JPH01233354A - Method and apparatus for crystal orientation analysis - Google Patents

Abstract

PURPOSE:To store results of an orientation analysis handily and quickly without requiring skill, by performing an automatic line drawing and analysis based on an ECP image obtained with a scan electron microscope having an ECP function to record the results of the orientation analysis. CONSTITUTION:An ECP image obtained with a scan electron microscope having an ECP function is recorded into a disc while line image information is obtained with an image processor to be recorded into the disc. Based on the line image information, an arithmetic device and a controller are used to generate several kinds of candidate patterns and the candidate pattern well matching a line image is selected to record the crystal orientation thereof into said disc. When no matched pattern is obtained, a candidate pattern is generated using a recombination of pair lines, a line image only by the pair lines and a corrected line image employing a digitizer; thus, a crystal orientation is obtained in the same procedure to be recorded into the disc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for automatically analyzing the crystal orientation of a material.

[Conventional technology]

The magnetic properties of electromagnetic steel, workability of thin sheets, etc. are controlled by the grain orientation distribution of the steel sheet. In order to create materials with good properties, it is necessary to appropriately control the orientation distribution of crystal grains, but simply average information on orientation is not sufficient, and it is necessary to accurately capture the orientation information of N[1i11 grains. required.

X-ray pole figures are normally used as a method to measure the orientation distribution, and can quickly and easily measure the orientation of a large number of grains, but this is average information and the orientation information of individual grains is not accurate. I can't.

Although it is necessary to measure the orientation of each individual crystal grain for a large number of crystal grains in order to extract the universal characteristics of a material, conventional methods such as the facet focusing method, Kotsu cell method, and transmission electron W4 microscopy method have been used. The mirror method, etc., all have advantages and disadvantages in terms of simplicity, speed, accuracy, precision, etc. when measuring a wide area, and are not always satisfactory.

In addition to this, Daishi magazine phi1. Mag,, 16 (196
7), pH 79, E CP
(Electron Channeling Pat
The tern) method is a method in which a locking coil for ECP generation is attached to a scanning electron microscope, and the electron channeling pattern at the location observed with the scanning electron microscope is measured and analyzed, making it easy and accurate to determine the orientation of the desired location in a bulk sample. It has been rapidly utilized in recent years due to its ability to determine the orientation and the ability to easily display graphics such as pole figures based on the results of the obtained orientation.

ECP is also called Coa L image or pseudo-Kikuchi image, and it always appears as a pair of parallel black and white lines, and when the crystal is tilted, these lines move as if they were fixed to the crystal. The shape and orientation of this ECP and the width of the black and white pairs vary depending on the crystal structure, lattice constant, crystal orientation, and measurement conditions, but the shape of the pattern obtained when measuring the same sample under the same conditions depends only on the crystal orientation.

The method of determining crystal orientation from ECP is described in the book Mo.
dern Diffraction and Imag
ing Techniquesin Material
5science, North Holland (
1970) +159, it determines the plane index and direction index of the principal orientation from the widths of three or more pairs of black and white lines and the angles formed by them, and determines the orientation of the target crystal from those principal directions. I have to calculate how much it's off.

However, although ECP measurement is relatively easy to perform, the conventional method for analyzing its orientation is: - After taking a photograph of the ECP, measurement and analysis calculations must be performed using a ruler, protractor, etc., which is labor-intensive. There are many problems, and the analysis accuracy is not very high.

■Magazine Tetsu to Hagane, 71 (1984), 51322
According to the description, there is a method in which an ECP corresponding to a typical crystal orientation is created in advance using an electronic computer, and the ECP is superimposed on an actually measured pattern to determine the deviation between the two. This poses a problem in that the work of searching for a low-multiplying surface close to the actually measured pattern requires considerable skill, as well as time and effort.

■Magazine Journal of the Japan Institute of Metals, 41 (1'977) 3
According to 26, bare wires and single wires (necessary to improve analysis accuracy) are used to construct ECP using a digitizer based on photographic fiN film or photographic paper (necessary for improving analysis accuracy).
is manually converted into a line drawing and displayed on a CRT. There is a method of determining the crystal orientation by generating a candidate pattern using an electronic computer based on the actual measurement value converted into a line drawing, and comparing and matching the candidate pattern with the line drawing image. Compared to the first two methods, this has the advantage that it does not require any particular experience, requires shorter analysis calculations, and can be analyzed automatically. However, although photo processing or digitizer-based ECP line drawing, which is pre-processing for automatic analysis, is easy to operate, it still requires a lot of time and effort.

