Preparation method of martensitic stainless steel specific crystal orientation relation interface APT sample

Abstract

The invention belongs to the technical field of APT sample preparation, and particularly relates to a preparation method of a specific crystal orientation relation interface APT sample in martensitic stainless steel. The preparation method comprises the following steps that according to the grain orientation distribution condition of a martensitic stainless steel sample obtained through EBSD treatment, a specific orientation relation interface area is divided; and carrying out fixed-point ion cutting on the region by adopting a first focused ion beam, and carrying out thinning treatment by adopting a second focused ion beam to obtain an APT sample. According to the preparation method, the grain orientation distribution condition of a martensitic stainless steel sample is obtained through electron backscatter diffraction (EBSD) treatment, then a specific orientation relation interface area is divided according to the grain orientation distribution condition, and the APT sample with the specific crystal orientation relation interface and the precision meeting the test requirement is cut according to the divided area.

Description

Technical Field

[0001] The invention belongs to the technical field of APT sample preparation, and in particular relates to a method for preparing an APT sample of a martensitic stainless steel specific crystal orientation relationship interface. Background Art

[0002] High carbon martensitic stainless steel, due to its high carbon and chromium content, greatly improves hardness and wear resistance while ensuring corrosion resistance, and is widely used in the manufacture of high-quality knives, scissors, surgical knives, etc. The metallographic structure of this type of stainless steel after quenching is generally martensitic matrix + eutectic carbide + residual austenite + secondary carbide. The morphology, size and distribution of carbides in martensitic stainless steel have a great influence on the material properties. The use of atom probe tomography (APT) can confirm the type of atoms and intuitively reconstruct their spatial positions, and relatively realistically display the three-dimensional spatial distribution of atoms of different elements in the material, becoming a high-resolution spatial analysis and testing method.

[0003] However, APT has high requirements for samples. Generally, the samples need to be prepared into needles with a tip radius of less than 100nm. The current method for preparing APT samples is mainly electrochemical polishing, but electrochemical polishing cannot locate specific positions such as grain boundaries and its accuracy is not easy to meet the high requirements of APT sample preparation, resulting in the problem of being unable to accurately detect the required information. Summary of the invention

[0004] To solve the above problems, the present invention proposes a method for preparing an APT sample of a specific crystal orientation relationship interface of martensitic stainless steel. The method combines electron backscatter diffraction (EBSD) and focused ion beam (FIB) to prepare an APT sample with a specific grain orientation and an accuracy that meets the test requirements, which is conducive to in-depth analysis of APT data.

[0005] The present invention is achieved through the following technical solutions:

[0006] One of the purposes of the present invention is to provide a method for preparing an APT sample of a martensitic stainless steel specific crystal orientation relationship interface, comprising the following steps:

[0007] The grain orientation distribution of the martensitic stainless steel sample was obtained by EBSD processing, and the interface area with specific orientation relationship was divided;

[0008] The first focused ion beam (FIB) is used to perform point ion cutting on the area, and the second focused ion beam is used to perform thinning (annular milling) to obtain an APT sample.

[0009] The method for preparing the APT sample of the specific crystal orientation relationship interface of martensitic stainless steel provided by the present invention uses electron backscatter diffraction (EBSD) processing to obtain the grain orientation distribution of the martensitic stainless steel sample, and then divides the specific orientation relationship interface area according to the grain orientation distribution, cuts out the APT sample at a fixed point according to the divided area, and performs thinning processing (circular milling). The preparation method obtains an APT sample with a specific crystal orientation relationship interface and an accuracy that meets the test requirements, which is conducive to in-depth analysis of APT data.

[0010] In some possible implementations, the EBSD processing includes the steps of: subjecting the martensitic stainless steel sample to mechanical polishing, electrolytic polishing, marking, EBSD data collection, and EBSD data processing to obtain the grain orientation distribution.

[0011] In some possible implementations, the mechanical polishing process includes rough grinding, fine grinding and mechanical polishing. Rough grinding, fine grinding and mechanical polishing are all conventional processes in the art and are not particularly limited in the present invention.

[0012] In some possible implementations, the electrolyte used in the electrolytic polishing process includes a mixed solution of perchloric acid and anhydrous ethanol.

[0013] In some possible implementations, in the mixed solution of perchloric acid and anhydrous ethanol, the mass fraction of the perchloric acid is 3% to 15%.

