JP2010256310A - Method, device and program for measuring plastic strain of steel - Google Patents
Method, device and program for measuring plastic strain of steel Download PDFInfo
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この発明は、結晶方位分布より鋼の金属組織内に蓄積した塑性歪を予測する方法装置、プログラムに関する。 The present invention relates to a method apparatus and a program for predicting plastic strain accumulated in a metal structure of steel from a crystal orientation distribution.
例えば、フェライト単相組織を有する鋼の引張変形等の大変形における塑性歪は平行部の伸びより歪を算出するという測定方法により求められる。しかし、金属の疲労やクリープでは材料内部で塑性歪が蓄積される静的な変形であり、その歪量の計測・測定が非常に困難である。 For example, the plastic strain in a large deformation such as a tensile deformation of steel having a ferrite single phase structure is obtained by a measurement method in which the strain is calculated from the elongation of the parallel portion. However, metal fatigue and creep are static deformations in which plastic strain accumulates inside the material, and it is very difficult to measure and measure the amount of strain.
金属が塑性変形を受けた際には組織内部に転位下部組織が発達することが知られており、従来、金属薄膜を作成し、透過電子顕微鏡による観察によって変形の進行を把握することが行われていた。また、近年では例えば非特許文献１に開示されているように金属結晶粒内の局所方位差により塑性歪量による定量化を行うことで損傷度を評価する提案もなされている。さらに、非特許文献２に開示されているように、後方散乱電子回折像のずれから、各歪成分を測定する手法が提案されている。 It is known that dislocation substructures develop inside the structure when the metal undergoes plastic deformation. Conventionally, metal thin films have been created and the progress of deformation has been grasped by observation with a transmission electron microscope. It was. In recent years, for example, as disclosed in Non-Patent Document 1, a proposal has been made to evaluate the degree of damage by quantifying the amount of plastic strain based on the local orientation difference in the metal crystal grains. Furthermore, as disclosed in Non-Patent Document 2, a method for measuring each distortion component from the deviation of the backscattered electron diffraction image has been proposed.
ところが、非特許文献２の方法では測定精度の影響を無視できないという問題があり、ｚ方向の成分が不確定となることが問題となる。 However, the method of Non-Patent Document 2 has a problem that the influence of measurement accuracy cannot be ignored, and the z-direction component becomes uncertain.
本発明の塑性歪測定方法は、結晶構造が立方晶系である金属材料の被測定部材、あるいは該被測定部材より採取した試験片の同一視野における塑性変形前と塑性変形後の結晶方位分布を取り込む工程と、前記塑性変形前の結晶方位分布に基づいて、任意の結晶方位測定点と隣接する結晶方位測定点間における結晶方位差より変形前の格子歪を算出する工程と、前記塑性変形後の結晶方位分布に基づいて、任意の結晶方位測定点と隣接する結晶方位測定点間における結晶方位差より変形後の格子歪を算出する工程と、前記変形前の格子歪と前記変形後の格子歪とにより結晶内に蓄積した塑性歪を測定する工程と、を有することを特徴とする。 The plastic strain measuring method of the present invention is a method of measuring crystal orientation distribution before plastic deformation and after plastic deformation in the same visual field of a metal member to be measured whose crystal structure is a cubic system, or a test piece collected from the member to be measured. A step of calculating, based on the crystal orientation distribution before plastic deformation, calculating a lattice strain before deformation from a crystal orientation difference between an arbitrary crystal orientation measurement point and an adjacent crystal orientation measurement point, and after the plastic deformation A step of calculating a lattice strain after deformation from a crystal orientation difference between an arbitrary crystal orientation measurement point and an adjacent crystal orientation measurement point based on the crystal orientation distribution of the crystal lattice, and the lattice strain before the deformation and the lattice after the deformation And measuring a plastic strain accumulated in the crystal due to the strain.
塑性変形前と塑性変形後の結晶方位分布を取り込む工程の前に、前記塑性変形前と塑性変形後の結晶方位分布を測定する工程を有するようにしてもよい。 Before the step of taking in the crystal orientation distribution before and after plastic deformation, a step of measuring the crystal orientation distribution before and after plastic deformation may be included.
本発明の塑性歪測定装置は、結晶構造が立方晶系である金属材料の被測定部材、あるいは該被測定部材より採取した試験片の同一視野における塑性変形前と塑性変形後の結晶方位分布を取り込む結晶方位分布取り込み手段と、前記取り込まれた結晶方位分布に基づいて、任意の結晶方位測定点と隣接する結晶方位測定点間における結晶方位差より格子歪を算出する格子歪算出手段と、前記塑性変形前と塑性変形後の結晶方位分布に基づいて前記格子歪算出手段により算出された変形前の格子歪と変形後の格子歪とにより結晶内に蓄積した塑性歪を測定する塑性歪測定手段と、を有することを特徴とする。 The plastic strain measuring device of the present invention is a method of measuring crystal orientation distribution before and after plastic deformation in the same visual field of a metal member to be measured whose crystal structure is a cubic system, or a specimen taken from the member to be measured. A crystal orientation distribution capturing means for capturing, a lattice strain calculating means for calculating a lattice strain from a crystal orientation difference between an arbitrary crystal orientation measurement point and an adjacent crystal orientation measurement point based on the captured crystal orientation distribution; Plastic strain measuring means for measuring the plastic strain accumulated in the crystal by the lattice strain before deformation calculated by the lattice strain calculating means and the lattice strain after deformation based on the crystal orientation distribution before and after plastic deformation. It is characterized by having.
