JPH02145948A - Measurement of texture by energy scattering - Google Patents

Abstract

PURPOSE:To enable highly accurate measurement of a texture on a plurality of grid surfaces simultaneously even for a sample that unavoidably causes overlapping of an escape peak by measuring the texture by an energy dispersion method. CONSTITUTION:An X-ray bulb 14 is provided to generate continuous X rays as incident X rays 12 and an X-ray generator 16 to apply a specified voltage and current. An angle theta at which the X rays 12 are incident into a sample 10 and an angle 2theta of diffraction of the X rays 12 which are diffracted in the sample 10 and incident into a semiconductor detector 30 are set by a goniometer 20. Then, a signal detected by the detector 30 undergoes an energy analysis by a multiple pulse height analyzer 34 after amplified. An output of the analyzer 34 is analyzed with a control/analysis central processing unit 36 to perform a background correction thereof while effect of an escape peak due to the detector 30 to determine an accurate diffraction peak intensity. Moreover, a relative intensity ratio is determined with respect to a random sample to plot an inverted pole point chart or a normal pole point chart on a plotter 38 while a data thereof is printed out.

Description

[Detailed description of the invention] [Industrial application field]

The present invention provides a method for measuring texture using an energy dispersive method for quickly and accurately measuring the texture of a metal sample, particularly a rolled metal plate.

[Conventional technology]

