A method for detecting a small-size dual-phase steel EBSD sample

Abstract

The present application relates to the technical field of metal sample preparation, and particularly relates to a detection method for a small-size dual-phase steel EBSD sample, which comprises the following steps: fixing the sample in a clamp; polishing the observation surface of the sample, mechanically polishing the polished observation surface, and cleaning the mechanically polished observation surface; placing the cleaned sample and the clamp in an electrolytic polishing device for electrolytic polishing, wherein: the electrolyte used is a mixed solution of 50%-70% perchloric acid, anhydrous ethanol and glycerol in a volume ratio of 1:6 to 8:1 to 3, the voltage is set to 20-25 V, the current density is 1.0-10.0 A / cm 2 , the polishing time is 10-25 s, and the electrolyte temperature is-20-5 DEG C; taking out the electrolytically polished sample from the clamp, cleaning the electrolytically polished observation surface, and obtaining the mirror surface observation surface for EBSD. The present application can improve the calibration rate during EBSD detection.

Description

Technical Field

[0001] This invention relates to the field of metal sample preparation technology, and specifically to a detection method for small-sized duplex steel EBSD samples. Background Technology

[0002] In the field of material microstructure characterization, electron backscatter diffraction (EBSD) is widely used to obtain information such as grain size, grain boundary feature distribution, crystal orientation, phase identification, and microtexture. It is an important tool for studying the relationship between material microstructure and properties. This technique has stringent requirements for sample surface quality, typically requiring mechanical grinding, fine polishing, or even vibratory polishing to remove surface stress layers and obtain a smooth surface free of residual stress.

[0003] Currently, the preparation of small-sized samples (length and width less than 5mm) mainly relies on hot or cold embedding methods. This method involves embedding the sample in a mold using acrylic or epoxy resin. After curing, the sample is polished to expose the test surface, and then removed through mechanical crushing or softening. While the sample can be removed, its small size makes it prone to chamfering (rounding edges) during subsequent polishing. Without the protection of the embedding material, uneven force during manual polishing can introduce deeper scratches and residual stress layers, leading to blurred EBSD Kikuchi bands and a significant decrease in calibration accuracy. Re-embedding and polishing is time-consuming and resource-intensive. Furthermore, the Joule heat generated during electropolishing can cause localized overheating, resulting in uneven current and potential distribution on the sample surface. This can not only cause unexpected phase transformations in the duplex steel structure but also exacerbate selective corrosion, making the over-polishing problem at the edges of small-sized samples even more pronounced. Summary of the Invention

[0004] To address the issues raised above regarding the reduced calibration rate of small-sized duplex steel EBSD samples when using traditional methods, which are prone to edge chamfering, surface scratches, and residual stress layers, and the resulting uneven current potential distribution, exacerbated selective corrosion, and excessive edge polishing during electropolishing, this invention provides a detection method for small-sized duplex steel EBSD samples. This invention primarily utilizes a specialized fixture to hold the small-sized sample and performs short-time electropolishing in a low-temperature electrolyte containing glycerol. This results in a smooth, undeformed mirror-like surface on the entire sample, ensuring high EBSD calibration rates and accurate microstructure.

[0005] The technical means employed in this invention are as follows:

[0006] A method for detecting EBSD in small-sized duplex steel specimens includes the following steps: The duplex steel was cut to obtain a sample of the target size; The sample is fixed in the fixture; The observation surface of the sample is ground, the ground observation surface is mechanically polished, and the mechanically polished observation surface is cleaned. The cleaned sample and fixture were placed together in an electropolishing apparatus for electropolishing. During the electropolishing process, the electrolyte was a mixed solution of 50%–70% perchloric acid, anhydrous ethanol, and glycerol in a volume ratio of 1:6 to 8:1 to 3. The voltage was set to 20–25V, and the current density was 1.0–10.0 A / cm². 2 The polishing time is 10-25 seconds, the electrolyte temperature is -20 to 5℃, and the electrolyte temperature is kept uniform by magnetic stirring. The upper limit of the motor speed during magnetic stirring is 2400 r / min. The electropolished sample is removed from the fixture, and the electropolished observation surface is cleaned to obtain the mirror observation surface of EBSD.

