JPH01182726A - Evaluation of crystal strain and apparatus therefor - Google Patents

Abstract

PURPOSE:To perform evaluation of the minute strain in a crystal and evaluation of the residual strain in a thermally elongated plate and the residual strain in a softening step with high accuracy, by determining the visibility of an ECP (Electron Channeling Pattern). CONSTITUTION:The visibility of an ECP is determined, and the degree of the strain of a crystal is detected based on the change in determined visibility of the ECP. The determination of the visibility of the ECP is performed by obtaining the area rate of a part of the ECP, where the change in brightness in the ECP is large. As an evaluating apparatus of the crystal strain, a scanning type electron microscope having the ECP function and an image analyzer, which determines the visibility of the ECP, is used. Since the minute stress in the crystal can be evaluated, the evaluation of the residual strain in a thermally elongated plate and the residual strain in a softening step can be performed with high accuracy. Checking and analysis of difference in accumulated strains due to nonuniform deformation in machining and the place and orientation in nucleus formation in recrystallization can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for evaluating crystal strain and an apparatus therefor.

[Conventional technology]

Conventionally, methods for measuring the width of X-ray diffraction lines, methods for measuring Pincus hardness, etc. have been generally used as methods for measuring the strain of crystalline materials such as steel.

In the method of measuring the width spread of X-ray diffraction lines, it is usually difficult to narrow down the X-ray beam to a minute area of about 10 μm or less, and this method is not suitable for strain estimation in a minute area. Furthermore, since the width changes slowly with respect to strain changes, there is a problem in that strain evaluation sensitivity is low.

In addition, the Vickers hardness measurement method is a measurement method that utilizes the fact that the hardness of the object to be measured changes depending on the dislocation density (strain) of the object, but solid solution elements and precipitates in the crystal also affect the hardness of the object. Therefore, there is a problem that the accuracy of distortion detection is low.

On the other hand, in recent years E CP (Electron Channel)
ling Pattern) was discovered (D, G, Co
ates: Ph11. Mag,, 16 (196
7).

P1179) is used to determine crystal orientation. It is also known that ECP gives information about the integrity of the crystal, and that ECP becomes unclear when strain is applied (D, E
, Newbury and H. Yakowitz:
Practical Scanning Elect
ron Microscopy, ed, by J.I.
.

Goldstein and H, Yakowit
z (1975) + P, 149 (PIenu
+wPress )) Due to the complexity of ECP images, etc., it has not been possible to quantitatively evaluate distortion.

In addition, evaluation of the local heterogeneity of strain due to processing, accumulated strain by crystal orientation, and residual strain during softening is extremely important in developing recrystallization and texture control technology, and in recent years reliable The need for developing strain evaluation methods has been increasing.

The present invention provides a method and apparatus for solving this problem.

[Means for Solving the Problems] The present invention provides a method for evaluating crystal strain by quantifying the clarity of ECP.

In addition to the above technique, the present invention also provides a method for evaluating crystal strain by determining the area ratio of a portion with a large brightness change in ECP, and an apparatus therefor.

The objects targeted for strain evaluation in the present invention are crystalline materials such as steel, and the present inventors have studied various methods for correctly evaluating minute strains for the above objects based on the principles.
We obtained new knowledge that the method of image analysis of ECP is extremely effective.

ECP was recently discovered by Coates and is known to provide information regarding crystal orientation and crystal integrity. The present inventors found that when microstrain is applied to a crystal, the EC
Focusing on the phenomenon that P suddenly becomes unclear, we conducted extensive analysis using an image analyzer. A detailed explanation will be given below based on experimental results.