In general, the texture of metal materials, especially steel sheets, has a significant effect on their processing characteristics and magnetic properties. For example, the deep drawing characteristics (Lankford value) of cold-rolled steel sheets are based on the (111) crystal lattice parallel to the surface of the steel sheet. The greater the surface strength, the better. In addition, in grain-oriented silicon steel sheets, the magnetic flux density and the secondary recrystallized grain size are larger as the secondary recrystallized grains are more concentrated in the <110>[001] orientation. In order to develop a strong (
110) The [0013 orientation texture and the subsequent primary recrystallization texture have (110)[001] orientation and <111)<
It is said to be advantageous to develop a texture with a 11.2> orientation. In order to control and improve the quality of such products, accurate measurement of texture over a wide range is essential. By the way, texture measurements are generally performed off-line using small test pieces taken from the material. Conventionally, the so-called angular dispersion method was used to count the diffraction intensity of each crystal lattice plane by scanning the goniometer in θ-2θ, which took a long time and made it difficult to quickly measure a large number of samples. It was impossible. In order to meet this demand, the applicant has already published Japanese Patent Application Laid-Open No. 56-8
533, proposes a method for measuring texture using an energy dispersive method using a semiconductor detector. This method irradiates a metal plate sample with continuous X-rays at a constant angle of incidence in a plane that includes the normal to the plate surface, and fixes the diffracted X-rays from the sample at a predetermined diffraction angle position. This is detected by a semiconductor detector, and the energy is analyzed to determine the diffracted X-ray intensity from each crystal lattice plane. By measuring the priority of the diffraction intensity from each crystal lattice plane in comparison with the intensity (random intensity), the aim is to rapidly measure texture in large quantities. Generally, a metal crystal is defined as a solid state in which atoms form a crystal lattice arranged periodically in three-dimensional space. All the lattice points of these spatial lattices can be arranged on a group of mutually parallel and equidistant planes called lattice planes. The orientation of a lattice plane, regardless of its position in space, is expressed by the normal level (hkl) lowered from the origin to each lattice plane, and this is generally called the Miller index.Generally practical materials are polycrystalline. Each grain in a polycrystalline sample has a distinct orientation.However, when looking at the sample as a whole statistically, it is possible to have a specific orientation representing the sample orientation, although there are differences in degree. Therefore, measuring the texture of a polycrystalline sample involves determining the crystal orientation as its preferred orientation and quantifying the degree of aggregation. It is to find the angular relationship between a fixed coordinate system and a coordinate system fixed to the crystal.
The coordinate system fixed to the sample here is, for a plate-shaped sample,
The rolling direction (hereinafter abbreviated as RD) and the sheet width direction (hereinafter TP)
In many cases, orthogonal coordinates are set in the normal direction (hereinafter abbreviated as ND) and plate surface normal direction (hereinafter abbreviated as ND).On the other hand, the coordinate system fixed to the crystal is [1001, [0101 and [00
1] is the setting of orthogonal coordinates in the three crystal axis directions. Next, the degree of aggregation in the preferred orientation is usually expressed by a polar density distribution function that indicates the distribution of (hkl) crystal planes in the sample.
To obtain the polar density distribution function from the diffraction intensity, it is necessary to theoretically correct the intensity change due to changes in the diffraction geometry, or to calculate the diffraction intensity from a certain crystal plane of the sample and the random intensity from the same crystal plane. It is quantified by the value of the ratio of Now, there are the following two ways to display the texture. (1) Fix the sample coordinate system and select a certain crystal plane, for example (hk
The intersection points of the crystal surface normal and the projection sphere are distributed in which directions and with what density (f! density distribution function) on the stereo projection drawing from the poles of l ) are plotted (hk
l) Method shown by positive pole figure. (2) A method in which the crystal coordinate system is fixed and in any direction of the sample, for example, only the existence intensity of the lattice plane (hkl > parallel to ND) is displayed as an inverse pole figure in that coordinate system. The figure or inverse pole figure is usually measured by X-ray diffraction as follows.Now, an X-ray with wavelength λ is
When incident X-rays are incident on a lattice plane having a Miller index (hkl) at an incident angle θ, diffraction occurs only in the direction 2θ with respect to the incident X-ray (that is, the direction of specular reflection with respect to the lattice plane). This relationship is described by the following Bragg's equation (1). Here, dhkl is (hkl > spacing between lattice planes, and is expressed by the following formula % formula % (2). Here, a is a lattice constant. In the measurement by the angular dispersion method, characteristic X-rays are used. Therefore, the wavelength λ is constant and the incident angle θhkl determined by equation (1)
