Preparation method of pure titanium EBSD sample

Abstract

The invention provides a preparation method of a pure titanium EBSD sample, and belongs to the field of preparation of metal material analysis samples. The invention provides a preparation method of a pure titanium EBSD (electron back scattered diffraction) sample, which comprises the following steps: sequentially grinding, polishing and chemically corroding an untreated pure titanium EBSD sample to obtain the pure titanium EBSD sample; the concentration of hydrofluoric acid in a chemical corrosion liquid used in the chemical corrosion is 0.02-0.03 g / mL, and the concentration of hydrogen peroxide is 0.05-0.07 g / mL. Under the synergistic effect of hydrofluoric acid and hydrogen peroxide, the high-quality pure titanium EBSD sample can be prepared by controlling the content of hydrofluoric acid and hydrogen peroxide in the chemical corrosive liquid.

Description

Technical Field

[0001] The present invention relates to the field of preparation of metal material analysis specimens, and particularly to a method for preparing a pure titanium EBSD sample. Background Art

[0002] Titanium is known as the "all-round metal" in metal materials. It has outstanding characteristics such as low density, high strength, good high and low temperature resistance, strong corrosion resistance, and excellent forming performance. It is widely used in fields such as aviation, aerospace, ships and weapons, biomedicine, chemical metallurgy, and ocean engineering.

[0003] Electron Backscattered Diffraction (EBSD) technology is a technology for quantitatively analyzing the crystal structure and orientation of sample micro-regions in a Scanning Electron Microscope (SEM). Using EBSD technology, various microstructure morphologies and quantitative analysis results of the sample can be obtained, such as crystal structure, phase distribution, grain size and shape, intragranular strain, small and large angle grain boundaries and special grain boundaries, microstructure and macrostructure, etc.; EBSD technology can also be used to characterize the microstructure of metal materials in order to better understand and control the physical properties of the materials. During the EBSD diffraction pattern acquisition process, it is necessary to ensure that there is no strain introduced by sample preparation on the sample surface, so sample preparation is crucial for EBSD data acquisition.

[0004] The prior art usually uses electrolytic polishing followed by chemical etching (the composition of the etching solution used for chemical etching is usually hydrofluoric acid and water), but the calibration rate of the obtained pure titanium EBSD specimen still needs to be improved. Summary of the Invention

[0005] The present invention provides a method for preparing a pure titanium EBSD sample, and the preparation method of the present invention improves the calibration rate of the pure titanium EBSD sample.

[0006] The present invention provides a method for preparing a pure titanium EBSD sample, comprising the following steps:

[0007] Successively grind, polish and chemically etch the untreated pure titanium EBSD sample to obtain a pure titanium EBSD sample;

[0008] The concentration of hydrofluoric acid in the chemical etching solution used for the chemical etching is 0.02 - 0.03 g / mL, and the concentration of hydrogen peroxide is 0.05 - 0.07 g / mL.

[0009] Preferably, before the grinding, it includes:

[0010] Place the untreated pure titanium EBSD sample in a metallographic embedding machine, embed it with metallographic embedding material, and then perform hot pressing.

[0011] Preferably, the temperature of the hot pressing is 150 - 180 °C, the time is 5 - 10 min, and the pressure is 25 - 35 MPa.

[0012] Preferably, the grinding includes mechanical grinding.

[0013] Preferably, the grinding includes rough grinding and fine grinding;

[0014] The grit number of the sandpaper used for rough grinding is 240 - 320 mesh; the grit number of the sandpaper used for fine grinding is 400 - 600 mesh.

[0015] Preferably, the polishing includes mechanical polishing.

[0016] Preferably, the polishing includes first polishing, second polishing, and third polishing;

[0017] The polishing liquid used for the first polishing includes a polishing liquid of first diamond;

[0018] The polishing liquid used for the second polishing includes a polishing liquid of second diamond;

[0019] The polishing liquid used for the third polishing includes an alumina polishing liquid.

[0020] Preferably, the particle size of the first diamond in the first diamond polishing liquid is 6 - 9 μm;

[0021] The particle size of the second diamond in the second diamond polishing liquid is 2 - 3 μm,

[0022] The particle size of the alumina in the alumina polishing liquid is 0.05 - 0.1 μm.

