High-strength multiphase steel test sample and preparation method thereof

Abstract

The invention provides a preparation method of a high-strength multi-phase steel test sample, and relates to the technical field of transmission electron microscope sample preparation, and the preparation method comprises the following steps: sequentially cutting, polishing, punching and mechanically grinding a high-strength multi-phase steel sample to obtain a first sample; performing electrolysis double-spraying treatment on the first sample to obtain a second sample; in the electrolysis double-spraying treatment, electrolyte comprises perchloric acid, methanol, citric acid and glycerol; and the second sample is cleaned, and the high-strength multiphase steel test sample is obtained. Compared with a physical thinning method, an electrochemical double-spraying (electrolytic double-spraying) method is adopted, the process is simple, the preparation period is short, and the efficiency is high; and citric acid and glycerol are added into the electrolyte, so that the carbide of the high-strength multiphase steel sample is prevented from falling off, the uniform thinning of the sample is realized, and the test effect of the transmission electron microscope is further ensured.

Description

Technical Field

[0001] This invention belongs to the field of transmission electron microscopy sample preparation technology, specifically relating to a high-strength multiphase steel test sample and its preparation method. Background Technology

[0002] Ultra-high strength and toughness steel is widely used in key load-bearing and compression components in various industrial fields such as engineering machinery and national defense. In recent years, with the rapid development of my country's economy, especially with its manufacturing scale ranking among the world's largest, and based on China's unique geographical and resource characteristics, there is an urgent need for ultra-high strength and high toughness steel in the development of national defense and engineering machinery equipment with Chinese characteristics. Martensitic multiphase steel is the most representative type of ultra-high strength steel. Through complex heat treatment processes and innovative alloy design concepts, it has achieved its superior performance, mainly through its complex microstructure. It is based on martensite as the main matrix, with multiple composite matrices, and also has precipitated nanophases. The extremely refined structure brings excellent material properties. Material optimization and iteration are based on the precise and detailed characterization of the microstructure. Transmission electron microscopy (TEM) is the main characterization method for studying the microstructure characteristics and evolution of materials, and it is essential for deeply revealing the microscopic potential mechanisms behind the macroscopic properties of materials. Therefore, obtaining TEM samples of martensitic multiphase steel with large thin-area areas has become a key link in the research of ultra-high strength and toughness steel materials.

[0003] Currently, the main methods for preparing martensitic multiphase steel samples for transmission electron microscopy (TEM) include electrolytic double-jet, ion thinning, and focused ion beam cutting. Among these, ion thinning has limited efficiency due to ion bombardment, typically requiring a thickness of several micrometers in the central region to shorten preparation time. However, manual grinding is insufficient to achieve this thickness, so electrolytic thinning or pitting thinning methods are commonly used. However, pitting inevitably introduces external interference factors such as stress and dislocations, and the preparation cycle is lengthy, sometimes requiring one to several days, resulting in significant time and equipment costs and low efficiency. Focused ion beam cutting involves prolonged bombardment of the sample surface by the ion beam, often leaving defects that affect the characterization results under TEM. Furthermore, focused ion beam cutting is extremely expensive, requires advanced technology, and carries a high risk of failure, making it unsuitable for observing samples in various states.

[0004] In summary, existing methods for preparing high-strength multiphase steel samples for transmission electron microscopy suffer from problems such as long preparation cycles, low efficiency, and poor results. Summary of the Invention

[0005] Therefore, the present invention provides a high-strength multiphase steel test sample and its preparation method, which can solve the problem of long preparation cycle of high-strength multiphase steel transmission electron microscopy samples in the prior art.

[0006] To address the aforementioned problems, this invention provides a method for preparing a high-strength multiphase steel test sample, which is used as a transmission electron microscopy (TEM) test sample. The method for preparing the high-strength multiphase steel test sample includes the following steps:

[0007] Step 1): Pre-treat the high-strength multiphase steel sample to obtain the first sample;

[0008] Step 2): The first sample is subjected to electrolytic double-spray treatment to obtain the second sample; in the electrolytic double-spray treatment, the electrolyte includes perchloric acid, methanol, citric acid and glycerol;

[0009] Step 3): Clean the second sample to obtain the high-strength multiphase steel test sample.

