JP2013148580A - Sample observation method - Google Patents
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Abstract
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本発明は、走査型電子顕微鏡（ＳＥＭ）を用いた試料観察方法に関し、特に、微細内部構造を有する第２相が母相中に分散した複相組織を有する試料について、走査型電子顕微鏡を用いて微細内部構造を有する第２相の状態を観察する際に好適に用いることができる試料観察方法に関するものである。 The present invention relates to a sample observation method using a scanning electron microscope (SEM), and in particular, to a sample having a multiphase structure in which a second phase having a fine internal structure is dispersed in a matrix, using a scanning electron microscope. The present invention relates to a sample observation method that can be suitably used for observing the state of a second phase having a fine internal structure.
従来、様々な性能を発揮し得る機能性材料として、２以上の相から構成される複相組織を有する金属材料等が用いられている。具体的には、例えば構造材料の分野では、省エネルギー化や安全性確保の観点から、様々な変態組織を活用した高強度複相組織鋼が使用されている。 Conventionally, metal materials having a multiphase structure composed of two or more phases have been used as functional materials that can exhibit various performances. Specifically, for example, in the field of structural materials, high-strength duplex steels using various transformation structures are used from the viewpoint of energy saving and ensuring safety.
ここで、高強度の複相組織鋼としては、特に限定されることなく、フェライト（母相）中にマルテンサイト（第２相）が分散したＤＰ（Dual-Phase）鋼や、フェライト（母相）中にマルテンサイトや残留オーステナイト等の第２相が分散したＴＲＩＰ（Transformation Induced Plasticity）鋼や、ベイナイト（母相）中に硬質な島状マルテンサイト（以下「ＭＡ」と称することがある。）からなる第２相が分散したベイナイト−ＭＡ鋼や、炭素鋼のＭＡを有する溶接熱影響部等を挙げることができる。そして、これらの複相組織鋼では、残留オーステナイトの加工誘起変態や、硬質のマルテンサイトを活用することにより、高価な合金元素を大量に使用することなく、高強度化を達成している。 Here, the high-strength dual-phase steel is not particularly limited, and DP (Dual-Phase) steel in which martensite (second phase) is dispersed in ferrite (matrix) or ferrite (matrix) ) TRIP (Transformation Induced Plasticity) steel in which a second phase such as martensite and retained austenite is dispersed, or hard island martensite (hereinafter referred to as “MA”) in bainite (matrix). Examples include bainite-MA steel in which a second phase composed of the above is dispersed, a welding heat-affected zone having MA of carbon steel, and the like. And in these double phase structure steel, the high intensity | strength is achieved by not using a large amount of an expensive alloy element by utilizing the processing induction transformation of a retained austenite and a hard martensite.
ところで、構造材料等として用いる複相組織鋼には、靭性や延性といった鋼材特性を低下させることなく高強度化を達成することが求められている。そして、上述した複相組織鋼では、マルテンサイトや残留オーステナイトからなる第２相の状態（例えば分散状態など）が、鋼材の強度、靭性および延性に影響を及ぼすことが知られている。 By the way, it is required for a multiphase steel used as a structural material to achieve high strength without degrading steel properties such as toughness and ductility. In the above-described multiphase steel, it is known that the state (for example, dispersed state) of the second phase composed of martensite and retained austenite affects the strength, toughness and ductility of the steel material.
そのため、性能を積極的に制御した機能性材料を開発する観点からは、複相組織鋼等の２以上の相から構成される複相組織を有する材料について、特定の第２相の状態を正確に把握することが必要とされている。特に、機能性材料のマクロな材質を制御する観点からは、特定の第２相(例えばマルテンサイト)の分散状態を巨視的かつ正確に把握することが求められている。 Therefore, from the viewpoint of developing functional materials with positively controlled performance, the state of the specific second phase is accurately determined for materials having a multiphase structure composed of two or more phases such as multiphase steel. It is necessary to grasp. In particular, from the viewpoint of controlling the macro material of the functional material, it is required to grasp the dispersion state of a specific second phase (for example, martensite) macroscopically and accurately.
そこで、従来、複相組織鋼の第２相のマクロな分散状態を把握する手法として、ナイタール液（硝酸−エタノール混合液）を用いて複相組織鋼よりなる試料の表面を化学エッチングし、第２相の組織を試料表面に現出させた後に、光学顕微鏡や走査型電子顕微鏡(ＳＥＭ)を用いて第２相の分散状態を観察する方法が用いられている（例えば、特許文献１参照）。 Therefore, conventionally, as a method for grasping the macroscopic dispersion state of the second phase of the duplex structure steel, the surface of the sample made of the duplex structure steel is chemically etched using a nital solution (nitric acid-ethanol mixed solution). A method of observing the dispersion state of the second phase using an optical microscope or a scanning electron microscope (SEM) after causing the two-phase structure to appear on the sample surface is used (for example, see Patent Document 1). .
しかし、ナイタール液を用いた化学エッチングにより第２相の組織を試料表面に現出させる上記従来の方法には、試料を化学エッチングした際に、特定の第２相以外の組織も現出してしまうため、特定の第２相のみの観察が困難になるという問題があった。即ち、複相組織鋼では、材質に影響を及ぼす第２相として、マルテンサイトや残留オーステナイトなどが挙げられるが、これらを区別して、それぞれの分散状態や定量を行なうことが困難であった。例えば、特定の第２相として、微細内部構造を有する第２相（マルテンサイト等）の分散状態のみを観察することが求められているところ、上記従来の方法では、観察対象となる、微細内部構造を有する第２相以外の組織も全て試料表面に現出してしまい（例えば、ＴＲＩＰ鋼においては、マルテンサイト以外に、ベイナイト、残留オーステナイト等も表面に現出してしまう）、特定の第２相(微細内部構造を有する第２相)の巨視的な分散状態を正確に観察することができなかった。 However, in the above-described conventional method in which the second phase structure appears on the sample surface by chemical etching using a nital solution, a structure other than the specific second phase appears when the sample is chemically etched. Therefore, there is a problem that it is difficult to observe only the specific second phase. That is, in the multi-phase structure steel, martensite, retained austenite, and the like are listed as the second phase that affects the material, but it has been difficult to distinguish between these and perform the respective dispersion states and determinations. For example, as a specific second phase, it is required to observe only the dispersion state of a second phase (such as martensite) having a fine internal structure. All the structures other than the second phase having a structure appear on the surface of the sample (for example, in TRIP steel, bainite, retained austenite, etc. appear on the surface in addition to martensite), and the specific second phase The macroscopic dispersion state (second phase having a fine internal structure) could not be observed accurately.
そこで、本発明は、第２相が母相中に分散した複相組織を有する材料からなる試料について、材質に影響を及ぼす微細内部構造を有する第２相の巨視的な分散状態を正確に観察することができる試料観察方法を提供することを目的とする。 Therefore, the present invention accurately observes the macroscopic dispersion state of the second phase having a fine internal structure that affects the material of a sample made of a material having a multiphase structure in which the second phase is dispersed in the matrix phase. It is an object of the present invention to provide a sample observation method that can be used.
本発明者らは、上記目的を達成するために鋭意検討を行った。そして、本発明者らは、走査型電子顕微鏡を用いて所定の条件下で試料の反射電子像を観察した際に、微細内部構造を有する第２相が位置する部分の輝度が第２相以外の部分に比べて著しく向上することを見出して本発明を完成させた。 The present inventors have intensively studied to achieve the above object. And when the present inventors observed the reflected-electron image of a sample on predetermined conditions using a scanning electron microscope, the brightness | luminance of the part in which the 2nd phase which has a fine internal structure is located is other than a 2nd phase As a result, the present invention was completed.
