JPH05288616A - X-ray residual stress measuring method - Google Patents

Abstract

PURPOSE:To provide a residual X-ray stress measuring method which enables the reducing of the number of position sensitive type X-ray detectors mounted on an X-ray diffraction device to one while enabling the measurement of a residual stress even when a limited number of crystal grains exist in an X-ray irradiation area or there is a deviation in distribution of directions crystal lattice faces of the crystal grains. CONSTITUTION:A sample support mechanism 6 of an X-ray diffraction device 1 is provided with an irradiation area turning function to rotate a sample 3 with an optical axis of an incident X-ray beam 4 as center axis of rotation. Thus, a residual stress is determined from a deviation of a peak angle in a peak profile which is detected by a position sensitive type X-ray detector 8 at two positions of an arbitrary angle alpha and (alpha+180 deg.) as angle of rotation of the sample 3 by the irradiation area turning function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray residual stress measuring method for measuring residual stress using an X-ray diffractometer.

[0002]

2. Description of the Related Art The sin ² ψ method is conventionally known as an X-ray residual stress measuring method for measuring residual stress using an X-ray diffractometer. In this method, the peak profile is measured while changing the angle ψ formed by the normal to the sample surface and the incident X-ray beam, and the residual stress is obtained from the change in the peak angle.

However, an object whose peak profile is measured using an X-ray diffractometer is, for example, a sample (polycrystalline sample).
In the case of the upper minute region, the peak detection is not performed because the number of crystal grains existing in the X-ray irradiation region is small and the direction distribution of the crystal lattice planes of the crystal grains is uneven. There is a risk that it will not be possible to obtain a continuous diffraction spectrum that does not leak.
In the sin ² ψ method, since the diffraction peak cannot be detected, it is not possible to accurately know the change in the peak angle with respect to the change in the angle ψ, which may cause a situation in which the residual stress cannot be obtained.

Therefore, as an X-ray residual stress measuring method suitable for the case where the object to be measured is such a minute region,
The single injection method has been proposed. In this method, the angle ψ formed by the normal to the sample surface and the incident X-ray beam is fixed, and the Debye ring is recorded on the X-ray film or two position-sensitive X-ray detectors. The residual stress is obtained from the Debye ring image.

[0005]

According to the single-incidence method described above, the number of crystal grains existing in the X-ray irradiation region is small, or the crystal lattice planes of the crystal grains are small, because the measurement target is a minute region or the like. It is possible to measure the residual stress even when there is a bias in the directional distribution of the distribution, but with the conventional single-incidence method, it is difficult to speed up the processing due to the exposure time required to take a picture of the Debye ring. Or, to equip an X-ray diffractometer with two position-sensitive X-ray detectors,
There are drawbacks that the X-ray diffractometer becomes large and the device cost becomes high.

The present invention has been made in view of the above circumstances, and in the case where the number of crystal grains existing in the X-ray irradiation region is small or the direction distribution of the crystal lattice planes of the crystal grains is uneven. However, it is possible to measure residual stress, and moreover, it is possible to use only one position-sensitive X-ray detector equipped in the X-ray diffractometer, which is suitable for reducing the device cost and making the device compact. It is an object of the present invention to provide an X-ray residual stress measuring method.

[0007]

An X-ray residual stress measuring method according to the present invention is a method for holding an X-ray source and a sample on the sample by holding the sample on the optical path of an incident X-ray beam output from the X-ray source. Sample support mechanism for operating the X-ray irradiation position and diffraction X from the sample
The residual stress is measured using an X-ray diffractometer equipped with a position-sensitive X-ray detector for detecting the rays.

Specifically, the sample support mechanism of the X-ray diffractometer has an irradiation area setting function capable of arranging an arbitrary position on the sample on the optical path of the incident X-ray beam at an arbitrary angle, and An irradiation area swirling function of rotating the sample with the optical axis of the incident X-ray beam as the rotation center axis is provided.

