JP2012154891A - Plastic strain amount estimation device and plastic strain amount estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic strain amount estimation device capable of accurately estimating a plastic strain amount of a cast material.SOLUTION: A plastic strain amount estimation device 10 to estimate a plastic strain amount of a cast material comprises: a crystal orientation measurement means 12 which measures a crystal orientation in a manner that selects a region equal to or less than 10 μm from a crystal grain boundary in a same crystal grain among the crystal grains composing a metallographic structure of a plastically-deformed measurement object, divides the region into a plurality of blocks having a same area, and measures the crystal orientations of the respective blocks; a KAM value calculation means 14 which first obtains crystal orientation differences, with one of the plurality of blocks as a reference block, between the reference block and the plurality of the blocks including the reference block and then calculates a KAM value by averaging the crystal orientation differences; and a plastic strain amount estimation means 16 which estimates the plastic strain amount of the measurement object by comparing the KAM value thereof with the preliminary obtained KAM value of the cast material which has the same composition as the measurement object and is subjected to a known plastic deformation.

Description

  The present invention relates to a plastic strain amount estimation device and a plastic strain amount estimation method, and more particularly to a plastic strain amount estimation device and a plastic strain amount estimation method for estimating a plastic strain amount of a cast material.

  Since turbocharger impellers and the like used in a high temperature environment are plastically deformed by use, it is necessary to estimate the amount of plastic strain caused by the plastic deformation in order to use them safely. For example, in Patent Document 1, in order to predict the creep life of a boiler member of a power plant or a structural material of a nuclear power plant, creep strain is estimated based on a crystal orientation difference caused by strain in crystal grains due to creep damage. It is described.

Japanese Patent No. 3252933

  By the way, in the conventional technique for estimating the plastic strain amount of a metal material, the crystal orientation in a crystal grain is measured by an EBSD method (Electron Back Scatter Diffraction) or the like, and the average crystal orientation in the whole crystal grain by GOS (Grain Orientation Spread) or the like. The plastic strain amount is estimated by obtaining the difference. As the plastic deformation of the metal material proceeds, the dislocation density in the crystal grains increases, so that the crystal rotates due to the dislocations and the crystal orientation difference in the crystal grains increases. Therefore, the amount of plastic strain of the plastically deformed metal material can be estimated by obtaining the average crystal orientation difference in the entire crystal grains.

  However, a material with a large crystal grain size (for example, a crystal grain size of 1 mm or more) such as a cast material is compared with a material with a small crystal grain size (for example, a crystal grain size of 0.1 mm or less) such as a forged material. When the plastic deformation progresses, the degree of increase in the dislocation density in the crystal grains becomes small. In addition, the crystal orientation difference in the crystal grains is generally proportional to the plastic strain amount and inversely proportional to the Burgers vector and the crystal grain size. Therefore, in a material having a large crystal grain size such as a cast material, The misorientation becomes smaller. Thus, in the case of a cast material, it may be difficult to estimate the amount of plastic strain from the average crystal orientation difference in the crystal grains.

  Therefore, an object of the present invention is to provide a plastic strain amount estimation apparatus and a plastic strain amount estimation method capable of estimating the plastic strain amount of a plastically deformed cast material with higher accuracy.

  The plastic strain amount estimation device for a cast material according to the present invention is a plastic strain amount estimation device for estimating the plastic strain amount of a cast material, and is the same among the crystal grains constituting the metal structure of the plastically measured object. A crystal orientation measuring means for measuring a crystal orientation in each section by dividing only a region within 10 μm from the grain boundary in the crystal grain into a plurality of sections having the same area, and one of the plurality of sections as a reference section A KAM value calculating means for calculating a KAM value for the reference section by averaging after obtaining the crystal orientation difference between the reference section and a plurality of sections surrounding the reference section, and The KAM value of the object to be measured is compared with the KAM value of a casting material having the same composition as that of the object to be measured and subjected to known plastic deformation, and the amount of plastic strain of the object to be measured is estimated. And a plastic strain amount evaluation means. And wherein the door.

  In the cast plastic deformation amount estimation apparatus according to the present invention, the KAM value calculating means sequentially moves the reference section to another section, and surrounds the moved reference section and the moved reference section. After calculating the crystal orientation difference between a plurality of sections, it is averaged to sequentially calculate the KAM values for the moved reference section, and the KAM values for the moved reference section are sequentially calculated and averaged. A KAM value is calculated, and the plastic strain amount evaluation means calculates an average KAM value of the measured object and an average KAM value of a casting material that has been obtained in advance and has the same composition as the measured object and has undergone known plastic deformation. It is preferable to estimate the amount of plastic strain of the object to be measured.

  The method for estimating the plastic strain amount of a cast material according to the present invention is a plastic strain amount estimation method for estimating the plastic strain amount of a cast material, wherein the same structure is obtained by observing the metal structure of the plastically deformed object under an electron microscope. A crystal orientation measuring step of dividing only a region within 10 μm from a grain boundary in a grain into a plurality of sections having the same area and measuring a crystal orientation for each section; and one of the plurality of sections as a reference section A KAM value calculating step of calculating a KAM value with respect to the reference section after obtaining crystal orientation differences between the reference section and a plurality of sections surrounding the reference section, The plasticity for estimating the plastic strain amount of the object to be measured by comparing the KAM value of the object to be measured with the KAM value of a casting material having the same composition as that of the object to be measured and subjected to known plastic deformation. A strain amount evaluation step. The features.

