A sample preparation method for observing notch line magnetic domains of oriented silicon steel and application thereof

Abstract

The application provides a sample preparation method for observing notch line magnetic domain of oriented silicon steel and application thereof, and belongs to the field of metal material detection. The method comprises the following steps: cutting an oriented silicon steel sample to obtain a first sample; distinguishing a notch surface and a non-notch surface of the first sample, and coating a protective glue on the notch surface to retain stress information and magnetic domain structure of the notch surface, thereby obtaining a second sample; removing an inorganic salt coating on the non-notch surface of the second sample to obtain a third sample; and sequentially performing SiC sandpaper preliminary polishing, silica suspension mechanical polishing and high-chloric acid electrolytic polishing on the non-notch surface of the third sample to improve surface smoothness of the non-notch surface and retain stress influence area at the notch line of the notch surface, thereby obtaining a sample to be observed. Through wire cutting sampling, notch surface protection and fine polishing of the non-notch surface, stress information and magnetic domain structure of the notch line of the sample can be retained, and magnetic domain information near and inside the notch line can be observed.

Description

Technical Field

[0001] This application relates to the field of metal material testing technology, and in particular to a sample preparation method for observing magnetic domains in grooved lines of oriented silicon steel and its application. Background Technology

[0002] Grain-oriented silicon steel is a key soft magnetic material widely used in electrical equipment such as transformers and motors. Its magnetic properties are affected by the magnetic domain structure inside the material, and laser marking technology, as an important means to refine the magnetic domain width, can effectively reduce iron loss and improve magnetic permeability. Studying the magnetic domain morphology at the laser marking location is of great significance for optimizing the marking process.

[0003] Currently, the main methods for observing magnetic domains include powder mapping and scanning electron microscopy (SEM). While powder mapping is simple to operate, it has low resolution, and the magnetic particles are easily affected by stray magnetic fields near the groove lines, making it impossible to visualize the magnetic domains inside the groove lines. Furthermore, it cannot quantitatively measure key parameters such as groove line width. In contrast, SEM (Forescattered electron) imaging technology has significant advantages in magnetic domain research due to its high resolution and excellent domain contrast. However, traditional SEM sample preparation methods often remove the stress layer near the groove lines during electropolishing, making it impossible to accurately observe the magnetic domain structure in this region and limiting in-depth research on the groove effect. Summary of the Invention

[0004] This application provides a sample preparation method for observing magnetic domains in oriented silicon steel with indentation lines and its application, in order to solve the following technical problem: how to retain the stress information and magnetic domain structure of the indentation lines of oriented silicon steel samples during the sample preparation process for electron microscopy, so as to observe the magnetic domain information near and inside the indentation lines.

[0005] In a first aspect, embodiments of this application provide a sample preparation method for observing magnetic domains along indentations in oriented silicon steel, the method comprising: The grain-oriented silicon steel sample was cut using wire cutting to obtain a first sample with a set size. The etched and non-etched surfaces of the first sample are distinguished, and a protective adhesive is applied to the etched surface to preserve the stress information and magnetic domain structure of the etched surface, thus obtaining the second sample; the protective adhesive is AB glue or 502 glue; The inorganic salt coating on the non-marked surface of the second sample is removed to obtain the third sample; and The non-marked surface of the third sample was subjected to SiC sandpaper preliminary polishing, silica suspension mechanical polishing, and perchloric acid electrolytic polishing in sequence to improve the surface smoothness of the non-marked surface and retain the stress-affected area at the mark line of the marked surface, thus obtaining the sample to be observed for magnetic domain observation of the mark line of oriented silicon steel.

[0006] Optionally, removing the inorganic salt coating from the non-marked surface of the second sample to obtain the third sample includes: The second sample was first immersed in dilute hydrochloric acid to remove the inorganic salt coating on the non-marked surface of the second sample; The second sample after the first soaking was then soaked in a sodium bicarbonate solution to remove residual dilute hydrochloric acid. The second sample after the second soaking was washed to obtain the third sample.

[0007] Optionally, the volume fraction of the dilute hydrochloric acid is 8%–10%, and the first soaking time is 3.5 h–4.5 h; and / or, The volume fraction of the sodium bicarbonate solution is 4% to 6%, and the second soaking time is 8 min to 12 min.

