Low-strength and high-corrosion-resistance metal test sample and preparation method thereof

Abstract

The invention provides a preparation method of a low-strength and high-corrosion-resistance metal test sample, and relates to the technical field of metal material structure texture characterization, and the preparation method comprises the following steps: carrying out surface polishing treatment on a low-strength and high-corrosion-resistance metal sample to obtain a polished sample; the polished sample is subjected to electrolytic polishing treatment, and an electrolytic polishing sample is obtained; the electrolytic polishing sample is cleaned, and a low-strength and high-corrosion-resistance metal test sample is obtained; and in the electrolytic polishing treatment process, a flowing electrolyte is adopted to wash the polished sample. The surface of the sample is scoured through the flowing electrolyte, a stress layer generated on the surface of the sample in the mechanical polishing process can be effectively removed, especially for some seriously deformed samples, strong diffraction patterns can still be generated in the EBSD test, the calibration rate is increased, and the polishing effect is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material tissue texture characterization, and particularly relates to a low-strength, high-corrosion-resistant metal test sample and a preparation method thereof. Background Art

[0002] Since its development in the 1990s, EBSD technology has provided crucial assistance for the analysis of crystal micro-orientation and crystal structure, and has become a widely used method for characterizing the microstructure and texture of materials. This technology is often used in conjunction with scanning electron microscopy (SEM) backscattered electron imaging, which utilizes the interaction between the sample surface and the electron beam surface to produce images with varying contrasts using backscattered electron imaging that contains information on morphology, atomic number, crystal structure, and orientation differences. Since the electrons diffracted by the SEM come from a sample surface that is only tens of nanometers thick, any surface defects, such as surface deformation, surface contamination, and oxide layers, will affect the electron diffraction signal, leading to a decrease in the quality of the EBSD pattern or errors. Therefore, the basic requirements for the surface of EBSD test samples are that they are flat, clean, and free of deformation layers left over from the sample preparation process.

[0003] Low-strength, highly corrosion-resistant metals have broad application prospects. For example, pure tantalum has a high melting point and density. Similar to many body-centered cubic metals, it maintains excellent performance over a wide temperature range and under high strain. Therefore, it is widely used in extreme service environments, such as as a structural component in major equipment such as nuclear reactors, rockets, satellites, and aircraft engines. As a key structural component, the relationship between the microstructure and mechanical properties of pure tantalum is crucial for optimizing the performance of such materials, especially in terms of improving their strength and toughness.

[0004] In order to effectively explore the microscopic interface and texture evolution of low-strength, high-corrosion-resistant metals under some mechanical deformation and heat treatment processes, EBSD and SEM observations are required. However, there is no universal electrolytic polishing process for pure tantalum materials. Since low-strength, high-corrosion-resistant metals have strong corrosion resistance, do not react with aqua regia or hydrochloric acid, and are soft (low strength), scratches are easily generated during the initial grinding and polishing process, and the stress-affected layer is thick, which affects EBSD and SEM observations. Conventional methods such as ion etching have long sample preparation times and high costs; other electrolytic polishing methods usually add 5-10 Vol.% HF to the polishing solution. HF is highly corrosive to human tissue, posing a major risk to experimental operation safety, and the polishing time is also long.

[0005] In summary, the preparation of existing low-strength, high-corrosion-resistant metal EBSD and SEM test samples has the following problems: (1) The stress layer is relatively thick, which affects the EBSD and SEM effects; (2) The preparation cycle is long, the cost is high, and the efficiency is low; (3) There are major safety hazards. Summary of the Invention

[0006] Therefore, the present invention provides a low-strength, high-corrosion-resistant metal test sample and a preparation method thereof, which can solve the problem of a thick stress layer of the test sample prepared in the prior art.