■Magazine Tetsu to Hagane, 70. (1984) 5132
According to the description in 1, the measured ECP@ is recorded in the image memory of an image processor and sequentially transferred and stored on the disk of an electronic computer. When all measurements are completed, the stored ECP images are sequentially recalled to the image memory and transferred to the CRT.
, manually convert it into a line drawing using the attached digitizer, and display it on a CRT. There is a method of determining the crystal orientation by generating a candidate pattern using an electronic computer based on the actual measurement value converted into a line drawing, and comparing and matching the candidate pattern with the line drawing image. Although this is simplified compared to ■, it requires a digitizer which is pre-processing for analysis.
There is still a problem in that drawing the ECP by using it requires a lot of time and effort.

Both methods have problems in terms of simplicity, speed, and labor when processing a large amount of ECP images.

[Problem to be solved by the invention]

As mentioned above, in crystal orientation measurement and analysis by ECP, it is necessary to process a large number of patterns easily, quickly, and without requiring labor. For this purpose, if the ECP image is automatically converted into a line drawing and automatic analysis calculations are performed based on the line drawing information, a large amount of processing can be performed without requiring human labor.

Therefore, the present invention solves all of these problems and provides a method and apparatus for sequentially automatically converting ECP images previously stored on a disk into line drawings and automatically analyzing the line information based on the line information. .

[Means and effects for solving the problem] ECP images are not always clear due to the size of crystal grains, the presence of strain, the presence of surface films, and the like. Manual input using a digitizer and automatic analysis require human intervention when creating line drawings, so pair lines and single lines can be selected accurately and there are almost no errors in the analysis. However, since there is no human intervention in full automation, there is no guarantee that the correct line drawing, pair line, or single line selection will be made.

Therefore, when converting an ECP image into a line drawing, we need a method that extracts all the line information necessary for crystal orientation analysis, and a method that automatically selects the line information necessary for analysis based on the extracted line information to automatically perform accurate crystal orientation analysis. As a result of various studies, it has been found that hardware and software that are equipped with the following functions and capable of high-speed processing are necessary as a means for carrying out this process.

FIG. 1 shows a flowchart of automatic line drawing and automatic analysis, and the present invention will be explained in detail below.

(About automatic line drawing processing) 0 Original image enhancement processing that performs various processing such as shading correction, filter correction, and differential processing on the ECP original image imported into the image memory to convert the original image into image data that enhances it ■ Original image enhancement processed image Level search processing that automatically calculates the brightness levels of white lines and black lines that form a pattern by searching the data; ■Ilow conversion that selects sample points with corresponding brightness from the data according to the determined brightness level and performs Hough conversion. Processing■Ho
Straight line parameter extraction process for extracting straight line parameters ρ and θ that are thought to have a straight line representation from the ρ-θ plane created by ugh transformation ■ Execute the above process ■■ for the white line and dotted line, respectively, Paired lines (parallel lines) consisting of a white line and a black line that can be subjected to ECP analysis are extracted from a large number of straight line parameters. At this time, the priority order of parallel line extraction is that the width is narrow, near the center, the intersection angle is right angles, etc., and two sets are selected and extracted in particular, and other parallel line extraction processing ■Above ■■ is excluded. Process for extracting a single line with a particularly strong straight line expression among straight line parameters ■Processing for recording the end point coordinates of each extracted pair line and single line on a disk (blAbout automatic analysis■Extracting the first two pairs of paired lines selected Based on this function, several candidate patterns are generated, the one that matches well with the line image is selected, and its crystal orientation is recorded on the disk.■ In the above ■, non-pair lines are mistakenly recognized as pairs, and candidate patterns are generated. The rate at which automatic analysis was possible (achievement rate) was approximately 60%, which was insufficient due to the lack of automatic analysis.In order to improve the success rate, we removed the erroneous paired line and selected two other paired lines, and sequentially created candidate patterns. Generate candidate patterns by rearranging the paired lines until a crystalline pattern is obtained, select the one that matches well with the line image, and record its crystal orientation on the disk ■ Even if you perform the process described in ■ above, the achievement rate is about 85.
%, this was often caused by the presence of an erroneous single line.

Therefore, we ignore the single line and generate candidate patterns using only bare lines, and select the one that matches well with the line image.
A function to record the crystal orientation on the disk ■When performing the above ■, automatic analysis processing was achieved with a success rate of over 94%, but the reason why it is still not 100% achieved is that it is difficult to create a line image due to the unclear ECP@ This was because automatic direction analysis could not be performed. Therefore, in order to perform a 100% analysis, we manually correct the line images that cannot be automatically analyzed using a digitizer, generate candidate patterns, select those that match well, and record their crystal orientations on a disk (C )About equipment for automatic line drawing and automatic analysisECPi
The following equipment is required to automatically perform line drawing and analysis based on an ECP image obtained from a scanning electron microscope with the following functions, and to automatically record the orientation analysis results.

