A method for preparing EBSD samples for longitudinal sections of metal microwires

Abstract

The present invention belongs to the field of EBSD sample preparation, and relates to a method for preparing EBSD samples of longitudinal sections of metal microwires, comprising: hot-mounting metal microwires to obtain hot-mounting blocks; grinding the bottom of the hot-mounting blocks, and after the position traces of the metal microwires are exposed, cutting the mounting blocks into a plurality of hot-mounting small blocks; cold-mounting the hot-mounting small blocks with thermoplastic resin to obtain a first cold-mounting block; grinding, mechanical polishing, and vibration polishing the surface to be tested of the first cold-mounting block to obtain a second cold-mounting block; heating the second cold-mounting block, and taking out the hot-mounting block of the metal microwires. The method of the present invention has high efficiency, large effective area, low preparation cost, and wide applicability, especially for metal microwires of various materials with diameters between 100 and 500 microns. Therefore, the present invention solves the problem of preparing EBSD samples of longitudinal sections of metal microwires efficiently and with high quality.

Description

Technical Field

[0001] The invention belongs to the field of EBSD sample preparation and relates to a method for preparing an EBSD sample of a longitudinal section of a metal microwire. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Metal microwires have excellent properties and are widely used in weaving materials, catalysis and other fields. Therefore, the development of high-performance metal microwires is critical to improving their performance. Generally, composition and structure are the key factors affecting material performance. Research on the grain morphology, grain size, texture, etc. of metal microwires is an important factor affecting the performance regulation of metal microwires. Electron backscatter diffraction analysis (EBSD) is an essential means for studying the crystal structure of metal materials. EBSD detection has extremely high requirements for the surface state of the sample. First, the sample surface must be smooth. Second, the mechanical residual stress layer on the sample surface must be removed (the mechanical residual stress layer is mostly introduced during mechanical polishing of the material. The presence of the mechanical stress layer will affect the normal diffraction of the backscattered electron signal). However, the size of metal microwires is small, and it is difficult to clamp the sample during the sample preparation process. Due to the size effect, the stiffness of the metal microwires is poor. Therefore, it is particularly difficult to obtain EBSD samples of metal microwire longitudinal sections with smooth longitudinal sections and no residual mechanical stress layer.

[0004] At present, the preparation of EBSD samples of metal microwire longitudinal sections mainly relies on the expensive focused ion beam technology. However, this technology has three main disadvantages: first, the equipment price is several million, which is expensive; second, the use cost is expensive. The sample preparation process uses Ga (gallium) ions for polishing, and the cost of Ga ions is high, which increases the preparation cost of a single sample; third, the preparation efficiency is low. The preparation of a single tiny area takes tens of minutes or even longer, and the actual effective area is small.

[0005] On the other hand, the EBSD samples prepared by the traditional cold mounting method cannot meet the requirements of conductivity. Although the surface state of the samples prepared by the hot mounting method can meet the EBSD test requirements for samples, the size of the corresponding cylindrical hot mounting block is very large, which is not convenient for subsequent electron microscope detection (the length and width of the sample generally need to be within 10mm), and only a single microwire can be prepared, and the sample preparation efficiency is extremely low.

[0006] Therefore, there is an urgent need to solve the current problems of high cost and low efficiency in EBSD sample preparation. Summary of the invention

[0007] In order to solve the above problems, the present invention proposes a method for preparing EBSD samples for longitudinal sections of metal microwires, especially for metal microwires of various materials with a diameter between 100-500 microns. The present invention first ensures the acquisition of the longitudinal section of a single metal microwire by hot mounting, and at the same time, the wrapping of the conductive material also ensures that the sample can meet the conductivity requirements of the EBSD test; then, by cold mounting, multiple vibration polishing samples are prepared at the same time, which improves the test efficiency. Finally, the hot mounting block is taken out by utilizing the heat softening property of the cold mounting resin to obtain multiple EBSD samples, and secondary contamination of the sample surface is avoided, which efficiently and high-quality solves the problem of longitudinal section EBSD sample preparation. The prepared samples can be reused many times, and no contamination is introduced during the sample preparation process, which not only improves the preparation efficiency but also reduces the production cost.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] The first aspect of the present invention provides a method for preparing a metal microwire longitudinal cross-section EBSD sample, comprising:

[0010] Performing hot embedding on a single metal microwire to obtain a hot embedding block;

[0011] The bottom of the hot-setting block is polished, and after the position traces of the metal microwires are exposed, the setting block is cut into small hot-setting blocks;

[0012] Cold mounting a plurality of hot-mounted small blocks using a thermoplastic resin to obtain a first cold-mounted block;

[0013] Grinding, mechanically polishing, and vibration polishing the surface to be tested of the first cold-mounted block to obtain a second cold-mounted block;

[0014] The second cold-mounted block is heated to soften the thermoplastic resin, and a plurality of hot-mounted small blocks, namely, a plurality of metal microwire longitudinal cross-section EBSD samples, are taken out.