[0008] Optionally, the step of sequentially performing SiC sandpaper preliminary polishing, silica suspension mechanical polishing, and perchloric acid electrolytic polishing on the non-marked surface of the third sample includes: The non-marked surface of the third sample was initially polished using SiC sandpaper to reduce surface roughness; the SiC sandpaper had a mesh size of 3000. The non-marked surface of the third sample after preliminary grinding was mechanically polished using SiO2 suspension as the polishing medium; the particle size of SiO2 was 0.04μm~0.06μm. The non-marked surface of the mechanically polished third sample was electropolished using a perchloric acid solution with a volume fraction of 5%–7%. The third sample, after electropolishing, was then cleaned.

[0009] Optionally, the mechanical polishing uses a Naibo LAP-2SE metallographic polishing machine, the polishing cloth is velvet cloth, the lubricating medium is anhydrous ethanol, and the polishing direction is along the rolling direction of the material.

[0010] Optionally, the mechanical polishing equipment has a rotation speed of 150 rpm / min to 200 rpm / min, and the mechanical polishing time is 8 min to 12 min.

[0011] Optionally, the electropolishing includes the following parameters: voltage of 30V, current of 1A to 2A, and polishing time of 10s to 25s.

[0012] Secondly, this application provides an application of a sample preparation method for observing magnetic domains in grooved lines of grain-oriented silicon steel, the application including: Using the powder method, the position of the scratch line on the scratched surface is initially located on the non-scratched surface of the sample to be observed obtained in any embodiment of the first aspect; the position of the scratch line is transferred to the non-scratched surface by the stress effect of the scratch line on the scratched surface; FSD magnetic domain imaging was performed at the location of the scribe line under a scanning electron microscope to obtain a high-resolution image of the FSD magnetic domain inside the scribe line.

[0013] Optionally, the application also includes: By combining an electron backscatter diffraction probe, magnetic domain images and crystal orientation information inside the scribe line can be obtained simultaneously.

[0014] Optionally, the FSD magnetic domain imaging includes the following parameters: sample tilt angle of 70° to 75°, accelerating voltage of 30 kV, working distance of 14 mm to 16 mm, and distance between the FSD probe and the sample surface of 150 mm.

[0015] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a sample preparation method for observing magnetic domains along the indentation lines of grain-oriented silicon steel. The method includes: cutting the grain-oriented silicon steel sample using wire cutting to obtain a first sample; distinguishing the indented surface and the non-indented surface of the first sample, and coating the indented surface with a protective adhesive to retain the stress information and magnetic domain structure of the indented surface, to obtain a second sample; removing the inorganic salt coating from the non-indented surface of the second sample to obtain a third sample; and sequentially performing SiC sandpaper preliminary polishing, silica suspension mechanical polishing, and perchloric acid electrolytic polishing on the non-indented surface to improve the surface finish of the non-indented surface and retain the stress-affected area at the indentation lines of the indented surface, to obtain the sample to be observed for observing the magnetic domains along the indentation lines of grain-oriented silicon steel. First, wire cutting sampling reduces local internal stress at the cutting point, improving sample integrity. Second, scratch surface protection preserves stress information near the scratch lines, ensuring the integrity of the magnetic domain structure and enhancing the realism of magnetic domain imaging. Third, fine polishing of the non-scratched surface improves its smoothness, ensuring clear identification of the magnetic domain structure and enabling refined observation. Finally, the scratch lines on the scratched surface are transmitted to the non-scratched surface through stress effects, allowing observation of magnetic domain information near and within the scratch lines on the non-scratched surface. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic flowchart illustrating a sample preparation method for observing magnetic domains along indentations in oriented silicon steel, provided in an embodiment of this application. Figure 2 This is a magnetic domain morphology diagram of the etched and non-etched surfaces under the powder etching method provided in Embodiment 1 of this application; Figure 3 This is a morphological image of the sample after applying an AB glue protective layer to the scored surface of the sample, as provided in Example 1 of this application. Figure 4 This is a morphological image of the sample after acid washing to remove the inorganic salt coating on the non-marked surface of the sample, as provided in Example 1 of this application. Figure 5 A morphological diagram of the sample after the non-scratched surface of the sample provided in Embodiment 1 of this application has been polished with 3000-grit sandpaper; Figure 6 This is a morphological image of the electropolished sample after the non-marked surface was obtained, as provided in Embodiment 1 of this application. Figure 7 The magnetic domain morphology of the sample to be observed at different positions of the etch marks provided in Embodiment 1 of this application is shown. The white dashed box represents the magnetic domains inside the etch marks, and the length of the arrow represents the width of the laser etch mark. Figure 8 A diagram showing the magnetic domain morphology and corresponding crystal orientation information of the sample to be observed provided in Embodiment 1 of this application; Figure 9 The magnetic domain morphology and corresponding crystal orientation information of the sample to be observed provided for Comparative Example 1 of this application are shown in the figure. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0021] Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts representation" such as parts by weight or parts by mass indicates the proportional relationship between components. In the proportional relationships discussed in this article, parameters that need to be described by proportion should be understood as the first term of the proportion in the order of description, while the proportion figure should be understood as the second term. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportion figure in the proportion in the order of description, i.e., the mass of substance A : the mass of substance B : the mass of substance C = 1:2:3.