[0010] Furthermore, in step 1):

[0011] The pretreatment steps include: sequentially cutting, grinding, punching, and mechanically grinding the high-strength multiphase steel sample.

[0012] Furthermore, the high-strength multiphase steel sample is cut using electrical discharge machining (EDM); preferably, the high-strength multiphase steel sample is cut into samples with a length of 5–15 mm, a width of 5–15 mm, and a thickness of less than 0.6 mm; and / or

[0013] The cut sample was polished sequentially using 1000#, 2000#, and 3000# silicon carbide sandpaper; and / or

[0014] The thickness of the sample after grinding is 60–80 μm.

[0015] Furthermore, the sample sheet is punched using a punching tool; preferably, after punching, a circular piece with a diameter of 3 mm is obtained; and / or

[0016] The samples were mechanically ground using 3000# silicon carbide sandpaper; and / or

[0017] The thickness of the first sample is 30–40 μm.

[0018] Furthermore, in step 1):

[0019] The high-strength multiphase steel is a martensitic dual-phase steel sample or a pearlitic steel sample; and / or

[0020] The strength of the high-strength multiphase steel sample exceeds 1.5 GPa; and / or

[0021] The microstructure of the high-strength multiphase steel sample includes a martensitic or ferrite matrix, as well as carbides.

[0022] Furthermore, in the electrolytic dual-spray treatment of step 2):

[0023] In the electrolyte, the volume ratio of perchloric acid to methanol is (1-1.2):(9-11); and / or

[0024] In the electrolyte, the citric acid has a volume fraction of 1-5 vol.%; and / or

[0025] In the electrolyte, the volume fraction of the glycerol is 1-5 vol.%; and / or

[0026] The temperature of the electrolyte is -30℃ to -15℃; preferably, liquid nitrogen is added to the electrolyte and stirred to make the temperature of the electrolyte -30℃ to -15℃.

[0027] Furthermore, in the electrolytic dual-spray treatment of step 2):

[0028] The voltage is 20–30V; and / or

[0029] The current is 30–50 mA; and / or

[0030] The electrolyte flow rate is 20–25; and / or

[0031] The photosensitivity value is 5 to 7.

[0032] Furthermore, in step 3):

[0033] The second sample was cleaned sequentially with deionized water and anhydrous ethanol.

[0034] On the other hand, the present invention provides a high-strength multiphase steel test sample, which is used as a transmission electron microscopy test sample.

[0035] Furthermore, the high-strength multiphase steel test sample is obtained using any of the preparation methods described above.

[0036] The high-strength multiphase steel test sample and its preparation method provided by this invention have the following beneficial effects:

[0037] 1. On one hand, this invention provides a method for preparing a high-strength multiphase steel test sample, comprising the following steps: sequentially cutting and grinding a high-strength multiphase steel sample to obtain a sample sheet; sequentially punching and mechanically grinding the sample sheet to obtain a first sample; subjecting the first sample to electrolytic double-spraying treatment to obtain a second sample; in the electrolytic double-spraying treatment, the electrolyte includes perchloric acid, methanol, citric acid, and glycerol; and cleaning the second sample to obtain the high-strength multiphase steel test sample. Compared with physical thinning methods, the electrochemical double-spraying (electrolytic double-spraying) method is simpler, has a shorter preparation cycle, and is more efficient; furthermore, the addition of citric acid and glycerol to the electrolyte prevents the detachment of carbides from the high-strength multiphase steel sample, thereby avoiding the impact of carbide detachment on the sample surface and ensuring the transmission electron microscopy test results.

[0038] 2. Furthermore, the present invention adds liquid nitrogen to the electrolyte and stirs it to make the electrolyte temperature -30℃ to -15℃. At low temperature, the corrosion and oxidation rate of the sample can be slowed down, thereby reducing the potential difference between the martensitic matrix and the carbides, achieving uniform thinning of the sample, and ensuring better polishing effect.