即ち、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の試料観察方法は、微細内部構造を有する第２相が母相中に分散した複相組織を有する試料について、微細内部構造を有する第２相の状態を観察する試料観察方法であって、走査型電子顕微鏡を用いて、加速電圧が７ｋＶ以上、且つ、取り込み角が６０°以上の条件下で試料の反射電子像を取得し、前記第２相の分散状態を観察する分散状態観察工程を含むことを特徴とする。
ここで、本発明において、「微細内部構造」とは、結晶方位が互いに異なる多数の結晶粒の集合体よりなる構造を指す。
That is, this invention aims to solve the above-mentioned problem advantageously, and the sample observation method of the present invention has a multiphase structure in which the second phase having a fine internal structure is dispersed in the matrix. A sample observation method for observing a state of a second phase having a fine internal structure with respect to a sample, using a scanning electron microscope under a condition where the acceleration voltage is 7 kV or more and the capture angle is 60 ° or more And a dispersion state observing step of observing the dispersion state of the second phase.
Here, in the present invention, the “fine internal structure” refers to a structure composed of an aggregate of a large number of crystal grains having different crystal orientations.
ここで、本発明の試料観察方法は、前記試料の観察面側の表層部を除去する試料調整工程と、前記試料調整工程の後に、前記第２相の微細内部構造を観察する微細構造観察工程とを更に含むことが好ましい。 Here, the sample observation method of the present invention includes a sample adjustment step for removing a surface layer portion on the observation surface side of the sample, and a fine structure observation step for observing the fine internal structure of the second phase after the sample adjustment step. It is preferable that these are further included.
また、本発明の試料観察方法は、前記微細構造観察工程が、走査型電子顕微鏡を用いて、加速電圧が２０ｋＶ以下の条件下で前記第２相の微細内部構造を観察する工程であり、前記分散状態観察工程および前記微細構造観察工程を、前記試料調整工程の後に実施することが好ましい。 In the sample observation method of the present invention, the fine structure observation step is a step of observing the fine internal structure of the second phase under a condition where the acceleration voltage is 20 kV or less using a scanning electron microscope, It is preferable that the dispersion state observation step and the microstructure observation step are performed after the sample preparation step.
そして、本発明の試料観察方法は、前記試料調整工程において、イオンエッチングを用いて前記試料の表層部を除去することが好ましい。 And it is preferable that the sample observation method of this invention removes the surface layer part of the said sample using ion etching in the said sample adjustment process.
本発明の試料観察方法によれば、分散状態観察工程において取得した反射電子像において、微細内部構造を有する第２相が位置する部分の輝度を、微細内部構造を有する第２相以外の部分に比べて著しく向上させることができるので、材質に影響を及ぼす特定の第２相の巨視的な分散状態を正確に観察することができる。 According to the sample observation method of the present invention, in the reflected electron image acquired in the dispersion state observation step, the luminance of the portion where the second phase having the fine internal structure is located is set to the portion other than the second phase having the fine internal structure. Since it can be remarkably improved, the macroscopic dispersion state of a specific second phase that affects the material can be accurately observed.
以下、図面を参照して本発明の実施の形態を説明する。ここで、本発明の試料観察方法は、特に限定されることなく、ＤＰ鋼や、ＴＲＩＰ鋼や、ベイナイト−ＭＡ鋼や、低炭素鋼の溶接熱影響部等の、微細内部構造を有する第２相が母相中に分散した複相組織を有する試料について、微細内部構造を有する第２相の状態を観察する際に好適に用いることができる。 Embodiments of the present invention will be described below with reference to the drawings. Here, the sample observation method of the present invention is not particularly limited, and is a second one having a fine internal structure such as a DP heat, a TRIP steel, a bainite-MA steel, a weld heat affected zone of a low carbon steel, or the like. A sample having a multiphase structure in which phases are dispersed in a matrix phase can be suitably used for observing the state of the second phase having a fine internal structure.
そして、本発明の試料観察方法は、走査型電子顕微鏡（ＳＥＭ）を用いて、加速電圧が７ｋＶ以上、且つ、取り込み角が６０°以上の条件下で試料の反射電子像を取得し、微細内部構造を有する第２相の分散状態を観察する分散状態観察工程を含むことを特徴とする。なお、「取り込み角」とは、試料からの反射電子がＳＥＭの反射電子検出器に入射する方向と、試料表面とがなす角度である。 Then, the sample observation method of the present invention uses a scanning electron microscope (SEM) to acquire a backscattered electron image of the sample under the conditions that the acceleration voltage is 7 kV or more and the capture angle is 60 ° or more. It includes a dispersion state observation step of observing the dispersion state of the second phase having a structure. The “take-in angle” is an angle formed by the direction in which the reflected electrons from the sample enter the reflected electron detector of the SEM and the sample surface.
ここで、通常、ＳＥＭを用いて試料の反射電子像を観察する際には、試料の微細な構造を高分解能で観察するために、加速電圧を低く（例えば５ｋＶ以下程度に）し、且つ、検出器を試料に近づけて試料からの反射電子の取り込み角を小さく（例えば４５°以下程度に）する。
しかし、本発明の試料観察方法は、本発明者らが、通常の反射電子像の観察条件とは逆の観察条件を採用した際に、微細内部構造を有する第２相が位置する部分の輝度が微細内部構造を有する第２相以外の部分に比べて著しく向上することを新たに見出して完成させたものである。そのため、本発明の試料観察方法では、加速電圧を高く（７ｋＶ以上に）し、且つ、反射電子の取り込み角を大きく（６０°以上に）することを特徴としている。
Here, usually, when observing a reflected electron image of a sample using an SEM, in order to observe the fine structure of the sample with high resolution, the acceleration voltage is lowered (for example, about 5 kV or less), and The detector is brought close to the sample to reduce the angle of capture of reflected electrons from the sample (for example, about 45 ° or less).
However, in the sample observation method of the present invention, when the present inventors adopt an observation condition opposite to the normal reflection electron image observation condition, the luminance of the portion where the second phase having the fine internal structure is located is determined. Was newly found and completed as compared with the portion other than the second phase having a fine internal structure. Therefore, the sample observation method of the present invention is characterized in that the acceleration voltage is increased (to 7 kV or more) and the reflected electron capture angle is increased (to 60 ° or more).
なお、加速電圧を高くし、反射電子の取り込み角を大きくした際に、微細内部構造を有する第２相が位置する部分の輝度が他の部分に比べて相対的に向上する現象は、明らかではないが以下の理由により起こると推察される。
即ち、図１にＳＥＭの要部の構成を模式的に示すように、通常、反射電子の取り込み角θを大きくした場合、微細内部構造を有する第２相が位置する部分以外の部分（微細内部構造を有さない部分）では、反射電子検出器１で検出される反射電子の量は少なくなり、観察される反射電子像では、結晶方位に応じたコントラスト（結晶方位コントラスト）が低下して輝度が低下する。しかし、結晶方位が互いに異なる多数の結晶粒の集合体よりなる微細内部構造を有する第２相部分では、所謂「多重散乱効果」により、反射電子検出器１で検出される反射電子の量が増加し、観察される反射電子像では、結晶方位に応じたコントラストの低下が抑制されるため、微細内部構造を有する第２相部分の輝度が相対的に増加する。
因みに、本明細書において、「多重散乱効果」とは、反射電子が試料２から出て行くまでに周囲に存在する結晶粒と衝突し、反射電子の進行方向が変わる（散乱する）ことにより、高い取り込み角では通常検出され得なかった反射電子が反射電子検出器に入射するようになることを指す。
It is clear that when the acceleration voltage is increased and the reflected electron capture angle is increased, the brightness of the portion where the second phase having the fine internal structure is relatively improved as compared with the other portions is not clear. It is presumed that this occurs for the following reasons.
