A rotary motion ebsd test sample automatic electrolytic polishing device and method

Abstract

A kind of rotary motion type EBSD test sample automatic electrolytic polishing method and device, the device includes liftable cantilever with positioning cone support (2), hemispherical inner bottom surface electrolytic polishing tank (6), herringbone clamp (7), position adjusting chuck (5) and motor (1).The method includes sample polishing, sample (10) installation, sample and anode connection, electrolytic polishing tank and cathode connection, configuration electrolytic polishing liquid (9), electrolytic polishing and sample post-processing.The application adopts hemispherical inner bottom surface electrolytic polishing tank as the cathode of electrolytic polishing, so that voltage and current density contour is concentric circle and uniformly distributed in electrolytic polishing liquid, greatly improves the stability of voltage and current of surface to be polished, so that the surface quality of electrolytic polishing is greatly improved.

Description

Technical Field

[0001] This invention relates to an automatic electrolytic polishing device and method for rotary motion EBSD test samples, belonging to the field of metal material analysis and testing. Background Technology

[0002] Electron backscatter diffraction (EBSD) is a technique based on the use of an electron beam in a scanning electron microscope (SEM) to excite and form diffraction Kikuchi bands on the surface of an inclined sample, thereby analyzing and determining the crystal structure, orientation, and related information. It is well known that microstructure, crystal structure, orientation distribution, and phase distribution are crucial information for characterizing crystalline materials and are key to determining their various properties. Obtaining this information greatly helps in understanding the microscopic mechanisms of material properties. Metallographic images or SEM images are the most commonly used microscopic images of materials, but from these images we can only obtain information related to grain size, shape, and distribution. EBSD can obtain much richer information. It not only clearly shows the morphological information of the material but also provides a wealth of quantitative information such as orientation distribution, phase distribution, grain (phase) boundary types, orientation relationships, and orientation difference relationships. It can even reflect more microscopic information such as dislocation density levels and internal stress levels, which are difficult to obtain with metallographic microscopes and ordinary SEMs. It is evident that EBSD technology is of great help to materials researchers in fully understanding the microscopic mechanisms and intrinsic nature of material properties, and is an advanced characterization method for developing new materials.

[0003] Electropolishing, which uses the principle of electrochemical corrosion, does not create a stress layer and is one of the ideal sample preparation methods for EBSD testing. Currently, there are two main methods of electropolishing: automated and manual. Automated electropolishing primarily uses the ElectroMet series electropolishing machine from Standard Instruments (USA). This equipment is expensive, and domestically produced equipment is limited, making it unavailable to most researchers. Domestically produced automated electropolishing machines are also scarce and expensive, resulting in limited usage. Most domestic researchers use simpler devices for manual electropolishing. During the polishing process, the sample is placed parallel to the center of the plate cathode and kept stationary to maintain stable voltage and current, or the sample is manually oscillated to promote timely shedding of the thin film on the sample surface and timely diffusion of solutes in the polishing solution. However, electropolishing the sample in a stationary state easily leads to the adhesion of a thin film to the sample surface, resulting in electropolishing failure. Manually oscillating the sample makes it difficult to maintain stable voltage and current, and also makes it difficult to obtain a high-quality surface. Summary of the Invention

[0004] The object of the present invention is to provide a rotary motion type automatic electrolytic polishing device and method for EBSD test specimens in view of the deficiencies of the existing electrolytic polishing for preparing EBSD specimens.

[0005] The technical solution achieved by the present invention is as follows. A rotary motion type electrolytic polishing device for EBSD test specimens includes a liftable cantilever with a positioning cone support, a hemispherical inner bottom electrolytic polishing tank, a chevron-shaped fixture, an adjustment chuck and a motor. The liftable cantilever with a positioning cone support is of a "C" type structure. The motor is placed above the cantilever and is connected to the center of the adjustment chuck through an insulating connecting rod and a metal connecting rod in sequence from top to bottom. The chevron-shaped fixture is arranged below the adjustment chuck and is used for clamping the electrolytic polishing specimen. The lower horizontal arm is a support with a positioning cone and is used for placing the hemispherical inner bottom electrolytic polishing tank.