[0015] The hot-mounting material must meet two basic requirements: first, excellent electrical conductivity (voltage loss less than 0.5%); second, only graphite filler, not aluminum, copper and other materials that can improve the conductivity of the mounting material, to avoid the introduction of crystalline materials, affecting the accuracy and effectiveness of test data statistics. Therefore, preferably, the filler of the hot-mounting material is graphite.

[0016] In order to achieve the embedding of metal microwires and improve the efficiency of hot embedding, the present invention studies the conditions for hot embedding. Preferably, the conditions for hot embedding are: the covering height is 2mm-3mm, and then the pressure is maintained at 160℃-180℃, the pressure is 80bar-90bar, and the pressure holding time is 13min-15min.

[0017] The present invention does not impose any particular limitation on the specific shape of the heat-mounted small block, as long as it can meet the requirements of subsequent electron microscope testing. Preferably, the heat-mounted small block is rectangular, cylindrical, trapezoidal or triangular.

[0018] In order to improve the efficiency of cold mounting, the present invention performs cold mounting under room temperature and pressure, that is, the cold mounting is performed at 20° C.-25° C. and 101 kPa-105 kPa.

[0019] In order to mount multiple samples simultaneously on the same cold mounting block, the present invention studies the thickness of the cold mounting block. Preferably, the thickness of the first cold mounting block is 15 mm-20 mm.

[0020] In order to remove the fine scratches left by grinding on the sample surface and make the sample surface a bright and traceless mirror, the present invention studies the process of mechanical polishing. Preferably, the mechanical polishing is divided into two steps: the first step, 1.5μm diamond polishing agent, the polishing disk speed is 300r / min-400r / min; the second step, 0.5μm diamond polishing agent, the polishing disk speed is 100r / min-200r / min.

[0021] In order to remove defects on the surface of metallographic samples and improve surface quality, thereby ensuring that the observation and analysis results under EBSD are accurate and reliable, the conditions for vibration polishing are studied in the present invention. Preferably, the amplitude of the vibration polishing is 45%-55%, the vibration frequency is 40Hz-50Hz, and the polishing time is 120min-180min.

[0022] In the process of removing the metal microwire hot-mounted block from the cold-mounted block, the resin needs to be softened but not fluid. Therefore, the present invention studies the heating temperature and time. Preferably, the heating temperature is 180°C-220°C and the heating time is 8min-15min.

[0023] Preferably, the metal microwires are made of nickel or tungsten.

[0024] Beneficial effects of the present invention

[0025] (1) The present invention solves the problem of preparing longitudinal cross-section EBSD samples of metal microwires, especially for metal microwires of various materials with a diameter between 100 and 500 μm. A reasonable preparation process is adopted to efficiently and high-quality solve the problem of preparing longitudinal cross-section EBSD samples thereof. The prepared samples can be reused multiple times, which not only improves the preparation efficiency but also reduces the production cost.

[0026] (2) The diameter of the metal microwire is very small, and the longitudinal section needs to be obtained very carefully. If you are not careful during the grinding process, it is possible that all of them will be ground off. If a large mosaic block is used directly to inlay multiple metal microwires, on the one hand, the metal microwires are small in size and it is difficult to distinguish the sample numbers. On the other hand, due to the problem of uneven load application during the grinding process, some metal microwires may be directly worn through, making it difficult to directly obtain multiple smooth and flat metal microwire longitudinal sections by grinding and polishing. Therefore, the present invention first prepares a single microwire mosaic block (diameter of about 20mm, thickness of 2mm-3mm) to ensure that a complete longitudinal section of the metal microwire can be obtained during the grinding process, and then cold-inserts multiple small mosaic blocks of metal microwire longitudinal sections to simultaneously obtain multiple high-quality EBSD samples corresponding to different types / different preparation processes; and the small size of the mosaic block can better meet the high-efficiency operation requirements of the electron microscope (multiple samples can be placed at a time, and the vacuum efficiency is greatly improved). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 The figure is a flow chart of sample preparation of the present invention.

[0029] Figure 2 This is a size diagram of annealed nickel metal microwires in Example 1 of the present invention;

[0030] Figure 3 The grain orientation distribution diagram of the collection area in Example 1 of the present invention;

[0031] Figure 4 A comparison diagram of the Kikuchi pattern diffraction bands in the acquisition area in Example 1 of the present invention;

[0032] Figure 5 This is a diagram showing the dimensions of the drawn tungsten metal microwire in Example 2 of the present invention;

[0033] Figure 6 The grain orientation distribution diagram of the acquisition area in Example 2 of the present invention;

[0034] Figure 7 This is a comparison diagram of the Kikuchi pattern diffraction bands in the collection area in Example 2 of the present invention. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0036] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0037] Example 1

[0038] Reference Figure 1 The sample preparation was carried out according to the process.