[0007] In order to solve the above problems, the present invention provides a method for preparing a low-strength, high-corrosion-resistant metal test sample, wherein the low-strength, high-corrosion-resistant metal test sample is used as an EBSD test sample and / or a SEM test sample. The method for preparing the low-strength, high-corrosion-resistant metal test sample comprises the following steps:

[0008] Step 1): performing surface polishing treatment on a low-strength, high-corrosion-resistant metal sample to obtain a polished sample;

[0009] Step 2): performing electrolytic polishing on the polished sample to obtain an electrolytically polished sample; during the electrolytic polishing process, flushing the polished sample with a flowing electrolyte;

[0010] Step 3): Cleaning the electrolytically polished sample to obtain the low-strength, high-corrosion-resistant metal test sample.

[0011] Furthermore, in step 1), the low-strength, high-corrosion-resistant metal sample is a metal sample with a strength lower than 200 MPa; preferably, the low-strength, high-corrosion-resistant metal sample is one of a pure molybdenum sample, a molybdenum alloy sample, a pure niobium sample, a niobium alloy sample, a pure tantalum sample, and a tantalum alloy sample.

[0012] Furthermore, in step 1), the surface polishing step includes:

[0013] Use 1000#, 2000# and 3000# silicon carbide sandpaper for wet grinding in sequence.

[0014] Furthermore, in the electrolytic polishing process of step 2):

[0015] The cathode is made of one of stainless steel, titanium and copper; and / or

[0016] The anode is the low-strength, high-corrosion-resistant metal sample.

[0017] Furthermore, in the electrolytic polishing process of step 2):

[0018] The electrolyte for the electrolytic polishing treatment includes sulfuric acid and methanol; preferably, in the electrolyte, the volume ratio of sulfuric acid to methanol is (1-1.5): (7-10).

[0019] Furthermore, it is characterized in that, in the electrolytic polishing process of step 2):

[0020] Voltage is 25-35V; and / or

[0021] The electrolytic polishing treatment time is 25 to 35 seconds; and / or

[0022] The temperature of the electrolyte is -15°C to -10°C; preferably, before the electrolytic polishing treatment, liquid nitrogen is added to the electrolyte to make the temperature of the electrolyte -15°C to -10°C.

[0023] Furthermore, in the electrolytic polishing process of step 2):

[0024] allowing the electrolyte to flow by a water pump to flush the polished sample;

[0025] Preferably, the flow rate of the electrolyte is 0.5-2 L / s.

[0026] Furthermore, in step 3), the cleaning step includes:

[0027] The electrolytically polished sample is rinsed with running tap water and then placed in anhydrous ethanol for ultrasonic cleaning;

[0028] Preferably, the flushing treatment time is 1 to 3 minutes;

[0029] Preferably, the ultrasonic cleaning treatment time is 30 to 60 seconds.

[0030] On the other hand, the present invention provides a low-strength, high-corrosion-resistant metal test sample, wherein the surface of the low-strength, high-corrosion-resistant metal test sample is flat and has no stress layer; the high-strength, high-corrosion-resistant metal test sample is used as an EBSD test sample and / or a SEM test sample.

[0031] Furthermore, the low-strength, high-corrosion-resistant metal test sample is obtained by using any of the preparation methods described above.

[0032] The present invention provides a low-strength, high-corrosion-resistant metal test sample and a preparation method thereof, which has the following characteristics:

[0033] Beneficial effects:

[0034] 1. On the one hand, the present invention provides a method for preparing a low-strength, high-corrosion-resistant metal test sample, which is used as an EBSD test sample and / or a SEM test sample; the method for preparing the low-strength, high-corrosion-resistant metal test sample comprises the following steps: performing surface polishing treatment on the low-strength, high-corrosion-resistant metal sample to obtain a polished sample; performing electrolytic polishing treatment on the polished sample to obtain an electrolytically polished sample; performing cleaning treatment on the electrolytically polished sample to obtain a low-strength, high-corrosion-resistant metal test sample; and during the electrolytic polishing treatment, flushing the polished sample with a flowing electrolyte. Based on the above method, a flowing electrolyte is used to flush the sample surface during the electrolytic polishing process. On the one hand, it can effectively remove the stress layer generated on the sample surface during the mechanical polishing process (burnishing treatment). In particular, for some severely deformed samples, strong diffraction patterns can still be produced during EBSD testing, and the comprehensive resolution rate can reach 99%. On the other hand, during the polishing process, the anodic reaction will promote the formation of oxide film and easily be oxidized, hindering subsequent polishing. The flowing electrolyte can carry away oxide residues, avoiding surface defects such as pitting and pitting, thereby ensuring the polishing effect.