[0023] Preferably, the time of the first polishing is 6 - 10 min, the time of the second polishing is 6 - 10 min, and the time of the third polishing is 10 - 12 min.

[0024] Preferably, the time of the chemical corrosion is 3 - 8 min.

[0025] When hydrofluoric acid is used alone in the chemical etching solution, the chemical reaction rate is too fast, and it is difficult to control the etching time, resulting in uneven surface etching and easy appearance of pits, which affects the calibration rate. Therefore, hydrogen peroxide and hydrofluoric acid in the chemical etching solution of the present invention participate in the etching reaction together. During the reaction process, hydrogen peroxide, as a strong oxidant, oxidizes titanium on the titanium surface to generate TiO2, and hydrofluoric acid can react with the generated TiO2 to form a soluble complex H2TiF6. Therefore, under the synergistic effect of hydrofluoric acid and hydrogen peroxide, and by controlling the contents of hydrofluoric acid and hydrogen peroxide in the chemical etching solution, high-quality (clear grain boundary profile, high calibration rate, accurate and reliable orientation characterization results) pure titanium EBSD samples can be prepared.

[0026] Furthermore, when preparing pure titanium EBSD samples by electrolytic polishing in the prior art, the cost of electrolytic polishing equipment and supporting power supply equipment is relatively high, and multiple parameters such as voltage, current, and electrolyte composition need to be precisely controlled, requiring the sample preparation personnel to have certain experience. In addition, uneven polishing may occur for samples of different shapes, affecting the analysis results. Moreover, the electrolyte used in electrolytic polishing is usually a perchloric acid system, and strict protection is required during the operation process, presenting certain safety risks. While the present invention uses a method combining mechanical rough grinding, mechanical fine grinding, and chemical etching to perform surface treatment on pure titanium samples, without the need to precisely control preparation parameters such as voltage and current of electrolytic polishing, pure titanium EBSD samples can be prepared quickly, the sample preparation process is simpler and has lower requirements for personnel, and the equipment cost is greatly reduced. Description of the Drawings

[0027] Figure 1 The grain boundary map of different sizes and angles of the pure titanium EBSD specimen prepared in Example 1;

[0028] Figure 2 The grain boundary map of different sizes and angles of the pure titanium EBSD specimen prepared in Example 2;

[0029] Figure 3 The grain boundary map of different sizes and angles of the pure titanium EBSD specimen prepared in Example 3;

[0030] Figure 4 The grain boundary map of different sizes and angles of the pure titanium EBSD specimen prepared in Comparative Example 1;

[0031] Figure 5 The grain boundary map of different sizes and angles of the pure titanium EBSD specimen prepared in Comparative Example 2;

[0032] Figure 6 The grain boundary map of different sizes and angles of the pure titanium EBSD specimen prepared in Comparative Example 3. Detailed Description of the Invention

[0033] The present invention provides a method for preparing a pure titanium EBSD sample, comprising the following steps:

[0034] The unprocessed pure titanium EBSD sample is polished, buffed, and chemically etched in sequence to obtain a pure titanium EBSD sample;

[0035] In the chemical etching solution used for the chemical etching, the concentration of hydrofluoric acid is 0.02 - 0.03 g / mL, and the concentration of hydrogen peroxide is 0.05 - 0.07 g / mL.

[0036] In the present invention, before the polishing, it preferably includes: placing the unprocessed pure titanium EBSD sample in a metallographic embedding machine, embedding it with a metallographic embedding material, and then performing hot pressing.

[0037] In the present invention, the temperature of the hot pressing is preferably 150 - 180 °C, the time is preferably 3 - 10 min, and the pressure is preferably 25 - 35 MPa. In specific embodiments of the present invention, the temperature of the hot pressing can be 150 °C, 160 °C, 170 °C, or 180 °C, the time can be 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min, and the pressure can be 25 MPa, 27 MPa, 30 MPa, 32 MPa, or 35 MPa.

[0038] After the hot pressing, the pure titanium EBSD sample is embedded in the metallographic embedding material.