[0014] In some possible implementations, during the electrolytic polishing process, the martensitic stainless steel sample is electrolytically polished using a constant pressure.

[0015] Furthermore, the constant voltage is 20V to 30V.

[0016] In some possible implementations, the EBSD data collection step includes: performing EBSD data collection on the sample in an electron microscope to obtain EBSD data. The beam current used for EBSD collection is (30 kV 13 nA) or (20 kV 18 nA), the collection area size is (30 microns to 100 microns)*(30 microns to 100 microns), the scanning step is controlled at 0.05 μm to 0.5 μm, the collection time is controlled at 20 min to 60 min, and at least 3 areas are selected for collection.

[0017] In some possible implementations, the EBSD data processing step includes: processing the EBSD data using CHANNEL 5 software to obtain the grain orientation distribution of the martensitic stainless steel sample. Taking grain boundaries as an example, according to the size of the orientation difference between adjacent grains, grain boundaries can be divided into small-angle grain boundaries and large-angle grain boundaries. When processing EBSD data using CHANNEL 5 software, it can be set according to the orientation difference (less than 5°, 5° to 15°, greater than 15°, etc.).

[0018] In some possible implementations, the marking step includes: randomly setting hardness pit marks along the center of the surface of the martensitic stainless steel sample outward. In some possible implementations, the hardness pit marks are set using a Vickers hardness tester.

[0019] Furthermore, the energy of the first focused ion beam is 20 kV to 30 kV, the intensity is 4 nA to 60 nA, and the cutting depth is 10 μm to 50 μm.

[0020] Furthermore, the ion type of the first focused ion beam includes at least one of a xenon ion beam and a gallium ion beam.

[0021] Furthermore, the energy of the second focused ion beam is 20 kV to 30 kV, the intensity is 0.1 nA to 4 nA, and the thinning thickness is 0.2 μm to 10 μm.

[0022] Furthermore, the ion type of the second focused ion beam includes at least one of a xenon ion beam and a gallium ion beam.

[0023] In some possible implementations, the martensitic stainless steel includes at least one of 2Cr13, 3Cr13, 4Cr13, 3Cr13N, 5Cr15, 9Cr18, S35VN, M390, and 5Cr15MoV.

[0024] The second object of the present invention is to provide an application of the method for preparing the APT sample of the martensitic stainless steel specific crystal orientation relationship interface provided by the present invention in the field of knife and scissors technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 EBSD characterization results and selected interface positions of the martensitic stainless steel sample in Example 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of an APT sample obtained by a method for preparing an APT sample of a martensitic stainless steel specific crystal orientation relationship interface in Example 1 of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the implementation of the present invention clearer, the technical scheme in the embodiment of the present invention will be described in more detail below in conjunction with the drawings in the embodiment of the present invention. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of the present invention, not all of the embodiments.

[0028] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be understood as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0029] A first aspect of an embodiment of the present invention provides a method for preparing an APT sample of a martensitic stainless steel specific crystal orientation relationship interface, comprising the following steps:

[0030] S1. The grain orientation distribution of the martensitic stainless steel sample is obtained based on EBSD data processing, and the interface area with specific orientation relationship is divided.

[0031] S2. Use the first focused ion beam (FIB) to perform point ion cutting on the interface area with a specific orientation relationship, and use the second focused ion beam to perform thinning (circular milling) to obtain an APT sample.

[0032] The method for preparing the APT sample of the specific crystal orientation relationship interface of martensitic stainless steel provided in the embodiment of the present invention uses electron backscatter diffraction (EBSD) processing to obtain the grain orientation distribution of the martensitic stainless steel sample, and then divides the specific orientation relationship interface area according to the grain orientation distribution, cuts out the APT sample at a fixed point according to the divided area, and performs thinning processing (circular milling). The preparation method obtains an APT sample with a specific crystal orientation relationship interface and an accuracy that meets the test requirements, which is conducive to in-depth analysis of APT data.

[0033] [Step S1]

[0034] In some embodiments, in the above step S1, the martensitic stainless steel includes at least one of 2Cr13, 3Cr13, 4Cr13, 3Cr13N, 5Cr15, 9Cr18, S35VN, M390, and 5Cr15MoV.

[0035] In some embodiments, in the above step S1, the source of the martensitic stainless steel sample is a knife and scissors product. In this case, the knife and scissors need to have high hardness and wear resistance when in use, and the presence of martensitic structure and carbide in the knife and scissors can improve the cutting performance of the knife and scissors, making them sharper during the cutting process, reducing wear and deformation; therefore, it is necessary to study the distribution of grains in the martensitic stainless steel sample for knife and scissors products.