[0035] 2. Furthermore, based on the fact that low-strength, high-corrosion-resistant metals are prone to produce oxide films at room temperature that hinder the progress of subsequent polishing, the present invention adds liquid nitrogen to the electrolyte and stirs it to adjust the temperature of the electrolyte to -15°C to -10°C. The passivation rate of the sample at low temperature is reduced, and a dissolution-passivation balance is achieved, thereby avoiding the oxide film from hindering the progress of subsequent polishing and ensuring the polishing effect.

[0036] 3. Furthermore, the flow rate of the electrolyte in the electropolishing process is 0.5-2L / s. If the flow rate is too high and excessive, it will damage the flatness of the sample surface. Considering that the solution has poor fluidity at low temperatures, if the flow rate is too low, effective mass transfer will not be possible, that is, it cannot ensure the effective removal of oxide residues. In addition, due to the low temperature of electropolishing, the viscosity of the electropolishing solution usually increases. If the flow rate is too low, the diffusion of surface metal ions will be hindered, the dissolution rate will be inhibited, and passivation will easily occur. At the same time, Joule heat may be generated by the passage of current during the electrolysis process, thereby increasing the local polishing solution temperature. An appropriate flow rate can enhance solution convection, promote uniform heat dissipation, and ensure a constant local electrolyte temperature.

[0037] 4. On the other hand, the present invention provides a low-strength, high-corrosion-resistant metal test sample obtained by any of the preparation methods described above, which is used as an EBSD test sample and / or a SEM test sample, and can produce a strong diffraction pattern during EBSD testing, with an overall resolution rate of up to 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. The drawings described below are merely exemplary. Those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0039] Figure 1 A diagram of the equipment used for the electrolytic polishing process of the present invention;

[0040] Figure 2 (a) and (b) are the SEM image and EBSD crystallographic IPF orientation image of the annealed tantalum sample surface obtained in Example 1, respectively;

[0041] Figure 3 (a) and (b) are the SEM image of the surface of the deformed tantalum sample obtained in Example 2 and the EBSD crystallography IPF orientation imaging diagram, respectively;

[0042] Figure 4 (a) and (b) are the surface SEM image and EBSD crystallography IPF orientation imaging of the Ta-2.5W sample obtained in Example 3, respectively;

[0043] Figure 5 This is a SEM photograph of the surface of the annealed tantalum sample obtained in Comparative Example 1;

[0044] Figure 6 This is a SEM photograph of the surface of the annealed tantalum sample obtained in Comparative Example 2;

[0045] Figure 7 (a), (b), (c) and (d) are EBSD crystallographic IPF orientation images of the sample surface after ion etching for 1 h, 4 h and 6 h of the annealed tantalum sample obtained in Comparative Example 3 and the corresponding SEM images after ion etching for 6 h;

[0046] The accompanying drawings are marked as follows: 1-power supply device, 2-electrolytic cell, 3-water pump, 4-clamping device, 5-polished sample, 6-304 stainless steel sheet, 7-thermometer. DETAILED DESCRIPTION

[0047] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. The drawings described below are merely exemplary. Those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0048] The present invention provides a method for preparing a low-strength, high-corrosion-resistant metal test sample, wherein the low-strength, high-corrosion-resistant metal test sample is used as an EBSD test sample and / or a SEM test sample. The method for preparing the low-strength, high-corrosion-resistant metal test sample comprises the following steps:

[0049] Step 1): Use electric spark wire cutting to cut the sample required for observation and clean it. Then, use 1000#, 2000#, and 3000# silicon carbide sandpaper to polish the surface of the low-strength, high-corrosion-resistant metal sample in sequence, ensuring that each sandpaper polishes away the scratches left by the previous sandpaper until the surface of the sample is flat and smooth. Wash it with anhydrous ethanol and blow it dry to obtain a polished sample; wherein the low-strength, high-corrosion-resistant metal sample is one of a pure molybdenum sample, a molybdenum alloy sample, a pure niobium sample, a niobium alloy sample, a pure tantalum sample, and a tantalum alloy sample.

