Metal microstructure strain acquisition method based on microstructure
Through the strain acquisition method based on microstructure, backscattered electron diffraction technology is used to detect the grain orientation and characteristic grain boundaries of metal microstructure devices, and a theoretical calculation model is established, which solves the problem of difficulty in accurately measuring the internal strain of metal microstructure devices in the existing technology, and realizes high-precision strain analysis, which is applied to new energy, microelectronics, biomedicine, petrochemical, aerospace and other fields.
Patent Information
- Application Number
- CN202510447232.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-10
- Publication Date
- 2025-08-01
AI Technical Summary
Existing strain measurement methods are difficult to accurately measure the non-uniform and non-linear strain inside metal microstructure devices, resulting in high cost and low accuracy of measurement equipment, and cannot provide a reliable theoretical basis for material selection, structural design and life design.
Based on the microstructure of metal microstructure strain acquisition method, we prepare pre-deformed samples of metal blanks of different strain sizes, use backscattered electron diffraction technology to detect grain orientation and characteristic grain boundaries, and establish a theoretical calculation model for the change of the crystallographic characteristics of the deformed metal with strain, so as to achieve accurate calculation and analysis of the strain size.
It realizes accurate calculation and analysis of the internal strain magnitude of plastic forming microstructured metal devices, providing a basic theoretical basis for material selection, structural design and life design, and is suitable for new energy, microelectronics, biomedicine, petrochemical, aerospace and other fields.
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Figure CN120403473A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of plastic forming of metal materials, and particularly relates to a method for obtaining metal microstructure strain based on microstructure. Background Art
[0002] The magnitude of the internal strain of a plastic formed metal microstructure device not only has an important impact on its mechanical properties, structural stability and reliability after forming, but also has a very significant impact on its electrical conductivity, thermal conductivity, corrosion resistance, etc. Accurately analyzing the magnitude of the internal strain of a metal microstructure device can provide a basic theoretical basis for its material selection, structural design, process parameter optimization, product performance and life design.
[0003] Currently, due to the characteristics of metal microstructure devices such as usually being small in size and having a relatively complex shape structure. At the same time, the internal strain of a plastic formed metal microstructure device generally shows characteristics such as non-uniform distribution and non-linear change, resulting in difficulty in accurately measuring it with existing strain measurement methods and testing equipment. In addition, the direct measurement of metal microstructure strain has extremely high requirements for aspects such as equipment resolution, motion accuracy, test accuracy, and data processing ability. Therefore, it is difficult, costly, and has low accuracy and reliability to research and develop corresponding micro-strain measurement systems.
[0004] Therefore, how to overcome the deficiencies of existing strain measurement methods, realize the calculation and analysis of the magnitude of the internal strain of a metal microstructure device, and further provide a basic theoretical basis for its material selection, structure and life design, has become a difficult problem that needs to be solved urgently by those skilled in the art. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for obtaining metal microstructure strain based on microstructure. It constructs a strain calculation model of a deformed metal material based on the change rules of the internal grain orientation and / or characteristic grain boundaries and other microstructures of the deformed metal, and can realize accurate and effective calculation and analysis of the magnitude of the internal strain of a plastic formed microstructure metal device.
[0006] To solve the above technical problem, the technical solution of the present invention is: A method for obtaining metal microstructure strain based on microstructure, comprising:
[0007] Step S1, preparing a plurality of mechanical property test specimens of the metal blank before forming;
[0008] Step S2, preparing the mechanical property test specimens into pre-deformed specimens of metal blanks with different strain magnitudes;
[0009] Step S3: Using electron backscatter diffraction technology, detect and analyze the crystallographic characteristics of each pre-deformed sample of the metal blank; wherein, the crystallographic characteristics include grain orientation and / or the proportion of characteristic grain boundaries;
[0010] Step S4: According to the crystallographic characteristics of the pre-deformed samples of the metal blank with different strain magnitudes, establish a theoretical calculation model of the change of the crystallographic characteristics of the deformed metal with strain;
[0011] Step S5: Using electron backscatter diffraction technology, detect and analyze the crystallographic characteristics in different regions of the to-be-tested plastic forming metal microstructure device;
[0012] Step S6: Based on the crystallographic characteristics in different regions of the to-be-tested plastic forming metal microstructure device, use the theoretical calculation model to calculate and analyze the strain magnitudes in different regions of the to-be-tested forming metal microstructure.
