A rapid preparation method of steel sample for transmission electron microscope detection

Abstract

This invention provides a rapid preparation method for steel samples for transmission electron microscopy (TEM), relating to the field of physical analysis of steel materials. It is applied to the preparation of various steel samples, including heat-sensitive steels, using a composite binder of cellulose acetate, acetone, silica, and alumina. The binder is used to adhere one side of a wire-cut steel sample sheet to the sheet fixing surface of a grinding aid. A grinding aid area, parallel to the bottom surface of the sheet fixing surface, is provided on the grinding aid device. The grinding aid area is pressed, and sandpaper with progressively increasing grit is used to grind one side until a first preset thickness is reached. Then, the other side is switched, and sandpaper with progressively increasing grit is used to grind the second side until a second preset thickness is reached. The ground sheet is removed, thinned, punched, and electropolished to obtain the target steel sample. This invention can rapidly prepare steel sample sheets with a thickness of 30-50 µm, and the method is simple and has a high success rate.

Description

Technical Field

[0001] This invention relates to the field of physical analysis technology for steel materials, and specifically to a rapid preparation method for steel samples for transmission electron microscopy (TEM) analysis. Background Technology

[0002] Transmission electron microscopy (TEM) analyzes samples by collecting electrons that pass through them, thereby obtaining information such as sample morphology, phase structure, dislocations, and atomic arrangement. Generally, a 200kV TEM can analyze samples with a maximum thickness of approximately 200nm. However, steel samples need to be thinned to below 100µm before TEM testing. For magnetic samples such as silicon steel and martensitic steel, the thickness needs to be controlled at around 40µm. Then, the thickness of the central region of the sample is reduced to just enough to create a perforation, resulting in a region less than 200nm thick near the perforation for microstructural observation. For high-resolution testing, the thickness of this thin region should be less than 20nm. Furthermore, in addition to controlling the sample thickness, it is crucial to avoid introducing stress during sample preparation. The presence of stress can cause the thin region to curl or crack during the final thinning stage due to stress release, resulting in a sample without a thin region for TEM observation. In severe cases, it can even directly lead to erroneous information such as dislocations within the sample.

[0003] Currently, there are two main methods for grinding steel samples to below 100µm: One method involves cutting the sample into thin slices of about 0.5mm thickness using wire cutting, and then grinding the slices with different grit sandpaper by pressing with fingers or with rubber or other objects until the slices are below 100µm. This method typically takes 2 hours or even longer to prepare a sample and has disadvantages such as low sample success rate, easy introduction of internal stress into the sample, long sample preparation time, and inability to guarantee success. The other method uses specialized equipment... After clamping the steel sample, it is ground to a thickness of less than 100µm using sandpaper of different grits. Solid paraffin wax is typically used to fix the sample to a standard fixture. The solid paraffin wax is melted into a liquid and then solidified to secure the sample to the fixture. Heating to 120℃ or even higher is generally required to melt the solid paraffin wax. Therefore, the sample needs to be heated during both fixing and sampling. When the sample is ground to less than 60µm, the thin sheet may bend upon heating, introducing stress into the sample. Some steel samples may also precipitate during heating. Grinding with a dedicated sample grinder has drawbacks: a small sample preparation area and long processing time. This method also requires heating during sampling, typically to 120℃ or higher. When the sample is ground to less than 60µm, the thin sheet may bend upon heating, introducing stress into the sample. Some steel samples may also precipitate during heating. Furthermore, this method is not suitable for analyzing some heat-sensitive materials in steel.

[0004] Therefore, there is a need to develop a new method for preparing steel samples with a thickness of less than 100 μm, which has the advantages of wide applicability and short processing time. Summary of the Invention

[0005] The purpose of this invention is to provide a rapid preparation method for steel samples for transmission electron microscopy (TEM) testing. This method can rapidly prepare steel sample thin sections with a thickness of 30~50µm within 0.5h, with a high sample success rate. It does not require sample heating, has low personnel requirements, and can be mastered with simple training. It is applicable to the preparation of thin section samples of various types of steel samples.

[0006] To achieve the above objectives, the present invention proposes the following technical solution: a rapid preparation method for steel samples for transmission electron microscopy (TEM) analysis, applicable to the preparation of various steel samples, including heat-sensitive steel grades, specifically comprising the following steps:

[0007] A binder is prepared, comprising cellulose acetate, acetone, silica, and alumina, wherein the ratio of cellulose acetate, acetone, silica, and alumina in the binder is 0.2~2g: 5~50mL: 0.1~0.3g: 0.1~0.3g;

[0008] A thin sheet of wire-cut steel sample is obtained, and one side of it is bonded to the sheet fixing surface of the grinding auxiliary device using an adhesive to obtain a sample to be ground. The grinding auxiliary device has a grinding auxiliary area on the side opposite to the sheet fixing surface. The bottom surface of the grinding auxiliary area is parallel to the sheet fixing surface, and the grinding auxiliary area and the sheet fixing surface are respectively located on two detachable parts of the grinding auxiliary device.