  In the method for estimating a plastic strain amount of a cast material according to the present invention, the KAM value calculating step sequentially moves the reference section to another section, and surrounds the moved reference section and the moved reference section. After calculating the crystal orientation difference between a plurality of sections, it is averaged to sequentially calculate the KAM values for the moved reference section, and the KAM values for the moved reference section are sequentially calculated and averaged. A KAM value is calculated, and the plastic strain evaluation step includes an average KAM value of the object to be measured and an average KAM value of a casting material having the same composition as that of the object to be measured and having undergone known plastic deformation. It is preferable to estimate the amount of plastic strain of the object to be measured.

  In the method for estimating a plastic strain amount of a cast material according to the present invention, the region is preferably only a region within 5 μm from the grain boundary.

  In the method for estimating a plastic strain amount of a cast material according to the present invention, the object to be measured is preferably polished and finished with colloidal silica.

  In the method for estimating a plastic strain amount of a cast material according to the present invention, the KAM value of the object to be measured is preferably equal to or less than a threshold value.

  In the method for estimating a plastic strain amount of a cast material according to the present invention, the cast material is preferably a Ni-based cast alloy, and the crystal grain size of the cast material is preferably 1 mm or more.

  According to the plastic strain amount estimation apparatus and the plastic strain amount estimation method in the above configuration, the crystal orientation of only the region within 10 μm from the grain boundary where dislocations are likely to be deposited when the cast material is plastically deformed is measured by the EBSD method or the like. Since the plastic strain amount is estimated based on the KAM (Kernel Average Misorientation) value obtained from the crystal orientation difference in the region, the plastic strain amount of the cast material can be estimated more accurately.

In embodiment of this invention, it is a block diagram which shows the structure of the plastic strain amount estimation apparatus. In embodiment of this invention, it is a flowchart which shows the procedure of the plastic strain amount estimation method. In embodiment of this invention, it is a schematic diagram which shows the measurement area | region which measures the crystal orientation in each crystal grain. In the embodiment of the present invention, it is the graph which showed typically the change of the average crystal orientation difference from the crystal grain boundary to the crystal grain in the plastically deformed cast material. In embodiment of this invention, it is a schematic diagram which shows the measurement area | region of the crystal orientation in the crystal grain boundary vicinity. In the embodiment of the present invention, it is a distribution diagram of a typical KAM value (10th) in plastically deformed Ni-base cast alloy Inconel 713C. In embodiment of this invention, it is a figure which shows the shape of a tensile test piece. In embodiment of this invention, it is a distribution map of KAM value (10th) in Ni base cast alloy before plastic deformation. In embodiment of this invention, it is a distribution map of KAM value (10th) in Ni base cast alloy with a plastic strain amount of 1.5%. In embodiment of this invention, it is a distribution map of KAM value (10th) in Ni base cast alloy with a plastic strain amount of 2.5%. In embodiment of this invention, it is a distribution map of KAM value (10th) in Ni base cast alloy with 4.41% of plastic strain. In embodiment of this invention, it is a graph which shows the relationship between the average KAM value (10th) of only the area | region within 5 micrometers from a crystal grain boundary, and the amount of plastic strain. In embodiment of this invention, it is a graph which shows the relationship between the average KAM value (10th) of the area | region of the whole crystal grain, and the amount of plastic strain. In embodiment of this invention, it is a distribution map of KAM value (10th) in Ni base cast alloy with a plastic strain amount of 1.5%. In embodiment of this invention, it is a distribution map of KAM value (10th) in Ni base cast alloy with a plastic strain amount of 2.5%. In embodiment of this invention, it is a distribution map of KAM value (10th) in Ni base cast alloy with a plastic strain amount of 3.5%. In embodiment of this invention, it is a distribution map of KAM value (10th) in Ni base cast alloy with 4.41% of plastic strain. In embodiment of this invention, it is a graph which shows the relationship between the average KAM value (10th) of only the area | region within 5 micrometers from a crystal grain boundary, and the amount of plastic strain.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the plastic strain amount estimating apparatus 10. The plastic strain amount estimation device 10 is a device that estimates the plastic strain amount of a cast material such as a Ni-base cast alloy or a Fe-base cast alloy. The plastic strain amount estimating apparatus 10 includes crystal orientation measuring means 12, KAM value calculating means 14, plastic strain amount evaluating means 16, storage means 18, and output means 20. The plastic strain amount estimation apparatus 10 can be configured using a general computer system.

  The crystal orientation measuring means 12 has a function of measuring a crystal orientation in the vicinity of a grain boundary using an electron microscope for a sample collected from a plastically deformed object to be measured. As the electron microscope, a scanning electron microscope or a transmission electron microscope is used. The crystal orientation in the vicinity of the crystal grain boundary is obtained by, for example, irradiating an electron beam onto a polished sample and measuring the Kikuchi pattern. For measurement of crystal orientation, it is preferable to use an EBSD method (electron beam backscatter diffraction method) using a scanning electron microscope because a large amount of crystal orientation data can be easily obtained over a wide range. Further, the vicinity of the crystal grain boundary is preferably only a region within 10 μm from the crystal grain boundary, and more preferably only a region within 5 μm from the crystal grain boundary.