[0007] Furthermore, the electropolishing process also includes: The observation surface of the cleaned sample is placed facing the cathode, which is a stainless steel plate with an area larger than the observation surface.

[0008] Furthermore, the grinding of the observation surface of the sample includes: The observation surface of the sample was polished step by step using sandpaper of grades 180#, 320#, 500#, 600#, 800#, 1000#, and 1200#.

[0009] Furthermore, the mechanical polishing of the observed surface after grinding includes: The observation surface after grinding was mechanically polished in sequence using diamond suspension and silica suspension. The polishing rate of diamond suspension was 300-600 r / min, and the polishing rate of silica suspension was 300-400 r / min.

[0010] Furthermore, when cleaning the observation surface after mechanical polishing, the fixture and the mechanically polished sample are placed in anhydrous ethanol and cleaned using ultrasonic equipment; when cleaning the observation surface after electrolytic polishing, the electrolytically polished sample is placed in anhydrous ethanol and cleaned using ultrasonic equipment.

[0011] Furthermore, the steps for detecting the EBSD sample include: After cleaning and electropolishing, the sample is clamped with a sample clip, fixed on the sample stage, placed in the sample chamber, and vacuumed. EBSD detection was performed on a vacuum-sealed sample using an electron beam spot with a diameter of 0.2 μm. The sample stage position was raised to a working distance of 13–14 mm to obtain a diffraction pattern. The optimization process of the diffraction pattern included: Adjust the detector exposure time to 160s~170s, select the center position of the diffraction image with MAD≤0.5 for optimization, repeat the above operation 2~3 times to obtain the optimized diffraction image.

[0012] Furthermore, the fixture used in the method includes: a fixture body, a through groove in the middle of the fixture body, a first through hole and a second through hole on both sides of the fixture body, a first pressure head and a first screw connected together, a second pressure head and a second screw connected together, the first pressure head and the first screw passing through the first through hole, the second pressure head and the second screw passing through the second through hole, and a sample placed between the first pressure head and the second pressure head.

[0013] Compared with the prior art, the present invention has the following advantages: 1. In this invention, adding glycerol to the electrolyte can increase viscosity, suppress solution convection, make the current and potential distribution on the sample surface more uniform, prevent local overheating, avoid selective corrosion of the duplex steel structure due to heat, and enable the sample to obtain a smooth, undeformed mirror surface, ensuring high EBSD calibration rate and true structure.

[0014] 2. This invention can avoid edge chamfering and surface stress damage caused by the inlay method, ensuring edge detection accuracy; it is easy to assemble and disassemble, improving sample preparation efficiency; it provides non-destructive clamping, ensuring sample recyclability; and it has a standardized sample preparation process, supporting high-quality EBSD detection.

[0015] Based on the above reasons, this invention can be widely applied in fields such as metal sample preparation. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic flowchart of a detection method for small-sized duplex steel EBSD samples according to the present invention.

[0018] Figure 2 This is a schematic diagram of a fixture for small-sized duplex steel EBSD specimens according to the present invention.

[0019] Figure 3The image shows the test results of the DP590 duplex steel EBSD sample prepared in Example 1.

[0020] Figure 4 This is a picture of the Kikuchi pattern of the DP590 duplex steel EBSD sample prepared in Example 1.

[0021] Figure 5 The image shows the test results of the DP780 duplex steel EBSD sample prepared in Example 2.

[0022] Figure 6 The image shows the Kikuchi pattern of the DP780 duplex steel EBSD sample prepared in Example 2.

[0023] Figure 7 The figure shows the test results of the DP590 duplex steel EBSD sample prepared in Comparative Example 1.

