JPH06317484A - X-ray exposure method and equipment for measuring stress in microregion - Google Patents

Abstract

PURPOSE:To provide a method and equipment for detecting a discontinuous X-ray diffraction arc in the measurement of stress at a microregion on a polycrystalline material while allowing accurate detection of angular variation. CONSTITUTION:X-rays 2 are projected through a slit 6 and a prestage screen 7 onto a microregion of a sample 8 and an X-ray diffraction arc 11 reflected thereon is directed to one stationary imaging plate 13 which is subjected to multiplex exposure every time when the incident angle of the X-rays 2 to the sample 8 is varied several times. This constitution allows the detection of discontinuous X-ray diffraction arc while reading out the angular variation highly accurately thus realizing short time measurement of stress in a microregion of a polycrystalline material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray diffraction image exposure apparatus for measuring stress of metal or non-metal using X-ray diffraction.

[0002]

2. Description of the Related Art Although X-ray stress measurement has an excellent feature of non-destructive stress measurement, currently, a counter tube (including a position detection type proportional counter tube) is generally used as an X-ray detector. There is.

A typical stress measuring method is the sin ² Ψ method. The sin ² Ψ method measures the diffraction angle of the reflected X-ray while changing the incident angle α of the X-ray several times, and the diffraction angle 2θ and s
In ² Ψ is shown in the figure and the stress is calculated by multiplying the gradient by the stress constant to calculate the stress σ (for example, “X-ray stress measurement method, edited by The Japan Society of Materials, published by Yokendo, 1
981 ". The confidence limit of the stress σ _X Δσ _X is described on page 81). Ψ is the angle between the normal to the sample surface and the normal to the diffractive surface. Corresponds to the incident angle α of.

According to this method, when the measurement area is wide and a large number of crystals exist in the measurement area, the X-ray diffraction arc is continuous and measurement is possible (about 2 mm × 15 mm).
If the measurement area is small and minute, the number of crystal grains decreases, and the X-ray diffraction arc has a discontinuous spot shape, which causes a serious problem that measurement becomes impossible. The X-ray diffraction arc refers to a part of the Debye ring generated by X-ray diffraction. The minute area refers to a small area such as a square having one side of 100 μm to 1 mm. In actual stress measurement, it is often required to measure such a minute area in the vicinity of a welded portion, a crack generation portion, a joint portion, a curved portion of a pressed material, or the like.

When the X-ray diffraction arc becomes discontinuous,
The X-ray diffraction arc can be made continuous by moving or rocking the sample. However, this method cannot be adopted because the measurement position becomes indefinite if the movement is performed and the stress measurement direction becomes indefinite if the oscillation is performed. As described above, the measurement position is determined to be, for example, a crack generation portion, a curved portion of the pressed material, or the like, and the stress measurement direction is determined to be, for example, a direction perpendicular to the crack or a radial direction of the press. A method has also been proposed in which a sample is oscillated to measure stress in a minute area, but the measurement direction of stress is indefinite and the measurement time is long because a counter tube is used (eg, “Material, 36
Vol. 405, 1987 ", 630-635).

In Japanese Patent Laid-Open No. 12043/1990, a plurality of measurement regions are set on the photosensitive surface of an imaging plate which is a two-dimensional detector, and X-ray diffraction images are sequentially exposed in each region while rotating the imaging plate. ,reading,
A continuous X-ray diffraction imaging method characterized by erasing is shown, and an example of stress measurement by setting a plurality of rectangular measurement areas on the imaging plate is described. In the method described in the above publication, the positional reproducibility of the imaging plate due to rotation reduces the reproducibility accuracy of the angle of the X-ray diffraction arc. Further, since the X-ray diffraction arc becomes spot-like discontinuity, the rectangular measurement area having a width of 20 mm cannot be applied to stress measurement in a minute area.

[0007]

Therefore, an object of the present invention is to apply to the stress measurement of a microscopic region of a polycrystalline material or a coarse-grained material, and it is possible to detect the angle change of the arc of X-ray diffraction with high accuracy. It is an object of the present invention to provide an exposure method and apparatus for an X-ray diffraction arc, which enables accurate stress measurement in a minute region of a material in a short time.

[0008]

In order to solve the above-mentioned problems, the X-ray exposure method for measuring micro-region stress of the present invention comprises:
Each time X-rays are made incident on a minute area on the sample through the slit and the front screen, and the incident angle of the X-ray on the sample is changed, the X-ray diffraction arc reflected from the minute area is passed through the rear screen. Multiple exposure is performed on the same measurement area on the fixed imaging plate.

Further, while the reflected X-ray diffraction arc is exposed on the imaging plate, the imaging plate is swung about the center of rotation of the optical axis of the incident X-ray. .