[0006] When the hemispherical inner bottom electrolytic polishing tank of the device is working properly, the electrolytic polishing specimen can be in a state of maintaining rotary motion while being electrolytically polished under the conditions of constant voltage and constant current.

[0007] A brush support rod is installed on the vertical arm of the liftable cantilever with a positioning cone support. One end of the brush support rod is a positive terminal, and the other end is connected to the metal connecting rod through a brush. A lift knob is installed at the lower end of the vertical arm and is used to adjust the lift of the cantilever and control the depth of the specimen immersed in the electrolyte. A positioning cone is provided on the support of the lower horizontal arm to ensure that the center of the spherical inner bottom polishing tank can be quickly and accurately positioned directly below the center of the adjustment chuck.

[0008] The adjustment chuck is of a disc structure. A groove is opened in the diameter direction of the chuck to facilitate the installation of the chevron-shaped fixture and can also adjust the placement position of the chevron-shaped fixture on the groove to assist in adjusting the rotation speed of the specimen.

[0009] The hemispherical inner bottom electrolytic polishing tank is a metal cup with good conductivity and corrosion resistance. The inner bottom shape is hemispherical and the periphery is a vertical wall. A negative terminal is provided at the upper end of the polishing tank, and a positioning groove is provided at the center of the bottom.

[0010] A rotary motion type electrolytic polishing method for EBSD test specimens according to the present invention is as follows:

[0011] (1) Grinding: Grinding is carried out by the conventional grinding method for EBSD test specimens.

[0012] (2) Specimen installation: The test surface of the specimen is facing downwards and is horizontally fixed at the end of the chevron-shaped fixture. The chevron-shaped fixture is fixed on the card slot of the adjustment chuck. The anode of the regulated DC power supply is connected to the positive terminal. Through the brush support rod, the brush, the metal connecting rod, the adjustment chuck and the chevron-shaped fixture, a circuit is formed to make the specimen the anode end. The cathode of the regulated DC power supply is connected to the negative terminal to make the metal electrolytic polishing tank the cathode end.

[0013] (3) Preparation of electrolytic polishing solution: Pour the electrolytic polishing solution into the electrolytic polishing tank on the inner bottom surface of the hemisphere. The liquid level should not be higher than the boundary line between the inner bottom surface of the hemisphere and the inner side surface of the straight wall.

[0014] (4) Electrolytic polishing: Start the motor, and the sample will rotate horizontally in a circular motion driven by the motor and the adjusting chuck. The rotation speed is 0.5~15 rpm. Turn on the regulated DC power supply and adjust the lifting knob so that the sample surface to be tested is immersed 3~15 mm below the surface of the electrolytic polishing solution. Electrolytic polishing is performed at a polishing temperature of 0~35℃, a voltage of 15~40V, a current of 0.2~1A, and a polishing time of 15~50s.

[0015] (5) Sample post-treatment: Rotate the lifting knob to remove the sample after electrolytic polishing from the electrolytic polishing solution. At the same time, turn off the regulated DC power supply, stop the motor, put the sample into alcohol to clean it, blow it dry with cold air, and place it in a vacuum desiccator with the test side facing up for storage.

[0016] The working principle and beneficial effects of this invention are as follows: During electropolishing, the sample maintains both motion and a constant voltage and current state. Voltage contour lines at any depth in the electropolishing solution are concentrically distributed around the center of that depth. Driven by the positioning chuck, the sample rotates in a circle around the center of the electropolishing solution at its current depth. The sample's trajectory coincides with the voltage contour lines, maintaining a constant voltage and current on the sample surface. Electropolishing under constant voltage and current conditions ensures stable film formation during the polishing process. Simultaneously, the sample movement effectively promotes timely film detachment and facilitates the timely diffusion of solute ions in the electropolishing solution, ensuring an effective concentration of the solution near the polished surface. Since obtaining a high-quality electropolished surface depends on the continuous formation and timely detachment of a stable film during electropolishing—that is, the orderly progression of this periodic process of "stable film formation - timely detachment"—the high-quality electropolished surface is achieved. This invention achieves a constant voltage and constant current state for the sample during electropolishing while it is in motion, ensuring the stable progress of the cyclical process of "stable film formation - timely shedding" during electropolishing. Compared with traditional manual electropolishing, the quality of electropolishing is significantly improved. Furthermore, compared with traditional manual electropolishing methods, it effectively avoids accidents such as the surface to be polished leaving the polishing solution or touching the cathode. It effectively prevents surface scorching caused by the surface leaving the polishing solution and short circuits and fires caused by the sample touching the cathode, thus improving the success rate of sample preparation and reducing safety hazards during the sample preparation process. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an automatic electrolytic polishing device for EBSD test specimens using a rotary motion method.