That is, as schematically shown in FIG. 1, the configuration of the main part of the SEM is generally such that when the reflected electron capture angle θ is increased, the portion other than the portion where the second phase having the fine internal structure is located (the fine internal structure). In the portion having no structure), the amount of reflected electrons detected by the backscattered electron detector 1 decreases, and in the backscattered electron image to be observed, the contrast corresponding to the crystal orientation (crystal orientation contrast) decreases and the brightness Decreases. However, in the second phase portion having a fine internal structure composed of an aggregate of a large number of crystal grains having different crystal orientations, the amount of reflected electrons detected by the reflected electron detector 1 increases due to the so-called “multiple scattering effect”. In the reflected electron image to be observed, since the decrease in contrast according to the crystal orientation is suppressed, the luminance of the second phase portion having the fine internal structure is relatively increased.
Incidentally, in this specification, the “multiple scattering effect” means that the reflected electrons collide with surrounding crystal grains before leaving the sample 2, and the traveling direction of the reflected electrons changes (scatters). It means that reflected electrons that could not be normally detected at a high angle of incidence become incident on the reflected electron detector.
ここで、本発明の試料観察方法の一例は、特に限定されることなく、ＴＲＩＰ鋼におけるマルテンサイトの分散状態および微細内部構造を観察する際に用いられる。そして、この一例の試料観察方法は、ＳＥＭを用いて所定の条件下で試料（ＴＲＩＰ鋼）の反射電子像を取得し、マルテンサイトよりなる第２相（微細内部構造を有する第２相）の分散状態を観察する分散状態観察工程と、試料の観察面側の表層部を所定の範囲内で除去する試料調整工程と、試料調整工程の後に、マルテンサイトよりなる第２相の微細内部構造を観察する微細構造観察工程とを含むことを特徴とする。
なお、本発明の試料観察方法では、微細内部構造を有する第２相の分散状態のみを観察する場合には、試料調整工程および微細構造観察工程を実施しなくても良い。また、試料調整工程は、微細構造観察工程よりも前に実施すれば、分散状態観察工程の前に実施しても良いし、分散状態観察工程の後に実施しても良い。
Here, an example of the sample observation method of the present invention is not particularly limited, and is used when observing the dispersion state and fine internal structure of martensite in TRIP steel. In this sample observation method, a reflected electron image of a sample (TRIP steel) is obtained under a predetermined condition using an SEM, and a second phase (second phase having a fine internal structure) made of martensite is obtained. A dispersion state observation step for observing the dispersion state, a sample adjustment step for removing the surface layer portion on the observation surface side of the sample within a predetermined range, and a fine internal structure of the second phase made of martensite after the sample adjustment step And a microstructure observation step of observing.
In the sample observation method of the present invention, when only the second phase dispersion state having a fine internal structure is observed, the sample adjustment step and the fine structure observation step need not be performed. In addition, if the sample adjustment step is performed before the microstructure observation step, it may be performed before the dispersion state observation step or after the dispersion state observation step.
（分散状態観察工程）
分散状態観察工程では、ＳＥＭを用いて、加速電圧が７ｋＶ以上、且つ、取り込み角が６０°以上の条件下で、試料であるＴＲＩＰ鋼の反射電子像を取得する。そして、取得した反射電子像に基づき、マルテンサイトよりなる第２相の分散状態を評価する。なお、図２（ｃ），（ｄ）および図３（ｂ），（ｃ）にこの分散状態観察工程で取得し得る反射電子像の一例を示すように、取得した反射電子像中では、微細内部構造を有する第２相の輝度が著しく向上し、マルテンサイトよりなる特定の第２相の位置が可視化されている。従って、マルテンサイトよりなる特定の第２相の分散状態は、輝度の高い部分の位置を観察することにより評価することができる。
因みに、分散状態観察工程は、マルテンサイトよりなる、微細内部構造を有する第２相の分散状態を巨視的に観察することを目的としている。従って、この分散状態観察工程では、例えば倍率２００〜３０００倍の低倍率の反射電子像を取得することで、マルテンサイトよりなる第２相の分散状態を巨視的に観察して相分率や組織形状を定量化することができる。
(Dispersed state observation process)
In the dispersion state observation step, a reflected electron image of TRIP steel as a sample is obtained using SEM under the conditions of an acceleration voltage of 7 kV or more and an intake angle of 60 ° or more. Then, based on the obtained reflected electron image, the dispersion state of the second phase made of martensite is evaluated. 2C, 2D, 3B, and 3C show examples of reflected electron images that can be acquired in this dispersion state observation step. The brightness of the second phase having the internal structure is remarkably improved, and the position of the specific second phase made of martensite is visualized. Therefore, the dispersion state of the specific second phase composed of martensite can be evaluated by observing the position of the portion with high luminance.
Incidentally, the dispersed state observation step is intended to macroscopically observe the dispersed state of the second phase having a fine internal structure made of martensite. Therefore, in this dispersion state observation step, for example, a low-magnification backscattered electron image having a magnification of 200 to 3000 times is acquired, so that the dispersion state of the second phase made of martensite is macroscopically observed to obtain a phase fraction or structure. The shape can be quantified.
［試料］
分散状態観察工程において観察対象となる試料は、ＳＥＭによる観察が可能であれば、任意の形状、寸法とすることができる。そして、観察対象となる試料の表面（観察面）には、特に限定されることなく、研磨やエッチング等の表面処理を施すことができる。具体的には、試料の観察面には、鏡面研磨、化学エッチング、電解研磨、イオンエッチング等の表面処理を施すことができる。因みに、表面処理を施す範囲は、観察面から極端に大きな歪を除去することができ、且つ、試料中に第２相が残存する範囲内であれば、任意の範囲とすることができる。
なお、観察対象となる試料は、後に詳細に説明する試料調整工程において観察面側の表層部を除去した試料であっても良い。
[sample]
The sample to be observed in the dispersion state observing step can have any shape and size as long as observation by SEM is possible. The surface (observation surface) of the sample to be observed is not particularly limited, and surface treatment such as polishing or etching can be performed. Specifically, a surface treatment such as mirror polishing, chemical etching, electrolytic polishing, or ion etching can be applied to the observation surface of the sample. Incidentally, the surface treatment range can be set to any range as long as extremely large strain can be removed from the observation surface and the second phase remains in the sample.
Note that the sample to be observed may be a sample from which the surface layer portion on the observation surface side has been removed in the sample adjustment step described in detail later.
［走査型電子顕微鏡（ＳＥＭ）］
分散状態観察工程において使用するＳＥＭとしては、特に限定されることなく、図１に要部の構成を示すような、試料２に対して電子線Ｅを照射する電子線源としての電子銃（図示せず）と、電子レンズ（図示せず）と、反射電子検出器１と、二次電子検出器（図示せず）と、試料２を載置する可動ステージ３とを備える既知のＳＥＭを用いることができる。なお、可動ステージ３は、少なくとも図１では上下方向に移動可能に構成されており、図１に示すＳＥＭでは、可動ステージ３を上下動させて反射電子検出器１と試料２との間の距離ＷＤを変化させることにより、反射電子の取り込み角θを変化させることができる。
[Scanning Electron Microscope (SEM)]
The SEM used in the dispersion state observation step is not particularly limited, and an electron gun as an electron beam source for irradiating the sample 2 with the electron beam E as shown in FIG. A known SEM including an electron lens (not shown), a backscattered electron detector 1, a secondary electron detector (not shown), and a movable stage 3 on which the sample 2 is placed is used. be able to. Note that the movable stage 3 is configured to be movable in the vertical direction at least in FIG. 1. In the SEM shown in FIG. 1, the movable stage 3 is moved up and down so that the distance between the reflected electron detector 1 and the sample 2 is increased. By changing the WD, the reflected electron capture angle θ can be changed.
