JP2000321224A - Method and device for dynamically observing change in crystal particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To observe the dynamic change in micro organization and a sample in a park shape by dynamically observing the change in a crystal particle in such state as heating and cooling with a secondary electron image or a reflection electron image from the sample where a condensation ion beam is applied. SOLUTION: The acceleration ion of a Ga ion source 1 scans a sample 5 by a deflection coil 2 after condensation. A sample surface is subjected to sputtering by the ion beam, and a secondary electron and a reflection electron being generated due to the collision of the ion against the sample 5 are detected by a secondary electron detector 3 and a reflection electron detector 4, respectively. A heating/cooling holder 6 for fixing the sample 5 can heat or cool the sample 5 indirectly up to 1,500 deg.C. The secondary electron detector 3 that is located at the upper portion of the sample 5 is positioned at an area that is not subjected to direct sunlight in observation where temperature is equal to or more than 1,000 deg.C since image quality deteriorates at 1,000 deg.C or higher due to directly sunlight caused by the temperature increase of the sample, thus bending the secondary electron and capturing it by the gradient of an electric field. Then, the change in the crystal particle is dynamically observed during heating, cooling, or the like by the detected secondary electron image or the reflection electron image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microscope technique, and more particularly to a change in a microstructure of a material during heating, cooling or isothermal holding at a high temperature, particularly a change in crystal grains and its crystal, which has been difficult in the past. The present invention provides a method for in-situ observation of grain orientation, and enables dynamic and continuous observation of phase transformation, recrystallization, crystal grain growth, etc. occurring in a material.

[0002]

2. Description of the Related Art It is known that the mechanical and physical properties of a material have an extremely close relationship with the crystal grain size and texture in the material. For example, the strength and toughness of a polycrystalline material increase in inverse proportion to the size of crystal grains, and the magnetic properties of an electrical steel sheet change depending on the size of magnetic domains (size of crystal grains) and texture. For this reason, control of crystal grain size and orientation is extremely important in material design, and various studies have been made to obtain such control guidelines. The most direct method for obtaining a quantitative control guideline is to determine the movement of crystal grains and the change in microstructure due to phase transformation and recrystallization during heating and cooling, and the crystal orientation in situ (in -situ)
Observe and understand its behavior.

As a method and an apparatus capable of in-situ observation of a microstructure change of a material during heating and cooling, a sample having a heating mechanism as disclosed in JP-A-5-114377 and JP-A-6-096709 is disclosed. An apparatus for observing with an electron microscope using a holder has been devised. However, these methods have the following disadvantages when the electron microscope is of a scanning type or a transmission type. That is, the scanning electron microscope (SEM) has the advantage of obtaining an observation magnification of several hundred to several tens of thousands times, which is suitable for observing the microstructure of a material, but has the advantage that the movement of crystal grain boundaries and There has been a problem that changes in the microstructure cannot be observed “dynamically”. This is because (1) the oxide layer or alloy layer is formed on the sample surface at high temperature, and information inside the bulk immediately below the oxide layer or alloy layer cannot be obtained. This is because the contrast of crystal grains existing in a smooth surface cannot be visually and clearly distinguished because the beam is an electron beam.

In the case of a transmission electron microscope (TEM),
Unlike SEM, it has the feature that crystal grain boundaries can be clearly observed, but there is a problem that the observable region has a surface area of only about 0.005 mm ² at most. Furthermore, the thickness of the sample must be reduced to 0.5 μm or less in order to allow electrons to pass through, so that the typical crystal grain size of practical materials is several μm.
There is also a problem that a change in crystal grains on the order of several millimeters cannot be observed.

As a method for solving the problem (1), an apparatus and a method for observing with a TEM while performing fine processing with a focused ion beam as disclosed in JP-A-7-92062 can be used. That is, it is considered effective to use a focused ion beam to remove an oxide layer generated on the surface of the sample during heating. However, the method of the present invention aims at providing a high-quality TEM thin film, and does not aim at observing a microstructure such as a grain boundary. Furthermore, this method does not aim at observing dynamic changes in the microstructure during heating, cooling or isothermal holding, and solves the problems of the narrow field of view and the thinning effect inherent to the TEM method. I can't do that.