[0039] In the present invention, the polishing preferably includes mechanical polishing, and the mechanical polishing preferably includes: rough grinding and fine grinding; the mesh number of the sandpaper used for rough grinding is preferably 240 - 320 mesh, and the pressure is preferably 20 - 25 N; the mesh number of the sandpaper used for fine grinding is preferably 400 - 600 mesh, and the pressure is preferably 15 - 20 N; in specific embodiments of the present invention, the mesh number of the sandpaper used for rough grinding can be 240 mesh, 260 mesh, 280 mesh, 300 mesh, or 320 mesh, and the mesh number of the sandpaper used for fine grinding can be 400 mesh, 450 mesh, 5000 mesh, 550 mesh, or 600 mesh. The total time of the polishing is 8 - 15 min, the time of rough grinding is preferably 2 - 5 min, and the time of fine grinding is preferably 6 - 10 min.

[0040] In the present invention, the polishing is preferably performed in a metallographic polishing machine. The rotational speed of the chassis of the metallographic polishing machine is preferably 120 - 160 r / min, and the rotational speed of the sample disk is preferably 80 - 120 r / min. In specific embodiments of the present invention, the rotational speed of the chassis of the metallographic polishing machine can be 120 r / min, 130 r / min, 140 r / min, or 150 r / min, and the rotational speed of the sample disk is preferably 80 r / min, 90 r / min, or 100 r / min.

[0041] During the polishing process, it is preferably kept cool by injecting water.

[0042] In the present invention, the polishing includes mechanical polishing, and the polishing is preferably carried out in a metallographic polishing machine. The rotational speed of the chassis of the metallographic polishing machine is preferably 120 - 150 r / min, and the rotational speed of the sample disk is preferably 70 - 100 r / min. In a specific embodiment of the present invention, the rotational speed of the chassis of the metallographic polishing machine can be 120 r / min, 130 r / min, 140 r / min or 150 r / min, and the rotational speed of the sample disk is preferably 70 r / min, 80 r / min, 90 r / min or 100 r / min.

[0043] The polishing preferably includes: first polishing, second polishing and third polishing;

[0044] The polishing liquid used for the first polishing preferably includes a polishing liquid of first diamond, and the particle size of the first diamond in the polishing liquid of first diamond is preferably 6 - 9 μm; the time of the first polishing is preferably 6 - 10 min. In a specific embodiment of the present invention, the particle size of the diamond can be 6 μm, 7 μm, 8 μm or 9 μm, and the time of the first polishing can be 6 min, 7 min, 8 min, 9 min or 10 min.

[0045] The polishing liquid used for the second polishing preferably includes a polishing liquid of second diamond, and the particle size of the second diamond in the polishing liquid of second diamond is preferably 2 - 3 μm; the time of the second polishing is preferably 6 - 10 min. In a specific embodiment of the present invention, the time of the second polishing can be 6 min, 7 min, 8 min, 9 min or 10 min.

[0046] The polishing liquid used for the third polishing preferably includes a polishing liquid of alumina, and the particle size of the alumina in the polishing liquid of alumina is preferably 0.05 - 0.1 μm. The time of the third polishing is preferably 10 - 12 min. In a specific embodiment of the present invention, the particle size of the alumina can be 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1 μm, and the time of the first polishing can be 10 min, 11 min or 12 min.

[0047] In the present invention, the concentration of hydrofluoric acid in the chemical etching solution used for chemical etching is preferably 0.02 - 0.03 g / mL, and the concentration of hydrogen peroxide is preferably 0.05 - 0.07 g / mL. In a specific embodiment of the present invention, the concentration of hydrofluoric acid can be 0.02 g / mL, 0.025 g / mL or 0.03 g / mL, and the concentration of hydrogen peroxide can be 0.05 g / mL, 0.06 g / mL or 0.07 g / mL; the solvent of the chemical etching solution is preferably water.

[0048] In the present invention, the time of the chemical etching is preferably 3 to 8 minutes. In specific embodiments of the present invention, the time of the chemical etching can be 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes or 8 minutes.

[0049] In the present invention, it is preferred to keep the sample shaking during the chemical etching. The purpose of shaking is to increase the collision frequency between reactants, break the local concentration difference, and improve the reaction efficiency.

