JPH0718821B2 - Crystal orientation analysis method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for automatically analyzing a crystal orientation of a material.

[Conventional technology]

Magnetic properties of electromagnetic steel, workability of thin plate, etc. are governed by the crystal grain orientation distribution of the steel plate. In order to create a material with good characteristics, it is necessary to properly control the orientation distribution of crystal grains, but simply averaging the orientation information is not enough, and it is possible to accurately capture the orientation information of each individual crystal grain. Required.

An X-ray pole figure is usually used as a method for measuring the orientation distribution, and orientation measurement of a large number of crystal grains can be performed quickly and simply. However, this is average information and the orientation information of individual crystal grains cannot be obtained. I can't.

Although it is necessary to measure the orientation of each crystal grain in a large number of crystal grains in order to extract the universal characteristics of the material, the facet pit method, the Cossel method, and the transmission electron microscopy method that have been conventionally used. , And the like have advantages and disadvantages in measuring a wide range region in terms of a simple method, rapidity, accuracy, precision, etc., and are not necessarily satisfactory methods.

On the other hand, as described in phil.Mag., 16 (1967), p1179, the ECP (Electron Channelling Patter
The n) method is a method of attaching a locking coil for ECP generation to a scanning electron microscope and measuring and analyzing the electron channeling pattern at the location observed with the scanning electron microscope.
It has been rapidly utilized in recent years due to the fact that the orientation of the intended location of the bulk sample can be determined easily and accurately, and that it is a means that can easily display a graphic such as a pole figure display based on the obtained orientation. Came.

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

The method of obtaining the crystal orientation from ECP is, for example, the book Modern
Diffraction and Imaging Techniques in Material Sci
ence, North Holland (1970), 159, it determines the plane index and direction index of the main orientation from the widths of three or more pairs of black and white lines and their angles, and Must deviate from their principal orientations.

However, although the ECP measurement can be performed relatively easily, the conventional method requires a lot of labor in the direction analysis because the ECP must be once photographed, and then the measurement and analysis calculation must be batch-processed using a ruler, protractor, etc. There is a problem that the analysis accuracy is not so high.

According to the magazine Iron and Steel, 71 (1984), S1322, a typical computer orientation is prepared in advance by using an electronic computer, and the ECP is determined in advance by superimposing it on the measured pattern and determining from the deviation between the two. There is. This involves the problem of requiring considerable skill in the work of finding a low index surface close to the actual measurement pattern, as well as the problem of requiring time and labor.

According to the Journal of the Japan Institute of Metals, 41 (1977) 326, a pair of wires and a single wire (necessary for improving the accuracy of analysis) that composes an ECP using a digitizer based on a film or photographic paper photographed are described in the manual. Line drawing with
Display on CRT. There is a method of determining a crystal orientation by causing a candidate pattern to be generated by an electronic computer based on the measured value obtained by the line drawing and matching and matching the candidate pattern and the line drawing image. Compared with the former two, this has the advantage that no special experience is required, the analysis calculation is short, and automatic analysis is possible. However, although the photographic processing, which is a preprocessing for automatic analysis, and the line drawing of the ECP by using a digitizer are easy to operate, they still have a problem that they require a lot of time and labor.

According to the magazine, Iron and Steel, 70, (1984) S1321, the measured ECP image is recorded in the image memory of the image processor and then sequentially transferred and stored in the disc of the computer. When all measurements are completed, the stored ECP images are sequentially loaded into the image memory and displayed on the CRT, and the attached digitizer is used to manually create a line drawing and display it on the CRT. There is a method of determining a crystal orientation by generating a candidate pattern by an electronic computer based on the measured value of the line drawing and matching and matching the candidate pattern and the line drawing image. Although this is simpler than that, there is a problem that the ECP line drawing using the digitizer, which is a pretreatment for analysis, still requires a lot of time and labor.

There is a problem with any of the methods in terms of simplicity, speed and labor in processing a large amount of ECP images.