  The KAM value calculation means 14 has a function of calculating a KAM value from the measured crystal orientation in the vicinity of the crystal grain boundary. The KAM value is an average of crystal orientation differences between neighboring sections when a region in a crystal grain is divided into a plurality of sections (pixels) having the same area. A detailed method for calculating the KAM value will be described later.

  The plastic strain amount evaluation means 16 compares the KAM value of the object to be measured with the KAM value of a cast material that has been obtained in advance and has the same composition as that of the object to be measured and has undergone known plastic deformation. It has a function to estimate the amount of plastic strain. In advance, the cast material having the same composition as the object to be measured is plastically deformed, and the relationship between the plastic strain amount and the KAM value is obtained. Then, the KAM value of the object to be measured is compared with the relationship (for example, a graph such as a master curve) between the plastic strain amount and the KAM value in the cast material having the same composition as the object to be measured. The amount of plastic strain of the measurement object can be estimated. The details of the plastic strain amount estimation method will be described later.

  The storage means 18 has a function of storing crystal orientation data, a KAM value, an estimated amount of plastic strain, and the like, and is composed of a CD-ROM, a DVD, or the like. The storage means 18 stores the relationship between the plastic strain amount and the KAM value obtained in advance in association with various cast materials. The plastic strain amount evaluation means 16 can call up the data of the casting material to be compared from the storage means 18 using the type of casting material as a search key.

  The output means 20 has a function of outputting crystal orientation data, KAM value, estimated plastic strain amount, and the like. The output means 20 is composed of, for example, a display or a printer.

  Next, a method for estimating the plastic strain amount of the cast material will be described.

  FIG. 2 is a flowchart showing the procedure of the plastic strain amount estimation method. The plastic strain amount estimation method includes a sample preparation step (S10), a crystal orientation measurement step (S12), a KAM value calculation step (S14), a plastic strain amount evaluation step (S16), and an output step (S18). I have.

  The sample preparation step (S10) is a step of preparing a sample for observation of a metal structure from a measurement object made of a cast material to which plastic deformation is applied. A specimen for observing the metal structure is cut out from an object to be plastically deformed under a tensile load, a compressive load, a creep load, or the like. The sample is taken along the stress axis direction in order to observe the structure of the surface along the stress axis direction. For example, when the object to be measured is subjected to a tensile load, the sample is collected along the tensile stress axis direction.

  The collected sample is filled with resin and polished with water-resistant abrasive paper, diamond, alumina abrasive, etc., and then polished with electrolytic polishing or colloidal silica. As the alumina abrasive, it is preferable to use an abrasive having an average particle size of 1.0 μm, and as the colloidal silica abrasive, it is preferable to use an abrasive having an average particle size of 0.04 μm. In addition, it is preferable to use colloidal silica for polishing finishing because the structure of the crystal grain boundary can be observed more clearly.

  In the crystal orientation measurement step (S12), the polished sample is observed with an electron microscope, and the vicinity of the crystal grain boundary in the same crystal grain (in one crystal grain of the crystal grains constituting the metal structure) has the same area. This is a step of dividing a plurality of sections and measuring the crystal orientation for each section. For the crystal orientation measurement, it is preferable to use the EBSD method as described above.

  FIG. 3 is a schematic diagram illustrating a measurement region (S) in which the crystal orientation in each crystal grain 30 is measured. As the plastic deformation of the cast material proceeds, the dislocations 32 in the crystal grains 30 move to the crystal grain boundaries 34 and accumulate. Therefore, as the amount of plastic deformation of the cast material increases, the dislocation density near the crystal grain boundary increases. In the region where the dislocation density is high, the crystal orientation difference increases due to the rotation of the crystal. Therefore, the plastic strain amount of the cast material can be estimated from the change in the crystal orientation difference near the crystal grain boundary.

  The crystal orientation measurement region (S) is provided in the vicinity of a crystal grain boundary in the same crystal grain in each crystal grain 30. The measurement region (S) is preferably only a region within 10 μm from the crystal grain boundary 34 of each crystal grain 30 in the intragranular direction, and is preferably only a region within 5 μm from the crystal grain boundary 34 to the intragranular direction. More preferred. This is because the dislocation 32 is likely to be deposited in a region within 10 μm from the grain boundary 34 and is most deposited in a region within 5 μm from the crystal grain boundary 34 as the plastic deformation of the cast material proceeds.

  FIG. 4 is a graph schematically showing changes in the average crystal orientation difference from the crystal grain boundaries to the crystal grains in the plastically deformed cast material. In the graph of FIG. 4, the horizontal axis represents the position from the crystal grain boundary (position 0) to the crystal grain inner direction, and the vertical axis represents the average crystal orientation difference (average value of crystal orientation differences).