[0022] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0023] like Figure 1As shown, this application provides a sample preparation method for observing magnetic domains along the indentation lines of grain-oriented silicon steel, the method comprising: S11. The grain-oriented silicon steel sample is cut by wire cutting to obtain a first sample with a set size; In this embodiment, wire cutting is used to sample oriented silicon steel specimens. Compared with mechanical shearing, wire cutting can significantly reduce local internal stress at the cutting point and improve the integrity of the sample.

[0024] In some embodiments, the set dimensions include: the length of the first sample is 5 mm to 15 mm, and the width of the first sample is 5 mm to 15 mm.

[0025] The sampling area depends on the requirements of the electron microscope sample stage, and can generally be 5 mm × 5 mm to 15 mm × 15 mm.

[0026] S12. Distinguish between the etched and non-etched surfaces of the first sample, and apply a protective adhesive to the etched surface to preserve the stress information and magnetic domain structure of the etched surface, thereby obtaining the second sample; the protective adhesive is AB glue or 502 glue; In this embodiment, by coating the scored surface with AB glue or 502 glue, the inorganic coating and scored lines on the scored surface are protected during the pickling process, while avoiding erosion during electrolytic polishing, thereby preserving the stress information and magnetic domain structure of the scored surface.

[0027] In this embodiment, the etched surface and the non-etched surface are distinguished by the powder texture method. The etched surface has a raised feel when touched, and the powder texture method shows a strong aggregation of magnetic particles near the etched lines.

[0028] It should be noted that the "powder texture method" is a method that reveals the magnetic domain structure by applying fine magnetic powder to the surface of a magnetized sample. After magnetizing the silicon steel plate with an external magnetic field, the fine magnetic particles are affected by the local magnetic field on the sample surface and align along the boundaries of the magnetic domains or magnetic field lines, thus revealing the distribution and structure of the magnetic domains of the sample to the naked eye or under a low-magnification microscope.

[0029] AB glue is a common organic adhesive. Component A is the main agent, primarily composed of epoxy resin (such as bisphenol A epoxy resin), while component B is the curing agent, primarily composed of polyamide. The application method for AB glue is as follows: mix the two components in a 1:1 ratio until homogeneous, then apply evenly to the sample surface. After 24 hours of curing, a surface adhesive layer will form on the sample surface.

[0030] In the adhesive layer formed by AB glue, the epoxy resin, after curing, forms a rigid structure that resists the erosion of acid pickling (such as 9% dilute hydrochloric acid) and electropolishing (6% perchloric acid solution), effectively protecting the inorganic coating and score lines on the scored surface from corrosion. Simultaneously, the AB glue forms a uniform insulating layer after curing, isolating the scored surface from the influence of external mechanical stress, preserving the original stress distribution in the scored area, and preventing distortion of the magnetic domain structure due to stress disturbance. Furthermore, epoxy resin has strong adhesion to metal substrates (such as silicon steel) and low curing shrinkage, preventing score line deformation or coating peeling due to adhesive layer shrinkage.