[0039] 3. On the other hand, the present invention provides a high-strength multiphase steel test sample, which is obtained by the above preparation method. The high-strength multiphase steel test sample can produce pores with a diameter of about 300 μm, which can be thinned to a thickness that can be penetrated by an electron beam, so as to be used as a transmission electron microscope test sample. Attached Figure Description

[0040] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0041] Figure 1 Macroscopic optical micrograph of the M50 bearing steel test sample prepared in Example 1 of this invention;

[0042] Figure 2 Transmission imaging of the martensitic structure in M50 bearing steel prepared in Example 1 of this invention;

[0043] Figure 3 Transmission image of the martensitic matrix distribution of carbide structure in M50 bearing steel prepared in Example 1 of this invention;

[0044] Figure 4 Transmission photograph of M50 bearing steel prepared in Example 2 of this invention;

[0045] Figure 5 Transmission photograph of M50 bearing steel prepared in Comparative Example 1;

[0046] Figure 6 Transmission image of M50 bearing steel prepared in Comparative Example 2. Detailed Implementation

[0047] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0048] This invention provides a method for preparing a high-strength multiphase steel test sample, which is used as a transmission electron microscopy (TEM) test sample. The method for preparing the high-strength multiphase steel test sample includes the following steps:

[0049] Step 1): The high-strength multiphase steel sample is cut using electrical discharge machining (EDM); the length of the cut sample is 5-15 mm, the width is 5-15 mm, and the thickness is less than 0.6 mm; then, the cut sample is polished with 1000#, 2000#, and 3000# silicon carbide sandpaper in sequence to obtain a sample sheet with a thickness of 60-80 μm.

[0050] Among them, the high-strength multiphase steel is a martensitic dual-phase steel sample or a pearlitic steel sample with a strength exceeding 1.5 GPa. Its microstructure includes a martensitic matrix or a ferrite matrix, as well as carbides. During the grinding process, a glass plate is placed under the sample and silicon carbide sandpaper, and a soft 4B rubber is used to cover the sample. The rubber is moved to drag the sample through friction, ensuring that only the side of the sample close to the metallographic sandpaper is worn during the grinding process, and ensuring that the sample is uniformly stressed, so as to achieve a flat and uniform sample preparation.

[0051] The sample sheet was then punched using a puncher to obtain a circular disc with a diameter of 3 mm. This disc was then mechanically ground with 3000# silicon carbide sandpaper to remove edge burrs, resulting in a first sample with a thickness of 30–40 μm. Ensuring a uniform sample surface is crucial; otherwise, electrolysis will preferentially corrode thinner areas, causing the perforation to be off-center. Pre-thinning the first sample reduces the time of the dual-jet electrolysis process, decreases the exposure time of the interface in the solution, and prevents preferential corrosion of the interface.

[0052] Step 2): The first sample is subjected to electrolytic double-spray treatment to obtain the second sample; in the electrolytic double-spray treatment, the electrolyte includes perchloric acid, methanol, citric acid and glycerol;

[0053] The specific steps are as follows: Add electrolyte to the electrolytic cell of the electrolytic double-jet thinning instrument, add liquid nitrogen to stir and cool, and simultaneously measure the temperature of the electrolyte. After it drops to the target temperature (-30℃~-15℃), place the first sample on the sample holder, insert it into the bottom of the electrolytic cell, connect the sample holder to the wire, and set parameters such as voltage, electrolyte flow rate, and photosensitivity. After the sample is perforated by double-jet spraying, the instrument alarm will sound when the photosensitivity value set by the electrolytic double-jet thinning instrument is reached, and the second sample will be removed.

[0054] The parameters for the electrolytic dual-spray treatment are as follows: voltage 20–30V; current 30–50mA; electrolyte flow rate 20–25 rpm; photosensitivity 5–7; in the electrolyte, the volume ratio of perchloric acid to methanol is (1–1.2):(9–11), the volume fraction of citric acid is 1–5 vol.%, and the volume fraction of glycerol is 1–5 vol.%. In this electrolyte, a lower electrolyte temperature reduces the potential difference between different phases, resulting in uniform corrosion. However, excessively high voltage leads to surface oxidation and blackening, while excessively low voltage results in scratches. At a suitable voltage, the sample polishing process ensures it remains in the passivation zone, rather than preferentially corroding carbides. Using methanol instead of ethanol allows for better fluidity of the solution at low temperatures. In the above electrolytic dual-spray treatment, the resulting bright surface indicates uniform corrosion and thinning of the sample without oxidation. If the flow rate is too high, thin areas of the sample will be damaged, leading to cracks. If the flow rate is too low, the sample will corrode severely but will not easily develop perforations. The photosensitive value ensures that the sample is sprayed with appropriately sized holes.