As described above, (1) during heating, during cooling, during isothermal holding at a high temperature, and after processing at a high temperature,
(2) With an observation magnification of about 100 to 100,000 times suitable for microstructure observation, (3) oxidation of the sample surface which is a problem during high temperature observation can be avoided, and (4) movement of crystal grains and microstructure There has been a demand for an invention of a method capable of clearly observing a dynamic change and (5) observing a sample in a bulk state without forming a thin film.

[0007]

SUMMARY OF THE INVENTION The present invention has been developed in view of the above-mentioned situation, and has a microstructure during heating, cooling, or isothermal holding at a high temperature, and furthermore, during or after processing at a high temperature. About 100x to 10 suitable for observation
With a magnification of about 10,000 times, it is possible to avoid oxidation of the sample surface, which is a problem during high-temperature observation, to clearly observe the movement of crystal grains and dynamic changes in microstructure, and to observe a bulk sample instead of a thin film. The purpose is to provide.

[0008]

According to the present invention, the following means are provided to solve the above-mentioned problems. That is, the first feature of the present invention is that during heating, a secondary electron image or a reflected electron image generated when the sample is irradiated with the focused ion beam is used.
This is a method of dynamically observing a crystal grain change in at least one state during cooling and holding at the same temperature.

A second feature is the method for dynamically observing a change in crystal grain according to claim 1, wherein the crystal orientation of each crystal grain is measured in-situ. High temperature refers to a temperature at which movement (change) of crystal grains in a sample can be observed, and differs depending on the sample type. For example, iron-based materials indicate temperatures of 300 ° C or higher, and aluminum materials indicate temperatures of 100 ° C or higher.

In order to measure the crystal orientation of each crystal grain, it is preferable to apply a focused electron beam to the sample, detect an electron back scattering pattern (EBSP) generated from the sample, and analyze the pattern. An electron beam backscattering pattern analyzer having a function of irradiating a focused ion beam and a function of detecting at least one kind of secondary electron and reflected electron from a sample by the irradiation is used. Further, in order to change the temperature of the sample, a heating and cooling mechanism is built in the sample holder, or a mechanism for injecting a cooling gas to the sample surface is adopted. Further, as a derivative of the method of the present invention, by additionally providing a tension or compression mechanism on the sample stage, it becomes possible to observe the movement of the grain boundaries or the change of the microstructure during or immediately after the high-temperature deformation.

[0011]

According to the above structure, an oxide layer formed on the surface of a sample can be continuously sputtered by a focused ion beam, so that a new surface of a bulk surface can be always observed even at a high temperature. Furthermore, since the focused ion beam is used at the same time as a primary probe (incident beam) for generating secondary electrons or reflected electrons,
Unlike the case where an electron beam is used as a primary probe, crystal grain boundaries can be clearly observed even in a bulk sample due to the channeling effect of ions. In addition, since a wide area can be observed in a bulk state without thinning the sample, it is possible to observe the movement of crystal grains in the true bulk or the change in microstructure. Further, in the present invention, a function of irradiating a focused ion beam to an electron beam backscattering pattern analysis device comprising an electron beam generation / focusing device and an EBSP detection mechanism,
In addition, by incorporating a function of detecting secondary electrons or reflected electrons from the sample due to the irradiation, it is possible to simultaneously perform dynamic observation of the crystal grains and analyze the orientation of the crystal grains being observed. Observable magnification can be from about 100 times to about 100,000 times suitable for microstructure observation.

[0012]

Embodiments of the present invention will be described below. The inventors first attempted dynamic observation of crystal grains by mounting sample heating and cooling holders for SEM and TEM on a focused ion beam (FIB) processing apparatus using Ga as an ion source. FIG. 1 shows a schematic diagram thereof.

The ions accelerated from the Ga ion source 1 are scanned on the sample by the deflection coil 2 after focusing. At the same time that the sample surface is sputtered by the ion beam, secondary electrons generated by the impact of ions on the sample are reflected by the secondary electron detector 3 and reflected electrons are reflected by the reflected electron detector 4.
Is detected by The beam type of the focused ion beam used as the sample observation probe is Ga, which has already been put into practical use as an FIB processing device, and A, which is a low melting point metal.
s, Bi, Cs, Ga, In, Li, Mg, Sb, Sn, Zn can be used.

The sample 5 is fixed by a heating / cooling holder 6. In the heating / cooling holder 6, the sample is indirectly heated by a tungsten filament placed under the sample, and is indirectly cooled by a water cooling tube arranged around the sample. With such an indirect sample heating method, 1500
Although heating up to ° C. is possible, a method of directly energizing the sample is preferred for further heating at a higher temperature.