[0031] 502 glue is an instant curing adhesive with ethyl α-cyanoacrylate as its main component. It is known as "all-purpose glue" because of its fast bonding ability and wide applicability.

[0032] S13. Remove the inorganic salt coating from the non-marked surface of the second sample to obtain the third sample; It should be noted that the inorganic salt coating of oriented silicon steel is an insulating protective layer mainly composed of inorganic components, which is mainly used to improve the electromagnetic properties, corrosion resistance and processing adaptability of the material.

[0033] In some embodiments, removing the inorganic salt coating from the non-marked surface of the second sample to obtain the third sample includes: The second sample was first immersed in dilute hydrochloric acid to remove the inorganic salt coating on the non-marked surface of the second sample; the second sample after the first immersion was then immersed in sodium bicarbonate solution to remove residual dilute hydrochloric acid; the second sample after the second immersion was then washed to obtain the third sample.

[0034] In some embodiments, the volume fraction of the dilute hydrochloric acid is 8%–10%, and the first soaking time is 3.5 h–4.5 h; and / or, The volume fraction of the sodium bicarbonate solution is 4% to 6%, and the second soaking time is 8 min to 12 min.

[0035] This application embodiment uses a dilute hydrochloric acid solution to remove the inorganic salt coating on the non-marked surface. Compared with mechanical polishing, this method can effectively avoid additional polishing stress, thereby obtaining a higher quality magnetic domain image. In addition, the sample needs to be cleaned with sodium bicarbonate solution to neutralize residual acid, prevent material corrosion, and prepare for subsequent fine polishing. For example, the volume fraction of dilute hydrochloric acid can be 8%, 8.5%, 9%, 9.5%, 10%, etc., the first immersion time can be 3.5h, 3.7h, 3.9h, 4.1h, 4.3h, 4.5h, etc., the volume fraction of sodium bicarbonate solution can be 4%, 4.5%, 5%, 5.5%, 6%, etc., and the second immersion time can be 8min, 9min, 10min, 11min, 12min, etc.

[0036] S14. The non-marked surface of the third sample is subjected to SiC sandpaper preliminary polishing, silica suspension mechanical polishing and perchloric acid electrolytic polishing in sequence to improve the surface smoothness of the non-marked surface and retain the stress-affected area at the mark line of the marked surface, so as to obtain the sample to be observed for magnetic domain observation of the mark line of oriented silicon steel.

[0037] In this embodiment, AB glue or 502 glue is applied to protect the scratched surface, followed by polishing of the non-scratched surface. This avoids the removal of the stress layer near the scratch lines by traditional electrolytic polishing, ensuring the integrity of the magnetic domain structure and improving the realism of magnetic domain imaging.

[0038] In some embodiments, the step of sequentially performing SiC sandpaper preliminary polishing, silica suspension mechanical polishing, and perchloric acid electrolytic polishing on the non-marked surface of the third sample includes: The non-marked surface of the third sample was initially polished using SiC sandpaper with a mesh size of 3000. A SiO2 suspension was used as the polishing medium to mechanically polish the non-marked surface of the third sample after initial polishing. The SiO2 particle size was 0.04 μm to 0.06 μm. A perchloric acid solution was used to electropolish the non-marked surface of the mechanically polished third sample. The volume fraction of the perchloric acid solution was 5% to 7%. The third sample was then cleaned after electropolishing.

[0039] In some embodiments, the mechanical polishing uses a Naibo LAP-2SE metallographic polishing machine, the polishing cloth is velvet cloth, the lubricating medium is anhydrous ethanol, and the polishing direction is along the rolling direction of the material.

[0040] In some embodiments, the mechanical polishing equipment rotates at a speed of 150 rpm / min to 200 rpm / min, and the mechanical polishing time is 8 min to 12 min.

[0041] In some embodiments, the electropolishing includes the following parameters: voltage of 30V, current of 1A to 2A, and polishing time of 10s to 25s.