[0013] Furthermore, the types of the mechanical property test specimens prepared in Step S1 include at least one of tension, compression, and bending.
[0014] Furthermore, in Step S2, when the metal material of the mechanical property test specimen has anisotropy, prepare the mechanical property test specimen according to the plastic forming direction of the metal material.
[0015] Furthermore, in Step S2, use a universal tensile testing machine to prepare the pre-deformed samples of the metal blank.
[0016] Furthermore, when using electron backscatter diffraction, for the pre-deformed samples of columnar or massive metal blanks and plastic forming metal microstructure devices, select a cross-section or plane parallel to the deformation direction as the observation surface; for the pre-deformed samples of metal blanks and plastic forming metal microstructure devices prepared from strip materials, select a cross-section perpendicular to the deformation direction as the observation surface; and there is no stress layer on the observation surface.
[0017] Furthermore, in Steps S3 and S5, during the process of performing electron backscatter diffraction, set the scanning area, scanning step size, electron beam current intensity, acceleration voltage, working distance, and diffraction angle based on the actual grain size and microstructure characteristics of the metal material.
[0018] Furthermore, the theoretical calculation model established in Step S4 uses the Boltzmann model.
[0019] After adopting the above technical solution, the present invention makes full use of the relationship between the microstructure such as grain orientation and characteristic grain boundaries and strain during the deformation process of metal microstructure devices. Based on the change rules of the internal grain orientation and / or characteristic grain boundaries and other microstructures of deformed metals, a strain calculation model of deformed metal materials is constructed, which can accurately and effectively calculate and analyze the internal strain of plastic forming microstructural metal devices with small sizes and relatively complex shapes and structures. Furthermore, it provides a basic theoretical basis for material selection, structure and life design of metal microstructure devices, and has wide applications in the fields of new energy, microelectronics, biomedicine, petrochemical industry, aerospace, etc. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 is a flowchart of the method for obtaining the strain of metal microstructures based on microstructures according to the present invention;
[0021] Figure 2 is a backscattered electron diffraction pattern of different strain tensile specimens according to the present invention;
[0022] Figure 3 is a graph showing the change rule of grain orientation with strain according to the present invention;
[0023] Figure 4 is a graph showing the change rule of the proportion of large-angle grain boundaries with strain according to the present invention;
[0024] Figure 5 is a cross-sectional view of a stamping-formed stainless steel bipolar plate according to the present invention;
[0025] Figure 6 is a grain orientation map of different regions of the cross-section of a stamping-formed stainless steel bipolar plate according to the present invention;
[0026] Figure 7 is a graph showing the proportion of large-angle grain boundaries in different regions of the cross-section of a stamping-formed stainless steel bipolar plate according to the present invention;
[0027] Wherein:
[0028] Figure 2 in, Figure 2 (a), Figure 2 (b), Figure 2 (c), Figure 2 (d) and Figure 2 (e) respectively represent pre-deformed specimens of metal billets with strains of 0, 0.1, 0.2, 0.3, and 0.4;
[0029] Figure 5 a, b, c, d, and e in are all regions to be calculated for strain in the stainless steel bipolar plate. DETAILED DESCRIPTION OF THE INVENTION
[0030] To make the content of the present invention easier to be clearly understood, the present invention will be further described in detail below according to specific embodiments in conjunction with the accompanying drawings.
[0031] As Figure 1 shown, a method for obtaining the strain of a metal microstructure based on the microstructure includes:
[0032] Step S1: Prepare a plurality of mechanical property test specimens of the metal blank before forming by wire cutting. The types of specimens include at least one of tensile, compressive, and bending.