[0009] Press down on the grinding auxiliary area on the sample to be ground, and start grinding one side in sequence with sandpaper of 180 grit, 800 grit, 1200 grit and 1500 grit, and stop grinding on that side of the sheet when the first preset thickness is reached;

[0010] Separate the thin sheet of the steel sample that has been ground on one side on the grinding auxiliary device, and use an adhesive to bond the grinding surface of the thin sheet to the sheet fixing surface of the grinding auxiliary device. Then, use 800-grit, 1200-grit, and 1500-grit sandpaper to grind the thin sheet on the second side in sequence until it is ground to the second preset thickness, and then end the grinding.

[0011] The thin sheet, after the second side grinding is completed, is removed from the grinding aid device and subjected to thinning, punching, and electrolytic polishing to obtain a target steel sample for transmission electron microscopy. The process of removing the thin sheet, after grinding on either side, from the grinding aid device is as follows: the entire grinding aid device with the thin sheet fixed is immersed in a mixed solvent of acetone, ethanol, and sodium dodecylbenzenesulfonate powder in a ratio of 10~15mL:5~7mL:0.1~0.2g for 1~5min, and then the grinding aid device is shaken to directly separate the thin sheet.

[0012] Furthermore, the ratio of cellulose acetate, acetone, silica, and alumina in the adhesive is 1g:10mL:0.2g:0.2g, wherein the silica is spherical particles with an average particle size of 0.02µm, and the alumina is polyhedral particles with an average particle size of 0.03µm.

[0013] Furthermore, the ratio of acetone, ethanol, and sodium dodecylbenzenesulfonate powder in the mixed solvent is 15 mL: 6 mL: 0.15 g.

[0014] Furthermore, the specific process of sequentially grinding the thin sheet on one side to the first preset thickness using 180-mesh, 800-mesh, 1200-mesh, and 1500-mesh sandpaper is as follows:

[0015] Grind the sheet to a thickness of no more than 250µm using 180-grit sandpaper, then replace with 800-grit sandpaper and continue grinding; grind the sheet to a thickness of no more than 200µm using 800-grit sandpaper, then replace with 1200-grit sandpaper and continue grinding; grind the sheet to a thickness of no more than 170µm using 1200-grit sandpaper, then replace with 1500-grit sandpaper and continue grinding to a thickness of no more than 140µm.

[0016] Furthermore, the specific process of sequentially grinding the thin sheet with 800-grit, 1200-grit, and 1500-grit sandpaper to the second side to the second preset thickness is as follows:

[0017] Grind the sheet to a thickness of no more than 100µm using 800-grit sandpaper, then replace with 1200-grit sandpaper and continue grinding; grind the sheet to a thickness of no more than 80µm using 1200-grit sandpaper, then replace with 1500-grit sandpaper and continue grinding to a thickness of no more than 50µm.

[0018] Furthermore, the initial thickness of the obtained wire-cut steel sample sheet was less than 300µm.

[0019] Furthermore, the grinding auxiliary device includes a substrate, a base plate, and a fixing part, wherein the fixing part is fixedly connected to the substrate and the base plate;

[0020] The substrate and the bottom sheet are configured as rectangular plates of equal size, and the surfaces of the substrate and the bottom sheet are parallel. The side of the substrate away from the bottom sheet is configured as a sheet fixing surface, and two pairs of limiting holes are symmetrically arranged on its surface near the four sides. Limiting posts are respectively arranged on the side of the bottom sheet near the substrate at positions corresponding to each of the limiting holes. The limiting posts are adapted to the limiting holes, and when the limiting posts are adapted to the limiting holes, the ends of the limiting posts that extend into the limiting holes are flush with the sheet fixing surface.

[0021] The grinding auxiliary area is disposed on the side of the film away from the substrate, and is configured as a groove structure recessed into the film; two pairs of grinding auxiliary areas are arranged on the side, the positions of which correspond to the limiting holes, and the center lines connecting the two pairs of grinding auxiliary areas are perpendicular to each other.

[0022] Furthermore, the grinding auxiliary device is made of transparent glass.

[0023] Furthermore, during the grinding process, any side of the sheet is repeatedly and alternately ground by switching grinding directions, and the grinding directions of two adjacent switching are perpendicular to each other.