■EC obtained from a scanning electron microscope with ECP function
A disk memory device that records the P image, line drawing information obtained by image processing and crystal orientation obtained by orientation analysis, and an image processor device that performs image processing such as obtaining a line image from the ECPiii image. A calculation and control device that calculates the line drawing information, controls the image processor, generates candidate patterns, matches them with the original image, and determines the crystal orientation ■For manually correcting ECP line images that are difficult to automatically analyze The crystal orientation analysis method and device according to the present invention are obtained from a scanning electron microscope having an ECP function. It has a function to automatically draw and analyze line drawings and automatically record the orientation analysis results based on This is an innovative method and device that can process line drawings and automatic analysis in a short time with an achievement rate of 94% or more.

〔Example〕

Since the ECP image is image information, it is shown here as a photograph. A 3.25% 5i-Fe annealed plate with a thickness of 0.3 am was used as the test material.

The following is an example of general automatic line drawing among many examples.

ECP original image (Figure 2), line drawing @ by manual input of digitizer (Figure 3), automatic line image by automatic crystal orientation analysis method and device (Figure 4), and simultaneous display of automatic line image and candidate pattern (Figure 4) As shown in Figure 4, the automatic line image is a line drawing that is sufficiently faithful to the original image, matches well with the candidate pattern, and is clearly a function that is sufficient for analysis. .

Crystal grains 2 of 5 samples using the same material but with different annealing conditions
236 pieces were routinely measured (ECP images of various sharpness and orientation), and automatic line drawing and automatic analysis were performed using an automatic crystal orientation analysis method and apparatus. According to the present invention, the ratio of the number of crystal grains for which the crystal orientation of several specimens could be automatically analyzed is shown in terms of achievement rate (Figure 6). Also 94%
It can be seen that processing is performed at a high rate.

In addition, as an example, the time required when using a 16-bit personal computer as part of an automatic crystal orientation analyzer (sequentially transferring original images stored on disk to image memory, automatic line drawing, automatic analysis, and orientation results) The time required to store the pattern on the disk is extremely quick, within about 4 minutes per pattern.

〔Effect of the invention〕

As is clear from the above embodiments, if the present invention is used, the ECP@ measured using the E CP/SEM can be stored sequentially on the disk, and even non-experts can set the necessary conditions. If you do this, ECP@ will be automatically converted into a line drawing,
It is possible to perform orientation analysis and store the orientation analysis results on a disk easily and quickly. This series of operations does not require any human intervention; for example, once ECP measurements are taken during the day and stored on a disk, the orientation analysis is automatically performed unattended at night. Furthermore, graphical displays such as pole figures can be displayed very easily based on the stored orientation results.

In order to obtain a universally accurate solution based on information on the orientation of individual crystal grains, a large amount of ECP measurement and analysis is essential, and for these purposes, the automatic crystal orientation analysis method and device according to the present invention are effective for ECP. /SEM automatic sample movement mechanism,
By directly connecting to an automatic ECP measurement system equipped with an automatic ECP measurement mechanism, a completely unmanned automatic crystal orientation analysis system can be easily constructed. This quickly provides extremely useful information for improving the magnetic properties of electromagnetic steel and the properties of steel sheets such as workability of thin plates.

[Brief explanation of the drawing]

FIG. 1 shows a flowchart of automatic line drawing and automatic analysis. Figure 2 is a photograph showing ECP@ obtained from a scanning electron microscope, Figure 3 is a diagram showing a line image created using a digitizer, and Figure 4 is an automatic line image obtained by the apparatus and method of the present invention. FIG. 5 is a photograph showing an image in which an automatic line image obtained by the apparatus and method of the present invention is matched with a candidate pattern. FIG. 6 is a bar graph showing the rate of automatic analysis (achievement rate) when various ECP images (2236 patterns) were subjected to automatic line drawing and automatic analysis using the method and apparatus of the present invention.

Claims (1)

[Claims] 1. Electron channeling pattern (abbreviated as EC)
P) Convert the ECP image from the sample obtained using a scanning electron microscope with the function into an enhanced image by applying various processing, and extract the features of the image to obtain the white and black straight lines that are the subject of ECP analysis. The paired lines that make up parallel lines and the other single lines are extracted separately, and a line image consisting of the extracted coordinate information is recorded on a disk, and candidates are generated based on the line information. Generating several types of patterns, selecting a candidate pattern that matches well with the line image, and recording the crystal on a disk, and when a matching pattern cannot be obtained, recombining paired lines, drawing only with paired lines, or using a digitizer. A crystal orientation analysis method characterized by automatically generating candidate patterns after correcting a line image, selecting a well-matched candidate pattern, and recording its crystal orientation on a disk. 2. E obtained from a scanning electron microscope with ECP function
A disk memory device that records the CP image, line drawing information obtained from image processing, and crystal orientation obtained by orientation analysis, an image processor device that performs image processing to obtain a line image from the ECP image, and line drawing information that constitutes the image. The invention is characterized by having a calculation and control device that performs calculations, controls an image processor, generates candidate patterns, matches them with the original image, and determines the crystal orientation, and a digitizer device for manually correcting the image. Crystal orientation analyzer.