Further, when the X-ray diffraction arc reflected from the sample is subjected to multiple exposure, the standard sample powder is placed on the sample and exposed simultaneously with the sample.

Further, when the X-ray diffraction arc reflected from the sample is exposed only once, the standard sample powder is placed on the sample and exposed simultaneously with the sample.

Further, in the exposure apparatus for measuring microscopic region stress of the present invention, the slit on the optical path of the incident X-ray and the front screen are arranged immediately before the sample stage mounted on the rotatable goniometer, and the incident X-ray is measured. An imaging plate support plate having an imaging plate is mounted on an arm rotatable about an optical axis, and a rear screen is installed on the front surface of the imaging plate.

[0013]

In order to measure the stress in the microscopic region of the polycrystalline material, it is first necessary to limit the incident X-ray according to the desired microscopic region by the slit. Although noise is generated due to the limitation of X-rays by the slit, this noise can be prevented by disposing the front screen on the downstream side of the slit. Further, the rear screen allows only the necessary diffracted X-rays to pass therethrough and prevents the exposure of unnecessary noise to the imaging plate.

As shown in FIG. 1, the imaging plate 1
The position of the X-ray diffraction arc 11 on 3 corresponds to the diffraction angle 2θ. X for a minute area of a diffraction arc or coarse crystal grains
The line diffraction arc becomes a spot. In order to measure the stress, it is necessary to read the change in the diffraction angle of these spots with the change in the incident angle α of the X-ray on the sample. Each time the incident angle of X-rays on the sample is changed several times, multiple exposures are made to the same measurement area on the fixed imaging plate with a spot-shaped X-ray diffraction arc, so that the diffraction angles 2θ of several diffraction spots are relative to each other. Change can be read accurately. By exchanging the imaging plate or moving the measurement area on the imaging plate for exposure, the reproducibility accuracy of the position of the imaging plate in the exposure device and
The accuracy of measuring the angle of the X-ray diffraction arc decreases due to the decrease in the position reproducibility accuracy of the reading device. Stress measurement is s
The in ² Ψ method is used. At this time, the number of times of multiple exposure for changing the incident angle of X-rays can be set to a minimum of 2, but about 4 times is preferable in order to improve the measurement accuracy.

When it is difficult to read the change in diffraction angle due to spot blurring due to X-ray divergence or crystal grain distortion, or when it is difficult to distinguish spot noise and spots that are unavoidable on the imaging plate. By swinging the imaging plate with the optical axis of the incident X-ray as the center of rotation, it is necessary to extend the discontinuous spot on the X-ray diffraction arc in a concentric circle shape to form an arc shape (arc shape). This makes it possible to accurately read the change in angle of the X-ray diffraction arc. Further, it becomes easy to distinguish the dot noise unavoidable on the imaging plate and the X-ray diffraction arc. Such swinging is also effective when a counter tube (including a position detection type proportional counter tube) is used as an X-ray detector.

When multiple exposures of the X-ray diffraction arc are performed, the standard sample powder is simultaneously exposed on the sample and compared with the diffraction angle of the X-ray diffraction arc of the standard sample powder to determine the angle of the X-ray diffraction arc. You can read the absolute value. Therefore, this method facilitates the determination of whether the X-ray diffraction arc is the target arc, and is also important as a reference for confirming the proper arrangement of the optical system and for correctly reading the diffraction angle.

Further, since the average value of the stress of the standard sample powder is considered to be zero, the X-ray diffraction arc of the standard sample powder displays a zero stress value. That is, the stress can be known by reading the deviation from the standard sample powder even with one exposure, which is extremely advantageous in terms of measurement efficiency. It is preferable that the standard sample powder generate a sharp continuous X-ray diffraction arc so that it can be distinguished from the X-ray diffraction arc of the measurement sample. If the same material as the measurement sample is used, an arc is generated near the X-ray diffraction arc of the measurement sample, which is convenient. For example, when measuring an iron sample, annealed iron powder with a crystal grain size adjusted to about 5 μm is preferable. The amount of the standard sample powder placed on the sample may be much smaller than that of the conventional counter tube method. For example, a few μm
It may be applied to a thickness.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an X-ray exposure apparatus for measuring microscopic region stress according to an embodiment of the present invention. The X-ray 2 generated by the X-ray source 1 is incident on the sample 8 via the shutter 3, the filter 4, and the collimator 5. Although the collimator 5 collimates the X-ray 2, the slit 6 limits and irradiates the X-ray according to a desired minute area. For example, a square having a side of 300 μm is used. Further, noise is reduced by the front screen 7. The opening of the front screen 7 is made slightly larger than the opening shape of the slit to avoid contact with the X-ray beam. For example, it is made larger than the X-ray beam size by about 100 μm.
It is necessary to make the outer dimensions of the front screen 7 as large as possible to prevent noise from entering from the outside. Since it is desirable that the position where the front screen 7 is set is immediately before the sample, the position is set close to the sample so that the rotation of the sample is not disturbed. The material of the slit 6 and the front screen 7 should be thick and made of a dense substance in order to shield X-rays. For example, brass or iron has a thickness of 2 mm.