[0055] Step 3): The second sample was washed five times with deionized water and five times with anhydrous ethanol to obtain the high-strength multiphase steel test sample. During the cleaning process, the sample was placed vertically into the liquid while being agitated up and down in the liquid to utilize the surface tension of the liquid for cleaning and to minimize the impact on thin areas. After cleaning, the sample was quickly transferred to a vacuum drying oven to dry, preventing galvanic corrosion between the two phases under atmospheric conditions.

[0056] Compared to physical thinning methods, this application uses an electrochemical double-spray (electrolytic double-spray) method, which is simple and efficient. Furthermore, the addition of citric acid and glycerol to the electrolyte prevents the carbide from falling off the high-strength multiphase steel sample, thereby avoiding the impact of carbide falling off on the sample surface and ensuring the transmission electron microscopy test results.

[0057] Electrolytic dual-spray treatment at low temperatures can slow down the corrosion and oxidation rates of the sample, thereby reducing the potential difference between the two phases (below 10V), achieving uniform thinning of the sample, and ensuring better polishing results.

[0058] On the other hand, the present invention provides a high-strength multiphase steel test sample, which is used as a transmission electron microscope (TEM) test sample. The surface of the high-strength multiphase steel test sample is bright and produces pores with a diameter of about 300 μm. The 300 μm pores provide a sufficiently large thin area to facilitate the positioning and observation of the microstructure of the high-strength multiphase steel (such as phase distribution, dislocations, precipitates, etc.).

[0059] Furthermore, the high-strength multiphase steel test samples were obtained using any of the above preparation methods.

[0060] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0061] Example 1

[0062] This embodiment provides a method for preparing a high-strength multiphase steel test sample, which is used as a transmission electron microscopy (TEM) test sample. The method for preparing the high-strength multiphase steel test sample includes the following steps:

[0063] Step 1): The M50 bearing steel sample was cut using electrical discharge machining (EDM); the length of the cut sample was 8 mm, the width was 6 mm, and the thickness was 0.5 mm; then, the cut sample was polished with 1000#, 2000#, and 3000# silicon carbide sandpaper in sequence to obtain a sample sheet with a thickness of 50 μm.

[0064] The microstructure of the high-strength multiphase steel sample includes a martensitic or ferritic matrix, as well as carbides. During the grinding process, a glass plate is placed under the sample and silicon carbide sandpaper, and a soft 4B rubber is used to cover the sample. The rubber is moved to drag the sample through friction, ensuring that only the side of the sample close to the metallographic sandpaper is worn during the grinding process, and ensuring that the sample is uniformly stressed, thus achieving a flat and uniform sample preparation.

[0065] The sample was then punched to obtain a 3mm diameter disc. Next, the disc was mechanically ground with 3000# silicon carbide sandpaper to remove edge burrs, resulting in a first sample with a thickness of 30μm. This process ensures a uniform sample surface; otherwise, electrolysis will preferentially corrode thinner areas, causing the pores to be outside the central region.

[0066] Step 2): Add electrolyte to the electrolytic cell of the electrolytic double-jet thinning instrument, add liquid nitrogen to stir and cool, and simultaneously measure the temperature of the electrolyte. After it drops to the target temperature of -25℃, place the first sample on the sample holder, insert it into the bottom of the electrolytic cell, connect the sample holder to the wire, and set parameters such as voltage, electrolyte flow rate, and photosensitivity to perform electrolytic double-jet treatment. After the sample is perforated by double-jet, the instrument alarm will sound when the photosensitivity value set by the electrolytic double-jet thinning instrument is reached, and the second sample will be removed.