Figure 1 shows the accuracy (ε), cold rolling ratio (CR) and ECP in cold rolling.
The relationship between sharpness (S/S) and half-width (FWHV) of (200) diffraction lines measured by X-ray measurement is shown. In this case 0.34
A 3.25% St-Fe annealed plate (crystal grain size: 10 to 50 μm) with a thickness of 0 ms was cold rolled, and the change in ECP sharpness due to the cold rolling was quantified using an image analyzer. The flow of image analysis is shown in Figure 2. The ECP measurement was carried out at the center of the thickness of the copper plate, and each point in Figure 1 is the average of the measured values of 50 points (5 points in the cold rolling direction x 10 points in the direction perpendicular to the cold rolling direction, each 1 crane pitch). S indicates the area ratio of the portion of the ECP with large brightness changes, and So is the S value in a state where no distortion is applied. As is clear from Figure 1, ECP clarity (S/S6)
is sensitive to minute strains, and the conventional method (diffraction line half width measurement method)
It can be seen that this method is extremely effective in evaluating minute distortions.

Although the mechanism of evaluation of crystal strain by quantifying the sharpness of ECP, which is a feature of the present invention, is not necessarily clear, the inventors of the present invention think as follows.

Each line of ECP is a diffraction line from each plane in the crystal,
When the crystal is distorted, the diffraction lines become unclear and the bright and dark areas of the ECP are reduced. Therefore, it is presumed that distortion can be evaluated by a method such as determining the area ratio of a portion having a sharpness below a certain darkness value.

Next, reasons for limiting the constituent elements of the present invention will be described.

The reason why the present invention stipulates that crystal strain is evaluated by quantifying the clarity of ECP is because, as is clear from FIG. 1, there is a strong correlation between the clarity of ECP and crystal strain.
This is because crystal strain can be evaluated by measuring the clarity of ECP.

The method for quantifying the clarity of ECP is not particularly limited. E
One-way differentiation of CP using an image analyzer, Sobel method, etc.) Method of measuring the area ratio of areas with high differential values, method of using the highest differential value as sharpness, brightest and darkest parts of ECP Any method that uses the difference in brightness and darkness as the sharpness may be used.

In addition to the above-mentioned invention, we stipulated that crystal strain be evaluated by determining the area ratio of areas with large brightness changes in ECP, because ECP is an extremely complex image in which diffraction lines from each surface of the crystal appear simultaneously. However, since the blurring of each diffraction line due to distortion is not uniform, the method of evaluating the average sharpness of the diffraction line that appears is to calculate the area ratio of the area where the brightness changes more than a certain threshold value. This is because it is effective. There is no particular limitation on the method for determining the change in brightness.

Any method such as one-way differentiation using an image analyzer or Sobel method may be used.

In addition to the above invention, a scanning electron microscope with ECP function (
The crystal strain evaluation device is defined as consisting of an SEM (hereinafter abbreviated as SEM) and an image analyzer that has the function of quantifying the clarity of ECP. This is because it is impossible to evaluate distortion of crystalline materials using the algorithm of the present invention without an image analyzer.

There are various ways to make ECP appear, but there are no particular limitations.

Further, specifications other than the ECP sharpness quantification function of the image analyzer are not particularly limited. There is also no particular limitation on the method of inputting the ECP image from the SEM into the image analyzer. Any method may be used, such as a method of directly transmitting an electric signal or the like, or a method of inputting an SEM image as a photograph using a television camera.

The present invention evaluates crystal strain by quantifying the sharpness of ECP, but the sharpness is quantified for a model that is basically equivalent to ECP and has improved measurement (e.g. EBSP). It is understood that the method of doing so is essentially equivalent to the present invention and included in the present invention.

Furthermore, according to the present invention, since micro-strains in crystals can be evaluated,
It is possible to accurately evaluate the residual strain of hot-rolled sheets, residual strain during the softening (recovery, recrystallization) process, and the ECP of the surface layer is 500λ.
In the following, information on crystal perfection in a region of about 3μ is expressed, so non-uniform deformation during processing,
Investigation of differences in accumulated strain due to recrystallization nucleation location and orientation,
Analysis is also possible.

ECP can express information on the completeness of a crystal in a region of about 3 μm or less, which is less than 500 Å in the surface layer, and strain can be interpreted as the amount of lattice defects. It is also possible to inspect defects in semiconductors and the like due to a large number of defects.