The sample 8 is mounted in a sample table 9 mounted on a rotatable goniometer 10. The supporting surface of the imaging plate support plate 14 is a spherical surface in order to make the incident angle of the diffracted X-rays 11 on the imaging plate 13 and the distance R from the sample constant, and to ensure quantitativeness. It is also possible to simply replace the spherical surface with a cylindrical surface. The imaging plate 13 is attached to the support surface of the support plate 14. The imaging plate support plate 14 is preferably made of a dense material to be thick in order to prevent the transmission of external radiation that becomes noise and to maintain the shape accurately, but it is lightweight because it is mounted on the swinging support arm 15. Sex is also required. For example, iron is 2 mm thick and aluminum is 6 mm thick.

The rear screen 12 has an opening so that only a necessary X-ray diffraction arc can pass therethrough. It is also effective to reduce noise that a film that blocks transmission of X-rays having a wavelength longer than the wavelength of diffracted X-rays is attached to the opening. In the case of a Cr tube, it is advisable to use a thin vinyl film and replace the X-ray passage in the goniometer 10 with helium gas. In the case of Mo tube, an aluminum plate is preferable.

The swing of the imaging plate 13 with the optical axis of the incident X-ray 2 as the rotation axis will be described. The swinging is effective even at a minimum of ± 1 ° for distinguishing the dot noise from the X-ray diffraction spot. The upper limit is not particularly set, but about ± 10 ° is sufficient for accurately reading the angle of the X-ray diffraction arc. In order to realize the swing, it is necessary to use a cam mechanism or control the drive of a stepping motor by a computer. Although swinging can be replaced by rotation, since the diffracted X-rays 11 are limited by the rear screen 12, the exposure time becomes long and the efficiency is poor.

When the distance R between the sample 8 and the imaging plate 13 is reduced, the diffracted X-ray intensity increases, but the angular resolution deteriorates. If it is too far away, the angular resolution will improve, but the diffraction X
The line strength is reduced, and the dimensions of the imaging plate 13, its supporting plate 14, and the supporting arm 15 are enormous, which makes manufacturing difficult. It is necessary to determine an appropriate value considering the balance between strength and angular resolution, but the distance R is 200 to 600 m.
m is considered appropriate.

Next, the present invention will be described with reference to a specific example of stress measurement in a minute area.

(Experimental Example 1) Using the apparatus shown in FIG. 1, the imaging plate supporting plate 14 was attached to the supporting arm 15 so that the surface of the imaging plate exposed was a cylindrical surface having a radius R = 300 mm centering on the sample. It was Square-shaped imaging plate 1 enclosed in an erased cassette
3 was attached to the imaging plate support plate 14. When the device can be kept dark by turning off the illumination from the start of exposure to the start of reading, it is not necessary to put it in the cassette. The imaging plate 13 had a length of 470 mm and a width of 200 mm, and the detectable diffraction angle range was 90 degrees. A characteristic X-ray generated from a Cr tube (40 Kv, 30 mA) in a laboratory was passed through a filter 4 and a collimator 5 to form a parallel beam having a diameter of 0.5 mm. Further, the light was made incident on the sample 8 through the slit 6 and the front screen 7. The opening of the slit 6 was a square having a side of 300 μm, and the opening of the front screen 7 was a square having a side of 400 μm.
Sample 8 is two pieces of steel plate having a length of 200 mm, a width of 50 mm and a thickness of 1 mm, spot-welded near the center. 0mm, 0.5mm, 1.0mm from the outer edge of spot welding
Was measured at three points. Diffracted X-rays 11 from the sample 8 pass through the rear screen 12 and produce an image of the X-ray diffraction arc on the imaging plate 13. The rear screen 12 was fixed so as to select an X-ray diffraction arc of 211 reflections of iron.

During the exposure of the imaging plate, the opening time of the shutter made of a steel plate was 120 seconds. The steel sheet samples were exposed one after another while changing the inclination angle. After making the sample perpendicular to the incident X-ray beam, tilt the sample in the rolling direction, α =
After a total of 4 exposures with tilts of 0, 15, 30, 45 °, reading was performed with another read-only device. The reading time was 5 minutes.