[0042] In the fine polishing process, firstly, the non-marked surfaces of the sample are initially polished using 3000-grit SiC sandpaper to obtain a smooth surface. Then, mechanical polishing is performed using a SiO2 suspension, with the polishing direction aligned with the rolling direction of the material to minimize additional polishing stress and improve magnetic domain imaging quality. Finally, electrolytic polishing with perchloric acid solution is performed, followed immediately by ultrasonic cleaning with alcohol to prevent corrosion of the sample by the perchloric acid solution. Throughout the fine polishing process, the non-marked surfaces of the material are polished to preserve the stress-affected areas at the mark lines. For example, the volume fraction of the perchloric acid solution can be 5%, 5.5%, 6%, 6.5%, 7%, etc., the rotation speed of the mechanical polishing equipment can be 150 rpm / min, 160 rpm / min, 170 rpm / min, 180 rpm / min, 190 rpm / min, 200 rpm / min, etc., the polishing time of mechanical polishing can be 8 min, 9 min, 10 min, 11 min, 12 min, etc., the current of electrolytic polishing can be 1A, 1.2A, 1.4A, 1.6A, 1.8A, 2A, etc., and the polishing time of electrolytic polishing can be 10s, 15s, 20s, 22s, 25s, etc.

[0043] In some embodiments, after the non-marked surface of the third sample is sequentially subjected to SiC sandpaper preliminary polishing, silica suspension mechanical polishing, and perchloric acid electrolytic polishing, the method further includes: Remove the protective adhesive layer from the scored surface of the third sample.

[0044] In the embodiments of this application, when the sample size is >10 mm × 10 mm, the adhesive will shrink to a certain volume during curing, which may affect the observation of magnetic domains. Acetone can be used to wipe it off, thereby removing the protective layer.

[0045] Therefore, this application employs AB glue or 502 glue to protect the scratched surface, effectively preserving the scratched surface coating during the acid etching process. This preserves stress information near the scratch lines during electropolishing, avoiding magnetic domain loss caused by traditional polishing methods. Because the scratched surface is protected, the scratch line effect is retained during subsequent electropolishing of the non-scratched surface. The stress effect of the scratch lines can be transmitted to the non-scratched surface through the material's interior, allowing magnetic domain information to be observed on the non-scratched surface. Furthermore, when observing magnetic domains, magnetic domain information near and within the scratch lines can be observed on the non-scratched surface.

[0046] Based on a general inventive concept, this application provides an application of a sample preparation method for observing magnetic domains along indentations in grain-oriented silicon steel, the application including: S21. Using the powder texture method, the position of the scratch line on the non-scratched surface of the sample to be observed obtained in any of the above embodiments is initially located; the position of the scratch line is transferred to the non-scratched surface by the stress effect of the scratch line on the scratched surface; S22. Perform FSD magnetic domain imaging at the location of the scribe line under a scanning electron microscope to obtain a high-resolution image of the FSD magnetic domain inside the scribe line.

[0047] In some implementations, the application further includes: By combining an electron backscatter diffraction probe, magnetic domain images and crystal orientation information inside the scribe line can be obtained simultaneously.

[0048] It should be noted that FSD (Front-Scatter Detector) technology is an imaging method used in scanning electron microscopy (SEM), which mainly utilizes electrons scattered from the sample to construct images. It can reveal magnetic domain information on the sample surface, but requires extremely high material surface quality.

[0049] Electron backscatter diffraction (EBSD) is an important technique for microstructure analysis in materials science. It uses scanning electron microscopy (SEM) combined with diffraction patterns to study the crystal structure and orientation of materials.

[0050] In some embodiments, the FSD magnetic domain imaging includes the following parameters: sample tilt angle of 70° to 75°, accelerating voltage of 30 kV, working distance of 14 mm to 16 mm, and distance between the FSD probe and the sample surface of 150 mm.

[0051] In this embodiment, the scanning electron microscope (SEM) imaging parameters are optimized, employing a tilt angle of 70°–75°, an accelerating voltage of 30 kV, and a working distance of 14 mm–16 mm. This not only ensures compatibility with EBSD data acquisition but also supports simultaneous observation of magnetic domains and crystal orientation (requiring both FSD and EBSD probes). This allows for combined analysis of magnetic domain and crystal orientation data, providing more precise microstructural information for studying stress-affected regions near the indentation lines. For example, the sample tilt angle can be 70°, 71°, 72°, 73°, 74°, 75°, etc., and the working distance can be 14 mm, 15 mm, 16 mm, etc.