［加速電圧］
分散状態観察工程において反射電子像を取得する際の電子線の加速電圧は、７ｋＶ以上とする必要がある。図３（ａ）〜（ｃ）に加速電圧のみを変化させた際の反射電子像の変化を示すように、加速電圧が７ｋＶ未満の場合、マルテンサイトよりなる第２相が位置する部分の輝度が十分に向上せず、微細内部構造を有する第２相の分散状態を正確に把握することができないからである。なお、微細内部構造を有する第２相が位置する部分の輝度を更に高め、微細内部構造を有する第２相の分散状態をより正確に把握する観点からは、加速電圧は１０ｋＶ以上とすることが好ましい。また、反射電子像の分解能を確保する観点からは、加速電圧は２５ｋＶ以下とすることが好ましい。
[Acceleration voltage]
The acceleration voltage of the electron beam when acquiring the reflected electron image in the dispersion state observation step needs to be 7 kV or more. As shown in FIGS. 3A to 3C, changes in the reflected electron image when only the acceleration voltage is changed. When the acceleration voltage is less than 7 kV, the luminance of the portion where the second phase made of martensite is located. This is because the dispersion state of the second phase having a fine internal structure cannot be accurately grasped. From the viewpoint of further increasing the brightness of the portion where the second phase having the fine internal structure is located and more accurately grasping the dispersion state of the second phase having the fine internal structure, the acceleration voltage should be 10 kV or more. preferable. From the viewpoint of ensuring the resolution of the reflected electron image, the acceleration voltage is preferably 25 kV or less.
［取り込み角］
また、分散状態観察工程において反射電子像を取得する際の反射電子の取り込み角は、６０°以上とする必要がある。図２（ａ）〜（ｄ）に取り込み角のみを変化させた際の反射電子像の変化を示すように、取り込み角が６０°未満の場合、微細内部構造を有する第２相が位置する部分以外の部分の結晶方位コントラストが低下せず、微細内部構造を有する第２相が位置する部分以外の部分の輝度が十分に低下しないため、微細内部構造を有する第２相の分散状態を正確に把握することができないからである。即ち、微細内部構造を有する第２相が位置する部分の輝度と、微細内部構造を有する第２相が位置する部分以外の部分の輝度との差が小さくなり、微細内部構造を有する第２相の分散状態を正確に評価することができないからである。なお、微細内部構造を有する第２相が位置する部分と、それ以外の部分との間の輝度の差を更に大きくし、微細内部構造を有する第２相の分散状態をより正確に把握する観点からは、取り込み角は６５°以上、更に好ましくは７０°以上とすることが好ましい。また、反射電子像の分解能を確保する観点からは、取り込み角は８５°以下とすることが好ましい。
ここで、ＳＥＭでは、入射電子の位置と、検出された信号電子（二次電子もしくは反射電子）の量を同期させ、各位置における信号電子の量を輝度信号に変換して顕微鏡像を形成している。反射電子像では信号検出器に反射電子検出器を用いる。そのため、反射電子像における「輝度の差」は、輝度信号の強度の差（即ち、検出された反射電子の量の差）に対応している。そして、本発明では、反射電子像中の着目している部分の輝度信号の平均強度が、当該着目している部分以外の輝度信号の平均強度の２．０倍以上の場合に「有意な輝度差がある」とし、３．０倍以上の場合に「充分に輝度差がある」とする。ここで、着目している部分以外の輝度信号の平均強度は、着目している部分を含んだ５〜５０μｍ角の部分において着目している部分を除いた部分における輝度信号の平均強度である。
[Capture angle]
In addition, the reflected electron capture angle when acquiring the reflected electron image in the dispersion state observation step needs to be 60 ° or more. As shown in FIGS. 2 (a) to (d), in which the reflected electron image changes when only the capture angle is changed, when the capture angle is less than 60 °, the portion where the second phase having a fine internal structure is located. Since the crystal orientation contrast of the portion other than the portion does not decrease and the luminance of the portion other than the portion where the second phase having the fine internal structure is not sufficiently lowered, the dispersion state of the second phase having the fine internal structure is accurately determined. It is because it cannot be grasped. That is, the difference between the luminance of the portion where the second phase having the fine internal structure is located and the luminance of the portion other than the portion where the second phase having the fine internal structure is small is reduced. This is because the dispersion state cannot be accurately evaluated. Note that the difference in luminance between the portion where the second phase having the fine internal structure is located and the other portion is further increased, and the dispersion state of the second phase having the fine internal structure is more accurately grasped. From the above, it is preferable that the uptake angle is 65 ° or more, more preferably 70 ° or more. Further, from the viewpoint of ensuring the resolution of the reflected electron image, the capture angle is preferably 85 ° or less.
Here, in SEM, the position of incident electrons and the amount of detected signal electrons (secondary electrons or reflected electrons) are synchronized, and the amount of signal electrons at each position is converted into a luminance signal to form a microscope image. ing. In the backscattered electron image, a backscattered electron detector is used as a signal detector. Therefore, the “brightness difference” in the reflected electron image corresponds to a difference in intensity of the luminance signal (that is, a difference in the amount of detected reflected electrons). In the present invention, when the average intensity of the luminance signal of the portion of interest in the backscattered electron image is 2.0 times or more the average intensity of the luminance signal other than the portion of interest, the “significant luminance” "There is a difference", and when it is 3.0 times or more, "There is a sufficient luminance difference". Here, the average intensity of the luminance signal other than the portion of interest is the average intensity of the luminance signal in the portion excluding the portion of interest in the 5 to 50 μm square portion including the portion of interest.
（試料調整工程）
試料調整工程では、化学エッチング、電解研磨、イオンエッチング等を用いて、試料の観察面側の表層部を試料表面から除去する。具体的には、試料調整工程では、特に限定されることなく、試料の観察面側の表面を鏡面研磨した後、化学エッチング、電解研磨、イオンエッチング等を用いて試料の観察面側の表層部を除去する。
(Sample preparation process)
In the sample preparation step, the surface layer portion on the observation surface side of the sample is removed from the sample surface using chemical etching, electrolytic polishing, ion etching, or the like. Specifically, in the sample adjustment step, the surface layer portion on the observation surface side of the sample is subjected to mirror polishing on the surface on the observation surface side of the sample, using chemical etching, electrolytic polishing, ion etching, etc. Remove.
［表層部の除去量］
ここで、試料の観察面側の表面を鏡面研磨した後の試料から除去する表層部の範囲は、５ｎｍ以上１０μｍ以下とすることが好ましい。表層部を５ｎｍ以上除去しなければ、試料調整工程の後に実施する微細構造観察工程において微細内部構造を有する第２相の微細内部構造を観察することが困難になるからである。また、１０μｍを超えて表層部を除去した場合、微細構造観察工程において微細内部構造を観察する第２相までが除去されてしまうことがあるからである。なお、第２相の微細内部構造を観察する観点からは、試料から除去する表層部の範囲は、５ｎｍ以上、５μｍ以下がより好ましい。
[Removal amount of surface layer]
Here, the range of the surface layer portion to be removed from the sample after mirror-polishing the surface on the observation surface side of the sample is preferably 5 nm or more and 10 μm or less. This is because if the surface layer portion is not removed by 5 nm or more, it is difficult to observe the second phase fine internal structure having the fine internal structure in the fine structure observation step performed after the sample preparation step. Further, when the surface layer portion is removed exceeding 10 μm, even the second phase for observing the fine internal structure may be removed in the fine structure observation step. From the viewpoint of observing the fine internal structure of the second phase, the range of the surface layer portion removed from the sample is more preferably 5 nm or more and 5 μm or less.
