Three-dimensional visualization method for deformation dislocation Schmidt factor distribution

Abstract

The invention discloses a three-dimensional visualization method for deformation dislocation Schmidt factor distribution, and the method comprises the steps: preparing a transmission sample based on a deformation sample, and obtaining a physical identifier marking the direction of an external load; dislocation images of a plurality of different angles of the transmission sample are obtained through a transmission electron microscope, three-dimensional reconstruction is carried out, and a dislocation three-dimensional image under a sample coordinate system is obtained; tilting the sample in situ, and obtaining conversion parameters of a sample coordinate system and a crystal coordinate system according to the tilting parameters and the diffraction pattern; acquiring optical images of the sample rod and the transmission sample through an optical microscope, acquiring an applied load direction under a sample coordinate system according to the optical images, and acquiring an applied load direction under a crystal coordinate system based on the conversion parameters; and determining a dislocation slippage system according to the dislocation Burkholtz vector and the dislocation three-dimensional image, and calculating to obtain a dislocation Schmidt factor by combining with the direction of the external load under the crystal coordinate system, and displaying the dislocation Schmidt factor in the three-dimensional image. According to the method, the deformation dislocation Schmidt factor can be accurately and intuitively represented in the dislocation three-dimensional image.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal analysis and characterization, and particularly to a three-dimensional visualization method for the distribution of deformation dislocation Schmidt factors. Background Art

[0002] Dislocations are the most basic and important linear defects in crystalline materials. When a crystal undergoes plastic deformation under an applied stress, dislocations usually migrate along specific slip planes and slip directions, forming a fixed slip system for the plastic deformation of the crystalline material. The Schmidt factor (SF) is a key parameter for evaluating the ease of activation of dislocation slip systems in crystalline materials. The specific calculation method is the cosine value of the angle between the normal vector of the slip plane and the external force, multiplied by the cosine value of the angle between the slip direction and the external force, and the specific value fluctuates between 0 and 0.5. The higher the Schmidt factor of a slip system, the easier it is for the dislocations in the corresponding slip system to start and migrate. Therefore, the Schmidt factor of the slip system is usually used as an important indicator for evaluating the slip ability of deformation dislocations.

[0003] The main research method for dislocation Schmidt factors is the trace analysis method based on scanning electron microscopy. This method requires first determining the crystal orientation of the grain, and then calculating and determining the theoretical slip trace positions of all potential slip systems. When the theoretical slip trace coincides with the experimentally observed trace, the mutual relationship between the slip trace and a specific slip system can be determined. Further, in combination with the macroscopic deformation conditions and the spatial relationship of the slip system, the Schmidt factor of the dislocations in this slip system can be calculated and determined. However, when dislocation sources from multiple slip systems are simultaneously activated, the rapidly increasing number of migrating dislocations, diverse dislocation slip modes, and complex dislocation interaction behaviors will result in complex shapes and contrasts of the slip traces on the sample surface. These phenomena not only reduce the analysis efficiency of the slip system, but may also lead to incorrect analysis results for the Schmidt factor. Particularly importantly, using the above surface trace method can only identify macroscopic slip bands and cannot distinguish the behavioral characteristics of a large number of individual dislocations inside the slip bands, which poses new challenges for the fine analysis of the Schmidt factor of dislocations, and thus for the intuitive analysis, prediction, and presentation of the slip ability of dislocations.

[0004] Transmission electron microscopy diffraction contrast imaging is a common method for observing and studying the morphological characteristics of dislocations. Based on a series of tilts of the transmission electron microscope, crystallographic analysis, and dislocation trace analysis, the spatial morphology of dislocations and the possible types of slip systems can be determined. In combination with macroscopic conditions, the Schmidt factor of the corresponding dislocations can be calculated. However, traditional transmission electron microscopes can only obtain two-dimensional images of dislocations, and the obtained dislocation morphological information cannot be coupled and analyzed with the crystallographic characteristics of dislocations. At the same time, this method is relatively complex to operate, and the determination of the slip system is easily affected by subjective judgment. Therefore, the dislocation Schmidt factor determined thereby may have different degrees of accuracy deviation.

[0005] With the development and application of three-dimensional characterization techniques for dislocation crystallography, it has become possible to directly obtain the coupled information of dislocation geometry and crystallography in three-dimensional space. Based on this, accurately determining the deformation dislocation slip system, calculating its Schmid factor, and presenting it in three-dimensional visualization have become important technical ideas for systematically and quantitatively studying the distribution of dislocation Schmid factors. Based on this idea, this method combines three-dimensional characterization techniques for dislocation crystallography, dislocation slip system analysis, and three-dimensional visualization methods to develop a three-dimensional visualization method for the distribution of deformation dislocation Schmid factors, aiming to achieve quantitative evaluation and three-dimensional visualization of the batch dislocation slip ability inside materials under external loading. This method has important scientific significance for quantitatively analyzing the migration ability of dislocations and enhancing the understanding of the dynamic behavior laws of dislocations during the plastic deformation process. Summary of the Invention

[0006] The object of the present invention is to provide a three-dimensional visualization method for the distribution of deformation dislocation Schmid factors, which can achieve quantitative evaluation and three-dimensional visualization of the batch dislocation slip ability inside materials under external loading.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A three-dimensional visualization method for the distribution of deformation dislocation Schmid factors, comprising:

[0009] Preparing a transmission sample based on a deformed sample, and obtaining a physical identifier for marking the direction of the external load on the transmission sample;

[0010] Obtaining dislocation images of the transmission sample at multiple different angles through a transmission electron microscope, and performing three-dimensional reconstruction based on the obtained dislocation images to obtain a three-dimensional dislocation image in the sample coordinate system; the sample coordinate system is a three-dimensional coordinate system established with the sample tilt axis when the transmission electron microscope images the transmission sample and the axis parallel to the electron beam incident direction as the coordinate axes;

[0011] In-situ tilting the transmission sample and obtaining the conversion parameters between the crystal coordinate system and the sample coordinate system according to the tilting parameters of the transmission sample and the diffraction pattern;

[0012] Obtaining an optical image of the transmission sample rod and the transmission sample through an optical microscope, obtaining the direction of the external load on the transmission sample in the sample coordinate system according to the optical image, and obtaining the direction of the external load on the transmission sample in the crystal coordinate system based on the conversion parameters;

[0013] Determining the dislocation slip system through the dislocation Burgers vector and the three-dimensional dislocation image, calculating the deformation dislocation Schmid factor according to the dislocation slip system combined with the direction of the external load on the transmission sample in the crystal coordinate system, and displaying it in the three-dimensional dislocation image.

[0014] Optionally, a physical identifier for marking the direction of the externally applied load is obtained on the transmission sample, including: obtaining the physical identifier by means of electrolytic twin-jet, focused ion beam spot cutting, or retaining specific geometric features of the deformed sample.

[0015] Optionally, the transmission sample is tilted in-situ and conversion parameters between the crystal coordinate system and the sample coordinate system are obtained based on the tilt parameters of the transmission sample and the diffraction pattern, including:

[0016] Tilt the transmission sample so that the incident direction of the transmission electron microscope electron beam is parallel to the preset zone axis of the transmission sample, and obtain the tilt parameter T and the reference orientation parameter G of the transmission sample in the sample coordinate system during the tilting process r ; The tilt parameter T refers to a parameter reflecting the tilt angle of the transmission sample from the initial position to the position where the incident direction of the electron beam is parallel to the preset zone axis, and the reference orientation parameter G r refers to a parameter reflecting the arrangement of the crystal coordinate axes of the transmission sample in the sample coordinate system;

[0017] Based on the tilt parameter T and the reference orientation parameter G r , obtain the conversion parameter G from the sample coordinate system to the crystal coordinate system, including: calculating by the following method:

[0018] G = G r ·T;

[0019] wherein, G represents the conversion parameter between the sample coordinate system and the crystal coordinate system, G r represents the reference orientation parameter, and T represents the tilt parameter.

[0020] Optionally, the tilt parameter T is expressed as:

[0021]

[0022] wherein, T represents the tilt parameter, α represents the tilt angle of the transmission sample around the OX axis of the sample coordinate system during the tilting process, and β represents the tilt angle of the transmission sample around the OY axis of the sample coordinate system during the tilting process;

[0023] The reference orientation parameter G r is expressed as:

[0024]

[0025] wherein, G r represents the reference orientation parameter, [uvw] represents the direction vector of the preset zone axis, and [hkl], [rst] respectively represent the diffraction vectors of two mutually perpendicular crystal planes under the preset zone axis, where the * sign represents normalization processing.

[0026] Optionally, obtaining the external loading direction of the transmitted sample in the sample coordinate system according to the optical image includes calculating using the following method:

[0027] V s = [cosγ, sinγ, 0];

[0028] where V s is the external loading direction of the transmitted sample in the sample coordinate system, and γ is the angle between the external loading direction of the transmitted sample and the OX axis of the sample coordinate system.

[0029] Optionally, obtaining the external loading direction of the transmitted sample in the crystal coordinate system based on the conversion parameter includes calculating using the following method:

[0030] V c = G·V s ;

[0031] where V c is the external loading direction of the transmitted sample in the crystal coordinate system, G represents the conversion parameter, and V s is the external loading direction of the transmitted sample in the sample coordinate system.

[0032] Optionally, determining the dislocation slip system through the dislocation Burgers vector and the three-dimensional image of the dislocation includes:

[0033] Selecting a plurality of diffraction vectors of the transmitted sample, obtaining the dislocation images of the transmitted sample under the plurality of diffraction vectors through a transmission electron microscope, obtaining the dislocation Burgers vector b based on the invisible rule according to the obtained plurality of dislocation images, the invisible rule criterion is expressed as g·b = 0, g represents the diffraction vector, b represents the Burgers vector, and determining the dislocation slip direction V slip , the dislocation slip direction V slip is parallel to the dislocation Burgers vector b;

[0034] Obtaining the local dislocation segment line direction V d of the dislocation according to the three-dimensional image of the dislocation in the sample coordinate system, and based on the conversion parameter, converting the local dislocation segment line direction V d in the sample coordinate system to the local dislocation segment line direction V d in the crystal coordinate system;

[0035] Respectively calculating the angle η between the local dislocation segment line direction V d of the dislocation in the crystal coordinate system and the plurality of slip planes constrained by the dislocation, and determining the dislocation slip plane based on the proximity principle. The calculation method of the angle η is:

[0036]

[0037] where η is the angle between the local dislocation line direction of the dislocation and the crystallographic plane of the slip plane constrained by the dislocation, V d is the local dislocation line direction of the dislocation, and n is the normal vector of the crystallographic plane of the slip plane constrained by the dislocation.