[0033] Among them, the preparation of corresponding mechanical property test specimens such as tensile, compressive, or bending needs to be carried out according to the plastic forming method and characteristics of the metal microstructure device in accordance with ISO or ASTM standards; at the same time, for anisotropic metal materials, the tensile, compressive, or bending mechanical property test specimens should be prepared according to the plastic forming direction of the metal microstructure device.
[0034] Step S2: Test the tensile, compressive, or bending mechanical properties of a plurality of mechanical property test specimens of the metal blank before forming. According to the test results of the tensile, compressive, or bending mechanical properties of the metal blank before forming, prepare metal blank pre-deformation specimens with different strain magnitudes.
[0035] Among them, when preparing metal blank pre-deformation specimens with different strain magnitudes, it should include zero strain and ultimate strain of the metal blank, and at least one intermediate value should be selected between the zero strain and ultimate strain of the metal blank to ensure that the strain magnitudes in the metal blank pre-deformation specimens increase uniformly.
[0036] Among them, mechanical property tests such as tensile, compressive, or bending need to be carried out on a universal tensile testing machine according to ISO or ASTM standards, so as to accurately obtain the mechanical property curve of the metal blank before forming in the corresponding direction.
[0037] Step S3: Use the electron backscatter diffraction technique to detect and analyze the crystallographic characteristics of each metal blank pre-deformation specimen; among them, the crystallographic characteristics include grain orientation and / or the proportion of characteristic grain boundaries;
[0038] Step S4: Establish a theoretical calculation model of the change of the crystallographic characteristics of the deformed metal with strain according to the crystallographic characteristics of the metal blank pre-deformation specimens with different strain magnitudes;
[0039] Among them, the established theoretical calculation model can adopt the Boltzmann model, and the specific description is as shown in formula (1):
[0040] f (ε) =(A1 - A2) / (1 + exp((ε - ε0) / dε)) + A2 (1)
[0041] Where, f (ε) is the dependent variable such as the internal grain orientation and / or characteristic grain boundary of the metal, ε is the true strain or engineering strain of the deformed metal, A1, A2, v0 and dε are constants, which are determined by the metal material type and the microstructure such as the original grain of the metal billet, and are obtained by parameter fitting using professional software.
[0042] It should be noted that the theoretical calculation model established is not limited to the Boltzmann model. (ε) When the internal grain orientation and characteristic grain boundaries of the metal are taken as independent variables, the weighted average method is used to calculate the final strain value.
[0043] Step S5, using backscattered electron diffraction technology to detect and analyze the crystallographic characteristics of different regions of the plastically formed metal microstructure device to be tested;
[0044] Step S6: Based on the crystallographic characteristics of different regions of the plastically formed metal microstructure device to be tested, a theoretical calculation model is used to calculate and analyze the strain magnitudes in different regions of the plastically formed metal microstructure to be tested.
[0045] Among them, when using backscattered electron diffraction, for pre-deformed specimens of columnar or block metal blanks and plastically formed metal microstructure devices, a section or plane parallel to the deformation direction is selected as the observation surface; for pre-deformed specimens of metal blanks prepared from plate and strip materials and plastically formed metal microstructure devices, a section perpendicular to the deformation direction is selected as the observation surface; and the observation surface has no stress layer (the specimen needs to be mechanically vibrated or electrolytically polished before observation to eliminate residual stress on the observation surface). For tensile and compressive specimens, the observation section should be a section or plane close to the tensile or compressive axis. In the process of backscattered electron diffraction, based on the actual grain size and microstructural characteristics of the metal material, parameters such as the scanning area, scanning step, electron beam current intensity, acceleration voltage, working distance and diffraction angle are set (the scanning area contains no less than 10 grains in the length and width directions, the scanning step is 0.1-0.2 times the grain size, the working distance is generally 10-15mm, and the sample tilt angle is 70°). After the test is completed, supporting software or professional analysis software is used for data processing, such as Channel 5, OIM analysis, AZtecCrystal and other backscattered electron diffraction data analysis and post-processing software.