  In a preliminary study, the average crystal orientation difference increased as it approached 5 μm from the crystal grain boundary, and hardly changed when it exceeded 10 μm from the crystal grain boundary. From the results of the preliminary study, it has been clarified that when plastic deformation of the cast material proceeds, dislocations are deposited in a region within 10 μm from the grain boundary and are most deposited in a region within 5 μm from the grain boundary. Therefore, by measuring the crystal orientation only in the region within 10 μm from the crystal grain boundary, the change in crystal orientation difference accompanying the change in dislocation density can be obtained with high accuracy. Note that the length of the measurement region in the direction along the crystal grain boundary is, for example, 50 μm to 1000 μm.

  FIG. 5 is a schematic diagram showing a crystal orientation measurement region in the vicinity of a crystal grain boundary. Divide the measurement region near the grain boundary in the same crystal grain into a plurality of sections (section 0, sections 1a to 1d, sections 2a to 2g, sections 3a to 3j, ... sections 10a to 10p, ...) having the same area. To do. In the schematic diagram shown in FIG. 5, the measurement region in the vicinity of the crystal grain boundary is divided into a plurality of regular hexagonal sections. In the crystal orientation measurement step (S12), the crystal orientation is measured for each section by the EBSD method or the like. The crystal orientation measurement pitch T (the length between the centers of adjacent sections) is the same. The measurement pitch T is, for example, 0.25 μm to 1 μm.

  The KAM value calculation step (S14) is a step of calculating the KAM value from the measured crystal orientation. The KAM value is calculated by averaging the crystal orientation differences between the reference section and the plurality of sections surrounding the reference section when one of the plurality of sections in the measurement region is set as the reference section. A method for calculating the KAM value will be specifically described based on the schematic diagram shown in FIG.

  First, a reference section (for example, section 0) is selected from a plurality of sections in the measurement region. A partition group that surrounds the reference section (section 0) and is adjacent to the reference section (section 0) is defined as a first section group (section 1a to section 1d). A partition group that surrounds the reference partition (section 0) and is adjacent to the first partition group (section 1a to section 1d) is defined as a second partition group (section 2a to section 2g). Thus, the third group of sections (section 3a to section 3j),... The tenth section group (section 10a to section 10p),... The nth (n is a natural number) section group. Group them as follows. In addition, the section beyond the crystal grain boundary or the section outside the measurement region is excluded from each section group.

  The first difference with respect to the reference section (section 0) is obtained by averaging the crystal orientation differences between the reference section (section 0) and each section of the first group of sections (section 1a to section 1d). The KAM value (1st) is assumed. In addition, the difference between the crystal orientation differences between the reference section (section 0) and each section of the tenth group of sections (sections 10a to 10p) surrounding the reference section (section 0) is averaged. The 10th KAM value (10th) for 0).

  In this way, the KAM value (n) that is the KAM value of the nth (n is a natural number) partition group with respect to the reference partition can be calculated. As described above, the KAM value (n) is calculated by averaging the crystal orientation difference with the neighboring sections, so that the degree of crystal orientation difference in the measurement region can be obtained with high accuracy.

  In the KAM value calculating step (S14), the reference section is sequentially moved to another section, and after calculating the crystal orientation difference between the moved reference section and a plurality of sections surrounding the moved reference section, the average is obtained. Then, it is preferable to calculate the average KAM value by sequentially calculating the KAM value for the moved reference section and averaging the sequentially calculated KAM values for the moved reference section. Based on the schematic diagram shown in FIG. 5, the calculation method of the average KAM value will be specifically described.

  First, a method for calculating the first average KAM value (1st) will be described. Move the reference section sequentially from section 0 to the other sections (sections 1a to 1d, sections 2a to 2g, sections 3a to 3j,..., Sections 10a to 10p. After obtaining the crystal orientation difference between the plurality of sections surrounding the reference section, the KAM values for the moved reference section are sequentially calculated and averaged. For example, when the reference section is moved to the section 2a, the crystal orientation difference between the reference section (section 2a) and each section of the first section group (sections 3a, 3b, 2b, 1a) is obtained. After that, the first KAM value (1st) for the reference section (section 2a) is calculated on average. Then, the first average KAM value (1st) is calculated by averaging the KAM values (1st) for the moved reference section calculated sequentially.

  When calculating the tenth average KAM value (10th), the reference section is divided from section 0 to other sections (sections 1a to 1d, sections 2a to 2g, sections 3a to 3j, ... sections 10a to 10p. ..) And sequentially calculate the same as the tenth KAM value (10th) for the reference section (section 0) described above. Then, the tenth average KAM value (10th) is calculated by averaging the KAM values (10st) for the moved reference section that are sequentially calculated.

  In this way, when the respective sections in the plurality of sections are set as the reference sections, the crystal orientation difference between the reference section and the plurality of sections surrounding the reference section is obtained, and then averaged, The n-th (n is a natural number) KAM value (n) is calculated, and the KAM values (n) of the respective sections are averaged to calculate the n-th (n is a natural number) average KAM value (n). It is more preferable to calculate the nth (n is a natural number) average KAM value (n) by moving the reference section to all sections in the measurement region.

  By calculating the average KAM value (n) in this way, the degree of crystal orientation difference in the measurement region can be determined more accurately than the KAM value (n) described above.

  Next, the nth (n is a natural number) KAM value (n) and average KAM value (n), the measurement pitch (T μm) of crystal orientation measurement, and the maximum distance from the grain boundary in the crystal orientation measurement region The relationship with L (μm) will be described.