[0038] Optionally, the deformation dislocation Schmidt factor is calculated based on the dislocation slip system and the external loading direction of the transmission sample in the crystal coordinate system, including: calculating the deformation dislocation Schmidt factor S by the following method:

[0039]

[0040] where λ is the external loading direction V of the transmission sample in the crystal coordinate system c and the dislocation slip direction V slip between them, is the external loading direction V of the transmission sample in the crystal coordinate system c and the angle between the dislocation slip plane normal n.

[0041] Optionally, it is displayed in the three-dimensional dislocation image, including:

[0042] Describing the magnitudes of the deformation dislocation Schmidt factors with different magnitudes of the same display element, and displaying the deformation dislocation Schmidt factor values in the three-dimensional dislocation image.

[0043] Optionally, two colors with distinct contrast are used to represent the Schmidt factor values of 0 and 0.5 respectively, and a gradient color scale between these two colors is set to represent the range of Schmidt factor values from 0 to 0.5.

[0044] As can be seen from the above technical solutions, a three-dimensional visualization method for the distribution of deformation dislocation Schmidt factors provided by the present invention prepares a transmission sample based on a deformed sample, and obtains a physical identifier for marking the external loading direction on the transmission sample; uses a transmission electron microscope to obtain dislocation images of the transmission sample at different tilting angles and performs three-dimensional reconstruction to obtain a three-dimensional dislocation image of the sample in the sample coordinate system; in-situ tilts the sample, and obtains the conversion parameters between the sample coordinate system and the crystal coordinate system according to the sample tilting parameters and diffraction patterns; obtains optical images of the sample rod and the transmission sample through an optical microscope, thereby determining the external loading direction of the transmission sample in the sample coordinate system; further determines the slip system of the dislocation according to the three-dimensional dislocation image and the Burgers vector, combines the external loading direction in the crystal coordinate system, calculates the deformation dislocation Schmidt factor and visually displays it in the three-dimensional dislocation image. The present invention realizes the accurate and intuitive characterization of the deformation dislocation Schmidt factor in the three-dimensional dislocation image, providing strong technical support for studying scientific problems related to metal plastic deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0046] Figure 1 It is a flowchart of a three-dimensional visualization method for the distribution of deformation dislocation Schmidt factors provided by an embodiment of the present invention;

[0047] Figure 2 It is a schematic diagram of a transmission sample with special markings provided by an embodiment of the present invention;

[0048] Figure 3 It is a schematic diagram for obtaining the external loading direction of a transmission sample in the sample coordinate system provided by an embodiment of the present invention;

[0049] Figure 4 It is a schematic diagram for calculating the dislocation Schmidt factor under the action of an external loading on a transmission sample in the crystal coordinate system provided by an embodiment of the present invention;

[0050] Figure 5 They are weak beam dark field images of deformation dislocations in pure aluminum collected by a transmission electron microscope at multiple different angles in a specific embodiment;

[0051] Figure 6 They are three-dimensional images of dislocations in pure aluminum in the sample coordinate system and the crystal coordinate system in a specific embodiment;

[0052] Figure 7 They are a dark field image of deformation dislocations and a three-dimensional distribution diagram of dislocation Schmidt factors in the sample coordinate system in a specific embodiment;

[0053] Figure 8 For Figure 7 They are a dark field image of the quadrilateral dislocation unit within the white dotted line frame in Detailed implementation manners

[0054] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0055] Please refer to Figure 1 ,Figure 1 The flowchart of a three-dimensional visualization method for the distribution of deformation dislocation Schmidt factors provided by an embodiment of the present invention is as follows: Figure 1 As shown, the three-dimensional visualization method for the distribution of deformation dislocation Schmidt factors includes the following steps:

[0056] S10: Prepare a transmission sample based on the deformed sample, and obtain a physical identifier for marking the external loading direction on the transmission sample.

[0057] In order to clearly mark the external loading direction on the transmission sample, methods such as, but not limited to, adding special marks to the deformed sample or retaining specific geometric features of the deformed sample can be adopted. Exemplarily, please refer to Figure 2 , Figure 2 The schematic diagram of a transmission sample with special marks provided by an embodiment of the present invention. The deformed sample is obtained by plastic deformation of a metal material, and then a transmission sample with special marks is prepared by electrolytic twin-jet or focused ion beam spot cutting technology, or a transmission sample with special marks is obtained by retaining specific geometric features of the deformed sample. The special mark refers to a physical identifier for marking the external loading direction of the transmission sample.