[0067] The voltage was 25V; the current was 40mA; the electrolyte flow rate was 20; the photosensitivity was 5; the electrolyte consisted of perchloric acid, methanol, citric acid, and glycerol; the volume ratio of perchloric acid to methanol was 1:9; the volume fraction of citric acid was 2 vol.%; and the volume fraction of glycerol was 5 vol.%.

[0068] Step 3): The second sample was washed 5 times with deionized water and 5 times with anhydrous ethanol to obtain the high-strength multiphase steel test sample.

[0069] Example 2

[0070] This embodiment provides a method for preparing a high-strength multiphase steel test sample, which is used as a transmission electron microscopy (TEM) test sample. The method for preparing the high-strength multiphase steel test sample includes the following steps:

[0071] Step 1): The M50 bearing steel sample was cut using electrical discharge machining (EDM); the length of the cut sample was 8 mm, the width was 6 mm, and the thickness was 0.5 mm; then, the cut sample was polished with 1000#, 2000#, and 3000# silicon carbide sandpaper in sequence to obtain a sample sheet with a thickness of 50 μm.

[0072] The microstructure of the high-strength multiphase steel sample includes a martensitic or ferritic matrix, as well as carbides. During the grinding process, a glass plate is placed under the sample and silicon carbide sandpaper, and a soft 4B rubber is used to cover the sample. The rubber is moved to drag the sample through friction, ensuring that only the side of the sample close to the metallographic sandpaper is worn during the grinding process, and ensuring that the sample is uniformly stressed, thus achieving a flat and uniform sample preparation.

[0073] The sample was then punched to obtain a 3mm diameter disc. Next, the disc was mechanically ground with 3000# silicon carbide sandpaper to remove edge burrs, resulting in a first sample with a thickness of 30μm. This process ensures a uniform sample surface; otherwise, electrolysis will preferentially corrode thinner areas, causing the pores to be outside the central region.

[0074] Step 2): Add electrolyte to the electrolytic cell of the electrolytic double-jet thinning instrument, add liquid nitrogen to stir and cool, and simultaneously measure the temperature of the electrolyte. After it drops to the target temperature of -15℃, place the first sample on the sample holder, insert it into the bottom of the electrolytic cell, connect the sample holder to the wire, and set parameters such as voltage, electrolyte flow rate, and photosensitivity to perform electrolytic double-jet treatment. After the sample is perforated by double-jet, the instrument alarm will sound when the photosensitivity value set by the electrolytic double-jet thinning instrument is reached, and the second sample will be removed.

[0075] The voltage was 20V; the current was 45mA; the electrolyte flow rate was 18; the photosensitivity was 6; the electrolyte consisted of perchloric acid, methanol, citric acid, and glycerol; the volume ratio of perchloric acid to methanol was 1:9; the volume fraction of citric acid was 2 vol.%; and the volume fraction of glycerol was 5 vol.%.

[0076] Step 3): The second sample was washed 5 times with deionized water and 5 times with anhydrous ethanol to obtain the high-strength multiphase steel test sample.

[0077] Comparative Example 1

[0078] This comparative example provides a method for preparing a high-strength multiphase steel test sample, which is used as a transmission electron microscopy (TEM) test sample. The method for preparing the high-strength multiphase steel test sample includes the following steps:

[0079] Step 1): The M50 bearing steel sample was cut using electrical discharge machining (EDM); the length of the cut sample was 8 mm, the width was 6 mm, and the thickness was 0.5 mm; then, the cut sample was polished with 1000#, 2000#, and 3000# silicon carbide sandpaper in sequence to obtain a sample sheet with a thickness of 50 μm.

[0080] The microstructure of the high-strength multiphase steel sample includes a martensitic or ferrite matrix, as well as carbides. During the grinding process, a glass plate is placed under the sample and silicon carbide sandpaper, and a soft 4B rubber is used to cover the sample. The rubber is moved to drag the sample through friction, ensuring that only the side of the sample close to the metallographic sandpaper is worn during the grinding process, and ensuring that the sample is uniformly stressed, thus achieving a flat and uniform sample preparation.