, by scanning the goniometer at the diffraction angle 2θhkl, (h
kl >Measure the intensity of diffracted X-rays from the lattice plane. On the other hand, in measurement using the energy dispersive method, continuous X-rays with good wavelength λ are used, so even if the incident angle θ (diffraction angle 2θ) is arbitrarily fixed in equation (1), the As shown in FIG.
If the detection signal is detected and the energy of the detected signal is analyzed, the intensity of the diffracted X-rays from each (hkl) lattice plane can be measured without scanning the goniometer 20. (hkl) Energy of diffracted X-rays from the lattice plane Ehk1
is given by the following equation. Ehkl = 12.4/2 sin θ, 1/dhk...
-(3) Here, θ is an arbitrary angle of incidence. As mentioned above, the inverse pole figure describes the intensity of the lattice plane (hkl) parallel to the normal to the sample surface (NO). line 1
Fix the sample 10 so that 8 is in the direction of specular reflection,
The intensity of the energy Ehk of each diffracted X-ray is measured. Thereafter, the same operation is performed on a random standard sample without crystal orientation, and the relative ratio between the intensity of each of the above-mentioned diffraction X-ray energy Ehkl and the corresponding random intensity is determined. This is the lattice plane (hkl) parallel to the sample surface normal (ND) in the sample coordinate system.
This corresponds to the existence strength of . On the other hand, in the case of a positive pole figure, the sample is rotated to each geometric position scaled in the sample coordinate system, the relative intensity ratio is measured, and the results are illustrated in the sample coordinate system by stereo projection. Alternatively, if there is no suitable random standard sample, the commonly known (i) 5chulz divergent beam reflection method correction formula (i
i) 5chulz divergent beam transmission method correction formula (iii
) D eCker-A Sp-Harker parallel beam parallel beam transmission method formalism ( ) is used to correct the diffraction geometry dependence of the diffracted X-ray intensity. It goes without saying that (i) to (iii) are selected depending on the measurement optical system. In the energy dispersive method, the incidence/diffraction angle (θ/2
By arbitrarily selecting θ), the energy E of each diffracted X-ray
hkl can be varied. The solid line in Figure 9 shows the relationship between the incident angle θ and the energy Ehkl of the diffracted X-rays of the (110), (200), and (211) lattice planes, which are most notable in the positive pole figure, for α iron. be.

[Problem to be achieved by the invention]

By the way, when an X-ray photon with energy greater than the absorption edge of a semiconductor element is incident on a semiconductor detector, ionization of the semiconductor element occurs in the intrinsic region of the detector, and for example, the semiconductor element becomes G
In the case of e, ionization of Ge and GeKa lines are generated. This X-ray is also normally consumed in the ionization of Ge in the intrinsic region, and a high-voltage electric field applied to the detector produces a pulse signal with an intensity proportional to the energy of the diffracted X-ray photon. However, when ionization of the semiconductor element occurs near the entrance surface of the detector, the probability that the generated X-rays escape from the intrinsic region increases. Therefore, eV is added to the energy (Ehkl - 9,87) obtained by subtracting the energy of the GeKa ray (9,87 KeV) from the energy Ehkl of the diffracted X-ray, and as a new escape peak, the intensity of this diffracted X-ray increases. It will be detected depending on the The broken lines in FIG. 9 indicate escape peaks of individual diffraction peaks. It can be seen that escape peaks appear at specific energies, corresponding to the number of diffraction peaks. Moreover, the intersection of the solid line and the broken line in FIG. 9 means that the escape peak overlaps the diffraction peak. Therefore, in measurements using the conventional energy dispersive method, the incident/diffraction angle must be selected such that the diffraction peak and the escape peak do not overlap. For example, in the measurement of γ iron, θ = 6.5 to 7°. This can prevent the above overlap. However, as is clear from Figure 9, α
In iron, the energy of the diffraction peak spreads slightly, so
There is no incident/diffraction angle condition such that there is no overlap between the diffraction peak and the escape peak for all three diffraction peaks of <110), (200), and (211>.However, conventionally, a semiconductor detector is used. It does not mention the problem of escape peaks that occur when
Depending on the sample (for example, alpha iron), the escape peak may overlap the diffraction peak required for measurement no matter how the incident/diffraction angle is set. For this reason, there were problems in the measurement of the positive pole figure, which reflects the accuracy of the diffraction peak intensity, and in the calculation of the three-dimensional pole figure that is synthesized from the positive pole figure. The present invention was made to solve this problem, and even if this escape peak cannot be removed from the diffraction peaks necessary for measurement, no matter how the geometry of the goniometer is set, it is possible to Set Gf1 using energy dispersion method that allows tissue to be measured quickly and with high precision
The purpose of this invention is to provide a method for measuring m.