前記塑性変形前と塑性変形後の結晶方位分布を測定する結晶方位分布測定手段を有するようにしてもよい。 You may make it have a crystal orientation distribution measurement means which measures the crystal orientation distribution before the plastic deformation and after plastic deformation.
本発明の塑性歪測定プログラムは、結晶構造が立方晶系である金属材料の被測定部材、あるいは該被測定部材より採取した試験片の同一視野における塑性変形前と塑性変形後の結晶方位分布をコンピュータの入力として、前記塑性変形前の結晶方位分布に基づいて、任意の結晶方位測定点と隣接する結晶方位測定点間における結晶方位差より変形前の格子歪を算出する手順と、前記塑性変形後の結晶方位分布に基づいて、任意の結晶方位測定点と隣接する結晶方位測定点間における結晶方位差より変形後の格子歪を算出する手順と、前記変形前の格子歪と前記変形後の格子歪とにより結晶内に蓄積した塑性歪を測定する手順と、を前記コンピュータに実行させることを特徴とする。さらに、本発明のコンピュータ読み取り可能な記録媒体は、塑性歪測定プログラムを記録したことを特徴とする。 The plastic strain measurement program of the present invention is a program for measuring a crystal orientation distribution before plastic deformation and after plastic deformation in the same visual field of a metal member to be measured whose crystal structure is a cubic system or a specimen taken from the member to be measured. As a computer input, based on the crystal orientation distribution before plastic deformation, a procedure for calculating lattice strain before deformation from a crystal orientation difference between an arbitrary crystal orientation measurement point and an adjacent crystal orientation measurement point, and the plastic deformation Based on the subsequent crystal orientation distribution, a procedure for calculating the lattice strain after deformation from the crystal orientation difference between an arbitrary crystal orientation measurement point and the adjacent crystal orientation measurement point, and the lattice strain before the deformation and the post-deformation And a step of causing the computer to execute a procedure for measuring plastic strain accumulated in the crystal by lattice strain. Furthermore, the computer-readable recording medium of the present invention is characterized by recording a plastic strain measurement program.
本発明により、結晶方位分布データを用いるのみで、より微小領域での塑性歪テンソルを簡易的に測定することが可能となる。 According to the present invention, it is possible to easily measure a plastic strain tensor in a finer region only by using crystal orientation distribution data.
本発明による塑性歪測定方法は、結晶構造が立方晶系である金属材料の被測定部材、あるいは測定部材より採取した試験片の同一視野における変形前と変形後の結晶方位分布を測定し、任意の結晶方位測定点と隣接する結晶方位測定点間における結晶方位差より見積もられる格子歪を求める。ここで結晶方位分布とは後方散乱電子回折像、収束Ｘ線回折法で測定された結晶方位点群とした。なお、この結晶方位点群の点間隔は電子線あるいはＸ線のビーム径以下であれば隣接測定点の測定範囲に干渉するため、結晶方位分布を測定した際の電子線あるいは収束Ｘ線のビーム径以上が好ましい。 The plastic strain measurement method according to the present invention measures a crystal orientation distribution before and after deformation in the same field of view of a specimen to be measured of a metal material having a cubic crystal structure or a test piece taken from the measurement member. The lattice strain estimated from the crystal orientation difference between the crystal orientation measurement point and the adjacent crystal orientation measurement point is obtained. Here, the crystal orientation distribution is a back-scattered electron diffraction image or a crystal orientation point group measured by a convergent X-ray diffraction method. If the point interval of the crystal orientation point group is equal to or smaller than the beam diameter of the electron beam or X-ray, it interferes with the measurement range of the adjacent measurement point. Therefore, the electron beam or the convergent X-ray beam when the crystal orientation distribution is measured. More than the diameter is preferable.
上記した結晶方位分布とは正方形あるいは三角形グリッドの各頂点に結晶方位情報を持つレイヤーが積み重なった結晶方位点群のことを意味する。結晶方位情報とは測定面法線方向に対し、任意の結晶のミラー指数へ回転行列により投影する際のオイラー角のことである。 The above-described crystal orientation distribution means a group of crystal orientation points in which layers having crystal orientation information are stacked on each vertex of a square or triangular grid. The crystal orientation information is the Euler angle at the time of projecting to the Miller index of an arbitrary crystal by a rotation matrix with respect to the normal direction of the measurement surface.