[0024] Furthermore, the aspect ratio of the rectangular plate structure's substrate is 8:5, its length is 40mm, and its thickness is 2mm.

[0025] As can be seen from the above technical solutions, the technical solutions of the present invention have achieved beneficial effects:

[0026] This invention discloses a rapid preparation method for steel samples used in transmission electron microscopy (TEM). This method is applied to the preparation of various steel samples, including heat-sensitive steels. Specifically, it includes: preparing an adhesive according to the following ratios: cellulose acetate, acetone, silica, and alumina: 0.2-2 g : 5-50 mL : 0.1-0.3 g : 0.1-0.3 g; using the adhesive to adhere one side of a wire-cut steel sample sheet to the sheet fixing surface of a grinding auxiliary device, thus obtaining the sample to be ground; a grinding auxiliary area is provided on the side of the grinding auxiliary device opposite to the sheet fixing surface, for grinding... The bottom surface of the grinding auxiliary area corresponds parallel to the sheet fixing surface, and the grinding auxiliary area and the sheet fixing surface are located on two separate components. Pressing down on the grinding auxiliary area of ​​the sample to be ground, grinding is initiated on one side using 180-grit, 800-grit, 1200-grit, and 1500-grit sandpaper sequentially. After grinding to the first preset thickness, the other side is switched, and 800-grit, 1200-grit, and 1500-grit sandpaper are used sequentially to grind the sheet on the second side until the second preset thickness is reached, ending the grinding process. The ground sheet is then removed, thinned, punched, and electrolytically polished to obtain the target steel sample. This invention can rapidly prepare steel sample sheets with a thickness of 30-50µm, and the method is simple and has a high success rate.

[0027] This invention addresses several issues in current transmission electron microscopy (TEM) sample preparation for steel, including sample deformation due to heating during sampling, high personnel requirements, high failure rates, and low efficiency. The method utilizes a specially formulated binder, a dedicated grinding aid, and a mixed solvent to ensure that the sheet does not detach from the substrate during grinding and allows for rapid sample removal after grinding without the need for heating. This solves the problem of temperature-induced changes in the internal structure and morphology of heat-sensitive steel samples ground to 30-50 µm thickness, which can mislead research results when heated during sampling. Furthermore, the dedicated grinding aid is simple to assemble and use. On the one hand, by separating the grinding auxiliary area and the sheet fixing surface onto two separate components, direct contact with the sheet during grinding can be avoided, thus preventing stress and improving the efficiency and success rate of grinding. On the other hand, even those without prior experience can easily master grinding after simple training, requiring no special skills from the sample preparation personnel. This solves the problems of high personnel requirements in current transmission sample preparation and the inability to accurately control thickness when using automated grinding and polishing machines, leading to high sample preparation failure rates. The disclosed grinding method significantly improves grinding efficiency, eliminates interference from human factors, and allows trained personnel to grind samples that meet requirements within 30 minutes, significantly improving sample preparation efficiency and success rate. In short, the method of this invention is simple, widely applicable, and highly efficient.

[0028] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other.

[0029] The foregoing and other aspects, embodiments, and features of the teachings of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0030] The accompanying drawings are not drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0031] Figure 1 This is a flowchart of the rapid preparation method for steel samples for transmission electron microscopy (TEM) analysis disclosed in this invention.

[0032] Figure 2 Explosion view of the grinding auxiliary device disclosed in this invention Figure 1 ;

[0033] Figure 3 Explosion view of the grinding auxiliary device disclosed in this invention Figure 2 ;

[0034] Figure 4 Post-assembly view of the grinding auxiliary device disclosed in this invention Figure 1 ;

[0035] Figure 5 Post-assembly view of the grinding auxiliary device disclosed in this invention Figure 2 ;

[0036] Figure 6 X70M pipeline steel samples were prepared using the method of this invention for transmission electron microscopy observation. Figure 1 ;

[0037] Figure 7 X70M pipeline steel samples were prepared using the method of this invention for transmission electron microscopy observation. Figure 2 ;

[0038] Figure 8 Microstructure diagram of sample No. 2 prepared using the method of the present invention;

[0039] Figure 9 The microstructure diagram of sample No. 2 was prepared using the method of Comparative Example 1.