[0052] In summary, this application proposes an innovative sample preparation method. Through wire cutting sampling, application of AB glue to protect the scored surface (the surface containing the scored line), mechanical polishing, and electrolytic polishing, stress information near the scored line is effectively preserved, preparing a scanning electron microscope sample for magnetic domain observation. Compared to the traditional powder method, this method not only obtains high-resolution images of magnetic domains within the scored line but also allows for precise measurement of microscopic parameters such as the scored line width using these images. Furthermore, by combining an electron backscatter diffraction (EBSD) probe, magnetic domain images and crystal orientation information can be acquired simultaneously, revealing the microstructural evolution of the stress-affected region near the scored line. This method provides an efficient and precise experimental tool for in-depth research on the microstructure and magnetic properties of grain-oriented silicon steel, and has significant technical value for the optimized design and application of grain-oriented silicon steel.

[0053] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0054] Example 1 This embodiment provides a sample preparation method for observing magnetic domains along the indentation lines of grain-oriented silicon steel, which may include the following steps: 1. Wire cutting sampling and preliminary observation of magnetic domains ① The grain-oriented silicon steel sample was cut by wire cutting to obtain the first sample; the sampling area depends on the requirements of the electron microscope sample stage. In order to observe the magnetic domains of the scribe line at different positions of the same grain-oriented silicon steel sample, multiple first samples of different sizes were cut.

[0055] ② The magnetic domain morphology of the first sample was observed using the powder etching method to distinguish between the etched and non-etched surfaces; the magnetic domain morphology at the etched lines was clearly visible on the etched surface. The magnetic domain morphology diagrams of the etched and non-etched surfaces under the powder etching method are shown below. Figure 2 As shown.

[0056] ③ Apply AB adhesive to the scored surface. Take 0.2 ml of adhesive A and 0.2 ml of adhesive B, mix them thoroughly, and then apply the mixture to the scored surface of the sample. Let it stand for 24 hours to cure, obtaining the second sample. The morphology of the sample after applying the AB adhesive protective layer to the scored surface is shown in the figure below. Figure 3 As shown.

[0057] 2. Remove the inorganic salt coating from the non-scratched surfaces. The second sample was immersed in a 9% dilute hydrochloric acid solution for 3 hours to remove the inorganic salt coating on the non-marked surfaces. The second sample was then removed and immersed in a 5% sodium bicarbonate solution for 10 minutes to remove residual hydrochloric acid. Finally, the sample was ultrasonically cleaned 2-3 times with alcohol to obtain the third sample. The morphology of the sample after removing the inorganic salt coating on the non-marked surfaces is shown in the image below. Figure 4 As shown.

[0058] 3. Polishing treatment ① The non-marked surface of the third sample was initially polished using 3000-grit SiC sandpaper to reduce surface roughness. The sample morphology after sanding the non-marked surface is shown in the image below. Figure 5 As shown.

[0059] ② A SiO2 suspension with a particle size of 0.05μm was used as the polishing medium, and mechanical polishing was performed using a Naibo LAP-2SE metallographic polishing machine. The selected polishing cloth was velvet cloth, and anhydrous ethanol was used as the lubricating medium. During the polishing process, the grinding direction should be along the rolling direction of the material, the machine speed should be controlled at 150rpm / min, and polishing should continue for 10 minutes.

[0060] ③ Electropolishing was performed using a perchloric acid solution (6% by volume), with a controlled voltage of 30V, a current of 1.5A, and a polishing time of 20s. Immediately after polishing, the sample was rinsed in anhydrous ethanol and sonicated for 2 minutes to obtain the sample to be observed for magnetic domain observation of the etched lines on oriented silicon steel. The morphology of the sample after electropolishing on the non-etched surface is shown in the image below. Figure 6 As shown.