[Problems to be Solved by the Invention]

As described above, in crystal orientation measurement and analysis by ECP, it is necessary to process a large number of patterns simply, quickly and without labor. For that purpose, if an ECP image is automatically drawn as a line and automatic analysis calculation is performed based on the line drawing information, a large amount of processing can be performed without human labor.

Therefore, the present invention solves all of these problems, and provides a method of automatically making an automatic line drawing of ECP images stored in advance on a disk and automatically analyzing it based on the line information.

[Means and Actions for Solving the Problems]

The ECP image shows the size of crystal grains, the presence of strain, the presence of surface film,
Therefore, a clear image cannot always be obtained. Manual input by a digitizer and automatic analysis involve human intervention in making a line drawing, so paired lines and single lines can be selected accurately, and analysis errors rarely occur. However, there is no guarantee that correct line drawing, pair line, or single line selection will be made because no human intervention is involved in the fully automated process.

Therefore, when converting an ECP image into a line drawing, a method for extracting all the line information necessary for crystal orientation analysis and a selection of the line information required for analysis based on the extracted line information will automatically perform accurate crystal orientation analysis. As a result of various studies, it has been found that the hardware and software that have the following functions and are capable of high-speed processing are the necessary conditions.

FIG. 1 shows a flowchart of automatic line drawing and automatic analysis. The details of the present invention will be described below.

(A) Automatic line drawing Original image enhancement processing that performs various processing such as shading correction, filter correction, and differentiation processing on the ECP original image that is loaded in the image memory to convert the original image into more emphasized image data Original image enhancement processed image data Level search processing that automatically calculates the brightness levels of the white and black lines that form the pattern by searching for the sampled points with the brightness corresponding to the calculated brightness level from the data and performs the Hough conversion processing Hough conversion processing Hough Extraction process of the straight line parameters to extract the straight line parameters ρ and θ that are considered to have a straight line expression from the ρ-θ plane created by the conversion. From the parameters, select a pair of lines (parallel lines) consisting of a white line and a black line that can be subject to ECP analysis. Extract. The priority of parallel line extraction at this time is narrow, and two sets are selected and extracted especially based on the criteria such as near the center and the intersection angle is right angle. Other parallel line extraction processing Extraction processing of single line having particularly strong straight line expression Processing of recording end point coordinates of extracted pair line and single line on the disk In the level search processing, the following processing is performed. That is,
A histogram of the luminance of each pixel (which is represented by 256 gradations, for example) enhanced by the original image enhancement processing is created, and an appropriate threshold value for determining white and black is determined on this histogram.

The following processing is performed in the above Hough conversion processing. That is, a pixel having a lower brightness than the black concealment value obtained in the above process,
Pixels with higher brightness than the white threshold are selected and used as black line sample points and white line sample points. By the way, if an arbitrary point on the two-dimensional plane represented by x, y rectangular coordinates is A (x, y), an arbitrary straight line L passing through this point is the length ρ of a perpendicular line drawn from the coordinate origin to the straight line. Angle θ between ₀ and the perpendicular to the x-axis
₀ is expressed as ρ ₀ = xCosθ ₀ + ySinθ ₀ (Hesse's standard form), and other straight lines passing through the point A are also displayed in the same manner, and their perpendicular length ρ _i (i = _{1, 2,} ...) and said vertical line is x axis and the angle θ _{i (i} = _1,2, is plotted ...) to [rho-theta plane (when Hough transform) sinusoidal curve is obtained. Then, other points B, C, ... On the straight line L are processed in the same manner to obtain other sinusoidal curves, and these curves intersect at one point (ρ ₀ , θ ₀ ). Conversely speaking, the sinusoidal curve is obtained for each point A, B, C, ... On the two-dimensional plane, and if these curves intersect at one point, these points A, B, C ,. It is on one straight line, and ρ and θ of the straight line are those of the above-mentioned one point. In the above, this Ho
The ugh transformation is performed for each black and white sample point.