［表層部の除去方法］
試料の表層部を除去する方法としては、特に限定されることなく、化学エッチング、電解研磨またはイオンエッチング、或いは、これらの組合せを用いることができる。なお、これらの中でも、表層部を除去する方法としては、イオンエッチングが好ましい。電解研磨では試料中の所定の組織が選択的に研磨される場合があり、ナイタール液等を用いた化学エッチングでは除去量の制御および平滑な観察面の調製が困難だからである。また、イオンエッチングを用いれば短時間で表層部を除去することができるからである。
[Removal method of surface layer]
The method for removing the surface layer portion of the sample is not particularly limited, and chemical etching, electrolytic polishing, ion etching, or a combination thereof can be used. Of these, ion etching is preferred as a method for removing the surface layer portion. This is because in electrolytic polishing, a predetermined structure in a sample may be selectively polished, and it is difficult to control the removal amount and prepare a smooth observation surface by chemical etching using a nital solution or the like. Further, if ion etching is used, the surface layer portion can be removed in a short time.
ここで、イオンエッチングによる試料の表層部の除去は、特に限定されることなく、例えば、集束イオンビーム（ＦＩＢ）装置を用いて試料にガリウムイオンビームを照射することにより行っても良いし、イオンミリング装置を用いて試料にアルゴンイオンビームを照射することにより行っても良い。なお、各イオンビームの強度は、例えば加速電圧１ｋＶ〜１０ｋＶとすることができ、照射時間は、例えば１〜１５分間とすることができる。 Here, the removal of the surface layer portion of the sample by ion etching is not particularly limited, and may be performed, for example, by irradiating the sample with a gallium ion beam using a focused ion beam (FIB) apparatus, or by ion You may carry out by irradiating a sample with an argon ion beam using a milling apparatus. In addition, the intensity | strength of each ion beam can be made into acceleration voltage 1kV-10kV, for example, and irradiation time can be made into 1-15 minutes, for example.
（微細構造観察工程）
試料調整工程の後に行う微細構造観察工程では、ＳＥＭや走査型イオン顕微鏡等を用いて、マルテンサイトよりなる第２相の微細内部構造を観察する。なお、ＳＥＭを使用して微細内部構造を観察する場合には、二次電子像を用いても良いし、反射電子像を用いても良いが、より詳細に微細内部構造を観察する観点からは、反射電子像を用いることが好ましい。また、走査型イオン顕微鏡を使用して微細内部構造を観察する場合には、試料調整工程において集束イオンビーム装置を用いたイオンエッチングを行い、その後、集束イオンビーム装置に付随している走査型イオン顕微鏡を用いて微細内部構造を観察することが、作業効率の観点から好ましい。
(Microstructure observation process)
In the fine structure observation step performed after the sample preparation step, the fine internal structure of the second phase made of martensite is observed using an SEM, a scanning ion microscope, or the like. In the case of observing the fine internal structure using SEM, a secondary electron image or a reflected electron image may be used, but from the viewpoint of observing the fine internal structure in more detail. It is preferable to use a reflected electron image. In addition, when observing the fine internal structure using a scanning ion microscope, ion etching using a focused ion beam device is performed in the sample preparation process, and then the scanning ion attached to the focused ion beam device is used. It is preferable from the viewpoint of work efficiency to observe the fine internal structure using a microscope.
ここで、ＳＥＭを使用して微細内部構造を観察する場合、観察に使用するＳＥＭとしては分散状態観察工程で用いたＳＥＭと同様のＳＥＭを用いることができる。また、高い分解能を得る観点からは、観察に二次電子像を用いる場合と、観察に反射電子像を用いる場合との何れの場合においても、微細内部構造を観察する際の加速電圧は例えば２０ｋＶ以下とすることができる。
因みに、より高い分解能を得る観点からは、加速電圧を１５ｋＶ以下とすることが好ましく、１０ｋＶ以下とすることが更に好ましい。また、更に高い分解能を得る観点からは、反射電子像を用いる場合には、反射電子の取り込み角を６５°以下とすることが好ましく、５５°以下とすることが更に好ましい。
Here, when observing the fine internal structure using the SEM, the SEM similar to the SEM used in the dispersion state observing step can be used as the SEM used for the observation. Further, from the viewpoint of obtaining a high resolution, the acceleration voltage for observing the fine internal structure is, for example, 20 kV in both cases of using a secondary electron image for observation and using a reflected electron image for observation. It can be as follows.
Incidentally, from the viewpoint of obtaining higher resolution, the acceleration voltage is preferably 15 kV or less, and more preferably 10 kV or less. Further, from the viewpoint of obtaining a higher resolution, when a reflected electron image is used, the reflected electron capture angle is preferably 65 ° or less, and more preferably 55 ° or less.
そして、上述した本発明の試料観察方法の一例によれば、所定の条件下で取得した反射電子像において微細内部構造を有するマルテンサイトよりなる第２相が位置する部分の輝度が向上することを利用し、微細内部構造を有する第２相の分散状態を正確に観察することができる。即ち、ナイタール液を用いて組織を試料表面に現出させる従来の試料観察方法では判別することができなかった、微細内部構造を有する第２相と、微細内部構造を有する第２相以外の組織との違いを目視で判別することができる。 And according to an example of the sample observation method of the present invention described above, the brightness of the portion where the second phase made of martensite having a fine internal structure is located in the reflected electron image acquired under a predetermined condition is improved. It is possible to accurately observe the dispersion state of the second phase having a fine internal structure. That is, a structure other than the second phase having the fine internal structure and the second phase having the fine internal structure, which could not be distinguished by the conventional sample observation method in which the structure appears on the sample surface using the nital liquid. And can be visually discriminated.
また、ナイタール液を用いて組織を試料表面に現出させる従来の試料観察方法では、組織を現出させる際に試料の表面を激しく化学エッチングするため、第２相の微細内部構造が化学腐食されてしまい、分散状態を観察した後に微細内部構造を観察することができなくなる。しかし、この一例の試料観察方法によれば、分散状態を観察する際にナイタール液等を用いて試料表面を激しく化学エッチングする必要がないので、分散状態を観察した試料と同一の試料について第２相の微細内部構造の観察を行うことができる。 In addition, in the conventional sample observation method in which the structure appears on the sample surface using a nital liquid, the surface of the sample is violently chemically etched when the structure is revealed, so that the fine internal structure of the second phase is chemically corroded. As a result, the fine internal structure cannot be observed after the dispersion state is observed. However, according to the sample observation method of this example, when the dispersion state is observed, it is not necessary to intensively chemically etch the sample surface using a nital liquid or the like. The fine internal structure of the phase can be observed.
なお、この一例の試料観察方法では、試料調整工程を実施した後に、同一のＳＥＭを用いて分散状態観察工程および微細構造観察工程を連続して実施すれば、より効率的に試料中の第２相の状態を観察することができる。 In the sample observation method of this example, if the dispersion state observation step and the fine structure observation step are continuously performed using the same SEM after the sample adjustment step, the second in the sample is more efficiently performed. The state of the phase can be observed.
以上、本発明の試料観察方法について実施形態を用いて説明したが、本発明の試料観察方法は、上記一例に限定されることはなく、本発明の試料観察方法には、適宜変更を加えることができる。具体的には、本発明の試料観察方法で観察する試料は、微細内部構造を有する第２相としてマルテンサイトを有する鉄鋼試料に限定されることはなく、本発明の試料観察方法は、微細内部構造を有する第２相が母相中に分散した複相組織を有する試料であれば、任意の試料に適用することができる。因みに、上記一例では、マルテンサイトの分散を直接観察することができるので、試料中のマルテンサイトと残留オーステナイトとを区別することができ、その結果、残留オーステナイトの分散状態を観察することもできる。 As described above, the sample observation method of the present invention has been described using the embodiment. However, the sample observation method of the present invention is not limited to the above example, and the sample observation method of the present invention is appropriately modified. Can do. Specifically, the sample observed by the sample observation method of the present invention is not limited to a steel sample having martensite as the second phase having a fine internal structure. Any sample can be applied as long as the second phase having a structure has a multiphase structure in which the second phase is dispersed in the matrix. Incidentally, in the above example, since the dispersion of martensite can be directly observed, it is possible to distinguish between martensite and residual austenite in the sample, and as a result, the dispersion state of residual austenite can also be observed.