[0039] (1) Hot embedding of metal microwires: Use a hot embedding material containing only graphite (Technotherm 3000, a commercially available product) to hot embed the annealed nickel microwires. When embedding, place the metal microwires horizontally at the bottom of the hot embedding mold and then cover them with the hot embedding material to a height of about 2 mm. Then, hold the mold at 160°C, 80 bar, and 13 minutes. Wait until it cools to room temperature before taking it out for use.

[0040] (2) Grinding and cutting of conductive thermal mosaic blocks: Use sandpaper to grind the bottom of the metal microwire mosaic block to find the specific position of the metal microwire in the mosaic block. Therefore, when grinding, use fine sandpaper with a mesh size of 1500 or above to grind slowly to avoid the metal microwire being completely worn away during the grinding process. After grinding until the position traces of the metal microwire are exposed, use a cutting machine to cut the mosaic block into small rectangular pieces. The recommended cutting size is about 6mm×5mm.

[0041] (3) Cold mounting of metal microwire hot mounting blocks: Use acrylic powder (cold mounting resin) to cold mount the cut hot mounting blocks under room temperature and temperature pressure (the mass ratio of cold mounting filler and curing agent is 5:4.5, and the curing time is 45 minutes). It is particularly pointed out that thermoplastic cold mounting resins (i.e., plastic changes will occur after heating, especially softening effects) must be used, and thermosetting resins (i.e., further curing after heating will not cause softening effects) must not be used for cold mounting. At the same time, multiple samples can be mounted simultaneously on the same cold mounting block according to actual test requirements. The thickness of the cold mounting block is 15 mm.

[0042] (4) Wait for the side to be further polished, mechanically polished and vibrated:

[0043] 4.1 Sandpaper polishing: Use sandpaper to further polish the surface to be tested after cold mounting: Use 1500#, 2000#, and 2500# water sandpaper in sequence, and polish gradually under the flushing of water flow.

[0044] 4.2 Mechanical polishing: The surface to be tested was further polished by mechanical polishing, and the polishing parameters were as follows: the first step, 1.5 μm diamond polishing agent, polishing disk speed 300 r / min; the second step, 0.5 μm diamond polishing agent, polishing disk speed 100 r / min.

[0045] 4.3 Vibration polishing: Use SiO with an average particle size of 50 nm 2 (Silicon dioxide) suspension, use a 1 kg counterweight, and vibrate polish the cold mounted block with the test surface facing down, with an amplitude of 45%, a vibration frequency of 40 Hz, and a polishing time of 120 min.

[0046] (5) Removal of the metal microwire hot-mounted block: Use a heating table to heat the cold-mounted resin block. In particular, the surface to be tested should face upward. At the same time, the cold-mounted block and the heating table should be isolated with aluminum foil to prevent the softened resin from contaminating the heating table. Set the heating table temperature to 220°C and the heating time to 8 minutes to make the resin soften but not fluid. Then, use a flat-blade screwdriver to remove the metal microwire hot-mounted blocks one by one and set them aside.

[0047] The metal microwire hot-mounted block was tested by EBSD. The test results are as follows: Figure 2-Figure 4 As shown, it can be seen that the EBSD sample test image of the longitudinal section of the metal microwire prepared by the present invention has high brightness, no scratches, no defects, no stress layer, and clear boundaries.

[0048] Example 2

[0049] (1) Hot embedding of metal microwires: A hot embedding material containing only graphite (Technotherm 3000, commercially available product) was used to hot embed the drawn metal tungsten microwires.

[0050] During inlaying, place the metal microwire horizontally at the bottom of the hot-mounted mold, and then cover it with hot-mounted material with a covering height of about 3 mm. Then, maintain pressure at 180°C, 90 bar, and 15 minutes. Wait for it to cool to room temperature before taking it out for use.

[0051] (2) Grinding and cutting of conductive thermal mosaic blocks: Use sandpaper to grind the bottom of the metal microwire mosaic block to find the specific position of the metal microwire in the mosaic block. Therefore, when grinding, use fine sandpaper with a mesh size of 1500 or above to grind slowly to avoid the metal microwire being completely worn away during the grinding process. After grinding until the position traces of the metal microwire are exposed, use a cutting machine to cut the mosaic block into small rectangular pieces. The recommended cutting size is about 6mm×5mm.