In the above extraction process, the intersection of the sinusoidal curves (this is ρ−
The parameters of the straight line are extracted as ρ and θ of (which can be detected by the density of points on the θ plane).

(B) About automatic analysis A function of generating several candidate patterns based on the initially selected two pairs of pair lines, selecting one that matches the line image well, and recording the crystal orientation on the disk. Candidate patterns may not occur if a non-null one is mistakenly recognized as a pair. In this case, the rate of automatic analysis (achievement rate) was insufficient at about 60%. Therefore, in order to improve the achievement rate, remove the wrong pair line and select the other two pairs of pair lines, and generate candidate patterns by recombining the pair lines until the candidate patterns are obtained sequentially, and select the one that matches the line image well. The function of recording the crystal orientation on the disc was about 85% even when the above-mentioned treatment was performed, and this was because it was often caused by the presence of an erroneous single line. Therefore, we exclude single lines with weaker linear expressions, generate candidate patterns, select those that match the remaining line image well, and record the crystal orientation on the disc. Although the automatic analysis processing was possible, the reason why it was not achieved 100% was that automatic orientation analysis could not be performed because it was difficult to create a line image due to the unclear ECP image. Therefore, in order to perform 100% analysis, a line image that cannot be automatically analyzed is manually corrected by using a digitizer, then a candidate pattern is generated and a good matching is selected, and the crystal orientation is recorded on the disk. If the image is not clear and cannot be converted into a line drawing even by manual processing, manual processing using a digitizer is unnecessary.

(C) Automatic line drawing and automatic analysis device As a function to automatically record line drawing and analysis based on the ECP image obtained from the scanning electron microscope with ECP function and automatically record the azimuth analysis result. The following equipment is required:

A disk memory device that records the ECP image obtained by a scanning electron microscope with ECP function, the line drawing information obtained by image processing and the crystal orientation obtained by the orientation analysis. Image processor device that performs image processing including image calculation of line drawing information that constitutes an image, control of the image processor, calculation that generates candidate patterns and matches with the original image to determine the crystal orientation, control device Automatic analysis difficult Digitizer device for manually correcting ECP line image The crystal orientation analysis according to the present invention automatically performs line drawing and analysis based on the ECP image obtained from the scanning electron microscope having the ECP function, and the orientation analysis result Has the function of automatically recording
It is an epoch-making one that solves all the problems in the conventional method as described above, and can process ECP images routinely measured by automatic line drawing and automatic analysis with a achievement rate of 94% or more in a short time.

〔Example〕

The ECP image is image information, but it is represented here by text and figures. As the test material, a 0.35% 3.25% Si-Fe annealed plate was used.

The following is an example of general automatic line drawing from many cases.

The ECP original image shows a specific pattern corresponding to the crystal orientation, and this pattern is composed of 512 × 480 points, and each point has a luminance signal of 256 steps. In converting this pattern into a line drawing, FIG. 2 shows conversion into a line drawing by manual input using a digitizer. On the other hand, FIG. 3 shows a line drawing automatically converted by the automatic crystal orientation analysis according to the present invention. FIG. 3 shows that the line drawing is faithfully and faithfully compared with FIG. FIG. 4 shows a candidate pattern of crystal orientation generated by the automatic crystal orientation analysis according to the present invention based on this automatic line image (FIG. 3).

The crystal orientation in Fig. 4 is (0.753, 0.643, −0.
143) plane, and the pattern of FIG. 3 matches this, so it can be said that the orientation of the crystal grains has the above-mentioned value. It is also possible to color-code the automatic line image on the display and the candidate line on the display for the red line, and display both of them at the same time, so that the determination of matching is extremely easy. As described above, it is apparent that the automatic crystal orientation analysis according to the present invention has a sufficient function for the analysis of crystal orientation.