[0050] Step 2): electrolytically polishing the polished sample to obtain an electrolytically polished sample;

[0051] During the electropolishing process, the polished sample is flushed with flowing electrolyte;

[0052] The steps are as follows: placing a metal sheet around the inner wall of a glass container, with the other end of the metal sheet connected to the negative electrode of a DC power supply as a cathode material, and a low-strength, high-corrosion-resistant metal sample as an anode; first adding liquid nitrogen to the electrolyte and stirring to maintain the temperature of the electrolyte at -15°C to -10°C; then placing a water pump in the electrolyte, with the water outlet of the water pump placed horizontally and facing the polished surface of the polished sample, so that the electrolyte flows and flushes the surface of the sample;

[0053] The flow rate of the electrolyte is 0.5-2 L / s; the voltage of the electrolytic polishing treatment is 25-35 V; the time of the electrolytic polishing treatment is 25-35 s; the electrolyte for the electrolytic polishing treatment is a mixed solution of sulfuric acid and methanol; in the electrolyte, the volume ratio of sulfuric acid to methanol is (1-1.5): (7-10).

[0054] Step 3): The electrolytically polished sample is rinsed with running tap water for 1 to 3 minutes, and then the sample is ultrasonically cleaned in anhydrous ethanol for 30 to 60 seconds. After drying, a low-strength, high-corrosion-resistant metal test sample is obtained.

[0055] Based on the above method, a flowing electrolyte is used to flush the sample surface during the electrolytic polishing process. On the one hand, this can effectively remove the stress layer generated on the sample surface during the mechanical polishing process. In particular, for some severely deformed samples, strong diffraction patterns can still be produced during EBSD testing, and the comprehensive resolution rate can reach 99%. On the other hand, during the polishing process, the anodic reaction will promote the formation of oxide film and easily be oxidized, hindering subsequent polishing. The flowing electrolyte can carry away oxide residues, avoiding surface defects such as pitting and pitting, thereby ensuring the polishing effect.

[0056] Because low-strength, high-corrosion-resistant metals are prone to forming oxide films at room temperature that hinder subsequent polishing, the present invention adds liquid nitrogen to the electrolyte and stirs it to a temperature of -15°C to -10°C. This reduces the passivation rate of the sample at low temperatures, achieving a dissolution-passivation equilibrium, thereby avoiding the oxide film from hindering subsequent polishing and ensuring the polishing effect. In addition, a sulfuric acid-methanol solution system replaces the HF used in traditional electrolytic polishing solutions, greatly reducing safety risks during operation.

[0057] The flow rate of the electrolyte in the electrolytic polishing process is 0.5-2L / s. If the flow rate is too high and the flow rate is too excessive, the flatness of the sample surface will be destroyed. Considering that the solution has poor fluidity at low temperatures, if the flow rate is too low, effective mass transfer cannot be achieved, that is, it cannot ensure the effective removal of oxide residues. In addition, due to the low temperature of electrolytic polishing, the viscosity of the electropolishing solution usually increases. If the flow rate is too low, the diffusion of surface metal ions will be hindered, the dissolution rate will be inhibited, and passivation will easily occur. At the same time, Joule heat may be generated during the electrolysis process due to the passage of current, thereby increasing the local polishing liquid temperature. An appropriate flow rate can enhance solution convection, promote uniform heat dissipation, and ensure the temperature of the electrolyte.