[0018] Figure 2 It is a schematic diagram of an adjustment chuck;

[0019] Figure 3 It is a Kikuchi pattern contrast Mapping diagram of pipeline steel obtained by EBSD testing;

[0020] In the figure, 1 is the motor, 2 is the liftable cantilever with a positioning cone support, 2a is the lift knob, 2b is the positioning cone, 3 is the insulating connecting rod, 4 is the metal connecting rod, 5 is the adjustment chuck, 6 is the electrolytic polishing tank on the inner bottom surface of the hemisphere, 6a is the negative terminal, 7 is the chevron-shaped fixture, 8 is the brush support rod, 8a is the positive terminal, 8b is the brush, 9 is the electrolytic polishing solution, and 10 is the specimen. Specific implementation mode

[0021] The following further elaborates on the present invention in detail with reference to the accompanying drawings and specific embodiments.

[0022] An automatic electrolytic polishing device for EBSD testing specimens with a rotary motion in this embodiment is as Figure 1 shown.

[0023] An electrolytic polishing device for EBSD testing specimens with a rotary motion, characterized in that the device includes a liftable cantilever with a positioning cone support 2, an electrolytic polishing tank on the inner bottom surface of the hemisphere 6, a chevron-shaped fixture 7, an adjustment chuck 5, and a motor 1. The liftable cantilever with a positioning cone support 2 has a "C" - shaped structure. The motor 1 is placed above the cantilever and is connected to the center of the adjustment chuck 5 through the insulating connecting rod 3 and the metal connecting rod 4 in sequence from top to bottom. The chevron-shaped fixture 7 is placed below the adjustment chuck 5 for clamping the electrolytic polishing specimen 10; the lower horizontal arm is a support with a positioning cone for placing the electrolytic polishing tank on the inner bottom surface of the hemisphere 6.

[0024] A brush support rod 8 is installed on the vertical arm of the liftable cantilever with a positioning cone support 2. The left end of the brush support rod 8 is the positive terminal 8a, and the right end is connected to the metal connecting rod 4 through the brush 8b; a lift knob 2a is installed at the lower end of the vertical arm for adjusting the lift of the cantilever and controlling the depth of the specimen 10 immersed in the electrolyte 9; a positioning cone 2b is provided on the lower horizontal arm support to ensure that the center of the hemispherical inner bottom surface polishing tank 6 is quickly and accurately positioned directly below the center of the adjustment chuck 5.

[0025] The adjustment chuck 5 has a disc structure. A groove is opened in the diameter direction of the chuck 5, which is convenient for installing the chevron-shaped fixture 7 and can also adjust the placement position of the chevron-shaped fixture 7 on the groove to assist in adjusting the rotation speed of the specimen 10.

[0026] The hemispherical inner bottom surface electrolytic polishing tank 6 is a metal cup with good conductivity and corrosion resistance, a hemispherical inner bottom surface, and vertical walls around the perimeter. A negative terminal 6a is provided at the upper end of the polishing tank 6.