As a method of cooling a sample, in addition to (1) a method of indirectly cooling by extending a cooling pipe around a sample as in this embodiment, (2) a method of reducing a current to be supplied,
(3) It is effective to directly inject a gas such as nitrogen, argon or helium into the sample and cool it. Usually, the method (1) or (2) is sufficient, but especially when observing the movement of the crystal grains (or the change of the microstructure) at a cooling rate of 10 ° C / s or more, the method (3) alone or The combination method of (2) and (3) is preferable. Reference numeral 7 denotes a gas injection mechanism for cooling the sample by injecting an inert gas such as nitrogen, argon, or helium directly onto the sample.

The secondary electron detector 3 is located above the sample. However, in this case, the image quality deteriorates at 1000 ° C. or higher due to direct light from the sample caused by the temperature rise of the sample. For this reason
In order to observe at 1000 ° C or higher, a detector is placed at a position where direct light from the sample does not shine,
It is desirable to use a method in which secondary electrons are bent by an electric field gradient and captured by the detector 3.

In the above mechanism, the sample is placed in a vacuum atmosphere in order to prevent rapid sample oxidation at a high temperature. The better the degree of vacuum, the better the observation of the sample. Further, the present inventors have incorporated an electron beam source and a detection mechanism of an EBSP (Electron Beam Back Scattering Pattern) analyzer into the above-described FIB apparatus in order to analyze the orientation of each crystal grain. According to the method of the present invention, a Kikuchi pattern of backscattered electrons at a high temperature can be clearly observed, and it is possible to analyze not only the structure of a crystal grain dynamically changing at a high temperature but also the orientation of the crystal grain.

Using the above apparatus and using polycrystalline iron as a sample, the heating rate was 100 ° C./sec or less, and the cooling rate was 50 ° C.
Within the range of / sec or less, the apparatus shown in Fig. 1 can be used to determine the behavior of α-γ phase transformation (during heating), grain growth (during heating and isothermal holding), and γ-α phase transformation (during cooling) in situ. (in-situ)
It was confirmed that observation was possible. 2 (a) and 2 (b) are examples of dynamic observation results of crystal grain change, and are examples of observing the time change of iron crystal grains at 1000 ° C.

[0019]

The present invention provides a means for dynamically observing grain growth, dynamic recrystallization, static recrystallization, phase transformation during heating, isothermal phase transformation, and phase transformation during cooling, which were not previously observable. And can greatly contribute to the elucidation of the above phenomena. Steel materials, aluminum materials, titanium materials, whose internal structure changes below 1500 ° C
It can be used as a method for observing the structure of metal materials represented by copper materials, and has the effect of advancing the research and development of these materials.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus including a sample stage having an ion focusing mechanism and a heating / cooling mechanism according to an embodiment of the present invention.

FIG. 2 is an example of observing the time change of the microstructure of polycrystalline iron at 1000 ° C., wherein FIG. 2 (a) is a photograph of a metal structure held for 0 minutes and FIG. 2 (b) is a photograph of a metal structure held for 30 minutes.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ga ion source (Ion-containing acceleration mechanism) 2 ... Ion beam focusing and deflection mechanism 3 ... Secondary electron detector 4 ... Reflection electron detector 5 ... Sample 6 ... Sample heating and cooling holder 7 ... Gas injection port

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G001 AA03 AA05 BA07 BA15 CA03 DA02 DA06 GA06 GA17 JA01 JA14 KA08 KA20 LA02 PA07 QA01 RA03 RA20 5C033 QQ05 QQ10 UU03 UU06

Claims (4)

[Claims] 1. A method for dynamically observing a change in crystal grains in at least one of a state of heating, a state of cooling and a state of isothermal holding by a secondary electron image or a reflected electron image from a sample irradiated with a focused ion beam. . 2. The dynamic observation method of crystal grain change according to claim 1, wherein the crystal orientation of each crystal grain is measured in situ. 3. An electron beam backscattering pattern analysis having a function of irradiating a focused ion beam and a function of detecting at least one kind of secondary electron and reflected electron from a sample by the irradiation. apparatus. 4. The apparatus according to claim 3, wherein the apparatus has at least one function of heating, cooling and processing the sample.