以下、実施例により本発明を更に詳細に説明するが、本発明は下記の実施例に何ら限定されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.
（観察用試料の調製）
ＴＲＩＰ鋼（Ｃ：０．１７質量％、Ｓｉ：１．５質量％、Ｍｎ：１．７質量％）に対し、イオンミリング装置（日立製作所製）を用いてアルゴンイオンビームを照射し（加速電圧：６ｋＶ、照射時間：３分）、ＴＲＩＰ鋼の表層部を５０ｎｍ除去して観察用試料Ａとした。
ＴＲＩＰ鋼（Ｃ：０．１７質量％、Ｓｉ：１．５質量％、Ｍｎ：１．７質量％）をナイタール液（３％硝酸−エタノール溶液）に３０秒間浸漬し、ＴＲＩＰ鋼の表層部を２０μｍ除去して観察用試料Ｂとした。
ベイナイト−ＭＡ鋼に対し、イオンミリング装置（日立製作所製）を用いて上記と同様にアルゴンイオンビームを照射し、ベイナイト−ＭＡ鋼の表層部を５０ｎｍ除去して観察用試料Ｃとした。
低炭素鋼の溶接熱影響部に対し、イオンミリング装置（日立製作所製）を用いて上記と同様にアルゴンイオンビームを照射し、低炭素鋼の溶接熱影響部の表層部を５０ｎｍ除去して観察用試料Ｄとした。
(Preparation of observation sample)
TRIP steel (C: 0.17% by mass, Si: 1.5% by mass, Mn: 1.7% by mass) is irradiated with an argon ion beam using an ion milling device (manufactured by Hitachi, Ltd.) (acceleration voltage) : 6 kV, irradiation time: 3 minutes), the surface layer of TRIP steel was removed by 50 nm to obtain an observation sample A.
TRIP steel (C: 0.17% by mass, Si: 1.5% by mass, Mn: 1.7% by mass) was immersed in a nital solution (3% nitric acid-ethanol solution) for 30 seconds, and the surface layer of TRIP steel was An observation sample B was obtained by removing 20 μm.
The bainite-MA steel was irradiated with an argon ion beam in the same manner as described above using an ion milling device (manufactured by Hitachi, Ltd.), and the surface layer of the bainite-MA steel was removed by 50 nm to obtain an observation sample C.
The low-carbon steel welding heat-affected zone is irradiated with an argon ion beam in the same manner as described above using an ion milling device (manufactured by Hitachi), and the surface layer of the low-carbon steel welding heat-affected zone is removed by 50 nm and observed. Sample D was obtained.
（観察例１〜４）
観察用試料Ａについて、走査型電子顕微鏡を用いて、加速電圧：１５ｋＶの条件下で取り込み角を表１に示すように変化させて反射電子像を観察した。得られた反射電子像を図２（ａ）〜（ｄ）に示す。
そして、ＦＩＢ装置を用いて、輝度の高い部分の組織から透過型電子顕微鏡（ＴＥＭ）観察用の試料を切り出し、透過型電子顕微鏡で組織観察および同定分析を行った。その結果、輝度の高い部分は微細内部構造を有するマルテンサイトよりなることが確認された。なお、輝度の高くない部分について、同様にして組織観察および同定分析を行ったところ、マルテンサイト以外の組織からなることが確認された。
(Observation examples 1 to 4)
With respect to the observation sample A, a reflected electron image was observed using a scanning electron microscope while changing the capture angle as shown in Table 1 under the condition of an acceleration voltage of 15 kV. The obtained backscattered electron images are shown in FIGS.
And using the FIB apparatus, the sample for transmission electron microscope (TEM) observation was cut out from the structure | tissue of a high brightness | luminance, and structure | tissue observation and identification analysis were performed with the transmission electron microscope. As a result, it was confirmed that the portion with high luminance was composed of martensite having a fine internal structure. In addition, when a structure | tissue observation and identification analysis were similarly performed about the part which is not high brightness | luminance, it confirmed that it consisted of structures | tissues other than a martensite.
（観察例５〜７）
観察用試料Ａについて、走査型電子顕微鏡を用いて、取り込み角：７５°の条件下で加速電圧を表１に示すように変化させて反射電子像を観察した。得られた反射電子像を図３（ａ）〜（ｃ）に示す。
また、ＦＩＢ装置を用いて、輝度の高い部分の組織から透過型電子顕微鏡（ＴＥＭ）観察用の試料を切り出し、透過型電子顕微鏡で組織観察および同定分析を行った。その結果、輝度の高い部分は微細内部構造を有するマルテンサイトよりなることが確認された。なお、輝度の高くない部分について、同様にして組織観察および同定分析を行ったところ、マルテンサイト以外の組織からなることが確認された。
(Observation Examples 5-7)
With respect to the observation sample A, a reflected electron image was observed using a scanning electron microscope while changing the acceleration voltage as shown in Table 1 under the condition of the capture angle: 75 °. The obtained backscattered electron images are shown in FIGS.
Further, using a FIB apparatus, a sample for observation with a transmission electron microscope (TEM) was cut out from a high-brightness tissue, and the tissue observation and identification analysis were performed with the transmission electron microscope. As a result, it was confirmed that the portion with high luminance was composed of martensite having a fine internal structure. In addition, when a structure | tissue observation and identification analysis were similarly performed about the part which is not high brightness | luminance, it confirmed that it consisted of structures | tissues other than a martensite.