Then, with respect to the incident X-ray beam that is incident at an angle ψ ₀ with respect to the normal to the sample surface, the rotation angle of the sample by the irradiation region turning function is an arbitrary angle α and (α + 180).
The position-sensitive X-ray detector detects the diffracted X-rays at two positions of (°) and remains due to the difference in peak angle between the peak profile at the arbitrary angle α and the peak profile at the angle (α + 180 °). Measure stress.

[0010]

According to the X-ray residual stress measuring method of the present invention, the optical axis of the incident X-ray beam of the sample is rotated from the angle α to the angle (α + 180 °), and the angle α and the angle (α + 180 °). ), The peak profile is measured at two positions. Even if the incident X-ray beam is incident at any angle with respect to the normal to the sample surface, the residual stress can be calculated from the deviation of the peak angle of the peak profile at the two positions. You can ask. Moreover, the value of the angle α is changed for one sample, the peak profile measurement at two positions of the angle α and the angle (α + 180 °) is repeated a plurality of times, and the plurality of measured values obtained by the comparison processing are compared. By doing so, it is easy to increase the measurement accuracy, and it is also possible to evaluate the error of the measurement value and increase the reliability.

Therefore, when the object to be measured is a minute region on the thin film sample, the number of crystal grains existing in the X-ray irradiation region is small, or the direction distribution of the crystal lattice planes of the crystal grains is uneven. However, it is possible to measure the residual stress, and at the same time, it is possible to evaluate the error of the measured value. Moreover, it is possible to use only one position-sensitive X-ray detector equipped in the X-ray diffractometer. As a result, the cost of the device can be reduced and the device can be made compact.

[0012]

EXAMPLE FIG. 1 shows a schematic structure of an X-ray diffractometer used in an X-ray residual stress measuring method according to an example of the present invention.

This X-ray diffractometer 1 collimates the X-rays output from the so-called micro-focus X-ray source 2 and the incident X-ray beam 4 for irradiating a micro area on the sample 3. X-ray generating means 5 for generating the X-ray, and a sample support for holding the sample 3 on the optical path of the incident X-ray beam 4 generated by the incident X-ray generating means 5 and operating the X-ray irradiation position on the sample 3. The mechanism 6, the single position-sensitive X-ray detector 8 for detecting the diffracted X-rays 7 from the sample 3, the operation of the sample support mechanism 6 and other movable parts, and the position-sensitive X-ray A control processing device 9 for processing the detection result of the line detector 8 is provided.

Although the detailed structure is not shown, the sample support mechanism 6 can move and rotate the sample 3 in an arbitrary direction by, for example, appropriately combining a rotation mechanism section and a parallel movement mechanism section. Sample 3
Irradiation area setting function capable of locating an arbitrary position on the optical path of the incident X-ray beam 4 at an arbitrary angle, and irradiation for rotating the sample 3 with the optical axis of the incident X-ray beam 4 as a rotation center axis. It has a region turning function.

In FIG. 1, reference numeral 10 is a sample plane normal line orthogonal to the surface 3a of the sample 3, 11 is a lattice plane normal line orthogonal to the crystal lattice plane involved in diffraction, and 12 is the incident X-ray beam 4. It is an extension of the optical axis. The extension line 12 corresponds to the central axis of rotation when the irradiation region turning function of the sample support mechanism 6 rotates the sample 3.

The angle ψ ₀ is the angle between the sample surface normal 10 and the incident X-ray beam 4, and the angle η is the lattice surface normal 1.
1 and the incident X-ray beam 4 (that is, the lattice plane normal 11
Is also the included angle between the diffracted X-ray 7).