[0040] The specific meanings of each mark in the diagram are as follows:

[0041] 1-Fasting screw, 2-Mounting hole, 3-Base plate, 4-Rectangular protrusion, 5-Cylindrical protrusion, 6-Base plate, 7-Rectangular hole, 8-Cylindrical hole, 9-Thin sheet, 10-Grinding auxiliary area. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0043] The terms "first," "second," and similar words used in the specification and claims of this patent application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" mean that the element or object preceding "comprising" encompasses the features, integrals, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0044] The existing methods for preparing steel samples for transmission electron microscopy (TEM) testing suffer from problems such as high skill requirements for sample preparation personnel, high failure rates, low efficiency, and sample deformation caused by heating during the sampling process using standard grinding tools. Therefore, this invention aims to propose a rapid preparation method for steel samples for TEM testing. By designing a new binder, a new grinding auxiliary device, and a new grinding method, a rapid sample preparation method with a high success rate is achieved, thus solving the aforementioned problems.

[0045] Specifically, the rapid preparation method for steel samples for transmission electron microscopy (TEM) disclosed in this invention is applicable to the preparation of various steel samples, including heat-sensitive steels, such as... Figure 1 As shown, the specific steps include the following:

[0046] Step S102: Prepare an adhesive, which includes cellulose acetate, acetone, silica, and alumina. The ratio of cellulose acetate, acetone, silica, and alumina in the adhesive is 0.2~2g: 5~50mL: 0.1~0.3g: 0.1~0.3g. In the example, the ratio of cellulose acetate, acetone, silica, and alumina in the adhesive is 1g: 10mL: 0.2g: 0.2g, wherein the silica is spherical particles with an average particle size of 0.02µm, and the alumina is polyhedral particles with an average particle size of 0.03µm.

[0047] Step S104: Obtain a thin sheet 9 of the wire-cut steel sample. The initial thickness of the thin sheet 9 is less than 300µm. Adhesive is used to attach one side of the thin sheet 9 to the sheet fixing surface of the grinding auxiliary device to obtain the sample to be ground. The grinding auxiliary device has a grinding auxiliary area 10 on the side opposite to the sheet fixing surface. The bottom surface of the grinding auxiliary area 10 is parallel to the sheet fixing surface. The grinding auxiliary area 10 and the sheet fixing surface are respectively located on two detachable parts of the grinding auxiliary device.

[0048] Step S106: Press the grinding auxiliary area 10 on the sample to be ground, and begin grinding one side sequentially with sandpaper of 180 grit, 800 grit, 1200 grit, and 1500 grit, stopping grinding on that side of the sheet 9 when it reaches a first preset thickness; specifically: grind the sheet 9 with 180 grit sandpaper until the thickness does not exceed 250µm, then replace with 800 grit sandpaper and continue grinding; grind the sheet 9 with 800 grit sandpaper until the thickness does not exceed 200µm, then replace with 1200 grit sandpaper and continue grinding; grind the sheet 9 with 1200 grit sandpaper until the thickness does not exceed 170µm, then replace with 1500 grit sandpaper and continue grinding until the thickness does not exceed 140µm. Of course, this invention only lists a preferred sandpaper combination; other combinations of sandpaper grits used to achieve the technical effect of grinding the sheet 9 with gradually increasing grit to reduce its thickness should also be within the scope of this invention.

[0049] Step S108: Separate the sheet 9 of the steel sample that has completed single-sided grinding on the grinding auxiliary device. Use an adhesive to bond the grinding surface of the sheet 9 to the sheet fixing surface of the grinding auxiliary device. Grind the sheet 9 on the second side sequentially with 800-grit, 1200-grit, and 1500-grit sandpaper until the second preset thickness is reached, and then end the grinding process. Specifically: grind the sheet 9 with 800-grit sandpaper until the thickness does not exceed 100µm, then replace with 1200-grit sandpaper and continue grinding; grind the sheet 9 with 1200-grit sandpaper until the thickness does not exceed 80µm, then replace with 1500-grit sandpaper and continue grinding until the thickness does not exceed 50µm.

[0050] Step S110: Remove the thin sheet 9, after grinding the second side, from the grinding auxiliary device to obtain the target steel sample for transmission electron microscopy. The process of removing the thin sheet after grinding either side from the grinding auxiliary device involves immersing the entire grinding auxiliary device, which holds the thin sheet, in a mixed solvent of acetone, ethanol, and sodium dodecylbenzenesulfonate powder in a ratio of 10-15 mL: 5-7 mL: 0.1-0.2 g for 1-5 minutes, then shaking the grinding auxiliary device to directly separate the thin sheet. In this embodiment, the ratio of acetone, ethanol, and sodium dodecylbenzenesulfonate powder in the mixed solvent is 15 mL: 6 mL: 0.15 g.