[0024] Figure 8 This is a Kikuchi pattern diagram of the DP590 duplex steel EBSD sample prepared in Comparative Example 1.

[0025] Figure 9 The figure shows the test results of the DP780 duplex steel EBSD sample prepared in Comparative Example 2.

[0026] Figure 10 The image shows the Kikuchi pattern of the DP780 duplex steel EBSD sample prepared in Comparative Example 2.

[0027] In the figure: 1. Fixture body; 2. Sample; 3. Through groove; 31. First pressure head; 32. Second pressure head; 41. First screw; 42. Second screw. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0029] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0030] like Figure 1 As shown, the present invention provides a detection method for small-sized duplex steel EBSD specimen 2, comprising the following steps: S1. Cut the duplex steel to obtain a sample 2 of the target size.

[0031] Specifically, sample 2 was processed using wire cutting. The length and width dimensions of sample 2 are 5mm × 5mm.

[0032] S2. Fix sample 2 in the fixture.

[0033] Place the small-sized duplex steel cross-section specimen with the observation surface facing down in the through slot of the fixture. After adjusting it to the target position, tighten the screws on both sides symmetrically. Clamp the specimen 2 on both sides using the pressure head (the pressure head and screws are integrally formed by welding), relying on friction to achieve fixation. Loosening the screws allows for quick disassembly. For stability and to prevent shifting, the observation surface and fixture must be ground parallel; therefore, place the specimen with the observation surface facing down in the through slot of the fixture.

[0034] The fixture is made of 304 stainless steel. Fixture dimensions: outer diameter 20-30mm, through groove (length and width) 10-20mm, thickness 2-5mm. Screw specifications are M3-M4 round head screws, length 8-12mm. The pressure head is made of brass (soft, undamaged). Pressure head dimensions are 3mm in diameter and 2mm in thickness.

[0035] S3. Grind the observation surface of sample 2, mechanically polish the ground observation surface, and clean the mechanically polished observation surface.

[0036] The observation surface of sample 2 was polished, including: The observation surface of sample 2 was polished step by step using sandpaper of grades 180#, 320#, 500#, 600#, 800#, 1000#, and 1200#.

[0037] The observed surface after grinding is mechanically polished, including: The observation surface after grinding was mechanically polished sequentially using diamond suspension (particle size: 3.5μm, 3min) and silica suspension (particle size: 0.5μm, 2min). The polishing rate of diamond suspension (coarse polishing) was 300-600 r / min, and the polishing rate of silica suspension (fine polishing) was 300-400 r / min.

[0038] When cleaning the observation surface after mechanical polishing, the fixture and the mechanically polished sample 2 are placed in anhydrous ethanol and cleaned with ultrasonic equipment to remove polishing agent residue, oil stains and grinding debris (working frequency: 40KHz, time: 5min).

[0039] S4. Place the cleaned sample 2 and the fixture together into the electropolishing apparatus for electropolishing. During the electropolishing process, the electrolyte used is a mixed solution of 50%~70% perchloric acid, anhydrous ethanol, and glycerol in a volume ratio of 1:(6~8):(1~3). The voltage is set to 20~25V, and the current density is 1.0~10.0A / cm². 2 The polishing time is 10-25 seconds, and the electrolyte temperature is -20 to 5℃.

[0040] Furthermore, the electropolishing process also includes: The observation surface of the cleaned sample 2 is placed facing the cathode, which is a stainless steel plate with an area larger than the observation surface. The electrolyte temperature is kept uniform by magnetic stirring, and the upper limit of the motor speed is 2400 r / min, in order to remove the residual stress layer and fine scratches on the surface of sample 2 and obtain a strain-free, highly flat mirror surface.

[0041] The electrolyte temperature is controlled by liquid nitrogen cooling, using a voltage-priority, constant-voltage mode.

[0042] S5. Remove the electropolished sample 2 from the fixture, clean the electropolished observation surface, and obtain the mirror observation surface of EBSD.