[0058] S11: Obtain dislocation images of the transmission sample at multiple different angles through a transmission electron microscope, and perform three-dimensional reconstruction based on the obtained dislocation images to obtain a three-dimensional dislocation image in the sample coordinate system. The sample coordinate system is a three-dimensional coordinate system established with the sample tilt axis and the axis parallel to the electron beam incident direction when the transmission electron microscope images the transmission sample as the coordinate axes. In an embodiment of the present application, based on the right-hand rule, the opposite direction of the electron beam incident direction of the transmission electron microscope when imaging the transmission sample is taken as the OZ axis direction, the direction parallel to the sample α tilt axis is taken as the OX axis, and the direction parallel to the sample β tilt axis is taken as the OY axis to establish a three-dimensional sample coordinate system. Please refer to Figure 3 , Figure 3 The right figure shows the sample coordinate system established in an embodiment.

[0059] In the actual operation process, in order to clearly obtain the dislocation image of the transmission sample, the dislocation image under the two-beam condition is obtained through a transmission electron microscope. Specifically, the following method can be adopted: After loading the transmission sample onto the transmission sample rod, rotate the sample in the sample plane to adjust the sample orientation so that the diffraction vector g of the region of interest always satisfies the two-beam imaging condition during the sample tilting process, and then obtain dislocation images of the transmission sample at multiple different tilting angles through the transmission electron microscope. According to the obtained dislocation images at different angles, optionally, a three-dimensional dislocation image in the sample coordinate system can be obtained by adopting image filtering processing, image coaxial processing, and corresponding three-dimensional reconstruction algorithms. This three-dimensional image contains the geometric information of the dislocations.

[0060] S12: Tilt the transmission sample in-situ and obtain the conversion parameters between the crystal coordinate system and the sample coordinate system according to the tilt parameters of the transmission sample and the diffraction pattern. In-situ tilting means that the state where the transmission sample remains stationary after being placed in the transmission electron microscope is the in-situ state, and the process of tilting the sample afterwards is the in-situ tilting of the sample. The conversion parameters describe the conversion relationship from the sample coordinate system of the transmission sample to the crystal coordinate system.

[0061] Optionally, the conversion parameters can be obtained through the following process, specifically:

[0062] S12-1: Tilt the transmission sample so that the electron beam incident direction is parallel to any selected preset zone axis of the transmission sample, and obtain the tilt parameters and reference orientation parameters of the transmission sample in the sample coordinate system during this tilting process. The tilt parameter refers to the parameter that reflects the tilt angle of the transmission sample from the initial position (i.e., α = 0°, β = 0°) to the state where the electron beam incident direction is parallel to the preset zone axis of the transmission sample. The reference orientation parameter refers to the parameter that reflects the arrangement of the crystal coordinate axes of the transmission sample in the sample coordinate system.

[0063] During the actual operation process, obtain the tilt angles α and β according to the diffraction vector g hkl of the transmission sample under the imaging conditions of the transmission electron microscope. Under the condition of obtaining the sample dislocation two-beam imaging, the diffraction vector g hkl remains parallel to the OX axis of the sample coordinate system. If the transmission sample is tilted so that the electron beam incident direction of the transmission electron microscope is parallel to the preset zone axis [uvw] of the transmission sample, record the tilt angle α of the transmission sample around the OX axis. At the same time, the diffraction vectors of two mutually perpendicular crystal planes under this preset zone axis [uvw] are [hkl] and [rst] respectively. Then, during this tilting process, the tilt angle β of the transmission sample around the OY axis can be calculated according to the crystal plane spacing formula and the Bragg equation. The calculation formula is:

[0064]

[0065] where β represents the tilt angle of the transmission sample around the OY axis, λ is the wavelength of the incident electron beam, and d is the crystal plane spacing corresponding to the diffraction vector g hkl of the crystal plane.

[0066] Calculate the tilt parameter T according to the tilt angles α and β. The tilt parameter T = T α T β , which is expressed as:

[0067]

[0068] Among them, T represents the sample tilting parameter, α represents the tilting angle of the transmission sample around the OX axis of the sample coordinate system during the tilting process, and β represents the tilting angle of the transmission sample around the OY axis of the sample coordinate system during the tilting process.

[0069] Further, the reference orientation parameter G of the transmission sample in the sample coordinate system is obtained according to the diffraction pattern under the preset zone axis [uvw]. r , the reference orientation parameter G r is expressed as:

[0070]

[0071] Among them, [uvw] represents the direction vector of the preset zone axis, [hkl], [rst] respectively represent the diffraction vectors of two mutually perpendicular crystal planes under the preset zone axis, where the * sign indicates normalization processing, and the diffraction vectors [hkl], [rst] and the direction vector [uvw] can be specifically determined according to the diffraction pattern.

[0072] S12-2: According to the tilting parameter T and the reference orientation parameter G r , the conversion parameter G from the sample coordinate system to the crystal coordinate system of the transmission sample is obtained, and the conversion parameter G is expressed as:

[0073] G = G r ·T; (4)

[0074] Among them, G represents the conversion parameter between the sample coordinate system and the crystal coordinate system, G r refers to the reference orientation parameter, and T represents the tilting parameter.

[0075] By using the conversion parameter G to realize the conversion between the sample coordinate system and the crystal coordinate system of the transmission sample, the integrated characterization of the dislocation geometric characteristics and crystallographic characteristics in the crystal coordinate system can be realized, thereby realizing the deep coupling of the dislocation geometric characteristics and crystallographic characteristics in the same coordinate system.