[0051] Combination Figures 2 to 5 As shown, the structure of the grinding auxiliary device disclosed in this invention is as follows: it includes a substrate 6, a bottom plate 3 and a fixing part, wherein the fixing part is fixedly connected to the substrate 6 and the bottom plate 3;

[0052] As shown in the figure, the substrate 6 and the bottom sheet 3 are rectangular plate structures of equal size, and the surfaces of the substrate 6 and the bottom sheet 3 are parallel. The side of the substrate 6 away from the bottom sheet 3 is a sheet fixing surface, and two pairs of limiting holes are symmetrically arranged on its surface near the four sides. Limiting posts are respectively arranged on the side of the bottom sheet 6 near the substrate 3 at positions corresponding to each of the limiting holes. The limiting posts are adapted to the limiting holes, and when the limiting posts are adapted to the limiting holes, their ends extending into the limiting holes are flush with the sheet fixing surface. The grinding auxiliary area 10 is arranged on the side of the bottom sheet 3 away from the substrate 6, and is a recessed groove structure that is recessed into the bottom sheet 3. In this embodiment, it is a rectangular groove structure. Two pairs of grinding auxiliary areas 10 are arranged on the side, corresponding to the limiting holes, and the center lines connecting the two pairs of grinding auxiliary areas 10 are perpendicular to each other. To ensure the adhesive adheres tightly to the sheet fixing surface, the grinding auxiliary device is made of transparent glass. In this embodiment, to facilitate transmission electron microscopy observation, the aspect ratio of the rectangular plate structure film 3 is set to 8:5, the length is set to 40mm, and the thickness is set to 2mm.

[0053] During the specific grinding process, any side of the thin slice 9 of the wire-cut steel sample is repeatedly and alternately ground by switching grinding directions, with adjacent grinding directions being perpendicular to each other. For sampling, the grinding aid device with the target steel sample adhering to it is immersed in the mixed solution. After waiting 1-5 minutes, such as 1 minute, the grinding aid device is shaken to directly separate the target steel sample. The inclusion of silica and alumina powder in the binder of this invention allows them to work together to create micro-gaps in the binder, enabling the mixed solvent to quickly dissolve and remove the binder while providing sufficient adhesion to achieve rapid sample detachment within 1 minute. The addition of sodium dodecylbenzenesulfonate and ethanol to the mixed solvent to increase the solvent penetration rate is another key factor in achieving rapid sample detachment.

[0054] The rapid preparation method for steel samples for transmission electron microscopy (TEM) analysis disclosed in this invention will be further described below with reference to specific embodiments.

[0055] Example 1

[0056] Prepare the binder: Weigh 5g of cellulose acetate using a balance and pour it into a beaker. Measure 50mL of acetone using a graduated cylinder and pour the acetone into the beaker containing the cellulose acetate. Weigh 1g of silicon dioxide and 1g of aluminum oxide separately using a balance and pour them into the beaker. Stir with a glass rod until the cellulose acetate is completely dissolved. Pour the mixed solution into a sealable brown bottle and let it stand until there are no more bubbles in the liquid before use.

[0057] Assembly and sample loading of the grinding auxiliary device: The substrate 6 and the film 3 are overlapped. The substrate 6 has two pairs of limiting holes, one pair of cylindrical holes 8 and one pair of rectangular holes 7. Correspondingly, the film 3 has two pairs of limiting posts, each set as a cylindrical protrusion 5 adapted to the cylindrical holes 8 and a rectangular protrusion 4 adapted to the rectangular holes 7. The fixing part consists of fastening screws 1 corresponding to the mounting holes 2 on the film 3 and the substrate 6. The fastening screws 1, through the mounting holes 2, fasten the film 3 and the substrate 6 to form the grinding auxiliary device, i.e., the stacked effect. The steel sample was made of X70M pipeline steel. The sample was cut into thin, non-deformable sheets 9 with a thickness of less than 300µm using a precision cutting machine. The width of sheet 9 was 15mm × 10mm. The thickness of sheet 9 was measured to be 270µm using a micrometer, and the initial thickness t0 was recorded. The assembled grinding auxiliary device was placed flat on the table with the substrate 6 facing upwards. Adhesive was dripped onto the substrate 6. Any side of the sample to be ground was pressed against the adhesive side of the substrate 6. The pressed surfaces were pressed until there were no air bubbles and left for 2 minutes.