[0027] This embodiment describes an automated electrolytic polishing method for rotary motion EBSD test specimens, implemented as follows:

[0028] (1) Grinding: The pipeline steel is cut into rectangular samples of 10mm×5mm×3mm by wire cutting. The EBSD sample is cleaned with alcohol to remove surface dirt. The surface of the sample is ground with 400 grit, 600 grit, 800 grit, 1500 grit and 2000 grit metallographic sandpaper in sequence. Each grinding direction is perpendicular to the previous grinding direction to ensure that the grinding marks of the previous grinding are completely eliminated and only the grinding marks of the current grinding direction remain on the sample surface. Then, the finer metallographic sandpaper is changed for grinding. The last grinding is done with 2000 grit metallographic sandpaper. Under the metallographic microscope, only the grinding marks parallel to the last grinding direction can be seen. Grinding is then completed. The sample is cleaned with alcohol 1 to 3 times and dried with cold air.

[0029] (2) Sample installation: Place the sample 10 with the test surface facing down, keeping the test surface horizontal, and fix it at the end of the herringbone clamp 7. Tighten the fastening nut to fix the sample at the end of the clamp 7. Tighten the fastening nut at the adjustment slot to fix the herringbone clamp 7 on the adjustment chuck 5 at a position 2 / 3 from the center of the chuck. The anode of the regulated DC power supply is connected to the positive terminal 8a, forming a circuit through the brush support rod 8, brush 8b, metal connecting rod 4, adjustment chuck 5, and herringbone clamp 7, making the sample 10 the anode end; the cathode of the regulated DC power supply is connected to the negative terminal 6a, making the metal electrolytic polishing tank 6 the cathode end.

[0030] (3) Preparation of electrolytic polishing solution: Mix perchloric acid and alcohol in a volume ratio of 5:95 to obtain electrolytic polishing solution 9. Pour electrolytic polishing solution 9 into the electrolytic polishing tank 6 on the inner bottom surface of the hemisphere. The liquid level is 5mm lower than the boundary line between the inner bottom surface of the hemisphere and the inner side of the straight wall.

[0031] (4) Electrolytic polishing: Start motor 1. The sample 10 rotates horizontally in a circular motion under the drive of motor 1 and adjusting chuck 5. The rotation speed is 3 revolutions / second. Turn on the regulated DC power supply and adjust the lifting knob 2a so that the test surface of sample 10 is immersed 5 mm below the surface of electrolytic polishing liquid 9 for electrolytic polishing. The polishing temperature is 15℃, the voltage is 28V, the current is 0.8A, and the polishing time is 35s.

[0032] (5) Sample post-treatment: Rotate the lifting knob 2a to remove the electropolishing sample 10 from the electropolishing solution 9 after electropolishing. At the same time, turn off the regulated DC power supply and stop the motor 1. Place the sample 10 into three cups of clean alcohol to clean it, dry it with cold air, and place it in a vacuum desiccator with the test side facing up for storage.

[0033] The electropolished sample was subjected to EBSD testing, and the results are as follows: Figure 3 As shown, its microstructure consists of various structures including polygonal ferrite, acicular ferrite, and martensite / austenite islands, with a calibration rate as high as 91.3%. Figure 3 As can be seen, the white area is the unlabeled area, the black area is the martensite / austenite phase area, and the gray area is the body-centered cubic phase area, which contains two types of microstructure: polygonal ferrite and acicular ferrite. Different shades of gray represent the quality of Kikuchi patterns.

[0034] It is evident that, through the specific implementation of the method and apparatus of this invention, even fine-grained multiphase materials that are difficult to electropolish can easily obtain high-quality electropolished surfaces and achieve an EBSD test calibration rate of over 90%.