（観察例８）
観察用試料Ａについて、走査型電子顕微鏡を用いて、観察例４と同様の方法にて微細内部構造を有する第２相の分散状態を把握した後、微細内部構造を有する第２相の部分につき、加速電圧：５ｋＶ、取り込み角：４５°の条件下で二次電子像を観察した。得られた二次電子像を図５に示す。
（観察例９）
観察用試料Ａについて、走査型電子顕微鏡を用いて、観察例４と同様の方法にて微細内部構造を有する第２相の分散状態を把握した後、微細内部構造を有する第２相の部分につき、走査型電子顕微鏡を用いて、加速電圧：１５ｋＶ、取り込み角：６５°の条件下で反射電子像を観察した。得られた反射電子像を図６（ａ）に示す。
（観察例１０）
観察用試料Ａについて、走査型電子顕微鏡を用いて、観察例９と同様の方法にて微細内部構造を有する第２相の分散状態を把握した後、微細内部構造を有する第２相の部分（観察例９と同じ部分）につき、走査型電子顕微鏡を用いて、加速電圧：５ｋＶ、取り込み角：３５°の条件下で反射電子像を観察した。得られた反射電子像を図６（ｂ）に示す。
（観察例１１）
観察用試料Ａについて、走査型電子顕微鏡を用いて、加速電圧：５ｋＶの条件下で取り込み角：３５°で、反射電子像を観察した。
（観察例１２）
観察用試料Ｂについて、走査型電子顕微鏡を用いて、加速電圧：１５ｋＶ、取り込み角：６５°の条件下で二次電子像を観察した。得られた二次電子像を図４に示す。
そして、ＦＩＢ装置を用いて、ナイタール液への浸漬により現出した組織から透過型電子顕微鏡（ＴＥＭ）観察用の試料を切り出し、透過型電子顕微鏡で組織観察および同定分析を行った。その結果、現出した組織の中には微細内部構造を有するマルテンサイト以外の組織よりなる部分が存在することが確認された。
（観察例１３）
観察用試料Ｂについて、走査型電子顕微鏡を用いて、加速電圧：１５ｋＶ、取り込み角：６５°の条件下で反射電子像を観察した。
そして、ＦＩＢ装置を用いて、反射電子像の輝度の高い部分の組織から透過型電子顕微鏡（ＴＥＭ）観察用の試料を切り出し、透過型電子顕微鏡で組織観察および同定分析を行った。
その結果、輝度の高い部分は微細内部構造を有するマルテンサイトよりなることが確認された。なお、輝度の高くない部分について、同様にして組織観察および同定分析を行ったところ、マルテンサイト以外の組織からなることが確認された。
（観察例１４）
観察用試料Ｂについて、走査型電子顕微鏡を用いて、観察例１３と同様の方法にて微細内部構造を有する第２相の分散状態を把握した後、微細内部構造を有する第２相の部分につき、加速電圧：１５ｋＶ、取り込み角：６５°の条件下で二次電子像を観察した。得られた二次電子像を図７に示す。
（観察例１５）
観察用試料Ｃについて、走査型電子顕微鏡を用いて、加速電圧：１５ｋＶ、取り込み角：７５°の条件下で反射電子像を観察した。得られた反射電子像を図８に示す。
そして、ＦＩＢ装置を用いて、反射電子像の輝度の高い部分から透過型電子顕微鏡（ＴＥＭ）観察用の試料を切り出し、透過型電子顕微鏡で組織観察および同定分析を行った。
その結果、輝度の高い部分は微細内部構造を有するＭＡよりなることが確認された。なお、輝度の高くない部分について、同様にして組織観察および同定分析を行ったところ、ＭＡ以外の組織からなることが確認された。
（観察例１６）
観察用試料Ｄについて、走査型電子顕微鏡を用いて、加速電圧：１５ｋＶ、取り込み角：７５°の条件下で反射電子像を観察した。得られた反射電子像を図９に示す。
そして、ＦＩＢ装置を用いて、反射電子像の輝度の高い部分から透過型電子顕微鏡（ＴＥＭ）観察用の試料を切り出し、透過型電子顕微鏡で組織観察および同定分析を行った。
その結果、輝度の高い部分は微細内部構造を有するＭＡよりなることが確認された。なお、輝度の高くない部分について、同様にして組織観察および同定分析を行ったところ、ＭＡ以外の組織からなることが確認された。
(Observation Example 8)
About the sample A for observation, after grasping the dispersion state of the second phase having the fine internal structure using the scanning electron microscope in the same manner as in Observation Example 4, the second phase portion having the fine internal structure A secondary electron image was observed under the conditions of an acceleration voltage of 5 kV and an intake angle of 45 °. The obtained secondary electron image is shown in FIG.
(Observation Example 9)
About the sample A for observation, after grasping the dispersion state of the second phase having the fine internal structure using the scanning electron microscope in the same manner as in Observation Example 4, the second phase portion having the fine internal structure Using a scanning electron microscope, a reflected electron image was observed under the conditions of an acceleration voltage of 15 kV and a capture angle of 65 °. The obtained reflected electron image is shown in FIG.
(Observation Example 10)
For the sample A for observation, using a scanning electron microscope, after grasping the dispersion state of the second phase having the fine internal structure in the same manner as in Observation Example 9, the portion of the second phase having the fine internal structure ( For the same part as in Observation Example 9), a reflected electron image was observed using a scanning electron microscope under the conditions of an acceleration voltage of 5 kV and a capture angle of 35 °. The obtained backscattered electron image is shown in FIG.
(Observation Example 11)
With respect to the observation sample A, a backscattered electron image was observed with a scanning electron microscope under an acceleration voltage of 5 kV and a capture angle of 35 °.
(Observation Example 12)
For the observation sample B, a secondary electron image was observed using a scanning electron microscope under the conditions of an acceleration voltage of 15 kV and a capture angle of 65 °. The obtained secondary electron image is shown in FIG.
And using the FIB apparatus, the sample for transmission electron microscope (TEM) observation was cut out from the structure | tissue which appeared by immersion in the nital liquid, and structure | tissue observation and identification analysis were performed with the transmission electron microscope. As a result, it was confirmed that a part composed of a structure other than martensite having a fine internal structure exists in the appearing structure.
(Observation Example 13)
With respect to the observation sample B, a reflected electron image was observed using a scanning electron microscope under the conditions of an acceleration voltage of 15 kV and a capture angle of 65 °.
Then, using a FIB apparatus, a sample for observation with a transmission electron microscope (TEM) was cut out from the tissue of a portion with high luminance in the reflected electron image, and the structure observation and identification analysis were performed with the transmission electron microscope.
As a result, it was confirmed that the portion with high luminance was composed of martensite having a fine internal structure. In addition, when a structure | tissue observation and identification analysis were similarly performed about the part which is not high brightness | luminance, it confirmed that it consisted of structures | tissues other than a martensite.
(Observation Example 14)
About the observation sample B, after grasping the dispersion state of the second phase having the fine internal structure using a scanning electron microscope in the same manner as in Observation Example 13, the second phase portion having the fine internal structure A secondary electron image was observed under the conditions of an acceleration voltage of 15 kV and an intake angle of 65 °. The obtained secondary electron image is shown in FIG.
(Observation Example 15)
With respect to the observation sample C, a reflected electron image was observed using a scanning electron microscope under the conditions of an acceleration voltage of 15 kV and a capture angle of 75 °. The obtained backscattered electron image is shown in FIG.
Then, using a FIB apparatus, a sample for observation with a transmission electron microscope (TEM) was cut out from the high-brightness portion of the reflected electron image, and tissue observation and identification analysis were performed with the transmission electron microscope.
As a result, it was confirmed that the portion with high luminance was made of MA having a fine internal structure. In addition, when the structure observation and identification analysis were similarly performed about the part which is not high brightness | luminance, it confirmed that it consisted of structures | tissues other than MA.
(Observation Example 16)
With respect to the observation sample D, a reflection electron image was observed using a scanning electron microscope under the conditions of an acceleration voltage of 15 kV and a capture angle of 75 °. The obtained backscattered electron image is shown in FIG.
Then, using a FIB apparatus, a sample for observation with a transmission electron microscope (TEM) was cut out from the high-brightness portion of the reflected electron image, and tissue observation and identification analysis were performed with the transmission electron microscope.
As a result, it was confirmed that the portion with high luminance was made of MA having a fine internal structure. In addition, when the structure observation and identification analysis were similarly performed about the part which is not high brightness | luminance, it confirmed that it consisted of structures | tissues other than MA.
［微細内部構造を有する第２相の分散状態観察結果］
走査型電子顕微鏡を用いて得た電子像において、第２相が他の部分より非常に輝度が高く、容易に他の部分と識別でき、かつ、その輝度の高い部分が微細内部構造を有する第２相のみからなっていた場合を「◎（優良）」とし、電子像において、第２相が他の部分より若干輝度が高く、他の部分と識別でき、かつ、その輝度の高い部分が微細内部構造を有する第２相のみからなっていた場合を「○（合格）」とし、電子像において、第２相の輝度と他の部分の輝度が同等で第２相が容易に識別できなかった場合を「×（不合格）」とし、表１に記載した。
なお、「第２相が他の部分より非常に輝度が高く、容易に他の部分と識別できる」場合とは、輝度信号の平均強度比（＝電子像中の着目している部分の輝度信号の平均強度／着目している部分の周囲に位置する部分の輝度信号の平均強度）が３．０以上の場合を指す。また、「第２相が他の部分より若干輝度が高く、他の部分と識別できる」場合とは、輝度信号の平均強度比が２．０以上３．０未満の場合を指し、「第２相の輝度と他の部分の輝度が同等で第２相が容易に識別できない」場合とは、輝度信号の平均強度比が２．０未満の場合を指す。
ここで、「着目している部分の周囲に位置する部分の輝度信号の平均強度」は、着目している部分を含んだ１０μｍ角の部分において、着目している部分を除いた部分における輝度信号の平均強度である。
［微細内部構造を有する第２相の微細内部構造観察結果］
微細内部構造を有する第２相の部分について、走査型電子顕微鏡を用いて得た電子像において微細な内部構造が観察できた場合を「○（合格）」とし、微細な内部構造が観察できなかった場合を「×（不合格）」とし、表１に記載した。
[Dispersion state observation result of second phase having fine internal structure]
In an electronic image obtained using a scanning electron microscope, the second phase is much brighter than the other part, can be easily distinguished from the other part, and the bright part has a fine internal structure. The case where it consists of only two phases is designated as “◎ (excellent)”, and in the electronic image, the second phase has a slightly higher luminance than the other portions and can be distinguished from the other portions, and the high luminance portion is fine. The case where it consisted only of the 2nd phase which has an internal structure was made into "(circle) (pass)", and the brightness | luminance of the 2nd phase and the brightness | luminance of another part were equivalent in an electronic image, and the 2nd phase was not easily identifiable The case was indicated as “x (failed)” in Table 1.