[0058] The equipment used in the electrolytic polishing process of this application method is as follows Figure 1 As shown, the apparatus includes a power supply 1, an electrolytic cell 2, a water pump 3, and a clamping device 4. The clamping device 4 utilizes tweezers, which stabilize the polished sample 5 and connect the tweezers to the anode of the power supply 1. A 304 stainless steel sheet 6 is connected to the cathode of the power supply 1. After the polished sample 5 is immersed in the electrolyte in the electrolytic cell 2, the power supply 1 is activated, and the water pump is simultaneously turned on to flow the electrolyte, thereby flushing the sample. Furthermore, a thermometer 7 is used to measure the temperature of the electrolyte before the electrolysis process.

[0059] Conventional ion etching methods take a long time and are expensive to prepare samples. The ion beam sweeping range is limited, making it difficult to prepare larger bulk samples. In addition, the traces left by the ion beam will also affect the observation during the subsequent SEM process due to the undulations on the sample surface. The preparation method of the present application is simple to operate, cost-effective and efficient.

[0060] On the other hand, the present invention provides a low-strength, high-corrosion-resistant metal test sample, the surface of the low-strength, high-corrosion-resistant metal test sample is smooth and has no stress layer; the low-strength, high-corrosion-resistant metal test sample is used as an EBSD test sample and / or SEM test sample.

[0061] Furthermore, a low-strength, high-corrosion-resistant metal test sample is obtained by using any of the above preparation methods.

[0062] The present invention is further described below with reference to specific examples and comparative examples.

[0063] Example 1

[0064] This embodiment provides a method for preparing a low-strength, high-corrosion-resistant metal test sample, which is used as an EBSD test sample and / or a SEM test sample. The method for preparing the low-strength, high-corrosion-resistant metal test sample includes the following steps:

[0065] Step 1): using 1000#, 2000#, and 3000# silicon carbide sandpaper to polish the surface of the annealed pure tantalum sample to obtain a polished sample;

[0066] Step 2): electrolytically polishing the polished sample to obtain an electrolytically polished sample;

[0067] A 304 stainless steel sheet was placed around the inner wall of a glass container, with the other end of the 304 stainless steel sheet connected to the negative electrode of a DC power supply as a cathode material, and a pure tantalum sample as an anode. Liquid nitrogen was first added to the electrolyte and stirred to maintain the electrolyte temperature at -10°C. A water pump was then placed in the electrolyte with the water outlet of the water pump placed horizontally and facing the polished surface of the polished sample so that the flowing water could flush the surface of the sample.

[0068] The flow rate of the electrolyte was 0.8 L / s; the voltage of the electrolytic polishing process was 30 V; the time of the electrolytic polishing process was 30 s; the electrolyte for the electrolytic polishing process was a mixed solution of sulfuric acid and methanol; in the electrolyte, the volume ratio of sulfuric acid to methanol was 1:7;

[0069] Step 3): The electrolytically polished sample was rinsed with running tap water for 1 minute, and then the sample was ultrasonically cleaned in anhydrous ethanol for 30 seconds. After drying, a pure tantalum test sample was obtained.

[0070] Example 2

[0071] This embodiment provides a method for preparing a low-strength, high-corrosion-resistant metal test sample, which is used as an EBSD test sample and / or a SEM test sample. The method for preparing the low-strength, high-corrosion-resistant metal test sample includes the following steps:

[0072] Step 1): The pure tantalum sample is polished using 1000#, 2000#, and 3000# silicon carbide sandpaper in sequence to obtain a polished sample; wherein the deformation of the pure tantalum sample is 0.4 (compared to the annealed sample, its structure is finer and the sample preparation requirements are higher);

[0073] Step 2): electrolytically polishing the polished sample to obtain an electrolytically polished sample;

[0074] A 304 stainless steel sheet was placed around the inner wall of a glass container, with the other end of the 304 stainless steel sheet connected to the negative electrode of a DC power supply as a cathode material, and a pure tantalum sample as an anode. Liquid nitrogen was first added to the electrolyte and stirred to maintain the electrolyte temperature at -15°C. A water pump was then placed in the electrolyte with the water outlet of the water pump placed horizontally and facing the polished surface of the polished sample so that the flowing water could flush the surface of the sample.