[0052] (3) Cold mounting of metal microwire hot mounting blocks: Use acrylic powder (cold mounting resin) to cold mount the cut hot mounting blocks under room temperature and temperature pressure (the mass ratio of cold mounting filler and curing agent is 5:4, and the curing time is 30 minutes). It is particularly pointed out that thermoplastic cold mounting resins (i.e., plastic changes will occur after heating, especially softening effects) must be used, and thermosetting resins (i.e., further curing after heating will not cause softening effects) must not be used for cold mounting. At the same time, multiple samples can be mounted simultaneously on the same cold mounting block according to actual test requirements. The thickness of the mounting block is 20 mm.

[0053] (4) Wait for the side to be further polished, mechanically polished and vibrated:

[0054] 4.1 Sandpaper polishing: Use sandpaper to further polish the surface to be tested after cold mounting: Use 1500#, 2000#, and 2500# water sandpaper in sequence, and polish gradually under the flushing of water flow.

[0055] 4.2 Mechanical polishing: The surface to be tested was further polished by mechanical polishing, and the polishing parameters were as follows: the first step, 1.5 μm diamond polishing agent, polishing disk speed 400 r / min; the second step, 0.5 μm diamond polishing agent, polishing disk speed 200 r / min.

[0056] 4.3 Vibration polishing: Use SiO with an average particle size of 50 nm 2 The suspension was vibrated and polished with the test surface of the cold mounted block facing downward using a 1 kg counterweight, with an amplitude of 55%, a vibration frequency of 50 Hz, and a polishing time of 180 min.

[0057] (5) Removal of the metal microwire hot-mounted block: Use a heating table to heat the cold-mounted resin block. In particular, the surface to be tested should face upward. At the same time, the cold-mounted block and the heating table should be isolated with aluminum foil to prevent the softened resin from contaminating the heating table. Set the heating table temperature to 180°C and the heating time to 15 minutes to make the resin soften but not fluid. Then, use a flat-blade screwdriver to remove the metal microwire hot-mounted blocks one by one and set them aside for later use.

[0058] The metal microwire hot-mounted block was tested by EBSD. The test results are as follows: Figure 5-Figure 7 As shown, it can be seen that the sample test image prepared by the present invention has high brightness, no scratches, no defects, no stress layer, and clear boundaries.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing EBSD samples of metal microwire longitudinal sections, characterized in that: include: Performing hot embedding on a single metal microwire to obtain a hot embedding block; The bottom of the hot-setting block is polished, and after the position traces of the metal microwires are exposed, the setting block is cut into small hot-setting blocks; Cold mounting a plurality of hot-mounted small blocks using a thermoplastic resin to obtain a first cold-mounted block; Grinding, mechanically polishing, and vibration polishing the surface to be tested of the first cold-mounted block to obtain a second cold-mounted block; heating the second cold-mounted block to soften the thermoplastic resin, and taking out a plurality of hot-mounted small blocks, namely, a plurality of metal microwire longitudinal cross-section EBSD samples; The diameter of the single metal microwire is 100-500 microns; The filler of the hot mounting material is graphite.

2. The method for preparing a metal microwire longitudinal cross-section EBSD sample according to claim 1, characterized in that: The conditions for the hot mounting are: a covering height of 2 mm to 3 mm, and then maintaining pressure at 160° C. to 180° C., a holding pressure of 80 bar to 90 bar, and a holding time of 13 min to 15 min.

3. The method for preparing a metal microwire longitudinal cross-section EBSD sample according to claim 1, characterized in that: The heat-mounted small block is rectangular, cylindrical, trapezoidal or triangular.

4. The method for preparing a metal microwire longitudinal cross-section EBSD sample according to claim 1, characterized in that: The cold mounting is carried out at 20°C-25°C and 101 kPa-105 kPa.

5. The method for preparing a metal microwire longitudinal cross-section EBSD sample according to claim 1, characterized in that: The thickness of the first cold-mounted block is 15 mm-20 mm.

6. The method for preparing a metal microwire longitudinal cross-section EBSD sample according to claim 1, characterized in that: The mechanical polishing is divided into two steps: the first step, 1.5 μm diamond polishing agent, the polishing disc speed is 300 r / min-400 r / min; the second step, 0.5 μm diamond polishing agent, the polishing disc speed is 100 r / min-200 r / min.

7. The method for preparing a metal microwire longitudinal cross-section EBSD sample according to claim 1, characterized in that: The amplitude of the vibration polishing is 45%-55%, the vibration frequency is 40Hz-50Hz, and the polishing time is 120min-180min.

8. The method for preparing a metal microwire longitudinal cross-section EBSD sample according to claim 1, characterized in that: The heating temperature is 180° C.-220° C., and the heating time is 8 min.-15 min.

9. The method for preparing a metal microwire longitudinal cross-section EBSD sample according to claim 1, characterized in that: The metal microwire is made of nickel or tungsten.

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