[0081] The sample was then punched to obtain a 3mm diameter disc. Next, the disc was mechanically ground with 3000# silicon carbide sandpaper to remove edge burrs, resulting in a first sample with a thickness of 30μm. This process ensures a uniform sample surface; otherwise, electrolysis will preferentially corrode thinner areas, causing the pores to be outside the central region.

[0082] Step 2): Add electrolyte to the electrolytic cell of the electrolytic double-jet thinning instrument, add liquid nitrogen to stir and cool, and simultaneously measure the temperature of the electrolyte. After it drops to the target temperature of -25℃, place the first sample on the sample holder, insert it into the bottom of the electrolytic cell, connect the sample holder to the wire, and set parameters such as voltage, electrolyte flow rate, and photosensitivity to perform electrolytic double-jet treatment. After the sample is perforated by double-jet, the instrument alarm will sound when the photosensitivity value set by the electrolytic double-jet thinning instrument is reached, and the second sample will be removed.

[0083] The voltage is 25V; the current is 40mA; the electrolyte flow rate is 20; the photosensitivity is 5; the electrolyte includes perchloric acid and methanol; the volume ratio of perchloric acid to methanol is 1:9.

[0084] Step 3): The second sample was washed 5 times with deionized water and 5 times with anhydrous ethanol to obtain the high-strength multiphase steel test sample.

[0085] Comparative Example 2

[0086] This embodiment provides a method for preparing a high-strength multiphase steel test sample, which is used as a transmission electron microscopy (TEM) test sample. The method for preparing the high-strength multiphase steel test sample includes the following steps:

[0087] Step 1): The M50 bearing steel sample was cut using electrical discharge machining (EDM); the length of the cut sample was 8 mm, the width was 6 mm, and the thickness was 0.5 mm; then, the cut sample was polished with 1000#, 2000#, and 3000# silicon carbide sandpaper in sequence to obtain a sample sheet with a thickness of 50 μm.

[0088] The microstructure of the high-strength multiphase steel sample includes a martensitic or ferritic matrix, as well as carbides. During the grinding process, a glass plate is placed under the sample and silicon carbide sandpaper, and a soft 4B rubber is used to cover the sample. The rubber is moved to drag the sample through friction, ensuring that only the side of the sample close to the metallographic sandpaper is worn during the grinding process, and ensuring that the sample is uniformly stressed, thus achieving a flat and uniform sample preparation.

[0089] The sample was then punched to obtain a 3mm diameter disc. Next, the disc was mechanically ground with 3000# silicon carbide sandpaper to remove edge burrs, resulting in a first sample with a thickness of 30μm. This process ensures a uniform sample surface; otherwise, electrolysis will preferentially corrode thinner areas, causing the pores to be outside the central region.

[0090] Step 2): Add electrolyte to the electrolytic cell of the electrolytic double-jet thinning instrument, add liquid nitrogen to stir and cool, and simultaneously measure the temperature of the electrolyte. After it drops to the target temperature of -5℃, place the first sample on the sample holder, insert it into the bottom of the electrolytic cell, connect the sample holder to the wire, and set parameters such as voltage, electrolyte flow rate, and photosensitivity to perform electrolytic double-jet treatment. After the sample is perforated by double-jet, the instrument alarm will sound when the photosensitivity value set by the electrolytic double-jet thinning instrument is reached, and the second sample will be removed.

[0091] The voltage was 25V; the current was 40mA; the electrolyte flow rate was 20; the photosensitivity was 5; the electrolyte consisted of perchloric acid, methanol, citric acid, and glycerol; the volume ratio of perchloric acid to methanol was 1:9; the volume fraction of citric acid was 2 vol.%; and the volume fraction of glycerol was 5 vol.%.