[0075] The flow rate of the electrolyte was 1.5 L / s; the voltage of the electrolytic polishing process was 25 V; the time of the electrolytic polishing process was 30 s; the electrolyte for the electrolytic polishing process was a mixed solution of sulfuric acid and methanol; in the electrolyte, the volume ratio of sulfuric acid to methanol was 1.5:8;

[0076] Step 3): The electrolytically polished sample was rinsed with running tap water for 2 minutes, and then the sample was ultrasonically cleaned in anhydrous ethanol for 50 seconds. After drying, a pure tantalum test sample was obtained.

[0077] Example 3

[0078] This embodiment provides a method for preparing a low-strength, high-corrosion-resistant metal test sample, which is used as an EBSD test sample and / or a SEM test sample. The method for preparing the low-strength, high-corrosion-resistant metal test sample includes the following steps:

[0079] Step 1): polishing the surface of the Ta-2.5W alloy sample using 1000#, 2000#, and 3000# silicon carbide sandpaper in sequence to obtain a polished sample;

[0080] Step 2): electrolytically polishing the polished sample to obtain an electrolytically polished sample;

[0081] A 304 stainless steel sheet is placed around the inner wall of a glass container, with the other end of the 304 stainless steel sheet connected to the negative electrode of a DC power supply as a cathode material, and a tantalum alloy sample is used as an anode. Liquid nitrogen is first added to the electrolyte and stirred to maintain the electrolyte temperature at -15°C. A water pump is then placed in the electrolyte with the water outlet of the water pump placed horizontally and facing the polished surface of the polished sample so that the flowing water flushes the surface of the sample.

[0082] The flow rate of the electrolyte was 1.5 L / s; the voltage of the electrolytic polishing process was 20 V; the time of the electrolytic polishing process was 30 s; the electrolyte for the electrolytic polishing process was a mixed solution of sulfuric acid and methanol; in the electrolyte, the volume ratio of sulfuric acid to methanol was 1.5:8;

[0083] Step 3): The electrolytically polished sample was rinsed with running tap water for 2 minutes, and then the sample was ultrasonically cleaned in anhydrous ethanol for 50 seconds. After drying, a pure tantalum test sample was obtained.

[0084] Comparative Example 1

[0085] This comparative example provides a method for preparing a low-strength, high-corrosion-resistant metal test sample, which is used as an EBSD test sample and / or a SEM test sample. The method for preparing the low-strength, high-corrosion-resistant metal test sample comprises the following steps:

[0086] Step 1): using 1000#, 2000#, and 3000# silicon carbide sandpaper to polish the surface of the annealed pure tantalum sample to obtain a polished sample;

[0087] Step 2): electrolytically polishing the polished sample to obtain an electrolytically polished sample;

[0088] A 304 stainless steel sheet is placed around the inner wall of a glass container, with the other end of the 304 stainless steel sheet connected to the negative electrode of a DC power supply as a cathode material, and a pure tantalum sample is used as an anode. A water pump is placed in the electrolyte, with the water outlet of the water pump placed horizontally and facing the polished surface of the polished sample, so that the flowing water flushes the surface of the sample.

[0089] The flow rate of the electrolyte was 0.8 L / s; the voltage of the electrolytic polishing process was 30 V; the time of the electrolytic polishing process was 30 s; the electrolyte for the electrolytic polishing process was a mixed solution of sulfuric acid and methanol; in the electrolyte, the volume ratio of sulfuric acid to methanol was 1:7;

[0090] Step 3): The electrolytically polished sample was rinsed with running tap water for 1 minute, and then the sample was ultrasonically cleaned in anhydrous ethanol for 30 seconds. After drying, a pure tantalum test sample was obtained.