Note that the case where “the second phase has a much higher luminance than other parts and can be easily distinguished from other parts” means that the average intensity ratio of the luminance signals (= the luminance signal of the part of interest in the electronic image) The average intensity of the luminance signal of the portion located around the focused portion) is 3.0 or more. The case where “the second phase is slightly higher in luminance than the other part and can be distinguished from the other part” refers to a case where the average intensity ratio of the luminance signal is 2.0 or more and less than 3.0. The case where the luminance of the phase is equal to the luminance of the other part and the second phase cannot be easily identified ”refers to the case where the average intensity ratio of the luminance signal is less than 2.0.
Here, “the average intensity of the luminance signal of the portion located around the portion of interest” is a luminance signal in a portion of the 10 μm square portion including the portion of interest excluding the portion of interest. Is the average intensity.
[Results of observation of fine internal structure of second phase with fine internal structure]
Regarding the part of the second phase having a fine internal structure, the case where the fine internal structure can be observed in an electronic image obtained using a scanning electron microscope is indicated as “◯ (pass)”, and the fine internal structure cannot be observed. The results are shown in Table 1 as “x (failed)”.
表１より、観察例３、４、６〜１０、１３〜１６は、走査型電子顕微鏡での観察条件が本発明の範囲内であり、微細内部構造を有するマルテンサイトよりなる第２相が高輝度になり、巨視的な分散状態を正確に観察できることが分かる。観察例１、２、５、１１、１２は、走査型電子顕微鏡の観察条件で加速電圧または取り込み角が本発明の範囲外であり、微細内部構造を有する第２相の分散状態を正確に評価することができないことが分かる。また、観察例１２では、マルテンサイトよりなる第２相以外の組織も現出してしまい、微細内部構造を有する第２相の分散状態のみを正確に評価することができないことが分かる。 From Table 1, in Observation Examples 3, 4, 6 to 10, and 13 to 16, the observation conditions with a scanning electron microscope are within the scope of the present invention, and the second phase composed of martensite having a fine internal structure is high. It turns out that the macroscopic dispersion state can be accurately observed. In Observation Examples 1, 2, 5, 11, and 12, the acceleration voltage or the capture angle is outside the range of the present invention under the observation conditions of the scanning electron microscope, and the dispersion state of the second phase having a fine internal structure is accurately evaluated. You can't do it. Moreover, in the observation example 12, it turns out that structures other than the 2nd phase which consists of a martensite also appear, and only the dispersion state of the 2nd phase which has a fine internal structure cannot be evaluated correctly.
観察例８、９、１０より、本発明の方法により容易にマルテンサイトの分散位置を特定でき、更に、その部分のマルテンサイトよりなる第２相の微細内部構造を観察し得ることが分かる。また、観察例１４は、化学エッチングした試料を観察した例で、本発明方法により微細内部構造を有する第２相の分散状態はわかるものの、その微細構造については観察できなかった。 From observation examples 8, 9, and 10 it can be seen that the dispersion position of martensite can be easily specified by the method of the present invention, and further, the fine internal structure of the second phase composed of martensite at that portion can be observed. Observation example 14 is an example of observing a chemically etched sample. Although the dispersion state of the second phase having a fine internal structure is known by the method of the present invention, the fine structure cannot be observed.
本発明の試料観察方法によれば、分散状態観察工程において取得した反射電子像において、微細内部構造を有する第２相が位置する部分の輝度を、微細内部構造を有する第２相以外の部分に比べて著しく向上させることができるので、材質に影響を及ぼす第２相の特定の相につき巨視的な分散状態を正確に観察することができる。 According to the sample observation method of the present invention, in the reflected electron image acquired in the dispersion state observation step, the luminance of the portion where the second phase having the fine internal structure is located is set to the portion other than the second phase having the fine internal structure. Since it can be remarkably improved, the macroscopic dispersion state can be accurately observed for the specific phase of the second phase that affects the material.
１ 反射電子検出器
２ 試料
３ 可動ステージ
Ｅ 電子線
1 Backscattered electron detector 2 Sample 3 Movable stage E Electron beam
Claims (4)
走査型電子顕微鏡を用いて、加速電圧が７ｋＶ以上、且つ、取り込み角が６０°以上の条件下で試料の反射電子像を取得し、前記第２相の分散状態を観察する分散状態観察工程を含むことを特徴とする、試料観察方法。 A sample observation method for observing a state of a second phase having a fine internal structure with respect to a sample having a multiphase structure in which a second phase having a fine internal structure is dispersed in a matrix phase,
A dispersion state observation step of obtaining a backscattered electron image of the sample under a condition that the acceleration voltage is 7 kV or more and the capture angle is 60 ° or more using a scanning electron microscope, and observing the dispersion state of the second phase. A sample observation method comprising:
前記試料調整工程の後に、前記第２相の微細内部構造を観察する微細構造観察工程と、を更に含むことを特徴とする、請求項１に記載の試料観察方法。 A sample adjustment step of removing the surface layer portion on the observation surface side of the sample;
The sample observation method according to claim 1, further comprising a fine structure observation step of observing the fine internal structure of the second phase after the sample preparation step.
前記分散状態観察工程および前記微細構造観察工程を、前記試料調整工程の後に実施することを特徴とする、請求項２に記載の試料観察方法。 The fine structure observation step is a step of observing the fine internal structure of the second phase under an acceleration voltage of 20 kV or less using a scanning electron microscope;
The sample observation method according to claim 2, wherein the dispersion state observation step and the microstructure observation step are performed after the sample adjustment step.
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| WO2018003128A1 (en) * | 2016-06-29 | 2018-01-04 | Jfe Steel Corporation | Method of separately visualizing austenite phase, martensite phase and bainitic-ferrite matrix in bainitic steel and bainitic steel specimen for microstructure observation |
| JP2018025513A (en) * | 2016-08-12 | 2018-02-15 | Ｊｆｅスチール株式会社 | Method for separate visualization of ferrite phase, martensite phase, and austenite phase in multiple-phase steel by observation with electron scanning microscope, and multiple-phase steel piece for tissue observation |
| JP2018163034A (en) * | 2017-03-27 | 2018-10-18 | Ｊｆｅスチール株式会社 | Method of assessing stability of steel |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2017149785A1 (en) * | 2016-03-02 | 2017-09-08 | Jfe Steel Corporation | Method of visualizing austenite phase in multiphase steel and multiphase steel specimen for microstructure observation |
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| JP2018025513A (en) * | 2016-08-12 | 2018-02-15 | Ｊｆｅスチール株式会社 | Method for separate visualization of ferrite phase, martensite phase, and austenite phase in multiple-phase steel by observation with electron scanning microscope, and multiple-phase steel piece for tissue observation |
| JP2018163034A (en) * | 2017-03-27 | 2018-10-18 | Ｊｆｅスチール株式会社 | Method of assessing stability of steel |
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