[0061] 4. Observation of magnetic domains after electrolytic polishing ① Magnetic domain observation of the sample was performed using the powder method. First, the magnetic fluid was prepared: 0.3 g of commercially available iron oxide particles (800-1000 mesh) was weighed, dissolved in 150 ml of deionized water, and placed in a rotating water bath for magnetic stirring. The stirring speed was set to 600 rpm / min, and the temperature was raised to 60℃ and maintained for 5 min. Then, 10 ml of 0.1 mol / L sodium benzenesulfonate activator was gradually added dropwise, the stirring speed was adjusted to 1000 rpm, and the temperature was maintained for another 30 min. After preparation, the magnetic fluid was added dropwise to the non-marked surface of the sample, allowed to stand for 10 min, and then the magnetic domain image was captured using the powder method. The positions of the mark lines were recorded.

[0062] ② FSD Magnetic Domain Imaging: Magnetic domain imaging is performed using the FSD detector in a scanning electron microscope (SEM). During observation, the sample is tilted to a range of 70°–75°, the accelerating voltage is set to 30 kV, and the working distance is adjusted to approximately 15 mm. Simultaneously, the distance between the FSD probe and the sample surface is adjusted to 150 mm to obtain high-resolution FSD magnetic domain images, enabling detailed observation of the magnetic domain structure. An EBSD probe can be connected simultaneously to obtain both magnetic domain and crystal orientation information.

[0063] The magnetic domain morphology of the sample under observation at different locations of the indentation is shown in the following figure. Figure 7 As shown, the area within the white dashed box represents the magnetic domains inside the etch line, and the length of the arrow represents the width of the laser etch.

[0064] The magnetic domain morphology and corresponding crystal orientation information of the sample to be observed in Example 1 are shown in the figure below. Figure 8 As shown. In Figure 8 In the diagram, within the white dashed line, fine comb-like magnetic domains are clearly visible inside the laser-etched marks, and the width of the etched lines can be obtained using the scale information. Simultaneously, this method also yields surfaces of good quality, and crystal orientation information can be obtained from the inverse pole figure.

[0065] Comparative Example 1 This comparative example is modified from the one disclosed in Example 1 as follows: In the process of preparing the sample to be observed for magnetic domain observation of the etched lines of oriented silicon steel, no AB glue is applied to the etched surface.

[0066] The magnetic domain morphology and corresponding crystal orientation information of the sample under observation in Comparison 1 are shown in the figure below. Figure 9 As shown. In Figure 9 In the image, the red box shows the wedge-shaped magnetic domains near the laser-etched surface. Without AB glue to protect the etched surface, the additional stress from the laser-etched surface almost disappears due to electropolishing; therefore, the effect of the laser-etched surface on the magnetic domains cannot be displayed through the magnetic domain diagram. EBSD crystal orientation information can be obtained from the inverse pole figure.

[0067] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages: In this embodiment, the stress information of the laser engraving is retained, avoiding the loss of magnetic domain information caused by traditional electrolytic polishing methods, thereby ensuring the integrity and authenticity of the magnetic domain structure.

[0068] In this embodiment, AB glue or 502 glue is used to apply a protective coating to the scratched surface. This effectively preserves the coating on the scratched surface during the sample preparation process of acid washing to remove the coating. Therefore, stress information near the scratched line is preserved during electrolytic polishing, avoiding magnetic domain loss caused by traditional polishing methods.

[0069] In this embodiment, the polishing process is optimized, including adjusting the polishing steps and optimizing the concentrations of the polishing slurry and electrolyte, to improve polishing quality and make the magnetic domain structure more clearly discernible. High-resolution magnetic domain images can be obtained in the FSD imaging mode of a scanning electron microscope (SEM), and microscopic parameters such as the width of the scribe lines can be accurately measured.

[0070] In this embodiment, the scanning electron microscope (SEM) imaging parameters are optimized, employing a 70° tilt angle, a 30 kV accelerating voltage, and a 15 mm working distance. These parameters not only ensure compatibility with EBSD data acquisition but also support simultaneous observation of magnetic domains and crystal orientation (requiring both FSD and EBSD probes). This allows for combined analysis of magnetic domain and crystal orientation data, providing more precise microstructural information for studying the stress-affected region near the indentation line.

[0071] In this embodiment, the traditional powder method for magnetic domain observation is suitable. The prepared sample can still be used for powder method magnetic domain imaging and can be compared and analyzed with electron microscopy magnetic domain images, which enhances the reliability of magnetic domain research and provides important support for the microstructure optimization and magnetic property analysis of oriented silicon steel.