[0076] S13: The optical image of the transmission sample rod and the transmission sample is obtained through an optical microscope, the external loading direction of the transmission sample in the sample coordinate system is obtained according to the optical image, and the external loading direction of the transmission sample in the crystal coordinate system is obtained based on the conversion parameter.

[0077] In actual operation, after taking out the transmission sample rod and the transmission sample from the transmission electron microscope, the optical image is obtained through an optical microscope, and the angle γ between the external loading direction of the transmission sample in the sample coordinate system and the OX axis is obtained according to the optical image, and the external loading direction V of the transmission sample in the sample coordinate system is obtained through calculation. s . Please refer to Figure 3 , Figure 3Schematic diagram of obtaining the external loading direction of the transmission sample in the sample coordinate system provided by an embodiment of the present invention. The optical images of the transmission sample rod and the transmission sample are as shown in Figure 3 the left figure. At this time, the OZ axis of the sample coordinate system is perpendicular to the paper and into the paper. In the optical image, the external loading direction (deformation direction) of the transmission sample can be identified by special markings. For the convenience of observation and measurement, the contour of the transmission sample at this time is calibrated as shown in Figure 3 the upper middle figure, and its mirror image along the XOY plane is obtained to obtain the contour of the transmission sample in the sample coordinate system as shown in Figure 3 the lower middle figure. At this time, the included angle γ between the external loading direction (deformation direction) of the transmission sample in the right figure and the OX axis of the sample coordinate system can be measured, and the external loading direction V of the transmission sample in the sample coordinate system can be calculated according to the included angle γ Figure 3 The external loading direction V of the transmission sample in the sample coordinate system s is expressed as: s V

[0078] V s =[cosγ, sinγ, 0]; (5) where Vs is the external loading direction of the transmission sample in the sample coordinate system, and γ is the included angle between the external loading direction and the OX axis of the sample coordinate system.

[0079] Furthermore, based on the conversion parameter G between the sample coordinate system and the crystal coordinate system, the external loading direction V of the transmission sample in the crystal coordinate system is calculated and obtained c , including: calculated by the following method:

[0080] V c =G·V s ; (6)

[0081] where V c represents the external loading direction of the transmission sample in the crystal coordinate system, G represents the conversion parameter between the sample coordinate system and the crystal coordinate system, and V s represents the external loading direction of the transmission sample in the sample coordinate system.

[0082] By obtaining the external loading direction of the transmission sample in the crystal coordinate system, the evaluation and characterization of the initiation tendency of the dislocation slip system in crystallography under the external loading direction can be realized.

[0083] S14: Determine the dislocation slip system through the dislocation Burgers vector and the three-dimensional image of the dislocation. Calculate the deformation dislocation Schmidt factor according to the dislocation slip system and the external loading direction of the transmission sample in the crystal coordinate system, and display it in the three-dimensional image of the dislocation.

[0084] Specifically, the Burgers vector of the dislocation of the transmission sample can be obtained through the following process, including: selecting a plurality of diffraction vectors of the transmission sample, obtaining the dislocation images of the transmission sample under the plurality of diffraction vectors through a transmission electron microscope, and obtaining the Burgers vector b of the dislocation based on the obtained plurality of dislocation images according to the invisibility rule. The invisibility criterion of the dislocation is expressed as g·b = 0, where g represents the diffraction vector and b represents the Burgers vector of the dislocation. However, this is not limited thereto, and other methods can also be used to obtain the Burgers vector of the dislocation of the transmission sample.

[0085] Further, obtaining the line direction of the dislocation in the crystal coordinate system according to the three-dimensional dislocation image includes:

[0086] Obtaining the local dislocation segment line direction V of the dislocation in the sample coordinate system based on the slicing method in the three-dimensional quantitative characterization method of dislocation by transmission electron microscope d . And based on the conversion parameter, converting the local dislocation segment line direction V in the sample coordinate system d to the local dislocation segment line direction V in the crystal coordinate system d ; determining the slip system of the dislocation according to the local dislocation segment line direction V of the dislocation in the crystal coordinate system d and the Burgers vector of the dislocation includes the following steps:

[0087] Determining the dislocation slip direction V based on the Burgers vector of the dislocation slip , and the dislocation slip direction V slip is parallel to the Burgers vector b of the present dislocation.

[0088] Further, respectively calculating the angle η between the local dislocation segment line direction V of the dislocation in the crystal coordinate system d and the slip plane constrained by the dislocation, and determining the dislocation slip plane based on the proximity principle. Specifically, respectively calculating the angles between the local dislocation segment line direction V of the dislocation in the crystal coordinate system d and the normal vectors n of the multiple crystallographic planes constrained by the dislocation, calculating the angle η between the dislocation segment and the crystallographic plane according to the angles, and determining the slip plane where the dislocation is located according to the angle. The angle η is expressed as:

[0089]

[0090] where η is the angle between the local dislocation segment line direction on the present dislocation and the crystallographic plane, V d is the local dislocation segment line direction on the present dislocation, and n is the normal vector of the crystallographic plane constrained by the present dislocation.