[0050] The preparation method of the pure titanium EBSD sample provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0051] Example 1

[0052] Step 1, sample cutting: The titanium target is processed by wire cutting to obtain a cutting sample that meets the EBSD characterization size;

[0053] The size of the sample is 12 mm × 8 mm × 6 mm;

[0054] Step 2, sample hot embedding: The cutting sample obtained in Step 1 is placed on a metallographic embedding machine, and metallographic embedding material is added, and the embedding sample block is obtained by heating and pressing;

[0055] The metallographic embedding temperature is 155 °C, the embedding time is 3 minutes, and the pressure is 30 MPa;

[0056] Step 3, mechanical grinding: The sample block prepared in Step 2 is placed on a metallographic polishing machine, and rough grinding and fine grinding are carried out successively with 320-mesh and 400-mesh Si-C sandpapers (the rough grinding time is 3 minutes, the pressure is 20 N; the fine grinding time is 10 minutes, the pressure is 20 N) to obtain a ground sample;

[0057] During the mechanical grinding process, the rotation speed of the chassis of the metallographic polishing machine is 150 r / min, the rotation speed of the sample disk is 120 r / min and water injection is maintained for lubrication and cooling;

[0058] Step 4, mechanical polishing: 9 μm diamond polishing liquid, 3 μm diamond polishing liquid, and 0.05 μm alumina polishing liquid are sprayed on the polishing disk in sequence for the sample polished in Step 3, and the sample disk and the chassis of the polishing machine rotate for polishing to obtain a polished sample;

[0059] During the mechanical polishing process, the rotation speed of the chassis of the metallographic polishing machine is 120 r / min, the rotation speed of the sample disk is 80 r / min, and the times are 7 minutes, 7 minutes, and 10 minutes respectively;

[0060] Step 5, sample etching: Chemically etch the polished sample obtained in Step 4 to obtain an EBSD sample of the titanium target; the etching solution used for the sample etching is a mixed solution of hydrofluoric acid, hydrogen peroxide, and distilled water;

[0061] The ratio of the chemical etching solution is 0.02 g / mL of hydrofluoric acid, 0.05 g / mL of hydrogen peroxide, and the balance is distilled water. The sample etching time is 4 min, and the sample is kept shaking during the etching process, and the polished surface of the sample preparation is always below the etching liquid level;

[0062] Figure 1 It is the large and small angle grain boundary map of the pure titanium EBSD specimen prepared in Example 1.

[0063] From Figure 1 it can be seen that the etching effect of the pure titanium EBSD specimen is good.

[0064] The calibration rate of the pure titanium EBSD specimen is 95.6%.

[0065] Example 2

[0066] Step 1, sample cutting: Use wire cutting to process the titanium target to obtain a cutting sample that meets the EBSD characterization size;

[0067] The sample size is 10 mm × 6 mm × 5 mm;

[0068] Step 2, sample hot embedding: Place the cutting sample obtained in Step 1 on a metallographic embedding machine, add metallographic embedding material, and heat and press to obtain an embedded sample block;

[0069] The metallographic embedding temperature is 160 °C, the embedding time is 4 min, and the pressure is 35 MPa;

[0070] Step 3, mechanical grinding: Place the sample block obtained in Step 2 on a metallographic polishing machine, and polish it successively with 240-mesh and 600-mesh Si-C sandpaper (the rough grinding time is 3 min, the pressure is 20 N; the fine grinding time is 10 min, the pressure is 20 N) to obtain a ground sample;

[0071] During the mechanical grinding process, the rotation speed of the chassis of the metallographic polishing machine is 155 r / min, and the rotation speed of the sample disk is 120 r / min and water injection is maintained for cooling;

[0072] Step 4, mechanical polishing: Spray 9-μm diamond polishing fluid, 3-μm diamond polishing fluid, and 0.05-μm alumina polishing fluid on the polishing disk in sequence for the sample polished in Step 3, and rotate the sample disk and the chassis of the polishing machine for polishing to obtain a polished sample;

[0073] During the mechanical polishing process, the rotation speed of the chassis of the metallographic polishing machine is 130 r / min, the rotation speed of the sample disk is 75 r / min, and the time is 8 min, 8 min, and 12 min respectively;

[0074] Step 5, sample etching: Chemically etch the polished sample obtained in step 4 to obtain an EBSD sample of the titanium target; The etching solution used for the sample etching is a mixed solution of hydrofluoric acid, hydrogen peroxide, and distilled water.