Furthermore, the present invention extracts a portion of an ECP image that has a sharpness higher than a certain darkness value, and by selecting the darkness value according to the purpose, it is possible to improve accuracy.

〔Example〕

Example 1 A 3.25% 5i-Fe annealed plate with a thickness of 0.340 tm was
~15% cold rolled, the area ratio (S) of the part with large brightness change of the ECP was calculated using the image analysis flow shown in Figure 2 for the ECP of each sample, and the results are shown in Figure 3 as a histogram. . The ECP measurement was carried out at 50 points each at the center of the plate thickness (5 points in the cold rolling direction x 10 points in the direction perpendicular to the cold rolling direction, 111 bifts each). 6 is true or false.

Example 2 A hot-rolled silicon steel plate with a thickness of 2.3×1 containing C: 0.054% and Si: 3.23% was held at 01150°C for 30 seconds and slowly cooled to 900°C for 2 minutes. Air cooling, 0900℃
After holding for 4 minutes, air-cooling, ■ Treated without annealing, ■ center of plate thickness, ■ 1/4 plate thickness of each sample (EC
P was measured, and the area ratio (S) of the portion of the ECP with a large change in brightness and darkness was determined using the image analysis flow shown in Figure 2, and the results were expressed in histograms. 1/4 of the plate thickness is shown in (part).

ECP measurement was carried out at 50 points each (5 points in the cold rolling direction x 10 points in the direction perpendicular to the cold rolling direction, 1 Tsuru pitch each. If carbides appeared in the measurement area, ECP was not taken and the number of points in the cold rolling direction was increased for a total of 50 points. point).

〔Effect of the invention〕

As described above, according to the present invention, crystal strain can be evaluated by quantifying the clarity of ECP, and it is possible to evaluate minute residual strain, non-uniform deformation during processing, recrystallization nucleation location, and accumulated strain due to orientation. Since it becomes possible to investigate and analyze differences, it has great academic and industrial effects.

[Brief explanation of the drawing]

Figure 1 shows the accuracy (ε) in cold rolling, cold rolling rate <c R; and EC.
P visibility (S/S, ), relationship diagram with half-value (FWHV) of (200) diffraction line by X-ray measurement, Figure 2 is ECP
FIGS. 3 to 5 of the image analysis flow are histograms of the area ratio (S) of the portion of the ECP where the brightness changes are large. CR ('/,) Procedural amendment (spontaneous) May 70, 1988 Director General of the Patent Office Kunio Ogawa 1, Indication of the case 1988 Patent Application No. 4969 2, Name of the invention Method for evaluating crystal distortion and Apparatus 3, relationship with the case of the person making the amendment Patent applicant name (665) Nippon Steel Corporation 4, agent address 5-8-10 Toranomon-chome, Minato-ku, Tokyo 105
Subject of amendment (1) "Detailed explanation of the invention" column 6 of the specification, contents of the amendment (11 "Detailed explanation of the invention" column (a) of the specification, ibid. 5)
Page 17, correct "less than or equal to" to "1 or more". (ff) Insert the following sentence between lines 15 and 16 on page 8 of the same book. r Also, in the case of a sample containing a mixture of amorphous and crystalline materials, a clear E
Since CP appears only from crystalline portions, the present invention allows detection of crystalline portions and evaluation of the ratio of crystallized portions. ”

Claims (1)

[Claims] 1) A method for detecting crystal distortion characterized by quantifying the clarity of ECP and detecting the degree of distortion of the crystal from a change in the quantified clarity of ECP. Evaluation method. 2) The method according to claim 1, wherein the means for quantifying the sharpness of the ECP is to obtain the area ratio of a portion of the ECP with a large change in brightness and darkness. 3) A crystal strain evaluation device comprising a scanning electron microscope having an ECP function and an image analyzer for quantifying the clarity of ECP.