[0043] Specifically, loosen the screws on both sides of the clamp and remove sample 2.

[0044] When cleaning the observation surface after electropolishing, the electropolished sample 2 was placed in anhydrous ethanol and cleaned using ultrasonic equipment.

[0045] Furthermore, the steps for EBSD detection include: After cleaning and electropolishing, sample 2 was clamped in a sample holder and fixed on the sample stage. It was then placed in the sample chamber and evacuated. The voltage was increased to an accelerating voltage of 20 kV to avoid blurring of the EBSD image or reduction in the signal-to-noise ratio due to excessively high or low voltage. EBSD detection was performed on the evacuated sample 2 using an electron beam spot with a diameter of 0.2 μm to ensure a sufficiently small electron beam interaction volume and avoid signal interference from adjacent grains, grain boundaries, or phase boundaries. The sample stage position was raised to a working distance WD = 13–14 mm to ensure the sample surface was parallel to the scanning electron beam, optimizing the clarity of the diffraction pattern and obtaining the diffraction image. The working distance is the distance from the pole piece to the sample surface.

[0046] The optimization process for diffraction images includes: Adjusting the detector's exposure time to 160-170 seconds yields a high-quality diffraction pattern. Optimize the diffraction image by selecting a center position with a MAD ≤ 0.5. Repeat this process 2-3 times to obtain the optimized diffraction image. This image is then ready for EBSD detection, and the calibration rate can be stably maintained above 95%.

[0047] If sample 2 shows excessive corrosion after electropolishing, there is no need to re-mount it. Simply fix it with a fixture again and then polish it. This method is more time-saving and efficient than traditional methods.

[0048] like Figure 2 As shown, the present invention also includes a fixture for a small-sized duplex steel EBSD sample 2. The fixture is used in the above method and includes: a fixture body 1, a through groove 3 in the middle of the fixture body 1, a first through hole and a second through hole on both sides of the fixture body 1, a first pressure head 31 connected to a first screw 41, a second pressure head 32 connected to a second screw 42, the first pressure head 31 and the first screw 41 passing through the first through hole, the second pressure head 32 and the second screw 42 passing through the second through hole, and the sample 2 placed between the first pressure head 31 and the second pressure head 32.

[0049] Example 1 This embodiment provides a method for detecting EBSD in small-sized DP590 duplex stainless steel, including the following steps: S1. Place the DP590 cross-section specimen 2 with the observation surface facing down in the through groove 3 of the fixture. After adjusting the observation surface of the specimen 2 and the fixture to the same plane, tighten the screws on both sides symmetrically and clamp the two sides of the specimen 2 with the pressure head.

[0050] S2. Sample 2 is polished sequentially using sandpaper of grades 180#, 320#, 500#, 600#, 800#, 1000#, and 1200#.

[0051] S3. After grinding, mechanical polishing is performed sequentially using diamond suspension (particle size: 3.5μm, 3min) and silica suspension (particle size: 0.5μm, 2min). The coarse polishing rate is 300r / min and the fine polishing rate is 300r / min.

[0052] S4. After mechanical polishing, place the fixture and sample 2 in anhydrous ethanol and clean them with an ultrasonic cleaner to remove polishing agent residue, oil, and grinding debris (working frequency: 40KHz, time: 5min).

[0053] S5. Place the fixture along with sample 2 in the electropolishing apparatus, with the observation surface of sample 2 facing the cathode, and perform electropolishing. The electrolyte used for electropolishing is a mixed solution of perchloric acid (65%), anhydrous ethanol, and glycerol in a volume ratio of 1:6:3. The electropolishing process parameters are set as follows: voltage 20V, current density 10.0 A / cm². 2 The polishing time was 10 seconds, the electrolyte temperature was controlled at -20℃, and a voltage-priority, constant-voltage mode was adopted. During the electropolishing process, the electrolyte temperature was kept uniform by magnetic stirring, and the upper limit of the motor speed during magnetic stirring was 2400 r / min, in order to remove the residual stress layer and fine scratches on the surface of sample 2 and obtain a strain-free, highly flat mirror surface.