[0058] Single-sided grinding of the sample: Before grinding, the overall thickness t of the stack containing the thin sheet sample was measured with a micrometer and found to be 2300µm. The maximum final thickness t of the first grinding with 180-grit sandpaper was also calculated. 1计算 =t+250-t0, i.e., 2280µm; the maximum final thickness t for grinding with 800-grit sandpaper. 2计算 =t+200-t0, which is 2230µm, the maximum final thickness t for grinding with 1200-grit sandpaper. 3计算 =t+170-t0, i.e., 2200µm; the maximum final thickness t for grinding with 1500-grit sandpaper. 4计算=t+140-t0, i.e., 2170µm; the final thickness of each type of sandpaper should not exceed its corresponding maximum final thickness; during grinding, place your fingers on the grinding auxiliary area 10, generally using the index and middle fingers of one hand to press down on two parallel areas of the grinding auxiliary area 10 respectively, and grind in one direction, rotating 90°, then switch to the other two parallel areas of the grinding auxiliary area 10 and press down to grind in one direction. The grinding directions should be consistent to ensure that the grinding directions of the two samples are basically 90°. After grinding for 1 minute, wash the entire grinding auxiliary device with water and blow it dry before measuring the thickness. Repeat this alternating grinding process; first use 180-grit sandpaper for grinding, pressing down on the long side with your fingers during grinding. For grinding auxiliary area 10, after grinding for 1 minute, rinse the entire grinding sample auxiliary device with water and dry it, then measure the thickness. When the actual thickness is 2275µm, replace with 800-grit sandpaper. Press down on the short side of grinding auxiliary area 10 with your finger, after grinding for 1 minute, rinse the entire grinding sample auxiliary device with water and dry it, then measure the thickness. When the thickness is 2228µm, replace with 1200-grit sandpaper. Continue pressing down on the long side of grinding auxiliary area 10, after grinding for 1 minute, rinse the entire grinding sample auxiliary device with water and dry it, then measure the thickness. When the thickness is 2196µm, replace with 1500-grit sandpaper. Press down on the short side of grinding auxiliary area 10, after grinding for 1 minute, rinse the entire grinding sample auxiliary device with water and dry it, then measure the thickness. When the thickness is 2168µm, stop grinding.

[0059] Second-side grinding of the sample: The grinding auxiliary device, which has been ground to the target thickness range on one side, is immersed in the mixed solvent for 1 minute. The auxiliary device is held with tweezers and gently swung in the solution until the sheet 9 falls off. The sheet 9 is removed, cleaned, and dried. The actual thickness T0 of the sheet 9 is measured to be 144µm. The surface that has been ground with 1500-grit sandpaper is then attached to the sheet fixing surface of the grinding auxiliary device with adhesive and glued together. The overall thickness T is measured to be 2168µm. The maximum termination thickness T of the second grinding with 800-grit sandpaper is calculated. 1计算 =T+100-T0, i.e., 2124µm; the maximum final thickness T for grinding with 1200-grit sandpaper. 2计算 =T+80-T0, i.e., 2104µm; the maximum final thickness T for grinding with 1500-grit sandpaper. 3计算=T+50-T0, i.e., 2074µm; In actual grinding, first use 800-grit sandpaper for grinding. While grinding, press down on the grinding auxiliary area 10 on the long side with your finger. After grinding for 1 minute, rinse the entire grinding sample auxiliary device with water and blow it dry, then measure the thickness. When the actual thickness is 2162µm, replace with 1200-grit sandpaper. Press down on the grinding auxiliary area 10 on the short side with your finger. After grinding for 1 minute, rinse the entire grinding sample auxiliary device with water and blow it dry, then measure the thickness. When the thickness is 2120µm, replace with 1500-grit sandpaper. Finally, press down on the grinding auxiliary area 10 on the long side. After grinding for 1 minute, rinse the entire grinding sample auxiliary device with water and blow it dry, then measure the thickness. When the thickness is 2070µm, stop grinding.

[0060] Sampling: The entire grinding auxiliary device was immersed in a mixed solvent for 1 minute. The auxiliary device was held with tweezers and gently agitated in the solution until sheet 9 detached. The sheet was removed, cleaned, and dried. The thickness of sheet 9 after grinding was measured to be 46 µm. The entire process took 22 minutes. The sample was then subjected to subsequent thinning, punching, and electrolytic polishing to obtain the target steel sample for transmission electron microscopy (TEM). The TEM observation results of the target steel sample are as follows: Figure 6 and Figure 7 As shown in the figure, the tissue and precipitated phase are clearly visible, and the sample is not deformed.