[0046] It should be noted that the scale of metal microstructures is generally 10nm to 5mm.
[0047] The solutions involved in the above embodiments are described in detail below in conjunction with specific embodiments.
[0048] The metal material in the specific embodiment is an ultra-thin stainless steel sheet with a thickness of 0.1 mm. The formed microstructural device is a stainless steel bipolar plate for fuel cells, and the forming process is stamping. However, it should be understood that the metal materials described in the present invention include all metal materials that can be plastically formed, such as steel, aluminum and its alloys, copper and its alloys, magnesium and its alloys, precious metals, etc. The material type is not limited to sheets only, but can also be bars, profiles, etc. At the same time, the forming processes described in the present invention are applicable to all plastic forming processes, such as stamping, hydraulic pressure, rolling, extrusion, drawing, and forging, etc. In addition, the formed metal microstructural devices can be applied not only to new energy technology fields such as fuel cells, but also widely to fields such as microelectronics, biomedicine, petrochemical industry, and aerospace, etc.
[0049] Example 1
[0050] As Figure 1 shown, a method for obtaining metal microstructural strain based on microstructure includes the following steps:
[0051] Step S1, using wire cutting, prepare tensile specimens of the stainless steel ultra-thin blank before forming according to the ISO 6892-12019 standard, and the sample preparation direction is the same as the rolling direction of the stainless steel ultra-thin blank;
[0052] Step S2, using wire cutting, test the tensile properties of the stainless steel ultra-thin blank before forming according to the ISO 6892-12019 standard, and prepare pre-tensioned deformed stainless steel specimens with strain magnitudes of 0, 0.1, 0.2, 0.3, and 0.4 respectively according to the tensile property test results of the stainless steel ultra-thin blank;
[0053] Step S3, select the cross-section parallel to the tensile direction as the backscattered electron diffraction observation surface. Before performing the backscattered electron diffraction test, perform vibratory polishing on the specimen to eliminate the surface residual stress layer; during the test, select a scanning area size of about 80 μm × 80 μm, a scanning step of 0.25 μm, an accelerating voltage of 20 kV, a working distance of 13 mm, and a diffraction angle of 70° and other parameters to perform the backscattered electron diffraction test; after the test is completed, use OIM analysis professional analysis software to analyze the grains and grain orientations in the pre-tensioned deformed stainless steel specimens with strain magnitudes of 0, 0.1, 0.2, 0.3, and 0.4 respectively, as Figure 2 and Figure 3 shown;
[0054] Step S4, according to the grain orientations in different pre-tensioned deformed stainless steel specimens, establish a theoretical calculation model for the change of the internal grain orientation of the tensile-formed stainless steel with strain, as shown in Equation (2):
[0055] f (ε)= 31.18 / (1 + exp((ε - 0.20) / 0.06)) + 18.29 (2)
[0056] In the formula, f (ε) is the grain orientation inside the pre-stretched deformed stainless steel specimen, and ε is the engineering strain magnitude of the pre-stretched deformed stainless steel specimen.
[0057] Step S5: Select the cross-sectional direction perpendicular to the flow channel of the stamped stainless steel bipolar plate as the backscattered electron diffraction observation surface, as Figure 5 shown. Before performing the backscattered electron diffraction test, the specimen is subjected to vibratory polishing treatment to eliminate the surface residual stress layer; during the test, the selected scanning area size is approximately 80 μm × 80 μm, the scanning step is 0.25 μm, the acceleration voltage is 20 kV, the working distance is 13 mm, and the diffraction angle is 70°. The backscattered electron diffraction test is carried out with these parameters; after the test is completed, the OIM analysis professional analysis software is used to Figure 5 statistically analyze the grains and grain orientations in the five regions a, b, c, d, and e of the pre-stretched deformed stainless steel specimen in Figure 6 shown;
[0058] S6. According to Figure 6 the grain orientations in the pre-stretched deformed stainless steel specimens with different strain magnitudes, using the theoretical calculation model formula (2) established in step S5, the strain magnitudes in the five regions a, b, c, d, and e of the cross-section of the stamped stainless steel bipolar plate are calculated and analyzed to be 0.09, 0.36, 0.35, 0.36, and 0.07 respectively.