[0054] S6. After electropolishing, loosen the screws on both sides of the fixture, take out sample 2, put it into anhydrous ethanol, and use ultrasonic equipment to clean the polished surface to remove electrolyte residue and obtain the mirror observation surface of EBSD.

[0055] The EBSD detection procedure includes: clamping the cleaned sample 2 with a stainless steel sample clamp, fixing it to the sample stage with conductive adhesive, placing it in the sample chamber, evacuating the vacuum, and increasing the voltage to an accelerating voltage of 20kV. Switching the electron beam spot diameter to 0.2μm, raising the sample stage position to a working distance WD=13mm, and adjusting the detector exposure time to 160s allows for the acquisition of high-quality diffraction patterns. Optimizing the image by selecting a position with a MAD ≤ 0.5 at the center is performed. After repeating the above diffraction image optimization operation twice, EBSD detection can be performed with a calibration rate of 95%.

[0056] like Figure 3 and Figure 4 The image shown is a diagram of the test results and a Kikuchi pattern of the DP590 duplex steel EBSD sample 2 prepared in this embodiment.

[0057] Example 2 This embodiment provides a method for detecting EBSD in small-sized DP780 duplex stainless steel, including the following steps: S1. Place the DP780 cross-section specimen 2 with the observation surface facing down in the through groove 3 of the fixture. After adjusting the observation surface of the specimen 2 and the fixture to the same plane, tighten the screws on both sides symmetrically and clamp the two sides of the specimen 2 with the pressure head.

[0058] S2. Sample 2 is polished sequentially using sandpaper of grades 180#, 320#, 500#, 600#, 800#, 1000#, and 1200#.

[0059] S3. After grinding, mechanical polishing is performed sequentially using diamond suspension (particle size: 3.5μm, 3min) and silica suspension (particle size: 0.5μm, 2min). The coarse polishing rate is 600r / min and the fine polishing rate is 400r / min.

[0060] S4. After mechanical polishing, place the fixture and sample 2 in anhydrous ethanol and clean them with an ultrasonic cleaner to remove polishing agent residue, oil, and grinding debris (working frequency: 40KHz, time: 5min).

[0061] S5. Place the fixture along with sample 2 in the electropolishing apparatus, with the observation surface of sample 2 facing the cathode, and perform electropolishing. The electrolyte used for electropolishing is a mixed solution of perchloric acid (70%), anhydrous ethanol, and glycerol in a volume ratio of 1:7:2. The electropolishing process parameters are set as follows: voltage 25V, current density 1.0A / cm². 2 The polishing time was 25 seconds, the electrolyte temperature was controlled at 5℃, and a voltage-priority, constant-voltage mode was adopted. During the electropolishing process, the electrolyte temperature was kept uniform by magnetic stirring, and the upper limit of the motor speed during magnetic stirring was 2400 r / min, in order to remove the residual stress layer and fine scratches on the surface of sample 2 and obtain a strain-free, highly flat mirror surface.

[0062] S6. After electropolishing, loosen the screws on both sides of the fixture, take out sample 2, put it into anhydrous ethanol, and use ultrasonic equipment to clean the polished surface to remove electrolyte residue and obtain the mirror observation surface of EBSD.

[0063] The EBSD detection steps include: clamping the cleaned sample 2 with a stainless steel sample clamp, fixing it to the sample stage with conductive adhesive, placing it in the sample chamber, evacuating the vacuum, and increasing the voltage to an accelerating voltage of 20kV; switching the electron beam spot diameter to 0.2μm, raising the sample stage position to a working distance WD=14mm, and adjusting the detector exposure time to 170s to obtain a high-quality diffraction pattern; selecting the position with MAD≤0.5 at the center of the image for optimization; repeating the above diffraction image optimization operation 3 times, EBSD detection can be performed with a calibration rate of 96%.