金属材料が塑性変形を受けた際にはすべり変形によってあるいは局所的に転位が続くことで結晶回転を生ずることが知られており、特に、多結晶体金属においては個々の結晶粒が独立にすべり変形を生じた際に隣接する結晶から拘束を受けることで、結晶粒内に局所的な結晶方位差を生じ、塑性変形が内部に蓄積される。したがって、変形に伴い塑性歪が導入されることで結晶方位差をもつミクロ組織となる。すなわち、本発明は、結晶内に蓄積した塑性歪を算出する塑性歪測定方法であって、変形前の格子歪および変形後の格子歪の差を求めることで、塑性歪の各成分を求める。 It is known that when a metal material undergoes plastic deformation, crystal rotation occurs due to slip deformation or local dislocations. In particular, in a polycrystalline metal, individual crystal grains slip independently. When deformation occurs, it is constrained by adjacent crystals, thereby causing local crystal orientation differences in the crystal grains, and plastic deformation is accumulated inside. Therefore, a microstructure having a crystal orientation difference is obtained by introducing plastic strain with deformation. That is, the present invention is a plastic strain measurement method for calculating plastic strain accumulated in a crystal, and obtains each component of plastic strain by obtaining a difference between lattice strain before deformation and lattice strain after deformation.
格子歪はこれまで、ＴＥＭ膜内でのディフラクションパターンから直接的に求められている。この方法で多視野の測定を行うには莫大な時間と労力を要する。また、試験片からＴＥＭ膜試料を切出すため、試験片に更なる変形を与えることは出来ない。その他金属組織表面に微粒子を蒸着させ、変形に伴う個々の粒子の動きから組織内変形量を測定する方法がある。この方法では非常に広範囲における歪量を簡易的に測定することが出来るが、結晶粒径が微小となった際には蒸着した粒子サイズや密度による影響が生じる。 Up to now, the lattice strain has been obtained directly from the diffraction pattern in the TEM film. To measure multiple fields of view by this method requires a great deal of time and effort. Further, since the TEM film sample is cut out from the test piece, the test piece cannot be further deformed. There is another method in which fine particles are vapor-deposited on the surface of a metal structure and the amount of deformation in the tissue is measured from the movement of individual particles accompanying the deformation. Although this method can easily measure the amount of strain in a very wide range, when the crystal grain size becomes minute, the effect of the deposited particle size and density occurs.
本発明では、電子線あるいは収束Ｘ線回折像を用いることで非常に微小な領域での塑性歪を広範囲において測定することを可能とした。また、変形させる試験片の表層歪を変形前に予め取り除く処理を施しておけば、測定用の試験片を新たに切出す必要はない。以下、結晶方位分布から格子歪を算出し、塑性歪を測定する具体的手法について述べる。 In the present invention, it is possible to measure a plastic strain in a very small region over a wide range by using an electron beam or a convergent X-ray diffraction image. Further, if the surface layer strain of the test piece to be deformed is previously removed before the deformation, it is not necessary to cut out a new test piece for measurement. Hereinafter, a specific method for calculating the lattice strain from the crystal orientation distribution and measuring the plastic strain will be described.
局所的に結晶粒内方位差を生じた結晶内の任意の結晶方位測定点とその隣接点での結晶格子像を描いた場合、各格子は相対的に結晶回転を生じた形となっている。しかし、結晶は連続であることから、各格子間にはその方位差を埋め合わせる格子歪が導入されていることとなり、結晶粒内方位差を生じた結晶方位分布情報から格子歪が描ける。そもそも塑性歪を測定するにはその領域の変形による変位量を求める、あるいは格子の歪を求める必要がある。これまで、この格子歪を求める際に結晶方位分布情報を用いる方法そのものが開発されていなかった。以下、その算出方法について説明する。 When a crystal lattice image is drawn at an arbitrary crystal orientation measurement point in a crystal that has locally produced a crystal grain orientation difference and its adjacent points, each lattice has a relatively crystallized shape. . However, since the crystal is continuous, a lattice strain that compensates for the orientation difference is introduced between the lattices, and the lattice strain can be drawn from the crystal orientation distribution information in which the orientation difference within the crystal grain is generated. In the first place, in order to measure the plastic strain, it is necessary to obtain the displacement amount due to the deformation of the region or the strain of the lattice. Until now, no method has been developed that uses crystal orientation distribution information to determine the lattice strain. Hereinafter, the calculation method will be described.
たとえば、測定点間隔ｄで正方格子状に測定された結晶方位分布の任意の測定点Ａと測定座標系に対してＸ軸方向（右手座標系で（１００）ベクトルの方向）に隣接する測定点Ｂの間に生じる格子歪量について具体的に説明する。 For example, a measurement point adjacent in the X-axis direction (in the direction of (100) vector in the right-handed coordinate system) with respect to an arbitrary measurement point A of the crystal orientation distribution measured in a square lattice pattern at a measurement point interval d and the measurement coordinate system The amount of lattice distortion generated during B will be specifically described.