[0075] The ratio of the chemical etching solution is 0.02 g / mL of hydrofluoric acid, 0.06 g / mL of hydrogen peroxide, and the balance is distilled water; The sample etching time is 6 min, and the sample is kept shaking during the etching process, and the polished surface of the sample preparation is always below the etching liquid level;

[0076] Figure 2 It is the large and small angle grain boundary map of the pure titanium EBSD specimen prepared in Example 2.

[0077] From Figure 2 it can be seen that the etching effect of the pure titanium EBSD specimen is good.

[0078] The calibration rate of the pure titanium EBSD specimen is 97.0%.

[0079] Example 3

[0080] Step 1, sample cutting: Use wire cutting to process the titanium target to obtain a cutting sample that meets the EBSD characterization size;

[0081] The sample size is 15 mm × 10 mm × 5 mm;

[0082] Step 2, sample hot inlay: Place the cutting sample obtained in step 1 on a metallographic inlay machine, add metallographic inlay material, and heat and press to obtain an inlaid sample block;

[0083] The metallographic inlay temperature is 170 °C, the inlay time is 3 min, and the pressure is 25 MPa;

[0084] Step 3, mechanical grinding: Place the sample block obtained in step 2 on a metallographic polishing machine, and polish it successively with 240-mesh and 400-mesh Si-C sandpaper (the rough grinding time is 3 min, the pressure is 20 N; the fine grinding time is 10 min, the pressure is 20 N) to obtain a ground sample;

[0085] During the mechanical grinding process, the rotation speed of the chassis of the metallographic polishing machine is 160 r / min, the rotation speed of the sample disk is 100 r / min and water injection is maintained for cooling;

[0086] Step 4, Mechanical polishing: Spray 9μm diamond polishing fluid, 3μm diamond polishing fluid, and 0.05μm alumina polishing fluid onto the polishing disc in sequence for the sample polished in Step 3. Rotate the sample disc and the polishing machine chassis to perform polishing, obtaining a polished sample;

[0087] During the mechanical polishing process, the rotation speed of the polishing machine chassis of the metallographic polishing machine is 120 r / min, the rotation speed of the sample disc is 80 r / min, and the times are 10 min, 10 min, and 12 min respectively;

[0088] Step 5, Sample etching: Chemically etch the polished sample obtained in Step 4 to obtain a titanium target EBSD sample; The etching solution used for the sample etching is a mixed solution of hydrofluoric acid, hydrogen peroxide, and distilled water;

[0089] The ratio of the chemical etching solution is 0.03 g / mL of hydrofluoric acid, 0.07 g / mL of hydrogen peroxide, and the balance is distilled water. The sample etching time is 8 min, and the sample is kept shaking during the etching process. The polished surface of the sample is always below the etching liquid level;

[0090] Figure 3 It is the large and small angle grain boundary map of the pure titanium EBSD specimen prepared in Example 3.

[0091] As can be seen from Figure 3 the corrosion effect of the pure titanium EBSD specimen is good.

[0092] The calibration rate of the pure titanium EBSD specimen is 96.7%.

[0093] Comparative Example 1

[0094] This example provides a method for preparing a pure titanium EBSD sample. The sample preparation method is the same as that of Example 1, except that: the concentration of hydrofluoric acid in the chemical etching solution is 0.1 g / mL, and the concentration of hydrogen peroxide is 0.2 g / mL, which fails to meet the requirements of this standard.

[0095] Figure 4 It is the large and small angle grain boundary map of the pure titanium EBSD specimen prepared in Comparative Example 1.

[0096] As can be seen from Figure 4 the pure titanium EBSD sample prepared in Comparative Example 1 shows multiple corrosion pits under the electron microscope. There is signal occlusion around the pits, and the resolution is low.