[0091] Please refer to Figure 4 , Figure 4 which is a schematic diagram for calculating the Schmid factor of the dislocation under the action of an external load provided by an embodiment of the present invention. According to the external load direction V of the transmission sample in the crystal coordinate system cObtaining the dislocation Schmidt factor from the slip system of dislocations, including:

[0092] The following method is used to calculate and obtain the dislocation Schmidt factor S:

[0093]

[0094] where λ is the angle between the external loading direction V of the transmission sample in the crystal coordinate system c and the dislocation slip direction V slip and is the angle between the external loading direction V of the transmission sample in the crystal coordinate system c and the normal n of the dislocation slip plane.

[0095] Furthermore, the obtained deformed dislocation Schmidt factor S is displayed in the three-dimensional dislocation image. Specifically, two colors with distinct contrasts can be used to represent the Schmidt factor values of 0 and 0.5 respectively, and a gradient color scale between these two colors is set to represent the range from 0 to 0.5. By combining the color information with the three-dimensional geometric feature information of the dislocations, the spatial distribution characteristics of the deformed dislocation Schmidt factor S can be visually presented.

[0096] In a specific embodiment of the present invention, the three-dimensional characterization of the deformed dislocation Schmidt factor in pure aluminum is taken as an example for explanation.

[0097] 1) The pure aluminum sheet is subjected to room-temperature cold rolling deformation with a reduction of 10% by the rolling deformation method. Subsequently, the transmission sample is obtained by thinning using the electrolytic twin-jet process, and a physical identifier of the external loading direction is marked on the transmission sample. After loading the transmission sample on the transmission sample rod, weak-beam dark-field images of the transmission sample at different tilting angles from -70° to +70° in the diffraction vector imaging condition and their corresponding Kikuchi images are obtained through a transmission electron microscope. The obtained dislocation images at multiple different angles are as Figure 5 shown. Then, the weighted back-projection (WBP) algorithm is used to filter, coaxial-align, and three-dimensionally reconstruct the collected series of weak-beam dark-field images. Finally, three-dimensional visualization software is used to display and quantitatively analyze the three-dimensional reconstruction results to obtain the three-dimensional dislocation image in the sample coordinate system, as Figure 6 shown in the figure. In the three-dimensional coordinate system, i.e., the sample coordinate system, the direction opposite to the incident direction of the electron beam of the transmission electron microscope is taken as the OZ-axis direction, the direction parallel to the α tilting axis of the sample is taken as the OX-axis, and the direction parallel to the β tilting axis of the sample is taken as the OY-axis. The diffraction vector of the transmission sample remains parallel to the OX-axis of the sample coordinate system.

[0098] 2) The tilt angle β of the transmission sample about the OY axis is calculated according to Formula 1 to be 0.78°. Subsequently, the sample is tilted in-situ to the preset zone axis

[121] . At this time, the tilt angle α of the transmission sample about the OX axis is -8.36°. The tilt parameter T of the transmission sample is calculated according to Formula 2, and T is expressed as:

[0099]

[0100] According to the diffraction pattern under the preset zone axis

[121] and Formula 3, the reference orientation parameter G of the transmission sample is obtained r , G r is expressed as:

[0101]

[0102] Thus, the conversion parameter G between the sample coordinate system and the crystal coordinate system is calculated according to Formula 4, and G is expressed as:

[0103]

[0104] The conversion between the three-dimensional dislocation images of the transmission sample in the sample coordinate system and the crystal coordinate system is realized through the conversion parameter G. The three-dimensional dislocation image of the transmission sample obtained after conversion in the crystal coordinate system is as Figure 6 shown in the right figure.

[0105] 3) Use an optical microscope to obtain the azimuth image of the transmission electron microscope sample rod and the transmission sample at this time, as Figure 3 shown in the right figure. By measurement, the angle between the external load direction of the transmission sample in the sample coordinate system and the OX axis is -12.8°. The external load direction V of the transmission sample in the sample coordinate system is calculated by Formula 5 s = [-0.22, 0.96, 0], and the external load direction V of the transmission sample in the crystal coordinate system is calculated by Formula 6 c = [0.84, -0.22, -0.50].

[0106] 4) Further select multiple diffraction vectors and to obtain the dislocation dark field image of the sample. Based on the invisibility criterion g·b = 0 of the perfect dislocation in the face-centered cubic crystal, the Burgers vectors of all dislocations in this region are determined. The Burgers vectors of the dislocations are a / 2

[101] , a / 2

[011] and as Figure 8 shown, Figure 8 is Figure 7 a quadrilateral dislocation network unit in the sample coordinate system within the white dotted line box in Figure 8 . It can be seen from that the Burgers vectors of this quadrilateral dislocation network unit are a / 2