上記測定条件下における結晶方位情報によれば、各測定点を中心とした１辺ｄの立方体の領域がその結晶方位であることになり、測定点Ａと測定点Ｂの境界面（測定点Ａの（１００）方向）の結晶面ミラー指数ｍは幾何学式から（１）式となる。 According to the crystal orientation information under the above measurement conditions, a cubic region with one side d centering on each measurement point is the crystal orientation, and the boundary surface between the measurement point A and the measurement point B (measurement point A The (100) direction) crystal plane mirror index m is given by equation (1) from the geometric equation.
ｕは測定座標系における境界面方向のベクトル、ｇＡは測定点Ａにおいて測定座標系から結晶座標系への回転行列である。一方で測定点Ｂの結晶において（１）式と同様のミラー指数となるベクトルは測定点Ａと隣接する測定点Ｂで測定座標系から結晶座標系へ変換する回転行列ｇＢを用いることで示される。すなわち、（２）式となる。 u is a vector in the interface direction in the measurement coordinate system, and g A is a rotation matrix from the measurement coordinate system to the crystal coordinate system at the measurement point A. On the other hand, in the crystal at the measurement point B, a vector having a Miller index similar to the equation (1) is indicated by using a rotation matrix gB that converts the measurement coordinate system from the measurement coordinate system to the crystal coordinate system at the measurement point B adjacent to the measurement point A. . That is, equation (2) is obtained.
このベクトルｕとベクトルｕ´は一致しておらず、実際の結晶は測定点Ａ−Ｂ間でこのベクトル差分の格子歪を持っている。蓄積された塑性歪は外力をもたらさないことから、格子歪相当の変位量は測定点ＡおよびＢのそれぞれが等しい量となる。すなわち、測定点ＡおよびＢの境界面上において、実際の結晶の局所的な結晶面は（３）式のような方向へ歪を持つこととなる。 The vector u and the vector u ′ do not coincide with each other, and the actual crystal has a lattice distortion of this vector difference between the measurement points A and B. Since the accumulated plastic strain does not bring about an external force, the displacement corresponding to the lattice strain is equal to each of the measurement points A and B. That is, on the boundary surface between the measurement points A and B, the local crystal plane of the actual crystal has a strain in the direction as shown in the equation (3).
上記したような隣接測定点間の格子歪を求めれば、歪をもった格子像が描ける。ここで、既知の変位量を持つ形状に対するひずみ量は形状関数を用いて幾何学的に決定される。
すなわち、εxxであれば格子頂点での各変位のｘ成分の和をその総数で除した値が、測定点上の結晶格子がもつ蓄積された格子歪量となる。この格子歪を変形前と変形後とで測定し、その差分を取ることで、変形に伴い蓄積された塑性歪量が測定されたことになる。
If the lattice strain between adjacent measurement points as described above is obtained, a lattice image with strain can be drawn. Here, the amount of strain for a shape having a known amount of displacement is geometrically determined using a shape function.
That is, if ε xx , the value obtained by dividing the sum of the x components of each displacement at the lattice vertex by the total number is the accumulated lattice strain amount of the crystal lattice on the measurement point. The lattice strain is measured before and after the deformation, and the difference between the lattice strains is measured to measure the amount of plastic strain accumulated with the deformation.
図１は、本発明に係る測定装置の構成例を示す図である。 FIG. 1 is a diagram showing a configuration example of a measuring apparatus according to the present invention.
後方散乱電子回折像を取得可能な電子ビーム装置１０の電子源１１から照射される電子ビームは、磁気アライメント装置１２により収束され、測定対象材料１３に衝突する。測定対象材料１３から得られる後方散乱電子回折像を検出器１５により検出して、結晶方位情報を処理する第１の情報処理装置ＰＣ１に入力する。第１の情報処理装置ＰＣ１では、結晶方位を同定する。 The electron beam irradiated from the electron source 11 of the electron beam apparatus 10 capable of acquiring a backscattered electron diffraction image is converged by the magnetic alignment apparatus 12 and collides with the measurement target material 13. The backscattered electron diffraction image obtained from the measurement target material 13 is detected by the detector 15 and input to the first information processing apparatus PC1 that processes the crystal orientation information. In the first information processing device PC1, the crystal orientation is identified.
本実施形態では、まず変形前の材料を測定対象材料１３として、後方散乱電子回折像に基づいて変形前の結晶方位情報を第１の情報処理装置ＰＣ１により取得する。次いで、変形前の結晶方位情報は、塑性ひずみ測定プログラムがインストールされた第２の情報処理装置ＰＣ２に入力し、塑性変形前の格子歪を求める。 In this embodiment, first, the material before deformation is used as the measurement target material 13, and crystal orientation information before deformation is acquired by the first information processing apparatus PC1 based on the backscattered electron diffraction image. Next, the crystal orientation information before deformation is input to the second information processing apparatus PC2 in which the plastic strain measurement program is installed, and the lattice strain before plastic deformation is obtained.