X-ray diffraction arc not detectable and 2θ-
The stress value obtained by multiplying the regression line of the sin ² Ψ diagram by the stress constant was compared with the confidence limit Δσ _X.

(Experimental Example 2) While the reflected X-ray diffraction arc was exposed on the imaging plate, the imaging plate was swung with the optical axis of the incident X-ray as the center of rotation. The swing angle was ± 2 °. Other conditions are the same as in Experimental Example 1.

(Experimental Example 3) A standard sample powder having an average diameter of 4
About 1 μm of iron powder was placed on the measurement area of the sample, and the X-ray diffraction arc of the standard sample powder and the X-ray diffraction arc of the sample were simultaneously exposed. Other conditions are the same as in Experimental Example 1.

(Experimental Example 4) As in Experimental Example 3, an iron powder having an average diameter of 4 μm was placed as a standard sample powder on the measurement region of the sample, and the sample was tilted in the rolling direction at α = 45 ° and exposed once. Let Other conditions are the same as in Experimental Example 1. The measuring time was reduced to 1/4 and the measuring efficiency was improved. The stress value was calculated from the change in the diffraction angle 2θ.

(Experimental Example 5) Synchrotron radiation (2.5 GeV, 20)
(0 mA) is converted into a single color with a monochromator and the wavelength is set to 2.2.
The experiment was conducted using a light source of 9 angstrom.
The exposure time was 9 seconds. Other conditions are the same as in Experimental Example 1.

(Comparative Experimental Example 1) Commercial X using a counter tube
It measured using the linear stress measuring device. A parallel beam having a diameter of 0.3 mm was passed through the collimator. The X-ray source, the sample, the inclination of the sample, and the like are the same as in Experimental Example 1. The measurement time was 60 minutes for each inclination of the sample, and a total of 4 measurements were performed.

(Comparative Experimental Example 2) A parallel beam having a diameter of 2.0 mm was passed through a collimator. The other conditions are the same as in Comparative Experimental Example 1.

The results of the above experiments are shown in Table 1 and FIG. The stress values in Table 1 are 0 mm from the outer edge of spot welding,
The number after ± indicates the confidence limit. Although the stress value was tentatively obtained in Comparative Experimental Example 2, the stress value in the minute region was not obtained because it was extremely low and affected by the value in the peripheral region. Moreover, the reliability limit is large and the measurement accuracy is extremely poor.

[0035]

According to the method and apparatus of the present invention, it is possible to detect an X-ray diffraction arc in a minute region of a polycrystalline material, read an angle change with high accuracy, and measure a stress in the minute region in a short time. Become.

[0036]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic configuration plan view of an X-ray exposure method and apparatus for microscopic region stress measurement according to an embodiment of the present invention.

FIG. 2 is a diagram showing a measurement position and a measurement result of a stress value according to an example of the present invention.

[Explanation of symbols]

 1 X-ray source 2 X-ray 3 Shutter 4 Filter 5 Collimator 6 Slit 7 Front screen 8 Sample 9 Sample stage 10 Goniometer 11 Diffractive X-ray 12 Rear screen 13 Imaging plate 14 Imaging plate support plate 15 Support arm 16 Oscillation drive device 17 Injector stand α X-ray incident angle on sample 2θ Diffraction angle R Distance between sample and imaging plate

Claims (5)

[Claims] 1. An X-ray is made to enter a minute area on a sample through a slit and a front screen, and each time the incident angle of the X-ray on the sample is changed, an X-ray diffraction arc reflected from the minute area is reflected. An X-ray exposure method for measuring micro-area stress, which comprises performing multiple exposure on the same measurement area on a fixed imaging plate via a stationary screen. 2. The minute according to claim 1, wherein when the reflected X-ray diffraction arc is exposed on the imaging plate, the imaging plate is swung about the optical axis of the incident X-ray as the center of rotation. X-ray exposure method for area stress measurement. 3. A standard sample powder is placed on a sample, and X-rays are incident thereon, and the X-ray diffraction arc of the standard sample powder and the X-ray diffraction arc of the sample are subjected to multiple exposure at the same time.
The X-ray exposure method for measuring microscopic region stress as described above. 4. The X-ray exposure method for measuring micro-area stress according to claim 3, wherein the X-ray diffraction arc reflected from the sample is exposed only once. 5. An imaging plate is provided on an arm rotatable about the optical axis of the incident X-ray by disposing a slit on the optical path of the incident X-ray and a front screen in front of a sample stage mounted on a rotatable goniometer. An X-ray exposure apparatus for microscopic region stress measurement, comprising: an imaging plate support plate equipped with; and a rear screen installed in front of the imaging plate.