Crystal grains of 5 samples with different annealing conditions using the same material 22
36 pieces were routinely measured (ECP images of various sharpness and orientation), and automatic line drawing and automatic analysis were performed by the automatic crystal orientation analysis according to the present invention. According to the present invention, the ratio of the number of crystal grains in which the crystal orientations of several test pieces could be automatically analyzed is shown by the achievement rate (Fig. 5), and the sharpness of the ECP image is not always sufficient, but in any of the examples. It can be seen that is also processed at a high rate of 94% or more.

Also, as an example, the required time when a 16-bit personal computer is used as a part of the automatic crystal orientation analyzer (original images stored on the disk are sequentially transferred to the image memory, automatic line drawing and automatic analysis are performed to obtain the orientation results. It takes about 4 minutes per pattern) to store the disk, which is extremely quick.

〔The invention's effect〕

As is clear from the above examples, if the present invention is used, the ECP images measured by using the ECP / SEM are only sequentially stored in the disk, and even if not a skilled person, if the necessary condition setting is performed, the sequential processing is performed. ECP image line drawing and orientation analysis are automatically performed, and orientation analysis results can be stored in a disk easily and quickly. These series of operations require no human work,
For example, if you perform ECP measurement during the day and store it on a disk, then the azimuth analysis will be performed automatically at night.
In addition, graphic display such as pole figure display is possible very easily based on the result of the stored orientation.

A large amount of ECP measurement and analysis is indispensable to obtain a universal correct solution from the orientation information of individual crystal grains. For these purposes, the automatic crystal orientation analysis according to the present invention is ECP / SEM.
An automatic crystal orientation analysis system that is completely unmanned can be easily constructed by directly connecting to the ECP automatic measurement system equipped with the automatic sample movement mechanism, the automatic ECP measurement mechanism, and so on.
This quickly gives extremely powerful information for improving the magnetic properties of electromagnetic steel and the steel plate properties such as workability of thin plates.

[Brief description of drawings]

FIG. 1 shows a flowchart of automatic line drawing and automatic analysis. 2 is a diagram showing a line image created by using a digitizer, FIG. 3 is a diagram showing an automatic line image obtained by the present invention, and FIG. 4 is a diagram showing candidate patterns obtained by the present invention. is there. FIG. 5 is a bar graph showing the ratio (achievement rate) of automatic analysis when various ECP images (2236 patterns) were subjected to automatic line drawing and automatic analysis according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Mitsuru Tanino 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Shinichi Nippon Steel Co., Ltd. Technical Research Institute No. 1 (72) Inventor, Nanshi Satoshi Nishi Shinjuku, Shinjuku-ku, Tokyo 7 Chome 7-33 Ratok. System Engineering Co., Ltd. (72) Inventor Toshifumi Kobayashi 7-33, Nishi-Shinjuku, Shinjuku-ku, Tokyo Ratok. System Engineering Co., Ltd. (72) Inventor Masaki Ito 3-11, Kandanishiki-cho, Chiyoda-ku, Tokyo Nexus company (72) Inventor Naotaka Ochifuji 3--11, Kandanishiki-cho, Chiyoda-ku, Tokyo Nexus company ( 56) References JP-A-60-91247 (JP, A) "Iron and Steel", 71 (1984), S1321, P. 269

Claims (1)

[Claims] 1. An ECP image obtained from a sample by using a scanning electron microscope having an electron channeling pattern (ECP for short) is converted into an emphasized image by various processing, and the image data is searched. Then, the brightness level of the white line and the black line is calculated, sample points having brightness equivalent to the obtained brightness level are selected from the image data, and the Hough transform is applied to the straight line passing through each sample point, and the ECP analysis target The white and black straight lines are extracted, and the paired lines forming the parallel lines and the other single lines are separated and extracted, and a line image composed of the coordinate information of the extracted lines is recorded on the disc. , Each process is automatically performed, several candidate patterns are generated based on the pair line information, the candidate pattern that matches well with the line image is selected, and its crystal orientation is recorded on the disc. In addition, when the matching pattern cannot be obtained, the pair lines are recombined to generate a few new candidate patterns, select a candidate pattern that is well matched, and record the crystal orientation on the disk automatically. And the crystal orientation analysis method.