[0092] Figure 1This is a macroscopic photograph of the sample pores obtained in Example 1 of the method of the present invention. It can be seen that the pores are of moderate size and have serrated edges. Upon further magnification, a fine martensitic structure can be seen in the sample, and there is no preferential corrosion around the carbides. Figure 2-3 ). Figure 4 The transmission image of the sample obtained in Example 2 of the method of the present invention shows that different configurations of the martensite matrix are clearly visible and the carbide edges are clear. Figure 5 For samples obtained without adding citric acid and glycerol to the electrolyte according to the method of this invention, it can be seen that obvious corrosion occurred around the carbides, and even the carbides were detached. The martensitic matrix did not form a thin and transparent area. This is because citric acid, as a corrosion inhibitor, can undergo esterification with methanol to form a complexing agent to protect the carbides and make their boundaries less susceptible to corrosion. At the same time, glycerol can increase the viscosity of the solution, making the surface reaction more uniform. Figure 5 For samples not prepared according to the low-temperature requirements of the method of the present invention, the samples have almost no thin areas and the carbides are obviously detached. At higher temperatures, the matrix and the carbide passivation area cannot overlap, and the carbides and surrounding areas are preferentially corroded and detached. The light transmittance v of the sample increases, making it impossible to obtain a good thin area of ​​martensite.

[0093] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0094] 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 should be included within the protection scope of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength multiphase steel test sample, characterized in that, The high-strength multiphase steel test sample is used as a transmission electron microscopy (TEM) test sample; the preparation method of the high-strength multiphase steel test sample includes the following steps: Step 1): Pre-treat the high-strength multiphase steel sample to obtain the first sample; Step 2): The first sample is subjected to electrolytic double-spray treatment to obtain the second sample; in the electrolytic double-spray treatment, the electrolyte includes perchloric acid, methanol, citric acid and glycerol; Step 3): Clean the second sample to obtain the high-strength multiphase steel test sample.

2. The method for preparing high-strength multiphase steel test samples according to claim 1, characterized in that, In step 1): The pretreatment steps include: sequentially cutting, grinding, punching, and mechanically grinding the high-strength multiphase steel sample.

3. The method for preparing high-strength multiphase steel test samples according to claim 2, characterized in that, The high-strength multiphase steel sample is cut using electrical discharge machining (EDM); preferably, the high-strength multiphase steel sample is cut into samples with a length of 5-15 mm, a width of 5-15 mm, and a thickness of less than 0.6 mm; and / or The cut sample was polished sequentially using 1000#, 2000#, and 3000# silicon carbide sandpaper; and / or The thickness of the sample after grinding is 60–80 μm.

4. The method for preparing high-strength multiphase steel test samples according to claim 2, characterized in that, The sample sheet is punched using a punch; preferably, after punching, a circular sheet with a diameter of 3 mm is obtained; and / or The samples were mechanically ground using 3000# silicon carbide sandpaper; and / or The thickness of the first sample is 30–40 μm.

5. The method for preparing high-strength multiphase steel test samples according to claim 1, characterized in that, In step 1): The high-strength multiphase steel is a martensitic dual-phase steel sample or a pearlitic steel sample; and / or The strength of the high-strength multiphase steel sample exceeds 1.5 GPa; and / or The microstructure of the high-strength multiphase steel sample includes a martensitic or ferrite matrix, as well as carbides.

6. The method for preparing high-strength multiphase steel test samples according to claim 1, characterized in that, In the electrolytic dual-spray treatment in step 2): In the electrolyte, the volume ratio of perchloric acid to methanol is (1-1.2):(9-11); and / or In the electrolyte, the citric acid has a volume fraction of 1-5 vol.%. and / or In the electrolyte, the volume fraction of glycerol is 1-5 vol.%. and / or The temperature of the electrolyte is -30℃ to -15℃; preferably, liquid nitrogen is added to the electrolyte and stirred to make the temperature of the electrolyte -30℃ to -15℃.

7. The method for preparing high-strength multiphase steel test samples according to claim 1, characterized in that, In the electrolytic dual-spray treatment in step 2): The voltage is 20–30V; and / or The current is 30–50 mA; and / or The electrolyte flow rate is 20–25; and / or The photosensitivity value is 5 to 7.

8. The method for preparing high-strength multiphase steel test samples according to claim 1, characterized in that, In step 3): The second sample was cleaned sequentially with deionized water and anhydrous ethanol.

9. A high-strength multiphase steel test sample, characterized in that, The high-strength multiphase steel test sample was used as a transmission electron microscopy (TEM) test sample.

10. The high-strength multiphase steel test sample according to claim 9, characterized in that, The high-strength multiphase steel test sample was obtained using the preparation method described in any one of claims 1 to 8.

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