[0036] In some embodiments, in the above step S1, the EBSD processing includes the steps of: subjecting the martensitic stainless steel sample to mechanical polishing, electrolytic polishing, marking, EBSD data collection, and EBSD data processing to obtain grain orientation distribution. In this case, the grain orientation distribution obtained by the EBSD processing is more accurate.

[0037] In some embodiments, the mechanical polishing process includes rough grinding, fine grinding and mechanical polishing. In this case, the martensitic stainless steel sample is subjected to mechanical polishing to remove cutting marks of the martensitic stainless steel sample.

[0038] In some embodiments, the electrolyte used in the electrolytic polishing process includes a mixed solution of perchloric acid and anhydrous ethanol. In this case, electrolytic polishing of stainless steel is a method of polishing the metal surface by electrolysis. Its mechanism is to use the current in the electrolyte to act on the anode and cathode of the stainless steel surface, so that the metal surface produces an oxidation-reduction reaction, thereby removing the oxides, scales and attachments on the surface, and making the surface smooth and bright. Using a mixed solution of perchloric acid and anhydrous ethanol with a suitable voltage can better electropolish martensitic stainless steel, and the effect is better.

[0039] In some embodiments, in the mixed solution of perchloric acid and anhydrous ethanol, the mass fraction of perchloric acid is 3% to 15%. In the exemplary embodiment, it can be 3%, 8%, 12%, 15% and other typical but non-limiting mass fractions or a range between any two mass fractions.

[0040] In some embodiments, during the electrolytic polishing process, the martensitic stainless steel sample is electrolytically polished using a constant pressure. In this case, the electrolytic polishing can evenly polish the martensitic stainless steel sample, improve the surface finish, and the like.

[0041] In some embodiments, the constant voltage is 20V to 30V, and in exemplary embodiments, it can be a typical but non-limiting voltage such as 20V, 25V, 30V, or a range between any two voltages. In this case, the voltage is suitable for electrolytic polishing of martensitic stainless steel, and the effect is better.

[0042] In some embodiments, the marking process includes: randomly setting hardness pit marks along the center of the surface of the martensitic stainless steel sample outward. In this case, using hardness pits as markings can guide the subsequent EBSD data collection steps and the selection of positions for subsequent fixed-point ion cutting. The reason for marking hardness pits from the center is that the center position and its vicinity have a high recognition and calibration rate in the EBSD collection after electrolytic polishing treatment, and the surface quality is good.

[0043] In some specific embodiments, the number of hardness pits is 6 to 10. In this case, since the EBSD collection area in general martensitic stainless steel is within the range of 50 microns * 50 microns, the range is very small and it is not easy to find the area in the focused ion beam (FIB), setting hardness pits on the martensitic stainless steel can facilitate finding the previous EBSD area when the focused ion beam (FIB) cuts the sample.

[0044] In some embodiments, when hardness pit marks are randomly set from the center of a surface of a martensitic stainless steel sample, the farthest distance from the center of the hardness pit is 500 microns to 1000 microns, and the closest distance is 100 microns to 200 microns. Generally, the EBSD acquisition area in martensitic stainless steel is in the range of 50 microns * 50 microns. The nearest 100 microns does not affect EBSD acquisition, and it is easy to find the hardness pit and mark the position in the field of view. The farthest 1000 microns, EBSD acquisition is basically within this area.

[0045] In some specific embodiments, the hardness pits are distributed asymmetrically. In this case, the hardness pits are marked randomly, so the collected data is closer to the real situation.

[0046] In some embodiments, a Vickers hardness tester is used to set hardness pit marks. The Vickers hardness test is an indentation method. Under a certain force value, the indenter is vertically pressed into the surface of the sample to be tested, and the sample surface undergoes plastic deformation, leaving a diamond-shaped indentation. When the sample surface has a certain inclination angle, the four corners of the diamond-shaped indenter are subjected to inconsistent forces, resulting in different indentation morphologies.

[0047] In some embodiments, the EBSD data collection step includes: performing EBSD data collection on the sample in an electron microscope to obtain EBSD data.

[0048] In some specific embodiments, the beam current used for EBSD acquisition is (30 kV 13 nA) or (20 kV 18 nA), the acquisition area size is (30 microns to 100 microns)*(30 microns to 100 microns), the scanning step is controlled at 0.05 μm to 0.5 μm, the acquisition time is controlled at 20 min to 60 min, and at least 3 areas are selected for acquisition.