[0091] Comparative Example 2

[0092] This embodiment provides a method for preparing a low-strength, high-corrosion-resistant metal test sample, which is used as an EBSD test sample and / or a SEM test sample. The method for preparing the low-strength, high-corrosion-resistant metal test sample includes the following steps:

[0093] Step 1): polishing the surface of the pure tantalum sample using 1000#, 2000#, and 3000# silicon carbide sandpaper in sequence to obtain a polished sample;

[0094] Step 2): electrolytically polishing the polished sample to obtain an electrolytically polished sample;

[0095] A 304 stainless steel sheet was placed around the inner wall of a glass container, with the other end of the sheet connected to the negative electrode of a DC power supply as the cathode material, and a pure tantalum sample as the anode. Liquid nitrogen was first added to the electrolyte and stirred to maintain the electrolyte temperature at -15°C.

[0096] The voltage of the electrolytic polishing process is 28V; the time of the electrolytic polishing process is 30s; the electrolyte of the electrolytic polishing process is a mixed solution of sulfuric acid and methanol; in the electrolyte, the volume ratio of sulfuric acid to methanol is 1.5:8;

[0097] Step 3): The electrolytically polished sample was rinsed with running tap water for 2 minutes, and then the sample was ultrasonically cleaned in anhydrous ethanol for 50 seconds. After drying, a pure tantalum test sample was obtained.

[0098] Comparative Example 3

[0099] This comparative example provides a method for preparing a low-strength, high-corrosion-resistant metal test sample, which is used as an EBSD test sample and / or a SEM test sample. The method for preparing the low-strength, high-corrosion-resistant metal test sample comprises the following steps:

[0100] Step 1): using 1000#, 2000#, and 3000# silicon carbide sandpaper to polish the surface of the annealed pure tantalum sample to obtain a polished sample;

[0101] Step 2): performing ion etching and polishing on the polished sample to obtain an electrolytically polished sample; wherein the process parameters of the ion etching are: voltage of 5 kV, angle of 7°, time of 1, 4, and 6 hours respectively, and rotation speed of 5 RPM;

[0102] Step 3): The electrolytically polished sample was rinsed with running tap water for 1 minute, and then the sample was ultrasonically cleaned in anhydrous ethanol for 30 seconds. After drying, a pure tantalum test sample was obtained.

[0103] like Figure 2 、 3 As shown in Figure 4, it can be seen that the surface of the test sample prepared by the method of the present invention is smooth, and a clean and clear EBSD grain morphology orientation map can be obtained, and the grain boundaries are clearly displayed. Figure 3 It shows obvious microscopic defect structures such as dislocation substructures, and the EBSD resolution rate reaches 99%.

[0104] Comparative Example 1: The sample prepared at room temperature is as follows Figure 5 As shown, a large number of etch pits appeared on the surface. This is because the temperature of the electrolyte in Comparative Example 1 is high, the ion activity is enhanced, and a large number of etch pits are generated on the surface in a short period of time, resulting in a decrease in the surface quality of the sample.

[0105] Comparative Example 2 did not add a water pump to make the electrolyte flow, and the prepared sample was as follows Figure 6 As shown, the surface is blurred under the scanning electron microscope. On the one hand, it is because the static electrolyte cannot effectively remove the stress layer generated on the sample surface during the mechanical polishing process, resulting in lattice distortion in the surface layer, which is difficult to analyze with the scanning electron microscope. On the other hand, the oxide residues produced by the anodic reaction cannot be quickly removed, which hinders the further progress of electrolytic polishing and causes the surface to be blurred.

[0106] Comparative Example 3 is a conventional ion beam bombardment method. Figure 7 It can be seen that as the ion beam bombardment time increases, the damaged and deformed layer on the sample surface is gradually removed, and the EBSD analysis quality is improved. However, due to the limited range of ion sweeping, it is difficult to prepare samples larger than 1 cm, and during the ion bombardment process, the sample surface will have bumps and undulations, such as Figure 7 As shown in (d), an illusion is formed, and the sample preparation cycle is long and the cost is high.