次に、当該材料に塑性変形を与え、変形後の材料を測定対象材料１３として、後方散乱電子回折像に基づいて、変形後の結晶方位情報を第１の情報処理装置ＰＣ１により取得する。次いで、第２の情報処理装置ＰＣ２に入力し、塑性変形後の格子歪を求める。さらに、第２の情報処理装置ＰＣ２では、塑性変形前の格子歪と塑性変形後の格子歪との差を求めることにより、組成歪を求める。 Next, plastic deformation is applied to the material, and the crystal orientation information after the deformation is acquired by the first information processing apparatus PC1 based on the backscattered electron diffraction image with the material after the deformation as the measurement target material 13. Subsequently, it inputs into 2nd information processing apparatus PC2, and calculates | requires the lattice distortion after plastic deformation. Further, in the second information processing apparatus PC2, the composition strain is obtained by obtaining the difference between the lattice strain before plastic deformation and the lattice strain after plastic deformation.
なお、電子ビーム装置１０と第２の情報処理装置ＰＣ２を接続するのではなく、変形前の結晶方位情報と変形後の結晶方位情報とを予め取得しておいて、第２の情報処理装置ＰＣ２への入力２０とすることによっても、組成歪を求めることができる。 Instead of connecting the electron beam apparatus 10 and the second information processing apparatus PC2, the crystal orientation information before deformation and the crystal orientation information after deformation are acquired in advance, and the second information processing apparatus PC2 is obtained. The composition strain can also be obtained by setting the input 20 to.
また、図１では、電子ビーム装置を用いているが、収束イオンビーム装置を用いることもできる。さらに。第１の情報処理装置ＰＣ１と第２の情報処理装置ＰＣ２を使用したが、これらに代えて単一の情報処理装置を使用することもできる。情報処理装置は、専用のコンピュータとすることもできるが、汎用のパーソナルコンピュータに必要とするプログラムをインストールすることによっても実現できる。 Further, although an electron beam apparatus is used in FIG. 1, a focused ion beam apparatus can also be used. further. Although the first information processing device PC1 and the second information processing device PC2 are used, a single information processing device can be used instead. The information processing apparatus can be a dedicated computer, but can also be realized by installing a necessary program in a general-purpose personal computer.
図２は、本実施形態による塑性歪を求める測定方法のフローの一例を示す図である。 FIG. 2 is a diagram illustrating an example of a flow of a measurement method for obtaining plastic strain according to the present embodiment.
測定方法を開始すると、まず測定対象材料の塑性変形前の結晶方位分布と塑性変形後の結晶方位分布が求められているか否かを確認する（ステップＳ１）。例えば、結晶方位分布を外部から入手することができる場合は、結晶方位分布を求める必要がない。 When the measurement method is started, first, it is confirmed whether or not the crystal orientation distribution before plastic deformation and the crystal orientation distribution after plastic deformation of the material to be measured are obtained (step S1). For example, when the crystal orientation distribution can be obtained from the outside, it is not necessary to obtain the crystal orientation distribution.
塑性変形前と塑性変形後の結晶方位分布が求められていれば、第２の情報処理装置ＰＣ２にこれらの結晶方位分布を入力し、塑性変形前と塑性変形後の格子歪を算出する（ステップＳ２）。次いで、算出した塑性変形前と塑性変形後の格子歪を比較して塑性変形量すなわち塑性歪を決定する（ステップＳ３）。その後さらに塑性変形を測定対象材料に与えるか否かが判定され（ステップＳ９）、塑性変形を導入する必要があれば、ステップ１に戻る。塑性変形を導入する必要がなければ、終了する。 If the crystal orientation distribution before plastic deformation and after plastic deformation is obtained, these crystal orientation distributions are input to the second information processing apparatus PC2, and lattice strains before and after plastic deformation are calculated (step) S2). Next, the amount of plastic deformation, that is, plastic strain is determined by comparing the calculated lattice strain before and after plastic deformation (step S3). Thereafter, it is determined whether further plastic deformation is to be applied to the measurement target material (step S9). If it is necessary to introduce plastic deformation, the process returns to step 1. If it is not necessary to introduce plastic deformation, the process ends.
ステップ１で、測定対象材料の塑性変形前の結晶方位分布と塑性変形後の結晶方位分布が求められていないことがわかると、例えば電子顕微鏡１０を使用して塑性変形が与えられていない測定対象材料の後方散乱電子回折像を求め、求められた後方散乱電子回折像から塑性変形前の結晶方位分布を取得する（ステップＳ４）。次いで、各測定点で求められた結晶方位情報から変形前の格子歪を決定する（ステップ５）。 If it is found in step 1 that the crystal orientation distribution before plastic deformation and the crystal orientation distribution after plastic deformation of the material to be measured have not been obtained, for example, the measurement object to which no plastic deformation has been applied using the electron microscope 10. A backscattered electron diffraction image of the material is obtained, and a crystal orientation distribution before plastic deformation is obtained from the obtained backscattered electron diffraction image (step S4). Next, the lattice strain before deformation is determined from the crystal orientation information obtained at each measurement point (step 5).