[0049] In some embodiments, EBSD data collection is performed using a scanning electron microscope equipped with an EBSD probe.

[0050] In some embodiments, the EBSD data processing step includes: using CHANNEL 5 software to process EBSD data to obtain the grain orientation distribution of the martensitic stainless steel sample. Taking grain boundaries as an example, according to the size of the orientation difference between adjacent grains, grain boundaries can be divided into small-angle grain boundaries and large-angle grain boundaries. When processing EBSD data with CHANNEL 5 software, it can be set according to the orientation difference (less than 5°, 5°~15°, greater than 15°, etc.). In this case, Channel 5EBSD data processing software is a data analysis tool for electron backscatter diffraction (EBSD) technology. EBSD technology is an analysis method widely used in fields such as materials science, geology, and biology, which can provide important information such as the crystal structure, phase change, and texture of materials. Channel 5 software helps researchers quickly and accurately analyze and interpret EBSD data through efficient data processing and graphical interface. Customizing the data processing process according to actual needs can reduce unnecessary repetitive operations and improve data analysis efficiency. Channel 5 can be integrated with other data processing and analysis software, such as Origin, Excel, etc. Through integration, seamless transmission and efficient processing of data can be achieved.

[0051] [Step S2]

[0052] In some embodiments, in the above step S2, the energy of the first focused ion beam is 20 kV to 30 kV, the intensity is 4 nA to 60 nA, and the cutting depth is 10 μm to 50 μm.

[0053] In some embodiments, in the above step S2, the ion type of the first focused ion beam includes at least one of a xenon ion beam and a gallium ion beam.

[0054] In some embodiments, in the above step S2, the energy of the second focused ion beam is 20 kV to 30 kV, the intensity is 0.1 nA to 4 nA, and the thinning thickness is 0.2 μm to 10 μm.

[0055] In some embodiments, in the above step S2, the ion type of the second focused ion beam includes at least one of a xenon ion beam and a gallium ion beam.

[0056] A second aspect of the embodiments of the present invention provides an application of the method for preparing an APT sample of a martensitic stainless steel specific crystal orientation relationship interface provided by the embodiments of the present invention in the field of knife and scissors technology.

[0057] The following is further described in conjunction with specific embodiments.

[0058] Example 1

[0059] Example 1 proposes a method for preparing an APT sample of a martensitic stainless steel with a specific crystal orientation relationship interface; the martensitic stainless steel sample material is 5Cr15MoV; and the method comprises the following steps:

[0060] (1) Obtain a stainless steel sample with a size of 10 mm*10 mm*4 mm.

[0061] (2) Polishing: Grind and mechanically polish the stainless steel sample until the surface of the sample is smooth and free of cutting marks.

[0062] (3) The polished sample was placed in a mixed solution of perchloric acid and anhydrous ethanol with a mass ratio of 5:95 for electrolytic polishing (voltage 30 V).

[0063] (4) Hardness pit marks are randomly set outward from the center of the sample surface.

[0064] (5) Use a scanning electron microscope equipped with an EBSD probe to collect EBSD data on the sample to obtain EBSD data. The beam current used for EBSD collection is (30 kV 13 nA), the collection area size is 30 microns * 50 microns, the scanning step size is controlled at 0.1 μm, and the collection time is controlled at 40 min.

[0065] (6) Use CHANNEL 5 software to process EBSD data and obtain the grain orientation distribution of the sample. When using CHANNEL 5 software to process EBSD data, you can set the orientation difference (less than 5°, 5° to 15°, greater than 15°, etc.) as shown in the attached manual. Figure 1 The positions are shown by the white and black lines.

[0066] (7) Divide the sample into specific orientation relationship interface areas according to the grain orientation distribution (see Appendix Figure 1 shown).

[0067] (8) Using the first focused ion beam (30 kV, 15 nA) to perform ion cutting on the area,

[0068] (9) The sample was thinned (circular milling) using a second focused ion beam (30 kV, 0.1 nA to 1 nA) to obtain an APT sample (see Appendix Figure 2 shown).

[0069] Example 2

[0070] Example 2 proposes a method for preparing an APT sample of a martensitic stainless steel specific crystal orientation relationship interface. The steps are basically the same as those of Example 1, except that the martensitic stainless steel material is 3Cr13N.