[0059] Example 2
[0060] Steps S1 and S2 of this example are the same as those of Example 1, and steps S3 to S6 are different from those of Example 1. The differences are as follows:
[0061] In step S3, the OIM analysis professional analysis software is used to statistically analyze the proportion of large-angle grain boundaries of 15 - 180° in the pre-stretched deformed stainless steel specimens with strain magnitudes of 0, 0.1, 0.2, 0.3, and 0.4 respectively, as Figure 2 and Figure 4 shown;
[0062] In step S4, according to the large-angle grain boundaries in the different pre-stretched deformed stainless steel specimens, a theoretical calculation model of the change of large-angle grain boundaries inside the stretched-formed stainless steel with strain is established, as shown in formula (3):
[0063] f (ε) = 0.65 / (1 + exp((ε - 0.20) / 0.06)) + 0.34 (3)
[0064] Where, f (ε) is the ratio of high-angle grain boundaries in the pre-tensioned stainless steel specimen, and ε is the engineering strain of the pre-tensioned stainless steel specimen.
[0065] In step S5, Figure 5 The high-angle grain boundary ratios of the five regions a, b, c, d and e of the pre-stretched stainless steel specimens were statistically analyzed. Figure 7 As shown;
[0066] In step S6, according to Figure 7 The ratio of high-angle grain boundaries in pre-stretched stainless steel specimens with different strain sizes is calculated and analyzed using the theoretical calculation model formula (3) established in step S4. The strain sizes of the five regions a, b, c, d and e in the cross section of the stamped stainless steel bipolar plate are 0.08, 0.36, 0.35, 0.35 and 0.06, respectively.
[0067] Example 3
[0068] Steps S1 and S2 of this embodiment are the same as those of the first embodiment, while steps S3 to S6 are different from those of the first embodiment in that:
[0069] In step S3, the OIM analysis professional analysis software is used to analyze the grains and grain orientations of the pre-stretched stainless steel specimens with strains of 0, 0.1, 0.2, 0.3 and 0.4, as shown in the following example: Figure 2 and Figure 3 As shown in Figure 2, the proportion of high-angle grain boundaries of 15 to 180° was statistically analyzed, as shown in Figure 2. Figure 2 and Figure 4 As shown;
[0070] In step S4, according to the grain orientation and high-angle grain boundary in different pre-stretched deformed stainless steel samples, theoretical calculation models of the variation of the grain orientation and high-angle grain boundary in the stretched stainless steel with strain are established, as shown in equations (4) and (5). The weights of the grain orientation and high-angle grain boundary in the microstructure of the formed stainless steel in the strain calculation process are both 0.5. Therefore, the multi-factor calculation theoretical model that comprehensively considers the grain orientation and high-angle grain boundary in the microstructure of the formed stainless steel is shown in equation (6):
[0071] f (ε1) =31.18 / (1+exp((ε1-0.20) / 0.06))+18.29 (4)
[0072] f (ε2) =0.65 / (1+exp((ε2-0.20) / 0.06))+0.34 (5)
[0073] ε = (ε1 + ε2) / 2 (6)
[0074] where f (ε1) and f (ε2) are respectively the grain orientation and the proportion of large - angle grain boundaries in the pre - stretched deformed stainless - steel specimen. ε1 and ε2 are respectively the engineering strain magnitudes corresponding to the grain orientation and the proportion of large - angle grain boundaries in the pre - stretched deformed stainless - steel specimen. ε is the calculated value of strain considering both the grain orientation and the large - angle grain boundaries in the internal microstructure of the formed stainless steel.