In the X-ray residual stress measuring method of one embodiment of the present invention, the operation of the sample support mechanism 6 is controlled by the program processing in the control processing unit 9 so that the necessary diffracted X-rays 7 can be detected by the position sensitive type. The X-ray detector 8 is made to detect. Specifically, with respect to the incident X-ray beam 4, the rotation angle of the sample 3 by the irradiation region turning function is an arbitrary angle α and (α + 1).
The position-sensitive X-ray detector 8 detects the diffracted X-rays 7 at two positions of 80 °), and detects the peak angle between the peak profile at the arbitrary angle α and the peak profile at the angle (α + 180 °). The residual stress is measured from the deviation. Hereinafter, it will be described that the residual stress can be measured by the method of this embodiment.

FIG. 2 shows the incident X-ray beam 4 on the sample 3.
And defines the relationship between principal strain and stress. The incident point of the incident X-ray beam 4 on the sample is set as an origin O, and _three axes of X ₁ , X ₂ , and X ₃ are taken from this origin O in the directions of main strains ε ₁ , ε ₂ , and ε ₃ . These three axes are orthogonal to each other, and the X3 axis is the sample surface normal 1 of FIG.
It is assumed to match 0.

Now, in order to measure the residual stress σ _f in the X-axis direction rotated by φ from the X ₁ axis in the X ₁ X ₂ plane,
In the XOX ₃ plane, incident with an angle ψ ₀ inclined with respect to the X ₃ axis X
It is assumed that the line beam 4 is incident. In addition, the axis O in FIG.
P is an extension of the incident X-ray beam 4 and corresponds to the axis 12 in FIG.

The principal strains ε ₁ , ε ₂ , ε ₃ and the stress σ
There is a relationship shown in the following equations (1) to (3) between ₁ , σ ₂ and σ ₃ .

[0021]

[Equation 1] However, in the formulas (1) to (3) and the formulas described below, E is an elastic constant, and ν is a Poisson's ratio.

Since the stress of the surface layer is measured in the X-ray stress measurement, a plane stress state is generally established.
It can be considered that σ ₃ = 0. Therefore, the above equations (1) to (3) can be converted into the following equations (4) to (6).

[0023]

[Equation 2] Further, in FIG. 2, the line OA shows the lattice plane normal line 11 in FIG. The angle η in FIG. 2 is the included angle between the incident X-ray beam 4 and the diffracted X-ray 7 with respect to the lattice plane normal 11, as also shown in FIG. 1.

There is a relation of 180 ° -2θ = 2η, that is, η = 90 ° -θ (7) between the angle η and the diffraction angle 2θ.

Now, let us consider a case where the sample is measured while being rotated around the axis OP by an angle α. In this state, the crystal plane normal 11 of the crystal satisfying the diffraction condition is
The line OA in FIG. 2 is located at a position tilted by an angle (ψ ₀ + η) from the X ₃ axis in the XOX ₃ plane (hereinafter,
(Φ ₀ + η) = φ).

The lattice plane normal vector at this time is (sin ψ,
0, cos ψ). When the measurement condition is returned to the state before rotating about the axis OP by the angle α, the lattice plane normal vector with respect to the lattice plane normal at that time is expressed by the following equation (8).

[0027]

[Equation 3] Then, in the equation (8), ψ ₀ −ψ = η = (90
The following equation (9) is established because of (-θ).

[0028]

[Equation 4] That is, in the X-ray diffractometer 1 shown in FIG. 1, when the sample 3 is rotated by the angle α and measured, the lattice plane normal vectors (n (α) ₁ , n (α )
₂ , n (α) ₃ ) is the same value as the measurement.

Now, with respect to the sample 3, the angle α and the angle (α + 18
Consider the case of measurement with a pair of 0 °). When the angle is (α + 180 °), the normal vector of the lattice plane is (n (
α + π) ₁ , n (α + π) ₂ , n (α + π) ₃ ), the strain in the direction of the normal vector at the angle α is ε (α) and the strain at the angle (α + 180 °) is When the strain in the direction of the line vector is ε (α + π), the strains in the direction of the normal vector are given by the following equations (10) and (11).

[0030]

[Equation 5] Here, by calculating [ε (α) −ε (α + π)], the following equation (12) can be obtained.