次に、変形前の格子歪が決定された測定対象材料に塑性変形を導入する（ステップＳ６）。そして、塑性変形が導入された測定対象材料について、例えば電子顕微鏡１０を使用して後方散乱電子回折像を求め、求められた後方散乱電子回折像から塑性変形後の結晶方位分布を取得する（ステップＳ７）。次いで、各測定点で求められた結晶方位情報から変形後の格子歪を決定する（ステップ８）。 Next, plastic deformation is introduced into the material to be measured whose lattice strain before deformation is determined (step S6). Then, for a measurement target material into which plastic deformation is introduced, for example, an electron microscope 10 is used to obtain a backscattered electron diffraction image, and a crystal orientation distribution after plastic deformation is obtained from the obtained backscattered electron diffraction image (step) S7). Next, the lattice strain after deformation is determined from the crystal orientation information obtained at each measurement point (step 8).
以上のようにして、変形前と変形後の格子歪が求まると、変形前と変形後の格子歪を比較して塑性変形量すなわち塑性歪を決定する（ステップ３）。塑性歪が決定すると、さらに塑性変形を導入するか否かが判断され（ステップ９）、塑性変形を導入する必要があれば、ステップ１に戻る。さらに塑性変形を導入する必要がなければ、終了する。 When the lattice strain before and after the deformation is obtained as described above, the amount of plastic deformation, that is, the plastic strain is determined by comparing the lattice strain before and after the deformation (step 3). When the plastic strain is determined, it is further determined whether or not plastic deformation is to be introduced (step 9). If it is necessary to introduce plastic deformation, the process returns to step 1. If it is not necessary to introduce further plastic deformation, the process ends.
本発明の方法によれば、結晶方位分布より３次元の格子歪を求めることで塑性歪の全成分を求めることが可能となる。また、後方散乱電子回折像から直接、塑性歪を測定する方法ではないので、既に求められた結晶方位分布データから塑性歪の定量化を行うことが可能となる。 According to the method of the present invention, all components of plastic strain can be obtained by obtaining a three-dimensional lattice strain from the crystal orientation distribution. In addition, since the plastic strain is not directly measured from the backscattered electron diffraction image, the plastic strain can be quantified from the crystal orientation distribution data already obtained.
次に、例として単純せん断変形を加えた予ひずみ材の塑性歪量を測定した例について説明する。本実施形態の一例として、質量％で、Ｃが０．００１％、Ｃｒが１６．４％、Ｎｉが０．１％ Ｐが０．０３％ Ｓが０．００６％、残部鉄および不可避的不純物からなり、フェライト単相組織を有するステンレス鋼板を用いた。なお、この鋼板は転炉で溶製し、連続鋳造後、粗圧延および仕上げ圧延を施し、板厚を１．９ｍｍとしたものである。得られた熱延板を１３００℃で７２時間保持し、結晶粒径を４ｍｍ程度まで成長させた。 Next, an example in which the amount of plastic strain of a pre-strained material subjected to simple shear deformation is measured will be described. As an example of this embodiment, in mass%, C is 0.001%, Cr is 16.4%, Ni is 0.1%, P is 0.03%, S is 0.006%, the remaining iron and inevitable impurities And a stainless steel plate having a ferrite single-phase structure was used. In addition, this steel plate is melted in a converter, subjected to rough rolling and finish rolling after continuous casting, and has a thickness of 1.9 mm. The obtained hot-rolled sheet was held at 1300 ° C. for 72 hours to grow the crystal grain size to about 4 mm.
上記した熱延板熱処理材の一部を長さ１６ｍｍ、幅３０ｍｍ、厚さ１．９ｍｍの形状に加工し、インストロン社の引張試験機を用いて真ひずみで５％、１０％、２０％まで単純せん断試験を行った。なお、ひずみ速度は１０-3（１／ｓｅｃ）とした。なお、ひずみ速度は１０-3（１／ｓｅｃ）とし、試験片両端をせん断試験片冶具で固定し試験片中央部２ｍｍ幅の領域に単純せん断変形を加えている。 A part of the above-mentioned hot-rolled sheet heat treatment material is processed into a shape having a length of 16 mm, a width of 30 mm, and a thickness of 1.9 mm, and using an Instron tensile tester, the true strain is 5%, 10%, and 20%. A simple shear test was conducted. The strain rate was 10 −3 (1 / sec). The strain rate is 10 −3 (1 / sec), both ends of the test piece are fixed with a shear test piece jig, and a simple shear deformation is applied to a 2 mm width region at the center of the test piece.