[101] andFurther, according to Figure 8 the three-dimensional dislocation image in the sample coordinate system shown, combined with the slicing method in the three-dimensional quantitative characterization method of dislocations by transmission electron microscopy, the local dislocation segment line direction V of the dislocation is obtained d . The slicing method in the three-dimensional quantitative characterization method of dislocations (reference can be made to the slicing method for obtaining the line direction of dislocations according to the three-dimensional dislocation image in the patent application with the application number 202110901900.3 and the invention name "A three-dimensional visualization method for dislocation characteristics"). Specifically, the three-dimensional dislocation image in the sample coordinate system is sliced successively along three orthogonal directions. Preferably, the thickness of the slice is the same as the length or width of the pixels of the three-dimensional image. A spatial coordinate system can be established by the three orthogonal directions, and the conversion relationship between this spatial coordinate system and the sample coordinate system is known; in each slice, the dislocation cross-section is identified, and the position of the center of the dislocation cross-section in each slice is determined. Optionally, but not limited to, the centerline image processing algorithm can be used to determine the geometric center of the dislocation cross-section. According to the coordinates of the center of the same dislocation cross-section corresponding to the three orthogonal directions, the position coordinates of the center of the dislocation cross-section in the three-dimensional image are determined; further, in the three-dimensional image, the centers of the dislocation cross-sections of each slice are connected in sequence to obtain the dislocation trace line, and the dislocation line direction is determined according to the positions of two points on the dislocation trace line. Based on the dislocation line direction, the slip plane and slip direction of the dislocation are determined. According to the three-dimensional dislocation image slicing method, the line direction of the D1 dislocation with a Burgers vector of a / 2

[101] in the sample coordinate system is [-0.087, 0.89, 0.732], and it is directly multiplied by the conversion parameter G to obtain the line direction in the crystal coordinate system as [0.033, 1, -0.579]. According to formula 7, the angle between it and the crystal plane is about 11.2°, and the angle between it and the crystal plane is about 53.6°. Therefore, the slip plane of this dislocation is At the same time, the slip direction of this dislocation is parallel to its Burgers vector direction

[101] ; similarly, according to the above method, the crystal plane where the D3 dislocation with a Burgers vector of a / 2

[101] is located is The slip direction is

[101] ; the Burgers vector is The crystal plane where the D2 dislocation is located is The slip direction is And the Burgers vector is The crystal plane where the D4 dislocation is located is (001), and the slip direction is Further, the Schmid factor of the dislocation with a Burgers vector of a / 2

[011] is calculated by formula 8 to be 0.21; the Schmid factor of the upper dislocation with a Burgers vector of a / 2

[101] is 0.114, and the Schmid factor of the lower dislocation is 0.295; the Schmid factor of the right dislocation with a Burgers vector of is 0.39, while the left dislocation deviates severely from the <111> plane constrained by its Burgers vector and is an immobile dislocation. Therefore, the Burgers vector is The left dislocation is likely to be a Hirth dislocation generated by the reaction between the dislocations with Burgers vectors a / 2

[101] and a / 2

[011] when they meet during migration. Then, two contrasting colors are used in the dislocation 3D image to represent the Schmidt factor values ​​of 0 and 0.5 respectively, and the gradient between the two colors is set to represent the range from 0 to 0.5. Then, dislocations with different Schmidt factor values ​​will appear in specific colors. Figure 7 The distribution diagram of the Schmidt factor of the deformation dislocation in the three-dimensional image of the dislocation in the sample coordinate system is shown in FIG. Figure 8 The distribution diagram of the deformation dislocation Schmidt factor in the three-dimensional image of the local dislocation in the crystal coordinate system is shown in FIG.

[0107] The three-dimensional visualization method of deformation dislocation Schmidt factor distribution provided by the present invention can realize the accurate calculation and three-dimensional graphical presentation of the dislocation Schmidt factor under the action of external load, combine color information with dislocation Schmidt factor information, and intuitively present the spatial distribution of the dislocation Schmidt factor.

[0108] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core ideas of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A three-dimensional visualization method for the distribution of Schmidt factors of deformation dislocations, characterized in that: include: Preparing a transmission sample based on the deformation sample, and obtaining a physical mark on the transmission sample for marking the direction of the applied load; Acquire dislocation images of the transmission sample at multiple different angles through a transmission electron microscope, and perform three-dimensional reconstruction based on the obtained dislocation images to obtain a three-dimensional dislocation image in a sample coordinate system; the sample coordinate system is a three-dimensional coordinate system established with the sample tilt axis and the axis parallel to the electron beam incident direction as coordinate axes when the transmission electron microscope images the transmission sample; In-situ tilting of the transmission sample and obtaining conversion parameters between the crystal coordinate system and the sample coordinate system according to the transmission sample tilting parameters and the diffraction pattern; Acquire an optical image of the transmission sample rod and the transmission sample through an optical microscope, acquire the direction of the external load of the transmission sample in a sample coordinate system according to the optical image, and acquire the direction of the external load of the transmission sample in a crystal coordinate system based on the conversion parameter; The dislocation slip system is determined by the dislocation Burgers vector and the dislocation three-dimensional image. The deformation dislocation Schmidt factor is calculated based on the dislocation slip system combined with the external load direction of the transmission sample in the crystal coordinate system and displayed in the dislocation three-dimensional image.

2. The three-dimensional visualization method of deformation dislocation Schmidt factor distribution according to claim 1, characterized in that: A physical mark for marking the direction of the applied load is obtained on the transmission sample, including: obtaining the physical mark by electrolytic double spraying, focused ion beam fixed-point cutting or retaining specific geometric features of the deformed sample.