[0107] It is easy for those skilled in the art to understand that, under the premise of no conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0108] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art may make various improvements and variations without departing from the technical principles of the present invention, and such improvements and variations shall also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a low-strength, high-corrosion-resistant metal test sample, characterized in that: The high-strength, high-corrosion-resistant metal test sample is used as an EBSD test sample and / or a SEM test sample; the preparation method of the low-strength, high-corrosion-resistant metal test sample comprises the following steps: Step 1): performing surface polishing treatment on a low-strength, high-corrosion-resistant metal sample to obtain a polished sample; Step 2): performing electrolytic polishing on the polished sample to obtain an electrolytically polished sample; during the electrolytic polishing process, flushing the polished sample with a flowing electrolyte; Step 3): Cleaning the electrolytically polished sample to obtain the low-strength, high-corrosion-resistant metal test sample.

2. The method for preparing a low-strength, high-corrosion-resistant metal test sample according to claim 1, characterized in that: In said step 1): The low-strength, high-corrosion-resistant metal sample is a metal sample with a strength lower than 200 MPa; Preferably, the low-strength, high-corrosion-resistant metal sample is one of a pure molybdenum sample, a molybdenum alloy sample, a pure niobium sample, a niobium alloy sample, a pure tantalum sample, and a tantalum alloy sample.

3. The method for preparing a low-strength, high-corrosion-resistant metal test sample according to claim 1, characterized in that: In step 1), the surface polishing step includes: Use 1000#, 2000# and 3000# silicon carbide sandpaper for wet grinding in sequence.

4. The method for preparing a low-strength, high-corrosion-resistant metal test sample according to claim 1, characterized in that: In the electrolytic polishing treatment of step 2): The cathode is made of one of stainless steel, titanium and copper; and / or The anode is the low-strength, high-corrosion-resistant metal sample.

5. The method for preparing a low-strength, high-corrosion-resistant metal test sample according to claim 1, characterized in that: In the electrolytic polishing treatment of step 2): The electrolyte for the electrolytic polishing treatment includes sulfuric acid and methanol; preferably, in the electrolyte, the volume ratio of sulfuric acid to methanol is (1-1.5): (7-10).

6. The method for preparing a low-strength, high-corrosion-resistant metal test sample according to claim 1, characterized in that: In the electrolytic polishing treatment of step 2): Voltage is 25-35V; and / or The electrolytic polishing treatment time is 25 to 35 seconds; and / or The temperature of the electrolyte is -15°C to -10°C; preferably, before the electrolytic polishing treatment, liquid nitrogen is added to the electrolyte and stirred to cool it down so that the temperature of the electrolyte is -15°C to -10°C.

7. The method for preparing a low-strength, high-corrosion-resistant metal test sample according to claim 1, characterized in that: In the electrolytic polishing treatment of step 2): allowing the electrolyte to flow by a water pump to flush the polished sample; Preferably, the flow rate of the electrolyte is 0.5-2 L / s.

8. The method for preparing a low-strength, high-corrosion-resistant metal test sample according to claim 1, characterized in that: In step 3), the cleaning step includes: The electrolytically polished sample is rinsed with running water and then placed in anhydrous ethanol for ultrasonic cleaning; Preferably, the flushing treatment time is 1 to 3 minutes; Preferably, the ultrasonic cleaning treatment time is 30 to 60 seconds.

9. A low-strength, high-corrosion-resistant metal test sample, characterized in that: The surface of the low-strength, high-corrosion-resistant metal test sample is smooth and has no stress layer; the high-strength, high-corrosion-resistant metal test sample is used as an EBSD test sample and / or a SEM test sample.

10. The low-strength, high-corrosion-resistant metal test sample according to claim 9, characterized in that: The low-strength, high-corrosion-resistant metal test sample is obtained by the preparation method according to any one of claims 1 to 8.

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