試験片の結晶方位は予め、単純せん断変形を加える前に測定間隔０．５μｍで結晶方位分布の測定を行っている。測定にはタングステンを半溶融状態の酸化ジルコニウムでコーティングしたフィラメントに電流１２３μＡを流し、加速電圧２５ｋＶで生じた収束電子線を試料面に対して７０°の方向に照射し、反射した菊池パターンより結晶方位を同定した。また、結晶方位の測定に際して、試験片は表面が鏡面となるまで、エメリー紙およびコロイダルシリカによる研磨を行った後、６ｖｏｌ．％過塩素酸による化学研磨を施した。 The crystal orientation of the test piece is measured in advance at a measurement interval of 0.5 μm before applying simple shear deformation. For the measurement, a current of 123 μA was passed through a filament coated with tungsten oxide in a semi-molten state of tungsten, and a focused electron beam generated at an acceleration voltage of 25 kV was irradiated in a direction of 70 ° with respect to the sample surface. The orientation was identified. When measuring the crystal orientation, the test piece was polished with emery paper and colloidal silica until the surface became a mirror surface, and then 6 vol. Chemical polishing with% perchloric acid was performed.
変形後の試験片についても同様に結晶方位分布の測定を行い、両者の格子歪量を求めることで塑性歪量を測定した。 The crystal orientation distribution was measured in the same way for the deformed test piece, and the plastic strain amount was measured by obtaining the lattice strain amount of both.
図３は単純せん断変形前およびせん断変形後の試験片変形部外観写真および結晶方位情報示を併せて示した。なお、せん断変形領域のコンターは図中の標準ステレオ三角形の色と一致する結晶方位となる。変形後のせん断変形領域の結晶粒内では色に変化が認められる。これは結晶粒内で変形が生ずる、すなわち、塑性ひずみが蓄積することで結晶方位が場所ごとで違う変化を示したためと考えられる。また、この結晶粒内の方位変化はせん断歪量の増加とともに増加することが確認された。なお、写真の結晶方位情報は、本発明の塑性歪測定装置を用いて測定した、せん断変形により組織内部に蓄積した塑性歪分布を図４に示した。なお、図のコンターは相当塑性ひずみを現している。試験片全体のマクロなひずみとして、５％せん断ひずみを生じているが、個々の結晶粒が受け持つ応力は結晶方位ごとに異なるため、変形量も異なる。５％せん断変形後では特定の結晶粒内で塑性変形が局在している。一方で、さらに変形が進んだ１０％せん断変形後の試料では測定した範囲での結晶ごとの蓄積された塑性歪差は減少する傾向にある。これは変形時に伴い、まず変形を容易に生じる結晶が優先的に変形し、変形が進むについてその結晶が硬化することで、試料全体で均一に塑性変形を担おうとしたためであると考えられる。ここで、図５には各試料のせん断応力−せん断ひずみ曲線を示した。 FIG. 3 also shows a photograph of the appearance of the deformed part of the specimen before simple shear deformation and after shear deformation, and crystal orientation information. The contour in the shear deformation region has a crystal orientation that matches the color of the standard stereo triangle in the figure. A change in color is observed in the crystal grains in the shear deformation region after deformation. This is considered to be because deformation occurs in the crystal grains, that is, the crystal orientation changes depending on the location due to accumulation of plastic strain. In addition, it was confirmed that the orientation change in the crystal grains increased as the shear strain increased. The crystal orientation information in the photograph shows the plastic strain distribution accumulated in the structure by shear deformation, measured using the plastic strain measuring apparatus of the present invention, as shown in FIG. The contour in the figure shows a considerable plastic strain. As a macro strain of the entire test piece, a 5% shear strain is generated. However, since the stress that each crystal grain has is different for each crystal orientation, the amount of deformation is also different. After 5% shear deformation, plastic deformation is localized in specific crystal grains. On the other hand, the accumulated plastic strain difference for each crystal in the measured range tends to decrease in the sample after 10% shear deformation in which the deformation has further progressed. This is presumably because the crystals that easily deform are preferentially deformed at the time of deformation, and the crystals harden as the deformation progresses, so that the entire sample is uniformly plastically deformed. Here, FIG. 5 shows a shear stress-shear strain curve of each sample.
図５での５％せん断変形時では材料が直線硬化領域に達していないのに対して、１０％せん断変形時では直線硬化を示しているものと考えられる。 In FIG. 5, the material does not reach the linear hardening region at the time of 5% shear deformation, whereas it is considered that the material shows linear hardening at the time of 10% shear deformation.
また、蓄積された塑性歪量に着目した場合、５％せん断変形後の組織内の平均は２．１５％であったのに対して、１０％せん断変形後では１．８８％であった。この蓄積された塑性歪が多い５％せん断に用いた試験片は１０％のものよりも大きく硬化しており、この蓄積された塑性歪は材料の硬化量に対応すると考えられる。また、蓄積された歪量の値は図５の横軸に示したせん断歪と異なる。本発明における蓄積された塑性歪量は上述したように、ｅｉｇｅｎ歪に対応し、個々の測定座標の変形に伴う移動量を含めその平均値を用いることで試験機から検出される歪量と対応する。 Further, when paying attention to the accumulated amount of plastic strain, the average in the structure after 5% shear deformation was 2.15%, and 1.88% after 10% shear deformation. The specimen used for 5% shear with much accumulated plastic strain is hardened more than 10%, and this accumulated plastic strain is considered to correspond to the amount of hardening of the material. Also, the accumulated strain value is different from the shear strain shown on the horizontal axis of FIG. As described above, the accumulated plastic strain amount in the present invention corresponds to the eigen strain, and corresponds to the strain amount detected from the testing machine by using the average value including the amount of movement accompanying the deformation of each measurement coordinate. To do.