[0075] It should be noted that the determination of the weights of the grain orientation and the large - angle grain boundaries in the strain calculation process generally needs to be determined according to the deformation characteristics of the metal material and the difficulty of the microstructure characterization analysis, that is: if during the deformation process, the change laws of both the grain orientation and the grain boundary characteristics are significant, and accurate data can be obtained during their characterization analysis, then the weights of the two are the same; if during the deformation process, the change law of one of the grain orientation and the grain boundary characteristics is not significant, or accurate results cannot be obtained during the characterization analysis, or to reduce the analysis and calculation cost, then the corresponding weight is taken as 0. The value of the weight is determined according to its significant situation.
[0076] In step S5, using the OIM analysis professional analysis software, for the grains and grain orientations in the pre - stretched deformed stainless - steel specimens with strain magnitudes of 0, 0.1, 0.2, 0.3, and 0.4 respectively, as Figure 6 shown, the proportion of large - angle grain boundaries of 15 - 180° is statistically analyzed, as Figure 7 shown;
[0077] S6. According to Figure 6 and Figure 7 the grain orientation and the proportion of large - angle grain boundaries in the pre - stretched deformed stainless - steel specimens with different strain magnitudes, using the theoretical calculation model formulas (4) - (6) established in step S4, calculate and analyze that the strain magnitudes in the five regions a, b, c, d, and e in the cross - section of the stamped - formed stainless - steel bipolar plate are 0.09, 0.36, 0.35, 0.36, and 0.07 respectively.
[0078] Taking the ideal embodiments according to the present invention as an inspiration, through the above - mentioned description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.
Claims
1. A method for obtaining the strain of a metal microstructure based on the microstructure, characterized in that: It includes: Step S1, preparing a plurality of mechanical property test specimens of the metal blank before forming; Step S2, preparing the metal blank pre-deformed specimens with different strain magnitudes from each mechanical property test specimen; Step S3, using the electron backscatter diffraction technique to detect and analyze the crystallographic characteristics of each metal blank pre-deformed specimen; wherein, the crystallographic characteristics include grain orientation and / or the proportion of characteristic grain boundaries; Step S4, establishing a theoretical calculation model of the change of the crystallographic characteristics of the deformed metal with strain according to the crystallographic characteristics of the metal blank pre-deformed specimens with different strain magnitudes; Step S5, using the electron backscatter diffraction technique to detect and analyze the crystallographic characteristics in different regions of the plastic forming metal microstructure device to be tested; Step S6, based on the crystallographic characteristics in different regions of the plastic forming metal microstructure device to be tested, using the theoretical calculation model to calculate and analyze the strain magnitudes in different regions of the forming metal microstructure to be tested.
2. The method for obtaining the strain of a metal microstructure based on the microstructure according to claim 1, characterized in that: The types of the mechanical property test specimens prepared in step S1 include at least one of tensile, compressive and bending.
3. The method for obtaining the strain of a metal microstructure based on the microstructure according to claim 1, characterized in that: In step S1, when the metal material of the mechanical property test specimen has anisotropy, the mechanical property test specimen is prepared according to the plastic forming direction of the metal material.
4. The method for obtaining the strain of a metal microstructure based on the microstructure according to claim 1, characterized in that: In step S2, a universal tensile testing machine is used to prepare the metal blank pre-deformed specimens.
5. The method for obtaining the strain of a metal microstructure based on the microstructure according to claim 1, characterized in that: When using electron backscatter diffraction, for the columnar or massive metal blank pre-deformed specimens and the plastic forming metal microstructure device, a cross-section or plane parallel to the deformation direction is selected as the observation surface; for the metal blank pre-deformed specimens and the plastic forming metal microstructure device prepared from strip materials, a cross-section perpendicular to the deformation direction is selected as the observation surface; And there is no stress layer on the observation surface.
6. The method for obtaining the strain of a metal microstructure based on the microstructure according to claim 5, characterized in that: In steps S3 and S5, during the process of performing electron backscatter diffraction, based on the actual grain size and the microstructure characteristics of the metal material, the scanning area, scanning step size, electron beam current intensity, acceleration voltage, working distance and diffraction angle are set.
7. The method for obtaining the strain of a metal microstructure based on the microstructure according to claim 1, characterized in that: The theoretical calculation model established in step S4 uses the Boltzmann model.