[0031]

[Equation 6] By substituting the above equations (4), (5), and (6) and the following equation (13) into the above equation 12, the following equation (14) can be obtained.

Ε _x = ε ₁ cos ² φ + ε ₂ sin ² φ (13)

[Equation 7] By substituting σ _f = σ ₁ cos ² φ + σ ₂ sin ² φ (15) into the above equation (14), the following equation (16) can be obtained.

[0033]

[Equation 8] Here, let d (α) be the lattice spacing measured when rotated by an angle α, and let d (α + π) be the lattice spacing measured when rotated by an angle (α + 180 °). Let d ₀ be the lattice spacing. The incident angle θ to the crystal lattice plane is θ _{1 for} the angle α, and the angle (α +
Letting θ ₂ be for π), the above ε (α) and ε (α + π) can be expressed as in the following equations (18) and (19).

[0034]

[Equation 9] Here, in the equations (18) and (19), it can be approximately regarded that cot θ ₁ = cot θ ₂ = cot θ, and therefore the following equation (20) is established.

Ε (α) −ε (α + π) = − cot θ · (Δθ ₁ −Δθ ₂ ) (20) Then, from this equation (20) and the above equation (16), Expression (21) is established, and from this expression (21), expression (2
2) and derive the gradient K (equation (23)) of the straight line of (Δ2θ ₁ −Δ2θ ₂ ): cos α to calculate the residual stress σ _f as shown in the following equation (24). You can

[0036]

[Equation 10] In the above, the value of the rotation angle α of the sample 3 by the irradiation region turning function provided in the sample support mechanism 6 is an arbitrary value as long as it can be measured at two positions of the angle α and the angle (α + 180 °). Good. Then, by measuring the peak profile at two positions of the angle α and the angle (α + 180 °), even if the incident X-ray beam 4 is incident on the sample surface normal 10 at any angle ψ ₀ , As shown in the above equation (24), the angle α and the angle (α
The residual stress can be obtained from the deviation of the peak angle in the peak profile at the two positions (+ 180 °). Moreover, the value of the angle α is changed for one sample, the peak profile measurement at two positions of the angle α and the angle (α + 180 °) is repeated a plurality of times, and the plurality of measured values obtained by the comparison processing are compared. By doing so, it is easy to increase the measurement accuracy, and it is also possible to evaluate the error of the measurement value and increase the reliability.

Therefore, according to the X-ray residual stress measuring method of the above-described embodiment, the object of measurement is a small area on the thin film sample, and the number of crystal grains existing in the X-ray irradiation area is small, or Even when the distribution of crystal grains in the crystal lattice plane is biased, residual stress can be measured, and at the same time, it is possible to evaluate the error of the measured value. Since only one position sensitive X-ray detector can be used, the cost of the device can be reduced and the device can be made compact.

In the embodiment described above, the position sensitive X
It was decided to equip only one line detector 8. However, in order to enable the measurement of the peak profile at the angle α and the measurement of the peak profile at the angle (α + 180 °) at the same time to increase the processing speed, the X-ray diffractometer detects position sensitive X-rays. It is also possible to equip two vessels.

FIG. 3 shows an example of the construction of an X-ray diffractometer equipped with two position-sensitive X-ray detectors. In this case, the two position-sensitive X-ray detectors 20 and 21 are arranged such that, when one of the position-sensitive X-ray detectors 20 is measuring a peak profile at an angle α, for example, the other position-sensitive X-ray detector 21. So that the peak profile at the angle (α + 180 °) can be measured at, so that each sensitive surface is located in the same plane containing the incident X-ray beam 4,
It is arranged so as to sandwich the incident X-ray beam 4.

In FIG. 3, reference numeral 22 is the rotation axis of the sample 3 which overlaps the extension line of the incident X-ray beam 4. Further, for the angles η ₁ and η ₂ in the figure, the following equation (25) is approximately established.