本発明の塑性歪測定方法を採用したことにより、試験片のマクロな挙動と試験片を構成する組織内における個々の結晶の変形挙動との関係を定量的に調査することを可能とした。その結果、材料の組織と強度の関係が明確に把握できるようになった。 By adopting the plastic strain measuring method of the present invention, it is possible to quantitatively investigate the relationship between the macroscopic behavior of the test piece and the deformation behavior of individual crystals in the structure constituting the test piece. As a result, the relationship between the structure and strength of the material can be clearly understood.
１０ 電子顕微鏡
１１ 電子源
１２ 磁気アライメント
１３ 被測定対象
１５ 検出器
２０ 入力
DESCRIPTION OF SYMBOLS 10 Electron microscope 11 Electron source 12 Magnetic alignment 13 Object to be measured 15 Detector 20 Input
Claims (6)
前記塑性変形前の結晶方位分布に基づいて、任意の結晶方位測定点と隣接する結晶方位測定点間における結晶方位差より変形前の格子歪を算出する工程と、
前記塑性変形後の結晶方位分布に基づいて、任意の結晶方位測定点と隣接する結晶方位測定点間における結晶方位差より変形後の格子歪を算出する工程と、
前記変形前の格子歪と前記変形後の格子歪とにより結晶内に蓄積した塑性歪を測定する工程と、
を有することを特徴とする塑性歪測定方法。 Incorporating crystal orientation distribution before plastic deformation and after plastic deformation in the same visual field of a metal member to be measured having a cubic crystal structure or a specimen taken from the member to be measured;
Based on the crystal orientation distribution before plastic deformation, calculating the lattice strain before deformation from the crystal orientation difference between an arbitrary crystal orientation measurement point and an adjacent crystal orientation measurement point;
Based on the crystal orientation distribution after plastic deformation, calculating the lattice strain after deformation from the crystal orientation difference between an arbitrary crystal orientation measurement point and an adjacent crystal orientation measurement point;
Measuring the plastic strain accumulated in the crystal by the lattice strain before deformation and the lattice strain after deformation;
A method for measuring plastic strain, comprising:
前記取り込まれた結晶方位分布に基づいて、任意の結晶方位測定点と隣接する結晶方位測定点間における結晶方位差より格子歪を算出する格子歪算出手段と、
前記塑性変形前と塑性変形後の結晶方位分布に基づいて前記格子歪算出手段により算出された変形前の格子歪と変形後の格子歪とにより結晶内に蓄積した塑性歪を測定する塑性歪測定手段と、
を有することを特徴とする塑性歪測定装置。 A crystal orientation distribution capturing means for capturing a crystal orientation distribution before and after plastic deformation in the same visual field of a test piece sampled from a metal material whose crystal structure is a cubic system, or a test piece collected from the measurement member;
Lattice strain calculation means for calculating a lattice strain from a crystal orientation difference between an arbitrary crystal orientation measurement point and an adjacent crystal orientation measurement point based on the captured crystal orientation distribution;
Plastic strain measurement for measuring the plastic strain accumulated in the crystal by the lattice strain before deformation and the lattice strain after deformation calculated by the lattice strain calculation means based on the crystal orientation distribution before and after plastic deformation Means,
A plastic strain measuring device characterized by comprising:
前記塑性変形前の結晶方位分布に基づいて、任意の結晶方位測定点と隣接する結晶方位測定点間における結晶方位差より変形前の格子歪を算出する手順と、
前記塑性変形後の結晶方位分布に基づいて、任意の結晶方位測定点と隣接する結晶方位測定点間における結晶方位差より変形後の格子歪を算出する手順と、
前記変形前の格子歪と前記変形後の格子歪とにより結晶内に蓄積した塑性歪を測定する手順と、
を前記コンピュータに実行させることを特徴とする塑性歪測定プログラム。 As an input of a computer, the crystal orientation distribution before plastic deformation and after plastic deformation in the same field of view of a specimen measured from a metallic material having a cubic crystal structure or a specimen taken from the measured member,
Based on the crystal orientation distribution before plastic deformation, a procedure for calculating a lattice strain before deformation from a crystal orientation difference between an arbitrary crystal orientation measurement point and an adjacent crystal orientation measurement point;
Based on the crystal orientation distribution after plastic deformation, a procedure for calculating lattice strain after deformation from a crystal orientation difference between an arbitrary crystal orientation measurement point and an adjacent crystal orientation measurement point;
Measuring the plastic strain accumulated in the crystal by the lattice strain before deformation and the lattice strain after deformation;
Is executed by the computer, and a plastic strain measuring program.
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