows:

[0036] S1. Determine the size of the sample to be analyzed: 8 mm in length, 4 mm in width, and 2 mm in thickness;

[0037] The surface to be analyzed was first ground with coarse and fine sandpaper, then placed on a metallographic polishing machine and mechanically polished, and finally vibration polishing was used to remove the deformation layer formed on the sample surface during grinding and mechanical polishing. The resolution rate of the pretreated sample was 95.2%.

[0038] S2. Place the above sample under a scanning electron microscope for observation, select the area to be measured, and the working parameters are: acceleration voltage 20 kV, working distance 18 mm, aperture 120 microns, and select a magnification of 200 times based on the sample characteristics.

[0039] S3. Use electron backscatter diffractometer EBSD to calibrate the crystal orientation information, and set the calibration step size to 1 / 10 of the average grain size; intercept the Kikuchi pattern on the fluorescent screen, and intercept the Kikuchi pattern in the analysis area point by point on the fluorescent screen to obtain the orientation information surface distribution map.

[0040] S4. After analysis and calibration in Channel5 post-processing software, the IPF diagram of grain orientation is obtained and the grain size is analyzed.

[0041] S5. According to the intra-grain orientation difference distribution parameter GOS, recrystallization, recovery and non-recrystallization are distinguished, a distribution diagram is formed, and the average grain size and shape factor can be calculated. Among them, by observing the distribution diagram formed by GOS, GOS less than or equal to 1.5 is characterized as recrystallized grains, 1.5 to 5 is characterized as recovered grains, and greater than 5 is characterized as non-recrystallized grains. The distribution forms a subset, and the recrystallization fraction is calculated to be 21.3%, the recovery fraction is 49.2%, and the non-recrystallization fraction is 29.2%. The average grain sizes are 14.5 microns, 21.9 microns and 35.5 microns, respectively, and the major and minor axis ratios of the grains are 1.78, 3.26 and 5.03, respectively.

[0042] The intra-grain orientation difference distribution GOS measures the orientation difference between each point in the grain and the average orientation of the grain. The grain orientation difference of plastically deformed grains is large, while the orientation difference of recrystallized grains is small. The degree of recrystallization can be characterized based on the intra-grain orientation difference distribution. It can not only give the volume fractions of recrystallization, recovery, and non-recrystallization, but also calculate the average grain size and shape factor and their distribution characteristics.

[0043] Matters not described in detail in the present invention are all known technologies.

[0044] The embodiments described above are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An EBSD characterization method for deformation recrystallization fraction, characterized in that: The method comprises the following steps: S1. Determine the size of the sample to be analyzed and pre-treat the surface of the sample to be analyzed; S2. Place the sample to be analyzed under a scanning electron microscope and select the area to be measured; S3, use electron backscatter diffractometer EBSD to calibrate crystal orientation information; S4, after parsing and calibration in Channel5 processing software, the IPF diagram is obtained and the grain size is analyzed; S5. Distinguish recrystallization, recovery and non-recrystallization according to the intra-grain orientation difference distribution parameter GOS, form a distribution diagram and calculate the average grain size and shape factor.

2. The EBSD characterization method of deformation recrystallization fraction according to claim 1, characterized in that: In step S1, the sample size is: length 2-10 mm, width 2-10 mm, and thickness not exceeding 6 mm.

3. The EBSD characterization method of deformation recrystallization fraction according to claim 1, characterized in that: In step S1, the pretreatment includes: firstly grinding the analysis surface with coarse and fine sandpaper, then mechanically polishing the sample surface on a metallographic polishing machine, and finally removing the deformation layer formed on the sample surface during grinding and mechanical polishing by vibration polishing or electrolytic polishing.

4. The EBSD characterization method of deformation recrystallization fraction according to claim 3, characterized in that: The resolution rate of the sample after the pretreatment is above 90%.

5. The EBSD characterization method of deformation recrystallization fraction according to claim 1, characterized in that: In step S2, the working parameters of the scanning electron microscope are: acceleration voltage 20-25 kV, working distance 15-25 mm, aperture 60-120 microns, and the appropriate magnification is selected according to the sample characteristics.

6. The EBSD characterization method of deformation recrystallization fraction according to claim 1, characterized in that: In step S3, the calibration step length is set to 1 / 10-1 / 20 of the average grain size; the fluorescent screen intercepts the Kikuchi pattern in the analysis area point by point to obtain the orientation information surface distribution map.

7. The EBSD characterization method of deformation recrystallization fraction according to claim 1, characterized in that: In step S5, the GOS threshold value of the recrystallized grains is 1-2, the GOS threshold value of the recovery interval is 1-7, and the GOS threshold value of the non-recrystallized grains is greater than 5.

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