Η ₁ = η ₂ = η = (90 ° −θ) (25) Then, the angles ψ ₁ and ψ ₂ in the figure are calculated by the following formula (26).
And according to (27). ψ ₁ = ψ ₀ −η
(26) ψ ₂ = ψ ₀ + η (27) In the X-ray diffractometer of FIG. 3, the position-sensitive X-ray detector 2 is used.
The crystal lattice plane normal detected at 0 is given by the above equation (9). For the crystal lattice plane normal detected by the position-sensitive X-ray detector 21, substitute ψ ₁ in place of ψ in the above formula (8) and use the relationship of the following formula (28). Thus, the following expression (29) is obtained.

Ψ−ψ ₀ = ψ ₁ −ψ ₀ = −η = (− 90 ° + θ) (28)

[Equation 11] Since this formula (29) is the same as the formula obtained by substituting (α + π) for the angle α in the above formula (9), the same is true for these two position-sensitive X-ray detectors 20 and 21. The residual stress can be detected from the difference between the peak angles of the peak profiles detected at the same time as in the case of the first embodiment.

[0043]

As is apparent from the above description, the X-ray residual stress measuring method according to the present invention has an angle (α + 180) from the angle α with the optical axis of the incident X-ray beam of the sample as the rotation center axis.
Rotate to the angle α and angle (α + 180)
The peak profile is measured at two positions of (°), and even if the incident X-ray beam is incident at any angle with respect to the normal to the sample surface, the residual stress can be calculated from the deviation of the peak angle of the peak profile at the two positions. Can be asked. Moreover, the value of the angle α is changed for one sample, the peak profile measurement at two positions of the angle α and the angle (α + 180 °) is repeated a plurality of times, and the plurality of measured values obtained by the comparison processing are compared. By,
It is easy to improve the measurement accuracy, and it is also possible to evaluate the error of the measurement value and improve the reliability.

Therefore, when the object to be measured is a minute area on the thin film sample, the number of crystal grains existing in the X-ray irradiation area is small, or the direction distribution of the crystal lattice planes of the crystal grains is uneven. However, it is possible to measure the residual stress, and at the same time, it is possible to evaluate the error of the measured value. Moreover, it is possible to use only one position-sensitive X-ray detector equipped in the X-ray diffractometer. As a result, the cost of the device can be reduced and the device can be made compact.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an X-ray diffractometer used in an embodiment of the present invention.

FIG. 2 is an explanatory view of the operation in one embodiment.

FIG. 3 is an explanatory diagram of an application example of the present invention.

[Explanation of symbols]

 1 X-ray diffractometer 2 X-ray source 3 Sample 3a Surface 4 Incident X-ray beam 6 Sample support mechanism 7 Diffractive X-ray 8 Position-sensitive X-ray detector 10 Sample surface normal 11 Lattice surface normal 12 Axes

Claims (1)

[Claims] 1. An X-ray source, a sample support mechanism for holding a sample on an optical path of an incident X-ray beam output from the X-ray source, and operating an X-ray irradiation position on the sample, and a sample support mechanism from the sample. Diffraction X
An X-ray residual stress measuring method for measuring residual stress using an X-ray diffractometer equipped with a position-sensitive X-ray detector for detecting X-rays, comprising: a sample support mechanism of the X-ray diffractometer; Irradiation area setting function capable of locating an arbitrary position on the optical path of the incident X-ray beam at an arbitrary angle, and irradiation area swiveling function of rotating the sample with the optical axis of the incident X-ray beam as a rotation center axis With respect to the incident X-ray beam which is incident at an angle ψ ₀ with respect to the normal to the sample surface, the rotation angle of the sample by the irradiation region turning function is at two positions of arbitrary angles α and (α + 180 °). The position-sensitive X-ray detector detects diffracted X-rays, and the peak profile and angle (α + 180 °) at the arbitrary angle α
An X-ray residual stress measuring method, characterized in that the residual stress is measured from the deviation of the peak angle from the peak profile at the time.