[Means to solve the problem]

In measuring the texture of a metal sample, the present invention irradiates continuous X-rays with the angle of incidence fixed at a constant angle, and diffracted X-rays from the sample at a position twice the angle of incidence. , and each crystal lattice obtained by detecting with a semiconductor detector fixed at a position where the diffraction peak and the escape generated from the detector overlap, and analyzing the energy of the detection signal with a pulse height analyzer to remove the influence of the escape peak. The above objective is achieved by determining the polar density distribution function from the diffracted X-ray intensity for each surface.

[Effect]

As already explained, in measurements using the energy dispersive method,
It is necessary to select an incident/diffraction angle such that the diffraction peak and the escape peak generated from the semiconductor detector J) do not overlap. However, as is clear from Figure 9, in the case of a sample whose diffraction peaks have energy spread (alpha iron in the example in Figure 9), all of the diffraction peaks to be measured include the diffraction peak and the escape peak. There is no condition for incident/diffraction angles such that there is no overlap.The present invention is used in such cases, and the diffraction spectrum is measured at an incident/diffraction angle such that the escape peak matches the diffraction peak. However, the intensity of this escape peak is calculated later and removed from the diffraction peak. An example of this is shown in Figure 2, which is a diffraction spectrum of alpha iron measured with the measuring device shown in Figure 1 with the incident angle θ fixed at 7°. apart from,
Escape peaks Ps and P6 appear. From Figure 9, P5 is due to the (110) diffraction peak, and P6 is due to the (110) diffraction peak.
211) It can be seen that this is due to the diffraction peak. Also, peaks P7 and Pa are characteristic X-rays included in the incident X-rays, in this case MOkcr line (8V at 17, 45) and MOk
The escape peak of the <200> diffraction peak, which is β-ray (19,61 eV), generally has lower energy than the diffraction peak, so it rarely overlaps with the diffraction peak. Like, (110)
It perfectly matches the diffraction peak. Therefore, the actual (1
10) The diffraction peak intensity may be the value obtained by subtracting the escape peak intensity of the (200) diffraction peak. By the way, in general, the diffraction peak intensity Ihk of a semiconductor detector
As shown in FIG. 3, the escape peak intensity ratio Jhkl with respect to l has its own energy dependence,
Therefore, if the energy dependence of the escape peak intensity ratio of the semiconductor detector is measured in advance, for example (200
>Intensity ratio J200 to the diffraction peak can be determined, and as a result, the (110) diffraction peak intensity is lll0-I2
It is obtained by calculating 00XJ200. The reason why it is good to set the incident/diffraction angle so that the diffraction peak and escape peak completely overlap is that if the escape peak is slightly shifted from the diffraction peak position and only partially overlap, then the diffraction peak This is because only the overlapping peak areas have to be subtracted, which is practically difficult. Further, the number of diffraction peaks from which the escape peak intensity must be subtracted may be one as described above, or may be more than this. By the way, to measure the area of each diffraction peak from the diffraction spectrum shown in Figure 2, any method commonly used in calculations may be used, but it can be determined as follows using a multiple wave height analyzer. You can also do that. That is, as shown in FIG. 4, by setting the baseline BL and the energy window EW to sandwich both ends of the diffraction peak P using a multiple wave height analyzer, the area of the peak between them can be measured. This also includes a portion Sb approximated by a hatched trapezoid as a background. The area Sb of this background can be determined by calculating the plane '$Asf of the flat portion of the background only in the diffraction spectrum in a similar manner, and multiplying this by the ratio of the window width to the energy window EW of the diffraction peak P. You can ask for it. In the manner described above, the intensity of only the accurate diffraction peaks excluding the background and escape peaks can be determined. fkt&, this operation is also performed for a random sample without orientation, and the relative intensity ratio of each corresponding (hkl) diffraction peak to the random sample is calculated, or the polar density is calculated by performing theoretical intensity correction on each diffraction intensity. Find the distribution function. In the above measurement, if the sample 10 is fixed at a mirror-symmetrical position with respect to the X-ray optical system, as shown in FIG. 1, the relative intensity ratio will be inverse pole figure data. On the other hand, if the sample 10 is not fixed and the relative intensity ratio is measured by rotationally moving to individual geometric positions scaled in the sample coordinate system, this becomes positive pole figure data.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As shown in Fig. 1, the texture measuring device using the energy dispersion method for carrying out this example
An X-ray tube 14 including, for example, a Mo rotating anticathode for generating rays 12, and an X-ray generator 16 that applies a predetermined voltage and current (for example, 60 KV, 300 mA) to the X-ray tube 14. It is included as an X-ray optical system. The incident angle θ of the incident X-ray 12 with respect to the sample 10 (for example, θ=
7') and is diffracted by the sample 10, and the semiconductor detector 30
The diffraction angle 2θ (for example, 2θ=1
4°) is set by the goniometer 20, and 22 is the goniometer drive unit. Note that when obtaining inverse pole figure data, it is not necessary to change the incident/diffraction angle during measurement, so it is also possible to omit this goniometer drive section 22. The signal detected by the semiconductor detector 30 is amplified by an amplifier 32 and then energy analyzed by a multiple pulse height analyzer 34. The output of the multiple wave height analyzer 34 is analyzed by a control/analysis central processing unit (CPU) 36, and the background is corrected, and the influence of escape peaks caused by the semiconductor detector 30 is removed, and accurate diffraction peak intensities are determined. Desired. Additionally, the relative intensity ratio for the random sample is determined and an inverse or positive pole figure is drawn on plotter 38, and
The data is printed out on the printer 40. In the figure, 42 is a control/analysis program and a flowchart for storing the data as necessary. According to this example, the positive pole figure of a cold rolled steel plate was measured under the following setting conditions. X-ray tube used = MO rotating anticathode (60KV, 300n+A) Incident/analysis angle: θ = 7°, 2θ = 14° Optical system used:
Figure 5 shows the (110) positive pole figure obtained by taking the relative intensity ratio of the (110) diffraction intensity obtained by the 5chulz bursting beam method and the (110) diffraction intensity of a random sample measured under the same conditions. In addition, the (110) positive pole figure obtained by correcting the theoretical intensity of the (110) diffraction intensity from the sample is shown in Figure 6, and there is almost no difference from the result measured by the angular dispersion method of the same sample shown in Figure 7. It turns out that this is not allowed. On the other hand, according to the conventional energy dispersion method, the incident/diffraction angle is set to θ
In FIG. 8, which was measured under the setting conditions of =8° 2θ = 16°, it can be seen that an error caused by the escape peak occurs.

【Effect of the invention】

As explained above, according to the present invention, even in a sample where overlapping of escape peaks cannot be avoided, the excellent effect of being able to simultaneously measure the texture of a plurality of lattice planes with high accuracy using the energy dispersion method can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a texture measuring apparatus using an energy dispersive method in which the present invention is implemented, and FIG. Figure 3 is a line representing the measured diffraction spectrum; Figure 3 is a diagram representing the energy dependence of the escape peak intensity ratio of a Ge semiconductor detector; Figure 4 is a diagram representing only the diffraction peak with the background removed. A schematic diagram illustrating the method for determining intensity; Figures 5 and 6 are diagrams showing measurement results according to the present invention; Figure 7 is a diagram showing measurement results using the angular dispersion method; Figure 9 is a diagram showing the fIA coefficient of the incident angle θ of α-iron and the energy of the diffraction peak and the corresponding escape peak. DESCRIPTION OF SYMBOLS 10... Sample, 12... Incident (continuous) X-ray, 14... X-ray tube, 18... Diffracted X-ray, 30... Semiconductor detector, 34... Multiple wave height analyzer , 36...control/analysis central processing unit 38...1
0 ivy, 40... printer. (CPU),

Claims (1)

[Claims] (1) When measuring the texture of a metal sample, irradiate continuous X-rays with the incident angle fixed at a constant angle, and diffract X-rays from the sample at a position twice the incident angle, and The diffraction peak and the escape generated from the detector are detected by a semiconductor detector fixed at a position where they overlap, the detected signal is energy analyzed by a pulse height analyzer, and the influence of the escape peak is removed. A method for measuring texture using an energy dispersion method, characterized by determining a polar density distribution function from the intensity of diffracted X-rays.