[0072] In this embodiment, not only is the preparation process of magnetic domain observation samples of oriented silicon steel optimized, but the imaging quality of magnetic domains is also improved. Furthermore, by combining crystal orientation information, the application field of magnetic property research is broadened, which has high technical innovation and practical value.

[0073] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An application of a sample preparation method for observing magnetic domains along indentation lines in grain-oriented silicon steel, characterized in that, The applications include: The powder texture method is used to initially locate the position of the scratch line on the non-scratched surface of the sample to be observed; the position of the scratch line is transferred to the non-scratched surface by the stress effect of the scratch line on the scratched surface. FSD magnetic domain imaging was performed at the location of the scribe line under a scanning electron microscope to obtain a high-resolution image of the FSD magnetic domain inside the scribe line. The sample preparation method for the sample to be observed includes: The grain-oriented silicon steel sample was cut using wire cutting to obtain a first sample with a set size. The etched and non-etched surfaces of the first sample are distinguished, and a protective adhesive is applied to the etched surface to preserve the stress information and magnetic domain structure of the etched surface, thus obtaining the second sample; the protective adhesive is AB glue or 502 glue; The inorganic salt coating on the non-marked surface of the second sample is removed to obtain the third sample; and The non-marked surface of the third sample was subjected to SiC sandpaper preliminary polishing, silica suspension mechanical polishing, and perchloric acid electrolytic polishing in sequence to improve the surface smoothness of the non-marked surface and retain the stress-affected area at the mark line of the marked surface, thus obtaining the sample to be observed for magnetic domain observation of the mark line of oriented silicon steel.

2. The application according to claim 1, characterized in that, The process of removing the inorganic salt coating from the non-marked surface of the second sample to obtain the third sample includes: The second sample was first immersed in dilute hydrochloric acid to remove the inorganic salt coating on the non-marked surface of the second sample; The second sample after the first soaking was then soaked in a sodium bicarbonate solution to remove residual dilute hydrochloric acid. The second sample after the second soaking was washed to obtain the third sample.

3. The application according to claim 2, characterized in that, The volume fraction of the dilute hydrochloric acid is 8%–10%, and the first soaking time is 3.5 h–4.5 h; and / or, The volume fraction of the sodium bicarbonate solution is 4% to 6%, and the second soaking time is 8 min to 12 min.

4. The application according to claim 1, characterized in that, The process of sequentially performing SiC sandpaper preliminary polishing, silica suspension mechanical polishing, and perchloric acid electrolytic polishing on the non-marked surface of the third sample includes: The non-marked surface of the third sample was initially polished using SiC sandpaper to reduce surface roughness; the SiC sandpaper had a mesh size of 3000. The non-marked surface of the third sample after preliminary grinding was mechanically polished using SiO2 suspension as the polishing medium; the particle size of SiO2 was 0.04μm~0.06μm. The non-marked surface of the mechanically polished third sample was electropolished using a perchloric acid solution with a volume fraction of 5%–7%. The third sample, after electropolishing, was then cleaned.

5. The application according to claim 4, characterized in that, The mechanical polishing uses a Naibo LAP-2SE metallographic polishing machine. The polishing cloth used in the mechanical polishing is velvet cloth, the lubricating medium used in the mechanical polishing is anhydrous ethanol, and the polishing direction of the mechanical polishing is along the rolling direction of the material.

6. The application according to claim 5, characterized in that, The mechanical polishing equipment operates at a speed of 150 rpm / min to 200 rpm / min, and the mechanical polishing time is 8 min to 12 min.

7. The application according to claim 4, characterized in that, The electropolishing process includes the following parameters: voltage of 30V, current of 1A to 2A, and polishing time of 10s to 25s.

8. The application according to claim 1, characterized in that, The application also includes: By combining an electron backscatter diffraction probe, magnetic domain images and crystal orientation information inside the scribe line can be obtained simultaneously.

9. The application according to claim 1, characterized in that, The FSD magnetic domain imaging includes the following parameters: sample tilt angle of 70° to 75°, accelerating voltage of 30 kV, working distance of 14 mm to 16 mm, and distance between the FSD probe and the sample surface of 150 mm.

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