  When the measurement region of the crystal orientation is only the region within L μm from the grain boundary, the relationship between the KAM value (n) and the average KAM value (n), the measurement pitch T, and the distance L from the grain boundary Preferably satisfies nT = L (n is a natural number). For example, when the crystal orientation measurement region is only a region within 5 μm from the grain boundary, it is preferable that nT = 5 (n is a natural number) is satisfied.

  As described in the graph shown in FIG. 4, when the measurement region of the crystal orientation is only the region within 5 μm from the crystal grain boundary, the average crystal orientation difference is the largest at the position of 5 μm from the crystal grain boundary to the intragranular direction. Therefore, by selecting the nth (n is a natural number) KAM value (n) and the average KAM value (n) satisfying nT = 5 with respect to the measurement pitch T, the degree of crystal orientation difference can be accurately determined. Can be sought.

  For example, when the measurement pitch is 0.25 μm, it is preferable to use the 20th KAM value (20th) or the average KAM value (20th), and when the measurement pitch is 0.5 μm, The 5th KAM value (10th) or the average KAM value (10th) is preferably used. When the measurement pitch is 1 μm, the 5th KAM value (5th) or the average KAM value (5th) is used. preferable. Among these, it is more preferable in terms of measurement accuracy and the like that the measurement pitch of crystal orientation measurement is 0.5 μm and the 10th KAM value (10th) or average KAM value (10th) is used.

  The KAM value (n) or average KAM value (n) of the object to be measured is selected from 3 to 5 measurement areas, and the KAM value (n) or average KAM value (n) for each measurement area is averaged. It is preferable to be obtained. Each measurement region may be selected from the vicinity of the crystal grain boundary in the same crystal grain, or may be selected from the vicinity of the crystal grain boundary in a different crystal grain.

  Moreover, it is preferable to provide a threshold value for the KAM value (n) of the object to be measured, and it is preferable to use a KAM value (n) equal to or lower than the threshold value.

  FIG. 6 is a distribution diagram of a typical KAM value (10th) in a plastically deformed Ni-base cast alloy Inconel 713C. The amount of plastic strain imparted to the Ni-base cast alloy Inconel 713C is 1.5%. The crystal orientation measurement pitch is 0.5 μm.

  In the distribution diagram of the KAM value (10th) shown in FIG. 6, the dark and light portions indicate areas where the KAM value (10th) is high, and the light and light portions indicate areas where the KAM value (10th) is low. . Even in the initial stage of plastic deformation, a region with a high KAM value (10th) is observed. In such a region where the KAM value (10th) is high, there is a high possibility that dislocations have accumulated from before the plastic deformation of the cast material. Therefore, by using the KAM value (n) below the threshold, it is possible to avoid a region in the vicinity of the grain boundary where dislocations are accumulated before plastic deformation, so that the dislocation that has moved to the grain boundary side due to plastic deformation. The influence of the crystal orientation difference due to can be obtained with higher accuracy. The threshold is determined based on the crystal orientation measurement pitch T and n of the nth KAM value (n). For example, in the case of a crystal orientation measurement pitch of 0.5 mm and a KAM value (10th), the threshold value is 1.5 degrees.

  More preferably, the threshold is set when estimating the amount of plastic strain from the initial stage to the middle stage of plastic deformation, and is set when estimating the amount of plastic strain between 2.5% before plastic deformation. More preferably.

  The plastic strain amount evaluation step (S16) is a step of estimating the plastic strain amount of the measured object from the KAM value of the measured object. The plastic strain amount of the object to be measured is the KAM value (n) or the average KAM value (n) of the object to be measured, and the KAM of the cast material that has been subjected to known plastic deformation with the same composition as the object to be measured previously obtained. It is estimated by comparing the value (n) or the average KAM value (n).

  The KAM value (n) or the average KAM value (n) of the cast material having the same composition as the object to be measured is obtained by the same calculation method as the KAM value (n) or the average KAM value (n) of the object to be measured. Further, the KAM value (n) or average KAM value (n) of the object to be measured and the KAM value (n) or average KAM value (n) of the cast material having the same composition as the object to be measured are measured at the same measurement pitch. The same nth KAM value (n) is used. For example, when the KAM value (n) or the average KAM value (n) of the object to be measured is calculated from the tenth KAM value (10th) at a measurement pitch of 0.5 μm, the cast material having the same composition as the object to be measured Is calculated from the measurement pitch of 0.5 μm and the 10th KAM value (10th).

  The form of plastic deformation in the cast material having the same composition as the object to be measured is preferably the same as the form of plastic deformation of the object to be measured. For example, when estimating the amount of plastic strain of a measurement object plastically deformed under a tensile load, the KAM value (n) or the average KAM for a cast material having the same composition as the measurement object plastically deformed by the tensile load. It is preferable to calculate the value (n). The same applies to an object to be measured that has undergone plastic deformation under a compression load, creep load, or the like.