[0064] like Figure 5 and Figure 6The image shown is a diagram of the test results and the Kikuchi pattern of the DP780 duplex steel EBSD sample 2 prepared in this embodiment.

[0065] Comparative Example 1 Taking DP590 duplex stainless steel as an example, this comparative example uses the traditional EBSD sample preparation and testing method. The specific steps are as follows: S1. Place the DP590 section specimen 2 with the observation surface facing down in the embedding mold, embed it with cold embedding resin (epoxy resin), and demold it after curing.

[0066] S2. The inlaid sample 2 is polished step by step using sandpaper of 180#, 320#, 500#, 600#, 800#, 1000# and 1200#.

[0067] S3. After grinding, use diamond suspension (particle size: 3.5μm) for coarse polishing and silica suspension (particle size: 0.5μm) for fine polishing.

[0068] S4. Use pliers to crush the inserts around sample 2 and peel out sample 2.

[0069] S5. Place sample 2 in anhydrous ethanol and clean it with an ultrasonic cleaner to remove polishing agent residue, oil, and grinding debris.

[0070] S6. Place sample 2 in the electropolishing apparatus with the observation surface of sample 2 facing the cathode and perform electropolishing. The electrolyte used for electropolishing is a mixture of perchloric acid and anhydrous ethanol with a volume ratio of 1:3. The electropolishing process parameters are set as follows: electropolishing voltage of 32V, electrolysis time of 11s, and electrolyte temperature controlled at 0℃.

[0071] S7. After electropolishing, take out sample 2, put it in anhydrous ethanol, and use ultrasonic equipment to clean the polished surface to remove electrolyte residue and obtain the mirror observation surface of EBSD.

[0072] The EBSD detection steps include: clamping the cleaned sample 2 with a stainless steel sample clamp, fixing it to the sample stage with conductive adhesive, placing it in the sample chamber, evacuating the vacuum, increasing the voltage to an accelerating voltage of 20kV; switching the electron beam spot diameter to 0.2μm, raising the sample stage position to a working distance WD=13mm, and adjusting the detector exposure time to perform EBSD detection with a calibration rate of 91%.

[0073] like Figure 7 and Figure 8 The image shown is a diagram of the test results and the Kikuchi pattern of the DP590 duplex steel EBSD sample 2 prepared in this comparative example.

[0074] Comparative Example 2 Taking DP780 duplex stainless steel as an example, this comparative example uses the traditional EBSD sample preparation and testing method. The specific steps are as follows: S1. Place the DP780 section specimen 2 with the observation surface facing down in the embedding mold, embed it with cold embedding resin (epoxy resin), and demold it after curing.

[0075] S2. The inlaid sample 2 is polished step by step using sandpaper of 180#, 320#, 500#, 600#, 800#, 1000# and 1200#.

[0076] S3. After grinding, use diamond suspension (particle size: 3.5μm) for coarse polishing and silica suspension (particle size: 0.5μm) for fine polishing.

[0077] S4. Use pliers to crush the inserts around sample 2 and peel out sample 2.

[0078] S5. Place sample 2 in anhydrous ethanol and clean it with an ultrasonic cleaner to remove polishing agent residue, oil, and grinding debris.

[0079] S6. Place sample 2 in the electropolishing apparatus with the observation surface of sample 2 facing the cathode, and perform electropolishing. The electrolyte used for electropolishing is a mixture of perchloric acid and anhydrous ethanol with a volume ratio of 1:3; the electropolishing process parameters are set as follows: electropolishing voltage of 32V, electrolysis time of 12s, and electrolyte temperature controlled at 0℃.

[0080] S7. After electropolishing, take out sample 2, put it in anhydrous ethanol, and use ultrasonic equipment to clean the polished surface to remove electrolyte residue and obtain the mirror observation surface of EBSD.