[0061] Comparative Example 1

[0062] An automated grinding and polishing sample preparation method using existing grinding and polishing machines was employed. After clamping the sample fixing device with a fixture, double-sided tape was used to adhere the sample sheet to the fixing device. Then, two corresponding sides of the sample were ground and polished in two separate processes. During each grinding and polishing process, the grinding and polishing were completed by controlling the pressure and time of the grinding and polishing machine. After grinding and polishing of either side, the entire sample fixing device was immersed in a glass containing acetone solution, and the glass was placed in an ultrasonic cleaner. The ultrasonic cleaner temperature was set to 50°C, and the cleaning time was approximately 2 minutes. Afterward, the edge of the sample sheet was gently pushed with tweezers to remove the sample sheet from the double-sided tape. Using Example 1 and Comparative Example 1, 10 wire-cut thin sections of cold-deformed 18Ni aging steel were prepared as steel samples for transmission electron microscopy (TEM) analysis. The preparation results are shown in Table 1 below.

[0063] Table 1 shows the sample preparation results of steel samples for transmission electron microscopy in Example 1 and Comparative Example 1, respectively.

[0064]

[0065] As shown in Table 1, the sample preparation method of this invention achieves a 100% success rate, while the success rate of the sample preparation method using an automatic grinding and polishing machine in Comparative Example 1 is only 40%. The reason is that, as is known to those skilled in the art, in the process of controlling the sample thickness by adjusting the pressure and grinding and polishing time of the grinding and polishing machine, the ultimate goal of pressure control is to control the downward pressure on the sample. However, pressure fluctuates, and the force exerted by the grinding and polishing machine on the sample also fluctuates. Therefore, automatic grinding and polishing machines have specific accessories for preparing samples with a fixed thickness, but this method also has micron-level deviations. In terms of micron-level thickness control, even slight fluctuations can lead to a rapid decrease in the sample grinding and polishing thickness, causing the sample to be ground away in the first grinding and polishing process, thus resulting in sample preparation failure.

[0066] Further monitoring of microscopic precipitates was conducted on the steel samples used for transmission electron microscopy in Example 1 and Comparative Example 2, with respect to sample number 2. The results are as follows: Figure 8 and Figure 9 As shown, the technical solution of this application utilizes a mixed solvent to sample, ensuring that the microscopic precipitates in the sample remain regular and minimal in their pre-polishing state, thus preserving the sample's microstructure. In contrast, the automated polishing sample preparation method using acetone combined with ultrasonic heating results in microscopic changes in the sample, leading to more irregular precipitates, altering the internal structure, and consequently failing to accurately reflect the sample's microstructure. The rapid sample preparation method proposed in this invention significantly improves the sample preparation success rate compared to existing technologies and effectively addresses the impact of thermal processes in existing sample preparation schemes on the microscopic state of heat-sensitive steel sheet.

[0067] This invention addresses the problems of sample deformation, high personnel requirements, high failure rate, and low efficiency in the preparation of 30-50 μm steel samples for transmission electron microscopy (TEM) testing. By configuring a new binder, designing a new grinding auxiliary device, and proposing a new grinding method, the preparation process for TEM steel samples is simplified and accelerated, eliminating the need for heating and significantly improving the success rate. The new binder allows for rapid sample removal without heating, resolving the issues of sample deformation and thermal changes to the sample structure and second phase during heating, thus improving the accuracy of subsequent analysis. The new grinding auxiliary device is simple to assemble and use, requires no special skills from the personnel, and reduces stress introduction during grinding, further enhancing the success rate when combined with the binder. The new grinding method allows for sample preparation to achieve the required thickness within 0.5 hours, significantly improving sample preparation efficiency.

[0068] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A rapid preparation method for steel samples for transmission electron microscopy (TEM) examination, characterized in that, This method is applied to the preparation of various steel samples, including heat-sensitive steels, and specifically includes the following steps: A binder is prepared, comprising cellulose acetate, acetone, silica, and alumina, wherein the ratio of cellulose acetate, acetone, silica, and alumina in the binder is 0.2~2g: 5~50mL: 0.1~0.3g: 0.1~0.3g; A thin sheet of wire-cut steel sample is obtained, and one side of it is bonded to the sheet fixing surface of the grinding auxiliary device using an adhesive to obtain a sample to be ground. The grinding auxiliary device has a grinding auxiliary area on the side opposite to the sheet fixing surface. The bottom surface of the grinding auxiliary area is parallel to the sheet fixing surface, and the grinding auxiliary area and the sheet fixing surface are respectively located on two detachable parts of the grinding auxiliary device. Press down on the grinding auxiliary area on the sample to be ground, and start grinding one side in sequence with sandpaper of 180 grit, 800 grit, 1200 grit and 1500 grit, and stop grinding on that side of the sheet when the first preset thickness is reached; Separate the thin sheet of the steel sample that has been ground on one side on the grinding auxiliary device, and use an adhesive to bond the grinding surface of the thin sheet to the sheet fixing surface of the grinding auxiliary device. Then, use 800-grit, 1200-grit, and 1500-grit sandpaper to grind the thin sheet on the second side in sequence until it is ground to the second preset thickness, and then end the grinding. The thin sheet, after the second side grinding is completed, is removed from the grinding aid device and subjected to thinning, punching, and electrolytic polishing to obtain a target steel sample for transmission electron microscopy. The process of removing the thin sheet, after grinding on either side, from the grinding aid device is as follows: the entire grinding aid device with the thin sheet fixed is immersed in a mixed solvent of acetone, ethanol, and sodium dodecylbenzenesulfonate powder in a ratio of 10~15mL:5~7mL:0.1~0.2g for 1~5min, and then the grinding aid device is shaken to directly separate the thin sheet.