  The KAM value (n) or the average KAM value (n) is obtained by changing the plastic strain amount of the cast material having the same composition as the object to be measured. For example, the plastic strain amount and the KAM value (n) or the average KAM value (n) Create a master curve showing the relationship between Then, the amount of plastic strain of the object to be measured is estimated by comparing the KAM value (n) or the average KAM value (n) of the object to be measured with a master curve obtained from a cast material having the same composition as the object to be measured. Is done.

  Since the master curve obtained from the casting material having the same composition as the object to be measured is stored in the storage means 18 in association with the type of the casting material, the plastic strain amount evaluating means 16 has a KAM value ( n) or the average KAM value (n) is compared with the master curve called from the storage means 18 to estimate the plastic strain amount of the object to be measured.

  The output step (S18) is a step of outputting the estimated plastic strain amount of the object to be measured. The KAM value (n) or average KAM value (n) of the object to be measured, the estimated plastic strain amount of the object to be measured, and the like are output to a printer, a display, or the like.

  As described above, according to the above configuration, when the cast material is plastically deformed, the crystal orientation in the vicinity of the crystal grain boundary where the dislocations move and deposit easily is measured, and the KAM value (n) or the average KAM value (n ) Is calculated, for example, the amount of plastic strain can be accurately estimated even in the case of a cast material made of large crystal grains having a crystal grain size of 1.0 mm or more.

  The cast material was subjected to a tensile test to evaluate the correlation between the KAM value and the amount of plastic strain.

  As the casting material, a Ni-base casting alloy Inconel 713C (registered trademark) was used. No heat treatment after casting was performed. A plastic strain was introduced by applying a tensile load to the Ni-base cast alloy. FIG. 7 is a diagram showing the shape of a tensile test piece. The tensile test was performed at room temperature according to JIS Z2241. The amount of plastic strain introduced into the evaluation part of the tensile test piece was 1.5%, 2.5%, and 4.41%. The tensile test was interrupted when each strain amount was introduced. The plastic strain amount of 4.41% is the breaking strain when the tensile test piece is broken.

  A sample was prepared after the tensile test. A sample was cut out from the evaluation part of the tensile test piece and filled with resin. The sample was filled with resin so that a surface along the tensile stress axis direction could be observed. Then, the resin-filled sample was polished in order from # 100 to # 1500 with water-resistant abrasive paper, then polished with an alumina abrasive and polished by electrolytic polishing. FUJIMI METAPOLISH FM No. manufactured by Fujimi Incorporated is used as the alumina abrasive. 3 (average particle size 1.0 μm) was used. As for the electropolishing conditions, 10% ethanol perchlorate was used as the electropolishing liquid, the temperature of the electropolishing liquid was 248K to 258K (-25 ° C to -20 ° C), the voltage was 16V, and the polishing time was 20 seconds. It was.

  After polishing, the sample was observed with a scanning electron microscope. The crystal grain size of the Ni-based cast alloy was 1.0 mm or more. Next, the crystal orientation was measured for each sample by the EBSD method. The measurement pitch for crystal orientation measurement was 0.5 μm. First, the region of the metal structure observed was divided into a plurality of regular hexagonal sections having the same area, and a KAM value (10th) was calculated for each section.

  FIG. 8 is a distribution diagram of the KAM value (10th) in the Ni-base cast alloy before plastic deformation. FIG. 9 is a distribution diagram of the KAM value (10th) in a Ni-based cast alloy having a plastic strain of 1.5%. FIG. 10 is a distribution diagram of KAM values (10th) in a Ni-based cast alloy having a plastic strain amount of 2.5%. FIG. 11 is a distribution diagram of KAM values (10th) in a Ni-based cast alloy having a plastic strain amount of 4.41%.

  In the distribution diagrams of the KAM value (10th) in FIG. 8 to FIG. 11, the portion where the density is high indicates that the KAM value (10th) is high. The threshold of the KAM value (10th) was set to 1.5 degrees, and the region where the KAM value (10th) in the vicinity of the grain boundary was larger than 1.5 degrees was excluded. As shown in the distribution diagrams of the KAM value (10th) in FIGS. 8 to 11, only the region within 5 μm from the grain boundary was extracted, and the average KAM value (10th) was calculated. In calculating the average KAM value (10th), the reference section was moved to all the sections in the measurement area. The average KAM value (10th) was calculated and further averaged for each of the three measurement regions for the samples to which each plastic strain amount was applied.

  For comparison, an average KAM value (10th) of the entire crystal grains was calculated. The measurement pitch of the crystal orientation was 0.5 μm. The average KAM value (10th) is calculated in the same way as the above-described average KAM value (10th) except that the crystal orientation measurement region is the entire crystal grain. The average KAM value (10th) was calculated for each of the three crystal grains for each plastic strain, and the average was further averaged.

[Average KAM value (10th) only in the region within 5 μm from the grain boundary, average value in three measurement regions]
Before deformation (strain amount 0%) 0.637 degrees Plastic strain amount 1.5% 0.659 degrees Plastic strain amount 2.5% 0.810 degrees Plastic strain amount 4.41% 1.242 degrees

[Average KAM value (10th) of the entire crystal grain region, average value of three crystal grains]
Before deformation (strain 0%) 0.859 degrees Plastic strain 1.5% 0.701 degrees Plastic strain 2.5% 0.790 degrees Plastic strain 4.41% 0.783 degrees

  FIG. 12 is a graph showing the relationship between the average KAM value (10th) and the plastic strain amount only in the region within 5 μm from the crystal grain boundary. FIG. 13 is a graph showing the relationship between the average KAM value (10th) of the entire crystal grain region and the amount of plastic strain. The horizontal axis of the graphs shown in FIGS. 12 and 13 indicates the plastic strain amount, the vertical axis of the graph indicates the average KAM value (10th), and the data of the average KAM value (10th) for each plastic strain amount is Indicated by black circles.