[0081] The EBSD detection steps include: clamping the cleaned sample 2 with a stainless steel sample clamp, fixing it to the sample stage with conductive adhesive, placing it in the sample chamber, evacuating the vacuum, increasing the voltage to an accelerating voltage of 20kV; switching the electron beam spot diameter to 0.2μm, raising the sample stage position to a working distance WD=13mm, and adjusting the detector exposure time to perform EBSD detection with a calibration rate of 89%.

[0082] like Figure 9 and Figure 10 The image shown is a diagram of the test results and the Kikuchi pattern of the DP780 duplex steel EBSD sample 2 prepared in this comparative example.

[0083] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0084] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting EBSD in small-sized duplex steel samples, characterized in that, Includes the following steps: The duplex steel was cut to obtain a sample of the target size; The sample is fixed in the fixture; The observation surface of the sample is ground, the ground observation surface is mechanically polished, and the mechanically polished observation surface is cleaned. The cleaned sample and fixture were placed together in an electropolishing apparatus for electropolishing. During the electropolishing process, the electrolyte was a mixed solution of 50%–70% perchloric acid, anhydrous ethanol, and glycerol in a volume ratio of 1:6 to 8:1 to 3. The voltage was set to 20–25V, and the current density was 1.0–10.0 A / cm². 2 The polishing time is 10-25 seconds, the electrolyte temperature is -20 to 5℃, and the electrolyte temperature is kept uniform by magnetic stirring. The upper limit of the motor speed during magnetic stirring is 2400 r / min. The electropolished sample is removed from the fixture, and the electropolished observation surface is cleaned to obtain the mirror observation surface of EBSD.

2. The detection method for small-sized duplex steel EBSD samples according to claim 1, characterized in that, The electropolishing process also includes: The observation surface of the cleaned sample is placed facing the cathode, which is a stainless steel plate with an area larger than the observation surface.

3. The detection method for small-sized duplex steel EBSD samples according to claim 1, characterized in that, The grinding of the observation surface of the sample includes: The observation surface of the sample was polished step by step using sandpaper of grades 180#, 320#, 500#, 600#, 800#, 1000#, and 1200#.

4. The detection method for small-sized duplex steel EBSD samples according to claim 1, characterized in that, The mechanical polishing of the observed surface after grinding includes: The observation surface after grinding was mechanically polished in sequence using diamond suspension and silica suspension. The polishing rate of diamond suspension was 300-600 r / min, and the polishing rate of silica suspension was 300-400 r / min.

5. The detection method for small-sized duplex steel EBSD samples according to claim 1, characterized in that, When cleaning the observation surface after mechanical polishing, the fixture and the mechanically polished sample are placed in anhydrous ethanol and cleaned using ultrasonic equipment; when cleaning the observation surface after electrolytic polishing, the electrolytically polished sample is placed in anhydrous ethanol and cleaned using ultrasonic equipment.

6. The detection method for small-sized duplex steel EBSD specimens according to claim 1, characterized in that, The steps for detecting the EBSD sample include: After cleaning and electropolishing, the sample is clamped with a sample clip, fixed on the sample stage, placed in the sample chamber, and vacuumed. EBSD detection was performed on a vacuum-sealed sample using an electron beam spot with a diameter of 0.2 μm. The sample stage position was raised to a working distance of 13–14 mm to obtain a diffraction pattern. The optimization process of the diffraction pattern included: Adjust the detector exposure time to 160s~170s, select the center position of the diffraction image with MAD≤0.5 for optimization, repeat the above operation 2~3 times to obtain the optimized diffraction image.

7. The detection method for small-sized duplex steel EBSD samples according to claim 1, characterized in that, The fixture used in the method includes: a fixture body, a through groove in the middle of the fixture body, a first through hole and a second through hole on both sides of the fixture body, a first pressure head and a first screw connected together, a second pressure head and a second screw connected together, the first pressure head and the first screw passing through the first through hole, the second pressure head and the second screw passing through the second through hole, and a sample placed between the first pressure head and the second pressure head.

Images