[0097] The calibration rate of the pure titanium EBSD specimen is 84.6%, and the calibration rate is significantly lower than that of Example 1.

[0098] Comparative Example 2

[0099] This embodiment provides a method for preparing a pure titanium EBSD sample. The sample preparation method is the same as that of Example 1, except that the concentration of hydrofluoric acid is 0.01 g / mL and the concentration of hydrogen peroxide is 0.03 g / mL, which fails to meet the requirements of this standard.

[0100] Figure 5 It is the large and small angle grain boundary map of the pure titanium EBSD specimen prepared for Comparative Example 2.

[0101] From Figure 5 it can be seen that the deformation layer on the sample surface is not completely removed.

[0102] The calibration rate of the prepared pure titanium EBSD specimen is 72.6%, and the calibration rate is significantly lower than that of Example 1.

[0103] Comparative Example 3

[0104] This embodiment provides a method for preparing a pure titanium EBSD sample. The sample preparation method is the same as that of Example 1, except that the hydrogen peroxide as the oxidant in the formula is changed to potassium permanganate with the same concentration, which fails to meet the requirements of this standard.

[0105] Figure 6 It is the large and small angle grain boundary map of the pure titanium EBSD specimen prepared for Comparative Example 3.

[0106] From Figure 6 it can be seen that after the oxidant in the formula is changed, potassium permanganate reacts with titanium to form a precipitate attached to the surface of the specimen, and the corrosion effect is poor.

[0107] The calibration rate of the prepared pure titanium EBSD specimen is 82.3%, and the calibration rate is significantly lower than that of Example 1.

[0108] By comparing the examples and comparative examples, it is found that the method for preparing a pure titanium EBSD sample provided by the present invention can quickly prepare a pure titanium EBSD sample, reduce the equipment cost, and improve the ease of operation; the obtained pure titanium EBSD sample has good quality, clear grain boundary contours, high calibration rate, and reliable orientation characterization results, which has a good effect on improving the EBSD detection efficiency, quality, and cost reduction of titanium.

[0109] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a pure titanium EBSD sample, characterized in that, It includes the following steps: Successively grind, polish, and chemically etch the untreated pure titanium EBSD sample to obtain a pure titanium EBSD sample; In the chemical etching solution used for the chemical etching, the concentration of hydrofluoric acid is 0.02 - 0.03 g / mL, and the concentration of hydrogen peroxide is 0.05 - 0.07 g / mL.

2. The preparation method according to claim 1, characterized in that, Before the grinding, it includes: Place the untreated pure titanium EBSD sample in a metallographic embedding machine, embed it with a metallographic embedding material, and then perform hot pressing.

3. The preparation method according to claim 2, wherein, The temperature of the hot pressing is 150 - 180 °C, the time is 5 - 10 min, and the pressure is 25 - 35 MPa.

4. The preparation method according to claim 1, wherein The grinding includes mechanical grinding.

5. The preparation method according to claim 1 or 4, characterized in that, The grinding includes rough grinding and fine grinding; The grit number of the sandpaper used for the rough grinding is 240 - 320 mesh; the grit number of the sandpaper used for the fine grinding is 400 - 600 mesh.

6. The preparation method according to claim 1, characterized in that, The polishing includes mechanical polishing.

7. The preparation method according to claim 1 or 6, characterized in that, The polishing includes first polishing, second polishing, and third polishing; The polishing liquid used for the first polishing includes a polishing liquid with first diamond; The polishing liquid used for the second polishing includes a polishing liquid with second diamond; The polishing liquid used for the third polishing includes a polishing liquid with alumina.

8. The preparation method according to claim 7, characterized in that, The particle size of the first diamond in the polishing liquid with first diamond is 6 - 9 μm; The particle size of the second diamond in the polishing liquid with second diamond is 2 - 3 μm, The particle size of the alumina in the polishing liquid with alumina is 0.05 - 0.1 μm.

9. The preparation method according to claim 8, characterized in that, The time of the first polishing is 6 - 10 min, the time of the second polishing is 6 - 10 min, and the time of the third polishing is 10 - 12 min.

10. The preparation method according to claim 1, characterized in that, The time of the chemical etching is 3 - 8 min.

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