2. The rapid preparation method for steel samples for transmission electron microscopy according to claim 1, characterized in that, The binder contains cellulose acetate, acetone, silica, and alumina in a ratio of 1g: 10mL: 0.2g: 0.2g, wherein the silica is spherical particles with an average particle size of 0.02µm and the alumina is polyhedral particles with an average particle size of 0.03µm.

3. The rapid preparation method for steel samples for transmission electron microscopy according to claim 1, characterized in that, The ratio of acetone, ethanol, and sodium dodecylbenzenesulfonate powder in the mixed solvent is 15 mL: 6 mL: 0.15 g.

4. The rapid preparation method for steel samples for transmission electron microscopy according to claim 1, characterized in that, The specific process of grinding the thin sheet to the first preset thickness using sandpaper of 180 grit, 800 grit, 1200 grit, and 1500 grit in sequence on one side is as follows: Grind the sheet to a thickness of no more than 250µm using 180-grit sandpaper, then replace with 800-grit sandpaper and continue grinding; grind the sheet to a thickness of no more than 200µm using 800-grit sandpaper, then replace with 1200-grit sandpaper and continue grinding; grind the sheet to a thickness of no more than 170µm using 1200-grit sandpaper, then replace with 1500-grit sandpaper and continue grinding to a thickness of no more than 140µm.

5. The rapid preparation method for steel samples for transmission electron microscopy (TEM) examination according to claim 4, characterized in that, The specific process of grinding the thin sheet to the second preset thickness using 800-grit, 1200-grit, and 1500-grit sandpaper in sequence is as follows: Grind the sheet to a thickness of no more than 100µm using 800-grit sandpaper, then replace with 1200-grit sandpaper and continue grinding; grind the sheet to a thickness of no more than 80µm using 1200-grit sandpaper, then replace with 1500-grit sandpaper and continue grinding to a thickness of no more than 50µm.

6. The rapid preparation method for steel samples for transmission electron microscopy according to claim 1, characterized in that, The initial thickness of the obtained wire-cut steel sample sheet was less than 300µm.

7. The rapid preparation method for steel samples for transmission electron microscopy according to claim 1, characterized in that, The grinding auxiliary device includes a substrate, a base plate, and a fixing part, wherein the fixing part is fixedly connected to the substrate and the base plate; The substrate and the bottom sheet are configured as rectangular plates of equal size, and the surfaces of the substrate and the bottom sheet are parallel. The side of the substrate away from the bottom sheet is configured as a sheet fixing surface, and two pairs of limiting holes are symmetrically arranged on its surface near the four sides. Limiting posts are respectively arranged on the side of the bottom sheet near the substrate at positions corresponding to each of the limiting holes. The limiting posts are adapted to the limiting holes, and when the limiting posts are adapted to the limiting holes, the ends of the limiting posts that extend into the limiting holes are flush with the sheet fixing surface. The grinding auxiliary area is disposed on the side of the film away from the substrate, and is configured as a groove structure recessed into the film; two pairs of grinding auxiliary areas are arranged on the side, the positions of which correspond to the limiting holes, and the center lines connecting the two pairs of grinding auxiliary areas are perpendicular to each other.

8. The rapid preparation method for steel samples for transmission electron microscopy according to claim 1, characterized in that, The grinding auxiliary device is made of transparent glass.

9. The rapid preparation method for steel samples for transmission electron microscopy according to claim 1, characterized in that, During the grinding process, each side of the sheet is repeatedly and alternately ground by switching grinding directions, and the grinding directions of two adjacent switching are perpendicular to each other.

10. The rapid preparation method for steel samples for transmission electron microscopy according to claim 7, characterized in that, The rectangular plate structure has an aspect ratio of 8:5, a length of 40mm, and a thickness of 2mm.

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