[0071] Example 3

[0072] Example 3 proposes a method for preparing an APT sample of a martensitic stainless steel specific crystal orientation relationship interface. The steps are basically the same as those of Example 1, except that the martensitic stainless steel material is M390.

[0073] Attached to the instruction manual Figure 1-2 At least the following conclusions can be drawn:

[0074] ① By Figure 1 and Figure 2 It can be seen that after EBSD processing, a clear grain orientation distribution of the martensitic stainless steel sample can be obtained, which improves the accuracy of obtaining APT samples with specific crystal orientation relationship interfaces.

[0075] ② By Figure 2 It can be seen that the sample meets the requirements of APT samples: (1) the sample is needle-shaped, with a top diameter of less than 100nm; (2) the sample has a smooth surface without burrs; (3) the height of the area to be tested is about 500nm, and the total height of the sample exceeds 5μm. The preparation method of the embodiment of the present invention can locate specific positions such as the grain boundary of martensitic stainless steel and the accuracy meets the requirements of APT samples.

[0076] The above description is only a preferred embodiment of the present invention and is 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 in the protection scope of the present invention.

Claims

1. A method for preparing APT samples of martensitic stainless steel with specific crystal orientation relationship interface, It is characterized in that The steps include: The grain orientation distribution of the martensitic stainless steel sample was obtained by EBSD processing, and the interface area with specific orientation relationship was divided; The region is subjected to point ion cutting by a first focused ion beam and thinning by a second focused ion beam to obtain an APT sample.

2. The method for preparing the APT sample of the martensitic stainless steel specific crystal orientation relationship interface according to claim 1, It is characterized in that The EBSD treatment comprises the steps of: subjecting the martensitic stainless steel sample to mechanical polishing treatment, electrolytic polishing treatment, position marking treatment, EBSD data collection, and EBSD data processing to obtain the grain orientation distribution.

3. The method for preparing the APT sample of the martensitic stainless steel specific crystal orientation relationship interface according to claim 2, It is characterized in that In the electrolytic polishing process, the electrolyte used includes a mixed solution of perchloric acid and anhydrous ethanol.

4. The method for preparing the APT sample of the martensitic stainless steel specific crystal orientation relationship interface according to claim 3, It is characterized in that In the mixed solution of perchloric acid and anhydrous ethanol, the mass fraction of perchloric acid is 3% to 15%.

5. The method for preparing the APT sample of the martensitic stainless steel specific crystal orientation relationship interface according to claim 4, It is characterized in that During the electrolytic polishing process, the martensitic stainless steel sample is electrolytically polished using a constant pressure.

6. The method for preparing the APT sample of the martensitic stainless steel specific crystal orientation relationship interface according to claim 5, It is characterized in that The constant voltage is 20V to 30V.

7. The method for preparing the APT sample of the martensitic stainless steel specific crystal orientation relationship interface according to claim 2, It is characterized in that The EBSD data collection step includes: collecting EBSD data on the sample in an electron microscope to obtain EBSD data; And / or, the EBSD data processing step includes: processing the EBSD data using CHANNEL 5 software to obtain the grain orientation distribution of the martensitic stainless steel sample.

8. The method for preparing the APT sample of the martensitic stainless steel specific crystal orientation relationship interface according to claim 2, It is characterized in that The marking step includes: randomly setting hardness pit marks outward from the center of the surface of the martensitic stainless steel sample.

9. The method for preparing the APT sample of the martensitic stainless steel specific crystal orientation relationship interface according to any one of claims 1 to 8, It is characterized in that The energy of the first focused ion beam is 20 kV to 30 kV, the intensity is 4 nA to 60 nA, and the cutting depth is 10 μm to 50 μm; And / or, the ion type of the first focused ion beam includes at least one of a xenon ion beam and a gallium ion beam; and / or, the energy of the second focused ion beam is 20 kV to 30 kV, the intensity is 0.1 nA to 4 nA, and the thinning thickness is 0.2 μm to 10 μm; And / or, the ion type of the second focused ion beam includes at least one of a xenon ion beam and a gallium ion beam.

10. The method for preparing the APT sample of the martensitic stainless steel specific crystal orientation relationship interface according to claim 9, It is characterized in that The martensitic stainless steel includes at least one of 2Cr13, 3Cr13, 4Cr13, 3Cr13N, 5Cr15, 9Cr18, S35VN, M390, and 5Cr15MoV.

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