Claims

1. A rotary motion-type electrolytic polishing device for EBSD test samples, characterized in that, The device includes a liftable cantilever with a positioning cone support, an electrolytic polishing tank with a hemispherical inner bottom surface, a chevron-shaped fixture, an adjustment chuck, and a motor; The liftable cantilever with a positioning cone support is of a "C" type structure. The motor is placed above the cantilever and is connected to the center of the adjustment chuck through an insulating connecting rod and a metal connecting rod in sequence from top to bottom. A chevron-shaped fixture is arranged below the adjustment chuck for clamping the electrolytic polishing sample. The lower horizontal arm is a support with a positioning cone for placing the electrolytic polishing tank with a hemispherical inner bottom surface. The electrolytic polishing solution is placed in the electrolytic polishing tank with a hemispherical inner bottom surface; When the electrolytic polishing tank with a hemispherical inner bottom surface of the device is working normally, the electrolytic polishing sample can be electrolytically polished while maintaining a rotating motion along the horizontal plane and maintaining a constant voltage and constant current state; The electrolytic polishing tank with a hemispherical inner bottom surface is a metal cup with good conductivity and corrosion resistance, and the inner bottom surface is hemispherical and the periphery is a vertical wall. A negative electrode terminal is arranged at the upper end of the polishing tank, making the metal electrolytic polishing tank the cathode end. A positioning groove is arranged at the center position of the bottom. The voltage contour lines of any depth liquid surface in the electrolytic polishing solution are concentric circles centered on the center of the liquid surface of that depth. The sample makes a circular rotational motion centered on the center of the liquid surface of the electrolytic polishing solution at the depth where it is located under the drive of the adjustment chuck, and the motion trajectory of the sample coincides with the voltage contour lines.

2. The rotary motion type EBSD test sample electropolishing device according to claim 1, characterized in that, A brush support rod is installed on the vertical arm of the liftable cantilever with a positioning cone support. One end of the brush support rod is a positive electrode terminal, and the other end is connected to the metal connecting rod through a brush. A lifting knob is installed at the lower end of the vertical arm for adjusting the lifting of the cantilever and controlling the depth of the sample immersed in the electrolyte. A positioning cone is arranged on the support of the lower horizontal arm to ensure that the center of the hemispherical inner bottom polishing tank is quickly and accurately positioned directly below the center of the adjustment chuck.

3. The rotary motion type EBSD test sample electropolishing device according to claim 1, characterized in that, The adjustment chuck is of a disc structure. A groove is opened in the diameter direction of the chuck for facilitating the installation of the chevron-shaped fixture and also for adjusting the placement position of the chevron-shaped fixture on the groove to assist in adjusting the rotation speed of the sample. There is an installation hole at the center of the adjustment chuck, and the end of the metal connecting rod is inserted into the hole, and the adjustment chuck is installed and fixed on the metal connecting rod through a nut.

4. A rotary motion EBSD test sample electropolishing method implemented by the test sample electropolishing apparatus according to any one of claims 1 to 3, characterized in that, The method steps are as follows: (1) Sample grinding: Grind the sample using the conventional grinding method for EBSD test samples; (a) Sample installation: Place the sample with the待测面 facing down and horizontally fix it at the end of the chevron-shaped fixture. The chevron-shaped fixture is fixed on the card slot of the adjustment chuck. The anode of the regulated DC power supply is connected to the positive electrode terminal, and through the brush support rod, brush, metal connecting rod, adjustment chuck, and chevron-shaped fixture, a circuit is formed to make the sample the anode end. The cathode of the regulated DC power supply is connected to the negative electrode terminal to make the metal electrolytic polishing tank the cathode end; (3) Preparation of electrolytic polishing solution: Pour the electrolytic polishing solution into the electrolytic polishing tank with a hemispherical inner bottom surface, and the liquid level height is not higher than the intersection line of the hemispherical inner bottom surface and the inner side surface of the straight wall; It should be noted that the Chinese term "待测面" in is not clear. I've translated it as "待测面" for now. You may need to clarify or correct it according to the actual situation. (4) Electrolytic polishing: Start the motor, and the sample will rotate horizontally in a circular motion under the drive of the motor and the adjusting chuck. The rotation speed is 0.5~15 rpm. Turn on the regulated DC power supply, adjust the lifting knob, and immerse the sample surface to be tested 3~15 mm below the surface of the electrolytic polishing solution for electrolytic polishing. The polishing temperature is 0~35℃, the voltage is 15~40V, the current is 0.2~1A, and the polishing time is 15~50s. (5) Sample post-treatment: Rotate the lifting knob to remove the sample after electrolytic polishing from the electrolytic polishing solution. At the same time, turn off the regulated DC power supply, stop the motor, put the sample into alcohol to clean it, blow it dry with cold air, and place it in a vacuum desiccator with the test side facing up for storage.

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