  As shown in the graph of FIG. 12, the relationship between the average KAM value (10th) and the plastic strain amount only in the region within 5 μm from the crystal grain boundary shows a correlation. That is, as the plastic strain amount of the Ni-base cast alloy increases, the average KAM value (10th) also increases. Thus, since the plastic strain amount and the average KAM value (10th) are in the above relationship, the plastic strain amount can be estimated from the average KAM value (10th). On the other hand, as shown in the graph of FIG. 13, no correlation was found between the average KAM value (10th) in the entire crystal grain region and the amount of plastic strain.

  Next, in order to evaluate the influence of the polishing finish of the sample, the polishing finish using a colloidal silica abrasive instead of electrolytic polishing after polishing with an alumina abrasive was evaluated. As the colloidal silica abrasive, an OP-S suspension (main component: colloidal silicon dioxide, PH: 9.8, average particle size: about 0.04 μm) manufactured by Struers was used. As the casting material, the Ni-base casting alloy Inconel 713C (registered trademark) was used in the same manner as in the evaluation test by electrolytic polishing. The tensile test method was also performed at room temperature in accordance with JIS Z2241 as in the above evaluation test.

  The amount of plastic strain introduced into the evaluation part of the tensile test piece was 1.5%, 2.5%, 3.5%, and 4.41%, and the tensile test was interrupted when each strain amount was introduced. The sample polishing method is the same as the above-described evaluation test except that a colloidal silica abrasive is used in the polishing finish.

  After polishing, the samples were observed with a scanning electron microscope, and the crystal orientation of each sample was measured by the EBSD method. The measurement pitch for crystal orientation measurement was 0.5 μm. First, the region observed in the metal structure was divided into a plurality of regular hexagonal sections having the same area, and a KAM value (10th) was calculated for each section.

  FIG. 14 is a distribution diagram of KAM values (10th) in a Ni-based cast alloy having a plastic strain of 1.5%. FIG. 15 is a distribution diagram of KAM values (10th) in a Ni-based cast alloy having a plastic strain amount of 2.5%. FIG. 16 is a distribution diagram of KAM values (10th) in a Ni-base cast alloy having a plastic strain amount of 3.5%. FIG. 17 is a distribution diagram of KAM values (10th) in a Ni-based cast alloy having a plastic strain amount of 4.41%.

  In the distribution diagrams of the KAM value (10th) in FIG. 14 to FIG. 17, the portion where the density is high indicates that the KAM value (10th) is high. As shown in the distribution chart of the KAM value (10th) in FIGS. 14 to 17, only the region within 5 μm from the grain boundary was extracted, and the average KAM value (10th) was calculated. In addition, the threshold value of the KAM value (10th) was set to 1.5 degrees, and the region where the KAM value (10th) near the crystal grain boundary was larger than 1.5 degrees was excluded. In calculating the average KAM value (10th), the reference section was moved to all the sections in the measurement area. The average KAM value (10th) was calculated and further averaged for each of the three measurement regions for the samples to which each plastic strain amount was applied.

[Average KAM value (10th) only in the region within 5 μm from the grain boundary, average value in three measurement regions]
Before deformation (strain 0%) 0.534 degrees Plastic strain 1.5% 0.559 degrees Plastic strain 2.5% 0.682 degrees Plastic strain 3.5% 1.013 degrees Plastic strain 4 41% 1.309 degrees

  FIG. 18 is a graph showing the relationship between the average KAM value (10th) and the plastic strain amount only in the region within 5 μm from the crystal grain boundary. The horizontal axis of the graph shown in FIG. 18 indicates the plastic strain amount, the vertical axis of the graph indicates the average KAM value (10th), and the data of the average KAM value (10th) for each plastic strain amount is indicated by black circles. Has been.

  As shown in the graph of FIG. 18, the relationship between the average KAM value (10th) and the plastic strain amount only in the region within 5 μm from the grain boundary shows a correlation. That is, as the plastic strain amount of the Ni-base cast alloy increases, the average KAM value (10th) also increases. Thus, even when polished with a colloidal silica abrasive, since the plastic strain amount and the average KAM value (10th) are in the above relationship, the plastic strain amount can be estimated from the average KAM value (10th).

  Next, when the graph shown in FIG. 12 and the graph shown in FIG. 18 are compared, when the plastic strain amount is 2.5% or more, the polishing finish is finished with a colloidal silica abrasive rather than the electrolytic finish. However, the change amount of the average KAM value (10th) with respect to the change amount of the plastic strain was larger. From this result, it has been clarified that the amount of plastic strain can be estimated more accurately from the average KAM value (10th) by polishing the sample with a colloidal silica abrasive rather than by electrolytic polishing.