3. The three-dimensional visualization method of deformation dislocation Schmidt factor distribution according to claim 1, characterized in that: The transmission sample is tilted in situ and a conversion parameter between a crystal coordinate system and a sample coordinate system is obtained according to the tilting parameter of the transmission sample and a diffraction pattern, including: Tilt the transmission sample so that the incident direction of the transmission electron microscope electron beam is parallel to the preset crystal zone axis of the transmission sample, and obtain the tilt parameter T and reference orientation parameter G of the transmission sample in the sample coordinate system during the tilting process. r The tilt parameter T refers to the parameter reflecting the tilt angle when the transmission sample is tilted from the initial position to the electron beam incident direction parallel to the preset crystal zone axis, and the reference orientation parameter G r Refers to the parameter reflecting the arrangement of the crystal coordinate axes of the transmission sample in the sample coordinate system; According to the tilt parameter T and the reference orientation parameter G r , obtaining the transformation parameter G from the sample coordinate system to the crystal coordinate system, including: calculating by the following method: G=G r ·T; Where G represents the conversion parameter between the sample coordinate system and the crystal coordinate system, G r represents the reference orientation parameter, and T represents the tilt parameter.

4. The three-dimensional visualization method of deformation dislocation Schmidt factor distribution according to claim 3, characterized in that: The tilt parameter T is expressed as: Wherein, T represents the tilting parameter, α represents the tilting angle of the transmission sample around the OX axis of the sample coordinate system during the tilting process, and β represents the tilting angle of the transmission sample around the OY axis of the sample coordinate system during the tilting process; The reference orientation parameter G r It is expressed as: Among them, G r represents the reference orientation parameter, [uvw] represents the direction vector of the preset crystal zone axis, [hkl] and [rst] respectively represent the diffraction vectors of two mutually perpendicular crystal planes under the preset crystal zone axis, and the * sign indicates normalization.

5. The three-dimensional visualization method of deformation dislocation Schmidt factor distribution according to claim 1, characterized in that: Obtaining the direction of the external load of the transmission sample in the sample coordinate system according to the optical image includes: calculating by the following method: In s = [cosγ,sinγ,0]; Among them, V s is the direction of the external load of the transmission sample in the sample coordinate system, and γ is the angle between the direction of the external load of the transmission sample and the OX axis of the sample coordinate system.

6. The three-dimensional visualization method of deformation dislocation Schmidt factor distribution according to claim 5, characterized in that: And obtaining the direction of the external load of the transmission sample in the crystal coordinate system based on the conversion parameter includes: calculating by the following method: V c =G·V s ; Among them, V c is the direction of the external load on the transmission sample in the crystal coordinate system, G represents the conversion parameter, V s is the direction of the external load on the transmission sample in the sample coordinate system.

7. The three-dimensional visualization method of deformation dislocation Schmidt factor distribution according to claim 1, characterized in that: Determining the dislocation slip system by the dislocation Burgers vector and the dislocation three-dimensional image includes: Select multiple diffraction vectors of the transmission sample, obtain dislocation images of the transmission sample under the multiple diffraction vectors through a transmission electron microscope, obtain the dislocation Burgers vector b based on the invisible rule according to the obtained multiple dislocation images, the invisible rule criterion is expressed as g·b=0, g represents the diffraction vector, b represents the Burgers vector, and determine the dislocation slip direction V based on the dislocation Burgers vector slip , dislocation slip direction V slip Parallel to the dislocation Burgers vector b; The local dislocation segment line direction V of the dislocation is obtained according to the three-dimensional dislocation image in the sample coordinate system. d , and based on the transformation parameter, the local dislocation segment line direction V in the sample coordinate system is d The local dislocation segment line direction V converted to the crystal coordinate system d ; Calculate the local dislocation segment line direction V of the dislocation in the crystal coordinate system respectively d The angle η between the multiple slip planes constrained by the dislocation is calculated based on the proximity principle to determine the dislocation slip plane. The angle η is calculated as follows: Where η is the angle between the local dislocation segment line direction of the dislocation and the crystallographic plane of the slip plane constrained by the dislocation, V d is the local dislocation segment line direction of the dislocation, and n is the crystallographic surface normal of the slip plane constrained by the dislocation.

8. The three-dimensional visualization method of deformation dislocation Schmidt factor distribution according to any one of claims 1 to 7, characterized in that: The deformation dislocation Schmidt factor is calculated based on the dislocation slip system combined with the external load direction of the transmission sample in the crystal coordinate system, including: the deformation dislocation Schmidt factor S is calculated by the following method: Wherein, λ is the external load direction V of the transmission sample in the crystal coordinate system c With the dislocation slip direction V slip The angle between is the direction of the external load V on the transmission sample in the crystal coordinate system c The angle between n and the normal direction n of the dislocation slip plane.

9. The three-dimensional visualization method of deformation dislocation Schmidt factor distribution according to any one of claims 1 to 7, characterized in that: And display it in the dislocation 3D image, including: The size of the deformation dislocation Schmidt factor is described by different values ​​of the same display element, and the deformation dislocation Schmidt factor value is displayed in the dislocation three-dimensional image.

10. The three-dimensional visualization method of deformation dislocation Schmidt factor distribution according to claim 9, characterized in that: Two contrasting colors are used to represent the Schmidt factor values ​​of 0 and 0.5 respectively, and a gradient color scale between the two colors is set to represent the Schmidt factor value range from 0 to 0.5.

Images