  Next, for example, a case where the plastic strain amount of an actual machine made of a Ni-base cast alloy rotor blade used for a predetermined time is estimated will be described. First, a sample is taken from an actual machine, filled with resin, polished with water-resistant abrasive paper, diamond, alumina abrasive, or the like, and then polished by electrolytic polishing or polished with a colloidal silica abrasive. The polished sample is observed with a scanning electron microscope, and only a region within 5 μm from the grain boundary in the same crystal grain is divided into a plurality of sections having the same area, and the crystal orientation is measured for each section. The measurement pitch is 0.5 μm. When each section in a plurality of sections is set as a reference section, the crystal orientation difference between the reference section and the plurality of sections surrounding the reference section is obtained and averaged, and the KAM value (10th) of each section is calculated. Then, the average KAM value (10th) is calculated by averaging the KAM values (10th) of the respective sections.

  Next, the average KAM value (10th) of the sample was compared with the average KAM value (10th) of the Ni-based cast alloy having the same composition as the sample and subjected to known plastic deformation, and the plasticity of the actual machine was compared. Estimate the amount of strain. The average KAM value (10th) of the Ni-based cast alloy having the same composition as that of the sample obtained in advance and subjected to known plastic deformation is the data of the graph shown in FIG. 12 or the data of the graph shown in FIG. 18 as a master curve. Use it. As described above, the plastic strain amount of the actual machine used for a predetermined time can be estimated.

  DESCRIPTION OF SYMBOLS 10 Plastic strain amount estimation apparatus, 12 Crystal orientation measuring means, 14 KAM value calculation means, 16 Plastic strain amount evaluation means, 18 Storage means, 20 Output means

Claims (8)

A plastic strain amount estimation device for estimating a plastic strain amount of a cast material,
Of the crystal grains constituting the metal structure of the plastically deformed object to be measured, only the region within 10 μm from the grain boundary within the same crystal grain is divided into a plurality of sections having the same area, and the crystal orientation is determined for each section. Crystal orientation measuring means for measuring,
When one of the plurality of sections is set as a reference section, a KAM value for the reference section is averaged after obtaining crystal orientation differences between the reference section and the plurality of sections surrounding the reference section. KAM value calculating means for calculating
The KAM value of the object to be measured is compared with the KAM value of a casting material having the same composition as that of the object to be measured and subjected to known plastic deformation, and the amount of plastic strain of the object to be measured is estimated. A plastic strain amount evaluation means,
An apparatus for estimating the amount of plastic strain, comprising: The plastic strain amount estimating apparatus according to claim 1,
The KAM value calculating means sequentially moves the reference section to another section, and obtains a crystal orientation difference between the moved reference section and a plurality of sections surrounding the moved reference section. On average, the KAM value for the moved reference section is sequentially calculated, and the average KAM value for the moved reference section is sequentially calculated to calculate the average KAM value.
The plastic strain amount evaluation means compares the average KAM value of the object to be measured with the average KAM value of a casting material that has been obtained in advance and has the same composition as the object to be measured and has undergone known plastic deformation, A plastic strain amount estimating apparatus for estimating a plastic strain amount of the object to be measured. A plastic strain amount estimation method for estimating a plastic strain amount of a cast material,
The microstructure of the plastically deformed object to be measured is observed with an electron microscope, and only the region within 10 μm from the grain boundary in the same crystal grain is divided into a plurality of sections having the same area, and the crystal orientation is measured for each section. A crystal orientation measuring step,
When one of the plurality of sections is set as a reference section, a KAM value for the reference section is averaged after obtaining crystal orientation differences between the reference section and the plurality of sections surrounding the reference section. A KAM value calculating step for calculating
The KAM value of the object to be measured is compared with the KAM value of a casting material having the same composition as that of the object to be measured and subjected to known plastic deformation, and the amount of plastic strain of the object to be measured is estimated. A plastic strain amount evaluation step to perform,
A plastic strain amount estimation method characterized by comprising: The plastic strain amount estimation method according to claim 3,
After the KAM value calculation step sequentially moves the reference section to another section and obtains a crystal orientation difference between the moved reference section and a plurality of sections surrounding the moved reference section. On average, the KAM value for the moved reference section is sequentially calculated, and the average KAM value for the moved reference section is sequentially calculated to calculate the average KAM value.
The plastic strain amount evaluation step compares the average KAM value of the object to be measured with the average KAM value of a casting material that has been obtained in advance and has the same composition as that of the object to be measured, and has undergone known plastic deformation. A plastic strain amount estimation method for estimating a plastic strain amount of the object to be measured. The plastic strain amount estimation method according to claim 3 or 4,
The plastic strain estimation method, wherein the region is only a region within 5 μm from the grain boundary. The plastic strain amount estimation method according to any one of claims 3 to 5,
A plastic strain amount estimation method, wherein the object to be measured is polished with colloidal silica. The plastic strain amount estimation method according to any one of claims 3 to 6,
A plastic strain amount estimation method, wherein a KAM value of the object to be measured is equal to or less than a threshold value. The plastic strain amount estimation method according to any one of claims 3 to 7,
The method for estimating the amount of plastic strain, wherein the cast material is a Ni-based cast alloy, and the crystal grain size of the cast material is 1 mm or more.